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충돌분무의 액적 거동에 미치는 비등방성 난류특성의 영향에 대한 수치해석 연구
고권현(G. H. Ko),유홍선(H. S. Ryou) 한국전산유체공학회 2003 한국전산유체공학회지 Vol.8 No.4
It is an aim of this study to perform extensive numerical study for analyzing the anisotropic turbulence effects on spatial and temporal behaviors of droplet for impinging sprays. The turbulence model of Durbin is used for comparisons with the k-E model. The turbulence-induced dispersions of droplets are consider to describe the anisotropy of turbulence effectively and spray/wall interactions are simulated using the model of Lee and Ryou. Present study investigates the overall and the internal structures of impinging diesel sprays such as spray shapes, radius and height of wall sprays, Sauter mean diameter (SMD), local droplet velocity, and local gas velocity and compared the results with experimental data by two adopted turbulence models. When the anisotropy effect of turbulence is included, better predictions for both gas and droplet tangential velocities are obtained, compared to the k-ε model. It is concluded that anisotropic effect of turbulence should be considered for simulating impinging diesel sprays.
Host People's Kindness and Migrant Workers' Cultural Adaptation: Evidence from South Korea
Jihyun Ryou(Jihyun Ryou),Sang-Yeon Kim(Sang-Yeon Kim) 한국학술연구원 2022 Korea Observer Vol.53 No.4
This study purports to determine the predictors of migrant workers' cultural adaptation in South Korea. In the main, we examined the extent to which the level of inter-/intracultural socializing, exposure to local/native media, and host culture receptivity affect the level of cultural adaptation in cognitive, affective, behavioral domains. Potential impacts of demographic factors (e.g., age, sex, ethnicity, marital status, living alone vs. with family, education level, residency in years, perceived cultural similarity) were also explored. To find answers to the research questions, a total of 634 migrant workers from 37 different nations were reached using a snowball sampling. Surveys were collected in 12 districts of Seoul, the capital of South Korea, and 21 adjacent metropolitan areas. Results indicate that intercultural interaction with host people and media exposure to local contents tend to help improve their knowledge about South Korea (e.g., language, culture). With all else equal, migrant workers treated kindly by Koreans at the workplace and in service sectors, and those living with family, compared to those who live alone, tended to enjoy a greater satisfaction with work and life in South Korea and were more willing to stay. Practical implications for Korean policymakers include encouraging competent migrant workers to move together with the family, making administrative efforts to further simplify the documentation process, and initiating public campaigns to raise host culture receptivity among Korean citizens.
Ryou, Hong-Sun,Lee, Seong-Hyuk,Ko, Gwon-Hyun,Hong, Ki-Bae The Korean Society of Mechanical Engineers 2001 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.15 No.7
The present article presents an extension to the computational model for spray/wall interaction and liquid film processes that has been dealt with in the earlier studies (Lee and Ryou, 2000a). The extensions incorporate film spread due to impingement forces and dynamic motion induced by film inertia to predict the dynamic characteristics of wall films effectively. The film model includes the impingement pressure of droplets, tangential momentum transfer due to the impinging droplets on the film surface and the gas shear force at the film surface. Validation of the spray/wall interaction model and the film model was carried out for non-evaporative diesel sprays against several sources of experimental data. The computational model for spray/wall interactions was in good agreement with experimental data for both spray radius and height. The film model in the present work was better than the previous static film model, indicating that the dynamic effects of film motion should be considered for wall films. On the overall the present film model was acceptable for predication of the film radius and thickness.
Numerical Evaluation of Crashworthiness of Automotive Sheets
Ryou, Han Sun,Lee, Myoung Gyu,Kim, Chong Min,Chung, Kwan Soo Trans Tech Publications, Ltd. 2007 Key Engineering Materials Vol.345-346 No.-
<P>Crash simulations were performed for automotive sheets. To understand the influence of crystal structures in sheet materials on crashworthiness, the effect of the yield function shape was studied by adopting the recently developed non-quadratic anisotropic yield surface, Yld2004-18p. The effect of the back-stress was also investigated by comparing simulation results obtained for the isotropic, kinematic and combined isotropic-kinematic hardening laws based on the modified Chaboche model. In addition, the effects of anisotropy and sheet thickness on crashworthiness were evaluated.</P>
Invariant Trace Fields of Chain Links
Ryou, Kazuhiro Department of Mathematics 2016 Kyungpook mathematical journal Vol.56 No.1
In this paper, we compute the trace field of C(2, s), the complement of two component chain link with s left half twists in ${\mathbb{S}}^3$, for every s. As a result, for every $n{\in}{\mathbb{N}}{\backslash}\{1\}$, we can find $s{\in}{\mathbb{Z}}$ such that the degree of the trace field of C(2, s) is n. We also prove that if for fixed p, the degree of the trace field of C(p, s) runs over ${\mathbb{N}}{\backslash}\{1\}$, then p is contained in {1, 2, 4, 8}.
Ryou, Myung-Hyun,Han, Young-Dal,Lee, Je-Nam,Lee, Dong-Jin,Park, Jung-Ki The Korean Electrochemical Society 2008 한국전기화학회지 Vol.11 No.3
The multilayered membrane for lithium rechargeable batteries based on poly (vinylidene fluoride) (PVdF) is prepared with the coated layer containing nano-sized filler. The prepared membranes were subjected to studies of mechanical strength, morphology, interfacial stability, impedance spectroscopy, ionic conductivity, and cycle performance. The localized inorganic filler in the PVdF composite membrane rendered mechanical strength much reduced because of its low stretching ratio and it results in around half value of the mechanical strength of highly stretched PVdF membrane. In order to achieve high ionic conductivity and interfacial stability without sacrificing high mechanical strength, coating layer with nano-filler was newly introduced to PVdF membrane. The ionic conductivity of the coated membrane was 1.03 mS/cm, and the interface between the coating layer and PVdF membrane was stable when the membrane was immersed into liquid electrolyte. The discharge capacity of the cell based on nano-filler coated PVdF membrane was around 91% of the initial discharge capacity after 250 cycles, which is an improvement in cycle performance compared to the case for the non-coated PVdF membrane.
Ryou, YoungSeok,Lee, Jaeha,Lee, Hyokyoung,Kim, Chang Hwan,Kim, Do Heui Elsevier 2019 CATALYSIS TODAY - Vol.320 No.-
<P><B>Abstract</B></P> <P>Various activation conditions such as temperature, time and the concentration of H<SUB>2</SUB>O during hydrothermal aging (HTA) treatment were extensively investigated to identify the proper ion-exchange conditions of Pd/SSZ-13 catalyst for low temperature NO adsorption performance. In addition, we examined how the cation in SSZ-13 (i.e. NH<SUB>4</SUB>-, Na- or K-SSZ-13) affects the low temperature NO adsorption performance of Pd/SSZ-13 after HTA treatment. It is found that NO adsorption ability begins to increase substantially when Pd/SSZ-13 is hydrothermally aged above 650°C. Pd/SSZ-13 demonstrated the maximum NO adsorption performance after hydrothermal aging treatment in the range of 700–750°C, followed by the severe decline above 850°C. Such deactivation is attributed to the agglomeration of Pd species due to the dealumination of SSZ-13, as indicated by XRD and NMR analysis. At least 15h of HTA treatment at 750°C is required to provide the optimum activation of Pd/SSZ-13. Water vapor is essential component to activate Pd/SSZ-13 during the hydrothermal aging treatment. Unlike NH<SUB>4</SUB>-SSZ-13, Na- or K-SSZ-13 cannot be activated even if the optimum hydrothermal aging condition (750°C for 25h with 10% H<SUB>2</SUB>O) is applied. EXAFS and XRD analysis provides the evidence about the sintering of Pd species of the Pd/Na- or Pd/K-SSZ-13 catalysts rather than Pd ion exchange, indicating that the pre-existing Na or K ion inhibits the ion exchange during hydrothermal aging treatment. It can be concluded that the selection of proper hydrothermal aging conditions and zeolite form is essentially required to obtain the excellent low temperature NO adsorption performance of Pd/SSZ-13 as a passive NOx adsorber.</P> <P><B>Highlights</B></P> <P> <UL> <LI> NO adsorption ability is affected by hydrothermal aging (HTA) temperature and time. </LI> <LI> HTA in the range of 650–800°C (for 25h) activates Pd/SSZ-13. </LI> <LI> At 750°C, 15h of aging time is regarded to fully activate Pd/SSZ-13. </LI> <LI> H<SUB>2</SUB>O is essential component for the activation of Pd/SSZ-13. </LI> <LI> The presence of Na or K ion in SSZ-13 inhibits the activation of Pd/SSZ-13. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>