455 research outputs found
CP violation effects in the diphoton spectrum of heavy scalars
In a class of new physics models, an extended Higgs sector and new
CP-violating sources are simultaneously present in order to explain the baryon
asymmetry in the Universe. The aim of this work is to study the implications of
beyond the Standard Model (SM) CP violation for the searches of heavy scalars
at the LHC. In particular, we focus on the diphoton channel searches in the
CP-violating two-Higgs-doublet model (CPV 2HDM). To have a sizable CPV in the
scalar sector, the two heavy neutral scalars in 2HDM tend to be nearly
degenerate. The theoretical constraints of unitarity, perturbativity and vacuum
stability are considered, which requires that the heavy scalars TeV in a large region of the parameter space. The experimental limits are
also taken into account, including the direct searches of heavy neutral scalars
in the final state of the SM , and bosons, the differential
data, those from the charged scalar sector which is implied by the
oblique parameter, as well as the precise measurements of the electric
dipole moments of electron and mercury. The quantum interference effects
between the resonances and the SM background are crucially important for the
diphoton signals, and the CPV mixing of the quasi-degenerate heavy scalars
could enhance significantly the resonance peak. With an integrated luminosity
of 3000 fb at the LHC, almost the whole parameter space of CPV 2HDM
could be probed in the diphoton channel, and the CPV could also be directly
detected via the diphoton spectrum.Comment: 32 pages (two columns), 20 figures, 1 table, minor changes, version
to appear in PR
D-type Minimal Conformal Matter: Quantum Curves, Elliptic Garnier Systems, and the 5d Descendants
We study the quantization of the 6d Seiberg-Witten curve for D-type minimal
conformal matter theories compactified on a two-torus. The quantized 6d curve
turns out to be a difference equation established via introducing codimension
two and four surface defects. We show that, in the Nekrasov-Shatashvili limit,
the 6d partition function with insertions of codimension two and four defects
serve as the eigenfunction and eigenvalues of the difference equation,
respectively. We further identify the quantum curve of D-type minimal conformal
matters with an elliptic Garnier system recently studied in the integrability
community. At last, as a concrete consequence of our elliptic quantum curve, we
study its RG flows to obtain various quantum curves of 5d theories.Comment: 36+6 page
Single-Source-Precursor Containing Derived Transition Metal Compounds Carbon Hybrid Nanocomposites for Electrochemical Applications
Advanced catalysts for the electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are required in the future to further develop an efficient and up-scalable water splitting process. Among all the potential candidates, carbon-supported transition metal-based nanomaterials are of great interest due to their low cost, high durability, and promising functional performance.
This dissertation presents an innovative and cost-effective approach to synthesize carbon shell-encapsulated transition metal alloys or phosphide nanoparticles supported on in-situ formed defective N-doped carbon/carbon nanotube hybrids, which are derived from novel single-source-precursors (SSPs). The precursor is synthesized by a facile one-pot reaction using cheap and environmentally friendly carbon and phosphorus sources. The obtained core-shell structured hybrids perform as highly active and durable electrocatalysts for HER and/or OER, benefiting from the following common features: (1) A synergistic electronic effect among transition metal compounds, heteroatom-doped carbon, and entangled carbon nanotubes. (2) Promotion of electrolyte penetration towards the active sites through the porous structure of the formed mesoporous carbon clusters. (3) The unique core-shell nanostructure of the hybrid material effectively curbs the degradation of the electrocatalyst by protecting the active nanoparticles from harsh electrolyte.
The present studies propose various strategies to enhance the electrocatalytic properties, utilizing both morphology-controlled and composition-controlled methods. Additionally, the studies also focus on the relationship between structure and property, which ultimately determines the electrocatalytic activity for the HER and OER. These findings may offer valuable insights for future applications in the field of electrochemical water splitting. Furthermore, the thesis aims to provide a cost-effective and straightforward approach for synthesizing hybrid materials comprised of transition metal compounds and carbon, with the goal of facilitating their potential utilization in energy storage and conversion applications
Failure Analysis
Two approaches to failure analysis are explained: analysis of individual failures and statistical analysis. Various criteria for failure sorting and classification are presented, as well as the main causes and mechanisms of failures. The text is accompanied by figures with characteristic fracture patterns. The chapter is complemented by an example of computer aided sorting of failures in railway driving vehicles
Scalable Multi-Robot Collaboration with Large Language Models: Centralized or Decentralized Systems?
A flurry of recent work has demonstrated that pre-trained large language
models (LLMs) can be effective task planners for a variety of single-robot
tasks. The planning performance of LLMs is significantly improved via prompting
techniques, such as in-context learning or re-prompting with state feedback,
placing new importance on the token budget for the context window. An
under-explored but natural next direction is to investigate LLMs as multi-robot
task planners. However, long-horizon, heterogeneous multi-robot planning
introduces new challenges of coordination while also pushing up against the
limits of context window length. It is therefore critical to find
token-efficient LLM planning frameworks that are also able to reason about the
complexities of multi-robot coordination. In this work, we compare the task
success rate and token efficiency of four multi-agent communication frameworks
(centralized, decentralized, and two hybrid) as applied to four
coordination-dependent multi-agent 2D task scenarios for increasing numbers of
agents. We find that a hybrid framework achieves better task success rates
across all four tasks and scales better to more agents. We further demonstrate
the hybrid frameworks in 3D simulations where the vision-to-text problem and
dynamical errors are considered. See our project website
https://yongchao98.github.io/MIT-REALM-Multi-Robot/ for prompts, videos, and
code.Comment: 6 pages, 8 figure
Numerical study on aerodynamic noise performances of axial spacing in a contra-rotating axial fan
In order to study the effect of axial spacing on behaviors of aerodynamic performance and aerodynamic noises in a contra-rotating fan, the steady/unsteady Reynolds-averaged Navier-Stokes equations are solved by the numerical method in conjunction with a SST turbulence model, and the effects of axial spacing on performance and aerodynamic characteristics are investigated. Furthermore, BEM is adopted to compute the radiation noise of the contra-rotating fan caused by unsteady pressure fluctuations. The results show that axial spacing is an important factor which can affect the aerodynamic performance of contra-rotating fan. As a whole, the effect of axial spacing on the blade loading of Rotor 2 is significantly greater than that of Rotor 1. For Rotor 2, the smaller axial spacing leads to the large secondary flow loss, and the larger axial spacing leads to the strong mixing loss. With the increase of axial spacing, the radiation noise at the characteristic frequency decreases, but showed different changing degrees. With consideration of the aerodynamic performance and aerodynamic noises of the contra-rotating fan, the optimal comprehensive performance appears at the axial spacing of 0.5 chord
Precision Enhancement in Spatial Measurement by Introducing Squeezed Light into Weak Value Amplification
The precision enhancement is demonstrated in an optical spatial measurement
based on weak value amplification (WVA) system and split-like detection, by
injecting a TEM10 squeezed vacuum beam. It is the first time combining the WVA
technique and squeezed beam injection to experimentally realize high-precision
optical spatial measurement beyond the standard quantum limit. As a result, the
precision enhancement of 1.3 times can be achieved at 500kHz by adding a
squeezed beam in the vacuum input port of the Mach-Zehnder interferometer. The
minimum measurable displacement is reduced from 1.08pm to 0.85pm and the
corresponding minimum measurable tilt is reduced from 0.86prad to 0.67prad.
Moreover, the spatial measurement at low-frequency band is also implemented and
the SNR is improved 2dB at 4kHz. Our work provides an effective method to
accomplish higher precision in optical spatial measurement, which has potential
applications in gravitational wave interferometer calibration, super-resolution
quantum imaging, etc.Comment: 4 pages, 5 figures
A Novel SVPWM Algorithm Considering Neutral-Point Potential Balancing for Three-Level NPC Inverter
For three-level inverter, complexity of control strategy and neutral-point potential imbalance problem of DC side is the bottleneck restricting its application. In order to solve the problem, a simplified implementation of three-level space vector pulse width modulation (SVPWM) considering neutral-point potential balancing is proposed in this paper. The proposed SVPWM algorithm is based on judging of three phase voltages and voltage-second balance principle, which does not need to perform the sine and cosine calculations, and thus it is more convenient and effective than traditional SVPWM algorithm. Also, the neutral-point potential balancing can be realized conveniently and effectively. The proposed algorithm can not only effectively simplify the calculation and reduce calculation time greatly, but also achieve the same control effect as traditional SVPWM. It has certain reference significance and can be used to shorten sampling time and improve the inverter performance. Finally, the proposed SVPWM algorithm is verified by simulation and experimental results
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