High Power Diode Laser을 이용한 금형재료용 구상화 주철의 모서리부 표면처리

황현태,송현수,김종도,송무근,김영국,Hwang, Hyun-Tae,Song, Hyeon-Soo,Kim, Jung-Do,Song, Moo-Keun,Kim, Young-Kuk 한국재료학회 2009 한국재료학회지 Vol.19 No.9

Recently, metal molding has become essential not only for automobile parts, but also mass production, and has greatly influenced production costs as well as the quality of products. Its surface has been treated by carburizing, nitriding and induction hardening, but these existing treatments cause considerable deformation and increase the expense of postprocessing after treatment; furthermore, these treatments cannot be easily applied to parts that requiring the hardening of only a certain section. This is because the treatment cannot heat the material homogeneously, nor can it heat all of it. Laser surface treatment was developed to overcome these disadvantages, and, when the laser beam is irradiated on the surface and laser speed is appropriate, the laser focal position is rapidly heated and the thermal energy of surface penetrates the material after irradiation, finally imbuing it with a new mechanical characteristic by the process of self-quenching. This research estimates the material characteristic after efficient and functional surface treatment using HPDL, which is more efficient than the existing CW Nd:YAG laser heat source. To estimate this, microstructural changes and hardness characteristics of three parts (the surface treatment part, heat affect zone, and parental material) are observed with the change of laser beam speed and surface temperature. Moreover, the depth of the hardened area is observed with the change of the laser beam speed and temperature.

금형재료용 주철강의 복합열처리 특성

황현태,소상우,김종도,Hwang, Hyun-Tae,So, Sang-Woo,Kim, Jong-Do 한국재료학회 2011 한국재료학회지 Vol.21 No.7

Currently, there are two main issues regarding the development of core technologies in the automotive industry: the development of environmentally friendly vehicles and securing a high level of safety in the event of an accident. As part of the efforts to address these issues, research into alternative materials and new car body manufacturing and assembly technologies is necessary, and this has been carried out mainly by the automotive industries. Large press molds for producing car body parts are made of cast iron. With the increase of automobile production and various changes of design, the press forming process of car body parts has become more difficult. In the case of large press molds, high hardness and abrasive resistance are needed. To overcome these problems, we attempted to develop a combined heat treatment process consisting of local laser heat treatment followed by plasma nitriding, and evaluated the characteristics of the proposed heat treatment method. From the results of the experiments, it has been shown that the maximum surface hardness is 864 Hv by the laser heat treatment, 953 Hv by the plasma nitriding, and 1,094 Hv by the combined heat treatment. It is anticipated that the suggested combined heat treatment can be used to evaluate the durability of press mold.

Couette-Taylor 흐름을 이용한 산화그래핀 합성과 특성분석

황현태,한종훈,양철민 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.1

An evaluation methodology for 3D deep neural networks using visualization in 3D data classification

황현태,이수홍,Hyung Gun Chi,강남규,공현배,Jiaqi Lu,옥형석 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.3

"Making 3D deep neural networks debuggable". In the study, we develop and propose a 3D deep neural network visualization methodology for performance evaluation of 3D deep neural networks. Our research was conducted using a 3D deep neural network model, which shows the best performance. The visualization method of the research is a method of visualizing part of the 3D object by analyzing the naive Bayesian 3D complement instance generation method and the prediction difference of each feature. The method emphasizes the influence of the network in the process of making decisions. The result of visualization through the algorithm of the study shows a clear difference based on the result class and the instance within the class, and the authors can obtain insight that can evaluate and improve the performance of the DNN (deep neural networks) model by the analyzed results. 3D deep neural networks can be made "indirectly debuggable", and after the completion of the visualization method and the analysis of the result, the method can be used as the evaluation method of "general non-debuggable DNN" and as a debugging method.

금속제창 분야에 대한 정부조달 우수제품 지정제도의 운영현황 및 개선방안

황현태,조은현,이동형 한국산업경영시스템학회 2024 한국산업경영시스템학회 학술대회 Vol.2024 No.춘계

Reinforced Graphene Oxide Fiber by Assistance of Polydopamine

황현태,신현석 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

In recent years, Graphene fiber, one of the carbonaceous fibers, is the one of attractive material to the many researchers because of its distinguished properties such as mechanical properties and electrical and thermal conductivity. However, the Graphene fiber is mechanically weaker than other carbonaceous fiber such as conventional carbon fiber and carbon nanotube fiber. In this work, we introduced dopamine hydrochloride (DA) as coagulation and reinforcing agent of the Graphene oxide fiber. And then coagulated graphene oxide fiber was polymerized to polydopamine functionalized graphene oxide fiber (pDA-GOF). The pDA-GOF shows enhanced tensile strength(~67%) than previously reported graphene oxide fiber (derived by CaCl₂ coagulation bath). Moreover, the pDA-GOF was reduced by microwave treatment to obtain nitrogen doped high quality graphene fiber. We expect that the microwave-reduced pDA-GOF can be used to various application such as improved electrochemical catalysts.

Deep Learning-Based Sound Localization Using Stereo Signals Based on Synchronized ILD

황현태,윤덕규,최승호 한국인터넷방송통신학회 2019 International Journal of Internet, Broadcasting an Vol.11 No.3

The interaural level difference (ILD) used for the sound localization using stereo signals is to find the difference in energy that the sound source reaches both ears. The conventional ILD does not consider the time difference of the stereo signals, which is a factor of lowering the accuracy. In this paper, we propose a synchronized ILD that obtains the ILD after synchronizing these time differences. This method uses the crosscorrelation function (CCF) to calculate the time difference to reach both ears and use it to obtain synchronized ILD. In order to prove the performance of the proposed method, we conducted two sound localization experiments. In each experiment, the synchronized ILD and CCF or only the synchronized ILD were given as inputs of the deep neural networks (DNN) [1-2], respectively. In this paper, we evaluate the performance of sound localization with mean error and accuracy of sound localization. Experimental results show that the proposed method has better performance than the conventional methods.

Hydrogeological fate of radionuclides at decommissioned nuclear power plant sites: Case studies for radionuclides transport model development

황현태,노수영,윤인호,진성욱 대한지질학회 2025 지질학회지 Vol.61 No.1

Motivated by the urgent need to understand and mitigate potential environmental and public health risks associated with decommissioned nuclear power plants, this review paper explores studies on radioactive contamination at these facilities, with a particular focus on the development of radionuclide transport models. It begins with a comprehensive literature review, examining various contaminant types, extents, effects, and site conditions. Through careful examination of case studies, the paper extracts valuable insights from historical contamination incidents to guide contemporary practices. The primary emphasis is on data utilized in modeling studies, highlighting the collection and processing of information from both existing literature and on-site observations. The paper discusses the quality assurance and quality control (QA/QC) procedures crucial for numerical modeling, including an in-depth assessment of modeling parameters to ensure the dependability and precision of inputs. Furthermore, it explores the development of a robust database system, strategically organized for machine learning inputs, laying the foundation for sophisticated data analysis. The review highlights that choosing the right numerical models for specific site conditions, conducting thorough data collection and processing, and developing reliable database systems are essential for the successful management of decommissioned nuclear power plants. This paper can contribute to developing a modeling strategy for predicting radionuclide transport in decommissioned nuclear power plant sites, ultimately supporting the effective management of these facilities.

Development of a transportability evaluation system using swept path analysis and multi-body dynamic simulation

황현태,이수홍,이지웅,김희찬,우민혁,문권우,Jiaqi Lu,옥형석,김재관,서효원 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.11

In this study, we develop a transportability evaluation system for the transportation process or design process in product development engineering. The system extracts the constraint condition and transportability using swept path analysis and multi-body dynamic simulation. This system consists of two main software modules: a feature curve extraction module and a multi-body dynamic simulation module. The feature curve extraction module extracts the feature curve list of the entire transportation path with swept path analysis to transmit the information to the simulation module. The multi-body dynamic simulation module extracts the constraint condition for the product design process that a designer uses as the transportation constraint in the design process or quick checks the transportability of the product files. The entire structure of the system is accessible by a web-based platform. When the user (designer) inputs the product files and the transportation information, the system gives the constraints and transportability to the user. The entire analysis is performed by a background process on the analysis server. We also propose a multimodal transportability evaluation algorithm that considers design and dynamic conditions.

사용 만족도를 고려한 금속제창 품목 조달청 우수제품 지정제도 개선방안 연구

황현태,김태구 한국산업경영시스템학회 2025 한국산업경영시스템학회지 Vol.48 No.3

The Public Procurement Service was established to ensure efficient supply of necessary goods for public institutions and their quality stability. The Public Procurement Service operates the Excellent Product Designation System for quality improvement. Due to the convenience of sole-source contracts and pricing advantages, suppliers prefer to obtain excellent product certification. However, despite these advantages, the designation does not guarantee customer satisfaction, as consumers pay higher prices without assured quality improvements. The goal of this study is to propose a new evaluation system better reflecting customer satisfaction and repurchase intention. Metal window products were selected as the study subject. Candidate factors were derived through literature review, and surveys were conducted to identify significant items for the new evaluation system. Item weights were then calculated using AHP analysis. The proposed system was validated through case analysis comparing two excellent products with two general products.