Unified convergence analysis of a second-order method of multipliers for nonlinear conic programming

Science China Mathematics - In this paper, we accomplish the unified convergence analysis of a second-order method of multipliers (i.e., a second-order augmented Lagrangian method) for solving the...     

An organoantimony nitrate complex with azastibocine framework as water tolerant Lewis acid catalyst for the synthesis of 1,2-disubstitued benzimidazoles

A novel organoantimony complex of 6-cyclohexyl-6,7-dihydrodibenzo[c,f] [1,5]azastibocin-12(5H)-yl nitrate ( 2 ) was synthesized and systematically characterized by techniques such as NMR spectra, TG-DSC, and X-ray diffraction. It was found that the complex 2 exhibits relatively strong Lewis acidity (3.3 < Ho ≤ 4.8) and could be employed as a water tolerant Lewis acid catalyst for the synthesis of synthetically valuable benzimidazole derivatives starting from aldehydes and arylenediamines. This catalytic system shows excellent tolerance toward a wide variety of functional groups, such as methyl, methoxyl, fluoro, chloro, bromo, nitro, cyan, trifluoromethyl, 1-naphthaldehyde, furfural and n-butyl, together with facile reusability in 5 times scale enlarged synthesis.     

Three channel GHz-ranged demultiplexer in solid-solid phononic crystals

We present the design procedure for the elastic GHz-ranged demultiplexer based on a solid-solid phononic crystal platform. It consists of a T-shaped waveguide with three arms. The PnC platform consists of a square array of infinitely long rods of Tungsten embedded in PMMA background. In order to have a wide band gap, it is essential that constituent materials have large contrast in physical properties. These materials have large contrast in their physical properties and it gives us the possibility of having complete band gaps with low filling fractions. To calculate the band diagram and transmission field map, the finite element method (FEM) has been employed. The main waveguides are made by removing one row or one column of rods. For each arm, the radius of rods is modified to have three different defects. Therefore, the designed demultiplexer can separate three frequencies in the range of GHz. To the best of our knowledge, it is for the first time.     

贵金属纳米颗粒的微生物合成

金属纳米颗粒在材料、催化、医学、环境等众多领域应用广泛,其中,金、银、铂、钯等贵金属的纳米颗粒作为良好的催化剂可提高反应的速率,因此,贵金属纳米颗粒的合成吸引了众多研究者的关注。传统的物理化学法虽能高效、可控地合成贵金属纳米颗粒,但是合成条件苛刻、成本昂贵、且会产生对环境有害的化学物质。因此,探索节能、环保、可持续的绿色合成方法成为纳米合成研究的热点之一。贵金属纳米颗粒的微生物合成法具备绿色合成技术的诸多要素,研究表明某些微生物能将金属盐转化成纳米材料,且微生物繁殖速度快、培养成本低、生长条件温和,从而得到了研究者们的广泛关注。本文归纳总结了目前微生物合成贵金属纳米颗粒的主要研究进展,包括贵金属纳米颗粒可能的合成机制以及尺寸与形貌控制方法,探讨了其在医学、催化、生物传感、环境方面的具体应用,并对贵金属纳米颗粒微生物合成的未来发展进行了展望。     

Recent advances in radical-mediated [2+2+m] annulation of 1,n-enynes

1,n-Enynes are a versatile class of unsaturated hydrocarbons that found broad applications in the synthetic community of natural products, biologically active structures and functional materials. Typical methods for the transformations of 1,n-enynes include the radical-mediated [2+2+m] annulation reaction as they are particularly efficient accesses to functionalized polycyclic compounds. We herein highlighted recent process in the radical-mediated [2+2+m] annulation of 1,n-enynes, including [2+2+1] and[2+2+2] modes, for the construction of five-to six-membered-ring-fused polycyclic scaffolds. Meanwhile, the mechanisms for these transformations were described.     

爆炸载荷作用下具有可折叠芯层夹芯梁的动态响应

基于目前研究最广泛的刚性折纸(Tachi-origami)样式，通过改变其初始折叠角度构建出4种不同的蜂窝胞元，并且通过排列分布将其组成夹芯梁。采用商用有限元软件Abaqus/explicit对准静态和爆炸载荷作用下可折叠芯层夹芯梁的力学响应进行研究，分析可折叠芯层的泊松比变化规律、夹芯梁背板挠度以及能量吸收机理；并将夹芯梁与等质量的实体梁进行对比。采用后面板最大挠度作为抗爆性能的评价，结果发现:可折叠芯层在准静态载荷下具有一定的负泊松比效应；夹芯梁的抗爆性能优于实体梁，曲边蜂窝的初始折角对其作为芯层夹芯梁的抗爆性能有较大影响，随着初始折角的逐渐增大，其抗爆性能逐渐下降；当初始折角为直角时对应于方孔直边蜂窝，其抗爆性能最差。     

振型归一化对梁结构柔度曲率损伤指标的影响

结构柔度矩阵需由质量矩阵归一化振型获得,而质量矩阵归一化振型难以直接测得,限制了柔度曲率类损伤指标的应用。为分析振型归一化方法对梁结构柔度曲率类损伤指标的影响,根据梁结构的刚度、弯矩和位移曲率的关系,建立了均布荷载作用下结构损伤前后位移曲率与损伤程度的理论表达式,实现定量分析均匀荷载面曲率结构损伤程度。提出P-范数振型归一化方法,通过均匀荷载面曲率指标推导了振型质量矩阵归一化系数差x_α与损伤程度的关系。以三跨连续梁算例对理论进行了验证,结果表明,损伤程度定量指标效果良好,不同P-范数振型归一化方法下,损伤程度的偏差可由2x_α估算;2-范数振型归一化方法的损伤识别结果与质量矩阵振型归一化结果最接近,故当无法获得质量矩阵归一化振型时,可采用2-范数归一化振型代替。     

An automated vane shear test tool for environmental monitoring with unmanned ground vehicles

The present work describes the development of a novel robotic vane shear test tool for characterization of soil parameters with high precision and accuracy. The tool automates industrial standards for testing procedures. The proposed system is capable of performing high resolution torque measurements, which are then used to estimate the shear strength of the soil. The design of the instrument and its advantages over traditional manual instruments are discussed, after which error sources, calibration, and test procedures are described. The developed tool was successfully validated against high-end commercial equipment. The built unit was employed for characterizing mine waste in a laboratory setting and also deployed in the field on board an Unmanned Ground Vehicle for remote soil characterization.     

A novel rigid wheel for agricultural machinery applicable to paddy field with muddy soil

The working performance of agricultural machinery is largely determined by the walking performance of the wheel when driving in complex unstructured soil. However, the driving performance of existing wheels is not satisfactory for paddy field with muddy soil. The purpose of the current study is therefore to propose a novel rigid wheel for agricultural machinery which is applicable to paddy field with muddy soil. Firstly, a novel arc edge shaped wheel was designed based on the principles of mechanics on the ground. Then the driving performance of this arc edge shaped wheel was evaluated using FE modeling of interaction between rigid wheel and soil. Finally, the structure originally designed arc edge shaped wheel was improved according to FE modeling results, and this improved design was further evaluated by both FE simulation and prototype experiments. Both FE modeling and experimental results indicate that the improved arc edge shaped wheel proposed in this study has a good driving performance with regarding to wheel sinkage and soil reaction force. The proposed arc edge shaped wheel could be used as an effective component of rice harvester for paddy field with muddy soil.     

Early fault detection of rotating machinery through chaotic vibration feature extraction of experimental data sets

Fault detection of rotating machinery by the complex and non-stationary vibration signals with noise is very difficult, especially at the early stages. Also, many failure mechanisms and various adverse operating conditions in rotating machinery involve significant nonlinear dynamical properties. As a novel method, phase space reconstruction is used to study the effect of faults on the chaotic behavior, for the first time. Strange attractors in reconstructed phase space proof the existence of chaotic behavior. To quantify the chaotic vibration for fault diagnosis, a set of new features are extracted. These features include the largest Lyapunov exponent; approximate entropy and correlation dimension which acquire more fault characteristic information. The variations of these features for different healthy/faulty conditions are very good for fault diagnosis and identification. For the first time, a new chaotic feature space is introduced for fault detection, which is made from chaotic behavior features. In this space, different conditions of rotating machinery are separated very well. To obtain more generalized results, the features are introduced into a neural network to identify different faults in rotating machinery. The effectiveness of the new features based on chaotic vibrations is demonstrated by the experimental data sets. The proposed approach can reliably recognize different fault types and have more accurate results. Also, the performance of the new procedure is robust to the variation of load values and shows good generalization capability for various load values.