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排序方式: 共有1470条查询结果,搜索用时 15 毫秒
101.
Eric N. Landis Edwin N. Nagy Denis T. Keane George Nagy 《Canadian Metallurgical Quarterly》1999,125(6):599-605
A high-resolution 3D scanning technique called X-ray microtomography was applied to measure internal damage and crack growth in small mortar cylinders loaded in compression. Synchrotron-based microtomography allows us to resolve internal features that are only a few microns in size. Multiple tomographic scans were made of the same specimen at different levels of deformation using a custom-built loading frame. 3D image analysis was used to measure internal crack growth during each deformation increment. Measured load-deformation curves were used to calculate the nonrecoverable work of the external load on the specimen. Nonrecoverable work of load was related to measured incremental change in crack surface area to estimate work-of-fracture in three dimensions. Initial results indicate a nearly constant work-of-fracture for the early stages of crack growth. These results show that basic fracture mechanics principles may be applied to concrete in compression; however, we must think in terms of 3D multiple crack systems rather than traditional 2D single crack systems. 相似文献
102.
The standard R&R study for evaluation of measurement systems assumes that participating observers constitute a random sample. Often there are only a few observers, all of them included in the study. An alternative measure for the gauge R&R is proposed for this situation, and it is shown that this may improve the perception of the quality of the measurement system markedly, especially with only a few observers. Finally it is shown that a simple estimator can be used, with a bias limited to just a few percent. 相似文献
103.
Trevor J. Manendo Michael A. Campbell Herbert H. Gilroy Edwin C. Masteller 《Journal of Great Lakes research》2008,34(1):204-209
Population structure and fecundity of freshwater mussels can be difficult to assess due to the benthic habitat and complex life cycles of these organisms. However, rapid and reliable classification of unionids can be accomplished with polymerase chain reaction if species-specific DNA primers are established. In this report we describe the sequence analysis of the ITS1 and ITS2 regions from five mussel species (Amblema plicata, Fusconia flava, Lampsilis siliquoidea, Ligumia nasuta, and Pyganodon grandis) isolated from a refuge in Lake Erie. Sequence comparison revealed strong similarities between A. plicata and F. flava and between L. siliquoidea and L.nasuta. P. grandis contained regions of additional DNA not present within the other species. Our study confirmed the placement of Ligumia nasuta within the Lampsilinae. The analysis also revealed DNA sequences within the ITS1 and ITS2 regions that are species-specific. Thus, the development of species-specific PCR primers can be utilized for analysis of adult populations and for glochidia on host fish. 相似文献
104.
Thompson Stewart; Recober Ana; Vogel Timothy W.; Kuburas Adisa; Owens Jessica A.; Sheffield Val C.; Russo Andrew F.; Stone Edwin M. 《Canadian Metallurgical Quarterly》2010,124(6):821
Detection of light in the eye underlies image-forming vision, but also regulates adaptive responses in physiology and behavior. Typically these adaptive responses do not involve image-forming vision, but depend on a relatively absolute measure of brightness (nonimage-forming irradiance detection). The goal of this study was to further understand how image-forming vision and nonimage-forming irradiance detection contribute to the effects of light on behavior. Three light dependent behaviors were assessed in wild-type, Rpe65-/- and rd1 mice. In Rpe65-/- mice, nonimage-forming irradiance detection is severely attenuated, but rod based visual acuity is relatively preserved. In rd1 mice visual acuity is nonrecordable, but nonimage-forming responses are less severely attenuated than Rpe65-/-. Positive masking, an image-forming vision dependent increase in wheel running, was absent in rd1 and restricted to higher irradiances in Rpe65-/-. Negative masking, a suppression of wheel running sensitivity with nonimage-forming irradiance detection input, was increased in rd1, but reduced in Rpe65-/- mice. By contrast, light aversion, an avoidance of brightly lit areas, was abolished in both Rpe65-/- and rd1. This shows that image-forming vision is not sufficient for light aversion, suggesting nonimage-forming irradiance detection motivates this behavior. Further, the differing effects of disease suggest that negative masking and light aversion are distinct responses with specialized nonimage-forming irradiance detection pathways. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
105.
Suggests, in reply to the analysis of B. Gholson and P. Barker (see PA, 73:10704), that they may have overlooked a single construct (the underlying metaphor of the psyche) that embodies incommensurable, although not necessarily competing, theories that may distinguish evolution in psychology from that of other sciences. It is contended that while technology, methodology, novelty, and empirical results are factors in the evolution of psychology, the evolution can be measured by changes in metaphor. (6 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
106.
Zusammenfassung. Aus finanzwirtschaftlicher Sicht k?nnen Kreditgarantien als Verkaufsoptionen auf das anteilige Gesamtverm?gen einer Unternehmung
interpretiert werden. Die Bewertung von Kreditgarantien erfolgt üblicherweise mit dem Ansatz von Merton. Bei diesem Modell
wird jedoch unterstellt, da? sowohl für den garantierten Kredit als auch für das nicht garantierte Fremdkapital vor Ablauf
der Laufzeit keinerlei Zins– und Tilgungszahlungen geleistet werden. Unsere Arbeit pr?sentiert ein Modell zur Bewertung von
Garantien auf Kredite mit beliebigen Zins– und Tilgungsmodalit?ten. Das vorgeschlagene Bewertungsmodell wird auf Kredite mit
unterschiedlichen Tilgungsformen angewendet. Darüber hinaus werden Sensitivit?tsanalysen bezüglich der Einflu?faktoren auf
die aus dem Modell resultierenden Pr?miens?tze durchgeführt.
Eingegangen: 2. Februar 1999 / Angenommen: 9. Dezember 1999 相似文献
107.
Joshua P. Schwarz Ruimin Liu David B. Newell Richard L. Steiner Edwin R. Williams Douglas Smith Ali Erdemir John Woodford 《Journal of research of the National Institute of Standards and Technology》2001,106(4):627-640
The NIST watt balance experiment is being completely rebuilt after its 1998 determination of the Planck constant. That measurement yielded a result with an approximately 1×10−7 relative standard uncertainty. Because the goal of the new incarnation of the experiment is a ten-fold decrease in uncertainty, it has been necessary to reexamine many sources of systematic error. Hysteresis effects account for a substantial portion of the projected uncertainty budget. They arise from mechanical, magnetic, and thermal sources. The new experiment incorporates several improvements in the apparatus to address these issues, including stiffer components for transferring the mass standard on and off the balance, better servo control of the balance, better pivot materials, and the incorporation of erasing techniques into the mass transfer servo system. We have carried out a series of tests of hysteresis sources on a separate system, and apply their results to the watt apparatus. The studies presented here suggest that our improvements can be expected to reduce hysteresis signals by at least a factor of 10—perhaps as much as a factor of 50—over the 1998 experiment. 相似文献
108.
Gardner Judith M.; Karmel Bernard Z.; Magnano Catherine L.; Norton Karen I.; Brown Edwin G. 《Canadian Metallurgical Quarterly》1990,26(4):563
Neurobehavioral (NB) performance was evaluated in 248 neurologically at-risk neonates at neonatal intensive care unit discharge to investigate the relation between behavior and brain insult. Six brain insult groups were defined on the basis of findings from cranial ultrasonography and brainstem auditory evoked response tests. The NB evaluation consisted of a modification and condensation of the Einstein Neonatal NB Assessment Scale and the assessment of activated motor patterns described by Katona. Logistic regression analysis of normal vs. abnormal judgments of behavioral categories revealed that, independent of the effects of prematurity, different patterns of NB abnormalities were associated with different degrees and types of brain insult. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
109.
Vratsanos Menas S. Thomas Edwin L. Farris Richard J. 《Journal of Materials Science》1987,22(2):419-428
A modified scarf joint specimen was developed for characterizing the adhesive behaviour of poly (p-phenylene benzobisthiazole) (PBT) film/epoxy composites. This method subjected samples to varying amounts of normal stress (tensile or compressive) and shear stress. This resulted in the determination of two adhesive strengths; one in the absence of shear stress and one in the absence of normal stress. As a result, the dependence of the adhesive strength on the degree of normal stress was determined. The adhesive behaviour of PBT/epoxy composites was investigated at cure temperatures of 55, 85, 115 and 215°C. Adhesive strengths of 3.5 and 8.2 MPa were measured in the absence of shear and normal stress, respectively, for samples cured at 55° C. A decrease in adhesive strength with increasing cure temperature was attributed to residual cure and thermal stresses. The fracture of these composites was predominantly adhesive, resulting in a clean delamination of the PBT film from the epoxy surface. A modified Tsai-Wu failure criterion is suggested for these composites. 相似文献
110.
Buffardi Louis C.; Fleishman Edwin A.; Morath Ray A.; McCarthy Patrick M. 《Canadian Metallurgical Quarterly》2000,85(4):551
This article describes a program of research investigating the relations between abilities required to perform job tasks and human error probabilities while performing these tasks. Study 1, using objectively derived human errors made in performing Air Force job tasks, evaluated an ability-requirements classification methodology and found that error rates were related to the numbers, types, and levels of different abilities required. In Study 2, subject matter expert panels used the methodology to identify the ability requirements of tasks in 2 different jobs found in each of 2 types of nuclear power plants. This study, using a task-anchored scale of human error probability, replicated the findings of Study 1, identified 2 ability requirements that cross-validated in predicting task-error probabilities across both jobs and plants, and identified other abilities specific to error probabilities in each job. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献