A high-speed digital correlator for radio astronomy

Design details for a high-speed digital cross correlator for the Owens Valley Millimeter Array are presented. The correlator uses ECL gate arrays operating at a 256-MHz clock rate to compute the real cross-correlation function for up to four independent frequency bands with bandwidths in the range of 2-128 MHz. For each baseline in the array the correlator provides 512 lags, giving a spectral resolution of 2 MHz at the maximum bandwidth. Two-bit digitization is used, and this results in a sensitivity of 0.88 relative to a perfect analog correlator     

Expressed and inventoried interests revisited: Perspicacity in the person.

Studied the relative validities of expressed choice vs inventoried interests for predicting college major and career choice outcomes. A total of 795 male National Merit Scholars in 16 college major categories and 609 male Scholars in 10 career fields provided data before college and 3 yrs later. The total percentage of accurate expressed choice predictions was over 50% for both outcomes, while the SVIB Men's Form (SVIB-M) was accurate for 30.8% of all college major predictions and 40.2% of all career field forecasts. When expressed choice and the SVIB agreed in prediction of outcome, the hit rate rose to over 70%. However, when expressed choice and SVIB predictions were not the same for a given person, expressed choice was found to be 2–3 times more accurate than the SVIB-M. These results highlight the importance of expressed interests in predicting vocational behavior and suggest ways in which expressed and inventoried interests might best be used in counseling. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relaxational behaviour and spin freezing in ferrates with iron in a pyramidal oxygen coordination

The crystal structure of both Bi_0.5Sr_1.5YCu_1.5Fe_0.5O₆ and Sr₂Pb_0.5Y_0.5CuFeO₆ is basically composed of double layers of (Cu,Fe)O₅ pyramids. In order to better understand the magnetic properties of this type of compound, a ⁵⁷Fe Mössbauer spectroscopy study in the temperature range 4.2–380 K was undertaken. The Mössbauer spectra of both compounds studied present a strong relaxational character. The lines, magnetically split at 4.2 K, become broader and more asymmetrical with increasing temperature. The amount of the paramagneticaphase increases drastically and the magnetic splitting vanishes at 340 K for Sr₂Pb_0.5Y_0.5CuFeO₆ and at 295 K for Bi_0.5Sr_1.5YCu_1.5Fe_0.5O₆. The results are discussed in terms of the superexchange interactions between the Fe atoms placed in the basal planes of the quadratic pyramidal layers and of the Fe---Cu superexchange. The relaxational character of the Mössbauer spectra offers evidence for a gradual freezing of the Fe spins, reminiscent of the behaviour of concentrated spin glasses.     

Comparison of baking tests using wholemeal and white wheat flour

Production of whole-grain products can provide more variety in bakery products and might impact positive health effects due to fermentable soluble fibers. To assess technological quality, micro-scale methods using 10 g of white flour are usually carried out, in particular if amount of material or additives is limited. Using wholemeal flour for micro-scale testing might enhance use efficiency of raw material. Up to date, there is no information, whether micro-scale testing of wholemeal flour provides the same information on techno-functionality as classical methods. Two wheat varieties with the same protein concentration but different bread-making performance were used to analyze this aspect. Micro-scale baking test was optimized for wholemeal flour concerning dough consistency and fermentation time. Wholemeal flour reduced loaf volume, but optimization was successful. Although all processing steps of wholemeal baking test were adapted, differences in loaf volume between the two varieties were only present with white flour. Coarse particles in wholemeal flour may be responsible for reduced gas retention. Decreasing particle size of bran material might reduce adverse effects on loaf volume. A micro-scale baking test using wholemeal flour would have several advantages after correct implementation: lower price, less time and material required, direct measurement of quality aspects.     

Uses of discriminant analysis following MANOVA: Multivariate statistics for multivariate purposes.

When a test of multiple ANOVA is found to be significant, it must be followed by other analyses before a researcher can arrive at an accurate understanding of the data set. Two possibilities for follow-up analyses include univariate ANOVA and discriminant analysis. This article presents the results of a Monte Carlo study (N?=?450) wherein typical, but simple, multivariate data were analyzed by the 2 techniques. Results demonstrate that discriminant analysis is capable of showing the underlying dimensionality of the data as well as determining the contribution of individual variables to the underlying dimensions, whereas ANOVA is limited to specifying the contribution of each variable to group separation. It is argued that when researchers analyze multivariate data, primary goals become interpretation and understanding the data set. It is concluded that discriminant analysis is most suitable for this purpose. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Charge Transfer Modulation in Vanadium-Doped WS2/Bi2O2Se Heterostructures

The field of photovoltaics is revolutionized in recent years by the development of two–dimensional (2D) type-II heterostructures. These heterostructures are made up of two different materials with different electronic properties, which allows for the capture of a broader spectrum of solar energy than traditional photovoltaic devices. In this study, the potential of vanadium (V)-doped WS₂ is investigated, hereafter labeled V-WS₂, in combination with air-stable Bi₂O₂Se for use in high-performance photovoltaic devices. Various techniques are used to confirm the charge transfer of these heterostructures, including photoluminescence (PL) and Raman spectroscopy, along with Kelvin probe force microscopy (KPFM). The results show that the PL is quenched by 40%, 95%, and 97% for WS₂/Bi₂O₂Se, 0.4 at.% V-WS₂/Bi₂O₂Se, and 2 at.% V-WS₂/Bi₂O₂Se, respectively, indicating a superior charge transfer in V-WS₂/Bi₂O₂Se compared to pristine WS₂/Bi₂O₂Se. The exciton binding energies for WS₂/Bi₂O₂Se, 0.4 at.% V-WS₂/Bi₂O₂Se and 2 at.% V-WS₂/Bi₂O₂Se heterostructures are estimated to be ≈130, 100, and 80 meV, respectively, which is much lower than that for monolayer WS₂. These findings confirm that by incorporating V-doped WS₂, charge transfer in WS₂/Bi₂O₂Se heterostructures can be tuned, providing a novel light-harvesting technique for the development of the next generation of photovoltaic devices based on V-doped transition metal dichalcogenides (TMDCs)/Bi₂O₂Se.     

The application of automatic gain control to microwave radiometers

An automatic gain control system for stabilizing the gain of microwave radiometers is described. System analysis sets forth the requirements for gain and bandwidth of the AGC loop. Two systems are described. One is a continuous AGC system that maintains a constant detector voltage and, as a result, the system gain is a function of the input signal. For input signals which are small compared to the system noise temperatures the nonlinearity due to the AGC system is negligible. In the second system, the output of the detector is sampled when the receiver comparison switch is connected to the reference termination. Therefore, the gain of the system is not affected by the signal and no nonlinearity is caused by the AGC system. The effect of noise in the AGC loop is analyzed and it is shown that the time constant of the AGC system can be made shorter than the final system output filter without increasing the over-all system noise.