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Kozu, H., Y. Jumonji, C. Yamazaki, Y. Shoji, S. Hashimoto y A. Ando. "A crowbarless power supply for klystrons". Journal of Synchrotron Radiation 5, n.º 3 (1 de mayo de 1998): 374–75. http://dx.doi.org/10.1107/s0909049597015331.
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A new crowbarless power supply is to be installed at the New SUBARU storage ring. A high-power switching inverter unit eliminates the need for expensive and unstable crowbar circuits for the klystron power supply. It also realizes a very small voltage ripple in the low-frequency region. This is an important characteristic, especially in a quasi-isochronous storage ring such as New SUBARU.
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Thul, Mayur, Yao-Peng Wu, Yi-Jyun Lin, Shu-Lin Du, Hsin-Ru Wu, Wen-Yueh Ho y Shun-Yuan Luo. "Ionic Liquid Catalyzed Per-O-Acetylation and Benzylidene Ring-Opening Reaction". Catalysts 10, n.º 6 (8 de junio de 2020): 642. http://dx.doi.org/10.3390/catal10060642.
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Tunable aryl imidazolium ionic liquids acting as Brønsted acid ionic liquids were found to be efficient catalysts for per-O-acetylation and reductive ring opening of benzylidene acetals. This method requires a truly catalytic amount of the least expensive available ionic liquids that are water-stable and reusable and also stable at room temperature. The reactions were obtained in one hour with good to excellent yields. These reactions can form C−O and C−H bonds with a high atom economy. Furthermore, the ionic liquid is an anomeric selective catalyst in per-O-acetylation and reductive ring opening of benzylidene acetals of sugar moieties.
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Chaudhary, MilindM. "Diamonds are expensive, rings are not: Mastering the paradoxical evolution of nonunion treatment". Journal of Limb Lengthening and Reconstruction 5, n.º 2 (2019): 51. http://dx.doi.org/10.4103/jllr.jllr_24_19.
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Krause, Cornelia y Hubert Morin. "Impact of spruce budworm defoliation on the number of latewood tracheids in balsam fir and black spruce". Canadian Journal of Forest Research 25, n.º 12 (1 de diciembre de 1995): 2029–34. http://dx.doi.org/10.1139/x95-219.
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The influence of spruce budworrn (Choristoneurafumiferana (Clem.)) defoliation was analysed at different stem heights by counting the number of latewood tracheids and measuring tree-ring width. The total height of the tree was divided into three different equal parts: the lower, the middle, and the upper sections of the total stem length. However, only the results of the lower and the upper sections will be presented in this paper. The reduction of ring widths started in the upper part for the living crown and continued downwards to the stem base (0 m) with a delay of 1–2 years. The number of latewood tracheids generally showed a reduction 1 year earlier than the ring widths, particularly in the crown, but also in the other parts of the stem. Considering this, we think that the reduction of the number of latewood tracheids may date the beginning of spruce budworm defoliation more accurately and present a better characterization of the first impact of spruce budworm than the measuring of the ring widths. This parameter will be particularly helpful (when expensive equipment, such as a densitometer or an image analysis system cannot be used) in detecting past outbreaks in the tree-ring records, especially when defoliation records are missing and when the reduction of the ring widths is not very pronounced.
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Wang, Lily, Serge Payette y Yves Bégin. "Relationships between anatomical and densitometric characteristics of black spruce and summer temperature at tree line in northern Quebec". Canadian Journal of Forest Research 32, n.º 3 (1 de marzo de 2002): 477–86. http://dx.doi.org/10.1139/x01-208.
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Tracheid cell number, cell diameter, and cell-wall thickness of black spruce (Picea mariana (Mill.) BSP) tree rings at the tree line (northern Quebec, Canada) were measured using image analysis. The densitometric data from the same samples were used to evaluate the features of image analysis. The anatomical data were correlated with summer temperature variables, including: means of pentad temperature (five consecutive days), growing season (May- September), sum of degree-days, and number of frost-free days. Our results suggest that the main cause of the pale appearance of light rings is thinner latewood cell-wall thickness. Some latewood variables are strongly correlated with corresponding indices for ring cell number and diameter, and ring cell wall thickness. Anatomical ring cell number and the sum of cell diameters (ring widths) were correlated to tree-ring width parameters derived from densitometry. Ring cell number and annual sum of cell diameter also showed very similar trends with both chronologies, suggesting that ring-width length may depend on the number of cells within a ring. Ratio diagram of double cell-wall thickness to cell radial diameter showed similar trend to wood density profile. There is a statistically significant correlation between maximum density and the highest annual ratio between cell wall thickness and lumen diameter. Cell-wall thickness was significantly correlated to maximum density, and both were significantly correlated with summer temperature variables. Our results suggest that wood anatomy may be used as a substitute to densitometry for climate reconstruction as densitometric data require expensive equipments. Also the anatomical method allows the recording of intra-annual information for dendroecological purposes.
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Zafar, Mohsin, Karl Kratkiewicz, Rayyan Manwar y Mohammad Avanaki. "Development of Low-Cost Fast Photoacoustic Computed Tomography: System Characterization and Phantom Study". Applied Sciences 9, n.º 3 (22 de enero de 2019): 374. http://dx.doi.org/10.3390/app9030374.
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A low-cost Photoacoustic Computed Tomography (PACT) system consisting of 16 single-element transducers has been developed. Our design proposes a fast rotating mechanism of 360o rotation around the imaging target, generating comparable images to those produced by large-number-element (e.g., 512, 1024, etc.) ring-array PACT systems. The 2D images with a temporal resolution of 1.5 s and a spatial resolution of 240 µm were achieved. The performance of the proposed system was evaluated by imaging complex phantom. The purpose of the proposed development is to provide researchers a low-cost alternative 2D photoacoustic computed tomography system with comparable resolution to the current high performance expensive ring-array PACT systems.
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ISLAM, SYED S. y A. F. M. ANWAR. "SPICE MODEL OF AlGaN/GaN HEMTs AND SIMULATION OF VCO AND POWER AMPLIFIER". International Journal of High Speed Electronics and Systems 14, n.º 03 (septiembre de 2004): 853–59. http://dx.doi.org/10.1142/s0129156404002946.
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SPICE model parameters are extracted from reported experimental data. The model is implemented in the Cadence Affirma Analog Circuit Design Environment and Spectre simulator is used to simulate class-E power amplifier and ring voltage controlled oscillator (VCO) circuits. The availability of the SPICE model for GaN HEMTs ensures optimization of analog/RF circuits before an expensive cut-and-try method is employed.
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Straže, Aleš, Klemen Novak y Katarina Čufar. "Quality and Price of Spruce Logs, Determined Conventionally and by Dendrochronological and NDE Techniques". Forests 13, n.º 5 (7 de mayo de 2022): 729. http://dx.doi.org/10.3390/f13050729.
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We examined valuable log assortments of Norway spruce (Picea abies) from a traditional auction in Slovenia where spruce growth on many sites is affected by climate change. From 6620 logs, we selected 817 that obtained the highest prices. Factors including log dimensions and geometry, tree-ring characteristics, quality grades according to the standard, properties measured by NDE stress wave testing, and their combined effect on price were modelled. The results showed that half of the auctioned logs were of highest quality (Q1, Q2), with diameters over 60 cm. These logs were more expensive than the thinner logs of lower quality (Q3, Q4). The quality class of the logs, determined by their external features and geometry, was associated with tree-ring and acoustic characteristics. The artificial neural network model (ANN) with feed-forward backpropagation using tree-ring data, longitudinal stress wave velocity, and damping showed that more than 75% of the logs could be accurately classified into quality classes. On the other hand, tree-ring data and acoustic characteristics could not adequately explain the price offered at auction, which probably also depends on unidentified individual requirements and the needs of the buyer.
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Gusev, A. S., C. B. Danilenko, S. A. Starodubtseva y V. Ya Teteryatnikov. "Dynamics of a "Hamster Wheel" Test Bench". Proceedings of Higher Educational Institutions. Маchine Building, n.º 5 (746) (mayo de 2022): 3–9. http://dx.doi.org/10.18698/0536-1044-2022-5-3-9.
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Ground tests of vehicles such as cars and tractors, including life tests and functional tests, are expensive and time-consuming. We propose to replace them with relatively inexpensive time-saving tests using a "hamster wheel" test bench. The vehicle inside a rotating ring remains at rest relative to the ground but in motion relative to the inner surface of the ring. This surface can be equipped with artificial obstacles to simulate actual road irregularities. We constructed differential equations of motion for the system and established the nature of the relative motion involving the outer ring and the test object, taking into account resonance phenomena and possible self-oscillations. We selected a disk simulating a vehicle wheel as our computational scheme. We studied the probability that self-oscillations appear in the system and determined their amplitude. We performed a qualitative assessment of possible dynamic effects. The paper proposes a system for arranging artificial obstacles on the inner surface of the wheel to simulate road bumps in terms of statistics.
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Deans, Douglas. "Effect of Openings in Ring-Reinforced Shells". Marine Technology and SNAME News 27, n.º 01 (1 de enero de 1990): 56–64. http://dx.doi.org/10.5957/mt1.1990.27.1.56.
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The ring-reinforced shell is a primary structure used in the marine and industrial world. Stress and buckling analysis of such structures is generally based on axisymmetric analysis wherein all openings in the shell are neglected. In real life, such structures have a large number of openings often made in a random manner. In order to design an appropriate reinforcement at such an opening, it is necessary to carry out a detailed local stress analysis. Such an analysis can be made either through the use of part models or by superelements which include the entire structure, as well as the local reinforcement. Zoom analysis using the whole model is expensive and requires knowledge of multilevel super element techniques. Analysis using part models is cheaper and can be equally reliable. This paper investigates the effects of openings on the stress distribution in ring-reinforced shells, such as submarines, using a finite element model. The stress concentration factors (SCF's) in areas adjacent to the opening are determined from this analysis. Using these SCF's, modeling rules for utilization of part models are developed and recommended for use.
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Tkachuk, Mykola M., Andrey Grabovskiy, Mykola А. Tkachuk, Oleksandr Shut, Andrii Lipeiko, Egor Ovcharov, Ganna Cymbal, Volodymyr Veiler, Illia Klochkov y Denys Kyslytsia. "ANALYSIS OF NONLINEAR RIGIDITY CHARACTERISTICS OF AIR BLOWER COMPRESSOR ELASTIC SUPPORTS". Bulletin of the National Technical University «KhPI» Series: Engineering and CAD, n.º 1 (7 de junio de 2023): 121–30. http://dx.doi.org/10.20998/2079-0775.2023.1.12.
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Vibrations of rotor systems are largely determined by elastic characteristics of supports. In the general case, the dependence of displacements on force for such supports is nonlinear. This applies to bearing supports of various types. In addition to bearings, elastic elements are also used in supports of rotor systems. They are designed to change the overall stiffness of the supports. The paper analyzes the radial stiffness of flexible ring dampers used in rotor supports. For this, two main approaches are proposed. The first is a conventional simulation of this problem of contact mechanics using the finite element method. The second is an analytical method that can be used as an alternative to expensive numerical calculations. This method is based on the principle of minimum additional energy. A special closed-form variational formulation is developed using the Euler-Bernoulli beam approximation for an elastic ring and a simplified model of normal contact on the ring flanges. It was shown that the surface tolerances of parts have a significant effect on the radial response of a flexible ring, which can become nonlinear. Tight fit of the ring on both sides makes it much stiffer, and non-tight fit leads to free movement of the rotor and much weaker damping of its movement. Both methods gave results that are consistent for the considered cases. By varying their design parameters, it is possible to adjust the rotor systems from critical modes of operation. Keywords: rotor system, elastic support, rigidity, finite element analysis, stress-strain state, contact interaction, principle of minimum additional energy
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Antonyuk, V. E., S. G. Sandomirski y V. V. Rudii. "TASKS OF TECHNOLOGICAL SUPPORT OF THE AUTOMATED RING ROLLING COMPLEX". Mechanics of Machines, Mechanisms and Materials 2, n.º 55 (junio de 2021): 42–53. http://dx.doi.org/10.46864/1995-0470-2021-2-55-42-53.
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The physical foundations and advantages of ring rolling are described. The materials science and technological processes of manufacture of products with its use are generalized. An analysis of the equipment of an automated ring rolling line was carried out, which showed that it is a complex and expensive technical solution. Moreover, the organization of the line with maximum load and efficiency is not included in the supplier’s tasks. The requirements for the maximum load of the line and its efficient operation have been determined. It is shown that the use of the experience of creating automated production of railway wheels when creating an automated production of ring blanks is impossible due to the need to ensure the production of rings of different structural shapes from different steel grades with different temperature ranges of plastic deformation and with different (from a hundred to several thousands) annual production programs. This requires the use of a different ratio of the radial and axial forces of the ring rolling, different technological equipment, taking into account different stiffness of the rings and their tendency to deformations during processing, transportation and cooling, a special development of mechanization means for readjustments. It is impossible to work out in advance all the technological options for the production of rings of different standard sizes on an automated line. In this regard, for the effective work of the complex, it is necessary to develop technological support and software for the manufacturing processes of each ring, to provide for the possibility of adjusting technological processes directly on the automated line with the participation of operators. On this basis, the tasks of technological support for the operation of the automated ring rolling complex at the OJSC “BELAZ” were formulated.
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DOBREV, STEFAN, NICOLA SANTORO y WEI SHI. "USING SCATTERED MOBILE AGENTS TO LOCATE A BLACK HOLE IN AN UN-ORIENTED RING WITH TOKENS". International Journal of Foundations of Computer Science 19, n.º 06 (diciembre de 2008): 1355–72. http://dx.doi.org/10.1142/s0129054108006327.
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A black hole in a network is a highly harmful host that disposes of any incoming agents upon their arrival. Determining the location of a black hole in a ring network has been studied when each node is equipped with a whiteboard. Recently, the Black Hole Search problem was solved in a less demanding and less expensive token model with co-located agents. Whether the problem can be solved with scattered agents in a token model remains an open problem. In this paper, we show not only that a black hole can be located in a ring using tokens with scattered agents, but also that the problem is solvable even if the ring is un-oriented. More precisely, first we prove that the black hole search problem can be solved using only three scattered agents. We then show that, with K (K ⩾ 4) scattered agents, the black hole can be located in O(kn + n log n) moves. Moreover, when K (K ⩾ K) is a constant number, the move cost can be reduced to O(n log n), which is optimal. These results hold even if both agents and nodes are anonymous.
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Prasath, Gm Arun. "INVENTORY MANAGEMENT THROUGH EXTENDED STAR-RING SUPPLY CHAIN NETWORK". Asian Journal of Pharmaceutical and Clinical Research 10, n.º 13 (1 de abril de 2017): 199. http://dx.doi.org/10.22159/ajpcr.2017.v10s1.19637.
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Objectives: The production-distribution inventory problem has two main sectors namely production and distribution. In this paper, the nonlinearmathematical model of extended star-ring supply chain network is developed.Methods: Planning a distribution network plays a vital role in minimizing the total expenditure of the project; to prove this, a ring network topology is taken to supply goods to the SWs and extended star network topology to supply goods to the selling stores. However, setting up separate SWs for each and every selling store will be highly expensive. Hence, keeping the minimum number of SWs is very important. Selection of SWs from the available SWs is done by replacing diverse values based on the distance limitation.Results: The suggested model is validated with the mathematical problem, and the optimum set of SWs is identified from the result. The result has been substantiated using analytic hierarchy process. Conclusion: The system of optimum number of SWs is obtained from the result.
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Yang, Li Jun, Ze Hui Zhang, Xin An Dang y Lin Li. "Properties of TiAl/TiAlN/TiAlCN Films Deposited by Arc Ion Plating on GCr15 Rings". Materials Science Forum 789 (abril de 2014): 449–54. http://dx.doi.org/10.4028/www.scientific.net/msf.789.449.
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Ring is one of the major textile spinning machine consumable part, it has an important influence on yarn quality and cost. Ring of domestic cotton spinning enterprises generally has poor hardness, bad accuracy, not durable and difficult to guarantee the quality of the yarn, foreign ring has excellent performance, but it is too expensive, so it is difficult to widely used in China[1]. Vacuum arc ion plating technology has a wide range of applications in the aerospace, automobile, mold, tool, electronics and other fields [2-3]. TiN film which is prepared by arc ion plating technology has been widely used because of the TiN film has poor oxidation resistance and wear resistance at high temperatures, so the ternary films are developed on TiN film, such as TiAlN [4], TiCN etc. Traveller circle in the ring on the slide to produce large amounts of heat, it makes the ring surface temperature reach 400°C. When higher than 400°C, the TiCN film failure, therefore, ring should not be plated on the TiCN films. While TiAlN film oxidation temperature reaches 800°C. In HSS twist drill, depositing of TiAlN film can improve the service life more than four times [5]. Studies [6-8] have found that using pulsed laser deposition and chemical vapor deposition technique to prepare TiAlCN film, its wear resistance, high temperature stability is better. Pulsed laser deposition is mainly used in laboratory research. It is difficult to deposit a large area uniform film. Chemical vapor deposition of deposition rate is less than the arc ion plating, and produces lots of waste gas, leading to the environment is polluted. Arc ion plating technology can deposit the uniform films of large area with high deposition rate and deposition with no environmental pollution, therefore, this study, by means of vacuum arc ion plating technology to prepare high-precision, long-life and low-cost domestic cotton spinning ring. In order to obtain the best film process parameters, the performance of film is investigated at different bias and arc current.
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Natalia, Monika, Zulfira Mirani y Yan Partawijaya. "Penerapan Pelapis Dinding Kawat Ayam di Desa Koto Marapak Kabupaten Padang Pariaman". Dinamisia : Jurnal Pengabdian Kepada Masyarakat 5, n.º 2 (27 de noviembre de 2020): 458–65. http://dx.doi.org/10.31849/dinamisia.v5i2.4682.
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Earthquake-safe house, the costs not expensive. We can eliminate earthquake damage by strengthening our house while paying attention the rules of structure. Use chicken wire reinforcement. Chicken wire reinforcement can strengthen the walls by wrapping. Chicken wire can also be used to strengthen practical columns as well as ring beams. And to improve the connection between practical column structural elements with ring beams and wall to column anchoring. Result is to be help the residents of Koto Marapak Village in Padang Pariaman to provide counseling and training to strengthen their homes so that they are earthquake resistant with economical costs. Because this area is very earthquake-prone. The method applied by conducting counseling, field surveys as well as discussions with community leaders, pilot / training (which is guided by the discovery team) that together with the community members work together to provide reinforcement of houses that are earthquake resistant.
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Hemalatha, Kanagarajan, Gunabalan Madhumitha, Amir Kajbafvala, Narayanan Anupama, Rajesh Sompalle y Selvaraj Mohana Roopan. "Function of Nanocatalyst in Chemistry of Organic Compounds Revolution: An Overview". Journal of Nanomaterials 2013 (2013): 1–23. http://dx.doi.org/10.1155/2013/341015.
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Heterocyclic motif is an important scaffold which has both industrial and pharmaceutical applications. These motifs can be prepared using wide variety of reaction conditions such as the use of expensive catalyst, toxic solvent, harsh reaction condition like the use of base, high temperature, and multistep reaction. Although various methods are involved, the chemistry arena is now shifted towards the greener way of synthesis. Nanocatalyst constitutes an important role in the green synthesis. This is because the activity of the catalyst resides in the exposed portion of the particles. By decreasing the size of the catalyst, advantages such as more surface area would be exposed to the reactant, only negligible amount would be required to give the significant result and selectivity could be achieved, thereby, eliminating the undesired products. The current review enlists the various types of nanocatalyst involved in the heterocyclic ring formation and also some other important functionalization over the ring.
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Alshehhi, Rasha, Chris S. Hanson, Laurent Gizon y Shravan Hanasoge. "Supervised neural networks for helioseismic ring-diagram inversions". Astronomy & Astrophysics 622 (febrero de 2019): A124. http://dx.doi.org/10.1051/0004-6361/201834237.
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Context. The inversion of ring fit parameters to obtain subsurface flow maps in ring-diagram analysis for eight years of SDO observations is computationally expensive, requiring ∼3200 CPU hours. Aims. In this paper we apply machine-learning techniques to the inversion step of the ring diagram pipeline in order to speed up the calculations. Specifically, we train a predictor for subsurface flows using the mode fit parameters and the previous inversion results to replace future inversion requirements. Methods. We utilize artificial neural networks (ANNs) as a supervised learning method for predicting the flows in 15° ring tiles. We discuss each step of the proposed method to determine the optimal approach. In order to demonstrate that the machine-learning results still contain the subtle signatures key to local helioseismic studies, we use the machine-learning results to study the recently discovered solar equatorial Rossby waves. Results. The ANN is computationally efficient, able to make future flow predictions of an entire Carrington rotation in a matter of seconds, which is much faster than the current ∼31 CPU hours. Initial training of the networks requires ∼3 CPU hours. The trained ANN can achieve a rms error equal to approximately half that reported for the velocity inversions, demonstrating the accuracy of the machine learning (and perhaps the overestimation of the original errors from the ring-diagram pipeline). We find the signature of equatorial Rossby waves in the machine-learning flows covering six years of data, demonstrating that small-amplitude signals are maintained. The recovery of Rossby waves in the machine-learning flow maps can be achieved with only one Carrington rotation (27.275 days) of training data. Conclusions. We show that machine learning can be applied to and perform more efficiently than the current ring-diagram inversion. The computation burden of the machine learning includes 3 CPU hours for initial training, then around 10−4 CPU hours for future predictions.
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Welker, Andrea, James Press, Kristin Sample-Lord y Virginia Smith. "Estimation of Rain Garden Field Hydraulic Conductivity Based on Spot Infiltration Tests". Water 17, n.º 3 (2 de febrero de 2025): 418. https://doi.org/10.3390/w17030418.
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Rain gardens are increasingly being used to control stormwater. Infiltration is a key component of volume control. Thus, determining the infiltration rate or field saturated hydraulic conductivity (Ksat) of rain gardens is critical to their continued successful operation. Designers and inspectors of rain gardens need to rapidly and efficiently determine the field Ksat. Prior research has found that single-ring infiltrometers (Princeton Hydro, Trenton, NJ, USA) can reliably be used to determine the infiltration rates of soils. The question often posed by designers and inspectors is “how many spot-infiltration tests are needed to sufficiently characterize the infiltration capacity of a rain garden?” Five rain gardens, varying in size from 62 to 429 m2, were analyzed for this study. Three different spot infiltration methods were used: single-ring (Princeton Hydro, Trenton, NJ, USA) (least sophisticated and expensive), modified Philip–Dunne (Villanova University, Villanova, PA, USA), and SATURO (METER Group, Pullman, WA, USA) (most sophisticated and expensive). These rain gardens also had been instrumented to capture the recession rates during either natural or artificial ponding events. The linear portion of the recession curve obtained during ponding events was used to provide the rain-garden-wide Ksat. It was found that the geometric mean of six spot infiltration tests provided a reliable Ksat value similar to that found by the recession rate, which best represents the value of Ksat for the entire rain garden. This indicates that an inspector can reliably determine the infiltration capacity of a rain garden in less than a day.
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Chandra, Anshuman, Krishnendu Chakrabarty y Mark C. Hansen. "Efficient Test Application for Core-Based Systems Using Twisted-Ring Counters". VLSI Design 12, n.º 4 (1 de enero de 2001): 475–86. http://dx.doi.org/10.1155/2001/75139.
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We present novel test set encoding and pattern decompression methods for core-based systems. These are based on the use of twisted-ring counters and offer a number of important advantages–significant test compression (over 10X in many cases), less tester memory and reduced testing time, the ability to use a slow tester without compromising test quality or testing time, and no performance degradation for the core under test. Surprisingly, the encoded test sets obtained from partially-specified test sets (test cubes) are often smaller than the compacted test sets generated by automatic test pattern generation programs. Moreover, a large number of patterns are applied test-per-clock to cores, thereby increasing the likelihood of detecting non-modeled faults. Experimental results for the ISCAS benchmark circuits demonstrate that the proposed test architecture offers an attractive solution to the problem of achieving high test quality and low testing time with relatively slower, less expensive testers.
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Li, Mengmeng, Sixuan Wang, Feifei Li, Lin Zhou y Lin Lei. "Iodine-mediated photo-controlled atom transfer radical polymerization (photo-ATRP) and block polymerization combined with ring-opening polymerization (ROP) via a superbase". Polymer Chemistry 11, n.º 41 (2020): 6591–98. http://dx.doi.org/10.1039/d0py01031f.
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Stepanenko, D. A. y A. N. Kindruk. "Variational Problem on Vibrations of Unequal-Thickness Rings and Its Application for Calculating Ultrasonic Vibration Concentrators". Science & Technique 23, n.º 4 (9 de agosto de 2024): 295–303. http://dx.doi.org/10.21122/2227-1031-2024-23-4-295-303.
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The paper considers a method for calculating the natural frequencies of vibrations of unequal-thickness rings, based on application of Hamilton’s variational principle and theories of vibrations of curved beams of the Euler-Bernoulli and Timoshenko type. Solutions of the problem are represented as Fourier series providing possibility of its reduction to the system of linear algebraic equations. The problem of determining natural frequencies is reduced to a generalized problem for the eigenvalues of matrices. Based on a comparison of the numerical results obtained for an eccentric ring with the results of calculations by the finite element method, the advantages of using the Timoshenko theory are shown, including increased calculation accuracy and the possibility to identify radial and radial-flexural eigenmodes. The possibility of reducing computational costs when using the Timoshenko theory is explored by representing the determinant of the block matrix describing the problem as a product of lower-order determinants. It is shown that the relations obtained on the basis of the Euler-Bernoulli theory, in the particular case of equal-thickness ring, lead to the well-known analytical formulas for the natural frequencies of the ring oscillations. The obtained results can be used to calculate ring concentrators of ultrasonic vibrations. The advantage of the proposed method in comparison with other known approaches, for example, the harmonic balance me-thod, consists in no need for the work with differential or integral-differential equations of vibrations, which are a rather complex structure for the case of unequal-thickness rings and require the use of computationally expensive operations, for example, discrete convolution, for their solution.
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Li, Guangzhi y Rahul Simha. "An efficient algorithm for reducing the number of Add‐Drop Multiplexers in SONET/WDM rings". Journal of High Speed Networks 11, n.º 1 (enero de 2002): 67–77. https://doi.org/10.3233/hsn-2002-215.
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This paper considers a network design problem introduced by Gerstel, Lin and Sasaki (INFOCOM'98) in which resource allocation is performed within a Wavelength Division Multiplexing (WDM) optical ring network to reduce overall equipment cost. The problem can be summarized as follows. The Add‐Drop Multiplexers (ADM's) that are used to terminate lightpaths in an optical (SONET/SDH) ring are expensive. A naive implementation would require ADM's for each wavelength at each node. However, by carefully assigning connections to wavelengths and routing the resulting lightpaths, one may avoid terminating all wavelengths at every node, and thereby reduce the number of ADM's needed. While Gerstel et al. consider wavelength assignment with respect to this problem, they do not consider the additional complication of routing. In this paper, we consider joint routing and wavelength assignment, and show that the number of ADM's required is significantly less than the number resulting from applying the heuristics in Gerstel et al. Our algorithm analyzes connection requirements and, using a decomposition based on Euler paths, performs routing and wavelength assignment.
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Varentsov, V. L., D. R. Hansevarov y D. V. Varentsov. "The generation of an internal molecular-beam target from expensive gaseous and nonvolatile substances for storage rings". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 352, n.º 3 (enero de 1995): 542–47. http://dx.doi.org/10.1016/0168-9002(95)90002-0.
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Kiernan, Philip y Klaus-Peter Henz. "Rings from the Forbidden Forest: the function and meaning of Roman trinket rings". Journal of Roman Archaeology 36, n.º 1 (junio de 2023): 73–95. http://dx.doi.org/10.1017/s1047759423000211.
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AbstractA group of 24 bronze finger-rings threaded onto a wire bracelet was unearthed in 2018 at the Roman vicus at Wareswald (the “Forbidden Forest”) in Gallia Belgica. The find is analyzed here alongside evidence for the use, sale, and production of Roman rings. The find represents the work of a local craftsman, active in the first quarter of the 4th c. CE. While the rings were made in a small rural town, they closely imitate expensive global ring forms. The function and meaning of the very common class of trinket rings to which the Wareswald rings belong are considered, along with how these rings were used to make statements about identity, including local and regional affiliations, literacy, marital status, or other social connections. It is suggested that the popularity of many trinket rings lay in their ability to provide a sense of participation in upper-class fashion at a very low price.
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Ilyin, Alexander, Igor Plokhov y Andrey Isakov. "The Simulation Model of a Sliding Contact". Environment. Technology. Resources. Proceedings of the International Scientific and Practical Conference 2 (8 de agosto de 2015): 111. http://dx.doi.org/10.17770/etr2013vol2.850.
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This paper deals with the brush slip ring contact modeling. Approaches the sliding contact problem with the synergy theory. The contact layer is considered using mechanical, electrical and thermal properties. The simulation model includes algorithms of: - generation of microscale contact surface, - approachment of two surfaces, - fritting and breakdown effects of oxide layer, - extracting clusters of conducting area, - calculating constriction resistance using fractal dimensionality, - generation of heat caused by electrical current and mechanical friction, - calculation of integral characteristics. The program implementing the model may be used to optimize the contact materials before time-consuming and expensive tests. Finally discusses the implemented model and its results, problems of verification and validation.
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Fenercioğlu, Tevfik Ozan y Tuncay Yalçinkaya. "Computational–Experimental Design Framework for Laser Path Length Controller". Sensors 21, n.º 15 (31 de julio de 2021): 5209. http://dx.doi.org/10.3390/s21155209.
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The application areas of piezoelectric materials are expanding rapidly in the form of piezo harvesters, sensors and actuators. A path length controller is a high-precision piezoelectric actuator used in laser oscillators, especially in ring laser gyroscopes. A path length controller alters the position of a mirror nanometrically by means of a control voltage to stabilize the route that a laser beam travels in an integral multiple of laser wavelength. The design and verification of a path length controller performance requires long (up to 3 months), expensive and precise production steps to be successfully terminated. In this study, a combined computational–experimental design framework was developed to control, optimize and verify the performance of the path length controller, without the need for ring laser gyroscope assembly. A novel framework was structured such that the piezoelectric performance characteristics were calculated using finite element analysis. Then, a stand-alone measurement system was developed to verify the finite element analysis results before system integration. The final performance of the novel framework was verified by a direct measurement method called mode-scanning, which is founded on laser interferometry. The study is concluded with the explanation of measurement errors and finite element correlations.
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Davies, Mark, Mannthalah Abubaker y Lorraine Bible. "A Flexible, Microfluidic, Dispensing System for Screening Drug Combinations". Micromachines 11, n.º 10 (18 de octubre de 2020): 943. http://dx.doi.org/10.3390/mi11100943.
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It is known that in many cases a combination of drugs is more effective than single-drug treatments both for reducing toxicity and increasing efficacy. With the advent of organoid screens, personalised medicine has become possible for many diseases. Automated pipetting to well plates is the pharmaceutical industry standard for drug screening, but this is relatively expensive and slow. Here, a rotary microfluidic system is presented that can test all possible drug combinations at speed with the use of droplets. For large numbers of combinations, it is shown how the experimental scale is reduced by considering drug dilutions and machine learning. As an example, two cases are considered; the first is a three-ring and three radii configuration and the second is a four ring and forty-eight radii configuration. Between these two, all other cases are shown to be possible. The proposed commercial instrument is shown to be flexible, the user choosing which wells to fill and which driver-computational sub-routine to select. The major issues addressed here are the programming theory of the instrument and the reduction of droplets to be generated by drug dilutions and machine learning.
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Fundarò, Pino, Paolo M. Tartara, Emmanuel Villa, Pasquale Fratto, Salvatore Campisi y Ettore O. Vitali. "Mitral Valve Repair: Is There Still a Place for Suture Annuloplasty?" Asian Cardiovascular and Thoracic Annals 15, n.º 4 (agosto de 2007): 351–58. http://dx.doi.org/10.1177/021849230701500420.
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Prosthetic ring annuloplasty is considered the gold standard technique for mitral valve repair, but it has been associated with some drawbacks. Suture annuloplasty is less expensive and may have some physiopathologic advantages. We reviewed the literature to assess clinical results of mitral suture annuloplasty. Thirteen series, each reporting more than 50 patients and published in the last 10 years, were included in the analysis. They comprised 1,648 patients with cumulative follow-up of 5,607 patient-years. Our review suggests that suture annuloplasty is a safe procedure, but a trend toward recurrence of annular dilatation with time was reported. In selected cases, suture annuloplasty is effective, and its mid-term clinical results are encouraging and compare well with those of prosthetic ring repair series. The quality of the results varies according to the particular annuloplasty technique used and to the mitral valve pathology treated. Recent technical modifications have been found to decrease the incidence of repair failure and promise to improve the reproducibility of the procedure. Further investigations are warranted to better assess the long-term results of suture annuloplasty, and to determine whether its theoretical functional advantages translate into a real clinical benefit.
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van der Borg, Guus, Harry Warner, Melina Ioannidis, Geert van den Bogaart y Wouter H. Roos. "PLA 3D Printing as a Straightforward and Versatile Fabrication Method for PDMS Molds". Polymers 15, n.º 6 (17 de marzo de 2023): 1498. http://dx.doi.org/10.3390/polym15061498.
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3D printing is gaining traction in research and development as a way to quickly, cheaply, and easily manufacture polydimethylsiloxane (PDMS) molds. The most commonly used method is resin printing, which is relatively expensive and requires specialized printers. This study shows that polylactic acid (PLA) filament printing is a cheaper, more readily available alternative to resin printing, that does not inhibit the curing of PDMS. As a proof of concept, a PLA mold for PDMS-based wells was designed, and 3D printed. We introduce an effective method to smooth the printed PLA mold, based on chloroform vapor treatment. After this chemical post-processing step, the smoothened mold was used to cast a ring of PDMS prepolymer. The PDMS ring was attached to a glass coverslip after oxygen plasma treatment. The PDMS–glass well showed no leakage and was well suited to its intended use. When used for cell culturing, monocyte-derived dendritic cells (moDCs) showed no morphological anomalies, as tested by confocal microscopy, nor did they show an increase in cytokines, as tested using ELISA. This underlines the versatility and strength of PLA filament printing and exemplifies how it can be valuable to a researcher’s toolset.
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Reynolds, T. P. S., H. C. Burridge, R. Johnston, G. Wu, D. U. Shah, O. A. Scherman, P. F. Linden y M. H. Ramage. "Cell geometry across the ring structure of Sitka spruce". Journal of The Royal Society Interface 15, n.º 142 (mayo de 2018): 20180144. http://dx.doi.org/10.1098/rsif.2018.0144.
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For wood to be used to its full potential as an engineering material, it is necessary to quantify links between its cell geometry and the properties it exhibits at bulk scale. Doing so will make it possible to predict timber properties crucial to engineering, such as mechanical strength and stiffness, and the resistance to fluid flow, and to inform strategies to improve those properties as required, as well as to measure the effects of interventions such as genetic manipulation and chemical modification. Strength, stiffness and permeability of timber all derive from the geometry of its cells, and yet current practice is to predict them based on properties, such as bulk density, that do not directly describe the cell structure. This work explores links between micro-computed tomography data for structural-size pieces of wood, which show the variation of porosity across the wood's ring structure, and high-resolution tomography showing the geometry of the cells, from which we measure cell length, lumen area, porosity, cell wall thickness and the number density of cells. High-resolution scans, while informative, are time-consuming and expensive to run on a large number of samples at the scale of building components. By scanning the same volume of timber at both low and high resolutions (high-resolution scans over a near-continuous volume of timber of approx. 20 mm 3 at 15 μm 3 per voxel), we are able to demonstrate correlations between the measurements at the two different resolutions, reveal the physical basis for these correlations, and demonstrate that the data from the low-resolution scan can be used to estimate the variation in (small-scale) cell geometry throughout a structural-size piece of wood.
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Chaojun, Yang, Amberbir Wondimu y Ayodeji Olalekan Salau. "Comparative study of passive magnetic bearing using four ring magnets: a critical review". International Journal of Power Electronics and Drive Systems (IJPEDS) 15, n.º 2 (1 de junio de 2024): 685. http://dx.doi.org/10.11591/ijpeds.v15.i2.pp685-695.
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Researchers on reducing energy losses caused by friction in small-scale wind turbines. This is crucial because a significant amount of energy is wasted due to friction in the main roller bearing. In order to overcome this, the concept of levitation has gained popularity. Levitation is achieved by employing the repelling forces between two opposing poles of a permanent magnet (PM), significantly reducing friction between the turbine stator and rotor. As a result, the overall energy production of the turbine increases. The use of passive permanent magnet bearings has several disadvantages, such as limited load-bearing capacity and rigidity. To address these limitations, we conducted numerical studies on four different configurations in order to enhance load-bearing capacity and stiffness. The results showed that the radial configuration outperformed the axial-type configuration in terms of stiffness and load-bearing capabilities in all four arrangements. Furthermore, it was revealed that radial passive magnetic bearings with adequate air gaps are not only more efficient but also less expensive than employing iron cores at the rear and between ring magnets for small-scale wind turbines.
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Araujo, Marcos E. V., Eloiny G. Barbosa, Marcio A. Martins, Paulo C. Corrêa, Elisa G. Barbosa, Rodrigo S. L. Araújo y Felipe A. Gomes. "CFD Analysis of Different Aeration Ducts on Temperature and Airflow in Stored Maize". Journal of Agricultural Science 11, n.º 2 (15 de enero de 2019): 301. http://dx.doi.org/10.5539/jas.v11n2p301.
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The conditions of temperature and airflow distribution in the mass of stored grains are highly influenced by the configuration of the aeration ducts. However, silos are large structures, and the physical experiments on them become expensive and slow. Thus, this study aimed model and evaluate the temperature and airflow distribution in a maize mass, stored in a metal silo with different geometries of aeration ducts, using CFD (computational fluid dynamic). CFD was used to model and evaluate aeration ducts of square, ring, double bar and single bar shape. The proposed model was validated from experimental data. The airflow distribution and temperature in the grain mass were analyzed at different points. The ducts of a square and a ring shape showed better distributions of airflow in the grain mass, with averages of 0.00236 m s-1 and 0.00275 m s-1, respectively. The square shape aeration duct, presented better temperature values in the middle layer of the grain mass during aeration, with average 25.09 °C. CFD can be used in decision making for the best design of a silo, saving financial resources and time, as long as the parameters used in the simulation are reliable and represent the reality.
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Lam, Wai Kit, Anton Krynkin y Shiu Keung Tang. "Topology optimization of array of split-ring resonators in two-dimensional acoustic waveguide for low-frequency transmission problems". Journal of the Acoustical Society of America 154, n.º 4_supplement (1 de octubre de 2023): A189. http://dx.doi.org/10.1121/10.0023223.
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This work focuses on the topology optimization of an array of split-ring resonators to achieve nearly zero transmission in the low-frequency regime ranging from 500 Hz to 1000 Hz in 2D waveguide, under the condition of normal-incident plane wave and based on a homogenization scheme known as the Effective Medium Approach (EMA). The EMA transforms each individual resonator defined by its outer radius (rout), neck thickness (h), and the slit width (d), into a homogenous medium characterized by frequency-dependent physical parameters. The transmission coefficient (Tcoeff) of the array can thus be easily evaluated without relying on computationally expensive Finite Element (FE) software. Two optimization algorithms, namely “Sequential Quadratic Programming (SQP)” and “Genetic Algorithm (GA),” have been implemented to the abovementioned topological parameters with sum of Tcoeff being the objective function to minimize. Accuracy of the results has also been validated using software COMSOL Multiphysics® and the satisfactory level of accuracy has proven this approach to be a more efficient and time-saving method to conduct topology optimization of split-ring resonators in low-frequency regime. Moreover, it is noteworthy that the optimized dimensions of resonators are over 20 times smaller than the wavelength in the low frequency range where almost-zero transmission is achieved.
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Wilson, Rob, Rohit Rao, Miloš Rydval, Cheryl Wood, Lars-Åke Larsson y Brian H. Luckman. "Blue Intensity for dendroclimatology: The BC blues: A case study from British Columbia, Canada". Holocene 24, n.º 11 (12 de agosto de 2014): 1428–38. http://dx.doi.org/10.1177/0959683614544051.
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Maximum latewood density (MXD) is a strong proxy of summer temperatures. Despite this, there is a paucity of long MXD chronologies in the Northern Hemisphere, which limits large-scale tree-ring-based reconstructions of past temperature which are dominated by ring-width (RW) data – a weaker temperature proxy at inter-annual time-scales. This paucity likely results from the relative expense of measuring MXD and the lack of laboratories with the facilities to measure it. Herein, we test the ability of a relatively new, less expensive, tree-ring parameter, Blue Intensity (BI), to act as a surrogate parameter for MXD. BI was measured on Engelmann spruce samples from British Columbia where MXD had previously been measured to allow direct comparison between the two parameters. Signal strength analyses indicate that 8 MXD series were needed to acquire a robust mean chronology while BI needed 14. Utilising different detrending methods and parameter choices (RW + MXD vs RW + BI), a suite of reconstruction variants was developed. The explained variance from the regression modelling (1901–1995) of May–August maximum temperatures ranged from 52% to 55%. Validation tests over the earlier 1870–1900 period could not statistically distinguish between the different variants, although spectral analysis identified more lower frequency information extant in the MXD-based reconstructions – although this result was sensitive to the detrending method used. Ultimately, despite the MXD-based reconstruction explaining slightly more of the climatic variance, statistically robust reconstructions of past summer temperatures were also derived using BI. These results suggest that there is great potential in utilising BI for dendroclimatology in place of MXD data. However, more experimentation is needed to understand (1) how well BI can capture centennial and lower frequency information and (2) what biases may result from wood discolouration, either from species showing a distinct heartwood/sapwood boundary or from partly decayed sub-fossil samples.
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WANG, Jun, Zhi LI, Quan ZHU, Yan-hu WU, Yong-feng SHAO, Jian-wei QIN, Yi-jiang CHEN y Liang CHEN. "A modified tricuspid valve annuloplasty technique for functional tricuspid regurgitation". Chinese Medical Journal 126, n.º 18 (20 de septiembre de 2013): 3634–38. http://dx.doi.org/10.3760/cma.j.issn.0366-6999.20122810.
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Background Functional tricuspid regurgitation often occurs in patients with concomitant left sided, valve disease. Several types of tricuspid valve annuloplasty have been described, but there is no consensus on the management of functional tricuspid regurgitation. We report a modified annuloplasty technique and compare its efficacy with the conventional Kay technique. Methods A retrospective review was made of 60 patients who received tricuspid valve annuloplasty (group A, modified method; group B, Kay technique) and the early and midterm outcomes of modified method and Kay technique were compared. Results Three patients underwent ring annuloplasty using a semirigid Carpentier-Edwards ring due to failing suture annuloplasty. All patients were completely cured when they left the hospital. The follow-up time was (32±7) months in group A and (30±7) months in group B. After three years, tricuspid regurgitation decreased by more than two grades in 13 patients in group A and 11 in group B. The mean postoperative regurgitation grade in group A was lower than group B at 12, 24 and 36 months but not significantly. Three of 28 patients developed recurrent tricuspid regurgitation in group A and five of 26 patients in group B during the follow-up period (three deaths and three ring annuloplasties excluded). Freedom from recurrent tricuspid regurgitation in group A was higher than that group B at all follow-up points. Postoperative right atrium diameter, right ventricle endodiastolic dimension and tricuspid regurgitation area decreased obviously in both groups. The right ventricle endodiastolic dimension and tricuspid regurgitation area improved more significantly in group A than group B over three years of follow-up, Conclusions The modified annuloplasty technique achieved the same outcomes as the conventional Kay annuloplasty over the first three years postoperation. As this modified technique is simple and less expensive, it is another option for correction of functional tricuspid regurgitation.
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Niu, Xiang Yu, Tong Wang y Kai Fan Zhang. "A Novel Network and its Application to Intelligent Community". Advanced Materials Research 622-623 (diciembre de 2012): 166–69. http://dx.doi.org/10.4028/www.scientific.net/amr.622-623.166.
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The level of performance of intelligent community is greatly promoted by the development of networking technologies. Some researchers obtained the achievement of intelligent community by utilizing complex algorithm and advanced equipment that makes the solution very expensive. Our research aims to find out a way to intellectualize residential community that is easy to implement, highly reliable and cost-effective. In this study, we present a system which consists of three layers based on the ring topology. For reliability and the ease of maintenance, we propose an automatic fault detection and handling function that is able to quickly detect any fault of the circuit and automatically eliminate the issue. Experiment results demonstrate that the proposed system is extremely efficient, intelligent, and environmentally friendly while being highly reliable and affordable.
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Vukšić, Milan, Martina Kocijan, Lidija Ćurković, Tina Radošević, Damjan Vengust y Matejka Podlogar. "Photocatalytic Properties of Immobilised Graphitic Carbon Nitride on the Alumina Substrate". Applied Sciences 12, n.º 19 (27 de septiembre de 2022): 9704. http://dx.doi.org/10.3390/app12199704.
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Textile industries significantly impact the contamination of wastewater. Conventional wastewater treatment methods consider the most common pollutants; however, they are very expensive and commonly produce toxic by-products. In the scientific community, advanced oxidation processes appear to be the most appealing, and a majority of the published work considers heterogeneous photocatalysis for the degradation of various toxic chemicals. For convenience, the reaction is performed directly in the water environment. In this work, a metal-free graphitic carbon nitride (g-C3N4) was prepared through a simple thermal method using urea as a precursor. Prepared g-C3N4 was deposited on the surface of the alumina ceramic ring by the dip-coating method using ethylene glycol as binder. The alumina ceramic ring, as substrate, was prepared by the slip casting method. Photocatalytic properties of immobilised graphitic carbon nitride were used for degradation of methylene blue as a model pollutant under simulated solar light irradiation. The photocatalyst was characterised by XRD, FTIR, UV-Vis DRS, TGA, BET and SEM/EDX analyses. The photocatalytic degradation of MB from an aqueous solution was found to increase with increasing irradiation time. It was found that the graphitic carbon nitride immobilised on alumina ceramic is convenient for largescale environmental applications because the whole setup is cheap, nontoxic, easy to operate and offers reusability with a high removal rate of MB after three consecutive cycles.
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Camacho, Jorge, Luis Medina, Jorge F. Cruza, José M. Moreno y Carlos Fritsch. "Multimodal Ultrasonic Imaging for Breast Cancer Detection". Archives of Acoustics 37, n.º 3 (1 de noviembre de 2012): 253–60. http://dx.doi.org/10.2478/v10168-012-0033-4.
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Abstract Ultrasound is used for breast cancer detection as a technique complementary to mammography, the standard screening method. Current practice is based on reflectivity images obtained with conventional instruments by an operator who positions the ultrasonic transducer by hand over the patient’s body. It is a non-ionizing radiation, pain-free and not expensive technique that provides a higher contrast than mammography to discriminate among fluid-filled cysts and solid masses, especially for dense breast tissue. However, results are quite dependent on the operator’s skills, images are difficult to reproduce, and state-of-the-art instruments have a limited resolution and contrast to show micro-calcifications and to discriminate between lesions and the surrounding tissue. In spite of their advantages, these factors have precluded the use of ultrasound for screening. This work approaches the ultrasound-based early detection of breast cancer with a different concept. A ring array with many elements to cover 360◦ around a hanging breast allows obtaining repeatable and operator-independent coronal slice images. Such an arrangement is well suited for multi-modal imaging that includes reflectivity, compounded, tomography, and phase coherence images for increased specificity in breast cancer detection. Preliminary work carried out with a mechanical emulation of the ring array and a standard breast phantom shows a high resolution and contrast, with an artifact-free capability provided by phase coherence processing.
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Khairedinova, Elzara А. "The Twelfth-Fourteenth-Century Finger-Rings and Signet-Rings from Eski-Kermen". Materials in Archaeology, History and Ethnography of Tauria, n.º XXVI (2021): 205–28. http://dx.doi.org/10.37279/2413-189x.2021.26.205-228.
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This paper introduces into the scholarship finger-rings and signet-rings discovered on the plateau of Eski-Kermen during the excavations in recent years. The twelfth- and thirteenth-century finger- and signet-rings uncovered in the churches in quarters I and II were modest bronze ornaments of featuring décor belonging to the group of Byzantine-circle artefacts. Adult women often wore a pair or a set of three pieces of the ornaments of the kind. The fourteenth-century hand ornaments comprise only signet-rings, partially attributable to the Byzantine circle and partially to the artefacts made by Seljuk artisans. Predominant were expensive ornaments of silver or gold. The difference between the assortment of ornaments from the twelfth and thirteenth centuries and those from the fourteenth century can be explained not only by the change of fashion, but also by the different social status of those who lived in various districts of the provincial town. In the twelfth and thirteenth centuries, only the ordinary townspeople lived in quarters I and II, where only the bronze ornaments originate from. In the fourteenth century, the members of wealthy families were buried into slabbed graves located in the area in front of the basilica in the town centre, where silver and gold signet-rings were found. In the fourteenth century, signet-rings made a part of women’s and children’s attire. Young women, 18–20 and 19–25 years old, wore one signet-ring at once, on the fourth finger of the right hand; older women, 30–35 years old, decorated their left hand with a set of two signet-rings made in the same style. Young girls wore only one signet-ring on the third finger of the left hand. There were no signet-rings specially made for children: they got reshaped adults’ ornaments.
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Siregar, Hairani y Fajar Utama. "Welfare of families who have children with disabilities through empowering the establishment of a curtain stitch business group". ABDIMAS TALENTA: Jurnal Pengabdian Kepada Masyarakat 5, n.º 2 (2 de diciembre de 2020): 479–89. http://dx.doi.org/10.32734/abdimastalenta.v5i2.4709.
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This Community Service program is one of the efforts made so that families of children with disabilities have a good source of income. The care of children with disabilities is different from other ordinary children. Children with disabilities need special protection, especially from their families. Caring for children with disabilities is very expensive, until children with disabilities get their basic rights as children. With this service program, children with disabilities can grow and develop like other ordinary children. The training was conducted by forming a curtain-tailing group from the Medan Polonia Women's Community (KPMP). From the results of this training, all group members can measure, sew and install pleated curtains and ring styles. This training gives parents who have children with disabilities have economic resources to continue a good life without having to leave their children at home alone.
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Lewerentz, Lars y Ralf Schneider. "Simplified Optimization of the Magnetic Configuration of HEMP-Thrusters". Applied Sciences 13, n.º 6 (9 de marzo de 2023): 3491. http://dx.doi.org/10.3390/app13063491.
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One type of ion thruster that has gained attention in recent years is the High Efficiency Multistage Plasma (HEMP) thruster. Optimizing the performance of these thrusters can be challenging due to the complexity of the underlying physics. Since the construction of new designs is expensive, cheaper methods for optimization, e.g., numerical optimization, are being sought. This paper presents a fast, analytical approach to finding realistic starting points for the magnetic geometry design of HEMP thrusters. First, a ratio of length to radius is presented, where the magnetic field is especially parallel at the center of the magnetic ring. This result is confirmed with the open-source library magpylib. Its speed and accuracy qualify this tool for further optimization processes. Here, we present some simple performance indicators, which may be beneficial to characterize the magnetic field structure for further optimization.
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Castellini, Mirko, Simone Di Prima, David Moret-Fernández y Laurent Lassabatere. "Rapid and accurate measurement methods for determining soil hydraulic properties: A review". Journal of Hydrology and Hydromechanics 69, n.º 2 (21 de mayo de 2021): 121–39. http://dx.doi.org/10.2478/johh-2021-0002.
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Abstract The determination of soil hydraulic properties is important in several environmental sciences but may be expensive and time consuming. Therefore, during the last decades, a great effort has been made in soil sciences to develop relatively easy, robust, and inexpensive methods for soil hydraulic characterization. In this manuscript, we reviewed and discussed different infiltrometer techniques in light of the available experimental applications. More specifically, we considered the simplified falling head (SFH) infiltrometer technique and the single-ring infiltration experiment of the Beerkan type. Concerning this latter method, we considered different algorithms for data analysis: two simplified methods based on the analysis of transient (TSBI) and steady (SSBI) Beerkan infiltration data, and the Beerkan Estimation of Soil pedoTransfer parameters algorithm (BEST), that allows to estimate the soil characteristics curves, i.e., the soil water retention curve and hydraulic conductivity functions. For a given method, after dealing briefly theory and practice, available literature references were reported to account for specific applications in order to provide findings on method validation and application. With the aim to provide practical information on available tools for a simpler application of the reviewed methods, several video tutorials were reported to show i) how to conduct correctly field experiments and ii) how to calculate saturated hydraulic conductivity or soil hydraulic functions using user-friendly tools for data analysis. Finally, details on a new automated single-ring infiltrometer for Beerkan infiltration experiments (i.e., construction, assembly and field use) were presented.
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Grover, Ronald O., Xiaofeng Yang, Scott Parrish, Lorenzo Nocivelli, Katherine J. Asztalos, Sibendu Som, Yanheng Li et al. "CFD simulations of electric motor end ring cooling for improved thermal management". Science and Technology for Energy Transition 77 (2022): 17. http://dx.doi.org/10.2516/stet/2022015.
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Proper thermal management of an electric motor for vehicle applications extends its operating range. One cooling approach is to impinge Automatic Transmission Fluid (ATF) onto the rotor end ring. Increased ATF coverage correlates to enhanced heat transfer. Computational Fluid Dynamics (CFD) analytical tools provide a mechanism to assess motor thermal management prior to hardware fabrication. The complexity of the fluid flow (e.g., jet atomization, interface tracking, wall impingement) and heat transfer makes these simulations challenging. Computational costs are high when solving these flows on high-speed rotating meshes. Typically, a Volume-of Fluid (VOF) technique (i.e., two-fluid system) is used to resolve ATF dynamics within this rotating framework. Suitable numerical resolution of the relevant physics for thin films under strong inertial forces at high rotor speeds is computationally expensive, further increasing the run times. In this work, a numerical study of rotor-ring cooling by ATF is presented using a patent automated Cartesian cut-cell based method coupled with Automatic Mesh Refinement (AMR). This approach automatically creates the Cartesian mesh on-the-fly and can effectively handle complex rotating geometries by adaptively refining the mesh based on local gradients in the flow field which results in better resolution of the air-ATF interface. A Single non-inertial Reference Frame (SRF) approach is used to account for the rotating geometry and to further improve the overall computational efficiency. Quasi-steady state conditions are targeted in the analysis of the results. Important physics such as ATF jet structure, velocity detail near the air-jet interface, ATF coverage/accumulation on the ring surface, and cooling capacity are presented for a low-resolution Reynolds averaged Navier-Stokes (RANS), high-resolution RANS, and high-resolution Large-Eddy Simulation (LES) models. Computations are scaled over hundreds of cores on a supercomputer to maximize turnaround time. Each numerical approach is shown to capture the general trajectory of the oil jet prior to surface impingement. The high-resolution LES simulation, however, is superior in capturing small scale details and heat transfer between the free jet and surrounding air.
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Singh, Maya Shankar, Pragya Pali, Dhananjay Yadav y Gaurav Shukla. "Copper(II)-Catalyzed [3+2] Annulation of Thioamides with AIBN: Facile Access to Highly Functionalized Thiazolidin-4-ones". Synthesis 54, n.º 06 (10 de noviembre de 2021): 1613–20. http://dx.doi.org/10.1055/a-1693-7535.
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AbstractAn efficient and versatile copper-catalyzed intermolecular radical [3+2] annulation of thioamides with azobisisobutyronitrile (AIBN) is described. This two-component copper(II)-catalyzed transformation is achieved in one pot via cascade formation of C–S/C–N bonds through cyclization of an in situ generated N,S-acetal intermediate derived from a β-ketothioamide. This operationally simple method allows direct access to synthetically demanding thiazolidin-4-ones in good to excellent yields containing diverse functional groups of different electronic and steric nature. The readily available reaction partners, the avoidance of expensive/toxic reagents and a gram-scale synthesis are additional attributes of this strategy. AIBN plays a dual role as a radical initiator and an unusual source of a two-carbon coupling partner. Notably, the products possess Z stereochemistry with regard to the exocyclic C=C double bond at position 2 of the thiazolidine ring.
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DIKAIAKOS, MARIOS D., ANNE ROGERS y KENNETH STEIGLITZ. "FUNCTIONAL ALGORITHM SIMULATION OF THE FAST MULTIPOLE METHOD: ARCHITECTURAL IMPLICATIONS". Parallel Processing Letters 06, n.º 01 (marzo de 1996): 55–66. http://dx.doi.org/10.1142/s0129626496000078.
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Functional Algorithm Simulation is a methodology for predicting the computation and communication characteristics of parallel algorithms for a class of scientific problems, without actually performing the expensive numerical computations involved. In this paper, we use Functional Algorithm Simulation to study the parallel Fast Multipole Method (FMM), which solves the N-body problem. Functional Algorithm Simulation provides us with useful information regarding communication patterns in the algorithm, the variation of available parallelism during different algorithmic phases, and upper bounds on available speedups for different problem sizes. Furthermore, it allows us to predict the performance of the FMM on message-passing multiprocessors with topologies such as cliques, hypercubes, rings, and multirings, over a wider range of problem sizes and numbers of processors than would be feasible by direct simulation. Our simulations show that an implementation of the FMM on low-cost, scalable ring or multiring architectures can attain satisfactory performance.
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Hoedlmoser, H., J. Brönner, V. Bandalo, F. Wahl y M. B. Greiter. "SIMULATION OF OSL AND TLD DOSEMETER RESPONSE FOR THE DEVELOPMENT OF NEW EXTREMITY DOSEMETERS". Radiation Protection Dosimetry 185, n.º 2 (21 de enero de 2019): 222–30. http://dx.doi.org/10.1093/rpd/ncy299.
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Abstract The individual monitoring service at the Helmholtz Zentrum München is currently developing a new eye lens dosemeter to be integrated in radiation protection glasses and a new ring dosemeter using a new BeOSL detector element for extremity dosimetry developed by Dosimetrics. In the design process for the new eye lens dosemeter, MCNP6 Monte Carlo simulations were used to model the energy and angular response of new dosemeters before ordering the expensive tools for injection molding. This study describes the simulation of the dosemeter and detector, and the involved calculations do obtain the response in terms of the radiation protection quantity Hp(3). Simulations were carried out also for existing whole body dosemeters and TLD rings in order to verify the MC tools. With the final dosemeter prototypes becoming available earlier this year, all MC models could be verified and show very good agreement with experimental data.
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Tretiak, Sergei. "(Invited) Machine Learning in Chemistry: Reactive Force Fields for Carbon Structure Formation". ECS Meeting Abstracts MA2024-01, n.º 9 (9 de agosto de 2024): 881. http://dx.doi.org/10.1149/ma2024-019881mtgabs.
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Machine learning (ML) became a premier tool for modeling chemical processes and materials properties. ML interatomic potentials have become an efficient alternative to computationally expensive quantum chemistry simulations. In the case of reactive chemistry designing high-quality training data sets is crucial to overall model accuracy. To address this challenge, we develop a general reactive ML interatomic potential through unbiased active learning with an atomic configuration sampler inspired by nanoreactor molecular dynamics. The resulting model is then applied to study five distinct condensed-phase reactive chemistry systems: carbon solid-phase nucleation, graphene ring formation from acetylene, biofuel additives, combustion of methane and the spontaneous formation of glycine from early-earth small molecules. In all cases, the results closely match experiment and/or previous studies using traditional model chemistry methods. Importantly, the model does not need to be refit for each application, enabling high throughput in silico reactive chemistry experimentation.
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Li, Xiang‐Yang, Liwu Liu, Peng‐Jun Wan y Ophir Frieder. "Practical traffic grooming scheme for single‐hub SONET/WDM rings". Journal of High Speed Networks 11, n.º 2 (enero de 2002): 103–19. https://doi.org/10.3233/hsn-2002-218.
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In SONET/WDM networks, one fiber supports multiple wavelengths and each wavelength supports several low rate tributary streams. ‘Traffic grooming’ then is defined as properly using SONET Add/Drop Multiplexer to electronically multiplex and demultiplex required tributary traffic patterns with minimal resource cost (wavelengths and ADMs). This paper studies traffic grooming problem in single hub SONET/WDM networks and extends existing results. We analyze the real deployments, generalize their results, and study the practical special cases. We prove that BLSR/2 would never be more expensive than UPSR under any traffic pattern. We also present the exact minimum costs of uniform traffic in both UPSR and BLSR/2. We give approximation algorithms for optimal grooming of non‐uniform traffic. Finally, we consider how to select the line speeds if there are two different line speeds available.
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Pericolo, Osvaldo, Camilla Avanzi, Andrea Piotti, Francesco Ripullone y Paola Nola. "A Novel Simplified Protocol for Pre-Processing Whole Wood Samples for Stable Isotope Analysis in Tree Rings". Forests 14, n.º 3 (20 de marzo de 2023): 631. http://dx.doi.org/10.3390/f14030631.
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In the context of climate change, the stable isotope analysis of tree rings may play a crucial role in deciphering the eco-physiological mechanisms underlying forest decline and dieback phenomena. However, this technique is often considered expensive, time-consuming, and with several methodological constraints. Specifically, milling and transferring the material from jars to vials during the different steps of sample preparation involve risk of contamination among samples and loss of sample material. When dealing with declining trees (i.e., trees affected by loss of vitality with strong percentage of defoliation and reduction in growth) and trees subjected to extreme events or negative pointer years (characterized by extremely narrow ring) the sample preparation is particularly difficult because of scarce amount of wood material. In such a case, pooling rings from several years to achieve the minimum weight of wood is often necessary, thus losing information at the annual resolution. In order to overcome such limitations, we developed a novel protocol for quick and accurate whole-wood pre-processing, testing it on oak tree rings of different widths taken from living trees. The main novelty introduced by our protocol was freezing tree-ring samples at −80 °C and milling multiple samples at a time by using a 24-tube plate. The results showed that our novel simplified protocol significantly reduced the pre-processing time with respect to the standard protocol (12 vs. 284 sec/sample), while achieving the same wood particle size, limiting the loss of wood material and reducing the risk of contamination among samples.