• Journal of the Korean Society for Precision Engineering
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• v.24 no.12
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• pp.95-103
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• 2007

This paper presents a liquid cooling concept for heat rejection of high power electronic devices existing in notebook computers etc. The design, fabrication, and performance of the planar ECF pump and farced-liquid cooling system are summarized. The electro-conjugate fluid (ECF) is a kind of dielectric and functional fluids, which generates jet flows (ECF-jets) by applying static electric field through a pair of rod-like electrodes. The ECF-jet directly acts on the working fluid, so the proposed planar ECF pump needs no moving part, produces no vibration and noise. The planar ECF pump, consists of a pump housing and electrode substrate, achieves maximum flow rate and output pressure of $5.5\;cm^3/s$ and 7.2 kPa, respectively, at an applied voltage of 2.0 kV. The farced-liquid cooling system, constructed with the planar ECF pump, liquid-cooled heat sink and thermal test chip, removes input power up to 80 W keeping the chip surface temperature below $70\;^{\circ}C$. The experimental results demonstrate that the feasibility of forced-liquid cooling system using ECF is confirmed as an advanced cooling solution on the next-generation high power electronic devices.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.54-59
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• 2007

In a view of capturing $CO_2$ as a greenhouse gas, an experimental study was conducted on the combustion characteristics of pulverized coal in $O_2$/$CO_2$ environment using TGA/DSC and DTF facilities. The effects of gas composition and concentration on the processes of devolatilization and char burning experienced by coal particles in combustion furnace and on the concentration of products such as $CO_2$, CO and $NO_x$ were observed using TGA/DSC and DTF respectively. As results, it were found that the rate of devolitilation is nearly independent on the $O_2$ concentration if it is over 20% but the char burning rate is a sensitive function of $O_2$ percent, and the two rates can be controlled by $O_2$ concentration in order to be similar with those of air combustion case. It was also found that high concentration $CO_2$ can be captured by oxy-coal combustion and high concentration of CO and low value of $NO_x$ are exhausted in that case. Additionally, NO reducing reaction by CO with char as catalyst was observed and a meaningful results were obtained.

• Proceedings of the Safety Management and Science Conference
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• 2009.04a
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• pp.413-421
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• 2009

This paper investigates tensile characteristics of the stress aging heat-treated SM45C steel which are aging temperature at $250^{\circ}C$, $300^{\circ}C$, aging time at 1, 3 hours, and applied load at 300, 400N conditions by using acoustic emission. Most suitable aging condition was aging temperature $300^{\circ}C$, aging time 1 hour, and aging applied load 300N. And increased yield load 28.3% than non-treatment specimen in this condition. AE energy in elastic limit increased about 16.7 times than non-treatment specimen. When aging time is 3 hours, yield load decreased than other conditions that possibility is high to have itself defect on inside the specimen or coarse grain size precipitation is different in happened over-aging phenomenon. Especially, in case of $300^{\circ}C$, 3 hours and 400N condition appeared AE energy in elastic limit fairly high about 30 times than non-treatment specimen. This is considered by emit a lot of energies when material causes plastic deformation because the ductility increases on specimen by over-aging phenomenon.

• Journal of Korean Elementary Science Education
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• v.35 no.4
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• pp.389-405
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• 2016

The purpose of this study was to analyze elementary school teachers' understanding, certainty, and familiarity with 13 key concepts of wave physics that are presented in textbook and teacher's guidebook. 123 elementary school teachers answered concept tests and questionnaires. In the results to these tests and questionnaires, teachers demonstrated a high level of understanding and high certainty in understanding with regard to the concepts of sound generation, effect of medium on wave, timbre, wavelength, and trough and crest of wave. For the topics of sound velocity, wave reflection and wave transmission, teachers demonstrated a high level of understanding but low certainty in understanding. With regard to sound propagation, teachers demonstrated a low level of understanding and an improperly high certainty in that low understanding. Teachers lacked knowledge, i.e., displayed a low level of understanding and low certainty in sound strength, sound frequency, constructive interference and destructive interference. In constructive and destructive interference, the teachers also displayed a low level of familiarity. We analyzed the differences in teacher's understanding, certainty, and familiarity according to teacher demographics defined by the teacher's gender, teaching experience with concepts of sound, career, curriculum track while in high school, and major in university. There were no significant differences in understanding, certainty, or familiarity as defined by gender, teaching experience, and career. However, these displays of knowledge were affected by the teacher's curriculum track in high school and their major. These results suggest that the teacher's understanding of, familiarity with, and certainty in wave physics concepts are more influenced by their learning experience than by their teaching experience. Therefore, we suggest additional learning opportunities for teachers (such as teacher training programs) in order to improve teacher knowledge and correct teacher misconceptions in wave physics.

• Nutrition Research and Practice
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• v.18 no.1
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• pp.132-148
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• 2024

BACKGROUND/OBJECTIVES: This study aimed to assess the current mean daily intake of 10 food groups, analyze the sociodemographic factors associated with food consumption, and determine the associations between food consumption/dietary intake and the prevalence rates of obesity, type 2 diabetes (T2D), and hypertension (HTN) in Jakarta, Indonesia. SUBJECTS/METHODS: A total of 600 participants aged 20-85 yrs were included in this cross-sectional study. Food consumption and dietary habits were assessed using a food frequency questionnaire. To determine the association between food consumption/dietary habits and the abovementioned diseases, logistic regression analysis was performed. RESULTS: The average vegetable and fruit intake was lower, while sugar and salt consumption were higher than that recommended by Indonesia's national dietary guidelines. A high intake of ultra-processed foods (UPFs) was associated with young age, men, "single" status, a high education level, and employment with a high monthly income. Obesity and T2D were positively correlated with high intakes of cereals and tubers, UPFs, sugars, fats, and oils. Conversely, an inverse association was found between legume, vegetable, and fruit consumption and obesity risk. An inverse correlation was also observed between vegetable consumption and T2D risk. Moreover, a high salt intake was inversely correlated with fruit consumption in terms of HTN risk. Non-indulgence in habitual late-night snacking and refrainment from consuming more than one dish at each meal were also negatively related to the prevalence of obesity, T2D, and HTN. Inverse correlations were also observed between the prevalence rates of T2D and HTN and abstaining from adding sugar to beverages. CONCLUSION: Foods high in fat, sugar, and sodium were strongly associated with the risks of obesity, T2D, and HTN. Additionally, poor eating habits were also associated with disease development.

• The Journal of Korean Academic Society of Nursing Education
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• v.11 no.2
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• pp.278-286
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• 2005

Purpose: The purpose of this study was to find out the effectiveness of the CPR training for non-healthcare providers by checking the performing ability of the subjects before and after the teaching class. Method: This study was a single primary experimental study designed with pre and post test. Study subjects were 37 office staffs who participated in all test from March, 10th, 2005 to April, 18th, 2005. The tools of this study were CPR performing evaluation sheet and CPR teaching computer program. Data analyzed by descriptive statistics, t-test, repeated ANOVA and Bonferroni with SPSS 12.0 program. Result: The CPR practice performing ability statistically significant increased by the step of test. The CPR practice performing ability of learning experience group had significantly high score than non experience group. The self-confidence about CPR practice when faced emergency situation was increased after practice training. Conclusion: One to one CPR practice teaching method using simulation by CPR teaching specialists was turned out to be very effective in improving the ability of CPR practice of non-healthcare providers in a tertiary hospital than self-study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.731-736
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• 2007

Vibration isolation equipments are mostly required in precise measurement and manufacturing system. Among all the vibration isolation system, air-spring is the most widely used equipment because of low resonant frequency and high damping ratio. In this study, Takagi-Sugeno fuzzy method is used to design an active vibration isolation system using air-spring, and compared the fuzzy method with passive control method and PID control method. Due to the non-linearity characteristics of air-spring, fuzzy controller was verified to be the most effective both in simulation and experiment.

• Journal of Korean Elementary Science Education
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• v.34 no.4
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• pp.357-371
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• 2015

Even after learning electric current, elementary school students have various non-scientific conceptions and difficulties. Because flow of charge is not visible. Also elementary school students do not learn theory but phenomena, so they cannot transfer theoretical perspective to new situation. In this research, we have designed instruction based on PhET simulation visualizing flow of electric charge and applied it to 37 science-gifted students in elementary school for measuring conceptual understanding. As a result, six out of the seven Hake gains of question set are high gain and just one is middle gain because the students have understood the flow pattern of the charge through circuit elements such as light bulbs, wire, as well as battery with PhET simulation and it gives a chance to create various questions spontaneously about electric current. Also they become able to do spontaneous mental simulation without PhET simulation about flow of charges. This research, suggest that developed materials using PhET simulation could be used as not only program for gifted students in elementary school, but also the electrical circuit section in an elementary science curriculum.

• Journal of Advanced Navigation Technology
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• v.17 no.1
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• pp.132-141
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• 2013

In this paper, method using electric braking from stop area to high-speed area was presented in order to improve air-brake. And electric braking method can be improved environmental problems, efficiency, economy, etc. Method for electrical complete braking are two ways that method of inserting series resistance between the motor and the inverter, and method of inverter output voltage increase. In this paper, use series resistance insert method because economical and easy to apply. In addition, Series resistor is used short circuit method for reduce the power loss. In improved efficiency and the laboratory environment for secure braking, resistance insert method and inverter output voltage increase method showed same characteristics in all areas.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.327_328
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• 2009

The insulator being used for transmission line is to mount the charged conductor on the tower or other supports. The insulators are classified according to its material: porcelain, glass and polymer. Polymer insulators are also called as composite insulator or non ceramic insulator (NCI). Insulators are a major element of a power transmission system. Since a faulty insulator can lead to a wide spreading blackout, it must have sufficient mechanical and electrical strength. It must be durable, have high electrical insulation and be able to withstand a leakage current. It must also be able to withstand the toughest weather conditions. In Korea, porcelain insulators have been used widely. However, to make compact equipment and keep up with global trends, we have enhanced domestic production of polymer insulator and are encouraging its applications. Accordingly, this thesis will look at types of insulators, use and trends, and prospects of insulators application in the field.