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Numerical Study of Free Surface Effect on Supercavitating Flows
Son-Tung Dang,Cong-Tu Ha,Van-Tu Nguyen,Warn-Gyu Park(박원규),Dong-Hyun Kim(김동현) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
In this paper, we focus on applying the volume of fluid (VOF) method coupled with an interface reconstruction technique to capture the free surface between liquid and gas. The governing equation is the compressible Navier-Stokes equations based on the homogeneous mixture model. A preconditioned method is applied for enhancing efficient and accurate computations over a wide range of Mach numbers. For evaluation, the present results have been compared with experiments and other numerical results. A fairly good agreement with the experimental data and other numerical results has been obtained. Finally, the simulation of natural supercavitating flows over a plate hydrofoil was conducted to show the effect of free surface on characteristic length of supercavitation.
Inhibitory Constituents against Cyclooxygenases from Aralia cordata Thunb
Dang Nguyen Hai,Zhang XinFeng,Zheng MingShan,Son Kun Ho,Chang Hyeun Wook,Kim Hyun Pyo,Bae KiHwan,Kang Sam Sik The Pharmaceutical Society of Korea 2005 Archives of Pharmacal Research Vol.28 No.1
Seven diterpenes, four polyacetylenes, a lipid glycerol, and two sterols were isolated from the methylene chloride fraction of the root of Aralia cordata. Their chemical structures were determined as (-)-pimara-8(14), 15-dien-19-oic acid (2), pimaric acid (3), (-)-kaur-16-en-19-oic acid (4), 17-hydroxy-ent-kaur-15-en-19-oic acid (9), $7{\alpha}$-hydroxy-(-)-pimara-8(14), 15-dien-19-oic acid (10), $16\alpha$, 17 -dihydroxy-(-)-kauran-19-oic acid (11), 16-hydroxy-17-isovaleroyloxy-ent-kauran-19oic acid (12), falcarindiol (5), dehydrofalcarindiol (6), dehydrofalcarindiol-8-acetate (7), falcarindiol-8-acetate (8), alpha-mono palmitin (13), stigmasterol (1), and daucosterol (14) by the spectral evidences. These compounds were tested with COX-1 and COX-2 inhibition assays. This study found that compounds 2, 4, 5, 6, 7, 8, and 10 inhibited COX-1 dependent conversion of the exogenous arachidonic acid to $PGE_2$ in a dose-dependent manner with $IC_{50}$ values of $134.2{\mu}M$, $121.6{\mu}M$, $170{\mu}M$, $50.4{\mu}M$, $11.7{\mu}M$, $99.6{\mu}M$, and $69.6{\mu}M$, respectively. But, most of these compounds weakly inhibited COX-2 dependent $PGE_2$ generation. Among them, only compound 4 showed relatively significant inhibitory activity $(IC_{50}\;:\;127.6{\mu}M)$.
Jungwon Huh(허정원),Nhu Son Doan(도안누손),Van Ha Mac(맥반하),Van Phu Dang(당반푸),Dong Hyawn Kim(김동현) 한국해안해양공학회 2021 한국해안해양공학회 논문집 Vol.33 No.6
하중·저항계수 설계는 일관된 시스템적 설계해를 제공하는 효율적인 설계 방식이다. 이 연구는 확률론적 프레임워크 내에서 방파제의 지반기초(foundation) 설계에 필요한 하중계수 및 저항계수를 결정하는 것을 목표로 하여 한국형 방파제의 대표적인 4가지 유형인 경사식 방파제, 무공케이슨 혼성식방파제, 유공케이슨 혼성식방파제, 소파블록 피복제를 대상으로 조사하였다. 파랑하중조건에서 방파제 기초의 지지력을 면밀히 조사하였다. 100,000회 샘플에 의한 Monte Carlo 시뮬레이션을 사용하여, 목표신뢰도지수(RI) 2.5와 3.0의 두 가지 수준을 선택하여 하중·저항계수의 보정을 수행하였다. 예상대로 더 높은 RI에 대해 정규화된 저항계수는 더 낮은 값을 갖는 것으로 확인되었다. 그 범위는 목표 RI 2.5의 경우 0.668~0.687이며, 목표 RI 3.0의 경우 0.576~0.634이다. Load and resistance factor design is an efficient design approach that provides a system of consistent design solutions. This study aims to determine the load and resistance factors needed for the design of breakwater foundations within a probabilistic framework. In the study, four typical types of Korean breakwaters, namely, rubble mound breakwaters, vertical composite caisson breakwaters, perforated caisson breakwaters, and horizontal composite breakwaters, are investigated. The bearing capacity of breakwater foundations under wave loading conditions is thoroughly examined. Two levels of the target reliability index (RI) of 2.5 and 3.0 are selected to implement the load and resistance factors calibration using Monte Carlo simulations with 100,000 cycles. The normalized resistance factors are found to be lower for the higher target RI as expected. Their ranges are from 0.668 to 0.687 for the target RI of 2.5 and from 0.576 to 0.634 for the target RI of 3.0.
A Study on Manufacturability and Assembly of Plastic Automobile Front Side Panel
Hong-Seok Park,Thanh-Son Tran,Xuan-Phuong Dang,Jung-Ho Kim,Tae-Hwa Kim 한국생산제조학회 2009 한국공작기계학회 추계학술대회논문집 Vol.2009 No.-
The application of plastics into the automotive industry has increased in recent decades. Due to its proficient properties such as light-weight, high-resistance to low-collision damage and, good shock and noise absorbance, easy to mold complex geometry; plastics can be better applied to both interior and exterior automotive components than steel originally could. This paper presents the development of a plastic front side panel (fender) of an automobile. The aim of this study is to design a plastic front side panel that meets the following vehicle design goals such as light in weight, less susceptible to damage from minor impact, easy for manufacturing and assembly. The thickness of plastic car fender, an important parameter that affects the material consumption and product weight, is computed based on its ability to resist low-collision damages and mold-ability in the injection molding process. To avoid the bugle of the fender during heat-treatment in in-and-online painting process, assembly holes and slots are designed to allow it to expand along the suitable predetermined directions.