• 한국생산제조학회지
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• 제19권6호
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• pp.889-894
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• 2010

Conventional shrink-fit tool holders have positive features, such as high accuracy, high strength, high stiffness and low sensitivity to centrifugal forces, but they require heavy investments for heating and cooling equipment. Generally the heating equipment has to heat the tool holder up to $200{\sim}300^{\circ}C$ for tool changes. This paper introduces a novel shrink-fit tool holder that is able to unclamp a tool at $40{\sim}50^{\circ}C$. This feature makes it possible to switch between the clamped and unclamped states by using a simple device, which has lower power, smaller size and lower cost than the heating equipment of the conventional shrink-fit tool holders. The proposed shrink-fit tool holder is able to expand its tool hole by using the shape memory alloys which are integrated in the tool holder body. Performances of the SMA shrink-fit tool holder were evaluated experimentally. The experimental results confirm that the proposed tool holder is feasible in aspects of clamping/unclamping operations, clamping force and repeatability of tool setup.

• 한국항행학회논문지
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• 제16권2호
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• pp.271-277
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• 2012

본 논문에서는 재난모니터링, 환경감시 및 재난구호 등의 정보 수집 및 정찰 등의 임무를 수행하는 다수의 UAV들로 구성된 편대비행 네트워크를 위해 동적 트리 형성 프로토콜을 제안하였다. 특히 무선 동적 환경에 적응한 최적의 트리를 구성하기 위한 링크 비용을 구하기 위해 거리에 따른 무선 신호 감쇄현상을 적용하여 Hop-LQI Weight 알고리즘을 고안하였으며 이를 MSP430 K-mote 센서 플랫폼에 TinyOS 코드를 구현하였다. 이를 무선 통신에서 링크 비용 산출 기법인 Minimum LQI 방법과 노드 수에 따른 평균 경로 설정시간을 비교를 통하여 성능을 검증하였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.111.1-111.1
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• 2011

Recently, comsumption of fossil fuel is causing many problems(oilflation, global warming, environmental pollution). For this reason Renewable energy is now becoming the center of interest as a solution to these problems. Bioethanol, especially, is able to substitute petroleum as fuel; making it a viable and promising renewable energy. In order to production of fuel bioethanol, Dehydration process is essential. Azeotropic distillation, extractive and pressure swing absorption(PSA) process are some of possible dehydration process, out of which, PSA process is attractive since it required less energy and lower setup cost. In this study, we produced fuel bioethanol using 2-step PSA(3 bed + 2 bed) process for more efficient and economical process. Through this study, we produced fuel bioethanol using 2-step PSA process and concentration of fuel bioethanol was 99.54wt%(feed ethanol: 92.4wt%). We expected that because of efficient use of absorbents(zeolite), 2 step PSA process contribute to economical operation.

• 한국자동차공학회논문집
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• 제15권3호
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• pp.99-105
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• 2007

Currently, BLDC fuel pump was applied on LPi vehicle using 3rd fuel supply system as liquified phase LPG injection method had already shown better performance than others. Its cost, however, is rather expensive because of drawbacks such as complicated structure, a fault of localization of system. In this work, demonstration system for a developed turbine type fuel pump to replace BLDC system was setup and investigated. This study results that fuel mass flow rate of turbine type pump and injection performance of injector were better compared to BLDC type. Comparing flow rate of summer LPG with that of winter LPG, the flow rate decreased about 25% using winter LPG. Performance applying turbine type LPi fuel pump to engine is confirmed.

• Mass Spectrometry Letters
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• 제3권4호
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• pp.87-92
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• 2012

In this study, we explored a new approach for generating ions of organics and biomolecules using contactless atmospheric pressure ionization (C-API). That is, a tapered capillary (~20 cm) was connected to a syringe, which was coupled to a syringe pump for providing a given flow rate to introduce sample solution to the proximity of a mass spectrometer. The gas phase ions derived from analytes were readily formed in the capillary outlet, which was very close to the mass spectrometer (~1 mm). No external electric connection was applied on the capillary emitter. This setup is very simple, but it can function as an ion source. This approach can be readily used for the analysis of small molecules such as amino acids and large molecules such as peptides and proteins. The limit of the detection of this approach was estimated to be ~10 pM when using bradykinin as the sample. Thus, we believe that this approach should be very useful for being used as an alternative ion source because of its low cost, high sensitivity, simplicity, and ease of operation.

• 디지털산업정보학회논문지
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• 제14권3호
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• pp.29-38
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• 2018

It is the approach of embedded system design that analyzes COS(Cut Out Switch) failure in the power distribution and an instantaneous breakdown of power distribution supply could cause the weakness of industrial competence and therefore we need to feed the stable power distribution with developing the technology of open-source embedded system. In this paper, we apply the LoRa technology which is the Internet of Things(IoT) protocol for low data rate, low power, low cost and long range sensor applications. We designed the hardware and software architecture setup and experimented the embedded system with network architecture and COS monitoring system including accelerometer for detecting the failure of distribution line and sensing the failure of its fuse holder by recognizing the variation and collision and afterwards sending the information to a gateway. With experimenting we designed the embedded platform for sensing the variation and collision according to the COS failure, monitoring its fuse holder status and transferring the information of states with LoRa technology.

• 한국산업융합학회 논문집
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• 제11권4호
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• pp.165-170
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• 2008

The demand for the lighter parts compels new composite materials composed of nylon66 and glass fiber to be used for the clutch control hydraulic system to achieve the low cost, light weight and the simple production process. In this paper the feasibility of using those composite materials for the clutch system has been investigated. And the efforts have been concentrated to enhance the durability and the credibility of the system. The procedure has been developed to design the clutch system to satisfy the categories mentioned above and to analyze the durability of the system and to setup a simulation program for the realistic driving situations.

• 인터넷정보학회논문지
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• 제9권1호
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• pp.1-8
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• 2008

Fost Hondovers for Mobile IPv6 (FMIPv6) 는 Mobile IPv6의 끊김 없는 핸드오버를 위해 제안된 프로토콜이다. 하지만 FMIPv6 의 보안의 취약점을 보완할 수 있는 메커니즘은 현재 미비한 상태이다. FMIPv6의 인증을 위한 현재까지의 대부분의 연구는 Authentication Authorization Accounting (AAA) (5) 또는 공인인증서와 (6) 같은 비대칭 암호알고리즘을 활용하는 Public Key Infrastructure (PKI)와 같은 기술들에 집중 되어있다. 이러한 기술들은 한정된 서비스 도메인만 적용할 수 있거나 복잡한 암호 수식을 처리하지 못하는 단말기에는 적용할 수 없다는 한계점을 가지고 있다. 따라서 본 논문은 Mobile IPv6의 기본 프로토콜인 Return Routability 만을 사용하여 인증에 필요한 별도의 인프라스트럭처나 많은 처리비용이 필요한 암호 알고리즘 없이 FMIPv6의 인증 메커니즘을 제공하는 방법을 제안한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권5호
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• pp.2499-2522
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• 2017

Multi-hop networks are a low-setup-cost solution for enlarging an area of network coverage through multi-hop routing. Carrier sense multiple access with collision avoidance (CSMA/CA) is frequently used in multi-hop networks. Multi-hop networks face multiple problems, such as a rise in contention for the medium, and packet loss under heavy-load, saturated conditions, which consumes more bandwidth due to re-transmissions. The number of re-transmissions carried out in a multi-hop network plays a major role in the achievable quality of service (QoS). This paper presents a statistical, analytical model for the end-to-end delay of contention-based medium access control (MAC) strategies. These strategies schedule a packet before performing the back-off contention for both differentiated heterogeneous data and homogeneous data under saturation conditions. The analytical model is an application of Markov chain theory and queuing theory. The M/M/1 model is used to derive access queue waiting times, and an absorbing Markov chain is used to determine the expected number of re-transmissions in a multi-hop scenario. This is then used to calculate the expected end-to-end delay. The prediction by the proposed model is compared to the simulation results, and shows close correlation for the different test cases with different arrival rates.

• 한국시뮬레이션학회논문지
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• 제17권1호
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• pp.1-8
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• 2008

센서 네트워크에서 싱크가 이동성을 가지게 되면, 네트워크의 라우팅에 변화가 그렇지 않은 경우 보다 심화된다. 이동싱크의 경우 센서 네트워크 지역을 지속적으로 이동하기 때문에 소스 센서 노드와의 통신상에서도 경로 변경이 발생하게 된다. 싱크의 이동으로 인한 경로변경은 많은 오버헤드를 부과할 수 있기 때문에 동적인 경로 변경에 대처하는 방안이 요구된다. 본 논문에서는 이러한 동적인 경로 변경을 위하여 사전 경로변경 방식을 제안한다. 동적 경로변경의 계산은 이동 싱크가 수행하여 네트워크의 오버헤드를 줄이며, 물리적 경로변경 이전에 경로를 배정함으로써 경로변경에 따른 지연을 최소화하고자 한다.