• Korean Journal of Ecology and Environment
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• v.56 no.4
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• pp.430-439
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• 2023

UV and O₃ are materials used in the water treatment process, and many studies have been reported to remove organic matters, contaminants, and microorganisms. In this study, we were investigated effects of Chirnomidae (Chironomus flaviplumus, Chironomus riparius), which are contamination indicator species to exposure UV and O₃ for the survival rate, body color change and gene expression response. The survival rate of C. flaviplumus exposed to UV decreased to about 70% after 24 hours, and C. riparius about 50%. There was no change in the survival rate of C. flaviplumus exposed to O₃, and C. riparius decreased to 95% after 10 minutes of exposure, but there was no change during the subsequent exposure time. In addition, UV and O₃ exposure to the two species in body color faded in a time-dependent. In the HSP70 gene expression, C. riparius showed an increase in expression after UV exposure compared to the control group, and a significant difference was shown 12 hours after exposure (P<0.05). C. flaviplumus exposed to O₃ showed a relatively low expression compared to the control group, and showed a significant difference at 10 minutes and 1 hour after exposure (P<0.05). These results reported the ecotoxicological effects on Chironomidae according to UV and O₃ exposure. Therefore, the results of this study can be used as basic data to understand the effects of UV and O₃, which are disinfectants used in water treatment plants, on Chirnomidae entering plants.

• Applied Chemistry for Engineering
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• v.18 no.3
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• pp.227-233
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• 2007

Carbon/carbon (C/C) composites as unique materials possess exceptional thermal resistance with light weight, high stiffness, and strength even at high temperature. However, one serious obstacle for application of the C/C composites is their poor oxidation resistance in high temperature oxidizing environments. SiC coating has been employed to protect the composites from oxidation. This study explored combustion characteristics of 4-directional (4D) carbon/carbon composites using liquid fuel rocket engine to investigate ablative motion of the materials. C/C composites were made of coal tar pitch as a matrix precursor, and heat-treated at $2300^{\circ}C$. Throughout repeated densification process, the density of the material reached $1.903g/cm^3$. After machining 4D C/C composites, the nozzle surface was coated by a SiC layer by pack-cementation method to improve oxidation resistance. Erosion characteristics of SiC-coated C/C composites were measured as function of the ratio of oxygen to fuel. The morphological change of the composites after combustion test was investigated using SEM and erosion mechanism also was discussed.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.12
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• pp.8-13
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• 2001

Cerium oxide ($CeO_2$) thin film has been proposed as a buffer layer between the ferroelectric thin film and the Si substrate in Metal-Ferroelectric-Insulator-Silicon (MFIS) structures for ferroelectric random access memory (FRAM) applications. In this study, $CeO_2$ thin films were etched with $Cl_2$/Ar gas mixture in an inductively coupled plasma (ICP). Etch properties were measured for different gas mixing ratio of $Cl_2$($Cl_2$+Ar) while the other process conditions were fixed at RF power (600 W), dc bias voltage (-200 V), and chamber pressure (15 mTorr). The highest etch rate of $CeO_2$ thin film was 230 ${\AA}$/min and the selectivity of $CeO_2$ to $YMnO_3$ was 1.83 at $Cl_2$($Cl_2$+Ar gas mixing ratio of 0.2. The surface reaction of the etched $CeO_2$ thin films was investigated using x-ray photoelectron spectroscopy (XPS) analysis. There is a Ce-Cl bonding by chemical reaction between Ce and Cl. The results of secondary ion mass spectrometer (SIMS) analysis were compared with the results of XPS analysis and the Ce-Cl bonding was monitored at 176.15 (a.m.u). These results confirm that Ce atoms of $CeO_2$ thin films react with chlorine and a compound such as CeCl remains on the surface of etched $CeO_2$ thin films. These products can be removed by Ar ion bombardment.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.2
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• pp.1-8
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• 2012

This paper presents the accelerometer which is a key component of TPMS(Tire Pressure Monitoring System). Generally a piezoresistive accelerometer has characteristics of lower cost, better linearity and better immunity about the environmnet noise than a capacitive one. Three types of piezoresistive accelerometers are degined and simulated using ANSYS program. The best one is a piezoresistive sensor which is supported by four beams located at the center of the edge of the mass after comparing the characteristics of resonant frequency of the three types. Considering the sensor size and a simulated maximum stress and maximum displacement, the length of beams is set as $200{\mu}m$. The size of a piezoresistive accelerometer is $3.0mm{\times}3.0mm{\times}0.4mm$. The sensor output is characterized by measuring the output characteristic depending on angle. As a result the offset voltage of the accelerometer is 43.2 mV and its sensitivity is $42.5{\mu}V/V/g$. The temperature bias drift is measured. The shock durability of the sensor is 1500g and the measuring range is 0 ~ 60 g.

• Korean Journal of Agricultural Science
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• v.30 no.2
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• pp.175-183
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• 2003

Fruit and vegetables are subjected to complex dynamic stresses in the transportation environment. During a long journey from the production area to markets, there is always some degree of vibration present. Vibration inputs are transmitted from the vehicle through the packaging to the fruit. Inside, these cause sustained bouncing of fruits against each other and container wall. These steady state vibration input may cause serious fruit injury, and this damage is particularly severe whenever the fruit inside the package is free to bounce, and is vibrated at its resonance frequency. The determination of the resonance frequencies of the fruit and vegetables may help the packaging designer to determine the proper packaging system providing adequate protection for the fruit, and to understand the complex interaction between the components of fruit when they relate to expected transportation vibration inputs. Instrumentation and technologies are described for determining the vibration response characteristics of the fruits with frequency range 3 to 150 Hz. The computer program for controlling the vibration exciter and the function generator and for measuring the vibration response characteristics of the fruits was developed. The resonance frequency of the pear ranged from 64.5 to 72.2 Hz and the amplitude at resonance was between 1.78 and 2.21 G-rms. The resonance frequency and amplitude at resonance decreased with the increase of the sample mass, and they were slightly affected by mechanical properties such as bioyield deformation and rupture deformation. Regression analysis was performed among the relatively high correlated parameters from the results of correlation coefficient analysis.

• Journal of the Korean Ceramic Society
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• v.41 no.12 s.271
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• pp.893-899
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• 2004

The mechanical properties and microstructure and thermal properties of Nitrided Pressureless Sintering(NPS) silicon nitride ceramics, containing three type of $Al_{2}O_3,\;Y_{2}O_3$ sintering additives, were investigated. Also, we have investigated the effect of silicon metal content changing with 0, 5, 10, 15, and $20wt\%$ Si in each composition. In $5wt\%\;Al_{2}O_3,\;5wt\%\;Y_{2}O_3,\;and\;5wt\%$ Si composition, silicon nitride sintered body was successfully densified to a high density. The average 4-point flexural strength and relative density of these specimens were 500 MPa and 98% respectively. Also, Thermal expansion coefficient and thermal conductivity of specimens at room temperature were $2.89{\times}10^{-6}/^{\circ}C\;and\;28W/m^{\circ}C$, respectively. The flexural strength of sintered specimens after thermal shock test of 20,000 cycles was maintained as-received value of 500 MPa.

• Journal of the Economic Geographical Society of Korea
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• v.14 no.3
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• pp.286-306
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• 2011

Based on the announcement by the National Competitiveness Council in 2008, this study analyzed the direction of the changing policy in Seoul Metropolitan Area promoted by the current government and to inquire into such the effect, research was done to study the changes in space demand by companies which respond sensitively to changes in regulation in Seoul Metropolitan Area. In addition, the effect of Seoul Metropolitan Area policy on company location is explored while company location changes and changes in direction of space demand due to easing of regulation in Seoul Metropolitan Area by the current government are examined. Research methods utilized empirical analysis and survey analysis. Empirical analysis utilized statistical data since 1980's. For survey analysis, the effect of changing policy in Seoul Metropolitan Area, which is an exogenous shock, on decision making of the enterprise is considered to derive the direction of demand for company manufacturing lots. The results of the study showed that decision for company location or factory size has been affected greatly by Seoul Metropolitan Area policy and domain regulation and institution to restrict permission area of a manufacturing building from the law of improvement plan of the Metropolitan area were the biggest regulatory policies. Due to easing of regulation in Seoul Metropolitan Area by the current government, the demand for manufacturing lot is expected to increase. In particular, the demand for manufacturing lot is expected to increase centered around Seoul Metropolitan Area and Chungcheong province while demand is expected to decrease in Gangwon province. The reason is because company preference is high for the Seoul Metropolitan Area which has the best transportation/logistics and market conditions in Korea. But in the case of Southeast region and Daegyung region that form exclusive economic zones, changing policy in Seoul Metropolitan Area has little impact. In the case of Seoul Metropolitan Area, demand increase does not occur in the entire area but instead, demand is expected to increase in growth management zones.

• The Journal of Korean Physical Therapy
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• v.14 no.1
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• pp.131-137
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• 2002

C-fos는 원종양유전자(proto-oncogene)인 v-fos의 세포 동족체로써, 성장인자나 신경전달 물질에 의해 수분 내에 다양한 형태의 세포에서 활성화된다. Fos단백질은 스트레스와 통증 과정의 신호전달기전에서 세포활동을 조절하는 3차전령으로 활동한다. 열충격 단백질(Heat shock protein : 이하 HSP)은 계통발생학적으로 초기 척추 동물에서부터 발현되며 생체방어체계의 중요한 인자로 세포가 고열, 외상, 허혈 등의 스트레스에 직면했을 때 발현이 증가하는 단백질로 알려져 있다. 본 연구에서는 캡사이신(capsaicin)으로 말초 신경병변을 유발시킨 후 통각신경활성의 지표로 이용되는 원종양 유전자인 c-fos의 발현과 열 또는 스트레스로 야기되는 손상에 대한 조직의 방어작용으로 발현되는 HSP 70의 발현을 동시에 관찰함으로서, 급성으로 유발된 말초 신경병변의 확인과 동시에 실험동물 체내에서 방어적인 역할을 밝히는 일환으로 이 실험을 실시하였다. 본 실험의 결과는 다음과 같다; 1. 척수 등쪽뿔 천층(Laminae I and II)에서 각각 c-fos와 HSP70을 항원으로 하는 면역조직화학적 방법으로 염색한 표본에서 0.9% NaCI 투여 2시간 후 c-fos와 HSP70의 양성을 나타내는 세포는 전혀 없음을 알 수 있었다. 2. 척수 등쪽뿔 천층에서 c-fos 단백질을 항원으로 하는 면역조직화학적 방법으로 염색한 표본에서 Capsaicin 투여 2시간 후 c-fos 단백질에 양성을 나타내는 세포가 많이 발현됨을 육안적 관찰로서 알 수 있었다. 3. 척수 등쪽뿔 천층에서 HSP70을 항원으로 하는 면역조직화확적 방법으로 염색한 표본에서 Capsaicin 투여 2시간 후 HSP7O의 양성을 나타내는 세포가 보통수준으로 발현됨을 육안적 관찰로서 알 수 있었다. 이 실험의 결과로 볼 때, 화학적인 신경병변 유발물질에 의한 손상을 방어하기 위해서 체내에는 내인성 물질이 형성될 것이라는 추측과 c-fos 가 다른 유전자의 발현을 유도한다는 점을 함께 고려 하였을때, Capsaicin에 의한 말초 신경병변에서 c-fos 발현이 많이 나타나는 것은 손상을 방어하는 물질의 생성에 관여하기 때문이며, 방어물질 중 이 실험에서 본 HSP70도 증가한 내인성 방어물질의 하나라고 할 수 있을 것이다.

• Polymer(Korea)
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• v.29 no.2
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• pp.127-134
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• 2005

The relationships among mechanical properties, rheological properties, and morphology by reactive extrusion based on commingled pckaging film wastes contains polypropylene (PP) pckaging film system [PP/polyethylene (PE)/aluminum (Al)/poly(ethylene terephthalate) (PET)] and Nylon packaging film system[Nylon/PE/linear-low density polyethylene (LLDPE)] were investigated to improve the compatibility and toughness of these wastes using various compatibilizers such as ethylene vinylacetate (EVA), styrene-ethylene/butylene-styrene triblock copolymer (SEBS), styrene-ethylene/butylene-styrene-graft-maleic anhydride copolymer (SEBS-g-MA), polyethylene-graft-maleic anhydride (PE-g-MA), polypropylene-graft-maleic anhydride (PP-g-MA) , polyethylene-graft-acrylic acid (PE-g-AA) and polypropylene-graft-acrylic acid (PP-g-AA). Compared with simple melt blend system, the blends showed improvement of about $50\%$ increase in physical properties when SEBS and EVA were added. However, SEBS-g-MA thermoplastic elastomer which is highly reactive with amine terminal group of nylon, resulted in about $200\%$ increase in impact strength. This compatibilization effect resulted from the increase of interfacial adhesion and the reduction of domain size of dispersed phase in PP/Nylon blend system.

• International Journal of Highway Engineering
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• v.16 no.3
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• pp.43-50
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• 2014

PURPOSES : The dynamic modulus can be determined by applying the various theories from the Impact Resonance Testing(IRT) Method. The objective of this paper is to determine the best theory to produce the dynamic modulus that has the lowest error as the dynamic modulus data obtained from these theories(Complex Wave equation Resonance Method related to either the transmissibility loss or not, Dynamic Stiffness Resonance Method) compared to the results for dynamic modulus determined by using the Universal Testing Machine. The ultimate object is to develop the predictive model for the dynamic modulus of a Linear Visco-Elastic specimen by using the Complex Wave equation Resonance Method(CWRM) came up for an existing study(S. O. Oyadiji; 1985) and the Optimization. METHODS : At the destructive test which uses the Universal Testing Machine, the dynamic modulus results along with the frequency can be used for determining the sigmoidal master curve function related to the reduced frequency by applying Time-Temperature Superposition Principle. RESULTS : The constant to be solved from Eq. (11) is a value of 14.13. The reduced dynamic modulus obtained from the IRT considering the loss factor related to the impact transmissibility has RMSE of 367.7MPa, MPE of 3.7%. When the predictive dynamic modulus model was applied to determine the master curve, the predictive model has RMSE of 583.5MPa, MPE of 3.5% compared to the destructive test results for the dynamic modulus. CONCLUSIONS : Because we considered that the results obtained from the destructive test had the most highest source credibility in this study, the dynamic modulus data obtained respectively from DSRM, CWRM were compared to the results obtained from the destructive test by using th IRT. At the result, the reduced dynamic modulus derived from DSRM has the most lowest error.