To simplify the complicated design process of deployable/retractable structures, a new design process is developed. The process is divided into three phases： the concept design phase, the model phase and the optimiza...To simplify the complicated design process of deployable/retractable structures, a new design process is developed. The process is divided into three phases： the concept design phase, the model phase and the optimization phase. In each phase, different parameter targets have to be fulfilled. According to three phases, a deployable/retractable mast composed of four right triangle prism modules in the longitudinal direction is designed. It can be deployed and folded simultaneously by the linear movements of sleeve-joints. The deployable and retractable movement of the mast is analyzed and key joint forms are designed. Then bar diameters and joint forms are modified based on mast structural mechanics characteristics in the optimization phase. Finally a 1：1 scaled model mast is built to verify the design and the optimization. Analytical results show that the model mast has the advantages of simple locking mechanism, fewer types of joints and bars, so it can be easily manufactured.展开更多
Deployable/retractable damped cantilever beams are a class of time-varying parametric structures which have attracted considerable research interest due to their many potential applications in the intelligent robot fi...Deployable/retractable damped cantilever beams are a class of time-varying parametric structures which have attracted considerable research interest due to their many potential applications in the intelligent robot field and aerospace.In the present work,the dynamic characteristics of a deployable/retractable damped cantilever beam are investigated experimentally and theoretically.The time-varying damping,as a function of the beam length,is obtained by both the enveloped fitting method and the period decrement method.Furthermore,the governing equation of the deployable/retractable damped cantilever beam is derived by introducing the time-varying damping parameter,and the corresponding closed-form solution and vibration principles are investigated based on the averaged method.The theoretical predictions for transient dynamic responses are in good agreement with the experimental results.The dynamic mechanism analysis on time-varying damping offers flexible technology in mechanical and aerospace fields.展开更多
Inflatable deployable structures inspired by origami have significant applications in space missions such as solar arrays and antennas.In this paper,a generalized Miura-ori tubular cell(GMTC)is presented as the basic ...Inflatable deployable structures inspired by origami have significant applications in space missions such as solar arrays and antennas.In this paper,a generalized Miura-ori tubular cell(GMTC)is presented as the basic cell to design a family of inflatable origami tubular structures with the targeted configuration.First,the classification of rigid foldable degree-4 vertices is studied thoroughly.Since the proposed GMTC is comprised of forming units(FU)and linking units(LU),types of FUs and LUs are investigated based on the classification of degree-4 vertices,respectively.The rigid foldability of the GMTC is presented by studying the kinematics of the FUs and LUs.Volume of the GMTC is analyzed to investigate multistable configurations of the basic cell.The variations in volume of the GMTC offer great potential for developing the inflatable tubular structure.Design method and parametric optimization of the tubular structure with targeted configuration are proposed.The feasibility of the approach is validated by the approximation of four different cases,namely parabolic,semicircular,trapezoidal,and straight-arc hybrid tubular structures.展开更多
The aim of this paper is to conduct experimental modal analysis and numerical simulation to verify the structural characteristics of a deployable-retractable wing for aircraft and spacecraft. A modal impact test was c...The aim of this paper is to conduct experimental modal analysis and numerical simulation to verify the structural characteristics of a deployable-retractable wing for aircraft and spacecraft. A modal impact test was conducted in order to determine the free vibration characteristics. Natural frequencies and vibration mode shapes were obtained via measurement in LMS Test. Lab. The frequency response functions were identified and computed by force and acceleration signals, and then mode shapes of this morphing wing structure were subsequently identified by PolyMAX modal parameter estimation method. FEM modal analysis was also implemented and its numerical results convincingly presented the mode shape and natural frequency characteristics were in good agreement with those obtained from experimental modal analysis. Experimental study in this paper focuses on the transverse response of morphing wing as its moveable part is deploying or retreating. Vibration response to different rotation speeds have been collected, managed and analyzed through the use of comparison methodology with each other. Evident phenomena have been discovered including the resonance on which most analysis is focused because of its potential use to generate large amplitude vibration of specific frequency or to avoid such resonant frequencies from a wide spectrum of response. Manufactured deployable-retractable wings are studied in stage of experimental modal analysis, in which some nonlinear vibration resulted should be particularly noted because such wing structure displays a low resonant frequency which is always optimal to be avoided for structural safety and stability.展开更多
Bistable Deployable Composite Boom(Bi-DCB)can achieve bistable function by storing and releasing strain energy,which has a good application prospect in space field.For example,it serves as the main support section of ...Bistable Deployable Composite Boom(Bi-DCB)can achieve bistable function by storing and releasing strain energy,which has a good application prospect in space field.For example,it serves as the main support section of deployable structures(e.g.,solar arrays and antennas).This paper investigates folding stable state of Bi-DCB through the analytical method.Based on Archimedes’helix and energy principle,an analytical model for predicting folding stable state of Bi-DCB was presented.The failure index of Bi-DCB in folding stable state were analyzed using the Tsai-Hill criterion and the maximum stress criterion.Then,a 2400 mm long Bi-DCB was fabricated using autoclave method.The prediction results of the proposed model were compared with experiments and results of two other analytical models.It is shown that the proposed model shows good prediction accuracy.Finally,the effect of geometric parameters on folding stable state of Bi-DCB was further investigated with the aid of the proposed model.展开更多
Mesh reflector antennas are widely used in space tasks owing to their light weight,high surface accuracy,and large folding ratio.They are stowed during launch and then fully deployed in orbit to form a mesh reflector ...Mesh reflector antennas are widely used in space tasks owing to their light weight,high surface accuracy,and large folding ratio.They are stowed during launch and then fully deployed in orbit to form a mesh reflector that transmits signals.Smooth deployment is essential for duty services;therefore,accurate and efficient dynamic modeling and analysis of the deployment process are essential.One major challenge is depicting time-varying resistance of the cable network and capturing the cable-truss coupling behavior during the deployment process.This paper proposes a general dynamic analysis methodology for cable-truss coupling.Considering the topological diversity and geometric nonlinearity,the cable network's equilibrium equation is derived,and an explicit expression of the time-varying tension of the boundary cables,which provides the main resistance in truss deployment,is obtained.The deployment dynamic model is established,which considers the coupling effect between the soft cables and deployable truss.The effects of the antenna's driving modes and parameters on the dynamic deployment performance were investigated.A scaled prototype was manufactured,and the deployment experiment was conducted to verify the accuracy of the proposed modeling method.The proposed methodology is suitable for general cable antennas with arbitrary topologies and parameters,providing theoretical guidance for the dynamic performance evaluation of antenna driving schemes.展开更多
With the rapid development of space science projects,large deployable mechanisms have been widely used.However,due to the effects of mechanical friction and gravitational acceleration,on-orbit mechanisms cannot be alw...With the rapid development of space science projects,large deployable mechanisms have been widely used.However,due to the effects of mechanical friction and gravitational acceleration,on-orbit mechanisms cannot be always deployed to the expected pose.For some precision optical mechanisms,even a minor deviation can result in significant error,so it needs to be measured and corrected.In this paper,the deployment process was modeled and simplified as rotation under single-rotation-axis constraint and translation under single-direction constraint.To solve the problem,a method based on cross-ratio invariability was proposed.The proposed method does not rely on camera calibration techniques,as well as artificial marking points,both of which are necessary in PnP.Instead,only three calibration images before launch and a measurement image on orbit were required.Simulations and experiments demonstrated that the proposed method is more accurate than PnP.In addition,experiments also proved that the feasibility of the proposed method under dark conditions with the aid of a light source and some reflective marking points.展开更多
Flasher origami pattern has been widely utilized to improve the stowage efficiency of deployable structures.Nevertheless,flasher origami cannot be folded fully flat,and they still have great potential for optimization...Flasher origami pattern has been widely utilized to improve the stowage efficiency of deployable structures.Nevertheless,flasher origami cannot be folded fully flat,and they still have great potential for optimization in terms of storage volume and folding creases.In this paper,a flat foldable equiangular spiral folding pattern inspired by the sunflower disk is introduced.Then,a parametric design method for this equiangular spiral crease diagram is introduced in detail.Subsequently,a kinematic model of the equiangular spiral folding pattern is established based on the kinematic equivalence between rigid origami and spherical linkages.A simulation of the developed model demonstrates that the equiangular spiral folding pattern can be folded flat.Using the folded ratio as an evaluation index,the calculated results and experiments show that the equiangular spiral crease pattern can yield fewer creases and improve stowage efficiency in comparison to flasher origami pattern.Equiangular spiral folding pattern can save a considerable amount of space and provide a new approach to spatially deployable structures.展开更多
1.Introduction Climate change mitigation pathways aimed at limiting global anthropogenic carbon dioxide(CO_(2))emissions while striving to constrain the global temperature increase to below 2℃—as outlined by the Int...1.Introduction Climate change mitigation pathways aimed at limiting global anthropogenic carbon dioxide(CO_(2))emissions while striving to constrain the global temperature increase to below 2℃—as outlined by the Intergovernmental Panel on Climate Change(IPCC)—consistently predict the widespread implementation of CO_(2)geological storage on a global scale.展开更多
Variable-diameter deployable carbon fiber reinforced polymer(CFRP)composites possess deformation and load-bearing functions and are composed of stiff-flexible coupled preforms and matrix.The stiff-flexible coupled pre...Variable-diameter deployable carbon fiber reinforced polymer(CFRP)composites possess deformation and load-bearing functions and are composed of stiff-flexible coupled preforms and matrix.The stiff-flexible coupled preform,serving as the reinforcing structure,directly determines the deployable properties,and its forming technology is currently a research challenge.This paper designs a braiding and needle-punching(BNP)composite preform forming technology suitable for stiff-flexible coupled preforms.Before forming,the preform is partitioned into flexible and rigid zones,with braiding and needle-punching performed layer by layer in the respective zones.A retractable rotating device is developed to form the stiff-flexible coupled preform,achieving a diameter variation rate of up to 26.6%for the BNP preform.A structural parameter model is also established to describe the geometric parameter changes in the deformation and load-bearing areas of the preform during deployment as a function of the braiding angle.Based on experiments,this paper explains the performance changes of BNP composites concerning the structural parameters of the preform.Experimental analysis shows that as the braiding angle increases,the tensile performance of BNP composites significantly decreases,with the change rate of tensile strength first decreasing and then increasing.Additionally,when the braiding angle is less than 21.89°,the impact toughness of BNP composites remains within the range of 83.66±2 kJ/m^(2).However,when the braiding angle exceeds 21.89°,the impact toughness of BNP composites gradually decreases with increasing braiding angle.Furthermore,a hybrid agent model based on Latin hypercube sampling and error back-propagation neural network is developed to predict the tensile and impact properties of BNP composites with different structural parameters,with maximum test relative errors of 1.89%for tensile strength and 2.37%for impact toughness.展开更多
The wireless signals emitted by base stations serve as a vital link connecting people in today’s society and have been occupying an increasingly important role in real life.The development of the Internet of Things(I...The wireless signals emitted by base stations serve as a vital link connecting people in today’s society and have been occupying an increasingly important role in real life.The development of the Internet of Things(IoT)relies on the support of base stations,which provide a solid foundation for achieving a more intelligent way of living.In a specific area,achieving higher signal coverage with fewer base stations has become an urgent problem.Therefore,this article focuses on the effective coverage area of base station signals and proposes a novel Evolutionary Particle Swarm Optimization(EPSO)algorithm based on collective prediction,referred to herein as ECPPSO.Introducing a new strategy called neighbor-based evolution prediction(NEP)addresses the issue of premature convergence often encountered by PSO.ECPPSO also employs a strengthening evolution(SE)strategy to enhance the algorithm’s global search capability and efficiency,ensuring enhanced robustness and a faster convergence speed when solving complex optimization problems.To better adapt to the actual communication needs of base stations,this article conducts simulation experiments by changing the number of base stations.The experimental results demonstrate thatunder the conditionof 50 ormore base stations,ECPPSOconsistently achieves the best coverage rate exceeding 95%,peaking at 99.4400%when the number of base stations reaches 80.These results validate the optimization capability of the ECPPSO algorithm,proving its feasibility and effectiveness.Further ablative experiments and comparisons with other algorithms highlight the advantages of ECPPSO.展开更多
Purpose:This study examines the impact of research policy changes on scientific retractions of publications authored by Romanian authors,focusing on national trends and the interplay between policy reforms and publish...Purpose:This study examines the impact of research policy changes on scientific retractions of publications authored by Romanian authors,focusing on national trends and the interplay between policy reforms and publishing practices.Design/methodology/approach:Using data from the Retraction Watch Database and Web of Science(WoS),188 unique retractions involving Romanian authors(2000-2022)were analyzed.The study compared retraction patterns before and after the 2016 reforms,which prioritized the publication of articles in WoS-indexed journals over non-WoS outputs.Findings:The analysis identified two key trends:(1)before the 2016 reforms,retractions predominantly involved non-WoS journals(99 non-WoS retractions to 38 WoS retractions),a trend that reversed post-reform(16 non-WoS to 35 WoS),and(2)while the total number of WoS-indexed retractions increased after the reforms,the retraction rates for WoS articles remained stable.Post-reform reliance on MDPI journals,which have low retraction rates,partially explains this stability.Excluding MDPI publications,retraction rates for articles and reviews increase by 14.91%,aligning with patterns seen elsewhere.Research limitations:The study focuses on retractions involving Romanian authors,limiting its generalizability.Furthermore,reliance on database records may not fully capture all retractions.Practical implications:These findings underscore the need for research policy reforms to consider a broader range of effects,and the need for nuanced interpretations of retraction data,which are influenced by a complex range of factors,including specific publisher practices.Originality/value:This research is the first to investigate the complex relationship between research policy reforms,publisher behavior,and retraction trends.展开更多
RETRACTION:P.Goyal and R.Malviya,“Challenges and Opportunities of Big Data Analytics in Healthcare,”Health Care Science 2,no.5(2023):328-338,https://doi.org/10.1002/hcs2.66.The above article,published online on 4 Oc...RETRACTION:P.Goyal and R.Malviya,“Challenges and Opportunities of Big Data Analytics in Healthcare,”Health Care Science 2,no.5(2023):328-338,https://doi.org/10.1002/hcs2.66.The above article,published online on 4 October 2023 in Wiley Online Library(wileyonlinelibrary.com),has been retracted by agreement between the journal Editor-in-Chief,Zongjiu Zhang;Tsinghua University Press;and John Wiley&Sons Ltd.展开更多
Traditionally,liver retraction for laparoscopic gastrectomy is done via manual methods,such as the placement of retractors through the accessory ports and using a Nathanson retractor.However,these techniques often pos...Traditionally,liver retraction for laparoscopic gastrectomy is done via manual methods,such as the placement of retractors through the accessory ports and using a Nathanson retractor.However,these techniques often posed issues including extra abdominal incisions,risk of liver injury or ischaemia,and the potential for compromised visualization.Over the years,the development of innovative liver retraction techniques has significantly improved the safety and efficacy of laparoscopic gastrectomy and similar other hiatal procedures.This editorial will comment on the article by Lin et al,and compare this to the other liver retractor techniques available for surgeons and highlight the pros and cons of each technique of liver retraction.展开更多
Following the publication,concerns have been raised about a number of figures in this article.An unexpected area of similarity was identified in terms of the cellular data,where the results from differently performed ...Following the publication,concerns have been raised about a number of figures in this article.An unexpected area of similarity was identified in terms of the cellular data,where the results from differently performed experiments were intended to have been shown,although the areas immediately surrounding this area featured comparatively different distributions of cells.In addition,the western blots in this article were presented with atypical,unusually shaped and possibly anomalous protein bands in many cases.展开更多
The published article titled“UCA1 Regulates the Growth and Metastasis of Pancreatic Cancer by Sponging miR-135a”has been retracted from Oncology Research,Vol.25,No.9,2017,pp.1529–1541.DOI:10.3727/096504017X14888987...The published article titled“UCA1 Regulates the Growth and Metastasis of Pancreatic Cancer by Sponging miR-135a”has been retracted from Oncology Research,Vol.25,No.9,2017,pp.1529–1541.DOI:10.3727/096504017X14888987683152 URL:https://www.techscience.com/or/v25n9/56938 Following the publication,concerns have been raised about a number of figures in this article.An unexpected area of similarity was identified in terms of the cellular data,where the results from differently performed experiments were intended to have been shown,although the areas immediately surrounding this area featured comparatively different distributions of cells.展开更多
The quantity of space debris on Earth orbit has escalated tremendously in recent years, presenting a significant hazard to human space operations. It is urgent to develop effective measures to capture and remove vario...The quantity of space debris on Earth orbit has escalated tremendously in recent years, presenting a significant hazard to human space operations. It is urgent to develop effective measures to capture and remove various space debris. For this purpose, this paper presents a tendon-actuated flexible deployable manipulator. The flexible manipulator consists of several deployable units connected by Cardan joints and actuated by tendons. Compared with the present technologies for capturing space debris such as rigid robotic arm or flying net, this flexible manipulator is deployable, reusable, lightweight and applicable to the capture of large space debris. In order to investigate its deployment dynamics, an accurate dynamic model of the flexible manipulator is established based on the natural coordinate formulation (NCF) and the absolute nodal coordinate formulation (ANCF). Subsequently, numerical simulations are carried out to study the effects of system parameters and the base satellite on its deployment dynamics. Finally, ground experiments for both deployment and bending of the flexible manipulator are conducted to verify its effectiveness and feasibility.展开更多
Following the publication,concerns have been raised about a number of figures in this article.The western blots in this article were presented with atypical,unusually shaped and possibly anomalous protein bands in man...Following the publication,concerns have been raised about a number of figures in this article.The western blots in this article were presented with atypical,unusually shaped and possibly anomalous protein bands in many cases.展开更多
Objective Traditional Chinese medicine(TCM)incorporates traditional diagnostic methods and several major treatment modalities including Chinese herbal medicine,Chinese patent medicine,and non-pharmacological methods s...Objective Traditional Chinese medicine(TCM)incorporates traditional diagnostic methods and several major treatment modalities including Chinese herbal medicine,Chinese patent medicine,and non-pharmacological methods such as acupuncture and tuina.Even though TCM is used daily by more than 70,000 healthcare facilities and over 700,000 clinical practitioners in China,there is a poor understanding of the extent to which TCM diagnostic methods are used,how different treatment modalities are deployed in general,and what major factors may affect the integration of TCM and Western medicine.This study aimed to fill this void in the literature.Methods In the 2021 National Healthcare Improvement Evaluation Survey,we included three questions gauging the perception and practices of TCM amongst physicians working in TCM-related facilities,investigating the frequency of their deployment of TCM diagnostic methods,and predominant TCM treatment methods.Our empirical analysis included descriptive statistics,intergroup chi-square analysis,and binary logistic regression to examine the association between different types of facilities and individual characteristics and TCM utilization patterns.Results A total of 7618 clinical physicians comprised our study sample.Among them,84.27%have integrated TCM and Western medicine in their clinical practice,and 80.77%of TCM practitioners used the 4 diagnostic methods as a tool in their clinical practice.Chinese herbal medicine was the most widely utilized modality by Chinese TCM physicians(used by 88.49%of respondents),compared with the Chinese patent medicine and non-pharmacological TCM methods,which were used by 73.14%,and 69.39%,respectively.Herbal tea as an out-of-pocket health-maintenance intervention is also a notable practice,recommended by 29.43%of physicians.Significant variations exist across certain institutions,departments,and individual practitioners.Conclusion Given that most of the surveyed physicians integrated TCM with Western medicine in their clinical practices,the practice of“pure TCM”appears to be obsolete in China’s tertiary healthcare institutions.Notably,remarkable variation exists in the use of different TCM modalities across institutions and among individuals,which might be related to and thus limited by the practitioners’experience.Future research focusing on the efficacy and safety of TCM interventions for specific diseases,the development of standardized clinical guidelines,and the enhancement of TCM education and training are called for to optimize TCM-Western medicine integration.展开更多
文摘To simplify the complicated design process of deployable/retractable structures, a new design process is developed. The process is divided into three phases： the concept design phase, the model phase and the optimization phase. In each phase, different parameter targets have to be fulfilled. According to three phases, a deployable/retractable mast composed of four right triangle prism modules in the longitudinal direction is designed. It can be deployed and folded simultaneously by the linear movements of sleeve-joints. The deployable and retractable movement of the mast is analyzed and key joint forms are designed. Then bar diameters and joint forms are modified based on mast structural mechanics characteristics in the optimization phase. Finally a 1：1 scaled model mast is built to verify the design and the optimization. Analytical results show that the model mast has the advantages of simple locking mechanism, fewer types of joints and bars, so it can be easily manufactured.
基金Project supported by the National Natural Science Foundation of China(Nos.11672007 and 11832002)the Graduate Technological Innovation Project of Beijing Institute of Technology(No.2017CX10037)。
文摘Deployable/retractable damped cantilever beams are a class of time-varying parametric structures which have attracted considerable research interest due to their many potential applications in the intelligent robot field and aerospace.In the present work,the dynamic characteristics of a deployable/retractable damped cantilever beam are investigated experimentally and theoretically.The time-varying damping,as a function of the beam length,is obtained by both the enveloped fitting method and the period decrement method.Furthermore,the governing equation of the deployable/retractable damped cantilever beam is derived by introducing the time-varying damping parameter,and the corresponding closed-form solution and vibration principles are investigated based on the averaged method.The theoretical predictions for transient dynamic responses are in good agreement with the experimental results.The dynamic mechanism analysis on time-varying damping offers flexible technology in mechanical and aerospace fields.
基金supported by the National Natural Science Foundation of China(No.52222501,52075016,52192632)the Fundamental Research Funds for the Central Universities(Grant No.YWF-23-L-904).
文摘Inflatable deployable structures inspired by origami have significant applications in space missions such as solar arrays and antennas.In this paper,a generalized Miura-ori tubular cell(GMTC)is presented as the basic cell to design a family of inflatable origami tubular structures with the targeted configuration.First,the classification of rigid foldable degree-4 vertices is studied thoroughly.Since the proposed GMTC is comprised of forming units(FU)and linking units(LU),types of FUs and LUs are investigated based on the classification of degree-4 vertices,respectively.The rigid foldability of the GMTC is presented by studying the kinematics of the FUs and LUs.Volume of the GMTC is analyzed to investigate multistable configurations of the basic cell.The variations in volume of the GMTC offer great potential for developing the inflatable tubular structure.Design method and parametric optimization of the tubular structure with targeted configuration are proposed.The feasibility of the approach is validated by the approximation of four different cases,namely parabolic,semicircular,trapezoidal,and straight-arc hybrid tubular structures.
文摘The aim of this paper is to conduct experimental modal analysis and numerical simulation to verify the structural characteristics of a deployable-retractable wing for aircraft and spacecraft. A modal impact test was conducted in order to determine the free vibration characteristics. Natural frequencies and vibration mode shapes were obtained via measurement in LMS Test. Lab. The frequency response functions were identified and computed by force and acceleration signals, and then mode shapes of this morphing wing structure were subsequently identified by PolyMAX modal parameter estimation method. FEM modal analysis was also implemented and its numerical results convincingly presented the mode shape and natural frequency characteristics were in good agreement with those obtained from experimental modal analysis. Experimental study in this paper focuses on the transverse response of morphing wing as its moveable part is deploying or retreating. Vibration response to different rotation speeds have been collected, managed and analyzed through the use of comparison methodology with each other. Evident phenomena have been discovered including the resonance on which most analysis is focused because of its potential use to generate large amplitude vibration of specific frequency or to avoid such resonant frequencies from a wide spectrum of response. Manufactured deployable-retractable wings are studied in stage of experimental modal analysis, in which some nonlinear vibration resulted should be particularly noted because such wing structure displays a low resonant frequency which is always optimal to be avoided for structural safety and stability.
基金supported by the National Natural Science Foundation of China(No.52275231)the National Defense Basic Scientific Research Program of China(No.JCKY2019205C002).
文摘Bistable Deployable Composite Boom(Bi-DCB)can achieve bistable function by storing and releasing strain energy,which has a good application prospect in space field.For example,it serves as the main support section of deployable structures(e.g.,solar arrays and antennas).This paper investigates folding stable state of Bi-DCB through the analytical method.Based on Archimedes’helix and energy principle,an analytical model for predicting folding stable state of Bi-DCB was presented.The failure index of Bi-DCB in folding stable state were analyzed using the Tsai-Hill criterion and the maximum stress criterion.Then,a 2400 mm long Bi-DCB was fabricated using autoclave method.The prediction results of the proposed model were compared with experiments and results of two other analytical models.It is shown that the proposed model shows good prediction accuracy.Finally,the effect of geometric parameters on folding stable state of Bi-DCB was further investigated with the aid of the proposed model.
基金Supported by National Key R&D Program of China (Grant No.2023YFB3407103)National Natural Science Foundation of China (Grant Nos.52175242,52175027)Young Elite Scientists Sponsorship Program by CAST (Grant No.2022QNRC001)。
文摘Mesh reflector antennas are widely used in space tasks owing to their light weight,high surface accuracy,and large folding ratio.They are stowed during launch and then fully deployed in orbit to form a mesh reflector that transmits signals.Smooth deployment is essential for duty services;therefore,accurate and efficient dynamic modeling and analysis of the deployment process are essential.One major challenge is depicting time-varying resistance of the cable network and capturing the cable-truss coupling behavior during the deployment process.This paper proposes a general dynamic analysis methodology for cable-truss coupling.Considering the topological diversity and geometric nonlinearity,the cable network's equilibrium equation is derived,and an explicit expression of the time-varying tension of the boundary cables,which provides the main resistance in truss deployment,is obtained.The deployment dynamic model is established,which considers the coupling effect between the soft cables and deployable truss.The effects of the antenna's driving modes and parameters on the dynamic deployment performance were investigated.A scaled prototype was manufactured,and the deployment experiment was conducted to verify the accuracy of the proposed modeling method.The proposed methodology is suitable for general cable antennas with arbitrary topologies and parameters,providing theoretical guidance for the dynamic performance evaluation of antenna driving schemes.
基金Supported in part by the National Natural Science Foundation of China(No.62271148).
文摘With the rapid development of space science projects,large deployable mechanisms have been widely used.However,due to the effects of mechanical friction and gravitational acceleration,on-orbit mechanisms cannot be always deployed to the expected pose.For some precision optical mechanisms,even a minor deviation can result in significant error,so it needs to be measured and corrected.In this paper,the deployment process was modeled and simplified as rotation under single-rotation-axis constraint and translation under single-direction constraint.To solve the problem,a method based on cross-ratio invariability was proposed.The proposed method does not rely on camera calibration techniques,as well as artificial marking points,both of which are necessary in PnP.Instead,only three calibration images before launch and a measurement image on orbit were required.Simulations and experiments demonstrated that the proposed method is more accurate than PnP.In addition,experiments also proved that the feasibility of the proposed method under dark conditions with the aid of a light source and some reflective marking points.
基金supported in part by National Key R&D Program of China(Grant No.2018YFB1304600)CAS Interdisciplinary Innovation Team(Grant No.JCTD-2018-11)the Natural Science Foundation of China(Grant No.51775541).
文摘Flasher origami pattern has been widely utilized to improve the stowage efficiency of deployable structures.Nevertheless,flasher origami cannot be folded fully flat,and they still have great potential for optimization in terms of storage volume and folding creases.In this paper,a flat foldable equiangular spiral folding pattern inspired by the sunflower disk is introduced.Then,a parametric design method for this equiangular spiral crease diagram is introduced in detail.Subsequently,a kinematic model of the equiangular spiral folding pattern is established based on the kinematic equivalence between rigid origami and spherical linkages.A simulation of the developed model demonstrates that the equiangular spiral folding pattern can be folded flat.Using the folded ratio as an evaluation index,the calculated results and experiments show that the equiangular spiral crease pattern can yield fewer creases and improve stowage efficiency in comparison to flasher origami pattern.Equiangular spiral folding pattern can save a considerable amount of space and provide a new approach to spatially deployable structures.
基金supported by the National Key Research and Development Program of China(2022YFE0206700)。
文摘1.Introduction Climate change mitigation pathways aimed at limiting global anthropogenic carbon dioxide(CO_(2))emissions while striving to constrain the global temperature increase to below 2℃—as outlined by the Intergovernmental Panel on Climate Change(IPCC)—consistently predict the widespread implementation of CO_(2)geological storage on a global scale.
基金Supported by Jiangsu Provincial Frontier Leading Technology Basic Research Project(Grant No.BK20212007)Aero-Engine and Gas Turbine Basic Science Center(Grant No.P2022-B-IV-014-001)+1 种基金China Postdoctoral Program Fund(Grant No.1005/YBA23044)China Postdoctoral Assistance Fund(Grant No.1005/YBA23031)。
文摘Variable-diameter deployable carbon fiber reinforced polymer(CFRP)composites possess deformation and load-bearing functions and are composed of stiff-flexible coupled preforms and matrix.The stiff-flexible coupled preform,serving as the reinforcing structure,directly determines the deployable properties,and its forming technology is currently a research challenge.This paper designs a braiding and needle-punching(BNP)composite preform forming technology suitable for stiff-flexible coupled preforms.Before forming,the preform is partitioned into flexible and rigid zones,with braiding and needle-punching performed layer by layer in the respective zones.A retractable rotating device is developed to form the stiff-flexible coupled preform,achieving a diameter variation rate of up to 26.6%for the BNP preform.A structural parameter model is also established to describe the geometric parameter changes in the deformation and load-bearing areas of the preform during deployment as a function of the braiding angle.Based on experiments,this paper explains the performance changes of BNP composites concerning the structural parameters of the preform.Experimental analysis shows that as the braiding angle increases,the tensile performance of BNP composites significantly decreases,with the change rate of tensile strength first decreasing and then increasing.Additionally,when the braiding angle is less than 21.89°,the impact toughness of BNP composites remains within the range of 83.66±2 kJ/m^(2).However,when the braiding angle exceeds 21.89°,the impact toughness of BNP composites gradually decreases with increasing braiding angle.Furthermore,a hybrid agent model based on Latin hypercube sampling and error back-propagation neural network is developed to predict the tensile and impact properties of BNP composites with different structural parameters,with maximum test relative errors of 1.89%for tensile strength and 2.37%for impact toughness.
基金supported by the National Natural Science Foundation of China(Nos.62272418,62102058)Basic Public Welfare Research Program of Zhejiang Province(No.LGG18E050011)the Major Open Project of Key Laboratory for Advanced Design and Intelligent Computing of the Ministry of Education under Grant ADIC2023ZD001,National Undergraduate Training Program on Innovation and Entrepreneurship(No.202410345054).
文摘The wireless signals emitted by base stations serve as a vital link connecting people in today’s society and have been occupying an increasingly important role in real life.The development of the Internet of Things(IoT)relies on the support of base stations,which provide a solid foundation for achieving a more intelligent way of living.In a specific area,achieving higher signal coverage with fewer base stations has become an urgent problem.Therefore,this article focuses on the effective coverage area of base station signals and proposes a novel Evolutionary Particle Swarm Optimization(EPSO)algorithm based on collective prediction,referred to herein as ECPPSO.Introducing a new strategy called neighbor-based evolution prediction(NEP)addresses the issue of premature convergence often encountered by PSO.ECPPSO also employs a strengthening evolution(SE)strategy to enhance the algorithm’s global search capability and efficiency,ensuring enhanced robustness and a faster convergence speed when solving complex optimization problems.To better adapt to the actual communication needs of base stations,this article conducts simulation experiments by changing the number of base stations.The experimental results demonstrate thatunder the conditionof 50 ormore base stations,ECPPSOconsistently achieves the best coverage rate exceeding 95%,peaking at 99.4400%when the number of base stations reaches 80.These results validate the optimization capability of the ECPPSO algorithm,proving its feasibility and effectiveness.Further ablative experiments and comparisons with other algorithms highlight the advantages of ECPPSO.
文摘Purpose:This study examines the impact of research policy changes on scientific retractions of publications authored by Romanian authors,focusing on national trends and the interplay between policy reforms and publishing practices.Design/methodology/approach:Using data from the Retraction Watch Database and Web of Science(WoS),188 unique retractions involving Romanian authors(2000-2022)were analyzed.The study compared retraction patterns before and after the 2016 reforms,which prioritized the publication of articles in WoS-indexed journals over non-WoS outputs.Findings:The analysis identified two key trends:(1)before the 2016 reforms,retractions predominantly involved non-WoS journals(99 non-WoS retractions to 38 WoS retractions),a trend that reversed post-reform(16 non-WoS to 35 WoS),and(2)while the total number of WoS-indexed retractions increased after the reforms,the retraction rates for WoS articles remained stable.Post-reform reliance on MDPI journals,which have low retraction rates,partially explains this stability.Excluding MDPI publications,retraction rates for articles and reviews increase by 14.91%,aligning with patterns seen elsewhere.Research limitations:The study focuses on retractions involving Romanian authors,limiting its generalizability.Furthermore,reliance on database records may not fully capture all retractions.Practical implications:These findings underscore the need for research policy reforms to consider a broader range of effects,and the need for nuanced interpretations of retraction data,which are influenced by a complex range of factors,including specific publisher practices.Originality/value:This research is the first to investigate the complex relationship between research policy reforms,publisher behavior,and retraction trends.
文摘RETRACTION:P.Goyal and R.Malviya,“Challenges and Opportunities of Big Data Analytics in Healthcare,”Health Care Science 2,no.5(2023):328-338,https://doi.org/10.1002/hcs2.66.The above article,published online on 4 October 2023 in Wiley Online Library(wileyonlinelibrary.com),has been retracted by agreement between the journal Editor-in-Chief,Zongjiu Zhang;Tsinghua University Press;and John Wiley&Sons Ltd.
文摘Traditionally,liver retraction for laparoscopic gastrectomy is done via manual methods,such as the placement of retractors through the accessory ports and using a Nathanson retractor.However,these techniques often posed issues including extra abdominal incisions,risk of liver injury or ischaemia,and the potential for compromised visualization.Over the years,the development of innovative liver retraction techniques has significantly improved the safety and efficacy of laparoscopic gastrectomy and similar other hiatal procedures.This editorial will comment on the article by Lin et al,and compare this to the other liver retractor techniques available for surgeons and highlight the pros and cons of each technique of liver retraction.
文摘Following the publication,concerns have been raised about a number of figures in this article.An unexpected area of similarity was identified in terms of the cellular data,where the results from differently performed experiments were intended to have been shown,although the areas immediately surrounding this area featured comparatively different distributions of cells.In addition,the western blots in this article were presented with atypical,unusually shaped and possibly anomalous protein bands in many cases.
文摘The published article titled“UCA1 Regulates the Growth and Metastasis of Pancreatic Cancer by Sponging miR-135a”has been retracted from Oncology Research,Vol.25,No.9,2017,pp.1529–1541.DOI:10.3727/096504017X14888987683152 URL:https://www.techscience.com/or/v25n9/56938 Following the publication,concerns have been raised about a number of figures in this article.An unexpected area of similarity was identified in terms of the cellular data,where the results from differently performed experiments were intended to have been shown,although the areas immediately surrounding this area featured comparatively different distributions of cells.
基金the National Natural Science Foundation of China(Nos.11832005,12372042,12232011)Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC001)+1 种基金the Fundamental Research Funds for the Central Universities(No.NS2023002)State Key Laboratory of Mechanics and Control for Aerospace Structures(Nanjing University of Aeronautics and Astronautics)(No.MCAS-S-0223K04).
文摘The quantity of space debris on Earth orbit has escalated tremendously in recent years, presenting a significant hazard to human space operations. It is urgent to develop effective measures to capture and remove various space debris. For this purpose, this paper presents a tendon-actuated flexible deployable manipulator. The flexible manipulator consists of several deployable units connected by Cardan joints and actuated by tendons. Compared with the present technologies for capturing space debris such as rigid robotic arm or flying net, this flexible manipulator is deployable, reusable, lightweight and applicable to the capture of large space debris. In order to investigate its deployment dynamics, an accurate dynamic model of the flexible manipulator is established based on the natural coordinate formulation (NCF) and the absolute nodal coordinate formulation (ANCF). Subsequently, numerical simulations are carried out to study the effects of system parameters and the base satellite on its deployment dynamics. Finally, ground experiments for both deployment and bending of the flexible manipulator are conducted to verify its effectiveness and feasibility.
文摘Following the publication,concerns have been raised about a number of figures in this article.The western blots in this article were presented with atypical,unusually shaped and possibly anomalous protein bands in many cases.
基金The Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences——A Strategic Study on Healthy China Development and Health System Reform(2021-I2M-1-046).
文摘Objective Traditional Chinese medicine(TCM)incorporates traditional diagnostic methods and several major treatment modalities including Chinese herbal medicine,Chinese patent medicine,and non-pharmacological methods such as acupuncture and tuina.Even though TCM is used daily by more than 70,000 healthcare facilities and over 700,000 clinical practitioners in China,there is a poor understanding of the extent to which TCM diagnostic methods are used,how different treatment modalities are deployed in general,and what major factors may affect the integration of TCM and Western medicine.This study aimed to fill this void in the literature.Methods In the 2021 National Healthcare Improvement Evaluation Survey,we included three questions gauging the perception and practices of TCM amongst physicians working in TCM-related facilities,investigating the frequency of their deployment of TCM diagnostic methods,and predominant TCM treatment methods.Our empirical analysis included descriptive statistics,intergroup chi-square analysis,and binary logistic regression to examine the association between different types of facilities and individual characteristics and TCM utilization patterns.Results A total of 7618 clinical physicians comprised our study sample.Among them,84.27%have integrated TCM and Western medicine in their clinical practice,and 80.77%of TCM practitioners used the 4 diagnostic methods as a tool in their clinical practice.Chinese herbal medicine was the most widely utilized modality by Chinese TCM physicians(used by 88.49%of respondents),compared with the Chinese patent medicine and non-pharmacological TCM methods,which were used by 73.14%,and 69.39%,respectively.Herbal tea as an out-of-pocket health-maintenance intervention is also a notable practice,recommended by 29.43%of physicians.Significant variations exist across certain institutions,departments,and individual practitioners.Conclusion Given that most of the surveyed physicians integrated TCM with Western medicine in their clinical practices,the practice of“pure TCM”appears to be obsolete in China’s tertiary healthcare institutions.Notably,remarkable variation exists in the use of different TCM modalities across institutions and among individuals,which might be related to and thus limited by the practitioners’experience.Future research focusing on the efficacy and safety of TCM interventions for specific diseases,the development of standardized clinical guidelines,and the enhancement of TCM education and training are called for to optimize TCM-Western medicine integration.
