共查询到20条相似文献，搜索用时 296 毫秒
1.
The problem of a transient, transverse electromagnetic wave incident on a non-homogeneous half space is considered. Solutions are obtained by both the Laplace transform technique (LT) and the method of characteristics (MOC). The former method yields an infinite number of exact solutions in closed-form provided that the dielectric and permeability parameters are distributed as power laws in the spacial coordinate. A method for systematically generating these solutions is given. The method of characteristics, in numerical form, provides approximate solutions along the curved characteristics. Agreement between the two methods is excellent, except for a certain anomalous class of inhomogeneities. Finally, certain quasi-static solutions, involving a variety of inhomogeneities, are demonstrated. 相似文献
2.
In this paper, based on the Smith iteration (Smith, 1968), an inner-outer (IO) iteration algorithm for solving the coupled Lyapunov matrix equations (CLMEs) is presented. First, the IO iteration algorithm for solving the Sylvester matrix equation is proposed, and its convergence is analyzed in detail. Second, the IO iteration algorithm for solving the CLMEs is constructed. By utilizing the latest estimation, a current-estimation-based and two weighted IO iteration algorithms are also given for solving the CLMEs, respectively. Convergence analyses indicate that the iteration solutions generated by these algorithms always converge to the unique solutions to the CLMEs for any initial conditions. Finally, Several numerical examples are provided to show the superiority of the proposed numerical algorithms. 相似文献
3.
Ibrahim Kocabas 《Journal of The Franklin Institute》2011,348(7):1339-1362
The Laplace transformation technique has been widely applied to modeling of tracer transport in oil and geothermal reservoirs, and in groundwater aquifers. However, mathematical models of many flow and transport problems could only be obtained as Laplace space solutions, and hence, their computations had to involve a numerical inversion technique.In this work, we employ the iterated Laplace transformation technique to develop novel closed form solutions to the tracer transport models in heterogeneous media. Two types of configurations have been considered: tracer transport in single fracture located in low-permeability matrix and tracer transport in a double porosity medium consisting of flowing and dead-end pore systems. In addition, both linear and radial flow geometries have been considered for both configurations. Applications of iterated Laplace transform technique to these four types of models are presented as fundamental examples and their numerical results were used as benchmarking for the numerical inversion results from Stehfest and Dubner and Abate algorithms.As the technique is quite versatile, we expect that the method should gain widespread acceptance to develop solutions to a wide range of problems in flow and transport in porous media and improve the application of nonlinear regression technique to these solutions.This work has achieved four important objectives: first, two novel Laplace transform relations that are useful in tracer studies are presented. Second, the present work serves to verify/invalidate the results of numerical inversion algorithms. In addition, it provides better insight into tracer transport mechanisms. Finally, it serves as a powerful tool of design and interpretation of tracer tests. All four objectives are illustrated in this work. 相似文献
4.
In this study, we show the importance of extensional rheology, in addition to the shear rheology, in the choice of blood analog solutions intended to be used in vitro for mimicking the microcirculatory system. For this purpose, we compare the flow of a Newtonian fluid and two well-established viscoelastic blood analog polymer solutions through microfluidic channels containing both hyperbolic and abrupt contractions∕expansions. The hyperbolic shape was selected in order to impose a nearly constant strain rate at the centerline of the microchannels and achieve a quasihomogeneous and strong extensional flow often found in features of the human microcirculatory system such as stenoses. The two blood analog fluids used are aqueous solutions of a polyacrylamide (125 ppm w∕w) and of a xanthan gum (500 ppm w∕w), which were characterized rheologically in steady-shear flow using a rotational rheometer and in extension using a capillary breakup extensional rheometer (CaBER). Both blood analogs exhibit a shear-thinning behavior similar to that of whole human blood, but their relaxation times, obtained from CaBER experiments, are substantially different (by one order of magnitude). Visualizations of the flow patterns using streak photography, measurements of the velocity field using microparticle image velocimetry, and pressure-drop measurements were carried out experimentally for a wide range of flow rates. The experimental results were also compared with the numerical simulations of the flow of a Newtonian fluid and a generalized Newtonian fluid with shear-thinning behavior. Our results show that the flow patterns of the two blood analog solutions are considerably different, despite their similar shear rheology. Furthermore, we demonstrate that the elastic properties of the fluid have a major impact on the flow characteristics, with the polyacrylamide solution exhibiting a much stronger elastic character. As such, these properties must be taken into account in the choice or development of analog fluids that are adequate to replicate blood behavior at the microscale. 相似文献
5.
朱传界 《中国科学院研究生院学报》2001,18(1):12-27
初步介绍了非对易场论中的孤子解和其它严格解.从系统讨论平直非对易空间的表示和基本运算开始，引入了非对易场论并求解了几种非对易场论中的孤子解和严格解，这些解包括含规范场的瞬子解和BPS孤子解.并讨论了这些解用来描述玻色弦理论和超弦理论中的D-膜的应用. 相似文献
6.
Janardan Krishna Yadav Deepika Chandra Verma Srinivas Jangirala Shashi Kant Srivastava 《The Journal of High Technology Management Research》2021,32(1):100404
The concept of smart tourism remains fuzzy when it comes to practice because of the lack of clarity on the roles and responsibilities of stakeholders in addition to complex institutional ecosystem that exist within the tourism industry. Further, trust and safety of the data generated due to the advancement of smart tourism in varied institutional arrangements pose huge challenges. Extant literature proposes that the application of decentralized ledger promises possible solutions to most of these problems due to the inherent features of the Blockchain technology. This suggestion raises two practical questions. First, does the sophisticated additional layer adds complexity to its practical application? Second, will the suggested solutions really lead to a win-win for all the stakeholders involved? In this study, we use Ostrom's action arena to examine the exchanges (information, contractual and monetary) between various stakeholders in a BCT enabled smart tourism of a Blockchain enabled tourism industry to answer these two questions. 相似文献
7.
分析了线性选择方法的两个缺陷,提出了一种基于聚集密度的非线性自适应选择方法。算法基本思想是：首先将每代种群划分成Pareto劣解集和Pareto非劣解集,然后依照个体的聚集密度分别在劣解集和非劣解集中构造一种偏序集,分别按照不同的等概率在这两个偏序集中选择个体,其中劣解偏序集的个体选择概率远小于非劣解偏序集的个体选择概率,根据两个偏序集中的容量自动计算出两个选择概率。这种非线性选择方法既体现了劣解集和非劣解集中个体的绝对平等性及非劣解集对劣解集的相对优先选择权,又充分考虑到了Pareto最优解的分布性。理论分析和数值计算表明,这种新的选择机制不仅能改善排序选择法的收敛性,而且能得到分布性良好的Pareto最优解。 相似文献
8.
针对初学者对线性规划问题解的判定准则的困惑,本文用实例阐明了如何判定线性规划问题的求解结果。教学实践证明例析方法更能够加深学生对线性规划问题解的认识和理解。 相似文献
9.
Geschiere SD Ziemecka I van Steijn V Koper GJ Esch JH Kreutzer MT 《Biomicrofluidics》2012,6(2):22007-2200711
This paper studies the Rayleigh-Plateau instability for co-flowing immiscible aqueous polymer solutions in a microfluidic channel. Careful vibration-free experiments with controlled actuation of the flow allowed direct measurement of the growth rate of this instability. Experiments for the well-known aqueous two phase system (ATPS, or aqueous biphasic systems) of dextran and polyethylene glycol solutions exhibited a growth rate of 1 s−1, which was more than an order of magnitude slower than an analogous experiment with two immiscible Newtonian fluids with viscosities and interfacial tension that closely matched the ATPS experiment. Viscoelastic effects and adhesion to the walls were ruled out as explanations for the observed behavior. The results are remarkable because all current theory suggests that such dilute polymer solutions should break up faster, not slower, than the analogous Newtonian case. Microfluidic uses of aqueous two phase systems include separation of labile biomolecules but have hitherto be limited because of the difficulty in making droplets. The results of this work teach how to design devices for biological microfluidic ATPS platforms. 相似文献
10.
M. Shamsul Alam Kamalesh Chandra Roy Md. Mossaraf Hossain 《Journal of The Franklin Institute》2011,348(5):899-916
Combining Krylov-Bogoliubov-Mitropolskii (KBM) and harmonic balance methods, an analytical technique is presented to determine approximate solutions of nonlinear oscillatory systems with damping. The first approximate perturbation solutions in which the unperturbed solutions contain two harmonic terms agree with numerical solutions nicely even if the damping force is significant. With suitable examples it has been shown that the combination of classical KBM and harmonic balance methods sometimes fails to measure satisfactory results; but the combination of extended KBM method (by Popov) and harmonic balance method always give the desired results. The method is illustrated by several examples and the solutions are compared to some existing solutions. 相似文献
11.
J.P. Den Hartog 《Journal of The Franklin Institute》1933,216(4):459-473
Two new approximate graphical solutions are given for the problem of forced vibration of an undamped single degree of freedom vibrating system with a non-linear spring, whose characteristic is given in the form of a curve. One of these solutions gives much more accurate results than the approximation known so far. 相似文献
12.
《Research Policy》2019,48(8):103716
Crowdsourcing challenges are fast emerging as an effective tool for solving complex innovation problems. The main strength of the crowdsourcing model is that it brings together a large number of diverse people from all over the world to focus on solving a problem. This openness, however, results in a large number of solutions that are not appropriate, and this inhibits organizations from leveraging the value of crowdsourcing efficiently and effectively. It is therefore essential to identify ways to increase the appropriateness of solutions generated in a crowdsourcing challenge. This paper takes a step towards that by exploring what motivates the crowd to participate in these challenges and how these motivations relate to solution appropriateness. Drawing on data from InnoCentive, one of the largest crowdsourcing platforms for innovation problems, this paper shows that the various types of motivation driving crowd members to participate were related in different ways to the appropriateness of the solutions generated. In particular, intrinsic and extrinsic motivation were positively related to appropriateness whereas for learning and prosocial motivation the relationship was negative. The association between social motivation and appropriateness was not significant. The results have important implications for how to better design crowdsourcing challenges. 相似文献
13.
量子不变量理论是研究几何相因子问题的有效方法。利用Ｌｅｗｉｓ－Ｒｉｅｓｅｎｆｅｌｄ不变量理论研究了谐振磁场中的自旋系统,给出了两种不同循环演化周期的精确解,并进而分别计算了此系统两种不同的几何相因子。研究表明,不同循环演化周期的几何相因子与初始态的选择有关。 相似文献
14.
We study the boundedness of the solutions to a non-autonomous and non-linear differential equation of second order with two constant deviating arguments. We give two examples to illustrate the main results. By this work, we extend some boundedness results obtained for a differential equation with a constant deviating argument in the literature to the boundedness of the solutions of a differential equation with two constant deviating arguments. 相似文献
15.
分支搜索：工厂平面布置的新算法 总被引：1，自引：0，他引：1
提出二种工厂平面布置新算法:受控分支搜索算法和预分支搜索算法.该二种算法将分支搜索和启发式优化结合起来,可以在较大的解范围内搜索,获取接近最优的解. 相似文献
16.
Electroosmotic flow (EOF) with two or more fluids is commonly encountered in various microfluidics applications. However, no investigation has hitherto been conducted to investigate the hysteretic or flow direction-dependent behavior during the displacement flow of solutions with dissimilar ionic species. In this investigation, electroosmotic displacement flow involving dissimilar ionic solutions was studied experimentally through a current monitoring method and numerically through finite element simulations. The flow hysteresis can be characterized by the turning and displacement times; turning time refers to the abrupt gradient change of current-time curve while displacement time is the time for one solution to completely displace the other solution. Both experimental and simulation results illustrate that the turning and displacement times for a particular solution pair can be directional-dependent, indicating that the flow conditions in the microchannel are not the same in the two different flow directions. The mechanics of EOF hysteresis was elucidated through the theoretical model which includes the ionic mobility of each species, a major governing parameter. Two distinct mechanics have been identified as the causes for the EOF hysteresis involving dissimilar ionic solutions: the widening/sharpening effect of interfacial region between the two solutions and the difference in ion concentration distributions (and thus average zeta potentials) in different flow directions. The outcome of this investigation contributes to the fundamental understanding of flow behavior in microfluidic systems involving solution pair with dissimilar ionic species. 相似文献
17.
18.
文章研究产品开发早期阶段中技术解决方案的决策,即概念决策。文章实证研究我国的一家汽车生产企业。研究结果显示,概念决策中一个主要的挑战是在系统解决方案完全成熟之前,产品各系统需要实现兼容。管理者与产品开发人员应当了解,即使缺乏详细的分析,概念解决方案也能发展成为详尽的产品开发方案。在概念决策过程中,一些内在冲突要加以确认。文章认为应提高管理者与产品开发人员对心理偏差的认识。为引导每个人的判断与权衡,大家应对产品及其开发过程具有清楚的认识。 相似文献
19.
人工智能领域的专利申请是否符合专利保护客体的规定,进而能否获得专利权,是人们十分关心的问题。为了进一步明确相关的审查标准,国家知识产权局于2019年12月31日发布了关于修改《专利审查指南》的公告,对于包含算法或商业规则和方法等智力活动的规则和方法特征的专利申请,如何判断其是否符合专利保护客体、如何进行创造性的判断,进行了具体的说明。在2020年11月10日发布的《专利审查指南修改草案(第二批征求意见稿)》中,同样涉及上述内容。本文重点针对这两次修改中的相关内容,对涉及人工智能方案的专利保护客体判断问题进行分析。 相似文献
20.
Laura Campo-Dea?o Roel P. A. Dullens Dirk G. A. L. Aarts Fernando T. Pinho Mónica S. N. Oliveira 《Biomicrofluidics》2013,7(3)
The non-Newtonian properties of blood are of great importance since they are closely related with incident cardiovascular diseases. A good understanding of the hemodynamics through the main vessels of the human circulatory system is thus fundamental in the detection and especially in the treatment of these diseases. Very often such studies take place in vitro for convenience and better flow control and these generally require blood analogue solutions that not only adequately mimic the viscoelastic properties of blood but also minimize undesirable optical distortions arising from vessel curvature that could interfere in flow visualizations or particle image velocimetry measurements. In this work, we present the viscoelastic moduli of whole human blood obtained by means of passive microrheology experiments. These results and existing shear and extensional rheological data for whole human blood in the literature enabled us to develop solutions with rheological behavior analogous to real whole blood and with a refractive index suited for PDMS (polydymethylsiloxane) micro- and milli-channels. In addition, these blood analogues can be modified in order to obtain a larger range of refractive indices from 1.38 to 1.43 to match the refractive index of several materials other than PDMS. 相似文献