David S. Kim

PROPERTIES OF MULTI-MODE RESOURCE-CONSTRAINED PROJECT SCHEDULING PROBLEMS WITH RESOURCE VACATIONS AND ACTIVITY SPLITTING

This paper presents results from an extensive computational study of the multi-mode resource-constrained project scheduling problem when activities can be split during scheduling under situations where resources may be temporarily not available. All resources considered are renewable and each resource unit may not be available at all times due to resource vacations, which are known in advance, and assignment to other finite duration activities. A designed experiment is conducted that investigates project makespan improvement when activity splitting is permitted in various project scenarios, where different project scenarios are defined by parameters that have been used in the research literature. A branch-and-bound procedure is applied to solve a number of small project scheduling problems with and without activity splitting. The results show that, in the presence of resource vacations and temporary resource unavailability, activity splitting can significantly improve the optimal project makespan in many scenarios, and that the makespan improvement is primarily dependent on those parameters that impact resource utilization.

Priority rule-based heuristic for multi-mode resource-constrained project scheduling problems with resource vacations and activity splitting

This paper presents a priority rule-based heuristic for the multi-mode resource-constrained project scheduling problem with the splitting of activities around unavailable resources allowed. All resources considered are renewable and each resource unit may not be available at all times due to resource vacations, which are known in advance. A new concept called moving resource strength is developed to help identify project situations where activity splitting is likely to be beneficial during scheduling. The moving resource strength concept is implemented in priority rule-based heuristics to control activity splitting when scheduling. Multiple comparisons of the performance of combination of activity–mode priority rules used in the heuristics are provided. Computational experiments demonstrate the effectiveness of the heuristic in reducing project makespan, and minimizing activity splitting.

General Motors Increases Its Production Throughput

In the late 1980s, General Motors Corporation (GM) initiated a long-term project to predict and improve the throughput performance of its production lines to increase productivity throughout its manufacturing operations and provide GM with a strategic competitive advantage. GM quantified throughput performance and focused improvement efforts in the design and operations of its manufacturing systems through coordinated activities in three areas: (1) it developed algorithms for estimating throughput performance, identifying bottlenecks, and optimizing buffer allocation, (2) it installed real-time plant-floor data-collection systems to support the algorithms, and (3) it established common processes for identifying opportunities and implementing performance improvements. Through these activities, GM has increased revenue and saved over 2.1 billion in over 30 vehicle plants and 10 countries.

A new method for the placement of buffers in serial production lines

The placement of buffers in a production line is an old and well-studied problem in industrial engineering/operations research that is still relevant today. Decisions regarding the amount and placement of buffers in a production line occur repeatedly in system design. In this paper we document a new buffer placement method for serial production lines that operate under a variety of assumptions. The method uses information generated in a production line simulation, whose conceptual representation of job flow and workstation interaction can be described with a network, to place buffers in order to maximise throughput. This buffer placement method is very efficient and can be implemented in a spreadsheet. We demonstrate the effectiveness of the method by comparing our results against those produced by a genetic algorithm for buffer placement. Experiments are conducted on a variety of test cases. This new buffer placement optimisation method will permit designers to quickly and effectively evaluate many design alternatives and thus improve final production system performance.

A new heuristic for the multi-mode resource investment problem

This paper considers the problem of minimizing resource investment required to execute the tasks in a project network by a given project due date. A project consists of non-pre-emptive tasks executed in a known and required precedence order. Each task is completed in one of its feasible modes, which may differ not only in task duration but also in consumption of renewable resources. A priority rule heuristic with polynomial computational complexity is presented for this computationally intractable problem. This heuristic simultaneously considers due date constraints and resource usage to select and schedule tasks with one decision rule. This differs from prior multi-mode priority rule scheduling heuristics that apply two consecutive decision rules to schedule tasks. Extensive computational testing indicates promising results.

Antenna Characterization for Bluetooth-Based Travel Time Data Collection

Several approaches for travel time data collection based on the reading of time-stamped media access control addresses from Bluetooth-enabled devices have been reported in the literature recently. This new approach offers a number of advantages over more conventional methods, including lower costs of hardware and software, the volume of data that can be collected over time, and ease of implementation. A fundamental component that may affect the quantity and the quality of the travel time samples collected with a Bluetooth-based system is the antenna type utilized. Antenna characteristics such as polarization and gain must be matched to specific application environments to optimize the performance of a Bluetooth reader unit. However, experimental data that focuses on antenna characterization as it relates to the use of Bluetooth technology to assess the performance of transportation facilities is lacking. In this study, five different types of antennas were characterized to assess their suitability to support a Bluetooth-based travel time data collection system. The results indicate that vertically polarized antennas with gains between 9dBi and 12dBi are good candidates for travel time data collection. Also, different antenna types are better suited to different uses of the Bluetooth-based system. If the main focus is the collection of travel time data, then an antenna with a lower sampling rate may provide more accurate travel time samples.

An upper bound for carriers in a three-workstation closed serial production system operating under production blocking

We develop and prove a rule for an upper bound on the optimal number of carriers (with respect to throughput) in a three-workstation closed serial production system with finite buffers, operating under production blocking (blocking-after-service). This system is, in fact, a three server (single server) closed tandem queueing system with finite buffers. Our assumptions regarding service time distributions are nonrestrictive and include the case of iid random variables.

Technology Evaluation of Oregon’s Vehicle-Miles-Traveled Revenue Collection System: Lessons Learned

Many states in the United States rely on fuel taxes to maintain roads. In 2005 eighty percent of Oregons road revenues depended either directly or indirectly on fuel taxes. However, Oregon has seen this flow of revenue slowly decline during the past 30 years. It is envisioned that further improvement of automobile fuel efficiency will have an even more dramatic effect on fuel tax revenues in the near future. In 2001 the Oregon Legislative Assembly passed House Bill 3946 mandating the Oregon Department of Transportation to examine alternatives to the current system of taxing highway use through fuel taxes. Since 2003 Oregon State University, in collaboration with the Oregon Department of Transportation and the Road User Fee Task Force, has investigated a vehicle miles traveled (VMT)-based alternative to the fuel tax. The design, development, and testing of the VMT-based solution was broken down into several phases, the last of which required the execution of a pilot test from June 19, 2006, to March 25, 2007, involving approximately 250 volunteer drivers. The main objectives of this paper are to present the technology performance results of the VMT-based solution gathered during the pilot test and to share the lessons learned from its subjective evaluation.

A Bayesian network-based approach for fault analysis

Abstract For high-value assets such as certain types of plant equipment, the total amount of resources devoted to Operation and Maintenance may substantially exceed the resources expended in acquisition and installation of the asset, because high-value assets have long useful lifetimes. Any asset failure during this useful lifetime risks large losses in income and goodwill, and decreased safety. With the continual development of information, communication, and sensor technologies, Condition-Based Maintenance (CBM) policies have gained popularity in industries. A successfully implemented CBM reduces the losses due to equipment failure by intelligently maintaining the equipment before catastrophic failures occur. However, effective CBM requires an effective fault analysis method based on gathered sensor data. In this vein, this paper proposes a Bayesian network-based fault analysis method, from which novel fault identification, inference, and sensitivity analysis methods are developed. As a case study, the fault analysis method was analyzed in a centrifugal compressor utilized in a plant.

Improving Accuracy and Precision of Travel Time Samples Collected at Signalized Arterial Roads with Bluetooth Sensors

Time-stamped, media access control addresses, acquired from Bluetooth-enabled devices to collect travel time data, have received significant attention in the past few years. Research has focused mainly on the application of Bluetooth technology to obtain travel time data on freely flowing roads. A few studies have addressed the use of Bluetooth data collection systems on arterial roads, particularly with respect to travel times between signalized intersections, with questionable accuracy. The objective of this research was to develop a methodology to collect accurate and precise travel time data between signalized intersections, with the use of a data collection system that had a Bluetooth basis. The developed methodology utilized received signal strength indicator (RSSI) data to improve signifi-cantly the accuracy of intersection-to-intersection travel time samples. Test results on a busy arterial road showed that the travel time samples generated with the RSSI method were significantly better (i.e., had less error) than the travel time samples calculated with other methods reported in the literature. The proposed RSSI travel time data collection method could be implemented with any wireless technology that provided a unique identification number to distinguish between different mobile devices and an associated signal strength measurement during the wireless communication process.