Posture and performance: sitting vs. standing for security screening

A classification of the literature on the effects of workplace posture on performance of different mental tasks showed few consistent patterns. A parallel classification of the complementary effect of performance on postural variables gave similar results. Because of a lack of data for signal detection tasks, an experiment was performed using 12 experienced security operators performing an X-ray baggage-screening task with three different workplace arrangements. The current workplace, sitting on a high chair viewing a screen placed on top of the X-ray machine, was compared to a standing workplace and a conventional desk-sitting workplace. No performance effects of workplace posture were found, although the experiment was able to measure performance effects of learning and body part discomfort effects of workplace posture. There are implications for the classification of posture and performance and for the justification of ergonomics improvements based on performance increases.     

Machine vision scheme for stain-release evaluation using Gabor filters with optimized coefficients

This paper presents an efficient and practical approach for automatic, unsupervised object detection and segmentation in two-texture images based on the concept of Gabor filter optimization. The entire process occurs within a hierarchical framework and consists of the steps of detection, coarse segmentation, and fine segmentation. In the object detection step, the image is first processed using a Gabor filter bank. Then, the histograms of the filtered responses are analyzed using the scale-space approach to predict the presence/absence of an object in the target image. If the presence of an object is reported, the proposed approach proceeds to the coarse segmentation stage, wherein the best Gabor filter (among the bank of filters) is automatically chosen, and used to segment the image into two distinct regions. Finally, in the fine segmentation step, the coefficients of the best Gabor filter (output from the previous stage) are iteratively refined in order to further fine-tune and improve the segmentation map produced by the coarse segmentation step. In the validation study, the proposed approach is applied as part of a machine vision scheme with the goal of quantifying the stain-release property of fabrics. To that end, the presented hierarchical scheme is used to detect and segment stains on a sizeable set of digitized fabric images, and the performance evaluation of the detection, coarse segmentation, and fine segmentation steps is conducted using appropriate metrics. The promising nature of these results bears testimony to the efficacy of the proposed approach.     

Electrokinetic transport in nanochannels. 2. Experiments

We present an experimental study of nanoscale electrokinetic transport in custom-fabricated quartz nanochannels using quantitative epifluorescence imaging and current monitoring techniques. One aim is to yield insight into electrical double layer physics and study the applicability of continuum theory to nanoscale electrokinetic systems. A second aim is to explore a new separation modality offered by nanoscale electrophoretic separations. We perform parametric variations of applied electric field, channel depth, background buffer concentration, and species valence to impose variations on zeta potential, effective mobility, and Debye length among other parameters. These measurements were used to validate a continuum theory-based analytical model presented in the first of this two-paper series. Our results confirm the usefulness of continuum theory in predicting electrokinetic transport and electrophoretic separations in nanochannels. Our model leverages independent measurements of zeta potential performed in a microchannel system at electrolyte concentrations of interest. These data yield a zeta potential versus concentration relation that is used as a boundary condition for the nanochannel electrokinetic transport model. The data and model comparisons together show that the effective mobility governing electrophoretic transport of charged species in nanochannels depends not only on ion mobility values but also on the shape of the electric double layer and analyte ion valence. We demonstrate a method we term electrokinetic separation by ion valence, whereby both ion valence and mobility may be determined independently from a comparison of micro- and nanoscale transport measurements.     

Spatial variation of heat flux at the metal–mold interface due to mold filling effects in gravity die-casting

Most of the research work pertaining to metal–mold heat transfer in casting solidification either assumes no spatial variation in the air gap formation or limits the study to only those experimental systems in which air gap formation is uniform. However, in gravity die-casting, filling effects induce variation in thermal field in the mold and casting regions. In this paper, we show that this thermal field variation greatly influences the time of air gap initiation along a vertical mold wall, which subsequently leads to the spatial variation of air gap and in turn, the heat flux at the metal–mold interface.In order to study the spatial variation of heat flux at the metal–mold interface, an experimental setup that involved mold filling was devised. A Serial-IHCP (inverse heat conduction problem) algorithm was used to estimate the multiple heat flux transients along the metal–mold interface. The analysis indicates that the fluxes at different mold segments (bottom, middle, and top) of the metal–mold interface reaches the peak value at different time steps, which shows that the initiation of air gap differs along the mold wall. The experimental and numerical results show that the heat transfer in the mold is two-dimensional during the entire period of phase change, which is initially caused by the filling effects and further enhanced by the spatial variation of the air gap at the metal–mold interface.     

Investigation of Hot-Staking Process Parameters and Evolution of Improvement in Joint Strength

The capability of hot-staking in providing mechanical as well as electrical joints along with its versatility and cost effectiveness makes it a process of preference in electrical and electronics appliances. However, the effectiveness of the process depends only on the mechanical contact and there is no welding or fusion between the joining surfaces. This necessitates proper selection and control of process parameters. This study investigates using Taguchi experiments the importance of process parameters for hot-staked joints in armatures of DC motors. Results show that the electrode material, geometry, and its position are significantly important. Based on the findings, a hypothesis is reasoned about process-product relationship to enable evolving in joint strength.     

Room Temperature Ferromagnetism in Dual Doped (Mn 2+ , Ni 2+ ) ZnO Codoped with Li 1+ Prepared Using EDTASintered at Low Temperature

Nanopowders of Znl_x_y_zMnxNiyLizO [（x = 0.04, y = 0, z = 0）, （x = 0.04, y = 0.03, z = 0） and （x = 0.04, y = 0.03, z = 0.03）] have been synthesized by sol-gel precursor route using ethylene diamine tetraacetic acid （EDTA） as a metal chelating agent. X-ray diffraction analysis confirms the formation of wurtzite hexagonal structure for all the three compositions. Mn2＋ doped ZnO exhibits room temperature ferromagnetism （RTFM）, and it is found that further Ni2＋ doping has decreased Ms because of limit of solid solubility of transition metal in ZnO. But codoping of monovalent Li1＋, further increases the ferromagnetism （FM） value, due to introduction of free carriers compared to the dual doped samples. Photoluminescence （PL） spectra of the system, exhibit near band edge （NBE） emission peak at --464 nm due to the electron transition from interstitials to the valence band. Recombination of conduction electron with hole trapped at oxygen vacancy, leads to prominent defect emission peaks at --482 nm and 532 nm. The evidence of the formation of metaI-EDTA complexes are found from the Fourier transform infrared spectra at 2800-3800 cm-1 with shifting, splitting of the peak and also drastic variations in the intensity.     

Preparation of catalytic films of platinum on Au substrates modified by self-assembled PAMAM dendrimer monolayers

In this work we demonstrate the preparation of highly catalytically active Pt formed by the galvanic replacement of the copper adlayer on Au substrates, modified by the self-assembly of fourth generation amine terminated PAMAM dendrimer (G4NH₂). The copper adlayer was formed on the dendrimer-modified gold substrate by chemical preconcentration of copper ions followed by electrochemical reduction. The Pt overlayer was characterized by SEM, XPS and by cyclic voltammetry. The catalytic efficiency of the modified film thus prepared through soft route was evaluated by the electro catalytic oxidation of methanol using cyclic voltammetry, chronoamperometry and AC impedance techniques. This work also demonstrates that the copper adlayer formed on the dendrimer-modified electrode can undergo galvanic replacement by nobler metals like Au and Ag, besides Pt. An elegant soft route involving a new three-step protocol to build the concentration of active Pt on the Au surface has been developed. Concentration of the same metal (Pt) or two different metals (Pt–Au) can be built at the interface in a stepwise manner at ambient temperature.     

"If I don't do well tomorrow, there's a reason": Predictors of adolescents' use of academic self-handicapping strategies.

It has been suggested that some students procrastinate, fool around, reduce effort, and use other self-handicapping strategies so that if subsequent performance is low, these circumstances will be seen as the cause. Surveys were given to 112 8th graders. The handicapping items formed a single factor with good internal consistency. Handicapping was positively associated with self-deprecation, negative attitudes toward education, ego-oriented goals, and low grades. There was a significant interaction between race and both ego-oriented goals and negative attitudes. The relation between ego-oriented goals and handicapping was stronger for African Americans than for European Americans, whereas the relation between negative attitudes and handicapping was stronger for European Americans than for African Americans. Path analysis revealed that handicapping mediated the relationship between negative attitudes about education and grade point average. (PsycINFO Database Record (c) 2010 APA, all rights reserved)