Design and Analysis of a Novel Shoulder Exoskeleton Based on a Parallel Mechanism

Power-assisted upper-limb exoskeletons are primarily used to improve the handling efficiency and load capacity.However,kinematic mismatch between the kinematics and biological joints is a major problem in most existing exoskeletons,because it reduces the boosting effect and causes pain and long-term joint damage in humans.In this study,a shoulder augmentation exoskeleton was designed based on a parallel mechanism that solves the shoulder dislocation problem using the upper arm as a passive limb.Consequently,the human–machine synergy and wearability of the exoskeleton system were improved without increasing the volume and weight of the system.A parallel mechanism was used as the structural body of the shoulder joint exoskeleton,and its workspace,dexterity,and stiffness were analyzed.Additionally,an ergonomic model was developed using the principle of virtual work,and a case analysis was performed considering the lifting of heavy objects.The results show that the upper arm reduces the driving force requirement in coordinated motion,enhances the load capacity of the system,and achieves excellent assistance.

General Kinetostatic Modeling and Deformation Analysis of a Two-Module Rod-Driven Continuum Robot with Friction Considered

Continuum robots actuated by flexible rods have large potential applications,such as detection and operation tasks in confined environments,since the push and pull actuation of flexible rods withstand tension and compressive force,and increase the structure's rigidity.In this paper,a generalized kinetostatics model for multi-module and multi-segment continuum robots considering the effect of friction based on the Cosserat rod theory is established.Then,the model is applied to a two-module rod-driven continuum robot with winding ropes to analyze its deformation and load characteristics.Four different in-plane configurations under the external load term as S1,S2,C1,and C2 are defined.Taking a bending plane as an example,the tip deformation along thex-axis of these shapes is simulated and compared,which shows that the load capacity of C1 and C2 is generally larger than that of S1 and S2.Furthermore,the deformation experiments and simulations show that the maximum error ratio without external loads relative to the total length is no more than 3%,and it is no more than 4.7%under the external load.The established kinetostatics model is proven sufficient to accurately analyze the rod-driven continuum robot with the consideration of internal friction.

HIF-1α对K562细胞血管生成相关因子的影响

目的:通过在K562细胞过表达和干扰HIF-1α后检测K562细胞分泌血管生成相关因子的水平,探讨慢性白血病血管生成的机制。方法:应用携带和干扰HIF-1α基因的慢病毒转染K562细胞,将转染携带和干扰HIF-1α基因的K562细胞分别纳入过表达组、干扰组,同时以空载病毒转染K562细胞纳入对照组。3组细胞在常氧状态下培养72 h后收集细胞,通过荧光显微镜观察3组转染效率,采用RT-PCR法检测HIF-1α和血管相关生成因子mRNA表达水平,ELISA法检测培养上清中血管相关细胞因子的浓度。结果:慢病毒转染K562细胞最佳转染复数(MOI)为10,转染效率为50%左右;经过嘌呤霉筛选后转染阳性细胞达90%以上。干扰组ANG-I、ANG-II、TGF-α和VEGF mRNA表达均低于过表达组,而干扰组TGF-β1 mRNA表达高于过表达组。干扰组ANG-I、VEGF mRNA表达低于对照组;培养上清中未检测到TGF-α,干扰组ANG-I和TNF-α水平低于过表达组,而干扰组VEGF水平高于过表达组;过表达组和干扰组TGF-β1水平均低于对照组,过表达组VEGF水平低于对照组,干扰组VEGF水平高于过表达组和对照组,上述差异具有统计学意义(P<0.05)。结论:通过嘌呤霉素筛选获得慢病毒转染K562细胞阳性细胞,HIF-1αmRNA正向调控K562细胞ANG-1、ANG-2、TGF-α、VEGF mRNA的表达,促进ANG-I和TNF-α自身分泌的能力,而不刺激TGF-α的自分泌,HIF-1α上调可抑制K562细胞TGF-β1的表达并抑制TGF-β的自分泌。

书籍装订中基于相位相关性的自适应梯标检测方法

目的针对传统人工检查书籍配帖是否合格的方法带来的劳动强度过大,且容易出错等问题,提出一种基于相位相关性的自适应梯标检测方法。方法通过相位相关配准技术,利用CCD摄像机采集到梯标视频帧,计算其与模板梯标的相位相关性,并进行2帧图像的配准,然后对2帧图像的帧差进行分析,从而判断配帖是否出错。结果实验结果显示,文中提出的方法可以减少合格配帖的误检率,还可以对不合格的配帖进行检测。结论文中所提出的方法可以提高配帖梯标检测的鲁棒性。

中澳职业技术教育对比研究与启示

借鉴澳大利亚职业教育的成功经验,从"制度、教学、评价"三方面对比分析了中澳职业教育的差异,阐述了各自的特点,从中探索适合中国职业教育改革的新思路。

多跳协同中继网络的安全性评估与仿真

为适应5G通信的发展与现实通信系统的需求,假设一个更为通用的多跳协同无线通信网络场景,并分析了在该场景下的系统安全容量,得出该指标的积分解析解。同时,通过基于蒙特卡洛算法的计算机数值仿真实验,安全容量的积分解析解的正确性得到验证。最后,通过对数值仿真的观察与讨论,可以得到一系列关于多跳协同中继无线通信网络的安全性能的结论。

Comparative analysis of twenty-five compounds in different parts of Astragalus membranaceus var.mongholicus and Astragalus membranaceus by UPLC-MS/MS

As a traditional Chinese medicine,the root of Astragalus membranaceus var.mongholicus(AMM)or A.membranaceus(AM)has been widely used in China and other Asian countries for thousands of years.Till now,the flavonoids,phenolic acids and saponins are considered as the main active components contributing to their therapeutic effect in these plants.In order to clarify the distribution and contents of these compounds in different organs of these plants,a rapid and sensitive analytical method for simultaneous determination of 25 active compounds including seven types(i.e.dihydroflavones,isoflavane,isoflavones,flavones,pterocarpans,phenolic acid and saponins)within 10 min was established using ultra-pressure liquid chromatography coupled with tandem mass spectrometry(UPLCeMS/MS).Then,the established method was fully validated and successfully applied to the determination of the contents of these analytes in different parts(root,rhizome,stem,leaf and flower)of AMM and AM.The results indicated that the contents of the same type of compounds in two different species plants were significantly different.Moreover,the obvious differences were also found for the distribution and contents of different type of compounds in five organs of the same species.The present study could provide necessary information for the rational development and utilization of AMM and AM resource.

Design of a Passive Gait‑based Ankle‑foot Exoskeleton with Self‑adaptive Capability

Propulsion during push-off is the key to realizing human locomotion.Humans have evolved a way of walking with high energy utilization,but it can be further improved.Drawing inspiration from the muscle-tendon unit,a passive spring-actuated ankle-foot exoskeleton is designed to assist with human walking and to lengthen walking duration by mechanically enhancing walking efficiency.Detection of the gait events is realized using a smart clutch,which is designed to detect the contact states between the shoe sole and the ground,and automatically switch its working state.The engagement of a suspended spring behind the human calf muscles is hence controlled and is in synchrony with gait.The device is completely passive and contains no external power source.Energy is stored and returned passively using the clutch.In our walking trials,the soleus electromyography activity is reduced by as much as 72.2%when the proposed ankle-foot exoskeleton is worn on the human body.The influence of the exoskeleton on walking habits is also studied.The results show the potential use of the exoskeleton in humans’daily life.

Design of Self‑Reconfigurable Multiarm Robot Mechanism Based on Deployable Kinematic Chains

As the structures of multiarm robots are serially arranged,the packaging and transportation of these robots are often inconvenient.The ability of these robots to operate objects must also be improved.Addressing this issue,this paper presents a type of multiarm robot that can be adequately folded into a designed area.The robot can achieve different operation modes by combining different arms and objects.First,deployable kinematic chains(DKCs)are designed,which can be folded into a designated area and be used as an arm structure in the multiarm robot mechanism.The strategy of a platform for storing DKCs is proposed.Based on the restrictions in the storage area and the characteristics of parallel mechanisms,a class of DKCs,called base assembly library,is obtained.Subsequently,an assembly method for the synthesis of the multiarm robot mechanism is proposed,which can be formed by the connection of a multiarm robot mechanism with an operation object based on a parallel mechanism structure.The formed parallel mechanism can achieve a reconfigurable characteristic when different DKCs connect to the operation object.Using this method,two types of multiarm robot mechanisms with four DKCs that can switch operation modes to perform different tasks through autonomous combination and release operation is proposed.The obtained mechanisms have observable advantages when compared with the traditional mechanisms,including optimizing the occupied volume during transportation and using parallel mechanism theory to analyze the switching of operation modes.

Dynamic Analysis and Performance Verification of a Novel Hip Prosthetic Mechanism

To assist an amputee in regaining his or her daily quality of life,based on analysis of the motion characteristics of the human hip,a 2-UPR/URR parallel mechanism with a passive limb was designed.The inverse kinematics of this mechanism was analyzed based on a closed-loop vector method.The constrained Jacobian matrix and kinematic Jacobian matrix of each limb were then analyzed,and a 6×6 fully Jacobian matrix was constructed.Based on this,kinematic performances were analyzed and summarized.Finally,the dynamic model of the mechanism was constructed based on the virtual work principle,and its theoretical solution was compared with the numerical results,which were obtained in a simulation environment.Results showed that the prosthetic mechanism had a larger rotating workspace and better mechanical performance,which accorded a range of motion and bearing capacity similar to that of the human hip in multiple gait modes.Moreover,the validity of the dynamic model and inverse kinematics were verified by comparing the theoretical and simulation results.Furthermore,with flexion and extension,the torque change in the hip prosthetic mechanism was similar to that of the human hip,which demonstrated the feasibility of the hip prosthetic mechanism and its good dynamic performance.

Structural Synthesis of Parallel Mechanisms with High Rotational Capability

Most parallel mechanisms(PMs) encountered today have a common disadvantage, i.e., their low rotational capability.In order to develop PMs with high rotational capability, a family of novel manipulators with one or two dimensional rotations is proposed. The planar one-rotational one-translational(1 R1 T) and one-rotational two-translational(1 R2 T)PMs evolved from the crank-and-rocker mechanism(CRM) are presented by means of Lie group theory. A spatial 2 R1 T PM and a 2 R parallel moving platform with bifurcated large-angle rotations are proposed by orthogonal combination of the RRRR limbs. According to the product principle of the displacement group theory, a hybrid 2 R3 T mechanism in possession of bifurcated motion is obtained by connecting the 2 R parallel moving platform with a parallel part, which is constructed by four 3 T1 R kinematic chains. The presented manipulators possess high rotational capability. The proposed research enriches the family of spatial mechanisms and the construction method provides an instruction to design more complex mechanisms.

Kinematics Analysis and Singularity Avoidance of a Parallel Mechanism with Kinematic Redundancy

The kinematic redundancy is considered as a way to improve the performance of the parallel mechanism.In this paper,the kinematics performance of a three degree-of-freedom parallel mechanism with kinematic redundancy(3-DOF PM-KR)and the influence of redundant parts on the PM-KR are analyzed.Firstly,the kinematics model of the PM-KR is established.The inverse solutions,the Jacobian matrix,and the workspace of the PM-KR are solved.Secondly,the influence of redundancy on the PM-KR is analyzed.Since there exists kinematic redundancy,the PM-KR possesses fault-tolerant performance.By locking one actuating joint or two actuating joints simultaneously,the fault-tolerant workspace is obtained.When the position of the redundant part is changed,the workspace and singularity will be changed.The results show that kinematic redundancy can be used to avoid singularity.Finally,the simulations are performed to prove the theoretical analysis.

Design of a novel side-mounted leg mechanism with high flexibility for a multi-mission quadruped earth rover BJTUBOT

Earth rover is a class of emerging wheeled-leg robots for nature exploration.At present,few methods for these robots’leg design utilize a side-mounted spatial parallel mechanism.Thus,this paper presents a complete design process of a novel 5-degree-of-freedom(5-DOF)hybrid leg mechanism for our quadruped earth rover BJTUBOT.First,a general approach is proposed for constructing the novel leg mechanism.Subsequently,by evaluating the basic locomotion task(LT)of the rover based on screw theory,we determine the desired motion characteristic of the sidemounted leg and carry out its two feasible configurations.With regard to the synthesis method of the parallel mechanism,a family of concise hybrid leg mechanisms using the 6-DOF limbs and an L1F1C limb(which can provide a constraint force and a couple)is designed.In verifying the motion characteristics of this kind of leg,we select a typical(3-UPRU&RRRR)&R mechanism and then analyze its kinematic model,singularities,velocity mapping,workspace,dexterity,statics,and kinetostatic performance.Furthermore,the virtual quadruped rover equipped with this innovative leg mechanism is built.Various basic and specific LTs of the rover are demonstrated by simulation,which indicates that the flexibility of the legs can help the rover achieve multitasking.

Effect of Fe content on type and distribution of carbides in medium-entropy high-speed steels

The effect of iron content on the type and distribution of carbides in the vacuum arc melted Fex(AlCoCrCuNiV)_(88.05-x)Mo_(5)W_(6)-C_(0.95)(x=69,76,83 wt%,respectively) medium-entropy high-speed steels(ME-HSSs) was studied.The homogeneous distribution of granular MC carbides(M refers to the carbides forming transition metal elements,such as W,Mo and V),both at the grain boundary and in the martensitic matrix,was obtained in the Fe_(76)(AlCoCrCuNiV)_(12.05)Mo_(5)W_(6)-C_(0.95)ME-HSS,after quenching at 1210 ℃ followed by triple tempering at 530 ℃.A maximum hardness of about 841 HV_(0.5) was achieved,even higher than the maximum hardness of the commercially available M_(2)(W_(6)Mo_(5)Cr_(4)V_(2)) HSS,826 HV_(0.5).The medium-entropy effect was shown to be beneficial to transform the solidified primary carbide network into finely dispersed granular MC.However,when the iron content was further reduced to 69 wt%,the enhanced entropy effect promoted the dispersion of carbides but at the same time led to a decrease in the carbide content,so that the maximum hardness(816 HV_(0.5)) was slightly lower than the maximum hardness of M2-HSS.The results provide a novel alloy system together with a simple heat treatment method to obtain hard HSSs,and more importantly to eliminate the primary carbide network which is harmful to the toughness of traditional HSS.

Enhanced photocatalytic degradation of organic contaminants over CaFe_(2)O_(4) under visible LED light irradiation mediated by peroxymonosulfate

A simple sol-gel approach is proposed herein to fabricate CaFe_(2)O_(4)for the degradation of various organic pollutants(rhodamine B(RhB),tetracycline hydrochloride,humic acid,and methylene orange)under LED light irradiation mediated by peroxymonosulfate(PMS).The results indicate that the calcination temperature can significantly influence the performance of CaFe_(2)O_(4)for PMS activation,and the CaFe_(2)O_(4)sample obtained at 800℃(CaFe_(2)O_(4)-800)exhibits the best efficiency in degrading RhB,which is much higher than that of Fe_2o_(3)-800.This can be attributed to the efficient separation of photogenerated electrons(e^(-))and holes(h^(+))by PMS,which is validated by transient photocurrent response and photoluminescence measurements.Results from density functio nal theo ry calculations indicate that the valence band of CaFe_(2)O_(4)-800 exhibits a high concentration of carriers and weak localization of electrons,which are favorable for PMS activation.Radical scavenging results confirm that h^(+)and O_(2)^(·-)are the dominant reactive species.Moreover,CaFe_(2)O_(4)-800 not only demonstrated a stable performance during eight cycling runs with negligible iron leaching but also exhibited excellent degradation efficiency under natural water and sunlight.Finally,the mechanism and pathway of RhB degradation by the CaFe_(2)O_(4)-800/PMS/LED system are also proposed.This work presents the enormous prospect of CaFe_(2)O_(4)as an environmentally benign photocatalyst for PMS activation.

Studies on morphology, electrical and optical characteristics of Al-doped ZnO thin films grown by atomic layer deposition

Al doped ZnO(AZO) films deposited on glass substrates through the atomic layer deposition(ALD)technique are investigated with various temperatures from 100 to 250 °C and different Zn : Al cycle ratios from20 : 0 to 20 : 3. Surface morphology, structure, optical and electrical properties of obtained AZO films are studied in detail. The Al composition of the AZO films is varied by controlling the ratio of Zn : Al. We achieve an excellent AZO thin film with a resistivity of 2.14 × 10^(-3)Ω·cm and high optical transmittance deposited at 150 °C with20 : 2 Zn : Al cycle ratio. This kind of AZO thin films exhibit great potential for optoelectronics device application.

Electrostatic self-assembly of 2D/2D CoWO_(4)/g-C_(3)N_(4)p-n heterojunction for improved photocatalytic hydrogen evolution:Built-in electric field modulated charge separation and mechanism unveiling

Two-dimensional(2D)semiconductor heterojunctions are considered as an effective strategy to achieve fast separation of photoinduced carriers.Herein,a novel CoWO_(4)/g-C_(3)N_(4)(CWO/CN)p–n junction was synthesized using an electrostatic selfassembly method.The constructed 2D/2D p–n heterostructure had a rich hetero-interface,increased charge density,and fast separation efficiency of photoinduced carriers.The in-situ Kelvin probe force microscopy confirmed that the separation pathway of photoinduced carriers through the interface obeyed an II-scheme charge transfer mechanism.Experimental results and density functional theory calculations indicated the differences of work function between CWO and CN induced the generation of built-in electric field,ensuring an efficient separation and transfer process of photoinduced carriers.Under the optimized conditions,the CWO/CN heterojunction displayed enhanced photocatalytic H_(2)generation activity under full spectrum and visible lights irradiation,respectively.Our study provides a novel approach to design 2D/2D hetero-structured photocatalysts based on p–n type semiconductor for photocatalytic H_(2)generation.

Synergetic effects of Bi^(5+)and oxygen vacancies in Bismuth(Ⅴ)-rich Bi_(4)O_(7)nanosheets for enhanced near-infrared light driven photocatalysis

The appropriate energy level position of photocatalysts dominates the photocatalytic redox reaction and utilization efficiency of solar energy for wastewater treatment.Herein,we report a near-infrared(NIR)light driven Bi^(5+)-rich Bi407 photocatalyst,achieving a greatly enhanced photocatalytic activity for pollutant removal compared with Bi3+-replenished Bi2O3.Density functional theory calculations show the formation of an intermediate band in the Bi_(4)O_(7)structure because of the hybridization of O 2p and Bi 4s orbits.The formation of the intermediate band not only narrows the band gap but also improves the optical absorption property and separation efficiency of the photoinduced carriers.The existence of the oxygen vacancies(OVs)in the Bi_(4)O_(7)nanosheets ensures high carriers’concentration,which is verified by the Hall effect test.The synergetic effects of the OVs and Bi^(5+)greatly accelerate the separation efficiency of the photogenerated carriers.Consequently,the Bi_(4)O_(7)nanosheets exhibit enhanced NIR light driven photocatalytic activity for the degradation of rhodamine B and ciprofloxacin compared with the bulk Bi2O3.This study paves the way to the design of highly efficient NIR light-responsive Bi-based photocatalysts for environmental purification.

Combustion synthesis of mesoporous CoAl_(2)O_(4)for peroxymonosulfate activation to degrade organic pollutants

A mesoporous cobalt aluminate(CoAl_(2)O_(4))spinel is synthesized through a combustion method and adopted for the activation of peroxymonosulfate(PMS)to degrade organic pollutants.Multiple characterization procedures are conducted to investigate the morphology and physicochemical properties of the CoAl_(2)O_(4)spinel.Due to its mesoporous structure,large surface area,and high electrical conductivity,the obtained CoAl_(2)O_(4)exhibits remarkable catalytic activity for Rhodamine B(RhB)degradation.Its RhB degradation rate is 89.0 and 10.5 times greater than those of Co_(3)O_(4) and CoAl_(2)O_(4)spinel prepared by a precipitation method,respectively.Moreover,the mesoporous CoAl_(2)O_(4)spinel demonstrates a broad operating pH range and excellent recyclability.The influence of several parameters(catalyst amount,PMS concentration,initial p H,and coexisting inorganic anions)on the oxidation of RhB is evaluated.Through quenching tests and electron paramagnetic resonance experiments,sulfate radicals are identified as the predominant reactive species in RhB degradation.This paper provides new insights for the development of efficient,stable,and reusable cobalt-based heterogeneous catalysts and promotes the application of persulfate activation technology for the treatment of refractory organic wastewater.

Annealing-induced Grain Refinement in a Nanostructured Ferritic Steel

A nanostructured surface layer with a mean ferrite grain size of ～8 nm was produced on a Fe-9Cr steel by means of surface mechanical attrition treatment. Upon annealing, ferrite grains coarsen with increasing temperature and their sizes increase to ～40 nm at 973 K. Further increasing annealing temperature leads to an obvious reduction of ferrite grain sizes, to ～14 nm at 1173 K. The annealing-induced grain refinement is analyzed in terms of phase transformations in the nanostructured steel.