Versatile energy recovery circuit for driving AC plasma display panel with single sustain circuit board

This paper presents an energy recovery (ER) circuit which can operate either in a series or a parallel resonance mode and can drive an AC plasma display panel (PDP) with a single sustain circuit board. The proposed ER circuit consists of one energy storage capacitor, two energy recovery inductors, and three insulated-gate bipolar transistors. The circuit operations in the series and parallel resonance modes are similar to conventional ones, except for the leading edge of the first sustain pulse and the trailing edge of the last sustain pulse. To reduce power consumption in the parallel resonance mode of operation, these two pulse edges are generated using a series resonance between the panel capacitance and the energy recovery inductor. The proposed circuit had energy recovery efficiencies in both the series and parallel resonance modes that were nearly the same as the efficiency of the conventional series resonance ER circuit. Experimental results on a 42-inch XGA single-scan PDP show that the proposed ER circuit is suitable for use in a PDP drive circuit.     

A novel uniplanar antenna with dual wideband characteristics for tablet/laptop applications

A novel uniplanar antenna design for tablet/laptop applications is proposed. The proposed antenna with a size of 68 × 12 × 0.8 mm³ is comprised of three strip sections, namely, the feeding strip, parasitic shorted strip, and tuning stub strip (or printed LC matching circuit). Five resonant modes are induced by the proposed antenna, and they are combined to yield two wide operating bands that have 6‐dB return loss bandwidths of more than 50% (695‐1190 MHz and 1690‐2930 MHz). Thus, the proposed antenna can easily cover the entire LTE/WWAN operations working in the 698‐960 MHz and 1710‐2690 MHz bands. Besides demonstrating good radiation efficiency of more than 60% for the two wide operating bands, the proposed antenna also exhibits reduced ground effects, in which reducing the ground size will not deteriorate the antenna's performances.     

基于碳纳米管的超级电容器聚吡咯电极复合方法

For the defect that the mechanical properties of polypyrrole supercapacitors decrease with charge and discharge cycles, and the cycle stability is poor, a compound method of polypyrrole electrode for supercapacitors based on multi-walled carbon nanotubes is proposed. The structure of the formed polypyrrole coated multi-walled carbon nanotubes effectively increase the specific surface area of the electrode material, the utilization rate of the active material and the electrical conductivity, improve the rapid charge and discharge performance of the electrode material, and greatly improve cyclic stability of polypyrrole. The composite electrode materi- al of polypyrrole and functionalized multi-walled carbon nanotubes for supercapacitors is prepared by pulse current deposition meth- od. It is scanned at a scanning rate of 1000mV?s -1 in a 3mol?L -1 potassium chloride electrolyte, after 100,000-cycle, the capacity on- ly declines by 16%.     

纳米Ag_2O修饰碳糊电极的电化学性能研究

采用化学方法制备纳米Ag2O粒子,研究了5种不同组成的纳米Ag2O碳糊电极在不同底液中的电化学行为。实验了不同pH值底液种类以及碳糊组成对电极性能的影响。结果表明:纳米Ag2O含量为16%的碳糊电极电化学性能、可逆性能及吸附性能好,传输电荷的能力强,表现出了优越的电极性能。     

A disposable electrochemical immunofiltration test strip for rapid detection of α-fetoprotein

A disposable electrochemical immunofiltration test strip for the rapid detection of α-fetoprotein (AFP) was developed. The test strip was constructed by assembly of screen-printed carbon electrodes, absorption-water pad, nitrocellulose membrane modified by anti-AFP antibody and glass fiber membrane conjugated with ferrocene monocarboxylic acid (FC) labeling AFP. The analytical system utilizes flow-through immunofiltration and competitive immunoassay techniques in combination with an amperometric sensor. The parameters affecting the immunoassay such as selection of filter membrane, membrane pore-size, and antibody binding capacity were investigated and optimized. The immunofiltration system allows us to specifically and directly detect AFP in serum with a low detection limit of 6 ng/mL. The working range is from 6 to 500 ng/mL with an overall analysis time of 5 min for one sample. This electrochemical immunoassay system enabled us to construct a novel point-of-care testing device for the monitoring of biomarker including AFP.     

A disposable single-use electrochemical sensor for the detection of uric acid in human whole blood

We report here a non-enzymatic detecting electrode strip for fast monitoring of uric acid in human whole blood. A single-use amperometric uric acid sensor strip, incorporating a three-electrode configuration, has been fabricated on a polypropylene substrate using low cost screen-printing (thick-film) technology. Both the working and counter electrodes were prepared by screen-printing commercial carbon ink. The integration on the same support of pseudo-reference electrode was obtained by screen-printing a commercial silver ink and subsequent electrochemical pretreatment. Simply by placing a 20 μl human whole blood drop on the strip is enough for uric acid analysis by square-wave voltammetry. Real human whole blood samples were analyzed by this method and compared to the phosphotungstic acid clinical test procedure with satisfactory results.     

Compact reconfigurable rat‐race coupler with tunable frequency and tunable power dividing ratio

A compact reconfigurable rat‐race coupler with tunable frequency and tunable power dividing ratio is proposed for the first time. Varactors and two single control voltages are used to obtain both the tunable frequency and the tunable power dividing ratio in this article. The structure of the rat‐race coupler involves 50 Ω parallel‐strip lines only and a phase inverter is used for size reduction. Theoretical equations for the relationship among S‐parameters and the capacitance of varactors are derived. The graphic method is used to choose capacitance for the desired operation frequency and the desired power dividing ratio. For demonstration, a prototype is designed and fabricated. The measured results show that the rat‐race coupler's frequency and the power dividing ratio can be effectively tuned in 0.69 GHz ～ 0.81 GHz and 3 dB ～ 14 dB, respectively with isolation better than 20 dB, phase difference less than 7°and return loss better than 20 dB. The theoretical simulation, electromagnetic simulation, and measured results show good agreement in this design.     

Energy storage options for wireless sensors powered by aircraft specific thermoelectric energy harvester

This paper describes an approach for efficiently storing the harvested energy from a thermoelectric module for powering autonomous wireless sensor nodes in aircraft health monitoring applications. Thermoelectric devices are the preferred option due to the widespread availability of significant levels of energy from the temperature gradients or variations at the aircraft, such as the cabin, the engine compartment, the fuel tanks or the inner and outer frame of the fuselage. Batteries and supercapacitors are popular choices of storage device, but neither represents the ideal solution, with, supercapacitors possessing low energy densities while batteries have low power density. When using a battery-only solution for storage, the runtime of a typical sensor node is typically reduced by the battery’s relatively high internal impedance and thermal loss. Supercapacitors can overcome some of these problems, but generally do not provide sufficient long-term energy to allow aircraft health monitoring applications to be operated over an extended period. A hybrid energy storage solution can provide both energy and power density to a wireless sensor node simultaneously. Techniques such as acoustic–ultrasonic, acoustic-emission, strain and crack wire sensors require storage approaches that can provide immediate energy on demand, usually in short, high intensity bursts, and that can be sustained over long periods of time, storing up to 40–50 J of energy. This application requirement is considered as a significant constraint when working with battery-only and supercapacitor-only solutions. The hybrid system described here provides an alternate viable solution.     

Multifrequency Wilkinson power divider using microstrip nonuniform transmission lines

A new idea is proposed to modify the conventional Wilkinson power dividers to operate at two or several desired frequencies. The proposed structure contains two Microstrip Nonuniform Transmission Lines (MNTLs) instead of two uniform ones with nearly the same length at the minimum frequency. The strip width of MNTLs is considered variable and is written as a truncated Fourier series. Three nonuniform power dividers are designed and one of them operating at frequencies 1.0, 2.8, and 4.5 GHz is fabricated and measured. The measured results of the fabricated diplexer have a good agreement with the theoretical results. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Learning and approximate inference in dynamic hierarchical models

A new variant of the dynamic hierarchical model (DHM) that describes a large number of parallel time series is presented. The separate series, which may be interdependent, are modeled through dynamic linear models (DLMs). This interdependence is included in the model through the definition of a ‘top-level’ or ‘average’ DLM. The model features explicit dependences between the latent states of the parallel DLMs and the states of the average model, and thus the many parallel time series are linked to each other. The combination of dependences within each time series and dependences between the different DLMs makes the computation time that is required for exact inference cubic in the number of parallel time series, however, which is unacceptable for practical tasks that involve large numbers of parallel time series. Therefore, two methods for fast, approximate inference are proposed: a variational approximation and a factorial approach. Under these approximations, inference can be performed in linear time, and it still features exact means. Learning is implemented through a maximum likelihood (ML) estimation of the model parameters. This estimation is realized through an expectation maximization (EM) algorithm with approximate inference in the E-step. Examples of learning and forecasting on two data sets show that the addition of direct dependences has a ‘smoothing’ effect on the evolution of the states of the individual time series, and leads to better prediction results. The use of approximate instead of exact inference is further shown not to lead to inferior results on either data set.     

碳纳米复合材料在电化学生物传感器中的研究进展

碳纳米材料以其优异的导电特性和机械性能及极佳的生物相容性在构建电化学生物传感器中备受关注,为电化学生物传感器的开发和研究开辟了一片广阔天地。将碳纳米材料与其它纳米材料复合,是一种拓展和增强其应用的有效方法。碳纳米材料在电化学生物传感器方面的应用主要是作为传感器界面的修饰材料、生物分子的固载基质以及信号标记物等。该文综述了碳纳米复合材料在电化学生物传感器中的应用,包括碳纳米管纳米复合物、石墨烯纳米复合物、富勒烯及碳量子点纳米复合物。并展望了未来基于碳纳米材料的电化学生物传感器的研究方向。     

电动汽车复合储能系统能量管理策略及其 快速控制原型验证

纯电动汽车储能系统需同时满足高功率密度与高能量密度的要求,但现阶段单一储能单元往 往难以同时具备这两种特点。将高能量密度的锂电池与高功率密度的超级电容进行合理搭配,形成复 合储能系统,是解决以上问题的一个有效方案。该文以宝马 I3 纯电动汽车作为目标车型,设计了锂电 池/超级电容复合储能系统,并制定了一种基于规则的能量管理策略,综合考虑了外部工况要求、锂电 池与超级电容的荷电状态,自动规划工作模式,充分发挥各储能单元自身优势,在极端状况下可自动 启动保护模式;同时,基于快速控制原型的思想,设计搭建了以 dSPACE 为控制中心的复合储能系统 能量管理策略快速控制验证平台,搭配可编辑电力参数的外部电子负载设备,完成了能量管理策略的 半实物实验验证。实验结果表明,电动汽车锂电池/超级电容复合储能系统搭配合理的能量管理策略, 能够充分发挥锂电池的能量特性与超级电容的功率特性,更好地满足了现代纯电动汽车对续航里程与 动力性能的要求,同时可节约能源,在一定程度上起到延长储能系统使用周期的作用。     

Comparison of Different Methods for Computing the Forward Kinematics of a Redundant Parallel Manipulator

In this paper, three numerical methods are presented to solve the forward kinematics of a three DOF actuator-redundant hydraulic parallel manipulator. It is known, that on the contrary to series manipulators, the forward kinematic map of parallel manipulators involves highly coupled nonlinear equations, whose closed-form solution derivation is a real challenge. This issue is of great importance noting that the forward kinematics solution is a key element in closed loop position control of parallel manipulators. The proposed methods, namely the Neural Network Estimation, the Quasi-closed Solution, and the Taylor series approximation, are using mainly numerical computations, with different ideas to solve the problem in hand. The latter two methods are proposed for the first time in literature to solve the forward kinematics of a parallel manipulator. These methods are compared in detail and the advantages or the disadvantages of each method in computing the forward kinematic map of the given mechanism is discussed. It is shown that a 4th order Taylor series approximation to the problem provides a good compromise for practical applications compared to that of other methods considered in this paper.     

Comparative study of tuning of microfabrication parameters for improving electrochemical performance of platinum and glassy carbon microelectrodes in neural prosthetics

Neural prosthetics, which are increasingly being considered for the dual functionalities of recording and stimulation, are implanted in a corrosive biochemical environment that requires them to possess superior electrical and electrochemical stability and performance. These probes are required to withstand these operating conditions through billions of cycles of pulses of electrical stimulations and also maintain electrochemical sensitivity for potential applications in voltammetry. In this research, microelectrodes made of two material systems; namely, platinum and glassy carbon, supported on a flexible substrate are fabricated and investigated for correlation between process parameters and the electrochemical efficacy of the neural interfaces, particularly charge storage capacity and corrosion rate. Using scanning electron and atomic force microscopies, the correlation between process parameters, surface morphology and topography in both platinum and glassy carbon were investigated. The results demonstrate that changes in surface topography and the rate of corrosion are correlated to variations in the process parameters. Furthermore, the results indicate a relationship between surface roughness and corrosion rate, in which the increase or decrease of the former corresponds to a similar change in the latter.

     

STRIP - a strip-based neural-network growth algorithm for learningmultiple-valued functions

We consider the problem of synthesizing multiple-valued logic functions by neural networks. A genetic algorithm (GA) which finds the longest strip in V subset, dbl equalsK(n) is described. A strip contains points located between two parallel hyperplanes. Repeated application of GA partitions the space V into certain number of strips, each of them corresponding to a hidden unit. We construct two neural networks based on these hidden units and show that they correctly compute the given but arbitrary multiple-valued function. Preliminary experimental results are presented and discussed.     

Investigation of joint clearance effects on the dynamic performance of a planar 2-DOF pick-and-place parallel manipulator

In this study, the effects of joint clearance on the dynamic performance of a planar 2-DOF pick-and-place parallel manipulator are investigated. The parallel manipulator is modeled by multi-body system dynamics. The contact effect in revolute joints with clearance is established by using a continuous analysis approach that is combined with a contact force model considering hysteretic damping. The evaluation of the contact force is based on Hertzian contact theory that accounts for the geometrical and material properties of the contacting bodies. Furthermore, the incorporation of the friction effect in clearance joints is performed using a modified Coulomb friction model. By numerical simulation, variations of the clearance joint's eccentric trajectory, the joint reaction force, the input torque, the acceleration, and trajectory of the end-effector are used to illustrate the dynamic behavior of the mechanism when multiple clearance revolute joints are considered. The results indicate that the clearance joints present two obvious separation leaps in a complete pick-and-place working cycle of the parallel manipulator, following a collision. The impact induces system vibration and thus reduces the dynamic stability of the system. The joint clearances affect the amplitudes of the joint reaction force, the input torque, and the end-effector's acceleration, additionally the joint clearances degrade the kinematic and dynamic accuracy of the manipulator's end-effector. Finally, this study proposes related approaches to decrease the effect of joint clearances on the system's dynamic properties for such parallel manipulator and prevent “separation-leap-impact” events in clearance joints.     

Electrophoretic motion of a colloidal cylinder near a plane wall

An analytical study is presented for the electrophoretic motion of a circular cylindrical particle in an electrolyte solution with a transversely imposed electric field near a large plane wall parallel to its axis in the quasisteady limit. The electric double layers at the solid surfaces are assumed to be thin relative to the particle radius and to the particle–wall gap width, but the polarization effect of the diffuse ions in the double layer surrounding the particle is incorporated. The presence of the confining wall causes two basic effects on the particle velocity: first, the local ionic electrochemical potential gradients on the particle surface are altered by the wall, thereby affecting the motion of the particle; secondly, the wall enhances the viscous retardation of the moving particle. Through the use of cylindrical bipolar coordinates, the transport equations governing this problem are solved and the wall effects on the electrophoresis of the cylinder are determined for various cases. The presence of the plane wall prescribed with the ionic electrochemical potentials consistent with the far-field distributions reduces the electrophoretic mobility of the particle, which depends upon the properties of the particle–solution system, the relative particle–wall separation distance, and the direction of the applied electric field relative to the plane wall. The direction of the electrophoretic migration of a cylindrical particle near a plane wall is different from that of the prescribed electric field, except when it is oriented parallel or perpendicular to the wall. The effects of the plane wall on the electrophoresis of a cylinder are found to be much more significant than those for a sphere at the same separation.     

Kinematic optimal design of a paramill: A multi‐SP device

In this paper, a manipulability analysis of a new parallel‐type rolling mill, named “paramill,” in its conceptual design stage is investigated. The paramill considered uses two Stewart platforms (SPs) in opposite directions for the generation of 6 degree‐of‐freedom motions of individual work‐rolls. The objective of this new approach is to pursue an integrated control of the strip thickness, strip shape, pair‐crossing angle, uniform wear of the rolls, and tension of the strip. The forward/inverse kinematics problems are formulated. Two main kinematic parameters, the size of the base and the acute angle made by two neighboring joints for a given size of the work‐roll, have been determined in the way that the force and moment transmission from the actuators to the work‐rolls is maximized. © 2004 Wiley Periodicals, Inc.     

A compact wideband balun design using double‐sided parallel strip lines with over 9:1 bandwidth

A simplified miniaturized wideband balun design covering (0.38‐3.5 GHz) is presented. The broadband balun structure occupies a small area of 20.7 mm × 20.8 mm. The balun is designed using low loss double‐sided parallel strip lines and is comprised of a two‐stage Wilkinson divider followed by loading, symmetrically, the two output ports. One port with a phase inverter circuit; while a very similar but non‐inverting circuit is placed in the other port for loading‐balance compensation. To realize the balun's function, different smooth transitions have been employed and were accounted for. The fabricated balun circuit demonstrated phase and amplitude imbalance of less than ±5° and ± 0.4 dB, respectively, over the band.     

Interconnecting interactive and remote parallel components using schooner

In scientific applications where parallel computation is used to model physical processes, enhancing the user's ability to monitor and control programs executing on remote parallel machines can improve the overall experimental process. Here, a simple approach to providing such facilities is presented in which a scientific visualization system and a remote parallel computation are incorporated into a single metacomputation using the Schooner software interconnection system. This scheme gives the user the ability to, for example, select dynamically the parallel platform to be used, monitor the progress of the computation, and modify parameters. To illustrate this approach, a series of experiments is described in which the AVS scientific visualization system and a parallel neural net code executing on either an Intel Paragon, Sequent Symmetry, or PVM-based Sun Sparcstation cluster are interconnected. These experiments demonstrate not just the feasibility of structuring parallel computations as part of a larger metacomputation using Schooner, but also that these benefits can be achieved with an adjustable cost that can be tuned to the specific needs of the application. © 1997 John Wiley & Sons, Ltd.