Analysis of hydrofilm extrusion of elliptic shapes using perturbation method

An approximate method of solution is proposed for the hydrofilm extrusion of elliptic shapes from round billets through optimized curved dies. A modified upper-bound theorem and hydrodynamic lubrication theory are used in combination, in order to analyze metal deformation and fluid flow respectively. The fluid analysis in hydrodynamic lubrication theory is simplified by use of elliptic transformation and perturbation technique. Strain-hardening effect of billet material and viscosity variation of fluid due to pressure are taken into consideration.For several reductions of area, experiments are carried out at room temperature by using mild steel specimens and caster oil as the lubricant.The experimental extrusion pressures are in good agreement with the theoretical predictions.     

Epitaxy of silicon doped gallium arsenide by molecular beam method

The molecular beam method is a versatile experimental technique which may be used to grow high quality single crystal thin films in the range from 100Å to several microns with precise control of uniformity and thickness. Films may be doped by an additional molecular beam containing the doping material simultaneously impinging on the substrate surface with the film molecular beams. Epitaxial GaAs thin films doped with silicon were grown by the molecular beam method in an ultrahigh vacuum system in which high energy electron diffraction and mass spectrometric measurements could be made during growth or by stopping growth momentarily. The crystallinity and beam intensity parameters of these films were thus studied during growth. The doping profiles and the amount of compensation were evaluated by the Schottky barrier diode method and the photo luminescence spectra.     

Static and Dynamic Equalization of the L5 Repeatered Line

The residual transmission deviation of the L5 repeatered line can be divided into two categories, static or time invariant and dynamic or time variant. The static deviation, which is due to design limitations and manufacturing deviations of the basic and regulating repeaters, is compensated for by manually adjustable equalizers designatedE1andE2. These equalizers are composed of 28 Bode bump networks whose gains are adjusted to minimize the total mean-squared error of the transmission channel. The residual dynamic transmission deviation, caused by temperature variations of the basic and regulating repeaters, is corrected continuously by an automatic equalizerE3. The time-varying transmission deviations are detected by four pilot tones spaced across the L5 frequency spectrum. Four electronically controlled networks in the equalizer respond to the pilots to correct the dynamic transmission deviations.     

Phase extraction from a single fringe pattern based on guidance of an extreme map

A method for automatic phase extraction from a single fringe pattern based on the guidance of an extreme map is introduced. The method uses an adaptive weighted filter to reduce noise and enhance contrast and to locate the fringe extremes. Wrapped phase values are calculated by use of an arccosine function obtained from the extreme map. With this method, wrapped phase values can be efficiently demodulated from a single fringe pattern without the need for assigning fringe order or interpolating fractional fringe order. The validity of the method is demonstrated by use of closed-fringe patterns generated by digital speckle interferometry.     

Water-soluble binder with high flexural modulus for powder injection molding

A new binder system, containing ternary polymer blends of poly(methyl methacrylate) (PMMA), cellulose acetate butyrate (CAB) and polyethylene glycol (PEG), was introduced for the powder injection molding of stainless steel powders. The weight fraction of PEG in the binder was maintained to be 0.65. When the weight fraction of PMMA in the binder was 0.1–0.25 (thus the weight fraction of CAB was 0.1–0.25), the feedstocks with 56 vol% of steel powders were successfully injection molded without showing any jetting. Furthermore, the feedstocks have much higher flexural modulus compared with those prepared by a binder consisting only 35/65 (wt/wt) CAB/PEG blend. Three binary blends, PMMA/CAB, PMMA/PEG, and CAB/PEG, were completely miscible at an injection molding temperature of 130^°C. The extraction process employed in this study becomes environmentally favorable due to the major component (PEG) of the binder which is easily extracted by a solvent of water or ethanol. Also, the shape maintenance during the solvent extraction was excellent, and final sintered parts had excellent dimensional stability. Due to high flexural modulus of feedstocks, this binder system can be employed for preparing large sized injection-mold articles.     

Roughening transition of grain boundaries in metals and oxides

Extensive theoretical analysis and experimental observations show surface roughening transitions of crystals. The surface roughening is characterized by step free energy, which gradually decreases to 0 at the roughening transition temperature. For a crystal of finite size, the surface roughening transition is manifested by gradual increase of the curved edge and corner areas. In alloys, the interfaces between the solid and the liquid phases can be either singular, partially rough, or completely rough at different temperatures. Their thermally induced roughening transitions are similar to those of the solid-vapor interfaces. The interface roughening and the reverse transition to singular structures can also be induced by additives. The grain boundaries of any misorientation angles in oxides and metals also show roughening transitions. The singular grain boundaries have either flat, hill-and-valley, or kinked shapes, and with temperature increase or composition changes, they become defaceted to curved shapes. These defaceted grain boundaries are rough. It is thus possible to produce either singular or rough grain boundaries by heat-treatment or additives to vary their properties.     

An enzyme immunoanalytical system based on sequential cross-flow chromatography

A new enzyme immunoanalytical concept that can be used for point-of-care testing has been investigated. Enzyme as a tracer requires a separate reaction step for signal generation, which follows the completion of immune complex formation with analyte (e.g., Hepatitis B surface antigen) in a sample. This has been a major factor limiting its utilization within the laboratory. We carried out such sequential processes employing chromatographic analysis, using two crosswise-arranged membrane pads in vertical and horizontal directions. The vertically arranged pads were the same as those in the usual format for pregnancy testing, for instance, with the exception of the use of horseradish peroxidase (HRP) as tracer. By placing the horizontally arranged pads on each lateral side of the signal generation pad in the vertical arrangement, they were employed to supply substrate to the enzyme present in the immune complexes. The substrate flow was initiated after the antigen-antibody bindings to produce a signal, which was typically a color change in proportion to the analyte concentration. Under optimal conditions, the use of HRP labeling increased the detection capability of the assay approximately 30 times compared to that of gold colloids. Potential advantages of using the concept investigated are (1) provision of a rapid and simple immunoassay, (2) satisfaction of a clinical need for highly sensitive determination of analyte, and (3) utilization of relatively inexpensive, portable quantitation means.     

Surface profiling of a transparent object by use of phase-shifting Talbot interferometry

Talbot interferometry is used to study the surface profile of a transparent object. Periodic patterns are produced by illuminating a grating with a collimated laser beam. The object is placed on the self-image plane of the grating. The deformed grating image, which interferes with another grating, results in the Talbot interferometric fringes. The fringe pattern is recorded on a CCD camera for subsequent analysis, and the phase variation is achieved by a linear translation stage. In this application two specimens are tested to demonstrate the validity of the method; one is a transparent object with a spherical shape with a height of less than 350 microm, and the other is a transparent object with an uneven surface of 50-microm average height. The experimental results are compared with the test results obtained with the mechanical stylus method.