航海雷达图像噪声抑制方法研究

针对航海雷达图像上常见的同频干扰噪声,提出了一种有效的抑制方法。该方法采用阈值分割技术对噪声进行检测,然后对检测出的噪声点进行插值修复。使用X波段航海雷达图像对该方法进行检验。采用信噪比、偏差指数和相关系数等指标进行定量评价。结果表明,提出的新方法既能显著地抑制航海雷达图像的同频干扰噪声,又能较好地保持原始图像的信息,具有良好的降噪效果。它的综合性能明显优于传统的均值滤波和中值滤波方法。     

Compositional controls on coexisting prehnite-actinolite and prehnite-pumpellyite facies assemblages in the Tal y Fan metabasite intrusion, North Wales: implications for Caledonian metamorphic field gradients

Abstract The Tal y Fan Intrusion is a 110 m thick sub-concordant metabasite sheet intruded into volcaniclastic and pyroclastic rocks of Ordovician age in North Wales. Despite low grade metamorphism, primary textural zones resulting from initial cooling of the sheet are preserved and retain primary mineralogical and chemical variations which influenced the nature and extent of metamorphic recrystallization. This has resulted in a vertical sequence of secondary mineral assemblages through the intrusion. During early hydrothermal alteration K-feldspar replaced plagioclase micropheno-crysts in the marginal and contact zones, and olivine in the central zone was replaced by saponite. Subsequent regional metamorphism resulted in the development of (metastable) prehnite-pumpellyite-epidote assemblages in two sub-zones characterized by high Fe₂O₃. Elsewhere the assemblage prehnite-actinolite-epidote developed except in the contact and marginal zones where activity of CO₂ suppressed both prehnite and pumpellyite. Both assemblages contain excess albite, quartz and chlorite and, on the basis of uniform mineral compositions over the area of an individual thin section, are considered to represent buffered equilibrium assemblages indicative of prehnite-pumpellyite and prehnite-actinolite facies conditions. A metamorphic temperature of 310° C at 1.85 kbar is obtained using the P-T-X grid of Liou, Maruyama & Cho (1985), which implies a field gradient of ～ 44° C km^-1. Assuming that metamorphism relates to burial, an overburden thickness of ～ 7 km is indicated. Total maximum thicknesses, however, of Ordovician, Silurian and Lower Devonian strata, in the area, do not exceed 6 km indicating a field gradient of 52° C km^-1. These relatively high gradients may possibly be related to concealed late Caledonian intrusions, or alternatively may result from high heat flow as a consequence of crustal thinning, rapid sedimentation and intense magmatic activity in a marginal basin setting.     

Natural occurrence of 4-methyl-phenanthrene in petroleums and recent marine sediments: A new sensitive method to identify and quantify isomers in a series of alkyl—PAH: High resolution spectrofluorimetry at 15 K in n-alkane (Shpolskii effect)

HPLC extracts of crude petroleums and of marine recent sediments, containing the monomethyl-phenanthrene series, are examined by high resolution spectrofluorimetry in n-hexane at 15 K (Shpolskii effect). Identification and relative quantification of each of the five isomers is obtained on six natural samples. The distribution of the monomethyl-phenanthrenes and the relative absence of 4-methyl-phenanthrene in petroleums compared to marine sediments may reflect steric inhibitions.     

潮汐淹水时间对秋茄幼苗生长的影响

模拟正规半日潮淹水的条件下,不同淹水时间对秋茄[Kandelia candel(L.)Druce]幼苗生长的影响.应用沙和土两种培养基质,制备盐度为15的人工海水栽培幼苗培养时间为70 d.不淹水(0 h)和长时间淹水(>8 h)对秋茄幼苗的生长有一定的抑制作用,而短时间淹水(淹水2~4 h)对幼苗生长有所促进.较长时间的淹水可促进贮气根的数量增加和长度的增长.在当前培养条件下,秋茄幼苗生长的最佳淹水时间是每个潮水循环淹水2~4 h.2 h处理的沙培秋茄幼苗总生物量和成熟叶面积最大,胚轴失重最小,土培幼苗也有相应的变化趋势.秋茄幼苗生长的临界淹水时间是每个潮水循环淹水8 h.秋茄幼苗有较强的抗淹水能力,适当的淹水对其生长有利.     

三丁基锡对文蛤外套膜代谢酶活性的影响

用实验生态学方法，观察浓度为0．1、1、10ng／dm^3的三丁基锡暴露2、8、20d以及恢复7、20d后对文蛤外套膜酸性磷酸酶、碱性磷酸酶以及Na^＋、K^＋-ATP酶活性的影响．结果表明各浓度组的三丁基锡在暴露早期（2d），外套膜中酸性、碱性磷酸酶和Na^＋、K^＋-ATP酶活性与对照组比较没有显著差异，随着暴露时间的延长，高浓度的TBT暴露对AKP表现出激活作用，对ACP和Na^＋、K^＋-ATP酶活性则具有抑制作用．结果显示Na^＋、K^＋-ATP酶可作为有机锡暴露的生物标志物．     

盘鲍幼体附着诱导的研究

在水温20.5±0.5℃和海水盐度29.3的条件下，盘鲍幼体在受精后约72h获得附着能力．GABA（γ-氨基丁酸）2～1000μmol/dm3GABA可有效诱导幼体的附着，其中1000μmol/dm     

保存液中Ca2+、Mg2+、K+对中华绒螯蟹（Eriocheir sinensis）精子体外保存存活率的影响

提要以伊红染色法检测样品精子存活率为依据,研究了4℃下5种保存液及Ca2 、Mg2 离子对中华绒螯蟹精子体外保存效果的影响。5种保存液分别为人工海水(ASW)、2倍钙离子人工海水(2×Ca2 -ASW)、无镁离子人工海水(Mg2 -FASW)、无钾离子人工海水(K -FASW)、无钙离子人工海水(Ca2 -FASW),经4天保存后,各保存液中精子样品的存活率和精子密度均出现明显差异,K -FASW、ASW及2×Ca2 -ASW三种保存液中的精子因发生顶体反应而大量死亡,而Mg2 -FASW、Ca2 -FASW的保存效果较好。在此基础上,进一步探讨了不同Mg2 和Ca2 浓度对精子存活率的影响,结果发现,经24h保存后各实验组精子存活率均随着两种离子浓度的增加而明显下降。上述结果表明:K -FASW、ASW及2×Ca2 -ASW不适合精子保存,而Mg2 -FASW和Ca2 -FASW均可作为该蟹精子的保存液;Ca2 因可引起精子顶体反应而造成保存液中精子的大量死亡,其浓度与存活率呈明显的负相关;无K 的保存液中,Ca2 、Mg2 的存在与否对精子的保存效果起关键作用;无Mg2 人工海水之所以具有较好的保存效果,可能与Mg2 的缺乏而导致Ca2 逆浓度差转运受阻,避免了因Ca2 进入而诱发顶体反应有关。     

Enzymatic mobilisation of trace metals from estuarine sediment

Proteinase K, a non-specific protease that is representative of enzymes encountered in the digestive environment of deposit-feeding organisms, has been employed to determine the nature and extent of enzymatic mobilisation of trace metals (Al, Fe, Mn, As, Cu, Pb and Zn) from contaminated estuarine sediment. The extent of metal release by the enzyme was critically dependent on whether and how the sample had been dried and, for all metals except Mn, mobilisation was greatest when the sample had not been dried. The fraction of metal available to the enzyme, f_e, defined as the amount of metal released from undried sediment after 4 h incubation relative to the total metal concentration, was less than 1% in all cases. Significantly, however, there was a strong correlation between f_e and published factors defining the enrichment of metals in the gut fluids of the deposit-feeding lugworm, Arenicola marina. This suggests that, at least qualitatively, the mechanics of metal mobilisation in situ are replicated by the commercial enzyme. Thermally denaturing the enzyme resulted in mobilisation that was greater than (As and Cu) or similar to (all other metals) release engendered by the active enzyme, suggesting that the principal mechanism of metal mobilisation is not related to proteolysis but more likely involves complexation or exchange with component amino acids of the enzyme.