Academic literature on the topic 'Space-time channel modelling'
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Journal articles on the topic "Space-time channel modelling"
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Babur, G., P. Aubry, and F. Le Chevalier. "Space-Time Radar Waveforms: Circulating Codes." Journal of Electrical and Computer Engineering 2013 (2013): 1–8. http://dx.doi.org/10.1155/2013/809691.
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This paper describes a concept of the circulating codes covering the whole class of the space-time codes. The circulating codes do not narrow the radiated pattern of the antenna array, thus providing a wide angular coverage, possibly tunable. In turn, the beam-forming on transmit is achievable by means of the signal processing in one (or each) receiver channel. The modelling results demonstrate the efficiency of the circulating codes based on their multidimensional ambiguity functions.
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Kharchenko, Volodymir, Bo Wang, Andrii Grekhov, and Anna Leschenko. "MODELLING THE SATELLITE COMMUNICATION LINKS WITH ORTHOGONAL FREQUENCY-DIVISION MULTIPLEXING." TRANSPORT 31, no. 1 (January 28, 2015): 22–28. http://dx.doi.org/10.3846/16484142.2014.1003599.
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Global technologies of data transmission in real time are developing constantly. Therefore, modelling of messages transmission through satellite constellations is an actual problem. In this paper the original model of a communication channel ‘Vehicle-to-Satellite-to-Ground Station’ based on principles of the IEEE 802.11a standard is designed using MatLab Sіmulіnk software. The model allows simulating data transmission with data rate from 6 to 54 Mbit/s using adaptive modulation. Two types of channels were analysed for uplink/downlink modulation – a free space path losses with phase/frequency offset and Additive White Gaussian Noise (AWGN) link. On the base of this model, channel integrity was investigated and dependences of a Signal-Noise Ratio (SNR) on free space path losses, antennas diameters, number of OFDM symbols and satellite transponder noise temperature were received.
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Larsson, E. G. "Unitary nonuniform space-time constellations for the broadcast channel." IEEE Communications Letters 7, no. 1 (January 2003): 21–23. http://dx.doi.org/10.1109/lcomm.2002.807432.
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Maa, C. S., Y. C. Wang, and J. T. Chen. "Low-Complexity Channel-Adapted Space-Time Coding Scheme for Frequency-Selective Wireless MIMO Channels." IEEE Communications Letters 8, no. 2 (February 2004): 93–95. http://dx.doi.org/10.1109/lcomm.2004.823420.
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Birkinshaw, S. J. "Technical Note: Automatic river network generation for a physically-based river catchment model." Hydrology and Earth System Sciences Discussions 7, no. 3 (May 31, 2010): 3237–48. http://dx.doi.org/10.5194/hessd-7-3237-2010.
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Abstract. SHETRAN is a physically-based distributed modelling system that gives detailed simulations in time and space of water flow and sediment and solute transport in river catchments. Standard algorithms for the automatic generation of river channel networks from digital elevation data are impossible to apply in SHETRAN and other similar models because the river channels are assumed to run along the edges of grid cells. In this work a new algorithm for the automatic generation of a river channel network in SHETRAN is described and its use in an example catchment demonstrated.
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Birkinshaw, S. J. "Technical Note: Automatic river network generation for a physically-based river catchment model." Hydrology and Earth System Sciences 14, no. 9 (September 17, 2010): 1767–71. http://dx.doi.org/10.5194/hess-14-1767-2010.
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Abstract. SHETRAN is a physically-based distributed modelling system that gives detailed simulations in time and space of water flow and sediment and solute transport in river catchments. Standard algorithms for the automatic generation of river channel networks from digital elevation data are impossible to apply in SHETRAN and other similar models because the river channels are assumed to run along the edges of grid cells. In this work a new algorithm for the automatic generation of a river channel network in SHETRAN is described and its use in an example catchment demonstrated.
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Ball, Frank G., Robin K. Milne, and Geoffrey F. Yeo. "Marked Continuous-Time Markov Chain Modelling of Burst Behaviour for Single Ion Channels." Journal of Applied Mathematics and Decision Sciences 2007 (October 29, 2007): 1–14. http://dx.doi.org/10.1155/2007/48138.
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Patch clamp recordings from ion channels often show bursting behaviour, that is, periods of repetitive activity, which are noticeably separated from each other by periods of inactivity. A number of authors have obtained results for important properties of theoretical and empirical bursts when channel gating is modelled by a continuous-time Markov chain with a finite-state space. We show how the use of marked continuous-time Markov chains can simplify the derivation of (i) the distributions of several burst properties, including the total open time, the total charge transfer, and the number of openings in a burst, and (ii) the form of these distributions when the underlying gating process is time reversible and in equilibrium.
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Tian, Xiaowen, Ming Li, Guangyu Ti, and Wenfei Liu. "Fast Detection of Orthogonal Space-Time Block Codes With Unknown Channel." IEEE Communications Letters 20, no. 9 (September 2016): 1896–99. http://dx.doi.org/10.1109/lcomm.2016.2591548.
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Ying, Tengda, Wenjiang Feng, and Guoling Liu. "Space-Time Interference Alignment: DoF of Two-User MIMO X Channel With Alternating CSIT." IEEE Communications Letters 21, no. 5 (May 2017): 1167–70. http://dx.doi.org/10.1109/lcomm.2017.2654340.
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Chalise, Batu, and L. Vandendorpe. "Outage probability analysis of a MIMO relay channel with orthogonal space-time block codes." IEEE Communications Letters 12, no. 4 (April 2008): 280–82. http://dx.doi.org/10.1109/lcomm.2008.072142.
Full textDissertations / Theses on the topic "Space-time channel modelling"
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Lamahewa, Tharaka Anuradha, and tharaka lamahewa@anu edu au. "Space-Time Coding and Space-Time Channel Modelling for Wireless Communications." The Australian National University. Research School of Information Sciences and Engineering, 2007. http://thesis.anu.edu.au./public/adt-ANU20070816.152647.
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In this thesis we investigate the effects of the physical
constraints such as antenna aperture size, antenna geometry and
non-isotropic scattering distribution parameters (angle of
arrival/departure and angular spread) on the performance of coherent
and non-coherent space-time coded wireless communication systems.
First, we derive analytical expressions for the exact pairwise error
probability (PEP) and PEP upper-bound of coherent and non-coherent
space-time coded systems operating over spatially correlated fading
channels using a moment-generating function-based approach. These
analytical expressions account for antenna spacing, antenna
geometries and scattering distribution models. Using these new PEP
expressions, the degree of the effect of antenna spacing, antenna
geometry and angular spread is quantified on the diversity advantage
(robustness) given by a space-time code. It is shown that the number
of antennas that can be employed in a fixed antenna aperture without
diminishing the diversity advantage of a space-time code is
determined by the size of the antenna aperture, antenna geometry and
the richness of the scattering environment.
¶
In realistic channel environments the performance of space-time
coded multiple-input multiple output (MIMO) systems is significantly
reduced due to non-ideal antenna placement and non-isotropic
scattering. In this thesis, by exploiting the spatial dimension of a
MIMO channel we introduce the novel use of linear spatial precoding
(or power-loading) based on fixed and known parameters of MIMO
channels to ameliorate the effects of non-ideal antenna placement on
the performance of coherent and non-coherent space-time codes. The
spatial precoder virtually arranges the antennas into an optimal
configuration so that the spatial correlation between all antenna
elements is minimum. With this design, the precoder is fixed for
fixed antenna placement and the transmitter does not require any
feedback of channel state information (partial or full) from the
receiver. We also derive precoding schemes to exploit non-isotropic
scattering distribution parameters of the scattering channel to
improve the performance of space-time codes applied on MIMO systems
in non-isotropic scattering environments. However, these schemes
require the receiver to estimate the non-isotropic parameters and
feed them back to the transmitter.
¶
The idea of precoding based on fixed parameters of MIMO channels is
extended to maximize the capacity of spatially constrained dense
antenna arrays. It is shown that the theoretical maximum capacity
available from a fixed region of space can be achieved by power
loading based on previously unutilized channel state information
contained in the antenna locations. We analyzed the correlation
between different modal orders generated at the transmitter region
due to spatially constrained antenna arrays in non-isotropic
scattering environments, and showed that adjacent modes contribute
to higher correlation at the transmitter region. Based on this
result, a power loading scheme is proposed which reduces the effects
of correlation between adjacent modes at the transmitter region by
nulling power onto adjacent transmit modes.
¶
Furthermore, in this thesis a general space-time channel model for
down-link transmission in a mobile multiple antenna communication
system is developed. The model incorporates deterministic
quantities such as physical antenna positions and the motion of the
mobile unit (velocity and the direction), and random quantities to
capture random scattering environment modeled using a bi-angular
power distribution and, in the simplest case, the covariance between
transmit and receive angles which captures statistical
interdependency. The Kronecker model is shown to be a special case
when the power distribution is separable and is shown to
overestimate MIMO system performance whenever there is more than one
scattering cluster. Expressions for space-time cross correlations
and space-frequency cross spectra are given for a number of
scattering distributions using Gaussian and Morgenstern's family of
multivariate distributions. These new expressions extend the
classical Jake's and Clarke's correlation models to general
non-isotropic scattering environments.
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Lamahewa, Tharaka Anuradha. "Space-time coding and space-time channel modelling for wireless communications /." View thesis entry in Australian Digital Theses Program, 2006. http://thesis.anu.edu.au/public/adt-ANU20070816.152647/index.html.
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Shang, Lei, and lei shang@ieee org. "Modelling of Mobile Fading Channels with Fading Mitigation Techniques." RMIT University. Electrical and Computer Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20061222.113303.
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This thesis aims to contribute to the developments of wireless communication systems. The work generally consists of three parts: the first part is a discussion on general digital communication systems, the second part focuses on wireless channel modelling and fading mitigation techniques, and in the third part we discuss the possible application of advanced digital signal processing, especially time-frequency representation and blind source separation, to wireless communication systems. The first part considers general digital communication systems which will be incorporated in later parts. Today's wireless communication system is a subbranch of a general digital communication system that employs various techniques of A/D (Analog to Digital) conversion, source coding, error correction, coding, modulation, and synchronization, signal detection in noise, channel estimation, and equalization. We study and develop the digital communication algorithms to enhance the performance of wireless communication systems. In the Second Part we focus on wireless channel modelling and fading mitigation techniques. A modified Jakes' method is developed for Rayleigh fading channels. We investigate the level-crossing rate (LCR), the average duration of fades (ADF), the probability density function (PDF), the cumulative distribution function (CDF) and the autocorrelation functions (ACF) of this model. The simulated results are verified against the analytical Clarke's channel model. We also construct frequency-selective geometrical-based hyperbolically distributed scatterers (GBHDS) for a macro-cell mobile environment with the proper statistical characteristics. The modified Clarke's model and the GBHDS model may be readily expanded to a MIMO channel model thus we study the MIMO fading channel, specifically we model the MIMO channel in the angular domain. A detailed analysis of Gauss-Markov approximation of the fading channel is also given. Two fading mitigation techniques are investigated: Orthogonal Frequency Division Multiplexing (OFDM) and spatial diversity. In the Third Part, we devote ourselves to the exciting fields of Time-Frequency Analysis and Blind Source Separation and investigate the application of these powerful Digital Signal Processing (DSP) tools to improve the performance of wireless communication systems.
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Lamahewa, Tharaka Anuradha. "Space-Time Coding and Space-Time Channel Modelling for Wireless Communications." Phd thesis, 2006. http://hdl.handle.net/1885/47658.
Full textAbstract:
In this thesis we investigate the effects of the physical constraints such as antenna aperture size, antenna geometry and non-isotropic scattering distribution parameters (angle of arrival/departure and angular spread) on the performance of coherent and non-coherent space-time coded wireless communication systems. First, we derive analytical expressions for the exact pairwise error probability (PEP) and PEP upper-bound of coherent and non-coherent space-time coded systems operating over spatially correlated fading channels using a moment-generating function-based approach. These analytical expressions account for antenna spacing, antenna geometries and scattering distribution models. Using these new PEP expressions, the degree of the effect of antenna spacing, antenna geometry and angular spread is quantified on the diversity advantage (robustness) given by a space-time code. It is shown that the number of antennas that can be employed in a fixed antenna aperture without diminishing the diversity advantage of a space-time code is determined by the size of the antenna aperture, antenna geometry and the richness of the scattering environment. ¶ In realistic channel environments the performance of space-time coded multiple-input multiple output (MIMO) systems is significantly reduced due to non-ideal antenna placement and non-isotropic scattering. In this thesis, by exploiting the spatial dimension of a MIMO channel we introduce the novel use of linear spatial precoding (or power-loading) based on fixed and known parameters of MIMO channels to ameliorate the effects of non-ideal antenna placement on the performance of coherent and non-coherent space-time codes. ...
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Nieman, Karl Frazier. "Space-time-frequency methods for interference-limited communication systems." Thesis, 2014. http://hdl.handle.net/2152/28137.
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Traditionally, noise in communication systems has been modeled as an additive, white Gaussian noise process with independent, identically distributed samples. Although this model accurately reflects thermal noise present in communication system electronics, it fails to capture the statistics of interference and other sources of noise, e.g. in unlicensed communication bands. Modern communication system designers must take into account interference and non-Gaussian noise to maximize efficiencies and capacities of current and future communication networks. In this work, I develop new multi-dimensional signal processing methods to improve performance of communication systems in three applications areas: (i) underwater acoustic, (ii) powerline, and (iii) multi-antenna cellular. In underwater acoustic communications, I address impairments caused by strong, time-varying and Doppler-spread reverberations (self-interference) using adaptive space-time signal processing methods. I apply these methods to array receivers with a large number of elements. In powerline communications, I address impairments caused by non-Gaussian noise arising from devices sharing the powerline. I develop and apply a cyclic adaptive modulation and coding scheme and a factor-graph-based impulsive noise mitigation method to improve signal quality and boost link throughput and robustness. In cellular communications, I develop a low-latency, high-throughput space-time-frequency processing framework used for large scale (up to 128 antenna) MIMO. This framework is used in the world's first 100-antenna MIMO system and processes up to 492 Gbps raw baseband samples in the uplink and downlink directions. My methods prove that multi-dimensional processing methods can be applied to increase communication system performance without sacrificing real-time requirements.text
Book chapters on the topic "Space-time channel modelling"
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Kalsnes, Bjørn, and Vittoria Capobianco. "Use of Vegetation for Landslide Risk Mitigation." In Springer Climate, 77–85. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-86211-4_10.
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AbstractLandslide risk management involves several activities, modelling being a required premise for most of them. Modelling of climate-induced landslides include both the analysis of the triggering process, i.e. static slope stability analysis and dynamic propagation (run-out) analysis. These analyses are vital for mapping purposes, as well as for selection of effective means to reduce the landslide risk when this exceeds a certain value of tolerance. With the prospect of increasing rainfall duration and intensity in parts of Europe, the need for further development of modelling tools is evident. In recent years, the use of Nature-Based Solutions (NBS) for mitigation of natural hazards has further demonstrated the need for developing the modelling tools. The use of vegetation as NBS is increasingly being used for erosion protection and shallow landslide mitigation. For slope stability analyses, the use of vegetation makes the modelling more complex for a number of reasons, mostly linked to the influence of vegetation on both the soil–atmosphere interaction (i.e. rainfall interception, evapotranspiration) and the soil hydro-mechanical properties. All effects that are difficult to model due to lack of knowledge and to large variations in time and space. Even though there is an increasing activity in the geotechnical environment to incorporate the effects of vegetation in the modelling for quantifying the change in slope stability (i.e. calculate slope safety factor), the status is far from being at the level of traditional landslide modelling tools. More efforts are therefore needed in the years to come to demonstrate that the use of vegetation as a viable and effective measure in landslide risk mitigation management can be verified in a more quantifiable manner.
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Zurell, Damaris, and Jan O. Engler. "Ecological niche modelling." In Effects of Climate Change on Birds, 60–73. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198824268.003.0006.
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Impact assessments increasingly rely on models to project the potential impacts of climate change on species distributions. Ecological niche models have become established as an efficient and widely used method for interpolating (and sometimes extrapolating) species’ distributions. They use statistical and machine-learning approaches to relate species’ observations to environmental predictor variables and identify the main environmental determinants of species’ ranges. Based on this estimated species–environment relationship, the species’ potential distribution can be mapped in space (and time). In this chapter, we explain the concept and underlying assumptions of ecological niche models, describe the basic modelling steps using the silvereye (Zosterops lateralis) as a simple real-world example, identify potential sources of uncertainty in underlying data and in the model, and discuss potential limitations as well as latest developments and future perspectives of ecological niche models in a global change context.
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Van Hoang, Nguyen. "Soil-Skeleton and Soil-Water Heavy Metal Contamination by Finite Element Modelling With Freundlich Isotherm Adsorption Parameters." In Heavy Metals - New Insights [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.101828.
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World research results indicate that untreated leachate contains high contents of heavy metals (HM) that are likely to pollute the soil and groundwater (GW) environment and contribute to the increase of HMs in soil and GW. The Freundlich isotherm adsorption parameters are essential to soil input parameters for modelling of HMs’ transport to access the soil skeleton and soil pore water contamination by HMs. Finite element (FE) modelling of advection-dispersion transport of HMs by GW movement along with Freundlich isotherm adsorption parameters which continuously change with space in the model domain and with time is sophisticated to accurately evaluate the HMs’ concentrations in soil skeleton and pore water. The chapter describes the background of the existing isotherm adsorption theory, the adaptation of the Freundlich isotherm adsorption in the soil skeleton and soil pore water contamination by HMs, method of determination of the Freundlich isotherm adsorption parameters, the FE procedure of modelling of advection-dispersion transport of HMs by GW movement in general and along with Freundlich isotherm adsorption parameters in particular. A case study modelling has been demonstrated.
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Shanmuganathan, Subana, Ajit Narayanan, and Nishantha Priyanka Kumara Medagoda. "Temporal Data Analysis and Mining Methods for Modelling the Climate Change Effects on Malaysia's Oil Palm Yield at Different Regional Scales." In Advances in Environmental Engineering and Green Technologies, 482–513. IGI Global, 2016. http://dx.doi.org/10.4018/978-1-4666-8814-8.ch025.
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Space and time related data generated is becoming ever more voluminous, noisy and heterogeneous outpacing the research efforts in the domain of climate. Nevertheless, this data portrays recent climate/ weather change patterns. Thus, insightful approaches are required to overcome the challenges when handling the so called “big data” to unravel the recent unprecedented climate change in particular, its variability, frequency and effects on key crops. Contemporary climate-crop models developed at least two decades ago are found to be unsuitable for analysing complex climate/weather data retrospectively. In this context, the chapter looks at the use of scalable time series analysis, namely ARIMA (Autoregressive integrated moving average) models and data mining techniques to extract new knowledge on the climate change effects on Malaysia's oil palm yield at the regional and administrative divisional scales. The results reveal recent trends and patterns in climate change and its effects on oil palm yield impossible otherwise e.g. Traditional statistical methods alone.
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Shanmuganathan, Subana, Ajit Narayanan, and Nishantha Priyanka Kumara Medagoda. "Temporal Data Analysis and Mining Methods for Modelling the Climate Change Effects on Malaysia's Oil Palm Yield at Different Regional Scales." In Natural Resources Management, 499–531. IGI Global, 2017. http://dx.doi.org/10.4018/978-1-5225-0803-8.ch024.
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Space and time related data generated is becoming ever more voluminous, noisy and heterogeneous outpacing the research efforts in the domain of climate. Nevertheless, this data portrays recent climate/ weather change patterns. Thus, insightful approaches are required to overcome the challenges when handling the so called “big data” to unravel the recent unprecedented climate change in particular, its variability, frequency and effects on key crops. Contemporary climate-crop models developed at least two decades ago are found to be unsuitable for analysing complex climate/weather data retrospectively. In this context, the chapter looks at the use of scalable time series analysis, namely ARIMA (Autoregressive integrated moving average) models and data mining techniques to extract new knowledge on the climate change effects on Malaysia's oil palm yield at the regional and administrative divisional scales. The results reveal recent trends and patterns in climate change and its effects on oil palm yield impossible otherwise e.g. Traditional statistical methods alone.
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Smith, Victoria Anne, Graham Appleby, Marek Ziebart, and Jose Rodriguez. "Twelve Years of High Frequency Absolute Gravity Measurements at the UK’s Space Geodesy Facility: Systematic Signals and Comparison with SLR Heights." In International Association of Geodesy Symposia. Berlin, Heidelberg: Springer Berlin Heidelberg, 2021. http://dx.doi.org/10.1007/1345_2021_129.
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AbstractAbsolute gravity measurements taken on a near-weekly basis at a single location is a rarity. Twelve years of data at the UK’s Space Geodesy Facility (SGF) provides evidence to show that the application of results from international comparisons of absolute gravimeters should be applied to data and are critical to the interpretation of theSGF gravity time series of data from 2007 to 2019. Though residual biases in the data are seen. The SGF time series comprises near weekly data, with exceptions for manufacturer services and participation in international instrument comparisons. Each data set comprises hourly data taken over 1 day, with between 100 and 200 drops per hour. Environmental modelling indicates that the annual groundwater variation at SGFof some 2 m influences the gravity data by 3.1 μGal, based upon some measured and estimated soil parameters. The soil parameters were also used in the calculation of the effect of an additional telescope dome, built above the gravity laboratory, and have been shown to be realistic. Sited in close proximity to the long-established satellite laser ranging (SLR) system and the global navigation satellite systems (GNSS) the absolute gravimetry (AG) measurements provide a complimentary geodetic technique, which is non space-based. The SLR-derived height time series provides an independent measurement of vertical motion at the site which may be used to assess the AG results, which are impacted by ground motion as well as mass changes above and below the instruments.
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Adero, Nashon Juma, and John Bosco Kyalo Kiema. "Flow-Based Structural Modelling and Dynamic Simulation of Lake Water Levels." In Green Technologies, 798–814. IGI Global, 2011. http://dx.doi.org/10.4018/978-1-60960-472-1.ch413.
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The continuing decline in lake water levels is both a concern and daunting challenge to scientists and policymakers in this era, demanding a rethinking of technological and policy interventions in the context of broader political and socio-economic realities. It is self-evident that diverse factors interact in space and time in complex dynamics to cause these water-level changes. However, the major question demanding sound answers is how these factors interact and by what magnitude they affect lake water balance with time. This chapter uses Lake Victoria’s hydrological system to shed light on the extensive and flexible modelling and simulation capabilities availed by modern computer models to understand the bigger picture of water balance dynamics. The study used the 1950-2000 hydrological data and riparian population growth to develop a dynamic simulation model for the lake’s water level. The intuitive structure of the model provided clear insights into the combined influence of the main drivers of the lake’s water balance. The falling lake water levels appeared to be mainly due to dam outflows at the outlet and reduced rainfall over the lake. The ensuing conclusions stressed the need for checks against over-release of lake water for hydropower production and measures for sustainable land and water management in the entire basin.
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Tinker, Peter B., and Peter Nye. "Solute Transport and Crop Growth Models in the Field." In Solute Movement in the Rhizosphere. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195124927.003.0015.
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In this chapter we deal with vegetation growing in the field. This introduces new and challenging questions of scale and heterogeneity, in time and space, of the environment in which plants grow. It builds on the concepts and methods explained in earlier chapters, especially the movement of water and solutes (chapters 2, 3 and 4) and the distribution of roots (chapter 9) in field soils. In some cases, it requires changes and simplifications in the methods that we have used earlier. The problems of dealing with water and nutrient movement and uptake at the field scale are discussed first. The modelling approach that we developed in the earlier chapters of this book, up to the end of chapter 10, logically resumes at section 11.3. This covers both uptake models and the more complex combined crop growth and uptake models that simulate the main interactions with the environment. This chapter considers increasingly complex systems: first, uniform monocultures, including models of a ‘green leaf crop’, a root crop, a cereal, and a tree crop. At this level, the presence of weeds or groundcover is deliberately ignored. Interspecies competition is included later, with vegetation composed of more or less regularly spaced plants of more than one species. This occurs in many agricultural systems, such as mixtures of forage species and agroforestry systems. The competition processes become even more complicated where there is no spatial symmetry, and models of crop/weed mixtures, grass/legume mixtures, and planted woodlands are used as examples. Progress with crops has been more rapid because of their more regular structure, so we deal mainly with these, but we believe that similar ideas will be applied to natural vegetation also, and this is discussed in section 11.5. Most of these models have a water submodel, or, if not, one could be added. As the physical basis is normally rather similar for all water models, one model for water uptake is explained in some detail (section 11.1.2), but elsewhere water uptake is dealt with very briefly. For each model, the preferred order of discussion is water; growth, including economic yield; nitrogen; potassium; phosphorus; and other nutrients, unless the logic of the subject demands a different order.
Conference papers on the topic "Space-time channel modelling"
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Castanet, Laurent, Joel Lemorton, Stefano Bertorelli, Carlo Capsoni, Frederic Lacoste, and Antonio Martellucci. "Advanced modelling of the space-time behaviour of the propagation channel for future Satcom systems." In 2006 1st European Conference on Antennas and Propagation (EuCAP). IEEE, 2006. http://dx.doi.org/10.1109/eucap.2006.4584830.
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Cao, Dayong. "Consciousness Changes the Output Signal of Solar Cell and the New Cognitive Model with Mass Energy Space Time System." In 2008 International Conference on Computational Intelligence for Modelling Control & Automation. IEEE, 2008. http://dx.doi.org/10.1109/cimca.2008.20.
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Saddawi, Salwan David, Timoleon Kipouros, and Mark Savill. "Computational Engineering Design for Micro-Scale Combustion Devices: A Thermally Improved Configuration." In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-94599.
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A multi-objective design optimisation study has been carried out with the objectives to improve the overall efficiency of the device and to reduce the fuel consumption for the proposed micro-scale combustor design configuration. In a previous study we identified the topology of the combustion chamber that produced improved behaviour of the device in terms of the above design criteria. We now extend our design approach, and we propose a new configuration by the addition of a micro-cooling channel that will improve the thermal behaviour of the design as previously suggested in literature. Our initial numerical results revealed an improvement of 2.6% in the combustion efficiency when we applied the micro-cooling channel to an optimum design configuration we identified from our earlier multi-objective optimisation study, and under the same operating conditions. The computational modelling of the combustion process is implemented in the commercial computational fluid dynamics package ANSYS-CFX using Finite Rate Chemistry and a single step hydrogen-air reaction. With this model we try to balance good accuracy of the combustion solution and at the same time practicality within the context of an optimisation process. The whole design system comprises also the ANSYS-ICEM CFD package for the automatic geometry and mesh generation and the Multi-Objective Tabu Search algorithm for the design space exploration. We model the design problem with 5 geometrical parameters and 3 operational parameters subject to 5 design constraints that secure practicality and feasibility of the new optimum design configurations. The final results demonstrate the reliability and efficiency of the developed computational design system and most importantly we assess the practicality and manufacturability of the revealed optimum design configurations of micro-combustor devices.
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Eichhorn, Geoffrey N., and Stuart K. Haigh. "Landslide Pipe-Soil Interaction: State of the Practice." In 2018 12th International Pipeline Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/ipc2018-78434.
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Current understanding of pipe-soil interaction during large ground movement events is insufficient due to their infrequency and the complexity of the infrastructure. Pipeline operators currently rely on a fully coupled continuum model of a landslide and pipeline interaction, or, more commonly, on a simplification of this interface using structural beam style soil-springs to transfer soil loads and displacements to the pipeline. The basis for soil-springs are laboratory studies based largely on clean sand or pure clay, and flat ground. Owing to the use of manufactured soils and flat ground, the soil-pipe interface modelling may not be valid for landslides. The loading of a pipeline in a landslide, and how the soil-spring factors should change with space and time are reviewed and may differ from commonly adopted guidelines. Physical modelling in research is emerging to study landslides and pipelines utilizing fully instrumented scale models. In the absence of fully instrumented field pipelines, physical modelling should be used to validate continuum models.
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Vanem, Erik, and Elzbieta M. Bitner-Gregersen. "Modelling Long-Term Trends in Significant Wave Height and its Potential Impacts on Ship Structural Loads." In ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-10023.
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This paper presents the results from a statistical model for significant wave height in space and time. In particular, various model alternatives were applied to extract long-term temporal trends towards the year 2100. Future projections of the North Atlantic ocean wave climate based on two of these alternatives are presented, i.e. an extrapolated linear trend and trends based on regression on atmospheric levels of CO2 and assuming future emission scenarios proposed by IPCC. It is further explored how such future trends can be related to the structural load calculations of ships. It will be demonstrated how the estimated future trends can be incorporated in joint environmental models to yield updated environmental contour lines that take possible changes in the ocean wave climate into account. In this way, the impact of climate change on the wave climate can be accounted for in stress and loads calculations and hence in the structural dimensioning of ships and offshore installations. The proposed approach is illustrated by an example showing the potential impact of the estimated long-term trends in the wave climate on the wave-induced structural loads of an oil tanker. Results indicate that the impact may be far from negligible, and that this may need to be considered in the future when performing loads calculations.
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Vinod-Buchinger, Aditya, and Sam Griffiths. "Spatial cultures of Soho, London. Exploring the evolution of space, culture and society of London's infamous cultural quarter." In Post-Oil City Planning for Urban Green Deals Virtual Congress. ISOCARP, 2020. http://dx.doi.org/10.47472/sxol5829.
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Space as affording social interaction is highly debated subject among various epistemic disciplines. This research contributes to the discussion by shedding light on urban culture and community organisation in spatialised ways. Providing a case of London’s famous cultural quarter, Soho, the research investigates the physical and cultural representation of the neighbourhood and relates it to the evolving socio-spatial logic of the area. Utilising analytical methods of space syntax and its network graph theories that are based on the human perception of space, the research narrates the evolution in spatial configuration and its implication on Soho’s social morphology. The method used examines the spatial changes over time to evaluate the shifting identity of the area that was in the past an immigrant quarter and presently a celebrated gay village. The approach, therefore, combines analytical methods, such as network analysis, historical morphology analysis and distribution of land uses over time, with empirical methods, such as observations, auto-ethnography, literature, and photographs. Dataset comprises of street network graphs, historical maps, and street telephone and trade directories, as well as a list of literature, and data collected by the author through surveys. Soho’s cosmopolitanism and its ability to reinvent over time, when viewed through the prism of spatial cultures, help understand the potential of urban fabric in maintaining a time-space relationship and organisation of community life. Social research often tends to overlook the relationship between people and culture with their physical environment, where they manifest through the various practices and occupational distribution. In the case of Soho, the research found that there was a clear distribution of specific communities along specific streets over a certain period in the history. The gay bars were situated along Rupert and Old Compton Street, whereas the Jewish and Irish traders were established on Berwick Street, and so on. Upon spatial analysis of Soho and its surrounding areas, it was found that the streets of Soho were unlike that of its surrounding neighbourhoods. In Soho, the streets were organised with a certain level of hierarchy, and this hierarchy also shifted over time. This impacted the distribution of landuses within the area over time. Street hierarchy was measured through mathematical modelling of streets as derived by space syntax. In doing so, the research enabled viewing spaces and communities as evolving in parallel over time. In conclusion, by mapping the activities and the spatiality of Soho’s various cultural inhabitants over three historical periods and connecting these changes to the changing spatial morphology of the region, the research highlighted the importance of space in establishing the evolving nature of Soho. Such changes are visible in both symbolic and functional ways, from the location of a Govinda temple on a Soho square street, to the rise and fall of culture specific landuses such as gay bars on Old Compton Street. The research concludes by highlighting gentrification as an example of this time-space relation and addresses the research gap of studying spaces for its ability to afford changeability over time.
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Chang Li Si, Claire, Kwang Chian Chiew, Kit Teng Chaw, Raja Zuhaili Aimran Raja Zainal Raffik, and Ryan Scott Guillory. "Multilayered Water Injection Zonal Allocation Without Intervention: Maximizing Value of a Smart Well by Harnessing Historical Data in Efforts to Expurgate Imprecise Injection Allocation." In SPE Asia Pacific Oil & Gas Conference and Exhibition. SPE, 2022. http://dx.doi.org/10.2118/210752-ms.
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Abstract Field A begun water injection in 2016 via four water injector smart wells, which were equipped with Permanent Downhole Gauges and Inflow Control Valves. The water injection module was housed on a rented MOPU due to space limitation. Amidst the study to revamp the reservoir management plan, the team found multiple discrepancies in the reservoir zonal allocation dating back to start of injection. Inherently, this affects the Voidage Replacement Ratio tracking. Hence, the question remains: How efficient is the water injection in Field A? As Field A injects from a rented facility, the long term RMP strongly influences annual OPEX. This paper explains the journey of reallocating Field A water injection volumes from 2016 until today, and how it affects the outcome of the RMP study. PETRONAS has an offshore monitoring system which visualizes historical pressure and temperature trends at any tagged equipment. Field A water injectors consists of multi-zones completed with ICVs and PDGs. ICVs allow choking and zone changes to happen without intervention, and PDGs show downhole pressure and temperature changes over time. Coupled with the manual database which tracks ICV changes and water injection rates, the team re-modelled the injected volume allocation changes to each zone by anchoring the model on PDG trends, ICV size and choke coefficient, and water injection rates via an advance nodal analysis software. For reservoir characteristics calibration, properties from past FBUS interpreted results were used as a basis. From the modelling journey, at the same injection scheme, results showed that zonal allocation with small PDG pressure changes of less than 5% during stable injection conditions does not significantly affect allocation ratio in the well. Overall, the allocation would change between 0 - 3% in total. As one of the objectives of the exercise was also to gauge expected injected volume allocation to a specific zone when there were obvious pressure changes but no records of changing ICV sizes, this could be achieved via a calibrated model. Once a good anchor was made on reservoir pressure, formation gas-oil ratio, permeability and skin, devoid periods in the past could be modelled for expected ICV sizes by varying the choke size openings till the pressure differential between tubing and annulus pressure was achieved. Hence, modelling the expected zonal allocation during that period. This improved VRR tracking for the injection reservoirs and aided to in the efforts to revamp the reservoir management plan. This paper will explain the lessons learnt of having proper surveillance data as the impact on long term reservoir management plan is significant. In future, fields with smart wells but disorganized data can utilize this alternate method to reallocate production/injection volumes without the need for intervention.
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Vanem, Erik. "A Stochastic Model for Long-Term Trends in Significant Wave Height With a CO2 Regression Component." In ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-83012.
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Bad weather and rough seas continue to be a major cause for ship losses and is thus a significant contributor to the risk to maritime transportation. This stresses the importance of taking severe sea state conditions adequately into account, with due treatment of the uncertainties involved, in ship design and operation. Hence, there is a need for appropriate stochastic models describing the variability of sea states. These should also incorporate realistic projections of future return levels of extreme sea states, taking into account long-term trends related to climate change and inherent uncertainties. The stochastic model presented in this paper allows for modelling of complex dependence structures in space and time and incorporation of physical features and prior knowledge, yet at the same time remains intuitive and easily interpreted. A regression component with CO2 as an explanatory variable has been introduced in order to extract and project long-term trends in the data. The model has been fitted by significant wave height data for an area in the North Atlantic ocean. The different components of the model will be outlined in the paper, and the results will be discussed.
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Huseby, Arne Bang, Erik Vanem, and Bent Natvig. "A New Method for Environmental Contours in Marine Structural Design." In ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-10053.
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The environmental contour concept is often applied in marine structural design in conjunction with the Inverse First Order Reliability Method (IFORM). It allows for the great advantage of considering the environmental loads independently of the structural response. In this way, design sea states may be identified along the contour and time consuming response calculations are only needed for a limited set of design sea states. The traditional way of establishing such environmental contour lines is by applying the Rosenblatt transformation and identify the circle (in two dimensions) with radius equal to the reliability index βr The points along this circle are then transformed back to the original environmental space, specifying the closed contour. In this paper, an alternative approach for establishing the environmental contour lines in the original environmental space is proposed, eliminating the need for any transformations. This approach utilizes Monte Carlo simulations of the joint environmental model and is generally found to perform well. Advantages are that it yields a more precise interpretation and allows for more flexible modelling of the environmental parameters. This makes it easier to modify the environmental models to account for effects such as climate change if this is desired. In addition, possible over- or underestimation of failure probabilities due to the Rosenblatt transformation inherent in the traditional approach can be avoided with the proposed method.
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Cheeseman, Mark J., Douglas K. Smith, and Graham B. Hesketh. "Understanding the Aftermarket: Applying Agent-Based Modelling to Service Infrastructure Design." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90465.
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In order to compete in challenging global markets, Rolls-Royce must have the capability to manage complex processes effectively. As the environment surrounding these processes is constantly changing, the ability to adapt to meet new requirements is essential. The challenge to the business is to quickly adopt an appropriate course of action for each set of circumstances, anticipated or otherwise. An individual decision-maker faced with this situation will normally have several options available. The difficulty is assessing the ramifications of each within a given time frame. To improve the quality of this evaluation, computerized decision support tools can be used. Such tools offer the ability to assess a multitude of options in a short space of time, using a combination of expert knowledge and real data. Having developed an extensive aero-engine service business, Rolls-Royce is required to maintain a highly dependable aftermarket infrastructure. Therefore, the ability to compare how any one particular aftermarket design would perform relative to another is an essential capability. Agent-based systems offer an approach that is both intuitive and interactive, modelling individual entities in the system from the bottom up, capturing low-level interactions that ultimately determine the overall performance of the system. This provides the flexibility and transparency to allow trustworthy analysis and evaluation to take place. To address this business need, an agent-based aftermarket model has been developed. An agent-based system is made up of small software programs built to operate just like a human team. Each agent has a set of capabilities and knowledge, but must work with other agents to achieve the overall goal. Agents can react to changes, adapting and re-planning if a better approach is identified. This paper describes how the model was constructed and the resulting analysis that it facilitates. The model has the ability to replicate the likely service characteristics that would be in place during the full lifecycle of the product. All aspects of the necessary infrastructure are captured, based upon the roles and capabilities of the constituent elements. Agents are used to represent a variety of objects and functions, including airports, airlines, aircraft, overhaul facilities and logistics. Through planning and negotiation, representative decisions are made by these agents to determine when an overhaul should take place and what the workscope should be based upon defined policies. A large selection of configurable parameters can be set by the user to accurately reflect the proposed scenario, providing a powerful what-if analysis tool that can be used to drive the design process, ensuring that product attributes and performance are aligned with the available maintenance infrastructure.