基于夜间灯光数据的环渤海地区城市化过程

利用1992年、1996年和1998年的三期DMSP/OLS夜间灯光数据,提取了区域尺度的环渤海地区20世纪90年代的城市群空间信息,建立了城市群地区面状、线状和点状城市化空间模式,分析了环渤海城市群地区20世纪90年代的城市化过程。基本结论如下:①20世纪90年代环渤海城市群地区城市斑块数量增长较快,城市化过程明显,但小斑块所占比重较大,城市斑块破碎度增加。同时,区域内城市重心基本维持在经度117.93o和纬度38.49o附近,整体上表现出向西北方向移动的趋势。②20世纪90年代环渤海城市群地区城市化过程基本上可以从空间上概括为在中心城市和大城市周围的面状城市化过程、沿交通干线周围的线状城市化过程和广大区域内以新兴小城市或小城镇出现为特征的点状城市化过程三种基本过程。其中,面状城市化过程一直居于优势地位,但面状城市化过程的基本有效范围主要局限在面状城市斑块周围3￣4km范围。线状城市化过程和点状城市过程所占的比例相对较小,但表现出明显的增强趋势,在区域内的影响范围正逐渐扩大。     

新疆阿勒泰克兰河中游地区冬季积雪分布及特性分析

新疆阿勒泰地区是中国季节性积雪水资源最为丰富的地区之一。2016年12月在克兰河中游地区开展了积雪观测,利用直尺和量雪筒测量雪深和雪密度,调查了积雪水资源的分布情况;利用针式温度计测量雪层温度,获取了雪层之间的温度梯度;利用雪特性分析仪和显微镜测量了积雪剖面的雪层密度、液态水含量、介电常数和雪粒径。通过分析研究区积雪水资源的空间分布和积雪特性的垂直分异发现：研究区雪深的分布非常不均匀,北部的雪深总体上大于南部,即使在同一地区,雪深也因风力等原因而分布不均匀;研究区总体上属于"干寒型"积雪,密度较小,且密实化迅速;各雪层属于干雪或者湿度极低的潮雪,绝大多数雪层的液态水含量在0.3%以下;积雪温度总体上从表层到底层逐渐升高,表层温度日变化较大;阴天积雪温度高于晴天,各雪层温度日变化小于晴天,且午后积雪会出现负温度梯度,冷中心出现在积雪次表层;雪粒径较小,雪粒长短轴比的最小值出现在中间层,且符合新雪的粒径特点。     

Harmonic Energy Transfer for Extreme Waves in Current

Ning et al. (2015) developed a 2D fully nonlinear potential model to investigate the interaction between focused waves and uniform currents. The effects of uniform current on focusing wave crest, focal time and focal position were given. As its extension, harmonic energy transfer for focused waves in uniform current is studied using the proposed model by Ning et al. (2015) and Fast Fourier Transformation (FFT) technique in this study. It shows that the strong opposing currents, inducing partial wave blocking and reducing the extreme wave crest, make the nonlinear energy transfer non-reversible in the focusing and defocusing processes. The numerical results also provide an explanation to address the shifts of focal points in consideration of the combination effects of wave nonlinearity and current.     

考虑饱和土的地铁车站结构非线性地震反应研究

饱和土广泛存在于自然界之中,将土体视为固－液二相介质,基于biot饱和土介质动力方程的u-p形式研究了反映饱和土无约束域能量辐射效应影响的等效黏弹性人工边界单元,基于地震波转化为作用于人工边界节点上等效荷载的方法实现了波动输入。采用算例验证了等效人工单元的精度。建立饱和土-地铁车站非线性有限元整体模型,分析了考虑双相介质饱和土的波动传播,对比了饱和土及单相土在地震作用下地铁车站的地震反应,并与振动台试验结果进行了比较,研究表明：地震作用下采用考虑多孔介质的特性分析地基土与单相固体介质相比更加合理。通过对车站结构关键构件的加速度、位移和内力等进行分析,研究了饱和土－地下结构相互作用体系的地震反应。     

我国城市蔓延概念的界定与思考

对国内外城市蔓延概念的界定研究进行综述,归纳了近50年来城市蔓延界定的内涵与主要特征。分析发现,多数界定在关注城市蔓延现象本身特征的同时往往包含蔓延的成因与影响后果,进而较为深入地分析了西方蔓延界定的适用性与局限性。结合我国与西方城市蔓延的比较与分析,总结我国城市蔓延的界定标准与核心内容,提出应遵循界定对象明确、严格区分蔓延现象本身与影响后果、特征明晰并易于度量及充分考虑我国蔓延特殊性4个标准。从城市用地扩张的空间形态、用地强度与使用功能、用地的扩张速度3个方面选择核心特征对蔓延进行界定,有助于区分城市内部扩张的合理扩展与蔓延区域,并为蔓延影响与对策等其他相关研究提供理论基础。     

新型兰炭企业生产污水“零排放”工艺研究

对榆林市兰炭企业生产污水"零排放"工艺进行了研究.结果表明,该工艺可实现兰炭企业生产废水"零排放",并且其建设与运营成本都可为大部分同等生产规模的兰炭企业所接受,既保证了环境效益又取得了一定的经济与社会效益,对构建陕北地区新型兰炭产业发展模式有重要意义.     

人类活动和气候变化对红碱淖水面面积的影响

红碱淖是我国面积最大的沙漠淡水湖泊, 也是全世界最大的遗鸥繁殖与栖息地, 对该地区水面面积变化进行动态监测分析具有重要意义. 利用TM、 中巴资源卫星影像对红碱淖水面面积进行解译, 结合前人的研究成果, 对红碱淖水面面积的动态变化进行了模拟, 分析了引起红碱淖水面面积急剧萎缩的原因. 结果表明: 20世纪90年代以来红碱淖水面面积在大幅度萎缩, 水位急剧下降. 红碱淖水面面积急剧萎缩是气候变化和人为影响因素综合作用的结果, 可能的影响因素有气候变化、灌溉用水、生态环境建设、煤矿开采用水排水和水源地开采等5个方面, 其中上游河流截流是主要原因.     

Phytolith Records in Vermicular Red Earth:Implications for Bioclimatic Variationsduring Pleistocene

INTRODUCTIONVermicular red earth is distributed widely in South China,significant for the research into Quaternary environment andglobal change. Huang (1993) discovered the evidence of human activities-popple tools in vermicular red earth of the middle-upper reaches of Hanshui Riverl Zhu et al. (1991 ) statedthat red earth was a good information carrier of global changeafter the research into tropic red earth and environment byweathered mineral and geochemistry. Zhao and Yang (1995)stud…     

结构抗震设计中的强度折减系数研究

借助于单自由度弹塑性动力时程分析程序，对延性结构的强度折减系数进行了研究，在统计平均和回归分析的基础上，建立了平均强度折系数的函数形式，本文所建立的平强度折减系数函数，从理论上明确了结构具有延性对弹性地震力的折减关系，研究成果可供结构抗震设计规范采纳应用。     

EXPERIMENTAL STUDY ON THE CHANGES OF ULTRASONIC CODA WAVE AND ACOUSTIC EMISSION DURING ROCK LOADING AND DEFORMATION

The coda wave propagation path has received extensive attention as it is more sensitive to small changes in the medium than the direct wave. During the process of loading, the wave velocity, medium or source changes may cause the coda wave to change. The physical mechanism of change in the ultrasonic coda wave varies during different deformation stages. Meanwhile, there exist local damages in the rock sample during the deformation, and it will be accompanied by acoustic emission. Combining the ultrasonic coda wave and acoustic emission is beneficial to characterize the coda wave characteristics and damage degree of the sample at different deformation stages. In this paper, three kinds of rocks, including granodiorite, marble and sandstone with the sizes of 50mm×50mm×150mm, are used to carry out observations of ultrasonic coda wave and acoustic emission during the whole process of loading so as to study characteristics of the coda wave at different deformation stages. The major results are given below: 1)There is a good correspondence between the coda wave variation and the acoustic emission evolution process. When the acoustic emission frequency increases, the coda wave changes accordingly. In particular, the coda wave changes in the early stages of increased acoustic emission frequency, which indicates that the early damage information of rock can be obtained by analysis of the coda wave. 2)The physical mechanism of the coda wave change is different in different deformation stages. At the initial stage of loading, there are obvious scatterer changes in the coda wave change; then, in the linear elastic deformation stage, the wave velocity change is dominating; in the late-stage of loading, the scatterer change increases and coexists with the wave velocity change, the scatterer change effect is related with the rock micro-fracture degree, the rock will locally be damaged before rupturing, and the role of the scatterer will be enhanced. 3)With the increase of loading, the amplitude of increase of the wave velocity generally decreases gradually, which is basically consistent with the understanding obtained through the direct wave. The interference of acoustic emission can be eliminated because of the Kaiser effect when analyzing the coda wave. The consistency of the wave velocity change and stress loading and unloading is further verified. 4)The micro-fracture generated during rock deformation will change the physical mechanism of the coda wave change, and the scatterer effect will be significantly enhanced. At the same time, the acoustic emission waveform will cause interference to the ultrasonic coda wave. This means that attention needs to be paid when analyzing rock damage using only coda wave data. In short, the ultrasonic coda wave and acoustic emission can reflect the damage inside the rock, and the change mechanism of the coda wave in different deformation stages is different. The joint observation of the two can play a mutual verification role, which is conducive to improving the reliability of the observation results.