感知蓝图模型在图书馆服务提升中的应用

服务蓝图展示了服务接触点,服务接触点是我们提高服务质量的着手点。服务质量差距模型调查了服务质量接触点的读者满意度。感知蓝图模型整合服务蓝图模型、服务质量差距模型和系统论思想。本文运用感知蓝图模型,探讨了提升图书馆服务质量的途径。     

Electric charge-mediated coalescence of water droplets for biochemical microreactors

This work proposes the use of charged droplets driven by the Coulombic force as solution-phase reaction chambers for biological microreactions. A droplet can be charged near an electrode under dc voltage by direct contact to the electrode. This process is called electrical charging of droplet (ECOD). This charged droplet can then be transported rapidly between electrodes following the arc of an electric field line by exploiting electrostatic force. As on-demand electrocoalescence, both alkalization of phenolphthalein and bioluminescence reaction of luciferase in the presence of adenosine triphosphate are studied to test the feasibility of the biochemical microreactors using ECOD. Two oppositely charged droplets are merged to have a color change immediately after microchemical reaction. The applicability of an ECOD-driven droplet to measurement of glucose concentration is also tested. The glucose concentration is measured using a colorimetric enzyme-kinetic method based on Trinder’s reaction [J. Clin. Pathol. 22, 158 (1969)]. The color change in the merged droplet is detected with an absorbance measurement system consisting of a photodiode and a light emitting diode.     

Repulsion-based model for contact angle saturation in electrowetting

We introduce a new model for contact angle saturation phenomenon in electrowetting on dielectric systems. This new model attributes contact angle saturation to repulsion between trapped charges on the cap and base surfaces of the droplet in the vicinity of the three-phase contact line, which prevents these surfaces from converging during contact angle reduction. This repulsion-based saturation is similar to repulsion between charges accumulated on the surfaces of conducting droplets which causes the well known Coulombic fission and Taylor cone formation phenomena. In our model, both the droplet and dielectric coating were treated as lossy dielectric media (i.e., having finite electrical conductivities and permittivities) contrary to the more common assumption of a perfectly conducting droplet and perfectly insulating dielectric. We used theoretical analysis and numerical simulations to find actual charge distribution on droplet surface, calculate repulsion energy, and minimize energy of the total system as a function of droplet contact angle. Resulting saturation curves were in good agreement with previously reported experimental results. We used this proposed model to predict effect of changing liquid properties, such as electrical conductivity, and system parameters, such as thickness of the dielectric layer, on the saturation angle, which also matched experimental results.     

Negative dielectrophoretic capture of bacterial spores in food matrices

A microfluidic device with planar square electrodes is developed for capturing particles from high conductivity media using negative dielectrophoresis (n-DEP). Specifically, Bacillus subtilis and Clostridium sporogenes spores, and polystyrene particles are tested in NaCl solution (0.05 and 0.225 S∕m), apple juice (0.225 S∕m), and milk (0.525 S∕m). Depending on the conductivity of the medium, the Joule heating produces electrothermal flow (ETF), which continuously circulates and transports the particles to the DEP capture sites. Combination of the ETF and n-DEP results in different particle capture efficiencies as a function of the conductivity. Utilizing 20 μm height DEP chambers, “almost complete” and rapid particle capture from lower conductivity (0.05 S∕m) medium is observed. Using DEP chambers above 150 μm in height, the onset of a global fluid motion for high conductivity media is observed. This motion enhances particle capture on the electrodes at the center of the DEP chamber. The n-DEP electrodes are designed to have well defined electric field minima, enabling sample concentration at 1000 distinct locations within the chip. The electrode design also facilitates integration of immunoassay and other surface sensors onto the particle capture sites for rapid detection of target micro-organisms in the future.     

Sliding mode control for active magnetic bearing system with flexible rotor

This paper presents the analysis and control of active magnetic bearing (AMB) systems with a flexible rotor. A sliding mode controller design scheme is proposed to compensate for the nonlinear effects of the AMB system. A nonlinear model of the AMB system with an electromagnetic actuator and a flexible rotor is proposed to facilitate the present system analysis and controller design. This nonlinear model takes into account the dynamics of the flexible rotor, the characteristics of the nonlinear electromagnetic suspended system, and the contact force between the auxiliary bearing and the shaft. This study also considers the auto-centering control of the AMB system when subjected to disturbances and variations in the system parameters. The numerical results show that the system exhibits a periodic motion and demonstrates high accuracy and robustness when operating under sliding mode control.     

Combined AC electroosmosis and dielectrophoresis for controlled rotation of microparticles

Electrorotation is widely used for characterization of biological cells and materials using a rotating electric field. Generally, multiphase AC electric fields and quadrupolar electrode configuration are needed to create a rotating electric field for electrorotation. In this study, we demonstrate a simple method to rotate dielectrophoretically trapped microparticles using a stationary AC electric field. Coplanar interdigitated electrodes are used to create a linearly polarized nonuniform AC electric field. This nonuniform electric field is employed for dielectrophoretic trapping of microparticles as well as for generating electroosmotic flow in the vicinity of the electrodes resulting in rotation of microparticles in a microfluidic device. The rotation of barium titanate microparticles is observed in 2-propanol and methanol solvent at a frequency below 1 kHz. A particle rotation rate as high as 240 revolutions per minute is observed. It is demonstrated that precise manipulation (both rotation rate and equilibrium position) of the particles is possible by controlling the frequency of the applied electric field. At low frequency range, the equilibrium positions of the microparticles are observed between the electrode edge and electrode center. This method of particle manipulation is different from electrorotation as it uses induced AC electroosmosis instead of electric torque as in the case of electrorotation. Moreover, it has been shown that a microparticle can be rotated along its own axis without any translational motion.     

A technology gap interpretation of growth paths in Asia and Latin America

This paper presents a North-South technology gap model which combines the Schumpeterian approach to technical and structural change with the Keynesian perspective on effective demand and the Balance-of-Payments (BOP) constraint as drivers of growth. Three are the contributions of the paper. First, it develops a model in which the technology gap, relative productivity and relative wages co-evolve and may generate different paths of convergence or divergence between South and North depending on the parameters of the model. Second, the parameters of the model are associated with different types of policies, which allows for discussing how these policies may change the growth path. Finally, the model is used to discuss the contrasting experiences of Asia and Latin America since 1970. Convergence in Asia and divergence in Latin America have been extensively debated topics in the literature on comparative economic development, which highlights the crucial role of industrial policy. It is argued that the results of the technology gap model are consistent with the findings of this literature and helps understand the forces behind convergence and divergence.     

The control of current across a spark gap by means of an external magnetic field

An experimental study was made of the electrical discharge between parallel plates when the pressure between the plates had been reduced to a value slightly less than the critical pressure—i.e. to the condition when a tube begins to harden. Under these conditions the application of a transverse magnetic field will produce a discharge between the electrodes for potentials less than the normal potential required. It is believed that this is due to the lengthening of the path traversed by the ions in crossing the gap. The results obtained may be harmonized by means of the values found by Carr (Proc. Roy. Soc. 1903) who made a study of Paschen's Law in the region of critical pressure. In general it is found possible, under the conditions studied, to start a discharge and control the value of the current through a circuit of which the gap is a part by means of varying the magnetic field superposed on the gap and without altering either the impressed E.M.F. or the ohmic resistance of the circuit.This control is effected by altering the effective length of the spark gap in the circuit by means of the external magnetic field.     

新贫困线下我国农村家庭户的贫困广度和深度--基于CGSS2008数据的研究

本文使用中国人民大学组织的全国综合性社会调查（CGSS）2008年的数据,按照2011年人均年收入2300元的新贫困线标准,采用描述性统计中分组比较的方法从地区差异、受教育程度、从业状态差异等不同角度对我国农村家庭户收入贫困的深度和广度进行测度,即贫困发生率和贫困缺口比。研究发现：与过去相比较我国农村家庭户的贫困发生率和贫困缺口指数总体上有很大提高（从事非农产业的农户除外）,贫困线标准变动比例越大,贫困发生率和贫困缺口指数变动越大。另外,农户因地区差异东、中、西部贫困发生率和贫困缺口比依次增大的现象仍然存在;受教育程度越低,农户贫困发生率越高,而初中文化水平的农户贫困缺口比最低;从事非农产业的农户贫困发生率上升,但贫困缺口比下降,贫困深度有所好转。     

基于SERVQUAL模型的广东企业科技特派员服务质量实证研究

依据PZB服务质量差距模型,在对广东企业科技特派员工作与传统服务在服务接触要素和服务差距2个方面对比分析的基础上对SERVQUAL量表进行修正,构建广东企业科技特派员服务质量测度模型,并对其服务质量进行实证研究。研究结果表明:广东企业科技特派员服务接触3要素——管理者、企业、企业科技特派员自身对企业科技特派员服务质量的期望与感知均存在差距。最后,根据实证结果,分别从政府、企业、企业科技特派员和高校4个方面有针对性地提出提升广东企业科技特派员服务质量的对策措施。     

Designing ionic channels in novel carbons for electrochemical energy storage

Tremendous efforts have been dedicated to developing high-performance energy storage devices based on the micro- or nano-manipulation of novel carbon electrodes, as certain nanocarbons are perceived to have advantages such as high specific surface areas, superior electric conductivities, excellent mechanical properties and so on. In typical electrochemical electrodes, ions are intercalated/deintercalated into/from the bulk (for batteries) or adsorbed/desorbed on/from the surface (for electrochemical capacitors). Fast ionic transport, significantly determined by ionic channels in active electrodes or supporting materials, is a prerequisite for the efficient energy storage with carbons. In this report, we summarize recent design strategies for ionic channels in novel carbons and give comments on the promising features based on those carbons towards tailorable ionic channels.     

The dynamics of the impact and coalescence of droplets on a solid surface

A simple experimental setup to study the impact and coalescence of deposited droplets is described. Droplet impact and coalescence have been investigated by high-speed particle image velocimetry. Velocity fields near the liquid-substrate interface have been observed for the impact and coalescence of 2.4 mm diameter droplets of glycerol∕water striking a flat transparent substrate in air. The experimental arrangement images the internal flow in the droplets from below the substrate with a high-speed camera and continuous laser illumination. Experimental results are in the form of digital images that are processed by particle image velocimetry and image processing algorithms to obtain velocity fields, droplet geometries, and contact line positions. Experimental results are compared with numerical simulations by the lattice Boltzmann method.     

Electronic detection of dielectrophoretic forces exerted on particles flowing over interdigitated electrodes

Dielectric particles flowing through a microfluidic channel over a set of coplanar electrodes can be simultaneously capacitively detected and dielectrophoretically (DEP) actuated when the high (1.45 GHz) and low (100 kHz–20 MHz) frequency electromagnetic fields are concurrently applied through the same set of electrodes. Assuming a simple model in which the only forces acting upon the particles are apparent gravity, hydrodynamic lift, DEP force, and fluid drag, actuated particle trajectories can be obtained as numerical solutions of the equations of motion. Numerically calculated changes of particle elevations resulting from the actuation simulated in this way agree with the corresponding elevation changes estimated from the electronic signatures generated by the experimentally actuated particles. This verifies the model and confirms the correlation between the DEP force and the electronic signature profile. It follows that the electronic signatures can be used to quantify the actuation that the dielectric particle experiences as it traverses the electrode region. Using this principle, particles with different dielectric properties can be effectively identified based exclusively on their signature profile. This approach was used to differentiate viable from non-viable yeast cells (Saccharomyces cerevisiae).     

Crowdfunding model for financing movies and web series

Movies and web series are the most popular destinations of crowdfunding, and various approaches have been followed by project initiators. Filmmakers may use specialized or general crowdfunding platforms to raise money, propose fixed or flexible budgets, and use reward-based or equity-based crowdfunding. Crowdfunding may entirely or just partially finance production. To date, no standard model has been used for the production of movies and web series through crowdfunding. Recently, content-based web series on over-the-top (OTT) platforms, such as Netflix and Amazon Prime, have gained popularity. The aim of this study is to fill this conceptual gap and propose a crowdfunding model for movies and web series that can be applied and used to benefit all stakeholders: filmmakers, backers, distributors, platform owners, and the entire future audience. The model consists of nine chronologically interlinked phases and six types of flows: information/content, funds, audition, decision-making, content, promotion, and rewards. The conceptual model proposed herein is based on a critical analysis of the extant literature in the field, mainly qualitative analyses performed on successfully and unsuccessfully crowdfunded and professional films in connection with the current technical platform functionalities.     

国际最低收入保障计划转移效果研究及启示

自现代福利制度建立以来,减缓贫困和缩小收入差距一直是贯穿一国政府社会政策目标的主线。不论发达国家还是发展中国家,都十分重视对低收入者提供收入援助,建立起了适合自己国情的最低收入保障计划。有鉴于此。对发达国家的社会救助制度、拉丁美洲“有条件的现金转移”项目的贫困减少和收入差距缩小效果研究进行梳理、归纳和总结。从而对中国城乡居民最低生活保障制度的转移效果评估提供有益的借鉴。     

基于Pro/E的直线段三等分尺结构的优化仿真设计

至今,国内外直线段三等分装置的设计仍是一片空白。本文用pro/e5.0软件对直线段三等分尺结构进行了仿真设计,建立了直线段三等分尺结构的三维模型,同时对结构进行了原理论证和误差分析,并针对初步模型的不足,提出了两种优化方案,最终成功提出了具有精确定位直线段三等分点功能的直线段三等分新型尺规结构。该结构的提出,填补了直线三等分尺装置设计的空白,为直线段的三等分作图提供了一种机械工具,为直线段n等分尺结构的设计提供了依据。     

Fault reconstruction using a LPV sliding mode observer for a class of LPV systems

This paper proposes a new sliding mode observer for fault reconstruction, applicable for a class of linear parameter varying (LPV) systems. Observer schemes for actuator and sensor fault reconstruction are presented. For the actuator fault reconstruction scheme, a virtual system comprising the system matrix and a fixed input distribution matrix is used for the design of the observer. The fixed input distribution matrix is instrumental in simplifying the synthesis procedure to create the observer gains to ensure a stable closed-loop reduced order sliding motion. The ‘output error injection signals’ from the observer are used as the basis for reconstructing the fault signals. For the sensor fault observer design, augmenting the LPV system with a filtered version of the faulty measurements allows the sensor fault reconstruction problem to be posed as an actuator fault reconstruction scenario. Simulation tests based on a high-fidelity nonlinear model of a transport aircraft have been used to demonstrate the proposed actuator and sensor FDI schemes. The simulation results show their efficacy.     

Rapid bench-top fabrication of poly(dimethylsiloxane)/polystyrene microfluidic devices incorporating high-surface-area sensing electrodes

The development of widely applicable point-of-care sensing and diagnostic devices can benefit from simple and inexpensive fabrication techniques that expedite the design, testing, and implementation of lab-on-a-chip devices. In particular, electrodes integrated within microfluidic devices enable the use of electrochemical techniques for the label-free detection of relevant analytes. This work presents a novel, simple, and cost-effective bench-top approach for the integration of high surface area three-dimensional structured electrodes fabricated on polystyrene (PS) within poly(dimethylsiloxane) (PDMS)-based microfluidics. Optimization of PS-PDMS bonding results in integrated devices that perform well under pressure and fluidic flow stress. Furthermore, the fabrication and bonding processes are shown to have no effect on sensing electrode performance. Finally, the on-chip sensing capabilities of a three-electrode electrochemical cell are demonstrated with a model redox compound, where the high surface area structured electrodes exhibit ultra-high sensitivity. We propose that the developed approach can significantly expedite and reduce the cost of fabrication of sensing devices where arrays of functionalized electrodes can be used for point-of-care analysis and diagnostics.     

Distinctive translational and self-rotational motion of lymphoma cells in an optically induced non-rotational alternating current electric field

In this paper, the translational motion and self-rotational behaviors of the Raji cells, a type of B-cell lymphoma cell, in an optically induced, non-rotational, electric field have been characterized by utilizing a digitally programmable and optically activated microfluidics chip with the assistance of an externally applied AC bias potential. The crossover frequency spectrum of the Raji cells was studied by observing the different linear translation responses of these cells to the positive and negative optically induced dielectrophoresis force generated by a projected light pattern. This digitally projected spot served as the virtual electrode to generate an axisymmetric and non-uniform electric field. Then, the membrane capacitance of the Raji cells could be directly measured. Furthermore, Raji cells under this condition also exhibited a self-rotation behavior. The repeatable and controlled self-rotation speeds of the Raji cells to the externally applied frequency and voltage were systematically investigated and characterized via computer-vision algorithms. The self-rotational speed of the Raji cells reached a maximum value at 60 kHz and demonstrated a quadratic relationship with respect to the applied voltage. Furthermore, optically projected patterns of four orthogonal electrodes were also employed as the virtual electrodes to manipulate the Raji cells. These results demonstrated that Raji cells located at the center of the four electrode pattern could not be self-rotated. Instead any Raji cells that deviated from this center area would also self-rotate. Most importantly, the Raji cells did not exhibit the self-rotational behavior after translating and rotating with respect to the center of any two adjacent electrodes. The spatial distributions of the electric field generated by the optically projected spot and the pattern of four electrodes were also modeled using a finite element numerical simulation. These simulations validated that the electric field distributions were non-uniform and non-rotational. Hence, the non-uniform electric field must play a key role in the self-rotation of the Raji cells. As a whole, this study elucidates an optoelectric-coupled microfluidics-based mechanism for cellular translation and self-rotation that can be used to extract the dielectric properties of the cells without using conventional metal-based microelectrodes. This technique may provide a simpler method for label-free identification of cancerous cells with many associated clinical applications.     

基于职业成长的知识型员工离职研究

知识型员工具有强烈的成就动机,在企业中非常重视个人的职业成长,而传统的＂工作视角＂的离职分析不能很好地解释知识型员工的离职过程。本文通过分析知识型员工离职的职业成长动机,提出＂职业视角＂的知识型员工离职框架,该框架的重要价值在于它考虑到知识型员工离职的成长性和职业性特征,结论对于知识型员工离职管理具有一定的探索价值。