Implementation of pollution source assessment and treatment strategy for plateau railway construction in China: an AHP-cloud model approach.

During the construction process of railways in the plateau region, various types of pollution sources can have serious or even irreversible impacts on the plateau ecology. To address pollution source treatment during the construction process, protect the ecological environment along the railway, and maintain the ecological balance, we collected geological and environmental data and analyzed the influencing factors of pollution sources. Taking sewage as the main research subject, we propose a new method based on the Analytic Hierarchy Process (AHP)-cloud model to classify the pollution source treatment level, establish an index system, and select the ecological environment level, sewage rate, and pollutant characteristics as the three main influencing factors. Finally, we divide the pollution source treatment level into I, II, and III, corresponding to V1 = {I-level} = {high impact}, V2 = {II-level} = {moderate impact}, and V3 = {III-level} = {low impact}. Based on the comprehensive factor weight analysis and the field engineering conditions of the studied railway in the western plateau of China, we classify the pollution source treatment level of six tunnels and propose treatment suggestions for each level. To advance the efficient implementation of environmental protection during the construction of the plateau railway, we propose three policy recommendations that can positively contribute to environmental protection and green development. This work provides theoretical and technical guidance for the treatment of pollution sources in the construction of the plateau railway, which also serves as a significant reference for other similar projects.

Hybrid camera array based calibration for computer-generated integral photography display.

Integral photography (IP) is one of the most promising 3D displays that can achieve a full parallax 3D display without glasses. There is a great need to render a correct, high-precision 3D image from an IP display. To achieve a correct 3D display, calibration is needed to correct optical misalignment and optical aberrations, while it is challenging to achieve correct mapping between a microlens array and matrix display. We propose an IP calibration method for a 3D autostereoscopic integral photography display based on a sparse camera array. Our method distinguishes itself from previous methods by estimating parameters for a dense correspondence map of an IP display with a relatively flexible setup and high precision in a reasonable time cost. We also propose a workflow to enable our method to handle both a visible and invisible microlens array and obtain a great outcome. One prototype is fabricated to evaluate the feasibility of the proposed method. Moreover, we evaluate our proposed method in geometry accuracy and image quality.

Design and Optimization of FBG Implantable Flexible Morphological Sensor to Realize the Intellisense for Displacement.

The measurement accuracy of the intelligent flexible morphological sensor based on fiber Bragg grating (FBG) structure was limited in the application of geotechnical engineering and other fields. In order to improve the precision of intellisense for displacement, an FBG implantable flexible morphological sensor was designed in this study, and the classification morphological correction method based on conjugate gradient method and extreme learning machine (ELM) algorithm was proposed. This study utilized finite element simulations and experiments, in order to analyze the feasibility of the proposed method. Then, following the corrections, the results indicated that the maximum relative error percentages of the displacements at measuring points in different bending shapes were determined to be 6.39% (Type 1), 7.04% (Type 2), and 7.02% (Type 3), respectively. Therefore, it was confirmed that the proposed correction method was feasible, and could effectively improve the abilities of sensors for displacement intellisense. In this paper, the designed intelligent sensor was characterized by temperature self-compensation, bending shape self-classification, and displacement error self-correction, which could be used for real-time monitoring of deformation field in rock, subgrade, bridge, and other geotechnical engineering, presenting the vital significance and application promotion value.

Structural Stability Monitoring of a Physical Model Test on an Underground Cavern Group during Deep Excavations Using FBG Sensors.

Fiber Bragg Grating (FBG) sensors are comprehensively recognized as a structural stability monitoring device for all kinds of geo-materials by either embedding into or bonding onto the structural entities. The physical model in geotechnical engineering, which could accurately simulate the construction processes and the effects on the stability of underground caverns on the basis of satisfying the similarity principles, is an actual physical entity. Using a physical model test of underground caverns in Shuangjiangkou Hydropower Station, FBG sensors were used to determine how to model the small displacements of some key monitoring points in the large-scale physical model during excavation. In the process of building the test specimen, it is most successful to embed FBG sensors in the physical model through making an opening and adding some quick-set silicon. The experimental results show that the FBG sensor has higher measuring accuracy than other conventional sensors like electrical resistance strain gages and extensometers. The experimental results are also in good agreement with the numerical simulation results. In conclusion, FBG sensors could effectively measure small displacements of monitoring points in the whole process of the physical model test. The experimental results reveal the deformation and failure characteristics of the surrounding rock mass and make some guidance for the in situ engineering construction.

Study on the law of initial gas expansion energy and its feasibility in coal and gas outburst prediction.

In order to explore the relationship between IEERG and outburst intensity and verify the feasibility of the former in predicting coal and gas outburst, a series tests with different gases and different gas pressures were conducted on the basis of self-developed coal and gas outburst simulation system and IEERG measuring instrument. The results show that with the increase of gas pressure, the IEERG increases gradually. Under the same gas pressure, the coal has the strongest adsorption capacity for CO2, followed by CH4 and N2. When the IEERG is less than 24.40 mJ·g-1, no outburst will occur. When the IEERG is greater than 24.40 mJ·g-1, weak outburst will occur. When the IEERG is greater than 34.72 mJ·g-1, strong outburst will occur. This shows that the magnitude of IEERG is closely related to the outburst. The larger the IEERG, the greater the possibility of outburst and the greater the intensity of outburst. It is feasible to predict the risk of outburst using IEERG, and it can be quantified.

Investigation on Preparation and Performance of High Ga CIGS Absorbers and Their Solar Cells.

Tandem solar cells usually use a wide band gap absorber for top cell. The band gap of CuIn(1-x)GaxSe2 can be changed from 1.04 eV to 1.68 eV with the ratio of Ga/(In+Ga) from 0 to 1. When the ratio of Ga/(In+Ga) is over 0.7, the band gap of CIGS absorber is over 1.48 eV. CIGS absorber with a high Ga content is a possible candidate one for the top cell. In this work, CuInGa precursors were prepared by magnetron sputtering with CuIn and CuGa targets, and CIGS absorbers were prepared by selenization annealing. The Ga/(In+Ga) is changed by changing the thickness of CuIn and CuGa layers. Additionally, CIGS solar cells were prepared using CdS buffer layer. The effects of Ga content on CIGS thin film and CIGS solar cell were studied. The band gap was measured by PL and EQE. The results show that using structure of CuIn/CuGa precursors can make the band gap of CIGS present a gradient band gap, which can obtain a high open circuit voltage and high short circuit current of the device. With the decrease in Ga content, the efficiency of the solar cell increases gradually. Additionally, the highest efficiency of the CIGS solar cells is 11.58% when the ratio of Ga/(In+Ga) is 0.72. The value of Voc is 702 mV. CIGS with high Ga content shows a great potential for the top cell of the tandem solar cell.

Physical simulation technologies and testing system for cavern shape control from single-well solution mining in rock salt.

The shape of the salt cavern is very important for the safe operation of gas storage facilities in rock salt. A physical simulation test is an effective means to study the shape control of salt caverns. To accurately simulate the process and parameters of single-well solution mining in rock salt, we developed simulation technologies and a testing system for cavern shape control. Based on the flow similarity principle, we established a sealing technology for dynamic-static disturbance and successfully replicated the solution mining process for forward and reverse circulations. Based on the requirement of protective fluid in the field, we developed a protection liquid unit to control the oil pad height to avoid overdissolution or uneven dissolution at the top of the salt cavern. From the principle of distance determination by laser and video, we developed a salt cavern shape visualization and micro-distance detection system that can realize the size measurement and real-time visualization of the salt cavern in pressurized corrosive environment. We put forward the control technology of the testing system that can achieve the integrated and collaborative control of inner and outer pipe spacing, water flow during injection-production circulations, and the height of protection fluid. Finally, we carried out a physical simulation test of solution mining for cavern shape control. The shape and size of the salt cavern from the test are in good agreement with the design. This study can provide an important basis for determining the optimal solution in mining technology and the parameters for cavern shape control.

Study on the Performance of Oxygen-Rich Zn(O,S) Buffers Fabricated by Sputtering Deposition and Zn(O,S)/Cu(In,Ga)(S,Se)2 Interfaces.

We developed a novel process for fabricating oxygen-rich Zn(O,S) buffer layers by magnetron reactive sputtering with a single oxygen-rich Zn(O,S) target, suitable for industrial all-dry production. Then, we successfully fabricated Cd-free Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells. By varying the oxygen partial pressure during sputtering from 0 to 20%, we precisely controlled the Zn(O,S) composition, then systematically investigated its effects on the quality of oxygen-rich Zn(O,S) films, the properties of formed p-n junctions, and the performance of CIGSSe solar cells with Zn(O,S) buffer. We demonstrated that reactive sputtering with a Zn(O,S) target can generate a homogeneous, high-quality oxygen-rich Zn(O,S) buffer on large-area substrates. We observed a unique and unusual phenomenon: the appropriate content of secondary phase ZnSO4 and ZnSO3 improved the band alignment for oxygen-rich Zn(O,S). Combining our proposed schematic diagram of band alignmentat the Zn(O,S)/CIGSSe interface, we established a crucial correlation between the device performance and the interfacial properties at the p-n junction. For the CIGSSe device performance, the band alignment matching at the heterojunction plays a primary role, and the quality of oxygen-rich Zn(O,S) films plays a secondary role. Consequently, an excellent oxygen-rich Zn(O,S) buffer can be obtained with 10% Zn(O,S) deposition oxygen partial pressure , and the optimized device shows a higher Voc (447 mV) and a similar conversion efficiency (11.2%) than conventional CIGSSe devices with CdS buffer.

A convenient and practical triaxial coupled seepage testing apparatus for deep buried coal.

As the world's shallow coal resources are being depleted, resource development continues to progress faster. To explore the coupled hydromechanical behavior of coal reserves that are buried deep underground under high stress, complex seepage, high temperature, adsorption, and desorption, we have developed a triaxial seepage testing apparatus under multifactor coupling effect. The system consists of a high-pressure and high-precision servo control loading system, a triaxial core holder (TEMCO), a seepage dynamic control system, a low-field Nuclear Magnetic Resonance (NMR) test system, a constant temperature control system, and a data acquisition and monitoring system. This system is capable of applying high pressure and long-term loading for specimens under adsorption or desorption. In addition, both steady-state method and pressure transient methods can be applied, thus covering the entire range for coal reserves buried deep from ultralow permeability to high permeability and significantly shortening the testing time. The characteristics of pores and fractures in the specimens and their impacts on permeability can be quantitatively evaluated by the low-field NMR experimental technique. We conducted experiments to understand the evolution of permeability of different gases under different stress conditions and to study the impact of adsorption on pore size distribution. Our experimental results show that the performance of this system is stable and reliable, which allow it to reflect the coupled hydromechanical response of coal buried deep underground. We envision this apparatus has a wide range of application value and can provide a scientific experimental basis for improving the recovery of coalbed methane and geological sequestration of CO2 in the future.

A Uniaxial Compression Experiment with CO2-Bearing Coal Using a Visualized and Constant-Volume Gas-Solid Coupling Test System.

Injecting carbon dioxide (CO2) into a deep coal seam is of great significance for reducing the concentration of greenhouse gases in the atmosphere and increasing the recovery of coalbed methane. A visualized and constant-volume gas-solid coupling system is introduced here to investigate the influence of CO2 sorption on the physical and mechanical properties of coal. Being able to keep a constant volume and monitor the sample using a camera, this system offers the potential to improve instrument accuracy and analyze fracture evolution with a fractal geometry method. This paper provides all steps to perform a uniaxial compression experiment with a briquette sample in different CO2 pressures with the gas-solid coupling test system. A briquette, cold-pressed by raw coal and sodium humate cement, is loaded in high-pressure CO2, and its surface is monitored in real-time using a camera. However, the similarity between the briquette and the raw coal still needs improvement, and a flammable gas such as methane (CH4) cannot be injected for the test. The results show that CO2 sorption leads to peak strength and elastic modulus reduction of the briquette, and the fracture evolution of the briquette in a failure state indicates fractal characteristics. The strength, elastic modulus, and fractal dimension are all correlated with CO2 pressure but not with a linear correlation. The visualized and constant-volume gas-solid coupling test system can serve as a platform for experimental research about rock mechanics considering the multifield coupling effect.

An Extended Depth-at-Field Volumetric Near-Eye Augmented Reality Display.

We introduce an optical design and a rendering pipeline for a full-color volumetric near-eye display which simultaneously presents imagery with near-accurate per-pixel focus across an extended volume ranging from 15cm (6.7 diopters) to 4M (0.25 diopters), allowing the viewer to accommodate freely across this entire depth range. This is achieved using a focus-tunable lens that continuously sweeps a sequence of 280 synchronized binary images from a high-speed, Digital Micromirror Device (DMD) projector and a high-speed, high dynamic range (HDR) light source that illuminates the DMD images with a distinct color and brightness at each binary frame. Our rendering pipeline converts 3-D scene information into a 2-D surface of color voxels, which are decomposed into 280 binary images in a voxel-oriented manner, such that 280 distinct depth positions for full-color voxels can be displayed.