柴达木盆地三湖坳陷横波勘探中的低幅异常消除技术

近年来,在柴达木盆地三湖坳陷开展了横波地震勘探,但是由于该区低幅度构造发育,横波静校正引起的"低幅"异常与上述低幅度构造相互混杂,难以区分。为此,针对该区横波表层调查难以控制表层横波速度模型的变化、横波近偏移距初至污染严重、横波折射层发育导致高速界面难以确定等问题,首先采用曲线拟合技术预测污染区横波初至时间确保初至完整性,然后采用面波模型与多层折射分层联合约束反演横波表层速度,最后通过基于速度谱分析的层位匹配建模技术确定合理的横波速度界面,形成了横波表层"低幅"异常消除技术,并进行了现场应用及效果评价。研究结果表明:①曲线拟合技术可以弥补近道污染区横波初至空白,保证层析反演模型的完整性;②基于瑞雷波的频散特性反演建模可以为确定该区浅层横波速度提供可靠的资料,提高浅层模型精度;③面波模型与多层折射分层联合约束反演能够更准确的反演该区表层横波速度场,较好地建立横波速度模型,消除横波剖面上"低幅"异常现象。结论认为,所形成的横波地震勘探低幅异常消除技术消除了横波静校正引起的"低幅"异常现象,提高了横波地震资料的成像品质。     

Axisymmetric hub-endwall profile optimization for a transonic fan to improve aerodynamic performance based on an integrated design optimization method

Structural and Multidisciplinary Optimization - This paper investigates an optimization for the axisymmetric hub-endwall profile of a transonic fan designed for a civil high bypass ratio turbofan...     

Field‐based robotic phenotyping of sorghum plant architecture using stereo vision

Sorghum (Sorghum bicolor) is known as a major feedstock for biofuel production. To improve its biomass yield through genetic research, manually measuring yield component traits (e.g. plant height, stem diameter, leaf angle, leaf area, leaf number, and panicle size) in the field is the current best practice. However, such laborious and time‐consuming tasks have become a bottleneck limiting experiment scale and data acquisition frequency. This paper presents a high‐throughput field‐based robotic phenotyping system which performed side‐view stereo imaging for dense sorghum plants with a wide range of plant heights throughout the growing season. Our study demonstrated the suitability of stereo vision for field‐based three‐dimensional plant phenotyping when recent advances in stereo matching algorithms were incorporated. A robust data processing pipeline was developed to quantify the variations or morphological traits in plant architecture, which included plot‐based plant height, plot‐based plant width, convex hull volume, plant surface area, and stem diameter (semiautomated). These image‐derived measurements were highly repeatable and showed high correlations with the in‐field manual measurements. Meanwhile, manually collecting the same traits required a large amount of manpower and time compared to the robotic system. The results demonstrated that the proposed system could be a promising tool for large‐scale field‐based high‐throughput plant phenotyping of bioenergy crops.     

Porous Si3N4 ceramics prepared by aqueous gelcasting using low–toxicity DMAA system: Regulatable microstructure and properties by monomer content

In this study, the low–toxicity monomer N, N–dimethylacrylamide (DMAA), serving as both gelling agent and pore–forming agent, was adopted to fabricate porous Si₃N₄ ceramics with a regulatable microstructure and property by aqueous gelcasting. Results indicate that monomer content played an important role in regulating and optimizing the properties of sintered bodies. With increasing monomer content (5.94–30.69?wt%), both slurry viscosity (maximum 0.14?Pa?s at 95.40 s^?1) and green body strength (11.35–49.23?MPa) exhibited monotonic increasing trends, demonstrating superior mechanical properties to those obtained using the neurovirulent acrylamide (AM) gelling system. The increased monomer content not only improved porosity, but also promoted α→β–Si₃N₄ transformation as well as β–Si₃N₄ grain growth through enhancing the connectivity of interlocking pores and accelerating the vapor phase transport during liquid–phase sintering. These variations in phase composition and microstructure derived from the varied monomer content further resulted in monotonic changes in porosity (40.32–51.50%), mean pore size (0.27–0.38?μm), flexural strength (202.77–132.15?MPa), fracture toughness (2.93–2.32?MPa?m^1/2), dielectric constant (3.48–2.78) and loss (3.52–3.09?×?10^?3) at 10?GHz for sintered bodies, displaying an excellent comprehensive properties. This study suggests a promising prospect for DMAA in preparation of high–performance porous Si₃N₄ ceramics by aqueous gelcasting.     

Materials Design of Solar Cell Absorbers Beyond Perovskites and Conventional Semiconductors via Combining Tetrahedral and Octahedral Coordination

Tetrahedral coordination structures, e.g. crystalline Si, GaAs, CdTe, and octahedral coordination structures, e.g. perovskites, represent two classes of successful crystal structures hitherto for solar cell absorbers. Here, via first‐principles calculations and crystal symmetry analysis, the two classes of semiconductors are shown exhibiting complementary properties in terms of bond covalency/ionicity, optical property, defect tolerance, and stability, which are correlated with their respective coordination number. Therefore, a spinel structure is proposed, which combines tetrahedral and octahedral coordination into a single crystal structure, as an alternative to perovskite and conventional semiconductors for potential photovoltaic applications. The case studies of a class of 105 spinel AB₂X₄ systems identify five spinel compounds HgAl₂Se₄, HgIn₂S₄, CdIn₂Se₄, HgSc₂S₄, and HgY₂S₄ as promising solar cell absorbers. In particular, HgAl₂Se₄ has suitable bandgap (1.36 eV by GW0 calculation), small direct–indirect bandgap difference (24 meV), appropriate carrier effective mass (m_e = 0.08 m₀, and m_h = 0.69 m₀), strong optical absorption, and high dynamic stability. This study suggests that crystal systems with mixed tetrahedral and octahedral coordination may open a viable route for emerging solar cell absorbers.     

最优化算法与纯元素谱剥离相结合的能量色散X射线荧光谱解谱方法

在进行能量色散X射线荧光光谱(EDXRF)解谱时,如果给定样品的元素构成,采用纯元素谱图剥离的方式会更加合理,但由于每个元素的谱线都不止一条,如果仅仅针对主线对齐做剥离,会导致结果的严重失真,同时剥离次序对解谱结果有较大影响。介绍了一种最优化算法与纯元素谱剥离相结合的EDXRF解谱方法,该方法以多个纯元素谱的强度大小和峰位漂移道数作为变量构建残差方程,并用最优化计算的方法去调整,直至残差达到极小。实验采用强度顺序剥离、能量顺序剥离和最优化算法拟合3种方法分别对谱线重叠较为严重的La-Ce-Pr-Nd混合液样品的L系谱线进行了解析,结果表明最优化计算方法拟合的谱图与原始谱的残差 (1415.0)比另两种方法(166094.0和3192.7)大幅度缩小,拟合谱与原始谱更为吻合,并且方法在实现时对初值不敏感,解谱精度也不依赖于剥离次序。     

Fenton 絮凝工艺去除废水中的有机物试验

为了研究废水中有机物的去除问题，针对某企业含有机物废水进行了对比试验，采用了Fenton 絮凝联合工艺去除废水中的COD（化学需氧量）和浊度，考察了初始pH值、H2O2投加量、H2O2与Fe2+投加物质的量比、反应时间、絮凝剂投加量以及絮凝剂投加时的pH值对COD以及浊度去除效果的影响。结果表明，采用最佳工艺参数组合后，浊度去除率和COD的去除率分别为99.32%和97.27%。     

中厚板减薄过程残余应力的演变行为

 针对中厚板使用过程中的变形行为，研究了中厚板因减薄引起横向残余应力重新分布规律。基于剥层法理论建立了中厚板减薄过程中残余应力分布模型和挠曲变形模型，应用有限元分析法模拟了厚板减薄过程。对比分析了残余应力分布形式和中厚板挠曲变形程度的计算结果和有限元仿真模拟结果，验证了两种分析方法的可行性，并进一步分析了应力分布状态及厚板减薄方式对薄板减薄过程变形的影响。结果表明，两种分析结果都能反映中厚板减薄变形特征，但有限元仿真模拟方法能够随薄板减薄而改变中厚板约束状态，结果更为准确；中厚板内部原始残余应力分布状态及使用过程减薄方式对其减薄过程变形有重要影响，为中厚板的合理生产设计和使用提供理论依据。