Multi‐objective crop planning using pareto‐based evolutionary algorithms

The scarcity of water is a growing problem worldwide. The increasing use of water in industrial, urban, and agricultural applications together with the continuous increase in population require the proposal of efficient solutions. In the case of agricultural use, it is necessary to not only maximize the economic benefits, but also to establish optimal water‐saving crop planning, especially for water‐deficient regions. Due to the multi‐objective nature of these problems, the decision‐making process is complex. Fortunately, the increase in computational resources available in recent years has allowed researchers to develop efficient computational algorithms to deal with real and complex optimization problems, including agricultural ones. In particular, multi‐objective evolutionary algorithms (MOEAs) are known for their ability to optimize several objective functions simultaneously to provide a representative set of the Pareto front, which is a set of problem solutions representing a trade‐off between the best values of each of the objectives. This article proposes solving a multi‐objective crop planning problem using two Pareto‐based MOEAs. Results obtained when solving this problem using real data collected from a large number of greenhouses in Spain to show the advantages of using these multi‐objective approaches.     

Jeffcott转子系统分岔点预测

首先简述了一种用于转子轴承系统的稳定性量化分析方法,即首先利用数值积分对高维非线性转子系统进行解耦,将Rn轨线映射为一系列R1映像轨线,然后在R1观察空间中定义轨线的稳定裕度,根据轨线稳定裕度利用灵敏度技术预测动力系统的分岔点。最后,对一个单跨转子模型试验台建立了动力学方程,并利用上述方法通过2个算例预测了系统发生分岔的参数值和分岔特性。预测结果与直接数值积分法在庞加莱截面得到的分岔参数值基本一致,但由于该方法利用了灵敏度技术,所以其分岔点的搜索过程比直接数值积分法中的试探法要快得多。     

Firm size-specific trade effects of regional trade agreements: Estimating extensive and intensive margins of trade

We estimate the impacts of Korean firms’ participation in regional trade agreements (RTAs) on the extensive and intensive export margins by identifying exporting firms based on their firm size—small and medium-sized enterprises (SMEs) and large enterprises (LEs) at the 5 399 HS six-digit commodity level—and specifying characteristics of RTAs from 2004 to 2015. We apply the EK Tobit estimation technique to control zero trade and the OLS estimation with importer-product and time fixed effects to alleviate the endogeneity problem. We find that firm size, product type, and depth of RTA significantly matter. Specifically, we find that deeper RTAs with larger, developing, and closer members significantly enhance the export creation effects of SMEs and LEs. Regarding the firm size-specific effects, we find that SMEs are less sensitive to exploiting RTA participation but more sensitive to the import market size, bilateral and relative trade costs, and the RTA characteristics. LEs’ export creation is mainly driven by the intensive margin, while SMEs’ export creation is driven by extensive and intensive margins (slightly more by the extensive margin). For the product-specific effects, we find that Korea's major exportable products such as chemicals, basic metals, motor vehicles, and transport equipment generate significantly strong export creation effects for both LEs and SMEs through their participation in RTAs.     

银行业竞争加剧还是抑制了企业金融化*

银行业竞争与企业金融化有多种关联机制，既可能加剧企业金融化，也可能抑制企业金融化。本文利用2007—2019年沪深两市A股非金融类上市公司的面板数据，考察了二者之间的关系。结果发现：（1）竞争性的银行业市场结构抑制了企业金融化。（2）银行业竞争不仅缓解了债务成本对企业利润的侵蚀，有助于缩小金融行业与实体企业之间的利润率差距，进而抑制企业利润追逐动机的金融化行为，而且通过引导信贷资源配置促进了企业创新，从而对实体企业金融投资产生挤出效应；此外，银行业竞争还通过促使银行积极发挥信息监督作用，抑制了企业内部人金融投机套利的机会主义行为。（3）银行业竞争对企业金融化的抑制效应在非国有企业、中小企业以及市场化水平较低地区的企业中更为显著。这些结果说明，提高银行业竞争水平有助于抑制企业金融化趋势，扭转经济“脱实向虚”的局面。     

中国出口制造业投入服务化水平测度——基于贸易增加值视角

本文根据2018版OECD-ICIO数据,采用贸易增加值测算法测度了2005-2015年中国出口制造业投入服务化水平,我们发现:在考虑出口二元结构的条件下,2005-2015年中国制造业整体投入服务化水平平均值为26.89%,呈上升趋势;国内投入服务化水平高于国外且呈现出不断"以国内服务替代国外服务"的变动趋势;相比于一般贸易,加工贸易出口制造业投入服务化水平更高但增速较缓,加工贸易国内服务投入比重较低但服务化增速较快;相比于资本和知识密集型制造业,劳动密集型制造业的高端生产性服务尤其是国内高端服务投入比重较低。     

基于二元边际和贸易关系的中国农产品出口动态研究

目的 文章基于动态的视角，测度中国农产品出口的贸易关系和二元边际变化，对农产品出口整体情况以及出口源地维度和出口目的国维度的时空分布进行研究。方法 基于2000—2016年中国海关贸易库数据，测算出口贸易关系、贸易二元边际和区位基尼系数，对农产品出口动态的整体情况及其在出口源地和出口目的国维度的时空分布进行描述，并进行聚类分析。结果 （1）从出口动态整体情况看，农产品出口增长迅速，集约边际占据主导，贸易关系“大进大出”。（2）从时空演化格局看，在出口源地维度，东部省份出口优势明显，空间格局高度集中，近年来集聚程度有所下降。（3）在出口目的国维度，东亚、东南亚、北美是主要的出口目的地和出口扩展地，集聚水平长期下降，原因是出口格局由“一超”变“多强”且中国出口到了更多的国家。（4）当同时考虑两个维度时，中国城市的出口扩展结构高度相似，绝大多数城市的扩展边际的贸易在全球分布相对均匀，东亚和东南亚为主要的出口扩展市场。结论 为了保障农产品出口的稳定增长，既要努力维护贸易关系、实现集约边际增长，也要积极扩展新贸易联系；为了优化农产品出口格局，要推进中西部地区因地制宜挖掘特色农产品、开拓新市场，进一步融入农产品出口进程；为了降低出口风险，要采取出口市场多元化战略，避免城市间农产品出口同质化竞争。     

The effect of the digital economy on services exports competitiveness and ternary margins

In the era of the digital economy, improving the level of information and communications technology (ICT) development is an important measure for achieving the high-quality development of the services exports. This study constructs a comprehensive development index for the digital economy based on the United Nations Conference on Trade and Development Statistics Database (UCTADstat) to calculate the services exports competitiveness of 75 countries (regions) around the world from 2010 to 2019 and conducts ternary margin decomposition. The study empirically verifies that the digital economy promotes the competitiveness of services exports, not only driving intensive growth of quantity margin and price margin but also enhances the expansion growth of category margin. Heterogeneity analysis reveals that the effect of the digital economy on improving low- and middle-income countries' services exports competitiveness and industries with low ICT intensity is more significant than that of high-income countries and high ICT-intensity industries. The impact of the digital economy on the ternary margin of countries’ different income levels and ICT-intensity sample groups exhibits differentiated estimation results. The conclusions of this study provide novel explanations regarding the effects of the digital economy in improving services exports competitiveness and new perspectives and evidence for strategic policymaking.     

Impact of China on trade in electronic products

Using 6-digit product-level data of exports in electronics, this paper finds robust evidence that China's exports adversely affect both the intensive export margin and the extensive export margin of its competitors for the 1992–2018 period. The displacement effects of China's exports on the intensive margin apply especially for the group of intermediate and capital electronic goods and are much more robust and significantly larger in magnitude than the displacement effects found in other studies using aggregated trade data. Finally, we find that China's displacement effect is increasing in China's advantage relative to its competitors in terms of human capital index and internet access of its population.     

“Love for variety,” outside option and extensive margin of demand

The paper models a uniform-price Bertrand-price-competition in a differentiated product oligopoly market, where the buyers' preference shows “love for variety.” The buyers differ from each other in their valuation of the differentiated product with a common outside option available to all. The model endogenously determines both the extensive and intensive margin of demand and the equilibrium number of varieties in the differentiated product market. It shows that in such a framework complementarity exists at the extensive margin of demand even in the presence of demand substitutability between the varieties. The results apply to the competition between brick and mortar shops and malls.