• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2005.11a
• /
• pp.425-428
• /
• 2005

A variety of wireless devices are commercially available now. Most of studies, however, have been directed to the biological effects of mobile-phone EMF. In this study, dosimetric analysis for wireless devices of head-mounted display type and a wristwatch type were made to investigate possible biological effects of these devices. SAR (Specific Absorption Rate) distributions were calculated using FDTD (Finite Difference Time Domain) method, for adult human models such as standard Korean human model and VHP(Visible Human Project) model, as well as scaled models. Measurements were also performed for SAM phantom wearing a simplified prototype for a wireless device for validation of the simulation results. It has been found that children are more vulnerable to such exposure, and these devices could cause some biological effects for relatively lower power compared to conventional mobile pones.

• Journal of the Korea Furniture Society
• /
• v.19 no.1
• /
• pp.33-43
• /
• 2008

This study intended to explore trends of furniture sold in general merchandise stores such as Lotte mart, E-mart, GSmart, Home ever, and Home plus, which are run by conglomerates in Korea. Through internet, related books and papers, interviews with the mart-related people, styles, items, prices, manufacturers, and materials of furniture well sold in the marts were researched and analyzed qualitatively. As the result of the analysis, the furniture expressed the scale to be able to put in the cart of the marts, knock-down and folding structure to be easy to disassemble, pack, and move, low prices below one hundred thousand won, the light materials like plastic, aluminum and the more MDF than hard wood. Each item was made of PB reflecting lower prices of 10 to 20 percentage for the consumer.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2010.05a
• /
• pp.207-211
• /
• 2010

As mega-sized and complex building construction projects are increased, the importance of project scheduling and control is emphasized. Project scheduling and control technic is not used widely yet in Korea, but interests in it is progressively increased. By now, most research projects mainly have focused on scheduling issues. Project progress management is also as much important as project scheduling issues. Current state about project progress management in Korea is analysed and way for improvements are suggested in this paper. At first, research projects undergone and practice are analysed and fields experts are survey about current state about project progress management. This study suggests the progress management method for quantitative and qualitative project progress analysis.

• Journal of Powder Materials
• /
• v.24 no.1
• /
• pp.17-23
• /
• 2017

In this study, a finite element analysis approach is proposed to predict the fluid-structure interaction behavior of active materials for lithium-ion batteries (LIBs), which are mainly composed of graphite powder. The porous matrix of graphite powder saturated with fluid electrolyte is considered a representative volume element (RVE) model. Three different RVE models are proposed to consider the uncertainty of the powder shape and the porosity. P-wave modulus from RVE solutions are analyzed based on the microstructure and the interaction between the fluid and the graphite powder matrix. From the results, it is found that the large surface area of the active material results in low mechanical properties of LIB, which leads to poor structural durability when subjected to dynamic loads. The results obtained in this study provide useful information for predicting the mechanical safety of a battery pack.

• Proceedings of the KIEE Conference
• /
• 2001.07a
• /
• pp.512-514
• /
• 2001

Recently, Korea's electric industry is in the midst of a period of profound changes in the structure and function, including the introduction of market competition in the generation sector. Korea is in the early stages of market competition, so the market price is chosen by generation costs but will be chosen by bids in future. Therefore, the profits of generators is determined by market pool price and the prospects of pool price are very important for new capacity investment determination of generators and IPPs. This study analyzes hourly marginal costs and LOLP considering basic generation mix and characteristics, develops the relationship of pool price using the above in competition market, and proposes basic direction for profits variation and supply-demand analysis in the electric market in future.

• Biomaterials and Biomechanics in Bioengineering
• /
• v.3 no.1
• /
• pp.47-57
• /
• 2016

Results from multiple high profile experiments on the parameters influencing the impacts that cause skull fractures to the frontal, temporal, and parietal bones were gathered and analyzed. The location of the impact as a binary function of frontal or lateral strike, the velocity, the striking area of the impactor, and the force needed to cause skull fracture in each experiment were subjected to statistical analysis using the JMP statistical software pack. A novel neural network model predicting skull fracture threshold was developed with a high statistical correlation ($R^2=0.978$) and presented in this text. Despite variation within individual studies, the equation herein proposes a 3 kN greater resistance to fracture for the frontal bone when compared to the temporoparietal bones. Additionally, impacts with low velocities (<4.1 m/s) were more prone to cause fracture in the lateral regions of the skull when compared to similar velocity frontal impacts. Conversely, higher velocity impacts (>4.1 m/s) showed a greater frontal sensitivity.

• Proceedings of the KIPE Conference
• /
• 2014.07a
• /
• pp.367-368
• /
• 2014

This paper investigates characteristics of high power semiconductor device losses in 5MW-class Permanent Magnet Synchronous Generator (PMSG) Medium Voltage (MV) wind turbines. High power semiconductor device of press-pack type IGCT of 6.5kV is considered in this paper. Analysis is performed based on neutral point clamped (NPC) 3-level back-to-back type voltage source converter (VSC) supplied from grid voltage of 4160V. This paper describes total loss distribution at worst case under inverter and rectifier operating mode for the power semiconductor switches. The loss analysis is confirmed through PLECS simulations. In addition, the loss factors due to di/dt snubber and ac input filter are presented. The investigation result shows that IGCT type semiconductor devices generate the total efficiency of 97.74% under the rated condition.

• Journal of Applied Biological Chemistry
• /
• v.64 no.1
• /
• pp.57-61
• /
• 2021

Saikosaponin derivatives such as saikosaponins A, B1, B2, B3, B4, C, and D present in Bupleurum falcatum were analyzed by a high performance liquid chromatograph equipped with an evaporative light scattering detector, using different extraction solvents (water and 70% ethanol). The samples were injected into a YMC Pack Pro C18 column and separated using a gradient elution system with a mobile phase composed of acetonitrile and water at a flow rate of 1.1 mL/min. The content of saikosaponin derivatives was higher in 70% ethanol extract than in water extract. This study provides an efficient analytical method for determining the optimal conditions for extraction of saikosaponin derivatives, which can be used as a basis for development of functional foods and pharmaceutical products from B. falcatum.

• Research in Community and Public Health Nursing
• /
• v.15 no.3
• /
• pp.353-364
• /
• 2004

Purpose: The purpose of this study was to investigate the types and frequencies of nursing intervention of home health care in Public Health Centers and its effects. Method: The data collection period for this study lasted from March 1 to December 31, 2003. The clients were sampled by a stratified randomized method among those who had been cared for at least 3 months. The data was analyzed by SPSS for description. ANOVA, paired t test, etc. Result: The types and frequencies of nursing intervention in major chronic health problems were significantly different. The main types of nursing intervention in hypertension and DM patients included education on disease management, regular exercise, stress management, diets, etc. CVA patients were intervened in pain control (ice or hot pack, massage), position changes, and ROM exercise. Cancer patients received imaginary or relaxation therapy, pain control (ice or hot pack, massage), hospice, etc. After the intervention, the drug compliance of hypertension (8.2 days per month) and DM patients (6.2 days per month) improved. Blood sugar levels (FBS 7.6, post partum 2hrs $21.4(mg/d{\ell})$ and blood pressure(systolic 9.8, diastolic 4.3 mmHg) lowered significantly. All aspects of QOL also improved (total 3.68). Conclusion: The types and frequencies of nursing intervention were determined by characteristics of the health problems, and home health care nursing intervention in Public Health Centers was effective to the elderly of the community in many aspects.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.8
• /
• pp.1565-1576
• /
• 2002

By way of driving a 2-way on/off solenoid hydraulic valve with a pulse width modulation (PWM) signal, control of the pressure in a certain volume is frequently used in various applications. However, the pressure built-up according to the duty ratio and carrier frequency of the PWM signal is not so well understood. In order to clarify the characteristics of 2-way valve hydraulic pressure control systems, in this paper two formula fur the mean and ripple of the load pressure were derived through theoretical analysis. And the accuracy of the derived formula were verified by comparison with the experimental test result. Generally 2-way valve systems are constructed as a bleed-off circuit, while 3-way valves are used as a control element in a meter-in circuit pressure control system. In a bleed-off circuit, the system supply pressure from a hydraulic power pack does not remain constant, but changes according to their external load. In turn, the relief valve in the hydraulic power pack reacts accordingly showing complicated dynamic behavior, which makes an analytical study difficult. In order to resolve the problem, simple but accurate empirical dynamic models fer a bleed-off system were used in the course of formula derivation. As the result, selection criteria for two major control parameters of the driving signal is established and the basic strategy to suppress the unnecessary pressure fluctuation can be provided for a hydraulic pressure control system using a 2-way on/off solenoid valve.