• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.1003-1006
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• 2002

In machining free-form curves with a machine tool equipped with parallel device, improving contouring accuracy is very important. In this paper, we present contouring control algorithm far parallel machine tool. The relation between the error in Joint space and the error in catesian space is evaluated, and we estimate contouring error vector which efficiently determines the variable gains for the cross coupled control. To show the validity of the algorithm, the contouring control is simulated for free form contour trajectory in cubic parallel machine tool model.

• Korean Journal of Materials Research
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• v.13 no.6
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• pp.394-397
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• 2003

MTJ devices are fabricated using metal shadow masks and switching characteristics are investigated under 2 dimensional magnetic field. When the hard axis field is less than $\pm$ 16 Oe, switching behavior is similar to that based on the Stoner-Wohlfarth model. As the hard axis field is larger than $\pm$ 16 Oe, deviation from the expectation by Stoner-Wohlfarth model is observed. These phenomena are induced by the generation of multi-domain and inhomogeneous magnetization reversal.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.156-159
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• 2003

A free piston and free displacer(FPFD) Stirling cryocooler for cooling infrared and cryo-sensors is currently under development at KIMM(Korea Institute of Machinery ＆ Materials). Our coolers are specifically designed to work in the thermal imaging device and to meet requirements such as cooling capacity, COP and high reliability. In this work, Stirling cryocooler is designed, manufactured and fabricated, and performance characteristics are investigated. This cooler delivers approximately 0.5W cooling at 77K for 30W ∼ 40W of input power from AC power supply. And, after the climate performance and reliability for the cryocooler is discussed, operating test without cooling load at the cold end is performed.

• Journal of the Semiconductor & Display Technology
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• v.6 no.3
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• pp.65-70
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• 2007

A method to focus the object in camera system by applying the Hill climb algorithm from optical lens moving device (VCM; Voice coil motor) is proposed. The focusing algorithm from VCM is focus on the object but in these criteria is a well-known drawback; the focus is good only at same distance objects but the focus is bad (blur image) at different distance objects because of the DOF (Depth of focus) or DOF (Depth of field) at the optical characteristic. Here, the new camera system that describes the Reflector of free curvature systems (or Diffractive Fresnel lens) and the partition of focusing window area is proposed. The method to improve the focus in all areas (different distance objects) is proposed by new optical system (discrete auto in-focus) using the Reflector of free curvature systems (or Diffractive Fresnel lens) and by applying the partition of all areas. The proposal is able to obtain good focus in all areas.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.320-323
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• 2003

This paper presents the results of a series of performance tests for the Stilting cryocooler. A free piston and free displacer(FPFD) Stilting cryocooler for cooling infrared and cryo-sensors is currently under development at KIMM. Our coolers are specifically designed to work in the thermal imaging device and to meet requirements such as cooling capacity, COP and high reliability. In this work, Stilting cryocooler is designed, manufactured and fabricated, and performance characteristics for the cooling capacity / applied input power and cool down time are investigated. This cooler delivers approximately 0.9W cooling at 80K for 30W ~ 40W of input power. And, It takes approximately 2 minutes to cool down to 80K at the ambient temperature of 23$^{\circ}C$.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.167-170
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• 2003

This paper presents the results of a series of performance tests for the Stilting cryocooler. A free piston and free displacer(FPFD) Stilting cryocooler for cooling infrared and cryo-sensors is currently under development at KIMM. Our coolers are specifically designed to work in the thermal imaging device and to meet requirements such as cooling capacity, COP and high reliability. In this work, Stilting cryocooler is designed, manufactured and fabricated, and performance characteristics for the vibration, acoustic noise, EMI and leak rate are evaluated. Vibration outputs are measured to 20KHz for compressor and expander, respectively. And, the objective of noise test is a noise level, less than 30㏈ at 5 m. EMI tests are carried out according to the standard MIL-STD-461C tests RE01 and RE02. Leak test for the Stilting cryocooler is performed by bombing method.

• The Journal of the Acoustical Society of Korea
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• v.18 no.2E
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• pp.45-52
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• 1999

This paper presents the integrated speech enhancement system for hands-free mobile communication. The proposed integrated system incorporates both acoustic echo cancellation and engine noise reduction device to provide signal enhancement of desired speech signal from the echoed plus noisy environments. To implement the system, a delayless subband adaptive structure is used for acoustic echo cancellation operation. The NLMS based adaptive noise canceller then applied to the residual echo removed noisy signal to achieve the selective engine noise attenuation in dominant frequency component. Two sets of computer simulations are conducted to demonstrate the effectiveness of the system; one for the fixed acoustical environment condition, the other for the robustness of the system in which, more realistic situation, the acoustic transmission environment change. Simulation results confirm the system performance of 20-25dB ERLE in acoustic echo cancellation and 9-19 dB engine noise attenuation in dominant frequency component for both cases.

• The Journal of Korea Robotics Society
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• v.14 no.3
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• pp.211-220
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• 2019

Surface electromyogram (sEMG), which is a bio-electrical signal originated from action potentials of nerves and muscle fibers activated by motor neurons, has been widely used for recognizing motion intention of robotic prosthesis for amputees because it enables a device to be operated intuitively by users without any artificial and additional work. In this paper, we propose a training-free unsupervised sEMG pattern recognition algorithm. It is useful for the gesture recognition for the amputees from whom we cannot achieve motion labels for the previous supervised pattern recognition algorithms. Using the proposed algorithm, we can classify the sEMG signals for gesture recognition and the calculated threshold probability value can be used as a sensitivity parameter for pattern registration. The proposed algorithm was verified by a case study of a patient with partial-hand amputation.

• Archives of Plastic Surgery
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• v.46 no.2
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• pp.176-180
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• 2019

Post-traumatic soft tissue defects sometimes require sequential flap coverage to achieve complete healing. In the era of propeller flaps, which were developed to reduce donor site morbidity, Feng et al. introduced the concept of the free-style puzzle flap, in which a previously harvested flap becomes its own donor site by recycling the perforator. However, when a perforator cannot be found with a Doppler device, we suggest performing a new type of flap, the flip-flap puzzle flap, which combines two concepts: the free-style puzzle flap and the flip-flap flap described by Voche et al. in the 1990s. We present the cases of three patients who achieved complete healing through this procedure.

• Journal of the Semiconductor & Display Technology
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• v.20 no.3
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• pp.167-171
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• 2021

The core-shell InGaN/GaN Multi Quantum Well-Nanowires (MQW-NWs) that were selectively grown on oxide templates with perfectly circular hole patterns were highly crystalline and were shaped as high-aspect-ratio pyramids with semi-polar facets, indicating hexagonal symmetry. The formation of the InGaN active layer was characterized at its various locations for two types of the substrates, one containing defect-free MQW-NWs with GQDs and the other containing MQW-NWs with defects by using HRTEM. The TEM of the defect-free NW showed a typical diode behavior, much larger than that of the NW with defects, resulting in stronger EL from the former device, which holds promise for the realization of high-performance nonpolar core-shell InGaN/GaN MQW-NW substrates. These results suggest that well-defined nonpolar InGaN/GaN MQW-NWs can be utilized for the realization of high-performance LEDs.