Ahmad Ahmad - Academia.edu (original) (raw)
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Papers by Ahmad Ahmad
The performance of polluted insulators is very much dependent on the degree of contamination. For... more The performance of polluted insulators is very much dependent on the degree of contamination. For the high voltage insulators to be installed in areas especially near the coast, determination of the contamination level becomes the major task to design the insulators appropriately. The aim of this paper is to obtain accurate information about the degree of contamination which the high voltage insulators are exposed to when they are installed in coastal areas. Regression technique has been used successfully in estimating the level of contamination on high voltage insulators surfaces in terms of equivalent salt deposit density (ESDD). This paper has also used artificial neural network algorithm to model ESDD as a function of various meteorological parameters. A comparative analysis has also been carried out between the two methods in this work.
The reliability of the power system mainly depends on the environmental and weather conditions wh... more The reliability of the power system mainly depends on the environmental and weather conditions which cause flashover on polluted insulators leading to system outages. It is generally recognized that the main causes leading to the contamination of insulators are marine pollution-found in the immediate neighborhood of the coastal regions and solid pollution-found in the dense industrial areas. This research is directed towards the study of contamination of insulator under marine pollution. The effects of various meteorological factors on the pollution severity have been investigated thoroughly. In the present paper an attempt has been made to estimate the pollution severity under various weather conditions using Artificial Neural Network. A new approach using ANN as a function estimator has been developed and used to model accurately the relationship between ESDD with temperature T, humidity H, pressure P, rainfall R and wind velocity WV.
Electric Power Systems Research, 2004
The environmental and weather conditions cause flashover on polluted insulators leading to outage... more The environmental and weather conditions cause flashover on polluted insulators leading to outages in a power system. It is generally recognized that the main causes leading to the contamination of insulators are marine pollution as found in the immediate neighborhood of the coastal regions, and solid pollution as found in the dense industrial areas. This research is directed towards the study of contamination of insulator under marine pollution. The effects of various meteorological factors on the pollution severity have been investigated thoroughly. A new approach using ANN as a function estimator has been developed and used to model accurately the relationship between ESDD with temperature (T), humidity (H), pressure (P), rainfall (R), and wind velocity (WV). The ANN-predicted ESDDs have been compared with the measured ones for a practical system.
Visual CAPTCHAs have been widely used across the Internet to defend against undesirable or malici... more Visual CAPTCHAs have been widely used across the Internet to defend against undesirable or malicious bot programs. In this paper, we document how we have broken most such visual schemes provided at Captchaservice.org, a publicly available web service for CAPTCHA generation. These schemes were effectively resistant to attacks conducted using a high-quality Optical Character Recognition program, but were broken with a near 100% success rate by our novel attacks. In contrast to early work that relied on sophisticated computer vision or machine learning algorithms, we used simple pattern recognition algorithms but exploited fatal design errors that we discovered in each scheme. Surprisingly, our simple attacks can also break many other schemes deployed on the Internet at the time of writing: their design had similar errors. We also discuss defence against our attacks and new insights on the design of visual CAPTCHA schemes.
Aquatic Ecosystem Health & Management, 2006
Page 1. Heavy metal pollution status in the Malaysian aquatic environment Noor Azhar M. Shazili,1... more Page 1. Heavy metal pollution status in the Malaysian aquatic environment Noor Azhar M. Shazili,1∗ Kamaruzaman Yunus,2 Ahmad Shamsudin Ahmad,1 Norantonina Abdullah,1 and Mohd Kamil Abd Rashid1 1Faculty of Science ...
The performance of polluted insulators is very much dependent on the degree of contamination. For... more The performance of polluted insulators is very much dependent on the degree of contamination. For the high voltage insulators to be installed in areas especially near the coast, determination of the contamination level becomes the major task to design the insulators appropriately. The aim of this paper is to obtain accurate information about the degree of contamination which the high voltage insulators are exposed to when they are installed in coastal areas. Regression technique has been used successfully in estimating the level of contamination on high voltage insulators surfaces in terms of equivalent salt deposit density (ESDD). This paper has also used artificial neural network algorithm to model ESDD as a function of various meteorological parameters. A comparative analysis has also been carried out between the two methods in this work.
The reliability of the power system mainly depends on the environmental and weather conditions wh... more The reliability of the power system mainly depends on the environmental and weather conditions which cause flashover on polluted insulators leading to system outages. It is generally recognized that the main causes leading to the contamination of insulators are marine pollution-found in the immediate neighborhood of the coastal regions and solid pollution-found in the dense industrial areas. This research is directed towards the study of contamination of insulator under marine pollution. The effects of various meteorological factors on the pollution severity have been investigated thoroughly. In the present paper an attempt has been made to estimate the pollution severity under various weather conditions using Artificial Neural Network. A new approach using ANN as a function estimator has been developed and used to model accurately the relationship between ESDD with temperature T, humidity H, pressure P, rainfall R and wind velocity WV.
Electric Power Systems Research, 2004
The environmental and weather conditions cause flashover on polluted insulators leading to outage... more The environmental and weather conditions cause flashover on polluted insulators leading to outages in a power system. It is generally recognized that the main causes leading to the contamination of insulators are marine pollution as found in the immediate neighborhood of the coastal regions, and solid pollution as found in the dense industrial areas. This research is directed towards the study of contamination of insulator under marine pollution. The effects of various meteorological factors on the pollution severity have been investigated thoroughly. A new approach using ANN as a function estimator has been developed and used to model accurately the relationship between ESDD with temperature (T), humidity (H), pressure (P), rainfall (R), and wind velocity (WV). The ANN-predicted ESDDs have been compared with the measured ones for a practical system.
Visual CAPTCHAs have been widely used across the Internet to defend against undesirable or malici... more Visual CAPTCHAs have been widely used across the Internet to defend against undesirable or malicious bot programs. In this paper, we document how we have broken most such visual schemes provided at Captchaservice.org, a publicly available web service for CAPTCHA generation. These schemes were effectively resistant to attacks conducted using a high-quality Optical Character Recognition program, but were broken with a near 100% success rate by our novel attacks. In contrast to early work that relied on sophisticated computer vision or machine learning algorithms, we used simple pattern recognition algorithms but exploited fatal design errors that we discovered in each scheme. Surprisingly, our simple attacks can also break many other schemes deployed on the Internet at the time of writing: their design had similar errors. We also discuss defence against our attacks and new insights on the design of visual CAPTCHA schemes.
Aquatic Ecosystem Health & Management, 2006
Page 1. Heavy metal pollution status in the Malaysian aquatic environment Noor Azhar M. Shazili,1... more Page 1. Heavy metal pollution status in the Malaysian aquatic environment Noor Azhar M. Shazili,1∗ Kamaruzaman Yunus,2 Ahmad Shamsudin Ahmad,1 Norantonina Abdullah,1 and Mohd Kamil Abd Rashid1 1Faculty of Science ...