A range-dependent echo-association algorithm and its application insplit-beam sonar tracking of migratory salmon in the Fraser Riverwatershed

Fish sonars have long been used to survey and monitor migratory salmon in rivers and at sea. However, research has been lacking in the development of algorithms to extract fish tracks from data collected in a riverine or oceanic environment. Current fish trackers, based on a pulse-to-pulse tracking method, only work well under ideal conditions when targets are well separated and the signal-to-noise ratio is high. Fisheries biologists often have to identify fish traces visually from raw echograms. This approach is both labor-intensive and time-consuming, limiting the usefulness of hydroacoustic techniques for fisheries management. This paper presents a fish-tracking algorithm which sorts randomly distributed echoes into coherent fish traces. Fish counts obtained with the algorithm compare well with visual counts at two quite different sites in the Fraser River watershed. The key features of the algorithm are: (1) the linking mechanisms among sequential fish echoes are range-dependent; (2) the growth echo for a developing track depends not only on its space-time relation with the previous track echo (the pulse-to-pulse statistics) but also on its relation to the entire track being constructed; (3) there are a total of only five echo-association criteria in the algorithm; (4) the simplicity of the algorithm structure provides a convenient platform for implementing specific and sophisticated tracking criteria to meet specific needs; and (5) the user can fully control the performance of the algorithm by choosing values for the 11 well-defined tracking parameters     

Evaporation of Accretion Disks around Black Holes: The Disk-Corona Transition and the Connection to the Advection-dominated Accretion Flow

We apply the disk-corona evaporation model (Meyer & Meyer-Hofmeister) originally derived for dwarf novae to black hole systems. This model describes the transition of a thin cool outer disk to a hot coronal flow. The mass accretion rate determines the location of this transition. For a number of well-studied black hole binaries, we take the mass flow rates derived from a fit of the advection-dominated accretion flow (ADAF) model to the observed spectra (for a review, see Narayan, Mahadevan, & Quataert) and determine where the transition of accretion via a cool disk to a coronal flow/ADAF would be located for these rates. We compare this with the observed location of the inner disk edge, as estimated from the maximum velocity of the Halpha emission line. We find that the transition caused by evaporation agrees with this determination in stellar disks. We also show that the ADAF and the "thin outer disk + corona" are compatible in terms of the physics in the transition region.     

湖南土地资源及其利用研究

本文论述湖南土地资源的主要特点，分析了土地利用现状及存在的主要问题，同时提出对土地资源的合理开发利用措施。     

福建山地气候生态特征及其宜茶气候带的划分

福建山地分布近海面至海拔2158米,立体气候特征极其明显。本文根据福建山地气候生态特征和茶树的生物学特性,将山地划分为:1.大叶种茶树最适宜、适宜、不适宜种植三个气候带;2.中、小叶种茶树最适宜、适宜、次适宜、不适宜四个气候带。并依此提出科学开发福建山地茶叶生产的五项关键技术措施。     

试论具有岭南文化特色的广州城市森林的建设

岭南文化作为一种地域文化,其标志和典范是广东文化,广州是岭南文化的中心,其特色须由岭南文化铸就,广州城市森林如何渗透岭南文化,具有独特的岭南风格,对于振兴岭南文化,塑造广州新的形象和风格,形成广州城市特色,具有重要意义,文中分析了广州城市森林实现具有备岭南文化特征的途径,认为根据文化内涵,表现形式和手法,具体体现为五个方面：（１）以营建岭南乡土树种片林为主体;（２）发展岭南园林;（３）引进抽象式园     

黄淮海平原农业综合开发的效益和粮食增产潜力

黄淮海平原经过1988-1993年农业综合开发,取得了明显的经济、生态和社会效益。改造中低产田409万ha,开发区粮食年平均增长率达4.0%,其增产量占全区增产总量的42.5%,农业开发的贡献几乎与传统农业的贡献相等。预测1995-2000年,即使是农业综合开发的规模与前六年相同,但是,由于水利工程效益更充分地发挥和农业的科技含量持续增长,开发区粮食完全可能增产达90亿kg.     

Newly identified Caledonian gabbro (450 Ma) in the eastern Guangxi,South China: Production of intraplate orogenic process

1.Objectives As one of three major tectonic blocks of China,the South China Block has undergone multiple periods of tectonic-magmatic-metamorphic events.Among t...     

Stratigraphic architectures and associated unconformities of Pearl River Mouth basin during rifting and lithospheric breakup of the South China Sea

Marine Geophysical Research - The lithosphere breakup processes from initial rifting of the crust to the complete rupture of the lithosphere underwent several tectonic evolution stages and resulted...     

Dynamic Behaviors of A Marine Riser Under Two Different Frequency Parametric Excitations

The marine risers are often subjected to parametric excitations from the fluctuation top tension. The top tension on the riser may fluctuate with multiple frequencies caused by irregular waves. In this paper, the influence between different frequency components in the top tension on the riser system is theoretically simulated and analyzed. With the Euler-Bernoulli beam theory, a dynamic model for the vibrations of the riser is established. The top tension is set as fluctuating with time and it has two different frequencies. The influences from the fluctuation amplitudes, circular frequencies and phase angles of these frequency components on the riser system are analyzed in detail. When these two frequencies are fluctuating in the stable regions, the riser system may become unstable because ω_1+ω_2≈2Ωn. The fluctuation amplitudes of these frequencies have little effect on the components of the vibration frequencies of the riser. For different phase angles, the stability and dynamic behaviors of the riser would be different.     

油型气湿度和成熟度的关系研究

通过分析国内外鄂尔多斯、四川、Fort Worth、Arkoma等盆地373个样品油型气湿度与镜质体反射率的关系,发现随热演化程度升高,油型气湿度变小,二者呈负对数相关关系,油型气湿度与热演化程度的这种负对数相关关系,可为页岩气勘探和天然气资源评价提供科学依据。同时,分析天然气湿度与热成熟度关系曲线图,发现干酪根降解气湿度随着热演化程度升高迅速减小,而裂解气湿度相对稳定,这也证实原油裂解气与干酪根直接降解生气的分子热动力学模型存在较大差异。