A Novel Approach for Evaluating Nonstationary Response of Dynamic Systems to Stochastic Excitation

The transient state of a dynamic system, such as offshore structures, to random excitation is always nonstationary. Many studies have contributed to evaluating response covariances at the transient state of a linear multi-degree-of-freedom(MDOF) system to random excitations, but a closed-form solution was not available unless the excitation was assumed to be a physically unrealizable white noise process. This study derives explicit, closed-form solutions for the response covariances at the transient state by using a pole-residue(PR) approach operated in the Laplace domain when the excitations are assumed to be stationary random processes described by physically realizable spectral density functions. By using the PR method, we can analytically solve the triple integral in evaluating the nonstationary response covariance. As this approach uses the poles and residues of system transfer functions, rather than the conventional mode superposition technique, the method is applicable to MDOF systems with non-classical damping models. Particular application of the proposed method is demonstrated for multi-story shear buildings to stochastic ground acceleration characterized by the Kanai–Tajimi spectral density function model, and a numerical example is provided to illustrate the detailed steps. No numerical integrations are required for computing the response covariances as the exact closed-form solution has been derived. The correctness of the proposed method is numerically verified by Monte Carlo simulations.     

Developing the science product algorithm testbed for Chinese next-generation geostationary meteorological satellites: Fengyun-4 series

Fengyun-4A (FY-4A), the first of the Chinese next-generation geostationary meteorological satellites, launched in 2016, offers several advances over the FY-2: more spectral bands, faster imaging, and infrared hyperspectral measurements. To support the major objective of developing the prototypes of FY-4 science algorithms, two science product algorithm testbeds for imagers and sounders have been developed by the scientists in the FY-4 Algorithm Working Group (AWG). Both testbeds, written in FORTRAN and C programming languages for Linux or UNIX systems, have been tested successfully by using Intel/g compilers. Some important FY-4 science products, including cloud mask, cloud properties, and temperature profiles, have been retrieved successfully through using a proxy imager, Himawari-8/Advanced Himawari Imager (AHI), and sounder data, obtained from the Atmospheric InfraRed Sounder, thus demonstrating their robustness. In addition, in early 2016, the FY-4 AWG was developed based on the imager testbed—a near real-time processing system for Himawari-8/AHI data for use by Chinese weather forecasters. Consequently, robust and flexible science product algorithm testbeds have provided essential and productive tools for popularizing FY-4 data and developing substantial improvements in FY-4 products.     

Relationship of boreal summer 10–20-day and 30–60-day intraseasonal oscillation intensity over the tropical western North Pacific to tropical Indo-Pacific SST

Climate Dynamics - The present study contrasts interannual variations in the intensity of boreal summer 10–20-day and 30–60-day intraseasonal oscillations (ISOs) over the tropical...     

不动产测绘关键技术初探

针对我国不动产统一登记工作对不动产测绘提出新的要求,为从技术上推进不动产统一登记工作、完善不动产测绘体系建设,该文对不动产测绘关键技术进行了初探。应用文献分析法、比较分析法,归纳并总结了不动产测绘的关键技术,指出不动产测绘关键技术主要包括数据标准、支撑技术和平台建设3方面,并提出统一数据分类体系、统一数据表达模式、统一空间基准、统一获取技术方法、统一管理平台的"五统一"技术方案。"五统一"技术方案可实现不动产测绘在空间基准,数据采集、转换、整合处理,质检,成果集成和展示等阶段的统一,促使不动产测绘清晰化、标准化、系统化,有助于提升不动产测绘体系的理论建设。     

辽宁省潜在蒸散发量及其敏感性规律分析

采用Penman-Monteith法和敏感系数法对辽宁省1965~2014年潜在蒸散发量及影响潜在蒸散发的气象因子敏感性进行分析,探讨气候变化下影响辽宁省潜在蒸散发量变化的主导因子及潜在蒸散发对气候变化的定量响应。结果表明：① 近50 a辽宁省潜在蒸散发呈现显著减少趋势,在空间上由西向东递减;② 潜在蒸散发对气象因子的敏感性在年尺度上表现为,水汽压最为敏感,其次为太阳辐射、风速、平均气温;在季节尺度上,春季和秋季对平均气温最不敏感,夏季对风速最不敏感,冬季对太阳辐射最不敏感;③ 空间分布上,气象因素的敏感系数与气象因子空间变化规律相吻合,潜在蒸散发对气温的敏感性由北部向南部递增,对水汽压、太阳辐射的敏感性由东部向西部递减,而风速与之变化趋势相反。④ 风速的显著降低是辽宁省潜在蒸散发量下降的主要原因,太阳辐射的下降及水汽压的升高也促使了潜在蒸散发量的下降。     

基于游客认同的文化遗产景区安全标识系统研究——以青城山-都江堰景区为例

文化遗产景区安全标识系统作为传播信息和规范观赏行为的有效方式,已成为影响游客旅游体验和衡量景区服务水准的重要因素。借助实地考察与随机抽样问卷调查,以青城山-都江堰世界文化遗产景区为例,综合利用文献分析和数理统计验证,拟定11项安全标识测量指标以调查游客对景区安全标识系统的认同感,研究结果表明:游客普遍认同遗产景区安全标识系统的重要性,但多是从利己角度的直观考虑;游客对青城山-都江堰文化遗产景区安全标识系统认同度低,安全标识系统各构成要素急需改进,尤其是安全标识的设计和功能;游客对文化遗产景区安全标识系统的认同度并不完全受人口统计特征影响;游客对文化遗产景区安全标识系统的认同度受游客出游频率和旅游形式影响。建议文化遗产景区从完善安全标识布局和基本功能、强调景观感设计、规范安全标识系统文字和色彩、改进标识的视觉尺寸和开展定期检查维护方面实施优化。     

基于景观基因“地域机制”的客家文化保护与传承开发——以湖南省炎陵县为例

根据客家文化景观基因理论及其"地域机制",以客家扩展聚居区炎陵县为例,结合历史文献查阅和实地调研,发掘分析该县客家文化的景观基因。研究结果表明:(1)迁徙由来、地域背景分别是客家文化景观的共同基因、本土基因;(2)由共同基因以"反客为主"的作用方式与本土基因形成了地方客家景观本质特性的主体基因;(3)保护与传承意识形态是决定其主体基因能否在世代遵循并坚守着"原汁原味"文化传统和文化精神传承过程中的人为基因。基于这些独特基因构成内在相关联的地域机制而所表达的特征,提出了应加强客家文化景观基因的数字化保护管理、传承开发政策等对策。     

河北省主要农作物生产时空格局变化特征及安全评价

阐述主要粮食作物的时空格局变化特征,对中国粮食安全决策意义重大。基于河北省县市近15 a (2001~2015年）的农业数据资料,采用分段线性趋势以及生产指标-产量波动系数来分析河北省主要粮食作物的时空变化特征,并对河北省粮食作物进行安全评价。结果表明：从产量与播种面积来看,近15 a河北省主要粮食作物变化趋势经历了由波动减少到稳步增长2个阶段,且变化趋势显著;从空间格局变化来看,大致呈由南向北逐渐递减的规律分布,其中不同农作物分布规律各有差异;从粮食安全方面来看,河北省70%以上年份粮食波动系数均超过中国粮食安全平均水平,粮食波动系数较高,粮食安全风险较大;但从人均粮食产量来看,安全程度相对比较乐观,粮食安全状况渐趋于平稳。研究可为河北省粮食生产时空布局的优化、结构调整与社会经济协调发展提供依据。     

Spatiotemporal changes of normalized difference vegetation index (NDVI) and response to climate extremes and ecological restoration in the Loess Plateau,China

Theoretical and Applied Climatology - Extreme drought, precipitation, and other extreme climatic events often have impacts on vegetation. Based on meteorological data from 52 stations in the Loess...     

Effects of an ecological conservation and restoration project in the Three-River Source Region,China

The first-stage of an ecological conservation and restoration project in the Three-River Source Region (TRSR), China, has been in progress for eight years. However, because the ecological effects of this project remain unknown, decision making for future project implementation is hindered. Thus, in this study, we developed an index system to evaluate the effects of the ecological restoration project, by integrating field observations, remote sensing, and process-based models. Effects were assessed using trend analyses of ecosystem structures and services. Results showed positive trends in the TRSR since the beginning of the project, but not yet a return to the optima of the 1970s. Specifically, while continued degradation in grassland has been initially contained, results are still far from the desired objective, ‘grassland coverage increasing by an average of 20%–40%’. In contrast, wetlands and water bodies have generally been restored, while the water conservation and water supply capacity of watersheds have increased. Indeed, the volume of water conservation achieved in the project meets the objective of a 1.32 billion m³ increase. The effects of ecological restoration inside project regions was more significant than outside, and, in addition to climate change projects, we concluded that the implementation of ecological conservation and restoration projects has substantially contributed to vegetation restoration. Nevertheless, the degradation of grasslands has not been fundamentally reversed, and to date the project has not prevented increasing soil erosion. In sum, the effects and challenges of this first-stage project highlight the necessity of continuous and long-term ecosystem conservation efforts in this region.