Learning Styles of Computer Programming Students: A Middle Eastern and American Comparison

Although there are many studies addressing the relationship of learning style to outcomes in engineering courses, few have attempted direct cross-cultural comparisons. This study investigates similarities and differences in the learning styles of computer science and engineering students at a Middle Eastern institution and an American university in the Midwestern United States. Comparative data on student learning style profiles and course outcomes suggest that, despite vast cultural differences, strong similarities exist between learning styles of these students. Seemingly, a consistent pattern in how these students learn across cultures also exists. These findings have significant implications for the creation of globally effective teaching materials     

The strong partial transitive-closure problem: algorithms andperformance evaluation

The development of efficient algorithms to process the different forms of transitive-closure (TC) queries within the context of large database systems has recently attracted a large volume of research efforts. In this paper, we present two new algorithms suitable for processing one of these forms, the so called strong partially instantiated transitive closure, in which one of the query's arguments is instantiated to a set of constants and the processing of which yields a set of tuples that draw their values from both of the query's instantiated and uninstantiated arguments. These algorithms avoids the redundant computations and high storage cost found in a number of similar algorithms. Using simulation, this paper compares the performance of the new algorithms with those found in literature and shows clearly the superiority of the new algorithms     

Efficient algorithms for the instantiated transitive closurequeries

The performances of several algorithms suitable for processing an important class of recursive queries called the instantiated transitive closure (TC) queries are studied and compared. These algorithms are the wavefront, δ-wavefront, and a generic algorithm called super-TC. During the evaluation of a TC query, the first two algorithms may read a given disk page more than once, whereas super-TC reads the disk page at most once. A comprehensive performance evaluation of these three algorithms using rigorous analytical and simulation models is presented. The study reveals that the relative performance of the algorithms is a strong function of the parameters which characterize the processed TC query and the relation referenced by that query. The superiority of one of the super-TC variants over all of the other presented algorithms is shown     

An efficient database transitive closure algorithm

The integration of logic rules and relational databases has recently emerged as an important technique for developing knowledge management systems. An important class of logic rules utilized by these systems is the so-called transitive closure rules, the processing of which requires the computation of the transitive closure of database relations referenced by these rules. This article presents a new algorithm suitable for computing the transitive closure of very large database relations. This algorithm proceeds in two phases. In the first phase, a general graph is condensed into an acyclic one, and at the same time a special sparse matrix is formed from the acyclic graph. The second phase is the main one, in which all the page I/O operations are minimized by removing most of the redundant operations that appear in previous algorithms. Using simulation, this article also studies and examines the performance of this algorithm and compares it with the previous algorithms.     

The join algorithms on a shared-memory multiprocessor databasemachine

The authors develop and present a large set of parallel algorithms for implementing the join operation on a shared-memory multiprocessor database machine. The development of these algorithms follows a structured approach. The major steps involved in the processing of the join operation by the machine are first identified. Then, alternative join algorithms are constructed by concatenating the different ways of performing these steps. A study of the performance of the proposed algorithms is presented. This study shows, among other things, that for a given hardware configuration there is not just one overall best performing join algorithm, but rather different algorithms score the best performance, depending on the characteristics of the data participating in the join operation     

Use of transplanted Zebra mussels (Dreissena polymorpha) to assess the bioavailability of microcontaminants in Flemish surface waters

Zebra mussels (Dreissena polymorpha) were translocated in cages to 56 water bodies in Flanders (Belgium) during summer 2001. After six weeks, concentrations of polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), p,p'-DDE, and trace metals were measured in the transplanted mussels. It was investigated whether total dissolved water and sediment pollutant levels or bioaccumulation factors (BAFs) and biota-sediment accumulation factors (BSAFs) were predictive for mussel tissue levels. The sample sites covered a broad range both in terms of the type and concentration of the pollutants, and this was reflected in large differences in tissue concentrations of all pollutants among the sites. The highest pollutant levels in mussels were among the highest reported in the literature. For Cd and Zn levels up to 33 and 1994 microg/g dry wt. respectively were found. The lowest levels were comparable to those from uncontaminated sites in Europe and the U.S. For Cd and Zn respectively 51 and 75% of the variation in tissue levels was described. For both metals, dissolved and particulate metal contributed to the variation in accumulation. For other pollutants, relationships between tissue concentration and water or sediment concentration were weak or nonsignificant. Then the measured environmental factors (dissolved calcium, pH, oxygen, organic carbon and clay content in the sediment) were taken into account applying multiple regression analysis, and no increase in the described variation of pollutant accumulation was observed. The BAF and BSAF for all pollutants varied up to 1000-fold even after TOC-normalization. Clear negative relationships were found between BAFs/ BSAFs and environmental levels. However, even at constant environmental concentrations a 10- to 100-fold variation in BAFs/BSAFs was observed. This study illustrated the need for biological monitoring since neither environmental