• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.7
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• pp.97-104
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• 2006

The spray and breakup characteristics of swirling liquid sheet were investigated by measuring the spray angle and breakup length as the axial Weber number Wel was increased up to 1554 and the ambient gas pressure up to 4.0MPa. As Wel and ambient gas density increased, the disturbances on the annular liquid sheet surface were amplified by the increase of the aerodynamic forces, and thus the liquid sheet disintegrated near from the injector exit. The measured spray angles according to the ambient gas density were different before and after the sheet breaks. Before the liquid sheet breaks, the spray angle was almost constant, but once the liquid sheet started to breakup, the spray angle decreased. And the breakup length decreased because of the increase of the aerodynamic force as the ambient gas density and Wel increased. Lastly, the measured breakup length according to the ambient gas density and Wel was compared with the result by the linear instability theory. We found that the corrected linear instability theory considering the attenuation of sheet thickness agrees well with our experimental results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.3
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• pp.64-76
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• 2002

기존의 이론적 연구와 실험적 연구를 바탕으로 충돌 제트의 수치 모델을 개발하였다. 본 모델은 like-doublet 충돌제트로부터 생성되는 액적의 모든 특성을 액막이 분열되는 시점에서 결정한다. 액적 특성을 결정하기 위해 이론적 연구로부터 얻어진 액막 두께, 액주의 직경, 액적 크기와 실험적 연구로부터 얻어진 액막/액적 속도, 액막 분열 거리, 분열 주파수, 액적 질량 유량 분포를 이용하였다. 액적의 질량 유량 분포는 Laplace 분포로부터 표준 편차를 이용하여 모사하였다. 또한 실험 결과를 이용하여 액막 분열 거리, 분열 주기, 표준 편차에 대한 경험식을 유도하였다. 개발된 모델은 정성적인 분무 패턴뿐만 아니라 정량적인 SMD 및 질량 유량 분포에서 실험 결과와 잘 일치한다.

• The Journal of the Korea Contents Association
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• v.16 no.11
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• pp.199-210
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• 2016

This study was conducted to examine the mediation effect of narcissistic personality traits and schizophrenic personality traits on the relationship between smartphone addiction and relational aggression of middle school girls. Data from 378 girls in Kyungki and Chungchoeng areas were analyzed. Main results were as follows. First, smartphone addiction showed significant positive correlations with narcissistic personality traits, schizophrenic personality traits and relational aggression. Both personality traits also showed positive relationship with relational aggression. Second, narcissistic personality traits fully mediated the relationship between smartphone addiction and reactive relational aggression. Third, schizophrenic personality traits partially mediated the relationship between smartphone addiction and relational aggression. Finally, clinical implications for adolescent girls at high risk of smartphone addiction and suggestions for future studies were discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.171-174
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• 2008

This paper presents disintegration process of the small rotational fuel injector. In order to understand disintegration precess, we measured droplet diameter, velocity and spray distribution by the PDPA(Phasse Doppler Particle Analyzer) system. Also spray was visualized by using Nd-Yag flash photography. From the test results, the liquid column emerging from the injection orifice is mainly controlled by the rotational speeds. Furthermore, droplet diameter(SMD) and spray distribution were strongly influenced by the diameter of the injection orifice.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.949-952
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• 2017

Spray characteristics of the impinging injectors in subsonic crossflows were experimentally studied and compared with the plain-orifice injectors. By changing the impingement angle (60, 90, 120) which is the same orifice length to diameter ratio (L/d = 5), spray characteristics were investigated. In the view of the top view from the impinging injectors, as the impingement angle increases, the liquid column breakup length in the y-direction was decreased. On the other hand, when the impinging injector is viewed from the side view, the breakup length in the x direction is smaller than the previous plain-orifice injectors, which mean that the atomizing performance of the impingement-type injector is better than that of the single-hole orifice.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.2
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• pp.1-9
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• 2010

LES(Large eddy simulation) of breakup and droplet atomization of a liquid jet into cross turbulent flow was performed. Two phase flow of gas and liquid phases were modeled by the mixed numerical scheme of both Eulerian and Lagrangian methods for gas and liquid droplet respectively. The breakup process of a liquid column and droplets was observed by implementing the blob-KH wave breakup model. The penetration depth into cross flow was comparable with experimental data for several variants of the liquid-gas momentum flux ratio by varying liquid injection velocity. SMD(Sauter Mean Diameter) distribution downstream of jet was analyzed.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.1
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• pp.16-22
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• 2008

The effect of two-phase spray injected into subsonic cross-flow was studied experimentally. External-mixing of two-phase spray from orifice nozzle with L/d of 3 was tested with various air-liquid ratio that ranges from 0 to 59.4%. Trajectory of spray and breakup phenomena were investigated by shadowgraph photography. Detailed spray structure was characterized in terms of SMD, droplet velocity, and volume flux using PDPA. Experimental results indicate that penetration length was increased and collision point of liquid jets approached to nozzle exit and distributions of mist-like spray were obtained by increasing air-liquid ratio.

• Journal of ILASS-Korea
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• v.9 no.4
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• pp.1-8
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• 2004

Breakup characteristics of liquid sheets formed by the impingement of two water jets, such as a breakup length and a breakup wavelength of sheet, were investigated as increasing the injection velocity up to 30m/s and the ambient gas pressure up to 4.0MPa. While round edged orifices formed a laminar sheet which has no waves on the sheet when the injection velocity is low, sharp edged orifices formed a turbulent sheet which has impact waves irrespective of the injection velocity. Thus we compared the differences of breakup characteristics between them. The results showed that the aerodynamic force significantly affects the breakup of laminar sheet when the gas based Weber number is higher than unity, It was also found that the turbulent sheets have three breakup regimes, i.e. expansion regime, wave breakup regime and catastrophic breakup regime according to the gas based Weber number.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.11 no.2
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• pp.262-281
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• 2000

We focused on the peer relationship of adolescent patients with schizophrenia, which usually occurs around puberty. Reviewing cases with schizophrenia and the literature extensively, we had come to the conclusion as follows；1) the most robust predictors among factors influencing the prognosis of schizophrenia are premorbid interpersonal relationship and adaptive functions. 2) Especially teachers’ reports about school life and peer relationship during school life are useful for predicting the occurrence of schizophrenia in adolescents. We described characteristic and behavioral childhood features which are important in pathogenesis of schizophrenia, based on high-risk studies and long term follow-up studies. Also, pathological profiles of the interpersonal relationship and pathology in adulthood were presented. We tried to integrate various aspects of interpersonal and social weaknesses of schizophrenics applying 'primary and secondary socialization' concept. Finally, five cases of adolescent schizophrenics were described briefly and proposal for the early detection and intervention for risk factors was introduced.

• Journal of Digital Convergence
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• v.11 no.4
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• pp.351-359
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• 2013

This study was conducted to investigate the factors that affect the length of stay in hospital for schizophrenic patients. Of the data from the in-depth injury patient surveillance system, the final subject included 2,239 patients with schizophrenia in their final diagnosis. Using SPSS 18.0, a hierarchical regression analysis was performed by sequentially entering the explanatory variables by setting sociodemographic characteristics, discharge characteristics and hospital characteristics as explanatory variables and the length of stay in hospital as a dependent variable. The findings showed that the sociodemographic characteristics had the highest explanatory power and the explanatory power changed when the explanatory variable of the hospital characteristics was added, as opposed to the discharge characteristics. Male, type-1 medicaid, Chungcheong-do and the number of beds were found to be the factors that mostly affect the length of stay. Since this study used the secondary data, it has a limitation in terms of additional variables that could better explain the length of stay for schizophrenic patients. Nevertheless, it has an implication in that it investigated a large scale of data on a national level. For the effort of reducing the length of stay, it is suggested that an effort should be made at the national level, by focusing more on the hospital characteristics as well as the individual characteristics of patients.