Failure Analysis of Leaked Stainless Steel Housing of Electro Chemical Hydrogen Metre

The failure of the stainless steel housing of Electro Chemical Hydrogen Metre (ECHM) in the Steam Generator Test Facility resulting in a minor sodium fire has been investigated through systematic metallographic and fractographic analyses. The root cause of the failure was identified as caustic stress corrosion of the stainless steel flange that forms a part of the ECHM housing.     

A new approach to sizing analog CMOS building blocks using pre-compiled neural network models

There has been a constant endeavor towards improving the available circuit design automation tools to match technological advancements in the electronic industry. However, inadequate research efforts in the analog domain are holding back the exploitation of advanced technologies. A dearth of design expertise in the analog domain is the principal driving force for the growth of Design Automation (DA) tools. Transistor sizing is one of the most crucial steps in the analog IC design. In this paper, we put forward a new computer aided design framework for the sizing of transistors in MOS Integrated Circuit (IC) amplifiers by incorporating powerful modeling capabilities of Artificial Neural Networks (ANN). ANNs have proven to be efficient and accurate modeling tools in several applications. The proposed tool is capable of directly computing transistor related design parameters, of the MOS IC amplifier and associated peripheral circuitry. The proposed tool thus avoids several time-consuming simulations and/or tuning runs at the very bottom level of analog IC amplifier implementation, using a given CMOS process. It also reduces manual intervention in the design process, thus enhancing the automation of the design process. This paper presents design examples of several analog IC functional modules that are developed and verified successfully.     

A filtered-laminar-flame PDF sub-grid scale closure for LES of premixed turbulent flames. Part I: Formalism and application to a bluff-body burner with differential diffusion

A sub-grid scale closure for Large Eddy Simulation (LES) of turbulent combustion based on physical-space filtering of laminar flames is discussed. Applied to an unstructured grid, the combustion LES filter size is not fixed in this novel approach devoted to LES with refined meshes, but calibrated depending on the local level of unresolved scalar fluctuations. The context is premixed or stratified flames, the derived model relies on four balance equations for mixture fraction and its variance, and a progress variable and its variance. The proposed formalism is based on a presumed probability density function (PDF) derived from the filtered flames. Closures for the terms of the equations that are unresolved over LES grids are achieved through the PDF. The method uses flamelet tabulated detailed chemistry and is first applied to the simulation of laminar flames (1D and 2D) over various grids for validation, before simulating a turbulent burner studied experimentally by Sweeney et al. (2012). Since this burner also features differential diffusion effects, the numerical model is modified to account for accumulation of carbon in the recirculation zone behind the bluff-body. A differential diffusion number based on the gradient of residence times is proposed, in an attempt to globally quantify differential diffusion effects in burners.     

Thermophoretic Deposition of Particles in Laminar and Turbulent Tube Flows

Thermophoretic deposition of aerosol particles (particle diameter ranges from 0.038 to 0.498 μm) was measured in a tube (1.18 m long, 0.43 cm inner diameter, stainless steel tube) using monodisperse NaCl test particles under laminar and turbulent flow conditions. In the previous study by Romay et al., theoretical thermophoretic deposition efficiencies in turbulent flow regime do not agree well with the experimental data. In this study, particle deposition efficiencies due to other deposition mechanisms such as electrostatic deposition for particles in Boltzmann charge equilibrium and laminar and turbulent diffusions were carefully assessed so that the deposition due to thermophoresis alone could be measured accurately. As a result, the semiempirical equation developed by Lin and Tsai in laminar flow regime and the theoretical equation of Romay et al. in turbulent flow regime are found to fit the experimental data of thermophoretic deposition efficiency very well with the differences of less than 1.0% in both flow regimes. It is also found that Talbot's formula for the thermophoretic coefficient is accurate while Waldmann's free molecular formula is only applicable when Kn is greater than about 3.0.     

PRODUCTION AND CHARACTERIZATION OF POROUS CARBON FROM DATE PALM SEEDS BY CHEMICAL ACTIVATION WITH H3PO4: PROCESS OPTIMIZATION FOR MAXIMIZING ADSORPTION OF METHYLENE BLUE

The potential of date palm pits to be a suitable precursor for preparation of porous carbon was explored in the present work, utilizing phosphoric acid as the activating agent. Experimental methods reported in the literature were chosen with certain modifications in order to simplify the process. Process optimization was performed using the popular response surface methodology (RSM) adopting a Box-Behnken design. Process optimization was intended to maximize the porous carbon yield and the methylene blue (MB) adsorption capacity, with the process variables being the activation temperature, impregnation ratio (IR), and activation time. The structural characteristics were assessed based on nitrogen adsorption isotherms, SEM, and FT-IR, while the adsorption capacity was estimated using MB adsorption. The optimized experimental conditions were identified to be an activation temperature of 400°C, IR of 3, and activation time of 58 min, with the resultant porous carbon having a yield of 44% and MB adsorption capacity of 345 mg/g. The structural characteristics of the porous carbon reveal the BET surface area to be 725 m²/g, with pore volume of 1.26 cc/g, an average pore diameter of 2.91 nm, and total micropore volume of 0.391 cc/g. The popular Langmuir and Freundlich adsorption isotherm models were tested, and a maximum monolayer adsorption capacity of MB was estimated to be 455 mg/g, which compares with the highest for MB reported in literature, evidencing the suitability of porous carbon for adsorption of macromolecular compounds. The low activation temperature and activation time with highest yield render the process technically and economically attractive for commercial use.     

Role of Chain Entanglements in the Electrospinning of Wheat Protein-Poly(Vinyl Alcohol) Blends

The aim of this investigation was to determine if the rapid solvent removal evaporation that occurs during electrospinning enabled the gluten protein and poly(vinyl alcohol) (PVOH) chains to remain at least partially entangled in the final product. Natural and synthetic biopolymer blends are known to phase separate in the melt. Differential scanning calorimetry (DSC) was used to test our hypothesis, which we achieved by systematically comparing the thermal profiles of the nonwoven fibrous sheets comprising: 1) 100% commercial wheat gluten, 2) 100% PVOH, and 3) the (75/25) wheat gluten/PVOH blend. The DSC scans of the two PVOH-containing, nonwoven fibrous sheets exhibited differences in the characteristics and positions of the melting peaks (T_m) of the PVOH crystalline phase, while the DSC scans of the nonwoven fibrous sheets comprising either 100% commercial wheat gluten or the wheat gluten/PVOH blend yielded neither a measurable glass transition temperature (T_g) nor a T_m. Energy dispersive spectroscopy (EDS) was used to compare the elemental compositions of the individual fibers with the compositions of the spherical domains found in the nonwoven fibrous mats. These scans revealed that the mineral matter found in commercial wheat gluten (roughly 1% by weight) had phase-separated from the bulk gluten protein as a result of electrospinning.     

STUDIES ON U-Th SEPARATION USING TRI-sec-BUTYL PHOSPHATE

In this work, the extraction of Am(III), U(VI), Th(IV) and Fe(III) by P,P′-di(2-ethylhexyl) methylene- (H₂DEH[MDP]), ethylene- (H₂DEH[EDP]), and butylene- (H₂DEH[BuDP]) diphosphonic acids dissolved in the monomerizing diluent 1-decanol has been investigated. A comparison of the acid dependencies with those observed in o-xylene has revealed a number of novel features which have been ascribed to extraction of metal nitrates through a solvation mechanism made possible by facile transfer of nitrate ions into the 1-decanol phase. The use of 1-decanol as the diluent gives rise to strong suppression of metal extraction, which increases along the series Fe(III)2DEH[MDP]2DEH[EDP]≤H₂DEH[BuDP]. The extractant dependencies of U(VI) and Th(IV) have slopes equal to 2 with all extractants. Those for Am(III) and Fe(III) exhibit variable slopes with limiting values of 1 at the lowest and 3 at the highest extractant concentrations. From the combined information provided by the acid and extractant dependencies, stoichiometries and probable structures for complexes formed in the organic phase have been proposed. The data obtained in this work suggest a simple route for actinide stripping from diphosphonic acid extractants loaded in nonpolar diluents.     

METAL-SOLVATE STOICHIOMETRY EVALUATION IN EXTRACTIONS BY SOLVATING TYPE NEUTRAL EXTRACTANTS-A NOVEL APPROACH

ABSTRACT

This paper reports a novel approach for the evaluation of the stoichiometry of the metal-solvate formed during the macro level extraction of metal salts from neutral media by neutral solvating type extractants. This method involves the measurement of the distribution coefficient for the extraction of the metal ion from neutral medium as a function of the concentration of the metal ion in the organic phase, and finding the organic loading at which the distribution coefficient is a maximum. This new approach has been verified by a study of the uranyl nitrate extraction by tri-n-butyl phosphate and di-n-butyl octanamide, as well as cerium(lll) nitrate extraction by TBP. In all these cases the solvation number measured by the new method was in agreement with the value reported by other techniques. The method was extended to a study of the thorium nitrate extraction by trialkyl phosphates, which yielded a solvation number of 3 for all the trialkyl phosphates studied.     

Solid particle erosion studies on polyphenylene sulfide composites and prediction on erosion data using artificial neural networks

Solid particle erosion behavior of polyphenylene sulfide, reinforced by short glass fibers with varying fiber content (0–40 wt%) has been studied. Steady-state erosion rates have been evaluated at different impact angles (15–90°) and impact velocities (25–66 m/s) using silica sand particles (200 ± 50 μm) as an erodent. PPS and its composites exhibited maximum erosion rate at 30° impact angle indicating ductile erosion behavior. Though PPS is a brittle thermoplastic, incubation period was found for neat resin and its composites at normal impact (α = 90°). The erosion rates of PPS composites increased with increasing amount of glass fiber. Morphology of eroded surfaces was examined using scanning electron microscopy (SEM) and possible wear mechanisms were discussed. Also, artificial neural networks (ANNs) technique has been used to predict the erosion rate based on the experimentally measured database of PPS composites. The results show that the predicted data are well acceptable when comparing them to measured values. A well-trained ANN is expected to be very helpful for prediction of wear data for systematic parameter studies.     

Suppression of Pain in the Late Phase of Chronic Trigeminal Neuropathic Pain Failed to Rescue the Decision-Making Deficits in Rats

Trigeminal neuropathic pain (TNP) led to vital cognitive functional deficits such as impaired decision-making abilities in a rat gambling task. Chronic TNP caused hypomyelination in the anterior cingulate cortex (ACC) associated with decreased synchronization between ACC spikes and basal lateral amygdala (BLA) theta oscillations. The aim of this study was to investigate the effect of pain suppression on cognitive impairment in the early or late phases of TNP. Blocking afferent signals with a tetrodotoxin (TTX)-ELVAX implanted immediately following nerve lesion suppressed the allodynia and rescued decision-making deficits. In contrast, the TTX used at a later phase could not suppress the allodynia nor rescue decision-making deficits. Intra-ACC administration of riluzole reduced the ACC neural sensitization but failed to restore ACC-BLA spike-field phase synchrony during the late stages of chronic neuropathic pain. Riluzole suppressed allodynia but failed to rescue the decision-making deficits during the late phase of TNP, suggesting that early pain relief is important for recovering from pain-related cognitive impairments. The functional disturbances in ACC neural circuitry may be relevant causes for the deficits in decision making in the chronic TNP state.