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11.
Organic carbon budget for the Gulf of Bothnia 总被引:1,自引:0,他引:1
Grete Algesten Lars Brydsten Per Jonsson Pirkko Kortelainen Stefan Lfgren Lars Rahm Antti Rike Sebastian Sobek Lars Tranvik Johan Wikner Mats Jansson 《Journal of Marine Systems》2006,63(3-4):155-161
We calculated input of organic carbon to the unproductive, brackish water basin of the Gulf of Bothnia from rivers, point sources and the atmosphere. We also calculated the net exchange of organic carbon between the Gulf of Bothnia and the adjacent marine system, the Baltic Proper. We compared the input with sinks for organic carbon; permanent incorporation in sediments and mineralization and subsequent evasion of CO2 to the atmosphere. The major fluxes were riverine input (1500 Gg C year− 1), exchange with the Baltic Proper (depending on which of several possible DOC concentration differences between the basins that was used in the calculation, the flux varied between an outflow of 466 and an input of 950 Gg C year− 1), sediment burial (1100 Gg C year− 1) and evasion to the atmosphere (3610 Gg C year− 1). The largest single net flux was the emission of CO2 to the atmosphere, mainly caused by bacterial mineralization of organic carbon. Input and output did not match in our budget which we ascribe uncertainties in the calculation of the exchange of organic carbon between the Gulf of Bothnia and the Baltic Proper, and the fact that CO2 emission, which in our calculation represented 1 year (2002) may have been overestimated in comparison with long-term means. We conclude that net heterotrophy of the Gulf of Bothnia was due to input of organic carbon from both the catchment and from the Baltic Proper and that the future degree of net heterotrophy will be sensible to both catchment export of organic carbon and to the ongoing eutrophication of the Baltic Proper. 相似文献
12.
Mitsuhisa Ikehata Takeshi Inoue Manabu Ozawa Shinya Matsumoto 《Journal of Marine Science and Technology》1997,2(2):62-76
To examine the flow field of a viscous fluid around the trailing edge of a wing with respect to the Kutta condition or the
Joukowski hypothesis, an experimental investigation into the velocity fields around two-dimensional (2D) wings NACA0012 and
NACA4412 was carried out using an X-type hot-wire anemometer in a wind tunnel and the method of colored milk injection in
a circulating water channel. The results of these investigations revealed that the flow of a viscous fluid at the trailing
edge of a 2D wing is tangential to the face on the pressure side, and that the flow is very slow or reversed on the suction
side due to separation when the angle of attack is greater than 7.5°. By flow visualization, a Kármán vortex street was found
in the wake of both wings (NACA0012 and NACA4412) when the angle of attack was 5°. These results show that the ordinary Kutta
condition with respect to the direction of outflow at the trailing edge is not necessarily satisfied in a viscous fluid, but
the Kutta condition with respect to the pressure at the trailing edge is satisfied as usual. Numerical results, which have
been obtained as the solution of Reynolds-averaged Navier-Stokes equations, show good agreement with above-mentioned experimental
results. Therefore, CFD (Computational Fluid Dynamics) simulation has proved to be very effective for studying steady viscous
flow around the trailing edge of a 2D wing. 相似文献
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14.
陈立华 《铁路通信信号工程技术》2006,3(6):11-12
本文从设计的角度,介绍了ZPW-2000A闭环电码化在既有线CTCS2区段的设计方案及其方案的完善。 相似文献
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16.
铁路移动信息传输安全平台的设计与实现 总被引:1,自引:1,他引:0
为铁路移动设备通过GPRS、Internet、网络动态隔离系统、铁路内部骨干计算机网实现与地面局域网间的实时数据通信,从实用、安全、可靠的角度出发,设计公用网与铁路专用网安全互联、移动设备与地面网络可靠互通的铁路移动信息传输安全平台。该平台硬件系统由内外网通信服务器、行车监控及业务系统设备为主的时实监控和传输设施组成,平台软件系统主要由外网传输处理子系统、内网传输处理子系统、管理监视子系统构成。将GPRS数据接入点部署在铁路局,每个铁路局设立统一的外网通信服务器,作为各个业务系统地面数据处理中心,承担所有应用系统车、地间和内、外网间的数据交换任务,使各应用系统中所有从GPRS下载的实时信息统一由铁路局外网通信服务器接收,再经网络安全传输平台进入铁路运输生产系统,提供给各个相关责任部门使用,从而确保铁路第6次大提速的行车安全。 相似文献
17.
终端位置更新速率又是卫星通信系统终端位置管理的重要指标,直接影响到海上卫星移动通信系统的性能。从位置区设置方式出发,探讨采用不同的位置管理策略下的位置更新速率计算,并通过STK4.02和OPNET8.0.平台下的数值仿真,分析不同参数影响下的各种管理策略的特点。 相似文献
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19.
Hironao Kawashima 《Transportation》1990,17(3):263-284
A perspective view of of Japanese R&D activities of Driver Information Systems is given from the standpoint of developing joint projects by public and private sectors. First, a brief history of the R&D activities is illustrated from above mentioned standpoint. Then, two major projects, AMTICS and RACS, and the social backgrounds of these projects are explained. In order to give a clear idea of both projects some technical details are treated.Based on the history and the present status of the developments, the basic design conceptions of Japanese Driver Information Systems are explained and several factors or reasons which have influenced to the design conception are discussed. Then, the promoting systems of the R&D activities are generally explained and present status of the projects and future problems in developing more advanced systems are also handled. A brief discussion on the establishment of international standard is also mentioned as a final comment. 相似文献
20.