The Experts below are selected from a list of 201 Experts worldwide ranked by ideXlab platform
Qiang Meng - One of the best experts on this subject based on the ideXlab platform.
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liner ship route schedule design with sea contingency time and port time uncertainty
Transportation Research Part B-methodological, 2012Co-Authors: Shuaia Wang, Qiang MengAbstract:This paper deals with a tactical-level liner ship route schedule design problem which aims to determine the arrival time of a ship at each portcall on a ship route and the sailing speed Function on each voyage leg by taking into account time uncertainties at sea and at port. It first derives the optimality condition for the sailing speed Function with sea contingency and subsequently demonstrates the convexity of the bunker Consumption Function. A mixed-integer non-linear stochastic programming model is developed for the proposed liner ship route schedule design problem by minimizing the ship cost and expected bunker cost while maintaining a required transit time service level. In view of the special structure of the model, an exact cutting-plane based solution algorithm is proposed. Numerical experiments on real data provided by a global liner shipping company demonstrate that the proposed algorithm can efficiently solve real-case problems.
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sailing speed optimization for container ships in a liner shipping network
Transportation Research Part E-logistics and Transportation Review, 2012Co-Authors: Shuaian Wang, Qiang MengAbstract:This paper first calibrates the bunker Consumption – sailing speed relation for container ships using historical operating data from a global liner shipping company. It proceeds to investigate the optimal sailing speed of container ships on each leg of each ship route in a liner shipping network while considering transshipment and container routing. This problem is formulated as a mixed-integer nonlinear programming model. In view of the convexity, non-negativity, and univariate properties of the bunker Consumption Function, an efficient outer-approximation method is proposed to obtain an e-optimal solution with a predetermined optimality tolerance level e. The proposed model and algorithm is applied to a real case study for a global liner shipping company.
Christopher D Carroll - One of the best experts on this subject based on the ideXlab platform.
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a theory of the Consumption Function with and without liquidity constraints
Journal of Economic Perspectives, 2001Co-Authors: Christopher D CarrollAbstract:Fifteen years ago, Milton Friedman’s 1957 treatise A Theory of the Consumption Function seemed badly dated. Dynamic optimization theory had not been employed much in economics when Friedman wrote, and utility theory was still comparatively primitive, so his statement of the “permanent income hypothesis” never actually specified a formal mathematical model of behavior derived explicitly from utility maximization. Instead, Friedman relied at crucial points on intuition and verbal descriptions of behavior. Although these descriptions sounded plausible, when other economists subsequently found multiperiod maximizing models that could be solved explicitly, the implications of those models differed sharply from Friedman’s intuitive description of his “model.” Furthermore, empirical tests in the 1970s and 1980s often rejected these rigorous versions of the permanent income hypothesis in favor of an alternative hypothesis that many households simply spent all of their current income. Today, with the benefit of a further round of mathematical (and computational) advances, Friedman’s (1957) original analysis looks more prescient than primitive. It turns out that when there is meaningful uncertainty in future labor income, the optimal behavior of moderately impatient consumers is much better described by Friedman’s original statement of the permanent income hypothesis than by the later explicit maximizing versions. Furthermore, in a remarkable irony, much of the empirical evidence that rejected the permanent income hypothesis as specified in tests of the 1970s and 1980s is actually consistent both with Friedman’s original description of the model and with the new version with serious uncertainty. There are four key differences between the explicit maximizing models
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on the concavity of the Consumption Function
1998Co-Authors: Christopher D Carroll, Miles S KimballAbstract:Zeldes (1989), Carroll (1992,1993), and others have shown that optimal Consumption behavior for consumers facing income uncertainty can be remarkably different from the certainty-equivalent case. Carroll (1992) observes that many of the differences can be attributed to the concavity of the Consumption Function under uncertainty, but he does not describe the conditions under which the Consumption Function will be concave. We show that if labor income is stochastic, the Consumption Function will be concave for many commonly used utility Functions, and if both labor income and capital income are stochastic, the Consumption Function is concave for an even broader group of utility Functions.
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on the concavity of the Consumption Function
Econometrica, 1996Co-Authors: Christopher D Carroll, Miles S KimballAbstract:At least since Keynes (1935), many economists have had the intuition that the marginal propensity to consume out of wealth declines as wealth increases. Nonetheless, standard perfect-certainty and certainty equivalent versions of intertemporal optimizing models of Consumption imply a marginal propensity to consume that is unrelated to the level of household wealth. We show that adding income uncertainty to the standard optimization problem induces a concave Consumption Function in which, as Keynes suggested, the marginal propensity to consume out of wealth or transitory income declines with the level of wealth.
Abgottspon Hubert - One of the best experts on this subject based on the ideXlab platform.
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Short-term hydro scheduling of a variable speed pumped storage hydropower plant considering head loss in a shared penstock
IoP, 2019Co-Authors: Kong Jiehong, Skjelbred, Hans Ivar, Abgottspon HubertAbstract:In this paper we present in detail how to handle the nonlinear and state-dependent elements in the power Consumption Function (PCF) of a variable speed pump (VP). The Function is formulated by piecewise linear approximations with dynamically specified breakpoints. In the proposed method, the head variation resulting from the change in the water level of the upstream and downstream reservoirs and head loss caused by the friction of water on the penstock wall are both considered. Furthermore, we put forward a heuristic to incorporate the head loss in a penstock shared by multiple VPs in a short-term hydro scheduling tool used for daily operation in the real world. The case study is taken from the Limmern pumped storage hydropower plant with 4×250 MW reversible Francis pump-turbines with variable speed technology. Each penstock is shared by two of the four units. The numerical results demonstrate that the appropriate formulation of the PCF and the accurate representation of the head loss in a shared penstock are crucial for obtaining realistic and optimal scheduling for VPs
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Short-term hydro scheduling of a variable speed pumped storage hydropower plant considering head loss in a shared penstock
'IOP Publishing', 2019Co-Authors: Kong Jiehong, Skjelbred, Hans Ivar, Abgottspon HubertAbstract:In this paper we present in detail how to handle the nonlinear and state-dependent elements in the power Consumption Function (PCF) of a variable speed pump (VP). The Function is formulated by piecewise linear approximations with dynamically specified breakpoints. In the proposed method, the head variation resulting from the change in the water level of the upstream and downstream reservoirs and head loss caused by the friction of water on the penstock wall are both considered. Furthermore, we put forward a heuristic to incorporate the head loss in a penstock shared by multiple VPs in a short-term hydro scheduling tool used for daily operation in the real world. The case study is taken from the Limmern pumped storage hydropower plant with 4×250 MW reversible Francis pump-turbines with variable speed technology. Each penstock is shared by two of the four units. The numerical results demonstrate that the appropriate formulation of the PCF and the accurate representation of the head loss in a shared penstock are crucial for obtaining realistic and optimal scheduling for VPs.Short-term hydro scheduling of a variable speed pumped storage hydropower plant considering head loss in a shared penstockpublishedVersio
Rabiah Rustam - One of the best experts on this subject based on the ideXlab platform.
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determinants of electricity Consumption Function in pakistan old wine in a new bottle
Energy Policy, 2012Co-Authors: Khalid Zaman, Muhammad Mushtaq Khan, Mehboob Ahmad, Rabiah RustamAbstract:Abstract The objective of the study is to re-investigate the multivariate electricity Consumption Function for Pakistan, particularly, economic growth, foreign direct investment and population growth over a 36-year time period, i.e., between 1975 and 2010. The study employed the bounds-testing procedure for cointegration which examines the short-run and long-run estimates. Dynamic short-run causality test is applied to determine the causality direction between electricity Consumption and its determinants, by using Wald- F statistics. The results reveal that determinants of electricity Consumption Function are cointegrated and influx of foreign direct investment, income and population growth is positively related to electricity Consumption in Pakistan. However, the intensity of these determinants is different on electricity Consumption. If there is 1% increase in income, foreign direct investment and population growth; electricity Consumption increases by 0.973%; 0.056% and 1.605%, respectively. This infers that income, foreign direct investment and population growth induce an increase in electricity Consumption in Pakistan. Dynamic short-run causality test indicates that there has been unidirectional causality which is running from population growth to electricity Consumption in Pakistan.
Kong Jiehong - One of the best experts on this subject based on the ideXlab platform.
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Short-term hydro scheduling of a variable speed pumped storage hydropower plant considering head loss in a shared penstock
IoP, 2019Co-Authors: Kong Jiehong, Skjelbred, Hans Ivar, Abgottspon HubertAbstract:In this paper we present in detail how to handle the nonlinear and state-dependent elements in the power Consumption Function (PCF) of a variable speed pump (VP). The Function is formulated by piecewise linear approximations with dynamically specified breakpoints. In the proposed method, the head variation resulting from the change in the water level of the upstream and downstream reservoirs and head loss caused by the friction of water on the penstock wall are both considered. Furthermore, we put forward a heuristic to incorporate the head loss in a penstock shared by multiple VPs in a short-term hydro scheduling tool used for daily operation in the real world. The case study is taken from the Limmern pumped storage hydropower plant with 4×250 MW reversible Francis pump-turbines with variable speed technology. Each penstock is shared by two of the four units. The numerical results demonstrate that the appropriate formulation of the PCF and the accurate representation of the head loss in a shared penstock are crucial for obtaining realistic and optimal scheduling for VPs
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Short-term hydro scheduling of a variable speed pumped storage hydropower plant considering head loss in a shared penstock
'IOP Publishing', 2019Co-Authors: Kong Jiehong, Skjelbred, Hans Ivar, Abgottspon HubertAbstract:In this paper we present in detail how to handle the nonlinear and state-dependent elements in the power Consumption Function (PCF) of a variable speed pump (VP). The Function is formulated by piecewise linear approximations with dynamically specified breakpoints. In the proposed method, the head variation resulting from the change in the water level of the upstream and downstream reservoirs and head loss caused by the friction of water on the penstock wall are both considered. Furthermore, we put forward a heuristic to incorporate the head loss in a penstock shared by multiple VPs in a short-term hydro scheduling tool used for daily operation in the real world. The case study is taken from the Limmern pumped storage hydropower plant with 4×250 MW reversible Francis pump-turbines with variable speed technology. Each penstock is shared by two of the four units. The numerical results demonstrate that the appropriate formulation of the PCF and the accurate representation of the head loss in a shared penstock are crucial for obtaining realistic and optimal scheduling for VPs.Short-term hydro scheduling of a variable speed pumped storage hydropower plant considering head loss in a shared penstockpublishedVersio
