Choice of optimization routine for multi-agent models: A case of viral video marketing campaign

Very few agent-base computational models are optimized because the usually used optimization routine, the genetic algorithm, is extremely time-consuming. This paper explores how much precision is lost if a simpler optimization routine, mutational hill climber, is used instead. It shows on the case of a viral-video marketing model that even though the standard genetic algorithm is slightly more precise, the mutation hill climbing could be used as an approximate optimization routine for robustness check and scenario analysis.Jen málo multiagentových modelů je optimalizováno, protože obvykle užívaná optimalizační rutina, genetické algoritmy, jsou extrémně výpočetně náročné. Tento článek zkoumá, jak velká část přesnosti se ztratí, pokud je použita jednodušší optimalizační rutina, mutational hill climber. Článek ukazuje na příkladu virální video-marketingové kampaně, že ačkoli je standardní genetický algoritmus poněkud přesnější, mutation hill climbing může být použit jako přibližná optimalizační rutina pro ověření robustnosti a analýzu scénářů.Very few agent-base computational models are optimized because the usually used optimization routine, the genetic algorithm, is extremely time-consuming. This paper explores how much precision is lost if a simpler optimization routine, mutational hill climber, is used instead. It shows on the case of a viral-video marketing model that even though the standard genetic algorithm is slightly more precise, the mutation hill climbing could be used as an approximate optimization routine for robustness check and scenario analysis

Testing of Blood Oxygenation for Pilots

Práce se zabývá studiem měření okysličenosti krve u pilotů, které je založeno na neinvazivní metodě pulsní oxymetrie. Tato metoda využívá selektivní absorpce záření oxyhemoglobinem a redukovaným hemoglobinem ve spektru infračerveného a červeného záření. Pro měření je rozhodující pulzující složka arteriální krve, ve které je měřena koncentrace okysličeného hemoglobinu ku celkovému množství hemoglobinu.This work investigates the measurement of blood oxygenation for pilots, which is based on noninvasively method of pulse oxymetry. This method is based on the selective light absorption in the spectrum of infrared and red light by oxyhemoglobin and reduced hemoglobin. For measurement is crucial a pulse component of arterial blood, in which is measured concentration of hemoglobin to total amount of hemoglobin.

Markets, Social Networks, and Endogenous Preferences

This paper generalizes the Bell’s model (“Locally interdependent preferences in a general equilibrium environment,” JEBO, 2002), and models an interaction between a market, endogenous preferences, and a general social network. Contrary to Bell’s results, 1) the system need not to converge, 2) the agents’ preferences need not to be polarized, 3) the agents’ preferences need not to adjust in the proportion to the availability (only the more abundant good can be consumed in one type of equilibrium), and 4) the agents with the same preferences need not to be clustered.Příspěvek zobecňuje model “Locally interdependent preferences in a general equilibrium environment,” (Bell, JEBO, 2002) a modeluje interakce mezi trhem, endogenními preferencemi a obecnou sociální sítí. Na rozdíl od výsledků Bell, 1) systém vždy nekonverguje, 2) preference agentů nemusejí být vždy polarizované, 3) preference agentů nemusejí vždy být proporcionální k dostupnosti statků (agenti mohou spotřebovávat pouze hojný statek) a 4) agenti se stejnými preferencemi nemusejí tvořit geografické klastry.This paper generalizes the Bell’s model (“Locally interdependent preferences in a general equilibrium environment,” JEBO, 2002), and models an interaction between a market, endogenous preferences, and a general social network. Contrary to Bell’s results, 1) the system need not to converge, 2) the agents’ preferences need not to be polarized, 3) the agents’ preferences need not to adjust in the proportion to the availability (only the more abundant good can be consumed in one type of equilibrium), and 4) the agents with the same preferences need not to be clustered

Search for the optimal strategy to spread a viral video: An agent-based model optimized with genetic algorithms

Agent-based computational papers on viral marketing have been so far focused on the study of the word-of-mouth knowledge diffusion that merges the decisions to adopt a product and to share information about it. This approach is not suitable for the analysis of the viral video sharing because it is shared with no regard whether the sender has adopted the advertised product or not. This paper presents a more realistic model of viral video diffusion in which every agent that viewed the video shares it once with a random subset of her neighbors. The optimal seeding strategy is then searched with genetic algorithms. The seeding strategy found by the genetic algorithm includes into the initial seed the agents with most connections and lowest clustering ratios; some agents are also selected randomly. However, this complex seeding strategy does not perform significantly better than a simple strategy of selecting agents with many connections.Články popisující multiagentové simulační modely virálního marketingu se dosud zaměřovaly na studium "word-of-mouth" šíření znalosti o produktu, které spojuje rozhodnutí koupit produkt a šířit o něm informace. Tento přístup není vhodný pro analýzu šíření virálního videa, protože to je šířeno bez ohledu na to, zda jeho šiřitel zakoupil propagovaný produkt, nebo ne. Příspěvek prezentuje realističtější model šíření virálního videa, ve kterém každý agent, který video shlédl, jej právě jednou rozešle náhodné podmnožině svých sousedů. Optimální strategie volby agentů, kterým marketer sám na začátku pošle video, je hledána pomocí genetických algoritmů. Optimální strategie nalezená pomocí genetického algoritmu na počátku oslovuje agenty, kteří mají nejvíce spojení a nejnižší clustering ratios; někteří agenti jsou také vybíráni náhodně. Nicméně, tato komplexní strategie nepodává výrazně lepší výsledky než jednoduchá strategie volby agentů s mnoha vazbami.Agent-based computational papers on viral marketing have been so far focused on the study of the word-of-mouth knowledge diffusion that merges the decisions to adopt a product and to share information about it. This approach is not suitable for the analysis of the viral video sharing because it is shared with no regard whether the sender has adopted the advertised product or not. This paper presents a more realistic model of viral video diffusion in which every agent that viewed the video shares it once with a random subset of her neighbors. The optimal seeding strategy is then searched with genetic algorithms. The seeding strategy found by the genetic algorithm includes into the initial seed the agents with most connections and lowest clustering ratios; some agents are also selected randomly. However, this complex seeding strategy does not perform significantly better than a simple strategy of selecting agents with many connections

Geotechnical Data Base for the City of Zagreb and its Application in Site Response Analyses

Geotechnical reports, filed in the city archives, are the source of data among which relevant properties for mechanical soil behavior and site response analyses are recognized and digitised. The properties are digitised in an organized manner into the GIS related software called “Techbase”, developed by “MINEsoft“, Lakewood, Colorado. The basic element of the database is a boring log containing distributions of soil properties with depth. More than 150 boring logs, located in the western part of Zagreb, are digitized and their coordinates mapped using “Techbase”. The aim of this paper is not only to describe the collection of the geotechnical database, but also to present its use for developing techniques for the estimation of soil-related response to earthquakes as well. The process of obtaining the seismic design model and its use in assessing free field ground acceleration are described. As borings usually do not reach deeper than ten meters, the influence of upper ten meters on amplification of maximum ground acceleration is pointed out

Analysis and Measurement of Foundation Vibrations at Two Compressor Stations in Yugoslavia

The design procedure and the measurements of foundation vibrations at two compressor stations are presented. Simple methods and models were used to predict machine foundation behavior-and it is shown that they were effective in estimating the expected range of amplitudes through simple parameter variation. In attempt to lower vibrations amplitudes, spreading of gravel layer under machine foundation was suggested, the effect of which is discussed in the paper

Geotehnička klasifikacija tla i hrvatski Nacionalni dodatak Eurokodu 8

One of the challenging tasks for Croatian accession to the European Union is the completion of the National Annex to Eurocode 8 (EC8) that calls for the development of national seismic hazard maps. These maps need to be developed for several return periods (probabilities of exceedance) and should consider both bedrock and soil conditions. The latter is especially challenging as it calls for site characterization at a microzonation level, i.e., site characterization based upon Vs,30, SPT blowcounts, and undrained shear strength, information available only in the departments of Public Works of major cities. In this paper, the authors discuss several shortcomings associated with the EC8 ground type definitions and propose their revision. The authors also present the ongoing work for preparation of the Croatian National Annex to EC8 and explain the rationale for the improvement of EC8 ground type definitions.U postupku pristupanja Europskoj uniji, jedna od obaveza Republike Hrvatske je da, u sklopu Nacionalnog dodatka za Eurokod 8, izradi karte seizmičkog hazarda. Te karte treba izraditi za nekoliko povratnih razdoblja (perioda) i to, za potresnu pobudu na osnovnoj stijeni i na površini tla. Ovo drugo uključuje i definiranje osobina slojeva tala na određenoj lokaciji, tzv. mikrozonaciju, i to na temelju brzina posmičnih elastičnih valova, Vs,30, broja udaraca standardnog penetracijskog pokusa, SPT i nedrenirane čvrstoće tla, podataka koji se mogu naći u arhivama gradskih uprava. U članku autori razmatraju klasifikaciju tipova tala za mikrozonaciju, kako ih definira Eurokod 8, i iznose neke nedostatke takve podjele, te predlažu određene izmjene. Autori također prezentiraju i neke elemente Hrvatskog nacionalnog dodatka za EC8

Diffusion through Pulverized Stone Compared to Other Mineral Barrier Materials

Construction of a waste disposal site requires an effective barrier that separates waste from a sub-base and minimizes the migration of contaminants from the site to an aquifer. Barrier layers most often used are natural clayey deposits or compacted clay liners and PEHD geomembranes. However, some regions, the Croatian karst for example, are mostly short of clay. For this reason, the use of pulverized stone, the by-product in the building-stone industry – as a potential liner material was investigated. Considering diffusion is an important mechanism of contaminant transport through barriers, this paper describes the method and apparatus for determining the diffusion coefficient of pulverized stone. Measured diffusion values were related to sample compaction and compared with the physical properties of clay, geosynthetic clay liners and PEHD geomembranes. Other physical properties of pulverized stone such as the filtration coefficient, density and particle size distribution are also presented. Finally, the suitability of pulverized stone for barrier construction is discussed based on the results obtained

Do R&D Subsidies Support Innovation or Imitation? Evidence from Four EU Countries

This paper presents an empirical analysis of the effects of public R&D subsidies on the innovative activities of private firms in Bulgaria, the Czech Republic, Germany, and Portugal. We investigate whether public R&D subsidies make firms’ activities more innovative. We measure these effects using firm-level data from the 2010 and 2012 Community Innovation Survey and estimated the effects by propensity score matching. We find that the subsidies do not fully crowd out private sources of R&D expenditure in any of these countries. However, there is a substantial heterogeneity in the impact of the subsidies on firms’ innovativeness. R&D subsidies do support true innovations in the Czech Republic and Germany, but they enhance only imitations in Bulgaria and Portugal.Tento příspěvek představuje empirickou analýzu dopadů veřejných dotací na výzkum a vývoj na inovační aktivity soukromých firem v Bulharsku, České republice, Německu a Portugalsku. Zkoumáme, zda veřejné dotace na výzkum a vývoj motivují firmy přicházet na trh s inovativnějšími produkty. Tyto efekty měříme pomocí dat z Community Innovation Survey za rok 2010 a 2012 a odhadujeme pomocí neparametrického matchingového estimátoru. Zjistili jsme, že dotace v žádné z těchto zemí zcela nevytěsňují soukromé zdroje výdajů na výzkum a vývoj. Existuje však značná heterogenita v dopadu dotací na inovativnost firem. Dotace v oblasti výzkumu a vývoje podporují skutečné inovace v České republice a Německu, ale financují pouze imitace v Bulharsku a Portugalsku