• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권9호
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• pp.4588-4608
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• 2017

The measurement of information security levels is a very important but difficult task. So far, various measurement methods have studied the development of new indices. Note, however, that researches have focused on the problem of attaining a certain level but largely neglecting research focused on the issue of how different types of possible flaws in security controls affect each other and which flaws are more critical because of these effects. Furthermore, applying the same weight across the board to these flaws has made it difficult to identify the relative importance. In this paper, the interrelationships among security flaws that occurred in the security controls of K-ISMS were analyzed, and the relative impact of each security control was measured. Additionally, a case-control study was applied using empirical data to eliminate subjective bias as a shortcoming of expert surveys and comparative studies. The security controls were divided into 2 groups depending on whether or not a security flaw occurs. The experimental results show the impact relationship and the severity among security flaws. We expect these results to be applied as good reference indices when making decisions on the removal of security flaws in an enterprise.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 B
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• pp.477-479
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• 1998

This paper presents the results of the field of an improved GPS navigation algorithm. The improved GPS navigation algorithm is a modified Kalman filter which is designed to be ideally suited to car navigation in urban area where lack of GPS visibility is the major problem because of the frequent blockage of the GPS signals by tall buildings and other structures. The method allows the user to estimate its position when the number of visible GPS satellites becomes less than four by using altitude fixing and clock bias estimation techniques. The two estimation techniques are integrated with the Kalman filter in a mutually compensating manner and it is shown that the 3-dimensional position accuracy is well maintained when the number of the visible satellites drops down to two for a reasonable period of time. The post processing results are included to show the improved performance of the modified algorithm over a normal conventional GPS Kalman filter.

• 한국주조공학회지
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• 제26권4호
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• pp.184-190
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• 2006

Presence of inclusions in Ti castings imparts detrimental effects on the mechanical performance of castings. However, actual inclusions do not occur very frequently and they are difficult to locate. As a result, acquirement of specimens for mechanical tests and thus in-depth research of the adverse influence of inclusions are challenging. To address this problem, artificial inclusion seeding methodology is developed to emulate actual inclusions in Ti investment castings. Firstly, to validate that this new methodology does not result in inherent mechanical property degradation, Ti specimens with machined, backfilled and HIPed holes are produced and compared to control (unaltered), cast Ti material. Fatigue test results indicate that this 'machine-and-HIP methodology without seeding' does not result in any fundamental mechanical property alteration, which would bias ensuing comparative results. Secondly, based on this result, validation of the artificially seeded inclusions being equivalent to 'as cast' inclusions is performed by comparing their fatigue behaviors. Test specimens created by the novel artificial inclusion seeding methodology are equivalent to Ti casting specimens containing actual cast-in inclusions, and an adverse effect of inclusions in investment castings is confirmed.

• 전자공학회논문지SC
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• 제42권4호
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• pp.1-10
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• 2005

본 논문에서는 다중 가설 기법을 이용한 차량 항법용 지도 정합법을 제안하였다. 다중가설기법을 지도 정합에 도입하기 위하여 GPS/DR 센서 출력 부근의 도로에 대하여 의사 측정치를 정의하였으며, 이를 이용하여 단일 표적문제로 다중 가설 기법을 유도하였다. 가설에 대한 확률식을 유도할 때 GPS/DR 센서 출력뿐만 아니라 디지털 지도의 위상정보가 포함되도록 하였다. 또한 지도 정합 성능의 향상을 위하여 디지털 지도의 바이어스 오차를 보상하기 위한 바이어스 칼만 필터를 제안하였다. 주행 실험결과 제안한 지도 정합법은 도로 밀집지역, 입체도로지역 등 지도 정합이 어려운 지역에서도 우수한 성능을 보였다.

• Journal of Power Electronics
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• 제6권1호
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• pp.73-82
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• 2006

Plasma display panels (PDPs) have a serious thermal problem, because the luminance efficiency of a conventional PDP is about 1.5 1m/W and it is less than $3\~5\;lm/W$ of a cathode ray tube (CRT). Thus there is a need for improving the luminance efficiency of the PDP. There are several approaches to improve the luminance efficiency of the PDP and we adopted a driving PDP at high frequency range from 400kHz up to over 700kHz. Since a PDP is regarded as an equivalent inherent capacitance, many types of sustaining drivers have been proposed and widely used to recover the energy stored in the PDP. However, these circuits have some drawbacks for driving PDPs at high frequency ranges. In this paper, we investigate the effect of the parasitic components on the PDP itself and on the driver when the reactive energy of the panel is recovered. Various drivers are classified and evaluated based on their suitability for high frequency drivers. Finally, a current-fed driver with a DC input voltage bias is proposed. This driver overcomes the effect of parasitic components in the panel and driver. It fully achieves a ZVS of all full-bridge switches and reduces the transition time of the panel polarity. It is tested to validate the high frequency sustaining driver and the experimental results are presented.

• Genomics & Informatics
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• 제6권3호
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• pp.136-141
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• 2008

A large number of studies have been performed to identify biomarkers that will allow efficient detection and determination of the precise status of a patient’s disease. The use of microarrays to assess biomarker status is expected to improve prediction accuracies, because a whole-genome approach is used. Despite their potential, however, patient samples can differ with respect to biomarker status when analyzed on different platforms, making it more difficult to make accurate predictions, because bias may exist between any two different experimental conditions. Because of this difficulty in experimental standardization of microarray data, it is currently difficult to utilize microarray-based gene sets in the clinic. To address this problem, we propose a method that predicts disease status using gene expression data that are transformed by their ranks, a concept that is easily applied to two datasets that are obtained using different experimental platforms. NCI and colon cancer datasets, which were assessed using both Affymetrix and cDNA microarray platforms, were used for method validation. Our results demonstrate that the proposed method is able to achieve good predictive performance for datasets that are obtained under different experimental conditions.

• ETRI Journal
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• 제36권6호
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• pp.924-930
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• 2014

This paper presents a $0.13{\mu}m$ CMOS 3-level envelope delta-sigma modulation (EDSM) RF signal generator, which synthesizes a 2.6 GHz-centered fully symmetrical 3-level EDSM signal for high-efficiency power amplifier architectures. It consists of an I-Q phase modulator, a Class B wideband buffer, an up-conversion mixer, a D2S, and a Class AB wideband drive amplifier. To preserve fast phase transition in the 3-state envelope level, the wideband buffer has an RLC load and the driver amplifier uses a second-order BPF as its load to provide enough bandwidth. To achieve an accurate 3-state envelope level in the up-mixer output, the LO bias level is optimized. The I-Q phase modulator adopts a modified quadrature passive mixer topology and mitigates the I-Q crosstalk problem using a 50% duty cycle in LO clocks. The fabricated chip provides an average output power of -1.5 dBm and an error vector magnitude (EVM) of 3.89% for 3GPP LTE 64 QAM input signals with a channel bandwidth of 10/20 MHz, as well as consuming 60 mW for both channels from a 1.2 V/2.5 V supply voltage.

• 한국수자원학회논문집
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• 제32권4호
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• pp.437-445
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• 1999

비모수능형회귀분석법을 이용하여 수문응답을 추정하는 방안에 대하여 연구하였다. 응답을 추정하기 위하여 평균제곱예측오차에 대한 추정량인 CL 통계량을 최소화하는 방법을 적용하였으며 가중행렬은 전통적으로 이용도는 단위행렬과 특수한 형태인 행렬인 Laplacian 행렬을 각각 이용하여 비교하였다. 또한 추정응답의 오차분산을 추정하는 방안에 대한 검토도 실행하였다. 합성자료와 실제자료에 대한 분석 결과 가중행렬과 Laplacian 행렬을 오차분산은 편기 수정된 추정치를 이용하는 것이 좋은 결과를 보여 주었다. 본 연구에서 제시된 절차 및 방법은 수문응답 분리에 있어서 안정적이고 효율적으로 적용될 수 있을 것으로 판단된다.

• 한국태양광발전학회지
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• 제3권2호
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• pp.42-47
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• 2017

The potential induced degradation (PID) phenomenon shows severe power loss within several years from the initial installation of solar power system. The accumulated power loss by PID is inevitable because the PID is suspected only if the power loss exceeds several percent. In this paper, we analyzed the cases of PID diagnosis and recovery by visiting the suspected PID site about 17 months after the installation of the 100kW PV system. The power difference of the two 50kW inverters was more than 20kWh, and the PR difference was more than 8%. From the beginning of the installation, the difference in power gradually increased. The recovery was observed for about 7 months by applying 1000V in the reverse bias at night. As a result, the power difference of the two inverters was recovered to within 2kWh. In the case of a power station suffering from PID in the field, it will be helpful for stable development operation by quick diagnosis and problem solving.

• 응용통계연구
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• 제28권1호
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• pp.23-31
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• 2015

통계적 분석을 할 때 결측치가 발생하는 것은 매우 통상적이다. 이러한 결측치를 대치하는 방법은 여러가지가 있으며, 기존에 사용되는 단일대치법으로 k-nearest neighbor(KNN) 방법이 있다. 하지만 KNN 방법은 k개의 최근접 이웃들 중 극단치나 이상치가 있을 때 편의를 일으킬 수 있다. 본 논문에서는 KNN 방법의 단점을 보완하여 가중 k-최근접이웃(Weighted k-Nearest Neighbors; WKNN) 대치법을 제안하였다. 또한 모의실험을 통해서 기존의 방법과 비교하였다.