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Coastal reservoirs can alleviate freshwater shortages occurring in the nearshore zone. Deep pools patched at the bottom of reservoirs at greater depths than their adjacent beds maintain a high salinity and possibly provide preferential paths for saltwater backfill. However, such processes are not well understood. Laboratory experiments and numerical simulations were conducted to investigate the effect of the deep pool on subsurface flow and the salinization of coastal reservoir and adjacent aquifers. When seawater intruded into the initially fresh aquifer, the deep pool accelerated the uptake of saltwater to the reservoir from the salt wedge, forming a temporary salt plume around the pool. The saltwater plume also accelerated salt ingress and the evolution of the total salt mass in the coastal reservoir, resulting in the earlier attainment of a quasi-steady state (a classical saltwater wedge) than that when the deep pool was absent. Under steady-state conditions, the deep pool greatly enhanced the exchange of water across the reservoir-aquifer interface by 107% and raised the salinization level of the coastal reservoir by at least 10.3%. Sensitivity analysis suggested that a deeper pool and/or a pool located closer to the reservoir dam may enhance the water exchange and salinity level in the reservoir because it accelerates the water/salt inflow to the freshwater body to a greater extent. These findings may further contribute to improving the predictability and management of water quality in these coastal facilities.

In this paper, a structure for isolating packaging stress in a sandwich MEMS capacitive accelerometer is proposed and verified. The structure is designed and analyzed by finite element modeling (FEM) using ABAQUS. Two kinds of MEMS accelerometer, one with the stress isolation structure and the other without it, were simulated and compared. Simulation results show that the structure can reduce packaging stress and avoid uneven stress distribution. And then, MEMS accelerometers with and without the stress isolation structure are fabricated based on bulk micromachining technology and experimentally verified. The experimental results show that stabilities of the bias temperature coefficient and scale factor temperature coefficient of the MEMS accelerometer with the stress isolation structure are significantly improved. The comparison results demonstrate that the stress isolating structure is working and the packaging stress is successfully isolated.

In order to protect the water environment in seriously polluted basins, the impacts of anthropogenic activities (sewage outfalls and land use) on water quality should be assessed. The Bayesian network (BN) provides a convenient way to model these complex processes. In this study, anthropogenic impacts on chemical oxygen demand (COD) and biochemical oxygen demand (BOD) were evaluated in the Huaihe River basin (HRB) considering dry and wet seasons and different spatial scales. The results showed that anthropogenic activities had the most significant impacts on COD and BOD at the catchment scale. In dry seasons, sewage outfalls played an important role in organic pollution. Farmland became the most important source in wet seasons although it had a &ldquo, sink&rdquo, process in dry seasons. Intensive human activities in urban made significant contributions to increased COD levels. Grassland had a negative relationship with organic pollution, especially in dry seasons. Therefore, governments should implement strategies to control organic matters transported from urban and farmland regions. Increasing the efficiency of wastewater treatments and the percentage of grassland in the riparian zone could improve water quality. These results can enhance understanding of anthropogenic impacts on water quality and contribute to efficient management for river basins.

Coastal reservoir provides the additional storage capacity of freshwater in coastal zone which greatly alleviate the water shortage in stressed areas, and the salinization of reservoir water degrade the utility of coastal reservoir. Salinization may result from inadequate desalinization in early operation stage, and groundwater as the important source of freshwater to coastal reservoir and adjacent aquifer was obviously have significant impacts on salinization which was in a dearth research. Laboratory experiments and mathematical model were designed to further discuss the influence of groundwater on the desalinization. The results from experiments shown that with the groundwater discharge rate increased, residual saltwater distribution result from intruded fresh groundwater was further moderated. Coastal reservoirs also greatly changed groundwater discharge pathways to sea. Without coastal reservoir, groundwater discharge to sea directly, while with coastal reservoir, part of groundwater would firstly discharge to coastal reservoir, desalinate the reservoir water, and then to sea. Mathematical model was designed for the prediction of the salinity of reservoir water, and the results from model could indicate the accuracy groundwater discharge pathways in coastal reservoir and adjacent aquifer. These results demonstrate the complexity of the groundwater system in adjacent aquifer of coastal reservoir, and may have great implications for future investigations on the predication of water quality during the full operational period.

Coastal reservoirs can alleviate the shortage of freshwater in the nearshore zone. Inland groundwater and tides can cause hydraulic gradients between seawater and reservoir water and affect the salt concentration of coastal reservoirs; however, the mechanism is poorly understood. Laboratory experiments and numerical simulations were conducted to investigate the combined effect of inland groundwater inputs and tides on the surface/subsurface flow and salinization dynamics of the coastal reservoir and adjacent aquifer. The results indicated that inland groundwater followed two pathways before discharging into the sea, regardless of the tidal conditions. The predominant pathway led inland groundwater to be discharged to the coastal reservoir and then to sea. The other pathway encompassed the entire aquifer underlying the reservoir bed and terminated at the aquifer–sea interface. As the inland groundwater input increased, the groundwater entering the reservoir also increased, whereas the ratio of the fresh groundwater transported through the reservoir to the total groundwater input decreased. Tidal pumping allowed more seawater to intrude into the coastal reservoir and adjacent aquifer compared with nontidal conditions. This caused a larger proportion of groundwater to be discharged to the coastal reservoir, with the density-driven flow and water/salt exchange across the aquifer-reservoir interface also enhanced. As the inland groundwater input increased, salinization of the coastal reservoir decreased and the inhibition of the inland groundwater input on salinization also decreased. This study contributes to the improved management of such coastal infrastructures.

In this study, the air damping ratios of an unsealed chip of a capacitive accelerometer subjected to different pressures were measured by a special designed circuit in a static state test. There are total eight trapezoid grooves on the top and bottom electrode wafers aiming at reducing air damping effect. Finite element method based on energy balance method and transient blade row model is used to simulate in ANSYS/CFX with a new formula of effective viscosity of the air derived from simulation and validated by experimental results. The numerical results are in good agreement with the experimental results. With the same method and the new formula of effective viscosity, the air damping ratio of a new chip without trapezoid grooves is simulated as well. The comparison of the two kind of chips shows that the air damping ratio decreases 63.4% after four trapezoid grooves were engrooved on the top and bottom electrode wafers. As a result, engrooving on the top and bottom electrode wafers provides a new way to reduce air damping effect.

The dynamics behavior of most micro-electro-mechanical-system (MEMS) devices is significantly affected by the squeeze-film air damping. Therefore, the correct prediction of the squeeze-film air damping ratio is essential in MEMS devices design. In the paper, a static state test is proposed to measure the squeeze-film air damping ratios of a silicon capacitive micromechanical accelerometer under different pressures. The unsealed chip of capacitive accelerometer is placed in a vacuum extraction chamber and an open loop circuit is developed to apply step signal. By charging the pressure and measuring the overshoot M p and the settling time t s from the time response of the chip, the damping ratio ξ under different pressures can be calculated. Finite element method (FEM) based on the modified Reynolds equation is utilized to simulate the transient response of the micro-structure. Good correlation between experimental and numerical results is obtained. The proposed static state test in this paper provides a new and much easy method to measure the dynamic performances of micro-structures under various pressures.

In most MEMS devices, the moving micro-structures are surrounded by air which significantly affects their dynamics behaviors. The correct prediction of the squeeze-film air damping ratio is essential in MEMS (Micro-Electro-Mechanical System) devices design. In the paper, a static test is proposed to measure the squeeze-film air damping ratios of capacitive MEMS accelerometer under different pressures. The unsealed chip of capacitive accelerometer is placed in vacuum extraction equipment and an open loop circuit is developed to apply step signal in the test. By charging the pressure and measuring the overshoot Mp and the settling time ts from the time response of the system, the damping ratio ξ under different pressures can be calculated. Finite element method (FEM) based on the modified Reynolds equation is utilized to simulate the transient response of the micro-structure. Good correlation between experiment and FEM analysis is obtained. The proposed static test in this paper provides a new method to more easily measure the dynamic performances of micro-structures under various pressures.

The rainfall patterns play an important role in determining the response of Suspended Sediment (SS) and Total Phosphorus (TP) to influence factors, which is complex and needs to be better understood. The Bayesian Network (BN), with each variable depending on only its immediate parent variables, can help to describe the complex processes involved. In this study, BNs were developed to assess the impacts of catchment characteristics and human activities on SS and TP loads under different rainfall patterns in the Huaihe River Basin (HRB). The results showed that SS made significant contributions to TP in rivers which increased with the rainfall intensity. Catchment characteristics (sub-catchment area, slope and soil erosion area) affected the SS and TP loads; however the influence of human activities (sewage outfalls and land use) was more significant. With the rainfall intensity rising, farmland switched from a “sink” to a “source” of nutrients. When the antecedent three-day-average rainfall intensity was high but the current one was low, the farmland became the most significant source of SS and TP. The urbanization had significant positive effects on SS (ranging from 10.9% to 15.1%) and TP (ranging from 8.3% to 10.5%), which was insensitive to rainfall patterns as a result of the high proportions of impervious surface coverage in the urban area. These results improve our understanding of influence factors on river water quality and will contribute to effective water environment management for rivers.

To better manage water environment in highly polluted rivers, the influence factors on water quality need to be investigated. With the effects of oxygen-demanding contaminants, it is difficult to resolve the complex interdependencies of the various factors using conventional methods. The Bayesian Networks (BNs), in which each variable only depends on its immediate parent variables, can solve this problem. In this study, the BNs were developed to assess the impacts of land use and sewage outfalls on Ammonia Nitrogen (AN) and Dissolved Oxygen (DO) concentrations in the Huaihe River Basin (HRB) for different seasons and spatial scales, where AN was a typical oxygen-demanding contaminant and the most serious contaminant in the area. The BNs gave the best explanations for variations in AN (NSE = 0.80) and DO (NSE = 0.72) concentrations by using land use and sewage outfalls data at the local scale (less than 20 km radii around monitor stations), suggesting that controlling water contaminant sources at local scales can improve water quality efficiently. AN negatively affected DO concentration, which was more significant in dry seasons. Wastewater from sewage outfalls was the largest contributor (26.2%) to AN pollution in dry seasons, which was weakened in wet seasons by an intensive dilution process. Farmland acted as a “sink” in dry seasons and as a “source” in wet seasons. The transition between two states was caused by large variations in surface runoff between dry and wet seasons. Urban land made a disproportionately large contribution to water pollution compared to other kinds of land use. These findings improve our understanding of influence factors on water quality and will contribute to effective river management.

Coastal reservoirs are a possible solution to water supply and management issues in coastal zones. However, salinization can degrade the utility of such reservoirs. Two related major challenges affecting the operation of a coastal reservoir are desalinization and seawater intrusion. The former arises mainly during the period following reservoir construction, while the latter is ongoing. This review discusses the salt dynamics of coastal reservoirs under the influence of surface-water flows, river inflows, reservoir water level, and tides. Various salt transport processes are examined in relation to water salinity changes in coastal reservoirs. The methods and limitations of existing numerical models for coastal reservoirs are also discussed. Given the difficulty in reproducing realistic boundary conditions for laboratory experiments, further research needs to focus on investigations that consider salinization in real coastal reservoirs. More broadly, there remains a need to unravel the impacts of coastal reservoirs on the surrounding environment, as they can significantly change the hydrodynamics and chemical transport pathways in coastal waters. A comprehensive understanding of coastal reservoir salinization will improve water management and thus contribute to alleviating overexploitation of water resources in coastal zones.

More than 145 million people live with at least one chronic condition, and almost half of them have multiple conditions. As a result, many managed care and integrated delivery systems have taken a great interest in alleviating the many deficiencies in managing the current care system that spans across various care delivery settings. In addition, many Americans have to rely on some social health insurance plan to cover her care expenses. As a result, these patients often may not been sufficiently cured but have to be transitioned to less expensive but less medically intensive facilities, due to the increasing pressure on the social health insurance programs to save their total spending. This in turns increases the risk of being readmitted to more expensive facilities sooner. In this thesis, we systematically study stochastic transitions within a system of care delivery. We investigate how to modify insurable length of stay to reduce the total care spending and improve the quality of care to individual patients. We first develop a chronic care cycle model to optimize the transitions between two types of settings: the inpatient care setting and the home- and community-based care setting. By optimizing the number of covered episodes, and the coverage LOS for each episode, this model is intended to balance the tradeoff between the cost of staying and the cost of (forced) transition, as well as the tradeoff between current cost and future (opportunity) cost. The results indicate that as a public insurer, the best strategy will be only focusing on the early episodes and covering them unlimitedly. We also develop a three-layer rehabilitation service process model and use discrete event simulation to study the transitions among three levels of rehabilitations: primary rehab, secondary rehab, and tertiary rehab. We test different values for on the coverage LOS for primary rehab and secondary rehab to balance the tradeoff between the current cost and future cost. We assume some relationship between the quantity of care and care transition probability, and observe their joint effect on cost and rehospitalization incidences in the given length of period. The results indicate that as a public insurer, the best strategy will be remaining current coverage on primary rehab but limiting coverage on secondary rehab.

Coastal reservoirs are a possible solution to water supply and management issues in coastal zones. However, salinization can degrade the utility of such reservoirs. Two related major challenges affecting the operation of a coastal reservoir are desalinization and seawater intrusion. The former arises mainly during the period following reservoir construction, while the latter is ongoing. This review discusses the salt dynamics of coastal reservoirs under the influence of surface-water flows, river inflows, reservoir water level, and tides. Various salt transport processes are examined in relation to water salinity changes in coastal reservoirs. The methods and limitations of existing numerical models for coastal reservoirs are also discussed. Given the difficulty in reproducing realistic boundary conditions for laboratory experiments, further research needs to focus on investigations that consider salinization in real coastal reservoirs. More broadly, there remains a need to unravel the impacts of coastal reservoirs on the surrounding environment, as they can significantly change the hydrodynamics and chemical transport pathways in coastal waters. A comprehensive understanding of coastal reservoir salinization will improve water management and thus contribute to alleviating overexploitation of water resources in coastal zones.

Coastal reservoir contributes to alleviating the freshwater shortage in stressed areas, and the salinization of reservoir water is one of the most important challenges that coastal reservoir faced. Field-investigation indicates that there are many deep pools located at reservoir bed, and a large amount of high-salinity water was found within a deep pool which was hardly be desalted. Laboratory experiments and numerical simulations with different depth and locations of deep pools were conducted to further discuss the influence of deep pool on the salinization of reservoir and adjacent aquifer. Results showed that deep pool has greatly increased the salinity of reservoir water due to high-salinity water stored in the deep pool, which may act as an extra source of saltwater to the coastal reservoir during the dry season. The increasing depth of the deep pool was found to have negative impacts on the salinity of reservoir water, and as the distance from the deep pools to dam increased, the salinization extent in coastal reservoir decreased. Salinity data from the numerical simulations in coastal reservoirs and adjacent aquifer were matched the experimental data well. Flow field indicates that there is a high exchange capacity zone occurred from the deep pool to the seaward boundary, which gave the reasonable reasons for the existence of high-salinity water within deep pools. Those findings highlight the significant influence of deep pool on the salinization of the coastal reservoir, and explain the increased salinization by the deep pool.