Organic structure and possible origin of ancient charred paddies at Chuodun Site in southern China

A number of ancient charred paddies with a ¹⁴C dating of about 5900 a BP were recovered in the sixth excavation at Chuodun Site and are assigned to the Majiabang culture (7–6 ka BP). To understand their formation mechanism, the ancient charred paddies were compared to modern paddies using FT-IR spectrum and thermaogravimetric analysis. At the same time, modern charred paddies were made in helium by the laboratory method, and the structural characteristics of them and the ancient ones were revealed using CP/MAS-¹³C-NMR. Our results show there are more aromatic moieties in ancient charred paddies compared to modern paddies. The aliphatic components of modern charred paddies decrease continuously, accompanied by the accumulation of aromatic components, when the duration and temperature of oxidation increase, and the structure buildings of modern charred paddies are more similar to ancient ones. Given the planting manner of paddies during Majiabang culture period, these ancient charred paddies might be a result of the original farming mode involving fire. Supported by the National Natural Science Foundation of China (Grant No. 40571088)     

北京大海坨4.9级地震前白家疃井地热地形变前兆异常

北京大海坨ＭＬ＝４．９地震前，白家疃地热，地形变两种观测项目，同时观测记录到明显的异常变化，具有短期和短促，突发的临震异常特点，采取针对性的分析方法，结果较好，为单台项（前兆方法）综合预报提供了震兆观测实例。     

Research on the regionalQ values of coda waves for the aftershocks in Luquan,Yunnan of 1985

Based on the scattering coda model by which local and regional earthquakes are interpreted (K. Aki, 1969), and using observational coda data of 68 aftershocks of the 1985 Luquan, Yunnan earthquake registered by the VGK seismographs installed at 12 stations in the Yunnan regional short-period network, theQ-values of coda waves are calculated respectively for 6 time intervals. It is observed that within the frequency range of 0.40–1.65 Hz of the observed data, theQ-values are closely related with the frequencies and the calculated codaQ ranges between 80–240 with the coefficient of frequency dependence η=0.45. The calculated source factorsB(f> _p) of the coda waves which indicate the scattering strength are mostly within the order 10^?23–10^?24. Areas with lowQ-values present high scattering. It should be noted that by comparing data obtained before and after the Luquan earthquake, clear changes can be detected in theQ-values measured at stations close to the epicentral region, and that theQ-values of the aftershock coda are less than about one half of the pre-shock values. It may be mentioned that the time-dependent regional variations of theQ-values might possibly bring about practical significance in earthquake prediction. Moreover, aftershock focal parameters are determined. Through discussions on the quantitative relations between the focal parameters, we get: 1gE=1.59M _L+ 11.335;E=(2.10 × 10^?5)M ₀; length of focal rupturea=0.40?0.80 km for 3.0≤M _L<5.0 events; stress drop Δσ=(6.0–130) ×10⁵ Pa. Through interpretation of the data, we have also learned the important characteristics that there is no linear relation between the stress drops and the earthquake magnitudes.     

Separation of magnetic anomalies into induced and remanent magnetization contributions

Inversion of magnetic data is complicated by the presence of remanent magnetization, and it provides limited information about the magnetic source because of the insufficiency of data and constraint information. We propose a Fourier domain transformation allowing the separation of magnetic anomalies into the components caused by induced and remanent magnetizations. The approach is based on the hypothesis that each isolated source is homogeneous with a uniform and specific Koenigsberger ratio. The distributions of susceptibility and remanent magnetization are subsequently recovered from the separated anomalies. Anomaly components, susceptibility distribution and distribution of the remanent and total magnetization vectors (direction and intensity) can be achieved through the processing of the anomaly components. The proposed method therefore provides a procedure to test the hypotheses about target source and magnetic field, by verifying these models based on available information or a priori information from geology. We test our methods using synthetic and real data acquired over the Zhangfushan iron-ore deposit and the Yeshan polymetallic deposit in eastern China. All the tests yield favourable results and the obtained models are helpful for the geological interpretation.     

Simulation of urban expansion based on cellular automata and maximum entropy model

Urban expansion is a hot topic in land use/land cover change(LUCC) researches. In this paper, maximum entropy model and cellular automata(CA) model are coupled into a new CA model(Maxent-CA) for urban expansion. This model can help to obtain transition rules from single-period dataset. Moreover, it can be constructed and calibrated easily with several steps.Firstly, Maxent-CA model was built by using remote sensing data of China in 2000(basic data) and spatial variables(such as population density and Euclidean distance to cities). Secondly, the proposed model was calibrated by analyzing training samples,neighborhood structure and spatial scale. Finally, this model was verified by comparing logistic regression CA model and their simulation results. Experiments showed that suitable sampling ratio(sampling ratio equals the proportion of urban land in the whole region) and von Neumann neighborhood structure will help to yield better results. Spatial structure of simulation results becomes simple as spatial resolution decreases. Besides, simulation accuracy is significantly affected by spatial resolution.Compared to simulation results of logistic regression CA model, Maxent-CA model can avoid clusters phenomenon and obtain better results matching actual situation. It is found that the proposed model performs well in simulating urban expansion of China. It will be helpful for simulating even larger study area in the background of global environment changes.     

基于系统动力学的巢湖流域水资源承载力动态预测与调控

湖泊流域水资源承载能力动态预测与调控是维护湖泊生态安全、保障社会经济健康持续发展的重要基础和手段.本文以巢湖流域为研究对象,提出基于系统动力学的湖泊流域水资源承载力动态预测技术和试验优化调控方法.首先以县(市)为基本单元构建水资源承载力系统动力学模拟与动态预测模型;再从空间上将各县(市)耦合为流域系统整体模型,并通过敏感性分析筛选量质要素调控指标;最后采用正交试验设计确定流域水资源承载力优化调控方案.结果表明:由于流域内产业规模的扩大以及城镇化率的提升,20172050年巢湖流域水资源承载状态值整体呈恶化趋势,并于2030年以后将长期处于超载状态,通过对影响要素针对性优化调控后,20172050年流域水资源承载状态均达到临界或可载.研究表明本文提出的方法对于促进区域社会经济环境协调发展和改善流域水资源承载力具有较好的实际应用价值.     

唐山地震序列特征及类型的讨论

本文根据截止到1978年底的地震资料,分析了唐山地震序列的基本特征。认为唐山地震序列具有强震多、能量衰减慢,起伏大,空间展布规模大等总体特征及各区地震活动差异明显的分区特征。由此出发,对唐山地震序列的类型作了一些讨论。作者强调唐山地震序列中三次最强地震(唐山7.8级、滦县7.1级、宁河6.9级)震级相近似而发震构造各异,以及以它们为首的三个次级地震序列的存在,认为把唐山地震序列称为多主震型地震序列比较合适。     

策克台井下宽频带地震计GL?S120B正弦波标定衰减因子的讨论

为解决EDAS?24GN6数据采集器对策克台井下宽频带地震计GL?S120B进行正弦标定的过程中产生的响应波形限幅问题,分析了数据采集器?地震计这一系统的标定过程及原理,结合GL?S120B的幅频响应特征,推导出正弦标定频点参数中的频率f、衰减因子λ与标定响应波形限幅之间的关系。分析表明,在GL?S120B平坦响应频带内,为避免出现标定波形响应限幅,频率f与衰减因子λ的乘积应至少大于限幅下限50.93;而在其衰减响应频带内,由于地震计电压灵敏度的衰减,频率f与衰减因子λ的乘积最小取值也相应减小。据此,对衰减因子λ进行校正,并再次对GL?S120B进行正弦标定。标定及计算结果显示:标定波形未限幅,GL?S120B三分向幅频响应特征较为一致;灵敏度对出厂值的变化率保持在5%范围内。本研究结论可为采用EDAS?24GN6和GL?S120B地震观测系统的台站进行正弦波标定提供频点参数,并为其他台站解决正弦标定波形限幅问题提供分析依据。     

A Stochastic Inversion Method for Potential Field Data: Ant Colony Optimization

Simulating natural ants’ foraging behavior, the ant colony optimization (ACO) algorithm performs excellently in combinational optimization problems, for example the traveling salesman problem and the quadratic assignment problem. However, the ACO is seldom used to inverted for gravitational and magnetic data. On the basis of the continuous and multi-dimensional objective function for potential field data optimization inversion, we present the node partition strategy ACO (NP-ACO) algorithm for inversion of model variables of fixed shape and recovery of physical property distributions of complicated shape models. We divide the continuous variables into discrete nodes and ants directionally tour the nodes by use of transition probabilities. We update the pheromone trails by use of Gaussian mapping between the objective function value and the quantity of pheromone. It can analyze the search results in real time and promote the rate of convergence and precision of inversion. Traditional mapping, including the ant-cycle system, weaken the differences between ant individuals and lead to premature convergence. We tested our method by use of synthetic data and real data from scenarios involving gravity and magnetic anomalies. The inverted model variables and recovered physical property distributions were in good agreement with the true values. The ACO algorithm for binary representation imaging and full imaging can recover sharper physical property distributions than traditional linear inversion methods. The ACO has good optimization capability and some excellent characteristics, for example robustness, parallel implementation, and portability, compared with other stochastic metaheuristics.     

A three-scale cracking criterion for drying soils

Cracking is a most unwanted development in soil structures undergoing periodic drying and wetting. Desiccation cracks arise in an apparent absence of external forces. Hence, either an internal, self-equilibrated stress pattern resulting from kinematic incompatibilities, or a stress resulting from reaction forces at the constraints appear as a cracking cause, when reaching tensile strength. At a meso-scale, tubular drying pores are considered in the vicinity of a random imperfection, inducing a stress concentration in the presence of significant pore suction. This approach allows one to use the effective stress analysis, which otherwise, away from the stress concentration, usually yields compressive effective stress and hence a physically incompatible criterion for a tensile crack. Recent experiments on idealized configurations of clusters of grains provide geometrical data suggesting that an imperfection as a result of air entry deep into the granular medium penetrates over 4 to 8 internal radii of a typical pore could yield a tensile effective stress sufficient for crack propagation.