• 한국초전도학회:학술대회논문집
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• v.15
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• pp.57-57
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• 2005

• Composites Research
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• v.35 no.6
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• pp.469-476
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• 2022

In this paper, the microwave absorbing characteristics after the impact of the radar-absorbing structure (RAS) consisting of periodic pattern sheet (PPS) and glass fiber-reinforced plastic (GFRP) were experimentally investigated. The fabricated RAS effectively absorbed the microwave in the X-band (8.2-12.4 GHz). In order to induce the damage to the RAS, a low-velocity impact test with various impact energy of 15, 40, and 60 J was conducted. Afterward, the impact damage was observed by using visual inspection, non-destructive test, and image processing method. Moreover, the absorbing performance of intact and damaged RAS was measured by the free-space measurement system. The experiment results revealed that the delamination damage from the impact energy of 15 J did not considerably affect the microwave absorbing performance of the RAS. However, fiber breakage and penetration damage with a relatively large damaged area were occuured when the impact energy was increased up to 40 J and 60 J, and these failures significantly degraded the microwave absorbing characteristics of the RAS.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.21 no.1
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• pp.27-34
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• 2015

Heating patterns depending on the packaging materials were examined in order to investigate the causes of thermal deformation of packages used for ready-to-eat foods for microwave heating due to the non-uniformity of microwaves. Physical properties including tensile strength, heat-resistance and elongation of four different CPP grades were compared. High retortable CPP had higher sealing strength and heat resistance compared to the conventional CPPs. All CPP samples tested were proved to have melting temperatures around $160^{\circ}C$. However, they were all thermally deformed by microwave heating due to a limited penetration of microwave and non-uniform heating within the spicy sauce of high viscosity contained high salt, especially on the above the filling line and sealing edge of pouches. When the laminated stand-up pouches composed of G-PET/PET/PET/CPP and G-PET/PET/NY/CPP were retorted and microwaved, significant deformations were noticed in both samples after retorting. Besides, pouches contained titanium dioxide showed more intense thermal deformation than the control. When the $10{\mu}m$ aluminium foil was affixed on the pouch, small thermal deformation was observed only in the bottom layer. More studies are required to prevent the thermal deformation of packaging materials used for RTE foods during microwave heating by developing the technologies to increase the thermal stability of CPP layer and the modification of packaging design to modify the microwave access into the package.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.766-771
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• 2016

This study examined the long-term durability of PC boxes, which was manufactured by low-carbon eco-friendly concrete using an alternative binder to cement and alternative fine aggregate to sand and microwave heat curing system to reduce the construction cost of a near-surface transit system. Based on the test results, the initial compressive strength of microwave heat cured concrete was higher than that of the steam cured concrete, but those were similar in the long-term age. In addition, there was no significant difference between the two curing conditions in the chemical resistance and the freeze-thawing resistance, and the chloride ion penetration level of the concrete cured by two methods was very low. Therefore, low-carbon eco-friendly concrete and microwave heat curing technology are expected to contribute to the economic construction of a near-surface transit system, and reduce carbon dioxide emissions and environmental impact.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.1
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• pp.101-110
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• 2022

In this study, water content tests were performed on various fresh concretes subjected to different binder compostions to review the estimation errors and reliability of water content test methods. Micro-oven drying method, air-meter method, capacitance method and microwave penetration method were used to estimate water content of fresh concrete. Errors in water content estimation were analyzed by each test method. Regardless of the test method of water content, the estimation error was less than 5 %, and in the case of the test using mortar, the error in the estimation value was relatively large. In addition, based on the test results of water content of various concrete, the probability density function in which the estimation error for each test method becomes the population was analyzed. Water content test methods of fresh concrete which using concrete samples showed high estimate reliability of 97 % within the estimation error range of ± 10 kg/m³. On the other hand, the reliability of water content test method using mortar samples was lower.

• Proceedings of the KSRS Conference
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• 2006.03a
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• pp.145-148
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• 2006

새로 조성된 간척지 갯벌이 건조 수축하면 지반 침하와 더불어 토양 내로의 마이크로파의 침투 깊이가 증가한다 따라서 인공위성 DInSAR를 이용하여 지반 침하량을 구하고자 할 때, 건조 시 동시에 발생하는 마이크로파의 개펄 침투 현상을 규명하여 보정해 주어야 한다. 이를 위하여 다편광 산란계(Polarimetric Scatterometer)를 구성하여 건조 개펄에 대한 실내실험을 실시하였다. PolScat의 구성은 5.0-5.6GHz 대역의 dual-polarization square horn antenna를 사용하였으며 Agilent 8753ES 벡터 네트워크 분석기를 사용하였다. 길이 2m, 폭 2m, 높이 20cm의 개펄 샘플을 약 6주 동안 실내에서 건조시켜 위상을 측정한 결과 지반 침하와 함께 약 4mm의 마이크로파 투과현상이 발견되었다. 따라서 인공위성 DInSAR 지반침하량 계산에 있어서 반드시 토양 수분에 따른 마이크로파의 토양 침투 깊이를 보정해 주어야 함이 밝혀졌다.

• Korean Journal of Food Science and Technology
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• v.28 no.3
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• pp.470-474
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• 1996

The dielectric properties, dielectric constant (${\varepsilon}‘$) and loss factor (${\varepsilon}’$), of skin and pulp of fresh ginseng were measured from $25^{\circ}C$ to $67^{\circ}C$ using an open-ended coaxial probe technique for 915 MHz and 2450 MHz. Pulp and skin had dielectric constant of $30{\sim}64$ and loss factor between 10 and 20, each variable having a respective frequency dependence typical of materials with high water content. Although the loss factor was nearly constant, the dielectric constant increased as moisture content increased. The dielectric constant of ginseng pulp increased as temperature increased (temperature ${\leq}56^{\circ}C$), but any significant differences were not found in skin dielectric properties. Penetration depth for fresh ginseng were about 2 cm at 91.5 MHz and 1cm at 2450 MHz.

• Journal of the Korean Wood Science and Technology
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• v.41 no.3
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• pp.234-246
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• 2013

It was found that test piece heated rapidly by 3 kW microwave for 5 minutes satisfies the targeted temperature and the percentage of moisture content, and the highest rate of weight increase is obtained in case of 120 minute immersion in the mixture of phosphates and heterocyclic compounds, from the result of such analysis as: kiln drying schedule, flame retardent by flammability test, insect resistance by termites, and permeability of combined penetrant for the wood after assigning multifunctional finish by immersing conifer structural frame, which is used for the frame work of wooden house and indoor/outdoor finishing in flame retardant and insect repellent materials mixture with the remaining heat of microwave. In addition, after a test of flame retardent treated item, it was identified that every mixture of phosphates corresponds with the standards of flame retardent, and upon investigation of moritality of 7 days after putting termites, it was showed that test piece immersed in the mixture of phosphates and heterocyclic compounds has the best characteristics, showing over 96% of high moritality. From the analysis of inward permeability of combined penetrant for the wood, it was decided that excellent performance in the flame retardent and insect resistance of the wood revealed due to full penetration of combined penetrant as it was found that combined penetrant penetrated through the whole inner cells of the wood.

• Korean journal of food and cookery science
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• v.28 no.6
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• pp.857-863
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• 2012

This study prepares dried sweet pumpkins to optimize pretreatment conditions of blanching, steaming and microwave heating and to investigate the quality characteristic of each method. The sweet pumpkin blanching treatment of moisture content decreased gradually with increasing temperature, and soluble solids, and weight loss was increased. Color temperature is lower, and a higher value of L value and b value increased. As for the sweet pumpkin steaming treatment of moisture content, it was observed that the longer the steaming time was decreased, sugar content was increased. Change of color in the L value, the longer the steaming time a and b values. Also, as for the microwave treatment of the sweet pumpkin, the longer the time the moisture content decreased, it slightly increased soluble solids and weight loss. Blanching showed the lowest hardness of texture, followed by steaming, and microwaves, in order. Penetration per 20 hours per type was determined by sensory evaluation of sugar, and sugar:fructose(1:2)ratio were higher in the composition.