Aluminum hierarchical tubular structure inspired by skeletal muscle tissues::Quasi-static and low-velocity impact testing

This paper investigates experimentally and numerically the protective capability of skeletal muscle-inspired hierarchical tubular (MHT) structures made of aluminum under both quasi-static and dynamic impact conditions. In the quasi-static compression tests, structures with higher hierarchical order were more deformable and had lower contact force. Dynamic impact tests were conducted for the first time on MHT specimens of three different hierarchical orders using a drop tower facility. The results indicated a significant reduction in both the maximum and mean contact forces on the protected body when shielded by the second- and third-order MHT structures. This suggested that increasing the hierarchical order of the structure effectively enhanced impact protection capability. Numerical models were developed using ABAQUS/Explicit to accurately reproduce the deformation process and force-time functions of the dynamic impact scenarios. A parametric study found that the impact resistance performance of the MHT structures was robust against various impact velocities and masses

Spatiotemporal distribution of malaria and the association between its epidemic and climate factors in Hainan, China

<p>Abstract</p> <p>Background</p> <p>Hainan is one of the provinces most severely affected by malaria epidemics in China. The distribution pattern and major determinant climate factors of malaria in this region have remained obscure, making it difficult to target countermeasures for malaria surveillance and control. This study detected the spatiotemporal distribution of malaria and explored the association between malaria epidemics and climate factors in Hainan.</p> <p>Methods</p> <p>The cumulative and annual malaria incidences of each county were calculated and mapped from 1995 to 2008 to show the spatial distribution of malaria in Hainan. The annual and monthly cumulative malaria incidences of the province between 1995 and 2008 were calculated and plotted to observe the annual and seasonal fluctuation. The Cochran-Armitage trend test was employed to explore the temporal trends in the annual malaria incidences. Cross correlation and autocorrelation analyses were performed to detect the lagged effect of climate factors on malaria transmission and the auto correlation of malaria incidence. A multivariate time series analysis was conducted to construct a model of climate factors to explore the association between malaria epidemics and climate factors.</p> <p>Results</p> <p>The highest malaria incidences were mainly distributed in the central-south counties of the province. A fluctuating but distinctly declining temporal trend of annual malaria incidences was identified (Cochran-Armitage trend test <it>Z </it>= -25.14, <it>P </it>< 0.05). The peak incidence period was May to October when nearly 70% of annual malaria cases were reported. The mean temperature of the previous month, of the previous two months and the number of cases during the previous month were included in the model. The model effectively explained the association between malaria epidemics and climate factors (<it>F </it>= 85.06, <it>P </it>< 0.05, adjusted <it>R </it>²= 0.81). The autocorrelations of the fitting residuals were not significant (<it>P </it>> 0.05), indicating that the model extracted information sufficiently. There was no significant difference between the monthly predicted value and the actual value (<it>t </it>= -1.91, <it>P </it>= 0.08). The <it>R </it>²for predicting was 0.70, and the autocorrelations of the predictive residuals were not significant (<it>P </it>> 0.05), indicating that the model had a good predictive ability.</p> <p>Discussion</p> <p>Public health resource allocations should focus on the areas and months with the highest malaria risk in Hainan. Malaria epidemics can be accurately predicted by monitoring the fluctuations of the mean temperature of the previous month and of the previous two months in the area. Therefore, targeted countermeasures can be taken ahead of time, which will make malaria surveillance and control in Hainan more effective and simpler. This model was constructed using relatively long-term data and had a good fit and predictive validity, making the results more reliable than the previous report.</p> <p>Conclusions</p> <p>The spatiotemporal distribution of malaria in Hainan varied in different areas and during different years. The monthly trends in the malaria epidemics in Hainan could be predicted effectively by using the multivariate time series model. This model will make malaria surveillance simpler and the control of malaria more targeted in Hainan.</p

Dynamic behaviour of lightweight automotive materials

The PhD research studied the dynamic behaviour of three types of lightweight automotive materials including aluminium foams, aluminium honeycombs and twinning induced plasticity steels. The strain rate sensitivity, strength enhancement and energy absorption of these materials under dynamic loadings were extensively studied. Analytical models were proposed based on the physical phenomenon observed in experiments. The research presented valuable experimental data and theoretical models for the optimized design of new lightweight vehicle structures. New structures made by these materials have excellent energy absorption capacity in a car crash and, therefore, protect passengers

Finite element analysis of the dynamic behavior of aluminum honeycombs

In this paper, a finite element model was built using ANSYS/LS-DYNA to study the effect of strain rate on the dynamic out-of-plane plateau stress of aluminum honeycombs under constant velocity impact. The strain rates vary from 102 to 104 s-1. It has been found that the t/l ratio (wall thickness to edge length ratio) and strain rate have great influence on deformation pattern and plateau stress. The effect of strain rate on the plateau stress under high velocity impact was found to be different from that under low strain rate compression. The threshold impact velocity is approximately 100 m/s for the aluminum honeycomb studied

Well-defined nanostructures for electrochemical energy conversion and storage

Electrochemical energy conversion and storage play crucial roles in meeting the increasing demand for renewable, portable, and affordable power supplies for society. The rapid development of nanostructured materials provides an alternative route by virtue of their unique and promising effects emerging at nanoscale. In addition to finding advanced materials, structure design and engineering of electrodes improves the electrochemical performance and the resultant commercial competitivity. Regarding the structural engineering, controlling the geometrical parameters (i.e., size, shape, hetero-architecture, and spatial arrangement) of nanostructures and thus forming well-defined nanostructure (WDN) electrodes have been the central aspects of investigations and practical applications. This review discusses the fundamental aspects and concept of WDNs for energy conversion and storage, with a strong emphasis on illuminating the relationship between the structural characteristics and the resultant electrochemical superiorities. Key strategies for actualizing well-defined features in nanostructures are summarized. Electrocatalysis and photoelectrocatalysis (for energy conversion) as well as metal-ion batteries and supercapacitors (for energy storage) are selected to illustrate the superiorities of WDNs in electrochemical reactions and charge carrier transportation. Finally, conclusions and perspectives regarding future research, development, and applications of WDNs are discussed

EyeScreen: A Vision-Based Desktop Interaction System

EyeScreen provides a natural HCI interface with vision-based hand tracking and gesture recognition techniques. Multi-view video images captured from two cameras facing a computer screen are used to track and recognize finger and hand motions. Finger tracking is achieved by skin color detection and particle filtering, and is greatly enhanced by the proposed screen background subtraction method that removes the screen images in advance. Finger click on the screen can also be detected from multi-view information. Gesture recognition based on binocular vision is presented to improve the recognition rate. The experimental results show that EyeScreen is able to perform natural and robust interaction in desktop environment

EyeScreen: A Vision-Based Desktop Interaction System

EyeScreen provides a natural HCI interface with vision-based hand tracking and gesture recognition techniques. Multi-view video images captured from two cameras facing a computer screen are used to track and recognize finger and hand motions. Finger tracking is achieved by skin color detection and particle filtering, and is greatly enhanced by the proposed screen background subtraction method that removes the screen images in advance. Finger click on the screen can also be detected from multi-view information. Gesture recognition based on binocular vision is presented to improve the recognition rate. The experimental results show that EyeScreen is able to perform natural and robust interaction in desktop environment

Crush responses of composite cylinder under quasi-static and dynamic loading

Despite the abundance of studies investigating the performance of composite structures under crush loading, disagreement remains in the literature regarding the effect of increased strain rate on the crush response. This study reports an experimental investigation of the behaviour of a carbon-epoxy composite energy absorber under static and dynamic loading with a strain rate of up to 100s-1. Consistent damage modes and measured force responses were obtained in samples tested under the same strain rate. The energy absorption was found to be independent of strain rate as the total energy absorption appeared to be largely associated with fibre-dominated fracture, which is independent of strain rate within the studied range. The results from this study are beneficial for the design of energy absorbing structures

Key Disaster-Causing Factors Chains on Urban Flood Risk Based on Bayesian Network

Drivers of urban flood disaster risk may be related to many factors from nature and society. However, it is unclear how these factors affect each other and how they ultimately affect the risk. From the perspective of risk uncertainty, flood inundation risk is considered to be the probability of inundation consequences under the influence of various factors. In this paper, urban flood inundation risk assessment model is established based on Bayesian network, and then key disaster-causing factors chains are explored through influence strength analysis. Jingdezhen City is selected as study area, where the flood inundation probability is calculated, and the paths of these influential factors are found. The results show that the probability of inundation in most areas is low. Risk greater than 0.8 account for about 9%, and most of these areas are located in the middle and southern section of the city. The influencing factors interact with each other in the form of factor chain and, finally, affect the flood inundation. Rainfall directly affects inundation, while river is the key factor on inundation which is influenced by elevation and slope. In addition, in the chain of socio-economic factors, the population will determine the pipe density through affecting gross domestic product (GDP), and lead to the inundation. The approach proposed in this study can be used to find key disaster-causing factors chains, which not only quantitatively reveal the formation of risks but also provide reference for early warning