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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.
The calculation of critical buckling loads of planar curved bars, subjected to a general co-planar continuous external load (or a general co-planar terminal loading), leads to the solution of transcendental (nonlinear) equations. In this investigation a new method for the closed-form solution of such types of equations is presented. In particular, the transcendental equation u tan γ cot uγ = 1, corresponding to the buckling problem of a cantilever circular bar of high curvature loaded by two co-planar forces acting along its chord, is solved in a closed-form. Finally, several numerical results are presented, based on the Gauss integration rule.  相似文献   

3.
In order for automated mobile vehicles to navigate in the real world with minimal collision risks, it is necessary for their planning algorithms to consider uncertainties from measurements and environmental disturbances. In this paper, we consider analytical solutions for a conservative approximation of the mutual probability of collision between two robotic vehicles in the presence of such uncertainties. Therein, we present two methods, which we call unitary scaling and principal axes rotation, for decoupling the bivariate integral required for efficient approximation of the probability of collision between two vehicles including orientation effects. We compare the conservatism of these methods analytically and numerically. By closing a control loop through a model predictive guidance scheme, we observe through Monte-Carlo simulations that directly implementing collision avoidance constraints from the conservative approximations remains infeasible for real-time planning. We then propose and implement a convexification approach based on the tightened collision constraints that significantly improves the computational efficiency and robustness of the predictive guidance scheme.  相似文献   

4.
In this paper, a study on the end-to-end performance of dual-hop non-regenerative relaying over independent generalized-K (KG) fading channels is presented. Using a suitable upper bound for the end-to-end signal-to-noise ratio (SNR), novel closed-form expressions for the cumulative distribution function (CDF), probability density function (PDF) and the moments of this bounded SNR are derived. These results can be afterwards used to obtain important performance metrics of the considered system such as the outage probability and the error performance of digital modulation schemes. In the case of independent but non-necessarily identical fading channels, lower bounds for the average bit error probability (ABEP) for different modulation schemes are determined by using the Padé approximants method. For the case of identical fading channels, closed-form lower bounds for the ABEP are derived. Various numerical and computer simulation results illustrate the proposed analysis.  相似文献   

5.
排房问题是宾馆中的一个非常重要的问题，同时也是比较难的课题。因为它是一个多目标的优化问题，并要求有较高的速度，现在宾馆中使用的都是特定的管理软件。本文在此基础上，通过模糊数学和概率统计的知识应用来实现自动排房的方法，从数学角度解决了这一难题。  相似文献   

6.
The shape of a caustic and its initial curve about a crack in fracture mechanics for plane elastic media is defined by a pair of equations, the first of which does not in general possess a closed-form solution, being of fifth or higher degree and, frequently, transcendental. A closed-form solution of this equation is obtained on this basis and after an appropriate modification of the method of Burniston and Siewert. An application to the problem of a straight crack under tensile loading at infinity is made and the diameters of the caustic and its initial curve are evaluated analytically and numerically with excellent accuracy after the solution of an equation of fifth degree in closed-form.  相似文献   

7.
Vehicles of different sizes are difficult to navigate in close vicinity. In this paper, we propose multi-vehicle coordination strategy by stochastic control and time scheduling to guarantee no collisions. We use contours and relative motions of vehicles to calculate collision time and use it in multi-vehicle scheduling and reduce computation burden. The proposed strategy enables the vehicles to add calculation delay when vehicles are moving towards the destinations. To avoid complicated control rule design for motion-restricted irregular vehicles, we propose stochastic control to provide satisfactory performance. By changing the frequency of control update, a modification is proposed to take congestion into account. Simulation examples are given to demonstrate the effectiveness of the proposed approach.  相似文献   

8.
Event-triggered mechanism can effectively save communication resources, however, when it encounters channel uncertainty, the remote receiver cannot distinguish between “the sender did not send data” and “the sender sent data but the data lost” when it does not receive data, which causes that it is difficult to make full use of the information provided by the event-triggered mechanism. This paper addresses the identification of FIR (Finite Impulse Response) systems with binary-valued observations and either-or communication mechanism when the packet loss probability is known and unknown respectively. When the packet loss probability is known, it is used for compensation in the parameter estimation. An online identification algorithm is proposed, its strong convergence is proved, and its asymptotic normality is given. Furthermore, how does the packet loss probability affect the algorithm performance is discussed. When the packet loss probability is unknown, an identification algorithm is proposed to jointly estimate it and unknown system parameters by redesigning the either-or communication mechanism. The strong convergence of the algorithm is shown. The tradeoff between the communication rate and the convergence performance of the identification algorithm is modelled as a constrained optimization problem, and its solution is obtained. The rationality of theoretical results is verified by numerical simulation.  相似文献   

9.
This paper describes the derivation of Heaviside's decomposition in matrix frame presentation. For simplicity, the response transform having one multiple pole and any number of distinct poles is considered. There is no restriction on the number and the order of zeros. The aim is to avoid the repeated differentiations in the algorithm for the computation of both residue and constituent coefficients about the multiple pole. This will be referred to as the RRM (Residue and Resolvent Matrices) method and adopted to time response derivation of dynamic systems. The RRM method is also applicable as a mathematical catalyst to the algebraic solution of differentiation and integration of complex functions in the s domain used for system optimisation.  相似文献   

10.
This paper focuses on four fusion algorithms for the estimation of nonlinear cost function (NCF) in a multisensory environment. In multisensory filtering and control problems, NCF represents a nonlinear multivariate functional of state variables, which can indicate useful information of the target systems for automatic control. To estimate the NCF using multisensory information, we propose one centralized and three decentralized estimation fusion algorithms. For multivariate polynomial NCFs, we propose a simple closed-form computation procedure. For general NCFs, the most popular procedure for the evaluation of their estimates is based on the unscented transformation. The effectiveness and estimation accuracy of the proposed fusion algorithms are demonstrated with theoretical and numerical examples.  相似文献   

11.
The multi-taper spectrum (MTS) estimator enjoys a relatively low computational complexity and high estimation accuracy making it an attractive method for spectrum sensing in cognitive radio (CR) networks. However, it is difficult to guarantee both detection and false alarm probabilities when its design is based on fixed threshold, especially when the noise power fluctuates due to channel conditions. In this paper, a new adaptive threshold method to guarantee both detection and false alarm probabilities for MTS based spectrum sensing is proposed. By means of estimating noise power and signal power, the decision of adaptive threshold is able to adapt the noise fluctuation and achieve efficient trade-off between detection and false alarm probabilities. A closed form expression for the adaptive threshold is derived for both additive white Gaussian noise (AWGN) channel and multipath fading channel. Several metrics are employed to compare the performance of the proposed adaptive threshold method with that of the fixed threshold methods such as: error decision probability, detection probability, false alarm probability and throughput. The obtained results show that the proposed method achieves better spectrum efficiency and high throughput in comparison with the conventional fixed and adaptive threshold methods presented in the literature.  相似文献   

12.
In the information retrieval systems, one of the most important and difficult operations is to extract appropriate keywords from documents. This paper proposes an effective substring search method by extending a pattern matching machine for multi-keyword based on Aho and Corasick (AC) called AC machine. The proposed method enables us to extract keyword candidates as much as possible and to select the suitable keywords for users' purpose at a retrieval stage. This method contains four types of substring search methods (exact, prefix, suffix and proper substring search). This paper also proposes a construction algorithm of the retrieval structure for speeding up the substring search. From the simulation results, it is shown that the retrieval time of the presented method is as fast as the key retrieval method based on the trie.  相似文献   

13.
This paper presents a new methodology for valuing new drug applications (NDA) and the R&D of pharmaceutical companies based on real option models. Traditional valuation models fail to capture the full value created by R&D to pharmaceutical companies, because they do not correctly model the nature of the process of developing a new drug. It is a series of consecutive phases from R&D to commercialisation, where each phase is in fact an option on executing the following phase, i.e. a compound option. For a NDA, the R&D phase can best be presented as a 6-fold compound option on the commercialisation phase. Using a generalisation of Geske’s compound option model, we derive a closed-form solution for a n-fold compound option model, and apply it to calculate the value of a NDA using sector average figures.  相似文献   

14.
The Discrete Tchebichef Transform (DTT) is widely used in signal processing applications such as image and video compression and digital watermarking due to its coding and decorrelation properties. In embedded systems and real-time applications, the need for fast, low complexity, and energy efficient algorithms is increasingly important. However, there is a limited number of such algorithms available for efficient computation of the DTT compared to the discrete cosine transform. To address this issue, a new DTT approximation is proposed, which provides a low-complexity and efficient solution by exploiting the deviation from orthogonality. The suggested algorithm requires fewer additions and bit-shifting operations compared to the existing ones. The implementation of this DTT approximation on the Xilinx Virtex-6 XC6VSX475T-1FF1759-2 FPGA resulted in a 19.20% decrease in hardware resources and 2% reduction in energy consumption for 1-D 8 inputs compared to the best candidate DTT approximation. With a low deviation from orthogonality, the efficiency of the proposed approximation has been confirmed in image compression and digital watermarking. The experimental results show an average quality improvement of 0.25 dB over the latest DTT approximation.  相似文献   

15.
双层地基一维非线性固结性状分析   总被引：1，自引：0，他引：1  
袁坚敏  谢康和 《科技通报》2005,21(4):471-475,490
由于层状土一维非线性固结问题的复杂性,其解析解一般不易求得。本文采用半解析法对多层地基一维非线性固结问题进行了求解,通过编程计算得到了相关沉降量与固结度随时间变化曲线．并详细分析了土性参数等对双层地基一维非线性固结性状的影响。  相似文献   

16.
A second-order phase-lock loop (PLL) that is based on a triangular-characteristic phase detector and imperfect-integrator loop filter is found in many applications where simplicity and economics are major considerations. For many of these applications, digital-logic-compatible reference and VCO signals are used, an exclusive-OR gate implements the phase detector, and the loop filter is constructed from passive components. When designing these loops, the half-plane pull-in range Ω2 is of interest. Until now, this important loop parameter could only be calculated by using a computer-based technique that numerically integrated the nonlinear differential equation that describes the PLL model. This requirement/limitation is removed here by the development of an exact closed-form formula for Ω2, the main contribution of this paper. More generally, the value of Ω2 is dependent on the PLL phase detector characteristic that is used, be it triangular, sinusoidal, or something else. With regard to the value of Ω2 produced, a comparison is given of two PLLs, both described by the same linear model so that the comparison is meaningful. The first PLL is based on a triangular-characteristic phase detector; the second loop is based on a sinusoidal phase detector.  相似文献   

17.
This paper presents general, closed-form, and exact expressions for cumulative distribution function, probability density function and average value for the ratio of independent η-μ random variables, with arbitrary parameters. More specifically, the outage capacity with peak interference power constraint, the delay-limited capacity, and the ergodic capacity considering constraints on the interference power are derived for non-homogeneous environments containing multipath waves clusters. Numerical curves are presented to evaluate the effects of the general fading variables in spectrum sharing systems. Besides, the results are validated by performing Monte-Carlo simulations. Notably, the provided results find important applications in cognitive radio systems considering the spectrum sharing approach and channels modeled by η-μ distribution.  相似文献   

18.
This paper presents a closed-form cooperative avoidance control design for 3-dimensional rigid-body agents. New avoidance functions are designed to integrate the collision risk with the addition of motion and posture information. Time-varying sensing regions enable the conflict resolution actions only when there is a potential risk of collision, thus further reducing some unnecessary interference with other objectives. These characteristics lead to the less-conservative avoidance response, smoother maneuvers, and milder motion trajectories. The stability of the proposed method is analyzed and the corresponding proofs and guaranties for collision-free maneuvering, are provided. Performance comparisons are presented for two simulation scenarios, which illustrate the effectiveness and reliability of the new method.  相似文献   

19.
孙发  曾为众 《现代情报》2011,31(11):142-145
为解决基于分类号或财产号随书光盘存取管理模式所存在的随书光盘难排架、难查询、难定位的问题,提出一种基于随书光盘工作流水号的存取模式,并采用数据库和Flash图形动画等技术,实现具有数据录入、记录查询和Flash图形动画定位等功能的可视化随书光盘存取管理系统。  相似文献   

20.
In this paper, we provide closed-form expressions for the symbol error probability of decode and forward cooperative diversity systems, when operating over independent but not necessarily identically distributed Nakagami-m fading channels. The results hold for arbitrary number of relays, and refer to the M-ary QAM and M-ary PSK modulations.  相似文献   

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