Self-tuning flexible ac transmission system controllers for power oscillation damping: a case study in real time

Design and real-time implementation of a self-tuning flexible ac transmission system (FACTS) controller is illustrated for power oscillation damping. Although the system model is not required for self-tuning control design, it is shown to perform similar to a model-based design. For parameter estimation, the classical recursive least square (RLS) is supplemented by a random walk (RW) with a switched structure and compared to standard variable forgetting factor (VFF) approach. It is shown that the RW improves the accuracy and convergence of the estimated system parameters, which is critical to self-tuning control following large disturbances. The performance is validated in real time using a commercial real-time simulation platform. The control computation time is shown to be considerably less than the typical sampling time used for power oscillation damping applications demonstrating the feasibility of self-tuning FACTS controllers in practice.     

Hydrogeochemistry and arsenic contamination of groundwater in the Ganges Delta Plain, Bangladesh

Geochemical composition and the level of Arsenic (As) contamination of groundwater in the Ganges Delta Plain, southwestern Bangladesh were elucidated. Hydrogeochemical data of tube well samples suggested that the groundwater is mostly Ca-Mg-HCO(3) type with bicarbonate (HCO(3)(-)) as the dominant anion, though other type waters are also observed. In contrast, the elevated EC, Cl(-) and high content of Na(+) relative to Ca(2+), Mg(2+) and K(+) in six groundwater samples suggest their saline origin. Low concentrations of NO(3)(-) and SO(4)(2-), and high concentrations of dissolved organic carbon (DOC), HCO(3)(-) and PO(4)(3-) indicate the reducing conditions of subsurface aquifer where sediments are deposited with abundant organic matter. The total As concentration in the analyzed samples is very high (0.0431-1.352 mg/L) along with high Fe (2.791-17.058 mg/L) and relatively low Mn (0.134-1.972 mg/L) at different depths. Distinct relationship of As with Fe and Mn, and strong correlation with DOC suggests that the biodegradation of organic matter and reductive dissolution of Fe-oxyhydroxide is considered to be the dominant processes to release As in aquifers. Moreover, negative correlation between As and SO(4)(2-) demonstrates the As may not be directly mobilized from sulfide minerals like arsenopyrite.     

Combined removal of BTEX in air stream by using mixture of sugar cane bagasse, compost and GAC as biofilter media

Biofiltration of air stream containing mixture of benzene, toluene, ethyl benzene and o-xylene (BTEX) has been studied in a lab-scale biofilter packed with a mixture of compost, sugar cane bagasse and granulated activated carbon (GAC) in the ratio 55:30:15 by weight. Microbial acclimation was achieved in 30 days by exposing the system to average BTEX inlet concentration of 0.4194 gm(-3) at an empty bed residence time (EBRT) of 2.3 min. Biofilter achieved maximum removal efficiency more than 99% of all four compounds for throughout its operation at an EBRT of 2.3 min for an inlet concentration of 0.681 gm(-3), which is quite significance than the values reported in the literature. The results indicate that when the influent BTEX loadings were less than 68 gm(-3)h(-1) in the biofilter, nearly 100% removal could be achieved. A maximum elimination capacity (EC) of 83.65 gm(-3)h(-1) of the biofilter was obtained at inlet BTEX load of 126.5 gm(-3)h(-1) in phase IV. Elimination capacities of BTEX increased with the increase in influent VOC loading, but an opposite trend was observed for the removal efficiency. The production of CO(2) in each phase (gm(-3)h(-1)) was also observed at steady state (i.e. at maximum removal efficiency). Moreover, the high concentrations of nitrogen in the nutrient solution may adversely affect the microbial activity possibly due to the presence of high salt concentrations. Furthermore, an attempt was also made to isolate the most profusely grown BTEX-degrading strain. A Gram-positive strain had a high BTEX-degrading activity and was identified as Bacillus sphaericus by taxonomical analysis, biochemical tests and 16S rDNA gene analysis methods.     

Short-term solar power prediction using multi-kernel-based random vector functional link with water cycle algorithm-based parameter optimization

Neural Computing and Applications - A new hybrid model combining the kernel functions along with the random vector functional link neural network (RVFLN) is proposed in this paper for an effective...     

Multiple-choice question generation with auto-generated distractors for computer-assisted educational assessment

Multimedia Tools and Applications - Multiple-choice questions (MCQs) are used as instrumental tool for assessment, not only in various competitive examinations but also in contemporary information...     

Pattern recognition,image processing and computer vision in fifth generation computer systems

It is well-known that one of the goals of research for the last two decades or so in pattern recognition and its sub-areas, such as processing, analysis and understanding of image, speech and natural language, and computer vision techniques etc., has always been to develop fundamental techniques for flexible interactive intelligent man-machine interfaces for computers. In this paper, the author tries to argue that for the evolution of fifth generation computer systems (FGCS) as defined by Japanese scientists, some of the things required are realisation and implementation of the advances in pattern recognition and its sub-areas, not only to achieve the man-machine interface with a natural mode of communication, but also for the realisation of the basic mechanisms of inference, association and learning, which are inherent both in pattern recognition and in the core functions of FGCS. The next generation computers will be knowledge-based systems, which form a subdomain of artificial intelligence (a1) techniques, and soa1 provides the essential link between pattern recognition domains and different application systems. No attempt is made to discuss other essential conceptual building blocks, such as software engineering, computer architecture and very large scale integration technology unless these become very relevant in the discussions of concerned topics of the paper. A section on limitations of perception, learning and knowledge for computing machines is also included. This work was funded by the Knowledge-based Computer Systems Project of the Department of Electronics, Government of India.     

Evaluation of standard thermodynamic parameters for the sorption of n-hexane and methanol in zeolites

Adsorption isotherms for n-hexane and methanol in mordenite and ZSM5 in the temperature range from 323 K to 473 K were found to be of type 1. The adsorbate-adsorbent interaction (C₁) and adsorbate-adsorbate interaction (C₂) wee computed according to Bradley and Wilkins model, whereas the Rees and Williams model predicts the adsorption characteristics. Finally, the thermodynamic parameters such as ΔG^o, ΔS^o, ΔH^o, K, K⁺ have been evaluated for the sorption of n-hexane in mordenite and ZSM5.     

Infant and child mortality determinants in Bangladesh: are they changing?

From the data of the 1989 Bangladesh Fertility Survey, aggregate deaths reported at ages 0-12 and 13-60 months are used to estimate infant and child mortality. Multivariate analysis shows that preceding birth interval length, followed by survival status of the immediately preceding child, are the most important factors associated with differential infant and child mortality risks; sex of the index child and mother's and father's education are also significant. Demographic factors are influential during infancy as well as childhood, but social factors, particularly mother's and father's education, now emerge as significant predictors of infant mortality risks. This indicates a change in the role of socioeconomic factors, since the earlier Bangladesh Fertility Survey in 1975.     

Androgen receptor mRNA detection in the human foetal prostate

OBJECTIVE: The objective of this study is to present our preliminary experience with pulmonary hypertension inhaled nitric oxide therapy with two newborns presenting with transposition of the great arteries, as well as the usefulness of the Doppler in pulmonary hypertension diagnosis. PATIENTS AND METHODS: Revision of the variations of the hypoxic parameters according to the therapy and revision of the diagnostic procedures in both cases was carried out. RESULTS: Nitric oxide therapy was followed by an evident improvement of the hypoxia and the patient's hemodynamic stabilization, which allowed surgical correction in optimal conditions. The ductal flow pattern allowed recognition of the presence of pulmonary hypertension. CONCLUSIONS: Inhaled nitric oxide must be taken into account as a very useful option in the treatment of this kind of patient and the Doppler examination allows the evaluation of the presence of pulmonary hypertensions.     

An expert system for land cover classification

A framework to represent a broad class of problems in the analysis of remote sensing imagery is proposed, and an inference engine to tackle such problems is derived. A simple model for spectral knowledge representation is used along with a method for quantification of knowledge through an evidential approach. An automatic knowledge extraction technique is also proposed to gather knowledge from training samples. The techniques of knowledge extraction, representation and inferencing have been used to do a land cover analysis on two data sets, and the results are compared with contemporary digital techniques. It is found that the proposed approach has the advantages of avoiding commission errors, and can incorporate non-spectral and collateral knowledge, while its accuracy using only spectral knowledge is comparable with standard digital methods