Papers by Keyword: Deviation

Abstract: Silicon carbide (SiC) is one of the ideal electronic materials for producing high-temperature, high-frequency, and high-power electronic devices. In the past 20 years, with the continuous improvement of silicon carbide material processing technology, its application have been expanding. Unlike Si devices, SiC devices cannot be directly fabricated on crude wafers. Instead, epitaxial films need to be deposited and grown on SiC wafers, then the epitaxial films will be used to produce devices. The doping concentration performance of the epitaxial layer can determine the device performance, making it the most important indicator of the epitaxial layer quality. For a long time, nitrogen has been used as the dopant in the production of SiC epi-wafers. Due to the difficulty of nitrogen cracking and its adsorption in graphite, the concentration is prone to significant drift, resulting in a decrease in yield and low production efficiency. In this research a vertical epitaxial equipment was used to consecutively grow 10 8-inch SiC substrate with nitrogen and ammonia as dopant separately. The concentration and thickness of the grown epitaxial films were measured and studied. The results indicate that compared to nitrogen as a dopant, the results of ammonia doping are significantly better in terms of intra-wafer concentration uniformity and inter-wafer consistency. Using nitrogen as the dopant, the doping concentrations uniformity of epi-layer ranges from 1.31% to 2.18%, and the deviation is between ± 8.0%. As a comparison, using ammonia as the dopant, the doping concentration uniformity of epi-layer ranges from 0.65% to 0.89%, and the deviation is between ± 1.0%. Meanwhile, the thickness performance is at the same level. Therefore, ammonia as a dopant can solve the concentration drift problem that has long been a headache in large-scale production of SiC epitaxy, greatly improving production efficiency. Its advantages are obvious. This study analyzed the possible reasons for the superior performance of ammonia gas as a dopant for 4H SiC epitaxy compared to nitrogen.

Abstract: Semisolid processing can provide an avenue to reduced rejection rates during casting and increased capability of thin-walled castings leading to improved resource efficiency and reduced climate impact. In the RheoMetal^TM process, the slurry is formed far from equilibrium. A consequence to the deviation from equilibrium is that conventional guidelines for process stability may not give the correct appreciation of the process window, nor on the correct solid fractions generated. The solid fraction provides the slurry properties and its dependence on temperature should in theory provide the stable process window. This is discussed using data from literature and an alternative approach to identify the process stability window is given.

Abstract: The thermal conductivity of metals and alloys is an important physical property. The thermal conductivity of metals and alloys in the liquid state is usually hard to be measured, because it is difficult to exclude the effect of convection. As such, as a convenient approach, the Wiedemann-Franz law has been used for the estimation of thermal conductivity of metals and alloys in the liquid state. However, some reports show the deviation from Wiedemann-Franz law of pure Sn and Sn-based metals in the liquid state. Measuring the thermal conductivity of various Sn-based alloys in the liquid state is of significant importance to identify its heat transfer in terms of whether the deviation from Wiedemann-Franz law is observed. In this study, Field’s metal is focused on as one of the Sn-based alloys. Then, its thermal conductivity in the solid and liquid states with various temperature ranges by employing the transient hot wire method. This method is appropriate due to its nature of dealing with the convection-including problems. Finally, the adaptability of Wiedemann-Franz law is analyzed by using the obtained thermal conductivity and electric conductivity data. In this study, the deviation from Wiedemann-Franz law was observed in the liquid state.

Abstract: Article is focused on using eddy current to measure of internal residual stress after milling. In presented article is described methodical process of identification residual stress in internal layers of the surface after machining of steel C45. Eddy current provides fast identification of residual stress directly in engineering areas without necessity to transfer samples in specialized laboratories. Presented article also describe procedure of evaluating measured values of deviation and its transformation to values of residual stress by conversion coefficients.

Abstract: With the Industrial revolution and modernization, many other issues related to it are also increasing. Problems of resource exploitation, pollution etc. has emerged as global issue and matter of high concern. Out of various industries, construction industry is one such sector which contributes highly for problems like emission of green house gases into atmosphere. Materials like cement, steel, bricks are highly energy intensive materials. Many of the conventional materials and technology options for building construction do not meet sustainability criteria. Lesser use of theses material and alternative environmentally friendly material contributes significantly in reducing CO₂ gas emission and problems associated with it. The strategy of 3R that is Reduce, Reuse and Recycle is one of the important techniques in the construction industry to achieve the sustainability. The same strategy is applied in this research work for finding appropriate substitute for major construction resource that is concrete and on basis of experimental strength results and property findings, the structural stability of various waste mix concrete elements is analyzed and designed so as to find corresponding changes in RCC design if any appears. The comparative results of analysis and design for various such percentage replaced waste mix concrete is highlighted. The analysis and design results obtained on the basis of innovative materials having specimen properties are fair enough for utilizing in construction practices.

Abstract: It is impossible to predict energy consumption without sufficient degree of accuracy for power-consuming nonlinear inertial industries at change of technological parameters. This problem is solved by the simplified and determined model based on the equations of material balance of streams for substance.

Abstract: This paper presents the results of some research with different heat treatments for the steel OSC10 compared to steel 205Cr115 of which have made the cut punches, each one realizing 16,000 stampings in the same technology. A study was done on the wear of used tools stamping operations using the method of deviation from circularity. Due to the fact that the material of workpiece sheet has fibers orientated in the direction of lamination the cutting tools encounters resistance in a different manner on their circumference. In some portions the edges penetrate perpendicularly to the fiber, the cutting material poses a higher resistance and obtains more pronounced wear of the edges. On the other portions, the edges penetrate parallel with the fiber, in this case the material strength is low and provides a wear less pronounced.

Abstract: With regard to the multi-criteria decision making (MCDM) problems that the criteria weights are unknown and the decision maker (DM) has avail preference information on alternatives. Firstly, a quadratic programming model is established by using the minimum sum of deviation squares between the subjective and objective decision-making preference information on alternatives. Secondly, the existent condition of solution is given and the calculated formula of the criteria weights are obtained by solving the model, thus the overall values of the alternatives are gained. Based on these values, the ranking priorities on alternatives are processed. Finally, a practical example is illustrated to show the feasibility and availability of the developed model and method.

Abstract: The uncertainty contribution related to linearity shall be considered in the calculation of measurement uncertainty when using the impulse voltage measuring system. Under the condition that the national standard is not yet established at present, the paper proposed an experimental method to measure the linearity of 600kV damped capacitive impulse divider (HCR600). The paper used low voltage resistance divider R200S to measure the linearity of generator, and obtained the linearity curve. With the increase of charging voltage, the linearity of divider can be obtained by measuring the charging voltage of impulse voltage generator precisely and its ratio of indicating value of the sample divider HCR600 after corrected. The result shows that the linearity of HCR600 decreases from +0.4% to-0.8%; the maximum difference between positive polarity and negative polarity is 0.14% and the linearity of negative polarity is superior to that of positive polarity. Besides, the paper used a 500kV resistance divider (SMR 7.7/ref500) calibrated by PTB to compare with HCR600, and obtained the linearity curve. By comparison, two curves show a good agreement, the maximum difference between them is 0.15% at the same voltage. The result shows that the method proposed in the paper can be used to measure the linearity of divider accurately. It also can be used as experimental verification in the process of the national standard establishing and to calibrate the ultrahigh voltage impulse voltage measuring equipments when equipments satisfy some requirements.

Abstract: If a certain type of tracked artillery to keep driving straight, it’s mobile devices must make the lef and the right speed equal to two tracks winding movement. But in the actual moving process, due to the poor working conditions,such as mud and water erosion, sand grinding, undulating slopes, etc, in the case of uneven wear on both sides of the track, tracked artillery in use for some time, and sometimes there will be automatic deviation phenomenon. For this failure phenomenon, the use of the vehicle and steering theory, from the track wear inconsistent, inconsistent tightness, old and new with inconsistencies and change on both sides of the road wheel locating inconsistencies four aspects of a certain type of tracked artillery deviation phenomenon analyzed, by analyzing the proposed treatment measures.