共查询到20条相似文献，搜索用时 31 毫秒
1.
This paper describes an architecture for a compact real-time time-delay sonar beamformer. The design is based on a time-domain interpolation concept, and includes shading, interpolation, and time-delay functions for up to 64 sensor data inputs. A one card per beam configuration has been achieved. The digital interpolation technique used improves the effective sampling rate by a factor of 128. The beamformer design features 16-bit arithmetic precision, up to approximately a 5-kHz sampling rate for each of the 64 sensor input channels, and adaptability to any type of array, e.g., linear, circular, or arrays with nonequal interelement spacings. A 31-beam beamformer system, performing more than 620-million arithmetic operations a second, is discussed. 相似文献
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介绍一种SWQ-1型多功能水质测定仪,以数字显示温度,盐度,溶解氧,pH和氧化还原电势。仪器用干电池供电,其结构是以一个带有多路模数转换器和液晶显示器的低功耗单片微计算机为基础而构成。通过微计算机按照存贮器中的物理化学公式和定标常数进行数据处理,并把结果送给显示器。温度和pH传感器用的是定型的商品—热敏电阻和玻璃电极。盐度和溶解氧分别采用由作者自行设计的铂电极电导池和薄膜原电池型传感器进行现场测量。溶解氧的测量采用了自动定标程序,减少了电位漂移对测量的影响,提高了测量的可靠性,并且便于操作。这种水质测定仪是一种尺寸小,重量轻,效率高的便携式仪器。 相似文献
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Image analysis techniques are used for retrieving water surface elevation fields spatially and temporally from CCD-images and CCD-image-sequences. The technique proposed herein utilizes binocular stereogrammetry to recover topographic information from a sequence of synchronous, overlapping video images. The method used differs from the traditional stereo-photogrammetric analysis of a single stereo-pair because the use of video allows for a continuous sequence of stereo-images to be digitally sampled and analyzed. For data acquisition two synchronized progressive-scan cameras were used.A partially supervised 3-D stereo system (called WASS, Wave Acquisition Stereo System) is shown here. It is used to reconstruct the 3-D shape of water surface waves, acquired at frame rate, with small computational time needed. The stereo method is presented, including the derivation of a relationship relating the geometry of the stereo rig and the expected errors. Finally, the 3-D calculated scattered points give the complete spatio-temporal distribution of the water surface elevations. The measurable length-scales depend on the pixel resolution, the triangulation accuracy, and the acquisition frame rate. Limitations in the stereo measurements are also discussed.Two experiments to test and to demonstrate the system took place: one on the Venice lagoon, north of the city of Venice in September 2004 and the second on the coast of California at San Diego in December 2005. For the second experiment, qualitative and quantitative intercomparisons of the stereo-matching and in-situ sensor measurements are presented. All the measurements of water surface waves indicate that the proposed approach is both accurate and applicable for measuring water surface waves. Moreover, shape estimates are accurately and extremely dense both in space and time, and the remote location of the instruments alleviates some difficulties associated with in situ instrumentation. 相似文献
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A rotating disk electrode (RDE) is applied as a dissolved oxygen sensor and corrosion rate probe. As an oxygen sensor, the RDE is capable ofpm0.004 -ml/l resolution andpm0.17 -ml/l accuracy. As a corrosion rate probe, the RDE behaves more closely to theory than stationary electrodes. These applications make use of the RDE's unique hydrodynamic properties. 相似文献
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Hirata K. Aoyagi M. Mikada H. Kawaguchi K. Kaiho Y. Iwase R. Morita S. Fujisawa I. Sugioka H. Mitsuzawa K. Suyehiro K. Kinoshita H. Fujiwara N. 《Oceanic Engineering, IEEE Journal of》2002,27(2):170-181
A permanent real-time geophysical observatory using a submarine cable was developed and deployed to monitor seismicity, tsunamis, and other geophysical phenomena in the southern Kurile subduction zone. The geophysical observatory comprises six bottom sensor units, two branching units, a main electro-optical cable with a length of 240 km and two land stations. The bottom sensor units are: 1) three ocean bottom broadband seismometers with hydrophone; 2) two pressure gauges (PGs); 3) a cable end station with environmental measurement sensors. Real-time data from all the undersea sensors are transmitted through the main electro-optical cable to the land station. The geophysical observatory was installed on the continental slope of the southern Kurile trench, southeast Hokkaido, Japan in July 1999. Examples of observed data are presented. Sensor noises and resolution are mentioned for the ocean bottom broadband seismometers and the PGs, respectively. An adaptable observation system including very broadband seismometers is scheduled to be connected to the branching unit in late 2001. The real-time geophysical observatory is expected to greatly advance the understanding of geophysical phenomena in the southern Kurile subduction zone 相似文献
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Long-term Sensor Drift Found in Recovered Argo Profiling Floats 总被引：5，自引：0，他引：5
We recovered three Argo profiling floats after 2 to 2.5 years of operation, and recalibrated their temperature, conductivity, and pressure sensors. The results demonstrate that these floats exhibited a significant drift in salinity of −0.0074 to −0.0125, primarily due to the conductivity sensor drift. Combined with the recalibration result for another previously recovered float, the indication is that the negative salinity drift increases nearly in proportion to the operating period of floats. The increasing rate is −0.0041 (±0.0015) year−1, which yields a salinity drift of −0.016 (±0.006) for the expected float lifetime of four years. The present result suggests that reducing the float surfacing time would improve the accuracy of the salinity measurements. 相似文献
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基于多参数化学传感器的海底热液探测方法研究 总被引：1，自引：0，他引：1
基于热液及其羽状流的化学异常提出了一种海底热液的化学式探测方法。根据自行开发的Eh.Ag/Ag2S和pH三种化学电极,设计了多参数化学传感器系统。通过海试证明多参数化学传感器可灵敏地检测出由热液异常引起的化学量变化,并在长达半年的多次使用中表现出其稳定性好、寿命长的特点。在东太平洋中脊(EPR)赤道区域和西南印度洋中脊(SWIR)的60条测线中,获得有效测线55条,其中在29条测线上发现明显或可能的热液异常。研究表明,应用多参数化学传感器探测进行海底热液化学异常,是一种有效的方法。 相似文献
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Toshihiko Teramoto 《Journal of Oceanography》1971,27(1):7-19
A formula to determine an effective electric conductivity of channel-bed from measurements of water velocity, cross-channel potential difference and electric current-density is presented. The effective conductivity defined in this paper is the conductivity averaged over depth from channel-bed surface to a depth of the order comparable to a breadth of the channel. Effective conductivities for the Izu Island region and the Straits of Tsugaru are estimated as 2.2×10–2 mhos/m and 6.0×10–2 mhos/m, which are considerably large and very large, respectively, in comparison to most of those determined for several regions near England. High conductivities for these regions are consistent with the distribution of underground conductivity anomaly deduced from that of geomagnetic field anomaly observed at the earth's surface in Japan. An influence of underground conductivity upon measurements of sea surface water velocity with towed electrodes is estimated for the regions. 相似文献
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热液喷口附近的羽状流中存在明显的化学及浊度异常,通过探测这些异常可判断是否存在热液喷口及确定喷口的具体位置。本文研制了一款可用于探测热液喷口的多通道化学传感器,该传感器具有体积小、精度高的特点,且可在4000米深海中进行工作。该化学传感器共配备五个全固态电极,一个为参比电极,其余四个为离子选择性电极,并且可根据所测量的化学离子进行更换。本文基于该化学传感器共进行了两组实验。在第一组浅海试验中,化学传感器集成了pH,Eh,CO32-和SO42-电极,在浅海海域中测量对应化学量,结果表明该化学传感器可在实际应用中获得高精度、稳定的测量数据。第二组实验为深海热液探测,装配了pH,Eh,CO32-和H2S电极的化学传感器在西南印度洋中脊区域的29次测线中投入使用,共获得有效数据27组。通过对测量所得到的化学量进行分析,本文提出了一种确定热液喷口的化学异常探测方法,若某时间段内Eh和H2S的电势降低,而pH和CO32-的电势上升则可判定存在化学异常。利用该方法对27组有效数据进行分析,共发现5个潜在的热液喷口。实验结果表明,该化学传感器可有效地探测由热液引起的化学异常,适用于实际热液探测中。 相似文献
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Robert E. Randall 《Ocean Engineering》1981,8(4):407-419
Continuous discharge of a nominal 230 part per thousand brine solution was initiated in March 1980 at a rate of approx. 225,000 barrels/day (3.58 × 10 7 l/day) from a submerged multiport diffuser in 70 ft (21.3 m) of water at a distance of 12.5 statute miles (20 km) off the Freeport, Texas coast. A measurement system is described which was designed and used to measure the excess salinity and areal extent of the negatively buoyant brine plume. This system consists of a towing sled in which an in situ conductivity, temperature and depth probe is mounted. The towing sled is towed by Texas A & M University's research vessel, R.V. Excellence, on a predetermined search course through the expected plume area. The probe continuously measures the salinity at distance of 10 in. (25.4 cm) above the sea floor.The measured salinity data are used to construct isohalines of the bottom area, or plume contours, which indicate the areal coverage of the plume and the magnitude of the excess salinity concentration. Vertical salinity profiles were also measured in the plume area to evaluate the vertical extent of the plume.Plume contours and vertical profiles constructed from the data collected on 22, 30 March and 10 April, 1980 are discussed. The largest excess salinity contour was 5 parts per thousand above ambient and the area inside this contour was 6 acres (0.02 km2. The highest vertical extent of the plume was 25 ft (4.6 m). These measurements indicated the bottom mounted diffuser system was successfully diluting the highly concentrated brine solution and natural processes of advection and diffusion were dispersing the plume satisfactorily. 相似文献
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Fine-grained sediments commonly occur in areas of the continental shelf where wave and current energy are weak. Bulk density,
compressional wave speed and attenuation are fundamental physical properties of these sediments required for predicting the
response of the seabed for diverse branches of marine science. The traditional coring approach is time and labor-intensive,
with large uncertainties associated with sediment disturbance in the sampling phase. Acoustic methods offer the advantages
of remote sensing, i.e., sampling the sediment structure without mechanical disturbance and a significantly larger seabed
coverage rate per unit time. Two different acoustic methods are described: one using short-range single-bounce interactions
with the seabed, and the second using long-range modal propagation to infer the sediment properties. The relative strengths
and sensitivities of each approach are explored through simulations guided by experience with measured data. 相似文献
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We compare the performance of four different bubble-sensing techniques in a range of environment from the surf zone to the open ocean: a remote sensing method using high-frequency backscatter, two in situ methods using an acoustical resonator and a pulse propagation sensor, and a bulk method using electrical conductivity. Comparisons between the techniques show general consistency within the appropriate operational bubble density ranges, although spatial variability in bubble clouds introduces substantial variance. Each technique has its strengths and limitations. Our acoustical resonator is suitable for bubble concentrations with air fractions greater than approximately 10 -9 and the pulse propagation sonar for air fractions from 10 -6; the upper limit for both is constrained by attenuation and the validity of the Foldy scattering approximation. Both sensors can be implemented to encompass a wide frequency range with high resolution, corresponding to resonant bubble radii of 10~1200 μm. For air fractions higher than ~5×10-4, bulk measurement using electrical conductivity provides a measure of air fraction. Sufficient overlap in operational air-fraction range exists between in situ acoustical techniques and conductivity measurement to permit comparison and demonstrate consistency in the measurement. Single- and multi-frequency backscatter sonars may be used for low air fractions (<1×10-5) and provide a continuous vertical profile from a deployment beneath the active surface zone, but are subject to masking by dense bubble clouds and are unable to resolve high air fractions close to the surface. This study suggests that the best approach is to use a combination of sensors to probe the bubble field 相似文献
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The purpose of this research work is to study the effect of specific surface s, the fluid–solid contact surface per volume unit, on the wave energy dissipation by porous structures consisting in dense arrays of emergent vertical cylinders. Experiments have been carried out in a 10 m long wave flume. Three cylinder diameters D are considered in order to study the effects of the specific surface while keeping the porosity constant. In a first series, the length of the porous zone is kept constant for the three cylinder diameters tested. The measurements, which include various wave steepness conditions, demonstrate the role of specific surface s on both wave attenuation and interference processes. The larger the specific surface is, the stronger the wave damping is. Damping is found to be almost proportional to 1/D when laminar, turbulent and inertial effects are of same order. Results are compared to numerical calculations based on either a constant rate of wave damping within the porous medium per unit wavelength or a quadratic damping developed using a force expression based on the work of [26]. This latter model, calibrated with drag and inertia coefficients, shows a good agreement with measurements. In a second series, both porous length and water depth are kept proportional to the cylinder diameter for the three diameters. Scale effects are then discussed and underline the importance of the flow regime within the porous medium. 相似文献
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The temperature measurement system of the standard Woods Hole Oceanographic Institution/Neil Brown Instrument Systems conductivity-temperature-depth microprofiler consists of a platinum thermometer, which has stable calibration characteristics but response time of order 200 ms combined with a fast response thermistor designed to sample the higher frequency temperature fluctuations. The calibration characteristics and temporal response of the individual sensors relative to the conductivity cell were studied using a modified instrument which digitized these data channels separately. The relative responses of the individual sensors were found to be fairly well modeled by a single pole filter, but the response of the standard temperature signal, which is an analog combination of the two temperature sensor outputs, exhibited a complicated behavior. Several methods for obtaining a well-calibrated fast-responding temperature signal from the digitized platinum thermometer and thermistor records are discussed. Preliminary results suggest that thermohaline features on scales of less than a meter in the vertical are resolvable. 相似文献
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《Coastal Engineering》2007,54(6-7):477-491
Over the past 25 years, optical remote sensing has been developed into a very useful tool for sampling the nearshore environment, principally through the use of Argus Stations. However, the capabilities of such systems as scientific tools depend on an understanding of the physics of the camera as an optical sensor (including a detailed knowledge of accuracies and resolution) and of the relationship of optical signals to the geophysical signals they represent. This paper describes the components of Argus Stations with an emphasis on quantitative characterization of the accuracies and resolution of system components. Algorithms for estimation of a range of important nearshore measurements are discussed and their accuracies and ground-truth test results referenced. References to a number of key examples of Argus-based contributions to the scientific literature are cited. Since Argus technology serves as the basis for the CoastView Program, the technical capabilities described below are part of the foundation of CoastView sampling. 相似文献
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Based on the non-Gaussian joint elevation and slope density function developed by Huang et al. (1984), the expected number of threshold crossing at an arbitrary level for a nonlinear wave field is derived. The distribution of the expected threshold crossing per unit time as a function of the crossing level is skewed with respect to the mean water level. This skewness also causes the mean zero crossing per unit time to deviate from the expected frequency of the wave field. 相似文献
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After recalibration of the temperature and conductivity sensors of three Argo profiling floats recovered after operations
for four to nine months, the results indicate that the floats basically showed no significant drift, either in temperature
or salinity, and adequately fulfilled the accuracy requirement of the Argo project (0.005°C for temperature and 0.01 psu for
salinity). Only the third float showed a significant offset in salinity of about −0.02 psu, as expected from comparison between
the float data and the shipboard conductivity-temperature-depth data. This offset was caused by the operational error of the
PROVOR-type float, in which the surface water was pumped immediately after the launch, fouling the conductivity sensor cell.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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ADCP对悬浮沉积物浓度的测量及其误差分析研究 总被引：6，自引：0，他引：6
为实时、连续地测量海水中悬浮沉积物,利用声学多普勒海流剖面仪(ADCP),可以在测流的同时,测量海洋悬浮沉积物浓度。描述了利用后散射强度,估计悬浮沉积物浓度的原理。在现场测试中,利用采水器采集水样,通过水样分析并结合声信号的衰减特征对AI)CP的测量结果进行修正。作者还结合现场测试结果,对这一测量方法的精度进行了分析。现场实验表明,经公式校正后,ADCP测得的后散射强度与实测水样所获得的悬浮沉积物浓度之间有很好的相关性,相关系数达0．88,由此证明,此测量方法具有很好的实用价值和应用前景。 相似文献