Seasonally frozen soil effects on the dynamic behavior of highway bridges

Frozen ground is significantly stiffer than unfrozen ground. For bridges supported on deep foundations, bridge stiffness is also measurably higher in winter months. Significant changes due to seasonal freezing in bridge pier boundary conditions require additional detailing in order to ensure a ductile performance of the bridge during a design earthquake event. This paper reports the latest results obtained from a project that systematically investigated the effects of seasonally frozen soil on the seismic behavior of highway bridges in cold regions. A bridge was chosen and was monitored to study its seismic performance and assess the impact of seasonally frozen soil on its dynamic properties. A Finite Element (FE) model was created for this bridge to analyze the impact of seasonal frost. It was found that when frost depth reaches 1.2 m, the first transverse modal frequency increases about 200% when compared with the no-frost case. The results show that seasonal frost has a significant impact on the overall dynamic behavior of bridges supported by pile foundations in cold regions, and that these effects should be accounted for in seismic design.     

Conversion of kinetic energy from synoptic scale disturbance to low-frequency fluctuation over the Yangtze River valley in the summers of 1997 and 1999

In order to investigate the conversion of kinetic energy from a synoptic scale disturbance （SSD; period≤seven days） to a low-frequency fluctuation （LFF; period〉seven days）, the budget equation of the LFF kinetic energy is derived. The energy conversion is then calculated and analyzed for the summers of 1997 and 1999. The results show that the energy conversion from the SSD to the LFF is obviously enhanced in the middle and lower troposphere during the heavy rainfall, suggesting this to be one of mechanisms inducing the heavy rainfall, although the local LFF kinetic energy may not be enhanced.     

基于局部一维模型与走时标定的区域三维速度模型构建技术研究

构建区域介质三维速度模型并以之获得准确的区域震相走时,是提高区域地震定位精度的重要手段之一.为充分利用已有的一维模型、GT事件、地质资料等实现三维模型构建,尝试基于目标区域内已有的部分局部一维模型,通过克里金空间插值建立初始三维模型,然后利用GT事件走时数据并参考其它地震地质资料对其不断进行修正,使得其走时偏差图与GT事件走时偏差图一致,进而获得能够提高区域地震定位精度的三维模型.使用不同模型进行的地震定位实验表明,以此方法建立的三维模型的定位偏差较初始模型减少约20％,较好地起到了减小区域震相走时残差,提高区域地震定位精度的作用.     

鹤岗地震台DSQ型水管仪观测系统日常问题分析及维护

针对鹤岗地震台在实际工作中遇到的各种问题,结合台站实际情况,分别从主机系统、电子记录系统等方面,提出仪器运行中经常出现的问题.并总结DSQ水管仪在日常问题中系统维护的具体解决办法,以此提高观测质量和工作效率.     

基于图像处理技术的岩心裂缝图像提取

基于数字图像处理技术,利用油田大量现场岩心纵向(或平面)劈开面图像资料,可直接分离出岩心剖面上裂缝信息.最大类间方差法的二值化算法是基于类间方差达到最大为准则,采用该法获得了理想的二值化效果,较准确地从岩心剖面中提取出裂缝图像信息.     

准格尔丘陵沟壑区五分地沟流域土地覆盖分析

以准格尔丘陵沟壑区五分地沟流域为研究区,应用彩红外航片和IKONOS卫星影像,绘制了1987、2002年土地覆盖/植被类型图,并数字化基于地面土地利用调查绘制的1979年土地利用图.利用景观格局指数,评价了研究区土地覆盖/植被空间格局现状及土地覆盖类型动态变化;并以ETM 数据为信息源,绘制了2002年土地覆盖/植被类型图.研究表明:2002年研究区土地覆盖/植被呈现出一个耕地、草地、人工乔木林和人工灌木林以及种植稀疏灌木的草地高度镶嵌的景观格局特征;20年内土地覆盖类型发生了显著的变化,景观异质性增强.基于研究区景观的高度破碎化,绘制小流域精细尺度土地覆盖图,高空间分辨率遥感数据十分必要.     

Numerical simulation for the coupling effect of local atmospheric circulations over the area of Beijing,Tianjin and Hebei Province

Using the model system MM5.V3 and multi-layer grid nesting technique, we have done a multi-scale numerical simulation over the area of Beijing, Tianjin and Hebei Province to analyze the temperature and wind field there and study its local circulations. The results show a coupling effect of Urban Heat Island Circulation (UHIC), Mountain Valley Breeze (MVB) and Sea Land Breeze (SLB) occurs in this area when the synoptic system is weak. The SLB can penetrate deep into the mainland for about 200 km when it is blooming. MVB can extend to south and cover almost the whole plain area in Beijing. Both MVB and SLB are diurnal periodical; meanwhile the phase of MVB drops behind that of SLB for about six hours. As a local circulation, the UHIC weakens the two circulations above, and it also has a diurnal period. As a result, the coupling effect of circulations reveals not only different features in spring-summer period and autumn-winter period in a year but also the difference between early morning to noonday and afternoon to night in a day. We noted the diffusion of contamination over the area around Beijing, and found the steady presence of a transport routine of contamination over North-China throughout the year caused by the Coupling Effect mentioned above. This find is important for studying the environment pollution in this area. Supported by Central Public Welfare Special Fund Program for the Institute and Higher Education (Grant No. IUMKY200701), Public Welfare Special Fund Program (Meteorology) of China Scientific and Technological Ministry (Grant Nos. CYHY20080620, CYHY200706004), Spread New Technology Program of China Meteorological Administration (Grant No. CMATG2007M15) and Urban Meteorology Scientific Research Fund Program of the Institute of Beijing Urban Meteorology, China Meteorological Administration (Grant No. UMRF200702)     

Deepwater Ventilation and Stratification in the Neogene South China Sea

Combined data of physical property, benthic foraminifera, and stable isotopes from ODP Sites 1148, 1146, and 1143 are used to discuss deep water evolution in the South China Sea (SCS) since the Early Miocene. The results indicate that 3 lithostratigraphic units, respectively corresponding to 21-17 Ma, 15-10 Ma, and 10-5 Ma with positive red parameter (a*) marking the red brown sediment color represent 3 periods of deep water ventilation. The first 2 periods show a closer link to contemporary production of the Antarctic Bottom Water (AABW) and Northern Component Water (NCW), indicating a free connection of deep waters between the SCS and the open ocean before 10 Ma. After 10 Ma, red parameter dropped but stayed higher than the modern value (a*=0), the CaCO3 percentage difference between Site 1148 from a lower deepwater setting and Site 1146 from an upper deepwater setting enlarged significantly, and benthic species which prefer oxygen-rich bottom conditions dramatically decreased. Coupled with a major negative excursion of benthic δ13C at ~10 Ma, these parameters may denote a weakening in the control of the SCS deep water by the open ocean. Probably they mark the birth of a local deep water due to shallow waterways or rise of sill depths during the course of sea basin closing from south to east by the west-moving Philippine Arc after the end of SCS seafloor spreading at 16-15 Ma. However, it took another 5 Ma before the dissolved oxygen approached close to the modern level. Although the oxygen level continued to stabilize, several Pacific Bottom Water (PBW) and Pacific Deep Water (PDW) marker species rapidly increased since ~6 Ma, followed by a dramatic escalation in planktonic fragmentation which indicates high dissolution especially after ~5 Ma. The period of 5-3 Ma saw the strongest stratified deepwater in the then SCS, as indicated by up to 40% CaCO3 difference between Sites 1148 and 1146. Apart from a strengthening PDW as a result of global cooling and ice cap buildup on northern high latitudes, a deepening sea basin due to stronger subduction eastward may also have triggered the influx of more corrosive waters from the deep western Pacific. Since 3 Ma, the evolution of the SCS deep water entered a modern phase, as characterized by relative stable 10% CaCO3 difference between the two sites and increase in infaunal benthic species which prefer a low oxygenated environment. Thesubsequent reduction of PBW and PDW marker species at about 1.2 Ma and 0.9 Ma and another significant negative excursion of benthic δ13C to a Neogene minimum at ~0.9 Ma together convey a clear message that the PBW largely disappeared and the PDW considerably weakened in the Mid-Pleistocene SCS. Therefore, the true modern mode SCS deep water started to form only during the "Mid-Pleistocene climatic transition" probably due to the rise of sill depths under the Bashi Strait.     

基于作物系数与水分生产函数的向日葵产量预测

利用河套灌区向日葵2012年田间水分、分期播种试验数据和两个站点的农业气象历史资料,研究基于向日葵作物系数和水分生产函数的产量预测方法。结果表明:向日葵标准作物系数在生育期内的变化规律是前期小、中期大、后期小, 最高值为1.21, 出现在开花期。标准作物系数与出苗后日数和大于0℃积温有很好的二次和三次多项式关系,拟合优度在0.93以上。在分析相对叶面积指数和作物系数关系的基础上,提出标准作物系数的相对叶面积指数订正方法,得出河套灌区向日葵作物系数的动态计算式,为水分生产函数中实际蒸散量的计算提供支撑。建立以Jensen模型为基础的向日葵水分生产函数,得到对水分亏缺的敏感顺序从高到低是开花期、花序形成期、成熟期、苗期。综合应用向日葵作物系数方程和水分生产函数模型计算分期播种产量,与实际产量分别相差4.4%和4.1%,初步证明该文提出的方法对产量预测较为理想,在该地区具有很好的适用性。