• The Journal of the Acoustical Society of Korea
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• v.43 no.4
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• pp.455-465
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• 2024

In shallow water, the array invariant, known as the effective range estimation method, is developed based on the broadband dispersion characteristics in an ideal waveguide, which can be summarized by the waveguide invariant. It is robust enough to estimate both the array tilt and range simultaneously, even in situations where array tilt exists. Recently, it has been extended to fully consider the angle dependence of the waveguide invariant. However, applying the array invariant in range-dependent environments instead of range-independent environments can lead to range estimation errors due to bathymetry mismatch. In this paper, we interpret such range estimation errors by introducing the concept of effective range. Through numerical simulations and experimental data in a weakly range-dependent environment, we demonstrate the relationship between range estimation errors and effective range.

• The Journal of the Acoustical Society of Korea
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• v.38 no.2
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• pp.231-239
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• 2019

In sonar systems, the passive ranging of a target is an active research area. This paper analyzed the performance of passive ranging based on an array invariant method for different environmental and sonar parameters. The array invariant developed for source range estimation in shallow water. The advantages of this method are that detailed environmental information is not required, and the real-time ranging is possible since the computational burden is very small. Simulation was performed to verify the algorithm. And this method is applied to sea-going experimental data in 2013 near Jinhae port. This study shows the performance of ranging for source orientation, transmission signal length, and length of a receiver through numerical simulation experiments. Also, the results using nested array and uniform line arrays are compared.

• The Journal of the Acoustical Society of Korea
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• v.36 no.1
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• pp.23-29
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• 2017

A concept of a VSA (Virtual Source Array) is the method for an acoustic spatio-temporal focus at a selected location in the outbound direction with respect to the VSA without the need of a probe source as combines a TRP (Time-Reversal Processing) and time-delay and beam-steering. However, in TRP using the VSA concept, it is limited to the critical angle and the short distances relevant to the VSA. In this paper, the waveguide invariant theory is applied to the VSA concept to refocus the received field at ranges greater other than the critical angle and the short ranges by shifting the focused field. The suggested method is verified via numerical simulation, and the results show that the robust acoustic focusing is achieved on the selected location regardless of the limitation on the conventional VSA concept.

• The Journal of the Acoustical Society of Korea
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• v.43 no.4
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• pp.466-475
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• 2024

Matched-Field Processing (MFP) is a model-based approach that requires accurate knowledge of the ocean environment and array geometry (e.g., array tilt) to localize underwater acoustic sources. Consequently, it is inherently sensitive to model mismatches. In contrast, the waveguide invariant-based approach (also known as array invariant) offers a simple and robust means for source-range estimation in shallow waters. This approach solely exploits the beam angles and travel times of multiple arrivals separated in the beam-time domain, requiring no modeling of the acoustic fields, unlike MFP. This paper extends the waveguide invariant-based approach to shallow water environments featuring a shallow pit, where the waveguide invariant is not defined due to the complex bathymetry. An in-depth performance analysis is conducted using experimental data and numerical simulations.

• The Journal of the Acoustical Society of Korea
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• v.25 no.6
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• pp.305-311
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• 2006

In this paper the performance of a array invariant method is evaluated for source-range estimation in horizontally stratified shallow water ocean waveguide. The method has advantage of little computationally effort over existing source-localization methods. such as matched field processing or the waveguide invariant and array gain is fully exploited. And. no knowledge of the environment is required except that the received field should not be dominated by purely interference This simple and instantaneous method is applied to simulated acoustic propagation filed for testing range estimation performance. The result of range estimation according to the SNR for the underwater impulsive source with broadband spectrum is demonstrated. The spatial smoothing method is applied to suppress the effect of mutipath propagation by high frequency signal. The result of performance test for range estimation shows that the error rate is within 20% at the SNR above 10dB.

• Journal of IKEEE
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• v.27 no.4
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• pp.624-629
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• 2023

Estimation of signal parameters via rotational invariance techniques (ESPRIT) is an algorithm that estimates the angle of a signal arriving at an array antenna using the shift invariance property of an array antenna. ESPRIT offers the good trade-off between performance and complexity. However, the ESPRIT algorithm still requires high-complexity operations such as covariance matrix and eigenvalue decomposition, so implementation with a hardware processor is essential to estimate the angle of arrival in real time. In addition, ESPRIT processors should have high performance. The performance is related to the number of antennas, and the number of antennas required for each application are different. Therefore, we proposed an ESPRIT processor that provides 2 to 8 variable antenna configurations to meet the performance and complexity requirements according to the applied field. The proposed ESPRIT processor was designed using the Verilog-HDL and implemented on a field programmable gate array (FPGA).

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.10 no.4
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• pp.78-84
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• 1996

In this study, 3-D object recognition and restoration independent of the object translation for automotive kind recognition in parking administration system using an ultrasonic sensor array, neural networks and invariant moments are presented. Using invariant moment vectors of the acquired data 16$\times$8 pixels, 3-D objects could be classified by SCL (Simple Competitive Learning) neural networks. Modified SCL neural networks using the 16$\times$8 low resolution image was used for object restoration of 32$\times$32 high resolution image. Invariant moment vectors kept constant independent of the object translation. The recognition rates for the training and the testing data were 98[%] and 95[%], respectively. The experimental results have shown that ultrasonic sensor array with the neural networks could be applied for the detection of the automobiles and classification of the automotive kind.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.2005-2006
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• 2011

Due to the advantages of small sizes, more I/O ports, etc., Ball Grid Array (BGA) has been used in the production of printed circuit board (PCB). However, BGA voids can degrade the performance of the board and cause failure. To automatically detect the voids in X-ray image, a novel blob filter that makes use of the local image gradient magnitude is proposed in this paper. The utilization of the local image gradient magnitude makes the proposed filter invariant to the image brightness, void shape, void position, and component interference. Furthermore, different sizes of box filters are employed to analyze the image in multi-scale, and as a result, the proposed blob filter is robust to void size. Experimental results show that the proposed method can obtain void detection accuracy up to 96.104% while keep low false ratio.

• Journal of Korean Medical classics
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• v.19 no.1 s.32
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• pp.47-109
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• 2006

서양의학상인위남녀근근시재생식기부동적인(西洋醫學上認爲男女僅僅是在生殖器不同的人). 최근(最近), Legato, Marianne J.박사창립료(博士創立了)‘성인지의학(性認知醫學)’학(學), 개시인식도남녀적차이(開始認識到男女的差異), 주장남녀재치료방법상역부동법(主張男女在治療方法上亦不同法), 종이저일연구진입도료신적단계(從而這一硏究進入到了新的段階). 단시한의학종(但是韓醫學從)${\ulcorner}$황제내경(黃帝內經)${\lrcorner}$개시(開始), 취인위남녀재구조상유근본적차이(就認爲男女在構造上有根本的差異), 이차재생리(而且在生理), 병리(病理), 진단(診斷), 치료상야부동(治療上也不同). 기록한의학기본원리적주역적상관서적화(記錄韓醫學基本原理的周易的相關書籍和)${\ulcorner}$황제내경(黃帝內經)${\lrcorner}$, 이급역대적주요한의서적급종사임상적한의사적서적상(以及歷代的主要韓醫書籍及從事臨床的韓醫師的書籍上), 역도인위남녀유차이(亦都認爲男女有差異). 관어남녀적생성(關於男女的生成), 재(在)${\ulcorner}$보제방(普濟方) 방맥총론(方脈總論)${\lrcorner}$적변남녀형생신육론중제출료(的辨男女形生神毓論中提出了男女的形成有異). ${\ulcorner}$동의보감(東醫寶鑑)${\lrcorner}$여기타한의서부동(與其他韓醫書不同), 불시이질병위주(不是以疾病爲主), 이시이신위중심(而是以身爲中心), 즉목차안형상진행료배열(卽目次按形象進行了排列), 차상세지언급료남녀(且詳細地言及了男女). 나요남녀시고정불변적마 불시적(不是的). ${\ulcorner}$동의보감(東醫寶鑑) 신형장부론(身形臟腑論)${\lrcorner}$인위(認爲)‘인적형색유차이(人的形色有差異), 장부이유이(臟腑易有異), 고외증수동(故外症雖同), 치법인인이이(治法因人而異).’ 안형상선용부동적치법적관점(按形象選用不同的治法的觀点), 이통과주단계지언이표명(已通過朱丹溪之言而表明). 불변관점상여자체격소이동(不變觀点上女子體格小易動), 남자체격대이와(男子體格大易臥). 남자속양기이산(男子屬陽氣易散). 여남자정서초차(如男子情緖稍差), 즉음주해수(卽飮酒解愁), 불이득우울증(不易得憂鬱症). 응보기정기(應補其精氣). 여자속음기이울체(女子屬陰氣易鬱滯), 다유인기지성질(多有忍氣之性質), 이득우울증(易得憂鬱症), 고다용산기약(故多用散氣藥). 간단이언(簡單而言)‘남자위병허증(男子爲病虛證), 여자위병실증(女子爲病實證).’ 종변화적관점래용약(從變化的觀点來用藥), 예여남자수소가용여자약적사물탕(例如男子瘦小可用女子藥的四物湯). 여자비가용남자약적사군자탕(女子肥可用男子藥的四君子湯). 여자골장가용남자약적육미지황환(女子骨壯可用男子藥的六味地黃丸). 위료갱용역이해(爲了更容易理解)‘남녀불변화변화적관점재의학적운용(男女不變和變化的觀点在醫學的運用)’, 이임상병례진행설명(以臨床病例進行說明). 재임상상통과형색맥증적합일화변증론치결정처방(在臨床上通過形色脈證的合一和辨證論治決定處方). 즉불능단순적인위(卽不能單純的認爲), 인위시남자취용육미지황환(因爲是男子就用六味地黃丸), 여자취용사물탕(女子就用四物湯). 남자약소가용사군자탕(男子若小可用四君子湯) 사물탕(四物湯) 육미지황탕(六味地黃湯), 이여자약대가용사군자탕(而女子若大可用四君子湯) 이진탕(二陳湯) 평위산(平胃散) 육군자탕(六君子湯). 인차(因此) 남녀재구조(男女在構造) 생리(生理) 병리유근본성차이(病理有根本性差異), 불이형상래구분(不以形象來區分), 용약상시지불변적입장(用藥上是持不變的立場), 이이형상용약(而以形象用藥), 시종변화적입장래고려적(是從變化的立場來考慮的). 인위이남녀위기준종사임상(認爲以男女爲基準從事臨床), 시부합한의학기본원리지음양관(是符合韓醫學基本原理之陰陽觀).