• Journal of Korean Society for Quality Management
• /
• v.28 no.3
• /
• pp.18-30
• /
• 2000

Recent studies have shown that the $\bar{X}$ chart with variable sampling intervals(VSI) and the $\bar{X}$ chart with variable sample size(VSS) are much quicker than Shewhart $\bar{X}$ chart in detecting shiks in the process. Shewhart $\bar{X}$ chart has been beneficial to detect large shifts but it is hard to apply Shewhart $\bar{X}$ chart in detecting moderate shifts in the process mean. In this article the $\bar{X}$ chart using variable sample size(VSS) and variable sampling Intervals(VSI) has been proposed to supplement the weak point mentioned above. So the purpose of this paper is to consider finding the design parameters which minimize expected loss costs for unit process time and measure the performance of VSSI(variable sample size and sampling interval) $\bar{X}$ chart. It is important that assignable causes be detected to maintain the process controlled. This paper has been studied under the assumption that one cycle is from starting of the process to eliminating the assignable causes in the process. The other purpose of this article is to represent the expected loss costs in one cycle with three process parameters(sample size, sampling interval and control limits) function and find the three parameters.

• Journal of Korean Society for Quality Management
• /
• v.45 no.4
• /
• pp.943-956
• /
• 2017

Purpose: This paper proposes a VSS(Variable Sample Size) ${\bar{X}}$ control chart using surrogate variable and shows its effectiveness compared with FSS(Fixed Sample Size) ${\bar{X}}$ control chart using either performance variable or surrogate variable. Methods: The expected cost function of VSS ${\bar{X}}$ control chart is derived. The optimal designs are then found for numerical examples using a GA(genetic algorithm) and compared to those of the FSS ${\bar{X}}$ control charts. Results: Computational results show that VSS ${\bar{X}}$ control chart using surrogate variables is superior to FSS ${\bar{X}}$ control chart using either performance variable or surrogate variable from the economic view points. Conclusion: The proposed VSS ${\bar{X}}$ control chart will be useful in industry fields where a performance variable is not avaliable or too costly.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05b
• /
• pp.129-132
• /
• 2006

This paper is to investigate passing performance of high performance concrete between reinforcing bar depending on maximum size of coarse aggregates. Increase in maximum size of coarse results in decrease in water demand and sand to aggregate to secure target slump flow. The larger the maximum size of coarse aggregates is, the denser the space between reinforcing bar is, the amount of concrete passed through the reinforcing bar cage shows to decrease. HPC has favorable passing performance, regardless of aggregate size, when only vertical reinforcing bar is arranged. Whereas, when vertical and horizontal reinforcing bar is arranged at the same time, proper space between reinforcing bar is considered larger than 32mm in case of using 20mm coarse aggregate, 38mm in case of using 25mm aggregate. The increase in maximum size of coarse aggregate leads to increase compressive strength slightly. Length change shows to be decreased with the increase in maximum size of coarse aggregate.

• Journal of the Korean Geographical Society
• /
• v.32 no.4
• /
• pp.435-444
• /
• 1997

Bars in a river bed show the flow of the river, the shape of a river bar can be easily measured in any river. The purpose of this study is to research the morphological characteristics of river bars. The case study area is the lower Golgi River, six bars were examined. All six bars are gravel bars with a grain size in excess of 2 millimeters. Four of the bars are longitudinal bars, in which the direction of the bar follows the river current. After analyzing the gravel in the bars, it was determined that as the gravel flows down the river, gravel grain size decreases while grain roundness increases. The shape of bar varies locally according to flow regime, channel slope, and w/d ratio.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.61 no.4
• /
• pp.220-224
• /
• 2012

The analysis on the bus bar effect is conducted to develop a cost effective 24kV/2,000A switchgear. The temperature enclosures and bus bars could rise due to several heat sources such as eddy current losses and copper losses. Therefore, a study on the characteristics of the electric field intensity and electromagnetic loss according to the bus bar size in a bus bar compartment is essential to design a electrically reliable high voltage switchgear. It is investigated that the electromagnetic influence to the temperature rising and the dielectric stability according to various bus bar sizes by using finite element method(FEM). The electric field intensity and electromagnetic loss according to various bus bar sizes are calculated to design a reliable and a high voltage switchgear. As results, it is found that the electromagnetic loss and the dielectric stability of bus bar could be determined by a bus bar size. It means that a cost effective 24kV/2,000A high voltage switchgear could be developed by selecting the proper size of a bus bar. Also, it is recognized that the electromagnetic characteristics according to various bus bar sizes in order to design an electrically stable high voltage switchgear when the enclosure size is determined as a fixed value. Futhermore, studies on the various nominal voltage class and bus bar sizes will be conducted to develop a cost effective high voltage switchgear.

• Structural Engineering and Mechanics
• /
• v.81 no.3
• /
• pp.367-378
• /
• 2022

In this study, combined size and shape optimization of spatial truss tower structures are presented by using new optimization algorithms named Rao-1, and Rao-2. The nodal displacements, allowable stress and buckling for compressive members are taken into account as structural constraints for truss towers. The discrete and continuous design variables are used as design variables for size and shape optimization. To show the efficiency of the proposed optimization algorithm, 25-bar, and 39-bar 3D truss towers are solved for combined size and shape optimization. The 72-bar, and 160-bar 3D truss towers are solved only by size optimization. The optimal results obtained from this study are compared to those given in the literature to illustrate the efficiency and robustness of the proposed algorithm. The structural analysis and the optimization process are coded in MATLAB programming.

• Magazine of the Korea Concrete Institute
• /
• v.7 no.6
• /
• pp.216-223
• /
• 1995

This research is aimed to investigate the influence of the structural parameters on dowel action of reinforcing bars in reinforced concrete members. I~ollowing the previous research, $^{(3.6)}$ a total of forty two specimens were tested to scrutinize the dowel action of reinforcing bars. Concrete cover, reinforcing bar size and bar distance were taken as main test variables for constant compressive strength of concrete. ]+om the test results, the structural behavior of all specimens was almost linear up to failure load. It is seen that dowel force increases as concrete cover increases. Reinforcing bar size and bar distance hardly affects dowel force. It is found that the dowel forces obtained by this experimental research is relatively close to that of regression analysis results and White's equation.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.10b
• /
• pp.873-878
• /
• 2000

Tension stiffening effects of reinforced concrete member with large diameter bar, mainly used at reactor building of nuclear power plant, are studied by uniaxial structural tests. Bond length and stress of steel bar, size of steel bar, and compressive strength of concrete are evaluated to tension stiffening by uniaxial tests. Problems and solution during the uniaxial test are suggested. The prevent splitting cracks, concrete cover-to-bar diameter ratio $c/d_{b}$ is kept 2.6~2.8. Because the bond length is increased as the size of steel bar, the specimen length of the D35 steel bar is required at least 2.0 m. The specimen length must be decided with bond length as well as concrete cover-to-bar diameter ratio to prevent splitting crack.

• Steel and Composite Structures
• /
• v.33 no.5
• /
• pp.747-753
• /
• 2019

Metaheuristic algorithm is used to solve the weight minimization problem of truss structures considering shape, and sizing design variables. The cross-sectional areas of the line element in trusses are the design variables for size optimization and the changeable joint coordinates are the shape optimization used in this study. The design of plane and spatial truss structures are optimized by metaheuristic technique named Teaching-Learning-Based Optimization (TLBO). Finite element analyses of structures and optimization process are carried out by the computer program visually developed by the authors coded in MATLAB. The four benchmark problems (trusses 2D ten-bar, 3D thirty-seven-bar, 3D seventy-two-bar and 2D two-hundred-bar) taken from literature are optimized and the optimal solution compared the results given by previous studies.

• Journal of Korean Society for Quality Management
• /
• v.32 no.4
• /
• pp.252-264
• /
• 2004

Variable sampling Interval (VSI) control charts vary the sampling interval according to value of the control statistic while the sample size is fixed. It is known that control charts with 2-state VSI scheme, which uses only two sampling intervals, give good statistical properties. Variable sample size (VSS) control charts vary the sample size according to value of the control statistic while the sampling interval is fixed. In the VSS scheme no optimal results are known for the number of sample sizes. It is also known that the variable sampling rate (VSR) $\bar{X}$ control chart with 2-state VSS and 2-state VSI scheme leads to large improvements In performance over the fixed sampling rate (FSR) $\bar{X}$ chart, but the optimal number of states for sample size Is not known. In this paper, the VSR Χ charts with multi-state VSS and 2-state VSI scheme are designed and compared to 2-state VSS and 2-state VSI scheme. The multi-state VSS scheme is considered to, achieve an additional improvement by switching from the 2-state VSS scheme. On the other hand, the multi-state VSI scheme is not considered because the 2-state scheme is known to be optimal. The 3-state VSS scheme improves substantially the sensitivity of the $\bar{X}$ chart especially for small and moderate mean shifts.