• Title/Summary/Keyword: ablation performance

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Strength Analysis of the High Performance Nozzle System(Jet Vane Type) (Jet Vane Type 추력방향제어 시스템 구조 해석)

  • 조용재
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 1998.04a
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    • pp.23-23
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    • 1998
  • Jet Vane Type 추력방향제어 시스템의 구조적 안정성을 검토하기 위해 시스템의 해석을 Vane, Ablation & Bracket Interface, Nozzle flange & Housing Interface 및 Fastener의 세 부분으로 나누어 수행하였다. 해석을 위한 외력조건은 유동해석을 통해 얻어진 온도 및 압력분포에 근거하였으며, Vane의 응력해석을 위해서는 상용 Software인 Patran 및 Nastran이 사용되었다. 이번 연구는 Test Model 단계로서 충분한 강도의 고정 Housing이 사용되어, 이에 대한 해석은 수행되지 않았지만 추후 Flight Model 단계에서는 함께 고려되어질 것이며, 각 경우의 Margin of Safety값들을 도출하여 구조적 안정성을 검토하였다.

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Validation of the Aerodynamic drag model in the multi-phase flow analysis

  • Morisaki, Masao;Shimada, Toru;Hanzawa, Masahisa;Kat, Takashi;Yoshikawa, Takashi
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.365-368
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    • 2004
  • The multi-phase flow analysis in a solid rocket motor is very important when performing the performance of a motor, and prediction of nozzle ablation. However, only in consideration of regular power, it has analyzed as power which a metal particle receives from a flow until now. We conduct analysis and an experiment about the virtual mass clause which will influence at the place where acceleration is big. We aim at the improvement in accuracy of multi-phase flow analysis from the result.

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An Architecture for the Expert System for the Telecommunications Internetworking Design

  • Cho, Dai Yon
    • Journal of Intelligence and Information Systems
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    • v.4 no.2
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    • pp.117-128
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    • 1998
  • CBR is a knowledge-based system that utilizes the previous knowledge or experience to solve the current problem. In previous CBR research, the emphases are mainly put on the development of more sophisticated indexing mechanism for past cases or the most similar case retrieving methodology out of a group of previous cases. In this paper, discussed is a CBR system that is able to take advantage of the case or knowledge that does not belong to the past in the telecommunications internetworking design area. And the architecture for such CBR system is proposed. Finally, the performance of the CBR system is shown through an ablation experiment.

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Decontamination Characteristics of 304 Stainless Steel Surfaces by a Q-switched Nd:YAG Laser at 532 nm (532 nm 파장의 큐스위치 Nd:YAG 레이저를 이용한 스테인리스 스틸 표면 제염특성)

  • Moon, Jei-Kwon;Baigalmaa, Byambatseren;Won, Hui-Jun;Lee, Kune-Woo
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.8 no.3
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    • pp.181-188
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    • 2010
  • Metal surface decontamination characteristics were investigated by using a laser ablation method. A second harmonic generation of a Q-switched Nd:YAG laser with a wave length of 532 nm, a pulse energy of 150 mJ and a pulse width of 5 ns was employed to assess the decontamination performance for metal surfaces contaminated with $CsNO_3$, $Co(NH_4)_2(SO_4)_2$, $Eu_2O_3$ and $CeO_2$. The ablation behavior was investigated for the decontamination variables such as a number of laser shots, laser fluence and an irradiation angle. Their optimum values were found to be 8, 13.3 J/$cm^2$ and $30^{\circ}$, respectively. The decontamination efficiency was different depending on the kinds of the contaminated ions, due to their different melting and boiling points and was in the order: $CsNO_3>Co(NH_4)_2(SO_4)_2>Eu_2O_3>CeO_2$. We also evaluated a correlation between the metal ablation thickness and the number of laser shots for the different laser fluences.

Synthesis of Ni-MWCNT by pulsed laser ablation and its water splitting properties (레이저 어블레이션 공정에 의한 Ni-MWCNT 합성 및 물분해 특성)

  • Cho, Kyoungwon;Chae, Hui Ra;Ryu, Jeong Ho
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.32 no.2
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    • pp.77-82
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    • 2022
  • Recently, research on the development of low-cost/high-efficiency water electrolysis catalysts to replace noble metal catalysts is being actively conducted. Since overvoltage reduces the overall efficiency of the water splitting device, lowering the overvoltage of the oxygen evolution reaction (OER) is the most important task in order to generate hydrogen more efficiently. Currently, noble metal catalysts show excellent characteristics in OER performance, but they are experiencing great difficulties in commercialization due to their high price and efficiency limitations due to low reactivity. In this study, a water electrolysis catalyst Ni-MWCNT was prepared by successfully doping Ni into the MWCNTs structure through the pulsed laser ablation in liquid (PLAL) process. High resolution-transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS) were performed for the structure and chemical composition of the synthesized Ni-MWCNT. Catalytic oxygen evolution reaction evaluation was performed by linear sweep voltammetry (LSV) overvoltage characteristics, Tafel slope, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and Chronoamperometry (CA) was used for measurement.

Prediction of Performance considering Ablated PTFE in High Voltage Self-blast Circuit Breaker (PTFE 용삭을 고려한 초고압 복합소호 차단기의 성능 예측)

  • Kim, Jin-Bum;Kweon, Ki-Yeoung;Lee, Hahk-Sung
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.695-698
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    • 2008
  • Self-blast circuit breakers utilize the energy dissipated by the arc itself to create the required conditions for arc quenching during the current zero. During the arcing period, high pressure, temperature and radiation of the arc could burn in pure SF6 gas and PTFE nozzle. Ablated nozzle shape and $SF_6$-PTFE mixture vapor affect the performance of an self-blast circuit breaker. After a number of tests, nozzle in circuit breaker is disassembled, a section of ablated nozzle is investigated precisely. Using computational fluid dynamics, the conservation equation for the gas and temperature, velocity and electric fields within breaker is solved. Before applying a section model, developed program is verified with experimental data. Performance of ablated nozzle shape is compared with original model through analysis program.

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Experimental Investigation for Ablation Characteristics of Polyimide Layer and Cu-metal Layer using High Power Nd:YAG UV Laser (고출력 Nd:YAG UV레이저를 이용한 polyimide층과 Cu-metal층의 가공상태에 대한 실험적 고찰)

  • Choi, Kyung-Jin;Lee, Young-Hyun
    • Journal of the Semiconductor & Display Technology
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    • v.8 no.4
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    • pp.31-36
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    • 2009
  • In this paper, the laser cutting characteristics of the flexible PCB using high power Nd:YAG UV laser were investigated. A specific FPCB model was selected for the experiment. Test sheets were made, which had equal materials and layer structure to those of the outline (OL) region and the contact pad (CP) region in the FPCB. The experiment is made up of two stages. In the first stage of the experiment, the laser cutting fluence was found, which is the threshold fluence to cut the test sheets completely. The laser cutting fluence of the OL sheet is $1781.26{\sim}1970.16\;J/cm^2$ and that of the CP sheet is $2109.34{\sim}2134.34\;J/cm^2$. In the second stage, cutting performance and its qualities were analyzed by the experiment. The laser cutting performance remained almost unchanged for all laser and process parameter sets. The average cutting width (top side/bottom side) of the OL sheet was $40.45\;{\mu}m/11.52\;{\mu}m$ and that of the CP sheet was $22.14\;{\mu}m/10.93\;{\mu}m$. However, the laser cutting qualities were different according to the parameters. The adjacent region of the cutting line on the OL sheet was carbonized as the beam speed was low and the overlap coefficient was high. The surface quality around the cutting line of the CP sheet was about the same. Carbonization and debris occurred on the surface of the cutting line. As a result of the experiment, the cutting qualities were better as the overlap coefficient was made low and beam speed high. Therefore, the overlap coefficient 2 or 3 is proper for the FPCB laser cutting.

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Analyzing the Impact of Multivariate Inputs on Deep Learning-Based Reservoir Level Prediction and Approaches for Mid to Long-Term Forecasting (다변량 입력이 딥러닝 기반 저수율 예측에 미치는 영향 분석과 중장기 예측 방안)

  • Hyeseung Park;Jongwook Yoon;Hojun Lee;Hyunho Yang
    • The Transactions of the Korea Information Processing Society
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    • v.13 no.4
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    • pp.199-207
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    • 2024
  • Local reservoirs are crucial sources for agricultural water supply, necessitating stable water level management to prepare for extreme climate conditions such as droughts. Water level prediction is significantly influenced by local climate characteristics, such as localized rainfall, as well as seasonal factors including cropping times, making it essential to understand the correlation between input and output data as much as selecting an appropriate prediction model. In this study, extensive multivariate data from over 400 reservoirs in Jeollabuk-do from 1991 to 2022 was utilized to train and validate a water level prediction model that comprehensively reflects the complex hydrological and climatological environmental factors of each reservoir, and to analyze the impact of each input feature on the prediction performance of water levels. Instead of focusing on improvements in water level performance through neural network structures, the study adopts a basic Feedforward Neural Network composed of fully connected layers, batch normalization, dropout, and activation functions, focusing on the correlation between multivariate input data and prediction performance. Additionally, most existing studies only present short-term prediction performance on a daily basis, which is not suitable for practical environments that require medium to long-term predictions, such as 10 days or a month. Therefore, this study measured the water level prediction performance up to one month ahead through a recursive method that uses daily prediction values as the next input. The experiment identified performance changes according to the prediction period and analyzed the impact of each input feature on the overall performance based on an Ablation study.

Analyzing Korean Math Word Problem Data Classification Difficulty Level Using the KoEPT Model (KoEPT 기반 한국어 수학 문장제 문제 데이터 분류 난도 분석)

  • Rhim, Sangkyu;Ki, Kyung Seo;Kim, Bugeun;Gweon, Gahgene
    • KIPS Transactions on Software and Data Engineering
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    • v.11 no.8
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    • pp.315-324
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    • 2022
  • In this paper, we propose KoEPT, a Transformer-based generative model for automatic math word problems solving. A math word problem written in human language which describes everyday situations in a mathematical form. Math word problem solving requires an artificial intelligence model to understand the implied logic within the problem. Therefore, it is being studied variously across the world to improve the language understanding ability of artificial intelligence. In the case of the Korean language, studies so far have mainly attempted to solve problems by classifying them into templates, but there is a limitation in that these techniques are difficult to apply to datasets with high classification difficulty. To solve this problem, this paper used the KoEPT model which uses 'expression' tokens and pointer networks. To measure the performance of this model, the classification difficulty scores of IL, CC, and ALG514, which are existing Korean mathematical sentence problem datasets, were measured, and then the performance of KoEPT was evaluated using 5-fold cross-validation. For the Korean datasets used for evaluation, KoEPT obtained the state-of-the-art(SOTA) performance with 99.1% in CC, which is comparable to the existing SOTA performance, and 89.3% and 80.5% in IL and ALG514, respectively. In addition, as a result of evaluation, KoEPT showed a relatively improved performance for datasets with high classification difficulty. Through an ablation study, we uncovered that the use of the 'expression' tokens and pointer networks contributed to KoEPT's state of being less affected by classification difficulty while obtaining good performance.

Performance Evaluation of C/SiC Composites (C/SiC 복합재료의 내열성능 평가)

  • Kim, Yun-Chul
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2007.04a
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    • pp.185-188
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    • 2007
  • The main objective of this research effort was to develope the performance of C/SiC composites manufactured by LSI (Liquid Silicon Infiltration) method for solid and liquid rocket propulsion system and ensure the performance analysis technique. The various carbon preform were manufactured by filament winding, tape rolling, involute layup and stack molding process. For the best performance of thermal and mechanical properties, many process conditions were tested and selected by varying preform, the content of SiC, temperature, impregnation resin and chemical vapour reaction. In conclusion, the high performance and reliability of C/SiC composite were proved for solid and liquid rocket propulsion system. And the performance analysis technique related to mathematical ablation model was originated.

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