Surface pre-treatment is one of the key processes in bonded repair of aircraft carbon fibre reinforced polymer composites. This paper investigates the surface modification of physical and chemical properties by laser ablation and conventional polish treatment techniques. Surface morphology analysed by laser scanning confocal microscopy and scanning electron microscopy showed that a laser-treated surface displayed higher roughness than that of a polish-treated specimen. The laser-treated laminate exhibited more functional groups in the form of O 1 s/C 1 s atomic ratio of 30.89% for laser-treated and 20.14% for polish-treated as evidenced by X-ray photoelectron spectroscopy observation. Contact angle goniometry demonstrated that laser treatment can provide increased surface free energy and wettability. In the light of mechanical interlocking, molecular bonding and thermodynamics theories on adhesion, laser etching process displayed enhanced bonding performance relative to the polishing surface treatment. These properties resulted in an increased single lap shear strength and a cohesive failure mode for laser etching while an adhesive failure mode occurred in polish-treated specimen.

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A new femtosecond, Extreme Ultraviolet (EUV), Time Resolved Spin-Angle Resolved Photo-Emission Spectroscopy (TR-Spin-ARPES) beamline was developed for ultrafast materials research and development. This 50-fs laser-driven, table-top beamline is an integral part of the “Ultrafast Spintronic Materials Facility”, dedicated to engineering ultrafast materials. This facility provides a fast and in-situ analysis and development of new materials. The EUV source based on high harmonic generation process emits 2.3 × 1011 photons/second (2.3 × 108 photons/pulse) at H23 (35.7 eV) and its photon energy ranges from 10 eV to 75 eV, which enables surface sensitive studies of the electronic structure dynamics. The EUV monochromator provides the narrow bandwidth of the EUV beamline while preserving its pulse duration in an energy range of 10–100 eV. Ultrafast surface photovoltaic effect with ~650 fs rise-time was observed in p-GaAs (100) from time-resolved ARPES spectra. The data acquisition time could be reduced by over two orders of magnitude by scaling the laser driver from 1 KHz, 4W to MHz, KW average power.

Traction current can to impose conductive interference on the railway signalling system, which is also known as unbalanced traction current interference. In the station turnout section, the traction current may cause obvious interference on both receiving apparatus of track circuit and cab signalling apparatus due to the installation of multi-jumpers, wing rails, and insulated joints inside the turnout. This paper analyzes the above structural characteristics of turnouts in depth. By establishing a comprehensive simulation model of one-transmitter and two-receiver track circuit in turnout section and simulating the complete return current path along with traction network–locomotive–rails, the mechanism of traction current conductive interference in the turnout section is then illustrated, using Multisim and MATLAB/Simulink simulation platform. Finally, based on the Analytic Hierarchy Process (AHP), an optimization method of switch jumper setting is studied. The simulation results show that the conductive interference in the turnout section mainly involves two factors: The inherent turnout structure definitely results in different impedance of two rails, and the inductive cab signal is partly bypassed in the turnout center (nose rail). Especially, conductive interference magnitude depends on the jumper location. Therefore, in engineering practice, it is feasible to reduce the interference to a certain degree by reasonable settings of the switch jumper.

Cab signaling apparatus is the critical equipment for ground-vehicle communication in electrified railways. With the rapid development of high-speed and heavy-haul railways, the immunity to unbalanced traction current interference for cab signaling apparatus in the onboard train control system is increasingly demanded. This paper analyzes the interference coupling mechanism of the ZPW-2000 track circuit. Based on electromagnetic field theory and the actual working parameters, a calculation model is established to complete the quantitative research of the cab signal induction process and traction current interference. Then, a finite element model is built to simulate the process. The simulation results under the signal frequency, fundamental and harmonic interference are all consistent with the theoretical calculation results. The practical measurement data verify the coupling relationship between cab signal inductive voltage and rail current. Finally, an indirect immunity test method applying this relation for the cab signals is proposed, and the voltage indexes of the disturbance sources are determined, i.e., the test limits. The results provide an accurate quantitative basis for the cab signaling research and design of the immunity test platform; besides, the proposed indirect test method can simplify the test configuration and improve test efficiency.

Recently, simultaneous emission of radially and non-radially polarized terahertz (THz) pulses during single-colour femtosecond laser filamentation has been reported. In this work, the latter radiation has been specifically investigated, instead of the well-studied THz radial polarization. Briefly, cut-back measurements have verified that the ellipticity of the generated THz pulse with non-radial polarization decreased (became more linearly polarized) with the increasing filament length. The underlying mechanism responsible for this phenomenon is the existence of a propagation effect of THz wave along the filament plasma channel. In this case, the resulted off-axis propagation of THz wave inside the plasma column played a dominant role on the generated non-radial THz polarization, rather than the expected on-axis THz birefringence induced by the high laser intensity. This discovery will greatly renew the understanding of THz emission from plasma sources.

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