• Ocean and Polar Research
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• 제25권4호
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• pp.557-567
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• 2003

High-resolution (3.5 kHz) subbottom profiles were analyzed in order to reveal sedimentation pattern of late Quaternary in the northern South Shetland continental margin and the South Scotia Sea, Antarctica. On the basis of clarity, continuity and geometry of surface and subbottom echoes together with seafloor topography, high-resolution echo characters are classified into eight echo types which represent rock basements (echo type III-1), coarse-grained subglacial till or moraine (echo type I-1), slides/slumps (echo type IV), debris-flow deposits (echo types II-3 and III-2), and bottom-current deposits (echo types I-2, II-1 and II-2). Subglacial till or moraine (echo type I-1) is mostly present in the lower continental shelf and upper continental slope of the northern South Shetland continental margin, which changes downslope to slides/slumps (echo type IV) and debris-flow deposits (echo types II-3 and III-2) in the middle to lower continental slope. This distribution suggests that the continental slopes of the northern South Shetland continental margin were mostly affected by downslope gravitational processes. Further downslope, bottom-current sediments (echo type I-2) deposited by the southwestward flowing Antarctic Deep Water (ADW) occur at the South Shetland Trench, reflecting an Interaction between mass flows and bottom currents in the area. In contrast to the northern South Shetland continental margin, the South Scotia Sea is dominated by bottom-current deposits (echo types II-1 and II-2), indicating that the sedimentation was mostly controlled by the westward flowing ADW. Flow intensity of the ADW has increased in the relative topographic highs, forming thin covers of coarse-grained contourites (echo type II-1), whereas it has decreased in the relative topographic lows, depositing thick, fine-grained contourites (echo type II-2). The poor development of wave geometry in the fine-grained bottom-current deposits (echo type II-2) is suggestive of the unsteady nature of the ADW flow.

• 전기학회논문지
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• 제64권6호
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• pp.922-934
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• 2015

In this paper, The classification between precipitation echo(PRE) and non-precipitation echo(N-PRE) (including ground echo and clear echo) is carried out from weather radar data using neuro-fuzzy algorithm. In order to classify between PRE and N-PRE, Input variables are built up through characteristic analysis of radar data. First, the event classifier as the first classification step is designed to classify precipitation event and non-precipitation event using input variables of RBFNNs such as DZ, DZ of Frequency(DZ_FR), SDZ, SDZ of Frequency(SDZ_FR), VGZ, VGZ of Frequency(VGZ_FR). After the event classification, in the precipitation event including non-precipitation echo, the non-precipitation echo is completely removed by the echo classifier of the second classifier step that is built as Type-2 FCM based RBFNNs. Also, parameters of classification system are acquired for effective performance using PSO(Particle Swarm Optimization). The performance results of the proposed echo classifier are compared with CZ. In the sequel, the proposed model architectures which use event classifier as well as the echo classifier of Interval Type-2 FCM based RBFNN show the superiority of output performance when compared with the conventional echo classifier based on RBFNN.

• 지구물리와물리탐사
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• 제16권3호
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• pp.145-153
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• 2013

황해 백령도 주변해역에 분포하는 해저면 연계퇴적층의 음향상 연구를 위해 고해상 탄성파 탐사자료를 분석하였다. 해저지형 및 내부 음향상 특징에 의하면 연구지역에 분포하는 천부퇴적층은 총 7개의 음향상으로 구분된다. 내부 반사면이 약간 혹은 양호하게 발달하거나 내부반사면을 전혀 수반하지 않는 평탄한 해저면(음향상 1-1, 1-2)은 연구지역의 남쪽에 주로 분포한다. 파형의 표면구조를 수반하는 평탄한 해저면(음향상 1-3)은 중부해역에 발달한다. 평탄한 해저면 혹은 파형의 표면구조를 수반하는 마운드 형태의 해저면 특징(음향상 2-1, 2-2, 2-3)은 중부해역에 분포한다. 내부 반사면이 발달하지 않고 불규칙한 침식흔적을 갖는 해저면(음향상 3-1)은 조사해역의 북부해역인 백령도 외해쪽에 주로 존재한다. 음향상의 분포 및 퇴적물 특성에 의하면 연구지역의 퇴적환경은 뚜렷한 3 지역으로 구분되는 바 (1) 강한 조류의 영향으로 심한 침식작용이 진행되고 있는 북쪽지역, (2) 해수면 상승과 연계된 조류의 영향으로 형성된 사퇴가 분포하는 중부해역, (3) 박층의 해침 사질층이 분포하고 있는 남부해역 등으로 구성된다. 연구지역에 분포하는 7 음향상을 포함하는 이와 같은 퇴적층은 홀로세 해침동안 해수면 상승 및 강한 조류와 연계된 퇴적작용을 반영한다.

• E2M - 전기 전자와 첨단 소재
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• 제9권10호
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• pp.1053-1059
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• 1996

The pulse-echo response of the piezoceramics PZT-polymer 3-3 type composite transducers with various PVA additions were investigated. The PZT powder was prepared by the molten salt synthesis method. The porous PZT specimens will be used as a filler to make 3-3 type comosite were prepared from a mixture of PZT and polyvinylalcohol(PVA) sphere by utilizing BURPS(Bumout Plastic Sphere) technique. It was shown that the transmitting and receiving sensitivity of 3-3 type piezoelectric composite transducers could be improved than that of solid PZT transducers. The reason is that 3-3 type piezoelectric composite have low dielectric constant, density and acoustic impedance. The distance between transducer and reflector was in good agreement with the distance calculated from the longitudinal velocity of the specimens and receiving time observed pulse-echo responses on the ultrasonic transducer analyzer.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계합동학술대회 논문집
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• pp.224-228
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• 2002

In this study, the piezoelectric ceramics PZT powder was synthesized by the Wet-Dry combination method. Flexible 1-3 type composite specimens were fabricated with the piezoceramics PZT filler phase and Eccogel polymer matrix phase. This paper represents the pulse-echo response of the 1-3 type composite transducer to check it out to investigate a basic property regarding a level limit switch. The acoustic impedance of 1-3 type composite was improved than that of single phase PZT ceramics. The pulse-echo response of transducer fabricated with the self-made 1-3 type composites resonator was better than that of the solid PZT transducer.

• Nuclear Engineering and Technology
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• 제17권1호
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• pp.25-33
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• 1985

경수형 원자로의 운전과 안전성 해석을 위해 열수력학적 모형을 개발하는 것이 하나의 중요한 과제이다. 특히, 2상류의 열수력학적 모형을 개발하기 위해서는 기포율, 액체막 두께, 유동 영역과 같은 중요한 변수들을 실제로 측정한 값이 필요하다. 본 연구의 목적은 초음파 Pulse-echo 방법을 이용하여 액체 두께를 실험적으로 측정하고, 이론치와 비교 분석하여 (1) 관벽의 두께, (2) 초음파의 주파수, (3) 관벽의 재질 등이 액체막 두께 측정에 미치는 영향을 분석하는 데에 있다. 평판협 (Plate-type)과 관(Tube-type)으로 된 시험관을 이용하여 수평으로 놓인 물-공기의 층류계 (a horizontal airwater stratified system)를 만들어 일련의 액체막 두께 측정 실험을 수행하였다. 시험관의 벽 두께와 초음파 Pulse-echo 의 주파수를 변화시키면서 액체막 두께 측정을 반복하였다. 또한, 관벽의 acoustic impedance가 초음파 Pulse-echo 방법으로 액체막 두께를 측정할 때, 어떠한 영향을 주는가도 아울러 파악하기 위해서 스텐레스 강과 폴리아크릴 (Polyacrylate) 등 재질이 다른 두 개의 격리봉 (Standonff rod) 을 사용하여 액체막 두께를 측정하였다. 이렇게 하여 얻은 실험 결과를 제시하고 실제로 측정한 액체막 두께와 비교 분석하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 추계학술대회 논문집
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• pp.205-208
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• 1995

PZT powders were prepared by the molten salt synthesis method. The porous PZT specimens were prepared from a mixture of PZT and Polyvinylalcohol(PVA) powders by BURPS(Burnout Plastic Sphere) technique. The pulse-echo response of PZT-polymer 3-3 type composite transducer with various PVA wt.% were studied, The fall time of pulse-echo response of PZT-polymer 3-3 type composite transducer was shorten to that of solid PZT-maded transducer. Therefore, a good transmitting and receiving properties could be obtained. The distance between transducer and reflector was in good agreement both solid PZT and PZT-polymer 3-3 type composite fabricated transducer.

• E2M - 전기 전자와 첨단 소재
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• 제8권2호
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• pp.211-216
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• 1995

In this study, the piezoelectric ceramics/polymer composite transducers with 1-3 connectivity have been studied. A piezoelectric ceramics PZT prepared by Wet-Dry Combination method was used as a filler in polymer matrix Eccogel. We've got the pulse-echo response for 1-3 type piezc-electric composite transducers in water. It was shown that the transmitting and receiving sensitivity of 1-3 type piezoelectric composite transducers could be improved in comparison with that- of solid PZT transducers. The reason is for that 1-3 type Piezoelectric composites have low dielectric constant and density. There was in a good agreement between the resonant frequencies calculated from one period and observed results on the Ultrasonic Transducer Analyzer. According to these results we could be figured out the distance in water by virture of the pulse-echo response.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.303-306
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• 1999

In this study, the piezoelectric ceramics PZT powder was synthesized by Wet-Dry combination method. The flexible 1-3-0 type composites were fabricated with piezoceramic PZT and Eccogel polymer matrix embedded 3rd phase. This paper represents the acoustic properties with various 3rd phase wt.%. The acoustic impedance of 1-3-0 type composites was lower than that of single phase PZT ceramics. The pulse-echo response of transducer fabricated with 1-3-0 type composites was better than solid PZT transducer.

• Asia pacific journal of information systems
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• 제9권2호
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• pp.1-17
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• 1999

A feedback echo is a structured restatement of the user's query and informs the user what the system intends to do for the query. This provides backtracking of the user's query so that the user knows how the system has interpreted the query. This study scrutinizes whether the feedback echo, as currently available in the INTELLECT commercial system, can improve the performance of a casual user using a restricted natural language database interface. This study concludes that the particular type of feedback echo available in this commercial system was not effective in terms of overall performance for casual users. It is worth mentioning, however, that the feedback echo was effective for the specific type of error: using wrong conditions for data retrieval.