arXiv subjects

Xiaodong Chen

Publications and source records attributed to Xiaodong Chen.

46 records · Page 3Linked to original sources

arXiv2019

Confinements regulate capillary instabilities of fluid threads

We study the breakup of confined fluid threads at low flow rates to understand instability mechanisms. To determine the critical conditions between the earlier quasi-stable necking stage and the later unstable collapse stage, simulations and experiments are designed to operate at an extremely low flow rate. Critical mean radii at neck centres are identified by the stop-flow method for elementary microfluidic configurations. Analytical investigations reveal two distinct origins of capillary instabilities. One is the gradient of capillary pressure induced by the confinements of geometry and external flow, whereas the other is the competition between local capillary pressure and internal pressure determined by the confinements.

physics.flu-dyn↗

arXiv2016

Valley-protected backscattering suppression in silicon photonic graphene

In this paper, we study valley degree of freedom in all dielectric silicon photonic graphene. Photonic band gap opening physics under inversion symmetry breaking is revisited by the viewpoint of nonzero valley Chern number. Bulk valley modes with opposite orbital angular momentum are unveiled by inspecting time-varying electric fields. Topological transition is well illustrated through photonic Dirac Hamiltonian. Valley dependent edge states and the associated valley-protected backscattering suppression around Z-shape bend waveguide have been demonstrated.

physics.optics↗

arXiv2013

Single-Layer MoS2 Phototransistors

A new phototransistor based on the mechanically-exfoliated single-layer MoS2 nanosheet is fabricated and its light-induced electric properties are investigated in details. Photocurrent generated from the phototransistor is solely determined by the illuminated optical power at a constant drain or gate voltage. The switching behavior of photocurrent generation and annihilation can be completely finished within ca. 50 ms and it shows good stability. Especially, the single-layer MoS2 phototransistor exhibits a better photoresponsivity as compared with the graphene-based device. The unique characteristics of incident-light control, prompt photoswitching and good photoresponsivity from the MoS2 phototransistor pave an avenue to develop the single-layer semiconducting materials for multi-functional optoelectronic device applications in future.

cond-mat.mtrl-sci↗

arXiv2012

Bouncing, Helical and Buckling Instabilities During Droplet Collision: Newtonian and Non-Newtonian Liquids

In this video, Ray-tracing data visualization technique was used to obtain realistic and detailed flow motions during droplet collision. The differences of collision outcome between Newtonian and non-Newtonian were compared. Various types of droplet collision were presented, including bouncing, coalescence, and stretching separation. Because of the reducing of equivalent viscosity caused by shear stress, the gas film between shear-thinning droplet is thinner than Newtonian liquid. Since thinner gas film promotes coalescence, shear thinning liquid has smaller area of bouncing regime in the diagram of Weber number and impact parameter. During the ligament/thread breakup process of stretching separation, two kinds of instabilities are identified, helical and buckling instabilities. Helical instability is analogous to a viscous rotating liquid jet, while the buckling instability is analogous to electrically charged liquid jets of polymer solutions.

physics.flu-dyn↗

arXiv2012

Impinging Jet Dynamics

In this fluid dynamics video, Ray-tracing data visualization technique was used to obtain realistic and detailed flow motions during impinging of two liquid jets. Different patterns of sheet and rim configurations were presented to shed light into the underlying physics, including liquid chain, closed rim, open rim, unstable rim and flapping sheet. In addition, stationary asymmetrical waves were observed and compared with existing theories. The generation of stationary capillary wave in respect to the liquid rim were explained by the classic shallow water wave theory. The atomization process caused by development of the impact waves were observed in detail, including fragmentation of liquid sheet, formation of liquid ligaments, and breakup of ligament into droplet. The locking-on feature of the wavelength of impact wave were also found to be similar to that of perturbed free shear layers.

physics.flu-dyn↗

arXiv2011

Impinging Jets and Droplet Dynamics

In this fluid dynamics video, results from high fidelity numerical simulations are presented, which have been carried out to study the flow and droplet dynamics of liquid sheets formed by two impinging jets. A three-dimensional Volume-of-Fluid (VOF) method with adaptive mesh refinement (AMR) based on octree meshes [1] is used to simulate the various flow patterns associated with impinging jets, secondary breakup and binary collision of droplets. In addition to AMR, a thickness based refinement algorithm is also developed and implemented to efficiently resolve the various scales of surface tension driven interfacial flows.

physics.flu-dyn↗

arXiv2005

Equations of Motion with Multiple Proper Time: A New Interpretation of Spin

The purpose of this paper is to show that: when a single particle moving under 3-proper time (three-dimensional time), the trajectories of a classical particle are equivalent to a quantum field with spin. Three-proper time models are built for spinless particle, particles with integer spin and half-integer spin respectively. The models recreate the same physical behavior as quantum field theory of free particles -- by using pure classical methods with three proper time. A new interpretation of spin is given. It provides us more evident that it is possible to interpret quantum physics by using multiple dimensional time. In the last part of this paper, Bose-Einstein statistics and Fermi-Dirac statistics are derived under classical method.

quant-ph↗

arXiv2005

6-dimensional Kaluza-Klein Theory for Basic Quantum Particles and Electron-Photon Interaction

By extending original Kaluza-Klein theory to 6-dimension, the basic quantum field equations for 0-spin particle, 1-spin particle and 1/2 spin particle with mass >0 are directly derived from 6-dimensional Einstein equations. It shows that the current quantum field equations of basic particles become pure geometry properties under 6-dimension time-space. The field equations of electron and photon can be unified in one 6-dimensional extended Maxwell equation. The equations containing interactions between electron and photon will be derived from Einstein equation under 6-dimension time-space. It shows that the interactions in QED can be considered as the effect of local geometry curvature changing instead of exchange virtual photons.

physics.gen-ph↗

arXiv2005

Modified Kaluza-Klein Theory, Quantum Hidden Variables and 3-Dimensional Time

In this paper, the basic quantum field equations of free particle with 0-spin, 1-spin (for case of massless and mass $>$ 0) and 1/2 spin are derived from Einstein equations under modified Kaluza-Klein metric, it shows that the equations of quantum fields can be interpreted as pure geometry properties of curved higher-dimensional time-space . One will find that if we interpret the 5th and 6th dimension as ``extra'' time dimension, the particle's wave-function can be naturally interpreted as a single particle moving along geodesic path in 6-dimensional modified Kaluza-Klein time-space. As the result, the fundamental physical effect of quantum theory such as double-slit interference of single particle, statistical effect of wave-function, wave-packet collapse, spin, Bose-Einstein condensation, Pauli exclusive principle can be interpreted as ``classical'' behavior in new time-space. In the last part of this paper, we will coupling field equations of 0-spin, 1-spin and 1/2-spin particles with gravity equations.

quant-ph↗

arXiv1999

A New Interpretation of Quantum Theory -- Time as Hidden Variable

Using 2 more time variables as the quantum hidden variables, we derive the equation of Dirac field under the principle of classical physics, then we extend our method into the quantum fields with arbitrary spin number. The spin of particle is shown naturally as the topological property of 3-dimensional time + 3-dimensional space . One will find that the quantum physics of single particle can be interpreted as the behavior of the single particle in 3+3 time-space .

quant-ph↗