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Abstract: This paper proposes two new distance-constrained capacitated vehicle routing problems (DCVRPs) to investigate for the first time, and study potential benefits in flexibly assigning start and end depots. The first problem, DCVRP_Fix is an extension of the traditional symmetric DCVRP, with additional service and travel time constraints, minimization of the number of vehicles and flexible application to both symmetric and asymmetric problems. The second problem, DCVRP_Flex is a relaxation of DCVRP_Fix to enable the flexible assignment of start and end depots. This allows vehicles the freedom to start and end their tour at different depots, while allowing for intermediate visits to any depot (for reloading) during the tour. Network models, integer programming formulations and solution algorithms for both problems are developed and presented in this paper. An analytical comparison of both problems is carried out with Singapore as a case study, considering the impact of depot locations and problem symmetry using four cases. Results show a generation of cost savings up to 49.1% by DCVRP_Flex across all the four cases. A significant portion of this stems from the flexibility to reload at any depot while the rest of it is derived from the flexibility to return to any depot. DCVRP_Flex’s adaptability and superior performance over DCVRP_Fix provides strong motivation for further research on improved exact algorithms and heuristics for this problem. [Copyright &y& Elsevier]

Abstract: In this paper, we investigate bidirectional associative memory Cohen–Grossberg neural networks with time delays. By applying the Young inequality technique, Dini derivative, and introducing many real parameters, a series of new and useful criteria on the existence and uniqueness of an equilibrium point and its global asymptotical stability are established. It is shown that in some special cases of the results, the stability criteria can be easily checked. Finally, an example is given to illustrate the result obtained in this paper. [Copyright &y& Elsevier]

Abstract: Churn is a basic and inherent problem in P2P networks. A lot of relevant studies have been carried out, but all lack versatility. In this paper, a general solution is proposed which makes a peer-to-peer (P2P) network need not pay much attention to churn problem by introducing a logic layer named Dechurn, and most of churn could be eliminated in the Dechurn layer. For utilizing the complementary nature of node joining and leaving, a network scheme, named Constellation, for handling churn is designed on the Dechurn layer through which the resources cached in a node for its spouse node who has left network would be succeeded by a node in latent period. The simulation results indicate that the proposed solution is effective and efficient in handling churn and easy to put into practice. [Copyright &y& Elsevier]

Abstract: This paper addresses the attitude control problem for a twin rotor unmanned helicopter driven by DC motors. The control objective is to have the helicopter attitude, i.e., pitch and yaw angles, track specified angles. From the considered dynamics of the plant, it is observed that the main difficulty of the control problem is due to the existing nonlinear coupling effects between the two perpendicular rotors. Hence, a novel adaptive control approach based on the backstepping concept is developed to solve the problem. In the controller design, the system parameters are assumed to be unavailable and are estimated on-line. The stability of the overall closed-loop system is proven to be asymptotically stable based on the Lyapunov theorem. In order to demonstrate the applicability of the proposed control scheme, computer simulations and experiments are shown. [Copyright &y& Elsevier]

Abstract: A number of models involving reaction–diffusion equations have been developed by different authors to describe the changes in frequency of alleles in a population. Each of these models describes the case in which there are only two possible alleles at the locus in question. In the present paper, we are interested in the more realistic possibility of three alternative alleles. A system of reaction–diffusion equations can be developed to describe this situation. After transforming to the traveling wave coordinates, we introduce a nonlinear transformation which allows us to find exact solutions under certain conditions imposed on two of the parameters. [Copyright &y& Elsevier]

Abstract: This paper deals with the qualitative analysis of a model describing the competition between tumor and immune cells. Such competition is characterized by proliferation–destruction phenomena and the interacting entities are characterized by a microscopic state which is modified by interactions. The model also includes the description of the natural trend of immune cells to reach a healthy or sentinel level, even when they have been involved in the competition with the tumor cells. The model is developed in the mathematical framework of the kinetic theory for active particles. [Copyright &y& Elsevier]

Abstract: In this paper, we consider the multipoint boundary value problem for one-dimensional -Laplacian subject to the boundary conditions: where . Applying the fixed point theorem due to Avery and Peterson, we study the existence of at least three symmetric positive solutions to the above boundary value problem. The interesting point is that the nonlinear term contains the first-order derivative explicitly and the boundary condition is of Sturm–Liouville type. [Copyright &y& Elsevier]

Abstract: In this paper, we give the solution of the inverse Sturm–Liouville problem on two partially coinciding spectra. In particular, in this case we obtain Hochstadt’s theorem concerning the structure of the difference for the singular Sturm Liouville problem defined on the finite interval having the singularity type at the points 0 and . [Copyright &y& Elsevier]

Abstract: This paper analyzes, on the basis of methods of the mathematical kinetic theory of active particles, some complexity problems related to the evolution of reciprocal feelings. Specifically, the analysis is focused on the complexity problems generated by triple interactions, with respect to simple binary encounters. Complexity refers not only to the structure of the equation, but also to the variable describing reciprocal feelings. [Copyright &y& Elsevier]

Abstract: Let be a sequence of i.i.d. random variables taking values in a real separable Hilbert space with mean zero and covariance and set . Let be the eigenvalues of arranged in non-increasing order and take into account the multiplicities. Let be the dimension of the corresponding eigenspace of largest eigenvalue . Let . This paper studies the precise rates for . We show that when and implies where is the Gamma function and . [Copyright &y& Elsevier]

Abstract: In this paper we have proven uniqueness theorems for estimation of the age-dependent parameter in the Gompertz survival model with a mortality deceleration rate, in the absence of age-specific mortality data. We obtained estimations dependent on and uniform in the population size . [Copyright &y& Elsevier]

Abstract: Upon demand realization in the newsvendor problem, it is often assumed that shortages result in lost sales penalties. However, in some practical situations, shortages are backlogged and the inventory manager is penalized based on the magnitude and duration of the shortage. In this paper, we investigate a variation of the newsvendor problem in which all shortages are backlogged and replenished through an emergency procurement process. Costs incurred during emergency procurement include a variable emergency ordering cost and a non-linear customer waiting cost. We derive closed form expressions for the optimal order quantity and emergency procurement rate for two special cases, and we propose a heuristic approximation for the general case. The effectiveness of the approximate solution is assessed through numerical experiments and sensitivity analysis. [Copyright &y& Elsevier]

Abstract: This paper presents the results of computer simulations of road safety barrier behaviour under vehicle crash conditions for high containment levels as mandated by the European standard EN 1317. Simulations were performed with the explicit finite element code LS-DYNA, running on a multiprocessor computational platform. A very good agreement of simulation and real crash tests results was observed, which in turn justifies the use of computer simulations in the process of development and certification of road safety barriers. [Copyright &y& Elsevier]

Abstract: This paper considers the Liénard-type systems with continuously distributed delays. Some sufficient conditions for the existence and exponential stability of the almost periodic solutions are established, which are new and complement previously known results. [Copyright &y& Elsevier]

Abstract: This paper presents a physically based simulation of atmospheric phenomena. It takes into account the physics of non-homogeneous media in which the index of refraction varies continuously, creating curved light paths. As opposed to previous research on this area, we solve the physically based differential equation that describes the trajectory of light. We develop an accurate expression of the index of refraction in the atmosphere as a function of wavelength, based on real measured data. We also describe our atmosphere profile manager, which lets us mimic the initial conditions of real-world scenes for our simulations. The method is validated both visually (by comparing the images with the real pictures) and numerically (with the extensive literature from other areas of research such as optics or meteorology). The phenomena simulated include the inferior and superior mirages, the Fata Morgana, the Novaya–Zemlya, the Viking''s end of the world, the distortions caused by heat waves and the green flash. [Copyright &y& Elsevier]

Abstract: Real-time computer simulation is required in a number of applications, where the simulated dynamic systems are directly coupled with systems in the real world or with other systems also running in real-time. Typical problems of real-time simulations are that the dynamics of the modeled system are not represented in enough detail, either by not sampling the inputs or not producing output values frequently enough or both. Increasing the sampling frequencies may lead, as an additional problem, to real-time violations caused by insufficient computing power. The latter problem is amplified if the real-time is accelerated to achieve a kind of fast motion and reduce experiment times. In this paper, we show how the first problem can be solved by automatic frequency adjustment, minimizing the number of computations and how the remaining second problem can be reduced by trading a graceful degradation of accuracy against the computing power requirements automatically. Experiments show that simulation times could be reduced by a factor of 100 without unacceptable simulation errors. [Copyright &y& Elsevier]

Abstract: In this paper, a Markovian queue with two heterogeneous servers and multiple vacations has been studied. For this system, the stationary queue length distribution and mean system size have been obtained by using matrix geometric method. The busy period analysis of the system and mean waiting time distribution are discussed. Extensive numerical illustrations are provided. [Copyright &y& Elsevier]

In this paper, we use a simplified model to simulate the amorphization phenomenon in metals under irradiation. The model has few parameters but can reflect the essential characteristics of the processes. Our simulation results show that the relaxation of collision cascades forms small crystal grains and the amorphization phenomenon is a result of total overlap of different grains, which depends on the irradiation temperature. [Copyright &y& Elsevier]