• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.7
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• pp.1158-1168
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• 1994

A variable structure control scheme(VSCS) with sliding mode that can be applied to the process with input/output(I/O) delay is proposed and its control performances is evaluated. The proposed VSCS with and output feedback scheme comprises a variable structure controller, a servo dynamic for tracking the set-poing, and a Smith predictor for compensating the effects of time delay. The robustness against the parameter variations and external disturbances can be achieved by the proposed VSCS even when the controlled process includes I/O delay. And the desired transient response is obtained by simple adjustment of the coefficients of the switching surface equation.

• Korean Journal of Computational Design and Engineering
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• v.14 no.4
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• pp.234-241
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• 2009

The use of aluminum parts in automobile structuraI applications has increased in an effort to reduce the weight of cars and hence improve fuel economy. But Aluminum bar, I-beam and channels need other processes to vary the cross section in the axial direction. Thus, applications of these parts are limited by high cost. If the cross section of the part is variable by using only extrusion, application of extruded bar, I-beam and channels will increase in the Aluminum industries. In this paper, we propose the variable-shape extrusion process which can control the thickness of Aluminum bar. And we can calculate the speed of center ram by varying the cross section in the extrusion to control the thickness of Aluminum bar.

• Journal of Biosystems Engineering
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• v.25 no.5
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• pp.341-350
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• 2000

This study was conducted to develop a control unit for a tying device of a variable chamber round baler. The work process of the tying device was thoroughly analyzed and the control sequence was established according to the work process. Based on this control sequence, a control unit using an 8 bit microprocessor AT 89C52 as a CPU was developed. The driving circuit to control the actuator motion was developed and the PWM method was used to regulate the velocity of the actuator. On the front panel of the control unit, indicators were also installed to show the operations being conducted. A prototype of the developed control unit was manufactured and tested. A total of 50 complete cycles of the control sequence was repeated and no failure was observed. It was evaluated that the developed control unit has an excellent performance and can be used practically for variable chamber round balers.

• Journal of the Korean Institute of Gas
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• v.17 no.4
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• pp.51-57
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• 2013

The process of liquefied natural gas is less then $-160^{\circ}C$ to natural gas by cooling at atmospheric pressure. When control strategy was made, one of the most significant is analysis of process. It is important to understand the control variable change according to manipulated variable change. In this study, we experiment natural gas liquefied process using C3MR(Propane Pre-cooled Mixed Refrigerant) process by BSU(Bench Scale Unit). We analyzed the change of refrigerant temperature and natural gas temperature according to the change of refrigerant flow rate so as to search an influence flow rate according to adjust each manipulated variables. One of the manipulated variable affected a number of control variables, but were able to confirm a control variable with a large response.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.6
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• pp.29-35
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• 2020

Transition Nozzles are used in industrial air-cooled heat exchangers and widely used in industrial sites as an important component in the heat energy transfer between a heat source and an actuating fluid. There is a worldwide demand for transition nozzles with various materials and shapes, depending on the use environment. This paper aims to improve the transition nozzle forging process suitable for the production of many varieties using Steps 1 to 6 of the TRIZ Methodology for Problem Solving. By utilizing the TRIZ Methodology, this study derives a method to design a variable mold, which is more efficient and can reduce costs compared with having to use several molds. To verify the suitability of the methods derived using the TRIZ technique, a forging analysis is performed on a transition nozzle using DEFORMⓇ, a commercial program for plasticity analysis, and the nozzle material is evaluated for damage as a result of deformation of the transition nozzle thickness. The derived methods can be applied to transition nozzle formation equipment to improve the efficiency of the formation process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.643-644
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• 2009

• Journal of Korean Society for Quality Management
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• v.44 no.4
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• pp.751-770
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• 2016

Purpose: Two-stage ${\bar{X}}$ chart is a useful tool for process control when a surrogate variable may be used together with a performance variable. This paper extends the two-stage ${\bar{X}}$ chart to a three stage version by decomposing the first stage into the preliminary stage and the main stage. Methods: The expected cost function is derived using Markov-chain approach. The optimal designs are found for numerical examples using a genetic algorithm combined with a pattern search algorithm and compared to those of the two-stage ${\bar{X}}$ chart. Sensitivity analysis is performed to see the parameter effects. Results: The proposed design outperforms the optimal design of the two-stage ${\bar{X}}$ chart in terms of the expected cost per unit time unless the correlation between the performance and surrogate variables is modest and the shift in process mean is smallish. Conclusion: Three-stage ${\bar{X}}$ chart may be a useful alternative to the two-stage ${\bar{X}}$ chart especially when the correlation between the performance and surrogate variables is relatively high and the shift in process mean is on the small side.

• KSBB Journal
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• v.26 no.5
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• pp.374-380
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• 2011

Earlier in Korea Kimchi was made in every family and every province has own taste and specialties. These days almost of the Kimchis are manufactured. We collected variable Kimchis, which were made for private use and isolated microorganisms. Some interesting micobial cells were identified and studied for its application as food and drinks. One of them was identified as Lactobacillus sakei KJ123. This strain is known as producing interesting aromatic components during Sakei fermentation like Kimchi in variable conditions. We tried to develop a health beverage with fermentation process. The Cucurbita maxima has been known as a traditional healthy food and variable positive effects on the human body were already reported. In this study we tried to develop a production process for a healthy fermented drink on this substrate with strains originated from Kimchi. Many kinds of lacctobacilli species existed in the fermented food cannot survive in the acidic conditions like human stomach. So we selected resisting strains in this conditions. The survival rate of Lactobacillus sakei cells in the artificial gastric juice and bile acid and other physiological characteristics at the variable conditions have been tested. After fermentation process some sensory tests on the product with panels were tried.

• 전기의세계
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• v.22 no.5
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• pp.12-18
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• 1973

This paper deals with Linear Programming by Signal Flow Graph technique which is different from that of Mason and Coates. The objective function is regarded as variable, and slack variable node, artificial variable node and objective function variable (constant) node are newly defined, which shows the process for optimization of solution very intuitively. Also methods for solving L.P. and examples with subject to Ax.leq.b, Ax=b and Ax.geq.b are presented.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.690-691
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• 2006

Variable valve timing unit, which is able to decrease environmental load and improve fuel economy is loaded onto many automobiles recently. This unit consists mainly of sprocket, housing and rotor. These parts are requested different properties according to environment. We produce sintered parts for variable valve timing unit by selecting compact, sinter process and special treatment according to demanded properties. In this paper, demanded properties of sintered parts for variable valve timing unit and adopted technique to satisfy them are presented.