• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.36-40
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• 2008

Minimization of nozzle induces many flow losses in micro-propulsion system. In this study, we studied about thermal transpiration based new conceptual micro propulsion system to overcome these losses. Thermal transpiration device(Knudsen pump) having no moving parts can self-pump the gaseous propellant by temperature gradient only (cold to hot). We designed, fabricated the knudsen pump and analyzed pressure gradient efficiency of membrane according to Knudsen number under vacuum condition. In this paper, we compared mass flow rate of Knudsen pump by using different membrane type ; Polyimide and Hangi, Korean traditional paper.

• Journal of Platform Technology
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• v.6 no.4
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• pp.41-48
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• 2018

Accidents involving infants and toddlers are occurring frequently, and if elementary measures are not smooth, they can lead to even greater accidents. Rapid elementary measures require an appropriate monitoring system, and it is necessary to build a system that can accurately monitor the child's living condition and notify the emergency situation immediately. Recently, with the development of IoT technology, various types of sensors are being developed in a very small size, and development of wearable devices connected with smart phones is accelerating with the development of smart phones. By using these wearable devices, it is possible to reduce the risk of infant accidents and to respond promptly in case of an accident. In this paper, we propose a wearable system that can monitor the infant condition and present a service to prevent infant accidents.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.15-20
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• 2019

Due to evolving IoT technologies, the various application services using clothing, sport equipment, and wearable devices equipped with extream small communication devices have been actively developed. On the other hands, since these serveices requires long distance communications, Long Distance wireless communication technology LPWAN Research has been proceeded due to limitation of the commuication distance of Wi-Fi and Zigbee which were considered as representative technologies for IoT. Iin this paper, we introduces LoRa technology in detail, which is a non-band network technology among LPWAN technologies, and investigates the use cases of domestic as well as international countries.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.1
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• pp.81-89
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• 1999

The fabrication process for miniaturizing the Electronic Article Surveillance (EAS) sensor was studied using micromachining technique. Two types of sensor structure, free standing membrane type and diving beard type, were proposed and researched for establishing the fabrication process. The membrane type structure was easy to change the sensor shape but had the limitation for miniaturizing, because the size of the sensor depends on the silicon substrate thickness. The diving board type structure has the advantage of miniaturization and of free motion. Since the elastic modulus is not trio high, SiN film is expected to be adequate for the supporting membrane of magnetic sensor. The selectivity of $H_2O_2$for sputtered W with respect to Fe-B-Si, which was studded for magnetic sensor materials, was high enough to be removed after using as a protection layer. Therefore, the diving board type process using the silicon nitride film for the supporter of the sensor material and the sputtered W for protection layer is expected to be useful fur miniaturizing the Electronic Article Surveillance (EAS) sensor.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.4
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• pp.15-20
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• 2016

Write amplification is a critical factor that limits the stable performance of flash-based storage systems. To reduce write amplification, this paper presents a new technique that cooperatively manages data in flash storage and nonvolatile memory (NVM). Our scheme basically considers NVM as the cache of flash storage, but allows the original data in flash storage to be invalidated if there is a cached copy in NVM, which can temporarily serve as the original data. This scheme eliminates the copy-out operation for a substantial number of cached data, thereby enhancing garbage collection efficiency. Experimental results show that the proposed scheme reduces the copy-out overhead of garbage collection by 51.4% and decreases the standard deviation of response time by 35.4% on average.

• Journal of Astronomy and Space Sciences
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• v.24 no.2
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• pp.155-166
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• 2007

We have designed a high resolution proton and electron telescope for the detection of high energy particles, which constitute a major part of the space environment. The flux of the particles, in the satellite orbits, can vary abruptly according to the position and solar activities. In this study, a conceptual design of the detector, for adapting these variations with a high energy resolution, was made and the performance was estimated. In addition, a parallel processing algorithm was devised and embodied using FPGA for the high speed data processing, capable of detecting high flux without losing energy resolution, on board a satellite.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9B
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• pp.832-844
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• 2008

Distributed localization algorithms are necessary for large-scale wireless sensor network applications. In this paper, we introduce an efficient node distribution based localization algorithm that emphasizes simple refinement and low system load for low-cost and low-rate wireless sensors. Each node adaptively chooses neighbor nodes for sensors, update its position estimate by minimizing a local cost function and then passes this update to the neighbor nodes. The update process considers a distribution of nodes for large-scale networks which have same density in a unit area for optimizing the system performance. Neighbor nodes are selected within a range which provides the smallest received signal strength error based on the real experiments. MATLAB simulation showed that the proposed algorithm is more accurate than trilateration and les complex than multidimensional scaling. The implementation on MicaZ using TinyOS-2.x confirmed the practicality of the proposed algorithm.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06d
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• pp.455-460
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• 2008

건설교통부는 국가미래에 대비해 실질적으로 기여할 수 있는 전략적이고 중장기적인 실효성 있는 R&D 혁신 로드맵인 VC-10 사업을 진행하고 있다. 이 과제의 핵심 기술 중에 하나인 유비쿼터스 센서네트워크는 초소형 센서들로 구성된 망으로써 환경 및 재난 재해, u-City 건설, 스마트 하이웨이, 방범 및 국방, 시설 관리, 유통, 등과 같은 다양한 분야에 사용할 수 있는 유비쿼터스 사회의 핵심 요소이다. 이것은 실시간 네트워크를 통해 전송 또는 관리되고 언제, 어디서나, 어떠한 대상과 의사소통이 가능한 지능형 컴퓨팅 환경을 구현하는 것이다. 그러나 이러한 기술을 바탕으로 하는 기존의 시스템들은 특정분야를 위한 독자적인 프로토콜이나 저전력 통신을 제공하는 ZigBee 기반으로 설계되었기 때문에 소규모 범위에서만 서비스 제공이 가능하며 시스템간의 연동이 어렵다. 따라서 본 논문에서는 유비쿼터스 센서네트워크간의 연동성을 고려한 대규모 실시간 모니터링 시스템을 설계하여 다양한 분야로 서비스할 수 있는 테스트베드 구축에 대한 방안을 제시하고자 한다. 여기서 모니터링 대상은 국토의 지반, 환경, 그리고 도심지역 등이다. 이렇게 제시된 방안은 국내실정에 적합한 모니터링 시나리오를 작성하여 테스트베드를 구축 시에 요구된 사항들에 대한 정당성을 입증한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.5
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• pp.154-161
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• 2009

Recently, as many functional blocks are integrated on a small area the high speed integrated circuits emerge as a critical electromagnetic interferer which causes mal-function of adjacent circuitries and lowers the sensitivity of the wireless receivers. Therefore, it is necessary to devise an precise analyzing tool to pinpoint the major electromagnetic noise contributor among the internal circuit blocks of high speed IC's. This paper presents the design, fabrication, and measurement results of the high resolution magnetic field probe which can measure the current density on the IC surface. In order to achieve the high resolution, the magnetic field probe is fabricated using 3-metal semiconductor process so that its thickness is reduced by 10% than that of conventional works. Through the magnetostatic analysis and EM simulation, spatial resolution and sensitivity to the nonmagnetic field components are analyzed. Experimentally, it is found that the fabricated probe can measure the current density on the IC surface with $210{\mu}m$-spatial-resolution.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.1
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• pp.209-218
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• 2017

Healthcare services can be provided through a number of independent service platforms for measurement of vital signs, diagnosis and prevention of diseases, and Information and communication technology(ICT) such as internet and mobile are converged to provide health information to users at anytime and anywhere, and it is in the center of the IoT(Internet of things). Accordingly, in this paper, we designed IoT based urination management system and evaluate the performance. A low - power Zigbee network was constructed for the configuration of the urination management system. The implemented capacitive diaper sensor was operable for the duration of 2,000 hours. We also built a database server using Raspberry Pi, a tiny embedded device, and stored the collected data to verify the data through an Android-based mobile application. The proposed urination management system can be utilized not only for the older patients, but also for the infants.