Modeling Evaporation-Seepage Losses for Reservoir Water Balance in Semi-arid Regions

In the water balance of reservoir system, evaporation plays a crucial role particularly so for the reservoir systems of smaller size located in the semi-arid or arid regions. Such regions are most often characterized by significant seepage losses from reservoirs, besides evaporation losses. Usually, in the optimization of a reservoir system, it is a common practice to assume evaporation loss either as some constant value or as negligible. Such assumptions, however, may affect the results of reservoir optimization. This is demonstrated in this study by a case study in the optimal scheduling of Pilavakkal reservoir system in Vaipar basin of Tamilnadu, India. For modeling reservoir losses, many models are available, of which, Penman combination model is most commonly used. In this study, an alternative approach based on Genetic Programming (GP) is proposed. The results of GP and Penman model for both evaporation loss estimation and reservoir scheduling are compared. It is found that while GP and Penman combination model performs equally well for estimating evaporation losses, GP is also able to model seepage losses (or other losses from reservoir) to a much better degree. It is also shown the reservoir scheduling does get influenced based on how the reservoir losses are modeled in the reservoir water balance equation.     

Electrochemical properties of self-assembled monolayer based on mono-(6-deoxy-6-mercapto)-β-cyclodextrin toward controlled molecular recognition

The present work describes the construction of nanoporous assemblies based on single self-assembled monolayer (SAM) of mono-(6-deoxy-6-mercapto)-β-cyclodextrin (βCDSH) and two-component monolayers of βCDSH and 11-mercaptoundecanoic acid. An investigation of its supramolecular properties toward the tricyclic antidepressants drugs chlorprothixene and imipramine is also presented. The adsorption process was investigated by using surface plasmon resonance and the selectivity of the SAM was verified by using electroactive species permeable and not permeable into the cyclodextrin SAM, such as ferrocenemonocarboxylic acid, hexacyanoferrate, methylene blue and hexamineruthenium (II). The redox probe was chosen based on its capability to permeate the grafted cyclodextrin molecules and its electrochemical characteristics. It was applied to imipramine and chlorprothixene competitive assay by the mono-(6-deoxy-6-mercapto)-β-cyclodextrin self-assembled cavity. Finally, the pK_a of the surface and its effects on thee host-guest interaction properties were also investigated.     

Advanced testing procedures for high performance coatings

In the first part of this work, an integrated approach incorporating electrochemical (electrochemical impedance spectroscopy), calorimetric (differential scanning calorimetry), mechanical (dynamic mechanical thermal analysis), and infrared spectroscopy (Fourier transform infrared spectroscopy) techniques was used to characterize some organic coatings from the automotive industry. Comparison of the results obtained with different techniques allows not only a higher precision in the evaluation of natural or artificial degradation, which is very difficult to obtain using traditional techniques, but also better data interpretation and, therefore, the possibility of understanding the different degradation mechanisms. In the second part, some preliminary results concerning the comparison of salt spray exposure and EIS measurements are discussed. The statistical analysis of the results showed that the degradation mechanism in the two cases is completely different and, therefore, the information which is obtained with the two testing approaches is also different. With EIS measurements obtained in immersion, it is possible to monitor, in particular, the barrier properties of the coatings, which are dominated by the presence of defects. In the case of salt spray (without scratch), the main property to be measured is the loss of adhesion which causes blister formation. Presented at the 77th Annual Meeting of the Federation of Societies for Coatings Technology, on October 18–22, 1999, in Dallas, TX. Dept. of Materials Engineering, Via Mesiano 77, Trento, Italy. e-mail: Flavio.Deflorian@ing.unitn.it; Stefano.Rossi@ing.unitn.it; Bonora@ing.unitn.it. Dept. ICMMPM, Via Eudossiana, Rome, Italy. e-mail: Lorenzo.Fedrizzi@ing.unitn.it.     

A low-power transmission-gate-based 16-bit multiplier for digital hearing aids

The most widespread 16-bit multiplier architectures are compared in terms of area occupation, dissipated energy, and EDP (Energy-Delay Product) in view of low-power low-voltage signal processing for digital hearing aids and similar applications. Transistor-level simulations including back-annotated wire parasitics confirm that the propagation of glitches along uneven and re-convergent paths results in large unproductive node activity. Because of their shorter full-adder chains, Wallace-tree multipliers indeed dissipate less energy than the carry-save (CSM) and other traditional array multipliers (6.0 µW/MHz versus 10.9 µW/MHz and more for 0.25 µm CMOS technology at 0.75 V). By combining the Wallace-tree architecture with transmission gates (TGs), a new approach is proposed to improve the energy efficiency further (3.1 µW/MHz), beyond recently published low-power architectures. Besides the reduction of the overall capacitance, minimum-sized transmission gate full-adders act as RC-low-pass filters that attenuate undesired switching. Finally, minimum size TGs increase the V _dd to ground resistance, hence decreasing leakage dissipation (0.55 nW versus 0.84 nW in CSM and 0.94 nW in Wallace).     

Drop in Combined Sewer Manhole for Supercritical Flow

Manholes often contain small drops for various reasons, the most important being submergence. While this may be appropriate for subcritical flow, its effect was considered doubtful for supercritical flow. This note aims at investigating the effect of a manhole drop on the hydraulics of sewer flow. Based on systematic experimental observations, the flow pattern associated with a manhole drop was established. A distinction was also made between small and intermediate drops. Then, the main wave features were analyzed to result in expressions that contain both the upstream filling ratio and the Froude number of the approach flow. In addition, the discharge capacity was also investigated, and selected photographs show typical drop flow in combined sewer manholes. The result of the present study is evident, based on these observations, and recommendations towards future design of combined sewer manholes are also made.     

Analysis and behavior of steel storage drive-in racks

This work presents a general analysis of drive-in racks, evaluating the influence of each of their components on global stability. In this study, a full-scale test of a drive-in system was carried out. Finite element models were also developed to evaluate global structural stability and component influence on system behavior. The experimental and numerical results show that the connections and base plates have the most significant influence on the system's behavior. This influence is analyzed, an equation that predicts base plate resistance is then proposed, and its results are compared with experimental and numerical results.     

Impact of biodiesel bulk modulus on injection pressure and injection timing. The effect of residual pressure

As the demand for energy rises fossil fuel reserves are depleted daily, increasing the interest in alternative fuels. Biodiesel is one of the best candidates in this class and its use is expected to expand rapidly throughout the world. Numerous researchers have been investigating how biodiesel affects combustion, pollutant formation and exhaust aftertreatment. There is general agreement that its combustion characteristics are similar to those of standard diesel fuel, except for a shorter ignition delay, a higher ignition temperature, and greater ignition pressure and peak heat release. Engine power output is similar with both fuels. As regards emissions, reductions in particulate matter (PM) and carbon monoxide (CO) and increases in nitrogen oxides (NOx) are described with most biodiesel blends. The latter is referred to as the ‘biodiesel NOx effect’. The vast majority of researchers who explored the effect of biodiesel did so in mechanical injection engines. They found that the primary mechanism by which biodiesel increases NOx emissions is by an inadvertent advance in the start of injection timing, caused by a higher modulus and viscosity. However, more recent studies show that NOx emissions also increase in biodiesel-fuelled common rail engines, and that in some cases they actually decrease in engines with mechanically controlled fuel injection systems. This cannot be explained solely by differences in compressibility and remains an open question. The present study provides a contribution to the discussion in this field by describing a new method to evaluate the injection advance in engines with mechanically controlled pumps. The experimental data show that the advances in the start of injection timing, using biodiesel rather than mineral diesel, are smaller than those calculated with standard methods and may even not occur at all, depending on injection system design. In addition, they demonstrate that, contrary to common belief, injection pressure does not always increase when using biodiesel. These data may help explain why some researchers have found similar or even reduced NOx emission also with mechanical injection systems.     

Reliability of RF MEMS switches due to charging effects and their circuital modelling

The reliability of RF MEMS switches is typically reduced by charging effects occurring in the dielectrics. The aim of this paper is to discuss these effects, and to propose analytical and equivalent circuit models which account for most of the physical contributions present in the structure.     

Threshold protocols in survivor set systems

Many replication protocols employ a threshold model when expressing failures they are able to tolerate. In this model, one assumes that no more than t out of n components can fail, which is a good representation when failures are independent and identically distributed (IID). In many real systems, however, failures are not IID, and a straightforward application of threshold protocols yields suboptimal results. Here, we examine the problem of transforming threshold protocols into survivor-set protocols tolerating dependent failures. Our main goal is to show the equivalence between the threshold model and the core/survivor set model. Toward this goal, we develop techniques to transform threshold protocols into survivor set ones. Our techniques do not require authentication, self-verification or encryption. Our results show in one case that we can transform a threshold protocol to a subset by spreading a number of processes across processors. This technique treats a given threshold algorithm as a black box, and consequently can transform any threshold algorithm. However, it has the disadvantage that the transformation is not possible for all sets of survivor sets. The second technique instead focuses on transforming voters: functions that evaluate to a value out of a set of tallied values in a replication protocol. Voters are an essential part of many fault-tolerant protocols, and we show a universal way of transforming them. With such a transformation we expect that a large number of protocols in the literature can be directly transformed with our technique. It is still an open problem, however, if the two models are equivalent, and our results constitute an important first step in this direction.