3,713 research outputs found
Gromov--Witten/Pandharipande--Thomas correspondence via conifold transitions
Given a (projective) conifold transition of smooth projective threefolds from
to , we show that if the Gromov--Witten/Pandharipande--Thomas descendent
correspondence holds for the resolution , then it also holds for the
smoothing with stationary descendent insertions. As applications, we show
the correspondence in new cases.Comment: 23 pages. Comments are welcome
Remarkable performance optimization of inverted p-i-n architecture perovskite solar cell with CZTS as hole transport material
Hole transport material (HTM) is a major component of perovskite solar cells (PSCs). PEDOT: PSS, an organic HTM, is widely used in inverted (p-i-n) PSCs. While PEDOT: PSS is unstable, expensive and it's acidic nature could deteriorate the absorber. Copper zinc tin sulphide (CZTS), an inorganic semiconductor can be used as HTM due to its properties such as low cost, ease of synthesis and high hole mobility. In this work, device simulation of inverted (p-i-n) PSC was performed with CZTS as HTM to exploit its maximum capability. Remarkable power conversion efficiency (PCE) of 25.43% was achieved after optimizing the performance. Device performance was strongly affected by thickness and electron affinity of HTM as well as diffusion length of carriers. PCE of real fabricated device was also found to be 9.72%. This work demonstrates CZTS is a promising candidate to replace PEDOT: PSS from both experimental and theoretical perspectives
A comprehensive device modelling of perovskite solar cell with inorganic copper iodide as hole transport material
Hole transport material (HTM) plays an important role in the efficiency and stability of perovskite solar cells (PSCs). Spiro-MeOTAD, the commonly used HTM, is costly and can be easily degraded by heat and moisture, thus offering hindrance to commercialize PSCs. There is dire need to find an alternate inorganic and stable HTM to exploit PSCs with their maximum capability. In this paper, a comprehensive device simulation is used to study various possible parameters that can influence the performance of perovskite solar cell with CuI as HTM. These include the effect of doping density, defect density and thickness of absorber layer, along with the influence of diffusion length of carriers as well as electron affinity of electron transport layer (ETM) and HTM on the performance of PSCs. In addition, hole mobility and doping density of HTM is also investigated. CuI is a p-type inorganic material with low cost and relatively high stability. It is found that concentration of dopant in absorber layer and HTM, the electron affinity of HTM and ETM affect the performance of solar cell minutely, while cell performance improves greatly with the reduction of defect density. Upon optimization of parameters, power conversion efficiency for this device is found to be 21.32%. The result shows that lead-based PSC with CuI as HTM is an efficient system. Enhancing the stability and reduction of defect density are critical factors for future research. These factors can be improved by better fabrication process and proper encapsulation of solar cell
Ising-like dynamical signatures and the end-point of the QCD transition line
An increase in the size of coherent domains in the one component
field theory under the influence of a uniformly changing external magnetic
field near the critical end-point was proposed
recently as an estimate also for the variation of the chiral correlation length
of QCD near its respective hypothetical end point in the
plane. The present detailed numerical investigation of the effective model
suggests that passing by the critical QCD end point with realistic rate of
temperature change will trigger large amplitude oscillations in the temporal
variation of the chiral correlation length. A simple mechanism for producing
this phenomenon is suggested.Comment: 10 pages, RevTeX, 5 figures. Version accepted for publication in PR
Out of Equilibrium Non-perturbative Quantum Field Dynamics in Homogeneous External Fields
The quantum dynamics of the symmetry broken lambda (Phi^2)^2 scalar field
theory in the presence of an homogeneous external field is investigated in the
large N limit. We choose as initial state the ground state for a constant
external field J .The sign of the external field is suddenly flipped from
J to - J at a given time and the subsequent quantum dynamics calculated.
Spinodal instabilities and parametric resonances produce large quantum
fluctuations in the field components transverse to the external field. This
allows the order parameter to turn around the maximum of the potential for
intermediate times. Subsequently, the order parameter starts to oscillate near
the global minimum for external field - J, entering a novel quasi-periodic
regime.Comment: LaTex, 30 pages, 12 .ps figures, improved version to appear in Phys
Rev
3D Face Reconstruction from Light Field Images: A Model-free Approach
Reconstructing 3D facial geometry from a single RGB image has recently
instigated wide research interest. However, it is still an ill-posed problem
and most methods rely on prior models hence undermining the accuracy of the
recovered 3D faces. In this paper, we exploit the Epipolar Plane Images (EPI)
obtained from light field cameras and learn CNN models that recover horizontal
and vertical 3D facial curves from the respective horizontal and vertical EPIs.
Our 3D face reconstruction network (FaceLFnet) comprises a densely connected
architecture to learn accurate 3D facial curves from low resolution EPIs. To
train the proposed FaceLFnets from scratch, we synthesize photo-realistic light
field images from 3D facial scans. The curve by curve 3D face estimation
approach allows the networks to learn from only 14K images of 80 identities,
which still comprises over 11 Million EPIs/curves. The estimated facial curves
are merged into a single pointcloud to which a surface is fitted to get the
final 3D face. Our method is model-free, requires only a few training samples
to learn FaceLFnet and can reconstruct 3D faces with high accuracy from single
light field images under varying poses, expressions and lighting conditions.
Comparison on the BU-3DFE and BU-4DFE datasets show that our method reduces
reconstruction errors by over 20% compared to recent state of the art
- …