Pub Date : 2014-04-07DOI: 10.1109/OCEANS-TAIPEI.2014.6964474
S. Nishida, K. Kawaguchi, T. Imaizumi, T. Akamatsu
DONET (Dense Ocean-floor Network system for Earthquakes and Tsunamis) is a submarine cabled real-time observation network for earthquakes and tsunamis monitoring around the Nankai trough, southwestern Japan. The scheduled twenty observatories have operated since August 2011. Various sensors such as a broadband seismometer, a pressure gauge, a hydrophone, etc. are equipped with each observatory, because DONET has expected to obtain the data to understand the Nankai trough mega thrust earthquake seismogenic zones. Therefore, in order to supply data stably, it's important to have a method of an investigation of the performance of each sensor in DONET. In this research, we will evaluate the performance of a hydrophone of DONET. The reference hydrophone was installed several meters from an observatory of DONET. Here, it assumes that both hydrophones will record the acoustic data according to same sound source. And, we will evaluate the performance of a hydrophone by the comparison between reference hydrophone and DONET's one in actual field, and will report the result of the evaluations.
{"title":"An evaluation of the performance of a hydrophone on sea floor","authors":"S. Nishida, K. Kawaguchi, T. Imaizumi, T. Akamatsu","doi":"10.1109/OCEANS-TAIPEI.2014.6964474","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964474","url":null,"abstract":"DONET (Dense Ocean-floor Network system for Earthquakes and Tsunamis) is a submarine cabled real-time observation network for earthquakes and tsunamis monitoring around the Nankai trough, southwestern Japan. The scheduled twenty observatories have operated since August 2011. Various sensors such as a broadband seismometer, a pressure gauge, a hydrophone, etc. are equipped with each observatory, because DONET has expected to obtain the data to understand the Nankai trough mega thrust earthquake seismogenic zones. Therefore, in order to supply data stably, it's important to have a method of an investigation of the performance of each sensor in DONET. In this research, we will evaluate the performance of a hydrophone of DONET. The reference hydrophone was installed several meters from an observatory of DONET. Here, it assumes that both hydrophones will record the acoustic data according to same sound source. And, we will evaluate the performance of a hydrophone by the comparison between reference hydrophone and DONET's one in actual field, and will report the result of the evaluations.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126315672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-04-07DOI: 10.1109/OCEANS-TAIPEI.2014.6964342
G. Page, S. Bainbridge, Scott Gardner, S. Hahn
This paper describes the design, installation and operation of a high-speed, real-time coral reef observing system network at Heron Island, within the Australian Great Barrier Reef. As part of the Queensland Integrated Marine Observing System (Q-IMOS) node of the Australian Integrated Marine Observing System (IMOS), a low data rate wireless sensor network has been operational at Heron Island since 2008. In 2013 a new surface reef pole and underwater cabled Ethernet network were installed on the edge of the Heron Island Reef lagoon, with telemetry back to the Heron Island Research Station achieved using a 300 Mbps wireless 802.11 link. The reef pole provides a network bridge to an underwater-cabled Ethernet network, and also provides an 802.11 wireless access point for the remainder of the Heron Island reef lagoon. Internet protocol networks provide for an extensible architecture, enabling the easy connection of any type of oceanographic instrument, camera or video system to the observing system. Acoustic monitoring receivers for fish tracking are connected to the network to allow for real-time monitoring. The underwater-cabled network is modular in design allowing for easy repair, expansion or reconfiguration of the network for any future requirements. This paper discusses the design considerations, system components and results of using affordable wireless 802.11 networks in a harsh marine environment for coral reef observing systems.
本文介绍了澳大利亚大堡礁Heron岛高速实时珊瑚礁观测系统网络的设计、安装和运行情况。作为澳大利亚综合海洋观测系统(IMOS)的昆士兰综合海洋观测系统(Q-IMOS)节点的一部分，自2008年以来，低数据速率无线传感器网络一直在Heron岛运行。2013年，在Heron Island reef lagoon的边缘安装了一个新的表面礁杆和水下有线以太网网络，通过300 Mbps的无线802.11链路实现遥测回Heron Island研究站。礁杆为水下有线以太网提供了一个网络桥梁，也为赫伦岛礁湖的其余部分提供了一个802.11无线接入点。互联网协议网络提供了一种可扩展的架构，使任何类型的海洋仪器、摄像机或视频系统能够轻松连接到观测系统。用于鱼类跟踪的声学监测接收器连接到网络，以便进行实时监测。水下电缆网络采用模块化设计，可以轻松修复、扩展或重新配置网络，以满足未来的任何需求。本文讨论了在恶劣的海洋环境中使用价格合理的无线802.11网络用于珊瑚礁观测系统的设计考虑、系统组成和结果。
{"title":"Development of a coral reef observing system using 802.11 wireless at Heron Island, Great Barrier Reef","authors":"G. Page, S. Bainbridge, Scott Gardner, S. Hahn","doi":"10.1109/OCEANS-TAIPEI.2014.6964342","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964342","url":null,"abstract":"This paper describes the design, installation and operation of a high-speed, real-time coral reef observing system network at Heron Island, within the Australian Great Barrier Reef. As part of the Queensland Integrated Marine Observing System (Q-IMOS) node of the Australian Integrated Marine Observing System (IMOS), a low data rate wireless sensor network has been operational at Heron Island since 2008. In 2013 a new surface reef pole and underwater cabled Ethernet network were installed on the edge of the Heron Island Reef lagoon, with telemetry back to the Heron Island Research Station achieved using a 300 Mbps wireless 802.11 link. The reef pole provides a network bridge to an underwater-cabled Ethernet network, and also provides an 802.11 wireless access point for the remainder of the Heron Island reef lagoon. Internet protocol networks provide for an extensible architecture, enabling the easy connection of any type of oceanographic instrument, camera or video system to the observing system. Acoustic monitoring receivers for fish tracking are connected to the network to allow for real-time monitoring. The underwater-cabled network is modular in design allowing for easy repair, expansion or reconfiguration of the network for any future requirements. This paper discusses the design considerations, system components and results of using affordable wireless 802.11 networks in a harsh marine environment for coral reef observing systems.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125889726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-04-07DOI: 10.1109/OCEANS-TAIPEI.2014.6964573
Yuehai Zhou, Kun Zeng, F. Tong, Yougan Chen
MIMO systems is capable of achieving two to three spatially parallel communication channels in very shallow water to improve communication performance as well as capacity. For MIMO communications, simultaneous presence of multipath and co-channel interference poses substantial difficulties for the design of receiver. While the classic space-time multi-channel DFE receiver consisting of multiple DFE equalizers is limited by high computational complexity when multipath time delay is large, the low complexity time reversal receiver needs a large number of receivers (>10) to achieve satisfactory performance. This paper presents the design of a selective time reversal underwater acoustic MIMO communication receiver to accommodate the small receiver number of space-time DFE and the multipath focusing capability of time reversal by coupling the time reversal with multi-channel DFE. Sea trial experiments are carried out to demonstrate the superior performance of the proposed method.
{"title":"Selective time reversal receiver for shallow water acoustic MIMO communications","authors":"Yuehai Zhou, Kun Zeng, F. Tong, Yougan Chen","doi":"10.1109/OCEANS-TAIPEI.2014.6964573","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964573","url":null,"abstract":"MIMO systems is capable of achieving two to three spatially parallel communication channels in very shallow water to improve communication performance as well as capacity. For MIMO communications, simultaneous presence of multipath and co-channel interference poses substantial difficulties for the design of receiver. While the classic space-time multi-channel DFE receiver consisting of multiple DFE equalizers is limited by high computational complexity when multipath time delay is large, the low complexity time reversal receiver needs a large number of receivers (>10) to achieve satisfactory performance. This paper presents the design of a selective time reversal underwater acoustic MIMO communication receiver to accommodate the small receiver number of space-time DFE and the multipath focusing capability of time reversal by coupling the time reversal with multi-channel DFE. Sea trial experiments are carried out to demonstrate the superior performance of the proposed method.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129874378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to solve the contradiction of high azimuth resolution and wide swath in sonar and radar imaging, narrowband compressed sensing (CS) imaging has been studied in depth. This paper studies the wideband sonar imaging method via CS. Wideband CS imaging model is constructed. Scaling and Doppler frequency shift are considered in the model. The effect of wideband signal to traditional narrowband model is analyzed. Wideband CS imaging method is constructed. A modified ℓ1-norm minimization algorithm is proposed. It is shown that it is possible to apply CS to wideband sonar imaging. Numerical experiments are conducted and demonstrates the analysis.
{"title":"Wideband sonar imaging via compressed sensing","authors":"Huichen Yan, Shibao Peng, Zhaotong Zhu, Jia Xu, Xudong Zhang","doi":"10.1109/OCEANS-TAIPEI.2014.6964457","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964457","url":null,"abstract":"In order to solve the contradiction of high azimuth resolution and wide swath in sonar and radar imaging, narrowband compressed sensing (CS) imaging has been studied in depth. This paper studies the wideband sonar imaging method via CS. Wideband CS imaging model is constructed. Scaling and Doppler frequency shift are considered in the model. The effect of wideband signal to traditional narrowband model is analyzed. Wideband CS imaging method is constructed. A modified ℓ1-norm minimization algorithm is proposed. It is shown that it is possible to apply CS to wideband sonar imaging. Numerical experiments are conducted and demonstrates the analysis.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129723060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-04-07DOI: 10.1109/OCEANS-TAIPEI.2014.6964288
Huang Mei, Haixin Sun, Qi Jie, Xiaoyan Kuai, Gu Ye
Orthogonal frequency division multiplexing (OFDM) is a promising alternative modulation for underwater acoustic communication due to its ability in mitigating multipath effects. However, the high peak-to-average ratio (PAPR) constraints the power value level especially for long distance transmission. The problem of non-linear distortion generated by using one or more non-linear devices cannot be ignored when the OFDM signal is used to transmit. A novel clipping system model is proposed to simulate the effect of the non-linear distortion, which exploits the clipping operation to reduce the Peak-to-Average-Power-Ratio (PAPR). A new method based on compressed sensing (CS) is used to estimate the clipping values and compensate the effect of the non-linear distortion. It is shown that the clipping and compensation scheme can simulate the nonlinear distortion and significantly alleviate the distortion using CS compensation. The simulation and experiment results will verify the feasibility and advantages of the method.
{"title":"The clipping and nonlinear distortion compensation for underwater acoustic OFDM system","authors":"Huang Mei, Haixin Sun, Qi Jie, Xiaoyan Kuai, Gu Ye","doi":"10.1109/OCEANS-TAIPEI.2014.6964288","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964288","url":null,"abstract":"Orthogonal frequency division multiplexing (OFDM) is a promising alternative modulation for underwater acoustic communication due to its ability in mitigating multipath effects. However, the high peak-to-average ratio (PAPR) constraints the power value level especially for long distance transmission. The problem of non-linear distortion generated by using one or more non-linear devices cannot be ignored when the OFDM signal is used to transmit. A novel clipping system model is proposed to simulate the effect of the non-linear distortion, which exploits the clipping operation to reduce the Peak-to-Average-Power-Ratio (PAPR). A new method based on compressed sensing (CS) is used to estimate the clipping values and compensate the effect of the non-linear distortion. It is shown that the clipping and compensation scheme can simulate the nonlinear distortion and significantly alleviate the distortion using CS compensation. The simulation and experiment results will verify the feasibility and advantages of the method.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128009127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-04-07DOI: 10.1109/OCEANS-TAIPEI.2014.6964436
Y. Kaneda, E. Araki, H. Matsumoto, Takeshi Nakamura, S. Kamiya, K. Ariyoshi, T. Hori, M. Takahashi, T. Baba, M. Nakano, Jin-Kyu Choi, S. Nishida
The Nankai trough is one of the largest and hazardous seismogenic zones in the world. Around the Nankai Trough, there are 3 mega thrust earthquake seismogenic zones such as the Tokai, Tonankai and Nakai seismogenic zones. Especially, the estimation of seismic linkage between the Tonankai and Nankai seismogenic zone is very important and indispensable for the reduction of earthquake and tsunami damages. Actually, the Tonankai and Nankai earthquake occurred in 1944/ 1946, 1854 as the seismic linkage events. Therefore, for understandings of early warning and prediction of erathquakes and tsunamis, the ocean floor network equipped with multi kinds of sensors such as seismometers and pressure gauges are very important and significant tool to monitor the broad band phenomena in the Nankai seismogenic zones. In the Tonankai seismogenic zone, we constructed DONET (Dense Ocean floor Network for Earthquakes and Tsunamis) with 20 observatories for early warning and improvement of prediction reliability. Multi kinds of sensors such as an accelerometer, a broad band seismometer, a precise pressure gauge, a differential pressure gauge and a precise thermometer are equipped in each observatory. Furthermore, the long term borehole observatory system with the seismometer, strainmeter, tiltmeter etc. is already installed in the drilled hole by IOPD NanTroSEIZE project, finally, this system will connect to DONET for the 3 dimensional real time monitoring. Now, we are already developing DONET2 with 31 observatories around the Nankai seismogenic zone and will complete deployments within 3 years. DONET2 system is more powerful rather than DONET system to monitor the large seismogenic zone areas. Especially, these offshore real time data will be applied to estimate of tsunami scales. We have to learn the lesson from tsunami damages of East Japan Earthquake 2011, Sumatra Earthquake 2004 etc. So, we are developing the advanced tsunami early estimation system using not only real time monitoring but also advanced simulation.
{"title":"Advanced technology and application of the ocean floor observatory around the Nankai trough, Southwestern Japan","authors":"Y. Kaneda, E. Araki, H. Matsumoto, Takeshi Nakamura, S. Kamiya, K. Ariyoshi, T. Hori, M. Takahashi, T. Baba, M. Nakano, Jin-Kyu Choi, S. Nishida","doi":"10.1109/OCEANS-TAIPEI.2014.6964436","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964436","url":null,"abstract":"The Nankai trough is one of the largest and hazardous seismogenic zones in the world. Around the Nankai Trough, there are 3 mega thrust earthquake seismogenic zones such as the Tokai, Tonankai and Nakai seismogenic zones. Especially, the estimation of seismic linkage between the Tonankai and Nankai seismogenic zone is very important and indispensable for the reduction of earthquake and tsunami damages. Actually, the Tonankai and Nankai earthquake occurred in 1944/ 1946, 1854 as the seismic linkage events. Therefore, for understandings of early warning and prediction of erathquakes and tsunamis, the ocean floor network equipped with multi kinds of sensors such as seismometers and pressure gauges are very important and significant tool to monitor the broad band phenomena in the Nankai seismogenic zones. In the Tonankai seismogenic zone, we constructed DONET (Dense Ocean floor Network for Earthquakes and Tsunamis) with 20 observatories for early warning and improvement of prediction reliability. Multi kinds of sensors such as an accelerometer, a broad band seismometer, a precise pressure gauge, a differential pressure gauge and a precise thermometer are equipped in each observatory. Furthermore, the long term borehole observatory system with the seismometer, strainmeter, tiltmeter etc. is already installed in the drilled hole by IOPD NanTroSEIZE project, finally, this system will connect to DONET for the 3 dimensional real time monitoring. Now, we are already developing DONET2 with 31 observatories around the Nankai seismogenic zone and will complete deployments within 3 years. DONET2 system is more powerful rather than DONET system to monitor the large seismogenic zone areas. Especially, these offshore real time data will be applied to estimate of tsunami scales. We have to learn the lesson from tsunami damages of East Japan Earthquake 2011, Sumatra Earthquake 2004 etc. So, we are developing the advanced tsunami early estimation system using not only real time monitoring but also advanced simulation.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130228323","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-04-07DOI: 10.1109/OCEANS-TAIPEI.2014.6964463
G. Too, Yi-Wei Lin, Yuhong Ke
In the shallow water environment, detecting and classifying buried objects is a challenging problem with high operational importance. Acoustical wave becomes an important tool in the detection of objects in underwater systems due to its effectiveness of propagation in the water. Later on, the acoustic scattered field modal for fluid-loaded and thin spherical shell have been determined by the shell's physical properties and appropriate boundary conditions at the fluid interface. These spherical elastic shells produce lamb waves that contain energy within corresponding frequency bandwidth. The iterative time reversal process is then performed to enhance energy of responding lamb waves and makes it possible to distinguish target characteristics. In addition, target distance can be determined from wave propagation time. The study is developing a procedure to distinguish target characteristics such as material and size by observing convergence frequency through iterative time reversal process. The proposed procedure is verified from designed simulations and experiments by using spherical elastic shells as targets. In experiments, interrogating signals are transmitted from an unfocused broadband underwater transducer and recorded received by another same type transducer. Due to the enhancing effect of iterative time reversal, energy of iterative receiving signals converges to certain frequencies. After comparing these frequencies from varying target characteristics such as diameter of target sphere shell and thick of target sphere shell, the result proves that the proposed procedure is capable to distinguished properties of different targets.
{"title":"Echoes analysis from spherical elastic shells by using iterative time reversal mirror","authors":"G. Too, Yi-Wei Lin, Yuhong Ke","doi":"10.1109/OCEANS-TAIPEI.2014.6964463","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964463","url":null,"abstract":"In the shallow water environment, detecting and classifying buried objects is a challenging problem with high operational importance. Acoustical wave becomes an important tool in the detection of objects in underwater systems due to its effectiveness of propagation in the water. Later on, the acoustic scattered field modal for fluid-loaded and thin spherical shell have been determined by the shell's physical properties and appropriate boundary conditions at the fluid interface. These spherical elastic shells produce lamb waves that contain energy within corresponding frequency bandwidth. The iterative time reversal process is then performed to enhance energy of responding lamb waves and makes it possible to distinguish target characteristics. In addition, target distance can be determined from wave propagation time. The study is developing a procedure to distinguish target characteristics such as material and size by observing convergence frequency through iterative time reversal process. The proposed procedure is verified from designed simulations and experiments by using spherical elastic shells as targets. In experiments, interrogating signals are transmitted from an unfocused broadband underwater transducer and recorded received by another same type transducer. Due to the enhancing effect of iterative time reversal, energy of iterative receiving signals converges to certain frequencies. After comparing these frequencies from varying target characteristics such as diameter of target sphere shell and thick of target sphere shell, the result proves that the proposed procedure is capable to distinguished properties of different targets.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"227 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122351237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-04-07DOI: 10.1109/OCEANS-TAIPEI.2014.6964532
S. Liang, N. Kuo, D. Doong, T. Hsu
Wind effect on Kuroshio-induced island wake downstream the Green Island, Taiwan is studied using a depth-averaged shallow-water model. Seasonal monsoon effect on spatial-temporal scales, such as aspect ratio, dimensionless width, and Strouhal number as well as propagation speed of the vortices of Reynolds number 50 is studied. It is found that northeast monsoon has more pronounced effect in wake characteristics than southwest monsoon does, in terms of flow speed and recirculation zone, the aspect ratio, and dimensionless width. Vortices are pushed back close to the island with a smaller size of recirculation when Kuroshio flows against the northeast monsoon; Vortices are pushed farther downstream with a larger size of recirculation when Kuroshio flows in favor of the southwest monsoon. However, wind effect on temporal variation of island wake seems insignificant. The Strouhal number is between 0.116 and 0.125 from numerical simulations. This value is close to result of previous reports.
{"title":"Numerical study of wind effect on green island wake","authors":"S. Liang, N. Kuo, D. Doong, T. Hsu","doi":"10.1109/OCEANS-TAIPEI.2014.6964532","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964532","url":null,"abstract":"Wind effect on Kuroshio-induced island wake downstream the Green Island, Taiwan is studied using a depth-averaged shallow-water model. Seasonal monsoon effect on spatial-temporal scales, such as aspect ratio, dimensionless width, and Strouhal number as well as propagation speed of the vortices of Reynolds number 50 is studied. It is found that northeast monsoon has more pronounced effect in wake characteristics than southwest monsoon does, in terms of flow speed and recirculation zone, the aspect ratio, and dimensionless width. Vortices are pushed back close to the island with a smaller size of recirculation when Kuroshio flows against the northeast monsoon; Vortices are pushed farther downstream with a larger size of recirculation when Kuroshio flows in favor of the southwest monsoon. However, wind effect on temporal variation of island wake seems insignificant. The Strouhal number is between 0.116 and 0.125 from numerical simulations. This value is close to result of previous reports.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125473585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-04-07DOI: 10.1109/OCEANS-TAIPEI.2014.6964585
J. Seemann, M. Stresser, F. Ziemer, J. Horstmann, Li-Chung Wu
This paper presents the dynamic features of gravity waves based on coherent radar observations. We demonstrate that it is practical to detect wave breaking events via the sea surface backscattering intensity and Doppler velocity. Both parameters are acquired from coherent X-band radars operating at grazing incidence. Our measurements show a range dependency of the Doppler velocity which results from the wave shoaling as well as wave shadowing due to the low grazing angle of the observations. After separating these two effects, we can estimate the energy loss due to wave shoaling and wave breaking.
{"title":"Coherent microwave radar backscatter from shoaling and breaking sea surface waves","authors":"J. Seemann, M. Stresser, F. Ziemer, J. Horstmann, Li-Chung Wu","doi":"10.1109/OCEANS-TAIPEI.2014.6964585","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964585","url":null,"abstract":"This paper presents the dynamic features of gravity waves based on coherent radar observations. We demonstrate that it is practical to detect wave breaking events via the sea surface backscattering intensity and Doppler velocity. Both parameters are acquired from coherent X-band radars operating at grazing incidence. Our measurements show a range dependency of the Doppler velocity which results from the wave shoaling as well as wave shadowing due to the low grazing angle of the observations. After separating these two effects, we can estimate the energy loss due to wave shoaling and wave breaking.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121537580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-04-07DOI: 10.1109/OCEANS-TAIPEI.2014.6964400
Rui Duan, Kunde Yang
Pulse propagation in the surface duct with the source far below the duct is analyzed. Experimental results show that through the duct, the sound can propagate to the range much farther than that predicted by the ray theory. Besides, the propagation range is strongly related with the signal frequency. This propagation path is reproduced using the normal mode model. Furthermore, the ray representation of the normal mode is used to illustrate the mechanism of this surface-duct-related arrival. It is found that the arrival is due to the diffraction when a ray grazes the bottom of the surface duct. For lower frequency, the grazing angle is larger. Therefore, the energy diffracted back to the surface duct is weaker.
{"title":"Analysis of pulse propagation in the surface duct with a deep source","authors":"Rui Duan, Kunde Yang","doi":"10.1109/OCEANS-TAIPEI.2014.6964400","DOIUrl":"https://doi.org/10.1109/OCEANS-TAIPEI.2014.6964400","url":null,"abstract":"Pulse propagation in the surface duct with the source far below the duct is analyzed. Experimental results show that through the duct, the sound can propagate to the range much farther than that predicted by the ray theory. Besides, the propagation range is strongly related with the signal frequency. This propagation path is reproduced using the normal mode model. Furthermore, the ray representation of the normal mode is used to illustrate the mechanism of this surface-duct-related arrival. It is found that the arrival is due to the diffraction when a ray grazes the bottom of the surface duct. For lower frequency, the grazing angle is larger. Therefore, the energy diffracted back to the surface duct is weaker.","PeriodicalId":114739,"journal":{"name":"OCEANS 2014 - TAIPEI","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124344269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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