• Journal of Communications and Networks
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• v.18 no.2
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• pp.150-161
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• 2016

Coordinated multi-point transmission (CoMP) techniques are being touted as enabling technologies for interference mitigation in next generation heterogeneous wireless networks (HetNets). In this paper, we present a comparative performance study of uplink (UL) CoMP algorithms for the 3GPP LTE HetNets. Focusing on a distributed and functionally-split architecture, we consider six distinct UL-CoMP algorithms: 1. Joint reception in the frequency-domain (JRFD) 2. Two-stage equalization (TSEQ) 3. Log-likelihood ratio exchange (LLR-E) 4. Symmetric TSEQ (S-TSEQ) 5. Transport block selection diversity (TBSD) 6. Coordinated scheduling with adaptive interference mitigation (CS-AIM) where JRFD, TSEQ, S-TSEQ, TBSD and CS-AIM are our main contributions in this paper, and quantify their relative performances via the post-processing signal-to-interference-plus-noise ratio distributions.We also compare the CoMP-specific front-haul rate requirements for all the schemes considered in this paper. Our results indicate that, with a linear minimum mean-square error receiver, the JRFD and TSEQ have identical performances, whereas S-TSEQ relaxes the front-haul latency requirements while approaching the performance of TSEQ. Furthermore, in a HetNet environment, we find that CS-AIM provides an attractive alternative to TBSD and LLR-E with a significantly reduced CoMP-specific front-haul rate requirement.

• Smart Structures and Systems
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• v.30 no.1
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• pp.89-106
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• 2022

The negative stiffness of an active or semi-active damper system has been proven to be very effective in reducing dynamic response. Therefore, energy dissipation devices possessing negative stiffness, such as viscous inertial mass dampers (VIMDs), have drawn much attention recently. The control performance of the VIMD for cable vibration mitigation has already been demonstrated by many researchers. In this paper, a new optimal design procedure for VIMD parameters for taut cable vibration control is presented based on the fixed-points method originally developed for tuned mass damper design. A model consisting of a taut cable and a VIMD installed near a cable end is studied. The frequency response function (FRF) of the cable under a sinusoidal load distributed proportionally to the mode shape is derived. Then, the fixed-points method is applied to the FRF curves. The performance of a VIMD with the optimal parameters is subsequently evaluated through simulations. A taut cable model with a tuned VIMD is established for several cases of external excitation. The performance of VIMDs using the proposed optimal parameters is compared with that in the literature. The results show that cable vibration can be significantly reduced using the proposed optimal VIMD with a relatively small amount of damping. Multiple VIMDs are applied effectively to reduce the cable vibration with multi-modal components.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2208-2213
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• 2007

In this study we have developed a hyperspectrum imaging system for highly sensitive and effective imaging analysis. An optical setup was designed using acoustic optical tunable filter (AOTF) for high sensitive hyperspectrum imaging. Light emitted by mercury lamp gets split in to diffracted and undiffracted beams while passing though AOTF. GFP transfected HEK-293 cell line was used as a model for in vitro imaging analysis. Cells were first, analyzed by fluorescence microscope followed by flow cytometric analysis. Flow cytometric analysis showed 66.31% transfection yield in GFP transfected HEK-293 cells. Various images of GFP transfected HEK-293 cell were grabbed by collecting the diffracted light using a CCD over a dynamic range of frequency of 129-171 MHz with an interval of 3 MHz. Subsequently, for in vivo image analysis of GFP transfected cells in mouse, a whole-body-imaging system was constructed. The blue light of 488 nm wavelength was obtained from a Xenon arc lamp using an appropriate filter and transmitted through an optical cable to a ring illuminator. To check the efficacy of the newly developed whole-body-imaging system, a comparative imaging analysis was performed on a normal mouse in presence and absence of Xenon arc irradiation. The developed hyperspectrum imaging analysis with AOTF showed the highest intensity of green fluorescent protein at 153 MHz of frequency and 494 nm of wavelength. However, the fluorescence intensity remained same as that of the background below 138 MHz (475 nm) and above 162 MHz (532 nm). The mouse images captured using the constructed whole-body-imaging system appeared monochromatic in absence of Xenon arc irradiation and blue when irradiated with Xenon arc lamp. Nevertheless, in either case mouse images appeared clearly.

• Journal of The Korean Society of Grassland and Forage Science
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• v.17 no.4
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• pp.371-378
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• 1997

The purpose of this research was to investigate the effect of P fertilization and cutting fkquency without N fertilizer on nutritive value and nitrogen fixation activity of alfalfa. A field experiment was conducted on the experimental farm of Kongju National University at Yesan from 1994 to 1996. The experimental design was a split plot design with two P levels as main plot and two cutting frequencies as the sub-plot. The results obtained are summarized as follows. Available phosphate, exchangeable Ca and Na in the soil were slightly increased with P fertilizer and basal treatment of lime. Average DM yield was 1.5 ton and 1.4 ton in second and third year. There was no significant difference within P level and cutting kquency. The first cut showed higest CP value as cutting times increased the value tend to be lowered. Crude protein content in 3 and 4 cutting regimes were from 16.3 to 16.6% 17.4 to 17.9% respectively, but no significant effect were found among the main and sub-plot. ADF and NDF in 1995 were ranged from 38.2 to 39.9, 45.1 to 58.1% respectively. ADF was 2% more higher in 1996 compared to previous year and NDF was slightly higher in 1996. There was significant difference of ADF between main plot in 1995. .P, Ca, K and Mg of 200kg P level with 3 times cutting treatment in 1995 and 1996 were 0.32 and 0.23, 0.95 and 0.84, 3.24 and 2.87, and 0.36 and 0.26. Significant difference of K and Mg between cutting frequency was observed in 1995. Nitrogen fixing activity of 400kg P fertilizer plots were higher than 200kg P level and 3 times cutting plot also showed higher acetylene reduction activity than that of 4 cutting per year. Phosphate level and cutting frequency treatment of did not significantly affect nitrogen fixation activity.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.05
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• pp.235-238
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• 1995

In this paper, we propose an effective coding method of the angiography by using the scalable structure in the frequency domain for MPACS(Medical Picture Archiving and Communication System). We employed the subband decomposition method and MPEG-2 system which is the international standard coding method of the general moving picture. After the subband decomposition is applied to split an input image into 4 bands in the spatial frequency domain, the motion compensated DPCM coding method of MPEG-2 is carried out for each subband. As a result, an easily controllable coding Structure is accomplished by composing the compound hit stream for each subband group. Follows are the simulation results of the proposed sheme for the angiography. A scalable structure which can be easily controlled for a loss of transmission or the band limit can be accomplisbed in the MPEG-2 stucture by the subband decomposition minimizing the side information. And by reducing the search area of the motion vector between -4 and 3, the processing speed of a codec is enhanced by more than two times without a loss of the picture quality compare with the conventional DCT coefficients decompositon method. And the processing speed is considerably improved in the case of the parallel construction of each subband in the hardware.

• Korean Journal of Optics and Photonics
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• v.31 no.1
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• pp.31-36
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• 2020

We propose a band-switchable terahertz metamaterial based on an etched vanadium dioxide (VO₂) thin film. A line of etched VO₂ thin film was placed in the center gap of the split square-loop shape for the tunability of the metamaterial. The resonance frequency of the metamaterial can be switched from the 1.4 THz band to the 0.7 THz band, according to the insulator-metal phase transition in the VO₂ thin film. The absolute difference in the transmittance of the metamaterial was 78.5% and 65.8% at 0.7 THz and 1.4 THz respectively, according to the band switching. The differential phase shift was around 90°, and the transmittance was stably maintained between 40% and 60% in the middle band of the two switchable resonance-frequency bands.

• The Research Journal of the Costume Culture
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• v.31 no.1
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• pp.34-52
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• 2023

In this study, text mining was conducted on the product names of skirts, pants, shirts/blouses, and dresses to analyze the characteristics of keywords appearing in online shopping product names. As a result of frequency analysis, the number of keywords that appeared 0.5% or more for each item was around 30, and the number of keywords that appeared 0.1% or more was around 150. The cumulative distribution rate of 150 terms was around 80%. Accordingly, information on 150 key terms was analyzed, from which item, clothing composition, and material information were the found to be the most important types of information (ranking in the top five of all items). In addition, fit and style information for skirts and pants and length information for skirts and dresses were also considered important information. Keywords representing clothing composition information were: banding, high waist, and split for skirts and pants; and V-neck, tie, long sleeves, and puff for shirts/blouses and dresses. It was possible to identify the current design characteristics preferred by consumers from this information. However, there were also problems with terminology that hindered the connection between sellers and consumers. The most common problems were the use of various terms with the same meaning and irregular use of Korean and English terms. However, as a result of using co-appearance frequency analysis, it can be interpreted that there is little intention for product exposure, so it is recommended to avoid it.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.190-190
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• 2022

최근 30년 강수량은 20세기 초보다 124mm 증가하였으며, 지역별 변동성 역시 매우 크다. 또한 일 강수량 80mm 이상의 강한 강수의 증가가 뚜렷하고 약한 강수가 감소하는 양극화로 인하여 홍수기에 홍수피해가 증가하는 추세를 보인다. 하지만 홍수에 대비하는 기간인 홍수기는 1970년 이전에 제정된 후 개선된 적이 없어 기후변화를 반영하지 못하고 있으며, 전국적으로 동일한 홍수기를 적용하고 있기에 최근 강수량의 지역특성이 강한 점을 반영하지 못하고 있다. 따라서 본 연구는 20세기와 21세기 두 그룹의 통계특성을 비교하여 홍수기의 강수량 변화를 정량화하여 기후변화를 보이고 국내 18개의 다목적댐 유역에서의 강수량 변화를 통계기법을 통해 지역 특성을 확인하였다. 이후 장마와 태풍을 기준으로 한 기존의 홍수기와 extension, shift, 그리고 split 등의 방법을 적용하여 개선한 홍수기를 비교하였다. 모의 방법은 댐 운영 기본 규칙에 국내 다목적댐에 가장 많이 활용되는 일정률-일정량 방식의 Rigid ROM과 예측한 유입수문곡선의 정확도가 관건인 일정량 방식의 Technical ROM을 활용하여 방류량을 결정하였다. 홍수저감효과는 계획방류량을 기준으로 한 세 가지 지표(frequency, duration, magnitude)를 통한 비교와 하천의 계획홍수량과 댐의 200년 빈도 계획홍수량을 기준으로 한 K-water 방법을 활용하여 평가하였다. 본 연구의 결과로 20세기와 21세기 홍수기의 통계량을 비교했을 때 강수량의 평균값이 86.55mm가 증가한 것을 확인할 수 있었으며, 각 댐 유역별로 비교하였을 때도 1개의 댐을 제외한 94%의 댐에서 증가 추세를 확인하였다. 추가적으로 모평균 차이를 95% 신뢰구간으로 확인한 결과 80% 이상의 범위에서 증가추세를 확인하였다. 가설검정 결과인 p-value가 최소 0.038에서 최대 0.3의 값을 가져 지역별 강수 차이 또한 유의미한 통계적 차이를 파악하였다. 홍수저감효과의 경우 2020년의 시범 유역에 대해서 15일의 extension을 적용한 홍수기가 기존의 홍수기에 비해 평균적으로 frequency는 0.002%, duration은 1.85hr, magnitude는 26.96% 정도 저감됨을 확인하였으며, flood의 횟수도 6회정도 적음을 확인할 수 있었다. 본 연구의 결과를 바탕으로 향후 기후변화에 대응한 새로운 홍수기의 기준을 제안할 수 있을 것으로 기대한다.

• Journal of The Geomorphological Association of Korea
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• v.27 no.1
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• pp.61-89
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• 2020

The objective of this study is to characterize landslide susceptibility depending on various geo-environmental variables as well as to compare the Frequency Ratio (FR) and Evidential Belief Function (EBF) methods for landslide susceptibility analysis of rainfall-induced landslides. In 2013, a total of 259 landslides occurred in Chuncheon, Gangwon Province, South Korea, due to heavy rainfall events with a total cumulative rainfall of 296~721mm in 106~231 hours duration. Landslides data were mapped with better accuracy using the geographic information system (ArcGIS 10.6 version) based on the historic landslide records in Chuncheon from the National Disaster Management System (NDMS), the 2013 landslide investigation report, orthographic images, and aerial photographs. Then the landslides were randomly split into a testing dataset (70%; 181 landslides) and validation dataset (30%; 78 landslides). First, geo-environmental variables were analyzed by using FR and EBF functions for the full data. The most significant factors related to landslides were altitude (100~200m), slope (15~25°), concave plan curvature, high SPI, young timber age, loose timber density, small timber diameter, artificial forests, coniferous forests, soil depth (50~100cm), very well-drained area, sandy loam soil and so on. Second, the landslide susceptibility index was calculated by using selected geo-environmental variables. The model fit and prediction performance were evaluated using the Receiver Operating Characteristic (ROC) curve and the Area Under Curve (AUC) methods. The AUC values of both model fit and prediction performance were 80.5% and 76.3% for FR and 76.6% and 74.9% for EBF respectively. However, the landslide susceptibility index, with classes of 'very high' and 'high', was detected by 73.1% of landslides in the EBF model rather than the FR model (66.7%). Therefore, the EBF can be a promising method for spatial prediction of landslide occurrence, while the FR is still a powerful method for the landslide susceptibility mapping.

• The Journal of the Acoustical Society of Korea
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• v.15 no.6
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• pp.81-89
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• 1996

It is very important for ultrasonic test method to evaluate the integrity of the class I components in nuclear power plants. However, as the rltrasonic test is affected by internal structures and configurations of test materials, backscattering, that is, time invariant noise is generated in large grain size materials. Due to the above reason, the received signal results in low signal to noise(S/N) ratio. Split spectrum processing(SSP) technique is effective to suppress the grain noise. The conventional SSP technique. however, has been applied to unique algorithm. This paper shows that MPO(minimization and polarity threshold) algorithm which two algorithms are applied simulatancously, was utilized, the signal processing time was shorten by using the new constant-Q SSP with the FIR filter which frequency to bandwidth ratio is constant and the optimum parameters were analysed for the signal processing to longitudinal wave and shear wave with the same requirements of inspection on nuclear power plant site. Moreover, the new ultrasonic test instrument, the reference block of the same product form and material specification, stainless stell test specimens and copper test specimens block of the same fabricated for the application of new SSP technique. As the result of experimental test with new ultrasonic test instrument and test specimens, the signal to noise ratio was improved by appying the new SSP technique.