760,407 research outputs found

    Laser induced fluorescence for axion dark matter detection: a feasibility study in YLiF4_4:Er3+^{3+}

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    We present a detection scheme to search for QCD axion dark matter, that is based on a direct interaction between axions and electrons explicitly predicted by DFSZ axion models. The local axion dark matter field shall drive transitions between Zeeman-split atomic levels separated by the axion rest mass energy mac2m_a c^2. Axion-related excitations are then detected with an upconversion scheme involving a pump laser that converts the absorbed axion energy (\sim hundreds of μ\mueV) to visible or infrared photons, where single photon detection is an established technique. The proposed scheme involves rare-earth ions doped into solid-state crystalline materials, and the optical transitions take place between energy levels of 4fN4f^N electron configuration. Beyond discussing theoretical aspects and requirements to achieve a cosmologically relevant sensitivity, especially in terms of spectroscopic material properties, we experimentally investigate backgrounds due to the pump laser at temperatures in the range 1.94.21.9-4.2 K. Our results rule out excitation of the upper Zeeman component of the ground state by laser-related heating effects, and are of some help in optimizing activated material parameters to suppress the multiphonon-assisted Stokes fluorescence.Comment: 8 pages, 5 figure

    INDICATORS AFFECTING VIDZEME REGION SMART DEVELOPMENT

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    The study aims to determine the main indicators of rural smart development concept for territorial development analysis and decision-making in Vidzeme region (Latvia). In the framework of the study the theoretical literature and planning documents were analysed, focusing on the indicators of rural areas and sustainable development. For a long time the development was associated primarily with the economic growth - GDP, employment and income growth. In recent years, the economic dimension is supplemented with social, environmental, cultural and political aspects. A holistic approach interprets close relations and balanced integration between the economic, social, political, ecological and cultural dimensions of local and regional development. Such approach requires the search for new indicators that describe the development of rural areas and are directly relevant to each individual area. The results present that in the development of Vidzeme smart specialization, the local governments and the state has the greatest impact. It is most affected by the local government's capacity to develop cooperation with residents and entrepreneurs, and a stable and sustainable economic situation in the country

    PRECEDENT STUDIES AND VISUAL ARCHITECTURE RESEARCH: IN SEARCH OF THEORETICAL CONCEPT OF CHINESE SHOP HOUSES FAÇADE STYLE (Case: Kampung Cina, Pekalongan, Central Java, Indonesia)

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    The in-depth discussion on architectural style of Chinese shop houses in Pekalongan has not been intensively exposed, whereas theoretical development of this understanding is required. This study aimed to search the theoretical concept on the style of Chinese shop houses facade that methodologically revealed through a qualitative approach. Data collection obtained through visual observation by focusing on the analysis of facade components. Further, precedent studies emphasizing on graphical time-lines were used to interpret the result. Theoretical concepts, as a formulation which was composed from the conceptual model, linked these aspects that affect facade appearance. The results show that the architectural facade style of Chinese shop houses should be seen as an entity concepts of: balance, geometry sequences, functions and time (historical point of view). This contributes to the knowledge of local architectural style which can be considered as reference to establish the theories of architectural style in general. Keywords: façade, style, Chinese shop houses

    Linking Search Space Structure, Run-Time Dynamics, and Problem Difficulty: A Step Toward Demystifying Tabu Search

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    Tabu search is one of the most effective heuristics for locating high-quality solutions to a diverse array of NP-hard combinatorial optimization problems. Despite the widespread success of tabu search, researchers have a poor understanding of many key theoretical aspects of this algorithm, including models of the high-level run-time dynamics and identification of those search space features that influence problem difficulty. We consider these questions in the context of the job-shop scheduling problem (JSP), a domain where tabu search algorithms have been shown to be remarkably effective. Previously, we demonstrated that the mean distance between random local optima and the nearest optimal solution is highly correlated with problem difficulty for a well-known tabu search algorithm for the JSP introduced by Taillard. In this paper, we discuss various shortcomings of this measure and develop a new model of problem difficulty that corrects these deficiencies. We show that Taillards algorithm can be modeled with high fidelity as a simple variant of a straightforward random walk. The random walk model accounts for nearly all of the variability in the cost required to locate both optimal and sub-optimal solutions to random JSPs, and provides an explanation for differences in the difficulty of random versus structured JSPs. Finally, we discuss and empirically substantiate two novel predictions regarding tabu search algorithm behavior. First, the method for constructing the initial solution is highly unlikely to impact the performance of tabu search. Second, tabu tenure should be selected to be as small as possible while simultaneously avoiding search stagnation; values larger than necessary lead to significant degradations in performance

    Local Optimal Sets and Bounded Archiving on Multi-objective NK-Landscapes with Correlated Objectives

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    The properties of local optimal solutions in multi-objective combinatorial optimization problems are crucial for the effectiveness of local search algorithms, particularly when these algorithms are based on Pareto dominance. Such local search algorithms typically return a set of mutually nondominated Pareto local optimal (PLO) solutions, that is, a PLO-set. This paper investigates two aspects of PLO-sets by means of experiments with Pareto local search (PLS). First, we examine the impact of several problem characteristics on the properties of PLO-sets for multi-objective NK-landscapes with correlated objectives. In particular, we report that either increasing the number of objectives or decreasing the correlation between objectives leads to an exponential increment on the size of PLO-sets, whereas the variable correlation has only a minor effect. Second, we study the running time and the quality reached when using bounding archiving methods to limit the size of the archive handled by PLS, and thus, the maximum size of the PLO-set found. We argue that there is a clear relationship between the running time of PLS and the difficulty of a problem instance.Comment: appears in Parallel Problem Solving from Nature - PPSN XIII, Ljubljana : Slovenia (2014
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