| 1. |
- Jafri, Syed Hassan Mujtaba, et al.
(author)
-
Conductivity engineering of graphene by defect formation
- 2010
-
In: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 43:4, s. 045404-
-
Journal article (peer-reviewed)abstract
- Transport measurements have revealed several exotic electronic properties of graphene. The possibility to influence the electronic structure and hence control the conductivity by adsorption or doping with adatoms is crucial in view of electronics applications. Here, we show that in contrast to expectation, the conductivity of graphene increases with increasing concentration of vacancy defects, by more than one order of magnitude. We obtain a pronounced enhancement of the conductivity after insertion of defects by both quantum mechanical transport calculations as well as experimental studies of carbon nano-sheets. Our finding is attributed to the defect induced mid-gap states, which create a region exhibiting metallic behaviour around the vacancy defects. The modification of the conductivity of graphene by the implementation of stable defects is crucial for the creation of electronic junctions in graphene-based electronics devices.
|
|
| 2. |
- Vieira, Tiago, 1984-, et al.
(author)
-
Evaluation of uncertainty on Shore hardness measurements of tyre treads and implications to tyre/road noise measurements with the Close Proximity method
- 2020
-
In: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 162
-
Journal article (peer-reviewed)abstract
- Shore hardness measurements subject rubber bodies to standardized indentations. While easily performed, the measurements are subject to uncertainties. Although typical variances for Shore hardness are found in standards, operator and instrument effects are not well described, requiring statistically designed experiments to estimate effects and variance components. This paper focuses on uncertainty in Shore A hardness measurements of tyre tread elements and quantifies operator and instrument effects. Evaluation of uncertainty of Shore A measurements were performed on tyres under controlled conditions using three instruments, two tyres and five operators. Results show that the operator variance component and instrument effects are larger than the reference variance contribution in ISO 11819-3:2017. The interaction between operator and instrument is estimated to be the largest source of variation, while operator and instrument main effects are of similar size as the error component. Recommendations to reduce uncertainties include ignoring instantaneous values and requiring an instrument stand.
|
|
| 3. |
- Sun, Weiwei, et al.
(author)
-
A new 2D monolayer BiXene, M2C (M = Mo, Tc, Os)
- 2016
-
In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 8:34, s. 15753-15762
-
Journal article (peer-reviewed)abstract
- The existence of BiXenes, a new family of 2D monolayers, is hereby predicted. Theoretically, BiXenes have 1H symmetry (P (6) over bar m2) and can be formed from the 4d/5d binary carbides. As the name suggests, they are close relatives of MXenes, which instead have 1T symmetry (P (3) over bar m1). The newly found BiXenes, as well as some new MXenes, are shown to have formation energies close to that of germanene, which suggests that these materials should be possible to be synthesised. Among them, we illustrate that 1H-Tc2C and 1T-Mo2C are dynamically stable at 0 K, while 1H-Mo2C, 1T-Tc2C, 1H-Os2C, and 1T-Rh2C are likely to be stabilised via strain or temperature. In addition, the nature of the chemical bonding is analysed, emphasizing that the covalency between the transition metal ions and carbon is much stronger in BiXenes than in MXenes. The emergence of BiXenes can not only open up a new era of conducting 2D monolayers, but also provide good candidates for carrier materials aimed at energy storage and spintronic devices that have already been unveiled in MXenes.
|
|
| 4. |
- Blissing, Björn, 1978-, et al.
(author)
-
Effects of Visual Latency on Vehicle Driving Behavior
- 2016
-
In: ACM Transactions on Applied Perception. - New York, NY, USA : ACM Digital Library. - 1544-3558 .- 1544-3965. ; 14:1, s. 5:1-5:12
-
Journal article (peer-reviewed)abstract
- Using mixed reality in vehicles provides a potential alternative to using driving simulators when studying driver-vehicle inter- action. However, virtual reality systems introduce latency in the visual system that may alter driving behavior, which, in turn, results in questionable validity. Previous studies have mainly focused on visual latency as a separate phenomenon. In this work, latency is studied from a task-dependent viewpoint to investigate how participants’ driving behavior changed with increased latency. In this study, the investigation was performed through experiments in which regular drivers were subjected to different levels of visual latency while performing a simple slalom driving task. The drivers’ performances were recorded and evaluated in both lateral and longitudinal directions along with self-assessment questionnaires regarding task performance and difficulty. All participants managed to complete the driving tasks successfully, even under high latency conditions, but were clearly affected by the increased visual latency. The results suggest that drivers compensate for longer latencies by steering more and increasing the safety margins but without reducing their speed.
|
|
| 5. |
- Nilsson, Peter, 1976, et al.
(author)
-
On actions of long combination vehicle drivers prior to lane changes in dense highway traffic : A driving simulator study
- 2018
-
In: Transportation Research Part F. - : Elsevier. - 1369-8478 .- 1873-5517. ; 55, s. 25-37
-
Journal article (peer-reviewed)abstract
- In this paper we address drivers’ actions prior to mandatory lane changes of long combination vehicles in dense highway traffic. The studied driver actions were: turn indicator activation, speed reduction and lateral intrusion. We categorised and compared the drivers’ actions with respect to the surrounding traffic cooperation and the level of urgency. Urgency here was based on the remaining distance to a targeted exit ramp. The results show that when the subject vehicle is close to the exit ramp, drivers used speed reduction significantly more than when the vehicle is further away. No significant difference was found for the use of lateral intrusion considering the distance to the exit ramp. As regards traffic cooperation, significant differences were found for both speed reduction and lateral intrusion. The drivers’ speed reduction and lateral intrusion were significantly greater when the surrounding traffic cooperation was low.
|
|
| 6. |
- Arapan, S., et al.
(author)
-
Influence of antiphase boundary of the MnAl tau-phase on the energy product
- 2019
-
In: Physical Review Materials. - : American Physical Society. - 2475-9953. ; 3:6
-
Journal article (peer-reviewed)abstract
- In this paper, we use a multiscale approach to describe a realistic model of a permanent magnet based on MnAl tau-phase and elucidate how the antiphase boundary defects present in this material affect the energy product. We show how the extrinsic properties of a microstructure depend on the intrinsic properties of a structure with defects by performing micromagnetic simulations. For an accurate estimation of the energy product of a realistic permanent magnet based on the MnAl tau-phase with antiphase boundaries, we quantify exchange interaction strength across the antiphase boundary defect with a simple approach derived from first-principles calculations. These two types of calculations, performed at different scales, are linked via atomistic spin-dynamics simulations.
|
|
| 7. |
- Dong, Zhihua, et al.
(author)
-
MnxCr0.3Fe0.5Co0.2Ni0.5Al0.3 high entropy alloys for magnetocaloric refrigeration near room temperature
- 2021
-
In: Journal of Materials Science & Technology. - : Chinese Society of Metals. - 1005-0302. ; 79, s. 15-20
-
Journal article (peer-reviewed)abstract
- High entropy alloys (HEAs) based on transition metals display rich magnetic characteristics, however attempts on their application in energy efficient technologies remain scarce. Here, we explore the magnetocaloric application for a series of MnxCr0.3Fe0.5Co0.2Ni0.5Al0.3 (0.8 < x < 1.1) HEAs by integrated theoretical and experimental methods. Both theory and experiment indicate the designed HEAs have the Curie temperature close to room temperature and is tunable with Mn concentration. A non-monotonic evolution is observed for both the entropy change and the relative cooling power with changing Mn concentration. The underlying atomic mechanism is found to primarily emerge from the complex impact of Mn on magnetism. Advanced magnetocaloric properties can be achieved by tuning Mn concentration in combination with controlling structural phase stability for the designed HEAs.
|
|
| 8. |
- Huang, Shuo, et al.
(author)
-
Chemical ordering controlled thermo-elasticity of AlTiVCr1-xNbx high-entropy alloys
- 2020
-
In: Acta Materialia. - : Pergamon Press. - 1359-6454 .- 1873-2453. ; 199, s. 53-62
-
Journal article (peer-reviewed)abstract
- The stability of constituent phases in multi-component system always plays a prominent role in tailoring their mechanical performance at elevated temperatures. In this work, we highlight a chemical ordering feature in the AlTiVCr1-xNbx (0 <= x <= 1) alloys with body-centered cubic crystal structure. The quantum-mechanical first-principle investigations of these alloys on the elemental distribution identify a family of B2 type of partially ordered configurations. We map out the elastic parameters in detail as a function of composition and temperature for disordered and partially ordered phases. A great sensitivity to the order-disorder transformation is revealed, especially for the Cr-rich system. Our results demonstrate that a proper control of the ordering level in these alloys can facilitate the optimal tuning of their mechanical performance while keeping the density almost unchanged. The study presented here further predicts that these alloys possess high specific stiffness, low thermal expansion, and large elastic softening resistance. It is demonstrated that the considered alloys have thermal and mechanical properties that compete with superalloys and other high temperature structural materials.
|
|
| 9. |
- Huang, Shuo, et al.
(author)
-
Magnetocaloric properties of melt-spun MnFe-rich high-entropy alloy
- 2021
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 119:14
-
Journal article (peer-reviewed)abstract
- High-entropy functional materials are of great interest in materials science and engineering community. In this work, ab initio electronic structure calculations of the phase stability and magnetic transition temperature of AlxCr0.25MnFeCo0.25-yNiy (x = 0-0.5, y = 0-0.25) alloys were performed to screen for compositions showing promising magnetocaloric properties in the vicinity of room temperature. The selected Al0.44Cr0.25MnFeCo0.05Ni0.2 alloy was synthesized via a rapid solidification technique and systematically characterized with respect to its structural and magnetocaloric properties. The results indicate that this alloy possesses a homogeneous microstructure based on an underlying body-centered cubic lattice and has a Curie temperature of & SIM;340 K. The temperature dependence of the adiabatic temperature change was evaluated using both direct and indirect methods. The ab initio-assisted design of 3d-metal-based high-entropy alloys, explored here, is intended to contribute to the development of magnetic refrigerators for room-temperature applications.
|
|
| 10. |
- Vieira, Tiago, 1984-, et al.
(author)
-
A round robin test on the close-proximity method : Comparison of results from four different CPX trailers measuring tyre/road noise properties of 10 Swedish road surfaces
- 2020
-
In: Noise Control Engineering Journal. - : Institute of Noise Control Engineering. - 0736-2501 .- 2168-8710. ; 68:6, s. 421-440
-
Journal article (peer-reviewed)abstract
- The standardization of the CPX method and the reference tyres in 2017 has made it possible to measure tyre/road noise in a standard and repeatable way. However, the reproducibility of the CPX method is still not well known. A trailer comparison in the Netherlands in 2017 indicated that different trailers led to comparable results, but only two road surfaces were used, and all measurements were made close in time and location. In practical measurements, more variations in CPX equipment occur, and it is not possible to predetermine a specific measurement day. This study used four trailers of different designs, and measurements were made over a time period of 90 days, which may happen in practical measurements. The trailers and road surfaces are described, and variations between measurements are analyzed. The maximum CPX level difference between trailers when taking the sample means (average without corrections for different number of observations on the surfaces) was 1.57 dB for tyre H1 and 1.29 dB for tyre P1, which is comparable to the uncertainty values in ISO 11819-2:2017. A statistical analysis showed that the estimated main effects, adjusted for imbalance in the sampling design, for three of the four trailers did not differ more than 0.41 dB, while the fourth trailer, having an unreliable calibration, differed by 0.94 dB from the others. This article shows the relevance of the corrections found in the standards and that having an enclosure over the tested tyres leads to a slightly sharper peak in the frequency spectra.
|
|
