Effect of temperature and cyclic heating on the structure and strength of glass textolite

The article established the regularities of change of the physicomechanical characteristics and strength of glass textolites in single and repeated thermal loading. It shows that under multiple loading the intense loss of strength of the investigated materials is due to increased porosity on account of the large number of microcracks appearing in the structure. A correlation is obtained between the elastic and strength characteristics and porosity in dependence on the temperature of multiple heating which in the first approximation is described by a polynomial of second degree with respect to temperature, multiplied by the reciprocal of porosity.Translated from Problemy Prochnosti, No. 6, pp. 53–58, June, 1991.     

Comfort limits for asymmetric thermal radiation

Groups of 32 and 16 subjects of both sexes were exposed in an environmental chamber to radiant asymmetry caused by a cool wall, a warm wall, and a cool ceiling. Each subject was tested individually while seated and clothed at 0.6 clo. During each 3.5-hour experiment the subject was exposed to six radiant temperature asymmetries. He was asked whether and where he experienced any local cool or warm sensation, and whether it was felt to be uncomfortable. During the entire experiment he was kept thermally neutral by changing the air temperature according to his wishes.For cool walls, warm walls, and cool ceilings curves have been established showing the percentage of dissatisfied subjects as a function of the radiant asymmetry. Radiant asymmetry at a warm wall caused less discomfort than a cool wall. A cool ceiling caused less discomfort than a warm ceiling. Accepting that 5% of the subjects may feel uncomfortable. a radiant temperature asymmetry of 10°C is allowable at a cool wall, 23°C at a warm wall, and 14°C under a cool ceiling. A previous study showed that 4°C is allowable under a warm ceiling. Radiant asymmetry had no significant impact on the operative temperatures preferred by the subjects. No significant differences were observed between the responses of men and women exposed to radiant asymmetry.     

Determination of precompression and compression force levels to minimize tablet friability using simplex

Pilot simplex experiments for improving the tablet strength of three aspirin tablet formulations based on precompression and compression forces were presented. As each simplex moved towards the direction of the optimum, the friability was being minimized and the crushing strength was concomittantly being maximized. Because it followed a systematic direction, simplex process would locate a local optimum rapidly. The appropriate levels of precompression and compression forces that produced tablets with the desired strength were attained in five trials. By contrast, random search for this force combination required at least ten trials. Simplex technique is a cost and time effective means for determining the precompression and compression forces that will reduce the friability or increase the hardness of a tablet formulation. Results appeared to also indicate that crushing strength might be a more reliable measure of tablet strength than friability.     

Criteria for evaluation of the hardening factor of machine parts

V. Ya. Chubar' Zaporozhe Machine Building Institute. Translated from Problemy Prochnosti, No. 3, pp. 62–65, March, 1989.     

Experimental abatement data of underflow baffles for removal of floatables in the CSOs of the Greater Montréal (Canada) area.

Underflow baffles have gained in popularity over the years as a viable mean to intercept floatables in Combined Sewer Overflows (CSOs). This choice was mainly justified by the extremely low capital cost (CAPEX) and operational cost (OPEX) of this solution, although the efficiency of underflow baffles has never been clearly proven. The only similar application to underflow baffles are scum boards in grit chambers and clarifier. However, the flow conditions at CSOs vary considerably from those in grit chambers and clarifier. For this reason, review of the behavior of floatables in a rapid flow is paramount. Only then can comprehensive design criteria for underflow baffles and overflow chambers be suggested. Pilot scale tests, performed in a 17 metres long basin at various flowrates, had already shown that a critical horizontal velocity for floatables (Vcr) may develop in the overflow chambers. In this follow up study, the fate of intercepted floatables was investigated. It appears from this latest data that permanent capture of floatables decreases rapidly with an increase in the horizontal velocity of the flow, no matter what the baffle depth. Baffle depth increases capture at lower velocities (0.17 m/s) but become irrelevant at higher velocities (0.61 m/s). This data suggests that capture efficiency of existing underflow baffles in overflow chambers can be, at best, very low whenever the horizontal velocity increases above 0.30 m/s or 1 ft/s.     

Indoor body-area channel model for narrowband communications

Using wireless sensors placed on a person to continuously monitor health information is a promising new application. At the same time, new low-power wireless standards such as Bluetooth and Zigbee have been proposed for short range, low data-rate communication matching the requirements of these bio-medical applications. However, there are currently few measurements or models describing propagation around the body. To address this problem, electromagnetic waves near the torso are measured and a statistical model is derived for communication in the 915 MHz and 2.45 GHz industrial, scientific and medical bands associated with Zigbee and Bluetooth. Measurement setup and statistical analysis are described.     

Finite element analysis of helicoidal waveguides

The purpose of the paper is to propose an efficient method to compute propagation modes in helicoidal waveguides. An helicoidal system of co-ordinates is introduced to define the structure and to set up the problem. These co-ordinates, albeit non-orthogonal, preserve the translational invariance in a way that allows a two-dimensional finite element model similar to that of classical straight waveguides     

Pesticide monitoring programme of the Ministry of Health of Brazil

The structure of the recently introduced Brazilian government programme for monitoring pesticide residues in six major agricultural products is described. Residues found from the analysis of samples of tomatoes and strawberries are discussed in detail. The much greater frequency of detection of pesticide residues, many of which are not approved for use in Brazil, in produce being sold on the domestic market, as opposed to that produced for export, is of major concern. It is perceived that this new monitoring programme will become permanent and be used to underpin enforcement actions that will need to be taken to reduce the numbers of incidents of illegal residues occurring, particularly in fresh fruits and vegetables.     

Surface barrier diode based on zinc selenide with a passivating zinc oxide film

We propose a method of fabricating surface barrier diodes with overlapped metal junction, which provides for a significant decrease in the reverse currents and an increase in the breakdown voltage.