Dominant design variables in pyrolysis of biomass particles of different geometries in thermally thick regime

In this study, a simultaneous chemical kinetics and heat transfer model is used to predict the effects of the most important physical and thermal properties (thermal conductivity, heat transfer coefficient, emissivity, reactor temperature and heat of reaction number) of the feedstock on the convective-radiant pyrolysis of biomass fuels for different geometries such as slab, cylinder and sphere. The pyrolysis rate is simulated by a kinetic scheme involving two parallel primary reactions and a third secondary reaction between volatile and gaseous products and the char. Finite difference pure implicit scheme utilizing the Tri-Diagonal Matrix Algorithm (TDMA) is employed for solving heat transfer model equation. Runge-Kutta fourth order method is used for solving the chemical kinetics model equations. Simulations are carried out for different geometries considering the equivalent radius ranging from to , and the temperature ranging from to .For conversion in the thermally thick regime (intra-particle heat transfer control), it is found that variations in the properties mainly affect the activity of primary reactions. The highest sensitivity is associated with reactor temperature and emissivity. Applications of these findings in reactor design and operation are discussed. The results obtained using the model used in the present study are in excellent agreement with many reported experimental studies, much better than the agreement with earlier models reported in the literature.     

Bias voltage dependence properties of cadmium oxide films deposited by d.c. reactive magnetron sputtering

Cadmium oxide films were grown on glass substrates using d.c. reactive magnetron sputtering technique by sputtering from a metallic cadmium target in an oxygen partial pressure of 1×10^–3 mbar under various substrate bias voltages. The substrate bias voltage significantly influences the crystallographic structure of the deposited films. The influence of substrate bias voltage on the electrical and optical properties of the films was systematically studied. The films formed at a substrate temperature of 473 K and bias voltage of –80 V showed an electrical resistivity of 1×10^–3 cm, optical transmittance of 86%, optical band gap of 2.47 eV and a figure of merit of 7×10^{–3 –1}.     

An error analysis for the finite element method applied to convection diffusion problems

This paper analyzes the finite element method applied to a convection diffusion model problem. Linear elements are used for the trial space. The error is measured in a norm closely related to the L_p norm. When the test space is composed of linear elements with parabolic upwinding, the method is shown to be optimal when the input data is piecewise smooth—a condition which is usually observed in practice. Without these smoothness assumptions, the method is shown to be non-optimal, even if the class of test spaces is extended to include any elements which have a shape independent of the mesh size.     

Conformations of gas-phase lysozyme ions produced from two different solution conformations

Near pH 2.0, lysozyme in water is in its native conformation, and in water/methanol (2/8) it adopts a helical denatured conformation (Kamatari et al. Protein Sci. 1998, 7, 681-688). Hydrogen/deuterium (H/D) exchange of lysozyme in solution confirms that it is partially unfolded at pH 2.0 in water/methanol (v/v = 2/8). With electrospray ionization (ESI) mass spectrometry (MS), lysozyme in water produces ions with charges +7 to +12, with the greatest intensity at +10, whereas lysozyme in water/methanol (2/8) produces ions with charges +6 to +12 with the greatest intensity at +7. Thus, lysozyme is an exception to the rule that a protein denatured in solution forms higher charge states than the same protein in its folded native conformations in solution. Because the same charge states are produced from these two solution conformations, a direct comparison of the properties of the gas-phase ions produced from two very different solution conformations is possible. The conformations of lysozyme ions in the gas phase were studied using cross section measurements and gas-phase H/D exchange. Similar cross sections and H/D exchange levels were observed for same-charge states of lysozyme ions formed from the native and helical denatured conformations in solution. Cross sections show that the ions have compact structures. Thus, disulfide-intact gaseous lysozyme ions generated from the denatured state in water/methanol (2/8) refold into compact structures in the gas phase on a time scale of milliseconds or less.     

Frequency distribution of daily clearness indices through generalized parameters

Noting that frequency distributions of clearness indices available in the literature are not applicable for all climates, the present article examines the suitability of a new parameter, , and a variable, , to depict generalized clearness index distributions. is a normalized monthly average daily clearness index, while is a normalized daily clearness index. These normalized clearness indices comprise maximum and minimum daily clearness indices (K_T,max and K_T,min), in a month, in addition to monthly average daily clearness index, , and daily clearness index, K_T. Correlations have been developed to predict K_T,max and K_T,min needed, in the absence of data. The distributions, developed in terms of and have been suitably represented and tested over 70 locations, latitudes ranging from 8°N to 64°N. The daily clearness index values have been predicted within a standard deviation of 0.034 with the expressions developed in the present study.     

Pullout Behavior of Granular Pile-Anchors in Expansive Clay Beds In Situ

Granular pile anchors (GPA) are one of the recent innovative foundation techniques devised for mitigating the problems posed by swelling clay beds. In a granular pile anchor, the footing is anchored to an anchor plate at the bottom of the granular pile. This makes the granular pile tension resistant and enables it to absorb the tensile force caused on the foundation by the swelling clay. An understanding of the amount of uplift resistance offered by the GPA is important in the design of granular pile-anchor foundations in field situations causing tensile forces on foundations, such as in expansive clay beds. This paper presents the results of a field-scale test program conducted to study the pullout response of GPAs embedded in expansive clay beds. Pullout load tests were conducted on GPAs of varying lengths and diameters. It was found from the field pullout load tests that granular pile anchors of larger surface area resulted in higher pullout capacity. Of the various single granular pile anchors with l/d values between 2.5 and 10, the GPA of length 1000?mm and diameter 200?mm (l/d = 5) showed the best pullout load response when tested alone, resulting in a failure uplift capacity of 14.71?kN. Increase in diameter and length of granular pile anchor increased the uplift capacity. When the length of the GPA was increased from 500 to 750 and 1000?mm, the percentage increase in the uplift load required for an upward movement of 25?mm was 33.3 and 55.5% respectively. The pullout load of the GPA when tested under group was 18?kN as against a 12?kN for the GPA when tested single.     

Assessment of the cost and accuracy of the generalized FEM

In this paper, we address the cost versus accuracy capabilities for the generalized FEM (GFEM) which was developed in (Comput. Methods Appl. Mech. Eng. 2003; 192 :3109–3161, Int. J. Numer. Meth. Engng 2004; 60 :1639–1672, Ph.D. Thesis, Texas A&M University, College Station, TX, August 2003 (Advisor: T. Strouboulis)), and also the construction of two‐sided a posteriori error estimates, which can be used to assess the achieved accuracy at all levels of the method. Copyright © 2006 John Wiley & Sons, Ltd.     

Software Operational Profile Based Test Case Allocation Using Fuzzy Logic

Software operational profile (SOP) is used in software reliability prediction,software quality assessment,performance analysis of software,test case allocation,determination of"when to stop testing,"etc.Due to the limited data resources and large efforts required to collect and convert the gathered data into point estimates,reluctance is observed by the software professionals to develop the SOP.A framework is proposed to develop SOP using fuzzy logic,which requires usage data in the form of linguistics.The resulting profile is named fuzzy software operational profile (FSOP).Based on this work,this paper proposes a generalized approach for the allocation of test cases,in which occurrence probability of operations obtained from FSOP are combined with the criticality of the operations using fuzzy inference system (FIS).Traditional methods for the allocation of test cases do not consider the application in which software operates.This is intuitively incorrect.To solve this problem,allocation of test cases with respect to software application using the FIS model is also proposed in this paper.     

Electrical and Reliability Studies of “Wet N2O” Tunnel Oxides Grown on Silicon for Flash Memory Applications

In this paper, we report the electrical characteristics and reliability studies on tunnel oxides fabricated by "wet N₂O" oxidation of silicon in an ambient of water vapor and N₂O at a furnace temperature of 800 degC. Tunnel oxides that have an equivalent oxide thickness of 67 A are subjected to a constant-current stress (CCS) amount of -100 mA/cm² using a MOS capacitor to obtain information on stress-induced leakage current (SILC), interface, and bulk trap generation. The obtained results clearly demonstrate the superior performance features of the present tunnel oxides with reduced SILC, lower trap generation, minimum change in gate voltage, and higher charge-to-breakdown during CCS studies. X-ray photoelectron spectroscopy depth profile studies of the tunnel oxide interfaces have shown that the improved performance characteristics and reliability can be attributed to the incorporation of about 8.5% nitrogen at the oxide-silicon interface of the samples formed by the "wet N₂O" process that involves low-temperature oxidation and annealing at 800 degC.