Zu-Hsu Lee

ESTIMATING MEDIAN VELOCITY INSTEAD OF MEAN VELOCITY AT SINGLE LOOP DETECTORS

Loop detectors are the preeminent vehicle detector for freeway traffic surveillance. Although single loops have been used for decades, debate continues on how to interpret the measurements. Many researchers have sought better estimates of velocity from single loops. The preceding work has emphasized techniques that use many samples of aggregate flow and occupancy to reduce the estimation error. Although rarely noted, these techniques effectively seek to reduce the bias due to long vehicles in measured occupancy. This paper presents a different approach, using a new aggregation methodology to estimate velocity and reduce the impact of long vehicles in the original traffic measurements. In contrast to conventional practice, the new estimate significantly reduces velocity estimation errors when it is not possible to control for a wide range of vehicle lengths.

Operational restructuring: reviving an ailing business

Purpose – When firms are dealing with negative earnings and/or economic downturns, operational restructuring is often initiated as a rescue tool. Some firms recover and prevail, while the others fail to survive and are subsequently delisted from stock exchange. The purpose of this paper is to identify factors that are significantly associated with the delisting risk of restructuring firms.Design/methodology/approach – The authors draw on a sample of firms with negative earnings that undertook restructuring during the 2001 economic recession. Logistic regression estimation is used to examine the delisting risk of these firms following the restructuring.Findings – The paper finds that delisting risk increases when firms undertake repetitive restructurings, massive workforce reduction, and large‐scale asset downsizing. Firms with high levels of debt and failure to cut costs and/or narrowing its focus on core competencies are also more likely to delist.Practical implications – By analyzing and synthesizing th...

A novel ant colony optimization approach for on-line scheduling and due date determination

This paper aims to develop an on-line Ant Colony Optimization (ACO) framework, where jobs arrive over time, and at any time we lack knowledge concerning future jobs. A due date is determined upon job arrival, and jobs are sequenced on the machine to optimize the sum of weighted lead times with all due dates met. We propose that each ant is associated with a sequence of waiting jobs with quoted due dates. This waiting sequence is constantly updated over time (whenever a job is selected to be processed or a new job arrives). The on-line schedule is constructed by selecting the first job in the waiting list of the “best” ant to process (along with its due date) as the machine becomes available. However, for the ant where this job is not the first one in the list, processing it pushes back the waiting jobs positioned before it. If such push back results in a due date violation, this ant will be eliminated. Further, our ACO framework does not include the iterative procedure due to the characteristics of the on-line problem; this is one difference from the traditional ACO framework besides ant elimination. The computational testing on generated instances shows that our ACO algorithm outperforms an existing effective on-line algorithm in the literature. Also, with local search incorporated using the EDD (Earliest Due Date) rule, improvements can be obtained in both computational outcome and time.

Heuristic design procedure for structures with displacement‐dependent damping devices

Purpose – The use of supplemental damping to dissipate energy is one of the most economical and effective ways to mitigate the effects of earthquake on structures. For practicing engineers, the ideal design procedure for buildings with supplemental damping should not be too complex to implement in practice. Building on the existing theoretical frame, the purpose of this paper is to develop simple and heuristic methods for the above design procedure.Design/methodology/approach – Passive displacement‐dependent devices are considered in this paper. Based on the theoretical results for added damping and added stiffness (ADAS) devices, the paper first analyzes the generated forces and the effects of ADAS devices on structures under seismic impact. We identify design parameters and variables are identified, and present the procedure of how the values of the variables (e.g. column shear force, ductility ratio) are finalized so that the design requirements can be met is presented. A four‐story six‐bay steel build...

Simulation methods for seismic behaviour of buildings in unbounded soil media with radiation damping

Mathematical and computer methods have been used by others to predict the seismic behaviour of viscous damped structures, yet most analyses have not accounted for the influence of an unbounded foundation. In order to better understand the motional behaviour of structures during earthquakes, this study considers the effects of radiation damping and flexibility when characterizing the interaction between damped structures and unbounded soil media. Two numerical methods, the consistent-infinitesimal finite element cell method and a new quiet boundary method, are introduced here. Also, computer simulation is used to demonstrate the effects of radiation damping for far field, unbounded media. The differences in seismic responses of structures with and without consideration of radiation damping are significant. The results also make clear the importance of accounting for such effects when, for example, structural engineers incorporate structural control devices into their designs.

Optimal selection of concrete anchors for connection cost reduction

A proprietary product such as a post‐installed concrete anchor has a unique place in the engineering community that includes product design, manufacturing, testing, evaluation and design for expected service conditions. An economic model in a non‐linear integer programming form is proposed for selection of concrete anchors in order to minimize connection cost. It is shown that the model can be easily incorporated with available computer software packages and generalized when different parameters and constraints are imposed to handle a variety of material selections. The information from recent testing conducted by CEL Consulting for a major engineering, procurement and construction (EPC) contractor is used to provide computational results. The method introduced here adds practical value to these types of industrial problems because it considers points of view from both structural engineers and project managers.

Decision model and analysis for investment interest expense deduction and allocation

Investment income tax planning requires informed, strategic choices. One must determine the amount of qualified dividends and net long-term capital gain to be included in investment income (against which investment interest expense can be deducted). This choice also determines the residual qualified dividends and net long-term capital gain which enjoy a reduced tax rate. Another important decision is whether all or some of this interest expense should be deducted in the current year or carried forward. This paper puts forward a new approach to formulate these questions as a generalized resource allocation problem which permits analysis of the interdependence between, and the tax consequences of, the above decisions. The commonly used approach - deducting investment interest expense sooner rather than later - we consider myopic since the benefit of deferring some of the deduction is not leveraged. Presented here is a tax planning guideline (a necessary and sufficient condition for optimality) to realize a more forward-looking strategy. We also show that, for certain income structures, the tax savings by deducting a one-dollar investment interest expense may be more than the tax rate on the dollar of investment income that is offset.

PREDICTORS OF CUSTOMER PREFERENCE FOR ONLINE VERSUS OFFLINE AIR TRAVEL BOOKING

Airlines increasingly use their own websites to sell products directly to customers. Because Internet- based distribution is low cost, this means lower prices for the consumer. To compete with such sales channels, global distribution systems (GDS) firms have made ready-made online booking tools available for conventional walk-in travel agencies. This presents such agencies with a choice?to use online or more traditional offline methods in dealing with their customers. This study has two goals: to identify a small set of predictive factors that effectively forecast customer preferences, and to demonstrate the utility of such factors for predicting customer choices. We began by designing and executing a detailed questionnaire fielding some 300 respondents, then applied hypothesis testing to extract important factors from the data, and finally, used the logistic regression methods applied with these factors to efficiently predict customer choices. The findings indicate that the majority of customers believe that online booking is cheaper and faster than offline. However, booking choice is strongly influenced by whether cost or service is the paramount emphasis. If customers want lower prices, they will typically book online. If they want service?such as help making special travel arrangements?they will usually choose offline.

Online MTO lead-time scheduling: a probabilistic approach

This paper considers a lead time (or due date) scheduling problem faced by a manufacturer that produces customised products according to specific customer orders. It uses a single sever model to design an effective, yet simple heuristic procedures for both sequencing and lead time determination decisions. Typically, a series of jobs with individual arrival times and weights must be sequenced on a single machine. With each arrival, a lead time must be determined, and the job completed before the promised due date. An on-line heuristic may be developed in certain situations, based on limited information about the future, with the objective of minimising the average (or total) weighted due date for large size instances. Computational testing shows that this heuristic is more effective than the conventional scheduling rules not only for the average weighted due date, but also for the average weighted lead time, for both stable systems and heavily loaded ones.

The cost of seismic structural damage and preventive action

Purpose – This paper first aims to estimate the economic loss due to an earthquake, such as building‐related losses, the damage of debris generation and fire, and the social impact. Then, it seeks to evaluate the feasibility of retrofit to prevent buildings from seismic structural damages.Design/methodology/approach – The HAZUS software is used for the seismic loss estimation using default demographic data, which were obtained from San Francisco Assessor record. The HAZUS estimates the damage using the earthquake of 6.7 magnitude. Based on the HAZUS report incorporated with probabilistic scenarios of earthquakes, Federal Emergency Management Agency (FEMA) guidelines are used to calculate the cost of structural rehabilitation in San Francisco.Findings – It is recommended that either Options 1 and 3 or Options 2 and 3 provided by FEMA 156 and 157 respectively should be used to calculate the cost of seismic rehabilitation of a structure. The results provide estimated costs of retrofit plans for different typ...