• Information and Communications Magazine
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• v.32 no.3
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• pp.77-84
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• 2015

본고에서는 IEEE 802.11에서 표준화가 진행중인 1 GHz 이하 비면허 주파수에서 동작하는 무선랜(WLAN, Wireless LAN) 표준인 IEEE 802.11ah 무선랜 기술에 대해 알아본다. IEEE 802.11ah 는 스마트 그리드, 센서 네트워크, M2M(machine-to-machine) 통신, 셀룰러 오프로딩, 광역 무선랜 서비스 등을 주된 응용 분야로 고려하고 있으며 이러한 응용들은 기존 무선랜 기술대비 보다 확장된 커버리지, 보다 많은 수의 단말 지원, 저전력 동작 지원 등을 요구한다. IEEE 802.11ah는 이러한 요구 사항을 만족하기 위한 Sub 1 GHz 대역을 사용하는 무선랜 PHY 및 MAC 규격을 개발하였다. 본 고에서는 이러한 IEEE 802.11ah 무선랜의 주요 기술 요소들에 대해 살펴본다.

• Information and Communications Magazine
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• v.27 no.7
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• pp.29-35
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• 2010

도로상의 이동 중의 차량 등으로 구성된 차량간 애드혹 네트워크는 과거에는 볼 수 없었던 수준으로 인간과 주변 환경과의 소통을 가능케 해 줄 미래 사물지능통신(M2M: Machine-to-Machine)의 한 축으로써 많은 역할을 수행할 것으로 예상되고 가까운 미래에 현실화될 사물지능통신의 한예로서 많은 관심을 받고 있다. 도심 전역에 산재하는 무수한 차량들을 연결하여 다양한 서비스의 제공이 가능한 새로운 광대역 기간망등으로 활용될 수 있을 뿐 아니라 각기 차량에 설치된 센서들이 기존의 시스템으로는 채집 불가능했던 다양한 자료의 수집을 가능하게 하여 인간의 주변 환경에 대한 이해를 높이는데 도움을 줄 것이다. 차량간 애드혹 네트워크는 위상 변화가 매우 심하고 구성원이 무수한 대규모 네트워크라는 특성이 있어 기존의 네트워크에서 볼 수 없었던 이동성 기반 정보 확산 (mobility-assisted data dissemination) 기법 등 새로운 형태의 정보 전송 기법들이 활용될 것이다. 본고에서는 향후 차량간 애드혹 네트워크등의 사물지능통신의 기반 기술이 될 이동성 기반 정보 확산 기법에 대하여 소개하고 어떻게 차량간 애드혹 네트워크에서 활용되어 여러 서비스들의 구현이 가능한지 전자상거래 서비스들을 중심으로 설명한다.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.291-296
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• 2000

Liner DC motors are widely used for servo-actuator, which would be applied for semiconductor equipments and precise machining systems. we have been developed linear DC motor with high speed, acceleration and position accuracy. From performance test, the position accuracy. From performance test, the position and repeatability accuracy were able to be controlled with 10 ${\mu}{\textrm}{m}$ and $\pm$1 ${\mu}{\textrm}{m}$, respectively. The highest acceleration and speed were obtained 3 G and 2m/sec, respectively. Static thrust force was 270N, and then error was 25%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.6
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• pp.1040-1047
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• 2015

This study is investigated for M2M Communication Network Standard based on 3GPP. The environment of M2M communication, we can predict the new mobile service that gathering, handling, controlling, transferring of the data for Intelligence, so that we can consider new direction for a lot of subject of study development issue. This study is shown three types of M2M network structure and four types of use cases on 3GPP International Standard. In Addition, we can introduce the future M2M communication network model, it can be propagate the industry and academic cooperation with 3GPP standards. The suggestion develops multiple applications and multiple devices for industry and academic. With the deployment of network provider, this environment support our current communication market that the standard devices of M2M network and service requirement. We are suggest this study for grasp the initial market with the intellectual property right (IPR) based on International Standards. In the future, we wish the success that grap the initial market or initial academic study with helpful issue.

• Journal of Internet Computing and Services
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• v.17 no.6
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• pp.17-23
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• 2016

In the future network such as Internet of Things (IoT), the number of computing devices are expected to grow exponentially, and each of the things communicates with the others and acquires information by itself. Due to the growing interest in IoT applications, the broadcasting in Opportunistic ad-hoc networks such as Machine-to-Machine (M2M) is very important transmission strategy which allows fast data dissemination. In distributed networks for IoT, the energy efficiency of the nodes is a key factor in the network performance. In this paper, we propose a fuzzy logic based probabilistic multi-hop broadcast (FPMCAST) algorithm which statistically disseminates data accordingly to the remaining energy rate, the replication density rate of sending node, and the distance rate between sending and receiving nodes. In proposed FPMCAST, the inference engine is based the fuzzy rule base which is consists of 27 if-then rules. It maps input and output parameters to membership functions of input and output. The output of fuzzy system defines the fuzzy sets for rebroadcasting probability, and defuzzification is used to extract a numeric result from the fuzzy set. Here Center of Gravity (COG) method is used to defuzzify the fuzzy set. Then, the performance of FPMCAST is evaluated through a simulation study. From the simulation, we demonstrate that the proposed FPMCAST algorithm significantly outperforms flooding and gossiping algorithms. Specially, the FPMCAST algorithm has longer network lifetime because the residual energy of each node consumes evenly.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.11
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• pp.221-227
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• 2002

Tapping is a machining process that makes a female screw on parts to be assembly together. Recently, as the number of small and compact products increases the radius of tap as small as 1 mm is not unusual and more accurate tapping is needed. In complying with those needs, some high-speed tapping machines with synchronizing function have been developed. This paper describes the development of an ultra high-speed tapping machine up to 10,000rpm. The key factors in the tapping speed are the acceleration/deceleration and the synchronizing errors between spindle motor and fred motor. To minimize the acceleration/deceleration time, a low inertia spindle with a synchronous built-in servo motor was developed. To minimize the synchronizing errors, the tapping cycle algorithm was optimized on an open architecture CNC. The developed tapping machine has the acceleration/deceleration time of 0.13sec/10,000rpm for rigid tapping and the synchronizing error below 4.4%. The cycle time for tapping a female screw of M3 and depth 2 times diameter was 0.55sec.

• Electronics and Telecommunications Trends
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• v.30 no.4
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• pp.92-101
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• 2015

미래 전장은 정보 지식 기반의 첨단 전력체계를 확충하기 위해 향후 전력구조를 통합, 지휘통제통신(C4I) 체계와 생존성과 통합성이 향상된 전장의 네트워크중심전(NCW) 수행능력을 향상시킬 것이다. 사이버물리시스템(Cyber-Physical Systems: CPS)은 함정전투체계에 적용되고 있는 DDS를 포함하여 국방 M&S의 근간인 Live, Virture, Constructive(L-V-C) 체계의 큰 축을 형성하고 있다. 사물인터넷(Internet of Things: IoT) 기술은 센서네트워크, 통신, Radio Frequency Identification(RFID), Ubiquitous Sensor Network(USN), Machine to Machine(M2M), D2D 기술 및 상황인지, 지능서비스를 위한 정보수집/가공/융합/분석/예측기술을 포괄적으로 포함한 기술로서 미래산업을 이끌어 갈 차세대 선도 기술이며, 특히 군사적으로도 감시정찰 센서네트워크(USN), 견마형로봇, 경전투로봇과 무인기 기술 및 전술정보통신망체계(TICN) 등 첨단 통신네트워크 기술의 전력화 추세는 IoT 기술의 적용영역을 넓혀주고 있다. 감시정찰체계(Sensor)에서는 감시정찰 분야 영상정보 처리, 표적탐지 등과 관련된 IoT 기술 소요와 지휘통제통신(C4I) 체계의 상호운용성, 데이터링크, 지능형 통신체계 등 C4I 관련 IoT 기술 소요 및 타격체계(Shooter)의 내장형 SW 등 유 무인 무기체계 관련 IoT 기술의 소요가 증대될 것으로 예상된다. 본고는 CPS 및 IoT 기술의 군사적 활용방안 및 획득전략에 대한 적용기술 및 발전방향을 살펴본다.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.11
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• pp.1129-1137
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• 2013

We report a centerless grinding machine which can perform multi-function with 600 mm wide grinding wheels. By increasing manufacturing area, long workpiece such as camshaft and steering shaft, is allowed to grind more quickly, compared with cylindrical grinding system. In this paper, the design of centerless grinding machine puts emphasis on symmetry to exploit the thermal stability. Results of finite element analysis shows that the difference of the structural deflection in the front and rear guideways is less than $1.5{\mu}m$ due to symmetric design. The difference is less than $3.0{\mu}m$, even though the thermal deformation is considered. According to the performance evaluation, the radial error motion of the G/W spindle, which is measured by applying Donaldson Ball Reversal, is about 1.1${\mu}m$. The yaw error of the G/W slide is improved from 2.1 arcsec to 0.5 arcsec by readjusting the slide preload and ball screw.

• Journal of Biomedical Engineering Research
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• v.32 no.2
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• pp.151-157
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• 2011

Tattooing is a performance for decorative and cosmetic marking by placing permanent ink into the skin. As the cultural meaning of tattoo in Korea is changing, the tattoo machines are widely spread n permanent cosmetic market. Though the use of the tattoo machine was increased, the evaluation standards of tattoo machine were not existed. Korea Food and Drug Association regulated the electrical and mechanical safety standards which were founded on the IEC 601-1 second edition. Also they regulated he biological safety standards which were derived from the ISO 10993 series, however, these general valuations of common medical device were insufficient for evaluating tattoo machine. We developed the standards of tattoo machine for safety and performance evaluation for tattoo machine by preliminary hazard analysis in ISO 14971. The evaluation criteria of tattoo machines are focused on the mechanical invasion. We suggested the additional evaluation items of the needle speed, length, vibration with general valuation criteria of common medical device. We anticipate that this research may be a primary stage to figure a standard regulation and evaluation for tattoo machine.

• Journal of Sericultural and Entomological Science
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• v.13 no.2
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• pp.155-160
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• 1971

This experiment was carried out to investigate the cocoon reeling condiditions required to technical balance work on the automatic silk reeling machine. The results obtained were as follows. 1) Reasonable reeling velocity with regard to raw silk yield and to reeling efficiency varied according to cocoon reelability. It was observed to be about 150m/min on good reelability cocoon (850m of nonbreaking bave length), about 120m/min on medium reelability cocoon (650m of nonbreaking bave length) and from 90m/min to 120m/min on bad reelability cocoon (500m of nonbreaking bave length) 2) Low temperature drying of cocoon (T$_3$) improved the reelability of cocoon, but increased the reeling accidance with deteriorating the quality of raw silk more than the control(T$_1$) or high temperature drying of cocoon (T$_2$). No significant difference was observed in its raw silk yield and silk by-product with regard to cocoon drying temperature. 3) Incomplete drying of cocoon (T$_3$) improved the reelability of cocoon, but increased the reeling accidance with deteriorating the quality of raw silk more than the control(T$_1$) or over drying of cocoon(T$_2$). No significant difference was observed in its raw silk yield and silk by-product with regard to cocoon drying degree. It was cocoon drying condition of cocoon was the control(T$_1$) or high temperature(T$_2$) rather than low temperature (T$_3$) in cocoon drying process. Control (T$_1$) or over drying of cocoon (T$_2$) was adequate rather than incomplete drying of cocoon (T$_3$) for the improvement of the quality of raw silk on the automatic silk reeling process. 4) It was found that the reasonable cooking condition of cocoon was optimum cooking with 4$0^{\circ}C$ of reeling temperature or incomplete cooking with 45$^{\circ}C$ of the reeling temperature in the automatic silk reeling of the domestic cocoon.