Air pollution, food production and food security: A review from the perspective of food system

Air pollution negatively impacts food security. This paper reviews the current literature on the relationship between air pollution and food security from the perspective of food system. It highlights that agricultural emissions which substantially contribute to air pollution could happen at every stage along the food supply chain. Meanwhile, air pollution can not only affect plant growth and animal health but also shift market equilibrium of both agro-inputs and outputs in the food supply chain and thereby affect food security indirectly. Furthermore, this study evaluates the effects of agricultural policy and energy policy on food security and air pollution, respectively, and provides an overview of potential policy instruments to reduce air pollution while ensuring food security. Finally, we identify the remaining research and policy issues for further studies, mainly focusing on the study of household＇s bounded rational behaviors and the issue of rural aging population.

A COMPARISON OF FORECASTING MODELS OF THE VOLATILITY IN SHENZHEN STOCK MARKET

Based on the weekly closing price of Shenzhen Integrated Index, this article studies the volatility of Shenzhen Stock Market using three different models： Logistic, AR（1） and AR（2）. The time-variable parameters of Logistic regression model is estimated by using both the index smoothing method and the time-variable parameter estimation method. And both the AR（1） model and the AR（2） model of zero-mean series of the weekly dosing price and its zero-mean series of volatility rate are established based on the analysis results of zero-mean series of the weekly closing price, Six common statistical methods for error prediction are used to test the predicting results. These methods are： mean error （ME）, mean absolute error （MAE）, root mean squared error （RMSE）, mean absolute percentage error （MAPE）, Akaike＇s information criterion （AIC）, and Bayesian information criterion （BIC）. The investigation shows that AR（1） model exhibits the best predicting result, whereas AR（2） model exhibits predicting results that is intermediate between AR（1） model and the Logistic regression model.

POSITIVE UPPER DENSITY POINTS AND CHAOS

In this work, we mainly investigate the problem of complexity for a topologically dynamical system （X, f）. We prove that f has a full measure center if there exists a countable base {Ui}i∞=0 of X satisfying that, for any i, there is y in X such that N（y, Ui） is a positive Banach upper density set. Moreover, we consider the chaotic property of （X, f）. We show that such a system is chaotic in the sense of Takens-Ruelle if it is transitive but not minimal.

Research on Realization Mechanism and Path of Beautiful Countryside under Perspective of Ecological Economic Compound System

The practice based on"beautiful countryside"studies the evolution of Chinese rural society from supply-demand resource allocation to welfare type,forms the symbiotic model for the mechanism of"One Belt,One Road", establishes regional macroeconomic fundamentals, conforms to the situation of the marketization of China’s rural society and the"integration"of urban &rural areas. And it reestablishes the welfare form of rural"phenomenological"philosophy and it develops economic, ecological &social macroeconomic model. The research and use on the openness of"rural system"can promote the formation of ecological structure of rural system, can construct the symbiotic model of rural society, can form the social welfare system including "ecological synthesis","industrial complex"and"institutional community", can realize rural social stratification,o rganization optimization & demand support,and can lay the foundation of stability with Chinese characteristics.

A note on the perturbed monomial mapping

In this paper, we present a necessary and suffcient condition that the perturbed monomial mapping is ergodic on a sphere S_(p-1)(1), which is in a combination with Anashin's earlier results about the perturbed monomial ergodic mappings on a sphere S_(p-r)(1), r > 1, completely solve a problem posed by A. Khrennikov about the ergodicity of a perturbed monomial mapping on a sphere.

A Local Property of Hausdorff Centered Measure of Self-Similar Sets

We analyze the local behavior of the Hausdorff centered measure for self- similar sets. If E is a self-similar set satisfying the open set condition, thenC^s（E∩B（x,r））≤（2r）^sfor all x ∈ E and r〉 0, where Cs denotes the s-dimensional Hausdorff centered measure. The above inequality is used to obtain the upper bound of the Hausdorff centered measure. As the applications of above inequality, We obtained the upper bound of the Hausdorff centered measure for some self-similar sets with Hausdorff dimension equal to 1, and prove that the upper bound reach the exact Hausdorff centered measure.

A Note on Upper Convex Density

For a self-similar set E satisfying the open set condition,upper convex density is an important concept for the computation of its Hausdorff measure,and it is well known that the set of relative interior points with upper convex density 1 has a full Hausdorff measure.But whether the upper convex densities of E at all the relative interior points are equal to 1？ In other words,whether there exists a relative interior point of E such that the upper convex density of E at this point is less than 1？ In this paper,the authors construct a self-similar set satisfying the open set condition,which has a relative interior point with upper convex density less than 1.Thereby,the above problem is sufficiently answered.

Special Economic Zones Blaze New Trails

Special economic zones(SEZ) are starting points of incremental reform and opening-up in China. On the 30th anniversay of reform and opening-up,this article attempts to present a systematic review of the evolution,mechanism and performance of special economic zones as well as a pespective on SEZs' furture development.

Institutional Distance and CrossNational Income Gaps

This paper examines the root causes of current cross-national institutional difference from the perspective of national hetereogeneity and provides detailed explanations on the justification and effectiveness of using cross-national genetic distance as the instrumental variable(IV) of institutional difference.We combined 10,585 samples by pairing 146 countries and regions,created a cross-national institutional distance variable composed of 14 indicators from the World Bank and the Heritage Foundation in three aspects including differences of political system,economic system and institutional implementation attributes,and conducted a cross-section IV estimation for the long-term effect of institutional differences on cross-national income gaps using data between 1996 and 2010.Empirical results indicate that institutional difference has a long-term significant positive effect on cross-national income gaps and such an effect has a tendency to increase during sample period.With factors like human capital,geographical factor,language and religion under control,we still arrived at similar conclusions.The empirical results are demonstrated to be robust using different genetic distance measurement indicators and estimation methods.

The Hausdorff Dimension and Hausdorff Measure of Full Parry Measure Subset of Finite Type

All the full Parry measure subsets of a given subshift of finite type determined by an irreducible 0-1 matrix have the same Hausdorrf dimension and Hausdorff measure which coincide with those of the set of finite type.

Artificial Intelligence,Structural Change and Labor Income Share

Artificial intelligence(AI)is a strategic technology that leads a new round of technological revolution and structural transformation.This paper studies the effects of AI on structural change and factor income shares.As a general purpose technology and new infrastructure,AI may substitute either labor or capital and its application has differential prospects across sectors.With a multi-sector general dynamic equilibrium model,we find that AI services or AI-specific technologies will reallocate factors between sectors.The direction of the reallocation depends on sectoral differences in the output elasticity of AI and in the elasticity of substitution between AI and traditional modes of production.The process of structural change will in turn change the labor income share.This paper presents the theoretical conditions for the direction of these changes and the underlying economic mechanism.We derive policy implications about how to promote high-quality development with AI.

Local Officials' Tactical Adjustment of Economic Growth Targets under China's Coordinated Regional Development Policy

This paper intends to examine Chinese local officials' behavior for economic growth after the central government's implementation of economic restructuring policy.Theoretically,this paper has demonstrated that when the central government credibly shifts its priority from overall national growth to regional economic restructuring,it will adopt an economic policy in favor of less developed region and local government officials will tactically adjust growth targets accordingly;when the restructuring policy has reached a wide enough coverage of benefit,officials of developed region will relatively lower growth targets for their respective jurisdictions.Empirically,this paper employs the growth targets laid out in the provincial Government Work Reports between 2001 and 2012 and the growth targets set in the five-year plans for the period between 1996 and 2015,and has discovered that changes of inter-provincial gaps are dominated by growth targets;after the central government has launched the program of regional economic restructuring on a full scale,developed provinces start to lower growth targets set for their respective jurisdictions.This paper's discoveries are robust and provide an explanation to the new tendency of China's economic growth in recent years,i.e.,economic growth of eastern region slows down,interprovincial gaps narrow and the central government has adopted the policy of coordinated regional development in favor of inland regions.

Effects of Infrastructure Investment on Structural Change and Productivity Growth in China

The rapid growth of infrastructure investment is a salient feature of China’s economy since the reform and opening-up in 1978,contributing to not only the aggregate demand but also the structural change and productivity growth on the supply-side.This paper builds a multi-sector general equilibrium model to show how infrastructure investment influences structural change through price,investment and income effects,and influences productivity growth through the intensive and extensive marginal effects.By quantifying the model with China’s economy for the period 1981-2017,the paper finds that the infrastructure investment restrained the rise of services,but boosted productivity growth over the period.The policy implication is that China should ramp up infrastructure investment to increase productivity as it pursues high-quality development,but give priority to new infrastructure and public-interest infrastructure to promote industrial structural upgrade.

A Class of Continuous Separable Nonlinear Multidimensional Knapsack Problems

The nonlinear multidimensional knapsack problem is defined as the minimization of a convex function with multiple linear constraints. The methods developed for nonlinear multidimensional programming problems are often applied to solve the nonlinear multidimensional knapsack problems, but they are inefficient or limited since most of them do not exploit the characteristics of the knapsack problems. In this paper, by establishing structural properties of the continuous separable nonlinear multidimensional knapsack problem, we develop a multi-tier binary solution method for solving the continuous nonlinear multidimensional knapsack problems with general structure. The computational complexity is polynomial in the number of variables. We presented two examples to illustrate the general application of our method and we used statistical results to show the effectiveness of our method.

Optimal Policy and Simple Algorithm for a Deteriorated Multi-Item EOQ Problem

This paper considers a deteriorated multi-item economic order quantity (EOQ) problem, which has been studied in literature, but the algorithms used in the literature are limited. In this paper, we explore the optimal policy of this inventory problem by analyzing the structural properties of the model, and introduce a simple algorithm for generating the optimal solution to this problem. Numerical results are reported to show effi-cacy of the proposed method.

U.S.,not China, is culprit of global deflation, inflation

This paper is an outcome of comprehensive and systematic research on whether China exports deflation and inflation using the newly developed DAG technique. Our results indicate that in the international transmission of inflation, the United States, as the world's largest economy, plays a dominant role. In contrast, during both deflation and inflation periods, China has a minimal impact on the price levels of major trading partners. Thus China is not to be blamed for global deflation or inflation. This research has made use of DAG and some other techniques to yield reliable and reasonable conclusions.

Economic Development and Social Integration of Migrants in China

Migrants often face challenges in social integration.Using a nationally representative sample of migrant workers and employing the epidemiological approach,this paper examines the determinants of social integration.It finds that,conditional on a set of individual features,the migrants from less-developed provinces have greater difficulty in integrating into local communities.These results still demonstrate robustness across alternative variables,samples,and various specifications.Mechanism analysis shows that educational and employment factors account for over 40 percent of the variance in social integration levels,suggesting their significant influence.Additionally,the analysis suggests that native bias against migrants,along with misunderstandings between them,may account for part of the remaining variation in social integration levels.Importantly,the ability to speak local dialects has been identified as a crucial factor that can significantly improve migrants'subjective experience of integrating into a new city.By identifying one specific cause of social integration,this paper provides information to individuals and governments and assists them to improve social integration.

A Structural Measurement of the Valuation Effect of China's External Assets:Method and Application

Existing research on the measurement of the valuation effect mainly follows the residual method proposed by Lane and Milesi-Ferretti(2001).This cannot be used to perform structural decomposition.We propose an aggregation approach rather than the residual method to measure structurally the investment flow and valuation effect of China's external assets.The results indicate that the valuation effect of China's external assets has been highly volatile and it was negative during the pandemic period.The structural decomposition shows that portfolio investment and direct investment made the main contributions to the valuation effect.The impact of exchange rates on the valuation effect has generally been higher than that of asset price in terms of direct investment and total external assets but the opposite has been true for portfolio investment.China's outward investments are currently more inclined to Asian countries and a few European countries but inflows to China still mainly come from developed countries.

Downstream Competition and Upstream Innovation:Theory and Evidence from China

Competition is the catalyst of corporate innovation,which is the foundation of a country's core competitiveness.From the view of vertical industrial chain,this paper examines how downstream competition affects upstream firms'innovation output.Given innovation helps reduce the production cost of each product,increasing demand of intermediate products caused by downstream competition enhances the marginal revenue of upstream firms'innovation,thus leading to an innovation incentive effect.To identify causality,we utilize China's WTO accession,a quasinatural experiment,to calculate downstream competition combined with import tariff reduction and input-output table,and then run a difference-in-difference regression.Using the data of Annual Survey of Industrial Firms and State Intellectual Property Office,our results find that downstream competition has a significantly positive impact on upstream firms'innovation,and this effect is more pronounced in firms with less industry competition,greater initial innovation capacity and weaker financial constraints.Moreover,the number of firms,the degree of industry competition and the scale of intermediate products in the downstream sector increase,confirming the market size channel.In sum,our findings document that downstream competition can motivate upstream firms to innovate through vertical industrial chain,providing some useful insights for China to build a fair market competition environment and promote innovation-driven growth regime.