An integrated model to assess critical rainfall thresholds for run-out distances of debris flows

A dramatic increase in debris flows occurred in the years after the 2008 Wenchuan earthquake in SW China due to the deposition of loose co-seismic landslide material. This paper proposes a preliminary integrated model, which describes the relationship between rain input and debris flow run-out in order to establish critical rain thresholds for mobilizing enough debris volume to reach the basin outlet. The model integrates in a simple way rainfall, surface runoff, and concentrated erosion of the loose material deposited in channels, propagation, and deposition of flow material. The model could be calibrated on total volumes of debris flow materials deposited at the outlet of the Shuida catchment during two successive rain events which occurred in August 2011. The calibrated model was used to construct critical rainfall intensity-duration graphs defining thresholds for a run-out distance until the outlet of the catchment. Model simulations show that threshold values increase after successive rain events due to a decrease in erodible material. The constructed rainfall intensity-duration threshold graphs for the Shuida catchment based on the current situation appeared to have basically the same exponential value as a threshold graph for debris flow occurrences, constructed for the Wenjia catchment on the basis of 5 observed triggering rain events. This may indicate that the triggering mechanism by intensive run-off erosion in channels in this catchment is the same. The model did not account for a supply of extra loose material by landslips transforming into debris flow or reaching the channels for transportation by run-off. In August 2012, two severe rain events were measured in the Shuida catchment, which did not produce debris flows. This could be confirmed by the threshold diagram constructed by the model.     

THE EARLY SUMMER FLOOD PERIODS OF SOUTHERN CHINA AND THE SUMMER MONSOON CIRCULATION OF EAST ASIA

Based on the thermodynamic characteristics of the summer monsoon and foe change of the lower layer wind fields, the relation between the early summer flood periods of southern China, Including the first flood period of South China and the plum rains period of the middle-lower reaches of the Yangtze River and the activities of the summer monsoon is analysed.The establishment processes of the summer monsoon circulation of East Asia are investigated.It is shown that the beginning and ending of the flood periods are exactly in accordance with the arrival and departure of the fore boundary of the summer monsoon.The establishment process of the circulation from the very beginning of the arrival of the monsoon to the time of great prosperity of development are not the same for each year.They can be classified into four categories.Each category may have four or three stages.Besides, the structure of the summer monsoon regime of East Asia is not unitary.There exist four types of structure model of the monsoon regime of East Asia.     

不同场地条件下非规则截面地铁地下车站结构地震反应特性研究

我国大型城市轨道交通地下结构建设处于蓬勃发展时期,建设场地条件日趋复杂,车站结构形式也复杂多样,呈现不规则特征。近年的地震灾害现象表明,地下结构在强地震作用下可能会出现严重的震害及次生灾害,城市大型地下结构工程的抗震安全性已成为倍受关注的社会问题之一。因此,研究不良地质条件下不规则地下结构的地震安全性具有重要的学术意义与工程应用价值。本文以苏州星海站的不规则(上层五跨下层三跨)地铁地下车站结构和场地条件为原型,分别采用模拟地震振动台试验和数值模拟方法开展研究,探讨饱和砂土地基和软弱粘土地基中非规则截面地铁地下车站结构的地震反应特性及损伤机理。为满足振动台试验中多种类型物理量的有效测试,采用了分布式柔性孔压传感链测试技术,阵列式位移计(SAA)测试技术,并基于机器视觉研发的非接触性动态位移测试技术实现地下结构灾变过程的可视化及数据化。论文的主要工作和成果如下:(1)将阵列式位移计(SAA)首次应用于地基土-地铁车站结构大型振动台系列模型试验中,实现土体变形的测量,并与基于机器视觉研发的非接触性动态位移测试结果相比较,表明采用SAA可较好地测试地震荷载作用下土体的位移响应;研发了分布式柔性孔压传感链测试技术,可以有效解决振动过程中传感器与土体惯性力不同而产生的自身摇摆、移位等问题。形成了地基土-地铁地下结构体系地震损伤与破坏时空演化过程的大型振动台试验可视化及数据化试验技术,可展现非规则截面地下结构的变形模式。(2)将研发的测试技术应用于大型振动台模型试验,开展了可液化地基和软弱粘土地基中非规则截面(上层五跨下层三跨)地铁地下车站结构的地震反应特性研究,给出了模型地基-结构体系加速度、变形、震陷特性,模型地基土与结构接触动土压力反应,模型结构动应变特性以及可液化地基土孔压反应及空间效应等,揭示了不良工程地质条件下地铁车站结构地震灾变特性和破坏机理。(3)对完成的不同场地条件下地铁地下车站结构的振动台系列试验结果进行对比分析,包括地铁车站模型结构周围地基土的加速度反应规律、地表震陷特征,模型地基土与结构接触动土压力反应特性,非规则截面地铁车站模型结构的加速度、侧向位移和动应变的反应规律等,得出了不同场地中非规则截面地铁地下结构地震反应特性的差异性。(4)基于有限元软件ABAQUS计算平台,形成了地基土-地下结构体系成套数值分析流程,开展了软弱场地中非规则截面地铁地下车站结构振动台试验的数值模拟,并与振动台模型试验结果进行了比较,验证了该数值分析方法的可行性和有效性。在此基础上,对复杂环境下足尺非规则截面地铁地下车站结构进行了数值模拟计算,给出了其地震反应特性。     

Relationships between carbon isotope evolution and variation of microbes during the Permian–Triassic transition at Meishan Section, South China

This paper investigates kerogen carbon isotopes, the difference between carbonate and kerogen carbon isotopes (Δ¹³C_carb-kero = δ ¹³C_carb − δ ¹³C_kero) and the difference between carbonate and n-C₁₉ alkane compound-specific carbon isotopes (Δ¹³C_carb-n-C19 = δ ¹³C_carb − δ ¹³C _n-C19) during the Permian–Triassic transition at Meishan, South China. The results show that kerogen carbon isotopes underwent both gradual and sharp shifts in beds 23–25 and 26–29, respectively. The differences between carbonate and organic carbon isotopes, both the Δ¹³C_carb-kero and Δ¹³C_carb-n-C19, which are mainly affected by CO₂-fixing enzyme and pCO₂, oscillated frequently during the Permian–Triassic transition. Both the variations of Δ¹³C_carb-n-C19 and Δ¹³C_carb-kero coupled with the alternation between cyanobacteria and green sulfur bacteria indicated by biomarkers. The episodic low values of Δ¹³C_carb-n-C19 corresponded to episodic blooms of green sulfur bacteria, while the episodic high values of Δ¹³C_carb-n-C19 corresponded to episodic blooms of cyanobacteria. The relationships between the variation of carbon isotopes and biota show that the microbes which flourished after the extinction of macroorganism affected the carbon isotope fractionation greatly. Combining the carbon isotope compositions and the pattern of size variation of the conodont Neogondolella, this paper supposes that anoxia of the photic zone at bed 24 was episodic and it would be caused by the degradation of terrigenous organic matters by sulfate reducing bacteria in the upper water column. Considered together with results from previous research, the high resolution variation of the biogeochemistry presents the sequence of the important geo-events during the Permian–Triassic crisis.     

高分辨天气雷达彩色回波图象的近程高速传输

实时雷达回波图象的传输对短期天气予报十分重要。本文给出RS422基带传输的硬件设计和软件流程图,详细分析了软件中有关波特率设置的问题,并给出了具体的解决方法。     

高原季风的年代际振荡及其原因探讨

一、高原季风的形成演化史高原季风是高原对大气的冷热源作用冬夏相反，从而引起的对流层中、低层冬季为反气旋环流，夏季为气旋性环流的总称。在青藏高原的隆升过程中，到渐新世初（约37Ma．B．P．）其水平尺度开始大于斜压大气地转适应的临界尺度’“，高原季风开始出现“’，全球气候经历了一次大转型，从以纬向分布为特征的准天文气候开始转向季风气候。值得提出的是，在早第三纪（如始新世），陆海分布已基本上是现代格局，海陆季风体系（东南季风、西南季风）应该已经形成，然而东亚、南亚地区非常干燥，为什么当时没有季风雨相伴呢…     

SZ36-1油田污水悬浮物无机组分研究

综合利用扫描电镜能谱分析、X-射线衍射仪等先进仪器对SZ36-1油田滤膜组分燃烧前后进行综合分析研究。通过分析无机组分中Fe、Ca等元素的变化规律,并结合现场水质监测数据,研究发现SZ36-1油田回注污水由CEP向AJ、平台输送过程中水质逐级恶化;同时污水由CEP到A平台再到J平台过程中,Fe原子百分比平均值依次为4.45%、13.03%、19.45%,Ca原子百分比平均值依次为4.33%、5.43%、5.66%。腐蚀、结垢现象逐渐加剧,是导致注水水质恶化的主要原因。     

Industrial structure optimization in central China under the energy constraint

Optimizing industrial structure is an important research object of human-economic geography, and it is also the object of government departments to strengthen macro-control. This has become even greater problem that China has entered the “new normal” in recent years. The study uses a multi-regional input-output model, with linear programming to build an optimal model of industrial structure as well as a model of optimization degree under the energy constraint. The results of the study revealed that: (1) the degree of optimization of industrial structure in Anhui Province is optimal (0.763), while that of Shanxi Province is the lowest (0.662); (2) the degree of optimization of industrial structure is negatively related to energy consumption per unit output value and the proportion of heavy industry; and (3) overall, central China should maintain or moderately increase the proportions of resource-based industry, greatly increase the proportions of manufacturing, including transport and telecommunications equipment, computers and other electronic equipment, and moderately reduce the proportions of smelting and pressing of metals and non-metal mineral products. In terms of service industries, the region should greatly increase the proportions of the production and supply of natural gas and tap water, moderately reduce or maintain the proportions of transport and storage as well as tourism, and maintain or moderately reduce the proportions of wholesale trade, retail trade and catering services.     

长江口外沉积物中多环芳烃结构类型的分布

本文采用色谱—质谱—质谱—计算机系统技术,分析了长江口外两个表层沉积物中多环芳烃组分,并探讨了其有机质的来源和地球化学特征。