• Journal of the Korean Geotechnical Society
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• v.22 no.12
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• pp.67-76
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• 2006

The reasonable assessment of the shear stiffness of a dredged soft ground and soft clay is difficult due to the soil disturbance. This study addresses the development and application of a new in-situ shear wave measuring apparatus (field velocity probe: FVP), which overcomes several of the limitations of conventional methods. Design concerns of this new apparatus include the disturbance of soils, cross-talking between transducers, electromagnetic coupling between cables, self acoustic insulation, the constant travel distance of S-wave, the rotation of the transducer, directly transmitted wave through a frame from transducer to transducer, and protection of the transducer and the cable. These concerns are effectively eliminated by continuous improvements through performing field and laboratory tests. The shear wave velocity of the FVP is simply calculated, without any inversion process, by using the travel distance and the first arrival time. The developed FVP Is tested in soil up to 30m in depth. The experimental results show that the FVP can produce every detailed shear wave velocity profiles in sand and clay layers. In addition, the shear wave velocity at the tested site correlates well with the cone tip resistance. This study suggests that the FVP may be an effective technique for measuring the shear wave velocity in the field to assess dynamic soil properties in soft ground.

• Tuberculosis and Respiratory Diseases
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• v.44 no.6
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• pp.1245-1255
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• 1997

Background : Rifampicin(RFP) is a key component of the antituberculous short-course chemotherapy and the RFP resistance is a marker of multi-drug resistant(MDR) tuberculosis. RPoB gene encodes the $\beta$-subunit of RNA polymerase of M. tuberculosis which is the target of RFP. And rpoB gene mutations are the cause of RFP resistance of M. tuberculosis. Although several reports showed that PCR-SSCP would be a rapid diagnostic method for identifying the RFP resistance, there were few reports Performed using direct, clinical specimens. So we Performed PCR-SSCP analysis of rpoB gene of M. tuberculosis in direct, clinical specimens. Methods : 75 clinical specimens were collected from patients at Asan Medical Center from June to August 1996. After PCR of IS 6110 fragments, 43 both AFB smear-positive and IS6110 fragment PCR-positive specimens were evaluated. The RFP susceptibility test was referred to the referral laboratory of the Korean Tuberculosis Institute. DNA was extracted by bead beater method. And heminested PCR was done using 0.1ul(1uCi) [$\alpha-^{32}P$]-dCTP. SSCP analysis was done using non-denaturating MDE gel electrophoresis. Results : The results of PCR of IS6110 fragments of M. tuberculosis were positive in 55(73%) cases of 75 AFB smear-positive clinical specimens. Of the 55 specimens, RFP susceptibility was confirmed in only 43 specimens. Of the 43 AFB smear-positive and IS6110 fragment-positive specimens, 29 were RFP susceptible and 14 were RFP resistant. All the RFP susceptible 29 strains showed the same mobility compared with that of RFP sensitive H37Rv in SSCP analysis of ropB gene. And all the other RFP resistant 13 strains showed the different mobility. In other words they showed 100% identical results between PCR-SSCP analysis and traditional susceptibility test. Conclusion : The PCR-sseP analysis of rpoB gene in direct clinical specimens could be used as a rapid diagnostic method for detecting RFP resistant M. tuberculosis.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.327-328
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• 2012

의료분야의 진단 방사선 장비는 초기의 필름방식 및 카세트에서 진보되어 현재는 디지털방식의 DR (Digital Radiography)이 널리 사용되며 이에 관한 연구개발이 활발히 진행 되고 있다. DR은 일반적으로 직접방식과 간접방식으로 나눌 수 있다. 직접방식의 원리는 X선을 흡수하면 전기적 신호를 발생 시키는 광도전체(Photoconductor)를 사용하여 광도전체 양단 전극에 전압을 인가하여 전기장을 유도한 가운데, X선을 조사하면 광도전체 내부에서 전자-전공쌍(Electron-hole pair)이 생성된다. 이것은 양단에 유도된 전기장의 영향으로 전자는 +극으로, 전공은 -극으로 이동하여 아래에 위치한 하부기판을 통하여 이미지로 변조된다. 간접방식은 X선을 흡수하면 가시광선으로 전환하는 형광체(Scintillator)를 사용하여 조사된 X선을 형광체에서 가시광선으로 전환하고, 이를 Photodiode와 같은 광변환소자로 전기적 신호로 변환하여 방사선을 검출하는 방식을 말한다. 본 연구에서는 직접방식에서 이용되는 광도전체 중 흡수효율이 높고 Mobility가 뛰어난 CdTe를 선정하여 PVD (Physical vapor deposition)방식으로 300 m의 두께를 목표로 하여 증착을 진행하였다. Chamber의 진공도가 $2.5{\times}10^{-2}$ Torr로 도달 시점부터, Substrate와 Boat에 열을 가하였다. Substrate온도는 $350^{\circ}C$, Boat온도는 $300^{\circ}C$도로 설정하여 11시간 동안 진행하였다. Substrate온도는 $303^{\circ}C$, Boat온도는 $297^{\circ}C$도부터 증착이 시작되어 선형적인 증가세 추이를 나타내어 Substrate 및 Boat온도가 설정 값에 도달 하였을 때, $25{\sim}34.4{\AA}/s$ 증착율을 나타내었다. 하부전극의 물질에 따른 CdTe증착 효율성 평가를 진행한 후, 그에 따른 전기적 특성을 알아보았다. 하부전극의 물질로는 ITO (Indium Tin Oxide), Parylene이 코팅 된 ITO, Au, Ag를 사용하였다. 하부전극의 물질 상단에 Thermal Evaporation System을 사용하여 CdTe를 증착한 후, Cdte 상단에 Au를 증착 시켜 민감도(Sensitivity)와 암전류(Dark current)를 측정하였다. 증착 결과 ITO와 Ag상단에 증착시킨 CdTe박막은 박리가 되었고, Au와 Parylene이 코팅 된 ITO에는 CdTe박막이 안정적이게 형성이 되었다. 이 두 샘플에 대하여 동일한 조건으로 민감도와 암전류를 측정 시, Parylene이 코팅된 ITO를 하부전극으로 사용한 CdTe박막은 0.1021 pA/$cm^2$의 암전류와 1.027 pC/$cm^2$의 민감도를 나타낸 반면, Au를 하부전극으로 사용한 CdTe박막은 0.0381 pA/$cm^2$의 암전류와 1.214 pC/$cm^2$의 민감도를 나타내어 Parylene이 코팅된 ITO보다 우수한 전기적 특성을 나타내었다. 따라서 Au는 CdTe박막 증착 시, 하부전극 기판으로서 뛰어난 특성을 나타내는 것을 알 수 있었다.

• The Journal of the Acoustical Society of Korea
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• v.38 no.1
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• pp.106-113
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• 2019

In this paper, we propose an algorithm to classify the received active pulse when the active sonar system is operated as a non-cooperative mode. The proposed algorithm uses CNN (Convolutional Neural Networks) which shows good performance in various fields. As an input of CNN, time frequency analysis data which performs STFT (Short Time Fourier Transform) of the received signal is used. The CNN used in this paper consists of two convolution and pulling layers. We designed a database based neural network and a pulse feature based neural network according to the output layer design. To verify the performance of the algorithm, the data of 3110 CW (Continuous Wave) pulses and LFM (Linear Frequency Modulated) pulses received from the actual ocean were processed to construct training data and test data. As a result of simulation, the database based neural network showed 99.9 % accuracy and the feature based neural network showed about 96 % accuracy when allowing 2 pixel error.

• Economic and Environmental Geology
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• v.27 no.1
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• pp.41-47
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• 1994

A fast Hankel transform (FHT) algorithm (Anderson, 1982) is applied to numerical evaluation of many Green's tensor integrals encountered in three-dimensional electromagnetic modeling using integral equations. Efficient computation of Hankel transforms is obtained by a combination of related and lagged convolutions which are available in the FHT. We express Green's tensor integrals for a layered half-space, and rewrite those to a form of related functions so that the FHT can be applied in an efficient manner. By use of the FHT, a complete or full matrix of the related Hankel transform can be rapidly and accurately calculated for about the same computation time as would be required for a single direct convolution. Computing time for a five-layer half-space shows that the FHT is about 117 and 4 times faster than conventional direct and multiple lagged convolution methods, respectively.

• Korean journal of food and cookery science
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• v.15 no.6
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• pp.611-617
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• 1999

Commercial soybean oil, which did not contain any antioxidant, were autoxidized at $60{\pm}2^{\circ}C$ for 79 days, and the changes of peroxide value(POV), thiobarbituric acid value(TBAV), conjugated dienoic acid(CDA) content, and fatty acid composition of the oil were studied during the 79 day-storage period. The samples with POV S of 0, 150, 300, 500, 450, 400 and 300 meq./kg oil were used for the test of mutagenic activity. The Ames test was carried out with and without metabolic activation. Bacterial strains used in this study were the histidine auxotrophic strains of S. typhimurium TA100, TA1535, and TA102 for the detection of base pair, and TA98 and TA1537 for frame shift mutations. Each series of samples was disso1ved in tetrahydrofuran(inhibitor free) and tested at doses ranging from 0.05 to 5 mg/plate. The autoxidized soybean oil increased significantly(p<0.05) the number of $His^+$ revertant colonies in cases of TA 98 with S9 mix, TA100 without S9 mix, 1535 and 1537 with and without S9, respectively. The samples having the highest peroxide values showed the strongest mutagenicity. It seemed that the amount of hydroperoxides in the oils was closely related to the mutagenic activity of the respective oils.

• Journal of the Korea Convergence Society
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• v.9 no.11
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• pp.53-60
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• 2018

This paper describes the experiments of gaze tracking utilizing a low-cost electrooculogram measuring device. The goal of the experiments is to verify whether the low-cost device can be used for a complicated human-computer interaction tool, such as the eye-writing. Two experiments are conducted for this goal: a simple gaze tracking of four directional eye-movements, and eye-writing-which is to draw letters or shapes in a virtual space. Eye-written alphabets were obtained by two PSL-iEOGs and an Arduino Uno; they were classified by dynamic positional warping after preprocessed by a wavelet function. The results show that the expected recognition accuracy of the four-directional recognition is close to 90% when noises are controlled, and the similar median accuracy (90.00%) was achieved for the eye-writing when the number of writing patterns are limited to five. In future works, additional algorithms for stabilizing the signal need to be developed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.11
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• pp.884-890
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• 2018

In this paper, an improved method of estimating static source location is proposed based on the direct position determination(DPD) method, which estimates a source position directly using received signals. When the source position is estimated using the conventional DPD method, the estimation accuracy and error depend on a pair of receivers: a reference receiver and one of the multiple moving receivers. Based on this, the weighting values of the estimating source location were obtained using the covariance matrix for the pair of receivers($S_1$, $S_{2i}$) and applied to the DPD algorithm. Finally, the source position was estimated using the proposed DPD algorithm, and it was verified that the estimation accuracy improved, compared to the conventional DPD algorithm.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.6
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• pp.527-534
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• 2015

This study offers a novel method for improving the physical contact between the anode and fuel in a direct carbon fuel cell (DCFC): a direct generation of carbon in a porous Ni anode through the thermal decomposition of gaseous hydrocarbons. Three kinds of alkane hydrocarbons with different carbon numbers (CH4, C2H6, and C3H8) are tested. From electron microscope observations of the carbon particles generated from each hydrocarbon, we confirm that more carbon spheres (CS), carbon nanotubes (CNT), and carbon nanofibers (CNF) were identified with increasing carbon number. Raman scattering results revealed that the carbon samples became less crystalline and more flexible with increasing carbon number. DCFC performance was measured at $700^{\circ}C$ with the anode fueled by the same mass of each carbon sample. One-dimensional carbon fuels of CNT and CNF more actively produced and had power densities 148 and 210 times higher than that of the CS, respectively. This difference is partly attributed to the findings that the less-crystalline CNT and CNF have much lower charge transfer resistances than the CS.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.5
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• pp.74-84
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• 2017

Since a soldier manages a hand-held landmine detector by hands, it is necessary to develop a system that can detect the target quickly and accurately. However, the hand-held landmine detector used in Korea has a problem that it can only detect the metal mines. Therefore, it is important to solve the problem and to develop a hand-held landmine detection system suitable for the Korean environment. In this paper, we propose a hand-held landmine detection system suitable for the Korean environment using ground penetrating radar. The proposed system uses depth compensation, matched filtering, and frequency shifting filtering for preprocessing. Then, in the detection step, the system detects the target using the edge ratio. In order to evaluate the proposed system, we buried landmines in sandy loam which is most of the soil in Korea and obtained a set of ground penetrating radar data by using a hand-held landmine detector. By using the obtained data, we carried out some experiments on the size and position of the patch and the shifting frequency to find the optimal parameter values and measured the detection performance using the optimized values. Experimental results show that the proposed preprocessing algorithms are suitable for detecting all landmines at low false alarm rate and the performance of the proposed system is superior to that of previous works.