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排序方式: 共有182条查询结果,搜索用时 187 毫秒
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Attention deficit/hyperactivity disorder (ADHD) and conduct disorder (CD) are both disorders of childhood and adolescence that all too frequently extend into adulthood. But just what is the relationship between these two disorders? This study explores the overlap between these two disorders as they relate to juvenile delinquency; both are significant risk factors for the development of antisocial behavior. But there is more significance to the presence or absence of ADHD or CD in later antisocial behavior. Higher levels of defiant and/or aggressive behavior lead to antisocial acts as compared with lower levels of defiance and antisocial acts. Boys diagnosed with ADHD have higher felony rates than normal control boys, yet ADHD is not nearly as strong a predictor of offending behavior as is CD in study subjects. The presence of both CD and ADHD contributes to illegal behavior, and it is likely that early intervention in both disorders will reduce the prevalence of antisocial behavior. 相似文献
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Ute C. Herzfeld Bruce F. Wallin Carlton J. LeuschenJoel Plummer 《Computers & Geosciences》2011,37(11):1793-1801
The objective of this paper is to derive an algorithm for preserving important subscale morphologic characteristics at grids of lower-resolution, in particular for linear features such as canyons and ridge lines. The development of such an algorithm is necessitated by applications that require reduced spatial resolution, as is common in cartographic generalization, GIS applications, and geophysical modeling. Since any algorithm that results in weighted averages, including optimum interpolation and ordinary kriging, cannot reproduce correct depths, a new algorithm is designed based on principles of mathematical morphology. The algorithm described here is applied to derive a subglacial bed of the Greenland Ice Sheet that includes the trough of Jakobshavn Isbræ as a continuous canyon at correct depth in a low-resolution (5-km) digital elevation model (DEM). Data from recent airborne radar measurements of the elevation of the subglacial bed as part of the CReSIS project are utilized. The morphologic algorithm is designed with geophysical ice-sheet modeling in mind, in the following context. Currently occurring changes in the Earth's climate and the cryosphere cause changes in sea level, and the societal relevance of these natural processes motivates estimation of maximal sea-level rise in the medium-term future. The fast-moving outlet glaciers are more sensitive to climatic change than other parts of the Greenland ice sheet. Jakobshavn Isbrae, the fastest-moving ice stream in Greenland, follows a subglacial geologic trough. Since the existence of the trough causes the acceleration of the slow-moving inland ice in the Jakobshavn region and the formation of the ice stream, correct representation of the trough in a DEM is essential to model changes in the dynamics of the ice sheet and resultant sea-level predictions, even if current ice-sheet models can typically be run only at 5-km resolution. The DEM resultant from this study helps to bridge the conceptual gap between data analysis and geophysical modeling approaches. It is available as SeaRISE Greenland bed data set dev1.2 at http://websrv.cs.umt.edu/isis/index.php/SeaRISE_Assessment. 相似文献
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Robert A. Carlton 《Scanning》1997,19(2):85-91
The objective of this investigation was to evaluate the practical effects of electron beam broadening in the environmental scanning electron microscope (ESEM) on particle x-ray microanalysis and to determine some of the optimum operating conditions for this type of analysis. Four sets of experiments were conducted using a Faraday cage and particles of copper, glass, cassiterite, andrutile. The accelerating voltage and chamber pressure varied from 20 to 10 kV and from 665–66 Pa (5.0 to 0.5 torr), respectively. The standard gaseous secondary electron detectors (GSED) and the long environmental secondary dectectors (ESD) for the ESEM were evaluated at different working distances. The effect of these parameters on the presence of artifact peaks was evaluated. The particles were mounted on carbon tape on an aluminum specimen mount and were analyzed individually and as a mixture. Substrate peaks were present in almost all of the spectra. The presence of neighboring particle peaks and the number of counts in these depended upon the operating conditions. In general, few of these peaks were observed with the long ESD detector at 19 mm working distance and at low chamber pressures. More peaks and counts were observed with a deviation from these conditions. The most neighboring peaks and counts were obtained with the GSED detector at 21.5 mm working distance, 10 kV accelerating voltage, and 665 Pa (5.0 torr) chamber pressure. The results of these experiments support the idea that the optimum instrumental operating conditions for EDS analysis in the ESEM occur by minimizing the gas path length and the chamber water vapor pressure, and by maximizing the accelerating voltage. The results suggest that the analyst can expect x-ray counts from the mounting materials. These tests strongly support the recommendation of the manufacturer to use the long ESD detector and a 19 mm working distance for EDS analysis. The results of these experiments indicate that neighboring particles millimeters from the target may contribute x-ray counts to the spectrum. 相似文献
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Jonathan D. Krug Andrew Dart Carlton L. Witherspoon Jerome Gilberry Quentin Malloy Surender Kaushik 《Aerosol science and technology》2017,51(7):868-878
Under the National Ambient Air Quality Standard (NAAQS) for airborne lead, measurements are conducted by means of a high-volume total suspended particulate matter (Hi-Vol TSP) sampler. In the decade between 1973 and 1983, there were 12 publications that explored the sampling characteristics and effectiveness of the Hi-Vol TSP, yet there persists uncertainty regarding its performance. This article presents an overview of the existing literature on the performance of the Hi-Vol TSP, and identifies the reported sampler effectiveness with respect to four factors: particle size (reported effectiveness of 7%–100%), wind speed (?36% to 100%), sampler orientation (7%–100%), and operational state (107%–140%). Effectiveness of the Hi-Vol TSP was evaluated with a solid, polydisperse aerosol in a controlled wind tunnel setting. Isokinetic samplers were deployed alongside the Hi-Vol TSP to investigate three wind speeds (2, 8, and 24 km h?1), three sampler orientations (0°, 45°, 90°), and two operational states (on, off) for aerosols with aerodynamic diameters from 5 to 35 µm. Results indicate that particle diameter was the largest determining factor of effectiveness followed by wind speed. Orientation of the sampler did not have a significant effect at 2 and 8 km h?1 but did at 24 km h?1. In a passive state, the Hi-Vol TSP was collected between 1% and 7% of available aerosol depending on particle size and wind speed. Results of this research do not invalidate results of previous studies but rather contribute to our overall understanding of the Hi-Vol TSP's size-selective performance. While results generally agreed with previous studies, the Hi-Vol TSP was found to exhibit less dependence on these four factors than previously reported.© 2017 American Association for Aerosol Research 相似文献
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Green Carlton E.; Chen Cynthia E.; Helms Janet E.; Henze Kevin T. 《Canadian Metallurgical Quarterly》2011,23(3):656
Helms, Henze, Sass, and Mifsud (2006) defined good practices for internal consistency reporting, interpretation, and analysis consistent with an alpha-as-data perspective. Their viewpoint (a) expands on previous arguments that reliability coefficients are group-level summary statistics of samples' responses rather than stable properties of scales or measures and (b) encourages researchers to investigate characteristics of reliability data for their own samples and subgroups within their samples. In Study 1, we reviewed past and current reliability reporting practices in a sample of Psychological Assessment articles published across 3 decades (i.e., from the years 1989, 1996, and 2006). Results suggested that contemporary and past researchers' reliability reporting practices have not improved over time and generally were not consistent with good practices. In Study 2, we analyzed an archival data set to illustrate the real-life repercussions of researchers' ongoing misconstrual and misuse of reliability data. Our analyses suggested that researchers should conduct preliminary analyses of their data to determine whether their data fit the assumptions of their reliability analyses. Also, the results indicated that reliability coefficients varied across racial or ethnic and gender subgroups, and these variations had implications for whether the same depression measure should be used across groups. We concluded that the alpha-as-data perspective has implications for one's choice of psychological measures and interpretation of results, which subsequently affect conclusions and recommendations. We encourage researchers to recognize the people behind their data by adopting better practices in internal consistency reporting, analysis, and interpretation. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
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A simple, fast, sensitive, and economical field method was developed and evaluated for the determination of hexavalent chromium (CrVI) in environmental and workplace air samples. By means of ultrasonic extraction in combination with a strong anion-exchange solid-phase extraction (SAE-SPE) technique, the filtration, isolation, and determination of CrVI in the presence of trivalent chromium (CrIII) and potential interferents was achieved. The method entails (1) ultrasonication in basic ammonium buffer solution to extract CrVI from environmental matrixes; (2) SAE-SPE to separate CrVI from CrIII and interferences; (3) elution/acidification of the eluate; (4) complexation of chromium with 1,5-diphenylcarbazide; and (5) spectrophotometric determination of the colored chromium-diphenylcarbazone complex. Several critical parameters were optimized in order to effect the extraction of both soluble (K2CrO4) and insoluble (PbCrO4) forms of CrVI without inducing CrIII oxidation or CrVI reduction. The method allowed for the dissolution and purification of CrVI from environmental and workplace air sample matrixes for up to 24 samples simultaneously in less than 90 min (including ultrasonication). The results demonstrated that the method was simple, fast, quantitative, and sufficiently sensitive for the determination of occupational exposures of CrVI. The method is applicable for on-site monitoring of CrVI in environmental and industrial hygiene samples. 相似文献
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Coal liquids distillation tower corrosion: chloride analysis of solvent refined coal process samples
Burtron H. Davis Gerald A. Thomas Alberto A. Sagüés Carlton H. Jewitt Kenneth L. Baumert 《Fuel Processing Technology》1983,8(1):77-93
Severe chloride corrosion incidents have occurred in the distillation area of major direct coal liquefaction plants. Chloride analyses have been carried out for samples collected at various process streams of one of these plants (the Wilsonville, Alabama SRC-1 pilot plant) in order to define the pathway of corrosive species to the distillation area. These analyses show that the major fraction of the chloride in the atmospheric distillation tower is carried there in the higher-boiling process streams. The chloride level at a particular point in the atmospheric distillation tower may be several times that of the tower feed liquid; this concentration contributes to the catastrophic corrosion experienced in these towers. This chloride concentration provides an explanation for the occurrence of the corrosion in the last distillation tower in the process stream, rather than in the tower(s) first contacted by the chloride containing distillate stream. It also accounts for the observed localization of the corrosion within narrow regions of the atmospheric distillation tower. The chloride concentration and the chloride pathway are factors which designers of coal liquefaction distillation processes need to consider in a design that will keep corrosion to a manageable level. 相似文献