Resource conflict detection and removal strategy for nondeterministic emergency response processes using Petri nets

Correctness of an emergency response process specification is critical to emergency mission success. Therefore, errors in the specification should be detected and corrected at build-time. In this paper, we propose a resource conflict detection approach and removal strategy for emergency response processes constrained by resources and time. In this kind of emergency response process, there are two timing functions representing the minimum and maximum execution time for each activity, respectively, and many activities require resources to be executed. Based on the RT_ERP_Net, the earliest time to start each activity and the ideal execution time of the process can be obtained. To detect and remove the resource conflicts in the process, the conflict detection algorithms and a priority-activity-first resolution strategy are given. In this way, real execution time for each activity is obtained and a conflict-free RT_ERP_Net is constructed by adding virtual activities. By experiments, it is proved that the resolution strategy proposed can shorten the execution time of the whole process to a great degree.     

Improving footprint calculations of small open economies: combining local with multi-regional input–output tables

In a small, open and resource-poor economy, import and export dependency have an ever-growing impact on local policy decisions, which makes local (environmental) policy-makers increasingly depend on global data. This increases the interest in models that link local production and consumption data to global production, trade and environmental data. The recent increase in availability of global environmentally extended multi-regional input-output tables (EE-MRIO tables) provides an opportunity to link them with existing local environmentally extended input-output tables (EE-RIO tables). These combined tables make it possible (1) to analyse the links between local and global production and consumption and (2) to study global value chains, material use and environmental impacts simultaneously. However, estimations using input-output (I–O) analyses contain errors due to imperfect databases. In this article the magnitude of specification, aggregation and time errors are estimated and compared. The results show the need to combine local datasets with multi-regional ones and show that highest detailed (country and sector levels) as well as time series of I–O tables are the way forward for using I–O analyses in local policy-making. The paper provides guidance on trading off investments in model adoption and/or extension and the reliability of estimation results.     

上海市交通拥堵成本测算及对策研究

依据美国德克萨斯运输学院交通拥挤外部成本的经典测算模型，将交通运输拥挤成本分为时间延误成本、额外燃油消耗成本、环境污染物排放成本和噪音成本三个方面，对于2015年上海市工作日高峰期交通拥挤的外部成本进行了详细的测算。结果表明，交通拥堵的外部成本约占当年上海市GDP的0.63%。最后，对于交通拥堵成本较高的现状提出了包括对上海市部分高度拥堵路段或区域收取拥堵费、大力发展上海市公共交通和发展交通快慢型出行方式共存在内的相关政策和建议。     

A Gendered Model of the Peasant Household: Time poverty and Farm Production in Rural Mozambique

Using insights from a case study on the allocation of labor in subsistence households in Mozambique, this study develops a conceptual framework for examining linkages between time poverty and farm production. An unexpected event such as a health crisis increases the demand for labor provided by women, thus making them more time poor. The model and numerical simulations show that a deterioration in a woman's time constraint will have an adverse effect on agricultural output of the household. This occurs because most women respond to an increase in household work by reducing their work hours on the farm and by reducing their leisure time. The latter outcome is expected to have a negative effect on women's physical and mental health, which will then cause a decline in their productivity on the farm.     

Identifying Discretionary Fiscal Policy Reactions with Real‐Time Data

We propose a method of identifying discretionary fiscal policy reactions using real‐time data. Automatic stabilizers should depend on true GDP, while discretionary fiscal policy is contingent on the information that policy makers have in real time. We can compute a real‐time measurement error by comparing the first release of GDP data with later revisions. Discretionary fiscal policy is influenced by this measurement error, whereas automatic fiscal policy is not. We use this identification approach to test the central identifying assumption of Blanchard and Perotti’s (2002) seminal structural vector autoregression (VAR). According to this assumption, fiscal policy makers do not react to GDP developments contemporaneously in a discretionary fashion. We find that government expenditure is adjusted upward if GDP growth in real time is lower than true GDP. This suggests that fiscal policy makers use short‐term funds to buy goods and services in response to their perception of GDP dynamics.     

全货运航空公司单分配严格枢纽航线网络优化设计

针对全货运航空公司，研究其货运航线网络的构建问题。基于单分配严格枢纽航线网络，对传统模型进行改进。以各航线上货物的委托运输成本和自有机队的运输成本，取代传统的单位运输成本和折扣因子，考虑枢纽点的中转成本和载运率对路径选择的影响。结合航空货运夜航的特征考虑各机队夜间可用时间的限制，以总成本最小为目标，构建数学模型，采用LINGO优化软件求解，验证模型的有效性，为全货运航空公司构建货运航线网络提供参考。     

Valuation of forward start options under affine jump-diffusion models

Under the general affine jump-diffusion framework of Duffie et al. [Econometrica, 2000, 68, 1343–1376], this paper proposes an alternative pricing methodology for European-style forward start options that does not require any parallel optimization routine to ensure square integrability. Therefore, the proposed methodology is shown to possess a better accuracy–efficiency trade-off than the usual and more general approach initiated by Hong [Forward Smile and Derivative Pricing. Working paper, UBS, 2004] that is based on the knowledge of the forward characteristic function. Explicit pricing solutions are also offered under the nested jump-diffusion setting proposed by Bakshi et al. [J. Finance, 1997, 52, 2003–2049], which accommodates stochastic volatility and stochastic interest rates, and different integration schemes are numerically tested.     

FIRE SALES FORENSICS: MEASURING ENDOGENOUS RISK

We propose a tractable framework for quantifying the impact of loss‐triggered fire sales on portfolio risk, in a multi‐asset setting. We derive analytical expressions for the impact of fire sales on the realized volatility and correlations of asset returns in a fire sales scenario and show that our results provide a quantitative explanation for the spikes in volatility and correlations observed during such deleveraging episodes. These results are then used to develop an econometric framework for the forensic analysis of fire sales episodes, using observations of market prices. We give conditions for the identifiability of model parameters from time series of asset prices, propose a statistical test for the presence of fire sales, and an estimator for the magnitude of fire sales in each asset class. Pathwise consistency and large sample properties of the estimator are studied in the high‐frequency asymptotic regime. We illustrate our methodology by applying it to the forensic analysis of two recent deleveraging episodes: the Quant Crash of August 2007 and the Great Deleveraging following the default of Lehman Brothers in Fall 2008.     

Towards the use of chronological age in research – A cautionary comment

In recent years, this journal published several articles that used chronological age in their models to distinguish customer behavior between younger and older people. While all these articles are in line with the growing importance of age-related research, chronological age is not discriminant when behavior and motivations enter the fray. By taking two recent articles in this journal as examples, this short note calls for a cautious application of chronological age and highlights other age-related constructs for research. The note ends with practical implications and avenues for further research in age-related projects.     

A MILP model for planning the trips of dynamic positioned tankers with variable travel time

The transportation of the crude oil produced in offshore oilfields to onshore terminals is performed by vessels, known as shuttle tankers. Scheduling shuttle-tanker operations entails solving complex problems to ensure a timely offloading of the platforms, taking into account several logistics and inventory constraints. This work proposes a new MILP formulation that advances previous works by considering variable travel time between platforms and terminals. The combination of the MILP formulation with an optimization solver constitutes a decision-support tool to aid engineers reach optimal decisions for a planning horizon. To handle large-scale instances, rolling-horizon and relax-and-fix strategies are proposed.