Transport of Sulphur dioxide with deposition and wash out in wet and dry regions

Here we have investigated theoretically the average integrated ground level concentration of sulphur dioxide in wet and dry regions due to the emission from an elevated point source. The profiles of concentration distribution have been obtained in wet and dry regions on various rates of rainfall.     

Computational study of 5<Emphasis Type="Italic">d</Emphasis> transition metal mononitrides and monoborides using density functional method

5d-metal mononitrides and monoborides viz. X-N and X-B (X = La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg) are studied using density functional method based B3LYP functional with LANL2DZ and SDD basis set. The lowest spin state, electron affinities, ionization potentials and binding energies for mononitrides and monoborides are obtained. The electronic state and electronic configuration of mononitrides and monoborides are discussed. Orbitals involved in bond formation are identified. The properties of mononitrides and monoborides are compared. It is found that 5d-metal atoms form stronger bond with nitrogen atom than the boron atom. The range of binding energy, electron affinity and ionization potential is wider for mononitrides than that for monoborides. The properties of 5d-metal mononitrides and 3d-metal mononitrides are also compared. The binding energies for the former are lower than those for the latter.     

Measurement and Stochastic Computational Modeling of the Elastic Properties of Parallel Strand Lumber

This paper describes a model for the spatial variation of the elastic modulus of parallel strand lumber (PSL) that is based on bending experiments and also describes a validated stochastic computational model that incorporates orthotropic elasticity and uncertainty in strand geometry and material properties. The PSL exhibits significant variability both within members and between members, but this variability is less than that of equivalent sawn-wood members, and decreases with increasing member size. The correlation length of the elastic modulus is found to be several meters and is independent of the cross-sectional size. The variance of PSL elastic modulus is found to scale inversely with the number of strands in the cross section. The validated computational model is flexible enough to allow preliminary exploration of the properties of new mixes of species and strand sizes in PSL material design.     

Electrohydrodynamic atomization (EHDA) of high-conductivity pure solvent

ABSTRACT

In this study, the effects of flow rate, liquid conductivity and neutralizer strength on the operating and output characteristics are examined for an Electrohydrodynamic atomization (EHDA)-based aerosol generator system, designed and built in our laboratory. Ethylene glycol is used for generating the droplets. It is seen that stable cone-jet mode could be obtained for solvent conductivity as high as 240 μS/cm. While the output number concentration was found to increase with both flow rate and conductivity, the mean particle diameters decreased with increasing conductivity and increased with flow rate. The mean droplet size and output number concentration are found to be about three times more sensitive to changes in conductivity as compared to that of flow rate in the range of 26–150 μS/cm. It is also observed that throughput from the system is strongly dependent on the strength of the charge neutralizer. In the present setup, 8 μCi ²⁴¹Am bipolar neutralizer in axisymmetric configuration was found to be sufficient to neutralize the generated droplets.     

Data Replication in Cooperative Mobile Ad-Hoc Networks

The mobile computing environment provides many benefits such as ubiquitous access to computing but includes constraints on resources such as available bandwidth and battery life. Replication is a widely recognized method for balancing the demands of storage space with bandwidth and battery life. We propose a novel scheme that seeks to strategically balance these constrained resources through a cooperative game-theory approach for replication in a mobile environment. Our replication strategy relies on the cooperation of the nodes within the network to make replica caching decisions which are spatiotemporally local-optimal for the network from an energy and bandwidth conservation standpoint. In cooperative altruistic data replication, each node calculates the net global benefit, for caching a replica of the requested data, as the result data is returned from the responding node to the requesting node, where it determines the spatiotemporally local-optimal node for replicating the data item. Performance results from our research indicate that our scheme, CADR, improves the query response time by 25 and 45 %, mean hop count is improved by 26 and 46 %, query error is reduced by 30 and 48 %, while energy utilization is reduced 30 and 57 % when compared with both another game theoretic replication approach and standard cooperative caching respectively.     

Multiple sourcing decisions using integrated AHP and knapsack model: a case on carton sourcing

Purchase allocation is a multi criteria decision making (MCDM) problem. Multitude of qualitative and quantitative factors is involved in the multiple sourcing decisions. Analytic hierarchy process (AHP) has widely been used to find out the relative rankings of suppliers. AHP can be combined with regular supplier quantitative audit process. In classical AHP, decision maker (DM) has to pair wise compare suppliers for each factor, whereas the proposed audit based simplified AHP will remove the complexity of comparison. Quarterly audit-based AHP rankings and supplier performance probability products can be used in place of revenues in the backward recursive resource allocation knapsack model. This combined model will decompose purchase allocation problem into different stages and combine one supplier at each stage and provide the optimum and feasible solution in the end. Solution at each stage is also a feasible option. This model is only applicable when the total order quantity and the capacity of all suppliers are integer multiples of economic or minimum order quantity. This integrated model thus provides number of orders/supplier.     

Field Assessment of the Performance of a Ballasted Rail Track with and without Geosynthetics

Understanding the complex mechanisms of stress transfer and strain accumulation in layers of track substructure under repeated wheel loading is essential to predict the desirable track maintenance cycle as well as the design of the new track. Various finite element and analytical techniques have been developed in the past to understand the behavior of composite track layers subjected to repeated wheel loads. The mechanical behavior of ballast is influenced by several factors, including the track confining pressure, type of aggregates, and the number of loading cycles. A field trial was conducted on an instrumented track at Bulli, New South Wales, Australia, with the specific aims of studying the benefits of a geocomposite installed at the ballast-capping interface, and to evaluate the performance of moderately graded recycled ballast in comparison to traditionally very uniform fresh ballast. It was found that recycled ballast can be effectively reused if reinforced with a geocomposite. It was also found that geocomposite can effectively reduce vertical and lateral strains of the ballast with obvious implications for improved track stability and reduced maintenance costs.     

Selection of a pull production control policy under different demand situations for a manufacturing system by AHP-algorithm

A multistage serial production system is considered in the present paper. A generalized model has been developed with the use of probabilistic demand situations for the end product. The demand situations considered are binomial, exponential, lognormal and Poisson. These demand patterns are used as input parameter for various production control policies. The output values for performance parameters are obtained by simulation. The production policies analyzed are Kanban, CONWIP and Hybrid as alternatives for controlling the engineering manufacture. In the presence of several performance measures, it often becomes difficult for the management to select the most appropriate policy. Analytic hierarchy process (AHP) has been implemented for the purpose of selection. Computational results have been reported along with the sensitivity analysis after designing and conducting various experiments.     

Advances in pulsed-laser-deposited AIN thin films for high-temperature capping, device passivation, and piezoelectric-based RF MEMS/NEMS resonator applications

In this paper we report recent advances in pulsed-laser-deposited AIN thin films for high-temperature capping of SiC, passivation of SiC-based devices, and fabrication of a piezoelectric MEMS/NEMS resonator on Pt-metallized SiO₂/Si. The AlN films grown using the reactive laser ablation technique were found to be highly stoichiometric, dense with an optical band gap of 6.2 eV, and with a surface smoothness of less than 1 nm. A low-temperature buffer-layer approach was used to reduce the lattice and thermal mismatch strains. The dependence of the quality of AlN thin films and its characteristics as a function of processing parameters are discussed. Due to high crystallinity, near-perfect stoichiometry, and high packing density, pulsed-laser-deposited AlN thin films show a tendency to withstand high temperatures up to 1600°C, and which enables it to be used as an anneal capping layer for SiC wafers for removing ion-implantation damage and dopant activation. The laser-deposited AlN thin films show conformal coverage on SiC-based devices and exhibit an electrical break-down strength of 1.66 MV/cm up to 350°C when used as an insulator in Ni/AlN/SiC metal-insulator-semiconductor (MIS) devices. Pulsed laser deposition (PLD) AlN films grown on Pt/SiO₂/Si (100) substrates for radio-frequency microelectrical and mechanical systems and nanoelectrical and mechanical systems (MEMS and NEMS) demonstrated resonators having high Q values ranging from 8,000 to 17,000 in the frequency range of 2.5–0.45 MHz. AlN thin films were characterized by x-ray diffraction, Rutherford backscattering spectrometry (in normal and oxygen resonance mode), atomic force microscopy, ultraviolet (UV)-visible spectroscopy, and scanning electron microscopy. Applications exploiting characteristics of high bandgap, high bond strength, excellent piezoelectric characteristics, extremely high chemical inertness, high electrical resistivity, high breakdown strength, and high thermal stability of the pulsed-laser-deposited thin films have been discussed in the context of emerging developments of SiC power devices, for high-temperature electronics, and for radio frequency (RF) MEMS.     

Design and manufacturing advisor for turbine disks

The design and manufacturing advisor (DMA) is a generic architecture for an expert system which assists in the process of product design. It integrates various parts of the production environment which affect the final product—such as fabrication, assembly, inspection and inventory. The design process can be partitioned into four stages: problem specification, feature specification, testing and generation. DMA facilitates the development of tractable designs, defined by the intersection of three spaces relating to specifications, features and productibility. The system consists of a domain-independent module and a domain-dependent module, each of which contains subcomponents; this modular structure facilitats system modification, expansion, and portability. The DMA has been validated by specializing the architecture to the design of gas-turbine disks for jet engines.