Loading [MathJax]/jax/output/CommonHTML/jax.js
  • Title/Summary/Keyword: Physical and Acoustic Properties

Search Result 82, Processing Time 0.055 seconds

Geoacoustic Model at the SSDP-105 Long-core Site of the Ulsan Coastal Area, the East Sea (동해 울산 연안해역 SSDP-105 심부코어 지점의 지음향 모델)

  • Ryang, Woo-Hun;Lee, Gwang-Soo;Hahn, Jooyoung
    • Journal of the Korean earth science society
    • /
    • v.39 no.2
    • /
    • pp.154-163
    • /
    • 2018
  • Geoacoustic model comprises physical and acoustic properties of submarine bottom layers influencing sound transmission through sea water and underwater. This study suggested for the first time that we made a geoacoustic model of long-coring bottom layers at the SSDP-105 drilling site of the Ulsan coastal area, which is located in the southwestern inner shelf of the East Sea. The geoacoustic model of 52 m depth below seafloor with three-layer geoacoustic units was reconstructed in the coastal sedimentary strata at 79 m in water depth. The geoacoustic model was based on the data of a deep-drilled sediment core of SSDP-105 and sparker seismic profiles in the study area. For actual modeling, the geoacoustic property values of the models were compensated to in situ depth values below the sea floor using the Hamilton modeling method. We suggest that the geoacoustic model be used for geoacoustic and underwater acoustic experiments of mid- and low-frequency reflecting on the deep bottom layers in the Ulsan coastal area of the East Sea.

The Fabrication of the Single Crystal Wire from Cu Single Crystal Grown by the Czochralski Method and its Physical Properties (Czochralski법을 이용한 금속 단결정의 성장과 구조적, 전기적 성질에 관한 연구)

  • Park, Jeung-Hun;Cha, Su-Young;Park, Sang-Eon;Kim, Sung-Kyu;Cho, Chae-Ryong;Park, Hyuk-K.;Kim, Hyung-Chan;Jeong, Myung-Hwa;Jeong, Se-Young
    • Korean Journal of Crystallography
    • /
    • v.16 no.2
    • /
    • pp.141-148
    • /
    • 2005
  • It is well known that the general metals have a lot of grain boundaries. The grain boundaries play a negative role to increase the resistivity and to decrease the conductivity. The small resistivity and the large conductivity have been a goal of the material scientists, and no signal noise, perfect signal transfer, and the realization of the real sound are the dream of electronic engineers and audio manias. Generally, oxygen free copper (OFC) and Ohno continuous casting (OCC) copper cables have been used for the purpose of the precise signal transfer and low noise. However they still include a lot of grain boundaries. In our study, we have grown the single crystal by the Czochralski method and succeeded to produce single crystal wires from the crystal in the dimension of 0.5×0.5×2500mm. The produced wire still possesses very good single crystal properties. We observed the structure of the wire, and measured the resistance and impedance. Glow Discharge Spectrometer (GDS) was used for analyzing the compositions of copper single crystals and commercial copper. Current-Voltage curve, resistance, total harmonic distortion and speaker frequency response were measured for comparing electrical and acoustic properties of two samples.

Multi regression analysis of water quality characteristics in lowland paddy fields

  • Kato, Tasuku
    • Proceedings of the Korea Water Resources Association Conference
    • /
    • 2012.05a
    • /
    • pp.36-36
    • /
    • 2012
  • Drainage water in lowland paddy fields is quantitatively influenced recycle and/or repeated irrigation by irrigation facilities, i.e. pumps, check gates, small reservoirs and so on. In those drainage channels, nutrients accumulation and increasing organic matters are considered to be occurred, and water quality would be degraded not only environmental aspect but irrigation purpose. In general, Total Nitrogen (T-N) is interested water quality index in irrigation water, because high nitrogen concentration sometimes caused decreasing rice production by excess growth and fallen or degrading quality of taste, then, farmers would like to clear water less than 1mg/L of T-N concentration. In drainage channel, it is known that the nitrogen concentration change is influenced by physical, chemical and biological properties, i.e, stream or river bed condition, water temperature, other water quality index, and plant cover condition. In this study, discharge data (velocity and level) in a drainage channel was monitored by an Acoustic Doppler system and water quality was sampled at same time in 2011. So those data was analyzed by multi regression model to realize hydrological and environmental factors to influence with nitrogen concentration. The results showed the difference tendency between irrigation and non-irrigation period, and those influenced factors would be considered in water quality model developing in future.

  • PDF

Production Processes of Porous Metals and Their Applications (다공질 금속의 제조와 응용)

  • Shim, Jae-Dong;Byun, Ji-Young
    • Korean Journal of Materials Research
    • /
    • v.25 no.3
    • /
    • pp.155-164
    • /
    • 2015
  • Porous metals are called as a new material of 21th century because they show not only extremely low density, but also novel physical, thermal, mechanical, electrical, and acoustic properties. Since the late in the 1990's, considerable progress has been made in the production technologies of many kinds of porous metals such as aluminum, titanium, nickel, copper, stainless steel, etc. The commercial applications of porous metals have been increased in the field of light weight structures, sound absorption, mechanical damping, bio-materials, thermal management for heat exchanger and heat sink. Especially, the porous metals are promising in automotive applications for light-weighting body sheets and various structural components due to the good relation between weight and stiffness. This paper reviews the recent progress of production techniques using molten metal bubbling, metal foaming, gas expansion, hollow sphere structure, unidirectional solidification, etc, which have been commercialized or under developing, and finally introduces several case studies on the potential applications of porous metals in the area of heat sink, automotive pannel, cathod for Ni-MH battery, golf putter and medical implant.

The Limit and Application of Two-microphone Impedance Tube Method to the Sound Transmission Loss Measurement of Sound Isolation Materials (차음재의 음향투과손실 측정에 Two-Microphone Impedance Tube Method의 적용과 한계)

  • Lee, Seung;Ahn, Min-Hong;Lee, Dong-Hoon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2002.05a
    • /
    • pp.883-888
    • /
    • 2002
  • This study describes the limit and application of the two-microphone impedance tube method to the sound transmission loss measurement of several sound isolation materials with different physical properties. For the sound isolation materials having small flexural rigidity, it is shown that the two-microphone impedance tube method is validated to practically measure the sound transmission loss. For the sound isolation materials having large flexural rigidity, on the other hand, it is found that the two-microphone impedance tube method is no longer valid to measure the sound transmission loss because the regions of resonance and mass law are moved into the higher frequencies. In addition, in order to accurately measure the sound transmission loss of sound isolation materials, their size should be decided based on the consideration of the effect of acoustic excitation on their vibration response.

  • PDF

Study of Imaging of Submarine Bubble Plume with Reverse Time Migration (역시간 구조보정을 활용한 해저 기포플룸 영상화 연구)

  • Dawoon Lee;Wookeen Chung;Won-Ki Kim;Ho Seuk Bae
    • Geophysics and Geophysical Exploration
    • /
    • v.26 no.1
    • /
    • pp.8-17
    • /
    • 2023
  • Various sources, such as wind, waves, ships, and gas leaks from the seafloor, forms bubbles in the ocean. Underwater bubbles cause signal scattering, considerably affecting acoustic measurements. This characteristic of bubbles is used to block underwater noise by attenuating the intensity of the propagated signal. Recently, researchers have been studying the large-scale release of methane gas as bubble plumes from the seabed. Understanding the physical properties and distribution of bubble plumes is crucial for studying the relation between leaked methane gas and climate change. Therefore, a water tank experiment was conducted to estimate the distribution of bubble plumes using seismic imaging techniques and acoustic signals obtained from artificially generated bubbles using a bubble generator. Reverse time migration was applied to image the bubble plumes while the acquired acoustic envelope signal was used to effectively estimate bubble distribution. Imaging results were compared with optical camera images to verify the estimated bubble distribution. The water tank experiment confirmed that the proposed system could successfully image the distribution of bubble plumes using reverse time migration and the envelope signal. The experiment showed that the scattering signal of artificial bubble plumes can be used for seismic imaging.

Geoacoustic Model of Surface Sediments in the East of Geoje Island, the South Sea of Korea (거제도 동쪽 해역 표층 퇴적물의 지음향모델)

  • KIM, GIL YOUNG;KIM, DAE CHOUL;SHIN, BO KYOUNG;SEO, YOYUNG KYO;LEE, GWANG HOON
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
    • /
    • v.10 no.2
    • /
    • pp.129-138
    • /
    • 2005
  • Sediment texture, physical (porosity, water content, bulk density, grain density, and shear strength), and geoacoustic properties (compressional wave velocity and attenuation) were measured on eighteen core samples collected from the shelf off eastern Geoje Island, the South Sea of Korea. Based on these properties, the study area is divided into three different sub-areas: (1) Area I affected directly by the Nakdong River discharge; (2) Area II covered by the southern branch of the Nakdong River discharge; and (3) Area III dominated by relict sediment. Mean grain size, velocity, and bulk density decrease from Area I(7.4Φ,1528m/s,1.6g/cm3,respectively) to Area II(8.1Φ,1485m/s,and1.5g/cm3), and then increase rather rapidly in Area III(1.4Φ,1664m/s,and2.2g/cm3). Porosity, on the other hand, exhibits an opposite trend, increasing from Area I(64.5%) to AreaII(73.9%) and then decreasing significantly in Area III(32.9%) From the results measured and calculated, we suggest a specified geoacoustic model in the study area.

Modified AWSSDR method for frequency-dependent reverberation time estimation (주파수 대역별 잔향시간 추정을 위한 변형된 AWSSDR 방식)

  • Min Sik Kim;Hyung Soon Kim
    • Phonetics and Speech Sciences
    • /
    • v.15 no.4
    • /
    • pp.91-100
    • /
    • 2023
  • Reverberation time (T60) is a typical acoustic parameter that provides information about reverberation. Since the impacts of reverberation vary depending on the frequency bands even in the same space, frequency-dependent (FD) T60, which offers detailed insights into the acoustic environments, can be useful. However, most conventional blind T60 estimation methods, which estimate the T60 from speech signals, focus on fullband T60 estimation, and a few blind FDT60 estimation methods commonly show poor performance in the low-frequency bands. This paper introduces a modified approach based on Attentive pooling based Weighted Sum of Spectral Decay Rates (AWSSDR), previously proposed for blind T60 estimation, by extending its target from fullband T60 to FDT60. The experimental results show that the proposed method outperforms conventional blind FDT60 estimation methods on the acoustic characterization of environments (ACE) challenge evaluation dataset. Notably, it consistently exhibits excellent estimation performance in all frequency bands. This demonstrates that the mechanism of the AWSSDR method is valuable for blind FDT60 estimation because it reflects the FD variations in the impact of reverberation, aggregating information about FDT60 from the speech signal by processing the spectral decay rates associated with the physical properties of reverberation in each frequency band.

A Study on Correlation between Heterogeneity Index and Mechanical Properties of Igneous Rocks using 3D X-ray Computed Tomography Image (3차원 X-ray CT 영상을 이용한 화성암 불균질 지수와 역학적 특성과의 상관관계에 대한 연구)

  • Jeong, Yeon Jong;Kim, Kwang Yeom;Yun, Tae Sup
    • Tunnel and Underground Space
    • /
    • v.27 no.5
    • /
    • pp.333-342
    • /
    • 2017
  • In this study, the heterogeneity of internal structure of various igneous rocks acquired in Korea was quantified and correlated with the seismic velocity and the point load strength. Three-dimensional X-ray Computed Tomography (CT) was used to obtain information on the internal structure of the rock specimen, and the representative unit length (LR) was calculated by applying a statistical technique to the CT images. We also proposed an estimation equation to predict the mechanical properties of rocks from the relationship between LR, acoustic velocity and point load strength. In the proposed method, it is shown that the characterization of internal structure of rocks could be utilized as an indirect index to account for the mechanical behavior of rocks by substituting physical laboratory testing for non-destructive test.

Feasibility of Ocean Survey by using Ocean Acoustic Tomography in southwestern part of the East Sea (동해 남서해역에서 해양음향 토모그래피 운용에 의한 해양탐사 가능성)

  • Han, Sang-Kyu;Na, Jung-Yul
    • The Journal of the Acoustical Society of Korea
    • /
    • v.13 no.6
    • /
    • pp.75-82
    • /
    • 1994
  • The ray paths and travel times of sound wave in the ocean depend on the physical properties of the propagating media. Ocean Acoustic Tomography(OAT), which is inversely estimate the travel time variations between fixed sources and receivers the physical properties of the corresponding media can he understood. To apply ocean survey technology by using the OAT, the tomographic procedure requires forward problem that variation of the travel times be identified with the variability of the medium. Also, received signals must be satisfied the necessary conditions of ray path stability, identification and resolution in order for OAT to work. The canonical ocean has been determined based on the historical data and its travel time and ray path are used as reference values. The sound speed of canonical ocean in the East Sea is about 1523 m/s at the surface and 1458 m/s at the sound channel axis(400m). Sound speeds in the East Sea are perturbed by warm eddy whose horizontal extension is more than 100 km with deeper than 200 m in depth scale. In this study, an acoustic source and receiver are placed at the depth above the sound channel axis, 350 m, and are separated by 200 km range. Ray paths are identified by the ray theory methed in a range dependent medium whose sound speeds are functions of a range and depth. The eigenray information obtained from interpolation between the rays bracketing the receiver are used to simulate the received signal by convolution of source signal with the eigenray informations. The source signal is taken as a 400 Hz rectangular pulse signal, bandwidth is 16 Hz and pulse length is 64 ms. According to the analysis of the received signal and identified ray path by using numerical model of underwater sound propagation, simulated signals satisfy the necessary conditions of OAT, applied in the East Sea.

  • PDF