신소재 복합재료 해석용 툴

신기훈 (사)한국CDE학회 2009 한국CAD/CAM학회학회지 Vol.15 No.2

pH, 구리 및 인의 상호 요인이 Scenedesmus maximus의 성장에 미치는 영향 ( Interactive Effects of Phosphorus, Copper and pH on the growth of Scenedesmus maximus )

신기훈,이기태 환경독성보건학회 1999 한국독성학회 심포지움 및 학술발표회 Vol.- No.-

임의 형상의 복합재 모델링을 위한 CSG 기반 표현

신기훈,이진구 한국CDE학회 2006 한국CDE학회 논문집 Vol.11 No.5

This paper proposes a CSG-based representation scheme for heterogeneous objects including multi-material objects and Functionally Graded Materials (FGMs). In particular, this scheme focuses on the construction of complicated heterogeneous objects guaranteeing desired material continuities at all the interfaces. In order to create various types of heterogeneous primitives, we first describe methods for specifying material composition functions such as geometry-independent, geometry-dependent functions. Constructive Material Composition (CMC) and corresponding heterogeneous Boolean Operators (e.g. material union, difference, intersection, and partition) are then proposed to illustrate how material continuities are dealt with. Finally, we describe the model hierarchy and data structure for computer representation. Even though the proposed scheme alone is sufficient for modeling all sorts of heterogeneous objects, the proposed scheme adopts a hybrid representation between CSG and decomposition. That is because hybrid representation can avoid the unnecessary growth of binary trees.

전략물자수출입고시에서 통제하는 정보보안품목(5A002.a)의 예외사항 적용에 따른 비해당 판정 사례 분석

신기훈,김형중 한국정보통신설비학회 2016 한국정보통신설비학회 학술대회 Vol.2016 No.09

Korea’s “Foreign Trade Act” states that the goods(including technology determined by Presidential Decree) on which restriction, such as export license, is required for maintaining international peace and security as well as national security in accordance with the principles of the International Export Control Regimes, are to be referred to as “Strategic Item” and the list of such goods designated are publicly notified by the “Public Notice on Trade of Strategic Goods(hereinafter, the Public Notice)”. Information security systems, equipment and components above control parameter specified under control number 5A002.a of such list are classified as “Strategic Items”. In fact, this entry covers the majority of the information security equipment such as switch, firewall, server and network equipment. This paper studies negative classification cases of items that meet the control threshold of the list on the Public Notice but nonetheless excluded by the de-control notes available for certain items such as those sold in mass market or those with encryption technology exclusively for authentication. The date of classification results issued through the Information System for Management of Export and Import of Strategic Items(Yestrade) over the past 5 years are used. By Analyzing such data, we try to make recommendations for improvements.

M&A 아카데미 - M&A유형과 사례(2)

신기훈,Sin, Gi-Hun 벤처기업협회 2009 벤처다이제스트 Vol.130 No.-

자바로 유명한 세계적 IT기업 썬마이크로시스템즈가 오라클과 합병한다는 소식이 세계 IT시장을 떠들썩하게 하고 있다. 썬은 이미 IBM과 상당히 발전된 M&A 논의를 진행시키다 오라클로 방향을 선회하는 깜짝쇼를 보여주었고, 이에 오라클은 첫 1년간 영업이익 15억 달러 증가를 예상하고 있다고 한다. 이미 피플소프트와 BEA 등 기업용 소프트웨어 및 서비스업체를 인수하며 성장해온 오라클은 서버기업인 썬을 인수하면서 SW/HW 모두를 망라하는 전방위 IT 기업으로 '단숨'에 성장하게 되었다. 그러나 이제부터다. 어떤 기업이든 M&A를 결정한 이후로 얼마나 전략적으로 과정을 진행하느냐에 따라 기업의 업그레이드를 이뤄낼 수 있다. 이번 호에서는 지난 호에 이어 주식스왑을 중심으로 M&A유형과 사례를 살펴보도록 하자. 아울러 또 다른 M&A의 유형인 주식의 포괄적교환과 꼭 알아두어야 할 몇 가지 항목을 살펴보도록 하자.

A method for representation and analysis of conformal cooling channels in molds made of functionally graded tool steel/Cu materials

신기훈 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.4

Advances in additive manufacturing technology (AMT) enable the direct fabrication of thermally conductive molds with heat sinks or conformal cooling channels. Although tool steels (e.g., P21, H13, SUS420J2) are popularly used as die materials because of high dimensional stability, tool steels are inefficient for cooling mold dies due to low thermal conductivity. Hence, the adoption of functionally graded tool steel/Cu materials (FGMs) has good potentials for thermally conductive molds to avoid thermal stress concentration while improving thermal conductivity. In this sense, this paper presents a new method for the representation and analysis of conformal cooling channels in molds (injection or blowing) made of functionally graded tool steel/Cu materials. A heterogeneous sweep operation combined with 2D material blending was proposed to construct heterogeneous solid models for conformal cooling channels. In addition, onedimensional P21/Cu FGMs were fabricated using DMT (laser-aided direct metal tooling). Material properties (such as density, specific heat, thermal conductivity, coefficient of thermal expansion, and hardness) were evaluated to obtain more accurate analysis results and to verify the feasibility of such a multi-functional mold. An example is shown to illustrate the entire representation and analysis procedure.

최대 절대값 기반 시계열 데이터 예측 모델 평가 기법

신기훈,김철,남상훈,박성재,유성수 한국에너지학회 2018 에너지공학 Vol.27 No.4

본 논문에서는 Mean Absolute Percentage Error (이하 MAPE)와 Symmetric Mean Absolute Percentage (이하sMAPE)의 새로운 접근법을 이용한 시계열 예측 모델의 평가 방법을 소개한다. MAPE, sMAPE 에는 다음과같은 문제점이 있다. 데이터 집합에서 관측 값이 0일 경우 평가할 수 없고, 관측 값이 0에 매우 가깝다면 과도한평가 값을 측정한다. 관측 값과 예측 값 간에 동일한 오차를 가지더라도 다른 값으로 평가하는 문제도 가지고있다. 동일한 오류 값이 과대 예측되었는지 아니면 과소 예측되었는지에 따라 다른 평가 값을 측정하거나 관측값의 부호와 예측 값의 부호가 서로 다르면 그 오차는 평가 값에 반영되지 않는다. 이러한 문제는 Maximum Mean Absolute Percentage Error (이하 mMAPE)에 의해 해결하였다. 우리는 MAPE평가 방법의 분모에서 관측 값을 사용하는 대신 최대 절대 값을 사용했다. 최대 절대 값이 1보다 작으면 분모를제거하여 0 값이 정의되지 않은 문제와 미세한 값일 경우 과대 측정되는 문제를 해결하였다. Beijing PM2.5의온도 데이터와 시뮬레이션 데이터를 통해 mMAPE 와 다른 평가 방법들의 결과 값을 비교하였으며, 위의 문제들을해결할 수 있음을 검증하였다.

[CAE] 응력집중과 특이점의 처리

신기훈 (사)한국CDE학회 2018 한국CAD/CAM학회학회지 Vol.24 No.1

Modeling of time-variant heterogeneous objects in micro-system package

신기훈 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.5

UBM (under bump metallurgy) of micro-system packages consists of several heterogeneous layers such as solder wetting, diffusion barrier, adhesion, and IMC (inter-metallic compound) layers. In particular, the IMC layer, formed between the solder wetting layer (e.g.,Cu or Ni) and the solder, grows gradually and thus its composition changes with time (i.e., time-variant). The primary failure mechanism of the solder joints in micro-system packages is widely known as the fatigue failure caused by thermal fatigue and electro-migration damage. However, these phenomena have thus far been viewed from experimental investigations. Therefore, finite element analysis (FEA) becomes an important step for the optimal design and reliability analysis of heterogeneous objects such as in micro-system packages. However, the accuracy of the FEA wholly depends on the quality of finite element models. There thus exists an increasing need for generating finite element models adaptive to both geometric complexity and material distribution. In this sense, this paper presents a new method for modeling of time-variant heterogeneous objects such as in micro-system packages whose composition changes with time. Heterogeneous Boolean operators based on the diffusion process are proposed to construct time-variant heterogeneous objects. Once a time-variant heterogeneous solid model is constructed, it is then discretized into an object model onto which appropriate material properties are mapped. Discretization converts continuous material variations inside an object into stepwise variations. Next, the object model is adaptively meshed and converted into a finite element model. FEA using commercial software is finally performed to check failure criteria. An example (UBM in micro-system package) is shown to illustrate the entire modeling procedure.

직접적인 모델 편집기능의 필요성

신기훈 (사)한국CDE학회 2005 한국CAD/CAM학회학회지 Vol.11 No.2