14,341 research outputs found
Modulation efficiency of LiNbO<sub>3</sub> waveguide electro-optic intensity modulator operating at high microwave frequency
The modulation efficiency, at high-frequency microwave modulation, of a LiNbO3 waveguide electro-optic modulator is shown to be degraded severely, especially when it is used as a frequency translator in a Brillouin-distributed fiber-sensing system. We derive an analytical expression for this attenuation regarding the phase-velocity mismatch and the impedance mismatch during the modulation process. Theoretical results are confirmed by experimental results based on a 15 Gb/s LiNbO3 optical intensity modulator
Mean-field embedding of the dual fermion approach for correlated electron systems
To reduce the rapidly growing computational cost of the dual fermion lattice
calculation with increasing system size, we introduce two embedding schemes.
One is the real fermion embedding, and the other is the dual fermion embedding.
Our numerical tests show that the real fermion and dual fermion embedding
approaches converge to essentially the same result. The application on the
Anderson disorder and Hubbard models shows that these embedding algorithms
converge more quickly with system size as compared to the conventional dual
fermion method, for the calculation of both single-particle and two-particle
quantities.Comment: 10 pages, 10 figure
Dual Fermion Method for Disordered Electronic Systems
While the coherent potential approximation (CPA) is the prevalent method for
the study of disordered electronic systems, it fails to capture non-local
correlations and Anderson localization. To incorporate such effects, we extend
the dual fermion approach to disordered non-interacting systems using the
replica method. Results for single- and two- particle quantities show good
agreement with cluster extensions of the CPA; moreover, weak localization is
captured. As a natural extension of the CPA, our method presents an alternative
to the existing cluster theories. It can be used in various applications,
including the study of disordered interacting systems, or for the description
of non-local effects in electronic structure calculations.Comment: 5 pages, 4 figure
Total Syntheses of Scabrolide A and Nominal Scabrolide B
The marine natural product scabrolide A was obtained by isomerization of the vinylogous 1,4-diketone entity of nominal scabrolide B as the purported pivot point of the biosynthesis of these polycyclic norcembranoids. Despite the success of this maneuver, the latter compound itself turned out not to be identical with the natural product of that name. The key steps en route to the carbocyclic core of these targets were a [2,3]-sigmatropic rearrangement of an allylic sulfur ylide to forge the overcrowded C12âC13 bond, an RCM reaction to close the congested central six-membered ring, and a hydroxy-directed epoxidation/epoxide opening/isomerization sequence to set the âumpoledâ 1,4-dicarbonyl motif and the correct angular configuration at C12
Observation of associated near-side and away-side long-range correlations in âsNN=5.02ââTeV proton-lead collisions with the ATLAS detector
Two-particle correlations in relative azimuthal angle (ÎÏ) and pseudorapidity (Îη) are measured in âsNN=5.02ââTeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1ââÎŒb-1 of data as a function of transverse momentum (pT) and the transverse energy (ÎŁETPb) summed over 3.1<η<4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2<|Îη|<5) ânear-sideâ (ÎÏâŒ0) correlation that grows rapidly with increasing ÎŁETPb. A long-range âaway-sideâ (ÎÏâŒÏ) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small ÎŁETPb, is found to match the near-side correlation in magnitude, shape (in Îη and ÎÏ) and ÎŁETPb dependence. The resultant ÎÏ correlation is approximately symmetric about Ï/2, and is consistent with a dominant cosâĄ2ÎÏ modulation for all ÎŁETPb ranges and particle pT
A Typical Medium Dynamical Cluster Approximation for the Study of Anderson Localization in Three Dimensions
We develop a systematic typical medium dynamical cluster approximation that
provides a proper description of the Anderson localization transition in three
dimensions (3D). Our method successfully captures the localization phenomenon
both in the low and large disorder regimes, and allows us to study the
localization in different momenta cells, which renders the discovery that the
Anderson localization transition occurs in a cell-selective fashion. As a
function of cluster size, our method systematically recovers the re-entrance
behavior of the mobility edge and obtains the correct critical disorder
strength for Anderson localization in 3D.Comment: 5 Pages, 4 Figures and Supplementary Material include
Quantum phase transitions in the Kane-Mele-Hubbard model
We study the two-dimensional Kane-Mele-Hubbard model at half filling by means
of quantum Monte Carlo simulations. We present a refined phase boundary for the
quantum spin liquid. The topological insulator at finite Hubbard interaction
strength is adiabatically connected to the groundstate of the Kane-Mele model.
In the presence of spin-orbit coupling, magnetic order at large Hubbard U is
restricted to the transverse direction. The transition from the topological
band insulator to the antiferromagnetic Mott insulator is in the universality
class of the three-dimensional XY model. The numerical data suggest that the
spin liquid to topological insulator and spin liquid to Mott insulator
transitions are both continuous.Comment: 13 pages, 10 figures; final version; new Figs. 4(b) and 8(b
Use of a student response system in Primary Schools â an empirical study
This paper reports a pilot study for a student response system (SRS) used in an English school. The technology used is the âWireless Response Systemâ â WRS developed at Huddersfield University, and the learning activities were conducted in Mathematics and English classes. The main concepts â activity based, problem based and opinion based learning â are adopted into the study. A case study was the method used in the investigation. The results show that the system is suitable for different sizes groups of users, who may choose their preferred question types. The school claims the use of WRS was successful, evidenced by the data collected, and the children and teachers were interested in using it. We conclude that the SRS can assist teachers in classroom teaching at primary school level, especially in the observations of engagement and effectiveness of studentsâ learning
Reusable Augmented Concrete System: Accessible Method for Formwork Manufacturing through Holographic Guidance
Reinforced concrete has been one of the essential materials for modern architecture for the last hundred years. Its use is entirely global, having been adopted by all cultures and styles since its invention in the late 19th century. Although its value is excellent due to its low cost, durability and adaptability, its environmental impact is significant, being, in fact, one of the most polluting industries in the world (Babor et al. 2009). This experimental project will research a more sustainable use of concrete, exploring a new form of reusable concrete formwork that will ideally reduce the CO2 footprint by removing wood waste in the casting process and replacing it with adaptable metal components. The modular part-based system for the concrete casting also attempts to simplify one of the current complexities for concrete construction, the Skilled-Labour shortage. (Yusoff et al. 2021). To mitigate this problem, the project also proposes using an Augmented Assembly logic for the casting parts to guide the ensemble and dismantle the formwork through an optimised algorithmic logic. The use of Augmented Reality as a replacement for traditional paper instructions will facilitate access to more workers to this construction art and potentially improve access to optimised use of concrete in developing communities with restricted building technological resources
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