基于广义逆矩阵理论的杆系结构形态创构方法#br#

广义逆矩阵理论被广泛应用于不稳定结构的形态分析。不稳定结构在荷载作用下，其形状会发生变化直至其势能达到最低，此时的结构处于无弯矩的平衡状态。根据该原理并结合广义逆矩阵理论提出一种适用于杆系结构的形态创构方法。该方法将杆系模型中杆单元进行分组，在每一组中杆单元总长度不变的条件下，建立控制结构形状变化的移形方程。利用广义逆矩阵理论和势能梯度确定使模型势能下降最快的方向，并逐步调整节点位置直至势能达到最低。临时单元和单元组的引入使得该方法可以应用于多种形式结构的形态创构，合理地设置单元组和临时单元可以实现单元长度与单元内力的重新分配进而实现诸多功能。算例分析说明该方法的特性并验证其有效性。     

Polyacrylonitrile/α-Fe2O3 Hybrid Photocatalytic Composite Adsorbents for Enhanced Dye Removal

The potential of a novel α-Fe₂O₃/polyacrylonitrile (PAN) hybrid composite adsorbent to eliminate methylene blue (MB) from aqueous solution was evaluated. PAN was selected as the base composite. The presence of α-Fe₂O₃ as nanophotocatalyst on the surface of PAN introduced an efficient photocatalytic hybrid composite adsorbent for degrading MB. Effects of α-Fe₂O₃ nanopowder loading, pH, temperature, MB initial concentration, solar light, and contact time were investigated. Langmuir, Freundlich, and Temkin isotherms were applied to analyze the adsorption behavior. The Freundlich equation provided the best correlation with experimental data. Pseudo-first-order, pseudo-second-order, and intraparticle models were employed. Thermodynamic studies indicated an endotherm and spontaneous adsorption process in a defined temperature range.     

Carborane-Containing Matrix Metalloprotease (MMP) Ligands as Candidates for Boron Neutron-Capture Therapy (BNCT)

Based on the previously reported potent and selective sulfone hydroxamate inhibitors SC-76276, SC-78080 (SD-2590), and SC-77964, potent MMP inhibitors have been designed and synthesized to append a boron-rich carborane cluster by employing click chemistry to target tumor cells that are known to upregulate gelatinases. Docking against MMP-2 suggests binding involving the hydroxamate zinc-binding group, key H-bonds by the sulfone moiety with the peptide backbone residues Leu82 and Leu83, and a hydrophobic interaction with the deep P1’ pocket. The more potent of the two triazole regioisomers exhibits an IC₅₀ of 3.7 nM versus MMP-2 and IC₅₀ of 46 nM versus MMP-9.     

Micromechanical properties and microstructural evolution of Amosic-3 SiC/SiC composites irradiated by silicon ions

In this work, Amosic-3 SiC/SiC composites were irradiated to 10 dpa and 115 dpa with 300 keV Si ions at 300 °C. To evaluate its irradiation behaviour and investigate the underlying mechanism, nanoindentation, AFM, Raman and electron microscopy were utilized. Nanoindentation showed that although micromechanical properties declined after irradiation, hardness and Young’s modulus were maintained better under 115 dpa. AFM manifested differential swelling among PyC interface, fiber and matrix and SEM showed irradiation-induced partial interface debonding, which are both more obvious under 115 dpa. TEM revealed the generation and proliferation of amorphous regions, which is according with the decline and broadening of peaks in Raman spectra. The material was almost completely amorphous after irradiated to 10 dpa while recrystallization occurred under 115 dpa. All results mentioned above contribute to the decline of hardness and Young’s modulus and may explain why the micromechanical degradation was more significant under 10 dpa.     

Investigation of improved dielectric and thermal properties of ternary nanocomposite PMMA/MXene/ZnO fabricated by in-situ bulk polymerization

Electric power system applications demand for high-temperature dielectric materials. The improved performance of polymer nanocomposites requires improvement in their thermal conductivity & stability, dielectric stability and processing technique. However, they often lose their dielectric properties with a rise in temperature. Here, we offer a solution by incorporating electrically conducting material (MXene) and semiconducting inorganic nanoparticles (ZnO NPs) into an insulating PMMA polymer matrix to maintain high dielectric constant, both at the room and high temperature. Therefore, to achieve desirable thermal and dielectric properties is the main objective of the present study based on the homogeneous distribution of the nanofillers by in-situ bulk polymerization assisted by strong sonication in the corresponding polymer. The introduction of MXene and ZnO NPs into the PMMA not only acquires a substantial increment in the dielectric constant, to attain a value 437, with minimum energy loss of 0.36 at 25 Hz, but also improves the thermal conductivity of PMMA up to 14 times by causing the reduction of thermal resistance, which is actually responsible for the poor thermal conductivity of amorphous pure PMMA polymer. More importantly, hybrid PMMA/4:2 wt% MXene:ZnO nanocomposite leads to an excellent thermal stability. Moreover, further characterization of the synthesized nanocomposites by FTIR, SEM and XRD leads to the evaluation of strong interaction of ternary components with PMMA matrix.     

Polytetrafluoroethylene-intercalated MXene membranes with good photothermal performance for enhanced laser ignition

Photothermal effect has been widely used in many areas such as cancer therapy, photothermal energy harvesting, and laser ignition. However, exploring reliable and efficient free-standing energy converter for enhancing the photothermal performance is still a challenge. Herein, free-standing membrane based on two-dimensional MXene (Ti₃C₂) nanosheets and polytetrafluoroethylene (PTFE) was fabricated and characterized by X-ray diffraction, scanning electron microscopy and differential scanning calorimetry, which demonstrated a drastic temperature rise by laser irradiation and was further used as energy converter for enhancing the photothermal performance of laser ignition. Furthermore, the initiating power of the laser initiator can be largely reduced by adding a thin layer of MXene/PTFE membrane above the B/KNO₃ cylinder. This work can give great promise for MXene-based membranes as the laser energy converter for reducing the initiating energy and promote the development of laser initiators with low initiating energy.     

Evaluation of the moulding process for production of short-fibre-reinforced C/C-SiC composites

For the production of C/C-SiC brake discs via the liquid silicon infiltration method (LSI), the hot pressing process is the state of art technique for the moulding of the CFRP composites. This technique consists of several manual steps which increase production cost. The overall cost can be reduced by implementing injection moulding process.In this paper the influence of the moulding process (hot pressing, injection moulding) on the properties of semi-finished and final products during the production of short-fibre-reinforced C/C-SiC composites by means of the LSI process are examined. The starting polymer is chemically characterised. Carbon-fibre-reinforced plastic (CFRP) composites are fabricated by hot pressing, as well as injection moulding process. The CFRP composites are converted into porous C/C composites by pyrolysis. Liquid silicon is infiltrated to form dense C/C-SiC composites, which are further investigated during the course of this paper. Significant differences in properties of the composites are discussed.     

匹配机械弹性车轮的电子稳定控制器参数分析

为了提高匹配机械弹性车轮(MEW)的某越野车操纵稳定性，考虑MEW与传统子午线轮胎侧偏特性存在的不确定性摄动，基于Lyapunov稳定性理论为电子稳定控制(ESC)程序设计了鲁棒反馈控制器；引入轮胎侧偏刚度不确定性的范数有界模型，运用Schur补引理和线性矩阵不等式(LMI)求解反馈矩阵。设定不同的车速和路面附着系数，通过搭建CarSim/Simulink联合仿真平台对控制器展开鱼钩试验，仿真结果表明，匹配MEW的ESC控制器能够保证车辆行驶的稳定性，横摆角速度与质心侧偏角跟踪误差分别稳定在0.03~0.3 rad/s与0.06~0.1 rad之内，并且设计的控制算法对MEW在05倍普通充气车轮侧偏刚度变化范围内具有很好的鲁棒性，从而为匹配MEW的整车主动安全控制提供了理论参考。     

钛合金表面多磁极耦合旋转磁场光整加工特性

面向激光增材制造钛合金表面的光整加工需求，设计出一种多磁极耦合旋转磁场光整加工装置来研究光整加工特性。基于ANSYS Maxwell仿真软件分析了光整加工装置的磁场强度分布。搭建了实验光整平台，分析了主轴转速、C轴转速和加工间隙对表面质量的影响。结果表明，在主轴转速500 r/min、C轴转速160 r/min和加工间隙0.7 mm的加工条件下，表面粗糙度Ra由5.991 μm下降至0793 μm。扫描电子显微镜(SEM)观测表明，光整后的钛合金表面沉积层消失，表面质量得到显著改善。     

改性氧化钛对羟乙基乙二胺水溶液解吸CO2的强化

羟乙基乙二胺（AEE）水溶液的CO₂循环吸收量高（1.2molCO₂/molAEE），吸收速度快，稳定性好，但解吸速度慢、解吸量少（0.8mol CO₂/mol AEE）是限制该技术广泛应用的主要原因。本文通过向AEE水溶液中添加质量分数为0.05%～0.20%的改性氧化钛（TiO₂-MWCNT和TiO₂-OH）强化AEE的解吸能力。CO₂循环吸收（40℃）-解吸（120℃）实验结果表明改性氧化钛的添加比氧化钛强化CO₂解吸效果更好，强化顺序为TiO₂-MWCNT＞TiO₂-OH；其对应的最大解吸速率分别为0.093L/min（质量分数0.15%）和0.083L/min（质量分数0.20%），相对于AEE水溶液，分别提高了32.9%和18.6%；其对应的最大解吸量分别为0.92molCO₂/molAEE（质量分数0.15%）和0.88molCO₂/molAEE（质量分数0.20%），分别提高了12.2%和9.7%；其对应的CO₂循环吸收量分别是0.95molCO₂/molAEE（质量分数0.15%）和0.89molCO₂/molAEE（质量分数0.15%），分别提高了18.75%和11.25%；5次循环吸收解吸实验结果表明改性氧化钛强化CO₂解吸效果稳定，具有较强的化学稳定性。对反应后的改性氧化钛进行XRD、BET、FTIR和SEM表征，结果表明改性氧化钛具有较强的结构稳定性。TiO₂-MWCNT和TiO₂-OH在促进有机胺溶液解吸CO₂方面具有一定的工业应用潜力。