• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.12
• /
• pp.785-792
• /
• 2016

In the present study, the effects of non-equilibrium condensation on the drag divergence Mach number with the angle of attack in a transonic 2D moist air flow of NACA0012 are investigated using the TVD finite difference scheme. For the same ${\alpha}$, the maximum upstream Mach number of the shock wave, Mmax, and the size of supersonic bubble decrease with the increase in ${\Phi}_0$. For the same $M_{\infty}$, ${\Phi}_0$, and $T_0$, the length of the non-equilibrium condensation zone ${\Delta}_z$ decreases with increasing ${\Phi}_0$. On the other hand, because of the attenuating effect of non-equilibrium condensation on wave drag, which is related to the interaction between the shock wave and the boundary layer, the drag coefficient $C_D$ decreases with an increase in ${\Phi}_0$ for the same $M_{\infty}$ and ${\alpha}$. For the same ${\alpha}$, $M_D$ increases with increasing ${\Phi}_0$, while $M_D$ decreases with an increase in ${\alpha}$.

• 한국전산유체공학회:학술대회논문집
• /
• 1995.10a
• /
• pp.31-36
• /
• 1995

비유선형의 물체 주위의 유동은 정체유동, 경계층 박리 및 주기적 와열 생성 등의 복잡한 유동현상이 공존한다. 본 연구에서는 비교적 단순한 형상인 정사각주 주위의 비정상 난류 유동을 2-방정식 와점성 난류모델인 표준 $k-{\varepsilon}$ 모델과 RNG $k-{\varepsilon}$ 모델을 이용하여 예측할 수 있는지를 검증하였다. 정교하게 수행된 최근의 실험과 대와류모사(LES)의 결과를 검증을 위한 비교의 자료로 삼았다. 적절한 난류모델의 선정과 더불어 시간 정확도, 공간 정확도 및 대류항 처리법 등이 해석결과에 미치는 영향도 살펴보았다. 기존의 표준 $k-{\varepsilon}$모델은 정체점 부근에서 난류 운동에너지를 과도하게 생성하는 근본적인 문제점 때문에 실험 및 LES의 결과를 제대로 예측할 수 없었다. 난류운동에너지의 초과 예측에 따른 운동량의 과도한 혼합으로 인해, 항력계수 및 양력계수의 비정상성 뿐 아니라 평균 항력계수도 부정확하게 예측하였다. RNG $k-{\varepsilon}$ 모델을 사용한 경우에는 정체점 주위 유동현상의 예측이 상당히 향상되어 항력계수 및 양력계수의 평균치, 진폭 및 비정상성의 주기 등을 정확하게 예측하는 것이 가능하였다. 그러나 이 경우에도 예측의 정확도가 시간 증분과 격자의 크기 및 대류항 처리법등에 영향을 받으며, 특별히 대류항 처리법에 상당히 민감하게 변하는 것을 알 수 있었다. 향상된 유동예측은 RNG $k-{\varepsilon}$ 모델의 난류에너지 소산율 방정식의 개선된 항이 과도하게 생성된 난류에너지를 정체점 부근에서 제거하기 때문에 가능하다는 것을 알 수 있었다.의 20세 이하 골절 및 탈구가$30.3\%까지 감소하게되어 년도가 증가함에 따라 청장년 층에 비하여 소아골절 및 탈구가 전체적으로 감소하는 경향을 보였다. 스키골절의 부위별 발생빈도는 1990년 이전까지 하지골절 및 탈구가 많았으나 이후 점차 상지의 골절 탈구가 증가하였다 하지에서 가장 많은 골절은 경골 골절이었으며, 경골골절은 회전력에 의한 나선형골절이 $76.5\%로 가장 많았고 년도에 따른 변화는 보이지 않았다. 스키손상의 발생빈도는 초기에 비하여 점차 감소하는 경향을 보였으며, 손상의 특성도 부위별, 연령별로 다양한 변화를 나타내었다.해가능성을 가진 균이 상당수 검출되므로 원료의 수송, 김치의 제조 및 유통과정에서 병원균에 대한 오염방지에 유의하여야 할 것이다. 확인할 수 있었다. 이상의 결과에 의하면 고농도의 유기물이 함유된 음식물쓰레기는 Hybrid Anaerobic Reactor (HAR)를 이용하여 HRT 30일 정도에서 충분히 직접 혐기성처리가 가능하며, 이때 발생된 $CH_{4}$를 회수하여 이용하면 대체에너지원으로 활용 가치가 높은 것으로 판단된다./207), $99.2\%$(238/240), $98.5\%$(133/135) 및 $100\%$ (313)였다. 각각 두 개의 요골동맥과 우내흉동맥에서 부분협착이나 경쟁혈류가 관찰되었다. 결론: 동맥 도관만을 이용한 Off pump CABG를 시행하여 감염의 위험성을 증가시키지 않으면서 영구적인 신경학적 합병증을 일으키지 않았고 좋은 혈관 개존율을 보여주었다. 따라서 동맥 도관을 이용한 Off pump CABG는 관상동맥의 협착의 정도에 따라 효율적으로 시행

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.10
• /
• pp.5078-5090
• /
• 2013

This study was to identify the relationship among small-medium sized hospitals nurse's career plateau, self-efficacy, job embeddedness and turnover intention. The study was conducted through a survey on 217 nurses in five small-medium sized hospitals in J city. The data were collected from August 5, 2013 to August 20, 2013. The data were analyzed by SPSS/WIN 18.0 program. The mean score of turnover intention was 3.07. The positive correlations between career plateau and turnover intention were found, but the negative correlation between self-efficacy, job embeddedness and turnover intention were found. The significant factors influencing turnover intention were job embeddedness, present clinical career, career plateau and work unit. To decrease turnover intention, therefore, nursing managers need to develop the nurse retention program for increasing job embeddedness and apply to nursing field.

• Journal of Advanced Marine Engineering and Technology
• /
• v.23 no.2
• /
• pp.131-139
• /
• 1999

An experimental study was conducted to investigate the fouling effects of geothermal water scale deposited onto a heating surface upon its forced convection heat transfer characteristics. Scales deposited onto the heating surfaces of heat exchangers seriously reduce the heat transfer perfor-mance and also increase the hydrodynamic drag. Accordingly fouling is an important problem in the design and operation of heat exchangers. The cylinders were settled in tandem with equal dis-tance between neighbouring cylinders and only the test cylinder was heated under the condition of constant heat flux. The Reynolds number was varied from 13000310 through 50003100. It is found that the heat transfer of the in-line tube banks greatly varies with the fouling of geothermal water scale especially its scale height. Further the local and average Nusselt numbers strongly depend upon the cylinder spacing and the Reynolds number.

• Journal of Korean Society of Transportation
• /
• v.24 no.4 s.90
• /
• pp.129-148
• /
• 2006

The objective of this thesis is to develop a capacity analysis and to develop a methodology to evaluate Level of Service over the entire freeway sections by single MOE (Measure of Effectiveness) This study set forth from a following viewpoint. to analyze entire freeway sections as freeway facility system, it is important to identify the exact point where congestion would occur and the extent of the congestion. Therefore, in this thesis, congestion mechanism on freeways was figured out and congestion analysis methodology was developed. Thereby maximum possible throughput rate and maximum throughput rate in bottleneck sections were calculated and a congestion analysis was carried out. The difference between the new method and existing Procedures is that maximum possible throughput rate and maximum throughput rate. that can be considered as capacities of un-congested and congested flow in the bottleneck section, are variable capacities dependent on demand flow.

• Journal of Korean Society of Transportation
• /
• v.23 no.2
• /
• pp.61-74
• /
• 2005

This study is to investigate the effects of driving anger and traffic congestion on drivers' behaviors. Driving anger is the propensity to become angry while driving, and people differ in the tendency to get angry when encountering frustration and provocation on the road. Individual differences of the propensity contribute to anger on the road and aggressive driving leading traffic vaiolations and accidents. In the experiment three traffic conditions (an open road condition, a bumper-to-bumper traffic condition and a being stuck behind a slower driver condition) were simulated and driving behaviors were collected with RTSA-DS(Road Traffic Safety Authority-Driving Simulator). The results were as follows: Most of high anger drives drove at higher speeds in an open road condition, and in the bumper-to-bumper condition they drove faster and had an higher crash rate, which suggests they did aggressive driving, and risky and unsafe behaviors.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.30 no.6
• /
• pp.495-500
• /
• 2017

In the boundary layer of supersonic or hypersonic vehicles, there is the conversion from kinetic energy to thermal energy, called aerodynamic heating. Aerodynamic heating has to be considered to design supersonic vehicles, because it induces severe heat flux to surface. Transient heat transfer analysis with CFD is used to predict thermal response of vehicles, however transient heat transfer analysis needs excessive computing powers. Loosely coupled method is widely used for evaluating thermal response, however it needs to be revised for overestimated heat flux. In this research, quasi-transient method, which is combined loosely coupled method and conjugate heat transfer analysis, is proposed for evaluating thermal response with efficiency and reliability. Defining reference time of splitting flight scenario for transient simulation is important on accuracy of quasi-transient method, however there is no algorithm to determine. Therefore the research suggests the algorithm with various flow conditions to define reference time. Supersonic flow field of blunt body with constant acceleration is calculated to evaluate quasi-transient method. Temperature difference between transient and quasi-transient method is about 11.4%, and calculation time reduces 28 times for using quasi-transient method.

• Journal of Korean Home Economics Education Association
• /
• v.20 no.3
• /
• pp.49-64
• /
• 2008

The purpose of this study was to identify the relationships between the self-identity and career maturity of middle school students in Gyeongnam province. For this purpose following questions were formulated. First. Are there statistically significant differences in middle school students' self-identity by their background variables? Second, Are there statistically significant differences in middle school students' career maturity by their background variables? Third, How is the relationship between self-identity and career maturity? Fourth, How are the influences of background variables and self-identity on students' career maturity? Self-identity and career maturity were measured over 551 9th grade students(317 male and 234 female students) in Changwon, Jinju, Geoje, Hadong, Sancheong, and Tongreong areas. Frequency analysis, Cronbach'$\alpha$, t-test, one-way ANOVA, and multiple regression were used for statistical analysis. The results indicated that: 1. There were statistically significant differences in self-identity by mother's educational level, student's GPA, and economical background; 2. There were statistically significant differences in career maturity by student's gender, mother's educational level, and student's GPA; 3. There was 3. There were high static correlation between self-identity and career maturity and its subordinate items; 4. Sex and self-identity and its sub-items of students' independence, self-receptiveness, firm future goals, goal-orientation, intimacy have relative influences on career maturity.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.10
• /
• pp.1393-1400
• /
• 2003

Ignition of hydrogen and oxygen in the "third limit" is theoretically investigated in the stagnation point flow with activation energy asymptotics. With the steady-state approximations of H, OH, O and HO$_2$, a two-step reduced kinetic mechanism is derived for the regime lower than the crossover temperature T$_{c}$ at which the rates of production and consumption of all radicals are equal. Appropriate scaling of Damkohler number successfully provides the explicit relationship between pressure, temperature and strain rate at ignition. It is shown that, compared with those for the counterflow, ignition temperatures for the stagnation point flow are considerably increased with increasing the system pressure. This is because ignition in the "third limit" is characterized by the production of reduction of $H_2O$$_2$, which is reduced by wall effect. Strain rate substantially affects ignition temperature because key reaction rates of $H_2O$$_2$ are comparably with its transport rate, while the mixture temperature and the hydrogen composition do not significantly affect ignition temperature.e.

• The Journal of the Korea Contents Association
• /
• v.15 no.5
• /
• pp.242-253
• /
• 2015

The purpose of this study was to identify the mediating effects of spiritual experience and depression between self-identity and subjective well-being. The subjects of this study were 138 pastor's wives, and mediating effects were analysed through path analysis and Sobel test. As a result of analysis, first, there were significant relationships among self-identity, spiritual experience, depression, and subjective well-being, but not between spiritual experience and depression. Second, spiritual experience and depression had significant mediating effect within the relationship of self-identity and subject well-being. Third, self-identity had not significant direct effect on subjective well-being. Forth, spiritual experience had not significant direct effect on depression. Implications of these results were explored in relation to the importance of self-identity and spiritual experience that could be taken to improve subjective well-being. In addition, suggestions for future research were discussed.