IR与RS-232的匹配技术

现代电子设备通常包含最新的数据通信接口，以实现更高的数据率或增进用户的便利性。红外技术(IR)是数据通信接口的一个很好例子，但有时单独使用这种最新接口还是不够的，设备还需要与采用传统接口如RS-232的老设备兼容才会被用户所接受。因此，常见的红外技术和RS-232共存于同一设备中。     

用于便携无线设备的Wireless TrenchTM技术

射频电路设计人员常用的一条经验法则是:有源器件的fT至少应为工作频率的十倍时,现代无线设备中的射频电路才会具有良好的性能.     

Curvilinear fatigue crack reliability analysis by stochastic boundary element method

In this paper, the stochastic boundary element method, which combines the mixed boundary integral equations method explored in Reference 1 with the first-order reliability method, is developed to study probabilistic fatigue crack growth. Due to the high degree of complexity and non-linearity of the response, direct differentiation coupied with the response-surface method is employed to determine the response gradient. Three random processes, the mode I and mode II. stress intensity factors and the crack direction angle, are included in the expression of the response gradient. The sensitivity of these random processes is determined using a first-order response model. An iteration scheme based on the HL-RF method² is applied to locate the most probable failure point on the limit-state surface. The accuracy and efficiency of the stochastic boundary element method are evaluated by comparing the cumulative distribution function of the fatigue life obtained with Monte Carlo simulation. The reliability index and the corresponding probability of failure are calculated for a fatigue crack growth problem with randomness in the crack geometry, defect geometry, fatigue parameters and external loads. The response sensitivity of each primary random variable at the design point is determined to show its role in the fatigue failure. The variation of each primary random variable at the design point with the change of probability of failure is also presented in numerical examples.     

Children's ascriptions of knowledge to others.

Piaget believed that young children were egocentric and would ascribe their own knowledge to another. In contrast, Wimmer, Hogrefe, and Perner (1988) found that children did not perform egocentrically when assessing another's knowledge. The present study was carried out to determine which claim was right. A familiar object was secretly placed in a box, and a child and others either looked in the box or did not look. Two of the main findings were that (a) 6-year-olds were significantly better than 3- to 4-year-olds at assessing the other's knowledge, even though both assessed the other's perception correctly (p?p?     

The role of modelling in identifying drug targets for diseases of the cell cycle.

The cell cycle is implicated in diseases that are the leading cause of mortality and morbidity in the developed world. Until recently, the search for drug targets has focused on relatively small parts of the regulatory network under the assumption that key events can be controlled by targeting single pathways. This is valid provided the impact of couplings to the wider scale context of the network can be ignored. The resulting depth of study has revealed many new insights; however, these have been won at the expense of breadth and a proper understanding of the consequences of links between the different parts of the network. Since it is now becoming clear that these early assumptions may not hold and successful treatments are likely to employ drugs that simultaneously target a number of different sites in the regulatory network, it is timely to redress this imbalance. However, the substantial increase in complexity presents new challenges and necessitates parallel theoretical and experimental approaches. We review the current status of theoretical models for the cell cycle in light of these new challenges. Many of the existing approaches are not sufficiently comprehensive to simultaneously incorporate the required extent of couplings. Where more appropriate levels of complexity are incorporated, the models are difficult to link directly to currently available data. Further progress requires a better integration of experiment and theory. New kinds of data are required that are quantitative, have a higher temporal resolution and that allow simultaneous quantitative comparison of the concentration of larger numbers of different proteins. More comprehensive models are required and must accommodate not only substantial uncertainties in the structure and kinetic parameters of the networks, but also high levels of ignorance. The most recent results relating network complexity to robustness of the dynamics provide clues that suggest progress is possible.     

Estimating the costs of occupational injury in the United States

This article estimates workplace injury costs in the U.S. These costs have been studied in less detail than most injury costs. Our methods, which mostly use regularly published data, produce order-of-magnitude estimates. Overall, workplace injuries cost the U.S. an estimated $140 billion annually. This estimate includes $17 billion in medical and emergency services, $60 billion in lost productivity, $5 billion in insurance costs, and $62 billion in lost quality of life. One sixth of the societal costs result from the 3% of workplace injuries in motor vehicle crashes. Motor vehicle costs per injury are almost 6 times the workplace injury average.     

Energy storage devices for future hybrid electric vehicles

Powertrain hybridization as well as electrical energy management are imposing new requirements on electrical storage systems in vehicles. This paper characterizes the associated vehicle attributes and, in particular, the various levels of hybrids. New requirements for the electrical storage system are derived, including: shallow-cycle life, high dynamic charge acceptance particularly for regenerative braking and robust service life in sustained partial-state-of-charge usage. Lead/acid, either with liquid or absorptive glass-fibre mat electrolyte, is expected to remain the predominant battery technology for 14 V systems, including micro-hybrids, and with a cost-effective battery monitoring system for demanding applications. Advanced AGM batteries may be considered for mild or even medium hybrids once they have proven robustness under real-world conditions, particularly with respect to cycle life at partial-states-of-charge and dynamic charge acceptance. For the foreseeable future, NiMH and Li-ion are the dominating current and potential battery technologies for higher-functionality HEVs. Li-ion, currently at development and demonstration stages, offers attractive opportunities for improvements in performance and cost. Supercapacitors may be considered for pulse power applications. Aside from cell technologies, attention to the issue of system integration of the battery into the powertrain and vehicle is growing. Opportunities and challenges for potential “battery pack” system suppliers are discussed.     

EVAPORATION FROM POROUS MEDIA: A CAPILLARY MODEL OF A PENETRATING FRONT

A capillary tube model was solved to investigate the influence of mass transfer coefficient, temperature, and front depth on the evaporation rate during the penetrating-front period of water-filled porous media dried in hot air. The results show that increasing the flow rate of the drying air is not so efficient as increasing the sample temperature. Due to attenuating diffusion rate, the rate of liquid front migration decreases with time. The calculations explain the falling rate period behavior of sandstone heated at 121°C. Trends depicted by the model may be useful for the design of heating conditions for drying processes.