• Particle and aerosol research
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• v.7 no.4
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• pp.113-121
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• 2011

The aerosol nanoparticles are suspected to be exposed to workers in nanomaterial manufacturing facilities. However, the exposure assessment method has not been established. One of important issues is to characterize background level of nanoparticles in workplaces. In this study, intensive aerosol measurements were made at a $TiO_2$ manufacturing laboratory for five consecutive days in May of 2010. The $TiO_2$ nanoparticles were manufactured by the thermal-condensation process in a heated tube furnace. The particle number size distribution was measured using a scanning mobility particle sizer every 5 min, in order to detect particles ranging from 14.5 to 664 nm in diameter. Total particle number concentration shows a severe diurnal variation irrespective of manufacturing process, which was governed by nanoparticles smaller than 50 nm in diameter. During the background monitoring periods, significant peak concentrations were observed between 2 p.m. and 3 p.m. due to the infiltration of secondary aerosol particles formed by photochemical smog. Although significant increase in nanoparticle concentration was also observed during the manufacturing process twice among three times, these particle peak concentrations were lower than those observed during the background measurement. It is suggested that the investigation of background particle contamination is needed prior to conducting main exposure assessment in nanomaterial manufacturing workplaces or laboratories.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2001.05a
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• pp.141-146
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• 2001

실내 공기조화를 하는 거주역에 대한 온열환경요소의 자극 변화를 통해 실내 에너지를 절약할 수도 있으며 쾌적감도 향상시킬 수 있다. 따라서 본 연구에서는 거주자의 온열감각을 자극할 수 있는 온열요소 중 비교적 영향이 크고 용이하게 제어할 수 있는 온도 및 기류의 변동으로 한국인의 온열감각(온냉감, 쾌적감, 만족감)에 미치는 영향을 실험을 통하여 파악하였다. 온도 및 기류별 실험을 통하여 22$^{\circ}C$, 24$^{\circ}C$, 26$^{\circ}C$의 각 온도에 대한 패케지 에어컨의 강, 중, 약 기류에 대한 인체순응 시간과 인체 변화를 파악하였다. 또한 인체순응시간을 고려한 온도 상승 실험을 통하여 24$^{\circ}C$, 26$^{\circ}C$에서 1$^{\circ}C$온도 상승시 인체의 온열쾌적감의 변화를 파악하였으며 온도 상승을 통한 인체 순응시간을 도출하였다. 본 실험을 통하여 초기공조 조건을 24C$^{\circ}C$ 로 한 경우 인체순응을 통한 온도 상승으로 30분 후의 공조중기와 공조후기에 온도 및 기류의 지속적인 변동 자극으로 온냉감은 "약간 서늘하다"를 지속적으로 유지하고 있으며 온도상승으로 인한 쾌적존의 높은 온도에서도 기류의 영향으로 쾌적감은 30분 이후부터 "쾌적"을 지속적으로 유지하는 것을 알 수 있었다. 따라서 본 연구를 통하여 인체순응을 고려한 온도 및 기류의 자극을 통하여 공조초기부터 공조말기의 장시간에도 인체가 지속적인 쾌적성을 유지한다는 것을 알 수 있었다.성을 유지한다는 것을 알 수 있었다.

• Korean Journal of Materials Research
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• v.21 no.3
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• pp.144-148
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• 2011

We have investigated the structural and optical properties of Ga-doped ZnO (GZO) thin films deposited by RF magnetron sputtering at various deposition temperatures from 100 to $500^{\circ}C$. All the GZO thin films are grown as a hexagonal wurtzite phase with highly c-axis preferred parameter. The structural and electrical properties are strongly related to deposition temperature. The grain size increases with the increasing deposition temperature up to $400^{\circ}C$ and then decreases at $500^{\circ}C$. The dependence of grain size on the deposition temperature results from the variation of thermal activation energy. The resistivity of GZO thin film decreases with the increasing deposition temperature up to $300^{\circ}C$ and then decreases up to $500^{\circ}C$. GZO thin film shows the lowest resistivity of $4.3{\times}10^{-4}\;{\Omega}cm$ and highest electron concentration of $1.0{\times}10^{21}\;cm^{-3}$ at $300^{\circ}C$. The mobility of GZO thin films increases with the increasing deposition temperature up to $400^{\circ}C$ and then decreases at $500^{\circ}C$. GZO thin film shows the highest resistivity of 14.1 $cm^2/Vs$. The transmittance of GZO thin films in the visible range is above 87% at all the deposition temperatures. GZO is a feasible transparent electrode for the application to the transparent electrode of thin film solar cells.

• Journal of Satellite, Information and Communications
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• v.6 no.1
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• pp.28-31
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• 2011

In this paper, a new set of structural and sacrificial material that is diamond like carbon (DLC)/photoresist for high performance piezoelectric RF-MEMS switches which are actuated in d33 mode is suggested. To avoid curing problem of photoresist sacrificial layer, DLC structure layer is deposited at room temperature by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) method. And lead zirconate titanate (PZT) piezoelectric layer is deposited on structure layer directly at room temperature by rf magnetron sputtering system and crystallized by rapid thermal annealing (RTA) equipment. Particular attention is paid to the annealing of PZT film in order to crystallize into perovskite and the variation of mechanical properties of DLC layer as a function of annealing temperature. The DLC layer shows good performance for structure layer in aspect to Young's modulus and hardness. The fabrication becomes much simpler and cheaper with use of a photoresist.

• Fire Science and Engineering
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• v.25 no.1
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• pp.63-71
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• 2011

When it comes to slim floor using asymmetric H-beam, it was designed that the steel member is embedded in concrete with relatively low thermal conductivity so as to minimize the deterioration of rigidity of steel member in fire. But given the bottom flange of asymmetric H-beam is directly exposed to the fire, the measure of applying the fireproof coating to improve the fire rate performance of slim floor beam was sought. The test was aimed at comparing the fireproof performance by adjusting the load ratio of 0.4 and 0.3, and The test was carried out to identify the 3-hour fire performance by reinforcing the beam as well as applying the fireproof coat, In the wake of comparing the specimen depending on variation of load ratio, lowering load ratio by 0.1 resulted in difference of 12 minutes and deflection was 39 mm. It was able to improve 12 minutes by reinforcing the beam and up to 102.4 mm in deflection.

• Journal of Navigation and Port Research
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• v.35 no.3
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• pp.265-270
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• 2011

The purpose of this study is to compare and analyze the differences of a building's heating and cooling loads depending on the weather variation. Followings are the results. The temperature, humidity and wind speeds of standard year are bigger than those of 2006~2009. The 2006~2009's total horizontal solar irradiance is greater than that of standard year, and the direct solar irradiance of standard year is bigger in winter and vice versa in summer. As results of simulation on heating and cooling loads, it is difficult to find out the bilateral influences between maximum thermal loads and annual's. The equivalent-time operating ratio(EOR) is defined on this study to estimate the differences between year and year, and the EOR of standard year shows low value comparing to 2006~2009 years'.

• Journal of Biosystems Engineering
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• v.35 no.1
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• pp.46-52
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• 2010

The temperature of root zone was known as an important factor for the growth of crops and reduction of energy in greenhouse. The purpose of this study was to design the apposite inflow of calories per the unit area by comparison of temperature in the warmed and non-warmed soil. The energy needed for soil warming about pipe length showed the change of temperature on inflow and outflow as $2^{\circ}C{\sim}3^{\circ}C$(average $2.5^{\circ}C$). Therefore, the inflow per the unit hour was 3,450, 57,5 kcal/$h{\cdot}m^2$ on soil heating respectively. The non-warmed soil temperature in greenhouse made a difference by depth and it was partially affected inner temperature under 15 cm, but it was not above 15 cm. The soil temperature would be raised over $5^{\circ}C$ than non-warmed soil to increase effect of soil warming. Therefore, the inflow per the unit area that should be provided was about 100 kcal/$h{\cdot}m^2$.

• Nuclear Engineering and Technology
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• v.38 no.1
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• pp.81-92
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• 2006

In this study, the core dynamics of a PWR reactor is identified online by a recursive least-squares method. Based on the identified reactor model consisting of the control rod position and the core average coolant temperature, the future average coolant temperature is predicted. A model predictive control method is applied to designing an automatic controller for the thermal power control of PWR reactors. The basic concept of the model predictive control is to solve an optimization problem for a finite future at current time and to implement as the current control input only the first optimal control input among the solutions of the finite time steps. At the next time step, this procedure for solving the optimization problem is repeated. The objectives of the proposed model predictive controller are to minimize both the difference between the predicted core coolant temperature and the desired temperature, as well as minimizing the variation of the control rod positions. In addition, the objectives are subject to the maximum and minimum control rod positions as well as the maximum control rod speed. Therefore, a genetic algorithm that is appropriate for the accomplishment of multiple objectives is utilized in order to optimize the model predictive controller. A three-dimensional nuclear reactor analysis code, MASTER that was developed by the Korea Atomic Energy Research Institute (KAERI) , is used to verify the proposed controller for a nuclear reactor. From the results of a numerical simulation that was carried out in order to verify the performance of the proposed controller with a $5\%/min$ ramp increase or decrease of a desired load and a $10\%$ step increase or decrease (which were design requirements), it was found that the nuclear power level controlled by the proposed controller could track the desired power level very well.

• Journal of Environmental Science International
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• v.22 no.1
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• pp.91-98
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• 2013

In order to study the seasonal patterns and possible origins of air concentrations of volatile organic compounds(VOC), measurements were taken with GC-MS at 3 sampling sites in Jinju for 12 months from Mar. 2010 to Feb. 2011. Atmospheric VOC are sampled on tubes containing solid adsorbents(Tenax TA) with a time resolution of 2hrs. Composition and concentration of VOC are analysed with a GC system equipped with thermal desorption apparatus(ATD). The most abundant compound appeared to be Toluene, Ethylbenzene and m,p-Xylene. The mean concentrations of Benzene were 0.20 ppb at GN site, 0.18 ppb at DA site, and 0.25 ppb at SP site, respectively. VOC concentration showed a strong seasonal variation, with higher concentrations during the spring and lower concentrations during the summer. The results showed that monthly fluctuations in measured VOC concentrations depended on variations in the strength of sources, as well as on photochemical activity and meteorological conditions. In Jinju, the total VOC emissions for 2009 were estimated to be 4,407 ton/year by Clean Air Policy Support System(CAPSS). It is shown that solvent use 57.5%(2,534 ton/yr), waste treatment and disposal 23.3%(1,025 ton/yr), and mobil source-road traffic 12.2%(537 ton/yr) are the most significant anthropogenic source.

• Transactions on Electrical and Electronic Materials
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• v.15 no.6
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• pp.328-332
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• 2014

Thin film transistors (TFTs) with an amorphous silicon zinc tin oxide (a-2SZTO) channel layer have been fabricated using an RF magnetron sputtering system. The effect of the change of excitation electron on the variation of the total interfacial trap states of a-2SZTO systems was investigated depending on sputtering power, since the interfacial state could be changed by changing sputtering power. It is well known that Si can effectively reduce the generation of the oxygen vacancies. However, The a-2SZTO systems of ZTO doped with 2 wt% Si could be degraded because the Si peripheral electron belonging to a p-orbital affects the amorphous zinc tin oxide (a-ZTO) TFTs of the s-orbital overlap structure. We fabricated amorphous 2 wt% Si-doped ZnSnO (a-2SZTO) TFTs using an RF magnetron sputtering system. The a-2SZTO TFTs show an improvement of the electrical property with increasing power. The a-2SZTO TFTs fabricated at a power of 30 W showed many of the total interfacial trap states. The a-2SZTO TFTs at a power of 30 W showed poor electrical property. However, at 50 W power, the total interfacial trap states showed improvement. In addition, the improved total interfacial states affected the thermal stress of a-2SZTO TFTs. Therefore, a-2SZTO TFTs fabricated at 50 W power showed a relatively small shift of threshold voltage. Similarly, the activation energy of a-2SZTO TFTs fabricated at 50 W power exhibits a relatively large falling rate (0.0475 eV/V) with a relatively high activation energy, which means that the a-2SZTO TFTs fabricated at 50 W power has a relatively lower trap density than other power cases. As a result, the electrical characteristics of a-2SZTO TFTs fabricated at a sputtering power of 50 W are enhanced. The TFTs fabricated by rf sputter should be carefully optimized to provide better stability for a-2SZTO in terms of the sputtering power, which is closely related to the interfacial trap states.