• Smart Structures and Systems
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• 제13권2호
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• pp.219-233
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• 2014

In a companion paper, Pasala and Nagarajaiah analytically and experimentally validate the Adaptive Length Pendulum Smart Tuned Mass Damper (ALP-STMD) on a primary structure (2 story steel structure) whose frequencies are time invariant (Pasala and Nagarajaiah 2012). In this paper, the ALP-STMD effectiveness on a primary structure whose frequencies are time varying is studied experimentally. This study experimentally validates the ability of an ALP-STMD to adequately control a structural system in the presence of real time changes in primary stiffness that are detected by a real time observer based system identification. The experiments implement the newly developed Adaptive Length Pendulum Smart Tuned Mass Damper (ALP-STMD) which was first introduced and developed by Nagarajaiah (2009), Nagarajaiah and Pasala (2010) and Nagarajaiah et al. (2010). The ALP-STMD employs a mass pendulum of variable length which can be tuned in real time to the parameters of the system using sensor feedback. The tuning action is made possible by applying a current to a shape memory alloy wire changing the effective length that supports the damper mass assembly in real time. Once a stiffness change in the structural system is detected by an open loop observer, the ALP-STMD is re-tuned to the modified system parameters which successfully reduce the response of the primary system. Significant performance improvement is illustrated for the stiffness modified system, which undergoes the re-tuning adaptation, when compared to the stiffness modified system without adaptive re-tuning.

• 한국철도학회논문집
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• 제12권4호
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• pp.506-511
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• 2009

본 연구에서는 대차에서 계측한 가속도 데이터를 사용하여 궤도틀림을 식별하기 위한 알고리즘을 제안하였다. 등가 SISO 모델에 의한 정상궤도틀림 상태에서의 대차진동과 궤도틀림과의 주파수영역 전달함수를 정의하고, 이를 역으로 이용하여 대차에서 계측한 가속도 데이터로 궤도틀림을 예측하였다. 예측된 값과 기준값과의 잔차의 분산 비로정의되는 틀림지수를 사용하여 궤도틀림의 이상을 분석하였다. 궤도틀림을 시간에 따라 변하는 변위 경계조건으로 고려하여 3차원 수치예제를 수행하였으며, 제안된 알고리즘의 타당성을 검증하였다.

• Journal of Electrical Engineering and Technology
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• 제12권5호
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• pp.1697-1708
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• 2017

This paper proposes an algorithm for the differential protection of an Indirect Symmetrical Phase Shift Transformer (ISPST) by considering the different behaviors of the compensated differential current under internal fault and magnetizing inrush conditions. In this algorithm, a criterion function is defined which is based on the difference of amplitude of the wavelet transformation over a specific frequency band. The function has been used for the discrimination between three phase magnetizing inrush and internal fault condition and requires less than a quarter cycle after disturbance. This method is independent of any coefficient or threshold values of wavelet transformation. The merit of this algorithm is demonstrated by the simulation of different faults in series and excitation unit and magnetizing inrush with varying switching conditions on ISPST using PSCAD/EMTDC. Due to unavailability of in-field large interconnected transformers for such a large number of destructive tests, the results are further verified by Real Time Digital Simulator (RSCAD/RTDS). The proposed algorithm has been compared with the conventional harmonic restraint based method that justifies the application of wavelet transform for differential protection of ISPST. The proposed algorithm has also been verified for different rating of ISPSTs and satisfactory results were obtained.

• 한국음향학회지
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• 제15권4호
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• pp.50-57
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• 1996

본 논문에서는 최적의 웨이브렛 선택방법과 이 선택된 웨이브렛으로 F-검정을 이용하여 AR파라메터를 전개시키는 방법을 제안하였으며 웨이브렛 선택 방법으로서 평가함수를 도입하였다. 이 평가함수를 이용하여 웨이브렛들(D4-D20)을 합성신호에 대해서 시험하였다. 이때 선택된 웨이브렛을 이용하여 합성신호와 실제 음성신호에 대해서 AR파라메터들을 웨이브렛 전개 했을때의 웨이브렛 계수를 구하였다. 제안된 방법을 평가하기 위해서 칼만필터 알고리즘과 비교하였다. 그 결과 제안된 알고리즘이 칼만필터보다 약5-10dB정도 더 우수한 성능을 나타내었다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 춘계학술대회 논문집
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• pp.109-114
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• 2003

Wireless communication systems are inevitable for efficient underwater activities. Because of the poor propagation characteristics of light and electromagnetic waves, acoustic waves are generally used for the underwater wireless communication. Although there are many kinds of information type, visual images take an essential role especially for search and identification activities. For this reason, we developed an acoustic-based underwater image transmission system under a dual use technology project supported by MOCIE (Ministry of Commerce, Industry and Energy). For the application to complicated and time-varying underwater environments all-digital transmitter and receiver systems are investigated. Array acoustic transducers are used at the receiver, which have the center frequency of 32kHz and the bandwidth of 4kHz. To improve transmission speed and quality, various algorithms and systems are used. The system design techniques will be discussed in detail including image compression/ decompression system, adaptive beam- forming, fast RLS adaptive equalizer, ${\partial}/4$ QPSK (Quadrilateral Phase Shift Keying) modulator/demodulator, and convolution coding/ Viterbi. Decoding.

• 대한의용생체공학회:의공학회지
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• 제15권2호
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• pp.167-174
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• 1994

In this paper, a DSP and microcomputer-based EMG controlled functional electrical stimulation (FES) system, for restoring walking of paraplegics at the patients' own command, is presented. The above-lesion EMG is a time-varying nonstationary signal and its autoregressive (AR) parameters are identified by the nonstationary identification algorithm using a DSP chip. The identified AR parameters are used for the cloassification of the function and the control of the movement. The below-lesion response-EMG signal is used as a measure of muscle fatigue. This FES system is designed to measure muscle fatigue and control the stimulation intensity according to the amplitude of the response-EMG signal. While the automatic electrical intensity control is obtained by identifying the movement, the proposed FES system is suitable for the automatic control of paraplegic walking.

• The Plant Pathology Journal
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• 제21권4호
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• pp.310-316
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• 2005

The objectives of this study were to identify the aecial host ranges of four Korean Gymnosporangium species, G. asiaticum, G. cornutum, Gjaponicum and Gyamadae, and to verify the morphological characteristics of telia as diagnostic keys to the species. Thirteen Korean Rosaceous woody species were artificially inoculated with teliospores obtained from Juniperus species. There was high specificity between telial and aecial hosts and the fungal species, providing the first experimental proof on host alternation of these rust fungi in Korea. Telia on the witches' broom and on the small galls were identified as new telial characteristics in G asiaticum and in G. yamadae, respectively. Aecial hosts of G. asiaticum and G. yamadae showed varying responses in their susceptibility and in the days required for formation and duration of spermogonia and aecia after inoculation. Four telial host species in Juniperus were confirmed for the first time in Korea, which include J. chinensis var. kaizuka, J. chinensis var. horizontalis and J. chinensis var. globosa for G. asiaticum; and J. chinensis var. kaizuka for G. yamadae.

• 천문학회보
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• 제41권1호
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• pp.56.2-56.2
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• 2016

We present a multi-aperture photometry pipeline for DEEP-South (Deep Ecliptic Patrol of the Southern Sky) time-series data, written in C. The pipeline is designed to do robust high-precision photometry and calibration of non-crowded fields with a varying point-spread function, allowing for the wholesale search and characterization of both temporal and spatial variabilities. Our time-series photometry method consists of three parts: (i) extracting all point sources with several pixel/blind parameters, (ii) determining the optimized aperture for each source where we consider whether the measured flux within the aperture is contaminated by unwanted artifacts, and (iii) correcting position-dependent variations in the PSF shape across the mosaic CCD. In order to provide faster access to the resultant catalogs, we also utilize an efficient indexing technique using compressed bitmap indices (FastBit). Lastly, we focus on the development and application of catalog-based searches that aid the identification of high-probable single events from the indexed database. This catalog-based approach is still useful to identify new point-sources or moving objects in non-crowded fields. The performance of the pipeline is being tested on various sets of time-series data available in several archives: DEEP-South asteroid survey and HAT-South/MMT exoplanet survey data sets.

• Journal of Radiation Protection and Research
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• 제48권2호
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• pp.100-106
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• 2023

Background: As breast tissue expanders consist of metallic materials in the needle guard and ferromagnetic injection port, irradiation can produce radioactivation. Materials and Methods: A CPX4 (Mentor Worldwide LLD) breast tissue expander was exposed using the Versa HD (Elekta) linear accelerator. Two photon energies of 6 and 10 MV-flattening filter free (FFF) beams with 5,000 monitor units (MU) were irradiated to identify the types of radiation. Furthermore, 300 MU with 10 MV-FFF beam was exposed to the CPX4 breast tissue expander by varying the machine dose rates (MDRs) 600, 1,200, and 2,200 MU/min. To assess the instantaneous dose rates (IDRs) solely from the CPX4, a tissue expander was placed outside the treatment room after beam irradiation, and a portable radioisotope identification device was used to identify the types of radiation and measure IDR. Results and Discussion: After 5,000 MU delivery to the CPX4 breast tissue expander, the energy spectrum whose peak energy of 511 keV was found with 10 MV-FFF, while there was no resultant one with 6 MV-FFF. The time of each measurement was 1 minute, and the mean IDRs from the 10 MV-FFF were 0.407, 0.231, and 0.180 μSv/hr for the three successive measurements. Following 10 MV-FFF beam irradiation with 300 MU indicated around the background level from the first measurement regardless of MDRs. Conclusion: As each institute room entry time protocol varies according to the working hours and occupational doses, we suggest an addition of 1 minute from the institutes' own room entry time protocol in patients with CPX4 tissue expander and the case of radiotherapy vaults equipped with a maximum energy of 10 MV photon beams.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2004년도 제5회 정기학술발표대회 논문집
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• pp.515-520
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• 2004

최근 건설산업은 구조물의 일부 또는 전체를 대상으로 제조업의 체계적인 생산시스템인 공장생산방식을 활용하여 생산성을 향상시키기 위한 방안을 마련하고 있다. 하지만 효과를 검증하지 않고 무조건적으로 공장생산방식을 도입한다면 생산 규모와 위치에 따라 현장생산보다 공사비용이나 공기가 증가되는 경우도 있다. 공장생산방식을 보다 효과적으로 활용하기 위해서는 공장생산방식과 현장생산방식을 다양한 기준으로 비교해본 후 적용여부에 대한 의사결정이 이루어져야한다. 본 연구는 기존의 연구와 사례분석을 통하여 공장생산방식의 적용에 필요한 의사결정요인을 도출하고 이를 고려한 의사결정모델을 제시하고자한다 크게 3단계의 연구방법을 거쳐 의사결정을 내릴 수 있는 의사결정순서도와 의사결정모형도를 작성하였다. (1) 공장생산방식 적용 의사결정요인을 도출하고 구조화하여 (2) 공장생산의 규모와 공장의 위치의 변화에 따른 이익, 비용, 공기를 산출한 후 (3) 현장생산방식과 공장생산방식을 반복적으로 비교함으로써 의사결정을 내릴 수 있는 모델을 제시하였다.