Tensile,creep, and low-cycle fatigue behavior of a cast γ-TiAl-based alloy for gas turbine applications

The influence of chemical composition on the microstructure of the γ-titanium aluminide alloy Ti-48Al-2W-0.5Si (at. pct) and the accompanying tensile, low-cycle fatigue, and creep properties has been evaluated. The study showed that small variations in chemical composition and casting procedures resulted in considerable variations in the microstructure, yielding vastly different mechanical properties. Low contents of aluminum and tungsten led to a coarse-grained lamellar (γ/α ₂) microstructure with high creep resistance. A composition close to the nominal one produced a duplex (γ+γ/α ₂) structure with favorable strength, ductility, and low-cycle fatigue properties. By controlling the solidification and cooling rates at casting, a pseudoduplex (PS-DP) microstructure with a unique combination of high strength and high fatigue and creep resistance can be obtained. These unique properties can be explained by the diffuse boundaries between the relatively small γ grains and the neighboring lamellar colonies, combined with semicoherent interfaces between the γ and α ₂ phases. At tensile and low-cycle fatigue loading, these boundaries act like high-angle boundaries, producing a virtually fine-grained material promoting strength, whereas at creep loading, grain-boundary sliding is hindered in the semicoherent interfaces leading to high creep resistance.     

Influence of wettability on the properties of thin porous platinum films as gates of metal-oxide-semiconductor devices in electrolytes

Thin discontinuous (4 and 35 nm thick) platinum films were used as the gate metal of metal-oxide-semiconductor capacitors. It was observed that the metal film acts as a gas permeable structure in electrolyte solutions when the surface was hydrophobic and sufficiently rough. The probable explanation to this is that the electrolyte does not penetrate into the voids of the metal film. The geometry of the surface was investigated by transsion electron microscopy and profilometer measurements. Surfaces with different contact angles were studied in order to determine whether the electrolyte penetrates into the voids in the platinum film when the surface is sufficiently hydrophilic.     

Are weaning foods causing impaired iron and zinc status in 1-year-old Swedish infants? A cohort study

Retrobulbar hematoma is a rare complication of blunt periorbital trauma with the potential disastrous consequence of visual impairment and blindness. The preoperative assessment, diagnostic symptoms and signs, as well as the treatment of this condition are reviewed. The patients presented as well as a review of the literature confirm that although retrobulbar hematoma is a rare complication of blunt periorbital trauma, irreversible visual sequelae can be prevented by prompt diagnosis and immediate surgical and pharmacological therapy.     

A Maximum Likelihood Stereo Algorithm

A stereo algorithm is presented that optimizes a maximum likelihood cost function. The maximum likelihood cost function assumes that corresponding features in the left and right images are normally distributed about a common true value and consists of a weighted squared error term if two features are matched or a (fixed) cost if a feature is determined to be occluded. The stereo algorithm finds the set of correspondences that maximize the cost function subject to ordering and uniqueness constraints. The stereo algorithm is independent of the matching primitives. However, for the experiments described in this paper, matching is performed on the $cf4$individual pixel intensities.$cf3$ Contrary to popular belief, the pixel-based stereo appears to be robust for a variety of images. It also has the advantages of (i) providing adensedisparity map, (ii) requiringnofeature extraction, and (iii)avoidingthe adaptive windowing problem of area-based correlation methods. Because feature extraction and windowing are unnecessary, a very fast implementation is possible. Experimental results reveal that good stereo correspondences can be found using only ordering and uniqueness constraints, i.e., withoutlocalsmoothness constraints. However, it is shown that the original maximum likelihood stereo algorithm exhibits multiple global minima. The dynamic programming algorithm is guaranteed to find one, but not necessarily the same one for each epipolar scanline, causing erroneous correspondences which are visible as small local differences between neighboring scanlines. Traditionally, regularization, which modifies the original cost function, has been applied to the problem of multiple global minima. We developed several variants of the algorithm that avoid classical regularization while imposing several global cohesiveness constraints. We believe this is a novel approach that has the advantage of guaranteeing that solutions minimize the original cost function and preserve discontinuities. The constraints are based on minimizing the total number of horizontal and/or vertical discontinuities along and/or between adjacent epipolar lines, and local smoothing is avoided. Experiments reveal that minimizing the sum of the horizontal and vertical discontinuities provides the most accurate results. A high percentage of correct matches and very little smearing of depth discontinuities are obtained. An alternative to imposing cohesiveness constraints to reduce the correspondence ambiguities is to use more than two cameras. We therefore extend the two camera maximum likelihood toNcameras. TheN-camera stereo algorithm determines the “best” set of correspondences between a given pair of cameras, referred to as the principal cameras. Knowledge of the relative positions of the cameras allows the 3D point hypothesized by an assumed correspondence of two features in the principal pair to be projected onto the image plane of the remainingN− 2 cameras. TheseN− 2 points are then used to verify proposed matches. Not only does the algorithm explicitly model occlusion between features of the principal pair, but the possibility of occlusions in theN− 2 additional views is also modeled. Previous work did not model this occlusion process, the benefits and importance of which are experimentally verified. Like other multiframe stereo algorithms, the computational and memory costs of this approach increase linearly with each additional view. Experimental results are shown for two outdoor scenes. It is clearly demonstrated that the number of correspondence errors is significantly reduced as the number of views/cameras is increased.     

Variation in light scattering and water-holding capacity along the porcine Longissimus dorsi muscle

The meat quality of M. longissimus muscle was evaluated in 851 pigs by using the Fibre Optic Probe (FOP) at three sites in the muscle and in both halves of the carcass. A systematic difference between sites was found, with the lowest light scattering (indicating the best meat quality) in the mid-part of the muscle and higher light scattering in the anterior and posterior parts. A non-systematic variation was also observed, with the opposite pattern in some animals, even though it was not frequent. A negative influence of the shackling was found, yielding higher FOP values in the shackled half.

Drip loss measurements in the Longissimus muscle, taken from another 100 pig carcasses, were evaluated using three methods. Drip loss, too, showed a considerable variation along the Longissimus muscle, with minimum losses around the last rib. Repeatability estimates, calculated from two non-consecutive pieces of the Longissimus dorsi muscle from each carcass, varied from 0·4 when keeping samples vacuum packed for 2 days, to 0·5 when the samples were either kept in plain plastic bags for 2 days or in a meat container with a squared inset for 1 or 2 days.     

Lipase-catalyzed transesterification of phosphatidylcholine at controlled water activity

The incorporation of a free fatty acid into thesn-1 position of phosphatidylcholine by lipase-catalyzed transesterification was investigated. The thermodynamic water activity of both the enzyme preparation and the substrate solution was adjusted to the same value prior to the reaction. The reaction rate increased with increasing water activity but the yield of modified phosphatidylcholine decreased due to hydrolysis. By using a large excess of the free fatty acid (heptadecanoic acid), the hydrolysis reaction was slowed down, so a higher yield was obtained at a given degree of incorporation. The best results were obtained withRhizopus arrhizus lipase immobilized by adsorption on a polypropylene support. With this preparation, a yield of 60% and nearly 50% incorporation of heptadecanoic acid (100% incorporation in thesn-1 position) was obtained at a water activity of 0.064. The enzyme preparation had good operational stability and position specificity. Little incorporation (<1%) was observed in thesn-2 position, when almost all the fatty acid in thesn-1 position was exchanged.     

Quasi three-dimensional, n-bit optical memory based on the ellipsometric principle: model calculations

Model calculations on the ellipsometric memory are presented. The ellipsometric memory is an n-bit optical memory whose information is extracted by use of the ellipsometric principle. The memory cells of the device consist of thin-film multilayer structures, and the information of each memory cell is contained in the optical properties of the thin films. Several thin-film multilayer structures were examined in order to find out how different choices of layer materials and other system parameters such as layer thicknesses and wavelength affect resolutions and limitations of the ellipsometric memory. Such calculations are also useful for optimizing the readout resolution. It was found that it is possible to use memory cells having up to at least eight layers, which would permit 8-bit words to be stored at each location. It was also found that, in principle, several types of materials can be used as layer materials, and various aspects of different choices of materials are discussed.     

Determination of grain size and lattice distortions in ground YBa2Cu3O7

Grain size and lattice distortions as a function of milling time have been determined using X-ray peak broadening analysis and Brunauer-Emmett-Teller (BET) measurements. The grain size decreases from 0.22 m in unmilled samples to 0.06 m at 25 h milling time. Prolonged milling produced no further decrease of the grain size. The unmilled powder contained lattice distortions of 0.06%. During the first 25 h of milling only small changes of the lattice distortions occurred; longer milling times resulted in a rapid increase of the lattice distortions. At 47 h of milling, the lattice distortions had increased to about 0.11%. The results obtained by BET measurements agreed well with those obtained by X-ray analysis. No anisotropic grain size decrease was indicated during milling.     

A Soft,Fast and Versatile Electrohydraulic Gripper with Capacitive Object Size Detection

Soft robotic grippers achieve increased versatility and reduced complexity through intelligence embodied in their flexible and conformal structures. The most widely used soft grippers are pneumatically driven; they are simple and effective but require bulky air compressors that limit their application space and external sensors or computationally expensive vision systems for pick verification. In this study, a multi-material architecture for self-sensing electrohydraulic bending actuators is presented that enables a new class of highly versatile and reconfigurable soft grippers that are electrically driven and feature capacitive pick verification and object size detection. These electrohydraulic grippers are fast (step input results in finger closure in 50 ms), draw low power (6.5 mW per finger to hold grasp), and can pick a wide variety of objects with simple binary electrical control. Integrated high-voltage driving electronics are presented that greatly increase the application space of the grippers and make them readily compatible with commercially available robotic arms.     

Early Post Mortem pH decrease in porcine M. longissimus dorsi of PSE, Normal and DFD quality

The purpose of this investigation was to compare the muscle pH at exsanguination and the rate of pH changes in porcine M. longissimus dorsi (LD) of normal, DFD (Dark, Firm, Dry) and PSE (Pale, Soft, Exudative) quality. The pH was continuously measured in the LD in 116 carcasses during the first 50 min post mortem. Calculations were made both on measured pH-values and on pH-values transformed to hydrogen ion concentrations. A regression of pH or hydrogen ion concentration on time was made for each animal. These individual regressions were then combined, using a multivariate analysis to estimate regression curves for each meat quality class. The two methods for expressing pH gave somewhat different results. The relationship between the hydrogen ion concentration and time was found to be linear for normal and DFD muscles and quadratic for PSE muscles. As a consequence of the mathematical properties of pH, the relationship between pH and time was found to be quadratic for the normal and DFD qualities, and linear for the PSE quality. For both methods of calculations the slopes for the regression curves were significantly different between PSE and the other two quality classes with both calculating methods, while the slopes did not differ between normal and DFD muscle qualities. The intercepts of the regression curves differed significantly between PSE and the other two quality classes only when the calculations were made on measured pH-values without transformation. A temporary increase in pH was seen in some normal and PSE carcasses during the measured time period. Development of muscles with PSE characteristics thus seems to be initiated by a combination of a lower muscle-pH already at exsanguination and a faster pH decrease. It is also of importance to consider the special mathematical properties of the pH-value.