• Journal of Ocean Engineering and Technology
• /
• v.16 no.5
• /
• pp.1-6
• /
• 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.

• Journal of the Society of Naval Architects of Korea
• /
• v.39 no.1
• /
• pp.38-48
• /
• 2002

Theoretical development to generate the directional extreme waves in model basin is established based on wave focusing method. The effects of associated parameters, such as the directional range, frequency width, and center frequency, are investigated in terms of wave focusing efficiency. The two different spectral models of constant wave amplitude and constant wave slope are applied to control the wave characteristics. The wave packets simulated by theory are compared with numerical results based on Boussinesq equation and FEM. Both controls of direction and frequency spectrum are essential to focus directional waves effectively. It is noticed that wave focusing ability depends on the frequency bandwidth of spectrum rather than center frequency, and both spectral models with same parameters result in the equivalent efficiency of wave focusing.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.9 no.1
• /
• pp.45-48
• /
• 2016

The treatment of obesity have been developed various devices for the treatment of obesity, the ultrasound is to be made after the state changes to become easy fat decomposition by heat and vibrations to facilitate the flow of blood and lymph fatty acid released into the blood. There is such ultrasonic transducer array is used in obesity therapy focusing angle of the transducer array and the frequency may have a significant impact on the degradation of fat. In this paper, we set the frequency that reaches the shortest time to a set temperature 27kHz, 1MHz, by applying a transducer with a diameter of 5mm, 10mm, 16mm for the frequency of 3MHz, obtain the wavelength and near the stomach in order to set the frequency of the transducer array, which was set to the focusing angle of the transducer with three contact surfaces. As a result, the time to reach the set temperature was short days when 3MHz frequency, the focusing angle is titrated is $40^{\circ}$.

• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.825-826
• /
• 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.

• Journal of Ocean Engineering and Technology
• /
• v.17 no.6
• /
• pp.1-6
• /
• 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.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.19 no.4
• /
• pp.13-27
• /
• 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.

• Proceedings of the Acoustical Society of Korea Conference
• /
• 1984.12a
• /
• pp.78-82
• /
• 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
• /
• 2007.06a
• /
• pp.145-150
• /
• 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.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.8 no.4
• /
• pp.159-165
• /
• 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.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.20 no.1
• /
• pp.1-15
• /
• 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.