Multi-objective stochastic groundwater management of nonuniform,homogeneous aquifers

Like any other resources planning and management, groundwater management is performed in a stochastic environment in which the system itself involves a number of random elements. Consequences as a result of decisions made based on analyses are not certain. This paper presents a management model using the chance-constrained framework which explicitly considers the random nature of aquifer properties. The model enables the derivation of an optimal groundwater management policy that would satisfy required operation performance reliability. Furthermore, the chance-constrained model is extended to the multi-objective optimization framework in which a tradeoff between total water supply pumpage and system performance reliability is explicitly considered. The models are applied to a hypothetical example of a steady, nonuniform, homogeneous confined aquifer.     

Designed Multifunctional Nanocomposites for Biomedical Applications

The assembly of multifunctional nanocomposite materials is demonstrated by exploiting the molecular sieving property of SBA‐16 nanoporous silica and using it as a template material. The cages of the pore networks are used to host iron oxide magnetic nanoparticles, leaving a pore volume of 0.29 cm³ g^?1 accessible for drug storage. This iron oxide–silica nanocomposite is then functionalized with amine groups. Finally the outside of the particle is decorated with antibodies. Since the size of many protein molecules, including that of antibodies, is too large to enter the pore system of SBA‐16, the amine groups inside the pores are preserved for drug binding. This is proven using a fluorescent protein, fluorescein‐isothiocyanate‐labeled bovine serum albumin (FITC‐BSA), with the unreacted amine groups inside the pores dyed with rhodamine B isothiocyanate (RITC). The resulting nanocomposite material offers a dual‐targeting drug delivery mechanism, i.e., magnetic and antibody‐targeting, while the functionalization approach is extendable to other applications, e.g., fluorescence–magnetic dual‐imaging diagnosis.     

Optimum Downlink Power Control of a DS-CDMA System via Convex Programming

An optimum downlink power control that maximizes the user-capacity of a Direct Sequence-Code Division Multiple Access (DS-CDMA) cellular system is proposed based on a convex programming method. First, the downlink beamforming weights for the base-station antenna-array are designed based on the maximum Signal-Interference-Ratio (SIR) criterion. Then by optimizing the downlink power subject to a fixed total transmit power constraint, we further increase the Signal-Interference-Noise-Ratio (SINR) at the mobile terminal, thus increasing the capacity of the system. With the same methodology, we can also minimize the required transmit power while satisfying the SINR threshold constraints. Additionally, a robust downlink power control approach for mitigating the performance degradation due to channel estimates error is also proposed. Computer simulations are given to demonstrate the improvement of downlink capacity, received SINR, robustness, and the minimization of the required transmit power for a DS-CDMA system with antenna-array at the base-station.     

Influence of ventilation on indoor radon level

Detailed radon measurements were conducted at different residential units in Hong Kong in winter time when air-conditioners were off and also in summer time when air-conditioners were on. Ventilation rates were measured concurrently to investigate the influence of ventilation on indoor radon level. The ratio of indoor radon level to outdoor radon level was plotted against ventilation rate, and it was found that a critical value existed after which the indoor radon level could be considered identical to the outdoor level. This result is important for use in ventilation design to reduce indoor radon pollution.     

Ultra-Low-Powered Aqueous Shear Stress Sensors Based on Bulk EG-CNTs Integrated in Microfluidic Systems

Novel aqueous shear stress sensors based on bulk carbon nanotubes (CNTs) were developed by utilizing microelectricalmechanical system (MEMS) compatible fabrication technology. The sensors were fabricated on glass substrates by batch assembling electronics-grade CNTs (EG-CNTs) as sensing elements between microelectrode pairs using dielectrophoretic technique. Then, the CNT sensors were permanently integrated in glass–polydimethylsiloxane (PDMS) microfluidic channels by using standard glass–PDMS bonding process. Upon exposure to deionized (DI) water flow in the microchannel, the characteristics of the CNT sensors were investigated at room temperature under constant current (CC) mode. The specific electrical responses of the CNT sensors at different currents have been measured. It was found that the electrical resistance of the CNT sensors increased noticeably in response to the introduction of fluid shear stress when low activation current (≪1 mA) was used, and unexpectedly decreased when the current exceeded 5 mA. We have shown that the sensor could be activated using input currents as low as 100 $mu$A to measure the flow shear stress. The experimental results showed that the output resistance change could be plotted as a linear function of the shear stress to the one-third power. This result proved that the EG-CNT sensors can be operated as conventional thermal flow sensors but only require ultra-low activation power ($sim 1$ $mu$W), which is $sim 1000$ times lower than the conventional MEMS thermal flow sensors.      

液—固磁场流态化模型及普遍化相图

本文考察了磁场流态化的基本特征,并结合实验分析了均匀磁场中液-固流态化模型参数的变化规律,对Ma 和 Kwauk 提出的指数模型作了补充,使之与经典流态化加以统一,并在此基础上获得了磁场流态化的普遍化关系图。完善后的模型可根据经典流态化的基础数据直接预示磁场作用下流态化的一些特征,模型计算结果与水-钢丸系统的实验数据吻合较好。     

The CLAS forward electromagnetic calorimeter

The CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab utilizes six iron-free superconducting coils to provide an approximately toroidal magnetic field. The six sectors are instrumented individually to form six independent spectrometers. The forward region (8°<θ<45°) of each sector is equipped with a lead–scintillator electromagnetic sampling calorimeter (EC), 16 radiation lengths thick, using a novel triangular geometry with stereo readout. With its good energy and position resolution, the EC is used to provide the primary electron trigger for CLAS. It is also used to reject pions, reconstruct π° and η decays and detect neutrons. This paper treats the design, construction and performance of the calorimeter.