• Title/Summary/Keyword: high wave

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Analysis Program for Offshore Wind Energy Substructures Embedded in AutoCAD (오토캐드 환경에서 구현한 해상풍력 지지구조 해석 프로그램)

  • James Ban;Chuan Ma;Sorrasak Vachirapanyakun;Pasin Plodpradit;Goangseup Zi
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.27 no.4
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    • pp.33-44
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    • 2023
  • Wind power is one of the most efficient and reliable energy sources in the transition to a low-carbon society. In particular, offshore wind power provides a high-quality and stable wind resource compared to onshore wind power while both present a higher installed capacity than other renewables. In this paper, we present our new program, the X-WIND program well suitable for the assessment of the substructure of offshore wind turbines. We have developed this program to increase the usability of analysis programs for offshore wind energy substructures by addressing the shortcomings of existing programs. Unlike the existing programs which cannot solely perform the substructure analyses or lack pre-post processors, our X-WIND program can complete the assessment analysis for the offshore wind turbines alone. The X-WIND program is embedded in AutoCAD so that both design and analysis are performed on a single platform. This also performs static and dynamic analysis for wind, wave, and current loads, essential for offshore wind power structures, and includes pre/post processors for designs, mesh developments, graph plotting, and code checking. With this expertise, our program enhances the usability of analysis programs for offshore wind energy substructures, promoting convenience and efficiency.

Prediction of Germination of Korean Red Pine (Pinus densiflora) Seed using FT NIR Spectroscopy and Binary Classification Machine Learning Methods (FT NIR 분광법 및 이진분류 머신러닝 방법을 이용한 소나무 종자 발아 예측)

  • Yong-Yul Kim;Ja-Jung Ku;Da-Eun Gu;Sim-Hee Han;Kyu-Suk Kang
    • Journal of Korean Society of Forest Science
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    • v.112 no.2
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    • pp.145-156
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    • 2023
  • In this study, Fourier-transform near-infrared (FT-NIR) spectra of Korean red pine seeds stored at -18℃ and 4℃ for 18 years were analyzed. To develop seed-germination prediction models, the performance of seven machine learning methods, namely XGBoost, Boosted Tree, Bootstrap Forest, Neural Networks, Decision Tree, Support Vector Machine, PLS-DA, were compared. The predictive performance, assessed by accuracy, misclassification, and area under the curve (0.9722, 0.0278, and 0.9735 for XGBoost, and 0.9653, 0.0347, and 0.9647 for Boosted Tree), was better for the XGBoost and decision tree models when compared with other models. The 54 wave-number variables of the two models were of high relative importance in seed-germination prediction and were grouped into six spectral ranges (811~1,088 nm, 1,137~1,273 nm, 1,336~1,453 nm, 1,666~1,671 nm, 1,879~2,045 nm, and 2,058~2,409 nm) for aromatic amino acids, cellulose, lignin, starch, fatty acids, and moisture, respectively. Use of the NIR spectral data and two machine learning models developed in this study gave >96% accuracy for the prediction of pine-seed germination after long-term storage, indicating this approach could be useful for non-destructive viability testing of stored seed genetic resources.

Measurement of a Phase Plate Simulates Atmospheric Turbulence Depending on Laser Power (레이저 출력에 따른 난류 모사 위상판 측정)

  • Han-Gyol Oh;Pilseong Kang;Jaehyun Lee;Hyug-Gyo Rhee;Young-Sik Ghim
    • Korean Journal of Optics and Photonics
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    • v.34 no.3
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    • pp.99-105
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    • 2023
  • The performance of astronomical telescopes can be negatively affected by atmospheric turbulence. To address this issue, techniques for atmospheric turbulence correction have been developed, requiring the simulation of atmospheric turbulence in the laboratory. The most practical way to simulate atmospheric turbulence is to use a phase plate. When measuring a phase plate that simulates strong turbulence, a Shack-Hartmann wave-front sensor is commonly used. However, the laser power decreases as it passes through the phase plate, potentially leading to a weak laser signal at the sensor. This paper investigates the need to control the laser power when measuring a phase plate that simulates strong atmospheric turbulence, and examines the effects of the laser power on the measured wavefront. For phase plates with relatively high Fried parameter r0, the laser power causes a variation of over 10% in r0. For phase plates with relatively low r0, the laser power causes a variation of less than 5%, which means that the influence of the laser power is negligible for phase plates that simulate strong atmospheric turbulence. Based on the system described in this paper, a phase plate simulating strong atmospheric turbulence can be measured at a laser power of 5 mW or higher. Therefore, controlling the laser's output power is necessary when measuring a phase plate for simulating atmospheric turbulence, especially for phase plates with low r0 values.

Fabrication and Electromechanical Behaviors of a SWNT/PANi Composite Film Actuator (탄소나노튜브/도전성폴리머 복합재 엑츄에이터의 제조 및 특성실험)

  • Zhang, Shuai;Kim, Cheol
    • Composites Research
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    • v.19 no.5
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    • pp.7-11
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    • 2006
  • The improved SWNTs/PANi composite actuator films applicable to an artificial muscle were fabricated successfully using a new process of manufacture that consists of 90% pure single-walled carbon nanotubes (SWNT) and chemical polymerization. PANi is electrically conducting polyaniline polymer. The conductivities of the composite SWNTs/PANi film-type actuators and the pure PANi films fabricated were measured as 56.15 S/cm and 17.38 S/cm, respectively, by the 4-prove method. The conductivity of the composite actuator is 3.2 times higher than the pure PANi film. The fabricated composite actuator showed higher conductivity than any other similar ones. The quality of samples was investigated by an electron scanning microscope (SEM). To measure the actuating strains, a specially designed beam balance apparatus was developed and strains of the composite actuators was measured by a laser displacement sensor subjected to electric currents. During the operation, the sample was soaked in the $NaNO_3$ solution and the sine-wave voltage in the range of $+1V{\sim}-1V$ was applied. The length of the composite actuator changed from $l_0=12.690$ mm to $l_1=12.733$ so that the change of length was l=0.043 mm and the strain was 0.34 %. This is a very high strain for this kind of a composite actuator. Other result reported by Tahhan showed 0.23 % strain, so that the present result is improved by 48%.

Underwater acoustic communication performance in reverberant water tank (잔향음 우세 수조 환경에서의 수중음향 통신성능 분석)

  • Choi, Kang-Hoon;Hwang, In-Seong;Lee, Sangkug;Choi, Jee Woong
    • The Journal of the Acoustical Society of Korea
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    • v.41 no.2
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    • pp.184-191
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    • 2022
  • Underwater acoustic wave in shallow water is propagated through multipath that has a large delay spread causing Inter-Symbol Interference (ISI) and these characteristics deteriorate the performance in the communication system. In order to analyze the communication performance and investigate the correlation with multipath delay spread in a reverberant environment, an underwater acoustic communication experiment using Binary Phase-Shift Keying (BPSK) signals with symbol rates from 100 sym/s to 8000 sym/s was conducted in a 5 × 5 × 5 m3 water tank. The acoustic channels in a well-controlled tank environment had the characteristics of dense multipath delay spread due to multiple reflections from the interfaces and walls within the tank and showed the maximum excess delay of 40 ms or less, and the Root Mean Squared (RMS) delay spread of 8 ms or less. In this paper, the performances of Bit Error Rate (BER) and output Signal-to-Noise Ratio (SNR) were analyzed using four types of communication demodulation techniques. And the parameter, Symbol interval to Delay spread Ratio in reverberant environment (SDRrev), which is the ratio of symbol interval to RMS delay spread in the reverberant environment is defined. Finally, the SDRrev was compared to the BER and the output SNR. The results present the reference symbol rate in which high communication performance can be guaranteed.

A Fundamental Study on Laboratory Experiments in Rock Mechanics for Characterizing K-COIN Test Site (K-COIN 시험부지 특성화를 위한 암석역학 실내실험 기초 연구)

  • Seungbeom Choi;Taehyun Kim;Saeha Kwon;Jin-Seop Kim
    • Tunnel and Underground Space
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    • v.33 no.3
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    • pp.109-125
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    • 2023
  • Disposal repository for high-level radioactive waste secures its safety by means of engineered and natural barriers. The performance of these barriers should be tested and verified through various aspects in terms of short and/or long-term. KAERI has been conducting various in-situ demonstrations in KURT (KAERI Underground Research Tunnel). After completing previous experiment, a conceptual design of an improved in-situ experiment, i.e. K-COIN (KURT experiment of THMC COupled and INteraction), was established and detailed planning for the experiment is underway. Preliminary characterizations were conducted in KURT for siting a K-COIN test site. 15 boreholes with a depth of about 20 m were drilled in three research galleries in KURT and intact rock specimens were prepared for laboratory tests. Using the specimens, physical measurements, uniaxial compression, indirect tension, and triaxial compression tests were conducted. As a result, specific gravity, porosity, elastic wave velocities, uniaxial compressive strength, Young's modulus, Poisson's ratio, Brazilian tensile strength, cohesion, and internal friction angle were estimated. Statistical analyses revealed that there did not exist meaningful differences in intact rock properties according to the drilled sites and the depth. Judging from the uniaxial compressive strength, which is one of the most important properties, all the specimens were classified as very strong rock so that mechanical safety was secured in all the regions.

Seismic analysis and dynamic behavior characterization of rib-reinforced pre-cast tunnels (리브 보강 프리캐스트 터널의 내진 해석 및 동적거동 특성 파악)

  • Song, Ki-Il;Jung, Sung-Hoon;Cho, Gye-Chun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.11 no.3
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    • pp.287-301
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    • 2009
  • The novel cut-and-cover tunnel construction method using rib-reinforced pre-cast arch segments has been recently developed and applied for practice to secure a structural stability of high covering and wide width section tunnels. Cut-and-cover tunnels are usually damaged by the seismic behavior of backfill grounds in case of a low covering condition. Seismic analyses are performed in this study to characterize the dynamic behavior of rib-reinforced pre-cast arch cut-and-cover tunnels. Seismic analyzes for 2 lane cast-in-place and rib-reinforced pre-cast arch cut-and-cover tunnels are carried out by using the commercial FDM program (FLAC2D) considering various field conditions such as the covering height embankment slope and excavation slope. It can be concluded that the amplification of seismic wave is reduced due to an increase in the structural stiffness induced by rib-reinforcement. The results show that the rib-reinforced pre-cast arch cut-and-cover tunnels are more effective against the seismic loading, compared to the cast-in-place cut-and-cover tunnels.

Integrity evaluation of rock bolts in the field by using hammer-impact reflection method (해머 타격 반사법을 이용한 현장 록볼트 건전도 평가)

  • Yu, Jung-Doung;Bae, Myeong-Ho;Lee, Yong-Jun;Min, Bok-Ki;Lee, In-Mo;Lee, Jong-Sub
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.11 no.1
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    • pp.47-56
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    • 2009
  • Rock bolts and shotcrete play a crucial role as a main support system in the underground space. Thus, the safety of the underground space may be affected by the defect of rock bolts. In order to evaluate the rock bolt integrity by using non-destructive technique, the transmission method of the guided ultrasonic waves, which are generated by using the piezo disk elements has been successfully performed. The energy generated by the piezo disk elements, however, is not enough for the rock bolts in the field. In addition, the piezo disk elements should be installed at the end of the steel bar during construction of the rock bolts. The purpose of this study is the devolvement of the reflection method, which may generate enough energy, and the application in the field rock bolts. Both laboratory and field tests are carried out. The guided ultrasonic waves with high energy are generated by the hammer impact with the center punch, and the AE sensor is used to measure the reflected guided waves. The received guided waves are analyzed by the wavelet transform. The peak value of the wavelet transform produces the energy velocity, which is used for the evaluation of the rock bolt integrity. The energy velocity increases with an increase in the defect ratio in both laboratory and field rock bolts. This study demonstrates that the hammer-impact reflection method may be a suitable method for the evaluation of the rock bolt in the field.

Oxidation behavior on the surface of titanium metal specimens at high temperatures (300~1000℃) (고온 (300~1000 ℃)에서 티타늄 금속시편의 표면 산화거동)

  • Park, Yang-Soon;Han, Sun-Ho;Song, Kyuseok
    • Analytical Science and Technology
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    • v.22 no.6
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    • pp.464-470
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    • 2009
  • For the investigation of the oxidation behavior for titanium metal at various temperatures, titanium specimens were heated for 2 hours in the range of $300{\sim}1000^{\circ}C$, individually. And then X-ray diffraction(XRD), scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopic analyses were carried out. At $300^{\circ}C$, infrared absorption bands on the surface of the titanium specimen were shown in a spectrum by the oxygen uptake of titanium metal(hexagonal). At increased temperature, not only infrared absorption bands but also X-ray diffraction peaks for the titanium oxide were grown and shifted to low wave number ($cm^{-1}$) and angle($^{\circ}$) due to the more oxygen diffusion into titanium metal. At $700^{\circ}C$, $Ti_3O$ (hexagonal phase) was identified by X-ray diffractometer. $TiO_2$ (rutile, tetragonal phase) layer was produced on the surface of the specimen below $1{\mu}m$ in thickness at $600^{\circ}C$, and grown about $2{\mu}m$ at $700^{\circ}C$ and with $110{\mu}m$ in thickness at $1000^{\circ}C$. Above $900^{\circ}C$, (110) plane of the crystal on the surface of rutile-$TiO_2$ layer was grown.

The realization of the inner self of Chosun dynasty's women-Be blessed life with Chosun Dynasty women, see the life of a Chosun Dynasty women as a picture of Hyewon (- 조선 여성이 누린 삶, 내적(內的) 자아경계(自我境界)의 체현(體現) - 혜원의 「전신첩(傳神帖)」으로 보다)

  • Kwon Yun Hee
    • The Journal of the Convergence on Culture Technology
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    • v.9 no.2
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    • pp.91-98
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    • 2023
  • Genre paintings, which describes the lives of ordinary people, has lifestyle and Pungnyu of our ancestors. Pungnyu is aesthetic consciousness and a way of lives. The culture of Pungnyu is a kind of art boundary that combines high spirits and art. The Pungnyu is an icon of Korean culture, realization of taste, and happens through "stroll", which means the walking peacefully, and "sightsee", which means go sightseeing. It shows through the rambling and the excursion. Hyewon's 'Jeonsincheob'('傳神帖', a kind of spirit transferred drawings book) is a genre painting which represents Pungnyu and shows various activities at that time. Therefore, we can understand our own spirit and soul through appreciating his paintings. Hyewon's 「Jeonsincheob」 has three special features. Firstly, it is the symbol of Korea traditional Pungnyu. Secondly, it contributes to development of the East art. Lastly, Hyewon's 「Jeonsincheob」 can be considered in terms of glocalism, which means the combination of globalization and localization and can be explained by the relation of the center=the periphery, the globalization=the Korean wave, the universality=the particularity. Hyewon's 'Jeonsincheob' has aesthetic boundaries. One aims at individual pleasure. Another aims at harmony with its natural environment in which you are. Also, it can be considered as the boundaries of enjoying together which aims at harmony with social environment among group members.