Исследование по разработке методики определения микроконцентраций висмута в олове высокой чистоты методом амальгамной полярографии с накоплением

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A Lazy SMT-Solver for a Non-Linear Subset of Real Algebra

There are several methods for the synthesis and analysis of hybrid systems that require efficient algorithms and tools for satisfiability checking. For analysis, e.g., bounded model checking describes counterexamples of a fixed length by logical formulas, whose satisfiability corresponds to the existence of such a counterexample. As an example for parameter synthesis, we can state the correctness of a parameterized system by a logical formula; the solution set of the formula gives us possible safe instances of the parameters. For discrete systems, which can be described by propositional logic formulas, SAT-solvers can be used for the satisfiability checks. For hybrid systems, having mixed discrete-continuous behavior, SMT-solvers are needed. SMT-solving extends SAT with theories, and has its main focus on linear arithmetic, which is sufficient to handle, e.g., linear hybrid systems. However, there are only few solvers for more expressive but still decidable logics like the first-order theory of the reals with addition and multiplication -- real algebra. Since the synthesis and analysis of non-linear hybrid systems requires such a powerful logic, we need efficient SMT-solvers for real algebra. Our goal is to develop such an SMT-solver for the real algebra, which is both complete and efficient

The variable mass loss of the AGB star WX Psc as traced by the CO J=1-0 through 7-6 lines and the dust emission

Low and intermediate mass stars lose a significant fraction of their mass through a dust-driven wind during the Asymptotic Giant Branch (AGB) phase. Recent studies show that winds from late-type stars are far from being smooth. Mass-loss variations occur on different time scales, from years to tens of thousands of years. The variations appear to be particularly prominent towards the end of the AGB evolution. The occurrence, amplitude and time scale of these variations are still not well understood. The goal of our study is to gain insight into the structure of the circumstellar envelope (CSE) of WX Psc and map the possible variability of the late-AGB mass-loss phenomenon. We have performed an in-depth analysis of the extreme infrared AGB star WX Psc by modeling (1) the CO J=1-0 through 7-6 rotational line profiles and the full spectral energy distribution (SED) ranging from 0.7 to 1300 micron. We hence are able to trace a geometrically extended region of the CSE. Both mass-loss diagnostics bear evidence of the occurrence of mass-loss modulations during the last ~2000 yr. In particular, WX Psc went through a high mass-loss phase (Mdot~5e-5 Msun/yr) some 800 yr ago. This phase lasted about 600 yr and was followed by a long period of low mass loss (Mdot~5e-8 Msun/yr). The present day mass-loss rate is estimated to be ~6e-6 Msun/yr. The AGB star WX Psc has undergone strong mass-loss rate variability on a time scale of several hundred years during the last few thousand years. These variations are traced in the strength and profile of the CO rotational lines and in the SED. We have consistently simulated the behaviour of both tracers using radiative transfer codes that allow for non-constant mass-loss rates.Comment: 12 pages, accepted for publication in A&

An interlinked research data infrastructure for time-series data from the Helmholtz Research Field Earth & Environment

Time-series data are crucial sources of reference information in all environmental sciences. And beyond typical research applications, the consistent and timely publication of such data is increasingly important for monitoring and issuing warnings, especially in times of growing frequencies of climatic extreme events. In this context, the seven Centres from the Helmholtz Research Field Earth and Environment (E&E) operate some of the largest environmental measurement-infrastructures worldwide. These infrastructures range from terrestrial observation systems in the TERENO observatories and ship-borne sensors to airborne and space-based systems, such as those integrated into the IAGOS infrastructures. In order to streamline and standardize the usage of the huge amount of data from these infrastructures, the seven Centres have jointly initiated the STAMPLATE project. This initiantive aims to adopt the Open Geospatial Consortium (OGC) SensorThings API (STA) as a consistent and modern interface tailored for time-series data. We evaluate STA for representative use-cases from environmental sciences and enhance the core data model with additional crucial metadata such as data quality, data provenance and extended sensor metadata. After centre-wide implementation, the standardized STA interface also serves community-based tools, e.g., for data visualization, data access, quality assurance/quality control (QA/QC), or the management of monitoring systems. By connecting the different STA endpoints of the participating research Centres, we establish an interlinked research data infrastructure (RDI) and a digital ecosystem around the OGC SensorThings API tailored towards environmental time-series data. In this presentation, we want to show the status of the project and give an overview of the current data inventory as well as linked tools and services. We will further demonstrate the practical application of our STA-based framework with simple and representative showcases. With our contribution, we want to promote STA for similar applications and communities beyond our research field. Ultimately, our goal is to provide an important building block towards fostering a more open, FAIR (Findable, Accessible, Interoperable, and Reusable), and harmonized research data landscape in the field of environmental sciences

Extending the Planck mission in “LFI only mode” beyond January 2013

We propose to extend the Planck mission in “LFI-only” mode until 13 August 2013, which will permit the completion of an 8th full-sky survey for all LFI detectors. This extension is made possible by the predicted lifetime of the 20K sorption cooler now in operation, which far exceeds previous projections. The additional observations will lead to a significant improvement in the control of systematic effects and calibration accuracy through a set of new powerful null tests probing the 6-months, 1-year, and 2-years time scales. The current status of the Planck data analysis indicates that such improvement may be very important for a full extraction of Planck cosmological science at low multipoles, especially for polarisation. We also note that the LFI may be the last instrument delivering full-sky temperature maps in its frequency range in a very long time, adding to its legacy value

On solving real-algebraic formulas in a satisfiability-modulo-theories framework

Quantifier-free real-algebraic formulas are Boolean combinations of polynomial equations and inequalities over the domain of the real numbers. Coming with a strong expressiveness and a still decidable satisfiability problem, real-algebraic formulas are a precious modeling language in many academic, industrial and commercial areas. However, only some classes of real-algebraic formulas allow an efficient solving in practice. For instance, conjunctions of linear real-algebraic constraints can be solved with the very successful simplex method. The virtual substitution method can solve also formulas containing quadratic polynomials and, based on recent developments, also polynomials of higher degrees. Other examples are solving methods based on interval constraint propagation, which are able to deal with even more expressive formulas, e.g.~including trigonometric functions. Although those computations are not always terminating with a conclusive answer, they often lead to a reliable result in a short running time. Further special examples are solving techniques based on Gröbner bases. They can be used to solve real-algebraic formulas in combination with other techniques, making the implementation a challenging task. The general quantifier-free real-algebraic satisfiability problem, however, has a worst-case time complexity bound which is exponential in the number of input variables. Methods solving this general problem directly are often inefficient in practice. The most popular method in this respect is the cylindrical algebraic decomposition (CAD) method. Its search space can grow doubly-exponentially with the number of input variables. Thus, its practical usefulness highly depends on search heuristics and search space pruning. In this thesis, both aspects are shed light on. In particular, the CAD method is analyzed in combination with other more specialized solving methods such as Gröbner bases. Moreover, bounds to the variables are used to prune the CAD search space, especially when combining the method with interval-arithmetic techniques. This thesis tackles the solving of general quantifier-free real-algebraic formulas with a combination of different methods in a satisfiability-modulo-theories (SMT) framework: A SAT solver computes partial assignments for the Boolean structure of the real-algebraic formula and real-algebraic solvers check these assignments for consistency in the real domain. If the assignment is infeasible in the real domain, the SAT solver would profit from a small reason for this conflict in terms of a subset of the constraints corresponding to the conflicting assignment. Preferably minimal reasons are a valuable good in an SMT solver. As a main part, this thesis comprises a description and evaluation of their computation using the CAD method. In addition, the new and interesting approach for real-algebraic solving by computing realizable sign conditions is analyzed in terms of its adaptability to the SMT framework

SMT-Solving for the First-Order Theory of the Reals

SAT-solving is a highly actual research area with increasing success and plenty of industrial applications. SMT-solving, extending SAT with theories, has its main focus on linear real constrains. However, there are only few solvers going further to more expressive but still decidable logics like the first-order theory of the reals with addition and multiplication. The main requests on theory solvers that must be fulfilled for their efficient embedding into an SMT solver are (a) incrementality, (b) the efficient computation of minimal infeasible subsets, and (c) the support of backtracking. For the first-order theory of the reals we are not aware of any solver offering those functionalities. In this work we address the possibilities to extend existing theory solving algorithms to come up with a theory solver suited for SMT