• ETRI Journal
• /
• 제44권5호
• /
• pp.794-804
• /
• 2022

Transformer models have had a great impact on natural language processing (NLP) in recent years by realizing outstanding and efficient contextualized language models. Recent studies have used transformer-based language models for various NLP tasks, including Persian named entity recognition (NER). However, in complex tasks, for example, NER, it is difficult to determine which contextualized embedding will produce the best representation for the tasks. Considering the lack of comparative studies to investigate the use of different contextualized pretrained models with sequence modeling classifiers, we conducted a comparative study about using different classifiers and embedding models. In this paper, we use different transformer-based language models tuned with different classifiers, and we evaluate these models on the Persian NER task. We perform a comparative analysis to assess the impact of text representation and text classification methods on Persian NER performance. We train and evaluate the models on three different Persian NER datasets, that is, MoNa, Peyma, and Arman. Experimental results demonstrate that XLM-R with a linear layer and conditional random field (CRF) layer exhibited the best performance. This model achieved phrase-based F-measures of 70.04, 86.37, and 79.25 and word-based F scores of 78, 84.02, and 89.73 on the MoNa, Peyma, and Arman datasets, respectively. These results represent state-of-the-art performance on the Persian NER task.

• 한국산학기술학회논문지
• /
• 제21권4호
• /
• pp.39-48
• /
• 2020

2017년 8월에 발생한 고창 전력시험센터를 시작으로, 현재까지 총 29건의 전기저장장치 화재가 발생하여 많은 재산피해가 보고되고 있다. 이에 대한 원인은 아직 정확하게 규명되지 않았으나, ESS(energy storage system)와 전력변환장치뿐만 아니라, 계통측 불평형 문제도 하나의 원인으로 고려되어야 할 것으로 보인다. 특히, 연계용변압기측의 순환전류가 자화전류에 영향을 미쳐, 의도치 않게 변압기의 철심이 포화되고 서지전압이 발생하여 ESS에 영향을 줄 수 있다. 따라서, 본 논문에서는 부하불평형에 의한 불평형전류 발생시, ESS 연계용변압기로 순환전류의 유입과 변압기 포화로 인한 서지전압 발생 현상을 해석하기 위하여, PSCAD/EMTDC를 이용한 배전용변전소, 연계용변압기 및 수용가부하로 구성된 배전계통의 모델링을 수행한다. 또한, 이러한 문제를 해결하기 위하여, 중성점 접지 저항기(neutral grounding resistor, NGR)를 통해 순환전류의 크기를 일정 값 이내로 저감시키는 방안을 제시하였다. 이를 바탕으로 시뮬레이션을 수행한 결과, 연계용변압기의 결선방식 및 철심구조에 따라 일정 값(10[A]) 이상의 순환전류가 발생하여, ESS에 전기적인 위해 요인이 될 수 있음을 알 수 있었고, 변압기 포화로 인해 2차측에 최대 3[pu]의 서지전압이 발생될 수 있음을 확인하였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
• /
• pp.519-520
• /
• 2006

In this paper, to evaluate the grid-connected 120kW class Photovoltaic(PV) system performance, as a consisted of solar cells, PCS, 150kVA transformer station. The paper address modeling and analysis of a grid-connected 120kW class photovoltaic generation system(PV system) PSCAD/EMTD and Psim. A PWM voltage source inverter(VIS) and its current control scheme have been implemented. A P&O(Perturbation and Observation) MPPT algorithms technique modeling has been simulated and analysed.

• 전기학회논문지P
• /
• 제66권1호
• /
• pp.33-37
• /
• 2017

This paper describes the modeling of the failure rate estimation technique for applying the asset management technique to electric power facilities. There are many modeling techniques to estimate the failure rate. In this paper, the characteristics of the normal distribution, exponential distribution, weibull distribution, and piecewise linear functions are discussed. When evaluating reliability, the evaluation may be less meaningful if the sample data is insufficient. Therefore, Weibull distribution and piecewise linear function are adopted as the most suitable functions for estimating the failure rate of power facilities and the resulting failure rate function is derived.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
• /
• pp.179-179
• /
• 2012

Low pressure radio-frequency glow discharges are investigated using theoretical modeling and various experimental diagnostic methods. In the calculations, global models and transformer models are developed to understand the chemical kinetics as well as the electrical properties such as the effective collision frequency, the heating mechanism and the power transferred to the plasma electrons. In addition, Boltzmann equation solver is used to compensate the effect of the electron energy distribution function (EEDF) shape in the global model, and the general expression of energy balance for non-Maxwellian electrons is developed. In the experiments, a number of traditional plasma diagnostic methods are used to compare with calculated results such as Langmuir probe, optical emission spectroscopy (OES), optical absorption spectroscopy (OAS) and two-photon absorption laser-induced fluorescence (TALIF). These theoretical and experimental methods are applied to understand several interesting phenomena in low pressure ICP discharges. The chemical and physical properties of low pressure ICP discharges are described and the applications of these methods are discussed.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2000년도 전력전자학술대회 논문집
• /
• pp.1-5
• /
• 2000

This paper deals with the modeling and analysis of the high voltage flyback transformer (HVFBT) often utilized in small-sized high voltage DC power supplies. The parasitic capacitance of th HVFBT with the large turns of the secondary winding causes the undesirable parasitic resonance in the transient state which produces the high current stress and limits the switching frequency of the converter. In order to analyze this phenomenon the equivalent circuit model including the parasitic capacitance is derived and the frequency characteristics are provided. The parasitic resonance in the switching states is also investigated based on this equivalent circuit model. The derived model and analysis is finally validated through the SPICE simulation and experiments.

• 전기학회논문지
• /
• 제66권5호
• /
• pp.857-862
• /
• 2017

The management of the electric power facilities became important in accordance with the industrial development and electric power facilities were influenced by weather. Even if the same kind of electric power facilities is estimated for extracting the time-varying failure rate, the failure rate could be different depending on external effect such as climate. This research will show the data mining modeling of the weather-related outage and influence of weather on the electric power facility with recent data.

• 전기학회논문지
• /
• 제61권11호
• /
• pp.1737-1742
• /
• 2012

The scott transformer is used to supply single-phase power to the AC railway system. Since the scott transformer is a passive facility, it cannot regulate load-side voltage according to load change. Meanwhile, the Voltage Source Converter (VSC) is able to convert the voltage and control active and reactive power. In this paper, the feasibility of a AC railway system based on Back-to-Back (BTB) VSC which is composed of a rectifier, a DC-DC converter, a inverter, has been proposed. A three-phase to single-phase BTB VSC is modeled. The proposed AC railway system based on BTB VSC is tested on Matlab/Simulink.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2002년도 전력전자학술대회 논문집
• /
• pp.551-554
• /
• 2002

This paper describes a new interactive inverter between a photovoltaic(PV) array and single-phase utility that avoid the bulky input (60Hz) transformer on the AC side. The interface employs a pwm boost converter on the DC side followed by a pwm current-forced single-phase rectifier for injecting the power from the PV array into the mains. The current waveform at the AC side remains sinusoidal and exactly in phase at all time. The circuit also has the advantage of requiring fewer switching device than high-frequency link system. This paper describes modeling of PV array and new system topology. Simulation results on the performance of the connection are also presented.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2002년도 전력전자학술대회 논문집
• /
• pp.237-240
• /
• 2002

A CCFL model for high frequency dimming electronic ballast simulation is presented in this paper. The model can be utilized for an electronic ballast simulation with continuous dimming and transient mode simulation such as step dimming. The piezoelectric transformer Is evaluated using an AC analysis. The electronic ballast composed of piezoelectric transformers and ZVS inverter was implemented. It enables a fluorescent lamp to be fumed on stably. Simulation of a high frequency electronic ballast which operates a fluorescent Imp at high frequency is proposed. Simulation is carried out using PSPICE program to illustrate the performance of the circuit