50 research outputs found
Fixed-Parameter Approximability of Boolean MinCSPs
The minimum unsatisfiability version of a constraint satisfaction problem (CSP) asks for an assignment where the number of unsatisfied constraints is minimum possible, or equivalently, asks for a minimum-size set of constraints whose deletion makes the instance satisfiable. For a finite set Gamma of constraints, we denote by CSP(Gamma) the restriction of the problem where each constraint is from Gamma. The polynomial-time solvability and the polynomial-time approximability of CSP(Gamma) were fully characterized by [Khanna et al. SICOMP 2000]. Here we study the fixed-parameter (FP-) approximability of the problem: given an instance and an integer k, one has to find a solution of size at most g(k) in time f(k)n^{O(1)} if a solution of size at most k exists. We especially focus on the case of constant-factor FP-approximability. Our main result classifies each finite constraint language Gamma into one of three classes: (1) CSP(Gamma) has a constant-factor FP-approximation; (2) CSP(Gamma) has a (constant-factor) FP-approximation if and only if Nearest Codeword has a (constant-factor) FP-approximation; (3) CSP(Gamma) has no FP-approximation, unless FPT=W[P]. We show that problems in the second class do not have constant-factor FP-approximations if both the Exponential-Time Hypothesis (ETH) and the Linear PCP Conjecture (LPC) hold. We also show that such an approximation would imply the existence of an FP-approximation for the k-Densest Subgraph problem with ratio 1-epsilon for any epsilon>0
Az atomi környezet hatása a rezonáns és nem rezonáns belsőhéj átmenetekre = Effects of the atomic environment on the resonant and non-resonant inner-shell transitions
KĂsĂ©rleti eredmĂ©nyeinkbĹ‘l meghatároztuk 3d fĂ©mek fotonindukált KLL Ă©s KLM Auger átmeneteinek energiáit Ă©s relatĂv intenzitásait, a rezonáns fotongerjesztĂ©ssel kapott, a lokális elektronszerkezetet tĂĽkrözĹ‘ KLL spektrumokat összehasonlĂtottuk modellszámĂtásainkkal. ElektronkorreláciĂłs szatelliteket azonosĂtottunk a 3d fĂ©mek mĂ©rt 1s fotoelektronspektrumaiban Ă©s modellszámĂtásainkkal Ă©rtelmeztĂĽk az 1s vonalak alakját. NiFe ötvözetek esetĂ©ben a mĂ©rt ötvözet-fĂ©m Auger paramĂ©ter eltolĂłdásokbĂłl meghatároztuk az összetevĹ‘k közötti töltĂ©sátadást, kielĂ©gĂtĹ‘ egyezĂ©st kapva modellszámĂtásainkkal. MĂłdszert Ă©s programcsomagot fejlesztettĂĽnk ki az elektronvisszaszĂłrásos kĂsĂ©rleteinkbĹ‘l kapott elektronspektrumokbĂłl a felĂĽleti rĂ©tegekben zajlĂł elektrontranszportot jellemzĹ‘ fizikai paramĂ©terek Ă©s eloszlások meghatározására, ezeket a mennyisĂ©geket kĂsĂ©rleti adatainkbĂłl meghatároztuk 3d fĂ©mek esetĂ©ben Ă©s alkalmaztuk a mĂ©rt fotonindukált K-Auger Ă©s belsĹ‘hĂ©j fotoelektron spektrumaink kiĂ©rtĂ©kelĂ©sĂ©re Ă©s modellezĂ©sĂ©re. Ăšj elektronszĂłrási jelensĂ©get (felĂĽlet fölötti szĂłrás) Ărtunk le, amelyet a kĂsĂ©rleti eredmĂ©nyek igazoltak. FĂ©lvezetĹ‘ detektorok töltĂ©stranszport folyamatai leĂrására, áramjelei meghatározására 3D MC szimuláciĂłs modellt dolgoztunk ki, ez a detektorban keltett szabad töltĂ©shordozĂłk mozgását korlátozĂł folyamatokat a korábbinál rĂ©szletesebben Ărja le. A modell Ă©rvĂ©nyĂ©t Ă©s a programot Si pin fotodiĂłda esetĂ©n korábbi kĂsĂ©rleti, ill. MC szimuláciĂłs diffĂşziĂłs Ă©s drift adatokkal ellenĹ‘riztĂĽk. | From new experiments the energies and relative intensities of the KLL and KLM Auger transitions photoinduced from 3d metals were determined and the KLL spectra obtained using resonant photoexcitation (reflecting the effects of the local electronic structure) were compared with model calculations. Electron correlátion satellites were identified in all measured 1s photoelectron spectra of 3d metals and the 1s lineshapes were interpreted by model calculations. In the case of NiFe alloys the charge transfer was derived from the measured alloy-metal Auger parameter shifts, in a satisfactory agreement with model calculations. A method and program package were developed for determining the physical parameters and distributions - characterizing the electron transport in surface layers – from spectra of electrons backscattered from 3d metals. These quantities were applied for evaluating and modeling the measured K-Auger and core photoelectron spectra. A new electron scattering phenomenon (super surface scattering) has been described and confirmed by experiments. A 3D MC model to simulate the charge transport and to aid the derivation of current signal in semiconductor radiation detectors was developed. The model describes the processes limiting the movement of free charge carriers in the detectors in more details than other models. The model and the program was tested for Si pin photodiode, its validity was verified by earlier experimental and MC simulated diffusion and drift data
Skalans betydelse vid utformning av stadsrum
When one experiences a place, it is a complex composition of both social and spatial factors.
One of these spatial elements, is scale, which is influenced both by the room size and its
proportions. This paper aims to explore both large and small scale concepts and thus increase
the understanding of how scale directly and indirectly affects the experiences and uses of
urban space.
First, is a theoretical discussion of scale in relation to aesthetics and the differences
between real scale and perceived scale. Next, is an analysis of spatial perception using
examples from two existing sites. One, which is understood to have been planned in a large
scale and one which is understood to have been planned in a small scale.
When preparing this paper, the focus quickly became the importance of scale as it
relates to street spaces. The perception of a street usually takes place while in motion, which
forces it to be perceived in sections. Depending on the design, these sections can create an
experience of the street space that could be large, small or diverse. The key to creating
interesting environments is to find the right balance between variation in scale and richness in
details
TermelĂ©si struktĂşrák, mint komplex, adaptĂv rendszerek = Production structures as Complex Adaptive Systems
A kutatás során fontos lĂ©pĂ©seket tettĂĽnk a dinamikus, rugalmas termelĂ©si struktĂşrák modellezĂ©sĂ©nek, tervezĂ©sĂ©nek, irányĂtásának Ă©s menedzsmentjĂ©nek elmĂ©leti megalapozása terĂ©n. Figyelembe vettĂĽk a termelĂ©si hierarchia kĂĽlönbözĹ‘ szintjeit, a műhelyektĹ‘l a vállalatokon át a termelĂ©si hálĂłzatokig, szinergiákra törekedve az optimálás, az autonĂłmia Ă©s a kooperáciĂł tekintetĂ©ben. Az OTKA-támogatás feltĂĽntetĂ©sĂ©vel 47 publikáciĂł szĂĽletett, melyek közĂĽl 17 folyĂłiratcikk (köztĂĽk 13 impaktos, 19,546-os összimpakttal), 1 könyvfejezet Ă©s 29 konferenciacikk. MegkezdĹ‘dött az eredmĂ©nyek ipari bevezetĂ©se (GE, Hitachi, Audi, GAMESA, Bosch, Knorr Bremse, Bosch-Rexroth, stb.)) az MTA SZTAKI keretĂ©ben működĹ‘ Fraunhofer TermelĂ©sirányĂtás Ă©s –informatika Projektközpont (http://www.fraunhofer.hu) keretĂ©ben. | Significant steps were made towards the theoretical foundation of modelling, planning, control and management of dynamic, flexible production structures. Levels from shop floors through enterprises to the production networks were considered, and a synergy between the aspects of optimization, autonomy, and cooperation was aimed at. With indications to the OTKA support, as a whole, 47 papers have been published, i.e., 17 journal papers (among them 13 in journals with impact factors, with a cumulative impact factor of 19,546), 1 book chapter and 29 conference papers. The industrial deployment of the results was partly started in GE, Hitachi, Audi, GAMESA, Bosch, Knorr Bremse, Bosch-Rexroth, etc., mainly in the framework of the SZTAKI-Fraunhofer Production Management and –Informatics Project Center (http://www.fraunhofer.hu)