• 한국분말재료학회지
• /
• 제19권2호
• /
• pp.127-133
• /
• 2012

The sintering behaviors and process parameters of some compounds (carbides, oxides, sulfides, borides) were investigated experimentally. These compounds were successfully consolidated and showed high densities. Some unique phenomena such as retardation of grain growth, suppression of thermal decomposition and maintenance of initial non-equilibrium phases, were observed by the proper control of process in spark sintering.

• 대한수학회지
• /
• 제47권6호
• /
• pp.1137-1146
• /
• 2010

In this paper, we study the divergence based goodness of fit test for partially observed sample from diffusion processes. In order to derive the limiting distribution of the test, we study the asymptotic behavior of the residual empirical process based on the observed sample. It is shown that the residual empirical process converges weakly to a Brownian bridge and the associated phi-divergence test has a chi-square limiting null distribution.

• Journal of the Korean Data and Information Science Society
• /
• 제20권1호
• /
• pp.191-202
• /
• 2009

In this study, we drive the one dimensional marginal transform function, probability density function and probability distribution function for the random variables $T_{{\xi}N}$ (Time taken by the servers during the vacations), ${\xi}_N$(Number of vacations taken by the servers) and ${\eta}_N$(Number of customers or units arrive in the system) by controlling the variability of two random variables simultaneously.

• 한국반도체및디스플레이장비학회:학술대회논문집
• /
• 한국반도체및디스플레이장비학회 2006년도 춘계학술대회
• /
• pp.156-159
• /
• 2006

In order to design an evaporation system, geometric simulation of film thickness distribution profile is required. In this paper, a geometric modeling algorithm is introduced for process simulation of the evaporating process. The physical fact of the evaporating process is modeled mathematically. Based on the developed method, the thickness of the thin-film layer can be successfully controlled.

• Journal of the Korean Data and Information Science Society
• /
• 제16권2호
• /
• pp.401-410
• /
• 2005

In this paper, we calculate the premium rate of reliability insurance policy for brake pads for automobiles using real failure data obtained from use-condition. We try process capability analysis for the manufacturing process of brake-system. We describe the performance factors which have an effect on failure characteristics of brake pads. We also obtain the maximum likelihood estimates of shape and scale parameters of the fitted Weibull distribution for brake pads.

• Journal of the Korean Data and Information Science Society
• /
• 제16권3호
• /
• pp.581-589
• /
• 2005

The purpose of this thesis is to develop and introduce Add-in program which we can systematically, visually and dynamically study discrete probability distribution of binomial distribution, poisson distribution and hypergeometric distribution, and continuous probability distribution of normal distribution, exponential distribution, and the definition and characteristics of t distribution, F distribution and ${\chi}^2$ distribution to be driven from normal distribution, and graphs, the computation process of probability by using VBA which is the device of Excel.

• 소성∙가공
• /
• 제11권1호
• /
• pp.45-53
• /
• 2002

The forming process of metal matrix composites by die casting and squeeze casting process are limited in size and dimension In term of final parts. The melt strirring method have the problems that the homogeneous distribution of the reinforcements is difficult due to the low weldability and the density difference between the molten metal and the reinforcement. The thixoforming process for metal matrix composites has numerous advantages compacted to die casting, squeeze casting and compocasting. However, for the thixofoming process, the billet with the desired volume fraction must be heated to obtain a uniform temperature distribution over the entire cross-sectional areas. To obtain the reheating conditions of composites, the particulate reinforced metal matrix composites for thixoforming were fabricated by combined stirring process which is simultaneously performed with electro-magnetic stirring and mechanical stirring process. The matrix alloy and reinforcement are used to aluminum alloy(A357) and SiCp with diameter 14, $25{\mu}m$, respectively. The microstructure characteristics were investigated by changing the volume fraction and reinforcement size. The heating conditions to obtain the uniform temperature distribution in cross section area of fabricated metal matrix composites billet are proposed with heating time, the heating temperature and the holding time.

• 품질경영학회지
• /
• 제51권4호
• /
• pp.663-675
• /
• 2023

Purpose: Skewness is an indicator used to measure the asymmetry of data distribution. In the past, product quality was judged only by mean and variance, but in modern management and manufacturing environments, various factors and volatility must be considered. Therefore, skewness helps accurately understand the shape of data distribution and identify outliers or problems, and skewness can be utilized from this new perspective. Therefore, we would like to propose a statistical quality control method using skewness. Methods: In order to generate data with the same mean and variance but different skewness, data was generated using normal distribution and gamma distribution. Using Minitab 18, we created 20 sets of 1,000 random data of normal distribution and gamma distribution. Using this data, it was proven that the process state can be sensitively identified by using skewness. Results: As a result of the analysis of this study, if the skewness is within ± 0.2, there is no difference in judgment from management based on the probability of errors that can be made in the management state as discussed in quality control. However, if the skewness exceeds ±0.2, the control chart considering only the standard deviation determines that it is in control, but it can be seen that the data is out of control. Conclusion: By using skewness in process management, the ability to evaluate data quality is improved and the ability to detect abnormal signals is excellent. By using this, process improvement and process non-sub-stitutability issues can be quickly identified and improved.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2003년도 춘계학술대회논문집
• /
• pp.180-183
• /
• 2003

In this research, on-line model for prediction of effective strain distribution hi strip on finishing mill process is prescribed. It has been developed using several selected non-dimensional parameters and previously made average effective strain model via series of finite element process simulations, $\Delta$$\varepsilon$ was introduced to describe the effective strain distribution in strip. To confirm adequate non-dimensional variables uniqueness test was done. And to decide the order of polynomial in on-line model equation tendency test for each variables was done. The prediction accuracy of the proposed model is examined through comparison with finite element calculation results.

• 한국정밀공학회지
• /
• 제20권1호
• /
• pp.85-90
• /
• 2003

Removal rate and Within Wafer Non-Uniformity (WIWNU), the most critical issues in Chemical Mechanical Polish (CMP) process, are related to the pressure distribution, wafer shape, slurry flow, mechanical property of pad and etc. Among them, wafer warp generated by other various manufacturing process of wafer may induce the deviation of pressure distribution on the backside of wafer. In the convex shaped wafer the pressure onto the backside of wafer is higher than that of perfectly flat shaped wafer. Besides, such an added pressure is in proportion to the curvature of wafer. That is, the bigger the curvature of wafer becomes the higher the removal rate goes. And the WIWNU is known to be directly related to the pressure distribution on the wafer as well. In other words, the deviation of pressure distribution is in proportion to the WIWNU. In this paper, it is found that the wafer shape may be modified through heating the backside of it and thus properly changed pressure onto the backside of it may improve the WIWNU.