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Nearly All Reals Can Be Sorted with Linear Time Complexity
Jiřina, Marcel
2021 - anglický
We propose a variant of the counting sort modified for sorting reals in a linear time. It is assumed that the sorting key and pointers to the items being sorted are moved and individual items remain at the same place in the memory (in place sorting). In this case, the space complexity of the new variant of the algorithm is the same as the complexity of the quicksort. We also quantify the practical limits for possible sorting reals in a linear time. This possibility is assured under additional assumptions on the distribution of the sorting key, mainly the independence and identity of the distribution. Here we give a more general criteria easily applicable in practice. We also show that the algorithm is applicable for data that do not fulfill criteria for linear time complexity but even that the computation is faster than the system quicksort. A new, faster version of the algorithm is attached.
Klíčová slova:
sorting; algorithm; real sorting key; time complexity; linear complexity
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Nearly All Reals Can Be Sorted with Linear Time Complexity
We propose a variant of the counting sort modified for sorting reals in a linear time. It is assumed that the sorting key and pointers to the items being sorted are moved and individual items remain ...
Shrinkage for Gaussian and t copulas in ultra-high dimensions
Anatolyev, Stanislav; Pyrlik, Vladimir
2021 - anglický
Copulas are a convenient framework to synthesize joint distributions, particularly in higher dimensions. Currently, copula-based high dimensional settings are used for as many as a few hundred variables and require large data samples for estimation to be precise. In this paper, we employ shrinkage techniques for large covariance matrices in the problem of estimation of Gaussian and t copulas whose dimensionality goes well beyond that typical in the literature. Specifically, we use the covariance matrix shrinkage of Ledoit and Wolf to estimate large matrix parameters of Gaussian and t copulas for up to thousands of variables, using up to 20 times lower sample sizes. The simulation study shows that the shrinkage estimation significantly outperforms traditional estimators, both in low and especially high dimensions. We also apply this approach to the problem of allocation of large portfolios.
Klíčová slova:
Gaussian copula; t copula; high dimensionality
Dokument je dostupný na externích webových stránkách.
Shrinkage for Gaussian and t copulas in ultra-high dimensions
Copulas are a convenient framework to synthesize joint distributions, particularly in higher dimensions. Currently, copula-based high dimensional settings are used for as many as a few hundred ...
Measurements on KR-D-4 Cascade
Šimurda, David; Radnic, Tomáš
2021 - anglický
This report contains results and evaluation of aerodynamic measurements conducted on a subsonic compressor blade cascade.
Klíčová slova:
compressor blade cascade; experiment; subsonic flow; transonic flow; AVDR
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Measurements on KR-D-4 Cascade
This report contains results and evaluation of aerodynamic measurements conducted on a subsonic compressor blade cascade.
Measurements on TR-W-4 Cascade
Luxa, Martin; Šimurda, David
2021 - anglický
The report contains results and evaluation of conducted optical /interferometry and schlieren technique) and pneumatic measurements on the transonic profile cascade intenden for root section of rotor turbine blade.
Klíčová slova:
turbine cascade; transonic flow; hub section
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Measurements on TR-W-4 Cascade
The report contains results and evaluation of conducted optical /interferometry and schlieren technique) and pneumatic measurements on the transonic profile cascade intenden for root section of rotor ...
Flutter methodology using reduced order aeroelastic model
Prasad, Chandra Shekhar; Pešek, Luděk; Šnábl, Pavel
2021 - anglický
The present research project is focused on development of fast and efficient numerical method based on reduced order aeroelastic method (ROAM) for modeling and analysis of \nclassical flutter in the low pressure (LP) stage steam turbine blade. Stability diagram such as aerodynamic damping (AD) of aeroelasticity of cascade of 3D turbine blades used as a prime \ncharacterization factor. In the calculation of the S-curve/AD, the problem of classical flutter formation associated with running waves is considered here. Running waves is simulated by \nthe inter-blade phase shift of the blades in the cascade. Panel method based boundary element flow solver is employed for calculation of unsteady aerodynamic forces. This method is good \ncompromise of speed and accuracy for the estimation of the stability of the blades on a classical flutter. One way loose coupling technique between PM based flow solver and the structural \nmodel. For the structural part modal model synthesis (MMS) method is adopted in the ROAM solver. MMS is adopted to further reduced the computational cost. The ROAM simulated AD \nand pressure distribution over blade is compared high fidelity CFD data on real blade geometry provided by Doosan Skoda Power s.r.o. Furthermore, the ROAM results are also compared \nwith experimentally obtained results on two different linear cascade. The ROAM model shows good agreement with linear cascade results, however, there is noticeable discrepancy with real blade CFD results.
Klíčová slova:
reduced order model (ROM); classical flutter; steam turbine blade; panel method
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Flutter methodology using reduced order aeroelastic model
The present research project is focused on development of fast and efficient numerical method based on reduced order aeroelastic method (ROAM) for modeling and analysis of \nclassical ...
Sentencing decisions around quantity thresholds: theory and experiment
Drápal, Jakub; Šoltés, Michal
2021 - anglický
We study the implications of the structure of criminal codes on sentencing decisions. To limit sentencing disparities, criminal codes typically divide offenses into subsections with specific sentencing ranges. The classification into corresponding subsections often depends on exceeding a given quantity threshold, such as drug amount. We study the consequences of these quantity thresholds on sentencing decisions and argue that the threshold effect can be decomposed into two opposing mechanisms: the severity mechanism and the reference one. An experiment with Czech prosecutors shows that thresholds drive substantial increases in sentences, leading to sentencing disparities. We further introduce empirical measures of (in)justice and quantify the consequences of quantity thresholds on the probability of imposing a just sentence.
Klíčová slova:
sentencing; quantity threshold; sentencing disparities
Dokument je dostupný na externích webových stránkách.
Sentencing decisions around quantity thresholds: theory and experiment
We study the implications of the structure of criminal codes on sentencing decisions. To limit sentencing disparities, criminal codes typically divide offenses into subsections with specific ...
Checkmate! Losing with borders, winning with centers. The case of European integration
Kapanadze, Ketevani
2021 - anglický
This paper studies two major stages of European integration, the expansion of the European Union (EU) in 2004 and the Schengen Area in 2008, and their impacts on economic performance in subregions of Central and Eastern European (CEE) countries. Using European regional data at the NUTS3 level and disaggregated synthetic control method, I construct counterfactuals for sub-regions of CEE countries. This approach allows me to assess regional treatment effects (RTEs) and to study the heterogeneous effects of European integration. I find that the benefits of EU and Schengen memberships to annual GDP per capita are approximately 10% less in border regions, relative to interior areas. The results expose regional economic disparities, as border regions lose relative to interior regions since European integration. Furthermore, integration facilitators in border regions such as fewer geographical barriers, more service employment, and positive attitudes toward the EU did not reduce economic disparities. The results show that the gap persists, regardless of some complementarities. Thus, the main implication of this paper is that sub-regions of CEE countries are far from being fully converged, and that European integration instead seems to have spurred sub-regional divergence.
Klíčová slova:
CEE countries; European integration; RTEs
Dokument je dostupný na externích webových stránkách.
Checkmate! Losing with borders, winning with centers. The case of European integration
This paper studies two major stages of European integration, the expansion of the European Union (EU) in 2004 and the Schengen Area in 2008, and their impacts on economic performance in subregions of ...
Wages, minimum wages, and price pass-through: the case of McDonald's restaurants
Ashenfelter, O.; Jurajda, Štěpán
2021 - anglický
We use highly consistent national-coverage price and wage data to provide evidence on wage increases, labor-saving technology introduction, and price pass-through by a large low-wage employer facing minimum wage hikes. Based on 2016-2020 hourly wage rates of McDonald’s Basic Crew and prices of the Big Mac sandwich collected simultaneously from almost all US McDonald’s restaurants, we find that in about 25% of instances of minimum wage increases, restaurants display a tendency to keep constant their wage ‘premium’ above the increasing minimum wage. Higher minimum wages are not associated with faster adoption of touch-screen ordering, and there is near-full price pass-through of minimum wages, with little heterogeneity related to how binding minimum wage increases are for restaurants. Minimum wage hikes lead to increases in real wages (expressed in Big Macs an hour of Basic Crew work can buy) that are one fifth lower than the corresponding increases in nominal wages.
Klíčová slova:
minimum wages; wage increases; McDonald’s
Dokument je dostupný na externích webových stránkách.
Wages, minimum wages, and price pass-through: the case of McDonald's restaurants
We use highly consistent national-coverage price and wage data to provide evidence on wage increases, labor-saving technology introduction, and price pass-through by a large low-wage employer facing ...
Unsupervised Verification of Fake News by Public Opinion
Grim, Jiří
2021 - anglický
In this paper we discuss a simple way to evaluate the messages in social networks automatically, without any special content analysis or external intervention. We presume, that a large number of social network participants is capable of a relatively reliable evaluation of materials presented in the network. Considering a simple binary evaluation scheme (like/dislike), we propose a transparent algorithm with the aim to increase the voting power of reliable network members by means of weights. The algorithm supports the votes which correlate with the more reliable weighted majority and, in turn, the modified weights improve the quality of the weighted majority voting. In this sense the weighting is controlled only by a general coincidence of voting members while the specific content of messages is unimportant. The iterative optimization procedure is unsupervised and does not require any external intervention with only one exception, as discussed in Sec. 5.2 .\n\nIn simulation experiments the algorithm nearly exactly identifies the reliable members by means of weights. Using the reinforced weights we can compute for a new message the weighted sum of votes as a quantitative measure of its positive or negative nature. In this way any fake news can be recognized as negative and indicated as controversial. The accuracy of the resulting weighted decision making was essentially higher than a simple majority voting and has been considerably robust with respect to possible external manipulations.\n\nThe main motivation of the proposed algorithm is its application in a large social network. The content of evaluated messages is unimportant, only the related decision making of participants is registered and compared with the weighted vote with the aim to identify the most reliable voters. A large number of participants and communicated messages should enable to design a reliable and robust weighted voting scheme. Ideally the resulting weighted vote should provide a generally acceptable emotional feedback for network participants and could be used to indicate positive or controversial news in a suitably chosen quantitative way. The optimization algorithm has to be simple, transparent and intuitive to make the weighted vote well acceptable as a general evaluation tool.\n
Klíčová slova:
weighted voting; unsupervised optimization
Dokument je dostupný na externích webových stránkách.
Unsupervised Verification of Fake News by Public Opinion
In this paper we discuss a simple way to evaluate the messages in social networks automatically, without any special content analysis or external intervention. We presume, that a large number of ...
Firm relocations, commuting and relationship stability
Hrehová, Kristína; Sandow, E.; Lindgren, U.
2021 - anglický
In this paper, we study the impact of firm relocations on commuting distance and the probability of married couples and cohabiting couples with children separating. We use Swedish register data for 2010-2016 and select employees of relocating firms with one workplace and more than 10 employees. Focusing on this sample allows us to use plausibly exogenous variation in the commuting distance arising from the relocation. We extend the literature on the effect of commuting on relationship stability by reducing the possibility for unobserved time-variant factors to bias our estimates. While previous literature has focused on the difference between short- and long-distance commuting, we focus on changes in the commuting distance that are externally induced by firm management. We find a small but statistically significant negative effect of increased firm relocation distance on family stability. A 10 km change in commuting distance leads to a 0.09 percentage point higher probability of separation if the commuter remains with the firm for the next 5 years.
Klíčová slova:
separation; marriage; commuting time
Dokument je dostupný na externích webových stránkách.
Firm relocations, commuting and relationship stability
In this paper, we study the impact of firm relocations on commuting distance and the probability of married couples and cohabiting couples with children separating. We use Swedish register data for ...
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