配置柔顺机构空间机器人双臂捕获卫星操作力学模拟及基于神经网络的全阶滑模避撞柔顺控制

讨论了空间机器人双臂捕获卫星操作过程避免关节冲击破坏的避撞柔顺控制问题. 为此在关节电机与机械臂之间设计了一种旋转 型串联弹性执行器(rotatory series elastic actuator, RSEA)--柔顺机构,其作用在于:(1) 通过其内置弹簧的拉伸或压缩变形来吸收捕获操作过程中被捕获卫星对空间机器人关节产生的冲击能量;(2) 可以利用合理设计的与之配合的避撞柔顺控制策略来保证关节冲击力矩受限在安全范围. 首先,利用第二类Lagrange方程分别建 立了捕获操作前含柔顺机构双臂空间机器人的开环分系统动力学模型与目标卫星的分系统动力学模型;之后,基于系统动量 守恒关系、闭链系统位置与速度几何约束关系,获得了捕获操作后空间机器人与被捕获卫星闭链混合体系统综合动力学方程; 最后,基于RBF神经网络提出了一种捕获操作后两者混合体系统镇定运动的全阶终端滑模避撞柔顺控制方案. 所提方案结合柔 顺机构在有效吸收、缓冲被捕获卫星冲击能量的同时,还在冲击能量过大时适时开、关空间机器人关节驱动器,以避免关节驱 动器过载、破坏;此外,还通过最小权值范数法分配了机械臂各关节力矩,以保证双臂协调操作. Lyapunov稳定性理论证明了 系统的全局稳定性,系统计算机数值仿真也验证了上述避撞柔顺控制策略的有效性.      

Transverse Vibrations of Buried Pipelines Under Axial Loading Within Geometrically Nonlinear Theory

International Applied Mechanics - The transverse motions of an underground pipeline located in water-saturated fine-grained soil are studied using the developed models of interaction in the...     

Surface modification by deposition of IPA plasma and gellan gum/chitosan hybrid hydrogel onto thermoplastic polyurethane for controlled release of N‐acetylcysteine

A thin film system composed of gellan gum and chitosan was fabricated through a combination of polyelectrolyte blend and hybrid hydrogel gelation for controlled release of drug. In this study, precursor isopropyl alcohol (IPA) was used to plasma deposit on the surface of thermoplastic polyurethane (TPU) to form a hydrophilic film. The features of the thin film were evaluated using water contact angle (WCA) measurement, scanning electron microscopy (SEM), Fourier transform infra‐red (FTIR), UV/Vis spectroscopy, and studies of controlled release of drugs. The hybrid hydrogel, pH‐sensitive, was tested at pH values of 1.2 and 7.4 of buffer solution and at a temperature of 37°C to observe its swelling ratio and drug delivery properties with N‐acetylcysteine as a drug material for controlled release. Furthermore, at pH 7.4, the hybrid hydrogel has an outstanding release ratio of up to about 90% absorption amounts of N‐acetylcysteine after 8 hr. The mechanism of drug release from thin film devices (n = 0.684) is anomalous (non‐Fickian) transport, the value of n lies between 0.43 and 0.85.     

AUTOMATIC IDENTIFICATION OF MESOSCOPIC PARAMETERS OF DISCRETE ELEMENTS OF SAND MATERIAL 1)

本文依照四川大学某理论力学教学班实际教学改革的经验,通过具体举例说明计算机技术在理论力学教学中尚未开发的巨大潜力,减小数学运算使学生重点关注理论力学基本原理,批量求解使学生提前接触实际应用案例,普适性求解使学生深化对处理多变量问题的认识。同时本文还探讨了理论力学教学改革的方向和目的,即把教学重点放在普适的教学方法上,借助计算机求解多刚体、多变量问题,以期有助于理论力学教材更好地适应时代发展。     

Synthesis and investigation of surface active properties of green glucosyl esters

We here reported on the regioselective biosynthesis of green glucosyl monoesters surfactants which were confirmed by chemical analysis methods using immobilized enzyme catalysis with N-fatty acyl amino acid and D-glucose as substrate. Lipozyme 435 was the most efficient lipase to catalyze the transesterification reaction in t-butanol at 50?°C. The target compounds showed good surface properties. The CMC values of glucosyl esters 15-22 were 4.97, 3.96, 1.87, 0.48?mmol/L, and 4.70, 3.53, 1.58 and 0.42?mmol/L at 25?°C, respectively. It was noteworthy that the micellization physiochemical parameters were calculated and the micellization was exothermic process. Meanwhile, it was entropy driven in the formation of micelles related to the structure of glucosyl esters at different temperature.     

On the Turán Density of Uniform Hypergraphs

Acta Mathematicae Applicatae Sinica, English Series - Let p, q be two positive integers. The 3-graph F(p, q) is obtained from the complete 3-graph K 3 by adding q new vertices and $$p(_2^q)$$ new...     

Cleavable bimetallic-organic polymers for ROS mediated cascaded cancer therapy under the guidance of MRI through tumor hypoxia relief strategy

Despite recent advances in tumor treatment, reactive oxygen species(ROS)-mediated therapy, such as photodynamic therapy(PDT) and chemical dynamic therapy(CDT), remains challenging mainly due to hypoxia in tumor microenviroment. Relieving the hypoxia of tumor tissue has been considered as an attractive strategy for enhancing efficacy of ROS-based cancer treatment.Herein, one cascaded platform was developed to overcome tumor hypoxia and synergistically enhance the effect of ROSmediated therapy. This platform is based on cleavable bimetallic metal organic polymers(DOX@Fe/Mn-THPPTK-PEG). As an efficient Fenton-like material, it could not only produce cytotoxic ·OH by catalyzing the decomposition of intracellular H_2O_2, but also generate O_2 to alleviate tumor hypoxia. In addition, the DOX-loaded metal organic polymers(MOPs could be disrupted after being exposed to laser irradiation or/and treated with H_2O_2, and then release the DOX for chemotherapy. Overall, 3 therapies(hypoxia-relieved PDT, photo-enhanced CDT, and ROS-mediated chemotherapy) could be achieved simultaneously by such a smart platform. Furthermore, T_1-weighted MRI imaging ability of the MOPs could be greatly improved under H_2O_2 treatment.Therefore, total four robust functions were realized in a simple platform. These findings demonstrate great clinical potentials of the MOPs for cancer theranostics.     

Difference of Mutant Knot Invariants and Their Differential Expansion

JETP Letters - We evaluate the differences of HOMFLY-PT invariants for pairs of mutant knots colored with representations of SL(N), which are large enough to distinguish between them. These mutant...