• 한국주조공학회지
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• 제7권3호
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• pp.199-206
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• 1987

This paper presents experimental data for the computerization of green sand control. The results can be summarized as follows: 1. To obtain the proper compactability at the mixer, the addtion of moisture is far more efficient than the control of mixing time or addtion of clay. 2. The log R(% clay/% moisture) vs. log compactability curve moves upward as the amount of clay increases and moves downward as the amount of seacoal, dead bentonite or coked seacoal increases. 3. The ratio of dead to initial clay amount or coked to initial seacoal amount is changed according to sand to metal ratio, mainly, and according to pouring temperature, partly, at a shake out time of 12hrs.

• 산업기술연구
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• 제34권
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• pp.15-20
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• 2014

Recently, PMSMs(Permanent Magnet Synchronous Motors) have become increasingly popular in various high-performance motor drive applications. However, the high-performance drive of PMSMs needs a position sensor such as a resolver, which increases not only the price of the system but also reduces the system reliability. This paper is on the implementation of sensorless control of a SPMSM, which drives a fan for cooling in appliances. In this paper, the rotor position for high-performance drive of a SPMSM is derived from back electromotive force (EMF) information proportional to the rotor speed. Also, the initial rotor position information for start-up is estimated from a saturation phenomenon of inductance. The validity of the proposed sensorless drives was confirmed by the experiment on the SPMSM drive systems for cooling fans of refrigerators and laptop computers.

• 한국식품저장유통학회지
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• 제3권1호
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• pp.33-38
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• 1996

To investigate the food preservative effects of mustard seed(Brassica juncea), mustard seed were added to Kimchi. Titratable acidity of Kimchi treated with mustard seed was higher than that of non-treated control at initial stage, but it was lower than control after 2 days of fermantation. The number of bacteria and lactic acid bacteria increased rapidly at the initial stage of fermentation and reached plateau by 2 days of fermentation. The number of bacteria and lactic acid bacteria of Kimchi treated with mustard seed was lower than that of control, and the more mustard seed added the less bacteria and lactic acid bacteria were observed.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제6권1호
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• pp.15-20
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• 2006

In this paper we study the exact controllability for the nonlinear fuzzy control system with nonlocal initial condition in $E_N^n$ by using the concept of fuzzy number of dimension n whose values are normal, convex, upper semicontinuous and compactly supported surface in $R^n$. $E_N^n$ be the set of all fuzzy numbers in $R^n$ with edges having bases parallel to axis $X_1,X_2,\;,X_n$.

• 대한산업공학회지
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• 제19권4호
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• pp.105-114
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• 1993

In this article, a planar geodesic (2-dimensional minimum length curve between two points) on which the maximum curvature is constrained and with prescribed initial and terminal directions is studied. A generic problem is formulated by the minimum-time optimal control problem in free terminal time. It is shown that the optimal path ($G^2$) may contain a singular arc or not and that the general types of $G^2$ can he classified into the 3 classes of control sequences. Finally, the explicit form of $G^2$ is derived geometrically as well as algebraically form the main theorem of this article.

• Computers and Concrete
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• 제24권3호
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• pp.207-222
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• 2019

This paper has presented an effective and accurate meso-scale finite element model for simulating the fracture process of concrete under compression-shear loading. In the proposed model, concrete is parted into four important phases: aggregates, cement matrix, interfacial transition zone (ITZ), and the initial defects. Aggregate particles were modelled as randomly distributed polygons with a varying size according to the sieve curve developed by Fuller and Thompson. With regard to initial defects, only voids are considered. Cohesive elements with zero thickness are inserted into the initial mesh of cement matrix and along the interface between aggregate and cement matrix to simulate the cracking process of concrete. The constitutive model provided by ABAQUS is modified based on Wang's experiment and used to describe the failure behaviour of cohesive elements. User defined programs for aggregate delivery, cohesive element insertion and modified facture constitutive model are developed based on Python language, and embedded into the commercial FEM package ABAQUS. The effectiveness and accuracy of the proposed model are firstly identified by comparing the numerical results with the experimental ones, and then it is used to investigate the effect of meso-structure on the macro behavior of concrete. The shear strength of concrete under different pressures is also involved in this study, which could provide a reference for the macroscopic simulation of concrete component under shear force.

• 한국음향학회지
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• 제26권1호
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• pp.32-41
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• 2007

엔지니어의 모니터링 위치가 한 지점에만 한정되어 있는 음향조정실의 기존개념을 여러 사람이 동시에 작업할 수 있는 지역적인 방식으로 개선하였다. 이를 위하여, Davis의 $LEDE^{TM}$ 방식을 도입하였고, 내부의 구조 및 흡음재료의 특성, 확산기 및 저역흡음기의 설치와 음상법 등을 활용하여 초기시간지연을 제어하였다. 따라서 여러 엔지니어들이 서로 유사한 음향특성 하에서 동시에 소리를 모니터링 할 수 있는 무반사지역을 형성시켰다. 뿐만 아니라, 음향조정실 (특히 무반사지역) 안에서 정재파, 음향초점, 컬러링, 하스효과 그리고 플러터 에코 등의 발생을 억제하거나 크게 감소시킬 수 있었다.

• 제어로봇시스템학회논문지
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• 제14권12호
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• pp.1266-1269
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• 2008

We propose an integral sliding mode control for robot manipulators guaranteeing that sliding motion exists starting from an initial time. Also, we prove the asymptotic stability for robot manipulators using three important properties in the robot dynamics: skew-symmetry, positive-definiteness, and boundedness of robot parameter matrices. From illustrative examples, we show that the proposed method effectively controls for robot manipulators.

• 산업경영시스템학회지
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• 제33권3호
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• pp.146-153
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• 2010

When the production run is short and process parameters change frequently, it is difficult to monitor the process using traditional control charts. In such a case, the coefficient of variation (CV) is very useful for monitoring the process variability. The CV control chart is an effective tool to control the mean and variability of process simultaneously. The CV control chart, however, is not sensitive at small shifts in the magnitude of CV. The CV-EWMA(exponentially weighted moving average) control chart which was developed recently is effective in detecting a small shifts of CV. Since the CV-EWMA control chart scheme can be viewed as a weighted average of all past and current CV values, it is very sensitive to small change of mean and variability of the process. In this paper, we propose an FIR(Fast initial response) CV-EWMA control chart to improve the sensitivity of a CV-EWMA scheme at process start-up or out-of-control process. Moreover, we suggest the values of design parameters and show the results of the performance study of FIR CV-EWMA control chart by the use of average run length(ARL). Also, we compared the performance of FIR CV-EWMA control chart with that of the CV-EWMA control chart and we found that the CV-EWMA control chart gives longer in-control ARL and much shorter out-of-control ARL.

• 한국학교보건학회지
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• 제12권1호
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• pp.27-44
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• 1999

Obesity in children is a major concern of public health. This study was performed to illuminate its effect on weight control program and the associated factors of obesity-related habits and obesity index in primary school obese children. Weight control program consisted of behavioral modification, nutrition education and exercise during 17 weeks. The sample consisted of treatment group(n=42) and control group(n=41). There was no statistical difference between the two groups in obesity index, socioeconomic status and grade. To assess the effects of weight control program, the subjects were given pre-test and post-test such as the measurement of anthropometric values and self-reporting questionnaire. This result of this study were as follows; 1. After weight control program was applied, there was a significant decrease in obesity index among the treatment group. Obesity-related habits score of the treatment group increased significantly, While there was not much difference between the pre-test and the post-test among the control group. But exercise habit didn't increase significantly in the both groups. 2. Correlation between obesity-related habits and obesity index were not evident. 3. After application of weight control program, the factors associated with change of eating habit were children's past experience of weight control, motivational change toward weight control program and friends' support for treatment group. The factors associated with change of exercise habit were post-test motivation score and friends' support. Motivational change toward weight control and pre-test self-efficacy of exercise behavior were counter-related to exercise habit. For change of other obesity-related habits, initial obesity index, motivational change, post-test self-efficacy score of exercise behavior and paternal educational status were closely associated. But post-test self-efficacy score of eating behavior was unrelated. 4. Only the factor of experience of weight control was associated with change of obesity index. 5. For the both groups, the factors associated with change of eating habits were post-test self-efficacy of eating behavior and family's support. The factors associated with change of exercise behavior were self-efficacy changes of exercise behavior and friends' support. The factors associated with change of other obesity-related habits were self-efficacy change of eating behavior. Initial obesity index was associated with change of obesity index. 6. The rate of dropouts from weight control program was 28.6% (12/42) in treatment group. Initial obesity index, other obesity-related habits except eating exercise habits, friend's support were associated with dropout. In conclusion, these results indicated that weight control program in primary school settings was effective. Direct exercise regimen and practice was demanded. In addition to the program itself, much of the success is dependent on the degree of motivation of the children involved and support provided by their parents and friends. Further study need to be performed under the condition that the weight control progrom is applied for a longer period.