带整流负载同步发电机稳定性研究

采用将带整流负载同步发电机中各变量的d、q轴低频分量和高频分量分别加以处理的方法，得出了带整流负载三相同步发电机的等效电路模型，以及小扰动条件下三相同步发电机整流系统的稳定条件，并通过试验加以验证，得到了阻尼绕组不能改善带整流负载同步发电机系统运行稳定性的结论。     

带整流负载同步发电机短路电流计算

该文对有阻尼绕组同步发电机整流系统和无阻尼绕组同步发电机整流系统直流侧短路时的最大短路电流进行了分析和计算，得出了随短路初始转子位置的不同，三相同步发电机整流系统直流侧短路电流峰值最大为交流侧最大短路电流，直流侧短路电流峰值最小可为交流侧量大短路电流值的0．933倍。     

带整流负载同步发电机阻尼绕组研究

阻尼绕组对发动机短路电流值大小起着决定性的影响,本文就阻尼绕组对同步发电机整流系统直流侧短路时的最大短路电流及对基本波形的影响分析别进行了分析计算和试验验证,得出了无限尼绕组同步发电机整流系统直流侧短路电流值较有阻尼绕组同步发电机有明显下降;阻尼绕组具有改善同步发电机整流系统交直流测电压波形的作用,去掉阻尼绕组使得交流电压波形谐波含量增大,波形畸变加剧;ｑ绕组对改善电压波形效果明显,可以弥补减弱阻     

永磁同步发电机PWM整流系统初步研究

针对传统发电机整流系统谐波含量大，功率因数低的特点，为永磁同步发电机设计了一套PWM整流系统，通过电流前馈解耦控制，实现有功无功解耦，实现发电机侧单位功率因数运行。实验结果验证了该控制方案的可行性，可有效减少发电机电流谐波含量，并能在发电频率较大范围变动时仍能保持系统稳定运行。     

带整流负载的交流同步脉冲发电机励磁控制的设计与仿真

当同步发电机带整流负载工作在连续脉冲工况时,通过整流装置调节励磁电流以控制输出电流的难度较大。本文对系统各个环节进行了理论分析,建立了各个环节的数学模型,然后借助Matlab/Simulink工具箱,建立了系统的仿真模型,并且利用控制理论对发电机励磁的控制结构和参数进行了设计,最后将仿真波形与实际工程中的波形进行了比较分析,结果表明这种同步脉冲发电机励磁控制方式是可行的。     

钻井平台自动无功功率分配的必要性

为研究钻井平台中带晶闸管整流的发电机组增加自动无功功率分配功能的必要性,从晶闸管整流的原理出发,研究了同步发电机励磁系统的无功分配原则,得出了带晶闸管整流器的发电机系统需要增加自动无功功率分配功能的结论,并在实际项目的调试中验证了该结论。     

基于同步发电机不控整流的消磁脉冲电源励磁控制系统研究

讨论了消磁脉冲电源的发展趋势以及基于同步发电机不控整流的消磁脉冲电源的优越性,接着分析了基于同步发电机不控整流的消磁脉冲电源的原理、组成和特性,采用了数字励磁方案,建立了其电气部分的的物理和数学模型,设计了数字励磁装置的相关控制参数靠。实验结果表明,该励磁装置使基于同步发电机不控整流的消磁脉冲电源输出了合格的消磁脉冲电流,廉价可靠。     

带交流和整流负载的三相同步发电机系统的稳定性分析

本文首先导出了同时带交流和整流负载的三相同步发电机系统的等效电路，在此基础上，运用谐波平衡原理，得到了该系统的数学模型及小扰动时的稳定判据，结果表明交流负载有助于提高该类系统的稳定性，电机参数与系统稳定性密切相关。     

十二相同步发电机的电路模型及仿真

在十二相同步发电机基本数学模型的基础上,根据整流绕组各参数间的等值关系,推导出其磁链方程及等效电路,并基于MATLAB/simulink的仿真环境建立了该型发电机的仿真模型。该模型考虑了整流绕组之间互感不相等的情况,使其更符合实际。利用此模型可以更方便地研究十二相同步整流发电机系统的各项性能。最后通过实机试验检验了模型的正确性。     

钻井平台自动无功功率分配的必要性

晶闸管由于其技术成熟且成本低,现仍广泛应用于钻井平台中,而由于晶闸管整流所造成的无功功率太大对于发电机组的问题,一直是需要解决的问题。为解决钻井平台中,带晶闸管整流的发电机组是否需要增加自动无功功率分配功能的问题,本文从晶闸管整流的原理出发,研究同步发电机励磁系统的无功分配原则,论述带晶闸管整流器的发电机系统需要增加自动无功功率分配功能的必要性。上述分析并在实际项目的调试中加以验证。     

Practical estimation method of the design loads for primary structural members of bulk carriers

Various design loads used in the strength evaluation of ship structures have been introduced currently by classification societies. As most of these design loads have been determined as standard loads for the sake of convenience, the relationships between the design loads and the sea states actually encountered by ships seem to be weak. Accordingly, it may be difficult to refer and utilize them as fundamental design concepts for ship designers or as operational guidelines for ship operators. In view of this background, various efforts (Trans. West-Jpn. Soc. Nav. Archi. 89 (1995) 191; 93 (1997) 121; Jap Shipbuild. Mar. Eng. 2 (1967) 13; Proceedings of the 18th International Conference on Offshore Mechanics and Arctic Engineering 1999; Mar. Struct. 13 (2000) 495; J. Ship. Res. 45 (2001) 228; J. Mar. Sci. Technol. 6 (2002) 122; J. Soc. Nav. Archi. Jpn. 186 (1999) 319; Technical guide regarding the strength evaluation of hull structures, 1999; Proceedings of the 14th International Conference on Offshore Mechanics and Arctic Engineering, 1995; Mar. Struct. 10 (1997) 611; Proceedings of the Eighth International Symposium on Practical Design of Ships and Other Floating Structures, Shanghai, Vol. 2, China, 2001, p. 1089; Mar. Struct. 12 (1999) 171; Mar. Struct. 4 (1991) 295) have been made in recent years for developing estimation methods of the design sea states in a rational manner. Furthermore, for more practical purposes, the authors have developed practical estimation methods of the design sea states, the design regular waves and the design loads having transparent and consistent backgrounds to the actual loads acting on primary structural members of tankers (Mar. Struct. 16 (2003) 275).In this paper, it is firstly confirmed that the proposed methods for tanker structures can also be applied to the primary structural members of bulk carriers. Furthermore, the necessary modifications are carried out considering the specific structural types and loading conditions of bulk carriers in order to improve the estimating accuracy of the proposed design loads. Finally, comparisons between the results obtained by the structural analysis of a hold model applying the proposed design loads and long-term values of stresses by the most advanced direct structural analyses for different loading conditions are introduced and discussed in detail.     

船舶动力系统S.S.S离合器运动特性仿真研究

中继式S.S.S.离合器主要应用在燃气轮机驱动的动力系统,其运动规律对动力系统的传动/切换性能具有重大影响.阐述中继式S.S.S.离合器的结构运动,并建立其虚拟样机.在不同约束条件下,对中继式S.S.S.离合器运动过程进行动态仿真研究,得到中继式S.S.S.离合器的运动特性及的阻尼特性.     

U.S. ports: evolution and structure

U.S. ports are facing competitive pressures similar to those being felt by ports elsewhere around the world. Despite the public enterprise nature of U.S. port authorities, they tend to function as 'business-like' organizations. This enterprise-like approach stems from their evolution from being primarily private railroad ports in the 19th century to public competitive port authorities in the 20th century. This paper provides an overview of the evolution of U.S. ports and the ongoing effect of earlier legislation, the varied resulting institutional structures, and current national and regional level issues. Although there is no national ports plan or strategy in the U.S.A. (the Constitution limits federal actions in the ports field) the federal government is involved in providing dredging services through the Army Corps of Engineers, navigation aids via the Coast Guard and other minor port-related services. U.S. ports typically come under the jurisdiction of state or local governments. Increasing competition coupled with other port issues (growing financial constraints, difficulties in obtaining dredging permits, environmental concerns and restricted landside access) is forcing some U.S. ports to enter into strategic alliances with others at a regional level.     

Primary productivity of the Palmer Long Term Ecological Research Area and the Southern Ocean

A major objective of the Palmer Long Term Ecological Research (Palmer LTER) project is to obtain a comprehensive understanding of the various components of the Antarctic marine ecosystem. Phytoplankton production plays a key role in this so-called high nutrient, low chlorophyll environment, and factors that regulate production include those that control cell growth (light, temperature, and nutrients) and those that control cell accumulation rate and hence population growth (water column stability, grazing, and sinking). Sea ice mediates several of these factors and frequently conditions the water column for a spring bloom which is characterized by a pulse of production restricted in both time and space. This study models the spatial and temporal variability of primary production within the Palmer LTER area west of the Antarctic Peninsula and discusses this production in the context of historical data for the Southern Ocean. Primary production for the Southern Ocean and the Palmer LTER area have been computed using both light-pigment production models [Smith, R.C., Bidigare, R.R., Prézelin, B.B., Baker, K.S., Brooks, J.M., 1987. Optical characterization of primary productivity across a coastal front. Mar. Biol. (96), 575–591; Bidigare, R.R., Smith, R.C., Baker, K.S., Marra, J., 1987. Oceanic primary production estimates from measurements of spectral irradiance and pigment concentrations. Global Biogeochem. Cycles (1), 171–186; Morel, A., Berthon, J.F., 1989. Surface pigments, algal biomass profiles and potential production of the euphotic layer—relationships reinvestigated in view of remote-sensing applications. Limnol. Oceanogr. (34), 1545–1562] and an ice edge production model [Nelson, D.M., Smith, W.O., 1986. Phytoplankton bloom dynamics of the western Ross Sea ice edge: II. Mesoscale cycling of nitrogen and silicon. Deep-Sea Res. (33), 1389–1412; Wilson, D.L., Smith, W.O., Nelson, D.M., 1986. Phytoplankton bloom dynamics of the Western Ross Sea ice edge: I. primary productivity and species-specific production. Deep-Sea Res., 33, 1375–1387; Smith, W.O., Nelson, D.M., 1986. Importance of ice edge phytoplankton production in the Southern Ocean. BioScience (36), 251–257]. Chlorophyll concentrations, total photosynthetically available radiation (PAR) and sea ice concentrations were derived from satellite data. These same parameters, in addition to hydrodynamic conditions, have also been determined from shipboard and Palmer Station observations during the LTER program. Model results are compared, sensitivity studies evaluated, and productivity of the Palmer LTER region is discussed in terms of its space time distribution, seasonal and interannual variability, and overall contribution to the marine ecology of the Southern Ocean.     

32000DWT散货船应急消防泵吸入能力核算

国际船级社协会(IACS)通过UI SC 178(rev.1)统一解释,明确规定了固定式应急消防泵吸口压头应满足《国际消防安全系统规则(FSS规则)》第12.2.2.1.3条的要求,并适用于合同建造日期为2012年1月1日及以后的船舶。基于EXCEL数据处理方法,以32 000 DWT散货船为例,详细核算了应急消防泵在统一解释规定的各种营运工况下的吸入能力。核算结果表明:该船应急消防泵吸口完全浸没在水线以下,故其吸入压头完全满足上述要求。     

Book reviews

R. S. Farrow, with J. M. Broadus, T. A. Grigalunas, P. Hoagland III, and J. J. Opaluch. 1990. Managing the Outer Continental Shelf Lands: Oceans of Controversy. New York: Taylor & Francis New York, 168 pp., paper.

Richard A. Kenchington. 1990. Managing Marine Environments. New York: Taylor & Francis, 248 pp.     

2 kHz high power smart transducer for acoustic sub-bottom profiling applications

In this study,a 2kHz Tonpilz projector was designed using a Terfenol-D and modeled in ATILA.For the purpose of modeling studies,it has been determined that a radiating head mass exhibits better transmitting current response（TCR） at 136 mm diameter,where the resonance occurs at 2.4kHz and the peak value of 118 dB re 1 μPa/A at 1 m occurs at 12 kHz.Also bolt at a 46mm distance from the center of the head mass offers resonance at 2.4kHz,and the peak value of 115.3 dB re 1 μPa/A at 1m occurs at 11.5kHz.This optimized design is fabricated and molded with polyurethane of 3mm thickness.The prototype was tested at the Acoustic Test Facility（ATF） of National Institute of Ocean Technology（NIOT） for its underwater performances.Based on the result,the fundamental resonance was determined to be 2.18kHz and the peak value of TCR of 182 dB re 1 μPa/A at 1m occurs at 14 kHz.The maximum value of the RS was found to be -190 dB re 1V/μPa at 1m at a frequency of 2.1kHz.     

Book review

Coastal Management: Readings and Notes. Edited by Marc J. Hershman and James H. Feldmann. Institute for Marine Studies, Coastal Resources Program, University of Washington, Seattle (January 1979), 806 pp. $22.50 (paper bound).

Tobey L. Winters, Deepwater Ports in the United States: An Economic and Environmental Impact Study. N.Y. Praeger, 1977, 201 pages.     

高置滑油循环柜在滑油系统中的应用

本文介绍高置滑油柜在滑油系统中的应用,阐明采用高置滑油柜可省略滑油抽吸泵的实用方法。     

Carbon flows in Baltic Sea food webs — a re-evaluation using a mass balance approach

The brackish Baltic Sea has been seen as particularly suitable for studies of food webs. Compared to fully marine ecosystems, it has low species diversity, which means fewer trophic linkages to analyse. The Baltic Sea is also one of the best-studied areas of the world, suggesting that most data requirements for food web models should be fulfilled. Nevertheless, the influence of physical and biological factors on trophic interactions and biogeochemical patterns varies spatially in the Baltic Sea, adding considerable complexity to food web studies. Food web structure and processes can be described and compared quantitatively between areas by estimating the flow of matter or energy through the organisms. Most such models have been based on carbon, though studies of complementary flows of other elements limiting production, such as nitrogen and phosphorus would be desirable. However, since ratios between carbon and other elements are used in calculating these flows, it is crucial, as a first step, to quantify the flows of carbon as accurately as possible.In this study, we used the EcopathII software (ver 3.1) to analyse models of carbon flow through the food webs in the three main areas of the Baltic Sea; the Baltic proper, Bothnian Sea and Bothnian Bay. A previously published study on carbon flow in the Baltic Sea [Elmgren, R. 1984. Trophic dynamics in the enclosed, brackish Baltic Sea. Rapp. P.-V. Reun. — Cons. Int. Explor. Mer. (183) 152–169.] was complemented with the data on respiration and flow to detritus [Wulff, F., Ulanowicz, R. 1989. A comparative anatomy of the Baltic Sea and Chesapeeake Bay ecosystems. In: F. Wulff, J.G. Field, K.H. Mann (Eds.), Flow Analysis of Marine Ecosystems: Theory and Practice. New York: Springer-Verlag.] in order to present complete mass balance models of carbon. The purpose of re-evaluating previous models with new analytic tools was to check how well their carbon flows balance, and to provide a basis for improved mass balance models using more recent data, including nutrients other than carbon.The resulting mass balance networks for the Baltic proper, Bothnian Sea and the Bothnian Bay were shown to deviate from steady state. There was an organic carbon surplus of 45, 25 and 18 g C m⁻² year⁻¹ in the pelagic zones of the Baltic proper, Bothnian Sea and Bothnian Bay, respectively. The Ecopath network analysis confirmed that the overall carbon flow was highest in the Baltic proper, somewhat lower in the Bothnian Sea and much lower in the Bothnian Bay. The only clear differences in food web structure between the basins was that the average trophic level was lower for demersal fish in the Bothnian Sea and higher for macrofauna in the Bothnian Bay, compared to the other basins. The analysis showed weakness in our current understanding in Baltic Sea food webs and highlighted areas where improvements could be made with more recent data.