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704 results on '"Cho, Young-Ho"'

2. Topology-aware Piecewise Linearization of the AC Power Flow through Generative Modeling

Author

Cho, Young-ho and Zhu, Hao

Subjects
Electrical Engineering and Systems Science - Systems and Control
Abstract

Effective power flow modeling critically affects the ability to efficiently solve large-scale grid optimization problems, especially those with topology-related decision variables. In this work, we put forth a generative modeling approach to obtain a piecewise linear (PWL) approximation of AC power flow by training a simple neural network model from actual data samples. By using the ReLU activation, the NN models can produce a PWL mapping from the input voltage magnitudes and angles to the output power flow and injection. Our proposed generative PWL model uniquely accounts for the nonlinear and topology-related couplings of power flow models, and thus it can greatly improve the accuracy and consistency of output power variables. Most importantly, it enables to reformulate the nonlinear power flow and line status-related constraints into mixed-integer linear ones, such that one can efficiently solve grid topology optimization tasks like the AC optimal transmission switching (OTS) problem. Numerical tests using the IEEE 14- and 118-bus test systems have demonstrated the modeling accuracy of the proposed PWL approximation using a generative approach, as well as its ability in enabling competitive OTS solutions at very low computation order.

Published
2023

3. Wind Power Scenario Generation Using Graph Convolutional Generative Adversarial Network

Author

Cho, Young-ho, Liu, Shaohui, Lee, Duehee, and Zhu, Hao

Subjects
Computer Science - Machine Learning, Computer Science - Artificial Intelligence, Electrical Engineering and Systems Science - Systems and Control
Abstract

Generating wind power scenarios is very important for studying the impacts of multiple wind farms that are interconnected to the grid. We develop a graph convolutional generative adversarial network (GCGAN) approach by leveraging GAN's capability in generating large number of realistic scenarios without using statistical modeling. Unlike existing GAN-based wind power data generation approaches, we design GAN's hidden layers to match the underlying spatial and temporal characteristics. We advocate the use of graph filters to embed the spatial correlation among multiple wind farms, and a one-dimensional (1D) convolutional layer to represent the temporal feature filters. The proposed graph and feature filter design significantly reduce the GAN model complexity, leading to improvements in training efficiency and computation complexity. Numerical results using real wind power data from Australia demonstrate that the scenarios generated by the proposed GCGAN exhibit more realistic spatial and temporal statistics than other GAN-based outputs.

Published
2022

27. Tunable absorptive bandpass filter with two transmission zeros based on image parameter method.

Author

Cho, Young‐Ho and Park, Cheolsoo

Subjects
*INSERTION loss (Telecommunication), *BANDPASS filters, *TRANSMISSION zeros, *COGNITIVE radio
Abstract

A tunable absorptive bandpass filter with two transmission zeros is presented. A lowpass absorptive filter prototype consisting of a matching section and a m‐drive filter section is established based on image parameter method, and the filter elements are easily derived through the image impedance with the required return loss and transmission zeros. Moreover, the two transmission zeros are controlled by adjusting the parameters of the m‐drive filter section. A distributed tunable absorptive bandpass filter is realized based on the proposed lowpass filter prototype. The fabricated filter shows a return loss of 21–25 dB and an insertion loss of 2.1–2.8 dB at the center frequency within the tuning range of 1.35–1.58 GHz. [ABSTRACT FROM AUTHOR]

Published
2024
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48. Effect of boron and manganese on hot crack resistance and toughness for flux cored arc weldments of 550 MPa grade tensile strength

Author

Kang Namhyun, Cho Young-Ho, Park Su-Kil, and Jee Chun-Ho

Subjects
Toughness, Materials science, Carbon steel, Metallurgy, chemistry.chemical_element, Fracture mechanics, Welding, Boron carbide, engineering.material, law.invention, chemistry.chemical_compound, chemistry, law, Ferrite (iron), Ultimate tensile strength, engineering, Boron
Abstract

The hot crack resistance and mechanical properties of flux cored arc (FCA) welds were investigated with three kinds of welding consumables having different boron (B) and manganese (Mn) contents for high strength carbon steel. The hot crack resistance measured from self-restraint testing strongly depended on the amount of B in the welding consumable. Welding consumable with higher B contents resulted in longer total crack length and an increased number of cracks. Boron was intensely detected near the grain boundary of the weld centerline by secondary ion mass spectrometry (SIMS) analysis, and precipitated with boron carbide (Fe23(C,B)6), as analyzed by transmission electron microscopy (TEM). This promoted hot crack propagation in the high strength carbon steel welds. However, removing B from the welding consumable decreased the low temperature toughness for root and face weld metal due to the growth of Ferrite Side Plate (FSP) in comparison with welding consumables having more B or Mn contents. The addition of Mn in the weld metal suppressed the formation of FSP and increased the low temperature toughness. Therefore, the minimization of B and the supplement of Mn successfully achieved hot crack resistance and low temperature toughness for high strength carbon steel welds of 550 MPa tensile strength.

Published
2021

50. The Reduplication Process of Balantak Language: A Minority Austronesian Language of Eastern Sulawesi

Author

Valentino Pamolango and Cho Young Ho

Abstract

Indonesia has many local languages. One of the local languages used in Indonesia is Balantak language. It is used by people who live in 5 (five) sub-districts in Banggai Regency, Central Sulawesi. In Balantak language, there are a number of words which are formed by using reduplication. Reduplication is found in many languages but is quite diverse as a process and in its. Due to reduplicated words in Balantak language, the writers are interested in analyzing the problem statement about: What are the forms of reduplicated words in Balantak language? Reduplication is the repetition of an entire word or part of the word. According to Haspelmath and Sims (2010), reduplications are a very common morphological operation, whereby part of the base orthe complete base is copied and attached to the base (either preceding or following it). In Balantak language both forms of reduplication are found full reduplication and partial reduplication, and each form consists of various kind of words.

Published
2020

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