Narrow Results

The constrained position shift (CPS) model is a famous model in the aircraft arrival sequencing and scheduling (ASS) problem, which allows each aircraft to shift forward or backward at most $k$ (a given integer number) positions in the first come first serve (FCFS) sequence. However, CPS is insufficient to cope with the case that some aircraft requiring more than $k$ positions shift. From this point, we modify it to be a more applicable model, named weighted constrained position shift (W-CPS) model. Three methods are developed to solve W-CPS, which are dynamic programming (DP), mixed integer programming (MIP) and ant colony (AC) algorithm. Numerical results validate the efficiency of these methods.

The fixed-charge capacitated multicommodity network design problem is a fundamental optimization problem arising in many network configurations. The solution of the problem provides an appropriate network design as well as routes of multicommodity flows aimed at minimizing the total cost, which is the sum of the flow costs and fixed-charge costs over a network with limited arc capacities. In the present paper, we introduce a combined approach with a capacity scaling procedure for finding an initial feasible solution and an MIP neighborhood search for improving the solutions. Besides, we modify the procedure for application to large-scale problems. Computational experiments demonstrate the effectiveness of the proposed approach, and high-quality solutions are obtained for two problem sets from the literature.

Internet protocol (IP)-based mobile systems are ushering new and faster technologies in wireless mobile networking. Therefore, the expectations from these network services with respect to data transfer rate and quality of service (QoS) are high. As such, meeting these requirements is the recent trend in modern wireless technologies. An important aspect regarding such improvements is the modification of handoff schemes between different networks. In this paper, we are focusing on the recent trends based on seamless handoff scheme in heterogeneous networks such as worldwide interoperability for microwave access (WiMAX) and long term evolution (LTE). The development of the session initiation protocol (SIP) Prior-INVITE scheme is an improvement on the earlier used SIP Re-INVITE method, which comes a long way in decreasing the average handoff delay. The performance analysis using software simulation on account of various parameters, such as handoff delay, cost of signaling and packet loss rate are accomplished in this work. The performance analysis demonstrates that the proposed scheme outperforms the ordinary cross-layer scheme and noncross-layer scheme in a vertical handover scenario.

In recent years modern methods of optimization have contributed greatly to the advances in data mining and related areas. These contributions continue today and promise to further advance the state of the art both in terms of modeling innovations and new solution methodologies. In this paper, we present a new modeling and solution methodology for unsupervised clustering. Preliminary computational experience is given to illustrate the approach. This methodology is part of our current research and offers considerable opportunity for additional investigation to be conducted by other researchers.