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김연보,한우석,노용래 한국전기전자재료학회 2000 전기전자재료학회논문지 Vol.13 No.4
The conventional ultrasonic linear motors developed so far utilize a standing wave and are of a pi-type or a hybrid transducer type structure. Traveling wave type bi-direction linear motors have not been developed yet. This paper describes design of a new bi-directional ultrasonic linear motor working by means of a traveling wave. With the finite element method we design and verify validity of the new structure. And we determine its optimal structure size of design variables material and boundary conditions for proper generation of the traveling wave.
김연보,노용래,남효덕 경북대학교 센서기술연구소 1994 센서技術學術大會論文集 Vol.5 No.1
Most of conventional ultrasonic probes are constructed to generate either longitudinal or shear waves, but not combination of both waves. The ultrasonic probe that generates both of the longitudinal and shear waves simultaneously with a single PZT element was investigated. We studied the performance of a PZT element as a function of its rotation angle so that its efficiency is optimized to excite the two waves equally strongly. The results are verified by checking the impedance variation of the element with Finite Element Methods, and checking the wave form by Pulse-Echo test simulation. The validity of the theoretical calculation is verified through experiments.
等方性 Ba-ferrite 磁石의 混合方法에 따른 特性의 變化
김연보 대구대학교 산업기술연구소 1985 産業技術硏究 Vol.4 No.-
The effects of Mixing Methods on the solid-state reaction in the system BaCO₃-Fe₂O₃ and magnetic properties of Barium Ferrite Magnets were studied. Mixtures were prepared by partial precipitation mixing and ball mill mixing methods using two different Fe₂O₃ powders. The samples of cylindrical shape were calcined at temperature 1000℃ for 4 hours and fired in the air 2 hours each between 1100℃ and 1300℃ at 50℃ intervals. Techniques used were Thermo gravimetry and DC Magnetic hysteresis loop tracter. Volume shrinkage, fired density, variation in weight and some magnetic properties were studied in two differant mixing methods. It is shown that the mixing methods have marked effects on the solid-state reaction and magnetic properties during calculation. as also on subsequents firing.
Fe₂O₃와 BaCO₃의 反應에 미치는 Fe₂O₃粉體의 영향
김연보 대구대학교 산업기술연구소 1984 産業技術硏究 Vol.3 No.-
The effects of Fe₂O₃ particle size on the reaction between Ferric oxide and Barium carbonate were studied. Mixtures were prepared by partial presipitation mixing and ball-mill mixing methods using two different Fe₂O₃ powders. Techniques employed were X-ray diffraction analysis, termo-gravimetry and d.c. hysteresis loop tracer. It is shown that the particle size of Fe₂O₃ powder, as well as mixing method, have marked effects on the solid-state reaction and magnetic properties. The ferrite BaO·Fe₂O₃ results from the direct reaction of Barium carbonate with Ferric oxide at low temperatures. The reaction of BaO·Fe₂O₃ with Fe₂O₃ to give BaO·Fe₂O₃ requires higher temperatures. Possibility of using partial presipitation mixing in the large-scale production of Ba-ferrites has been proposed.
김연보,김종성 대구대학교 (한사대학) 산업기술연구소 1994 産業技術硏究 Vol.13 No.-
Aluminum-doped amorphous silicon carbide films were prepared by RF co-sputtering of SiC and Al-doped Sic. Auger electron spectroscopy(AES) and X-ray photoelectron spectroscopy(XPS) were used to determine composition of the resultant films. XPS results showed that concentration of aluminum around 1.0 atm % was achieved. Electrical conductivity was measured for a temperature range of 150 to 400K and subjected to Mott analysis. Conductivity of Al-doped a-SiC films was about five orders of magnitude higher that that of undoped films. Optical gap derived from the Tauc plot was 1.19 eV for Al-doped unhydrogenated film and 1.55 eV for hydrogenated film.
Sensor Circuit Design using Carbon Nanotube FET for Artificial Skin
김연보,김경기 한국산업정보학회 2014 한국산업정보학회논문지 Vol.19 No.3
This paper proposes a new sensor circuit using a 32 nm carbon nanotube FET (CNFET) technology for artificial skin. For future robotic and prosthetic applications, it is essential to develop a robust and low power artificial skin for detecting the environment through touch. Therefore, a sensor circuit for the artificial skin also has to be developed to detect the sensor signals and convert them into digital bits. The artificial skin sensor is based on a mesh of sensors consisting of a nxn matrix using CNFET, and the sensor outputs are connected to a current monitoring circuit proposed as the sensor circuit. The proposed sensor provides pressure measurements and shape information about pressure distribution.
김연보,류정탁 대구대학교 정보통신연구소 2003 情報通信硏究 Vol.1 No.2
In this study, we have investigated on the development of ultrasonic transducers with 2-2 mode piezocomposites that have better piezoelectric activity and lower acoustic impedance than those of conventional piezoceramics. The piezocomposite ultrasonic transducer can solve the traditional acoustic impedance mismatching problems without the help of matching layers. In this study we have designed optimal material properties of the piezocomposite, and volume fraction and geometric shape of the piezoceramic. The accoustic impedance of 2-2 mode piezocomposite was linearly decreased with PZT volume fraction. The electromechanical coupling factor(kt) was uniformed about 0.68 in the 0.2 to 0.6. When the volume fraction of PZT was 0.2 the accoustic impedance was 3.2 Mrayl.