• Title/Summary/Keyword: Observation Error

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Analysis of axisymmetric extrusion through curved dies by using the method of weighted residuals (가중잔류항법을 이용한 곡면금형의 축대칭 전방압출해석)

  • 조종래;양동열
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.11 no.3
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    • pp.509-518
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    • 1987
  • The paper is concerned with the analysis of axisymmetric forward extrusion by using the method of weighted residuals. In the method of weighted residuals, the flow function and the stress functions are assumed so as to cover the global control volume. The derived stress and strain components are used to formulate a constitutive equation in the error form, so that the error is minimized to determine the stress and strain components. The method of least squares is then chosen for the minimization of errors. The distribution of stresses and strains and the forming load are determined for the workhardening material considering the frictional effect at the die surface. The computed results are very similar to those obtained by the finite element method. The method is simpler in application and requires less computational time than the finite element method. Experiments are carried out for aluminum and steel specimens using curved dies. It is found that the experimental observation is mostly in agreement with the computed results by the method of weighted residuals.

A Study on MPPT Control using the Maximum Power Balance/Unbalance Boundary Point Control (최대 전력 평형/불평형 경계점 제어를 이용한 MPPT제어에 관한 연구)

  • Koh Kang-Hoon;Kang Tae-Kyeng;Lee Hyun-Woo;Woo Jung-In
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.55 no.1
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    • pp.33-38
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    • 2006
  • This paper proposes a simple MPPT control scheme of a based Current-Control-Loop system that can be obtains a lot of advantage to compare with another digital control method, P&O(Perturbation and Observation) and IncCond(Incremental Conductance) algorithm, that is applied mostly a PV system. An existent method is needed an expensive processor such as DSP that calculated to change the measure power of a using current and voltage sensor at the once. Therefore, it is applied a small home power generation system that required many expenses. But, a proposed method is easy to solve the cost reduction and power unbalance Problems that it is used by control scheme to limit error of a current control of common sensor. This proposed algorithm had verified through a simulation and an experiment results on battery charger using PIC that is the microprocessor of a low price.

A Study on the Development of Simple DGPS for the Coastal Survey (연안 해양 관측을 위한 간역 DGPS 개발 연구)

  • 이상룡;문동준;전호경
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.8 no.1
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    • pp.10-17
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    • 1996
  • A real time simple DGPS (SDGPS) for coastal survey is developed and in situ tested. While the accuracy of the system is almost the same as that of existing commercially available DGPS, it is very economical compared to the commercial ones. The RMS error of the positions fired by the system is estimated to be less than 2 m within the range of 30 km from the reference station. Even if the coordinates of the reference station are uncertain, they can be fixed, from the continuous GPS observation of one day, with the maximum error less than 1 m. The system is believed to be helpfully utilized to most of coastal surveys despite of some minor defects.

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A New Techniques for Estimation of Carrier Frequency Offset in MIMO OFDM Systems (다중 입출력 직교 주파수 분할 다중화 시스템에서의 반송파 주파수 오프셋 추정을 위한 새로운 기법)

  • Altaha, Mustafa;Hwang, Humor
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.6
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    • pp.949-954
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    • 2017
  • Multiple input, multiple output orthogonal frequency division multiplexing (MIMO OFDM) systems are the candidate for the future wireless communications. However, the main drawback of MIMO OFDM systems is their sensitivity to carrier frequency offset (CFO) similar to the single input, single output OFDM (SISO OFDM) systems. The demodulation of a signal with CFO causes large bit error rate and degrade the performance of a symbol synchronizer. It is important to estimate the frequency offset and minimize or eliminate its impact. In this paper, we propose a technique based on observation training symbols for estimating CFO by employing block-by-block estimation for SISO OFDM systems. The technique of SISO OFDM is extended to the MIMO OFDM systems. Simulation results show that the proposed techniques have a superior performance and better accuracy compared to the conventional techniques in the sense of mean square error.

Validation of chlorophyll algorithm in Ulleung Basin, East/Japan Sea

  • Yoo, Sin-Jae;Kim, Hyun-Cheol;Lee, Jeong-ah;Park, Mi-Ok
    • Korean Journal of Remote Sensing
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    • v.18 no.1
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    • pp.35-42
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    • 2002
  • The results of our observation in May 2000 indicated that the SeaWiFS algorithm (O'Reilley et al., 1998), which was adopted for OSMI data processing, overestimated the actual chlorophyll values. This was rather unexpected in that there were good reasons to expect that the bio-optical properties of East/Japan Sea belonged to Case 1 water and in such case, the OC2 algorithm would give unbiased estimates of actual chlorophyll a values. In November 2000, a cruise conducted bio-optical surveys in the same area. This time we added HPLC (High Performance Liquid Chromatography) method for measuring chlorophyll a concentration to the standard fluorometric method, which we hale been using during the past Fluorometric method with acidification is known to result in under/overestimation of chlorophyll values in many parts of the world oceans, while it is easier and cheaper than HPLC method. To our surprise, the comparison of HPLC chlorophyll and fluorometric chlorophyll values show that fluorometric values gave an underestimation up to 50%. This error was due to the presence of accessory pigments such as chlorophyll b. Considering this error, our precious result of May 2000(Yoo et al., 2000) might have to be reinterpreted. Calculation of reflectance at 490 and 555nm, however, indicated that this is not still enough to explain the discrepancies.

Mean Velocity Distribution of Natural Stream using Entropy Concept in Jeju (엔트로피 개념을 이용한 제주도 상시하천의 평균유속분포 추정)

  • Yang, Se-Chang;Yang, Sung-Kee;Kim, Yong-Suk
    • Journal of Environmental Science International
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    • v.28 no.6
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    • pp.535-544
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    • 2019
  • We computed parameters that affect velocity distribution by applying Chiu's two-dimensional velocity distribution equation based on the theory of entropy probability and acoustic doppler current profiler (ADCP) of Jungmun-stream, Akgeun-stream, and Yeonoe-stream among the nine streams in Jeju Province between July 2011 and June 2015. In addition, velocity and flow were calculated using a surface image velocimeter to evaluate the parameters estimated in the velocity observation section of the streams. The mean error rate of flow based on ADCP velocity data was 16.01% with flow calculated using the conventional depth-averaged velocity conversion factor (0.85), 6.02% with flow calculated using the surface velocity and mean velocity regression factor, and 4.58% with flow calculated using Chiu's two-dimensional velocity distribution equation. If surface velocity by a non-contact velocimeter is calculated as mean velocity, the error rate increases for large streams in the inland areas of Korea. Therefore, flow can be calculated precisely by utilizing the velocity distribution equation that accounts for stream flow characteristics and velocity distribution, instead of the conventional depth-averaged conversion factor (0.85).

A Model Stacking Algorithm for Indoor Positioning System using WiFi Fingerprinting

  • JinQuan Wang;YiJun Wang;GuangWen Liu;GuiFen Chen
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.17 no.4
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    • pp.1200-1215
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    • 2023
  • With the development of IoT and artificial intelligence, location-based services are getting more and more attention. For solving the current problem that indoor positioning error is large and generalization is poor, this paper proposes a Model Stacking Algorithm for Indoor Positioning System using WiFi fingerprinting. Firstly, we adopt a model stacking method based on Bayesian optimization to predict the location of indoor targets to improve indoor localization accuracy and model generalization. Secondly, Taking the predicted position based on model stacking as the observation value of particle filter, collaborative particle filter localization based on model stacking algorithm is realized. The experimental results show that the algorithm can control the position error within 2m, which is superior to KNN, GBDT, Xgboost, LightGBM, RF. The location accuracy of the fusion particle filter algorithm is improved by 31%, and the predicted trajectory is close to the real trajectory. The algorithm can also adapt to the application scenarios with fewer wireless access points.

Voice Activity Detection Based on Discriminative Weight Training with Feedback (궤환구조를 가지는 변별적 가중치 학습에 기반한 음성검출기)

  • Kang, Sang-Ick;Chang, Joon-Hyuk
    • The Journal of the Acoustical Society of Korea
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    • v.27 no.8
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    • pp.443-449
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    • 2008
  • One of the key issues in practical speech processing is to achieve robust Voice Activity Deteciton (VAD) against the background noise. Most of the statistical model-based approaches have tried to employ equally weighted likelihood ratios (LRs), which, however, deviates from the real observation. Furthermore voice activities in the adjacent frames have strong correlation. In other words, the current frame is highly correlated with previous frame. In this paper, we propose the effective VAD approach based on a minimum classification error (MCE) method which is different from the previous works in that different weights are assigned to both the likelihood ratio on the current frame and the decision statistics of the previous frame.

Sampling Error of Areal Average Rainfall due to Radar Partial Coverage (부분적 레이더 정보에 따른 면적평균강우의 관측오차)

  • Yoo, Chul-Sang;Ha, Eun-Ho;Kim, Byoung-Soo;Kim, Kyoung-Jun;Choi, Jeong-Ho
    • Journal of Korea Water Resources Association
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    • v.41 no.5
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    • pp.545-558
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    • 2008
  • This study estimated the error involved in the areal average rainfall derived from incomplete radar information due to radar partial coverage of a basin or sub-basin. This study considers the Han-River Basin as an application example for the rainfall observation using the Ganghwa rain radar. Among the total of 20 mid-sized sub-basins of the Han-River Basin evaluated in this study, only five sub-basins are fully covered by the radar and three are totally uncovered. Remaining 12 sub-basins are partially covered by the radar to result in incomplete radar information available. When only partial radar information is available, the sampling error decreases proportional to the size of the radar coverage, which also varies depending on the number of clusters. Conditioned that the total area coverage remains the same, the sampling error decreases as the number of clusters increases. This study estimated the sampling error of the areal average rainfall of partially-covered mid-sized sub-basins of the Han- River Basin, and the results show that the sampling error could be at least several % to maximum tens % depending on the relative coverage area.

Object Tracking Based on Exactly Reweighted Online Total-Error-Rate Minimization (정확히 재가중되는 온라인 전체 에러율 최소화 기반의 객체 추적)

  • JANG, Se-In;PARK, Choong-Shik
    • Journal of Intelligence and Information Systems
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    • v.25 no.4
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    • pp.53-65
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    • 2019
  • Object tracking is one of important steps to achieve video-based surveillance systems. Object tracking is considered as an essential task similar to object detection and recognition. In order to perform object tracking, various machine learning methods (e.g., least-squares, perceptron and support vector machine) can be applied for different designs of tracking systems. In general, generative methods (e.g., principal component analysis) were utilized due to its simplicity and effectiveness. However, the generative methods were only focused on modeling the target object. Due to this limitation, discriminative methods (e.g., binary classification) were adopted to distinguish the target object and the background. Among the machine learning methods for binary classification, total error rate minimization can be used as one of successful machine learning methods for binary classification. The total error rate minimization can achieve a global minimum due to a quadratic approximation to a step function while other methods (e.g., support vector machine) seek local minima using nonlinear functions (e.g., hinge loss function). Due to this quadratic approximation, the total error rate minimization could obtain appropriate properties in solving optimization problems for binary classification. However, this total error rate minimization was based on a batch mode setting. The batch mode setting can be limited to several applications under offline learning. Due to limited computing resources, offline learning could not handle large scale data sets. Compared to offline learning, online learning can update its solution without storing all training samples in learning process. Due to increment of large scale data sets, online learning becomes one of essential properties for various applications. Since object tracking needs to handle data samples in real time, online learning based total error rate minimization methods are necessary to efficiently address object tracking problems. Due to the need of the online learning, an online learning based total error rate minimization method was developed. However, an approximately reweighted technique was developed. Although the approximation technique is utilized, this online version of the total error rate minimization could achieve good performances in biometric applications. However, this method is assumed that the total error rate minimization can be asymptotically achieved when only the number of training samples is infinite. Although there is the assumption to achieve the total error rate minimization, the approximation issue can continuously accumulate learning errors according to increment of training samples. Due to this reason, the approximated online learning solution can then lead a wrong solution. The wrong solution can make significant errors when it is applied to surveillance systems. In this paper, we propose an exactly reweighted technique to recursively update the solution of the total error rate minimization in online learning manner. Compared to the approximately reweighted online total error rate minimization, an exactly reweighted online total error rate minimization is achieved. The proposed exact online learning method based on the total error rate minimization is then applied to object tracking problems. In our object tracking system, particle filtering is adopted. In particle filtering, our observation model is consisted of both generative and discriminative methods to leverage the advantages between generative and discriminative properties. In our experiments, our proposed object tracking system achieves promising performances on 8 public video sequences over competing object tracking systems. The paired t-test is also reported to evaluate its quality of the results. Our proposed online learning method can be extended under the deep learning architecture which can cover the shallow and deep networks. Moreover, online learning methods, that need the exact reweighting process, can use our proposed reweighting technique. In addition to object tracking, the proposed online learning method can be easily applied to object detection and recognition. Therefore, our proposed methods can contribute to online learning community and object tracking, detection and recognition communities.