Steel buckling‐restrained braced frames with single and dual corner gusset connections: seismic tests and analyses

The design of a three‐story buckling‐restrained braced frame (BRBF) with a single‐diagonal sandwiched BRB and corner gusset was evaluated in cyclic tests of a one‐story, one‐bay BRBF subassembly and dynamic analyses of the frame subjected to earthquakes. The test focused on evaluating (1) the seismic performance of a sandwiched BRB installed in a frame, (2) the effects of free‐edge stiffeners and dual gusset configurations on the corner gusset behavior, (3) the frame and brace action forces in the corner gusset, and (4) the failure mode of the BRBF under the maximum considerable earthquake level. The subassembly frame performed well up to a drift of 2.5% with a maximum axial strain of 1.7% in the BRB. Without free‐edge stiffeners, the single corner gusset plate buckled at a significantly lower strength than that predicted by the specificationof American Institute of Steel Construction (2005). The buckling could be eliminated by using dual corner gusset plates similar in size to the single gusset plate. At low drifts, the frame action force on the corner gusset was of the same magnitude as the brace force. At high drifts, however, the frame action force significantly increased and caused weld fractures at column‐to‐gusset edges. Nonlinear time history analyses were performed on the three‐story BRBF to obtain seismic demands under both design and maximum considerable levels of earthquake loading. The analytical results confirmed that the BRB and corner gusset plate achieved peak drift under cyclic loading test. Copyright © 2011 John Wiley & Sons, Ltd.     

Two modes of climatic control in the Holocene stalagmite record from the Japan Sea side of the Japanese islands

The Holocene stalagmite FG01 collected at the Fukugaguchi Cave in Itoigawa, central Japan provides a unique high‐resolution record of the East Asian winter monsoon. Because of the climate conditions on the Japan Sea side of the Japanese islands, the volume of precipitation during the winter is strongly reflected in the stalagmite δ¹⁸O signal. Examination of the carbon isotopes and the Mg/Ca ratio of FG01 provided additional information on the Holocene climate in Itoigawa, which is characterized by two different modes separated at 6.4 ka. Dripwater composition and the correlation between the δ¹³C and Mg/Ca data of FG01 indicate the importance of prior calcite precipitation (PCP), a process that selectively eliminated ¹²C and calcium ions from infiltrating water from CO₂ degassing and calcite precipitation. In an earlier period (10.0–6.4 ka), an increase in soil pCO₂ associated with warming and wetting climate trends was a critical factor that enhanced PCP, and resulted in an increasing trend in the Mg/Ca and δ¹³C data and a negative correlation between the δ¹³C and δ¹⁸O profiles. A distinct peak in the δ¹³C age profile at 6.8 ka could be a response to an increase of approximately 10% in C4 plants in the recharge area. At 6.4 ka, the climate mode changed to another, and correlation between δ¹⁸O and δ¹³C became positive. In addition, a millennial‐scale variation in δ¹⁸O and pulsed changes in δ¹³C and Mg/Ca became distinct. Assuming that δ¹⁸O and PCP were controlled by moisture in the later period, the volume of precipitation was high during 6.0–5.2, 4.4–4.0, and 3.0–2.0 ka. In contrast, the driest interval in Itoigawa was during 0.2–0.4 ka, and broadly corresponds to the Little Ice Age.     

气候变化对我国农作物宜播种面积的影响

基于气候条件与农作物熟制的相互关系,得到农作物潜在播种面积,分析气候变化对我国农作物播种面积的影响和其他因子对其综合作用。结果表明：我国实际播种面积增长缓慢,空间差异明显,华中实际播种面积占比最大而新疆最少,西南、华中、东北和新疆面积增加,西北、华南、华东和华北减少;在≥10℃积温指标下,1986-2009年我国潜在的不可耕地面积平均值相对1961-1985年减少约34.33%,一年一熟区面积有所减少,但仍占约50%面积,一年两熟和一年三熟地区面积均呈增加趋势;综合≥10℃和≥0℃两个积温指标,我国潜在播种面积缓慢增长,与实际播种面积的变化趋势一致,其他综合因子则在总体上对潜在播种面积的增长有微弱抑制作用。     

应力场数值模拟与油藏有利区预测-以松辽盆地乾安地区归字井青三段为例

构造应力场在油气运聚成藏中具有重要的作用。明水组沉积末期是松辽盆地乾安地区高台子油层的一个主要成藏期, 期间烃源岩的生、排烃高峰与大规模油气运聚和圈闭的形成在时间上具良好的匹配关系。利用ANSYS有限元模拟软件, 对归字井地区明水组沉积末期构造应力场进行了初步模拟; 同时利用地应力驱动油气运移理论, 对运移势场进行了数值模拟。模拟结果表明, 最大主应力受岩性控制明显, 而最小主应力主要受埋深控制。已有的试油试气资料表明, 具油气显示的井, 大部分都位于地应力区和地势区。依据地应力和运移势场的分布, 并结合地质构造特征, 对油藏有利区进行了预测, 为油田的勘探开发提供了科学依据。      

Quality of the Log-Geometric Distribution Extrapolation for Smaller Undiscovered Oil and Gas Pool Size

The U.S. Geological Survey procedure for the estimation of the general form of the parent distribution requires that the parameters of the log-geometric distribution be calculated and analyzed for the sensitivity of these parameters to different conditions. In this study, we derive the shape factor of a log-geometric distribution from the ratio of frequencies between adjacent bins. The shape factor has a log straight-line relationship with the ratio of frequencies. Additionally, the calculation equations of a ratio of the mean size to the lower size-class boundary are deduced. For a specific log-geometric distribution, we find that the ratio of the mean size to the lower size-class boundary is the same. We apply our analysis to simulations based on oil and gas pool distributions from four petroleum systems of Alberta, Canada and four generated distributions. Each petroleum system in Alberta has a different shape factor. Generally, the shape factors in the four petroleum systems stabilize with the increase of discovered pool numbers. For a log-geometric distribution, the shape factor becomes stable when discovered pool numbers exceed 50 and the shape factor is influenced by the exploration efficiency when the exploration efficiency is less than 1. The simulation results show that calculated shape factors increase with those of the parent distributions, and undiscovered oil and gas resources estimated through the log-geometric distribution extrapolation are smaller than the actual values.     

Recovery Factors of Oil Resources in China

This paper provides a new method to estimate recovery factors of oil resources. The China National Petroleum Assessment (2003–2007) (CNPA 2007) evaluates in-place oil resources and applies the recovery factor (RF) to estimate recoverable oil resources. The RF of oil resources plays an important role in the CNPA 2007. Based on the geological features, 24 types of oil assessment units are defined, such as the Mesozoic rift unit, the Mesozoic and Cenozoic foreland unit, etc. Through the recovery factor statistics of oil reserves (discovered) in different accumulations, as well as the potential analyses of enhanced petroleum recovery, appropriate RF valuing standards of oil resources (discovered and undiscovered) in different assessment units are developed. Calculation methods of oil resource RFs are established, including the appraisal standards, scoring, and calculation steps of oil resource RFs. Through the case studies, the valuing and appraisal standards of oil resource RFs are verified. Robust appraisal standards allow the RF method to be a valuable tool to effective assessment of China’s recoverable oil resources.     

基于混沌加权一阶局域法的IGS超快星历钟差预报

为提高IGS超快星历钟差预报产品的精度,针对卫星钟差数据具有确定项和随机项成分的特点,在采用多项式模型对钟差确定项建模的基础上,提出采用混沌加权一阶局域法对钟差随机项进行建模预报。仿真结果表明,采用混沌加权一阶局域法的预报精度优于超快星历钟差预报产品。     

Reducing the impacts of flood-induced reservoir turbidity on a regional water supply system

This paper proposed an integrated simulation model to incorporate the impact of flood-induced reservoir turbidity into water supply. The integrated model includes a regional water allocation model and a one-dimensional settling model of cohesive particles based on Kynch’s theory. It simulates the settling of sediment flocculation in a turbid reservoir. The restrictions of water supply during floods is mimicked by simulating turbidity profiles for control points and then quantifying the associated treatment capability of raw water in the regional water allocation model for each time step. This framework can simulate shortages caused by flood-induced high turbidity as well as extended droughts, thus provide a basis for comprehensive evaluations of emergent and regular water supply facilities. A case study of evaluating different measures to mitigate the impact of turbid reservoir on water supply in northern Taiwan is presented to demonstrate the efficacy of the proposed approach.     

Selection of bioindicators for monitoring marine environmental quality in the Bay of Fundy,Atlantic Canada

Distribution of metals, PAH's and PCB's in lobsters, mussels, and sediments were used to assess marine environmental quality of the Bay of Fundy. This study demonstrates that the lobster (Homarus americanus) is a better bioindicator for monitoring contaminants in the marine environment and has a greater capacity for the uptake and accumulation of contaminants than the mussel (Mytilus edulis) and sediments. A definite pattern in the spatial distribution of lobster Cu, Cd, and Ag was evident. The distribution of organic contaminants for both mussels and lobsters in the Bay of Fundy lacked a spatial trend, and organic contaminants were undetectable in sediments from all sites. The Gulf Watch Programme, which monitors chemicals in mussels in the Bay of Fundy, did not indicate a problem with high levels of Cu, Cd, and Zn in the ecosystem. Analytes below the detection limit, such as in mussels and sediments, increase the difficulties of chemical analysis and detection for environmental monitoring. Deficiencies of mussels in monitoring the Bay of Fundy were discussed.