A Method of Using a Carbon Fiber Spiral-Contact Electrode to Achieve Atmospheric Pressure Glow Discharge in Air

During discharge, appropriately changing the development paths of electron avalanches and increasing the number of initial electrons can effectively inhibit the formation of filamentary discharge. Based on the aforementioned phenomenon, we propose a method of using microdischarge electrodes to produce a macroscopic discharge phenomenon. In the form of an asymmetric structure composed of a carbon fiber electrode, an electrode structure of carbon fiber spiral-contact type is designed to achieve an atmospheric pressure glow discharge in air, which is characterized by low discharge voltage, low energy consumption, good diffusion and less ozone generation.

An Effective Thermal Splicing Method to Join Fluoride and Silica Fibers for a High Power Regime

A repeatable and simple thermal splicing method for low loss splice between fluoride and silica fibers is presented. The minimum splicing loss of 0.58 dB is achieved experimentally with this approach, Meanwhile, the power capacity of this splicing joint is also tested with a high power fiber laser. The maximum input power is up to 15 W, only limited by the available power of the laser source. To the best of our knowledge, this is the first report on thermal splicing between fluoride and silica fibers operating in a high power regime without any complicated ion-assisted deposition process.

Progressive collapse resisting capacity of reinforced concrete load bearing wall structures

Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the "load factor" parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.

An improved calculation method for fiber Raman amplifier equations with multi-wavelength pumping

A novel numerical method for fiber Raman amplifier (FRA) from standard propagation equations is presented and derived based on the one-step method for ordinary differential equation (ODE). The proposed algorithm is effective in solving FRA equations including all the interactions among pumps, signals, and noises. Applications of the numerical analysis to practical FRA-based systems show a great reduction in computation time in comparison with the average power method and the fourth-order Runge-Kutta (RK) method, under the same condition. Also the proposed method can decrease the computing time over three orders of magnitude with excellent accuracy promises in comparison with the direct integration method.

Parameter analysis of a photonic crystal fiber with raised-core index profile based on effective index method

Photonic crystal fibers （PCFs） with a stepped raised-core profile and one layer equally spaced holes in the cladding are analyzed. Using effective index method and considering a raised step refractive index difference between the index of the core and the effective index of the cladding, we improve the characteristic parameters such as numerical aperture and V-parameter, and reduce its bending loss to about one tenth of a conventional PCF. Implementing such a structure in PCFs may be one step forward to achieve low loss PCFs for communication applications.

A Novel Method for Measuring Photo-Induced Birefringence of Photosensitive Fibers

In this paper, we report a novel method for accurately measuring the photo-induced birefringence of photosensitive fiber by using Mach-Zehnder interferometer. The results indicate that the normalized birefringence can attain 10-5.

A useful method for determination of optimal fiber input power in spontaneous Brillouin-scattering-based sensing system

A method for the optimal fiber input power determination is presented by employing the variation characteristics of signal to noise ratio(SNR) in spontaneous Brillouin-scattering-based sensing system. And a heterodyne detection system is constructed for measuring the Brillouin scattering spectra with different fiber input powers. The Brillouin spectrum width and system SNR can be simultaneously measured from these spectra, and the optimal fiber input power can be obtained from such information. In the experiment, for 48.8-km-long standard single-mode fiber(SSMF), the optimal fiber input power values are all approximately 0 dBm obtained by the maximum SNR position for different local oscillator power values and average times.

High temperature-sensitivity sensor based on long period fiber grating inscribed with femtosecond laser transversal-scanning method

We propose a high temperature-sensitive long period fiber grating（LPFG） sensor fabricated by using the femtosecond laser transversal-scanning method. The femtosecond pulses scan over the whole fiber core and some part of the cladding region; the modified regions are more extended. It is found that the LPFG-I fabricated by the transversal-scanning method shows higher temperature sensitivity and better temperature uniformity than that of LPFG-II written by the femtosecond laser point-by-point method. The LPFG-I with a temperature sensitivity of 75.96 pm/°C in the range of 25°C–400°C is measured. Moreover, in the range from 400°C to 800°C, a higher temperature sensitivity of 148.64 pm/°C and good linearity of 0.99 are achieved, while the temperature sensitivity of LPFG-II is only 95.55 pm/°C. LPFG-I exhibits better temperature characteristics, which, to the best of our knowledge, has the highest sensitivity in silica fiber temperature sensors.

Effect of Scanning Beam Profile to Fabricate Fused Fiber Tapers by CO_2 Laser Irradiation Method

Beam uniformity is a crucial building block of CO2 experiments aimed at fusing and stretching optical fibers in a lossless manner. When the irradiation beam is expanded through a galvanometer mirror, ways to achieve beam uniformity are investigated.

A novel control method for on-off gain and gain tilt of fiber Raman amplifiers

Considering spectrum tilt due to signal-to-signal Raman scattering (SSRS) in backward distributed fiber Raman amplifiers (B-DFRA),an inverse tilted on-off gain profile is adopted to achieve flat net gain.A simple approximate linear relationship of pump power at each wavelength versus on-off gain level and tilt was derived numerically and experimentally so that a novel control method was established.Since there are only 3 pre-determinable constants required for individual pump wave,it is easy to be realized.As an example,maximum errors less than 0.2 and 0.4 dB respectively for average gain and gain tilt were achieved over C+L band in 100-km back-pumped standard single-mode fiber (SMF) experimentally.

EXISTENCE OF SOLUTIONS FOR A CLASS OF QUASILINEAR ELLIPTIC SYSTEMS WITH INDEFINITE WEIGHTS

By use of the fibering method introduced by Pohozaev S I, the existence of positive solutions for homogeneous Dirichlet problem of a class of quasilinear elliptic systems with indefinite weights is obtained.

EXISTENCE OF TWO POSITIVE SOLUTIONS TO SINGULAR ELLIPTIC SYSTEMS WITH WEIGHTS

In this paper,a class of singular elliptic systems involving weight functions and nonlinear terms are studied. By the fibering method introduced by Pohozaev and the strong maximum principle,the existence of two positive solutions to the elliptic systems are obtained.

Experimental-computational study of fibrous particle transport and deposition in a bifurcating lung model

Experiments carried out using a lung model with a single horizontal bifurcation under different steady inhalation conditions explored the orientation of depositing carbon fibers, and particle deposition frac- tions. The orientations of deposited fibers were obtained from micrographs. Specifically, the effects of the sedimentation parameter （γ）, fiber length, and flow rate on orientations were analyzed. Our results indicate that gravitational effect on deposition cannot be neglected for 0.0228 〈 γ 〈 0.247. The absolute orientation angle of depositing fibers decreased linearly with increasing y for values 0.0228 〈 γ 〈 0.15. Correspondence between Stokes numbers and y suggests these characteristics can be used to estimate fiber deposition in the lower airways. Computer simulations with sphere-equivalent diameter models for the fibers explored deposition efficiency vs. Stokes number. Using the volume-equivalent diameter model, our experimental data for the horizontal bifurcation were replicated. Results for particle deposition using a lung model with a vertical bifurcation indicate that body position also affects deposition.

Properties of Steel Fiber Reinforced Coal Gangue Coarse Aggregate Concrete

In this paper,workability,strength and durability of coal gangue coarse aggregate concrete with different steel fiber content levels have been studied.The results indicate that the concrete compressive strength,flexural strength and tensile splitting strength at the age of 28 days increase with the steel fiber content increasing,while cost and impermeability reduce with steel fiber content increasing.Based on the data of the workability of fresh concrete,mechanical properties and durability of hardened concrete,the concrete cost index system are established to evaluate and optimize the steel fiber content in coal gangue concrete by Efficacy Coefficient Method.The optimization result reveals that the maximum value of the system efficacy coefficient is up to0.87,the coal gangue concrete with steel fiber 1.5%（V︰V）performs better.