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1.
Construction kits have played a significant part in nurturing the growth and development of the minds and manipulation-based skills of children (and adults) in formal and non-formal education settings. These kits have origins rooted in the representation of the built world and now have a diversity of form and function, including technical versions with moving parts. This article examines some of the historically based ideas that lie behind the role that kits may have in terms of physical modelling. The article traces the transformation of kits from simple bricks and blocks into more complicated pieces for space-filling and achieving the transfer of forces and motion. This transformation occurred during the Victorian era when the influence of the ideas of educationalists and, perhaps rather strangely, exponents of early aviation, played major roles in determining the diversity of forms of construction kit and modelled possibilities that are now to be seen in classrooms and homes. The article ends with a review of some of the lessons from the past and present that will need to be considered in relation to concrete modelling in schools for the future. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
2.
The open door policy of China’s economic reform since the 1980s has attracted heavy foreign direct investment (FDI) flows into China and especially to Guangdong (particularly the Pearl River Delta region, PRD) and induced significant economic growth during the past two decades. While there exist various classical theories of FDI in attempting to identify the determinants of FDI inflow and to explain the behavior of FDI flows, limited attention has been given from the perspective of agglomeration effects generated by a core-periphery (CP) relation.This paper intends to study the impacts of agglomerations on FDI inflows in the context of Krugman’s CP relation (1991) by investigating (1) the formation of a CP relation via gravity model analysis; (2) whether different types of industry FDI flows will respond differently in the CP-system, given agglomeration effects; and (3) whether FDI origin and firm scale matter in affecting FDI flows.A database consisting of a population frame of 37,742 firm-level manufacturing and services joint ventures investing in Guangdong in 1998 was used. Empirical results show that the agglomerations of the CP relation have affected FDI flow patterns. While both manufacturing and services FDI and sources of investment responded differently to the impacts, smaller firms were found more responsive to the CP-agglomeration settings regardless of FDI by industry type and by source. The significance and implications of the CP-system to further facilitate FDI in the region are discussed.  相似文献   
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In this paper we offer a method for deciding how to aggregate a set of elementary industries. The method is then applied to the problem of estimating a wage equation that allows for industry-specific effects. Our method explicitly formalizes the trade-off between goodness-of-fit and parsimony implicit in an aggregation problem. By varying the parameter of the assumed loss function, one obtains a whole sequence of aggregation levels. Further, the resulting sequence is consistent; that is, groupings formed at one level of aggregation will never be undone when one aggregates further.  相似文献   
5.
We examine the role of index futures trading in spot market volatility. We use the exponential generalized autoregressive conditional heteroskedasticity (EGARCH) approach to measure volatility, analyze causality and feedback relations between volatilities in the spot and futures markets, and test various hypotheses in the context of a multivariate model that incorporates other macrostate variables. Our empirical results suggest index futures trading may not be blamed for the observed volatility in the spot market. Rather, we find stronger and more consistent support for the alternative posture that volatility in the futures market is an outgrowth of a turbulent cash market. We use the regret (cognitive dissonance) theory to explain our results.  相似文献   
6.
Canada's wheat grading system is largely based on visual criteria and it is based on relatively high quality standards. A strict varieties licensing system exists to maintain the integrity of the grade standards. One of the consequences of the licensing system is that higher yielding, lower or different quality wheats have not been grown in Canada until recently. The basic objective of this paper is to examine some of the consequences of the regulatory strategy of limiting wheat production to the traditional high quality wheats. This question is analyzed in the context of important changes in the international grain markets. Using a partial equilibrium trade model this paper estimates that if higher yielding wheats were permitted to be grown, annual producer gains would be 5 to 17 percent of current net farm income.
Le classement des blés au Canada est basé sur des critères visuels qui sont de hautes qualités. Le système actuel d'homologation des variétés est tel que l'intégrité de ce système est maintenue. En conséquent, ce système n'a pas encouragé la cultivation des blés de hauts rendements ou des varietés différentes que tout récemment. L'objectif principal de cette étude est d'examiner quelques unes des conséquences de la stratégic de la réglementation visant à limiter la production du blé aux variétés de hautes qualités. Cette question est adressée dans le contexte des changements importants qui ont eu lieu dans le marché international des grains. A l'aide d'un modèle d'équilibre partiel des échanges, la présente étude démontre gu'en permettant la production des blés de hauts rendements, le gain annuel aux producteurs serait de 5 à 17 pourcent du revenue agricole net.  相似文献   
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We model an accession country facing a Maastricht‐type inflation criterion that specifies an inflation ceiling. In addition to deciding whether or not to satisfy this criterion, the country must decide how much costly economic reform to undertake. If the country puts enough weight on the future that it can credibly meet the inflation criterion no matter what the ceiling is, then the inflation criterion benefits the country but lowers reform. If the country puts less weight on the future, then a criterion with a properly chosen inflation ceiling can increase reform. We derive the inflation ceilings that maximize the country's welfare and its reform.  相似文献   
9.
Agricultural trade impasses have again frustrated the GATT process. Interest in preferential/regional trading blocs is increasing. the paper probes the theoretical and empirical consequences of preferential arrangements instead of multilateral liberalization. It concludes that in a second-best world preferential arrangements could either improve or decrease global welfare. For agricultural trade, previous experience suggests that in regional groupings such as the EC trade diversion exceeded trade creation. This results from trade distorting domestic policies. Prospects for liberalization of agricultural trade under either GATT or preferential arrangements are limited. the consequences for small agricultural exporters are not positive.  相似文献   
10.
We examine the impact of initial public offerings (IPOs) on rival firms and find that the valuation effects are insignificant. This insignificant reaction can be explained by offsetting information and competitive effects. Significant positive information effects are associated with IPOs in regulated industries and the first IPO in an industry following a period of dormancy. Significant negative competitive effects are associated with larger IPOs in competitive industries, those in relatively risky industries, those in high‐performing industries, and those in the technology sector. IPO firms that use the proceeds for debt repayment appear to represent a more significant competitive threat to rival firms relative to IPO firms that use their proceeds for other purposes.  相似文献   
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