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Fiber laser twist sensor with hybrid few-mode tilted Bragg grating and few-mode long period grating

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Optoelectronics Letters 2019年第3期15卷 161-164页

作者： YANG Kang LIU Yan-ge WANG Zhi LI Guo-yu HAN Ya ZHANG Hong-wei MAO Bai-wei Tianjin Key Laboratory of Optoelectronic Sensor and Sensing Network Technology Institute of Modern OpticsNankai UniversityTianjin300350China Institute of Information Technology Handan UniversityHandan056005China

A twist sensor with hybrid few-mode tilted fiber Bragg grating(FM-TFBG) and few-mode long period grating(FM-LPG) in fiber laser cavity is demonstrated. The FM-LPG is utilized to excite LP11 core mode. The FM-TFBG is used for sensing. The transverse modes at 1 553.9 nm and 1 550.5 nm are LP01 and LP21 core modes, respectively, which are coupled from forward-propagating LP11 core mode. These two excitation wavelengths have opposite variation tendencies, which participate in sensing. The twist sensitivity of 0.16 dB/° from-40° to 40° is achieved. The proposed sensor has potentially used for structure monitoring in many areas.

关键词： LPG Fiber laser twist sensor with hybrid few-mode tilted Bragg grating and few-mode long period grating

Fabrication of kW-level chirped and tilted fiber Bragg gratings and filtering of stimulated Raman scattering in high-power CW oscillators

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High Power Laser Science and Engineering 2019年第2期7卷 76-82页

作者： Kerong Jiao Jian Shu Hua Shen Zhiwen Guan Feiyan Yang Rihong Zhu MIIT Key Laboratory of Advanced Solid Laser Nanjing University of Science and TechnologyNanjing 210094China School of Electronic Engineering and Optoelectronic Technology Nanjing University of Science and Technology.Nanjing 210094.China

Suppression of stimulated Raman scattering(SRS)by means of chirped and tilted fiber Bragg gratings(CTFBGs)has become a key ***,research on high-power systems is still lacking due to two ***,after the inscription,there are a large number of hydroxyl compounds and hydrogen molecules in CTFBGs that cause significant heating due to their strong infrared ***,CTFBGs can couple Stokes light from the core to the cladding and the coating,which causes serious heating in the coating of the *** at overcoming these bottlenecks,a process that combines constant-low-temperature and variable-high-temperature annealing is used to reduce the thermal slope of the ***,a segmented-corrosion cladding power stripping technology is used on the CTFBG to remove the Stokes light which is coupled to the cladding,which solves the problem of overheating in the coating of the ***,a CTFBG with both a kilowatt-level power-carrying load and the ability to suppress SRS in a fiber laser has been ***,we establish a kW-level CW oscillator to test the *** results demonstrate that the power-carrying load of the CTFBG is close to 1 kW,the thermal slope is lower than 0.015 ℃/W,and the SRS suppression ratio is nearly 23 dB.

关键词： chirped and tilted fiber Bragg gratings fiber optics components high-power fiber laser stimulated Raman scattering

Power Tapping Function in Near Infra-Red Region Based on 45°tilted Fiber Gratings

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Optics and Photonics Journal 2013年第2期3卷 158-162页

作者： Adedotun Adebayo Zhijun Yan Kaiming Zhou Lin Zhang Hongyan Fu David Robinson Arden Photonics Ltd. Solihull UK Aston Institute of Photonics Technology School of Engineering and Applied Science Aston University Birmingham UK Department of Electronic Engineering School of Information Science and Engineering Xiamen University Xiamen China

We report an efficient power tapping device working in near infra-red (800 nm) wavelength region based on UV-in- scribed 45° tilted fiber grating (45°-TFG) structure. Five 45°-TFGs were UV-inscribed in hydrogenated PS750 fiber using a custom-designed phase mask with different grating lengths of 3 mm, 5 mm, 9 mm, 12 mm and 15 mm, showing polarization dependent losses (PDLs) of 1 dB, 3 dB, 7 dB, 10 dB and 13 dB, respectively. The power side-tapping efficiency is clearly depending on the grating strength. It has been identified that the power tapping efficiency increases with the grating strength and deceases along the grating length. The side-tapped power profile has also been examined in azimuthal direction, showing a near-Gaussian distribution. These experimental results clearly demonstrated that 45°- TFGs may be used as in-fiber power tapping devices for applications requiring in-line signal monitoring.

关键词： Power Tapping tilted Fiber Grating Polarization Dependent Loss In-Fiber Polarizer

tilted Bianchi Type VI0 Cosmological Model in Saez and Ballester Scalar Tensor Theory of Gravitation

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Journal of Modern Physics 2010年第1期1卷 67-69页

作者： Subrata Kumar Sahu 不详

tilted Bianchi type VI0 cosmological model is investigated in a new scalar tensor theory of gravitation pro-posed by Saez and Ballester (Physics Letters A 113:467, 1986). Exact solutions to the field equations are derived when the metric potentials are functions of cosmic time only. Some physical and geometrical proper-ties of the solutions are also discussed.

关键词： Saez and Ballester Theory tilted Cosmological Model Scalar Field

Tunable Reflection Bands and Defect Modes in One-Dimensional tilted Photonic Crystal Structure

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Optics and Photonics Journal 2012年第3期2卷 230-236页

作者： Sanjeev K. Srivastava Maitreyi Upadhyay Suneet K. Awasthi S. P. Ojha Department of Physics and Material Science and Engineering Jaypee Institute of Information Technology Deemed University Noida India Department of Physics Amity Institute of Applied Sciences Amity University Noida India Department of Physics Shobhit University Meerut India

We show theoretically that range of reflection bands and defect modes inside the band gap can be tuned by using a one-dimensional tilted photonic crystal (TPC) structure. A TPC structure is similar to the conventional PC structure with the only difference that in this case alternate layers are inclined at certain angle in the direction of periodicity of the structure. In order to obtain the reflectance spectra of the proposed structure transfer matrix method (TMM) has been employed. From the analysis of the reflectance curve, it is found that 100% reflectance range can be varied and enhanced by using TPC structure for both (TE- and TM-) polarizations. The enhancement in reflection bands increases as the tilt angle increases for both the polarizations and hence the enlarged omni-reflectance bands are obtained. Further, we study the properties of the defect modes in TPC structure by introducing the tilted defect at the different tilt angle. The results show that defect modes (tunneling modes) can be tuned at different wavelengths by changing the tilt angle of the structure without changing other parameters. Finally, the effect of variation thickness of defect layers on the tunneling mode has been studied for both TPC and conventional PC structure. The proposed model might be used as a tunable broadband omnidirectional reflector as well as tunable tunneling or transmission mode, which has potential applications in the field of photonics and optoelectronics.

关键词： Photonic Crystal Structure Photonic Band Gap (PBG) Omnidirectional Reflector tilted PC Structure De-fect Modes

Optimization of the tilted Fibre Bragg Gratings for the Fibre Accelerometric Sensor

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Journal of Computer and Communications 2014年第7期2卷 36-41页

作者： Frantisek Urban 1Dept of Microelectronics Brno University of Technology FEEC Brno Czech Republic 2Network Group s.r.o. Brno Czech Republic

The presentation shows the principle and construction of the fibre optic accelerometric sensor. The sensor element is based on the use of the tilted fibre Bragg grating (TFBG) that is imprinted to the bend insensitive single-mode telecommunication grade fibre. The fibre section with TFBG is then coupled to the evaluation fibre circuit with the cladding-core mode conversion element that provides the core re-coupling of the optical power injected by TFBG to the fibre cladding. The cladding-core mode conversion efficiency is sensitive to the acceleration generated fibre bending. It is shown that the sensitivity of the device depends on the rate of the main core reflection versus cladding ghost reflection induced by the grating. The analysis of the core reflection power coupling on the angle of the grating tilt and the analysis of the cladding ghost reflection power coupling on the angle of the grating tilt is presented and the optimal parameters of the tilt and refractive index modulation are derived. The presentation gives the experimental results of the TFBG sensor prepared according to the optimization process.

关键词： Optical Fibre tilted Fibre Bragg Grating Accelerometric Sensor Cladding Modes Reflected Spectrum

What Is the Association between an Anteriorly tilted Pelvis and Trendelenburg Gait?

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Open Journal of Orthopedics 2018年第12期8卷 464-475页

作者： Yvonne Paul Mariette Swanepoel Terry J. Ellapen Marco Barnard Henriette V. Hammill Reino W. Müller Juandré Williams Department of Sport and Dental Therapy Faculty of Health Science Tshwane University of Technology Pretoria South Africa School of Human Movement Science (PhASRec) Faculty of Health Science North-West University Potchefstroom South Africa

Lower back pain (LBP) is a widespread, painful medical condition that has been plaguing society for many years. Present conservative rehabilitation focus is on lumbo-pelvic hip stability exercises in individual planes. However, a functional integrative rehabilitative approach addressing lumbo-pelvic misalignment in the sagittal (anteriorly tilted pelvis) and frontal (Trendelenburg gait) planes has not been presented. The aforementioned patho-biomechanical conditions and their management are often discussed estranged from each other rather than functionally integrated. This paper serves as a short communication which discusses the lumbo-pelvic anatomy, identifies the anatomical and biomechanical associations between the anteriorly tilted pelvic and Trendelenburg gait. Through an analysis of relevant literature, recommendations were made on the improvement of flexibility of the hip flexors, taut iliofemoral and pubofemoral ligaments to resolve the primary abnormal force-couple, with improved flexibility of the erector spinae and quadratus lumborum to resolve the secondary abnormal force-couple. In addition, improved flexibility of the hip flexors should coincide with closed-kinetic chain concentric strengthening of the ipsi-lateral hip abductors and contralateral external obliques. Patient education is also needed for self-re-alignment of the lower extremity to a neutral position and neutral foot stance. Biokineticists/exercise therapists should also review the patient’s gait biomechanics to determine whether sartorius synergistic dominance is in play. In conclusion, the association between an anteriorly tilted pelvis and Trendelenburg gait, is in regard to taut anterior acetabulofemoral ligaments and femoral retroversion torsion angle that is both preceded and followed by the biomechanical influence of various anatomical structures. These anatomical and biomechanical factors must be evaluated by the biokineticists/exercise therapists before prescribing a rehabilitati

关键词： Anteriorly tilted Pelvis Trendelenburg Gait Interactive Functional Rehabilitation

Preparation of large size aluminium alloy cylindrical preforms by multi-layer spray deposition

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中国有色金属学会会刊：英文版 2000年第2期10卷 196-199页

作者：康智涛袁武华陈振华周多三 Cent S Univ Technol Non Equilibrium Mat Res Inst Changsha 410083 Peoples R China

Preparation of large scale aluminium alloy cylindrical preforms have been studied by the methods of vertical spray deposition and tilted spray deposition respectively. The results show that aluminium alloy cylindrical preforms of a size up to d 320 mm×500 mm can take shape well by applying multi layer tilted spray deposition technology if the process is controlled properly. The spray system scans in a radius ranging from the center to the rim of the preform, and the velocity is inversely proportional to the displacement. The multi layer deposited preforms exhibit high cooling rate. The larger the diameter is and the higher the cooling rate and yield are.

关键词： multi-layer spray deposition vertical spray tilted spray

Estimating the maximum impact force of dry granular flow based on pileup characteristics

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Journal of Mountain Science 2019年第10期16卷 2435-2452页

作者： XIAO Si-you SU Li-jun JIANG Yuan-jun MEHTAB Alam LI Cheng LIU Dao-chuan Key Laboratory of Mountain Hazards and Earth Surface Processes and Institute of Mountain Hazards andEnvironmentChinese Academy of SciencesChengdu610041China University of Chinese Academy of Sciences Beijing100049China CAS Center for Excellence in Tibetan Plateau Earth Sciences Beijing100101China Sichuan Highway Planning DesignResearch Institute LtdChengdu610041China

The maximum normal impact resultant force(NIRF)is usually regarded as the sum of the static earth pressure of the dead zone and the dynamic impact pressure of the flowing *** influence of the interaction between the flowing layer and dead zone on the impact force is *** this study,we classified two impact models with respect to the pileup characteristics of the dead ***,we employed the discrete element method to investigate the influences of the pileup characteristics on the impact force of dry granular flow on a tilted rigid *** the final pileup height is equal to the critical value,the maximum NIRF can be estimated using a hydrostatic model,because the main contribution to the maximum NIRF is the static earth pressure of the dead *** the final pileup height is less than the critical value,however,the particles in the dead zone are squeezed along the slope surface by the impact ofthe flowing layer on the dead zone,and because of shear effects,the flowing layer causes an entrainment in the dead *** results in a decrease in the volume of the dead zone at the moment of maximum NIRF with increases in the slope *** such,the maximum NIRF mainly comprises the instant impact force of the flowing layer,so hydro-dynamic models are effective for estimating the maximum *** models will benefit from further study of the components and distribution of the impact force of dry granular flow.

关键词： Dry granular flow tilted retaining wall Impact force Discrete element method Pileup height