سال:1387 | دوره: | شماره: |تعداد مقالات:9

This work presents an experimental study realized at the materials laboratory of the University of M’sila. It consists to vary the percentage of the pozzolanic admixture (waste bricks) in cement by the substitution method (partial replacement of the clinker by the calcined clay). The characteristics of cement at anhydrous state and the hydrated state (chemical composition, specific weight and fineness, consistency of the cement paste, setting times and shrinkage) were studied thus that the mechanical behavior (flexural and compressive strengths) for the mortar was determined. According to the experimental results obtained, it comes that the quantity of pozzolanic admixture (calcined clay) and the chemical composition of cement manufactured are the principal parameters that influence on the variation of the mechanical strengths (flexural and compressive) of the mortars tested.

The occurrence of cycle slips is a major limiting factor for achievement of sub-decimeter accuracy in positioning with GPS (Global Positioning System). In the past, several authors introduced a method based on different combinations of GPS data together with Kalman filter to solve the problem of the cycle slips. In this paper the same philosophy is used but with discrete wavelet transforms. For experiments we simulated artificial cycle slips in real data. Studies show that the selection of a proper wavelet basis functional basis for wavelet is a very important problem in wavelet transforms. Wavelet transforms accurately detects the place of cycle slips, especially in low noise test quantities.

Homotopy Perturbation Method is an effective method to find a solution of a nonlinear differential equation, subjected to a set of boundary condition. In this method a nonlinear and complex differential equation is transformed to series of linear and nonlinear and almost simpler differential equations. These set of equations are then solved secularly. Finally a linear combination of the solutions completes the answer if the convergence is maintained. HPM based solution incorporates some reasonable assumptions. These are inspired from the boundary condition and a separation mechanism. In this paper, the need for stability verification is shown trough some examples. The novel idea is to keep the inherent stability of nonlinear dynamic in whole term, even if the selected linear part is not stable. Consequently, HPM is enhanced by a preliminary assumption. The proposed method is applied to Riccati equation as well as some other problems. The simulation result verifies the significance of the method whilst numerical and the exact solutions confirm the achievement.

Background modeling is an important step in moving object detection and tracking. In this paper, we propose a new statistical approach in which, a sequence of frames are selected according to velocity and direction of some moving objects and then an initial background is modeled, based on the detection of gray pixel's value changes. To have used this sequence of frames, no estimator or distribution is required. In this work, smoothly changing pixels are modeled by averaging and other statistical calculations are done for more varying pixels. The proposed algorithm works well, even if the moving objects are present in all frames. We have evaluated this novel method successfully on highly textured scenes, with challenging phenomena such as dynamic background, area of high foreground traffic and moving objects with different speeds and sizes. 

The secondary cone crusher's shields at Sarcheshmeh Copper Complex of Iran are made of Hadfield steel with a nominal composition of Fe-1.3 % C-12 % Mn. They have a cut-off in the shape of a cone with an upper end diameter of 80cm and an approximate lower end diameter of 200 cm whose main problem is an unexpected early failure under normal working condition. In this paper, the results of metallographic and fractographic studies carried out on a failed shield at various depths and analytical examinations of the fractured regions are presented. It is revealed that crack propagation starts from the pre-existing microcracks in the internal regions of the shield and results in a catastrophic failure. Analytical examinations indicated other problems associated with the chemical composition of the shield. An Mn/C ratio of < 10 and high sulfur and phosphorus concentrations in the inclusions as compared to that of bulk are typical examples. The latter together with the carbide precipitation in the grain boundaries can be regarded as the pre-existing crack path in these high energy regions of the shield substructure.

Two-stage chemical deposition (TSCD) technique is used to produce ZnO, Mn2O3 and NiO films on soda-lime glass (SL-G) from an aqueous solution of zinc, manganese and nickel complex, respectively. The TSCD method enables the deposition of metal oxide thin films with a thickness which can be controlled during the preparation procedure. The ZnO, Mn2O3and NiO thin films were polycrystalline films which were adherent well to the substrates. The SEM micrographs clearly indicate that the zinc oxide layer is composed of oval shaped crystallites preferably orientated perpendicular to the surface of the substrate. The Mn2O3and NiO layers were closely packed on the substrate. These particles seem to grow from the surface of the substrate.

This paper presents an Artificial Neural Network (ANN)-based modeling technique for prediction of outlet temperature, pressure and mass flow rate of gas turbine combustor. Results obtained by present modeling were compared with those obtained by experiment. The results showed the effectiveness and capability of the proposed modeling technique with reasonable accuracies of about 95 percent. This paper describes a nonlinear SVFAC (State Vector Feedback Adaptive Control) controller scheme for gas turbine combustor. In order to achieve the satisfied control performance, we have to consider the effect of nonlinear factors contained in controller. The controller is adaptively trained to force the plant output and to track an output reference. The proposed Adaptive control system configuration uses two neural networks, a controller network and a model network. The control performance of designed controller is compared with inverse control method and results have shown that, the proposed method has good performance for nonlinear plants such as gas turbine combustor. SVFAC technique is finally generalized for MIMO systems in this paper.

In this paper, the first and second order approximations of Taylor expansion are used for calculating the change of each natural frequency by modifying an arbitrary parameter of a system with a known amount and based on this approximation, the inverse eigenvalue problem is transformed to a solvable algebraic equation. The finite element formulation, based on the classical laminated plate theory (CLPT) is presented for laminated composite plates with piezoelectric patches. Using the proposed FE model, sensitivity analysis is carried out, to find the effects of the changes made in the design parameters such as the piezoelectric patch thickness and the fiber angles in each layer on the natural frequencies of the structure. The inverse eigenvalue problem is solved in order to find the thickness of piezoelectric patches and stacking sequence for relocating the natural frequencies.

This paper investigates the effect of ethanol-unleaded gasoline blends (E0, E10, E25, E35, and E65) computer interfaced, four-stroke single cylinder compression ignition engine. The said engine was converted to spark ignition and carburetion to suit ethanol fuel. A suitable provision was provided on the engine to vary the compression ratio thereby making the engine adaptable to operate at lower compression ratios. The tests were performed by varying the ignition timing, equivalence ratio, and compression ratio at a constant speed of 1500 rpm and at wide open throttle (WOT). Effect of ethanolunleadedgasoline blends and tests variables on engine torque and specific fuel consumption were examined experimentally. The results of this investigation, is believed, to contribute substantially to the knowledge, aimed to ensure a secure future energy.