The volume integral method of eddy-current modeling: Verification

The volume integral method of eddy-current modeling represents a flaw in metal as a set of electric dipoles located within volume elements or cells defining the flaw volume. Given this dipole distribution, impedance changes may be computed. The electric field of the dipole distribution is determined by an integral equation relating, by means of the electric field Green's tensor, the electric field due to the source to the total electric field in the flaw. The integral equation is solved by assuming that the total electric field is constant in each volume element, resulting in a matrix equation. The method has been programmed for use on a microcomputer. The method and computer program are verified using the analytical solution for a small spherical flaw and three sets of measured impedance data, measured by air-core coils along profiles overlying both surface-breaking and buried simulated flaws of known dimensions. Operating frequencies ranged between 900 and 4000 Hz. Generally agreement is good at lower frequencies ( 1000 Hz). At higher frequencies ( 4000 Hz), the agreement is not as good. This is thought to be due to the inability of the constant electric field approximation to model the steep electric field gradients present in the host metal at high frequency. The results are also sensitive to the method of computation of the electric field due to the source. Some improvements can and should be made to the method.     

Attenuation of second sound in bulk flowing He II

New measurements of second sound attenuation in bulk flowing He II are reported which extend to a region of higher Reynolds number. An expression for the attenuation explicitly containing the quantum vortex line density is developed which allows comparison with vortex line density data taken by other means. A bellows driven experimental apparatus is used to produce bulk flow velocities of 0 to 1 m/sec in a channel of 4.064 mm square internal cross section. Second sound pulses are produced by applying a square voltage pulse 200 s width and variable height to a strain gauge heater. The second sound pulses are detected with thin film sensors mounted 56 and 119 mm downstream. The velocity-dependent attenuation, measured as a function of bulk flow velocity at 1.5, 1.8, and 2.0 K, is compared with data from other researchers. The attenuation, and thus the vortex line density, appears to follow a gradual transition from laminar to turbulent behavior. Current theories do not account for the presence of quantized vortices in bulk flowing He II, where (v _n–v _s), and thus do not explain the observed second sound attentuation in this regime.     

Higher-Order and Modal Logic as a Framework for Explanation-Based Generalization

Certain tasks, such as formal program development and theorem proving, fundamentally rely upon the manipulation of higher-order objects such as functions and predicates. Computing tools intended to assist in performing these tasks are at present inadequate in both the amount of knowledge they contain (i.e., the level of support they provide) and in their ability to learn (i.e., their capacity to enhance that support over time). The application of a relevant machine learning technique—explanation-based generalization (EBG)—has thus far been limited to first-order problem representations. We extend EBG to generalize higher-order values, thereby enabling its application to higher-order problem encodings.Logic programming provides a uniform framework in which all aspects of explanation-based generalization and learning may be defined and carried out. First-order Horn logics (e.g., Prolog) are not, however, well suited to higher-order applications. Instead, we employ Prolog, a higher-order logic programming language, as our basic framework for realizing higher-order EBG. In order to capture the distinction between domain theory and training instance upon which EBG relies, we extend Prolog with the necessity operator of modal logic. We develop a meta-interpreter realizing EBG for the extended language, Prolog, and provide examples of higher-order EBG.     

A Universal Method of Scientific Inquiry

A paradigm of scientific discovery is defined within a first-order logical framework. Within this paradigm, the concept of successful scientific inquiry is formalized and investigated. Among other results, it is shown that a simple method of scientific inquiry is universal in the sense that it leads to success on every problem for which success is in principle possible.     

A comparison of distribution and composition of intramuscular fat in Duroc Jersey and Hampshire pigs at 100 kg liveweight

The intramuscular fat content, its fatty acid composition and that from the triglyceride fraction, were determined in several muscles from the right sides of four Duroc Jersey and four Hampshire castrated male pigs slaughtered at 100 kg liveweight. The Hampshires had heavier muscles than the Duroc Jersey pigs, but did not show significant differences in the percentages of intramuscular fat. The concentrations of linoleic acid were, in general, higher in the Hampshire than in the Duroc Jersey pigs and in many muscles the differences were highly significant (p < 0·05) The concentrations of linoleic acid (18:2) in the triglyceride fraction did not differ among muscles within breeds but were higher in Hampshire than in Duroc Jersey pigs.     

Surface mass transport of alumina

The kinetics of thermal grooving at the intersection of rhombohedral twin boundaries with the \((10\bar 10)\) plane in aluminium oxide were measured from 1773 to 2273 K. Analysis of the data using the model of Mullins showed that surface diffusion was the dominant mechanism for mass transport. The results were compared with other similar published work on alumina, and the following equation for surface diffusion was determined: $$D_s (cm^2 sec^{ - 1} ) = 4.05 x 10^5 exp - (452kJ mol^{ - 1} /RT).$$      

Molecular Mechanisms Underlying the Beneficial Effects of Exercise on Brain Function and Neurological Disorders

As life expectancy has increased, particularly in developed countries, due to medical advances and increased prosperity, age-related neurological diseases and mental health disorders have become more prevalent health issues, reducing the well-being and quality of life of sufferers and their families. In recent decades, due to reduced work-related levels of physical activity, and key research insights, prescribing adequate exercise has become an innovative strategy to prevent or delay the onset of these pathologies and has been demonstrated to have therapeutic benefits when used as a sole or combination treatment. Recent evidence suggests that the beneficial effects of exercise on the brain are related to several underlying mechanisms related to muscle–brain, liver–brain and gut–brain crosstalk. Therefore, this review aims to summarize the most relevant current knowledge of the impact of exercise on mood disorders and neurodegenerative diseases, and to highlight the established and potential underlying mechanisms involved in exercise–brain communication and their benefits for physiology and brain function.     

Quantitative analysis of complex carbo-nitride precipitates in steels

Two new types of extraction replicas for precipitate analysis in steels have been developed. These replicas, based on alumina, allow accurate quantification of the carbon to nitrogen ratios in carbo-nitride precipitates using parallel electron energy loss spectroscopy in the TEM. Experiments on microalloyed steels show the importance of the nitrogen content in promoting precipitation even at low temperatures.     

SULFUR RECOVERY WITH REDUCED EMISSIONS, LOW CAPITAL INVESTMENT AND HYDROGEN CO-PRODUCTION

The main disadvantage of the Claus process is that by introducing air as oxidant a large volume of tail gas is produced. This must be treated to reduce atmospheric emissions of sulfur-containing gases. The costs of the tail-gas unit are a significant fraction of the total capital and operating costs for sulfur recovery. A new process uses thermal decomposition of hydrogen sulfide in the presence of carbon dioxide instead of air oxidation. The products of this reaction are hydrogen, carbon monoxide, elemental sulfur, water vapor and carbonyl sulfide. Carbonyl sulfide is easily converted to H₂S and C0₂ by liquid- or vapor-phase hydrolysis. Unreacted H₂S and C0₂ are recovered by absorption and recycled to the reactor. Since no air is introduced, there is no tail gas and the tail-gas unit is eliminated, giving a substantial reduction in capital investment. The concentrations of sulfur-containing gases in the product streams depend only on the operation of the absorber and stripper units and can be controlled to very low levels by increasing stripper boil-up. Process operating costs depend on the level of sulfur recovery required and can also be much lower than those of the modified Claus Process.

The process chemistry depends on a shift in the equilibrium of H₂S decomposition caused by reaction of hydrogen with C0₂ by the reverse of the water-gas-shift reaction. Catalysts for this chemistry have been identified. Reactor conversion is further improved by rapid cooling of the reactor effluent gas. Other aspects of process design and operation confer further advantages with respect to the Claus process; however, the process equipment used is similar to that used in a Claus plant. Retrofit of existing plant to the new technology can therefore be considered.     

Racking focus and tracking focus on live video streams: a stereo solution

The ability to produce dynamic Depth of Field effects in live video streams was until recently a quality unique to movie cameras. In this paper, we present a computational camera solution coupled with real-time GPU processing to produce runtime dynamic Depth of Field effects. We first construct a hybrid-resolution stereo camera with a high-res/low-res camera pair. We recover a low-res disparity map of the scene using GPU-based Belief Propagation, and subsequently upsample it via fast Cross/Joint Bilateral Upsampling. With the recovered high-resolution disparity map, we warp the high-resolution video stream to nearby viewpoints to synthesize a light field toward the scene. We exploit parallel processing and atomic operations on the GPU to resolve visibility when multiple pixels warp to the same image location. Finally, we generate racking focus and tracking focus effects from the synthesized light field rendering. All processing stages are mapped onto NVIDIA’s CUDA architecture. Our system can produce racking and tracking focus effects for the resolution of 640×480 at 15 fps.