• 대한기계학회논문집A
• /
• 제26권10호
• /
• pp.2034-2043
• /
• 2002

The process design to produce a near net shape home-appliance compressor component using semi-solid die casting process is performed. In order to obtain a good component without defects such as liquid segregation and porosity, the relationship between pressure and time, and plunger tip displacement and injection velocity are proposed with repeated trial and error. The effect of the velocity variation in the process parameters on liquid segregation and extraction is investigated to produce the aluminum frame part(a kind of compressor part) with good mechanical properties. The mechanical characteristic of semi-solid die casting formed parts for AlSi7Mg0.65r(A357) and AlSi17Cu4Mg(A390) are investigated with a view to minimizing the occurrence of defects. To investigate of application possibility at industry field, A380 aluminum alloy with 8∼9% silicon contents used for the squeeze casting process. The obtained mechanical properties is compared with semi-solid die casting.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제13권7호
• /
• pp.3550-3565
• /
• 2019

This paper proposes a new measurement method for the effective measurement of the 99% occupied bandwidth (OBW) at monitoring stations. Although the OBW measurement of radio signal is recommended by the International Telecommunication Union Radio (ITU-R) with several methods, there still does not exist a clear measurement recommendation or standard for terrestrial DTV signal on-air environment. Modified adjacent channel power ratio (MACPR), which can be applied to 8-VSB (Vestigial Side Band) DTV (Digital Television) signal, is herein defined to verify the results of measurements obtained using the proposed measurement method. MACPR is a proper measuring parameter for determining the measuring area of a monitoring station. From measurement results obtained in real field environment, it has been found that the OBW of 8-VSB DTV signal can be effectively measured in areas where the MACPR value is over 35 dB and when the measurements are repeated more than 600 times in the same reception site. It also has been verified that measured results are within an error range of +/-0.1% compared to results directly obtained at a transmission station. It is expected that the proposed method is able to be employed in order to determine the proper location of monitoring station and provide a reliable OBW measurement procedure for 8-VSB DTV signal on-air environment.

• 한국의사학회지
• /
• 제31권2호
• /
• pp.9-16
• /
• 2018

Eoyakwonbang is a collection of prescriptions of Yuyaoyuan, an imperial medical bureau of China. While the first edition of this book does not exist at present, two versions printed in Korea, and one printed in Japan, which is the well-known Gyesasingan Eoyakwonbang have been passed down. Eoyakwonbang is a meaningful text for the history of medical communication between China, Japan and Korea, but research on the different versions and contents of Eoyakwonbang have been insufficient. Out of the 2 versions published in Korea, Eulheja Eoyakwonbang is different from Gapjinja Eoyakwonbang [another version in Korea] and Gwanjeong Eoyakwonbang of Japan, in that the prescriptions are organized, the ingredients are organized according to the amount of each ingredient for each formula, and the amounts are recorded in an accurate manner. On the other hand, the Gapjinja version has many mistakes in the characters and content. The Gwanjeong version has lesser mistakes in characters, but repeats the content error of the Gapjinja version. Eulheja was printed after correction based on the original version or unknown version from China. Gapjinja was re-printed based on the Gyesasingan version, while Gwanjeong seems to have used the Gapjinja version as its original script, as the mistakes made in the Gapjinja version are repeated in the Gwanjeong version as well.

• 한국기계가공학회지
• /
• 제19권12호
• /
• pp.80-86
• /
• 2020

With the exception of welding activities, it is forbidden to use electricity in shipyards, owing to safety concerns such as the possibility of fire, explosions, and short circuits. In this paper, an automatic chamfering machine using pneumatics is proposed for use in such environments. Customers specify their requirements and the machine derives the corresponding theoretical design conditions. The proposed machine was used to perform 3D modeling, and its suitability and performance were confirmed via cutting experiments of the manufactured device. Two types of sensors may be used in this system: contact and non-contact. In the case of the contact type, an end-stop switch that can recognize the end of the material is installed, and when the machine reaches the end of the material, the end-stop switch is operated to cut off the air pressure. In the non-contact type, four sensors were used: photonic, ultrasonic, metal detection, and encoder. The use of the four sensors was repeated 30 times, and the average error determined. Thus, the optimum sensor was identified.

• 한국보육지원학회지
• /
• 제17권4호
• /
• pp.29-47
• /
• 2021

Objective: The purpose of this study was to understand the teacher's role as play supporter in a carry out play generated curriculum and develop and implement an action plan in order to indoor free play. Methods: Participants were 14 kindergartners (9 boys, 5 girls) and one teacher. Processes of planning-implementation and observation- reflection were repeated in a cyclical procedure and the 3rd action plan was conducted based on strategies to support children's play. Results: Children experienced the following: Continuing and immersive play, play filled with experiments and challenges, play to make together, attitude to enjoy novelty and respect differences, and play of trial and error. And the researcher changed the following: Be sensitive to the child's words and actions, finding the 'real interest' of children in 'waiting', acquiring the perception that 'children are the masters of play', seeing the value of learning in children's expressive play, and gain confidence in play support. Conclusion/Implications: This study suggested the need for teacher to have patience and demonstrate reflective thinking in order to support children's play.

• 한국컴퓨터정보학회논문지
• /
• 제27권9호
• /
• pp.77-89
• /
• 2022

본 논문에서는 RML 매핑 방식으로 구축한 RDF 지식 그래프의 구조를 묘사하고 검증할 용도의 SHACL 스키마를 자동으로 생성하는 시스템을 제안한다. 제안하는 시스템은 기존 연구와는 달리 RML 매핑 규칙 뿐만 아니라 RML 매핑의 입력인 CSV, JSON, XML, 데이터베이스와 같은 다양한 포맷의 데이터에서 추출한 메타데이터도 함께 사용하여 스키마를 생성한다. 따라서 기존 연구 기반의 스키마에서는 부재했던 데이터 타입, 문자열 길이, 값의 범위, 차수 관련 제약 조건이 스키마에 포함된다. 그리고 기존 연구에서 간과한 소위 반복된 속성 문제를 제안하는 시스템은 해결한다. 297개의 케이스로 구성된 적합성 테스트를 통해 제안된 시스템이 그래프에 대한 올바른 제약 조건을 생성함을 보여준다. 제안된 시스템은 오류가 발생하기 쉬운 기존 수동 검증 프로세스를 자동화하는 데 기여할 수 있다.

• 한국컴퓨터정보학회논문지
• /
• 제14권6호
• /
• pp.73-81
• /
• 2009

TCP는 혼잡이 발생하는 유선망에서는 항상 패킷 손실이 발생하지만, 혼잡 손실과 전송 에러 손싱을 분별할 수 있는 것은 아니다. 이는 송신자의 혼잡 윈도우 크기와 잃어버린 패킷의 재전송에 의해 무선망에서의 불필요한 TCP 성능 저하를 가져오게 된다는 가정을 유발한다. 또한 중복된 재전송은 이동 단말의 제한된 전원을 소비하게 한다. 본 논문에서는 네트워크 상태를 파악하고, 무선 애드혹 망에서의 에너지 효율과 TCP 성능 향상을 위한 혼잡을 방지하기 위한 알고리즘을 제안하였다. NS2를 이용하여 에너지 효율과 성능 향상을 이루어짐을 확인하였다.

• 대한임베디드공학회논문지
• /
• 제18권2호
• /
• pp.75-80
• /
• 2023

Unmanned drone stations for automatic charging have been developed in order to overcome the flying time limitation of rotary wing drones. Since the drone stations is an unmanned operating system, each of the drones will be required to have a high degree of landing accuracy. Drone precision landing has been mainly studied depended on image processing technologies, but the image processing systems make several problems, such as the mission weight, the drone cost, and the development complexity increases, and the flight time decrease. Thus, this paper researched accuracy of precision landing based on RTK (real time kinetics) for rotary wing drones. For the experiments of RTK based precision landing, a drone repeatedly performed three missions. The survey accuracies of the RTK about missions respectively were set as 0.3, 0.2, and 0.1 meters. Each mission has one take-off point, two way-points and one landing-point, and was repeated ten times. The experiment results revealed landing error distance means of around 0.258, 0.12 and 0.057 meters on each of RTK setting.

• 신재생에너지
• /
• 제18권1호
• /
• pp.17-28
• /
• 2022

This paper presents an effective Markov transition matrix (EMTM), which will be used to calculate the wind speed at the target site in a wind farm to accurately predict wind energy production. The existing MTS prediction method using a Markov transition matrix (MTM) exhibits a limitation where significant prediction variations are observed owing to random selection errors and its bin width. The proposed method selects the effective states of the MTM and refines its bin width to reduce the error of random selection during a gap filling procedure in MTS. The EMTM reduces the level of variation in the repeated prediction of wind speed by using the coefficient of variations and range of variations. In a case study, MTS exhibited better performance than other MCP models when EMTM was applied to estimate a one-day wind speed, by using mean relative and root mean square errors.

• Structural Engineering and Mechanics
• /
• 제88권5호
• /
• pp.501-519
• /
• 2023

This paper introduces a new hybrid structural connection joint that combines shear walls with section steel beams, fundamentally resolving the construction complexity issue of requiring pre-embedded connectors in the connection between shear walls and steel beams. Initially, a quasi-static loading scheme with load-deformation dual control was employed to conduct low-cycle repeated loading experiments on five new connection joints. Data was acquired using displacement and strain gauges to compare the energy dissipation coefficients of each specimen. The destruction process of the new connection joints was meticulously observed and recorded, delineating it into three stages. Hysteresis curves and skeleton curves of the joint specimens were plotted based on experimental results, summarizing the energy dissipation performance of the joints. It's noteworthy that the addition of shear walls led to an approximate 17% increase in the energy dissipation coefficient. The energy dissipation coefficients of dog-bone-shaped connection joints with shear walls and cover plates reached 2.043 and 2.059, respectively, exhibiting the most comprehensive hysteresis curves. Additionally, the impact of laminated steel plates covering composite concrete floors on the stiffness of semi-rigid joint ends under excessive stretching should not be disregarded. A comparison with finite element analysis results yielded an error of merely 2.2%, offering substantial evidence for the wide-ranging application prospects of this innovative joint in seismic performance.