Enhancing power transfer capability through flexible AC transmission system devices:a review

Global demand for power has significantly increased, but power generation and transmission capacities have not increased proportionally with this demand. As a result, power consumers suffer from variou...     

Discussion A note on ‘Similarity of a new greedy heuristic for facility layout by graph theory to an existing approach’

A recent paper by Boswell claims the development of a new greedy heuristic for constructing a maximal planar weighted graph. This paper points out that Boswell's procedure is not actually new since it has similiarity to an approach introduced earlier by Hassan and Hogg. The paper also points out the advantages of the Hassan and Hogg approach over Boswell's procedure.     

Forest recreation planning in Langkawi Island,Malaysia, using Landsat TM

There is an increasing demand for development of new recreation areas and more intensive management of existing areas. With an eye to the design and implementation of comprehensive zoning plans, satellite remote sensing should provide an ideal tool for terrain analysis, vegetation, and cover type mapping, which are vital to intensive recreation planning. The study undertaken was aimed at examining the applicability of satellite remote sensing for providing necessary information to be used in forest recreation planning. A Landsat TM scene (path row 128/ 56) taken on 30 January 1992 was processed digitally on a Meridian PC image processing system by selecting a representative subsection of the scene that covered the study area. Existing land use, topographical maps, and other related ground information as well as contrast stretching and a maximum likelihood classifier ( MLC) technique were used to assist in the classification. The selection of potential recreation sites was based from potential surface analysis ( PSA ). The results showed that most of the undeveloped forest area located in the north-eastern part of Langkawi Island, Malaysia, was the most potential sites for recreational development, while the moderate recreation potential zones lay on the western part of the island. The mean overall classification accuracy obtained was 82% Therefore the study implies that it is possible to select potential recreation sites ranging from most potential to least potential in Langkawi Island using Landsat TM.     

Optimum synthesis conditions of nanometric Fe50Ni50 alloy formed by chemical reduction in aqueous solution

In the present article, various nanometric Fe₅₀Ni₅₀ alloys were synthesized by chemical reduction of the corresponding metal ions, with hydrazine in an aqueous solution. Process variables of reaction temperature, pH of the hydrazine solution and concentration of metal ions were varied in order to determine the optimum synthesis conditions regarding quality, productivity and cost. It is found that pH of hydrazine solution, at low concentration of metal ions, is the most crucial variable affecting the reaction rate, average crystallite and particle sizes of the synthesized nanometric Fe₅₀Ni₅₀ alloy, followed by the total concentration of metal ions. Thus, increase of pH of hydrazine solution acts as an efficient stabilizer in reducing the particle size. On the contrary, at high concentration of metal ions, the structural characteristics of the nanometric Fe₅₀Ni₅₀ alloy are almost insensitive to reaction temperature and pH of hydrazine solution, but the reduction rate is remarkably sensitive to reaction temperature. Based on these results, it is decided that a reaction temperature of 80 °C, pH of the hydrazine solution of 12·5 and concentration of metal ions of 0·6 M represent the optimum synthesis conditions. The role of pH of hydrazine solution in reducing the alloy’s average particle size as well as efficient stabilizer confirms tremendous effect of synthesis conditions on the alloy structure and therefore, the importance of this study for industrial production of nanometric Fe₅₀Ni₅₀ alloy.     

CONTROL OF CONSTRUCTION ACTIVITIES: III. FUZZY-BASED CONTROLLER

In this paper, a real-time fuzzy-based controller of construction activities is proposed. Because of the numerous uncertainties associated with construction activities, their control requires a different approach than the traditional feedback methods. These methods are essentially based on the knowledge of a transfer function that models the input/output relationships for the controlled system. For a highly complex and uncertain system such as a construction activity, a fuzzy-based control strategy was found to be a suitable and effective approach. The proposed control system is built in two main levels, the process and the activity levels. Each level comprises two main units, namely, the fuzzy controller and the self learning algorithm. The implementation of the control actions can be performed by either manipulating the states of the variables for the purpose of improving the process output, or changing the process behavior function for the same purpose. Practical examples are presented wherever possible to illustrate the proposed control strategy.     

EFFECT OF ADDING A PASSIVE CONDENSER ON SOLAR STILL PERFORMANCE

A theoretical and experimental study was carried out to investigate the effect of adding a passive condenser on the performance of the single slope, basin type solar still. A theoretical model based on Dunkle [1] mass transfer (evaporation) rate was developed. The model assumes that the transfer of water vapour from the still to the condenser is due to one or more of the following mass transfer modes; (i) diffusion, (ii) purging and (iii) natural circulation. The theoretical results indicate that diffusion contribution is relatively small. The contribution through purging represents the fraction [V(cond)/(V(cond) + V(s))] of the still yield, while it represents 75% of the still yield through natural circulation. An experimental study that simulates the purging mass transfer mode was investigated. The experimental results show good agreement with the theoretical predictions and an increase of 45% in solar still efficiency was obtained.     

Time-optimal output regulators for linear multivariable discrete-time systems Part 1. Right invertible decouplable systems

Corsetti and Houpis (1985) presented a simple algebraic solution for the timeoptimal output regulator problem. This solution has been obtained for a special class of right invertible decouplable systems S(A, B, C) satisfying the condition that CB is of full rank. In this paper a general method is presented to extend the results of Corsetti and Houpis to all classes of right invertible decouplable systems S(A, B, C, E). It is shown that a simple state feedback control law drives each output of S(A, B, C, E) in a minimum number of steps equal to the order of the associated infinite zero. This state feedback represents the optimal solution for the considered time-optimal output regulator problem. A class of optimal solutions, parametrized by a free parameter matrix K, is obtained for non-square systems. The properties of the resulting optimal closed-loop system is given and a numerical example is worked out to illustrate the generality and feasibility of the proposed method.     

Spray Drying of Roselle (Hibiscus sabdariffa L.) Extract

Hibiscus sabdariffa (Roselle) powder was produced by pilot scale spray drying using single strength and vacuum concentrated water extract of its calyces. Powders were analyzed for moisture, protein, vitamin C, total soluble solids (TSS), pH, particle size, bulk density, solubility, dispersibility, hygroscopicity, and microbiological status. The lowest inlet air temperature (198.5°C) resulted in the product with best protein content (12.43%), retention of vitamin C (82.76 mg/ 100g), and solubility (dissolving in 97 sec); as well as the highest moisture content (3.78%) in the product. The powder showed a noticeable tendency to stick to internal surfaces of the drying chamber particularly with concentrated solutions at higher temperatures.     

Electrochemical corrosion behavior of bulk ultra-fine grained Fe-Ni-Cr alloy

The corrosion behavior of bulk ultra-fine grained (UFG) Fe-Ni-Cr alloy prepared by equal-channel angular pressing technique was investigated in 0.25 mol/L Na₂SO₄+0.05 mol/L H₂SO₄ solution by electrochemical measurements. As compared to the coarse grained (CG) counterpart, the UFG alloy exhibits an acceleration of the active dissolution and a shrunk passive region with a higher passive current. The Mott-Schottky analysis in conjunction with the point defect model indicates that the donor diffusion coefficient in the passive films of the UFG sample increases greatly to one magnitude order higher and the donor density is slightly lower than that of the CG sample.