Solid-liquid phase equilibria of benzene + 2-methyl-2-propanol system under high pressures

Solid-liquid phase equilibria of the benzene + 2-methyl-2-propanol system have been investigated at temperatures from 278 to 323 K and pressures up to 300 MPa using a high-pressure optical vessel. The uncertainties of the measurements of temperature, pressure and composition are within ±0.1 K, ±0.5 MPa, and ±0.001 mole fraction, respectively. The freezing pressure at a constant composition increases monotonously with pressure. The eutectic point shifts to a higher temperature and benzene-rich composition with increasing pressure. In order to describe the pressure-temperature-composition relation of high-pressure solid-liquid phase equilibria, a new simple equation has been proposed as follows:

Experimental determination of dynamic Young's modulus and mechanical damping,and theoretical prediction of dislocation density for depleted uranium-0.75 wt% titanium using the PUCOT

Dynamic Young's modulus (E) and mechanical damping (Q ^–1) measurements were made for three microstructures (, + , and ) of a depleted uranium-0.75 wt% titanium alloy. The temperature range covered was 298 to 1123 K. The apparatus was the piezoelectric ultrasonic composite oscillator technique (PUCOT) operated at 80 kHz. The ranges of values for E and Q ^–1 were 193 to 99 GPa and 3×10^–3 to 8×10^–2, respectively. Correlations for E of each heat treatment as functions of temperature are presented. In addition, the mechanical damping against strain amplitude plots generated from PUCOT data were analysed using the Granato-Luecke zero Kelvin and high-temperature theories of dislocation damping. Computed dislocation densities ranged up to 10¹⁶m^–2.     

Thin-film ferroelectrics of PZT of sol-gel processing

The ferroelectric effect has been demonstrated for sol-gel derived lead zirconate titanate (PZT) (53/47) thin films. The respective values of coercive field and remanent polarization were 4x10(6) V/m and 0.36 C/m(2). The thin-film fabrication process is simple and compatible with Si planar technology, and offers a wide variety of potential uses for counting, memory, and integrated optical circuit applications.     

On finding optimal and near-optimal lineal spanning trees

The search for good lineal, or depth-first, spanning trees is an important aspect in the implementation of a wide assortment of graph algorithms. We consider the complexity of findingoptimal lineal spanning trees under various notions of optimality. In particular, we show that several natural problems, such as constructing a shortest or a tallest lineal tree, are NP-hard. We also address the issue of polynomial-time, near-optimization strategies for these difficult problems, showing that efficient absolute approximation algorithms cannot exist unlessP = NP.     

The incorporation of yield surface distortion into a unified constitutive model,part 2: Predictive capabilities

Summary The MATMOD-4V-DISTORTION model has been derived [1] with the intent of improving the MATMOD-4V model by adding the capability to predict distortions of small strain offset yield surfaces. This model is compared against a variety of experimental data to verify its behavior. Model simulations are compared with experimental data for proportional and nonproportional prestress histories and the effect of yield definition is also investigated. Finally, the same model which predicts a flattening of the yield surface in space is used to predict a rotation of the yield surface in ₁-₂ coordinates.With 9 Figures     

FTIR investigation of ethylene coordination and polymerization on reduced Cr/SiO2 catalyst

FTIR spectroscopy was applied to study the initial steps of ethylene polymerization on reduced chromia-silica (0.5 wt% Cr/SiO₂). To decrease the speed of the reaction small doses of gas were introduced to the catalyst in each run and C₂D₄ was used to confirm band assignments. At the initial steps of the reaction only ethylene molecules coordinated to probably Cr _A ²⁺ cations were observed. The concentration of such complexes was estimated to be about 50% of the total amount of Cr atoms in the sample. The FTIR spectrum of the polymer formed at the initial doses of C₂H₄ (when [C₂H₄] [Cr]) was found to be slightly different from that formed after excess ethylene was introduced onto the catalyst ([C₂H₄] > [Cr]).     

Goodwin House, a place for healing

The following report is excerpted from a senior thesis project prepared by Kirstin Shank. For her thesis, Shank produced an exceptionally thorough and thoughtful proposal for a home for people living with AIDS and HIV. The specifics of her plan may not be easily translated for all such centers, but her holistic approach to designing a therapeutic environment can indeed serve as a models for designers across the country grappling with similar challenges.     

Synthesis of ceramic membranes

Non-supported -alumina films are prepared from a boehmite colloidal suspension. After calcination at 600°C, the microstructure is characterized by a mean pore diameter of 3 nm, a porosity of 50% and a tortuosity of 5.5. The structure is formed by card packed, plate-shaped particles, giving rise to slit-shaped pores. Supported -alumina films, made by a slipcasting process using the same boehmite precursor, have a similar structure as the non-supported films. The slipcasting process is very sensitive to support characteristics and frequently yields defect films. Polyvinylalcohol (PVA) (molecular weight 72000 g mol^–1) is added to the boehmite precursor (0.25 gg^–1 film) to improve this process. This addition results in a less critical and better controllable drying and calcining procedure. The addition of PVA is necessary to slipcast defect free -alumina films on supports with pore diameters of 0.4 m or smaller and on multi-layer supports. It has no significant effect on the resultant microstructure of the -alumina film, provided all PVA is removed by appropriate thermal treatment. The slipcasting rate is slower, resulting in thinner films of 3–5 m at identical slipcasting times.