• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.8
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• pp.847-853
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• 2011

In this study, a hybrid powder-extrusion process involving the control of temperature dwelling time for improving the formability of Zn-22Al powder was developed and the effect of dwelling time on the mechanical properties of a spur gear with a pitch circle having a diameter of 1.8 mm was investigated. General extrusion experiments were carried out at different temperatures such as 290, 300, and $310^{\circ}C$. Spur gears with good qualities and without any surface defects were obtained in the case of extrusion temperature of $310^{\circ}C$ and ball-milling duration of 32 h. The Vickers hardness distribution was non-uniform, and after the sintering process, an internal crack was generated because of the different deformation energy between gear central part and teeth. To overcome the abovementioned problems, research on controlling the dwelling time of the extrusion temperature in the powder-extrusion process was carried out. Good-quality spur gears were obtained when the dwelling time was 15 min.

• The Korean Journal of Air & Space Law and Policy
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• v.20 no.2
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• pp.253-276
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• 2005

A pilot logbook is an essential data for proving pilot's flight experience. the reason for maintaining this information is to fulfill the requirement for pilot certificates, manage internationally shared career placement. this study focuses on the instrument flight related items among other flight time items which are included in a pilot logbook. By comparing the way of flight time logging among Korean Aviation Law, Federal Aviation Regulation and Joint Aviation Requirements, this study concludes intensively how to define items for flight time, to amend the definition and to apply the policy in Korea with respect to the pilot logbook.

• Journal of KIISE:Information Networking
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• v.35 no.5
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• pp.367-373
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• 2008

Recently, the NAT middlebox widely deployed in the home network environment prohibits DM operations from reaching user devices behind NAT. In this article, we focus on NAT issues to manage home network devices. Particularly, we discuss standardization efforts, and present our proposal to deploy DM services for VoIP and IPTV devices under NAT. By slightly changing behaviors of Simple Network Management Protocol (SNMP) Manager and Agent, and defining additional Management Objects (MOs) to gather NAT binding information, we could solve the NAT traversal problem under symmetric NAT. Moreover, we propose an enhanced method to search the UDP hole binding time of the NAT box. We applied our method to randomly selected 22 VoIP devices out of 194 NATed hosts in the real broadband network and have achieved 99% of the success ratio for exchanging SNMP request messages and 26% of enhancement for searching the UDP hole binding time.

• Proceedings of the KWS Conference
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• 2006.10a
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• pp.196-198
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• 2006

이 연구는 CBN을 건전한 브레이징을 하기 위해서, CBN과 금속필러메탈 접합계면에서의 금속성분과 산화물, 탄화물의 거동을 분석하는데 있다. 진공 인덕션 브레이징으로 온도는 $950{\sim}1100^{\circ}C$에서 브레이징 유지시간은 $5{\sim}30$분로 실시하였다. 금속필러로는 Ni-7Cr-3Fe-3B-4Si(wt.%)와 Ag-25Cu-5Ti(wt.%)을 사용하여 브레이징된 CBN은 $950{\sim}1000$도, 유지시간 10분 사이에서 각각 건전한 계면과 표면을 얻을 수 있었으며, 계면에서 Ti-rich상과 화합물이 확인되었다. 이상의 결과로 부터 화합물의 생성과 건전한 접합공정은 브레이징 온도와 시간이 좌우하며, N과 B, Ti의 함유량이 CBN의 브레이징 접합 특성의 중요변수로 생각되어진다. CBN과 Ni계/Ag계 브레이징 필러의 계면에서의 미세조직 및 화학반응의 메커니즘은 SEM, EPMA, XRD를 이용하여 분석하였다.

• Korean Journal of Materials Research
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• v.5 no.3
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• pp.288-296
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• 1995

본 연구에서는 석재공장 주변의 오염원으로 되고 있는 화강암 폐재의 고화체의 형성과 평가 기술에 관한 내용을 다루었다. 이를 위해, 최근 고화체의 함성기술로서 높이 평가받고 있는 수열 Hot press법을 이용하여 분말형태의 화강암 폐기물을 고화시키는데 필요한 조건을 찾아내었다. 아울러 고화체의 기계적 성질과 파면의 양상 및 수열실험동안 발생된 생성물 사이의 상호 관계를 고찰하였다. 고화체의 기계적 성질은 수열실험조건에 의존성이 있었으며, 적절한 고화조건은 반응온도 30$0^{\circ}C$, 유지시간 1시간이었다. 또한 고화체의 파면은 반응온도 및 유지시간에 따라 현저히 다른 양상을 보였으며, 수열실험동안 다양한 화합물이 생성되었다. 그 중에서 Xonotlite와 Talc는 고화체의 강도를 저하시키는 주된 화합물이었다.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.423-425
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• 2003

철도차량의 유지보수 분야에서 시간, 인력 등의 낭비요소를 제거하기 위한 효율적인 유지보수 업무를 수행할 수 있는 정보화시스템의 도입이 요구되고 있다. 그러나, 정보화시스템을 구축한 후 잘못된 정보의 입력, 이중 작업 등이 발생하면 또다른 시간적, 인적손실을 발생시킬 수 있다. 이를 방지하기 위하여 차상정보 수집을 위한 시스템에 무선통신기술을 적용하여 기초정보수집에 소요되는 인적, 시간적 손실을 최소화 하고 전동차 검 수고에서 전동차를 검수할 때 작업조회에서 작업결과 등록, 부품신청/조회 등에 무선단말기를 이용함으로써 효율적인 유지보수 작업이 될 수 있도록 한다.

• Food Science and Preservation
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• v.15 no.1
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• pp.15-20
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• 2008

By considering the storage temperatures of agricultural products, three types of PCMs $(K_1$, $K_2$, $K_3$) were developed to be used in temperature ranges of $0{\sim}5^{\circ}C$, $5{\sim}10^{\circ}C$ and $10{\sim}15^{\circ}C$, $K_1$ PCM for $0{\sim}5^{\circ}C$ was developed by mixture of $C_{14}H_{30}$ and soduim polyacrylate, and $K_2$ PCM for $5{\sim}10^{\circ}C$ and $K_3$ PCM for $10{\sim}15^{\circ}C$ were mixture of $C_{14}H_{30}$, $C_{18}H_{38}$ and soduim polyacrylate with different composition ratio. 'The target temperatures of cold chain system were set at $7^{\circ}C$, $13^{\circ}C$, and $17^{\circ}C$ with $K_{1-3}$, $K_{2-3}$ and $K_{3-1}$ PCMs, respectively. The times to reach the target temperatures in the storage chamber were 21 hours, 18 hours, and 61 hours with $K_1$, $K_2$, and $K_3$ PCMs, respectively. The performances of natural convection type and forced convection of the temperature controlled portable container were analyzed Apples were stored in the portable container of $5^{\circ}C$, and temperatures at surface and center were measured. The initial temperature of the apple was $25^{\circ}C$. The temperatures of apple at the surface and the center were $15^{\circ}C$ and $16^{\circ}C$, respectively, after 5 hours with natural convection type. However, the temperatures at the surface and the center were already reached to $7^{\circ}C$ within 1 hour with forced convection type. The forced convection type showed the better performance and the temperatures of portable container were maintained more than 15 hours.

• Korean Journal of Food Science and Technology
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• v.5 no.1
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• pp.36-41
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• 1973

Chemical changes with time of frying-fats during the frying process (beef tallow with 0.01% BHA and 0.01% BHT, turnover rate 9%/hr and $140{\pm}10^{\circ}C$ temperature) of Ramyon on a commercial scale were studied. No significant changes of carbonyl value and peroxide value were noted up to 120 hrs. However, small increases in acid value, color and dimeric fatty acid were noted. Small decreases in iodine value and the content of unsaturated fatty acids were also observed. Under the experimental storage condition, when the stability of fats heated were compared to fresh fat, minor differences in carbonyl value and weight gain were noted. All of these demonstrated that frying-fats commercially used in Ramyon frying system were maintained in good quality during the frying process.

• Journal of the Korean Geotechnical Society
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• v.40 no.4
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• pp.81-90
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• 2024

With the discovery of energy resources such as water ice on the Moon's surface, the Moon is attracting attention as an outpost for deep space exploration. As the concept of in situ resource utilization (ISRU) for establishing sustainable deep space exploration outposts gains traction, there is an increasing demand for technology to solidify lunar regolith as an in situ resource. In this study, sintered blocks were manufactured using a hybrid microwave sintering furnace. The effects of system configuration and dwell time on the microwave sintering efficiency were assessed. The results indicated that the composition of the SiC susceptor and its distance from the magnetron influenced the manufacturing of homogeneous sintered blocks. Additionally, varying the dwell time at a sintering temperature of 1,080℃ under optimal conditions revealed that exceeding the threshold dwell time caused the sintered blocks to become heterogeneous, thereby reducing the sintering efficiency.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.229-231
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• 2005

수 많은 노드들이 협력적인 작업을 통하여 이루어지는 무선 센서 망에서는 노드 하나 하나의 제한된 에너지를 효율적으로 사용하고 보다 오랜 시간 동안 망을 유지하는 것이 큰 이슈이다. 하지만 센서 망 안에 위치한 노드 하나 하나를 고려할 때 망이 유지되고 있다고 하더라도 그 노드가 목적된 지역을 모니터링 하지 못한다면 그 지역에서는 망이 유지되는 것이 의미가 없다. 따라서 본 논문에서는 센서 망의 라이프 타임 연장을 목적된 지역을 계속해서 모니터링 할 수 있을 때 망의 유지 시간 연장 이라는 관점에서 해석할 것이다. 이러한 관점에서 기존의 센서 앙 유지 프로토콜에서 망이 유지되는 한 모니터링 또한 계속해서 할 수 있는 방법을 제안한다.