423 research outputs found

    The Diffusion of Humans and Cultures in the Course of the Spread of Farming

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    The most profound change in the relationship between humans and their environment was the introduction of agriculture and pastoralism. [....] For an understanding of the expansion process, it appears appropriate to apply a diffusive model. Broadly, these numerical modeling approaches can be catego- rized in correlative, continuous and discrete. Common to all approaches is the comparison to collections of radiocarbon data that show the apparent wave of advance of the transition to farming. However, these data sets differ in entry density and data quality. Often they disregard local and regional specifics and research gaps, or dating uncertainties. Thus, most of these data bases may only be used on a very general, broad scale. One of the pitfalls of using irregularly spaced or irregularly documented radiocarbon data becomes evident from the map generated by Fort (this volume, Chapter 16): while the general east-west and south-north trends become evident, some areas appear as having undergone anomalously early transitions to farming. This may be due to faulty entries into the data base or regional problems with radiocarbon dating, if not unnoticed or undocumented laboratory mistakes.Comment: 20 pages, 5 figures, submitted to Diffusive Spreading in Nature, Technology and Society, edited by Armin Bunde, J\"urgen Caro, J\"org K\"arger, Gero Vogl, Chapter 1

    A modular standard for the cadastral domain

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    Active cancellation of unwanted excitation when measuring dynamic stiffness of resilient elements

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    Laboratory measurements of the vibro-acoustic transfer properties of resilient elements are dealt with in a series of ve International Standards (ISO-10846-1 through 10486-5, partly still forthcoming). The measured quantity that is standardised, is dynamic stiness. Because of the multidirectional nature of the vibration transmission, the standards cover separate measurements of stiness for three perpendicular excitation directions. For each of the three orthogonal translational excitations, the input for the unwanted directions have to be at least 15 dB lower. To meet this requirement over a large frequency band may be quite dicult, especially in case of `transverse' excitation. Then special measures have to be taken to suppress rotation inputs. In this paper active vibration control on the input side of a test element is shown to be useful to suppress unwanted input rotations. The applicable frequency range depends on the controller available. The results presented show the feasibility of the method and good suppression results up to 250 Hz. New tests with a state-of-the-art controller are planned to cover a wider frequency range and to enable the use of a chirp as a driving signal

    A LADM-based temporal cadastral information system for modelling of easement rights – A case study of Turkey

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    Type people to land relations are dynamic and, as a consequence, the nature of land title and cadastral data is of a dynamic nature. Land title and cadastral data are core components for a lot of property applications (e.g. taxation, valuation, mortgage). Those applications require up to date, complete and reliable data–including temporal data as in use in application forms and transactions. In this paper, the modelling of Rights, Restrictions and Responsibilities (RRR) is discussed with a focus on the modelling of easement rights in a case study in Turkey. Functional requirements with respect to the characteristics of easement rights are investigated based upon interviews with professional experts in the public and private sector. Then a prototype model was built based on a simple implementation of the Land Administration Domain Model (LADM) RRR classes and by conforming to the national cadastral data management standards related to land registration systems. This new proposed model includes temporal cadastral attributes related to easements. This is materialised in the ‘Administrative Package’ and illustrated in the Turkey LADM country profile. We show that the LADM can be used to describe for the time dimension of cadastral information in Turkey, but that there are semantic differences, similarities and mismatches of classes and attributes between the LADM and the cadastral information system in Turkey. Proposed LADM-based model for the time dimension of cadastral information will be of immense advantage to land administrators, the governments and land users in Turkey

    Fluorescence excitation spectrum, lifetimes and photoisomerization of jet-cooled conformers of 1,1 '- bi(benzocyclobutylidene)

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    First measurements of fluorescence excitation spectra of the recently synthesized rigid stilbene analogue 1,1'- bi(benzocyclobutylidene) in a supersonic jet expansion show that, in contrast to the parent compound, both the trans- and the cis-conformer fluoresce under these conditions. The excitation energy dependence of fluorescence lifetimes indicates the onset of an efficient non-radiative decay channel above energy thresholds of 1340 cm(-1) and 990 cm(-1) for the trans- and cis-form, respectively, which is assigned to photoisomerization in the singlet state. From an RRKM analysis of the microcanonical rate coefficients an estimate of the high pressure limit of the thermal photoisomerization rate coefficient is obtained and compared with photoisomerization rate coefficients measured in low viscosity solution and in thermal vapor. There are strong indications that for this compound there are no dynamic or static solvent induced effects that lead to an anomalous acceleration of the reaction in solution
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