| 1. |
- Chen, Gang, et al.
(författare)
-
On the kinematic algebra for BCJ numerators beyond the MHV sector
- 2019
-
Ingår i: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :11
-
Tidskriftsartikel (refereegranskat)abstract
- The duality between color and kinematics present in scattering amplitudes of Yang-Mills theory strongly suggests the existence of a hidden kinematic Lie algebra that controls the gauge theory. While associated BCJ numerators are known on closed forms to any multiplicity at tree level, the kinematic algebra has only been partially explored for the simplest of four-dimensional amplitudes: up to the MHV sector. In this paper we introduce a framework that allows us to characterize the algebra beyond the MHV sector. This allows us to both constrain some of the ambiguities of the kinematic algebra, and better control the generalized gauge freedom that is associated with the BCJ numerators. Specifically, in this paper, we work in dimension-agnostic notation and determine the kinematic algebra valid up to certain ? ((epsilon i .epsilon j )(2)) terms that in four dimensions compute the next-to-MHV sector involving two scalars. The kinematic algebra in this sector is simple, given that we introduce tensor currents that generalize standard Yang-Mills vector currents. These tensor currents control the generalized gauge freedom, allowing us to generate multiple different versions of BCJ numerators from the same kinematic algebra. The framework should generalize to other sectors in Yang-Mills theory.
|
|
| 2. |
- Jiang, Jin-gang, et al.
(författare)
-
Medical robotics
- 2015
-
Ingår i: Advances in Mechanical Engineering. - : SAGE Publications. - 1687-8132 .- 1687-8140. ; 7:7
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 3. |
- Onishi, Keiji, et al.
(författare)
-
A Deployment of HPC Algorithm into Pre/Post-Processing for Industrial CFD on K-Computer
- 2017
-
Konferensbidrag (refereegranskat)abstract
- Pre- and post-processing is still a major problem in industrial computational fluid dynamics (CFD). With the rapid development of computers, physical solvers are getting faster, while pre- remains slow because it's mainly a serial process. A methodology using MPI+OpenMP hybrid parallelization has been proposed to eliminate the manual work required during pre-processing for correcting the surface imperfections of CAD data. Compared to the rapidly increasing amount of data in recent years, the speed-up of visualization is insufficient. We address this limitation of post- by adapting the in-situ visualization to parallelize the post-processing using libsim (Visit) library. The performance of pre-/post- processing is investigated in this work, and we show that the pre-processing time has been reduced from several days in the conventional framework to order of minutes. The post-processing time has been reduced seconds order per frame, and approximately 30% increase of computational time was observed in vehicle aerodynamics cases.
|
|
| 4. |
- Qin, Gang, et al.
(författare)
-
A novel face-centered-cubic high-entropy alloy strengthened by nanoscale precipitates
- 2019
-
Ingår i: Scripta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6462 .- 1872-8456. ; 172, s. 51-55
-
Tidskriftsartikel (refereegranskat)abstract
- A new single-phase face-centered-cubic (FCC) Co9Cr7Cu36Mn25Ni23 [atomic percent, similar hereinafter] high-entropy alloy (HEA) was prepared by arc melting. A uniform distribution of nanometer-sized precipitates was achieved. The tensile yield strength, ultimate tensile strength, and elongation were 401 MPa, 700 MPa, and 36%, respectively. The energy-dispersive spectrometer results showed that the nano-precipitates were rich in Co and Cr elements. Moreover, the crystal-forming behavior and the nanoscale-precipitates-forming mechanism were revealed. Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
|
|
| 5. |
- Wang, Jingjing, et al.
(författare)
-
Thermodynamic and diffusion kinetic studies of the Fe-Co system
- 2017
-
Ingår i: Calphad. - : Elsevier. - 0364-5916 .- 1873-2984. ; 58, s. 82-100
-
Tidskriftsartikel (refereegranskat)abstract
- The phase equilibria, thermodynamic properties and diffusion mobilities of the Fe-Co system were carefully assessed through the CALPHAD methods. As an indispensable tool, the first-principles calculations were carried out to study the magnetic moments and the enthalpies of mixing of the bcc_A2, bcc_B2, fcc_A1 and hcp_A3 phases as well as the point defect types of the bcc_B2 phase. In order to verify the heat capacities reported in the literature, new measurements were conducted in a high-temperature calorimetric apparatus using the three-dimensional calorimetric method. Because of the revision of the thermodynamic parameters in the present work, the diffusion mobilities for the fcc_Al phase were reassessed. The diffusion mobilities for the bcc_A2 phase were established for the first time based on the experimental diffusion coefficients. For the low temperature bcc_B2 phase, the diffusion couple experiments conducted in the present work show that the diffusion process is sluggish and the interdiffusion coefficients are difficult to determine. Therefore the tracer diffusivities of Co and Fe in the Fe-Co alloys were used to assess the diffusion mobilities for the bcc_B2 phase, while the composition-distance profile of one diffusion couple was served as a validation of its diffusion mobilities.
|
|
| 6. |
- Wang, Sheng-Quan, et al.
(författare)
-
Application of the principle of maximum conformality to the hadroproduction of the Higgs boson at the LHC
- 2016
-
Ingår i: Physical Review D. - : American Physical Society (APS). - 2470-0010. ; 94:5
-
Tidskriftsartikel (refereegranskat)abstract
- We present improved perturbative QCD (pQCD) predictions for Higgs boson hadroproduction at the LHC by applying the principle of maximum conformality (PMC), a procedure which resums the pQCD series using the renormalization group (RG), thereby eliminating the dependence of the predictions on the choice of the renormalization scheme while minimizing sensitivity to the initial choice of the renormalization scale. In previous pQCD predictions for Higgs boson hadroproduction, it has been conventional to assume that the renormalization scale mu(r) of the QCD coupling sigma(s)(mu(r)) is the Higgs mass and then to vary this choice over the range 1/2m(H) < mu(r) < 2m(H) in order to estimate the theory uncertainty. However, this error estimate is only sensitive to the nonconformal beta terms in the pQCD series, and thus it fails to correctly estimate the theory uncertainty in cases where a pQCD series has large higher-order contributions, as is the case for Higgs boson hadroproduction. Furthermore, this ad hoc choice of scale and range gives pQCD predictions which depend on the renormalization scheme being used, in contradiction to basic RG principles. In contrast, after applying the PMC, we obtain next-to-next-to-leading-order RG resummed pQCD predictions for Higgs boson hadroproduction which are renormalization-scheme independent and have minimal sensitivity to the choice of the initial renormalization scale. Taking m(H) = 125 GeV, the PMC predictions for the pp -> HX Higgs inclusive hadroproduction cross sections for various LHC center-of-mass energies are sigma(Incl vertical bar 7 TeV) = 21.21(-1.32)(+1.36) pb, sigma(Incl vertical bar 8 TeV) = 27.37(-1.59)(+1.65) pb, and sigma I-ncl vertical bar 13 TeV = 65.72(-3.01)(+3.46) pb. We also predict the fiducial cross section sigma fid(pp -> H -> gamma gamma): sigma(fid vertical bar 7 TeV) = 30.1(-2.2)(+2.3) fb, sigma(fid vertical bar 8 TeV) = 38.3(-2.8)(+2.9) fb, and sigma(fid vertical bar 13 TeV) = 85.8(-5.3)(+5.7) fb. The error limits in these predictions include the small residual high-order renormalization-scale dependence plus the uncertainty from the factorization scale. The PMC predictions show better agreement with the ATLAS measurements than the LHC Higgs Cross Section Working Group predictions which are based on conventional renormalization-scale setting.
|
|
| 7. |
- Wu, Ming-Hsiung, et al.
(författare)
-
Terahertz parametric amplification using KTiOPO4
- 2016
-
Ingår i: 2016 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO). - Washington, D.C. : IEEE conference proceedings. - 9781943580118
-
Konferensbidrag (refereegranskat)abstract
- We show superior terahertz parametric generation from potassium titanyl phosphate over lithium niobate and lithium tantalate, and demonstrate seeded terahertz parametric amplification in KTP at 5.7 THz.
|
|
| 8. |
- Wu, Ming-Hsiung, et al.
(författare)
-
Terahertz parametric generation and amplification from potassium titanyl phosphate in comparison with lithium niobate and lithium tantalate
- 2016
-
Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 24:23, s. 25964-25973
-
Tidskriftsartikel (refereegranskat)abstract
- We report superior terahertz parametric generation from potassium titanyl phosphate (KTP) over congruent-grown lithium niobate (CLN) and lithium tantalate (CLT) in terms of parametric gain and laser damage resistance. Under the same pump and crystal configurations, the signal emerged first from KTP, 5% Mg-doped CLN, CLN, and then finally from CLT. The signal growth rate in KTP was comparable to that in 5%-Mg-doped CLN, but the signal power from KTP reached a much higher value after all the other crystals were damaged by the pump laser. We further demonstrate seeded terahertz parametric amplification in an edge-cut KTP at 5.74 THz. The THz parametric amplifier (TPA) employs a 17-mm long KTP gain crystal, pumped by a passively Q-switched pump laser at 1064 nm and seeded by a continuous-wave diode laser tuned to the signal wavelength at 1086.2 nm. With 5.8-mJ energy in a 520-ps pump pulse and 100-mW seed signal power, we measured 5W peak-power THz output from the KTP TPA with 22% pump depletion. In comparison, we measured no detectable THz output power from a similar edge-cut CLN TPA under the same pump power, detection scheme, and crystal configuration, when tuning the seed laser wavelength to 1072.2 nm and attempting to generate a radiation at 2.1 THz.
|
|
| 9. |
- Wu, Zhimao, et al.
(författare)
-
Nanofire and scale effects of heat
- 2019
-
Ingår i: Nano Convergence. - : Springer. - 2196-5404. ; 6
-
Forskningsöversikt (refereegranskat)abstract
- Combustion is a chemical reaction that emits heat and light. Nanofire is a kind of flameless combustion that occurs on the micro-nano scale. Pt/Al2O3 film with a thickness of 20 nm can be prepared as a catalyst by micro-nano processing. When the methanol-air mixture gas passes through the surface of the catalyst, a chemical reaction begins and a significant temperature rise occurs in the catalyst region. Compared to macroscopic combustion, Nanofire has many special properties, such as large temperature gradients, uniform temperature distribution, and fast temperature response. The large temperature gradient is the most important property of Nanofire, which can reach 1330 K/mm. Combined with thermoelectric materials, it can realize the efficient conversion of chemical energy to electric energy. Nanoscale thickness offers the possibility of establishing thermal gradient. On the other hand, large thermal gradient has an effect on the transport properties of phonons and electrons in film materials. From these we can get the scale effects of heat. This article will provide an overview of the preparation, properties and applications of Nanofire, and then a comprehensive introduction to the thermal scale and thermal scale effects.
|
|
| 10. |
- Xia, Chen, et al.
(författare)
-
Shaping triple-conducting semiconductor BaCo0.4Fe0.4Zr0.1Y0.1O3-delta into an electrolyte for low-temperature solid oxide fuel cells
- 2019
-
Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- Interest in low-temperature operation of solid oxide fuel cells is growing. Recent advances in perovskite phases have resulted in an efficient H+/O2-/e(-) triple-conducting electrode BaCo0.4Fe0.4Zr0.1Y0.1O3-delta for low-temperature fuel cells. Here, we further develop BaCo0.4Fe0.4Zr0.1Y0.1O3-delta for electrolyte applications by taking advantage of its high ionic conduction while suppressing its electronic conduction through constructing a BaCo0.4Fe0.4Zr0.1Y0.1O3-delta-ZnO p-n heterostructure. With this approach, it has been demonstrated that BaCo0.4Fe0.4Zr0.1Y0.1O3-delta can be applied in a fuel cell with good electrolyte functionality, achieving attractive ionic conductivity and cell performance. Further investigation confirms the hybrid H+/O2- conducting capability of BaCo0.4Fe0.4Zr0.1Y0.1O3-delta-ZnO. An energy band alignment mechanism based on a p-n heterojunction is proposed to explain the suppression of electronic conductivity and promotion of ionic conductivity in the heterostructure. Our findings demonstrate that BaCo0.4Fe0.4Zr0.1Y0.1O3-delta is not only a good electrode but also a highly promising electrolyte. The approach reveals insight for developing advanced low-temperature solid oxide fuel cell electrolytes.
|
|
