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Search Results: 1 - 10 of 4407 matches for " Joel Lindkvist "
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Twin paradox with macroscopic clocks in superconducting circuits
Joel Lindkvist,Carlos Sabín,Ivette Fuentes,Andrzej Dragan,Ida-Maria Svensson,Per Delsing,G?ran Johansson
Physics , 2013, DOI: 10.1103/PhysRevA.90.052113
Abstract: We propose an implementation of a twin paradox scenario in superconducting circuits, with velocities as large as a few percent of the speed of light. Ultrafast modulation of the boundary conditions for the electromagnetic field in a microwave cavity simulates a clock moving at relativistic speeds. Since our cavity has a finite length, the setup allows us to investigate the role of clock size as well as interesting quantum effects on time dilation. In particular, our theoretical results show that the time dilation increases for larger cavity lengths and is shifted due to quantum particle creation.
Microwave Quantum Optics with an Artificial Atom
Io-Chun Hoi,C. M. Wilson,G?ran Johansson,Joel Lindkvist,Borja Peropadre,Tauno Palomaki,Per Delsing
Physics , 2012, DOI: 10.1088/1367-2630/15/2/025011
Abstract: We address the recent advances on microwave quantum optics with artificial atoms. This field relies on the fact that the coupling between a superconducting artificial atom and propagating microwave photons in a 1D open transmission line can be made strong enough to observe quantum coherent effects, without using any cavity to confine the microwave photons. We investigate the scattering properties in such a system with resonant coherent microwaves. We observe the strong nonlinearity of the artificial atom and under strong driving we observe the Mollow triplet. By applying two resonant tones, we also observe the Autler-Townes splitting. By exploiting these effects, we demonstrate two quantum devices at the single-photon level in the microwave regime: the single-photon router and the photon-number filter. These devices provide essential steps towards the realization of an on-chip quantum network.
Inhomogeneous structure formation may alleviate need for accelerating universe
Johan Hansson,Jesper Lindkvist
Physics , 2009, DOI: 10.2174/1874381101003010145
Abstract: When taking the real, inhomogeneous and anisotropic matter distribution in the semi-local universe into account, there may be no need to postulate an accelerating expansion of the universe despite recent type Ia supernova data. Local curvatures must be integrated (over all space) to obtain the global curvature of the universe, which seems to be very close to zero from cosmic microwave background data. As gravitational structure formation creates bound regions of positive curvature, the regions in between become negatively curved in order to comply with a vanishing global curvature. The actual dynamics of the universe is altered due to the self-induced inhomogeneities, again more prominently so as structure formation progresses. Furthermore, this negative curvature will increase as a function of time as structure formation proceeds, which mimics the effect of "dark energy" with negative pressure. Hence, the "acceleration" may be merely a mirage. We make a qualitative and semi-quantitative analysis, using newtonian gravity corrected for special relativistic effects, which works surprisingly well, to corroborate and illustrate/visualize these statements. This article may be seen as a plea to start taking seriously the observed inhomogeneous distribution and the nonlinearities of nonperturbative general relativity, and their impact on the dynamics and behavior of the cosmos.
Intensive Forestry as Progress or Decay? An Analysis of the Debate about Forest Fertilization in Sweden, 1960–2010
Anna Lindkvist,?rjan Kardell,Christer Nordlund
Forests , 2011, DOI: 10.3390/f2010112
Abstract: In the mid-1960s, fertilization (with nitrogen) had a breakthrough as a promising forest management method in Swedish company owned forests. The activity grew and peaked during the 1970s but then lost ground and stabilized at a low level in the 1990s and early 2000s. Over the last five years, however, interest in fertilizing Swedish forests has increased again. In this article both the forestry industry’s, and the environmental movement’s, attitudes toward forest fertilization over time are investigated. Furthermore, conflicting persistent ideas about nature and future, i.e., “figures of thought”, within interest groups, representing forestry and the environmental movement respectively, are identified and analyzed in relation to the debate on fertilization. The analysis reveals mainly three figures of thought that have influenced this debate during the period, “the idea of progress”, “the idea of decay” and “the idea of the great chain of being”. The study thus sheds light on how the relationship between forestry and the environmental movement has evolved from the 1960s until today and uncovers thought patterns that have stood, and continue to stand, in opposition to one another.
Finite Element Wear Behavior Modeling of Al/Al2SiO5/C Chilled Hybrid Metal Matrix Composites (CHMMCs)  [PDF]
Joel Hemanth
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.27118
Abstract: This paper describes research on aluminum based metal matrix hybrid composites reinforced with kaolinite (Al2SiO5) and carbon (C) particulates cast using high rate heat transfer technique during solidification by employing metallic, non-metallic and cryogenic end chills. The effect of reinforcement and chilling on strength, hardness and wear behavior are discussed in this paper. It is discovered that cryogenic chilled MMCs with Al2SiO5-9 vol.%/C-3 vol.% dispersoid content proved to be the best in enhancing the mechanical and wear properties. A physically based Finite element (FE) model for the abrasive wear of the hybrid composite developed is based on the mechanisms associated with sliding wear of ductile aluminum matrix of the composite containing hard Al2SiO5 and soft carbon (dry lubricant) reinforcement particles. Finally the results reveal that there is a good agreement that exists between the simulated (FE) values and those of the experimental values, proving the suitability of the boundary conditions.
The Impact of ‘Violating the Heterosexual Norm’ on Reading Speed and Accuracy  [PDF]
Joel Dickinson
Psychology (PSYCH) , 2011, DOI: 10.4236/psych.2011.25071
Abstract: This study explores the impact of “schema non-congruent” content on reading speed that has been found in relation to non-stereotypical gender roles. The goal of the present study is to assess if this effect translates to material that violates the “heterosexual norm”. Further, the present study explores whether the impact can be minimized by providing context prior to the exposure of sentences. Data indicated that the impact of sexuality was dependent on the gender of the main character and whether participants had been primed with context or not. Regardless of the time taken to read sentences, accuracy of material was recalled at a constant rate. In conclusion, the activation of “heterosexuality” does seem to be an automatic process such as the activation of gender.
Heat Transfer Analysis during External Chilling of Composite Material Castings through Experimental and Finite Element (FE) Modelling  [PDF]
Joel Hemanth
Modeling and Numerical Simulation of Material Science (MNSMS) , 2014, DOI: 10.4236/mnsms.2014.41001
Abstract:
In controlled solidification, one of the important factors that affects heat transfer from the solidifying casting is the resistance offered at the casting/chill interface. In the present investigation, heat transfer analysis during solidification of Al-12%Si (LM 13) alloy is carried out by collecting temperature history of the solidifying casting. The temperature distribution during solidification in the present investigation is obtained using ANSYS multiphysics software and further for comparison. The temperature profiles are also obtained by FE (Finite Element) modelling using the same software. By using a temperature data logger and lab view based software, the temperature data is acquired and processed at every second. The cooling curves obtained are analysed to know the effect of chilling on solidification behaviour of Al-12%Si alloy castings. Finally, it is concluded from the above research that the cooling curves and temperature distribution obtained by FE analysis do not so closely converge with the experimental data due to modelling limitations.
Effect of Metallic, Nonmetallic, Water Cooled and Cryogenic Chills on Pearlite Content (PC), Eutectic Cell Count (ECC) and Grain Size (GS) of Hypo Eutectic Nickel Alloyed Cast Iron  [PDF]
Joel Hemanth
Modeling and Numerical Simulation of Material Science (MNSMS) , 2017, DOI: 10.4236/mnsms.2017.71001
Abstract: This paper presents the results obtained, deductions made from solidification behaviour and a series of micro structural studies such as pearlite content, eu-tectic cell count and grain size of hypoeutectic gray cast iron which was sand cast (CO2 moulding) using metallic, nonmetallic, water cooled and subzero (cryogenic) end chills. Hypo-eutectic cast irons containing C 3.42, Si 2.4 and Ni 1.5 with impurity contents (S, P, Mn etc.) were solidified unidirectionally in an American Foundrymen Society (AFS) standard mould, the end of which was provided with different end chills to study the effect of chilling during solidifi-cation. The melts were inoculated with 0.3% Fe-Si to promote graphitization. It was observed that the transition from one structure to another is more gradual than normally obtained in the structure of cast irons solidified mul-ti-directionally in a sand mould at room temperature. Austenite dendrite interactions were shown to be a major factor in determining the microstructure, in which the higher dendrite reaction leads to changes in DAS, ECC and GS. It is observed that, the number of eutectic cells is an index of graphite nucleation and the effect of these on structure, since the eutectic cells are developed on the graphite nuclei during solidification.
Scanning Electron Microscopy (SEM) Analysis and Hardness of Diffusion Bonded Titanium-Titanium and Titanium-Copper Plates with Static Force and without Interlayers  [PDF]
Joel Hemanth
Open Journal of Composite Materials (OJCM) , 2017, DOI: 10.4236/ojcm.2017.72007
Abstract: In the present research, commercially pure Ti (grade-2) has been diffusion bonded with Ti and Cu plate under static force without any interlayers. The diffusion bonded samples were tested for micro hardness and micro structural analysis through optical microscopy and SEM. It is found from the present investigation that the bonded zone is affected by the processing variables such as bonding time (1 - 2 h), bonding force (250 N), bonding temperature (973 - 1073 K) and surface roughness. Results of the investigation revealed that temperature range of ?973 - 1073 K along with time duration of 1 - 2 hours in vacuum has resulted in a joint having high hardness with minimum pores. Hardness of the bond depends on the grain boundary diffusion at the interface and maximum hardness was achieved in the case of Ti-Cu joints. When Ti-Cu plates were used for bonding at 973 K for 2 hours, Cu-Ti solid solution along with a zone of different intermetallics was formed in the bonded zone. However, at higher temperatures, no continuous zone of intermetallics was found in the bonded region but instead Ti-Cu solid solution appeared.
Experimental, Mathematical and Finite Element Analysis (FEA) of Temperature Distribution through Rectangular Fin with Circular Perforations  [PDF]
Joel Hemanth
Modeling and Numerical Simulation of Material Science (MNSMS) , 2017, DOI: 10.4236/mnsms.2017.72002
Abstract: Fins are the extended surfaces through which heat transfer takes place to keep the surface cool. Fins of various configurations are presently used ranging from automobile engine cooling to cooling of computer parts. Note that in a fin majority of the heat transfer to atmosphere is by convection and therefore in the present research, and importance is given to variation of temperature along the length of the fin which in turn gives rate of heat transfer. In the present research a solid rectangular aluminum fin and the same rectangular fin with different perforations (2, 4, 8 and 10) were compared analytically, experimentally and its validity through finite element analysis for its temperature distribution along the length. From the present research it is observed that the mathematical and FEA for a solid rectangular fin without perforations are converging within ±1°C and rectangular fin with 10 perforations are converging within ±2°C and hence the validity.
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