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The increasing peak-valley differences pose a major threat to safe operation of the thermal-dominant power grid in China. Cascade hydropower stations, especially for one-reservoir and multi-cascade hydropower stations (OMHS), as the second largest power supply in China form an important part of peak shaving operation. However, nonconvex and nonlinear constraints have made it deeply difficult to perform the daily peak shaving operation (DPSO) of OMHS. In this paper, an improved DPSO model of OMHS considering water delay time is formulated and solved. Firstly, the confluence coefficient method (CCM) is developed to accurately describe the water delay time of OMHS. Secondly, to reduce the errors and water spillage, aggregation of nonlinear constraints, selection of the linearized area and periodic hypothesis are performed. Finally, an MIQP model integrated CCM is established by considering one-reservoir and six-cascade hydropower stations from the Hongshui River of China as a case study. The optimization results demonstrate that the proposed model can accurately simulate real-world system, and the optimized peak-valley differences on typical days in dry season and wet season reduce by 25% and 33%, respectively. Moreover, the CCM can produce more realistic and executable generation scheduling than the state-of-the-art description method of water delay time. [ABSTRACT FROM AUTHOR]

Highlights • A single-lens 3D-digital image correlation method was developed in this manuscript. • The surface 3D shape and Displacement of a bubbling test was measured, using a light field camera. • The correctness of this method was verified by comparing the results with commercial software's. • Some characteristics of the light field camera was discussed in this manuscript. Abstract With the recent development of computer vision and photographic technology, many three-dimensional (3D) modelling methods have emerged. This paper introduces a new method that combines digital image correlation (DIC) with a light field camera to reconstruct the surface of an object. Before experimentation, the surface of the object was sprayed with a speckle pattern. The parameters of the light field camera, such as the micro-lens, focus, and lens distortion, were pre-calibrated. During the experiments, raw images of the samples were recorded by a light field camera, then each was extracted to two sub-aperture images. Using the digital image correlation method, feature point matching of the corresponding sub-images was executed and the 3D space coordinates of all of the matching points were calculated using the binocular vision principle with surface topography information. The experimental results demonstrate that the method can realise 3D reshape and 3D deformation measurements using a single camera. The system has the advantage of a simple structure, large depth of field, and wide measurement range for out-of-plane deformation. The light field camera is also applied to 3D-DIC. [ABSTRACT FROM AUTHOR]

Highlights • The thermal response fringes excited by the line laser are distorted by the specimen topography. • Laser fringes are converted into temperature fringes by thermal response information. • Some algorithms are proposed to greatly improve the measurement accuracy. Abstract Linear laser fast scanning thermography technology has a good application prospect in the nondestructive detection of defects. Meanwhile, due to the modulation of the surface topography, the thermal response fringes excited by the line laser are distorted in the scanning process, whereby the three-dimensional topography of the specimen can be reconstructed. However, the accuracy of this method is currently limited by unfavorable factors, such as background noise of the specimen surface and the extraction error of the deformed temperature fringes. In this paper, by optimizing the initial position difference during line laser scanning and converting the laser fringes with specific position difference into temperature fringes with specific phase difference, the phase shift technique is combined with the temperature fringe method. What's more, some post-processing algorithms were developed to further develop the temperature fringe method and greatly improve the accuracy of the method. By measuring some specimens with different shapes and different colors, the results show that the technology and algorithms developed here can obtain the three-dimensional shape of the measured specimen with high accuracy while having a non-destructive testing function, without interference from the surface color of the specimen. [ABSTRACT FROM AUTHOR]

This paper proposes a novel approach to sulfur removal with active carbon supplementation in alkali digestion process. The effects of active carbon dosage on the concentrations of different valence sulfur in sodium aluminate solution were investigated. The results demonstrated that along with increases of active carbon dosage high-valence sulfur (S 2 O 3 2− , SO 3 2− , SO 4 2− ) concentration decreased, but the concentration of the S 2− increased. This suggests that active carbon reacts with high-valence sulfur to generate low-valence sulfur at digestion temperature, which is consistent with our thermodynamic calculation results. As active carbon dosage increases, sulfur digestion rate decreases while sulfur content in red mud markedly increases; the alumina digestion rate, conversely, remains fairly stable. This suggests that high-valence sulfur in the sodium aluminate solution can be converted to S 2− and then enter red mud by adding active carbon during the digestion process. [ABSTRACT FROM AUTHOR]

This paper proposes a novel approach to sulfur removal by adding aluminum in the bayer process of high-sulfur bauxite. The effects of aluminum dosage on the concentrations of different valence sulfur in sodium aluminate solution were investigated at length to find that high-valence sulfur (S 2 O 3 2− , SO 3 2− , SO 4 2− ) concentration in sodium aluminate solution decreases, but the concentration of the S 2− in the sodium aluminate solution increases as aluminum dosage increases. This suggests that aluminum reacts with high-valence sulfur to generate low-valence sulfur at digestion temperature, which is consistent with our thermodynamic calculation results. As aluminum dosage increases, sulfur digestion rate decreases notably, and the alumina digestion rate decreases slightly, while sulfur content in red mud markedly increases. This suggests that high-valence sulfur in sodium aluminate solution can be converted to S 2− and then enter red mud by adding aluminum during the digestion process. [ABSTRACT FROM AUTHOR]

Multi-droplet motion in gas flow is a significant two-phase flow in nuclear power plant, chemical industry and environmental engineering. In contrast to droplet generation and collision in microscopic view, multi-droplet motion presents both macroscopic interaction with gas flow and microscopic single droplet motion characteristic. To simulate the multi-droplet motion, we presented the Euler grid approximation method to update the multi-droplet imformation in all nodes under each calculation step, and constructed a criterion about droplet velocity and direction to ensure droplet motion limited on grid nodes without loss of accuracy. The novelty of this method lies in its description of the virtual streamlines of multiple particles in the same state, as well as the discontinuous flow field composed of these virtual streamlines, furthermore, this method is independent of the time step and can simultaneously calculate droplet information of the entire field. Meanwhile, this paper focuses on the two-phase gas-liquid flow in the gravity separation space of the rotary vane separator, and the motion behavior of multiple droplets in the flow field is simulated based on the parameters of the actual steam-water separator.The result shows that the droplets tend to gather towards the center of the main stream, which is the focus area for droplet separation, and the position with higher density may be the point where the droplets collide. The model can be adopted to calculate the separation efficiency in the process of multi-droplet motion in the gravity separation space, rotary vane separator and other steam separation devices, and the results will help guide the optimal design of the separation device structure. [ABSTRACT FROM AUTHOR]

Failures resulting from thermal mismatch between the layers in a multilayer thin Film/Substrate structure (F/S) are fatal for the reliability of F/S-based electron devices. In this paper, a bilayer F/S consisting of a silicon substrate, a chromium film layer and a copper film layer is investigated under external thermal cycling loads. Grid method combining with the stereovision model in a Scanning Electron Microscope (SEM) system is developed to realize the measurement of three-dimensional deformation at microscale. The Focused Ion Beam (FIB) deposition technology is employed to fabricate micro-scale grid pattern with the spatial frequency of 1000 lines/mm on the test sample surface. The thermal fatigue mismatch between the film layers gives rise to intense 3D deformation near the interface area. The out-of-plane deformation as well as the in-plane deformation of the interface area is measured to achieve the genuine 3D deformation characterization. The accuracy analysis validates the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Large amounts of organic-containing bauxite ores are used during alumina production. Here, based on sulfur removal by NaNO 3 oxidation during actual production, we propose a method involving NaNO 3 wet oxidation to remove organic matter during bauxite dissolution. The effects of different dosages of NaNO 3 , oxidation temperatures, and oxidation times on the organic carbon removal efficiency, sodium oxalate concentration, and sodium humate concentration were studied. The organic carbon removal efficiency was 85.2% under the most suitable conditions (5% NaNO 3 and 13% CaO relative to the mass of bauxite; oxidation temperature of 260 °C; oxidation time of 60 min). The oxidation and removal of sodium humate were high, but those of sodium oxalate were poor. The red mud obtained under the optimal conditions was analyzed. • Use sodium nitrate as an oxidant to remove organic matter in sodium aluminate solution. • The optimum conditions for removal of organic matter in sodium aluminate solution were obtained. • Through the analysis of red mud, it is clear that the addition of NaNO 3 will not affect the dissolution of alumina. [ABSTRACT FROM AUTHOR]

Geometrical phase analysis (GPA) is typically a powerful tool to investigate the deformation in high resolution transmission electron microscopy images and has been used in various fields. The traditional GPA method using the fast Fourier transform, referred to as global-GPA (G-GPA) here, is based on the relationship between the displacement and the phase difference. In this paper, a subset-GPA (S-GPA) is introduced for further improvement. The S-GPA performs the windowed Fourier transform block by block in the image. The maximum strain measurement scale of the GPA method is theoretically analyzed on the basic of the phase spectrum extraction process. The upper limit is one third of the atomic spacing. The results of various numerical simulations verified that the S-GPA method performs better than the traditional G-GPA method in both the homogeneous and inhomogeneous deformation conditions, with the evaluation parameter of calculation reliability of S-GPA 10% higher than G-GPA. Specifically, the measurement accuracy of S-GPA is about three times higher than the G-GPA when calculating small strain (less than 2000με). For the large strain (greater than 150000με), the measurement accuracy of S-GPA is about 50% higher than that of the G-GPA. Besides, the S-GPA method can significantly eliminate the phase filling effect, while the G-GPA cannot. The S-GPA method has been successfully applied to analyze the strain field distribution in an lnGaAs/InAlAs supperlattice heterostructure. [ABSTRACT FROM AUTHOR]

The accurate measurement for the surface profiles of transparent object is of significance for quality control in optical devices and precision instruments. Here, a double transmission-mediums based geometric phase analysis method has been developed to evaluate both the upper and lower surface profiles of transparent object. To do this, the tested transparent object is placed above a preprinted lattice pattern. When viewed from above with a CCD camera, any slope variations of the surfaces will lead to distortions of the transmission-lattice patterns. And when changing one side of object’s contact medium, the lattice virtual image with modulated phase is distorted once again. Combined with the derived relationship between phase variations of transmission-lattice patterns and out-of-plane heights of two surfaces, the double-sided surface profiles of transparent object can be reconstructed successfully. With this, the technique, which is verified experimentally, is demonstrated to be a feasible and reliable method. The advantage of this method is that it simplifies the setup and allows a fast estimation of the geometry of a transparent specimen. The double-sided profiles can be decoupled easily according to the big difference of refractive indexes between contact mediums. And the calculation accuracy can be guaranteed by the weighted average from four directions. [ABSTRACT FROM AUTHOR]

In this paper, a method based on transmission-speckle correlation is proposed for measuring static and dynamic deformation of liquid surface. In the method, a high-speed camera placed vertically above the tested liquid surface is used to observe and record a special speckle pattern put in advance at the bottom of liquid. According to the Snell׳s law, the deformation of liquid surface will lead to the movement of the transmission-speckles. In terms of this, the quantitative relationship between height changes of liquid surface and the in-plane displacement of transmission-speckles can be deduced. Combining with multi-directional Newton iteration algorithm, the dynamic deformation field of liquid surface can be calculated from the in-plane displacement vector field of transmission-speckle images in different moment using speckle correlation method. The sensitivity of the method in measuring height changes of liquid surface is discussed. In this paper, a validation test to measure the surface morphology of a plano-convex lens demonstrates the feasibility and the effectiveness of the method. In addition, the dynamic deformation and propagation process of ripples in the water surface caused by a droplet were investigated. [ABSTRACT FROM AUTHOR]

Highlights: [•] A mini desktop impact test system using multistage electromagnetic launch was developed. [•] The principle of eliminating the electromagnetic effect in strain signal was described. [•] The validation tests on aluminum alloy for impact compression test system were carried out. [•] The validation tests on polyimide/SiO2 film for impact tension test system were carried out. [Copyright &y& Elsevier]

Abstract: Deformed liquid surface directly involves the surface tension, which can always be used to account for the kinematics of aquatic insects in gas–liquid interface and the light metal floating on the water surface. In this paper a novel method based upon deformed transmission-virtual grating is proposed for determination of deformed liquid surface. By addressing an orthogonal grating (1–5line/mm) under the transparent water groove and then capturing images from upset of the deformed water surface, a displacement vector of full-field which directly associates the 3-D deformed liquid surface then can be evaluated by processing the recorded deformed fringe pattern in the two directions (x- and y-direction). Theories and equations for the method are thoroughly delivered. Validation test to measure the deformed water surface caused by a Chinese 1-cent coin has been conducted to demonstrate the ability of the developed method. The obtained results show that the method is robust in determination of micro 3-D surface of deformed liquid with a submicron scale resolution and with a wide range application scope. [Copyright &y& Elsevier]

Abstract: In this paper, the capabilities of shearography for detecting hole and crack type defects in polymeric and metallic materials using thermal loading were investigated. In order to improve the ability of the identifying defect, the fringe multiplication technique was applied to some suspectable shearography fringe patterns. Based on the test results empirical rules for inspection plates of different material with specific thicknesses were established. For aluminium plates with thicknesses of 3mm, minimum diameter of a surface breaking hole which is detectable is approximately equal to 2.5–3.0 times the depth of the defect, and for polymer plates with a thickness of 10mm, the minimum detectable diameter is 0.8–1.3 times of the depth. For polymeric materials results from the increasing temperature period are approximately the same as those from the decreasing temperature period. When the orientation of the image shearing is not perpendicular to the longitudinal direction of the crack type defects, the sensitivity for defect detection is relatively higher than with perpendicular image shearing. [Copyright &y& Elsevier]

Abstract: Quantitative deformation analysis of micro-fabricated electromechanical systems is of importance for the design and functional control of microsystems. In this paper, two modified digital moiré processing methods, Gaussian blurring algorithm combined with digital phase shifting and geometrical phase analysis (GPA) technique based on digital moiré method, are developed to quantitatively analyse the deformation behaviour of micro-electro-mechanical system (MEMS) structures. Measuring principles and experimental procedures of the two methods are described in detail. A digital moiré fringe pattern is generated by superimposing a specimen grating etched directly on a microstructure surface with a digital reference grating (DRG). Most of the grating noise is removed from the digital moiré fringes, which enables the phase distribution of the moiré fringes to be obtained directly. Strain measurement result of a MEMS structure demonstrates the feasibility of the two methods. [ABSTRACT FROM AUTHOR]

• The digestion behaviors of pyrite and gypsum were understood by thermodynamic analysis and experiments. • Pyrite reacts with alkali solution to generate S2-, S 2 O 3 2-, SO 3 2-, SO 4 2-, Fe 2 O 3 , and Fe 3 O 4. • Gypsum reacts with alkali solution to generate SO 4 2- and some complex compounds containing sulfur and calcium. • Appropriate methods of S2- and SO 4 2- removal were proposed. The pyrite and sulfate digestion behaviors and sulfur removal of high sulfur bauxite during Bayer process were studied in this paper. The thermodynamic analysis shows that pyrite reacts with alkali solution to generate different valence sulfur (S2-, S 2 O 3 2-, SO 3 2-, SO 4 2-), Fe 2 O 3 , and Fe 3 O 4 ; the standard Gibbs free energy of these reactions is negative and decreases with the increasing of temperature in range from 473 K to 573 K; the generation order of different valence sulfur is easily determined: S2-﹥SO 4 2-﹥SO 3 2-﹥S 2 O 3 2-; the gypsum reacts with sodium aluminate solution to generate SO 4 2- and Ca(OH) 2. The digestion experiment researches indicates that pyrite and sulfate enter solution mainly in the form of S2- and SO 4 2- respectively, the Fe 2 O 3 and Fe 3 O 4 are also found in red mud, experiment results are consistent with our thermodynamic calculation results. Based on the digestion behaviors of pyrite and sulfate, we propose appropriate methods of S2- and SO 4 2- removal. The S2- which is the main form of sulfur in digestion liquor A was removed completely by adding ZnO in digestion process, and the SO 4 2- which is the main form of sulfur in digestion liquor B was removed completely by adding BaO·Al 2 O 3. The results may throw a new light upon the sulfur removal of high-sulfur bauxite in alumina production. [ABSTRACT FROM AUTHOR]

Abstract: The mechanical behaviors of microstructures and micro-devices have drawn the attention from researchers on materials and mechanics in recent years. To understand the rule of these behaviors, the deformation measurement techniques with micro/nanometer sensitivity and spatial resolution are required. In this paper, a micro-marker identification method is developed to measure microstructure deformation. The micro-markers were directly produced on the top surface of microstructures by taking advantage of ion milling of focused ion beam (FIB) system. Based on the analysis of marker images captured by electronic microscope with specific correlation software, the deformation information in microstructures can be easily obtained. The principle of the technique is introduced in detail in the paper. An example experiment was executed to measure the displacement and strain distribution in a MEMS device. Obtained results show that the technique can be well applied to the deformation measurement of the micro/nano-electro-mechanical-systems (MEMS/NEMS). [Copyright &y& Elsevier]

Abstract: Fracture behavior of ferroelectric ceramics during in-plane and out-of-plane 90° domain switching was studied using the moiré interferometry technique. The specimens used in the experiment were three-point-bending beams, each with a single through-notch, which were subjected to a mechanical load, an electrical load and a combined electrical and mechanical load, respectively. The main subject of interest is to investigate the influence of 90° domain switching induced by the electrical load on fracture toughness and material brittleness. In the experiment, compared with out-of-plane 90° domain switching, in-plane 90° domain switching occurs in the region of approximately a 45° band. It causes larger in-plane tensile strain ε xx in almost all regions of a specimen, especially in the 45° band. In-plane 90° domain switching greatly decreases fracture toughness and weakens the material brittleness of ferroelectric ceramics. The out-of-plane 90° domain switching does not exhibit such a great influence on fracture toughness and material brittleness as the in-plane 90° domain switching does. [Copyright &y& Elsevier]

Abstract: Some novel nano-Moiré methods have been developed at failure mechanics lab in the Tsinghua University, recently. This paper offers an introduction of these new methods, which can be realized under the atomic force microscope, scanning tunneling microscope, as well as the transmission electron microscope. These nano-Moiré methods are able to offer quantitative analysis to nano-deformation of object. The measurement principles and experimental techniques of these methods are described in detail. A new digital nano-Moiré technique is proposed. Some typical applications to these methods are discussed. The successful experimental results demonstrate the feasibility of these methods and also verify that the methods can offer a high sensitivity for displacement measurement with nano-meter spatial resolution. [Copyright &y& Elsevier]

• The sulfur behavior has been clarified by thermodynamic analysis and experiments. • The sulfur concentration orders in liquor are as follows: S2− > SO 4 2− > SO 3 2− > S 2 O 3 2−. • The S2− can be removed completely by adding ZnO during digestion process. In this paper, digestion behavior and removal of sulfur in high-sulfur bauxite during Bayer process were studied. The thermodynamic analysis shows that pyrite reacts with alkali solution to generate different valence sulfur (S2−, S 2 O 3 2−, SO 3 2−, SO 4 2−), Fe 2 O 3 , and Fe 3 O 4 ; the standard Gibbs free energy of these reactions is negative and decreases with the increasing of temperature in range from 473 K to 573 K; the generation orders of different valence sulfur can be easily determined: S2− > SO 4 2− > SO 3 2− > S 2 O 3 2−. The digestion experiment researches indicated that sulfur in high-sulfur bauxite entered solution mainly in the form of S2−, the digestion rates of sulfur increased with the increase of temperature, which was consistent with our thermodynamic calculation results. Based on the digestion behavior of sulfur, an appropriate method of sulfur removal was proposed, the S2− which is the main form of sulfur in liquor can be removed completely by adding ZnO during digestion process. [ABSTRACT FROM AUTHOR]

The nanoindentation test is utilized to measure the hardness and elastic modulus of various components within Ceramic Matrix Composites (CMCs), including continuous stiffness measurement (CSM) and quasi-static testing. To further characterize the elastic-plastic properties of CMCs, an efficient method is proposed by using backpropagation (BP) neural network inversion, which is based on the relationship between load and depth obtained by the nanoindentation experiment and Abaqus finite element simulation. As part of the analysis, the load-depth (p-h) curve is simplified to six characteristic parameters through the fitting of the experimental results. The pre-estimated elastic-plastic characteristics are utilized to model the nanoindentation test for CMCs. A BP neural network is used to perform deep learning on simulation data, which leads to a network structure that matches the trained parameters of the p-h curve and elastic-plastic properties. The experimental data for fiber is inputted into the network to acquire the elastic-plastic properties required in practice. The accuracy of the proposed method is verified by comparing the inversion results with the simulation outcomes. [ABSTRACT FROM AUTHOR]

Extreme weather lasting for 5–15 days not only brings large inflows in the medium-term but also causes sharp fluctuations in the daytime load of the power grid which imposes considerable challenges to the modeling and solving of medium-term power grid scheduling. The complex nonlinear constraints and water delay times of cascade hydropower plants significantly increase the difficulty of finding solutions. Hence, this study first advocates an accurate optimization model for determining the medium-term peak shaving operation of cascade hydropower plants considering the water delay time. The objective is to minimize the variance of the remaining load and maximize energy production that aims to regulate the load fluctuation and enhance hydropower efficiency. Then, to describe the water delay time of cascade hydropower plants, a piecewise delay time method (PDTM) is proposed based on the water balance equation. Finally, cascade comprehensive benefits (CCB) are established to alleviate the deviations from the scheduling plan and actual plan affected by the lag time. The developed model is implemented on the eleven cascade hydropower plants of the Lancang River in China. Simulation results demonstrate that the model is able to provide more realistic and executable generation scheduling while obtaining larger hydropower generation benefits and good peak shaving performance. • Piecewise delay time method describes medium-term water delay time relationship. • Medium-term peak shaving model coupling lag time makes realistic generation plan. • Cascade comprehensive benefits reduce scheduling deviation and promote generation. • Multiobjective model has good peak shaving performance and enhances generation. [ABSTRACT FROM AUTHOR]

In this study, aluminothermic reduction and molten salt electrolysis were combined to prepare titanium powder. In this combined method, titanium dioxide was first deoxidized to produce titanium–aluminum alloy through an aluminothermic reduction reaction, and then the titanium–aluminum alloy was separated through chloride molten salt electrolysis to generate titanium powder. The obtained titanium powder, titanium aluminum alloy and slag was analyzed using several techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. A mass ratio of 2:3 of titanium dioxide and aluminum was suitable for the production of titanium–aluminum alloys. A large amount of alumina generated through the aluminothermic reduction reaction was separated into slag phases using cryolite. Then, the phases were electrolyzed into aluminum and cryolite, which were reused as raw materials. The final titanium–aluminum alloy product was electrolyzed in a chloride molten salt system to separate titanium and aluminum and produce titanium powder. Therefore, the combination of thermal reduction and molten salt electrolysis is efficient and has great potential for producing high-purity titanium powder. Effective separation of aluminothermic reduction products through molten salt electrolysis. [Display omitted] • The slag separated by aluminum thermal reduction can recover electrolytic aluminum. • Titanium aluminum alloy is separated by electrolysis to obtain titanium powder. • A new method for preparing titanium powder from TiO 2 is provided. [ABSTRACT FROM AUTHOR]

The characterization and correction of lens distortion is an important part of optical measurement. This work analyzes the formation mechanism of color fringes and multiplication moiré, and discusses modification of the color CCD moiré method for correcting lens distortion. A demosaicing algorithm was used to simulate the color fringes in a CCD moiré pattern. We then performed a detailed analysis of the carrier field, and adopted a universal polynomial distortion model to characterize lens distortion, which increased the accuracy of distortion correction. Comparison experiments verified the feasibility of the modified method and the correctness of the formation mechanism for color CCD moiré. The modified method was then applied to lens distortion correction in the DIC measurement process, effectively reducing errors in displacement measurement. • The formation mechanism of color fringes and multiplication moiré were analyzed. • The color CCD moiré method for correcting lens distortion was modified. • The color fringes in a CCD moiré pattern has been successfully simulated. • The modified method was then applied to characterize chromatic aberration. [ABSTRACT FROM AUTHOR]

Accurate measurement of the dynamic deformation of double-layer liquid surfaces plays an important role in many fields, such as fluid mechanics, biomechanics, petrochemical industry and aerospace engineering. It is difficult to measure dynamic deformation of double-layer liquid surfaces synchronously for traditional methods. In this paper, a novel and effective method for full-field static and dynamic deformation measurement of double-layer liquid surfaces has been developed, that is wavefront distortion of double-wavelength transmission light with geometric phase analysis (GPA) method. Double wavelength lattice patterns used here are produced by two techniques, one is by double wavelength laser, and the other is by liquid crystal display (LCD). The techniques combine the characteristics such as high transparency, low reflectivity and fluidity of liquid. Two color lattice patterns produced by laser and LCD were adjusted at a certain angle through the tested double-layer liquid surfaces simultaneously. On the basis of the refractive indexes difference of two transmitted lights, the double-layer liquid surfaces were decoupled with GPA method. Combined with the derived relationship between phase variation of transmission-lattice patterns and out-of plane heights of two surfaces, as well as considering the height curves of the liquid level, the double-layer liquid surfaces can be reconstructed successfully. Compared with the traditional measurement method, the developed method not only has the common advantages of the optical measurement methods, such as high-precision, full-field and non-contact, but also simple, low cost and easy to set up. [ABSTRACT FROM AUTHOR]

The increasing research focus on micro- or nano-mechanics at high temperature poses new challenges for researchers to realize the deformation measurement by means of microscopic devices. SEM (Scanning Electron Microscope)-based optical methods are desirable approaches due to their full field, high magnification and high sensitivity. The SEM with an electron optical system is to some extent preferable for high temperature experiments compared with those traditional optical methods. In this study, a novel SEM-based measurement method aiming at the characterization of mechanical properties of high temperature alloys is proposed. By designing and employing a dual frequency grids pattern, the in-plane and out-of-plane deformation measurement of a specimen with U-shaped notch (U-notch) can be realized simultaneously at temperature up to 650 °C. The mechanical parameters of the tested specimen are determined and the stress concentration effect at elevated temperatures is analyzed. The Baratta-Neal stress concentration solution is adopted to be compared with the experimental results. The measurement accuracy is also discussed in detail. [ABSTRACT FROM AUTHOR]

Micro-scale residual stress in carbon fiber reinforced polymers have a significant impact on their mechanical performance. The residual stresses in the carbon fibers were released by micro-slotting and micro-ring-core methods using focused ion beam (FIB). The released deformation fields were captured by cross-gratings and mapped by geometric phase analysis (GPA) and digital image correlation (DIC) methods. The in-plane residual stresses in the carbon fibers were experimentally determined to be −40.5 MPa using elastic constitutive relations, which is consistent with the composites cylinder model. The axial compressive residual stresses in the fibers were found to be greater than −100 MPa. Moreover, the maximum value of residual stress in the polymer matrix was observed at the interface, potentially serving as a crack initiation site. [Display omitted] [ABSTRACT FROM AUTHOR]

• Developed a method that can measure the microscale residual stress in interface of SiC f /Ti17 composite. • The micro-slotting method based on focus ion beam is used to release the residual stress in radial and tangential direction at the cross-section of unidirectional composite. • The microscopic deformation field is obtained by Subset-geometric phase analysis (S-GPA) via high-frequency grating. • The residual stress distribution around the interface layer of the composites is determined and analyzed. Residual stresses in the interface layer significantly affects the mechanical properties of SiC f /Ti17 composites, which inevitably occurs due to the difference in the thermal expansion coefficient during the fabrication process. Therefore, the micro-residual stress at interface layer of SiC f /Ti17 composites should be quantitatively characterized. In this study, the micro-residual stresses at the interface of the composite are released and mapped via micro-slotting method and subset geometric phase analysis (S-GPA). Based on the material microstructure, a residual stress measurement scheme is designed for the interface layer in the radial and tangential directions. And the deformation field, which is calculated via S-GPA, is released, while the corresponding deformation field is obtained via finite element analysis, so that the residual stress can be fitted by above two deformation fields. The results indicate that, in the cross-setion of the fiber, the residual stresses at carbon interface are tensile, which may be beneficial to improve the mechanical properties of the materials. Meanwhile, tensile residual stresses, instead of compressive stresses in the interface layer, do not inhibit energy dissipation during the fracture of the composite. [ABSTRACT FROM AUTHOR]

Abstract: Based on the combined milling-imaging capabilities of focused ion-beam equipment, a novel approach of measuring residual stress of interconnects by slot milling and geometric phase analysis is presented. This method is performed through measuring the displacement field perpendicular to the slot due to the stress release by geometric phase analysis, and then solving the residual stress along the interconnect line by finite element method. Grating fabrication, slot milling and micrographs capturing are implemented in focused ion-beam equipment. The displacement at the edge of the slot and the residual stress of a copper interconnect line were found to be in the range 26–45nm and 265–467MPa, respectively. This work provides an effective way to determine the residual stress of film lines. [ABSTRACT FROM AUTHOR]

Abstract: An epoxy resin was chosen as the substrate of a grating for a curved surface moiré interferometry study because of its chemical properties and convenience in processing. Considering the low toughness of the epoxy resin, di-n-butyl was used to modify the resin''s mechanical properties. A number of films with different amounts of di-n-butyl and undergoing differing lengths of time in the centrifuge were made. The mechanical properties of these films were then studied. A loading apparatus driven by a step motor was used to apply a load and an optical extensometer, based on the mark shearing method, was used to measure the strain of the film. The nominal stress–strain curves of these films were obtained which yielded useful results. The experimental results also demonstrated the feasibility of the testing system for film-like specimen measurements. [Copyright &y& Elsevier]

In this paper, a new nano-moire´ method using scanning tunneling microscope (STM) is proposed. This method is capable of measuring nanoscopic deformation of matter. The formation mechanism of the STM moire´ fringe and the phase shifting technique used in STM moire´ fringes are explained in details. Typical experiments are conducted with the crystal lattices of freshly cleaved highly oriented pyrolytic graphite, are used as specimen grating, to generate STM moire´ fringe patterns. Phase shifting is realized in four steps from 0 to 2π by controlling the PZT in the STM system to shift the specimen in the vertical direction. This method provides a new way for disposal of moire´ fringes pattern in the nano-moire´ measurement. [Copyright &y& Elsevier]

Studies key problems in automatic layout design of spacecraft modules. Representation and formulation of the problem in mathematics; Pragmatic approaches in engineering practice.

The mechanical properties of rubber materials changes with the service time and the material parameters have a corresponding relationship with the aging time. In this paper, an in-situ non-destructive characterization technique of structural material parameters evaluation was developed, and the mechanical parameters for the silicone rubber during accelerated aging were measured by the developed method. This work combined the local indentation method to develop an in-situ stereo Finite element model updating method based on optical full-field deformation measurement, which realized constitutive parameters inversion of rubber. By comparing the inversion results with the test results, the validity and accuracy of the developed method were proved. Then, this method was applied to determine changes in the mechanical parameters during rubber aging. The proposed method is potential to predict the remaining lifetime of rubber material by using the parameter-aging time curve. • This work developed an in-situ measurement method of rubber material constitutive parameters. • The developed method was applied to characterize mechanical properties of rubber materials during accelerated aging testing. • The Poisson's ratio was reduced during the accelerated aging, indicating an decrease in the atomic packing density. • The proposed method is potential to predict the remaining lifetime of rubber material by the parameter-aging time curve. [ABSTRACT FROM AUTHOR]