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Purpose The purpose of this study is to conduct research on a new kind of division microchannel heat sink (D-MCHS), which can distribute cooling water along the channel-length direction. First, the pressure drops in the D-MCHS with different division region numbers were compared. Then, the cooling performance of the D-MCHS with different division region numbers was also comparatively investigated. Finally, the temperature distribution on the bottom surface of the D-MCHS was analyzed. Design/methodology/approach First, experiments were conducted to investigate the numerical calculation method. Then, a three-dimensional steady, single-phase, laminar flow and solid-fluid conjugate heat transfer numerical model was used to research the flow and heat transfer characteristics in microchannels. Findings The pressure drop in the D-MCHS could be reduced by increasing the number of divided flow regions along the channel-length direction. The bottom average temperature of the D-MCHS could be simultaneously affected by the number of divided flow regions and the water flow rate. The thermal uniformity performance of the D-MCHS could be improved by increasing the number of division flow regions. The number of low-temperature and high-temperature areas on the bottom surface of the D-MCHS is corresponding to the division flow region number. Originality/value The D-MCHS exhibited a positive effect on the pressure drop decrease and thermal uniformity improvement. It not only keeps the electronic module working in a secure temperature environment but also consumes less pump power for a lower pressure drop.

N-type vapor diffusions in p-GaSb wafers is investigated using the group-VI elements S, Se and Te as diffusion sources. The group-VI elements are found difficult to diffuse in bare p-GaSb wafers because they react with Ga atoms to form compounds, thus hindering the diffusion. Deposition of a SiO layer on the p-GaSb surface is found to be crucial for realizing n-type diffusion. With this SiO coating layer, the concentration of group-VI atoms decreased to a low value limiting the reaction with Ga atoms. Se atoms are found to be good n-type diffusion sources. GaSb thermophotovoltaic cells with n-on-p structures are fabricated using Se diffusion. Compared with a traditional GaSb cell with a p-on-n structure, the cell with the n-on-p structure had a higher quantum efficiency at wavelengths beyond 1000 nm. The output power density was also 1.42 times higher compared to the traditional cell when measured with a 1300 °C - SiN ceramic IR emitter.

A 3D macroporous conductive polymer foam of thin 2D polypyrrole (PPy) nanosheets is developed by adopting a novel intercalation of guest (monomer Py) between the layers of the lamellar host (3D vanadium oxide foam) template-replication strategy. The 3D PPy foam of thin 2D nanosheets exhibits diverse functions including reversible compressibility, shape memory, absorption/adsorption and mechanically deformable supercapacitor characteristics. The as-prepared 3D PPy foam of thin nanosheets is highly light weight with a density of 12 mg·cm-3 which can bear the large compressive strain up to 80% whether in wet or dry states; and can absorb organic solutions or extract dye molecules fast and efficiently. In particular, the PPy nanosheet-based foam as a mechanically deformable electrode material for supercapacitors exhibits high specific capacitance of 70 F·g-1 at a fast charge-discharge rate of 50 mA·g-1, superior to that of any other typical pure PPy-based capacitor. We envision that the strategy presented here should be applicable to fabrication of a wide variety of organic polymer foams and hydrogels of low-dimensional nanostructures and even inorganic foams and hydrogels of low-dimensional nanostructures, and thus allow for exploration of their advanced physical and chemical properties.

The GaSb cells are commonly fabricated using Zn diffusion into n-GaSb substrates. The doping of GaSb cells for both base and emitter regions is optimized for increasing the quantum efficiency (QE) in the long wave range, which will enhance the cell performance in thermophotovoltaic systems. Selection of lightly Te-doped n-GaSb substrates is an effective method. The surface recombination velocity (S) has a direct impact on the emitter doping. The optimal diffusion depth increases with the decreasing of S value. The QE in the long wave range will increase with the deepening of diffusion depth if the S is kept at a low value. The GaSb cells with different junction depths were fabricated using Zn diffusion and sulfur passivation, the cell with a deep junction has the larger QE in the long wave range, which is consistent with our simulation results.

Firstly, we describe the principle and the details of our home-built visible light-based thermoreflectance imaging setup. Based on the prototype, a transient temperature measurement of a micro resistance in operation were undertaken. With this technique, a high-resolution thermal distribution of devices can be achieved in real time. The factors influencing spatial resolution, time resolution and temperature resolution of the temperature measurement were analyzed and discussed further. The analysis and results showed that the prototype, which based on a visible light-based thermoreflectance imaging technique, could achieve a spatial resolution of 663nm, a time resolution of 2μs, and a temperature resolution of 0.1K.

GaSb cells are commonly fabricated using Zn diffusion into n-GaSb, and in this paper they have been designed inversely using Te diffusion into unintentionally p-doped GaSb. Numerical simulation is used to analyze the cell performance. We found that a GaSb cell with n-type emitters showed a significantly higher output power density compared with that of the cell with p-type emitters under 1500 K-blackbody radiation. The performance improvement is owing to the good matching of the diffusion length of minority carriers with the depth of their moving regions. Several parameters that affect the cell performance were analyzed, such as doping depth, substrate thickness, and surface recombination velocity. The cell performance was evaluated under low temperature radiations and found to have huge potentials for the use in low-temperature thermophotovoltaic systems.

Power converter is going in the direction of the high power density. Aimed at the trend, a 1200V/300A planar double-side cooling IGBT module has been designed, packaged. Comparing with conventional IGBT module, Parasitic inductance is reduced by 43.26%; Thermal resistance is 26.7% lower; Turn-on time and turn-off time are decreased by 35% and 15.8% respectively; The total power losses are reduced by 8.68%. Therefore the overall performances of the planar double-side cooling IGBT module are superior to the conventional IGBT module. Furthermore, it is possible for IGBT module to improving its current handling capability and power density by designing its packaging structure and packaging process.

Zn diffusion processes in n-Ga0.78In0.22As0.2Sb0.8 epitaxial films are studied using different diffusion sources, a series of the Zn profiles with single and double humps are obtained. The group V-atoms (As and Sb) are found to have little effect on suppressing the surface “dead region”. The Ga and In atoms have entirely different effect on diffusion although they are both group III-atoms. The “dead region” is suppressed completely under Ga-rich conditions, while the suppression will not occur under In-rich conditions. The GaInAsSb cells are fabricated under pure Zn and Ga-rich conditions. An electrical heating thermophotovoltaic system is fabricated for cell testing. Under the radiation from 1055 °C-SiN ceramics emitter, the output power density of the GaInAsSb cell obtained under Ga-rich condition is much larger than that of the cell obtained under pure Zn condition, which demonstrated that the GaInAsSb cells can be fabricated without precise etching under Ga-rich conditions.

It has been demonstrated that a single thermophotovoltaic (TPV) cell can produce a high-output power density. In practical applications, many such cells are arrayed to obtain a high level of output. However, the irradiance on the surface of each cell of an array may be different. This nonuniformity causes mismatch loss in the array and reduces the reliability of the cells. To address these problems, a novel TPV optical cavity with reflectors was proposed to improve the irradiance uniformity of the cell array. A model TPV system using the proposed cavity was built and evaluated for comparison with traditional systems. TracePro and MATLAB software were used to examine the irradiance uniformity of cell arrays and the electrical performance of TPV systems that incorporate these arrays. Besides system efficiency ηsystem and maximum output power Pmax, several critical parameters degree of uniformity N, network efficiency ηnet, and average cell electric power density Wave, were used to evaluate the performance of the TPV systems. The results indicate that the proposed cavity improved the irradiance uniformity of the TPV cell array, thereby reducing mismatch loss and enhancing system performance, and it did so with a reduced number of cells.

The power output and the efficiency of a thermophotovoltaic (TPV) system are determined by the radiation from a heat source, TPV cells, system parasitic losses, cell cooling subsystems, etc. The cells are core devices of a system, and the performance of the cells can be characterized by a number of parameters, including open circuit voltage (Voc), short circuit current density (Isc), and maximum output power density (Pm). The cell temperature has a great effect on these parameters. Although several papers have reported the dependence of these parameters on the cell temperature, few studies experimentally examined the temperature-dependent performance of the TPV cells or comparatively analyzed them. In this study, we investigated how the fundamental parameters of GaSb, Ge, and InGaAsSb cells varied with their operating temperatures using a home-built TPV prototype. The measured data indicate that the cell temperature significantly affects the performance of the TPV cells. Variations of these parameters with the cell temperature are different for various TPV cells. The Voc and Pm of the GaSb, Ge, and InGaAsSb cells decreased linearly with increasing cell temperature, while the Isc increased slightly. The normalized value of the temperature coefficient for the Pm of the GaSb was lower than those for the Ge and InGaAsSb cells, which indicated that the GaSb cells were relatively less sensitive to cell temperature. The results provided in this study are useful to improve cell performance and design TPV systems.

This paper proposes a heuristic triple layered particle swarm optimization–back-propagation (PSO-BP) neural network method for improving the convergence and prediction accuracy of the fault diagnosis system of the photovoltaic (PV) array. The parameters, open-circuit voltage (Voc), short-circuit current (Isc), maximum power (Pm) and voltage at maximum power point (Vm) are extracted from the output curve of the PV array as identification parameters for the fault diagnosis system. This study compares performances of two methods, the back-propagation neural network method, which is widely used, and the heuristic method with MATLAB. In the training phase, the back-propagation method takes about 425 steps to convergence, while the heuristic method needs only 312 steps. In the fault diagnosis phase, the prediction accuracy of the heuristic method is 93.33%, while the back-propagation method scores 86.67%. It is concluded that the heuristic method can not only improve the convergence of the simulation but also significantly improve the prediction accuracy of the fault diagnosis system.

Shading is one of the main reasons for the heat spot effect of a photovoltaic array, which causes electrical mismatch and seriously affects its output characteristics. Based on the widely adopted photovoltaic array with series-parallel architecture, we present an optimized online localization method about the photovoltaic shading faults. By optimizing voltage sensor configurations, the method not only simplifies the topology of the fault detection system, but can also ascertain the fault locations with varying shadow degrees of the photovoltaic array quickly and accurately. It can also forecast the illumination intensity on the photovoltaic cells online. We demonstrate that for a 4×4 series-parallel photovoltaic array, 8 voltage sensors can achieve fault localization with an accuracy up to a single cell of any column or row. Simulation with MATLAB proves that this method improved the efficiency and accuracy of fault detection in the series-parallel photovoltaic array.

Energy harvesting from environmental vibrations attracts increasing interest in wireless sensor networks and microsystems. In this paper, we examine the feasibility of increasing the output power of cantilever energy harvesters through segmentation of the piezoelectric layer. Finite element method is used to calculate the static and dynamic performance of energy harvester for different segmentations.

Using scanning near-field lithography (SNP), it is possible to pattern molecules at surfaces with a resolution as good as 9 nm [M. Montague, R. E. Ducker, K. S. L. Chong, R. J. Manning, F. J. M. Rutten, M. C. Davies and G. J. Leggett, Langmuir 23 (13), 7328–7337 (2007)]. However, in common with other scanning probe techniques, SNP has previously been considered a serial process, hindering its use in many applications. IBM’s “Millipede” addresses this problem by utilizing an array of local probes operating in parallel. Here, we describe the construction of two instruments (Snomipedes) that integrate near-field optical methods into the parallel probe paradigm and promise the integration of top–down and bottom–up fabrication methods over macroscopic areas. Both are capable of performing near-field lithography with 16 probes in parallel spanning approximately 2 mm. The instruments can work in both ambient and liquid environments, key to many applications in nanobiology. In both, separate control of writing is possible for each probe. We demonstrate the deprotection of self-assembled monolayers of alkylsilanes with photocleavable protecting groups and subsequent growth of nanostructured polymer brushes from these nanopatterned surfaces by atom-transfer radical polymerization.

Scanning near-field photolithography (SNPL) has recently shown its great potential for fabricating various structures at the nanoscale. However, the low throughput of SNPL is a barrier to wider applications. Additionally, to extend SNPL to operation in aqueous environments is of significant importance to applications in nanobiology, such as sensing, screening and protein adsorption studies. Here we describe a new instrument (a ''Snomipede'') that facilitates the parallel execution of SNPL under water using an AFM-style cantilever probe array and liquid cell. A feature size (full width at half maximum (FWHM)) of around 70nm has been achieved for dot arrays fabricated in parallel under water.

In the recent development on biosensors, coplanar waveguide based microwave dielectric sensors have been attracting more and more attentions. In this paper, microwave performance of a suspended coplanar waveguide subject to temperature variations, particularly in a small range, is studied. The prototype is realized through a MEMS fabrication foundry. The thermal transfer analysis of the device is conducted using finite element method, and the microwave properties of the device are characterized. One of the results shows that at 20 GHz, the S11 has decreased by 7.4%, and S21 has increased by 3.5% when the voltage applied to the heaters varies from 9 V to 29 V.

The “Millipede”, developed by Binnig and co-workers (Bining, G. K.; et al. IBM J. Res. Devel. 2000, 44, 323.), elegantly solves the problem of the serial nature of scanning probe lithography processes, by deploying massive parallelism. Here we fuse the “Millipede” concept with scanning near-field photolithography to yield a “Snomipede” that is capable of executing parallel chemical transformations at high resolution over macroscopic areas. Our prototype has sixteen probes that are separately controllable using a methodology that is, in principle, scalable to much larger arrays. Light beams generated by a spatial modulator or a zone plate array are coupled to arrays of cantilever probes with hollow, pyramidal tips. We demonstrate selective photodeprotection of nitrophenylpropyloxycarbonyl-protected aminosiloxane monolayers on silicon dioxide and subsequent growth of nanostructured polymer brushes by atom-transfer radical polymerization, and the fabrication of 70 nm structures in photoresist by a Snomipede probe array immersed under water. Such approaches offer a powerful means of integrating the top-down and bottom-up fabrication paradigms, facilitating the reactive processing of materials at nanometer resolution over macroscopic areas.

Analysis and new structure is introduced to correct eddy current in electron beam focusing-deflection system. Maximum errors caused by eddy current are computed by changing permeability of the conductive materials at time t"0 (t"0=0, @m=0) and t"~ (t"0=~, @[email protected]"r) with the aid of Munro's software. The new double ferrite structure includes outer- and inner-layer ferrite rings which are spaced by ceramic spacer uniformly and staggered each other in radial direction. Basic principle for eddy current correction in this paper is that ferrite materials prevent the flow of magnetic flux from the deflection coil to the polepiece without perturbing the lens field. Magnetic flux of various lens structures and magnetic scalar equipotential lines of various deflectors illustrate the principle. Correction and performance versus the values of the gap (G) and the space (S) between the ferrite rings are considered. The new double ferrite structure not only corrects the eddy current, but also increases the sensitivity of the deflection without decreasing the performance.

Most scanning near-field photolithographs (SNP) operate in ambient environment. Recently, operation in aqueous environment has been introduced, which has extended SNP application in nanobiology. Moreover we found aqueous environment improved performance of SNP platform as aqueous environment significantly decreases adhesion force between the probe and sample surfaces. To better understand interactions between the probe and sample surface in SNP, force analysis in both ambient and aqueous conditions were investigated. Demonstrated experiments and discussion are presented.

A new square shaped piezoelectric bimorph structure for energy scavenging purposes has been proposed and simulated. It is derived from theoretical analysis that the output power of the structure is proportional to the value of the resonant frequency. The device working in Lame mode has a much higher resonant frequency of 2.39 MHz than devices working in ordinary bending modes, which is expected to significantly increase the energy output of radioisotope power generators (RPGs). The results of static analysis and dynamic response show that output voltage is linear with the applied load; the output power is quadratic with the applied load.

Background Current knowledge about incident dementia is mainly derived from studies undertaken in the West, showing that dementia is related to older age, low socio-economic status, lack of social network, depression and cardiovascular disease risk factors. We know little about incidence and predictors of dementia in China, where the prevalence is increasing and the patterns of risk factors are different. Methods Using a standard interview method, we examined 1526 non-demented people aged ≥65 years who had at least minimal educational level in China in a 7.5-year follow up. Incident dementia was diagnosed by GMS-AGECAT algorithms and psychiatrists. Results Age-standardised incidence of dementia was 14.7 per 1000 person-years (95%CI 11.3–18.2 per 1000 person-years). The increased risk was significantly associated with age, female gender (adjusted odds ratio 2.48, 95%CI 1.20–5.13), low educational levels, smoking, angina (2.58, 1.01–6.59) and living with fewer family members. Among participants with low educational level, the increased risk was associated with higher income, and with the highest and lowest occupational classes; adjusted odds ratio 2.74 (95%CI 1.12–6.70) for officers/teachers, 3.11 (1.61–6.01) for manual labourers/peasants. Conclusions Our findings of high incidence of dementia and increased risk among people having low education levels but high income suggest a more potential epidemic and burden of dementia populations in China. Maintaining social network and activities and reducing cardiovascular factors in late life could be integrated into current multi-faceted preventive strategies for curbing the epidemic of dementia.

Piezoelectric materials have been widely used in transducers to convert mechanical deformation to electrical energy for power scavenging applications. Piezoelectric energy harvesting in bimetallic cantilever configuration is the most popular approach which scavenges mechanical energy predominantly from bending motions. A new piezoelectric cantilever design is proposed, which consists of a piezoelectric layer being split into two separate parts and a supporting substrate. This design enables energy conversion in both bending and torsional motions, which expands the bandwidth of harvesting devices and increases the energy converting efficiency. Structural optimization for the new design is conducted using a commercial multiphysical FEM (finite element method) software. Static and dynamic simulations of the proposed structure have been conducted, and the results are discussed and presented in this paper.

An optical leveling technique is reported for a compact parallel (multi-cantilever) scanning near-field photolithography (SNP) prototype. This instrument operates in liquid and was designed to overcome the challenge of low sample throughput of previous serial scanning SNPs. A combination of zone plate lens array, probe array, and standard atomic force microscope feedback technique are employed to deliver parallel probe operation in the current SNP. Compared to the commonly used two-end or multi-end “force feedback” alignment techniques, the optical levelling technique applied provides a simple solution to maintaining all levers in an array within the near-field region. As a proof-of-principle experiment, the operation of the prototype was demonstrated by producing nano-scale patterns in parallel using scanning near-field photolithography.

To develop a nano-lithography system based on scanning electron microscopy, a high-speed and high-precision deflection system including two prelens magnetic deflectors is introduced in this article. Best length ratio between two deflectors is achieved, which attributes to high sensitivity without loss of resolution. Some trade-off has been taken between aberrations and landing angle to get optimum performance of deflection system. The art of wire electron discharge machining is used to guarantee geometric accuracy and lower inductance. Frequency response test and lithographic experiments confirm the design.