Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: odcinek czasu

Sortuj według:

Ogranicz wyniki do:

Modeling and querying facts with period timestamps in data warehouses

Mahlknecht Giovanni, Dignös Anton, Kozmina Natalija

International Journal of Applied Mathematics and Computer Science

2019

Vol. 29, no. 1

31--49

In this paper, we study various ways of representing and querying fact data that are time-stamped with a time period in a data warehouse. The main focus is on how to represent the time periods that are associated with the facts in order to support convenient and efficient aggregations over time. We propose three distinct logical models that represent time periods as sets of all time points in a period (instant model), as pairs of start and end time points of a period (period model), and as atomic units that are explicitly stored in a new period dimension (period∗ model). The period dimension is enriched with information about the days of each period, thereby combining the former two models. We use four different classes of aggregation queries to analyze query formulation, query execution, and query performance over the three models. An extensive empirical evaluation on synthetic and real-world datasets and the analysis of the query execution plans reveal that the period model is the best choice in terms of runtime and space for all four query classes.

High-resolution time-interval generator

Chaberski D.

Przegląd Elektrotechniczny

2017

R. 93, nr 10

25--32

The paper presents the design of a high-resolution TI (Time-Interval) generator implemented into FPGA (Field-Programmable-Gate-Array) Xilinx Virtex 5 device and obtained experimental test results. The improvement of resolution is realized by the use of a chain of DCDEs (Digitally- Controlled-Delay-Elements). The presented TI generator allows for generating either TIs of constant length or TIs of specified Gaussian distribution. Experimental results include TI histograms measured by the LeCroy 804Zi oscilloscope.

Artykuł przedstawia projekt wysokorozdzielczego generatora odcinków czasu zaimplementowanego w strukturze programowalnej FPGA Xilinx Virtex 5 wraz z wynikami eksperymentalnymi uzyskanymi z wykorzystaniem oscyloskopu LeCroy 804Zi. Wzrost rozdzielczości jest możliwy dzięki stosowaniu łańcucha zbudowanego z elementów opóźniających sterowanych cyfrowo. Prezentowany generator pozwala na generowanie odcinków czasu o określonych przez użytkownika parametrach rozkładu Gausa.