• Title/Summary/Keyword: Model mismatch

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Question Classification Based on Word Association for Question and Answer Archives (질문대답 아카이브에서 어휘 연관성을 이용한 질문 분류)

  • Jin, Xueying;Lee, Kyung-Soon
    • The KIPS Transactions:PartB
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    • v.17B no.4
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    • pp.327-332
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    • 2010
  • Word mismatch is the most significant problem that causes low performance in question classification, whose questions consist of only two or three words that expressed in many different ways. So, it is necessary to apply word association in question classification. In this paper, we propose question classification method using translation-based language model, which use word translation probabilities for question-question pair that is learned in the same category. In the experiment, we prove that translation probabilities of question-question pairs in the same category is more effective than question-answer pairs in total collection.

A Study of Dynamic Simulation of a Hybrid Absorption Chiller Utilizing Solar Power (태양열을 이용한 일이중 겸용 흡수식 냉온수기 동적성능 모사연구)

  • Shin, Young-Gy;Seo, Jung-A;Woo, Sung-Min;Kim, Hyo-Sang
    • Proceedings of the SAREK Conference
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    • 2009.06a
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    • pp.967-972
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    • 2009
  • A dynamic model has been developed to investigate the operability of a single and double-effect solar energy assisted parallel type absorption chiller. In the study, main components and fluid transport mechanism were modeled. And solar radiation and the solar collector also were also modeled along with its control design. The model was run for the single mode with solar energy supply only and the solar/gas driving double effect mode. From the simulation results, it was found that the present configuration of the chiller is not capable of regulating solution flow rates according to variable solar energy input. And the issues of the excessive circulation flowrate and the mismatch between available solar power and cooling load discourages the use of the single mode, but the dual use of gas and solar power is recommendable in view of controllability and enhanced COP.

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Low Parameter Sensitivity Deadbeat Direct Torque Control for Surface Mounted Permanent Magnet Synchronous Motors

  • Zhang, Xiao-Guang;Wang, Ke-Qin;Hou, Ben-Shuai
    • Journal of Power Electronics
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    • v.17 no.5
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    • pp.1211-1222
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    • 2017
  • In order to decrease the parameter sensitivity of deadbeat direct torque control (DB-DTC), an improved deadbeat direct torque control method for surface mounted permanent-magnet synchronous motor (SPMSM) drives is proposed. First, the track errors of the stator flux and torque that are caused by model parameter mismatch are analyzed. Then a sliding mode observer is designed, which is able to predict the d-q axis currents of the next control period for one-step delay compensation, and to simultaneously estimate the model parameter disturbance. The estimated disturbance of this observer is used to estimate the stator resistance offline. Then the estimated resistance is required to update the designed sliding-mode observer, which can be used to estimate the inductance and permanent-magnetic flux linkage online. In addition, the flux and torque estimation of the next control period, which is unaffected by the model parameter disturbance, is achieved by using predictive d-q axis currents and estimated parameters. Hence, a low parameter sensitivity DB-DTC method is developed. Simulation and experimental results show the validity of the proposed direct control method.

Elasto-Plastic Finite Element Analysis in Consideration of Phase Transformations (상변태를 고려한 탄소성 유한요소 해석)

  • Lee, M.G.;Kim, S.J.;Jeong, W.C.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.05a
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    • pp.334-336
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    • 2009
  • An elastic-plasticity model during the austenitic decomposition was derived and implemented to incorporate the two important deformation behaviors observed during the phase transformations: the volumetric strain and transformation induced plasticity due to the temperature change and phase transformation. To obtain transformed phase volume fractions during cooling, the fourth order Runge-Kutta method was used to solve the Kirkaldy's phase kinetics model which is function of temperature, austenitic grain size and chemical composition. The volumetric strain was calculated by considering the densities of constituent phases, while the transformation induced plasticity was based on the micro-plasticity due to the volume mismatch between soft austenitic phase and other harder phases. The constitutive equations were implemented into the implicit finite element software and a simple boundary value problem was chosen as a model problem to validate the effect of transformation plasticity on the deformation behavior of steel under cooling from high temperature. It was preliminary concluded that the transformation plasticity plays a critical role in relaxing the developed stress during forming and thus reducing the magnitude of springback.

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Dynamic Simulation of Transient Operations of a Solar Power-Assisted Absorption Chiller (태양열 보조열원을 이용한 흡수식 시스템의 동적 시뮬레이션에 의한 과도운전 특성 평가)

  • Shin, Young-Gy;Seo, Jung-A;Woo, Sung-Min
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.22 no.2
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    • pp.78-85
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    • 2010
  • A dynamic model has been developed to investigate the operability of a single and double-effect solar energy assisted parallel type absorption chiller. In the study, main components and fluid transport mechanism were modeled. And solar radiation and the solar collector were also modeled along with its control design. The model was run for the single mode with solar energy supply only and the solar/gas driving double effect mode. From the simulation results, it was found that the present configuration of the chiller is not capable of regulating solution flow rates according to variable solar energy input. And the issues of the excessive circulation flow rate and the mismatch between available solar power and cooling load discourages the use of the single mode, but the dual use of gas and solar power is recommendable in view of controllability and enhanced COP.

A Study on Estimation Model of Resistance Value from Change of PTH Crack Size (PTH Crack을 고려한 저항 변화 추정 모델)

  • Kim, Gi-Young;Park, Boo-Hee;Kim, Seon-Jin;Yoo, Ki-Hun;Seol, Dong-Jin;Jang, Joong-Soon;Lee, Hyung-Rok;Kim, Tae-Hyuk
    • Journal of Applied Reliability
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    • v.8 no.4
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    • pp.155-166
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    • 2008
  • PTH cracks are caused by the mismatch of coefficient of thermal expansion(CTE) between polymer and laminated materials, and are one of the main failure mechanisms of multi layer boards. In spite of its importance, it is usually hard to measure or detect them because of its small size and invisibility. To detect PTH cracks more effectively, this paper proposes a theoretical model that can estimate the resistance value from crack size of PTHs. Using four-point probe resistance measurement method, the resistance value of test coupons is measured. Through measured data, we verify the validity of the proposed theoretical model and set up criteria of failure.

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Noise Robust Automatic Speech Recognition Scheme with Histogram of Oriented Gradient Features

  • Park, Taejin;Beack, SeungKwan;Lee, Taejin
    • IEIE Transactions on Smart Processing and Computing
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    • v.3 no.5
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    • pp.259-266
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    • 2014
  • In this paper, we propose a novel technique for noise robust automatic speech recognition (ASR). The development of ASR techniques has made it possible to recognize isolated words with a near perfect word recognition rate. However, in a highly noisy environment, a distinct mismatch between the trained speech and the test data results in a significantly degraded word recognition rate (WRA). Unlike conventional ASR systems employing Mel-frequency cepstral coefficients (MFCCs) and a hidden Markov model (HMM), this study employ histogram of oriented gradient (HOG) features and a Support Vector Machine (SVM) to ASR tasks to overcome this problem. Our proposed ASR system is less vulnerable to external interference noise, and achieves a higher WRA compared to a conventional ASR system equipped with MFCCs and an HMM. The performance of our proposed ASR system was evaluated using a phonetically balanced word (PBW) set mixed with artificially added noise.

Robust Sensorless Sliding Mode Flux Observer for DTC-SVM-based Drive with Inverter Nonlinearity Compensation

  • Aimad, Ahriche;Madjid, Kidouche;Mekhilef, Saad
    • Journal of Power Electronics
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    • v.14 no.1
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    • pp.125-134
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    • 2014
  • This paper presents a robust and speed-sensorless stator flux estimation for induction motor direct torque control. The proposed observer is based on sliding mode approach. Stator electrical equations are used in the rotor orientation reference frame to eliminate the observer dependence on rotor speed. Lyapunov's concept for systems stability is adopted to confine the observer gain. Furthermore, the sensitivity of the observer to parameter mismatch is recovered with an adaptation technique. The nonlinearities of the pulse width modulation voltage source inverter are estimated and compensated to enhance stability at low speeds. Therefore, a new method based on the model reference adaptive system is proposed. Simulation and experimental results are shown to verify the feasibility and effectiveness of the proposed algorithms.

Effects of LDPC Code on the BER Performance of MPSK System with Imperfect Receiver Components over Rician Channels

  • Djordjevic, Goran T.;Djordjevic, Ivan B.;Ivanis, Predrag N.
    • ETRI Journal
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    • v.31 no.5
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    • pp.619-621
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    • 2009
  • In this letter, we study the influence of receiver imperfections on bit error rate (BER) degradations in detecting low-density parity-check coded multilevel phase-shift keying signals transmitted over a Rician fading channel. Based on the analytical system model which we previously developed using Monte Carlo simulations, we determine the BER degradations caused by the simultaneous influences of stochastic phase error, quadrature error, in-phase-quadrature mismatch, and the fading severity.

Thermal Fatigue Reliability of Solder Joints in a Thin Film Optical Filter Device (박막 광학 필터 디바이스의 패키징시 솔더 조인트의 피로 신뢰성 해석)

  • Lee, Sung-Chul;Hyun, Chung-Min;Lee, Hyung-Man;Kim, Myoung-Jin;Kim, Hwe-Kyung;Kim, Ki-Tae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.6
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    • pp.677-684
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    • 2004
  • Plastic and creep deformations of solder joints during thermal cycling are the main factors of misalignments and power losses in optical telecommunication components. Furthermore, the increased mismatch between solder Joint-bonded areas may cause severe failure in the components. Darveaux's creep model was implemented into a finite element program (ABAQUS) to simulate creep response of solder. Based on the finite element results, thermal fatigue reliability was predicted by using various fatigue life prediction models. Also, the effects of ramp conditions, dwelling time, and solder joint-embedding materials on the reliability were investigated under the thermal cycling conditions of the Telcordia schedule (-40∼75$^{\circ}C$).