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Phetchaburi, Thailand

Khansalee E.,Chulalongkorn University | Nuanyai K.,Phetchaburi Rajabhat University | Zhao Y.,Chulalongkorn University
Engineering Journal

Our cities are surrounded by a large number of radio frequency (RF) signals broadcasted by various wireless systems. In order to enhance the efficiency of energy usage in addition to the purpose of communication, ambient RF energy harvesting systems are designed to harvest and recycle wireless energy for many applications such as battery chargers, sensor devices and portable devices. The main element of the ambient RF energy harvesting system is a rectenna which is the combination of an antenna and a rectifying circuit. Even though the ambient RF energy is widely broadcasted by many systems, the energy is extremely low. Therefore, high performance antenna and rectifying circuits have to be designed for supporting small incident power; also the number of frequency channels of the rectenna can enhance the performance and support different harvesting locations. This paper proposes a dual-band rectifier for RF energy harvesting which is designed to operate at 2.1 GHz and 2.45 GHz. The first channel can provide the maximum efficiency of 24% with 1.9 V of the output voltage at 10 dBm of input power. On the other hand, a maximum efficiency of 18% and 1.7 V of the output voltage can be achieved by the second channel at 10 dBm of input power. © 2015, Chulalongkorn University 1. All rights reserved. Source

Pasteurized palm sap is well known juice in many tropical countries. It has unique flavor and taste but is not available throughout year. Consequently there are many palm sap manufacturers trying to increase their production quantities by addition of other substances such as water and other cheaper syrups or sugar. The objective of this research was to discriminate the commercially pasteurized palm sap samples into adulterated and non-adulterated groups using their physical and chemical properties combined with canonical discriminant analysis. The result found that six from nine variables including total soluble solid, reducing sugar, titratable acidity, pH, L*, and b* values were selected for the discriminant analysis. A good discrimination between the non-adulterated and adulterated samples was attained by applying one canonical discriminant function, which provided 100% of the 14 palm sap samples correctly classified. While L* and b* values as well as total soluble solid were found to be the most important predictor variables for the classification of the adulterated palm sap samples, the reducing sugar, titratable acidity, and pH value were of the most significance for that of the non-adulterated ones. © All Rights Reserved. Source

Wiboonsirikul J.,Phetchaburi Rajabhat University | Mori M.,Kyoto University | Khuwijitjaru P.,Silpakorn University | Adachi S.,Kyoto University
International Journal of Food Properties

Okara was treated with subcritical water at temperatures ranging from 170 to 260°C for various times. After clarification, the extracts were analyzed for their protein and carbohydrate contents, DPPH radical scavenging activity, and antioxidative activity. The carbohydrate content significantly decreased with the increasing treatment temperature and time. The protein content, however, increased with the increasing treatment temperature and slightly decreased with a heating time longer than 10 min. The extract obtained from the subcritical water treatment at 240°C for 5 min, which would be used to evaluate the antioxidative activity, provided the relatively highest radical scavenging activity and the activity tended to decrease with the prolonging heating time and temperature. The extract also exhibited a suppressive activity to the autoxidation of linoleic acid with the increasing weight ratio of the extract to linoleic acid. The results clearly showed okara still contained highly valuable substances for human consumption. Copyright © 2013 Taylor & Francis Group, LLC. Source

Ketcham M.,KING.INFO | Yimyam W.,Phetchaburi Rajabhat University | Chumuang N.,Muban Chombueng Rajabhat University
Advances in Intelligent Systems and Computing

The segmentation is the first important step for optical character recognition (OCR) system. It separate the image text documents into line, characters and word. The accuracy of the recognition system mainly rely on the algorithm in segmentation. The challenge of segmentation is overlapping therefore this paper presents a new high performance algorithm in the segmentation on Palm leaf manuscript’s Isan Dhamma overlap characters. © Springer International Publishing Switzerland 2016. Source

Pitak P.,Mahanakorn University of Technology | Petpices E.-A.,Phetchaburi Rajabhat University | Withada J.,King Mongkuts University of Technology Thonburi | Smith E.-A.,Mahanakorn University of Technology
Journal of Hydrodynamics

Turbulent periodic flow, heat transfer, friction loss and thermal enhancement characteristics in a three-dimensional horizo- ntal square channel with broken V-ribs (B-VR) are numerically investigated. The computations are based on the finite volume method, and the SIMPLE algorithm with QUICK scheme is implemented. The B-VR were installed on both sides of a plate which was diagonally placed in a square channel to produce longitudinal vortex flows through the tested section. Effects of different open corner ratios (d/H 0, 0.01, 0.02, 0.03, 0.04 and 0.05) on heat transfer and pressure loss in the channel and the results of the B-VR are studied. The pitch ratio (PR = p/H) and blockage ratio (BR = p/H) of B-VRs were fixed at 1.0 and 0.15, respectively. As compared with the channel without V-rib, the one with B-VRs possessed considerably higher heat transfer and friction loss. It is observed that apart from the rise of Reynolds number, the reduction of the open corner ratios leads to an increase in the Nusselt number and friction factor due to the weaker turbulence and lower resistance to the flow. According to the computational results for B-VRs, the optimum thermal enhancement is found at d/H = 0. © 2016 Publishing House for Journal of Hydrodynamics. Source

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