Atomic-scale visualization of quasiparticle interference on a type-II Weyl semimetal surface

We combine quasiparticle interference simulation (theory) and atomic resolution scanning tunneling spectro-microscopy (experiment) to visualize the interference patterns on a type-II Weyl semimetal Mo$_{x}$W$_{1-x}$Te$_2$ for the first time. Our simulation based on first-principles band topology theoretically reveals the surface electron scattering behavior. We identify the topological Fermi arc states and reveal the scattering properties of the surface states in Mo$_{0.66}$W$_{0.34}$Te$_2$. In addition, our result reveals an experimental signature of the topology via the interconnectivity of bulk and surface states, which is essential for understanding the unusual nature of this material.Comment: To appear in Phys. Rev. Let

Economic Assessment of Autonomous Electric Microtransit Vehicles

There is rapidly growing interest in autonomous electric vehicles due to their potential in improving safety, accessibility, and environmental outcomes. However, their market penetration rate is dependent on costs. Use of autonomous electric vehicles for shared-use mobility may improve their cost competitiveness. So far, most of the research has focused on the cost impact of autonomy on taxis and ridesourcing services. Singapore is planning for island-wide deployment of autonomous vehicles for both scheduled and on-demand services as part of their transit system in the year 2030. TUMCREATE developed an autonomous electric vehicle concept, a microtransit vehicle with 30-passenger capacity, which can complement the existing bus transit system. This study aims to determine the cost of autonomous electric microtransit vehicles and compare them to those of buses. A total cost of ownership (TCO) approach was used to compare the lifecycle costs. It was shown that although the acquisition costs of autonomous electric vehicles are higher than those of their conventional counterparts, they can reduce the TCO per passenger-km up to 75% and 60% compared to their conventional counterparts and buses, respectively. Document type: Articl

Gradient microstructures and mechanical properties of Ti–6Al–4V alloy induced by laser surface quenching

Laser surface quenching (LSQ) was employed to fabricate gradient microstructures in a Ti–6Al–4V alloy. The influence of the LSQ parameters on the surface morphology, the depth of the LSQ layer, gradient microstructure, and microhardness were investigated. The results showed that as the laser energy density increases, the surface roughness and thickness of the heat-affected zone (HAZ) increase. From the internal matrix to the surface, the microstructure in the HAZ changes from the equiaxed structure to the mixt structure, martensitic structure, Widmanstätten structure, and then the oxide layer. The size of the β grains gradually decreases as the distance from the surface increases. The different microstructures and elemental distributions in the HAZ result in different microhardness values, which gradually decrease from the surface to the matrix. The laser energy density of 8.0 J/mm2 is recommended to obtain a HAZ with a thickness of 1200 μm and a peak microhardness of 393 ± 7.3 H V without surface remelting. The LSQ process may help to increase the longevity of Ti–6Al–4V alloy implants by hardening the surface

Light-induced giant enhancement of nonreciprocal transport at KTaO3-based interfaces

Nonlinear transport is a unique functionality of noncentrosymmetric systems, which reflects profound physics, such as spin-orbit interaction, superconductivity and band geometry. However, it remains highly challenging to enhance the nonreciprocal transport for promising rectification devices. Here, we observe a light-induced giant enhancement of nonreciprocal transport at the superconducting and epitaxial CaZrO3/KTaO3 (111) interfaces. The nonreciprocal transport coefficient undergoes a giant increase with three orders of magnitude up to 105 A-1T-1. Furthermore, a strong Rashba spin-orbit coupling effective field of 14.7 T is achieved with abundant high-mobility photocarriers under ultraviolet illumination, which accounts for the giant enhancement of nonreciprocal transport coefficient. Our first-principles calculations further disclose the stronger Rashba spin-orbit coupling strength and the longer relaxation time in the photocarrier excitation process, bridging the light-property quantitative relationship. Our work provides an alternative pathway to boost nonreciprocal transport in noncentrosymmetric systems and facilitates the promising applications in opto-rectification devices and spin-orbitronic devices.Comment: 38 pages, 17 figure

Natural Variation in Arabidopsis thaliana as a Tool for Highlighting Differential Drought Responses

To test whether natural variation in Arabidopsis could be used to dissect out the genetic basis of responses to drought stress, we characterised a number of accessions. Most of the accessions belong to a core collection that was shown to maximise the genetic diversity captured for a given number of individual accessions in Arabidopsis thaliana. We measured total leaf area (TLA), Electrolyte Leakage (EL), Relative Water Content (RWC), and Cut Rosette Water Loss (CRWL) in control and mild water deficit conditions. A Principal Component Analysis revealed which traits explain most of the variation and showed that some accessions behave differently compared to the others in drought conditions, these included Ita-0, Cvi-0 and Shahdara. This study relied on genetic variation found naturally within the species, in which populations are assumed to be adapted to their environment. Overall, Arabidopsis thaliana showed interesting phenotypic variations in response to mild water deficit that can be exploited to identify genes and alleles important for this complex trait

Progress in dark tourism and thanatourism research: An uneasy relationship with heritage tourism

This paper reviews academic research into dark tourism and thanatourism over the 1996–2016 period. The aims of this paper are threefold. First, it reviews the evolution of the concepts of dark tourism and thanatourism, highlighting similarities and differences between them. Second it evaluates progress in 6 key themes and debates. These are: issues of the definition and scope of the concepts; ethical issues associated with such forms of tourism; the political and ideological dimensions of dark tourism and thanatourism; the nature of demand for places of death and suffering; the management of such places; and the methods of research used for investigating such tourism. Third, research gaps and issues that demand fuller scrutiny are identified. The paper argues that two decades of research have not convincingly demonstrated that dark tourism and thanatourism are distinct forms of tourism, and in many ways they appear to be little different from heritage tourism

Modelling and Evaluation of Battery Packs with Different Number of Paralleled Cells

To better evaluate the configuration of battery packs in electric vehicles (EV) in the early design phase, this paper proposes a mathematic model for the simulation of battery packs based on the elementwise calculations of matrices. This model is compatible with the different battery models and has a fast simulation speed. An experimental platform is built for the verification. Based on the proposed model and the statistic features of battery cells, the influence of the number of paralleled cells in a battery pack is evaluated in Monte-Carlo experiments. The simulation results obtained from Monte-Carlo experiments show that the parallel number is able to influence the total energy loss inside the cells, the energy loss caused by the balancing of the battery management system (BMS) and the degradation of the battery pack. Modelling and Evaluation of Battery Packs with Different Number of Paralleled Cells. Available from: https://www.researchgate.net/publication/320710436_Modelling_and_Evaluation_of_Battery_Packs_with_Different_Number_of_Paralleled_Cells [accessed Dec 15 2017]

Verbesserung der Teillasteffizienz eines elektrischen Antriebsstranges mittels Silizium MOSFET Multilevel Wechselrichter

The dissertation evaluates the usability of Cascaded H-Bridge (CHB) inverters composed of low voltage Si MOSFETs for a higher efficiency. The CHB can improve the efficiency by 7% in comprehensive driving cycles. The CHB has a lower system cost compared to an IGBT inverter. The influence on battery aging and reliability of the CHB are also investigated, where the CHB does not significantly accelerate the aging, and its reliability is higher than an IGBT inverter. Hence, the CHB is concluded to be a promising concept for future electric vehicles.Die Dissertation untersucht die Verwendung eines kaskadierten H-Brücken Wechselrichters (Cascaded H-Bridge, CHB) bestehend aus siliziumsbasierenden Niederspannungs MOSFET, um die Effizienz zu steigern. Der Einsatz eines CHB Wechselrichters kann in Standard Fahrzyklen die Effizienz um 7 % steigern. Die Systemkosten ist geringer im Vergleich zu IGBT Wechselrichtern. Ebenso werden die Einflüsse auf Batteriealterung und Zuverlässigkeit des CHB Systems untersucht. Der CHB Wechselrichter beschleunigt die Alterung nicht signifikant. Und das System ist zuverlässiger als der IGBT Wechselrichter. Daraus wird abgeleitet, das der CHB Wechselrichter ein aussichtsreiches Konzept für elektrische Fahrzeuge darstellt

A modular multilevel topology using power electronic transformers for the modular drivetrains of electric vehicles

This paper proposed a modular multilevel topology using power electronics transformers for the modular drivetrain of electric vehicles (EV). Because of its high modularity, the topology can be easily applied to a wide range of EVs, from personal vehicles to passenger cars. Compared with two conventional modular multilevel converters, fewer submodules are needed and its control is thus simpler. The topology can also balance voltage of batteries without an equalization circuit and has low harmonics distortion. Moreover, according to the simulation results, the topology has higher overall efficiency than the conventional 6-switch 2-level inverter structure in synthesized driving cycle