Ali Al-Lawati

Solar radiation estimation using artificial neural networks

Artificial Neural Network Methods are discussed for estimating solar radiation by first estimating the clearness index. Radial Basis Functions, RBF, and Multilayer Perceptron, MLP, models have been investigated using long-term data from eight stations in Oman. It is shown that both the RBF and MLP models performed well based on the root-mean-square error between the observed and estimated solar radiations. However, the RBF models are preferred since they require less computing power. The RBF model, obtained by training with data from the meteorological stations at Masirah, Salalah, Seeb, Sur, Fahud and Sohar, and testing with those from Buraimi and Marmul, was the best. This model can be used to estimate the solar radiation at any location in Oman.

Solar cell parameter extraction using genetic algorithms

In this paper, a technique based on genetic algorithms is proposed for improving the accuracy of solar cell parameters extracted using conventional techniques. The approach is based on formulating the parameter extraction as a search and optimization problem. Current–voltage data used were generated by simulating a two-diode solar cell model of specified parameters. The genetic algorithm search range that simulates the error in the extracted parameters was varied from ± 5t o±100% of the specified parameter values. Results obtained show that for a simulated error of ±5% in the solar cell model values, the deviation of the extracted parameters varied from 0.1 to 1% of the specified values. Even with a simulated error of as high as ±100%, the resulting deviation only varied from 2 to 36%. The performance of this technique is also shown to surpass the quasi-Newton method, a calculus-based search and optimization algorithm.

Enhancement of on chip chemiluminescence signal intensity of tris(1,10-phenanthroline)-ruthenium(II) peroxydisulphate system for analysis of chlorpheniramine maleate in pharmaceutical formulations.

The effect of detection chip geometry on chemiluminescence (CL) signal intensity of tris(1,10-phenanthroline)-ruthenium(II) peroxydisulphate system for analysis of chlorpheniramine maleate (CPM) in pharmaceutical formulations was investigated. It was observed that the design of the detection chip is very crucial and can play an important role in enhancing the CL signal intensity in this system. The CL signal intensity was enhanced 250% when a teardrop micromixer chip was used, compared to the commonly used serpentine chip geometry. The study was conducted using a multi-chip device. In this device, chip 1 was used to prepare and pump the reagent mixture, whereas chip 3 was used for pumping the sample. The two chips were connected to the teardrop chip (2) via silica capillary where detection took place. Non-linear regression curve fitting of the calibration data revealed that the calibration curves are best described by third order polynomial equation with excellent correlation coefficients (R(2)=0.9998) for the concentration range 7.69 × 10(-8) to 5.12 ×1 0(-5)mol L(-1). A linear response is also observed over the range 7.69 × 10(-8) to 1.28 × 10(-5)mol L(-1) (R(2)=0.9996) and the detection limit was found to be 5.49 × 10(-8)mol L(-1). The device was successfully used for the analysis of CPM in tablets and a multi-component cough syrup. Results were reproducible with relative standard deviation (RSD) of 0.6-1.1%.

Monthly average daily solar radiation and clearness index contour maps over Oman

Using meteorological data spanning more than ten years in Oman, radial basis function neural networks were developed for estimation of the solar radiation and clearness index for any location in Oman, given its longitude, latitude, altitude, sunshine hours and month of the year. Data generated for 25 different locations were then used to plot contour maps for monthly average daily solar radiation and clearness index over Oman. These maps will serve as a much needed reference for design and performance evaluation of solar energy conversion systems in this region.

Analysis of fexofenadine in pharmaceutical formulations using tris(1,10-phenanthroline)–ruthenium(II) peroxydisulphate chemiluminescence system in a multichip device

A simple, rapid and sensitive method has been developed for the analysis of fexofenadine (FEX) in pharmaceutical formulations, using a tris(1,10-phenanthroline)-ruthenium(II) [Ru(phen)(3)(2+)] peroxydisulphate chemiluminescence (CL) system in a multichip device. Various parameters that influence the CL signal intensity were optimized. These included pH, flow rates and concentration of reagents used. Under optimum conditions, a linear calibration curve in the range 0.05-5.0 µg/mL was obtained. The detection limit was found to be 0.001 µg/mL. The procedure was applied to the analysis of FEX in pharmaceutical products and was found to be free from interference from concomitants usually present in these preparations.

Contour maps for sunshine ratio for Oman using radial basis function generated data

Contour maps for sunshine hours and sunshine ratios for Oman have been generated. The data to generate these maps were obtained using an RBF neural network model. This model estimates sunshine hours and ratios for a given point based on its latitude, longitude, altitude and month of the year. Data from 25 locations were used to plot the contour maps. These maps provide a needed reference for the spatial distribution of sunshine hours and sunshine ratios on a monthly basis for the whole of Oman from which estimates can be made for any location.

On locking conditions in m-sequence generators for the use in digital watermarking

The maximal length pseudo random binary sequence is known as m-sequence. The m-sequence of domain {0, 1} can be represented in bipolar form of sequence in domain {−1, 1}. The m-sequences are used for watermarking because of their very good correlation properties, noise like characteristics and resistance to interference. This paper investigates a new locking condition in the operations of an m-sequence generator. Through this finding it is revealed that an LFSR structure may turn into locking state due to particular seed selection other than the all zeros or all ones.

Reducing test time via an optimal selection of LFSR feedback taps

The results of a simulation study demonstrate that in linear feedback shift register-based built-in VLSI testing, the selection of proper feedback taps can reduce the test application time while retaining the testability goals.

Balancing cost and protection of submarine fiber optic cables

This paper presents a model to calculate different costs associated with submarine fiber optic cable protection during design and installation phase and cost related to cable cuts and repairs. It offers a non-existing and much needed tool to help submarine cables operators to decide on the type of cable, protection, length and depth of burial and compare cost of cuts repair and data rerouting during cuts with cost of cable protection schemes.

Development of a MATLAB tool based on graph theory for evaluating reliability of complex mechatronic systems

Evaluation of reliability is very important entity for the design and operation of systems. The safety, dependability, availability, Mean Time To Failure (MTTF), Mean Time Between Failure (MTBF), Mean Time To Repair (MTTR) and life cycle of the designed system can be judged from this reliability evaluation. For simple systems, the evaluation is straightforward. However, for complex systems, an algorithmic procedure is required. This paper presents an algorithmic procedure based on information matrices derived from graph theoretic approach. A simulation tool is developed that applies the algorithm to evaluate the reliability of complex systems.