Evaluating the effects of topographical factors on the precipitation simulated by kilometer-scale versus quarter-degree dynamical downscaling models in eastern China

与传统的1/4度(≈25-30 km)动力降尺度模拟相比,公里尺度模拟的降水空间分布与观测结果更为接近.为了研究这一差异原因,本研究以华东地区为例,探究了地形因子在观测和模拟的降水中的作用.为了更好地体现地形因子对降水分布非均匀性的影响,以及不同地形因子作用的尺度差异,本研究采用多尺度地理加权回归模型,对五个主要地形因子与公里尺度和1/4度分辨率模拟的降水的关系进行了评估.基于观测数据的研究结果显示地形起伏度,地形高程和离海岸线距离对华东地区降水分布的非均匀性都有重要影响,其中地形起伏度在研究区大部分站点降水分布中起主导作用;公里尺度模拟结果基本反映了地形起伏度的主导作用;而1/4度模拟结果表现出降水对地形高程的过度依赖.本研究揭示了公里尺度地形分布对中国东部降水的非均匀分布的关键作用,研究结果可以为改进降水模拟提供新的思路.

Hazard degree identification of goafs based on scale effect of structure by RS-TOPSIS method

In order to precisely predict the hazard degree of goaf(HDG), the RS-TOPSIS model was built based on the results of expert investigation. To evaluate the HDG in the underground mine, five structure size factors, i.e. goaf span, exposed area, goaf height, goaf depth, and pillar width, were selected as the evaluation indexes. And based on rough dependability in rough set(RS)theory, the weights of evaluation indexes were identified by calculating rough dependability between evaluation indexes and evaluation results. Fourty goafs in some mines of western China, whose indexes parameters were measured by cavity monitoring system(CMS), were taken as evaluation objects. In addition, the characteristic parameters of five grades' typical goafs were built according to the interval limits value of single index evaluation. Then, using the technique for order preference by similarity to ideal solution(TOPSIS), five-category classification of HDG was realized based on closeness degree, and the HDG was also identified.Results show that the five-category identification of mine goafs could be realized by RS-TOPSIS method, based on the structure-scale-effect. The classification results are consistent with those of numerical simulation based on stress and displacement,while the coincidence rate is up to 92.5%. Furthermore, the results are more conservative to safety evaluation than numerical simulation, thus demonstrating that the proposed method is more easier, reasonable and more definite for HDG identification.

Formula for calculating spatial similarity degrees between point clouds on multi-scale maps taking map scale change as the only independent variable

The degree of spatial similarity plays an important role in map generalization, yet there has been no quantitative research into it. To fill this gap, this study first defines map scale change and spatial similarity degree/relation in multi-scale map spaces and then proposes a model for calculating the degree of spatial similarity between a point cloud at one scale and its gener- alized counterpart at another scale. After validation, the new model features 16 points with map scale change as the x coordinate and the degree of spatial similarity as the y coordinate. Finally, using an application for curve fitting, the model achieves an empirical formula that can calculate the degree of spatial similarity using map scale change as the sole independent variable, and vice versa. This formula can be used to automate algorithms for point feature generalization and to determine when to terminate them during the generalization.

Evolvement of the System Complexity Degree under Different Time Scalings:an Illustration of the Traffic Flow System

It is investigable how the system scaling affects the system complexity degree. The traffic flow system is taken in this paper as an illustration to study this question. First, the Lempel-Ziv algorithm is introduced for accurate depiction of the complexity degree of the traffic flow system. We gain 3 actual sequences and 20s period traffic flow sequences on the basis of the measure of the traffic flow data; we gain 5 traffic flow sequences whose periods are between 1-5min by simulating the traffic flow system. By calculating the complicacy of the 11 sequences, we obtain two hypothesis: the complicacies of the same system are different under different time scalings; negative correlation exists between the complicacy and the time scaling of the system.

Degree distribution and robustness of cooperative communication network with scale-free model

With the requirements of users enhanced for wireless communication, the cooperative communication will become a development trend in future. In this paper, a model based on complex networks with both preferential attachment is researched to solve an actual network CCN （Cooperative Communication Network）. Firstly, the evolution of CCN is given by four steps with different probabilities. At the same time, the rate equations of nodes degree are presented to analyze the evolution of CCN. Secondly, the degree distribution is analyzed by calculating the rate equation and numerical simulation. Finally, the robustness of CCN is studied by numerical simulation with random attack and intentional attack to analyze the effects of degree distribution and average path length. The results of this paper are more significant for building CCN to programme the resource of communication.

Degree and connectivity of the Internet's scale-free topology

This paper theoretically and empirically studies the degree and connectivity of the Internet＇s scale-free topology at an autonomous system （AS） level. The basic features of scale-free networks influence the normalization constant of degree distribution p（k）. It develops a new mathematic model for describing the power-law relationships of Internet topology. From this model we theoretically obtain formulas to calculate the average degree, the ratios of the kmin-degree （minimum degree） nodes and the kmax-degree （maximum degree） nodes, and the fraction of the degrees （or links） in the hands of the richer （top best-connected） nodes. It finds that the average degree is larger for a smaller power-law exponent A and a larger minimum or maximum degree. The ratio of the kmin-degree nodes is larger for larger λ and smaller kmin or kmax. The ratio of the kmax-degree ones is larger for smaller λ and kmax or larger kmin. The richer nodes hold most of the total degrees of Internet AS-level topology. In addition, it is revealed that the increased rate of the average degree or the ratio of the kmin-degree nodes has power-law decay with the increase of kmin. The ratio of the kmax-degree nodes has a power-law decay with the increase of kmax, and the fraction of the degrees in the hands of the richer 27% nodes is about 73% （the 73/27 rule＇）. Finally, empirically calculations are made, based on the empirical data extracted from the Border Gateway Protocol, of the average degree, ratio and fraction using this method and other methods, and find that this method is rigorous and effective for Internet AS-level topology.

ON THE HOMOCLINIC ORBITS IN A CLASS OF TWO-DEGREE-OF-FREEDOM SYSTEMS UNDER THE RESONANCE CONDITIONS

A class of two-degree-of-freedom systems in resonance with an external, parametric excitation is investigated, the existence of the periodic solutions locked to Omega is proved by the use of the method of multiple scales. This systems can be transformed into the systems of Wiggins under some conditions. A calculating formula which determines the existence of homoclinic orbits of the systems is given.

An Analytical Approach for Degree Correlations in Complex Network

We investigate correlations between neighbor degrees in the scale-free network. According to the empirical studies, it is known that the degree correlations exhibit nontrivial statistical behaviors. With using an analytical approach, we show that the scale-freeness and one of statistical laws for degree correlations can be reproduced consistently in a unified framework. Our result would have its importance in understanding the mechanisms which generate the complex network.

Earthquake Barcode from a Single-Degree-of-Freedom System

Earthquake is a violent and irregular ground motion that can severely damage structures. In this paper we subject a single-degree-of-freedom system, consisting of spring and damper, to an earthquake excitation, and meanwhile investigate the response behavior from a novel theory about the dynamical system, by viewing the time-varying signum function of It can reflect the characteristic property of each earthquake through and the second component of f, where is a time-sampling record of the acceleration of a ground motion. The barcode is formed by plotting with respect to time. We analyze the complex jumping behavior in a barcode and an essential property of a high percentage occupation of the first set of dis-connectivity in the barcode from four strong earthquake records: 1940 El Centro earthquake, 1989 Loma earthquake, and two records of 1999 Chi-Chi earthquake. Through the comparisons of four earthquakes, we can observe that strong earthquake leads to large percentage of the first set of dis-connectivity.

Evaluation of Land-Use Efficiency Based on Regional Scale——A Case Study in Zhanjiang,Guangdong Province

Evaluating land use efficiency is critical to the revision of general land use planning. An assessment indicator system for regional land use efficiency was established in this paper from the aspects of society,economy,ecology and environment. The weight of each indicator was defined by an analytical hierarchy process (AHP) and the entropy method (EM). Then,a case study in Zhanjiang was carried out to analyze the regional land use efficiency from 1996 to 2004 and its development by using the method of multifactor composite evaluation and an analytical model of the de-gree of coordination. The results indicate that land use efficiency with respect to society and the economy improved,whereas the ecological and environmental efficiencies were found to decrease. The degree of coordination in Zhanjiang is still at the status of basic coordination. Finally,measures for enhancing the ecological and environmental establish-ment are suggested in order to improve the regulations of land use structure and patterns,establish ecological forests for the public good and green corridors and prevent the soil erosion.

Periodic Solutions to a Delayed Semi-ratio Dependent Diffusion System on Time Scales

In this paper,we investigate the existence of periodic solutions of a semi-ratiodependent predator-prey diffusion system with functional responses and time delays in a two-patch environment on time scales by using a continuation theorem based on coincidence degree theory.

A novel evolving scale-free model with tunable attractiveness

In this paper, a new evolving model with tunable attractiveness is presented. Based on the Barabasi-Albert （BA） model, we introduce the attractiveness of node which can change with node degree. Using the mean-field theory, we obtain the analytical expression of power-law degree distribution with the exponent γ∈ （3, ∞）. The new model is more homogeneous and has a lower clustering coefficient and bigger average path length than the BA model.

EXISTENCE OF PERIODIC SOLUTIONS TO A SYSTEM WITH FUNCTIONAL RESPONSE ON TIME SCALES

This paper investigates the existence of periodic solutions of a three-species food-chain diffusive system with Beddington-DeAngelis functional responses and time delays in a two-patch environment on time scales. By using a continuation theorem based on coincidence degree theory, we obtain sufficient criteria for the existence of periodic solutions for the system. Moreover, when the time scale T is chosen as R or Z, the existence of the periodic solutions of the corresponding continuous and discrete models follows. Therefore, the method is unified to provide the existence of the desired solutions for continuous differential equations and discrete difference equations.

A Multilevel Design Method of Large-scale Machine System Oriented Network Environment

The design of large-scale machine system is a very complex problem.These design problems usually have a lot of design variables and constraints so that they are difficult to be solved rapidly and efficiently by using conventional methods.In this paper,a new multilevel design method oriented network environment is proposed,which maps the design problem of large-scale machine system into a hypergraph with degree of linking strength (DLS) between vertices.By decomposition of hypergraph,this method can divide the complex design problem into some small and simple subproblems that can be solved concurrently in a network.

加入合作社对家庭农场适度规模经营的影响

本文在探讨家庭农场适度规模经营两种理论观点之争的基础上,基于中国社会科学院农村发展研究所2020年中国乡村振兴综合调查(CRRS)数据,采用普通最小二乘法(OLS)系统考察了家庭农场加入合作社的规模扩大效应及其作用机制。研究发现:首先,加入合作社能够扩大家庭农场经营规模,推动家庭农场适度规模经营。经测算,当前中国家庭农场最优经营规模为188亩,因而家庭农场经营规模仍有扩大的空间。其次,家庭农场加入合作社的规模扩大效应存在异质性,收入水平高、社会资本水平低和自有机械化水平低的家庭农场加入合作社的规模扩大效应更明显。再次,加入合作社扩大家庭农场经营规模主要来自内部服务获取机制和外部资源获取机制,且合作社所提供的销售服务和金融支持对家庭农场经营规模扩大具有更强的促进效应。最后,耕地细碎化程度负向调节家庭农场加入合作社的规模扩大效应,耕地细碎化不利于加入合作社的家庭农场扩大经营规模。本文的研究为推动家庭农场适度规模经营,促进其与合作社融合发展提供了理论指导和决策依据。

基于自然地下水矿化度分布的北方沿海区水稻适宜规模研究

基于自然地下水矿化度分布规律,探究北方沿海区水稻合理种植规模具有重要的节水压盐意义。本研究以唐山市为例,基于地下水矿化度监测及Landsat遥感影像等数据,分析了水稻种植规模时空分布,结合水稻生长的矿化度阈值,利用叠加分析法提出适宜种植规模和调整措施。结果表明:受水资源短缺影响,1991年以来唐山沿海区的水稻种植面积逐年减少,现状水稻种植面积基本稳定在6.28万hm^(2)。地下水矿化度大于3、1~3 g/L和小于1 g/L的区域分别为水稻保留区、探索退减区和优先调减区,面积分别为4.80、1.69和1.05万hm^(2)。结合国家粮食安全要求,唐山市沿海区适宜水稻种植面积为5.00~5.33万hm^(2)。研究成果为北方沿海区水田的开发利用和粮食节水增产策略提供了新思路。

技术进步能有效促进粮食安全与农民增收双目标实现吗?——来自全国省级面板数据的经验证据

技术进步能显著提高粮食安全与农民增收双目标实现的有效性。论文基于2002—2022年全国31省的面板数据,通过耦合协调度模型、DEA-Malmquist指数模型及面板数据双向固定效应模型等进行实证分析。研究表明:技术进步能明显提高粮食安全与农民收入一致性水平,其中,技术变化对粮食安全与农民收入一致性水平的影响更为显著,该结论在经过一系列稳健性检验后依旧成立。在经济发展水平相对落后的西部地区以及地形更为崎岖的丘陵地区,技术进步对粮食安全与农民收入一致性水平的促进作用更强。此外,技术进步可以通过促进农业适度经营规模水平提升进而间接作用于粮食安全与农民增收双目标的实现。以此为基础,论文提出了相应的政策建议,以充分发挥技术进步对粮食安全与农民增收双目标实现的促进作用。

社区尺度斜入射波场下场地-建筑群耦合作用模拟方法

场地-城市相互作用(site-city interaction,SCI)效应会显著改变场地地震波场分布及建筑反应,基于SCI效应理论计算研究方法的发展现状,发挥谱元(spectral element,SE)法可快速高效求解三维地震波场传播和多自由度(multi-degree of freedom,MDOF)模型计算量小且可同时模拟大量建筑的优势,同时,结合频率波数域(frequency wave number analysis,FK)方法,以等效地震荷载的方式施加地震波场,建立了FK-SE-MDOF耦合方法,实现了SE-MDOF耦合模型中多种波型(P波、SV波和SH波)的斜入射输入,解决了当前三维SCI效应研究方法中未能同时考虑建筑非线性、频谱特性、地震波波型及入射角度影响的问题。首先对方法原理进行了介绍;然后,通过与振动台试验的对比,验证了方法的正确性;进而,采用该方法建立理想场地-城市建筑群相互作用耦合模型,主要探讨了入射角度和地震波波型对SCI效应的影响,得到了一些有益结论。该方法较为真实地反映SCI效应影响的同时,可反映建筑基础轮廓对地震波场的影响,适用于需考虑建筑轮廓信息的社区尺度SCI效应研究,可为城市规划、抗震设计、风险评估以及震后救援等工作提供定量指导。

马来酸酐与烯丙基磺酸钠共聚物的聚合过程及阻垢性能

为了分析马来酸酐(MA)与烯丙基磺酸钠(SAS)聚合过程的影响因素,在配方和工艺基本不变的情况下,设计了两种变量:中和度和引发剂加量。通过改变其中一个变量,合成了一系列MA/SAS共聚物,采用核磁共振波谱仪和凝胶渗透色谱仪对产物进行了表征。结果表明,MA与SAS共聚活性良好,中和度不超过100%时(相对于MA的物质的量分数),少量引发剂加量(2.4 g过硫酸钠)下就有较高的单体转化率,但仍有6%~8%的单体未聚合。剩余单体的种类和数量与中和度以及引发剂加量息息相关。MA在水溶液中部分水解成了马来酸,尽管马来酸数量较少,但其聚合活性相对较差,导致共聚物的分子量呈双峰分布。添加碱可以中和马来酸,当中和度不超过100%时,马来酸主要变为具有较好聚合活性的马来酸单钠盐,间接促进了MA类单体的聚合;当中和度为200%时,马来酸主要变为马来酸二钠盐,其聚合活性相对较差,严重阻碍了聚合;未中和以及中和度为100%时,需7.0~7.2 g引发剂才能将单体全部转化,而在适当的中和度(约20%)下,用少量引发剂(4.0~4.2 g)就可以获得聚合较完全的共聚物,节约了大约40%的引发剂用量。用较佳条件下合成的MA/SAS共聚物对碳酸钙、磷酸钙和硫酸钙的静态阻垢性能进行了研究,共聚物表现出良好的阻磷酸钙垢和阻硫酸钙垢、较好的阻碳酸钙垢性能,对应的最大阻垢率分别为94.38%、100.00%、59.03%。

1961—2021年世界油菜生产时空演变特征及我国油菜优势度分析

【目的】分析世界油菜生产的时空演变格局,为我国油菜产业的可持续发展提供参考。【方法】基于联合国粮农组织(FAO)发布的1961—2021年世界油菜收获面积、单产和总产量等相关数据,运用一元线性回归模型和优势指标体系,分析世界油菜生产上时空变化特征。【结果】世界油菜发展在1980和2000年出现明显的时空演变特征,整个发展过程可分为3个阶段。总体来看,世界油菜生产重心始终集中于亚洲、欧洲和美洲,且收获面积、单产和总产量均呈稳定增长的趋势。其中,阶段Ⅰ(1961—1980年),亚洲总产量高于欧洲15.2%,尽管亚洲的收获面积比欧洲高460.9%,但欧洲的单产比亚洲高250.7%;阶段Ⅱ(1981—2000年)和阶段Ⅲ(2001—2021年),亚洲总产量仍高于欧洲,且在阶段Ⅱ收获面积增长明显。整个过程美洲收获面积中等,大洋洲和非洲的收获面积和总产量占世界的比例较小。同时,在阶段Ⅰ,中国、加拿大和印度等9个国家的油菜总产量占世界的89.7%,收获面积占世界的92.5%;阶段Ⅱ,加拿大和中国的油菜发展最为迅速;阶段Ⅲ,仅加拿大收获面积和总产量增幅大。此外,巴基斯坦和瑞典在阶段Ⅰ和阶段Ⅱ出现油菜发展退步的现象,德国、中国和英国在阶段Ⅲ也出现此现象。贡献度分析表明,与加拿大和印度等主产国相比,我国油菜生产的效率和规模上均不具备优势,但是油菜生产效率优势在每个阶段依次递增。【建议】我国需要充分利用先进的信息技术和自动化设备监测油菜生产过程,扩大油菜的种植比例和收获面积,同时还要注重油菜价值发掘,开发深加工产品,加大集约化、规模化种植,采取合理的种植模式和施肥处理,从而进一步提升我国油菜的竞争力。