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- 摘要
- 关键词
- 实验方案
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<i>In vivo</i> detection of endotracheal tube biofilms in intubated critical care patients using catheter-based optical coherence tomography
摘要： The formation of biofilms in the endotracheal tubes (ETTs) of intubated patients on mechanical ventilation is associated with a greater risk of ventilator-associated pneumonia (VAP) and death. New technologies are needed to detect and monitor ETTs in vivo for the presence of these biofilms. Longitudinal OCT imaging was performed in mechanically ventilated subjects at 24 hr intervals until extubation to detect the formation and temporal changes of in vivo ETT biofilms. OCT-derived attenuation coefficient images were used to differentiate between mucus and biofilm. Extubated ETTs were examined with optical and electron microscopy, and all imaging results were correlated with standard-of-care clinical test reports. OCT and attenuation coefficient images from 4 subjects were positive for ETT biofilms and were negative for 2 subjects. The processed and stained extubated ETTs and clinical reports confirmed the presence/absence of biofilms in all subjects. Our findings confirm that OCT can detect and differentiate between biofilm-positive and biofilm-negative groups (p < 10-5). OCT image-based features may serve as biomarkers for direct in vivo detection of ETT biofilms and help drive investigation of new management strategies to reduce the incidence of VAP.
关键词： attenuation coefficient image,endotracheal tube,biofilm,optical coherence tomography,ventilator-associated pneumonia
更新于2025-11-21 11:24:58
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[IEEE 2019 International Conference on Advances in Computing and Communication Engineering (ICACCE) - Sathyamangalam, Tamil Nadu, India (2019.4.4-2019.4.6)] 2019 International Conference on Advances in Computing and Communication Engineering (ICACCE) - Estimation of maximum range for underwater optical communication using PIN and avalanche photodetectors
摘要： This paper presents an estimate of underwater optical communication (UWOC) range, using PIN and avalanche photodetectors (APDs). In this simulation-based study, the maximum range while transmitting high-quality video at 6Mbps speed is estimated as 520m in Pure Sea water, 65m in Clear Ocean and 44m in Coastal waters, when using a 100mW laser and APD. The channel here is modeled to include the effect of attenuation and noise. This work quantifies the benefits of using an adaptive system where the wavelength (blue, blue-green and green) of transmission and modulation scheme is changed based on water transmission. Wavelength adaptation according to varying water transmission was found to provide 16 to 40dB advantage in SNR, compared to a system with fixed wavelength, in different waters. A recommendation for wavelength adaptable transmitter design is made based on this. This study assumes the current state of the art in commercially available components.
关键词： Laser,photodetector,underwater communication,range,attenuation
更新于2025-11-14 15:24:45
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[IEEE 2018 International Conference on Intelligent and Innovative Computing Applications (ICONIC) - Mon Tresor, Plaine Magnien, Mauritius (2018.12.6-2018.12.7)] 2018 International Conference on Intelligent and Innovative Computing Applications (ICONIC) - Climatic Effects on Free Space Optics Link: South African Climate
摘要： The growth in demand of high data rate, reliable quality of service, low cost technology and secured connectivity have been telecommunication users' concerns. Free Space Optics (FSO) is the best choice for meeting these demands as it offers data rates in Gbps with the most secure communication because light beam is prone to eavesdropping. However, usage of FSO as a communication link relies upon local weather condition. Atmospheric attenuation of fog, rain and snow are the most limitation of free space optic availability, as they lead to the diminution of limited available bandwidth. This paper investigated the link performance under climatic conditions such as fog, rain and snow by at various wavelengths of 650nm, 750nm, 850nm, 950nm and 1550nm. It is further deals with FSO performance targeting to acquire minimal Bit Error Rate (BER), suitable transmitting power, optimum link margin and reliable data transmission rate at maximum link distance of 1km. The studies observed that received power signal and the link distance have an inverse correlation because once the signal reaches to an extended distance; it faces greater climatic attenuation due to scattering and absorption lessening.
关键词： communication link,Free space optics,atmospheric attenuation,light beam,bit error rate
更新于2025-09-23 15:22:29
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[IEEE 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Atlanta, GA (2017.10.21-2017.10.28)] 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Joint Reconstruction of PET Attenuation and Activity from Scattered and Unscattered Data
摘要： In previous work, we have proposed scatter-to-attenuation reconstruction for positron emission tomography (PET). Scatter-to-attenuation reconstruction aims at recovering object attenuation information in the form of spatial electron-density distributions from pairs of coincident photons, one of which has been single-scattered. One idea is to interleave scatter-to-attenuation reconstruction, which inputs an activity distribution and outputs an attenuation map, with trues-to-activity reconstruction, which inputs said attenuation map and outputs an improved activity distribution. However, major uncertainties regarding the applicability of this approach revolve around a) the unknown impact of the initial activity estimate; b) evaluation of reconstructed activity distributions, and c) convergence to the correct solution. Methods: Using low-dimensional simulated PET data (mouse-sized, 18x18-voxels phantom), we start with mostly uniform initial activity and attenuation estimates and iteratively apply maximum-likelihood expectation-maximization (MLEM) and a maximum-likelihood gradient-ascent (MLGA) algorithm to update activity (from unscattered data) and attenuation (from scattered data), respectively. We evaluate results in terms of log-likelihoods of the expected scatter histograms, and normalized mean squared errors with respect to reference image-space distributions of activity and attenuation. Results: In our study, both attenuation and activity converged to the reference distributions, despite MLEM and MLGA starting with incorrect attenuation and activity estimates, respectively. Conclusion: The MLGA scatter-to-attenuation reconstruction algorithm, in combination with MLEM trues-to-activity reconstruction, jointly reconstructs attenuation maps and attenuation-corrected activity distributions from scattered and unscattered coincidences without reliance on a-priori information about the activity distribution.
关键词： image reconstruction,PET,attenuation,Compton scattering,algorithms
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Radar (RADAR) - Brisbane, Australia (2018.8.27-2018.8.31)] 2018 International Conference on Radar (RADAR) - Low-THz Wave Snow Attenuation
摘要： This paper assesses the attenuation of Low-THz waves through various intensities of snowfall experimentally at 300 GHz, and is characterized by measuring the ratio of the received power from the target through the snow precipitation and through the same path with no precipitation. Higher attenuation is measured at higher snowfall rate. Snow events are categorized as "dry snow" and "wet snow". The comparison between the measured attenuation through wet and dry snowfall shows larger attenuation is expected through wet snowfall compared to the same snowfall rate of dry snow. This study is fundamentally important to investigate the effect of adverse weather condition on Low-THz waves and to assess their feasibility for outdoor applications.
关键词： snowfall,specific attenuation,Low-THz wave
更新于2025-09-23 15:22:29
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A linear state space model for photoacoustic imaging in an acoustic attenuating media
摘要： In photoacoustic imaging, ultrasound waves generated by a temperature rise after illumination of light absorbing structures are measured on the sample surface. These measurements are then used to reconstruct the optical absorption. We develop a method for reconstructing the absorption inside the sample based on a discrete linear state space reformulation of a partial differential equation that describes the propagation of the ultrasound waves. Fundamental properties of the corresponding state space model such as stability, observability and controllability are also analyzed. By using Stokes’ equation, the frequency dependent attenuation of the ultrasound waves is incorporated into our model, therefore the proposed method is of general nature. This approach allows for inhomogeneous probes with arbitrary absorption profiles and it accounts for the decrease in laser intensity due to absorption. Furthermore, it provides a method for optimizing the laser modulation signal such that the accuracy of the estimated absorption profile is maximized. Utilizing the optimized laser modulation signal yields an increase in reconstruction accuracy compared to short laser pulses as well as chirp modulation in many scenarios.
关键词： optimal temporal laser excitation,photoacoustic image reconstruction,acoustic attenuation,linear state space model
更新于2025-09-23 15:22:29
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Love-type waves in a piezoelectric-viscoelastic bimaterial composite structure due to an impulsive point source
摘要： The analysis of wave propagation phenomenon piezoelectric-viscoelastic composites still remains an unexplored field of research. The usage of a passive polymer (Epoxy) with active piezoelectric ceramic causes viscoelasticity in the piezoelectric material which results into a piezoelectric-viscoelastic composite. The present study aims to analyze the propagation behavior of Love-type wave in an exponentially graded piezoelectric-viscoelastic material (EGPVM) stratum lying over a functionally graded piezoelectric-viscoelastic material (FGPVM) substrate due to an impulsive point source at its interfacial surface. The electro-visco-mechanical field equations are laid down for the piezoelectric-viscoelastic medium.The analytical solution procedure involves the use of suitable Green’s function and admissible boundary conditions. The established frequency equation is in complex form; of which the real expression imparts the frequency curve and imaginary expression gives the attenuation curve of Love-type wave. To depict the results numerically, two distinct piezoelectric-viscoelastic materials (Epoxy-BNKLBTand Epoxy-KNLNTSceramics) for EGPVM stratum and FGPVM substrate are taken into account.The phase velocity profile and attenuation coefficient profile of Love-type wave is portrayed graphically. Diagnostic results are simulated numerically which forefronts the effect of distinct parameters. The study manifests the impact of the material medium parameters, viz. piezoelectric constants, dielectric constants, piezoelectric loss moduli, dielectric loss moduli, exponential gradient parameter and magnifying gradient parameters on the phase velocity and attenuation coefficient of Love-type wave. For sake of validation, the obtained results are matched with the classical one, as a special case of the problem. The outcomes of the study may find its worth in better and optimum design of surface acoustic wave devices and Love wave sensors, keeping efficiency at its premium.
关键词： Piezoelectric-viscoelastic,damping equation,frequency equation,point source,Green’s function,attenuation coefficient.
更新于2025-09-23 15:22:29
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An investigation on shielding properties of BaO, MoO3 and P2O5 based glasses using MCNPX code
摘要： In the present work, some radiation shielding quantities (mass attenuation coefficients, effective atomic number, effective electron density, half value layer and mean free path) for various BaO–MoO3–P2O5 ternary glass systems have been determined within the 0.015–15 MeV energy range, using WinXCom program. Additionally, the mass attenuation coefficients of all the investigated glasses have been calculated using MCNPX simulation code (version 2.6.0) and compared to those of WinXCom results. Among the studied glasses, BaMoP8 glass sample with MoO3 content of 70% mol is found to have superior gamma-ray shielding characteristics. Moreover, the glasses studied in this paper possess better radiation shielding properties by providing shorter half value layer (HVL) than RS-253 G18 commercial glass and some concrete samples namely ordinary, hematite-serpentine and ilmanite-limonite.
关键词： Attenuation coefficients,MCNPX,MoO3-based glass,WinXCom,Radiation shielding
更新于2025-09-23 15:22:29
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Superpositions of Gaussian beams and column Gaussian packets in heterogeneous anisotropic media
摘要： Based on the integral superposition of Gaussian packets, we derive the equations for the integral superposition of Gaussian beams and for the integral superposition of column Gaussian packets in smoothly heterogeneous media. Whereas Gaussian beams extend along their central rays, column Gaussian packets extend along an arbitrary system of lines. The equations are applicable to both the anisotropic ray theory and the coupling ray theory in anisotropic media, or to the isotropic ray theory in isotropic media. The superpositions corresponding to the coupling ray theory can be applied to various kinds of reference rays. The equations can be used in both Cartesian and curvilinear coordinates.
关键词： Electromagnetic anisotropy,Seismic attenuation,Body waves,Theoretical seismology,Wave propagation,Seismic anisotropy
更新于2025-09-23 15:22:29
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[IEEE 2018 Applications of Electromagnetics in Modern Techniques and Medicine (PTZE) - Rac?awice (2018.9.9-2018.9.12)] 2018 Applications of Electromagnetics in Modern Techniques and Medicine (PTZE) - Attenuation of High Frequency Electromagnetic Waves by Polymer Composites with Waste Materials
摘要： Composite materials with polymers and waste materials like zinc ore, mill scale, and iron dust are studied with respect to attenuation of electromagnetic radiation of high frequency. Samples of such composites were prepared and tested for several frequencies in 8-12 GHz band. The composites relatively strongly attenuate electromagnetic radiation in the considered band. Using various waste materials has also ecological aspect.
关键词： electromagnetic radiation,high frequency,attenuation,polymer composites,waste materials
更新于2025-09-23 15:22:29