Decomposition of hydrogen peroxide in the presence of mixed oxide catalysts

The decompn. of H2O2 in the presence of TiO2-​ZrO2, SiO2-​ZrO2, Al2O3-​ThO2, SiO2-​ThO2, Al2O3-​MoO3, SiO2-​MoO3, Al2O3-​WO3, and SiO2-​WO3 catalysts, ignited 6 hr at 120-​1000°, was studied chem. anal. and kinetically. Due to the bifunctional nature of these catalyst the effect of the acidic and basic sites on the decompn. was studied by poisoning the sites with Neutral Red and HCl, resp. Both the acidic and basic sites catalyze the decompn. The activation energy for the sites is inversely proportional to the acidity and basicity as calcd. from the initial slopes of the rate curves. The decompn. mechanism in the presence of acidic and basic sites is of similar character. Only acid sites of pKa -​3.0 and basic sites of pKa 10 catalyze the decompn

Vibrational transition probabilities of the bands of the barium oxide (A 1SIGMA-​X 1SIGMA) system

The band spectrum of BaO has been obtained by spraying BaCl2 soln. into a flame. The integrated intensities of the bands have been detd. by photographic photometry. The exptl. results along with the theoretically computed Franck-​Condon factors have been used to evaluate a relation between Re, the electronic transition moment, and r, the internuclear sepn., in the form, Re(r v'v'') = const.(1 - 0.536r)​. This relation has been used to obtain improved Franck-​Condon factors. The theoretically computed Franck-​Condon factors, with and without the inclusion of Re variation, have been compared with the exptl. band strengths

Simulation of Liquid-Liquid Dispersed Flow in Horizontal Pipe Using Computational Fluid Dynamics

Liquid-liquid dispersed flows are commonly encountered in many of the industrial applications such as polymerization, emulsification, batch and continuous stirred reactors and pipeline flows such as in petroleum industries. Liquid-liquid two phase flows are very complex due to the existence of several flow patterns and mechanisms. Numerical approaches offer the flexibility to construct computational models which can adapt large variety of physical conditions without constructing large scale prototypes. The present work focuses on predicting the phase hold-up across a pipe cross-section and ambivalence range for phase inversion phenomena at different mixture velocity and range of input water fraction. The Computational Fluid Dynamics (CFD) computations were carried using FLUENT 6.2.16 while the geometry was created in pre-processor, GAMBIT 2.2.3. Dispersed phase dynamics and the turbulent continuous phase are modeled using an Eulerian-Eulerian approach and standard ε−k turbulence model. To check the reliability of the CFD code, the predicted results were validated with experimental results of previous work at different mixture velocities and phase fractions. CFD predicted the flow phenomenon such as phase transition from water-in-oil dispersion to oil-in-water dispersion and flow development along the length of the pipe. CFD code also predicted the phase hold-up distributions at pipe cross section. The pressure gradient trends similar to those observed in previous experimental results were obtained using CFD code. The phase inversion point obtained was within the ambivalence range suggested in literature. The numerical CFD simulations also confirmed that interphase drag, lift and turbulent dispersion forces has significant influence on spatial phase distribution. CFD simulations so obtained were subsequently compared with experimental results from previous researchers and correlation featuring range of mixture velocities and phase inputs. The predicted hold-up profiles were in good agreement with the previous experimental results for high mixture velocities and were in reasonable agreement with those of lower mixture velocity. Overall good qualitative agreement was achieved between physical model and simulated results

Cleavage of anisole by hydrogen chloride in nonaqueous media in the presence of inorganic catalysts

Anisole is cleaved and rearranged with HCl and Al2O3 or Cr2O3 catalysts, but is rearranged without cleavage by HCl-​SiO2 or by catalysts alone. A mechanism is proposed

Waste tire rubber in polymer blends: a review on the evolution, properties and future

This review addresses the progress in waste tire recycling with a particular attention to incorporation of waste tire rubber (WTR) into polymeric matrices. Methods of waste tire downsizing, importance of WTR characterization and current practice of WTR modification has been emphasized. Detailed discussion on influence of WTR size, loading, modification, compatibilization and crosslinking on the rheological, mechanical and thermal properties of rubber, thermoplastic and thermoplastic elastomer blends utilizing WTR has been reported. By far, thermoplastic elastomer blends; though still in its infancy; has shown the most promising properties balance which is capable of commercialization. Rubber/WTR blends also show ease of processing and acceptable properties. Thermoplastic/WTR blends suffers in term of toughness and elongation at break. However, the waste thermoplastic/WTR is a viable solution to address polymeric waste problem. Review also highlights the lack of studies concentrating on dynamic mechanical, aging, thermal and swelling properties of WTR polymeric blends

Investigations of Material Response to Fatigue Phenomena in Contacting Bodies

Investigating the fatigue performance of machine components has been of significant interest to improve reliability and reduce the maintenance costs. In the current work, analytical as well as experimental approaches are used to investigate material response to contact fatigue damage. In particular, two fatigue phenomena namely; fretting fatigue and rolling contact fatigue (RCF) are studied. Fretting fatigue is a damage mechanism observed in machine components subjected to fretting in tandem with fluctuating bulk stresses. A fretting test fixture was developed to investigate fretting fatigue behavior of AISI 4140 vs. Ti-6Al-4V in a cylinder-on-flat contact configuration. The critical damage value for AISI 4140 was extracted using the method of variation of elasticity modulus. The fretting fatigue lives obtained from the proposed computational fatigue damage model were found to be in good agreement with the experimental results. The RCF investigation focuses on developing a modified 2D numerical model to simulate RCF damage in line contact configuration. First, a new computationally efficient approach is developed to investigate sub-surface initiated spalling in large bearings. Previously developed continuum damage mechanics based 2D fatigue model was modified to incorporate stress mapping procedure and dynamic remeshing tool to make the model computationally efficient. The new approach was validated against the previous numerical model for small rolling contacts. The scatter in the RCF lives and the progression of fatigue spalling for large bearings obtained from the model show good agreement with experimental results available in open literature. The ratio of L10 lives for different sized bearings computed from the model correlate well with the formula derived from the basic life rating for radial roller bearing as per ISO 281. Furthermore, the RCF model was extended to incorporate elastic-plastic material in order to investigate RCF of case carburized steels. A series of micro-indentation tests were conducted to obtain the hardness gradient in the case carburized 8620 steel. The hardness gradient in the material was modeled by changing the yield strength as a function of depth. The residual stress distribution due to carburization process was modeled by modifying the damage evolution law. The model was used to compare the rolling contact fatigue (RCF) lives of through hardened and case carburized bearing steel with different case depths. Based on the model results, the optimum case depths to maximize the RCF lives of the case carburized bearings at different loading conditions were obtained. This model was then modified to investigate RCF in refurbished case carburized bearings. Refurbishing process was simulated by removing a layer of material from the original surface after a set number of fatigue cycles. The original material properties, residual stresses and the fatigue damage accumulated prior to refurbishing in the remaining material were preserved. The refurbished geometry was then subjected to additional fatigue cycles until damage was detected. According to model results, more fatigue cycles prior to refurbishing enhance the total fatigue life of refurbished bearings. It was also found that beneficial impact of refurbishing on RCF lives of case carburized bearings depends on the relative values of case depth, contact half width, refurbishing depth

A 3 D- FEM Study on the Stress Distributions in Pediatric Skull due to Impact from Free Fall

Abstract Brain is vulnerable to injuries even from low heights of fall. There are many infant casualties who get severe brain injury each year. This research is a simulated study of the stress patterns and values when human infant skull is subjected to free fall. The input velocity was calculated using simple free fall velocity formulas and was fed into the simulation. Model was meshed and refined using Hypermesh software. RADIOSS solver of the Hyperworks package was used to analyze and draw results for the simulation process. Various types of stresses and strains were extracted and plotted against respective drop heights