994 resultados para Space Weather
Resumo:
This paper offers a mediation on disaster, recovery, resilience, and restoration of balance, in both a material and a metaphorical sense, when ‘disaster’ befalls not the body politic of the nation but the body personal. In the past few decades, of course, artists, activists and scholars have deliberately tried to avoid describing personal, physical and phenomenological experiences of the disabled body in terms of difficulty and disaster. This has been part of a political move, from a medical model, in which disability, disease and illness are positioned as personal catastrophes, to a social model, in which disability is positioned as a social construct that comes from systems, institutions and infrastructure designed to exclude different bodies. It is a move that is responsible for a certain discomfort people with disabilities, and artists with disabilities, today feel towards performances that deploy disability as a metaphor for disaster, from Hijikata, to Theatre Hora. In the past five years, though, this particular discourse has begun rising again, particularly as people with disabilities fact their own anything but natural disasters as a result of the austerity measures now widespread across the US, UK, Europe and elsewhere. Measures that threaten people’s ability to live, and take part in social and institutional life, in any meaningful way. Measures that, as artist Katherine Araniello notes, also bring additional difficulty, danger, and potential for disaster as they ripple outwards across the tides of familial ties, threatening family, friends, and careers who become bound up in the struggle to do more with less. In this paper, I consider how people with disabilities use performance, particularly public space interventionalist performance, to reengage, renact and reenvisage the discourse of national, economic, environmental or other forms of disaster, the need for austerity, the need to avoid providing people with support for desires and interests as well as basic daily needs, particularly when fraud and corruption is so right, and other such ideas that have become an all too unpleasant reality for many people. Performances, for instance, like Liz Crow’s Bedding Out, where she invited people into her bed – for people with disabilities a symbolic space, which necessarily becomes more a public living room restaurant, office and so forth than a private space when poor mobility means they spend much time it in – to talk about their lives, their difficulties, and dealing with austerity. Or, for instance, like the Bolshy Divas, who mimic public and political policy, reports and advertising paranoia to undermine their discourses about austerity. I examine the effects, politics and ethics of such interventions, including examination of the comparative effect of highly bodied interventions (like Crow’s) and highly disembodied interventions (like the Bolshy Diva’s) in discourses of difficulty, disaster and austerity on a range of target spectator communities.
Resumo:
Though there is much interest in mobilities and performing mobilities as a characteristic of modern, urban, social life today, this is not always matched by attention to immobilities, as the flipside of mobility in modern life. In this paper, I investigate public space performances designed to draw attention to precisely this counterpoint to current discourses of mobilities – performances about the socially produced immobilities many people with disabilities find a more fundamental feature of day-to-day life, the fight for mobility, and the freedom found when accommodations for alternative mobilities are made available. Although public policy is increasingly aligned with a social model of disability, which sees disability as socially constructed through systems, institutions and infrastructure deliberately designed to exclude specific bodies – stairs, curbs, queues and so forth – and although governments in the US, UK, and to a lesser degree Australia, New Zealand and other Commonwealth nations aim to address these inequalities, the experience of immobility is still every-present for many people. This often comes not just from pain, or from impairment, or event from lack of accommodations for alternative mobilities, but from fellow social performers’ antipathy to, appropriation of, or destruction of accommodations designed to facilitate access for a range of different bodies in public space, and thus the public sphere. The archetypal instance of this tension between the mobile, and those needing accommodations to allow mobility, is, of course, the antipathy many able bodied people feel towards the provision of disabled parking spaces. A cursory search online shows thousands of accounts of antagonism, vitriol, and even violence prompted by disputes which began when a disabled person asked an able person to exit a designated disabled parking space. For many, it seems, expecting them to pass by such parks so others can experience the mobility they take for granted is too much. In this paper, I examine a number of protest performances in public space in which activist present actions – for example, placing wheelchairs in every regular parking space in a precinct – to give bystanders, passersby and spectators, as well as antagonistic fellow social performers, a sense of what socially produced immobility feels like. I examine responses to such protest performances, and what they say about the potential social, political and ethical impacts of such protests, in terms of their potential to produce new attitudes to mobility, alternative mobility, and access to alternative modes of mobility.
Resumo:
Data assimilation provides an initial atmospheric state, called the analysis, for Numerical Weather Prediction (NWP). This analysis consists of pressure, temperature, wind, and humidity on a three-dimensional NWP model grid. Data assimilation blends meteorological observations with the NWP model in a statistically optimal way. The objective of this thesis is to describe methodological development carried out in order to allow data assimilation of ground-based measurements of the Global Positioning System (GPS) into the High Resolution Limited Area Model (HIRLAM) NWP system. Geodetic processing produces observations of tropospheric delay. These observations can be processed either for vertical columns at each GPS receiver station, or for the individual propagation paths of the microwave signals. These alternative processing methods result in Zenith Total Delay (ZTD) and Slant Delay (SD) observations, respectively. ZTD and SD observations are of use in the analysis of atmospheric humidity. A method is introduced for estimation of the horizontal error covariance of ZTD observations. The method makes use of observation minus model background (OmB) sequences of ZTD and conventional observations. It is demonstrated that the ZTD observation error covariance is relatively large in station separations shorter than 200 km, but non-zero covariances also appear at considerably larger station separations. The relatively low density of radiosonde observing stations limits the ability of the proposed estimation method to resolve the shortest length-scales of error covariance. SD observations are shown to contain a statistically significant signal on the asymmetry of the atmospheric humidity field. However, the asymmetric component of SD is found to be nearly always smaller than the standard deviation of the SD observation error. SD observation modelling is described in detail, and other issues relating to SD data assimilation are also discussed. These include the determination of error statistics, the tuning of observation quality control and allowing the taking into account of local observation error correlation. The experiments made show that the data assimilation system is able to retrieve the asymmetric information content of hypothetical SD observations at a single receiver station. Moreover, the impact of real SD observations on humidity analysis is comparable to that of other observing systems.
Resumo:
Modern-day weather forecasting is highly dependent on Numerical Weather Prediction (NWP) models as the main data source. The evolving state of the atmosphere with time can be numerically predicted by solving a set of hydrodynamic equations, if the initial state is known. However, such a modelling approach always contains approximations that by and large depend on the purpose of use and resolution of the models. Present-day NWP systems operate with horizontal model resolutions in the range from about 40 km to 10 km. Recently, the aim has been to reach operationally to scales of 1 4 km. This requires less approximations in the model equations, more complex treatment of physical processes and, furthermore, more computing power. This thesis concentrates on the physical parameterization methods used in high-resolution NWP models. The main emphasis is on the validation of the grid-size-dependent convection parameterization in the High Resolution Limited Area Model (HIRLAM) and on a comprehensive intercomparison of radiative-flux parameterizations. In addition, the problems related to wind prediction near the coastline are addressed with high-resolution meso-scale models. The grid-size-dependent convection parameterization is clearly beneficial for NWP models operating with a dense grid. Results show that the current convection scheme in HIRLAM is still applicable down to a 5.6 km grid size. However, with further improved model resolution, the tendency of the model to overestimate strong precipitation intensities increases in all the experiment runs. For the clear-sky longwave radiation parameterization, schemes used in NWP-models provide much better results in comparison with simple empirical schemes. On the other hand, for the shortwave part of the spectrum, the empirical schemes are more competitive for producing fairly accurate surface fluxes. Overall, even the complex radiation parameterization schemes used in NWP-models seem to be slightly too transparent for both long- and shortwave radiation in clear-sky conditions. For cloudy conditions, simple cloud correction functions are tested. In case of longwave radiation, the empirical cloud correction methods provide rather accurate results, whereas for shortwave radiation the benefit is only marginal. Idealised high-resolution two-dimensional meso-scale model experiments suggest that the reason for the observed formation of the afternoon low level jet (LLJ) over the Gulf of Finland is an inertial oscillation mechanism, when the large-scale flow is from the south-east or west directions. The LLJ is further enhanced by the sea-breeze circulation. A three-dimensional HIRLAM experiment, with a 7.7 km grid size, is able to generate a similar LLJ flow structure as suggested by the 2D-experiments and observations. It is also pointed out that improved model resolution does not necessary lead to better wind forecasts in the statistical sense. In nested systems, the quality of the large-scale host model is really important, especially if the inner meso-scale model domain is small.
Resumo:
A novel dodecagonal space vector structure for induction motor drive is presented in this paper. It consists of two dodecagons, with the radius of the outer one twice the inner one. Compared to existing dodecagonal space vector structures, to achieve the same PWM output voltage quality, the proposed topology lowers the switching frequency of the inverters and reduces the device ratings to half. At the same time, other benefits obtained from existing dodecagonal space vector structure are retained here. This includes the extension of the linear modulation range and elimination of all 6+/-1 harmonics (n=odd) from the phase voltage. The proposed structure is realized by feeding an open-end winding induction motor with two conventional three level inverters. A detailed calculation of the PWM timings for switching the space vector points is also presented. Simulation and experimental results indicate the possible application of the proposed idea for high power drives.
Resumo:
Arguments arising from quantum mechanics and gravitation theory as well as from string theory, indicate that the description of space-time as a continuous manifold is not adequate at very short distances. An important candidate for the description of space-time at such scales is provided by noncommutative space-time where the coordinates are promoted to noncommuting operators. Thus, the study of quantum field theory in noncommutative space-time provides an interesting interface where ordinary field theoretic tools can be used to study the properties of quantum spacetime. The three original publications in this thesis encompass various aspects in the still developing area of noncommutative quantum field theory, ranging from fundamental concepts to model building. One of the key features of noncommutative space-time is the apparent loss of Lorentz invariance that has been addressed in different ways in the literature. One recently developed approach is to eliminate the Lorentz violating effects by integrating over the parameter of noncommutativity. Fundamental properties of such theories are investigated in this thesis. Another issue addressed is model building, which is difficult in the noncommutative setting due to severe restrictions on the possible gauge symmetries imposed by the noncommutativity of the space-time. Possible ways to relieve these restrictions are investigated and applied and a noncommutative version of the Minimal Supersymmetric Standard Model is presented. While putting the results obtained in the three original publications into their proper context, the introductory part of this thesis aims to provide an overview of the present situation in the field.
Resumo:
While the majority of violent threats – defined as an expression of intent to do harm or act out violently against someone or something – do not progress to actual violence, a small proportion of threateners do go on to enact violence. Most researchers argue that violence risk assessments are inadequate for assessing threats of violence, which raises the question: how should a threat assessment (TA) be conducted? To begin to understand available frameworks for assessing threats, a systematic review of TA research literature was conducted. Most TA literature pertains to a specific domain (schools, public figure threats, workplaces) and target audience (clinicians, school personnel, law enforcement). TA guidelines are typically based on literature reviews with some based on empirical measures and others having no strong evidential basis. The most common concepts in TA are exploration of the threatener's mental health, the motivation for the threat and the presence of any plans. Rather than advocating for the development of a protocol for conducting TA, this article outlines the common areas of inquiry in assessing threats and highlights the limitations of current TA guidelines.
Resumo:
Numerical models, used for atmospheric research, weather prediction and climate simulation, describe the state of the atmosphere over the heterogeneous surface of the Earth. Several fundamental properties of atmospheric models depend on orography, i.e. on the average elevation of land over a model area. The higher is the models' resolution, the more the details of orography directly influence the simulated atmospheric processes. This sets new requirements for the accuracy of the model formulations with respect to the spatially varying orography. Orography is always averaged, representing the surface elevation within the horizontal resolution of the model. In order to remove the smallest scales and steepest slopes, the continuous spectrum of orography is normally filtered (truncated) even more, typically beyond a few gridlengths of the model. This means, that in the numerical weather prediction (NWP) models, there will always be subgridscale orography effects, which cannot be explicitly resolved by numerical integration of the basic equations, but require parametrization. In the subgrid-scale, different physical processes contribute in different scales. The parametrized processes interact with the resolved-scale processes and with each other. This study contributes to building of a consistent, scale-dependent system of orography-related parametrizations for the High Resolution Limited Area Model (HIRLAM). The system comprises schemes for handling the effects of mesoscale (MSO) and small-scale (SSO) orographic effects on the simulated flow and a scheme of orographic effects on the surface-level radiation fluxes. Representation of orography, scale-dependencies of the simulated processes and interactions between the parametrized and resolved processes are discussed. From the high-resolution digital elevation data, orographic parameters are derived for both momentum and radiation flux parametrizations. Tools for diagnostics and validation are developed and presented. The parametrization schemes applied, developed and validated in this study, are currently being implemented into the reference version of HIRLAM.
Resumo:
Writing has long played an important role in the progression of architecture and the built environment. Histories of architecture are written, manifestoes that form the basis for a designer’s work are written and most importantly, the built environment advances itself through the act of critical writing. Not unlike the visual arts, literature and poetry, the tradition of written criticism has been crucial to the progression of architecture and its allied professions (Franz 2003). This article contributes to architecture and the built environment through the act of a written essay that critiques the problem of bodily diversity to architecture. In particular, the article explores the implications of body-space politics and abstracted body thinking on diverse bodies and their spatial justice. Using Soja’s Spatial Justice theory (2008), we seek to point out the underlying conceptions and power differentials assigned to different bodies spatially and how this leads to spatial injustices and contested spaces. The article also critically analyses the historical emergence of ‘the standardised body’ in architecture and its application in design theory and practice , and looks at how bodies often found on the outside of architecture highlight how such thinking creates in justices. Different theories are drawn on to help point to how design through the use of the upright, forward facing, male bod willingly and unwillingly denies access to resources and spatialities of everyday life. We also suggest ways to re-conceptualise the body in design practice and teaching.
Resumo:
It is known that by employing space-time-frequency codes (STFCs) to frequency selective MIMO-OFDM systems, all the three diversity viz spatial, temporal and multipath can be exploited. There exists space-time-frequency block codes (STFBCs) designed using orthogonal designs with constellation precoder to get full diversity (Z.Liu, Y.Xin and G.Giannakis IEEE Trans. Signal Processing, Oct. 2002). Since orthogonal designs of rate one exists only for two transmit antennas, for more than two transmit antennas STFBCs of rate-one and full-diversity cannot be constructed using orthogonal designs. This paper presents a STFBC scheme of rate one for four transmit antennas designed using quasi-orthogonal designs along with co-ordinate interleaved orthogonal designs (Zafar Ali Khan and B. Sundar Rajan Proc: ISIT 2002). Conditions on the signal sets that give full-diversity are identified. Simulation results are presented to show the superiority of our codes over the existing ones.
Resumo:
This paper presents a systematic construction of high-rate and full-diversity space-frequency block codes for MIMO-OFDM systems. While all prior constructions offer only a maximum rate of one complex symbol per channel use, our construction yields rate equal to the number of transmit antennas and simultaneously achieves full-diversity. The proposed construction works for arbitrary number of transmit antennas and arbitrary channel power delay profile. A key step in this construction is the generalization of the stacked matrix code design criteria given by Bolcskei et.al., (IEEE WCNC 2000). Explicit equivalence of our generalized code design criteria with the Hadamard-product based criteria of W. Su et.al., (lEEE Trans. Sig. Proc. Nov 2003) is established and new high-rate codes are constructed using our criteria.