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Residual stress is a key factor that directly affects fatigue, stress corrosion, fretting wear and other performance of engineering materials and components. However, it is difficult to accurately obtain the distribution of the deep residual stress field of the components using theoretical analysis and traditional non-destructive testing methods, which greatly hinders the development of advanced components. Due to the high penetration ability of thermal neutrons, neutron diffraction is an excellent engineering tool for providing mapping of residual stresses nondestructively in bulk components. Therefore, neutron diffraction was the most suitable non-destructive technique to characterize the deep residual stresses distribution. Therefore, National Important Project on Scientific Instrument and Equipment “the Neutron Diffractometer for Residual Stress and Defect in Materials and Components” was funded to built Engineering and Scientific Stress Diffractometer at China Advanced Research Reactor (CARR), which will serve the development of national important equipments, provide testing technique for manufacturing process of large-scale component and accumulate technical data for new material design. In order to fully play the role of Engineering and Scientific Stress Diffractometer in residual stress characterization of the engineering components, the mostly used crystal planes and the required wavelength for diffraction angle of about 90° of steel, nickel, copper, aluminum and titanium were analyzed. Thus, the optimal wavelength of the diffractometer was chosen to be around 0.164 nm, which satisfies the residual stress measurement for most commonly used metal materials. With this wavelength, the error of Fe(211) diffraction peak position was used as figure of Merit for the optics optimization. Optimized optics was obtained by tuning the horizontal and vertical focusing parameters. The neutron flux at the sample position that measured at the optimized optics with wavelength of 0.164 nm is a key parameter for the intensity performance of diffractometer. The activation method is the most commonly used technique to measure the distribution of neutron flux, which has the advantages of flexibility, adaptability, wide sensitivity and small disturbance to neutron field. In this work, the neutron flux at the sample is 3.0×107 cm−2·s−1 (±4.5%) at full reactor power of 60 MW. The resolution at the diffraction angle of about 90° is 0.42% by analyzing Fe(211) diffraction peak. The position resolution of the area detector was tested using a cadmium plate with three slit with known size. The horizontal position resolution is (1.44±0.03) mm. In this work, the optical optimization and performance calibration of Engineering and Scientific Stress Diffractometer at CARR were completed, which provides an experimental foundation for the instrument operation.

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In this paper, we demonstrated a very competitive RGB tandem OLED based on ViP technology that showed low power consumption and long lifetime. Compared to the traditional single OLED for mass production, panels based on tandem OLED can reduce power consumption by 29% and increase lifetime by more than 3.3 times. In combination with ViP technology, 8% efficiency improvement was obtained by optimizing the light‐emitting layer positions of RGB tandem OLEDs and thickness of cathode and capping layer (CPL), respectively, achieving a white light emission current efficiency over 134 cd/A. [ABSTRACT FROM AUTHOR]

In a typical parabolic trough collector (PTC), sunlight is concentrated at the bottom of the absorber tube. This concentrated solar flux leads to uneven heat distribution, resulting in high local temperatures and significant thermal stress on the absorber tube. These limitations have restricted the application of PTCs in solar thermochemistry and other fields and have impacted their safe operation. In this study, a new PTC with dual planar mirrors (DPMS) is proposed to homogenize the circumferential solar flux distribution of the absorber tube. A design method and single-objective optimization of the new PTC with a DPMS are proposed, and an uncertainty analysis of the operational and structural parameters is performed. A coupled light-heat-structure numerical model was developed to study the heat transfer performance and structural mechanical properties. The thermodynamic properties of the PTC with DPMS under different boundary conditions were analyzed. The results show that the circumferential temperature difference of the new PTC is within 2.6 K, and the circumferential thermal deformation is within 0.9 mm under typical working conditions (the inlet velocity of the heat transfer fluid is 3 m/s, inlet temperature is 573.15 K, and the direct normal irradiance is 1000 W/m2). Compared with conventional PTCs, the circumferential temperature difference is reduced by 74%–90%, and the maximum thermal deformation along the y-axis is reduced by more than 95% under all working conditions (1–5 m/s, 373.5–675.15 K, 200–1000 W/m2). The new PTC maintains the uniformity of the circumferential solar flux distribution for different operating parameters (sun incident angle of 0°–3°) and installation errors (±3 mm), is suitable for solar energy applications in various fields, and has the potential for large-scale applications. [ABSTRACT FROM AUTHOR]

A multi-pixel photon counter (MPPC) is applied to three-dimensional imaging, and combined with the optical imaging structure an optical path is designed for the LLL imaging experimental platform. The optical path design changes the planar detection to physical stereoscopic detection, and achieves target imaging at very low illumination. In the light path section, the light path design principle is introduced, an optical imaging structure with a focal length of 30 85 mm, a field of view greater than 20° and a field curvature of less than 2% is designed. The optical design software is used to optimize the optical structure to meet the design indexes. A two-dimensional LLL imaging system is built to detect real objects. It is verified by experiments that the system can realize the two-dimensional imaging of the target object with a distance of 40 cm under LLL environment with 10-4 lx and lower illumination. [ABSTRACT FROM AUTHOR]

Highlights • A secondary booster reflector is examined in a parabolic trough collector. • The optical enhancement is found to be higher in greater incident angles. • The optical enhancement is greater during the winter period. • The yearly enhancement is found to be 21.7% for Athens, Greece. • The thermal enhancement is more intense in higher operating temperatures. Abstract The objective of this work is the investigation of a novel booster reflector in a parabolic trough collector (PTC). More specifically, a vertical secondary booster reflector is located at the end of the trough in order to enhance the optical performance of the solar collector. This extra concentrator reduces the end optical losses of the PTC by reflecting back them in the receiver. Moreover, it acts as an extra reflecting area which captures extra solar beam irradiation in the cases with a non-zero incident angle. The collector is examined optically and thermally in order to determine both the optical and the thermal gain by the use of this novel idea. The overall analysis is conducted for steady-state conditions, as well as the yearly evaluation of the suggested idea is given. According to the final results, the use of the extra booster leads always to optical and thermal enhancement, especially in greater incident angles. The yearly optical enhancement, for a collector with a focal distance to length ratio of 0.236, is calculated at 21.7% and it is more intense in the months with greater incident angles. More specifically, it was calculated at 8.7% in June, 24.2% in September and 77.1% in December. The thermal analysis proved that the thermal enhancement is greater than the optical and it is higher when the system operates with great fluid temperature levels. [ABSTRACT FROM AUTHOR]

In this paper, a new optical optimization model for linear Fresnel reflector concentrators (LFRCs) was developed, based on the population-based particle swarm optimization (PSO) algorithm and the statistics-based Monte Carlo ray-tracing (MCRT) method, with a validated LFRC MCRT optical module we developed. To significantly reduce the computing time, this LFRC MCRT module was redesigned using a previously proposed MCRT runtime reduction method and a newly proposed nominal annual LFRC optical efficiency together. Optimization results of the model validation were found to agree well with the known data, with average deviations in the optimized nominal annual LFRC optical efficiency being about 1%, while the computing time reduces by almost four orders of magnitude, proving that our novel optical optimization method and model are feasible, reliable and more time-efficient. After validation, optimizations, analyses and comparisons were carried out for LFRCs of different mirrors and geometrical parameters. It is revealed that the LFRC system of flat mirrors studied can also be optimized to obtain a higher annual optical efficiency (over 60%) as compared with those of parabolic or cylindrical mirrors, while the flat mirror is much easier to manufacture than the other two mirrors, with a much lower price due to the use of inexpensive planar mirrors. [ABSTRACT FROM AUTHOR]

This paper describes the implementation and optimization of a dual-confocal autofocusing system that can easily describe a real-time position by measuring the response signal (i.e., intensity) of the front and the rear focal points of the system. This is a new and systematic design strategy that would make it possible to use this system for other applications while retrieving their characteristic curves experimentally; there is even a good chance of this technique becoming the gold standard for optimizing these dual-confocal configurations. We adopt two indexes to predict our system performance and discover that the rear focal position and its physical design are major factors. A laboratory-built prototype was constructed and demonstrated to ensure that its optimization was valid. The experimental results showed that a total optical difference from 150 to 400 mm significantly affected the effective volume of our designed autofocusing system. The results also showed that the sensitivity of the dual-confocal autofocusing system is affected more by the position of the rear focal point than the position of the front focal point. The final optimizing setup indicated that the rear focal length and the front focal length should be set at 200 and 100 mm, respectively. In addition, the characteristic curve between the focus error signal and its position could successfully define the exact position by a polynomial equation of the sixth order, meaning that the system can be straightforwardly applied to an accurate micro-optical auto-focusing system.

The proliferation of data centers deployed within the networks of national and international operators is enabling the creation of innovative added-value services offered through consumer and business applications. This trend is constantly triggering the adaptation of network operations to the needs of the applications. Indeed, they would be better served by a flexible infrastructure that accomodates and optimizes resources based on their constraints, parameters of interest, and priorities. The required network optimization can be carried out considering each single layer of the infrastructure. However, multilayer optimization gives the opportunity to further diminish CAPEX expenditures by identifying the network configuration that jointly optimizes packet and transport resources. Unfortunately, in current deployments, the planning process is not carried out considering the impact of both layer at same time. In this paper, we walk the reader through the manifold aspects of planning in multilayer environments. We first provide an illustrative guide by means of relevant operator-driven use-cases, also taking into account key network operations. The following step in this evolutionary path is the introduction of application-awareness in network planning, which has the potential of increasing savings, while offering a better adaptation of network services to applications’ requirements. Without such feature, the network will become an inefficient dumb pipe, with dramatically increasing costs. Finally, we discuss a use case for in-operation application-aware network planning, where optimization is dynamically performed over running networks, and we present the overall operations workflow for provisioning and optimizing resources that includes it. [ABSTRACT FROM PUBLISHER]

Black phosphorus (BP), widely studied in nanophotonics, has shown great potential applications in the field of thin film solar cells due to the wide absorption wavelength range and the tunable band-gap. Here, a tandem solar cell with BP and crystalline silicon (c-Si) as top and bottom active layer are proposed. Two types of optical design strategies such as one dimensional photonic crystal interlayers and top nanopyramid antireflective layer are employed to optimize the BP/c-Si tandem cell device structure to enhance the light absorption. Simulation results show that the one dimensional photonic crystal interlayers significantly enhance the light absorption in the tandem solar cell while nanopyramid antireflective layer hardly works. With optimized structure parameters, a maximum short-circuit current of 18.50 mA/cm 2 for BP/c-Si tandem solar cell with one dimensional photonic crystal interlayers has been achieved which is enhanced by 19.4% compare to that of the counterpart without interlayers. • Demonstrate a tandem solar cell with BP and crystalline silicon as top and bottom active layer. • With inserted one dimensional photonic crystal interlayers, the short-circuit current of the tandem cell reaches 18.50 mA/cm2. • The J sc is 19.4% higher than that of the referenced tandem cell without interlayer. • Demonstrate the nanopyramid top surface is not suitable to be adopted as antireflective coating for the proposed BP/c-Si tandem solar cell. • For tandem solar cells where the refractive indices of each layer are mismatched, ILs are preferred to be employed as an effective light management strategy. [ABSTRACT FROM AUTHOR]

Automatic optimization algorithms have been recently introduced as nonimaging optics design techniques. Unlike optimization of imaging systems, nonsequential ray tracing simulations and complex noncentered systems design must be considered, adding complexity to the problem. The merit function is a key element in the automatic optimization algorithm; nevertheless, the selection of each objective's weight, {wi}, inside the merit function needs a prior trial and error process for each optimization. The problem then is to determine appropriate weights' values for each objective. We propose a new dynamic merit function with variable weight factors {win}. The proposed algorithm automatically adapts weight factors during the evolution of the optimization process. This dynamic merit function avoids the previous trial and error procedure by selecting the right merit function and provides better results than conventional merit functions. [ABSTRACT FROM AUTHOR]

Linear Fresnel collector arrays present some relevant advantages in the domain of concentrating solar power because of their simplicity, robustness and low capital cost. However, they also present important drawbacks and limitations, notably their average concentration ratio, which seems to limit significantly the performance of these systems. First, the paper addresses the problem of characterizing the mirror field configuration assuming hourly data of a typical year, in reference to a configuration similar to that of Fresdemo. For a proper comparative study, it is necessary to define a comparison criterion. In that sense, a new variable is defined, the useful energy efficiency, which only accounts for the radiation that impinges on the receiver with intensities above a reference value. As a second step, a comparative study between central linear Fresnel reflectors and compact linear Fresnel reflectors is carried out. This analysis shows that compact linear Fresnel reflectors minimize blocking and shading losses compared to a central configuration. However this minimization is not enough to overcome other negative effects of the compact Fresnel collectors, as the greater dispersion of the rays reaching the receiver, caused by the fact that mirrors must be located farther from the receiver, which yields to lower efficiencies. [ABSTRACT FROM AUTHOR]

Abstract: A numerical process is developed on a Transfer-Matrix Method (TMM) to calculate the optical properties of multilayers involved in thin film solar cells. Using the bulk complex refractive indices in a considered spectral range for each material allows us to calculate the transmittance of the whole structure and the intrinsic absorption inside the sole active layer. An optical optimization of oxide|metal|oxide trilayer electrode in the air and with a (poly-3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) bulk heterojunction based organic solar cell is performed. The ZnO|Ag|ZnO structure is specifically studied in order to avoid the use of indium in such photovoltaic components. [Copyright &y& Elsevier]

Abstract: An all-solution process was developed to prepare VO2-based double-layered films containing SiO2 and TiO2 antireflection layers. These double-layered films were optimized to improve luminous transmittance (T lum) and switching efficiency (ΔT sol). The substrate/VO2/TiO2 double-layered structure showed the largest improvement of 21.2% in T lum (from 40.3% to 61.5%). T lum could be further improved to the maximum of 84.8% by combining film thickness optimization and antireflection layer deposition. ΔT sol (usually below 10% for single VO2 films) could be improved by adjusting the position of antireflection peaks (the highest ΔT sol was 15.1%). A sample with balanced T lum and ΔT sol showed T lum of about 58% (20°C) and 54% (90°C), and ΔT sol of 10.9%. This work is an important technical breakthrough toward the practical application of VO2-based smart windows. [Copyright &y& Elsevier]

Enhancement of the optical confinement effect by an intermediate layer (IML) between Si and alumina substrate in thin film Si solar cells was studied. The dependence of the optical confinement effect on refractive index of the IML and on thickness of Si was separately investigated by hemispherical reflectance measurement of the following two series of samples. In the first case, SiOxNy, SiNx or TiO2 was deposited as the IML in the multilayer, Si/IML/alumina. In the second case, Si layers with different thicknesses were formed. The study showed that in certain conditions the IML could enhance the optical absorption of Si layer in thin film Si solar cells. [Copyright &y& Elsevier]

In concentrated solar power (CSP), selective solar absorber coatings increase absorbed solar flux (high solar absorptance A S) while reducing radiative losses (low thermal emittance E BB). Coating developers usually maximize the selective ratio A s /E BB (highest A s , lowest E BB). The solar-to-heat conversion (heliothermal) efficiency R h of a solar absorber is however a more relevant optimization target. It is deduced from A s and E BB , but is more sensitive to A s. It also strongly depends on operating conditions, solar concentration ratio C and absorber temperature T A , radically varying between CSP technologies. This allows different optimal designs and leads to more efficient selective coatings, adapted to their specific application. In this paper, the influence of operating conditions on the optimal selective coating design is investigated. A popular selective coating design, W/W–Al 2 O 3 /Al 2 O 3 , was chosen as illustrative example. Coating structure and composition, i.e., cermet composition and layer thicknesses, were optimized to maximize R h for a wide range of operating conditions: concentration ratios from 10 to 300, absorber temperatures from 50 to 550 °C. Optimal coating characteristics are illustrated on 3D maps over the entire (C , T A) range, showing the existence of three operating regions. Each region gives an optimization priority on either A s , E BB or a combination of both, leading to specific optimized coating characteristics for each region, which should be considered when designing selective coatings for given operating conditions. Based on one example, this study provides a better understanding of the optimal design and use of selective coatings in the different operating conditions of CSP technologies. • Solar selective absorber coating optimization depends on CSP operating conditions. • A typical SSAC is optimized for a large range of CSP operating conditions. • Solar-to-heat conversion (heliothermal) efficiency is the optimization target. • Three distinct optimization strategies are found depending on operating conditions. • Recommendations are given for solar selective absorber coating developers. [ABSTRACT FROM AUTHOR]

The optical analysis of any reflector of sunrays is a major task, because it is never easy to predict the quantity and the quality of the solar flux radiation falling on a receiver. Two algorithms can be used for the calculation of the flux distribution and thus temperatures in the receiver, namely, the Ray-Tracing and cones optics methods. We propose for the optics of the Fresnel concentrator a modeling and numerical simulation of the optical performances of Fresnel's type solar field based on Monte Carlo ray-tracing (MCRT). This article presents an optical optimization of a solar prototype with Fresnel type concentration. This optimization was carried out through a parametric study, and a dimensioning calculation to determine the influence of each parameter on performance i.e the impact of the glass and the impact of the geometry of the receiver. The analysis of the results presented in the form of tables and curves allowed us to determine the optimal configuration of our solar prototype. This configuration gives better theoretical and experimental performances. On the basis of this optimal configuration, several thermal power stations based on LFR technology have been built and marketed. As well, several numerical models have been verified and validated through the usage of highly developed and very reliable measuring instruments. The removal of the glass resulted in an estimated gain in annual optical efficiency of 5.6% (from 40.49% to 42.75%). The use of two absorber tubes resulted in an annual gain in optical efficiency estimated at 15.5% (from 40.49 to 46.79%). • Modeling the optical behavior of the linear Fresnel concentrator prototype. • Optimize solar linear Fresnel concentrator prototype using the Ray Tracing-Monte Carlo's method. • A detailed parametric study was carried out for the linear Fresnel concentrator prototype. • Effects of receiver parameters on the optical performance are analyzed. [ABSTRACT FROM AUTHOR]

This paper describes the implementation and optimization of a dual-confocal autofocusing system that can easily describe a real-time position by measuring the response signal (i.e., intensity) of the front and the rear focal points of the system. This is a new and systematic design strategy that would make it possible to use this system for other applications while retrieving their characteristic curves experimentally; there is even a good chance of this technique becoming the gold standard for optimizing these dual-confocal configurations. We adopt two indexes to predict our system performance and discover that the rear focal position and its physical design are major factors. A laboratory-built prototype was constructed and demonstrated to ensure that its optimization was valid. The experimental results showed that a total optical difference from 150 to 400 mm significantly affected the effective volume of our designed autofocusing system. The results also showed that the sensitivity of the dual-confocal autofocusing system is affected more by the position of the rear focal point than the position of the front focal point. The final optimizing setup indicated that the rear focal length and the front focal length should be set at 200 and 100 mm, respectively. In addition, the characteristic curve between the focus error signal and its position could successfully define the exact position by a polynomial equation of the sixth order, meaning that the system can be straightforwardly applied to an accurate micro-optical auto-focusing system. [ABSTRACT FROM AUTHOR]