Previous work has demonstrated modulated imaging with binary masks. We present a new microscope that provides continuous modulation with a spatial light modulator, which can modulate through multiple methods: amplitud...
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Graphene has attracted an explosion of interest for photonic applications as it provides a degree of freedom to manipulate electromagnetic waves. In this work, we propose a new one-dimensional system composed of multi...
Graphene has attracted an explosion of interest for photonic applications as it provides a degree of freedom to manipulate electromagnetic waves. In this work, we propose a new one-dimensional system composed of multiple graphene and hexagonal boron nitride (hBN) with varying aperiodic thicknesses in between the graphene layers. A hybrid optimization method, consisting of a micro-genetic global optimization algorithm coupled to a local optimization algorithm, indicates that absorption efficiency close to 100% can be achieved at very narrow frequency range under normal incidence. This efficiency can be significantly decreased by tuning the chemical potential and the corresponding carrier density in graphene. It thus enables a promising way to design electrically controllable thermal emitter. Fig. 1(a) shows the proposed device structure composed of 23 graphene layers and 22 alternating layers of hexagonal boron nitride (hBN) insulator, which sandwiches between two thick silicon carbide (SiC) layers. The hBN has two-dimensional atomic structure similar to graphene and has been proposed as its promising complementary insulator layer. The ambient temperature of 873 K is assumed, in which the semi-infinite tungsten substrate creates the thermal emission of black body radiation with maximum emission at infrared range. Since the tungsten substrate is taken to be semi-infinite, the transmittance is identically zero (Absorption = 1-Reflection) and the calculated absorption can be equated to emittance because of Kirchhoff's second law and conservation of energy. The Kubo formula is used to extract the optical conductivity and consequently the refractive index of graphene while the experimental data is used for the wavelength-dependent indices of refraction of other materials. Fig. 1(b) shows the normalized power radiated per unit area and unit wavelength by the structure. In order to find the optimized structure with narrowband thermal emittance, the chemical potential initia
A vibration isolation system called Type-Bp system used for power recycling mirrors has been developed for KAGRA, the interferometric gravitational-wave observatory in Japan. A suspension of the Type-Bp system passive...
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controlling the magnetic anisotropy in epitaxial Y3Fe5O12 (YIG) thin films is critical for magnonic and photonic device applications. In this paper, we report the crystal structure, magnetic properties, and magnetic a...
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controlling the magnetic anisotropy in epitaxial Y3Fe5O12 (YIG) thin films is critical for magnonic and photonic device applications. In this paper, we report the crystal structure, magnetic properties, and magnetic anisotropy of epitaxial Y3(Fe5−xMnx)O12 (Mn:YIG) thin films grown on Gd3Ga5O12 (111) (GGG) substrates by pulsed-laser deposition. Mn doping is observed to strongly enhance the magnetoelastic coefficient of YIG thin films, which leads to large tunability of the thin film magnetic anisotropy by lattice strain. With increasing Mn concentration from x=0 to x=1.25, a continuous increase of out-of-plane magnetic anisotropy ranging from −644.4 Oe to 1337.5 Oe is observed. In particular, a perpendicular magnetic anisotropy (PMA) is achieved in Mn:YIG thin films with a high Mn concentration of x=1.12. Ferromagnetic resonance (FMR) measurements show low FMR linewidths of 3.4 Oe to 129 Oe at 9.5 GHz in Mn:YIG thin films. Our paper demonstrates manganese doping as an effective way to enhance the magnetoelastic anisotropy of YIG thin films by strain, which is useful for magnonic and magneto-optical device applications.
An adaptive decentralized strategy for active queue management of TCP flows over communication networks is presented. The proposed strategy solves locally, at each link, an optimal control problem, minimizing a cost c...
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ISBN:
(纸本)9781467386838
An adaptive decentralized strategy for active queue management of TCP flows over communication networks is presented. The proposed strategy solves locally, at each link, an optimal control problem, minimizing a cost composed of residual capacity and buffer queue size. The solution of the optimal control problem exploits an adaptive optimization algorithm aiming at adaptively minimizing a suitable approximation of the Hamilton-Jacobi-Bellman equation associated with the optimal control problem. Simulations results, obtained by using a fluid flow based model of the communication network and a common network topology, show improvement with respect to the Random Early Detection strategy. Besides, it is shown that the performance of the proposed decentralized solution is comparable with the performance obtained with a centralized strategy, which solves the optimal control problem via a central unit that maintains the flow states of the entire network.
A fully homomorphic encryption system hides data from unauthorized parties, while still allowing them to perform computations on the encrypted data. Aside from the straightforward benefit of allowing users to delegate...
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The paper presents a new bridgeless Power Factor Correction (PFC) topology, using a recently proposed controllable LCL filter, namely Active Virtual Ground (AVG) to achieve efficient power conversion and high frequenc...
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ISBN:
(纸本)9781509007387
The paper presents a new bridgeless Power Factor Correction (PFC) topology, using a recently proposed controllable LCL filter, namely Active Virtual Ground (AVG) to achieve efficient power conversion and high frequency (HF) common mode voltage (CM) reduction. The proposed PFC circuit consists of high frequency semiconductors for shaping inductor current, and low frequency semiconductors to form two different LCL structures for different conditions. This reduces grid differential mode (DM) current ripple or inductance. Besides, the PFC CM voltage, a main problem of bridgeless PFCs, is significantly reduced, since the capacitor in the LCL filter clamps the voltage between the grid and the converter ground. The performance of the proposed PFC is experimentally verified. The results show that the proposed PFC guarantees sinusoidal input current, low high frequency common-mode voltage noise and has a good agreement with the theoretical findings.
In this paper, we analyze the L2-gain of sampled-data systems with asynchronous sensing and control. The closed-loop system has time-varying clock offsets and sampling intervals and can be modeled as a parameter-uncer...
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ISBN:
(纸本)9781467386838
In this paper, we analyze the L2-gain of sampled-data systems with asynchronous sensing and control. The closed-loop system has time-varying clock offsets and sampling intervals and can be modeled as a parameter-uncertain system. We use a lifting approach and a gridding and norm-bounded approach in order to analyze intersample behavior and deal with parameter uncertainty, respectively. An upper bound on the L~2-gain is derived via linear matrix inequalities. We illustrate the proposed method by applying it to an active suspension system.
The ranging and positioning accuracy of an impulse radio (IR) 60 GHz system is investigated. The corresponding Cramér-Rao lower bound (CRLB) over an additive white Gaussian noise (AWGN) channel is analyzed. The s...
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ISBN:
(纸本)9781509006915
The ranging and positioning accuracy of an impulse radio (IR) 60 GHz system is investigated. The corresponding Cramér-Rao lower bound (CRLB) over an additive white Gaussian noise (AWGN) channel is analyzed. The signal parameters which may affect the accuracy are examined. Performance results over AWGN and indoor residential channels are presented. In particular, the indoor residential channel models recommended by the IEEE 802.15.3c task group are employed. The theoretical and simulation results obtained show that the IR 60 GHz system can achieve millimeter accuracy in residential line-of-sight (LOS) environments even with a low signal-to-noise ratio (SNR) of 5 dB. For a residential non-line-of-sight (NLOS) environment with the same SNR, centimeter accuracy can be obtained.
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