• Journal of the korean Society of Automotive Engineers
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• v.6 no.2
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• pp.14-19
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• 1984

종래에 많이 사용된 각양의 계측 방법을 일일이 설명하는 것은 본 해설의 목적이 아니기 때문에 개략적으로 분류하여 설명하면 다음과 같다. 1) 시간 평균유속은 주로 프로브(probe)를 경유하여 동압과 정압의 측정에 의하여 수행되어 왔다. 연소반응이 있으면 밀도의 변화가 있게 되는데 밀도는 후술하는 농도의 계측과 온도의 계측에 의하여 정해져 동압과 정압으로부터 유속으로 변환된다. 시간분해능이 높은 비접촉식(직접 프 로브를 측정부에 삽입하지 않는 방법) 유속측정이 가능한 방법으로는 레이저 도플러 유속계 (Laser Doppler Velocimetry, 이하 LDV로 표현)를 들 수 있다. LDV는 압력측정에 의한 유속 산출법에서와 같은 온도 및 농도 등의 부수적인 계측이 필요없이, 직접 유속을 검출할 수 있으며 또한 검정이 필요없는 절대유속 측정이 가능하며 현재 연소반응이 있는 흐름에 대한 대부분의 연구에 적용되고 있는 실정이다. 2) 시간평균 화학종 농도측정에 가장 많이 쓰이는 방법은, 연소가스를 채취하여 가스 크로마토 그라프(Gas Chromatograph)로 분석하는 것을 들 수 있다. 한편, 시간 분해능이 높은 화학종 농 도의 계측은 레이저를 사용하여 각 화학종의 발광, 산란 및 흡수성을 이용, 측정한다. 3) 온도측정은 대부분 열전대를 사용하고 있다. 그러나 이 방법은 직접 프로브를 삽입해야 하므로 사용한계의 범위가 지극히 좁으며, 연소반응이 일어나므로 프로브 자체의 촉매반응 및 복사 열전달에 의한 보정 등이 사용상 큰 문제로 제기된다. 그러나 최근 레이저 이용기술의 발달로 (2)항에서의 농도 계측과 같이 반응기체의 온도 및 성분의 동시측정이 가능한 방법도 점차 현 실화 되어가고 있다. 그 대표적인 예로 CARS법(Coherent Anti-Stokes Raman Spectroscopy)을 들 수 있다. 이상으로부터 연소반응이 일어나는 흐름에서의 각종 계측에서는, 비접촉 측정의 가능성과 시간 공간 분해능의 특징으로 미루어 앞으로는 레이저를 이용한 계측 방법이 그 주류를 이룰 것으로 사료된다. 우선 본 해설은 기체의 온도 및 농도의 광학적 측정방법중 Raman산란광 검출법에 대하여 실제로 측정하는 입장에서 간단히 소개한다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.2
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• pp.154-160
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• 1982

One dimensional unsteady heat conduction was studied on soybean curd as a water-protein-fat food system. This heterogeneous soybean curd could be treated as homogeneous material as for the unsteady heat conduction by 'effectiver' thermal diffusivity. Measurements were made with a apparatus designed and constructed by the author and also made with ice to establish the reliability, the reproducibility and the accuracy of the apparatus. It was found that the effective thermal diffusivity of soybean curd was substantially dependent on the fraction of protein and fat as well as water.

• Journal of Sensor Science and Technology
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• v.1 no.1
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• pp.77-83
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• 1992

A primary standard of ac current at low frequency is derived from the standard of dc current by ac-dc transfer instrument. A set of 15 thermal current converters(TCCs) have been constructed as the primary current standards from 5 mA to 20 A at the frequency range of 10 Hz to 100 kHz. It is evaluated that the uncertainties for the maintenance and dissemination of ac current standard are less than 52 ppm up to 20 mA and 20 kHz, 60 ppm up to 100 mA and 20 kHz, and rising to 200 ppm at higher currents and frequencies.

• Journal of the Korean GEO-environmental Society
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• v.20 no.1
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• pp.51-56
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• 2019

This paper presents a method to deice concrete pavement with carbon nanotube(CNT) as an heating material so as to avoid the adverse effects of conventional deicing method such as salt on the structure, function and environment. To this end, laboratory tests integrated with numerical simulations were conducted. In the laboratory tests, the CNT was embedded inside the concrete slab and generated the heat up to the target temperature of $60^{\circ}C$ in the freezer at temperature of $-10^{\circ}C$. Then, the surface temperature was measured to investigate how far the heat transfers on the surface at temperature of above $0^{\circ}C$. Also, three different spacings of 15, 20 and 30cm between CNTs were conducted to determine the maximum allowable spacing of CNT. Along with these experimental tests, heat transferring analysis conducted to validate the test results.

• Composites Research
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• v.37 no.6
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• pp.435-440
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• 2024

In this study, an aluminum metal matrix composite (AMC) with uniformly dispersed B₄C (boron carbide) and cBN (cubic boron nitride) particles was fabricated using a stir casting process followed by hot rolling. The microstructure, thermal conductivity, relative density, and thermal neutron absorption characteristics of the composite were analyzed. The volume fraction measured through image analysis was nearly identical to the target volume fraction of the reinforcement, confirming an even distribution of the reinforcing particles. The thermal conductivity and thermal neutron absorption capacity of the AMC reinforced with B₄C and cBN particles were 152 W/mK and 93.8%(@1.58 mm), respectively.

• Journal of the Korean Geotechnical Society
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• v.37 no.8
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• pp.51-58
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• 2021

South Korea, as the 10th country to join the Artemis program led by NASA, is actively supporting various researches related to the lunar exploration. In particular, the utilization of water as a resource in the Moon has been focused since it was discovered that ice exists at the lunar pole as a form of frozen soil. Information on the thermal conductivity of lunar regolith can be used to estimate the existence for ice water extraction by thermal mining. In this study, the vacuum pressure effect on thermal conductivity of KLS-1 was investigated with a DTVC (Dusty Thermal Vacuum Chamber). The reliability of KLS-1 was reconfirmed through comparison with thermal conductivity of known standard lunar regolith simulants such as JSC-1A. An empirical equation to assess thermal conductivity considering dry unit weight and vacuum pressure was proposed. The results from this study can be implemented to simulate lunar cryogenic environment using the DTVC.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.4
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• pp.182-189
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• 2021

Porous ceramics were manufactured using the foaming method for the development of inorganic insulating materials. Silica fume and SiO₂ were used as main raw materials, and bentonite was used as a rapid setting agent for uniform structure formation of porous ceramics. The porous ceramics were sintered at 1200℃, and porosity, density, compressive strength, microstructure and thermal conductivity were analyzed. As the content of silica fume to SiO₂ of the porous ceramics increased 70 to 90 %, the specific gravity increased from 0.63 to 0.69, and the compressive strength increased from 9.41 Mpa to 12.86 Mpa. But, the porosity showed a tendency to decrease from 72.07 % to 70.82 %, contrary to the specific gravity. As a result of measuring the thermal conductivity, the porous ceramic with a silica fume content of 70 % showed a thermal conductivity of 0.75 to 0.72 W/m·K at 25 to 800℃, respectively, and, another that a silica fume content of 90 % showed a 0.66~0.86 W/m·K. So the lower the silica f ume content, the lower the thermal conductivity, which was conf irmed to be consistent with porosity result. As a result of microstructure analysis using SEM (Scanning Electron Microscope), pores in the range of tens to hundreds ㎛ were observed inside and outside the porous ceramic, and it was confirmed that the pore distribution was relatively uniform.

• Resources Recycling
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• v.17 no.4
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• pp.30-36
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• 2008

The preparation of porous lightweight materials as well as the measurement of physical properties has been performed by using SSA(sewage sludge ash) as the raw material. For this aim, two types of lightweight filler, that is, perlite and silica sphere were employed respectively and bentonite was also used as an inorganic binder. The properties of lightweight specimen calcined at 1,000 were measured in terms of density, compressive strength, thermal conductivity and sound absorption to examine the effect of material composition as well as the preparation condition on the properties of lightweight material. As a result, the density of specimen prepared with perlite was ranged from 1.23 to $1.37g/cm^3$ and the compressive strength was ranged from 242.3 to $370.5kg/cm^2$. In case of specimen prepared with silica sphere, it was found that the compressive strength was less than $100kg/cm^2$ even though density was lower than that of specimen with perlite. As far as the thermal conductivity of specimen was concerned, it was ranged from 0.3 to $0.5W/m^{\circ}K$ depending on material composition so that the insulation effect was superior to conventional concrete.

• Economic and Environmental Geology
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• v.47 no.4
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• pp.441-453
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• 2014

Thermal and physical properties were measured on 206 Jurassic granite samples obtained from three boreholes in the central part of Korea. Thermal conductivity(${\lambda}$), thermal diffusivity(${\alpha}$), and specific heat(Cp) were measured in a laboratory; the average values are ${\lambda}$=2.813 W/mK, ${\alpha}=1.296mm^2/sec$, and Cp=0.816 J/gK, respectively. In addition, porosity(${\phi}$), and dry and saturated density(${\rho}$) were measured in the laboratory; the average values are ${\phi}$=0.01, ${\rho}(dry)=2.662g/cm^3$ and ${\rho}(saturated)=2.67g/cm^3$, respectively. Thermal diffusivity of 10 granite samples were measured with increasing temperature from $25^{\circ}C$ to $200^{\circ}C$. In this study, we found that thermal diffusivity at $200^{\circ}C$ is about 30% lower than thermal diffusivity at $25^{\circ}C$. In correlation analysis, thermal conductivity increases with increasing thermal diffusivity. However, thermal conductivity does not show good correlation with porosity and density. Consequently, we know that thermal conductivity of granite would be more influenced by mineral composition than by porosity. We also derived ${\rho}=-2.393{\times}{\phi}+2.705$ from density and porosity data. XRD and XRF analysis were performed to investigate effects of mineral and chemical composition on thermal conductivity. From those results, we found that thermal conductivity increases with increasing quartz and $SiO_2$, and decreases with increasing albite and $Al_2O_3$. Regression analysis using those mineral and chemical composition were carried out ; we found $K=0.0294V_{Quartz}+1.93$ for quartz, $K=0.237W_{SiO_2}-14.09$ for $SiO_2$, and $K=0.053W_{SiO_2}-0.476W_{Al_2O_3}+6.52$ for $SiO_2$ and $Al_2O_3$. Specific gravities were measured on 10 granite samples in the laboratory. The measured specific gravity depends on chemical compositions of granite. Therefore, specific gravity can be estimated by the felsic-mafic index(F) that is calculated from chemical composition. The estimated specific gravity ranges from 2.643 to 2.658. The average relative error between measured and estimated specific gravities is 0.677%.

• Polymer(Korea)
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• v.36 no.1
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• pp.22-28
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• 2012

Functionalized graphene/epoxy composites were prepared to miprove thermal conductivities of epoxy composites and to maintain electrical insulating property. Graphene oxide (GO) was prepared using Hummers method, and then GO was reacted with aluminum isopropoxide to functionalize $Al(OH)_3$ layer onto GO surface by a simple sol-gel method (Al-GO). GO and Al-GO were characterized by X-ray photoelectron spectroscopy, field emission scanning electron microscopy and transmission electron microscopy. The analyses confirm that GO was coated with a large and dense coverage of $Al(OH)_3$. GO and Al-GO (1 and 3 wt%) were embedded in bisphenol A (DGEBA) to investigate the effects of electrical insulating property. Electrical resistivity showed that Al-GO had better insulating property than GO. Further, the thermal conductivity of GO and Al-GO/epoxy composites was higher than that of neat epoxy resins. In particular, the thermal conductivity of Al-GO/bisphenol F (DGEBF) improved by 23.3% and Al-GO/DGEBA enhanced by 21.8% compared with pure epoxy resins.