• Title/Summary/Keyword: time domain method

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Restoration, Prediction and Noise Analysis of Geomagnetic Time-series Data (시계열 지자기 측정 자료의 복원, 예측 및 잡음 분석 연구)

  • Ji, Yoon-Soo;Oh, Seok-Hoon;Suh, Baek-Soo;Lee, Duk-Kee
    • Journal of the Korean earth science society
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    • v.32 no.6
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    • pp.613-628
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    • 2011
  • Restoration, prediction and noise analysis of geomagnetic data measured in the Korean Peninsula were performed. Restoration methods based on an optimized principal component analysis (PCA) and the geostatistical kriging approach were proposed, and its effectiveness was also interpreted. The PCA-based method seemed to be effective to restore the periodical signals and the geostatistical approach was stable to fill the gaps of measurements. To analyze the noise level for each observatory, the geomagnetic time-series was plotted by scattergram which reflects the spatial variation, using data observed during same period. The scattergram showed that the observation made at Cheongyang seemed to have better quality in spatial continuity and stability, and the restoration result was also better than that of Icheon site. For the restoration, both of the methods, geostatistical and optimizaed PCA, showed stable result when the missing of observation was within 20 points. However, in case of more missing observations than 20 points and prediction problem, the optimized PCA seemed to be closer to the real observation considering the frequency-domain characteristics. The prediction using the optimized PCA seems to be plausible for one day of period for interpretation.

Non-homogeneous noise removal for side scan sonar images using a structural sparsity based compressive sensing algorithm (구조적 희소성 기반 압축 센싱 알고리즘을 통한 측면주사소나 영상의 비균일 잡음 제거)

  • Chen, Youngseng;Ku, Bonwha;Lee, Seungho;Kim, Seongil;Ko, Hanseok
    • The Journal of the Acoustical Society of Korea
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    • v.37 no.1
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    • pp.73-81
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    • 2018
  • The quality of side scan sonar images is determined by the frequency of a sonar. A side scan sonar with a low frequency creates low-quality images. One of the factors that lead to low quality is a high-level noise. The noise is occurred by the underwater environment such as equipment noise, signal interference and so on. In addition, in order to compensate for the transmission loss of sonar signals, the received signal is recovered by TVG (Time-Varied Gain), and consequently the side scan sonar images contain non-homogeneous noise which is opposite to optic images whose noise is assumed as homogeneous noise. In this paper, the SSCS (Structural Sparsity based Compressive Sensing) is proposed for removing non-homogeneous noise. The algorithm incorporates both local and non-local models in a structural feature domain so that it guarantees the sparsity and enhances the property of non-local self-similarity. Moreover, the non-local model is corrected in consideration of non-homogeneity of noises. Various experimental results show that the proposed algorithm is superior to existing method.

A Coupled Analysis of Finite Elements and Boundary Elements for Time Dependent Inelastic Problems (시간의존 비탄성 문제의 유한요소-경계요소 조합에 의한 해석)

  • Kim, Moon Kyum;Huh, Taik Nyung;Jang, Jung Bum;Oh, Se Ho
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.13 no.3
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    • pp.25-34
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    • 1993
  • The long-term behavior, such as in excavation problems of weak medium, can be dealt with by the elasto-viscoplasticity models. In this paper, a combined formulation of elasto-viscoplasticity using boundary elements and finite elements without using internal cells is presented. The domain integral introduced due to the viscoplastic stresses is transformed into a boundary integral applying direct integration in cylindrical coordinates. The results of the developed boundary element analysis are compared with those from the explicit solution and from the finite element analysis. It is observed that the boundary element analysis without internal cells results in some error because of its deficiency in handling the nonlinearity in local stress concentration. Therefore, a coupled analysis of boundary elements and finite elements, in which finite elements are used in the area of stress concentration, is developed. The coupled method is applied to a time dependent inelastic problem with semi-infinite boundaries. It results in reasonable solution compared with other methods where relatively higher degree of freedoms are employed. Thus, it is concluded that the combined analysis may be used for such problems in the effective manner.

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Boundary conditions for Time-Domain Finite-Difference Elastic Wave Modeling in Anisotropic Media (이방성을 고려한 시간영역 유한차분법 탄성파 모델링에서의 경계조건)

  • Lee, Ho-Yong;Min, Dong-Joo;Kwoon, Byung-Doo;Lim, Seung-Chul;Yoo, Hai-Soo
    • Geophysics and Geophysical Exploration
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    • v.11 no.2
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    • pp.153-160
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    • 2008
  • Seismic modeling is used to simulate wave propagation in the earth. Although the earth's subsurface is usually semi-infinite, we cannot handle the semi-infinite model in seismic modeling because of limited computational resources. For this reason, we usually assume a finite-sized model in seismic modeling. In that case, we need to eliminate the edge reflections arising from the artificial boundaries introducing a proper boundary condition. In this study, we changed three kinds of boundary conditions (sponge boundary condition, Clayton and Engquist's absorbing boundary condition, and Higdon's transparent boundary condition) so that they can be applied in elastic wave modeling for anisotropic media. We then apply them to several models whose Poisson's ratios are different. Clayton and Engquist's absorbing boundary condition is unstable in both isotropic and anisotropic media, when Poisson's ratio is large. This indicates that the absorbing boundary condition can be applied in anisotropic media restrictively. Although the sponge boundary condition yields good results for both isotropic and anisotropic media, it requires too much computational memory and time. On the other hand, Higdon's transparent boundary condition is not only inexpensive, but also reduce reflections over a wide range of incident angles. We think that Higdon's transparent boundary condition can be a method of choice for anisotropic media, where Poisson's ratio is large.

LiDAR Chip for Automated Geo-referencing of High-Resolution Satellite Imagery (라이다 칩을 이용한 고해상도 위성영상의 자동좌표등록)

  • Lee, Chang No;Oh, Jae Hong
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.32 no.4_1
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    • pp.319-326
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    • 2014
  • The accurate geo-referencing processes that apply ground control points is prerequisite for effective end use of HRSI (High-resolution satellite imagery). Since the conventional control point acquisition by human operator takes long time, demands for the automated matching to existing reference data has been increasing its popularity. Among many options of reference data, the airborne LiDAR (Light Detection And Ranging) data shows high potential due to its high spatial resolution and vertical accuracy. Additionally, it is in the form of 3-dimensional point cloud free from the relief displacement. Recently, a new matching method between LiDAR data and HRSI was proposed that is based on the image projection of whole LiDAR data into HRSI domain, however, importing and processing the large amount of LiDAR data considered as time-consuming. Therefore, we wmotivated to ere propose a local LiDAR chip generation for the HRSI geo-referencing. In the procedure, a LiDAR point cloud was rasterized into an ortho image with the digital elevation model. After then, we selected local areas, which of containing meaningful amount of edge information to create LiDAR chips of small data size. We tested the LiDAR chips for fully-automated geo-referencing with Kompsat-2 and Kompsat-3 data. Finally, the experimental results showed one-pixel level of mean accuracy.

Analysis of General Characteristics and Structural Characteristics Centering on Offline Board Games (오프라인 보드게임을 중심으로한 일반적 특성과 구조적 특성 분석)

  • Park, Bo-Ra;Lim, Hee-Jung;Lee, Ye-Jin;Yi, Ryun-Jae;Yang, Yeong-Ae
    • The Journal of the Korea Contents Association
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    • v.17 no.5
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    • pp.234-242
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    • 2017
  • This study selected 60 board games that have a high sales rate and awareness in the board game market, and analyzed 37 board games that were selected through the advice of experts. According to the analysis of general characteristics, there was the highest number of board games that more than 2 people could participate and people from ages 7 to 11 could use, and the most common play time was from 20 minutes to 30 minutes. Also, there was the largest number of board games produced in 2000s, and Germany was the most common producer of board games. Next, the content analysis showed that abstract strategy was the most common game genre, and cognitive domain was the most common in the development area. The analysis based on how to play the game showed that games that had to go through 4 stages were the most common. Card games were the most common form of game, group was the most common in organization form, and reaching goal was most common among result analysis method. According to the analysis of correlation by items, the number of people and work analysis had a statistical correlation, and the playing age, time, and genre had a correlation. The origin of the game and game genre were also correlated to each other, and game form, game genre, organization form, and result analysis had a statistical correlation as well. The purpose of this study is to analyze the board game in terms of structural characteristics and to provide a foundation for future research.

Comparison of Demographic Characteristics, Health and Quality of Life between General Adults and Adults Living with Dementia Patients : The 2016 Community Health Survey (치매 환자와 함께 거주하는 성인과 일반 성인 사이의 인구사회학적 특성, 건강 및 삶의 질 비교 : 2016년 지역사회건강조사 원시자료를 이용하여)

  • Moon, Jong-Hoon;Kim, Ye-Soon
    • Journal of Society of Occupational Therapy for the Aged and Dementia
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    • v.12 no.2
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    • pp.57-65
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    • 2018
  • Objective : The purpose of this study was to compare the demographic characteristics, health and quality of life between general adults and adults living with dementia. Method : The data were collected using raw data of the 2016 community health survey and compared between 2,592 adults living with dementia patients and 225,840 general adults. health were assessed for sleep time, stress level, depression, and subjective health status, and quality of life was measured by EQ-5D. Result : In comparison of demographic characteristics, age and family number of adults living with dementia patients were significantly higher than general adults (p<.001), income and eduation levels were low (p<.001), and marital status was higher rate of living with spouse (p<.05). In comparison of health status, adults living with dementia patients were significantly longer in sleep time than the general adults (p<.001), and stress level was higher (p<.001), the percentage of experience of depression was higher (p<.001), and the subjective health status was worse (p<.001). Adults living with dementia patients were significantly lower in quality of life total score and all sub-domain than general adults (p<.001). Conclusion : Based on the results of this study, it is necessary to seek ways to improve the health and quality of life of dementia patients' families.

A Comparative Study of Block Chain : Bitcoin·Namecoin·MediBloc (블록체인 비교연구: 비트코인·네임코인·메디블록)

  • Kim, Ji Yeon
    • Journal of Science and Technology Studies
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    • v.18 no.3
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    • pp.217-255
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    • 2018
  • Bitcoin, which appeared in 2008, was merely a conceptual virtual currency, but it now enjoys the status as actual money. Bitcoin is an electronic money system that can be traded directly without a central trust institution. Thanks to the popularization of Bitcoin, blockchain technology has become a widespread concern. That technology is expanding not only the currency mechanism, but also a variety of other services. The possibility of a blockchain in relation to actual currency is ongoing. This paper investigates the technological characteristics and social construction of the blockchain by comparing the cases of Bitcoin, Namecoin, and MediBloc among blockchain applications. Namecoin emerged in 2013 is an attempt to replace the centralized Internet Domain Name System(DNS). There has been controversy over that current system for a long time, but replacing the already established system is not easy. Nevertheless, Namecoin has potential as an alternative. Meanwhile, MediBloc is an application that involves distributed management of medical data in South Korea. MediBloc claims that the key producers of medical data are patients themselves. This is to challenge to the question who is a knowledge producer of medical data. Through these three cases, it has discussed that blockchain technology does supports to form more democratic decision-making or simply provide a technical solution as automation. As a citizen, we can intervene in the realization of blockchains by presenting social agenda. This will be a method of the social construction of technology.

Diagnosis of Valve Internal Leakage for Ship Piping System using Acoustic Emission Signal-based Machine Learning Approach (선박용 밸브의 내부 누설 진단을 위한 음향방출신호의 머신러닝 기법 적용 연구)

  • Lee, Jung-Hyung
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.28 no.1
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    • pp.184-192
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    • 2022
  • Valve internal leakage is caused by damage to the internal parts of the valve, resulting in accidents and shutdowns of the piping system. This study investigated the possibility of a real-time leak detection method using the acoustic emission (AE) signal generated from the piping system during the internal leakage of a butterfly valve. Datasets of raw time-domain AE signals were collected and postprocessed for each operation mode of the valve in a systematic manner to develop a data-driven model for the detection and classification of internal leakage, by applying machine learning algorithms. The aim of this study was to determine whether it is possible to treat leak detection as a classification problem by applying two classification algorithms: support vector machine (SVM) and convolutional neural network (CNN). The results showed different performances for the algorithms and datasets used. The SVM-based binary classification models, based on feature extraction of data, achieved an overall accuracy of 83% to 90%, while in the case of a multiple classification model, the accuracy was reduced to 66%. By contrast, the CNN-based classification model achieved an accuracy of 99.85%, which is superior to those of any other models based on the SVM algorithm. The results revealed that the SVM classification model requires effective feature extraction of the AE signals to improve the accuracy of multi-class classification. Moreover, the CNN-based classification can be a promising approach to detect both leakage and valve opening as long as the performance of the processor does not degrade.

An Ethnographic Study about Taegyo Practice in Korea (태교 실천에 대한 일상생활 기술적 연구)

  • 김현옥
    • Journal of Korean Academy of Nursing
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    • v.27 no.2
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    • pp.411-422
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    • 1997
  • The purpose of this study is twofold : (i) to investigate how much effort the married couples are making for the good health of both the pregnant woman and her unborn child from the time of their marriage to and during the period of conception : and (ii) to comprehensive investigate socio-cultural back-grounds which affect prenatal effort. Result of this study provide a basis for the prenatal care program which will be appropriate to our culture. This study has been done by the ethnographic research method. The subjects of this study are 53 people in all consisting of 33 pregnant women and 20 husbands. In order to investigate socio-cultural factors which influence Taegyo, producers of Taegyo music were interviewed. In addition the researcher surveyed the markets of Taegyo music, participated in special courses of prenatal education, analyzed the content of the books and periodicals dealing with Taegyo, and collected the concept of Taegyo distributed by the mass media. The full-fledged study continued for eight months from February to August.1996. The data were analyzed as soon as they were collected. Spradly's(1979, 1980) developmental, sequential method of domain analysis. taxonomic analysis, componential analysis, and theme analysis in this order was adopted as the procedure of analyzing the data. To obtain the exactness of study, Sandelowski's (1986) four criteria, that is, Credibility, Fittingness, Auditability, and Confirmability were applied to all stages of data collection, data analysis, the interpretation of the result, and the description of the result. The following are the result : 1. The couples' Taegyo at the stage of preconception was related to their physical, psychological, spiritual conditions under which a healthy baby will be born. Specific methods they prefer are : "the choice of one's spouse." "physical check-up," "physical good health, " "praying, " and so on. 2. When the marriod couple have sex in order to conceive, their Taegyo was related to the imposition of their physical, psychological, and environmental conditions. Specific methods they prefer are : "having sex at specific time, " "having sex in nice place." "to purify their minds while having sex," and so on. 3. The married couples' Taegyo while they are in pregnancy was related to the imposition of their physical. psychological, emotionmental. environmental, social and spiritual conditions. Specific methods they prefer are : "listening to music. " "reading," "looking at beautiful things only," "to avoid looking at or listening to bad things." "to eat food in good shape, " "to avoid drugs," "eating Korean herbal medicine." "sexual abstinence," "to avoid dangerous places," "to keep emotional tranquility," "moderate exercises and rest." "leading a pure life." "praying." "being aware of their words and behavior." "for the couple to keep a good relationship." "interaction with their unborn child," "to support Taegyo for pregnant women," and so on. 4. The married couple put Taegyo into practice on the basis of the following principles : the principle of respecting an unborn child, the principle of forming a good disposition. the principle of top-down parental love, the principle of synergy between a pregnant woman and her unborn child, the principle of expecting a good child, the principle of forming a good habit, and the principle of acquiring a parental role. 5. The practice of Taegyo is influenced by such factors as the married couple, the supporting system, and the mass media. As the husband -and-wife factor, their information of Taegyo, the degree of importance is assigned to their characters, their time to spare, their healthiness, the age of pregnant woman, their conception plan, their religion, their belief of the Taegyo effects, and the birth of a baby in this order. The factor of the supporting system consists of her husband's support, her family support, and her neighbor's support. The mass media factors include the broadcasting media, books specialized in Taegyo, periodicals for pregnant women, booklets for advertizing powdered milk, Taegyo music of record manufacturing companies, and the teaching materials for gifted children. Among these the mass media is especially taking advantage of Taegyo as its main source of economic profits are leading the public behavior pattern to a prodigal one. Taegyo is a self-control behavior which requires practice for the following : the physical and psychological good health of the pregnant woman and her unborn child, the development of the unborn child's good character, the development of the unborn child's intelligence and talents, the expectation of the unborn child's good features. shape a good habit, the expectation of the unborn child's bright future, and the learning of a parental role, the expectation of male birth. Above all it is a type of our good cultural tradition which pursues a value higher than the one that the prenatal care does. The principles of pregnancy care inherent in the habit of Taegyo will provide us a guideline for the development of the prenatal care.

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