An Algorithm for Combined Code and Carrier Phase Based GPS Positioning

The Global Positioning System (GPS) is a satellite based navigation system. GPS satellites transmit signals that allow one to quite accurately estimate the location of GPS receivers. In GPS a typical technique for kinematic position estimation is relative positioning where two receivers are used, one receiver is stationary and its exact position is known, the other is roving and its position is to be estimated. We describe the physical situation and give the mathematical model based on the difference of the measurements at the stationary and roving receivers. The model we consider combines both the code and carrier phase measurements. We then present a recursive least squares approach for position estimation. We take full account of the structure of the problem to make our algorithm efficient, and use orthogonal transformations to ensure numerical reliability of the algorithm. Real data test results suggest our algorithm is effective. An additional benefit of this approach is that the drawbacks of double differencing are avoided. The paper could also serve as a straightforward introduction for numerical analysts to an interesting area of GPS.This revised version was published online in October 2005 with corrections to the Cover Date.     

Common due window size and location determination in a single machine scheduling problem

We consider a single machine static and deterministic scheduling problem in which jobs have a common due window. Jobs completed within the window incur no penalties, other jobs incur either earliness or tardiness penalties. The objective is to find the optimal size and location of the window as well as an optimal sequence to minimise a cost function based on earliness, tardiness, window size, and window location. We propose an O(n log n) algorithm to solve the problem.     

A Branch and Bound algorithm for minimizing the energy consumption of an electrical vehicle

The problem we address in this paper, is the minimization of the energy consumption of an electrical vehicle achievable on a given driving cycle. This can be formulated as an optimal control problem with a discrete switch control. In this paper, we present a new formulation of this problem by taking into account the electrical and mechanical parts of the vehicle. By using prototype optimal control shooting techniques, we did not provide efficient solutions. Consequently, we focused on an operational method based on a Branch and Bound algorithm to solve this optimal switching control problem. Some numerical experiments validate our methodology.     

Circularly polarized wave propagation in a class of bodies defined by a new class of implicit constitutive relations

In this paper, we show that circularly polarized transverse stress waves, standing shear stress waves, and oscillatory shear stress waves can propagate in a new class of viscoelastic solid bodies which are a subclass of bodies described by implicit constitutive theories. The class of models that is being considered includes as sub-classes, the classical Kelvin–Voigt model, the new models introduced by Rajagopal wherein the Cauchy–Green tensor is a non-linear function of the stress, and the Navier–Stokes fluid model. The solutions established in this paper are generalizations of solutions that have been established within the context of nonlinear elasticity by Carroll, and Destrade and Saccomandi, to the new class of elastic and viscoelastic bodies that are being considered.     

A simulated annealing heuristic for the team orienteering problem with time windows

This paper presents a simulated annealing based heuristic approach for the team orienteering problem with time windows (TOPTW). Given a set of known locations, each with a score, a service time, and a time window, the TOPTW finds a set of vehicle tours that maximizes the total collected scores. Each tour is limited in length and a visit to a location must start within the location’s service time window. The proposed heuristic is applied to benchmark instances. Computational results indicate that the proposed heuristic is competitive with other solution approaches in the literature.     

Asymptotic waves and collapse of self-gravitating gaseous systems

The asymptotic wave approach has been used to study the gravitational collapse of self-gravitating gaseous systems. In the case of sonic waves it is shown that macroscopic phenomena, such as shock-waves formation, can arise even if initial perturbations are confined in layers of linear dimensions very small compared to the dimensions of the medium. The occurring of critical times in a model of spherically symmetric self-gravitating interstellar gas cloud, suggests a mechanism in which the strong shock waves so generated might explain the formation of a cluster of protostars in the framework of the modern theory of Star Formation. A procedure is also described which let to overcome the solving of the wave front equation which turns out to be very useful in numerical applications.     

Production of X-radiation in the Crab nebula

It is suggested that the X-rays from the Crab nebula are due to the synchrotron radiation of electrons of energy ～4×10¹² eV in the magnetic field of the central region of the nebula, the magnetic field being enhanced by hydromagnetic waves. The consistency of the model with experimental X-ray observations and the energetics of the nebula are shown.     

Measurements of total electron content over Ahmedabad and Bombay from Beacon satellite data

The paper outlines the method used at Ahmedabad for determining the total electron content in the ionosphere from differential Faraday rotations of plane polarised radio waves on 40.010 and 41.010 Mc./s. transmitted by NASA satellite 64-64A. The observations made during the period October 1964 to April 1965 are utilised to determine the diurnal variation of the total electron content up to the satellite height which was about 1,000 km. over Ahmedabad and Bombay latitudes. The curve of total electron content up to the satellite height shows similarity to the curve of maximum electron density at the F2 peak. The total electron contents over Bombay are in general higher than those over Ahmedabad.     

BV Estimates on Lax–Friedrichs' Scheme or a Model of Radiating Gas

In this article, we give a uniform BV estimates and L ¹-stability of solutions to the Lax–Friedrichs' scheme for a model of radiating gas when the strict C–F–L (Courant–Friedrichs–Levy) condition is satisfied. This result implies that the approximate solutions generated by the Lax–Friedrichs' scheme converge to the solution given by the method of vanishing viscosity [C. Lattanzio and P. Marcati (2003 Lattanzio, C and Marcati, P. 2003. Global well-posedness and relaxation limits of a model for radiating gas. Journal of Differential Equations, 190: 439–465. [Crossref], [Web of Science ®] , [Google Scholar]). Global well-posedness and relaxation limits of a model for radiating gas. Journal of Differential Equations, 190, 439–465].     

基于交通流的多模糊时间窗车辆路径优化

研究了基于交通流的多模糊时间窗车辆路径问题,考虑了实际中不断变化的交通流以及客户具有多个模糊时间窗的情况,以最小化配送总成本和最大化客户满意度为目标,构建基于交通流的多模糊时间窗车辆路径模型。根据伊藤算法的基本原理,设计了求解该模型的改进伊藤算法,结合仿真算例进行了模拟计算,并与蚁群算法的计算结果进行了对比分析,结果表明,利用改进伊藤算法求解基于交通流的多模糊时间窗车辆路径问题,迭代次数小,效率更高,能够在较短的时间内收敛到全局最优解,可以有效的求解多模糊时间窗车辆路径问题。     

Sliding Mode Control of a Remotely Operated Underwater Vehicle with Adaptive Fuzzy Dead-Zone Compensation

Due to the great technological improvement obtained in the last decades, it became possible to use robotic vehicles for underwater exploration. During the execution of a certain task with a remotely operated underwater vehicle, the operator needs to monitor and control a number of parameters. If some of these parameters, as for instance position and attitude, could be controlled automatically, the teleoperation of the vehicle can be enormously facilitated. Based on experimental tests, it was verified that marine thrusters can exhibit dead-zone nonlinearities. This work describes the development of a variable structure control strategy for an underwater vehicle with a thrust system subject to dead-zone input. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A numerical study of an MPI/OpenMP implementation based on asynchronous threads for a three-dimensional splitting scheme in heat transfer problems

We present the results of a study of the parallel algorithms based on MPI and OpenMP for vector splitting schemes in heat transfer problems. We compare the three parallel implementations: MPI, “simple” MPI/OpenMP (#pragma omp directives applied to MPI-based code), and MPI/OpenMP with “postman” threads. The main idea of the last algorithm is to assign one thread within each computational node to perform the data transfer. This approach allows us to implement overlapping of useful computations and data transfer. The results show that the introducing postman threads can significantly improve the performance of an MPI/OpenMP implementation; nevertheless, for the considered class of numerical algorithms, it is more reasonable to use an MPI implementation.     

Ultrasonic velocity in epoxy resin at temperatures down to 4.2 K

Results are presented from measurements of the velocity of longitudinal and shear elastic waves (f=5 MHz) in ÉD-20 epoxy resin, at temperatures from 4.2 to 293 K. These data were used to calculate the moduli of elasticity E and G. Also, the moduli E (f=250 Hz) and G (f=2 Hz) of the ÉD-20 resin were measured directly. The calculated velocities of the low-frequency elastic waves c_t=(E/p)^1/2 and c_t=(G/p)^1/2 (where p is the density) were compared with the results from the ultrasonic measurements. The frequency dependence of elastic-wave velocity in the epoxy resin was evaluated. It was found that when the frequency was varied by four orders of magnitude, the dispersion of longitudinal-wave velocity was 18% at 4.2 K and 39% at 293 K. A quantitative criterion is proposed for estimation of the dispersion of sonic velocity from the results of measurements at any two frequencies. It was established that the sonic velocity at low temperatures varies linearly with the temperature, and in the case of longitudinal waves changes from c_l-3360 m/sec at 4.2 K to 2820 m/sec at 293 K. The shear-wave velocity changes from c_t=1630 m/sec at 5 K to 1340 m/sec at 293 K. The values of the dynamic Young's modulus E and shear modulus G at 4.2 K are 8.6 and 3.2 GPa, respectively. On a plot of c=f(T) for ED-20, a transition is observed at 180 K, due to reorientational rotation of methyl groups. The activation energy of the relaxation process is 3.6 kcal/mole. Large values are obtained for the dispersion of the dynamic modulus E:37.8% at 4.2 K and 93% at 293 K.Paper presented at 9th International Conference on the Mechanics of Composite Materials Riga, October, 1995.Moscow State Academy of Automotive Vehicle and Tractor Machinery Construction, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 32, No. 4, pp. 460–466, July–August, 1996.     

泡沫覆盖层对水下爆炸气泡射流防护机理缩比试验研究

水下爆炸会对水中结构物造成严重威胁。柔性覆盖层或夹层板能够降低水中结构物水下爆炸冲击响应，因此成为研究的热点。以往的研究多集中于覆盖层对冲击波的防护机理，适用于较远距离的水下爆炸情况。近距离水下爆炸除了冲击波外，爆炸气泡溃灭时产生的朝向结构物的高速水射流更为致命。该文针对这种情况，基于量纲原理，推导缩比相似关系，通过缩比模型水下爆炸试验发现了覆盖层表面空化微气泡群对爆炸气泡形成高速水射流过程产生干扰，提出了泡沫覆盖层钢板水下爆炸气泡射流防护机理。     

Pure Cognitivism and Beyond

The article begins with Jonathan Dancy’s attempt to refute the Humean Theory of Motivation. It first spells out Dancy’s argument for his alternative position, the view he labels ‘Pure Cognitivism’, according to which what motivate are always beliefs, never desires. The article next argues that Dancy’s argument for his position is flawed. On the one hand, it is not true that desire always comes with motivation in the agent; on the other, even if this was the case, it would still not follow that desire is identical with the state of being motivated. When this negative work is done, the article turns to some positive, albeit admittedly tentative remarks about what sort of cognitivist theory of motivation one should endorse. The aim at this point is not to present a brand new theory, but rather to sketch an alternative that stems from what Dancy himself says and is in line with many of his endorsed commitments in other areas. In this way, by moving beyond Pure Cognitivism, the paper sketches a different, but still ‘Dancyesque’ theory of motivation.     

Asymptotic stability of a pendulum with quadratic damping

The equation considered in this paper is $$x'' + h(t)\:x'|x'| + \omega^2\sin x = 0,$$ where h(t) is continuous and nonnegative for \({t \geq 0}\) and ω is a positive real number. This may be regarded as an equation of motion of an underwater pendulum. The damping force is proportional to the square of the velocity. The primary purpose is to establish necessary and sufficient conditions on the time-varying coefficient h(t) for the origin to be asymptotically stable. The phase plane analysis concerning the positive orbits of an equivalent planar system to the above-mentioned equation is used to obtain the main results. In addition, solutions of the system are compared with a particular solution of the first-order nonlinear differential equation $$u' + h(t)u|u| + 1 = 0.$$ Some examples are also included to illustrate our results. Finally, the present results are extended to be applied to an equation with a nonnegative real-power damping force.     

Integrating nonlinear branch-and-bound and outer approximation for convex Mixed Integer Nonlinear Programming

In this paper, we present a new hybrid algorithm for convex Mixed Integer Nonlinear Programming (MINLP). The proposed hybrid algorithm is an improved version of the classical nonlinear branch-and-bound (BB) procedure, where the enhancements are obtained with the application of the outer approximation algorithm on some nodes of the enumeration tree. The two methods are combined in such a way that each one collaborates to the convergence of the other. Computational experiments with benchmark instances of the MINLP problem show the good performance of the proposed algorithm, which is compared to the outer approximation algorithm, the nonlinear BB algorithm and the hybrid algorithm implemented in the solver Bonmin.     

Relief distribution networks: a systematic review

In the last 20 years, Emergency Management has received increasing attention from the scientific community. Meanwhile, the study of relief distribution networks has become one of the most popular topics within the Emergency Management field. In fact, the number and variety of contributions devoted to the design or the management of relief distribution networks has exploded in the recent years, motivating the need for a structured and systematic analysis of the works on this specific topic. To this end, this paper presents a systematic review of contributions on relief distribution networks in response to disasters. Through a systematic and scientific methodology, it gathers and consolidates the published research works in a transparent and objective way. It pursues three goals. First, to conduct an up-to-date survey of the research in relief distribution networks focusing on the logistics aspects of the problem, which despite the number of previous reviews has been overlooked in the past. Second, to highlight the trends and the most promising challenges in the modeling and resolution approaches and, finally, to identify future research perspectives that need to be explored.