Signatures: A language extension for improving type abstraction and subtype polymorphism in C++

C++ uses inheritance as a substitute for subtype polymorphism. We give examples where this makes the type system too inflexible. We then describe a conservative language extension that allows a programmer to define an abstract type hierarchy independent of any implementation hierarchies, to retroactively abstract over an implementation, and to decouple subtyping from inheritance. This extension gives the user more of the flexibility of dynamic typing while retaining the efficiency and security of static typing. With default implementations and views flexible mechanisms are provided for implementing an abstract type by different concrete class types. We first show how the language extension can be implemented in a preprocessor to a C++ compiler, and then detail and analyse the efficiency of an implementation we directly incorporated in the GNU C++ compiler.     

Thermal properties of an epoxide resin cured with bicyclo Diels-Alder anhydride adducts

The thermal properties of polymers derived from resorcinol diglycidyl ether cured with several bicyclo Diels-Alder anhydride adducts have been investigated. Increased char yields and decreased rates of weight loss were observed for these systems as compared to polymers cured by Diels–Alder adducts from acyclic dienes. This is explained on the basis of a reverse Diels-Alder reaction which these bicyclo adducts undergo at lower temperatures than do adducts from acyclic dienes.     

Convention note.

Presents information about the 1968 Convention of the American Psychological Association, held in San Francisco, California. Information includes the names of committee chairmen, committee members, and volunteers who assisted at the Convention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Coal liquids distillation tower corrosion: chloride analysis of solvent refined coal process samples

Severe chloride corrosion incidents have occurred in the distillation area of major direct coal liquefaction plants. Chloride analyses have been carried out for samples collected at various process streams of one of these plants (the Wilsonville, Alabama SRC-1 pilot plant) in order to define the pathway of corrosive species to the distillation area. These analyses show that the major fraction of the chloride in the atmospheric distillation tower is carried there in the higher-boiling process streams. The chloride level at a particular point in the atmospheric distillation tower may be several times that of the tower feed liquid; this concentration contributes to the catastrophic corrosion experienced in these towers. This chloride concentration provides an explanation for the occurrence of the corrosion in the last distillation tower in the process stream, rather than in the tower(s) first contacted by the chloride containing distillate stream. It also accounts for the observed localization of the corrosion within narrow regions of the atmospheric distillation tower. The chloride concentration and the chloride pathway are factors which designers of coal liquefaction distillation processes need to consider in a design that will keep corrosion to a manageable level.     

Numerical determination of the parity-condition parameter for lanchester-type equations of modern warfare

This paper presents a simple numerical procedure for determining the parity-condition parameter for deterministic Lanchester-type combat between two homogeneous forces. Deterministic differentialequation combat models are commonly used in parametric studies for computational reasons, since they give essentially the same results for the mean course of combat as do corresponding stochastic attrition models. The combat studied in this paper is modelled by Lanchester-type equations of modern warfare with time-dependent attrition-rate coefficients. Previous research has generalized Lanchester's classic “square law” to such variable-coefficient combat. It has shown that the prediction of battle outcome (in particular, force annihilation) without having to spend the time and effort of computing force-level trajectories depends on a single parameter, the so-called parity-condition parameter, which is “the enemy force equivalent of a friendly force of unit strength” and depends on only the attrition-rate coefficients. Unfortunately, previous research did not show generally how to determine this parameter. We present general theoretical considerations for its numerical noniterative determination. This general theory is applied to an important class of attrition-rate coefficients (offset power-rate coefficients). Our results allow one to study such variable-coefficient combat models almost as easily and thoroughly as Lanchester's classic constant-coefficient model.     

Winter Temperature Structure in Lake Huron

Water temperatures at depths 15, 25, and 50 m below the surface and 2 m above the bottom were continuously recorded at 17 mooring sites in Lake Huron during the 1974–75 winter. Monthly isotherm patterns show that the shore regions rapidly cooled to near 0° C by early February, while the deep northern basin reached a minimum of 1.5° C in mid-April. The initial stages of the fall overturn at depths greater than 100 m exhibited temperature fluctuations due to wind mixing and advection. By mid- to late December, Lake Huron was isothermal at all recording stations and remained so through April, except in the deep basins where a weak winter thermocline developed in March.     

Response productivity: A methodological problem in content analysis studies in psychotherapy.

Contends that most content analysts of psychotherapy materials have failed to consider the possibility that the frequency of units coded to the categories of the content analysis system might be correlated with the total number of units produced. The existence of such relationships may confound interpretation of the association between content analysis variables and other external variables. When investigators have attempted to control for response productivity, they have usually divided the frequency of units in each category by the total number of units. This procedure does not control for response productivity and is often uninterpretable. The issues involved are discussed and demonstrated, and appropriate techniques of controlling for productivity are described. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intermittent Occlusion System

A deformable cuff attached to a hydraulic activating mechanism provides a system suitable for intermittently occluding a collapsible tubular structure. When the apparatus in the system is constructed of materials such as silicon rubber and stainless steel, the system is chronically implantable. The system is designed so that it can be externally controlled after implantation.