726 research outputs found

    Restriction Testing in Binary Choice Model with I(1) Regressors

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    This paper deals with the problem of nonstationarity of regressors in binary choice model. The limit distribution of the ML-estimator is mixed normal, but restriction testing shall not be based on standard t-statistic. The results of the conducted Monte Carlo experiment demonstrate that the true size of the restriction test is far from the significance level. Therefore, the t -Student statistic should be modified and this paper proposes its modification. The results of the Monte Carlo investigation point to the superiority of the new statistic.nonstationarity, maximum likelihood, restriction testing

    Tight and simple Web graph compression

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    Analysing Web graphs has applications in determining page ranks, fighting Web spam, detecting communities and mirror sites, and more. This study is however hampered by the necessity of storing a major part of huge graphs in the external memory, which prevents efficient random access to edge (hyperlink) lists. A number of algorithms involving compression techniques have thus been presented, to represent Web graphs succinctly but also providing random access. Those techniques are usually based on differential encodings of the adjacency lists, finding repeating nodes or node regions in the successive lists, more general grammar-based transformations or 2-dimensional representations of the binary matrix of the graph. In this paper we present two Web graph compression algorithms. The first can be seen as engineering of the Boldi and Vigna (2004) method. We extend the notion of similarity between link lists, and use a more compact encoding of residuals. The algorithm works on blocks of varying size (in the number of input lines) and sacrifices access time for better compression ratio, achieving more succinct graph representation than other algorithms reported in the literature. The second algorithm works on blocks of the same size, in the number of input lines, and its key mechanism is merging the block into a single ordered list. This method achieves much more attractive space-time tradeoffs.Comment: 15 page

    Innovation and the Growth of Service Firms: The Polish Case

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    Differences in the growth of firms remain a major topic in economics and strategy research. In this paper we investigated the link between innovation performance and employment growth. First we discuss the problem from the theoretical point of view and then we analyze the relationship between innovation performance and the dynamics of employment in the Polish service firms in 2004-2009. Firms that introduced new services or marketing techniques experienced stronger growth. Process innovations contributed to employment reduction. Tellingly, this effect could only be observed in 2008-2009, a subperiod which saw the lowest levels of aggregate demand. This conclusion yields support to the presumption formulated by Pianta (2005) that the impact of innovation on employment growth depends on the macroeconomic situation

    libcloudph++ 0.2: single-moment bulk, double-moment bulk, and particle-based warm-rain microphysics library in C++

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    This paper introduces a library of algorithms for representing cloud microphysics in numerical models. The library is written in C++, hence the name libcloudph++. In the current release, the library covers three warm-rain schemes: the single- and double-moment bulk schemes, and the particle-based scheme with Monte-Carlo coalescence. The three schemes are intended for modelling frameworks of different dimensionality and complexity ranging from parcel models to multi-dimensional cloud-resolving (e.g. large-eddy) simulations. A two-dimensional prescribed-flow framework is used in example simulations presented in the paper with the aim of highlighting the library features. The libcloudph++ and all its mandatory dependencies are free and open-source software. The Boost.units library is used for zero-overhead dimensional analysis of the code at compile time. The particle-based scheme is implemented using the Thrust library that allows to leverage the power of graphics processing units (GPU), retaining the possibility to compile the unchanged code for execution on single or multiple standard processors (CPUs). The paper includes complete description of the programming interface (API) of the library and a performance analysis including comparison of GPU and CPU setups.Comment: The library description has been updated to the new library API (i.e. v0.1 -> v0.2 update). The key difference is that the model state variables are now mixing ratios as opposed to densities. The particle-based scheme was supplemented with the "particle recycling" process. Numerous editorial corrections were mad

    Relacje arabsko-irańskie w subregionie Zatoki Perskiej

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    The purpose of the article is to show economic, political, and geopolitical factors that have infl uenced relations between Iran and the countries of the Persian Gulf on the other. It is material that they are examined separately at the level of the Cooperation Council for the Arab States of the Gulf and separately for the individual Arab states that belong to the Council. The article suggests that each state in the Gulf runs its individual policy toward Iran, and a diff erent one as part of cooperation within the Council. In result, the Council itself is weakened and its balancing role in the region is decreasing. Policies of Arab states outside the Council are more critical for the relations with Iran than the policy of the Cooperation Council itself

    Stock Markets of the Visegrad Countries after Their Accession to the European Union

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    In this chapter, interlinkages between stock markets in CEE-4 countries and capital markets in developed countries are analyzed. Changes of variance on stock markets in Poland, the Czech Republic, Slovakia, and Hungary are identified. Differences among countries are analyzed. Capital markets of these countries are compared in terms of market efficiency. Moreover, co-movements of stock markets in Visegrad countries with capital markets in developed countries are studied. Different specifications of multivariate GARCH models are studied. Asymmetric GARCH-BEKK model and Asymmetric Generalized Dynamic Conditional Correlation model are considered

    Geopolityczna analiza potêgi w subregionie Zatoki Perskiej

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    The sub-region of the Persian Gulf, being rich in oil and gas, has become an object of rivalry between regional and global influences. If the countries want to compete effectively though, they need to have power. This article analyzes the elements that comprise the power in the Persian Gulf, which is necessary to understand contemporary balance of power in this region. Analysis is based on the triad of American political scientist – Joseph Nye, who has distinguished soft, hard and smart power. Consequently, the author of the article has presented not only the current balance of power, but also potential balances in the sub-region. There is also an attempt to find an answer to the question: which of these balances of power would be the safest for the Persian Gulf
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