Microdroplet anodic stripping voltammetry at the in situ preparing antimony-modified rotating disk electrode for determination of Cd(II) and Pb(II)

A simple electroanalytical method for Cd(II) and Pb(II) detection based on differential pulse anodic stripping voltammetry (DPSV) with in situ prepared antimony-modified glassy carbon rotating disk electrode (in situ Sb-GC-RDE) was developed. The electrochemical detection was performed in a microdroplet (50 μL) of 0.01 M hydrochloric acid that is placed between the electrode surface (top) and a Parafilm®-covered glass slide to maintain a hydrophobic surface (bottom). This method includes a preconcentration process using a membrane filter (MF). The target metal ions were complexed with 1-(2-pyridylazo)-2-naphthol (PAN) as a chelating agent, which was accumulated on the MF via filtration. The RDE microdroplet anodic stripping voltammetry was suitable for the elution and determination of metal ions accumulated on the MF. The in situ preparation of antimony-modified electrode allows the use of common GC electrode with high performance. The detection limits for Cd(II) and Pb(II) were 1.4 and 1.1 μg/L, respectively. The proposed method was successfully used in natural water samples for the simultaneous determination of Cd(II) and Pb(II).     

Optical characteristics of an afterglow extracted from an inductively coupled plasma

An inductively coupled plasma is extracted into a quartz vacuum chamber through an orifice to observe optical characteristics of the extracted afterglow. The Mach disk, the barrel shock and the zone of silence, which are familiar in supersonic molecular beam experiments with neutral gases, are clearly observed. Axial profiles of the emission of various lines are measured with a photodiode array spectrometer. Intensities of ionic lines as well as atomic lines are stronger at the Mach disk than in the zone of silence. The location of the Mach disk with varying chamber presure is in conformity with an experimental equation obtained in supersonic molecular beam experiments.     

Sobolev圆盘代数的不变子空间

研究了Sobolev圆盘代数R(D)上乘自变量算子M_z的不变子空间,给出了M_z在任何不变子空间上限制的基本性质,证明了M_z分别限制在两个不变子空间上酉等价当且仅当这两个不变子空间相等,并描述了M_z的一类公共零点在边界的不变子空间的结构.     

Numerical simulation of turbulent impinging jet on a rotating disk

The calculations of quasi‐three‐dimensional momentum equations were carried out to study the influence of wall rotation on the characteristics of an impinging jet. The pressure coefficient, the mean velocity distributions and the components of Reynolds stress are calculated. The flow is assumed to be steady, incompressible and turbulent. The finite volume scheme is used to solve the continuity equation, momentum equations and k–ε model equations. The flow characteristics were studied by varying rotation speed ω for 0?ω?167.6 rad/s, the distance from nozzle to disk (H/d) was (3, 5, 8 and 10) and the Reynolds number Re base on V_J and d was 1.45 × 10⁴. The results showed that, the radial velocity and turbulence intensity increase by increasing the rotation speed and decrease in the impingement zone as nozzle to disk spacing increases. When the centrifugal force increases, the radial normal stresses and shear stresses increase. The location of maximum radial velocity decreases as the local velocity ratio (α) increases. The pressure coefficient depends on the centrifugal force and it decreases as the distance from nozzle to plate increases. In impingement zone and radial wall jet, the spread of flow increases as the angular velocity decreases The numerical results give good agreement with the experiment data of Minagawa and Obi (Int. J. of Heat and Fluid Flow 2004; 25 :759–766). Copyright © 2006 John Wiley & Sons, Ltd.     

Spatial ordering of self-organized InGaAs/AlGaAs quantum disks on GaAs (311)B substrates

We report the control of self-organization of In_xGa_1−xAs/AlGaAs quantum disks on GaAs (311)B surfaces using a novel technique based upon lithography-defined SiN dot arrays. A strained InGaAs island array selectively grown using the SiN dots provides periodic strain field. When the pitch of lateral ordering corresponds with the period of the strain field, self-organized quantum disks stacked on the InGaAs islands are precisely arranged just as the buried SiN dot array. The spacing of the array element is 250–300 nm (x = 0.3) and around 150 nm (x = 0.4). Vertical alignment by strain is achieved at a very thick (95 nm) separating layer. Characterization using atomic force microscopy reveals the size-fluctuation of disk is dramatically improved with spatial ordering.     

失谐叶片-轮盘结构系统振动局部化问题的研究进展

对近２０年来国内外关于失谐叶片－轮盘结构系统振动局部化问题研究的进展进行了较为详细的评述和讨论,文中首先说明了振动局部化问题的基本概念,然后对失谐叶片－轮盘结构系统模态局部化和动态响应局部化在分析模型、求解方法及其基本性质和规律等方面的研究进展进行了较为全面的评述,最后提出了今后应深入研究的问题．     

Von Kármán rotating flow of Maxwell nanofluids featuring the Cattaneo-Christov theory with a Buongiorno model

This research paper analyzes the transport of thermal and solutal energy in the Maxwell nanofluid flow induced above the disk which is rotating with a constant angular velocity.The significant features of thermal and solutal relaxation times of fluids are studied with a Cattaneo-Christov double diffusion theory rather than the classical Fourier’s and Fick’s laws.A novel idea of a Buongiorno nanofluid model together with the Cattaneo-Christov theory is introduced for the first time for the Maxwel...     

基于SMART数据模式的HDD硬盘状态预测方法

硬盘广泛应用于各类信息系统中,其工作状态预测对信息系统的正常运行管理有着重要意义。现有基于SMART(Self Monitoring Analysis and Reporting Technology)属性的机器学习预测算法为保证其通用性,普遍选取部分典型属性作为特征,带来一定的信息丢失。在分析SMART数据特点的基础上,提出数据模式分类后再进行机器学习预测的SMART数据处理方法。实际测试结果表明,经分类处理后,采用简单的机器学习算法即可获得与强分类器接近的性能,同时,该方法可有效简化SMART数据机器学习时的特征选择过程,有效降低算法的资源消耗。     

Integration of microcolumns and microfluidic fractionators on multitasking centrifugal microfluidic platforms for the analysis of biomolecules

This work demonstrates the development of microfluidic compact discs (CDs) for protein purification and fractionation integrating a series of microfluidic features, such as microreservoirs, microchannels, and microfluidic fractionators. The CDs were fabricated with polydimethylsiloxane (PDMS), and each device contained multiple identical microfluidic patterns. Each pattern employed a microfluidic fractionation feature with operation that was based on the redirection of fluid into an isolation chamber as a result of an overflow. This feature offers the advantage of automated operation without the need for any external manipulation, which is independent of the size and the charge of the fractionated molecules. The performance of the microfluidic fractionator was evaluated by its integration into a protein purification microfluidic architecture. The microfluidic architecture employed a microchamber that accommodated a monolithic microcolumn, the fractionator, and an isolation chamber, which was also utilized for the optical detection of the purified protein. The monolithic microcolumn was polymerized “in situ” on the CD from a monolith precursor solution by microwave-initiated polymerization. This technique enabled the fast, efficient, and simultaneous polymerization of monoliths on disposable CD microfluidic platforms. The design of the CD employed allows the integration of various processes on a single microfluidic device, including protein purification, fractionation, isolation, and detection.