基于快速数字锁相的溶解氧检测优化设计

溶解氧浓度检测在水产养殖和环境监测中具有重要的意义。本文提出了一种基于快速数字锁相的溶解氧检测优化设计，利用快速数字锁相算法与过采样技术，实现了荧光信号和调制信号的快速相位解调，并得到二者相位差，根据Stern-Volmer方程求出溶解氧浓度值。本文分析了调制频率对测量结果的影响，选择合适的调制频率用于测量，并利用最小二乘法对测量结果进行拟合，拟合后的确定系数R-square为0.999 25。实验数据表明，测量结果相对误差（RE）小于±1.5%，相对标准差（RSD）小于4%，稳定时间小于50 s。本文提出的优化设计不仅具有较高的测量精度，还简化了硬件设计，降低了成本。     

Expulsion of Shallow Gas in the Skagerrak—Evidence from Sub-bottom Profiling, Seismic, Hydroacoustical and Geochemical Data

A combined high resolution seismic, sub-bottom profiling, and multi-beam echo-sounding survey in the Skagerrak (Danish sector of the North Sea) together with gas analyses at a station along the profile exhibit the expulsion of gas (mainly methane) and the presence of gas-charged sediments at shallow depth. The echo-soundings yield detailed insight into the distribution and shape of typical sea-floor features associated with gas seepage, such as pockmarks. The pockmarks reach dimensions of 800 m in length, 300 m in width, and 15 m in depth, with the long axis running parallel to the slope of the Norwegian Trench. Processing of the multi-channel high resolution seismic data and the digitally recorded sub-bottom profiler signals indicate an internal compressional velocity of about 1050 m s^-1 within the gas-charged sediments reaching from the sea-floor to a sub-bottom depth of about 23 m. Using the lateral distribution and thickness of the gas-charged sediments in conjunction with a mean concentration of gas of 3000 ppb, the present amount of trapped gas is estimated to be 6·45 × 10¹¹ g CH₄. The flux of methane through the sea-bed into the water column appears to be 7·2 × 10¹⁰ g CH₄ per year. To explain the small difference in size between the methane pool in near-surface sediments and the annual flux through the sea-bed, a constantly high supply of methane from leaking hydrocarbon reservoirs at greater depths has to be active.     

中国对虾幼体对运动物体的感觉能力及其与环境照度的关系

甲壳动物具有明显的视觉运动反应。这种对视野内移动目标的反应有两种形式,一种是眼柄的颤动反应(Optokinetic response),另一种为全身性的视觉运动反应(Optomotor response)。对于前一种反应形式国外已有许多研究,尤其对爬行亚目某些种类眼柄颤动反应特点和机制进行了大量实验。后一种反应形式的研究工作较少。有关游泳亚目视觉     

A comparison of four methods for bubble size and void fractionmeasurements

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     

A HIGH-EFFICIENCY TANDEM PISTON AIR GUN

The high-efficiency tandem piston air gun is a new pneumatic seismic source with simple structure, convenient operation and low cost. It can create high-energy acoustic pulse signals, and effectively attenuate bubble responses. This paper briefly introduces the air gun with 0.8 liter at a pressure of 140 kg/cm2. The measurement shows that the gun has reached a maximum peak-peak sound pressure up to about 11.7 bar-meters. The ratio (P1-P2) is about 2.79. The energy of the acoustic pulse is concentrated within 200 Hz and the main frequency corresponding to the spectrum value is about 30 Hz. Its lowest frequency is below 10 Hz.     

中国近海潮汐响应峰值估算的数值模拟

A numerical method is designed to examine the response properties of real sea areas to open ocean forcing. The application of this method to modeling the China’s adjacent seas shows that the Bohai Sea has a highest peak response frequency(PRF) of 1.52 d-1; the northern Yellow Sea has a PRF of 1.69 d-1; the Gyeonggi Bay has a high amplitude gain plateau in the frequency band roughly from 1.7 to 2.7 d-1; the Yellow Sea(including the Gyeonggi Bay), the East China Sea shelf and the Taiwan Strait have a common high amplitude gain band with frequencies around 1.76 to 1.78 d-1 and are shown to be a system that responds to the open ocean forcing in favor of amplifying the waves with frequencies in this band; the Beibu Gulf, the Gulf of Thailand and the South China Sea deep basin have PRFs of 0.91, 1.01 and 0.98 d-1 respectively. In addition, the East China Sea has a Poincare mode PRF of 3.91 d-1. The PRFs of the Bohai Sea, the northern Yellow Sea, the Beibu Gulf and the South China Sea can be explained by a classical quarter(half for the Bohai Sea) wavelength resonance theory. The results show that further investigations are needed for the response dynamics of the Yellow Sea-East China Sea-Taiwan Strait system, the East China Sea Poincare mode, the Taiwan Strait, and the Gulf of Thailand.     

Installation of ocean bottom bases for observation of seafloor crustal movement

Abstract

Ocean bottom bases (OBBs) have been installed on both sides of the axis of the Sagami Trough east of the Izu Peninsula, central Japan, as the first step toward long‐term geodetic and geophysical observations at the plate boundary (subduction zone). The OBB is a platform for seafloor measurements; otherwise it is difficult to find an appropriate place for precise seafloor measurements in the subduction zones. It is made of a nonmagnetic concrete block of size 1100 × 1100 × 500 mm. It was lowered from a ship using a winch wire and installed on a predetermined place with its position being monitored by an acoustic transponder system and a 30‐kHz bottom pinger with an accuracy of about 2 m.

It was confirmed later during the divings on board the submersible Shinkai 2000 that the OBB was installed on a flat mud bottom in normal condition. No change has been recognized in the installation condition in 3 years; the OBB is stable enough to be used for acoustic range measurements on the seafloor as well as for several geophysical measurements.

The resolution of seafloor range measurement can be improved by two orders by using phase measurement techniques with the aid of pulse compression. Precise acoustic range measurement of the order of 10^?5 is feasible under the following conditions: two‐way measurements between the two OBBs installed on the slope facing each other with angles larger than 1.5°. Correction is necessary for the effect of long‐term temperature variation.     

海水油荧光测量方法实验研究

根据荧光测量方法的原理,采和双光路,双通道及单片微机控制,数据自动采集的技术,于１９９７年研制成功用于海洋现场探测的单波段水中油荧光计。应用该水中油荧光计进行了海水中微量油份的测量实验研究。     

Properties study of LiNbO3 lateral field excited device working on thickness extension mode

This paper investigates the properties of thickness extension mode excited by lateral electric field on LiNbO₃ by using the extended Christoffel--Bechmann method. It finds that the lateral field excitation coupling factor for a-mode (quasi-extensional mode) reaches its maximum value of 28% on X-cut LiNbO₃. The characteristics of a lateral field excitation device made of X-cut LiNbO₃ have been investigated and the lateral field excitation device is used for the design of a high frequency ultrasonic transducer. The time and frequency domain pulse/echo response of the LiNbO₃ lateral field excitation ultrasonic transducer is analysed with the modified Krimholtz--Leedom--Matthae model and tested using traditional pulse/echo method. A LiNbO₃ lateral field excitation ultrasonic transducer with the centre frequency of 33.44 MHz and the --6 dB bandwidth of 33.8% is acquired, which is in good agreement with the results of the Krimholtz--Leedom--Matthae model. Further analysis suggests that the LiNbO₃ lateral field excitation device has great potential in the design of broadband high frequency ultrasonic transducers.     

薛家岛岬湾型海岸侵蚀演化的定量性研究

在4a连续观测的基础上,确定薛家岛周边大部分是抗蚀强度大的基岩岬湾海蚀岸,海蚀崖蚀退和海蚀平台蚀低的平均速率分别为10-2和10-4m/a量级;弓形海湾湾顶有薄层现代海滩砂砾,石雀湾和银沙滩崖前和后滨有大量海滩相大砾石(粒度为20～30cm).外侧海岸直濒开阔海,水下岸坡为深陡型,气象水文等外营力因素作用强度较大,显示中—高能海岸环境地质地貌特征.薛家岛外海海岸冲积物供给源贫乏,小于2×104m3/a.沿岸冲积物流流向北东至南西,采用目前国际较通用的波浪辐射应力模式方法计算其容量达13×104m3/a,这种源-运量的不平衡是造成基岩海蚀岸的机制.     

一种优化模糊度搜索方法的研究

对于高精度测量和导航,GPS载波相位整周模糊度的快速求解仍然是一个难点,尤其对于单频接收机。提出一种快速求解整周模糊度的方法,其基本思想采用分步求解,首先应用最小二乘模糊去耦调节法(LAMBDA)搜索出来的模糊度作为初始值,然后应用卫星分组方法降低搜索维数,并应用极大似然准则,构造搜索函数,最后应用最优化原理,搜索出最优的模糊度参数,并从三个方面对其进行检验,即RATIO检验,OVT检验,多项式拟合残差检验。为验证该算法,我们用单频GPS接收机进行了实验,利用本文方法在11 S以内正确确定了模糊度,其基线长误差小于3MM,表明该方法不但可以改进模糊度的搜索速度,而且可以进一步提高其可靠性和成功率。该方法可广泛应用于定向及姿态测量。     

ATI-SAR平地相位去除的改进频移法

本文提出了一种改进的频移方法以去除ATI-SAR海洋表面运动探测中的平地相位。首先，介绍和比较两种常规的平地效应去除方法（即，频移方法和轨道参数方法）。然后，对频移方法提出了两项改进措施。第一，干涉相位图被分成几个子块，分别计算相位条纹空间频率。第二，基于在顺轨干涉相位图中陆地区域的相位趋于零的特点，拟合陆地区域的相位与其位置之间的函数关系，进一步校正残余平地相位。结果表明，改进后的频移法去除平地效应的效果得到了很大改善。改进方法的结果与轨道参数法一致性更好，精度趋于轨道参数法的精度水平。     

吐噶喇海峡黑潮流速结构和流量的研究

利用1977－1991年日本“KuroshioExploitationandUtilizationResearch”（KER）资料和日本气象厅海洋观测资料计算吐噶喇海峡的黑潮流速和流量。结果表明，海峡处黑潮主轴的平均核心流速为92．0cm／s，平均流量为周．1×106m3/s；揭示了吐噶喇海峡黑潮流速的多核结构和多股流动的突出特征。探讨了海峡中流量分布状况和季节变化。     

吕宋海峡水交换季节和年际变化特征的数值模拟研究

利用ROMS(Regional Ocean Modeling System)建立了一套覆盖西北太平洋的涡尺度分辨率环流模型,并对吕宋海峡附近的环流进行了模拟研究。结果表明,吕宋海峡120.75°E断面净流量季节变化显著,全年均为西向输运,6月份达到最小,为0.40×106 m3/s,然后逐渐增大,在12月份达到最大,为6.14×106 m3/s,全年平均流量为3.04×106 m3/s。在500 m以浅,秋、冬季都有明显的黑潮流套存在,并伴有黑潮分支入侵南海,而春、夏季黑潮南海分支减弱或消失,黑潮入侵不明显。在500 m以深,冬、春季,吕宋海峡以东有非常明显的南向流存在,流速约10 cm/s,而到了夏、秋季该南向流出现明显的减弱,黑潮与南海的水交换主要通过吕宋海峡以北的吕宋海沟进行。在垂向结构上,120.75°E断面浅层呈多流核结构,并且流核的位置和强弱受黑潮的季节性变化影响显著,深层流的季节变化不大。在年际尺度方面,吕宋海峡年际体积输运量异常与Niño3.4滞后6个月相关系数达到41.6%,吕宋海峡水交换与ENSO现象有较为显著的正相关关系,并存在2~3 a和准8 a周期的年际变化。     

黄河口及渤海湾海水的密度

用磁力浮沉子法溶液密度测量装置,在15—25℃之间的三个温度下测定了黄河口渤海湾36个站位海水样品(于1989年7月和1990年7月采集)的密度,发现所有实验测定值与根据其盐度和温度由1980年国际海水状态方程的计算值比较,均有明显的正偏差,此正偏差随海水盐度降低而增大。在黄河口渤海湾海水样品全部盐度范围内,已发现其海水密度正偏差与海水[Ca~(2+)]/s,[Mg~(2+)]/s,[SO_4~(2-)]/s之间呈指数曲线相关,而与碱度之间呈S形曲线相关,但在盐度25.72—31.57范围内都可近似看作直线相关。黄河口渤海湾海水的高碱度、高[Ca~(2+)]/s为其特征,这也是其密度正偏差的主要影响因素。本文还给出了计算黄河口及渤海湾海水密度的公式。     

Optimisation of a catalytic procedure for the determination of total iodine in seawater

A precise method for the determination of total iodine in seawater, which uses a Technicon Auto-Analyser II system and is based on Truesdale and Spencer's (1974) and Truesdale and Smith's (1975) earlier works with a catalytic procedure, is described. The procedure operates over a range of 30–80 μg1^?1 of iodine. As requested by Mark (1973), the way in which the procedure can be varied to suit other applications, and therefore ranges, is explained in detail. The standard deviation at the 50 μg1^?1 level was found to be 0.12 μ1^?1 showing that the method's precision exceeds most, if not all, previously published procedures for this variable. This high degree of resolution makes the procedure suitable for oceanic investigations. The effects of varying the reaction time, the temperature at which the reaction proceeds and the salinity of samples and standards are described. The advantages of using a Technicon Auto-Analyser II system rather than an Auto-Analyser I system are discussed. With slight modification the procedure can also be used in the measurement of river flow where sodium iodide is used as tracer in the dilution method.     

Turbulence investigation in a tidal coastal region

A high-frequency (1.2 MHz) four-beam Acoustic Doppler Current Profiler (ADCP) moored on the sea bottom was used for the direct measurements of the turbulence parameters in the shallow (20 m) coastal zone of the eastern English Channel. The measurements were as long as four tidal cycles during the period of the spring tide development. The measurements in the ocean and estimates showed that the Reynolds stress variability coincided with the semidiurnal tide. Their maximum values during the flood phase were approximately 1.5 Pa, while, during the ebb phase, they reached −1.2 Pa. The variations of the turbulence’s kinetic energy (TKE) and the rate of its production (P) coincided with the period of the tidal harmonic M4. Their maximum values were found during the flood phase near the bottom, and they were approximately equal to 0.03 m²/s² and 0.8 W/m³, respectively. These values decreased rapidly with the distance from the bottom. During the periods of low stagnant water, the values of TKE and P in the water column decreased to the minimum values (2 × 10⁻³ m²/s² and 3 × 10⁻⁵ W/m³, respectively), which coincided with the moment of the current’s reversal flow. The results demonstrated the dominating role of the tidal motion, which controls the structure and intensity of the turbulence in the bottom layer, and revealed the characteristic asymmetry of its distribution related to the nonlinear character of the tidal cycle.     

YZ-l型遥控遥测波浪仪

可以连续进行波浪测量的仪器被通称为“自记波浪仪”。按其测量讯号的传输方式划分,可分为有线传输型自记波浪仪和无线传输型自记波浪仪两类。 使用无线传输型自记波浪仪进行海上波浪测量,具有便于取得大风天气下的波浪资料、可长时间(几天或几十天)在离岸较远的海上连续进行波浪测量和节省调查费用等优点。笔     

Study on Sound-Speed Dispersion in A Sandy Sediment at Frequency Ranges of 0.5-3 kHz and 90-170 kHz

In order to study the properties of sound-speed dispersion in a sandy sediment, the sound speed was measured both at high frequency (90-170 kHz) and low frequency (0.5-3 kHz) in laboratory environments. At high frequency, a sampling measurement was conducted with boiled and uncooked sand samples collected from the bottom of a large water tank. The sound speed was directly obtained through transmission measurement using single source and single hydrophone. At low frequency, an in situ measurement was conducted in the water tank, where the sandy sediment had been homogeneously paved at the bottom for a long time. The sound speed was indirectly inverted according to the traveling time of signals received by three buried hydrophones in the sandy sediment and the geometry in experiment. The results show that the mean sound speed is approximate 1710-1713 m/s with a weak positive gradient in the sand sample after being boiled (as a method to eliminate bubbles as much as possible) at high frequency, which agrees well with the predictions of Biot theory, the effective density fluid model (EDFM) and Buckingham''s theory. However, the sound speed in the uncooked sandy sediment obviously decreases (about 80%) both at high frequency and low frequency due to plenty of bubbles in existence. And the sound-speed dispersion performs a weak negative gradient at high frequency. Finally, a water-unsaturated Biot model is presented for trying to explain the decrease of sound speed in the sandy sediment with plenty of bubbles.     

Quantitative estimation of intertidal sediment characteristics using remote sensing and GIS

High spatial resolution satellite data (IKONOS) combined with in situ data was used to quantitatively estimate the spatial distribution of tidal flat characteristics for the Hwangdo tidal flat, Cheonsu Bay, Korea. The classification result was accurate in terms of a comparison with the in situ data, and the overall accuracy was 90.7%, which confirmed the validity of the classification. GIS analysis based on a probabilistic model was applied to a quantitative estimation of the relationship between each surface sediment facies and the spectral reflectance. Mud flat facies showed a high positive correlation (R² = 0.91), and sand flat facies showed a high negative correlation (R² = 1.00), which was a good reflection of the sedimentary characteristics of Hwangdo tidal flat. Relationships between each sediment facies and DEM also showed good agreement with the topographic characteristics in the study area. The study revealed that intertidal surface sediment classification using high resolution remote sensing imagery and in situ data successfully shows spectral and topographic characteristics of the study area. It was noted that spectral reflectance was affected by a combination of environmental factors, including grain size, topography, and remnant surface water. It is possible to determine the type of tidal flat through quantitative estimates of the spatial distribution of surface sediments according to their spectral reflectance.