台湾地震对福建地区基岩地震动的影响

福建沿海城市长期受台湾地震影响,虽少有破坏发生,但震感明显,特别是高层建筑,经常有持续时间较长的摇晃.本文选取了福建省基岩台站记录到的252条宽频带水平向加速度记录,这些记录来自近年发生在台湾的35次不同震级的地震,震级范围Ms=4.0 ～6.8,震中距R=214～650 km,震源深度d=6～40 km,经回归统计得...     

北太平洋和北冰洋大气中多氯联苯的浓度与气固分配行为

Polychlorinated biphenyls(PCBs) were measured in atmospheric samples collected from the North Pacific to the Arctic Ocean between July and September 2012 to study the atmospheric concentration characteristics of PCBs and their gas/particle partitioning. The mean concentration of 26 ∑PCBs(vapor plus particulate phase)(∑PCBs) was 19.116 pg/m3 with a standard deviation of 13.833 pg/m3. Three most abundant congeners were CB-28,-52 and-77, accounting for 43.0% to ∑PCBs. The predominance of vapor PCBs(79.0% to ∑PCBs) in the atmosphere was observed. PCBs were negative correlated with the latitudes and inverse of the absolute temperature(1/T). The significant correlation for most congeners was also observed between the logarithm of gas/particle partition coefficient(log KP) and 1/T. Shallower slopes(from-0.15 to-0.46, average-0.27) were measured from the regression of the logarithm of sub-cooled liquid vapor pressures(logpo L) and log KP for all samples. The difference of the slopes and intercepts among samples was insignificant(p0.1), implying adsorption and/or absorption processes and the aerosol composition did not differ significantly among different samples. By comparing three models, the J-P adsorption model, the octanol/air partition coefficient(KOA) based model and the soot-air model, the gas/particle partitioning of PCBs in the Arctic atmosphere was simulated more precisely by the soot-air model, and the adsorption onto elemental carbon is more sensitive than the absorption into organic matters of aerosols, especially for lowchlorinated PCB congeners.     

基于FFT稀疏压缩感知域内遥感图像融合

压缩感知理论因其远低于乃奎斯特采样率的特性,减少了大量的采样数据。基于这一特性,提出一种在压缩感知域内进行遥感图像融合的方法。该方法首先对图像作快速傅里叶变换(FFT);然后进行测量采样获取压缩感知域数据;再采用权重法对数据进行融合;最后通过重构算法得到融合图像。通过实验得出压缩感知域内遥感图像融合具有数据量少,融合效果好等特点。     

东北黑土区主要黑土土种的容许土壤流失量

容许土壤流失量(T 值) 是进行水土流失治理的定量标准,目前以专家经验确定为主,缺乏定量研究。本文以我国重要的粮食生产基地东北黑土区为研究区,实地调查区内21 个黑土土种典型剖面的厚度,采集分层土壤样品测定理化性质后,利用修订的生产力指数模型计算了21 个土种的T值,并分析其影响因素。结果显示：21 个土种的T值变化于68~358 t/km²×a,平均141 t/km²×a。按亚类T 值为白浆化黑土(漂白滞水湿润均腐土) 106 t/km²×a,黑土(简育湿润均腐土)129 t/km²×a,草甸黑土(斑纹简育湿润均腐土) 为184 t/km²×a。土壤厚度和土壤侵蚀脆弱性指数是影响T值的主要因素,它们与T值的相关系数分别为0.750 和0.605。草甸黑土厚度明显高于其它两个土壤亚类,脆弱性指数与黑土接近,其T值较黑土T值大42.6%。白浆化黑土厚度较黑土厚度大22.1%,但T值却比黑土T值小21.7%,因为白浆化黑土有明显的障碍层存在。因此确定不同土种或亚类的T值,更能反映土壤剖面特性,对于指导水土流失治理更具实际意义。     

中间球海胆群体遗传学研究中AFLP引物数量及样本量的选择

采用10,20,30,40,50,60,70,80共8个样本量梯度,随机选择并逐步增加AFIP引物组合,研究了AFLP标记数量及样本量对中间球海胆(Strongylocentrotus intermedius)群体遗传学指标的影响。结果表明:基因多样性指数(H)、Shannon氏指数(I)和多态位点比例(PP)3个遗传学指标对样本量的敏感程度不同,PP指标受样本量影响较大,样本量≥50个时方稳定,H指标在样本量≥30时稳定下来,而I指标在样本量≥20时即不再出现显著差异。共采用6对A FIP引物对80只海胆进行群体遗传学研究。通过每1对、每2对、每3对、每4对、每5对引物组合分别计算各遗传学指标,发现前二者所得各值之间以及其与对照值(6对引物所得值)之间存在显著差异,而每三对引物组合计算的各指标间不存在显著差异。据此推测,对中间球海胆进行AFLP标记研究中,样本数量最好不少于50个;而若样本量足够大(80个个体),则至少需要3对AFLP引物(或不少于100个标记),方能对海胆群体进行准确的遗传学评价。     

环境变化对信阳测震台背景噪声水平的影响

利用均方根速度值计算方法及背景噪声功率谱概率密度函数方法,对信阳测震台20082013年数据进行计算,得到不同时期背景噪声水平,分析环境变化对背景噪声的影响.     

三维街景数据在特大城市街区道路环境现状评估中的应用——以北京市为例

从特大城市街区单元的道路环境问题入手,在明确了三维街景数据获取方式与特点的基础上,设计了基于三维街景数据的城市区域街区单元的评估模式。这种借助于倾斜摄影测量和车载移动设备的三维街景数据,将大大提高城市区域评估的效率和准确率,并高效扩大评估的范围。本文基于这种最新的城市区域评估模式,利用街区道路环境现状评估模型对北京市典型区域实现了街道环境的评估。通过对街区单元的道路环境现状评估结果发现,基于三维街景数据的特大城市街区单元道路环境现状评估模型对于提高评估效率和准确率具有大幅帮助。同时发现,北京市机动车占道、绿蔽缺乏、栏杆恶劣、街道失落的情况仍很严重,街区单元道路环境的改善任务仍很重。研究成果将为城市精细化管理和城市设计提供数据支撑,为城市形象改善提供坚实基础。     

Marginal revenue of land and total factor productivity in Chinese agriculture: Evidence from spatial analysis

This paper attempts to explore the temporal and spatial nature of the marginal revenue of land, total factor productivity (TFP) change and its three components: technical change (TC), technical efficiency change (TEC) and scale efficiency change (SEC) as seen in Chinese agricultural production from 1995 to 1999. Based on county-level data, the study utilized both stochastic frontier and mapping analyses methods. The results show that growth in the marginal revenue of land was diverse across various regions, where most gain occurred in eastern coastal zone, while loss was in Northwest and North China. China has experienced moderate decreases in annual TFP change (-0.26%) with considerable regional variations. Specifically, the administrative intervention in grain production and the deterioration of the agricultural technology diffusion system led to a moderate drop in annual TFP change. County-level mapping analyses took into account interregional variances in TFP and its components. Regarding components of TFP, TEC differences explain the majority of regional dispersions in TFP. As developed areas in China, the Huang-Huai-Hai region and the Beijing-Tianjin-Tangshan economic zone face the challenges of land conversion and grain security amidst the process of urbanization.     

非均质地基浅埋水平条形锚板承载力上限分析

考虑地基土体的非均质特性,采用非线性Mohr-Coulomb强度准则及其关联流动法则构造了浅埋水平条形锚板的曲线型破裂机制与机动许可速度场,根据极限分析上限定理推导了条形锚板抗拔承载力的表达式。利用变分极值原理求得了锚板抗拔承载力及其上方土体破裂面的上限解,分析了锚板埋深、土体非均质和非线性强度特性对锚板抗拔承载特性的影响,并将该上限解与已有计算方法进行了对比。结果表明:锚板埋深、土体非均质和非线性强度特性对其抗拔承载力与破裂面特征具有明显的影响。锚板埋深和土体非均质系数越大以及土体非线性强度系数越小,锚板抗拔承载力和土体破裂面深度、宽度均是越大。该上限解与极限平衡和极限分析有限元方法的计算结果基本一致,验证了所采用的曲线型破裂机制和地基非均质变化规律有效性,为条形锚板设计提供了一定的参考。     

兰州轨道交通扰动场地黄土浸水试验研究

由于受长期地表降水与排水下渗、前期施工、拆迁等加卸载作用及车辆交通荷载的扰动影响,城市拆迁场地土体的特性与处于原始地形地貌和地层分布的土体情况有所不同。目前尽管已经发表了大量黄土浸水试验的成果,但基本都是在原状黄土场地进行,而在这类扰动场地黄土中开展浸水试验的研究尚不多见。在兰州东岗轨道交通车辆段建设场地进行了累计观测时间超过100天的试坑原位浸水试验。结合室内土工试验和现场测试结果,讨论了该扰动场地黄土浸水产生沉降变形的特征。结果表明:该扰动场地浸水发生沉降变形的时间发展过程具有"缓慢增长-突增-趋于稳定"的特点,其总沉降也远小于既有原状黄土场地的实测结果,应理解为广义的浸水增湿湿陷,其变形包括压缩变形和湿陷变形两部分,二者比例近似为7:3;前期扰动导致的较低的孔隙比和试坑开挖造成的卸荷是其总变形量较小的原因,但是其浸水沉降变形增长过程中突增的湿陷变形和土层空间分布不均匀引起的差异沉降值得引起注意。研究结果对于进一步加深对黄土湿陷变形与水稳定性的理解,选择扰动场地黄土地基处理和防排水措施具有一定的参考价值。