盾构机自动控制技术现状与展望

随着我国社会主义市场经济的迅速发展以及科技水平的不断提升,交通运输行业得到了蓬勃发展。当前,随着我国地下隧道等各项工程建设数量的不断上升,盾构机的重要性不言而喻。加强对盾构机自动控制技术的研究工作,不断解决该技术应用过程中存在的问题,才能有效地促进技术应用,为提升我国地下工程施工安全性能奠定技术支持。     

Network based evidence of the financial impact of Covid-19 pandemic

How much the largest worldwide companies, belonging to different sectors of the economy, are suffering from the pandemic? Are economic relations among them changing? In this paper, we address such issues by analyzing the top 50 S&P companies by means of market and textual data. Our work proposes a network analysis model that combines such two types of information to highlight the connections among companies with the purpose of investigating the relationships before and during the pandemic crisis. In doing so, we leverage a large amount of textual data through the employment of a sentiment score which is coupled with standard market data. Our results show that the COVID-19 pandemic has largely affected the US productive system, however differently sector by sector and with more impact during the second wave compared to the first.     

Potential user factors driving adoption of IPTV. What are customers expecting from IPTV?

Internet Protocol Television (IPTV), the convergence services of television and Internet, is being rapidly developed around the world. The advent of digital technologies has changed the convergence market dramatically with the wide diffusion of the convergent services. Using the Technology Acceptance Model as a conceptual framework and method of logistic regression, this research analyzes the demand for IPTV by drawing data from 452 consumers. Individuals' responses to questions about whether they accept IPTV are collected and combined with observations of their socio-economic status and intrinsic/extrinsic factors modified from the Technology Acceptance Model. Results of logistic regression show two variables (intrinsic and extrinsic factors) that seem to explain what influences consumer behavior towards adopting IPTV. Overall, the logistic regression model explains over 50% of the variance in the IPTV adoption. The variances shed light on the multi-open platform environment that IPTV will forge.     

保险公司偿付能力恶化预测研究

文章在分析公司财务预测研究方法应用前提的基础上,运用MDA模型和Logistic线性回归模型预测方法对我国保险公司偿付能力恶化进行预测研究。结果表明两个主流模型均能在保险公司偿付能力恶化前1~2年较好地进行预测,但是由于两类错估率的不同,MDA模型要优于Logistic模型。     

从广西看大西南出海通道建设

广西在大西南出海通道的建设中占有极其重要的地位，本文采用网络模型，按现状与规划路网两种情况，综合考虑陆上距离和去不同方向市场的海上距离，分析了北海（代表广西港口群）、湛江、广州等三条出海通道的三个港。各自的吸引范围。并由此得出了一些有益的结论。     

Hedonic models and air pollution: Twenty-five years and counting

This paper reports a meta analysis of how effectively hedonic property models have detected the influence of air pollution on housing prices. Probit estimates are reported describing how data, model specification, and local property market conditions in cities represented in thirty-seven studies influence the ability of hedonic models to uncover negative, statistically significant relationships between housing prices and air pollution measures.Partial support for this research was provided by the Russell Sage Foundation. Thanks are due David Cordray, Heidi Hartman, and Larry Hedges of the Foundation's Meta-Analysis Panel for constructive comments, to Ray Palmquist for suggestions and assistance in assembling the results from his studies, to Rick Freeman and Tom Tietenberg and two anonymous referees for comments on the research, and to Barbara Scott for constructive editing of earlier drafts of this paper.     

Economic Valuation of Health for Environmental Policy: Comparing Alternative Approaches. Introduction and Overview

Protecting human health is a primary goal of environmental policy and economic evaluation of health can help policy-makers judge the relative worth of alternative actions. Economists use two distinct approaches in normatively evaluating health. Whereas environmental economists use benefit-cost analysis supported by monetary valuation in terms of willingness-to-pay, health economists evaluate interventions based on cost-effectiveness or cost-utility analysis (CEA), using quality-adjusted life-years (QALY) or similar indexes. This paper provides background on the controversy about the relative merits of these approaches and introduces the remaining papers in the special issue. These papers (with one exception) were presented at a conference sponsored by the Department of Economics at the University of Central Florida with support from the US Environmental Protection Agency. Although CEA might not lead to substantially different implications for environmental policy than benefit-cost analysis, and QALY may provide a benefit transfer tool to fill gaps in the morbidity valuation literature, the papers in this issue raise serious concerns about the suitability of QALY-based CEA for environmental regulatory analysis. QALY does not in general appropriately represent individual preferences for health and CEA is neither independent of income distribution nor adequate to assess efficiency.     

The Austrian current account deficit: Driven by twin deficits or by intertemporal expenditure allocation?

The evidence presented in the paper rejects the twin deficit hypothesis for the Austrian current account balance during the last two decades. The results are based on an estimate of a vector error correction model including quarterly data for the current account balance and potentially relevant variables driving its dynamics. We compute the variance decomposition of the current account's forecast error and its generalized impulse responses to shocks in the innovations of the system. The results in favor of intertemporal expenditure reallocation cannot be reproduced within a second analysis including the current account and a measure of net output, however. The estimated implicit current account balance, interpreted as the discounted expected change in future net output, does not follow the actual behaviour of the current account. First version received: June 1999/Final version received: March 2001     

湖南信息化带动工业化机制研究

人类社会已入入21世纪，对处于工业化中期初级阶段的湖南而言，继续完成工业化无疑是现代化过程中艰巨的历史任务，与此同时，大力国民经济和社会信息化，也是覆盖湖南现代化建设全民的战略措施，为此，正确处理工业化与信息化的关系，以信息化带动工业化，是关系湖南现代化建设的一个极为重要的问题，本文首先分析了湖南信息化和工业化的现状，然后对80年代中期以来的湖南信息化水平和工业化水平进行相关分析，在此基础上对他们相互影响的机制进行分析，最后就湖南今后实际信息化带动工业化提出具体措施。     

Norwegian Emissions of CO2 1987–1994 A Study of Some Effects of the CO2 Tax

Several countries have introduced taxes on fossil fuels with the aim of reducing atmospheric emissions, partly because of local environmental goals (SO₂, NO_x) and partly to participate in a global effort to reduce emissions of greenhouse gases. Many macroeconomic studies, based on both global and national models, have been made of how emissions can be reduced with the help of taxes and the consequent reduction in GDP following the introduction of such taxes. Norway has had a CO₂ tax for five years, thereby providing a unique opportunity to evaluate the effects of this tax on emissions. The paper provides a counterfactual analysis of energy consumption and emissions if no CO₂ taxes had been introduced, compared with the actual situation in which such taxes exist. The effect of a CO₂ tax on oil consumption, and thus CO₂ emissions is studied on the basis of partial economic models for various sectors of the Norwegian economy. The study indicates that the CO₂ tax has had an impact on CO₂ emissions in Norway.