Gain Properties of Triply-Doped Graphene-Insulator-Graphene Nanosheet Waveguide

Er~(3+)-Tm~(3+)-Pr~(3+)triply-doped graphene-glass-graphene(GGG) nanosheet waveguide amplifier, which is a promising candidate for integrated photonic devices, is modelled and numerically analyzed. The designed waveguide is composed of a triply-doped tellurite glass core. The core is sandwiched between two graphene layers.The rate and power propagation equations of a heterogeneous multi-level laser medium are set up and solved numerically to study the effects of waveguide length and active ion concentrations on amplifier performance at five different input signal wavelengths(1.310, 1.470, 1.530, 1.600 and 1.650 μm). The analytical results show that rareearth ion dopant concentrations at an order of 10~(26) ion/m~3, waveguide length at 0.1 m and pump power at 100 m W can amplify 1.530 and 1.600 μm input signals with 1 μW power up to approximately 20.0 and 24.0 dB respectively.Finite-difference time-domain(FDTD) simulation results show that mode field radius of GGG waveguide is smaller than that of silicon waveguide. Consequently, GGG waveguide with the same pump and signal power and the same gain-medium length can produce higher gain than silicon waveguide.     

Modeling Nd~(3+)-Yb~(3+)-Tm~(3+)-Er~(3+) Codoped Telluride Glass Fiber for 0.4 to 2.0 μm Emission Spectra

The modeling of rare-earth-doped fiber amplifier is accomplished by utilizing the rate and propagation equations of distinct levels for a laser medium. A complex theoretical model for neodymium(Nd~(3+)), erbium(Er~(3+)),thulium(Tm~(3+)) and ytterbium(Yb~(3+)) codoped telluride glass fiber covering 0.4—2.0 μm emission spectra is presented. The emission spectra of Nd~(3+)-Er~(3+)-Tm~(3+)-Yb~(3+)codoped telluride fiber are realized with the excitation of both 808 and 980 nm lasers pumped at 500 mW. Numerical methods are used to calculate the emission spectra covering 0.4—2.0 μm. With the Nd~(3+), Tm~(3+)and Yb~(3+)ion concentrations fixed at 2 × 1020 ion/m~3, the Er~(3+)ion concentration optimized to 8 × 10~(20) ion/m~3 and the fiber length spanning from 0.5 to 2 m, a peak amplified spontaneous emission(ASE) power of 19.8 mW is attainable, and a minimum ASE power of 7.96 mW can also be achieved. The analytical techniques and results indicate that when a telluride codoped fiber with suitable ion concentrations of Nd~(3+), Er~(3+), Tm~(3+)and Yb~(3+)is excited by both 980 and 808 nm pump lasers, 0.4—2.0 μm emission spectra are attainable for vast optical applications.     

Gain and Emission Spectrum Characteristics of 465 nm Laser Diode Pumped Tm~(3+)-Doped Telluride Glass Fibers

Gain and emission spectrum characteristics of Tm~(3+)-doped telluride glass fibers pumped with 465 nm lasers are analyzed. The rate and power propagation equation groups of the fibers are solved numerically and the effects of the fiber parameters including active ion concentration, length and pump power on the gain spectra and amplified spontaneous emission(ASE) spectra are analyzed. The results show that with a pump parameter of 465 nm/200 mW, a doping concentration of 2.5 × 10~(25) ion/m~3 and a fiber length of 16 m, the gain and ASE spectra can cover from 1.100 to 1.900 μm, and the gain and ASE power peaks can reach 52 dB and 8 mW, respectively.     

Gain and Noise Figure Analysis of Er~(3+)-Doped YAG Transparent Ceramic Microchip Amplifier

The rate equations and the power evolution equations based on excited state absorption(ESA) and cooperative upconversion(CUC) of high concentration erbium-doped yttrium aluminum garnet(YAG) transparent ceramic waveguide amplifier are set up to analyze the effects of the pump power, active ion concentration and waveguide length on the amplifier gain and noise figure(NF). The numerical analysis predicts that with a pump power of 100 mW, an active ion concentration of 1.0 × 10~(26) ion/m~3 and a waveguide length of 3 cm, a small-signal gain of 30 dB and an NF of 5 dB can be achieved in the micro-chip amplifier.     

Gain Characteristics of Fiber Optical Parametric Amplifier

The theory model of fiber optical parametric amplifier (FOPA) was introduced, which is based on optical nonlinear effect. And then numerical simulation was done to analyze and discuss the gain spectral characteristics of one-pump and two-pump FOPA. The results show that for one-pump FOPA, when pump wavelength is near to fiber zero-dispersion wavelength (ZDW), the gain flatness is better, and with the increase of the pump power,fiber length and its nonlinear coefficient, the gain value will increase while the gain bandwidth will become narrow.For two pump FOPA, when the pump central wavelength is near to fiber ZDW, the gain flatness is better. Moreover, by decreasing the space of two pumps wavelength, the gain flatness can be improved. Finally, some problems existing in FOPA were addressed.     

Theoretical Modelling of Cascaded Er~(3+)-Doped,Tm~(3+)-Doped and Nd~(3+)-Doped Fibers for 0.4 to 2.0 μm Emission Spectra

We present a cascaded system designed with Er~(3+)-doped, Tm~(3+)-doped and Nd~(3+)-doped fibers to realize amplified spontaneous emission(ASE) spectra covering 0.4—2.0 μm. The system is excited with a pump laser emitting 808 nm photons with 500 m W pump power. The emission spectra of the cascaded system covering0.4—2.0 μm are realized with the Er~(3+), Tm~(3+)and Nd~(3+)ion doping densities optimized to 8 × 1019, 2 × 1020 and8 × 1020 ion/m3, respectively, and the fiber length optimized to 1 m. Numerical methods reveal that the peak ASE power for the cascaded system can reach 20.9 m W. A minimum ASE power of 4.39 m W is attainable. Using numerical calculations and analytical techniques, we provide a detailed insight into optimized Er~(3+)-doped, Tm~(3+)-doped and Nd~(3+)-doped fiber lengths and their doping concentrations for ASE power spectra covering 0.4—2.0 μm.We believe that the cascaded system can potentially provide significant applications in various optical fields which include but not limited to wavelength-division multiplexing, various optical communications and other salient medical imaging processes.     

A New Full Bridge High Intensity Focused Ultrasound Power System with Harmonic Cancellation

The feasibility of a new full bridge high intensity focused ultrasound(HIFU) amplifier system with harmonic cancellation is evaluated in this study. Harmonic cancellation technique is applied to these power amplifiers, which can eliminate the 3rd harmonic and all even harmonics. Since this technique requires two channels of phase signal to control one channel of power amplifier, the signal generator is required to double its output. The transducer array proposed in this study has 100 elements. So we choose an FPGA chip to generate 200 driving signals, and each channel has a phase resolution of 2ns, less than 1°. The phase signal from the FPGA meets the requirement of driving the power amplifiers. The output waveform of one channel of power amplifier(voltage across the transducer) is evaluated, and shows fewer harmonic components.     

Research on High Power Inter-Channel Crosstalk Attack in Optical Networks

While all-optical networks become more and more popular as the basis of the next generation Internet(NGI)infrastructure,such networks raise many critical security issues.High power inter-channel crosstalk attack is one of the security issues which have negative effect on information security in optical networks.Optical fiber in optical networks has some nonlinear characteristics,such as self phase modulation(SPM),cross phase modulation(XPM),four-wave mixing(FWM)and stimulated Raman scattering(SRS).They can be used to implement high power inter-channel crosstalk attack by malicious attackers.The mechanism of high power inter-channel crosstalk attack is analyzed.When an attack occurs,attack signal power and fiber nonlinear refractive index are the main factors which affect quality of legitimate signals.The effect of high power inter-channel crosstalk attack on quality of legitimate signals is investigated by building simulation system in VPI software.The results show that interchannel crosstalk caused by high power attack signal leads to quality deterioration of legitimate signals propagated in the same fiber.The higher the power of attack signal is,the greater the fiber nonlinear refractive index is.The closer the channel spacing away from the attack signal is,the more seriously the legitimate signals are affected by attack.We also find that when attack position and power of attack signal are constant,attack signal cannot infinitely spread,while its attack ability shows a fading trend with the extension of propagation distance.     

Capacitance Sensing and Software-Realized Lock-in Amplifier for the Electromagnetically Levitated Micro Gyroscope

In the novel prototype of micro-gyroscope structure,the new configured capacitance sensing scheme for the micro gyroscope was analyzed and the virtual instrument based detection scheme was implemented.The digital lock-in amplifier was employed in the capacitance detection to restrain the noise interference.The capacitance analysis shows that 1 fF capacitance variation corresponds to 0.1 degree of the turn angle.The differential capacitance bridge and the charge integral amplifier were used as the front signal input interface.In the implementation of digital lock-in amplifier,a new routine which warranted the exactly matching of the reference phase to signal phase was proposed.The result of the experiment shows that digital lock-in amplifier can greatly eliminate the noise in the output signal.The non linearity of the turn angle output is 2.3% and the minimum resolution of turn angle is 0.04 degrees.The application of the software demodulation in the signal detection of micro-electro-mechanical-system(MEMS)device is a new attempt,and it shows the prospective for a high-performance application.     

A cryogenic 10-bit successive approximation register analog-to-digital converter design with modified device model

A 10-bit 500 kHz low-power successive approximation register（SAR）analog-to-digital converter（ADC）for cryogenic infrared readout circuit is proposed.To improve the simulation accuracy of metal-oxidesemiconductor field-efect transistors（MOSFETs）,corresponding modification in device model is presented on the basis of BSIM3v3 with parameter extraction at 77 K.Corresponding timing is adopted in comparator to eliminate the influence caused by abnormal performance of MOSFETs at 77 K.The SAR ADC is fabricated and verified by standard 0.35μm complementary metal oxide semiconductor（CMOS）process.At 77 K,measurement results show that signal to noise and distortion ratio（SNDR）is 54.74 dB and efective number of bits（ENOB）is 8.8 at the sampling rate of 500 kHz.The total circuit consumes 0.6 mW at 3.3 V power supply.     

A Simple Approach to Determine Noise Frequency of Boiler Drum Level

IntroductionSince much of emergency shutdowns arecaused by poor drum level control in power plant,stable drum level control is critical to economic op-eration of any power plant steam generator sys-tem.The control gain setting must be reduced inorder not to respond excessively to thc drum levelerrors[1].Due to the uncertainty of operating con-dition point,surface wave of drum water is stimu-lated to fluctuate frequently and subsequently tomake oscillatory disturbance signal,which is com-bined …     

Efficient Design and Optimization Method for Distributed Amplifiers

A novel design and optimization method for distributed amplifiers(DAs)is proposed to make the circuit design more convenient and efficient.This method combines artificial intelligence(AI)optimization with manual design by two loops,i.e.,outer manual loop and inner AI loop.The layout design is followed by AI optimization to take more influencing factors such as parasitic effect into account for the practicability.A DA with three gain cells is designed and optimized in a standard 0.18μm complementary metal-oxide-semiconductor(CMOS)technology to verify the proposed method.With a chip area of only 0.55 mm2,the DA provides 9.8 dB average forward gain from 1 to 15.2 GHz.The output power at 1 dB output compression point is more than 7.7 dBm in the 2-14 GHz frequency band and the peak power-added efficiency(PAE)is 10.6%.The measurement results validate the proposed method as a robust DA design procedure for improving circuit performance and design efficiency.     

Free vibration analysis of cylindrical and rectangular sandwich panels with a functionally graded core

Based on the Reissner assumptions, the free vibration analysis of simply supported cylindrical and rectangular sandwich panels with isotropic face sheets and a functionally graded core is concerned. Firstly, the expressions of the displacements, stresses and internal forces are presented according to the constitutive relations and stress states of the core and face sheets. Then, the dynamic stability and compatibility equations are given for cylindrical sandwich panels with functionally graded core, elastic modulus and density in which vary continuously in the thickness direction. Finally, the proposed solutions are validated by comparing the results of degenerate example with classical solutions, and a numerical analysis is performed on the example of simply supported cylindrical and rectangular sandwich panels. The elastic modulus and density of the functionally graded core are assumed to be graded by a power law distribution of volume fractions of the constituents, and the Poisson ratio is held constant. The effects of the distribution of functionally graded core's properties, the thickness-side ratios and ratio of radius(R) to length(l) κ = R/l are also examined.     

Design of rail pressure tracking controller for novel fuel injection system

This paper proposes a rail pressure tracking controller based on a novel common rail system. A mathematical model, based on physical equations, is developed and used for feed forward control design. Rail pressure peak sampling mechanism is designed to remove the disturbance of rail pressure due to fuel injection. An enhanced tracking differentiator is designed to get smooth tracking signal and exact differential signal from signal with noise. Double loop control strategy is designed to decouple the system and to improve dynamic performance of the system. Experimental results indicate that fluctuation of rail pressure is within ±1 MPa in steady condition, while within ±3 MPa in transient condition, which verifies the effectiveness of the proposed rail pressure control strategy.     

Characteristics of Trihalomethanes in Water Distribution System

To investigate the characteristics of disinfection by-products (DBPs) in an actual water distribution system using the raw water with high bromide ion concentration, the composition and concentration of trihalomethanes (THMs) formed by chlorination of the water in the presence of bromide ion were measured in a city water distribution system during one year. The results show that brominated THMs contributed a great part (83%-89%) to the index for additive toxicity (ATI) and resulted in the ATI of most of the samples exceeding WHO guideline standard for total THMs (TTHMs), especially during the summer (rainy season). This indicates that the chlorination of water in the presence of bromide ion leaded to high ratios of brominated THMs to TTHMs. However, a visible increase in the concentration of THMs with increasing residence time in the distribution system was not observed. Additionally, based on alternatives analysis, packed tower aeration method is proposed to reduce THMs level of the finished water leaving the treatment plant.     

A Polynomial Time Algorithm for Checking Regularity of Totally Normed Process Algebra

A polynomial algorithm for the regularity problem of weak and branching bisimilarity on totally normed process algebra(PA) processes is given. Its time complexity is O(n3+ mn), where n is the number of transition rules and m is the maximal length of the rules. The algorithm works for totally normed basic process algebra(BPA) as well as basic parallel process(BPP).     

Kinetic characteristic for a synchronal rotary compressor

The synchronal rotary compressor is si mple instructure,but it has stronger adaptability for a vari-ety of working medium,so it is a good type as aircompressor,oil pump andrefrigerationsystemcom-pressor.The geometric theory and structure charac-teristics of this mechanis m are introduced[1].Itgives the designing background for the synchronalrotary compressor.The calculational methods of arotary speed of cylinder and relative speed bet weenthe cylinder and bladed rotor are deduced in detail;the…     

A Hemodynamic Study of the Effect of Neuromuscular Electrical Stimulation on Enhancing Popliteal Venous Flow

Neuromuscular electrical stimulation has been studied to be a method of prophylaxis for deep venous thrombosis by activating the calf muscle pump. However, there is little evidence of the effects of different stimulating parameters on hemodynamics and comfort levels. The objective of this paper is to compare the effects of different stimulating parameters(current amplitude, pulse-width) on hemodynamic alterations of the popliteal vein and the comfort levels in a group of fourteen healthy subjects. Doppler ultrasound detection of peak venous velocity and blood volume were taken from baseline, twelve sequential electrical stimulations and foot dorsiflexion for each subject. A visual analogue scale was used to assess the subjects' pain perception of neuromuscular electrical stimulation. The results showed that peak venous velocity and blood volume augmented as current amplitude and pulse-width increased while pain level also increased. A compromise was reached that parameters consisting of an amplitude of 10 m A and a pulse-width of 500 μs would obtain a high-peak venous velocity and blood flow volume with a relatively comfortable perception. In addition, parameters consisting of an amplitude of 20 m A and a pulse-width of 300 μs were also shown to be a promising choice. However, further studies need to be done to validate and enrich these findings.     

Cable Sliding at Supports in Cable Structures

To develop an effective numerical method for the cable sliding problem in cable structures，two-node catenary cable element was built to model the cables based on analytical solution of elastic catenary．Cooperated with Newton method，continuation method Was used to solve the nonlinear equations．This approach is more efficient than using Newton method only and has a wider range to select initial values for the process to converge．The relationship between the tension on a cable segment and its unstrained length was derived and used to calculate the unbalanced cable tensions at the supports．An example is presented to show the correctness and efficiency of the proposed method．     

Effect of carbon nanotube concentration on cooling behaviors of oil-based nanofluids during the immersion quenching

Oil-based nanofluids including 0.75%—1.75%(mass fraction) carbon nanotubes(CNTs) without any surfactants have been synthesized by a two-step process. The probes machined from 45~# steel with 22 mm diameter and 50 mm length are quenched in the as-synthesized CNT nanofluids for testing the cooling behaviors of the nanofluids. The laser diffraction particle size analyzer, scanning electronic microscope(SEM), X-ray diffractometer and transmission electron microscope(TEM) are used to characterize the quality and distribution of CNTs in the nanofluids. The wettability and viscosity of 30~# oil and oil-based CNT nanofluids are measured by a goniometer at 15℃ and a rotational type viscometer at 40℃, respectively. The results show that the cooling efficiency of the oil-based CNT nanofluids is better than that of 30~# oil. Moreover, the cooling rate of the naonofluids increases with the further increase of the CNT concentration. When the mass fraction of CNTs increases to 1.75%, the cooling rate of the naonofluids reaches a maximum at 760℃ and it is increased by 77.8% as compared to that of base oil. The improved cooling rate of oil by CNTs is mainly due to the uniform distribution and excellent thermal conductivity of CNTs.