OPTIMUM DESIGN OF SMALL DISTRIBUTION TRANSFORMER USING ALUMINIUM CONDUCTORS

ABSTRACT

Design Optimization of distribution transformer of small KVA rating using aluminium conductors is considered as a nonlinear multivariable constrained programming problem. For this purpose a set of five independent design variables is identified and suitable constraints are imposed to meet the thermal and other performance requirements of the transformer. The various objective functions are formed in terms of cost of active material, capitalized cost of losses as the operating cost and the overall cost as the sum of these two. This is done to select most effective and appropriate optimized design for these types of transformers. The optimization is achieved through Rosenbrock's method of direct search in conjunction with the sequential unconstrained minimization Technique (SUMT). The optimized design results for a 25 KVA distribution transformer using aluminium conductors are presented along with the design results using copper as the winding material for different objective functions.     

Experimental determination of mechanical parameters in sensorless vector-controlled induction motor drive

High-performance industrial drives widely employ induction motors with position sensorless vector control (SLVC). The state-of-the-art SLVC is first reviewed in this paper. An improved design procedure for current and flux controllers is proposed for SLVC drives when the inverter delay is significant. The speed controller design in such a drive is highly sensitive to the mechanical parameters of the induction motor. These mechanical parameters change with the load coupled. This paper proposes a method to experimentally determine the moment of inertia and mechanical time constant of the induction motor drive along with the load driven. The proposed method is based on acceleration and deceleration of the motor under constant torque, which is achieved using a sensorless vector-controlled drive itself. Experimental results from a 5-hp induction motor drive are presented.     

Varna-based optimization: a novel method for capacitated controller placement problem in SDN

Recently,software defined networking(SDN)is a promising paradigm shift that decouples the control plane from the data plane.It can centrally monitor and control the network through softwarization,i.e.,controller.Multiple controllers are a necessity of current SDN based WAN.Placing multiple controllers in an optimum way is known as controller placement problem(CPP).Earlier,solutions of CPP only concentrated on propagation latency but overlooked the capacity of controllers and the dynamic load on switches,which is a significant factor in real networks.In this paper,we develop a novel optimization algorithm named varna-based optimization(VBO)and use it to solve CPP.To the best of our knowledge,this is the first attempt to minimize the total average latency of SDN along with the implementation of TLBO and Jaya algorithms to solve CPP for all twelve possible scenarios.Our experimental results show that TLBO outperforms PSO,and VBO outperforms TLBO and Jaya algorithms in all scenarios for all topologies.     

Rheological Properties and Microstructure of Acid Milk Gels as Affected by Fat Content and Heat Treatment

Gels were made from recombined milks containing 0, 1.5 or 3.5% fat that were heated at 75, 80 or 90°C for 30 min, followed by acidification with glucono-8-lactone at 30°C. The rheological and microstructural properties of acid gels were investigated using dynamic low-amplitude oscillatory rheology and confocal scanning laser microscopy (CSLM). Heating milks, at temperatures ≥80°C, increased the storage moduli (G′) and decreased the gelation time. Recombined milks containing high fat (3.5%) had higher G′ than gels made from low-fat or skim milk. Milk heat treatment resulted in gels with a cross-linked microstructure. Recombined fat globules appeared to be embedded in the protein matrix.     

EFFECT OF PAPAYA PULP ADDITION ON THE GROWTH OF LACTOBACILLUS ACIDOPHILUS

Effect of papaya pulp addition to skim milk on the growth characteristics of five strains of Lactobacillus acidophilus was investigated. All the strains tested exhibited higher viable counts, shorter generation time, increased acid production, greater sugar utilization and fall in pH upon addition of papaya pulp. The generation time, acid production, sugar utilization and pH values at the end of 18 h fermentation of skim milk by different strains were 150–200 min, 0.29–1.73%, 0.39–2.22 g/100 mL and 3.85–6.10, respectively. The corresponding values for 10% papaya pulp added skim milk blend were 120–143 min, 0.51–1.84%, 0.70–2.79 g/100 mL and 3.70–5.10, respectively. Organoleptic evaluation revealed that papaya pulp addition imparted firmness to the coagulum and thus enhanced the acceptability of the product by eliminating the problem of wheying-off and improved flavor.     

Corporate Strategy in the Intelligent Island: the Case of Singapore Telecom

This paper focuses on the major telecommunications policiesand corporate strategies that have allowed Singapore to achievea high degree of success in designing and implementing a modernand high-quality telecommunications infrastructure. This successhas been achieved with a specific type of industry structurethat is marked by a single public organization protected frommarket competition by government regulations.     

Crack resistance of austenitic stainless steel pipe and pipe welds with a circumferential crack under monotonic loading

This paper describes the experimental studies carried out on cracked austenitic stainless steel pipe and pipe welds under bending loads. Pipe welds were produced by gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW). Fracture resistance curves for pipe and pipe welds were compared. Results indicate that the fracture resistance of pipe and pipe weld (GTAW) is comparable but that of pipe weld (GTAW+SMAW) is inferior. Cracks do not deviate from their original plane during propagation as observed in the cases of carbon steel pipe and pipe welds. The fracture resistance of pipe welds does not depend on the loading histories to which it has been subjected prior to fracture test. Initiation and crack propagation were observed prior to the maximum moment. An existing limit load expression is applicable for the pipe base material but gives non‐conservative results for the pipe welds. Multiplication factors have been suggested for the pipe welds for evaluation of limit loads using the existing expression. Fracture resistance for the pipe and compact tension specimens have also been compared for base material and welds.