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1
van der Krogt, Marjolein M., Wendy W. de Graaf, Claire T. Farley, Chet T. Moritz, L. J. Richard Casius, and Maarten F. Bobbert. "Robust passive dynamics of the musculoskeletal system compensate for unexpected surface changes during human hopping." Journal of Applied Physiology 107, no. 3 (September 2009): 801–8. http://dx.doi.org/10.1152/japplphysiol.91189.2008.
Повний текст джерелаАнотація:
When human hoppers are surprised by a change in surface stiffness, they adapt almost instantly by changing leg stiffness, implying that neural feedback is not necessary. The goal of this simulation study was first to investigate whether leg stiffness can change without neural control adjustment when landing on an unexpected hard or unexpected compliant (soft) surface, and second to determine what underlying mechanisms are responsible for this change in leg stiffness. The muscle stimulation pattern of a forward dynamic musculoskeletal model was optimized to make the model match experimental hopping kinematics on hard and soft surfaces. Next, only surface stiffness was changed to determine how the mechanical interaction of the musculoskeletal model with the unexpected surface affected leg stiffness. It was found that leg stiffness adapted passively to both unexpected surfaces. On the unexpected hard surface, leg stiffness was lower than on the soft surface, resulting in close-to-normal center of mass displacement. This reduction in leg stiffness was a result of reduced joint stiffness caused by lower effective muscle stiffness. Faster flexion of the joints due to the interaction with the hard surface led to larger changes in muscle length, while the prescribed increase in active state and resulting muscle force remained nearly constant in time. Opposite effects were found on the unexpected soft surface, demonstrating the bidirectional stabilizing properties of passive dynamics. These passive adaptations to unexpected surfaces may be critical when negotiating disturbances during locomotion across variable terrain.
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Khellouki, A., J. Rech, and H. Zahouani. "Influence of the belt-finishing process on the surface texture obtained by hard turning." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 221, no. 7 (July 1, 2007): 1129–37. http://dx.doi.org/10.1243/09544054jem776.
Повний текст джерелаАнотація:
The belt-finishing process is a recent manufacturing technique in industry, the mechanisms and characteristics of which have not yet been fully explained. This paper attempts to make a contribution to the understanding of the consequences of the process on the surface roughness of surfaces prepared by hard turning. Abrasive film wear and contact parameters between grains and surfaces are analysed. The effects and significant interactions of the most influential belt-finishing parameters on the surface roughness are then investigated. It was shown that the applied force and the hardness of the roller have a great influence on the surface roughness. Furthermore, the film feed rate influences considerably the wear of grains and, as a consequence, this parameter has an important impact on the material removal mode and on the surface roughness.
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Rusu, Laura-Cristina, Lavinia Cosmina Ardelean, Adriana-Andreea Jitariu, Catalin Adrian Miu, and Caius Glad Streian. "An Insight into the Structural Diversity and Clinical Applicability of Polyurethanes in Biomedicine." Polymers 12, no. 5 (May 24, 2020): 1197. http://dx.doi.org/10.3390/polym12051197.
Повний текст джерелаАнотація:
Due to their mechanical properties, ranging from flexible to hard materials, polyurethanes (PUs) have been widely used in many industrial and biomedical applications. PUs’ characteristics, along with their biocompatibility, make them successful biomaterials for short and medium-duration applications. The morphology of PUs includes two structural phases: hard and soft segments. Their high mechanical resistance featuresare determined by the hard segment, while the elastomeric behaviour is established by the soft segment. The most important biomedical applications of PUs include antibacterial surfaces and catheters, blood oxygenators, dialysis devices, stents, cardiac valves, vascular prostheses, bioadhesives/surgical dressings/pressure-sensitive adhesives, drug delivery systems, tissue engineering scaffolds and electrospinning, nerve generation, pacemaker lead insulation and coatings for breast implants. The diversity of polyurethane properties, due to the ease of bulk and surface modification, plays a vital role in their applications.
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Hu, Yong, and David B. Bogy. "Effects of Laser Textured Disk Surfaces on a Slider’s Flying Characteristics." Journal of Tribology 120, no. 2 (April 1, 1998): 266–71. http://dx.doi.org/10.1115/1.2834421.
Повний текст джерелаАнотація:
Recently, laser texturing has captured the attention of head/media interface engineers in the hard disk drive industry because it provides precision in the landing zone placement while eliminating the transition zone of a mechanically textured landing zone. It also offers excellent tribological performance in terms of low CSS stiction and good durability. These advantages make it the solution of choice for high-end magnetic hard disk drives. This paper models the effects of laser bumps and laser textured disk surfaces on the Headway AAB slider’s flying characteristics. Two commonly used laser bump profiles (“Sombrero” and “Volcano” types) and various texture patterns are numerically generated in the simulator. The slider’s dynamic responses to these moving laser bumps and textures under two outer rail flying conditions are simulated, and the effects of various bump/texture parameters on the slider’s fly height, pitch, roll and their modulations are discussed. The laser texture mechanism is explained by examining the air bearing pressure profiles induced by the moving laser textures.
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Pascu, Doru Romulus, Ramona Monica Buzdugan, Aurel Valentin Bîrdeanu, Daniel Tihanov, and Emilia Binchiciu. "Structural Hardening of Excavator Teeth Used in Exploitation of Magmatic Rocks." Advanced Materials Research 1111 (July 2015): 246–51. http://dx.doi.org/10.4028/www.scientific.net/amr.1111.246.
Повний текст джерелаАнотація:
The teeth of specialized excavators used in exploitation of magmatic rocks are made by forging from alloyed steels having 3.4%Mn, and the value of hardness less than 38HRC. The usual working time is about 15,000 hours.This paper estimates the possibility to make a structural hardening of the excavator teeth using the deposition by welding of hard layers. These hard layers are obtained by using the electrodes type Cr-W-V-Ti, having the hardness between 48 and 50HRC. In these conditions, the austenitic hard structures with complex carbides of W, V, Ti are developed.The presence of the hard layers on the active surfaces of teeth, deposited using an homologated technology, will allow to increase the life time of these components with minimum 30% in usually working conditions.
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McKay, I., and T. A. Gillespie. "Bacterial Contamination of Children's Toys Used in a General Practitioner's Surgery." Scottish Medical Journal 45, no. 1 (February 2000): 12–13. http://dx.doi.org/10.1177/003693300004500104.
Повний текст джерелаАнотація:
General practitioners — and other healthcare professionals are encouraged to make their premises child friendly. One way of doing this is to provide toys for children to use. We looked at the appearance and bacterial colonisation of 50 toys after a busy morning surgery in an inner city general practice. The toys appeared generally unclean and 10% were contaminated by potential pathogens. Bacteria were cultured more frequently from soft toys than from hard toys (odds ratio 8.14; 95% confidence range 0.74 − 107.49). Although toys may appear to be physically dirty after use, the bacteria isolated from their surfaces are generally non-pathogenic to children with normal immune function and probably no worse than other objects in the environment. However, there does exist an appreciable (1 in 10) risk of cross-infection with the use of toys in a clinic. Toys with a hard surface are preferred as these are less likely to be contaminated and are more easily disinfected.
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Creton, Costantino, and Stanislav Gorb. "Sticky Feet: From Animals to Materials." MRS Bulletin 32, no. 6 (June 2007): 466–72. http://dx.doi.org/10.1557/mrs2007.79.
Повний текст джерелаАнотація:
AbstractMany insects and some larger animals, such as geckos, skinks, and tree frogs, can easily climb vertical walls and even walk on the ceiling. These abilities require a method to attach the feet strongly but reversibly to a variety of surfaces—smooth or rough, hydrophilic or hydrophobic, clean or containing contaminants. This issue of MRS Bulletin examines how fibrils, absorbed water layers, geometry, and other factors make reversible adhesion possible, and how this understanding might be applied to robots and other artificially created structures that can climb walls, walk on ceilings, and get to other hard-to-reach places.
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Gryadunov, Sergey S., and Vladimir V. Sivakov. "The Use of Surfacing Materials to Increase the Durability of Disc Harrow Working Elements." Engineering Technologies and Systems 31, no. 4 (December 30, 2021): 544–58. http://dx.doi.org/10.15507/2658-4123.031.202104.544-558.
Повний текст джерелаАнотація:
Introduction. For surface tillage operation there widely used disc harrows, working bodies of which are discs wearing out during operation. The wear intensity of discs depends on the wear resistance of their working surfaces, working modes and properties of the cultivated soil. It has been found that an effective way to increase the life of discs is surfacing them with wear-resistant materials. The aim of the work is to study the wear out of surfacing materials, which can be used to harden discs and to make recommendation for the use of these materials in the repair departments of agricultural enterprises. Materials and Methods. Surfacing with electrodes T-590 and powder wires PP-Np200Kh15S1GRT, VELTEK-N560.02 and PP-Np280Kh9F7SG4 were taken as test materials. For wear tests of materials in abrasive mass, there was used an apparatus to simulate the moisture content and composition (sandy loam or loam) of the soil. In the disk-pad tests, the effect of abrasive particle size, load and sliding friction velocity on the wear of the materials was studied. In field tests, wear of the disks made of 65G steel, surfaced toothed and solid disks were monitored. Results. Laboratory studies of the materials revealed the effect of soil moisture and composition, load, abrasive grit and sliding friction velocity on wear. The main factor determining the wear resistance of materials is their structural state. The indexes of wear resistance of surfacing were determined during the laboratory tests and confirmed by field tests. Discussion and Conclusion. Surfacing with flux-cored wire PP-Np280Kh9F7SG4 has the highest wear resistance of the studied materials. The technology of hard-facing disks with modern materials, in particular with flux-cored wire PP-Np280Kh9F7SG4, can be implemented in repair departments of agricultural enterprises when they have the equipment for hard-facing and sharpening of working surfaces.
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Santiago-Medina, P., P. A. Sundaram, and N. Diffoot-Carlo. "Titanium Oxide: A Bioactive Factor in Osteoblast Differentiation." International Journal of Dentistry 2015 (2015): 1–9. http://dx.doi.org/10.1155/2015/357653.
Повний текст джерелаАнотація:
Titanium and titanium alloys are currently accepted as the gold standard in dental applications. Their excellent biocompatibility has been attributed to the inert titanium surface through the formation of a thin native oxide which has been correlated to the excellent corrosion resistance of this material in body fluids. Whether this titanium oxide layer is essential to the outstanding biocompatibility of titanium surfaces in orthopedic biomaterial applications is still a moot point. To study this critical aspect further, human fetal osteoblasts were cultured on thermally oxidized and microarc oxidized (MAO) surfaces and cell differentiation, a key indicator in bone tissue growth, was quantified by measuring the expression of alkaline phosphatase (ALP) using a commercial assay kit. Cell attachment was similar on all the oxidized surfaces although ALP expression was highest on the oxidized titanium alloy surfaces. Untreated titanium alloy surfaces showed a distinctly lower degree of ALP activity. This indicates that titanium oxide clearly upregulates ALP expression in human fetal osteoblasts and may be a key bioactive factor that causes the excellent biocompatibility of titanium alloys. This result may make it imperative to incorporate titanium oxide in all hard tissue applications involving titanium and other alloys.
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Sohrabi, Mehri, Saeed Hesaraki, and Asghar Kazemzadeh. "Injectable Bioactive Glass/Polysaccharide Polymers Nanocomposites for Bone Substitution." Key Engineering Materials 614 (June 2014): 41–46. http://dx.doi.org/10.4028/www.scientific.net/kem.614.41.
Повний текст джерелаАнотація:
nanobioactive glasses are biocompatible and osteoconductive materials which can be mixed with solution of biocompatible polymers to make nanobiocomposite paste for hard and even soft tissue treatment. In this study, bioactive glass based on CaO-SiO2-P2O5 system was produced via sol-gel technique and mixed with a solution phase. The solution phase was a 1:1 mixture of 3% hyaluronic acid solution and 3% sodium alginate solution in v/v. Rheological behaviors of the paste in rotation and oscillation modes were measured. For surface reactivity measurements, the paste was immersed in simulated body fluid (SBF) for different intervals and then characterized by SEM. The paste exhibited a superior injectability even from syringes with too narrow tips. It was a thixotropic fluid with shear thinning behavior. The results of surface reactivity revealed precipitation of apatite phase on the paste surfaces meanwhile an appropriate structural stability was observed against disintegration (anti-washout behavior). It seems that this biocomposite paste is an appropriate alternative for injectable bone substitute materials.
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Heelan, Joseph, Sean M. Langan, Caitlin Walde, Aaron Nardi, Matthew Siopis, Robert Barth, Timothy Landry, and Aaron Birt. "Effect of WC-Ni Powder Composition and Preparation on Cold Spray Performance." Coatings 10, no. 12 (December 8, 2020): 1196. http://dx.doi.org/10.3390/coatings10121196.
Повний текст джерелаАнотація:
Toxic metal reduction is at the forefront of many design considerations today; additive manufacturing has the ability to combine materials in ways other traditional processes cannot and has the potential to offer unique solutions to reduce hazardous materials needed in manufacturing. Tungsten carbide (WC) has been used as a substitute in wear applications where toxic processes are traditionally utilized, but it can be difficult to deposit high-quality, hard and durable coatings. Additionally, there is a need to apply WC coatings on surfaces not feasible with the current processes. Cold spray, a solid-state directed powder deposition process, is effective at depositing carbides, though powders must be thoughtfully designed to achieve desired mechanical properties. In this study, WC was investigated as a hard chrome alternative for wear applications. Various blend ratios and preparation methods were evaluated as feedstock powder and then sprayed. Feedstock characteristics were compared to cold spray performance. Cold spray consolidations were evaluated for coating porosity and hardness. It was found that when powder make-up and composition were optimized, a high-hardness and low-porosity material was made that will contribute to the reduction in dependency of Cr in wear-facing components.
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Radek, Norbert, Jacek Pietraszek, and Bogdan Antoszewski. "The Average Friction Coefficient of Laser Textured Surfaces of Silicon Carbide Identified by RSM Methodology." Advanced Materials Research 874 (January 2014): 29–34. http://dx.doi.org/10.4028/www.scientific.net/amr.874.29.
Повний текст джерелаАнотація:
The electrospark deposition (ESD) is a well-known cheap method utilizing concentrated energy flux to transfer a material of an electrode onto the surface of the machined material for enhancing properties of its surface layer. Typically, a hard material of an electrode may be deposited onto the surface of materials with lower hardness to make such an object more robust for wearing. Coatings produced by ESD may be applied to protect new elements or to recover the properties of worn elements. Unfortunately, ESD process produces a surface with high roughness. The laser beam machining (LBM) has been involved to lower roughness of the coating made by ESD. The elements coated by ESD have been tested to determine tribological properties and they were compared before and after LBM. To achieve high reliability of the results, the test has been conducted in accordance with design of experiments (DoE) methodology and the results which were obtained have been processed by a statistical analysis. The description of such an experiment performed for a silicon carbide SiC coating, the obtained results and the conclusions are included in this paper.
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Shmatko, Olexandr, Valerii Volosyuk, Simeon Zhyla, Vladimir Pavlikov, Nikolay Ruzhentsev, Eduard Tserne, Anatoliy Popov, et al. "Synthesis of the optimal algorithm and structure of contactless optical device for estimating the parameters of statistically uneven surfaces." RADIOELECTRONIC AND COMPUTER SYSTEMS, no. 4 (November 29, 2021): 199–213. http://dx.doi.org/10.32620/reks.2021.4.16.
Повний текст джерелаАнотація:
The production of parts and (or) finished products in electronics, mechanical engineering and other industries is inextricably linked with the control of the accuracy and cleanliness of the processed surfaces. Currently existing meters of parameters of statistically uneven surfaces, both contact and non-contact have some disadvantages, as well as limitations due to methods and design features of measurement. Speckle interferometric methods for measuring parameters of statistically uneven surfaces make it possible to get away from some disadvantages inherent in existing methods and measurements. The use of methods of statistical radio engineering, methods of optimization of statistical solutions and estimates of parameters of predictive distributions for optimal radio engineering system synthesis is promising for the analysis and processing optical-electronic coherent laser space-time signals (speckle images) form with the laser radiation scattered by statistically uneven surfaces. This work synthesizes the optimal algorithm and structure for analyzing the parameters of statistically-temporal surfaces based on spatio-temporal processing of optical speckle interference signals and images using modern methods of optimal synthesis of radio engineering and coherent optoelectronic systems. In this work, an algorithm for processing optical signals scattered by statistically uneven surfaces is synthesized and investigated for problems of optimal estimation of parameters and statistical characteristics of statistically uneven surfaces. A block diagram of the optical contactless device for evaluating the parameters of statistically uneven surfaces is proposed. The limiting errors of estimation parameters of statistically uneven surfaces and the optimal installation angles of the emitters and the optical receiver are investigated. Equations are obtained for estimating the root-mean-square height of the ridges and the correlation radius of small-scale statistically uneven surfaces in the approximation of small perturbations. The proposed method for evaluating the parameters of statistically uneven surfaces allows to increase the accuracy of measurements, to conduct a non-contact assessment of the parameters - even statistically uneven surfaces that have geometric surface irregularities or located in hard-to-reach places, for example, grooves, holes, as well as products of cylindrical, spherical and other shapes.
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Puttichaem, Chanida, Guilherme P. Souza, Kurt C. Ruthe, and Kittipong Chainok. "Characterization of Ultra-Thin Diamond-Like Carbon Films by SEM/EDX." Coatings 11, no. 6 (June 17, 2021): 729. http://dx.doi.org/10.3390/coatings11060729.
Повний текст джерелаАнотація:
A novel, high throughput method to characterize the chemistry of ultra-thin diamond-like carbon films is discussed. The method uses surface sensitive SEM/EDX to provide substrate-specific, semi-quantitative silicon nitride/DLC stack composition of protective films extensively used in the hard disk drives industry and at Angstrom-level. SEM/EDX output is correlated to TEM to provide direct, gauge-capable film thickness information using multiple regression models that make predictions based on film constituents. The best model uses the N/Si ratio in the films, instead of separate Si and N contributions. Topography of substrate/film after undergoing wear is correlatively and compositionally described based on chemical changes detected via the SEM/EDX method without the need for tedious cross-sectional workflows. Wear track regions of the substrate have a film depleted of carbon, as well as Si and N in the most severe cases, also revealing iron oxide formation. Analysis of film composition variations around industry-level thicknesses reveals a complex interplay between oxygen, silicon and nitrogen, which has been reflected mathematically in the regression models, as well as used to provide valuable insights into the as-deposited physics of the film.
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Altshuler, Kenneth J., Joshua C. Harrison, and Evelyn Ackerman. "The Physical Effects of Intra-Drive Particulate Contamination on the Head-Disk Interface in Magnetic Hard Disk Drives." Journal of Tribology 121, no. 2 (April 1, 1999): 352–58. http://dx.doi.org/10.1115/1.2833945.
Повний текст джерелаАнотація:
The physical damage at the Head-Disk Interface (HDI), caused by common ceramic particles found in the manufacturing environments of the heads and disks in hard magnetic disk drives, is reported. The need for this study arises from industry wide reliability problems due to particulate induced damage at the HDL The intent of this study is to characterize the head/disk damage caused by 1 μm diamond, 1–2 pm Tie particles, 0.2–1 μm alumina particles, the alumina and TiC grains sintered to make Al-TiC (the slider body), and sputtered alumina. These particles were introduced to the HDI in over thirty disk drives. The drives were then made to perform magnetic recording and retrieval operations for known data sequences, with the resultant reading errors tabulated. After the functional testing, the drives were opened and resulting damage was examined with a number of surface characterization tools. This study confirms that the severity of problems with the read-back signal, caused by particle damage, has an inverse relationship with the magnetic track width. In addition, the harshness of physical damage to the HDI has a positive relationship with particle hardness. Finally, particle shape and size can be contributing factors in damaging the HDL.
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Немировский, Я. Б., И. В. Шепеленко, С. Е. Шейкин, Ю. А. Цеханов, Ф. Й. Златопольский, О. И. Попова, and М. И. Попова. "DESIGN FEATURES OF CARBIDE ASSEMBLY WORKING ELEMENTS OF DEFORMING BROACHES." ВЕСТНИК ВОРОНЕЖСКОГО ГОСУДАРСТВЕННОГО ТЕХНИЧЕСКОГО УНИВЕРСИТЕТА, no. 4 (October 20, 2021): 134–42. http://dx.doi.org/10.36622/vstu.2021.17.4.019.
Повний текст джерелаАнотація:
Разработан алгоритм и проведена оценка прочности сборных твердосплавных элементов со сплошной и дискретной рабочими поверхностями. Получены зависимости, позволяющие установить связь между конструктивными параметрами сборных деформирующих инструментов и их прочностью. Выполнены прочностные расчеты деформирующего инструмента для обработки отверстий значительного диаметра со сплошной и дискретной рабочими поверхностями. Численным моделированием, методом конечных элементов получены распределения эквивалентных напряжений в элементах инструмента и контактных напряжений по поверхности контакта твердосплавная вставка-корпус, что позволило проанализировать прочность инструмента под нагрузкой. Определены конструктивные параметры инструмента и приведены алгоритмы последовательности расчета сборных деформирующих элементов (ДЭ). Разработан алгоритм последовательности расчета сборного ДЭ для дискретного протягивания. Предложенная конструкция сборного рабочего элемента позволяет не только улучшить обрабатываемость изделия резания, но и уменьшить расход остродефицитного твердого сплава по сравнению с твердосплавным ДЭ аналогичных размеров на 6 кг. Полученные результаты можно использовать в инженерных расчетах при проектировании сборного инструмента для дискретного деформирования, а также для оценки прочности сборных инструментов, например, фрез, зенкеров, разверток при уточнении внешних нагрузок We developed an algorithm and assessed the strength of prefabricated carbide elements with solid and discrete working surfaces. We obtained dependencies that make it possible to establish a relationship between the design parameters of prefabricated deforming tools and their strength. We performed strength calculations of the deforming tool for machining holes of significant diameter with solid and discrete working surfaces. We obtained the distributions of equivalent stresses in the elements of the tool and contact stresses over the contact surface of the hard-alloy insert - body by numerical modeling, by the finite element method, which made it possible to analyze the strength of the tool under load. We determined the design parameters of the tool and here we give algorithms for the sequence of calculation of prefabricated deforming elements (DE). We developed an algorithm for the sequence of calculating the prefabricated DE for discrete broaching. The proposed design of the prefabricated working element allows not only to improve the machinability of the cutting product but also to reduce the consumption of an acutely deficient hard alloy in comparison with a hard alloy DE of similar dimensions by 6 kg. The results obtained can be used in engineering calculations when designing a prefabricated tool for discrete deformation, as well as for assessing the strength of prefabricated tools, for example, cutters, countersinks, reamers when specifying external loads
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Sovinsky, John, and Geoff Sylvester. "The Future of Maximum CAD/CAM Automation for Ceramic Hybrids." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2011, CICMT (September 1, 2011): 000283–94. http://dx.doi.org/10.4071/cicmt-2011-tha22.
Повний текст джерелаАнотація:
New concepts developed maximize CAD/CAM automation for all types of Ceramic Hybrids including Thick Film, Thin Film, LTCC and HTCC. Designs can go quickly from concept to manufactured product, which will fuel more progress to bring a largely manual process to maximum automation, to include automatic masks, panels and generation of 3D analysis models. Maximum automation results in expanded use of technologies that are now shrinking. Technologies that have complex and difficult to understand design and manufacturing steps have a hard time gaining wide acceptance. CDS is tackling this complex challenge and is designing and implementing the following processes to solve the most difficult CAD/CAM problems:1. Be a true CAM tool that reads in designs from any other EDA (layout) system. Y2. Run all possible DRC checks necessary for high fabrication and assembly yield. Y3. Make all manufacturing masks automatically from very basic designs by using settings in an automatically configurable table. Y4. Panelize all types of Ceramic designs in preparation for manufacturing. Y5. Generate documentation automatically through from stored configuration files. D6. In LTCC and HTCC, place cavity punches (nibbles and rubs) automatically and feed correct machine data to the punch machine. Y7. Export resistor trimming data directly to the laser trimming machine. F8. Feed flying probe test data directly to the flying probe tester. D9. Automatically make a 3D Image and export ACIS or STEP for thermal analysis. D10. Export data directly to all electrical analysis and thermal analysis tools. P11. Support circuit fabrication non-planar surfaces. F12. Make full 3D analysis models of circuits non-planar surfaces. FThe purpose of this paper is to define what is required for the Ceramic Hybrid industry to realize full automation in design, checking and output to manufacturing. Your ideas are welcome.
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Yildiz, Adnan, Tugba Gür, and Serafettin Alper. "A Study on Removing of Some Organic and Inorganic Substances using the Tutmaç Clay Via Adsorption Method." Biosciences, Biotechnology Research Asia 16, no. 04 (December 30, 2019): 805–10. http://dx.doi.org/10.13005/bbra/2797.
Повний текст джерелаАнотація:
In this investigation, the removing of some substances via adsorption onto tutmaç clay were performed in aqueous and organic solutions using batch system. It was aimed to remove the inorganic ions Mg2+ and Ca2+ (Excess of; Mg2+ and Ca2+ ions make water hard and cause to serious healt problems) organic substance cholest (its removing is important as by means of health and cosmetically) from the solution by adsorption method using the active surfaces of Tutmac clay was charactized by XRD. The amount of the substances adsorbed on the clay surface in the solutions were analyzed using AAS and UV spectroscopic methods. The experimental data have indicated that Tutmaç clay is good adsorbent and physical adsorption methot is quite suitable for the removing of Mg2+, Ca2+ and cholesterol from solutions. The adsorption data determined from experimental results best fitted Langmuir Isotherms. The obtained results also confirmed that the applicability of Tutmaç clay is an efficient supporter material for removing contaminations of inorganic and organic substances. And Tutmaç clay material can be used as a very effective adsorbent in removing of pollutants from organic and aqueous solutions.
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Cherednichenko, Kirill, Dmitry Kopitsyn, Svetlana Batasheva, and Rawil Fakhrullin. "Probing Antimicrobial Halloysite/Biopolymer Composites with Electron Microscopy: Advantages and Limitations." Polymers 13, no. 20 (October 13, 2021): 3510. http://dx.doi.org/10.3390/polym13203510.
Повний текст джерелаАнотація:
Halloysite is a tubular clay nanomaterial of the kaolin group with a characteristic feature of oppositely charged outer and inner surfaces, allowing its selective spatial modification. The natural origin and specific properties of halloysite make it a potent material for inclusion in biopolymer composites with polysaccharides, nucleic acids and proteins. The applications of halloysite/biopolymer composites range from drug delivery and tissue engineering to food packaging and the creation of stable enzyme-based catalysts. Another important application field for the halloysite complexes with biopolymers is surface coatings resistant to formation of microbial biofilms (elaborated communities of various microorganisms attached to biotic or abiotic surfaces and embedded in an extracellular polymeric matrix). Within biofilms, the microorganisms are protected from the action of antibiotics, engendering the problem of hard-to-treat recurrent infectious diseases. The clay/biopolymer composites can be characterized by a number of methods, including dynamic light scattering, thermo gravimetric analysis, Fourier-transform infrared spectroscopy as well as a range of microscopic techniques. However, most of the above methods provide general information about a bulk sample. In contrast, the combination of electron microscopy with energy-dispersive X-ray spectroscopy allows assessment of the appearance and composition of biopolymeric coatings on individual nanotubes or the distribution of the nanotubes in biopolymeric matrices. In this review, recent contributions of electron microscopy to the studies of halloysite/biopolymer composites are reviewed along with the challenges and perspectives in the field.
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Dabo, M. Noor I., and M. S. Aldlemey. "Improvement of the Adhesive Wear Resistance and Mechanical Properties of Low-Carbon Steel by Solid Carbonization." Key Engineering Materials 553 (June 2013): 81–86. http://dx.doi.org/10.4028/www.scientific.net/kem.553.81.
Повний текст джерелаАнотація:
Wear is one of the problems that occurs in moving parts, whether rolling or sliding. Since the wear resistance is closely linked to the hardness of the involved surfaces, this research studies the possibility of increasing the hardness of low carbon steel, which is used extensively because its ductility and its shock resistance and being one of the inexpensive metals. A lot of mechanical parts require an external hard surface, resistant to wear, and at the same time high resistance to shocks. The main hardening process used in this research is the increase of the carbon proportion on the external surfaces of the equipment made of low carbon steel and thus, to make the heat treatments necessary to obtain the required properties of these surfaces such as hardness and high resistance to shocks. The study of the process of carbonization by using the solid carbonization as one of the ways of hardening the surface at temperatures in the austenite range of low carbon steels give an impression about the possibility of improvement in the qualities of hardness and resistance to wear. In order to obtain a variable thickness of the carbonated layer, a carbonization process was performed at different temperatures and times to demonstrate the effect of these two important factors to the amount of diffused carbon to the surface of the solid and thus the extent of its influence to obtain the required properties of the process. The mechanical and microscopic tests conducted on samples proved the success of the carbonization process to achieve the purpose and goal of the preparation of this paper. Finally experimental results have shown good correlation between the wear resistance and mechanical properties with temperature and carbonization time. The analysis of the variance of the results in this study indicated that the best mechanical properties are achieved when one performs the process of carbonization at 975°C for 20 hours.
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Alaabed, Abdullah Abdulhaq Hussien. "Title: The Great Gatsby: A Story of The American Dream and The Social Conflict." Advances in Social Sciences Research Journal 8, no. 10 (October 29, 2021): 245–52. http://dx.doi.org/10.14738/assrj.810.11034.
Повний текст джерелаАнотація:
The Great Gatsby is a novel that was written in 1925 by Scott Fitzgerald. it represents The American Dream and the desire of achieving it through the protagonist attempts to achieve The American Dream. The protagonist is Jay Gatsby he is a self-made man who belongs to the working class of society, he gained his wealth through the organized crime and illegal business, Jay was charmed by the lifestyle of the rich people and the identity of being one of them. He used his fortune to make incredible parties in his mansion showing his wealth power and to attract Daisy’s attention, the women he loves most. Gatsby represents the American dreamers who belong to the repressed class of society, this young generation who believes in The American Dream and the possibility of achieving it. The American Dream was created by the dominant class of society in order to control the economic system.
The falsie fact that this dream was built upon is the social justice, the social equality that gives equal chances to everyone to achieve their desires via hard work without concern about their social background. The American Dream is mainly about either wealth obtaining which was the aspiration of these young working-class people or social ascendency. Gatsby despite his recent gained fortune and new identity as he changed his name from James to Jay Gatsby was not able to be a member of the bourgeoisies; he was rejected due to his social background. Therefore, the social equality concept was denied alongside the hard work and equality of chances in achieving The American Dream was denied by the illegal career of Gatsby.
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Bikker, Floris J., Michel A. Hoogenkamp, Amine Malhaoui, Kamran Nazmi, Jessica Neilands, and Bastiaan P. Krom. "Phytosphingosine Prevents the Formation of Young Salivary Biofilms in vitro." Caries Research 52, no. 1-2 (December 13, 2017): 7–13. http://dx.doi.org/10.1159/000480712.
Повний текст джерелаАнотація:
Dental biofilms are formed in a multistep process that is initiated by the adhesion of oral bacteria to the dental hard surface. As dental biofilms are associated with oral diseases their control is necessary in order to maintain oral health. Recently, it was revealed that phytosphingosine (PHS)-treated hydroxyapatite discs showed anti-adhesive activity in a static in vitro biofilm model against Streptococcus mutans. The goal of the present study was to further unravel the anti-adhesive and anti-biofilm properties of PHS in both static and dynamic in vitro biofilm models against a full salivary inoculum. After 3 h under static conditions, bacterial adherence on PHS-treated cover glass slides was reduced by 60% compared to the untreated surface. After 6 and 24 h under static conditions, no significant differences in bacterial adherence were observed between PHS-treated and untreated cover glass slides. However, under dynamic conditions, i.e., the presence of shear forces, virtually no bacterial adherence was observed for up to 16 h on PHS-coated surfaces. Besides, PHS showed a strong bactericidal activity on salivary biofilms. Treatment of a 3- and 6-h statically grown biofilm resulted in a 99 and 94% reduction of viable cells, respectively, which was effectuated within minutes. In principle, these anti-adherence and anti-biofilm properties make PHS a promising candidate ingredient for use in oral care products aimed at oral microbial control.
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Ingram, Martin. "How to extend Elo: a Bayesian perspective." Journal of Quantitative Analysis in Sports 17, no. 3 (January 7, 2021): 203–19. http://dx.doi.org/10.1515/jqas-2020-0066.
Повний текст джерелаАнотація:
Abstract The Elo rating system, originally designed for rating chess players, has since become a popular way to estimate competitors’ time-varying skills in many sports. Though the self-correcting Elo algorithm is simple and intuitive, it lacks a probabilistic justification which can make it hard to extend. In this paper, we present a simple connection between approximate Bayesian posterior mode estimation and Elo. We provide a novel justification of the approximations made by linking Elo to steady-state Kalman filtering. Our second key contribution is to observe that the derivation suggests a straightforward procedure for extending Elo. We use the procedure to derive versions of Elo incorporating margins of victory, correlated skills across different playing surfaces, and differing skills by tournament level in tennis. Combining all these extensions results in the most complete version of Elo presented for the sport yet. We evaluate the derived models on two seasons of men’s professional tennis matches (2018 and 2019). The best-performing model was able to predict matches with higher accuracy than both Elo and Glicko (65.8% compared to 63.7 and 63.5%, respectively) and a higher mean log-likelihood (−0.615 compared to −0.632 and −0.633, respectively), demonstrating the proposed model’s ability to improve predictions.
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Lafontaine, Yves de, and Julie Veillette. "Antifouling Effectiveness and Potential Toxicological Risk of an Elastomer-Based Coating against Zebra Mussels." Environment and Natural Resources Research 6, no. 4 (November 30, 2016): 125. http://dx.doi.org/10.5539/enrr.v6n4p125.
Повний текст джерелаАнотація:
The fouling of hard substrates by zebra mussels (Dreissena sp.) in freshwater ecosystems is a persistent problem which calls for antifouling treatments being fully efficient, long-lasting, and environmentally safe. The present study assessed the potential toxicological impact and the effectiveness of an elastomer-based coating containing salts that would make surfaces repulsive to zebra mussel attachment. Laboratory testing using standard analytical methods for water and wastewater, and a battery of six bioassays confirmed that the leachates from the coating exhibited no toxic response suggesting its safety to the receiving environment. In situ experiments using multi-plate collectors indicated that biofouling by zebra mussels and sponges on coated surfaces was effectively reduced by up to 97% over one growing season. Effectiveness of the coating was slightly less (82%) during the second growing season. Results suggested that the repulsive effect would be due to the presence of salts within the elastomer-based coating affecting both zebra mussels and other freshwater organisms. Saltwater experiments indicated that the coating was totally ineffective to prevent biofouling in marine environments. In addition of being environmentally safe to use, results suggested that the coating can be an effective antifouling product for submerged structures in freshwater environments.
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Li, Jian, Fuping Dong, Liangyu Lu, Hongwei Li, Yuzhu Xiong, and Chang-Sik Ha. "Raspberry-Like Polysilsesquioxane Particles with Hollow-Spheres-on-Sphere Structure: Rational Design, Controllable Synthesis, and Catalytic Application." Polymers 11, no. 8 (August 14, 2019): 1350. http://dx.doi.org/10.3390/polym11081350.
Повний текст джерелаАнотація:
Raspberry-like hollow-spheres-on-sphere (HSOS) particles with reactive surfaces, uniform sizes and monodisperse properties were rational designed and fabricated to immobilize gold nanoparticles for the catalytic reduction of 4-nitrophenol. HSOS polysilsesquioxane (PSQ) particles were constructed by an organic alkali catalyzed sol-gel process from trialkoxysilane precursors with stabilized polystyrene (PS) nanoparticles as both a sacrifice template and a Pickering emulsifier. The PSQ particles were fabricated in an ice bath with methyltrimethoxysilane and mercaptopropyltrimethoxysiane as a co-precursor, tetramethylammonium hydroxide (TMAH) as a catalyst, polyvinylpyrrolidone (PVP) and sodium lignosulfonat as co-stabilizers and PS latex as a hard template. The formation mechanism of the hierarchical particles was investigated in detail by the time study through imaging the particles at regular time intervals during the reaction process. Various effect factors on the morphology were studied systematically which showed that the precursor composition, the content of PS, TMAH and PVP are the most important factors. The hierarchical structure combined with the mercaptopropyl groups on both the surface and the skeleton to make it possible to adsorb guest molecules. Au nanoparticles were immobilized on the particles for the catalytic reduction of 4-nitrophenol to 4-aminophenol. The unique PSQ colloids with hollow-spheres-on-sphere extended the family of the hierarchical structures and has shown the potential applications in separations, drug delivery and heterogeneous catalysts.
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Sumrall, Colin D., and James Sprinkle. "Could edrioasteroids move?" Paleontological Society Special Publications 6 (1992): 284. http://dx.doi.org/10.1017/s2475262200008443.
Повний текст джерелаАнотація:
Edrioasteroids are an extinct group of primitive echinoderms whose geologic range is Early Cambrian to Late Pennsylvanian. Several authors have argued whether edrioasteroids could freely move about on the sea floor or were firmly attached to a hard substrate throughout post-larval life. Arguments that edrioasteroids were mobile are based primarily on orientation of individuals within a population and positioning of individuals on a host shell. We disagree with these arguments based on overwhelming evidence that edrioasteroids could not move and remained firmly attached throughout post-larval life.Edrioasteroids have specialized attachment structures that are almost always found on hard substrates such as hardgrounds, fossil shells or fragments, and conglomerate pebbles. There are two types of edrioasteroid attachment structures, an aboral disk and a peripheral rim. Edrioasteroids with an aboral disk are typically found attached to hard substrates. Although some individuals have been found loose in muddy sediment, many of these individuals show signs of being torn loose from their attachment surface based on their inverted orientation, disrupted attachment structures, and shingling by currents. Edrioasteroids with a peripheral rim are almost never found free in the sediment, and the few known examples of this are either small juveniles indicating that soft substrates probably could not support adult edrioasteroids or else thick-rimmed adults apparently attached to soft algae.In uncrowded conditions, edrioasteroids are circular in outline, but they become polygonal and abutting under crowded conditions. Other encrusters such as tube worms also affect their peripheral outline. Edrioasteroids occur in crowded clumps even though nearby skeletal grains are uncolonized. In these individuals, peripheral rims and oral surfaces are severely distorted which would make living conditions and continued growth difficult. Also, some individuals attach to objects much smaller than their eventual thecal diameter. In such conditions, the edrioasteroid gradually engulfs the object it is attached to, severely distorting the animal, with the peripheral rim migrating toward the bottom of the attachment object. Under either of these conditions, individuals would almost certainly have moved to nearby open spots or to larger, uncolonized clasts if they could.In crowded conditions, individuals of the same species do not overgrow one another, but individuals of one species will overgrow living individuals of another species competing for the same attachment space. Two localities preserve large edrioasteroids partially overgrowing smaller articulated individuals of a different species. Because they are fully articulated, overgrown individuals must have been alive during the overgrowth, but were not able to move out of the way.Disrupted edrioasteroids are often found with the oral surface completely disarticulated or missing, but with a completely articulated peripheral rim. Apparently, the peripheral rim was firmly attached to the substrate and more strongly constructed than the oral surface and therefore better able to withstand wave activity, death and decay, and subsequent disarticulation than the oral surface. This firm attachment to hard substrates also suggests lack of movement.The edrioasteroid attachment grows from the periphery. New ossicles are added to distal plate circlets of the attachment while plates in more proximal circlets enlarge. Clearly some degree of movement is required for this type of growth but not active locomotion. Large edrioasteroids growing along the margin of a large skeletal fragment show an underdevelopment of the peripheral rim along this edge even though the rest of the animal is round and symmetrical.Some authors have used living psolid holothurians as a good analog for extinct edrioasteroids with a peripheral rim. Psolids will move using tube feet under the theca in the ventrally positioned A, B, and E rays under extreme disturbance, but only at the rate of a few millimeters per day. Edrioasteroids have all the ambulacra dorsally oriented away from the substrate and therefore have no similar mechanism for locomotion. We suggest balanimorph barnacles as a better analog for the vast majority of edrioasteroids. They firmly attach to a hard substrate, become polygonal in crowded conditions, have feeding structures facing upward, grow from the periphery of the attachment surface, and do not move as adults.
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Hashish, M., and D. C. Echert. "Abrasive-Waterjet Deep Kerfing and Waterjet Surface Cleaning for Nuclear Facilities." Journal of Engineering for Industry 111, no. 3 (August 1, 1989): 269–81. http://dx.doi.org/10.1115/1.3188759.
Повний текст джерелаАнотація:
A deep kerf tool was designed to cut through the thick, reinforced concrete structures of nuclear facilities to help make the decommissioning process more efficient. Abrasive-waterjet (AWJ) cutting technology is used as the basis of the system. The cutting tool has a rotary nozzle that directs a high-pressure AWJ in a circular pattern. The circular pattern and the angle of jet impact create a slot wider in diameter than the tool itself as the tool moves across the face of the concrete. This makes it possible to insert the tool into the slot and create a deep cut for each pass along it until the desired depth is reached. In this testing program, concrete as thick as 1.5 meters was cut through from one side. The cutting rate of the tool ranges from 0.2 to 0.6 m2/hr. The tool employs a computer-controlled traverse mechanism with a simple device that can detect obstacles, such as uncut reinforcing bars (rebar) or hard aggregate. An electronic sensor system to identify, in real-time, when rebar is being cut was developed and tested with good results. A cleaner/scarifier tool for removing the surface layers of contaminated concrete and decontaminating metal surface was also designed and tested. It uses ultrahigh-pressure waterjets mounted on a rotating arm to remove or clean the target surface. Concrete can be scarified to a depth of 7 mm at a rate of 11 m2/hr. Concrete and metal surfaces can be cleaned of paint and corrosion at a rate of 33 m2/hr. Spoils recovery using a shroud/vacuum system is more than 99 percent for each tool.
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Tennyson, Jonathan, Laura K. McKemmish, and Tom Rivlin. "Low-temperature chemistry using the R-matrix method." Faraday Discussions 195 (2016): 31–48. http://dx.doi.org/10.1039/c6fd00110f.
Повний текст джерелаАнотація:
Techniques for producing cold and ultracold molecules are enabling the study of chemical reactions and scattering at the quantum scattering limit, with only a few partial waves contributing to the incident channel, leading to the observation and even full control of state-to-state collisions in this regime. A new R-matrix formalism is presented for tackling problems involving low- and ultra-low energy collisions. This general formalism is particularly appropriate for slow collisions occurring on potential energy surfaces with deep wells. The many resonance states make such systems hard to treat theoretically but offer the best prospects for novel physics: resonances are already being widely used to control diatomic systems and should provide the route to steering ultracold reactions. Our R-matrix-based formalism builds on the progress made in variational calculations of molecular spectra by using these methods to provide wavefunctions for the whole system at short internuclear distances, (a regime known as the inner region). These wavefunctions are used to construct collision energy-dependent R-matrices which can then be propagated to give cross sections at each collision energy. The method is formulated for ultracold collision systems with differing numbers of atoms.
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Klocke, Fritz, Olaf Dambon, and Kyriakos Georgiadis. "Comparison of Nitride and Noble Metal Coatings for Precision Glass Molding Tools." Key Engineering Materials 438 (May 2010): 9–16. http://dx.doi.org/10.4028/www.scientific.net/kem.438.9.
Повний текст джерелаАнотація:
The complexity of optical components increases steadily in recent years, while their dimension de-crease. This situation makes the production of state of the art optical components by grinding and polishing very difficult and expensive. However, the technology of precision glass molding can be used to replace these traditional manufacturing methods by a single step replicative process. To achieve economies of scale with precision glass molding, a long molding tool lifetime is necessary. This can only be realized by applying protective PVD coatings on the molding tool surfaces. Well known thin hard coatings like TiAlN or CrN, as well as noble metal coatings are possible candidates. However, practical testing of carious coating-glass combinations in precision glass molding machines is not feasible due to long process times that make such testing very expensive and time consuming. In this work, these coatings are compared with each other and in combination with various glass types by performing oxidation and contact angle tests. The results of these tests are compared to the results of practical tests, in order to determine to which extent such model tests can replace practical testing.
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Таmarkina, Yu V., V. M. Anishchenko, A. M. Red'ko, and V. O. Kucherenko. "Alkali activated coals. Microporous structure and capability to adsorb phenol compounds." Himia, Fizika ta Tehnologia Poverhni 13, no. 1 (March 30, 2022): 111–24. http://dx.doi.org/10.15407/hftp13.01.111.
Повний текст джерелаАнотація:
The aim of the work is to compare the microporous structure characteristics of activated carbons (ACs) prepared from coals of different coals rank (CR) by alkaline activation (RKOH = 1 g/g, 800 °C) and to determine the ACs capability to adsorb phenol and 4-chlorophenol from aqueous solutions. Starting materials are coals with increasing carbon content (Cdaf = 80.0–95.6 %) selected as a CR criterion. ACs were obtained in argon in three stages: 1) thermoprogrammed heating (4 grad/min) to 800 °С; 2) isothermal exposure 1 h; 3) cooling, washing from alkali and drying. Based on low-temperature (77 K) nitrogen adsorption-desorption isotherms, integral and differential dependences of the specific surface area S (m2/g) and pore volume V (cm3/g) on the average pore diameter (D, nm) were calculated. They were used to define volumes of ultramicropores (Vumi), supermicropores (Vsmi) and micropores (Vmi). The total pore volume Vt was calculated from the nitrogen amount adsorbed at a relative pressure p/p0 ~ 1.0. The S values of ultramicropores (Sumi), supermicropores (Ssmi) and micropores (Smi) were similarly determined. The volumes and specific surfaces of different categories of pores were found to decrease with CR increase: volume Vt – from 0.59 to 0.23 cm3/g; Vmi – from 0.51 to 0.17 cm3/g; the ultramicropores volume – from 0.31 cm3/g to zero in anthracite AC. The supermicropores volume is almost independent on CR and varies in the wide range Vsmi = 0.15–0.22 cm3/h. The specific surface area is the maximum (S = 1547 m2/g) in AC from the coal of the lowest CR and decreases with coal metamorphism up to 322 m2/g. The micropores surfaces make dominant contributions to the S values: its portion is 94.7–99.4 %. For all ACs, the adsorption of phenol (Ph) and 4-chlorophenol (CPh) from aqueous solutions at 25 °C was studied. Adsorption kinetics and isotherms are best described by the pseudo-second order model and the Langmuir model (R2 ≥ 0.998). With increasing CR, the maximum adsorption capacities decrease from 3.113 to 1.498 mmol/g (Ph) and from 3.9 to 2.1 mmol/g (CPh), that is approximately ~2 times when the specific surface area decreases by ~5 times. The Ph and CPh specific capacities, characterizing the adsorption capacity of 1 m2 of surface, change little at Cdaf≤86 %, but markedly increase (2.3–2.5 times) for anthracite AСs. The Ph and CPh capacitances were determined to increase linearly (R2 ≥ 0.966) with increasing ACs specific surface area. Similar dependences were found on the Sumi and Smi parameters. The phenols were concluded to be equally adsorbed on the surface of pores of any size. A general trend was found for ACs from hard coals and anthracite: an increase in CR reduces the ACs microporosity and surface, decreases Ph and CPh capacities but increases specific capacities, i.e. concentrations of surface adsorption centers. The Ph and CPh adsorption was accepted to include the interaction of π-electrons of phenolic rings and π-electrons of graphene layers in ACs, the formation of complexes with surface groups and forming hydrogen bonds with OH-groups. Their contributions depend on adsorbate nature and change with the growth of fossil coals CR.
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Turpie, Edward Jonathan. "Drawing Ed Ruscha." Drawing: Research, Theory, Practice 5, no. 2 (December 1, 2020): 291–303. http://dx.doi.org/10.1386/drtp_00038_1.
Повний текст джерелаАнотація:
This project aims to discuss drawing as a method of bridging the void between digital imaging technologies and physical drawing in the fine art domain. It does so by investigating the role of drawing and printing in contemporary portraiture. Drawn and printed silkscreen portraits are made from a synthesis of graphite marks, digital pixels and water-based ink deposited on paper surfaces. The practice-led research described here explores the materiality of the emergent image when drawing is impressed on an electronic media trace. This investigation is timely in the context of the unprecedented impact of digital technologies on contemporary culture that tend to displace the physicality of drawing. By taking an approach to portraiture whereby artist and sitter do not meet in person, the project initiates a portrait of Ed Ruscha using the medium of video images. Digital electronic images held pixel by pixel in smartphone camera and computer hard disks are interpreted into physical drawing environments to make an expressive representation of a human form. Tactile gestural mark-making is contrasted with electronic imaging to create a pensive image where techniques are blended. The process and methodology are described, and the artistic outputs are shared across the globe through digital and analogue communication systems.
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White, James. "Design of Optimized Opposed Slider Air Bearings for High-Speed Recording on a Metal Foil Disk." Journal of Tribology 128, no. 2 (November 3, 2005): 327–34. http://dx.doi.org/10.1115/1.2162917.
Повний текст джерелаАнотація:
A metal foil disk offers some of the best characteristics of both the hard disk and floppy disk for digital data storage. The current work defines an opposed slider air-bearing arrangement that provides advantages when used with a high-speed metal foil disk in either a fixed or removable format. Use is made of the fact that the opposing sliders interact through their influence on the flexible disk that is sandwiched between them. Asymmetry of opposing air bearings is created by etching the air-bearing pad opposite the recording element pad to a depth sufficient that the flying height and air film stiffness of the opposing pad reach desired levels. The result is an air-bearing interface with low flying height and high stiffness over the recording element directly opposed by a high flying height and low stiffness on the other side of the disk. This air-bearing interface was found to provide an enhanced dynamic flexibility to the metal foil disk when it is subjected to mechanical shock. As a result, the opposed slider arrangement with metal foil disk is able to avoid contact and impact when subjected to substantial levels of mechanical shock. Thus, wear and damage to slider and disk surfaces are reduced as well as the possibility of lost recorded data. This should make the metal foil disk a strong candidate as a rotating storage medium for mobile and portable applications where a shock environment is common. Computer simulation of the new air-bearing configuration will be presented and discussed. The current work is related to but distinct from that reported recently by White (2005, ASME J. Tribol., 127, pp. 522–529) for a Mylar disk.
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Radhi, Sabaa S., Zainab S. Al-Khafaji, and Mayadah W. Falah. "Sustainable heating system by infrared radiators." Heritage and Sustainable Development 4, no. 1 (March 17, 2022): 42–52. http://dx.doi.org/10.37868/hsd.v4i1.82.
Повний текст джерелаАнотація:
Maintaining the optimum temperature in the living quarters is the key to a comfortable stay. Due to the lack of a central heating system or in the event of its insufficiency, they resort to the installation of additional heat sources. There is a wide range of devices on the market with different operating principles, hence the difficulty of which is better - a convector or infrared heater. A comparative analysis of devices will help you make the right choice. Asking the question of which is better a convection heater or an infrared heater, one must decide on its role in heating the house. It is better to use them as additional equipment with an existing heating system. One of the effective sources of additional heating are infrared radiators. Its principle of operation is based on infrared radiation, which provides a quick and qualitative increase in temperature in any part of your apartment. Today, more and more people prefer infrared radiators. From the usual electric convector, they differ in that they heat not the air in the room, but hard surfaces (floors, walls) and objects, and these, in turn, leak heat into the surrounding space. So, the entire room is heated up unnoticeably.
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Wu, Weiwei, and Mukul M. Sharma. "A Model for the Conductivity and Compliance of Unpropped and Natural Fractures." SPE Journal 22, no. 06 (October 3, 2017): 1893–914. http://dx.doi.org/10.2118/184852-pa.
Повний текст джерелаАнотація:
Summary Fluid flow in unpropped and natural fractures is critical in many geophysical processes and engineering applications. The flow conductivity in these fractures depends on their closure under stress, which is a complicated mechanical process that is challenging to model. The challenges come from the deformation interaction and the close coupling among the fracture geometry, pressure, and deformation, making the closure computationally expensive to describe. Hence, most of the previous models either use a small grid system or disregard deformation interaction or plastic deformation. In this study, a numerical model is developed to simulate the stress-driven closure and the conductivity for fractures with rough surfaces. The model integrates elastoplastic deformation and deformation interaction, and can handle contact between heterogeneous surfaces. Computation is optimized and accelerated by use of an algorithm that combines the conjugate-gradient (CG) method and the fast-Fourier-transform (FFT) technique. Computation time is significantly reduced compared with traditional methods. For example, a speedup of five orders of magnitude is obtained for a grid size of 512 × 512. The model is validated against analytical problems and experiments, for both elastic-only and elastoplastic scenarios. It is shown that interaction between asperities and plastic deformation cannot be ignored when modeling fracture closure. By applying our model, roughness and yield stress are found to have a larger effect on fracture closure and compliance than Young's modulus. Plastic deformation is a dominant contributor to closure and can make up more than 70% of the total closure in some shales. The plastic deformation also significantly alters the relationship between fracture stiffness and conductivity. Surfaces with reduced correlation length produce greater conductivity because of their larger apertures, despite more fracture closure. They have a similar fraction of area in contact as compared with surfaces with longer fracture length, but the pattern of area in contact is more scattered. Contact between heterogeneous surfaces with more soft minerals leads to increased plastic deformation and fracture closure, and results in lower fracture conductivity. Fracture compliance appears not to be as sensitive to the distribution pattern of hard and soft minerals. Our model compares well with experimental data for fracture closure, and can be applied to unpropped or natural fractures. These results are obtained for a wide range of conditions: surface profile following Gaussian distribution with correlation length of 50 µm and roughness of 4 to 50 µm, yield stress of 100 to 1500 MPa, and Young's modulus of 20 to 60 GPa. The results may be different for situations outside this range of parameters.
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ROMANOV, IL’YA, and ROMAN ZADOROZHNIY. "EVALUATION OF TRIBOTECHNICAL PROPERTIES OF THE COATING OBTAINED BY ELECTRIC SPARK HARDENING." Tekhnicheskiy servis mashin 4, no. 141 (December 2020): 157–63. http://dx.doi.org/10.22314/2618-8287-2020-58-1-157-163.
Повний текст джерелаАнотація:
When applying coatings using various methods on the surfaces of moving parts that work in joints, it is important to make sure that the coatings are strong and wear-resistant in order to return them to their original resource. All existing hardening technologies and materials used to perform coatings have their own characteristics, therefore, the quality of the resulting coatings can be judged only after specific tests. (Research purpose) The research purpose is in evaluating the properties of the coating obtained by the method of electric spark hardening, and its ability to resist friction and mechanical wear. (Materials and methods) Authors conducted tests on the basis of the "Nano-Center" center for collective use. A coating was applied on the BIG-4M unit with a VK-8 hard alloy electrode, tribological properties were evaluated on a CSM Instruments TRB-S-DE-0000 tribometer, the width of the friction track was measured after the test using an inverted OLYMPUS gx51 optical microscope, and samples were weighed before and after the test on a VLR-200 analytical balance. Conducted research in accordance with GOST 23.224-86 and RD 50-662-88 guidelines. (Results and discussion) The article presents performed tests on the run-in and wear resistance of the coating. The samples were worked on with a step-by-step increase in the load. During the tests, the friction force was drawed on the diagram. Authors compared the results with the reference sample, an uncoated surface. (Conclusions) The resulting coating has better run-in and wear resistance compared to the standard, and the increase in wear resistance in dry friction conditions is very significant.
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ABDULRAHMAN, Hayder J., and Suzan B. MOHAMMED. "DEVELOPMENT OF ULTRA-SHORT HIGH INTENSITY LASERS FOR THE VISIBLE SPECTRA RANGE." Periódico Tchê Química 17, no. 35 (July 20, 2020): 739–52. http://dx.doi.org/10.52571/ptq.v17.n35.2020.63_abdulrahman_pgs_739_752.pdf.
Повний текст джерелаАнотація:
Ultra-short laser pulses are particularly suitable for processing micro tools made of ultra-hard and dielectric materials. Ultra-short laser pulses provide a contact-free and precise fabrication of heat-sensitive materials such as visible spectra range. Visible spectra range has unique properties, which makes it an essential material in the tool, jewelry, and semiconductor industries. The processing of visible spectra range by ultra-short laser pulses is complex, as visible and near-infrared light is generally not absorbed. However, the intensity of ultra-short laser pulses is extremely high, so that the absorption scales nonlinearly with the intensity and, thus, visible or near-infrared light can be absorbed. The complexity also results from many partially interdependent process variables, such as the repetition rate, pulse overlap, track overlap, and scan speed. Excellent knowledge of the process is, therefore, essential for the production of micro tools. To make the laser processing accessible to a broader user field, the operator can be supported by a computer-aided design (CAD). The aim of this research was to the modeling of an ultra-short high-intensity laser for the visible spectra range in different environments of the angle of incidence, scanning speed, pulse, and track overlap. The experimental process included ultra-short pulsed laser processing of visible spectra range and surface analysis concerning modifications and ablation of the ultra-short laser. Ablation volumes were analyzed for single pulses, multi-pulses, and pockets. Pump-probe experiments reveal transient optical properties such as transmission or reflectivity. It was concluded that ultraviolet laser pulses are best suited to induce damage or modifications to visible spectra range surfaces. Additionally, shorter wavelengths have further advantages such as potentially longer Rayleigh lengths and smaller spot sizes.
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Pilz, Florian, Johannes Henneberg, and Marion Merklein. "Extension of the forming limits of extrusion processes in sheet-bulk metal forming for production of minute functional elements." Manufacturing Review 7 (2020): 9. http://dx.doi.org/10.1051/mfreview/2020003.
Повний текст джерелаАнотація:
Increasing demands in modern production pose new challenges to established forming processes. One approach to meet these challenges is the combined use of established process classes such as sheet and bulk forming. This innovative process class, also called sheet-bulk metal forming (SBMF), facilitates the forming of minute functional elements such as lock toothing and gear toothing on sheet-metal bodies. High tool loads and a complex material flow that is hard to control are characteristic of SBMF. Due to these challenging process conditions, the forming of functional elements is often insufficient and necessitates rework. This negatively affects economic efficiency. In order to make use of SBMF in industrial contexts, it is necessary to develop measures for improving the forming of functional elements and thereby push existing forming boundaries. This paper describes the design and numerical replication of both a forward and a lateral extrusion process so as to create involute gearing in combination with carrier teeth. In a combined numerical-experimental approach, measures for extending the die filling in sheet-metal extrusion processes are identified and investigated. Here, the focus is on approaches such as process parameters, component design and locally adjusted tribological conditions; so-called ‘tailored surfaces’. Based on the findings, fundamental mechanisms of action are identified, and measures are assessed with regard to their potential for application. The examined approaches show their potential for improving the forming of functional elements and, consequently, the improvement of geometrical accuracies in functional areas of the workpieces.
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Mammoliti, Elisa, Francesco Di Stefano, Davide Fronzi, Adriano Mancini, Eva Savina Malinverni, and Alberto Tazioli. "A Machine Learning Approach to Extract Rock Mass Discontinuity Orientation and Spacing, from Laser Scanner Point Clouds." Remote Sensing 14, no. 10 (May 13, 2022): 2365. http://dx.doi.org/10.3390/rs14102365.
Повний текст джерелаАнотація:
This study wants to give a contribution to the semi-automatic evaluation of rock mass discontinuities, orientation and spacing, as important parameters used in Engineering. In complex and inaccessible study areas, a traditional geological survey is hard to conduct, therefore, remote sensing techniques have proven to be a very useful tool for discontinuity analysis. However, critical expert judgment is necessary to make reliable analyses. For this reason, the open-source Python tool named DCS (Discontinuities Classification and Spacing) was developed to manage point cloud data. The tool is written in Python and is based on semi-supervised clustering. By this approach the users can: (a) estimate the number of discontinuity sets (here referred to as “clusters”) using the Error Sum of Squares (SSE) method and the K-means algorithm; (b) evaluate step by step the quality of the classification visualizing the stereonet and the scatterplot of dip vs. dip direction from the clustering; (c) supervise the clustering procedure through a manual initialization of centroids; (d) calculate the normal spacing. In contrast to other algorithms available in the literature, the DCS method does not require complex parameters as inputs for the classification and permits the users to supervise the procedure at each step. The DCS approach was tested on the steep coastal cliff of Ancona town (Italy), called the Cardeto–Passetto cliff, which is characterized by a complex fracturing and is largely affected by rockfall phenomena. The results of discontinuity orientation were validated with the field survey and compared with the ones of the FACETS plug-in of CloudCompare. In addition, the algorithm was tested and validated on regular surfaces of an anthropic wall located at the bottom of the cliff. Eventually, a kinematic analysis of rock slope stability was performed, discussing the advantages and limitations of the methods considered and making fundamental considerations on their use.
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Seppänen, Henri. "Ultrasonic Bonding on Unstable Pin." International Symposium on Microelectronics 2016, no. 1 (October 1, 2016): 000398–401. http://dx.doi.org/10.4071/isom-2016-tha15.
Повний текст джерелаАнотація:
Abstract In power electronics modules, ultrasonic wire bonding is a common method to make electronic connections between the connector pins and the IGBTs. In these modules the connector pins are often residing on top of the plastic frame. Due to the pins being in positions which are hard to reach, clamping of these pins is either suboptimal or not used. This poor or absent clamping combined with the plastic frame's elasticity (softness) means that the pin has more freedom to move compared to the bonding on a metal substrate or IC. In our experiments we measured the pin and the plastic frame displacement with a laser Doppler vibrometer during the ultrasonic heavy wire (400 um in diameter Al wire) bonding process. We measured that the press fitted pin can move laterally along the ultrasonic excitation axis (2.0 ± 0.2) um whereas the frame under the pin moved (0.3 ± 0.1) um. This indicates that the pin slips over the frame while bonding. The slipping of the pin is also visible on the ultrasonic frequency waveforms of the transducer. While molded pins in general are thought to be more stable compared to the press fitted pins, similar behavior is seen in heavy wire bonding where high ultrasonic power is needed. We measured molded frame displacement (0.6 ± 0.2) um while bonding on the pin. In this paper we show how to use process traces and visual inspection to detect unstable pins and how to improve bondability on unstable pins by selecting process parameters that are optimized for the unstable pins rather than stable surfaces.
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Geer, A. J., and F. Baordo. "Improved scattering radiative transfer for frozen hydrometeors at microwave frequencies." Atmospheric Measurement Techniques 7, no. 6 (June 25, 2014): 1839–60. http://dx.doi.org/10.5194/amt-7-1839-2014.
Повний текст джерелаАнотація:
Abstract. To simulate passive microwave radiances in all-sky conditions requires better knowledge of the scattering properties of frozen hydrometeors. Typically, snow particles are represented as spheres and their scattering properties are calculated using Mie theory, but this is unrealistic and, particularly in deep-convective areas, it produces too much scattering in mid-frequencies (e.g. 30–50 GHz) and too little scattering at high frequencies (e.g. 150–183 GHz). These problems make it hard to assimilate microwave observations in numerical weather prediction (NWP) models, particularly in situations where scattering effects are most important, such as over land surfaces or in moisture sounding channels. Using the discrete dipole approximation to compute scattering properties, more accurate results can be generated by modelling frozen particles as ice rosettes or simplified snowflakes, though hexagonal plates and columns often give worse results than Mie spheres. To objectively decide on the best particle shape (and size distribution) this study uses global forecast departures from an NWP system (e.g. observation minus forecast differences) to indicate the quality of agreement between model and observations. It is easy to improve results in one situation but worsen them in others, so a rigorous method is needed: four different statistics are checked; these statistics are required to stay the same or improve in all channels between 10 GHz and 183 GHz and in all weather situations globally. The optimal choice of snow particle shape and size distribution is better across all frequencies and all weather conditions, giving confidence in its physical realism. Compared to the Mie sphere, most of the systematic error is removed and departure statistics are improved by 10 to 60%. However, this improvement is achieved with a simple "one-size-fits-all" shape for snow; there is little additional benefit in choosing the particle shape according to the precipitation type. These developments have improved the accuracy of scattering radiative transfer sufficiently that microwave all-sky assimilation is being extended to land surfaces, to higher frequencies and to sounding channels.
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Geer, A. J., and F. Baordo. "Improved scattering radiative transfer for frozen hydrometeors at microwave frequencies." Atmospheric Measurement Techniques Discussions 7, no. 2 (February 18, 2014): 1749–805. http://dx.doi.org/10.5194/amtd-7-1749-2014.
Повний текст джерелаАнотація:
Abstract. To simulate passive microwave radiances in all-sky conditions requires better knowledge of the scattering properties of frozen hydrometeors. Typically, snow particles are represented as spheres and their scattering properties are calculated using Mie theory, but this is unrealistic and particularly in deep-convective areas, it produces too much scattering in mid frequencies (e.g. 30–50 GHz) and too little scattering at high frequencies (e.g. 150–183 GHz). These problems make it hard to assimilate microwave observations in numerical weather prediction (NWP) models, particularly in situations where scattering effects are most important such as over land surfaces or in moisture sounding channels. Using the discrete dipole approximation to compute scattering properties, more accurate results can be generated by modelling frozen particles as ice rosettes or simplified snowflakes, though hexagonal plates and columns often give worse results than Mie spheres. To objectively decide on the best particle shape (and size distribution) this study uses global forecast departures from an NWP system (e.g. observation minus forecast differences) to indicate the quality of agreement between model and observations. It is easy to improve results in one situation but worsen them in others, so a rigorous method is needed: four different statistics are checked; these statistics are required to stay the same or improve in all channels between 10 GHz and 183 GHz and in all weather situations globally. The optimal choice of snow particle shape and size distribution is better across all frequencies and all weather conditions, giving confidence in its physical realism. Compared to the Mie sphere, most of the systematic error is removed and departure statistics are improved by 10 to 60%. However, this improvement is achieved with a simple “one-size-fits-all” shape for snow; there is little additional benefit in choosing the particle shape according to the precipitation type. These developments have improved the accuracy of scattering radiative transfer sufficiently that microwave all-sky assimilation is being extended to land surfaces, to higher frequencies and to sounding channels.
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Savelyev, K. S., M. V. Ilyushkin, and E. S. Kiselev. "Use of digital twins for mathematical modeling of ultrasonic drilling of titanium blanks." Vektor nauki Tol'yattinskogo gosudarstvennogo universiteta, no. 1 (2021): 42–54. http://dx.doi.org/10.18323/2073-5073-2021-1-42-54.
Повний текст джерелаАнотація:
The paper considers the creation and research of a virtual prototype of titanium blanks drilling using the Lagrange and Galerkin method. The developed finite-element models are designed to study the process of mechanical treatment and optimize technological cutting parameters. The paper presents the results of computational investigation of titanium blanks drilling using mathematical modeling programs, which allow complete simulating operating procedures in a computer (digital twin). As a program to simulate the process of removing the allowance from a titanium workpiece, the authors used a multipurpose software product of finite-element modeling and analysis of highly-linear dynamic processes using various Ls-DYNA time integration schemes. The application of the Galerkin method allows adequately describing the drilling process with the introduction of the ultrasonic field energy into a treatment zone, can significantly reduce the duration of experimental research and evaluates the influence of the cutting mode elements and the tool design parameters on the power and energy aspects of the formation of new machine parts surfaces. Both methods are applicable to create various processes of mechanical treatment, however, the Lagrange method is less sensitive to the ultrasonic field energy. The introduction of the ultrasonic field energy into the drilling zone of workpieces made of hard-processing titanium alloys can significantly reduce energy costs. As a result of the simulation, the authors obtained a calculation file containing the simulation process, the solution of which visually reflects the drilling process of a titanium workpiece in a real-life setting with the removal of chips. However, for complete verification of numerical study results, it is necessary to carry out an experimental check and make adjustments to the calculated data.
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Yan, Lin, Lei Zhang, Hongyan Ma, David Chiu, and James D. Bryers. "A Single B-Repeat of Staphylococcus epidermidis Accumulation-Associated Protein Induces Protective Immune Responses in an Experimental Biomaterial-Associated Infection Mouse Model." Clinical and Vaccine Immunology 21, no. 9 (June 11, 2014): 1206–14. http://dx.doi.org/10.1128/cvi.00306-14.
Повний текст джерелаАнотація:
ABSTRACTNosocomial infections are the fourth leading cause of morbidity and mortality in the United States, resulting in 2 million infections and ∼100,000 deaths each year. More than 60% of these infections are associated with some type of biomedical device.Staphylococcus epidermidisis a commensal bacterium of the human skin and is the most common nosocomial pathogen infecting implanted medical devices, especially those in the cardiovasculature.S. epidermidisantibiotic resistance and biofilm formation on inert surfaces make these infections hard to treat. Accumulation-associated protein (Aap), a cell wall-anchored protein ofS. epidermidis, is considered one of the most important proteins involved in the formation ofS. epidermidisbiofilm. A small recombinant protein vaccine comprising a single B-repeat domain (Brpt1.0) ofS. epidermidisRP62A Aap was developed, and the vaccine's efficacy was evaluatedin vitrowith a biofilm inhibition assay andin vivoin a murine model of biomaterial-associated infection. A high IgG antibody response againstS. epidermidisRP62A was detected in the sera of the mice after two subcutaneous immunizations with Brpt1.0 coadministered with Freund's adjuvant. Sera from Brpt1.0-immunized mice inhibitedin vitroS. epidermidisRP62A biofilm formation in a dose-dependent pattern. After receiving two immunizations, each mouse was surgically implanted with a porous scaffold disk containing 5 × 106CFU ofS. epidermidisRP62A. Weight changes, inflammatory markers, and histological assay results after challenge withS. epidermidisindicated that the mice immunized with Brpt1.0 exhibited significantly higher resistance toS. epidermidisRP62A implant infection than the control mice. Day 8 postchallenge, there was a significantly lower number of bacteria in scaffold sections and surrounding tissues and a lower residual inflammatory response to the infected scaffold disks for the Brpt1.0-immunized mice than for of the ovalbumin (Ova)-immunized mice.
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Sovinsky, John. "The Future of Maximum CAD/CAM Automation for Ceramic Hybrids." International Symposium on Microelectronics 2010, no. 1 (January 1, 2010): 000268–83. http://dx.doi.org/10.4071/isom-2010-tp3-paper5.
Повний текст джерелаАнотація:
New concepts recently developed maximize CAD/CAM automation for all types of Ceramic Hybrids including Thick Film, Thin Film, LTCC and HTCC. Designs can now go quickly from concept to manufactured product, which will fuel more progress to bring a largely manual process to maximum automation, to include automatic masks, panels and generation of 3D analysis models. Maximum automation results in expanded use of technologies that are now shrinking. Technologies that have complex and difficult to understand design and manufacturing steps have a hard time gaining wide acceptance. CDS is tackling this complex challenge and is designing and implementing the following processes to solve the most difficult CAD/CAM problems:Be a true CAM tool that reads in designs from any other EDA (layout) system. YRun all possible DRC checks necessary for high fabrication and assembly yield. YMake all manufacturing masks automatically from very basic designs by using settings in an automatically configurable table. YPanelize all types of Ceramic designs in preparation for manufacturing. YGenerate documentation automatically through from stored configuration files. DIn LTCC and HTCC, place cavity punches (nibbles and rubs) automatically and feed correct machine data to the punch machine. YExport resistor trimming data directly to the laser trimming machine. FFeed flying probe test data directly to the flying probe tester. DAutomatically make a 3D Image and export ACIS or STEP for thermal analysis. DExport data directly to all electrical analysis and thermal analysis tools. PSupport circuit fabrication on non-planar surfaces. FMake full 3D analysis models of circuits on non-planar surfaces.F The purpose of this paper is to define what is required for the Ceramic Hybrid Microelectronics industry to realize full automation in design, checking and output to manufacturing. Your ideas are welcome.
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Samborski, Sylwester, Jerzy Józwik, Jakub Skoczylas, and Mariusz Kłonica. "Adaptation of Fracture Mechanics Methods for Quality Assessment of Tungsten Carbide Cutting Inserts." Materials 14, no. 13 (June 22, 2021): 3441. http://dx.doi.org/10.3390/ma14133441.
Повний текст джерелаАнотація:
Tungsten carbide (WC) is well known as one of the hardest materials widely used in machining, cutting and drilling, especially for cutting tools production. Knowing fracture toughness grants the opportunity to prevent catastrophic wear of a tool. Moreover, fracture toughness of WC-based materials may vary because of different material compositions, as well as a different way of production. Hence, each material should be treated individually. In this paper, SM25T (HW) tungsten carbide (HW—uncoated grade, TNMR 401060 SM25T, manufactured by Baildonit company, Katowice, Poland) was taken into consideration. Sintered carbides—designated as S—are designed to be applied for machining steel, cast steel and malleable cast iron. Fracture mechanics methods were adapted to make a quality assessment of WC cutting inserts. Both quasi-statical three-point bending tests, as well as Charpy dynamic impact tests, were performed to calculate static and dynamic fracture toughness (KIC and KID, respectively). In addition, a special emphasis was placed on the microscopic analysis of fracture surfaces after impact tests to discuss material irregularities, such as porosity, cracks and so-called “river patterns”. There is a lack of scientific works in this field of study. However, cutting engineers are interested in obtaining the experimental results of that kind. Although there are a few standardized methods that may be used to determine fracture toughness of hard metals, none of them is expected to be the most reliable. Moreover, there is a lack of scientific works in the field of determining static and dynamic fracture toughness of WC by the presented method. The proposed examination solution can be then successfully used to calculate toughness properties of WC-based materials, as the results obtained seem to be with a good agreement with other works.
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Vukovic, Jasna. "Pottery shreds as tools in late Neolithic Vinca." Starinar, no. 63 (2013): 191–207. http://dx.doi.org/10.2298/sta1363191v.
Повний текст джерелаАнотація:
Over the last few years, careful analysis of a large quantity of ceramic material found during excavation at Vinca has identified a significant number of ceramic fragments with clear use-wear traces. Recycled fragments of ceramic vessels are characterized by the presence of damage and deformation caused by abrasive processes i.e. contact of the fragments with hard material. All recorded recycled fragments can generally be divided into two basic groups: fragments representing tools with a working edge, and fragments with traces of abrasion on their outer surface. The largest group comprises fragments whose edges form the working edge of a tool, rounded or flattened through use and so becoming smooth. In contrast to so-called burnishers (the secondarily used, striped handles with traces of the action of water, manifesting in a uniformly rounded break) with ceramic tools only one edge of the fragment is rounded and used; the remaining edge indicates a completely normal break. In addition, most fragments also have abrasions directly beneath the working edge, which indicates holding the tool at a certain angle during use. That damage can occur both on the exterior and interior surfaces. It is striking that in a large group of fragments, the rim is used as a working edge. Tools are mostly fragmented, but it appears that their shape was not modified before use. In that sense, two straight polygonal tools can be distinguished (T. I/1a-b), or tools which are rectangular in shape with rounded corners (T. II4a-b), preserved complete. In most cases, these are fragments of bowls, so tools usually have polished or burnished surfaces, but ornamental parts formed by burnished lines or channelling are also noticeable. Fragments of rough fabric were never used as tools, but only those with an admixture of fine sand. Very rarely, actually in two cases, fragments of amphorae were used as tools (T. IV/2,5). Usually the upper parts of vessels were used, although there are several exceptions, where parts of the base and body were used as well (T. IV/3). Also, in the damaged area straight depressions can often be noticed, which apparently represent some kind of negative impression of the object on which they were used, or, in rare cases, the whole working surface is step-like. The second group of fragments do not generally differ from the first group as regards their form and the surface treatment. The difference can be seen in the distribution of damage. To be precise, the zone of intensive abrasion lies on the surface of fragments and is manifested by complete removal of original surface, while across it, marks caused by contact with hard material often result in deep incisions, which can be seen with the naked eye. These marks can be found on the most protruted parts of vessels i.e. on the shoulder, apart from two cases concerning the shoulder, or the thickened rim of an amphora (T.V/1,5). Finally, we should emphasise the fact that not one ceramic tool has been found around an architectural structure. Specimens originate from archaeological layers or contexts which do not represent a specific zone of activity (destruction layers, ditch filling, posthole, levelling layers etc) but in contexts in which waste material was deposited. From that perspective, one example can particularly be distinguished, a tool with a working edge found near the ceramic substructure of a oven. By analysis of the distribution, shape and kind of damage, as well as the position and shape of the working edge, it is possible to reconstruct the direction of movement and position of the tool during use. Scraping tools show marks in the form of dense incisions, visible both macroscopically and microscopically. They can also be characterised by a pronouncedly rounded working edge. Bearing these characteristics in mind, tools from Vinca with rounded working edges can be categorized as tools for scraping away excess clay and for thinning the surface of unfired vessels. They were held at right angles or slanting in relation to the vessel, with the working edge horizontal or also at an angle or lateral to the working edge, so that the vessels walls were thinned by movements in various directions. Ceramic tools were not specialized, and were undoubtedly multi-functional. They could have been used for smoothing and polishing. This is supported by the fact that abrasion traces are parallel or distributed in various directions. A group of tools with a flattened working edge, judging by preserved marks, had a rather different function. There are indications that these were held at right angles to the vessel but that the movement was not lateral. The tool was probably held with the working edge in a vertical position, so that burnished decoration could be carried out by using up/down movements, when it was necessary to make thin burnished lines of uniform thickness and with clearly defined edges. Bearing in mind traces of 'negative' impressions of the item on which the tools were used, the tool could also have been used in a left-right direction, when it was used to execute the burnished zone typical for upper bowls' parts. One of the important characteristics of ceramic tools is the use of the rim of a broken vessel as a working edge. This is a very logical choice. Bowl rims have a naturally rounded and often symmetrical, sharpened shape. Thus, craftsmen got a ready-made thin, relatively sharp tool, so there was no need to modify a fragment or re-shape it for the working edge to obtain the desired shape. Likewise, as mentioned before, the existence of a negative impression on work edges, usually rims, makes it probable that such tools were used to shape and burnish the rims of vessels. It is an interesting fact that most of these tools comprise fragments of bowls, and this is not coincidental. Important role in the appearance and form of traces caused by abrasive processes is played by characteristics of the abrasive, i.e. tool, such as hardness and granulation. All bowls are characterised by their fine fabric and fine-sand admixture, thin walls, burnished or polished surfaces and firing in a reduced atmosphere. These characteristics are very significant regarding the reaction of material to mechanical stress. A reduced atmosphere during firing increases the hardness of ceramics. Ceramics with fine granulation and lower porosity show greater resistance to mechanical stress than ceramics of rougher fabric with larger quantities of a coarse admixture. Burnishing and polishing lead to the compression of particles on surfaces, which creates a hard, compact structure, resistant to abrasion. It was especially convenient to have tools made of materials with identical characteristics as material they were used on. Analysis of ceramic fragments from the early phase of the Late Neolithic settlement at Vinca indicated an exceptional number of recycled vessel fragments, shaped as tools and used in the process of shaping and modifying ceramic surfaces. Since this concerns a new class of archaeological finds, it is necessary to suggest a direction for future research, particularly experimental, which would, together with microscopic identification of use-wear traces, reveal completely the activities in which ceramic tools were used.
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Mann, William C., Dianne Hurren, Machiko Tomita, and Barbara Charvat. "Use of Assistive Devices for Bathing by Elderly Who are Not Institutionalized." Occupational Therapy Journal of Research 16, no. 4 (October 1996): 261–86. http://dx.doi.org/10.1177/153944929601600403.
Повний текст джерелаАнотація:
For elderly persons with disabilities, bathing is a frequent activity that can be both pleasant and dangerous. Bathing involves using water in an environment with hard, smooth surfaces that become slippery when wet, and many falls occur in the bathroom. A variety of assistive devices are available to make bathing safer and more comfortable. Bathing devices rank as one of the most frequently used categories of assistive devices, yet many elders experience problems in the use of bathing devices. Study of bathing devices has been little beyond determination of the frequency of their use. In this article, we developed a hierarchical model for use in prescribing bathing devices related to mobility and support. This model, based on level of disability, is called the Bath Device Prescription Model (BDPM). Subjects were drawn from the University at Buffalo Consumer Assessments Study (n=319), which considers persons older than 60 years with disabilities. Subjects who reported difficulty with bathing (n=294) were divided into two groups based on mental status (Mini Mental Status Exam [MMSE] scores ⩾24 or ⩾23). This model was tested by first determining the level of disability of satisfied users of (1) bath mats, (2) grab bars in the bath area, (3) bath stools, (4) bath chairs, and (5) bath transfer benches. Level of disability was measured with the Sickness Impact Profile-physical dysfunction section (SIP-PDS), the body care and movement subsection of the SIP-PDS, the motor section of the Functional Independence Measure (FIM), and the bathing-washing and drying item of the FIM. Subjects who were having a problem with a bath device, other than installation, maintenance, or access to the bathroom, were considered. Disability scores for these dissatisfied owners of bath devices were compared with the mean score of satisfied users of each bath device. Typically, dissatisfied owners of bath devices were more disabled than satisfied users, suggesting that they would benefit from a higher level device, following the BDPM. This study represents the first reported investigation testing a model for use in the prescription of bath devices.
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Chen, Guang Jun, Xian Li Liu, and Cai Xu Yue. "Study on Causes of Material Plastic Side Flow in Precision Hard Cutting Process." Advanced Materials Research 97-101 (March 2010): 1875–78. http://dx.doi.org/10.4028/www.scientific.net/amr.97-101.1875.
Повний текст джерелаАнотація:
There are many special cutting disciplines needed to research in precision hard cutting process. The plastic side flow on machining surface influences machining surface roughness great. The mathematical model of hump height for surface plastic side flow is built based on the model of precision hard cutting and forming mechanism of surface plastic side flow is analyzed. Effect of cutting feed on the maximum scallop height of machining surface is researched and microscopic observation of surface topography is made through the hard cutting experiment. In certain conditions, the machining surface roughness and the cutting off trace increase with cutting feed. Because of the metal softening, some metal which formed side flow fall off immediately but make plastic flow on the strip edge of machining surface when it flows out tool surface. This research supplied theoretical basis for prediction of hard cutting process surface quality.
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Yin, Shao Hui, Jing Wang, Feng Jun Chen, Jian Wu Yu, Yu Wang, Qing Liang Zhao, and Hong Liang Li. "Inclined Axis Ultra-Precision Grinding for Spherical Surface." Solid State Phenomena 175 (June 2011): 145–49. http://dx.doi.org/10.4028/www.scientific.net/ssp.175.145.
Повний текст джерелаАнотація:
Through establishing the mathematical models of velocity and grinding force to optimize the installation angle with inclined axis grinding technology, the spherical surface of the ultra-hard alloy material was ground by formed electroplated diamond wheel. After analyzing the abrasion of grinding wheel, the results show that the inclined axis grinding technology of the formed grinding wheel can avoid the rotation dead spots of grinding wheel, and can make the grinding wheel surface contacted with work-piece fully which could make the worn more evenly. Finally, it obtains a surface in a high quality with the surface roughness of Ra is 12.88nm, and the form accuracy of PV is 124nm.
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Silverman, Helaine, and David Browne. "New evidence for the date of the Nazca lines." Antiquity 65, no. 247 (June 1991): 208–20. http://dx.doi.org/10.1017/s0003598x00079667.
Повний текст джерелаАнотація:
Surface features that possess no useful stratigraphy and are not, by their own nature, informative about their age, are notoriously hard to date. A study of associations now defines with good confidence the dates of the surface arrangements of stones and of cleared areas that make up some of the celebrated Nazca lines, Peru.