• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.11
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• pp.1124-1131
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• 2014

The chirp spread spectrum (CSS) technique that transmits data signal by using a chirp signal is often used for maritime wireless communication systems such as sound detection radar systems for submarines. However, maritime multipath environment could reduce the data rate of the CSS system. To tackle the problem, an overlap-based CSS transmission scheme is proposed and analyzed in this paper: Based on the approximated Gaussian Q function, we derive a closed form expression of the bit error rate (BER) of the proposed overlap-based CSS system and investigate the mathematical relationship between the number of overlaps and the intersymbol interference (ISI).

• Korean Journal of Environment and Ecology
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• v.10 no.1
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• pp.66-75
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• 1996

To propose basic information for national resource management and planting disign, plant community structure of evergreen broad-leaved forest was investigated. Fifty-two plots(each size 300m$^{2}$) were set up at Ch'omch'alsan area of Chindo, Korea. TWINSPAN and DCA methods were used for classification and ordination analysis. Fifty-two plots were divided into seven groups, which were Quercus variabilis-Carpinus tschonoskii community, Q. glauca community, Castanepsis cuspidata var. sieboldii-Q. stenophylla community, Castanopsis cuspidata var. sieboldii-Camelia japonica community, Q. acuta-Camelia japonica community, Carpinus coreaca-Q spp. community, C. coreana community. Pinus densiflora almost have been selected. Carpinus tschomoskii, Q. variabillis and Q. serrata were to be succeeded by Castanea cuspidata var. sieboldii, Q. stenophylla, Q. acuta and Neolitsea sericea in canopy layer. And Neolitsea sericea, Q. glauca and Camellia japonica was showed high importance values in fertile soil condition. Future restoration plan was necessary for a tourist resort or national forest in warm temperate region. And evergreen broad-leaved plants shall be planted in considering of environmental condition at warm temperate and industrial complex area.

• Korean Journal of Environment and Ecology
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• v.28 no.1
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• pp.45-54
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• 2014

This study was carried out to investigate the ecological succession sere and conservative value, and to provide the basic data in Woonsooam Valley, in Jogyesan (Mt.) (altitude 884m), Suncheon City, Korea by analysing the structure of the plant community. Fifteen plots (size is $20m{\times}20m$) were set up at an altitude of range from 255m to 495m. As a result of analysis of DCA which is one of the ordination technique, the plant communities were divided into five groups which are community I (Pinus densiflora community), community II (Quercus variabilis-Quercus serrata community), community III (Q. serrata-Q. variabilis community), and community IV (Carpinus tschonoskii-Q. serrata community) and community v(Deciduous broad-leaved forest community). We found out that the vegetation of the study site located in the South Temperate Climate Zone. The study site is found out that Q. serrata community 34.4%, part of slope in valley is the distribution that dominant species is Q. serrata-Q. variabilis community 32.1%. And in valley showed Carpinus tschonoskii community 5.5%. And Sasa borealis was dominant species in the shrub layer. We couldn't supposed that the ecological succession sere of the study site, however we should do a long-term monitoring to investigate the changes of the ecological succession each plant community, According to the index of Shannon's diversity (unit: $400m^2$), community III was ranged from 1.0102 to 1.1013, community V was 0.9945, community II was ranged from 0.7913 to 1.1503, community IV was ranged from 0.8081 to 1.0749 and community I was 0.9273.

• Journal of the military operations research society of Korea
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• v.33 no.1
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• pp.31-42
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• 2007

While Defense Agency fur Technology and Quality(DTaQ) has been utilized a risk assessment method as a quality assurance activity for defense goods since 1999, a risk assessment method is known to be ineffective to identify defective items. The objective of this study is to propose the new evaluation method, that adjusts a relative priority of evaluation elements using AHP(Analytic Hierarchy Process). Newly evaluated scores have been applied to the risk assessment result of 2005 defective items to test a validity of the new evaluation model. The new model is capable to identify more high and medium risk-level items than the current method. The company risk-level gets more scores than the item risk-level in the new model.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.307-312
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• 1999

A piezoelectric flextentional sonar transducer has been simulated using a coupled FE-BEM. The dynamics of the sonar transducer is modelled in three dimensions and is analyzed with external electrical excitation conditions. Different results are available such as steady-state displacement modes, underwater directivity patterns. It is shown that the present barrel-stave sonar transducer of the piezoelectric material produces flextentional displacements which could be related with higher output power, lower quality factor and more omnidirectional beam pattern than other types of sonar transducers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.420-426
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• 2020

The purpose and main points of the ROK-US Navy were analyzed from various angles using the big data technology Word Cloud for efficient sea trials. First, a comparison of words extracted through keyword cleansing in the ROK-US Navy sea trial showed that the ROK Navy conducted a single equipment test, and the US Navy conducted an integrated test run focusing on the system. Second, an analysis of the ROK-US Navy sea trials showed that approximately 66.6% were analyzed as similar items, of which more than two items were 112 items Approximately 44% of the 252 items of the ROK Navy sea trials overlapped, and that 89 items (35% of the total) could be reduced when integrated into the US Navy sea trials. A ship is a complex system in which multiple equipment operates simultaneously. The focus on checking the functions and performance of individual equipment, such as the ROK Navy's sea trials, will increase the sea trial period because of the excessive number of sea trial targets. In addition, the budget required will inevitably increase due to an increase in schedule and evaluation costs. In the future, further research will be needed to achieve more efficient and accurate sea trials through integrated system evaluations, such as the U.S. Navy sea trials.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.5
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• pp.675-682
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• 2013

Reliability analysis and prediction of next failure time is critical to sustain weapon systems, concerning scheduled maintenance, spare parts replacement and maintenance interventions, etc. Since 1981, many methodology derived from various probabilistic and statistical theories has been suggested to do that activity. Nowadays, many A.I. tools have been used to support these predictions. Support Vector Regression(SVR) is a nonlinear regression technique extended from support vector machine. SVR can fit data flexibly and it has a wide variety of applications. This paper utilizes SVM and SVR with combining time series to predict the next failure time based on historical failure data. A numerical case using failure data from the military equipment is presented to demonstrate the performance of the proposed approach. Finally, the proposed approach is proved meaningful to predict next failure point and to estimate instantaneous failure rate and MTBF.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2002.05a
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• pp.797-803
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• 2002

다양한 리스크 문제가 발생하고 있는 기업 환경 속에서 세계선도 기업들은 이미 효과적인 리스크 관리시스템의 운영을 통하여 개업의 손실을 최소화함으로써 이윤을 극대화하고 있으나 우리 기업들은 아직 그렇지 못한 실정이다. 본 연구에서는 국제규격인 ISO14971과 IEC62198, JIS Q2001의 리스크 경영 규격을 중심으로 리스크 경영 시스템(Risk Management System :RMS)의 구성을 분석 비교한다. 각각의 규격에서 사용되는 적용범위, 용어 및 정의 리스크 경영의 개념과 절차, 경영 시스템에 적용되는 기법들을 비교, 분석하여 우리 기업들이 가지고있는 리스크 문제를 효과적으로 관리할 수 있는 대안 모색을 가능하도록 하는 기초 자료를 제시하고자 한다.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.356-356
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• 2017

최근 국토교통부 홍수통제소에서는 가뭄대응을 위해 1, 3개월 갈수예보를 시범적으로 운영하고 있다. 국가재난 위기경보단계(관심, 주의, 경계, 심각)에 따라 분류된 기준유량과 예측유량의 비교를 통해 갈수상황을 판단하며, 그 중 기준유량은 일본의 정상유량 산정 기법에 의해 계산된다. 그러나 우기 건기에 따라 상이한 유입량 및 물 사용량이 정상유량 산정에 고려되지 않았고, 각 위기단계별 물 부족상황이 재현되지 못하였다. 또한, 하천유량 부족은 가뭄과 관계가 밀접함에도 불구하고, 가뭄상황과의 연계분석이 이뤄지지 않았다. 본 연구에서는 갈수빈도와 정상유량산정 모델을 이용하여 기준유량을 재설정하고 가뭄상황을 분석하였다. 대상유역은 영산강유역으로 선정하였고, 보고된 하천수사용허가량, 댐 용수 공급량 및 10년 이상 장기간 관측된 관측소별 일 유량자료를 활용하였다. 일 관측유량을 7일 이동평균으로 변환한 후, 유황분석을 통해 $Q_{90}$을 산정하였으며, 빈도별 $Q_{90}$을 계산하였다. 정상유량 산정 모델에서 입력 자료(자연유량, 댐 공급량 및 하천수 허가량)에 가중치를 두어 양을 조절하고 각 빈도에 맞는 관개기 및 비관개기 기준유량을 산정 하였다. 가뭄지수로는 국내 활용성이 높은 Standardized Precipitaion Index (SPI) 및 Standardized Runoff Index (SRI)를 선정하였고, 이를 지속기간 1, 3, 6, 12개월에 따라 일별로 계산하였다. 7일 평균 관측유량이 기준유량 이하일 때, 이시점을 전 후로 가뭄지수의 시공간적 특성과 가뭄의 지속기간 및 심도를 분석하여 가뭄상황을 제시하였다. 본 연구의 결과는 갈수예보 시 하천유량 부족에 따른 물수지 및 가뭄상황에 대한 직관적인 판단과 갈수기 효율적인 하천수 조정 협의에 기여할 것으로 본다.

• International Area Studies Review
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• v.14 no.1
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• pp.185-202
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• 2010

While it is often assumed that a country's trade balance will improve in the long-run if its currency is allowed to depreciate, this is not necessarily the case for specific industry. This paper is to examine the long-run relationships between trade balance and real exchange rate using bilateral data of SITC 10 Industry Classification for Korea vis-${\grave{a}}$-vis her trading partners Indonesia, India, China, Japan on a quarterly basis over the period of 1999Q1 to 2008Q4. I applied the recent panel cointegration technique to reduce the small sample problems and improving power performance of the relevant estimation and inference procedures. The results reveal evidence of the Marshall-Lerner Condition in Indonesia 2 industries, India 5 industries, Japanese 4 industries, Chinese 6 industries. Whole group's cointegration statistic of India, China, Japan was supported Marshall-Lerner Condition but Indonesia was rejected.