共查询到20条相似文献,搜索用时 15 毫秒
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Sushil K. Singh 《Canadian Metallurgical Quarterly》2003,129(6):470-473
Advection-dispersion in streams encounters pockets of stagnant or dead zones in the flow, which trap the injected tracer. Treatment of stagnant or dead zones for dispersion is presented using one-dimensional advection-dispersion equation. A method is suggested for simultaneous estimation of dispersion coefficient, apparent (or effective) velocity, and effective injected mass of tracer, from a temporal concentration profile observed at a downstream section. The method is robust and uses a nonlinear optimization. Using the method procedure for estimation of adsorption coefficient for riverine advection-dispersion has also been suggested. The effective velocity is related to the stagnant zone fraction (average fraction of cross-sectional area attributed to stagnant zones) and adsorption. The application of the method on published data sets show that the parameter-estimates are reliable and the observed concentration profiles are closely reproduced. The analytical procedure described for the treatment of stagnant zones may have a wide application in civil engineering as well as other fields. The amount of chemicals released from the industrial units or by an accident can be estimated. 相似文献
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Sushil K. Singh 《Canadian Metallurgical Quarterly》2008,134(6):853-856
The modified advection dispersion equation (MADE) model is compared to the transient storage model (TSM) and fractional advection dispersion equation (FRADE) model for modeling riverine transport. The comparisons are illustrated using field examples. The parameter F of the FRADE model is found to be inconsistent to its physical meaning and is unrelated to dead zone fraction. Also, the estimated parameters of TSM are found to be inconsistent to their physical meaning. On the contrary, the parameters of MADE are consistent and related to the dead zone fraction. It is observed that the MADE model is easy to use and yields reliable and consistent results. 相似文献
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Chronic deep brain stimulation (DBS) is a promising technique for the treatment of movement disorders. Thalamic stimulation is now an established surgical procedure for parkinsonian and essential tremor. Pallidal and subthalamic stimulation are under active investigation as treatments for Parkinson's disease. Although high-frequency DBS at these sites has similar behavioral effects as lesioning, the physiologic mechanisms underlying the beneficial effect of DBS is not well understood and may be extremely complex. DBS offers a potential advantage over ablative therapy because stimulation-induced complications are reversible, and the stimulation parameters are adjustable to minimize complications and maximize therapeutic effects. With this added safety, bilateral stimulation or use of a stimulator following a prior procedure may be preferable to bilateral ablative procedures. 相似文献
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JP Hubble KL Busenbark S Wilkinson RD Penn K Lyons WC Koller 《Canadian Metallurgical Quarterly》1996,46(4):1150-1153
We examined the effects and safety of deep brain stimulation (DBS) as a treatment for essential tremor (ET). Ten ET patients with disabling medication-refractory tremor underwent stereotactic implantation of a DBS lead in the left Vim thalamic nucleus and completed a 6-month follow-up. The Clinical Tremor Rating Scale and disability assessments were performed at baseline, 1-, 3-, and 6-month follow-up. There were significant improvements in dressing, drinking, eating, bathing, and handwriting as reported by the subjects. Tremor severity, writing, pouring, and spiral and line drawing were significantly improved as rated by the examiner. Improvements persisted through the 6-month follow-up period. Although global disability significantly lessened in the group as a whole, one subject with hand-finger tremor accentuated by writing had no change in disability status. In this 6-month open-label study, DBS was effective and safe in reducing tremor and functional disability in ET. 相似文献
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The third-order analytical solutions for the strong interactions among three free-wave components are derived using two well-known perturbation methods, namely, the mode-coupling method and the Zakharov equation method. A term-by-term comparison of their solutions shows that the two methods render virtually identical results. The validity and convergence range of the solution are investigated for the interacting free-wave components of various frequencies but within the frequency range of storm seas. It is found that the solution may encounter two types of convergence difficulties, which occur, respectively, in the cases (1) when two of the interacting free-wave components are of quite different frequencies; and (2) when two of the interacting free-wave components are very close in frequency but the frequency of the third free-wave component is relatively larger or smaller. 相似文献
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RH用低碳深脱硫预熔渣 总被引:1,自引:0,他引:1
为实现低碳、超低碳钢在RH中进行深脱硫且钢水不增碳,在200kg真空感应炉上对RH用低碳深脱硫预熔渣进行了脱硫试验研究,结果表明:以CaO-Al2O3-SiO2-MgO为主的低碳深脱硫预熔渣熔点低、脱硫率高,可在真空条件下将钢液中硫的质量分数由30×10-6~50×10-6脱至10×10-6~20×10-6以下,脱硫率达到55%以上,脱硫效果好,脱硫率稳定。该预熔渣中碳的质量分数小于0.05%,在脱硫过程中钢水几乎不增碳,适用于在RH中低碳、超低碳钢深脱硫。研究表明:适当地提高炉渣的光学碱度,可大大地提高其硫容量,增强炉渣的脱硫能力。使用该预熔渣处理钢水有利于钢中夹杂物的去除和细化。 相似文献
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RH精炼过程深脱硫的试验研究 总被引:8,自引:0,他引:8
实验室钢液真空脱硫试验表明,组成为65% ̄85%石灰和15% ̄35%萤石的粉剂,粒度为5mm以下,加入量在3 ̄8kg/t的条件下,可使初始硫含量为0.0035% ̄0.0065%的钢液脱硫至0.0020%以下,脱硫时间为10 ̄15min,脱硫率在60% ̄80%。 相似文献
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深基坑土钉支护数值模拟 总被引:2,自引:0,他引:2
基于FLAC3D的基本原理及其求解过程,对深基坑工程土钉墙支护做了数值模拟,对不同土钉长度、倾角的4种支护方案进行了对比选择。对所选支护方案的计算结果进行分析,得出一些有用的结论,对深基坑土钉墙支护设计及合理施工有一定的指导意义。 相似文献
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S. Yimsiri K. Soga K. Yoshizaki G. R. Dasari T. D. O’Rourke 《Canadian Metallurgical Quarterly》2004,130(8):830-842
The soil–pipeline interactions in sand under lateral and upward movements are investigated with particular attention to the peak forces exerted on the pipe. The analytical solutions for estimating the peak forces are summarized and it is shown that, for deep embedment condition, there is large uncertainty in the true values since the bounds established by the analytical solutions are large. In order to find the solution for the peak force and to investigate its transition from shallow to deep failure mechanism, finite element analyses of lateral and upward pipe movements are performed for different embedment conditions. Two different soil models (Mohr–Coulomb and Nor–Sand models) are used for the simulations. The accuracy of the analysis is first examined by simulating experimental tank tests. The analysis is further extended to deeper embedment ratios of as large as 100. The obtained finite element results are used to construct a design chart for deep embedded pipelines. 相似文献
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以赞比亚康科拉竖井项目为例,通过对该项目设计与施工服务过程中的实践经验,探讨了中国国际工程公司在国际工程项目中应注意的事项。 相似文献
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钢材延伸产业链作为钢铁产业链的重要组成部分,其发展快慢与好坏直接影响到我国钢铁业自身发展。通过不同类型钢材深加工现状的分析,国内外钢铁企业发展深加工实践的探讨,我国应采用大力发展钢材深加工产业应对激烈市场竞争的发展策略。 相似文献
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吕亚 《金属材料与冶金工程》2014,(3):22-24
介绍和分析了安阳钢铁集团150t LF钢包精炼炉深脱硫工艺。生产实践表明:合理的渣系组成、渣量、温度控制、吹氩搅拌及喂线技术是实现快速深脱硫的关键环节。 相似文献