International Journal of Engineering
Volume:14 Issue: 1, Feb 2001

In a previous paper, pressure drop, flooding and mass-transfer characteristics of a novel pilot-scale distillation column called spinning cone column (SCC) were presented. Here, we present the result of comparison of mass-transfer efficiencies of SCC and structured packing. Comparison of SCC and structured packing mass-transfer characteristics show that the gas and liquid-side height of transfer units (HTUs) of the SCC are on the average 20% and 50% lower than the corresponding values for structured packing respectively. This in turn results in lower HETPs of the SCC for practical applications. Predicted HETPs in ethanol distillation using SCC are 30% lower than those of structured packing. Predicted HETPs for fusel oil and orange oil distillations are also 45% and 35% lower respectively than the experimental values obtained for structured packing. From these results, it is concluded that SCCs are more efficient with respect to mass-transfer than this particular structured packing, but to draw a general conclusion, more specific data on pressure drop per NTS, and liquid hold-up and residence time of the two columns should be available.

the nonlinear discrete crack modeling of Shahid Rajaee thin arch dam is considered. The interface elements are positioned such that certain potential separated blocks can form possible failure mechanisms. The dynamic stability of theses blocks are investigated by a special finite element program "MAP-73" which its nonlinear algorithm and interface elements formulation are presented.

Most of the Codes of Practice (API, BSI, DnV, NPD) uses Morison''s equation to estimate hydrodynamic loads on fixed and moving offshore structures. The significant difference in the prediction of the loads mainly arises from the assumption of the values of hydrodynamic coefficients. In this paper by analysing a full scale set of data in large KC''s numbers collected from Delta Wave Flume in the Netherlands the effects of random waves (JONSWAP spectrum) and uniform current over the artificially rough cylinder have been investigated. The prediction of water particle kinematics has been made from the surface elevation measurements using Stokes fifth order wave theory. By using the Weighted Least Squares technique the hydrodynamic coefficients have been estimated. A comparison between measured force and predicted force shows that although the accuracy of prediction over the whole data is about 90%, the errors on the local peaks are significant (24%) the case which is of interest in the ultimate limit state involving a single extreme wave.

This paper presents a new data compression method for current loop transmitters. In this method, the 4-20 mA current domain is divided into some equal pieces that are used for distinct data domain with a constant relative resolution, resulting in widening the signal span. This technique eliminated the need for high resolution ADC’s or DAC’s in communication of 4-20mA current loop signals. Furthermore, because of high amplitude of current steps the sensitivity of transmitter and receiver to noise and interference is reduced. As this is a software-based technique, there is no need to change the structure of the intelligent transmitters.

In the Railgun which is used to accelerate objects, electrical energy is used to drive the system. In order to reach hypervelocities, a power supply with immense amount of energy must be used which causes an extra ordinary current on the rail and the armature. This current makes thermal energy by the ohmic attenuation and warms up various points and therefore changes the electrical, thermal and mechanical specifications of the structure. In this article, a method will be presented by which one can consider the inhomogenity created by temperature changes along the structure. In this method, the instantaneous current distribution in the structure and the heat caused by it are calculated, and then the temperature distribution is obtained. The electrical conductivity (σ), thermal conductivity (k) and specific-heat (c) are considered inhomogeneous and are calculated at every instant until the specifications of the material forming the structure are corrected at any instant. We have used three-dimensional finite element method with non-uniform meshing at any instant.

In this paper, a Multivariate-Multistage Quality Control (MVMSQC) procedure is investigated. In this procedure discriminate analysis, linear regression and control chart theory are combined to control the means of correlated characteristics of a process, which involves several serial stages. Furthermore, the quality of the output at each stage depends on the output of the previous stage as well as the process of the current stage. The theoretical aspects and the applications of this procedure are enhanced and clarified and its performance is evaluated through a series of simulated data. Both in-control (type one error) and out-of-control (type two error) Average Run Length (ARL) studies are made and the performance of the MVMSQC methodology is discussed.

We study the single server queueing system with two types of Abstract failure to servicechannels including the preemptive priority to the repair of major failure. The units arrive at thesystem in a poisson fashion and are served exponenitally. The steady - state probabilities ofvarious states by using generating function have been obtained.

In this paper instability of planar anisotropic sheet metal during a few forming processes is investigated for the first time. For this reason components of the constitutive tangent tensor for planar anisotropic sheets are developed. By using the above tensor location of necking is predicted. Direction of the shear band is also predicted using the acoustic tensor. A finite element program is prepared based on large deformations of planar anisotropic sheet metals. In this program rotations of principal directions of anisotropy are also taken in to account. Results obtained from the presented model are in good agreement with experimental observations.

Several optimal three-dimensional orbital transfer problems are solved for thrust-limited spacecrafts using collocation and nonlinear programming techniques. The solutions for full nonlinear equations of motion are obtained where the integrals of the free Keplerian motion in three dimensions are utilized for coasting arcs. In order to limit the solution space, interior-point constraints are used which proved to be beneficial in finding the optimal results by making initial estimates more sensible. The application of this methodology to the design of several three dimensional optimal trajectories is also investigated. The results indicate that the method is suitable for any 3D transfer between noncoplanar and non-coaxial orbits.