An APL implementation of level 2 core graphics system

The graphics community is recently taking a close look at graphics standardization prompted by issues such as portability of software, application program structure, diverse hardware, etc. Through these efforts, the Graphic Standards Planning Committee of ACM/SIGGRAPH has proposed a standard. This standard advocates four levels of the Core system, namely basic, buffered, interactive and complete. This paper describes a Level 2 (i.e. buffered) implementation of the Core system in APL, referred to as 0SCUBA (APL BUffered Core System). The details of the structure and organization of 0SCUBA are given. The implementation is highly modular in nature, provides both two and three dimensional capabilities with several types of projective transformations and supports full segmentation capabilities. Several examples illustrating the use of the system are included. The interactive nature of APL is found to be attractive. Some deviations from the Core system have been incorporated. These include a modular hardcopy interface to produce graphics on plotters etc. and a facility to retain world coordinates of the objects. The system, though appearing to be satisfactory, has to undergo further testing to gain user confidence.     

A new method for nuclear ADCs using the vernier approximation technique

The paper describes a new method of analog-to-digital conversion. The method named the vernier approximation technique utilizes two scales made of chains of resistors sliding over each other, one being called the main scale and the other the vernier scale. The vernier scale is moved by applying the input analog voltage as a voltage shift at both ends. This voltage shift is digitized using the comparators connected between the corresponding points on main and vernier scales. All the quantization steps are derived from a single quantization step using the process of sliding and vernier scaling resulting in high differential linearity. The scheme uses a balancing technique to balance the points on the main scale with the corresponding points on the vernier scale. The scheme works with the speed of a “sequential parallel approximation technique” giving a higher speed of operation than either the Wilkinson technique or the successive approximation technique used for nuclear ADCs. The technique gives high accuracy even with use of ordinary components such as 1% resistors.     

Impact of load on winding inductances of permanent magnetgenerators with multiple damping circuits using energy perturbation

A computer-aided method for determining the impact of load on winding inductances and other machine parameters of permanent magnet generators with multiple damping circuits is presented. The method is general in nature so that it can be applied to detailed computer-aided design processes of permanent magnet generator systems. The method is based on use of the abc frame of reference for development of the necessary state equations     

Novel Process for the Preparation of Fiber-Reinforced Ceramic-Matrix Composites

A procedure for the reproducible production of monofilament/powder composites has been developed. The process consists of making a slurry of the powder in a solventless ultraviolet-curing resin, and coating the fiber with this slurry in a continuous process whereby the coating solidifies immediately after leaving the coater. The fast curing prevents the breakup of coating into globules, which usually occurs with monofilaments. This technique can be applied to any composite using continuous filaments and matrices available in the form of particulate precursors. The application of the technique for preparing a silicon carbide monofilament/glass composite is demonstrated.     

Scanner design

The scanner is a subroutine which is frequently called by an application program like a compiler. The primary function of a scanner is to combine characters from the input stream into recognizable units called tokens. A method has been presented in this paper for designing such a scanner, also frequently referred to as a lexical analyser in the current literature. The major steps involved in this design process are: identification of tokens, construction of a state diagram, building driver tables and finally writing a scanning routine. The rules for generating the driver tables are described and an algorithm for the scanner, utilizing these driver tables, is included. The method has been successfully used to build the system scanner for a user oriented plotting language. It is concluded that the method is well defined, gives rise to a modular design and as such easily lends itself to language extensions.     

Immunological properties of human decidual macrophages--a possible role in intrauterine immunity

Our aim was to investigate the contribution of decidual macrophages, which constitute an important immune component of the decidua in late gestation, to intrauterine defence mechanisms. Using flow cytometry we examined the ability of decidual macrophages, isolated from term decidua, to bind and phagocytose fluorescence-labelled bacterial and yeast bioparticles. We also assessed their ability to generate superoxide radicals and tumour necrosis factor-alpha following lipopolysaccharide challenge. Decidual macrophages bound bacterial and yeast particles in a dose-dependent manner, which subsequently led to phagocytosis. These macrophages also produced superoxide radicals and the pro-inflammatory cytokine TNF-alpha when challenged with bacterial lipopolysaccharides. These results suggest a role for decidual macrophages in pathogen recognition and clearance during pregnancy, and, therefore, they are likely to protect the fetus against intrauterine infections which might otherwise lead to preterm labour.     

The kinetics of the gaseous extraction of gallium from mica

The gaseous reduction of gallium in white mica has been studied using natural gas as the reducing gas. From a study at three temperatures, the initial extraction was observed to be linear with time and independent of particle size. The results suggest that delamination of the mica lattice is important. The measured activation energy for the loss of gallium from the white mica is 184 × 21 kJ mol^?1.     

Ageing response and mechanical properties of a SiCp/Al-Li (8090) composite

The ageing kinetics of a silicon carbide particle-reinforced Al-Li (8090) matrix composite and unreinforced alloy, both made by spray forming, were investigated. Ageing treatments, without any straining after solutionizing, and with a 2% plastic strain after solutionizing, were employed. The peak ageing times of the matrix in the composite was shorter than that of the unreinforced alloy. The enhanced hardening rate of the matrix in the composite was attributed to the higher dislocation density induced as a result of the plastic deformation occurring at the particle/matrix interface. This plastic deformation is a result of the large difference in the coefficient of thermal expansion between the particles and matrix. Subjecting the samples to a 2% plastic strain reduced the peak ageing times even further. The tensile strength of the composite samples was marginally higher than that of the unreinforced alloy. Samples subjected to 2% plastic straining prior to ageing also exhibited higher strength values. The strain to failure of all the samples did not recover in the over-aged state.