Energy and Spectral Efficiency of Very Large Multiuser MIMO Systems
A multiplicity of autonomous terminals simultaneously transmits data streams to a compact array of antennas. The array uses imperfect channel-state information derived from transmitted pilots to extract the individual data streams. The power radiated by the terminals can be made inversely proportional to the square-root of the number of base station antennas with no reduction in performance. In contrast if perfect channel-state information were available the power could be made inversely proportional to the number of antennas. Lower capacity bounds for maximum-ratio combining (MRC), zero-forcing (ZF) and minimum mean-square error (MMSE) detection are derived. An MRC receiver normally performs worse than ZF and MMSE. However as power levels are reduced, the cross-talk introduced by the inferior maximum-ratio receiver eventually falls below the noise level and this simple receiver becomes a viable option. The tradeoff between the energy efficiency (as measured in bits/J) and spectral efficiency (as measured in bits/channel use/terminal) is quantified for a channel model that includes small-scale fading but not large-scale fading. It is shown that the use of moderately large antenna arrays can improve the spectral and energy efficiency with orders of magnitude compared to a single-antenna system.
Global Positioning System constraints on plate kinematics and dynamics in the eastern Mediterranean and Caucasus
We present and interpret Global Positioning System (GPS) measurements of crustal motions for the period 1988–1997 at 189 sites extending east-west from the Caucasus mountains to the Adriatic Sea and north-south from the southern edge of the Eurasian plate to the northern edge of the African plate. Sites on the northern Arabian platform move 18±2 mm/yr at N25°±5°W relative to Eurasia, less than the NUVEL-1A circuit closure rate (25±1 mm/yr at N21°±7°W). Preliminary motion estimates (1994–1997) for stations located in Egypt on the northeastern part of Africa show northward motion at 5–6±2 mm/yr, also slower than NUVEL-IA estimates (10±1 mm/yr at N2°±4°E). Eastern Turkey is characterized by distributed deformation, while central Turkey is characterized by coherent plate motion (internal deformation of <2 mm/yr) involving westward displacement and counterclockwise rotation of the Anatolian plate. The Anatolian plate is de-coupled from Eurasia along the right-lateral, strike-slip North Anatolian fault (NAF). We derive a best fitting Euler vector for Anatolia-Eurasia motion of 30.7°± 0.8°N, 32.6°± 0.4°E, 1.2°±0.1°/Myr. The Euler vector gives an upper bound for NAF slip rate of 24±1 mm/yr. We determine a preliminary GPS Arabia-Anatolia Euler vector of 32.9°±1.2°N, 40.3°±1.1°E, 0.8°±0.2°/Myr and an upper bound on left-lateral slip on the East Anatolian fault (EAF) of 9±1 mm/yr. The central and southern Aegean is characterized by coherent motion (internal deformation of <2 mm/yr) toward the SW at 30±1 mm/yr relative to Eurasia. Stations in the SE Aegean deviate significantly from the overall motion of the southern Aegean, showing increasing velocities toward the trench and reaching 10±1 mm/yr relative to the southern Aegean as a whole.
Fostering Critical Reflection in Adulthood: A Guide to Transformative and Emancipatory Learning
Precipitating Critical Self--Reflection: Six Exemplary Programs. Helping Learners Become Critically Reflective: Six Key Approaches. Uncovering and Mapping the Personal Perspectives of Learners.
Global Positioning System constraints on plate kinematics and dynamics in the eastern Mediterranean and Caucasus
We present and interpret Global Positioning System (GPS) measurements of crustal motions for the period 1988–1997 at 189 sites extending east-west from the Caucasus mountains to the Adriatic Sea and north-south from the southern edge of the Eurasian plate to the northern edge of the African plate. Sites on the northern Arabian platform move 18±2 mm/yr at N25°±5°W relative to Eurasia, less than the NUVEL-1A circuit closure rate (25±1 mm/yr at N21°±7°W). Preliminary motion estimates (1994–1997) for stations located in Egypt on the northeastern part of Africa show northward motion at 5–6±2 mm/yr, also slower than NUVEL-IA estimates (10±1 mm/yr at N2°±4°E). Eastern Turkey is characterized by distributed deformation, while central Turkey is characterized by coherent plate motion (internal deformation of <2 mm/yr) involving westward displacement and counterclockwise rotation of the Anatolian plate. The Anatolian plate is de-coupled from Eurasia along the right-lateral, strike-slip North Anatolian fault (NAF). We derive a best fitting Euler vector for Anatolia-Eurasia motion of 30.7°± 0.8°N, 32.6°± 0.4°E, 1.2°±0.1°/Myr. The Euler vector gives an upper bound for NAF slip rate of 24±1 mm/yr. We determine a preliminary GPS Arabia-Anatolia Euler vector of 32.9°±1.2°N, 40.3°±1.1°E, 0.8°±0.2°/Myr and an upper bound on left-lateral slip on the East Anatolian fault (EAF) of 9±1 mm/yr. The central and southern Aegean is characterized by coherent motion (internal deformation of <2 mm/yr) toward the SW at 30±1 mm/yr relative to Eurasia. Stations in the SE Aegean deviate significantly from the overall motion of the southern Aegean, showing increasing velocities toward the trench and reaching 10±1 mm/yr relative to the southern Aegean as a whole.
Exhibiting Cultures: The Poetics and Politics of Museum Display
"Throwing open to debate the practices of museums, galleries, and festivals, Exhibiting Cultures probes the often politically charged relationships among aesthetics, contexts, and implicit assumptions that govern how cultural differences and art objects are displayed. This innovative volume brings together museum directors and curators, art historians, anthropologists, folklorists, and historians to examine how diverse settings have appealed to audiences and represented the intentions and cultures of the makers of objects. The essays address such major issues in the politics of culture as how the learned experience of everyday life is used to make exhibitions comprehensible, what happens to minority and exotic arts when they are assimilated into the hegemonic context of the "great" museums, and why ethnographic museums have been neglected in an age of museum expansions" -- p.[4] of cover.
Imaging topological edge states in silicon photonics
Topological edge states of light are observed in a two-dimensional array of coupled optical ring resonators, which induce a virtual magnetic field for photons using silicon-on-insulator technology. The edge states are experimentally demonstrated to be robust against intrinsic and introduced disorder, which is a hallmark of topological order.
A transmit preprocessing technique for multiuser MIMO systems using a decomposition approach
We introduce a transmit preprocessing technique for the downlink of multiuser multiple-input multiple-output (MIMO) systems. It decomposes the multiuser MIMO downlink channel into multiple parallel independent single-user MIMO downlink channels. Some key properties are that each equivalent single-user MIMO channel has the same properties as a conventional single-user MIMO channel, and that increasing the number of transmit antennas of the multiuser system by one increases the number of spatial channels to each user by one. Simulation results are also provided and these results demonstrate the potential of our technique in terms of performance and capacity.
An introduction to Docker for reproducible research
As computational work becomes more and more integral to many aspects of scientific research, computational reproducibility has become an issue of increasing importance to computer systems researchers and domain scientists alike. Though computational reproducibility seems more straight forward than replicating physical experiments, the complex and rapidly changing nature of computer environments makes being able to reproduce and extend such work a serious challenge. In this paper, I explore common reasons that code developed for one research project cannot be successfully executed or extended by subsequent researchers. I review current approaches to these issues, including virtual machines and workflow systems, and their limitations. I then examine how the popular emerging technology Docker combines several areas from systems research - such as operating system virtualization, cross-platform portability, modular re-usable elements, versioning, and a 'DevOps' philosophy, to address these challenges. I illustrate this with several examples of Docker use with a focus on the R statistical environment.
Guiding, modulating, and emitting light on Silicon-challenges and opportunities
Silicon photonics could enable a chip-scale platform for monolithic integration of optics and microelectronics for applications of optical interconnects in which high data streams are required in a small footprint. This paper discusses mechanisms in silicon photonics for waveguiding, modulating, light amplification, and emission. These mechanisms, together with recent advances of fabrication techniques, have enabled the demonstration of ultracompact passive and active silicon photonic components with very low loss.
The Soil Management Assessment Framework
Erosion rates and annual soil loss tolerance (T) values in evaluations of soil management practices have served as focal points for soil quality (SQ) research and assessment programs for decades. Our objective is to enhance and extend current soil assessment efforts by presenting a framework for assessing the impact of soil management practices on soil function. The tool consists of three steps: indicator selection, indicator interpretation, and integration into an index. The tool's framework design allows researchers to continually update and refine the interpretations for many soils, climates, and land use practices. The tool was demonstrated using data from case studies in Georgia, Iowa, California, and the Pacific Northwest (WA, ID, OR). Using an expert system of decision rules as an indicator selection step successfully identified indicators for the minimum data set (MDS) in the case study data sets. In the indicator interpretation step, observed indicator data were transformed into unitless scores based on site-specific algorithmic relationships to soil function. The scored data resulted in scientifically defensible and statistically different treatment means in the four case studies. The efficacy of the indicator interpretation step was evaluated with stepwise regressions using scored and observed indicators as independent variables and endpoint data as iterative dependent variables. Scored indicators usually had coefficients of determination (R 2 ) that were similar or greater than those of the observed indicator values. In some cases, the R 2 values for indicators and endpoint regressions were higher when examined for individual treatments rather than the entire data set. This study demonstrates significant progress toward development of a SQ assessment framework for adaptive soil resource management or monitoring that is transferable to a variety of climates, soil types, and soil management systems.
Roadmap on silicon photonics
Silicon photonics research can be dated back to the 1980s. However, the previous decade has witnessed an explosive growth in the field. Silicon photonics is a disruptive technology that is poised to revolutionize a number of application areas, for example, data centers, high-performance computing and sensing. The key driving force behind silicon photonics is the ability to use CMOS-like fabrication resulting in high-volume production at low cost. This is a key enabling factor for bringing photonics to a range of technology areas where the costs of implementation using traditional photonic elements such as those used for the telecommunications industry would be prohibitive. Silicon does however have a number of shortcomings as a photonic material. In its basic form it is not an ideal material in which to produce light sources, optical modulators or photodetectors for example. A wealth of research effort from both academia and industry in recent years has fueled the demonstration of multiple solutions to these and other problems, and as time progresses new approaches are increasingly being conceived. It is clear that silicon photonics has a bright future. However, with a growing number of approaches available, what will the silicon photonic integrated circuit of the future look like? This roadmap on silicon photonics delves into the different technology and application areas of the field giving an insight into the state-of-the-art as well as current and future challenges faced by researchers worldwide. Contributions authored by experts from both industry and academia provide an overview and outlook for the silicon waveguide platform, optical sources, optical modulators, photodetectors, integration approaches, packaging, applications of silicon photonics and approaches required to satisfy applications at mid-infrared wavelengths. Advances in science and technology required to meet challenges faced by the field in each of these areas are also addressed together with predictions of where the field is destined to reach.
On Critical Reflection
This paper presents an analysis and clarification of the major role of critical reflection of assumptions (CRA) in adult learning. It examines the differences among types of critical reflection, the role of CRA in the Transformation Theory of adult learning, philosophical foundations of CRA, its development over the lifespan, non-cognitive aspects, its function in both tacit and explicit decision-making, and its role in the validation of beliefs and expressions of feelings through discourse. The paper includes a taxonomy of applications of CRA and discussion of educational implications of this construct.
Structuralist Poetics: Structuralism, Linguistics and the Study of Literature
A work of technical skill as well as outstanding literary merit, Structuralist Poetics was awarded the 1975 James Russell Lowell Prize of the Modern Language Association. It was during the writing of this book that Culler developed his now famous and remarkably complex theory of poetics and narrative, and while never a populariser he nonetheless makes it crystal clear within these pages.
Analytical modelling of wind speed deficit in large offshore wind farms
The proposed model for the wind speed deficit in wind farms is analytical and encompasses both small wind farms and wind farms extending over large areas. As is often the need for offshore wind farms, the model handles a regular array geometry with straight rows of wind turbines and equidistant spacing between units in each row and equidistant spacing between rows. Firstly, the case with the flow direction being parallel to rows in a rectangular geometry is considered by defining three flow regimes. Secondly, when the flow is not in line with the main rows, solutions are suggested for the patterns of wind turbine units corresponding to each wind direction. The presentation is an outline of a model complex that will be adjusted and calibrated with measurements in the near future. Copyright © 2006 John Wiley & Sons, Ltd.
Piranha: a scalable architecture based on single-chip multiprocessing
This paper describes the Piranha system, a research prototype being developed at Compaq that aggressively exploits chip multiprocessing by integrating eight simple Alpha processor cores along with a two-level cache hierarchy onto a single chip. Piranha also integrates further on-chip functionality to allow for scalable multiprocessor configurations to be built in a glueless and modular fashion. The use of simple processor cores combined with an industry-standard ASIC design methodology allow us to complete our prototype within a short time-frame, with a team size and investment that are an order of magnitude smaller than that of a commercial microprocessor. Our detailed simulation results show that while each Piranha processor core is substantially slower than an aggressive next-generation processor, the integration of eight cores onto a single chip allows Piranha to outperform next-generation processors by up to 2.9 times (on a per chip basis) on important workloads such as OLTP. This performance advantage can approach a factor of five by using full-custom instead of ASIC logic. In addition to exploiting chip multiprocessing, the Piranha prototype incorporates several other unique design choices including a shared second-level cache with no inclusion, a highly optimized cache coherence protocol, and a novel I/O architecture.
MIMO Networks: The Effects of Interference
Multiple-input multiple-output (MIMO) systems are being considered as one of the key enabling technologies for future wireless networks. However, the decrease in capacity due to the presence of interferers in MIMO networks is not well understood. In this paper, we develop an analytical framework to characterize the capacity of MIMO communication systems in the presence of multiple MIMO co-channel interferers and noise. We consider the situation in which transmitters have no channel state information, and all links undergo Rayleigh fading. We first generalize the determinant representation of hypergeometric functions with matrix arguments to the case when the argument matrices have eigenvalues of arbitrary multiplicity. This enables the derivation of the distribution of the eigenvalues of Gaussian quadratic forms and Wishart matrices with arbitrary correlation, with application to both single-user and multiuser MIMO systems. In particular, we derive the ergodic mutual information for MIMO systems in the presence of multiple MIMO interferers. Our analysis is valid for any number of interferers, each with arbitrary number of antennas having possibly unequal power levels. This framework, therefore, accommodates the study of distributed MIMO systems and accounts for different spatial positions of the MIMO interferers.
iDistance: An adaptive B+-tree based indexing method for nearest neighbor search
In this article, we present an efficient B+-tree based indexing method, called iDistance, for K-nearest neighbor (KNN) search in a high-dimensional metric space. iDistance partitions the data based on a space- or data-partitioning strategy, and selects a reference point for each partition. The data points in each partition are transformed into a single dimensional value based on their similarity with respect to the reference point. This allows the points to be indexed using a B+-tree structure and KNN search to be performed using one-dimensional range search. The choice of partition and reference points adapts the index structure to the data distribution.We conducted extensive experiments to evaluate the iDistance technique, and report results demonstrating its effectiveness. We also present a cost model for iDistance KNN search, which can be exploited in query optimization.
WaveLab and Reproducible Research
Wavelab is a library of wavelet-packet analysis, cosine-packet analysis and matching pursuit. The library is available free of charge over the Internet. Versions are provided for Macintosh, UNIX and Windows machines.
Progressive collapse of multi-storey buildings due to sudden column loss — Part I: Simplified assessment framework
This paper proposes a novel simplified framework for progressive collapse assessment of multi-storey buildings, considering sudden column loss as a design scenario. The proposed framework offers a practical means for assessing structural robustness at various levels of structural idealisation, and importantly it takes the debate on the factors influencing robustness away from the generalities towards the quantifiable. A major feature of the new approach is its ability to accommodate simplified as well as detailed models of the nonlinear structural response, with the additional benefit of allowing incremental assessment over successive levels of structural idealisation. Three main stages are utilised in the proposed assessment framework, including the determination of the nonlinear static response, dynamic assessment using a novel simplified approach, and ductility assessment. The conceptual clarity of the proposed framework sheds considerable light on the adequacy of commonly advocated measures and indicators of structural robustness, culminating in the proposal of a single rational measure of robustness that is applicable to building structures subject to sudden column loss. The companion paper details the application of the new approach to progressive collapse assessment of real steel-framed composite multi-storey buildings, making in the process important conclusions on the inherent robustness of such structures and the adequacy of current design provisions.
Using Blogs to Enhance Critical Reflection and Community of Practice
Using the theories of critical reflection and community of practice, the aim of this paper was to explore the use of blogs as a reflective platform in the training processes of English as a Foreign Language (EFL) student teachers, who were learning to teach English for future employment in Taiwan. They made use of blogs as a platform to critically reflect on their learning processes as well as to gauge the impact of blogs on their own professional growth. Forty-three student teachers in two teacher-education programs at two science and technology institutions in central Taiwan participated in this study. Two instructors created a blog for use as a discussion forum so that the student teachers could engage in and examine their own reflection process. The data collected was qualitative in nature, consisting of student teachers’ posting messages and comments on the blog, surveys on the student teachers’ reflective experiences using blogs as reflection tools, and group reflective dialogues recorded by instructors in class meetings over the implementation of blogs during the course. The results showed that the student teachers actively discussed teaching theories and their implications through blogs. All of the 43 teachers who took part in this study were reflective, and some critically reflected on their thoughts and made significant comments; and the participants considered technology a useful platform for reflecting and communicating with each other. The positive implications for the use of blogs as a medium to provide and promote critical reflection for EFL teachers are discussed.
neural network machine learning big datum wind turbine nonlinear system life cycle integrated circuit mimo system positioning system global positioning system wind farm frequency domain systems based point cloud wind energy wind speed life cycle assessment global positioning offshore wind big data analytic diffusion equation frequency control photonic crystal power output channel model critical review offshore wind turbine north sea axis wind turbine voltage source converter offshore wind farm hvdc system axis wind cloud based site selection hvdc transmission coherent optical multiuser mimo massive multiple-input multiple-output arduino uno power loss wind generation tree based vertical axis wind silicon photonic ring resonator assessment framework cell line offshore wind power photonic integrated circuit multiuser mimo system offshore wind energy wind direction large wind hvdc link large wind turbine based prediction unknown control unknown control direction control direction multi-terminal hvdc kinematics and dynamic impedance model reproducible research critical reflection large wind farm multiuser multiple-input multiple-output wind farm layout large antenna large antenna array point cloud based large offshore wind wind power development wind turbine wake farm layout large offshore multi-terminal hvdc system stochastic diffusion wind power project eastern mediterranean photonic circuit onshore wind grating coupler photonics technology adriatic sea turbine wake multiterminal hvdc farm layout optimization wind farm model future city photonic integration system constraint based big datum photonic crystal cavity large-scale offshore wind management learning all-optical switching wind farm design based big silicon photonic crystal wind farm development silicon photonic integrated silicon photonic device massive multiuser offshore grid multicell multiuser stochastic diffusion equation wind development power losses due horns rev offshore wind development onshore wind power massive multiuser mimo offshore wind generation monolithic silicon future offshore wind photonic wire smart future photonic crystal nanocavity silicon photonic circuit euler vector rev wind farm north anatolian fault physical channel model cloud based big multicell multiuser mimo crystal nanocavity wind power