Accurate Acoustic Signal Parameter Estimation for Marine Geodesy Surveys

Acoustic signal parameter estimation is important for diverse marine geodesy surveys and several other applications. However, the received signal from a far-field target characterized by planar wavefront propagation is frequently affected by strong nearby interfering signals. Their presence deteriorates the performance of direction-of-arrival (DOA) estimation for far-field target. In order to enhance the reception of signal from far-field target, the near-field/far-field (NFFF) beamformer is proposed. Such a beamformer optimizes beam pattern for far-field detection by maximizing beamformer output in the direction of the far-field target with the imposed condition to eliminate interfering signals generated in near-field locations. As the interference suppression only occurs at the position of near-field interference, a possible blind zone for far-field detection in conventional methods is not created. The NFFF beamformer is applicable for coherent signals and the scenario with multi interferences. For stationary situation where interferers locations are fixed, the NFFF beamformer computations do not require time updates with associated computational load. Furthermore the proposed method can be extended to several new situations such as acoustic monitoring performed from a stationary platform subjected to water currents, waves, winds and other variables, all of them generating nearby interferences and also to different array configurations including 2D and 3D arrays.     

南海北部冬、夏季海表浮游植物光合作用速率对光强的响应特征

本文通过南海北部冬、夏季航次的现场观测,研究了海表浮游植物光合作用速率对光强的响应特征(P-E曲线)。结果表明南海北部浮游植物P-E曲线存在明显的季节变化。在冬季,P-E曲线呈现高P_mB、高α、高β的特征,这表明冬季浮游植物在低光照环境中光合作用速率增加迅速,其最大光合作用速率较高但容易受到光抑制。与冬季相反,夏季P-E曲线呈现低P_mB、低α、低β的特征,浮游植物受光抑制影响小,但最大光合作用速率低于冬季。水温和粒级结构等指标与P-E参数存在显著相关,这意味着环境和群落的季节变化可能对光合作用特性有一定影响。通过P-E参数模拟得到真光层内光合作用速率,模拟值与现场结果之间呈明显的线性相关但存在高估。此研究有助于认识南海浮游植物光合作用特征,并为初级生产力模型研究提供依据。     

大洋桥石藻Gephyrocapsa oceanica对海水酸化与营养盐胁迫的复合响应

本文选取了大洋桥石藻(Gephyrocapsa oceanica)作为实验对象,通过CO₂加富实验模拟海水酸化环境,分析了氮充足和氮相对不足条件下海洋颗石藻对海水酸化的生理响应。结果发现在两种营养盐状态下,CO₂加富均能一定程度促进大洋桥石藻种群增长与Chl a浓度的增加。对比两种营养盐状态,氮相对不足条件下的大洋桥石藻细胞密度和叶绿素含量均有最显著的提高,表明低营养盐浓度和低的氮磷比可能更有利于大洋桥石藻的生长繁殖。电镜观测结果显示酸化对大洋桥石藻的钙化作用具有显著的负影响,并且在氮相对不足条件下,大洋桥石藻的细胞个体变小及比表面积升高。研究结果表明在未来寡营养的大洋上层水体,大气CO₂浓度升高会对大洋桥石藻的生理功能产生负面影响,但可能刺激大洋桥石藻的生长。     

珠江口海域主导光学因子的遥感分类及其变化特征

基于2014年5月和8月珠江口海域的现场和实验测量数据,分析了光学因子和生态参数的动态变化特征,并找出该海域的主导光学因子;基于模拟的MODIS数据,构建了水体组分特征波长处吸收系数的遥感反演模型,并结合MODIS卫星遥感影像,依据IOCCG规则对主导光学因子进行遥感分类,揭示了珠江口海域2014年逐月水体主导光学因子的动态变化特征。结果表明,珠江口海域水体以a_d、a_g以及两种共同主导类型为主,并且a_g、a_d两种光学因子主导类型所占比例最大,其次是a_g主导类型,a_d主导类型所占比例最小。同时发现a_d（442）、a_dg（442）均与无机悬浮物浓度有较好的正相关关系,说明CDOM和悬浮泥沙具有相似的来源和动力变化过程。     

夏季南极长城湾海流变化特征及其对浮游植物生物量的影响

通过对2010/2011年夏季南极长城湾叶绿素a浓度和海流等环境参数的传感器连续观测;研究其时空变化特征及海流对浮游植物生物量的影响。结果表明;12.9 m水层叶绿素a浓度从12月中旬开始增长;直至2月上旬开始维持相对稳定;期间出现两个高值点（2.74 μg/L和3.76 μg/L）。叶绿素a浓度表现出了24 h周期变化特征;每日叶绿素a浓度最高值出现在正午前后时段的概率要高于其他时段。表层海水受西北风影响;流速较大;约为60~100 cm/s;中层和底层水体流速较小;约为10 cm/s。表层的风海流使海水在长城湾发生辐散;下层海水向上涌升;驱动了水体的垂直交换。长城湾与麦克斯韦尔湾存在水体交换;水体主要从中层进入湾内;从表层输出。长城湾的叶绿素a浓度与流速呈显著负相关;表明低流速环境有利于长城湾浮游植物的生长。     

福建兴化湾中部表层海水及沉积物中重金属含量特征与生态风险评价

分析研究了兴化湾中部表层海水Cu、Pb、Zn、Cd、Cr、Hg、As的含量发现,表层海水中Cu、Pb、Zn、Cd、Cr、Hg、As含量均符合海水水质一类标准,对表层沉积物中Cu、Pb、Hg、Cr、Cd、As等6种重金属含量分析表明,6种重金属含量均符合海洋沉积物质量一类标准.表层海水中重金属与环境因子相关性分析表明,6种重金属与环境的相关性在不同季节中存在差异;而表层沉积物中重金属与环境因子的分析表明,重金属具有相近的来源,有机质对沉积物中重金属的含量分布具有重要影响.主成分分析结果表明,兴化湾中部表层沉积物7种重金属主要来源为有机质的降解、沉积环境本身及工业排污的影响,其贡献率分别为59.48%、15.30%、10.98%,3个主成分的贡献率合计达到85.76%.潜在生态危害指数法评价结果表明,Cu、Pb、Zn、Cd、Cr、Hg、As均属轻微生态危害.     

Stabilization Mechanism and Effect Evaluation of Stabilized Silt with Lignin Based on Laboratory Data

The potential of a lignin-based by-product to stabilize silt was evaluated. The physical and mechanical properties of silt in its natural state, as well as when treated with varying proportions of lignin, were analyzed. The parameters tested include the particle size distribution, Atterberg limits, compaction characteristics, unconfined compressed strength, pH value, and electrical resistivity. To understand the stabilization mechanism of lignin-treated silt at a microscopic level, scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, and Fourier transform infrared resonance (FTIR) spectroscopy were also carried out on lignin and representative samples after 28 days of curing. The results indicate that the engineering properties of silt are improved by the addition of lignin. Particle size distribution is changed and plastic index is reduced from 8.8 to 7.7. After improvement, the maximum dry density increases and the optimum moisture content decreases, while the change of dry density with moisture content is enhanced. The treated silt has greater strength performance than the natural silt in terms of unconfined compressed strength and all of the samples have a pH value lower than 10. Curing time and moisture content have a significant impact on unconfined compressed strength but almost no effect on pH. Micro-chemical analysis reveals that the improvement of performance exhibited by lignin-treated silt may be mainly attributed to the cation exchange and the formation of more stable soil structure by lignin cementing. The stabilization mechanism of lignin-treated silt was proposed according to the results of chemical analysis. It is shown that lignin-based stabilizers have potential to improve the engineering properties of silt.     

Geomagnetic Models and Edge Recognition of Hydrothermal Sulfide Deposits at Mid-ocean Ridges

Near-bottom magnetic prospecting is considered to be an efficient method for investigating inactive hydrothermal areas and the study of the spatial structure of hydrothermal systems. Furthermore, geophysical forward modeling is widely used to simulate the anomalous characteristics of geological bodies. To understand the magnetic and magnetic structure features of hydrothermal sulfide deposits at mid-ocean ridges, we built 3D forward models for both mafic- and ultramafic-hosted hydrothermal sulfide deposits to simulate the near-bottom magnetic field. Our modeling results showed a low amplitude magnetic anomaly above the mafic-hosted hydrothermal sulfide deposits, and a high amplitude magnetic anomaly above the ultramafic-hosted deposits. These features allow us to identify and classify the host rocks of hydrothermal sulfide deposits. Moreover, we can recognize the edge of the magnetic anomalies using the intensity of the spatial differential vector method, considering variables such as the width of the alteration zone, the height of the observation platform, and the magnetic inclination and declination. Therefore, we propose the intensity of the spatial differential vector method as an effective approach to define the boundaries of hydrothermal sulfide deposits.     

人口城镇化与土地城镇化协调性测度及优化——以南昌市为例

人口与土地是城镇化的重要组成部分,分析二者之间状态演化对促进城市健康发展具有重要意义。在界定人口城镇化与土地城镇化二者概念基础上,基于人口构成、人口素质、人口生活、城镇规模、城镇投入、城镇产出等构建评价指标体系,并通过耦合协调模型对省会型城市南昌市2002~2011年两者之间的协调关系进行测度和分析,结果表明：① 人口城镇化指数与土地城镇化指数呈波动变化并持续上涨,城镇发展由土地滞后型向人口滞后型转变;② 人口城镇化与土地城镇化的协调状态由失调衰退区向过渡协调区演进,发展类型则由高度不协调状态向勉强协调状态过渡。在此基础上分析了南昌市人口城镇化速度滞后于土地城镇化速度的原因,指出两者关系主要受到城市发展外在制度与内在基础的共同作用,并认为构建人口与土地城镇化双重优化路径是协调人口城镇化与土地城镇化同步发展的有效途径。