• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.38.3-38.3
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• 2021

We are developing an optomechanical design of infrared telescope for the CubeSat and Unmanned Aerial Vehicle (UAV) which adapts the Linear Astigmatism Free- Three Mirror System in the confocal off-axis condition. The small entrance pupil (diameter of 40 mm) and the fast telescope (f-number of 1.9) can survey large areas. The telescope structure consists of three mirror modules and a sensor module, which are assembled on the base frame. The mirror structure has duplex layers to minimize a surface deformation and physical size of a mirror mount. All the optomechanical parts and three freeform mirrors are made from the same material, i.e., aluminum 6061-T6. The Coefficient of Thermal Expansion matching single material structure makes the imaging performance to be independent of the thermal expansion. We investigated structural characteristics against external loads through Finite Element Analysis. We confirmed the mirror surface distortion by the gravity and screw tightening, and the overall contraction/expansion following the external temperature environment change (from -30℃ to +30℃).

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1673-1675
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• 2004

The design, modeling and measurement of RF switch module for GSM applications is presented in this paper. RF switch module is constructed using a LTCC multi-layer switching circuit and integrated low pass filter. Insertion and return loss of the low pass filter were designed less than 0.3 dB and better than 12.7 dB at 900 MHz. The RF switch module contained 10 embedded passives and 3 surface mount components integrated on $4.6{\times}4.8{\times}1.2$ mm, 6-layer multi-layer integrated circuit. The insertion loss of switch module was measured at 900 MHz was 11 dB.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.83-86
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• 2006

A grid-connected distributed generation system which consists of engine generator, dc link with multiple energy sources and inverter is proposed. All six of the stator leads of the generator, which is a surface mount permanent magnet machine, are brought out to the terminal of the generator. Three leads are connected to the inverter and the others are connected to the utility grid. In this proposed system the power from the engine-generator and the power from dc link can be controlled simultaneously by only one three-phase power converter. A control algorithm for the system is developed and verified by experiment results.

• Journal of Mechanical Science and Technology
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• v.16 no.12
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• pp.1664-1672
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• 2002

Gantry mechanisms have been widely used for precision manufacturing and material handling in electronics, nuclear, and automotive industries. Dual-drive servo mechanism is a way to increase control bandwidth, in which two primary axes aligned in parallel are synchronously driven by identical servo motors. With this mechanism, a flexible coupling (compliance mechanism) is often introduced in order to avoid the damage by the servo mismatch between the primary drives located at each side of gantry. This paper describes the design guidelines of the dual-drive servo mechanism with focus on its dynamic characteristics and control ramifications. That is, the effect on the system bandwidth which is critical on the system performance, the errors and torques exerted on guide ways in case of servo mismatch, the vibration characteristics concerned with dynamic error and settling time, and the driving force required at each axis for control are thoroughly investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.355-360
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• 1996

When the operational strains of a structure can not be directly measured in order to predict the life of the structure due to the problem of the attachment, those must be obtained indirectly. Since the displacement and the strain are interrelated, the strain can be predicted from the measured displacement and displacement-strain transformation matrix. The transformation matrix is dependent on the boundary condition, unfortunately, and it is also difficult to know exactly that of the operational system. In this study, for the structure with arbitrary boundary condition under the operation, the approximate method is proposed in order to predict the operational strains using the transformation matrix obtained by using free boundary conditions. And the method is applied to predict the strains of leads of surface mount component under the vibration of the printed circuit board.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.11 s.116
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• pp.1165-1171
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• 2006

This paper presents a new type of jetting dispenser for the integrated circuit (IC) fabrication and surface mount technology The proposed system is featured by the piezoelectric actuator and hydraulic magnification device. After describing structural component of the dispensing mechanism and its operation principle, both the fluid modeling and the hydraulic magnification modeling are undertaken with a lumped-parameter method based on the analogy of the fluid system and mechanical system. A mathematical governing equation is then derived by integrating the fluid model with the mechanical model of the driving piston and piezoelectric actuator. Subsequently, in order to achieve a desired dispensing amount, control algorithm adjusting duty cycle of the driving voltage is synthesized and control responses are presented in time domain.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1566-1570
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• 2005

The aspherical lenses are used as optical lens of HMD optical system. The optimum cutting condition of PMMA lens sample with ultra precision SPDT, the diamond tool nose radius, the cutting speed, the feed rate, the depth of cut, and cutting fluid type are found. The demanded surface roughness 10 nm Ra, aspherical form error $1.0\;\mu{m}$ P-V for aspherical lens of optical data storage device are satisfied.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.428-433
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• 2006

This paper presents a new type of jetting dispenser for the integrated circuit(IC) fabrication and surface mount technology. The proposed system is featured by the piezoelectric actuator and hydraulic magnification device. After describing structural component of the dispensing mechanism and its operation principle, both the fluid modeling and the hydraulic magnification modeling are undertaken with a lumped-parameter method based on the analogy of the fluid system and mechanical system. A mathematical governing equation is then derived by integrating the fluid model with the mechanical model of the driving piston and piezoelectric actuator. Subsequently, in order to achieve a desired dispensing amount, control algorithm adjusting duty cycle of the driving voltage is synthesized and control responses are presented in time domain.

• Smart Structures and Systems
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• v.4 no.5
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• pp.565-582
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• 2008

This paper presents a feasibility study of flexible piezoelectric paint for use in wide-band low-profile surface-mount or embeddable ultrasonic sensor for in situ structural health monitoring. Piezoelectric paint is a piezoelectric composite with 0-3 connectivity. Because of its ease of application, piezoelectric paint can be readily fabricated into sensing element with complex pattern. This study examines the characteristics of piezoelectric paint in acoustic emission signal and ultrasonic guided wave sensing. A series of ultrasonic tests including pitch catch and pencil break tests were performed to validate the ultrasonic wave sensing capability of piezoelectric paint. The results of finite element simulation of ultrasonic wave propagation, and acoustic emission generated by a pencil lead break on an aluminum plate are also presented in this paper along with corresponding experimental data. Based on the preliminary experimental results, the piezoelectric paint appears to offer a promising sensing material for use in real-time monitoring of crack initiation and propagation in both metallic and composite structures.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.83-89
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• 2014

Solder paste plays a crucial role as the widely used joining material in surface mount technology (SMT). The understanding of its behaviour and properties is essential to ensure the proper functioning of the electronic assemblies. The composition of the solder paste is known to be directly related to its rheological behaviour. This paper provides a brief overview of the solder paste behaviour of four different solder paste formulations, stencil printing processes, and techniques to characterize solder paste behaviour adequately. The solder pastes are based on the Sn-3.0Ag-0.5Cu alloy, are different in their particle size, metal content and flux system. The solder pastes are characterized in terms of solder particle size and shape as well as the rheological characterizations such as oscillatory sweep tests, viscosity, and creep recovery behaviour of pastes.