• Computers and Concrete
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• 제20권4호
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• pp.491-502
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• 2017

In this research, the application of ultrasonic pulse velocity (UPV) test as a nondestructive method for estimating some of the mechanical and dynamic properties of reactive powder concrete (RPC) containing steel and polyvinyl alcohol (PVA) fibers, as well as their combination was explored. In doing so, ten different mix designs were prepared in 19 experimental groups of specimens containing three different volume contents of steel fibers (i.e., 1, 2, and 3 %) and PVA fibers (i.e., 0.25, 0.5, and 0.75 %), as well as hybrid fibers (i.e., 0.25-0.75, 0.5-0.5, and 0.75-0.25 %). The specimens in these groups were prepared under the two curing regimes of normal and heat treatment. Moreover, the UPV test results were employed to estimate the compressive strength, dynamic modulus, shear modulus, and Poisson's ratio of the RPC concrete and to investigate the quality level of the used concrete. At the end, the effect of the specimen shape and in fact the measuring distance length on the UPV results was explored. The results of this research suggest that the steel fiber-containing RPC specimens demonstrate the highest level of ultrasonic pulse velocity as well as the highest values of the mechanical and dynamic properties. Moreover, heat treatment has a positive effect on the density, UPV, dynamic modulus, Poisson's ratio, and compressive strength of the RPC specimens, whereas it leads to a negligible increase or decrease in the shear modulus and static modulus of elasticity. Furthermore, the specimen shape affects the UPV of fiber-lacking specimens while negligibly affecting that of fiber-reinforced specimens.

• 센서학회지
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• 제17권6호
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• pp.462-469
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• 2008

In this study, we have fabricated a fiber-optic radiation sensor using an organic scintillator and plastic optical fiber for brachytherapy dosimetry. Also, we have measured relative depth dose rates of Ir-192 source using a fiber-optic sensor and compared them with the results obtained using a conventional EBT film. Cerenkov lights which can be a noise in measuring scintillating light with a fiber-optic sensor are measured and eliminated by using of a background optical fiber. It is expected that a fiber-optic radiation sensor can be used in brachytherapy dosimetry due to its advantages such as a low cost, simple usage and a small volume.

• 한국지역지리학회지
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• 제21권1호
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• pp.21-38
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• 2015

본 연구는 21개 영남권 도시들 간 네트워크 시간거리와 유동량자료를 이용하여 이들 간의 상보성을 추정하고자 하였다. 이를 위해 사람, 화물, 정보, 금융 등 네 가지 유형의 유동이 고려되었다. 이들 중 사람과 화물의 유동은 교통 네트워크상에서, 그리고 정보와 금융의 유동은 통신 네트워크상에서 이루어지는 것으로 구분되어 분석되었다. 연구의 목적을 위하여 먼저 도시들 간 유동의 기댓값이 중력모형에 기초한 회귀분석모형과 이중제약 엔트로피 극대화모형을 통해 추정되었다. 이를 통해 추정된 유동량은 사람 및 화물의 경우 실측 유동량으로부터 그리고 정보와 금융의 경우 추정유동량으로부터 차감하여 양의 결과값, 즉 상보성을 가지는 지를 확인하였다. 분석 결과는 이들 네 가지 유형의 상보성 유동이 공간패턴과 도시계층이라는 측면에서 각각 독특한 도시 네트워크를 형성하고 있음을 보여주고 있다. 이는 이 지역에서 네트워크 도시 모형을 추진하는 과정에서 네트워크 기반시설 공급과 관련된 이슈들을 적절한 방식으로 해결하기 위해서는 상보성의 각 유형별로 맞춤형의 전략이 바람직할 것임을 시사한다.

• 센서학회지
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• 제6권4호
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• pp.307-315
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• 1997

본 논문에서는 센서교환이 용이하고 소량의 샘플을 요구하는 ISFET 센서용 전해질 분석기의 샘플챔버(sample chamber)를 설계하였으며, 이를 이용한 2점 교정방식의 4채널 전해질 분석기를 구현하였다. 샘플과 교정용액들의 사용을 최소화하기 위한 샘플의 로딩상태 감지회로를 제안하였으며 이를 실현하였다. 구현된 전해질 분석기는 제어계통과 액류흐름계통으로 구성되어 있으며 전해질 분석기의 효과적인 제어를 위하여 측정루틴, 교정루틴 및 세척루틴의 시스템 소프트웨어를 각각 개발하였다.

• Environmental Analysis Health and Toxicology
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• 제26권
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• pp.12.1-12.7
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• 2011

Objectives: Perchlorate is an emerging contaminant that is found everywhere, including various foods. Perchlorate is known to disturb the production of thyroid hormones and leads to mental disorders in fetuses and infants, as well as metabolic problems in adults. In this study, we attempted to establish an LC-MS/MS method for measuring perchlorate in dairy products and used this developed method to investigate perchlorate levels in Korean milk and yogurt samples. Methods: The developed method of perchlorate analysis requires a shaker and 1% acetic acid/acetonitrile as the extracting solvent. Briefly, the samples were extracted and then centrifuged (4000 rpm, 1hour), and the supernatant was then passed through a $Envi^{TM}$ Carb SPE cartridge that had been prewashed sequentially with 6 mL of acetonitrile and 6 mL of 1% acetic acid in water. The final volume of the sample extract was adjusted to 40 mL with reagent water and the final sample was filtered through a 0.20-${\mu}m$ pore size PTFE (Polytetrafluoroethylene) syringe filter prior to LC-MS/MS. Results: The average levels of perchlorate in milk and yogurt samples were $5.63{\pm}3.49\;{\mu}g/L$ and $3.65{\pm}2.42\;{\mu}g/L$, respectively. The perchlorate levels observed in milk samples in this study were similar to those reported from China, Japan, and the United States. Conclusions: The exposure of Koreans to perchlorate through the consumption of dairy products was calculated based on the results of this study. For all age groups, the calculated exposure to perchlorate was below the reference of dose (0.7 ${\mu}g/kg$-day) proposed by the National Academy of Science, USA, but the perchlorate exposure of children was higher than that of adults. Therefore, further investigation of perchlorate in other food samples is needed to enable a more exact assessment of exposure of children to perchlorate.

• 전기학회논문지
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• 제66권2호
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• pp.357-362
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• 2017

Among the lithium metal oxides for asymmetric hybrid supercapacitor, $Li_4Ti_5O_{12}(LTO)$ is an emerging electrode material as zero-stain material in volume change during the with the charging and discharging processes. The pulverized LTO powder was observed to show the enhanced capacity from 120 mAh/g to 156 mAh/g at C-rate (10, 100 C). Hybrid supercapacitor module(48V, 416F) was fabricated using an asymmetric hybrid capacitor with a capacitance of 7500F. As a result of the measurement of C-rate characteristics, the module shows that the discharge time is drastically reduced at more than 50C, and the ESR and voltage drop characteristics are increased. The energy density and power density were reduced under high C-rate conditions. When designing asymmetric hybrid supercapacitor module, the C-rate and ESR should be considered As a result of measuring the 5 kw UPS, it was discharged at the current of 116A~170A during the discharge in the voltage range of 48V~30V, and the compensation time at discharge was measured to be about 33.2s. Experimental results show that it can be applied to applications related to stabilization of power quality by applying hybrid supercapacitor module.

• 한국정보전자통신기술학회논문지
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• 제10권6호
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• pp.522-528
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• 2017

논문에서는 메탈 프레임 커플링을 이용한 웨어러블 디바이스용 다중대역 안테나를 제안하였다. 제안된 안테나는 $45mm{\times}35mm$ 크기의 메탈 프레임을 이용한 안테나와 접지면 이중 커플링 구조를 가지고 있다. 본 논문에서 제안한 다중대역 안테나는 웨어러블 디바이스와 같은 소형 디바이스에 최적화 된 구조이다. 메탈 프레임을 안테나의 일부로 사용함으로써 안테나 체적을 축소시키고 VSWR 3:1 이하 기준으로 저주파 대역에서 70 MHz (870~40 MHz), 고주파 대역에서 280 MHz (1600~880 MHz) 과 280 MHz (1900~170 MHz) 임피던스 대역폭을 만족한다. 또한, 무선 성능 지표들인 TRP/TIS 측정을 통해 웨어러블 디바이스 적용 가능성을 검증하였다.

• 한국산학기술학회논문지
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• 제10권7호
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• pp.1642-1647
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• 2009

황사기간 중 천안시 대기 입자의 특성 변화를 파악하기 위해, Cascade Impactor를 장착한 High Volume Air Sampler를 이용하여 대기 시료를 채취하여, 대기 입자의 입경별 질량농도 및 이온, 금속 성분의 농도를 황사기간과 비황사기간에 비교 측정하였다. 황사기간 중 일평균 TSP, PM10, PM2.5 평균 농도가 각각 214.9, 160.3, 95.9${\mu}\;g/m^3$으로, 비황사기간에 비해 각각 평균 3.08, 2.58, 1.95배 증가하였으며, 최대 농도는 TSP, PM10, PM2.5가 각각 850.1, 534.4, 233.3${\mu}\;g/m^3$으로, 비황사기간에 비해 각각 12.19, 8.60, 4.76배까지 증가하였다. 황사기간 중 농도의 증가는 미세입자보다는 조대입자에서 현저하였으며, 미세입자와 조대입자 모두 수용성 이온성분의 증가는 미미한 반면, 토양의 주요 구성 성분인 Fe, Al, Ti의 증가가 뚜렷이 관측되어, 토양구성 금속성분이 황사기간 중 입자 농도 증가의 주요원인 물질임을 확인할 수 있었다.

• 한국산학기술학회논문지
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• 제10권8호
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• pp.1926-1938
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• 2009

본 연구에서는 혈압 측정 시 생체 임피던스가 변화하는 현상을 이용하여 혈류량 변화를 검출하는 시스템을 구현하였다. 혈압의 측정은 오실로메트릭법을 적용하였으며, MAA 알고리즘을 이용하여 평균 동맥압을 산출한 후 평균 동맥압에 대한 여러 가지 특성비율을 설정하여 수축기 및 이완기 혈압을 추정하였다. 인체 임피던스 측정은 교류 정전류원과 락인-증폭기를 이용하였으며, 측정 부위에 인가되는 커프 압력에 의해 생체 임피던스 변화량을 이용하여 혈류량 변화를 측정하였다.

• 한국연초학회지
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• 제29권1호
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• pp.23-29
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• 2007

The measurement of physical properties such as apparent density and void fraction of tobacco materials, which is so bulky, is a main theme with regard to tobacco process, quality control, cigarette combustion and smoke generation. Except Solution Impregnation Method, there was no alternative method for measuring those properties in the porous material so far. However, experimental processes of that method are so complicated as to cost much time and labor, the main solution such as mercury to apply to the method is usually very hazard. Therefore, we had developed a new method to determine them easily in our other paper by the mathematical equations derived from the Ergun equation for the purpose of it, and then already evaluated our method through applying some basic data from Muramatsu et at. (1979) with regard to our developed equations. Then, we found our method best fit to experimental one (Oh et al., 2001). In this study we tried to establish our method to conveniently determine those physical properties. Especially, we have focused on the development the easy way to measure surface area and the volume of single shred in a tobacco column. As a result of that, we found that the computer image analyzer was best fit for it. Then, we have finally determined apparent density and void fraction for our domestic tobacco shred.