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Search Results: 1 - 10 of 826 matches for " Armin Biere "
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Covered Clause Elimination
Marijn Heule,Matti J?rvisalo,Armin Biere
Computer Science , 2010,
Abstract: Generalizing the novel clause elimination procedures developed in [M. Heule, M. J\"arvisalo, and A. Biere. Clause elimination procedures for CNF formulas. In Proc. LPAR-17, volume 6397 of LNCS, pages 357-371. Springer, 2010.], we introduce explicit (CCE), hidden (HCCE), and asymmetric (ACCE) variants of a procedure that eliminates covered clauses from CNF formulas. We show that these procedures are more effective in reducing CNF formulas than the respective variants of blocked clause elimination, and may hence be interesting as new preprocessing/simplification techniques for SAT solving.
Linear Encodings of Bounded LTL Model Checking
Armin Biere,Keijo Heljanko,Tommi Junttila,Timo Latvala,Viktor Schuppan
Computer Science , 2006, DOI: 10.2168/LMCS-2(5:5)2006
Abstract: We consider the problem of bounded model checking (BMC) for linear temporal logic (LTL). We present several efficient encodings that have size linear in the bound. Furthermore, we show how the encodings can be extended to LTL with past operators (PLTL). The generalised encoding is still of linear size, but cannot detect minimal length counterexamples. By using the virtual unrolling technique minimal length counterexamples can be captured, however, the size of the encoding is quadratic in the specification. We also extend virtual unrolling to Buchi automata, enabling them to accept minimal length counterexamples. Our BMC encodings can be made incremental in order to benefit from incremental SAT technology. With fairly small modifications the incremental encoding can be further enhanced with a termination check, allowing us to prove properties with BMC. Experiments clearly show that our new encodings improve performance of BMC considerably, particularly in the case of the incremental encoding, and that they are very competitive for finding bugs. An analysis of the liveness-to-safety transformation reveals many similarities to the BMC encodings in this paper. Using the liveness-to-safety translation with BDD-based invariant checking results in an efficient method to find shortest counterexamples that complements the BMC-based approach.
Concurrent Cube-and-Conquer
Peter van der Tak,Marijn J. H. Heule,Armin Biere
Computer Science , 2014,
Abstract: Recent work introduced the cube-and-conquer technique to solve hard SAT instances. It partitions the search space into cubes using a lookahead solver. Each cube is tackled by a conflict-driven clause learning (CDCL) solver. Crucial for strong performance is the cutoff heuristic that decides when to switch from lookahead to CDCL. Yet, this offline heuristic is far from ideal. In this paper, we present a novel hybrid solver that applies the cube and conquer steps simultaneously. A lookahead and a CDCL solver work together on each cube, while communication is restricted to synchronization. Our concurrent cube-and-conquer solver can solve many instances faster than pure lookahead, pure CDCL and offline cube-and-conquer, and can abort early in favor of a pure CDCL search if an instance is not suitable for cube-and-conquer techniques.
Geographic parthenogenesis and plant-enemy interactions in the common dandelion
Verhoeven Koen JF,Biere Arjen
BMC Evolutionary Biology , 2013, DOI: 10.1186/1471-2148-13-23
Abstract: Background Many species with sexual and asexual variants show a pattern of geographic parthenogenesis where asexuals have broader and higher-latitude distribution than sexuals. Because sexual reproduction is often considered a costly evolutionary strategy that is advantageous in the face of selection by coevolving pests and pathogens, one possible explanation for geographic parthenogenesis is that populations at higher latitudes are exposed to fewer pests and pathogens. We tested this hypothesis in the common dandelion (Taraxacum officinale), a species with well-established geographic parthenogenesis, by screening prevalence and effects of several specialized pests and pathogens in natural dandelion populations. Results We did a population survey of 18 dandelion populations along a geographic transect that ranged from the area where sexual and asexual dandelions co-occur northward into the area where only asexuals occur. In addition we used four southern and four northern populations in a 8x8 cross-inoculation greenhouse experiment in which plants were exposed experimentally to each other’s natural field soil microbial communities. The cross-inoculation experiment indicated a higher pathogenicity of soil microbial communities from the southern, mostly sexual, populations compared to soil microbial communities from the northern asexual populations. Northern dandelion populations also showed reduced infestation by a specialized seed-eating weevil. A similar trend of reduced rust fungus infection in northern populations was observed but this trend was not statistically significant. Conclusions The prevalence of pests and pathogens decreased along the south-to-north axis of geographic parthenogenesis. This highlights the potential of biotic interactions in shaping patterns of geographic parthenogenesis.
Improved Variance Reduced Monte-Carlo Simulation of in-the-Money Options  [PDF]
Armin Müller
Journal of Mathematical Finance (JMF) , 2016, DOI: 10.4236/jmf.2016.63029
Abstract: Pricing derivatives with Monte-Carlo simulations involve standard errors that typically decrease at a rate proportional to\"\" where N is the sample size. Several approaches have been discussed to reduce the empirical variance for a given sample size. This article analyzes the joint application of the put-call-parity approach and importance sampling to variance reduced option pricing. For this purpose, we examine non-path-dependent and path-dependent options. For European options, we observe dramatic variance reduction, especially for in-the-money options. Also for arithmetic Asian options, a significant variance reduction is achieved.
Clear Cell Papillary Renal Cell Carcinoma: A Rare Subtype  [PDF]
Armin Kamyab, Michael J. Jacobs
Journal of Cancer Therapy (JCT) , 2011, DOI: 10.4236/jct.2011.25091
Abstract: Introduction: Renal cell carcinoma (RCC) is generally divided into clear cell, papillary, and chromophobe subtypes. Clear cell papillary RCC is a recently described subtype. Case report: We report the case of a 42 year old female who was found on computed tomography scan of the abdomen to have a cyst which appeared to involve the right kidney. Pathology of the cyst wall revealed features consistent with a RCC, clear cell papillary type. Discussion: Clear cell papillary RCC are a recently described entity with less than 100 cases reported in the literature. Most cases in the literature have been associated with end-stage renal disease, however more case are being reported in patients without renal disease. Conclusion: Clear cell papillary RCC is a rare distinct entity in the spectrum of renal cell carcinoma. Based on the literature they appear to be clinically indolent tumors; however, more research is required to further characterize and prognosticate these rare tumors.
Retroperitoneal High Grade Undifferentiated Pleomorphic Sarcoma as a Second Metachronous Neoplasm Following Intracranial Meningioma  [PDF]
Armin Kamyab, Michael John Jacobs
Journal of Cancer Therapy (JCT) , 2011, DOI: 10.4236/jct.2011.24070
Abstract: Introduction: Meningiomas and retroperitoneal sarcomas are two distinct rare tumors, with an incidence of 2 and 0.4 cases per 100,000 respectively. Case Report: We report the case of a 39 year old woman with a history of intracranial meningioma who was found two months later to have a large retroperitoneal sarcoma on CT scan after presenting to the emergency department complaining of abdominal pain. Pathologic evaluation was consistent with a high grade undifferentiated sarcoma. Discussion: It is highly unusual for a 39 year old otherwise healthy patient to present with two rare, seemingly unrelated tumors. It is our suspicion that there is a genetic component involved, however to date no association has been described in the literature between intracranial meningiomas and extracranial sarcomas. Conclusion: Besides being the first report of a retroperitoneal sarcoma occurring as a second metachronous neoplasm following an intracranial meningioma, we suspect that there is a genetic component involved. Further studies may indicate a genetic mutational link.
Is Mehrabad Airport a Brownfield Site?  [PDF]
Armin Mehdipour, Hoda Rashidi Nia
Current Urban Studies (CUS) , 2014, DOI: 10.4236/cus.2014.21002

At the present time brownfield sites do not have a common definition yet. Each nation has already defined the term Brownfield based on their prioritized targets due to their diverse organizational, geographical, social and economic statuses. In Iranian context, any types of previously developed land—whether contaminated or not—and old urban property that its existence has perceived negative influences on the coherence of the surrounding land are defined as a brownfield site. These sites are mostly recognized as inner-city urban fabrics affected by former industrial and military actions that have considerable potential for regeneration practice. Mehrabad airport, as the third oldest airport in Iran, is currently dealing with various problems and constraints that not only put this immense urban space through adverse condition but also caused considerable difficulties for the surrounding residential neighborhoods. This article is basically intended to explore the recent environmental, physical and socio-economic problems of Mehrabad airport in order to raise the question as to whether this airport can be viewed as being a brownfield site or not.

A Novel Model of Intelligent Electrical Load Management by Goal Programming for Smart Houses, Respecting Consumer Preferences  [PDF]
Armin Dehnad, Hamed Shakouri Shakouri
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.510068

Energy management is being highly regarded throughout the world. High-energy consumption in residential buildings is one of the dominant reasons of excessive energy consumption. There are many recent works on the demand-side management (DSM) and smart homes to keep control on electricity consumption. The paper is an intelligence to modify patterns, by proposing a time scheduling consumers, such that they can maintain their welfare while saving benefits from time varying tariffs; a model of household loads is proposed; constraints, including daily energy requirements and consumer preferences are considered in the framework, and the model is solved using mixed integer linear programming. The model is developed for three scenarios, and the results are compared: the 1st scenario aims Peak Shaving; the 2nd minimizes Electricity Cost, and the 3rd one, which distinguishes this study from the other related works, is a combination of the 1st and 2nd Scenarios. Goal programming is applied to solve the 3rd scenario. Finally, the best schedules for household loads are presented by analyzing power distribution curves and comparing results obtained by these scenarios. It is shown that for the case study of this paper with the implementation of 3rd scenario, it is possible to gain 7% saving in the electricity cost without any increasing in the lowest peak power consumption.

The Compound Spectral Indices of Human Stress  [PDF]
Petr Kloucek, Armin Von Gunten
Applied Mathematics (AM) , 2018, DOI: 10.4236/am.2018.912090
Temporally fine-grained and objective measures of mental states or their surrogate states are desperately needed in clinical psychiatry. Stress, both acute and especially chronic stress, is an important mental and physiological state observed in many mental disorders. It is a potential precipitant of acute psychiatric decompensations, be they anxious, affective, psychotic, or behavioural. Thus, being able to objectively follow stress or its surrogate parameters over time in a clinician-friendly way would help predict and prevent decompensations and monitor subsequent treatment success. Thus, we introduce the Compound Spectral Stress Indices (CSSI) that are derived from sensing data of various physiological and physiological and behavioural parameters we use as surrogate stress measures. To obtain the CSSI we use a hierarchical approach provided by adaptability, congruency and derived stress coefficient matrices. Adaptability is defined as a macroscopic characterisation of physiological and physiological and behavioural performance constructed as a product of the total variation of time-segmented complexity indices multiplied by the frequency of the time-varying distribution of complexity indices of the measured physiological or physiological and behavioural parameters, where complexity is expressed in terms of the Hurst exponent. Congruency is expressed by a constant characterising a demand-resource balance and it is then expressed in the form of a stress coefficient matrix. The CSSI is given by the spectral distance of the stress coefficient matrices from the ideal demand-resource matrix.
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