Numerical modeling of DPSK pressure signals and their transmission characteristics in mud channels

A numerical model and transmission characteristic analysis of DPSK （differential phase shift keying） pressure signals in mud channels is introduced. With the control logic analysis of the rotary valve mud telemetry, a logical control signal is built from a Gate function sequence according to the binary symbols of transmitted data and a phase-shift function is obtained by integrating the logical control signal. A mathematical model of the DPSK pressure signal is built based on principles of communications by modulating carrier phase with the phase-shift function and a numerical simulation of the pressure wave is implemented with the mathematical model by MATLAB programming. Considering drillpipe pressure and drilling fluid temperature profile along drillpipes, the drillpipe of a vertical well is divided into a number of sections. With water-based drilling fluids, the impacts of travel distance, carrier frequency, drillpipe size, and drilling fluids on the signal transmission were studied by signal transmission characteristic analysis for all the sections. Numerical calculation results indicate that the influences of the viscosity of drilling fluids and volume fraction of gas in drilling fluids on the DPSK signal transmission are more notable than the others and the signal will distort in waveform with differential attenuations of the signal frequent component.

Study on optical constants inversion and infrared transmission characteristics of aerosol particles

Based on the experimental infrared spectral transmittances,an inverse model has been developed to determine the optical constants of the aerosol particles (SiO2 and Al2O3).Combined with the Mie theory and Kramers-Kronig (K-K) relations,the complex refractive indices of the SiO2 and Al2O3 particles are retrieved.The effects of the measurement errors on the inverse results are also investigated.With the optical constants inversed from the experiment,the discrete ordinate method (DOM) is used to calculate the infrared transmission characteristics of the aerosol particle cloud.Considering the multi-scattering and self-emission of the particles,the equivalent transmittance ratio (ETR) is suggested to evaluate the infrared transmission characteristics of the aerosol particles.Particular attention is given to analyze the effects of the volume fraction and diameters on infrared transmission characteristics.When the volume fraction is larger than 0.001,the particle diameter has little effect on the infrared transmission characteristics.For the uniform monodisperse particles in the detection waveband range of 3-5 μm and 8-12 μm,there exists a critical diameter where the ETR reaches the minimum value.In addition,the ETR of 3-5 μm is smaller than that of 8-12 μm with the same volume fraction and particle diameter.

Influence of intra-cavity loss on transmission characteristics of fiber Bragg grating Fabry–Perot cavity

A theoretical model of the fiber Bragg grating Fabry–Perot（FBG-FP） transmission spectrum considering loss of FBG and intra-cavity fiber is presented. Several types of FBG-FPs are inscribed experimentally, and their spectra are measured.The results confirm that weak intra-cavity loss is enhanced at the resonance transmission peak, that is, loss of transmission peaks is observably larger than other wavelengths. For FBG-FPs with multi resonance peaks, when the resonance peak wavelength is closer to the Bragg wavelength, the more significant loss effect of resonance transmission peak is exhibited.The measured spectra are fitted with the presented theoretical model. The fitted coefficient of determinations are near 1,which proves the validity of the theoretical model. This study can be applied to measure FBG loss more accurately, without a reference light. It can play an important role in FBG and FBG-FP writing process optimization and application parameter optimization.

An Experimental Research to Study the Microwaves transmission Characteristics of Ablating Material in Arc-Heated Plasma Flow

in this paper, an experimental research the effect of ablating material on the reflection and the transmission of microwaves in arc-heated plasma flow is presented by using the C band microwave measuring system. The results show that the ablating material with accidented surface and its high temperature have remarkably affected the reflection and the transmission of microwaves. The experiment proves that the system has outstanding precision and reliability.

Influence of substrate process tolerances on transmission characteristics of frequency-selective surface

Frequency-selective surface （FSS） is a two-dimensional periodic structure consisting of a dielectric substrate and the metal units （or apertures） arranged periodically on it. When manufacturing the substrate, its thickness and dielectric constant suffer process tolerances. This may induce the center frequency of the FSS to shift, and consequently influence its characteristics. In this paper, a bandpass FSS structure is designed. The units are the Jerusalem crosses arranged squarely. The mode-matching technique is used for simulation. The influence of the tolerances of the substrate＇s thickness and dielectric constant on the center frequency is analyzed. Results show that the tolerances of thickness and dielectric constant have different influences on the center frequency of the FSS. It is necessary to ensure the process tolerance of the dielectric constant in the design and manufacturing of the substrate in order to stabilize the center frequency.

Intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics:Theoretical and numerical analysis and application

The modal vibration of the rotor is the main cause of excessive vibration of the aeroengine overall structure.To attenuate the vibration of the rotor under different modal shapes from the perspective of energy control,the intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics is derived from the general equation of motion base on the structural intensity method.A dual-rotor-support-casing coupling model subjected to the rotor unbalanced forces is established by the finite element method in this paper.The transmission,conversion and balance relationships of the vibrational energy flow for the rotors in the first-order bending modal shape,the conical whirling modal shape and the translational modal shape are analyzed,respectively.The results show that the vibrational energy flow transmitted to the structure can be converted into the strain energy,the kinetic energy and the energy dissipated by the damping of the structure.The vibrational energy flow transmission characteristics of rotors with different modal shapes are quite different.Especially for the first-order bending modal shape,the vibrational energy flow and the strain energy are transmitted and converted to each other in the middle part of the rotor shaft,resulting in large deformation at this part.To attenuate this harmful vibration,the influences of grooving on the shaft on the first-order bending vibration are studied from the perspective of transmission control of vibrational energy flow.This study can provide theoretical references and guidance for the vibration attenuation of the rotors in different modal shapes from a more essential perspective.

Development of an ONU Using a Reflective Semiconductor Optical Amplifier Transmitter and Its Transmission Characteristic

We propose a WDM-PON system as one of the promising candidates for next generation high capacity, cost-effective and inter-operable optical access network system and develop an ONU using reflective SOA transmitter for the WDM-PON system.

Transmission Spectral Characteristics of Photonic Crystals Milled in Annealed Proton-Exchange LiNbO_3 Waveguide

Transmission spectra of triangular lattice photonic crystals milled in the top surface of an annealed proton- exchange waveguide are numerically simulated. The effects of the finite depth, conical shape, trapezoidal shape and hybrid shape of holes are theoretically analyzed. Due to the difficulty of milling high aspect-ratio cylindrical holes in lithium niobate （LiNbO3 ）, a compromised solution is proposed to improve the overlap between shallow holes and the waveguide mode, and useful transmission spectra with strong contrast and sharp band edges are achieved.

Research and Test of Three-Pulley Noncircular Synchronous Pulley Transmission Mechanism with Minimum Slack

The noncircular synchronous belt drive mechanism has demonstrated certain achievements and has been used in special fields.Research regarding noncircular synchronous belt drive mechanisms has focused on optimization design and kinematic analysis in China,whereas two pulley noncircular synchronous belt transmissions have been developed overseas.However,owing to the noncircular characteristics of the belt pulley,the real-time variation in the belt length slack during the transmission of the noncircular synchronous belt is significant,resulting in high probabilities of skipping and vibration.In this study,a noncircular tensioning pulley is added to create a stable three-pulley noncircular synchronous belt driving mechanism and a good synchronous belt tensioning,with no skipping;hence,the non-uniform output characteristic of the driven pulley is consistent with the theoretical value.In the circular noncircular noncircular three-pulley noncircular synchronous belt mechanism,the pitch curve of the driving synchronous belt pulley is circular,whereas those of the driven synchronous belt and tensioning pulleys are noncircular.To minimize the slack of the belt length of the synchronous belt and the constraint of the concavity and circumference of the tensioning pulley,an automatic optimization model of the tensioning pulley pitch curve is established.The motion simulation,analysis,and optimization code for a three-belt-pulley noncircular synchronous belt drive mechanism is written,and the variation in belt length slack under different speed ratios is analyzed based on several examples.The testbed for a circular-noncircular-noncircular three-pulley noncircular synchronous belt transmission mechanism is developed.The test shows that the three-pulley noncircular synchronous belt drives well.This study proposes an automatic optimization algorithm for the tensioning pulley pitch curve of a noncircular synchronous belt transmission mechanism;it yields a stable transmission of the noncircular synchronous belt transmission mechanism as well as non-uniform output characteristics.

Design of(GO/TiO2)N one-dimensional photonic crystal photocatalysts with improved photocatalytic activity for tetracycline degradation

(GO/TiO2)N(GO represents graphene oxide,and N represents the period number of alternate superposition of two dielectrics)onedimensional photonic crystal with different lattice constants was prepared via the sol–gel technique,and its transmission characteristics for photocatalysis were tested.The results show that the lattice constant,filling ratio,number of periodic layers,and incident angle had effects on the band gap.When the lattice constant,filling ratio,number of periodic layers,and incident angle were set to 125 nm,0.45,21,and 0°,respectively,a gap width of 53 nm appeared at the central wavelength(322 nm).The absorption peak of the photocatalyst at 357 nm overlapped the blue edge of the photonic band gap.A slow photon effect region above 96%reflectivity appeared.The degradation rate of tetracycline in(GO/TiO2)N photonic crystal was enhanced to 64%within 60 min.Meanwhile,the degradation efficiency of(GO/TiO2)N one-dimensional photonic crystal was effectively improved compared with those of the GO/TiO2 composite film and GO/TiO2 powder.

Mass-spring model for elastic wave propagation in multilayered van der Waals metamaterials

Multilayered van der Waals(vdW)materials have attracted increasing interest because of the manipulability of their superior optical,electrical,thermal,and mechanical properties.A mass-spring model(MSM)for elastic wave propagation in multilayered vdW metamaterials is reported in this paper.Molecular dynamics(MD)simulations are adopted to simulate the propagation of elastic waves in multilayered vdW metamaterials.The results show that the graphene/MoS_(2)metamaterials have an elastic wave bandgap in the terahertz range.The MSM for the multilayered vdW metamaterials is proposed,and the numerical simulation results show that this model can well describe the dispersion and transmission characteristics of the multilayered vdW metamaterials.The MSM can predict elastic wave transmission characteristics in multilayered vdW metamaterials stacked with different two-dimensional(2D)materials.The results presented in this paper offer theoretical help for the vibration reduction of multilayered vdW semiconductors.

The analysis of the electromagnetic characteristics of composite materials with negative effective permittivity

A new method based on the finite difference time domain(FDTD)method is presented to numerically analyze the transmission and reflection characteristic of composite materials with negative effective permittivity.The numerical results are compared with the results of the existing theoretical model and the experimental data.The feasibility of analyzing the composite materials using the FDTD method is validated.It is useful for the design and application of the composite materials.