• Title/Summary/Keyword: K Least Time Path

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Percolation Threshold and Critical Exponent of Dielectric Breakdown Strength of Polyethylene Matrix Composites added Carbon Black (카본블랙 첨가 PMC(Polyethylene Matrix Composites)의 문턱스며들기(Percolation Threshold)와 절연파괴 강도 임계지수)

  • Shin, Soon-Gi
    • Korean Journal of Materials Research
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    • v.21 no.9
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    • pp.477-481
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    • 2011
  • Composites of insulating polyethylene and carbon black are widely used in switching elements, conductive paint, and other applications due to the large gap of resistance value. This research addresses the critical exponent of dielectric breakdown strength of polymer matrix composites (PMC) made with carbon black and polyethylene below the percolation threshold (Pt) for the first time. Here, Pt means the volume fraction of carbon black of which the resistance of the PMC is transferred from its sharp decrease to gradual decrease in accordance with the increase of carbon-black-filled content. First, the Pt is determined based on the critical exponents of resistivity and relative permittivity. Although huge cohesive bodies of carbon black are formed in case of being less than the Pt, a percolation path connecting the conducting phases is not formed. The dielectric breakdown strength (Dbs) of the PMC below Pt is measured by using an impulse voltage in the range from 10 kV to 40 kV to avoid the effect of joule heating. Although the observed Dbs data seems to be well fitted to a straight line with a slope of 0.9 on a double logarithm of (Pt-$V_{CB}$) and Dbs, the least squares method gives a slope of 0.97 for the PMC. It has been found that finite carbon-black clusters play an important role in dielectric breakdown.

Study on Error Correction of Impact Sound Position Estimation Using Ray Tracing (음선 추적을 이용한 폭발음 위치추정 오차 보정에 대한 연구)

  • Choi, Donghun;Go, Yeong-Ju;Lee, Jaehyung;Na, Taeheum;Choi, Jong-Soo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.26 no.1
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    • pp.89-96
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    • 2016
  • TDOA(time delay of arrival) position estimate from acoustic measurement of artillery shell impact is studied in order to develop a targeting evaluation system. Impact position is calculated from the intersections of hyperbolic estimates based on the least square Taylor series method. The mathematical process of Taylor series estimation is known to be robust. However, the concern lays with the accuracy because it is sensitive to the bias caused by the randomness of measurement situation. The measurement error typically occurs from the distortion of waveform, change of travelling path, and sensor position error. For outdoor measurement, a consideration should be made on the atmospheric condition such as temperature and wind which can possibly change the trajectories of rays of sound. It produces wrong propagation time events accordingly. Ray tracing and optimization techniques are introduced in this study to minimize the bias induced by the ray of sound. The numerical simulation shows that the atmospheric correction improves the estimation accuracy.

Active Vibration Control of Vehicle by Active Linear Actuator and Filtered-x LMS Algorithm (전동식 동흡진기와 Filtered-X LMS알고리즘을 이용한 차량의 능동진동제어 실험)

  • Lee, Han-Dong;Kwak, Moon-K.;Kim, Jeong-Hoon;Song, Yoon-Chul;Park, Woon-Han
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2009.10a
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    • pp.357-363
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    • 2009
  • This paper deals with the Filtered-x Least Mean Square algorithm for a active vibration control in vehicle vibration reduction. Before applying the proposed FxLMS algorithm to automobile, the performance of the FxLMS algorithm is simulated using sensor data of a vehicle. The FxLMS algorithm requires that reference signal be a representation of disturbance signal and the plant model be incorporated into the computation path. To this end, The system identification is carried out to obtain the plant model based on the measurement results. A tachometer signal is used as reference signal. The FxLMS control algorithm is first tested using simulation and applied to a vehicle. Experimental results show that the proposed control algorithm can reduce vibration level in a short period of time.

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A Study on Selection Criterions for Selection Diversity in WAVE Systems (WAVE 시스템에서 선택 다이버시티를 위한 선택 기준에 대한 연구)

  • Hong, Dae-Ki
    • Journal of the Semiconductor & Display Technology
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    • v.14 no.2
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    • pp.9-16
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    • 2015
  • In this paper, selection criterions on selection diversity are researched. The diversity is applied to the multiple antenna system based on wireless access in vehicular environment (WAVE) standard for rapid varying channel. Least squares (LS) based decision feedback equalizer (DFE) are used for channel equalization. Received signal is regenerated by means of the decision feedback path. In the selection diversity, the regenerated signal as well as the received signal is selected according to selection criterion. The decision feedback algorithm can follow the fast speed of WAVE fading channel. To control the tracking speed of the time-varying channel, simple low pass filter is used. Finally, the estimated channel value recovers the distorted payloads. Signal power before automatic gain control (AGC) in analog stage can be used as a selection criterion. In the digital stage, signal power after AGC, noise power after AGC, signal to noise ratio after AGC and cross-correlation method can be used as selection criterions. According to the simulation results, the performance of the selection diversity is improved in comparison with that of the combining diversity for the WAVE fading channel.

Application of Deep Learning: A Review for Firefighting

  • Shaikh, Muhammad Khalid
    • International Journal of Computer Science & Network Security
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    • v.22 no.5
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    • pp.73-78
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    • 2022
  • The aim of this paper is to investigate the prevalence of Deep Learning in the literature on Fire & Rescue Service. It is found that deep learning techniques are only beginning to benefit the firefighters. The popular areas where deep learning techniques are making an impact are situational awareness, decision making, mental stress, injuries, well-being of the firefighter such as his sudden fall, inability to move and breathlessness, path planning by the firefighters while getting to an fire scene, wayfinding, tracking firefighters, firefighter physical fitness, employment, prediction of firefighter intervention, firefighter operations such as object recognition in smoky areas, firefighter efficacy, smart firefighting using edge computing, firefighting in teams, and firefighter clothing and safety. The techniques that were found applied in firefighting were Deep learning, Traditional K-Means clustering with engineered time and frequency domain features, Convolutional autoencoders, Long Short-Term Memory (LSTM), Deep Neural Networks, Simulation, VR, ANN, Deep Q Learning, Deep learning based on conditional generative adversarial networks, Decision Trees, Kalman Filters, Computational models, Partial Least Squares, Logistic Regression, Random Forest, Edge computing, C5 Decision Tree, Restricted Boltzmann Machine, Reinforcement Learning, and Recurrent LSTM. The literature review is centered on Firefighters/firemen not involved in wildland fires. The focus was also not on the fire itself. It must also be noted that several deep learning techniques such as CNN were mostly used in fire behavior, fire imaging and identification as well. Those papers that deal with fire behavior were also not part of this literature review.

Multiple model switching adaptive control for vibration control of cantilever beam with varying load using MFC actuators and sensors

  • Gao, Zhiyuan;Huang, Jiaqi;Miao, Zhonghua;Zhu, Xiaojin
    • Smart Structures and Systems
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    • v.25 no.5
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    • pp.559-567
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    • 2020
  • Vibration at the tip of various flexible manipulators may affect their operation accuracy and work efficiency. To suppress such vibrations, the feasibility of using MFC actuators and sensors is investigated in this paper. Considering the convergence of the famous filtered-x least mean square (FXLMS) algorithm could not be guaranteed while it is employed for vibration suppression of plants with varying secondary path, this paper proposes a new multiple model switching adaptive control algorithm to implement the real time active vibration suppression tests with a new multiple switching strategy. The new switching strategy is based on a cost function with reconstructed error signal and disturbance signal instead of the error signal from the error sensor. And from a robustness perspective, a new variable step-size sign algorithm (VSSA) based FXLMS algorithm is proposed to improve the convergence rate. A cantilever beam with varying tip mass is employed as flexible manipulator model. MFC layers are attached on both sides of it as sensors and actuators. A co-simulation platform was built using ADAMS and MATLAB to test the feasibility of the proposed algorithms. And an experimental platform was constructed to verify the effectiveness of MFC actuators and sensors and the real-time vibration control performance. Simulation and experiment results show that the proposed FXLMS algorithm based multiple model adaptive control approach has good convergence performance under varying load conditions for the flexible cantilever beam, and the proposed FX-VSSA-LMS algorithm based multiple model adaptive control algorithm has the best vibration suppression performance.

A Method of ISAR Geometric Calibration for Point Target Using Impulse-Radio UWB (임펄스 초광대역 레이다를 이용한 점표적의 ISAR 기하 보정 방법)

  • Yu, Jiwoong;Nikitin, Konstantin;Paek, Inchan;Jang, Jong Hun;Ka, Min-Ho
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.26 no.4
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    • pp.397-403
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    • 2015
  • In this paper, a method of ISAR geometric calibration is represented by using impulse-radio UWB radar. The ir-UWB is good for using a signal processing in time domain, so, it does not occur a multi-path or coupling problem. If a signal that between antennas and target is assumed a plane wave, a center of rotation in ISAR geometry model can be estimated by using point target. Before image is reconstructed with sinogram, the center of rotation can be calculated by using least square fitting. This method can be obtained a more contrast image, and a maximum value of entropy of image. The method, that estimates a center of rotation in received data, will be used a initial setup of instruments or a periodic compensation to reconstruct image. It would be useful in medical, security and surveillance imaging equipments that have a fixed geometry.

Adaptive Feedback Interference Cancellation Using Correlations for WCDMA Wireless Repeaters (WCDMA용 무선중계기에서 상관도를 이용한 적응적 궤환 간섭 제거)

  • Moon, Woo-Sik;Im, Sung-Bin;Kim, Chong-Hoon
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.44 no.7 s.361
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    • pp.35-40
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    • 2007
  • As the mobile communication service is widely used and the demand for wireless repeaters is rapidly increasing because of the easiness of extending service areas. But a wireless repeater has a problem that the output of the transmit antenna is partially fed back to the receive antenna, which results in feedback interference. In this paper, we propose a new varable step-size LMS algorithm which utilizes correlation between reference and error signals to adjust the step sizes, for cancelling the feedback interference signals in the WCDMA repeater under time-varying multi-path channels. The proposed algorithm was evaluated through computer simualation by being applied to the feedback canceling filter of the WCDMA repeater. The simulation results demonstrated that the proposed one is superior to the conventional ones in terms of the cancelation perormance.

A PLS Path Modeling Approach on the Cause-and-Effect Relationships among BSC Critical Success Factors for IT Organizations (PLS 경로모형을 이용한 IT 조직의 BSC 성공요인간의 인과관계 분석)

  • Lee, Jung-Hoon;Shin, Taek-Soo;Lim, Jong-Ho
    • Asia pacific journal of information systems
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    • v.17 no.4
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    • pp.207-228
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    • 2007
  • Measuring Information Technology(IT) organizations' activities have been limited to mainly measure financial indicators for a long time. However, according to the multifarious functions of Information System, a number of researches have been done for the new trends on measurement methodologies that come with financial measurement as well as new measurement methods. Especially, the researches on IT Balanced Scorecard(BSC), concept from BSC measuring IT activities have been done as well in recent years. BSC provides more advantages than only integration of non-financial measures in a performance measurement system. The core of BSC rests on the cause-and-effect relationships between measures to allow prediction of value chain performance measures to allow prediction of value chain performance measures, communication, and realization of the corporate strategy and incentive controlled actions. More recently, BSC proponents have focused on the need to tie measures together into a causal chain of performance, and to test the validity of these hypothesized effects to guide the development of strategy. Kaplan and Norton[2001] argue that one of the primary benefits of the balanced scorecard is its use in gauging the success of strategy. Norreklit[2000] insist that the cause-and-effect chain is central to the balanced scorecard. The cause-and-effect chain is also central to the IT BSC. However, prior researches on relationship between information system and enterprise strategies as well as connection between various IT performance measurement indicators are not so much studied. Ittner et al.[2003] report that 77% of all surveyed companies with an implemented BSC place no or only little interest on soundly modeled cause-and-effect relationships despite of the importance of cause-and-effect chains as an integral part of BSC. This shortcoming can be explained with one theoretical and one practical reason[Blumenberg and Hinz, 2006]. From a theoretical point of view, causalities within the BSC method and their application are only vaguely described by Kaplan and Norton. From a practical consideration, modeling corporate causalities is a complex task due to tedious data acquisition and following reliability maintenance. However, cause-and effect relationships are an essential part of BSCs because they differentiate performance measurement systems like BSCs from simple key performance indicator(KPI) lists. KPI lists present an ad-hoc collection of measures to managers but do not allow for a comprehensive view on corporate performance. Instead, performance measurement system like BSCs tries to model the relationships of the underlying value chain in cause-and-effect relationships. Therefore, to overcome the deficiencies of causal modeling in IT BSC, sound and robust causal modeling approaches are required in theory as well as in practice for offering a solution. The propose of this study is to suggest critical success factors(CSFs) and KPIs for measuring performance for IT organizations and empirically validate the casual relationships between those CSFs. For this purpose, we define four perspectives of BSC for IT organizations according to Van Grembergen's study[2000] as follows. The Future Orientation perspective represents the human and technology resources needed by IT to deliver its services. The Operational Excellence perspective represents the IT processes employed to develop and deliver the applications. The User Orientation perspective represents the user evaluation of IT. The Business Contribution perspective captures the business value of the IT investments. Each of these perspectives has to be translated into corresponding metrics and measures that assess the current situations. This study suggests 12 CSFs for IT BSC based on the previous IT BSC's studies and COBIT 4.1. These CSFs consist of 51 KPIs. We defines the cause-and-effect relationships among BSC CSFs for IT Organizations as follows. The Future Orientation perspective will have positive effects on the Operational Excellence perspective. Then the Operational Excellence perspective will have positive effects on the User Orientation perspective. Finally, the User Orientation perspective will have positive effects on the Business Contribution perspective. This research tests the validity of these hypothesized casual effects and the sub-hypothesized causal relationships. For the purpose, we used the Partial Least Squares approach to Structural Equation Modeling(or PLS Path Modeling) for analyzing multiple IT BSC CSFs. The PLS path modeling has special abilities that make it more appropriate than other techniques, such as multiple regression and LISREL, when analyzing small sample sizes. Recently the use of PLS path modeling has been gaining interests and use among IS researchers in recent years because of its ability to model latent constructs under conditions of nonormality and with small to medium sample sizes(Chin et al., 2003). The empirical results of our study using PLS path modeling show that the casual effects in IT BSC significantly exist partially in our hypotheses.

Stable and Precise Multi-Lane Detection Algorithm Using Lidar in Challenging Highway Scenario (어려운 고속도로 환경에서 Lidar를 이용한 안정적이고 정확한 다중 차선 인식 알고리즘)

  • Lee, Hanseul;Seo, Seung-Woo
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.12
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    • pp.158-164
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    • 2015
  • Lane detection is one of the key parts among autonomous vehicle technologies because lane keeping and path planning are based on lane detection. Camera is used for lane detection but there are severe limitations such as narrow field of view and effect of illumination. On the other hands, Lidar sensor has the merits of having large field of view and being little influenced by illumination because it uses intensity information. Existing researches that use methods such as Hough transform, histogram hardly handle multiple lanes in the co-occuring situation of lanes and road marking. In this paper, we propose a method based on RANSAC and regularization which provides a stable and precise detection result in the co-occuring situation of lanes and road marking in highway scenarios. This is performed by precise lane point extraction using circular model RANSAC and regularization aided least square fitting. Through quantitative evaluation, we verify that the proposed algorithm is capable of multi lane detection with high accuracy in real-time on our own acquired road data.