纳米二氧化钛光催化降解罗丹明6G的应用研究

采用醇盐水解法制备纳米二氧化钛,最佳制备条件为醇：酯：蒸馏水=1：1：10（体积比）;搅拌时间1h;煅烧温度为500℃;煅烧时间为2h。制得的纳米TiO2为单一晶型即锐钛矿型,平均粒径为17．32nm,比表面积为73．683m^2／g。光催化降解罗丹明6G的最佳操作条件是：TiO2用量0．5g;0．594％的H2O2溶液5mL;1．05％的FeCl3溶液1．5mL;反应时间为30min。脱色率达到98．51％。由于H2O2和FeCl3的协同作用,缩短了反应时间,提高了光催化效率。     

Multitask principal-agent problems: Optimal contracts, fragility, and effort misallocation

We analyze a tractable class of multitask principal-agent problems, such as the one faced by a firm with a manager overseeing several projects. We allow for tasks to be complements or substitutes. We avoid the problems associated with the first-order approach by directly characterizing the shape of the agent's indirect utility function, which exhibits a convex then concave shape in effort. We identify a new source of allocational inefficiency across tasks: excessive concentration, and its consequence, insufficient risk taking. Optimal incentive schemes in our environment are generally “fragile”: small changes in fundamentals can cause the agent's effort to collapse.     

Social class, family background, and intergenerational mobility

This research examines the various approaches taken by economists and sociologists for analyzing intergenerational mobility. Social mobility models based on social classes arising from an occupational classification scheme are analysed. A test for the statistical validity of classification schemes is proposed and tested using Danish sample survey data that was first collected in 1976 and augmented in 2000. This is referred to as a homogeneity test and is a likelihood ratio test of a set of linear restrictions which define social classes. For Denmark it is shown that this test fails for an Erikson-Goldthorpe classification system, raising doubts about the statistical validity of occupational classification systems in general. We also estimate regression models of occupational earnings, household earnings, and educational attainment using family background variables as covariates controlling for unobservables, measurement error, and simultaneous equation bias. In these models homogeneity tests are also rejected. We conclude from these results that the individual's family background has a small but significant impact on lifetime chances which is not captured by the Erikson-Goldthorpe classification scheme.     

双协议栈在IPv4过渡到IPv6过程中的应用

随着IPv6的迅速发展,IPv4的不足暴露的越来越明显,本文阐述了AKIPv4过渡到IPv6的必然性,重点论述了过渡机制中的双栈技术及其实现模型.     

GOVERNANCE INSTITUTIONS AND PRIVATE INVESTMENT: AN APPLICATION TO THE MIDDLE EAST AND NORTH AFRICA

This paper addresses the issue of the low level of private investment in the Middle East and North Africa (MENA) region, with special emphasis on the role of governance. Based on the existing published reports, we categorize what types of governance institutions are more detrimental to entrepreneurial investments. We then estimate a simultaneous model of private investment and governance quality where economic policies concurrently explain both variables. Our empirical results show that governance plays a significant role in private investment decisions. This result is particularly true in the case of “administrative quality” in the form of control of corruption, bureaucratic quality, investment‐friendly profile of administration, law and order, as well as for “political stability.” Evidence in favor of “public accountability” is also found. Our estimations also stress that structural reforms like financial development, trade openness, and human development affect private‐investment decisions directly, and/or through their positive effect on governance.     

Global Value Chains and Effective Exchange Rates at the Country‐Sector Level

The real effective exchange rate (REER) is one of the most cited statistics in open‐economy macroeconomics. We show that the models used to compute these numbers are not rich enough to allow for the rising importance of global value chains. Moreover, because different sectors within a country participate in international production sharing at different stages, sector‐level variations are also important for determining competitiveness. Incorporating these features, we develop a framework to compute REER at both the sector and country level and apply it on intercountry input‐output tables to study the properties of the new measures.     

Mad about Austerity? The Effect of Fiscal Consolidation on Public Opinion

We explore the impact of fiscal austerity on three different dimensions of public opinion in 26 European Union countries (consumer confidence, attitude toward national authorities, and European institutions) on annual data between 1997 and 2017. Our main finding is that the independent effect of a tighter fiscal stance on public opinion is not large and, when present, seems to closely follow the impact of fiscal austerity on economic activity. Our results therefore are inconsistent with the view that fiscal austerity necessarily implies a negative effect on public opinion and a decline in popularity of national and European institutions.     

Off‐Shoring,Specialization and R&D

This paper investigates whether off‐shoring promotes technological specialization by reallocating resources towards high‐tech industries and/or stimulating within industry R&D. Using data for the USA, Japan and Europe, our results show that material off‐shoring promotes high‐tech specialization through input reallocation between sectors, while service off‐shoring favors technologically advanced production by increasing within‐industry productivity, mainly via its positive impact on R&D. Conversely, we find that the increasing fragmentation of core production tasks, captured by narrow off‐shoring, has adverse effects on technological specialisation, which suggests that this type of off‐shoring is mainly pursued for cost‐reduction motives.     

Labor reallocation and demographics

We explore data from all transition economies over nearly two decades, providing insights on the mechanisms behind labor force reallocation. We show that worker flows between jobs in different industries are rare relative to the demographic flows of youth entry and elderly exit. The same applies to the flows between state-owned enterprises and private firms. In fact, evidence suggest that changes in the demand for labor were accommodated mostly through demographic flows, with a smaller role left for job transitions. We also show that the speed of changing the ownership structure in the economy has driven exits to retirement, in particular the early exits.     

未来无线移动互联网技术的发展探讨

随着移动通信与互联网的日益结合,无线移动互联网技术的发展成为目前的一个研究热点。文中从物理层、数据链路层和网络层入手,对无线移动互联网技术现状作了简要介绍并分析了其所存在的问题,重点对在今后发展中可能会采用的关键技术进行了研究与探讨。