A dimensional compensation algorithm for vertical bending deformation of 3D printed parts in selective laser sintering

Ha, Sangho,Ransikarbum, Kasin,Han, Hweeyoung,Kwon, Daeil,Kim, Hyeonnam,Kim, Namhun MCB UNIVERSITY PRESS 2018 RAPID PROTOTYPING JOURNAL Vol.24 No.6

Analysis of Shape Deformation from Densification of Additive Manufacturing Parts in Selective Laser Sintering

Sangho Ha,Eunju Park,Namhun Kim 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.8

Additive Manufacturing (AM) has recently attracted huge attentions as a technology for the next generation of industry. Particularly for the manufacturing purposes, various aspects of AM are being studied and applied, such as prototypes for assembly tests, jig production, and actual parts manufacturing. Selective Laser Sintering (SLS) using polyamide is easy to apply to various industries, such as its superior mechanical properties and higher design freedom, but design that takes into account variation in dimensions after manufacture often leads to costly and time-consuming problems. As a way to reduce deformation in the production process, previous studies approached experimentally about the effects of thermal deformation or residual stress on deformation. This is difficult to apply to a specimen of various shapes and sizes and also has limitations as a common solution to dimensional inaccuracies. To propose a solution for mitigating shape deformation of AM part, this paper focused on the effect of phase change of material among various processing parameters that cause shape deformation and tries to present an analytic model. Modeling on the melting and sintering phenomena of powder was presented using Euler-Bernui beam equation. The proposed model was verified by measuring the density variation of manufactured AM components and analyzing the correlation between the degree of contraction and the energy density. Factors such as layer thickness, part thickness, and part placement height were identified to have significant effects on the actual deformation. It is also confirmed that dimensional accuracy of parts that show large deformation by bending has increased by 64.2% when a calibration model is applied through manufacturing of actual parts. Time and cost can be saved for industrial application of AM by applying this proposed calibration model. In addition, by using this model more efficiently in the CAD design process, dimensional accuracy can be enhanced.

Design and Implementation of a Massively Parallel Multithreaded Architecture: DAVRID

Sangho Ha,Junghwan Kim,Eunha Rho,Yoonhee Nah,Sangyong Han,Daejoon Hwang,Heunghwan Kim,Seungho Cho 한국정보과학회 1996 Journal of Electrical Engineering and Information Vol.1 No.2

MPAs(Massively Parallel Architectures) should address two fundamental issues for scalability: synchronization and communication latency. Dataflow architecture faces problems of excessive synchronization overhead and inefficient execution of sequential programs while they offer the ability to exploit massive parallelism inherent in programs. In contrast, MPAs. based on von Neumann computational model may suffer from inefficient synchronization mechanism and communication latency. DAVRID(DAtaflow/Von Neumann RISe hybrID) is a massively parallel multithreaded architecture which takes advantages of von Neumann and dataflow models. It has good single thread performance as well as tolerates synchronization and communication latency. In this paper, we describe the DAVRID architecture in detail and evaluate its performance through simulation runs over several benchmarks.

Design and Implementation of a Massively Parallel Multithreaded Architecture: DAVRID

Sangho Ha,Junghwan Kim,Enha Rho,Yoonhee Nah,Sangyong Han,Daejoon Hwang,Heunghwan Kim,Seungho Cho 대한전기학회 1996 Journal of Electical Engineering and information S Vol.1 No.2

Study on Gesture and Voice-based Interaction in Perspective of a Presentation Support Tool

Sangho Ha,Soyoung Park,Hyesoo Hong,Namhun Kim 대한인간공학회 2012 大韓人間工學會誌 Vol.31 No.4

Objective: This study aims to implement a non-contact gesture-based interface for presentation purposes and to analyze the effect of the proposed interface as information transfer assisted device. Background: Recently, research on control device using gesture recognition or speech recognition is being conducted with rapid technological growth in UI/UX area and appearance of smart service products which requires a new human-machine interface. However, few quantitative researches on practical effects of the new interface type have been done relatively, while activities on system implementation are very popular. Method: The system presented in this study is implemented with KINECT<SUP>®</SUP> sensor offered by Microsoft Corporation. To investigate whether the proposed system is effective as a presentation support tool or not, we conduct experiments by giving several lectures to 40 participants in both a traditional lecture room(keyboard-based presentation control) and a non-contact gesture-based lecture room(KINECT-based presentation control), evaluating their interests and immersion based on contents of the lecture and lecturing methods, and analyzing their understanding about contents of the lecture. Result: We check that whether the gesture-based presentation system can play effective role as presentation supporting tools or not depending on the level of difficulty of contents using ANOVA. Conclusion: We check that a non-contact gesture-based interface is a meaningful tool as a sportive device when delivering easy and simple information. However, the effect can vary with the contents and the level of difficulty of information provided. Application: The results presented in this paper might help to design a new human-machine(computer) interface for communication support tools.

Oracle8i XDK를 이용한 XML 문서의 질의

하상호(Sangho Ha),이강석(Gangseog Lee) 대한전자공학회 2000 대한전자공학회 학술대회 Vol.2000 No.6

비정형성 함수 언어를 위한 향상된 스레드 형성 기법

하상호(Sangho Ha),한상영(Sangyong Han),김흥환(Heunghwan kim),김수홍(Soohong Kim) 한국정보과학회 1994 정보과학회논문지 Vol.21 No.12

다중스레딩은 전역 메모리 참조등 긴 지체시간을 초래하는 연산을 분할하여 수행토록 하고, 프로세서의 유휴시간을 초래하지 않고서 계산들간에 빠른 문맥 교환을 가능하게 함에 따라 대규모 병렬 시스템에 매우 효과적이다. 다중스레드 컴퓨터의 성능은 다중스레드 코드의 질의 좌우된다. 본 논문은 비정형성 함수 언어 Id￣[1]로 작성된 프로그램으로부터 효율적인 다중 순차 스레드를 생성하는 향상된 스레드 형성 기법을 제안한다. 이 스레드 형성 기법은 긴 지체시간을 초래하는 명령어에 기준한 데이타플로우 프로그램 그래프의 분할, 일반화된 스위치와 합병 노드의 새로운 도입을 통한 여러 스위치와 합병 노드의 결합, 스레드 선행 관계에 기반한 스레드 합병 및 중복된 아크 제거 등의 특징을 갖는다. 시뮬레이션을 통해 스레드의 합병과 중복 아크 제거의 효과를 분석하고, 제안된 스레드 형성 기법과 Schauser[2]의 기법을 비교한다. 시뮬레이션 결과는 본 논문의 기법이 다중스레딩의 부담인 코드의 제어 부분과 branch 명령어를 효과적으로 감소하고 있음을 보여준다. Multithreading is attractive for a large-scale parallel system since it allows long latency instructions to be dealt with as split-phase transactions as well as fast context switching between computations without blocking the processor. Performance of multithreaded architectures depends significantly on the quality of multi-threaded codes. In this paper, we describe an enhanced thread formation scheme to produce efficient sequential threads from programs written in a non-strict functional language Id￣ [1]. This scheme features dataflow program graph partitioning based on only long latency instructions, combination of switch and merge introducing a generalized switch and merge, thread merging and redundant arc elimination using thread precedence relation. We analyze the effect of thread merging and redundant arc elimination, and compare our scheme with Schauser's[2] through simulation. Simulation results show that our scheme reduces the control portion of codes, which is overheads due to multithreading, and branch instructions effectively.

Human-in-the-loop 에이전트 기반 모델링 및 시뮬레이션 구현

하상호(Sangho Ha),모제스 부소기(Moses Busogi),김남훈(Namhun Kim) 한국HCI학회 2014 한국HCI학회 학술대회 Vol.2014 No.2

Human-Machine Interaction (HMI) 분야에서 인간과 시스템 간의 상호작용을 정량적으로 분석하여 인간 행동을 모사 하는 연구가 진행되고 있다. 특히 가상현실 기반의 Human-in-the-loop(HITL) 시뮬레이션을 이용하여 인간 에이전트의 행동을 분석하고 시뮬레이션 모델에 인풋 데이터로 사용함으로써 시스템 내에서의 인간의 행동을 모사하기 위한 데이터 획득을 위한 기본적인 프레임워크로 사용될 수 있다. 이 연구를 통하여, 시뮬레이션 목적의 인간 에이전트의 모델 개발 및 구현을 위한 Human-in-the-loop 기반 HMI 가상실험환경을 구현하고자 한다. 구현된 시스템은 다양하고 복잡한 상황에서 인간의 행동과 그 반응에 대한 실시간 데이터의 이는 에이전트 시뮬레이션 모델과의 연동을 통해 인간 에이전트와 시스템 혹은 인간 에이전트들 사이의 상호작용에 대한 보다 현실적인 시뮬레이션을 가능하게 해 줄 것으로 기대된다. Modeling of human-included systems and analysis of their performance are challenging, but important in Human-Machine Interaction (HMI) research. Using 3D virtual reality (VR) based HITL simulation environments, especially, the verification and validation of the human-involved complex systems can be much easier when developing a new HMI environs. In this research, therefore, a new framework of HITL based agent-based simulation is suggested. HITL simulation is used for analyzing quantified data of human behaviors/interactions within virtual environments, and agent-based simulation model is built with the data from HILT in real-time. An illustrative example of collaborative HITL-agent-based simulation framework for getting and analyzing human behavioral data in HMI system, including evacuation scenario from a fire situation which is not able to be tested in physical systems, is presented at the end of this presentation.

선택적 레이저 소결방식의 적층 제조 공법에서 열변형 경향 분석

하상호(Sangho Ha),한휘영(Hweeyoung Han),김현남(Hyeonnam Kim),김남훈(Namhun Kim) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.4

HMI 연구를 위한 3D 가상현실환경 구현

하상호(Sangho Ha),고승모(Seungmo Ko),김남훈(Namhun Kim) 한국HCI학회 2013 한국HCI학회 학술대회 Vol.2013 No.1