Investigation of a New Formula for Gurney Velocity Estimation

The formula for the analytical calculations of the shaped charge jetting parameters exhibit an explicit dependence upon the Gurney velocity of an explosive material.Many attempts have been done to approximate the characteristic constant 2E~(1/2) and to make its use more efficient.It is shown herein that the characteristic Gurney velocity parameter depends on the ratio of the Chapman Jouguet-pressure to explosive impulse ratio by the formula:2E~(1/2)=0.2415(P_(CJ)/I_(SP)ρ_0)-970.76,where PCJis the Chapman Jouguet pressure(Pa),ISPis the specific impulse of the explosive used as a monopropellant(N·s/kg)andρois the explosive density(kg/m~3).The proposed empirical formula was found to be reasonable and quite accurate approximation that can be implemented over a wide range of explosives,where the maximum deviation between the measured and the calculated Gurney velocities was nearly 6%.Besides,the proposed approach has been used analytically to calculate the jet tip velocity of a small caliber shaped charge,which is measured experimentally.The difference between the measured and the calculated jet tip velocity was only 1.6%.     

Quality evaluation of fish and other seafood by traditional and nondestructive instrumental methods: Advantages and limitations

Although being one of the most vulnerable and perishable products, fish and other seafoods provide a wide range of health-promoting compounds. Recently, the growing interest of consumers in food quality and safety issues has contributed to the increasing demand for sensitive and rapid analytical technologies. Several traditional physicochemical, textural, sensory, and electrical methods have been used to evaluate freshness and authentication of fish and other seafood products. Despite the importance of these standard methods, they are expensive and time-consuming, and often susceptible to large sources of variation. Recently, spectroscopic methods and other emerging techniques have shown great potential due to speed of analysis, minimal sample preparation, high repeatability, low cost, and, most of all, the fact that these techniques are noninvasive and nondestructive and, therefore, could be applied to any online monitoring system. This review describes firstly and briefly the basic principles of multivariate data analysis, followed by the most commonly traditional methods used for the determination of the freshness and authenticity of fish and other seafood products. A special focus is put on the use of rapid and nondestructive techniques (spectroscopic techniques and instrumental sensors) to address several issues related to the quality of these products. Moreover, the advantages and limitations of each technique are reviewed and some perspectives are also given.     

A review on zeolite imidazole frameworks: synthesis,properties, and applications

Journal of Porous Materials - Zeolitic imidazolate frameworks (ZIFs) consist of transition metal ions (Zinc or Cobalt) and imidazolate (Im) linkers in tetrahedral coordination surrounded by...     

EVALUATION OF SELF-ATTENUATION COEFFICIENTS OF OIL-PRODUCED SCALES FOR GAMMA-RAY SPECTROSCOPIC ANALYSIS

This study focuses on the evaluation of self-attenuation correction factors (C_f) and linear?attenuation coefficients (μ) of scale samples, produced from the oil fields. This was performed using ¹⁵²Eu point source at the optimal geometry found (i.e., 3 mm). The scale samples were of apparent density ranging 1.04 ? 3.08 g cm^?3. The results illustrated that self-attenuation correction values were as high as 5.08 for the most dense samples at γ-energy line of 45.5 keV. High correlation was observed by Pearson matrix between self-attenuation correction factor and sample density (correlation coefficient of 0.967 at γ-energy of 45.5 keV). A simplified model of the relationship between these variables was proposed. The remarkable finding was that when scale sample density increased self-absorption extended to occur to a higher energy line. Hence, self-attenuation correction was negligible at γ-energies of 122, 222, and 344 keV for samples with density ranging 1.04–1.41, 1.45–2.04, and 2.12–3.08 g cm^?3, respectively. Since linear attenuation coefficient is material sensitive, it was calculated for each sample. Analysis of variance (ANOVA) reflected the linear relationship between linear-attenuation coefficient and sample density up to 344 keV which disappeared thereafter. The data obtained allowed an accurate determination of the concentrations of γ-emitters in scale samples within the energy range of 45.5–1408 keV.     

Characterization of flow behavior of semi-solid slurries containing low solid fractions in high-pressure die casting

Understanding the flow behavior of semi-solid slurries containing low solid fractions is key to the success in applying this process in the die casting industry. With these low initial solid fractions, the flow behavior of semi-solid slurries is quite complicated, making it difficult to model accurately. This present work developed and studied characterization methods for the flow behavior of semi-solid slurries at low solid fractions in high-pressure die casting. A new parameter, the ratio of gate speed to initial solid fraction (V_g/f_s), was proposed to be correlated to the normalized flow interface length, blister area and tensile properties. Results from the flow pattern analysis suggest that the flow behavior can be controlled to achieve laminar flow by varying the initial solid fraction. Blister test results show the trend that slurry die casting conditions with high V_g/f_s values exhibit high blister areas. Die casting conditions with excessively high gate speeds and insufficient solid fractions result in turbulent flow patterns and high levels of blister defect. The results of tensile test and fracture surface analysis are consistent with other analysis results. The samples formed by liquid die casting and slurry die casting with high V_g/f_s values have gas porosity due to turbulent flow pattern during die filling. On the other hand, the samples formed by slurry die casting with too low V_g/f_s values contain shrinkage porosity. This is because of insufficient time for shrinkage feeding due to a combination of a high solid fraction and a low gate speed. This study has demonstrated that die casting with slurries containing low initial solid fractions gives die casters another process parameter to adjust, which can help reduce and control the gas and shrinkage porosities.     

The effect of frequency of vibration and humidity on the stick–slip amplitude

This work examines the variation of stick–slip amplitude with the variation of frequency of vibration and relative humidity on a mild steel disc. A pin-on-disc machine, developed by the authors, capable of vibrating the disc at different frequency is used for the experiments. During the experiments, normal load, speed, relative humidity and frequency of vibration were varied. The results reveal that, depending on the conditions, a different stick–slip behavior can arise in the same system. It is found that the rate of reduction of stick–slip amplitude has a particular relationship with the frequency of vibration and the relative humidity. It is also observed that the transition from irregular to regular stick–slip behavior is load dependent, while the transition from irregular to smooth sliding is load independent.     

The use of nutshell carbons in drinking water filters for removal of chlorination by‐products

Chlorination of drinking water is a common practice, used by numerous municipalities in the United States (US) to safeguard their water supplies. However, the chlorine used can chemically react with organic components in the drinking water to produce unwanted chlorination by‐products. The objective of this investigation was to evaluate the use of granular activated carbon produced from nutshells (almond, English walnut, pecan) in a point‐of‐use (POU) water filtration system designated ‘Envirofilter’ and to determine its efficacy in removing select, potentially carcinogenic chlorination by‐products, namely the trihalomethanes (THMs) bromodichloromethane, bromoform and dibromochloromethane. The POU water filtration system that contained the nutshell‐based carbons was designated ‘Envirofilter’ and adsorption efficiencies of this system were compared to that of four commercially available POU home water filter systems, namely, BRITA, Omni Filter, PūR and Teledyne Water Pik. Eight different ‘Envirofilters’ were constructed of individual or binary mixtures of carbons produced from acid‐activated almond or pecan shells and steam‐activated pecan or walnut shells and evaluated for adsorption of the three chlorination by‐products. The results indicate that only two of the eight ‘Envirofilters’ failed to remove more THMs than the commercial POU systems. In both cases, these filters contained carbons with either 100% acid‐activated almond shells or 100% acid‐activated pecan shells. All six of the other filters contained carbons with either 50% or 100% steam‐activated pecan shells or steam‐activated walnut shells. Therefore, ‘Envirofilters’ appeared to depend on the presence of steam‐activated nutshell carbons for their success. The six effective ‘Envirofilters’ reduced THM levels to below the Maximum Contaminant Levels (MCL) required by the US Environmental Protection Agency (US EPA). Based on these results, these six ‘Envirofilters’ may be considered as a replacement for existing commercial filter systems because of their efficacy and projected cost. Copyright © 2004 Society of Chemical Industry