| 1. |
- Hong, Kuo Bin, et al.
(författare)
-
Monolithic high-index contrast grating mirror for a GaN-based vertical-cavity surface-emitting laser
- 2021
-
Ingår i: Photonics Research. - 2327-9125. ; 9:11, s. 2214-2221
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, a pulsed electrically pumped GaN-based vertical-cavity surface-emitting laser (VCSEL) with one dielectric distributed Bragg reflector and one n-GaN monolithic high-index contrast grating (MHCG) mirror was demonstrated at room temperature. The reflectance of the n-GaN MHCG and cavity mode behaviors of the VCSEL with MHCG for varying n-GaN thickness, MHCG pattern diameter, and current aperture size were numerically investigated. Measured characteristics of the fabricated device showed that the lasing action started at an injection current of 10.2 mA, corresponding to a current density of about 15.1 kA=cm2. Above threshold, the measured slope efficiency was 6.2 × 10−3 W∕A, and the output power was 0.13 mW at 30 mA. Moreover, the measured lasing peak occurring at 403.4 nm and the longitudinal mode spacing of 5.6 nm were in good agreement with simulations. The incorporation of an n-GaN MHCG mirror not only greatly simplified the fabrication but also substantially improved the lasing characteristics in comparison to the previous work applying TiO2 HCG mirrors.
|
|
| 2. |
- Kristan, Matej, et al.
(författare)
-
The Visual Object Tracking VOT2015 challenge results
- 2015
-
Ingår i: Proceedings 2015 IEEE International Conference on Computer Vision Workshops ICCVW 2015. - : IEEE. - 9780769557205 ; , s. 564-586
-
Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge 2015, VOT2015, aims at comparing short-term single-object visual trackers that do not apply pre-learned models of object appearance. Results of 62 trackers are presented. The number of tested trackers makes VOT 2015 the largest benchmark on short-term tracking to date. For each participating tracker, a short description is provided in the appendix. Features of the VOT2015 challenge that go beyond its VOT2014 predecessor are: (i) a new VOT2015 dataset twice as large as in VOT2014 with full annotation of targets by rotated bounding boxes and per-frame attribute, (ii) extensions of the VOT2014 evaluation methodology by introduction of a new performance measure. The dataset, the evaluation kit as well as the results are publicly available at the challenge website(1).
|
|
| 3. |
- Meher, Pramod Kumar, et al.
(författare)
-
Shift‐Add Circuits for Constant Multiplications
- 2017
-
Ingår i: Arithmetic Circuits for DSP Applications. - Hoboken, NJ, USA : John Wiley & Sons. - 9781119206774 - 9781119206798 - 9781119206804 ; , s. 33-76
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The optimization of shift‐and‐add network for constant multiplications is found to have great potential for reducing the area, delay, and power consumption of implementation of multiplications in several computation‐intensive applications not only in dedicated hardware but also in programmable computing systems. To simplify the shift‐and‐add network in single constant multiplication (SCM) circuits, this chapter discusses three design approaches, including direct simplification from a given number representation, simplification by redundant signed digit (SD) representation, and simplification by adder graph. Examples of the multiple constant multiplication (MCM) methods are constant matrix multiplication, discrete cosine transform (DCT) or fast Fourier transform (FFT), and polyphase finite impulse response (FIR) filters and filter banks. The given constant multiplication methods can be used for matrix multiplications and inner‐product; and can be applied easily to image/video processing and graphics applications. The chapter further discusses some of the shortcomings in the current research on constant multiplications, and possible scopes of improvement.
|
|
| 4. |
- Silva, Mickael, et al.
(författare)
-
Computational assessment of effects of throat diameter on combustion and turbulence characteristics in a pre-chamber engine
- 2022
-
Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 212
-
Tidskriftsartikel (refereegranskat)abstract
- Towards fundamental investigation of key physical aspects of pre-chamber combustion, the current work utilizes computational fluid dynamics to comprehend the effect of the throat diameter in an engine operated with methane. Previous studies showed that this parameter is dominant in pressure build-up and flow pattern inside the pre-chamber, suggesting that a detailed characterization is necessary. This pre-chamber type is composed of an upper conical part that lodges the spark plug and fuel injector, followed by a straight and tubular region called throat, which tip accommodates the nozzles responsible for the charge exchange between pre and main chambers. Two types of pre-chamber having distinct throat diameters are investigated, while utilizing consistent experimental data for validation of the model. The combustion process is modeled with the G-Equation model; the laminar flame speed was tabulated from a methane oxidation mechanism reduced from the GRI 3.0; the turbulent flame speed was computed using Peters' relation. The simulations were run for a full cycle, starting at exhaust valve opening. A homogeneous charge of methane is considered at the intake port, maintaining a global λ = 1.8, while 3% of total energy fuel is added through the pre-chamber. The results show that the throat changes the flow field inside the pre-chamber, impacts the air-fuel ratio, stratification, turbulence, jet dynamics, and ultimately the pre and main chambers combustion processes and heat fluxes. The combustion regime according to the Borghi-Peters diagram were found to lay in the thin reaction zone and in the flamelet regime.
|
|
| 5. |
- Gharbia, Marwan, et al.
(författare)
-
Building Code Compliance for Off-Site Construction
- 2023
-
Ingår i: Journal of Legal Affairs and Dispute Resolution in Engineering and Construction. - : American Society of Civil Engineers (ASCE). - 1943-4162 .- 1943-4170. ; 15:2
-
Tidskriftsartikel (refereegranskat)abstract
- There are increasing concerns over building code, regulation compliance, and quality assurance issues in adopting off-site construction techniques in the construction industry related to meeting client expectations and regulatory requirements. Performance-based building regulations often allow for space for innovation but not a safe space for those who intend to introduce new construction techniques not prescribed in building regulations. Through a series of surveys conducted in Sweden, Switzerland, the UK, China, Singapore, and Australia, this study identified approaches and practices used in these countries that overcome compliance challenges when off-site construction techniques are used. The findings showed that manufacturer self-certification is the predominant approach for meeting code compliance requirements. A fit-for-purpose regulatory compliance system also warrants fair allocation of risks and liabilities to anyone involved in the supply chain. However, a healthy and functional regulatory system for off-site compliance requires third-party certification for products and factories and traceability. It is hoped that the lessons learned from this study can help policymakers introduce changes in product standards and legislation in order to improve the compliance and performance of off-site construction. This study concluded that a chain of custody approach is necessary in order to address quality concerns surrounding the adoption of prefabrication technology in countries that are increasingly exploring greater use of manufacturing in construction.
|
|
| 6. |
- Huang, Shen-Che, et al.
(författare)
-
Two-dimensional designed fabrication of subwavelength grating HCG mirror on Silicon-on-insulator
- 2016
-
Ingår i: HIGH CONTRAST METASTRUCTURES V. - : SPIE - International Society for Optical Engineering. - 9781628419924
-
Konferensbidrag (refereegranskat)abstract
- We designed and fabricated a two dimensional high contrast subwavelength grating (HCG) mirrors. The computer-aided software was employed to verify the structural parameters including grating periods and filling factors. From the optimized simulation results, the designed HCG structure has a wide reflection stopband (reflectivity (R) >90%) of over 200 nm, which centered at telecommunication wavelength. The optimized HCG mirrors were fabricated by electron-beam lithography and inductively coupled plasma process technique. The experimental result was almost consistent with calculated data. This achievement should have an impact on numerous photonic devices helpful attribution to the integrated HCG VCSELs in the future.
|
|
| 7. |
- Liu, Tie, et al.
(författare)
-
Effects of high magnetic fields on solidification microstructure of Al-Si alloys
- 2011
-
Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 46:6, s. 1628-1634
-
Tidskriftsartikel (refereegranskat)abstract
- The effects of high magnetic fields on the solidification microstructure of Al-Si alloys were investigated. Al-7.2 wt%Si and Al-11.8 wt%Si alloys were solidified in various high magnetic fields at different cooling rates. The secondary dendrite arm spacing (SDAS) of the primary Al dendrites and the lamellar spacing (LS) of the eutectics were measured. It was found that the application of a high magnetic field could decrease the SDAS of the primary Al dendrites in Al-7.2 wt% Si alloys and the LS of the eutectics in Al-11.8 wt% Si alloys. The effects of the high magnetic field on the SDAS decreased with increasing cooling rate. The decrease in the SDAS and LS can be attributed to the decrease of the solute diffusivity in the liquid ahead of the solid/liquid interface during the growth of the dendrite and eutectic. This decrease is caused by the high magnetic field which can damp the convection and avoid its contributions to the diffusion.
|
|
| 8. |
- Haw, Shu Chih, et al.
(författare)
-
Single antiferromagnetic axis of Fe in orthorhombic YMn0.5Fe0.5O3 films observed by x-ray magnetic linear dichroism
- 2019
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388. ; 780, s. 79-84
-
Tidskriftsartikel (refereegranskat)abstract
- The electronic and magnetic structure of orthorhombic (o-) YMn0.5Fe0.5O3 (YMFO) epitaxial film (space group Pbnm) deposited on the YAlO3 (010) substrate have been investigated using linear polarization-dependent x-ray absorption spectroscopy and magnetization measurements. The magnetic-ordering temperature of around 280 K is observed in o-YMFO film. The x-ray absorption spectra at the Fe-K and the Mn-K edges indicate the existence of anisotropic crystal field in o-YMFO film, with the longest and shortest Fe–O and Mn–O bonds tend to align with the crystallographic b- and a-axis, respectively, whereas the medium Fe(Mn)–O bond is aligned with the c-axis. The experimental x-ray magnetic linear dichroism at the Fe-L2 edges demonstrate an unusual single antiferromagnetic axis of Fe3+ ions below magnetic-ordering temperature, while a multi antiferromagnetic axis is generally observed in o-RFeO3 (R = rare earth) thin films. Our configuration-interaction cluster calculations also reveal that the single antiferromagnetic axis of the Fe sublattice is aligned with the b-axis in o-YMFO film, whereas it is directed along the a-axis in the bulk o-YFeO3.
|
|
| 9. |
- Xu, Guangfu, et al.
(författare)
-
Evaluation of variable compression ratio (VCR)and variable valve timing (VVT)strategies in a heavy-duty diesel engine with reactivity controlled compression ignition (RCCI)combustion under a wide load range
- 2019
-
Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 253, s. 114-128
-
Tidskriftsartikel (refereegranskat)abstract
- Variable compression ratio (VCR)and variable valve timing (VVT)are two effective strategies to adjust the effective compression ratio, which is beneficial for controlling the combustion process of advanced combustion modes. In this study, systematic evaluation of the two strategies was conducted based on reactivity controlled compression ignition (RCCI)engine in terms of combustion process control, fuel efficiency, and emission characteristics. By coupling an updated KIVA-3V code with the genetic algorithm, the combustion of a heavy-duty RCCI engine with VCR and VVT strategies was respectively optimized, aiming to simultaneously realize high fuel efficiency and low emissions. The optimal VCR and VVT strategies were compared under a wide load range. The results indicate that, at low and mid loads, high effective compression ratio, large premix ratio, and early fuel injection can be utilized to realize Euro 6 nitrogen oxides (NO x )limit with ultra-low soot emissions and low fuel consumption for both VCR and VVT strategies. The increase of load from low to mid narrows the optimal range of exhaust gas recirculation (EGR)rate for VVT strategy whereas the range for VCR strategy is still wide. At high load, compared to VVT strategy, a further decreased effective compression ratio can be utilized for VCR strategy, which allows early fuel injection, leading to the improvements of fuel efficiency and soot emissions. This suggests that the VCR strategy is more practical for high-load operation of RCCI combustion and the commercialization the RCCI engine in the future compared to VVT strategy.
|
|
| 10. |
|
|
