• 한국음향학회지
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• 제14권6호
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• pp.13-20
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• 1995

본 논문에서는 열음향 냉장시스템을 실제로 설계, 제작하고 그 동작을 확인하였다. 제작된 시스템은 4인치의 중음부 스피커로 구동되며 스피커 하우징, 챔버, 스택하우징, 스택, 열교환기, 가는관, 그리고 공명구로 구성되었으며 내부에 10기압의 He을 채워 실험하였다. 실행 중 온도하강측정을 위하여 T 타입의 열전쌍을 열교환기에 부착하였고, 내부음압측정용 콘덴서 마이크로폰을 장착하였다. 스피커의 열손상을 막고 고온 열교환기를 냉각시키기 위하여 냉각수를 공급하였다. 실제 실험을 위하여 제작된 열음향기관의 전기적인 임피던스를 측정하여 공진특성을 파악하였는데, 실험 결과 설계치와는 약간 다르게 340Hz로 구동하는 것이 효율적이었다. 이러한 해석을 기초로 실제 냉장실험을 수행한 결과 $30^\circ{C}$의 조건하에서 340Hz, 50W로 구동하였을 때 $16^\circ{C}$의 냉장효과를 관찰하였다. 관찰된 냉각효과와 설계치의 차이를 규명하기 위하여 제작된 열음향기관의 미비점을 고찰하였는 바, 냉각부의 단열이 제일 중요한 문제임을 파악하였으며 그외의 보완이 필요한 사항은 이후의 진행될 연구의 과제로서 제시하였다.

• 한국진공학회지
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• 제14권3호
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• pp.119-125
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• 2005

원자로의 중성자 빔을 사용하는 수평형 반사율 장치는 중성자 고유의 투과성 및 낮은 에너지의 비파괴성과 함께 시편을 수평으로 놓을 수 있는 장점을 가지고 수 나노미터 이내의 박막의 두께와 밀도를 측정하기 위하여 활용되는 새로운 장치이다. 원자력연구소에 열 중성자를 기반으로 개발을 추진하고 있으나, 아직 국내에 설치되어 있지 않아서 장치의 개념 및 최적화를 위한 시뮬레이션이 시급하다. 따라서 열중성자에 해당하는 $2.5{\AA}$를 기반으로 몬테카를로 시뮬레이션을 이용하는 MCSTAS를 이용하여 장치의 개념을 설계하였다. 단색기와 collimator, 그리고 초거울등의 설계 및 각 변수들은 설계의 목표인 최대 Flux를 갖는 중성자 빔 세기를 고려하여 결정하였다.

• 산업식품공학
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• 제14권3호
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• pp.202-207
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• 2010

저온에서 미생물을 사멸시킬 수 있는 비열살균기술로 감압 플라즈마를 활용하고자 생성기체별 감압 플라즈마 특성을 비교하고 Escherichia coli 살균효과를 조사하였다. 1 Torr이하로 감압시킨 상태에서 공기, 산소, 질소를 350 mL/min으로 공급하며 플라즈마를 발생시킨 결과 아크발생 없이 균일한 플라즈마가 생성되었다. 감압 플라즈마에 의한 온도 상승은 5분 처리 시 ${10^{\circ}C}$ 내외, 10분 처리 시 ${25^{\circ}C}$ 미만이었으며, 기체 종류별로는 공기, 산소, 질소 순으로 상승도가 낮았다. 감압 플라즈마 5분간 처리로 E. coli는 5 log 이상 감소하였으며, 이후 감소율이 둔화되어 10분간 처리 후 6-7 log 정도의 감소를 보였다. 감압 플라즈마에 의한 E. coli 살균패턴은 살균속도가 높은 초기와 낮은 후기로 구분되는 2단계 1차 반응으로 확인되었으며, 초기 살균속도상수($k_{1}$)는 공기, 산소, 질소 순으로 감소하였다. 감압 공기플라즈마 살균의 작은 D값 또한 식품 표면의 오염도를 낮추기 위한 비열살균기술로서의 가능성을 제시하였다.

• 한국산업융합학회 논문집
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• 제21권6호
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• pp.265-271
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• 2018

DC-DC buck converter is a critical building block in the power management integrated circuit (PMIC) architecture for the portable devices such as cellular phone, personal digital assistance (PDA) because of its power efficiency over a wide range of conversion ratio. To ensure a safe operation, avoid unexpected damages and enhance the reliability of the converter, fully-integrated protection circuits such as over voltage protection (OVP), under voltage lock out (UVLO), startup, and thermal shutdown (TSD) blocks are designed. In this paper, these three fully-integrated protection circuit blocks are proposed for use in the DC-DC buck converter. The buck converter with proposed protection blocks is operated with a switching frequency of 1 MHz in continuous conduction mode (CCM). In order to verify the proposed scheme, the buck converter has been designed using a 180 nm CMOS technology. The UVLO circuit is designed to track the input voltage and turns on/off the buck converter when the input voltage is higher/lower than 2.6 V, respectively. The OVP circuit blocks the buck converter's operation when the input voltage is over 3.3 V, thereby preventing the destruction of the devices inside the controller IC. The TSD circuit shuts down the converter's operation when the temperature is over $85^{\circ}C$. In order to verify the proposed scheme, these protection circuits were firstly verified through the simulation in SPICE. The proposed protection circuits were then fabricated and the measured results showed a good matching with the simulation results.

• 식품과학과 산업
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• 제53권3호
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• pp.277-283
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• 2020

식품의 보존성 및 안전성 증대를 위해 살균이 필수적이다. 일반적으로 가열 살균 기술이 가장 많이 사용되고 있으나, 공정 중 식품의 품질 저하를 막기 위한 살균 기술로 신공정 기술을 활용한 비가열 살균 기술의 중요성이 대두되고 있다. 그 중에서도 초음파 기술은 특유의 캐비테이션 현상으로 미생물의 파괴가 촉진되어 살균 효과를 내는 것으로 알려져 있다. 초음파 기술 단독으로는 사멸 효과가 낮으며, 다양한 공정기술과 함께 적용하여 사멸 효과를 극대화할 수 있는 기술 개발을 위한 연구가 활발히 진행되고 있다. 초음파와 함께 처리할 수 있는 공정으로는 가열, 고압, 화학적 처리 등 전통적인 살균 방법 뿐 아니라 자외선 조사, PEF 등 신공정 기술이 있다. 초음파 기술을 적용한 다른 공정과 달리 살균 기술은 아직 실험실 수준에 머물러 있어 산업적 적용을 위한 장치의 개발, 최적 공정 확립 등 추가 연구가 필요하다.

• 한국지형학회지
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• 제25권4호
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• pp.89-101
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• 2018

In Mt. Halla, an arctic-alpine plant Diapensia lapponica var. obovata largely clings to rock surfaces. We observed the rock-surface temperatures of a rocky ridge on the summit area of the mountain from late April 2009 to early May 2010 in order to examine the diurnal and annual temperature variations and the thermal amplitude. We also investigated temperature regimes such as the frequency of freeze-thaw cycles and the temperature change, which might endanger the habitat through frost weathering. For comparison of slope aspects, temperature monitoring was carried out on the north and south faces of the same rocky ridge. The south face experiences the high daily maximum rock-surface temperatures and the high thermal amplitudes during the unfreezing season of May to November 2009. The temperature regimes are considered to exert physiological stress to the arctic-alpine plant. In addition, the south face shows the high frequency of freeze-thaw cycles during the seasonal freezing period of December 2009 to April 2010. This indicates that the south face is susceptible the exfoliation and granular disintegration of rock surfaces, which results in habitat destruction. As a consequence, the south face is believed to be less favorable for the establishment and growth of the arctic-alpine plant than the north face on the summit area of Mt. Halla.

• Medical Lasers
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• 제8권2호
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• pp.64-73
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• 2019

Background and Objectives The effectiveness of many physiotherapy modalities in reducing subcutaneous fat has been investigated in numerous previous studies. However, to the best of our knowledge, there have been no attempts to determine the effectiveness of physiotherapy modalities in body contouring. The present report determined the effect of 448-kHz capacitive resistive monopolar radiofrequency (CRMRF) in a porcine model. Materials and Methods This study investigated the effect of selective destruction of the subcutaneous fat layer in abdominal fat tissue using CRMRF. The effects of two types of CRMRF (capacitive electric transfer (CET) and resistive electric transfer (RET)) treatment were evaluated using regular digital photography in addition to thermal imaging evaluation, ultrasound measurement, hematological evaluation, and histologic analyses (H&E (hematoxylin and eosin), Oil red O, and immunohistochemistry staining). Results Preclinical evaluation was performed to obtain the data for comparison of the safety and efficacy of the subcutaneous fat reduction after applying CRMRF using CET and RET. After treatment, the thermal transmission was effective, and a 42-47℃ temperature change was observed in the fat layer while an approximately temperature of 42℃ was confirmed on the skin surface. Moreover, after the application of both types of CRMRF treatment, fibrotic septa were observed in the adipose tissue induced by heat at the treatment sites. TUNEL staining was also performed to confirm the process of apoptosis in the adipocytes. Conclusion These results suggest that both CET and RET for CRMRF treatment are safe and effective for subcutaneous fat reduction in a porcine model.

• 대한소아치과학회지
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• 제24권1호
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• pp.139-147
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• 1997

Argon laser used in this case report, is special in having two wavelength of 488, 514nm blue-green visible light spectrum. Blue light is used for composite resin polymerization and caries detection. Green light is used for soft tissue surgery and coagulation. Maximum absorption of this laser light occurs in red pigmentation such as hemoglobin. The argon laser may be well-suited for selective destruction of blood clots and hemangioma with minimal damage to adjacent tissues. Argon laser light penetrates tissue to the 1 mm depth, so its thermal intensity is lower than $CO_2$ laser light. Also, due to its short wavelength it can be focused in a small spot and even single gene can be excised by this laser and microscopy. After applicating argon laser to 4 patient for surgical procedure and to 1 patient for curing the composite resin, following results were obtained. 1. Improved visibility were gained due to hemostasis and no specific technique were needed according to easy recontouring of the tissue. 2. Ability to use by contact mode, tactile sense was superior but tissue dragability and accumulation of tissue on the tip needed sweeping motion. 3. Additive local anesthetic procedure was needed. 4. No suture and less curing time reduced chair time, this made argon laser available in pediatric dentistry.

• 상하수도학회지
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• 제32권3호
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• pp.269-277
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• 2018

Burials for the rapid disposal of carcasses have diverse and profound effects on the rural living condition, natural environment, and local economy throughout construction, management and final destruction of burials. In this study, possible residue excavated from standard burials, storage using FRP (Fiberglass Reinforced Plastic) tanks, and microbial-treated burials are characterized as carcasses, contaminated soil by leachate, and wasted plastic film. Treatment technologies for volume reduction of the residue including composting, rendering, and thermal hydrolysis were investigated. If the solid and liquid residues generated during volume reduction treatment are directly transferred to the environmental facilities, it may cause disorder due to high concentrations of organics, antibiotics, and lipid. Benefits and drawbacks of composting as a volume reduction techniques are extensively investigated. We also discussed that proper treatment of excavated soils and the reusing the treated soil as agricultural purpose. For the protection of public health and worker's hygiene, treatment criteria including produced residue qualities, and quality standards for the treated soil as agricultural use are required. In addition, Scientific manual for the proper treatment of residues is required. It is necessary to consider the establishment of a pretreatment facility to the occurrence of large-scale residue treatment.

• 한국농공학회논문집
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• 제49권5호
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• pp.23-30
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• 2007

This research was to evaluate the shrinkage and durability performance of latex modified repair mortar and to improve the service lift of the agricultural concrete structures. The shrinkage characteristics of the repair material creates the delamination of repair materials and existing concrete. It may reduce the service life of structures. Also the reduction of durability performance of the repair materials induces the destruction of the repaired concrete structures at early stage. In this research, plastic and drying shrinkage, thermal expansion coefficient for shrinkage properties, durability performance, permeability, repeated freezing and thawing, and resistance of chemical solution test were performed. Test results showed that the latex modified repair mortar indicated the shrinkage amount which the delamination does not happen, and the latex modified repair mortar appeared excellent long-term durability performance which can increase the service life.