The baroclinic response to wind in a small two-basin lake

Field data and two linear layered models were used to examine the baroclinic response to wind in a small elongated two-basin lake, Amisk Lake (Alberta, Canada). For the first vertical baroclinic mode, wind-forced horizontal modes were simulated using a dynamic two-layer variable cross-section (TVC) model. The first horizontal mode, H1, was found to dominate the exchange between the two basins of Amisk Lake. The highest velocities associated with H1 occurred in the constricted channel connecting the two basins. This high velocity led to strong damping which brought H1 in near-resonance with the diurnal wind despite a difference in periods. Along with H1, the second horizontal mode, H2, was detected at a thermistor mooring. The TVC showed that H2 resulted from the coupling between along-thalweg wind distribution and the bathymetry of Amisk Lake. The damping for H2 was found to be weaker than for H1, likely because of weaker bottom drag in the connecting channel. The evolution of vertical H1 modes were simulated using a multi-layered box model. In response to wind pulses, the first vertical mode V1H1 initially dominated over higher vertical modes causing two-layer exchange. Following the faster decay of V1H1, higher vertical modes shifted the exchange to three and more layers. Our study shows the importance of the coupling between wind stress distribution and lake bathymetry in exciting horizontal modes, reveals the effect of damping on resonance with wind, and explains the evolution of exchange associated with vertical modes.     

Impact of control structures on assimilative capacity of rivers and fish habitat

This research studies the impact of water level control structures on self-assimilative capacity of rivers and on fish habitat. Constructing a water level control structure in a river reach will alter its hydraulics as well as its water quality, thermal regime and fish habitat. A mathematical model is developed to simulate river hydraulics, water quality, temperature and fish habitat. Diurnal dissolved oxygen concentrations are investigated to show their impact on fish. A case of a Nile River reach was studied to investigate the impact of the existence of the Esna barrage on the water quality and fish in its upstream reach. The barrage has negative impacts on the upstream self-assimilative capacity of the rivers. The waste load that the river could absorb was only 54 % (at low flow) and 78 % (at high flow) of the entire load if no barrage was present. Including in the simulation of the effects of photosynthesis and respiration, the above mentioned percentages were raised to 54 % and 91 %, respectively. Although water level control structures have negative impacts on the upstream self-assimilative capacity of the rivers, they have positive effect on downstream dissolved oxygen concentrations due to reaeration that happens across them. Downstream dissolved oxygen concentration increased by 6 % from its upstream concentration value. The barrage has a positive effect on fish habitat in the upstream section. The weighted usable area of Tilapia fish is doubled in case of barrage existence. The barrage causes a slight decrease in water temperature that reaches an average of 0.13 degree in the month of June.     

Adaptive neuro-fuzzy evaluation of wind farm power production as function of wind speed and direction

Wind velocity assumes a critical part for measuring the power created by the wind turbines. Nonetheless, power production from wind has a few weaknesses. One significant issue is that wind is a discontinuous energy source which implies that there exists substantial variability in the generation of vigor because of different variables, for example, wind speed. Wind direction is a significant variable for proficient turbine control for getting the most energy with a given wind speed. Taking into account the conjectures on wind heading, it might be conceivable to adjust the turbine to the wind bearing to get the most energy yield. Since both forecasts of wind speed and direction are basic for effective wind energy collecting it is crucial to develop a methodology for estimation of wind speed and direction and afterwards to estimate wind farm power production as function of wind pace and heading distribution. Despite the fact that various numerical functions have been proposed for demonstrating the wind speed and direction frequency distribution, there are still disadvantages of the models like very demanding in terms of calculation time. In this investigation adaptive neuro-fuzzy inference system (ANFIS), which is a particular sort of the artificial neural networks (ANN) family, was used to anticipate the wind speed and direction frequency dispersion. Thereafter, the ANFIS system was utilized to gauge wind homestead power creation as function of wind velocity and bearing. Neural system in ANFIS modifies parameters of enrollment capacity in the fuzzy logic of the fuzzy inference system. The reenactment outcomes exhibited in this paper demonstrate the adequacy of the created technique.     

The characteristics and distribution of International Medical Graduates from mainland China, Taiwan, and Hong Kong in the US

As healthcare systems around the world are facing increasing physician shortages, more physicians are migrating from low to high income countries. Differences in medical education and international interaction may have significant effect on physician flows. The Chinese Medical Graduates (CMGs) in the US present an interesting case to examine this effect. This paper evaluated the current number and historical trends of CMGs in the US from mainland China, Taiwan, and Hong Kong comparing their differences and similarities in terms of demographic and geographic characteristics. Since 2000, the number of CMGs in the US showed a consistent upward trend at a rate of approximately 206 additional graduates per year. In 2010, there were 8,797 CMGs in the US. Compared to CMGs from mainland China, CMGs from Taiwan and Hong Kong were much older. Much larger proportion of Taiwan and Hong Kong CMGs were male. However, they were more likely to practice in solo settings than mainland CMGs. The vast majority of CMGs are concentrated in urban areas and no significant differences were found for their distributions in underserved areas. However, a larger proportion of Taiwan and Hong Kong CMGs were in western coastal states; whereas a larger proportion of mainland CMGs were located in eastern coastal states. Fluctuations in CMG numbers in the US reflect the significant differences within the medical education systems among the three. The seemingly homogenous CMGs in the US do show significant differences. Given the magnitude and historical trends of migration of CMGs to the US, further exploration of its causes and impact is needed.     

The role of hydrograph indices in parameter estimation of rainfall–runoff models

A reliable prediction of hydrologic models, among other things, requires a set of plausible parameters that correspond with physiographic properties of the basin. This study proposes a parameter estimation approach, which is based on extracting, through hydrograph diagnoses, information in the form of indices that carry intrinsic properties of a basin. This concept is demonstrated by introducing two indices that describe the shape of a streamflow hydrograph in an integrated manner. Nineteen mid‐size (223–4790 km²) perennial headwater basins with a long record of streamflow data were selected to evaluate the ability of these indices to capture basin response characteristics. An examination of the utility of the proposed indices in parameter estimation is conducted for a five‐parameter hydrologic model using data from the Leaf River, located in Fort Collins, Mississippi. It is shown that constraining the parameter estimation by selecting only those parameters that result in model output which maintains the indices as found in the historical data can improve the reliability of model predictions. These improvements were manifested in (a) improvement of the prediction of low and high flow, (b) improvement of the overall total biases, and (c) maintenance of the hydrograph's shape for both long‐term and short‐term predictions. Copyright © 2005 John Wiley & Sons, Ltd.     

Holocene stratigraphy-of the Lower Ganges-Brahmaputra River delta in Bangladesh

Major part of the Holocene Ganges-Brahmaputra delta occupies the southern and southwestern part of Bangladesh with a smaller part extending beyond the international boundary in the west. Five facies assemblages are documented in the lower deltaic plain in five different depositional environments: levee or levee complex, bil or depression, abandoned meander belt, interdistributary plain and estuarine plain. The thickness of the Holocene sediments ranges from 30 m to 70 m in the deltaic plain, usually floored by the Pleistocene stiff clays, with the exception of the abandoned meander belt deposit where Holocene channel sand deposited directly on the Pleistocene sand. Radiocarbon dates indicate that low-rate sedimentation has occurred in the northern part, where 4-6 m thick sediments were deposited since the mid-Holocene, whereas 10-30 mthick sediments were deposited in the southern part during the same span of time. In addition, significant coastal subsidence (3 mm/a on average), added by sea-level rise (1.5 mm/a, conservative rate) occurs in the study area, which serves as a negative factor in degrading the coastal plain of Bangladesh in the future, while taking into consideration the weaker sedimentation in the area.     

Simulation and design of pumped storm water systems

Flow and damage in pumped storm water systems are simulated, taking into consideration surcharged flow, basement and street storage. The simulation model is used in a design model to obtain practical global optimum values for the sewer depth, slope and diameter as well as sump and pump sizes.