arXiv subjects

Jiahui Wang

Publications and source records attributed to Jiahui Wang.

83 records · Page 5Linked to original sources

arXiv2021

Violating Kirchhoff's Law of Thermal Radiation in Semitransparent Structures

Kirchhoff's law of thermal radiation imposes a constraint on photon-based energy harvesting processes since part of the incident energy flux is inevitably emitted back to the source. By breaking the reciprocity of the system, it is possible to overcome this restriction and improve the efficiency of energy harvesting. Here, we design and analyze a semitransparent emitter that fully absorbs normally incident energy from a given direction with zero backward and unity forward emissivity. The nearly ideal performance with wavelength-scale thickness is achieved due to the magneto-optical effect and the guided-mode resonance engineered in the emitter structure. We derive the general requirements for the nonreciprocal emitter using the temporal coupled mode theory and the symmetry considerations. Finally, we provide a realistic emitter design based on a photonic crystal slab consisting of a magnetic Weyl semimetal and silicon.

physics.optics↗

arXiv2021

Photonic modal circulator using temporal refractive-index modulation with spatial inversion symmetry

It has been demonstrated that dynamic refractive index modulation, which breaks time-reversal symmetry, can be used to create on-chip non-reciprocal photonic devices. In order to achieve amplitude non-reciprocity, all such devices moreover require modulations that break spatial symmetries, which adds complexity in implementations. Here we introduce a modal circulator, which achieves amplitude non-reciprocity through a circulation motion among three modes. We show that such a circulator can be achieved in a dynamically-modulated structure that preserves mirror symmetry, and as a result can be implemented using only a single standing-wave modulator, which significantly simplifies the implementation of dynamically-modulated non-reciprocal device. We also prove that in terms of the number of modes involved in the transport process, the modal circulator represents the minimum configuration in which complete amplitude non-reciprocity can be achieved while preserving spatial symmetry.

physics.optics↗

arXiv2020

Integrated Nonreciprocal Photonic Devices with Dynamic Modulation

Nonreciprocal components, such as isolators and circulators, are crucial components for photonic systems. In this article we review theoretical and experimental progress towards developing nonreciprocal photonic devices based on dynamic modulation. In particular, we focus on approaches that operate at optical wavelengths and device architectures that have the potential for chip-scale integration. We first discuss the requirements for constructing an isolator or circulator using dynamic modulation. We review a number of different isolator and circulator architectures, including waveguide and resonant devices, and describe their underlying operating principles. We then compare these device architectures from a system-level performance perspective, considering how their figures of merit, such as footprint, bandwidth, isolation, and insertion loss scale with respect to device parameters.

physics.optics↗

arXiv2019

Chaos Phase Induced Mass-producible Monolayer Two-dimensional Material

Crystal phase is well studied and presents a periodical atom arrangement in three dimensions lattice, but the "amorphous phase" is poorly understood. Here, by starting from cage-like bicyclocalix[2]arene[2]triazines building block, a brand-new 2D MOF is constructed with extremely weak interlaminar interaction existing between two adjacent 2D-crystal layer. Inter-layer slip happens under external disturbance and leads to the loss of periodicity at one dimension in the crystal lattice, resulting in an interim phase between the crystal and amorphous phase - the chaos phase, non-periodical in microscopic scale but orderly in mesoscopic scale. This chaos phase 2D MOF is a disordered self-assembly of black-phosphorus like 3D-layer, which has excellent mechanical-strength and a thickness of 1.15 nm. The bulky 2D-MOF material is readily to be exfoliated into monolayer nanosheets in gram-scale with unprecedented evenness and homogeneity, as well as previously unattained lateral size (>10 um), which present the first mass-producible monolayer 2D material and can form wafer-scale film on substrate.

cond-mat.mtrl-sci↗

arXiv2019

The Dynamic Shift of Neuron Excitability Observed with Enveloped High Frequency Stimulation

Neuronal excitability is known to be affected by transcranial electrical stimulation. However, due to the existence of both excitatory and inhibitory neurons in the cortex, the mechanism of neuronal excitability shift is still not clear. Here, we study electrical stimulation disturbance on neuronal excitability in the neuromuscular system on an acute rat model. We design a special stimulation waveform of enveloped high frequency stimulation (EHFS). With modeling and in vivo measurements, EHFS is confirmed to synchronize the neuronal recruitment at the positive and negative electrode. This unique synchronization property of EHFS amplifies the electrical stimulation disturbance on neuronal excitability, to enable the macroscopic observations of large increase and decrease of force output. By eliminating the complicated inhibitory interneuron effects in the cortex, our observations on the neuromuscular system supports the argument that electrical stimulation dynamically shifts neuronal excitability, by inducing depolarization during anodal stimulation and hyperpolarization during cathodal stimulation.

q-bio.NC↗

arXiv2019

A Static Distributed-parameter Circuit Model Explains Electrical Stimulation on the Neuromuscular System

Finite Element Modeling (FEM) has been widely used to model the electric field distribution, to study the interaction between stimulation electrodes and neural tissue. However, due to the insufficient computational capability to represent neural tissue down to an atom-level, the existing FEM fails to model the real electric field that is perpendicular to neuron membrane to initiate an action potential. Thus, to reveal the real electrode-tissue interactions, we developed a circuit to model transmembrane voltage waveforms. Here, we show a distributed-parameter circuit model to systematically study how electrode-tissue interaction is affected by electrode position, input current waveform, and biological structures in the neuromuscular system. Our model explains and predicts various phenomena in neuromuscular stimulation, guides new stimulation electrode and method design, and more importantly, facilitates a fundamental understanding of the physical process during electrode-tissue interaction. In our model, myelin is assumed to be inductive. The voltage waveform resonance caused by this inductive myelin accounts for the much lower stimulation threshold to activate motoneurons than muscle fibers, which is observed with in vivo measurements. These findings confirmed the feasibility of studying electrode-tissue interaction using a proper distributed-parameter circuit. Our current application on the neuromuscular system also raises the possibility that this distributed-parameter circuit model could potentially be applied to study other neural tissues, including the Peripheral Nervous System (PNS) and the Central Nervous System (CNS).

q-bio.NC↗

arXiv2018

A quantized physical framework for understanding the working mechanism of ion channels

A quantized physical framework, called the five-anchor model, is developed for a general understanding of the working mechanism of ion channels. According to the hypotheses of this model, the following two basic physical principles are assigned to each anchor: the polarity change induced by an electron transition and the mutual repulsion and attraction induced by an electrostatic force. Consequently, many unique phenomena, such as fast and slow inactivation, the stochastic gating pattern and constant conductance of a single ion channel, the difference between electrical and optical stimulation (optogenetics), nerve conduction block and the generation of an action potential, become intrinsic features of this physical model. Moreover, this model also provides a foundation for the probability equation used to calculate the results of electrical stimulation in our previous C-P theory.

q-bio.NC↗

arXiv2018

Unveiling Stimulation Secrets of Electrical Excitation of Neural Tissue Using a Circuit Probability Theory

A new theory, named the Circuit-Probability theory, is proposed to unveil the secret of electrical nerve stimulation, essentially explain the nonlinear and resonant phenomena observed when neural and non-neural tissues are electrically stimulated. For the explanation of frequency dependent response, an inductor is involved in the neural circuit model. Furthermore, predicted response to varied stimulation strength is calculated stochastically. Based on this theory, many empirical models, such as strength-duration relationship and LNP model, can be theoretically explained, derived, and amended. This theory can explain the complex nonlinear interactions in electrical stimulation and fit in vivo experiment data on stimulation-responses of many experiments. As such, the C-P theory should be able to guide novel experiments and more importantly, offer an in-depth physical understanding of the neural tissue. As a promising neural model, we can even further explore the more accurate circuit configuration and probability equation to better describe the electrical stimulation of neural tissues in the future.

q-bio.NC↗

arXiv2018

The first principle of neural circuit and the general Circuit-Probability theory

A new neural circuit is proposed by considering the myelin as an inductor. This new neural circuit can explain why the lump-parameter circuit used in previous C-P theory is valid. Meanwhile, it provides a new explanation of the biological function of myelin for neural signal propagation. Furthermore, a new model for magnetic nerve stimulation is built and all phenomena in magnetic nerve stimulation can be well explained. Based on this model, the coil structure can be optimized.

q-bio.NC↗

arXiv2016

A Deduction from Dirac Sea Model

Whether the Dirac sea model is right is verifiable. Assuming the Dirac sea is a physical reality, we have one imagination that a negative energy particle(s) in the sea and a usual positive energy particle(s) will form a neutral atom. The features of the atom can be studied using the nonrelativistic reduction of the Bethe-Salpeter equation, especially for a two body system. This work is dedicated to discuss the bound state of spin-0 and spin-$\frac{\displaystyle 1}{\displaystyle 2}$ constituents. The study shows that an atom consisting of a negative energy particle $(e^-$ or $hc)$ and a positive energy particle $(u\overline{d}$ or $hc)$ has some features of a neutrino, such as spin, lepton number and oscillation. One deduction is that if the atom is a real particle, an atom $X$ consisting of two negative energy particles and a nucleus with double charges exists in nature, which can be observed in Strangeonium, Charmonium and Bottomonium decays $[s\overline{s}]$, $[c\overline{c}]$ and $[b\overline{b}]\rightarrow X π^-π^- e^+e^+~+~hc$ with $X$ invisible at KLOE, CLEOc, BESIII, Belle and BaBar.

physics.gen-ph↗

arXiv2010

A Novel Scheme to Search for Fractional Charge Particles in Low Energy Accelerator Experiments

In the Standard Model of particle physics, the quarks and anti-quarks have fractional charge equal to $\pm1/3$ or $\pm2/3$ of the electron's charge. There has been a large number of experiments searching for fractional charge, isolatable, elementary particles using a variety of methods, including $e^+e^-$ collisions using dE/dx ionization energy loss measurements, but no evidence has been found to confirm existence of free fractional charge particles, which leads to the quark confinement theory. In this paper, a proposal to search for this kind particles is presented, which is based on the conservation law of four-momentum. Thanks to the CLEOc and BESIII detectors' large coverage, good particle identification, precision measurements of tracks' momenta and their large recorded data samples, these features make the scheme feasible in practice. The advantage of the scheme is independent of any theoretical models and sensitive for a small fraction of the quarks transitioning to the unconfinement phase from the confinement phase.

hep-ex↗