INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE (ENGLISH)
Year:2003 | Volume:14 | Issue:4|Papers Count:29

In this paper, results obtained from investigations on a typical reverse osmosis (RO) membrane fouled by precipitation of materials which exist in water are presented. In these studies, effect of different cleaning agents on recovery of the fouled membrane has been shown. Results show that a combination of sodium dodecyl sulfate, Na-EDTA and sodium hydroxide must be used as a cleaning material to reach the optimum recovery of the polyamide membrane employed in petrochemical industries. It was found that cleaning efficiency depends on type of the cleaning agent and its concentration. It has been shown that the efficiency increases with increasing the concentration of cleaning agent and reaches to a maximum value. The concentration that provides the highest cleaning efficiency can be considered as the optimum concentration. This depends on the type of cleaning agent. Operating conditions such as cross flow velocity, turbulence in the vicinity of the membrane surface, temperature, pH and cleaning time also play an important role in the cleaning processes. membrane cleaning requires deep understanding of the interactions between the foulants and the membrane as well as the effect of the cleaning procedure on deposit removal. In this paper the mechanism of deposit removal is also investigated.

The main objective of this paper is to develop proper theorems for fuzzy folwshop problems (FFSPs) with trapezoidal processing times. The paper concentrates on the relationship between reverse and original problems. The obtained results from this research work are extensively applied to develop the multi-attribute approach for solving FFSPs. Meanwhile, this approach removes the dimensionality associated with the application of traditional scheduling theory. As a preliminary stage, the relationship between the starting times and the makespam has been scrutinized in general for two-job problems. Several propositions have been developed and proved. For the proof process, it has been required to develop a proper method for determining the starting times. Based on the theoretical results, the relationship between the reverse and original completion times and makespans has been investigated. The results may be extended for n-job problems, which is the subject of another paper. Prior to prove the required theorems in fuzzy environment, some properties of an inequality relation between fuzzy numbers are identified and proved.

The rate equations of a bistable laser diode with detuned frequency chirped optical input are modified. Based on the steady state characteristics of optical output can be switched and locked to the optical input wavelength in a relatively fast switching time by increasing optical input power. The effects of frequency chirping are brought into account which we mean mainly the effect of diminution of external modulator on the dynamic behavior of laser diode subjected to an optical input.

Let R be a commutative ring with identity and M a unitary R-module. The concept of prime submodule of an R-module M has been discussed. In this paper, we investigate the concept of semiprime submodule of an R-module M. We also, consider relation between the semiprime submodule N of an r-module M and the semiprime ideal (N: M) of R and we focus our attention on relation between E (N) and N.

This paper presents an integrated production and marketing planning model. The model aims at maximizing production and minimizing the cost of production and marketing expenditure. The resulted model which is highly nonlinear and non-convex is solved by Geometric Programming (GP) in order to provide the closed form solution. The solution of the proposed model is analyzed in different cases in order to study the behavior of the marketing planning. A Numerical example is used to demonstrate the implementation of the closed form solution.

Traditional Shewhart-type charting methods assume high volume manufacturing processes where a large number of samples can be gathered to estimate the process parameters before on-line charting actually begins. However, in situations involving low-volume or short-run productions where total output is not sufficiently large, the fairly minimal data requirements of standard control charts may not be achieved, making it necessary to find a new approach in establishing control chart limits. In this paper, control charts that use "Likelihood Ratio" statistics are suggested so that they can be reliably used when fewer than the usually recommended samples are available.

The treatment of pharmaceutical non-penicillin wastewater was conducted in the biological aerobic process. The oxygen transfer rate played the major role to reduce the organic pollutants of the wastewater by removing gases, oils, volatile acids and odor. The microbial culture used in the experiment was the ethanol producers, isolated form the wastewater. Optical density, COD and concentration of chemicals equivalent to carbohydrate were measured in a time period of 3-4 days of aeration. The propagation of bacteria was monitored and its growth rate was determined. Oxygen transfer rate and mass transfer coefficients were found to be affected by airflow rate, bubble size and agitation rate. Dissolved oxygen was shown as an indication of microbial growth and limitation of mass transfer. The dissolved oxygen was about 7.89 ppm from the starting point and then is dropped to 2 ppm by the end of the first day. After the second day of aeration the oxygen depletion was obviously observed since the DO meter showed 0.14 ppm. Aeration rate was 0.2-1.3 liters per minute for working volume of 3 liters and 5-10liters per minute for 15 liters aerated tank. Maximum optical density was obtained with high aeration rate at the first day of aeration, 0.95 g/l, as the aeration was reduced the cell propagation was also reduced. The maximum cell growth was obtained by the end of 3 days of aeration with minimum airflow rate. The maximum COD and carbohydrate reduction was 58 and 90 percent respectively with 1.15 liter/min airflow rate in the 3 liters aeration system. The bubble size affected the mass transfer coefficient (K__L.a), as the contract surface of gas exposure to liquid increased the mass transfer coefficient was increased. As the dissolved oxygen concentration dropped the K__L.a was also decreased. The values of K__L.a for the 5 and 10 liters/min airflow rate for 15 liters aerated tank were 0.055h^-1 and 0.3975h^-1 respectively.

This paper proposes a method for assessing the functionality of the urban transportation systems during earthquake in large and populated, cities with special consideration of the traffic problems including supply and demand issues. Attention has been paid to the travels caused by the earthquake in addition to the normal city travels, and also to achieving the minimum total-travel-time of rescue and relief teams, in the aftermath of earthquake. These are of great value for decreasing the life loss as well as products and materials losses. Six stages are considered for system efficiency evaluation: 1) defining earthquake scenarios, 2) demand estimation, 3) supply estimation, 4) travel distribution, 5) travel assignment, finally, 6) Obtaining the average travel time in the entire network. A through formulation has been developed by the authors, which are discussed in detail. Application of the proposed method to the case of Tehran metropolis is also given for a part of the city. The used of the method for the whole city is presently under investigation for the effective rescue and relief activities, which are necessities for a successful disaster management. Based on the features of the proposed evaluation procedure and formulation for transportation system it can be said that the demand and supply concepts can be included in the modeling process of the transportation network with a reasonable attempt. Since the time of earthquake occurrence is a very important factor in both public reaction and the traffic flow, special care should be taken in this regard.

Fermentation of sugar by Saccharomyces cerevisiae for production of ethanol under anaerobic and partial vacuum condition was successfully experimented. The fermentation system was vacuumed periodically for removed of product inhibition. The glucose concentration played the major role to increase the concentration of ethanol and cell growth rate in the fermentation broth. The cell density, ethanol concentration and glucose concentration were measured for incubation period of 48 hours. The maximum specific growth rate for 7 hours of incubation and glucose concentration of 30g/L, was 0.341 hr-1 . The maximum ethanol concentration was 26.69 g/L. The ethanol productivity was about 75 percent of ethanol produced under absolute vacuum fermentation. The cell growth rate was based on Monod rate equation. The maximum growth rate (µ_max) and saturation constant (K_s) were experimentally determined to be 4.43 hr-1 and 1.71 g/L. Respectively.

This paper develops an approach to solve 0-1 multiple attribute knapsack problem (MAKP) in which some objectives are qualitative. The approach consists of two modules. The first module is a fuzzy expert system that evaluates the qualitative objectives. Acting as a framework, the second module generates the different combinations and finds the (near) optimal solution using a genetic algorithm model. The results of conducted experiments show the capability of proposed approach to deal with MAKP problems.

A high-resolution machine vision system is presented for strain analysis at high temperatures. The system uses a frame grabber with a spatial resolution of 1300x1030 and 10-bit gray-level. The main merits of the proposed system are: (1) it is a whole-field measuring technique; (2) it is non-contact technique and (3) it is easy to set up and apply. It is shown that the proposed system can measure strains at high temperatures with an error less than 2%.

In many applications it is necessary to have a reference beam of the laser light and for this purpose a beam splitter is usually used. The goal of this paper is to show the potentials of photon drag monitors to be used in place of the conventional beam splitters. Characteristics, advantages and disadvantages of the longitudinal and transverse devices are reported in this article. Recorded signal for typical silicon monitored by using a laser beam at wavelength 496 µm (CH__3F laser) is presented here. Variation of the noise equivalent power as a function of the radiation wavelength is also given for different monitor resistivity. The reported photon drag monitor can be used as an "on-line" device for monitoring reference pulses in variety of signal processing and pulse shaping in laser applications.

In this paper we give a method to determine the controllability of the time-varying systems. For this purpose, we define a problem in calculus of variations over state function, their derivatives and control function corresponding to original system. Discretizing the new problem, we reach to a finite dimensional linear programming problem. Finally we solve this LP and find that the system is controllable or not. Also we may obtain a pair of admissible control and state.

The System of Ax=b in which A is a Toeplitz and symmetric positive definite (SPD) is derived from convolution-type integral equations. At normal state, the system contains in appropriate eigenvalues not clustering around 1. In the present paper, the preconditioned CG method is used to solve the above-mentioned system. The using of CG method with suitable preconditioners causes clustering eigenvalues of the new system around 1. As a result, the stability and convergence rate are guaranteed and at most we reach the answer in a steps.

A three point variable mesh finite difference method of third order, have been derived to solve the singular two-point boundary value problems. The method reduces to a method of order four for the uniform mesh case and may be considered as a modification of the well known Numerov"s method. The methods are self starting and are exact for y=1/x. The convergence of the fourth order method has also been discussed. The various measures of error for solution of two problems, using the methods and the fourth order method in [1] are listed. The numerical results are also compared with five well known classical methods to show the self starting and accuracy of the present methods. Subject Classifications: AMS 64L10, CR: G1.7

Over the last several years, integration of multiple media sources into a single information system has been rapidly developing. With the recent introduction of many high level authoring, animation, modeling, and rendering programs for personal computers, significant multimedia courseware programs can now be developed by professors and students. Even with these new tools, a considerable amount of time is required to produce an interactive multimedia program for engineering education. This paper examines various multimedia development tools and how they can be used for education courseware. It discusses the development of a multimedia training material for mechanical robotic manipulators. The instructional material is developed to assist trainees in acquiring skills needed for mechanical manipulator. Finally, actuators of an industrial robot are modeled by pneumatic systems and then programmed and controlled by programmable logic controllers (PLC). Software for simulating and controlling a 3 DOF robot was designed by PLC to give a better understanding of the power of PLC in robot control and programming.