中国区域城市体系演化实证研究

针对我国区域城市体系发展现状,对该体系的演化过程进行了实证分析,考察了我国城市体系的区域分布特征、区域城市体系的分布密度以及规模结构.研究结论显示,东部省份城市的数量和空间分布密度要明显高于中西部地区,说明东部地区城市体系的发育程度处于领先地位;同时,分析结果也表明,各地区城市体系的规模结构演化趋势较为一致,都经历了一个先分散、后集中的过程.     

国外城市蔓延研究进展

在对国外关于"城市蔓延"概念的界定进行综述的基础上,对"城市蔓延"的成本效益、肌理、定量化方法及其对环境的影响进行分析,最后得出对我国城市化的有益启示。     

Urban density and pupil attainment

We explore the association between urban density and pupil attainment using three cohorts of pupils in schooling in England. Although—as widely recognised—attainment in dense urban places is low on average, this is not because urban environments disadvantage pupils, but because the most disadvantaged pupils with low average attainments attend the most urbanised schools. To control for this, we exploit changes in urban density faced by pupils during compulsory transition from Primary to Secondary school, and measure educational progress at the end of the Secondary phase, relative to attainment at the end of Primary schooling. Our results suggest that there are small but significant benefits from education in schools in more densely urbanised settings. We detect this density advantage even amongst pupils moving relatively short distances between Primary and Secondary schools within urban areas, so we cannot attribute it to broad urbanisation effects experienced by pupils making rural–urban school moves. A more likely explanation lies in greater school choice and competition between closely co-located educational providers.     

Optimal portfolio allocation under the probabilistic VaR constraint and incentives for financial innovation

We characterize the investor’s optimal portfolio allocation subject to a budget constraint and a probabilistic VaR constraint in complete markets environments with a finite number of states. The set of feasible portfolios might no longer be connected or convex, while the number of local optima increases exponentially with the number of states, implying computational complexity. The optimal constrained portfolio allocation may therefore not be monotonic in the state–price density. We propose a type of financial innovation, which splits states of nature, that is shown to weakly enhance welfare, restore monotonicity of the optimal portfolio allocation in the state-price density, and reduce computational complexity. We are grateful to Ken Kavajecz and seminar participants at Harvard Business School, London School of Economics, Maastrict University, ZEI Bonn, and Danske Bank Symposium on Asset allocation and Value-at-Risk: Where Theory Meets Practice for comments on an earlier version of this paper. We also benefitted from the suggestions of two anonymous referees. Our papers can be downloaded from www.RiskResearch.org.     

低温低密度水泥复合减轻材料研究

深水固井一直存在低环境温度、低破裂压力梯度、潜在浅层流、材料成本较高等技术难题。针对这些问题开发出了一种适用于低温（10 ℃）深水固井的低密度水泥复合减轻材料体系KBS1053,该水泥体系的密度为1.55 g/cm3,具有低温下凝结速度较快、低温强度发展较好、浆体流动性较好等特点,其早期抗压强度高于同等密度空心玻璃微珠低密度水泥体系,且原材料来源广泛,具有良好的工程性能和经济效益。     

工程物探技术在地下库可研阶段勘察中的应用

根据某大型地下水封石油油库可研阶段勘察实施过程,介绍大型地下水封石油油库可研阶段工程勘察的要求和方法、工程物探种类、高密度电法和地震反射法的原理、方法、实施过程中的应用情况、勘察成果整理分析。阐述了物探与钻探、地质测绘相互验证对建库条件的评价。     

大秦线增加资本投入提高运输密度的分析

资本投入对产出数量起决定性作用。通过对大秦线的资本投入对运量增加的影响情况进行分析,说明加强影响列车质量和密度相关设施的资本投入,对提高产出起到重要作用。同时指出对投向大秦线的资本,应向发展重载技术方面倾斜,能对大秦线运输能力的提高起持续性影响作用。     

Analysing Tax–Benefit Reforms Using Non‐Parametric Methods*

Static tax–benefit microsimulation models (MSMs) are widely used and well‐regarded tools for public policy analysis, but it is essential to use them very carefully. This paper focuses on the analysis of MSM output, suggesting the use of non‐parametric methods as a useful, informative and relatively straightforward complement to detect effects not always captured by measures often used to present MSM results. Non‐parametric methods are used here to analyse the output of an MSM applied to the 1998 Italian personal income tax reform, the main change in which concerned the tax schedule: the first tax rate was increased from 10 per cent to 18.5 per cent and the top one was reduced by 4.5 percentage points. Non‐parametric methods highlight that the effects of this reform were very different for different types of households, with low‐income pensioner households among the main losers. Results are checked for robustness by standard statistical methods and compared with empirical results obtainable using quintile histograms.     

The shape of small sample biases in pricing kernel estimations

Numerous empirical studies find pricing kernels that are not-monotonically decreasing; the findings are at odds with the pricing kernel being marginal utility of a risk-averse, so-called representative agent. We study in detail the common procedure which estimates the pricing kernel as the ratio of two separate density estimations. In the first step, we analyse theoretically the functional dependence for the ratio of a density to its estimated density; this cautions the reader regarding potential computational issues coupled with statistical techniques. In the second step, we study this quantitatively; we show that small sample biases shape the estimated pricing kernel, and that estimated pricing kernels typically violate the commonly believed monotonicity at the centre even when the true pricing kernel fulfils these. This contributes to an alternative, statistical explanation for the puzzling shape in pricing kernel estimations.     

Recovering the real-world density and liquidity premia from option data

In this paper, we develop a methodology for simultaneous recovery of the real-world probability density and liquidity premia from observed S&P 500 index option prices. Assuming the existence of a numéraire portfolio for the US equity market, fair prices of derivatives under the benchmark approach can be obtained directly under the real-world measure. Under this modelling framework, there exists a direct link between observed call option prices on the index and the real-world density for the underlying index. We use a novel method for the estimation of option-implied volatility surfaces of high quality, which enables the subsequent analysis. We show that the real-world density that we recover is consistent with the observed realized dynamics of the underlying index. This admits the identification of liquidity premia embedded in option price data. We identify and estimate two separate liquidity premia embedded in S&P 500 index options that are consistent with previous findings in the literature.