Heuristics in Multi-Winner Approval Voting

In many real world situations, collective decisions are made using voting. Moreover, scenarios such as committee or board elections require voting rules that return multiple winners. In multi-winner approval voting (AV), an agent may vote for as many candidates as they wish. Winners are chosen by tallying up the votes and choosing the top-$k$ candidates receiving the most votes. An agent may manipulate the vote to achieve a better outcome by voting in a way that does not reflect their true preferences. In complex and uncertain situations, agents may use heuristics to strategize, instead of incurring the additional effort required to compute the manipulation which most favors them. In this paper, we examine voting behavior in multi-winner approval voting scenarios with complete information. We show that people generally manipulate their vote to obtain a better outcome, but often do not identify the optimal manipulation. Instead, voters tend to prioritize the candidates with the highest utilities. Using simulations, we demonstrate the effectiveness of these heuristics in situations where agents only have access to partial information

A Robust Filter for the BeppoSAX Gamma Ray Burst Monitor Triggers

The BeppoSAX Gamma Ray Burst Monitor (GRBM) is triggered any time a statistically significant counting excess is simultaneously revealed by at least two of its four independent detectors. Several spurious effects, including highly ionizing particles crossing two detectors, are recorded as onboard triggers. In fact, a large number of false triggers is detected, in the order of 10/day. A software code, based on an heuristic algorithm, was written to discriminate between real and false triggers. We present the results of the analysis on an homogeneous sample of GRBM triggers, thus providing an estimate of the efficiency of the GRB detection system consisting of the GRBM and the software.Comment: Proc. 5th Huntsville GRB Symposiu

Engineering gels with time-evolving viscoelasticity

From a mechanical point of view, a native extracellular matrix (ECM) is viscoelastic. It also possesses time-evolving or dynamic behaviour, since pathophysiological processes such as ageing alter their mechanical properties over time. On the other hand, biomaterial research on mechanobiology has focused mainly on the development of substrates with varying stiffness, with a few recent contributions on time- or space-dependent substrate mechanics. This work reports on a new method for engineering dynamic viscoelastic substrates, i.e., substrates in which viscoelastic parameters can change or evolve with time, providing a tool for investigating cell response to the mechanical microenvironment. In particular, a two-step (chemical and enzymatic) crosslinking strategy was implemented to modulate the viscoelastic properties of gelatin hydrogels. First, gels with different glutaraldehyde concentrations were developed to mimic a wide range of soft tissue viscoelastic behaviours. Then their mechanical behaviour was modulated over time using microbial transglutaminase. Typically, enzymatically induced mechanical alterations occurred within the first 24 h of reaction and then the characteristic time constant decreased although the elastic properties were maintained almost constant for up to seven days. Preliminary cell culture tests showed that cells adhered to the gels, and their viability was similar to that of controls. Thus, the strategy proposed in this work is suitable for studying cell response and adaptation to temporal variations of substrate mechanics during culture

Multiperiodicity in semiregular variables II. Systematic amplitude variations

We present a detailed lightcurve analysis for a sample of bright semiregular variables based on long-term (70--90 years) visual magnitude estimates carried out by amateur astronomers. Fundamental changes of the physical state (amplitude and/or frequency modulations, mode change and switching) are studied with the conventional Fourier- and wavelet analysis. The light curve of the carbon Mira Y Per showing a gradual amplitude decrease has been re-analysed after collecting and adding current data to earlier ones. The time scales of the sudden change and convection are compared and their similar order of magnitude is interpreted to be a possible hint for strong coupling between pulsation and convection. The periods of the biperiodic low-amplitude light curve and their ratios suggest a pulsation in the first and third overtone modes. An alternative explanation of the observed behaviour could be a period halving due to the presence of weak chaos. Beside two examples of repetitive mode changes (AF Cyg and W Cyg) we report three stars with significant amplitude modulations (RY Leo, RX UMa and RY UMa). A simple geometric model of a rotationally induced amplitude modulation in RY UMa is outlined assuming low-order nonradial oscillation, while the observed behaviour of RX UMa and RY Leo is explained as a beating of two closely separated modes of pulsation. This phenomenon is detected unambiguously in V CVn, too. The period ratios found in these stars (1.03-1.10) suggest either high-order overtone or radial+non-radial oscillation.Comment: 11 pages + 17 figures, accepted for publication in A&A Supplement Serie

A Relevância Da Família Como Unidade De Análise Nos Estudos Sobre Pluriatividade

The pluriactivity phenomenon has been more studied in Brazil in the 1990's, when increased the papers about it in many regions of the country. The main issue related with the pluriactivity theme is the relevant unit of analyses. In according to the international literature, this article defends the idea that the family, and not the production unit, should be the north of the studies of pluriactivity in the Brazilian family farming.45410551073ALMEIDA, M.W.B., Redescobrindo a família rural. (1986) Revista Brasileira de Ciências Sociais, 1 (1), pp. 66-83BARTHEZ, A. (1987). Familia, actividad y pluriactividad en la agricultura. In: Arkleton Research: cambio rural en Europa. Colóquio de Montpellier, pp.161-177BLANC, M. (1987). Pluriactividad y movilidad del trabajo: un enfoque macroeconomico. In: Arkleton Research: cambio rural en Europa. Colóquio de Montpellier, pp.89-109BRYDEN, J. (1995). Pluriactividad rural en Europa: el proyecto rural change in Europe. In: Real, E.R. & Villalión, J.C. (coord.). Hacia un nuevo sistema rural. Ministerio de Agricultura, Pesca y Alimentacion, (série estudios), pp.459-481BRUN, A., A família como unidade de análise do setor agrícola. Tradução de Marcelino de Souza (1989) Économie Rurale, (194), pp. 3-8BUTTEL, F., The Political Economy of Part-time farming (1982) GeoJournal, (6), pp. 293-300CARNEIRO, M. J. (2000). Política de desenvolvimento rural e o novo rural. In: O novo rural brasileiro. Camponha, C. & Grazinao da Silva, J. (org.). Jaguariúna (SP): EMBRAPA Meio Ambiente, 4CARNEIRO, M.J., Camponeses, agricultores e pluriatividade (1998) Rio de Janeiro: Contra Capa Livraria, , 228 pCARNEIRO, M.J., Pluriatividade no campo: O caso francês. (1996) Revista Brasileira de Ciências Sociais, 11 (32), pp. 89-105DEL GROSSI, M.E. & GRAZIANO DA SILVA, J. (1998). A pluriatividade na agropecuária brasileira em 1995. In: Estudos Sociedade e Agricultura, n.11, pp.26-52EVANS, N.J., ILBERY, B.W., The pluriactivity, part-time farming and farm diversification debate (1993) Environment and Planning, 25, pp. 945-959FULLER, A. (1987). Introducción. In: Arkleton Research: cambio rural en Europa. Colóquio de Montpellier, pp. 9-21FULLER, A.M., From part-time farming to pluriactivity: A decade of change in rural Europe (1990) Journal of Rural Studies, 6, pp. 361-373GRAZIANO DA SILVA, J. (1997a). O novo rural brasileiro. In: Nova Economia. Revista do Departamento de Ciências-Econômicas da UFMG, 7(1), pp.43-81LACOMBE, P. (1984). La pluriactivité et l'evolution des explotations agricoles. In ARF, p.35-54LE HERON, R., ROCHE, M., JOHNSTON, T., Pluriactivity in New Zeland Agriculture in the 1980s - a benchmark study of livestock and fruit agro-commodity systems (1994) Geoforum, 25, pp. 155-172MARSDEN, T., Exploring a rural sociology for the fordist transition: Incorporating social relations into economic restructuring (1992) Sociologia Ruralis, 32 (2-3)MARSDEN, T., Beyond Agriculture? regulating the new rural spaces (1995) Journal of Rural Studies, 11 (3), pp. 285-296NEWBY, H. (1987). La familia y la explotación agraria. In: Arkleton Research: cambio rural en Europa. Colóquio de Montpellier, pp.155-159SCHNEIDER, S., As transformações recentes da agricultura familiar no Rio Grande do Sul: O caso da agricultura em tempo parcial (1995) Ensaios FEE, (16): 105-129SCHNEIDER, S., A pluriatividade como estratégia de reprodução social da agricultura familiar no Sul do Brasil (2001) Estudos Sociedade e Agricultura, (16), pp. 164-184SCHNEIDER, S., (2003) A pluriatividade na agricultura familiar, , Porto Alegre: Editora da UFRGS, 359 pSHUCKSMITH, D., SMITH, R., Farm household strategies and pluriactivity in Upland Scotland (1991) Journal of agricultual Economics, 42, pp. 340-35