谱图重排的谱分解理论及其在储层探测中的应用

谱分解理论是把单道地震记录分解为连续的时频谱平面,是地震资料处理和解释的重要技术之一.由于谱分解方法的多解性,所以同一道地震记录因为分解方法不同,得到的时频谱是不一样的.短时傅里叶变换,小波变换,S变换和匹配追踪算法都是对信号开窗分析,这些方法都受到不确定性原理的限制.Wigner-Ville变换避开了不确定性原理的限制,但是交叉项的存在限制了本方法的使用.本文利用谱图重排的时频分析方法(RSPWV)对合成的单道地震记录和实际的地震资料进行了分析.与短时傅里叶变换和匹配追踪算法的比较得出:此方法具有较高的时频分辨率,能够很好地识别气层.     

损伤条件下深部岩体巷道光面爆破参数研究

岩体条件复杂多变,为了提高光面爆破的适应性、改善光面爆破效果,对损伤条件下深部岩体巷道光面爆破参数进行研究。通过对深部岩体巷道光爆层原岩应力场、光面爆破机制和振动损伤特征进行分析,基于爆炸应力波和爆生气体综合作用理论,考虑高原岩应力和岩石损伤影响,提出了损伤条件下深部岩体巷道光面爆破参数确定的计算方法。研究表明, （1）高原岩应力相当于提高了岩石的抗拉强度,不利于炮孔初始裂纹的形成及贯通,宜减小周边眼间距;（2）岩石损伤后,其他条件不变,光面爆破的炮孔间距和抵抗线值可适当加大;（3）高原岩应力和损伤条件下,光面爆破的炮孔间距较小时,容易造成爆后围岩损伤,降低围岩的稳定性能,因此,提高爆破效果的同时应及时加强支护,以确保施工安全和围岩稳定;（4）本文提出的光面爆破参数计算公式,经现场爆破验证效果良好,适用于复杂多变的岩体环境。     

基于小波变换的分频最小光滑滤波去噪

在地震勘探中,随机噪音是一种频带较宽,严重影响有效波信噪比的干扰波。一般的去噪方法有:f-x、w-x、f-x奇异值分解等,但这些都只考虑横向上随机噪音的不相关性,而在一维方向上研究甚少。小波变换是一种时频分析的方法,根据它的分频和局部分析能力,结合一维方向上去噪的光滑滤波,就能有效地消除随机干扰,且保证了有效波的中、高频成份,经过小波包重构,可恢复有效波信号。该方法在去噪方面是十分有效的。     

Parametric study of the smooth‐joint contact model on the mechanical behavior of jointed rock

The smooth‐joint contact model based on distinct element method has been widely used to represent discontinuity in the simulation of fractured rock mass, but there is rare efficient guidance for the selection of proper parameters of smooth‐joint contact model, which is the basement for using this model properly. In this paper, the effect of smooth joint parameters on the macroscopic properties and failure mechanism of jointed rock under triaxial compression test is investigated. The numerical results reveal that the friction coefficient of smooth joint plays a dominant role in controlling mechanical behaviors. The stiffness of smooth joint has a relative small influence on the mechanical behaviors. Poisson ratio decreases with the reduction of normal stiffness but increases with the reduction of shear stiffness. The reduction of smooth joint strength, which is determined by normal strength, cohesion, and friction angle of smooth joint, contributes to the breakage of bonded smooth joint and ultimately decreases the strength of the specimen. We proposed a detailed calibration process for smooth‐joint contact model according to the relationship between smooth‐joint parameters and mechanical properties. By following this process, the numerical results are validated against corresponding experimental results and good agreement between them can be found in stress‐strain curves and failure modes of different joint orientations. Further analyses from the microperspective are performed by looking at transmission of contact force, the nature and distribution of microcracks, and the particle displacement to show the failure process and failure modes.     

A new smooth hysteretic model for ductile flexural‐dominated reinforced concrete bridge columns

A new smooth hysteretic model is proposed for ductile, flexural‐dominated reinforced concrete bridge columns. Four columns designed per modern seismic codes were tested using monotonically increasing and variable‐amplitude cyclic loading protocols and ground motion loading to develop the model. Based on the test results, hysteretic rules for damage accumulation and path dependence of reloading were constructed. For damage accumulation, unloading stiffness degradation is correlated with the maximum displacement and hysteretic energy dissipation, while reloading stiffness degradation is set equal to the unloading stiffness degradation. Pinching severity is related to the residual displacement in the direction opposite to the loading direction. Strength deterioration is correlated with the damage index and does not occur until the damage index reaches a threshold, after which the deterioration is proportional to the increase of the damage index. For path dependence of reloading, reloading paths are classified into primary paths and associate paths. The primary paths are those that start from a residual displacement that is equal to or larger than the previous maximum one. The associate paths are those that do not belong to primary paths and tend to be directed towards certain points. Reloading without load reversal is assumed to be linear. Comparison with the results of pseudo‐dynamic tests using three consecutive ground motions showed that the proposed model closely matched the test results. Copyright © 2017 John Wiley & Sons, Ltd.     

Seismic analysis of a curved bridge considering deck‐abutment pounding interaction: an analytical investigation on the post‐impact response

Horizontal curved bridges are very common at intersections and at the changing angle of bridge alignment. Almost in every previous earthquake report, it can be seen that the columns of a curved segment experience torsional damage, and the curved decks are unseated from the abutment support. The main reason behind that phenomenon is the in‐plane deck rotation which results because of the complex dynamic coupling between two longitudinal directional vibrations. The curved decks are susceptible to deck rotation because in a curved segment, the centre of mass and the centre of stiffness generally lie outside the bridge deck and are not located at the same point. The pounding with the abutment often increases the rotational tendency of the deck. In this paper, a classical mechanics‐based approach is adopted to analytically estimate the deck rotation potential of curved bridge considering the deck‐abutment pounding interaction. The deck‐abutment pounding is modelled using non‐smooth techniques considering the Newton's impact law in the normal and Coulomb's friction in the tangential direction. Within the scope of this paper, a parametric study is performed to get the ideal combination of the column and bent arrangement and the gap distance. Copyright © 2016 John Wiley & Sons, Ltd.     

Long-term evapotranspiration rates for rainfed corn versus perennial bioenergy crops in a mesic landscape

Perennial cellulosic crops are promoted for their potential contributions to a sustainable energy future. However, a large-scale perennial bioenergy production requires extensive land use changes through diversion of croplands or conversion of uncultivated lands, with potential implications for local and regional hydrology. To assess the impact of such land use conversions on ecosystem water use, we converted three 22 year-old Conservation Reserve Program (CRP) grasslands and three 50+ year-old conventionally tilled corn-soybean crop fields (AGR) to either no-till continuous maize (corn) or perennial (switchgrass or restored prairie) bioenergy crops. We also maintained one CRP grassland without conversion. We measured evapotranspiration (ET) rates on all fields for 9 years using eddy covariance methods. Results show that: (a) mean growing-season ET rates for perennial crops were similar to the ET rate of the corn they replaced at the previously cultivated (AGR) field but ET rates for perennial crops at CRP fields were 5–9% higher than ET rate for corn on former CRP fields; and (b) mean nongrowing season ET rates for perennial fields were 11–15% lower than those for corn fields, regardless of land use history. On an annual basis, mean ET rates for perennial crops tended to be lower (4–7%) than ET rate of the corn that they replaced at AGR fields but ET rates for perennial crops and corn at CRP fields were similar. Over 9 years, mean ET rates for the same crop across land use histories were remarkably similar for corn, whereas for the perennial crops they were 4–10% higher at former CRP than at former AGR fields, mainly due to differences in growing season ET. Over the 9 years and across all fields, ET returned ~60% of the precipitation back to the atmosphere. These findings suggest that large-scale substitution of perennial bioenergy crops for rainfed corn in mesic landscapes would have little if any (0 to −3%) impact on terrestrial water balances.     

5种南海海藻醇提取物活性初步研究

海藻是海洋生物代谢产物的主要来源之一,能产生丰富多样的生物活性物质.为了更好地利用中国南海的海藻资源,分别对采自中国湛江硇洲岛的1种绿藻基根硬毛藻Chaetomorpha basiretorsa Setchell和4种红藻刺状鱼栖苔Acantophora spicififera (Vahl) Boerg、三列凹顶藻Laurencia tristicha Tseng, Chang et Xia、紫杉状海门冬Asparagopsis taxiformis (Delile) Trevisan、鸡毛菜Pterocladia tenuis Okam进行了生物活性研究,分别对细胞毒活性(KB、Bel-7402、PC-3M、Ketr3和MCF-7)、Na~+,K~+-ATPase抑制活性以及犬血管平滑肌细胞增殖抑制活性进行了筛选,部分海藻提取物表现出一定的生理活性.     

Nonlinear elastic and inelastic spectra with inherent and supplemental damping

During severe seismic events, structures designed according to current standards yield and develop inelastic deformations. While the acceleration responses are limited by the yielding strength, these structures develop permanent deformations (and possible damage) due to such yielding. Spectra developed for inelastic structures can help in determining the desired yield levels and the associated inelastic deformations. Some structures made of special materials or equipped with innovative structural systems may yield, but can recover the deformation upon unloading and, thus, may avoid permanent deformations. These structures are known as nonlinear elastic. Often the post yielding excursions are very large and may exceed their toughness (or deformability). By introducing damping in form of supplemental devices, it is possible to control such deformations and keep them within acceptable limits. Spectra for such nonlinear elastic structures and inelastic structures are developed herein, by considering both inherent and supplemental damping. The difference between the two types of damping is addressed both theoretically and numerically. Design examples of several simple structures using the newly developed spectra are presented, which illustrate the importance of lower strength and damping in these nonlinear elastic or inelastic systems. Copyright © 2013 John Wiley & Sons, Ltd.     

折线光滑处理的三点算法研究

在地理信息系统（GIS）中,为了使地图线状要素数据的可视化有较高的质量,就需要对线状要素进行光滑处理。如何使得折线光滑后,让原始点更多地保留下来,是衡量该类地图数据精度的重要依据。本文提出了一种折线光滑处理的三点算法,该方法拟合精度高且算法简单,具有较强的实用性,可用于自动化制图、GIS等地图线状要素的绘制中。