• 대한화학회지
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• 제38권9호
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• pp.660-666
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• 1994

이웃하는 란탄족 원소의 분리에서 온도와 흐름속도의 영향을 치환크로마토그래피로 연구하였다. 일렬로 연결된 두 컬럼에 Amberlite 120 양이온 교환수지를 채워서 충전용과 분리용으로 나누어 사용하였다. 보유이온은 $H^+$을, 흐름용액은 0.012M과 0.015M의 EDTA 용액을 사용하였다. 실험중에는 관의 온도를 90$^{\circ}C$로 유지하였으며 이온교환수지 관 속에 생기는 기포를 줄이기 위해 일정한 압력을 걸었다. 용출액은 ICP-AES로 직접 분석하였다. 이 실험에서 란탄족 원소쌍 La: Ce, Ce :Pr, Pr: Nd에 대한 분리인자는 각각 4.6, 2.8, 1.9이었으며 이것은 25$^{\circ}C$에서 이론적으로 얻은 것보다 큰 값이다. 흐름속도를 2.5 ml/min에서 1.5 ml/min로 줄이면 이론단해당높이(HETP)도 1.60 cm에서 0.88 cm로 줄었다. 따라서 용리액의 흐름속도를 줄이고 온도를 높이므로써 분리효율을 증가시킬 수 있었다. 이 실험에서 99.9% 이상의 순수 란탄족 원소에 대한 회수율은 49∼77%이었다.

• Structural Engineering and Mechanics
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• 제73권4호
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• pp.427-436
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• 2020

The use of final IGS precise orbit and clock products for high-rate GNSS-PPP proved its effectiveness in capturing dynamic displacement of engineering structures caused by earthquakes. However, the main drawback of using the final products is that they are available after approximately two weeks of data collection, which is not suitable for timely measures after an event. In this study, the use of ultra-rapid products (observed part), which are available after a few hours of data collection, and rapid products, which are available in less than 24 hrs, are investigated and their results are compared to the more precise final products. The tests are designed such that harmonic oscillations with different frequencies and amplitudes and ground motion of a simulated real earthquake are generated using a single axis shake table and the PPP was used to capture these movements by monitoring time-change of the table positions. To evaluate the accuracy of PPP using ultra-rapid, rapid and final products, their results were compared with relative GNSS positioning and LVDT (Linear Variable Differential Transformer) data, treated as reference. The results show that the high-rate GNSS-PPP solutions based on the three products can capture frequencies of harmonic oscillations and dynamic displacement with good accuracy. There were slight differences between ultra-rapid, rapid and final products, where some of the tested events indicated that the latter two produced are more accurate and provide better results compared to the ultra-rapid product for monitoring short-term dynamic displacements.

• Journal of Korean Neurosurgical Society
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• 제57권4호
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• pp.266-270
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• 2015

Objective : Chronic subdural hematoma (CSDH) is one of the most frequent problems encountered in neurosurgery. Although burr-hole trephination is widely performed to treat CSDH, the incidence rate of recurrent CSDH is still 2-37%. The goal of this study is to determine the risk factors that affect recurrent CSDH. Methods : A total of 182 patients were included in this study who underwent burr-hole trephination. The clinical factors and radiographic features between the recurrence and the no recurrence groups were analyzed to find the parameters related to the postoperative recurrence of CSDH. Results : For the recurrence of CSDH that occurred in 25 patients (13.7%), among various risk factors, pre and postoperative midline displacements, which are more than 10 mm (p=0.000), and preoperative hemiparesis (p=0.026) had contributed to recurrent CSDH with statistical significance by univariate analysis. Unilateral CSDH were more frequently related to recurrent CSDH (16.3%), although it was not a statistical significant result (p=0.052). Furthermore, preoperative midline displacement only had statistical meaning for the recurrence of CSDH by multivariate analysis. Conclusion : This study indicates that the midline displacement on the preoperative computed tomography scan is the only independent predictor for the recurrence of CSDH.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2529-2534
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• 2012

Poly(3,4-ethylenedioxythiophene) coated Manganese Dioxide (PEDOT/$MnO_2$) composite electrode was fabricated by simply immersing the $MnO_2$ electrode in an acidic aqueous solution containing 3,4-ethylenedioxythiophene (EDOT) monomers. Analysis of open-circuit potential of the $MnO_2$ electrode in the solution indicates the reduction of outer surface of $MnO_2$ to dissolved $Mn^{2+}$ ions and simultaneously oxidation of EDOT monomer to PEDOT on the $MnO_2$ surface to form a PEDOT shell via a galvanic displacement reaction. Analysis of cyclic voltammograms and specific capacitance of the PEDOT/$MnO_2$, conductive carbon added $MnO_2$ and conductive carbon added PEDOT/$MnO_2$ electrodes suggests that the conductive carbon acted mainly to provide a continuous conducting path in the electrode to improve the rate capability and the PEDOT layer on $MnO_2$ acts to increase the active reaction site of $MnO_2$.

• 한국항행학회논문지
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• 제13권2호
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• pp.187-193
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• 2009

렌즈는 고정밀 레이저 거리 측정기에서 중요한 핵심 부품의 하나이다. 렌즈는 레이저 다이오드로부터 나온 광을 렌즈를 통하여 목표물로 보내고 또한 표적을 통하여 반사된 레이저 광을 다시 수신하여 그 위상 변위를 측정함으로서 거리를 계산하는데 이용한다. 본 논문에서는 렌즈의 곡률이 일정하기 않음으로서 발생하는 문제를 해결하기 위하여, 광을 일정하게 모아, 송수신이 가능한 새로운 연마기법의 레이저 거리 계측기용 렌즈를 설계하고 이를 기반으로 한 레이저 거리계를 구현한다. 구현한 레이저 거리계는 기존의 방법에 비해 오차가 적어 보다 정밀한 거리 계측에 적용 가능할 것으로 예상하고 있다.

• 한국공작기계학회논문집
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• 제16권5호
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• pp.108-114
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• 2007

A new cutting force estimating approach and machining state monitoring examples are presented which uses a cylindrical displacement sensor built into the spindle. To identify the tool-spindle system dynamics with frequency up to 2 kHz, a home-built electro-magnetic exciter is used. The result is used to build an algorithm to extract the dynamic cutting force signal from the spindle error motion; because the built-in spindle sensor signal contains both spindle-tool dynamics and tool-workpiece interactions. This sensor is very sensitive and can measure broadband signal without affecting the system dynamics. The main characteristic is that it is designed so that the measurement is irrelevant to the geometric errors by covering the entire circumferential area between the target and sensor. It is also very simple to be installed. Usually the spindle front cover part is copied and replaced with a new one with this sensor added. It gives valuable information about the operating condition of the spindle at any time. It can be used to monitor cutting force and chatter vibration, to predict roughness and to compensate the form error by overriding spindle speed or feed rate. This approach is particularly useful in monitoring a high speed machining process.

• Computers and Concrete
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• 제21권4호
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• pp.399-406
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• 2018

The present study focuses on the performance of basalt fiber reinforced concrete (BFRC) lining in tunnel situated in sandstone rock when subjected to internal blast loading. The blast analysis of the lined tunnel is carried out using the three-dimensional (3-D) nonlinear finite element (FE) method. The stress-strain response of the sandstone rock is simulated using a crushable plasticity model which can simulate the brittle behavior of rock and that of BFRC lining is analyzed using a damaged plasticity model for concrete capturing damage response. The strain rate dependent material properties of BFRC are collected from the literature and that of rock are taken from the authors' previous work using split Hopkinson pressure bar (SHPB). The constitutive model performance is validated through the FE simulation of SHPB test and the comparison of simulation results with the experimental data. Further, blast loading in the tunnel is simulated for 10 kg and 50 kg Trinitrotoluene (TNT) charge weights using the equivalent pressure-time curves obtained through hydrocode simulations. The analysis results are studied for the stress and displacement response of rock and tunnel lining. Blast performance of BFRC lining is compared with that of plain concrete (PC) and steel fiber reinforced concrete (SFRC) lining materials. It is observed that the BFRC lining exhibits almost 65% lesser displacement as compared to PC and 30% lesser displacement as compared to SFRC tunnel linings.

• 대한기계학회논문집
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• 제13권1호
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• pp.77-86
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• 1989

본 연구에서는 $C^{*}$ 적분을 수정하여 균열 진전의 효과를 배제하는 새로운 크립 파괴의 하중 매개변수 $C_{m}$ 을 제안하고 그 타당성을 검토한다. 또한 $C_{m}$ 의 전개 과정에서 유도되는 다른 하중 매개변수들의 특성과 그 이용가능성을 조사한다. 균열 진전 속도가 $C^{*}$ 의 지배를 받는 것으로 알려져 있는 스테인레스 강(stainless steel) STS 304(KS 규격)를 사용한 크립파괴 실험을 600.deg. C에서 수행하여 $C_{m}$ 의 크립 파괴에 대한 적용 가능성을 조사하도록 한다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2007년도 공동학술대회 논문집
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• pp.291-296
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• 2007

We measured potential waveform of load, displacement, micro electric signal generated by rock and mortar fracture using PXI A/D Converter. The rock type used for measurement was used granite, limestone and sandstone, and mortar specimen. we made measuring equipment of physical properties to confirm basic information of physical properties, measured physical properties of rock engineering, electric resistivity and seismic velocity. Potential waveform system was built using PXI A/D Converter and measured potential waveform of load, displacement, micro-electric signal generated using this during uniaxial compressive test by the specimen finished such test of physical properties. Using the saturated rock and mortar specimen, micro electric signal increased, and It didn't increase a signal in dried rock and mortar specimen according as load and strain rate increases. But signal also increased in saturated or dried specimen in case of sandstone. It was possible to check the close correlation relationship the signal and fracture behavior by a compressive load as the signal of fracture position was increased bigger than the other position. It was also possible to check the correlation relationship between physical properties and micro geo-electric signal.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.487-492
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• 2007

The enhancement of the service life of damaged or cracked structures is a major issue for researchers and engineers. The hierarchical void element with the integrals of Legend polynomials is used to characterize the fracture behavior of unpatched crack as well as repaired crack with bonded composite patches by computing the stress intensity factors and stress contours at the crack tip. The numerical approach is based on the v-version degenerate shell element including the theory of anisotropic laminated composites. Since the equivalent single layer approach is adopted in this study, the proposed element is necessary to represent a discontinuous crack part as a continuum body with zero stiffness of materials. Thus the aspect ratio of this element to represent the crack should be extremely slender. The sensitivity of numerical solution with respect to energy release rate, displacement and stress has been tested to show the robustness of hierarchical void element as the aspect ratio is increased up to 2000. The stiffness derivative method and displacement extrapolation method have been applied to calculate the stress intensity factors of Mode I problem.