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581.
王渤洪 《变流技术与电力牵引》2006,(6):39-42
过去几年里风能设备发展兴旺,电机制造有大量的创新.用作发电机的滑环转子交流异步电机的功率已达兆瓦级.与直接驱动的多极数同步电机相比,这种发电机有很多优点. 相似文献
582.
Whitecap coverage in coastal environment for steady and unsteady wave field conditions 总被引:1,自引:0,他引:1
Breaking waves represent a “key” parameter for many applications involved with a large number of environmental phenomena. In particular, it is well recognized that the whitecap cover induced by breaking waves allows substantial enhancement of heat, momentum, gas and particle transfer at the air–sea interface. A large number of studies were conducted during the last decades on the variation of the whitecap fraction, commonly noted W. The results presented in this paper deal with the evolution of the whitecap coverage in coastal zone. In such areas, the wave field is often unsteady with an important variety of sea state developments. The present analysis is based on an extensive series of data obtained during an experimental campaign which took place on the Mediterranean coast in 2001. The results allow observation of the influence of the sea state conditions of the wave field on the whitecap coverage. In addition, this paper confirms the occurrence of a peak in the variations of the whitecap fraction with the wave age for coastal areas as suggested by Lafon et al. [Lafon, C., Piazzola, J., Forget, P., Le Calvé, O. and Despiau, S., 2004. Analysis of the variations of the whitecap fraction as measured in a coastal zone. Boundary-Layer Meteorol., 111: 339-360.]. A wave age dependent model for the whitecap fraction is then proposed, which takes into account both the wind and the wave influence, and hence, is characteristics of the different sea state conditions. 相似文献
583.
Richard P. Signell Sandro Carniel Luigi Cavaleri Jacopo Chiggiato James D. Doyle Julie Pullen Mauro Sclavo 《Journal of Marine Systems》2005,53(1-4):217-233
The quality of surface winds derived from four meteorological models is assessed in the semi-enclosed Adriatic Sea over a 2-month period: a global hydrostatic model ECMWF T511 (40 km resolution), a hydrostatic limited area model LAMBO (20 km), and two non-hydrostatic limited area models: LAMI (7 km) and COAMPS™ (4 km). These wind models are used to drive a 2 km resolution wave model (SWAN) of the Adriatic, and wind and wave results are compared with observations at the ISMAR oceanographic tower off Venice. Waves are also compared at buoy locations near Ancona and Ortona. Consistently with earlier studies, the ECMWF fields underestimate the wind magnitude and do not reproduce the known spatial structure of strong wind events. The results show that the higher-resolution, limited area models LAMI and COAMPS exhibit better amplitude response than the coarser ECMWF: there is a 3- to 4-fold reduction of the wind underestimation at the platform (from 36% to 8–11%). The wave response is also improved with LAMI and COAMPS: there is a 2-fold reduction in the underestimation of wave heights at the platform. These non-hydrostatic models also produce wind fields with more realistic small-scale, spatial structure during strong wind events. The temporal correlation between observed and modelled wind, however, is highest with the global ECMWF model due to the fact that large-scale features can be predicted deterministically, whereas small-scale features can only be predicted stochastically. Models with less small-scale structure have better correlation because they have less “noise.” This explanation is supported by increased correlation between modelled and observed waves, the waves representing a smoothing of the wind over fetch and duration. Although there is room for improvement, the high-resolution, non-hydrostatic models (LAMI and COAMPS) offer significant advantages for driving oceanographic simulations in semi-enclosed basins such as the Adriatic Sea. 相似文献
584.
李虎松 《西安交通大学学报(英文版)》1995,(2)
PRODUCTIONOFPARATHYROIDHORMONE-RELATEDPROTEIN(PTHrP)BYAHUMANHEPATOMACELLLINELiHusong;PK.Seitz,P.Selvanayagam,S.Rajaraman,C.Co... 相似文献
585.
王志恩 《西安交通大学学报(英文版)》1995,(2)
TARGETEDACTIVATIONOFCD_(8)~(+)CELLSANDINFECTIONOFβ_2-MICROGLOBULIN-DEFICIENTMICE FAILTOCONFIRMAPRIMARYPROTECTIVEROLEFORCD(8)~(+... 相似文献
586.
Z. C. Liu K. B. Yu J. Tian Y. Q. Han S. L. Qi P. K. Teng 《International Journal of Automotive Technology》2017,18(1):19-29
The demand for continually improving the transient performance of diesel engines requires higher rail pressure and more efficient turbocharger. Before the test, a two-stage turbocharger with a turbine by-pass valve (TBV) had been matched reasonably with the base engine. In order to reduce smoke emission under the typical 5-second transient process of constant speed and increasing torque, the influence of rail pressure on combustion, emissions and performance characteristics was experimentally investigated. The results showed that the two-stage turbocharger was helpful in improving transient performance. Moreover, the full-stage rail pressure (FSRP) strategies (increasing rail pressure during the whole transient process) could reduce smoke emission when the TBV was closed. However, smoke deteriorated once TBV opening got larger. Then the sectional-stage rail pressure (SSRP) strategies (increasing rail pressure from a pre-set load to 100 % load) were presented under small TBV opening to improve in-cylinder thermal condition. Hence, the air-fuel mixing process was improved at medium and large loads. Then the maximum decline of smoke opacity peak was 56.3 %, which happened under 10 % TBV opening. In addition, fuel consumption of FSRP strategies got worse under larger TBV opening. However, this deterioration situation could be effectively restrained by the utilization of SSRP strategies. 相似文献
587.
P. E. Pfeffer M. Harrer D. N. Johnston 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2008,46(5):413-428
For the on-centre handling behaviour of vehicles the steering system is absolutely important. To investigate the interaction of the vehicle and steering system a validated, especially tailored simulation model was developed. Some meaningful vehicle and steering system parameters are altered to show the influence on steering wheel torque, steering feel and understeer. The results underline the importance of an accurate steering system model. Identified measures to improve the centre feel and steering response were a stiffer torsion bar, a higher cornering stiffness or a lower overall steering ratio. The steering response, however, suffers when the centre feel is improved by a higher trail. The steering rack friction reduces mainly the steering response while the steering column friction decreases the centre feel whereas a stiffer torsion bar lessens the understeer tendency. 相似文献
588.
Defining and understanding trip chaining behaviour 总被引:4,自引:0,他引:4
Frank Primerano Michael A. P. Taylor Ladda Pitaksringkarn Peter Tisato 《Transportation》2008,35(1):55-72
Trip chaining is a phenomenon that we know exists but rarely investigate. This could be attributed to either the difficulty
in defining trip chains, extracting such information from travel diary surveys, the difficulty in analysing all the possible
trip chain types, or all of the above. Household travel diary surveys provide a wealth of information on the travel patterns
of individuals and households. Since such surveys collect all information related to travel undertaken, in theory it should
be possible to extract trip-chaining characteristics of travel from them. Due to the difficulty in establishing and analysing
all of the possible trip chain types, the majority of research on trip chaining has appeared to focus on work travel only.
However, work related travel in many cities does not represent the majority of activities undertaken and, for some age groups,
does not represent any travel at all. This paper begins by reviewing existing research in the field of trip chaining. In particular,
investigations into the definitions of trip chaining, the defined typologies of trip chains and the research questions that
have been addressed are explored. This review of previous research into trip chaining facilitates the following tasks: the
identification of the most useful questions to be addressed by this research; defining trip chaining and associated typologies
and defining data structures to extract trip chaining information from the household travel surveys conducted in metropolitan
Adelaide, South Australia. The definition and typology developed in our research was then used to extract trip-chaining information
from the household travel diary survey (MAHTS99) conducted in Adelaide in 1999. The extracted trip chaining information was
then used to investigate trip-chaining behaviour by households. The paper reports the results of this analysis and concludes
with a summary of the findings and recommendations for further investigations. 相似文献
589.
This study used goal interference theory to examine the recreation conflict among motorboat users, personal watercraft users, and riparian landowners. Data were collected from three types of owners in the New York Great Lake coastal area. Results indicated each of the four recreation conflict dimensions proposed in goal interference theory contained multiple factors. Logistic regression models indicated that one or more dimensions were significant in predicting perceived conflict and the models correctly predicted conflict in over 70% to 100% of the cases. Goal interference theory can be seen as a general model, but significance of the four dimensions depends on types of recreation activities and users. 相似文献
590.
Abstract The Virginia Wetlands Act of 1972 provides the localities of Tidewater Virginia an opportunity to participate in the management of the state's coastal wetlands resources. This study attempts to analyze the effectiveness of this legislation and to examine the implications of a local management scheme for coastal resource management on a broader scale. Criteria are also established that can be used to evaluate the effectiveness of such a law. When examined in the light of these criteria, the Virginia Wetlands Act emerges, for the most part, as an effective piece of environmental quality legislation that has had a significant impact on wetlands destruction in the state of Virginia. During the two‐year period following the passage of the Act, wetlands losses through the permitting process showed an 18‐fold decrease from previous estimates. The Wetlands Act appears to have been generally accepted by the public and has resulted in consistently uniform decisions, which have reduced wetlands losses without unduly restricting the necessary and legitimate development of the state's wetlands. 相似文献