Photoreaction of gold ions from potassium gold cyanide wastewater using solution-combusted ZnO nanopowders

Photoreduction of gold ions from potassium gold cyanide wastewater was tried using the ZnO nanopowder which was synthesized by a unique solution combustion method (SCM). The SCM produced instantaneous high pressure and high temperature (1500–1800 °C) conditions which are desirable to obtain high quality ZnO nanopowders, even though it was not intentionally heated at higher than 100 °C during the synthesis reaction. The high crystalline quality of the ZnO nanopowder seemed to result in high efficiency of gold recovery compared to other commercial photocatalysts such as P-25 TiO₂ nanopowder (Degussa). The wastewater contains many kinds of ions such as K, P, Au, Na, Ni, Cu and Zn ions. Only the gold ions were selectively recovered out of these ions. The gold recovery efficiency of the SCM ZnO nanopowder was about 8.6 folds higher than that of the P-25 TiO₂ nanopowder. The very high selectivity of Au³⁺ ions could be explained by the reduction potential which is placed near the edge of valence band.     

新型摩擦焊机变频调速系统设计与应用

摩擦焊具有焊接接头强度高、焊接效率高、质量稳定、一致性好、可实现异种材料之间焊接的优点。焊接件变频驱动控制是摩擦焊接机关键技术之一,其调速性能直接影响着焊接性能和效率。从摩擦焊基本工作原理出发,针对某电解铝用专用焊接机的特定工艺要求,开发一种以西门子S120高性能变频器、S7-400型可编程逻辑控制器为核心的新型摩擦焊机控制系统。设备现场运行结果表明:该方案完全满足新型摩擦焊接机的技术要求,性能良好,运行可靠。     

一种精确的相机景深计算方法

首先给出了传统的景深计算公式及其推导过程,并对其进行了深入分析,然后通过光学系统成像原理推导出景深的精确计算公式,并将其和传统的景深计算公式进行了深入的比较和分析,最后从计算机视觉角度阐述了景深计算公式的优点。     

基于C8051和Si4432无线收发透明模块设计与实现

为了节省成本和降低用户对无线通信使用的难度。设计基于C8051F340和Si4432的一款无线收发模块。通过大量的干扰实验,证实模块在一些比较恶劣的环境下也能稳定工作。此模块具有较小的PCB尺寸,通过串口透明传输,方便嵌入到用户的产品中,缩短了用户开发无线产品的周期。     

Scheduling algorithm based on prefetching in MapReduce clusters

Due to cluster resource competition and task scheduling policy, some map tasks are assigned to nodes without input data, which causes significant data access delay. Data locality is becoming one of the most critical factors to affect performance of MapReduce clusters. As machines in MapReduce clusters have large memory capacities, which are often underutilized, in-memory prefetching input data is an effective way to improve data locality. However, it is still posing serious challenges to cluster designers on what and when to prefetch. To effectively use prefetching, we have built HPSO (High Performance Scheduling Optimizer), a prefetching service based task scheduler to improve data locality for MapReduce jobs. The basic idea is to predict the most appropriate nodes for future map tasks based on current pending tasks and then preload the needed data to memory without any delaying on launching new tasks. To this end, we have implemented HPSO in Hadoop-1.1.2. The experiment results have shown that the method can reduce the map tasks causing remote data delay, and improves the performance of Hadoop clusters.     

Impact of hardware impairments on large-scale MIMO systems over composite RG fading channels

In this paper, we analyze the impact of receiver hardware impairments on the achievable sum rate of multiple-input multiple-output (MIMO) systems, where the channel follows composite Rician-Gamma (RG) distribution and may be correlated at the transmitters. More specifically, we derive the analytical expressions on the lower bound for the achievable sum rate of regular and large-scale MIMO systems with zero-forcing (ZF) receivers. In order to obtain deeper insights, the asymptotic analysis for the achievable sum rate of regular MIMO systems at high signal-to-noise ratio (SNR) regime is explored. It explicitly reveals that there is a finite rate ceiling on the achievable sum rate for regular MIMO systems at high SNRs, which is irrespective of the transmit power. Additionally, for large antenna configuration, three representative cases are considered insightfully by deriving in closed-form expressions for the asymptotic achievable sum rate. It demonstrates that the finite rate ceiling vanishes for large-scale MIMO limits, which means that large-scale MIMO systems are robust to hardware impairments.     

基于SOM网络的织物起球客观评价

提出一种基于自组织映射算法的神经网络,用于织物起球的等级评定。起球织物都包含有重要的纹理信息,首先创建起球图像的灰度共生矩阵,从这些矩阵中提取特征向量,再以这些特征值作为网络的输入信息,建立SOM神经网络对图像的特征值进行训练、分类,也就是将不同等级的起球图像进行分类。本文详细介绍SOM网络的基本原理与学习算法,以及共生矩阵的计算,最后提取7种起球特征参数进行实验,结果表明该方法有效可行。     

Preparation and DSC application of the size-tuned ZnO nanoarrays

ZnO nanoarray was successfully prepared by a simple chemical bath deposition method on the glass slide deposited with a spin-coated ZnO seed crystal layer. With the measurements of SEM, XRD and UV–vis absorption spectra, the properties of the ZnO nanoarray were characterized in detail. The results show that the ZnO nanoarray is the hexagonal wurtzite structure and grow along the [0 0 1] axis. Furthermore, the energy-conversion property of the device was investigated in such ZnO nanoarray constructed dye-sensitized solar cells (DSCs), which has potential applications in the new-concept photovoltaic devices.     

Antiferroelectricity in tantalum doped (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free ceramics

(Bi_0.5Na_0.5)_0.94Ba_0.06(Ti_1−xTa_x)O₃ (x=0.00–0.04) lead-free polycrystalline ceramics were synthesized using the solid state reaction route, and their crystal structures and electrical properties were systematically studied. With the introduction of Ta substitution, the relaxor antiferroelectric phase with tetragonal P4bm symmetry is stabilized. The representative double polarization hysteresis loops and sprout shaped strain curves for antiferroelectric ceramics are observed at higher Ta contents with x=0.01–0.02 at room temperature. x=0.01 shows the largest strain of 3.81‰ under 60 kV/cm, indicating a good candidate for actuator applications. The polarization and strain hysteresis loops are also evaluated to verify the temperature-induced normal ferroelectric phase to relaxor antiferroelectric phase transition at temperature up to 120 °C. The energy storage density and efficiency at various temperatures are calculated and analyzed in the compositions of x=0.00–0.02. The results indicate that the energy storage density becomes more temperature independent with the increase of Ta concentration, which are promising for applications in high-temperature capacitors.     

Analysis of effective capacity for visible light communication systems with mobility support

Visible light communications (VLCs) are competitive and attractive candidates for next generation indoor communication networks which are required to support mobility and guarantee delay QoS (Quality of Service) for users. User movement in VLC systems changes the propagation path, including the distance, the angle of incidence and irradiance, all of which have a significant impact on channel gain and link capacity. In this paper, we present a user mobility model for indoor VLC systems with the help of discrete time Markov chain theory. Considering a service process with temporal correlation caused by user mobility, we derive the effective capacity (EC) for VLC systems which characterizes the capacity performance subject to the user’s statistical delay QoS. Moreover, the effect of the user’s mobility on effective capacity is revealed.