230,838 research outputs found
An improved moving particle semi-implicit method for dam break simulation
No full textDam break is quite a common and hazard phenomenon in shipbuilding and ocean engineering. The objective of this study is to investigate dam break hydrodynamics with improved Moving Particle Semi-implicit method (MPS). Compared to traditional mesh methods, MPS is feasible to simulate surface flows with large deformation, however, during the simulation, the pressure oscillates violently, due to misjudgment of surface particles as well as particles gathering together. To modify these problems, a new arc method is applied to judge free surface particles, and a collision model is introduced to avoid particles from gathering together. Hydrostatic pressure is simulated by original and improved MPS. The results verify that improved MPS method is more effective. Based on these, dam break model is investigated with improved MPS
Does Small Dam Removal Affect Local Property Values? An Empirical Analysis
No full textThis paper uses hedonic analysis to examine the impact of small dam removal on property values in South-central Wiscosin. Data on residential property sales were obtained for three categories of sites: those where a dam is intact, those where a dam was recently removed, and those where the stream has been free-flowing for at least 20 years. The primary conclusions that emerge from the data are that residential property located in the vicinity of a free-flowing stream is more valuable than identical property in the vicinity of a small impoundment, and that shoreline frontage along small impoundments confers no increase in residential property value compared to frontage along free-flowing streams.
Interaction of Chinese institutions with host governments in dam construction: the Bui Dam in Ghana
No full textThe study analyses the role of Chinese companies and financing institutions and Ghanaian governmental agencies in planning and constructing the Bui Dam. The analysis focuses on the division of responsibilities between Sinohydro and China Exim Bank on the one side and the Ghanaian government on the other side. The findings show that environmental and resettlement planning for Bui was commissioned and financed by the Government of Ghana without Sinohydro’s involvement. The obligation of the firm is to abide by the environmental regulations that are monitored by the regulatory authorities. The role of Sinohydro consists in building the dam, maintaining the construction site, contracting workers, and providing for workers’ health and safety. The firm has no role in resettlement, which is carried out by the Bui Power Authority. While there is clear evidence that the Bui Power Authority does not follow the recommendations of the Resettlement Planning Framework, Sinohydro appears to abide largely by the conditions set out in the Environmental Impact Assessment study whose implementation is monitored by the Ghanaian Environmental Protection Agency and the Ghanaian Water Resources Commission
Updating PMP to provide better dam and spillway design
No full textPresented at the Protections 2016: 2nd international seminar on dam protection against overtopping: concrete dams, embankment dams, levees, tailings dams held on 7th-9th September, 2016, at Colorado State University in Fort Collins, Colorado, USA. The increasing demand for dam and levee safety and flood protection has motivated new research and advancements and a greater need for cost-effective measures in overtopping protection as a solution for overtopping concerns at levees and dams. This seminar will bring together leading experts from practice, research, development, and implementation for two days of knowledge exchange followed by a technical tour of the Colorado State University Hydraulic Laboratory with overtopping flume and wave simulator. This seminar will focus on: Critical issues related to levees and dams; New developments and advanced tools; Overtopping protection systems; System design and performance; Applications and innovative solutions; Case histories of overtopping events; Physical modeling techniques and recent studies; and Numerical modeling methods.Includes bibliographical references.Probable Maximum Precipitation (PMP) is used as input to derive the Probable Maximum Flood (PMF) for high hazard dams across the United States. The PMF is used to design high hazard dams to ensure they do not overtop and fail during a PMP/PMF event. PMP values were developed for most of the United States by the National Weather Service (NWS) in a series of Hydrometeorological Reports (HMRs) starting in 1940 and continuing through 1999. However, the NWS stopped updating the HMRs and the storms used to derive the PMP values. Since that time the meteorological understanding of extreme rainfall has advanced significantly and numerous large rainfall events have occurred which affect PMP. Because the dam safety community required updated PMP values which incorporated these updated data and meteorological understanding to ensure proper design and rehab of dams, Applied Weather Associates (AWA) has been performing site-specific, statewide, and regional PMP studies to update these data and advance the science regarding PMP. Beginning in the 1990's, AWA has completed more than 100 PMP studies, which have been accepted by state and Federal dam safety regulators. Each of these provide updated PMP values which replace those from the HMRs. In this process, AWA has analyzed hundreds of the most extreme rainfall events, which are required for proper PMP development. This presentation will detail the history of PMP development in the United States, provide an understanding of current PMP development, discuss the storm analysis process, and detail future improvements that are needed for dam safety
Overflow for the complete failure of the downstream shell of a rockfill dam
No full textPresented at the Protections 2016: 2nd international seminar on dam protection against overtopping: concrete dams, embankment dams, levees, tailings dams held on 7th-9th September, 2016, at Colorado State University in Fort Collins, Colorado, USA. The increasing demand for dam and levee safety and flood protection has motivated new research and advancements and a greater need for cost-effective measures in overtopping protection as a solution for overtopping concerns at levees and dams. This seminar will bring together leading experts from practice, research, development, and implementation for two days of knowledge exchange followed by a technical tour of the Colorado State University Hydraulic Laboratory with overtopping flume and wave simulator. This seminar will focus on: Critical issues related to levees and dams; New developments and advanced tools; Overtopping protection systems; System design and performance; Applications and innovative solutions; Case histories of overtopping events; Physical modeling techniques and recent studies; and Numerical modeling methods.Includes bibliographical references.This paper presents the results of experimental research using physical models regarding the failure of the downstream shoulder of rockfill dams caused by overtopping. The aim of this investigation is to analyze how different parameters such as the rockfill permeability, the main geometric dimensions of the dam, or the impervious element type affect the flow that initiates failure and also the ultimate flow needed to break the downstream shell of the dam. The primary objective of this study is to develop predictive models for both discharge flows. For this purpose, tests with stepwise flow increments were performed by varying the rockfill size, the height and width of the dam, the downstream slope and the type of impervious element. The regression analysis was based on results from 61 experimental tests: 50 tests were used to calibrate the formulas and 11 were used for validation. The analysis shows that, for a given dam height, the failure and the initiation discharges depend essentially on the rockfill permeability and, to a lesser extent, on the slope of the downstream shell. The type of impervious element, central core, upstream face or the absence of this element, seems to have no significant effect
Sustainable dam development in China between global norms and local practices
No full textThe paper explores reforms of China’s environmental and resettlement policies and the influence of domestic and external actors on Chinese dam-related legislation. It also analyses the impact of these reforms on the Nu River Project and the Xiaolangdi Multipurpose Dam Project. The analysis starts with an overview of the strategic role of hydropower in the economic development plans of central and local government. The paper then analyses decision-making processes in the Chinese dam bureaucracy and the role allotted to civil society. By singling out the environmental impact assessment and resettlement the paper examines legal changes and the reasons for them. <br/
Quantitative analyses of ageing status of dam concrete for a 25-year-old dam
No full textIn order to evaluate the aging status of the dam concrete for a 25-years-old concrete dam, the internal concrete and surface layer of the dam were tested by elastic wave computerized tomography (CT) and spectral analysis of surface wave (SASW). Also mechanical strength and elastic wave velocity were tested for the concrete cores from the dam. The CT results show that the elastic wave velocities of the three dam sections are basically around 4400~4500m/s and no obvious low-speed zone could be detected, indicating the quality of the internal concrete is good without aging signs. The SASW results show that the Rayleigh wave velocity of the surface layer (deeper than 25cm) is about 2500 m/s (the corresponding P wave velocity is 4500 m/s) which is basically consistent with the CT results. The average compressive strength of the concrete cores is over 40 MPa (higher than the design values) while the elastic wave velocities are between 3600 and 4400 m/s. Microstructural analysis results show that the a few microcracks could be observed in all the 16 cores from the upstream, the downstream, the gallery and the spillway. The overall results indicate that the dam concrete is of good quality and no obvious aging signs could be found
Benefit of Grand Ethiopian Renaissance Dam Project (GERDP) for Sudan and Egypt
No full textThis article quantifies the major benefits of the Grand Ethiopian Renaissance Dam Project for Sudan and Egypt based on GERDP technical design and quantitative analysis. Before discussing the benefits, the article will brief the general technical overview of the GERDP. Then, it shows how the GERDP will benefit East Africa by filling the wide gab in electricity power shortage based on the World Bank data. It has answered as how much sedimentation will GERDP remove from Blue Nile River per annum? How much do it cost for Sudan and Egypt to remove this sedimentation from their dam? How the Blue Nile flow looks like after GERDP is working with full capacity? How do Sudan and Egypt will be benefited by having regular water flow throughout the year due to GERDP? How do GERDP will play vital role in conservation of water in Ethiopian highlands? Finally a summary note and a recommendation will be given to indicate the way forward in handling the GERDP for the benefit of the region specifically Ethiopia, Sudan and Egypt
Influence of dam weight on her productivity
No full textA useful criterion for evaluating the productivity of a cow is the total weight her calves attain. This measure of productivity is a function of weight, lifetime fertility and the gain potential of the calves. Weights studied were birth weight, 180-day weaning weight and yearling weight of calf and weight of dam usually taken within 10 days after parturition. The data were collected at the Texas A&M Agricultural Research Center at McGregor from 1950 to 1970. All weights were transformed to natural logarithms before analyses. Homogeneity of regressions of progeny birth and weaning weight on weight of the dam was tested across age of dam, sex of calf classes on 901 pairs of Hereford calves and their dams. No significant heterogeneity of regressions was found among age of dam or sex subclasses. Homogeneity of regressions of progeny birth, weaning and yearling weight on weight of the dam was tested for breed of dam groups. Dams were grouped into 15 breed of dam groups for birth and weaning weight analyses and in to 14 for yearling weight analyses. The number of dam and progeny pairs were 2804 for birth and weaning weight and 2166 for yearling weight. Regressions of progeny weight on weight of the dam were not significantly heterogeneous for progeny birth or yearling weight. They were heterogeneous for progeny weaning weight; but the heterogeneity was of small magnitude. ..
Absence in Bacillus subtilis and Staphylococcus aureus of the sequence-specific deoxyribonucleic acid methylation that is conferred in Escherichia coli K-12 by the dam and dcm enzymes
No full textDreiseikelmann B, Wackernagel W. Absence in Bacillus subtilis and Staphylococcus aureus of the sequence-specific deoxyribonucleic acid methylation that is conferred in Escherichia coli K-12 by the dam and dcm enzymes. Journal of Bacteriology. 1981;147(1):259-261.Restriction analysis of plasmid pHV14 deoxyribonucleic acid isolated from Escherichia coli K-12, Bacillus subtilis, and Staphylococcus aureus with restriction endonucleases MboI, Sau3AI, and EcoRII was used to study the methylation of those nucleotide sequences which in E. coli contain the major portions of N6-methyladenine and 5-methylcytosine. The results showed that neither B. subtilis nor S. aureus methylates deoxyribonucleic acid at the same sites and nucleotides which are recognized and methylated by dam and dcm enzymes in E. coli K-12
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