Using a global reference sample set and a cropland map for area estimation in China

A technically transparent and freely available reference sample set for validation of global land cover mapping was recently established to assess the accuracies of land cover maps with multiple resolutions. This sample set can be used to estimate areas because of its equal-area hexagon-based sampling design. The capabilities of these sample set-based area estimates for cropland were investigated in this paper. A 30-m cropland map for China was consolidated using three thematic maps (cropland, forest and wetland maps) to reduce confusion between cropland and forest/wetland. We compared three area estimation methods using the sample set and the 30 m cropland map. The methods investigated were: (1) pixel counting from a complete coverage map, (2) direct estimation from reference samples, and (3) model-assisted estimation combining the map with samples. Our results indicated that all three methods produced generally consistent estimates which agreed with cropland area measured from an independent national land use dataset. Areas estimated from the reference sample set were less biased by comparing with a National Land Use Dataset of China (NLUD-C). This study indicates that the reference sample set can be used as an alternative source to estimate areas over large regions.     

A simplified design method for metallic dampers used in the transverse direction of cable-stayed bridges

The aseismic design of cable-stayed bridges in the transverse direction with newly proposed metallic dampers that can accommodate both longitudinal and transverse movement of the deck has recently been considered. This work focuses on developing a simplified method to design an appropriate metallic damper. The seismic performance of cablestayed bridges with different damper stiffness, main span lengths, tower shapes and types of deck in the transverse direction are investigated. The transverse displacement of the deck of a cable-stayed bridge increases significantly with the increment of the damper stiffness, which proves that the design of the damper stiffness is crucial. A simplified model considering the damper stiffness, cable system and tower in the transverse direction is developed to evaluate the period and lateral displacement of a complicated cable-stayed bridge. Based on the simplified model, a design method is proposed and assessed using two cable-stayed bridges as examples. The results show that metallic dampers can be designed with high efficiency, and the optimal ductility of the damper can be selected.     

Study of seismic behavior of PHC piles with partial normal-strength deformed bars

Nine PHC piles with partial normal-strength deformed bars were prepared in present study, and cyclic loading tests were implemented to evaluate these piles’ seismic performance. The influence of the axial compression ratio and the amount of normal-strength deformed bars on failure modes, crack patterns, strength, stiffness, and ductility were examined. The test findings indicate that the change of axial compression ratio has a noticeable influence on the failure mode of PHC piles. A larger axial compression ratio results in a higher cracking bending resistance, ultimate bending resistance, and initial stiffness, but the propagation heights of flexural cracks decrease as the axial compression ratio increases. Furthermore, increasing the amount of normal-strength deformed bars causes a slight decrease in ductility. Finally, a calculation formula was proposed to predict the flexural capacity of PHC piles with partial normal-strength deformed bars.     

Quantitative assessment of adaptive measures on optimal water resources allocation by using reliability,resilience, vulnerability indicators

Stochastic Environmental Research and Risk Assessment - Water resources allocation is facing great challenge, since hydrological series have shown non-stationarity with high uncertainty due to...     

Impulsive control of stochastic system under the sense of stochastic asymptotical stability

This paper studies the stochastic asymptotical stability of stochastic impulsive differential equations, and establishes a comparison theory to ensure the trivial solution's stochastic asymptotical stability. From the comparison theory, it can find out whether the stochastic impulsive differential system is stable just by studying the stability of a deterministic comparison system. As a general application of this theory, it controls the chaos of stochastic Lü system using impulsive control method, and numerical simulations are employed to verify the feasibility of this method.     

崇明东北潮滩泥沙输运过程的研究

潮滩泥沙的输运过程是河口近岸泥沙输运的重要组成部分,也是诊断潮滩侵蚀-淤积的重要动力指标,特别是在地貌演变过程显著的区域更具指示意义.本研究选择长江口崇明岛东北部潮滩,在2018年3月30日-4月10日进行三脚架多参数观测,获取了高分辨率的流速、含沙量等剖面数据,运用机制分解法分析了连续21个潮周期的泥沙输运过程.结果...     

基于谱分析的低频阴影检测技术

基于小波变换的瞬时谱分析方法,克服了传统傅立叶时频转换时的时窗问题,提高了地震资料频域内的分辨能力。通过谱分析方法的比较,介绍了瞬时谱分析方法比传统傅立叶变换的改进效果,以及利用瞬时谱分析方法在分频数据体低频部分识别富气层下方的低频阴影来综合预测储层的横向展布特征和含气性异常的检测。研究实例表明低频阴影检测技术可以作为一种储层预测和油气检测的有效辅助方法。     

Characteristics of rock fragments in different forest stony soil and its relationship with macropore characteristics in mountain area,northern China

Rock fragments have major effect on soil macropores and water movement. However, the characteristics of rock fragments and their relationship with macropore characteristics remain elusive in forest stony soils in northern mountainous area of China. The objectives of this study are to (1) use Industrial Computed Tomography (CT) scanning to quantitatively analyze rock fragment characteristics in intact soil columns in different forest lands and (2) identify the relationship between characteristics of rock fragments and that of the macropores. Intact soil columns that were 100 mm in diameter and 300 mm long were randomly taken from six local forest stony soils in Wuzuolou Forest Station in Miyun, Beijing. Industrial CT was used to scan all soil column samples, and then the scanned images were utilized to obtain the three-dimensional (3D) images of rock fragments and macropore structures. Next, the parameters of the rock fragments and macropore structure were measured, including the volume, diameter, surface area, and number of rock fragments, as well as the volume, diameter, surface area, length, angle, tortuosity and number of macropores. The results showed that no significant difference was found in soil rock fragments content in the 10-30 cm layer between mixed forest and pure forest, but in the 0-10 cm soil layer, the rock fragments in mixed forest were significantly less than in pure forest. The number density of macropores has significant negative correlation with the number of rock fragments in the 0-10 cm soil layer, whereas this correlation is not significant in 10-20 cm and 20-30 cm soil layers. The volume density of macropore was not correlated with the volume density of rock fragments, and there is no correlation between the density of macropore surface area and the density of rock fragment surface area. Industrial CT scanning combined with image processing technology can provide a better way to explore 3D distribution of rock fragments in soil. The content of rock fragments in soil is mainly determined by parent rocks. The surface soil (0-10 cm) of forest contains fewer rock fragments and more macropores, which may be caused by bioturbation, root systems, gravitational settling and faunal undermining.     

The design and implementation of a ROACH2+GPU based correlator on the Tianlai dish array

A digital correlator is a crucial element in a modern radio telescope. In this paper, we describe a scalable design for the correlator system of the Tianlai pathfinder array, which is an experiment dedicated to testing key technologies for conducting a 21 cm intensity mapping survey. The correlator implements the FX design, which firstly performs a fast Fourier transform(FFT) including polyphase filter bank(PFB) computation using a Collaboration for Astronomy Signal Processing and Electronics Research(CASPER) Reconfigurable Open Architecture Computing Hardware-2(ROACH2) board, then computes cross-correlations by employing Graphics Processing Units(GPUs). The design has been tested both in laboratory and in actual observation.     

桐柏——大别山主要构造热事件及40Ar/39Ar地质定年研究

桐柏——大别山是一条复合造山带。在其演化过程中曾经历了扬子旋回（1000Ma-761Ma）和加里东旋回（470Ma-401Ma）两个板块构造旋回的俯冲-碰撞造山作用，之后又经历了早、中华力西（357Ma-314Ma）的平移走滑和晚华力西（286Ma-261Ma）、印支期（224Ma-185Ma）、燕山期（130Ma-111Ma）逆掩或逆冲推覆的陆-陆叠覆造山作用。印支期的高压超高压变质岩系是在陆-陆叠覆造山作用下形成的。燕山期的造山不仅具显著的深层次构造岩浆作用特点，而且还伴随快速的隆升作用。