共查询到20条相似文献，搜索用时 31 毫秒
1.
The Huai River Basin is a unique area in P. R. China with the highest densities of population and water projects. It is also subject to the most serious water pollution. We proposed a distributional SWAT （Soil and Water Assessment Tool） model coupled with a water quality-quantity balance model to evaluate dam impacts on river flow regimes and water quality in the middle and upper reaches of the Huai River Basin. We calibrated and validated the SWAT model with data from 29 selected cross-sections in four typical years （1971, 1981, 1991 and 1999） and used scenario analysis to compensate for the unavailability of historical data regarding uninterrupted river flows before dam and floodgate construction, a problem of prediction for ungauged basins. The results indicate that dam and floodgate operations tended to reduce runoff, decrease peak value and shift peaking time. The contribution of water projects to river water quality deterioration in the concerned river system was between 0 to 40%, while pollutant discharge contributed to 60% to 100% of the water pollution. Pollution control should therefore be the key to the water quality rehabilitation in the Huai River Basin. 相似文献
2.
采用的非线性方法是基于24 h的平均温度,通过下列4种方法计算得到的逐时平均、四次平均、三次观测数据加上加权订正所得数据的平均、最高最低平均法得到的日平均温度与逐时平均比较,同时求出各种结果和24 h计算所得平均温度之间的离散度,发现在日平均温度的计算上,除了所述的24 h平均温度计算方法外,4次平均方法求出的日平均温度具有较好代表性,其他两种方法计算偏差相对较大。 相似文献
3.
选取了澜沧江—湄公河流域的干流和部分支流,对鱼类种类数与水文及流域特征的关系进行了统计分析.在一元线性回归分析中：特有种类数与鱼类种类数呈极显著性正相关;鱼类种类数和特有种类数的绝对数与干流长、流域面积、多年平均流量呈极显著性正相关.全部种类数和特有种类数的多元逐步回归分析得到的最优回归方程分别保留了多年平均流量、含沙量以及流域面积和含沙量.主成分分析得到的第1和第2主成分分别反映了不同水域中鱼类相对数目、绝对数目与流域的水文特征之间的关系. 相似文献
4.
近来,美国学者HOOS等人,提出一种新的洪水预报动力模型,该模型具有预见期,能直接应用于河系连续洪水预报,具有很大实用价值。 本文将该模型对闽江洪水预报的应用进行了初步探讨,说明了该模型的实用性。 相似文献
5.
《Early education and development》2013,24(2):173-187
The proliferation of early childhood programs for children with and without disabilities has occurred without clear indicators or standards of program quality. Evaluations of these programs often consist of compliance monitoring or outcome assessment. Little attention is given to program context or the quality of individual components of the program. In this paper, an alternative evaluation model, a connoisseurship or professional review model using on-site observations, interviews, and document review, was used to identify exemplary practices in early childhood education in one large midwestern state. The results indicated that with proper training and support, early childhood professionals without experience in qualitative methods can become proficient in interviewing techniques, observation, and document review. The resulting case study reports were useful for identifying and describing exemplary practices across the state, demonstrating the potential for this alternative approach to evaluation in early childhood education. 相似文献
6.
Lizanne DeStefano Susan P. Maude Sandra Heinzel Crews Linda Mabry 《Early education and development》1992,3(2):173-187
The proliferation of early childhood programs for children with and without disabilities has occurred without clear indicators or standards of program quality. Evaluations of these programs often consist of compliance monitoring or outcome assessment. Little attention is given to program context or the quality of individual components of the program. In this paper, an alternative evaluation model, a connoisseurship or professional review model using on-site observations, interviews, and document review, was used to identify exemplary practices in early childhood education in one large midwestern state. The results indicated that with proper training and support, early childhood professionals without experience in qualitative methods can become proficient in interviewing techniques, observation, and document review. The resulting case study reports were useful for identifying and describing exemplary practices across the state, demonstrating the potential for this alternative approach to evaluation in early childhood education. 相似文献
7.
汉代黄河屡次决口兖州附近河段,除了与当地土质疏松、河道复杂有关外,最主要因素是：当时的决策者、河道治理的指挥者、治河制度的不完善程度以及国家财政的支持力度。只有这四方面同时满足并有机结合,才能彻底治理好黄河水患,使黄河造福人民。 相似文献
8.
刘长生 《安阳师范学院学报》2008,(1):85-89
旧中国历代政府水务荒废,黄河南下长期侵蚀淮河水道,致使淮河流域灾害频仍。1950年淮河再次发生流域性水灾,淮河干支流堤坝溃漫无数,村没物毁,损失惨重。严重的灾情引起以毛泽东为首的中央领导集体的关注,发出根治淮河的号召;周恩来主持召开中央治淮工作会议,确定了治淮方针,并成立专门的治淮领导机构治淮委员会。在广大干部群众的努力之下,初期治淮取得了显著成绩,实现了新中国治淮的良好起步。 相似文献
9.
《天津大学学报(英文版)》2017,(6)
In this study, a continuous and airtight twinspiral dryer was developed in accordance with the characteristics and challenges in the process of disposing polysilicon slurry. Computational fluid dynamics(CFD)simulations were used to investigate the flow field in the rotating twin-spiral continuous dryer and an original discrete phase model was also elaborated to compare with the cold-modeling experimental results. The corresponding flow field was obtained using the available inlet velocity of 0.05-0.3 m/s and the rotational speed of the inner cone of 12-44 r/min, the residence time distribution, and tracked particles trajectory. Results showed that the residence time of the tracer particles in the cone cylinder was about 15.8-25.4% of the time spent out of it, and the particle's residence time was much shorter in contrast to the rotational speed and inlet velocity. The external ribbon had a larger influence on the fluid, thereby leading to a larger velocity in the region outside the cone compared to that in the region inside the cone. In addition, the appearance of the vortex and boundary layer separation at the back of the ribbon and the spoke bar had secondary diversion effects on the fluid. Furthermore, the inlet velocity had little influence on the flow field while the rotational speed of the cone greatly affected the flow field. Hence, the CFD simulations showed good agreement with the experimental results. 相似文献
10.
姚胜利 《杨凌职业技术学院学报》2006,5(4):20-22
对渭河下游河势及水文状况的多年变化情况进行了介绍和分析,分析认为三门峡水库的修建,使渭河水流变缓,挟沙能力降低,中游大量泥沙在渭河入黄河口大量堆积,造成潼关高程显著抬升,渭河水平面升高,这是渭河下游淤积严重的重要原因。洪水期渭河过流能力急剧减小,防洪能力十分严峻。通过资料分析表明,渭河各段淤积量与潼关高程呈现出一种线形相关规律,由此得出降低三门峡水库运行水位,从而降低潼关高程,减小渭河下游泥沙淤积,提高渭河过水能力,对渭河流域防洪减灾有重要的现实意义。 相似文献
11.
邱紫华 《郧阳师范高等专科学校学报》2009,29(1):18-19
《汉水文化论纲》一书立足于文化历史学、文化哲学和文化地理学等学科背景,着眼于全面性、典型性、学术性和普及性等写作定位,运用现代学术规范,首次从六个层面系统地梳理了汉水文化的形成和发展的古今概貌,揭示了汉水文化的基本内涵和特征。全面地描绘了汉水流域具有典型意义、五彩纷呈的文化事象和民风民俗,填补了地域文化研究、流域与河流文化研究、乃至中国传统文化研究的一大空白。 相似文献
12.
Volume rendering of 3D data sets composed of sequential 2D medical images has become an important branch in image processing and computer graphics.To help physicians fully understand deep-seated human organs and focuses(e.g.a tumour)as 3D structures.in this paper,we present a modified volume rendering algorithm to render volumetric data,Using this method.the projection images of structures of interest from different viewing directions can be obtained satisfactorily.By rotating the light source and the observer eyepoint,this method avoids rotates the whole volumetric data in main memory and thus reduces computational complexity and rendering time.Experiments on CT images suggest that the proposed method is useful and efficient for rendering 3D data sets. 相似文献
13.
基于河流生态系统健康的内涵,建立包括河流自然结构、生态系统、社会服务等3个方面12个指标的河流生态系统健康指标评价体系.以梅江河主干流为例,通过应用评价方法和数学模型,对梅江河多个河段进行综合评估.结果表明:梅江河总体健康指数为0.611,处于"基本健康"等级状态,但其社会服务指数较低,为0.521,主要由于河道水质和通航情况不良. 相似文献
14.
Robert L. McKinley 《Journal of Educational Measurement》1988,25(3):233-246
Six procedures for combining sets of IRT item parameter estimates obtained from different samples were evaluated using real and simulated response data. In the simulated data analyses, true item and person parameters were used to generate response data for three different-sized samples. Each sample was calibrated separately to obtain three sets of item parameter estimates for each item. The six procedures for combining multiple estimates were each applied, and the results were evaluated by comparing the true and estimated item characteristic curves. For the real data, the two best methods from the simulation data analyses were applied to three different-sized samples and the resulting estimated item characteristic curves were compared to the curves obtained when the three samples were combined and calibrated simultaneously. The results support the use of covariance matrix-weighted averaging and a procedure that involves sample-size-weighted averaging of estimated item characteristic curves at the center of the ability distribution 相似文献
15.
龙川江是云南滇中高原面上最大的河流,其对楚雄州生态环境意义重大。龙川江经常出现断流现象,估算龙川江河道的生态需水量,可为龙川江的水量调控提供依据。通过对国内外河流生态需水量研究现状的梳理,选取曲率湿周法计算龙川江河道内最小生态需水量（MEIFR）。选取楚雄小河口、元谋小黄瓜园两个水文观测站的水文数据,估算出各观测站的MEIFR值：最大为6．8m3s^-1,最小为0m3s^-1。应用Tennant法研究结论分析龙川江MEIFR值,结果表明：按照龙川江整条河流多年平均径流量33．8m3s^-1计,需要MEIFR达到3．38m3s^-1,才能保护龙川江河道基本功能50％至全部,因此龙川江河道内现在的最小生态需水量并不能完全满足其河流的基本功能的需水量。 相似文献
16.
略论黄河史研究：——关于黄河文化生态的思考 总被引：1，自引：0，他引：1
鲁枢元 《黄河科技大学学报》2000,2(1):1-12
黄河即是一条自然的河,又是一条文化的河,一部黄河史,不只应当记述黄河的自然变迁,还应当阐明黄河的文化内涵,黄河在漫长的岁月中哺育了一代又一代黄河人,而黄河人同样在漫长的岁月中为黄河贯注了精气与灵魂,黄河与黄河流域的人类,将决定着黄河与黄河人的命运,已经流淌了百万年的黄河还将在地球的东方流淌下去,我们期待在新的世纪中,人类与黄河一道用更加协调的笔调,谱写出后续的篇章。 相似文献
17.
讨论了长江水质评价与预测问题,根据过去长江水质污染状况,建立的模糊优化评价模型,差值评判模型,水质污染回归模型及污水处理函数,评价且预测了长江水质污染情况,对长江水质污染问题的解决有一定的现实指导意义,提出的建议是切实可行的. 相似文献
18.
For river basin management, the reliability of the rating curves mainly depends on the accuracy and time period of the observed discharge and water level data. In the Elbe decision support system （DSS）, the rating curves are combined with the HEC-6 model to investigate the effects of river engineering measures on the Elbe River system. In such situations, the uncertainty originating from the HEC-6 model is of significant importance for the reliability of the rating curves and the corresponding DSS results. This paper proposes a two-step approach to analyze the uncertainty in the rating curves and propagate it into the Elbe DSS： analytic method and Latin Hypercube simulation. Via this approach the uncertainty and sensitivity of model outputs to input parameters are successfully investigated. The results show that the proposed approach is very efficient in investigating the effect of uncertainty and can play an important role in improving decision-making under uncertainty. 相似文献
19.
20.
潘世东 《郧阳师范高等专科学校学报》2014,(2):8-11
在中国古代历史上长江、黄河、淮河和汉水共同号称“四渎”,是四条著名的文化大河.其中,长江与黄河历来更被视为中华民族的父亲河和母亲河,其地位无比崇高.但近年研究考古却发现,文化历史也有自身的盲区和失误.在中国历史上最为古老悠久、最应享有尊崇地位的河流应该是汉江.只是汉水固有的历史文化光芒被长久地、偏执地遮蔽起来了而已. 相似文献