神经能量

2010年,美国艺术家Warren Neidich的研究项目Neuropower(神经能量)获得了弗鲁塞尔理论奖。神经能量项目尝试使用哲学的方法对艺术与文化进行分析,在今天这个艺术文化杂糅的社会里,艺术产物如何诠释自身,艺术家应如何应对接踵而来的变化,如何重塑人类的精神,是神经能量项目研究的主题。     

Mechanics of Hertzian cracking

We review the progress made at Oxford in recent years in the quantification of surface damage of ceramics by application of the Hertzian indentation test. This includes using micro-indenters to search out the surface density of flaws, as well as assessing the size distribution. Many analytical tools have been developed for processing the data obtained, including refined methods of analysing the cone crack using distributed strain nuclei techniques which accurately model the behaviour of cracks in steep stress gradients, and in particular the use of eigenstrain methods to quantify the growth of an initial surface thumbnail crack. The influence of elastic mismatch on the state of stress induced by the indenter is also discussed, and it is shown that the use of an indenter more compliant than the substrate leads to a more extensive annular zone of tension, thereby encouraging the formation of a ring crack. The remaining problem is an accurate analysis of the full cone crack itself, which has already been analysed using a special finite element formulation, and which is currently being re-examined by the use of axi-symmetric ring nuclei: this promises to provide a more complete and precise solution.     

应用Micromine软件实现矿山井巷工程的可视化管理

井巷工程工作面的可视化管理对矿山安全生产和品位控制具有重要的意义。从井巷工程施工设计说明中提取相关参数并结合地质编录数据建立了满足井巷工程工作面实时监控所需的数学模型,使用Excel完成数学模型的计算求解过程和建立包含施工进展和地质特征等信息的井巷工程工作面数据表格。基于所获得数据运用Micromine矿山软件建立蔡家营锌矿井巷工程工作面施工进展的地质数据库,结合Micromine软件中可视化功能实现井巷工程工作面的可视化管理。井巷工程的工作面样品及其硐壁采样都可应用Micromine钻孔数据库进行管理,可结合钻探样品对仅基于钻探样品构建的矿块模型（block model）进行局部修正,进而能获得比较逼真的矿块模型。     

Incidence of Clostridium perfringens in commercially produced cured raw meat product mixtures and behavior in cooked products during chilling and refrigerated storage

A total of 445 whole-muscle and ground or emulsified raw pork, beef, and chicken product mixtures acquired from industry sources were monitored over a 10-month period for vegetative and spore forms of Clostridium perfringens. Black colonies that formed on Shahidi-Ferguson perfringens (SFP) agar after 24 h at 37 degrees C were considered presumptive positive. Samples that were positive after a 15-min heat shock at 75 degrees C were considered presumptive positive for spores. Of 194 cured whole-muscle samples, 1.6% were positive; spores were not detected from those samples. Populations of vegetative cells did not exceed 1.70 log10 CFU/g and averaged 1.56 log10 CFU/g. Of 152 cured ground or emulsified samples, 48.7% were positive, and 5.3% were positive for spores. Populations of vegetative cells did not exceed 2.72 log10 CFU/g and averaged 1.98 log10 CFU/g; spores did not exceed 2.00 log10 CFU/g and averaged 1.56 log10 CFU/g. Raw bologna (70% chicken), chunked ham with emulsion, and whole-muscle ham product mixtures were inoculated with C. perfringens spores (ATCC 12916, ATCC 3624, FD1041, and two product isolates) to ca. 3.0 log10 CFU/g before being subjected either to thermal processes mimicking cooking and chilling regimes determined by in-plant temperature probing or to cooking and extended chilling regimes. Populations of C. perfringens were recovered on SFP from each product at the peak cook temperatures, at 54.4, 26.7, and 7.2 degrees C, and after up to 14 days of storage under vacuum at 4.4 degrees C. In each product, populations remained relatively unchanged during chilling from 54.4 to 7.2 degrees C and declined slightly during refrigerated storage. These findings indicate processed meat products cured with sodium nitrite are not at risk for the growth of C. perfringens during extended chilling and cold storage.     

Characterization of an alternative oxidase activity of Histoplasma capsulatum

Histoplasma capsulatum possesses a branched mitochondrial electron transport chain, with both cyanide-sensitive and -insensitive oxygen-consuming activities. The latter, carried out by a single subunit enzyme termed 'alternative oxidase', is the focus of this report. AOX1 cDNA clones were isolated and direct evidence that the cDNA ORF encodes functional alternative oxidase is reported. Also reported are the generation of an antiserum to the AOX1 protein product, and specific detection in vivo of the mRNA and protein products of the AOX1 gene. Finally, initial studies of regulation of H. capsulatum AOX1 gene expression demonstrated that RNA abundance was increased after hydrogen peroxide-mediated oxidative stress and after inhibition of mitochondrial electron transport enzymes with antimycin A or sodium cyanide. This pattern of regulation is consistent with the hypothesis that alternative oxidase contributes to survival of H. capsulatum after oxidative or metabolic stress and may be important for virulence of this pathogenic organism. The GenBank Accession Nos for the cDNA sequences reported in this paper are AF133236, AF133237 (AOX1).     

Local wind-energy potential for the city of Guelph,Ontario (Canada)

Municipalities around the world are using community energy plans (CEPs) to drive progress towards a more sustainable energy future. Many recognize the supply of local and renewable energy as a crucial component of a resilient future including the potential use of wind power generation. The city of Guelph (Ontario, Canada) included wind energy as a component of its CEP. The goal of this work was to estimate the potential for wind power generation within the municipal boundaries of this city. This paper summarizes the methodology used and results obtained with site and meteorological data, wind maps, and turbine power curves. The methodology relies on the use of a geographically uniform array of turbines, spread throughout the community. An array of utility-scale turbines could potentially generate 29% of Guelph’s 2005 total electricity demand, whereas one consisting of small-scale turbines could achieve 10% of that demand.     

Relative demand by double-crested cormorants and anglers for fish production from lakes on Manitoulin Island,Lake Huron

The magnitude of angler harvest (kg·ha^− 1·yr^− 1) and cormorant consumption (kg·ha^− 1·yr^− 1) were compared for a set of lakes (N = 11) on Manitoulin Island. Empirical models relating total phosphorus to total fish production as well as production to body mass were used to scope the possible range of fish production and to partition production among small, medium and large size segments of fish populations, respectively. Medium (66–112 g) and large (> 200 g) size segments were defined as size categories targeted by cormorants (stomach diet analysis) and anglers (creel interviews), respectively. Angling effort and cormorant density were estimated from aerial surveys of the lake set during the open water season and for anglers during the winter ice-fishing season. Results showed that anglers harvested almost all large fish production, assuming the mean total fish production model, and 43% of large fish production under the more optimistic upper 80% prediction limit of total fish production. Cormorant consumption of medium fish production was less (39% using mean regression model; 15% using upper 80% prediction model) than angler consumption of large fish production. Anglers therefore imposed more population stress on their preferred sizes of fish than cormorants imposed on their preferred sizes of fish. Population stress was increased when cormorant consumption of medium size fish was discounted from contributing to large fish production. Angler harvest near (or above) sustainable yield levels will be exacerbated and appear as a fish collapse when cormorants consume fish production destined for fish size segments preferred by anglers.     

Asymptotic tracking by a reinforcement learning-based adaptive critic controller

Adaptive critic (AC) based controllers are typically discrete and/or yield a uniformly ultimately bounded stability result because of the presence of disturbances and unknown approximation errors. A continuous-time AC controller is developed that yields asymptotic tracking of a class of uncertain nonlinear systems with bounded disturbances. The proposed AC-based controller consists of two neural networks (NNs) – an action NN, also called the actor, which approximates the plant dynamics and generates appropriate control actions; and a critic NN, which evaluates the performance of the actor based on some performance index. The reinforcement signal from the critic is used to develop a composite weight tuning law for the action NN based on Lyapunov stability analysis. A recently developed robust feedback technique, robust integral of the sign of the error (RISE), is used in conjunction with the feedforward action neural network to yield a semiglobal asymptotic result. Experimental results are provided that illustrate the performance of the developed controller.     

Understanding civic engagement behaviour on Facebook from a social capital theory perspective

This paper applies the social capital theory to construct a model for investigating the factors that influence online civic engagement behaviour on Facebook. While there is promising evidence that people are making concerted efforts to adopt Facebook to address social issues, research on their civic behaviour from a social capital viewpoint in the social media context remains limited. This study introduces new insights into how Facebook is shaping the landscape of civic engagement by examining three dimensions of social capital – social interaction ties (structural), trust (relational), and shared languages and vision (cognitive). The study contends that these dimensions will influence individuals’ online civic engagement behaviour on Facebook. We also argue that social interaction ties can engender trust, and shared languages and vision among its members, and that shared languages and vision can increase trust among Facebook members. Empirical data collected from 1233 Facebook users provide support for the proposed model. The results help in identifying the motivation underlying the online civic engagement behaviour of individuals in a public virtual community. The implications for theory and practice and future research directions are discussed.     

A Dynamical Model of Visually-Guided Steering,Obstacle Avoidance,and Route Selection

Using a biologically-inspired model, we show how successful route selection through a cluttered environment can emerge from on-line steering dynamics, without explicit path planning. The model is derived from experiments on human walking performed in the Virtual Environment Navigation Lab (VENLab) at Brown. We find that goals and obstacles behave as attractors and repellors of heading, the direction of locomotion, for an observer moving at a constant speed. The influence of a goal on turning rate increases with its angle from the heading and decreases exponentially with its distance; the influence of an obstacle decreases exponentially with angle and distance. Linearly combining goal and obstacle terms allows us to simulate paths through arbitrarily complex scenes, based on information about obstacles in view near the heading direction and a few meters ahead. We simulated the model on a variety of scene configurations and observed generally efficient routes, and verified this behavior on a mobile robot. Discussion focuses on comparisons between dynamical models and other approaches, including potential field models and explicit path planning. Effective route selection can thus be performed on-line, in simple environments as a consequence of elementary behaviors for steering and obstacle avoidance.