Bicriteria data compression

The advent of massive datasets (and the consequent design of high-performing distributed storage systems) have reignited the interest of the scientific and engineering community towards the design of lossless data compressors which achieve effective compression ratio and very efficient decompression speed. Lempel-Ziv's LZ77 algorithm is the de facto choice in this scenario because of its decompression speed and its flexibility in trading decompression speed versus compressed-space efficiency. Each of the existing implementations offers a trade-off between space occupancy and decompression speed, so software engineers have to content themselves by picking the one which comes closer to the requirements of the application in their hands. Starting from these premises, and for the first time in the literature, we address in this paper the problem of trading optimally, and in a principled way, the consumption of these two resources by introducing the Bicriteria LZ77-Parsing problem, which formalizes in a principled way what data-compressors have traditionally approached by means of heuristics. The goal is to determine an LZ77 parsing which minimizes the space occupancy in bits of the compressed file, provided that the decompression time is bounded by a fixed amount (or vice-versa). This way, the software engineer can set its space (or time) requirements and then derive the LZ77 parsing which optimizes the decompression speed (or the space occupancy, respectively). We solve this problem efficiently in O(n log^2 n) time and optimal linear space within a small, additive approximation, by proving and deploying some specific structural properties of the weighted graph derived from the possible LZ77-parsings of the input file. The preliminary set of experiments shows that our novel proposal dominates all the highly engineered competitors, hence offering a win-win situation in theory&practice

"Les imitacions que tenen un component creatiu també són bones per als països industrialitzats"

El sistema de patents afecta negativament la innovació. Entrevista al premi Nobel Eric Maskin

"Imitations having a creative component are also good for industrialised countries"

The patent system adversely affects innovation Interview to Nobel price Eric Maski

Thermo-economic assessment of a olive pomace gasifier for cogeneration applications

A thermo-economic analysis of a combined heat and power (CHP) plant fed by syngas produced through the gasification of dry olive pomace is presented. The plant is composed by a 800 kWtdowndraft gasifier, a gas clean-up system, a 200 kWemicroturbine (MGT) and a heat recovery system to cogenerate hot water. Surplus heat is used to dry olive pomace from 50% to 17% wb moisture content. The plant is modeled in ASPEN Plus. Real data from experimental tests are used to calibrate the gasifier model, while the technical specification and performance of the CHP plant are collected from commercial plants in operation and data from manufacturers. Mass and energy balances are reported throughout the paper. The thermodynamic simulation of the biomass gasifier coupled to the MGT, the thermal and electrical conversion efficiency and temperature of cogenerated heat available are also presented. A thermo-economic assessment is then proposed, to investigate the economic profitability of this small scale CHP plant in the Italian energy policy scenario and considering the subsidies available for renewable electricity in the form of feed-in tariffs. For this purpose, the case study of base load CHP plant operation and heat supplied to different typologies of energy end user is assumed. The results allow quantifying the most influencing economic and technical factors that affect the performance and profitability of such investment and the bottlenecks that should be faced to facilitate a broader implementation of such CHP schemes for on site generation

Performance analysis of a common-rail Diesel engine fuelled with different blends of waste cooking oil and gasoil

An experimental campaign was performed to study the behavior of a common-rail Diesel engine in automotive configuration when it is fuelled with blends of Diesel fuel (DF) and waste cooking oil (WCO). In particular the tested fuels are: B20 blend, composed of 20% WCO and 80% DF; B50, composed of 50% WCO and 50% DF; WCO 100% and 100% DF. In order to fuel the engine with fuel having a similar viscosity, this quantity, together with density, has been meas-ured at temperature ranging from rom to about 80 °C. According to these measurements, before fuelling the engine B20 was heated up to 35 °C and B50 to 75 °C. An in-house software was developed to acquire the data elaborated by the electronic control unit. Results show the trend in torque and global efficiency at different gas pedal position (gpp) and different engine speed. The experiments show that larger discrepancies are measured at smaller gpp values, while at larger ones dif-ferences become smaller. A similar trend is noticed for engine global efficiency

Strategic Voting with Almost Perfect Signals

A standard assumption in the literature of strategic voting is the independence of signals. Each juror observes a signal at the interim stage of the game. Then she votes according to her private information in order to maximize her expected utility. This work introduces a dependency between signals, reflecting a more realistic situation, in which evidences can be incontrovertible. We give a full characterization of the symmetric equilibria in non-weakly dominated strategies and we provide a benchmark between the classical approach and this new one

LÂ’utilizzo degli indicatori compositi nell'analisi congiunturale territoriale: un'applicazione all'economia del Veneto

This paper analyses the business cycle properties of 150 time series, including real and monetary variables, relevant to the regional economy. Following the methodology adopted by Altissimo, Marchetti and Oneto (2000), we propose new monthly coincident and leading composite indicators for the regional business cycle; the leading indicator anticipates the turning points of the coincident indicator on average by five months. With respect to the Italian indicator, recently proposed by ISAE and Bank of Italy, the regional indicator turns out to be particularly sensitive to the evolution of external conditions, revealing cyclical fluctuations not exhibited by the national one. The chronology confirms the peculiarity of the local economy, characterised by a very long expansion lasting from March 1993 to November 1996, tied to the depreciation of the exchange rate as a consequence of the exit from the EMS, and by two idiosyncratic fluctuations. The first one is a short and pronounced cycle occurred during the period 1990-91, coinciding with the Gulf war and the subsequent short recovery driven by the German fiscal expansion tied to the re-unification process. The second is characterised by the relevant recession occurred between February 1998 and April 1999, following the Asian currency and financial crisis.business cycle, coincident and leading indicator, Veneto Region

Strategic Voting with Almost Perfect Signals

A standard assumption in the literature of strategic voting is the independence of signals. Each juror observes a signal at the interim stage of the game. Then she votes according to her private information in order to maximize her expected utility. This work introduces a dependency between signals, reflecting a more realistic situation, in which evidences can be incontrovertible. We give a full characterization of the symmetric equilibria in non-weakly dominated strategies and we provide a benchmark between the classical approach and this new one

Editorial Note

The Review of Economics and Institutions is the New Series of Economia, Società e Istituzioni, edited by Luiss University Press up to 2005. The New Series is published by the University of Perugia maintaining the founders' idea that political economy scholars should aim at understanding social and economic issues in their concreteness and completeness, in their historical perspective and within their institutional framework. The nature and scope of the Review remain general. Although submissions of high-quality theoretical articles will be considered, a privileged attention will be paid to applied contributions. A distinctive feature of the New Series is that it offers authors the possibility to have their papers accepted in less than three months; specifically, it is conceived for attracting high quality works of young economists at their earlier phase of research activity. This First Issue of the New Series is a collection of invited works by international leading scholars; these articles provide clear examples of the fields of research and the quality standards the Review aims at attaining