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RISS 인기검색어
- 검색키워드
- 저자 : Kee-Joe Lim (검색결과 225 건)
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김유민, 이한주, 오진헌, 임기조 충북대학교 컴퓨터정보통신연구소 2012 컴퓨터정보통신연구 Vol.20 No.1
In this paper, a novel type ultrasonic linear motor is proposed. The proposed motor consists of a ring type stator and a mover. They have spirals on their inner and outer surface, respectively. Along the spiral, a mover is travelled by a travelling extensional vibration mode of a ring type stator. Hence, a linear up-and-down motion is possible. Through the experimental results, we can verify the applicability regarding the autofocus lens driver. keywords : Ultrasonic linear motor, Autofocusing driver, ring type stator
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전기절연유의 절연파괴에 미치는 전극간격 및 곡률반경의 영향
강성화,채홍인,이종필,임기조 한국안전학회 2004 한국안전학회지 Vol.19 No.1
In this paper, we investigated the influence of gap length and tip radius on breakdown of mineral based insulation oil. Applied voltages were DC and AC voltage. Electrode system was needle-plane structure. The tip radius of needle electrode was 5, 10, 20 and 25μm, respectively. We measured breakdown voltage for each of tip radius with increasing electrode gap, 2mm to 12mm. Electric breakdown strength at tip was calculated using Mason's equation contained geometric figure. As gap length increased, breakdown strength increased linearly. But, as tip radius of needle increased, breakdown strength decreased exponentially. It can be explained by the phenomenon that electron is easily injected, as tip radius increases, and effective work function decreases. When appling DC voltage, breakdown strength was higher when polarity of needle was negative than positive. It is because of the space charge effect in accordance with the influence of liquid motion.
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이청,김기엽,류부형,임기조 한국안전학회 2003 한국안전학회지 Vol.18 No.2
Radiation degradation of crosslinked polyethylene(XLPE) was investigated using thermogravimetric analysis (TGA), The results of TGA were compared with FT-IR, melting temperature, oxidation induction time, and elongation al break on the XLPE exposed by γ-ray. 5% decomposition temperature of γ-ray irradiated XLPE showed similar tendencies with the case of elongation at break. Both properties agreed below 1000 kGy, however, did not show any remarkable characteristics above 1000 kGy, these properties can be useful to evaluate the radiation degradation of XLPE for only low irradiated region. Above 1000 kGy, the thermal decomposition activation energy showed decreased, on the contrary, increasing below 1000 kGy. Compared with FT-IR spectrum of irradiated XLPE, it was confirmed that the oxidation reaction was still occurring below 1000 kGy. Radiation degradation of XLPE was dependent upon the irradiation doses, TGA can be a useful tool to evaluate the degradation.
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Characteristics of a Miniaturized Ultrasonic Motor for Auto-focusing of a Mobile Phone
Lim Kee-Joe,Lee Jong-Sub,Kang Seong-Hwa The Korean Institute of Electrical Engineers 2006 Journal of Electrical Engineering & Technology Vol.1 No.1
In this paper, the design and characteristics of a novel ultrasonic motor are investigated. Such a motor is appropriate far use in the optical zoom or auto focusing functions of the lens system in mobile phones. Its design and simulation of performances are carried out by FEM commercial software (ATILA). The shape of the motor is similar to a square without one side, on which an optical lens can be mounted. Two sheets of piezoelectric ceramics are adhered to both sides of two legs of the elastic body, respectively To drive the ultrasonic motor, the voltage is applied to two sheets of piezoelectric ceramics bonded to one leg. The rotation direction can be easily changed by switching the piezoelectric sheets bonded to the other leg, to which voltage is applied. A proto type of the motor is fabricated and its outer size is $10^*10^*2[mm3]$ including the camera lens of which the diameter is 7.5(mm). Its power consumption is about 0.3[W] and the speed of rotation is adjustable from 10 to 200[rpm] according to the applied voltage
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Characteristics of Disk-type Linear Ultrasonic Motor for Application to x-y Stage
Lim Kee-Joe,Park Seong-Bee,Yun Yong-Jin,Lee Kee-Young,Kang Seong-Hwa,Lee Jong-Sub,Jeong Su-Hyun The Korean Institute of Electrical Engineers 2006 Journal of Electrical Engineering & Technology Vol.1 No.1
In this paper, a disk-type ultrasonic motor using a combination of radial and bending vibration modes is newly designed and fabricated. The characteristics of the test motor are also measured. By means of traveling elastic wave induced at the surface of circumference of the elastic disk, a steel bar in contact with the surface of circumference of the elastic disk bonded onto the piezoelectric ceramic disks is driven in both directions by changing the sine and cosine voltage inputs. The stator of the motor is composed of two sheets of piezoelectric ceramic disks to bond onto both surfaces of an elastic disk, respectively. As a result, the diameter of the elastic body is increased and the resonant frequency is decreased. The resonant frequency of the stator is about 92 kHz, which is composed with piezoelectric ceramic disks of 28 mm in diameter and 2 mm in thickness, and an elastic body of 32 mm in diameter and 2 mm in thickness. A driving voltage of 20 VPP Produces 200 rpm with a torque of 1Nm and an efficiency of about 10%.
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Step-down Piezoelectric Transformer Using PZT PMNS Ceramics
Lim Kee-Joe,Park Seong-Hee,Kwon Oh-Deok,Kang Seong-Hwa The Korean Institute of Electrical Engineers 2005 KIEE International Transactions on Electrophysics Vol.5C No.3
Piezoelectric transformers(PT) are expected to be small, thin and highly efficient, and which are attractive as a transformer with high power density for step down voltage. For these reasons, we have attempted to develop a step-down PT for the miniaturized adaptor. We propose a PT, operating in thickness extensional vibration mode for step-down voltage. This PT consists of a multi-layered construction in the thickness direction. In order to develop the step-down PT of 10 W class and turn ratio of 0.1 with high efficiency and miniaturization, the piezoelectric ceramics and PT designs are estimated with a variety of characteristics. The basic composition of piezoelectric ceramics consists of ternary yPb(Zr$_{x}$Ti$_{1-x}$)O$_{3}$-(1-y)Pb(Mn$_{1/3}$Nb1$_{1/3}$Sb$_{1/3}$)O$_{3}$. In the piezoelectric characteristics evaluations, at y=0.95 and x=0.505, the electromechanical coupling factor(K$_{p}$) is 58$\%$, piezoelectric strain constant(d$_{33}$) is 270 pC/N, mechanical quality factor(Qr$_{m}$) is 1520, permittivity($\varepsilon$/ 0) is 1500, and Curie temperature is 350 $^{\circ}C$. At y = 0.90 and x = 0.500, kp is 56$\%$, d33 is 250 pC/N, Q$_{m}$ is 1820, $\varepsilon$$_{33}$$^{T}$/$\varepsilon$$_{0}$ is 1120, and Curie temperature is 290 $^{\circ}C$. It shows the excellent properties at morphotropic phase boundary regions. PZT-PMNS ceramic may be available for high power piezoelectric devices such as PTs. The design of step-down PTs for adaptor proposes a multi-layer structure to overcome some structural defects of conventional PTs. In order to design PTs and analyze their performances, the finite element analysis and equivalent circuit analysis method are applied. The maximum peak of gain G as a first mode for thickness extensional vibration occurs near 0.85 MHz at load resistance of 10 .The peak of second mode at 1.7 MHz is 0.12 and the efficiency is 92$\%$.
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Characteristics of π-shaped Ultrasonic Motor
Lim Kee-Joe,Park Seong-Hee,Yun Yong-Jin,Park Cheol-Hyun,Kang Seong-Hwa,Lee Jong-Sub The Korean Institute of Electrical Engineers 2006 Journal of Electrical Engineering & Technology Vol.1 No.2
In this paper, the design and characteristics of a $\pi-shaped$ ultrasonic motor that is applicable to optical zoom operation of a lens system for mobile phones are investigated. Its design and simulation of performances are carried out by FEM (finite element method) commercial software. As a simulation result, by applying voltage with single phase, a combined vibration is produced at the surface of a stator arm. A prototype of the motor is fabricated and its outer size is $8*4*2mm^3$ including the cylindrical steel rod of 2 mm in diameter as the rotor. The motor exhibits a maximum speed of 500 rpm and a power consumption of 0.3 W when driven at 20 Vpp and 64 kHz.
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