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直方管内充分发展湍流的大涡模拟 第二部分 被引量:6
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作者 苏铭德 《空气动力学学报》 CSCD 北大核心 1995年第1期9-18,共10页
本文第一部分用大涡模拟的方法对直方管内Re=4.9×10^4的充分发展湍流运动进行了数值模拟。所得结果证实大涡模拟是高雷诺数复杂湍流运动数值模拟的一个有效手段。在本文第二部分用所得的数据库对湍流运动的结构和形态进... 本文第一部分用大涡模拟的方法对直方管内Re=4.9×10^4的充分发展湍流运动进行了数值模拟。所得结果证实大涡模拟是高雷诺数复杂湍流运动数值模拟的一个有效手段。在本文第二部分用所得的数据库对湍流运动的结构和形态进行了分析,并且用流体质点运动图形显示了湍流运动的二次流。 展开更多
关键词 湍流 数值模拟 大涡模拟 直方管
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直方管内充分发展湍流的大涡模拟 第一部分 被引量:3
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作者 苏铭德 《空气动力学学报》 CSCD 北大核心 1995年第1期1-8,共8页
本文用大涡模拟的方法对直方管内Re=4.9×10^4的充分发展湍流运动进行数值模拟,所得结果清楚地显示了二次流的存在。统计平均量的数值结果也与实验结果吻合甚好,这表明大涡模拟是高雷诺数复杂湍流运动数值模拟的一个有... 本文用大涡模拟的方法对直方管内Re=4.9×10^4的充分发展湍流运动进行数值模拟,所得结果清楚地显示了二次流的存在。统计平均量的数值结果也与实验结果吻合甚好,这表明大涡模拟是高雷诺数复杂湍流运动数值模拟的一个有效手段。 展开更多
关键词 湍流 数值模拟 大涡模拟 直方管
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入口非均匀性对直方管内湍流影响的大涡模拟研究
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作者 王永康 刘向军 《冶金动力》 2006年第6期39-43,共5页
采用大涡模拟方法对直方管内的湍流流动进行了研究,对比计算了进口处为均匀来流和非均匀来流三种工况。从瞬时速度、脉动速度和平均速度分布等方面对湍流流动进行了分析。计算结果表明:入口处均匀来流和非均匀来流在横截面都会产生二次... 采用大涡模拟方法对直方管内的湍流流动进行了研究,对比计算了进口处为均匀来流和非均匀来流三种工况。从瞬时速度、脉动速度和平均速度分布等方面对湍流流动进行了分析。计算结果表明:入口处均匀来流和非均匀来流在横截面都会产生二次流运动;四个角域强化了壁面流体和主流流体的动量交换;在平均雷诺数相同情况下,非均匀来流时湍流程度大,各方向湍流脉动加强,横截面二次流加强,出现多个复杂的涡流区,瞬时流场结构、涡结构要复杂得多。 展开更多
关键词 大涡模拟 湍流 直方管
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Endoscopic submucosal dissection for gastrointestinal neoplasms 被引量:95
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作者 Naomi Kakushima Mitsuhiro Fujishiro 《World Journal of Gastroenterology》 SCIE CAS CSCD 2008年第19期2962-2967,共6页
Endoscopic submucosal dissection (ESD) is an advanced technique of therapeutic endoscopy for superficial gastrointestinal neoplasms. Three steps characterize it:injecting fluid into the submucosa to elevate the lesion... Endoscopic submucosal dissection (ESD) is an advanced technique of therapeutic endoscopy for superficial gastrointestinal neoplasms. Three steps characterize it:injecting fluid into the submucosa to elevate the lesion, cutting the surrounding mucosa of the lesion, and dissecting the submucosa beneath the lesion. The ESD technique has rapidly permeated in Japan for treatment of early gastric cancer, due to its excellent results of en- bloc resection compared to endoscopic mucosal resection (EMR). Although there is still room for improvement to lessen its technical difficulty, ESD has recently been applied to esophageal and colorectal neoplasms. Favorable short-term results have been reported, but the application of ESD should be well considered by three aspects:(1) the possibility of nodal metastases of the lesion, (2) technical difficulty such as location, ulceration and operator’s skill, and (3) organ characteristics. 展开更多
关键词 Endoscopic submucosal dissection Gastric cancer Esophageal cancer Colorectal cancer Endoscopic mucosal resection Therapeutic endoscopy
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Management of stage Ⅳ rectal cancer: Palliative options 被引量:5
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作者 Sean M Ronnekleiv-Kelly Gregory D Kennedy 《World Journal of Gastroenterology》 SCIE CAS CSCD 2011年第7期835-847,共13页
Approximately 30% of patients with rectal cancer present with metastatic disease. Many of these patients have symptoms of bleeding or obstruction. Several treatment options are available to deal with the various compl... Approximately 30% of patients with rectal cancer present with metastatic disease. Many of these patients have symptoms of bleeding or obstruction. Several treatment options are available to deal with the various complications that may afflict these patients. Endorectal stenting, laser ablation, and operative resection are a few of the options available to the patient with a malignant large bowel obstruction. A thorough understanding of treatment options will ensure the patient is offered the most effective therapy with the least amount of associated morbidity. In this review, we describe various options for palliation of symptoms in patients with metastatic rectal cancer. Additionally, we briefly discuss treatment for asymptomatic patients with metastatic disease. 展开更多
关键词 Palliative therapy Rectal cancer Malignant bleeding Malignant obstruction Endorectal stenting Laser ablation
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Boundary Control of Coupled Nonlinear Three Dimensional Marine Risers 被引量:2
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作者 T. L. Nguyen K. D. Do J. Pan 《Journal of Marine Science and Application》 2013年第1期72-88,共17页
This paper presents a design of boundary controllers implemented at the top end for global stabilization of a marine riser in a three dimensional space under environmental loadings. Based on the energy approach, nonli... This paper presents a design of boundary controllers implemented at the top end for global stabilization of a marine riser in a three dimensional space under environmental loadings. Based on the energy approach, nonlinear partial differential equations of motion, including bending-bending and longitudinal-bending couplings for the risers are derived. The couplings cause mutual effects between the three independent directions in the riser's motions, and make it difficult to minimize its vibrations. The Lyapunov direct method is employed to design the boundary controller. It is shown that the proposed boundary controllers can effectively reduce the riser's vibration. Stability analysis of the closed-loop system is performed using the Lyapunov direct method. Numerical simulations illustrate the results. 展开更多
关键词 marine risers boundary control nonlinear dynamics equations of motion nonlinear couplings
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Synthesis of aligned carbon nanotube with straight-chained alkanes by nebulization method
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作者 刘云泉 陈小华 +2 位作者 杨植 蒲玉兴 易斌 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2010年第6期1012-1016,共5页
Aligned carbon nanotubes(CNTs)were synthesized by nebulized spray pyrolysis of solutions of organometallics in carbon precursor solvents.Four types of straight-chained alkanes including n-pentane,n-hexane,n-heptane an... Aligned carbon nanotubes(CNTs)were synthesized by nebulized spray pyrolysis of solutions of organometallics in carbon precursor solvents.Four types of straight-chained alkanes including n-pentane,n-hexane,n-heptane and n-octane were used as precursor solvents for synthesis of aligned CNTs.The results from scanning electron microscopy,transmission electron microscopy and Raman spectroscopy show that the CNTs obtained from them have different diameters and degrees of graphitization. It is found that the n-heptane is the most suitable for the growth of aligned CNTs with high quality and yield.The thermodynamic properties of precursory carbon sources such as boiling point and formation enthalpy are considered to play a decisive role in the synthesis of CNTs.It will be very helpful for the controllable preparation of aligned CNTs at relatively low cost. 展开更多
关键词 aligned carbon nanotubes NEBULIZATION straight-chained alkanes thermodynamic property
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Fabrication and Characterization of VO_2 Thin Films by Direct Current Facing Targets Magnetron Sputtering and Low Temperature Oxidation
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作者 梁继然 胡明 +2 位作者 刘志刚 韩雷 陈涛 《Transactions of Tianjin University》 EI CAS 2008年第3期173-177,共5页
Low valence vanadium oxide(VO2-x) thin films were prepared on SiO2/Si substrates at room temperature by direct current facing targets reactive magnetron sputtering, and then proc- essed through rapid thermal annealing... Low valence vanadium oxide(VO2-x) thin films were prepared on SiO2/Si substrates at room temperature by direct current facing targets reactive magnetron sputtering, and then proc- essed through rapid thermal annealing. The effects of the annealing on the structure and phase transition property of VO2 were discussed. X-ray photoelectron spectroscopy, X-ray diffraction tech- nique and Fourier transform infrared spectroscopy were employed to study the phase composition and structure of the thin films. The resistance-temperature property was measured. The results show that VO2 thin film is obtained after annealed at 320 ℃ for 3 h, its phase transition tempera- ture is 56 ℃, and the resistance changes by more than 2 orders. The vanadium oxide thin films are applicable in thermochromic smart windows, and the deposition and annealing process is compatible with micro electromechanical system process. 展开更多
关键词 vanadium dioxide direct current facing targets magnetron sputtering low temperature oxidation: microstructure
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