大跨度PC连续刚构桥徐变预测模型

为了能准确预测混凝土收缩徐变,提出了一系列徐变预测模型,但传统的徐变理论研究主要是针对普通混凝土进行的,所提出的徐变模型并不能完全适用于高强混凝土。对各徐变预测模型进行分析比较,最终参考了日本混凝土示方书建议模型,并在高强混凝土徐变试验的基础上,提出了一个适用于高强混凝土的徐变预测模型。基于Abaqus平台,使用Python语言进行二次开发,定义了修正模型的徐变规律,并采用修正后的模型计算牛角坪大桥的徐变应变。结果表明,修正模型的精度,能很好的满足工程需求。     

Regional Equality and National Development in China: Is There a Trade‐Off?

Despite high economic growth over the past 30 years, China's substantial and persistent regional disparities have been the subject of continuing concern to policy makers, as well as the target of a wide variety of policies. An important issue in the policy debate about whether and how best to attack these disparities is whether measures designed to improve regional equality come at a cost to national development, i.e., whether there is a trade‐off between the level of national output and the equality of its distribution across the regions. There is little analysis of this issue in the literature. We help fill this gap by setting up a two‐region model designed to capture some of the salient features of the Chinese economy. We subject this model to a number of policy shocks and assess the effects on regional disparities in per capita output, on the one hand, and on aggregate output on the other to investigate the trade‐off. We also consider income and welfare as alternatives to output. We find, first, that disparities in per capita output, income, and welfare may move in different directions so that it is important to specify which disparity is being targeted. Second, since both disparities and aggregate outcomes are endogenous, how they move together depends on the nature of the shock driving the model. Thus, some policies designed to reduce disparities face a trade‐off and others do not. Only a reduction in internal migration restrictions unambiguously reduces all three disparity measures and increases aggregate output, income, and welfare. All other policies considered face a trade‐off in at least one dimension. Third, whether there is a trade‐off depends also on the time horizon—some policies face a trade‐off in the short run and not in the long run and vice versa.     

The Strange Case of the Missing West Virginia Labor Force

The rate of labor force participation in West Virginia is far below all other states. This study finds that little of the participation rate gap can be attributed to traditional economic or institutional factors. For example, the high long-term unemployment rate in West Virginia accounts for less than 10 percent of the adult male participation gap. Most of the difference is associated with a large Appalachian population, and a high rate of federal disability benefits receipt. The latter, which we argue reflects tastes for nonmarket activities, also is a major factor in low participation rates of West Virginia adult females and teenagers. Unemployment does explain a significant portion of low participation rates for these groups. However, we estimate that a decline in the state's long-term unemployment rate to the nation's average would raise its aggregate participation rate by 3.9 percentage points, or just 28 percent of the total gap. It appears that nonparticipating West Virginians are not just “discouraged workers,” and that economic development policies should explore ways to increase aggregate labor supply, as well as labor demand.     

The Geography of a Mixed‐Race Society

The pattern and level of separation among ethnic groups continues to change, and there are certainly more mixed neighborhoods both in cities and suburbs than two decades ago. The immigration flows of the past decade have substantially altered the ethnic mix and neighborhood mixing. In addition, multi‐ethnic individuals themselves are altering the level of mixing among racial and ethnic groups. The research in this article shows that those who report themselves of more than one race have high levels of residential integration both in central cities and suburbs. These residential patterns can be interpreted as further evidence of tentative steps to a society in which race per se is less critical in residential patterning. The level of integration, for Asian mixed and black mixed is different and substantially higher than for those who report one race alone. The research in this article builds on previous aggregate studies of mixed‐race individuals to show substantial patterns of integration in California's metropolitan areas.     

U.S. Farm Wages and Labor Market Efficiency

This study examines convergence in real wages for hired farm labor in the U.S. agricultural sector over the period 1978‐92,using the ‘average farm’ in each county as an observation. Convergence is investigated at the aggregate (or the entire U.S. level)and regional levels. Evidence supports convergence with a slower rate at the aggregate level than that at the regional level. Suggested by the evidence is the possibility that absolute benefits of wage equalization across states are ‘contagious’—that one state's successful investment raises productivity and factor payments in neighboring states and that agricultural labor markets are efficient and integrated all over the country.     

Fluctuations and Downturns in a “Company Town”

ABSTRACT A semi-structural VAR time-series model was used to examine movements in Flint Metropolitan Statistical Area (MSA) employment levels and determine how area employment was affected by movements in different sectors of the U.S. economy. Flint was chosen because in 1958 over 50 percent of the area's population was employed by the transportation industry, the majority in automobile production, and therefore Flint should be considered as a company town prototype for this modeling technique. Due to the dependency of this area's employment base on the automotive industry and the highly volatile nature of area employment levels, the Choleski decomposition was used instead of the structural Bernanke method. It was found that the effects of movements in the automotive industry were a major impact on aggregate area employment as well as on virtually all manufacturing sectors. These results are more robust than those for the Detroit Metropolitan Statistical Area (PSA) ¹ 1 As found in Rushen (1993).
. This is due primarily to Flint's greater degree of area dependency on the automotive-industry.     

Women in community-involved tourism enterprises: Experiences in the Philippines

The tourism industry has long been recognised for supporting women in achieving economic empowerment and social freedom through entrepreneurial and employment opportunities. Widely recognised as a women-dominated sector, tourism is deemed to be a facilitator of women's development following the UN Sustainable Development Goals (SDGs). As the existing literature suggests, women's involvement in tourism activities supports local economic growth and development, while facilitating social transformation that enables them to create their own identities. Despite these achievements, several studies noted the persisting issues women face in participating in tourism. With the goal of contributing to existing discourses, this paper aims to analyse their experiences in community entrepreneurship by examining several community-involved tourism enterprises in the Philippines. The findings of this study reveal that women have been largely involved in tourism activities in that country, yet their experiences working in these enterprises vary. The opportunities and challenges identified in this study can serve as a springboard for further analysis of the experience of women working in the Philippine tourism industry.     

冻融损伤对再生混凝土耐久性及与钢筋粘结性能分析

制作掺入引气剂和未掺入引气剂的100%粗骨料取代率的再生混凝土RC1和RC2两组试件以及掺入引气剂和未掺入引气剂的普通混凝土NC1和NC2两组试件,并分别对经过不同次数冻融循环试件的抗压强度、质量损失率、动弹性模量损失率进行研究。结果表明,冻融后各组试件的抗压强度、质量损失率及动弹性模量损失率均降低,对于添加引气剂的NC1和RC1两组试件损失较小,其中RC1组试件在200次冻融后抗压强度损失接近40%,质量损失率达0.5%,动弹性模量损失率38.5%。100%取代率并加入引气剂的ZRC组试件冻融后进行中心拨出实验,发生劈裂破坏和钢筋拔出破坏2种形式。再生粗骨料混凝土与钢筋的极限粘结应力均随冻融次数的增加而降低,200次冻融后极限粘结应力下降33.5,荷载滑移曲线既有上升段也有下降段。     

Regional Economic Activity and Petroleum Industry Incentive Policies: Utah's Uintah Basin

ABSTRACT Proponents of petroleum industry subsidies often assert that such policies will have positive economic implications for rural communities. This paper examines the economic impacts of such a policy in Utah. Specifically, this paper quantifies the direct and indirect economic and fiscal impacts of a tax credit granted for oil and gas well workovers in Utah's Uintah Basin. The analysis is made possible by an input-output model constructed specifically for Utah's oil producing economy. The tax credit policy was found to generate a net fiscal loss for the state. However, it does generate employment in the Uintah Basin. The total per job cost to the state of generating an average of one job per year for 5 years through the tax credit policy is $24,056 (1991 dollars). However, if the public expenditure impacts are taken into account, then the cost per job could be as high as $48,423 (1991 dollars). Whether there are other ways to generate the same employment gains at a lower cost was lost in the political debate surrounding this petroleum industry tax credit.     

The effects of China’s growth slowdown on its provinces: Disentangling the sources

Since 2007, China's growth has fallen from around 10% to about 6%–7% per annum. This paper investigates the experience of this slowdown at the provincial level. We use a vector‐autoregressive modelling approach and annual data from 1978 to decompose each province's growth into various factors. We find that (a) all provinces experienced the slowdown; (b) there is considerable variation in this experience across provinces; (c) national factors dominate the provincial slowdown while province‐specific factors explain most of the interprovincial variation; (d) when the national factor is separated into supply and demand components, the supply component dominates.     

Manufacturing

While not as bad as the loss of 80,000 manufacturing jobs in the 1980s, the loss of a further 30,000 jobs in the 1990s showed that the process of restructuring did not stop in 1990. The picture that emerges is more varied than the destruction of the earlier decade. There is certainly evidence of a lean, mean, more export‐orientated group of firms that are competing internationally under the new low protection regime. On the other hand, it is clear that the process of restructuring and the removal of protection did not stop in the 1990s. There has been a sizeable loss of larger factories and a 22 per cent increase in smaller businesses, while surprisingly the level of foreign controlled enterprises has not increased significantly. In terms of manufacturing's contribution to exports there is both good and bad news. Exports of machinery, for example, increased by 518 per cent between 1989 and 1999. The bad news is that this is still only 18 per cent of total dairy exports, 29 per cent of meat, and only marginally ahead of wool exports, which have declined by 58 per cent in value between 1989 and 1999.     

China's compliance in global environmental affairs

Abstract: As the most populous country on earth with 10 per cent of its rare species of flora and fauna, China's environmental practice is of great importance. Already the country is one of the most polluted places in the world. At least seven out of the ten of the world's most polluted cities are located in China. It is the second largest producer of greenhouse gases after the United States, inflicting heavy, long‐term casualties on its own public health and economic development as well as on those of its close neighbours in the Asia‐Pacific region. How to strike a proper balance between environmental protection and fast economic growth will have an important impact on China's modernisation outcome and its international standing. The country began to pay serious attention to environment problems in the 1970s. Since the adoption of the reform and opening‐up policy in the late 1970s, it has signed or ratified many international treaties dealing with environmental issues. By now, it has entered into most international environmental regimes. But how compliant is China with respect to commitments made to these regimes? How willing and capable is it in complying with international environmental norms and rules? What does sustainable development mean to China? How do red tape, fear, inexperience, and ignorance affect China's efforts to protect its environment? And how do inter‐ministerial wrangling and the growth of green NGOs within China affect its compliance? This paper tries to answer these questions.     

Maize participatory breeding in Portugal: Comparison of farmer's and breeder's on‐farm selection

“VASO” is a Portuguese participatory maize breeding project (1984), where several maize landraces such as “Pigarro” have been selected both by a farmer's (phenotypic recurrent selection) and a breeder's approach (S2 lines recurrent selection). The objectives of this study were to determine the phenotypic and genotypic responses to participatory selection using these two different approaches, to clarify to which extent both selection methods preserve genetic diversity, and conclude what is the preferred method to apply in sustainable farming systems. The results, obtained via ANOVA, regression analyses and molecular markers, indicate that for both selection methods, genetic diversity was not significantly reduced, even with the most intensive breeder's selection. Although there were some common outputs, such as the determinated versus indeterminated ears, cob and ear weight ratio per ear and rachis 2, specific phenotypic traits evolved in opposite directions between the two selection approaches. Yield increase was only detected during farmer selection, indicating its interest on PPB. Candidate genes were identified for a few of the traits under selection as potential functional markers in participatory plant breeding.     

Interstate Differences in State and Local Revenues

The focus of this study is the examination of the interstate differences in per capita state and local revenues. On one side free competition among states is supposed to keep the interstate differences in per capita state and local revenues at a minimum level. On the other side, the interstate differences in variables like income and taste of consumers, natural conditions (like climate), state's size (scale effect), and others may explain the existing interstate differences in per capita state and local revenues. The empirical results indicate that we successfully explained over 90 percent of the variance in per capita state and local revenues. Additional empirical results reveal that the federal government distributes money among states in a discriminate fashion based on region and size.     

Monetary policy and regional economic performance in Mexico: A structural panel VAR approach

The aim of this article is to investigate the dynamic effects of monetary policy shocks on economic activity and aggregate price levels across Mexican states. To do this, a recursive structural panel VAR model is implemented as proposed by Pedroni which allows for regional heterogeneity and structural identifying restrictions of common monetary policy shocks. Empirical evidence suggests a common monetary policy shock to short‐term interest rates induces significant cross‐state variation in prices and output level responses. Additional analysis indicates that structural features, such as the industry mix and the small versus large firm mix, are possible sources of the observed cross‐state variation influenced by interest rates and credit channels. We conclude that the observed differentiated regional impacts are sufficiently important to justify rethinking Mexico's current monetary policy framework in order to explicitly consider a regional view.     

Economic Valuation of Varieties and Breeding Objectives

Breeding planning and variety valuation can be supported only if weighting factors for the economically relevant performance traits are available. In plant breeding they are necessary for the calculation of selection indices as well as for the comparison of varieties and for quantifying the monetary impact of breeding progress. In this article the economic weights for the most important performance traits of sugar beet are calculated from the farmer's, the sugar factory's, and the national economy's point of view. Based upon economic weights for beet yield, sugar content, potassium, sodium, and ammo nitrogen content, a total of 19 varieties was compared with regard to physical and economic performance. The investigation shows that “best” and “worst” varieties differ in gross margin per ha by 270.— to 330.— DM. Indications were given for possibilities and limitations of the application of economic weights in breeding planning.     

The ethnic geography of New Zealand: A decade of growth and change, 1991–2001

Abstract: New Zealand's population growth of 10 per cent over the decade 1991–2001 resulted substantially from an increasing number of those claiming Pacific Island and Asian ethnicity, and to a lesser extent of the New Zealand Maori. Using census data for a comparable set of small areas with average populations of just over 100, this paper examines the changing geography of the four main ethnic categories – New Zealand European, New Zealand Maori, Pacific Island Peoples, and Asians – across the country as a whole and in its major settlements, especially Auckland. There is little extreme segregation of the three minority groups, but most of the Europeans live in areas where there is little exposure to those of other ethnicities. Most of the changes in segregation reflect the growth of Auckland's Pacific Island and, especially, Asian populations.     

Preliminary Discussion on Mixing Design of Porous Concrete

Porous concrete is an eco-concrete with high porosity and high strength,whose application was restricted to some extent,because there is lack of appropriate and unitive mixing design method.According to the features of porous concrete,proportion design idea of porous concrete whose major design parameter was porosity and strength was satisfied by changing variety of cementing material and aggregate size.The design method of porous concrete was that the raw materials were selected according to design requirement at first,secondly,aggregate dosage per unit volume of porous concrete was calculated,thirdly,dosage of cementing material was calculated by apparent density of aggregate and porosity of design requirement,finally,cement dosage of the unit physical volume and water dosage were calculated by water cement ratio deter mined by requirement of forming process.The test result indicated that this mixing design method of porous concrete was reliable and feasible.     

Logistics Strategy and Transport Service Choices: An Adaptive Stated Preference Experiment

ABSTRACT This paper presents the results of a microanalysis of freight transport demand in a logistics context. Current research concentrates, with few exceptions, on shippers’ choice of a transport mode. However, in a global context, shippers’ behavior has to be conceived as a complex decision, which considers transport mode choice as only a part of a firm's logistics strategy. Since no data exist to directly estimate the marginal values for different qualities of transport and logistics services, a stated preference approach is applied. Adaptive stated preference experiments were performed for twenty‐two firms in Italy and in Switzerland. The experimental results—forty hypothetical binary choices per firm—were completed by background information on the firms’ long‐term logistics strategies. The results confirm the relevance of the logistics context (e.g., JIT strategies on the supplier's or customer's side) for transport demand. The calculated marginal values of time and characteristics (reliability, frequency, etc.) provide important insights and permit generalized costs in freight transport models to be recalibrated.     

Study on the Inheritance and Relationship of Some Morphological and Fertility Characters in Faba Bean (Vicia faba L.)

Inheritance of several morphological and fertility characters was studied in F2 generation of two sets of diallel cross, using Griffing's analysis of variance. A paramount importance of general combining ability (GCA) over specific combining ability was measured for most studied characteristics. Correlations among GCA values for seed yield, morphological and fertility characters do not give a clear definition of the plant ideotype. “Terminal inflorescence” character appeared to reduce the seed per ovule ratio. Higher additive component was found for the ovule per pod than for seed per pod characters.