• 분석과학
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• 제28권4호
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• pp.270-277
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• 2015

비등점은 유기물의 물리화학적 성질을 특정하는데 있어 매우 근본적 요소 중 하나이다. 그러나 기존의 정량적 구조-물성 상관관계식들은 고에너지 물질 등과 같은 특정 물질 군에 대한 실험값들의 부족 등으로 인해 제한적인 응용성을 가지고 있었다. 본 연구에서는 서로 다른 출처로부터의 5,923개의 비등점 자료를 확보하였으며, 이에는 일반적 유기화합물과 더불어 특수목적을 가지는 분자들을 포함하였고, 이들 수집된 데이터 셋을 이용하여 새로운 비등점 예측모델을 개발하는데 사용하였다. 다양한 학습 방법을 이용하여 새로이 수집된 데이터 셋을 이용한 2차원 분자 표현자에 기반한 비등점 모델을 도출하였다. 개발된 예측모델의 적정성과 견고성을 확인하였고, 훈련 셋의 표현자에 기반한 비등점 예측모델의 적용구역을 도출하였다.

• 정보보호학회논문지
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• 제34권1호
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• pp.31-40
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• 2024

최근 정적분석 기반의 시그니처 및 패턴 탐지 기술은 고도화되는 IT 기술에 따라 한계점이 드러나고 있다. 이는 여러 아키텍처에 대한 호환 문제와 시그니처 및 패턴 탐지의 본질적인 문제이다. 악성코드는 자신의 정체를 숨기기 위하여 난독화, 패킹 기법 등을 사용하고 있으며 또한, 코드 재정렬, 레지스터 변경, 분기문 추가 등 기존 정적분석 기반의 시그니처 및 패턴 탐지 기법을 회피하고 있다. 이에 본 논문에서는 이러한 문제를 해결할 수 있는 머신러닝을 통한 LLVM IR 코드 이미지 기반 악성코드 정적분석 자동화 기술을 제안한다. 바이너리가 난독화되거나 패킹된 사실에 불구하고 정적 분석 및 최적화를 위한 중간언어인 LLVM IR로 디컴파일한다. 이후 LLVM IR 코드를 이미지로 변환하여 CNN을 이용한 알고리즘 중 전이 학습 및 Keras에서 지원하는 ResNet50v2으로 학습하여 악성코드를 탐지하는 모델을 제시한다.

• 한국CDE학회논문집
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• 제12권1호
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• pp.39-49
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• 2007

Recently three-dimensional (3-D) die design and production process has been widely introduced into the tooling shops of automotive manufacturers to reduce time-to-production of brand-new automobiles. 3-D solid models created in CAD systems are used not only for various simulations for design verification, but also for NC tool path generation to machine dies and their Styrofoam patterns. However, a lot of time and cost will be required to build solid models for dies if designers use only the generalized modeling capabilities of commercial 3-D CAD systems. To solve this problem, it is necessary to customize 3-D CAD system for the specific die design and manufacturing process. This paper describes a dedicated 3-D CAD system based on Unigraphics for die design for automotive body panels. The system provides not only 3-D design capabilities, but also standard part libraries, to enhance design productivity. The design process modeling technology has been introduced to facilitate redesign of the die for the modified panel. By introducing this system, dies can be designed more rapidly in the 3-D space, and their solid data can be directly transferred to CAM tools for NC tool path generation and simulation tools for virtual manufacturing.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1285-1288
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• 2005

Screw rotors, the key parts of screw compressors, are used in compressing air and refrigerant due to their high productivity, compact size, low noise and maintenance. In general, a screw compressor is composed of a pair of rotors of complex geometric shape. The manufacturing cost of the screw rotors is high because the complicated helical shapes of the screw rotors are manufactured usually by the dedicated machine tools. In this study, rotor profile is divided into three parts for the efficient machining. The formed tools are designed and shared for the respective split region. By cutting the screw rotor using the formed tools, this method is more efficient than the end mill in machining rotor. Experimental results show that 4-axis machining using formed tools needs less time and has the accuracy.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1424-1428
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• 2005

This paper describes a dedicated three-dimensional CAD system for design of drawing dies for automotive body panels. Since solid die models are useful not only for simulations for design verification, but also for NC tool path generation to machine dies and their Styrofoam patterns, 3-D CAD systems have been introduced in the tooling shop of automotive manufacturers. However, the work to build solid models requires a lot of time and effort if the designer uses only the general modeling capabilities of commercial 3-D CAD systems. To solve this problem, we customized a 3-D CAD system for the drawing die design. The system provides not only 3-D design capabilities, but also standard part libraries to enhance design productivity. By introducing this system, the drawing dies can be designed more rapidly in the 3-D space, and their solid data can be directly transferred to CAM tools for NC tool path generation and simulation tools for virtual manufacturing

• Journal of Power Electronics
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• 제10권5호
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• pp.468-476
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• 2010

This paper proposes and develops a new direct voltage control (DVC) approach. This method is designed to be applied in various applications for AC drives fed with a three-phase voltage source inverter (VSI) working with a constant switching time interval as in the standard direct torque control (DTC) scheme. Based on a very strong min(max) criterion dedicated to selecting the inverter voltage vector, the developed DVC scheme allows the generation of accurate voltage forms of waves. The DVC algorithm is implemented on a dSPACE DS1104 controller board and then compared with the space vector pulse width modulation technique (SVPWM) in an open loop AC drive circuit. To demonstrate the efficiency of the developed algorithm in real time and in closed loop AC drive applications, a scalar control scheme for induction motors is successfully implemented and experimentally studied. Practical results prove the excellent performance of the proposed control approach.

• 한국정밀공학회지
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• 제19권8호
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• pp.100-107
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• 2002

The extruder screw is a part for extruding material in a injection molding machine. The screw's geometrical shape can mathematically be described by a sweep surface which is constructed by sweeping a section curve composed of a few circular arcs, along a helical guide curve. In the paper we developed a dedicated CAD system which basically is parametric in a sense that the system initially takes several design parameters to construct the geometric elements including the final sweep surface of the screw as well as section & guiding curves, along with feasibility check of the input parameter values, without further user interaction. The system has been developed as a built-in module onto a commercial CAD system, which can further incorporate additional NC-out functions with ease.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.15-19
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• 2001

A dedicated reverse engineering(RE) system for rapid manufacturing of human head in a 3D bust has been developed. The first step in the process is to capture the surface details of a human head and shoulder by three scanners based upon the digital moire fringe technique. Then the multiple scans captured from different angles are aligned and merged into a single polygonal mesh, and the aligned data set is refined by smoothing, subdividing or hole filling process. Finally, the refined data set is sent to a 4-axis computer numerically control(NC) machine to manufacture a replica. In this paper, we mainly describe on the algorithms and software for aligning multiple data sets. The method is based on the recently popular Iterative Closest Point(ICP) algorithm that aligns different polygonal meshes into one common coordinate system. The ICP algorithm finds the nearest positions on one scan to a collection of points on the other scan by minimizing the collective distance between different scans. We also integrate some heuristics into the ICP to enhance the aligning process. A typical example is presented to validate the system and further research work is also discussed.

• 한국기계가공학회지
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• 제19권4호
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• pp.71-78
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• 2020

The rotary feed axes of a 5-axis machine tool can increase the freedom of the tool posture, while reducing feed speed and rigidity. In addition, as a ball-end mill is inevitably used during machining by rotational feed, the step-over length is reduced compared to the flat-end mill, thereby reducing the material removal rate. Therefore, this study attempts to improve the material removal rate, feed speed, and machining stability using the corner radius flat-end mill and a fixed controlled machining method for the rotary feed axes during roughing. In addition, the tapered ball-end mill and simultaneously controlled machining method for the rotary feed axes were used for finishing to improve the propeller's 5-axis machining efficiency by enhancing the surface quality. In order to create the tool path effectively and easily, we propose a specific approach for using the propeller's geometric properties and evaluate the effectiveness of the proposed method by comparing it with the method of the dedicated module.

• 한국기계가공학회지
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• 제19권4호
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• pp.30-35
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• 2020

The light guide plate (LGP) provides a surface light source on the back of the liquid crystal display (LCD), which is not self-emitting; thus, it is an essential component of display units requiring sufficient brightness. To maximize the light-emitting effect of an LGP, enough incident light, from the light source, should enter into its side. However, the current trend in LCD panels is represented by larger and thinner screens and this smaller thickness prevents the accordingly thin LGPs from providing sufficient brightness. This paper proposes a process for manufacturing wedge-type LGPs, which might increase the amount of incident light and, consequently the surface light emission, for applications in large LCDs. The proposed method was validated by building a dedicated manufacturing machine and performing illuminance experiments on the fabricated LGP.