Bibliographies thématiques / Path length enhancement

Littérature scientifique sur le sujet « Path length enhancement »

Auteur : Grafiati
Publié le 10 mars 2023
Mis à jour le 11 mars 2023

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Articles de revues sur le sujet "Path length enhancement"

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Mupparapu, Rajeshkumar, Kevin Vynck, Tomas Svensson, Matteo Burresi et Diederik S. Wiersma. « Path length enhancement in disordered media for increased absorption ». Optics Express 23, no 24 (8 octobre 2015) : A1472. http://dx.doi.org/10.1364/oe.23.0a1472.

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David, Michael, Tay Ching En Marcus, Maslina Yaacob, Mohd Rashidi Salim, Nabihah Hussin, Mohd Haniff Ibrahim, Sevia Mahdaliza Idrus, Nor Hafizah Ngajikin et Asrul Izam Azmi. « Incident Angle Approach to Sensitivity Enhancement for Ozone Sensor ». Applied Mechanics and Materials 735 (février 2015) : 255–59. http://dx.doi.org/10.4028/www.scientific.net/amm.735.255.

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The design and mathematical model of a reflective type optical gas sensor is presented. Light source is radiated at an incident angle for 10 cm gas cell with an internal diameter of 0.4 cm. At an incident angle of 1o, optical path length obtained is 342.7886 cm, at 27o incident angle, optical path length is 10.4926 cm and at an incident angle of 28o, optical path length is 9.9631 cm. The model is most efficient at lower incident angles, precisely between (1o and 27o). Effects of variation in diameter and length of gas cell are also demonstrated.
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Liu, Jun Xia, Shao Hua Liu, Jun Sheng Yu, Peng Xie, Ze Jian Lu et Xiao Dong Chen. « Optimizing Navigation Satellite Enhancement Information Distribution Network Based on X10 and MPI ». Applied Mechanics and Materials 58-60 (juin 2011) : 2177–82. http://dx.doi.org/10.4028/www.scientific.net/amm.58-60.2177.

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To meet large-scale and time-sensitive needs of navigation Satellite enhance information distribution network in Global Position System(GPS)/Beidou and other systems [1], use small-world network model of complex network to study the topology. Small-world model has a large clustering coefficient and smaller average shortest path length so it can meet performance requirements better. Use Python language to product WS model, and simulate the important parameter-the average shortest path length. Use Dijkstra parallel algorithm and sparse matrix storage method to simulate under the use of X10 parallel language. Analyze the relationship between average shortest path length and random reconnection probability. Additionally, simulate in parallel MPI library and compare the two.
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Fortes, M., E. Comesaña, J. A. Rodríguez, P. Otero et A. J. Garcia-Loureiro. « Evaluation of the Collection Length and Optical Path Enhancement in a-Si:H Solar Cells ». Journal of Physics : Conference Series 647 (13 octobre 2015) : 012047. http://dx.doi.org/10.1088/1742-6596/647/1/012047.

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Guo, Xiaonan, Tiago Simas, Meng‐Chuan Lai, Michael V. Lombardo, Bhismadev Chakrabarti, Amber N. V. Ruigrok, Edward T. Bullmore, Simon Baron‐Cohen, Huafu Chen et John Suckling. « Enhancement of indirect functional connections with shortest path length in the adult autistic brain ». Human Brain Mapping 40, no 18 (29 août 2019) : 5354–69. http://dx.doi.org/10.1002/hbm.24777.

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Kamble, Kanishka N., et Suresh K. Shirgave. « Hybrid Method for Semantic Similarity Computation Using Weighted Components in Ontology ». International Journal of Software Innovation 10, no 1 (1 janvier 2022) : 1–12. http://dx.doi.org/10.4018/ijsi.309734.

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In this paper, the researchers propose an approach to measure the semantic similarity between two concepts in an ontology like WordNet and DBpedia. Some earlier semantic similarity approaches proposed concentrated on the ontology structure between concepts and some concentrated only on the information content of concepts. This paper proposes a semantic similarity approach with path length, information content, and semantic depth (i.e., PLICD) to combine both path length as well as information content-based approaches. This proposed approach uses weighted shortest path length and information content calculated using semantic depth and hyponyms of the concepts to measure semantic similarity between two concepts. Through experimentations performed on WordNet and DBpedia, the researchers note that the PLICD semantic similarity approach has delivered a statistically meaningful enhancement as compared to the other semantic similarity approaches concerning accuracy and F score.
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Shribak, Michael, Kieran G. Larkin et David Biggs. « Mapping optical path length and image enhancement using quantitative orientation-independent differential interference contrast microscopy ». Journal of Biomedical Optics 22, no 1 (6 janvier 2017) : 016006. http://dx.doi.org/10.1117/1.jbo.22.1.016006.

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Beghou, Lotfi. « Methodology for the design of multi-source transmitters dedicated to perpendicular dynamic wireless power transfer : theoretical study ». Wireless Power Transfer 5, no 1 (21 janvier 2018) : 54–63. http://dx.doi.org/10.1017/wpt.2017.20.

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In this paper, a theoretical study for the design of multi-source transmitters suitable for perpendicular dynamic wireless power transfer is presented. Unlike conventional systems, the concept presented here overcomes the traditional limitation on the receiver's orientation by providing an optimal distribution of the transmitted energy obtained by using different sources. For this purpose, a theoretical study of different transmitters has been achieved by solving the inverse problem. Comparison with conventional single-source transmitters carrying the same total current as the multi-source transmitters, shows a significant enhancement of the power gain when a Genetic Algorithm is used. The obtained theoretical results show power gain levels over 7.5 dB for different path lengths at different heights. At the end, a solution for a path of an infinite length is presented.
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Dubois, S., A. Michel, J. P. Eymery, J. L. Duvail et L. Piraux. « Fabrication and properties of arrays of superconducting nanowires ». Journal of Materials Research 14, no 3 (mars 1999) : 665–71. http://dx.doi.org/10.1557/jmr.1999.0091.

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We report on the fabrication and structural characterization of arrays of superconducting nanowires by electroplating lead into the nanopores of track-etched polymer membranes. The diameters of the lead nanowires range from 400 down to 70 nm, whereas their length is about 20 μm. Large enhancement of the critical field has been observed in good agreement with the Ginsburg–Landau–Silin theory. By comparing the predicted critical field enhancement for thin cylinders with experimental results, we have extracted the effective penetration depth. The dependence of the effective penetration depth and electron mean free path on the wire diameter is also discussed.
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Xiao, Ruoxiu, Cheng Chen, Hanying Zou, Ying Luo, Jiayu Wang, Muxi Zha et Ming-An Yu. « Segmentation of Cerebrovascular Anatomy from TOF-MRA Using Length-Strained Enhancement and Random Walker ». BioMed Research International 2020 (21 septembre 2020) : 1–16. http://dx.doi.org/10.1155/2020/9347215.

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Cerebrovascular rupture can cause a severe stroke. Three-dimensional time-of-flight (TOF) magnetic resonance angiography (MRA) is a common method of obtaining vascular information. This work proposes a fully automated segmentation method for extracting the vascular anatomy from TOF-MRA. The steps of the method are as follows. First, the brain is extracted on the basis of regional growth and path planning. Next, the brain’s highlighted connected area is explored to obtain seed point information, and the Hessian matrix is used to enhance the contrast of image. Finally, a random walker combined with seed points and enhanced images is used to complete vascular anatomy segmentation. The method is tested using 12 sets of data and compared with two traditional vascular segmentation methods. Results show that the described method obtains an average Dice coefficient of 90.68%, and better results were obtained in comparison with the traditional methods.
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Thèses sur le sujet "Path length enhancement"

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MUPPARAPU, RAJESHKUMAR. « Absorption Enhancement by Light Scattering for Solar Energy Applications ». Doctoral thesis, 2013. http://hdl.handle.net/2158/796858.

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In this thesis, I discuss few novel approaches to enhance the light-matter interaction, which have applications in solar energy. Enhancement of absorption/ fluorescence is a topic of immense interest in recent years for its importance in various fields: bio-sensing and diagnostics, solar energy, imaging, forensics, etc.. Often, applications involving fluorescence are quite low efficient, and which is mainly attributed to poor fluorescence from constituent fluorescent molecules. Enhancing fluorescence of molecules can enable to realize very efficient applications. And, one such application which needs attention is Luminescent solar concentrator, which is a main topic of discussion in this thesis. Luminescent solar concentrators (LSCs) are polymer slabs filled with fluorescent molecules which absorb incoming sunlight and emit fluorescence inside the slab, and which is partially guided to the edges where photovoltaic cells are attached. Poor absorption/fluorescence of organic molecules is due to their intrinsic chemical structure, due to which either they display huge non-radiative decay losses or poor absorption efficiency, etc.. It is well know that the amount of light emitted by molecules also depends on their surrounding medium properties. Modifying the surrounding environment very close to the molecules can actually modify the intrinsic fluorescence properties of molecules. This idea has been applied quite a lot to modify the properties of molecules close to metallic nanostructures/nanoparticles. When it comes to enhance the fluorescence of molecules embedded in polymer slabs like LSCs all existing approaches fail to work. In thesis, I discuss elaborately, in particular answering following questions: why existing approaches fail to work, essentially what kind of approaches are needed, and how they should be implemented.
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Chapitres de livres sur le sujet "Path length enhancement"

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« niques were prepared using pentane as the solvent. Similar methods were used in preparing calibration samples with the mold release, solder flux, and hydraulic oil samples. All contaminated coupons were gentl y heated in an oven at 50°C for several days to remove both semi-volatile and volatile components. This served to stabi-lize the contaminants, allowing for quantification by weighing. Once the weights became stable, the coupons were cooled and weighed to determine the amount of contaminant present on the surface. When not being weighed or examined, the coupons were kept in a desiccator. 3. RESULTS AND DISCUSSION Grazing-angle incidence reflectance spectroscopy acts to enhance the detection sensitivity for thin layers of residue predominantly through improved coupling of th e electric field intensity of the incident beam with the vibrating dipoles of the surface contaminant layer perpendicular to the metallic surface. Some additional enhancement of the infrared absorption spectrum will also occur due to a length-ening of the effective path length through the absorbing thin film layer [4-6]. If the optical properties of both thin film and substrate are known (or can be de-termined), the reflection-absorption spectrum can be calculated as a function of film thickness and angle of incidence. This capability is particularly useful for in-terpreting experimental data and designing optical instrumentation. Computer codes written at Sandia [7] performed these calculations for a variety of materials. 3.1. FTIR measurements FTIR reflectance data for the full drawing-agent sample set were obtained at NFESC and Sandia using angles of incidence of 75 and 60° for average film thickness ranging from 0.1 to 1 |im, and aluminum substrates with surface finish ranging from 600 to 80 grit. Since the surface finishing operation produced a highly directional roughness, measurements were made both longitudinally and transversely with respect to the polishing grooves. R values were determined at ». Dans Surface Contamination and Cleaning, 17–20. CRC Press, 2003. http://dx.doi.org/10.1201/9789047403289-5.

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Actes de conférences sur le sujet "Path length enhancement"

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Almeida, Daniel Diaz, Pablo Ferrada, Aitor Marzo, Enrique Cabrera, Elias Urrejola, Dario Espinoza, Rodrigo Castillo, Jaime Llanos et Carlos Portillo. « Theoretical Calculation of the Photo-generated Current Density by Using Optical Path-length Enhancement Factor for Si-based PV Devices in the Atacama Desert ». Dans 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC). IEEE, 2018. http://dx.doi.org/10.1109/pvsc.2018.8548230.

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Fan, Yan Feng, et Ibrahim Hassan. « The Numerical Investigation of an Interdigital Micromixer With the Circular-Sector Obstacles ». Dans ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer. ASMEDC, 2009. http://dx.doi.org/10.1115/mnhmt2009-18385.

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In this paper, a passive interdigital micromixer with the circular-sector obstacles is proposed and the mixing performance is estimated by numerical simulation. The tested Reynolds numbers range from 0.01 to 10. Flow recirculation or vortices seems impossible to generate to enhance the mixing at such low Reynolds numbers. Hence, molecular diffusion is the dominant mixing mechanism. Based on the diffusion principle, enlarging the mixing length, reducing the diffusion length and increasing the surface area between species are major methods to obtain mixing enhancement. In order to achieve rapid mixing, shortening the mixing length is necessary. However, the reduced mixing length induces the decreased mixing time which the species take to mix. The circular-section obstacles are placed in the straight microchannels to enlarge the contact surface area between species. The flow path is distorted after passing the obstacles so that the real mixing length increases compared with traditional T-shape micromixers. Furthermore, flow advection takes a part role in mixing since the velocity direction is no longer perpendicular to diffusion direction. Different geometries and layouts of obstacles are analyzed for optimization. The results of optimal design show the worst mixing efficiency, around 50%, occurs at Re = 1. In order to improve the lower limitation of mixing efficiency, the duplicated layouts of obstacles in lateral direction with interdigital inlet are applied to reduce the diffusion path and increase the interface area so that the mixing efficiency could be enhanced. The results show that the mixing efficiency could achieve 85% at Re ≤ 1 with a low pressure drop of 100 Pa. It has the potential to be used in applications with low Reynolds numbers.
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Yoon, G., D. N. G. Roy, R. E. Benner et R. C. Straight. « Weak localization of photons in biological tissue using a cw laser ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oam.1991.mmm6.

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When light is scattered through a randomly in homogeneous medium, backscattering within a narrow cone is enhanced.1 This enhancement occurs because of the phase coherence between waves that travel the same paths in opposite directions. Recently, a femtosecond laser with a synchroscan streak camera was used to measure the enhanced backscattering.2 However, the technique is equipment-intensive. In our experiment, a simpler setup using the CCD array and cw lasers, such as a He-Ne, are used to measure the coherent peaks from biological tissues. Unlike from a liquid medium with scattering particles, the images from a solid surface show specklelike fluctuations. Ensemble averaging is required to reveal the coherent peak. The peak shapes are influenced by the beam polarization. With the polarization parallel to the plane of incidence, a sharper peak is observed. In addition, the relation of the peak shape to the optical properties such as transport mean free path and absorption length are discussed.
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Chiou, Shang-Hau, et Chun-Hway Hsueh. « TiO2 Branched Nanorods-Modified ZnO Nanorods Decorated with An Nanoparticles for Plasmon-Enhanced Photoelectrochemical Water Splitting ». Dans JSAP-OSA Joint Symposia. Washington, D.C. : Optica Publishing Group, 2019. http://dx.doi.org/10.1364/jsap.2019.18p_e208_10.

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Nowadays, with the rise of environmental awareness and energy crisis, sustainable energy has been widely studied. Photoelectrochemical (PEC) water splitting is one of the most environment friendly ways in which the process of converting solar energy into fuels only produces hydrogen and oxygen. Semiconductor metal oxides such as ZnO and TiO2 have been generally explored for PEC water splitting because they possess high chemical stability, low cost, and proper band gap. In addition, the gold nanoparticles exhibiting distinctive localized surface plasmon resonance (ESPR) cause optical scattering and near-field enhancement to trap the incident light in the semiconductor and to improve the light absorption and effective optical path length [1].
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Simon, U., C. E. Miller, R. F. Curl et F. K. Tittel. « Infrared difference frequency spectrometer for high resolution spectroscopy of molecular transients ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1992. http://dx.doi.org/10.1364/oam.1992.ft4.

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Infrared absorption spectroscopy is an effective spectroscopic technique for studying transient molecules since it combines high spectral resolution and high detection sensitivity. The recent availability of novel nonlinear materials such as AgGaS2 and AgGaSe2 makes it now possible to generate narrowband coherent radiation over a wide range (4–18 µm) by means of difference frequency generation. This letter reports on the mixing of a tunable cw dye and dye/Ti:sapphire laser system in a AgGaS2 crystal 45 mm in length. By using 90° type I phase matching, cw infrared output powers at the 50 µW level can be provided for spectroscopic application. Continuous scans of up to 1 cm‒1 width have been achieved. Transient molecules can be generated conveniently by excimer laser photolysis with an appropriate precursor. For a sensitivity enhancement a 1 m White cell with a variable optical path length of up to 60 m is employed. The signal is acquired by a transient digitizer interfaced with a computer. First spectra of molecular transients will be presented.
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Zhao, Xin Miao, Jean-Claude Diels, Alan Braun, Xinbing Liu, Detao Du, Georg Korn, Gerard Mourou et Juan M. Elizondo. « Use of self-trapped filaments in air to trigger lightning ». Dans International Conference on Ultrafast Phenomena. Washington, D.C. : Optica Publishing Group, 1994. http://dx.doi.org/10.1364/up.1994.thd.24.

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A study of the possibility of triggering lightning with optical pulses has been investigated. A theoretical analysis shows that a continuous ionized path of several tens of meters should be created. In recent experiments, long focal length lens were used to confine a low energy (≈ 200 μJ) femtosecond ultra-violet laser pulse, resulting in a weak ionization (< 10−6 of the air molecules) in a column between two electrodes spaced by 25 cm. A discharge was induced with this technique at half the self breakdown field of air [1]. The mechanism of laser induced guided discharge is a local field enhancement resulting from the migration of charges in the applied electric field. This mechanism is different from the standard laser induced spark gap, where the laser energy is sufficient to induce a plasma between the electrodes. Self-trapped filaments can create a continuously ionized path over very long distances, which is the main requirement for “seeding” and guiding a discharge over long distances with minimal laser energy.
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Morjan, Saleh, Badih A. Jawad, Liping Liu, Kingman Yee et Vernon Fernandez. « Investigation of the Effect of Vortex Generation on Heat Transfer Enhancement in Horizontal Channel Flow ». Dans ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-65446.

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In this experimental work, a flow field test system was installed to investigate the impact of vortex generators on the flow structure and heat transfer of air flow in a horizontal channel. Three different configurations of vortex generators, a small single delta winglet pair, a large single delta winglet pair, and two delta winglet pairs developed in a V-formation array were fitted vertically on an aluminum plate and tested in a small wind path system of open circuit with horizontal test section of dimensions 70 mm (width) × 35 mm (height) × 1600 mm (length). An axial AC fan was used to supply the flow of air through the test section. The air flow was cooling the flat plate which had embedded electric heating constructed as a layered structure. Temperature distributions along the heated plate were measured using thermocouples to obtain the Nusselt numbers. The effect of three different attack angles, 15°, 30°, and 45° of the selected VGs were investigated in this work. The experimental results showed that under the tested Reynolds number of 10145, the presence of vortex generators had considerable effect on temperature distribution, pressure drop and heat transfer augmentation in the channel flow. Compared with the plain channel; the heat transfer rate was enhanced by (31.9% – 51.0%), (30.8% – 53.7 %), and (18.2 % – 36.2%) while the pressure drop increased by (1.8% – 11.0%), (4.5% – 35.4%), and (6.0 % – 30.0%) with the small single delta winglet pair, the large single delta winglet pair, and two pairs deployed in a V-formation array, respectively.
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Singh, Prashant, Yongbin Ji, Mingyang Zhang et Srinath V. Ekkad. « Heat Transfer Enhancement by Criss-Cross Pattern Formed by 45° Angled Rib Turbulators in a Straight Square Duct ». Dans ASME 2017 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/ht2017-4908.

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The need for higher turbine efficiency has been constantly pushing the turbine inlet temperatures to elevated levels. Hot gas path temperatures are much higher than the typical blade material yield temperature. Efficient internal cooling technologies are required for safe operation of gas turbine. Several internal cooling technologies have been developed in order to enhance the heat transfer from relatively hotter walls of turbine blade. For mid-chord region of turbine blade, rib turbulators are typically installed in multi-pass channels. Rib turbulators trip the boundary layer, induce secondary flows which enhance near wall shear as well as enhance turbulent mixing when they interact with surrounding walls. Research has been carried out on several aspects of rib turbulated passages in order to achieve higher thermal hydraulic performance. Generally, rib turbulators are installed on two opposite walls of serpentine passages in order to enhance heat transfer from both pressure and suction sides of blade through coolant flowing through complicated paths. Typical arrangement of rib turbulators were parallel to each other or having some offset from each other. In the present study, an attempt has been made to arrange 45° angled ribs in a way that they form a Criss-Cross pattern. Two ribbed configurations with Criss-Cross pattern - Inline and staggered, have been studied where the baseline case was smooth duct with no rib turbulators. The effective rib-pitch-to-rib-height ratio (p/e) was 8.6 and rib-height-to-channel-hydraulic diameter ratio (e/dh) was 0.1. The channel had a total length of 20 hydraulic diameters and the rib turbulators were installed at a distance of six hydraulic diameters from the inlet of the test section to allow flow development. Detailed heat transfer coefficients were measured using transient liquid crystal thermography employing 1D semi-infinite conduction model. Globally averaged Nusselt numbers are calculated from the detailed measurements and thermal hydraulic performance of configurations have been reported with respect to Reynolds number. The aim of this study was to develop a cooling configuration which has higher thermal-hydraulic performance compared to other traditional rib configurations. It has been found that the heat transfer characteristics of the inline and staggered configurations were similar to each other and ranged between three times D-B correlation to 2.7 times, for Reynolds number ranging from 30000 to 60000. Inline configuration had relatively lower frictional losses, however the thermal hydraulic performances of both the configurations were similar.
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Tafti, D. K. « Computational Insights Into Air-Side Flow and Heat Transfer in Compact Heat Exchangers ». Dans ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72846.

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The paper describes two- and three-dimensional computer simulations which are used to study fundamental flow and thermal phenomena in multilouvered fins used for air-side heat transfer enhancement in compact heat exchangers. Results pertaining to flow transition, thermal wake interference, and fintube junction effects are presented. It is shown that a Reynolds number based on flow path rather than louver pitch is more appropriate in defining the onset of transition, and characteristic frequencies in the louver bank scale better with a global length scale such as fin pitch than with louver pitch or thickness. With the aid of computer experiments, the effect of thermal wakes is quantified on the heat capacity of the fin as well as the heat transfer coefficient, and it is established that experiments which neglect accounting for thermal wakes can introduce large errors in the measurement of heat transfer coefficients. Further, it is shown that the geometry of the louver in the vicinity of the tube surface has a large effect on tube heat transfer and can have a substantial impact on the overall heat capacity.
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Choa, F. S., et P. L. Liu. « k-Ratio improvement by a sharp p-n junction ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1988. http://dx.doi.org/10.1364/oam.1988.thaa5.

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A large difference in the ionization rates for electrons and holes is essential for a low-noise avalanche photodiode (APD). Enhancement of electron impact ionization in a heterojunction superlattice has been experimentally demonstrated since 1982. However, the trapped carriers in heterostructures can occasionally contribute to impact ionization, and charging or discharging delay, therefore, degrades the originally expected performance. We propose to use a sharp p-n junction to improve the k-ratio. Such a scheme can be applied to both the heterojunction and homojunction and is free of the miscibility problem and trapping effect. The length of the sharp p-n junction is much shorter than its carrier energy relaxation mean free path. Impact ionization happens in the region right after the junction. Because the carrier distribution function is a nonlinear function of energy, an equal amount of injection level from the junction affects electrons and holes differently when their ionization thresholds are different. Calculations based on a lucky-drift model1 show that the k-ratio improvement increases with the height of the injection level and becomes extremely significant when the level approaches the lower one of the thresholds.
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