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排序方式: 共有1237条查询结果,搜索用时 15 毫秒
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This paper presents a mechanism which infers a user's plans from his/her utterances by directing the inference process towards the more likely interpretations of a speaker's statements among many possible interpretations. Our mechanism uses Bayesian theory of probability to assess the likelihood of an interpretation, and it complements this assessment by taking into consideration two aspects of an interpretation: its coherence and its information content. The coherence of an interpretation is determined by the relationships between the different statements in the discourse. The information content of an interpretation is a measure of how well defined the interpretation is in terms of the actions to be performed on the basis of this interpretation. This measure is used to guide the inference process towards interpretations with higher information content. The information content of an interpretation depends on the specificity and the certainty of the inferences in it, where the certainty of an inference depends on the knowledge on which the inference is based. Our mechanism has been developed for use in task-oriented consultation systems. The particular domain that we have chosen for exploration is that of travel booking. 相似文献
3.
Yu Yang Hugo Bender Kai Arstila Bart Swinnen Bert Verlinden Ingrid De Wolf 《Microelectronics Reliability》2008,48(8-9):1517-1520
Focused ion beam (FIB) and nano-probing were applied for failure analysis of three-dimensional stacked circuits with copper through-silicon-vias between the stacked chips. The failure analysis was done after high temperature storage and thermal cycling tests. Passive voltage contrast in FIB allowed to pinpoint the open sites. FIB cross-sections showed the presence of opens at the bottom of the copper vias. The failure cause was suspected to be an interlayer particle, which was confirmed by optical profilometry. Nano-probing was used on another sample to pinpoint the failure location through the measurement of the local resistance within the daisy chains. The failure was traced out to be related with surface contamination. 相似文献
4.
Ingrid Martorell Francesc X Grau 《International Journal of Heat and Mass Transfer》2003,46(13):2389-2402
The present work deals with the natural convection flow and heat transfer from a horizontal plate cooled from above. Experiments are carried out for rectangular plates having aspect ratios between φ=0.036 and 0.43 and Rayleigh numbers in the range 290?Raw?3.3×105. These values of Raw and φ have been selected below those commonly considered in previous research in view of a future application to the design of printed circuit boards. The plates are made of two different metals, copper and steel. The choice of a metal is relevant to the present problem because the plates are heated by means of an electric current. Important variations of the surface temperature are observed along the transverse direction for the steel plates. The surface of the copper plates is almost isothermal because of the high thermal conductivity of the metal.Calculations for a semi-infinite plate are carried out to predict the transverse profiles of the surface temperature and heat flux and to visualize the structure of the flow. Three-dimensional calculations are also used at a qualitative level to observe the changes in the flow structure due to the finite length of the plate. Present results are compared with both previous experimental work and analyses that are based on boundary layer theory. It is shown that analyses for an infinite boundary layer are not completely applicable to the present problem because of its different physics. The most relevant feature of the natural convection flow, which is not predicted by boundary layer analyses, is a thermal plume rising near the center of the plate.Present heat transfer results differ from previous experimental work because of the lower Rayleigh numbers and aspect ratios investigated here. The Nusselt number is found to depend on Rawn, with the exponent n=0.17 being lower than most of the values reported in the literature. This comparatively low value is related to the transverse conduction of heat through the air, which becomes increasingly significant as Raw approaches zero. It is shown that such a low-Raw effect can be accounted for in a physically consistent manner by adding a constant term to the heat transfer correlation. On the other hand, it is found that the Nusselt number does not significantly depend on the aspect ratio in the range of φ investigated contrary to what has been previously reported for wider plates. 相似文献
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M Müller-Schimpfle K Ohmenhaüser P Stoll K Dietz CD Claussen 《Canadian Metallurgical Quarterly》1997,203(1):145-149
PURPOSE: To quantify how frequently mesenteric adenitis clinically mimics appendicitis and to determine its appearance at computed tomography (CT). MATERIALS AND METHODS: The medical records of 651 consecutive patients with an admission diagnosis of appendicitis were reviewed to determine how often mesenteric adenitis was the discharge diagnosis. The CT scans of a separate group of 18 patients with a discharge diagnosis of mesenteric adenitis were reviewed. These patients were part of a group of 100 consecutive patients prospectively evaluated with CT of the appendix for clinically suspected appendicitis. RESULTS: Fifty of 651 patients (7.7%) with an admission diagnosis of appendicitis had a discharge diagnosis of mesenteric adenitis. Mesenteric adenitis constituted 50 of the 252 (19.8%) discharge diagnoses other than appendicitis. All 18 CT scans of mesenteric adenitis showed three or more nodes that measured at least 5 mm in shortest axis clustered in the right lower quadrant, with a normal appendix identified. Eight patients had associated ileal or ileocecal wall thickening. CONCLUSION: Mesenteric adenitis is an important clinical mimic of appendicitis. It appears at CT as clustered, enlarged mesenteric lymph nodes with a normal appendix, and there may be associated ileitis or ileocolitis noted. 相似文献
7.
The electrochemical behaviour of Cu-xZn alloys, as well as their constituent metals, in a borate buffer containing chloride ions in the molar range from 0.01 to 1 M are studied. Characteristics of these materials under anodic polarization are compared and the composition and morphology of the corrosion products formed in the course of polarization experiment are analysed by SEM and EDS. X-ray photoelectron spectroscopy and electrochemical impedance measurements are used for characterization of the surface layers formed on Cu, Zn and Cu-40Zn alloy during 2-h immersion at Eoc in a borate buffer containing two different concentrations of chloride ions. New aspects of the behaviour of brass under Eoc condition are revealed. The improved corrosion resistance of brass in chloride media, if compared to zinc metal, is attributed to a Cu-rich layer formed by the selective dissolution of zinc. Based on the results, a structural model describing the improved corrosion resistance of Cu-40Zn alloy with respect to Zn metal is proposed. 相似文献
8.
Holger Claussen 《International Journal of Wireless Information Networks》2008,15(3-4):137-147
In this paper, the feasibility of user-deployed femtocells in the same frequency band as an existing macrocell network is investigated. Key requirements for co-channel operation of femtocells such as auto-configuration and public access are discussed. Methods for femtocell power auto-configuration that ensure a constant cell radius in the downlink, and a low pre-definable interference impact on co-channel macrocells in the uplink are proposed. The theoretical performance of randomly deployed femtocells in such a hierarchical cell structure and the resulting impact on existing co-channel macrocells is analysed for a cellular UMTS network using system level simulations. 相似文献
9.
F Ribichini G Steffenino A Dellavalle A Vado V Ferrero T Camilla S Giubergia E Uslenghi 《Canadian Metallurgical Quarterly》1998,98(12):1172-1177
BACKGROUND: Preceding mucosal response to one allergen leads to the priming of the nasal mucosal response to another allergen. This study aimed to determine whether environmental allergens, especially ubiquitous animal dander, can induce nasal priming. METHODS: We investigated 26 grass-pollen-allergic subjects with additional sensitization to other aeroallergens. We performed continuous allergen challenge for 2 h with 1500 Dactylis glomerata pollen/m3 in the Vienna challenge chamber. The nasal flow at 150 Pa was examined, and subjective scores were obtained every 15 min. Statistical analysis was calculated from the area under curve of nasal flow reduction by Student's t-test and the Mann-Whitney U-test. Alpha was 0.05. RESULTS: In subjects with positive cat-dander RAST (class of > or = 3), besides grass-pollen allergy, the specific nasal allergic reaction to Dactylis challenge was significantly pronounced (P < 0.01), and an earlier onset of reaction was evident. The same results were obtained with additional sensitization to dog dander (P < 0.05). Concomitant sensitization to mugwort also led to escalating symptoms (P < 0.05). CONCLUSIONS: These results indicate that a specific nasal allergic reaction is augmented by environmental priming caused by ubiquitous animal dander and possibly is influenced by the daily use of spices. 相似文献
10.
Susanna Eberhartinger Ingrid Steiner Josef Washüttl und Gerhard Kroyer 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1990,191(4-5):286-289
Zusammenfassung Mittels verschiedener Untersuchungen wurden Aussagen über das Migrationsverhalten von Acetaldehyd aus Polyethylenterephthalat (PET) getroffen. Die Analyse des Acetaldehyds erfolgte durch Kopfraum-Gaschromatographie mit Flammenionisationsdetektion. Die Bestimmung des Restgehaltes an Acetaldehyd in neuen PET-Flaschen ergab Werte um 6,3 mg/kg, woraus sich eine maximal mögliche Migratmenge von etwa 200 (g/L errechnen läßt. Migrationsstudien bei verschiedenen Temperaturen zeigten die für das Verpakkungssystem typischen Zeitverläufe. Die Diffusion des Acetaldehyds aus dem Kunststoff erreichte bei einer Inkubationstemperatur von 40 °C nach ca. 4 Tagen ein konstantes Niveau, welches ca. 10% des ermittelten Restgehaltes an Acetaldehyd beträgt. Bei einer Temperaturerhöhung um 20 °C kam es zu einer Erhöhung dieses Niveaus auf das 5fache. Die Versuchsergebnisse der Bestimmung des Acetaldehyds in Getränken zeigte, daß in der Praxis nur mit einer geringen Migration zu rechnen ist, die bei den kohlensäurehaltigen Erfrischungsgetränken wegen des intensiven Eigengeschmacks ohne Belang ist. Eine Geschmacksbeeinträchtigung könnte sich höchstens bei Mineral- und Sodawässern ergeben, wenn diese längerfristig, wie sich aus den Migrationsstudien ableiten läßt, Temperaturen um 40 °C ausgesetzt werden.
Study of the migration of acetaldehyde from PET bottles into soft drinks containing carbonic acid
Summary The migration of acetaldehyde from polyethyleneterephthalate (PET) under various conditions was analysed by headspace gas chromatography and flame ionisation detection. The residual amounts of new PET bottles were about 6.3 mg/kg with a migration value of 200 g/1. On studying the migration at different temperatures and times, behaviour curves characteristic of packing materials made from plastics are obtaind. The amount of acetaldehyde diffusing from PET at a temperature of 40° C reached a constant level after 4 days which was about 10% of the residual value of acetaldehyde. On increasing the temperature by 20° C, this level was raised up to 50%. The results of the analysis of acetaldehyde in soft drinks containing carbonic acid show that the migration in fact is not sufficiently high to influence the taste of these soft drinks. A negative effect on the taste may be recognized with mineral waters and soda when they are exposed to higher temperatures (e.g. 40° C or more) over a longer period of time.相似文献