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Ute Risse-Buhl, Christine Anlanger, Katalin Kalla, Thomas R Neu, Christian Noss, Andreas Lorke, Markus Weitere
Previous laboratory and on-site experiments have highlighted the importance of hydrodynamics in shaping biofilm composition and architecture. In how far responses to hydrodynamics can be found in natural flows under the complex interplay of environmental factors is still unknown. In this study we investigated the effect of near streambed turbulence in terms of turbulent kinetic energy (TKE) on the composition and architecture of biofilms matured in two mountainous streams differing in dissolved nutrient concentrations...
September 28, 2017: Water Research
Shohei Miyazaki, Kagami Miyaji, Keiichi Itatani, Norihiko Oka, Shinji Goto, Masanori Nakamura, Tadashi Kitamura, Tetsuya Horai, Koichi Sughimoto, Yuki Nakamura, Naoki Yoshimura
OBJECTIVES: Inefficient aortic flow after the Norwood procedure is known to lead to the deterioration of ventricular function due to an increased cardiac workload. To prevent the progression of aortic arch obstruction, arch reconstruction concomitant with second-stage surgery is recommended. The aim of this study was to determine the indications for reconstruction based on numerical simulation and to reveal the morphology that affects the haemodynamic parameters. METHODS: Fifteen patients who underwent the Norwood procedure or arch repair and Damus-Kaye-Stansel anastomosis were enrolled...
October 17, 2017: Interactive Cardiovascular and Thoracic Surgery
Nobuyasu Kato, Masaaki Yamagishi, Keiichi Itatani, Takako Miyazaki, Yoshinobu Maeda, Satoshi Asada, Yoshiro Matsui, Hitoshi Yaku
OBJECTIVES: To clarify the risk factors for abnormal degeneration of autologous pericardium, the mechanical stress on the endothelial tissue caused by turbulent blood flow in the pulmonary artery (PA) reconstructed with autologous pericardium and major aortopulmonary collateral arteries was assumed in pulmonary atresia and ventricular septal defect. METHODS: Patient-specific PA models were created for 6 patients based on their past computed tomography images taken after unifocalization of major aortopulmonary collateral arteries...
October 12, 2017: Interactive Cardiovascular and Thoracic Surgery
Guowei Yang, Shengzui You, Meihua Bi, Bing Fan, Yang Lu, Xuefang Zhou, Jing Li, Hujun Geng, Tianshu Wang
Free-space optical (FSO) communication utilizing a modulating retro-reflector (MRR) is an innovative way to convey information between the traditional optical transceiver and the semi-passive MRR unit that reflects optical signals. The reflected signals experience turbulence-induced fading in the double-pass channel, which is very different from that in the traditional single-pass FSO channel. In this paper, we consider the corner cube reflector (CCR) as the retro-reflective device in the MRR. A general geometrical model of the CCR is established based on the ray tracing method to describe the ray trajectory inside the CCR...
September 10, 2017: Applied Optics
Khadijeh Mohri, Simon Görs, Jonathan Schöler, Andreas Rittler, Thomas Dreier, Christof Schulz, Andreas Kempf
The computed tomography of chemiluminescence (CTC) technique was applied for the first time to a real highly turbulent swirl flame setup, using a large number of CCD cameras (Nq=24 views), to directly reconstruct the three-dimensional instantaneous and time-averaged chemiluminescence fields. The views were obtained from a 172.5° region (in one plane) around the flame, and the CTC algorithm [Floyd et al., Combust. Flame158, 376 (2011)CBFMAO0010-2180] was used to reconstruct the flame by discretizing the domain into voxels...
September 10, 2017: Applied Optics
Yanqiu Yang, Lin Yu, Qiu Wang, Yixin Zhang
The models of the short-term spreading and wander of the short-term spreading filter for partially coherent Gaussian beams propagating in an anisotropic oceanic turbulence are established by considering the effect of irradiance fluctuations on beam wander. The results of beam wander based on our model are larger than Andrews and Phillips's model, which considers the effect of the beam wander twice and weakens the effect of irradiance fluctuations on the beam wander. The results of our model show that the short-term spreading and wander of beams increase as the rate of dissipation of kinetic energy per unit mass of fluid and the emitting beam radius decrease, but they increase as the dissipation rate of temperature variance increases...
September 1, 2017: Applied Optics
Yinzhu He, Shijie Zhao, Haoyun Wei, Yan Li
In this paper, a quasi-common-path method to improve the stability of laser measurement instruments is proposed. The method releases the strictness of the common-path structure and enables the compensation of errors caused by air turbulence. A wavefront measurement system is set up to simultaneously detect both the wavefronts of the quasi-common-path beams, of which the orthogonal distance varies from 0 to 4 times the beam diameter. The correlation coefficient between two wavefronts remains around 0.9 in turbulence, which verifies the feasibility...
August 10, 2017: Applied Optics
Chuanyi Lu, Daomu Zhao
The analytical formula for the cross-spectral density function of the rectangular cusped random beams, also known as fractional multi-Gaussian Schell-model beams, propagating in oceanic turbulence, is derived. The statistical properties incorporating the spectral density and the spectral degree of coherence of the beams on propagation are investigated. It is found that the beams maintain a rectangular-shaped cusped profile in weak turbulence just as in free space, whereas in strong turbulence or at sufficiently long propagation distances, the beams profile would be destroyed little by little, turning out to be Gaussian profile eventually...
August 10, 2017: Applied Optics
Huihua Fu, Ping Wang, Tao Liu, Tian Cao, Lixin Guo, Jiao Qin
The average bit error rate (ABER) performance of an avalanche-photodiode (APD)-based pulse-position modulation (PPM) free-space optical (FSO) communication system is investigated considering the aperture averaging effect. The approximate ABER expression is theoretically derived in terms of M and exponentiated Weibull (EW) distributions under weak-to-strong turbulent atmosphere conditions with a binary PPM (BPPM) scheme. Union-bound and Hermite polynomials are then considered to estimate the performance of M-ary PPM FSO systems...
August 10, 2017: Applied Optics
Flavien Blary, Julien Chabé, Aziz Ziad, Julien Borgnino, Yan Fanteï-Caujolle, Arnaud Liotard, Frédéric Falzon
Optical system performances can be affected by local optical turbulence created by its surrounding environment (telescope dome, clean room, or atmospheric layer). This paper follows a previous one introducing the INdoor TurbulENce SEnsor (INTENSE) instrument for optical turbulence characterization in a local area by exploitation of laser beam angle-of-arrival fluctuations. After a brief summary of the theoretical background, we present in this part results obtained using the INTENSE instrument in various optical integration testing clean rooms and telescope domes, each with specific air behavior conditions...
August 1, 2017: Applied Optics
Gero Nootz, Silvia Matt, Andrey Kanaev, Kyle P Judd, Weilin Hou
The propagation of a laser beam through Rayleigh-Bénard (RB) turbulence is investigated experimentally and by way of numerical simulation. For the experimental part, a focused laser beam transversed a 5  m×0.5  m×0.5  m water filled tank lengthwise. The tank is heated from the bottom and cooled from the top to produce convective RB turbulence. The effect of the turbulence on the beam is recorded on the exit of the beam from the tank. From the centroid motion of the beam, the index of refraction structure constant Cn2 is determined...
August 1, 2017: Applied Optics
Haolin Ding, Shihe Yi, Yangzhu Zhu, Lin He
Nanoparticle-based planar laser scattering was used to measure the density distribution of the supersonic (Ma=3.0) turbulent boundary layer and the optical path difference (OPD), which is quite crucial for aero-optics study. Results were obtained using ray tracing. The influences of different layers in the boundary layer, turbulence scales, and light incident angle on aero-optics were examined, and the underlying flow physics were analyzed. The inner layer plays a dominant role, followed by the outer layer...
September 20, 2017: Applied Optics
Hanjun Luo, Zhengbiao Ouyang, Qiang Liu, Zhenli Lu, Bin Li
There exists a performance limitation in a pulsed Geiger-mode avalanche photodiode laser ranging system because of the echo intensity random fluctuation caused by turbulence effects. To suppress the influence of turbulence effects, we present a cumulative pulse detection technique with the ability to achieve improved cumulative probabilities and range accuracy. Based on the modulated Poisson model, the cumulative probabilities, range accuracy, and their influencing factors are investigated for a cumulative Q-switched laser pulse train...
October 10, 2017: Applied Optics
Xueliang Li, Tianwen Geng, Shuang Ma, Yatian Li, Shijie Gao, Zhiyong Wu
The performance of coherent free-space optical (CFSO) communication with phase modulation is limited by both phase fluctuations and intensity scintillations induced by atmospheric turbulence. To improve the system performance, one effective way is to use digital phase estimation. In this paper, a CFSO communication system with quadrature phase-shift keying modulation is studied. With consideration of the effects of log-normal amplitude fluctuations and Gauss phase fluctuations, a two-stage Mth power carrier phase estimation (CPE) scheme is proposed...
June 1, 2017: Applied Optics
Jiankun Zhang, Shengli Ding, Anhong Dang
We theoretically analyze and experimentally verify the performance of multiple polarization parameters in the presence of atmospheric turbulence for a terrestrial optical transmission. First, both the first- and second-moment characteristic of polarization parameters are derived based on the extended Huygens-Fresnel principle. Then, numerical simulations are presented for different propagating distances, optical source properties, and turbulent strengths. Finally, a series of well-designed experiments are carried out to verify the theory with turbulence-controlled conditions, where the polarization states are measured at two wavelengths, respectively...
June 20, 2017: Applied Optics
Pedro Escárate, Rodrigo Carvajal, Laird Close, Jared Males, Katie Morzinski, Juan C Agüero
In this paper, we address the design of a minimum variance controller (MVC) for the mitigation of vibrations in modern telescope adaptive optics (AO) systems. It is widely accepted that a main source of non-turbulent perturbations is the mechanical resonance induced by the wind or the instrumentation systems, such as fans and cooling pumps. To adequately mitigate vibrations, the application of frequency-based controllers has been considered in the past decade. In this work, we express the system model in terms of the tracking of a zero-input signal via the MVC...
July 1, 2017: Applied Optics
Andrew T Young, Eric Frappa
Fata Morgana mirages are frequently seen at Lake Geneva. We show the first photographs of them, including a real-time video, and explain their main features, which are due to the very turbulent entrainment zones of capping inversions, especially in valley circulations.
July 1, 2017: Applied Optics
Ashley Marchese, Melissa L. Langhan
Stridor is a result of turbulent air-flow through the trachea from upper airway obstruction, and although in children it is often due to croup, it can also be caused by noninfectious and/or congenital conditions as well as life-threatening etiologies. The history and physical examination guide initial management, which includes reduction of airway inflammation, treatment of bacterial infection, and, less often, imaging, emergent airway stabilization, or surgical management. This issue discusses the most common as well as the life-threatening etiologies of acute and chronic stridor and its management in the emergency department...
November 2017: Pediatric Emergency Medicine Practice
Jie Zhu, Xiaoli Li, Huiqin Tang, Kaicheng Zhu
We introduce a class of random stationary, scalar source named as multi-cosine-Laguerre-Gaussian-correlated Schell-model (McLGCSM) source whose spectral degree of coherence (SDOC) is a combination of the Laguerre-Gaussian correlated Schell-model (LGCSM) and multi-cosine-Gaussian correlated Schell-model (McGCSM) sources. The analytical expressions for the spectral density function and the propagation factor of a McLGCSM beam propagating in turbulent atmosphere are derived. The statistical properties, such as the spectral intensity and the propagation factor, of a McLGCSM beam are illustrated numerically...
August 21, 2017: Optics Express
Yan Zhang, Ping Wang, Lixin Guo, Wei Wang, Hongxin Tian
The average bit error rate (ABER) performance of an orbital angular momentum (OAM) multiplexing-based free-space optical (FSO) system with multiple-input multiple-output (MIMO) architecture has been investigated over atmospheric turbulence considering channel estimation and space-time coding. The impact of different types of space-time coding, modulation orders, turbulence strengths, receive antenna numbers on the transmission performance of this OAM-FSO system is also taken into account. On the basis of the proposed system model, the analytical expressions of the received signals carried by the k-th OAM mode of the n-th receive antenna for the vertical bell labs layered space-time (V-Blast) and space-time block codes (STBC) are derived, respectively...
August 21, 2017: Optics Express
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