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991.
Ohtsu M. Liou K.-Y. Burrows E.C. Burrus C.A. Eisenstein G. 《Electronics letters》1987,23(21):1111-1113
A problem in frequency-tuning of external-cavity lasers is mode-hopping between neighbouring external-cavity modes. We demonstrate a new interferometric method for monitoring mode-hoping and an automatic control circuit for a 1.3 ?m grating external-cavity laser that maintains single-mode operation when the lasing frequency is tuned. 相似文献
992.
P. Gallone 《Electrochimica acta》1986,31(12):1485-1490
On 30 October 1786 Luigi Galvani gave the first account, at the Academy of Sciences of Bologna, about his experiments on animal electricity, of which he thought to have obtained evidence from the convulsions shown by a dissected frog, as soon as its hind-limbs were connected with the spinal cord by means of a metallic conductor. The publication of these experiments gave rise to Galvani's controversy with Volta, who denied the existence of animal electricity after discovering that there exists a potential difference between any couple of dissimilar conductors. This was a preliminary step that led Volta to the invention of the voltaic pile. Evidence of animal electricity was given about 1840 by Carlo Matteucci, using the astatic galvanometer invented by Leopoldo Nobili. This fundamental property of living organisms is now a well-advanced field of investigation by electrophysiology and bioelectrochemistry. 相似文献
993.
Surveyed the prevalence of weight reducing and weight gaining in 1,373 high school students. 63% of the girls and 16.2% of the boys reported being on weight-reducing regimens; 9.1% of the girls and 28.4% of the boys were trying to gain weight. Most female reducers and male gainers were already normal weight. Whites and Hispanics were more likely to be reducing, whereas Blacks were more likely to be gaining. Exercise and moderate caloric reduction were most popular for weight reducing, and a small but significant number were regularly using fasting, vomiting, laxatives, and appetite suppressants. The rate of weight reducing in female high school adolescents has increased significantly since similar surveys of American youths 20 yrs ago. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
994.
The exfiltration of wastewater from sewer systems in urban areas causes a deterioration of soil and possibly groundwater quality. Beside the simulation of transport and degradation processes in the unsaturated zone and in the aquifer the analysis of the potential impact requires the estimation of quantity and temporal variation of wastewater exfiltration. Exfiltration can be assessed by the application of a leakage model. The hydrological approach was originally developed to simulate the interactions between the groundwater and surface water, it was adapted to allow for modelling of interactions between groundwater and sewer system. In order to approximate the exfiltration specific model parameters infiltration specific parameters were used as a basis. Scenario analysis of the exfiltration in the City of Dresden from 1997 to 1999 and during the flood event in August 2002 shows the variation and the extent of exfiltration rates. 相似文献
995.
An asymptotically efficient autoregressive moving-average (ARMA) spectral estimator is presented, based on the sample covariances of observed time series. The estimate of the autoregressive (AR) part is shown to be identical to the optimal instrumental variable (IV) estimator in [7] although derived here using a different approach. The moving-average (MA) spectral parameter estimate is new. 相似文献
996.
RICHARD C. HULA 《Journal of Urban Affairs》1985,7(3):39-56
This paper attempts to measure the effect of a court-ordered desegregation plan on three aspects of the housing market in Dallas County, Texas. The indicators include sale price, number of sales, and proportion of home sales financed by conventional mortgages. Monthly data from 1969 to 1979 are analyzed using Box-Jenkins time series models. After best fit models are determined, various intervention terms are introduced into the models to assess the impact of both a 1975 Circuit Court Order and a 1976 District Court Order. The analysis suggests neither order had a measurable effect on the housing market in Dallas. 相似文献
997.
998.
Analysis and synthesis of on-chip spiral inductors 总被引:3,自引:0,他引:3
This paper presents a physically based compact model for estimating high-frequency performance of spiral inductors. The model accurately accounts for skin and proximity effects in the metal conductors as well as eddy current losses in the substrate. The model shows excellent agreement with measured data mostly within 10% across a variety of inductor geometries and substrate dopings up to 20 GHz. A web-based spiral inductor synthesis and analysis tool COILS, which makes use of the compact models, is presented. An optimization algorithm using binary searches speeds up the synthesis of inductor designs. 相似文献
999.
This paper presents the main current theoretical issues in Information Retrieval. The principles of conceptual modelling, as they have emerged in the database area, are presented and their application to document modelling in order to enhance document retrieval is discussed. Finally, the main features of the MULTOS project are presented and critically reviewed confronting them with the requirements which have been identified during the general discussion on document conceptual modelling for information retrieval. 相似文献
1000.
P. C. Campbell E. B. Hawbolt J. K. Brimacombe 《Metallurgical and Materials Transactions A》1991,22(11):2769-2778
The goal of this study was to develop a mathematical model which incorporates heat flow, phase transformation kinetics, and
property-structure-composition relationships to predict the mechanical properties of steel rod being control cooled under
industrial conditions. Thus, the principles of microstructural engineering have been brought to bear on this interdisciplinary
problem by combining computer modeling with laboratory measurements of heat flow, austenite decomposition kinetics, microstructure
and mechanical properties, and industrial trials to determine heat transfer and obtain rod samples under known conditions.
Owing to the length and diversity of the study, it is reported in three parts,[8191]the first of which is concerned with the heat flow measurements. A relatively simple and reliable technique, involving a preheated
steel rod instrumented with a thermocouple secured at its centerline, has been devised to determine the cooling rate in different
regions of the moving bed of rod loops on an operating Stelmor line. The measured thermal response of the rod has been analyzed
by two transient conduction models (lumped and distributed parameter, respectively) to yield overall heat-transfer coefficients
for radiation and convection. The adequacy of the technique has been checked by cooling instrumented rods under well-defined,
air crossflow conditions in the laboratory and comparing measured heat-transfer coefficients to values predicted from well-established
equations. The industrial thermal measurements have permitted the characterization of a coefficient to account for radiative
interaction among adjacent rod loops near the edge and at the center of the bed.
Formerly Graduate Student, The University of British Columbia. 相似文献