• 한국세라믹학회지
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• 제45권10호
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• pp.625-630
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• 2008

In the bone cement composed of dense granules of $\beta-Ca_3(PO_4){_2}(\beta-TCP)$ and $Ca(H_2PO_4){_2}H_2O$, the compressive strength, setting time and temperature rise were measured to observe the degradation of cement with respect to the stored days before setting. Decreases of compressive strength and temperature rise were observed, while setting time increased with respect to the stored days. The similar trends were repeated with the increase of temperature of storage. Such a change virtually meant the fading of the character of cement and it took place only when the two starting materials were mixed during storage. The degradation could be mitigated taking advantage of granular $\beta$-TCP instead of powdery one. The formation of $CaHPO_4$, which resulted from reaction with ambient humidity, was attributed to the degradation observed during storage. Dependence of the degradation behavior on mixing and temperature during storage was discussed in terms of the driving force for reaction of cement.

• 천문학회보
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• 제42권1호
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• pp.38.1-38.1
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• 2017

We report the results of three-dimensional radiation hydrodynamic simulations of star cluster formation in turbulent molecular clouds, with primary attention to how stellar radiation feedback controls the lifetime and net star formation efficiency (SFE) of their natal clouds. We examine the combined effects of photoionization and radiation pressure for a wide range of cloud masses (10^4 - 10^6 Msun) and radii (2 - 80 pc). In all simulations, stars form in densest regions of filaments until feedback becomes strong enough to clear the remaining gas out of the system. We find that the SFE is primarily a function of the initial cloud surface density, Sigma, (SFE increasing from ~7% to ~50% as Sigma increases from ~30 Msun/pc^2 to ~10^3 Msun/pc^2), with weak dependence on the initial cloud mass. Control runs with the same initial conditions but without either radiation pressure or photoionization show that photoionization is the dominant feedback mechanism for clouds typical in normal disk galaxies, while they are equally important for more dense, compact clouds. For low-Sigma clouds, more than 80% of the initial cloud mass is lost by photoevaporation flows off the surface of dense clumps. The cloud becomes unbound within ~0.5-2.5 initial free-fall times after the first star-formation event, implying that cloud dispersal is rapid once massive star formation takes place. We briefly discuss implications and limitations of our work in relation to observations.

• 대한기계학회논문집B
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• 제20권11호
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• pp.3706-3713
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• 1996

A numerical study on natural convection induced by free surface heat flux and cold left and hot right walls in glass melting furnaces has been performed. A function of heat flux derived from the combustion environments of actual glass melting furnace is applied to thermal boundary condition at free surface. Fundamentally there exist two flow cells in cavity (left counterclockwise one and right clockwise one). The effects of heat flux and Rayleigh number are investigated through two-dimensional steady-state assumption. The convection strength of two flow cell located in left region continuously increases. In the mean time the strength of flow cell in right region increases and then decreases. Critical Rayleigh number in which two flow cells take place above and below show linear dependence on the free surface heat flux. To maintain the traditional flow pattern (left and right flow cells) in glass melting furnace, Rayleigh number is recommended to be below 10$^{5}$ .

• 한국경영과학회지
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• 제37권3호
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• pp.79-94
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• 2012

According to the higher dependence of contemporary firms on data digitalization and the information technology, the role and importance of Information Security Management (ISM) is getting higher. Thus, there is a need to arrange proper procedure and a series of device within the organization in order to reduce diverse security risks, which take place from the inside and the outside of firm. In other words, prior examination for reinforcing recognition of ISM, and of a systematic performance method in the refined form is important. This study investigate the key variables influencing the ISM. Thus, this study suggests firm environmental factors that include four exogenous variables, market volatility, task interdependence, perceived benefits, and coordination mechanism affecting awareness of ISM. In addition, it proposes a concept of the ISM process with awareness, development, and performance, and examines the moderating effects of regulatory influence. The research model was tested by using Structural Equation Modeling, via SmartPLS 2.0 analysis on a sample collected from 186 employees in various industries. The research results provide the evidence that supports the tested hypotheses except significance of coordination mechanism. The implications of the findings suggest a new theoretical framework of the ISM and offers important solutions for the practical application guidelines.

• 성인간호학회지
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• 제15권1호
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• pp.56-66
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• 2003

Purpose: The purpose of this study is to describe the psychological aspects of experiences of men living in a homeless shelter in Seoul. This study focused on understanding about the life of the homeless in the shelter by Phenomenological method. Method: The participants in this study were seven men who are living in a homeless shelter in Seoul. The following data were collected though the in-depth interviews and analyzed by the Phenomenological analytic method of Giorgi. Result: There are five focal significances about the life of the homeless. (1) Unplanned Life : Difficult life comes from outside situation, Freedom, The acceptance of unconsciousness life, Laziness, Unreliability, The dissolute life, No purpose to life, Relying on drinking, (2) Self-rationalization : Feeling of defeat, Give up, Desire for a support system, Lack of willingness, Anxiety, Chivalry, Falsehoods, (3) Superficial Interpersonal Relationships : Ignorance, Pressure, Discord, Hiding from one anther, avoidance. (4) A sense of devestation : Negative perspective, Mental weakness, Difficulties in employment, ambivalance with social structure, The place to escape, Complaining against the opposite sex, Sense of regret, Lack of relationship with family, The lack of self-confidence, Loss of volition (5) The Hope of new life : Realization, Desire for change, Dreaming of married life, Dependence in God Conclusion: The conclusion of this study shows that the men in the shelter had various psychological reasons for being in the homeless shelter. Further studies need to be done to validate this information and formulate ways to assist these men with their psychological needs.

• Asian Pacific Journal of Cancer Prevention
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• 제15권14호
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• pp.5633-5638
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• 2014

Purpose: Our research project aimed at presenting midwifery student self-assessment of performing the role of breast cancer prevention educator. Materials and Methods: Investigations were carried out in 2011 at the Medical University of Lublin in Poland, and Katolieke Hogeschool of Kortrijk in Belgium, after obtaining approval of the ethical committee of Polish Midwives Association (III/EC/2011/PMA). The project involved a total of 155 midwifery students, made up of 95 from Poland, and 60 from Belgium. Relations between opposing characteristics were tested with Chi-square ($x^2$) test for independent traits. To assess the dependence relation between the examined variables Pearson's corrected coefficient was used. Data base and statistics were carried out with computer software STATISTICA 9.0 (StatSoftPoland). Conclusions: Student knowledge on prevention against breast cancer was unsatisfactory. The students place of residence determined their self-estimation of personal knowledge of breast cancer prevention and diagnosing methods to assess the incidence of the disease, this knowledge being better with the students of Lublin. Better self-estimation in the students of Lublin of their personal knowledge on factors rising the risk of breast cancer, such as alimentation method, application of oral contraceptives and breast feeding was found than in Belgian students.

• 한국전기전자재료학회논문지
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• 제20권8호
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• pp.661-665
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• 2007

This paper presents the electrical properties of SiGe HBTs designed with bottom collector and single metal layer structure for RF power amplifier. Base layer was formed with graded-SiGe/Si structures and the collector place to the bottom of the device. Bottom collector and single metal layer structures could significantly simplify the fabrication process. We studied about the influence of SiGe base thickness, number of emitter fingers and temperature dependence $(<200^{\circ}C)$ on electrical properties. The feasible application in $1{\sim}2GHz$ frequency from measured data $BV_{CEO}{\sim}10V,\;f_T{\sim}14GHz,\;{\beta}{\simeq}110,\;NF{\sim}1dB$ using packaged SiGe HBTs. We will discuss the temperature dependent current flow through the e-b, b-c junctions to understand stability and performance of the device.

• 기술사
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• 제16권3호
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• pp.68-73
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• 1983

IC전자부품 중 DIP계 종류를 바렐을 사용하여 주석도금 할 때에 그 전착현상을 조사하여 부분전류의 동태를 설명할 수 있는 변화인자를 알아보려 하였다. DIP와 같은 모양인 IC부품은 부분전도체로 구분되어지며 그 전착상태를 one-dimensional model로 분석하였을때, 가입전류밀도, 바렐의 회전속도, 용액중 금속이온 농도와 깊은 관계가 있음을 보인다. 다공질과 같은 것으로 간주한 one-dimensional model로서 의 이론식은 J=$\delta$'/$\beta$-{-c$^3$/${\gamma}$-exp-(1-$\alpha$)n$\Phi$}로 표현된다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.686-691
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• 2010

Flash boiling takes place when the thermodynamic state of the liquid deviates from its saturation limit over which the liquid temperature exceeds by a certain degree of superheat. The liquid jet introduced into the lower pressure zone than the liquid saturation pressure experiences a sequence of the atomization and disintegrated into numerous faster and smaller droplets. In the present study spray characteristics for a flash swirl spray were experimentally investigated. Injectant temperature is raised by a high frequency dielectric heating method and local spray characteristics are instantly measured by Global Sizing Velocimetry (GSV, TSI Inc.). Dependence of dimensionless superheat degree and injection pressure on total and local SMDs and mean droplet size is quantitatively examined. The flash swirl spray has the relation in the injection pressure and nozzle diameter in order to determine the spray quality, including the dimensionless superheat degree. Small droplets occur in the void core and local droplet size distributions largely depend on the dimensionless superheat degree and the injection pressure.

• Journal of Electrical Engineering and Technology
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• 제3권2호
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• pp.177-183
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• 2008

The particle swarm optimization(PSO) has been shown to converge rapidly during the initial stages of a global search, but around global optimum, the search process becomes very slow. On the other hand, the genetic algorithm is very sensitive to the initial population. In fact, the random nature of the GA operators makes the algorithm sensitive to initial population. This dependence to the initial population is in such a manner that the algorithm may not converge if the initial population is not well selected. In this paper, we have proposed a new algorithm which combines PSO and GA in such a way that the new algorithm is more effective and efficient and can find the optimal solution more accurately and with less computational time. Optimal location of SVC using this hybrid PSO-GA algorithm is found. We have also found the optimal place of SVC using GA and PSO separately and have compared the results. It has been shown that the new algorithm is more effective and efficient. An IEEE 68 bus test system is used for simulation.