TY - CONF AB - Access to precise meteorological data is crucial to be able to plan and install renewable energy systems such as solar power plants and wind farms. In case of solar energy, knowledge of local irradiance and air temperature values is very important. For this, various methods can be used such as installing local weather stations or using meteorological data from different organizations such as Meteonorm or official Deutscher Wetterdienst (DWD). An alternative is to use satellite reanalysis datasets provided by organizations like the National Aeronautics and Space Administration (NASA) and European Centre for Medium-Range Weather Forecasts (ECMWF). In this paper the “Modern-Era Retrospective analysis for Research and Applications” dataset version 2 (MERRA-2) will be presented, and its performance will be evaluated by comparing it to locally measured datasets provided by Meteonorm and DWD. The analysis shows very high correlation between MERRA-2 and local measurements (correlation coefficients of 0.99) for monthly global irradiance and air temperature values. The results prove the suitability of MERRA-2 data for applications requiring long historical data. Moreover, availability of MERRA-2 for the whole world with an acceptable resolution makes it a very valuable dataset. AU - Khatibi, Arash AU - Krauter, Stefan ID - 24551 KW - Energy potential estimation KW - Photovoltaic KW - Solar radiation KW - Temperature measurement KW - Satellite data KW - Meteonorm KW - MERRA-2 KW - DWD SN - 3-936338-78-7 T2 - Proceedings of the 38th European Photovoltaic Solar Energy Conference and Exhibition (EUPVSEC 2021) TI - Comparison and Validation of Irradiance Data: Satellite Meteorological Dataset MERRA-2 vs. Meteonorm and German Weather Service (DWD) ER - TY - JOUR AB - Fast-growing energy demand of the world makes the researchers focus on finding new energy sources or optimizing already-developed approaches. For an efficient use of solar and wind energy in an energy system, correct design and sizing of a power system is of high importance and improving or optimizing the process of data obtaining for this purpose leads to higher performance and lower cost per unit of energy. It is essential to have the most precise possible estimation of solar and wind energy potential and other local weather parameters in order to fully feed the demand and avoid extra costs. There are various methods for obtaining local data, such as local measurements, official organizational data, satellite obtained, and reanalysis data. In this paper, the Modern-Era Retrospective analysis for Research and Applications dataset version 2 (MERRA-2) dataset provided by NASA is introduced and its performance is evaluated by comparison to various locally measured datasets offered by meteorological institutions such as Meteonorm and Deutscher Wetterdienst (DWD, or Germany’s National Meteorological Service) around the world. After comparison, correlation coefficients from 0.95 to 0.99 are observed for monthly global horizontal irradiance values. In the case of air temperature, correlation coefficients of 0.99 and for wind speed from 0.81 to 0.99 are observed. High correlation with ground measurements and relatively low errors are confirmed, especially for irradiance and temperature values, that makes MERRA-2 a valuable dataset, considering its world coverage and availability. AU - Khatibi, Arash AU - Krauter, Stefan ID - 21265 IS - 4 JF - Energies KW - Solar irradiance KW - MERRA 2 KW - Meteonorm KW - DWD SN - 1996-1073 TI - Validation and Performance of Satellite Meteorological Dataset MERRA-2 for Solar and Wind Applications VL - 14 ER - TY - GEN AU - Ludwig, Janis AU - Kykal, Carsten AU - Schmid, Hans-Joachim ID - 27551 KW - aerosol spreading KW - SARS-CoV-2 KW - indoor air filtration T2 - Book of abstracts for the 2021 European Aerosol Conference TI - Assessing spreading and removal of virus laden aerosols in different settings using an aerosol method (Presentation) ER - TY - CONF AB - The polynomial-time hierarchy (PH) has proven to be a powerful tool for providing separations in computational complexity theory (modulo standard conjectures such as PH does not collapse). Here, we study whether two quantum generalizations of PH can similarly prove separations in the quantum setting. The first generalization, QCPH, uses classical proofs, and the second, QPH, uses quantum proofs. For the former, we show quantum variants of the Karp-Lipton theorem and Toda's theorem. For the latter, we place its third level, Q Sigma_3, into NEXP using the Ellipsoid Method for efficiently solving semidefinite programs. These results yield two implications for QMA(2), the variant of Quantum Merlin-Arthur (QMA) with two unentangled proofs, a complexity class whose characterization has proven difficult. First, if QCPH=QPH (i.e., alternating quantifiers are sufficiently powerful so as to make classical and quantum proofs "equivalent"), then QMA(2) is in the Counting Hierarchy (specifically, in P^{PP^{PP}}). Second, unless QMA(2)= Q Sigma_3 (i.e., alternating quantifiers do not help in the presence of "unentanglement"), QMA(2) is strictly contained in NEXP. AU - Gharibian, Sevag AU - Santha, Miklos AU - Sikora, Jamie AU - Sundaram, Aarthi AU - Yirka, Justin ED - Potapov, Igor ED - Spirakis, Paul ED - Worrell, James ID - 8161 KW - Complexity Theory KW - Quantum Computing KW - Polynomial Hierarchy KW - Semidefinite Programming KW - QMA(2) KW - Quantum Complexity T2 - 43rd International Symposium on Mathematical Foundations of Computer Science (MFCS 2018) TI - Quantum Generalizations of the Polynomial Hierarchy with Applications to QMA(2) VL - 117 ER - TY - CONF AB - An important task in quantum physics is the estimation of local quantities for ground states of local Hamiltonians. Recently, Ambainis defined the complexity class P^QMA[log], and motivated its study by showing that the physical task of estimating the expectation value of a local observable against the ground state of a local Hamiltonian is P^QMA[log]-complete. In this paper, we continue the study of P^QMA[log], obtaining the following results. The P^QMA[log]-completeness result of Ambainis requires O(log n)-local observ- ables and Hamiltonians. We show that simulating even a single qubit measurement on ground states of 5-local Hamiltonians is P^QMA[log]-complete, resolving an open question of Ambainis. We formalize the complexity theoretic study of estimating two-point correlation functions against ground states, and show that this task is similarly P^QMA[log]-complete. P^QMA[log] is thought of as "slightly harder" than QMA. We justify this formally by exploiting the hierarchical voting technique of Beigel, Hemachandra, and Wechsung to show P^QMA[log] \subseteq PP. This improves the containment QMA \subseteq PP from Kitaev and Watrous. A central theme of this work is the subtlety involved in the study of oracle classes in which the oracle solves a promise problem. In this vein, we identify a flaw in Ambainis' prior work regarding a P^UQMA[log]-hardness proof for estimating spectral gaps of local Hamiltonians. By introducing a "query validation" technique, we build on his prior work to obtain P^UQMA[log]-hardness for estimating spectral gaps under polynomial-time Turing reductions. AU - Gharibian, Sevag AU - Yirka, Justin ED - Wilde, Mark ID - 8160 KW - Complexity theory KW - Quantum Merlin Arthur (QMA) KW - local Hamiltonian KW - local measurement KW - spectral gap T2 - 12th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2017) TI - The Complexity of Simulating Local Measurements on Quantum Systems VL - 73 ER - TY - CONF AB - The Boolean constraint satisfaction problem 3-SAT is arguably the canonical NP-complete problem. In contrast, 2-SAT can not only be decided in polynomial time, but in fact in deterministic linear time. In 2006, Bravyi proposed a physically motivated generalization of k-SAT to the quantum setting, defining the problem "quantum k-SAT". He showed that quantum 2-SAT is also solvable in polynomial time on a classical computer, in particular in deterministic time O(n^4), assuming unit-cost arithmetic over a field extension of the rational numbers, where n is number of variables. In this paper, we present an algorithm for quantum 2-SAT which runs in linear time, i.e. deterministic time O(n+m) for n and m the number of variables and clauses, respectively. Our approach exploits the transfer matrix techniques of Laumann et al. [QIC, 2010] used in the study of phase transitions for random quantum 2-SAT, and bears similarities with both the linear time 2-SAT algorithms of Even, Itai, and Shamir (based on backtracking) [SICOMP, 1976] and Aspvall, Plass, and Tarjan (based on strongly connected components) [IPL, 1979]. AU - de Beaudrap, Niel AU - Gharibian, Sevag ED - Raz, Ran ID - 8159 KW - quantum 2-SAT KW - transfer matrix KW - strongly connected components KW - limited backtracking KW - local Hamiltonian SN - 978-3-95977-008-8 T2 - Proceedings of the 31st Conference on Computational Complexity (CCC 2016) TI - A Linear Time Algorithm for Quantum 2-SAT VL - 50 ER - TY - JOUR AB - Meta-heuristics are frequently used to tackle NP-hard combinatorial optimization problems. With this paper we contribute to the understanding of the success of 2-opt based local search algorithms for solving the traveling salesperson problem (TSP). Although 2-opt is widely used in practice, it is hard to understand its success from a theoretical perspective. We take a statistical approach and examine the features of TSP instances that make the problem either hard or easy to solve. As a measure of problem difficulty for 2-opt we use the approximation ratio that it achieves on a given instance. Our investigations point out important features that make TSP instances hard or easy to be approximated by 2-opt. AU - Mersmann, Olaf AU - Bischl, Bernd AU - Trautmann, Heike AU - Wagner, Markus AU - Bossek, Jakob AU - Neumann, Frank ID - 48889 IS - 2 JF - Annals of Mathematics and Artificial Intelligence KW - 2-opt KW - 90B06 KW - Classification KW - Feature selection KW - MARS KW - TSP SN - 1012-2443 TI - A Novel Feature-Based Approach to Characterize Algorithm Performance for the Traveling Salesperson Problem VL - 69 ER - TY - CONF AB - With this paper we contribute to the understanding of the success of 2-opt based local search algorithms for solving the traveling salesman problem TSP. Although 2-opt is widely used in practice, it is hard to understand its success from a theoretical perspective. We take a statistical approach and examine the features of TSP instances that make the problem either hard or easy to solve. As a measure of problem difficulty for 2-opt we use the approximation ratio that it achieves on a given instance. Our investigations point out important features that make TSP instances hard or easy to be approximated by 2-opt. AU - Mersmann, Olaf AU - Bischl, Bernd AU - Bossek, Jakob AU - Trautmann, Heike AU - Wagner, Markus AU - Neumann, Frank ID - 48890 KW - 2-opt KW - Classification KW - Feature Selection KW - MARS KW - TSP SN - 978-3-642-34412-1 T2 - Revised Selected Papers of the 6th International Conference on Learning and Intelligent Optimization - Volume 7219 TI - Local Search and the Traveling Salesman Problem: A Feature-Based Characterization of Problem Hardness ER -