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排序方式: 共有1750条查询结果,搜索用时 0 毫秒
91.
Jane Ndungu Bruce C. Monger Denie C.M. Augustijn Suzanne J.M.H. Hulscher Nzula Kitaka Jude M. Mathooko 《International journal of remote sensing》2013,34(22):8142-8155
Restoration of the ecosystem services and functions of lakes requires an understanding of the turbidity dynamics in order to arrive at informed environmental management decisions. The understanding of the spatio-temporal dynamics of turbidity requires frequent monitoring of the turbidity components such as chlorophyll-a concentration. In this study, we explored the use of Moderate Resolution Imaging Spectroradiometer Aqua (MODIS-Aqua) satellite data in studying the spatio-temporal changes in chlorophyll-a concentration in Lake Naivasha, a turbid tropical system. The temporal trend of chlorophyll-a concentration over the study period in the lake was also evaluated. The temporal trend assessment was achieved through the removal of periodic seasonal interference using Seasonal-Trend decomposition based on the LOESS (Local Regression) procedure. The resultant chlorophyll-a concentration maps derived from MODIS-Aqua satellite data give an indication of the monthly spatial variation in chlorophyll-a concentration from 2002 to 2012. The results of regression analyses between satellite-derived chlorophyll-a and in situ measurements reveal a high level of precision, but with a measureable bias with the satellite underestimating actual in situ measurements (R2 = 0.65, P < 0.001). Although the actual values of the chlorophyll-a concentrations are underestimated, the significant relationship between satellite-derived chlorophyll-a and in situ measurements provides reliable information for studying spatial variations and temporal trends. In 2009 and 2010, it was difficult to detect chlorophyll-a from the MODIS-Aqua imagery, and this coincided with a period of the lowest water levels in Lake Naivasha. An inverse relationship between de-seasoned water level and chlorophyll-a concentration was evident. This study shows that MODIS-Aqua satellite data provide useful information on the spatio-temporal variations in Lake Naivasha, which is useful in establishing general trends that are more difficult to determine through routine ground measurements. 相似文献
92.
Moriguchi CS Carnaz L Veiersted KB Hanvold TN Hæg LB Hansson GÅ Cote Gil Coury HJ 《Applied ergonomics》2013,44(1):86-92
The aim of this study is to record, objectively describe and compare working postures of Brazilian and Norwegian construction electricians. Postures of the upper arms, head, and neck during work and breaks were quantified by means of inclinometry for a representative sample of 12 Brazilian and 12 Norwegian electricians in the construction industry during a full work-shift. Despite that differences were found between specific work-related factors, Brazilian and Norwegian workers revealed a high and very similar level and pattern of postures for all evaluated body regions, suggesting that results could be extrapolated to other electricians. Upper arm elevation was high and similar for both groups and head flexion and extension was pronounced compared to other occupations. Thus, extreme postures were identified for construction electricians in both countries, with similar exposure pattern also for defined tasks (planning, support and wiredraw), suggesting that this job is risky regardless organizational differences. 相似文献
93.
Stout Julie C.; Paulsen Jane S.; Queller Sarah; Solomon Andrea C.; Whitlock Kathryn B.; Campbell J. Colin; Carlozzi Noelle; Duff Kevin; Beglinger Leigh J.; Langbehn Douglas R.; Johnson Shannon A.; Biglan Kevin M.; Aylward Elizabeth H. 《Canadian Metallurgical Quarterly》2011,25(1):1
Objective: PREDICT-HD is a large-scale international study of people with the Huntington disease (HD) CAG-repeat expansion who are not yet diagnosed with HD. The objective of this study was to determine the stage in the HD prodrome at which cognitive differences from CAG-normal controls can be reliably detected. Method: For each of 738 HD CAG-expanded participants, we computed estimated years to clinical diagnosis and probability of diagnosis in 5 years based on age and CAG-repeat expansion number (Langbehn, Brinkman, Falush, Paulsen, & Hayden, 2004). We then stratified the sample into groups: NEAR, estimated to be ≤9 years; MID, between 9 and 15 years; and FAR, ≥15 years. The control sample included 168 CAG-normal participants. Nineteen cognitive tasks were used to assess attention, working memory, psychomotor functions, episodic memory, language, recognition of facial emotion, sensory–perceptual functions, and executive functions. Results: Compared with the controls, the NEAR group showed significantly poorer performance on nearly all of the cognitive tests and the MID group on about half of the cognitive tests (p = .05, Cohen's d NEAR as large as ?1.17, MID as large as ?0.61). One test even revealed significantly poorer performance in the FAR group (Cohen's d = ?0.26). Individual tasks accounted for 0.2% to 9.7% of the variance in estimated proximity to diagnosis. Overall, the cognitive battery accounted for 34% of the variance; in comparison, the Unified Huntington's Disease Rating Scale motor score accounted for 11.7%. Conclusions: Neurocognitive tests are robust clinical indicators of the disease process prior to reaching criteria for motor diagnosis of HD. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
94.
从代理、到自己投入半导体尖端制程设备研发,汉辰科技董事长黄民奇,日前在捐赠先进半导体制程设备予台湾国研院奈米组件实验室的仪式后,很多人都说,半导体尖端制程设备研发是精密机械工业,但他认为,应该称之为“制程工业”才对! 相似文献
95.
R?ikk?nen Katri; Matthews Karen A.; Flory Janine D.; Owens Jane F. 《Canadian Metallurgical Quarterly》1999,18(1):44
This study (a) tested the effects of hostile attributes on ambulatory blood pressure (BP), heart rate, and mood monitored repeatedly over 3 days in 100 healthy men and women and (b) determined whether the cardiovascular effects of trait hostility were moderated by mood. Multilevel random-coefficients regression analyses showed that hostile individuals exhibited higher systolic and diastolic BP and rated their current moods as more negative and less positive throughout the monitoring. Individuals low in hostility exhibited high BP only during the few occasions when they experienced negative mood. However, these patterns were true only when participants were classified by Potential for Hostility ratings from the Structured Interview (R. H. Rosenman, 1978), not by the Cynical Hostile Attitudes score derived from the Cook-Medley scale. Results provide convergent and ecological validity of interview rating of hostility and illuminate one possible dynamic mechanism by which overt hostile behaviors might contribute to the rates of increased cardiovascular morbidity and mortality. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
96.
This paper focuses on extensions of Abstract State Machines (ASMs) for the benefit of a refinement calculus in the area of
data-intensive applications, in particular data warehouses and on-line analytical processing. The extensions lead to a typed
version of ASMs and a more specific notion of strong data refinement, which incorporates the preservation of information content
by means of schema dominance. Each typed ASM can be effectively translated into an equivalent ordinary one. Providing typed
ASMs helps to exploit the existing logical formalisms used in data-intensive applications to define a ground model. Furthermore,
strong data refinement helps to set up a refinement-based development method that uses provably correct standard refinement
rules. 相似文献
97.
D'Amico Elizabeth J.; Metrik Jane; McCarthy Denis M.; Frissell Kevin C.; Applebaum Mark; Brown Sandra A. 《Canadian Metallurgical Quarterly》2001,15(4):341
The current study examined binge drinking among high school students over an academic year. Adolescent drinkers (N?=?621; 58% female) were grouped into 4 trajectories: drinkers (35%), increasers (14%), decreasers (16%), and persistent binge drinkers (35%). Prospective analyses indicated several factors that predicted escalation and de-escalation of binge drinking. Increasers were more likely to regularly use alcohol and cigarettes at a younger age than drinkers. Compared with decreasers, persistent binge drinkers reported regular alcohol and marijuana use at younger ages. Lower levels of perceived student drinking appeared to be a protective factor for onset of binge drinking. The results highlight the need to study precursors to the naturally occurring fluctuations in binge drinking and suggest factors that may accentuate the risk of binge drinking. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
98.
99.
The primary goal of this research is to provide recommendations for the eventual development of more effective and efficient fire sensors to be installed in space vehicles and habitats. An entirely new ground-based testing facility that generated fire signatures was developed to perform the combustion and pyrolysis experiments of eight different practical spacecraft materials. The flaming and smoldering of polymers approved by the National Aeronautics and Space Administration (NASA) generate three types of residues: condensables, light gases, and particulates. The residues were characterized by gas chromatography (GC), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The analysis was interpreted as a function of oxygen concentration, temperature, and flow direction. Key findings are that the combustion of some materials such as Kevlar and cotton can only be identified by light gases, while the combustion of other materials, such as silicone and melamine, is best detected using a particulate-specific sensor. The implications during a fire event, its suppression, astronaut health in post-event cleanup as well as material recommendations are briefly discussed. 相似文献
100.
The successful use of polymer components in solar hot water systems requires an understanding and method of predicting material degradation in water. The relevant degradation mechanism is oxidation. Degradation from oxidation can be delayed through the use of antioxidant additives. However, once the antioxidants have been depleted, oxidation of the polymer and subsequent loss of mechanical integrity occur rapidly. In this study, antioxidant loss from polymer tubes is modeled. Dimensional analysis and results of the model show the rate of antioxidant loss is controlled by diffusion through the polymer. The diffusion time scale is dictated by the tube wall thickness. Antioxidant concentration profiles and depletion rates are presented for three representative tube geometries and temperatures of 293 and 333 K. The time to deplete 90% of the antioxidant is on the order of 1000–10,000 h. 相似文献