轮腿可切换机器人步态切换动作设计及其机体位姿测量仿真

轮腿可切换机器人在不同的环境下具有不同的运动性能,研制一款新型轮腿可切换机器人。该机器人可实现轮式步态和腿式步态的切换以适应不同环境,最大限度提高机器人运动性能。本文研究了机器人进行步态切换时,机器人机体位姿变化及机器人机体质心在空间的位移及机器人腿各个关节的旋转角度的变化的测量方法,为机器人稳定性研究提供依据。通过对机器人步态切换动作进行仿真,测量机器人质心在空间的变化量及关节角度变换,分析测量结果表明机器人位姿变换平稳,证明机器人步态切换动作的合理性。     

不同钙硅比水化硅酸钙力学性能的分子动力学模拟

基于Pellenq等的建模思路,构造了不同钙硅比(C/S)的水化硅酸钙(C-S-H)原子模型,采用分子动力学方法模拟了C-S-H在轴向拉伸载荷作用下的力学性能。重点比较分析了不同钙硅比的C-S-H在无水及含水情况下的拉伸应力-应变曲线。模拟结果表明:(1)与钙硅比为1.0的情况相比,钙硅比大于1.0时C-S-H结构的抗拉强度显著下降;(2)钙硅比大于1.0时,钙氧间的相互作用在承受载荷方面起重要作用,有效弥补了结构中因SiO_2基团缺失引起的缺陷,使得C-S-H的强度下降程度趋缓;(3)当应变达到一定程度时,水分子能够切断钙氧间的相互作用,使得C-S-H结构的强度进一步降低甚至引起断裂失效。     

低温预氧化对PIP-SiCf/SiC复合材料介电性能的影响

分析了低温预氧化过程对聚碳硅烷(PCS)先驱体结构的影响,研究了不同预氧化温度和时间下SiCf/SiC复合材料室温和高温介电性能的演变规律。结果表明:经预氧化处理后基体中的氧含量增加,生成具有低介电常数的Si CxOy相,且其含量随着预氧化温度的升高或时间的延长逐渐增加,SiC微晶和自由碳的含量均减少,因此SiCf/SiC复合材料的复介电常数明显降低,同时高温复介电常数的升高幅度显著减小。经260℃-6 h预氧化处理后,700℃时复合材料在整个X波段的反射率均达到-8 d B以下,高温吸波性能得到有效改善。     

电流互感器故障分析及诊断

介绍了一起电流互感器故障的现场情况,分析诊断出了故障发生的原因为生产制造过程中,人工操作误差导致二次绕组间绝缘裕度过小,长时间运行后发生绝缘劣化击穿,并给出了预防此类故障的建议.     

Routes for high-performance thermoelectric materials

Thermoelectric materials can be used in direct conversion of heat to electricity and vice versa. The past decade has witnessed the rapid growth of thermoelectric research, targeting high thermoelectric performance either via reduction in the lattice thermal conductivity or via enhancement of the power factor. In this review, we firstly summarize the recent advances in bulk thermoelectric materials with reduced lattice thermal conductivity by nano-microstructure control and also newly discovered materials with intrinsically low lattice thermal conductivity. We then discuss ways to enhance the electron transport abilities for achieving higher power factor by both novel and traditional methods. Finally, we highlight the recent development in single-crystal thermoelectric materials. These strategies are successful in synergistically manipulating the thermal conductivity and electron transport properties, which have significantly advanced thermoelectric performance on materials. For device applications on these high-performance materials, new opportunities may arise though stability, electrode contacts, mechanical properties, and other problems need to be solved in the near future.     

Let There be Light: Polymeric Micelles with Upper Critical Solution Temperature as Light‐Triggered Heat Nanogenerators for Combating Drug‐Resistant Cancer

Complete drug release and efficient drug retention are two critical factors in reversing drug resistance in cancer therapy. In this regard, polymeric micelles with an upper critical solution temperature (UCST) are designed as a new exploration to reverse drug resistance. The amphiphilic UCST‐type block copolymers are used to encapsulate photothermal agent IR780 and doxorubicin (DOX) simultaneously. The integrated UCST‐type drug nanocarriers show light‐triggered multiple synergistic effects to reverse drug resistance and are expected to kill three birds with one stone: First, owing to the photothermal effect of IR780, the nanocarriers will be dissociated upon exposure to laser irradiation, leading to complete drug release. Second, the photothermal effect‐induced hyperthermia is expected to avoid the efflux of DOX and realize efficient drug retention. Last but not least, photothermal ablation of cancer cells can be achieved after laser irradiation. Therefore, the UCST‐type drug nanocarriers provide a new strategy in reversing drug resistance in cancer therapy.     

Modelling and simulation of chlorophyll fluorescence from photosystem II as affected by temperature

Emission of chlorophyll fluorescence (ChlF) from photosystem II (PSII) is affected by both plant status and environmental conditions. In this work, a state space model structure for ChlF from PSII with temperature as a variable model parameter was developed to provide insights into the temperature effects on photosynthesis and greenhouse temperature control. Experiments were carried out at 20, 25, and 30°C to validate the capability and flexibility of the developed model structure. Simulations of ChlF emission were performed for different temperatures. The results demonstrated the effectiveness of the ChlF model structure and the findings are useful for the development of greenhouse temperature control strategies.Inspec keywords: fluorescence, state‐space methods, photosynthesis, temperature control, vegetationOther keywords: chlorophyll fluorescence, photosystem II, PSII, plant status, environmental conditions, state space model structure, variable model parameter, temperature effects, photosynthesis, ChlF emission, ChlF model structure, greenhouse temperature control strategies, temperature 20.0 degC, temperature 25.0 degC, temperature 30.0 degC     

Unique role of non-mercapto groups in thiol-pinning-mediated Ag growth on Au nanoparticles

Owing to the strong affinity of thiols to Au and Ag, they are often employed to modify the surfaces of nanoparticles (NPs). Recently, these strong ligand-interface interactions have been employed to control NP growth, and this technique has emerged as a unique modulation strategy for creating unconventional plasmonic hybrid nanostructures. In these systems, the roles of the non-mercapto components of the thiol molecules and their structures are still unknown. Therefore, we herein present our investigation into this phenomenon. Primary amino (–NH₂) groups in thiols are found to play a key role in regulating growth kinetics, i.e., in accelerating Ag deposition on Au NPs. The–NH₂ groups are thought to bring Ag ions to the particle surface by coordinating to them, and thereby assist their reduction. The effect of molecular structure is non-trivial and thus provides the possibility of selective thiol detection. Based on the dependence of kinetic modulation on the non-mercapto components and molecular structures of molecules, we demonstrate the highly sensitive and specific detection of cysteine (limit of detection: 6 nM) in a mixture of 19 natural amino acids based on Ag growth on Au nanospheres. In addition, based on this modulation effect, we reveal the entrapping of chiral thiols within the growth layer through their plasmonic circular dichroism (PCD) responses. We believe that thiol-based growth regulation has great potential for creating plasmonic nanostructures with novel functionalities.

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引入扰动补偿的多电机滑模协同控制研究

目的 解决多电机协同控制时容易受到非线性和外界扰动等不定因素的影响。方法 基于多电机偏差耦合控制结构,与引入扰动补偿的混合非奇异终端滑模变结构控制相结合,并与传统PI(Proportional Integral)调节器控制效果做仿真对比。结果 本文所提控制算法通过计算机仿真软件进行验证分析,该算法能够使得电机在启动时效果较好,转速误差在受到扰动时效果优于传统PI控制约8.50%;电机转矩在受到扰动后控制效果更加理想,几乎不存在迟滞时间就能达到新的负载转矩值;在受到负载扰动时转速误差波动较小,优于传统PI控制约8.83%。结论 通过计算机仿真验证得出,引入扰动补偿后的混合非奇异终端滑模变结构控制系统的响应时间和收敛速度、控制性能和鲁棒性都要优于传统PI控制的。