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排序方式: 共有1046条查询结果,搜索用时 15 毫秒
981.
982.
983.
Psychophysical evaluation of in-situ ultrasound visualization 总被引:1,自引:0,他引:1
Wu B Klatzky RL Shelton D Stetten GD 《IEEE transactions on visualization and computer graphics》2005,11(6):684-693
We present a novel psychophysical method for evaluating ultrasonography based on real-time tomographic reflection (RTTR), in comparison to conventional ultrasound (CUS). The method measures the user's perception of the location of an ultrasound-imaged target independently from assessing the action employed to reach it. Three experiments were conducted with the sonic flashlight (SF), an RTTR device, and CUS. The first two experiments determined subjects' perception of target location with a triangulation-by-pointing task. Depth perception with the SF was comparable to direct vision, while CUS caused considerable underestimation of target depth. Binocular depth information in the SF was shown to significantly contribute to its superiority. The third experiment tested subjects in an ultrasound-guided needle insertion task. Because the SF provides visualization of the target at its actual location, subjects performed insertions faster and more accurately by using the SF rather than CUS. Furthermore, the trajectory analysis showed that insertions with the SF generally went directly to the target along the desired path, while CUS often led to a large deviation from the correct path consistent with the observed underestimation of target depth. These findings lend great promise to the use of RTTR-based imaging in clinical practice and provide precise means of assessing efficacy. 相似文献
984.
Radiances simulated in the presence of clouds by use of a fast radiative transfer model and a multiple-scattering scheme 总被引:1,自引:0,他引:1
A fast-forward radiative transfer (RTF) model is presented that includes cloud-radiation interaction for any number of cloud layers. Layer cloud fraction and transmittance are treated separately and combined with that of gaseous transmittances. RTF is tested against a reference procedure that uses line-by-line gaseous transmittances and solves the radiative transfer equation by use of the adding-doubling method to handle multiple-scattering conditions properly. The comparison is carried out for channels 8, 12, and 14 of the High Resolution Infrared Radiation Sounder (HIRS/2) and for the geostationary satellite METEOSAT thermal infrared and water vapor channels. Fairly large differences in simulated radiances by the two schemes are found in clear conditions for upper- and mid-tropospheric channels; the cause of the differences is discussed. For cloudy situations an improved layer source function is shown to be required when rapid changes in atmospheric transmission are experienced within the model layers. The roles of scattering processes are discussed; results with and without scattering, both obtained by use of a reference code, are compared. Overall, the presented results show that the fast model is capable of reproducing the cloudy results of the much more complex and time-consuming reference scheme. 相似文献
985.
986.
Bertini I Luchinat C Parigi G Pierattelli R 《Chembiochem : a European journal of chemical biology》2005,6(9):1536-1549
This article deals with the solution structure determination of paramagnetic metalloproteins by NMR spectroscopy. These proteins were believed not to be suitable for NMR investigations for structure determination until a decade ago, but eventually novel experiments and software protocols were developed, with the aim of making the approach suitable for the goal and as user-friendly and safe as possible. In the article, we also give hints for the optimization of experiments with respect to each particular metal ion, with the aim of also providing a handy tool for nonspecialists. Finally, a section is dedicated to the significant progress made on 13C direct detection, which reduces the negative effects of paramagnetism and may constitute a new chapter in the whole field of NMR spectroscopy. 相似文献
987.
988.
Enzo Bianchi Roberta Bruschi Rosa Draisci Luca Lucentini 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1995,200(4):256-260
Ion chromatography and colorimetry were used to determine nitrate ion concentration in 76 different pork meat products (salami, mortadella, wurstel, raw and cooked ham and other whole-muscle cooked products) and the results were compared. The comparison revealed that the two techniques yield quantitatively similar results, except in cases where the matrix was so complex that it might have influenced the analytical data. These results are consistent with those obtained by other authors who used UV spectrophotometric detection.
Vergleich zwischen ionenchromatographischer und spektrophotometrischer Methode zur Bestimmung von Nitrat in Fleischwaren
Zusammenfassung Es wurden zwei Analysetechniken, Ionenchromatographie mit konduktimetrischem Detektor und Kolorimetrie, für die Mengenbestimmung des Nitrat-Ions in Fleischerzeugnissen verglichen. Die Ergebnisse der Untersuchungen an 76 verschiedenen Schweinefleischprodukten (Salami, Mortadella, Würstchen, Roh- und Kochschinken und andere gekochte Erzeugnisse mit ganzem Muskel) beweisen, daß die beiden Methoden im allgemeinen sich entsprechende Werte liefern, außer in den Fällen, in denen der komplizierte Charakter der Matrix den Analysewert beeinflussen kann. Die Ergebnisse sind mit denen von Autoren vergleichbar, die mit UV-Detektor gearbeitet haben.相似文献
989.
990.
Lederman Susan J.; Klatzky Roberta L.; Collins April; Wardell Jackie 《Canadian Metallurgical Quarterly》1987,13(4):606
In Experiment 1, blindfolded observers judged (a) the distance of pathways felt by hand and (b) the straight-line distance between pathway endpoints inferred from such exploration. In Experiment 2, blindfolded observers made corresponding estimates after traversing similar pathways on foot. Pathways were explored under three different speeds. Under both manipulatory and ambulatory exploration, there was substantial length distortion of inferred distance; the straight-line distance was increasingly overestimated with increases in the length of the explored pathway. With manipulatory exploration, slower movements increased length distortion, but duration effects proved secondary to effects of spatial extent. For ambulatory exploration, no duration effects were obtained. Observers used time-independent heuristics, that is, a footstep metric for estimating the pathway actually travelled and a spatial imaging strategy for estimating the inferred line between pathway endpoints. The studies establish length distortion as a general phenomenon in movement space and identify its major causes as spatial rather than temporal. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献