• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7A
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• pp.668-675
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• 2002

This paper proposes pre-distorter combined LUT with 2ιpartition interpolation method to reduce nonlinear distortion which was caused by high PAPR and to update LUT quickly. Pre-distorted gain and phase can be found by using LUT which consisted of AM/AM and AM/PM value, and OFDM signal amplitude. The proposed 2ιpartition interpolation can accurately find predistorted gain and phase using bit shift and add component instead of increasing size of LUT which requires increasing the amount of computation. The performance of the proposed method was measured by the difference between HPA input and output characteristics by the LUT size, constellation, SER performance by the HPA, and LUT update error by the HPA characteristic changes. As a result, it is shown that when the size of the LUT is 32 and 64 for 16-QAM and 64-QAM, nonlinear distortion nearly didn't occurred.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2C
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• pp.105-111
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• 2011

In this paper, we propose a novel Alamouti space-time transmission scheme for orthogonal frequency division multiplexing (OFDM) based asynchronous cooperative communication systems with low relay complexity. The conventional scheme requires an additional operation likes time-reversal at the relay nodes besides the simple multiplications at the relay nodes, which result in increasing the complexity of relay nodes. Unlike the conventional scheme, exploiting the simple combination of the symbols at the source node and the simple multiplications at the relay nodes, the proposed scheme achieves the second order diversity gain by obtaining the Alamouti code structure at the destination node. Simulation results show that the proposed scheme achieves the second order diversity gain and has the same bit error rate performance as the conventional scheme.

• KDI Journal of Economic Policy
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• v.15 no.2
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• pp.121-160
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• 1993

본고(本稿) 1981~92년의 부당한 공동행위(共同行爲) 및 사업자단체금지행위(事業者團體禁止行爲) 심결례(審決例)들을 통해 우리나라 사업자들의 담합(談合)패턴과 특징(特徵)을 살펴보고 이를 바탕으로 담합규제법제(談合規制法制)와 그 운용상(運用上)의 문제(問題)들을 검토하여 담합규제(談合規制)의 실효성(實效性) 제고(提高)를 위한 경쟁정책적(競爭政策的) 대안(代案)들을 제시하고 있다. 우리의 담합규제법제(談合規制法制)와 법시행방법(法施行方法)은 은밀하고 지속적인 담합(談合)보다는 담합(談合)의 직접적 증거를 남길 가망이 많은 명시적(明示的) 공모행위(共謀行爲)의 적발(摘發)로 기울어져 있는 것으로 보인다. 사실, 담합사건(談合事件)들이 경쟁적(競爭的) 시장(市場)에 편재(偏在)되어 있고 사업자간(事業者間) 및 사업자단체(事業者團體) 공동행위(共同行爲)의 평균공모기간(平均共謀期間)이 각각 8개월과 10.7개월에 지나지 않는다는 것은 적발 시정조치된 행위(行爲)가 주로 담합(談合)의 시도(試圖)였음을 시사하는 것이다. 또한 가격고정공모(價格固定共謀)의 평균가격인상율(平均價格引上率)이 18%임을 감안할 때 담합실행기간(談合實行期間) 매출액(賣出額)의 1%라는 현재의 최고(最高) 과징금액(課徵金額)은 부당이득환수(不當利得還收)나 행정제재(行政制裁)의 어떤 측면에서도 그 실효성(實效性)이 극히 의심스러운 적은 금액이며, 거의 모든 위법행위(違法行爲)에 대하여 시정조치(是正措置)만이 취해지고 담합사업자(談合事業者)들에게 과징금(課徵金)이나 형사벌(刑事罰)이 부과되는 경우도 극히 드물어 담합억지효과(談合抑止效果)가 의문시되고 있다. 담합규제(談合規制)의 실효성(實效性) 제고(提高)를 위해서는 경쟁(競爭)의 실질적(實質的) 제한성(制限性)이 아니라 경쟁제한(競爭制限)의 부당성(不當性)을 위법성(違法性) 판단기준으로 하여 가격고정(價格固定), 입찰조작(入札操作), 시장분할(市場分割) 등 '적나라한' 담합(談合)에 대한 당연위법원칙(當然違法原則)을 확립하고, 과징금(課徵金)을 담합기간(談合期間) 매출액(賣出額)의 20% 정도로 상향조정(上向調整)하여 담합(談合)에 대한 핵심적 제재수단(制裁手段)으로 활용하여야 한다, 또한 담합(談合)의 적발(摘發) 입증노력(立證努力)에 경제적(經濟的) 분석(分析)과 증거(證據)를 이용하고, 특히 입찰조작(入札操作)의 감시(監視) 적발체제(摘發體制)를 확립하여 공공조달분야(公共調達分野)에 대한 경쟁정책(競爭政策)을 강화해야 하며, 묵시적(默示的) 담합(談合)을 가능케 하면서도 합의(合意)로 간주될 수 없는 담합촉진(談合促進) 기도행위(企圖行爲)를 금지할 법적(法的) 근거(根據)를 마련해야 할 것이다.

• Journal of the Korea Society of Computer and Information
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• v.10 no.4 s.36
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• pp.385-396
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• 2005

In this paper, a new structural approach to on-line signature verification is presented. A primitive pattern is defined as a part segmented by a local minimal position of speed. And a structural description of signature is composed of subpatterns which are defined as such forms as rotation shape, cusp shape and bell shape, acquired by composition of the primitives regarding the directional changes. As the matching method to find identical parts between two signatures, a modified DP(dynamic programming) matching algorithm is presented. And also, variation and complexity of local parts are computed from the training samples, and reference model and decision boundary are derived from these. Error rate, execution time and memory usage are compared among the functional approach, the parametric approach and the proposed structural approach. It is found that the average error rate can be reduced from 14.2% to 4.05% when the local parts of a signature are weighted and the complexity is used as a factor of decision threshold. Though the error rate is similar to that of functional approaches. time consumption and memory usage of the proposed structural approach are shown to be very effective.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.9 no.2
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• pp.74-85
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• 1997

Accurate analysis of water budget and seawater exchange characteristics is essential for the improvement and management of the degraded water quality in Masan Bay. In this study, water budget is simulated for the four divided coastal zones on the monthly base, and watershed runoff discharges which are important as input parameters are estimated using the runoff coefficient(=0.7). The main results are as follows : The runoff-contribution rate due to water supply discharge is increased from 10% in 1978 to the equivalent amount at present. The reduction quantity due to the wastewater interception is about 25% of total inflow discharges, and the net effects of both precipitation and evaporation is about 10%. As the hydraulic detention time in Masan Bay is estimated about 3 months, water exchange rate is to be very low. From the analysis of the salinity variation on account of water mixing, it appears no temporal correlation between monthly average precipitation and salinity, whereas only regional correlation is apparent.

• Journal of Digital Contents Society
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• v.9 no.3
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• pp.471-481
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• 2008

Test scheduling considering power dissipation is an effective technique to reduce the testing time of complex SoCs and to enhance fault coverage under limitation of allowed maximum power dissipation. In this paper, a modeling technique of test resources and a test scheduling algorithm for efficient test procedures are proposed and confirmed. For test resources modeling, two methods are described. One is to use the maximum point and next maximum point of power dissipation in test resources, the other one is to model test resources by partitioning of them. A novel heuristic test scheduling algorithm, using the extended-tree-growing-graph for generation of maximum embedded cores usable simultaneously by using relations between test resources and cores and power-dissipation-changing-graph for power optimization, is presented and compared with conventional algorithms to verify its efficiency.

• Journal of the Korea Society of Computer and Information
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• v.15 no.12
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• pp.37-45
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• 2010

This paper proposes a novel contrast enhancement method which determines the stretching ranges based on the distribution densities of segmented sub-histogram. In order to enhance the quality of image effectively, the contrast histogram is segmented into sub-histograms based on the density in each brightness region. Then the stretching range of each sub-histogram is determined by analysing its distribution density. The higher density region is extended wider than lower density region in the histogram. This method solves the over stretching problem, because it stretches using density rate of each area on the histogram. To evaluate the performance of the proposed algorithm, the experiments have been carried out on complex contrast images, and its superiority has been confirmed by comparing with the conventional methods.

• Membrane Journal
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• v.16 no.1
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• pp.1-8
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• 2006

Nanofiber is a broad phrase generally referring to a fiber with diameter less than 1 micron. Various polymers have been successfully electrospun into nanofibers in recent years. These nanofibers, due to their high surface area and porosity, have a great potential for use as filter medium, adsorption layers in protective clothing, etc. Nanofiber filters will enable new levels of filtration performance in the field of air filtration. In particular, nanofibers provide marked increases in filtration efficiency at relatively small pressure drop in permeability. Therefore, nanofiber filters could be substituted for conventional filter market due to the easy application of process and the possibility of coating to micron-sized non-woven sheets. This review is discussed on the trend of researche and development related to nanofiber filter including future marketability.

• KSBB Journal
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• v.19 no.6 s.89
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• pp.451-456
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• 2004

The effects of variation in composition of the medium on the conversion of Gluconacetobacter hanseii PJK cells producing cellulose ($Cel^+$) to non-cellulose producing ($Cel^-$) mutants and the production of bacterial cellulose (BC) in an agitated culture were investigated. The impeller speed greater than 500 rpm was required to decrease the population of $Cel^-$ mutants to minimum in a basal medium containing $1.5\%$ ethanol because the optimum impeller speed to minimize the population of $Cel^-$ mutants increased with the concentration of ethanol added to a basal medium. Ethanol fed-batch culture could not increase the BC production in an agitated culture unlike that of a shaking culture. The amount of BC produced in a basal medium containing $1\%$ ethanol was $39\%$ more than that of the same medium with $0.27\%\;Na_{2}HPO_4$. Increase in the concentration of acetic acid in a basal medium decreased the BC production. The pH control of the culture broth increased the cell mass in the batch culture and improved the production yield of water-soluble polysaccharide (WSPS), but did not affect the production of BC.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4B
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• pp.153-161
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• 2005

In a multi-channel network based of wavelength division multiplexing (WDM) technology, an efficient protocol is needed in order for the transmitter and receiver to be tuned to the same wavelength during message transmission time. This paper proposes a priority-based reservation protocol that can efficiently support variable-length messages that require different QoS requirements. In this proposed protocol, high-priority nodes can reserve the data channel before low-priority nodes. However, once a node reserves a data channel successfully, it can persistently use the reserved channel till message transmission is finished regardless of the priority of the node. Moreover, the protocol can operate independently of the number of nodes, and any new node can join the network anytime without requiring network re-initialization. The protocol is analyzed with a finite population model and the throughput-delay characteristics are investigated as performance measures.