A two-step procedure for discrete minimization of truss weight

Five optimization methods are investigated to solve for the combination of standard-size members that minimizes the weight of a truss subjected to stress, displacement, and minimumgage constraints. After comparing the performance of the five methods on four case studies, the writers recommend a two-step procedure. First, Sequential Quadratic Programming (SQP) is applied to solve the equivalent continuous problem, and crosssections are rounded up to standard sizes. Second, a Genetic Algorithm (GA) is applied to search locally for a better configuration of standard-size members. From the problems studied (having 16 standard sizes and up to 96 design variables) a weight reduction of the order of 5% appears possible from the second stage at an additional computational cost of about 20%.     

A versatile structure for on-chip extraction of resistance matchingproperties

This paper describes a simple test structure to accurately characterize resistance mismatch. The process engineer would use this structure to monitor process variations with respect to contact resistance, spreading resistance, sheet resistance and encroachment, the circuit designer would use the structure to determine the matching properties of the line and how to optimize a resistor layout for matching given a maximum physical size. By direct measurements on the structure, the user will know how well resistors can be matched, and what factors introduce the dominant components of the mismatch     

Chemical pathways for the polymerization of enines

AM1 calculations are reported for enines with aromatic substituents. It was found that the position of the unsaturated bonds in each molecule may account for the reactivity of each isomer via different polymerization pathways. The resonant structure of the charged form of one of the molecules allowed speculation about the observed inhibition of the polymerization reaction.     

Complex segregation analysis of leprosy in southern Vietnam

To investigate the nature of the genetic component controlling susceptibility to leprosy and its subtypes, 402 nuclear families were ascertained through a leprosy patient followed at the Dermatology Hospital in Ho Chi Minh City, Vietnam; 285 families were of Vietnamese origin and 117 were of Chinese origin with a higher proportion of lepromatous forms among Chinese patients. Segregation analyses were conducted using the model developed by Abel and Bonney [(1990) Genet Epidemiol 7:391-407], which accounted for variable age of onset and time-dependent covariates. Three phenotypes were considered: leprosy per se (all forms of leprosy together), nonlepromatous leprosy, and lepromatous leprosy. For each of this phenotype, analyses were performed on the whole sample and separately on the Vietnamese and the Chinese families. The results showed that a single Mendelian gene could not account for the familial distributions of leprosy per se and its two subtypes in the whole sample. However, these results were different according to the ethnic origin of the families. In the Vietnamese subsample, there was evidence for a codominant major gene with residual familial dependences for the leprosy per se phenotype, and borderline rejection of the Mendelian transmission hypothesis for the nonlepromatous phenotype. In Chinese families, strong rejection of Mendelian transmission was obtained in the analysis of leprosy per se, and no evidence for a familial component in the distribution of the nonlepromatous phenotype was observed. For the lepromatous phenotype, the discrimination between models was poor, and no definitive conclusion could be reached. Referring to immunological data, we suggest that these results could be explained by a heterogeneity in the definition of the lepromatous phenotype. It is likely that progress in the understanding of the genetic components involved in the expression of leprosy will come from a better definition of the phenotype under study, and immunological studies are ongoing in this population to investigate this hypothesis.     

OPERATING REGIME DECOMPOSITION USING NEURAL NETWORKS

This article addresses the problem of identification of a nonlinear process operating over a wide range of conditions. The global space is divided into multiple local regimes, a nonlinear model is developed for each regime, and a quadratic programming-based algorithm is used to ensure smooth transition between the regimes on-line. The use of nonlinear models as opposed to linear models reduces the number of local regimes needed. Neural networks are used to model these regimes because of their strong ability to capture nonlinearity, and their combination with the switching algorithm improves transient performance. The performance of the method is demonstrated on an exothermic CSTR and a pH neutralization process.     

The Ocean Color Experiment (OCE) on the Second Orbital Flight Test of the Space Shuttle (OSTA-I)

The Ocean Color Experiment was one of the six remote-sensing experiments which for the first time were launched and success fully operated on board of the second flight of the Space Shuttle during November 1981. The experiment consists of a multispectral image scanner dedicated to the measurement of water color and its interpretation in terms of major water constituents and circulation patterns. The objectives of the experiment, the test site selection, and associated activities are described. The actual mission and results of an initial data analysis is discussed.     

Influence of mineral oils on polystyrene fracture

Polystyrene specimens coated with mineral oils of different viscosities were tested in tension. It was found that craze initiation and tensile fracture stresses, and also the breaking energy decreased with decreasing oil viscosity, all being lower than for specimens tested in air. Crazes formed in oil showed a lower fibril volume fraction and thicker fibrils than air crazes. The most striking difference in the fracture patterns was found in the initiation regions, where a globular morphology appears as a result of fibrils breakage at the stages of slow propagation, these globules becoming bigger with decreasing viscosity of the oil environment. Since the polymer-oil interfacial tensions are similar for the different oils, the trends in mechanical properties and craze and fracture morphologies cannot be attributed to a surface energy effect, but to plasticization because the deterioration in the polymer properties and the increasing craze fibrils thickness go along with the plasticizing ability of the oils.     

Korrosionsverhalten von Konstruktionsteilen mit Kondenswasserbelastung – Kanäle,Schächte,Fassaden

The influence of condensed water on the corrosion resistance of structural parts - channels, chutes, facades In the following report the corrosion behaviour of various metals (unalloyed steel, galvanized steel, stainless steel, copper and copper alloys), affected by condensed water, is discussed at first. Moreover, in this connection the possibility of dissolving corrosive substances out of insulating materials has been taken into consideration. The diffusion resistance of water vapour of various insulating materials is subsequently compared among one another. Finally, suggestions on protective arrangements against corrosion are given.