Hygrothermal degradation of 977-2A carbon/epoxy composite laminates cured in autoclave and Quickstep

While there are reports concerning the processing and properties of materials using Quickstep technique, little attention has been paid to the hygrothermal degradation of the flexural, interfacial and glass transition behaviours of polymeric composites cured at a relatively high ramp rate of 10 K min^?1 (typical of Quickstep processing). Composite laminates were manufactured in an autoclave and using Quickstep and then conditioned in a climatic chamber at 70 °C and 85% RH until reaching the limit of saturation. The interfacial (interlaminar shear strength (ILSS)), flexural (flexural strength) and glass transition (T_g) properties of the conditioned and unconditioned panels were evaluated. The results demonstrated that the moisture absorption caused the deleterious effect on the properties and that the reduction in the flexural, interfacial and glass transition properties of Quickstep panels was comparable to that observed in autoclave cured panels. Thermal stability, reversible and irreversible effects of hygrothermal conditioning using TGA, DMTA and FT-IR spectroscopy was also investigated and discussed.     

Computational analysis of neutronic parameters for TRIGA Mark-II research reactor using evaluated nuclear data libraries

The aim of this study is to analyze the neutronic parameters of TRIGA Mark-II research reactor using the chain of NJOY-WIMS-CITATION computer codes based on evaluated nuclear data libraries CENDL-2.2 and JEFF-3.1.1. The nuclear data processing code NJOY99.0 has been employed to generate the 69 group WIMS library for the isotopes of TRIGA core. The cell code WIMSD-5B was used to generate the cross sections in CITATION format and then 3-dimensional diffusion code CITTATION was used to calculate the neutronic parameters of the TRIGA Mark-II research reactor. All the analyses were performed using the 7-group macroscopic cross section library. The CITATION test-runs using different cross section sets based on different models applied in WIMS calculations have shown a strong influence of those models on the final integral parameters. Some of the cells were specially treated with PRIZE options available in WIMSD-5B to take into account the fine structure of the flux gradient in the fuel-reflector interface region. It was observed that two basic parameters, the effective multiplication factor, k_eff and the thermal neutron flux, were in good agreement among the calculated results with each other as well as the measured values. The maximum power densities at the hot spot were 1.0446E02 W/cc and 1.0426E02 W/cc for the libraries CENDL-2.2 and JEFF-3.1.1 respectively. The calculated total peaking factors 5.793 and 5.745 were compared to the original SAR value of 5.6325 as well as MCNP result. Consequently, this analysis will be helpful to enhance the neutronic calculations and also be used for the further thermal–hydraulics study of the TRIGA core.     

Stress distributions in a horizontal pressure vessel and the saddle supports

This paper presents analysis results of stress distributions in a horizontal pressure vessel and the saddle supports. The results are obtained from a 3D finite element analysis. A quarter of the pressure vessel is modeled with realistic details of saddle supports. In addition to presenting the stress distribution in the pressure vessel, the results provide details of stress distribution in different parts of the saddle separately, i.e. wear, web, flange and base plates. The effect of changing the load and various geometric parameters is investigated and recommendations are made for the optimal values of ratio of the distance of support from the end of the vessel to the length of the vessel and ratio of the length of the vessel to the radius of the vessel for minimum stresses both in the pressure vessel and the saddle structure. Physical reasons for favoring of a particular value of ratio of the distance of support from the end of the vessel to the length of the vessel are also outlined.     

Improving performance through deep value profiling and specialization with code transformation

Specialization of code is used to improve the performance of the applications. However, specialization based on ineffective profiles deteriorates the performance. Existing value profiling algorithms are not yet able to address the issue of code size explosion incurred due to specialization of code. This problem can be mitigated by capturing data through profiling that would be useful for specialization of code with minimum code size.In this article, we present an approach to optimize code through value profiling and specialization with code transformation. The values of the parameters selected through an analysis of code are captured in the intervals which are automatically adapted to dynamic behavior of the application. The code is then specialized based on value profiles. The specialized code contains optimizations and may be converted back to the generalized code through a transformation. This approach facilitates the code to obtain optimizations through specialization with minimum size, and no runtime overhead.Using this approach, the experiments performed on Itanium-II (IA-64) architecture with icc compiler v 9.0 show a significant improvement in the performance of the SPEC 2000 benchmarks.     

Electrical and thermo-mechanical analysis of beam recovery system for megawatt power gyrotron

The paper presents the electrical and thermo-mechanical design of single stage beam recovery system for 120 GHz, 1 MW gyrotron. The electrical study shows that the cylindrical shape single stage beam recovery system enhances the efficiency by 66.26%. The maximum power deposited to collector in depressed collector operation is 0.48 MW for electronic efficiency, 30% and 1.44 MW for DC electron beam. The thermo-mechanical analysis has been performed to evaluate the water cooling system. The cooling system has capability of accommodating a peak wall loading, 0.9 kW/cm² at flow rate of 1500 l/min for safe operating time, 60 ms. Further, a high voltage analysis is also carried out to appraise the electric field distribution in the collector.     

Interaction of cetyltrimethylammonium bromide with drug in aqueous/ electrolyte solution: A combined conductometric and molecular dynamics method study

Interaction between beta-lactum antibiotic drug ciprofloxacin hydrochloride(CFH)and cationic surfactant cetyltrimethylammonium bromide(CTAB)was performed conductometrically in aqueous as well as in the occurrence of different salts(NaCl,KCl as well as NH_4Cl)over the temperature range of 298.15–323.15 K at the regular interval of 5 K.CFH drug has been suggested for the treatment of bacterial infections such as urinary tract infections and acute sinusitis.A clear critical micelle concentration(CMC)was obtained for pure CTAB as well as(CFH+CTAB)mixed systems.The decrease in CMC values of CTAB caused by the addition of CFH reveals the existence of the interaction between the components and therefore it is the indication of micelle formation at lower concentration of CTAB and their CMC values further decrease in attendance of salts.A nonlinear behavior in the CMC versus T plot was observed in all the cases.The ΔG_m~0 values are found to be negative in present study systems demonstrated the stability of the solution.The values of ΔH_m~0 and ΔS_m~0 reveal the existence of hydrophobic and electrostatic interactions between CFH and CTAB.The thermodynamic properties of transfer for the micellization were also evaluated and discussed in detail.Molecular dynamic simulation disclosed that environment of water and salts have impact on the hydrophobic interaction between CFH and CTAB.In water and salts,CTAB adopts spherical micelle in which charged hydrophilic groups are interacted with waters whereas hydrophobic tails form the core of the micelle.This hydrophobic core region is highly conserved and protected.In addition,micelle formation is more favorable in aqueous Na Cl solution than other solutions.     

Microstructure Characterization and Corrosion Resistance Behavior of New Cobalt-Free Maraging Steel Produced Through ESR Techniques

In this study, two different grades (M23 and M29) of cobalt-free low nickel maraging steel have been produced through electroslag remelting (ESR) process. The corrosion resistance of these ESR steels was investigated in 1 M H₂SO₄ solution using linear potentiodynamic polarization (LPP) and electrochemical impedance spectroscopy (EIS) techniques. The experiments were performed for different immersion time and solution temperature. To evaluate the corrosion resistance of the ESR steels, some significant characterization parameters from LPP and EIS curves were analyzed and compared with that of conventional C250 maraging steel. Irrespective of measurement techniques used, the results show that the corrosion resistance of the ESR steels was higher than the C250 steel. The microstructure of ESR steels was composed of uniform and well-distributed martensite accompanied with little amount of retained austenite in comparison with C250 steel.