391 research outputs found
A parametric study of the influence of ion and electron properties on the excitation of electromagnetic ion cyclotron waves in coronal mass ejections
No full textInterplanetary coronal mass ejections (ICMEs) often possess a negative proton thermal anisotropy, Ap = T⊥,p/T ∥.p - 1 < 0 (T∥, T⊥: parallel and perpendicular temperatures, respectively) so that right-hand polarized electromagnetic ion cyclotron waves (EICWs) may be amplified by a kinetic instability [Famigia et ai, 1998a]. However, in view of the low proton beta of ICMEs, several physical parameters, besides Ap, need to be in the right range to excite this instability with significant growth rates. In this paper we present a parametric study of EICWs aimed at identifying those parameters which are most influential in fostering the emission of these waves in ICME scenarios. We analyze here the influence of: (1) thermal and suprathermal protons, (2) thermal alpha particles (αs), and (3) thermal electrons. We solve the dispersion relation of EICWs including protons, αs and electrons, all modeled with bi-Maxwellian distribution functions, and a minority population of suprathermal protons using a kappa function for the velocity component along the field. For physical regimes of ICMEs we find that the instability depends critically on the values of the following parameters: proton beta, proton thermal anisotropy, relative abundance of the suprathermal protons, α-to-proton relative abundance, α-to-proton temperature ratio, α particle thermal anisotropy, electron-to-proton temperature ratio, and thermal anisotropy of electrons. The effect of these parameters on the instability is either direct (when they increase the number of resonant particles) or indirect (when they decrease the phase speed of the wave so that more particles can resonate). Data surveys òn EICWs should take into account the whole set of parameters indicated here, since the expected level of wave excitation results from their combined action. The study may be useful in understanding the considerable level of magnetic fluctuations observed in interplanetary CMEs by the Wind spacecraft. Copyright 2003 by the American Geophysical Union.Fil:Dasso, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Gratton, F.T. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
A parametric study of the influence of ion and electron properties on the excitation of electromagnetic ion cyclotron waves in coronal mass ejections
No full textInterplanetary coronal mass ejections (ICMEs) often possess a negative proton thermal anisotropy, Ap = T⊥,p/T ∥.p - 1 < 0 (T∥, T⊥: parallel and perpendicular temperatures, respectively) so that right-hand polarized electromagnetic ion cyclotron waves (EICWs) may be amplified by a kinetic instability [Famigia et ai, 1998a]. However, in view of the low proton beta of ICMEs, several physical parameters, besides Ap, need to be in the right range to excite this instability with significant growth rates. In this paper we present a parametric study of EICWs aimed at identifying those parameters which are most influential in fostering the emission of these waves in ICME scenarios. We analyze here the influence of: (1) thermal and suprathermal protons, (2) thermal alpha particles (αs), and (3) thermal electrons. We solve the dispersion relation of EICWs including protons, αs and electrons, all modeled with bi-Maxwellian distribution functions, and a minority population of suprathermal protons using a kappa function for the velocity component along the field. For physical regimes of ICMEs we find that the instability depends critically on the values of the following parameters: proton beta, proton thermal anisotropy, relative abundance of the suprathermal protons, α-to-proton relative abundance, α-to-proton temperature ratio, α particle thermal anisotropy, electron-to-proton temperature ratio, and thermal anisotropy of electrons. The effect of these parameters on the instability is either direct (when they increase the number of resonant particles) or indirect (when they decrease the phase speed of the wave so that more particles can resonate). Data surveys òn EICWs should take into account the whole set of parameters indicated here, since the expected level of wave excitation results from their combined action. The study may be useful in understanding the considerable level of magnetic fluctuations observed in interplanetary CMEs by the Wind spacecraft. Copyright 2003 by the American Geophysical Union.Fil:Dasso, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Gratton, F.T. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
Enif Robert, F.T. Marinetti e il romanzo Un ventre di donna: bisessualità, trauma e mito dell'isteria
No full textThis article provides the first in-depth and contextual study of the experimental futurist novel Un ventre di donna , written during the First World War by the Italian author and stage actress Enif Robert in collaboration with F.T. Marinetti, who allowed some of his wartime letters from the front to be included in the novel. Un ventre di donna also incorporates letters by the famous actress Eleonora Duse, who was a close friend of Robert’s. The article explores in particular the theme of bisexuality and female homosexuality in the novel in the context of the ideology of gender in Italy and in Europe in the early 20 th century, and in particular with reference to the influential work of Otto Weininger and concurrent theories of hysteria and bisexuality, as well as the so-called “gender inversion” generated by the war.  
Fugitive Pieces: F.T. Prince and Sculpture
No full textThis is the author accepted manuscript. The final version is available from the publisher via the link in this record.This chapter explores a neglected aspect of mid-twentieth-century poetry: the creative and
economic interplay between architecture, language, and form. It takes as a focal point the work of
a lesser-known poet, F.T. Prince, making use of underexplored material in his archive. Such poetry
calls for closer critical attention to the re-fashioning of material across disciplines. For instance, the
‘delightful voids ‘ and ‘long fractures’ of Prince’s work oscillate between word and sculptural matter,
creating ‘fugitive’ pieces that are at once verbally and spatially coercive. It offers a case in which
twentieth-century poetry, through the architecture of the page, subtly and insistently reminds
readers of the politics and economics of its production as commissioned word and work.
Bringing to light material from the new Prince archive, this chapter examines the author’s skilful
negotiations of the processes of artistic dissemination and patronage, as well as his intimate
relationship with the politics of commission and production across historical time. It reads early
modern and twentieth-century buildings – in print and in place – not as neutral structures, but as
forms of argument that persuade and coerce, in their inhabitability. It argues for closer attention in
current poetic criticism to the materiality of the work, which foregrounds its fraught aesthetic and
economic self-interest. Prince’s poetry, in reaching back to cinquecento sculpture and artwork,
insists that its readers recognise that the artist’s skill in physical rendering – in the praise-poem, the
commemorative object, the structure built or work painted to ‘your’ honour – is required in order
successfully to negotiate a commissioner’s and an audience’s, as well as its own agendas
Supersonic mixing layers: Stability of magnetospheric flanks models
No full textCompressibility has a strong influence on the stability of velocity shear layers when the difference of velocity ΔV across the flow becomes supersonic. The flanks of the Earth's magnetopause are normally supersonic Ms > 1, and super-Alfvénic MA > 1, depending on the distance from the dayside terminator (Ms and MA are the sonic and Alfvén Mach numbers of the magnetosheath plasma, respectively). The stability of MHD supersonic flows depends, also on several other features, such as the finite thickness Δ of the boundary layer, the relative orientation of velocity and magnetic fields, the density jump across the boundary and the magnetic shear angle. We analyze the MHD stability of some representative flank sites modeled after data from spacecraft crossings of the magnetopause under different interplanetary conditions, complementing these cases with extrapolations of likely conditions upstream, and downstream of the crossing site. Under northward interplanetary magnetic field conditions, there are solar wind regimes such that the near, but already supersonic, flank of the magnetopause may be locally stable. Stability is possible, e.g., when M s becomes larger than ∼1.2-1.4 while MA remains smaller than 1.2, and there is magnetic shear between the geomagnetic and the interplanetary magnetic field. Solar winds favouring local stability of the boundary layer are cold, not-too-dense plasmas, with strong magnetic fields, so that MA is smaller, while Ms is larger, than normal values of the magnetosheath flow. A gap between dayside and tail amplifying regions of Kelvin-Helmholtz disturbances over the magnetopause may exist when the above conditions are realized. © 2009 IOP Publishing Ltd.Fil:Gnavi, G. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Gratton, F.T. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Bilbao, L.E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
A Novel Heatsink Attached mm-Wave Active Patch Antenna With Adjustable Frequency and Cooling
No full textIn this study, the thermal management problem of the modern communication systems with small array sizes is addressed. A novel dual-functional active antenna design strategy is introduced for adjustable frequency of operation and cooling extension at millimeter-wave bands. The concept is based on placing different types of heatsinks on the same patch antenna. The electromagnetic and thermal behavior of the proposed heatsink structures are presented via simulations. Reconfigurable operation at 24, 26, and 28 GHz frequencies with 23 to 28 degrees of extra cooling in the chip as compared to the conventional patch is achieved.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.MicroelectronicsMicrowave Sensing, Signals & System
A Filtering Dipole Antenna Design with Bandwidth Enhancement for 5G
No full textThe present study proposes a dipole filtering antenna with wide-band characteristics for communication. The filtering is achieved by employing parasitic elements and wide-band characteristic is obtained by reshaping the dipole and using specially designed balun structure. One radiation null is optimized at the higher frequency band limit for sharp transition from pass band to stop band via two half-rectangular ring resonators. The antenna operates between 2.6 and 5 GHz and has maximum realized gain of 8.39 dBi. The |S11| is less than -10 dB in the operating frequency band. The simulation results and evolution of the design procedure are presented.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Microelectronic
Retirement 20/20: Innovation in Pension Design
No full textToday, both the United States and Canada are experiencing a decline in Single-Employer Sponsored Defined Benefit (DB) Pension plans. In some instances, they are being replaced by Defined Contribution (DC) or Individual Account [e.g., 401(k)] plans; in other cases, by nothing. It appears that traditional sponsors of DB plans have concluded that their cost (or its variability) is larger than the rewards (e.g., a loyal work force). At the same time, two stock market meltdowns in less than a decade have indicated to all the frailties of Individual Account DC systems. What we need is a new pension system that brings most of the advantages of the DB and DC plans to the participants, while minimizing their disadvantages. We must also recognize the skill set of the participants (e.g., do not expect a blue collar worker to be an investment professional) and not anticipate or require anomalous markets (e.g., ever-stronger equity returns). Size matters. Larger plans can run at lower per unit expense ratios, and can also achieve entry into a wide variety of investment products (e.g., private placements) not available to a small plan. Larger funds also benefit from risk sharing through “Law of Large Numbers”. The model proposed is a “Jointly Governed Target Benefit Pension plan”. Such plans would have many features in common with today’s Ontario Multi-Employer Pension Plans (MEPPs), the Canada/Quebec Pension Plans (C/QPP), TIAA-CREF in the United States and the Dutch national plan. For the plan sponsor, this is a DC plan. Inherent in the concept are that smaller plans (and even individual plans) could commingle their assets to achieve “size” (e.g. a minimum investment portfolio of $10B). Investment management would be at arm’s length from the plan itself.Target Benefit, Joint Governance, Commingled Assets
Is Foreign-Owned Capital a Bad Thing to Tax?
No full textThe aging population has raised at least two concerns about tax policy. First, taxes will need to be increased to cover higher public-pension and medical-care expenses when baby boomers have retired. Second, taxes can be cut in the meantime, as the government realizes the "fiscal dividend" that accompanies its debt reduction program (that has been motivated by the aging population development). This paper uses a simple endogenous growth analysis to examine these issues. It is assumed that sales tax increases are infeasible on political grounds. Two conclusions emerge: the income tax rate levied on domestic residents should be cut during the debt-reduction period, and the tax rate on foreigners whose capital is operating in Canada should be increased later on when the bulk of the baby boomers have retired.fiscal policy, endogenous growth, open economy
Quadruple-Junction Thin-Film Silicon-Based Solar Cells
No full textThe direct utilization of sunlight is a critical energy source in a sustainable future. One of the options is to convert the solar energy into electricity using thin-film silicon-based solar cells (TFSSCs). Solar cells in a triple-junction configuration have exhibited the highest energy conversion efficiencies within the thin-film silicon photovoltaic technology. Going further from the state-of-the-art device structures, this thesis works on the concept of quadruple-junction TFSSCs, and explores the potential and feasibility of such configuration.The initial experimental realization of quadruple-junction TFSSCs is demonstrated in Chapter 2. The fabricated thin-film a-SiOx:H/a-Si:H/nc-Si:H/nc-Si:H solar cells showed favorable fill factors (FF) and exceptionally high open-circuit voltages (VOC) up to 2.91 V, suggesting a high quality of the material depositions and of the process control. Optical simulations were used in the design of the device structure, to precisely control the thickness and optical absorption in the layers. This preliminary experiment indicated how improvements can be made by better light management.The spectral response of the component subcells is important information for the study of multi-junction solar cells, and the accurate measurement of such properties turns out to be challenging. Chapter 3 analyzes the mechanism of the spectral response measurement of multi-junction solar cells, by means of modeling the optoelectrical response of the subcells and their internal interactions. The formation of measurement artifacts, and their dependence on cell properties and measurement conditions, are elucidated. The analyses lead to comprehensive guidelines on how to conduct a trustworthy measurement and sensible data interpretation.Absorbing semiconductor materials with different bandgaps are desirable for multi-junction solar cells. Thin-film a-SiGex:H cells have been developed to accommodate an absorber material with an intermediate bandgap between that of a-Si:H and nc-Si:H. Chapter 4 reports the development of a-SiGex:H cells using mixed-phase SiOx:H materials in the doped layers. Bearing the band alignment in mind, the optimization of p- and n-type SiOx:H layers resulted in satisfying device performance. The use of SiOx:H p- and n-layers offers great flexibility when integrating the cell in a multi-junction solar cell. Chapter 5 describes the development of quadruple-junction TFSSCs using four different absorber materials. The thin-film wide-gap a-Si:H/narrow-gap a-Si:H/a-SiGex:H/nc-Si:H solar cells promotes reasonable spectral utilization because of the descending bandgap along the direction of light incidence. The tunnel recombination junctions between the subcells have been optimized to ensure effective interconnections thus the proper functioning of the multi-junction device. Advanced light management, which involved the use of modulated surface textured front electrode, was arranged for enhancing the optical performance. These investigations reveal the potential of quadruple-junction TFSSCs.Chapter 6 evaluates the benefit of multi-junction solar cells with different number of subcells. The gains and losses inherent in adding more subcells have been critically assessed from the optical and electrical points of view. The effects of optical reflection, parasitic absorption, tunnel recombination junctions, and filtered illumination in multi-junction cells on the performance were investigated. In general, all types of losses increase with the number of subcells. Among them, the filtered illumination in the subcells can play a significant role in case of a large number of subcells. These results show that such comprehensive analysis helps to judge whether it is reasonable to develop a multi-junction solar cell with a certain structure.Photovoltaic Materials and Device
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