Acrylic acid controlled reusable temperature-sensitive hydrogel phantoms for thermal ablation therapy

Polymerization of N-isopropylacrylamide (NIPAM) with acrylic acid (AAc) has been adopted to fabricate reusable tissue-mimicking hydrogel phantoms designed for the real-time visualization and examination of thermal lesion formation in ablation and hyperthermia therapies. It is shown that the cloud point temperature of the NIPAM-based hydrogel phantoms can be adjusted by the concentration of AAc to represent the threshold temperature of pain (42 °C) or tissue damage (52 °C). The mechanical, thermal and acoustic properties of the developed phantoms are similar to those of human soft tissues. The ability of the phantoms to provide visualization of thermal lesions produced by either microwave or high-intensity focused ultrasound (HIFU) ablation was examined. Evolution of the optical transparency of the phantoms with temperature was found to be a stable hysteretic behavior and reproducible in consecutive heating–cooling cycles, demonstrating the reusability of the phantoms. By processing the optical images of the phantoms at different stages of the heating process, a thermal lesion can be considered formed (i.e., threshold temperature reached) when the grayscale value reaches the half-saturation point. The image processing method proposed for the NIPAM-based hydrogel phantoms is shown to be independent on the type of heating device used.     

飞行器控制舵疏导式组合结构热防护性能试验与数值分析

为适应飞行器舵/翼在临近空间长航程飞行过程中气动维形的需求,以碱金属为工质,将具有高温热疏导能力的钨、钼固溶强化镍基合金疏导装置嵌套在高导热C/C防热罩和碳基柔性高导热夹层内侧。通过仿形石英灯加热器设计,开展了不同飞行环境条件下的地面性能测试试验。结合试验结果利用数值分析方法对其整体传热能力和各工况下的热防护效果进行了分析。结果表明,疏导装置启动时有效导热系数可由18.42 W/(m.K)提升至1390.00 W/(m.K),稳定状态可降低前缘峰值温度21.70%~23.04%,疏导式组合结构表面最大温差降幅64.80%,极大减小由温度梯度产生的热应力,有效提升高温环境下热结构匹配性和材料可靠性,可多次重复使用。该组合式热防护结构是解决高速飞行器前缘等高气动加热区烧蚀防热变形问题行之有效的技术途径之一,可针对新一代飞行器气动外形和飞行环境开展进一步工程应用研究。     

基于圆柱形单元的储热装置放热实验研究

蓄热水箱作为太阳能供暖系统的重要核心设备,其性能直接影响着储能系统的整体运行效率。设计一种基于圆柱形相变单元的相变储热装置,并搭建相变蓄热水箱性能测试平台,通过单一控制变量法得到储热装置放热过程的温度变化曲线。研究表明：对于空间一定的储热装置,在等质量相变材料（PCM）时,相变单元的直径对装置放热速率的影响较大;相变单元之间的间距对装置放热速率的影响较小;当增大换热流体（HTF）的入口流量及降低HTF入口温度时,能大大减少储热装置的放热时间,提高储热装置的整体性能。     

Evaluating the performance of microbial fuel cells powering electronic devices

A microbial fuel cell (MFC) is capable of powering an electronic device if we store the energy in an external storage device, such as a capacitor, and dispense that energy intermittently in bursts of high-power when needed. Therefore its performance needs to be evaluated using an energy-storing device such as a capacitor which can be charged and discharged rather than other evaluation techniques, such as continuous energy dissipation through a resistor. In this study, we develop a method of testing microbial fuel cell performance based on storing energy in a capacitor. When a capacitor is connected to a MFC it acts like a variable resistor and stores energy from the MFC at a variable rate. In practice the application of this method to testing microbial fuel cells is very challenging and time consuming; therefore we have custom-designed a microbial fuel cell tester (MFCT). The MFCT evaluates the performance of a MFC as a power source. It uses a capacitor as an energy storing device and waits until a desired amount of energy is stored then discharges the capacitor. The entire process is controlled using an analog-to-digital converter (ADC) board controlled by a custom-written computer program. The utility of our method and the MFCT is demonstrated using a laboratory microbial fuel cell (LMFC) and a sediment microbial fuel cell (SMFC). We determine (1) how frequently a MFC can charge a capacitor, (2) which electrode is current-limiting, (3) what capacitor value will allow the maximum harvested energy from a MFC, which is called the “optimum charging capacitor value,” and (4) what capacitor charging potential will harvest the maximum energy from a MFC, which is called the “optimum charging potential.” Using a LMFC we find that (1) the time needed to charge a 3-F capacitor from 0 to 500 mV is 108 min, (2) the optimum charging capacitor value is 3 F, and (3) the optimum charging potential is 300 mV. Using a SMFC we find that (1) the time needed to charge a 3-F capacitor from 0 to 500 mV is 5 min, (2) the optimum charging capacitor value is 3 F, and (3) the optimum charging potential is 500 mV. Our results demonstrate that the developed method and the MFCT can be used to evaluate and optimize energy harvesting when a MFC is used with a capacitor to power wireless sensors monitoring the environment.     

Numerical simulation and experiment research of radiation performance in a dish solar collector system

The Monte Carlo ray-tracing method is applied and coupled with optical properties to predict the radiation performance of solar concentrator/cavity receiver systems. Several different cavity geometries are compared on the radiation performance. A flux density distribution measurement system for dish parabolic concentrators is developed. The contours of the flux distribution for target placements at different distances from the dish vertex of a solar concentrator are taken by using an indirect method with a Lambert and a charge coupled device (CCD) camera. Further, the measured flux distributions are compared with a Monte Carlo-predicted distribution. The results can be a valuable reference for the design and assemblage of the solar collector system.     

Dryout analysis of overloaded microscale capillary-driven two-phase heat transfer devices

Dryout occurrence at high heat input is one of the detrimental factors that limit the thermal efficiency of a phase-change heat transfer device. In this work, we demonstrate that by employing visualization method, the dryout occurrence of an elongated liquid droplet in a transparent evacuated microscale two-phase flow device can be scrutinized. The circulation of liquid from the condenser to the evaporator is driven by the capillary action which is the primary limitation that governs the maximum heat transport capability of the device. When the evaporation rate exceeds the circulation rate of condensate, dryout will take place in the evaporator end. The propagation of dryout lengths can be accurately determined directly from visualization and a more accurate evaluation of the dryout length compared to the conventional method by measuring the axial temperatures has been developed. By quantifying the performance indicators of the cooling device over a wide range of operating conditions, including the underloaded and overloaded operations, the observation of dryout occurrence in this study correlates highly with the anticipated heat transfer characteristics of a phase-change heat transfer device. This study provides essential insights, particularly on the overloaded conditions, to the design of a microscale two-phase heat transfer device.     

海洋能发电装置叶片翼形的性能分析与优化

鉴于水轮机叶片翼形是影响叶片水动力性能的关键指标之一,总结了现有海洋能发电装置使用的叶片类型及翼形结构,基于数值模拟仿真方法,分析了10种不同型号的叶片翼形的水动力性能,包括升阻力力学性能及表面压力分布、压强与速度分布性能指标,并对比了不同翼形的升阻力系数与升阻力比。在此基础上,初步提出了一种叶片翼形优化方法,为提高海洋能发电装置效率及装置叶片水动力分析与优化提供参考。     

A thermal-ablation bioheat model including liquid-to-vapor phase change,pressure- and necrosis-dependent perfusion,and moisture-dependent properties

A new bioheat model is applied to evaluate the use of elevated-temperature thermal therapies for the non-surgical ablation of diseased tissue. The new model is based on the use of the enthalpy method to account for liquid-to-vapor phase change. In addition, the model includes thermophysical property dependence on liquid content and variations of blood perfusion rates dependent on the local necrotic state of the tissue or external pressure applied by the therapy-delivering device. This model is applied here specifically to endometrial ablation for the treatment of menorrhagia. The results of the implementation of the model yielded the depth of tissue necrosis corresponding to a given application of heat at the exposed inner surface of the uterine tissue. These results definitively establish the occurrence of phase change and the complete suppression of perfusion as the major factors governing the necrosis depth. The accounting of moisture-dependent properties had a negligible effect on necrosis.     

Heat Transfer Design Methodology Treating a Heat Exchange Device and Its Fluid-Mover Partner as a Single System

When a heat exchange device and its fluid-mover partner are modeled simultaneously, as a single system, the predicted performance of the device can be substantially different from modeling the heat exchange device separately. This conclusion is based on realistic models of the underlying heat transfer and fluid flow phenomena, on the rotational motions occurring within the fluid mover, and on the geometry of both the heat transfer device and the fluid mover. Here, an unsteady three-dimensional model was implemented by numerical simulation as a case study of a thermal management system that is frequently encountered with electronic equipment. As a comparison case, the same thermal management system was evaluated using a common design method where the fluid mover (fan) in the system is removed and replaced by a prescribed magnitude and distribution of fluid flow (the fan curve). It was found that the local and overall heat transfer and the fluid flow delivered to the heat exchanger were significantly overpredicted by the simplified design model relative to those from a more rigorous approach. A broad conclusion of the present work is that better results can be obtained when the heat exchange device and the fluid mover are modeled simultaneously.     

微水头水流能水轮机水动力性能研究

针对微水头低流速水域流速梯度的问题,在水轮机导流罩基础上设计一种采集装置,使水轮机能提前采集低流速水流, 用结构补偿流量, 并通过数值模拟与试验相结合的方法,研究在非均匀流中加装采集装置对水轮机水动力性能的影响。结果表明：加装采集装置可减弱流速梯度对水轮机水动力性能的影响, 在低流速时作用明显。同时加装采集装置可增大水轮机输出功率, 减小启动流速,输出功率最多增大约2.2倍,启动流速可减小约0.1 m/s。     

一种聚合物/C60异质结有机太阳电池

用MEH-PPV为给体(空穴传输)、C60为受体(电子传输)首先制备了分层和体异质结结构的两种器件,器件结构为ITO/PEDOT:PSS/MEH-PPV/C60/Al和ITO/PEDOT:PSS/MEH-PPV:C60/Al。之后又制备了结构为ITO/PE-DOT:PSS/MEH-PPV:C60/C60/Al的第3个器件。作者比较了这3种器件的光伏性质,发现器件3的短路电流密度(JSC)比器件1和器件2的分别增加了300%和150%,开路电压(VOC)分别增加了100%和20%。这主要是由于C60层增加了电子由受体传输到负电极的通道并增大了给体受体界面面积。另一原因是此C60层一定程度地阻挡了空穴从有机物向负极的传输,从而有效地改善了太阳电池的性能。     

太阳能电池冷却器的设计与研究

介绍了一种太阳能电池冷却的方法,对太阳能电池冷却器进行了设计。讨论了不同结构参数对于冷却器性能的影响。结果表明,当翅片高度为10-20mm,间距为20-40mm时,冷却效果最好。搭建了冷却器性能实验台,并对其冷却性能做了实验研究,发现经过冷却的电池板,其背板温度最高可以降低15℃,相对电效率平均提高约12％。     

Thermal Analysis for Package Cooling Technology Using Phase-Change Material by Using Thermal Network Analysis and CFD Analysis With Enthalpy Porosity Method

This paper describes a transient cooling technology for electronic equipments using phase-change material (PCM). The module is made of low-cost materials, yet it is designed to achieve a reasonably high level of heat transfer performance. Paraffin is used as the PCM. In previous our report, we can estimate the cooling performance of PCM by using a thermal network method, which cannot calculate melted PCM flow. In this paper, we consider the heat transfer phenomena of PCM module more deeply by using computational fluid dynamics (CFD) analysis with an enthalpy porosity method. By using this method, we can calculate phase-change phenomena and flow phenomena of melted PCM with CFD analysis. First, we briefly explain the results of the experiment and the thermal network analysis. Then we describe the details of CFD analysis with the enthalpy porosity method. In this calculation, melted PCM flow and heat absorption of latent heat can be analyzed. Therefore, we can discuss the reason why the thermal network analysis can estimate cooling performance of PCM module without dealing with melted PCM flow. The calculation results showed that natural convective flow of melted PCM affects the cooling performance of the PCM module. In the case where the PCM module is set vertically, high temperature and low temperature locations exist on the substrate. If several devices are cooled with the PCM module, device consuming the most power must be set in the lower part of the PCM module. From these results, we can conclude that no natural convective flow occurs in our experiment due to the shape of the PCM module.     

电阻炉温度控制系统

电阻炉模型参数具有随温度而变化的时变特性,当炉温大范围变化时采用常规PID控制方法不能满足较高工艺要求,为此,文中提出了一种自适应控制方法,并研制了基于单片机的温度控制装置,实际运行证明;控制方法具有较高的稳态精度和跟踪特性,且超调量小,控制装置简单、可靠。     

海上风力机多层材料防护装置在船舶碰撞下动力响应分析

为研究橡胶-泡沫铝-钢结构新型防护装置不同厚度组合对碰撞过程中海上风力机结构动力响应的影响,基于非线性动力学理论,采用LS-DYNA软件模拟5 000 t级船舶与4 MW海上风力机单立柱三桩基础碰撞过程,对比分析泡沫铝和橡胶分别组成4种厚度防护装置海上风力机与船舶碰撞时系统能量转换、最大碰撞力及碰撞处的应力分布。结果表明:防护装置橡胶与泡沫铝厚度变化,橡胶对防护装置整体性能提高具有明显作用,同时抑制塔顶风力机动力响应效果显著。提出应力衰减率作为评估防护装置性能优劣指标,随着橡胶厚度与泡沫铝厚度改变,单立柱三桩基础所受最大碰撞力分别减少6.3%、12.7%,最大应力衰减率7.03%、4.8%,橡胶用于防护装置中整体性能优越,而泡沫铝可作为辅助材料迅速提高防护性能。     

Opto-electrical and morphological characterization of water soluble conjugated polymers for eco-friendly hybrid solar cells

Solid-state Dye-Sensitized Solar Cells (ss-DSSCs) are promising candidates for future low cost photovoltaic energy generation and are based on polymer/metal oxide donor/acceptor heterojunctions. However, a crucial drawback of hybrid solar cells is the use of environmental unfriendly solvents, such as toluene, chloroform, chlorobenzene, etc. in the phase of preparation. In this work towards eco-friendly processing, we use water as a solvent in the preparation of the photo-active layer for hybrid solar cells. We demonstrate eco-friendly hybrid polymer/titania solar cells consisting of water soluble polythiophene as light-absorber, donor and Hole Transporting Layer (HTL), above a TiO₂ layer that acts as an acceptor and electron conductor. The water soluble conjugated polymer materials are studied in terms of their opto-electrical and morphological properties, leading to a better understanding of the resulting photovoltaic performance. An alternative new processing method in device preparation is introduced; yielding prototype solar cells with an efficiency of 0.7%. This promising solar cell device performance can be considered as a proof-of-principle for future eco-friendly solar cells.     

SQL代理隔离装置在电力行业的应用研究和测试验证

随着电力信息化的不断发展,电力信息网络结构日益复杂。国家电网有限公司通过在管理信息大区和互联网大区的网络边界部署结构化查询语言(SQL)代理隔离装置,提升信息网络边界安全防护能力。文章主要介绍SQL代理隔离装置的部署和应用,并通过设计自动化测试用例模拟业务接口调用和并发的方式,对装置的功能和性能进行测试验证。验证结果表明SQL代理隔离装置能够实现内外部网络和数据安全隔离,且性能良好。     

点火器控制模块设计

点火器是汽油机点火系最重要的零部件之一，其性能直接影响到汽车的动力性和经济性等性能。本文提出了在电控汽油机上点火触发信号进行点火能量自适应控制的方法，采用开闭环相结合的控制方式；采用PIC16C62单片机为核心，设计了自适应点火器控制模块的软硬件。该点火器经调试匹配试验，可满足各种电控发动机点火要求。     

Engineering of a-Si:H device stability by suitable design of interfaces

Where a-Si:H pin devices are concerned, one of the main obstacles regarding improved performance is device stability, usually attributed to adverse behaviour at various interfaces within the device. Several attempts have been made to overcome this problem, such as the use of blocking layers at the interfaces. Although these have led to some improvements in device performance, most of the problems associated with device stability remain. This is mainly due to the defects at the interfaces, since the blocking layers (silicon alloys with carbon, nitrogen or oxygen) usually have a high density of bulk states, in comparison to intrinsic a-Si:H films.In this paper, we present a method that seems to be capable of improving device stability. It consists of performing a controlled removal of oxide interlayers at the interfaces, by an appropriate etching process. This enables the production of highly smoothed interfaces, and reduces possible cross-contamination of the i-layer from the adjacent doped layers. This amounts to a new design of typical pin devices, in which thin absorber layers are placed at the p/i and i/n interfaces. Their purpose is to trap most of the impurity atoms diffused from the doped layers, after which they are removed by appropriate etching.The fabrication of the absorbers (sacrificial layers), the nature of the etching and the tailoring of the defect profile at the interfaces will be discussed, including the performance exhibited by the resulting devices.