城市群落学:城市群现象的生态学解读

以现代城市是具有生态智慧的特殊生命体为理论前提,认为应当用生态学的方法和理论对城市群现象进行重新解读。首先,阐述不同历史时期城市之间的作用形式,指出新经济时期城市群的生物群落特性,并对城市群落和城市群落学进行概念界定。进而,解析城市群落的组成和空间结构,将城市群落的成员划分为优势城市和从属城市以及关键城市和冗余城市,将城市群落空间结构划分为“城市生态金字塔”垂直结构和“缀块、廊道、基底”水平结构。最后,阐述城市个体间的竞争、捕食、寄生和共生等生态行为以及城市群落的自然选择、协同进化和演替等生态功能。     

长三角城市群城市宜居水平时空演化及影响因素

在新型城镇化和生态文明建设背景下,城市宜居水平日益成为人们关注的热点问题。以2004—2017年长三角城市群城市宜居要素空间数据库为基础,首先运用熵值法和Moran's I指数探讨了长三角城市群城市宜居水平时空演变特征,其次利用面板数据模型分析其宜居水平演化的影响因素。研究发现:①从宜居水平的时间演变来看,长三角城市群城市宜居水平位序变化明显且中低水平城市提升较快,城市间差距不断缩小。②从宜居水平的空间演变来看,长三角城市群城市宜居水平参差不齐且空间相关性较弱。③各城市宜居水平在单一标准层下的地域分异与综合标准层下的地域分异存在显著差异,单一标准层下各城市均有其优势与不足。④自然地理环境与区位的优劣对宜居城市建设具有直接影响,社会经济方面,人均市政设施维护建设投资额、人均住宅房地产开发投资额、年末居民储蓄存款余额及人口密度与城市宜居水平呈正相关,而工业SO2排放量与城市宜居水平呈负相关。     

Local equilibrium equivalence in probabilistic voting models

Electoral equilibria depend upon candidates' motivations. Maximization of expected vote share may not lead to the same behavior as maximization of the probability of winning the election. Accordingly, it is desirable to understand when electoral equilibria are insensitive to the choice of candidate motivations. This paper examines sufficient conditions for local equilibrium equivalence between expected vote share maximization and maximization of probability of victory in the spatial model of elections with probabilistic voters.     

多元要素流动对城市群高质量发展的影响——以长株潭城市群为例

利用熵值法测度2011—2020年长株潭城市群高质量发展水平，并在梳理多元要素流动影响城市群高质量发展作用机制的基础上，选取全局与局域莫兰指数检验城市群高质量发展水平的空间关联特征，采用3种空间面板模型实证分析R&D人才流、R&D资金流和信息流对高质量发展的影响。研究结果表明：①长株潭城市群高质量发展水平均值为0.433，经济全面发展与社会协调发展水平明显偏低，高质量发展水平在全局范围内存在显著的空间正相关性；②长株潭城市群空间结构呈现出以长沙为核心的单极化发展趋势，长沙的各要素流和综合流强度均明显高于其它城市；③城市群高质量发展与R&D人才流呈显著的线性正相关，与R&D资金流呈显著的U型曲线关系，经济全面发展、社会协调发展与环境友好发展在城市群内均存在显著的空间正相关。     

The indeterminacy of equilibrium city formation under monopolistic competition and increasing returns

We study the indeterminacy of equilibrium in the Fujita–Krugman [When is the economy monocentric?: von Thünen and Chamberlin unified, Reg. Sci. Urban Econ. 25 (1995) 505–528] model of city formation under monopolistic competition and increasing returns. Both the number and the locations of cities are endogenously determined. Assuming smooth transportation costs, we examine equilibria in city-economies where a finite number of cities form endogenously. For any positive integer K, the set of equilibria with K distinct cities has a smooth manifold of dimension K-1 as its interior for almost all parameter values in a regular parameterization. The disjoint union of these sets over all positive integers K constitutes the entire equilibrium set.     

Collateral fluctuations in a monetary economy

This paper studies economy-wide fluctuations that occur endogenously in the presence of monetary and real assets. Using a standard monetary search model, we consider an economy in which agents can increase consumption, over and above what their liquid monetary asset holdings would allow, pledging real assets as collateral for monetary loans. It is shown that, if the liquidation value of real assets is below full market value, a stable cyclical equilibrium can emerge in consumption and capital around the unstable steady state. We also provide conditions for the existence of cycles of higher order, chaos and sunspot equilibria.     

Non-cooperative solutions for estate division problems

In an estate division problem an estate has to be divided among several players whose total entitlement to the estate exceeds its size. This paper extends the non-cooperative approach through a claim game, as initiated by O?Neill (1982), by allowing players to put multiple claims on the same part of the estate, and by considering the case where individual entitlements may exceed the estate. A full characterization of the set of Nash equilibria of the claim game is obtained both for restricted estate division problems, where individual entitlements do not exceed the estate, and for the general case. Variations on the claim game are considered, which result in proportional division in equilibrium.     

Endogenous public policy and multiple equilibria

One of the well known roles of public policy in models with indeterminacy is to reduce the set of equilibria. However, agents' expectations regarding future policy may be self fulfilling when public policy is endogenized. We show that a simple overlapping generations economy with public education may yield multiple equilibria. Under a laissez-faire system, our model has a unique equilibrium. Thus, the presence of public policy may generate, rather than eliminate, multiple equilibria.     

产业互动外部性、生产性服务业集聚与城市创新力--对我国七大城市群的一项实证比较

城市群经济在我国经济版图中扮演越来越重要的角色,正成为创新扩散的主要载体和经济增长的新引擎。生产性服务业作为高技术含量的知识密集型产业,其分布与结构的合理性对城市及城市群形成创新竞争力有重要意义。从产业互动外部性与产业集聚外部性角度切入,将城市群作为产业集聚的空间载体,利用2003-2016年我国七大城市群127个城市的面板数据构建动态空间面板模型,考察生产性服务业相对专业化集聚及相对多样化集聚对城市创新力的影响,进而探讨这种影响在城市群之间的差异性。实证结果显示:(1)生产性服务业相对集聚具有空间溢出效应,即某一城市创新力受当地和相邻地区生产性服务业相对集聚水平的影响。(2)就全国整体而言,对城市创新力有持续性影响的主要是相对多样化集聚而非相对专业化集聚,通过生产性服务业嵌入制造业价值链形成动态比较优势来实现城市创新能力的提升。(3)考虑区域异质性的回归结果表明,生产性服务业相对集聚程度对不同发展阶段不同发展模式的城市群内城市创新产生显著的差异性影响。     

论城市群经济整合内涵、特征及其空间过程

城市群的存在是区域城市化与城市区域化的重要表现,经济全球化与区域经济一体化必然要求重视和加强城市群经济的发展。城市群经济整合是城市群进一步发展的内在要求。处在高速成长阶段的城市群在经济发展上应当考虑整体布局,更加强化横向联系,而事实是城市群内部的核心城市间在发展上往往没有重视横向协作与整合,共同发展。对城市群经济整合内涵、特征以及城市群经济整合过程等基本问题展开系统而深入的分析研究,有利于更好地把握城市群经济整合的实质,并从操作层面上展开行动。     

长三角城市群高技术产业集聚空间溢出效应研究

以长三角城市群为研究对象,利用2010-2018年26个城市面板数据,对城市群内各城市高技术产业集聚水平进行测度,进一步运用空间计量模型,实证探究长三角城市群高技术产业集聚对城市创新的直接效应与空间溢出效应,并考察城市经济发展水平与外商直接投资两个环境变量如何通过长三角城市群高技术产业集聚对城市创新产出产生直接影响,以及在空间溢出过程中如何发挥调节效应。结果发现：各城市创新活动存在明显正向关联;城市高技术产业集聚对本城市创新产出具有显著直接促进作用,而对邻近城市的空间溢出效应显著为负;城市经济发展水平与外商直接投资在长三角城市群高技术产业集聚对城市创新的直接效应与空间溢出效应中均发挥显著调节作用。     

A spatial theory of urban segregation

We provide a competitive equilibrium theory of urban segregation in a linear city. Households demand consumption and housing along the city and are exposed to neighborhood externalities. We show that equilibria that are robust to small coalitional deviations are segregated. Our results explain urban segregation in a standard neoclassical framework and shed new light on the difficulties faced by authorities to integrate cities.     

A characterization of strategic complementarities

I characterize games for which there is an order on strategies such that the game has strategic complementarities. I prove that, with some qualifications, games with a unique equilibrium have complementarities if and only if Cournot best-response dynamics has no cycles; and that all games with multiple equilibria have complementarities. As applications of my results, I show that: (1) generic 2×2 games either have no pure-strategy equilibria, or have complementarities; (2) generic two-player finite ordinal potential games have complementarities.     

Welfare and excess volatility of exchange rates

We study the properties of a GEI model with nominal assets, outside money (injected into the economy as in Magill and Quinzii (J Math Econ 21:301–342, 1992)), and multiple currencies. We analyze the existence of monetary equilibria and the structure of the equilibrium set under two different assumptions on the determination of the exchange rates. If currencies are perfect substitutes, equilibrium allocations are indeterminate and, generically, sunspot equilibria exist. Generically, given a nonsunspot equilibrium, there are Pareto improving (and Pareto worsening) sunspot equilibria associated with an increase in the volatility of the future exchange rates. We interpret this property as showing that, in general, there is no clear-cut effect on welfare of the excess volatility of exchange rates, even when due to purely extrinsic phenomena.     

黄河流域城市群高质量发展评估与空间格局分异

城市群是黄河流域高质量发展的主要载体,黄河流域的高质量发展重点取决于城市群的发展质量及辐射带动作用。通过构建城市群高质量发展评价指标体系,从创新、协调、绿色、开放、共享五个维度对2016年黄河流域7个城市群及内部所有地级城市进行高质量发展评估,研究发现:①黄河流域城市群高质量发展水平空间差异显著,中下游的城市群高质量发展指数高于中上游城市群;②黄河流域城市群高质量发展空间格局中存在"中部塌陷",处于中部地区的中原和晋中城市群多个维度上低于东西部城市群;③城市群内部城市的高质量发展水平呈现明显的"中心-外围"格局,核心城市高质量发展水平显著高于外围城市;④行政等级高和区位条件好的城市往往拥有较高的高质量发展水平,受所处黄河位置的影响并不显著。研究认为,黄河流域城市群应该加强核心城市对城市群整体的辐射带动作用,通过城市群整体的高质量发展影响带动整个黄河流域的高质量发展。     

EXISTENCE AND UNIQUENESS OF EQUILIBRIUM FOR A SPATIAL MODEL OF SOCIAL INTERACTIONS*

We extend Beckmann's spatial model of social interactions to the case of a two‐dimensional spatial economy with a large class of utility functions, accessing costs, and space‐dependent amenities. We show that spatial equilibria derive from a potential functional. By proving the existence of a minimizer of the functional, we obtain that of spatial equilibrium. Under mild conditions on the primitives of the economy, the functional is shown to satisfy displacement convexity. Moreover, the strict displacement convexity of the functional ensures the uniqueness of equilibrium. Also, the spatial symmetry of equilibrium is derived from that of the primitives of the economy.     

多中心城市的内生形成与政府政策的影响

用主流经济学的工具研究空间经济问题有两个难点,即对规模经济和不同地区不同生产、消费和价格体系难以模型化.本文的贡献之一是通过界定合成实物资本和产量的真实货币价值两个概念,赋予了柯-道生产函数新的内涵,使其可以直接比较厂商和工人在不同地区的收益,而不必考虑价格因素.在此基础上,本文考察了城市空间形态的内生演变及政府政策的影响,发现对中心城市的倾斜性投资政策阻碍了大城市向多中心城市的转变.     

中国城市群科技脆弱性波浪收敛规律的定量模拟与验证

伴随城市群发展,各区域以核心城市为中心,不断联合周边城市共同承担区域科技创新风险,从而实现科技系统稳定可持续发展目标。结合几何推导对城市群科技脆弱性波动规律进行分析,运用VHSD-EM法计算城市群及群内城市科技脆弱性,同时,利用ArcGIS10.2进行空间趋势面分析以及分级后的空间格局演化分析,进而对城市群科技风险联合防控需求进行实证分析,最后运用Matlab进行波浪收敛曲线拟合。结果表明：中国城市群科技脆弱性呈波浪性收敛特征并存在联合防控门槛限制,同时,各城市群科技脆弱性收敛曲线相似性较大、模拟效果较好。     

城市间技术交易网络结构与空间特征

基于2011-2015年我国287个地级及以上城市电子信息产业联合申请专利数据，运用社会网络分析方法和GIS空间分析方法，研究我国地级市核心城市之间、城市群内部以及城市群之间技术交易网络结构和空间特征。结果表明，我国电子信息产业技术交易市场发展不平衡，核心城市之间、城市群区域内部技术交易存在结构性差异，跨区域、跨企业、跨机构交易存在壁垒。