• 한국해양공학회지
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• 제16권5호
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• pp.1-6
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• 2002

Extreme waves are generated in a model basin based on directional wave focusing. The targeted wave field is described by double summation method and it is applied to serpent-type wavemaker system. The extreme crest amplitude at a designed location is obtained by syncronizing the phases and focusing the directions of wave components. Two distinguished spectrums of constant wave amplitude and constant wave steepness are adapted to describe the frequency distribution of component waves. The surface profile of generated wave packets is measured by wave guage array and the effects of dominant spectral parameters governing extreme wave characteristics are investigated. It is found that frequency bandwidth, center frequency, shape of frequency spectrum and directional range play a significant role in the wave focusing. In particular, the directional effect significantly enhances the wave focusing efficiency.

• 대한조선학회논문집
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• 제39권1호
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• pp.38-48
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• 2002

파랑집중 이론에 기초하여 모형시험수조에서 다방향 극한파를 생성하는 연구를 수행하였다. 파랑의 집중도에 대한 파향 범위, 주파수 폭, 중심 주파수 등의 영향을 고찰하였다. 등파고와 등기 울기 스펙트럼 모델에 의한 결과를 서로 비교하였으며, Boussinesq 방정식과 유한요소법에 기초한 수치해와 이론해를 또한 서로 비교하였다. 효율적인 파랑집중을 위해서는 파향과 주파수 모두를 효과적으로 제어하는 것이 필수적이다. 파랑집중도는 중심주파수 보다는 주파수 폭에 좌우되며, 동일한 조건하에서 두 스펙트럼 모델은 동등한 정도의 파랑집중 효율을 나타낸다.

• 한국정보전자통신기술학회논문지
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• 제9권1호
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• pp.45-48
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• 2016

비만을 치료하기 위해 다양한 비만 치료기가 개발되어 왔으며, 초음파는 온열 및 진동작용으로 지방이 분해가 되기 쉬운 상태로 변하게 만든 후 혈액 및 림프액의 흐름을 촉진시켜 혈액으로 지방산 배출이 될 수 있도록 한다. 이러한 초음파 비만 치료기에 트랜스듀서 어레이가 사용되는데 트랜스듀서 어레이의 집속각도와 주파수는 지방을 분해하는데 중요한 영향을 미칠 수 있다. 본 논문에서는 트랜스듀서 어레이의 주파수를 설정하기 위해 27kHz, 1MHz, 3MHz의 주파수에 직경 5mm, 10mm, 16mm의 트랜스 듀서를 적용하여 파장과 근위장을 구하여 설정온도에 가장 짧은 시간에 도달하는 주파수를 설정하고, 3개 면이 닿는 트랜스듀서의 집속 각도를 설정하였다. 결과적으로 3MHz 주파수 일 때 설정온도에 도달하는 시간이 짧았으며, 집속각도는 $40^{\circ}$가 적정하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.825-826
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• 2008

Focusing is the principal factor that decides the image quality. In the low illuminance condition, captured images with a digital camera usually blurred because the autofocus system of the camera fail to detect the in-focus position. The failure of focusing is due to thermal noise in the captured image. In this paper, we propose a new focus detection algorithm. The proposed algorithm use the new focusing index which is weighted sum of the high-frequency energy and mid-frequency energy. The weight is determined by the local variance of the image. The proposed algorithm performs stable focusing detection with in the low illuminance condition.

• 한국해양공학회지
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• 제17권6호
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• pp.1-6
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• 2003

Wave energy dissipation and energy transfer between wave components, during the directional wave breakings, are investigated. Directional incipient and plunging breakers were generated by focusing the multi-frequency and multi-directional wave components at a designed location, based on a constant wave amplitude and a constant wave steepness frequency spectrum. The time series of surface wave elevation was measured at 9 different locations around the wave focusing point, using a wave gauge array. In order to examine the variation of the directional spreading function, the horizontal velocity of fluid motion was also measured. By comparing energy spectrums, before and after the breaking, the characteristics of energy dissipation and energy transfer, caused by wave breaking, are investigated. Their dependencies on directionality, as well as frequency, are analyzed. The breakings significantly dissipate wave energy, through energy transfer, in the upper region of the peak-frequency band, while enhancing wave energy in the low-frequency band.

• 디지털산업정보학회논문지
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• 제19권4호
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• pp.13-27
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• 2023

In this study, we tried to identify research trends on artificial intelligence security focusing on the United States, United Kingdom, and South Korea. In Elsevier's Scopus We collected 4,983 papers related to artificial intelligence security published from 2018 to 2022 and by using the abstracts of the collected papers, Keyword frequency and centrality analysis were conducted. By calculating keyword frequency, keywords with high frequency of appearance were identified and through the centrality analysis, central research keywords were identified by country. Through the analysis results, research related to artificial intelligence, machine learning, Internet of Things, and cybersecurity in each country was conducted as the most central and highly mediating research. The implication for Korea is that research related to cybersecurity, privacy, and anomaly detection has lower centralities compared to the United States and research related to big data has lower centralities compared to United Kingdom. Therefore, various researches that intensively apply artificial intelligence technology to these fields are needed.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1984년도 추계학술발표회 논문집
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• pp.78-82
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• 1984

The purposed of this paper is to realize two dimensional acoustic image using focusing method. In the experiment, it consists of phase delay part, 14 analog multiplexers, multi-amplifiers, A/D converter, DMA interfacing parts, two linear arrays(resonance frequency 25 KHz, radius 0.75 Cm diac type). Finally in this experimental result, both electrical deflection and dynamic focusing are realized and gets two dimensional acoustic image using focusing method.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2007년도 공동학술대회 논문집
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• pp.145-150
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• 2007

We briefly introduce the theory of GB-SAR focusing and interferometry. Deramp-FFT algorithm is evaluated as a far-range, partial focusing method along with its limitations in the near-range application. Various interferometric configurations with temporal, spatial, and/or frequency baselines are also discussed.

• 디지털산업정보학회논문지
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• 제8권4호
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• pp.159-165
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• 2012

The accurate focusing position should be determined for accurate measurements In VMS. Camera lens focusing is an important problem in computer vision and video measuring systems (VMS) that use CCD cameras and high precision XYZ stages. Camera focusing is a very important step in high precision measurement systems that use computer vision technique. The auto focusing process consists of two steps, the focus value measurement step and the exact focusing position determination step. It is suitable for eliminating high frequency noises with lower processing time and without blurring. An automatic focusing technique is applied to measure a crater with a one-dimensional search algorithm for finding the best focus. Throughout this paper, the suggested algorithm for the Auto focusing was combined with the learning. As a result, it is expected that such a combination would be expanded into the system of recognizing voices in a noisy environment.

• 디지털산업정보학회논문지
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• 제20권1호
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• pp.1-15
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• 2024

This study aims to analyze research trends in blockchain-based Internet of Things focusing on the US, UK, and Korea. In Elsevier's Scopus, we collected 2,174 papers about blockchain-based Internet of Things published in from 2018 to 2023. Keyword frequency and centrality analysis were conducted on the abstracts of the collected papers. Through the obtained keyword frequencies, we tried to identify keywords with high frequency of occurrence and through centrality analysis, we tried to identify central research keywords for each country. As a result of the centrality analysis, research on blockchain, smart contracts, Internet of Things, security and personal information protection was conducted as the most central research in each country. The implication for Korea is that cybersecurity, authentication research appears to have been conducted with a lower centrality compared to the United States and the United Kingdom. Thus, it seems that intensive research related to cybersecurity and authentication is needed.