Effect of subsurface thermocouple installation on the discrepancy of the measured thermal history and predicted surface heat flux during a quench operation

Water quenching plays an important role in metallurgical and materials manufacturing operations to control both the temperature of the product during processing and its final microstructure. In order to control a water-quench process, the surface heat-transfer coefficient or heat flux must be quantified accurately. A common procedure to do this is to use an inverse heat conduction (IHC) model to estimate the heat-transfer boundary condition (heat flux or heat- transfer coefficient) based on the measured thermal history during the quench operation at a known interior location in the sample. Traditionally, thermocouples (TCs) have been extensively used during quench tests to measure the sample temperature history. This article will examine the effect of the hole used to insert the thermocouple into the sample and its orientation with respect to the quenched surface, on the perturbation in the thermal field around the TC measurement point during water-quench operations characterized by boiling heat transfer. The effect of some other factors on the perturbation of the thermal field at the TC measurement point during water-quench operations such as the diameter of the thermocouple hole, thermocouple distance from the quench surface, sample thermal conductivity, and quench intensity were also investigated. A two-dimensional (2-D) axisymmetric IHC model developed at the University of British Columbia is used to estimate the error in the predicted heat fluxes based on the thermal history measured at the thermocouple measurement point. The study showed, for some quench conditions, that the thermocouple hole must be included in the IHC analysis as an independent body with its own thermophysical and geometrical characteristics. Validation of these model-predicted results was done using water-quench experiments performed on samples of steel and aluminum plates at the University of British Columbia. Using the Biot number (Bi), a simple criterion is developed to determine when the TC hole needs to be included in the heat-transfer analysis.     

Eyewitness Identification Accuracy and Response Latency: The Unruly 10-12-Second Rule.

Data are reported from 3,213 research eyewitnesses confirming that accurate eyewitness identifications from lineups are made faster than are inaccurate identifications. However, consistent with predictions from the recognition and search literatures, the authors did not find support for the "10-12-s rule" in which lineup identifications faster than 10-12 s maximally discriminate between accurate and inaccurate identifications (D. Dunning & S. Perretta, 2002). Instead, the time frame that proved most discriminating was highly variable across experiments, ranging from 5 s to 29 s, and the maximally discriminating time was often unimpressive in its ability to sort accurate from inaccurate identifications. The authors suggest several factors that are likely to moderate the 10-12-s rule. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Facebook User Research Using a Probability‐Based Sample and Behavioral Data

Research on Facebook users is often based on small convenience samples and on usage data collected through survey self‐reports. The current research contributes to Facebook user research, as it is based on a large, nationally representative, probability‐based, U.S. sample with Internet usage data collected from meters. Results revealed that 50% of sample members are recent Facebook users. However, within this group, there is wide variation in amount of usage between heavy, medium, and light users. Finally, based on a multivariate analysis, Facebook users are significantly more likely to be women, teens, whites, and adults with at least a high school diploma. These demographic patterns apply to heavy, medium, and light Facebook users.     

Phase Stability and Optoelectronic Properties of the Bixbyite Phase in the Gallium–Indium–Tin–Oxide System

X‐ray diffraction techniques were used to determine the phase boundaries of the In₂O₃ solid solution phase in the Ga₂O₃–In₂O₃–SnO₂ ternary system. The effects of Ga and Sn content on the unit cell dimensions of the bixbyite phase were calculated by a linear regression fit, the results of which indicate the two substitutive cations have opposite and independent effects on the lattice parameter. These results suggest that the cations do not strongly interact with each other in the crystal. Measurements of optoelectronic properties were also taken on single‐phase bulk specimens within the solid solution to establish their dependence on composition. As anticipated, Sn doping yields corresponding increases in conductivity, reduction in the absolute value of Seebeck coefficient, and increase in optical band gap. In contrast, these properties are not significantly affected by varying Ga content, confirming that Ga behaves as an isovalent dopant at the low doping levels involved.     

Chemical Ecology of the host searching behavior in an Egg Parasitoid: are Common Chemical Cues exploited to locate hosts in Taxonomically Distant Plant Species?

Parasitoids are known to exploit volatile cues emitted by plants after herbivore attack to locate their hosts. Feeding and oviposition of a polyphagous herbivore can induce the emission of odor blends that differ among distant plant species, and parasitoids have evolved an incredible ability to discriminate them and locate their hosts relying on olfactive cues. We evaluated the host searching behavior of the egg parasitoid Cosmocomoidea annulicornis (Ogloblin) (Hymenoptera: Mymaridae) in response to odors emitted by two taxonomically distant host plants, citrus and Johnson grass, after infestation by the sharpshooter Tapajosa rubromarginata (Signoret) (Hemiptera: Cicadellidae), vector of Citrus Variegated Chlorosis. Olfactory response of female parasitoids toward plants with no herbivore damage and plants with feeding damage, oviposition damage, and parasitized eggs was tested in a Y-tube olfactometer. In addition, volatiles released by the two host plant species constitutively and under herbivore attack were characterized. Females of C. annulicornis were able to detect and significantly preferred plants with host eggs, irrespectively of plant species. However, wasps were unable to discriminate between plants with healthy eggs and those with eggs previously parasitized by conspecifics. Analysis of plant volatiles induced after sharpshooter attack showed only two common volatiles between the two plant species, indole and β-caryophyllene. Our results suggest that this parasitoid wasp uses common chemical cues released by many different plants after herbivory at long range and, once on the plant, other more specific chemical cues could trigger the final decision to oviposit.

     

Intrinsic carrier multiplication in layered Bi2O2Se avalanche photodiodes with gain bandwidth product exceeding 1 GHz

Emerging layered semiconductors present multiple advantages for optoelectronic technologies including high carrier mobilities, strong light-matter interactions, and tunable optical absorption and emission. Here, metal-semiconductor-metal avalanche photodiodes (APDs) are fabricated from Bi₂O₂Se crystals, which consist of electrostatically bound [Bi₂O₂]²⁺ and [Se]²⁻ layers. The resulting APDs possess an intrinsic carrier multiplication factor up to 400 at 7 K with a responsivity gain exceeding 3,000 A/W and bandwidth of ~ 400 kHz at a visible wavelength of 515.6 nm, ultimately resulting in a gain bandwidth product exceeding 1 GHz. Due to exceptionally low dark currents, Bi₂O₂Se APDs also yield high detectivities up to 4.6 × 10¹⁴ Jones. A systematic analysis of the photocurrent temperature and bias dependence reveals that the carrier multiplication process in Bi₂O₂Se APDs is consistent with a reverse biased Schottky diode model with a barrier height of ~ 44 meV, in contrast to the charge trapping extrinsic gain mechanism that dominates most layered semiconductor phototransistors. In this manner, layered Bi₂O₂Se APDs provide a unique platform that can be exploited in a diverse range of high-performance photodetector applications.

     

Relay and sequential cropping corn with winter oilseed crops in northern climates

Nutrient Cycling in Agroecosystems - Winter oilseed crops camelina [Camelina sativa (L.) Crantz] and field pennycress (Thlaspi arvense L.) are potential candidates for diversifying the...