Room temperature crack growth rates and -20 deg F fracture toughness of welded 1 1/4 inch A-285 steel plate

Data are presented which were developed in support of a structural assessment of NASA-LEWIS' 10-foot by 10-foot supersonic wind tunnel, critical portions of which are fabricated from rolled and welded 1 1/4 inch thick A-285 steel plate. Test material was flame cut from the tunnel wall and included longitudinal and circumferential weld joints. Parent metal, welds, and weld heat affected zone were tested. Tensile strength and fracture toughness were determined at -20 F, the estimated lowest tunnel operating temperature. Crack growth rates were measured at room temperature, where growth rates in service are expected to be highest

Generalized Hurst exponent and multifractal function of original and translated texts mapped into frequency and length time series

A nonlinear dynamics approach can be used in order to quantify complexity in written texts. As a first step, a one-dimensional system is examined : two written texts by one author (Lewis Carroll) are considered, together with one translation, into an artificial language, i.e. Esperanto are mapped into time series. Their corresponding shuffled versions are used for obtaining a "base line". Two different one-dimensional time series are used here: (i) one based on word lengths (LTS), (ii) the other on word frequencies (FTS). It is shown that the generalized Hurst exponent $h(q)$ and the derived $f(\alpha)$ curves of the original and translated texts show marked differences. The original "texts" are far from giving a parabolic $f(\alpha)$ function, - in contrast to the shuffled texts. Moreover, the Esperanto text has more extreme values. This suggests cascade model-like, with multiscale time asymmetric features as finally written texts. A discussion of the difference and complementarity of mapping into a LTS or FTS is presented. The FTS $f(\alpha)$ curves are more opened than the LTS onesComment: preprint for PRE; 2 columns; 10 pages; 6 (multifigures); 3 Tables; 70 reference

Configurational entropy of network-forming materials

We present a computationally efficient method to calculate the configurational entropy of network-forming materials. The method requires only the atomic coordinates and bonds of a single well-relaxed configuration. This is in contrast to the multiple simulations that are required for other methods to determine entropy, such as thermodynamic integration. We use our method to obtain the configurational entropy of well-relaxed networks of amorphous silicon and vitreous silica. For these materials we find configurational entropies of 1.02 kb and 0.97 kb per silicon atom, respectively, with kb the Boltzmann constant.Comment: 4 pages, 4 figure

LOGISTICAL COSTS AND RISKS OF MARKETING GENETICALLY MODIFIED WHEAT

Genetically modified (GM) grains have increased in importance. Moving biotech grains from producers to processors is a challenge for the grain handling system that could involve increased segregations. The objective of this research is to determine how testing strategies affect the logistical costs of a grain pipeline when GM wheat is present. A logistical model was developed and simulated to analyze impacts of uncertainty in demand, receipts, test accuracy, rail deliveries, and transit time. Sensitivities were conducted on certain variables to determine their effects on logistical costs. Analysis revealed that logistical costs are impacted by the number of quality categories and uncertainties in the system. Adding GM grains increased costs due to testing requirements and increased segregation demands as the number of wheat categories rises.Genetically Modified (GM) Grains, Logistical Costs, Testing, Risk, Segregation, Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies,

LOGISTICAL COSTS AND STRATEGIES FOR WHEAT SEGREGATION

Special segregations that provide unique qualities for end use products are being specified by buyers. As users of wheat become more specific about quality, the number of quality segregations that the logistical pipeline must accommodate increases. The additional cost of increased grain segregations will influence the optimal level of wheat variety segregations marketed in a supply chain. The primary objective of this research is to develop a model that captures the logistical costs of increased grain segregations in the marketing system. A simulation model was developed to add logistical uncertainty in demand, receipts, rail deliveries, and transit time. Sensitivities were conducted on certain variables to determine their effects on logistical costs. Logistical costs increase as more segregations are added. In addition, increasing uncertainty into the system raises logistical costs. Pipeline configuration also affects costs as the number of categories/storage bins present at origin may differ from the wheat categories demanded or the number of storage bins present at the export elevator.wheat, segregations, Crop Production/Industries,

Photoelectrochemical water splitting: silicon photocathodes for hydrogen evolution

The development of low cost, scalable, renewable energy technologies is one of today's most pressing scientific challenges. We report on progress towards the development of a photoelectrochemical water-splitting system that will use sunlight and water as the inputs to produce renewable hydrogen with oxygen as a by-product. This system is based on the design principle of incorporating two separate, photosensitive inorganic semiconductor/liquid junctions to collectively generate the 1.7-1.9 V at open circuit needed to support both the oxidation of H_2O (or OH^-) and the reduction of H^+ (or H_2O). Si microwire arrays are a promising photocathode material because the high aspect-ratio electrode architecture allows for the use of low cost, earth-abundant materials without sacrificing energy-conversion efficiency, due to the orthogonalization of light absorption and charge-carrier collection. Additionally, the high surfacearea design of the rod-based semiconductor array inherently lowers the flux of charge carriers over the rod array surface relative to the projected geometric surface of the photoelectrode, thus lowering the photocurrent density at the solid/liquid junction and thereby relaxing the demands on the activity (and cost) of any electrocatalysts. Arrays of Si microwires grown using the Vapor Liquid Solid (VLS) mechanism have been shown to have desirable electronic light absorption properties. We have demonstrated that these arrays can be coated with earth-abundant metallic catalysts and used for photoelectrochemical production of hydrogen. This development is a step towards the demonstration of a complete artificial photosynthetic system, composed of only inexpensive, earth-abundant materials, that is simultaneously efficient, durable, and scalable

Closed form expressions for crack mouth displacements and stress intensity factors for chevron notched short bar and short rod specimens based on experimental compliance measurements

A set of equations are presented describing certain fracture mechanics parameters for chevron notch bar and rod specimens. They are developed by fitting compliance calibration data reported earlier. The equations present the various parameters in their most useful forms. The data encompass the entire range of the specimen geometries most commonly used. Their use will facilitate the testing and analysis of brittle metals, ceramics, and glasses

A Comparison of Face-to-Face Versus Online Instruction in the Correct Pronunciation of Anatomical Terms in Communication Sciences and Disorders. An Initial Investigation

Accurate pronunciation of anatomical terms in the clinical practice of speech-language pathology (SLP) and audiology (AUD) enables a clinician to express and comprehend a conversation with peers and other professionals. It is also an important component of ensuring patient safety and in providing quality, patient-centered care. To date, no studies have explored whether differences may exist between the pronunciation skills of students who elect to complete a human anatomy and physiology course online versus in a face-to-face (FTF) format. This pilot study explored the ability of 98 undergraduate student participants to correctly pronounce 20 identical key terms that were a part of the course Anatomy and Physiology of the Speech and Hearing Mechanism. Students were enrolled in either an online or a FTF format of this course. Student participants were also asked to self-rate their perceived ability to pronounce these terms correctly using a Likert-type rating scale. The results indicated that students enrolled in the FTF format produced a significantly greater percentage of correct terms and rated their pronunciation ability significantly higher compared to those enrolled online. Performance of both groups was positively correlated to the self-ratings of pronunciation accuracy. These results suggest that an Internet-based, multimedia teaching method that incorporates tools for improving the pronunciation skills of students who complete a human anatomy and physiology course is warranted

Fracture toughness of brittle materials determined with chevron notch specimens

The use of chevron-notch specimens for determining the plane strain fracture toughness (K sub Ic) of brittle materials is discussed. Three chevron-notch specimens were investigated: short bar, short rod, and four-point-bend. The dimensionless stress intensity coefficient used in computing K sub Ic is derived for the short bar specimen from the superposition of ligament-dependent and ligament-independent solutions for the straight through crack, and also from experimental compliance calibrations. Coefficients for the four-point-bend specimen were developed by the same superposition procedure, and with additional refinement using the slice model of Bluhm. Short rod specimen stress intensity coefficients were determined only by experimental compliance calibration. Performance of the three chevron-notch specimens and their stress intensity factor relations were evaluated by tests on hot-pressed silicon nitride and sintered aluminum oxide. Results obtained with the short bar and the four-point-bend specimens on silicon nitride are in good agreement and relatively free of specimen geometry and size effects within the range investigated. Results on aluminum oxide were affected by specimen size and chevron-notch geometry, believed due to a rising crack growth resistance curve for the material. Only the results for the short bar specimen are presented in detail

Quantum Analogue Computing

We briefly review what a quantum computer is, what it promises to do for us, and why it is so hard to build one. Among the first applications anticipated to bear fruit is quantum simulation of quantum systems. While most quantum computation is an extension of classical digital computation, quantum simulation differs fundamentally in how the data is encoded in the quantum computer. To perform a quantum simulation, the Hilbert space of the system to be simulated is mapped directly onto the Hilbert space of the (logical) qubits in the quantum computer. This type of direct correspondence is how data is encoded in a classical analogue computer. There is no binary encoding, and increasing precision becomes exponentially costly: an extra bit of precision doubles the size of the computer. This has important consequences for both the precision and error correction requirements of quantum simulation, and significant open questions remain about its practicality. It also means that the quantum version of analogue computers, continuous variable quantum computers (CVQC) becomes an equally efficient architecture for quantum simulation. Lessons from past use of classical analogue computers can help us to build better quantum simulators in future.Comment: 10 pages, to appear in the Visions 2010 issue of Phil. Trans. Roy. Soc.