• 전자공학회논문지SC
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• 제45권2호
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• pp.1-7
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• 2008

본 논문에서는 원격 센싱이나 보안에 사용할 수 있는 밀리미터파 수동 이미징 센서를 제작하였다. 영상의 밝기 온도는 $3^{\circ}$의 분해능으로 안테나에서 측정된다. 제작한 센서는 PC에서 제어되며 pan/tilter 장치를 통해 빠른 성능을 얻는다. Pan/tilter 장치는 래스터 스캔을 통해서 2-D 영상을 스캔할 수 있다. 상하좌우로 기계적인 스캔에 의해서 $20{\times}20$ 픽셀의 영상은 400초 이내로 얻어진다. 영상은 측정 후 바로 표시되며 후처리를 위해 저장된다.

• 대한기계학회논문집A
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• 제22권1호
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• pp.80-89
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• 1998

The measuring method of structural strain by a 3*3 passive-demodulated fiber optic interferometric sensor was developed to implement the real-time monitoring of structural status. A 3*3 fiber optic Michelson interferometric sensor was constructed to sense the value and the direction of structural strain. This sensor was applied on the cantilevered aluminum beam to experiment the sensing of the structural deformation. The digital signal processing was programmed by LabVIEW to determine the structural strain from the fiber optic signals. This program was verified by various simulated fiber optic signals. Finally, the structural was well determined by this developed program from real fiber optic signals.

• Smart Structures and Systems
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• 제12권5호
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• pp.547-577
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• 2013

To suppress vibration and noise of mechanical structures piezoelectric ceramics play an increasing role as effective, simple and light-weighted damping devices as they are suitable for sensing and actuating. Out of the various piezoelectric damping methods this paper compares mode based active control strategies to passive shunt damping for thin plates. Therefore, a new approach for the optimal placement of the piezoelectric sensors/actuators, or more general transducers, is proposed after intense theoretical investigations based on the Kirchhoff kinematical hypotheses of plates; in particular, modal and nilpotent transducers are discussed in detail. Based on the proposed distribution a discrete design for modal transducers is implemented, tested and verified on an experimental setup. For active control the modal sensors clearly identify the eigenmodes, whereas the modal actuators impose distributed eigenstrains in order to reduce the transverse plate vibrations. In contrast to the modal control, passive shunt damping works without requiring additional actuators or auxiliary power and can therefore act as an autonomous system, but it is less effective compensating the flexible vibrations. Exemplarily, an acryl glass plate disturbed by an arbitrary force initialized by a loudspeaker is investigated. Comparing the different methods their specific advantages are highlighted and a significant broadband reduction of the vibrations of up to -20dB is obtained.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.474-477
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• 2005

In tactical theater, it is crucial to detect ground moving targets and to locate them precisely. This problem can be resolved by using SAR (Synthetic Aperture Radar) sensors providing GMTI (Ground Moving Target Indication) capability. In general, to implement a robust GMTI sensor is not simple because of the strong competitions between target signals and clutter signals on the ground, and low speed of moving targets. Contrary to the case that a delay canceller is mostly suitable for ground surveillance radars, DPCA (Displaced Phase Centered Antenna) or STAP (Space Time Adaptive Processing) techniques have been adapted for GMT! function of modem airborne radars. In this paper, anew scheme of DPCA using two passive antennas with vertical separation is proposed, which also provides good clutter cancellation performance. The proposed scheme enables us to scan straight ahead of the carrying platform that is impossible with typical DPCA configuration. Simulations using various conditions have been performed to validate the proposed scheme, and the results are acceptable.

• Nuclear Engineering and Technology
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• 제31권6호
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• pp.1-7
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• 1999

An innovative concept for a passive reactor shutdown system, so called self-actuated shutdown system(SASS), is inevitably required for the inherent safety in liquid metal reactor, which is designed with the totally different concept from the usual reactor shutdown system in LWR. SASS using Curie point electromagnet(CPEM) was selected as the passive reactor shutdown system for KALIMER (Korea Advanced Liquid MEtal Reactor). A mock-up of the SASS was designed, fabricated and tested. From the test it was confirmed that the mockup was self-actuated at the Curie point of the temperature sensing material used in the mockup. An articulated control rod was also fabricated and assembled with the CPEM to confirm that the control rod can be inserted into core even when the control rod guide tube is deformed due to earthquake. The operability of SASS in the actual sodium environment should be confirmed in the future. All the design and test data will be applied to the KALIMER design.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.378-381
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• 2007

Analyses of Tropical Rainfall Measuring Mission (TRMM) microwave radiometer (TMI) and precipitation radar (PR) data show that the rainfall inhomogeneity, represented by the coefficient of variation, decreases as rain rate increases at the low resolution (the footprint size of TMI 10 GHz channel). The rainfall inhomogeneity, however, is relatively constant for all rain rates at the high resolution (the footprint size of TMI 37 GHz channel). Consequently, radiometric signatures at lower spatial resolutions are characterized by larger dynamic range and smaller variability than those at higher spatial resolution. Based on the observed characteristics, this study develops a low-resolution (${\sim}40{\times}40$ km) rainfall retrieval algorithm utilizing realistic rainfall distributions in the a-priori databases. The purpose of the low-resolution rainfall algorithm is to make more reliable climatological rainfalls from various microwave sensors, including low-resolution radiometers.

• 전기학회논문지P
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• 제57권3호
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• pp.270-274
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• 2008

The microwave sensor in which the sensitivity was excellent and a structure is simple was developed and it manufactured. And the sensing range that uses the developed product was confirmed. When the developed microwave sensor was set up in the ceiling of a building, we confirmed that the amplitude of the sensitive area increased as the tilting angle was enlarged. The sensitive area became a greatest in case the tilting angle was 65 degree. According to the height of a ceiling, because the sensing range is determined, in case of using in the building in which the height of a ceiling is enough secured it is determined to secure the more wide sensitive area. Moreover, the configuration of the circuit having the simple structure makes the miniaturization of a product, and the light weight possible. It is considered to have the price competitive power which it reduces the manufacturing cost, is sufficient.

• Journal of the Optical Society of Korea
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• 제20권5호
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• pp.579-585
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• 2016

Integral imaging combined with photon-counting detection has been researched for three-dimensional information sensing under low-light-level conditions. This paper addresses the extraction of distance information with photon-counting integral imaging. The longitudinal distance to the object is obtained utilizing photon-counting elemental images. The pixel disparity is estimated by maximizing the nonlinear correlation of photocounts. The first- and second-order statistical properties of the nonlinear correlation are theoretically derived. In the experiments, these properties are verified by varying the mean number of photocounts in the scene. The average distance is compared to that from the intensity information, showing the robustness of the proposed system even at low photocounts.

• 한국음향학회지
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• 제39권3호
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• pp.191-199
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• 2020

현재 압축센싱 기반 도래각 추정 알고리듬의 연구는 활발히 진행 중이나 비균일 센서 배열 기반 공분산 fitting 알고리듬의 성능에 대한 연구는 진행되지 않았다. 본 논문에서는 주파수 영역으로 확장된 압축센싱 기반 공분산 fitting 알고리듬의 유도과정을 다루며 센서배열이 비균일하게 배치된 경우와 센서배열의 일부 소자에 고장이 발생한 경우에 대한 해당 알고리듬의 도래각 추정 성능을 비교하였다.

• 대한원격탐사학회지
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• 제19권1호
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• pp.53-59
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• 2003

The passive microwave remote sensing has progressed considerably in recent years Important earth surface parameters are detected and monitored by airborne and space born radiometers. However the spatial resolution of real aperture measurements is constrained by the antenna aperture size available on orbiting platforms and on the ground. The inverse problem technique is researched in order to improve the spatial resolution of microwave scanning radiometer. We solve a two-dimensional (surface) temperature-imaging problem with a major intention to develop high-resolution methods. In this paper, the scenario for estimation of both radiometer point spread function (PSF) and target configuration is explained. The PSF of the radiometer is assumed to be unknown and estimated from the observations. The configuration and brightness temperature of targets are also estimated. To do this, we deal with the parametric modeling of observation scenario. The performance of developed algorithms is illustrated on two-dimensional experimental data obtained by the water vapor radiometer.