• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.5
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• pp.439-446
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• 2016

The characteristics of bearingless main rotor of helicopter are investigated through non-rotating tests and rotating tests. The stiffness and natural frequencies of rotor blades, flexbeam, and torque tube which are core components of baearingless rotor are measured to obtain input material properties for rotor analysis. The functional test on ground for assembly of one hub with damper, snubber, and no blade is carried out to check interfaces between components, kinematics of components, and pitch motion ranges under applied loads including centrifugal load. The 4-bladed bearingless rotor with 5.82m of rotor radius is tested on the whirl tower with rotation plane of 9.65m height. The thrust and power are measured to obtain hover performance and the frequencies and dampings of the rotor are obtained by excitation of cyclic pitch by hydraulic actuators.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.4045-4052
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• 2012

The aim of this single blind intervation study was to compare the analgesic effects of transcutaneous electrical nerve stimulation (TENS) and interferential currents (IFC) on cold-induced pain in healthy volunteers. Sixteen subjects completed six cycles of the cold-induced pain test. During each cycle pain threshold was recorded as the time from immersion of the subject is hand in cold water to the first sensation of pain and pain intensity and unpleasantness ratings were recorded using visual analogue scales. Subjects were randomly allocated to receive each 50 Hz-TENS, 50 Hz-IFC, 100 Hz-TENS and 100 Hz-IFC. Statistical analysis showed that four interventions elevated the cold pain threshold significantly and the difference between interventions was not simply significant. But, no significant differences were identified in pain intensity and unpleasantness ratings. We conclude that there were no differences in the analgesic effects of the four interventions under the present experimental conditions. But, 50 Hz-IFC has been shown to be more comfortable than other interventions.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1245-1258
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• 2023

To efficiently manage forest resources, it is essential to deploy multiple unmanned aerial vehicles equipped with various sensors simultaneously. Consequently, the ground control station antenna should not only maintain continuous tracking of the target station but also minimize the impact of radio interference on other unmanned aerial vehicle stations. In this paper, we presented beam forming techniques based on the VPR algorithm within a ground control station constructed using a phased array antenna system. Through simulation experiments in diverse unmanned aerial vehicle operating environments, it was demonstrated that the presented method enables not only the continuous tracking of operational unmanned aerial vehicles but also the suppression of radio interference by establishing a continuous pattern null for multiple operational radio interference sources.

• Journal of the Institute of Convergence Signal Processing
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• v.16 no.2
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• pp.69-73
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• 2015

In this study, a method for estimating the amount of urination for men, was suggested and its performance was evaluated. This study is a preliminary one for the development of a health monitoring system that needs un-constraining, non-intrusive and long-term measurements in daily life. To estimate the amount of urination, a wide weighing plate with load cell was built and the difference in a man's weights between before and after urination was measured while he was standing on the plate. The results showed that the amount of urination can be estimated with the measured weight difference under the condition of mild movements. The largest measurement error of the suggested method was 40g, which means that this method can be applied to health monitoring in daily life. It is expected that the results of this study will be the basis for developing practical un-constraining and non-intrusive health monitoring system for daily use at home.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.455-463
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• 2007

In this paper, it is proposed how to implement the object detection system which is able to apply to vehicular applications, unmanned facilities, automatic door and others with microwave. As the technology which detects an object with microwave is becoming more popular, it seems impossible to avoid mutual interference and jamming caused by limited frequency bandwidth. The system in this paper detects an object by correlating the code of TX and RX signals with the pseudo-random code having best quality in interference and jamming environment. In order to generate simulant doppler signal for detecting the distance of an fixed object where there is no doppler effect, the phase of TX signal is shifted continually. Also, the saturation of receiver was removed and the error of distance measurement was decreased by controlling the power of TX signal for getting constant RX signal. The proposed system detects a object which ranges from 0.5 m to 2.0 m and informs vocally whether there is the object within 1.0 m or not.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2447-2458
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• 2009

Ad hoc wireless networks operate without any infrastructure where a node can be a source and a router at the same time. This indispensably requires high throughput and low delay performance throughout the wireless network coverage span, particularly under heavy traffic conditions. Recent research on using multiple antennas in beam-forming or multiplexing modes over a wireless channel has shown promising results in terms of high throughput and low delay. Directional antennas have shown to increase spatial reuse by allowing multiple transmitters and receivers to communicate using. directional beams as long as they do not significantly interfere with each other. However directional antenna performance asymptotically approaches the omni-directional performance in a high density ad hoc network. Simulation results in QualNet validate that average throughput and packet corruption ratio of directional antenna approach omni-directional performance. Moreover, we further highlight some important issues pertaining to the directional antenna performance in wireless networks.

• Korean Journal of Optics and Photonics
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• v.16 no.5
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• pp.417-422
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• 2005

When an optical pulse propagates through the atmospheric channel, it is attenuated and spreaded by the atmospheric turbulence. This pulse broadening produces the intersymbol interference(ISI) between adjacent pulses. Therefore, adjacent pulses are overlapped, and the bit rates and the repeaterless transmission length are limited by the ISI. In this paper, the ISI as a function of the refractive index structure constant that presents the strength of atmospheric turbulence is found using the temporal momentum function, and is numerically analyzed fer the basic SONET transmission rates. The numerical results show that ISI is gradually increasing at the lower transmission rate than the OC-192(9.953 Gb/s) system and is slowly converging after rapid increasing at the higher transmission rate than the OC-768(39.813 Gb/s) system as the turbulence is stronger. Also, we know that accurate information transmission is possible to 10[km] at the OC-48(2.488 Gb/s) system under any atmospheric turbulence, but is impossible under the stronger turbulence than $10^{-14}[m^{-2/3}]$ at the 100 Gb/s system, $10^{-13}[m^{-2/3}]$ at the OC-768 system, and $10^{-12}[m^{-2/3}]$ at the OC-192 system, because the ISI is seriously induced.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.25-30
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• 2003

The total relaxed stress in annealing and the thermal strain/stress were obtained from the identification of the residual stress-free state using electronic speckle pattern interferometry (ESPI). The residual stress fields in case of both single and film/substrate systems were modeled using the thermo-elastic theory and the relationship between relaxed stresses and displacements. We mapped the surface residual stress fields on the indented bulk Cu and the 0.5 ${\mu}m$ Au film by ESPI. In indented Cu, the normal and shear residual stress are distributed over -1.7 GPa to 700 MPa and -800 GPa to 600 MPa respectively around the indented point and in deposited Au film on Si wafer, the tensile residual stress is uniformly distributed on the Au film from 500 MPa to 800 MPa. Also we measured the residual stress by the x-ray diffractometer (XRD) for the verification of above residual stress results by ESPI.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.266-267
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• 2012

아연계 합금도금강판은 내식성이 향상되는 반면 아연 이외의 원소 성분에 의해 고온다습에서 변색되기 쉽기 때문에 이를 억제하기 위한 후처리 기술이 필요하다. 또한, 아연계 합금도금 강판이 자동차 부품으로 적용되기 위해서는 변색 억제를 위해 처리한 후처리제가 쉽게 제거되어 인산염처리 공정에서 도금 표면에 인산염결정이 용이하게 형성되어야 한다. 본 연구에서는 건식공정으로 제작된 아연계 합금도금 강판에 우레탄계 알칼리 후처리제를 도포하고, 고온다습 환경에서의 변색 억제 특성과 적정 부착량에서의 인산염처리 및 전착도장 특성에 대해 평가하였다. 두 형태의 후처리제는 건식 아연계 합금도금 강판에 도포 직후 표면에 간섭색을 나타내었으며, 첨가제를 통해 간섭색 제어가 가능하였다. 또한, 두 형태의 후처리제 모두가 고온다습 환경에서 무처리 강판에 비교하여 월등히 우수한 변색 억제 효과를 보였으며, 인산염처리 및 전착도장이 양호하게 얻어지는 것을 알 수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.6
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• pp.52-60
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• 2003

In aviation navigation using GPS, requirements on availability and integrity must be absolutely satisfied. Current study on accomplishing this integrity includes RAIM(Receiver Autonomous Integrity Monitoring), monitoring integrity internaIly in GPS receiver itself. Parity space technique as one of RAIM techniques has shown the advantages in fault detection and isolation due to each use of its magnitude and direction under the assumption of one fault. ln case of multiple fault, as biases in errors interact decreasing the effect of multiple fault in parity space, the exact fault detection and identification(FDI) may be difficult to be conducted. This paper focuses on FDI study on two faults and explains why parity space techniques applied on single fault is not adequate to the application of multiple fault case and shows that extended parity space technique may improve the performance of RAIM on two faults.