Browsing by Author "Wang, WC"

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A new high-performance CMOS GHZ power amplifier design with common-mode signal cancellation technique
(2002)
Wu, CY
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Wang, WC
;
Chen, TM
;
電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
This work describes a novel common-made signal rejection method for power amplifiers. A power amplifier with standard 1P5M 0.25mum CMOS technology was simulated and analyzed. This common-mode signal cancellation method makes the performance, in terms of output power and efficiency of the power amplifier, more immune to input common-mode signals than conventional power amplifiers. Simulated results indicate that this fully balanced differential power amplifier yields 24dBm output power at 2.45GHz, from a 3.3V power supply. The simulated drain efficiency is 33.21%, and the overall power-added efficiency is 32.84%. The power amplifier is highly linear.
Application example for evaluating networks considering correlation
(2000-11-01)
Wang, WC
;
Demsetz, LA
;
土木工程學系
;
Department of Civil Engineering
Current approaches to network scheduling do not consider the correlation between activity durations. When activity durations are correlated, the variability of path and project durations may be increased. High variability in a project's duration increases the uncertainty of completing the project by a target date. The model NETCOR (NETworks under CORrelated uncertainty) has been developed to evaluate schedule networks when activity durations are correlated. The NETCOR model builds upon a factor-based procedure to indirectly elicit correlation. An activity duration model disaggregates the effect of uncertainty by factors from a duration distribution (grandparent) for each activity. Correlation is captured by a child-distribution approach that further breaks down the factor-subdistribution (:parent) based on the factor conditions. This paper demonstrates the practical application of NETCOR to a current construction project. Using the same inputs, the program evaluation and review technique and several simulation analyses that do not consider correlation also are evaluated. Comparison of the results shows the significance of considering correlation in scheduling analysis.
Applications of electronically facilitated bidding model to preventing construction disputes
(2005-10-01)
Wang, WC
;
Yang, JB
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土木工程學系
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Department of Civil Engineering
When a lump-sum public construction project is implemented, disputes often arise concerning issues around the accuracy of contracted quantities, the acceptability of unit prices of cost items, and whether an "equal (or equivalenty)" for a product (equipment or material) can be used. In Taiwan, contracted quantities and unit prices are primarily based on owner's estimations, and the trademarks of a product specified in a tendering documentation are only for reference. A contractor has to struggle for profit when the amount of work completed differs from the contracted amount, when change orders are priced according to the owner's estimates, and when inexpensive equals may be used. This work comprehensively elaborates the background of the current practice, and presents experience of applying an electronically facilitated bidding model to evaluating the bidder's submitted quantities, unit prices and equals in several practical projects in Taiwan. Results of this study indicate that the aforementioned construction disputes can be prevented or at least mitigated. (c) 2005 Elsevier B.V. All rights reserved.
Automatic schedule integration for highway projects
(2003-07-01)
Dzeng, RJ
;
Wang, WC
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土木工程學系
;
Department of Civil Engineering
The construction of a highway/expressway, which involves a complex combination of roads, bridges, and tunnels, is generally separated into several projects. Various contractors thus execute different projects and often apply differing scheduling practices. Since all projects involved in highway construction must be completed for the highway to be useful, the management of the various projects should preferably be integrated. To assist project controllers in schedule integration, this study proposes algorithms based on standardized codes and network modules. A computer system was also designed to help contractors use these modules for scheduling, and ultimately to let project controllers combine these schedules electronically. A questionnaire survey and industry feedback revealed the potential benefits of using the proposed algorithms for generating and integrating schedules, respectively. Contractors' computation capabilities must be improved before the proposed scheduling algorithms can be fully implemented. (C) 2003 Elsevier Science B.V. All rights reserved.
Automating schedule review for expressway construction
(2005-01-01)
Dzeng, RJ
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Tserng, HP
;
Wang, WC
;
土木工程學系
;
Department of Civil Engineering
An expressway project is often divided into subprojects with different tendering packages, and carried out by several general contractors that apply different scheduling practices. Each schedule may contain hundreds of activities, each of which is associated with multiple pay items that determine its earned monetary value. With such huge amount of information, the reviewer can only check a sample piece of information, and the quality of review highly depends on the reviewer's experience and devotion. Automated schedule review provides a solution to reduce such problems encountered in the industry. This paper presents a module-based schedule generation and review model, which includes a predefined set of network modules, network builder assistant computer system that helps schedulers manage and reuse the modules to build a new schedule, and another computer system network review assistant (NRA) that helps reviewers review schedules. The NRA uses generalized rule forms to represent the schedule critique knowledge collected from the industry. When potential errors are found, the NRA adopts case-based reasoning to suggest possible correction based on similar cases. The evaluation conducted by the practitioners using real projects indicates that NRA reduces review time, and provides more accurate review on finding activities and related pay items not conforming to standards, and reminding users of important but often omitted activities.
Chaotic behaviors of bistable laser diodes and its application in synchronization of optical communication
(2001-10-01)
Wang, WC
;
Hwang, TM
;
Juang, C
;
Juang, J
;
Liu, CY
Period-doubling routes to chaos behavior in bistable laser diodes is examined numerically, An external sinusoidal electronic drive is injected to generate chaotic light output. Phase portrait, Poincare map, bifurcation diagram, and Lyapunov exponent are then calculated to assert the existence of chaos. Furthermore, according to Pecora and Carroll's theory, a drive-response system is constructed by using the bistable laser diodes to mask the sinusoidal electronic signal with chaotic light. Synchronization can be achieved for optical simplex and duplex transmissions using bistable laser diodes. The proposed synchronization scheme between two separate chaotic systems provides a key step toward optical chaotic communication.
Closure to "Electronic-Based procedure for managing unbalanced bids" by Wei-Chih Wang
(2005-09-01)
Wang, WC
;
土木工程學系
;
Department of Civil Engineering
Contractor selection by the most advantageous tendering approach in Taiwan
(2003-05-01)
Yang, JB
;
Wang, WC
;
土木工程學系
;
Department of Civil Engineering
Construction clients usually tender their projects by either the lowest bid tendering method or the A-plus-B method to find a bidder that provides the lowest cost or highest profit. However, choosing a contractor that provides assured quality by examining his construction proposals along with his bid price and bid duration will compensate for the uncertainty in the lowest bid system, while retaining the advantages of the A-plus-B method. This paper presents a novel tendering method (the Most Advantageous Tendering approach) using a practical example in Taiwan. The rationales for contractor selection of the Government Procurement Law in Taiwan are reviewed herein. Several valuable issues regarding contractor selection in this case study are also presented.
Electronic-based procedure for managing unbalanced bids
(2004-05-01)
Wang, WC
;
土木工程學系
;
Department of Civil Engineering
Construction lump sum lowest bid procurement is one of the most prevalent methods of awarding construction contracts. For a lump sum bidding practice in Taiwan, after the lowest bidder is awarded a construction project contract, the contractual unit price for each cost item is taken as the product of the owner's estimated unit price and a discounting ratio equal to the total bid price divided by the owner's project cost estimate. This owner-based approach is inequitable because the bidder is denied the right to allocate the risks associated with the costs of performing the work. In U.S. practice, while the unit prices submitted by the bidder are usually considered as the contractual ones, unbalanced bids may occur. This work presents a bidder-based quantitative procedure, built on an electronic-based bidding process for effectively and efficiently supporting reviewing and adjusting the bidder's proposed unit prices for a lump sum procurement project. The advantages of this procedure include that the unit prices electronically obtained front the owner and all qualified bidders are included in analyses during unit-price evaluation, and that rules for unit-price adjustment along with maintaining the total contractual price are included. The novel procedure has been successfully applied to several construction projects in Taiwan and the results have been greatly appreciated by both governments and contractors.
Fixed-point methods for a semiconductor quantum dot model
(2004-09-01)
Hwang, TM
;
Lin, WW
;
Liu, JL
;
Wang, WC
;
應用數學系
This paper presents various fixed-point methods for computing the ground state energy and its associated wave function of a semiconductor quantum dot model. The discretization of the three-dimensional Schrodinger equation leads to a large-scale cubic matrix polynomial eigenvalue problem for which the desired eigenvalue is embedded in the interior of the spectrum. The cubic problem is reformulated in several forms so that the desired eigenpair becomes a fixed point of the new formulations. Several algorithms are then proposed for solving the fixed-point problem. Numerical results show that the simple fixed-point method with acceleration schemes can be very efficient and stable. (C) 2004 Elsevier Ltd. All rights reserved.
Jacobi-Davidson methods for cubic eigenvalue problems
(2005-09-01)
Hwang, TM
;
Lin, WW
;
Liu, JL
;
Wang, WC
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應用數學系
Several Jacobi-Davidson type methods are proposed for computing interior eigenpairs of large-scale cubic eigenvalue problems. To successively compute the eigenpairs, a novel explicit non-equivalence deflation method with low-rank updates is developed and analysed. Various techniques such as locking, search direction transformation, restarting, and preconditioning are incorporated into the methods to improve stability and efficiency. A semiconductor quantum dot model is given as an example to illustrate the cubic nature of the eigenvalue system resulting from the finite difference approximation. Numerical results of this model are given to demonstrate the convergence and effectiveness of the methods. Comparison results are also provided to indicate advantages and disadvantages among the various methods. Copyright (c) 2004 John Wiley & Sons, Ltd.
Model for evaluating networks under correlated uncertainty - NETCOR
(2000-11-01)
Wang, WC
;
Demsetz, LA
;
土木工程學系
;
Department of Civil Engineering
Construction activities are often influenced by factors such as weather, labor, and site conditions. When several activities are influenced by the same factor, their durations may be correlated. If many activities along a path are correlated, the variability of path duration will increase, possibly increasing the uncertainty of completing the project by a target date. This paper presents the simulation-based model NETCOR (NETworks under CORrelated uncertainty) to evaluate schedule networks when activity durations are correlated. Based on qualitative estimates of the sensitivity of each activity to each factor, uncertainty in an activity's duration distribution (grandparent) is distributed to several factor subdistributions (parents). Each subdistribution is broken down further into a family of distributions (children), with each child corresponding to a factor condition. Correlation is captured by sampling from the same-condition child distributions for a given iteration of the simulation. NETCOR integrates the effect due to each factor at the path level. Awareness of the factors to which a path is sensitive can provide management with a better sense of what to control on each path, particularly on large projects.
Module-based construction schedule administration for public infrastructure agencies
(2004-01-01)
Dzeng, RJ
;
Wang, WC
;
Tserng, HP
;
土木工程學系
;
Department of Civil Engineering
Infrastructure projects such as the construction of expressways are often distributed over different regions and must therefore be divided into several tendering packages. The public agencies that administrate such projects manage project packages that must be integrated. All project packages may involve similar work. However, they are carried out by different contractors each with their own scheduling practices. Standardization provides a foundation for more efficient and effective schedule integration, but cannot easily be enforced without objections from contractors. This paper presents a three-stage standardization implementation framework using modularization. A set of network modules that involve normal, repetitive, cyclic, and merging activities was developed for expressway projects. Two computer systems were developed to help contractors use these modules to create schedules, and to help the owner review schedules submitted by contractors. Experiments and a survey were also carried out to validate the proposed framework, demonstrating a significant amount of time saving and errors reduced by using network modules.
New formulations for interface problems in polar coordinates
(2003)
Li, ZL
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Wang, WC
;
Chern, IL
;
Lai, MC
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應用數學系
In this paper, numerical methods are proposed for some interface problems in polar or Cartesian coordinates. The new methods are based on a formulation that transforms the interface problem with a nonsmooth or discontinuous solution into a problem with a smooth solution. The new formulation leads to a simple second order finite difference scheme for the partial differential equation and a new interpolation scheme for the normal derivative of the solution. In conjunction with the fast immersed interface method, a fast solver has been developed for the interface problems with a piecewise constant but a discontinuous coefficient using the new formulation in a polar coordinate system.
Numerical methods for semiconductor heterostructures with band nonparabolicity
(2003-09-01)
Wang, WC
;
Hwang, TM
;
Lin, WW
;
Liu, JL
;
應用數學系
This article presents numerical methods for computing bound state energies and associated wave functions of three-dimensional semiconductor heterostructures with special interest in the numerical treatment of the effect of band nonparabolicity. A nonuniform finite difference method is presented to approximate a model of a cylindrical-shaped semiconductor quantum dot embedded in another semiconductor matrix. A matrix reduction method is then proposed to dramatically reduce huge eigenvalue systems to relatively very small subsystems. Moreover, the nonparabolic band structure results in a cubic type of nonlinear eigenvalue problems for which a cubic Jacobi-Davidson method with an explicit nonequivalence deflation method are proposed to compute all the desired eigenpairs. Numerical results are given to illustrate the spectrum of energy levels and the corresponding wave functions in rather detail. (C) 2003 Elsevier B.V. All rights reserved.
SIM-UTILITY: Model for project ceiling price determination
(2002-01-01)
Wang, WC
;
土木工程學系
;
Department of Civil Engineering
Before considering bids submitted by competing contractors for a public procurement project, the owner should determine a project ceiling price or cost estimate to use as a reference point for evaluating the bids. A high ceiling price conflicts with the owner's interests in minimizing costs. Meanwhile, a low ceiling price can jeopardize the project if all bids exceed the ceiling price. This paper proposes a model for determining a reasonable project ceiling price. The model, called SIM-UTILITY, is based on a utility theory and facilitated by a cost simulation approach. The utility theory is applied to reflect the owner's preferences regarding the determination criteria, while the simulation approach is used to generate more objective project cost data to support execution of the utility theory. The advantages of SIM-UTILITY are proven by its successful application to three construction projects in Taiwan. A computerized SIM-UTILITY is expected to be broadly applicable to public construction projects in Taiwan.
Simulation-based safety evaluation model integrated with network schedule
(2006-05-01)
Wang, WC
;
Liu, JJ
;
Chou, SC
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土木工程學系
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Department of Civil Engineering
Construction accidents often lead to project delays. However, in practice, construction safety and schedule control are managed separately. This work develops an innovative simulation-based model, SimSAFE, that assesses the hazard (or expected accident costs) for each activity in a network schedule. Thus, at any time point, safety managers can pay considerable attention to activities (or paths or working zones) with high expected accident costs. Additionally, by breaking down the uncertainty of an accident cause occurring, SimSAFE provides factor-sensitivity information to support safety risk management. Enhancing knowledge of the safety factors (such as safety training and site environment) to which an activity (or path or zone) is sensitive, and also of the activities (or paths or zones) that are most sensitive to a particular factor can provide management with a better sense of what factors and activities (or paths or zones) need to be controlled for reducing construction accidents, especially for a large project or multiple projects. (c) 2005 Elsevier B.V. All rights reserved.
Simulation-facilitated model for assessing cost correlations
(2002-09-01)
Wang, WC
;
土木工程學系
;
Department of Civil Engineering
Project cost becomes increasingly variable if many cost items for a construction project are correlated, and this can increase the uncertainty of completing a project within a target budget. This work presents a factor based computer simulation model (COSTCOR) for evaluating project costs given correlations among cost items. Uncertainty in the total cost distribution of an item (grandparent) is transferred to several factor cost distributions (parents) according to qualitative estimates of the sensitivity of each cost item to each factor Each cost distribution is then decomposed further into a family of distributions (children; costs given factor conditions), with each child corresponding to a factor condition. Correlations are retrieved by sampling from the child distributions with the same condition for a given iteration of the simulation. COSTCOR integrates the uncertainty effects caused by each factor at the project cost level, thus making it easier for management to determine what parts of the project need to be controlled.
Structure-stability-activity relationship in covalently cross-linked N-carbamoyl D-amino acid amidohydrolase and N-acylamino acid racemase
(2006-06-09)
Chiu, WC
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You, JY
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Liu, JS
;
Hsu, SK
;
Hsu, WH
N-Acylamino acid racemase (NAAAR) and N-carbamoyl-D-amino-acid amidohydrolase (D-NCAase) are important biocatalysts for producing enantiopure a-amino acids. NAAAR forms an octameric assembly and displays induced fit movements upon substrate binding, while D-NCAase is a tetramer that does not change conformation in the presence of a ligand. To investigate the effects of introducing potentially stabilizing S-S bridges in these different multimeric enzymes, cysteine residues predicted to form inter or intra-subunit disulfide bonds were introduced by site-directed mutagenesis. Inter-subunit S-S bonds were formed in two NAAAR variants (A68C-D72C and P60C-Y100C) and two D-NCAase variants (A302C and P295C-F304C). Intra-subunit S-S bonds were formed in two additional NAAAR variants (E149C-A182C and V265C). Crystal structures of NAAARs variants show limited deviations from the wild-type overall tertiary structure. An apo A68C-D72C subunit differs from the wild-type enzyme, in which it has an ordered lid loop, resembling ligand-bound NAAAR. The structures of A222C and A302C D-NCAases are nearly identical to the wild-type enzyme. All mutants with inter-subunit bridges had increases in thermostability. Compared with the wild-type enzyme, A68C-D72C NAAAR showed similar k(cat)/K-m ratios, whereas mutant D-NCAases demonstrated increased k(cat)/K-m ratios at high temperatures (A302C: 4.2-fold at 65 degrees C). Furthermore, molecular dynamic simulations reveal that A302C substantially sustains the fine-tuned catalytic site as temperature increases, achieving enhanced activity. (c) 2006 Elsevier Ltd. All rights reserved.
Subcarrier multiplexing by chaotic multitone modulation
(2003-10-01)
Juang, C
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Huang, ST
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Liu, CY
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Wang, WC
;
Hwang, TM
Subcarrier multiplexing by chaotic multitone modulation is investigated. Optical chaotic light can be achieved by injecting multiple subcarriers into a self-pulsating laser diode. Synchronization between two identical chaotic systems (drive and response) can be implemented provided that the conditional Lyapunov exponents are all negative. By adding amplitude modulation (AM) signals to each subcarrier, the two systems become asymptotically synchronized. The AM signals in each subcarrier can be recovered by the introduction of a filtering process where the Lyapunov exponent of the synchronized error function matches the cutoff frequency of a first order low pass filter.