西宁城市居民家内外活动时间分配及影响因素——基于结构方程模型的分析     

张雪  柴彦威 《地域研究与开发》2017,36(5)

为深入挖掘居民不同类型活动的出行需求,进而制定更加精细化的交通政策,从活动分析法的视角出发,基于结构方程模型分析西宁城市居民家内外活动时间分配的机理及影响因素。结果表明:工作日,居民的通勤出行仍然是城市交通需要重点解决的问题。休息日,工作和通勤时间长的居民更倾向于在家内进行维持活动;而休息日不工作的居民更容易产生进行家外维持活动的出行需求。不同社会经济属性的居民对于家内外时间分配具有差异化特征。单位大院职住接近的特征对于减少居民通勤出行时间仍然具有积极作用,但维持性活动时间分配与其他类型社区居民已经没有显著差异。  相似文献   

太平洋几种海面要素的升降趋势及其对海平面上升的影响     

马继瑞  田素珍  张冬生  柴新敏 《热带海洋学报》1995,(4)

对ＣＯＡＤＳ资料中１９５０－１９９２年太平洋４°×８°方区的海水表层温度及海面气温、气压、风速序列数据，进行了时间序列分析。分析结果表明：太平洋海表气温和水温年上升率分别为０．００６３℃·ａ（－１）和０．００２６℃·ａ（－１）。两者的变化趋势在赤道太平洋都有一个年上升率高值区；而在东海以北的西北太平洋广大海区，都有一个年下降率的低值区。西太平洋海面气压呈上升趋势，东太平洋则相反。气温和水温的升降区域分布特征与风速分量增强和减弱的变化趋势有关。文章还指出，中国和日本沿岸今后几十年海平面变化趋势的预测模式，应以太平洋或全球海平面上升趋势的预测为基础，加上本海区海平面的局地变化订正。  相似文献   

The buckling of GRP hemi-ellipsoidal dome shells under external hydrostatic pressure     

C. T. F. Ross  Bak Hock Huat  Tay Boon Chei  Chai Min Chong  M. D. A. Mackney 《Ocean Engineering》2003,30(5):691-705

The paper reports on a theoretical and an experimental investigation into six GRP hemi-ellipsoidal dome shells, which were tested to destruction under external hydrostatic pressure. All six domes were of oblate shape and of three different aspect ratios. Each aspect ratio consisted of two dome shells, one made from two layers of glass fibre and one made from three layers of glass fibre. The theoretical analysis was via the finite element method where a non-linear theory was used which allowed for both geometrical and material non-linearity. Comparison between theory and experiment was good.  相似文献   

Size-fractionated phytoplankton standing stock and primary production in the Bohai Sea during late spring     

Ning Xiuren  Cai Yuming  Liu Zilin  Chai Fei 《海洋学报(英文版)》2002,21(3):423-435

During June 1997 cruise by R/V Science No.l, observations on temporal and spatialvariations of the size-fractionated phytoplankton standing stock and primary production were carried out in the Bohai Sea. The size-fractionated chlorophyll a (Chl a) and primary production, photosynthet-ically available radiation (PAR), as well as the related physico-oceanographic and zooplanktonic parameters were measured at five time-series observation stations representing sub-areas of the sea. Results obtained show that there were the marked features of spatial zonation of Chl a and primary production in the Bohai Sea. The values in the Laizhou Bay, the Liaodong Gulf and the Bohai Gulf were high and showed close relation with tidal fluctuations, i.e. high Chl a concentration occurred during high tide in the Laizhou Bay, and during low tide in the Liaodong Gulf and the Bohai Gulf. In the strait and the central region of the Bohai Sea, the values were relatively low and no relationship with tidal fluctuation could be foun  相似文献   

Brief Account of Breakwater Construction in China     

Chai Changqing Chief Engineer  First Navigational Engineering Bureau  Ministry of Communications of China  Jianjin 《中国海洋工程》1994,(1)

-The construction of breakwaters in China in more than 40 years since the founding of the People's Republic of China is reviewed. The construction of two main types of breakwater, upright breakwaters and rubble mound breakwaters, and the way in which they are built are expounded. Recommendations to improve the technology for future breakwater construction are presented.  相似文献   

Period components in the monthly mean sea level variations in the Pacific Ocean     

Tian Suzhen  Ma Jirui  Zheng Wenzhen  Chai Xinmin  Zhang Qin 《海洋学报(英文版)》1995,14(2):191-200

ＰｅｒｉｏｄｃｏｍｐｏｎｅｎｔｓｉｎｔｈｅｍｏｎｔｈｌｙｍｅａｎｓｅａｌｅｖｅｌｖａｒｉａｔｉｏｎｓｉｎｔｈｅＰａｃｉｆｉｃＯｃｅａｎ￥ＴｉａｎＳｕｚｈｅｎ；ＭａＪｉｒｕｉ；ＺｈｅｎｇＷｅｎｚｈｅｎ；ＣｈａｉＸｉｎｍｉｎａｎｄＺｈａｎｇＱｉｎ（Ｒｅｃ...  相似文献   

罗非鱼椭圆囊电生理学研究     

黄玉霖  贾俊成 《台湾海峡》1996,15(2):182-190

罗非鱼球状囊微音器电位是一个双峰波。峰频与刺激声频成２：１关系；在２０－８０Ｈｚ电位波形不规则。在３００－９００Ｈｚ电位波呈矩形。实验表明，球状囊不同区域对一一的声频敏感性不一样；延脑－脊髓连结处的诱发电位与球状囊微音器电位相似，但在１３０Ｈｚ电位呈单峰波；罗非鱼可闻频域在２０－９００Ｈｚ，最大敏感声频在１３０Ｈｚ，其相对敏感性为２３．０１ｄＢ；延脑－脊髓连接处诱发电位最大值在６３Ｈｚ和１３０Ｈｚ  相似文献   

基于Hoek-Brown准则的节理岩体能量参数估算          下载免费PDF全文

柴波  陶阳阳  杜娟  台大平  王禹 《地质科技通报》2020,39(1):78-85

岩体变形和破坏可以看作能量耗散和释放的过程.由于节理岩体结构复杂且难以开展室内试验,因此无法通过试验直接求取其能量学参数.基于Hoek-Brown准则和岩石能量理论,提出了节理岩体在临界状态能量学参数的估算方法.针对含贯通节理(或层面)岩体,通过修正岩块单轴抗压强度以体现贯通节理的方向效应.采用PFC3D分别模拟小尺寸岩样(Φ50mm×100mm)和大尺寸岩体(Φ2m×2m)的三轴压缩试验,通过岩石三轴试验结果拟合岩石数值模拟的细观参数并应用于节理岩体的模拟.根据节理岩体模拟得到应力应变曲线和能量流,验证了Hoek-Brown准则对节理岩体能量参数估算的合理性.  相似文献   

小麦玉米田耕作模式的防风蚀效果   总被引：2，自引：0，他引：2  

杨彩红  冯福学  柴强  耿艳香  伏星舟 《中国沙漠》2019,39(4):9-15

通过风洞实验，在5个风速下对6种耕作方式下农田土壤风蚀速率、0~20 cm风沙流结构进行了模拟研究。结果表明：保护性耕作土壤风蚀速率较传统耕作平均降低20%~40%；保护性耕作和传统耕作条件下土壤风蚀速率均随风速的增大呈幂函数递增，但在传统耕作条件下递增较快；风速14 m·s^-1是荒漠绿洲农田土壤风蚀加剧转折点，当风速>14 m·s^-1时保护性耕作下风蚀速率较传统耕作明显降低；0~20 cm内，传统耕作和保护性耕作下输沙率与高度分别呈线性和指数关系，保护性耕作下0~4 cm输沙量和输沙量百分比（Q_0~4/Q_0~20）均低于传统耕作。  相似文献   

Statistical Elmore delay of RC interconnect tree     

董刚  杨杨  柴常春  杨银堂 《海洋学报(英文版)》2010,29(11)

As feature size keeps scaling down, process variations can dramatically reduce the accuracy in the estimation of interconnect performance. This paper proposes a statistical Elmore delay model for RC interconnect tree in the presence of process variations. The suggested method translates the process variations into parasitic parameter extraction and statistical Elmore delay evaluation. Analytical expressions of mean and standard deviation of interconnect delay can be obtained in a given fluctuation range of interconnect geometric parameters. Experimental results demonstrate that the approach matches well with Monte Carlo simulations. The errors of proposed mean and standard deviation are less than 1% and 7%, respectively. Simulations prove that our model is efficient and accurate.  相似文献