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Analytical and numerical investigation into the longitudinal vibration of uniform nanotubes

null

《机械工程前沿（英文）》 2014年 第9卷 第2期   页码 142-149 doi: 10.1007/s11465-014-0292-z

摘要：

In recent years, prediction of the behaviors of micro and nanostructures is going to be a matter of increasing concern considering their developments and uses in various engineering fields. Since carbon nanotubes show the specific properties such as strength and special electrical behaviors, they have become the main subject in nanotechnology researches. On the grounds that the classical continuum theory cannot accurately predict the mechanical behavior of nanostructures, nonlocal elasticity theory is used to model the nanoscaled systems. In this paper, a nonlocal model for nanorods is developed, and it is used to model the carbon nanotubes with the aim of the investigating into their longitudinal vibration. Following the derivation of governing equation of nanorods and estimation of nondimensional frequencies, the effect of nonlocal parameter and the length of the nanotube on the obtained frequencies are studied. Furthermore, differential quadrature method, as a numerical solution technique, is used to study the effect of these parameters on estimated frequencies for both classical and nonlocal theories.

关键词： continuum theory     differential quadrature method     nanorod     longitudinal vibration    

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Design and modeling of continuum robot based on virtual-center of motion mechanism

《机械工程前沿（英文）》 2023年 第18卷 第2期 doi: 10.1007/s11465-022-0739-6

摘要： Continuum robot has attracted extensive attention since its emergence. It has multi-degree of freedom and high compliance, which give it significant advantages when traveling and operating in narrow spaces. The flexural virtual-center of motion (VCM) mechanism can be machined integrally, and this way eliminates the assembly between joints. Thus, it is well suited for use as a continuum robot joint. Therefore, a design method for continuum robots based on the VCM mechanism is proposed in this study. First, a novel VCM mechanism is formed using a double leaf-type isosceles-trapezoidal flexural pivot (D-LITFP), which is composed of a series of superimposed LITFPs, to enlarge its stroke. Then, the pseudo-rigid body (PRB) model of the leaf is extended to the VCM mechanism, and the stiffness and stroke of the D-LITFP are modeled. Second, the VCM mechanism is combined to form a flexural joint suitable for the continuum robot. Finally, experiments and simulations are used to validate the accuracy and validity of the PRB model by analyzing the performance (stiffness and stroke) of the VCM mechanism. Furthermore, the motion performance of the designed continuum robot is evaluated. Results show that the maximum stroke of the VCM mechanism is approximately 14.2°, the axial compressive strength is approximately 1915 N/mm, and the repeatable positioning accuracies of the continuum robot is approximately ±1.47° (bending angle) and ±2.46° (bending direction).

关键词： VCM mechanism     continuum robot     flexural joint     pseudo-rigid body model     cable-driven    

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Creep life assessment of aero-engine recuperator based on continuum damage mechanics approach

《机械工程前沿（英文）》 2022年 第17卷 第4期 doi: 10.1007/s11465-022-0702-6

摘要： The creep life of an aeroengine recuperator is investigated in terms of continuum damage mechanics by using finite element simulations. The effects of the manifold wall thickness and creep properties of brazing filler metal on the operating life of the recuperator are analyzed. Results show that the crack initiates from the brazing filler metal located on the outer surface of the manifold with the wall thickness of 2 mm and propagates throughout the whole region of the brazing filler metal when the creep time reaches 34900 h. The creep life of the recuperator meets the requirement of 40000 h continuous operation when the wall thickness increases to 3.5 mm, but its total weight increases by 15%. Decreasing the minimum creep strain rate with the enhancement of the creep strength of the brazing filler metal presents an obvious effect on the creep life of the recuperator. At the same stress level, the creep rupture time of the recuperator is enhanced by 13 times if the mismatch between the minimum creep rate of the filler and base metal is reduced by 20%.

关键词： creep     life assessment     brazed joint     continuum damage mechanics     aeroengine recuperator    

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Comprehensive kinetostatic modeling and morphology characterization of cable-driven continuum robots

《机械工程前沿（英文）》 2023年 第18卷 第3期 doi: 10.1007/s11465-023-0756-0

摘要： In-situ maintenance is of great significance for improving the efficiency and ensuring the safety of aero-engines. The cable-driven continuum robot (CDCR) with twin-pivot compliant mechanisms, which is enabled with flexible deformation capability and confined space accessibility, has emerged as a novel tool that aims to promote the development of intelligence and efficiency for in-situ aero-engine maintenance. The high-fidelity model that describes the kinematic and morphology of CDCR lays the foundation for the accurate operation and control for in-situ maintenance. However, this model was not well addressed in previous literature. In this study, a general kinetostatic modeling and morphology characterization methodology that comprehensively contains the effects of cable-hole friction, gravity, and payloads is proposed for the CDCR with twin-pivot compliant mechanisms. First, a novel cable-hole friction model with the variable friction coefficient and adaptive friction direction criterion is proposed through structure optimization and kinematic parameter analysis. Second, the cable-hole friction, all-component gravities, deflection-induced center-of-gravity shift of compliant joints, and payloads are all considered to deduce a comprehensive kinetostatic model enabled with the capacity of accurate morphology characterization for CDCR. Finally, a compact continuum robot system is integrated to experimentally validate the proposed kinetostatic model and the concept of in-situ aero-engine maintenance. Results indicate that the proposed model precisely predicts the morphology of CDCR and outperforms conventional models. The compact continuum robot system could be considered a novel solution to perform in-situ maintenance tasks of aero-engines in an invasive manner.

关键词： kinetostatic modeling     morphology characterization     variable friction     continuum robots     in-situ maintenance    

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Modeling of shear walls using finite shear connector elements based on continuum plasticity

Ulf Arne GIRHAMMAR, Per Johan GUSTAFSSON, Bo KÄLLSNER

《结构与土木工程前沿（英文）》 2017年 第11卷 第2期   页码 143-157 doi: 10.1007/s11709-016-0377-3

摘要： Light-frame timber buildings are often stabilized against lateral loads by using diaphragm action of roofs, floors and walls. The mechanical behavior of the sheathing-to-framing joints has a significant impact on the structural performance of shear walls. Most sheathing-to-framing joints show nonlinear load-displacement characteristics with plastic behavior. This paper is focused on the finite element modeling of shear walls. The purpose is to present a new shear connector element based on the theory of continuum plasticity. The incremental load-displacement relationship is derived based on the elastic-plastic stiffness tensor including the elastic stiffness tensor, the plastic modulus, a function representing the yield criterion and a hardening rule, and function representing the plastic potential. The plastic properties are determined from experimental results obtained from testing actual connections. Load-displacement curves for shear walls are calculated using the shear connector model and they are compared with experimental and other computational results. Also, the ultimate horizontal load-carrying capacity is compared to results obtained by an analytical plastic design method. Good agreements are found.

关键词： shear walls     wall diaphragms     finite element modelling     plastic shear connector     analytical modelling     experimental comparison    

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Layout optimization of steel reinforcement in concrete structure using a truss-continuum model

《结构与土木工程前沿（英文）》 2023年 第17卷 第5期   页码 669-685 doi: 10.1007/s11709-023-0963-0

摘要： Owing to advancement in advanced manufacturing technology, the reinforcement design of concrete structures has become an important topic in structural engineering. Based on bi-directional evolutionary structural optimization (BESO), a new approach is developed in this study to optimize the reinforcement layout in steel-reinforced concrete (SRC) structures. This approach combines a minimum compliance objective function with a hybrid truss-continuum model. Furthermore, a modified bi-directional evolutionary structural optimization (M-BESO) method is proposed to control the level of tensile stress in concrete. To fully utilize the tensile strength of steel and the compressive strength of concrete, the optimization sensitivity of steel in a concrete–steel composite is integrated with the average normal stress of a neighboring concrete. To demonstrate the effectiveness of the proposed procedures, reinforcement layout optimizations of a simply supported beam, a corbel, and a wall with a window are conducted. Clear steel trajectories of SRC structures can be obtained using both methods. The area of ​​critical tensile stress in concrete yielded by the M-BESO is more than 40% lower than that yielded by the uniform design and BESO. Hence, the M-BESO facilitates a fully digital workflow that can be extremely effective for improving the design of steel reinforcements in concrete structures.

关键词： bi-directional evolutionary structural optimization     steel-reinforced concrete     concrete stress     reinforcement method     hybrid model    

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Modeling water and heat transfer in soil-plant-atmosphere continuum applied to maize growth under plastic

Meng DUAN, Jin XIE, Xiaomin MAO

《农业科学与工程前沿（英文）》 2019年 第6卷 第2期   页码 144-161 doi: 10.15302/J-FASE-2019258

摘要：

Based on our previous work modeling crop growth (CropSPAC) and water and heat transfer in the soil-plant-atmosphere continuum (SPAC), the model was improved by considering the effect of plastic film mulching applied to field-grown maize in North-west China. In CropSPAC, a single layer canopy model and a multi-layer soil model were adopted to simulate the energy partition between the canopy and water and heat transfer in the soil, respectively. The maize growth module included photosynthesis, growth stage calculation, biomass accumulation, and participation. The CropSPAC model coupled the maize growth module and SPAC water and heat transfer module through leaf area index (LAI), plant height and soil moisture condition in the root zone. The LAI and plant height were calculated from the maize growth module and used as input for the SPAC water and heat transfer module, and the SPAC module output for soil water stress conditions used as an input for maize growth module. We used , the representation of evaporation resistance, instead of the commonly used evaporation resistance to reflect the change of latent heat flux of soil evaporation under film mulching as well as the induced change in energy partition. The model was tested in a maize field at Yingke irrigation area in North-west China. Results showed reasonable agreement between the simulations and measurements of LAI, above-ground biomass and soil water content. Compared with the original model, the modified model was more reliable for maize growth simulation under film mulching and showed better accuracy for the LAI (with the coefficient of determination = 0.92, the root mean square of error RMSE= 1.23, and the Nush-Suttclife efficiency E = 0.87), the above-ground biomass (with = 0.96, RMSE= 7.17 t·ha and E = 0.95) and the soil water content in 0–1 m soil layer (with = 0.78, RMSE= 49.44 mm and E = 0.26). Scenarios were considered to simulate the influence of future climate change and film mulching on crop growth, soil water and heat conditions, and crop yield. The simulations indicated that the change of LAI, leaf biomass and yield are negatively correlated with temperature change, but the growing degree-days, evaporation, soil water content and soil temperature are positively correlated with temperature change. With an increase in the ratio of film mulching area, the evaporation will decrease, while the impact of film mulching on crop transpiration is not significant. In general, film mulching is effective in saving water, preserving soil moisture, increasing soil surface temperature, shortening the potential growth period, and increasing the potential yield of maize.

关键词： film mulching     growth stage     leaf area index     maize growth     water and heat transfer    

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解读建筑理论

顾孟潮

《中国工程科学》 2007年 第9卷 第11期   页码 100-102

摘要：

从解读建筑理论的定义与概念入手，对有中国特色的建筑理论框架及建筑理论的创新等问题提出 了自己的见解。

关键词： 建筑理论     建筑理论框架     建筑理论纵横框架     建筑理论的起点和终点     建筑理论创新    

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Usability perceptions and beliefs about smart thermostats by chi-square test, signal detection theory, and fuzzy detection theory in regions of Mexico

Pedro PONCE, Therese PEFFER, Arturo MOLINA

《能源前沿（英文）》 2019年 第13卷 第3期   页码 522-538 doi: 10.1007/s11708-018-0562-2

摘要： It is well known that smart thermostats (STs) have become key devices in the implementation of smart homes; thus, they are considered as primary elements for the control of electrical energy consumption in households. Moreover, energy consumption is drastically affected when the end users select unsuitable STs or when they do not use the STs correctly. Furthermore, in future, Mexico will face serious electrical energy challenges that can be considerably resolved if the end users operate the STs in a correct manner. Hence, it is important to carry out an in-depth study and analysis on thermostats, by focusing on social aspects that influence the technological use and performance of the thermostats. This paper proposes the use of a signal detection theory (SDT), fuzzy detection theory (FDT), and chi-square (CS) test in order to understand the perceptions and beliefs of end users about the use of STs in Mexico. This paper extensively shows the perceptions and beliefs about the selected thermostats in Mexico. Besides, it presents an in-depth discussion on the cognitive perceptions and beliefs of end users. Moreover, it shows why the expectations of the end users about STs are not met. It also promotes the technological and social development of STs such that they are relatively more accepted in complex electrical grids such as smart grids.

关键词： thermostats     perceptions     beliefs     signal detection theory (SDT)     fuzzy signal detection theory (FSDT)     chi-square (CS) test    

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知行学引论——信息 知识 智能的统一理论

钟义信

《中国工程科学》 2004年 第6卷 第6期   页码 1-8

摘要：

资源乃人类生存之源。科学技术的任务就要揭示资源的性质及其转换规律，以创造先进工具，扩展人的能力，改善人类的生存发展条件。近代科学揭示了物质和能量两类资源的性质和转换规律，创造和不断改进了人力工具和动力工具，创造了辉煌的工业时代文明：文章试图总结信息资源的性质及其转换规律，阐明信息—知识—智能的统一理论，构建知行学，为创造各种智能工具奠定理论基础。

关键词： 信息论     知识论     智能论     知行学    

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An application of game theory in distributed collaborative decision making

Angran XIAO

《机械工程前沿（英文）》 2019年 第14卷 第1期   页码 85-101 doi: 10.1007/s11465-019-0523-4

摘要： In a distributed product realization environment, new paradigms and accompanying software systems are necessary to support the collaborative work of geographically dispersed engineering teams from different disciplines who have different knowledge, experience, tools and resources. To verify the concept of collaboration by separation, we propose a generic information communication medium to enable knowledge representation and exchange between engineering teams, a digital interface. Across digital interfaces, each engineering team maintains its own perspective towards the product realization problem, and each controls a subset of design variables and seeks to maximize its own payoff function subject to individual constraints. Hence, we postulate the use of principles from game theory to model the relationships between engineering teams and facilitate collaborative decision making without causing unnecessary information exchange or iteration across digital interfaces. A product design and manufacturing scenario is introduced to demonstrate the efficacy of using game theory to maintain a clean interface between design and manufacturing teams.

关键词： collaboration     distributed product realization     game theory     digital interface    

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Individualized medicine, health medicine, and constitutional theory in Chinese medicine

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《医学前沿（英文）》 2012年 第6卷 第1期   页码 1-7 doi: 10.1007/s11684-012-0173-y

摘要：

The patterns of modern science and changes in the medical model can result in the transformation of the current state of individualized and health medicines into being the primary trend in medical development. Chinese and Western medical systems are dissimilar in terms of value orientations, thinking style, and research directions because of their different historical and cultural backgrounds. Individualized treatment in modern medicine is mainly established based on individual genome information and the differences in mononucleotide polymorphi-sms. However, such treatment method is expensive, creates an uncertain genetic marker, and leads to different result interpretations, among other problems. The Chinese constitutional theory developed in the 1970s expresses the principle behind Chinese health medicine and individual treatment and provides the corresponding methods. The Chinese constitutional theory divides the constitution of the Chinese population into nine categories based on established classification criteria. It promotes the study of the relationship of each constitution to diseases and Chinese medicine preparation toward adjusting the constitution and preventing diseases. The theory also provides methods and tools for individualized treatment. Constitution identification shows the direction and provides the core technology for the evaluation of the health status. By combining the developments in modern biotechnology, new diagnostic techniques and treatment models of constitution-differentiation, disease-differentiation, and syndrome-differentiation can be established for the development of individualized Chinese medicine treatment and health medicine for the international medical community.

关键词： individualized medicine     health medicine     constitutional theory in Chinese medicine    

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Independent continuous and mapping method of structural topology optimization based on the global stress approach

Yunkang SUI, Jili FENG, Hongling YE, Xirong PENG,

《机械工程前沿（英文）》 2010年 第5卷 第2期   页码 130-142 doi: 10.1007/s11465-010-0011-3

摘要： There are three difficulties in topology optimization of continuum structures. 1) The topology under multiple load case is more difficult to be optimized than under single load case, because the former becomes a multiple objective based on compliance objective functions. 2) With local constraints, such as an elemental stress limit, the topology is more difficult to be solved than with global constraints, such as the displacement or frequency limits, because the sensitivity analysis of the former has very expensive computation. 3) With the phenomenon of load illness, which is similar with stiffness illness in the structural analysis, it is not easy to get the reasonable final topological structure, because it is difficult to consider different influences between the loads with small forces and big forces, and some topology paths of transferring small forces may disappear during the iteration process. To overcome difficulties above, four measures are adopted. 1) Topology optimization model is established by independent continuous mapping (ICM) method. 2) Based on the von Mises strength theory, all elements’ stress constraints are transformed into a structural energy constraint. 3) The phenomenon of load illness is divided to classify into three cases. 4) A strategy based on strain energy is proposed to adopt ICM method with stress globalization, and the problems of the above mentioned three cases of load illness are solved in terms of different complementary approaches. Several numerical examples show that the topology path of transferring forces can be obtained more easily by substituting global strain energy constraints for local stresses constraints, and the problem of load illness can be solved well by the weighting method that takes the structural energy as a weighting coefficient.

关键词： independent continuous mapping (ICM) method     global stresses constraints     topology optimization     continuum structure     load illness    

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Construction of the vessel-collateral theory and its guidance for prevention and treatment of vasculopathy

Yiling Wu

《医学前沿（英文）》 2011年 第5卷 第2期   页码 118-122 doi: 10.1007/s11684-011-0140-z

摘要： According to the self-discipline of traditional Chinese medicine, vessel-collateral theory was constructed systematically, which was important to improving prevention and treatment level of vasculopathy. The hypothesis of “homeostasis ( ), compensatory auto-adaptation ( ), regulation ( ) and equilibrium ( )” based on the “qi–yin-yang–five elements” coupled with the (nutrients)- (defense) theory, has become the core content of the vessel-collateral theory. Clinical and laboratory trials have been developed to further confirm the scientific connotations of the hypothesis, such as capsule, as the representative drugs of vessel collateral theory, showed good efficacy in protecting the vascular endothelium, stabilizing the vulnerable plaque and reducing the blood vessel spasm. “Sou, ti, shu, tong” was the characteristics of capsule in treating “microvascular damage” as the core mechanism of acute myocardial infarction, cerebral infarction and microvascular complications of diabetes. capsules in the treatment of arrhythmia have made integrated adjustment advantage. capsules have been made treating both manifestation and root cause of chronic heart failure. These research have improved prevention and treatment level of major vascular system diseases.

关键词： vessel-collateral theory     vasculopathy     prevention and treatment    

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The fundamental theory of traditional Chinese medicine and the consideration in its research strategy

Zhenji Li, Chunbo Xu

《医学前沿（英文）》 2011年 第5卷 第2期   页码 208-211 doi: 10.1007/s11684-011-0126-x

摘要： Stressing the uniqueness and complexity of traditional Chinese medicine (TCM) theory system, this paper analyzes the characteristics of TCM as a discipline from four perspectives: scientific nature, fundamental theory, clinical practice, and pharmacological action. It suggests that when the research strategy of TCM theory is designed, the core theory of TCM should be emphasized on the theoretical research on TCM original thinking theory, TCM theory, Chinese materia medica and formulas, acupuncture and moxibustion, meridians and collaterals, and other related fields. Researchers and practitioners should ensure that the basic research on TCM theory is based on clinical practice, research methods (both traditional and contemporary) are exploited, and methodological innovation is underscored. The rule of TCM development should be followed and the characteristics and advantages of TCM carried forward. Meanwhile, the methods and theory of contemporary science and technology should be exploited to fulfill the goal of inheriting, enriching, and developing the fundamental theory of TCM.

关键词： fundamental theory     traditional Chinese medicine     research strategy    

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标题 作者 时间 类型 操作

Analytical and numerical investigation into the longitudinal vibration of uniform nanotubes

null

期刊论文

Design and modeling of continuum robot based on virtual-center of motion mechanism

期刊论文

Creep life assessment of aero-engine recuperator based on continuum damage mechanics approach

期刊论文

Comprehensive kinetostatic modeling and morphology characterization of cable-driven continuum robots

期刊论文

Modeling of shear walls using finite shear connector elements based on continuum plasticity

Ulf Arne GIRHAMMAR, Per Johan GUSTAFSSON, Bo KÄLLSNER

期刊论文

Layout optimization of steel reinforcement in concrete structure using a truss-continuum model

期刊论文

Modeling water and heat transfer in soil-plant-atmosphere continuum applied to maize growth under plastic

Meng DUAN, Jin XIE, Xiaomin MAO

期刊论文

解读建筑理论

顾孟潮

期刊论文

Usability perceptions and beliefs about smart thermostats by chi-square test, signal detection theory, and fuzzy detection theory in regions of Mexico

Pedro PONCE, Therese PEFFER, Arturo MOLINA

期刊论文

知行学引论——信息 知识 智能的统一理论

钟义信

期刊论文

An application of game theory in distributed collaborative decision making

Angran XIAO

期刊论文

Individualized medicine, health medicine, and constitutional theory in Chinese medicine

null

期刊论文

Independent continuous and mapping method of structural topology optimization based on the global stress approach

Yunkang SUI, Jili FENG, Hongling YE, Xirong PENG,

期刊论文

Construction of the vessel-collateral theory and its guidance for prevention and treatment of vasculopathy

Yiling Wu

期刊论文

The fundamental theory of traditional Chinese medicine and the consideration in its research strategy

Zhenji Li, Chunbo Xu

期刊论文