International Journal of Engineering
Volume:13 Issue: 2, May 2000

A formulation for finite element analysis of tapered and monosymmetric I shaped beam-columns is presented. This is a general way to analyze these types of complex elements. Based upon the formulation, member stiffness matrix is obtained explicitly. The element considered has seven nodal degrees of freedom. In addition, the related stability matrix is found. Numerical studies of the aforementioned members show the validity and accuracy of the formulation in comparison to the other ones.

This paper presents a theoretical derivation and computer simulation of an optimal speed controller for a brushless dc motor using feedback from a linear model running in parallel with the inverter-fed model. The intent of the feedback from the linear model is to eliminate torque ripples from the inverter drive. A nonlinear model of such a motor, transformed into a linear model by a local dipheomorphism (defined in section 2) and a new model is introduced in order to eliminate the undesirable effects of the inverter harmonics.

This paper addresses the issue of cell loss and its consequent effect on video quality in a packet video system, and examines possible compensative measures. In the system''s enconder, adaptive spectral separation is used to develop a two-layer coding scheme comprising a high priority layer to carry essential video data and a low priority layer with data to enhance the video image. A two-step error detection scheme using cell numbering and variable length decoder is incorporated in the system to detect cell loss in the bit-stream without long mis-interpretation. In the system''s decoder, cell loss is compensated by a two-step recovery procedure based in temporal error concealment to maintain high picture quality. The simulated performance of the proposed two-layer system is studied and compared with that of the single layer system. It is shown that good resilience and PSNR improvement can be achieved even at quite high error rates. Statistics such as the cell-rate distribution and autocorrelation function of both high and low priority streams generated by the adaptive system are analyzed. It is observed that two different classes of gamma function can represent the cell distribution in each layer. A multiplicative – ARIMA (autoregressive integrated moving average) model is proposed to represent and forecast the number of cells per frame for the encoded video traffic and its goodness-of-fit is compared with AR (1) (autoregressive) model. The cells per frame measured from a sample video sequence compare favorably with those obtained by the ARIMA model. Simulations were performed using three five-second video sequences to demonstrate the efficiency of the two-layer enconding algorithm for sequences with different characteristics. Statistics gathered from these prioritization schemes are claimed to be useful for network design and resource management.

Reducing the exhaust emissions of an spark ignition engine by means of engine modifications requires consideration of the effects of these modifications on the variations of crankshaft torque and the engine roughness respectively. Only if the roughness does not exceed a certain level the vehicle do not begin to surge. This paper presents a method for controlling the air-fuel ratio for a lean burn engine. Fuzzy rules and reasoning are utilized on-line to determine the control parameters. The main advantages of this method are simple structure and robust performance in a wide range of operating conditions. A non-linear model of an SI engine with the engine torque irregularity simulation is used in this study.

The dual-fuel diesel engine (D.F.D.E) is a conventional diesel engine in which much of the energy released, hence power, comes from the combustion of gaseous fuel such as natural gas. The exhaust emission characteristics of the D.F.D.E needs further refinements, particularly in terms of reduction of Unburnt Hydrocarbons (U7HC) and Carbon Monoxide (CO) emission, because the concentration of these pollutants are higher than that of the baseline diesel engine. Furthermore, the combustion process in a typical D.F.D.E tends to be complex, showing combination of the problems encountered both in diesel and spark ignition (SI.) engines. In this work, a computer code has been modified for simulation of D.F.D.E combustion process. This model simulates D.F.D.E combustion by using a Multi-Zone Combustion Model (MZCM) for diesel pilot jet combustion and a conventional S. 1. combustion model for modeling of combustion of premixed gas/air charge. Also, in this model, there are four sub models for prediction of major emission pollutants such as: UHC, NO, CO and soot which are emitted from D.F.D.E. For prediction of formation and oxidation rates of pollutants, relevant conventional kinetically-controlled mechanisms and mass balances are used. The model has been verified by experimental data obtained from a heavy-duty truck and bus diesel engines. The comparison shows that, there exist good agreements between the experimental and predicted results from the D.F.D.E

Design and construction of a capacitor sensor with a precise readout system are described in this paper. A variable air-gap capacitive transducer was constructed and for signalmeasurement a successful attempt was made to exploit the capacitance changes in terms of the phase angle of the detected signal. The reported setup makes it possible to detect capacitance changes of the order of 2.5 fF in a 4.5 pF range and the readout circuit can detect a capacitance change of about 22 aF (5 in 106). There is a linear relation between the air-gap distance and the output of the sensor over an experimented gap range of 0.5-4.5 mm. It shows a nonlinearity deviation factor of 1% from the expected theoretical line. The dynamic range of the system is variable from 5 μm to 2.5mm and it mainly depends on the initial air-gap distance. Adding a stray capacitance of 180 pF to the system only causes a 0.1% error in the sensor output. In comparison with the other sensor systems the one reported in this paper is much more sensitive, reliable, and stray-immune to electrical interferences.

From the standpoint of processing, hard chromium layer plate may be applied to steels, cast iron, aluminum and nickel base alloys. Cast iron can be plated provided that the surface is capable of conducting the required current and is reasonably free of voids, pits, gross silicate inclusions, and massive segregation. There are many difficulties arising from graphite phase and deposition of hydrogen on the surface of gray cast iron (G.C.J). To obtain desired hard chromium coating with acceptable adhesion, special pretreatments should be used. In this paper the surfaces of G.C.I. were prepared in sulphuric acid, chromic acid + S04-- by anodic etching phosphoric acid + sulphuric acid solution by electro polishing and sulphuric acid + fluoridric solution by dipping in the different conditions. The best results for removal of graphite from the surface of specimens are obtained after anodic etching in 60% H2S04 solution.

Abstract In tidally affected coastal catchments detention pond should be provided to store flood surface water. A comparison between the full simulation approach based on the joint probability method and time series rainfall modeling via the annual maximum of pond level was undertaken to investigate the assumptions of independence between variables that are necessary in the joint probability method. The rainfall data was run through a catchment model and the inflow hydrograph was obtained. This inflow was run through a detention pond with an outfall significantly affected by tidal action. The tidal variations were determined at that exact historical time of the time series rainfall. A continuous record of time series pond level was therefore determined and the peak pond level for each year was used to generate the annual maximum series of pond levels. A comparison between the growth curves of full simulation approach, and the time series rainfall modeling was undertaken. The results indicate that there are no significant differences between the two growth curves generated.