| 1121. |
- Lenells, Jonatan, 1981-
(författare)
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Traveling wave solutions of the Camassa-Holm equation
- 2005
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Ingår i: Journal of Differential Equations. - : Elsevier BV. - 0022-0396 .- 1090-2732. ; 217:2, s. 393-430
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Tidskriftsartikel (refereegranskat)abstract
- All weak traveling wave solutions of the Camassa-Holm equation are classified. We show that, in addition to smooth solutions, there are a multitude of traveling waves with singularities: peakons, cuspons, stumpons, and composite waves.
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| 1122. |
- Lenells, Jonatan
(författare)
-
Traveling wave solutions of the Degasperis-Procesi equation
- 2005
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Ingår i: Journal of Mathematical Analysis and Applications. - : Elsevier BV. - 0022-247X .- 1096-0813. ; 306:1, s. 72-82
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Tidskriftsartikel (refereegranskat)abstract
- We classify all weak traveling wave solutions of the Degasperis-Procesi equation. In addition to smooth and peaked solutions, the equation is shown to admit more exotic traveling waves such as cuspons, stumpons, and composite waves.
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| 1123. |
- Lenells, Jonatan, 1981-
(författare)
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Traveling waves in compressible elastic rods
- 2006
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Ingår i: Discrete and continuous dynamical systems. Series B. - 1531-3492 .- 1553-524X. ; 6:1, s. 151-167
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Tidskriftsartikel (refereegranskat)abstract
- We determine all weak traveling wave solutions of a model for nonlinear dispersive waves in cylindrical compressible hyperelastic rods. Besides the previously known smooth, peaked, and cusped solutions, the equation is shown to admit compactons, stumpons, and fractal-like waves.
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| 1124. |
- Levola, Helena, et al.
(författare)
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Ionization-site effects on the photofragmentation of chloro- and bromoacetic acid molecules
- 2015
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 92:6
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Tidskriftsartikel (refereegranskat)abstract
- Fragmentation of gas-phase chloro-and bromoacetic acid samples, particularly its dependency on the atomic site of the initial core ionization, was studied in photoelectron-photoion-photoion coincidence (PEPIPICO) measurements. The fragmentation was investigated after ionizing carbon 1s and bromine 3d or chlorine 2p core orbitals. It was observed that the samples had many similar fragmentation pathways and that their relative weights depended strongly on the initial ionization site. Additional Auger PEPIPICO measurements revealed a clear dependence of fragment pair intensities on the kinetic energy of the emitted Auger electrons. The modeled and measured Auger electron spectra indicated that the average internal energy of the molecule was larger following the carbon 1s core-hole decay than after the decay of the halogen core hole. This difference in the internal energies was found to be the source of the site-dependent photofragmentation behavior.
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| 1125. |
- Lewen, R., et al.
(författare)
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High frequency characterization of a GaInAs/InP electronic waveguide T-branch switch
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 91:4, s. 2398-2402
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Tidskriftsartikel (refereegranskat)abstract
- We report comprehensive microwave measurements on a T-branch switch; a GaInAs/InP electron waveguide based structure. The study includes a small signal model of the device where limitations of high frequency operation are discussed. An example of large signal operation where the nonlinearity of the device is exploited by operating the T-branch switch as a frequency multiplier is demonstrated.
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| 1126. |
- Li, Bin, et al.
(författare)
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Fused coarse-grained model of aromatic ionic liquids and their behaviour at electrodes
- 2016
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 18:11, s. 8165-8173
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Tidskriftsartikel (refereegranskat)abstract
- A fused coarse-grained model of aromatic ionic liquids 1-alkyl-3-methylimidazoliums tetrafluoroborate ([CnMIM+][BF4-]) has been constructed. Structural and dynamical properties calculated from our model are compared with experimental data as well as with corresponding results from simulations of other suggested models. Specifically, we adopt a fused-sphere coarse-grained model for cations and anions. This model is utilized to study structure and differential capacitance in models of flat and porous carbon electrodes. We find that the capacitance varies with pore size, in a manner that is related to the packing of ions inside the pore. For very narrow pores, diffusion is slow and the establishment of thermodynamic equilibrium may exceed the practical limits for our molecular dynamics simulations.
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| 1127. |
- Li, Cong, et al.
(författare)
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Coexistence of two intertwined charge density waves in a kagome system
- 2022
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Ingår i: Physical Review Research. - : American Physical Society (APS). - 2643-1564. ; 4:3
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Tidskriftsartikel (refereegranskat)abstract
- Materials with a kagome lattice structure display a wealth of intriguing magnetic properties due to their geometric frustration and intrinsically flat band structure. Recently, topological and superconducting states have also been observed in kagome systems. The kagome lattice may also host a "breathing" mode that leads to charge density wave (CDW) states, if there is strong electron-phonon coupling, electron-electron interaction, or external excitation of the material. This "breathing" mode can give rise to candidate distortions such as the star of David (SoD) or its inverse structure [trihexagonal (TrH)]. To date, in most materials, only a single type of distortion has been observed. Here, we present angle-resolved photoemission spectroscopy measurements on the kagome superconductor CsV3Sb5 at multiple temperatures and photon energies to reveal the nature of the CDW in this material. It is shown that CsV3Sb5 displays two intertwined CDW orders corresponding to the SoD and TrH distortions. These two distinct types of distortions are stacked along the c direction to form a three-dimensional CDW order where the two 2-fold CDWs are phase shifted along the c axis. The presented results provide not only key insights into the nature of the unconventional CDW order in CsV3Sb5, but also an important reference for further studies on the relationship between the CDW and superconducting order.
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| 1128. |
- Li, Cong, et al.
(författare)
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Emergence of Weyl fermions by ferrimagnetism in a noncentrosymmetric magnetic Weyl semimetal
- 2023
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Condensed matter physics has often provided a platform for investigating the interplay between particles and fields in cases that have not been observed in high-energy physics. Here, using angle-resolved photoemission spectroscopy, we provide an example of this by visualizing the electronic structure of a noncentrosymmetric magnetic Weyl semimetal candidate NdAlSi in both the paramagnetic and ferrimagnetic states. We observe surface Fermi arcs and bulk Weyl fermion dispersion as well as the emergence of new Weyl fermions in the ferrimagnetic state. Our results establish NdAlSi as a magnetic Weyl semimetal and provide an experimental observation of ferrimagnetic regulation of Weyl fermions in condensed matter.
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| 1129. |
- Li, Hui, et al.
(författare)
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Characteristic Mode Based Tradeoff Analysis of Antenna-Chassis Interactions for Multiple Antenna Terminals
- 2012
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 60:2, s. 490-502
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Tidskriftsartikel (refereegranskat)abstract
- The design of multiple antennas in compact mobile terminals is a significant challenge, due to both practical and fundamental design tradeoffs. In this paper, fundamental antenna design tradeoffs of multiple antenna terminals are presented in the framework of characteristic mode analysis. In particular, interactions between the antenna elements and the characteristic modes and their impact on design tradeoffs are investigated in both theory and simulations. The results reveal that the characteristic modes play an important role in determining the optimal placement of antennas for low mutual coupling. Moreover, the ability of antenna elements to localize the excitation currents on the chassis can significantly influence the final performance. To demonstrate the effectiveness of the proposed approach, a dual-band, dual-antenna terminal is designed to provide an isolation of over 10 dB for the 900 MHz band without additional matching or decoupling structures. A tradeoff analysis of bandwidth, efficiency, effective diversity gain and capacity is performed over different antenna locations. Finally, three fabricated prototypes verify the simulation results for representative cases.
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| 1130. |
- Li, Hui, et al.
(författare)
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Decoupling of Multiple Antennas in Terminals With Chassis Excitation Using Polarization Diversity, Angle Diversity and Current Control
- 2012
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 60:12, s. 5947-5957
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Tidskriftsartikel (refereegranskat)abstract
- Excitation of the chassis enables single-antenna terminals to achieve good bandwidth and radiation performance, due to the entire chassis being utilized as the main radiator. In contrast, the same chassis excitation phenomenon complicates the design of multiple antennas for MIMO applications, since the same characteristic mode of the chassis may be effectively excited by more than one antenna, leading to strong mutual coupling and severe MIMO performance degradation. In this paper, we introduce a design concept for MIMO antennas to mitigate the chassis-induced mutual coupling, which is especially relevant for frequency bands below 1 GHz. We illustrate the design concept on a dual-antenna terminal at 0.93 GHz, where a folded monopole at one chassis edge excites the chassis' fundamental electric dipolemode and a coupled loop at the other chassis edge excites its own fundamental magnetic dipole mode. Since the two radiationmodes are nearly orthogonal to each other, an isolation of over 30 dB is achieved. Moreover, we show that the antenna system can be conveniently modified for multiband operation, such as in the 900/1800/2600MHz bands. Furthermore, by controlling the phase of the feed current on the folded monopole, the two antennas can be co-located on the same chassis edge with an isolation of over 20 dB. The co-located dual-antenna prototype was fabricated and verified in the measurements.
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