The reaction of acrylonitrile and fumaronitrile with alpha-and beta-eleostearates. Plasticizer properties of the n-butyl esters of the adducts

Summary Acrylonitrile and fumaronitrile have been employed as dienophiles in the Diels-Alder reaction with butylalpha- andbeta-eleostearates, and infrared and ultraviolet spectra determined for the addition product as well as for the dienophiles. The adducts have been tested as primary plasticizers for vinyl resins and compared with dioctyl phthalate. The fumaronitrile adducts were found superior to the acrylonitrile adducts with regard to compatibility; however the latter are satisfactory as secondary plasticizers. By incorporating the acrylonitrile adducts with DOP or TCP, it is possible to achieve either a reduction in volatility of DOP plasticized stocks or an improvement in the modulus and low-temperature performance of TCP plasticized stocks. This does not entail any sacrifice in the desirable plasticizing characteristics of DOP or TCP. One of the laboratories of the Southern Utilization Research Branch, Agricultural Research Service, United States Department of Agriculture.     

A Controlled Experiment Comparing the Maintainability of Programs Designed with and without Design Patterns—A Replication in a Real Programming Environment

Software design patterns seek to package proven solutions to design problems in a form that makes it possible to find, adapt and reuse them. To support the industrial use of design patterns, this research investigates when, and how, using patterns is beneficial, and whether some patterns are more difficult to use than others. This paper describes a replication of an earlier controlled experiment on design patterns in maintenance, with major extensions. Experimental realism was increased by using a real programming environment instead of pen and paper, and paid professionals from multiple major consultancy companies as subjects. Measurements of elapsed time and correctness were analyzed using regression models and an estimation method that took into account the correlations present in the raw data. Together with on-line logging of the subjects work, this made possible a better qualitative understanding of the results. The results indicate quite strongly that some patterns are much easier to understand and use than others. In particular, the Visitor pattern caused much confusion. Conversely, the patterns Observer and, to a certain extent, Decorator were grasped and used intuitively, even by subjects with little or no knowledge of patterns. The implication is that design patterns are not universally good or bad, but must be used in a way that matches the problem and the people. When approaching a program with documented design patterns, even basic training can improve both the speed and quality of maintenance activities.     

Superchilling of food: A review

Food preservation is very important for the safety and the reliability of the product. Superchilling as used for preserving foods, has been defined as a process by which the temperature of a food product is lowered to 1-2 °C below the initial freezing point. Fresh and high quality food products are in great demand worldwide. Temperature is a major factor determining the shelf life and quality of food products. Fish and meat are perishable food commodities, where better and more advanced preservation technology is needed. Deterioration of these foods mainly occurs as a result of chemical, enzymatic and bacteriological activities leading to loss of quality and subsequent spoilage. Storing food at superchilling temperature has three distinct advantages: maintaining food freshness, retaining high food quality and suppressing growth of harmful microbes. It can reduce the use of freezing/thawing for production and thereby increase yield, reduce energy, labour and transport costs. The study on the growth mechanism of ice crystals, modelling and computer simulation of foods during superchilling and superchilling storage is needed.     

Towards automatic adaptive geometrically non-linear shell analysis. Part I: Implementation of an h-adaptive mesh refinement procedure

Effective methods leading to automated adaptive numerical solutions to geometrically non-linear shell-type problems are studied in this work. In particular, procedures for improving the accuracy, the reliability and the computational efficiency of the finite element solutions are of primary interest here. This is addressed using h-adaptive mesh refinement based on a posteriori error estimation, self-adaptive methods in global incremental/iterative processes, as well as smart algorithms and heuristic approaches based on methods of knowledge engineering. Seemless integration of h-adaptive finite element methods with adaptive step-length control makes it possible to maintain a prescribed accuracy while maintaining the solution efficiency without user intervention throughout the process of a non-linear analysis. Several examples illustrate the merit and potential of the approach studied herein and confirm the feasibility of developing an automatic adaptive environment for geometrically non-linear analysis of shell structures.     

How does project size affect cost estimation error? Statistical artifacts and methodological challenges

Empirical studies differ in what they report as the underlying relation between project size and percent cost overrun. As a consequence, the studies also differ in their project management recommendations. We show that studies with a project size measure based on the actual cost systematically report an increase in percent cost overrun with increased project size, whereas studies with a project size measure based on the estimated cost report a decrease or no change in percent cost overrun with increased project size. The observed pattern is, we argue, to some extent a statistical artifact caused by imperfect correlation between the estimated and the actual cost. We conclude that the previous observational studies cannot be considered to provide reliable evidence in favor of an underlying project size related cost estimation bias. We discuss the limited, statistically robust evidence and the need for other types of studies.     

Superconvergent Patch Recovery for plate problems using statically admissible stress resultant fields

In this paper, we study an approach for recovery of an improved stress resultant field for plate bending problems, which then is used for a posteriori error estimation of the finite element solution. The new recovery procedure can be classified as Superconvergent Patch Recovery (SPR) enhanced with approximate satisfaction of interior equilibrium and natural boundary conditions. The interior equilibrium is satisfied a priori over each nodal patch by selecting polynomial basis functions that fulfil the point‐wise equilibrium equations. The natural boundary conditions are accounted for in a discrete least‐squares manner. The performance of the developed recovery procedure is illustrated by analysing two plate bending problems with known analytical solutions. Compared to the original SPR‐method, which usually underestimates the true error, the present approach gives a more conservative error estimate. Copyright © 1999 John Wiley & Sons, Ltd.