• Journal of Sensor Science and Technology
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• v.19 no.5
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• pp.361-368
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• 2010

ACROSS device, which is composed of an implantable microphone, a signal processor, and a vibrating transducer, is a fullyimplantable middle ear hearing device(F-IMEHD) for the recovery of patients with hearing loss. And since a microphone is implanted under skin and tissue at the temporal bones, the amplitude of the sound wave is attenuated by absorption and scattering. And the vibrating transducer attached to the ossicular chain caused also the different displacement from characteristic of the stapes. For the gain control of auditory signals, most of implantable hearing devices with the digital audio signal processor still apply to fitting rules of conventional hearing aid without regard to the effect of the implanted microphone and the vibrating transducer. So it should be taken into account the effect of the implantable microphone and the vibrating transducer to use the conventional audio fitting rule. The aim of this study was to measure gain characteristics caused by the implanted microphone and the vibrating transducer attached to the ossicle chains for the gain compensation of ACROSS device. Differential floating mass transducers (DFMT) of ACROSS device were clipped on four cadaver temporal bones. And after placing the DFMT on them, displacements of the ossicle chain with the DFMT operated by 1 $mA_{peak}$ current was measured using laser Doppler vibrometer. And the sensitivity of microphones under the sampled pig skin and the skin of 3 rat back were measured by stimulus of pure tones in frequency from 0.1 to 8.9 kHz. And we confirmed that the microphone implanted under skin showed poorer frequency response in the acoustic high-frequency band than it in the low- to mid- frequency band, and the resonant frequency of the stapes vibration was changed by attaching the DFMT on the incus, the displacement of the DFMT driven with 1 $mA_{rms}$ was higher by the amount of about 20 dB than that of cadaver's stapes driven by the sound presssure of 94 dB SPL in resonance frequency range.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.138-141
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• 2004

[ $MnO_2$ ]가 첨가된 $0.9Pb(Zr_{0.5}Ti_{0.5})O_3-0.2Pb[(Zn_{0.8}Ni_{0.2})_{1/3}Nb_{2/3}]O_3$(0.8PZT-0.2PZNN) 세라믹스는 그 압전특성과 유전특성이 뛰어나지만 $1000^{\circ}C$ 이하의 낮은 소결 온도에서는 소결되지 않는다. $1000^{\circ}C$이하의 낮은 소결온도에서 소결하기 위해 CuO를 첨가한 결과, 소결온도 $920^{\circ}C$에서 소결성은 우수하였으나 그 압전 특성의 저하가 두드러졌다. 이는 XRD에서 확인한 결과에 따르면 CuO의 첨가가 우수한 MPB 조성으로 판명된 $MnO_2$ 가 첨가된 0.8PZT-0.2PZNN 세라믹스의 결정구조를 Rhombohedral 구조로 바꾸기 때문인 것으로 보였으며 이러한 문제는 PZNN의 비율을 조절하여 0.875PZT-0.125PZNN 세라믹스를 선택함으로 인해 해결할 수 있었다. 그러나 여전히 낮은 $Q_m$값을 높이기 위해서 $Al_2O_3$를 첨가하였고 그 결과 시편의 tetragonality 감소와 $Q_m$값의 증가를 확인할 수 있었으나 그 첨가량이 0.2wt% 이상일 경우에는 밀도의 감소로 인한 압전특성의 저하가 나타났다. 밀도의 향상을 위해 Zn and Ni excess 조성을 선택하였고 그 결과 0.5wt% $MnO_2$와 0.2wt% CuO 그리고 0.3wt% $Al_2O_3$를 첨가한 0.875PZT-0.125PZNN 세라믹스(Zn and Ni excess 조성)를 $920^{\circ}C$에서 소결한 경우 $k_p=0.581,\;Q_m=809,\;d_{33}=345\;pC/N\;and\;{\varepsilon}_{33}/{\varepsilon}_0=1345$의 빼어난 압전 및 유전특성과 $330^{\circ}C$의 높은 $T_c$를 보였고 그 조성의 vibration velocity는 약4.5 m/s로 나타났다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.32 no.4_1
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• pp.363-371
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• 2014

Most space-borne optical scanning systems adopt linear arrayconfigurations. The well-knownthree different types of space-borne sensors arealong-track line scanner, across-track linescanner, and three line scanner. To acquire accurate location information of an object on the ground withthose sensors, the exterior and interior orientation parameters are critical factors for both of space-borne and airborne missions. Since the imaging geometry of sensors mightchange time to time due to thermal influence, vibration, and wind, it is very important to analyze the Interior Orientation Parameters (IOP) effects on the ground. The experiments based on synthetic datasets arecarried out while the focal length biases are changing. Also, both high and low altitudes of the imagingsensor were applied. In case with the along-track line scanner, the focal length bias caused errors along the scanline direction. In the other case with the across-track one, the focal length bias caused errors alongthe scan line and vertical directions. Lastly, vertical errors were observed in the case ofthree-line scanner. Those results from this study will be able to provide the guideline for developing new linearsensors, so as for improving the accuracy of laboratory or in-flight sensor calibrations.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.1
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• pp.49-55
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• 2009

Our domestic economy has been developed very rapidly after 1960's. Also, it is dramatically increasing traffic on road and surround environmental issues. Especially, rapid economic growth has been induced large construction of pavement, and bigger and higher traffic for transportation. These are making air pollution, traffic noise and vibration. The social requirement against the revealed road environment and traffic sound reduction is being demanded. Traffic noise of city zone is showed over the environmental specification more than 57%. In order to overcome these situations, the social attention is being increased. The quiet pavement is the same format of permeable pavement, but is not same for functional performance. In this research, it has been carried out to evaluate the fundamental-mechanical properties of hot mix asphalt for quiet pavement. Especially, couple of laboratory tests are conducted like marshall stability, resilient modulus, indirect tensile test, and compaction energy analysis with gyratory compaction curve. Also, two-layer pavement system has been adopted for developing of quiet pavement. The basic performance of hot mix asphalt of quiet pavement show a satisfaction of specification of hot mix asphalt.

• Journal of the Korean GEO-environmental Society
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• v.16 no.7
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• pp.5-13
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• 2015

The pressure penetrating steel pipe pile method which can be constructed in a narrow space using the hydraulic jack is used on the foundation reinforcement, extension of the structure and basement, restoration of the differential settlement etc.. This method is possible to construct in narrow areas and low story height, the non-noise and non-vibration works, and it is possible for the construction site to be clean without slime. And it is possible to confirm the bearing capacity of pile due to penetrating the pile with the compression load of hydraulic jack. In this study, the static load test with the load-transfer test was carried out to investigate the bearing behavior characteristics of the pressure penetrating steel pipe pile. Four series of static load test were executed to investigate the variation of bearing behavior of the pressure penetrating steel pipe pile. As a result of these tests, the allowable load of the pressure penetrating steel pipe was evaluated more than 637 kN, and the shaft resistance corresponding to 81~86% of each applied load was mobilized with only a small portion of the base resistance acting. And it was also evaluated that the unit skin friction was mobilized to maximum value after two months.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.4
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• pp.265-280
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• 2021

Population density due to urbanization is making people interested in underground space development and much interest in TBM construction with low vibration and noise. This led to a lot of research on TBM. However, research on the characteristics of the cutterhead opening of the TBM equipment being occluded under the ground conditions under which it is excavated is insufficient. Accordingly, a study was conducted to investigate clogging of the cutterhead opening during the shield TBM rolling. To identify the clogging of cutterhead openings in SHIELD TBM equipment, the reduced model experiment was divided into clay rate (10%, 30%, 50%, 60%), cutterhead opening rate (30%, 50%, 60%), and cutterhead rotation direction (one-way, two-way) and rotational speed (3 RPM) and conducted in 36 cases. Results of scale model test on shield TBM clogging, it was analyzed that the ground condition containing clay soil increased the clogging effect in both directions than the unidirectional rotation, and that the lower the rotational speed of the cutterhead, the less the clogging effect. Accordingly, the direction of cutterhead rotation, rotational speed and opening rate are calculated by taking into account ground conditions during ground excavation, the clogging effect can be reduced. It is believed to be effective in saving air as the clogging effect is reduced. Therefore, this study is expected to be an important material for domestic use of shield TBM.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.135-142
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• 2020

In the case of a concrete structure, vibration problems occur under various conditions because of its low damping performance. To solve this problem, a study on the high damping performance of the polymer concrete with hybrid damper has recently been increased. Since water is not used in polymer concrete, the curing time is short. Also, the physical properties and dynamic properties of polymer concrete are quite excellent. So polymer concrete is widely expected to be used for structural materials. The hybrid damper is the structural system that consists of steel balls and viscous fluid inside the pipe which is embedded in polymer concrete. It can reduce the structural vibrations through the energy dissipation mechanism of viscous fluid and steel balls. In this study, the physical and dynamic properties of polymer concrete with hybrid damper were compared with ordinary concrete. As a result, the elasticity coefficient and the strength of the polymer concrete with hybrid damper were so much excellent. In particular, the tensile strength was 6.5 to 10 times higher than ordinary concrete. The frequency response function and damping ratio were also compared. As a result, the dynamic Stiffness of the polymer concrete was 25% greater than that of ordinary concrete. The damping ratio of the polymer concrete was approximately 3 times higher than that of ordinary concrete. Although the dynamic stiffness of the hybrid damper showed similar tendency, the damping ratio was 3.5 times higher than that of ordinary concrete. Therefore, the polymer concrete with hybrid damper was superior to ordinary concrete.

• Composites Research
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• v.35 no.4
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• pp.277-282
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• 2022

In this study, a smart material applicable to speed bumps was developed using low-cost starch and waterbased suspensions, and their properties were investigated. Viscosity and shear stress according to the shear rate was measured by a rheometer to observe shear thickening behavior according to starch concentration. The shear thickening phenomenon and applicability to speed bumps were identified macroscopically via drop weight test and bike driving test, measuring the vibration after impact with a driving speed of 5-25 km/h. As a result of the viscosity measurement, shear thickening occurred after the shear thinning region at the beginning, and the critical strain causing the shear thickening phenomenon decreased as the concentration of starch increased. Also, the viscosity and shear stress increased significantly with the increase of the starch concentration. As a result of the drop weight test and the bike driving test, the suspension was changed to a solid-like state in a short time, and the impact energy was absorbed in the fluid. The shear thickening phenomenon easily occurred as the concentration of the fluid and the applied impact (velocity) increased. Therefore, it can be proposed the development of a smart speed bump material that operates in the range of 5-25 km/h with a Non-Newtonian fluid based on water and starch.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.5
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• pp.395-409
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• 2022

To overcome the limitation of conventional rock excavation methods, the excavation with abrasive waterjet has been actively developed. The abrasive waterjet excavation method has the effect of reducing blasting vibration and enhancing the excavation efficiency by forming a continuous free surface on the rock. However, the waterjet cutting performance varies with rock fracturing characteristics. Thus, it is necessary to analyze the cutting performance for various rocks in order to effectively utilize the waterjet excavation. In this study, cutting experiments with the high pressure waterjet system were performed for basalt and granite specimens. Water pressure, standoff distance, and traverse speed were determined as effective parameters for the abrasive waterjet cutting. The cutting depth and width of basalt specimens were analyzed to compare with granite results. The averaged cutting depth of basalt was shown in 41% deeper than granite; in addition, the averaged cutting width of basalt was formed by 18.5% narrower than granite. The results of this study are expected to be useful basic data for applying rock excavation site with low strength and high porosity such as basalt.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.2
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• pp.153-170
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• 2022

Waterjet has been comprehensively used in urban areas owing to a suitable technique for cutting concrete and rock, and low noise and vibration. Recently, the abrasive waterjet technique has been adopted and applied by the Korea Atomic Energy Research Institute to demolish concrete plugging without disturbing and damaging In-situ Demonstration of Engineered Barrier System in the disposal research tunnel. In this study, the use of abrasive waterjet in the tunnel was evaluated for practical applicability and the existing cutting model was compared with the experimental results. As a variable for waterjet cutting, multi-cutting, water flow rate, abrasive flow rate, and standoff distance were selected for the diversity of analysis. As regarding the practical application, the waterjet facilitated path selection for cutting the concrete plugging and prevented additional disturbances in the periphery. The pump's noise at idling was 64.9 dB which is satisfied with the noise regulatory standard, but it exceeded the standard at ejection to air and target concrete because the experiment was performed in the tunnel space. The experimental result showed that the error between the predicted and measured cutting volume was 12~13% for the first cut and 16% for second cut. The standoff distance had a significant influence on the cutting depth and width, and the error tended to decrease with decrement of standoff distance.