PARAMETER SELECTION FOR SAFE DESIGN UNDER UNCERTAIN CONDITIONS: A TRUSS EXAMPLE

This paper focuses on the derivation of safe parameters for the design of the bars and joints of a roof truss system. The loading, material and geometrical properties are treated as random quantities with assumed practical probability distributions. The numerical values of the design variables are derived in a manner, which leads to a constant overall safety level of the system under varying inputs. The concept of the most likely failure point of the reliability analysis is employed utilizing the BS 5950’ design requirements for members and joints which are assumed filet-welded. The intent of the work is realized through user friendly computer modules developed in FORTRAN programming language

A TUTORIAL ON ADAPTIVE ROBUST POSITION CONTROL OF DC MOTOR USING FUZZY LOGIC COMPENSATION

This article presents a tutorial on adaptive fuzzy sliding mode control for position control of DC servo motor which is subjected to nonlinear friction and external disturbance torque. Friction phenomenon is simulated using Lugre dynamic model. Adaptive fuzzy system is used to approximate nonlinear friction and external disturbance. Assuming that system state matrixes are known, model based robust controller is formulated using sliding mode control method. Adaptive fuzzy system formulated using Lyapunov function. The proposed controller is derived for DC motor position control system and numerical simulations are presented to verify its effectiveness

SOLAR STILL PERFORMANCE FOR SEA WATER PURIFICATION: A STATISTICAL AND EXPERIMENTAL STUDY

  Sudden rise of fossil fuel prices and its scarce resources have caused the energy crises for the past few years. Current research has been focused primarily using renewable source of energy. The solar energy has been proved to be an economical alternative renewable energy used to extract the fresh water from sea water. The principle objective of the study is to purify the sea water by using solar energy. A pilot scale solar still has been designed, fabricated and optimized for maximum evaporation rate of model sea water. The various parameters such as water depth in still, average day temperature and average water temperature in still were studied experimentally and verified statistically though ANOVA (analysis of variance). It was found that the water temperature in the still is the most significant parameter that largely affects the evaporation rate. The fresh water with 240 mg/L dissolved salt has been extracted from the model sea water having dissolved salts of 35000 mg/L. The efficiency of a single basin solar still is improved up to 80 percent

ASSESSMENT OF SEDIMENT TRANSPORT LOAD FROM GOAML RIVER AND ITS IMPACT ON THE GOMAL ZAM DAM LIFESPAN

This paper estimates the sediment load transported by Gomal River at Khajuri Katch and Kot Murtaza on yearly-basis. An eight years sediment data (1981-88) compiled by the surface water hydrology division of WAPDA was analyzed. Based on the available data and using regression analysis a model is developed to establish a correlation between water discharge and sediment load. The model is an attempt to ascertain the rate of erosion in the catchment of the Gomal River since no generalized model has so far been developed to explain the nature of such weathering activities and all such works are situation specific. Relation between the water discharges to sediment load that it carries has been developed to signify the Gomal River catchment’s erosion. The analysis shows that the catchments is  eroding at the rate of 1.67 acre-feet and the sediment water ratio is 3.0% which is the second highest value the world over after Yellow River in China. The variation of different parameters in sediment-water system i.e. water discharge, sediment load, sediment concentration and sediment quality have been estimated from the actual data and are shown by histograms and bar graphs. The relations developed are applicable only to the Gomal River system. It is hoped that the study will invite interest and attention of planners, researchers, and all those concerned with the problems and menace of soil erosion, sediment load concentration in hydraulic structures and its impact over the life span of hydraulic structures i.e dams deemed to be constructed across the river with the objective to minimize the sedimentation problems. Indexin

DYNAMIC MODELING AND CONTROLLER DESIGN FOR NUCLEAR POWER PLANT

Higher order mathematical modeling and discrete fast output sampling control synthesis for PHWR (Pressurized Heavy Water Reactor)-type nuclear power plant is presented in this paper. The nonlinear dynamic model of PHWR power reactor is developed based on reactor, logarithmic amplifier, moderator level control valve and reactivity system. The nonlinear model is characterized by 15 state variables and one input. This higher order nonlinear model is linearized at full power operating point. A standard higher order state space model is realized for controller design purpose. An advanced discrete controller is synthesized for state space model of PHWR using fast output sampling methodology. Noise sensitivity is a typical problem with this type of controller. In this research work, a small deviation is allowed in order to reduce the noise sensitivity. Theproblems of noise sensitivity and poor output error dynamics are addressed and a multi-objective optimization problem is solved using LMI (Linear Matrix Inequalities) formulation. Fast output feedback gains are computed using LMI tool for MATLAB. An advanced fast output sampling controller is evaluated for power maneuvering from 270 MWth to 310 MWth on the nuclear power plant in Pakistan and found highly efficient and satisfactory within the control design constraints

Identification of the Optimal Operating Parameters of Locally Available Coal for Use in Pakistani Industries

A parametric study intended to determine optimum burning parameters of locally available coal from mines in Darra Adam Khel is being reported. The coal samples were tested in a cyclone combustor using the pulverized coal combustion technique. Effect of mesh size, primary and secondary air velocity at various air fuel ratios was investigated to quantify the combustion performance by measuring the furnace temperature. Mesh size 200 was found to be readily combustible within the operating ranges, while tight control of the operating parameters was required to combust coal at mesh size 150. Optimum ranges of primary air and Air-Fuel Ratio are suggested for effective combustion. The study will help in effective utilization of indigenous coal reserves of Pakistan

TRAVEL AND SPREAD OF CONTAMINANTS IN GROUNDWATER

This paper presents the results of an extensive investigation conducted to determine the travel and spread pattern of selected contaminants due to disposal of sewage from a large subsurface system. The contaminants concentration tended to decrease with an increase in distance away from the leaching bed. The time and distance curves plotted for the selected contaminants at the concentration C/Co =0.1 became asymptotic after reaching the maximum distance in the week 146. The maximum distance traveled by the contaminants at the concentration C/Co=0.1, observed for 134 weeks, was 104 mfrom the center of the leaching bed. The maximum area of the contaminants spread was approximately 33,975 square meters

Performance Evaluation of Aquatic Macrophytes for Municipal Wastewater Treatment

Municipal Sewage of Taxila was selected for evaluation and comparison of the performance of three aquatic macrophytes regarding sewage treatment. A bench scale laboratory model was developed and used for experimentation. Six experimental runs were conducted and each run laps over thirty (30) days. In each experimental run continuous monitoring of municipal sewage was done for each macrophyte specie. The aquatic macrophyte species used for the performance comparison were Water Hyacinth, Duckweed & Water Lettuce. For performance comparison four parameters including BOD5, COD, Nitrogen and Phosphorus were selected. These parameters were monitored for both the influent and effluent sewage samples. During the entire study, the average reduction of 51% for BOD5, 47% for COD, 19% for phosphorus, and 41% for nitrogen were found with water hyacinth. When the same sewage was treated with Duckweed the values came out to be 34% for BOD5, 27% for COD, 16% for phosphorus and 18% for nitrogen. Similar trend was observed in the experiments with Water Lettuce as 33 % for BOD5, 29% for COD, 11% for phosphorus and 15% for nitrogen. Sewage treatment in macrophyte based system included both the anaerobic & aerobic microbial processes. The treatment is further followed by chemical conversions, sedimentation & volatilization. The highest pollutant removals were observed for at temperature range of 15-38 oC and at pH variation between 6 and 9. In developing countries like Pakistan, where no importance is being given to municipal sewage treatment, the method found to be environmentally and financially sustainable.&nbsp

COMPARATIVE STUDY OF RELAY PROTOCOLS USING SIMULATION

Cooperative communication has gained a lot of interest due to its ability to exploit the spatial diversity or antenna diversity. The implementation of the cooperative relaying systems involves less hardware and lowcomplexity but gives comparable performance and diversity gains to the actual multiple antenna systems. The aim of this paper is to compare various techniques used in cooperative relaying protocols. The performanceis evaluated in terms of average symbol error under various ranges of signal-to-noise ratio (SNR) probabilities. A three node system i.e. source, relay and destination, placed on the edges of equilateral triangle, has been proposed using Maximal ratio Combiner (MRC) method by combining signals from source and relay at destination point. The transmission path is modeled as a frequency non-selective Rayleigh fading in the presence of additive white Gaussian noise (AWGN). The results show that at high SNR decode-and-forward performs well, while at low SNR amplify-and-forward works well. A selective relaying scheme called selective detect-and-forward is also simulated which shows better performance than its fixed counterparts for a wide range of SNR

RESILIENT CHARACTERISTICS OF SUBGRADE SOILS IN SAUDI ARABIA

Subgrade soil samples were collected along major highways of Saudi Arabia. The properties of AASHOTO class A-2-4 soil samples, including resilient modulus, were determined and analyzed. The main purpose was to correlate resilient behaviour with other soil properties. First, resilient modulus was modeled in terms of stress state (deviator and confining stresses). Then, model constants were related by regression equations to soil properties. The developed models can be used to predict resilient modulus values based on soil properties and expected stress state under the pavement