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本文建立了水轮发电机组仿真模型,并以某电站的水流特性、机组惯性等实际参数作为仿真模型参数,着重研究水轮发电机组的两种开机控制规律,分析了原有以空载开度为限制的机组开机控制技术,提出以恒转速变化率为控制目标的机组开机控制技术,并将两种开机控制技术进行了仿真比较。通过仿真波形分析比较表明,两种开机控制技术各自具有的优越动态性能。在工程实践中,将这两种开机控制技术都应用到水轮机调速器开机程序中,可以根据水电站现场对开机动态性能的不同要求在停机态切换两种开机控制流程。 相似文献
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Abstract: San Antonio Bay is located on the coast of Texas between Galveston Bay and Corpus Christi Bay and is the primary bay in the Guadalupe Estuary. Three rivers feed San Antonio Bay from two river basins, including the Blanco and Guadalupe Rivers in the Guadalupe River Basin and the San Antonio River in the San Antonio River Basin. The Canyon Reservoir regulates the flow of fresh water in the middle and lower reaches of the Guadalupe River. These inflows are a primary regulator of salinity and, thus, the productivity of commercially important estuarine species. Increasing demand for water has prompted plans for an increased diversion of 49.3 million m3 (40,000 acre‐feet) from the reservoir. An additional amount of 61.6 million m3 (50,000 acre‐feet) from the mouth of the river is to be pumped back to San Antonio to relieve over‐pumping of the Edwards Aquifer. Because the Guadalupe River Basin contributes 58.1 percent of the freshwater inflow to the estuary, it is not known what the impact of these actions will have on the ecological integrity of the San Antonio Bay. Water resource management in the San Antonio Basin consists of decision making under risk and uncertainty related to randomness in the critical parameters such as the salinity in the bay, biological productivity, and total flow into the bay. The aim of this study is to investigate the trade‐offs between the competing objectives of maximizing biological productivity in the bay and minimizing flow using Stochastic Compromise Programming (SCP). The SCP model solves a multi‐objective function subject to constraints that must be maintained at three different prescribed levels of probability providing a global set of solutions for the water resource management problem under input uncertainty. The SCP model provides information on the trade‐offs among the objective function value, tolerance values of the constraint at the prescribed levels of probability, which could be valuable to policy makers in risk assessment. Solutions were found using three distance functions. Model outputs may suggest the minimum amount of freshwater needed to maximize biological productivity of the bay at specified risk level for assessing the impact of upcoming diversion program. Results indicate that current flows in the Guadalupe River are of sufficient volume to satisfy harvest requirements. 相似文献
54.
Six methods, QiAamp DNA Mini Kit (Q), Q with Sepharose 4B gel column (Q/G), Q with low melting point agarose (Q/L), freeze-thaw/phenol-chloroform lysis (FT-PC), FT-PC/G, and FT-PC/L, were evaluated for their ability to isolate DNA of sufficient quality to quantify Legionella using qPCR. Samples of mixing Legionella pneumophila (ATCC33152) and humic acid (HA, 0-126.8 mg/l) were treated by the six methods. Q, Q/G, Q/L, FT-PC/G, and FT-PC/L removed HA from 1.9-126.8 to <1 mg/l determined by A260 with a spectrophotometer. Q obtained the highest DNA yield, followed by Q/G. Dilution (10- to 100-fold) of DNA arising from extraction using Q, Q/G, FT-PC, or FT-PC/G prevented qPCR inhibition. The highest recovery of cells was found in DNA extracted by Q and diluted 100-fold, and followed by Q/G. The applicability of Q and Q/G with dilution was further validated with cooling tower waters. Q or Q/G with 10-fold dilution increased L. pneumophila detection, whereas 100-fold dilution obtained the highest cell concentrations. Similar results were found for Legionella spp. except that both 10- and 100-fold dilutions increased cell concentrations. Thus, Q with 10-fold dilution is suggested to detect and quantify Legionella spp. and detect L. pneumophila. For L. pneumophila-positive samples, 100-fold diluted DNA must be re-analyzed to accurately quantify L. pneumophila. 相似文献
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本文研究的汛限水位动态控制即为发掘水库潜能,促使洪水资源化、提高水资源利用率的有效方法之一.在分析我国水资源形势的基础上,汛限水位动态控制是在我国特殊国情国策下具有中国特色的产物,先确定某水库的汛限水位动态控制范围,然后用“实时预蓄预泄法”对水库汛限水位进行动态控制实例研究. 相似文献
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在缺乏卖空机制的环境下,可转债相对价值的实现将主要来源于转债与股票之间的资产替换。尤其是在杠杆放大的资产替代策略下,可转债投资的盈利模式将出现根本性变化,股票价格的波动成为影响策略应用效果的最重要因素。本从对冲套利的角度,通过对等额和杠杆放大资产替换策略的模拟与分析,就资产替换策略的应用环境、杠杆选择与实证效果等问题进行了较为详尽的研究。 相似文献
58.
This paper reports the results of the quantitative analysis of international experience of the relationship between infrastructure investment in the deployment of capacity that can carry large volumes of voice and data traffic and regulatory policy changes in the telecommunications sectors. It looks at the relationship between infrastructure investment for these infrastructure assets and the access pricing régimes for local exchange carriers in the United States and Europe. It then looks at the relationship between various aspects of regulatory and institutional policy changes in Europe and how they affect access prices.The paper finds that a lower access price promotes greater deployment of digital technology among US incumbent local exchange carriers (ILECs). Based on this finding, it suggests that it is in the ILECs interest to have access to their networks encouraged.The European data for interconnection are recent and far reaching conclusions are not feasible, but the findings, however, suggest that competition has worked by facilitating new entry through decreasing interconnection prices, although path dependencies, of existing and traditional concepts, in the mindsets of operators as well as regulators, may account for these findings. 相似文献
59.
Charles Goodhart Yuanchen Chang Richard Payne 《Journal of International Money and Finance》1997,16(6):921-930
In this paper we investigate the efficiency of a class of transaction-generating algorithms, originally suggested in Bollerslev and Domowitz (1993). Our comparison utilizes real transaction data recorded over Reuters D2000-2 electronic broking system for 7 h in June 1993 and transaction data generated from FXFX quotations over an identical period. Results suggest that, at this high-frequency data sampling, the performance of these transaction-generating algorithms is poor, with the most likely explanation of this outcome due to the high-frequency characteristics of FXFX spreads and quotation intensity. 相似文献
60.