• Transactions of Materials Processing
• /
• v.15 no.4 s.85
• /
• pp.295-303
• /
• 2006

Optimization is carried out to determine process parameters which reduce the amount of springback and improve shape accuracy of a deep drawn product in sheet metal forming process. The study uses the amount of stress deviation along the thickness direction in the deep drawn product as an indicator of springback instead of springback simulation. The scheme incorporates with an explicit elasto-plastic finite element method for calculation of the final shape and the stress deviation The optimization method adopts the response surface method in order to seek for the optimum condition of process parameters such as the blank holding force and the draw-bead force. The present scheme is applied to design of the variable blank holding force in an U-draw bending process and the application is further extend ε d to the design of draw-bead force in a front side member formed with advanced high strength steel (AHSS) sheets of DP60. Results show that design of process parameter is well performed to decrease the stress deviation through the thickness and to reduce the amount of springback. The present analysis provides a guideline in a design stage for controlling the springback based on the finite element simulation of the complicated parts.

• Journal of the Optical Society of Korea
• /
• v.18 no.6
• /
• pp.657-662
• /
• 2014

We demonstrate a simulation of a parallel hybrid fiber amplifier in the C+L-band with a gain controlling technique. A variable optical coupler is used to control the input signal power for both EDFA and RFA branches. The gain spectra of the C+L-band are flattened by optimizing the coupling ratio of the input signal power. In order to enhance the pump conversion efficiency, the EDFA branch was pumped by the residual Raman pump power. A gain bandwidth of 60 nm from 1530 nm to 1590 nm is obtained with large input signal power less than -5 dBm. The gain variation is about 1.06 dB at a small input signal power of -30 dBm, and it is reduced to 0.77 dB at the large input signal power of -5 dBm. The experimental results show close agreement with the simulation results.

• Asian Pacific Journal of Cancer Prevention
• /
• v.17 no.sup1
• /
• pp.55-63
• /
• 2016

Smoking and harmful drinking dramatically increase health risks but little is known about their cooccurrence and factors that influence this co-habit, limiting development and implementation of appropriately targeted prevention interventions. This study was conducted among youth aged 10-24 years old in the Chi Linh Demographic - Epidemiological Surveillance System (CHILILAB DESS). The total numbers in the first, second and third rounds in 2006, 2009 and 2013 were 12,406, 10,211, and 7,654, respectively. A random-effects logit model controlling for both time-variant and time-invariant variables was applied to explore factors associated with current smoking, harmful drinking, and occurrence of smoking and harmful drinking together. We found dramatically increasing trends in current smoking, harmful drinking and co-occurrence among youth. Our results indicate similar health problems among youth in peri-urban areas in Vietnam. Demographic characteristics (older age, being male, being unmarried, and having informal work) appeared to be predictors for smoking and drinking behaviour. Besides, peer and family members had significant influence on smoking, whereas having a close-friend who was smoking was the most important variable. The results suggested that smoking and harmful drinking should not be solved with separate, stand-alone interventions but rather with integrated efforts.

• Journal of the Korea Society of Computer and Information
• /
• v.21 no.10
• /
• pp.29-35
• /
• 2016

In this paper, we propose a scheme to prolong the lifetime of the sensor network by reducing the power consumption of the sensor node. The proposed algorithm reduces the number of transmissions and sensing at the application layer. We combine the VIS scheme with the MSZ algorithm and call it as the SZM/VIS algorithm. The actual temperature data was collected using the sensor nodes to assess the performance of the proposed algorithm. The proposed algorithm was implemented through the programming and was evaluated under various setting values. Experimental results show that the SZM/VIS has a slightly improved transmission ratio than that of the MSZ while has the periodic transmission capability like as the MSZ. Also the SZM/VIS can significantly reduces the sensing ratio like that of the VIS. Our algorithm has the advantages of instantaneous, simplicity, small overhead and robustness. Our algorithm has just negligible side effects by controlling the parameter properly depending on the application types. The SZM/VIS algorithm will be able to be used effectively for the applications that need to be managed within a certain range of specific properties, such like crop management.

• Journal of Environmental Health Sciences
• /
• v.44 no.4
• /
• pp.348-359
• /
• 2018

Objectives: The purpose of this study was to investigate the relationship between frequency of alcohol drinking and blood mercury concentration in Korea. Methods: This was a cross-sectional study that used data from the Korean National Health and Nutrition Examination Survey. Among them, 3,174 persons were selected for the final study. Results: The concentration of mercury in the blood increased as the frequency of drinking soju or beer increased. Similarly, in the multiple-linear regression analysis model, the frequency of soju drinking was identified as an independent variable showing a statistically significant positive linearity (p<0.001). After controlling for confounding factors, comparing those drinking 'more than twice a week' with those who almost do not drink alcohol, the adjusted ORs for exposure to high concentrations of mercury were 3.24 (95% CI, 2.10-4.99) for drinking soju and 2.07 (95% CI, 1.33-3.22) for drinking beer. The interaction effect between 'soju drinking' and 'spicy pollack and seafood stew' was not statistically significant (p=0.098) for evaluating the interaction effect between the two variables. Conclusions: The concentration of mercury in the blood increased as the frequency of drinking of soju or beer increased. The higher the frequency of alcohol drinking, the more likely is the blood mercury to be included in the high-concentration group. The results of this study can be used as important scientific evidence for the field of environmental health related to alcohol drinking and blood heavy metal exposure in Korea.

• Journal of the Korean earth science society
• /
• v.23 no.2
• /
• pp.154-165
• /
• 2002

The purpose of this study was to examine the effects of metastrategic exercise on a scientific reasoning strategy to control variables, and investigate the developmental patterns in the strategy usage within a given period. Two groups composed of 90 fifth grade students engaged in a scientific reasoning task over six daily sessions. Additionally, one group engaged in metastrategic exercise on fictional students' strategies of controlling variables on the task, while the other spent equivalent time on an unrelated task. Based upon results of the study, the following conclusions can be drawn. First, the metacognitive exercise on the strategy to control variables has positive and long-standing effects on the strategy performance at the reasoning task. The exercise also takes effect of near-transfer. Taking into consideration only about sixty minutes of metastrategic practice, the results provide the validity of the activity in order to develop children's reasoning strategies. Second, in a scientific reasoning task, each child seems to go through one out of two developmental patterns in their usage of reasoning strategies: gradual change or fundamental change. Considering the ratio of pattern of fundamental change between the two groups, it is clear that the metacognitive exercise influences the developmental pattern of strategy usage.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.54 no.12
• /
• pp.698-704
• /
• 2005

Passive suspensions with fixed design constants are very restrictive in the inherent suspension problem, the trade-off between the ride quality and the suspension travel. Active suspensions are used to solve some drawbacks of passive suspensions. In this paper, we propose a controller design for vehicle active suspensions considering variable driving conditions. Our controller estimates the current driving conditions by detecting the road frequencies gotten from Fourier Transform and decides which factor must be emphasized between the ride quality and the suspension travel. In one case of focusing on the ride quality, we use the skyhook control law and in the other case of focusing on the suspension travel, the double skyhook control law is used. The control law modified by various road situations outputs the reference force value the electro-hydraulic actuator in active suspension system must generate. To track the reference force, we adopt the sliding control law which is very useful in controlling the nonlinear system like the electro-hydraulic actuator.

• Proceedings of the KIEE Conference
• /
• 2004.07d
• /
• pp.2307-2309
• /
• 2004

This paper presents a modeling and simulation of a fuzzy controller for maximum power extraction of a grid-connected wind energy conversion system with a link of a rectifier and an inverter. It discusses the maximum power control algorithm for a wind turbine and proposes, in a graphical form, the relationships of wind turbine output, rotor speed, power coefficient, tip-speed ratio with wind speed when the wind turbine is operated under the maximum power control. The control objective is to always extract maximum power from wind and transfer the power to the utility by controlling both the pitch angle of the wind turbine blades and the inverter firing angle. Pitch control method is mechanically complicated, but the control performance is better than that of the stall regulation method. The simulation results performed on MATLAB will show the variation of generator's rotor angle and rotor speed, pitch angle, and generator output.

• Preventive Nutrition and Food Science
• /
• v.17 no.3
• /
• pp.203-209
• /
• 2012

The effects of variable moisture content, screw speed and barrel temperature on the physicochemical properties of red ginseng powder extrudates were investigated. The raw red ginseng powders were processed in a co-rotating intermeshing twin-screw extruder. Primary extrusion variables were feed moisture content (20 and 30%), screw speed (200 and 250 rpm) and barrel temperature (115 and $130^{\circ}C$). Extruded red ginseng showed higher crude saponin contents (6.72~7.18%) than raw red ginseng (5.50%). Tested extrusion conditions did not significantly affect the crude saponin content of extrudates. Increased feed moisture content resulted in increased bulk density, specific length, water absorption index (WAI), breaking strength, elastic modulus and crude protein content and decreased water solubility index (WSI) and expansion (p<0.05). Increased barrel temperature resulted in increased total sugar content, but decreased reducing sugar content in the extrudate (p<0.05). Furthermore, increased barrel temperature resulted in increased amino acid content and specific length and decreased expansion and bulk density of extrudates only at a higher feed moisture content. The physicochemical properties of extrudates were mainly dependent on the feed moisture content and barrel temperature, whereas the screw speed showed a lesser effect. These results will be used to help define optimized process conditions for controlling and predicting qualities and characteristics of extruded red ginseng.

• Journal of ILASS-Korea
• /
• v.22 no.3
• /
• pp.146-152
• /
• 2017

An experimental study was carried out to investigate the spray characteristics of non-circular effervescent twin-fluid nozzles. For this purpose, two types of non-circular nozzles (E1, E2) and circular nozzle (C) were used. Three types of aerorators with hole diameters of 1.2, 1.7 and 2.1 mm were used. Each aerorator has a total of 12 holes. It is defined by area ratio which is ratio of exit orifice area and aerator hole area. Experiments were carried out by controlling the amount of air flowing after fixing the flow rate of the liquid, and the nozzle internal pressure and SMD were measured, and the jet image was taken from the nozzles. The discharge coefficients of the three kinds of nozzles were compared with the used in plain orifice's equation and the Jedelsky's equation, and the Jedelsky's equation was found to be about 3 times larger. In addition, empirical formula based on ALR, which is the largest variable in Jedelsky's equation, was derived. The droplet sizes(SMD) were found to be smaller in the non-circular shape than in the circular shape, which is concluded to be caused by the difference of the discharge coefficients.