• Title/Summary/Keyword: low frequency

Search Result 11,436, Processing Time 0.038 seconds

A study on the low-frequency of acoustic sensor using single mode FBG (Fiber Bragg Grating). (단일모드 광섬유 브래그 격자를 이용한 저주파수 대역의 음향 센서에 관한 연구)

  • Kim, Kyung-Bok;Kwack, Kae-Dal
    • Journal of Sensor Science and Technology
    • /
    • v.9 no.6
    • /
    • pp.396-403
    • /
    • 2000
  • The low- frequency acoustic sensor using the recently developed FBG has an excellent merits which the existing fiber-optic sensor has and also it has an excellent signal sensing effect in the environment of low-frequency($30Hz{\sim}300Hz$). Furthermore, we can expect the utilization of low-frequency signal defection instead of existing microphones in the environment of electric noise and also it can be developed as the high-sensibility multiplexing through the sensor array system.

  • PDF

A Study on the Still Image Compression using the Low Pass Filter (로우 패스 필터를 이용한 정지 영상 압축에 관한 연구)

  • 김성종;신인철
    • Proceedings of the Korea Society for Industrial Systems Conference
    • /
    • 1997.11a
    • /
    • pp.91-101
    • /
    • 1997
  • The demand for handling images in digital form has increased dramatically in recent years. Digital image compression is required to store and transmit mass information in different from general information. JPEG(Joint Photographic Experts Group) committee founded by CCITT and ISO is define the still-image standard compression/restoration algorithm. JPEG is proposed the standard of grayscale and color still-image compression/restoration. In the image quality, JPEG is applicable to the various applications in which compression is able to from 1/10 to 1/50 without the visible obstacle. In this paper, we proposed that the proposed method enhance the compression ratio which is reducing the higher frequency in order to increasing the spatial redundancy in the image. The proposed method is using the low pass filter in order to reducing the higher frequency. The low-pass filters are using the median filter and convolution filter in the spatial domain, FFT filter in the frequency domain. We acquired the additive compression ratio reducing the higher frequency using the low-pass filter.

  • PDF

Evaluation on Vibration Characteristics of an Apartment Building Structure (아파트 구조물의 진동특성 평가에 관한 연구)

  • Choi, Chang-Sik;Lee, Li-Hyung
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.2 no.3
    • /
    • pp.161-167
    • /
    • 1998
  • A problem of frequency in the field of low-frequencies such as high-rise apartment building or construction vibration are often found. In this study, damage reason of a 25 stories apartment building was searched on the basis of actual damage. To find the damage reason, structural design procedure were reviewed and low-frequency vibration test was conducted. The results indicate that the main damage reason is not by the low-frequency vibration but the asymmetrical plan of that building.

  • PDF

Automatic algorithm for Numerical conformal mapping based on the Hubner's Method (Hubner 방법에 기초한 수치등각사상의 자동화 알고리즘)

  • Song, Eun-Ji
    • The Transactions of the Korea Information Processing Society
    • /
    • v.6 no.10
    • /
    • pp.2716-2721
    • /
    • 1999
  • The problem of determining the conformal maps from the unit disk onto a jordan region has been completed by solving the theodorsen equation that is nonlinear. For the hubners method, which has been well known for the efficient method among the many suggestions for the Theodorsen equation, it has been reproved in our early study that the convergence rate could be remarkably improved by exploring and applying a low-frequency pass filter[1]. However, in the Hubner's method with the low-frequency filter, the discrete numbers and parameters of the low-frequency filter were able to be acquired only by experience. In this paper we show algorithms that determine the discrete numbers and parameters of the low-frequency filter automatically in accordance with the given region. This results from analyzing the function, which decides the shape of the given domain under the assumption that the degree of the problem depends of the transformation of a given domain, as seen in the Fourier Transform.

  • PDF

Low-frequency Ultrasound Enhanced Transdermal Drug Delivery Across Rat Skin

  • Lee, Hwa-Jin;Kim, Jong-Youl;Park, Jin-Nam;Shin, Young-Hee
    • Journal of Pharmaceutical Investigation
    • /
    • v.37 no.6
    • /
    • pp.365-368
    • /
    • 2007
  • The primary aim of this study was to investigate the enhancement effect of low-frequency ultrasound on skin permeation. In vitro permeation experiments were performed using Franz modified diffusion cells with ketoprofen as model drug. The effect of various ultrasound factors-ultrasound application mode (continuous mode and discontinuous mode), ultrasound intensity (0.26 $W/cm^2$, and 0.29 $W/cm^2$) and duty cycle (3%, 16%, 50%, and 83%) were studied. The highest permeation was observed at 0.29 $W/cm^2$ intensity, 50% duty cycle, and discontinuous mode. The result suggested the feasibility of low frequency ultrasound application for the phonophoretic transdermal drug delivery system.

Study on Multiscale Analysis on Drought Characteristics

  • Uranchimeg, Sumiya;Kwon, Hyun Han
    • Proceedings of the Korea Water Resources Association Conference
    • /
    • 2015.05a
    • /
    • pp.611-611
    • /
    • 2015
  • One of the hazard of nature is a drought. Its impact varies from region to region and it is difficult for people to understand and define due to differences in hydrometeorological and social economic aspects across much of the country. In the most general sense, drought originates from a deficiency of precipitation over an extended period of time, usually month, season or more, resulting in a water shortage for some activity, group, or environmental sector. Palmer Drought Severity Index (PDSI) is well known and has been used to study aridity changes in modern and past climates. The PDSI index is estimated over US using USHCN historical data.(e.g. precipitation, temperature, latitude and soil moisture). In this study, low frequency drought variability associated with climate variability such as El-Nino and ENSO is mainly investigated. With respect to the multi-scale analysis, wavelet transform analysis is applied to the PDSI index in order to extract the low frequency band corresponding to 2-8 years. Finally, low frequency patterns associated with drought by comparing global wavelet power, with significance test are explored.

  • PDF

Machine Learning Model for Low Frequency Noise and Bias Temperature Instability (저주파 노이즈와 BTI의 머신 러닝 모델)

  • Kim, Yongwoo;Lee, Jonghwan
    • Journal of the Semiconductor & Display Technology
    • /
    • v.19 no.4
    • /
    • pp.88-93
    • /
    • 2020
  • Based on the capture-emission energy (CEE) maps of CMOS devices, a physics-informed machine learning model for the bias temperature instability (BTI)-induced threshold voltage shifts and low frequency noise is presented. In order to incorporate physics theories into the machine learning model, the integration of artificial neural network (IANN) is employed for the computation of the threshold voltage shifts and low frequency noise. The model combines the computational efficiency of IANN with the optimal estimation of Gaussian mixture model (GMM) with soft clustering. It enables full lifetime prediction of BTI under various stress and recovery conditions and provides accurate prediction of the dynamic behavior of the original measured data.

Non-Parametric Low-Flow Frequency Analysis Using RCPs Scenario Data : A Case Study of the Gwangdong Storage Reservoir, Korea (RCPs 시나리오 자료를 이용한 비매개변수적 갈수빈도 해석: 광동댐 유역을 중심으로)

  • Yoon, Sun Kwon;Cho, Jae Pil;Moon, Young Il
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.34 no.4
    • /
    • pp.1125-1138
    • /
    • 2014
  • In this study, we applied an advanced non-parametric low-flow frequency analysis using boundary kernel by Representative Concentration Pathways (RCPs) climate change scenarios through Arc-SWAT long-term runoff model simulation at the Gwangdong storage reservoir located in Taeback, Gangwondo. The results show that drought frequency under RCPs was expected to increase due to reduced runoff during the near future, and the variation of low-flow time series was appeared greatly under RCP8.5 scenario, respectively. The result from drought frequency of Median flow in the near future (2030s) compared historic period, the case of 30-year low-flow frequency was increased (the RCP4.5 shows +22.4% and the RCP8.5 shows +40.4%), but in the distant future (2080s) expected increase of drought frequency due to the reduction of low-flow (under RCP4.5: -4.7% and RCP8.5: -52.9%), respectively. In case of Quantile 25% flow time series data also expected that the severe drought frequency will be increased in the distant future by reducing low-flow (the RCP4.5 shows -20.8% to -60.0% and the RCP8.5 shows -30.4% to -96.0%). This non-parametric low-flow frequency analysis results according to the RCPs scenarios have expected to consider to take advantage of as a basis data for water resources management and countermeasures of climate change in the mid-watershed over the Korean Peninsula.

Implementation of Platform System for IEEE 802.15.4 Low Rate WPAN

  • Park, Joo-Ho;Kang, Young-Jin;Kim, Jae-Young
    • Proceedings of the Korea Society of Information Technology Applications Conference
    • /
    • 2005.11a
    • /
    • pp.191-194
    • /
    • 2005
  • In this paper the platform system for IEEE 802.15.4 Low Rate WPAN is designed and fabricated. IEEE 802.15.4 Low Rate WP AN system serves the functions and realization of home-area network. According to the IEEE 802.15.4 standard, there are two modes, One is BPSK modulation in 868/915MHz frequency band. The other is O-QPSK modulation in 2.45GHz frequency band. In this paper we implemented the platform system mounted in one PCB board in 868/915MHz frequency band of IEEE 802.15.4 Low Rate WPAN system. We measured that the platform system which consists of digital part and RF part has good performance. Also RF part is realized by design and fabrication of the RF transceiver IC. The key issue is to make the platform system which provides the function of Low Rate WPAN system to meet the requirement of IEEE 802.15.4 standards.

  • PDF

Characteristic Impedances in Low-Voltage Distribution Systems for Power Line Communication

  • Kim, Young-Sung;Kim, Jae-Chul
    • Journal of Electrical Engineering and Technology
    • /
    • v.2 no.1
    • /
    • pp.29-34
    • /
    • 2007
  • The input and output impedances in a low voltage distribution system is one of the most important matters for power line communication because from the viewpoint of communication, the attenuation characteristic of the high frequency signals is greatly caused by impedance mismatch during sending and receiving. The frequency range is from 1MHz to 30MHz. Therefore, this paper investigates the input and output impedances in order to understand the characteristic of high frequency signals in the low voltage distribution system between a pole transformer and an end user. For power line communication, the model of Korea's low voltage distribution system is proposed in a residential area and then the low voltage distribution system is set up in a laboratory. In the low voltage distribution system, S parameters are measured by using a network analyzer. Finally, input and output impedances are calculated using S parameters.