大跨波形钢腹板箱梁桥日照温度场及温差效应研究

针对目前我国桥涵设计规范未给出波形钢腹板箱梁日照温度梯度,和其温度梯度研究工作的不足。以港珠澳大桥连接线工程某特大跨波形钢腹板连续箱梁桥为研究对象,对其波形钢腹板箱室断面,进行了3 d的日照温度场观测。研究了其日照温度场分布规律,继而提出波形钢腹板箱梁竖向和横向温度梯度数学计算模型,并对温差参数的取值进行了探讨。结合现场实测数据和有限元软件,对比不同温度梯度模式的温差计算值,分析了其温差效应。研究结果表明:实测波形钢腹板箱梁温度场分布与传统箱梁相差较大;温度梯度模式为指数函数和线性函数组成的分段函数;该模式计算得到的竖向及横向温差值与实测结果十分吻合,其他模式与实测结果相差较大;由于温差效应影响,顶板中轴线下缘产生了较大的横向拉应力,设计中应给予关注。该模式可为不同气候条件地区同类桥梁温度荷载计算提供重要参考。     

光线弯曲对激光测量热钢板厚度的影响

以无热源大平面空气壁模型,用传热学理论计算了大平面热钢板附近空所的一维温度分布,从而得到了大平面热钢板附近空气的一维折射率分布。利用光线折射理论,求出了光线的传输路径和像点的偏离量。分析和计算表明：当钢板温度、测量角和测量距离等参数增大时,像点偏离值就随着增大。对于钢板激光测厚系统,采用单表面单光路时,光线弯曲引起的测量误差较大,并且基本不随测量厚度减小而减小。采用完全对称的双面双光路时,左右光路的像点偏离正好抵消,光线弯曲引起的测量总误差很小,而且随测量厚度减小而减小。     

中空板在电池片包装中的应用

目的推广中空板作为太阳能电池片等光伏产品的新型环保包装板材。方法通过与当前普遍使用的瓦楞纸盒电池片包装方案对比,在防氧化性、破片率、防静电效果、成本分析等方面进行一一比较。结果中空板盒的破片率更低,其防氧化性和防水的效果比瓦楞纸盒好,成本比瓦楞纸盒略高,但因其使用寿命长,若多次使用,成本会降低。结论作为新型包装材料,中空板可广泛使用于电池片的运输包装方案中。     

Monitoring of concentrated radiation beam for photovoltaic and thermal solar energy conversion applications

Methods for evaluating the light intensity distribution on receivers of concentrated solar radiation systems are described. They are based on the use of Lambertian diffusers in place of the illuminated receiver and on the acquisition of the scattered light, in reflection or transmission mode, by a CCD camera. The spatial distribution of intensity radiation is then numerically derived from the recorded images via a proprietary code. The details of the method are presented and a short survey of the main applications of the method in the photovoltaic and thermal solar energy conversion field is proposed. Methods for investigating the Lambertian character of commercial diffusers are also discussed.     

大靶面光幕靶中发光二极管阵列线光源的设计

采用发光二极管阵列构造线了一种大尺度线光源．文中分析了发光二极管阵列光源能量在空间上的分布,用光照度计实测能量分布数据．以二维坐标给出了能量平面分布图．设计的线光源满足大靶面弹丸测速光幕靶的要求,文中给出了在光幕靶接收器件处阵列线光源光能量的计算公式．实验验证了分析的正确性．     

正交异性钢桥面构造细节的日照温度次应力分析

为研究正交异性钢桥面板构造细节的日照温度次应力行为，多次在高温和强日照天气下现场实测了某自锚式悬索桥钢箱梁外周和实腹式横隔板上温度场，基于观测到的最大顶底板温差拟合了横隔板竖向温度梯度表达式；在ANSYS中建立了钢箱梁节段有限元模型并施加外周温度，计算其24 h温度场，并与横隔板实测竖向温度的对比校验了温度场模拟的合理性；开展了钢箱梁节段和子模型的精细化热应力分析，得到了纵肋?横隔板和弧形切口共4个构造细节的温度应力时程曲线。研究表明:在强太阳辐射和高温环境下，钢箱梁横向温差不明显，但存在明显的竖向温度梯度，横隔板竖向温度梯度可拟合为四折线形式，最大温差明显小于欧规值。正交异性钢桥面板产生热变形并在构造细节处产生明显热应力集中，特别是弧形切口热应力大。仅日照竖向温度梯度作用，或仅桥面货车通行加载，弧形切口均为无限疲劳寿命；但二者共同作用产生的应力幅，大于构造细节的常幅疲劳极限，可能是该构造细节出现疲劳开裂的原因。     

Evaluation and optimization of the optical performance of low-concentrating dielectric compound parabolic concentrator using ray-tracing methods

We present a detailed design concept and optical performance evaluation of stationary dielectric asymmetric compound parabolic concentrators (DiACPCs) using ray-tracing methods. Three DiACPC designs, DiACPC-55, DiACPC-66, and DiACPC-77, of acceptance half-angles (0° and 55°), (0° and 66°), and (0° and 77°), respectively, are designed in order to optimize the concentrator for building fa?ade photovoltaic applications in northern latitudes (>55 °N). The dielectric concentrator profiles have been realized via truncation of the complete compound parabolic concentrator profiles to achieve a geometric concentration ratio of 2.82. Ray-tracing simulation results show that all rays entering the designed concentrators within the acceptance half-angle range can be collected without escaping from the parabolic sides and aperture. The maximum optical efficiency of the designed concentrators is found to be 83%, which tends to decrease with the increase in incidence angle. The intensity is found to be distributed at the receiver (solar cell) area in an inhomogeneous pattern for a wide range of incident angles of direct solar irradiance with high-intensity peaks at certain points of the receiver. However, peaks become more intense for the irradiation incident close to the extreme acceptance angles, shifting the peaks to the edge of the receiver. Energy flux distribution at the receiver for diffuse radiation is found to be homogeneous within ±12% with an average intensity of 520 W/m2.     

Increasing Solar Absorption of Atomically Thin 2D Carbon Nitride Sheets for Enhanced Visible‐Light Photocatalysis

Atomically thin 2D carbon nitride sheets (CNS) are promising materials for photocatalytic applications due to their large surface area and very short charge‐carrier diffusion distance from the bulk to the surface. However, compared to their bulk counterpart, CNS' applications always suffer from an enlarged bandgap and thus narrowed solar absorption range. Here, an approach to significantly increase solar absorption of the atomically thin CNS via fluorination followed by thermal defluorination is reported. This approach can greatly increase the visible‐light absorption of CNS by extending the absorption edge up to 578 nm. The modulated CNS loaded with Pt cocatalyst as a photocatalyst shows a superior photocatalytic hydrogen production activity under visible‐light irradiation to Pt‐CNS. Combining experimental characterization with theoretical calculations shows that this approach can introduce cyano groups into the framework of CNS as well as the accompanied nitrogen vacancies at the edges, which leads to both narrowing the bandgap and changing the charge distribution. This study will provide an effective strategy to increase solar absorption of carbon‐nitride‐based photocatalysts for solar energy conversion applications.     

Nonuniform phase distribution in ultrasound speckle analysis. I. Background and experimental demonstration

In some cases, the statistical properties of the phase of ultrasound speckle in B-scan images differ from the uniform distribution characteristic exhibited by the fully developed speckle. This phenomenon has been noted when examining scattering structures with a somewhat regular spacing using wideband pulse excitation. It is shown by computer simulation and experiments on phantoms that when the mean scatterer spacing is equal to multiples of a half wavelength at the reference frequency of the receiver quadrature demodulator, the center of the echo phase distribution, plotted on the complex plane, will shift away from the origin. When the spacing is equal to an odd multiple of a quarter wavelength, the phase distribution will have a figure ;8' shape. By noticing those noncircular phase distributions while changing the demodulation frequency, the mean scatterer spacing can be estimated.     

Quantitative Determination of Contribution by Enhanced Local Electric Field,Antenna‐Amplified Light Scattering,and Surface Energy Transfer to the Performance of Plasmonic Organic Solar Cells

Plasmonic metal nanostructures are widely used as subwavelength light concentrators to enhance light harvesting of organic solar cells through two photophysical effects, including enhanced local electric field (ELEF) and antenna‐amplified light scattering (AALS), while their adverse quenching effect from surface energy transfer (SET) should be suppressed. In this work, a comprehensive study to unambiguously distinguish and quantitatively determine the specific influence and contribution of each effect on the overall performance of organic solar cells incorporated with Ag@SiO₂ core–shell nanoparticles (NPs) is presented. By investigating the photon conversion efficiency (PCE) as a function of the SiO₂ shell thickness, a strong competition between the ELEF and SET effects in the performance of the devices with the NPs embedded in the active layers is found, leading to a maximum PCE enhancement of 12.4% at the shell thickness of 5 nm. The results give new insights into the fundamental understanding of the photophysical mechanisms responsible for the performance enhancement of plasmonic organic solar cells and provide important guidelines for designing more‐efficient plasmonic solar cells in general.     

Optical Edge Enhancement Applied to Scenes with Natural Vegetation Backgrounds

Edge enhancement of images performed by optical subtraction using multiple holographic diffraction gratings mounted in the Fourier plane of an optical processor has been found to be advantageous in enhancing the images of vehicles photographed against natural vegetation backgrounds. The grating method has been used with a liquid crystal light valve at the input to the processor and edge enhancement can be performed in near real time using a television input to the liquid crystal light valve.     

Test and simulation of a solar powered solid sorption cooling machine

At the Institut für Thermodynamik und Wärmetechnik (ITW) a solar powered cooling machine with no moving parts has been built for demonstration purposes. The main part of the device is an absorber/desorber unit which is mounted inside a concentrating solar collector. The heat of absorption is transported out of the solar collector by means of two horizontally working heatpipes. The working pair consists of NH₃ used as the refrigerant and SrCl₂ as the absorbing medium. The performance of the solar refrigeration unit was measured in a field test.The working principle of a discontinuously working, solid sorption cooling machine will be explained using the demonstration machine as an example. Results obtained from a field test performed in 1995 are presented and discussed. Furthermore, a simulation program for the numerical simulation of a solar powered solid sorption cooling machine has been developed and tested.Finally, to confirm a problem-free continuous operation of a solid sorption system, a long term study over 14 months was carried out using NH₃/SrCl₂ as the working pair.     

Nanoantennas for enhanced light trapping in transparent organic solar cells

We propose a light-trapping structure offering a significant enhancement of photovoltaic absorption in transparent organic solar cells operating at infrared, while the visible light transmission keeps sufficiently high. The main mechanism of light trapping is related with the excitation of collective oscillations of the metal nanoantenna arrays, characterized by advantageous field distribution in the volume of the solar cell. It allows more than triple increase in infrared photovoltaic absorption.     

Anlagen für die Solarzellen‐Schichterzeugung benötigen hervorragend ausgelegte Vakuumsysteme

Vacuum pumps are an enabling technology for solar power because all modules require vacuum processing at various stages of production. Specially engineered products that are helping to make solar modules more affordable by reducing equipment downtime and improving process performance are essential to become a successful partner for the solar industry. The processes used for thin film technology are extremely demanding. Pump performance for high flows of light gases must be achieved and in parallel safety aspects must be considered carefully. The pump solutions must be extreme reliable in order to guarantee maximum tool up‐time which is mandatory for a production line in order to be cost competitive. Design and performance of such solutions must be qualified in close collaboration between pump supplier and the equipment producer together wi^th the user of the equipment. Experience and know how from industries using similar processes like semiconductor, large area coating or FPD production can be applied for solar production lines which can help to reduce time to market. The article will outline the specific needs for thin film solar cells based on amorphous silicon and CdTe.     

A stable quasi-solid-state dye-sensitized solar cell with an amphiphilic ruthenium sensitizer and polymer gel electrolyte

Dye-sensitized nanocrystalline solar cells (DSC) have received considerable attention as a cost-effective alternative to conventional solar cells. One of the main factors that has hampered widespread practical use of DSC is the poor thermostability encountered so far with these devices. Here we show a DSC with unprecedented stable performance under both thermal stress and soaking with light, matching the durability criteria applied to silicon solar cells for outdoor applications. The cell uses the amphiphilic ruthenium sensitizer cis-RuLL'(SCN)(2) (L = 4,4'-dicarboxylic acid-2,2'-bipyridine, L' = 4,4'-dinonyl-2,2'-bipyridine) in conjunction with a quasi-solid-state polymer gel electrolyte, reaching an efficiency of >6% in full sunlight (air mass 1.5, 100 mW cm(-2)). A convenient and versatile new route is reported for the synthesis of the heteroleptic ruthenium complex, which plays a key role in achieving the high-temperature stability. Ultramicroelectrode voltammetric measurements show that the triiodide/iodide couple can perform charge transport freely in the polymer gel. The cell sustained heating for 1,000 h at 80 degrees C, maintaining 94% of its initial performance. The device also showed excellent stability under light soaking at 55 degrees C for 1,000 h in a solar simulator (100 mW cm(-2)) equipped with a ultraviolet filter. The present findings should foster widespread practical application of dye-sensitized solar cells.     

Design of a lidar receiver with fiber-optic output

Design considerations for a coaxial lidar receiver are examined, including details of coupling to an optical fiber for transfer of return light to a remote detector box. Attention is concentrated on the influence of fiber position on return-light capture efficiency and dynamic range of the return signal. The effect of a central obstruction on short-range signals is included. The analysis is augmented with simulations of lidar receiver performance.