基于概率密度演化的基础隔震结构随机响应分析

针对抗震结构和基础隔震结构,应用概率密度演化方法对其进行多遇地震作用下的线性随机响应分析.通过引入工程地震动物理随机函数模型,采用数论选点法对多维外荷载随机变量进行离散代表点的生成并求得其赋得概率,利用离散代表点合成地震动加速度时程样本作为输入结构的随机激励,对于每条地震波,相当于对结构进行确定性动力反应分析.在求得结...     

富川地区风能资源分析

利用富川县虎头测风塔的实测资料,计算分析了富川地区的风能资源参数。结果表明,该地区的风能资源丰富,年平均风速、风功率密度和有效风速小时数都随高度的增高而增大;秋冬季是该地区风能资源利用的最佳时期,夏季次之,春季最差;而白天特别是中午一般是每天资源量最好的时段;该地区的主导风向集中,且最多风向与次多风向完全相反,各风向上的风能分布规律与风向频率分布一致,并且比风向频率分布更集中在主导风向上。     

石家庄秋季大气气溶胶物理特征分析

利用１９９０年秋季在石家庄地区不同天气条件下飞机观测对流层低层（距地面４０００ｍ以下高度）大气气溶胶的观测资料，分析了气溶胶粒子数密度、质量浓度水平和垂直分布特征及其日变化。结果表明，晴空下，石家庄地区气溶胶源于本地，地面质量浓度为０．１５×１０－９—０．８５×１０－９·ｃｍ－３，高度４０００ｍ以下谱分布特征值逆温层影响气溶胶粒子的向上输送，使其在送温层上下出现不连续分布；气溶胶的日变化表现为上午数密度大于下午，但下午粒子谱变宽；城市效应影响气溶胶粒子分布，城市上空气溶胶粒子数密度比郊区高１５％－３０％。     

粗粒料级配缩尺后最大干密度试验研究

对某级配粗粒料,采用剔除法、等量替代法、相似级配法和混合法等4种不同缩尺方法,依据规范要求进行缩尺。缩尺后替代级配料的最大颗粒粒径分别为20、40、60mm。对各替代级配料采用振动台法进行了最大干密度试验,基于试验成果,结合分形理论,提出了一种将最大干密度与级配及细粒含量之间关系归一化的方法,并拟合了最大干密度与试验前级配的分形维数、小于5 mm颗粒的含量及最大粒径之间的关系,据此可推求出原型级配料的最大干密度,探讨了缩尺方法对替代料试验前后粒径分布曲线变化幅度的影响,总结出颗粒破碎分形维数与试验前级配的分形维数、小于5 mm颗粒含量及最大粒径之间的关系式,据此可推求出填筑后原型级配料的颗粒破碎分形维数。     

裂隙蠕变的稳定性准则

介绍了最小耗能原理及其建立材料强度准则的一般步骤,在强度准则通常为能量蓄积程度表达式这一前提下,从最小耗能原理出发,利用线粘弹性断裂理论推导了裂纹蠕变的稳定性准则。为对比起见,将线弹性断裂理论的应变能密度因子断裂判据直接推广到粘弹性状态,得到了与最小耗能原理相同的稳定性准则表达式,并分析了几种流变材料中裂纹蠕变的长期稳定性。     

Extending the Place Glacier mass-balance record to AD 1585, using tree rings and wood density

Recognizing that climate influences both annual tree-ring growth and glacier mass balance, changes in the mass balance of Place Glacier, British Columbia, were documented from increment core records. Annually resolved ring-width (RW), maximum (MXD), and mean density (MD) chronologies were developed from Engelmann spruce and Douglas-fir trees sampled at sites within the surrounding region. A snowpack record dating to AD 1730 was reconstructed using a multivariate regression of spruce MD and fir RW chronologies. Spruce MXD and RW chronologies were used to reconstruct winter mass balance (Bw) for Place Glacier to AD 1585. Summer mass balance (Bs) was reconstructed using the RW chronology from spruce, and net balance was calculated from Bw and Bs. The reconstructions provide insight into the changes that snowpack and mass balance have undergone in the last 400 years, as well as identifying relationships to air temperature and circulation indices in southern British Columbia. These changes are consistent with other regional mass-balance reconstructions and indicate that the persistent weather systems characterizing large scale climate-forcing mechanisms play a significant glaciological role in this region. A comparison to dated moraine surfaces in the surrounding region substantiates that the mass-balance shifts recorded in the proxy data are evident in the response of glaciers throughout the region.     

基于长期密度试验的杉木人工林自然稀疏线研究（英文）

采用杉木人工同龄纯林26年连续观测数据,拟合Reineke(1933)经典的林分密度效应法则、Yoda(1963)基于欧几里德几何的自疏法则以及West, Brown和Enquist的分形几何(1997, 1999)。通过OLS、RMA和SFF算法得到7种枯损率区间(2%-80%, 5%-80%, 10%-80%, 15%-80%, 20%-80%, 25%-80%and 30%-80%)的自稀疏指数,对这些指数与考虑的几种法则相应指数进行验证。发现Reineke密度效应法则的指数显著区别于-1.605和-2,而不是预想的欧几里德分形几何结果。Yoda自疏法则指数在-3/2左右变动,但显著区别于-4/3。West、Brown和Enquist的分形几何式中指数参数既不趋向于8/3,亦不趋向于3。     

Influence of stocking density on growth,body composition and energy budget of Atlantic salmon Salmo salar L. in recirculating aquaculture systems

Atlantic salmon Salmo salar were reared at four stocking densities—high density D 1(final density ~39 kg/m 3), medium densities D 2(~29 kg/m 3) and D 3(~19 kg/m 3), and low density D 4(~12 kg/m 3)—for 40 days to investigate the effect of stocking density on their growth performance, body composition and energy budgets. Stocking density did not significantly affect specific growth rate in terms of weight(SGR w) but did affect specific growth rate in terms of energy(SGR e). Stocking density significantly influenced the ration level(RL w and RL e), feed conversion ratio(FCR w and FCR e) and apparent digestibility rate(ADR). Ration level and FCR w tended to increase with increasing density. Fish at the highest density D 1 and lowest density D 4 showed lower FCR e and higher ADR than at medium densities. Stocking density significantly affected protein and energy contents of the body but did not affect its moisture, lipid, or ash contents. The expenditure of energy for metabolism in the low-density and high-density groups was lower than that in the medium-density groups. Stocking density affected energy utilization from the feces but had no effect on excretion rate. The greater energy allocation to growth at high density and low density may be attributed to reduced metabolic rate and increased apparent digestibility rate. These findings provide information that will assist selection of suitable stocking densities in the Atlantic-salmon-farming industry.