• Journal of applied mathematics & informatics
• /
• v.20 no.1_2
• /
• pp.603-610
• /
• 2006

In this paper we discuss the complete convergence of the linear process generated by negatively orthant dependent random variables under suitable conditions.

• International Journal of Aeronautical and Space Sciences
• /
• v.5 no.2
• /
• pp.1-8
• /
• 2004

Real-Time Kinematic GPS positioning is widely used for many applications.Resolving ambiguities is the key to precise positioning. Integer ambiguity resolution isthe process of resolving the unknown cycle ambiguities of double difference carrierphase data as integers. Two important issues of resolving are efficiency andreliability. In the conventional search techniques, we generally used chi-squarerandom variables for decision variables. Mathematically, a chi-square random variableis the sum of mutually independent, squared zero-mean unit-variance normal(Gaussian) random variables. With this base knowledge, we can separate decisionvariables to several normal random variables. We showed it with related equationsand conceptual diagrams. With this separation, we can improve the computationalefficiency of the process without losing the needed performance. If we averageseparated normal random variables sequentially, averaged values are also normalrandom variables. So we can use them as decision variables, which prevent from asudden increase of some decision variable. With the method using averaged decisionvalues, we can get the solution more quicklv and more reliably.To verify the performance of our proposed algorithm, we conducted simulations.We used some visual diagrams that are useful for intuitional approach. We analyzedthe performance of the proposed algorithm and compared it to the conventionalmethods.

• Transactions of Materials Processing
• /
• v.30 no.6
• /
• pp.291-300
• /
• 2021

Currently, starting with electric vehicles, the application of ultra-high-strength steel sheets and light metals has expanded to improve mileage by reducing vehicle weight. At a time when internal combustion engine vehicles are rapidly changing to electric vehicles, the application of ultra-high-strength steel is expanding to satisfy both weight reductions and the performance safety of the chassis parts. There is an urgent need to improve the quality of parts without defects. It is particularly difficult to estimate the part formability through the finite element method (FEM) in the burring operation, so product design has been based on the hole expansion ratio (HER) and experience. In this study, design of experiment (DOE), analysis of variance (ANOVA), and regression analysis were combined to optimize the formability by adjusting the process variables affecting the burring formability of ultra-high-strength steel parts. The optimal variables were derived by analyzing the influence of variables and the correlation between the variables through FE analysis. Finally, the optimized process parameters were verified by comparing experiment with simulation. As for the main influence of each process variable, the initial hole diameter of the piercing process and the shape height of the preforming process had the greatest effects on burring formability, while the effect of a lower round of punching in the burring process was the least. Moreover, as the diameter of the initial hole increased, the thickness reduction rate in the burring part decreased, and the final burring height increased as the shape height during preforming increased.

• Proceedings of the KSME Conference
• /
• 2001.06c
• /
• pp.240-245
• /
• 2001

In axiomatic approach for design evaluation, even if a mutual relation don't appear physical mapping of high level, it can appear in process mapping of low level through coupled PVs(Process Variables), but we must solve it for correct design evaluation. This paper handle a method for solving of coupled PVs by using axiomatic approach and CBR(Case-Based Reasoning). The methodology of proposal took still more shape through the instance of MCPs(Microcellular Plastics).

• Journal of the Korean Statistical Society
• /
• v.31 no.4
• /
• pp.483-490
• /
• 2002

A weak convergence is obtained for a linear process of the form (equation omitted) where {$\varepsilon$$_{t}$ } is a strictly stationary sequence of associated random variables with E$\varepsilon$$_{t}$ = 0 and E$\varepsilon$$^{^2}$$_{t}$ < $\infty$ and {a $_{j}$ } is a sequence of real numbers with (equation omitted). We also apply this idea to the case of linearly positive quadrant dependent sequence.

• Transactions of Materials Processing
• /
• v.16 no.3 s.93
• /
• pp.172-177
• /
• 2007

The process design for large-scale ring rolling of Ti-6Al-4V alloy was performed by calculation method, processing map approach and FEM simulation. The ring rolling design includes geometry design and optimization of process variables. The calculation method was used to make geometry design such as initial billet and blank sizes, and final rolled ring shape. A commercial FEM code, SHAPE-RR was used to simulate the effect of process variables in ring rolling on the distribution of the internal state variables such as strain, strain rate and temperature. In order to predict the forming defects during ring rolling and the formation of over-heating above $\beta$-transus temperature due to deformation heating, the process-map approach based on Ziegler's instability criterion was used with FEM simulation. Finally, an optimum process design to obtain sound Ti-6Al-4V rings without forming defects was suggested through combined approach of Ziegler's instability map and FEM simulation results.

• Transactions on Electrical and Electronic Materials
• /
• v.13 no.3
• /
• pp.129-135
• /
• 2012

A number of surface mount technology (SMT) process variables including land design are considered for minimizing tombstone defect in flexible printed circuit assembly in high volume manufacturing. As SMT chip components have been reduced over the past years with their weights in milligrams, the torque that once helped self-centering of chips, gears to tombstone defects. In this paper, we have investigated the correlation of the assembly process variables with respect to the tombstone defect by employing statistically designed experiment. After the statistical analysis is performed, we have setup hypotheses for the root causes of tombstone defect and derived main effects and interactions of the process parameters affecting the hypothesis. Based on the designed experiments, statistical analysis was performed to investigate significant process variable for the purpose of process control in flexible printed circuit manufacturing area. Finally, we provide beneficial suggestions for find-pitch PCB design, screen printing process, chip-mounting process, and reflow process to minimize the tombstone defects.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2008.11a
• /
• pp.207-208
• /
• 2008

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2007.11a
• /
• pp.91-92
• /
• 2007

• Journal of the Korean Home Economics Association
• /
• v.46 no.4
• /
• pp.1-13
• /
• 2008

The purpose of this study is to identify variables that influence the family decision-making process when planning a wedding. In this case the planning refers to: the procedure of the wedding: yedan, which means presents for parents and relatives: and yemul, which means wedding gifts. Decision-making was categorized into four types: decisions led by the bride and groom, decisions led by the groom's parents, decisions led by the bride's parents, and co-decisions by the two families. Resource theory was used as a conceptual framework. Data for this study were collected from 305 adults who got married after 1977 and lived in Seoul. Multinomial logistic regression models were used to analyze the data. Variables determining the decision-making of wedding procedure were the groom's age at marriage, the level of familism, and the major source for the wedding expenses. When it came to decisions on yedan, gender, the bride's year of education, and the major source for wedding expenses had significant influence on the decision-making. Variables that affected decision-making on yemul were the bride's year of education, and the major source for wedding expenses. This study suggested the power structure among bride, groom, and their parents through variables which exert influence on family decision-making.