• 한국건축시공학회지
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• 제17권2호
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• pp.127-134
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• 2017

최근 국내 아파트의 외벽 거푸집공사의 경우 대부분 갱폼 시스템을 통해 철근콘크리트 구조체를 시공하고 있다. 이러한 갱폼 거푸집을 사용한 콘크리트의 경우는 거푸집 탈형 후 외부환경에 노출되고 특히, 건조한 봄, 가을과 일사량이 높은 서중시기의 벽량이 많은 아파트 측벽에 다량의 균열이 발생되어지고 있다. 이에, 본 연구에서는 신축 아파트 건설현장 중심으로 균열량이 많은 아파트 측벽부분의 갱폼시스템에 습윤양생 자동설비장치를 적용하여 초기 콘크리트 양생에 필요한 수분을 공급함으로써 콘크리트의 품질확보와 다량의 측벽균열 저감을 통한 습윤양생 자동장치의 효율성 및 활용성을 검토하고자 하였는데, 그 결과, 양생 효과 및 낙수량 고려 시 습윤양생 자동장치에 0.3mm 사이즈의 노즐을 사용하여 살수양생을 실시할 경우, 자원낭비 없이 콘크리트의 품질향상 및 균열저감에 효과적인 것으로 판단되었다.

• 한국분무공학회지
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• 제21권4호
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• pp.184-194
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• 2016

Many industrial processes require reliable temperature measurements in harsh environments with high temperature, dust, humidity, and pressure. However, commercially-available conventional temperature measurement devices are not suitable for use in such conditions. This study thus proposes a reliable, durable two-color radiation thermometer (RT) for harsh environments that was developed by selecting the appropriate components, designing a suitable mechanical structure, and compensating environmental factors such as absorption by particles and gases. The two-color RT has a simple, compactly-designed probe with a well-structured data acquisition system combined with efficient LabVIEW-based code. As a result, the RT can measure the temperature in real time, ranging from 300 to $900^{\circ}C$ in extremely harsh environments, such as that above the burden zone of a blast furnace. The error in the temperature measurements taken with the proposed two-color RT compared to that obtained using K-type thermocouple readouts was within 6.1 to $1.4^{\circ}C$ at a temperature range from 200 to $700^{\circ}C$. The effects of absorption by gases including $CO_2$, CO and $H_2O$ and the scattering by fine particles were calculated to find the transmittance of the two wavelength bands of operation through the path between the measured burden surface and the two-color probe. This method is applied to determine the transmittance of the short and long wavelength bands to be 0.31 and 0.51, respectively. Accordingly, the signals that were measured were corrected, and the true burden surface temperature was calculated. The proposed two-color RT and the correction method can be applied to measure temperatures in harsh environments where light-absorbing gases and scattering particles exist and optical components can be contaminated.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.125-130
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• 2001

Experimental and analytical researches have been conducted on the twin-fluid atomizers for better droplet breakup during the past decades. But, the studies on the disintegration mechanism still present a great challenge to understand the drop behavior and breakup structure. In an effort to describe the aerodynamic behavior of the sprays issuing from the internal mixing counter-swirling nozzle, the spatial distribution of axial (U) radial (V) and tangential (W) components of droplet velocities are investigated across the radial distance at several axial locations of Z=30, 50, 80, 120 and 170mm, respectively. Experiments were conducted for the liquid flow rates which was kept constant at 7.95 g/s and the air injection pressures were varied from 20 kPa to 140 kPa. Counter-swirling internal mixing nozzles manufactured at angles of $15^{\circ},\;30^{\circ},\;45^{\circ}$ and $60^{\circ}$ the central axis with axi-symmetric tangential-drilled holes was considered. The distributions of velocities and turbulence intensities are comparatively analyzed. PDPA is installed to specify spray flows, which have been conducted along the axial downstream distance from the nozzle exit. Ten thousand of sampling data was collected at each point with time limits of 30 second. 3-D automatic traversing system is used to control the exact measurement. It is observed that the sprays with all swirl angle have the maximum SMD for on air injection pressure of 20 kPa and 140 kPa with centerline, respectively. The nozzle with swirl angle of $60^{\circ}$ has vest performance.

• 한국입자에어로졸학회지
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• 제7권3호
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• pp.79-85
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• 2011

Porous $TiO_2-SiO_2$ particles were synthesized by co-assembly of nanoparticles of $TiO_2$ and $SiO_2$ in evaporating aerosol droplets. Poly styrene latex (PSL) particles were employed as a template of porous particles. Flowrate of dispersion gas, weight ratio of $TiO_2/SiO_2$ and $SiO_2$ concentration in the precursor, and PSL size were chosen as process variables. The morphology, crystal structure, chemical bonding, and pore size distribution were analyzed by FE-SEM, XRD, FT-IR, BET. The morphology of porous $TiO_2-SiO_2$ particles was spherical and the average particle size range were from 1 to $10{\mu}m$. The particles were composed of meso and macro pores. The average particle diameter and pore volume of the as prepared particles were dependant on process variables. It was found that UV-Vis absorption of the porous particles was comparable with pure $TiO_2$ nanoparticles even though $TiO_2/SiO_2$ ratio is low in the porous particles.

• 대한화학회지
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• 제42권1호
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• pp.42-50
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• 1998

산화티탄을 전극 재료로 사용하기 위해서는 투명하고 수용액에 안정한 재료가 필요하다.아세틸 아세톤 티탄(IV)으로부터 분사방법을 이용하여 산화티탄의 안정한 박막을 얻었다. 결정 모양은 구형을 나타내었으며, 결정의 크기는 온도가 증가함에 따라 증가하였고 두께는 감소하는 경향을 나타내었다. XRD 데이타로부터 아나타제 결정이 400$^{\circ}C$ 에서부터 얻어지기 시작함을 관찰하였다. 440$^{\circ}C$ 에서 만들어진 산화티탄이 고유 광전류가 최대값을 나타냈으며 가시광 영역에서 광전류가 증가하는 결과를 나타냈다. 가시광 영역에서의 광전류는 프탈로시아닌의 흡수 스펙트럼과 같은 ${\lambda}$max 위치에서 얻어졌고 이와 같은 결과는 프탈로시아닌의 결정 특성에 따른 광전류 특성으로 나타났다.

• 대한기계학회논문집B
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• 제20권7호
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• pp.2267-2276
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• 1996

공정산업분야 및 분무연소분야에서 많이 사용되고 있는 2유체 분무기에서 출구 초음속유동의 가시화와 하류의 가스압력 측정 결과로부터 다음과 같은 결론을 얻었다. 1) 과소팽창 또는 과대팽창 초음속노즐 유동에서 출구 Mach수가 일정한 경우, 유동이 박리하지 않는다면 가스의 정체압력(유량)이 증가함에 따라 노즐출구에서 충돌정체점까지의 길이와 초음속 유동영역의 길이는 증가한다. 2) 스피팅 현상은 액체공급관 출구의 흡인압력은 분사가스압력이 증가함에 따라 단조증가하지만 분사가스압력이 0.5MPa이상이 되면 증감현상이 커지며 돌출형 노즐에서 유동박리시 급격히 증가한 다음 거의 일정하게 유지된다. 4) 액체공급관 하류축상의 압력변화는 출구의 음압에서 충돌정체점까지 상승한 다음 급강하하고 충격파 세포상의 구조에 따라 진동하면서 대기압에 도달한다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.35.1-35.1
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• 2011

New photovoltaic (PV) materials and manufacturing approaches are needed for meeting the demand for lower-cost solar cells. The prototypal thin-film photovoltaic absorbers (CdTe and $Cu(In,Ga)Se_2$) can achieve solar conversion efficiencies of up to 20% and are now commercially available, but the presence of toxic (Cd,Se) and expensive elemental components (In, Te) is a real issue as the demand for photovoltaics rapidly increases. To overcome these limitations, there has been substantial interest in developing viable alternative materials, such as $Cu_2ZnSnS_4$ (CZTS) is an emerging solar absorber that is structurally similar to CIGS, but contains only earth abundant, non-toxic elements and has a near optimal direct band gap energy of 1.4~1.6 ev and a large absorption coefficient of ${\sim}10^4\;cm^{-1}$. The CZTS absorber layers are grown and investigated by various fabrication methods, such as thermal evaporation, e-beam evaporation with a post sulfurization, sputtering, non-vacuum sol-gel, pulsed laser, spray-pyrolysis method and electrodeposition technique. In the present work, we report an alternative method for large area deposition of CZTS thin films that is potentially high throughput and inexpensive when used to produce monolithically integrated solar panel modules. Specifically, we have developed an aqueous chemical approach based on chemical bath deposition (CBD) with a subsequent sulfurization heat treatment. Samples produced by our method were analyzed by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, absorbance and photoluminescence. The results show that this inexpensive and relatively benign process produces thin films of CZTS exhibiting uniform composition, kesterite crystal structure, and good optical properties. A preliminary solar cell device was fabricated to demonstrate rectifying and photovoltaic behavior.

• 생물환경조절학회지
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• 제20권2호
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• pp.144-149
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• 2011

본 연구는 품질증진제 처리가 산취(Chamaecereus silvestrii) '희망'의 모구품질과 표피 변화에 미치는 영향을 연구하였다. 생체중은 D-sorbitol 처리구보다 D-mannitol 처리구에서 감소율이 낮아 효과적이었다. Diniconazole 200ppm처리는 산취의 자구생육을 어느 정도(수치화) 억제하여 장기수송(50일)에 더 적합하였으며 자구색의 발현 어느 정도(수치화)에도 효과적이었다. 산취 모구의 표피구조는 비모란에 비해 하피 발달이 저조하고 어느 정도(수치화) 단층이며 세포벽도 얇아 어느 정도(수치화) 수송조건에 불리하였는데 생육의 억제효과가 높은 diniconazole 200ppm + D-mannitol 10,000ppm과 발색효과가 좋은 diniconazole 200ppm + wax 살포가 저장 중의 품질 유지에 적합하다고 판단된다.

• 한국소음진동공학회논문집
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• 제24권3호
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• pp.247-252
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• 2014

This paper presents a novel impact sensor which can be fabricated with smart paint made of grapheme. This smart nano paint can be easily installed on structures using a spray-on technique and that can make the sensor low cost and practical. The graphene effectively improves the piezoresistivity of the smart paint and that is available to achieve sensitive impact sensor with high gauge factor. The nano smart-paint can detect sufficient impact to cover the damaged energy range of the composite around 1~3J. The voltage outputs from the sprayed paints show fairly linear responses after signal processing. The impact makes deformation of the structure and it brings change of piezoresistivity of the paint and those converts into voltage output consequently by means of a simple signal processing system. The nano smart paint is lightweight and easily applied to the structural surface, and there is no stress concentration. The nano smart paint is expected to be a cost effective and sensitive multi-functional sensor for composites and other damage monitoring applications in the field of structural health monitoring.

• 한국세라믹학회지
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• 제45권3호
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• pp.167-171
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• 2008

Zirconium-doped $Li_{1.1}Co_{1-x}Zr_xO_2(0{\leq}x{\leq}0.05)$ powders as cathode materials for lithium ion batteries were synthesized using an ultrasonic spray pyrolysis method. Cyclic voltammetry and cyclic stability tests were performed, and the changes of microstructure were observed. The solubility limit of zirconium into $Li_{1.1}CoO_2$ was less than 5 mol%, and monoclinic $Li_2ZrO_3$ phase was formed above the limit. The Zr-doping suppressed the grain growth and increased the lattice parameters of the hexagonal $LiCoO_2$ phase. The Zr-dopiong of 1mol% resulted in the best cyclic performance in the range of $3.0{\sim}4.3V$ at 1C rate (140 mA/g); the initial discharge capacity decreased from 158 mAh/g to 60 mAh/g in the undoped powder, while from 154 mAh/g to 135 mAh/g in the Zr-doped powder of 1 mol% after 30 cycles. The excellent cycle stability of Zr-doped powder was due to the low polarization during chargedischarge processes which resulted from the delayed collapse of the crystal structure of the active materials with Zr-doping.