控制技术在钢管自动化生产中的应用

钢管自动化控制系统在钢管生产中的有效应用极大地提升了钢管的生产效率和生产质量,减少了人力资源的投入,降低了钢管的生产成本,对于钢铁行业的发展具有至关重要的作用。论文主要针对控制技术在钢管自动化生产中的实际应用进行探究,指出控制技术在钢管自动化生产中应用的效果和作用,希望为钢铁行业的运行提供一定的参考。     

一种基于SIR结构的三通带带通滤波器

应用双指耦合结构和枝节加载谐振器（Stub-loaded Resonator，SLR）实现了一款基于阶梯阻抗谐振器（Stepped Impedance Resonator，SIR）的滤波器。该滤波器具有3个通带，带外抑制较好，工作频段提高。通过调整阻抗比可调节第二、三通带的谐振频率；SLR结构能够增加通带数量；SLR结构和双指耦合结构均能改善滤波器的S参数。HFSS软件仿真表明，3个通带的中心频率分别为3.5 GHz、6.6 GHz、9.2 GHz，对应的分数带宽分别为5.7%、3%、2%，S11分别为-18 dB、-22 dB、-24 dB，通带内的S21分别为-1.8 dB、-1 dB、-1 dB。电路的测量结果与仿真结果较为吻合。该滤波器在5G通信的低频段具有应用前景。     

Are aquaculture growth policies in high-income countries due diligence or illusionary dreams? Foreseeing policy implications on seafood production in Singapore

In the beginning of 2019, the Singaporean government announced its desire to increase domestic food production and, in particular, aquaculture to reach 30% of self-sufficiency by 2030. Similar policies aiming at encouraging aquaculture growth abound in high-income countries in recent years, but have had limited success. Hence, this paper investigates the potential implications of such policies to foresee consequences beforehand and improve the policy’s chances of success. Three scenarios of aquaculture development are built for Singapore until 2040, among which a business-as-usual scenario and two explorative scenarios aiming at increasing aquaculture production, the first emphasizing existing technologies and the second giving priority to novel and innovative ones, like recirculating aquaculture systems. These scenarios are assessed using an adapted version of the supply-demand partial equilibrium model Asiafish to challenge their viability in the socioeconomic context of Singapore. Only the two explorative scenarios are found to allow the Singaporean government to reach its goal in terms of seafood self-sufficiency by 2030, one of which appears to have strong advantages. In this scenario, imports decrease by 28% by 2040, seafood self-sufficiency reaches 69% and 90% of all aquaculture originates from innovative technologies, which would make Singapore an aquaculture tech-hub. It also has higher benefits within Singapore environmental, social and economic constraints such as land and aquafeed scarcity.     

自然保护区生态旅游发展对贫困农户生产经营能力的影响研究

基于云南省轿子山国家级自然保护区的调查数据,从3个维度构建农户生产经营能力指标体系,运用熵值法及多元线性回归模型研究保护区生态旅游发展对贫困农户生产经营能力的影响。结果表明:轿子山国家级自然保护区样本贫困农户生产经营能力总体处于中等水平,且呈现出区域差异性;社区社会保障缺乏和政府帮扶政策措施滞后是造成农户生产经营能力不足的主要原因;在控制“农户家庭基本特征”类别下的4个变量中,保护区开展生态旅游效果的主客观认知是影响贫困农户生产经营能力的一个重要因素,贫困农户参与保护区生态旅游相关工作正向显著影响农户生产经营能力,并对保护区生态旅游扶贫效果起到中介效应。因此,提出政府相关部门应合理规划,构建全域化生态旅游发展体系;增强基层治理水平,提供就业创业培训路径;转变观念,提升自我脱贫可持续能力等建议。     

中国农业竞争力提升视域下的小农户发展

目前我国农业发展面临一个急需破解的重大悖论：如何在发展小农户的基础上提升中国农业竞争力。论文提出中国特色农业竞争力具有三重内涵：以生产竞争力为基本要求，以安全竞争力为战略底线，以市场竞争力为主攻方向。小农户发展对于提升中国农业竞争力有重要作用，这体现于小农户发展有助于提升农业生产竞争力、安全竞争力和市场竞争力并推动提升机制之间联动。因此，提升中国农业竞争力必须促进小农户发展，并且小农户发展有提升农业竞争力的可能性，但当前小农户发展受到内外条件的约束。据此，本文提出以下政策建议：完善政府支持、发挥小农户主体作用、发展和推广农业科技和物质装备以及将小农户融入产业链。     

为了指标而竞争*——来自中国煤矿企业的证据#br#

中国矿难治理取得了不可忽视的成就，但总结其成功经验的研究尚显不足。本文认为安全生产的总量指标控制是一种降低中国煤矿企业矿难死亡人数的有效方式。笔者手工搜集了2002—2006年中国煤矿企业矿难死亡人数和省级安全生产控制考核数据，并与工业企业数据库进行匹配，发现单个煤矿事故死亡人数和同地区其他煤矿事故死亡人数之间显著负相关，说明企业间存在指标竞争现象。广义双重差分回归结果显示，在控制指标越少的省份，企业间指标竞争越激烈。异质性分析发现，在超标省份或者主管官员晋升的关键时期，指标竞争更加激烈。最后，单个煤矿企业死亡人数与异省邻市矿难死亡人数不相关，排除了矿难导致监管加强的“威慑效应”。本文的研究结果表明，煤矿安全生产总量指标控制对企业安全生产有显著作用。     

The restructuring of Italian agriculture and its impact upon capital–labour relations: Labour contracting and exploitation in the fresh fruit and vegetable supply chain of the Lazio Region,Central Italy

Labour contracting is anywhere on the rise globally, even in fully developed capitalist countries. Far from being an anomaly in the smooth everyday functioning of the economy, contractors are a crucial node in facilitating and ensuring global capital's control over local labour regimes. This article uses a global value chain perspective to investigate the re‐emergence of gangmasters and gang labour in the agricultural sector of Lazio, Central Italy. It analyses the fruit and vegetable supply chain formation and configuration in the Lazio Region with the aim of identifying the underlying processes leading to the creation of gangmasters by capital to have a cheap and disposable, especially migrant, labour force. It also intends to give a more nuanced understanding of labour contracting in this context.     

生产分工视角的中国对美国货物出口竞争力验证

考虑生产分工对中美间经贸联系程度、贸易规模和结构的影响,基于生产分工下价值链视角,构建出口竞争力测度指标体系,验证中国对美国货物出口竞争力。结果显示:2016年及之前,中国仅在杂项制品大类上,对美国显示出较强出口竞争力,机械和运输设备、动物和植物油、油脂和蜡我国具有比较优势,化学成品及有关产品、按原料分类的制成品双方竞争性较强,其余大类上,中国对美国出口竞争力不具优势。引入其他国家作对比的分析结果表明:中国对对比国家均无显著出口竞争力,而且对美国出口具有单价优势的资本技术密集型产品,对这些国家出口多缺乏单价优势,而2017年以来对美国和对比国家的贸易变化,进一步勾画出中国对美国货物出口竞争力不足。在生产分工主导全球产业发展背景下,提升我国在全球生产分工中的参与地位,宜强化自主技术研发、提升外资质量和技术外溢、加快"走出去"学习先进技术。     

土地产权稳定能促进农户绿色生产行为吗？——以广东省确权颁证与农户采纳测土配方施肥技术为例证

土地产权趋于稳定将强化农户的剩余控制权和剩余索取权，进而激励农户改进农业生产行为，但这种激励具有情景依赖性：由于农户进行农业生产经营的能力和目的不同，并不是所有的农户都会因此而改进农业生产行为。采用2018年广东省“千村调研”数据，分析确权颁证对农户采纳测土配方施肥技术的影响，结果表明：农地确权颁证虽然赋予农户实现农地价值的剩余权，但能否促进农户采纳测土配方施肥技术还取决于农户自身的获益能力和收益本身的效用。如果农户缺乏实现农业生产超额利润的能力（低收入农户），即使土地产权趋向稳定，也难以产生采纳测土配方施肥技术的动力；如果实现农地价值的最优方式是“他用”而非“自用”，即使采纳测土配方施肥技术会带来农业生产超额利润，农户也不会积极采纳；如果农户具有实现农业超额利润的能力（高收入农户）和预期（以农业为主业的农户），则确权颁证会促进其采纳测土配方施肥技术。农地确权颁证对农户绿色生产行为的促进有着情景依赖性，因而，在农地确权颁证的同时要完善农地流转制度，通过土地产权稳定和流转稳定的双重激励更有效地促进农业生产经营主体积极施行绿色生产行为。     

The nature of trade,global production fragmentation and inflationary dynamics: Cross-country evidence

This study investigates under which circumstances trade has impact on inflation dynamics by examining the independent effects of trade intensity, intra-industry trade and trade on value added. Trade in goods is decomposed into consumption (final) goods and intermediate inputs to deepen the assessment of the role of the globalisation of production activities on inflation dynamics. Open-economy new Keynesian Phillips curve (NKPC) analyses suggest that inflation is sensitive to domestic factors and that the relevance of external factors changes with respect to the nature of trade, country groups and time. Vertical intra-industry trade in intermediate inputs and value-added trade play important role, whereas final goods trade has no statistically significant effect on inflation dynamics.