• Journal of the Korean Society for Precision Engineering
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• v.13 no.11
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• pp.106-113
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• 1996

Using stainless steel as the cold forged parts especially the outer parts of automobile is gradually increasing because it can bear up against the erosion and the wear. During cold forging of the stainless steel the working pressure acting on die surface are very high therefore the wear on die surface can be greatly increased. In cold forging processes, die failure must be considered before die design. One of the main reasons of die failure in industrial application of metal forming technologies is wear. The die wear affects the tolerances of forged parts, metal flow and costs of processes etc. The only way to to control these failures is to develop methods which allow prediction of the die wear and which are suited to be used in the desing stage in order to optimize the process. In this paper, the rigid-plastic finite element method was combined with the wear prediction routine and then the forward extrusion process using stainless steel was analysed simultaneously. To minimize the die wear the FPS algorithm was applied and the optimal conditions of die configuration are suggested.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.20-20
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• 2000

Back-propagation neural network (BPNN) is the most prevalently used paradigm in modeling semiconductor manufacturing processes, which as a neuron activation function typically employs a bipolar or unipolar sigmoid function in either hidden and output layers. In this study, applicability of another linear function as a neuron activation function is investigated. The linear function was operated in combination with other sigmoid functions. Comparison revealed that a particular combination, the bipolar sigmoid function in hidden layer and the linear function in output layer, is found to be the best combination that yields the highest prediction accuracy. For BPNN with this combination, predictive performance once again optimized by incrementally adjusting the gradients respective to each function. A total of 121 combinations of gradients were examined and out of them one optimal set was determined. Predictive performance of the corresponding model were compared to non-optimized, revealing that optimized models are more accurate over non-optimized counterparts by an improvement of more than 30%. This demonstrates that the proposed gradient-optimized teaming for BPNN with a linear function in output layer is an effective means to construct plasma models. The plasma modeled is a hemispherical inductively coupled plasma, which was characterized by a 24 full factorial design. To validate models, another eight experiments were conducted. process variables that were varied in the design include source polver, pressure, position of chuck holder and chroline flow rate. Plasma attributes measured using Langmuir probe are electron density, electron temperature, and plasma potential.

• Journal of Life Science
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• v.11 no.3
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• pp.284-290
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• 2001

Changes in chemical components of small black bean chungkugjang(SBBC) added with kiwi and radish as foodstuffs to repress off-odor and enhance the quality of SBBC suring fermentation were investigated. Optimal pretreatment conditions of small black bean suitable to the fermentation of chungkugjang were 3 hrs of soaking time 1.5 times of ratio of water to black bean. 1.0 atm of high pressure, 20 min of heating time, cutting and crushing of heat-treated black bean. Moisture content of SBBC was remarkably lower than that of soybean chungkugjang(SBC) as control. Crude protein of SBBC was in the range 23.37∼25.71% and higher than that of SBC, Crude lipid of SBBC was lower than that of SBC. Crude lipid of SBBC added with kiwi and radish paste was decreased than that of SBBC without two foodstuffs. pH of SBBC were rapidly increased to 24 hrs of fermentation and gradually increased thereafter. Total acidity was shown to be reversely decreased as compared to pH tendency. Reducing sugar was increased to 24 hrs of fermentation and then decreased. In SBBC and SBC, potassium was the most abundant followed by phosphorus, magnesium and calcium.

• Transactions on Electrical and Electronic Materials
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• v.5 no.1
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• pp.11-14
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• 2004

An rf triode magnetron sputtering system is designed and installed its construction in vacuum chamber. In order to calibrate the rf triode magnetron sputtering for thin films deposition processes, the effects of different glow discharge conditions were investigated in terms of the deposition rate measurements. The basic parameters for calibrating experiment in this sputtering system are rf power input, gas pressure, plasma current, and target-to-substrate distance. Because a knowledge of the deposition rate is necessary to control film thickness and to evaluate optimal conditions which are an important consideration in preparing better thin films, the deposition rates of copper as a testing material under the various sputtering conditions are investigated. Furthermore, a triode sputtering system designed in our team is simulated by the SIMION program. As a result, it is sure that the simulation of electron trajectories in the sputtering system is confined directly above the target surface by the force of E${\times}$B field. Finally, some teats with the above 4 different sputtering conditions demonstrate that the deposition rate of rf triode magnetron sputtering is relatively higher than that of the conventional sputtering system. This means that the higher deposition rate is probably caused by a high ion density in the triode and magnetron system. The erosion area of target surface bombarded by Ar ion is sputtered widely on the whole target except on both magnet sides. Therefore, the designed rf triode magnetron sputtering is a powerful deposition system.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.5
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• pp.58-64
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• 2006

Homogeneous charge compression ignition(HCCI) combustion is an advanced technique for reducing the hazardous nitrogen oxide(NOx) and particulate matter(PM) in a diesel engine. NOx could be reduced by achieving lean homogeneous mixture resulting in combustion temperature. PM could be also reduced by eliminating fuel-rich zones which exist in conventional diesel combustion. However previous researches have reported that power-output of HCCI engine is limited by the high intensive knock and misfiring. In an attempt to extend the upper load limit for HCCI operation, supercharging in combination with Exhaust Gas Recirculation(EGR) has been applied: supercharging to increase the power density and EGR to control the combustion phase. The test was performed in a single cylinder engine operated at 1200 rpm. Boost pressures of 1.1 and 1.2 bar were applied. High EGR rates up to 45% were supplied. Most of fuel was injected at early timing to make homogeneous mixture. Small amount of fuel injection was followed near TDC to assist ignition. Results showed increasing boost pressure resulted in much higher power-output. Optimal EGR rate influenced by longer ignition delay and charge dilution simultaneously was observed.

• Fire Science and Engineering
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• v.18 no.2
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• pp.73-78
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• 2004

This study investigated about smoke/heat interception screen that can protect underneath of fire door and floor when occur fire, and keep out leakage or diffusion of smoke/heat. In this study, to considered differential pressure form smoke control area and mechanical force by fluid buoyancy of smoke when occur fire and stream of heat, are analyzed to used $ANSYS^{\circledR}$ of finite element analysis code. It presented direction of optimal design of smoke/heat interception screens that can minimize loading condition from study results, and helped that construct basic engineering data of smoke/heat interception systems as that utilize its shape design of smoke/heat interception screens.

• Journal of Drive and Control
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• v.18 no.4
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• pp.84-90
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• 2021

Viscosity of hydraulic oils decreases due to loss reduction and efficiency increase of fluid power systems. However, low viscosity is not always appropriate due to the induction of large leakage and small lubricity. Therefore, a detailed study on the optimum viscosity of hydraulic oils is necessary. In this study, based on the thermohydrodynamic lubrication theory, numerical simulation was conducted using the slipper model of swashplate-type axial piston pumps and motors. The viscosity grades' (VG) effects of oils on power losses are mainly discussed numerically in fluid film lubrication, including changes in temperature and viscosity. The simulation results reveal that the flow rate increases and the friction torque decreases as VG decreases. The film temperature and power loss were minimised for a specific oil with a VG. The minimum conditions regarding the temperature and loss were different and closed. Under various operating conditions, the film temperature and power loss were minimised, suggesting that an optimum hydraulic oil with a specific VG could be selected for given operating conditions of pressure and speed. Otherwise, a preferable operating condition must be established to determine a specific VG oil.

• Journal of Drive and Control
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• v.21 no.2
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• pp.1-7
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• 2024

This paper proposes a novel cooling system for hydrogen fuel cell cooling systems by integrating heat pump technology to enhance operational efficiency. The study analyzed the cooling efficiency of the fuel cell cooling system. With the increasing focus on eco-friendly vehicle technologies to address environmental concerns and global warming, the transportation sector, a major contributor to greenhouse gas emissions, needs technological enhancements for better efficiency. The proposed cooling system was modeled through 1-D simulations. The analysis results of parameters such as thermal balance, temperature, and pressure of each component confirmed the stable operation of the system. By examining variations in the cooling system's flow rate, compressor RPM, and the Coefficient of Performance (COP) based on different refrigerants, initial research was conducted to derive optimal operating conditions and parameter values.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.9 no.1
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• pp.27-44
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• 2002

The main purpose of this study was to identify the effect of hand massage on pain and anxiety related to chest tube removal in patients with a lobectomy. The research design of this study was a nonequivalent control group non-synchronized design. Of the twenty nine adult subjects, fourteen were assigned to the experimental group and fifteen to the control group. The data were obtained over 3 months from a medical center in Seoul. The instruments used to assess trait state anxiety was the Spielberger Trait-State anxiety Inventory. For pain and psychological anxiety. The Visual Analogue Scale was used. Hiko analogue sphygmo-manometer(2001) was used to check blood pressure and pulse rate as indicators of physiological anxiety Subjects in the experimental group received hand massage for 5 minutes just before chest tube was removed, and subjects assigned to the control group did not receive hand massage. Data were analysed with $x^2$-test and Mann-Whitney U test using the SPSSWIN 10.0 program. The results of the study are as follows : 1. Hypothesis 1: 'there will be a significant difference between two groups in the level of pain after chest tube removal' was supported (u = 23.00, p < 0.001). 2. Hypothesis 2: 'there will be a significant difference between the two groups in the level of psychological anxiety after chest tube removal' was supported (u = 3.00, p < 0.001). 3. Hypothesis 3: 'there will be a significant difference between the two groups in physiological anxiety(systolic, diastolic blood pressure and pulse rate) after chest tube removal' was supported(u =55.50, p = 0.01 ; u = 41.50, p = 0.01 ; u = 20.50, p < 0.001, relatively). The findings of this study indicate that hand massage is effective for pain and anxiety related to chest tube removal in patients with lobectomy. Therefore, hand massage is recommended as an effective nursing intervention for relieving pain and anxiety in patients undergoing chest tube removal. Further research is needed to identify the proper duration and timing to achieve the optimal effect of hand massage. A larger subject population is required to apply the current findings to the general population. Further research is also needed to assess the effects of hand massage in other patient subsets. Finally, it would be interesting to see if the effects of hand massaging would be attenuated when performed by a non-medical specialist.

• The Journal of Internal Korean Medicine
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• v.30 no.2
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• pp.270-287
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• 2009

Objective : Yinjinchunggan-tang(YJCGT) is reported previously as having theraputic effects on hepatitis such as anti-implammatory, anti-apoptotic, anti-viral(HBV), etc. Though this prescription is not studied on its anti-fibrogenic effect, it is still expected to have the effect in the liver. Thus, this study was performed to investigate the anti-fibrogenic effect of YJCGT on thioacetamide(TAA)-induced liver fibrosis in rats. Method: Rat liver fibrosis was induced by intraperitoneal TAA injection(150mg/kg) 3 times a week for 5 weeks. After the YJCGT (YJCGT 1g/kg, YJCGT 2g/kg)-treatment, body weight, liver and spleen weights, liver function test, the complete blood count and the portal pressure were studied. In addition, gene expressions of ASMA, procollagen type Ia2, MMP2, TIMP1 and TIMP2, all of which are known to be associated with liver fibrosis, were analyzed by RT-PCR. After YJCGT (YJCGT 1g/kg, YJCGT 2g/kg) treatment, percentages of collagen in TAA-induced rat liver tissue were measured by image analyzer. Results : The body weight of the normal group increased more than that of the control and YJCGT-treated groups. The AST level of the YJCGT lg/kg-treated group significantly decreased compared to that of the control. The ALT and the GGT levels of the YJCGT 2g/kg-treated group significantly increased compared to those of the control. In the YJCGT-treated groups. WBC, RBC and Hgb elevated by TAA injection decreased but platelet count increased. In the YJCGT lg/kg-treated group, the portal pressure elevated by TAA injection significantly decreased. The significant decreases in the gene expressions of procollagen type Ia2, MMP2 and TIMP2 were observed in the YJCGT-treated groups. In histological findings. TAA injections caused severe liver fibrosis, but the YJCGT treatment significantly reduced the amounts of hepatic collagens. Conclusions: These results suggest that YJCGT has beneficial effects on the treatment of patients with liver cirrhosis as well as chronic hepatitis. Further study should be done to decide the optimal concentration of the YJCGT for the treatment of liver cirrhosis.