• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.989-996
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• 2009

RF and microwave power is a basic quantity in electromagnetic metrology which linked directly to major electro-magnetic quantities such as attenuation, RF voltage, antenna characteristics and field strength. This paper deals with a power meter and power sensor with associated theory for RF and microwave power measurement. We study the theory and the key aspects in design of a 3.5 mm coaxial microcalorimeter which works from 50 MHz to 26.5 GHz as a primary microwave power standard.

• Food Science and Preservation
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• v.13 no.6
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• pp.732-739
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• 2006

This study was performed to investigate the changes in quality properties of extract from roasted Pleurotus eryngii by microwave-assisted extraction (MAE). MAE was carried out under different conditions including ethanol concentration, extraction time and microwave power. Total phenolics compound contents, electron donating ability (EDA) and nitrite-scavenging ability at pH 1.2 were high at 50% ethanol concentration. Superoxide dismutase (SOD)-like activity was high at 75% ethanol concentration. Soluble solid and total phenolics compound content decreased as extending extraction time up to 7 min. EDA decreased as increased extraction time. SOD-like activity and nitrite-scavenging ability were not significantly different. The highest soluble solid content, total phenolics compound content and EDA were obtained at 100 W extraction of microwave power. SOD-like activity was high at 25 W. But microwave power did not significantly affect the nitrite-scavenging ability.

• Journal of Biosystems Engineering
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• v.43 no.3
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• pp.237-246
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• 2018

Purpose: This study (a) investigated the effect of microwave power intensity and sample thickness on microwave drying characteristics of radish strips, and (b) determined the best-fit drying model for describing experimental drying data, effective moisture diffusivity ($D_{eff}$), and activation energy ($E_a$) for all drying conditions. Methods: A domestic microwave oven was modified for microwave drying and equipped with a small fan installed on the left upper side for removing water vapor during the drying process. Radishes were cut into two fixed-size strip shapes (6 and 9 mm in thickness). For drying experiments, the applied microwave power intensities ranged from 180 to 630 W at intervals of 90 W. Six drying models were evaluated to delineate the experimental drying curves of both radish strip samples. The effective moisture diffusivity ($D_{eff}$) was determined from Fick's diffusion method, and the Arrhenius equation was applied to calculate the activation energy ($E_a$). Results: The drying time was profoundly decreased as the microwave power intensity was increased regardless of the thickness of the radish strips; however, the drying rate of thicker strips was faster than that of the thinner strips up to a certain moisture content of the strip samples. The majority of the applied drying models were suitable to describe the drying characteristics of the radish strips for all drying conditions. Among the drying models, based on the model indices, the best model was the Page model. The range of estimated $D_{eff}$ for both strip samples was from $2.907{\times}10^{-9}$ to $1.215{\times}10^{-8}m^2/s$. $E_a$ for the 6- and 9-mm strips was 3.537 and 3.179 W/g, respectively. Conclusions: The microwave drying characteristics varied depending on the microwave power intensity and the thickness of the strips. In order to produce high-quality dried radish strips, the microwave power intensity should be lower than 180 W.

• Korean journal of food and cookery science
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• v.11 no.2
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• pp.98-103
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• 1995

The effect of blanching time, blanching water and power settings of microwave oven on the minerals retention in spinach and broccoli were investigated. The vegetables were blanched for 60, 120 and 180 sec, with water 0ml, 50ml and 100ml every 100 g of raw material at two different power settings (700w, 400w). The retention of minerals(Ca,K,Mg,Cu,Fe,Na,p) in spinach and broccoli were higher at the 400w power than 700w power level, regardless of blanching time. At the high power, the retention of minerals in spinach and broccoli were reduced remarkably as the blanching time increased. The reason for this is that the increasing power level results in greater water coming ou from the vegetable. Also, minerals in vegetable as coming out with this water loss in proportion to the blanching time.

• Journal of the Semiconductor & Display Technology
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• v.18 no.1
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• pp.21-24
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• 2019

In this paper, 5.8GHz 25W microwave wireless power transmission system was developed. The transmission system is composed of a signal generator, a 1W drive amplifier, a 25W power amplifier, and a circularly polarized transmission antenna. The receiving system was fabricated with an integrated receiver that combines a circularly polarized receiving antenna, a pass band filter, and an RF-DC converter. And a multi-integrated receiver had twelve parts, including an integrated receiver. Under the conditions, voltage and current were measured for the system at 5cm intervals from a minimum distance of 5cm to a maximum distance of 80cm. The power was calculated for the system. The results of the system are shown in tables and graphs. The power decreases with distance, but the power does not drop sharply due to a multi-integrated receiver.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.6
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• pp.872-877
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• 2017

Objective: In order to utilize fat from broiler byproducts efficiently, it is necessary to develop an appropriate rendering procedure and establish quality information for the rendered fat. A study was therefore undertaken to evaluate the influence of rendering methods on the amounts and general properties of the fat recovered from broiler skin. Methods: The yield and quality of the broiler skin fat rendered through high and lower energy microwave rendering (3.6 W/g for 10 min and 2.4 W/g for 10 min for high power microwave rendering (HPMR) and high power microwave rendering (LPMR), respectively), oven baking (OB, at $180^{\circ}C$ for 40 min), and water cooking (WC, boiling for 40 min) were compared. Results: Microwave-rendered skin exhibited the highest yields and fat recovery rates, followed by OB, and WC fats (p<0.05). HPMR fat had the highest $L^{\star}$, $a^{\star}$, and $b^{\star}$ values, whereas WC fat had the highest moisture content, acid values, and thiobarbituric acid (TBA) values (p<0.05). There was no significant difference in the acid value, peroxide value, and TBA values between HPMR and LPMR fats. Conclusion: Microwave rendering at a power level of 3.6 W/g for 10 min is suggested base on the yield and quality of chicken fat.

• Journal of Radiation Protection and Research
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• v.35 no.3
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• pp.99-104
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• 2010

The potential ability of environmental temperature to enhance the effect of microwave radiation (7 GHz) was experimentally studied for rabbit heating after simultaneous application of both agents. The tested ambient temperatures (30 and $38^{\circ}C$) didn't exert a considerable influence upon rabbit heat homeostasis after the used duration of exposure (3 hours and 15 minutes, correspondingly). The synergistic interaction of microwave irradiation and ambient temperature was demonstrated for rabbit heating. Power flux density of microwave irradiation was shown to be a determinant of the synergistic interaction effectiveness. For the fixed ambient temperature ($30^{\circ}C$), the synergism was shown to be observed only within a definite power flux density ($0-100\;mW{\cdot}cm^{-2}$), inside of which there was an optimal intensity ($20\;mW{\cdot}cm^{-2}$), which maximized the synergistic effect. Any deviation of the power flux density from the optimal value resulted in a reduction of the synergy. It is concluded that any assessment of the health or environmental risks should take into account the synergistic interaction between ambient temperature and microwave radiation.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.3
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• pp.225-230
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• 2018

This paper proposes a parametric design of an LLC resonant inverter used for a microwave oven. To improve the harmonic performance of the microwave oven, a current controller with a variable PI gain is proposed. Due to the recent strengthening of harmonics regulations, inverter control technology for microwave ovens is now required to satisfy harmonic performance. In an LLC resonant inverter, the voltage gain varies remarkably depending on the magnetron voltage, output power, and input voltage. To satisfy harmonic performance, a controller that can maintain operation in the zero-voltage switching (ZVS) region and control changes in voltage gain is required. The modified design of the LLC resonant inverter ensures ZVS operation even when the magnetron is heated. Application of the variable current controller improves harmonic control according to the instantaneous gain curve change. The validity of the proposed power control with a variable current controller is verified by experiments with a 1200 W microwave oven.

• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.427-433
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• 2005

The use of the microwave-assisted process for the extraction of effective constituents from ginseng was investigated at various operating conditions. The influence of solvent (ethanol-water, 50% v/v) to ginseng ratio, particle size and applied microwave power on the efficiency of extraction was examined. The microwave extraction system used was custom manufactured so that the intensity of microwave may be varied by using anode-voltage controller. It was found that the ratio of 6 : 1 (vol/mass) gave a good extraction efficiency. Small particle size gave high yield but it caused difficulties in the separation of solvent from the sludge. The higher power was no guarantee of the efficient extraction yield. The more important factor than the employed power was the adequate temperature under sufficient contact time. Using deionized-water as swelling agent, the degree of swelling of ginseng by microwave heating and conventional heating in water-bath was also studied. It was observed that the microwave heating enhanced the swelling much more than the conventional heating. It is believed that this enhanced swelling was responsible for the rapid microwave-assisted extraction rate.

• Journal of Biosystems Engineering
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• v.32 no.2 s.121
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• pp.121-129
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• 2007

This study was conducted to elucidate extraction efficiency by microwave technique in comparison with sonication technique for extraction of insecticide residue in pear. In the analysis of the extraction efficiency of microwave for a pear spiked with imidacloprid, the extraction efficiency by microwave power of 300 W with extraction temperature of $80^{\circ}C$, heating time of 1 to 3 minute was shown to be similar with the extraction time 20 minutes by sonication. The optimal condition. in consideration of economical condition and treatment time, for microwave extraction of imidacloprid in the pear were 300 watts of power supply, $100^{\circ}C$ of extraction temperature, 1 minute of heating time and 10 mL of acetone volume. A new microwave vessel was developed to rapidly process the sample of the insecticide imidacloprid residues in the pear. This vessel was designed to include a reaction chamber and a filtration equipment, and a gathering chamber. The system could curtail a pretreatment time to 21 minutes than sonication and 7.9 minutes than the previous microwave vessel.