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1
Zhao, Lian Hua, Bao Ling Xie, and Li Hua Fan. "CR/EPDM Blends with Steel Friction and Wear Characteristics under Dry Sliding." Applied Mechanics and Materials 341-342 (July 2013): 291–95. http://dx.doi.org/10.4028/www.scientific.net/amm.341-342.291.
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CR is often used to make the foreskin material transport belts, wires, cables, and the manufacture of oil hose, gaskets, equipment and chemical resistant bushing. EPDM is often used to produce heat-resistant conveyor belts, cables, wires, anti-corrosion lining, gaskets, waterproof sheet, door and window seals, etc. The same hardness and different proportions of CR/EPDM blends with steel under dry friction pair as the research object to seek friction characteristics of different formulations of rubber with steel metal in the dynamic coordination. Friction test at a constant low load, constant temperature, the different mixing ratio of CR/EPDM blends, friction, wear, friction coefficient variation with engine speed. The test results to a reasonable choice of conveyor belts to improve the overall efficiency and life of rubber - metal friction pairs.
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Саврико, А. В., С. Н. Лымич, К. В. Кружаев, В. С. Левин, and А. В. Москвичев. "INFLUENCE OF GAS-DYNAMIC TESTING RIG PIPELINES MATERIAL ON THEIR DYNAMIC CHARACTERISTICS." ВЕСТНИК ВОРОНЕЖСКОГО ГОСУДАРСТВЕННОГО ТЕХНИЧЕСКОГО УНИВЕРСИТЕТА, no. 5 (November 19, 2021): 118–25. http://dx.doi.org/10.36622/vstu.2021.15.5.017.
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Приведено исследование зависимости газодинамических характеристик стенда от применяемого материала трубопровода. Oсновополагающими факторами, влияющими на работоспособность стенда, являются выходные параметры - давление и расход рабочего тела, которые напрямую зависят от потерь давления на трение, создаваемого элементами стенда. Для оценки степени влияния материалов на потери стенда выбраны два вида труб: полипропиленовые и металлические. Аналитические расчёты потери давления рассматриваемых трубопроводов из различного материала показали, что трубопроводы из полипропилена предпочтительнее. Однако при проведении эксперимента получены противоположные данные, которые показали, что в полипропиленовых магистралях возможно присутствие значительного количества диафрагм: в местах пайки труб, образовавшихся в процессе изготовления. Именно этот факт способствует существенному повышению значений сопротивлений в полипропиленовых трубопроводах на 20 % по сравнению со стальными трубами, где диафрагмы отсутствуют. В результате проведения исследования был введен коэффициент, учитывающий влияние диафрагм полипропиленового трубопровода при аналитическом расчете на сопротивление. Для сохранения более точных снимаемых значений с газодинамических стендов целесообразнее использовать трубопроводы из металла, в которых рассчитать потери возможно с отклонениями до 3 % Here we give the study of the dependence of the gas-dynamic characteristics of the stand on the pipeline material used. The fundamental factors affecting the performance of the stand are the output parameters-the pressure and flow rate of the working fluid, which directly depend on the friction pressure losses created by the elements of the stand. To assess the degree of influence of materials on the losses of the stand, we selected two types of pipes: polypropylene and metal. Analytical calculations of the pressure loss of the considered pipelines made of various materials have shown that pipelines made of polypropylene are preferable. However, during the experiment, we obtained the opposite data, which showed that a significant number of diaphragms may be present in polypropylene pipelines: in the places of soldering of pipes formed during the manufacturing process. This fact contributes to a significant increase in the resistance values in polypropylene pipelines by 20 % compared to steel pipes, where there are no diaphragms. As a result of the study, we introduced a coefficient that takes into account the influence of polypropylene pipeline diaphragms in the analytical calculation of resistance. To preserve more accurate values taken from gas-dynamic stands, it is more expedient to use metal pipelines in which it is possible to calculate losses with deviations of up to 3 %
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Xu, Xing Xin, Xiao Hui Zhang, Chuan Shao Liu, and Bo Zhao. "Drilling Characteristics of SiC Particle Reinforced Aluminum-Matrix Composites with Ultrasonic Vibration." Key Engineering Materials 455 (December 2010): 302–6. http://dx.doi.org/10.4028/www.scientific.net/kem.455.302.
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With the rapid development of aviation at home, particle reinforced metal matrix composites (PRMMCs) has been widely applied recently. But at the same time, the difficult machining has gradually been one of the most outstanding bottle-necks that restrict the rapid enhancement of productivity. Here, in virtue of the self-developed ultrasonic drilling equipment, hole-making experiments of common and ultrasonic vibration drilling are performed on SiC particle reinforced aluminum-matrix composites （SiCp/Al）with different content of SiC by using two types of tungsten carbide drill. Drilling characteristics of machining composites with ultrasonic vibration are analyzed from such respects as the composites crush, drilling force, drill wear and hole surface quality. Studies show that, during the ultrasonic vibration drilling process, SiC particle in the composites is prone to break along the crystal connection boundary or suffer ductile fracture under the dynamic ultrasonic impulse, in which the cutting resistance could be reduced and the tool edge could be protected. Thereby, drilling locating precision and hole surface quality could be enhanced, wear of the drill chisel edge effectively improved, and the drilling torque reduced about 30%.
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Wieckowski, Andrzej, and Matthew Neurock. "Contrast and Synergy between Electrocatalysis and Heterogeneous Catalysis." Advances in Physical Chemistry 2011 (November 24, 2011): 1–18. http://dx.doi.org/10.1155/2011/907129.
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The advances in spectroscopy and theory that have occurred over the past two decades begin to provide detailed in situ resolution of the molecular transformations that occur at both gas/metal as well as aqueous/metal interfaces. These advances begin to allow for a more direct comparison of heterogeneous catalysis and electrocatalysis. Such comparisons become important, as many of the current energy conversion strategies involve catalytic and electrocatalytic processes that occur at fluid/solid interfaces and display very similar characteristics. Herein, we compare and contrast a few different catalytic and electrocatalytic systems to elucidate the principles that cross-cut both areas and establish characteristic differences between the two with the hope of advancing both areas.
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Han, Tae-Hee, So-Young Bak, Sangwoo Kim, Se Hyeong Lee, Ye-Ji Han, and Moonsuk Yi. "Decoration of CuO NWs Gas Sensor with ZnO NPs for Improving NO2 Sensing Characteristics." Sensors 21, no. 6 (March 17, 2021): 2103. http://dx.doi.org/10.3390/s21062103.
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This paper introduces a method for improving the sensitivity to NO2 gas of a p-type metal oxide semiconductor gas sensor. The gas sensor was fabricated using CuO nanowires (NWs) grown through thermal oxidation and decorated with ZnO nanoparticles (NPs) using a sol-gel method. The CuO gas sensor with a ZnO heterojunction exhibited better sensitivity to NO2 gas than the pristine CuO gas sensor. The heterojunction in CuO/ZnO gas sensors caused a decrease in the width of the hole accumulation layer (HAL) and an increase in the initial resistance. The possibility to influence the width of the HAL helped improve the NO2 sensing characteristics of the gas sensor. The growth morphology, atomic composition, and crystal structure of the gas sensors were analyzed using field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy, and X-ray diffraction, respectively.
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Bykov, I. Yu, I. N. Birillo, and P. A. Kuzbozhev. "STUDY OF CHARACTERISTICS OF MECHANICAL PROPERTIES OF GAS-DISTRIBUTING STATION PIPES METAL AFTER LONG-TERM OPERATION." Oil and Gas Studies, no. 2 (April 30, 2015): 86–91. http://dx.doi.org/10.31660/0445-0108-2015-2-86-91.
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During operation the technological pipelines of gas-distributing station are affected by mechanical static loading resulted from internal pressure of gas in the high pressure pipelines and a dynamic loading from a high-speed stream of gas in low pressure pipelines. A comparison is made of characteristics of mechanical properties of gas-distributing station pipes metal after a long-term operation for the conditions of static and dynamic loading effects.
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Camporeale, S. M., B. Fortunato, and A. Dumas. "Dynamic modelling of recuperative gas turbines." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 214, no. 3 (May 1, 2000): 213–25. http://dx.doi.org/10.1243/0957650001538317.
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This paper describes the mathematical model and the computational procedure adopted for the development of a modularly structured computer code able to simulate the dynamic behaviour of recuperative gas turbine power plants. For accurate simulation of the turbine components, the model includes a stage-by-stage procedure for the air-cooled turbine based on the blade geometry and the characteristics of the cooling system. The counter-flow surface heat exchanger, assumed as recuperator, is described by a set of partial differential equations, giving à One-dimensional description of the temperature for air, hot gas and metal. A single-shaft recuperated cycle gas turbine, provided with compressor variable inlet guide vanes, is analysed. The transient cases caused by a step variation in the fuel flow and compressor guide vanes geometry are simulated and a linearized model is obtained, in order to identify the dynamic behaviour of the gas turbine and to design a multivariable controller. Finally, the transient case of a controlled turbine after a sudden variation in the electric load is simulated.
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Amaechi, Chiemela Victor, Facheng Wang, and Jianqiao Ye. "Investigation on Hydrodynamic Characteristics, Wave–Current Interaction and Sensitivity Analysis of Submarine Hoses Attached to a CALM Buoy." Journal of Marine Science and Engineering 10, no. 1 (January 17, 2022): 120. http://dx.doi.org/10.3390/jmse10010120.
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There is an increase in the utilization of the floating offshore structure (FOS) called Catenary Anchor Leg Mooring (CALM) buoys and the attached marine hoses due to the increasing demand for oil and gas products. These hoses are flexible and easier to use but have a short service life of about 25 years. They are adaptable in ocean locations of shallow, intermediate and deep waters. In this research, a numerical model was developed using a coupling method modeled by utilizing ANSYS AQWA and Orcaflex (Orcina Ltd., Ulverston, UK) dynamic models of the CALM buoy hoses. Two cases were comparatively studied: Lazy-S and Chinese-lantern configurations, under ocean waves and current. Comparisons were also made between coupled and uncoupled models. This research presents the hydrodynamic characteristics with a sensitivity analysis on the influence of waves, current attack angle, soil gradient, soil stiffness and environmental conditions that influence the performance of marine hoses. The study comparatively looked at the configurations from dynamic amplification factors (DAF) on marine hoses. The results show that marine hoses can be easily configured to suit the designer’s need, seabed soil type, seabed topography and the profiles that are useful for manufacturers. The sensitivity analysis also shows the effect of hose parameters on its hydrodynamic behavior from the wave–current interaction (WCI).
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Ponomarev, Alexey, Sergey Plakhov, Andrew Aksenov, and Andrey Popov. "Effect of gas-dynamic spraying parameters on the characteristics of coatings for steel shaft." MATEC Web of Conferences 329 (2020): 02012. http://dx.doi.org/10.1051/matecconf/202032902012.
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In this article, the effect of the powder composition and energy parameters of the gas-dynamic deposition mode on the hardness of coatings of low-carbon steel samples was studied. Technological recommendations for preliminary preparation of the base metal of shafts before gas-dynamic spraying of thin layers in order to increase the strength of their adhesion are proposed.
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Valsalal, P., S. Usa, and K. Udayakumar. "Response of metal oxide arrester in gas-insulated substation and methods to improve its dynamic characteristics." IET Science, Measurement & Technology 6, no. 4 (2012): 222. http://dx.doi.org/10.1049/iet-smt.2011.0051.
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Kozenkova, G. L., V. N. Talamanov, V. A. Kozenkov, S. I. Kondratyev, E. V. Khekert, and M. A. Modina. "Study of pneumatic sources of elastic waves for marine seismic exploration." Journal of Physics: Conference Series 2061, no. 1 (October 1, 2021): 012068. http://dx.doi.org/10.1088/1742-6596/2061/1/012068.
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Abstract An extensive use of geophysical methods necessitates the development of new methods and improvement of existing methods for seismic exploration to provide reliable data on the structure of the environment in difficult geological conditions. Therefore, it is especially relevant to solve the problems arising in marine petroleum geophysics, which require constant improvement of the methodology and technology of work, and the development and implementation of the advanced seismic equipment. Pneumatic sources that use compressed air as a working medium are among the most effective non-explosive sources for marine seismic exploration. Pneumatic sources exhibit high-energy characteristics, reliability and versatility. Compressor equipment that provide pneumatic sources with high-pressure compressed air is relatively easy to embed into the marine vessel’s power system. The above requires the development and improvement of theoretical methods for studying dynamic problems of a liquid half-space with buried sources of various types. A theoretical description of the formation of an elastic signal in water is given in a number of works. However, the authors of these works do not perform the analysis of gas transportation. The paper considers a number of characteristics of gas flow at a subsonic speed along the high-pressure hose from a vessel’s compressor unit to a pneumatic source. The airflow rate in the receiver-pneumatic source system is determined, and the friction force at a quasi-steady isothermal mode of gas flow is calculated. The paper presents recommendations for planning geophysical works.
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Wen, Wei-Chih, Ting-I. Chou, and Kea-Tiong Tang. "A Gas Mixture Prediction Model Based on the Dynamic Response of a Metal-Oxide Sensor." Micromachines 10, no. 9 (September 11, 2019): 598. http://dx.doi.org/10.3390/mi10090598.
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Metal-oxide (MOX) gas sensors are widely used for gas concentration estimation and gas identification due to their low cost, high sensitivity, and stability. However, MOX sensors have low selectivity to different gases, which leads to the problem of classification for mixtures and pure gases. In this study, a square wave was applied as the heater waveform to generate a dynamic response on the sensor. The information of the dynamic response, which includes different characteristics for different gases due to temperature changes, enhanced the selectivity of the MOX sensor. Moreover, a polynomial interaction term mixture model with a dynamic response is proposed to predict the concentration of the binary mixtures and pure gases. The proposed method improved the classification accuracy to 100%. Moreover, the relative error of quantification decreased to 1.4% for pure gases and 13.0% for mixtures.
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Sharma, N. Yagnesh, Chandrakanth Kini, Deepak D, and Pratik Shamrao Joshi. "A Computational Fluid Dynamic Study on Transient Thermal Characteristics of Two-Phase Gas Metal Arc Welding Process." International Journal of Recent advances in Mechanical Engineering 3, no. 2 (May 31, 2014): 27–34. http://dx.doi.org/10.14810/ijmech.2014.3203.
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Harb, Alaa Abu, Ion Ciuca, Robert Ciocoiu, Mihai Vasile, Adrian Bibis, Bilel Rahali, and Ismaiel Al Hawamda. "Effect of TIG Welding and Manual Metal Arc Welding on Mechanical Properties of AISI 304 and 316L Austenitic Stainless Steel Sheets." Key Engineering Materials 750 (August 2017): 26–33. http://dx.doi.org/10.4028/www.scientific.net/kem.750.26.
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The welding technique used for ASIS 304 and 316L austenitic stainless steel sheets both with a thickness of 3mm is gas tungsten arc welding (TIG) and manual metal arc welding (MMAW). Mechanical properties that were verified include: hardness test and tensile test before welding and after it. The welding process was done on two types of specimens: with a central hole and without hole. We concluded that there was a decrease in the properties of tensile for both specimens with central hole, and 316L had tensile characteristics better than 304 when using the technique TIG. As for 304, it had tensile characteristics better than 316L when using the technique MMAW. We also concluded that the existence of central holes had an influence on the hardness characteristics on both types. The hardness increased in 304 but decreased in 316L. The welding process also showed that there was no influence of MMAW on hardness on both specimens. However it showed that there was no influence of TIG on the hardness for 304, but for 316L values increased.
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Latifah Husni, Nyayu, Ade Silvia, Siti Nurmaini, and Irsyadi Yani. "Metal Oxides Semiconductor Sensors for Odor Classification." International Journal of Reconfigurable and Embedded Systems (IJRES) 6, no. 3 (November 1, 2017): 133. http://dx.doi.org/10.11591/ijres.v6.i3.pp133-149.
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<span>The performance of gas sensor will differ and vary due to the surrounding environment changing, the way of implementation, and the position of the sensors to the source. To reach a good result on gas sensors implementation, a performance test on sensors is needed. The results of the tests are useful for characterizing the properties of the particular material or device. This paper discusses the performances of metal oxides semiconductor (MOS) sensors. The sensors are tested to determine the sensors' time response, sensors' peak duration, sensors' sensitivity, and sensors' stability of the sensor when applied to the various sources at different range. Three sources were used in experimental test, namely: ethanol, methanol, and acetone. The gas sensors characteristics are analyzed in open sampling method in order to see the sensors' sensitivity to the uncertainty disturbances, such as wind. The result shows that metal oxides semiconductor sensor was responsive to the 3 sources not only in static but also dynamic conditions. The expected outcome of this study is to predict the MOS sensors' performance when they are applied in robotic implementation. This performance was considered as the training datasets of the sensor for odor classification in this research. From the experiments, It was got, in dynamic experiment, the senrors has average of precision of 93.8-97%, the accuracy 93.3-96.7%, and the recall 93.3-96.7%. This values indicates that the sensors were selective to the odor they sensed.</span>
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Strelnik, A. S., S. V. Dvoinishnikov, V. G. Meledin, V. V. Rahmanov, G. V. Bakakin, I. K. Kabardin, and A. K. Kabardin. "Developing the software and hardware complex to diagnose the ascent of gas bubbles in a liquid metal by the Doppler anemometry method." Journal of Physics: Conference Series 2057, no. 1 (October 1, 2021): 012093. http://dx.doi.org/10.1088/1742-6596/2057/1/012093.
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Abstract The complex method of ultrasonic diagnostics of two-phase flows in a liquid metal medium is developed. It allows measuring the dynamic and structural characteristics of the floating inhomogeneity. A software and hardware complex that implements the proposed method is developed and tested for ultrasonic diagnostics of two-phase flows in water and liquid metal medium.
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Tovstonog, V. A. "Comparative Assessment of Thermal Protective Characteristics of Metal and Ceramic Shields of Flow Paths of High-Temperature Gas Dynamic Facilities." Herald of the Bauman Moscow State Technical University. Series Mechanical Engineering, no. 2 (131) (April 2020): 52–75. http://dx.doi.org/10.18698/0236-3941-2020-2-52-75.
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In modern technology, gas dynamic facilities with a flow path of a high-temperature working fluid are widely used. Their effectiveness largely depends on the maximum achievable temperature, which is to a great extent determined by the heat resistance of structural materials and thermal protection systems of the most heat-stressed structural units. Most often, mass transfer thermal protection methods using the coolant of fuel components are used in such plants. However, in some gas dynamic facilities, such as high-speed ramjet engines, the use of such methods is only sufficient to maintain an acceptable temperature level for the elements of the flow path itself. As for the thermal protection of the enclosing structural elements which are adjacent to the path, it can be provided with either uncooled screens or heat-insulating linings. The study gives a comparative assessment of the temperature regime and characteristics of alternative types of heat shields
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Cai, Dong, Lin, Murphy, Fan, and Yang. "Heat Source Characteristics of Ternary-Gas-Shielded Tandem Narrow-Gap GMAW." Materials 12, no. 9 (April 29, 2019): 1397. http://dx.doi.org/10.3390/ma12091397.
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: The characteristics of the welding heat source for tandem narrow-gap gas metal arc welding are examined for different ternary shielding gas (Ar-CO2-He) compositions. Results of previous calculations of arc properties for bead-on-plate geometry are adapted to the narrow-gap geometry to predict these characteristics. The heat source concentration factor decreases and the maximum heat flux density increases as the helium content increases, which leads to an increased welding heat efficiency. Addition of CO2 up to around 10% also increases the heat efficiency. When the CO2 content exceeds 10%, the heat source concentration factor increases significantly and the heat efficiency decreases. The shielding gas composition also affects the heat source distribution. The heat source characteristics are applied to a computational fluid dynamic model of the weld pool to predict the weld shape, and the predictions are verified by experiment. The results indicate that the appropriate addition of helium to the shielding gas can increase the heat transferred to the peripheral regions of the arc and increase the sidewall penetration.
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Chen, Bin, Ge Liu, Xian Ming Zhang, and Lang Huang. "Analysis Coupling Vibration Characteristic of HVAS Droplets Based on Wave-Like Disturbance." Applied Mechanics and Materials 71-78 (July 2011): 5068–73. http://dx.doi.org/10.4028/www.scientific.net/amm.71-78.5068.
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Characteristics of vibration molten metal droplets are decisive importance to performance of high velocity arc sprayed coating, it is hardly that detected the dynamic action of liquid droplets owing to the limitation of experimental technique. The gas fluid-liquid droplet coupling vibration system of equations were established based on wave-like disturbance, the governing equation for fastest-growing wave number is derived. The agreement of predicted fastest-growing wave number and data of Bradley, which has the deviation within the±2% limits,indicares that the gas fluid-liquid droplet coupling vibration system of equations is effective. By the use of the coupling vibration system of equations, the effects of gas velocity, gas type and molten metal type to vibration characteristics of HVAS droplets is researched. The results show that selected N2gas sprayed and increasing the gas velocity would be raise adhesive strength of the spraying coating, and provides theoretical evidence for choice of spraying materials and control in HVAS.
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Yazzie, Sheldwin A., Scott Davis, Noah Seixas, and Michael G. Yost. "Assessing the Impact of Housing Features and Environmental Factors on Home Indoor Radon Concentration Levels on the Navajo Nation." International Journal of Environmental Research and Public Health 17, no. 8 (April 19, 2020): 2813. http://dx.doi.org/10.3390/ijerph17082813.
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Uranium is naturally found in the environment as a radioactive metal element with high concentrations in the Southwestern US. In this region is the Navajo Nation, which spans approximately 69,930 square kilometers. A decay product of uranium is radon gas, a lung carcinogen that has no color, odor, or taste. Radon gas may pass from soil into homes; and, indoor accumulation has been associated with geographical location, seasonality, home construction materials, and home ventilation. A home and indoor radon survey was conducted from November 2014 through May 2015, with volunteers who reported residence on the Navajo Nation. Home geolocation, structural characteristics, temperature (°C) during radon testing, and elevation (meters) were recorded. Short-term indoor radon kits were used to measure indoor radon levels. 51 homes were measured for indoor radon levels, with an arithmetic mean concentration of 60.5 Becquerels per cubic meter (Bq/m3) (SD = 42.7). The mean indoor radon concentrations (Bq/m3) by house type were: mobile, 29.0 (SD = 22.9); wood, 58.6 (SD = 36.0); hogan, 74.0 (SD = 0.0); homes constructed of cement and wood, 82.6 (SD = 3.5); and homes constructed of concrete and cement, 105.7 (SD = 55.8). A key observation is that house construction type appears to be associated with the mean home indoor radon concentration. This observation has been published in that the basic structural make-up of the home may affect home ventilation and therefore indoor radon concentration levels.
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Zarko, Vladimir, and Anatoly Glazunov. "Review of Experimental Methods for Measuring the Ignition and Combustion Characteristics of Metal Nanoparticles." Nanomaterials 10, no. 10 (October 12, 2020): 2008. http://dx.doi.org/10.3390/nano10102008.
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Investigations in recent decades have shown that the combustion mechanism of metal particles changes dramatically with diminishing size. Consequently, theoretical description of the ignition and combustion of metal nanoparticles requires additional research. At the same time, to substantiate theoretical models, it is necessary to obtain objective experimental information about characteristics of ignition and combustion processes, which is associated with solving serious technical problems. The presented review analyzes specific features of existing experimental methods implied for studying ignition and combustion of metal nanoparticles. This particularly concerns the methods for correct determination of nanoparticles size, correct description of their heat-exchange parameters, and determining the ignition delay and combustion times. It is stressed that the problem exists of adequate comparison of the data obtained with the use of different techniques of particles’ injection into a hot gas zone and the use of different methods of reaction time measurement. Additionally, available in the literature, data are obtained for particles of different material purity and different state of oxide layer. Obviously, it is necessary to characterize in detail all relevant parameters of a particle’s material and measurement techniques. It is also necessary to continue developing advanced approaches for obtaining narrow fractions of nanoparticles and for detailed recording of dynamic particles’ behavior in a hot gas environment.
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Bagraev, Nikolai T., L. E. Klyachkin, A. M. Malyarenko, A. S. Shcheulin, and Alexandr I. Ryskin. "p+-CdB2 - n-CdF2 and p+-Si - p-CdB2 - n-CdF2 Diffusion Heterostructures." Defect and Diffusion Forum 237-240 (April 2005): 1060–65. http://dx.doi.org/10.4028/www.scientific.net/ddf.237-240.1060.
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The ionic semiconductor CdF2 that is of extraordinary interest for the modern optics and optoelectronics because of the largest band-gap value, 7.8 eV, from all wide-gap semiconductors and of the n-type conductivity caused by doping with the III group elements and subsequent thermal colouring is used to prepare the ultra-shallow p+- n junctions and p+-Si - n-CdF2 heterostructures by the short-time diffusion of boron from the gas phase. The forward branches of the I-V characteristics of the quantum-size p+-n junctions and heterostructures are shown to reveal not only the CdF2 gap value, but also the CdF2 valence band structure as well thereby identifying the ballistic character of the transport of holes. The studies of the I-V characteristics under the voltage applied along the p+-n junction plane demonstrate the metal conductivity of the two-dimensional hole gas, which seems to be evidence of the formation of the p-CdB2 compounds on the n-CdF2 surface in the process of doping with boron.
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Kodnyanko, V. A. "Modeling Movement of Gas-Static Bearings." Mechanical Engineering and Computer Science, no. 1 (March 1, 2019): 13–28. http://dx.doi.org/10.24108/0119.0001450.
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The competitiveness of gas-static sliding bearings, which are assemblies of cutting-edge machines, in particular, precision metal-cutting machines, largely depends on their creation rapidity, which is determined by their mobility of modeling and quality of theoretical study for the later use in designing constructions. The objective is to develop a computer-aided mobile modeling technology for designing the gas-static bearings, which enables quick calculation and study of their static characteristics, quality criteria for their dynamics, and drawing-up recommendations for rapid designing of bearings to ensure performance characteristics and appropriate dynamics quality of designs through automation of procedures, their mathematical modeling, and theoretical study. As a result, there has been developed a technology concept for modeling of gas-static bearings and numerical methods, which allow us to find a solution for exploring tasks with a desirable accuracy. Based on the approximate and proposed numerical methods, the developed modeling technology rapidity was studied, and high comparative efficiency of this technology was found. Practical relevance of technology lies in significant acceleration of modeling processes, calculation and study of static and dynamic characteristics of gas-static bearings that is provided by application of developed methods, algorithms, and modeling technology. There are also reducing the complexity of research processes, and the capability for quick learning of complex bearing structures rapid exploration of which is hard or inconceivable using the traditional “manual” technology.
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Crichton, John H. M. "Falls in Scottish homicide: Lessons for homicide reduction in mental health patients." BJPsych Bulletin 41, no. 4 (August 2017): 185–86. http://dx.doi.org/10.1192/pb.bp.116.054924.
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SummaryThe sustained fall in Scottish homicide rates follows crime reduction measures informed by the epidemiology of suicide. The violence reduction unit targeted young men carrying knives in public. The restriction of weapons immediately to hand appears to have caused an absolute fall in homicide just as suicide reduction was observed following changes to domestic gas supply. Further homicide reduction may be accomplished in the domestic setting with targeted changes in kitchen knife design in home safety planning for high-risk households. Most commonly homicides involving those in recent contact with mental health services in the UK have domestic characteristics and similar safety planning may be targeted at those with mental disorder and a history of violence.
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Li, Wen-Yi. "Experimental Research on the Sensitivity of Partial Discharge Ultra High Frequency Sensor Structure Parameters." Journal of Nanoelectronics and Optoelectronics 16, no. 6 (June 1, 2021): 911–18. http://dx.doi.org/10.1166/jno.2021.3034.
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With the development of intelligent high voltage switch, online gas insulated switchgear discharge detection technology has been more and more widely applied. Because of the high sensing sensitivity and good antiinterference performance of build-in partial discharge sensor, it is currently required to install them on gas insulated switchgear products with voltage levels of 220 kV and above at the factory. The structural parameters of the build-in partial discharge sensor is of great importance to its sensing sensitivity. Therefore, in this paper, the influence of the structure change on the sensitivity of axisymmetric gas insulated switchgear build-in partial discharge sensor is experimentally studied. A practical gas insulated switchgear test model was established in the laboratory, and the frequency domain measurement system based on Spectrogram analyzer and synchronous sweep signal generator was adopted. By comparing the insertion loss generated by the build-in sensor when receiving sweep signal, the influence of structural parameter changes on the sensing sensitivity was analyzed. The results show that the diameter of the build-in sensor should be matched with the diameter of the hand-hole. The match of the larger diameter of the hand-hole and the smaller diameter of the sensor can increase the sensing sensitivity, but when the diameter of the sensor is close to the diameter of the hand-hole, the sensitivity will be significantly reduced. In addition, metal bolts with the sensor electrode and its insulating support fixed to the hand-hole cover can also result in a significant reduction in sensing sensitivity. Using the same measuring principle and system, the propagation attenuation characteristics of partial discharge ultra high frequency signal in gas insulated switchgear typical structures (linear and L-shaped structures) are also experimentally studied. The results show that the average attenuation of partial discharge ultra high frequency signal in gas insulated switchgear along the linear distance is 0.3 dB/m, and the attenuation through every L-shaped structure is 4.2 dB.
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Feng, Hao, Qungui Du, Yuxian Huang, and Yongbin Chi. "Modeling Study on Stiffness Characteristics of Hydraulic Cylinder under Multi-Factors." Strojniški vestnik - Journal of Mechanical Engineering 63, no. 7-8 (July 17, 2017): 447. http://dx.doi.org/10.5545/sv-jme.2017.4313.
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For a complex mechanical system driven by hydraulic cylinders, the dynamic response characteristics of the mechanical system are significantly affected by the stiffness characteristics of hydraulic cylinders. This paper comprehensively studies the impacts of various factors on the stiffness characteristics of the hydraulic cylinders, including the oil bulk modulus, the air content in the hydraulic oil, the axial deformation of the piston rod, the volume expansion of the cylinder barrel, the volume expansion of the metal pipes and the flexible hoses, and the deformation of the hydraulic cylinder sealing. By combining the theoretical analysis and the experimental results, the level of each impacting factor was quantified, and the stiffness model of the hydraulic cylinder was established. Finally, comparative analysis of the stiffness was conducted by taking the experimental hydraulic cylinder as an example; it was verified that the calculated results of the proposed hydraulic cylinder stiffness model approximated the experimental results. Compared with stiffness models presented in current literature, the average accuracy was improved by more than 15 %.
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Bingül, Z. "Instability phenomena in the gas—metal arc welding self-regulation process." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 216, no. 6 (June 1, 2002): 899–910. http://dx.doi.org/10.1243/095440502320192897.
Full textAbstract:
Arc instability is a very important determinant of weld quality. The instability behaviour of the gas-metal arc welding (GMAW) process is characterized by strong oscillations in arc length and current. This phenomenon was reported by Halmoy [1] for the short electrode extension and by Lebedev [2] for the long electrode extension, particularly as related to the arc voltage-current characteristics and the thermal inertia of the electrode wire respectively. However, with these studies, a complete theoretical explanation of the instability phenomena is lacking since the process is not modelled dynamically. In the present work, a model of the GMAW process is developed using an exact arc voltage characteristic. This model is used to study stability of the self-regulation process and to develop a simulation program that helps to understand the transient or dynamic nature of the GMAW process and relationships among current, electrode extension and contact tube-work distance (CTWD). The process is shown to exhibit instabilities at both long electrode extension and normal extension. The experimental results agree closely with both Lebedev's and Halmoy's results. Results obtained from simulation runs of the model were also experimentally confirmed by the present author, as reported in this study. In order to explain the concept of the instability phenomena, the metal transfer mode and the arc voltage-current characteristic were examined. Based on this examination, the conclusion of this study is that their combined effects lead to the oscillations in arc current and length.
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GUAN, LEDING, BIAO YAN, LING LONG, and SHA YANG. "PRELIMINARY STUDY OF FABRICATING BULK FE-BASED AMORPHOUS ALLOY BY COLD GAS DYNAMIC SPRAYING." International Journal of Modern Physics B 23, no. 06n07 (March 20, 2009): 1288–93. http://dx.doi.org/10.1142/s021797920906083x.
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Cold gas dynamic spraying (CGDS) technique makes use of high-speed gas current to spray diversified metal, alloy and composite materials under room temperature or with a little heated. It is one kind of novel surface engineering technologies, aimed at eliminating such negative influences as oxidation, gasification, melt, crystallization and gas decomposition and so on existing in hot spraying technologies. Due to its peculiar characteristics such as low spraying temperature, non-oxidation, low stress among coating layers, compactification, and high utilization rate of raw materials, as well as effective applications in the domain of fabricating coatings, the CGDS technique has attracted great attention. As it has the advantages aforementioned, especially avoiding the changes of material properties resulted from high spraying temperature, CGDS provides a kind of revolutionary means for fabricating such heat-sensitive materials as amorphous alloys. The paper reviews the current situation and application development of the CGDS technique, and presents our preliminary exploration of fabricating bulk Fe -based amorphous alloy via CGDS together with mechanical milling process.
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Zhang, Xueqing, Xiaojing Li, and Tianzhe Shi. "Molecular Dynamics Simulation on the Deposition Characteristics between Pt Cluster and Ni Substrate in Cold Gas Dynamic Spraying." Coatings 12, no. 2 (January 25, 2022): 142. http://dx.doi.org/10.3390/coatings12020142.
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During the process of cold spraying, the motion behavior and the arrangement of clusters, before impacting the substrate, have great influences on the coating/substrate bonding strength and the coating morphologies. In this work, the scattering and self-rotating movement of a single cluster and the different spatial positions of two clusters were taken into account to analyze the deposition characteristics between Pt clusters and Ni substrate by using the molecular dynamics method. We found that an excessively high normal velocity results in the failure of mechanical interlocking. Meanwhile, the increasing tangential velocity mainly enhances the mechanical interlocking. Moreover, the mechanical interlocking and the metallurgic bonding always are enhanced by increasing the impact torque around x-axis, but the metallurgic bonding increases only if the impact torque around z-axis is beyond a certain value. The results further show that, for the two neighboring clusters arranged horizontally, the thermal-softening effect of the first cluster impacting onto the substrate contributes more to its own metallurgic bonding and the mechanical interlocking of the latter one. In addition, for the two vertical clusters colliding with each other during their flying course, the smaller velocity difference can largely enhance the metal interlocking and the metallurgic bonding by shortening the cooling and solidifying times.
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SHELKE, P. N., Y. B. KHOLLAM, P. N. PABREKAR, P. S. MORE, A. M. DATIR, S. D. CHAKANE, K. C. MOHITE, and PANKAJ KOINKAR. "SYNTHESIS AND CHARACTERIZATION OF Co3O4 POWDERS FOR HUMIDITY SENSING." International Journal of Modern Physics: Conference Series 06 (January 2012): 197–202. http://dx.doi.org/10.1142/s2010194512003170.
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In last few decades, great deal of research efforts were directed towards the development of miniaturized gas-sensing devices, particularly for toxic gas detection and for pollution monitoring. Though various techniques are available for gas detection, solid state metal oxides offer wide spectrum of materials with their high sensitivities for the detection of different gaseous species. In this paper, we report the humidity sensing behavior of cobalt oxide ( Co 3 O 4) pellets. The Co 3 O 4 powder was prepared from the precipitation of CoSO 4 using NaOH solution. This as-prepared powder was heated at 600 °C for 2hr. The as-prepared powder was characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The humidity sensing behavior of Co 3 O 4 pellets (wt. ~ 0.5 gm, diameter ~ 10 mm) was noted by using home-built static gas sensing system. The characterization studies showed the high material purity and single phase Co 3 O 4 with cubic spinel symmetry in the as-prepared particles of resultant powders. The humidity sensing characteristics of Co 3 O 4 pellets were found to be good. The recovery time (~ 20 sec) was found to be small as compared to its response time (~ 60 sec).
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Matviychuk, Viktor, and Oleg Gaidamak. "INCREASING OF THE DURABILITY OF DETAILS WORKING UNDER REPEATABLE- LOADS." Vibrations in engineering and technology, no. 1(96) (August 27, 2020): 5–14. http://dx.doi.org/10.37128/2306-8744-2020-1-1.
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The article develops processes of increase the durability of parts operating under repeated loads, by justifying the parameters of surface plastic deformation (SPD) and cold gas-dynamic coating. The influence on the depth of the reinforced surface layer, the nature of the distribution of the stress-strain state of the material and residual compressive stresses, as well as the value of the used plasticity of the metal, the parameters of the SPD process. The hypothesis is substantiated that the main factor in the formation of residual compressive stresses during SPD is the decrease in metal density, which is associated with the use of the plasticity resource. The model of definition of the used resource of plasticity of metals at SPD is developed, that allows to provide qualitative characteristics of a surface layer of details. Methods for shifting the layer with maximum hardening and residual compressive stresses to the surface of the part by using a deformable tool of smaller dimensions in subsequent passes and gas-dynamic coating before SPD. The vast majority of traditional gas-thermal coating methods occur at significant temperature effects on the surface of the part, which is unacceptable for the surface treated by SPD methods. Cold gas-dynamic spraying provides an allowable temperature regime for the creation of special auxiliary coatings while maintaining the properties of the surface treated by SPD methods. The technology of gas-dynamic coating includes heating the compressed gas (air), feeding it into the nozzle and forming a supersonic air stream in this nozzle, introducing a powder material into this stream, accelerating this material in the nozzle by a supersonic air flow and directing it to the surface of the workpiece. As a result, a special auxiliary coating is formed on the surface of the product, which provides optimal parameters of the SPD process.
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Li, Guang Fu, Guan Jun Li, Jun Peng, Mao Long Zhang, and Zhi Yuan Sun. "Mechanical Behavior of a Dissimilar Metal Weld Used for Nuclear Power Plants." Applied Mechanics and Materials 675-677 (October 2014): 47–51. http://dx.doi.org/10.4028/www.scientific.net/amm.675-677.47.
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The mechanical behaviors of dissimilar metal weld SA508-52M-316L in several environments were investigated by using tensile tests with smooth specimens, focusing on the behavior of SA508-52M weld part during slow strain rates testing (SSRT) at 290°C in nitrogen gas and in simulated primary water at different electrode potentials. The mechanical properties at room temperature of main materials were obtained first. When tested at 290°C, the weld exhibited characteristics of dynamic strain ageing (DSA), which was more significant when strain rate was decreased from 1x10-6(1/s) to 3.1 x10-7(1/s). When tested in the water at the potentials from-720 to +200mV(SHE) , SA508-52M specimens showed the mechanical behaviors almost the same as that in nitrogen gas, with ductile failure happened in the 52M bulk weld metal. When the potential was raised to +300 and +400mV(SHE), brittle failure of stress corrosion cracking (SCC) took place around the interface, causing the significant drop of elongation and reduction in area.
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Love, Calvin, Haleh Nazemi, Eman El-Masri, Kenson Ambrose, Michael S. Freund, and Arezoo Emadi. "A Review on Advanced Sensing Materials for Agricultural Gas Sensors." Sensors 21, no. 10 (May 14, 2021): 3423. http://dx.doi.org/10.3390/s21103423.
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This work is a comprehensive review of sensing materials, which interact with several target gases pertinent to agricultural monitoring applications. Sensing materials which interact with carbon dioxide, water vapor (relative humidity), hydrogen sulfide, ethylene and ethanol are the focus of this work. Performance characteristics such as dynamic range, recovery time, operating temperature, long-term stability and method of deposition are discussed to determine the commercial viability of the sensing materials considered in this work. In addition to the sensing materials, deposition methods are considered to obtain the desired sensing material thickness based on the sensor’s mechanism of operation. Various material classes including metal oxides, conductive polymers and carbon allotropes are included in this review. By implementing multiple sensing materials to detect a single target analyte, the issue of selectivity due to cross sensitivity can be mitigated. For this reason, where possible, it is desirable to utilize more than one sensing material to monitor a single target gas. Among those considered in this work, it is observed that PEDOT PSS/graphene and TiO2-coated g-C3N4 NS are best suited for CO2 detection, given their wide dynamic range and modest operating temperature. To monitor the presence of ethylene, BMIM-NTf2, SWCNTs and PtTiO2 offer a dynamic range most suitable for the application and require no active heating. Due to the wide dynamic range offered by SiO2/Si nanowires, this material is best suited for the detection of ethanol; a gas artificially introduced to prolong the shelf life of the harvested crop. Finally, among all other sensing materials investigated, it observed that both SWCNTs and CNTs/SnO2/CuO are most suitable for H2S detection in the given application.
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Tasneem Abdalla, Tasneem Abdalla, Tasneem Abdalla Tasneem Abdalla, Qian Wang, Qian Wang, Tan Xiaoqiang, and Tan Xiaoqiang. "The Study on Dual Fuel Spray and Characteristics of Combustion of Diesel, Natural Gas and Dual Fuel." Journal of Energy Conservation 1, no. 1 (June 11, 2018): 14–30. http://dx.doi.org/10.14302/issn.2642-3146.jec-18-2135.
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Combustion of fossil fuels provides around 88% of total energy supply for modern society, and meanwhile causes many environ mental problems and social problems such as air pollution and energy crisis. Therefore，both at home and abroad are focusing on the research and development of natural gas engine recently. However, the mass production and application of this kind of engine are restricted by some unsolved technical difficulties. This paper explored the injection, combustion and emission processes of diesel/ natural gas and dual fuel engine based on Chemkin II, Fire software and Schlieren method. The experimental study on the mixing process of dual fuel jet was carried out by using high-speed Schlieren method in a constant volume bomb. Based on the Fire software, and then applied to Chemkin II software to analyze the effect of the initial temperature and pressure on the net heat production and combustion emissions. The results show that Dual fuel mechanism is capable of producing different heat production behaviors when varying the initial pressure and temperature CO2 emissions are minimized by changing the initial pressure above or below the atmospheric value. However, CO emissions are peaked when diesel fuel is used. The dual fuel engine minimizes the CO emissions amount caused by diesel fuel. Increasing the initial pressure eliminates dual fuel CO2 combustion emissions. The research of this paper is important to optimize the in cylinder combustion processes of natural gas engine, and have a certain important meaning to guide the development of diesel ignition dual fuel engine.
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Zhabanov, Yuriy A., Alexey V. Eroshin, Igor V. Ryzhov, Ilya A. Kuzmin, Daniil N. Finogenov, and Pavel A. Stuzhin. "Molecular Structure, Thermodynamic and Spectral Characteristics of Metal-Free and Nickel Complex of Tetrakis(1,2,5-thiadiazolo)porphyrazine." Molecules 26, no. 10 (May 15, 2021): 2945. http://dx.doi.org/10.3390/molecules26102945.
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The Knudsen effusion method with mass spectrometric control of the vapor composition was used to study the possibility of a congruent transition to the gas phase and to estimate the enthalpy of sublimation of metal-free tetrakis(1,2,5-thiadiazolo)porphyrazine and its nickel complex (H2TTDPz and NiTTDPz, respectively). The geometrical and electronic structure of H2TTDPz and NiTTDPz in ground and low-lying excited electronic states were determined by DFT calculations. The electronic structure of NiTTDPz was studied by the complete active space (CASSCF) method, following accounting dynamic correlation by multiconfigurational quasi-degenerate second-order perturbation theory (MCQDPT2). A geometrical structure of D2h and D4h symmetry was obtained for H2TTDPz and NiTTDPz, respectively. According to data obtained by the MCQDPT2 method, the nickel complex possesses the ground state 1A1g, and the wave function of the ground state has the form of a single determinant. Electronic absorption and vibrational (IR and resonance Raman) spectra of H2TTDPz and NiTTDPz were studied experimentally and simulated theoretically.
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Rubino, Felice, Paola Ammendola, Antonello Astarita, Federica Raganati, Antonino Squillace, Antonio Viscusi, Riccardo Chirone, and Luigi Carrino. "An Innovative Method to Produce Metal Foam Using Cold Gas Dynamic Spray Process Assisted by Fluidized Bed Mixing of Precursors." Key Engineering Materials 651-653 (July 2015): 913–18. http://dx.doi.org/10.4028/www.scientific.net/kem.651-653.913.
Full textAbstract:
Metallic foams are known for their interesting physical and mechanical properties such as high stiffness, very low specific weight, high compression strength, unusual acoustic and thermal properties and good energy absorption characteristics. These materials are currently manufactured by means of several different processes. The limit of these conventional technologies is the impossibility to produce foams with complex geometry.This paper deals with the study of an innovative method to produce complex shaped precursors for aluminum foams through cold gas dynamic spray deposition process (CGDS). Aluminum alloy (Al-Si) fine powders were previously mixed with the blowing agent (titanium-hydride, TiH2). The mixing process was carried out by means of sound-assisted fluidized bed apparatus that allows to obtain an homogeneous mixture of the two elements. The mixed particles were then sprayed by means of the CGDS process on a stainless steel sheet that simulates the real component to be reinforced with the foam. Subsequently the obtained precursor was heated up in a furnace The produced metal foam was characterized using optical and electron microscopy in order to study the cell morphology and distribution.The obtained results showed the effectiveness of this method to produce aluminum foams with complex shape.
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ZOU, SHUANGYANG, ZHIJIANG WANG, SHENG-SUN HU, GUANCHENG ZHAO, WANDONG WANG, and YOUQUAN CHEN. "Effects of Filler Wire Intervention on Gas Tungsten Arc: Part I - Mechanism." Welding Journal 99, no. 9 (September 1, 2020): 246s—254s. http://dx.doi.org/10.29391/2020.99.023.
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For gas tungsten arc welding (GTAW), the effects of filler wire on the GTA are worth being clarified, which will help deepen the understanding of arc characteristics and in-spire new ideas for the real-time monitoring of weld quality. To this end, this work proposed a novel sensing method of detecting probe voltages (i.e., the voltage signals between a filler wire and tungsten electrode/workpiece). Based on this method, in this first part of the work, a tungsten probe was used to replace the filler wire and to interact with the arc in the specific experiments to elucidate the static and dynamic interaction mechanisms between the GTA and filler wire. The results showed that the filler wire intervention deflects the arc to various degrees and will change the volt-age signals. As a metal conductor, the filler wire will in-crease the arc voltage by increasing the average electric field strength. However, its effects on the different areas of the arc are not always consistent, which makes the change trend of the probe voltages not always the same. Moreover, due to thermal inertia, the probe voltage does not strictly change synchronously with the arc voltage under the dynamic disturbance. This work lays a theoretical foundation for monitoring the stability of the GTAW process.
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Yunus, Mohammed, and Mohammad S. Alsoufi. "Mathematical Modeling of Multiple Quality Characteristics of a Laser Microdrilling Process Used in Al7075/SiCp Metal Matrix Composite Using Genetic Programming." Modelling and Simulation in Engineering 2019 (January 2, 2019): 1–15. http://dx.doi.org/10.1155/2019/1024365.
Full textAbstract:
The conventional method for machining metal matrix composites (MMCs) is difficult on account of their excellent characteristics compared with those of their source materials. Modern laser machining technology is a suitable noncontact method for machining operations of advanced engineering materials due to its novel advantages such as higher productivity, ease of adaptation to automation, minimum heat affected zone (HAZ), green manufacturing, decreased processing costs, improved quality, reduced wastage, removal of finishing operations, and so on. Their application includes hole drilling in an aircraft engine components such as combustion chambers, nozzle guide vanes, and turbine blades made up of MMCs which meet quality standards that determine their suitability for service use. This paper presents a derived mathematical model based on evolutionary computation methods using multivariate regression fitting for the prediction of multiple characteristics (circularity, taper, spatter, and HAZ) of neodymium: yttrium aluminum garnet laser drilling of aluminum matrix/silicon carbide particulate (Al/SiCp) MMCs using genetic programming. Laser drilling input factors such as laser power, pulse frequency, gas pressure, and pulse width are utilized. From a training dataset, different genetic models for multiple quality characteristics were obtained with great accuracy during simulated evolution to provide a more accurate prediction compared to empirical correlations.
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Mair, Josef, Robert Canti, Roland Golle, Wolfram Volk, and Hartmut Hoffmann. "Dynamic Strength Behaviour of Punch Connections in Shear Cutting Processes." Key Engineering Materials 549 (April 2013): 262–69. http://dx.doi.org/10.4028/www.scientific.net/kem.549.262.
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Two basic types of load for the tool active elements can be distinguished for the shear cutting process of sheet metal. For high strength, brittle materials, the stamping punch will be exposed to distinctive oscillating axial dynamic loads as a result of abrupt released potential energy, from the tool active elements, the blanking tool and the stamping press, caused by a sudden cracking of the sheet. In contrast, when shear cutting ductile materials, sheet metal will be drawn into the die clearance and the resulting friction between the punch and the cut surface can cause high forces when pulling the punch out of the hole. When using punches featuring a complex cutting peripheral form, - not available as a standard part - it is necessary to decide between head and shank of the punch manufactured out of one part or a shaft without head, which is usually cheaper and can be manufactured by electro-erosive wire-cutting. In the second case, a linking element must be accepted, transferring the load transmission between shaft and tool. This linking element, realized by a form lock or traction, can be the reason for premature failure of the punch. The two described cases of load, in combination with lacking knowledge of the real load on the link as well as eligibility of different punch linking types for each case of loading, cause unnecessary cost in tool manufacturing by oversizing or punch fracture. For this, solid punches as well as joined punches with dowelled or screwed heads have been compared in systematic tests. Brazed and bonded punch heads have been involved in the test series as cost-efficient alternatives to custom punches. Collaterally, characteristic values have been determined for each type of punch in static and dynamic measurements. Especially impact absorption and stiffness of the connection represent non-destructive measureable values allowing a comparison of stamping punches in terms of their dynamic fatigue limit.
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Zhou, Li Shan. "A Research on Detection and Identification of Harmful Gas Utilizing Cataluminescence-Based Sensor Array." Applied Mechanics and Materials 288 (February 2013): 109–13. http://dx.doi.org/10.4028/www.scientific.net/amm.288.109.
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A novel cataluminescence(CTL)-based sensor array consisting of 9 types of catalytic nanomaterials was developed for the determination and identification of harmful gas. The sensing nanomaterials, including nano-sized metal oxides, carbonates and decorated nanoparticles, have been selected carefully. A 3 x 3 array was integrated by depositing these nanosized catalysts onto the ceramic chip. Dynamic and static analysis methods were utilized to characterize the performance of the sensor array to 4 kinds of harmful gas. Each compound gives its unique CTL pattern after interact with the sensor array, which can be employed to recognize ether, acetone, chloroform, and toluene. PCA was conducted to classify the harmful gas and the plots showed that the groups were well classified. In addition, the patterns obtained at different working temperature and the analytical characteristics of array were investigated. The CTL-based sensor array shows promising perspective for the recognition and discrimination of harmful gas.
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Heuser, Thomas A., Caitlin A. Chapin, Max A. Holliday, Yongqiang Wang, and Debbie G. Senesky. "Effect of proton irradiation temperature on persistent photoconductivity in zinc oxide metal-semiconductor-metal ultraviolet photodetectors." Journal of Applied Physics 131, no. 15 (April 21, 2022): 155701. http://dx.doi.org/10.1063/5.0077210.
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The electrical and structural characteristics of 50-nm-thick zinc oxide (ZnO) metal-semiconductor-metal ultraviolet (UV) photodetectors subjected to proton irradiation at different temperatures are reported and compared. The devices were irradiated with 200 keV protons to a fluence of 1016 cm[Formula: see text]2. Examination of the x-ray diffraction (XRD) rocking curves indicates a preferred (100) orientation prior to irradiation, with decrease in crystal quality afterward. Additionally, peak shifts in XRD and Raman spectra of the control sample relative to well-known theoretical positions are indicative of tensile strain in the as-deposited ZnO films. Shifts toward theoretical unstrained positions are observed in the irradiated films, which indicates partial relaxation. Raman spectra also indicate increase in oxygen vacancies (VO) and zinc interstitial defects (Zni) compared to the control sample. Additionally, transient photocurrent measurements performed on each sample at different temperatures showed up to 2[Formula: see text] increase in photocurrent decay time constants for irradiated samples vs the control. This persistent photoconductive behavior is linked to the activation of electron and hole traps near the surface, and to the desorption and reabsorption of O2 molecules on the ZnO surface under the influence of UV light. Using an Arrhenius model, trap activation energies were extracted and, by comparing with known energies from the literature, the dominant defects contributing to persistent photoconductivity for each irradiation condition were identified. The persistence of differences in photocurrent transients between different samples months after irradiation indicates that the defects introduced by the suppression of thermally activated dynamic annealing processes have a long-term deleterious effect on device performance.
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Annerstedt, Lena, Junko Sanada, and Lars Gustafson. "A Dynamic Long-Term Care System for the Demented Elderly." International Psychogeriatrics 8, no. 4 (December 1996): 561–74. http://dx.doi.org/10.1017/s1041610296002888.
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The dynamic processes and the way they interact in shaping a care system for demented patients are analyzed and discussed. The development of disability/dependency, interpreted in a simulation model based on Katz's index of ADL and Berger's scale “Rating the severity of senility,” gave insight into the interplay of four care levels: psychogenatric long-term care for patients with severe behavioral disturbances, nursing-home care for patients with highly reduced ADL capacity who are often moderately to severely demented, group-living care for the demented with less dominating ADL dependency, and residential care for the elderly frail with or without symptoms of dementia. For each facility in this chain of care, characteristics in patients' symptomatology and behavior could also be identified. Resources necessary in order to fulfill goals in caring differed between each facility.
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Yin, Zichao, Jianfei Lu, Lin Li, Tong Wang, Ronghui Wang, Xinghua Fan, Houkai Lin, Yuanshun Huang, and Dapeng Tan. "Optimized Scheme for Accelerating the Slagging Reaction and Slag–Metal–Gas Emulsification in a Basic Oxygen Furnace." Applied Sciences 10, no. 15 (July 24, 2020): 5101. http://dx.doi.org/10.3390/app10155101.
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Basic oxygen furnace (BOF) steelmaking is widely used in the metallurgy field. The slagging reaction is a necessary process that oxidizes C, Mn, Si, P, S, and other impurities and therefore directly affects the quality of the resultant steel. Relevant research has suggested that intensifying the stirring effect can accelerate the slagging reaction and that the dynamic characteristics of the top blow are the key factor in exploring the related complex physical and chemical phenomena. To address the issue, the standard k-ω turbulence model and level-set method were adopted in the present work and a fluid dynamics model was developed for a BOF. Accordingly, the slag–metal–gas emulsion interaction and stirring effect were investigated, and the interference mechanism of a multi-nozzle supersonic coherent jet was revealed. Finally, a self-adjustment method based on fuzzy control is proposed for the oxygen lance. The results indicate that the transfer efficiency of jet kinetic energy at the gas–liquid interface is the critical factor for the slagging reaction and that multi-nozzle oxygen lances with a certain twisted angle have important advantages with respect to stirring effects and splashing inhibition. The fuzzy control method predicts that the optimal nozzle twist angle is within the range of 7.2° to 7.8°. The results presented herein can provide theoretical support and beneficial reference information for BOF steelmaking.
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Spirin, Nikolay, Oleg Onorin, and Alexander Istomin. "Prediction of Blast Furnace Thermal State in Real-Time Operation." Solid State Phenomena 299 (January 2020): 518–23. http://dx.doi.org/10.4028/www.scientific.net/ssp.299.518.
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The paper gives a general description of the dynamic model of the blast-furnace process that enables to calculate transition processes of the blast furnace thermal state, evaluated by the content of silicon in hot metal. It provides calculation results of the transition processes to be subjected to changes in control actions: ore load from the top and oxygen concentration in blast, natural gas flow rate and hot blast temperature from the bottom. Specific features of these transition processes during blast-furnace smelting are analyzed. The paper shows that the dynamic characteristics of blast furnaces change are subjected to control actions and depend significantly on properties of melted raw materials and operating parameters of blast furnaces. The oscillatory transition process in the blast furnace is observed in the case after disturbance it has an opposite influence on the thermal state of the lower and uppers stages of heat exchange. The paper presents prediction results of the silicon content in hot metal. It gives practical recommendations for selection of control actions.
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Husni, Nyayu Latifah, Siti Nurmaini, Irsyadi Yani, and Ade Silvia. "Intelligent Sensing Using Metal Oxide Semiconductor Based-on Support Vector Machine for Odor Classification." International Journal of Electrical and Computer Engineering (IJECE) 8, no. 6 (December 1, 2018): 4133. http://dx.doi.org/10.11591/ijece.v8i6.pp4133-4147.
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Classifying odor in real experiment presents some challenges, especially the uncertainty of the odor concentration and dispersion that can lead to a difficulty in obtaining an accurate datasets. In this study, to enhance the accuracy, datasets arrangement based on MOS sensors parameters using SVM approach for odor classification is proposed. The sensors are tested to determine the sensors' time response, sensors' peak duration, sensors' sensitivity, and sensors' stability when applied to the various sources at different range. Three sources were used in experimental test, namely: ethanol, methanol, and acetone. The gas sensors characteristics are analyzed in open sampling method to see the sensors' performance in real situation. These performances are considered as the base of choosing the position in collecting the datasets. The sensors in dynamic experiment have average of precision of 93.8-97.0%, the accuracy 93.3-96.7%, and the recall 93.3-96.7%. This values indicates that the collected datasets can support the SVM in improving the intelligent sensing when conducting odor classification work.
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Chang, Baohua, Hong Xiao, Jinle Zeng, Shuo Yang, Dong Du, Jianling Song, and Guoliang Han. "Fluid Flow Characteristics and Weld Formation Quality in Gas Tungsten Arc Welding of a Thick-Sheet Aluminum Alloy Structure by Varying Welding Position." Applied Sciences 8, no. 8 (July 24, 2018): 1215. http://dx.doi.org/10.3390/app8081215.
Full textAbstract:
This study aims to reveal the cause of different weld formation quality for varying welding position in the GTAW (Gas Tungsten Arc Welding) of a thick-sheet aluminum alloy structure. The fluid flow characteristics of weld pools are investigated by CFD (Computational Fluid Dynamic) modeling and high-speed imaging for the climbing and flat welding positions, which correspond to the start and finish ends of the welds of the structure, respectively. Results show that the directions of gravity relative to weld pools may notably affect the fluid flows in weld pools for different welding positions. For flat welding, gravity will accelerate the fluid flow in the direction of sheet thickness only and in turn result in a high velocity downwards, which implies a good penetrating capability. Welds of good formation with smooth surface and consistent width can be produced under flat welding position. In contrast, for climbing welding, gravity will act on the molten metal in both the direction of sheet thickness and the lateral direction of the weld pool. As a result, the velocity in sheet-thickness direction is decreased, which implies a decreased penetrating capability. Meanwhile, the velocity backwards is increased in the top portion of the weld pool, which makes the molten metal apt to flow out of the weld pool. Both the decreased penetrating capability and the accelerated molten metal outflow would render the climbing welding process unstable, and result in welds of poor formation with uneven weld surface and inconsistent weld width. Based on the study, possible methods are proposed that could be used to improve the weld formation quality when welding thick-sheet aluminum alloys structures using various welding positions.
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Yu, Jiang Hong. "Magnetic Memory Testing and Intensity Failure Analysis of Fractured Bolt of Cylinder Head on Hydrogen Gas Compressor." Advanced Materials Research 503-504 (April 2012): 772–75. http://dx.doi.org/10.4028/www.scientific.net/amr.503-504.772.
Full textAbstract:
Along with the wide application of pressure energy, large scale reciprocating compressor unit is becoming one of the necessary key equipments in petrochemical industry. The reciprocating compressor has complicated structure and it is very difficult to carry out measurement & analysis to the operation status of various components. Above all, as the most important fastener of the compressor, once fracture of cylinder head bolt of the reciprocating compressor occurs, major disaster will occur. Metal magnetic memory testing technology is a nondestructive examination technology based on magneto-mechanical effect principle. Specific change of leakage magnetic field will occur in stress & deformation concentrated region under combined action of alternate work load and geomagnetic field, macroscopic cracking can be detected and stress concentration and early state damage can be evaluated by utilizing this specific change, We carried out on-site examination on the fractured bolt of cylinder head of hydrogen gas compressor unit in refinery of certain petrochemical corporation with latest metal magnetic memory testing technology. On the basis of intensity analysis and dynamic load calculation to cylinder head bolt of the reciprocating compressor, we analyzed the cause of bolt fracture by using metal magnetic memory testing technology and drew out the magnetic memory signal distribution characteristics of the bolt and its fracture. We verified the correctness of testing result of the metal magnetic memory technology on cylinder head bolt and its fracture with metallographic examination technology; furthermore, we studied the reliability of bolt fatigue crack & fracture analysis and investigation of accident cause by using magnetic memory characteristic distribution signal.
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Sun, Dezhang, Endong Guo, Houli Wu, Zhibin Liu, Chenxi Mao, Haoyu Zhang, and Xun Sun. "Shaking Table Test of a Full-Scale RC Frame Structure with an Indoor Gas Piping System." Advances in Civil Engineering 2022 (April 13, 2022): 1–15. http://dx.doi.org/10.1155/2022/6869621.
Full textAbstract:
To investigate the seismic behavior of a two-story RC frame structure with an indoor gas piping system, a shaking table test was performed and the data obtained from the shaking table test were analyzed in this paper. The detailing of the structural elements was compliant with the Chinese seismic design code, whereas minor modifications were applied to the pipe materials and joint arrangements. In the test, three kinds of pipe materials (galvanized steel, thin-walled stainless steel, and polyethylene) combined with three types of joint arrangements were selected. The filling materials of the joint were epoxy resin, batched jute, and asbestos cement. A series of full-scale shake table tests were performed by gradually increasing the three ground motions for reaching to the near collapse limit state. The dynamic characteristics and the responses of the model were investigated via analyzing shaking table test data and the observed damage. The test results also indicated that different joint arrangements had a different impact on the dynamic response of the pipes when subjected to strong ground motions. The peak acceleration of metal pipes with a rigid joint was higher than that of flexible ones, and the peak acceleration of plastic pipes with flexible joint connection was higher than that of rigid ones.
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Huang, Yan Lu, Xin You Ke, and Yi Bin Li. "Numerical Coupling Analysis of Droplets’ Behaviors in GMAW." Advanced Materials Research 139-141 (October 2010): 981–85. http://dx.doi.org/10.4028/www.scientific.net/amr.139-141.981.
Full textAbstract:
The forming process and dynamic behaviors of droplets in gas metal arc welding (GMAW) were numerically simulated by using weak electromagnetic coupling method, with considering the gravity, the electromagnetic force, the free surface and the turbulent flow in the droplets. The shape update of the droplets was calculated on basis of VOF and CSF theories. The Gaussian electric current density was identified as boundary conditions for calculating electromagnetic force. A weak electromagnetic coupling model was used to study the characteristics of relevant physical variables and their roles in metal transfer. The simulation results suggest that the maximal value of electric current density lies in the neck of droplets, and the electromagnetic force has great effects of accelerating droplets’ contraction and shortening their falling time. Under the action of strong electromagnetic force, the metal transfer is in a spray form rather than a globular one in GMAW process. The simulated results agree well with theoretical analyses and predecessors’ experiments.
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Matviychuk, Viktor, Oleg Haidamak, and Mykola Kolesnik. "IMPROVEMENT OF OFFICIAL CHARACTERISTICS OF THE SURFACE LAYER DETAILS BY APPLICATION OF SURFACE PLASTIC DEFORMATION AND GASODYNAMYNAMYNAMINE." Vibrations in engineering and technology, no. 2(97) (August 27, 2020): 90–100. http://dx.doi.org/10.37128/2306-8744-2020-2-10.
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The article investigates changes in the characteristics of the surface layers of parts processed by methods of surface plastic deformation (SPD). It is shown that at SPD the strength and hardness characteristics of the material increase and residual compression stresses are formed. On the basis of the study of the stress-strain state of the material at the SPD, its non-monotonicity is established, which is manifested in the gradual change of sign of the components of deformations and stresses. In this regard, a tensor-nonlinear damage accumulation model was used to evaluate the deformability of the material, which takes into account the directional nature of the damage and the anisotropy of the plasticity of the deformed metal. Based on this model, an expression was obtained to determine the plasticity resource used in the case of multi-stage SPD. According to the results of the calculations, it is established that the maximum plasticity resource used in the SPD is at a depth of approximately 0.1 of the diameter of the plastic footprint of the tool, and destruction at full exhaustion of the plasticity resource occurs in the form of peeling of thin plates of appropriate thickness. Recommendations for displacement of the most reinforced layers to the surface of the workpiece are developed, as well as recommendations for limiting deformation by the amount of plasticity resource used. The conducted research allows to assign the optimal modes of SPD at the stage of technological process design. A device for cold gas-dynamic spraying was developed and the possibility of creating antifriction sections using it was investigated. Graphs of dependence of geometrical parameters of the deposited layer on the sputtering distance are constructed and methods and schemes of preparation for deposition of the surface of the workpiece using SPD methods are developed. Experimental cold gas-dynamic spraying was carried out and optimal parameters of the process of spraying of antifriction layers of bronze and metal polymers (pressure, and the temperature of the compressed air and the temperature of the workpiece) on the formed roller surface were determined. A new concept of increasing the contact strength and durability of friction pairs is proposed.