International Journal of Engineering
Year:2003 | Volume:16 | Issue:2 (TRANSACTIONS B: APPLICATIONS)|Papers Count:9

Response of a transversely isotropic 3-D half-space subjected to a surface time-‎harmonic excitation is presented in analytical form. The derivation of the ‎fundamental solutions expressed in terms of displacements is based on the prefect ‎series of displacement potential functions that have been obtained in the companion ‎by the authors. First the governing equations are uncoupled in the cylindrical ‎coordinates. Then , the uncoupled equations are analytically solved to obtain Green ‎functions that are expressed in terms of Fourier series in the tangential direction of the ‎coordinates and in the terms of Hankel functions in its radial direction. The analytical ‎Green functions of this paper are exactly same as the results of lamb (1904) in the ‎case of isotropic material. The green functions can be used as the kernel functions of ‎the boundary integral equation that is used to solve elastodynamic boundary value ‎problems‏.‏

ParLeda is a software library that provides the basic primitives for parallel ‎implementation of computational geometry applications. It can also be used in ‎implementing a parallel application that uses geometric data structures. The parallel ‎model that we use is based on a new heterogeneous parallel model HBSP, which is ‎based on BSP and is introduced here. ParLeda uses two main libraries that are widely ‎used: MPI for its message passing in the parallel environment and LEDA for its data ‎structures and computations. Dynamic load balancing and replicating C++ objects are ‎two key features of this library. This library was implemented after a survey in ‎research on parallel computational geometry algorithms and selection of their ‎common primitives‏.‏

Interconnected power system networks are multi loop structured. Settings ‎determination of all over current and distance relays in such networks can be in ‎different forms and complicated. The main problem is the determination of starting ‎points i.e. the location of starting relays in the procedure for settings, which is referred ‎to as break points. In this paper, a new approach based on graph theory is introduced ‎in which the relevant matrices dimensions are much reduced. The method is flexible ‎and achievement of the desired solution can be obtained in a relatively short time‏.‏

Performance of a rotating biological contactor (RBC) in treating municipal ‎wastewater from primary sedimentation basin and anaerobically treated industrial ‎effluent from an up flow anaerobic sludge blanket (UASB) reactor was investigated. ‎The 280-L six-stage RBC pilot was operated at different organic loading rates and ‎biodisc speeds. The overall removal efficiencies of soluble BOD decreased with ‎increasing organic loading rates. Disk rotational speed did not have significant effect ‎on performance in the range studied. The results showed that satisfactory treatment of ‎UASB effluent to meet regulatory requirement for agricultural purposes (effluent ‎BOD of 100 mg L^-1) can be achieved with sufficient margin margin of safety at ‎organic loading rate of up to 4.9±0.4g SBOD m^-2 d^-1 with SBOD removal ‎efficiency of 59±9%. For municipal wastewater, it was possible to achieve SBOD ‎effluent values of below 20 mgL^-1 all the time. Most of the organics were removed ‎in the first three stages with minimal contribution form the remaining stages of the ‎RBC reactor. There was a decrease in SBOD removal efficiency to 74±3% at OLR ‎value of 17.8±2.1g SBOD m^-2 d^-1 and 66±6% at OLR value of 4.7±1.9g SBOD ‎m^-2 d^-1 for UASB effluent and municipal wastewater, respectively. The results for ‎elimination capacity (EC) values indicated a linear relationship with first stage ‎organic loading rates without any signs of limitation in the range of OLR values ‎investigated in this study. However, average first-stage elimination capacity rates of ‎‎3.2 and 2 at OLR values of 17.8 and 11g SBOD m^-2 d^-1 for UASB effluent and 1.3 ‎and 2 at OLR values of 4.7 and 5.3g SBOD m^-2 d^-1 for municipal wastewater were ‎relatively lower than previous studies of RBC performance using domestic or ‎industrial wastewater without anaerobic pretreatment. It was suggested that the lower ‎EC values were due to the fact that a smaller fraction of UASB effluent was ‎biodegradable as reflected in SBOD/SCOD ratios of 0.47±0.04. For municipal ‎wastewater, even though SBOD/SCOD ratios were 0.49±0.03, the low EC values ‎were suggested to be contributed to lower influent concentration potential considering ‎first-order kinetics governing biochemical reactions‏.‏

Packed bed units generally, represent the most suitable storage units for air heating ‎solar systems. In these systems the storage unit receives the heat from the collector ‎during the collection period and discharges the heat to the building at the retrieval ‎process. A method for sizing of packed bed storage in an air heating system is ‎represented. The design is based on te K-S curves, which have been generated for the ‎storage used in the CSU solar House II through simulation. The complete simple solar ‎heating system is simulated numerically during both the heating and retrieval ‎processes. The simulation, which utilizes the hourly meteorological data, takes into ‎account consideration of the principle parameters such as pressure drop across the ‎bed, particle diameter, and mean voidage. The results are compared with the reported ‎data from a real size of storage and also with the criteria of f-chart recommendation‏.‏

In this paper, results of an investigation on the strain hardening responses of ‎superalloy MP35N with two average grain sizes of 38 and 1 m#m, during room ‎temperature tensile testing are reported. The micro structural evolution of the ‎deformed samples was studied using optical and transmission electron microscopy ‎‎(TEM) techniques. The strain hardening behavior of the 38 m#m material was rather ‎similar to that previously reported for low stacking fault energy FCC alloys. The ‎plastic behavior of the fine-grained material, however, was unexpected. In the strain ‎range of 0.1-0.4, the work hardening rate of the fine grain size sample was evidently ‎lower than that of the large grain size material. Based on the TEM results obtained in ‎this study, it is suggested that the unusual strain hardening response of MP35N alloy ‎of 1m#m grain size is related to the difficulty of formation of deformation twins in ‎these samples. Results obtained in this study further support the effectiveness of ‎deformation twins in hindering crystallographic slip in low SFE FCC polycrystals and ‎the need to develop new plasticity models to include the role of deformation twinning ‎in these materials‏.‏

This paper presents a new methodology for complete solution of general shape deep ‎drawn parts. Evaluation of forming severity, estimation of the punch load and ‎prediction of the thickness variation are the major results obtained in this work. The ‎punch work is the summation of the homogenous work of flange deformation and ‎bending and bending and frictional words. To evaluate the strain energy of the flange, ‎the so-called matrix method of slip line is used. To overcome the weakness of slip line ‎field in prediction of the thickness variation, the so-called genetic algorithm has been ‎adopted. In this procedure, the actual velocity field has been computed and used in ‎energy formulation. The predicted thickness strain, punch load and forming severity ‎have been compared with some published experimental results‏.‏

In this work, Boltzmann transform has been used to analyze the problem of freezing ‎of pure Aluminum in semi-infinite domain. The uniqueness of solution (solidification ‎front location) has been proved using the characteristics of the functions appeared in ‎solution. The effect of density change on temperature distribution and errors resulting ‎from ignoring this change have been investigated. The solidification problem in finite ‎media was solved using the boundary element method (BEM), with quadratic shape ‎functions. The applicability of the fundamental solution, as weighting function in ‎BEM, in finite domain has been investigated. The accuracy of the method is ‎illustrated through one-dimensional numerical examples. Some careful experiments ‎were carried out, using the facilities of the School of Metallurgy and Materials at the ‎University of Birmingham, UK, to obtain the data. Comparison of theoretical, ‎numerical and experimental results revealed that good agreement exists between ‎them. However, minor differences were observed due to imposing of the simplifying ‎boundary conditions. The effects of density change may be ignored in small volumes, ‎but they must be taken into account in real applications‏.‏

This paper deals with evaluation of the mechanical properties of woven fabrics. Method of evaluation is concentrated loading system. A total of 17 pieces of woven fabric is used. The most related parts of the curve to the properties are shown and as a result, effective features are lightened up.