• Title/Summary/Keyword: Long-term monitoring

Search Result 1,354, Processing Time 0.028 seconds

Electromechanical impedance-based long-term SHM for jacket-type tidal current power plant structure

  • Min, Jiyoung;Yi, Jin-Hak;Yun, Chung-Bang
    • Smart Structures and Systems
    • /
    • v.15 no.2
    • /
    • pp.283-297
    • /
    • 2015
  • Jacket-type offshore structures are always exposed to severe environmental conditions such as salt, high speed of current, wave, and wind compared with other onshore structures. In spite of the importance of maintaining the structural integrity for an offshore structure, there are few cases to apply a structural health monitoring (SHM) system in practice. The impedance-based SHM is a kind of local SHM techniques and to date, numerous techniques and algorithms have been proposed for local SHM of real-scale structures. However, it still requires a significant challenge for practical applications to compensate unknown environmental effects and to extract only damage features from impedance signals. In this study, the impedance-based SHM was carried out on a 1/20-scaled model of an Uldolmok current power plant structure in Korea under changes in temperature and transverse loadings. Principal component analysis (PCA)-based approach was applied with a conventional damage index to eliminate environmental changes by removing principal components sensitive to them. Experimental results showed that the proposed approach is an effective tool for long-term SHM under significant environmental changes.

이상파랑하에서의 해빈변화특성 해석

  • Kim, Hui-Jae;An, Hyo-Jae;Kim, Gang-Min;Lee, Jung-U
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
    • /
    • 2014.06a
    • /
    • pp.241-243
    • /
    • 2014
  • Recently, as the coastal erosion impacts greats to both social and economical aspects, each local government is trying to setup its countermeasures. However, it is necessary to survey the change of sediment movement characteristics and investigate the continuous environment change by long-term monitoring after building prevention constructions. In this study, predictions on wave deformation and sediment movement deduced through the numerical modeling are made, based on the ordinary and extraordinary wave through seasonal superiority wave direction, height, period and long-term wave characteristics on the eroded beach of central West sea.

  • PDF

Long-Term Variation of the Spin Period of a Magnetic Cataclysmic Variable, MU Camelopardalis

  • Yun, A-Mi;Kim, Yong-Gi;Choi, Chul-Sung
    • Journal of Astronomy and Space Sciences
    • /
    • v.28 no.1
    • /
    • pp.9-12
    • /
    • 2011
  • Results of an analysis of 11 nights of R-filter CCD photometry data of an intermediate polar MU Camelopardalis (MU Cam) obtained at the Korean 1.0 m telescope at Mt. Lemmon are reported. After checking the spin period with our data, $P_{spin}=0.^d01373801(59)$, we compiled the reported data of maxima timing and an O-C diagram analysis has been carried out to understand the spin period variation. A significant spin period variation was detected, and fitting the O-C points to a cubic parabola led to an ephemeris of $BJD_{max}=2453682.4178(94)+0.0137380(13)E-2.07(55){\times}10^{-11}E^2+2.28(52){\times}10^{-15}E^3$. The torque experienced by the magnetic compact star accreting in a disk is estimated as ${\tau}{\approx}1.815{\times}10^{35}gcm^2/s^2$ in a simple approximation in order to show how important monitoring the period variation is. Thus we conclude that monitoring the long-term spin period variation will help to understand the physical condition of magnetic compact stars.

Identification of High Frequency Peakers with long-term monitoring observation at 22 and 43 GHz

  • Jeong, Yongjin;Sohn, Bong Won;Chung, Aeree
    • The Bulletin of The Korean Astronomical Society
    • /
    • v.39 no.2
    • /
    • pp.68.2-68.2
    • /
    • 2014
  • High Frequency Peakers (HFPs) are radio-loud Active Galactic Nuclei (AGN), which are regarded as being in the earliest evolutionary phase (102-103 years) of radio galaxies. They are expected to be small in size (< ~1 kpc) compared to their host galaxies (~a few 10s kpc), and have convex spectra, which are peaking at high radio frequency (> 5 GHz). Their size and spectral shape are the most obvious supporting evidence of extremely young ages. HFPs are therefore ideal targets to probe the earliest stage of radio sources. To date however, the young radio source classification has been relying mainly on the spectral shape which usually does not cover high enough frequencies where the true peak flux is located. Hence HFPs are often confused with blazars which may show a similar spectral shape and apparent compactness but are a somewhat evolved form of AGNs. Therefore, we have been challenging to identify HFPs among the sample of 19 candidates using the Korean VLBI Network (KVN) which enables us to extend the radio spectrum baseline up to 22 and 43 GHz. These are higher than the frequencies used in most previous studies of HFPs, allowing us to select genuine HFPs. By long-term monitoring of 18 epochs, we have also inspected the variability of the sample to select out blazars which are highly variable yet with a similar radio spectrum. In this work, we present the light curves and spectral properties of the HFP candidates. We discuss the results of our re-identification of HFPs.

  • PDF

Development of Portable Measurement Unit with Wireless Transmission by Wireless LAN for Long-term Monitoring (장기간 소자 모니터링이 용이한 소형 무선랜 무선송신 계측장치 개발)

  • Park, So Jeong;Park, Il-Hoo;Moon, Young-Sun;Lee, Kook Jin;Kim, Gyu-Tae
    • Journal of the Semiconductor & Display Technology
    • /
    • v.17 no.1
    • /
    • pp.45-49
    • /
    • 2018
  • Portable microcontroller based measurement unit is demonstrated using digital-to-analog convertor module, analog-to-digital convertor module and additional preamplifier circuit with low-budget but excellent performances. Using the designed measurement unit, the measurement of current below 1 nA with applying voltage up to 5 V is successfully carried out. With the WiFi module in microcontroller, measured data is transferred to the user's computer. To evaluate the performance of the measurement unit, the transfer curve of a commercial N-type field effect transistor was measured with the measurement unit and the results is well consistent with that measured using commercial characterization system.

Predicting the lateral displacement of tall buildings using an LSTM-based deep learning approach

  • Bubryur Kim;K.R. Sri Preethaa;Zengshun Chen;Yuvaraj Natarajan;Gitanjali Wadhwa;Hong Min Lee
    • Wind and Structures
    • /
    • v.36 no.6
    • /
    • pp.379-392
    • /
    • 2023
  • Structural health monitoring is used to ensure the well-being of civil structures by detecting damage and estimating deterioration. Wind flow applies external loads to high-rise buildings, with the horizontal force component of the wind causing structural displacements in high-rise buildings. This study proposes a deep learning-based predictive model for measuring lateral displacement response in high-rise buildings. The proposed long short-term memory model functions as a sequence generator to generate displacements on building floors depending on the displacement statistics collected on the top floor. The model was trained with wind-induced displacement data for the top floor of a high-rise building as input. The outcomes demonstrate that the model can forecast wind-induced displacement on the remaining floors of a building. Further, displacement was predicted for each floor of the high-rise buildings at wind flow angles of 0° and 45°. The proposed model accurately predicted a high-rise building model's story drift and lateral displacement. The outcomes of this proposed work are anticipated to serve as a guide for assessing the overall lateral displacement of high-rise buildings.

Back-calculation of Skin Friction Coefficient ($\alpha$, $\beta$) on a Single Pile by Long-Tenn Field Monitoring (현장 계측 사례를 통한 단독 말뚝의 주면마찰계수($\alpha$, $\beta$ 계수) 역산정)

  • Ko, Jun-Young;Kim, Young-Ho;Choi, Yong-Kyu;Jeong, Sang-Seom
    • Journal of the Korean Geotechnical Society
    • /
    • v.26 no.11
    • /
    • pp.99-110
    • /
    • 2010
  • A fundamental study of the pile-soil systems subjected to negative skin friction in soft soil was conducted using the long-term field measurements. The emphasis was on the identification of the magnitude and distribution of skin frictions ($\alpha$ and $\beta$ coefficients) in bitumen coated and uncoated piles. A skin friction coefficient of instrumented piles is back-calculated by varying degrees of consolidation (U) of surrounding soils. It is shown that the bitumen coated pile is capable of reducing the negative skin friction up to almost 50 to 90 percents. Through comparisons with the existing friction coefficient values ($\alpha$ and $\beta$ coefficients), the calculated coefficients are within the appropriate range, and thus we can suggest basic materials to estimate the realistic pile behavior in the short-term and long-term analysis.

Long-term impacts of Argentine ant invasion of urban parks in Hiroshima, Japan

  • Park, Sang-Hyun;Hosoishi, Shingo;Ogata, Kazuo
    • Journal of Ecology and Environment
    • /
    • v.37 no.3
    • /
    • pp.123-129
    • /
    • 2014
  • Ant communities are well suited for monitoring changes in ecosystems. Although numerous studies have examined the responses of ant communities to environmental disturbance, relatively few long-term studies on ant communities have been undertaken in urban environments. We examined species richness in nine urban parks in Hiroshima, Japan, and compared the survey results with data collected at the same sites by using the same methods in 1999. In both surveys, total of 25 species was recorded: 23 species in 1999 and 20 species in 2012. Non-metric multidimensional scaling analysis revealed that the ant communities consisted of two distinct groups, which could in turn be characterized by three patterns of ant community changes in between the two groups. The first of these community change patterns was characterized by a shift within group 1, but the number of species remained constant (approx. 10 species). The second pattern was characterized by a shift within group 2, but the number of species remained low (approx. 4 species). The third pattern was characterized by a shift from group 1 to group 2 as the abundance of Linepithema humile (Mayr) increased over time. Unlike the first and second patterns, the number of ant species in communities of the third type decreased significantly. These findings suggest that L. humile has a marked effect on the species diversity of indigenous ant communities in urban environments.

Behavioral Strategies for Weight Loss Maintenance (체중감량 이후 장기적인 유지를 위한 다양한 행동전략)

  • Young Hye Cho
    • Archives of Obesity and Metabolism
    • /
    • v.2 no.1
    • /
    • pp.6-10
    • /
    • 2023
  • Compensatory changes in energy consumption and neuro-hormonal changes following weight loss make it difficult to maintain the reduced weight and may cause weight regain. Therefore, establishing a long-term weight control plan and strategy starting from the initial weight loss period is necessary. Both the patient and doctor should know that weight loss cannot occur continuously, and that maintaining weight after the weight loss period is the basic course of obesity treatment. No single dietary pattern is effective for weight maintenance, and a variety of dietary control methods - such as calorie restriction and healthy proportions of carbohydrates, proteins, fats, and meal replacements - should be used to target an integrated and healthy dietary habit. An increase in physical activity is needed for weight loss and maintenance; however, rather than recommending an excessive amount of exercise, it is better to set realistic and long-term achievable goals. It is necessary to reset the goal according to the patient's weight maintenance stage and continuously apply behavioral therapies, such as self-monitoring and stress management. In previous studies, since the degree of weight loss and changes in behavioral patterns over the course of one year were important factors in maintaining long-term weight loss, obesity therapists should closely examine patient data and behavioral patterns across a period of one year and actively intervene when needed.

Rapid full-scale expansion joint monitoring using wireless hybrid sensor

  • Jang, Shinae;Dahal, Sushil;Li, Jingcheng
    • Smart Structures and Systems
    • /
    • v.12 no.3_4
    • /
    • pp.415-426
    • /
    • 2013
  • Condition assessment and monitoring of bridges is critical for safe passenger travel, public transportation, and efficient freight. In monitoring, displacement measurement capability is important to keep track of performance of bridge, in part or as whole. One of the most important parts of a bridge is the expansion joint, which accommodates continuous cyclic thermal expansion of the whole bridge. Though expansion joint is critical for bridge performance, its inspection and monitoring has not been considered significantly because the monitoring requires long-term data using cost intensive equipment. Recently, a wireless smart sensor network (WSSN) has drawn significant attention for transportation infrastructure monitoring because of its merits in low cost, easy installation, and versatile on-board computation capability. In this paper, a rapid wireless displacement monitoring system, wireless hybrid sensor (WHS), has been developed to monitor displacement of expansion joints of bridges. The WHS has been calibrated for both static and dynamic displacement measurement in laboratory environment, and deployed on an in-service highway bridge to demonstrate rapid expansion joint monitoring. The test-bed is a continuous steel girder bridge, the Founders Bridge, in East Hartford, Connecticut. Using the WHS system, the static and dynamic displacement of the expansion joint has been measured. The short-term displacement trend in terms of temperature is calculated. With the WHS system, approximately 6% of the time has been spent for installation, and 94% of time for the measurement showing strong potential of the developed system for rapid displacement monitoring.