Carbide Coatings on Graphite Fibers by Liquid Metal Transfer Agent Method

Titanium and zirconium carbide layers were produced on the surface of graphite fibers. The process allows a controlled reaction of the fibers with the carbide-forming elements dissolved hi a molten tin bath, which acts as the transferring medium. The coatings were analyzed by optical and scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction. It was found that they consist of two distinct layers, one with the binary carbide composition in contact with the fiber core and an exterior one having a ternary carbide composition. The coatings are brittle, continuous, and uniform along and across the fibers and show good adherence to the carbon core. The carbide growth process is diffusion-controlled with an activation energy of 184 kJ/mol. The coated fibers are readily wetted by molten aluminum.     

Microwave assisted synthesis of poly(2-hydroxyethylmethacrylate) grafted agar (Ag-g-P(HEMA)) and its application as a flocculant for wastewater treatment

Poly(2-hydroxyethylmethacrylate) chains were grafted onto the backbone of agar using a microwave assisted method involving a combination of microwave irradiation and ceric ammonium nitrate to initiate the grafting reaction. The synthesized graft copolymers were characterized by intrinsic viscosity measurements, Fourier transform infrared spectroscopy, elemental analysis (C, H, N, O and S) and scanning electron microscopy. Ag-g-P(HEMA)-2 showed a much higher flocculation efficacy than agar. The optimized dosage of flocculation for Ag-g-P(HEMA)-2 in the wastewater was found to be 0.75 ppm. Compared to agar, Ag-g-P(HEMA)-2 was found to considerably reduce the pollutant load in the wastewater.     

MEASUREMENT AND CONTROL OF ELECTROSTATIC CHARGES ON PULVERIZED COAL IN A PNEUMATIC PIPELINE∗

Abstract

Pulverized coal particles flowing in a pneumatic pipeline are naturally charged to a detectable level due to collisions with pipe walls. Systematic charge measurements of Anthracite (AN) coals, Medium Volatile Bituminous (MVB) coals and Lignite A (LIGA) coals in a grounded copper pipe have been made with an upgraded charge measuring system. The net particle charges were found to be positive, although both negative and positive charges were detected in all experiments. Effects of air humidity and conveying velocity on particle charges were examined. The mean particle charge was found in the order of 10^?12 Coulomb and the charge-to-mass ratio in the order of 10^?5 C/kg. Charge elimination techniques by strict humidity control and by introducing neutralizing charge carriers, such as minus 1 μm activated charcoal fines, ammonia, and piezoelectric ionized gas were explored. Effective reduction of 70 % to 85 % of particle charges was achieved. A charge neutralization mechanism was proposed to interpretate the measured results.     

Mobility,lifetime and diffusion length in polycrystalline materials

Theoretical investigations of the influence of grain size on mobility, lifetime and diffusion length in a polycrystalline material are made. it is found that the variation of diffusion length with grain size can be accounted for if the dependence of mobility and lifetime on grain size are considered. The calculations reasonably represent the experimentally observed variations of diffusion lengths with grain size.     

Radiometric studies of transportation of water vapour over Calcutta

A characteristic feature of the lingering of post-rain attenuation over Calcutta, India, has been observed by 22·235 GH_z radiometer. This feature is presumably due to the injection of extra water vapour during the post-rain period in the presence of large ambient humidity and low wind activity. Experimentally observed post-rain attenuation was found to be mostly due to the vertical diffusion of water vapour into the raining zone, the contribution due to horizontal diffusion being small compared to that of the vertical diffusion.     

Optimum harvesting policy for an age-structured forest

In this paper, an attempt has been made to develop a model for determining the optimal policy for felling and planting trees of a particular species in a forest, in order to maximize the total yield over a specified period of time. The model takes into account not only the time at which trees should be felled but also how many trees and of what age.     

Minimization of interfaces and interconnections in a digital system satisfying concurrency constraints

The problem of minimizing the number of links and buses in a digital system subject to a given set of concurrency constraints among data transfers is studied. The notion of the transfer graph (TG) is introduced which depicts the data transfer paths and concurrency requirements in the system, A very simple node labelling procedure is applied on the nodes of the TG, which enables one to make a direct assignment of transfers to buses without going through any elaborate computational steps.     

国产加工中心故障模式及影响分析(FMEA)

应用FMEA法对国产VMC系列加工中心进行故障分析.查清整机各故障部位、故障模式的比率,找到可靠性薄弱环节,并把故障分析的结果反馈给设计、制造、装配等部门,从各方面采取措施,明显提高了VMC加工中心产品的可靠性水平.     

INTERACTION OF GRAVITY AND ELECTROSTATIC EFFECTS IN PIPE FLOW OF A GAS-PARTICLE SUSPENSION

ABSTRACT

The interaction of gravity and electrostatic effects in isothermal, fully developed, horizontal turbulent pipe flow of dilute suspensions has been examined. Experimental study has validated the fact that, in the presence of gravity, increased space charge associated with increased local concentration due to gravity accentuates the asymmetry in mass flux and particles density distributions in the vertical plane passing through the pipe centerline. The space charge effect on the particle mass flux distribution near the pipe bottom is enhanced by increased particle density. Measurements were made with air suspensions of monodispensed particles of alumina and latex with non-uniform particle charge in pipes of 51 mm and 127 mm diameters.