• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.91-96
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• 2001

Restoration of contaminated soils to an environmentally acceptable condition is important. One of the newer techniques in soil remediation is a method based on electrokinetic phenomena in soils. The technology uses electricity to affect chemical concentrations and water flow through the pores of soils. An important advantage of electrokinetic soil remediation over other in-situ processes such as soil flushing is the capability of control over the movement of the contaminants. Because the migration of the contaminants is confined by the electric field, there is little dispersion outside the treatment zone. Furthermore, the process is effective for soils with low and variable permeability. In the present study, the distributions of cadmium in the electrokinetic processing of kaolinite under the condition of constant applied voltage are investigated. Cadmium accumulates near the cathode without reducing the diffusion of hydroxide ion into the soil. In keeping the catholyte pH at neutrality, cadmium migrates toward the cathode without any accumulation of cadmium near the cathode and is successfully removed at the cathode reservoir. It was also found that the progress of electrokinetic processing of cadmium could be gasped to a certain extent by monitoring the local voltage and the current density.

• 전기학회논문지
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• 제61권8호
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• pp.1159-1163
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• 2012

In this paper, a new method is suggested to reduce the size of a wide-band array antenna. The power-divider for the feeding structure is made compact as ${\lambda}/8$ with the help of a novel Metamaterial UWB bandpass filter. This power divider is clearly different from others in that the proposed design uses microstrip structured Composite Right and Left-Handed (CRLH) filters, while others use two dielectric layers or long tapered transmission lines. In order to validate the proposed design method, the circuit and full-wave simulated results of the power divider with the Metamaterial UWB filters are compared to each other, and the Metamaterial properties of the structure are shown with the electric field at the ZOR and dispersion diagram. Furthermore, the antenna performance of the fabricated antenna with the power divider is measured and compared with the prediction. Also, the size reduction effect by the proposed scheme is addressed.

• Current Optics and Photonics
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• 제5권4호
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• pp.370-374
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• 2021

Corals are the remains of animals that grow on warm beaches. They have been used as decorative jewels because of their variety of colors, and as medicinal materials for treating cancers, AIDS, and other therapeutic uses because of their chemical elements. Corals are mainly composed of calcium carbonate (CaCO₃) and have many air pores, tens to hundreds of micrometers in size. The refractive indices and absorption coefficients of dried sliced staghorn corals are investigated using terahertz time-domain spectroscopy. The measured values are similar to those for CaCO₃, as expected. It is observed that a sample with a microstructure formed by air pores can guide terahertz waves. The dispersion, effective index, and loss of the guiding modes of coral core surrounded by five triangular air pores are numerically calculated. The simulated spatial distribution of the electric field of the guide mode at 1.25 THz shows the mode to be tightly confined to the core.

• Advances in nano research
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• 제15권2호
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• pp.175-189
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• 2023

The under-evaluation structure includes a functionally graded porous (FGP) core which is confined by two piezoelectric carbon nanotubes reinforced composite (CNTRC) layers. The whole structure rests on the Pasternak foundation. Using quasi-3D hyperbolic shear deformation theory, governing equations of a sandwich plate are driven. Moreover, face sheets are subjected to the electric field and the whole model is under thermal loading. The properties of all layers alter continuously along with thickness direction due to the CNTs and pores distributions. By conducting the current study, the results emerged in detail to assess the effects of different parameters on buckling of structure. As instance, it is revealed that highest and lowest critical buckling load and consequently stiffness, is due to the V-A and A-V CNTs dispersion type, respectively. Furthermore, it is revealed that by porosity coefficient enhancement, critical buckling load and consequently, stiffness reduces dramatically. Current paper results can be used in various high-tech industries as aerospace factories.

• 천문학회보
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• 제36권2호
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• pp.86.1-86.1
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• 2011

We are developing a new universal spectropolarimeter on the Domeless Solar Telescope (DST) at the Hida Observatory to realize precise spectropolarimetric observations in a wide range of wavelength in visible and near infrared. The system aims to open a new window of plasma diagnostics by using Zeeman effect, Hanle effect, Stark effect, impact polarization, and atomic polarization for measuring the external magnetic field, electric field, or an anisotropy in the excitation of the atoms. The polarimeter is a successor of formerly developed polarimeter on DST, which make possible to observe a polarization in a photospheric spectral line with polarimetric accuracy of 10-2 (Kiyohara et al. 2004). The new system consists of a 60cm aperture vacuum telescope, a high dispersion vacuum spectrograph, polarization modulator / analyzer composed of a rotating waveplate whose retardation is constant for a wide range of wavelength and Wallaston prism, and a fast and large format CCD camera or IR camera. Spectral images in both orthogonal polarizations are taken simultaneously with a frame rate of ~20Hz while the waveplate rotates continuously in a rate of 1rev./sec. Thus It takes 5 ~ 60 sec to observe polarization with accuracy of 10-3 in a wide wavelength range (400 - 1100nm). We also examined a polarimetric model of the telescope with accuracy of 10-3 to calibrate instrumental polarization on some wavelengths. In this talk, I will focus on the performance of the instrument.

• 한국전자파학회논문지
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• 제30권3호
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• pp.202-208
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• 2019

본 논문에서는 일차원 배열과 이차원 배열일 때 프린티드 다이폴의 스캔 블라인드니스 특성을 분석한다. 먼저 시뮬레이션을 이용하여 일차원과 이차원 배열일 때 프린티드 다이폴안테나의 능동소자패턴을 구한다. 이차원 배열에서는 E-면 방향으로 스캔 블라인드니스가 ${\pm}36^{\circ}$ 부근에서 발생하였으나, 일차원 배열에서는 스캔 블라인드현상이 거의 관측되지 않았다. 이차원 스캔 블라인드니스 원인을 분석하기 위해 먼저 이차원 배열의 단위 셀 분산 특성을 구하고, 주파수에 따른 스캔 블라인드니스와 비교한다. 그리고 일차원 배열과 이차원 배열에서의 단위 셀에서 Q 값을 비교함으로써 일차원과 이차원 배열에서 스캔 블라인드현상 차이를 설명한다. 선형으로 배열된 다이폴 구조에서 두 포트 사이에 아홉 개의 소자가 떨어져 있을 때 E-면 방향으로 전기장의 커플링을 시뮬레이션을 통하여 관측함으로써 이론의 타당성을 보인다. 마지막으로 프린티드 다이폴 배열을 제작하고, $11{\times}1$ 부배열과 $11{\times}3$ 부배열에 대해 능동소자패턴을 각각 측정하여, 시뮬레이션 결과와 비교함으로 이론을 검증한다.

• Journal of Ginseng Research
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• 제45권1호
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• pp.1-21
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• 2021

Panax species have gained numerous attentions because of their various biological effects on cardiovascular, kidney, reproductive diseases known for a long time. Recently, advanced analytical methods including thin layer chromatography, high-performance thin layer chromatography, gas chromatography, high-performance liquid chromatography, ultra-high performance liquid chromatography with tandem ultraviolet, diode array detector, evaporative light scattering detector, and mass detector, two-dimensional high-performance liquid chromatography, high speed counter-current chromatography, high speed centrifugal partition chromatography, micellar electrokinetic chromatography, high-performance anion-exchange chromatography, ambient ionization mass spectrometry, molecularly imprinted polymer, enzyme immunoassay, 1H-NMR, and infrared spectroscopy have been used to identify and evaluate chemical constituents in Panax species. Moreover, Soxhlet extraction, heat reflux extraction, ultrasonic extraction, solid phase extraction, microwave-assisted extraction, pressurized liquid extraction, enzyme-assisted extraction, acceleration solvent extraction, matrix solid phase dispersion extraction, and pulsed electric field are discussed. In this review, a total of 219 articles published from 1980 to 2018 are investigated. Panax species including P. notoginseng, P. quinquefolius, sand P. ginseng in the raw and processed forms from different parts, geographical origins, and growing times are studied. Furthermore, the potential biomarkers are screened through the previous articles. It is expected that the review can provide a fundamental for further studies.

• Korean Chemical Engineering Research
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• 제50권4호
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• pp.684-689
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• 2012

Poly(acrylic acid) (PAA) 구형 입자는 바이오 분야의 소재에서부터 전자 재료에 이르기까지 다양한 분야에 사용되는 고분자 물질이다. 이를 생산하기 위해서는, 분산제(surfactant)를 이용한 중합 방법으로 합성을 한 후, 사용한 분산제를 제거하기 위한 별도의 Purification 과정을 거치게 된다. 일반 유기 용매를 사용하면 막대한 폐수 발생, 별도의 분리 공정 추가, 잔류 용매의 가능성 등의 문제점이 발생한다. 이에 이러한 문제를 해결하고자, 액체 이산화탄소를 용매로 하여, high-pressure Soxhlet extraction 방법을 개발하였다. 본 연구에서는 compressed liquid dimethyl ether (DME) 상에서 PAA 분산 중합에 사용된 pyrrolidene carboxylic acid-g-poly (siloxane) 계열의 분산제, Monasil PCA 제거하는 연구를 진행하였다. 추출된 PAA 입자의 모양은 field emission scanning electron microscopy (FE-SEM)으로 확인을 하였고, Monasil PCA의 농도는 Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES)로 분석하였다. 용매의 효과를 비교하기 위해서, 액체 이산화탄소와 n-hexane과 liquid DME를 대상으로 추출 실험을 하였다. 그 결과 n-hexane의 경우 일부 정제된 PAA 구형 입자를 얻을 수 있었지만, 일부는 n-hexane 증기의 높은 열에 의해서 변형된 형태의 입자를 얻었다. Liquid DME의 경우엔, 추출이 잘 되지 않았다. 액체 $CO_2$를 이용하는 경우에 구형의 형태는 유지하면서 분산제가 제거된 입자를 얻을 수 있었다. 그리고 최적 운전 조건을 알기 위해서 8시간 동안 재비기와 응축기의 온도를 달리하면서 실험을 실시하였다. 그 결과 추출기의 온도가 $19.6{\pm}0.2^{\circ}C$, 압력이 $51.5{\pm}0.5$ bar일 때, 가장 좋은 제거 효율을 보였다.