2,880 research outputs found
Seismic assessment of the Qutb Minar in Delhi, India
The present paper describes the seismic assessment of the Qutb Minar in Delhi, India. Three models with different levels of complexity and simplifications were developed. The use of these models allows to overcome the complexity on the study of the seismic behavior of ancient masonry structures; by combining the results of the different models it is possible to obtain a better and more comprehensive interpretation of the seismic behavior. The models were used for non-linear static (pushover) and non-linear dynamic analyses. The static and dynamic analyses give different behaviors, indicating that push-over analysis should be used carefully in the seismic assessment of masonry structures. For the static analysis, the base of the tower is the most vulnerable part; while according to the dynamic analysis, it is the upper part of the tower. This last behavior is according to the historical damage suffered by the tower due to earthquakes. The different behaviors can be explained by the influence of the higher modes of vibration
Analyzing a Bose polaron across resonant interactions
Recently, two independent experiments reported the observation of long-lived
polarons in a Bose-Einstein condensate, providing an excellent setting to study
the generic scenario of a mobile impurity interacting with a quantum reservoir.
Here, we expand the experimental analysis by disentangling the effects of trap
inhomogeneities and the many-body continuum in one of these experiments. This
makes it possible to extract the energy of the polaron at a well-defined
density as a function of the interaction strength. Comparisons with quantum
Monte-Carlo as well as diagrammatic calculations show good agreement, and
provide a more detailed picture of the polaron properties at stronger
interactions than previously possible. Moreover, we develop a semi-classical
theory for the motional dynamics and three-body loss of the polarons, which
partly explains a previously unresolved discrepancy between theory and
experimental observations for repulsive interactions. Finally, we utilize
quantum Monte-Carlo calculations to demonstrate that the findings reported in
the two experiments are consistent with each other
Nonuniversal dynamic conductance fluctuations in disordered systems
Sample-to-sample fluctuations of the time-dependent conductance of a system
with static disorder have been studied by means of diagrammatic theory and
microwave pulsed transmission measurements. The fluctuations of time-dependent
conductance are not universal, i.e., depend on sample parameters, in contrast
to the universal conductance fluctuations in the steady-state regime. The
variance of normalized conductance, determined by the infinite-range intensity
correlation C_3(t), is found to increase as a third power of delay time from an
exciting pulse, t. C_3(t) grows larger than the long-range intensity
correlation C_2(t) after a time t_q ~ ^{1/2} t_D (t_D being the diffusion
time, being the average dimensionless conductance).Comment: Revised version, 6 pages, 5 figure
Numerical models for the seismic assessment of an old masonry tower
The present paper describes the seismic assessment of the Qutb Minar in Delhi, India. Three models with different levels of complexity and simplifications were developed. The use of these models allows to overcome the complexity on the study of the seismic behavior of ancient masonry structures; by combining the results of the different models it is possible to obtain a better and more comprehensive interpretation of the seismic behavior. The models were used for non-linear static (pushover) and non-linear dynamic analyses. The static and dynamic analyses give different behaviors, indicating that push-over analysis should be used carefully in the seismic assessment of masonry structures. For the static analysis, the base of the tower is the most vulnerable part; while according to the dynamic analysis, it is the upper part of the tower. This last behavior is according to the historical damage suffered by the tower due to earthquakes. The different behaviors can be explained by the influence of the higher modes of vibration.This research was part of the activities of the EU-India Economic Cross Cultural Programme "Improving the Seismic Resistance of Cultural Heritage Buildings", Contract ALA-95-23-2003-077-122. F. Pefia acknowledges funding from the FCT grant contract SFRH/BPD/17449/2004, as well as the partial support of the project PAPIIT IN105409
Desempenho sĂsmico de um minarete de alvenaria
Esta comunicação apresenta a avaliação do desempenho sĂsmico do Qutb Minar, minarete em Nova Deli, ĂŤndia. A modelação numĂ©rica foi realizada com recurso a trĂŞs modelos diferentes, calibrados atravĂ©s de ensaios de identificação dinâmica. A combinação de resultados dos modelos permitiu compreender melhor o comportamento do minarete e validar os modelos mais simples. No estudo do desempenho sĂsmico da estrutura foram consideradas a análise nĂŁo-linear estática e a análise nĂŁo-linear dinâmica com integração no tempo. As tĂ©cnicas de análise conduziram a resultados diferentes em termos de capacidade e mecanismo de colapso, indicando que o uso de análises estáticas para a avaliação do desempenho sĂsmico de construções histĂłricas de alvenaria deve ser realizado com precaução. Os resultados da análise nĂŁo-linear dinâmica estĂŁo de acordo com os danos causados por sismos no passado e com os modos identificados experimentalmente, concluindo-se que os dois Ăşltimos pisos correspondem Ă parte mais vulnerável do minarete
On the puzzle of Bremsstrahlung as described by coaccelerated observers
We consider anew some puzzling aspects of the equivalence of the quantum
field theoretical description of Bremsstrahlung from the inertial and
accelerated observer's perspectives. More concretely, we focus on the seemingly
paradoxical situation that arises when noting that the radiating source is in
thermal equilibrium with the thermal state of the quantum field in the wedge in
which it is located, and thus its presence does not change there the state of
the field, while it clearly does not affect the state of the field on the
opposite wedge. How then is the state of the quantum field on the future wedge
changed, as it must in order to account for the changed energy momentum tensor
there? This and related issues are carefully discussed.Comment: 29 pages, 1 figure; Revtex, minor changes, PACS correcte
Bioeutectic® ceramics for biomedical application obtained by laser floating zone method. In vivo evaluation
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license.In this study, the Bioeutectic® blocks were inserted into the critical size defects of eight rabbits, using both tibiae, and the physical and chemical nature of the remodeled interface between the Bioeutectic® implants and the surrounding bone were performed at four and 15 months. The results showed a new fully mineralized bone growing in direct contact with the implants. The ionic exchange, taking place at the implant interface with the body fluids was essential in the process of the implant integration through a dissolution-precipitation-transformation mechanism. The study found the interface biologically and chemically active over the 15 months implantation period. The osteoblastic cells migrated towards the interface and colonized the surface at the contact areas with the bone. The new developed apatite structure of porous morphology mimics natural bone. © 2014 by the authors.The authors wish to acknowledge funding from the European Community at the 7th Framework Program EU No. 314630-UV Marking and Generalitat Valenciana (GVA) within the Project ACOMP/2009/173.Peer Reviewe
The Geometry of Integrable and Superintegrable Systems
The group of automorphisms of the geometry of an integrable system is
considered. The geometrical structure used to obtain it is provided by a normal
form representation of integrable systems that do not depend on any additional
geometrical structure like symplectic, Poisson, etc. Such geometrical structure
provides a generalized toroidal bundle on the carrier space of the system.
Non--canonical diffeomorphisms of such structure generate alternative
Hamiltonian structures for complete integrable Hamiltonian systems. The
energy-period theorem provides the first non--trivial obstruction for the
equivalence of integrable systems
Radon, water chemistry and pollution check by volatile organic compounds in springs around Popocatepetl volcano, Mexico
Popocatepetl volcano is a high-risk active volcano in Central Mexico where the highest population density in the country
is settled. Radon in the soil and groundwater together with water chemistry from samples of nearby springs were
analysed as a function of the 2002-2003 volcanic activity. The measurements of soil radon indicated fluctuations related
to both the meteorological and sporadic explosive events. Groundwater radon showed essential differences in
concentration due to the specific characteristics of the studied springs. Water chemistry showed also stability along
the monitoring period. No anthropogenic pollution from Volatile Organic Compounds (VOCs) was observed. An
overview of the soil radon behaviour as a function of the volcanic activity in the period 1994-2002 is also discussed
Mechanical 144 GHz beam steering with all-metallic epsilon-near-zero lens antenna
The following article appeared in Pacheco-Peña, V., Torres, V., Orazbayev, B., Beruete, M., Sorolla, M., Navarro-CĂa, M., & Engheta, N. (2014). Mechanical 144GHz beam steering with all-metallic epsilon-near-zero lens antenna. Applied Physics Letters, 105(24), doi:10.1063/1.4903865, and may be found at http://dx.doi.org/10.1063/1.4903865.An all-metallic steerable beam antenna composed of an ε-near-zero (ENZ) metamaterial lens is experimentally demonstrated at 144 GHz (λ0 = 2.083 mm). The ENZ lens is realized by an array of narrow hollow rectangular waveguides working just near and above the cut-off of the TE10 mode. The lens focal arc on the xz-plane is initially estimated analytically as well as numerically and compared with experimental results demonstrating good agreement. Next, an open-ended waveguide is placed along the lens focal arc to evaluate the ENZ-lens antenna steerability. A gain scan loss below 3 dB is achieved for angles up to plus/minus 15Âş.This work was supported in part by the Spanish
Government under Contract Consolider Engineering
Metamaterials CSD2008-00066 and Contract TEC2011-
28664-C02-01. V.P.-P. is sponsored by Spanish Ministerio
de Educacion, Cultura y Deporte under grant FPU AP-2012-
3796. V.T. is sponsored by the Universidad Publica de
Navarra. B.O. is sponsored by Spanish Ministerio de
Economıa y Competitividad under Grant FPI BES-2012-
054909. M.B. is sponsored by the Spanish Government via
RYC-2011-08221. M.N.-C. is supported by the Imperial
College Junior Research Fellowship
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