- 标题
- 摘要
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- 实验方案
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Heart rate estimation using remote photoplethysmography with multi-objective optimization
摘要： Remote photoplethysmography (rPPG) is being increasingly used to measure heart rate from recorded or live videos. The rhythmic flow of arterial blood, referred to as the blood volume pulse, results in periodic variations in the skin color which are then quantified into a temporal signal for analysis. Independent Component Analysis (ICA) has been used to extract the blood volume pulse which is assumed to have been mixed into the RGB channels of the skin pixels. We propose a novel semi-blind source extraction method for measuring rPPG using a multi-objective optimization approach with autocorrelation as a periodicity measure. Our method was tested on our inhouse video database UBFC-RPPG and the MMSE-HR database [33]. Our in-house database is made publicly available and is specifically aimed towards testing rPPG measurements. Our method showed improved performance over other state of the art rPPG algorithms in terms of accuracy with all the databases.
关键词： Semi-blind source separation,Remote heart rate measurement,Constrained Independent Component Analysis,Multi-objective optimization,Independent Component Analysis,Remote photoplethysmography
更新于2025-09-10 09:29:36
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Dual-Input Single-Resonant Tank LLC Converter with Phase Shift Control for PV Applications
摘要： This paper proposes a dual-input LLC resonant converter that interfaces with two PV panels. The topology is a dual half-bridge LLC circuit with four active switches. This topology allows the two sources to share the same resonant tank for transferring energy to the load without the need for additional circuit components. A phase-shift pulse width modulation independent maximum power point tracking (MPPT) for each PV panel. Independent MPPT is achieved by varying the PWM phase shift of each source. Zero-voltage-switching (ZVS) is realized in all switches over the entire range of source voltage and load conditions. In addition, voltage stress across switches does not exceed the input PV voltage. A 500-W prototype was built to demonstrate the performance of the proposed topology. The input voltage range was selected between 25 V to 50 V with an output voltage regulated at 220 V DC. Experimental results show that the proposed converter can achieve the peak efficiency of 95.8% while maintaining a wide input voltage range and implementing MPPT for each PV panel.
关键词： dual-input LLC,DC gain analysis,independent MPPT,PWM phase shift,LLC resonant converter
更新于2025-09-10 09:29:36
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Embossing Reactive Mesogens: A Facile Approach to Polarization-Independent Liquid Crystal Devices
摘要： Reactive mesogens (RMs) are used in a wide variety of applications, from retardation plates for organic light-emitting display screens, liquid crystal phase stabilization, optical or electrically active elastomers to novel optic components. They can be processed as standard liquid crystals and subsequently polymerized to stabilize both shape and anisotropic properties. However, creating complex shapes while maintaining good alignment of the RM optical axis can be a challenge. In the present work, embossing is used to replicate a wide variety of RM structures in several electro-optic devices. A novel device geometry is proposed where a polarization-independent lens is formed by opposing birefringent Fresnel zone plates embossed in aligned RM. The RM forms the optical elements and alignment layers for an index-matched liquid crystal, arranged to produce the twisted nematic configuration. Low voltages switch the device between nonfocusing and focusing states. After characterizing lens efficiency and beam properties, the method is used to fabricate a switchable multilevel Fresnel zone plate with optical efficiencies beyond 50%, and theoretically able to produce polarization-independent lenses with efficiencies approaching 100% from a single structure. Finally, manufactured polarization-independent gratings and microlens arrays are presented using the method to illustrate the wide range of applicability.
关键词： liquid crystals,embossing,reactive mesogens,polarization-independent devices
更新于2025-09-10 09:29:36
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Polarization-independent and super broadband flat lens composed of graded index annular photonic crystals
摘要： In this paper, we propose two types of all-dielectric polarization-independent graded index annular flat lens with a wide operating frequency range. The lenses are composed of two-dimensional triangular and square lattice photonic crystals with circular silica (SiO2) rods in the air. We assume in both square and triangular structures, the lenses are obtained by making air holes within each dielectric rod and we consider that the outer radius of the created annular rods are maintained constant while the size of the inner air holes varies along the transverse direction whose the air holes variation follow linear and parabolic function. The graded structures are made in such a way that the modulus of the refractive index is biggest at the center and decreases toward the edges. The optical properties and the physical background of the polarization-independent focusing mechanism are studied in frequency and spatial domains, using plane wave expansion and finite-difference time-domain methods. Our numerical results show that, through an appropriate set of design, the deigned lenses are able to focus the light regardless of polarization for a wide frequency range into approximately same focal length in which difference between focal distance of TE and TM polarization modes stays below λ/4. Compared to previously polarization-independent designed photonic crystal based lenses, our proposed structures work under much wider frequency range. Also, in contrast with most of the graded structures, our graded lens are made without altering the lattice constant along optical axis or transverse to optical axis. Moreover, the design approach is restricted to use of silica and non-use of more complicate materials such as liquid crystals, plasma, and the like. Thus, the designed systems can be constructed easier relative to the previously designed lenses.
关键词： Graded index annular photonic crystals,Optical beam focusing,broadband frequency lens,Polarization-independent lens
更新于2025-09-10 09:29:36
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Reduced Graphene Oxide Membrane induced Robust Structural Colors towards Personal Thermal Management
摘要： Angle-independent structural colors are prepared by membrane separation-assisted assembly (MSAA) method with modified reduced graphene oxide (rGO) as the substrate membrane. We show that the wrinkled and crumpled rGO laminates not only ensure uneven morphology of colloidal film but improve color saturation by decreasing coherent scattering. In addition, we study the influence of stopband position on thermal insulation property of the colloidal film for the first time. High absolute temperature difference of 6.9 oC is achieved comparing with control sample. And films with longer stopband positions indicate better thermal insulation performance because of inherent slow photon effect in photonic structure. This general principle of thermal insulation by colloidal films opens the way to new generation of thermal management materials.
关键词： angle-independent,thermal management,human body cooling,graphene,structural color
更新于2025-09-10 09:29:36
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Two dimensional sinusoidal Ag nanograting exhibits polarization-independent surface-enhanced Raman spectroscopy and its surface plasmon polariton and localized surface plasmon coupling with Au nanospheres colloids
摘要： A reproducible surface‐enhanced Raman scattering (SERS) substrate based on two dimensional (2D) sinusoidal Ag nanograting is presented. This SERS substrate with large area can be easily fabricated by maskless laser interference photolithography. The potential SERS polarization‐independent performance of 2D sinusoidal Ag nanograting is deduced by finite difference time domain and demonstrated by SERS detection experiments. A double‐enhanced Raman scattering (DERS) substrate by coupling 2D sinusoidal Ag nanograting with Au nanospheres colloids is created. With the optimal DERS substrate, SERS enhancement factor can be 10 orders of magnitude as possible. The DERS substrate was fabricated and an extra SERS effect was proved by experiments. This DERS substrate will be fabricated in a microfluidics‐based sensor in the next work and used for in situ, real‐time, continuous monitoring of trace water soluble gas‐phase or airborne agents, such as trace explosives in air.
关键词： surface plasmon polaritons,surface enhanced Raman scattering,localized surface plasmons,two dimensional sinusoidal nanograting,polarization‐independent
更新于2025-09-10 09:29:36
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On independent resolving number of TiO 2 [m, n] nanotubes
摘要： Let G(V, E) be a Graph. A set W ? V of vertices resolves a graph G if every vertex of G is uniquely determined by its vector of distances to the vertices in W. The metric dimension of G is the minimum cardinality of a resolving set. By imposing different conditions on W we get conditional resolving sets. A resolving set W is said to be an independent resolving set if W contains isolated vertices. Independent resolving number denoted by ir(G) is referred to its cardinality. In this paper we investigate independent resolving number for Titanium dioxide Nanotube.
关键词： independent resolving number,Metric dimension,Titanium dioxide,Nanotube,independent resolving set,Nanostructure
更新于2025-09-09 09:28:46
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High-dimensional measurement-device-independent quantum key distribution on two-dimensional subspaces
摘要： Quantum key distribution (QKD) provides ultimate cryptographic security based on the laws of quantum mechanics. For point-to-point QKD protocols, the security of the generated key is compromised by detector side channel attacks. This problem can be solved with measurement-device-independent QKD (mdi-QKD). However, mdi-QKD has shown limited performances in terms of the secret key generation rate, due to postselection in the Bell measurements. We show that high-dimensional (Hi-D) encoding (qudits) improves the performance of current mdi-QKD implementations. The scheme is proven to be unconditionally secure even for weak coherent pulses with decoy states, while the secret key rate is derived in the single-photon case. Our analysis includes phase errors, imperfect sources, and dark counts to mimic real systems. Compared to the standard bidimensional case, we show an improvement in the key generation rate.
关键词： Quantum key distribution,High-dimensional encoding,Measurement-device-independent QKD,Qudits,Cryptographic security
更新于2025-09-09 09:28:46
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Device-independent witness of arbitrary-dimensional quantum systems employing binary-outcome measurements
摘要： Device-independent dimension witnesses (DWs) are a remarkable way to test the dimension of a quantum system in a prepare-and-measure scenario imposing minimal assumptions on the internal features of the devices. However, as the dimension increases, the major obstacle in the realization of DWs arises due to the requirement of many-outcome quantum measurements. In this article we propose a variant of a widely studied communication task (random access code) and take its average payoff as the DW. The presented DW applies to arbitrarily large quantum systems employing only binary-outcome measurements.
关键词： device-independent dimension witnesses,binary-outcome measurements,quantum systems,random access code
更新于2025-09-09 09:28:46
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Self-testing using only marginal information
摘要： The partial states of a multipartite quantum state may carry a lot of information: in some cases, they determine the global state uniquely. This result is known for tomographic information, that is for fully characterized measurements. We extend it to the device-independent framework by exhibiting sets of two-party correlations that self-test pure three-qubit states.
关键词： multipartite,correlations,quantum state,device-independent,self-testing
更新于2025-09-09 09:28:46