A tabu search with an oscillation strategy for the discriminant analysis problem

This article proposes a tabu search approach to solve a mathematical programming formulation of the linear classification problem, which consists of determining an hyperplane that separates two groups of points as well as possible in ?^m. The tabu search approach proposed is based on a non-standard formulation using linear system infeasibility. The search space is the set of bases defined on the matrix that describes the linear system. The moves are performed by pivoting on a specified row and column. On real machine learning databases, our approach compares favorably with implementations based on parametric programming and irreducible infeasible constraint sets. Additional computational results for randomly generated instances confirm that our method provides a suitable alternative to the mixed integer programming formulation that is solved by a commercial code when the number of attributes m increases.     

A graph approach to generate all possible regression submodels

A regression graph to enumerate and evaluate all possible subset regression models is introduced. The graph is a generalization of a regression tree. All the spanning trees of the graph are minimum spanning trees and provide an optimal computational procedure for generating all possible submodels. Each minimum spanning tree has a different structure and characteristics. An adaptation of a branch-and-bound algorithm which computes the best-subset models using the regression graph framework is proposed. Experimental results and comparison with an existing method based on a regression tree are presented and discussed.     

The SQUG program for resolution of USI A-46 — Status and implementation plans

In response to U.S. Nuclear Regulatory Commission (NRC) Unresolved Safety Issue (USI) A-46, “Seismic Qualification of Equipment and Operating Nuclear Power Plants”, the Seismic Qualification Utility Group (SQUG), with the support of the Electric Power Research Institute (EPRI), developed a comprehensive program to verify the seismic adequacy of equipment in operating nuclear power plants. The primary thrust of the program has been the development of procedures, criteria, and data to apply actual experience on the performance of equipment during earthquakes to the verification of seismic ruggedness of similar equipment in nuclear plants. While the use of such experience data continues to play a primary part in the SQUG program for resolution of USI A-46, the overall SQUG program includes a number of other significant elements which, taken together, provide a comprehensive approach for verification of the seismic adequacy of equipment in nuclear plants. These elements of the SQUG program include the assimilation and use of seismic shake table data in a generic way; the development of simplified analytical tools and criteria for evaluation of equipment anchorage, tanks, heat exchangers and cable trays; and the development of procedures for identifying and evaluating electrical relays, which are essential to plant shutdown in response to an earthquake. Procedures and data bases for performing and documenting the various seismic evaluations and plant walkdowns, and a program for training the large number of engineers who will be required to implement the SQUG methodology, have also been developed. This paper describes the main elements of the SQUG program for resolution of USI A-46 and provides a status report on the plans for their implementation in SQUG member plants.     

Bridge Maintenance Level Assessment

Parameters in assessing the effectiveness of maintenance tasks on the overall cost of a bridge or system of bridges are identified and the linkage among maintenance, condition rating, and cost is made by subdividing the subjective process into smaller parts. Experience with New York City bridges is used to develop a life expectancy model once the maintenance and repair protocol is specified. Results for several sample maintenance allocations are given to show how a rapid spreadsheet calculation can provide a basis for comparing maintenance alternatives and to point in the direction of an optimized allocation of limited budgets.     

A multioctave (0.5–12.0 GHz) low-noise transistor amplifier

An effective method of computer calculation and optimization of characteristics of multioctave low-noise transistor amplifiers is presented. The method was used to design a three-stage amplifier built on the basis of microstrip technology using packaged transistors and chip resistors and capacitors. In a 0.5- to 12.0-GHz frequency band, the following characteristics are obtained: a noise ratio of 2.2–3.2 dB, a gain of >25.6 dB, a gain flatness of ±1.2 dB, a voltage standing wave ratio of <2.8 and <2.2 at the input and output, respectively.     

Changes in arterial-veinous coronary difference of substrates from the carbohydrate-energetic and fatty metabolism during experimental hypertensive reaction caused by sympathomimetic preparation VMI 20-4

Plasma renin concentration (PRC) was measured in 46 patients with essential hypertension before and after treatment for 4 weeks with alprenolol 600-1200 mg daily. In 27 of these patients PRC was measured after 4 weeks of combined treatment with alprenolol and hydralizine. During alprenolol treatment PRC and blood pressure were reduced, but the changes were not correlated. Alprenolol treatment caused similar blood pressure reductions in patients with high and low PRC, and the antihypertensive efficacy of beta-adrenergic blocking agents could not be predicted from the pretreatment PRC. When beta-adrenergic blockade was supplemented with hydralazine, blood pressure was further reduced, but PRC remained unchanged. Although a causal relationship between blood pressure reduction and suppression of renin, production might exist at low doses of beta-adrenergic blocking agents, the present study did not indicate such a relationship when higher doses were used. It was shown that alprenolol inhibited the increase in PRC usually induced by hydralazine, but it is not known whether this was important for the effectiveness of the fall in blood pressure produced by hydralazine.     

A wideband uniplanar 180-degree hybrid ring coupler

A wideband uniplanar 180-degree hybrid ring coupler implemented in coplanar and slot transmission lines is described. An equivalent circuit of the device is developed. The device is analyzed on a computer and its characteristics are optimized. Experimental results show that the inphase and antiphase power division losses are <1.5 dB and the port-to-port isolation is >20 dB over frequency bands ranging from 4 to 12 GHz. The measured characteristics are in good agreement with the calculated ones.     

Wide-band balanced active HEMT mixer

The design and characteristics of a balanced active high electron-mobility transistor (HEMT) mixer operating in the 4.5-10-GHz frequency band are described in this paper. It consists of two parts implemented as independent hybrid circuits, namely, an microwave part fabricated by using a uniplanar technology and comprising a 180° hybrid ring coupler, HEMTs, and input-output matching circuits, and a low-frequency part consisting of an L-C balun and a low-pass filter built of discrete elements. The design of the microwave part of the mixer ensures a high degree of isolation between the signal and local-oscillator (LO) inputs within a wide frequency band at low IF. The measurements show a conversion gain of 5-7 dB, noise figure of 5-7.5 dB, and isolation between the signal and LO ports greater than 20 dB within the 4.5-10-GHz range