UET Peshawar Publications Site (University of Engineering and Technology, Peshawar)
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A MODEL FOR ASSESSING RELIABILITY OF UPS IN DEVELOPING COUNTRIES
No full textThis paper presents a computer model for assessing the reliability of uninterruptible power supply (UPS) system in developing countries using the part stress method. Data on failure of APC BK65OMI UPS in Nigeria were used as a case study. Special consideration was given to factors like environment, quality of utility and service personnel. From the point of view of part stress, the block diagram of a UPS comprise basically of two sub-units: the charger and the inverter, consequently, a mathematical model used to determine the reliability of the UPS, can by used for another UPS as long as the block diagrams are identical, the number and the quality of constituent parts are taken into consideration in each case
AN EXPRESSION FOR FAN SELECTION IN RECTANGULAR AIR CONDITIONING DUCT SYSTEMS
No full textA fluid mechanics analysis was carried out to derive an equation of system static pressure in terms of air conditioning fan discharge for a standardized rectangular duct work system. The standardized system parameters include the maximum length of the index duct run, the number and type of each duct fitting and accessory, and the air flow velocity. The derived expression can be used to select fans for different air conditioning duct systems, thereby speeding up the fan selection process
COMPARISON OF LINKER AND DIETERICH FRICTION MODELS WITH PRAKASH MODELS FOR SIMULATION OF HIGH-SPEED FRICTION
No full textThis paper compares Linker and Dieterich models with Prakash models to simulate shear resistance. One of the mathematical models on sliding friction was developed by Linker and Dieterich (1992) under quasistatic conditions using low normal stresses and low sliding velocities. Prakash (1998) developed mathematical models under High Speed Machining applications, using high normal stresses and high sliding velocities. Linker and Dieterich models show that a step change in normal stress causes a sudden change in shear stress, while Prakash models show that a step change in normal pressure gives an exponential change of the shear stress to a new steady stale, characteristic of the current normal pressure and the current slip velocity. Prakash models have been found suitable for simulation of shear resistance at tool-workpiece interface during high speed machining applications
WASTE MINIMIZATION OF A PROCESS FLUID THROUGH EFFECTIVE CONTROL UNDER VARIOUS CONTROLLERS TUNING
No full textWhenever a process is disturbed either by servo System or regulatory system, the control action is applied to trace the desired point. An efficient controller setting should be selected in order to get speedy response under the pattern or constraints of quality of the product. The effective control action is desired to utilize the maximum of raw material and to minimize the waste. This is a critical problem in cases where the raw material or product is valuable and costly, e.g., pharmaceuticals. This problem has been addressed in this work on a laboratory scale plant. The plant consists of feed tank, pumps, plate and frame heat exchanger and hot water re-circulator tank. The system responses were logged with computer while the controller was tuned with Ziegler-Nichols (Z-N) and Cohen-Coon (C-C) tunings. A detailed study indicates that Ziegler-Nichols Controller tunings is better than Cohen-Coon as waste production was minimized
ECONOMICAL SIZING OF SINGLY REINFORCED CONCRETE BEAMS AND FOOTING SLABS
No full textReinforced concrete beams and footing slabs play an important role in any type of frame or even wall supported structure. The sizing and proportioning of beams and footing slabs are important aspects related with the strength as well as the economy. In this study, a mathematical expression is formulated and minimized for the cost to obtain an optimum solution for beam and foundation slab depths. The results may be used for initial sizing of the member in order to reduce the amount of steel up to the most economic limits maintaining the strength and satisfying the code provision
STRUCTURAL PROPERTIES OF CONCRETE WITH SULPHATE RESISTING CEMENT
No full textDue to the fact that in waterlogged and salinity affected areas more commonly ordinary Portland cement particles are attacked chemically and therefore their decay and their decomposition occurs leading to disintegration of concrete at ground level and below, sulphate resisting cement is used as binding material instead of O.P.C. in such situations. Therefore, experimental study has been conducted to determine fundamental structural properties of micro-concrete consisting of hill sand and sulphate resisting cement in various proportion. From the results it has been observed that strength of micro concrete with S.R. Cement is considerably less than that with O.P.C. This is in contrast with the values of compressive strength quoted by the manufacturers where the difference of strength between O.P.C. and S.R.C. is negligibly small. This implies that for the same grade of concrete more cement content will have to be added than O.P.C
SMOOTHED SEMI-PARAMETRIC REGRESSION IN HEAVY CENSORING
No full textRegression with censored data is important in the inferences of the survival or failure time data. Present study focuses on the problem of modeling heavy censored survival data.In the class of Accelerated Failure Models, a new semi-parametric model is proposed to consider situations where the functional form of the effect of one or more covariates is unknown. This proposal is based on a model that does not need to assume any distribution for the survival time, or the proportionality of the hazard functions for different individuals. The effect of covariate is modeled directly on time, instead of the conditional probability or hazard. It is tried to improve estimation procedure to make inferences on parameters through the sum of the weighted squared residuals using the non-censored rate as proposed weights. A simulation study has been carried out to show the performance of the proposed estimation process and to analyze the effect of censorship
ANALYSIS OF POWER TRANSMISSION POLES
No full textAnalysis of high voltage transmission poles has been made using different techniques employing their loading. Due to large displacements produced. the secondary effects have to be accounted for in the solution of pole structure. Therefore. it becomes necessary to consider the geometric non-linearity.For the analysis purpose, three new mast modeling techniques are introduced by the Authors, which are referred to as;1) Tapered Model 2) Prismatic Model3) Non-linear Flexibility Model
The development of new techniques was considered necessary due to limitations of available methods of analysis for pole structures. The method, considered to be providing exact solution is based on use of thin shell elements, requires a considerable degree of computer lime and memory. Other modeling techniques are based on frame elements, solution of which are not found in good agreement with the exact solution unless nodes selected are appreciable in number.
In this work the analysis of poles is carried out by tapered model along with one of the standard packages based on finite element method it is gratifying to note that the results obtained from developed tapered model are observed to be having good agreement with those of exact method
CFD MODELING OF AN INDUSTRIAL MUNICIPAL SOLID WASTE COMBUSTOR
No full textThe average amount of municipal solid waste (MSW) generated in Malaysia is 0.5—0.8 kg/person/day and has increased to 1.7 kg/person/day in major cities. Due to rapid development and lack of space for new landfills, big cities in Malaysia are now switching to incineration. However, a major public concern over this technology also is the perception of the emission of pollutants of any form. Design requirements of high-performance incinerators are sometimes summarized as the achievement of 3Ts (time,temperature, and turbulence). An adequate retention time in hot environment is crucial to destroy the products of incomplete combustion and organic pollutants. Also turbulent mixing enhances uniform distributions of temperature and oxygen availability. CFD modeling ¡s now in the development phase of becoming a useful fool for 3D modeling of the complex geometry and flow conditions in incinerators. However, CFD flow simulations enable detailed parametric variations of design variables, CFD modeling of an industrial scale MSW incinerator was done using FLUENT Ver. 6.1. The 3D modeling was based on conversation equations for mass, momentum and energy. The differential equations were discretized by the Finite Volume Method and were solved by the SIMPLE algorithm. The k-e turbulence model was employed. The meshing was done using Gambit 2.0. The cold flow simulations were performed initially to develop the flow and velocity field. Numerical simulations of the flow field inside the primary and secondary combustion chambers provided the temperature profiles and the concentration data at the nodal points of computational grids. Parametric study was also done to minimize the NOx emissions
KINEMATIC SEISMIC RESPONSE OF PILES IN LAYERED SOIL PROFILE
No full textThis paper is aimed at highlighting the importance of Kinematic Seismic Response of Piles, a phenomenon often ignored in dynamic analysis. A case study is presented where the end bearing pile is embedded in two layer soil system of highly contrasting stiffness; a typical case where kinematic loading plays important role. The pile soil system is modeled as continuous system and as discrete parameter system. both are based on BDWF (Beam on Dynamic Winkler Foundation) formulation. For discrete parameter system, a finite element software SA P2000 is used and the modeling technique of kinematic interaction in finite element software is discussed. For pile soil system modeled as continuous system, a general MATLAB code is developed capable of performing elastic sate response analysis in two layer soil system, solving differential equation governing kinematic interaction, and giving as output the maximum ground displacement, maximum pile displacement, rotation, moment and shear distribution along pile length. The paper concludes that kinematic seismic actions must be evaluated particularly at the interface of soil layers of significantly differing soil stiffnesses