考虑水-桩-土相互作用的单桩式海上风机结构系统自振频率解析解

海上风机结构系统频率是海上风机结构和基础设计考虑的关键因素之一,桩-土相互作用对海上风机结构系统频率影响显著。基于欧拉-伯努利梁理论和传递矩阵方法,考虑水-桩-土相互作用及塔筒变截面特性,建立单桩式海上风机结构系统横向振动自振频率特征方程;将桩-水相互作用等效为附加质量、桩-土相互作用等效为线性弹簧,变截面塔筒等效为多段均匀梁,利用MATLAB中fsolve函数求解固有频率。通过与有限元分析结果进行对比,验证本文方法精度与有效性,并将本文方法应用于实际工程中,研究桩基础埋深、上部质量、转动惯量和桩-水相互作用对单桩式海上风机结构系统自振频率的影响。     

冻土区天然气水合物各向异性储层的AMT响应特征

陆域天然气水合物通常发育于冻土层下方破碎带和岩层裂隙处,其储层会表现明显电性各向异性特征.音频大地电磁法（AMT）能有效探测陆域水合物储藏范围,且不易受高阻冻土层的压制和干扰,可用于陆域天然气水合物探测研究.本文采用AMT对角各向异性二维正演方法,对多种陆域天然气水合物各向异性储层模型及相关参数进行了模拟试算,分析其视电阻率和相位响应特征.结果表明AMT能清晰显示各向异性储层空间位置和分布情况,并对储层的水合物饱和度变化以及储层数量等特征都有所反映.天然气水合物电性各向异性模拟研究为这一新型潜力能源的勘查工作提供了新的思路.     

Fluorescence as a Tool for Tracing the Organic Contamination from Pulp Mill Effluents in Surface Waters

Three‐dimensional fluorescence spectra of water samples from an eucalyptus bleached kraft pulp mill and from a river, upstream and downstream of the discharge of the effluent, revealed the existence of a peak at δ_exc = 280 nm and δ_em = 340 nm Δδ = 60 nm), characteristic of effluentπs organic matter. Humic substances were isolated from the effluent by sequential adsorption onto resins XAD‐8 and XAD‐4 in series. Their synchronous fluorescence spectra with Δδ = 60 nm do also exhibit an intense signal at δ_exc = 280 nm (≈ 300 nm in the humic acid fraction). The peak is absent in the spectra of humic substances isolated from a non‐polluted site of the river, but it is clearly seen in the spectra of the humic substances from a site downstream of the discharge of the effluent. Synchronous fluorescence spectra (Δδ = 60 nm) of water samples from the river and its lagoon were recorded and revealed to be an easy and fast way of tracing the organic contamination from the effluent.     

Differences between Humic Substances from Riverine,Estuarine, and Marine Environments Observed by Fluorescence Spectroscopy

Sixteen samples of fulvic acids and XAD‐4 fractions of riverine, estuarine, coastal, and open ocean origin have been studied by emission and synchronous molecular fluorescence spectroscopy. Certain features of the molecular fluorescence are related to the nature, the content, and the origin of those aquatic humic substances (HS). Riverine HS appear several times richer in fluorophores than marine HS, which can be well observed by emission fluorescence spectroscopy. Synchronous‐scan spectra of fulvic acids and of XAD‐4 fractions from the aquatic environments studied, emphasized the quality differences of their fluorophores. These features are useful as tracers of humic substances related with their natural environment source or even with their anthropogenic origin.     

Measurement of small strain shear modulus of clean and natural sands in saturated condition using bender element test

Bender element (BE) tests of saturated sand have increased interest to researchers currently. However, the measurement of small strain modulus from BE tests shows large difference between saturated and dry conditions. In this study, BE tests of a type of clean sand (Fujian sand) and two types of natural sands (Hangzhou sand and Nanjing sand) were performed. For the purposes of comparison, resonant column (RC) test and torsional shear (TS) test were also carried out on the same specimen. The factors that influence the determination of the travel time of shear wave in BE tests are discussed and a reliable method for the determination of the shear-wave velocity is obtained. It is found that the shear-wave velocities V_s of saturated Fujian sand (clean sand) and Hangzhou sand (natural sand) obtained from BE tests are 5–10% greater than those obtained from RC and TS tests. However, the V_s of saturated Nanjing sand (natural sand) obtained from BE, RC and TS tests show good agreement with a maximum difference of about 3%. Sands with various fines contents were also tested in an attempt to explain the differences between the two saturated natural sands. Biot׳s theory accounting for the dispersion of shear wave was employed to interpret the results of BE tests. The results indicate that the fines content of natural sand plays an important effect on the hydraulic conductivity, which affects the relative motion between soil particles and fluid when a high frequency shear wave propagates in the specimen. Based on this, a method for the determination of small strain shear modulus in BE test was proposed for both saturated clean sands and natural sands.     

中国对虾(Fenneropenaeus Chinensis)自然感染与人工感染WSSV抗病力的比较

取30个通过人工授精和自然交尾建立的中国对虾家系,分别进行人工感染和自然感染实验。实验过程中,两实验组样本总体存活率在35%左右时统计各家系的存活率,以分析其抗白斑综合征病毒情况。用四格表的卡方检验分析中国对虾各家系存活率,结果发现23个家系的存活率在两种感染方式实验间差异不显著(P0.05),两种感染方式实验间家系存活率一致性为77%。用独立样本T检验对两种感染方式实验中4个杂交组合的存活率进行比较,结果发现4个杂交组合的存活率在两种感染方式实验间差异不显著(P0.05),说明人工感染和自然感染实验对中国对虾抗病力的反映情况基本是一致的。另外,对两个实验中各家系的抗病力进行分析,综合结果表明有5个家系对WSSV可能有较强的抗病力。