Experimental investigation of the Cu/R141b nanofluids on the evaporation/boiling heat transfer characteristics for surface with capillary micro-channels

An experimental study was conducted to investigate the heat transfer characteristic of a vertical copper plate with rectangular micro-channels. In this research, Cu/R141b nanofluids were used as the working fluid. Three different volume concentrations—0.001, 0.01, and 0.1 %—of Cu nanoparticles with an average diameter of 20 nm dispersed in R141b were prepared. Experiments were performed to measure thermal resistance of the microchannel surface under a steady operating pressure range of 0.86 × 10⁵ Pa to 2 × 10⁵ Pa. Thermal resistance weakened with addition of nanoparticles into the base fluid. The maximum reduction effect of the thermal resistance was 50 %, which corresponds to 0.01 % volume concentration of nanofluid at low operating pressure. The operating pressure significantly affects thermal performance of the microchannel surface. This paper also studied heat transfer characteristics for a Cu nanoparticle-coated surface with rectangular microchannels, which were produced by heating in different volume concentrations from 0.001 to 0.1 %. Nanoparticle layer on the micro-channel surface is responsible for enhanced heat transfer of nanofluids with 0.001 and 0.01 % volume concentrations.     

基于低散射和高增益全息液晶/聚合物光栅的分布反馈式激光器

利用低官能度的丙烯酸酯单体进行全息液晶/聚合物光栅的制备, 获得了具有聚合物支撑形貌的光栅结构. 由于这种光栅内部不存在液晶微滴, 当作为分布反馈式激光器的谐振腔时, 可以有效降低光栅内部的散射损失(<4%), 降低激光腔损耗. 此外, 选用的高折射率单体提升了光栅的折射率调制量, 增强了光栅的反馈增益. 在以上两种因素的共同作用下, 采用染料DCM为激光工作物质, 以532 nm的Nd:YAG脉冲激光器作为抽运光源, 最终获得了中心波长为635 nm, 转化效率为1.2%的高性能激光, 在以阈值能量0.8 μJ/pulse抽运下获得激光线宽0.3 nm, 较之国内外同类激光器的报道, 在阈值、线宽、转化效率三方面均有不同程度提升.     

Look fast: Crystallization of conjugated molecules during solution shearing probed in‐situ and in real time by X‐ray scattering

High‐speed solution shearing, in which a drop of dissolved material is spread by a coating knife onto the substrate, has emerged as a versatile, yet simple coating technique to prepare high‐mobility organic thin film transistors. Solution shearing and subsequent drying and crystallization of a thin film of conjugated molecules is probed in situ using microbeam grazing incidence wide‐angle X‐ray scattering (μGIWAXS). We demonstrate the advantages of this approach to study solution based crystal nucleation and growth, and identify casting parameter combinations to cast highly ordered and laterally aligned molecular thin films.

     

The universality of the quantum Fourier transform in forming the basis of quantum computing algorithms

The quantum Fourier transform (QFT) is a powerful tool in quantum computing. The main ingredients of QFT are formed by the Walsh-Hadamard transform H and phase shifts P(·), both of which are 2×2 unitary matrices as operators on the two-dimensional 1-qubit space. In this paper, we show that H and P(·) suffice to generate the unitary group U(2) and, consequently, through controlled-U operations and their concatenations, the entire unitary group U(2ⁿ) on n qubits can be generated. Since any quantum computing algorithm in an n-qubit quantum computer is based on operations by matrices in U(2ⁿ), in this sense we have the universality of the QFT.     

Solubility enhancement of phenanthrene using novel chelating surfactant

A novel chelating surfactant denoted as sodium N-lauroyl ethylenediamine triacetate (N-LED3A) with both surface activity and chelation functions was studied for phenanthrene (PHE) solubilisation ability. The critical micelle concentration (CMC) of N-LED3A was measured, and the effects of the initial N-LED3A concentration, temperature, pH value and coexisting ions (Na⁺, Ca²⁺ and Cu²⁺) on PHE solubilisation by N-LED3A were investigated. The results demonstrated that PHE solubility was efficiently enhanced by N-LED3A, especially with N-LED3A concentrations above the CMC, which was 707 mg L^?1 when measured at 25°C. The temperature influenced the apparent PHE solubility slightly and the apparent solubility of PHE was significantly affected by the pH. Na and Ca were shown to increase the PHE solubility, while Ca exhibited a better promoting ability than Na⁺. A suitable quantity of Cu could significantly enhance the solubilisation capacities of N-LED3A at pH 5. The mechanism of the interaction between Cu⁺ and N-LED3A was further confirmed by Fourier transform infrared spectroscopy (FTIR). These results reveal that Cu²⁺ can be chelated with N-LED3A to form a chelate complex. The results implied that N-LED3A had the potential to remediate soils contaminated by both organics and heavy metals.     

FeCl3.6H2O作用的a-羰基-a-乙酰/羧基二硫缩烯酮的脱乙酰/羧基反应

探讨了价廉易得、环境友好和无毒性的FeCl3.6H2O作用的a-羰基-a-乙酰/羧基二硫缩烯酮的脱乙酰/羧基反应,高产率合成a-羰基二硫缩烯酮。该反应具有反应条件温和、环境友好和操作简单等优点。     

Photographic study of bubble dynamics for pool boiling of refrigerant R11

A digital photographic study of pool boiling with R11 was performed on a horizontal transparent heater at pressure at 0.1 MPa. A high-speed digital camera was applied to record the bubble behaviors of boiling process. The departure diameter, departure time, and nucleation site density at different heat flux were obtained. From the video images, it can be concluded that evaporation of microlayer is very important to the growth of bubble. It was also observed that there is not any liquid replenished into the microlayer below the bubble. In addition, bubble growth curve and dry-out area growth curve could be determined by analyzing the images. Based on the experimental result, boiling curve for R11 was predicted by using the dynamic microlayer model. As a result, the agreement between the predictions and the experiment data is good at high heat flux.     

Small sample statistical condition estimation for the total least squares problem

In this paper, under the genericity condition, we study the condition estimation of the total least squares (TLS) problem based on small sample condition estimation (SCE), which can be incorporated into the direct solver for the TLS problem via the singular value decomposition (SVD) of the augmented matrix [A, b]. Our proposed condition estimation algorithms are efficient for the small and medium size TLS problem because they utilize the computed SVD of [A, b] during the numerical solution to the TLS problem. Numerical examples illustrate the reliability of the algorithms. Both normwise and componentwise perturbations are considered. Moreover, structured condition estimations are investigated for the structured TLS problem.     

Time Domain BEM Based on Generalised Convolution Quadrature

We present the application of the generalised convolution quadrature (gCQ) technique to the time domain boundary element method (BEM) which solves the retarded potential boundary integral equation (RPBIE). Our result allows to employ the multi-stage Runge-Kutta method as the time stepping scheme for the generalised convolution quadrature which is used in the time domain BEM for acoustic problems in either a bounded three-dimensional domain or in its unbounded exterior. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Formation mechanisms of tripod and tetrapod CdTe0.67Se0.33 nanocrystals

CdTe_0.67Se_0.33 nanocrystals were synthesized using a typical organic route. Two major morphologies are observed from transmission electron microscopy (TEM) images, one being a tripod, and the other being a tripod‐like with a black dot in the center of the nanocrystal. The nanocrystals have two distinct geometrical shapes, one being a tripod, and the other being a tetrapod. High‐resolution TEM (HRTEM) examinations show that the tetrapod nanocrystals consist of a zinc‐blende nucleus and four wurtzite arms connected through a common facet, whereas the tripod nanocrystals result from the coalescence of three zinc‐blende nanorods. These results are helpful to interpret the growth process of other II–VI semiconductor NCs.