• 한국항공우주학회지
• /
• 제31권8호
• /
• pp.69-76
• /
• 2003

액체로켓 연소기 내의 막냉각 특성 분석을 위한 비회체 분무연소에 대한 수치해석을 수행하였다. 막냉각 연료의 특성에 따른 연소기 벽면의 온도변화를 살펴보기 위하여 막냉각용 연료의 유랑, 막냉각용 액적의 직경, 그리고 공기/연료 혼합비를 매개변수로 한 수치해석을 수행하여 연소기 벽면의 온도는 막냉각용 연료 액적 직경의 변화에는 큰 영향을 받지 않지만 막냉각용 연료 유량 및 공기/연료 혼합비에 영향을 받고 있음을 확인하였다. 또한, 추진기관 벽면으로 전달되는 전도 및 복사열유속을 고찰함으로서 이러한 액체 추진기관의 연소특성을 이해하기 위해서는 열복사 및 물성치의 적절한 고찰이 필요함을 지적하였다.

• 패션비즈니스
• /
• 제21권3호
• /
• pp.29-42
• /
• 2017

This study investigates the impact of female consumer self-image on pursued fashion style. A survey was carried out among 717 women between the ages of 20 and 60 living in Seoul, Incheon, and Gyeonggi. Analysis was conducted in the following manner: SPSS 18.0 was used to perform an Exploratory Factor Analysis (descriptive analysis, principal factor analysis, Pearson correlation analysis, frequency analysis, and reliability analysis) and AMOS 21.0 was used to carry out a Confirmatory Factor Analysis. Based on a Structure Equation Model, results show that ideal self-image and realistic self-image, which are factors derived from psychology, affect pursued fashion style. By contrast, social self-image - derived from social contexts - does not. Therefore, the female consumers' self-image influences pursued fashion style; this is opposed to the relationship between the realistic self-image and ideal self-image of women, which is more unconscious and self-satisfying. The presented results indicate that we should respond to changes in the fashion industry and develop a deeper understanding of consumer niches to discover the factors that predict purchasing behavior. This knowledge can then be applied to establish market strategies. This study contributes to the literature by producing preliminary data that can help support such strategy formulation in the fashion and clothing industry.

• 수산해양기술연구
• /
• 제31권1호
• /
• pp.107-119
• /
• 1995

3차원 실내공간의 상부에서 일정유속이 유입하여 양측면 하부쪽으로 유출될 경우, 책상형의 가열 장애물 영향에 의한 유동장의 변화와 온도분포를 수치계산 한 결과 다음과 같은 결론을 얻었다. (1)표준 k-$\varepsilon$ 2 방정식 모델로 난류유동장을 해석한 결과 장애물을 기준으로 상하부에는 독립적인 큰 재순환 영역이 존재함을 알 수 있었다. (2) 유입류의 속도 변화에 따른 전제적인 유동패턴은 큰 변화없이 상사적인 분포를 하는 것을 알 수 있었다. (3) 유입속도가 감소함에 따라서, 공간에 대한 발열체의 온도영향이 커진다. (4) Re수가 작은 범위 (10 상(4)-10 상(5)에서는 열전달이 급격히 상승하여, Re수가 10 상(5)이상이 도면 열전달이 거의 일정하다.

• The Journal of Asian Finance, Economics and Business
• /
• 제7권3호
• /
• pp.303-310
• /
• 2020

The study aims to evaluate the factors affecting the intention to use digital banking in Vietnam. Multivariate data analysis techniques (Cronbach's Alpha test, Confirmatory Factor Analysis, Structure equation model) are used for the survey data collected from 201 customers who have access to digital banking. The analysis results show that: (1) attitude towards the service, perceived usefulness has a positive impacts on the intention to use; (2) convenience does not affect the intention to use digital banking services; (3) perceived usefulness factor has a positive effect on the attitude towards the service; (4) The perceived risk has a negative impact on attitude towards the service; (5) trust has no effect on the attitude towards the service; (6) ease of use has a positive impact on perceived usefulness; (7) trust has a positive effect on perceived risk. From the results of this study, perceived usefulness has a positive effect on attitude and intention to use the service. Therefore, it is necessary to enhance the sense of the usefulness of customers through media advertising and consulting so that customers fully understand the benefits brought about by using digital banking services. Perceived risk has a negative impact on attitude towards the service.

• Macromolecular Research
• /
• 제14권2호
• /
• pp.155-165
• /
• 2006

The present article describes the experimental and theoretical observations on the formation of holographic, polymer-dispersed, liquid crystals and electrically switchable, photonic crystals. A phase diagram of the starting mixture of nematic liquid crystal and photo-reactive triacrylate monomer was established by means of differential scanning calorimetry (DSC) and cloud point measurement. Photolithographic patterns were imprinted on the starting mixture of LC/triacrylate via multi-beam interference. A similar study was extended to a dendrimer/photocurative mixture as well as to a single component system (tetra-acrylate). Theoretical modeling and numerical simulation were carried out based on the combination of Flory-Huggins free energy of mixing and Maier-Saupe free energy of nematic ordering. The combined free energy densities were incorporated into the time-dependent Ginzburg-Landau (Model C) equations coupled with the photopolymerization rate equation to elucidate the spatio-temporal structure growth. The 2-D photonic structures thus simulated were consistent with the experimental observations. Furthermore, 3-D simulation was performed to guide the fabrication of assorted photonic crystals under various beam-geometries. Electro-optical performance such as diffraction efficiency was evaluated during the pattern photopolymerization process and also as a function of driving voltage.

• 한국컴퓨터정보학회논문지
• /
• 제21권10호
• /
• pp.167-174
• /
• 2016

This study aims to reveal the influence of praise effects of elementary school students on their self-esteem and school adjustment resilience. First, it conducted theoretical study and reviewed the preceding studies and assumed that verbal and physical praise which are sub-factors of praise effects in elementary school students affected their self-esteem and school adjustment resilience. It was also assumed that there was a mediating effects of self-esteem between praise effect and school adjustment resilience of elementary school students. As a result of study on praise effects of elementary school students, it was found that verbal praise had an influence on their self-esteem and school adjustment resilience and physical praise affected their learning attitude. Self-esteem of elementary school students had an influence on their school adjustment resilience. Verbal praise of elementary school students had the greatest influence on their learning attitude. This study proposed policy suggestions of self-esteem and school adjustment resilience as an alternative based on the results of the study.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2009년도 춘계학술대회 논문집
• /
• pp.311-314
• /
• 2009

고체추진기관의 연소 환경에서 복잡한 형상을 갖는 내열 복합재료의 온도 및 밀도분포를 예측할 수 있는 방법을 개발하였다. 복합재료의 내부 열반응은 Arrhenius 모델을 이용하였으며, 표면 삭마반응은 Zvyagin 이론을 사용하였다. 표면 삭마에 의한 경계조건 및 격자 이동은 Rezoning 기법을 사용하였으며 열분해에 의한 흡열반응 효과는 열분해 가스의 조성비에 기준한 유효 비열 값을 이용하여 계산되었다. 형상이 복잡한 부품으로 이루어진 2차원 축대칭 노즐 조립체에 적용된 방법은 향후 3차원 FEM 열구조 해석에 활용을 목표로 발전될 것이다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2009년도 춘계학술대회 논문집
• /
• pp.315-319
• /
• 2009

Investigation of the lateral force fluctuations in an axisymmetric overexpanded compressed truncated perfect (CTP) nozzle for the shutdown transient is presented. These nozzles experience side-loads during start-up and shut-down operations, because of the flow separation at nozzle walls. Two types of flow separations such as free shock separation (FSS) and restricted shock separation (RSS) shock structure occur. A two-dimensional unsteady numerical simulation has been carried out over an axisymmetric CTP nozzle to simulate the lateral force fluctuations in nozzle during shutdown process. Reynolds Averaged Navier-Stokes equations are numerically solved using a fully implicit finite volume scheme. Governing equations are solved by coupled implicit scheme. Two equation k-$\omega$ SST turbulence model is selected. Unsteady pressure is measured at four locations along the nozzle wall. Present pressure variation compared well with the experimental data. During shutdown transient, separation pattern varies from FSS to RSS and finally returns to FSS. Several pressure peaks are observed during the RSS separation pattern. These pressure peaks generate lateral force or side loads in rocket nozzle.

• Journal of Mechanical Science and Technology
• /
• 제17권9호
• /
• pp.1249-1260
• /
• 2003

This present work focuses on the influence of nonlinearities associated with impact on the rocking behavior of a rigid body block subjected to a two-dimensional excitation in the horizontal and vertical directions. The nonlinearities in rocking system are found to be strongly dependent on the impact between the block and the base that abruptly reduces the kinetic energy. In this study, the rocking systems of the two types are considered : The first is an undamped rocking system model that disregards the energy dissipation during the impact and the second is a damped rocking system, which incorporates energy dissipation during the impact. The response analysis is carried out by a numerical method using a non-dimensional rocking equation in which the variations in the excitation levels are considered. Chaos responses are observed over a wide range of parameter values, and particularly in the case of large vertical displacements, the chaotic characteristics are observed in the time histories, Poincare sections, the power spectral density and the largest Lyapunov exponents of the rocking responses. Complex behavior characteristics of rocking responses are illustrated by the Poincare sections.

• 대한기계학회논문집B
• /
• 제33권7호
• /
• pp.552-558
• /
• 2009

An experimental study using the combustor with branch tube was conducted in order to model the industry combustor with FGR (flue gas recirculation) system and to study a thermo-acoustic instability generated by a branch tube. The branch tube is a structure used to modify a system geometry and then to change its pressure field, and the thermo-acoustic instability, usually occurs in a confined geometry, can result in serious problems on industrial combustors. Thus understanding of the instability created by modifying geometry of combustor is necessary to design and operate combustor with FGR system. Pressure fluctuation in the combustion chamber was observed according to diameter and length of branch and it was compared with the solution of 1-D wave equation. It was found that branch tube affects the pressure field in the combustion chamber, and the pressure fluctuation in the combustion chamber was reduced to almost zero when phase difference between an incipient wave in the combustion chamber and a reflected wave in the branch tube is $\pi$ at the branch point. Also, the reduction of pressure fluctuation is irrespective of the installed height of branch tube if it is below $h^*=0.9$ in the close-open tube and open-open tube.