• 한국음향학회지
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• 제37권5호
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• pp.338-342
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• 2018

상하층 간 공동주택의 바닥충격음 문제를 해결하기 위해 국토교통부에서는 바닥충격음 레벨에 영향을 미치는 완충재에 대한 물성 기준도 함께 고시하고 있다. 완충재에 대한 물성 기준중 가열전후 동탄성계수, 손실계수는 특히 바닥충격음과 가장 연관되어 있다. 따라서 본 연구에서는 기준에서 명시하고 있는 $70^{\circ}C$의 온도 조건을 기준으로 $10^{\circ}C$씩 증가시키고 $10^{\circ}C$씩 저감시켜 온도변화에 따른 동탄성계수 및 손실계수에 대하여 변화율을 검토하였다. 총 8가지 종류의 시료에 대하여 동탄성계수 및 손실계수 측정 방법은 펄스 가진법으로 수행되었으며 결과 산출방법은 감쇠 진동 파형을 이용한 시계열 해석법으로 산출하였다.

• 한국기계가공학회지
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• 제15권4호
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• pp.83-92
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• 2016

The Korean government has been making efforts to use renewable energy to reduce the consumption of fossil fuels for the heating system in greenhouses. The number of greenhouses that installed a geothermal heat pump system is 201 EA with the volume of 132.8 ha and 108,467kW from 2010-2014. The geothermal system, called a shallow geothermal system, with the temperature of $10-20^{\circ}C$ has accessories composed of a BHE and heat pump. Moreover, it is necessary to have a wide area to install the BHE and to drill to the depth of 200 m. On the other hand, even though the deep geothermal system needs a high drilling cost to obtain the temperature of $40-150^{\circ}C$, the system has the advantages of the small area required for the BHE and operation without a heat pump. In this study, the temperature of the return water and heat capacity were measured to obtain the geothermal energy efficiently on the condition of the water flow being changed in the BHE. The temperature according to the return water changes through the heat conduction based on the increase of ground temperature up to the underground depth has been calculated to conduct a simulation and is compared with the field experiment test results.

• 한국재료학회지
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• 제20권12호
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• pp.636-639
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• 2010

ZnO thin films were prepared on a glass substrate by radio frequency (RF) magnetron sputtering without intentional substrate heating and then surfaces of the ZnO films were irradiated with intense electrons in vacuum condition to investigate the effect of electron bombardment on crystallization, surface roughness, morphology and hydrogen gas sensitivity. In XRD pattern, as deposited ZnO films show a higher ZnO (002) peak intensity. However, the peak intensity for ZnO (002) is decreased with increase of electron bombarding energy. Atomic force microscope images show that surface morphology is also dependent on electron bombarding energy. The surface roughness increases due to intense electron bombardment as high as 2.7 nm. The observed optical transmittance means that the films irradiated with intense electron beams at 900 eV show lower transmittance than the others due to their rough surfaces. In addition, ZnO films irradiated by the electron beam at 900 eV show higher hydrogen gas sensitivity than the films that were electron beam irradiated at 450 eV. From XRD pattern and atomic force microscope observations, it is supposed that intense electron bombardment promotes a rough surface due to the intense bombardments and increased gas sensitivity of ZnO films for hydrogen gas. These results suggest that ZnO films irradiated with intense electron beams are promising for practical high performance hydrogen gas sensors.

• 한국재료학회지
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• 제12권12호
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• pp.897-903
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• 2002

Morphological evolution and growth mechanism at the solid/liquid interface during solidification were investigated in the Ni-base superalloy GTD111M by directional soldification and quenching(DSQ) technique. The experiments were conducted by changing solidification rate(V) and thermal gradient(G) which are major solidification process variables. High thermal gradient condition could be obtained by increasing the furnace temperature and closely attaching the heating and cooling zones in the Bridgeman type furnace. The dendritic/equiaxed transition was found in the G/V value lower than $0.05$\times$10{^3}^{\circ}C$s/$\textrm{mm}^2$, and the planar interface of the MC-${\gamma}$ eutectic was found under $17 $\times$ 10{^3}^{\circ}C$ s/$\textrm{mm}^2$. It was confirmed that the dendrite spacing depended on the cooling rate(GV), and the primary spacing was affected by the thermal gradient more than solidification rate. The dendrite lengths were decreased as increasing the thermal graditne, and the dendrite tip temperature was close to the liquidus temperature at $50 \mu\textrm{m}$/s.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 춘계 학술논문 발표대회
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• pp.35-41
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• 2008

Qualitative enhancement of dwelling life has changing the recognition for the environment friendly wood which is being highlighted for its usage as an interior materials. This trend may prove the excellent performance of wood whose inherent characteristics has its comfortable, mild feeling of material, sound resistance and stabilities and the market of interior woods including floor, moulding and wooden panel as finishing interior materials is growing sustainably. However, since this materials is vulnerable to humidity and flame, waterproofing and flame retarding stability, an essential condition for interior materials, together with maintenance, are the main topics to be resolved. From the above-mentioned results, as a result of waterdrop contact angle, wood absorption volume and water content percentage test and the performance test of the processed materials after flame retardant, though there was some submerging time changes among types of woods for ensuring waterproofing performance improvement but as time passes, similar tendency was noticed to be formulated. As the submerging time is increased, so does the absorption volume and accordingly optimal level of range is judged to be drawn in order to ensure excellent performance, taking optimal economy into consideration. Therefore, it is considered that above-mentioned woods could be utilized for waterproof and flame retardant processed interior materials using uniform microwave and in order to put this technology into practical application, a research by way of diversified performance proving is required to be carried out.

• 한국산학기술학회논문지
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• 제16권10호
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• pp.7138-7145
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• 2015

본 연구에서는 KS C 9306에 따른 난방 제상능력 시험조건(건구온도 $2^{\circ}C$/습구온도 $1^{\circ}C$)에서 확대모형이 아닌 실제 열교환기의 전방에 디지탈 현미경과 광센서의 발광부와 수광부를 나란히 설치하여 광센서 출력전압과 서리 높이간의 연관성을 규명하기 위한 실험을 수행하였다. 150개의 실험 데이터로부터 서리높이를 예측할 수 있는 선형 상관식을 개발하여 계산한 결과, 측정값의 54%가 상관식으로 예측한 값의 ${\pm}10%$ 이내에서 일치하였으며 서리 높이가 0.3mm 이상의 실험데이터에서는 데이터의 90% 이상이 ${\pm}10%$ 이내에서 일치하였다. Xiao 등의 상관식과 비교하였을 때 출력전압 변화에 따른 서리 높이의 변화를 나타내는 기울기는 2.3% 오차 범위에서 일치하였으나 Xiao 등의 상관식은 실제 열교환기가 아닌 모사 열교환기를 사용한 이상적인 조건에서 개발되었기 때문에 절편 값에서는 큰 차이를 보였다.

• 한국분말재료학회지
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• 제22권4호
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• pp.283-288
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• 2015

Two sintering methods of a pressureless sintering and a spark-plasma sintering are tested to densify the Fe-TiC composite powders which are fabricated by high-energy ball-milling. A powder mixture of Fe and TiC is prepared in a planetary ball mill at a rotation speed of 500 rpm for 1h. Pressureless sintering is performed at 1100, 1200 and $1300^{\circ}C$ for 1-3 hours in a tube furnace under flowing argon gas atmosphere. Spark-plasma sintering is carried out under the following condition: sintering temperature of $1050^{\circ}C$, soaking time of 10 min, sintering pressure of 50 MPa, heating rate of $50^{\circ}C$, and in a vacuum of 0.1 Pa. The curves of shrinkage and its derivative (shrinkage rate) are obtained from the data stored automatically during sintering process. The densification behaviors are investigated from the observation of fracture surface and cross-section of the sintered compacts. The pressureless-sintered powder compacts show incomplete densification with a relative denstiy of 86.1% after sintering at $1300^{\circ}C$ for 3h. Spark-plasma sintering at $1050^{\circ}C$ for 10 min exhibits nearly complete densification of 98.6% relative density under the sintering pressure of 50 MPa.

• 대한지리학회지
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• 제43권5호
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• pp.701-714
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• 2008

본 연구는 미국 지역을 사례로 겨울철 및 여름철에 장기간 지속되는 이상고온기 발생에 유리한 종관 규모의 매커니즘을 밝힌다. 여름철 이상고온기는 주로 미국의 남중부 지역에서 발생하는 반면, 겨울철 이상고온기는 미서부 지역에서 발생한다. 지상 및 상층 기압장 자료 분석 결과, 이러한 이상고온기는 태평양과 대서양의 아열대 고기압들의 활동과 밀접하게 관련되어있다. 장기간 지속되는 여름철 이상고온기는 중층 및 상층 블러킹 고기압의 활동에 의해 형성되는 매우 안정된 대기 조건하에서 주로 발생한다. 또한 이 시기에는 지표강제력으로 상대적으로 높은 보웬비(Bowen ratio)가 나타나지만, 따뜻한 공기의 이류의 영향은 크지 않다. 반면, 장기간 지속되는 겨울철 이상고온기는 블러킹 고기압에 의한 단열 기온 상승뿐만 아니라 따뜻한 공기의 이류의 복합적인 작용에 의해 나타난다. 그러나 이 시기의 지표 강제력의 영향은 약하다.

• 한국식품과학회지
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• 제17권6호
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• pp.447-453
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• 1985

숙성중 무우 김치 조직의 연부현상을 방지하기 위하여 예비열처리와 $CaCl_2$의 효과를 조사하고 이를 이용하여 무우조직의 경도가 높은 김치를 제조하였다. 무우조직중의 펙틴분해효소인 폴리갈락투로나제(PG)는 펙틴에스테라제(PE)보다 더 낮은 농도의 $CaCl_2$에서 저해되었고, PE의 최적온도는 $50{\sim}55^{\circ}C,$ PG는 $45^{\circ}C$이었다. 따라서 0.05M $CaCl_2$용액에서 $55^{\circ}C$로 2시간동안 열처리 하여 PE는 활성화 시키고 PG는 억제시킬 수 있었다. 최적조건하에서 예비열처리를 하여 김치를 제조한 후 냉장고($4{\sim}10^{\circ}C$에서 저장하려면 pH, 환원당, 경도, 펙틴분해효소의 역가 그리고 펙틴물질의 변화를 측정하였다. 처리구의 무우김치는 비교구보다 숙성중 계속해서 높은 경도를 유지하였고 조직내에 있는 PE는 숙성중 계속 감소하였으며 PG는 초기에는 감소하다가 저장 말기에 가서는 증가하였다. 저장중 펙틴물질 조성의 변화는 비교구가 처리구에 비해 열수가용 펙틴질이 더 많이 증가하였으며 Sodium hexa meta phosphate soluble 펙틴은 더 많이 감소하였다.

• 한국대기환경학회지
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• 제22권6호
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• pp.831-841
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• 2006

The study on school indoor air quality was carried out at classrooms, computer-rooms, laboratories and play- grounds for carbonyl compounds including formaldehyde during the winter time from November to December 2004 and during the summer time from June to July 2005. The sampling was conducted under the general school condition without any artificial intervention such as the sealing, ventilating or heating at indoor environments. The concentrations of formaldehyde at all types of indoor environments were lower than air quality standard of $120{\mu}g/m^3$ for public facilities. The mean concentrations of formaldehyde at indoors were $4.5{\sim}6.1$ times higher than those at outdoors. From the comparison between two year and one year old schools after construction, the concentrations of formaldehyde in two year old school were $30{\sim}38%$ lower than those in one year old school measured at classrooms and laboratories.