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11.
We describe a middleware framework for the adaptive delivery of context information to context-aware applications. The framework abstracts the applications from the sensors that provide context. Further applications define utility functions on the quality of context attributes that describe the context providers. Then, given multiple alternatives for providing the same type of context, the middleware applies the utility function to each alternative and choose the one with maximum utility. By allowing applications to delegate the selection of context source to the middleware, our middleware can implement autonomic properties, such as self-configuration when new context providers appear and resilience to failures of context providers.
  相似文献   
12.
We define a concurrent mobile system as one where independently executing components may migrate through some space during the course of the computation, and where the pattern of connectivity among the components changes as they move in and out of proximity. The definition is general enough to encompass a system of mobile hosts moving in physical space as well as a system of migrating software agents implemented on a set of possibly non-mobile hosts. In this paper, we present Mobile UNITY, a notation for expressing mobile computations and a logic for reasoning about their temporal properties. Our goal is to find a minimalist model of mobile computation that will allow us to express mobile components in a modular fashion and to reason formally about the possible behaviors of a system composed from mobile components. A simplified serial communication protocol among components which can move in space serves as an illustration for the notation.  相似文献   
13.
This review provides a discussion of cancer risk assessment methodology pertinent to developing a strategy for extremely low frequency electric and magnetic fields (EMF). Approaches taken for chemical agents or ionizing radiation in six key topic areas are briefly reviewed, and then those areas are examined from the perspective of EMF, identifying issues to be addressed in developing a risk assessment strategy. The following recommendations are offered: 1) risk assessment should be viewed as an iterative process that informs an overall judgment as to health risk and consists of a complex of related activities incorporating both positive and negative data, tumor and nontumor end points, and human and nonhuman sources of information; 2) a hazard identification resulting in a conclusion of weak or null effects, such as may be associated with EMF, will need to assign significant weight to animal cancer bioassays conducted under defined exposure conditions as well as to human epidemiologic studies; 3) a default factor to account for possible age differences in sensitivity to carcinogenesis should be included in an EMF risk assessment; 4) lack of evidence of dose response and the apparent lack of DNA reactivity of EMF suggest that a safety (or uncertainty) factor or margin of exposure type of risk characterization may be most appropriate; and 5) an EMF risk assessment should permit at least tentative conclusions to be reached as to the limits of carcinogenic risk from exposure to EMF, and should also define an efficient research agenda aimed at clarifying uncertainties appropriate to a more complete assessment.  相似文献   
14.
In-circuit emulation is the ability to imitate electrically a target microprocessor, responding to system inputs or instructions, and producing accurately the expected outputs or responses to the instructions. A modular building block approach to microprocessor-based design is given, the Slave Emulator Control Unit (SECU) is described and its flexibility shown.  相似文献   
15.
Abstract— High‐dynamic‐range (HDR) image capture and display has become an important engineering topic. The discipline of reproducing scenes with a high range of luminances has a five‐century history that includes painting, photography, electronic imaging, and image processing. HDR images are superior to conventional images. There are two fundamental scientific issues that control HDR image capture and reproduction. The first is the range of information that can be measured using different techniques. The second is the range of image information that can be utilized by humans. Optical veiling glare severely limits the range of luminance that can be captured and seen. It is the improved quantization of digital data and the preservation of the scene's spatial information that causes the improvement in quality in HDR reproductions.  相似文献   
16.
Abstract— Intraocular glare and simultaneous contrast control appearance in high‐dynamic‐range (HDR) images. This paper describes unique test targets that simulate real images. These targets change the HDR range by 500 times, without significantly changing the veiling glare on the retina. As well, these targets have nearly constant simultaneous contrast. The range of appearances possible from HDR images with different average luminances were measured. The targets displayed a maximum luminance range of 5.4 log units. Using magnitude estimates (MagEst) of appearances, the relationship between luminance and lightness from white to black was measured. With one exception, only small changes in appearance with large changes in dynamic range were found. It was also found that appearance was scene‐dependent. The same dark grays (MagEst = 10) were observed with luminances of 10, 4.2, 1.1, and 0.063, depending on the percentage of white area in the surround. Glare from more white increases the retinal luminance of the test areas. Simultaneous contrast counteracts glare by making the appearance range (white‐black) with a much smaller range of luminances. Appearance is controlled by both the optical scattered light and the spatial processing. A single tone‐scale function of luminance cannot describe appearance controlled by scatter and spatial processing.  相似文献   
17.
Pronunciation performance under speeded conditions was examined for various kinds of letter strings, including pseudohomophones (e.g., TRAX), their real word counterparts (e.g., TRACKS), and a set of nonword controls (e.g., PRAX). Experiment 1 yielded a pronunciation advantage for the pseudohomophones relative to the controls, which was largest among items having few or no orthographic neighbors. Experiment 2 ruled out an account of the pseudohomophone advantage based on differences between pseudohomophones and controls in initial phonemes. Experiment 3 established the existence of a large frequency effect on pronunciation of the base words themselves. These results suggest that whole word representations in the phonological output lexicon are consulted in the course of assembling a pronunciation and that representations in a phonological output lexicon are insensitive to word frequency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
18.
OBJECTIVE: To describe the changes in the characteristics of human immunodeficiency virus (HIV)-related deaths in children with perinatally acquired infection. METHODS: A retrospective review of all deaths that occurred in HIV-infected children managed at The New York Hospital-Program for Children with AIDS during a 7-year period from January, 1990, to December, 1996. Differences in the characteristics at death between 15 children who died in 1990 and 10 children who died in 1996 were analyzed. RESULTS: Fifty-eight deaths in our cohort of HIV-infected children were identified during the 7-year period. The mean age at death was 4.43 years. Sixty-nine percent of children were black, 55% were male and 94% were receiving Medicaid. The mean weight/age Z score was -3.9 and the mean CD4 index was 0.067 with 65% having <50 CD4 cells/microl at the time of death (TOD). The most common organ/organ systems to be involved at the TOD were lung (78%) and central nervous system (61%). Mycobacterium avium complex (MAC) was the most common isolate at the TOD (26%) followed by Pneumocystis carinii (20%) and Pseudomonas aeruginosa (17%). The leading non-infectious cause of death was cardiac failure (9%). Comparison of the characteristics at the TOD between 1990 and 1996 revealed significant differences in mean age (2.1 vs. 9.2 years, P < 0.0001), mean CD4 count index (0.18 vs. 0.02, P < 0.03), mean number of organ/organ system involvement (3.9 vs. 5.9, P < 0.05), percent receiving antiretroviral therapy (33% vs. 70%, P < 0.02), mean number of years receiving antiretroviral therapy (0.88 vs. 3.86 years, P < 0.01), percent receiving P. carinii pneumonia prophylaxis (27% vs. 100%, P < 0.001), percent receiving MAC prophylaxis/therapy (0% vs. 100%, P < 0.0001), and cause of death from P. carinii pneumonia (53% vs. 0%, P < 0.01). CONCLUSIONS: Compared with children who died in 1990, HIV-infected children who died in 1996 were significantly older, more lymphopenic and more likely to have a greater number of organ system involvements and to have received antiviral therapy and antimicrobial prophylaxis. In 1996 no child died of P. carinii pneumonia. In 1996 MAC and P. aeruginosa were the two most important opportunistic infections causing death. These changes in the characteristics at death will warrant review of resources used in treating these children and may be critical in advising parents and care givers about the prognosis of this chronic infection.  相似文献   
19.
On the basis of K. Stenner's (2005) authoritarian dynamic theory, it was hypothesized that the number of death sentences and executions would be higher in more threatened conservative states than in less threatened conservative states, and would be lower in more threatened liberal states than in less threatened liberal states. Threat was based on state homicide rate, violent crime rate, and non-White percentage of population. Conservatism was based on state voter ideological identification, Democratic and Republican Party elite liberalism-conservatism, policy liberalism-conservatism, religious fundamentalism, degree of economic freedom, and 2004 presidential election results. For 1977-2004, with controls for state population and years with a death penalty provision, the interactive hypothesis received consistent support using the state conservatism composite and voter ideological identification alone. As well, state conservatism was related to death penalties and executions, but state threat was not. The temporal stability of the findings was demonstrated with a split-half internal replication using the periods 1977-1990 and 1991-2004. The interactive hypothesis and the results also are discussed in the context of other threat-authoritarianism theories and terror management theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
20.
Dietary isothiocyanates are a group of promising chemopreventive agents obtained primarily from cruciferous vegetables. Due to their potent chemopreventive and/or anti-cancer activities, there is a growing interest in assessing dietary isothiocyanate exposure and its impact on human health. Using the HPLC-based cyclocondensation assay, the current study measured total isothiocyanate yield from raw cruciferous vegetables. A total of 73 samples comprising nine types of cruciferous vegetables were analyzed. We observed a wide range of isothiocyanate content across the individual vegetables with an average level of 16.2 μmol/100 g wet weight, ranging from 1.5 μmol in raw cauliflower to 61.3 μmol in raw mustard greens. The data represent the maximum amount of isothiocyanates released from the intake of raw cruciferous vegetables. Given that the vegetables assayed in this study include the most commonly consumed cruciferous vegetables in western diets, the data may be particularly useful in estimation of dietary isothiocyanate exposure in these populations. However, due to the variation observed within each vegetable, biomarkers such as urinary isothiocyanate level may be necessary for accurate estimation of individual exposure.  相似文献   
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