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EN
The Department of Geotechnical Equipment is involved since two decades in research and development of teeth, buckets and other active parts of different kinds of mining excavators. The actual study is devoted to reveal new difficulties arising when excavating in the sandstone as overburden rock, mainly regarding the buckets of bucket wheel excavators. As a consequence of the increased cutting forces, the buckets suffer deformations. In case of the change of cutting geometry, as a result of renewal (strengthening) of buckets, the winning becomes no-optimal and there will be more breakdowns. The investigations made and reported in the actual paper led to provide guidelines for a better renewal method of buckets.
PL
Department of Geotechnical Equipment od dwóch dekad zajmuje się badaniami i rozwojem zębów, czerpaków oraz innych aktywnych elementów różnych maszyn podstawowych. Aktualne badania służą rozwiązaniu problemów związanych z pracą koparek wielonaczyniowych kołowych w nadkładzie zawierającym piaskowce. W wyniku pracy w takim środowisku, a co za tym idzie, zwiększonych sił skrawania, czerpaki koparek ulegają odkształceniom. Zmiana geometrii procesu cięcia skały, która jest rezultatem renowacji czerpaków prowadzi do nieoptymalnego urabiania skutkującego zwiększoną ilością awarii. Przeprowadzone badania, przedstawione w niniejszym artykule, doprowadziły do opracowania wytycznych nowej, lepszej metody renowacji czerpaków.
EN
A widely used class of approximate pattern matching algorithms work in two stages, the first being a filtering stage that uses spaced seeds to quickly discards regions where a match is not likely to occur. The design of effective spaced seeds is known to be a hard problem. In this setting, we propose a family of lossless spaced seeds for matching with up to two errors based on mathematical objects known as perfect rulers. We analyze these seeds with respect to the tradeoff they offer between seed weight and the minimum length of the pattern to be matched. We identify a specific property of rulers, namely their skewness, which is closely related to the minimum pattern length of the derived seeds. In this context, we study in depth the specific case of Wichmann rulers and investigate the generalization of our approach to the larger class of unrestricted rulers. Although our analysis is mainly of theoretical interest, we show that for pattern lengths of practical relevance our seeds have a larger weight, hence a better filtration efficiency, than the ones known in the literature.
EN
This paper presents an application of methods from the machine learning domain to solving the task of DNA sequence recognition. We present an algorithm that learns to recognize groups of DNA sequences sharing common features such as sequence functionality. We demonstrate application of the algorithm to find splice sites, i.e., to properly detect donor and acceptor sequences. We compare the results with those of reference methods that have been designed and tuned to detect splice sites. We also show how to use the algorithm to find a human readable model of the IRE (Iron-Responsive Element) and to find IRE sequences. The method, although universal, yields results which are of quality comparable to those obtained by reference methods. In contrast to reference methods, this approach uses models that operate on sequence patterns, which facilitates interpretation of the results by humans.
EN
The existing literature, including records of both fossil and extant echinoid encrustation, is quantitatively analysed and reviewed. This shows that echinoid encrustation (number of encrusted echinoid taphocoenoses) has increased nearly continuously and dramatically to the present day, as confirmed by linear regression values of more than 85 per cent. It also demonstrates that current levels of echinoid fouling stabilised by the Miocene, while there has been a more or less continuous record of echinoid encrustation since the Late Cretaceous. Several increases have been identified since echinoid encrustation first noted occurrence from the Late Carboniferous. This trend is explained as the probable result of corresponding increases in productivity (richness, biomass, energetics, ecospace utilisation) and resources in the marine environment, including epibionts and their hosts. This conclusion matches other indicators, including the number and thickness of shell beds, bioerosion and predation intensity or biodiversity. The trajectory might have been altered to some degree by biases (e.g. selective recording, sampling effort, outcrop area, rock volume) in the same way as palaeobiodiversity estimates. Two recognised long-term gaps in echinoid encrustation (Upper Ordovician–Lower Carboniferous and Permian–Lower Cretaceous) are explained in part as bias and as biological and taphonomic signals. These gaps are caused mostly by the rapid disarticulation of Palaeozoic-type echinoids, the methodology applied here, and a lack of interest in the encrustation of Jurassic echinoids. Conversely, three short-term gaps in the Cenozoic are interpreted exclusively as bias. If correct, the present study demonstrates quantitatively the step-wise increase of productivity through time. It also suggests potential focus on further study, including the collection of new data from the field and pre-existing collections, as best for other encrustation proxies (e.g., percent of coverage by epibionts, ratio of encrusted to nonencrusted shells, taxa richness or numerical abundance of sclerobionts) in cases of large-scale analyses.
EN
With the vastly growing data resources on the Internet, XML is one of the most important standards for document management. Not only does it provide enhancements to document exchange and storage, but it is also helpful in a variety of information retrieval tasks. Document clustering is one of the most interesting research areas that utilize semi-structural nature of XML. In this paper, we put forward a new XML clustering algorithm that relies solely on document structure. We propose the use of maximal frequent subtrees and an operator called Satisf/Violate to divide documents into groups. The algorithm is experimentally evaluated on real and synthetic data sets with promising results.
PL
Artykuł dotyczy analizy wzorców danych dotyczących stanu ruchu pojazdów. W szczególności skupiono się na analizie częstych sekwencji. Analizowane dane zostały pozyskane w oparciu o wieloagentowy symulator do modelowania i optymalizacji ruchu drogowego.
EN
The paper concerns the analysis of data about road traffic. We are focusing our analysis on the frequent sequences. The analysed data was obtained using multi-agent simulator for modelling and optimisation of road traffic.
EN
To explore and describe the species richness patterns along altitudinal, high mountain gradients, two transects . northern exposure (YG) and southern exposure (TD) at Mt. Jiuding (1200.4200 m) in Western China (31[degrees]13'- 31[degrees]46'N, 103[degrees]29'-104[degrees]05'E) were selected. They differ from south to north in climate conditions and vegetation zonation, and each transect was sampled according to a uniform method. Every 200 m along the altitudinal gradient we set a sampling belt of 3000 m x 5 m to record the tree species, and 30 plots of 5 m x 5 m within every vegetation belt were used to investigate shrub and herb species. We compared the composition of plant species and calculated the coefficient of similarity between the two transects. A Generalized Additive Model (GAM) was used to describe the richness patterns. For the whole Mt. Jiuding, the richness at all three levels (species, genus and family) showed a monotonically decreasing pattern. As for the different growth forms, richness of the trees, shrubs and pteridophytes showed hump-shaped patterns; and herbs showed a slow decreasing pattern along the altitudinal gradients. In TD transect, the richness of species, genus and family also showed monotonically decreasing patterns; tree richness decreased with the increase of altitude; the shrub richness showed a humpshaped pattern; but pteridophytes and other herbs showed wave-like patterns. In YG transect, altitudinal gradient of richness at different taxonomic levels all showed hump-shaped patterns; and the species richness patterns for different growth forms peaked at middle attitude except for the graminoids and other herbs. The evolutionary history of the vegetation in Mt. Jiuding was quite consistent, and different richness patterns along altitudinal gradients might be resulted from different contemporary ecological conditions. Human disturbance and different range of altitudinal gradients were also important factors for different richness patterns between the two transects. In our study, species in different growth forms showed different altitudinal patterns, but those species with similar requirements to environmental conditions showed similar richness patterns along altitudinal gradients.
8
Content available remote The effect of refractory coating permeability on the Lost Foam Process
EN
The article analyses the effect of refractory coating permeability on the process of casting manufacture by the Lost Foam technique. The analysis was focussed on simulation tests examining the effect of coating permeability on the mould cavity filling rate, pressure in gas gap, and the size of this gap. In simulation tests of the Lost Foam Process, a mathematical model of the process presented in this study and the author's own computation algorithm were used. The computations have proved that with increasing permeability of the protective coating, the pouring rate increases, too, while pressure of gas in the gas gap and the size of the gap are decreasing. The increasing pouring rate ensures correct making of castings, even if their shape is very intricate and the wall cross-sections are very small. Smaller size of the gas gap and lower gas pressure in the gap reduce the risk of mould damage. The author's own investigations confirmed the importance of the refractory coating permeability and its effect on the casting process, mould pouring rate - in particular.
EN
At the Department of Manufacturing systems at Technical University of Liberec the FDM method of RP with Stratasys PRODIGY is applied. Here are expressed some experiences with models grater than working area, made of more parts that were assembled by gluing and mechanical support. Explained are the new possibilities of investment castings describing material behaviour and possibility to extend material choices. Development of non-contact scanning head and application in fast tool manufacture e.g. moulds for polyurethane parts, made of composites and testing their features.
EN
This paper addresses the problem of fixed channel assignment in cellular communication systems with nonuniform traffic distribution. The objective of the channel assignment is to minimise the average blocking probability. Methods for finding a good allocation can be based on first building a number of sets of cochannel cells or allocation patterns and then assigning them to channels. This usually implies that only a subset of the feasible region is attainable. The approach suggested in this paper uses the concept of packed pattern, since all patterns in an optimal solution will be of that kind. With a constructive method, the entire set of packed patterns is built and used in the optimisation process. The complexity (large-scale and nonlinearity) of the resulting problem suggested the use of general search procedures (local search, tabu search, simulated annealing, etc.), which have the further advantage of flexibility when dealing with extensions to the problem. A neighbouring structure was used, that facilitated the calculations while still allowing for the search in the entire solution space. A summary of extensive numerical experiments is presented. The outcome is an improvement over previous results.
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