Browsing by Subject "Distribution systems"

Now showing 1 - 5 of 5

Open Access
A hierarchical solution approach for a multicommodity distribution problem under a special cost structure
(2012) Koca, E.; Yıldırım, E. A.
Motivated by the spare parts distribution system of a major automotive manufacturer in Turkey, we consider a multicommodity distribution problem from a central depot to a number of geographically dispersed demand points. The distribution of the items is carried out by a set of identical vehicles. The demand of each demand point can be satisfied by several vehicles and a single vehicle is allowed to serve multiple demand points. For a given vehicle, the cost structure is dictated by the farthest demand point from the depot among all demand points served by that vehicle. The objective is to satisfy the demand of each demand point with the minimum total distribution cost. We present a novel integer linear programming formulation of the problem as a variant of the network design problem. The resulting optimization problem becomes computationally infeasible for real-life problems due to the large number of integer variables. In an attempt to circumvent this disadvantage of using the direct formulation especially for larger problems, we propose a Hierarchical Approach that is aimed at solving the problem in two stages using partial demand aggregation followed by a disaggregation scheme. We study the properties of the solution returned by the Hierarchical Approach. We perform computational studies on a data set adapted from a major automotive manufacturer in Turkey. Our results reveal that the Hierarchical Approach significantly outperforms the direct formulation approach in terms of both the running time and the quality of the resulting solution especially on large instances.
Open Access
High-precision laser master oscillators for optical timing distribution systems in future light sources
(European Physical Society Accelerator Group (EPS-AG), 2006) Winter, A.; Schmüser, P.; Ludwig, F.; Schlarb, H.; Chen, J.; Kärtner, F. X.; ilday, F. ÖMER
An ultra-stable timing and synchronization system for linac-driven FELs has been designed providing 10 fs precision over distances of several kilometers. Mode-locked fiber lasers serve as master oscillators. The optical pulse train is distributed through length-stabilized fiber links. The layout of the optical synchronization system and its phase noise properties are described. A prototype system has been tested in an accelerator environment and has achieved the required stability.
Open Access
An integrated femtosecond timing distribution system for XFELS
(Massachusetts Institute of Technology, 2006) Kim, J.; Burnham, J.; Chen, J.; Kartner, F. X.; İlday, Fatih Ömer; Ludwig, F.; Schlarb, H.; Winter, A.; Ferianis, M.; Cheever, D.
Tightly synchronized lasers and RF-systems with timing jitter in the few femtoseconds range are necessary sub-systems for future X-ray free electron laser facilities. In this paper, we present an optical-microwave phase detector that is capable of extracting an RF-signal from an optical pulse stream without amplitude-to-phase conversion. Extraction of a microwave signal with 3 fs timing jitter (from 1 Hz to 10 MHz) from an optical pulse stream is demonstrated. Scaling of this component to subfemtosecond resolution is discussed. Together with low noise mode-locked lasers, timing-stabilized optical fiber links and compact optical cross-correlators, a flexible femtosecond timing distribution system with potentially sub-10 fs precision over distances of a few kilometers can be constructed. Experimental results on both synchronized RF and laser sources will be presented.
Open Access
Organization and functioning of liberalized electricity markets: An overview of the Dutch market
(Elsevier Ltd, 2015) Tanrisever, F.; Derinkuyu, K.; Jongen, G.
Abstract In this paper, we examine the organization and the functioning of the Dutch electricity market. First we describe the organization of the Dutch electricity supply chain and the role of the main market participants including the transmission system operator, distribution system operators, program responsible parties and metering companies. We then describe the organization of financial trading and clearing mechanism of electricity through the organized futures exchange (The European Energy Derivatives Exchange), and the spot market (Amsterdam Power Exchange) which includes the day-ahead market and intra-day markets. We also detail the functioning of the imbalance market and reserve capacity management in the Netherlands. Through a set of numerical analysis, we provide an exploratory analysis of the APX day-ahead spot prices and the real-time imbalance prices using electricity price data from 2002 to 2013. We observe the price spikes both in the day-ahead and imbalance markets usually occur around 6-10 AM and 5-7 PM. We also observe that in the imbalance market system overages happen significantly more often than shortages pointing out that the market tends to buy more than what is demanded. This could be explained by the risk attitude of the market participants in the imbalance market.
Embargo
Risk pooling under demand and price uncertainty
(Elsevier BV, 2023-11-22) Güllü, Refik; Erkip, Nesim
This paper studies purchasing a commodity or a perishable item under stochastically evolving and correlated prices for a distribution system environment. We consider the central purchasing of the commodity under the demand process correlated with the random price and decide on the timing and quantity of allocation to demand locations. As an implementation of the physical pooling concept, we investigate the benefits of pooling price and demand risk when the forward purchase is realized for all demand locations. We also study the benefits of informational pooling concepts by deciding on the allocation timing. Even when the demand locations are independent entities, organizing joint purchasing of a commodity may take advantage of economies of scale with a more reliable and less expensive delivery option. We develop a model to guide the purchasing and allocation of quantities and employ multi-echelon inventory theory methods and stochastic processes commonly used in financial engineering and operations management literature.