In multi-component seismic exploration, the horizontal and vertical components both contain P- and SV-waves. The P- and SV-wavefields in a seismic record can be separated by their horizontal and vertical displacements...In multi-component seismic exploration, the horizontal and vertical components both contain P- and SV-waves. The P- and SV-wavefields in a seismic record can be separated by their horizontal and vertical displacements when upgoing P- and SV-waves arrive at the sea floor. If the sea floor P wave velocity, S wave velocity, and density are known, the separation can be achieved in ther-p domain. The separated wavefields are then transformed to the time domain. A method of separating P- and SV-wavefields is presented in this paper and used to effectively separate P- and SV-wavefields in synthetic and real data. The application to real data shows that this method is feasible and effective. It also can be used for free surface data.展开更多
Wave energy resources assessment is a very important process before the exploitation and utilization of the wave energy. At present, the existing wave energy assessment is focused on theoretical wave energy conditions...Wave energy resources assessment is a very important process before the exploitation and utilization of the wave energy. At present, the existing wave energy assessment is focused on theoretical wave energy conditions for interesting areas. While the evaluation for exploitable wave energy conditions is scarcely ever performed. Generally speaking, the wave energy are non-exploitable under a high sea state and a lower sea state which must be ignored when assessing wave energy. Aiming at this situation, a case study of the East China Sea and the South China Sea is performed. First, a division basis between the theoretical wave energy and the exploitable wave energy is studied. Next, based on recent 20 a ERA-Interim wave field data, some indexes including the spatial and temporal distribution of wave power density, a wave energy exploitable ratio, a wave energy level, a wave energy stability, a total wave energy density, the seasonal variation of the total wave energy and a high sea condition frequency are calculated. And then the theoretical wave energy and the exploitable wave energy are compared each other; the distributions of the exploitable wave energy are assessed and a regional division for exploitable wave energy resources is carried out; the influence of the high sea state is evaluated. The results show that considering collapsing force of the high sea state and the utilization efficiency for wave energy, it is determined that the energy by wave with a significant wave height being not less 1 m or not greater than 4 m is the exploitable wave energy. Compared with the theoretical wave energy, the average wave power density, energy level, total wave energy density and total wave energy of the exploitable wave energy decrease obviously and the stability enhances somewhat. Pronounced differences between the theoretical wave energy and the exploitable wave energy are present. In the East China Sea and the South China Sea, the areas of an abundant and stable exploitable wave energy are primarily located in the north-central part of the South China Sea, the Luzon Strait, east of Taiwan, China and north of Ryukyu Islands; annual average exploitable wave power density values in these areas are approximately 10-15 kW/m; the exploitable coefficient of variation （COV） and seasonal variation （SV） values in these areas are less than 1.2 and 1, respectively. Some coastal areas of the Beibu Gulf, the Changjiang Estuary, the Hangzhou Bay and the Zhujiang Estuary are the poor areas of the wave energy. The areas of the high wave energy exploitable ratio is primarily in nearshore waters. The influence of the high sea state for the wave energy in nearshore waters is less than that in offshore waters. In the areas of the abundant wave energy, the influence of the high sea state for the wave energy is prominent and the utilization of wave energy is relatively difficult. The developed evaluation method may give some references for an exploitable wave energy assessment and is valuable for practical applications.展开更多
In marine seismic exploration, ocean-bottom cable techniques accurately record the multicomponent seismic wavefield; however, the seismic wave propagation in fluid–solid media cannot be simulated by a single wave equ...In marine seismic exploration, ocean-bottom cable techniques accurately record the multicomponent seismic wavefield; however, the seismic wave propagation in fluid–solid media cannot be simulated by a single wave equation. In addition, when the seabed interface is irregular, traditional finite-difference schemes cannot simulate the seismic wave propagation across the irregular seabed interface. Therefore, an acoustic–elastic forward modeling and vector-based P-and S-wave separation method is proposed. In this method, we divide the fluid–solid elastic media with irregular interface into orthogonal grids and map the irregular interface in the Cartesian coordinates system into a horizontal interface in the curvilinear coordinates system of the computational domain using coordinates transformation. The acoustic and elastic wave equations in the curvilinear coordinates system are applied to the fluid and solid medium, respectively. At the irregular interface, the two equations are combined into an acoustic–elastic equation in the curvilinear coordinates system. We next introduce a full staggered-grid scheme to improve the stability of the numerical simulation. Thus, separate P-and S-wave equations in the curvilinear coordinates system are derived to realize the P-and S-wave separation method.展开更多
Wind and wave data are essential in climatological and engineering design applications.In this study,data from 15 buoys located throughout the South China Sea(SCS)were used to evaluate the ERA5 wind and wave data.Appl...Wind and wave data are essential in climatological and engineering design applications.In this study,data from 15 buoys located throughout the South China Sea(SCS)were used to evaluate the ERA5 wind and wave data.Applicability assessment are beneficial for gaining insight into the reliability of the ERA5 data in the SCS.The bias range between the ERA5 and observed wind-speed data was-0.78-0.99 m/s.The result indicates that,while the ERA5 wind-speed data underestimation was dominate,the overestimation of such data existed as well.Additionally,the ERA5 data underestimated annual maximum wind-speed by up to 38%,with a correlation coefficient>0.87.The bias between the ERA5 and observed significant wave height(SWH)data varied from-0.24 to 0.28 m.And the ERA5 data showed positive SWH bias,which implied a general underestimation at all locations,except those in the Beibu Gulf and centralwestern SCS,where overestimation was observed.Under extreme conditions,annual maximum SWH in the ERA5 data was underestimated by up to 30%.The correlation coefficients between the ERA5 and observed SWH data at all locations were greater than 0.92,except in the central-western SCS(0.84).The bias between the ERA5 and observed mean wave period(MWP)data varied from-0.74 to 0.57 s.The ERA5 data showed negative MWP biases implying a general overestimation at all locations,except for B1(the Beibu Gulf)and B7(the northeastern SCS),where underestimation was observed.The correlation coefficient between the ERA5 and observed MWP data in the Beibu Gulf was the smallest(0.56),and those of other locations fluctuated within a narrow range from 0.82 to 0.90.The intercomparison indicates that during the analyzed time-span,the ERA5 data generally underestimated wind-speed and SWH,but overestimated MWP.Under non-extreme conditions,the ERA5 wind-speed and SWH data can be used with confidence in most regions of the SCS,except in the central-western SCS.展开更多
Wave energy resource is a very important ocean renewable energy. A reliable assessment of wave energy resources must be performed before they can be exploited. Compared with wave model, altimeter can provide more accu...Wave energy resource is a very important ocean renewable energy. A reliable assessment of wave energy resources must be performed before they can be exploited. Compared with wave model, altimeter can provide more accurate in situ observations for ocean wave which can be as a novel method for wave energy assessment.The advantage of altimeter data is to provide accurate significant wave height observations for wave. In order to develop characteristic and advantage of altimeter data and apply altimeter data to wave energy assessment, in this study, we established an assessing method for wave energy in local sea area which is dedicated to altimeter data.This method includes three parts including data selection and processing, establishment of evaluation indexes system and criterion of regional division. Then a case study of Northwest Pacific was performed to discuss specific application for this method. The results show that assessing method in this paper can assess reserves and temporal and spatial distribution effectively and provide scientific references for the siting of wave power plants and the design of wave energy convertors.展开更多
Coastal defenses such as the breakwaters are important structures to maintain the navigation conditions in a harbor.The estimation of their hydrodynamic characteristics is conventionally done using physical models,sub...Coastal defenses such as the breakwaters are important structures to maintain the navigation conditions in a harbor.The estimation of their hydrodynamic characteristics is conventionally done using physical models,subjecting to higher costs and prolonged procedures.Soft computing methods prove to be useful tools,in cases where the data availability from physical models is limited.The present paper employs adaptive neuro-fuzzy inference system(ANFIS)and artificial neural network(ANN)models to the data obtained from physical model studies to develop a novel methodology to predict the reflection coefficient(Kr)of seaside perforated semicircular breakwaters under low wave heights,for which no physical model data is available.The prediction was done using the input parameters viz.,incident wave height(Hi),wave period(T),center-to-center spacing of perforations(S),diameter of perforations(D),radius of semicircular caisson(R),water depth(d),and semicircular breakwater structure height(hs).The study shows the prediction below the available data range of wave heights is possible by ANFIS and ANN models.However,the ANFIS performed better with R^2=0.9775 and the error reduced in comparison with the ANN model with R2=0.9751.Study includes conventional data segregation and prediction using ANN and ANFIS.展开更多
The vertical cable method for acquiring and processing pre-stack 3-D marine seismic data is based on the technology developed by the US Navy for antisubmarine warfare. In order to achieve the maximum utili- zation of ...The vertical cable method for acquiring and processing pre-stack 3-D marine seismic data is based on the technology developed by the US Navy for antisubmarine warfare. In order to achieve the maximum utili- zation of vertical cable field data, a new separation method of the up-going and down-going wave fields of the vertical cable data processing was developed in this paper, which is different from the separation of the down-going and up-going wave fields of normal VSP data processing. In tests with synthetic modeling data and actual field data, this newly developed method performs well and is also computationally simpler without pre-assumption conditions.展开更多
For sequential performance of wave variational data assimilation, we proposed a temporal sliding method in which the temporal overlap is considered. The advantage of this method is that the initial wave spectrum of th...For sequential performance of wave variational data assimilation, we proposed a temporal sliding method in which the temporal overlap is considered. The advantage of this method is that the initial wave spectrum of the optimization process is modified by the observations in latter and former times. This temporal sliding procedure is important for marginal region, such as the China seas, where the duration of assimilation effectiveness is 2-3 days. Experiments were performed in the whole course of Cyclone 9403 （Russ）. Around the cyclone center, the maximum value of wave elements did not change much by assimilation, because the extreme value was determined by wind energy input that was not yet optimized. In the area outside the cyclone center, this modification is evident especially for wind wave growth.展开更多
This study applies Ensemble Optimal Interpolation(EnOI)to assimilate individual spectral components derived from National Data Buoy Center(NDBC)buoy directional spectra into the WAVEWATCHⅢ(WW3)wave model during tropi...This study applies Ensemble Optimal Interpolation(EnOI)to assimilate individual spectral components derived from National Data Buoy Center(NDBC)buoy directional spectra into the WAVEWATCHⅢ(WW3)wave model during tropical cyclone(TC)Isaias(2020).The analysis provides a comprehensive evaluation of the assimilation’s impact on wave parameters,frequency spectra,and directional spectra.Two series of assimilation experiments—one based on spectral components(Exp^(*)-DaSpec)and the other on significant wave height(Exp^(*)-DaSWH)—are evaluated against a non-assimilated control run(Exp-NoDa).Particular focus is placed on six key parameters:SWH,mean wave period(MWP),mean wave direction(MWD),mean wave directional spread(MWS),dominant wave period(DWP),and dominant wave direction(DWD).Sensitivity analyses suggest 400 km and 0.30 as appropriate values for the localization radius and observation error variance,respectively,though no single setting is optimal across all wave parameters.Exp4-DaSWH and Exp4-DaSpec are therefore selected as representative experiments.In non-independent validation,Exp4-DaSpec generally outperforms Exp-NoDa across MWP,MWD,MWS,DWP,and DWD,demonstrating closer agreement with observed frequency spectra and directional patterns.In independent validation,Exp4-DaSpec maintains superior overall performance,whereas Exp4-DaSWH shows only limited improvement.Exp4-DaSWH may capture the spectral peak near 0.1 Hz,although its directional characteristics remain largely similar to those of Exp-NoDa.Importantly,the assimilation experiments significantly improve SWH in both non-independent and independent validations,with Exp4-DaSWH slightly outperforming Exp4-DaSpec overall.展开更多
Studies of offshore wave climate based on satellite altimeter significant wave height（SWH） have widespread application value. This study used a calibrated multi-altimeter SWH dataset to investigate the wave climate ...Studies of offshore wave climate based on satellite altimeter significant wave height（SWH） have widespread application value. This study used a calibrated multi-altimeter SWH dataset to investigate the wave climate characteristics in the offshore areas of China. First, the SWH measurements from 28 buoys located in China＇s coastal seas were compared with an Ifremer calibrated altimeter SWH dataset. Although the altimeter dataset tended to slightly overestimate SWH, it was in good agreement with the in situ data in general. The correlation coefficient was 0.97 and the root-mean-square（RMS） of differences was 0.30 m. The validation results showed a slight difference in different areas. The correlation coefficient was the maximum（0.97） and the RMS difference was the minimum（0.28 m） in the area from the East China Sea to the north of the South China Sea.The correlation coefficient of approximately 0.95 was relatively low in the seas off the Changjiang（Yangtze River） Estuary. The RMS difference was the maximum（0.32 m） in the seas off the Changjiang Estuary and was0.30 m in the Bohai Sea and the Yellow Sea. Based on the above evidence, it is confirmed that the multialtimeter wave data are reliable in China＇s offshore areas. Then, the characteristics of the wave field, including the frequency of huge waves and the multi-year return SWH in China＇s offshore seas were analyzed using the23-year altimeter wave dataset. The 23-year mean SWH generally ranged from 0.6-2.2 m. The greatest SWH appeared in the southeast of the China East Sea, the Taiwan Strait and the northeast of the South China Sea.Obvious seasonal variation of SWH was found in most areas; SWH was greater in winter and autumn than in summer and spring. Extreme waves greater than 4 m in height mainly occurred in the following areas： the southeast of the East China Sea, the south of the Ryukyu Islands, the east of Taiwan-Luzon Island, and the Dongsha Islands extending to the Zhongsha Islands, and the frequency of extreme waves was 3%-6%. Extreme waves occurred most frequently in autumn and rarely in spring. The 100-year return wave height was greatest from the northwest Pacific seas extending to southeast of the Ryukyu Islands（9-12 m）, and the northeast of the South China Sea and the East China Sea had the second largest wave heights（7-11 m）. For inshore areas, the100-year return wave height was the greatest in the waters off the east coast of Guangdong Province and the south coast of Zhejiang Province（7-8 m）, whereas it was at a minimum in the area from the Changjiang Estuary to the Bohai Sea（4-6 m）. An investigation of sampling effects indicates that when using the 1°×1°grid dataset, although the combination of nine altimeters obviously enhanced the time and space coverage of sampling, the accuracy of statistical results, particularly extreme values obtained from the dataset, still suffered from undersampling problems because the time sampling percent in each 1°×1°grid cell was always less than33%.展开更多
The sea-surface height （SSH） signatures of internal tides extracted from the TOPEX/Poseidon （T/P） altimeter data along satellite tracks are fitted with superposition of several plane waves which have different wav...The sea-surface height （SSH） signatures of internal tides extracted from the TOPEX/Poseidon （T/P） altimeter data along satellite tracks are fitted with superposition of several plane waves which have different wavenumber vectors. The key problem of plane wave fitting with iterative method is how to determine the initial value of wavenumber of each plane wave. The previous solving method is to analyze the internal tidal SSH signatures along each track with wavenumber spectrum. But it is found that the problem cannot be solved completely with the wavenumber spectrum analysis method only. The method based on the combination of wavenumber spectrum analysis method and the exhaustive method is proposed to determine the initial values of wavenumbers for iteration. Numerical results indicate that the proposed method is not only reasonable and feasible but also better than the previous method. The proposed method is an improvement of the previous one, which is beneficial to improving the precision of plane wave fitting of the T/P internal tidal SSH signatures and deepening the understanding of the internal tides in ocean.展开更多
This article provides a method by which the scour depth and scour width below pipelines,and the scour depth around single vertical piles as well as the time scales of scour for both structures due to bichromatic and b...This article provides a method by which the scour depth and scour width below pipelines,and the scour depth around single vertical piles as well as the time scales of scour for both structures due to bichromatic and bidirectional waves are calculated.The scour and time scale formulae summarized by Sumer and Fredsøe(2002)as well as the bottom shear stress formulae under bichromatic and bidirectional waves by Myrhaug et al.(2023)are used.Results for unidirectional bichromatic waves and symmetrically bidirectional monochromatic waves are provided,showing qualitative agreement with what is expected physically.Qualitative comparisons are made with the data from Schendel et al.’s(2020)small scale laboratory tests on scour around a monopile induced by directionally spread waves.Applications to related cases for pipelines are also suggested.In order to conclude regarding the validity of the method for pipelines and vertical piles,it is required to compare with data in its validity range.展开更多
Wave steepness is an important characteristic of a high sea state, and is widely applied on wave propagations at ports, ships, offshore platforms, and CO2 circulation in the ocean. Obtaining wave steepness is a diffic...Wave steepness is an important characteristic of a high sea state, and is widely applied on wave propagations at ports, ships, offshore platforms, and CO2 circulation in the ocean. Obtaining wave steepness is a difficult task that depends heavily on theoretical research on wavelength distribution and direct observations. Development of remote-sensing techniques provides new opportunities to study wave steepness. At present, two formulas are proposed to estimate wave steepness from QuikSCAT and ERS-1/2 scatterometer data. We found that wave steepness retrieving is not affected by radar band, and polarization method, and that relationship of wave steepness with radar backscattering cross section is similar to that with wind. Therefore, we adopted and modified a genetic algorithm for relating wave steepness with radar backscattering cross section. Results show that the root-mean-square error of the wave steepness retrieved is 0.005 in two cases from ERS-1/2 scatterometer data and from QuikSCAT scatterometer data.展开更多
BACKGROUND Diagnostic errors in critical care settings are a significant challenge,often leading to adverse patient outcomes and increased healthcare costs.Millimeter-wave(mmWave)technology,with its ability to provide...BACKGROUND Diagnostic errors in critical care settings are a significant challenge,often leading to adverse patient outcomes and increased healthcare costs.Millimeter-wave(mmWave)technology,with its ability to provide high-resolution,real-time data,offers a transformative solution to enhance diagnostic accuracy and patient safety.This paper explores the integration of mmWave technology in intensive care units(ICUs)to enable non-invasive monitoring,minimize diagnostic errors,and improve clinical decision-making.By addressing key challenges,including data latency,signal interference,and implementation feasibility,this approach has the potential to revolutionize patient monitoring systems and set a new standard for critical care delivery.The paper discusses the high prevalence of diagnostic errors in medical care,particularly in primary care and ICUs,and emphasizes the need for improvement in diagnostic accuracy.Diagnostic errors are responsible for a significant number of deaths,disabilities,prolonged hospitalizations and delays in diagnosis worldwide.AIM To address this issue,the paper proposes the use of ultrafast wireless medical big data transmission in primary care,specifically in remote smart sensors monitoring devices.It suggests that wireless transmission with a speed up to 100 Gb/s(12.5 Gbytes/s)within a short distance(1-10 meters)is necessary to reduce diagnostic errors.METHODS The method used in the study,includes system design and testing a channel sounder operating at 63.4-64.4 GHz frequency range.The system demonstrated dynamic range of 70 dB,noise level of-110 dBm,and a time resolution of 1 ns.The experiment measured the impulse response of the channel in 36 locations within the primary care/ICU scenario.RESULTS The system was tested in a simulated ICU environment to evaluate the Latency:Assessing the time delay in data transmission and processing.The results of the study showed that the system met the requirements of ICUs,providing excellent latency values.The delay spread and excess delay values were within acceptable limits,indicating successful resolution of ICU requirements.The paper suggests timely deployment of such a system.Impact on data transmission:A 100 MB magnetic resonance imaging scan can be transmitted in approximately 0.008 seconds;A 1 GB scan would take approximately 0.08 seconds;This capability could revolutionize healthcare,enabling real-time remote diagnostics and comparisons with artificial Intelligence models,even in large-scale systems.CONCLUSION The experiment demonstrated the feasibility of using high-speed wireless transmission for improved diagnostics in ICUs,offering potential benefits in terms of reduced errors and improved patient outcomes.The findings are deemed valuable to the medical community and public healthcare systems,and it is suggested further research in this area.展开更多
With the observation of a series of ground-based laser interferometer gravitational wave(GW)detectors such as LIGO and Virgo,nearly 100 GW events have been detected successively.At present,all detected GW events are g...With the observation of a series of ground-based laser interferometer gravitational wave(GW)detectors such as LIGO and Virgo,nearly 100 GW events have been detected successively.At present,all detected GW events are generated by the mergers of compact binary systems and are identified through the data processing of matched filtering.Based on matched filtering,we use the GW waveform of the Newtonian approximate(NA)model constructed by linearized theory to match the events detected by LIGO and injections to determine the coalescence time and utilize the frequency curve for data fitting to estimate the parameters of the chirp masses of binary black holes(BBHs).The average chirp mass of our results is 22.05_(-6.31)^(+6.31)M_(⊙),which is very close to 23.80_(-3.52)^(+4.83)M_(⊙)provided by GWOSC.In the process,we can analyze LIGO GW events and estimate the chirp masses of the BBHs.This work presents the feasibility and accuracy of the low-order approximate model and data fitting in the application of GW data processing.It is beneficial for further data processing and has certain research value for the preliminary application of GW data.展开更多
目的:分析心电图P波参数对高血压心房颤动(Atrial fibrillation,AF)患者消融术后复发的预测价值。方法:回顾性分析2023年1月至2024年10月我院首次接受消融术的87例高血压AF患者资料,参考术后12 m内是否复发分复发组(21例)和非复发组(66...目的:分析心电图P波参数对高血压心房颤动(Atrial fibrillation,AF)患者消融术后复发的预测价值。方法:回顾性分析2023年1月至2024年10月我院首次接受消融术的87例高血压AF患者资料,参考术后12 m内是否复发分复发组(21例)和非复发组(66例),比较两组P波终末电势(P-wave terminal force in lead V1,PtfV1)、P波离散度(P-wave dispersion,Pd)、P波变异(P-wave variation,Pv)及最大P波时限(Maximum P-wave duration,Pmax),分析上述指标与术后复发的关系及预测价值。结果:与非复发组对比,复发组Pd、Pv、Pmax均更高(P<0.05),但对比两组PtfV1,差异无统计学意义(P>0.05);多因素Logistic回归分析显示,Pd、Pv、Pmax与高血压AF患者术后复发显著相关(P<0.05);绘制受试者工作特征曲线结果显示,Pd、Pv、Pmax三者联合预测高血压AF患者复发的曲线下面积为0.840,均高于单一指标预测(P<0.05)。结论:Pd、Pv、Pmax三者联合在高血压AF患者术后复发中预测价值较高。展开更多
基金This research is sponsored by National Natural Science Foundation of China （No. 40272041） and Innovative Foundation of CNPC （N0. 04E702）.
文摘In multi-component seismic exploration, the horizontal and vertical components both contain P- and SV-waves. The P- and SV-wavefields in a seismic record can be separated by their horizontal and vertical displacements when upgoing P- and SV-waves arrive at the sea floor. If the sea floor P wave velocity, S wave velocity, and density are known, the separation can be achieved in ther-p domain. The separated wavefields are then transformed to the time domain. A method of separating P- and SV-wavefields is presented in this paper and used to effectively separate P- and SV-wavefields in synthetic and real data. The application to real data shows that this method is feasible and effective. It also can be used for free surface data.
基金The Dragon III Project of the European Space Agency and Ministry of Science and Technology of China under contract No.10412the Ocean Renewable Energy Special Fund Project of State Oceanic Administration of China under contract No.GHME2011ZC07the National Natural Science Foundation of China(NSFC)under contract No.41176157
文摘Wave energy resources assessment is a very important process before the exploitation and utilization of the wave energy. At present, the existing wave energy assessment is focused on theoretical wave energy conditions for interesting areas. While the evaluation for exploitable wave energy conditions is scarcely ever performed. Generally speaking, the wave energy are non-exploitable under a high sea state and a lower sea state which must be ignored when assessing wave energy. Aiming at this situation, a case study of the East China Sea and the South China Sea is performed. First, a division basis between the theoretical wave energy and the exploitable wave energy is studied. Next, based on recent 20 a ERA-Interim wave field data, some indexes including the spatial and temporal distribution of wave power density, a wave energy exploitable ratio, a wave energy level, a wave energy stability, a total wave energy density, the seasonal variation of the total wave energy and a high sea condition frequency are calculated. And then the theoretical wave energy and the exploitable wave energy are compared each other; the distributions of the exploitable wave energy are assessed and a regional division for exploitable wave energy resources is carried out; the influence of the high sea state is evaluated. The results show that considering collapsing force of the high sea state and the utilization efficiency for wave energy, it is determined that the energy by wave with a significant wave height being not less 1 m or not greater than 4 m is the exploitable wave energy. Compared with the theoretical wave energy, the average wave power density, energy level, total wave energy density and total wave energy of the exploitable wave energy decrease obviously and the stability enhances somewhat. Pronounced differences between the theoretical wave energy and the exploitable wave energy are present. In the East China Sea and the South China Sea, the areas of an abundant and stable exploitable wave energy are primarily located in the north-central part of the South China Sea, the Luzon Strait, east of Taiwan, China and north of Ryukyu Islands; annual average exploitable wave power density values in these areas are approximately 10-15 kW/m; the exploitable coefficient of variation （COV） and seasonal variation （SV） values in these areas are less than 1.2 and 1, respectively. Some coastal areas of the Beibu Gulf, the Changjiang Estuary, the Hangzhou Bay and the Zhujiang Estuary are the poor areas of the wave energy. The areas of the high wave energy exploitable ratio is primarily in nearshore waters. The influence of the high sea state for the wave energy in nearshore waters is less than that in offshore waters. In the areas of the abundant wave energy, the influence of the high sea state for the wave energy is prominent and the utilization of wave energy is relatively difficult. The developed evaluation method may give some references for an exploitable wave energy assessment and is valuable for practical applications.
基金financially supported by the Natural Science Foundation of China(No.41774133)the Open Funds of SINOPEC Key Laboratory of Geophysics(No.wtyjy-wx2017-01-04)National Science and Technology Major Project of the Ministry of Science and Technology of China(No.2016ZX05024-003-011)
文摘In marine seismic exploration, ocean-bottom cable techniques accurately record the multicomponent seismic wavefield; however, the seismic wave propagation in fluid–solid media cannot be simulated by a single wave equation. In addition, when the seabed interface is irregular, traditional finite-difference schemes cannot simulate the seismic wave propagation across the irregular seabed interface. Therefore, an acoustic–elastic forward modeling and vector-based P-and S-wave separation method is proposed. In this method, we divide the fluid–solid elastic media with irregular interface into orthogonal grids and map the irregular interface in the Cartesian coordinates system into a horizontal interface in the curvilinear coordinates system of the computational domain using coordinates transformation. The acoustic and elastic wave equations in the curvilinear coordinates system are applied to the fluid and solid medium, respectively. At the irregular interface, the two equations are combined into an acoustic–elastic equation in the curvilinear coordinates system. We next introduce a full staggered-grid scheme to improve the stability of the numerical simulation. Thus, separate P-and S-wave equations in the curvilinear coordinates system are derived to realize the P-and S-wave separation method.
基金Supported by the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(No.SML2021SP102)the Key Laboratory of Marine Environmental Survey Technology and Application+2 种基金Ministry of Natural Resources(Nos.MESTA-2020-C003,MESTA-2020-C004)the Key Research and Development Project of Guangdong Province(No.2020B1111020003)the Science and Technology Research Project of Jiangxi Provincial Department of Education(No.GJJ200330)。
文摘Wind and wave data are essential in climatological and engineering design applications.In this study,data from 15 buoys located throughout the South China Sea(SCS)were used to evaluate the ERA5 wind and wave data.Applicability assessment are beneficial for gaining insight into the reliability of the ERA5 data in the SCS.The bias range between the ERA5 and observed wind-speed data was-0.78-0.99 m/s.The result indicates that,while the ERA5 wind-speed data underestimation was dominate,the overestimation of such data existed as well.Additionally,the ERA5 data underestimated annual maximum wind-speed by up to 38%,with a correlation coefficient>0.87.The bias between the ERA5 and observed significant wave height(SWH)data varied from-0.24 to 0.28 m.And the ERA5 data showed positive SWH bias,which implied a general underestimation at all locations,except those in the Beibu Gulf and centralwestern SCS,where overestimation was observed.Under extreme conditions,annual maximum SWH in the ERA5 data was underestimated by up to 30%.The correlation coefficients between the ERA5 and observed SWH data at all locations were greater than 0.92,except in the central-western SCS(0.84).The bias between the ERA5 and observed mean wave period(MWP)data varied from-0.74 to 0.57 s.The ERA5 data showed negative MWP biases implying a general overestimation at all locations,except for B1(the Beibu Gulf)and B7(the northeastern SCS),where underestimation was observed.The correlation coefficient between the ERA5 and observed MWP data in the Beibu Gulf was the smallest(0.56),and those of other locations fluctuated within a narrow range from 0.82 to 0.90.The intercomparison indicates that during the analyzed time-span,the ERA5 data generally underestimated wind-speed and SWH,but overestimated MWP.Under non-extreme conditions,the ERA5 wind-speed and SWH data can be used with confidence in most regions of the SCS,except in the central-western SCS.
基金The Dragon III Project of ESA-MOST Dragon Cooperation under contract No.10412the Ocean Renewable Energy Special Fund Project of State Oceanic Administration under contract No.GHME2011ZC07the National Natural Science Foundation of China(NSFC)under contract No.41176157
文摘Wave energy resource is a very important ocean renewable energy. A reliable assessment of wave energy resources must be performed before they can be exploited. Compared with wave model, altimeter can provide more accurate in situ observations for ocean wave which can be as a novel method for wave energy assessment.The advantage of altimeter data is to provide accurate significant wave height observations for wave. In order to develop characteristic and advantage of altimeter data and apply altimeter data to wave energy assessment, in this study, we established an assessing method for wave energy in local sea area which is dedicated to altimeter data.This method includes three parts including data selection and processing, establishment of evaluation indexes system and criterion of regional division. Then a case study of Northwest Pacific was performed to discuss specific application for this method. The results show that assessing method in this paper can assess reserves and temporal and spatial distribution effectively and provide scientific references for the siting of wave power plants and the design of wave energy convertors.
文摘Coastal defenses such as the breakwaters are important structures to maintain the navigation conditions in a harbor.The estimation of their hydrodynamic characteristics is conventionally done using physical models,subjecting to higher costs and prolonged procedures.Soft computing methods prove to be useful tools,in cases where the data availability from physical models is limited.The present paper employs adaptive neuro-fuzzy inference system(ANFIS)and artificial neural network(ANN)models to the data obtained from physical model studies to develop a novel methodology to predict the reflection coefficient(Kr)of seaside perforated semicircular breakwaters under low wave heights,for which no physical model data is available.The prediction was done using the input parameters viz.,incident wave height(Hi),wave period(T),center-to-center spacing of perforations(S),diameter of perforations(D),radius of semicircular caisson(R),water depth(d),and semicircular breakwater structure height(hs).The study shows the prediction below the available data range of wave heights is possible by ANFIS and ANN models.However,the ANFIS performed better with R^2=0.9775 and the error reduced in comparison with the ANN model with R2=0.9751.Study includes conventional data segregation and prediction using ANN and ANFIS.
文摘The vertical cable method for acquiring and processing pre-stack 3-D marine seismic data is based on the technology developed by the US Navy for antisubmarine warfare. In order to achieve the maximum utili- zation of vertical cable field data, a new separation method of the up-going and down-going wave fields of the vertical cable data processing was developed in this paper, which is different from the separation of the down-going and up-going wave fields of normal VSP data processing. In tests with synthetic modeling data and actual field data, this newly developed method performs well and is also computationally simpler without pre-assumption conditions.
基金Supported by the High-Tech Research and Development Program of China (863 Program, No. 2001AA633070 2003AA604040)Na- tional Natural Science Foundation of China (No. 40206003).
文摘For sequential performance of wave variational data assimilation, we proposed a temporal sliding method in which the temporal overlap is considered. The advantage of this method is that the initial wave spectrum of the optimization process is modified by the observations in latter and former times. This temporal sliding procedure is important for marginal region, such as the China seas, where the duration of assimilation effectiveness is 2-3 days. Experiments were performed in the whole course of Cyclone 9403 （Russ）. Around the cyclone center, the maximum value of wave elements did not change much by assimilation, because the extreme value was determined by wind energy input that was not yet optimized. In the area outside the cyclone center, this modification is evident especially for wind wave growth.
基金The Youth Talent Support Program for Doctoral Students of the China Association for Science and Technologythe Key Laboratory of Space Ocean Remote Sensing and Application at Ministry of Natural Resources under contract No.2023CFO005+1 种基金the National Natural Science Foundation of China under contract No.42176011the Fundamental Research Funds for the Central Universities under contract No.24CX03001A.
文摘This study applies Ensemble Optimal Interpolation(EnOI)to assimilate individual spectral components derived from National Data Buoy Center(NDBC)buoy directional spectra into the WAVEWATCHⅢ(WW3)wave model during tropical cyclone(TC)Isaias(2020).The analysis provides a comprehensive evaluation of the assimilation’s impact on wave parameters,frequency spectra,and directional spectra.Two series of assimilation experiments—one based on spectral components(Exp^(*)-DaSpec)and the other on significant wave height(Exp^(*)-DaSWH)—are evaluated against a non-assimilated control run(Exp-NoDa).Particular focus is placed on six key parameters:SWH,mean wave period(MWP),mean wave direction(MWD),mean wave directional spread(MWS),dominant wave period(DWP),and dominant wave direction(DWD).Sensitivity analyses suggest 400 km and 0.30 as appropriate values for the localization radius and observation error variance,respectively,though no single setting is optimal across all wave parameters.Exp4-DaSWH and Exp4-DaSpec are therefore selected as representative experiments.In non-independent validation,Exp4-DaSpec generally outperforms Exp-NoDa across MWP,MWD,MWS,DWP,and DWD,demonstrating closer agreement with observed frequency spectra and directional patterns.In independent validation,Exp4-DaSpec maintains superior overall performance,whereas Exp4-DaSWH shows only limited improvement.Exp4-DaSWH may capture the spectral peak near 0.1 Hz,although its directional characteristics remain largely similar to those of Exp-NoDa.Importantly,the assimilation experiments significantly improve SWH in both non-independent and independent validations,with Exp4-DaSWH slightly outperforming Exp4-DaSpec overall.
基金The National Natural Science Foundation of China under contract No.41276009
文摘Studies of offshore wave climate based on satellite altimeter significant wave height（SWH） have widespread application value. This study used a calibrated multi-altimeter SWH dataset to investigate the wave climate characteristics in the offshore areas of China. First, the SWH measurements from 28 buoys located in China＇s coastal seas were compared with an Ifremer calibrated altimeter SWH dataset. Although the altimeter dataset tended to slightly overestimate SWH, it was in good agreement with the in situ data in general. The correlation coefficient was 0.97 and the root-mean-square（RMS） of differences was 0.30 m. The validation results showed a slight difference in different areas. The correlation coefficient was the maximum（0.97） and the RMS difference was the minimum（0.28 m） in the area from the East China Sea to the north of the South China Sea.The correlation coefficient of approximately 0.95 was relatively low in the seas off the Changjiang（Yangtze River） Estuary. The RMS difference was the maximum（0.32 m） in the seas off the Changjiang Estuary and was0.30 m in the Bohai Sea and the Yellow Sea. Based on the above evidence, it is confirmed that the multialtimeter wave data are reliable in China＇s offshore areas. Then, the characteristics of the wave field, including the frequency of huge waves and the multi-year return SWH in China＇s offshore seas were analyzed using the23-year altimeter wave dataset. The 23-year mean SWH generally ranged from 0.6-2.2 m. The greatest SWH appeared in the southeast of the China East Sea, the Taiwan Strait and the northeast of the South China Sea.Obvious seasonal variation of SWH was found in most areas; SWH was greater in winter and autumn than in summer and spring. Extreme waves greater than 4 m in height mainly occurred in the following areas： the southeast of the East China Sea, the south of the Ryukyu Islands, the east of Taiwan-Luzon Island, and the Dongsha Islands extending to the Zhongsha Islands, and the frequency of extreme waves was 3%-6%. Extreme waves occurred most frequently in autumn and rarely in spring. The 100-year return wave height was greatest from the northwest Pacific seas extending to southeast of the Ryukyu Islands（9-12 m）, and the northeast of the South China Sea and the East China Sea had the second largest wave heights（7-11 m）. For inshore areas, the100-year return wave height was the greatest in the waters off the east coast of Guangdong Province and the south coast of Zhejiang Province（7-8 m）, whereas it was at a minimum in the area from the Changjiang Estuary to the Bohai Sea（4-6 m）. An investigation of sampling effects indicates that when using the 1°×1°grid dataset, although the combination of nine altimeters obviously enhanced the time and space coverage of sampling, the accuracy of statistical results, particularly extreme values obtained from the dataset, still suffered from undersampling problems because the time sampling percent in each 1°×1°grid cell was always less than33%.
基金The National Natural Science Foundation of China under contract No. 41076006the State Ministry of Science and Technology of China under contract No. 2008AA09A402the Ministry of Education’s "111" Project of China under contract No. B07036
文摘The sea-surface height （SSH） signatures of internal tides extracted from the TOPEX/Poseidon （T/P） altimeter data along satellite tracks are fitted with superposition of several plane waves which have different wavenumber vectors. The key problem of plane wave fitting with iterative method is how to determine the initial value of wavenumber of each plane wave. The previous solving method is to analyze the internal tidal SSH signatures along each track with wavenumber spectrum. But it is found that the problem cannot be solved completely with the wavenumber spectrum analysis method only. The method based on the combination of wavenumber spectrum analysis method and the exhaustive method is proposed to determine the initial values of wavenumbers for iteration. Numerical results indicate that the proposed method is not only reasonable and feasible but also better than the previous method. The proposed method is an improvement of the previous one, which is beneficial to improving the precision of plane wave fitting of the T/P internal tidal SSH signatures and deepening the understanding of the internal tides in ocean.
文摘This article provides a method by which the scour depth and scour width below pipelines,and the scour depth around single vertical piles as well as the time scales of scour for both structures due to bichromatic and bidirectional waves are calculated.The scour and time scale formulae summarized by Sumer and Fredsøe(2002)as well as the bottom shear stress formulae under bichromatic and bidirectional waves by Myrhaug et al.(2023)are used.Results for unidirectional bichromatic waves and symmetrically bidirectional monochromatic waves are provided,showing qualitative agreement with what is expected physically.Qualitative comparisons are made with the data from Schendel et al.’s(2020)small scale laboratory tests on scour around a monopile induced by directionally spread waves.Applications to related cases for pipelines are also suggested.In order to conclude regarding the validity of the method for pipelines and vertical piles,it is required to compare with data in its validity range.
基金Supported by the National High Technology Research and Development Program of China(863Program)(No.2008AA09Z102)Data were provided by the European Space Agency
文摘Wave steepness is an important characteristic of a high sea state, and is widely applied on wave propagations at ports, ships, offshore platforms, and CO2 circulation in the ocean. Obtaining wave steepness is a difficult task that depends heavily on theoretical research on wavelength distribution and direct observations. Development of remote-sensing techniques provides new opportunities to study wave steepness. At present, two formulas are proposed to estimate wave steepness from QuikSCAT and ERS-1/2 scatterometer data. We found that wave steepness retrieving is not affected by radar band, and polarization method, and that relationship of wave steepness with radar backscattering cross section is similar to that with wind. Therefore, we adopted and modified a genetic algorithm for relating wave steepness with radar backscattering cross section. Results show that the root-mean-square error of the wave steepness retrieved is 0.005 in two cases from ERS-1/2 scatterometer data and from QuikSCAT scatterometer data.
文摘BACKGROUND Diagnostic errors in critical care settings are a significant challenge,often leading to adverse patient outcomes and increased healthcare costs.Millimeter-wave(mmWave)technology,with its ability to provide high-resolution,real-time data,offers a transformative solution to enhance diagnostic accuracy and patient safety.This paper explores the integration of mmWave technology in intensive care units(ICUs)to enable non-invasive monitoring,minimize diagnostic errors,and improve clinical decision-making.By addressing key challenges,including data latency,signal interference,and implementation feasibility,this approach has the potential to revolutionize patient monitoring systems and set a new standard for critical care delivery.The paper discusses the high prevalence of diagnostic errors in medical care,particularly in primary care and ICUs,and emphasizes the need for improvement in diagnostic accuracy.Diagnostic errors are responsible for a significant number of deaths,disabilities,prolonged hospitalizations and delays in diagnosis worldwide.AIM To address this issue,the paper proposes the use of ultrafast wireless medical big data transmission in primary care,specifically in remote smart sensors monitoring devices.It suggests that wireless transmission with a speed up to 100 Gb/s(12.5 Gbytes/s)within a short distance(1-10 meters)is necessary to reduce diagnostic errors.METHODS The method used in the study,includes system design and testing a channel sounder operating at 63.4-64.4 GHz frequency range.The system demonstrated dynamic range of 70 dB,noise level of-110 dBm,and a time resolution of 1 ns.The experiment measured the impulse response of the channel in 36 locations within the primary care/ICU scenario.RESULTS The system was tested in a simulated ICU environment to evaluate the Latency:Assessing the time delay in data transmission and processing.The results of the study showed that the system met the requirements of ICUs,providing excellent latency values.The delay spread and excess delay values were within acceptable limits,indicating successful resolution of ICU requirements.The paper suggests timely deployment of such a system.Impact on data transmission:A 100 MB magnetic resonance imaging scan can be transmitted in approximately 0.008 seconds;A 1 GB scan would take approximately 0.08 seconds;This capability could revolutionize healthcare,enabling real-time remote diagnostics and comparisons with artificial Intelligence models,even in large-scale systems.CONCLUSION The experiment demonstrated the feasibility of using high-speed wireless transmission for improved diagnostics in ICUs,offering potential benefits in terms of reduced errors and improved patient outcomes.The findings are deemed valuable to the medical community and public healthcare systems,and it is suggested further research in this area.
基金the National Key Research and Development Program of China(Grant No.2021YFC2203004)the National Natural Science Foundation of China(Grant No.12147102)the Sichuan Youth Science and Technology Innovation Research Team(Grant No.21CXTD0038)。
文摘With the observation of a series of ground-based laser interferometer gravitational wave(GW)detectors such as LIGO and Virgo,nearly 100 GW events have been detected successively.At present,all detected GW events are generated by the mergers of compact binary systems and are identified through the data processing of matched filtering.Based on matched filtering,we use the GW waveform of the Newtonian approximate(NA)model constructed by linearized theory to match the events detected by LIGO and injections to determine the coalescence time and utilize the frequency curve for data fitting to estimate the parameters of the chirp masses of binary black holes(BBHs).The average chirp mass of our results is 22.05_(-6.31)^(+6.31)M_(⊙),which is very close to 23.80_(-3.52)^(+4.83)M_(⊙)provided by GWOSC.In the process,we can analyze LIGO GW events and estimate the chirp masses of the BBHs.This work presents the feasibility and accuracy of the low-order approximate model and data fitting in the application of GW data processing.It is beneficial for further data processing and has certain research value for the preliminary application of GW data.
文摘目的:分析心电图P波参数对高血压心房颤动(Atrial fibrillation,AF)患者消融术后复发的预测价值。方法:回顾性分析2023年1月至2024年10月我院首次接受消融术的87例高血压AF患者资料,参考术后12 m内是否复发分复发组(21例)和非复发组(66例),比较两组P波终末电势(P-wave terminal force in lead V1,PtfV1)、P波离散度(P-wave dispersion,Pd)、P波变异(P-wave variation,Pv)及最大P波时限(Maximum P-wave duration,Pmax),分析上述指标与术后复发的关系及预测价值。结果:与非复发组对比,复发组Pd、Pv、Pmax均更高(P<0.05),但对比两组PtfV1,差异无统计学意义(P>0.05);多因素Logistic回归分析显示,Pd、Pv、Pmax与高血压AF患者术后复发显著相关(P<0.05);绘制受试者工作特征曲线结果显示,Pd、Pv、Pmax三者联合预测高血压AF患者复发的曲线下面积为0.840,均高于单一指标预测(P<0.05)。结论:Pd、Pv、Pmax三者联合在高血压AF患者术后复发中预测价值较高。
