• Title/Summary/Keyword: magnitude estimation

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Estimation of the Regional Future Sea Level Rise Using Long-term Tidal Data in the Korean Peninsula (장기 조위자료를 이용한 한반도 권역별 미래 해수면 상승 추정)

  • Lee, Cheol-Eung;Kim, Sang Ug;Lee, Yeong Seob
    • Journal of Korea Water Resources Association
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    • v.47 no.9
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    • pp.753-766
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    • 2014
  • The future mean sea level rise (MSLR) due to climate change in major harbors of Korean Peninsula has been estimated by some statistical methods in this article. Firstly, Mann-Kendall non-parametric trend test to find some trend in the observed long-term tidal data has been performed and also Bayesian change point analysis has been used also to detect the location of change points and their magnitude quantitatively. Especially, in this study, the results from Bayesian change point analysis have been applied to combine 4 future MSLR scenario projections with local MSLR data at 5 tidal gauges. This proposed procedure including Bayesian change point analysis results can improve the step for the determination of starting years of future MLSR scenario projections with 18.6-year lunar node tidal cycle and effectively consider local characteristics at each gauge. The final results by the proposed procedure in this study have shown that the future MSLR in Jeju region (Jeju tidal gauge) is in the largest increment and also the future MSLRs in Western region (Boryeong tidal gauge) and Southern region (Busan tidal gauge) are in the second largest one. Finally, it has been shown that the future MSLRs in Southern region (Yeosu tidal gauge) and Eastern region (Sokcho tidal gauge) seem to be in the relatively smallest growth among 5 gauges.

Analysis of the Dynamic Characteristics on Aerodynamic Loads of Wind Turbine Blade with New Airfoil KA2 (신규 익형 KA2가 적용된 풍력 블레이드의 공력 하중에 대한 동특성 해석)

  • Kang, Sang-Kyun;Lee, Ji-Hyun;Lee, Jang-Ho
    • The KSFM Journal of Fluid Machinery
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    • v.18 no.6
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    • pp.63-70
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    • 2015
  • This paper proposes a novel airfoil named "KA2" for the blade of the wind turbine systems. Dynamic loads characteristics are analyzed and compared using aerodynamic data of ten airfoils including the proposed airfoil. The blade is divided into the sixteen elements in the longitudinal direction of the blade for applying the Blade Element Method Theory (BEMT) method, and in each element, torque, thrust, and pitching moment are calculated using turbulent time varying wind speed and aerodynamic data of each wing. Additionally, each force and torque is accumulated in the whole region of the blade for the estimation of representative values. The magnitude of such forces is comparatively analyzed for different airfoils. The angle of attack is constant below the rated wind speed due to the fact that the tip speed ratio is kept at the constant value, and it increases in the region of over rated wind speed as the tip speed ratio decreasing with constant rated rpm and increasing wind speed. Such increase in the angle of attack causes the changes of the force acting on the airfoil with different characteristics of lift and drag in the stall region of each different airfoil. Even though the mean wind speed is in the rated speed in a given time, because of the turbulence, it has either the over rated or under rated speed most of the time. Furthermore, the dynamic properties of each force are analyzed in this rated wind speed in order to objectively understand the dynamic properties of the blades which are designed based on the different airfoils. These dynamic properties are also compared by the standard deviation of time varying characteristics. Moreover, the output characteristics of the wind turbine are investigated with different airfoils and wind speeds. Based on these investigations, it was revealed that the proposed airfoil (KA2) is well applicable to the blade with passive pitch control system.

Sound quality metrics to express the discomfort of overload excavator noise during operation (과부하 굴삭기 소음의 불쾌감 표현인자)

  • Sim, Sangdeok;Song, Ohseop
    • The Journal of the Acoustical Society of Korea
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    • v.37 no.3
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    • pp.147-155
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    • 2018
  • In this paper, we tried to find out sound quality metrics to express discomfort of overload excavator noise and to develop sound quality indexes through multiple regression analysis by using them. For this purpose, the interior noise of cabin under overload condition was recorded for six excavator models with different noise properties and Jury test was carried out by PCM (Paired Comparison Method) and MEM (Magnitude Estimation Method). Jury test result with low consistency was classified into two groups with different preference tendencies by cluster analysis and multiple regression analysis was conducted in order to find out which sound quality metrics have significant effects on discomfort(low preference). As a result, we figured out that the sound quality metrics to express the discomfort were the partial loudness (= $PN_{10Bark}$) between 0 and 10 Bark in case of group1 and the difference between engine noise(= $dB_{EG}$) and hydraulic system noise ($dB_1$) in case of group2. Using the results of preference ranking and tendency analysis of PCM followed by the correlation analysis between PCM and MEM, the more reliable results were adopted by excluding the data with low consistency obtained from Jury test via MEM.

Localization Using Extended Kalman Filter based on Chirp Spread Spectrum Ranging (확장 Kalman 필터를 적용한 첩 신호 대역확산 거리 측정 기반의 위치추정시스템)

  • Bae, Byoung-Chul;Nam, Yoon-Seok
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.49 no.4
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    • pp.45-54
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    • 2012
  • Location-based services with GPS positioning technology as a key technology, but recognizing the current location through satellite communication is not possible in an indoor location-aware technology, low-power short-range communication is primarily made of the study. Especially, as Chirp Spread Spectrum(CSS) based location-aware approach for low-power physical layer IEEE802.15.4a is selected as a standard, Ranging distance estimation techniques and data transfer speed enhancements have been more developed. It is known that the distance measured by CSS ranging has quite a lot of noise as well as its bias. However, the noise problem can be adjusted by modeling the non-zero mean noise value by a scaling factor which corresponds to the change of magnitude of a measured distance vector. In this paper, we propose a localization system using the CSS signal to measure distance for a mobile node taken a measurement of the exact coordinates. By applying the extended kalman filter and least mean squares method, the localization system is faster, more stable. Finally, we evaluate the reliability and accuracy of the proposed algorithm's performance by the experiment for the realization of localization system.

The Estimation of Annual Net Ecosystem Exchange of CO2 in an Apple Orchard Ecosystem of South Korea (국내 사과원 생태계에서 CO2의 연간 순생태 교환량 추정)

  • Shim, Kyo-Moon;Min, Sung-Hyun;Kim, Yong-Seok;Jung, Myung-Pyo;Choi, In-Tae;Kang, Kee-Kyung
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.18 no.4
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    • pp.348-356
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    • 2016
  • Carbon dioxide ($CO_2$) gases concentration in atmosphere has been growing since preindustrial times. By sequestering a large amount of atmospheric carbon (C), terrestrial ecosystems are thought to offer a mitigation strategy for reducing global warming. Woody agro-ecosystems such as fruit tree are among the least quantified and most uncertain elements in the terrestrial carbon cycle. $CO_2$ and energy fluxes were measured by the eddy covariance method on a 15-year old apple orchard of South Korea in 2006. Environmental parameters (net radiation, precipitation, etc.) were measured along with fluxes. The results showed that during late June, the ability to sequestrate C was significant at an apple orchard ecosystem and it reached on the peak of $-6.5g\;C\;m^{-2}\;d^{-1}$. We found that in the apple orchard, the daily average of net ecosystem exchange of $CO_2$ (NEE) and cumulative NEE on a yearly basis were $-1.1g\;C\;m^{-2}$ and $-396.9g\;C\;m^{-2}$, respectively. These results reveal that there is high carbon sequestration in the apple orchard of South Korea, which is the same magnitude with repect to that of a natural forested ecosystem of the same biome rank (temperate-humid deciduous forest).

A Methodology for 3-D Optimally-Interpolated Satellite Sea Surface Temperature Field and Limitation (인공위성 해수면온도 3-D 최적 내삽 합성장 생산 방법과 한계점)

  • Park, Kyung-Ae;Kim, Young-Ho
    • Journal of the Korean earth science society
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    • v.30 no.2
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    • pp.223-233
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    • 2009
  • Three-dimensional (3-D) optimally-interpolated sea surface temperature (SST) field was produced by using AQUA/AMSR-E satellite data, and its limitations were described by comparing the temporal average of sea surface temperatures. The 3-D OI (Optimum Interpolation) SST showed a small error of less than $0.05^{\circ}C$ in the central North Pacific, but yielded large errors of greater than $0.4^{\circ}C$ at the coastal area where the satellite microwave data were not available. OI SST composite around pixels with no observation due to heavy rainfall or cloudy pixels had estimation errors of $0.1-0.15^{\circ}C$. Comparison with temporal means showed a tendency that overall OI SSTs were underestimated around heavy cloudy pixels and smoothed out by reducing the magnitude of SST fronts. In the low-latitude areas near the equator, OI SST field produced discontinuity, originated from the window size for the OI procedure. This was mainly caused by differences in the spatial scale of oceanic features. Infernal Rossby deformation radius, as a measure of spatial stale, showed dominant latitudinal variations with O(1) difference in the North Pacific. This study suggests that OI SST methodology should consider latitudinally-varying size of window and the characteristics of spatial scales of oceanic phenomena with substantial dependency on latitude and vertical structure of density.

Performance Evaluation of Hash Join Algorithm on Flash Memory SSDs (플래쉬 메모리 SSD 기반 해쉬 조인 알고리즘의 성능 평가)

  • Park, Jang-Woo;Park, Sang-Shin;Lee, Sang-Won;Park, Chan-Ik
    • Journal of KIISE:Computing Practices and Letters
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    • v.16 no.11
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    • pp.1031-1040
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    • 2010
  • Hash join is one of the core algorithms in databases management systems. If a hash join cannot complete in one-pass because the available memory is insufficient (i.e., hash table overflow), however, it may incur a few sequential writes and excessive random reads. With harddisk as the tempoary storage for hash joins, the I/O time would be dominated by slow random reads in its probing phase. Meanwhile, flash memory based SSDs (flash SSDs) are becoming popular, and we will witness in the foreseeable future that flash SSDs replace harddisks in enterprise databases. In contrast to harddisk, flash SSD without any mechanical component has fast latency in random reads, and thus it can boost hash join performance. In this paper, we investigate several important and practical issues when flash SSD is used as tempoary storage for hash join. First, we reveal the va patterns of hash join in detail and explain why flash SSD can outperform harddisk by more than an order of magnitude. Second, we present and analyze the impact of cluster size (i.e., va unit in hash join) on performance. Finally, we emperically demonstrate that, while a commerical query optimizer is error-prone in predicting the execution time with harddisk as temporary storage, it can precisely estimate the execution time with flash SSD. In summary, we show that, when used as temporary storage for hash join, flash SSD will provide more reliable cost estimation as well as fast performance.

A Prediction Method on the Accelerometer Data of the Formation Flying Low Earth Orbit Satellites Using Neural Network (신경망 모델을 사용한 편대비행 저궤도위성 가속도계 데이터 예측 기법)

  • Kim, Mingyu;Kim, Jeongrae
    • Korean Journal of Remote Sensing
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    • v.37 no.5_1
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    • pp.927-938
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    • 2021
  • A similar magnitude of non-gravitational perturbations are act on the formation flying low earth orbit satellites with a certain time difference. Using this temporal correlation, the non-gravity acceleration of the low earth orbiting satellites can be transferred for the othersatellites. There is a period in which the accelerometer data of one satellite is unavailable for GRACE and GRACE-FO satellites. In this case, the accelerometer data transplant method described above is officially used to recover the accelerometer data at the Jet Propulsion Laboratory (JPL). In this paper, we proposed a model for predicting accelerometer data of formation flying low earth orbit satellites using a neural network (NN) model to improve the estimation accuracy of the transplant method. Although the transplant method cannot reflect the satellite's position and space environmental factors, the NN model can use them as model inputs to increase the prediction accuracy. A prediction test of an accelerometer data using NN model was performed for one month, and the prediction accuracy was compared with the transplant method. The NN model outperformsthe transplant method with 55.0% and 40.1% error reduction in the along-track and radial directions, respectively.

TLS (Total Least-Squares) within Gauss-Helmert Model: 3D Planar Fitting and Helmert Transformation of Geodetic Reference Frames (가우스-헬머트 모델 전최소제곱: 평면방정식과 측지좌표계 변환)

  • Bae, Tae-Suk;Hong, Chang-Ki;Lim, Soo-Hyeon
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.40 no.4
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    • pp.315-324
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    • 2022
  • The conventional LESS (LEast-Squares Solution) is calculated under the assumption that there is no errors in independent variables. However, the coordinates of a point, either from traditional ground surveying such as slant distances, horizontal and/or vertical angles, or GNSS (Global Navigation Satellite System) positioning, cannot be determined independently (and the components are correlated each other). Therefore, the TLS (Total Least Squares) adjustment should be applied for all applications related to the coordinates. Many approaches were suggested in order to solve this problem, resulting in equivalent solutions except some restrictions. In this study, we calculated the normal vector of the 3D plane determined by the trace of the VLBI targets based on TLS within GHM (Gauss-Helmert Model). Another numerical test was conducted for the estimation of the Helmert transformation parameters. Since the errors in the horizontal components are very small compared to the radius of the circle, the final estimates are almost identical. However, the estimated variance components are significantly reduced as well as show a different characteristic depending on the target location. The Helmert transformation parameters are estimated more precisely compared to the conventional LESS case. Furthermore, the residuals can be predicted on both reference frames with much smaller magnitude (in absolute sense).

Permanent Deformations of Piles in Sand Under Cyclic Lateral Loads (모래지반에서 반복수평하중을 받는 말뚝의 영구변형)

  • Paik, Kyu-Ho;Park, Won-Woo
    • Journal of the Korean Geotechnical Society
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    • v.26 no.11
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    • pp.63-73
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    • 2010
  • Monopiles, used as one foundation option for offshore wind turbines, are usually subjected to great cyclic lateral loads due to wind and wave. In this study, model pile load tests were performed using calibration chamber and three model piles with different pile lengths in order to investigate the behavior of laterally cyclic loaded piles driven into sand. Model test results show that the first loading cycle generates a bigger displacement than the following ones, and the permanent displacement of piles by one loading cycle decreases with increasing the number of cycles. 1-way cyclic loading causes the permanent displacement in the same direction as cyclic loading, whereas 2-way cyclic loading causes the permanent displacement in the reverse direction of initial loading. It is also observed that the permanent displacement of piles due to cyclic lateral loads increases with decreasing relative density of soil and with increasing the magnitude of cyclic loads. However, it is insensitive to the earth pressure ratio of soil and embedded pile length. In addition, based on the model pile load test results, equations for estimation of the permanent lateral displacement and rotation angle of piles due to 1-way cyclic lateral loads are proposed.