Increasing Water Security: An Algorithm to Improve Water Distribution Performance

Water Distribution Systems (WDSs) are indispensable infrastructures for urban societies. Due to vitality of continuous supply of drinking water in urban areas, it is necessary to have a performance evaluation and monitoring system to provide the expected level of security in water distribution systems. A main weakness point of these systems is the physical break of pipes which results in high level of water loss, pollution risk and public unsatisfactory. In this study, a framework is developed to increase physical water supply security in urban areas. For this purpose, a physical vulnerability index (PVI) is developed for evaluation of physical statues of water mains. In quantifying PVI, pipe characteristics and bedding soil specifications are considered. The importance of these factors on PVI is determined using Analytical Hierarchy Process (AHP). In system performance evaluation, the pipe role in system performance is incorporated regarding pipe location in WDS, distance of pipe from reservoir and average pressure of pipe. Then, System Physical Performance Index (SPVI) is evaluated. An optimization algorithm is employed to determine ways to improve the system performance through enhancing the physical condition of the pipe in the system at a minimum cost. The genetic algorithm is employed for solving the optimization model. A global sensitivity analysis method named FAST, is used for sensitivity analysis to incorporate the correlation between different parameters in analysis. The proposed framework is applied to a case study located in Tehran metropolitan area. The results of this study show the significant value of the proposed algorithm in supporting decision makers to better choose vulnerable pipes for rehabilitation practices in order to decrease system vulnerability against physical failures.     

<Emphasis Type="SmallCaps">l</Emphasis>-Aspartic acid incorporated optically active poly(amide-imide)s: synthesis and characterization

N-trimelliticimido-l-aspartic acid (1) was prepared from the reaction of trimellitic anhydride with l-aspartic acid in a mixture of glacial acetic acid and pyridine solution (3/2 ratio) under refluxing conditions. The solution polycondensation of the corresponding activated monomer with eight aromatic diamines were carried out in DMAc. The resulting poly(amide-imide)s were obtained in quantitative yields, showed admirable inherent viscosities (0.20–0.36 dl g⁻¹), good optical activity (+7.32o to +15.24o), and were readily soluble in polar aprotic solvents. They start to decompose (T _10%) above 170 °C and display glass-transition temperatures at 120–237 °C. All of the above polymers were fully characterized by UV, FT–IR, and ¹HNMR spectroscopy, elemental analysis, thermogravimetric analyses, DSC, inherent viscosity measurement, and specific rotation.     

Synthesis and characterization of new optically active and photolable poly (amide-imide)s from N,N ′-(3,3′,4,4′-benzophenonetetracarboxylic)-3,3′,4,4′-diimido-di-L-methionine and different diamines

Summary N,N^′-(3,3^′,4,4^′-benzophenonetetracarboxylic)-3,3^′,4,4^′-diimido-di-L-methionine (3) was prepared from the reaction of 3,3^′,4,4^′-benzophenonetetracarboxylic-3,3^′,4,4^′-dianhydride (1) with L-methionine (2) in a solution of (glacial acetic acid/pyridine) at refluxing temperature. The phosphorylation polycondensation of the diimide-diacid monomer (3) with 1,3-phenylenediamine (4a), 1,4-phenylenediamine (4b), 2,6-diaminopyridine (4c), 3,5-diaminopyridine (4d), 4,4^′-diaminobiphenyl (4e) and 4,4^′-diaminodiphenylsulfone (4f) was carried out in N-methyl-2-pyrolidone (NMP). The resulting poly (amide-imide)s showed admirable moderate inherent viscosities (0.23–0.48 dl g^-1), good thermal stability and improved optical activity. All of the above compounds were fully characterized by IR spectroscopy, elemental analysis and specific rotation. Some structural characterization and physical properties of these new poly (amide-imide)s are presented.     

Synthesis and characterization of heterocyclic,and optically active poly(amide-imide)s by phosphorylation polycondensation

Summary N,N′-Pyromelliticdiimido-di-L-methionine (1), N,N′-Pyromelliticdiimido-di-L-alanine (2), N,N′-Pyromelliticdiimido-di-L-phenylalanine (3) , and N,N′-Pyromelliticdiimido-di-L-leucine (4) were prepared from the reaction of Pyromellitic dianhydride with corresponding L-amino acids in a mixture of glacial acetic acid and pyridine solution (3/2 ratio) under refluxing conditions. The phosphorylation polycondensation of the corresponding diimide-diacid monomers with 4-phenyl-2,6-bis(4-aminophenyl) pyridine (6) or 4-(p-methylthiophenyl)-2,6-bis(4-aminophenyl) pyridine (8) were carried out in N-methyl-2-pyrolidone (NMP). The resulting poly (amide-imide)s were obtained in quantitative yields, showed admirable inherent viscosities (0.20-0.97 dl g^-1), were soluble in polar aprotic solvents, showed good thermal stability and high optical purity. The synthetic compounds were characterized by IR, MS, ¹H NMR and ¹³C NMR spectroscopy, elemental analysis and specific rotation.     

Electrical properties of sub-100 nm SiGe nanowires

In this study, the electrical properties of SiGe nanowires in terms of process and fabrication integrity, measurement reliability, width scaling, and doping levels were investigated. Nanowires were fabricated on SiGe-on oxide (SGOI) wafers with thickness of 52 nm and Ge content of 47%. The first group of SiGe wires was initially formed by using conventional I-line lithography and then their size was longitudinally reduced by cutting with a focused ion beam (FIB) to any desired nanometer range down to 60 nm. The other nanowire group was manufactured directly to a chosen nanometer level by using sidewall transfer lithography (STL). It has been shown that the FIB fabrication process allows manipulation of the line width and doping level of nanowires using Ga atoms. The resistance of wires thinned by FIB was 10 times lower than STL wires which shows the possible dependency of electrical behavior on fabrication method.     

Oscillatory mixed convection in the jet impingement cooling of a horizontal surface immersed in a nanofluid-saturated porous medium

Oscillatory mixed convection in the jet impingement cooling of a partially heated horizontal surface immersed in a nanofluid-saturated porous medium is simulated and discussed in this study. This situation appears when the jet flow and the flow due to buoyancy have opposing effects and are in conflict for domination. The aim of the present contribution is to explore how governing parameters may alter these oscillations and the resulting heat exchange. It is demonstrated that the final steady or oscillatory flow response depends on the values of the Reynolds number, the Grashof number, and the Darcy number but not influenced by the medium porosity and the nanoparticles fraction.     

Development of an Optimal Reservoir Operation Scheme Using Extended Evolutionary Computing Algorithms Based on Conflict Resolution Approach: A Case Study

Optimal reservoir operation and water allocation are critical issues in sustainable water resource management due to increasing water demand. Multiplicity of stockholders with different objectives and utilities makes reservoir operation a complicated problem with a variety of constraints and objectives to be considered. In this case, the conflict resolution models can be efficiently used to determine the optimal water allocation scheme considering the utility and relative authority of different stakeholders. In this study, the Nash product is used for formulation of the objective function of a reservoir water allocation model. The Analytic Hierarchy Process (AHP) is used to determine the importance of each stockholder in bargaining for water. The Particle Swarm Optimization algorithm (PSO) and the Imperialism Competitive Algorithm (ICA) are applied to solve the proposed optimization model. System performance indices including reliability, resiliency and vulnerability are used to evaluate the performance of optimization algorithms. The simplest and most often-used reservoir policy (Standard Operating Policy, SOP) is also used in order to evaluate the performance of the proposed models. The proposed model is applied to the Karkheh River-Reservoir system located in south western part of Iran as a case study. Results show the significance of the application of conflict resolution models, such as the Nash theory and proposed optimization algorithms, for water allocation in the regional scale especially in complicated water supply systems.     

On the importance of thermophoresis and Brownian diffusion for the deposition of micro- and nanoparticles

The aim of the present paper is to analyze the importance of thermophoresis as well as Brownian diffusion for the deposition of micro- and nanoparticles in the presence of temperature gradient. A hybrid Eulerian–Lagrangian procedure is invoked to evaluate the air flow and temperature distribution as well as particles dispersion and deposition. Inspection of the results indicates that, the dominant mechanism for the deposition of ∼ 100 μm particles belongs to inertial impaction. The results reveal that, ∼ 10 μm particles are mainly influenced by thermophoresis. For finer particles (10 nm < particle < 1 μm), it is demonstrated that, depending upon temperature gradient, varied degrees of thermophoresis and Brownian diffusion may contribute on the particle deposition. Nevertheless, as temperature gradient increases, the relative role of thermophoresis enhances.     

<Emphasis Type="SmallCaps">l</Emphasis>-Lysine derived novel optically active poly(ester-imide)/clay nanocomposites: study on synthesis and characterization

A new optically active poly(ester-imide) (PEI) was synthesized from the interfacial polymerization of Ethyl l-lysine-N,N′-ditrimellitoyl diacyl chloride with bis phenol A. Ultrasonic irradiation was applied to compose nanocomposites from the synthetic polymer and different ratios of organo-modified montmorillonite (MMT). The formation of PEI was confirmed by ¹H NMR, FT–IR spectroscopy, specific rotation, and elemental analysis. The resulting nanocomposites were characterized by FT–IR, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The results indicated that the composites were dispersed homogeneously in PEI matrix on nanoscale. An improvement in heat stability is indicated from TGA analysis.     

Controller Placement in Software-Defined Multihop Wireless Networks: Optimal Solution and GA-based Approximation

In a multi-controller software-defined networking (SDN) architecture, solving the controller placement problem (CPP) has a direct effect on the generated control overhead in the network. We aim to minimize the control overhead exchanged in the network, especially in software-defined multihop wireless networks (SDMWN), i.e., a network that is built on multihop communications using a wireless medium. We solve this problem both optimally, using a nonlinear optimization model, and via a heuristic algorithm. The proposed heuristic approach is based on the genetic algorithm (GA). The objective of both the proposed optimization problem and the proposed GA algorithm is to find a given number of controllers, controller placements and assignments of controllers to devices while minimizing the generated control overhead in the network. Our results show the impact of different metrics, including the number of controllers, the arrival rate of new flows and the capacity limit of wireless links on the control overhead and the average number of controller-device and inter-controller hops. In addition, our results demonstrate that the GA-based heuristic approach can derive the same optimal solution for a small network with much less computational overhead, and can solve larger networks in a short period of time, making it feasible for non-trivial network sizes.