基于深度学习模型的种植结构复杂区农作物精细分类研究

目的 卫星遥感技术具有覆盖范围广、探测周期短、调查成本低等优势而广泛应用于大区域农作物分类。然而在种植结构复杂区（如城乡结合部）,因其地块破碎、同期生长的作物种类多且分布分散,利用传统的统计分类或机器学习方法进行农作物分类时仍存在精度不高的问题。为提高种植结构复杂区农作物分类精度。方法 文章选取河北省廊坊市广阳区为研究区,以GF-1 PMS全色多光谱融合影像为数据源,采用U-Net、PSPNet及DeepLabv3+,3种深度学习模型进行农作物分类研究。分析模型参数对农作物分类精度的影响,评价3种深度学习模型的农作物分类精度,优选农作物精细分类方法。结果 （1）学习率与3种深度学习模型的分类精度呈正相关关系,较大的学习率（0.01,0.001）下,3种模型收敛速度快,分类精度高。批样本量与模型分类稳定性相关,批样本量设为100时,3种模型的分类稳定性最好。（2）相比PSPNet、DeepLabv3+模型,U-Net模型分类效果最好,总体分类精度为89.32%。（3）GF-1 PMS影像结合U-Net模型可有效提升种植结构复杂区农作物分类精度,大宗作物春玉米、夏玉米的分类精度在80%以上,花生、红薯、蔬菜小宗作物分类精度在60%以上。结论 该研究可为准确获取种植结构复杂区的农作物类型、面积及空间分布信息提供参考依据。     

Opinion convergence in location: A spatial version of the Delphi method

This paper proposes a modified version of the Delphi method, starting from the assumption that in many situations the convergence of opinions can be considered in a spatial context. The Spatial Delphi we suggest is based, like the classical Delphi, on the judgments of experts, and it is useful in the consultations for decision and/or forecast purposes, provided that they concern matters of spatial location. The basis for the questionnaire is a map, on which each expert provides, as answer(s), one or more opinion-points, i.e., locations that, according to their opinion, are best for a specific purpose. We propose a method for narrowing the area of convergence along a multi-step procedure so that the final result of the consultation is a small portion of the initial territory with respect to the initial area considered. Besides a simulation study, we report also a prototype application with a panel of twelve experts.     

Disequilibrium models due to a “learning by doing” process

Sommario Si considerino fluttuazioni e crescita in un modello neo-keynesiano in tre diverse ipotesi macroeconomiche, che danno origine a diversi modelli matematici in tempo discreto, o mappe. In particolare si analizza un modello di crescita bidimensionale, rappresentato da un endomorfismo lineare a tratti. Separando il comportamento dinamico delle pendenze di rette che escono dall'origine, dalla dinamica dei punti su tali rette, si mostra che il comportamento dinamico del modello è governato dalla dinamica di un endomorfismo unidimensionale. Ciò semplifica lo studio dei valori di biforcazione che creano rette invarianti, su cui le traiettorie sono divergenti, e consente di determinare il bacino di attrazione di regioni assorbenti che contengono i cammini di crescita, regolari o caotici.

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Fluctuations and growth in a new-keynesian model are considered in three different macroeconomic assumptions, giving rise to different mathematical models in discrete time, or maps. In particular a two-dimensional growth model represented by a piecewise linear endomorphism is analysed. Separating the dynamics of the slopes of straight lines issuing from the origin, from those of the points on these lines, it is shown that the dynamics of the model are governed by the dynamics of a one-dimensional endomorphism. This simplifies the study of the bifurcation values which create invariant lines on which the trajectories are divergent, and enable us to determine the basin of attraction of the absorbing region which includes regular or chaotic growth paths.

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This paper relates to the activities of the M.U.R.S.T. Group Dinamiche Nonlineari ed Applicazioni alle Scienze Economiche e Sociali.     

风险税务筹划决策方法探讨

随着税务筹划理论与实务的研究与发展,风险已经成为人们在税务筹划决策中关注的重要因素之一.对涉及风险的税务筹划,筹划者需要重点解决两大问题:第一,税务筹划风险的度量问题;第二,恰当地选择风险税务筹划决策方法.关于第一个问题,我们曾在《风险税务筹划方案的衡量与选择》(经济与管理研究,2005.9)一文中进行过探讨.本文将集中探讨风险税务筹划决策方法问题,即运用风险型决策方法解决风险税务筹划决策问题.     

Estimating the Marginal Contribution to Systemic Risk by A CoVaR‐model Based on Copula Functions and Extreme Value Theory

In this paper, we quantify the contribution to systemic risk of a single financial institution by utilizing a analytical framework based on the principles of Extreme Value Theory (EVT) for modelling the marginal distributions and on the properties of copula functions for describing the dependence structure between the financial system and the single financial institution. Among the several systemic risk measures proposed nowadays by academics and estimated by public data, we choose to adopt as systemic risk metric the Conditional Value‐at‐Risk (CoVaR). We select a co‐risk measure like the CoVaR because of its macro‐dimension that allows us to integrate the dependence structure of the single financial institution and of the whole financial system in the systemic risk measurement. While the copula functions have been utilized in some pioneer studies on this area, the EVT principles have not yet been implemented in such a context of systemic risk contribution measurement.     

中国省域劳动就业影响因素的空间计量分析

利用2000-2009年中国29个省级单位数据建立空间计量模型对影响劳动就业的各因素及其空间效应进行检验分析。结果显示:省际劳动就业存在显著的空间相关性,邻近省域就业的溢出效应对本省具有正向影响,且该效应从东部到西部地区呈阶梯状依次递减,东部地区就业较中西部地区具有更强的区间联动性。省域技术进步、财政支出、市场化和产业结构优化无论从全国层面还是地区层面均对劳动就业具有显著的促进作用,且财政支出对中西部就业的影响明显大于东部地区;城市化与实际工资对东部就业影响不显著,但能够显著促进中西部地区就业增长。促进区间联动、加快市场化、城市化和产业结构优化步伐、完善和优化财政支出结构是增加就业的重要举措。     

产业技术创新战略联盟的性质、分类与政府支持

产业技术创新战略联盟是合作研发的组织模式之一,承载着产业发展的目标,通过合作研发取得产业共性技术,并在联盟和全行业中扩散,最终实现产业竞争力的提升。产业共性技术的复杂性和准公共品性质、联盟合作创新的困境,决定了政府支持产业技术创新战略联盟的必要性。产业技术创新战略联盟有多种类型,政府应针对不同类型的联盟提供不同的支持。在明确产业技术创新战略联盟的内涵及性质的基础上,按照3个维度对其进行了分类,并借鉴国外经验给出了当前我国政府提供政策支持的建议。     

Profitability and Efficiency of High Nature Value Marginal Farming in England

The UK Brexit vote triggered a new wave of policy developments for a future outside the EU. In this context, we analyse the business performance of English hill and upland farms, characterised by marginal economic conditions but also high nature value (HNV). The analysis aims to help identify farm-level management and policy options for greater economic, environmental and social sustainability. Business performance is measured as technical efficiency and the occurrence and persistence of abnormal profits, estimated through stochastic frontier analysis and static and dynamic panel-data methods. The results help indicate rationales for recent trends including farm enlargement, farm family diversification, and agri-environment scheme entry. The single farm payment is found to be negatively associated with farm technical efficiency while agri-environmental subsidies were positively associated to short-term farm profitability. Farm adaptation and resilience during a period of likely turbulence in external circumstances is discussed in light of these findings, as well as potential parallels with marginal HNV areas across Europe.     

刺芪参胶囊的制备工艺研究

目的:探索刺芪参胶囊的制备工艺。方法:采用正交实验,以总皂苷质量为指标,优化提取工艺;采用单因素实验优化制剂工艺。结果:在最佳提取工艺条件下,刺芪参胶囊提取物中的总皂苷含量为12.19 mg·g-1;以糊精作为填充剂、硬脂酸镁为助流剂、95%乙醇为黏合剂制备胶囊剂。结论:刺芪参胶囊的制备工艺稳定可行。     

Consumer arbitrage in cross‐border e‐commerce

In today’s internet markets consumers can search for, find and compare prices worldwide. Online, information circulates faster than offline and arbitrage opportunities such as the ones arising from currency shocks are easily unveiled. In this paper, we estimate for the first‐time exchange rate elasticities for cross‐border e‐commerce transactions. Exploiting a new high‐frequency database on international transactions of parcels, we find that a 1% appreciation of the domestic currency increases e‐commerce imports by 0.7%. Comparing the result with traditional estimates in offline markets, this implies a 50% exchange rate pass‐through online.