Risk analysis of the EASA minimum fuel requirements considering the ACARE-defined safety target

We present the results of flight simulator experiments (60 runs) with randomly selected airline pilots under realistic operational conditions and discuss them in light of current fuel regulations and potential fuel starvation. The experiments were conducted to assess flight crew performance in handling complex technical malfunctions including decision-making in fourth-generation jet aircraft. Our analysis shows that the current fuel requirements of the European Aviation Safety Agency (EASA) are not sufficient to guarantee the safety target of the Advisory Council for Aviation Research and Innovation in Europe (ACARE), which is less than one accident in 10 million flights. To comply with this safety target, we recommend increasing the Final Reserve Fuel from 30 min to 45 min for jet aircraft. The minimum dispatched fuel upon landing should be at least 1 h.     

Mobility in the transition to retirement – the intertwining of transportation and everyday projects

Through travel diaries and interviews with newly retired urban residents in Sweden our aim was to explore (1) mobility patterns in the transition to retirement, (2) the influence of space–time restrictions and resources on mobility and (3) the meaning and embodied experience of mobility. This time-geographic study contributes with knowledge on how mobility is influenced by individual, social and geographical contexts. Illustrated by four cases, our result show that retirement changes the preconditions for mobility and creates new space–time restrictions. To spend more time on projects that were previously carried out outside working time, such as caring for grandchildren, volunteer work and household responsibilities, influenced the informants’ demands for mobility and choice of transport mode. However, the informants have resources that can be seen as strategies to overcome space–time restrictions. Most of the informants found it important to structure the day, to some it was vital to have something to do during the day while others enjoyed the possibility to take each day as it comes. Everyday mobility was a way of forming a structure by getting out of the house, either just for a walk or for making errands. The informants’ embodied experiences of mobility influenced their choice to walk and cycle for transport for the reasons of comfort, get fresh air, or simply to get out of the house. The daily mobility pattern that was established was a result of individual preferences and resources as well as negotiations with family members. We conclude that the transition to retirement is a period when new mobility patterns are considered, evaluated and practiced.     

Land use and land cover scenarios: An interdisciplinary approach integrating local conditions and the global shared socioeconomic pathways

Land Use and Land Cover (LULC) changes have profound impacts on the functioning of (agro)ecosystems and have potential to mitigate global climate change. However, we still lack interdisciplinary methods to project future LULC scenarios at spatial scales that are relevant for local decision making and future environmental assessments. Here we apply an interdisciplinary approach to develop spatially explicit projections of LULC at a resolution of 30 × 30 m informed by historic relationships between LULC and their key drivers, within the context of the four qualitative scenarios of global shared socioeconomic pathways. We apply this methodology to a case study in the Zona da Mata, Brazil, which has a history of major LULC changes. The analysis of LULC changes from 1986 to 2015 indicates that pasture area decreased from 76 to 58 % of total area, while forest areas increased from 18 to 24 %, and coffee from 3 to 11 %. Environmental protection legislation, rural credit for smallholder farmers, and demand for agricultural and raw products were identified as main drivers of LULC changes. Projected LULC for 2045 strongly depends on the global socioeconomic pathway scenarios, and forest and coffee areas may increase substantially under strong government measures in the environmentally conscious Green Road scenario or decrease in the high consumption Rocky Road scenario. Our study shows that under the set of drivers during the past three decades reforestation can go hand in hand with increase of agricultural production, but that major and contrasting changes in LULC can be expected depending on the socioeconomic pathway that will be followed in the future. To guide this process, LULC scenarios at the local scale can inform the planning of local and regional development and forest conservation.     

Rural Residential Land Transition in the Beijing-Tianjin-Hebei Region: Spatial-Temporal Patterns and Policy Implications

Rural residential land transition (RRLT) dominates rural land use transition. Therefore, analysing the laws of transition and differentiation of land use is not only the basis for the differential management of rural residential areas but key to the sustainable use of rural land. This study constructs a conceptual model of RRLT using multi-period remote sensing monitoring data based on a comprehensive index method, ArcGIS, and FRAGSTATS landscape pattern analysis, among others. It also analyses the characteristics of the transition extent, transition trend, transition morphology, and transition intensity of rural residential land in the Beijing-Tianjin-Hebei (BTH) region from 1980 to 2018. The results show that, from a vertical comparison of long time series, the transition extent is characterised by a process of ‘slow growth—expanding start—fast expansion—slowing down’; the transition trend is characterised by an increase in the amount of cultivated land occupied by rural residential land, followed by a large number of rural residential land is reclaimed as cultivated land; the transition morphology is characterised by an increase in mean patch size and degree of irregularity, as well as aggregation; and the transition intensity is characterised by fluctuations in the process of ‘small-scale reduction—small-scale growth—substantial growth—small-scale growth and reduction’. A horizontal comparison of counties in the BTH region reveals a long-lasting and active growth trend in transition extent and transition intensity in the Beijing-Tianjin region, and a gradually slowing trend in the areas around the region. The transition morphology features of the northwest Hebei region are more prominent, and show that the scale of rural settlements is small, the plaques fragmented and irregular, and the layout more scattered. The BTH region should formulate a differentiated transition direction for rural residential areas based on the different functional areas, and play into the agglomeration, scale, and synergy effects of urban agglomerations. It should also coordinate and improve the human–land relationship in rural areas, and construct an orderly and densely distributed pattern of urban and rural spatial development with a reasonable layout and complementary functions.     

Demographic Transition and Fertility Rebound in Economic Development*

Recent evidence on the “fertility rebound” offers credence to the idea that, from the onset of early industrialization to the present day, the dynamics of fertility can be represented by an N-shaped curve. An overlapping generations model with parental investment in human capital can account for these observed movements in fertility rates during the different stages of demographic change. A demographic transition with declining fertility emerges at the intermediate stage, when parents engage on a child quantity–quality trade-off. At later stages, however, the process of economic growth generates sufficient resources so that households can rear more children while still providing the desirable amount of education investment per child.     

Arrow–Debreu equilibria for rank‐dependent utilities with heterogeneous probability weighting

We study Arrow–Debreu equilibria for a one‐period‐two‐date pure exchange economy with rank‐dependent utility agents having heterogeneous probability weighting and outcome utility functions. In particular, we allow the economy to have a mix of expected utility agents and rank‐dependent utility ones, with nonconvex probability weighting functions. The standard approach for convex economy equilibria fails due to the incompatibility with second‐order stochastic dominance. The representative agent approach devised in Xia and Zhou (2016) does not work either due to the heterogeneity of the weighting functions. We overcome these difficulties by considering the comonotone allocations, on which the rank‐dependent utilities become concave. Accordingly, we introduce the notion of comonotone Pareto optima, and derive their characterizing conditions. With the aid of the auxiliary problem of price equilibria with transfers, we provide a sufficient condition in terms of the model primitives under which an Arrow–Debreu equilibrium exists, along with the explicit expression of the state‐price density in equilibrium. This new, general sufficient condition distinguishes the paper from previous related studies with homogeneous and/or convex probability weightings.     

基于风险中性路径概率的三叉树期权定价模型

树方法是给经典期权进行定价的非常实用的数值方法,目前最流行的是二叉树模型。三叉树定价模型作为二叉树的一个扩展,其同样是在风险中性概率的基础上给经典期权进行定价,并且可以通过MATLAB实现。相比于二叉树而言,三叉树模型的定价结果具有更好的收敛性。除此之外,用三叉树模型对影响期权价格的一些因素进行敏感性分析,可以验证该模型的合理性。     

Robust Markowitz mean‐variance portfolio selection under ambiguous covariance matrix

This paper studies a robust continuous‐time Markowitz portfolio selection problem where the model uncertainty affects the covariance matrix of multiple risky assets. This problem is formulated into a min–max mean‐variance problem over a set of nondominated probability measures that is solved by a McKean–Vlasov dynamic programming approach, which allows us to characterize the solution in terms of a Bellman–Isaacs equation in the Wasserstein space of probability measures. We provide explicit solutions for the optimal robust portfolio strategies and illustrate our results in the case of uncertain volatilities and ambiguous correlation between two risky assets. We then derive the robust efficient frontier in closed form, and obtain a lower bound for the Sharpe ratio of any robust efficient portfolio strategy. Finally, we compare the performance of Sharpe ratios for a robust investor and for an investor with a misspecified model.     

Trade and dietary diversity in Eastern Europe and Central Asia

In public and academic debates, the linkages between agricultural markets and nutrition across the world are vividly discussed. This paper contributes to the ongoing debate by analyzing the relationship between greater openness to trade and dietary diversity. It focuses on the post-communist countries of Eastern Europe and Central Asia where trade reforms triggered growth in trade flows and foreign direct investment, which in turn affected food systems in these countries. This shift provides a natural experiment for studying the effects of trade openness on agricultural markets and consumer behaviour. Reduction in trade barriers, for instance in the context of the accession to the WTO and the EU, and the gradual integration with world markets after 1991 had implications for diets through changes in production, prices and incomes. We utilize country-level panel data for 26 post-communist countries in the period 1996–2013 to assess the effects of trade costs, agricultural trade openness and incomes on dietary diversity measured by the Shannon entropy index. The results from fixed effects and instrumental variables estimation are consistent with previous findings that income growth affects dietary diversity positively. They also provide novel evidence that trade barriers reduce variety of products available in domestic markets, in particular fruits and vegetables.     

关于公路与桥梁之间过渡段施工技术初探

本文主要分析了公路桥梁间过渡段出现不均沉降的原因以及公路桥梁间过渡段的施工技术的应用情况,此项技术对降低施工成本,提升桥梁的可靠性与安全性有重要作用。