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Peng Jin

Publications and source records attributed to Peng Jin.

105 records · Page 6Linked to original sources
arXiv2018

Optimized Hierarchical Power Oscillations Control for Distributed Generation Under Unbalanced Conditions

Control structures have critical influences on converter-interfaced distributed generations (DG) under unbalanced conditions. Most of previous works focus on suppressing active power oscillations and ripples of DC bus voltage. In this paper, the relationship between amplitudes of the active power oscillations and the reactive power oscillations are firstly deduced and the hierarchical control of DG is proposed to reduce power oscillations. The hierarchical control consists of primary and secondary levels. Current references are generated in primary control level and the active power oscillations can be suppressed by a dual current controller. Secondary control reduces the active power and reactive power oscillations simultaneously by optimal model aiming for minimum amplitudes of oscillations. Simulation results show that the proposed secondary control with less injecting negative-sequence current than traditional control methods can effectively limit both active power and reactive power oscillations.

eess.SY↗
arXiv2018

Observation of unusual optical band structure of CH3NH3PbI3 perovskite single crystal

Extensive efforts have been undertaken on the photoelectric physics of hybrid organolead halide perovskites to unveil the reason for the attractive photovoltaic performance. Yet, the resulting evidences are far from being fully conclusive. Herein, we provide another direct support for this issue. In addition to the observation on the conventional band edge at 1.58 eV that presents a blueshift toward temperature increase, interestingly, we also observe an unusual optical band edge at 1.48 eV in CH3NH3PbI3 perovskite single crystals. Contrary to the conventional band edge, this one shows an obvious redshift toward the enhancement in temperature, in agreement with the Varshni relation. More interestingly, the unusual band edge exhibits a series of obvious absorption and photocurrent signals, but the according photoluminescence signals are not observable. This indicates that this band edge is particularly beneficial for the photovoltaic effect due to the inhibited radiative recombination. The kinetics on photo-involved charge transition and transfer are investigated using the pump-probe photoconductivity technique, and a changeable band structure model was proposed.

cond-mat.mtrl-sci↗
arXiv2018

Snapshot light-field laryngoscope

The convergence of recent advances in optical fabrication and digital processing yields a new generation of imaging technology: light-field cameras, which bridge the realms of applied mathematics, optics, and high-performance computing. Herein for the first time, we introduce the paradigm of light-field imaging into laryngoscopy. The resultant probe can image the three-dimensional (3D) shape of vocal folds within a single camera exposure. Furthermore, to improve the spatial resolution, we developed an image fusion algorithm, providing a simple solution to a long-standing problem in light-field imaging.

eess.IV↗
arXiv2018

Moments and ergodicity of the jump-diffusion CIR process

We study the jump-diffusion CIR process, which is an extension of the Cox-Ingersoll-Ross model and whose jumps are introduced by a subordinator. We provide sufficient conditions on the Lévy measure of the subordinator under which the jump-diffusion CIR process is ergodic and exponentially ergodic, respectively. Furthermore, we characterize the existence of the $κ$-moment ($κ>0$) of the jump-diffusion CIR process by an integrability condition on the Lévy measure of the subordinator.

math.PR↗
arXiv2017

Brownian Motion with Singular Time-Dependent Drift

In this paper we study weak solutions for the following type of stochastic differential equation \[ dX_{t}=dW_{t}+b(t, X_{t})dt, \quad t\ge s, \quad X_{s}=x, \] where $b: [0,\infty) \times \mathbb{R}^{d} \to \mathbb{R}^{d}$ is a measurable drift, $W=(W_{t})_{t \ge 0}$ is a $d$-dimensional Brownian motion and $(s,x)\in [0,\infty) \times \mathbb{R}^{d}$ is the starting point. A solution $X=(X_t)_{t \ge s}$ for the above SDE is called a Brownian motion with time-dependent drift $b$ starting from $(s,x)$. Under the assumption that $|b|$ belongs to the forward-Kato class $\mathcal{F} \mathcal{K}_{d-1}^α$ for some $α\in (0,1/2)$, we prove that the above SDE has a unique weak solution for every starting point $(s,x)\in [0,\infty) \times \mathbb{R}^{d}$.

math.PR↗
arXiv2017

Heat kernel estimates for non-symmetric stable-like processes

Let $d\ge1$ and $0<α<2$. Consider the integro-differential operator \[ \mathcal{L}f(x) =\int_{\mathbb{R}^{d}\backslash\{0\}}\left[f(x+h)-f(x)-χ_α(h)\nabla f(x)\cdot h\right]\frac{n(x,h)}{|h|^{d+α}}\mathrm{d}h+\mathbf{1}_{α>1}b(x)\cdot\nabla f(x), \] where $χ_α(h):=\mathbf{1}_{α>1}+\mathbf{1}_{α=1}\mathbf{1}_{\{|h|\le1\}}$, $b:\mathbb{R}^{d}\to\mathbb{R}^{d}$ is bounded measurable, and $n:\mathbb{R}^{d}\times\mathbb{R}^{d}\to\mathbb{R}$ is measurable and bounded above and below respectively by two positive constants. Further, we assume that $n(x,h)$ is Hölder continuous in $x$, uniformly with respect to $h\in\mathbb{R}^{d}$. In the case $α=1,$ we assume additionally $\int_{\partial B_{r}}n(x,h)h\mathrm{d}S_{r}(h)=0$, $\forall r \in (0,\infty)$, where $\mathrm{d}S_{r}$ is the surface measure on $\partial B_{r}$, the boundary of the ball with radius $r$ and center $0$. In this paper, we establish two-sided estimates for the heat kernel of the Markov process associated with the operator $\mathcal{L}$. This extends a recent result of Z.-Q. Chen and X. Zhang.

math.PR↗
arXiv2017

Well-posedness of the martingale problem for non-local perturbations of Lévy-type generators

Let $L$ be a Lévy-type generator whose Lévy measure is controlled from below by that of a non-degenerate $α$-stable ($0<α<2$) process. In this paper, we study the martingale problem for the operator $\mathcal{L}_{t}=L+K_{t}$, with $K_{t}$ being a time-dependent non-local operator defined by \[ K_{t}f(x):=\int_{\mathbb{R}^{d}\backslash\{0\}}[f(x+y)-f(x)-\mathbf{1}_{α>1}\mathbf{1}_{\{|y|\le1\}}y\cdot\nabla f(x)]M(t,x,dy), \] where $M(t,x,\cdot)$ is a Lévy measure on $\mathbb{R}^{d}\backslash\{0\}$ for each $(t,x)\in \mathbb{R}_+ \times \mathbb{R}^{d}$. We show that if \[ \sup_{t\geq0,x\in\mathbb{R}^{d}}\int_{\mathbb{R}^{d}\backslash\{0\}}1\wedge|y|^βM(t,x,dy)<\infty \] for some $0<β<α$, then the martingale problem for $\mathcal{L}_{t}$ is well-posed.

math.PR↗
arXiv2015

On Weak Solutions of SDEs with Singular Time-Dependent Drift and Driven by Stable Processes

Let $d \ge 2$. In this paper, we study weak solutions for the following type of stochastic differential equation \[ dX_{t}=dS_{t}+b(s+t, X_{t})dt, \quad X_{0}=x, \] where $(s,x)\in \mathbb{R}_+ \times \mathbb{R}^{d}$ is the initial starting point, $b: \mathbb{R}_+ \times \mathbb{R}^{d} \to \mathbb{R}^{d}$ is measurable, and $S=(S_{t})_{t \ge 0}$ is a $d$-dimensional $α$-stable process with index $α\in (1,2)$. We show that if the $α$-stable process $S$ is non-degenerate and $b \in L_{loc}^{\infty}(\mathbb{R}_{+};L^{\infty}(\mathbb{R}^{d}))+ L_{loc}^{q}(\mathbb{R}_{+};L^{p}(\mathbb{R}^{d}))$ for some $p,q>0$ with $d/ p+α/q <α-1$, then the above SDE has a unique weak solution for every starting point $(s,x)\in \mathbb{R}_+ \times \mathbb{R}^{d}$.

math.PR↗
arXiv2015

Exponential ergodicity of the jump-diffusion CIR process

In this paper we study the jump-diffusion CIR process (shorted as JCIR), which is an extension of the classical CIR model. The jumps of the JCIR are introduced with the help of a pure-jump Lévy process $(J_t, t \ge 0)$. Under some suitable conditions on the Lévy measure of $(J_t, t \ge 0)$, we derive a lower bound for the transition densities of the JCIR process. We also find some sufficient condition guaranteeing the existence of a Forster-Lyapunov function for the JCIR process, which allows us to prove its exponential ergodicity.

math.PR↗
arXiv2015

Positive Harris recurrence and exponential ergodicity of the basic affine jump-diffusion

In this paper we find the transition densities of the basic affine jump-diffusion (BAJD), which is introduced by Duffie and Garleanu [D. Duffie and N. Garleanu, Risk and valuation of collateralized debt obligations, Financial Analysts Journal 57(1) (2001), pp. 41--59] as an extension of the CIR model with jumps. We prove the positive Harris recurrence and exponential ergodicity of the BAJD. Furthermore we prove that the unique invariant probability measure $π$ of the BAJD is absolutely continuous with respect to the Lebesgue measure and we also derive a closed form formula for the density function of $π$.

math.PR↗
arXiv2010

Study of magnetic alloy cores for HIRFL-CSRm compressor cavity

For selecting the properly magnetic alloy (MA) material to load the RF compression cavity, the measurement of the MA cores which is produced by Liyuan Company has been carried out at IMP. We measured 4 kinds of MA core materials, type V1, V2, A1 and A2. And we mainly focus on the permeability, quality factor (Q value) and shunt impedance of the MA core. The MA cores which have higher permeability, lower Q value and higher shunt impedance will be selected to load RF compression cavity. According to the results of measurement, the type V1, V2 and A2 material will be chosen as candidate to load RF cavity.

physics.acc-ph↗
arXiv2007

Electron resonant tunneling through InAs/GaAs quantum dots embedded in a Schottky diode with an AlAs insertion layer

Molecular beam epitaxy is employed to manufacture self-assembled InAs/GaAs quantum dot Schottky resonant tunneling diodes. By virtue of a thin AlAs insertion barrier, the thermal current is effectively reduced and electron resonant tunneling through quantum dots under both forward and reverse biased conditions is observed at relatively high temperature of 77K. The ground states of quantum dots are found to be at ~0.19eV below the conduction band of GaAs matrix. The theoretical computations are in conformity with experimental data.

cond-mat.mes-hall↗
arXiv2007

Research progress of electronic properties of self-assembled semiconductor quantum dots

Self-assembled semiconductor quantum dot is a new type of artificially designed and grown function material which exhibits quantum size effect, quantum interference effect, surface effect, quantum tunneling-Coulumb-blockade effect and nonlinear optical effect. Due to advantages like less crystal defects and relatively simpler fabrication technology, that material may be of important value in future nanoelectronic device researches. In the order of vertical transport, lateral transport and charge storage, this paper gives a brief introduction of recent advances in the electronic properties of that material and an analysis of problems and perspectives.

cond-mat.mes-hall↗
arXiv2002

Vortex avalanches and self organized criticality in superconducting niobium

In 1993 Tang proposed [1] that vortex avalanches should produce a self organized critical state in superconductors, but conclusive evidence for this has heretofore been lacking. In the present paper, we report extensive micro-Hall probe data from the vortex dynamics in superconducting niobium, where a broad distribution of avalanche sizes scaling as a power-law for more than two decades is found. The measurements are combined with magneto-optical imaging, and show that over a widely varying magnetic landscape the scaling behaviour does not change, hence establishing that the dynamics of superconducting vortices is a SOC phenomenon.

cond-mat.supr-con↗