16150196
Waste collection vehicle routing problem with time windows
In this paper, we address a real life waste collection vehicle routing problem with time windows (VRPTW) with consideration of multiple disposal trips and drivers' lunch breaks. Solomon's well-known insertion algorithm is extended for the problem. While minimizing the number of vehicles and total traveling time is the major objective of vehicle routing problems in the literature, here we also consider the route compactness and workload balancing of a solution since they are very important aspects in practical applications. In order to improve the route compactness and workload balancing, a capacitated clustering-based waste collection VRPTW algorithm is developed. The proposed algorithms have been successfully implemented and deployed for the real life waste collection problems at Waste Management, Inc. A set of waste collection VRPTW benchmark problems is also presented in this paper.Waste collection problems are frequently considered as arc routing problems without time windows. However, that point of view can be applied only to residential waste collection problems. In the waste collection industry, there are three major areas: commercial waste collection, residential waste collection and roll-on-roll-off. In this paper, we mainly focus on the commercial waste collection problem. The problem can be characterized as a variant of VRPTW since commercial waste collection stops may have time windows. The major variation from a standard VRPTW is due to disposal operations and driver's lunch break. When a vehicle is full, it needs to go to one of the disposal facilities (landfill or transfer station). Each vehicle can, and typically does, make multiple disposal trips per day. The purpose of this paper is to introduce the waste collection VRPTW, benchmark problem sets, and a solution approach for the problem. The proposed algorithms have been successfully implemented and deployed for the real life waste collection problems of Waste Management, the leading provider of comprehensive waste management services in North America with nearly 26,000 collection and transfer vehicles.
8735453
Intelligent agent based framework for manufacturing systems control
Existing modeling frameworks for manufacturing system control can be classified into hierarchical, heterarchical, and hybrid control frameworks. The main drawbacks of existing frameworks are discussed in this paper. A new hybrid modeling framework is also described. It is a hybrid of the two: hierarchical and heterarchical frameworks. In this proposed framework, entities (e.g., parts) and resources (e.g., material handling devices, machines, cells, departments) are modeled as holonic structures that use intelligent agents to function in a cooperative manner so as to accomplish individual, as well as cell-wide and system-wide objectives. To overcome the structural rigidity and lack of flexibility, negotiation mechanisms for real-time task allocation are used. Lower-level holons may autonomously make their negotiations within the boundary conditions that the higher-level holons set. Horizontal, as well as vertical decisions, are made between various levels of controllers, and these are explicitly captured in the model.
45107585
DC Built-In Self-Test for Linear Analog Circuits
DC testing of analog circuits is cheaper than AC testing and covers many fault classes, including some that AC tests cannot detect. This efficient, low-cost, built-in self-test (BIST) methodology uses the checksum encodings of matrix representations to uncover faults that affect a circuit's DC transfer function.
5682535
Power-Efficient Packet Scheduling Method for IEEE 802.15.3 WPAN
Power efficiency is the key issue for mobile devices, which mainly rely on limited battery power. The IEEE 802.15.3 wireless personal area network (WPAN) standard adopts a time division multiple access (TDMA) protocol controlled by a central device to support isochronous traffics. In the TDMA-based wireless packet networks, the packet scheduling algorithm plays a key role in power efficiency. However, the standard suffers from long access delay and association delay which increase the power consumption. In this paper, we propose a packet scheduling method to improve the power efficiency. Performance evaluations are carried out through simulations and significant performance enhancements are observed. Furthermore, the performance of the proposed scheme remains stable regardless of the variable system parameters such as the number of devices and superframe size.
43612641
Evaluation of nondominated solution sets for k
Abstract Integrated Preference Functional (IPF) is a set functional that, given a discrete set of points for a multiple objective optimization problem, assigns a numerical value to that point set. This value provides a quantitative measure for comparing different sets of points generated by solution procedures for difficult multiple objective optimization problems. We introduced the IPF for bi-criteria optimization problems in [Carlyle, W.M., Fowler, J.W., Gel, E., Kim, B., 2003. Quantitative comparison of approximate solution sets for bi-criteria optimization problems. Decision Sciences 34 (1), 63–82]. As indicated in that paper, the computational effort to obtain IPF is negligible for bi-criteria problems. For three or more objective function cases, however, the exact calculation of IPF is computationally demanding, since this requires k (⩾3) dimensional integration. In this paper, we suggest a theoretical framework for obtaining IPF for k (⩾3) objectives. The exact method includes solving two main sub-problems: (1) finding the optimality region of weights for all potentially optimal points, and (2) computing volumes of k dimensional convex polytopes. Several different algorithms for both sub-problems can be found in the literature. We use existing methods from computational geometry (i.e., triangulation and convex hull algorithms) to develop a reasonable exact method for obtaining IPF. We have also experimented with a Monte Carlo approximation method and compared the results to those with the exact IPF method.
34460188
Incorporating proxy services into wide area cellular IP networks
Performance enhancing proxies have drawn considerable interests from the network community as an effective approach to improve user experience in cellular networks. Previous research on this subject has been focusing on the design of proxy servers as well as the functions that these servers provide. In this paper, we study the placement of proxy servers, especially the approach of incorporating proxies into cellular networks, which allows better, faster, and more secure proxy services. We discuss various factors that must be considered when placing proxies inside cellular networks, including the information requirements of the proxies, the network requirements for supporting the proxy functions, and mobility management. Using GPRS as an example, we lay out a procedure for adding proxies into data transmission paths in cellular networks. Copyright © 2001 John Wiley & Sons, Ltd.
32825020
An exploratory inquiry into the perceived effectiveness of a global information system
As globalization has driven and has also been driven by innovation in information technology (IT), an effective utilization of IT has become critical in improving global operations. In this paper, we report an exploratory inquiry into what factors influence the effectiveness of IT on coordinating international operations as perceived by managers at global firms. As an initial study, our research focuses on a specific set of variables which we propose are fundamental elements for determining the IT effectiveness in the global context, i.e. firm’s globalization level, IT application, and IT department dedication. We put forth two propositions: first, a global firm can enhance its IT effectiveness by advancing the IT application level; second, as its globalization level expands, the global firm must put in place a comparable amount of organizational support (measured by IT department dedication) for the global IT system if it wants to heighten IT performance by raising the IT application level. In order to verify the propositions, we collected survey data from 35 Korean firms, each of which operates on a global scale, doing operations in foreign countries through subsidiaries. Our analysis result led us to reach conclusions upholding the propositions.