关键词： Polymer gels   Ionic liquids   Network formation  

摘要： We report an ion gel with ultralow polymer content based on two key materials: 1 wt% tetra-arm poly(ethylene glycol) (TetraPEG) and 99 wt% ionic liquid (herein, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide, [C(2)mIm] [FSA]). We performed kinetics analysis on the TetraPEG network formation in [C(2)mIm] [FSA], i.e., AB-type cross-end coupling reaction of two different TetraPEGs with thiol (SH) and maleimide (MA) terminals (TetraPEG-SH and TetraPEG-MA). In neat [C(2)mIm] [FSA], no gelation occurred at room temperature, whereas the reaction successfully proceeded when 1-ethylimidazole (C(2)Im) was added in this reaction as a catalyst. The apparent reaction rate constant (k(gel)') was determined by varying C(2)Im concentration, and the network connectivity (p) was estimated to be p similar to 98% toward the end of the reaction. The results indicated that the TetraPEG prepolymers could be successfully gelled in [C(2)mIm] [FSA] despite extremely low polymer content (1 wt%), which allows us to prepare an ideally homogeneous polymer network gel with a large amount of ionic liquid. The ionic conductivity measurements demonstrated that the 1 wt% TetraPEG ion gel showed ideal liquid-like ion-conducing properties that were comparable to those of neat ionic liquid.

关键词： snake   locomotion   neuromechanics   biomechanics   collisions  

摘要： Limbless animals like snakes inhabit most terrestrial environments, generating thrust to overcome drag on the elongate body via contacts with heterogeneities. The complex body postures of some snakes and the unknown physics of most terrestrial materials frustrates understanding of strategies for effective locomotion. As a result, little is known about how limbless animals contend with unplanned obstacle contacts. We studied a desert snake, Chionactis occipitalis, which uses a stereotyped head-to-tail traveling wave to move quickly on homogeneous sand. In laboratory experiments, we challenged snakes to move across a uniform substrate and through a regular array of force-sensitive posts. The snakes were reoriented by the array in a manner reminiscent of the matter-wave diffraction of subatomic particles. Force patterns indicated the animals did not change their self-deformation pattern to avoid or grab the posts. A model using open-loop control incorporating previously described snake muscle activation patterns and body-buckling dynamics reproduced the observed patterns, suggesting a similar control strategy may be used by the animals. Our results reveal how passive dynamics can benefit limbless locomotors by allowing robust transit in heterogeneous environments with minimal sensing.

关键词： Kinetic parameters   Oxidation   Vinyl   Cations   Extrusion  

摘要： This work presents ferrate(VI) ((FeO42-)-O-VI, Fe-VI) oxidation of a wide range of sulfonamide antibiotics (SAs) containing five- and six-membered heterocyclic moieties (R) in their molecular structures. Kinetics measurements of the reactions between Fe-VI and SAs at different pH (6.5-10.0) give species specific second-order rate constants, k(5) and k(6) of the reactions of protonated Fe-VI (HFeO4-) and unprotonated Fe-VI ((FeO42-)-O-VI) with protonated SAs (FIX), respectively. The values of k5 varied from (1.2 +/- 0.1) x 10(3) to (2.2 +/- 0.2) x 10(4) M-1 s(-1) while the range of k(6) was from (1.1 +/- 0.1) x 10(2) to (1.0 +/- 0.1) x 10(3) M-1 s(-1) for different SAs. The transformation products of reaction between Fe-VI and sulfadiazine (SDZ, contains a six-membered R) include SO2 extrusion oxidized products (OPs) and aniline hydroxylated products. Comparatively, oxidation of sulfisoxazole (SIZ, a five-membered R) by Fe-VI has OPs that have no SO2 extrusion in their structures. Density functional theory calculations are performed to demonstrate SO2 extrusion in oxidation of SDZ by Fe-VI. The detailed mechanisms of oxidation are proposed to describe the differences in the oxidation of six- and five-membered heterocyclic moieties (R) containing SAs (i.e., SDZ versus SIZ) by Fe-VI.

关键词： Inverse problem   Force reconstruction   Augmented Kalman Filter   Structural dynamics  

摘要： Kalman-type filtering tends to become one of the favorite approaches for solving joint input-state estimation problems in the structural dynamics community. This article focuses on the applicability of the Augmented Kalman Filter (AKF) for reconstructing mechanical sources, addressing a set of practical issues that are frequently encountered in the engineering practice. In particular, this paper aims to help the reader to better apprehend some of the advantages and limitations of the application of the AKF in the context of purely input estimation problems. The present paper is not a simple collection of test cases, since it introduces a novel state-space representation of dynamical systems, based on the generalized-a method, as well as further insights in the tuning of Kalman filters from the Bayesian perspective. In this work, the various practical situations considered lead us to recommend to employ collocated acceleration measurements, when reconstructing excitation sources from the AKF. It is also demonstrated that the violation of some of the feasibility conditions proposed in the literature doesn't necessarily imply the failure of the estimation process. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： 室间隔缺损   机械通气   脑血流速度   血流动力学  

摘要： 目的分析婴儿室间隔缺损术中,不同机械通气下,脑血流动力学与体循环血流动力学的变化及其关系。方法择期行室间隔缺损修补术婴儿83例,随机分为传统组(T组,34例)和调控组(C组,49例)。诱导插管后维持T组呼气末二氧化碳分压(PetCO2)于30～35 mmHg,C组40～45 mmHg。应用血流动力学监测仪(Mostcare)监测体循环,应用经颅多普勒超声(TCD)监测脑循环,于麻醉诱导后(T1)、开心包(T2)、体外循环结束(T3)、改良超滤结束(T4)、术毕(T5)分别记录右侧大脑中动脉脑血流速度(CBFV)及搏动指数(PI)、阻力指数(RI)并记录收缩压(Psys)、舒张压(Pdia)、重脉压(Pdic)、心率(HR)、心指数(CI)、全身血管阻力指数(SVRI)、脉压变异度(PPV)、心脏循环效率(CCE)和最大压力梯度(dp/dt)。根据潮气量(Vt/kg)和呼吸频率(F),计算每分钟通气量(Mv/kg)。结果组间比较,除T3点外,C组脑血流速度平均值(Vmean)明显高于传统组(P <0.05)。组内比较,两组患儿CBFV、Psys、Pdia、Pdic、CI在T3点明显低于其他各点,PI、RI、SVRI、PPV在T3点明显高于其他各点(P <0.05)。结论在婴儿室间隔缺损修补术中,与体循环血流动力学相比,机械通气的变化对脑血流速度的影响更为明显,调控组脑血流动力学优于传统组。

关键词： 计量   气动肌肉   动力学建模   膝关节   四连杆   力矩控制  

摘要： 目的:为实现气动肌肉机械腿关节角度跟踪,设计两自由度气动肌肉机械腿。方法:对拮抗气动肌肉到关节传动问题,建立关节驱动机构模型;主要分析四连杆膝关节力矩静态特性,设计膝关节力矩到气动肌肉拉力的映射关系。机械腿摆动采用双闭环控制策略,外环为位置PD控制,在控制输出中加上机械腿动力学计算力矩项;内环为气动肌肉拉力控制,设计拉力前馈控制器和误差补偿控制器。结果:进行机械腿摆动控制仿真和实验,关节角度跟踪误差在±3°以内。结论:结果表明关节建模有效,动力学控制可实现机械腿关节角度跟踪。

关键词： Polymer-matrix composites (PMCs)   Wear   Mechanical properties   Interface/interphase  

摘要： This paper reviews the application of molecular dynamics simulations on mechanical and tribological properties of polymer composites reinforced by carbon nanotubes and graphene sheet as reinforcements. A variety of simulation studies on modelling, calculation and analysis on enhanced elastic, tensile, fracture properties of carbon nanotubes and graphene sheet/polymer composites are introduced and reviewed. The capabilities of molecular dynamics simulations on exploring inherent mechanisms on improved tribological properties of carbon nanotubes and graphene sheet/polymer composites from atomic views are particularly discussed. Different methods of surface modifications of the two nano reinforcements on further enhancing the strength of polymer composites are summarized. Summary and recommendations for potential researches are also provided. This review is intended to provide a state-of-the-art and better understanding on applications of carbon nano tubes and graphene sheet for enhancing mechanical and tribological properties of polymer composites by molecular dynamics simulations, and inspire future efforts in this area.

关键词： 供电所   塞罕坝机械林场  

摘要： 2月4日,农历大年三十,国网冀北承德供电公司塞罕坝机械林场供电所所长袁辉和同事付文涛、董成苍,驱车来到塞罕坝林场最高点——海拔1940米的大光顶子望火楼,为林场火情监测员刘军、齐淑艳夫妇检查楼内的供电线路。每逢节假日,供电所员工都会到望火楼上门走访,了解用电需求。塞罕坝机械林场供电所坐落在河北围场县城最北部。

关键词： 轨行机械   传动系统   混合动力   节能减排  

摘要： 概述混合动力传动系统的分类,对比分析各种混合驱动方案的优势劣势,得出液力传动+电传动为混合动力传动系统的最优方案,对其系统组成及布置、动力传递方式进行详细的介绍。该方案中的液力传动系统利用柴油机为动力驱动,电传动系统利用蓄电池(或接触网)供电为动力驱动,2套传动系统相对独立。该方案在HDX型混合动力接触网检修作业车上成功应用表明,其在节能减排、互换性、传动效率、性价比及安全性方面有明显优势,尤其是在节能减排方面,与单一内燃动力传动系统相比,效果显著。

关键词： 软体机械臂   在轨服务   动力学建模   目标检测与识别   智能控制  

摘要： 空间智能软体机械臂因其结构轻巧、灵活可变、可折叠收缩等特性,在航天器在轨服务任务中,将具有广阔的应用前景。首先提出了一种全向驱动的模块化软体机械臂设计方案,利用刚柔耦合动力学理论建立了气控驱动的软体机械臂动力学模型,基于深度回归卷积神经网络理论建立了空间非合作目标检测与识别算法,为空间软体机械臂智能控制奠定了技术基础。进一步地,设计并研制了软体机械臂地面原理样机及其试验系统,通过地面试验,对软体机械臂的自主运动控制和识别算法进行了初步验证。