20,017 research outputs found
Letter from Dean Chien-pin Li
Full text linkA letter from Chien-pin Li, the dean of the College of Humanities and Social Sciences at Sam Houston State University
Numerical Simulation of the Motion of A Floating Body with Partially Filled Tanks by A Pressure-Convection Particle Method
No full textA novel design for an RF MEMS resistive switch on PCB substrate
No full textCopyright @ 2008 Stimulation Action on MEM
Numerical Study on Sheet Cavitation Flow of Two Dimension Hydrofoil
No full text空化(Cavitation)現象在流體中是普遍存在的現象，在造船產業的應用上尤其有很多明顯的例子，如螺槳和噴射推進器等。空化現象除了會造成流體機械效率的衰減，同時並產生震動、噪音和侵蝕問題。對於高速船舶，空化現象一直是重要的研究主題。然而高速推進器如噴射推進器、超空化螺槳、穿水式螺槳等也皆面臨來自空化現象的挑戰，因此有必要對空化現象進行完整的研究。由於分析空化現象的複雜度與困難度高，大部分的研究多以實驗方式進行。目前因為計算流體力學技術的快速發展，對於空化現象的紊流模式計算似乎變得較為可行。為了模擬片狀空化流場，本篇研究擬以自行建立完成之二維黏性流計算方法出發，導入以流體體積法為觀念之二相流的數值模型，利用等效流體模型，考慮流場中每一個控制體積內的兩種流體的分佈，使計算方法得以考慮流場中兩種不同的流體，再利用壓力、速度和密度之間的偶合關係使流場之計算可趨於穩定，其中經由疊代方式進行計算，直到片狀空化流場的形狀穩定為止。本文是應用二相流法來模擬二維水翼之片狀空化流場，進而預測空化區大小、形狀以及空化水翼的升力和阻力係數衰減。Marine applications involving attached bubbles on propellers and underwater vehicles are obvious examples of cavitation phenomena. For naval architecture issues, cavitation is always a very important topic related to high-speed ships. However, high-speed propulsors, including water jet system, super-cavitating propeller and surface-piercing propeller, are facing critical challenge from cavitation problems. For this reason, it is necessary to make a thorough study of cavitation phenomena. Due to the complexities and difficulties of theoretical analysis of cavitation, most of the researches are based on experimental approaches. With the fast development of computational fluid dynamics techniques, computations of turbulent flow for cavitation problems seem to become popular. In order to simulate sheet cavitation flows, the present method started from a two-dimensional flow code capable of computing turbulent hydrofoil flows. In order to take cavitation region into account, a two-phase flow scheme was further implemented. The proposed approach treats gas and liquid phases as an effective fluid with density varied in space. The flow field was computed in both phases with vapor pressure recovered inside the cavitation cavity via a pressure-velocity-density coupling scheme. The computation is iteratively conducted, until the shape of the sheet cavitation become stable. This thesis is to simulate steady sheet cavitation flows of a two-dimensional hydrofoil using a two-phase approach. The size and shape of sheet cavitation, and the lift and drag coefficient of a cavitating hydrofoil are predicted.誌謝……………………………………………….…. 一
摘要……………………………………………….…. 二
Abstract……………………………………………… 三
目錄……………………………….………………... 四
圖例目錄……………………………………………. 七
表格目錄…………………………………………..... 九
符號說明………………………………..…………... 十
第一章 緒論
1-1 研究目的及方向…………………………………. 1
1-2 空化介紹…………………………………………. 3
1-3 本文架構…………………………………………. 4
第二章 理論基礎
2-1 統御方程式………………………………………. 6
2-1-1 Reynolds–Averaged Navier-Stokes 方程式. 6
2-1-2 連續方程式及體積比率方程式…. 6
2-2 型…………………………………………………. 7
2-3 紊流模型……………………………….………… 8
2-4 邊界條件……………………………….………… 9
2-4-1 入口條件…………………………. 9
2-4-2 出口條件…………………………. 10
2-4-3 壁面函數…………………………. 10
第三章 數值方法
3-1 有限體積法……………………………………… 11
3-1-1 交錯放置…………………………. 11
3-1-2 非交錯放置………………………. 12
3-1-3 有限體積法………………………. 13
3-2 壓力修正方程式…………………………………. 16
3-3 數值網格產生及流場邊界條件…………………. 17
3-4 流場求解流程及參數設定………………………. 20
3-4-1 流場求解流場……………………. 20
3-4-2 計算流程…………………………. 21
3-4-3 參數設定…………………………. 21
第四章 計算結果與討論
4-1 網格密度的比較…………………………………. 22
4-2 不同參和係
Numerical Simulation of Free Surface Flow by Applying Particle Method
No full textWith fast development of the computer science, substantive efforts have been made in the computational fluid dynamics (CFD). Particularly a strong interest is focused on a new numerical method, namely, the meshless method. Since there is no mesh to distort, the meshless method can cope with large deformation in a Lagrangian framework. As a meshless method, the MPS (Moving Particle Semi-implicit) method has proven robust in a wide variety of naval architecture and ocean engineering including free surface flows. The MPS method is capable of dealing with problems in free surface, moving interface and wave propagation. Despite its applicability in many fields, the MPS method suffers unphysical numerical fluctuation of pressure with high frequencies. It leads the MPS method can not obtain accurate impact pressures. By implementing a new kernel function and the source term of Poisson pressure equation, a modified MPS method is proposed to suppress the pressure oscillation and obtained precise results in impact pressure prediction. The improved performance of the modified MPS method is validated by simulating the wave impact problems, such as the dam break problem, the droplet and wedge impact problem. Based on the previous research, some naval applications including bow flare impact and a floating body rolling in waves are introduced. The analyses show special advantage in simulating free surface flows
Simulation of a Ship with Partially Filled Tanks Rolling in Waves by Applying Moving Particle Semi-Implicit Method
No full textGeostatistical method to delineate anomalies of multi-scale spatial variation in hydrogeological changes due to the ChiChi earthquake in the ChouShui River alluvial fan in Taiwan
No full textStudies on the roles and mechanisms of RIS1 gene in human bladder cancer-derived cell lines
No full textUrinary bladder urothelial carcinoma (UBUC) is a common urologic cancer that has the highest recurrence rate of any malignancy, Men are about three to four times more likely than women to get bladder cancer, but women are typically diagnosed with more-advanced cancer and have a worse prognosis. It is hard to treat and has the highest recurrence, and therefore the treatment of the time and cost is relatively high. at the present, molecular target drug is not approved to treat the disease. Non-muscle-invasive bladder cancers (NMIBCs) frequently recur (50\ue270%) but infrequently progress to invasion (10\ue215%) and five-year survival is 90%. In recent years, studies have found that bladder cancer is associated with gene abnormal. Preliminary data analysis found that RIS1 in bladder cancer cells have abnormal expression. Thus, we want to further study RIS1 gene in bladder cancer. We then went further to highly express the RIS1 gene in bladder cancer cell of BFTC905, which showed increased cell cycle S phase and promoted cell viability, cell proliferation, invasion,migration. In contrast, knockdown of RIS1 in bladder cancer cells induced cell cycle arrest in G1 phase and inhibited cell viability, cell proliferation, invasion,migration. Mutations on threonine 261 of the RIS1 protein decreases cell proliferation and colony formation/anchorage-independent cell growth in J82 cell line. Then, the next generation sequencing (NGS) was used to analyze the related pathways of RIS1 in bladder cancer cell lines, and extracellular matrix/structure organization genes was screened out. The results show that RIS1 plays the role of oncogene in bladder cancer. However, the study of RIS1 in bladder cancer is still rarely. Therefore, our study explore the function and regulatory mechanisms of RIS1 in cancer
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