A planning method for safe interaction between human arms and robot manipulators

This paper presents a planning method based on mapping moving obstacles into C-space for safe interaction between human arms and robot manipulators. In pre-processing phase, a hybrid distance metric is defined to select neighboring sampled nodes in C-space to construct a roadmap. Then, two kinds of mapping are constructed to determine invalid and dangerous edges in the roadmap for each basic cell decomposed in workspace. For updating the roadmap when an obstacle is moving, basic cells covering the obstacle's surfaces are mapped into the roadmap by using new positions of the surfaces points sampled on the obstacle. In query phase, in order to predict and avoid coming collisions and reach the goal efficiently, an interaction strategy with six kinds of planning actions of searching, updating, walking, waiting, dodging and pausing are designed. Simulated experiments show that the proposed method is efficient for safe interaction between two working robot manipulators and two randomly moving human arms.Computer Science, Artificial IntelligenceRoboticsCPCI-S(ISTP)

Quantum simulation of low-temperature metallic liquid hydrogen

The melting temperature of solid hydrogen drops with pressure above ~65 GPa, suggesting that a liquid state might exist at low temperatures. It has also been suggested that this low-temperature liquid state might be non-molecular and metallic, although evidence for such behaviour is lacking. Here we report results for hydrogen at high pressures using ab initio methods, which include a description of the quantum motion of the protons. We determine the melting temperature as a function of pressure and find an atomic solid phase from 500 to 800 GPa, which melts at <200 K. Beyond this and up to 1,200 GPa, a metallic atomic liquid is stable at temperatures as low as 50 K. The quantum motion of the protons is critical to the low melting temperature reported, as simulations with classical nuclei lead to considerably higher melting temperatures of ~300 K across the entire pressure range considered

Prevalence and trend of hepatitis C virus infection among blood donors in Chinese mainland: a systematic review and meta-analysis

<p>Abstract</p> <p>Background</p> <p>Blood transfusion is one of the most common transmission pathways of hepatitis C virus (HCV). This paper aims to provide a comprehensive and reliable tabulation of available data on the epidemiological characteristics and risk factors for HCV infection among blood donors in Chinese mainland, so as to help make prevention strategies and guide further research.</p> <p>Methods</p> <p>A systematic review was constructed based on the computerized literature database. Infection rates and 95% confidence intervals (95% CI) were calculated using the approximate normal distribution model. Odds ratios and 95% CI were calculated by fixed or random effects models. Data manipulation and statistical analyses were performed using STATA 10.0 and ArcGIS 9.3 was used for map construction.</p> <p>Results</p> <p>Two hundred and sixty-five studies met our inclusion criteria. The pooled prevalence of HCV infection among blood donors in Chinese mainland was 8.68% (95% CI: 8.01%-9.39%), and the epidemic was severer in North and Central China, especially in Henan and Hebei. While a significant lower rate was found in Yunnan. Notably, before 1998 the pooled prevalence of HCV infection was 12.87% (95%CI: 11.25%-14.56%) among blood donors, but decreased to 1.71% (95%CI: 1.43%-1.99%) after 1998. No significant difference was found in HCV infection rates between male and female blood donors, or among different blood type donors. The prevalence of HCV infection was found to increase with age. During 1994-1995, the prevalence rate reached the highest with a percentage of 15.78% (95%CI: 12.21%-19.75%), and showed a decreasing trend in the following years. A significant difference was found among groups with different blood donation types, Plasma donors had a relatively higher prevalence than whole blood donors of HCV infection (33.95% <it>vs </it>7.9%).</p> <p>Conclusions</p> <p>The prevalence of HCV infection has rapidly decreased since 1998 and kept a low level in recent years, but some provinces showed relatively higher prevalence than the general population. It is urgent to make efficient measures to prevent HCV secondary transmission and control chronic progress, and the key to reduce the HCV incidence among blood donors is to encourage true voluntary blood donors, strictly implement blood donation law, and avoid cross-infection.</p

The effects of substrate temperature on the structure and properties of ZnO films prepared by pulsed laser deposition

ZnO thin films were prepared by pulsed laser deposition (PLD) on glass substrates with growth temperature from room temperature (RT) to 500 degrees C. The effects of substrate temperature on the structural and optical properties of ZnO films have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission spectra, and RT photoluminescence (PL) measurements. The results showed that crystalline and (0 0 2)-oriented ZnO films were obtained at all substrate temperatures. As the substrate temperature increased from RT to 500 degrees C, the ratio of grain size in height direction to that in the lateral direction gradually decreased. The same grain size in two directions was obtained at 200 degrees C, and the size was smallest in all samples, which may result in maximum E, and E-0 of the films. UV emission was observed only in the films grown at 200 degrees C, which is probably because the stoichiometry of ZnO films was improved at a suitable substrate temperature. It was suggested that the UV emission might be related to the stoichiometry in the ZnO film rather than the grain size of the thin film. (c) 2007 Elsevier Ltd. All rights reserved