• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.5
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• pp.73-79
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• 2021

This study was carried out to analyze the properties of the gel propellant and spray characteristics according to the addition of fine particles. The multi-hole diameter was 0.4 mm to induce a high shear rate, and a kerosene gel propellant was prepared using 5 wt% of the Thixatrol ST and SUS304 of 100 nm. The experiment was conducted by fixing the supply pressure in the axial direction to 0.7 MPa and adjusting the supply pressure in the radial direction from 0.7 MPa to 2.1 MPa. Due to the addition of fine particles, pressure vibration during spraying, a small TMR(Total Momentum Ratio) of up to 0.19, and a phenomenon that the spraying angle rapidly increased to more than 70 degrees occurred.

• Physical Therapy Korea
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• v.31 no.1
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• pp.8-17
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• 2024

Background: Sleep accounts for approximately one-third of a person's lifetime. It is a relaxing activity that relieves mental and physical fatigue. Pillows of different sizes, shapes, and materials have been designed to improve sleep quality by achieving an optimal sleep posture. Objects: This study aimed to determine which pillow provides the most comfortable and supports the head and neck during sleep, which may enhance sleep quality. Methods: Twenty-eight healthy adults (19 males and 9 females) with an average age of 29 years participated in this cross-sectional study. This experiment was conducted while the participants laid down for 5 minutes in four different pillow conditions: (1) no pillow (NP), (2) neck support foam pillow (NSFP), (3) standard microfiber filled pillow (SFP), and (4) hybrid foam pillow (HFP). The head-neck peak pressure, cranio-vertebral angle in supine (CVAs), cranio-horizontal angle in supine (CHAs), chin-sternum distance (CSD), and muscle tone of sternocleidomastoid were analyzed using one-way repeated measures analysis of variance (ANOVA). The significance level was set at p < 0.05. Results: The head-neck peak pressure was the highest in the NSFP condition, followed by the NP, SFP, and HFP conditions. The CVAs, CHAs, and CSD of the SFP were lower than those of the other pillows. Muscle tone was the highest in the NP condition, followed by the of NSFP, HFP, and SFP conditions. The participants subjective comfort level in both the supine and side-lying postures was highest in the HFP condition, followed by the SFP and NSFP conditions. Conclusion: This study can be used to establish the importance of pillow selection for high-quality sleep. The results of this study, suggest that a hybrid pillow with a good supportive core and appropriate fluffiness can maintain comfort and correct cervical spine alignment during sleep.

• Journal of Chest Surgery
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• v.37 no.1
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• pp.1-10
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• 2004

Background: Currently, the cardiopulmonary machine with non-pulsatile pumps, which are low in internal circuit pressure and cause little damage to blood cells, is widely used. However, a great number of experimental studies shows that pulsatile perfusions are more useful than non-pulsatile counterparts in many areas, such as homodynamic, metabolism, organ functions, and micro-circulation. Yet, many concerns relating to pulsatile cardiopulmonary machines, such as high internal circuit pressure and blood cell damage, have long hindered the development of pulsatile cardiopulmonary machines. Against this backdrop, this study focuses on the safety and effectiveness of the pulsatile cardiopulmonary machines developed by a domestic research lab. Material and Method: The dual-pulsatile cardiopulmonary bypass experiment with total extracorporeal circulation was conducted on six calves, Extracorporeal circulation was provided between superior/inferior vena cava and aorta. The membrane oxygenator, which was placed between the left and right pumps, was used for blood oxygenation. Circulation took four hours. Arterial blood gas analysis and blood tests were also conducted. Plasma hemoglobin levels were calculated, while pulse pressure and internal circuit pressure were carefully observed. Measurement was taken five times; once before the operation of the cardiopulmonary bypass, and after its operation it was taken every hour for four hours. Result: Through the arterial blood gas analysis, PCO2 and pH remained within normal levels. PO2 in arterial blood showed enough oxygenation of over 100 mmHg. The level of plasma hemoglobin, which had total cardiopulmonary circulation, steadily increased to 15.87 $\pm$ 5.63 after four hours passed, but remained below 20 mg/㎗. There was no obvious abnormal findings in blood test. Systolic blood pressure which was at 97.5$\pm$5.7 mmHg during the pre-circulation contraction period, was maintained over 100 mmHg as time passed. Moreover, diastolic blood pressure was 72.2 $\pm$ 7.7 mmHg during the expansion period and well kept at the appropriate level with time passing by. Average blood pressure which was 83$\pm$9.2 mmHg before circulation, increased as time passed, while pump flow was maintained over 3.3 L/min. Blood pressure fluctuation during total extracorporeal circulation showed a similar level of arterial blood pressure of pre-circulation heart. Conclusion: In the experiment mentioned above, pulsatile cardiopulmonary machines using the doual-pulsatile structure provided effective pulsatile blood flow with little damage in blood cells, showing excellence in the aspects of hematology and hemodynamic. Therefore, it is expected that the pulsatile cardiopulmonary machine, if it becomes a standard cardiopulmonary machine in all heart operations, will provide stable blood flow to end-organs.

• Tribology and Lubricants
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• v.32 no.2
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• pp.56-60
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• 2016

Sapphire has a high hardness and strength and chemical stability as a superior material. It is used mainly as a material for a semiconductor as well as LED. Recently, the cover glass industry used by a sapphire is getting a lot of attention. The sapphire substrate is manufactured through ingot sawing, lapping, diamond mechanical polishing (DMP) and chemical mechanical polishing (CMP) process. DMP is an important process to ensure the surface quality of several nm for CMP process as well as to determine the final form accuracy of the substrate. In DMP process, the material removal is achieved by using the mechanical energy of the relative motion to each other in the state that the diamond slurry is disposed between the sapphire substrate and the polishing platen. The polishing platen is one of the most important factors that determine the material removal characteristics in DMP. Especially, it is known that the geometric characteristics of the polishing platen affects the material removal amount and its distribution. This paper investigated the material removal characteristics and the effects of the polishing platen groove in sapphire DMP. The experiments were preliminarily carried out to evaluate the sapphire material removal characteristics according to process parameters such as pressure, relative velocity and so on. In the experiment, the monitoring apparatus was applied to analyze process phenomena in accordance with the processing conditions. From the experimental results, the correlation was analyzed among process parameters, polishing phenomena and the material removal characteristics. The material removal equation based on phenomenological factors could be derived. And the experiment was followed to investigate the effects of platen groove on material removal characteristics.

• Atmosphere
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• v.28 no.1
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• pp.53-67
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• 2018

This study examined the lake effect of the Yellow Sea which was induced by the Siberian High pressure system moving over the open waters. The development mechanism of the convective cells over the ocean was studied in detail using the Weather Research and Forecasting model. Numerical experiments consist of the control experiment (CTL) and an experiment changing the yellow sea to dry land (EXP). The CTL simulation result showed distinct high area of relative vorticity, convergence and low-level atmospheric instability than that of the EXP. The result indicates that large surface vorticity and convergence induced vertical motion and low level instability over the ocean when the arctic Siberian air mass moved south over the Yellow Sea. The sensible heat flux at the sea surface gradually decreased while latent heat flux gradually increased. At the beginning stage of air mass modification, sensible heat was the main energy source for convective cell generation. However, in the later stage, latent heat became the main energy source for the development of convective cells. In conclusion, the mechanism of the west coast heavy snowfall caused by modification of the Siberian air mass over the Yellow Sea can be explained by air-sea interaction instability in the following order: (a) cyclonic vorticity caused by diabatic heating induce Ekman pumping and convergence at the surface, (b) sensible heat at the sea surface produce convection, and (c) this leads to latent heat release, and the development of convective cells. The overall process is a manifestation of air-sea interaction and enhancement of convection from positive feedback mechanism.

• Journal of The Korean Association For Science Education
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• v.25 no.5
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• pp.547-554
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• 2005

A developed Web-aided laboratory program visualized invisible gas. In the Web-aided laboratory temperature and pressure were controlled and the resultant findings were presented as types of graphs, disclosed in the form of an analyzed report. A Web-aided laboratory experiment and traditional experiment group(2 classes) were assembled from a farming village co-educational high school and taught the motion of molecule lesson for 2 class hours. Before actual class instruction, to survey learner motivation characteristics, the short-version GALT, the test of attitudes toward science instruction, was administered. After instruction, student learning achievement, TOSRA, and IMMS, were administered to the two groups. To analyze data ANCOVA was administrated. Result found that attitudes towards science instruction did not significantly differ, but learning motivation and achievement were significantly altered.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.441-443
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• 2005

According as CCFL(Cold Cathode Fluorescent lamp) of light source in Backlight unit for Note PC (Personal computer) is presently needed to low power consumption and long life time, the development focus of CCFL is going on the discharge gas, phosphor and electrode material. First of all, discharge voltage characteristic of CCFL is closely connected with electrode material For low discharge voltage, the characteristic of electrode material is needed to low work function, low sputtering ratio and superior manufacturing property. We developed new CCFL with Nb/Ni Clad electrode superior to conventional CCFL. Because Nb/Ni Clad electrode with Ni material and Nb material, the electrical characteristic is superior to other electrode materials. The electrode of Nb/Ni Clad is composed that Ni of outside material has superior manufacturing property and Nb of inside material has low work function. Nb/Ni Clad of new electrode material is made by process of Rolling mill at high pressure and heat treatment. We compared electrical characteristic of Nb/Ni clad electrode with conventional Mo electrode by measurement. Mo electrode and Nb/Ni Clad electrode of cup type with diameter 1.1 mm and length 3.0mm are used to this experiment. Material content of Mo electrode is Mo 100%. But, Nb/Ni Clad electrode is composed by content of Nb 40% and Ni 60%. The result of comparison measurement between new CCFL with Nb/Ni Clad electrode and conventional CCFL was appeared that CCFL with Nb/Ni Clad electrode had superior characteristic than conventional CCFL. As a result of experiment, we completed Note PC with low power consumption and long life time by application of new CCFL with Nb/Ni Clad electrode.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.1
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• pp.63-70
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• 2024

Lithium-ion batteries (LIB) are widely used in various sectors, such as transportation (e.g., electric vehicles (EV)) and energy (e.g., energy storage facilities) due to their high energy density, broad operating temperature (-20 ℃ ~ 60 ℃), and high capacities. LIBs are powerful but fragile on external factors, including pressure, physical damage, overheating, and overcharging, that cause thermal runaway causing fires and explosions. During a LIB fire, a large amount of oxygen is generated from the decomposition of ionogenic materials. A water fire extinguisher that helps with cooling and suffocating must be essentially required at the same time. In fact, however, it is difficult to suppress LIB fires in the case of EVs because a LIB is installed with a battery pack housing that interrupts direct extinguishing by water. Thus, this study aims to investigate effective fire extinguishing measurements for LIB fires by using an EV. Relevant documents, including research articles and reports, were reviewed to identify effective ways of LIBs fire extinguishing. A real-scale fire experiment generating thermal runaway was carried out to figure out the combustion characteristics of EVs. This study revealed that the most effective fire extinguishing measurements for LIB fires are applying fire blankets and water tanks. However, there is still a lack of adequate regulation and guidelines for LIB fire extinguishment. Taking this into account, developing functional fire extinguishment measurements and available regulatory instruments is an urgent issue to secure the safety of firefighters and citizens.

• Journal of Nutrition and Health
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• v.53 no.5
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• pp.464-475
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• 2020

Purpose: This study compared the effects of a high glycemic load (high GL) diet and low glycemic load (low GL) diet on the body weight, body fat, blood pressure, and blood lipid indicators. Methods: Twenty-one young adults aged between 21 and 28 years who were overweighted or obese (body mass index [BMI] between 23 and 33.5 kg/㎡) before the study and after calorie reduction diets with either low GL or high GL for 2 weeks each were examined. The study was a randomized crossover design with a 2-week washout period between the 2 types of diet. The order of the low GL and high GL diet periods was randomized. The body weight, body fat, blood pressure, levels of blood lipids, fasting glucose, insulin, homeostatic model assessment (HOMA) insulin, C-peptide, and HOMA C-peptide were measured at the baseline, as well as 2, 4, and 6 weeks after starting the experiment. Results: When subjects were on the low GL diet, they lost more weight than those eating the high GL diet (mean ± SD, -2.77 ± 1.09 vs. -1.56 ± 0.78 kg; p < 0.001); there were greater decreases in body fat mass (-1.62 ± 1.19 vs. -0.88 ± 0.91 kg; p = 0.024) and BMI (-0.95 ± 0.32 vs. -0.56 ± 1.08 kg/㎡; p < 0.001). On the other hand, there were no significant differences in changes in biochemical parameters, such as blood lipids and fasting glucose levels, and blood pressure. The body weight, body fat mass, BMI, percent body fat, blood pressure, cholesterol (total, low-density lipoprotein, and high-density lipoprotein), fasting glucose, C-peptide, HOMA-insulin resistance-C-peptide levels were decreased significantly at 6 weeks. Conclusion: The low GL diet may be more effective in losing body weight, body fat mass, and BMI than the high GL diet for 2 weeks in healthy young overweight or obese adults.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2000.11a
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• pp.1-2
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• 2000

In chip plating, several parameters must be taken into consideration. Current density, solution concentration, pH, solution temperature, components volume, chip and media ratio, barrel geometrical shape were most likely found to have an effect to the process yields. The 3 types of barrels utilized in chip plating industry are the onventional rotating barrel, vibrational barrel(vibarrel), and the centrifugal type. Conventional rotating barrel is a close type and is commonly used. The components inside the barrel are circulated by the barrel's rotation at a horizontal axis. Process yield has known to have higher thickness deviation. The vibrational barrel is an open type which offers a wide exposure to electrolyte resulting to a stable thickness deviation. It rotates in a vertical axis coupled with multi-vibration action to facilitate mixed up and easy transportation of components. The centrifugal barrel has its plated work centrifugally compacted against the cathode ring for superior electrical contact with simultaneous rotary motion. This experiment has determined the effect of barrel vibration intensity to the plating thickness distribution. The procedures carried out in the experiment involved the overall plating process., cleaning, rinse, Nickel plating, Tin-Lead plating. Plating time was adjusted to meet the required specification. All other parameters were maintained constant. Two trials were performed to confirm the consistency of the result. The thickness data of the experiment conducted showed thatbthe average mean value obtained from higher vibrational intensity is nearer to the standard mean. The distribution curve shown has a narrower specification limits and it has a reduced variation around the target value. Generally, intensity control in vi-barrel facilitates mixed up and easy transportation of components. However, it is desirable to maintain an optimum vibration intensity to prevent solution intrusion into the chips' internal electrode. A cathodic reaction can occur in the interface of the external and internal electrode. 2H20 + e $\rightarrow$M/TEX> 20H + H2.. Hydrogen can penetrate into the body and create pressure which can cause cracks. At high intensity, the chip's motion becomes stronger, its contact between each other is delayed and so plating action is being controlled. However, the strong impact created by its collision can damage the external electrode's structure there by resulting to bad plating condition.