199,443 research outputs found
Fodor vs. Darwin: A Methodological Follow-Up
No full textIn a series of recent publications Jerry Fodor has attacked what many believe is the core of Darwinian theory of evolution – the theory of natural selection. Not surprisingly, Fodor’s attack has provoked a strong negative reaction. Fodor’s critics have insisted both that his main argument is unsound and that his central claim that the theory of natural selection “can’t explain the distribution of phenotypic traits in biological populations” is untenable. I can generally agree with the first part of the launched criticism: Fodor’s “putative argument” does rely on controversial premises which make it unsound. However, I don’t think that Fodor’s critics have succeeded in their attempts to refute his central claim. The refutation strategy that most of them have undertaken is to show examples of successful evolutionary explanations by natural selection. In what follows, two of these examples are put into scrutiny. The analysis reveals that: (1) The theory of natural selection should be only partially credited with the explanatory success of evolutionary explanations by natural selection because these explanations rely on additional empirical hypotheses which might be true or false. That means that the selectionist explanations are fallible statements the truth value of which depends crucially on the truth value of the empirical assumptions which have been premised. (2) In both cases alternative non-selectionist explanations can be found that fit the same empirical data and no reason has been given (or could be given) why these alternative explanations should be ignored a priori as inferior. The observations (1) and (2) stand against the claim that theory of natural selection is the only legitimate explanance for the distribution of phenotypic traits. This does not mean, of course, that natural selection does not play any explanatory role or that the theory of natural selection is a false theory (as Fodor is inclined to argue for). This only means that there is indeed a problem of understanding the proper explanatory role of natural selection and that this problem is not only Fodor’s problem. The paper ends with a suggestion of what should be admitted in order to get to a better understanding of the proper role that the theory of natural selection plays in evolutionary explanations
Studia in honorem Aegonis Maróti sexagenarii. Édité par I. Fodor et V. M. Korchmáros
No full textStudia in honorem Aegonis Maróti sexagenarii. Édité par I. Fodor et V. M. Korchmáros. In: Revue des études byzantines, tome 47, 1989. p. 326
Studia in honorem Aegonis Maróti sexagenarii. Édité par I. Fodor et V. M. Korchmáros
No full textStudia in honorem Aegonis Maróti sexagenarii. Édité par I. Fodor et V. M. Korchmáros. In: Revue des études byzantines, tome 47, 1989. p. 326
Homocord mesterlemezeken Week-endre Fekete Pál, Verbőczy Ila, Bodán Margit...
No full textM. Fodor Ete
On the tradeoff between blocking and dropping probabilities in CDMA networks supporting elastic services
No full textThis paper is a sequel of previous work, in which we proposed a model and computational technique to calculate the Erlang capacity of a single CDMA cell that supports elastic services. The present paper extends that base model by taking into account two important features of CDMA. First, we capture the impact of soft blocking by modeling the neighbor cell interference as a lognormally distributed random variable. Secondly, we model the impact of the outage by taking into account that in-progress sessions can be dropped with a probability that depends on the current load in the system. We then consider a system with elastic and rigid service classes and analyze the trade-off between the total (soft and hard) blocking probabilities on the one hand and the throughput and the session drop probabilities on the other
Performance Analysis of a Distributed Resource Allocation Scheme for D2D Communications
No full textDevice-to-device (D2D) communications underlaying a cellular infrastructure has recently been proposed as a means of increasing the cellular capacity, improving the user throughput and extending the battery lifetime of user equipments by facilitating the reuse of spectrum resources between D2D and cellular links. In network assisted D2D communications, when two devices are in the proximity of each other, the network can not only help the devices to set the appropriate transmit power and schedule time and frequency resources but also to determine whether communication should take place via the direct D2D link (D2D mode) or via the cellular base station (cellular mode). In this paper we formulate the joint mode selection, scheduling and power control task as an optimization problem that we first solve assuming the availability of a central entity. We also propose a distributed suboptimal joint mode selection and resource allocation scheme that we benchmark with respect to the centralized optimal solution. We find that the distributed scheme performs close to the optimal scheme both in terms of resource efficiency and user fairness
Diszkrét geometria és geometriai algebra = Discrete geometry and geometric algebra
No full textNagy G. olyan geometriai struktúrákat vizsgált, melyek Moufang-féle és Bol-féle egységelemes kvázicsoportokkal (loopokkal) koordinátázhatóak. a) Kis Frattini 2-loopok, azaz melyeknél L/A elemi Abel 2-csoport valamely 2-rendű A normális részloopra. A Bol-esetben explicit formulát, a Moufang-esetben új globális konstrukciót adott. b) Moufang-féle p-loopok, p>3. Ilyen loopokra korábban nagyon kevés példa volt ismert. Nagy G. M. Valsecchivel fontos azonosságokat talált nilpotens Moufang-loopokra és egy általános új konstrukciót talált, továbbá osztályozták a p^5 (p>3) rendű Moufang-loopokat is. c) Kis Moufang- és Bol-loopok osztályozása, a P. Vojtechovsky-val közösen készített komputeralgebrai programcsomag felhasználásával. Fodor F. megtalálta 13 és 14 egybevágó kör körbe való legsűrűbb elhelyezéseit. Ambrus G.-vel közösen Fodor F. új alsó korlátot bizonyított 3-dimenziós egységgömb elhelyezésekbeli Voronoi cellák felszínére. T. Bisztriczkyvel és D. Oliverosszal közösen Fodor F. bebizonyította, hogy ha egy páronként diszjunkt körökből álló rendszerben minden 4-elemű részhalmaznak van transzverzálisa, akkor van olyan egyenes, ami legfeljebb egy kivételével a rendszer minden elemét metszi. Ambrus G.-vel és Bezdek A.-val közösen Fodor F. megmutatta, hogy ha egy n-dimenziós egységgömbökből álló rendszerben, ahol a középpontok távolsága legalább 3.6955..., minden n^2-elemű részhalmaznak van transzverzálisa, akkor az egész rendszernek is van transzverzálisa. Fodor F. W. Kuperberggel és T. Bisztriczkyvel közösen ""Discrete Geometry"" című konferenciakötetet szerkesztett. | G. Nagy studied geometric structures which can be coordinatized by Moufang and Bol loops. a) Small Frattini 2-loops are loops L with a normal subloop A of order 2 such that L/A is an elementary Abelian 2-group. Nagy gave an explicit formula in the Bol case and a new global construction in the Moufang case. b) Moufang p-loops with p>3. Before, there were not many examples known for such loops. Together with M. Valsecchi, G. Nagy found some important identities for this class of loops. Using these, they gave a very general new construction and classified all Moufang loops of order p^5 for p>3. c) Jointly with P. Vojtechovsky, G. Nagy wrote a computer algebra package for loops. They used this package to classify small Moufang and Bol loops. F. Fodor found the densest packings of 13 and 14 congruent circles in a circle. Jointly with G. Ambrus, F. Fodor proved a new lower bound for the surface area of Voronoi polyhedra in 3-dimensional unit ball packings. With T. Bisztriczky and D. Oliveros, F. Fodor proved that if in a family of pairwise disjoint unit disks every 4-membered subfamily has a transversal line, then there is a line that intersects all members of the family with the possible exception of at most one. Jointly with G. Ambrus and A. Bezdek, F. Fodor showed that if in a family of n-dimensional unit balls in which the centres of the balls are at least 3.6955... apart every n^2-membered subfamily has a transversal, then the whole family has a transversal. F. Fodor co-edited a conference proceedings volume ""Discrete Geometry"" with T. Bisztriczky and W. Kuperberg
MMSE Receiver Design and SINR Calculation in MU-MIMO Systems with Imperfect CSI
No full textThe performance of the uplink of multiuser multiple input multiple output systems depends critically on the receiver architecture and on the quality of the acquired channel state information. A popular approach is to design linear receivers that minimize the mean squared error (MSE) of the received data symbols. Unfortunately, most of the literature does not take into account the presence of channel state information errors in the MSE minimization. In this letter we develop a linear minimum MSE (MMSE) receiver that employs the noisy instantaneous channel estimates to minimize the MSE, and highlight the dependence of the receiver performance on the pilot-to-data power ratio. By invoking the theory of random matrices, we calculate the users’ signal-to-interference-plus-noise ratio as a function of the number of antennas and the pilot-to-data power ratio of all users. Numerical results indicate that this new linear receiver outperforms the classical mismatched MMSE receiver
A Message Passing Approach for Resource Allocation in Cellular OFDMA Communications
No full textThis paper proposes a distributed and low-complexity resource allocation scheme for cellular OFDMA networks. In particular, we consider ReMP, a reweighted message passing algorithm that perturbs the standard max-sum algorithm by suitably reweighting messages. In a single-cell scenario, such a scheme allows to achieve convergence to a fixed and provably optimum point without employing any central controller. The ReMP algorithm is then adapted to a multi-cell environment. To this aim, we devise X-ReMP, a ReMP-based algorithm that combines cross-cell signaling and the regular ReMP routine that still runs within each cell. The cross-signaling among cells aids ReMP to deal with the inter-cell multiple-access interference, so that X-ReMP allows convergence to a good working point in terms of system throughput even in presence of strong inter-cell interference
On the impact of antenna correlation and CSI errors on the pilot-to-data power ratio. IEEE Transactions on Communications
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