Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand.

*Author for correspondence, e-mail : nuansri1@yahoo.com

Keywords : antioxidant, Thai vegetables and herbs

Environmental Technology and Management, Field of Study; Urban Environmental Engineering and Management (UEEM) Program, Asian Institute of Technology (AIT)

Author for correspondence, e-mail: kamalasm@hotmail.com, kamalasm@ait.ac.th

Arsenic in water, soil, hair, and biological samples from potentially arsenic risk Hizla, Bangladesh (vegetables, fish, and meat) was determined to identify the source of arsenic contamination. Mostly (84 water samples out of 125) shallow tubewell (10-30 m) water, but none (out of 52 samples) deep tubewell (more than 200 m) water was contaminated. Arsenic in groundwater was found to increase proportionally with iron but decrease inversely with well depth. Hair samples from the villagers, who have been drinking arsenic contaminated water for several years with preliminary skin lesions, showed significant results (5.5 to 11.1 mg Kg^-1). The soil and biological samples did not show any significant result, as a source of arsenic contamination in Hizla. All samples except water were analyzed by X-Ray Fluorescence method and total arsenic in groundwater was determined by field kit and cross-checked by Total Reflection X-Ray Fluorescence method at Chemistry Division, Atomic Energy Center, Dhaka, Bangladesh.

Keywords : groundwater contamination, arsenic determination, source of arsenic

[a] Department of Industrial Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand.

[b] National Metal and Materials Technology Center, Bangkok, Thailand.

*Author for correspondence, e-mail : torra@chmai.loxinfo.co.th

Interfaces between a borosilicate glass and a Fe-Ni-Co alloy joined by direct fusion of glass to metal were studied by using scanning electron microscopy and energy dispersive X-ray microanalysis to examine interfacial characteristics and the mechanism of adhesion. Both chemical and mechanical bondings were found to contribute to adhesion. Migration of Fe into the glass phase and penetration of glass into the alloy causing mechanical interlock were observed in the case of joining without pre-oxidation of the alloy surface. Where the alloy surface was pre-oxidised, an oxide layer and migration of Fe and Co into the glass phase were found. For the case of no pre-oxidation, the alloy acted as a sink for site vacancies, but when the alloy was pre-oxidised, then the sink was in the oxide layer.

Keywords : Interface, borosilicate glass, Fe-Ni-Co alloy, direct fusion

Department of Physics, Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand.

e-mail: sukanda_jian@hotmail.com

The growth behavior of cracks in both poled and unpoled Lead-Zirconate-Titanate (PZT) piezoelectric ceramics was studied by using indentation technique. The values of Vickers hardness (H_v) and fracture hardness (K_IC) of this material were measured. In the poled samples, the radial crack length was found to be dependent on the orientation of ferroelectric dipole moments with respect to the poling direction, which affected the K_IC value. Thus K_IC shows significant anisotropy in poled samples. The crack profiles produced by the indentaions both on the indented surface and beneath the indentation were studied in both poled and unpoled samples in order to observe the crack behavior. The physically deformed zone below the indentation presented anisotropy in the poled sample, this could possible explain the anisotropy observed in K_IC value.

Department Mathematics, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand.

*Author for correspondence, e-mail : scmti004@chiangmai.ac.th

Keywords : co-semisimple module, multiplication module.

[a] Faculty of Computer Science and Information System, Universiti Teknologi Malaysia, Malaysia.

[b] Faculty of Sciences & Technology, Universiti Kebangsaan Malaysia, Malaysia.

*Author for correspondence, e-mail : mariyam@fsksm.utm.my

In Malaysian’s economy there are many factors needed to be considered in order to maintain the economic growth. For instance, prices, interest rates, and employment level always react with each other in the form of nonlinear relationship. In a nonlinear system, the effect depends on the values of other inputs, thus the relationship is a higher-order function. Neural network (NN) is an approach that can cater nonlinear problems, and an implementation of an algorithm inspired by research into the brain. NN is a technology in which computer learns directly from data, thereby assisting in classification, function estimation, data compression, and similar tasks. In this paper, we introduce neural network model with an improved backpropagation error function for predicting profitability of selected firms at Kuala Lumpur Stock Exchange (KLSE). The results obtained are compared to the standard backpropagation model with mean square error function (MSE).

Keywords : neural network; improved backpropagation, profitability, mean square error.

School of Information Technology, Universiti Utara Malaysia, Kedah, Malaysia

*Author for correspondence, e-mail: ruhana@uum.edu.my

Obtaining a good multilayer perceptron prediction model depends on the choice of data preprocessing techniques. In this study, data were preprocessed, represented and scaled, using two data representation techniques combined with four data scaling techniques. The prediction capability of the network can be enhanced using the proposed techniques.

Keywords : multilayer perceptron, data scaling, data normalizing, data pre-processing.

Research Unit of Mathematical Statistics and Its Application, Department of Statistics,

Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand.

**Author for correspondence, e-mail : sciskhnb@chiangmai.ac.th

Sensitive questions could be considered too personal for the respondent to answer truthfully or, indeed answer at all. Sample surveys using direct questions always show biased estimators in the results. A randomized response technique was suggested by Warner in 1965. Five years later, Greenberg et al. developed the technique called "unrelated question randomized technique". The two techniques are always used with qualitative data. The technique used in this paper is modified from the unrelated question randomized technique. Two sensitive questions are asked, one in positive form and the other in negative form. Respondents draw one question by using a randomized device and then answer the question truthly either as "Yes" or "No". Statistics and probability are used to find two unbiased estimators of the true proportions.

Keywords : randomized response model, sensitive question, device of randomness, unbiased estimator.

* This paper was presented at the 27^th Congress on Science and Technology of Thailand, 16-18 October 2001, Hat Yai City, Songkhla Province, Thailand.