Synthesis and nonlinear optical characterization of new poly{2,2′-(3,4-didodecyloxythiophene-2,5-diyl)bis[5-(2-thienyl)-1,3,4-oxadiazole]}

A new donor–acceptor type poly{2,2′-(3,4-didodecyloxythiophene-2,5-diyl)bis[5-(2-thienyl)-1,3,4-oxadiazole]} (P) was synthesized starting from thiodiglycolic acid and diethyl oxalate through multistep reactions. The polymerization was carried out using chemical polymerization technique. The optical and charge-transporting property of the copolymer was investigated by UV–vis, fluorescence emission spectroscopic and cyclic voltammetric studies. The copolymer shows UV absorption maxima at 375 nm and displays bluish-green fluorescence in DMF solution. Its electrochemical band gap was determined to be 2.07 eV. The nonlinear optical (NLO) properties of the copolymer was investigated at 532 nm using single beam Z-scan and degenerate four-wave mixing (DFWM) techniques with nanosecond laser pulses. The copolymer exhibits strong optical limiting behavior due to effective three-photon absorption (3PA). Values of the effective 3PA coefficient (γ), third-order nonlinear susceptibility (χ⁽³⁾) and figure of merit (F) have been calculated.     

Antibacterial Property of Cold Sprayed Chitosan-Cu/Al Coating

The antibacterial behavior of CS-Cu (chitosan-copper complex) powder and their composite coatings were investigated against Escherichia coli (DH5α). CS-Cu powder and Al (aluminum) based CS-Cu composite powders were synthesized using in-house powder processing techniques. The results indicated that the antibacterial effect of all the powders increased with the proportion of CS-Cu powder. These composite powders were subsequently used as feedstock to generate antibacterial coatings via cold spray technology. The ratios of CS-Cu to Al in their composite powders were 25:75, 50:50, and 75:25 (wt.%). Microstructural characterization and phase analysis of feedstock powders and as-deposited coatings were carried out using FESEM/EDX and FTIR. Antibacterial composite CS-Cu/Al coatings were successfully deposited using cold spraying parameters of 6-8 bars at preheated helium gas, temperature between 140 and 150 °C. The coatings retained the antibacterial properties of the original feedstock powders.     

高性能LCoS虚拟显示器的光学特性

本文叙述一种用于LCoS双瞳虚拟显示器的新型光路结构,它首次达到或超过了pSi(多晶硅)头戴装置的性能36°的视场,801的对比度,无需IPD调节(12mm出射光瞳),并且整个电-光模件的封装配合并不比奥林巴斯EyeTrek和索尼Glasstron的工业标准更复杂.     

Experimental investigation and three-dimensional computational fluid-dynamics modeling of the flash-converting furnace shaft: Part II. Formulation of three-dimensional computational fluid-dynamics model incorporating the particle-cloud description

A fluid-dynamics computer model of the flash-converting furnace shaft, which is based on basic principles, is presented. The model is fully three-dimensional and incorporates the transport of momentum, heat, and mass and the reaction kinetics between the gas and particles in a particle-laden turbulent gas jet. The k-ɛ model was used to describe gas-phase turbulence in an Eulerian framework. The particle-cloud model was used to track the particle phase in a Lagrangian framework. The coupling of gas and particle equations was performed through the source terms in the Eulerian gas-phase governing equations. Copper matte particles were represented as Cu₂S · yFeS _x . Based on experimental observation, the oxidation products were assumed to be Cu₂O, CuO, Fe₃O₄, and SO₂. A reaction mechanism involving the external mass transfer of oxygen from the gas to the particle surface and diffusion of the oxygen through the successive layers of Cu₂O-Fe₃O₄ and CuO-Fe₃O₄ was proposed. The predictions of the computer model were compared with the experimental data collected in a large laboratory furnace. Reasonable agreement between the model predictions and the measurements was obtained in terms of the fractional completion of the oxidation reactions and the sulfur remaining in the reacted particles. The relevance of the computational model for further analysis and optimization of an industrial flash-converting operation is discussed.     

An Introduction to Engineering Through an Integrated Reverse Engineering and Design Graphics Project

This paper discusses a new freshman course that merges previous topics in the “Introduction to Mechanical Engineering” and “Engineering Design Graphics” courses into a single integrated teaching effort. The main objective of the new course is to introduce students to mechanical engineering education and practice through lectures and laboratory experiences. A major effort in the course is devoted to a reverse engineering team project. The students are divided into four‐member teams and are instructed to select a simple mechanical assembly for dissection. They study and disassemble their object into basic constituent components, documenting this process with freehand sketches and notes. They use these sketches and other measured dimensions to construct 3‐D solid computer models of each major component. The teams then obtain .STL files of the solid models, which are used to make rapid physical prototypes of their parts. The teams conclude their project activities by generating engineering drawings directly from the 3‐D geometric data base. All of these efforts are integrated, documented, and submitted to the instructor as a final team project report.     

Heterogeneity of popular boys: Antisocial and prosocial configurations.

This study examined subtypes of popular 4th–6th grade boys (N?=?452). Popular-prosocial (model) and popular-antisocial (tough) configurations were identified by means of teacher ratings and compared with peer and self-assessments and social centrality measures. Peers perceived model boys as cool, athletic, leaders, cooperative, studious, not shy, and nonaggressive. Peers perceived tough boys as cool, athletic, and antisocial. Model boys saw themselves as nonaggressive and academically competent. Tough boys saw themselves as popular, aggressive, and physically competent. Tough boys were disproportionately African American, particularly when African Americans were a minority in their classrooms. Model and tough boys were overrepresented at nuclear social centrality levels. These findings suggest that highly aggressive boys can be among the most popular and socially connected children in elementary classrooms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Normative data for normative comparisons.

Normative comparisons are a procedure for evaluating the clinical significance of therapeutic interventions. Although a step-by-step statistical methodology for conducting normative comparisons has been reported elsewhere (P. C. Kendall, A. Marrs-Garcia, S. R. Nath, & R. C. Sheldrick, 1999), questions regarding the collecting of normative data remain. For this study, all treatment outcome studies published in the Journal of Consulting and Clinical Psychology from 1988 to 1997 were examined and reviewed, and the 5 most commonly used outcome measures were identified. For these outcome measures, multiple sources of normative data were located. Although we identified a dearth of normative data on measures used for treatment outcome, results discussed here nevertheless provide information that may be of use to therapy outcome evaluators when conducting normative comparisons. In addition, equations to determine the minimum sample size needed in a normative sample for a given treatment outcome study are provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention and luminance detection: Effects of cues, masks, and pedestals.

Three experiments investigated the effects of attention on the detection of luminance targets in a spatial-cuing paradigm. Gabor patch stimuli of 30, 60, or 90 ms duration, equated for detectability, were presented (a) against a uniform field with a checkerboard backward mask, (b) atop a 15% luminance pedestal with a backward mask, or (c) atop a luminance pedestal with no backward mask. Signal detection analysis showed that detection sensitivity was significantly enhanced at attended locations for all observers when backward masks were used, both when targets were presented against a uniform field and when a pedestal was used. However, when no masks were used there was no cuing advantage of any kind. The results show that the cuing effect in simple detection depends on the use of backward masks, a finding that resolves the inconsistencies previously associated with studies of this type. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Self‐sustained oscillations in opposed impinging jets in an enclosure

The flow of jets in confining enclosures has significant application in many engineering processes. In particular, the impingement of axisymmetric jets in a confined space has been examined using flow visualization, laser Doppler anemometry, and numerical simulations. Several flow regions were found; stable steady, regular oscillatory, and irregular oscillatory. Initially, a steady flow field existed for all arrangements for Re_d < ?90 (based on the nozzle diameter d, the fluid kinematic viscosity v and the volumetric flow rate Q through the nozzle (Q = πd²/4U_avg)) but subsequent increments in the fluid velocity caused a regularly oscillating flow field to emerge. The onset of the oscillations and the upper limit of finite oscillations were found to be a function of the Re_d, and the nozzle diameter to chamber dimension ratio. Steady numerical simulations predicted the steady flow field well and good agreement was obtained in unsteady simulations of the oscillating flow field. The oscillating flow field is considered to be a class of self‐sustaining oscillations where instabilities in the jet shear layer are amplified because of feed back from pressure disturbances in the impingement region.     

DDR DRAM削减膝上计算机功耗

看第一眼,你觉得PC100／133与DDRDRAM在省电方面似乎没有什么两样,但仔细分析以后,你会发现DDR是更好的选择。为了探索更高的性能和更低的功耗,膝上计算机的设计正开始从SDRAM（PC10O／133）转向双速率（Doub卜DataRate,DDR）的DDRDRAM。在采用新的DDR做设计时,有几个因素是系统工程师必须考虑的,其中主要的因素是功耗问题。影响设计和布局布线的新结构特点也必须加以考虑。同样重要的是对成本与性能特性的理解。DDR功率分析比较两种不同的存储器系统的功耗是很有意义的,其中一个采用PC133SDRAM,另～个采用266M…