JOURNAL OF SCHOOL OF ENGINEERING
Year:2000 | Volume:12 | Issue:2|Papers Count:7

High velocity oxy-fuel (HVOF) sprayed coatings are used increasingly in industries because of high quality coatings produced by this method. In this investigation NiCr-Cr3C2 sintered and crushed powder is coated on the substrate of 316L stainless steel by HVOF method. Microstructural characterization of coatings is studied using X-ray diffraction (XRD) techniques, optical microscopy and electron microscopy of scanning (SEM) and transmition (TEM). It is realized that the coatings microstructure are included methallic phases from chromium with nickel to nickel with chromium, which deponds on spray conditions. The structure is also included oxides of Cr2O3 and NiCr204. High carbon phases with unmelted carbide particle present in coatings. TEM study shows considerable amount of amorphous phases and presented in coatings layer.

Cells-In-Frames mechanism proposed by CIT in 1996 is an efficient way Local Area Network-ATM Network interconnection. According to this mechanism, connection oriented services are supported by connectionless UN workstations. In this technique ATM cells are carried by LAN frames. Each frame may include one or more A TM cells, but any given LAN frame is associated with only one ATM virtual circuit. There have not been any careful studies of Cells-In-Frames behavior since its proposal in 1996. In this paper the Cell-In-Frames mechanism for Ethenet LAN-ATM Network interconnection is first implemented, then its performance for data transmission is studied from various points of views in order to highlight its strong and weak points. Finally a novel technique which greatly improves its performance is introduced. The simulation studies show that the new technique offers significant improvements at a very little hardware and software extra cost.

Metallic coatings increase corrosion and oxidation resistance of steel. Aluminum coating is one of the most effective methods and hot dipping is the most economic one. This process is known aluminizing. In this research, aluminized layers were studied by optical microscopy, metallographic methods, microhardness, x-ray diffraction (XRD) and electron probe micro analyzer (EPMA). The properties of aluminized coating evaluated by bending, .oxidation and corrosion tests.

The water penetrated into the pores, cracks, joints and seams of concrete dams, creates uplift pressure within the dam and foundation. The distribution of pressure through a horizontal section of the dam is assumed to vary linearly from a full hydrostatic head at the upstream face to zero, or tailwater, at the downstream face, supposing that the dam has no drains. If drains are constructed and work, the internal pressure distribution will be dependent on size, location (distance from the upstream face) and spacing of drains. In this study, a computer program is presented to calculate the distribution of internal pressure at any section of a concrete gravity dam having a system of equally spaced drains of uniform diameter, using Finite Elements Method. An optimum area/or the location of drains, causing the minimum uplift force, is also identified.        

This paper deals with constrained two-dimensional guillotine cutting of a rectangular plate for demanded rectangular pieces. Maximum number of pieces for each piece-type is known and waste pieces are considered to have value. Rotation of pieces on the plate is not allowed. The goal is to maximize total value of pattern including desired pieces and waste pieces. Also, the shape of waste pieces, i.e., being narrow wide, is another factor that is considered here. This research has improved the results in [1, 2, 3]. The improvement is in assigning value to waste pieces and their shapes. An AND/OR graph and heuristic search techniques are used in developing the cutting algorithm.    

A one - dimensional dynamic mathematical model was developed to simulate the total sediment load in stream system. This model is based on mass balance equation including advective-diffusive transport, deposition, and erosion, inflow of point and nonpoint sources and rate of bed-load transport. The mathematical solution is obtained by a finite element method. Bedload rate is calculated from 19 methods and then the best method is used in mathematical model as sources of sinks. The model is calibrated and confirmed using data collected from the Ghare - Aghaj river in Band-e-Bahman measurement station in the site of Mirazi-e-Shirazi dam. The simulated are in good agreement with measured values.