The development of radiation embrittlement models for US power reactor pressure vessel steels

A new approach of utilizing information fusion technique is developed to predict the radiation embrittlement of reactor pressure vessel steels. The Charpy transition temperature shift data contained in the Power Reactor Embrittlement Database is used in this study. Six parameters-Cu, Ni, P, neutron fluence, irradiation time, and irradiation temperature - are used in the embrittlement prediction models. The results indicate that this new embrittlement predictor achieved reductions of about 49.5% and 52% in the uncertainties for plate and weld data, respectively, for pressurized water reactor and boiling water reactor data, compared with the Nuclear Regulatory Commission Regulatory Guide 1.99, Rev. 2. The implications of dose-rate effect and irradiation temperature effects for the development of radiation embrittlement models are also discussed.     

Effect of Ni on Microstructure and Mechanical Properties of CrMnFeCoNi High Entropy Alloy

The effect of Ni content on microstructure and mechanical properties of the CrMnFeCoNi high entropy alloy (HEA) has been studied. The Ni content varied from 0 to 20 at% in the composition (CrMnFeMn)_100?xNi_x, where x?=?0, 2.5, 5, 10, 15, and 20 at%. The alloys were synthesized by vacuum arc melting and the microstructure as well as hardness of the as-cast alloys were studied. Alloys with low Ni content (x?≤?2.5%) consists of a two-phase microstructure of dendritic and inter-dendritic regions with fcc (matrix) and tetragonal (sigma) crystal structure, respectively. When the Ni content is 5 at%, two-phase structure with fcc (matrix) and bcc (secondary phase) is observed, with the addition of Mn-rich inclusions that are present in the entire matrix. Alloys with higher Ni content (x?≥?10, at%) exhibit a single phase of fcc structure. Hardness of the HEAs decreases from 320 to 120 Hv with increase in Ni content, and the high hardness of these alloys with low Ni content is due to the mixture of both fcc and hard tetragonal (sigma) phases.

     

Effect of pro‐oxidants on biodegradation of polyethylene (LDPE) by indigenous fungal isolate,Aspergillus oryzae

Proxidant additives represent a promising solution to the problem of the environment contamination with polyethylene film litter. Pro‐oxidants accelerate photo‐ and thermo‐oxidation and consequent polymer chain cleavage rendering the product apparently more susceptible to biodegradation. In the present study, fungal strain, Aspergillus oryzae isolated from HDPE film (buried in soil for 3 months) utilized abiotically treated polyethylene (LDPE) as a sole carbon source and degraded it. Treatment with pro‐oxidant, manganese stearate followed by UV irradiation and incubation with A. oryzae resulted in maximum decrease in percentage of elongation and tensile strength by 62 and 51%, respectively, compared with other pro‐oxidant treated LDPE films which showed 45% (titanium stearate), 40% (iron stearate), and 39% (cobalt stearate) decrease in tensile strength. Fourier transform infrared (FTIR) analysis of proxidant treated LDPE films revealed generation of more number of carbonyl and carboxylic groups (1630–1840 cm⁻¹ and 1220–1340 cm⁻¹) compared with UV treated film. When these films were incubated with A. oryzae for 3 months complete degradation of carbonyl and carboxylic groups was achieved. Scanning electron microscopy of untreated and treated LDPE films also revealed that polymer has undergone degradation after abiotic and biotic treatments. This concludes proxidant treatment before UV irradiation accelerated photo‐oxidation of LDPE, caused functional groups to be generated in the polyethylene film and this resulted in biodegradation due to the consumption of carbonyl and carboxylic groups by A. oryzae which was evident by reduction in carbonyl peaks. Among the pro‐oxidants, manganese stearate treatment caused maximum degradation of polyethylene. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Atmospheric spouted bed combustion: The role of hydrodynamics in emissions generation and control

Recent studies have reaffirmed the utility of spouted beds as potential combustion devices for a variety of fuels: solid, liquid and gaseous fuels (Arbib and Levy, 1982; Weinberg et al., 1988; Zhao et al., 1987; Altwicker et al., 1989; Altwicker and Lin, 1991; Altwicker et al., 1993; Konduri et al., 1994). In this study, the role of annulus residence time on the performance of such a spouted bed combustor is investigated. The experiments presented here show that fluid hydrodynamics in the annulus of a spouted bed combustor can significantly influence the overall performance; changing the residence time in the annulus significantly affects the concentrations of products due to incomplete combustion at the exit of the combustor. The annular residence time is varied by changing the shape of the bottom of the reactor, by introducing a draft tube and by changing the bed heighn. Propane is used as the fuel and sand as the bed medium. Inferences from the combustion results are supported by pressure and temperature profiles. A streamtube model (Lim and Mathur, 1976) was used to obtain an estimate of the residence time in the annulus. It is concluded that the flame processes taking place at the top of the annulus play a critical role in the emission generation and that more information is needed to understand the annulus-flame.     

A simultaneous equations model of crash frequency by severity level for freeway sections

This paper presents a simultaneous equations model of crash frequencies by severity level for freeway sections using five-year crash severity frequency data for 275 multilane freeway segments in the State of Washington. Crash severity is a subject of much interest in the context of freeway safety due to higher speeds of travel on freeways and the desire of transportation professionals to implement measures that could potentially reduce crash severity on such facilities. This paper applies a joint Poisson regression model with multivariate normal heterogeneities using the method of Maximum Simulated Likelihood Estimation (MSLE). MSLE serves as a computationally viable alternative to the Bayesian approach that has been adopted in the literature for estimating multivariate simultaneous equations models of crash frequencies. The empirical results presented in this paper suggest the presence of statistically significant error correlations across crash frequencies by severity level. The significant error correlations point to the presence of common unobserved factors related to driver behavior and roadway, traffic and environmental characteristics that influence crash frequencies of different severity levels. It is found that the joint Poisson regression model can improve the efficiency of most model coefficient estimators by reducing their standard deviations. In addition, the empirical results show that observed factors generally do not have the same impact on crash frequencies at different levels of severity.     

Mutation of charged residues in the TR3 death domain does not perturb interaction with TRADD

Members of the death receptor family play a prominent role indevelopmental and pathological neuronal cell death. The deathsignal is transduced via interaction between the death domainof the receptor and an intracellular adapter, TRADD. We performedalanine-scanning mutagenesis of specific charged residues inthe TR3 death domain to determine whether they play a crucialrole in TR3–TR3 and TR3–TRADD interaction. Mutationof charged residues in the second and third helices of the TR3death domain failed to perturb self-interaction or interactionwith TRADD. These data suggest that despite some similaritybetween the death domains of TR3 and TNFR1 the nature of theinteraction with TRADD differs from that reported for TNFR1.     

Discrete Element Modelling on a Cluster of Workstations

We describe a distributed computing system for discrete element modelling that has been designed for loosely-coupled networks of workstations. The implementation is based on DM 2 , a state-of-the-art discrete element modelling technique for simulating the behaviour of energetic materials and modelling shock compaction phenomena. The underlying computational approach is derived from particle methods, where short-range interactions, both mechanical and thermochemical, determine individual particle movement and state. Using spatial decomposition, a client-server software architecture distributes the computations and, at the language level, Berkeley sockets enable communication between conventional Unix processes on workstations connected by an Ethernet. We evaluate the performance of the system in terms of overall execution time and efficiency, and develop a simple model of computational and communication costs that enables us to predict its performance in other contexts. We conclude that distributed implementations of short-range particle methods can be very effective, even on non-dedicated communication networks.     

Detection and determination of manganese concentration in water using a fiber Bragg grating coupled with nanotechnology

Through this paper we experimentally demonstrate the fabrication of a fiber Bragg grating (FBG) chemical sensor to detect and determine the manganese concentration in water and compare our results with sophisticated spectroscopic methods, such as atomic absorption spectrometry and the inductively coupled plasma method. Here we propose a simple method to develop a thin layer of gold nanoparticles above the etched grating region to enhance the sensitivity of the reflected spectrum of the FBG. By doing so, we achieve a sensitivity of 1.26 nm/parts per million in determining the trace level of Mn in water. Proper reagents are used to detect manganese in water.