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Cuff-less continuous measurement of blood pressure using wrist and fingertip photo-plethysmograms: Evaluation and feature analysis
摘要： Continuous monitoring of blood pressure improves prevention and control of cardiovascular diseases. Currently, cuff-based oscillometric sphygmomanometers are commonly used to monitor the systolic and diastolic blood pressure. However, this technique is discontinuous in nature and inconvenient for repeated measurements. Here we have proposed indirect measurement of blood pressure from photo-plethysmograms (PPG) simultaneously recorded from wrist and fingertip. The signals were recorded from 111 participants and different morphological features were obtained from PPG and its second derivative, acceleration plethysmograms (APG). Moreover, different measures of pulse transit time (PTT) and pulse wave velocity (PWV) were obtained from the recorded PPGs. Multi-layer Neural Networks were used to estimate the non-linear relationship between these features and systolic and diastolic blood pressures (SBP and DBP). Mean absolute errors of 6.77 and 4.82 mmHg were achieved in comparison with measurements from a validated commercial oscillometric sphygmomanometer. Feature analysis provided insight about the importance of features for estimating BP, and demonstrated that these features are not the same for SBP and DBP. Using the highest-ranked 15 and 13 features obtained from moving-backward algorithm the mean absolute errors were reduced to 5.31 and 4.62 mmHg for SBP and DBP. However, the optimum optimal feature sets provided by a genetic algorithm for estimating SBP/DBP led to the lowest mean absolute errors of 4.94/4.03. These results compared to previous studies and the available standards suggest that the method is a promising substitute for oscillometric sphygmomanometers which can be used conveniently for continuous monitoring of blood pressure.
关键词： Genetic algorithms,Non-obstructive blood pressure measurement,Multi-layer neural networks,Photo-plethysmography
更新于2025-09-23 15:23:52
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Preparation and optical properties of angle-dependent photonic crystals based on multi-layer films
摘要： The CreSiO2 photonic crystals, featured with two-dimensional structure and optical variation, was prepared by magnetron sputtering and electron beam lithography method. The finite difference time domain method (FDTD) is used to study the light-modulated characteristics of photonic crystals. Hue difference (⊿H) was used to evaluate the optical variations of photonic crystals, and bigger ⊿H indicates stronger angle dependency of color variation. Various parameters are analyzed for their impact upon ⊿H, including hole geometry (radium, r), hole gap (distance between the centers of two circles, d) and hole depth (h). The results matched the ones from simulation. Carbon quantum dots and up-conversion nanocrystals NaYF4 were inserted into the photonic crystals, and testing results of these doped crystals showed optical variation of fluorescence in the UV and IR region.
关键词： Finite difference time domain,Multi-layer films,Photonic crystal,Optical variability
更新于2025-09-23 15:23:52
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Theoretical studies on the mechanical and electronic properties of 2D and 3D structures of Beryllium-Oxide graphene and graphene nanobud
摘要： In the present study, ab initio-based density functional theory (DFT) calculations were used to determine the effects of certain phenomena that can occur in the synthesis of Beryllium-Oxide (BeO) few-layer sheets, such as various types of defects, attaching nanocages onto the surface of graphene and attaching layers to each side of it on the mechanical and electronic properties of BeO graphene sheets. We also used the density of states (DOS) calculations to obtain a better understanding of the electronic properties of the studied nanostructures. In the first step, we calculated Young’s modulus for the pristine BeO graphene sheet that was found to be equal to 1.110 TPa. Next, the effect of small and large defects on the mechanical properties of the BeO graphene-like structure was examined, and we found that extracting one Be atom resulted in a lower Young’s modulus compared to that obtained after extracting one oxygen atom (1.087 TPa versus 1.104 TPa), demonstrating that Be had a greater effect on the stability and mechanical strength of BeO graphene than did oxygen. The same trend was found when comparing three atom vacancies with two missing Be atoms to those with two missing oxygen atoms. Furthermore, the effect of circular and rectangular shape defects was investigated, and the obtained results demonstrated that the increase in the diameter of defects with both shapes significantly decreased Young’s modulus and band gap energy values. Additionally, due to the number of detached atoms in shape defects which are more than those of small defects, this type of defect had a more destructive effect on the structure’s stability so that it decreased the Young’s modulus more than small defects. Moreover, the mechanical properties of the BeO graphene nanobud structure were determined in terms of placing different numbers of Be12O12 nanocages onto the graphene surface, and a similar decreasing trend was observed for Young’s modulus. Finally, we considered the mechanical properties of the bi- and three-layer BeO graphene-like structures and found that increasing the number of layers reduced Young’s modulus slightly. For both of the latter phenomena of attaching nanocages and layers, the band gap energy decreased.
关键词： BeO Graphene,Multi-layer,DFT,Defect,Young’s Modulus,Graphene Nanobud
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE International Workshop on Electromagnetics: Applications and Student Innovation Competition (iWEM) - Nagoya (2018.8.29-2018.8.31)] 2018 IEEE International Workshop on Electromagnetics:Applications and Student Innovation Competition (iWEM) - E-Plane Beam-Forming Performance of Rotman-Lens in Multi-Layer Substrate
摘要： A two-dimensional Rotman-lens feeding circuit was proposed for planar two-dimensional multi-beam antenna using multi-layer substrate integrated waveguide in the millimeter-wave band. In this work, an E-plane Rotman-lens for two-dimensional Rotman-lens was designed and the E-plane beam-forming performance was evaluated by array factors from the simulated S-parameters.
关键词： multi-beam antenna,feeding circuit,multi-layer substrate,millimeter-wave,Rotman-lens
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE 10th Sensor Array and Multichannel Signal Processing Workshop (SAM) - Sheffield (2018.7.8-2018.7.11)] 2018 IEEE 10th Sensor Array and Multichannel Signal Processing Workshop (SAM) - Multi-Layer Terahertz Imaging of Non-Overlapping Contents
摘要： This paper considers terahertz (THz) imaging of multi-layer non-overlapping contents with compressed measurements. One issue here is the shadow effect from front layers to deep layers due to the non-uniform penetrating illumination. In the case of non-overlapping contents in layered structures, the shadow effect can be utilized to improve recovery performance and reduce the number of measurements. To this end, we propose several approaches based on the total variation (TV) minimization principle and take into account individual-layer sparsity, group sparsity over layers, and hierarchical group sparsity over layers to reduce the number of measurements. Numerical evaluation confirms the effectiveness of the proposed approaches.
关键词： compressed measurements,content extraction,Terahertz,multi-layer structure
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE 13th Annual International Conference on Nano/Micro Engineered and Molecular Systems (NEMS) - Singapore, Singapore (2018.4.22-2018.4.26)] 2018 IEEE 13th Annual International Conference on Nano/Micro Engineered and Molecular Systems (NEMS) - Temperature Sensor Based on Multimode Fiber Bragg Grating
摘要： A multi-layer film fiber Bragg grating (FBG) is used for high temperature measurement. In order to realize the temperature measurement in a wide dynamic range, a multi-layer film fiber Bragg grating (MFBG) is fabricated. Due to its multi-layer structure, the MFBG has been widely studied extensively for temperature measurement. Most of its operation principle is based on the variation analysis of the spectrum caused by temperature change. For measuring temperature, fiber Bragg grating (FBG) temperature sensor has been widely used due to its advantages of good insulation, light weight, low cost, compact structure, chemical property and ability to sense in harsh environment. However, the FBG has been widely studied extensively for temperature measurement. Most of its operation principle is based on the variation analysis of the spectrum caused by temperature change. For measuring temperature, fiber Bragg grating (FBG) temperature sensor has been widely used due to its advantages of good insulation, light weight, low cost, compact structure, chemical property and ability to sense in harsh environment. However, the FBG is difficult to couple with other optical devices, the MFBG has been used to measure the ambient temperature. In order to realize the temperature measurement in a wide dynamic range, a multi-layer film fiber Bragg grating (MFBG) is fabricated. Due to its multi-layer structure, the MFBG has been widely studied extensively for temperature measurement. The working principle is discussed and different reflection peaks are separated from the transmission spectrum. The experimental results show that the temperature response at different peaks is similar, and the optical fiber sensor has a great potential for temperature measurement.
关键词： fiber Bragg grating,multi-layer film,optical fiber sensor,temperature sensor
更新于2025-09-23 15:22:29
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Efficient method to calculate the optical quantities of multi-layer systems with randomly rough boundaries using the Rayleigh-Rice theory
摘要： An efficient and numerically stable method for calculating the optical quantities of multi-layer systems with slightly rough boundaries using the second order Rayleigh–Rice theory is developed. It is assumed that the mean planes of the boundaries are parallel and all the media forming the system are nonmagnetic, isotropic and homogeneous. The perturbation series is formulated using the four-dimensional formalism inspired by the Yeh matrix formalism, but the final result is written using the two-dimensional formalism which is more efficient for the numerical calculations. The final formulae, which are expressed using an arbitrary power spectral density function, include the mixing between the p and s polarizations occurring for anisotropic roughness. Although in the general case the calculation of optical quantities requires evaluation of double integrals, it is shown that for the power spectral density function given by the isotropic Gaussian function some integrals can be calculated analytically and only single integrals have to be evaluated numerically. The random roughness of boundaries is a defect that occurs frequently in practice, and it must be taken into account in the optical characterization and synthesis of thin film systems exhibiting this defect. The presented method is suitable for these purposes, since both of the mentioned applications require methods that are very fast.
关键词： multi-layer systems,optical quantities,Rayleigh–Rice theory,random boundary roughness
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - An Optimized Ultrathin and Broadband Metamaterial Absorber Using Slotted Square Loop with Multi Layers
摘要： An optimized ultrathin and broadband absorber is proposed in this paper. It is composed of a periodic array of slotted square loop-dielectric multilayered structure. The bottom layer consists of one dielectric with edge-overlapped slotted square metal loop on it. The simulated results indicate that the absorption at normal incidence is above 90% in almost the whole frequency range of 6.25-18GHz. Moreover, the designed absorber is ultrathin with a thickness of only 0.13-0.38 free-space wavelength at the lowest and highest frequencies, respectively.
关键词： broadband absorber,slotted square loop,Metamaterial,anti-reflection,multi-layer
更新于2025-09-23 15:22:29
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Transparent colored display enabled by flat glass waveguide and nanoimprinted multi-layer gratings
摘要： In this paper, a type of transparent colored static display consisting of a flat glass waveguide and embedded multi-layer gratings is presented, by which multiple patterns and colors with a wide field of view (FOV) can be displayed. The embedded grating is achieved by nanoimprinting followed by deposition of a high refractive index dielectric layer. The process can be repeated to produce multi-layer gratings, which are shaped into specific patterns to be displayed, and they are designed to have proper periods and orientations to independently extract light incident from different edges of the glass plate. Such transparent display offers the advantages of low cost, easy fabrication and wide FOV, and it is suitable for colored signage and decorative applications.
关键词： multi-layer gratings,transparent display,waveguide display,nanoimprint lithography,multi-color display
更新于2025-09-23 15:21:01
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Integration of RF rectenna with thin film solar cell to power wearable electronics
摘要： This paper reports an integration of dual band microstrip antenna with thin film amorphous silicon solar cell which creates a wearable system to harvest microwave energy. The multiple layers in the encapsulation of the thin film solar cell are used as a substrate for microstrip antenna. The rectifier and matching circuit are designed on cotton jeans material and the whole system is mechanically supported by the foam of 5 mm thick. The performance of the antenna is studied for the mechanical bending condition. The device has maintained good power conversion efficiency. The efficiency of the voltage doubler is tested by varying radio frequency power levels from ?30 to10 dBm. The voltage doubler conversion efficiency at 1.85 and 2.45 GHz are 58 and 43%, respectively, for a load of 7.5 kΩ for an input power level of ?5 dBm.
关键词： solar cell,ring antenna,multi-layer,wearable,flexible substrate,Dual band
更新于2025-09-23 15:21:01