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1

Analiza drgań kładki kompozytowej wywołanych działaniem wiatru

Sobczyk B., Chróścielewski J., Witkowski W.

Biuletyn Wojskowej Akademii Technicznej

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2015

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Vol. 64, nr 1

91-101

PL

W pracy omówiono sposób przeprowadzenia uproszczonej, numerycznej analizy drgań kładki kompozytowej wywołanych działaniem wiatru. Rozważaniom poddano swobodnie podpartą konstrukcję o rozpiętości 16 m i przekroju w kształcie litery U. W pierwszej kolejności przeprowadzono dwuwymiarową analizę opływu niepodatnego kształtu przekroju kładki w poziomym strumieniu wiatru o prędkości 10 m/s. Obliczenia numeryczne przeprowadzono programem ANSYSFLUENT14. Rezultaty analizy opływu - liczbę Strouhala - porównano z wynikami zawartymi w monografii A. Flagi pt. Inżynieria wiatrowa. Podstawy i zastosowania, Arkady, Warszawa, 2008, w celu oceny poprawności obliczeń. W kolejnym etapie zbudowano przestrzenny model konstrukcji w programie ABAQUS6.12-3. Wykonano analizę drgań konstrukcji metodą modalną, w której obciążeniem jest ciśnienie działające na powierzchni pomostu, zmienne w czasie, o wartościach wyznaczonych na podstawie analizy opływu. Dla badanej konstrukcji sprawdzono kryteria komfortu przyszłych użytkowników obiektu, który jest w fazie wytwarzania.

EN

In the work, we describe a simplified method for numerical analysis of a FRP composite footbridge in the field of wind induced vibrations. We consider a simply supported structure with a span length of 16 m and U-shape cross-section. Firstly, a two dimensional flow analysis is performed of the fixed bridge cross-section which is subjected to a lateral wind action with 10 m/s velocity. Calculations are performed using ANSYSFLUENT14 software. Results of the flow analysis (Strouhal’s number) are compared with the results presented in a monograph by A. Flaga, entitled Inżynieria Wiatrowa. Podstawy i zastosowania (Wind Engineering. The bases and applications) (in Polish), Arkady, Warszawa, 2008, in order to validate calculations. After that, a three dimensional spatial model of the footbridge is built in ABAQUS6.12-3 finite element method software. Amodal dynamics problem is solved, where the loading conditions are adopted on the basis of the flow analysis and applied as an evenly distributed pressure on the bridge deck surface. Finally, the users’ vibration comfort criterion is checked for the considered structure.

2

Polarization-selective beam splitter by a sandwiched grating

Wang B, Chen L, Lei L, Zhou J

Optica Applicata

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2013

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Vol. 43, nr 2

s. 229-236

EN

We describe a polarization-selective beam splitter by a sandwiched grating, which can fulfill the high efficiency element for TE polarization and the two-port output for TM polarization. The modal method and the rigorous coupled-wave analysis (RCWA) are employed together to optimize the polarization-selective beam splitter. According to the modal method, the grating duty cycle and period are discussed to analyze the physical mechanism of such a dual-function element. Using RCWA, grating depth and thickness of the covering layer are accurately optimized to design such a polarization-selective beam splitter. With the optimized grating duty cycle, period, depth and covering layer thickness, TE polarization can be mainly diffracted in the –1st order and two-port output can be achieved for TM polarization in the 0th and the –1st orders. The polarization-selective beam splitter should be a useful element in a variety of applications with advantages of high efficiency, wideband property, and dual functions based on a sandwich grating.

3

Sandwiched grating for high efficiency with wide bandwidth and polarization independence

Wang B, Lei L, Chen L, Zhou J

Optica Applicata

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2012

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Vol. 42, nr 4

743--749

EN

We describe novel sandwiched grating for high efficiency with polarization independence. The grating parameters can be optimized based on modal method and rigorous coupled-wave analysis (RCWA). According to modal method, grating period and duty cycle are prescribed for polarization independence by excited modes with different effective indices. Using RCWA, accurate grating depth and covering layer thickness are optimized by numerical calculation. The sandwiched grating can show high efficiency for both TE and TM polarizations with the optimized grating period, duty cycle, depth, and covering layer thickness. Most importantly, wideband property can be obtained for operation around the central wavelength of 800 nm. The presented novel sandwiched grating can have merits of high efficiency, polarization independence, and wideband property, which should be of great significance for numerous applications.

4

Reflective diffraction with high efficiency and beam splitter by metal-mirror-based grating

Wang B., Lei L., Chen L., Zhou J.

Optica Applicata

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2012

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Vol. 42, nr 3

473-479

EN

It is interesting and desirable to achieve two functions of high efficiency and two-port output with one reflective grating, which is not easy to acquire by multilayer coatings. We describe the reflective high efficiency element and the two-port beam splitter by the metal-mirror-based grating. By modal method, the design guideline is proposed according to the two-beam interference of the excited modes by incident TE and TM polarizations. Using rigorous coupled-wave analysis (RCWA), accurate grating parameters are optimized by numerical calculation. This indicates that wideband property can be achieved for such a reflective dual-function grating. Furthermore, the element can also be used for beam splitting for TE polarization with the pre-determined angle of incidence. With merits of wideband and so many functions, the reflective elements presented should be useful in a variety of optical systems.

5

Numerical optimization of polarizing beam splitter gratings and modal explanation

Wang B.

Optica Applicata

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2010

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Vol. 40, nr 1

101--107

EN

We describe high-density deep-etched fused-silica transmission polarizing beam splitter (PBS) gratings and their simple physical explanation. Optimized numerical results of the grating depth and period are given using the rigorous coupled-wave analysis in order to achieve high extinction ratio and efficiency for the usual laser wavelengths 351, 441.6, 532, 632.8, 800, and 1053 nm. The physical mechanism of such a PBS grating can be well explained with the effective indices of the modes for TE/TM polarization, which is a useful extension of the modal method for different structures reported in this paper. Compared with the work of Clausnitzer et al., fused-silica gratings can work as PBSs for not only the special duty cycle of 0.51 but also the usual duty cycle of 0.50. These numerical results and simple physical explanation provide a useful guideline for the design of a PBS grating.