المؤلفون: Ibukunoluwa Adetutu Olajide, Samson A. Oyetunji, Yekeen Olasoji, Wasiu O. Popoola, Muhammad Ijaz

مصطلحات موضوعية: Optical Wireless Communication Systems and Technologies, Electrical and Electronic Engineering, FOS Electrical engineering, electronic engineering, information engineering, Engineering, Physical Sciences, Radar Wave Propagation and Refractivity Estimation, Aerospace Engineering, FOS Mechanical engineering, Free-Space Optical Communication, MIMO Techniques, Visibility, Attenuation, Wavelength, Environmental science, Mie scattering, Meteorology, Temperate climate, Remote sensing, Scattering, Atmospheric sciences, Optics, Light scattering, Geography, Physics, Botany, Biology

الوصف: In this paper, an investigation of some selected Mie and geometric Scattering models for free space optical (FSO) communication was done on available atmospheric data in Nigeria. The Kim and Kruse models have been established for the temperate region. In this work, the models were examined using the visibility data from the year 2008 to 2019. The models were examined under the 2% and 5% transmission threshold and under the wavelengths 780nm, 850nm, 1100nm, and 1550nm. The results indicates a higher attenuation at 780nm, supporting what is available in literature. The Suriza et al, ITU-R(Carbonneau) and Gailani et al models were investigated using the rain intensity data. The Suriza et al model indicates a reduced attenuation compared to the other two models. ... : في هذه الورقة، تم إجراء تحقيق في بعض نماذج MIE والنثر الهندسي المختارة للاتصالات البصرية للفضاء الحر (FSO) على البيانات الجوية المتاحة في نيجيريا. تم إنشاء نموذجي كيم وكروس للمنطقة المعتدلة. في هذا العمل، تم فحص النماذج باستخدام بيانات الرؤية من عام 2008 إلى عام 2019. تم فحص النماذج تحت عتبة الإرسال 2 ٪ و 5 ٪ وتحت الأطوال الموجية 780 نانومتر و 850 نانومتر و 1100 نانومتر و 1550 نانومتر. تشير النتائج إلى انخفاض أعلى عند 780 نانومتر، مما يدعم ما هو متاح في الأدبيات. تم التحقيق في نماذج سوريزا وآخرون وITU - R(كاربونو) وغيلاني وآخرون باستخدام بيانات كثافة الأمطار. يشير نموذج سوريزا وآخرون إلى انخفاض التوهين مقارنة بالنموذجين الآخرين. ...

العلاقة: https://dx.doi.org/10.60692/xhch4-bvd82Test

الإتاحة: https://doi.org/10.60692/xy07m-hj66810.60692/xhch4-bvd82Test

المؤلفون: O.R. Asfar, Bruno Morvan

مصطلحات موضوعية: Guided Wave Structural Health Monitoring in Materials, Mechanics of Materials, Engineering, Physical Sciences, Structural Health Monitoring Techniques, Civil and Structural Engineering, Fracture Mechanics Modeling and Simulation, Wave Propagation, Wavenumber, Equilateral triangle, Physics, Plane wave, Geometry, Eigenfunction, Mathematics, FOS Mathematics, Optics, Eigenvalues and eigenvectors, Quantum mechanics

الوصف: Shear wave excitation of an equilateral triangular solid bar shows the existence of horizontally polarized (SH) and vertically polarized (SV) shear waves. The SH wave modes are Lamé solutions of the Neumann problem for displacement and Dirichlet problem for stress in the equilateral triangle. It is shown that Lamé's solutions are obtained from superposition of three equal plane waves and their reflections. The Neumann SH modes have cutoff wavenumber 4mπ/(3a), where m=1,2,3,…, a being the side length of triangular cross section. The first Dirichlet SH mode has a higher cutoff wavenumber 4π7/(3a). The SV modes are related to the 30°–60°–90° and 30°–120°–30° sub triangles. Their cutoff wavenumbers lie between those of the first (m = 1) and second (m = 2) Neumann SH modes. The standing wave condition in each sub triangle is related to three unequal plane waves which decompose via symmetrical component analysis into two different sets of equal plane waves. A nonlinear product solution based on the new plane wave ... : يُظهر استثارة موجة القص لشريط صلب مثلث متساوي الأضلاع وجود موجات قص مستقطبة أفقيًا (SH) ومستقطبة رأسيًا (SV). أوضاع موجة SH هي حلول لامي لمشكلة نيومان للإزاحة ومشكلة ديريتشليت للإجهاد في المثلث متساوي الأضلاع. يتضح أن حلول لاميه يتم الحصول عليها من تراكب ثلاث موجات مستوية متساوية وانعكاساتها. تحتوي أوضاع نيومان إس إتش على عدد موجي مقطوع 4mπ /( 3a)، حيث m=1،2،3،...، وهو الطول الجانبي للمقطع العرضي الثلاثي. يحتوي وضع Dirichlet SH الأول على رقم موجة قطع أعلى 4 π 7 /( 3a). ترتبط أوضاع SV بالمثلثات الفرعية 30درجة–60درجة–90درجة و 30درجة–120 درجة –30درجة. تقع أرقام الموجات المقطوعة الخاصة بهم بين تلك الخاصة بأوضاع نيومان إس إتش الأولى (م = 1) والثانية (م = 2). ترتبط حالة الموجة الدائمة في كل مثلث فرعي بثلاث موجات مستوية غير متساوية تتحلل عبر تحليل المكون المتماثل إلى مجموعتين مختلفتين من موجات المستوى المتساوية. يؤدي حل المنتج غير الخطي القائم على مجموعة الموجات المستوية الجديدة إلى حلول موجات SV الشكلية. تؤكد منحنيات التشتت المحسوبة باستخدام COMSOL أرقام الموجات المقطوعة الصحيحة لكل من موجات SH وSV. يتم حساب أشكال ...

العلاقة: https://dx.doi.org/10.60692/ax6kk-wz077Test

الإتاحة: https://doi.org/10.60692/hjjm0-ew36210.60692/ax6kk-wz077Test

المؤلفون: Ghasemi, Masih¹, Choudhury, P.K.¹

المصدر: Journal of Modern Optics. Oct2014, Vol. 61 Issue 18, p1509-1518. 10p.

مصطلحات موضوعية: DIELECTRICS, ELECTROMAGNETIC wave propagation, WAVEGUIDES, NANOELECTRONICS, QUANTUM confinement effects, OPTICS

مستخلص: An investigation has been made of the propagation of electromagnetic waves through dielectric optical guide loaded with conducting sheath helix at the core–clad interface. The guide structure falls into the category of complex media, wherein it has been assumed that the helix sheath remains continuous in nature along with each of the turns being isolated from the adjacent ones. Power confinement factors in the two regions of guide under consideration have been evaluated under the situation of varying values of helix pitch angle – from its orientation being parallel to the optical axis to the perpendicular orientation. Two different illustrative values of guide dimensions have been taken into account, and the effect on the propagation of power have been demonstrated under the variations in helix pitch angle. [ABSTRACT FROM AUTHOR]

: Copyright of Journal of Modern Optics is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Randrianalisoa, Jaona¹ jaona.randrianalisoa@univ-reims.fr, Haussener, Sophia² sophia.haussener@epfl.ch, Baillis, Dominique³, Lipiński, Wojciech⁴

المصدر: Journal of Quantitative Spectroscopy & Radiative Transfer. Nov2017, Vol. 202, p220-232. 13p.

مصطلحات موضوعية: *RADIATIVE transfer, *ELECTROMAGNETIC wave propagation, *RADIATION, *FIBERS, *HEAT transfer, *HEAT conduction, *OPTICS

مستخلص: Radiative heat transfer is analyzed in participating media consisting of long cylindrical fibers with a diameter in the limit of geometrical optics. The absorption and scattering coefficients and the scattering phase function of the medium are determined based on the discrete-level medium geometry and optical properties of individual fibers. The fibers are assumed to be randomly oriented and positioned inside the medium. Two approaches are employed: a volume-averaged two-intensity approach referred to as multi-RTE approach and a homogenized single-intensity approach referred to as the single-RTE approach . Both approaches require effective properties, determined using direct Monte Carlo ray tracing techniques. The macroscopic radiative transfer equations (for single intensity or two volume-averaged intensities) with the corresponding effective properties are solved using Monte Carlo techniques and allow for the determination of the radiative flux distribution as well as overall transmittance and reflectance of the medium. The results are compared against predictions by the direct Monte Carlo simulation on the exact morphology. The effects of fiber volume fraction and optical properties on the effective radiative properties and the overall slab radiative characteristics are investigated. The single-RTE approach gives accurate predictions for high porosity fibrous media (porosity about 95%). The multi-RTE approach is recommended for isotropic fibrous media with porosity in the range of 79−95%. [ABSTRACT FROM AUTHOR]

المؤلفون: Omenka E. Jackson, Muhammad Uthman, Sadiq Umar

مصطلحات موضوعية: Millimeter Wave Communications for 5G and Beyond, Electrical and Electronic Engineering, FOS Electrical engineering, electronic engineering, information engineering, Engineering, Physical Sciences, Radar Wave Propagation and Refractivity Estimation, Aerospace Engineering, FOS Mechanical engineering, Next Generation 5G Wireless Networks, Propagation Models, Radar Propagation, Refractivity Estimation, Path loss, Computer science, Mean squared error, Attenuation, Radio propagation, SIGNAL programming language, Telecommunications, Log-distance path loss model, Radio propagation model, Path computing, Statistics, FOS Mathematics, Mathematics, Wireless, Computer network, Physics, Optics, Programming language

الوصف: Implementations of Radio frequency wave propagation models are necessary to determine propagation characteristics through a medium. Its study provides an estimation of signal characteristics and the effect of environment and the medium over which it travels. This paper performs some analysis on few empirical Propagation models the mechanisms, their path loss behavior suitable for path loss prediction techniques in broadcast communication. Experimental measurements of received signal strength indication for the 92.9 MHz Radio broadcasting Station were made in urban areas of Federal Capital Territory Abuja, Nigeria. Measured data were compared with those obtained by three prediction models: COST-231, ECC-33 and OKUMURA-HATA models, the results show that in general the ECC-33 Model over-predicted the path loss in all environments with Root Means Square error (RMSE) of 166.46, while the COST-231 model has 18.33 having the best results. Okumura-Hata predicted well in the near field with 16.50 and deviated from ... : تعتبر تطبيقات نماذج انتشار موجة الترددات الراديوية ضرورية لتحديد خصائص الانتشار من خلال وسيط. وتقدم دراستها تقديرًا لخصائص الإشارة وتأثير البيئة والوسيط الذي تنتقل فوقه. تجري هذه الورقة بعض التحليل على عدد قليل من نماذج الانتشار التجريبية للآليات، وسلوك فقدان المسار المناسب لتقنيات التنبؤ بفقدان المسار في الاتصالات الإذاعية. تم إجراء قياسات تجريبية لمؤشر قوة الإشارة المستقبلة لمحطة البث الإذاعي 92.9 ميجا هرتز في المناطق الحضرية في إقليم العاصمة الفيدرالية أبوجا، نيجيريا. تمت مقارنة البيانات المقاسة مع تلك التي تم الحصول عليها من خلال ثلاثة نماذج تنبؤية: نماذج COST -231 و ECC -33 و OKUMURA - HATA، وتظهر النتائج بشكل عام أن نموذج ECC -33 قد بالغ في التنبؤ بفقدان المسار في جميع البيئات مع خطأ Root Means Square (RMSE) البالغ 166.46، في حين أن نموذج COST -231 لديه 18.33 يحقق أفضل النتائج. تنبأ أوكومورا هاتا بشكل جيد في المجال القريب مع 16.50 وانحرف عن البيانات المقاسة في المجال البعيد. كما وصل تحليل التنبؤ إلى مؤشر قوة الإشارة المستقبلة لكابيتال إف إم في عشرين (20) موقعًا في أبوجا ؛ وبالتالي، فإنه يحدد الطريق أ ...

العلاقة: https://dx.doi.org/10.60692/9be9w-wca66Test

الإتاحة: https://doi.org/10.60692/mfb8m-ahb9410.60692/9be9w-wca66Test

المؤلفون: Fikret MEHDİ, Adem Doğangün, Yasin Fahjan

مصطلحات موضوعية: Seismic Engineering and Ground Motion Analysis, Civil and Structural Engineering, Engineering, Physical Sciences, Structural Health Monitoring Techniques, Urban Wind Environment and Air Quality Modeling, Environmental Engineering, FOS Environmental engineering, Environmental Science, Structural Damage Detection, Structural Dynamics, Dynamic Analysis, Structural engineering, Wave propagation, Phenomenon, Bending moment, Seismic analysis, Shear force, Bending, Mechanics, Physics, Optics, Quantum mechanics

الوصف: This paper numerically investigates the impact of considering the seismic wave propagation phenomenon on the dynamic response of high-rise buildings. A core wall and a frame are analyzed under seismic loading considering wave propagation phenomenon and ignoring it. The bending moment, shear force, axial force, and inter-story drift for both analyzed systems are evaluated. The amplitude Fourier response spectra for the dynamic response at different stories are discussed as well. Forty-six stories each, both systems are subjected to transverse and longitudinal seismic waves at the fixed base. The results show that considering the wave propagation phenomenon yields a slight decrease in the inter-story drift, shear force, and bending moment. It is found that considering wave propagation phenomenon increases the axial force significantly, especially for the core wall at the floors of the top third part. It is worth pointing out that high-rise buildings cannot be categorized, and every single different detail can ... : تبحث هذه الورقة عدديًا في تأثير النظر في ظاهرة انتشار الموجات الزلزالية على الاستجابة الديناميكية للمباني الشاهقة. يتم تحليل الجدار الأساسي والإطار تحت التحميل الزلزالي مع الأخذ في الاعتبار ظاهرة انتشار الموجة وتجاهلها. يتم تقييم عزم الانحناء وقوة القص والقوة المحورية والانجراف بين الطوابق لكلا النظامين اللذين تم تحليلهما. كما تمت مناقشة أطياف استجابة فورييه واسعة النطاق للاستجابة الديناميكية في قصص مختلفة. ستة وأربعون طابقًا لكل منهما، يخضع كلا النظامين لموجات زلزالية عرضية وطولية في القاعدة الثابتة. تظهر النتائج أن النظر في ظاهرة انتشار الموجة يؤدي إلى انخفاض طفيف في الانجراف بين القصص، وقوة القص، وعزم الانحناء. وجد أن النظر في ظاهرة انتشار الموجة يزيد من القوة المحورية بشكل كبير، خاصة بالنسبة للجدار الأساسي في أرضيات الجزء الثالث العلوي. تجدر الإشارة إلى أنه لا يمكن تصنيف المباني الشاهقة، ويمكن أن تؤدي كل تفاصيل مختلفة إلى استجابة مختلفة. وبالتالي، فإن المساهمة الرئيسية لهذه الورقة هي تسليط الضوء على الحاجة الماسة إلى النظر في ظاهرة انتشار الموجات في مثل هذه المباني "خارج الكود". والأهم من ذلك هو الحاجة ...

العلاقة: https://dx.doi.org/10.60692/6b0n7-8j160Test

الإتاحة: https://doi.org/10.60692/gqy59-zya1410.60692/6b0n7-8j160Test

المؤلفون: Metcalf, Mekena, Chern, Gia-Wei, Di Ventra, Massimiliano, Chien, Chih-Chun

المصدر: Journal of Physics B Atomic Molecular and Optical Physics. 49(7)

مصطلحات موضوعية: Quantum Physics, Atomic, Molecular and Optical Physics, Physical Sciences, optical lattice, flat band, matter-wave propagation, quantum transport, cond-mat.quant-gas, cond-mat.mes-hall, quant-ph, Optics

الوصف: The geometry of optical lattices can be engineered allowing the study ofatomic transport along paths arranged in patterns that are otherwise difficultto probe in the solid state. A question readily accessible to atomic systems isrelated to the speed of propagation of matter-waves as a function of thelattice geometry. To address this issue, we have investigated theoretically thequantum transport of non-interacting and weakly-interacting ultracold fermionicatoms in several 2D optical lattice geometries. We find that the triangularlattice has a higher propagation velocity compared to the square lattice,despite supporting longer paths. The body-centered square lattice has evenlonger paths, nonetheless the propagation velocity is yet faster. This apparentparadox arises from the mixing of the momentum states which leads to differentgroup velocities in quantum systems. Standard band theory provides anexplanation and allows for a systematic way to search and design systems withcontrollable matter-wave propagation. Moreover, the presence of a flat bandsuch as in a two-leg ladder geometry leads to a dynamical densitydiscontinuity, which contrasts the behavior of mobile and localized atoms inquantum transport. Our predictions are realizable with present experimentalcapability.

وصف الملف: application/pdf

الوصول الحر: https://escholarship.org/uc/item/3db0q4v8Test

المؤلفون: Dongmei Li^1,2, Tian Guan^1,2, Jingying Jiang³, Yonghong He^1,2 heyh@sz.tsinghua.edu.cn

المصدر: Optical Engineering. Mar2017, Vol. 56 Issue 3, p1-7. 7p. 1 Diagram, 4 Graphs.

مصطلحات موضوعية: *OPTICAL sensors, *ACOUSTIC wave propagation, *OPTICAL phase shifters

مستخلص: We proposed an optical sensing scheme, based on the mechanism of weak measurement, to detect the sonic pressure transversally without any disturbance. According to the theory of weak measurement in frequency domain, a tiny phase difference between the two eigenstates of the system could be detected, depending on the shift of central wavelength of output spectra. The optical path difference between two paths of a Mach– Zehnder interferometer is induced by the varied acoustic waves propagating in liquid. The propagating direction of the testing light beam is orthogonal to that of the acoustic wave. Thus, the phase shift corresponding to the changing acoustic pressure could be monitored transversally. The experiment with the hydrophone is implemented as a reference to demonstrate the feasibility and authenticity of this weak measurement scheme. With this method, an optical phase resolution of 1.12 × 10−5 rad was acquired in such a weak measurement system. [ABSTRACT FROM AUTHOR]

المؤلفون: Ying Xu¹, Qiwu Tan² qtan@tmantennas.com, Erricolo, Danilo¹ erricolo@ece.uic.edu, Uslenghi, Piergiorgio L. E.¹ uslenghi@uic.edu

المصدر: IEEE Transactions on Antennas & Propagation. Nov2005, Vol. 53 Issue 11, p3757-3766. 10p.

مصطلحات موضوعية: RADIO wave propagation, FRESNEL integrals, NOISE, OPTICS, ELECTROMAGNETIC waves, CITIES & towns

مستخلص: A deterministic model for propagation in outdoor urban environments based on the Fresnel-Kirchhoff integral is presented. Both two-dimensional (2-D) and three-dimensional (3-D) formulations considering reflection and diffraction are given. The theoretical predictions are compared with 2-D and 3-D measurements and good agreement is achieved. The 3-D experiments, conducted in an anechoic chamber with scaled models representing buildings, are described in detail and provide a benchmark for comparisons with other methods. [ABSTRACT FROM AUTHOR]

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المؤلفون: Coleman, Chris J.¹ ccoleman@eleceng.adelaide.edu.au

المصدر: IEEE Transactions on Antennas & Propagation. Oct2005, Vol. 53 Issue 10, p3174-3179. 6p.

مصطلحات موضوعية: RADIO wave propagation, ELECTROMAGNETIC waves, OPTICAL diffraction, OPTICS, RADIO frequency, ELECTRIC waves

مستخلص: For terrestrial radio wave propagation, it has been previously demonstrated that second order effects, such as diffraction, can be estimated through a combination of geometric optics and Kirchhoff style integral relations. In the present paper, it is shown that the approach can also yield accurate estimates when refractive effects, such as atmospheric ducting, are present. [ABSTRACT FROM AUTHOR]

: Copyright of IEEE Transactions on Antennas & Propagation is the property of IEEE and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)