Below-Average Bidding Method

The low-bid method, typically used for competitive bidding in the United States, may result in a contract with a firm that submits either accidentally or deliberately an unrealistically low-bid price. Such an occurrence hurts both the owner and the contractor by promoting disputes, increased costs, and schedule delays. To address this problem, other countries have adopted bidding methods based on the average of the bids submitted. One such approach is the below-average method where the winning bid is closest to but below the average of all bids. A competitive bidding model for the below-average-bid method is presented and its merits relative to the average-bid method and the low-bid method are explored. The below-average-bid process is investigated analytically and through Monte Carlo simulation. The results of bidding models for the below-average, the average, and the low-bid methods are presented in four easy-to-use nomograms which allow contractors to determine the optimal lump-sum bid price for each method without the need for complicated analysis. A comparison of the three methods provides information and insights to help owners with the difficult choice of a suitable bidding method for the project at hand.     

A new indirect adaptive control scheme for time-varying plants

Structures are developed for the control and estimation parts of the indirect adaptive scheme which are more appropriate for time-varying plants. In contrast to the usual pointwise schemes, the new controller structure can meet the control objective exactly for a wide class of plants with smooth but otherwise unrestricted parameter variations. On the other hand, the possibly available knowledge of the form or frequency of variation of the fast parameters is included in the new estimator structure so that, for successful estimation, the overall plant is not restricted to varying slowly with time. The new estimator and control law are combined using the certainty equivalence principle to develop an indirect adaptive control scheme meeting the control objective for plants with time-varying parameters whose fast varying parts are of known form and unknown parts are slow in the mean     

Robust adaptive control: a unified approach

A complete tutorial review of the entire field is presented, beginning with simple instability examples to identify the causes of nonrobust behavior in adaptive control. Some of the mathematical groundwork is presented, and the theory for the design and analysis of adaptive laws is developed. Commonly used adaptive controller structures are discussed, highlighting their particular robustness properties. Particular attention is paid to model reference, pole placement, and linear quadratic controller structures. Designs and analyses of model reference, pole placement, and linear quadratic controllers, based on combining the corresponding controller structures with the various robust adaptive laws, are presented. Suggestions for future research are given     

Characterization of carrier generation in enhancement-mode SOIMOSFET's

The carrier generation in enhancement-mode SOI MOSFETs is studied by applying a suitable bias step on one gate, which drives it from depletion of accumulation to stronger accumulation and creates a deep-depletion condition under the other gate. An accurate analysis of this technique is made through a critical reexamination of the physical mechanisms and assumptions involved. By carefully considering all the essential events taking place in the device as it relaxes back to steady state, a Zerbst-type expression is obtained for the resulting current transients, which leads to a straightforward evaluation of the generation lifetime and surface generation velocity. The method is used to study SIMOX transistors, and it is shown that a very long lifetime can be achieved by multiple oxygen implants     

Robust redesign of adaptive control

Effects of unmodeled high frequency dynamics on stability and performance of adaptive control schemes are analyzed. In the regulation problem global stability properties are no longer guaranteed, but a region of attraction exists for exact adaptive regulation. The dependence of the region of attraction on unmodeled parasitics is examined first. Then the general case of model reference adaptive control is considered in which parasitics can destroy stability and boundedness properties. A modified adaptive law is proposed guaranteeing the existence of a region of attraction from which all signals converge to a residual set which contains the equilibrium for exact tracking. The size of this set depends on design parameters, the frequency range of parasitics, and the reference input signal characteristics.     

ESD-induced oxide breakdown on self-protecting GG-nMOSFET in 0.1-/spl mu/m CMOS technology

Historically, the failure mode of the nMOS/lateral n-p-n (L/sub npn/) bipolar junction transistor (BJT) due to electrostatic discharge (ESD) is source-to-drain filamentation, as the temperature exceeds the melting temperature of silicon. However, as the gate-oxide thickness shrinks, the ESD failure changes over to oxide breakdown. In this paper, transmission line pulse (TLP) testing is combined with measurements of various leakage currents and numerical simulations of the electric field to examine the failure mode of an advanced 0.1-/spl mu/m CMOS technology, which is shown to be through gate-oxide breakdown. It is also shown by I/sub D/-V/sub G/ and I/sub G/-V/sub G/ measurements that the application of nondestructive ESD pulses causes gradual degradation of the oxide well before failure is reached, under the (leakage current) failure criteria used. Finally, the latent effects of stress-induced oxide degradation on the failure current I/sub f/ of the nMOS/L/sub npn/ are studied, and it is shown that as the device ages from an oxide perspective, its ESD protection capabilities decrease.     

Longitudinal control of heavy trucks in mixed traffic: environmental and fuel economy considerations

In this paper, longitudinal vehicle-following controllers for heavy trucks with different spacing policies are designed, analyzed, simulated, and experimentally tested, and their performance in mixed traffic with passenger vehicles is evaluated. A new vehicle-following controller for trucks, which has better properties than existing ones with respect to performance and impact on fuel economy and pollution during traffic disturbances, is developed. The response of trucks to disturbances caused by lead passenger vehicles is smooth due to the limited acceleration capabilities of trucks whether they are manual or equipped with adaptive cruise control (ACC) systems. Vehicles following the truck are therefore presented with a smoother speed trajectory to track. This filtering effect of trucks is shown to have beneficial effects on fuel economy and pollution. However, it creates large intervehicle gaps that invite cut-ins from neighboring lanes, creating additional disturbances. These cut-ins, under certain realistic scenarios, may reduce any benefits obtained by the smooth response of trucks as well as increase travel time. The results of this paper indicate possible benefits trucks may have in mixed traffic and also reinforces what is already known-that trucks could be detrimental to traffic flow.     

Web Access to Large Audiovisual Assets Based on User Preferences

Current multimedia databases contain a wealth of information in the form of audiovisual as well as text data. Even though efficient search algorithms have been developed for either media, there still exists the need for abstract presentation and summarization of the results of database users' queries. Moreover, multimedia retrieval systems should be capable of providing the user with additional information related to the specific subject of the query, as well as suggest other topics which could be identified to attract the interest of users with a similar profile. In this paper, we present solutions to these issues, giving as an example an integrated architecture we have developed, along with notions that support efficient and secure Internet access to audiovisual/video databases. Segmentation of each video in shots is followed by shot classification in a number of predetermined categories. Generation of users' profiles according to the categories, enhanced by relevance feedback, permits an efficient presentation of retrieved video shots or characteristic frames in terms of the user interest in them. Moreover, this clustering scheme assists the notion of lateral links that enable the user to continue retrieval with data of similar nature or content to those already returned. Furthermore, user groups are formed and modeled by registering actual preferences and practices. This enables the system to predict information that is possibly relevant to the user's interest and present it along with the returned results. The concepts utilized in this system can be smoothly integrated in MPEG-7 compatible multimedia database systems.     

Sequencing material handling equipment in production facilities

In this article we consider the problem of sequencing material handling equipment in manufacturing systems, subject to constraints that restrict the start and end time of each production activity, according to pre‐specified daily resource operational schedules and process planning information. The underlying decision problem is modeled using an integer programming formulation similar to vehicle routing with time windows (VRPTW). To take advantage of standard approaches for the VRPTW, we develop a transformation schema that allows a one‐to‐one mapping between the manufacturing problem and VRPTW. An efficient heuristic to solve the resulting transformed problem is proposed. The method, which is a penalty‐based sequential insertion heuristic, allows routes to be constructed by exploiting the tradeoff between material handling and resource starvation costs. The steps of the method are illustrated via a comprehensive example and results on benchmark problems are reported.