A new chip-thickness model for performance assessment of silicon carbide grinding

The chip-thickness models, used to assess the performance of grinding processes, play a major role in predicting the surface quality. In the present paper, an attempt has been made to develop a new chip-thickness model for the performance assessment of silicon carbide grinding by incorporating the modulus of elasticities of the grinding wheel and the workpiece in the existing basic chip-thickness model to account for elastic deformation. The new model has been validated by conducting experiments, taking the surface roughness as a parameter of evaluation .     

Room temperature synthesis of crystalline metal oxides

Crystalline titanium dioxide powders have been synthesized as either rutile or anatase from aqueous solutions at low temperatures (T≤100°C) and atmospheric pressure. First, a sol is prepared by the hydrolysis of a titanium alkoxide in an acidic solution. The sol is subsequently heated at different rates to produce the different crystalline phases of titanium dioxide. Powder characterization was carried out using X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy. In general, the precipitate size was observed to be between 50 and 100 nm. Possible mechanisms involved in determining the crystal variants are discussed. This revised version was published online in November 2006 with corrections to the Cover Date.     

Countercurrent water-heating system with a heat exchanger in a solar energy collector loop

The counter current heat exchanger theory with periodic inlet temperatures has been applied to analyze the thermal performance of a water heating system. The theoretical results obtained are in agreement with the experimental data reported in the literature.     

A scheduling decision aid in glass fiber manufacturing

A decision aid for scheduling production in glass fiber manufacturing industry is described. The methodology combines a linear programming (LP) optimization model with a heuristic model. The LP model determines production goals; the heuristic model then uses the LP output to incorporate system-specific constraints in developing processing sequences.     

The GEM MAP algorithm with 3-D SPECT system response

In single photon emission computed tomography (SPECT), every reconstruction algorithm must use some model for the response of the gamma camera to emitted gamma-rays. The true camera response is both spatially variant and object dependent. These two properties result from the effects of scatter, septal penetration, and attenuation, and they forestall determination of the true response with any precision. This motivates the investigation of the performance of reconstruction algorithms when there are errors between the camera response used in the reconstruction algorithm and the true response of the gamma camera. In this regard, the authors compare the filtered backprojection algorithm, the expectation-maximization maximum likelihood algorithm, and the generalized expectation maximization (GEM) maximum a posteriori (MAP) algorithm, a Bayesian algorithm which uses a Markov random field prior.     

Water table fluctuation with a random initial condition

The nonlinear Boussinesq equation is used to understand water table fluctuations in various ditch drainage problems. An approximate solution of this equation with a random initial condition and deterministic boundary conditions, recharge rate and aquifer parameters has been developed to predict a transient water table in a ditch-drainage system. The effects of uncertainty in the initial condition on the water table are illustrated with the help of a synthetic example. These results would find applications in ditch-drainage design.Notation A / tanh t - a lower value of the random variable representing the initial water table height at the mid point - a+b Upper value of the random variable representing the initial water table height at the midpoint - B tanh t - C 4/ - h variable water table height - h mean of the variable water table height - h _m variable water table height at the mid point - h _m mean of the variable water table height at the mid point - K hydraulic conductivity - L half spacing between the ditches - m ₀ initial water table height at the mid point - N Uniform rate of recharge - S specific yield - t time of observation - x distance measured from the ditch boundary - (4/SL)(NK)^1/2 - (L/4)(N/K)^1/2 - dummy integral variable     

Possibility of superconductivity with highT c in La-Sr-Nb-O system

We prepared La-Sr-Nb-O system samples both in bulk form and as a film, with sharp resistive transitions at temperatures of 228–323 K, depending on the annealing conditions. The sharp resistive transitions might be attributable to superconductivity. Magnetic ordering was observed over a narrow temperature range around 40 K for some of the samples.