Journal articles on the topic 'Global space-time structure'
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1
Duggal, K. L. "Space time manifolds and contact structures." International Journal of Mathematics and Mathematical Sciences 13, no. 3 (1990): 545–53. http://dx.doi.org/10.1155/s0161171290000783.
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A new class of contact manifolds (carring a global non-vanishing timelike vector field) is introduced to establish a relation between spacetime manifolds and contact structures. We show that odd dimensional strongly causal (in particular, globally hyperbolic) spacetimes can carry a regular contact structure. As examples, we present a causal spacetime with a non regular contact structure and a physical model [Gödel Universe] of Homogeneous contact manifold. Finally, we construct a model of 4-dimensional spacetime of general relativity as a contact CR-submanifold.
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Wang, Anzhong, and Patricio S. Letelier. "Local and global structure of a thick-domain-wall space-time." Physical Review D 51, no. 12 (June 15, 1995): R6612—R6616. http://dx.doi.org/10.1103/physrevd.51.r6612.
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GUERREIRO, A. "On the quantum space–time structure of light." Journal of Plasma Physics 76, no. 6 (August 17, 2010): 833–43. http://dx.doi.org/10.1017/s0022377810000425.
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AbstractWe extend the quantum theory of Time Refraction for a generic spatial and temporal modulation of the optical properties of a medium, such as a dielectric or a gravitational field. The derivation of the local Bogoliubov transformations relating the global electromagnetic modes (valid over the entire span of space and time) with the local modes (valid for the vicinity of each spatial and temporal position) is presented and used in the evaluation of vacuum photon creation by the optical modulations of the medium. We use this approach to relate and review the results of different quantum effects such as the dynamical Casimir effect, space and Time Refraction, the Unruh effect and radiation from superluminal non-accelerated optical boundaries.
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Moreno, Adam, Mathias Neumann, and Hubert Hasenauer. "Climate limits on European forest structure across space and time." Global and Planetary Change 169 (October 2018): 168–78. http://dx.doi.org/10.1016/j.gloplacha.2018.07.018.
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Beer, Randall D. "Parameter Space Structure of Continuous-Time Recurrent Neural Networks." Neural Computation 18, no. 12 (December 2006): 3009–51. http://dx.doi.org/10.1162/neco.2006.18.12.3009.
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A fundamental challenge for any general theory of neural circuits is how to characterize the structure of the space of all possible circuits over a given model neuron. As a first step in this direction, this letter begins a systematic study of the global parameter space structure of continuous-time recurrent neural networks (CTRNNs), a class of neural models that is simple but dynamically universal. First, we explicitly compute the local bifurcation manifolds of CTRNNs. We then visualize the structure of these manifolds in net input space for small circuits. These visualizations reveal a set of extremal saddle node bifurcation manifolds that divide CTRNN parameter space into regions of dynamics with different effective dimensionality. Next, we completely characterize the combinatorics and geometry of an asymptotically exact approximation to these regions for circuits of arbitrary size. Finally, we show how these regions can be used to calculate estimates of the probability of encountering different kinds of dynamics in CTRNN parameter space.
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Lovejoy, S., J. Pinel, and D. Schertzer. "The global space–time cascade structure of precipitation: Satellites, gridded gauges and reanalyses." Advances in Water Resources 45 (September 2012): 37–50. http://dx.doi.org/10.1016/j.advwatres.2012.03.024.
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Sheftel, V. M., O. I. Bandilet, A. N. Yaroshenko, and A. K. Chernyshev. "Space-time structure and reasons of global, regional, and local variations of atmospheric electricity." Journal of Geophysical Research 99, no. D5 (1994): 10797. http://dx.doi.org/10.1029/93jd02857.
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Cuozzo, Gianluca. "Waste 4.0. Perceptual alterations of space and time." E3S Web of Conferences 119 (2019): 00009. http://dx.doi.org/10.1051/e3sconf/201911900009.
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Living in today’s disfigured environment, where nature is but a fragment of an ancient beauty and richness, means living in a global allegory, where humans are forced to dwell in a lunar landscape – a locus of rotting trash, made up of all our discarded technological gadgets, where everything is swiftly reduced to “kipple” and “gubble” (Philip K. Dick). To put an end to this strabismus, we need to fully investigate the new4.0 e-wastes and expose their ontological and circumstantial structure, which profoundly affects our concept of space (in terms of geopolitics) and of time (as for the durability of our sensations of wellness).
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BARBOSA, D., E. R. BEZERRA DE MELLO, and J. SPINELLY. "INDUCED ELECTROSTATIC SELF-INTERACTION IN THE SPACE–TIME OF A GLOBAL MONOPOLE WITH INNER STRUCTURE." International Journal of Modern Physics D 18, no. 07 (July 2009): 1085–99. http://dx.doi.org/10.1142/s0218271809014960.
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In this work we analyze the electrostatic self-energy and self-force on a pointlike electric-charged particle induced by a global monopole space–time considering an inner structure for it. In order to develop this analysis we calculate the three-dimensional Green function associated with this physical system. We explicitly show that for points inside and outside the monopole's core the self-energy presents two distinct contributions. The first is induced by the geometry associated with the space–time under consideration, and the second is a correction due to the nonvanishing inner structure attributed to it. Considering specifically the ballpoint pen model for the region inside, we are able to obtain exact expressions for the self-energies in the regions outside and inside the monopole's core.
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Dzwinel, W., D. A. Yuen, K. Boryczko, Y. Ben-Zion, S. Yoshioka, and T. Ito. "Nonlinear multidimensional scaling and visualization of earthquake clusters over space, time and feature space." Nonlinear Processes in Geophysics 12, no. 1 (January 28, 2005): 117–28. http://dx.doi.org/10.5194/npg-12-117-2005.
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Abstract. We present a novel technique based on a multi-resolutional clustering and nonlinear multi-dimensional scaling of earthquake patterns to investigate observed and synthetic seismic catalogs. The observed data represent seismic activities around the Japanese islands during 1997-2003. The synthetic data were generated by numerical simulations for various cases of a heterogeneous fault governed by 3-D elastic dislocation and power-law creep. At the highest resolution, we analyze the local cluster structures in the data space of seismic events for the two types of catalogs by using an agglomerative clustering algorithm. We demonstrate that small magnitude events produce local spatio-temporal patches delineating neighboring large events. Seismic events, quantized in space and time, generate the multi-dimensional feature space characterized by the earthquake parameters. Using a non-hierarchical clustering algorithm and nonlinear multi-dimensional scaling, we explore the multitudinous earthquakes by real-time 3-D visualization and inspection of the multivariate clusters. At the spatial resolutions characteristic of the earthquake parameters, all of the ongoing seismicity both before and after the largest events accumulates to a global structure consisting of a few separate clusters in the feature space. We show that by combining the results of clustering in both low and high resolution spaces, we can recognize precursory events more precisely and unravel vital information that cannot be discerned at a single resolution.
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ADOMAITIS, RAYMOND A., IOANNIS G. KEVREKIDIS, and RAFAEL DE LA LLAVE. "A COMPUTER-ASSISTED STUDY OF GLOBAL DYNAMIC TRANSITIONS FOR A NONINVERTIBLE SYSTEM." International Journal of Bifurcation and Chaos 17, no. 04 (April 2007): 1305–21. http://dx.doi.org/10.1142/s021812740701780x.
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We present a computer-assisted analysis of the phase space features and bifurcations of a noninvertible, discrete-time system. Our focus is on the role played by noninvertibility in generating disconnected basins of attraction and the breakup of invariant circle solutions. Transitions between basin of attraction structures are identified and organized according to "levels of complexity," a term we define in this paper. In particular, we present an algorithm that provides a computational approximation to the boundary (in phase space) separating points with different preimage behavior. The interplay between this boundary and other phase space features is shown to be crucial in understanding global bifurcations and transitions in the structure of the basin of attraction.
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BARBOSA, D., J. SPINELLY, and E. R. BEZERRA DE MELLO. "ERRATUM: "INDUCED ELECTROSTATIC SELF-INTERACTION IN THE SPACE–TIME OF A GLOBAL MONOPOLE WITH INNER STRUCTURE"." International Journal of Modern Physics D 20, no. 01 (January 2011): 119–20. http://dx.doi.org/10.1142/s0218271811018664.
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Netrdová, Pavlína, and Vojtěch Nosek. "Spatial Dimension of Unemployment: Space-Time Analysis Using Real-Time Accessibility in Czechia." ISPRS International Journal of Geo-Information 9, no. 6 (June 18, 2020): 401. http://dx.doi.org/10.3390/ijgi9060401.
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This paper focuses on the analysis of unemployment data in Czechia on a very detailed spatial structure and yearly, extended time series (2002–2019). The main goal of the study was to examine the spatial dimension of disparities in regional unemployment and its evolutionary tendencies on a municipal level. To achieve this goal, global and local spatial autocorrelation methods were used. Besides spatial and space-time analyses, special attention was given to spatial weight matrix selection. The spatial weights were created according to real-time accessibilities between the municipalities based on the Czech road network. The results of spatial autocorrelation analyses based on network spatial weights were compared to the traditional distance-based spatial weights. Despite significant methodological differences between applied spatial weights, the resulting spatial pattern of unemployment proved to be very similar. Empirically, relative stability of spatial patterns of unemployment with only slow shift of differentiation from macro- to microlevels could be observed.
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Kim, Seong-Eun, Michael K. Behr, Demba Ba, and Emery N. Brown. "State-space multitaper time-frequency analysis." Proceedings of the National Academy of Sciences 115, no. 1 (December 18, 2017): E5—E14. http://dx.doi.org/10.1073/pnas.1702877115.
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Time series are an important data class that includes recordings ranging from radio emissions, seismic activity, global positioning data, and stock prices to EEG measurements, vital signs, and voice recordings. Rapid growth in sensor and recording technologies is increasing the production of time series data and the importance of rapid, accurate analyses. Time series data are commonly analyzed using time-varying spectral methods to characterize their nonstationary and often oscillatory structure. Current methods provide local estimates of data features. However, they do not offer a statistical inference framework that applies to the entire time series. The important advances that we report are state-space multitaper (SS-MT) methods, which provide a statistical inference framework for time-varying spectral analysis of nonstationary time series. We model nonstationary time series as a sequence of second-order stationary Gaussian processes defined on nonoverlapping intervals. We use a frequency-domain random-walk model to relate the spectral representations of the Gaussian processes across intervals. The SS-MT algorithm efficiently computes spectral updates using parallel 1D complex Kalman filters. An expectation–maximization algorithm computes static and dynamic model parameter estimates. We test the framework in time-varying spectral analyses of simulated time series and EEG recordings from patients receiving general anesthesia. Relative to standard multitaper (MT), SS-MT gave enhanced spectral resolution and noise reduction (>10 dB) and allowed statistical comparisons of spectral properties among arbitrary time series segments. SS-MT also extracts time-domain estimates of signal components. The SS-MT paradigm is a broadly applicable, empirical Bayes’ framework for statistical inference that can help ensure accurate, reproducible findings from nonstationary time series analyses.
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Emmrich, Claudio. "Local spin base invariance from a global differential–geometrical point of view." Journal of Mathematical Physics 63, no. 4 (April 1, 2022): 042302. http://dx.doi.org/10.1063/5.0081140.
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This article gives a geometric interpretation of the spin base formulation with local spin base invariance of spinors on a curved space-time and, in particular, of a central element, the global Dirac structure, in terms of principal and vector bundles and their endomorphisms. It is shown that this is intimately related to Spin and [Formula: see text] structures in the sense that the existence of one of those implies the existence of a Dirac structure and allows for an extension to local spin base invariance. Vice versa, as a central result, the existence of a Dirac structure implies the existence of a [Formula: see text] structure. Nevertheless, the spin base invariant setting may be considered more general, allowing for more physical degrees of freedom. Furthermore, arguments are given that the Dirac structure is a more natural choice as a variable for (quantum) gravity than tetrads/vielbeins.
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Small, Christopher, and Daniel Sousa. "The Climatic Temporal Feature Space: Continuous and Discrete." Advances in Artificial Intelligence and Machine Learning 01, no. 02 (2021): 171–90. http://dx.doi.org/10.54364/aaiml.2021.1111.
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Climatic zones, representing seasonal variations in temperature (T) and precipitation (P), are generally mapped geographically using discrete classifications with distinct boundaries. However, it is well known that global T and P vary continuously in space and time with steep gradients occurring infrequently. The objective of this analysis is to use complementary forms of dimensionality reduction to quantify the spatiotemporal dimensionality of the climate system and to produce a continuous representation of global climate based on the temporal feature space of historical T and P alone. We characterize the continuous global feature space using principal components (PCs) to identify a parsimonious set of temporal endmember T and P patterns bounding the feature space of all observed T and P patterns. These endmember T and P patterns provide the basis for a linear temporal mixture model that can represent decadal T and P patterns of any geographic location as fractions of the endmember T and P patterns. Inverting this linear mixture model for each geographic T+P time series gives an estimate of the fractional contribution of each endmember to the observed time series. The resulting temporal endmember fraction maps provide a continuous representation of the Euclidean proximity of T and P observations at every geographic location to each of the temporal endmember climates bounding the space. The spatiotemporal dimensionality implied by the variance partition of T + P time series for 67,420 land-based observations suggests that the T + P temporal feature space is effectively 3D, accounting for 92% of total variance. From the topology of the feature space, we identify 4 bounding temporal endmembers upon which to base the linear temporal mixture model. Inversion of the model for each normalized observed time series yields endmember fraction estimates and a model misfit distribution with 99% of misfit < 0.21. For comparison, we also render temporal feature spaces from ensembles of 2D manifolds within the T + P space derived from suites of t-distributed Stochastic Neighbor Embeddings (t-SNE) to identify discontinuities in the feature space. Comparison of spatial PC(t-SNE) across hyperparameter settings reveals consistent structure and little hyperparameter sensitivity to temporal feature spaces rendered by t-SNE. Combining the physically interpretable continuous global structure resolved by the PC feature space with the finer scale manifold structure resolved by the t-SNE feature space provides a continuous alternative to discrete classifications of climate that cannot represent the continuous character of its temporal feature space.
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Deng, Xiaodi, and Cheng Dong. "EPCryst: a computer program for solving crystal structures from powder diffraction data." Journal of Applied Crystallography 44, no. 1 (January 11, 2011): 230–37. http://dx.doi.org/10.1107/s0021889810053835.
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Recently, a new algorithm has been proposed to generate a full set of trial structure models (TSMs) by enumerating all possible equivalent position combinations (EPCs) based on the unit-cell content and space-group information [Deng & Dong (2009).J. Appl. Cryst.42, 953–958]. Using this algorithm, a new computer program namedEPCrysthas been developed for crystal structure determination from powder diffraction data. It is designed to solve a crystal structure as efficiently as possible. Rather than applying a time-consuming global optimization procedure on each TSM,EPCrystfirstly tries to eliminate improbable TSMs. Several methods (such as the statistical analysis method and direct-space heavy-atom method) are designed to achieve this goal. Usually, a lot of improbable TSMs can be eliminated and only a few promising TSMs are preserved for global optimization by grid search or simulated annealing. These methods can greatly increase the efficiency of structure solution in direct space. Bond-length checking is available inEPCrystas a tool for crystal structure validation.EPCrystwas successfully applied to determine several inorganic crystal structures using powder diffraction data obtained from PowBase [Le Bail (2000). http://sdpd.univ-lemans.fr/powbase/].
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Sun, Qiong, Chi Zhang, Min Liu, and Yongjing Zhang. "Land use and land cover change based on historical space–time model." Solid Earth 7, no. 5 (September 27, 2016): 1395–403. http://dx.doi.org/10.5194/se-7-1395-2016.
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Abstract. Land use and cover change is a leading edge topic in the current research field of global environmental changes and case study of typical areas is an important approach understanding global environmental changes. Taking the Qiantang River (Zhejiang, China) as an example, this study explores automatic classification of land use using remote sensing technology and analyzes historical space–time change by remote sensing monitoring. This study combines spectral angle mapping (SAM) with multi-source information and creates a convenient and efficient high-precision land use computer automatic classification method which meets the application requirements and is suitable for complex landform of the studied area. This work analyzes the histological space–time characteristics of land use and cover change in the Qiantang River basin in 2001, 2007 and 2014, in order to (i) verify the feasibility of studying land use change with remote sensing technology, (ii) accurately understand the change of land use and cover as well as historical space–time evolution trend, (iii) provide a realistic basis for the sustainable development of the Qiantang River basin and (iv) provide a strong information support and new research method for optimizing the Qiantang River land use structure and achieving optimal allocation of land resources and scientific management.
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Montavon, Thomas, and Denis Duboule. "Chromatin organization and global regulation of Hox gene clusters." Philosophical Transactions of the Royal Society B: Biological Sciences 368, no. 1620 (June 19, 2013): 20120367. http://dx.doi.org/10.1098/rstb.2012.0367.
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During development, a properly coordinated expression of Hox genes, within their different genomic clusters is critical for patterning the body plans of many animals with a bilateral symmetry. The fascinating correspondence between the topological organization of Hox clusters and their transcriptional activation in space and time has served as a paradigm for understanding the relationships between genome structure and function. Here, we review some recent observations, which revealed highly dynamic changes in the structure of chromatin at Hox clusters, in parallel with their activation during embryonic development. We discuss the relevance of these findings for our understanding of large-scale gene regulation.
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HUANG, MAO LIN, PETER EADES, and WEI LAI. "ON-LINE VISUALIZATION AND NAVIGATION OF THE GLOBAL WEB STRUCTURE." International Journal of Software Engineering and Knowledge Engineering 13, no. 01 (February 2003): 27–52. http://dx.doi.org/10.1142/s0218194003001196.
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The current generation of web browsers, such as Netscape and Microsoft Explorer, excites people because of the structure of hyper-documents that provides users with an effective and convenient way to move in cyberspace. This is done through clicking on a series of hyperlinks embedded in hyper-documents. However, this arrangement does not give users a visual "map" to guide them in their web journey. It does not provide sense of "space" while the user is exploring the (cyber) space; instead it only gives a series of lists. This is mainly because of the difficulty of constructing such a huge, complex, and dynamic map with an (virtually) unlimited number of nodes and edges. Because the whole web is partially unknown, it is difficult for mapmaker to draw the map. Further, the computation of the overall geometrical structure of such a huge map (with millions or perhaps billions of nodes) is impossible as most visualization algorithms have super-linear time complexity and only scale to a few hundred nodes. Most existing visualization techniques and current research interests emphasize "site mapping". That is, they try to find an effective way of constructing a structured geometrical map for one web site (a local map). This can only guide the user through a very limited region of cyberspace, and does not help users in their overall journey through the cyberspace. In this paper, we look at the whole journey through the cyberspace as one graph; a huge and partially unknown graph. We use our new on-line exploratory visualization technique [7] to maintain and display a subset of this huge graph incrementally. The Visual Web Browser consists of three major components: a fast accessible linkage server, a filtering mechanism, and an on-line exploratory visualization. The framework of these components provides the user with a dynamic graphical map for guiding the web journey.
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Yizengaw, Endawoke. "Global Longitudinal Dependence Observation of the Neutral Wind and Ionospheric Density Distribution." International Journal of Geophysics 2012 (2012): 1–11. http://dx.doi.org/10.1155/2012/342581.
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The statistical global view of the low-latitude ionospheric density stimulates further interest in studying the strong longitudinal variability of the ionospheric density structures in low-to-equatorial latitudes. However, we are not completely certain how the electrodynamics and ion-neutral coupling proceeds at low latitudes; in particular, the longitudinal difference in the dynamics of plasma structures in the low-to-mid latitude ionosphere is not yet fully understood. Numerical studies of latent heat release in the troposphere have indicated that the lower atmosphere can indeed introduce a longitudinal dependence and variability of the low-latitude ionosphere during quiet conditions. For the first time, we present simultaneous observations of the tidally modulated global wind structure, using TIDI observations, in the E-region and the ionospheric density distribution using ground (global GPS receivers) and space-based (C/NOFS in situ density and GPS TEC on CHAMP) instruments. Our results show that the longitudinally structured zonal wind component could be responsible for the formation of wave number four pattern of the equatorial anomaly.
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Cooke, Philip. "Gigafactory Logistics in Space and Time: Tesla’s Fourth Gigafactory and Its Rivals." Sustainability 12, no. 5 (March 6, 2020): 2044. http://dx.doi.org/10.3390/su12052044.
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This paper concerns the spatial structure of Tesla’s four ‘gigafactories’ (‘giga’ is gigawatt hour, GWh) which are located in Tesla’s first Gigafacility (1) at Sparks, near Reno, Nevada; the Solar City Gigafactory (2) at Buffalo, New York state; the 2019 Tesla plant at Shanghai, China Gigafactory (3); and the new Tesla gigafactory Europe Gigafactory (4), which is a manufacturing plant to be constructed in Grünheide, near Berlin, Germany. The newest campus is 20 miles southeast of central Berlin on the main railway line to Wrocław, Poland. Three main features of the ‘gigafactory’ phenomenon, apart from their scale, are in the industry organisation of production, which thus far reverses much current conventional wisdom regarding production geography. Thus, Tesla’s automotive facility in Fremont California reconcentrates manufacturing on site as in-house own brand componentry, especially heavy parts, or by requiring hitherto distant global suppliers to locate in proximity to the main manufacturing plant. Second, as an electric vehicle (EV) producer, the contributions of Tesla’s production infrastructure and logistics infrastructure are important in meeting greenhouse gas mitigation and the reduction of global warming. Finally, the deployment of Big Data analytics, artificial intelligence (AI) and ‘predictive management’ are important. This lies in gigafactory logistics contributing to production and distribution efficiency and effectiveness as a primer for all future industry and services in seeking to minimise time-management issues. This too potentially contributes significantly to the reduction of wasteful energy usage.
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Chen, Hao, Zheng-Wen Long, Yi Yang, Zi-Long Zhao, and Chao-Yun Long. "The study of the generalized boson oscillator in a chiral conical space–time." International Journal of Modern Physics A 35, no. 20 (July 15, 2020): 2050107. http://dx.doi.org/10.1142/s0217751x20501079.
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Our work mainly study the relativistic generalized boson oscillator namely generalized Duffin–Kemmer–Petiau (DKP) oscillator with the function [Formula: see text] considered as the Cornell potential under the chiral conical space–time background. We obtain the wave function and energy spectrum of radial equation by using commonly used the Nikiforov–Uvarov method. It is shows that the energy spectrum of the generalized DKP oscillator depend explicitly on the angular deficit [Formula: see text], related rotation parameter [Formula: see text] and torsion parameter [Formula: see text], which characterize the global structure of the metric in the chiral conical space–time. In addition, the Cornell potential parameters [Formula: see text] have non-negligible influence on the energy spectrum of the studied systems.
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Wang, Zhi, Zheng-wen Long, Chao-yun Long, and Bing-qian Wang. "The study of a spinless relativistic particle in the spinning cosmic string space–time." Canadian Journal of Physics 95, no. 4 (April 2017): 331–35. http://dx.doi.org/10.1139/cjp-2015-0144.
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In this paper we analyze a spinless relativistic particle depicted by the Klein–Gordon equation in the spinning cosmic string space–time. The solutions of the Klein–Gordon equation in the presence of a uniform magnetic field and the Klein–Gordon equation with two common cylindrically symmetric scalar potentials under the background space–time are presented; the energy spectrum and the corresponding wave functions of these systems are obtained by using the functional analysis method. It is shown that the energy levels of the considered physical systems depend explicitly on the angular deficit α and the rotational parameter a, which characterize the global structure of the metric in the space–time of the spinning cosmic string.
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Panthou, G., T. Vischel, T. Lebel, G. Quantin, and G. Molinié. "Characterizing the space–time structure of rainfall in the Sahel with a view to estimating IDAF curves." Hydrology and Earth System Sciences Discussions 11, no. 7 (July 23, 2014): 8409–41. http://dx.doi.org/10.5194/hessd-11-8409-2014.
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Abstract. Intensity–duration–area–frequency (IDAF) curves are increasingly demanded for characterizing the severity of storms and for designing hydraulic structures. Their computation requires inferring areal rainfall distributions over the range of space–time scales that are the most relevant for hydrological studies at catchment scale. In this study, IDAF curves are computed for the first time in West Africa, based on the data provided by the AMMA-CATCH Niger network, composed of 30 recording rain gauges having operated since 1990 over a 16 000 km2 area in South West Niger. The IDAF curves are obtained by separately considering the time (IDF) and space (Areal Reduction Factor – ARF) components of the extreme rainfall distribution. Annual maximum intensities are extracted for resolutions between 1 and 24 h in time and from point (rain-gauge) to 2500 km2 in space. The IDF model used is based on the concept of scale invariance (simple scaling) which allows the normalization of the different temporal resolutions of maxima series to which a global GEV is fitted. This parsimonious framework allows using the concept of dynamic scaling to describe the ARF. The results show that coupling a simple scaling in space and time with a dynamical scaling relating space and time allows modeling satisfactorily the effect of space–time aggregation on the distribution of extreme rainfall.
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Guo, Qiang, Lian-gang Qi, and Jianhong Xiang. "Space-Time-Frequency Adaptive Processor for Multiple Interference Suppression in GNSS Applications." International Journal of Antennas and Propagation 2018 (2018): 1–9. http://dx.doi.org/10.1155/2018/2301052.
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To enhance the multiple interference suppression performance of global navigation satellite system (GNSS) receivers without extra antenna elements, a space-time-frequency adaptive processor (STFAP) is investigated. Firstly, based on the analysis of the autocorrelation function of the multicomponent signal, we propose a common period estimation and data block technique to segment the received signal data into blocks. Secondly, the signal data in each block are short-time Fourier transformed into time-frequency (TF) domain, and the corresponding TF points with similar frequency characteristics are regrouped to structure space-time-frequency (STF) data matrixes. Finally, a space-time-frequency minimum output power- (STF-MOP) based weight calculation method is introduced to suppress multiple interfering signals according to their sparse characteristics in TF and space domains. Simulation results show that the proposed STFAP can effectively combat more wideband periodic frequency-modulated (WBPFM) interferences even some of them arriving from the same direction as GNSS signals without increasing the number of antenna elements.
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Guendelman, Eduardo, Emil Nissimov, and Svetlana Pacheva. "Vacuum structure and gravitational bags produced by metric-independent space–time volume-form dynamics." International Journal of Modern Physics A 30, no. 22 (August 5, 2015): 1550133. http://dx.doi.org/10.1142/s0217751x1550133x.
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We propose a new class of gravity-matter theories, describing [Formula: see text] gravity interacting with a nonstandard nonlinear gauge field system and a scalar “dilaton,” formulated in terms of two different non-Riemannian volume-forms (generally covariant integration measure densities) on the underlying space–time manifold, which are independent of the Riemannian metric. The nonlinear gauge field system contains a square-root [Formula: see text] of the standard Maxwell Lagrangian which is known to describe charge confinement in flat space–time. The initial new gravity-matter model is invariant under global Weyl-scale symmetry which undergoes a spontaneous breakdown upon integration of the non-Riemannian volume-form degrees of freedom. In the physical Einstein frame we obtain an effective matter-gauge-field Lagrangian of “k-essence” type with quadratic dependence on the scalar “dilaton” field kinetic term [Formula: see text], with a remarkable effective scalar potential possessing two infinitely large flat regions as well as with nontrivial effective gauge coupling constants running with the “dilaton” [Formula: see text]. Corresponding to each of the two flat regions we find “vacuum” configurations of the following types: (i) [Formula: see text] and a nonzero gauge field vacuum [Formula: see text], which corresponds to a charge confining phase; (ii) [Formula: see text] (“kinetic vacuum”) and ordinary gauge field vacuum [Formula: see text] which supports confinement-free charge dynamics. In one of the flat regions of the effective scalar potential we also find: (iii) [Formula: see text] (“kinetic vacuum”) and a nonzero gauge field vacuum [Formula: see text], which again corresponds to a charge confining phase. In all three cases, the space–time metric is de Sitter or Schwarzschild–de Sitter. Both “kinetic vacuums” (ii) and (iii) can exist only within a finite-volume space region below a de Sitter horizon. Extension to the whole space requires matching the latter with the exterior region with a nonstandard Reissner–Nordström–de Sitter geometry carrying an additional constant radial background electric field. As a result, we obtain two classes of gravitational bag-like configurations with properties, which on one hand partially parallel some of the properties of the solitonic “constituent quark” model and, on the other hand, partially mimic some of the properties of MIT bags in QCD phenomenology.
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Panthou, G., T. Vischel, T. Lebel, G. Quantin, and G. Molinié. "Characterising the space–time structure of rainfall in the Sahel with a view to estimating IDAF curves." Hydrology and Earth System Sciences 18, no. 12 (December 11, 2014): 5093–107. http://dx.doi.org/10.5194/hess-18-5093-2014.
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Abstract. Intensity–duration–area–frequency (IDAF) curves are increasingly demanded for characterising the severity of storms and for designing hydraulic structures. Their computation requires inferring areal rainfall distributions over the range of space scales and timescales that are the most relevant for hydrological studies at catchment scale. In this study, IDAF curves are computed for the first time in West Africa, based on the data provided by the AMMA-CATCH Niger network, composed of 30 recording rain gauges having operated since 1990 over a 16 000 km2 area in south-western Niger. The IDAF curves are obtained by separately considering the time (intensity–duration–frequency, IDF) and space (areal reduction factor, ARF) components of the extreme rainfall distribution. Annual maximum intensities are extracted for resolutions between 1 and 24 h in time and from point (rain gauge) to 2500 km2 in space. The IDF model used is based on the concept of scale invariance (simple scaling) which allows the normalisation of the different temporal resolutions of maxima series to which a global generalised extreme value (GEV) is fitted. This parsimonious framework allows one to use the concept of dynamic scaling to describe the ARF. The results show that coupling a simple scaling in space and time with a dynamical scaling that relates to space and time allows one to satisfactorily model the effect of space–time aggregation on the distribution of extreme rainfall.
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Li, Minmin, Wenhua Guo, Renzhong Guo, Biao He, Zhichao Li, Xiaoming Li, Wenchao Liu, and Yong Fan. "Urban Network Spatial Connection and Structure in China Based on Railway Passenger Flow Big Data." Land 11, no. 2 (February 2, 2022): 225. http://dx.doi.org/10.3390/land11020225.
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China’s transportation industry has made great achievements in the past 40 years of reform and opening up. At the same time, it has gradually accumulated a series of problems. These problems have led to closer and more complex social and economic connection within and between regions of different scales. The existing research only carries out the characteristic analysis of urban network spatial connection and pattern from a single perspective such as “flow space” theory, spatial interaction model and accessibility method, and fails to accurately describe the complex socio-economic relations between regions. Based on the big data of railway passenger flow, this study selected weighted average travel time, railway network density, and the economic connection model to express the urban network spatial connection and structure of China in 2016 from the perspectives of time, space, and interaction. In 2016, the accessibility, connectivity, and total urban external economic connection of the railway network showed a trend of declining from the east to the west. The top 50 cities ranked by interurban economic connection were all located in the central and eastern regions and showed “diamond shape” distribution characteristics. The four diamond-shaped pairs were Beijing-Tianjin-Hebei, Yangtze River Delta, Pearl River Delta, and Chengyu urban agglomerations. This shape was basically in line with the T-shaped space that has existed for a long time in China’s regional development. The accessibility, connectivity, and total external economic connection of national-level urban agglomerations were greater than those of regional-level urban agglomerations, and far greater than those of local-level urban agglomerations. The results showed that there was a mismatch between the layout of the railway network and the population. It will still be necessary to focus on strengthening the construction of transportation infrastructure in urban agglomerations and densely populated areas in the future. This study enriches the “flow space” theory, more fully describes urban network spatial connection and structure in China by considering the three perspectives of time, space, and interaction, and can provides reasonable suggestions for the development of national comprehensive three-dimensional transportation network planning, regional spatial structure optimization, and sustainable development.
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Altomare, Angela, Nicola Corriero, Corrado Cuocci, Anna Moliterni, and Rosanna Rizzi. "The hybrid big bang–big crunch method for solving crystal structure from powder diffraction data." Journal of Applied Crystallography 46, no. 3 (May 15, 2013): 779–87. http://dx.doi.org/10.1107/s0021889813010571.
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The big bang–big crunch method is a global optimization approach developed upon the analogy of one of the cosmological theories of the evolution of the universe. It has been suitably combined with a simulated annealing algorithm and used for solving crystal structure from powder diffraction data in direct space. When compared with the traditional simulated annealing method, it provides a significant advance: good solutions are attained in a shorter time. The new method has been implemented in theEXPOpackage. Its successful application is demonstrated with examples of already known structures.
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Wang, Bing-Qian, Zheng-Wen Long, Chao-Yun Long, and Shu-Rui Wu. "The study of a half-spin relativistic particle in the rotating cosmic string space–time." International Journal of Modern Physics A 33, no. 27 (September 27, 2018): 1850158. http://dx.doi.org/10.1142/s0217751x18501580.
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In this paper, a charged half-spin particle depicted by the Dirac equation in the presence of a uniform magnetic field and a mixed potential are analyzed in the rotating cosmic string space–time. In order to facilitate this study, we assume that the symmetrical center of the potential is on the string and the magnetic field is parallel to the string. Based on the functional analysis method, we obtain the energy eigenvalues for different physical situations. It shows that the energy levels of the system depend explicitly on the angular deficit [Formula: see text] and the rotational parameter [Formula: see text] which characterize the global structure of the metric in the space–time of the rotating cosmic string.
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Liu, Fuchen, David Choi, Lu Xie, and Kathryn Roeder. "Global spectral clustering in dynamic networks." Proceedings of the National Academy of Sciences 115, no. 5 (January 16, 2018): 927–32. http://dx.doi.org/10.1073/pnas.1718449115.
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Community detection is challenging when the network structure is estimated with uncertainty. Dynamic networks present additional challenges but also add information across time periods. We propose a global community detection method, persistent communities by eigenvector smoothing (PisCES), that combines information across a series of networks, longitudinally, to strengthen the inference for each period. Our method is derived from evolutionary spectral clustering and degree correction methods. Data-driven solutions to the problem of tuning parameter selection are provided. In simulations we find that PisCES performs better than competing methods designed for a low signal-to-noise ratio. Recently obtained gene expression data from rhesus monkey brains provide samples from finely partitioned brain regions over a broad time span including pre- and postnatal periods. Of interest is how gene communities develop over space and time; however, once the data are divided into homogeneous spatial and temporal periods, sample sizes are very small, making inference quite challenging. Applying PisCES to medial prefrontal cortex in monkey rhesus brains from near conception to adulthood reveals dense communities that persist, merge, and diverge over time and others that are loosely organized and short lived, illustrating how dynamic community detection can yield interesting insights into processes such as brain development.
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Hesthaven, Jan S., Cecilia Pagliantini, and Nicolò Ripamonti. "Rank-adaptive structure-preserving model order reduction of Hamiltonian systems." ESAIM: Mathematical Modelling and Numerical Analysis 56, no. 2 (March 2022): 617–50. http://dx.doi.org/10.1051/m2an/2022013.
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This work proposes an adaptive structure-preserving model order reduction method for finite-dimensional parametrized Hamiltonian systems modeling non-dissipative phenomena. To overcome the slowly decaying Kolmogorov width typical of transport problems, the full model is approximated on local reduced spaces that are adapted in time using dynamical low-rank approximation techniques. The reduced dynamics is prescribed by approximating the symplectic projection of the Hamiltonian vector field in the tangent space to the local reduced space. This ensures that the canonical symplectic structure of the Hamiltonian dynamics is preserved during the reduction. In addition, accurate approximations with low-rank reduced solutions are obtained by allowing the dimension of the reduced space to change during the time evolution. Whenever the quality of the reduced solution, assessed via an error indicator, is not satisfactory, the reduced basis is augmented in the parameter direction that is worst approximated by the current basis. Extensive numerical tests involving wave interactions, nonlinear transport problems, and the Vlasov equation demonstrate the superior stability properties and considerable runtime speedups of the proposed method as compared to global and traditional reduced basis approaches.
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Horváth, Ivan. "The analysis of space–time structure in QCD vacuum, I: localization vs global behavior in local observables and Dirac eigenmodes." Nuclear Physics B 710, no. 1-2 (March 2005): 464–84. http://dx.doi.org/10.1016/j.nuclphysb.2004.12.038.
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Boyce, Mark S., Justin Pitt, Joseph M. Northrup, Andrea T. Morehouse, Kyle H. Knopff, Bogdan Cristescu, and Gordon B. Stenhouse. "Temporal autocorrelation functions for movement rates from global positioning system radiotelemetry data." Philosophical Transactions of the Royal Society B: Biological Sciences 365, no. 1550 (July 27, 2010): 2213–19. http://dx.doi.org/10.1098/rstb.2010.0080.
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Autocorrelation has been viewed as a problem in telemetry studies because sequential observations are not independent in time or space, therefore violating assumptions for statistical inference. Yet nearly all ecological and behavioural data are autocorrelated in both space and time. We argue that there is much to learn about the structure of ecological and behavioural data from patterns of autocorrelation. Such patterns include periodicity in movement and patchiness in spatial data, which can be characterized by an autocorrelogram, semivariogram or spectrum. We illustrate the utility of temporal autocorrelation functions (ACFs) for analysing step-length data from GPS telemetry of wolves ( Canis lupus ), cougars ( Puma concolor ), grizzly bears ( Ursus arctos ) and elk ( Cervus elaphus ) in western Alberta. ACFs often differ by season, reflecting differences in foraging behaviour. In wilderness landscapes, step-length ACFs for predators decay slowly to apparently random patterns, but sometimes display strong daily rhythms in areas of human disturbance. In contrast, step lengths of elk are consistently periodic, reflecting crepuscular activity.
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Wang, Shilei, Yanbo Qu, Weiying Zhao, Mei Guan, and Zongli Ping. "Evolution and Optimization of Territorial-Space Structure Based on Regional Function Orientation." Land 11, no. 4 (March 31, 2022): 505. http://dx.doi.org/10.3390/land11040505.
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In accordance with the ecological civilization strategy, it is necessary to conduct in-depth analyses and provide a systematic elaboration of the characteristics of territorial-space structure (TSS). In the present paper, we examine Shandong Province and construct a framework for the evolution and optimization of TSS based on regional functions. The evolutionary process, pattern, and driving mechanisms of TSS are clarified using a geo-information atlas, the gravity center shift model, spatial autocorrelation analyses, and a geographic detector model. Furthermore, multi-scenario territorial-space simulations are carried out using the CA–Markov model, based on which an optimal pattern of territorial space is constructed. The results show that the comprehensive dynamic degree of territorial space in Shandong Province was valued at 0.56% from 2000 to 2020. Furthermore, six geo-information Tupu of TSS evolution changed, with a total area of 35,485 km2, distributed mainly in the Yellow River Delta, the central and southern Shandong Mountain area, and the Jiaodong Peninsula. The migration route of the TSS gravity center curved over time. Territorial spaces are characterized by the exchange of ecological and agricultural space, while urban spaces occupy agricultural ones. The level of economic development, policy, and the institutional environment are driving forces in the transformation of ecological into agricultural spaces, as well as in transforming agricultural space into ecological and urban spaces. The trade-off connection of TSSs is made evident after a multi-scenario simulation of territorial space considering the 2020–2025 timeframe. Based on the goal of regional function co-ordination, Shandong Province is divided into three and four types of single and complex TSS, respectively. The obtained results may provide scientific reference for the co-ordination between human–land relationships and the sustainable use of territorial space, and serve to guide territorial spatial planning.
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Baffetta, F., P. Corona, and L. Fattorini. "Design-based diagnostics for k-NN estimators of forest resourcesThis article is one of a selection of papers from Extending Forest Inventory and Monitoring over Space and Time." Canadian Journal of Forest Research 41, no. 1 (January 2011): 59–72. http://dx.doi.org/10.1139/x10-157.
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The k-nearest neighbours (k-NN) method constitutes a possible approach to improve the precision of the Horvitz–Thompson estimator of a single interest variable using auxiliary information at the estimation stage. Improvements are likely to occur when the neighbouring structure in the space of auxiliary variables is similar to the neighbouring structure in the space of the survey variables. Populations suitable for k-NN can be identified via the scores of the first principal component computed on the variance–covariance matrix of auxiliary variables. If the first principal component explains a large portion of the whole variability, distances among scores provide good approximations of distances in the space of auxiliary variables in such a way that the effectiveness of k-NN can be assessed by plotting the first principal component scores versus the sampled values of each of the interest variables. Monotone relationships with high values of Spearman’s correlation coefficients should denote effectiveness. Otherwise, when the first principal component explains small fractions of the total variation, an index that directly quantifies the similarity between the neighbouring structure in the space of interest and auxiliary variables is proposed. The validity of the proposed diagnostics is theoretically argued and empirically proven by a simulation study performed on a wide range of artificial and real populations.
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Porazinska, Dorota L., Diana H. Wall, and Ross A. Virginia. "Population Age Structure of Nematodes in the Antarctic Dry Valleys: Perspectives on Time, Space, and Habitat Suitability." Arctic, Antarctic, and Alpine Research 34, no. 2 (May 2002): 159. http://dx.doi.org/10.2307/1552467.
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Porazinska, Dorota L., Diana H. Wall, and Ross A. Virginia. "Population Age Structure of Nematodes in the Antarctic Dry Valleys: Perspectives on Time, Space, and Habitat Suitability." Arctic, Antarctic, and Alpine Research 34, no. 2 (May 2002): 159–68. http://dx.doi.org/10.1080/15230430.2002.12003480.
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Li, Yi, Jihong Yu, and Ruren Xu. "FraGen: a computer program for real-space structure solution of extended inorganic frameworks." Journal of Applied Crystallography 45, no. 4 (June 12, 2012): 855–61. http://dx.doi.org/10.1107/s002188981201878x.
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TheFraGen(framework generator) program has been developed for real-space structure solution. It has been designed especially for the generation of extended inorganic frameworks in a given unit cell.FraGenis based on the parallel tempering global optimization method. Various restraints can be introduced intoFraGen, such as restraints on bonding geometry, relative reflection intensities and three-dimensional density maps. The basic inputs forFraGenare the space group and cell parameters. The number of unique atoms is not a necessary input, since it can be estimated from certain constraints.FraGenalso has the ability to exit unpromising simulation cycles to save computation time for promising ones. Program features, methods and three examples are demonstrated. TheFraGenprogram for the Windows platform is available from the authors upon request.
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Irons, Rebecca. "Quarantime." Anthropology in Action 27, no. 3 (December 1, 2020): 87–92. http://dx.doi.org/10.3167/aia.2020.270318.
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Global lockdowns have resulted in a challenge to our carefully constructed notions of time, the work week and time-space compression. For the past few months, we have been living in ‘Quarantime’. Quarantime moves differently than our daily lived temporalities of routine and order, and forces us to question the intimate relationship that we may have with how we structure our daily lives around a clock and timesheet. This article questions the challenges and opportunities inherent within the disruption of routine intimacies enacted through Quarantime, drawing on case studies of clock time and the work week, and through examining Quarantime’s unique relationship to time-space compression. It will suggest that Quarantime opens up a space for us to question intimate attachments to enforced routine and wide institutionalised concepts of clock time.
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ZHAO, YINCHUAN, TAO TANG, and JINGHUA WANG. "REGULARITY AND GLOBAL STRUCTURE OF SOLUTIONS TO HAMILTON–JACOBI EQUATIONS I: CONVEX HAMILTONIANS." Journal of Hyperbolic Differential Equations 05, no. 03 (September 2008): 663–80. http://dx.doi.org/10.1142/s0219891608001647.
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This paper is concerned with the Hamilton–Jacobi (HJ) equations of multidimensional space variables with convex Hamiltonians. Using Hopf's formula (I), we will study the differentiability of the HJ solutions. For any given point, we give a sufficient and necessary condition under which the solutions are Ck smooth in some neighborhood of the point. We also study the characteristics of the HJ equations. It is shown that there are only two kinds of characteristics, one never touches the singularity point, and the other touches the singularity point in a finite time. The sufficient and necessary condition under which the characteristic never touches the singularity point is given. Based on these results, we study the global structure of the set of singularity points for the HJ solutions. It is shown that there exists a one-to-one correspondence between the path connected components of the set of singularity points and the path connected components of a set on which the initial function does not attain its minimum. A path connected component of the set of singularity points never terminates at a finite time. Our results are independent of the particular forms of the equations as long as the Hamiltonians are convex.
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Wang, Ning, and Zhi-Cheng Wang. "Propagation dynamics of a nonlocal time-space periodic reaction-diffusion model with delay." Discrete & Continuous Dynamical Systems 42, no. 4 (2022): 1599. http://dx.doi.org/10.3934/dcds.2021166.
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<p style='text-indent:20px;'>This paper is concerned with a nonlocal time-space periodic reaction diffusion model with age structure. We first prove the existence and global attractivity of time-space periodic solution for the model. Next, by a family of principal eigenvalues associated with linear operators, we characterize the asymptotic speed of spread of the model in the monotone and non-monotone cases. Furthermore, we introduce a notion of transition semi-waves for the model, and then by constructing appropriate upper and lower solutions, and using the results of the asymptotic speed of spread, we show that transition semi-waves of the model in the non-monotone case exist when their wave speed is above a critical speed, and transition semi-waves do not exist anymore when their wave speed is less than the critical speed. It turns out that the asymptotic speed of spread coincides with the critical wave speed of transition semi-waves in the non-monotone case. In addition, we show that the obtained transition semi-waves are actually transition waves in the monotone case. Finally, numerical simulations for various cases are carried out to support our theoretical results.</p>
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Bilchenko, Yevheniia. "Тhe Transnational Paradoxes of the Global World: Cultural Analysis." Culturology Ideas, no. 17 (1'2020) (2020): 54–64. http://dx.doi.org/10.37627/2311-9489-17-2020-1.54-64.
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The article deals with the critical analysis of the symptoms of the transnational world, which is interpreted as a symbolic order, prone to automatic self-reproduction and inertia of functioning in the machine mode of transgression through the legitimation of its own shortcomings. The main trauma is the basic conflict between the owners of the capital and the employees expressed at the level of everyday reality due to the change of the structure in communication between "people of time" (third wave) and "people of space" (first wave). The "people of time" appear as ideologues who create manipulative realities for "people of space", as dogmatists held in a situation of partial control and utilitarian use. The result of the ideological shift of the basic conflict into the field of culture are the numerous secondary conflicts, one of which is the paradox generated at the level of the symbolic order between globalism and multiculturalism itself, between the politics of unification and the politics of identities as a mechanism for supporting homeostasis. The appearance of this paradox indicates a real socio-economic contradiction masked by the "open suture" (tactics of uncovered information in hyper-realism). At the level of regional politics, this is manifested in a selective attitude to the locations in their struggle against unitary state governments and to those governments themselves, depending on their globalist or anti-globalist orientation.
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Chen, Lin, Wen Bing Yu, Wei Bo Liu, and Xin Yi. "Numerical Simulation of Pile Foundations of Qinghai-Tibet Power Transmission Line: Influence of Temperature Region." Applied Mechanics and Materials 501-504 (January 2014): 218–23. http://dx.doi.org/10.4028/www.scientific.net/amm.501-504.218.
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To analyze the thermal effect of the pile foundation of permafrost, a two-dimensional transient finite element model of the thermal fields with phase change were established. The developments of heat influence limit and maximum thawed depth with and without climate warming were predicted and analyzed. Results indicate that (1) the heat influence limit and maximum thaw depth in permafrost regions enlarge with time elapse, while the global climate warming will have a greater influence to full-space pile foundation compared with the cone-cylinder pile foundation; (2) Considering the global climate warming, heat influence limit (Lmax) and maximum thaw depth (Hmax) in 50th year for full-space pile foundation, cone-cylinder pile foundation are 10.1m, 5.2m, 4.1m, 3.7m, respectively; the maximum thaw depth of full-space pile foundation during the operation will have exceeded the depth of structure (2.5m), which might put the structure at risk; (3) the structure of cone-cylinder pile foundation could effectively preserve permafrost and avoid pile foundations failure; (4) the spacing of cone-cylinder pile foundations is reasonable and the interaction of temperature distribution among cone-cylinder pile foundations can be negligible.
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MUKHOPADHYAY, S., and T. K. BALLABH. "RETRIEVAL OF SURFACE STRUCTURAL PARAMETERS FROM MULTILAYER RELAXED SURFACES." Surface Review and Letters 24, no. 01 (December 22, 2016): 1750004. http://dx.doi.org/10.1142/s0218625x17500044.
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Trial search method of determination of structure from LEED I–V curves is to compute the same including multiple scattering for plausible guess structures and finding the actual structure from the best match. This requires enormous amount of computer time and for some cases even may turn unsuccessful. Using change of computational techniques and different search algorithms tremendous advancement have been made, but still it is possible to get struck in a local minima rather than global one. Therefore a method for determination of surface structure from LEED I–V curves, avoiding a search in the parameter space, is always considered important not only for reducing computational time enormously but also for avoiding the trapping in local minima. To this end, we have investigated the possibilities of retrieval of surface structural parameters by reversing the process of layer doubling method of conventional LEED theory.
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LUSANNA, LUCA. "THE CHRONO-GEOMETRICAL STRUCTURE OF SPECIAL AND GENERAL RELATIVITY: A RE-VISITATION OF CANONICAL GEOMETRODYNAMICS." International Journal of Geometric Methods in Modern Physics 04, no. 01 (February 2007): 79–114. http://dx.doi.org/10.1142/s0219887807001874.
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A modern re-visitation of the consequences of the lack of an intrinsic notion of instantaneous 3-space in relativistic theories leads to a reformulation of their kinematical basis emphasizing the role of non-inertial frames centered on an arbitrary accelerated observer. In special relativity the exigence of predictability implies the adoption of the 3 + 1 point of view, which leads to a well posed initial value problem for field equations in a framework where the change of the convention of synchronization of distant clocks is realized by means of a gauge transformation. This point of view is also at the heart of the canonical approach to metric and tetrad gravity in globally hyperbolic asymptotically flat space-times, where the use of Shanmugadhasan canonical transformations allows the separation of the physical degrees of freedom of the gravitational field (the tidal effects) from the arbitrary gauge variables. Since a global vision of the equivalence principle implies that only global non-inertial frames can exist in general relativity, the gauge variables are naturally interpreted as generalized relativistic inertial effects, which have to be fixed to get a deterministic evolution in a given non-inertial frame. As a consequence, in each Einstein's space-time in this class the whole chrono-geometrical structure, including also the clock synchronization convention, is dynamically determined and a new approach to the Hole Argument leads to the conclusion that "gravitational field" and "space-time" are two faces of the same entity. This view allows to get a classical scenario for the unification of the four interactions in a scheme suited to the description of the solar system or our galaxy with a deparametrization to special relativity and the subsequent possibility to take the non-relativistic limit.
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Dymnikova, Irina, Anna Dobosz, and Bożena Sołtysek. "Cosmological model favored by the holographic principle." International Journal of Modern Physics: Conference Series 41 (January 2016): 1660127. http://dx.doi.org/10.1142/s2010194516601277.
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We present a regular spherically symmetric cosmological model of the Lemaitre class distinguished by the holographic principle as the thermodynamically stable end-point of quantum evaporation of the cosmological horizon. A source term in the Einstein equations connects smoothly two de Sitter vacua with different values of cosmological constant and corresponds to anisotropic vacuum dark fluid defined by symmetry of its stress-energy tensor which is invariant under the radial boosts. Global structure of space-time is the same as for the de Sitter space-time. Cosmological evolution goes from a big initial value of the cosmological constant towards its presently observed value.
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Ivanov, E. V. "Large-Scale Coronal Magnetic Structure and Its Variations during an 11-year Solar Cycle." International Astronomical Union Colloquium 144 (1994): 35–39. http://dx.doi.org/10.1017/s0252921100024957.
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AbstractMaps of coronal magnetic fields at different heights calculated under potential approximation, have been used to reconstruct the corona shape in different phases of solar cycles 21 and 22. The shape of the solar corona depends on the maximum heliolatitudes and the structure of the heliospheric current sheet (HCS) that, in turn, are determined by space-time variations of the 3 main components of the global magnetic field of the Sun: 1) the axial dipole component; 2) the inclined dipole component; and 3) the quadrupole component. Variations of theHCSmaximum heliolatitudes and the width of the corona at 2.5R⊙during a solar cycle are compared with variations of the global magnetic field indices in the photosphere and at the source surface. The role of the solar cycle reference points and the global magnetic field indices in the corona shape variations over a solar cycle are discussed.
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Gajjar, J., and F. T. Smith. "On the global instability of free disturbances with a time-dependent nonlinear viscous critical layer." Journal of Fluid Mechanics 157 (August 1985): 53–77. http://dx.doi.org/10.1017/s0022112085002300.
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A theoretical study is made of the global nonlinear growth or decay, in space and time, of an unsteady non-neutral disturbance/wavepacket when a time-dependent nonlinear viscous critical layer is present. The basic flow considered is a steady quasiparallel channel flow, boundary layer or liquid-layer flow at high Reynolds number. The unsteadiness with regard to the critical layer shows itself less in the internal dynamics than in the relatively slow movement of the layer across the flow, the temporal and spatial rate of movement discussed being sufficient to affect the nonlinear viscous balance in the layer. This greatly reduces the mean-flow distortions produced. The disturbance amplitude, in contrast, responds nonlinearly on faster time- and space-scales, both inside and outside the critical layer. These slower- and faster-scale properties inside the critical layer and outside, i.e. globally, are coupled together in general. The work addresses first the structure and nonlinear evolution equations for the growing or decaying free disturbance and the critical layer. But preliminary analysis in special cases suggests, among other things, the significant result that previous nonlinear studies based on quasineutral assumptions give unstable subcritical threshold amplitudes, above which increasingly fast disturbance growth takes place globally.