坐姿状态下人-结构相互作用体系水平振动特性

针对人-结构系统水平振动问题,建立质量轻基频低的试验平台,研究人端坐于试验平台时该人-结构相互作用体系的水平振动特性.试验结果表明:自然端坐状态下,人体的不同朝向对结构的动力特性的影响不同.当人朝x向端坐时,结构多出一个振型频率,而基频恰好分布于两振型中间;而当人朝y向端坐时,结构仅有共振频率高于原结构基频.在研究中,人通常比较成质量块放在结构装置上,而事实上质量块对结构的振型阻尼比影响很小,人体能显著增大结构振型阻尼比.因此,不能将水平向自然端坐的人仅仅看作质量块,而应当成质量-弹簧-阻尼完整的体系.

Self-organized architecture for outdoor mobile robot navigation

This paper proposed a multi-agent based architecture for outdoor mobile robot navigation where event-driven control is used to handle the dynamically changing of the environment. With the support of a distributed communication infrastructure and an event-driven situation evaluation agent, the robot can initiate action adaptive to the dynamical changes in the environment through reorganize its internal architecture. Adaptiveness and feasibility of the proposed architecture is validated through navi- gation experiments on the robot in a variety of natural outdoor environments.

Safety architecture of internet based multi-robot teleoperation system

Safety subsystem is one of the important parts in robot teleoperation system. In this paper, a safety architecture of safety subsystem in Internet based multi-operator-multi-robot (MOMR) teleoperation system is presented. The subsystem is divided into three layers in its logic architecture: interactive monitor layer, collaborative control layer and real-time control layer. The safety problems and the related strategy are clarified by detailed analysis of each layer and relationship among the layers. So we can obtain a high performance MOMR teleoperation system with multi-layer safety architecture.

METHODS OF IMPROVING COMPUTATIONAL ACCURACY OF ROBOT DYNAMICS

In this paper the geometric meaning of robot systems is expounded based on the theory of multibody system. The error accumulation for the known algorithm is analyzed and the cause of ‘Energy consumption’ is revealed, the relationship between the coefficients of dynamic equation is derived so as to establish the canonical equations. The error accumulation of dynamics can be eliminated by using canonical equations and the symplectic integral method so that the computational accuracy can be ensured effectively. As an example, a planar robotics system is considered.

Demographic, Economic, and Social Challenges of the Population Ageing in Cameroon

The elderly represent a growing proportion of the overall population and household＇s heads in Cameroon. This demographic change has some impact on the economic and social situation of the latter, in particular, the functioning of the family structure and solidarity between generations. The successive crises （food and financial） coupled with structural adjustment programs have in fact worsened the problems of the elderly, without having for compensation, provided the corresponding benefits for other age groups. This study contributes to the analysis of changes over time in the family support system, especially with regard to household＇s heads aged in Cameroon. To achieve this, the discussion turns around three questions： （1） what is the extent and nature of the ageing in Cameroon？ （2） what are the demographic, economic, and social implications？ and （3） what is the impact of economic and social change on intergenerational relationships？ The data used come from the Population Census （1976, 1987, and 2005）, and the Cameroonian Household Survey of 2007. The gradual deterioration of the support system for the family, especially due to modernization, and the current and future numbers of older should bring more policymakers to meet the specific needs of this group in Cameroon.

Concept and Evaluation of Ecosystem Intrinsic Value

Ecosystem valuation can serve as a basis of scientific support for decision-making. So far, the most popular methods for ecosystem valuation are ecosystem service valuation （ESV）, which is based on the utility of ecosystem to human beings rather than on the objective value of the ecosystem. After more than 10 years＇ application, it has been found that all losses of ESV were about 10% of the benefits of human activities. In this paper, the ecosystem intrinsic value （EIV） is defined. EIV is an objective value that emerges from the existence, structures, functions and processes of ecosystem, but independent with man, man＇s will and preferences. The valuating approach and methods used for EIV were developed by using energy approach and the methods of emergy analysis and eco-exergy analysis. The EIV calculated by emergy from the substance, energy and information of ecosystem and by eco-exergy from the structure and function of ecosystem represents the existent value and the externally working capacity of ecosystem, respectively. The approach and methods of EIV evaluation were applied to Xiamen Bay, China. The results showed that the marine EIV in Xiamen Bay was 209 billion RMB, including 116 billion RMB of emergy and 92.4 billion RMB of eco-exergy in 2010, nearly 30 times of ESV and 8.5 times of the GDP of Xiamen marine industry in 2010. The EIV in unit area of Xiarnen Bay is more than 10 times higher than the average global ESV in estuaries. It implied a potential undervaluation to ecosystem value by ESV calculation, which may mislead decisions-making processes.

Seismic Health Monitoring of Foundations Using Artificial Neural Networks

Damage identification plays an important role in structural health monitoring systems. Despite variety in damage identification methods, little attention has been paid to the seismic damage identification of foundations. When shear walls serve as the lateral load resistance system of structures, foundations may subject to the high level of concentrated moment and shear forces. Consequently, they can experience severe damage. Since such damage is often internal and not visible, visual inspections cannot identify the location and the severity of damage. Therefore, a robust method is required for damage localization and quantification of foundations. According to the concept of performance-based seismic design of structures, the seismic behavior of foundations is considered as Force-Controlled. Therefore, for damage identification of foundation, internal forces should be estimated during ground motions. In this study, for real-time seismic damage detection of foundations, a method based on artificial neural networks was proposed. A feed-forward multilayer neural network with one hidden layer was selected to map input samples to output parameters. The lateral displacements of stories were considered as the input parameters of the neural network while moment and shear force demands at critical points of foundations were taken into account as the output parameters. In order to prepare well-distributed data sets for training the neural network, several nonlinear time history analyses were carried out. The proposed method was tested on the foundation of a five-story concrete shear wall building. The obtained results revealed that the proposed method was successfully estimated moment and shear force demands at the critical points of the foundation.

Three-layer intelligence of planetary exploration wheeled mobile robots:Robint,virtint,and humint

The great success of the Sojourner rover in the Mars Pathfinder mission set off a global upsurge of planetary exploration with autonomous wheeled mobile robots(WMRs),or rovers.Planetary WMRs are among the most intelligent space systems that combine robotic intelligence(robint),virtual intelligence(virtint),and human intelligence(humint) synergetically.This article extends the architecture of the three-layer intelligence stemming from successful Mars rovers and related technologies in order to support the R&D of future tele-operated robotic systems.Double-layer human-machine interfaces are suggested to support the integration of humint from scientists and engineers through supervisory(Mars rovers) or three-dimensional(3D) predictive direct tele-operation(lunar rovers).The concept of multilevel autonomy to realize robint,in particular,the Coupled-Layer Architecture for Robotic Autonomy developed for Mars rovers,is introduced.The challenging issues of intelligent perception(proprioception and exteroception),navigation,and motion control of rovers are discussed,where the terrains' mechanical properties and wheel-terrain interaction mechanics are considered to be key.Double-level virtual simulation architecture to realize virtint is proposed.Key technologies of virtint are summarized:virtual planetary terrain modeling,virtual intelligent rover,and wheel-terrain interaction mechanics.This generalized three-layer intelligence framework is also applicable to other systems that require human intervention,such as space robotic arms,robonauts,unmanned deep-sea vehicles,and rescue robots,particularly when there is considerable time delay.

Rethinking phylogeographic structure and historical refugia in the rufous-capped babbler Cyanoderma ruficeps in light of range-wide genetic sampling and paleodistributional reconstructions

Combining ecological niche modeling with phylogeography has become a popular approach to understand how historical climate changes have created and maintained population structure. However, methodological choices in geographic extents and environmental layer sets employed in modeling may affect results and interpretations profoundly. Here, we infer range-wide phylogeographic structure and model ecological niches of Cyanoderrna ruficeps, and compare results to previous studies that examined this species across China's Mainland and Taiwan only. Use of dense taxon sampling of closely related species as outgroups question C. ruficeps monophyly. Furthermore, previously unsampled C. ruficeps populations from central Vietnam were closely related to disjunct western populations （Nepal, Tibet, Myanmar, Yunnan）, rather than to geographically proximate populations in northern Vietnam and eastern China. Phylogeographic structure is more complex than previously appreciated; niche model projections to Last Glacial Maximum climate scenarios identified larger areas of suitable conditions than previous studies, but potential distributional limits differed markedly between climate models employed and were dependent upon interpretation of non-analogous historical climate scenarios. Previously identified population expansion across central China may result from colonization from refugial distributions during the Last Interglacial, rather than the Last Glacial Maximum, as previously understood [Current Zoology 61 （5）： 901-909, 2015].

ROLE OF HARVESTING IN CONTROLLING CHAOTIC DYNAMICS IN THE PREDATOR-PREY MODEL WITH DISEASE IN THE PREDATOR

Predator prey model with harvesting is well studied. The role of disease in such system has a great importance and cannot be ignored. In this study we have considered a predator prey model with disease circulating in the predator population only and we have also considered harvesting in the prey and in the susceptible predator. We have studied the local stability, Hopf bifurcation of the model system around the equilibria. We have derived the ecological and the disease basic reproduction numbers and we have observed its importance in the community structure of the model system and in controlling disease propagation in the predator population. We have paid attention to chaotic dynamics for increasing the force of infection in the predator. Chaotic population dynamics can exhibit irregular fluctuations and violent oscillations with extremely small or large population abundances. In this study main objective is to show the role of harvesting in controlling chaotic dynamics. It is observed that reasonable harvesting on the prey and the susceptible predator prevents chaotic dynamics.

In vivo investigation of the role of SfmO2 in saframycin A biosynthesis by structural characterization of the analogue saframycin O

Saframycin A(SFM-A),a tetrahydroisoquinoline antibiotic isolated from Streptomyces lavendulae,shows potent anti-proliferation activities against a variety of tumor cell lines,and shares the core structure with ecteinascidin 743(ET-743),the anticancer drug for soft-tissue sarcoma.Characterization of the SFM-A biosynthetic gene cluster revealed three nonribosomal peptide synthetase genes and a series of genes encoding oxygenases.To investigate the function of sfmO2 gene,encoding a FAD-dependent monooxygenase/hydroxylase,we constructed the gene replacement mutant(△sfmO2) strain S.lavendulae TL2007 and the corresponding gene complementation mutant strain S.lavendulae TL2008.A novel compound,SFM-O,was isolated from the △sfmO2 replacement mutant strain and its structure was characterized by comparison to the HRMS and NMR spectra of SFM-A.These findings indicated that SfmO2 is responsible for the oxidation of ring A in the biosynthetic pathway of SFM-A,and the new compound SFM-O could be considered as an advanced intermediate in the semisynthesis of ET-743.