• 한국해양공학회지
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• 제28권3호
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• pp.254-259
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• 2014

The infrared signature of a ship is largely influenced by the ocean environment of the operating area, which has been known to cause large changes in the signature. As a result, the weather condition has to be clearly set for an analysis of the infrared signatures. It is necessary to analyze meteorological data for all the oceans where the ship is supposed to be operated. This is impossibly costly and time consuming because of the huge size of the data. Therefore, the creation of a standard environmental variable for an infrared signature research is necessary. In this study, we compared and analyzed sampling methods to represent ocean data close to the Korean peninsula. In order to perform this research, we collected ocean meteorological records from KMA (Korea Meteorological Administration), and sampled these in numerous ways considering five variables that are known to affect the infrared signature. Specifically, a simple random sampling method for all the data and 1-D, 2-D, and 3-D stratified sampling methods were compared and analyzed by considering the mean square errors for each method.

• 한국산업정보학회논문지
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• 제23권2호
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• pp.19-28
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• 2018

본 연구에서는 함정 신호해석 연구에 필요한 해양기상환경 자료의 표본추출에 관한 연구를 수행하였다. 이를 위해 한국 기상청으로부터 품질검사가 완료된 최신의 해양 기상자료를 수집하고, 측정 자료의 가용 구간을 설정하여 이상치를 제거하였다. 품질검사와 이상치를 제거한 자료는 함정 신호의 확률론적 해석을 위해 지정학적 위협과 부이의 유효면적을 고려하여 단순임의추출법을 통해 축소되었다. 이후 표본의 크기는 모집단의 크기와 신뢰수준 95%를 고려하여 100, 200 그리고 400개로 설정하였으며, 상관관계가 높은 수온과 기온을 기준으로 하는 2차원 층화추출법으로 최종표본을 추출하였다. 추출 표본은 제곱오차의 합과 신뢰구간을 추정하고 이를 비교하여 함정의 확률론적 신호해석을 위해 필요한 해양기상조건의 크기를 제시하였다.

• 대한조선학회논문집
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• 제51권3호
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• pp.193-202
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• 2014

This paper presents a new method of sampling the climatic data for infrared signature analysis. Historical hourly data from a stationary marine buoy of KMA(Korean Meteorological Administration) are used to select a small number of sample points (N=100) to adequately cover the range of statistics(PDF, CDF) displayed by the original data set (S=56,670). The method uses a coarse bin to subdivide the variable space ($3^5$=243 bins) to make sample points cover the original data range, and a single-point ranking system to select individual points so that uniform coverage (1/N = 0.01) is obtained for each variable. The principal component analysis is used to calculate a joint probability of the coupled climatic variables. The selected sample data show good agreement to the original data set in statistical distribution and they will be used for statistical analysis of infrared signature and susceptibility of naval ships.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권8호
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• pp.3911-3924
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• 2016

Compared to the classical cryptography, lattice-based cryptography is more secure, flexible and simple, and it is believed to be secure against quantum computers. In this paper, an efficient signature scheme is proposed from the ring learning with errors (R-LWE), which avoids sampling from discrete Gaussians and has the characteristics of the much simpler description etc. Then, the scheme is implemented in C/C++ and makes a comparison with the RSA signature scheme in detail. Additionally, a linearly homomorphic signature scheme without trapdoor is proposed from the R-LWE assumption. The security of the above two schemes are reducible to the worst-case hardness of shortest vectors on ideal lattices. The security analyses indicate the proposed schemes are unforgeable under chosen message attack model, and the efficiency analyses also show that the above schemes are much more efficient than other correlative signature schemes.

• 대한조선학회논문집
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• 제56권5호
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• pp.383-388
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• 2019

It is essential to reduce the Infra-red signature for increasing ship's survivability in ship design stage. However the ship's IR signature is quite sensitive to the maritime and atmosphere. Therefore, it is very important to select the marine meteorological data to be applied to the signature analysis. In this study, we selected the three meteorological sample sets from the population of the Korea Meteorological Administration's marine environment data in 2017. These samples were selected through the two-dimensional stratified sampling method, taking into account the geopolitical threats of the Korean peninsula and the effective area of the buoy. These sample sets were applied to three naval ships classified by their tonnage, and then the IR signature analysis was performed to derive the Contrast Radiant Intensity (CRI) values. Based on the CRI values, the validity of each sample set was determined by comparing Cumulative Distribution Function (CDF), and Probability Density Function (PDF). Also, we checked the degree of scattering in each sample set and determined the efficiency of analysis time and cost according to marine meteorological sample sets to confirm the possibility of a probabilistic method. Through this process, we selected the standard for optimization of marine meteorological sample for ship IR signature analysis. Based on this optimization sample, by applying probabilistic method to the management of IR signature for naval ships, the robust design is possible.

• 정보보호학회논문지
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• 제21권1호
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• pp.125-133
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• 2011

최근 들어, 모바일 단말의 폭발적인 보급 더불어 단말 내의 중요정보가 외부 저장 매체로 불법적으로 유출되는 보안 위협이 증가되고 있다. 따라서, 본 논문에서는 단말 내 중요정보의 외부 저장 매체로의 유출 방지 기법을 설계 및 구현한다. 이 기법은 파일의 임의위치에서 시그니처를 샘플링하고 이를 이용하여 유출 탐지, 차단 기능을 수행한다. 시그니처 샘플링 과정은 대상 파일을 일정 크기의 추출 윈도우로 구분한 후 이 영역 내에서 임의의 위치에서 1개 이상의 시그니처를 추출한다. 그리고, 가장 효과적인 샘플링을 수행하기 위하여 전체 샘플링, 이항분포 샘플링, 동적 샘플링의 다양한 추출 방식을 구현 및 시뮬레이션을 수행 한다. 제안된 기법은 파일의 임의 위치에서 시그니처를 샘플링하여 공격자의 시그니처 예측성을 낮출 수 있고 원본 데이터에 대한 변형 없이 유출 방지기능을 효과적으로 구현할 수 있다는 장점을 가진다. 따라서, 사용자 편의성이 중시되고 비교적 저 사양의 시스템인 모바일 단말에서 효과적으로 유출방지 기능을 구현할 수 있는 기법이다.

• Journal of Communications and Networks
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• 제4권3호
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• pp.189-198
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• 2002

Precoder has been shown to be able to provide source diversity and design flexibility. In this paper we employ precoding techniques for block transmission based on a multirate filterbank structure. To accommodate multiuser communication with variable data rates, different precoders with corresponding coefficients and up/down sampling rates are used. However, due to unknown multipath distortion, different interferences may exist in the received data, such as multiuser interference, intersymbol interference and interblock interference. To estimate channel parameters for a desired user, we employ all structured signature waveforms associated with different symbols of that user and apply subspace techniques. Therefore better performance of channel estimator can be achieved than the conventional subspace method based only on the signature of the current symbol. The delay for that user can also be jointly estimated. Channel identifiability conditions and asymptotic channel estimation error are investigated in detail. Numerical examples are provided to justify the proposed method. gest either multicode (MC) or multiple processing gain (MPG) mechanism [2], while requiring data rates to be integral multiples of some basic low-rate. In order to support variable rate transmission however, a comprehensive scheme needs to be investigated.

• 응용통계연구
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• 제25권1호
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• pp.15-27
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• 2012

본 논문에서는 KOSPI 시가총액기준 상위 4종목(삼성전자, 현대차, 현대모비스, POSCO)의 고빈도 거래 데이터를 바탕으로 일중 수익률의 실현변동성과 시장미시구조잡음에 대해 연구한다. Volatility signature plot을 통해 실현변동성(Realized Variance; RV)과 편의수정 실현변동성($RV_{AC_1}$)의 편의를 확인하고 시장미시구조 잡음의 특징을 실증적으로 파악한다. 또한, 잡음 대 신호비(Noise-to-Signal Ratio; NSR)를 사용하여, 평균제곱오차(Mean Square Error; MSE) 기준의 실현변동성(RV)과 편의수정 실현변동성($RV_{AC_1}$)의 최적 추출 빈도수를 추정해본다.

• 한국지구과학회지
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• 제28권5호
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• pp.572-584
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• 2007

The quantification of ammonia concentrations has received a lot of scientific attention. Numerous devices for the quantification of $NH_3$ in the ambient air have been developed to provide more technical possibilities for research in abating $NH_3$ emission from various source processes. For the proper quantification of $NH_3$, a number of sampling methods have been discussed by grouping them into different categories based on the principle of functioning. In general, active samplers employ pumps to draw air in, while passive samplers are exposed to air over a certain period of time to obtain integrated signature of $NH_3$. In case of the former, impingers and absorption flasks can be employed simultaneously with suitable absorbents to capture $NH_3$ passing through them. The methods of analysis include both in-situ and laboratory determination. In the laboratory, colorimetric or ion chromatographic methods are generally used for its quantification. In the field, a number of real time analyzers have been proven to be useful. These real time analyzers can be grouped according to their principle of operation. These analyzers may use the principle of spectroscopy (e.g. DOAS), photoacousticics (e.g. photoacoustic monitor) or Chemiluminescence ($NO_x$ analyzer). The automated annular denuder sampling system with on-line analyzer is also suitable for continuous monitoring of ammonia in air.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.550-553
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• 2005

To acquire radar target signature, various kinds of target are necessary. Measurement is one of the data acquiring method, but much time and high cost is required to get the target data from the real targets. Even if we can afford that, the targets we can access are very limited. To obtain target signatures avoiding these problems, we build the target CAD (Computer Aided Design) model for the calculation of target signatures. To speed up RCS calculation, we applied adaptive super-sampling and tested quite complex tank CAD model which is 1.4 hundred of thousands facet. We use calculated RCS data for ID range profile and 2D ISAR (Inverse Synthetic Aperture Radar) image formation. We adopted IFFT (Inverse Fast Fourier Transform) algorithm combined with polar formatting algorithm for the ISAR imaging. We could confirm the possibility of the construction of database from the images of CAD models for target classification applications.