Papers by cristina serban
Studies in Informatics and Control, 2016
One indicator for efficient management in a port is the time spent by a ship in the port quays. T... more One indicator for efficient management in a port is the time spent by a ship in the port quays. The time allowed for loading-unloading into a specialized quay is mentioned in the management contract. Because the cost of the overtime is very high, it is very important to have a special plan to unload the container ship in a short time. Given the number of containers to be unloaded from a vessel and the initial state (in regards of number of slots) of a block, the genetic algorithm that we propose in this paper finds the plan of container stacking in the block, whilst the objective function is to minimize summation of handling time of yard crane in placing the containers in the available storage cells of the stacking area. The performance of the proposed method is evaluated through several sets of tests on control parameters of the algorithm.
Studies in Informatics and Control, 2017
At each port of destination, some containers are unloaded from a vessel and stored in the termina... more At each port of destination, some containers are unloaded from a vessel and stored in the terminal to be delivered to their customers. One of the strategies used to arrange the containers in a terminal is residence time strategy: based on their delivery deadlines, each incoming container being assigned to a priority class. The aim of this study is to determine a valid arrangement of incoming containers in a block (part) of the terminal, in the shortest amount of time, with higher priority containers located above lower priority ones. In this way, some of the main objectives of a container terminal may be achieved: avoiding further reshuffles (number of relocations) and reducing the vessel berthing time. We developed a genetic algorithm and its performance is evaluated against a random stacking strategy used as benchmark for the experiments, and through several sets of tests on control parameters. All the tests showed that, if a reliable estimation of the delivery time can be assigned to every incoming container, the proposed method may be a useful tool for container terminal operators.
Archives of Transport, 2016
The transportation problem, as a particular case of a linear programme, has probably the highest ... more The transportation problem, as a particular case of a linear programme, has probably the highest relative frequency with which appears in applications. At least in its classical formulation, it involves demands and supplies. When, for practical reasons, the total demand cannot satisfy the total supply, the problem becomes unbalanced and inconsistent, and must be reformulated as e.g. finding a least squares solution of an inconsistent system of linear inequalities. A general iterative solver for this class of problems has been proposed by S. P. Han in his 1980 original paper. The drawback of Han’s algorithm consists in the fact that it uses in each iteration the computation of the Moore-Penrose pseudoinverse numerical solution of a subsystem of the initial one, which for bigger dimensions can cause serious computational troubles. In order to overcome these difficulties we propose in this paper a general projection-based minimal norm solution approximant to be used within Han-type alg...
Proceedings of the 14th Wseas International Conference on Computers Part of the 14th Wseas Cscc Multiconference Volume Ii, Jul 23, 2010
The paper presents the GESKEE (Global Econometric Scaling using Knowledge on Earthquake Effects) ... more The paper presents the GESKEE (Global Econometric Scaling using Knowledge on Earthquake Effects) database developed by authors which is an indispensable tool in econometric scaling approach of vulnerability and risk on building stock to major seismic events. Due to the use of a large amount of information in GESKEE Disaster Scale, it was a high necessity to create this database in order to automate the calculation process, to manage the data easier and also to represent the results in a manner as suggestive as possible.
Extreme Weather and Impacts of Climate Change on Water Resources in the Dobrogea Region
A major issue in time series analysis and particularly in the study of meteorological time series... more A major issue in time series analysis and particularly in the study of meteorological time series is to model and to predict their behaviour. The first step to reach this goal is the data analysis. It is what we shall do in this article, focusing on the long range dependence (LRD) property. Various estimators of LRD have been proposed. Their accuracy have been generally tested using simulated time series since sometimes only their asymptotic property are known, or worse, no asymptotic property have been proved. For ten annual and monthly data series collected in Dobrudja region, for 41 years, we did the statistical analysis and we compare the results.
TransNav, the International Journal on Marine Navigation and Safety of Sea Transportation, 2014
In this paper we analyse several ways to compute the weights from the Regularized Han (RH) algori... more In this paper we analyse several ways to compute the weights from the Regularized Han (RH) algorithm, the regularized version of Han's algorithm for approximating the least squares solutions of inconsistent (incompatible) systems of linear inequalities. We tested our approaches on a classical transportation problem, aiming to provide a cost optimized solution to real world transportation problems, which often are unbalanced and inconsistent. http://www.transnav.eu the International Journal on Marine Navigation and Safety of Sea Transportation Volume 8 Number 4
PAMM, 2013
In 1980 S.P. Han proposed a finitely terminating (in exact arithmetic) algorithm for solving an i... more In 1980 S.P. Han proposed a finitely terminating (in exact arithmetic) algorithm for solving an inconsistent system of linear inequalities in a least squares sense. This algorithm uses a singular value decomposition of a submatrix of the problem matrix on each iteration, making it impractical for all but only smaller problems. In this paper we show that a modification of Han's algorithm allows us to introduce an iterative approximation to the singular value decomposition solution.
Proceedings of the 13th …, 2011
International journal of Computer Networks & Communications, 2011
Studies in Informatics and Control
WSEAS Transactions on …, 2010
Abstract: - Econometric scaling approach of vulnerability and risk on building stock to major sei... more Abstract: - Econometric scaling approach of vulnerability and risk on building stock to major seismic events is essential for understanding the impact and the consequences of these earthquakes. It also has a predictive value for loss estimation of next events. Due to use of ...
TransNav, the International Journal on Marine Navigation and Safety of Sea Transportation, 2014
PAMM, 2013
In 1980 S.P. Han proposed a finitely terminating (in exact arithmetic) algorithm for solving an i... more In 1980 S.P. Han proposed a finitely terminating (in exact arithmetic) algorithm for solving an inconsistent system of linear inequalities in a least squares sense. This algorithm uses a singular value decomposition of a submatrix of the problem matrix on each iteration, making it impractical for all but only smaller problems. In this paper we show that a modification of Han's algorithm allows us to introduce an iterative approximation to the singular value decomposition solution.
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Papers by cristina serban