• 한국산학기술학회논문지
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• 제11권1호
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• pp.125-129
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• 2010

본 논문에서는 절전센서용 10GHz 대역 마이크로스트립 구형패치 배열 안테나의 설계 방법을 제안 하였다. 안테나는 송신안테나 $1{\times}2$배열, 수신안테나 $1{\times}2$배열로 각각 구성 하였다. 안테나는 CST MWS를 사용하여 시뮬레이션 하였고 FR-4 기판(h=1.0mm, ${\varepsilon}r=4.4$)을 사용하여 제작하였다. 시뮬레이션에서 대역폭은 4%(VSWR$\leq$2), 이득은 6.3dBi, 빔폭은 약 60o(El)/15o(Az)로 예측되었다. 시뮬레이션 결과를 이용하여 안테나가 제작되었고 안테나는 절전센서용 RF 송수신기 회로 뒷면에 설치되어 측정 되었다. 측정된 안테나의 대역폭은 7%(VSWR$\leq$2), 이득은 4.8dBi, 빔폭은 약 55o(El)/15o(Az)로 예상과 유사한 결과를 얻었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권3호
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• pp.149-155
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• 2006

This paper presents a torsional micromirror detached from PZT actuators (TMD), whose rotational motion is achieved by push bars in the PZT actuators detached from the micromirror. The push bar mechanism is intended to reduce the bending, tensile and torsional constraints generated by the conventional bending bar mechanism, where the torsional micromirror is attached to the PZT actuators (TMA). We have designed, fabricated and tested prototypes of TMDs for single-axis and dual-axis rotation, respectively. The single-axis TMD generates the static rotational angle of $6.1^{\circ}$ at 16 VDC, which is 6 times larger than that of single-axis TMA, $0.9^{\circ}$. However, the rotational response curve of TMD shows hysteresis due to the static friction between the cover and the push bar in the PZT actuator. We have shown that 63.2% of the hysteresis is due to the static friction caused by the initial contact force of the PZT actuaor. Without the initial contact force, the rotational response curve of TMD shows linear voltage-angle characteristics. The dual-axis TMD generates the static rotational angles of $5.5^{\circ}$ and $4.7^{\circ}$ in x-axis and y-axis, respectively at 16 VDC. The measured resonant frequencies of dual-axis TMD are $2.1\pm0.1$ kHz in x-axis and $1.7\pm0.1$ kHz in y-axis. The dual-axis TMD shows stable operation without severe wear for 21.6 million cycles driven by 16 Vp-p sinusoidal wave signal at room temperature.

• 한국해안·해양공학회논문집
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• 제22권2호
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• pp.73-78
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• 2010

파에너지는 쇄파되기 이전까지 주로 해저면과의 마찰력에 의하여 감소한다. 파마찰력을 산정하기 위한 연구는 여러 연구자들에 의해 진행되어 왔으며 어느 특정지점에서의 파마찰력 또는 파마찰손실률은 선형파이론으로 주어지는 해저면 입자유속과 연관된 파마찰계수의 도입으로 상당히 정확하게 간단하게 산정할 수 있다. 그러나 장구간에 걸쳐 파마찰력에 의하여 점차적으로 감소되는 파고변이는 상당한 반복 과정을 거쳐야 산정할 수 있었다. 본 연구에서는 기존 경험식을 이용해 전난류, 완난류 경우에 대해 일정경사면에서 천수효과와 마찰손실에 의한 파고 변화를 비교적 간단한 방법으로 추정하는 방법을 제시하였다. 해빈경사가 일정할 때 파고 변이률은 천수계수와 파고 마찰손실계수의 곱으로 간단히 구할 수 있다. 실제 해안과 비슷한 조건의 경우에 대하여 반복시산 과정으로 구한 수치와 간편 산정식으로 간단히 계산한 결과를 비교하여 제시하였다.

• Design & Manufacturing
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• 제2권1호
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• pp.33-38
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• 2008

As consumer in optics, electronics, aerospace and electronics industry grow, the demand for ultra precision aspherical surface lens increases higher. Precision turning with single-diamond tools has a long history of development for fabrication of optical quality surfaces since the advent of aerostatic rotary spindles and precise linear motion guide ways. To enhance the precision and productivity of ultra precision aspherical surface micro lens, the following specification of ultra precision grinding system is required: the highest rotational speed of the grinder is 100,000rpm and its turning accuracy is $0.1{\mu}m$, positioning accuracy is $0.1{\mu}m$. The development process of the grinding system for the ultra precision aspherical surface micro lens for optoelectronics industry is introduced. In the work reported in this paper, an intelligent grinding system for ultra precision aspherical surface machining was designed by considering the factors affecting the surface roughness and profiles accuracy. An aerostatic form was adopted to build the spindle of the workpiece and the spindle of grinder and ultra precision LM guide way was adopted in this system. And this paper deals with mirror grinding of an aspheric surface micro lens by resin bonded diamond wheel and spherical lens of BK7. It results was that a form accuracy of $0.6{\mu}m$ P-V and a surface roughness of $0.006{\mu}m$ Rmax.

• 한국운동역학회지
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• 제26권3호
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• pp.265-272
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• 2016

Objective: The aim of this study was to analyze X-factor, triple X-factor, and the center of pressure (COP) according to the feel of golf driver swing. Method: For this research, 9 golfers from the Korea Professional Golfers' Association (age: $30.11{\pm}2.98yrs$, height: $178.00{\pm}8.42cm$, weight: $76.22{\pm}8.42kg$, experience: $10.06{\pm}3.11yrs$) were recruited to participate in the experiment. Twelve Motion Analysis Eagle-4 cameras were installed and an image analysis was conducted by using the NLT (non-linear transformation) method, and 2 units of Kistler type 5233A dynamometer were used to measure ground reaction force. The sampling ratio was set at 1000 Hz. The golfers each took 10 swings by using their own driver, and chose the best and worse feel from among 10 shots. A paired-sample t-test was used to analyze the results. Results: In regard to feel, no change in head speed, X-factor, and the triple X-factor's X-factor stretch, hip rise, and head swivel, was observed (p>.05). Regarding ground reaction force, a difference was observed between the top of the backswing (p<.05) and impact (p<.05) in the vertical force of the left foot. For COP, a difference was also observed between the mid backswing (p<.001), late backswing (p<.001), and top of the backswing (p<.05) for the right foot X-axis and Y-axis mid follow through (p<.01). Conclusion: It can be reasoned that, irrespective of feel, the head speed, X-factor and triple X-factor's X-factor stretch, hip rise and head swivel did not have an effect on drive distance for domestic golfers, and the vertical reaction force of the left foot and left-right movement span's pressure dispersal of the right foot had an increasing effect on drive distance.

• 대한기계학회논문집B
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• 제31권3호
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• pp.209-216
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• 2007

Bacterial chemotaxis is essential to the study of structure and function of bacteria. Although many studies have accumulated the knowledge about chemotaxis in the past, the motion of a single bacterium has not been studied much yet. In this study, we have developed a device microfabricated by soft lithography and consisting of microfluidic channels. The microfluidic assay generates a concentration gradient of chemoattractant linearly in the main channel by only diffusion of the chemicals. Bacteria are injected into the main channel in a single row by hydrodynamic focusing technique. We measured the velocity of bacteria in response to a given concentration gradient of chemoattractant using the microfludic assay, optical systems with CCD camera and simple PTV (Particle Tracking Velocimetry) algorithm. The advantage of this assay and experiment is to measure the velocity of a single bacterium and to quantify the degree of chemotaxis by statistically analyzing the velocity at the same time. Specifically, we measured and analyzed the motility of Escherichia coli strain RP437 in response to various concentration gradients of L-aspartate statistically and quantitatively by using this microfluidic assay. We obtained the probability density of the velocity while RP437 cells are swimming and tumbling in the presence of the linear concentration gradient of L-aspartate, and quantified the degree of chemotaxis by analyzing the probability density.

• 대한기계학회논문집A
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• 제36권4호
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• pp.387-393
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• 2012

본 논문에서는 기존 랙-피니언 시스템의 랙 치형을 핀 또는 롤러로 대체한 롤러 랙 피니언 (RRP) 시스템의 표면피로 향상방안을 고찰하였다. 우선 전위계수(profile shift coefficient)를 고려하여 RRP 시스템의 캠 피니언(cam pinion)에 대한 엄밀 치형설계 방법 및 언더컷 방지 조건을 소개하였고, 이를 바탕으로 설계인자의 변화에 따른 하중 및 하중응력계수(load stress factor)의 변화를 검토하였다. 이를 통해 RRP 시스템의 표면 내구성을 향상시킬 수 있는 방안으로 전위계수의 증가가 효과적임을 알 수 있었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.572-578
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• 2003

The free vibration of a spinning flexible disk-spindle system supported by hydro dynamic bearings in a HDD is analyzed by FEM. The spinning flexible disk is described using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. It is discretized by annular sector element. The rotating spindle which includes the clamp, hub, permanent magnet and yoke, is modeled by Timoshenko beam including the gyroscopic effect. The flexible supporting structure with a complex shape which includes stator core, housing, base plate, sleeve and thrust pad is modeled by using a 4-node tetrahedron element with rotational degrees of freedom to satisfy the geometric compatibility. The dynamic coefficients of HDB are calculated from the HDB analysis program, which solves the perturbed Raynolds equation using FEM. Introducing the virtual nodes and the rigid link constraints defined in the center of HDB, beam elements of the shaft are connected to the solid elements of the sleeve and thrust pad through the spring and damper element. The global matrix equation obtained by assembling the finite element equations of each substructure is transformed to the state-space matrix-vector equation, and the associated eigenvalue problem is solved by using the restarted Arnoldi iteration method. The validity of this research is verified by comparing the numerical results of the natural frequencies with the experimental ones. Also the effect of supporting structures to the natural modes of the total HDD system is rigorously analyzed.

• 한국소음진동공학회논문집
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• 제22권11호
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• pp.1042-1048
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• 2012

A 2-axis gimbal system is one of main disturbance sources affecting image jitter response of a satellite. The gimbal system comprises azimuth stage and elevation stage, and these pointing mechanism can be rotated by stepping motors about its azimuth and elevation axes simultaneously. Because of the complex and coupled dynamic motion of the gimbal system, its moment of inertia and structural modes can be changed according to the system configuration, and thus the gimbal system generates complicated and non-linear disturbance characteristics. In order to improve the jitter response of a spacecraft, it is an indispensable process to reduce the micro-vibration disturbance level of the antenna system. In the present research, a 2-axis gimbal system was manufactured and then its micro-vibration test was performed in terms of two types of stepping motors(2-phase and 5-phase). The test results show that the disturbance level of the gimbal system can be reduced by replacing the 2-phase stepping motor with the 5-phase one, and the average disturbance attenuation ratio is 56 % in peak level and 48 % in standard deviation level. The experimental results confirm that it is an efficient jitter reduction method to adopt a high-phase stepping motor.

• 조명전기설비학회논문지
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• 제16권2호
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• pp.71-80
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• 2002

영구자석형 선형동기전동기(PMLSM)는 고속, 고추력의 직선추진이 가능하므로 산업현장에서 위치결정장치나 물류반송시스템 및 공작기계 등의 선형 서보 시스템에 이용이 되고 있다. 본 논문에서는 PMLSM의 AC 서보화를 위해 동기 프레임상에서 제어구조가 미리 설정된 스위칭 함수에 따라 불연속적으로 변화되는 가변구조 전류제어방식 및 간접 벡터제어이론을 기본으로하여 도달시간을 제거하고, 구동시스템의 추력 이용도를 높이기 위해 파라미터 변동과 한정된 외란에 거의 영향을 받지 않으며 오버슈트가 없는 고속응답을 실현하기 위해 슬라이딩 모드제어 알고리즘을 제안하여 PMLSM의 위치제어에 적용하고자 한다.