Evaluating the performance of an integrated CALPUFF-MM5 modeling system for predicting SO<Subscript>2</Subscript> emission from a refinery

Oil refineries are one of the proven sources of environmental pollution as they emit more than 100 chemicals into the atmosphere including sulfur dioxide (SO₂). The dispersion patterns of SO₂ from emissions of Sohar refinery was simulated by employing California Puff (CALPUFF) model integrated with state of the art meteorological Mesoscale Model (MM5). The results of this simulation were used to quantify the ground level concentrations of SO₂ in and around the refinery. The evaluation of the CALPUFF and MM5 modeling system was carried out by comparing the estimated results with that of observed data of the same area. The predicted concentrations of SO₂ agreed well with the observed data, with minor differences in magnitudes. In addition, the ambient air quality of the area was checked by comparing the model results with the regulatory limits for SO₂ set by the Ministry of Environment and Climate Affairs (MECA) in Oman. From the analysis of results, it was found that the concentration of SO₂ in the nearby communities of Sohar refinery is well within the regulatory limits specified by MECA. Based on these results, it was concluded that no health risk, due to SO₂ emissions, is present in areas adjacent to the refinery.     

Effect of simulated reclamation treatments on chemical properties and nitrogen mineralising characteristics of saline and alkali soils from West Pakistan

Nitrogen mineralisation and nitrification during incubation of alkali, saline-alkali, highly saline and moderately saline soils were studied in the laboratory before and after simulated reclamation treatment, in which water plus calcium sulphate were used for the two alkali soils and water alone for the two saline soils. The reclamation processes reduced exchangeable sodium and soluble salts to low levels. Mineral nitrogen accumulation during incubation of original and ‘reclaimed’ soils was accounted for entirely as nitrate. The ‘reclaimed’ soils showed a lag phase in mineral nitrogen accumulation. The moderately saline soil was the only one to show increased mineralisable nitrogen, whilst the alkali and saline-alkali soils, in particular, and the highly saline soil showed reduced mineralisable nitrogen after ‘reclamation’.     

Comparison of performance parameters of poly(3,4 ethylenedioxythiophene) (PEDOT) based electrochromic device on glass with and without counter electrode

Conjugated polymers are promising materials for electrochromic device technology. Aqueous dispersions of poly(3,4-ethylenedioxythiophene)-(PEDOT) were spin coated onto transparent conducting oxide (TCO) coated glass substrates. A seven-layer electrochromic device was fabricated with the following configuration: glass/transparent conducting oxide (TCO)/PEDOT (main electrochromic layer)/gel electrolyte/prussian blue (counter electrode)/TCO/glass. The device fabricated with counter electrode (Prussian blue) showed a contrast of 18% and without counter electrode showed visible contrast of 5% at 632 nm at a voltage of 1.9 V. The comparison of the device is done in terms of the colouration efficiency of the devices with and without counter electrode.     

An SRAM-based novel hardware architecture for longest prefix matching for IP route lookup

A static random access memory (SRAM)-based novel hardware architecture for longest prefix match (LPM) search scheme has been proposed in this paper. The key concept of this architecture is to store the IP prefixes virtually in the forwarding table. This architecture reduces memory consumption by using a two-tier hierarchical SRAM-based memory structure for maintaining the next hop port information. Originally, next hop addresses are kept in the shared global memory called next hop global memory (NHGM) and its links are maintained in another memory, called next hop link memory (NHLM). This approximately reduces memory consumption by 50–62.5% compared to existing SRAM-based schemes. The proposed architecture consumes single memory write cycle to store an IP prefix and also takes single memory read cycle for LPM search. However, finding next hop information incurs two memory read cycles due to hierarchical next hop memory structure. The proposed scheme performs an LPM lookup operation in 1.05–1.31 ns in IPv4 and between 1.05 and 1.6 ns in IPv6. This results into LPM search throughput of 950 million lookups per second (MLPS) to 760 MLPS in IPv4 and between 620 and 950 MLPS in IPv6. The average search throughput achievable from this architecture is roughly 850 MLPS in IPv4 and 780 MLPS in IPv6. The numerical results show that this architecture significantly reduces memory requirement, power consumption, and transistor-count/bit requirement.     

Mixed monolayer protected gold atom-oxide cluster synthesis and characterization

Small atomic gold clusters in solution, Au(n), stabilized by cetyl trimethylammonium bromide (CTAB) and cysteine, have been synthesized potentiodynamically in quiescent aqueous solutions. The electrodissolution of gold to gold ions during an anodic scan and subsequent cluster formation during a cathodic scan in underpotential (UPDD) and overpotential dissolution-deposition (OPDD) regions were studied. The experimental potentiodynamic I-E profiles and chronoamperometric i-t transients are fit into reported theoretical models of adsorption and electrocrystallization. The plausible application of clusters/cluster film to cysteine sensing based on fluorescence quenching and square wave stripping voltammetry is demonstrated.     

Size-fractionated measurements of ambient ultrafine particle chemical composition in Los Angeles using the NanoMOUDI

Ambient ultrafine particles have gained attention with recent evidence showing them to be more toxic than larger ambient particles. Few studies have investigated the distribution of chemical constituents within the ultrafine range. The current study explores the size-fractionated ultrafine (10-180 nm) chemical composition at urban source sites (USC and Long Beach) and inland receptor sites (Riverside and Upland) in the Los Angeles basin over three different seasons. Size-fractionated ultrafine particles were collected by a NanoMOUDI over a period of 2 weeks at each site. Measurements of ultrafine mass concentrations varied from 0.86 to 3.5 microg/m3 with the highest concentrations observed in the fall. The chemical composition of ultrafine particles ranged from 32 to 69% for organic carbon (OC), 1-34% for elemental carbon (EC), 0-24% for sulfate, and 0-4% for nitrate. A distinct OC mode was observed between 18 and 56 nm in the summer, possibly indicating photochemical secondary organic aerosol formation. The EC levels are higher in winter at the source sites due to lower inversion heights and are higher in summer at the receptor sites due to increased long-range transport from upwind source areas. Nitrate and sulfate were measurable only in the larger particle size ranges of ultrafine PM. Collocated continuous measurements of particle size distributions and gaseous pollutants helped to differentiate ultrafine particle sources at each site.     

Towards Probabilistic Formal Analysis of SATS-Simultaneously Moving Aircraft (SATS-SMA)

The objective of NASA’s Small Aircraft Transportation System (SATS) Concept of Operations (ConOps) is to facilitate high volume operation of advanced small aircraft operating in non-towered, non-radar airports. This system can provide improved and accessible air travel at a lower cost. Given the safety-critical nature of SATS, its analysis accuracy is extremely important. However, the commonly used analysis techniques, like pilot/computer simulation and traditional model checking, do not ascertain an error-free and complete verification of SATS due to the wide range of possibilities involved in SATS or the inability to capture the randomized and unpredictable aspects of the SATS ConOps environment in their models. Another limitation of these studies is that a limited speed range was used in the analysis. To overcome these limitations, we propose to formulate the SATS ConOps as a fully synchronous and probabilistic model, i.e., SATS-SMA, that supports simultaneously moving aircraft. The distinguishing features of our work include the preservation of safety of aircraft while providing a precise timing model, which is closer to reality compared to the previous hybrid analyses. Important insights related to the aircraft take-off and landing operations during the instrument meteorological conditions are also presented.     

Effects of high hydrostatic pressure on the mechanical behavior of a crystalline polymer–polyoxymethylene

The true stress-true strain behavior of polyoxymethylene, n(-CH₂O), as an example of a bulk semi-crystalline polymer, has been investigated for constant hydrostatic environmental pressures from 1 atmosphere to 8 kilobars with the principal objectives of elucidating the factors controlling flow and fracture. Experiments were conducted in uniaxial tension at room temperature and constant strain rate. The tensile observations were supplemented by measurements of bulk compressibility and stress relaxation behavior at pressure. In contrast with metals and inorganic compounds, the modulus, yield stress and fracture stress of POM increase strongly with pressure by a factor of approximately three at 8 kilobars. The modulus increase is shown from the stress relaxation measurements to be associated with a pressure-induced increase in the β-transition temperature which points to the potential usefulness of the concept of pressure-temperature super-position of mechanical behavior. The characteristics of the pressure dependence of the yield stress demonstrate that yield criteria based on continum mechanics considerations, including the Mohr or Coulomb-Navier criterion, are not valid for general deformation (non-plane strain) conditions in this polymer. The concept of a critical volume change determining the initiation of yielding is suggested to be applicable to semi-crystalline polymers. Comparison with analogous changes in yield stress with temperature points to an increasing contribution to the control of yielding by the initially disordered regions with increasing pressure or decreasing temperature. The fracture behavior observed at pressure eliminates the concepts of a critical stress as a fracture criterion for POM and of a simple reduction in normal stress at points of stress concentration as the principal effect of the applied pressure on fracture.     

L-Ornithine Monohydrochloride Doped Zinc Tris-Thiourea Sulphate Single Crystals for NLO Applications

Silicon - In the current study, transparent and bulk sized L-ornithine monohydrochloride (LOMHC) added zinc tris-thiourea sulphate (LOMHC-ZTS) single crystals are synthesized successfully by...     

Estimation of Uncertainty in the Calibration of Industrial Platinum Resistance Thermometers (IPRT) Using Monte Carlo Method

Monte Carlo method has been implemented for uncertainty estimation in IPRT calibration. The work is based on the Callendar van Dusen equation for 0–500 °C calibration range. Derivation of the mathematics model for running the simulation is also described. Results are compared with output from the traditional GUM method and we find close agreement between two methods.