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排序方式: 共有630条查询结果,搜索用时 171 毫秒
91.
Tessaleno Devezas Francisco Cristovão L. de Melo Maria Luisa Gregori Maria Cristina V. Salgado Joana R. Ribeiro Christian B.C. Devezas 《Technological Forecasting and Social Change》2012,79(5):963-985
This article is geared toward shedding some more light on what may be the next space race and its contours.Space flight is undoubtedly a human achievement of the second half of the 20th century, and probably the most audacious one of the past century. The space race started suddenly in the 1950s and has grown explosively during the following two decades, but decreased steadily after the 1970s. After the 1990s, however, we have seen a shy rebirth of space-related activities, when many other actors (states) entered the stage, adding up to the agonizing role of the two-actor piece that we have witnessed during the so-called Cold War.The opening years of the 21st century provided a more complex narrative for space exploration. At the start of the new millennium a new technosphere [1] emerged, dominated by what is used to be called as the Information and Communications Technologies (ICT), with the Internet playing the leading role among the bandwagon of technological novelties that appeared during the twilight of space activities. In despite of the fact that artificial satellites represent the very backbone of the global communications system, space activities seem to play a secondary role amidst the apparently accelerated rate of change concerning the technological systems of the present technosphere. But, as it is demonstrated in this paper, things are changing, and very probably a renewed space race will unfold in the coming decades.A question may be placed: what happened? Why the Earth stood still with regard to the race toward the cosmos? Answer: futurists, even prestigious ones like Herman Kahn and Arthur Clarke, did not consider the existence of socioeconomic long waves (Kondratieff waves, or K-waves for short) with their two decades long economic downturn, which has contributed to the deceleration of space-related activities.Analyzing the worldwide evolving scenario of space-related activities during the last eighty years under the framework of the succeeding K-waves and applying some technological forecasting tools, namely the logistic analysis, technological surveillance and intensive data mining, scrutinizing more than 7500 events occurred in the period 1930–2010 related with space activities, it is demonstrated that the space race like the one that we have witnessed until now is a natural growth process that has saturated at the dawn of this century. The same analysis demonstrates that a new growth process in this field might be nowadays under way with contours very different from that imagined by futurists and science fiction writers sixty years ago. Also the main trends in the usage of launching vehicles and satellites are framed and discussed in this paper. 相似文献
92.
Leonel M. Pereira Celma de Oliveira Ribeiro José R. Securato 《The Australian journal of agricultural and resource economics》2012,56(4):542-557
This article suggests a pricing model for commodities used to produce biofuel. The model is based on the concept that the deterministic component of the Wiener process is not constant and depends on time and exogenous variables. The model, which incorporates theory of storage, the convenience yield and the seasonality of harvests, was applied in the Brazilian sugar market. After predictions were made with the Kalman filter, the model produced results that were statistically more accurate than those returned by the two‐factor model available in the literature. 相似文献
93.
This paper aims to shed light on the role of the ideologyof political parties in shaping the evolution of the welfarestate in 18 developed democracies, by providing empirical findingson the determinants of social-programme entitlements and socialspending over the period 198199. The paper shows thatstructural change is a major determinant of the extent of socialprotection. Our results suggest that overall spending is drivenup by structural change. On the other hand, strong structuralchange has a negative influence on welfare entitlements measuredby the net rate of sickness insurance. Partisan influence playsan important role in the dynamics of the welfare state. Left-winggovernments strengthen the positive effect of shocks on aggregatesocial expenditure, while right-wing governments undertake evenstronger cutbacks in replacement rates as a reaction to structuralchange.
Footnotes
1 E-mail addresses: bruno.amable{at}ens.fr; donatella.gatti{at}cepremap.cnrs.fr;jan.schumacher{at}wiwi.uni-regensburg.de 相似文献
94.
Castellano Nicola Giuseppe Cerqueti Roy Franceschetti Bruno Maria 《Review of Quantitative Finance and Accounting》2021,57(4):1463-1486
Review of Quantitative Finance and Accounting - This paper presents a data-driven complex network approach, to show similarities and differences—in terms of financial risks—between the... 相似文献
95.
Bruno Dupire 《Quantitative Finance》2019,19(5):721-729
We extend some results of the Itô calculus to functionals of the current path of a process to reflect the fact that often the impact of randomness is cumulative and depends on the history of the process, not merely on its current value. We express the differential of the functional in terms of adequately defined partial derivatives to obtain an Itô formula. We develop an extension of the Feynman-Kac formula to the functional case and an explicit expression of the integrand in the Martingale Representation Theorem. We establish that under certain conditions, even path dependent options prices satisfy a partial differential equation in a local sense. We exploit this fact to find an expression of the price difference between two models and compute variational derivatives with respect to the volatility surface. 相似文献
96.
Cássio G. Ribeiro Edmundo Inacio Junior Yanchao Li Andre Furtado Nanci Gardim 《Technology Analysis & Strategic Management》2020,32(2):119-132
ABSTRACTThis paper analyses the role of user-supplier relationships in the innovation dynamics of the Oil and Gas (O&G) industry, from an analysis supported by R&D and patent application data. This paper points to some recent interesting phenomena in the O&G sector, such as: (i) the remarkable advancement of two Chinese oil companies; (ii) the significant growth in O&G companies’ technological engagement in exploration and production (E&P) from the 2000s; (iii) the non-negligible increase in the application of O&G companies’ patents for renewable energy. Moreover, by working with the oil and gas chain complete, we show that the performance of the companies oil and gas equipment and services industry (O&GES) is restricted to the upstream activities. Finally, we bring up some arguments that have as objective relativise the typology of R&D intensity adopted by OECD. 相似文献
97.
98.
Regis A. Ely Rafael Parfitt Andr Carraro Felipe Garcia Ribeiro 《Review of Development Economics》2019,23(4):1863-1890
This paper evaluates the impact of Brazil's National Program to Strengthen Family Farming (PRONAF) on the time allocation of household members. We use data from the 2014 Pesquisa Nacional por Amostra de Domicílios, and we apply propensity score methods to complex surveys recently recommended in the literature. We find that PRONAF helps to increase focus on agricultural activities, but it also stimulates female partners to engage in unpaid work. The results show significant effects of PRONAF on child labor and on the gender‐specific division of labor within households, although it does not have the usual adverse effects of rural credit programs on school attendance. 相似文献
99.
We consider a discrete‐time financial market with proportional transaction cost under model uncertainty, and study a superreplication problem. We recover the duality results that are well known in the classical dominated context. Our key argument consists in using a randomization technique together with the minimax theorem to convert the initial problem to a frictionless problem on an enlarged space. This allows us to appeal to the techniques and results of Bouchard and Nutz to obtain the duality result. 相似文献
100.
In this paper, we study the effect of subsidised on-the-jobtraining, training for the unemployed and pure wage subsidieson job tenure. Correcting for selection biases, we find thateach of the labour market policies increases the length of jobtenure. Despite the sensitivity of the estimates to the parametricassumptions with respect to the unobservables, the effect ofsubsidised on-the-job training schemes is always found to besignificantly positive. Training programs for the unemployedand pure wage subsidies always have a positive, but statisticallynon-significant effect Our results provide some support forhuman capital theories as opposed to matching theories. 相似文献