arXiv subjects

J. P. Huang

Publications and source records attributed to J. P. Huang.

At least 19 recordsLinked to original sources

arXiv2022

Higher-order-modes enhanced phase-matched dispersive-wave generation in the deep-blue and UV spectral region

During the last few decades, solid-core photonic crystal fibers (PCFs) have been extensively explored to generate broadband, high-coherence supercontinua (SC). Limited by the material absorption and relatively low nonlinearity of fused silica, spectral broadening in silica PCF-based SCs is usually restricted to the blue to near-infrared spectral regions, even in developed commercial sources. The output spectra of these sources are missing short wavelengths of the full range. Many efforts have been spent to break the limitation. Among them, dispersive-wave (DW) generation has been investigated for triggering new frequencies in short wavelengths. With satisfied phase-matching conditions, excessive energy can be directly transferred from solitons of the anomalous dispersion region to DWs of the short wavelengths. However, a systematical study of factors, including phase-matched DWs, strongly related to the dispersion tailoring of higher-order modes (HOMs), has rarely been shown. This study reports the experimental observations of HOM-enhanced phase-matchings for the DW generation in the deep-blue and ultraviolet regions. A solid-core PCF-based, UV-extended SC source spanning a 2.8-octave-wide (350 nm to 2500 nm) is demonstrated. Meanwhile, we carefully verify our findings via numerical calculations.

physics.optics↗

arXiv2015

Engineering the accurate distortion of an object's temperature-distribution signature

It is up to now a challenge to control the conduction of heat. Here we develop a method to distort the temperature distribution signature of an object at will. As a result, the object accurately exhibits the same temperature distribution signature as another object that is predetermined, but actually does not exist in the system. Our finite element simulations confirm the desired effect for different objects with various geometries and compositions. The underlying mechanism lies in the effects of thermal metamaterials designed by using this method. Our work is of value for applications in thermal engineering.

cond-mat.mtrl-sci↗

arXiv2014

Big data need physical ideas and methods

If a person looks at WHITE paper through BLUE glasses, the paper will become BLUE in the eye of the person. Likewise, in the current study of big data which play the same role as the white paper being looked at, various statistical methods just serve as the blue glasses. That is, results obtained from big data often depend on the statistical methods in use, which may often defy reality. Here I suggest using physical ideas and methods to overcome this problem to the greatest extent. This suggestion is helpful to development and application of big data.

physics.data-an↗

arXiv2014

Manipulating local heat flux with different patterns

Since the thermal conduction equation has form invariance under coordinate transformation, one can design thermal metamaterials with novel functions by tailoring materials' thermal conductivities. In this work, we establish a different transformation theory, and propose a layered device with anisotropic thermal conductivities. The device is able to convert heat flux from parallel patterns into non-parallel patterns and vice versa. In the mean time, the heat flux pattern outside the device keeps undisturbed as if this device is absent. We perform finite-element simulations to confirm the converting behavior. This work paves a different way to manipulate the flow of heat at will.

cond-mat.mtrl-sci↗

arXiv2013

Unconventional thermal cloak hiding an object outside the cloak

All the thermal cloaks reported in the literature can be used to thermally hide an object inside the cloak. However, a common limitation of this kind of thermal cloaks is that the cloaked object cannot feel the external heat flow since it is located inside the cloak; thus we call these cloaks ``conventional thermal cloaks''. Here we manage to overcome this limitation by exploiting a class of unconventional thermal cloaks that enable the cloaked object to feel the external heat flow. Our finite element simulations in two dimensions show the desired cloaking effect. The underlying mechanism originates from the complementary effect of thermal metamaterials with negative thermal conductivities. This work suggests a different method to design thermal devices where heat conduction can be controlled at will.

cond-mat.mtrl-sci↗

arXiv2009

Mathematical irrational numbers not so physically irrational

We investigate the topological structure of the decimal expansions of the three famous naturally occurring irrational numbers, $π$, $e$, and golden ratio, by explicitly calculating the diversity of the pair distributions of the ten digits ranging from 0 to 9. And we find that there is a universal two-phase behavior, which collapses into a single curve with a power law phenomenon. We further reveal that the two-phase behavior is closely related to general aspects of phase transitions in physical systems. It is then numerically shown that such characteristics originate from an intrinsic property of genuine random distribution of the digits in decimal expansions. Thus, mathematical irrational numbers are not so physically irrational as long as they have such an intrinsic property.

physics.data-an↗

arXiv2008

Structure of polydisperse inverse ferrofluids: Theory and computer simulation

By using theoretical analysis and molecular dynamics simulations, we investigate the structure of colloidal crystals formed by nonmagnetic microparticles (or magnetic holes) suspended in ferrofluids (called inverse ferrofluids), by taking into account the effect of polydispersity in size of the nonmagnetic microparticles. Such polydispersity often exists in real situations. We obtain an analytical expression for the interaction energy of monodisperse, bidisperse, and polydisperse inverse ferrofluids. Body-centered tetragonal (bct) lattices are shown to possess the lowest energy when compared with other sorts of lattices and thus serve as the ground state of the systems. Also, the effect of microparticle size distributions (namely, polydispersity in size) plays an important role in the formation of various kinds of structural configurations. Thus, it seems possible to fabricate colloidal crystals by choosing appropriate polydispersity in size.

cond-mat.soft↗

arXiv2008

Magnetophoresis of nonmagnetic particles in ferrofluids

Ferrofluids containing nonmagnetic particles are called inverse ferrofluids. On the basis of the Ewald-Kornfeld formulation and the Maxwell-Garnett theory, we theoretically investigate the magnetophoretic force exerting on the nonmagnetic particles in inverse ferrofluids due to the presence of a nonuniform magnetic field, by taking into account the structural transition and long-range interaction. We numerically demonstrate that the force can be adjusted by choosing appropriate lattices, volume fractions, geometric shapes, and conductivities of the nonmagnetic particles, as well as frequencies of external magnetic fields.

physics.chem-ph↗

arXiv2008

Theory of second-harmonic generation in colloidal crystals

On the basis of the Edward-Kornfeld formulation, we study the effective susceptibility of secondharmonic generation (SHG) in colloidal crystals, which are made of graded metallodielectric nanoparticles with an intrinsic SHG susceptibility suspended in a host liquid. We find a large enhancement and redshift of SHG responses, which arises from the periodic structure, local field effects and gradation in the metallic cores. The optimization of the Ewald-Kornfeld formulation is also investigated.

physics.optics↗

arXiv2008

Dynamic polarizability of rotating particles in electrorheological fluids

A rotating particle in electrorheological (ER) fluid leads to a displacement of its polarization charges on the surface which relax towards the external applied field ${\bf E}_0$, resulting in a steady-state polarization at an angle with respect to ${\bf E}_0$. This dynamic effect has shown to affect the ER fluids properties dramatically. In this paper, we develop a dynamic effective medium theory (EMT) for a system containing rotating particles of finite volume fraction. This is a generalization of established EMT to account for the interactions between many rotating particles. While the theory is valid for three dimensions, the results in a special two dimensional configuration show that the system exhibits an off-diagonal polarization response, in addition to a diagonal polarization response, which resembles the classic Hall effect. The diagonal response monotonically decreases with an increasing rotational speed, whereas the off-diagonal response exhibits a maximum at a reduced rotational angular velocity $ω_0$ comparing to the case of isolated rotating particles. This implies a way of measurement on the interacting relaxation time. The dependencies of the diagonal and off-diagonal responses on various factors, such as $ω_0$, the volume fraction, and the dielectric contrast, are discussed.

physics.chem-ph↗

arXiv2008

Geometrically controllable electric fields

According to a first-principles approach, we clarify electric cloaks universality concerning a new class of phase transitions between negative pathway (NGP) and normal pathway of electric displacement fields, which are driven by the geometric shape of the cloak. We report that the NGP arises from shape-enhanced strong negative electric polarization, and that it is related to a symmetric oscillation of the paired electric permittivities, which are shown to satisfy a sum rule. The NGP does not occur for a spherical cloak, but appears up to maximum as the ratio a/b between the long and short principal axis of the spheroidal cloak is about 5/2, and eventually disappears as a/b becomes large enough corresponding to a rod-like shape. Then, the cloaking efficiency is compared between different geometrical shapes. The possibility of experiments is discussed. This work has relevance to crucial control of electric fields and to general physics of phase transitions.

physics.class-ph↗

arXiv2006

Nonlinear response of the magnetophoresis in inverse ferrofluids

Taking into account the structural transition and long-range interaction (lattice effect), we resort to the Ewald-Kornfeld formulation and developed Maxwell-Garnett theory for uniaxially anisotropic suspensions to calculate the effective permeability of inverse ferrofluids. And we also consider the effect of volume fraction to the magnetophoretic force on the nonmagnetic spherical particles submerged in ferrofluids in the presence of nonuniform magnetic field. We find that the coupling of ac and dc field case can lead to fundamental and third harmonic response in the effective magnetophoresis and changing the aspect ratio in both prolate and oblate particles can alter the harmonic and nonharmonic response and cause the magnetophoretic force vanish.

cond-mat.soft↗

arXiv2006

Magnetophoresis of ferrofluid in microchannel system and its nonlinear effect

We have studied the magnetophoretic particle separation and its nonlinear behavior of ferrofluids in microchannel which is proposed by Furlani. The magnetic gradient force is caused by an bias field and the polarized magnets and is found to be spatially uniform in the channel section which can be used for particle selecting or separation. We have derived the equations of nonlinear magnetization of magnetic particles which cause the harmonics of magnetophoresis. The Langevin model and generalized Clausius-Mossotti equation used show how the normal and longitude anomalous anisotropic effect the permeability of ferrofluids, thus the magnetic force. Our analysis demonstrates the viability of using the microchannel system for various bioapplications and other characterization of fluid transporting and the time-varying magnetic field can be potentially used for an integrated magnetometer and influences the the viscosity and effective permeability in ferrofluids.

physics.bio-ph↗

arXiv2005

Multipole polarizability of a graded spherical particle

We have studied the multipole polarizability of a graded spherical particle in a nonuniform electric field, in which the conductivity can vary radially inside the particle. The main objective of this work is to access the effects of multipole interactions at small interparticle separations, which can be important in non-dilute suspensions of functionally graded materials. The nonuniform electric field arises either from that applied on the particle or from the local field of all other particles. We developed a differential effective multipole moment approximation (DEMMA) to compute the multipole moment of a graded spherical particle in a nonuniform external field. Moreover, we compare the DEMMA results with the exact results of the power-law graded profile and the agreement is excellent. The extension to anisotropic DEMMA will be studied in an Appendix.

cond-mat.mtrl-sci↗

arXiv2005

Dielectric response of spherical particles of graded materials

We have studied the effective response of composites of spherical particles with a dielectric profile which varies along the radius of the particles. We developed a differential effective dipole theory to compute the dipole moment of individual spherical particle and hence the effective dielectric response of a dilute suspension. The theory has been applied to two model dielectric profiles. Moreover, we compare the approximate results with the exact results of the power-law profile and the agreement is excellent.

cond-mat.soft↗

arXiv2005

Theory of ac electrokinetic behavior of spheroidal cell suspensions with an intrinsic dispersion

The dielectric dispersion, dielectrophoretic (DEP) and electrorotational (ER) spectra of spheroidal biological cell suspensions with an intrinsic dispersion in the constituent dielectric constants are investigated. By means of the spectral representation method, we express analytically the characteristic frequencies and dispersion strengths both for the effective dielectric constant and the Clausius-Mossotti factor (CMF). We identify four and six characteristic frequencies for the effective dielectric spectra and CMF respectively, all of them being dependent on the depolarization factor (or the cell shape). The analytical results allow us to examine the effects of the cell shape, the dispersion strength and the intrinsic frequency on the dielectric dispersion, DEP and ER spectra. Furthermore, we include the local-field effects due to the mutual interactions between cells in a dense suspension, and study the dependence of co-field or anti-field dispersion peaks on the volume fractions.

cond-mat.soft↗

arXiv2005

Second-harmonic generation in graded metallic films

We study the effective second-harmonic generation (SHG) susceptibility in graded metallic films by invoking the local field effects exactly, and further numerically demonstrate that the graded metallic films can serve as a novel optical material for producing a broad structure in both the linear and SHG response and an enhancement in the SHG signal.

physics.optics↗

arXiv2004

Magneto-controlled nonlinear optical materials

We exploit theoretically a magneto-controlled nonlinear optical material which contains ferromagnetic nanoparticles with a non-magnetic metallic nonlinear shell in a host fluid. Such an optical material can have anisotropic linear and nonlinear optical properties and a giant enhancement of nonlinearity, as well as an attractive figure of merit.

cond-mat.mtrl-sci↗