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1.
声散射是重要的声学现象,海洋水体产生的高频声散射信号既可用于开展多种目的的声学海洋学研究,也可能对水下声学设备产生干扰,而海洋水体背景声散射具有显著的时空变异特征,因此针对特定海区开展声散射时变观测具有重要意义。本文利用在南海北部布放的锚系系统所搭载的声学多普勒流速剖面仪,获取了覆盖4个季节的累计约80 d的声散射数据,数据包括75 kHz和300 kHz两个频段,观测水深几乎覆盖了从海面到约600 m水深的整个水体。结果表明,水体在垂向上分布着上散射层和深散射层2个主要散射层。上散射层分布深度在冬夏较浅,位于约100 m以浅,在春秋较深,位于约200 m以浅;深散射层分布深度同样为冬季最浅,位于约300 m以深,但夏季则最深,位于约400 m以深。因此,两散射层的距离在夏季最远,在春秋最近。2个散射层的声散射强度（Sv）同样具有明显的季节变化,上散射层散射强度夏秋较强而春冬较弱,深散射层则正好相反。 相似文献
2.
鲐鱼灯光围网渔船水上集鱼灯水中照度分布及优化配置的理论计算 总被引：2，自引：0，他引：2
采用叠加法照度计算模式,根据一组鲐鱼灯光围网渔船中3艘不同渔船的水上集鱼灯布置参数,使用自行开发的水上集鱼灯水下光场计算系统,对各船的水中照度分布进行了计算,获得船舷右侧中部水深方向200 m范围内不同深度的照度,并使用Surfer 8.0软件绘制等值曲线图,结果表明:主灯船在总功率为180 kW的情况下,10 lx的等照度曲线水平方向最远在56 m左右,水深方向不超过20 m;离船水平距离40 m、垂直距离40 m处的照度约为0.01 lx。副灯船在总功率为120 kW的情况下,10 lx的等照度曲线水平方向最远在46 m左右,水深方向不超过18 m;离船水平距离33 m、垂直距离38 m处的照度约为0.01 lx。网船在总功率为40 kW的情况下,10 lx的等照度曲线水平方向最远在45 m左右,水深方向不超过15 m;离船水平距离30 m、垂直距离35 m处的照度为0.01 lx左右。从集鱼灯的配置情况来看,主灯船、副灯船与网船目前的配置均较好,但主灯船在灯距增大到0.26 m、灯高增大到5 m时可增加1.6%的有效水体体积,副灯船在灯距减少到0.28 m、灯高增大到5 m时可增加2.1%的有效水体体积,网船在灯距增大到0.64 m、灯高增大到9 m时可增加1.7%的有效水体体积。计算结果还表明,大幅度的增加光诱渔船的集鱼灯功率并不能很有效的提高该船的光诱范围。 相似文献
3.
提出了将具有比声学高达几倍的数据通信速率,良好的安全性和隐蔽性的光学无线通信技术应用于海军、海洋科学研究和水下工程等领域,实现高速率的水下无线通信技术实现海量数据的信息交换.基于生物光学特性的水下光学信道模型,建立了水下光学通信系统性能分析方法.并对基于发光二极管(LED)的水下光学无线通信系统进行了仿真,其结果表明所建立的方法可以进行各种海域水质环境的模拟,便于时水下光学无线通信系统性能进行预测评估,为水下光学无线通信系统的设计方案的评估提供了依据. 相似文献
4.
Jong Ryeol Choe Yoon Sub Shin Ji Yong Choi Tae Hwan Kim Min-Min Jung Cheol Young Choi 《Ocean Science Journal》2017,52(4):501-509
We investigated the effect of light wavelengths on antioxidant and immunity parameters in juvenile rock bream, Oplegnathus fasciatus, exposed to thermal stress (25 and 30°C). We exposed the fish to light emitting diodes (LEDs) emitting green (520 nm) and red light (630 nm) of 0.25 and 0.5 W/m2 intensity, and measured the activity, and mRNA and protein expression levels of the antioxidant enzymes, superoxide dismutase, catalase, and glutathione peroxidase. We also determined the levels of plasma hydrogen peroxide (H2O2), melatonin, and lysozyme. Furthermore, the mRNA and protein levels of caspase-3 were measured and terminal transferase dUTP nick end labeling (TUNEL) assays were performed. We observed that mRNA expression and activities of antioxidant enzymes and plasma H2O2 levels were significantly higher after exposure to high temperatures. However, increases in these parameters were significantly lower after exposure to green LED light. The plasma melatonin and lysozyme levels were significantly lower in the different groups after exposure to high temperatures; however, in groups exposed to green LED light, their levels were significantly higher than those in the control group. The expression pattern of caspase-3 mRNA was similar to that of H2O2. The TUNEL assay showed that apoptosis was markedly higher at higher water temperatures than that at 20°C. These results indicate that high water temperatures induce oxidative stress and decrease the immunity in juvenile rock bream but green LED light inhibits the rise in oxidative stress and combats the decrease in immunity and should, thus, be useful in the culture of rock bream. 相似文献
5.
水平光梯度下三疣梭子蟹趋光反应的实验研究 总被引：4，自引：0，他引：4
三疣梭子蟹(Portunus trituberculatus(Miers))分布黄海、东海和日本近海,其经济价值高、资源丰富,是一种重要的海产品,也是一种大有捕捞前途的渔业资源。然而,由于对它的趋光生理生态学问题缺乏研究,致使捕蟹技术长期未能得到改进,迄今基本上仍停留在底拖网和笼诱捕的旧渔法水平上[1-3],捕捞量的提高受到很大限制。 相似文献
6.
Design and projected performance of a flapping foil AUV 总被引：1，自引：0，他引：1
Licht S. Polidoro V. Flores M. Hover F.S. Triantafyllou M.S. 《Oceanic Engineering, IEEE Journal of》2004,29(3):786-794
The design and construction of a biomimetic flapping foil autonomous underwater vehicle is detailed. The vehicle was designed as a proof of concept for the use of oscillating foils as the sole source of motive power for a cruising and hovering underwater vehicle. Primary vehicle design requirements included scalability and flexibility in terms of the number and placement of foils, so as to maximize experimental functionality. This goal was met by designing an independent self-contained module to house each foil, requiring only direct current power and a connection to the vehicle's Ethernet local area network for operation. The results of tests on the foil modules in the Massachusetts Institute of Technology (MIT) Marine Hydrodynamics Water Tunnel and the MIT Ship Model Testing Tank are both used to demonstrate fundamental properties of flapping foils and to predict the performance of the specific vehicle design based on the limits of the actuators. The maximum speed of the vehicle is estimated based on the limitations of the specific actuator and is shown to be a strong function of the vehicle drag coefficient. When using four foils, the maximum speed increases from 1 m/s with a vehicle C/sub D/ of 1.4 to 2 m/s when C/sub D/=0.1, where C/sub D/ is based on vehicle frontal area. Finally, issues of vehicle control are considered, including the decoupling of speed and pitch control using pitch-biased maneuvering and the tradeoff between actuator bandwidth and authority during both the cruising and hovering operation. 相似文献
7.
Sound sources and levels in the ocean 总被引：1，自引：0，他引：1
The standard definitions found in the American National Standards on Acoustics are applied to common sound sources used in both underwater acoustics research and naval sonar system operation. Recommended metrics are quantified for both continuous and transient sources of sound. Standard definitions are reviewed with theoretical sound source models. Requisite metrics are derived and applied to examples of energy sources of sound, such as transients from a small omnidirectional explosive, an air gun, a light bulb, and a dolphin click. A generic quantitative model of surface ship sonar system emissions is developed. Active sonar transmissions are analyzed with the requisite quantitative metrics required to characterize these emissions. These results should be useful in environmental assessments, biological experiments, and the sonar system design. 相似文献
8.
针对半潜式超大型浮式结构中典型的移动式海上基地(Mobile Offshore Base,MOB)在高等级海况下的动力响应问题展开研究。在MOB结构"刚性模块-柔性连接构件(Rigid Modules and Flexible Connectors,RMFC)"模型的前提下,根据动力学基本原理,经理论推导并计算得到MOB分别在6、7、8级海况的随机波激励下,其上各模块的动力响应位移结果。详细分析了MOB结构同一模块在不同海况条件下的动力响应位移随浪向角及连接构件刚度的变化规律。研究成果可为半潜式超大型浮式结构动力响应研究及结构优化设计提供一定的技术支撑。 相似文献
9.
The opportunities of diagnosing wind roughness with the help of underwater vision systems have been investigated. The model
of the rough sea surface image observed from under water under conditions of natural illumination has been developed. It has
been shown that the statistical processing of the image of a solar path which is formed as a result of light refraction at
randomly irregular air-water interface allows one to define not only the slope variance and the curvature variance of the
surface, but also the coefficient of spatial correlation of slopes. The algorithms for defining of characteristics of wind
roughness on the basis of images of underwater solar path and the results of their testing using the data of numerical and
natural experiments are given. It was found that waves of very small amplitude images with high contrast near borders of the
Snell’s circle (the underwater image of the sky). 相似文献
10.
11.
In this paper, we experimentally perform the measurement of the backscattered light intensity from the underwater targets with different size. We develop a simple system, which can easily measure the intensity of the backscattered light, after the laser is scattered at the target underwater. We find that, the signal period is related to the particle size, and the stability of the intensity (standard deviation) varies linearly with changing the particle size. After the calibration, our system can be used to precisely determine the particle size of arbitrary targets. Our method could open a new opportunity for the future underwater detection using femtosecond pulse laser. 相似文献
12.
In experiments aimed at measuring the spectral volume scattering function of light, we obtain an additional confirmation of
the existence of two-dimensional inhomogeneities of water on scales of 10-7–10-3 m. In the case of mixing of pure water with small amounts of filtered water with different temperature or salinity, we observe
an 1.8–4.5-fold intensification of the scattering of light in the entire range of angles. It is shown that this effect can
be explained neither by turbulence nor by the formation of dissipative structures. We estimate the sizes of inhomogeneities
affecting the spectral volume scattering function of light. 相似文献
13.
Mechanics and control of swimming: a review 总被引：2，自引：0，他引：2
The bodies and brains of fish have evolved to achieve control objectives beyond the capabilities of current underwater vehicles. One route toward designing underwater vehicles with similar capabilities is to better understand fish physiological design and control strategies. This paper has two objectives: 1) to review clues to artificial swimmer design taken from fish physiology and 2) to formalize and review the control problems that must be solved by a robot fish. The goal is to exploit fish locomotion principles to address the truly difficult control challenges of station keeping under large perturbations, rapid maneuvering, power-efficient endurance swimming, and trajectory planning and tracking. The design and control of biomimetic swimming machines meeting these challenges will require state-of-the-art engineering and biology. 相似文献
14.
位于台湾岛东北部的龟山岛热液区属浅水型海底热液活动区,已探明有超过30处的热液喷口分布在约1030m的水深范围内。通过机械封装、硬件电路以及配套软件的设计和加工,自制了散射光式水下浊度仪;2011年5月2530日,使用该浊度仪,对龟山岛附近海域进行了拖航作业,在此次作业的东北方向发现一处新的热液喷口(24°50′09″N、121°58′08″E);海试结果表明,该水下浊度仪对于浊度较大海域有探测能力,对浊度较小海域的探测精度不高,还有待进一步改进。 相似文献
15.
Tracing carbon transfer and assimilation by invertebrates and fish across a tropical mangrove ecosystem using stable isotopes 
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下载免费PDF全文 Nguyen Tai Tue Tran Dang Quy Mai Trong Nhuan Luu Viet Dung Nguyen Dinh Thai 《Marine Ecology》2017,38(5)
Mangroves are highly productive ecosystems that exhibit a diverse range of habitats, including tidal creeks and flats, forest gaps and interior forest with varying understory light intensity, tidal dynamics, geomorphological settings, and overall biological production. Within mangrove ecosystems, invertebrates and fish feed on heterogeneous food sources, the occurrence of which is unevenly distributed across the system. This provides a basis for testing models of carbon transfer across mangrove ecosystems. We hypothesized that the carbon transfer and assimilation by fish and invertebrates will vary across the different mangrove habitats and that such variations can be predicted by their stable isotope compositions. We analysed δ13C and δ15N signatures of consumers and their potential organic carbon sources across a tropical mangrove ecosystem in Vietnam. The δ13C values of crabs and snails significantly decreased from the tidal flat to interior forest, indicating that variations in carbon transfer and assimilation occurred at small scales <30 m. Reduced variation in δ13C of suspension‐feeding bivalves suggested that tidal water was a vector for large‐scale transport of carbon across the mangrove ecosystem. An analysis of co‐variance using habitat as a fixed factor and feeding habit and movement capacity of consumers as co‐variates indicated that habitat and feeding types were major features that affected the δ13C values of invertebrates and fish. The findings demonstrate that carbon transfer and assimilation across mangrove ecosystems occur as a diverse combination of small (<30 m) and large (>30 m) scale processes. 相似文献
16.
A Mobile Offshore Base (MOB) is a multi-purpose logistics base, which can be stationed in coastal or international waters. In the conceptual design of the MOB, attention should be paid to the dynamic responses of the inter-module connectors because tremendous loads occur in the connectors. In this paper, a study on dynamic responses of the MOB connectors is carried out by use of the Rigid Module Flexible Connector (RMFC) model which assumes that the module stiffness is significantly larger than that of the connector. In the analysis, the connector is modeled as a linear spring, which restricts relative translations but allows for relative rotations of modules. The 3-D source distribution method is adopted to determine the hydrodynamic forces of the modules, and the hydrodynamic interaction between modules is taken into account. The module motions and connector loads for 12 connector stiffness cases in regular and irregular waves are calculated with the multi-rigid-body motion equations. And the calculat 相似文献
17.
The paper describes the phototactic types of fishes in the photogradient. The phototactic behaviour depends not only on the strength of illumination, but also on the wavelength of various light. Influence of moonlight was also investigated. It is found that the degree of inhibition depends on the relative intensity between background light and stimulating light and on the phototactic character of fishes. Finally, a theoretical analysis for phototactic behaviour of fishes is suggested.Basic research on the phototactic behaviour of fishes is not only significant for understanding the influence of light on fish behaviour, but also has implication for production. 相似文献
18.
Owing to the multipath effect, the source localization in shallow water has been an area of active interest. However, most methods for source localization in shallow water are sensitive to the assumed model of the underwater environment and have poor robustness against the underwater channel uncertainty, which limit their further application in practical engineering. In this paper, a new method of source localization in shallow water, based on vector optimization concept, is described, which is highly robust against environmental factors affecting the localization, such as the channel depth, the bottom reflection coefficients, and so on. Through constructing the uncertainty set of the source vector errors and extracting the multi-path sound rays from the sea surface and bottom, the proposed method can accurately localize one or more sources in shallow water dominated by multipath propagation. It turns out that the natural formulation of our approach involves minimization of two quadratic functions subject to infinitely many nonconvex quadratic constraints. It shows that this problem (originally intractable) can be reformulated in a convex form as the so-called second-order cone program (SOCP) and solved efficiently by using the well-established interior point method, such as the software tool, SeDuMi. Computer simulations show better performance of the proposed method as compared with existing algorithms and establish a theoretical foundation for the practical engineering application. 相似文献
19.
M. M. Divizinyuk 《Physical Oceanography》2001,11(5):473-481
We consider the results of instrumental investigations of specific features of reverberation in the Black Sea and obtain qualitative
dependences of the duration of volume reverberation on the parameters of the Black-Sea underwater sound channel, (width, drop
of the sound velocity, and dimensions of the inhomogeneities of stratification). We also analyse the behaviour of the intensity
of surface reverberation in the far-field zone of acoustic illumination and the influence of bottom reverberation on the detection
of underwater objects.
Translated by Peter V. Malyshev and Dmitry V. Malyshev 相似文献
20.
LED单色光谱及复合光谱对赤潮优势种中肋骨条藻生长的作用 总被引：1，自引：0，他引：1
以赤潮优势种中肋骨条藻(Skeletonema costatum)为研究对象,荧光灯和自制LED(light-emitting diode)控制灯为光源,研究不同LED单色光谱及复合光谱(蓝光,绿光,红光,白光,蓝红光,绿红光)对中肋骨条藻生长的作用。实验结果表明,在相同的光合有效量子通量密度条件下,对于单色光,中肋骨条藻在蓝光下生长较快,红光次之,在绿光下生长最慢;对于复合光,中肋骨条藻在荧光灯下生长最快,而在蓝红光下生长略高于在绿红光下生长。各光源下中肋骨条藻生长速率的顺序为:荧光灯>蓝红光LED>绿红光LED>蓝光LED>红光LED>绿光LED。通过比较在不同光照条件下中肋骨条藻的生长速率,表明不同光谱对中肋骨条藻生长的作用不同。 相似文献