• 한국기계가공학회지
• /
• 제21권9호
• /
• pp.21-27
• /
• 2022

The rotorcraft engine gearbox transmits the power generated by the turboshaft engine to the rotor by reducing the rotational speed and increasing the torque. The core of the rotorcraft engine gearbox is lightweight performance, which requires maximum weight reduction within the range that meets various requirements and constraints. Therefore, lightweight design through gear macro geometry optimization is necessary. In this study, gear macro geometry optimization was performed to reduce the weight of a rotorcraft engine gearbox. NSGA-III was used for the optimization, resulting in a combination of the gear ratio and macro geometry that minimizes the weight of the total gear. In addition, the safety factor of the gears satisfied the given conditions.

• 한국기계가공학회지
• /
• 제21권2호
• /
• pp.116-122
• /
• 2022

This study proposed a method of testing the stability when selecting gears to reduce the weight of a 3-DOF wrist mechanism for a pick-and-place 3-DOF parallel robot with an increased workspace by using an additional straight axis at its top. We performed SolidWorks^® modeling- and ANSYS^®-based structural analysis of a pinion gear, which is most vulnerable to the force from a 3-DOF wrist mechanism, to lighten the robot weight for performing various tasks. When the initial analysis results considerably differed from the theoretical values calculated in advance, we checked and identified the errors in the contact conditions or input values. Ultimately, it is believed that the methodology presented in this paper will help in mitigating errors during analysis and determine the accurate values for a lightweight 3-DOF wrist mechanism for a parallel robot with an expanded workspace.

• ETRI Journal
• /
• 제46권4호
• /
• pp.683-696
• /
• 2024

The point cloud provides viewers with intuitive geometric understanding but requires a huge amount of data. Moving Picture Experts Group (MPEG) has developed video-based point-cloud compression in the range of 300-700. As the compression rate increases, the complexity increases to the extent that it takes 101.36 s to compress one frame in an experimental environment using a personal computer. To realize real-time point-cloud compression processing, the direct patch projection (DPP) method proposed herein simplifies the complex patch segmentation process by classifying and projecting points according to their geometric positions. The DPP method decreases the complexity of the patch segmentation from 25.75 s to 0.10 s per frame, and the entire process becomes 8.76 times faster than the conventional one. Consequently, this proposed DPP method yields similar peak signal-to-noise ratio (PSNR) outcomes to those of the conventional method at reduced times (4.7-5.5 times) at the cost of bitrate overhead. The objective and subjective results show that the proposed DPP method can be considered when low-complexity requirements are required in lightweight device environments.

• 한국기계가공학회지
• /
• 제19권10호
• /
• pp.98-104
• /
• 2020

Recently, friction stir welding of dissimilar materials has become one of the biggest issues in lightweight and eco-friendly bonding technology. In this study, a lightweight torsion beam axle, which is an automobile chassis component, was used in the welding to cast aluminum material. The friction stir welding process of A357 cast aluminum and FB590 high-strength steel as well as the effects of the process parameters were investigated and optimized using a novel definitive screening design (DSD). ANOVA was used to predict the importance of the process parameters with 13 degradation experiments using the proposed DSD. Also, FSWed experiments were conducted using an optical microscope analysis to investigate the tensile strength behavior in the weld area. In addition to determining the interaction between the tool's rotational speed and the plunge speed, results indicate that the influence of the plunge depth was the most significant.

• 한국산학기술학회논문지
• /
• 제20권1호
• /
• pp.9-20
• /
• 2019

국내에서의 지진과 같은 자연재해의 발생횟수가 증가하고 있다. 이에 따라 재해, 재난 환경에 적합한 임시거주공간 혹은 피난시설의 필요성이 증대되고 있다. 본 연구에서는 경량 복합패널을 이용하여 기존 피난시설과는 차별화된 구호주거를 제작하고자 하였다. 이를 위해 경량 복합패널에 대한 구조적 성능을 검증하고자 하였으며, 패널에 대한 성능 시험 방법 중 ASTM E72 기준에 따른 면내 전단 강도 실험을 진행하였다. 실험 결과, 각 실험체가 면내 하중을 받을 때의 최대하중을 알아내었다. 모든 실험체는 가력 부분의 패널이 찢어지면서 실험이 종료되었다. 실험체의 초기 강성은 계산을 통해 예측한 강성과 일치하였다. 하지만 패널의 특성인 국부적인 찌그러짐과 찢어짐으로 인해 강성저하와 최종파괴가 발생하였다. 개구부가 있는 실험체들은 개구부의 위치와 형태에 따라 기본 실험체와 강성과 강도에서 차이를 보였다. 또한 모든 실험 결과를 종합하여 패널이 받는 최대하중과 힘을 받는 면적이 비례한다는 것을 확인하였다. 이를 통해 실험체들의 극한전단응력을 계산하였으며, 평균 극한전단응력을 산정하였다. 경량 복합패널의 평균 극한전단응력은 $0.047N/mm^2$이며, 이 값을 통해 패널의 면적에 따른 허용하중을 합리적으로 예측할 수 있는 근거를 제시하였다.

• 정보보호학회논문지
• /
• 제32권3호
• /
• pp.465-475
• /
• 2022

코로나19의 영향으로 사람들은 편리함, 건강 등에 관심을 두게 되었고, 이를 도와주는 IoT 기기의 사용량은 늘어나고 있다. 리소스가 제한적이지만 민감한 정보를 다뤄야 하는 IoT 기기들에 경량 보안요소를 내장하기 위해서는 경량 S-box의 개발이 필수적이다. 2021년 이전까지 경량 4-bit S-box는 휴리스틱 방법으로 개발하고, 더 큰 크기의 경량 S-box는 확장구조 혹은 같은 연산을 반복하여 개발하는 것이 일반적이었다. 그러나 2022년 1월, MISTY 확장구조로 생성한 S-box보다 더 좋은 차분 균일성(Differential uniformity)과 선형성(Linearity)을 갖는 8-bit S-box를 찾을 수 있는 휴리스틱 알고리즘을 제안한 논문이 게재되었다[1]. 해당 논문에서 제안한 휴리스틱 알고리즘은 AND 연산자를 한 개씩 추가하면서 S-box를 생성하는데, AND 연산자를 추가할 때마다 차분 균일성을 계산하여 원하는 기준에 도달할 수 없는 S-box를 사전에 제거하는 방식을 사용한다. 본 논문에서는 이 휴리스틱 알고리즘의 성능을 향상한다. 차분 균일성뿐만 아니라 또 다른 차분성질을 사용하여 사전제거하는 양을 늘리고, 선형성을 계산하여 사전제거하는 프로세스를 추가함으로써 차분안전성뿐만 아니라 선형안전성까지도 동시에 만족할 수 있게 한다.

• 대한기계학회논문집A
• /
• 제30권7호
• /
• pp.816-825
• /
• 2006

This paper describes the development of a web-based interference verification system in the mold design process. Although several commercial CAD systems furnish interference verification functions, those systems are very expensive and inadequate to perform collaborative works over the Internet. In this paper, an efficient and precision hybrid interference verification algorithm for the web-based interference verification system over the distributed environment has been studied. The proposed system uses lightweight CAD files produced from the optimally transformed CAD data through ACIS kernel and InterOp. Collaborators related to the development of a new product are able to verify the interference verification over the Internet without commercial CAD systems. The system reduces production cost, errors and lead-time to the market. Validity of the developed system is confirmed through case studies.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2012년도 추계 학술논문 발표대회
• /
• pp.177-180
• /
• 2012

Korea residential housing generally use wet floor heating system 'Ondol' which consist of insulation cushioning, lightweight foamed concrete, hot water pipe and mortar on top of reinforced concrete slab. Wet floor heating system's installation process is too complicate and difficult to supervise field for continuing assurance quality. Also, this method has a huge impact on the progress of construction because it take a long time to cure finishing mortar and lightweight foamed concrete. Therefore, it is considered a disturbance factor of reduction of construction duration for enhancing competitiveness. In this study, we conducted an experiment about the radiant heat performance and temperature difference on upper panel of rolled dry floor heating systems which is jointly developed by Kolon global and Sumisho Metalex for remodeling housing, studio apartment and the urban-life housing.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1990년도 봄 학술발표회 논문집
• /
• pp.11-15
• /
• 1990

Results of an experimental study on the manufacture and the mechanical properties of carbon fiber reinforced fly ash-cement composites are presented in this paper. The carbon fiber reinforced fly ash-cement composites using silica powder and a small amount of Ethylene vinyl acetate emulsion are prepared with carbon fiber, foaming agents and curing conditions. As a result, the manufacturing process technology of carbon fiber reinforced fly ash-cement composites is developed. And the mechanical properties such as compressive, tensile and flexural strengths and drying shrinkage of lightweight carbon fiber reinforced fly ash-cement composites are improved by using a small amount of Ethylene vinyle acetate emulsion. The development and applications of precast products and the design systems of lightweight carbon fiber reinforced fly ash-cement composites are expected in the near future.

• 한국포장학회지
• /
• 제15권3호
• /
• pp.105-111
• /
• 2009

In this work, source reduction of poly ethylene terephthalate (PET) packaging are discussed as aspect of sustainability, such as reuse, refill and recycling through the various treatment methods and historical studies for municipal solid waste (MSW) disposal. Since PET has good chemical, physical and mechanical properties, and provides good oxygen and carbon dioxide barrier properties, PET is one of the most widely used thermoplastic polyester in the U.S. and around the world. As the demand for non-renewable PET is increasing, several approaches have been developed to meet economical feasibility and environmental responsibility without degrading material performance. Several companies, such as Coca-Cola Co., Easterform Packaging Co. and Kraft, have tried to develop lightweight PET bottle, and some of lightweight PET bottles are already commercialized. Reuse and refilling for PET container is well developed in Europe, such as Denmark, German and Netherland by supportive legislation and policies. Recycling process is the best way to economically reduce PET waste. In consequence, advanced technique and further development must be provided due to increasing PET packaging waste.