Assessment of institutional and policy conditions in Turkey: implications for the implementation of autonomous desalination systems

This paper provides an overview of the existing situation in Turkey and studies how this could become more attractive for the implementation of autonomous desalination systems (ADS). The analysis covers relevant policy and programmes, legislation and administrative procedures, water prices and subsidies, institutional framework of the water sector, capacity building and general awareness. In general, the framework conditions in Turkey are relatively good. The policy direction towards decentralisation will favour ADS. Many programmes offer support for water supply and renewable energy and there are simplified administrative procedures. On the other hand, water policy favours traditionally centralised conventional solutions. The awareness about ADS is very low and the research in the field still restricted. In this paper, concrete recommendations have been developed that suggest simple steps for the establishment of ADS in Turkey.     

A statistical significance testing approach to mining the most informative set of patterns

Hypothesis testing using constrained null models can be used to compute the significance of data mining results given what is already known about the data. We study the novel problem of finding the smallest set of patterns that explains most about the data in terms of a global p value. The resulting set of patterns, such as frequent patterns or clusterings, is the smallest set that statistically explains the data. We show that the newly formulated problem is, in its general form, NP-hard and there exists no efficient algorithm with finite approximation ratio. However, we show that in a special case a solution can be computed efficiently with a provable approximation ratio. We find that a greedy algorithm gives good results on real data and that, using our approach, we can formulate and solve many known data-mining tasks. We demonstrate our method on several data mining tasks. We conclude that our framework is able to identify in various settings a small set of patterns that statistically explains the data and to formulate data mining problems in the terms of statistical significance.     

Improved throughput bit-serial multiplier for GF(2) fields

High throughput is a crucial factor in bit-serial GF(2^m) fields multiplication for a variety of different applications including cryptography, error coding detection and computer algebra. The throughput of a multiplier is dependent on the required number of clock cycles to reach a result and its critical path delay. However, most bit-serial GF(2^m) multipliers do not manage to reduce the required number of clock cycles below the threshold of m clock cycles without increasing dramatically their critical path delay. This increase is more evident if a multiplier is designed to be versatile. In this article, a new versatile bit-serial MSB multiplier for GF(2^m) fields is proposed that achieves a 50% increase on average in throughput when compared to other designs, with a very small increase in its critical path delay. This is achieved by an average 33.4% reduction in the required number of clock cycles below m. The proposed design can handle arbitrary bit-lengths upper bounded by m and is suitable for applications where the field order may vary.     

Satellite handover techniques for LEO networks

Low earth orbit satellite constellations could play an important role in future mobile communication networks due to their characteristics, such as global coverage and low propagation delays. However, because of the non‐stationarity of the satellites, a call may be subjected to handovers, which can be cell or satellite handovers. Quite many techniques have been proposed in the literature dealing with the cell handover issue. In this paper, a satellite handover procedure is proposed, that investigates and exploits the partial satellite diversity (namely, the existing common coverage area between contiguous satellites) in order to provide an efficient handover strategy, based always on a tradeoff of blocking and forced termination probabilities for a fair treatment of new and handover calls. Three different criteria were examined for the selection of a satellite. Each one of them could be applied either to new or handover calls, therefore we investigated nine different service schemes. A simulation tool was implemented in order to compare the different service schemes and simulation results are presented at the end of the paper. Copyright © 2004 John Wiley & Sons, Ltd.     

The GMAP: a versatile tool for physical data independence

Physical data independence is touted as a central feature of modern database systems. It allows users to frame queries in terms of the logical structure of the data, letting a query processor automatically translate them into optimal plans that access physical storage structures. Both relational and object-oriented systems, however, force users to frame their queries in terms of a logical schema that is directly tied to physical structures. We present an approach that eliminates this dependence. All storage structures are defined in a declarative language based on relational algebra as functions of a logical schema. We present an algorithm, integrated with a conventional query optimizer, that translates queries over this logical schema into plans that access the storage structures. We also show how to compile update requests into plans that update all relevant storage structures consistently and optimally. Finally, we report on experiments with a prototype implementation of our approach that demonstrate how it allows storage structures to be tuned to the expected or observed workload to achieve significantly better performance than is possible with conventional techniques. Edited by Matthias Jarke, Jorge Bocca, Carlo Zaniolo. Received September 15, 1994 / Accepted September 1, 1995     

FEC in optical communications - A tutorial overview on the evolution of architectures and the future prospects of outband and inband FEC for optical communications

The recent establishment of the 10/40 Gbps technology in DWDM optical links heralds a new era of bandwidth abundance, in response to an explosive growth of services provided through the Internet. Forward error correction (FEC) is one of the key-enabling elements in this long-awaited achievement. Borrowed from the wireless world, FEC was initially introduced in wavelength-division multiplex (WDM) optical-systems to combat amplified spontaneous emission (ASE), a form of noise native in optical amplifiers (OAs). These first generation FEC systems have been associated with a coding-gain of approximately 6 dB. However, as transmission rates gradually scaled towards 10 Gbps, other optical-impairments gained in significance, primarily nonlinear (NL) effects but also chromatic-dispersion (CD) and polarization mode dispersion (PMD). FEC turned out to be invaluable in mitigating these impairments as well