Initial transient process in a simple helical flux compression generator

An analytical scheme on the initial transient process in a simple helical flux compression generator, which includes the distributions of both the magnetic field in the hollow of an armature and the conducting current density in the stator, is developed by means of a diffusion equation. A relationship between frequency of the conducting current, root of the characteristic function of Bessel equation and decay time in the armature is given. The skin depth in the helical stator is calculated and is compared with the approximate one which is widely used in the calculation of magnetic diffusion. Our analytical results are helpful to understanding the mechanism of the loss of magnetic flux in both the armature and stator and to suggesting an optimal design for improving performance of the helical flux compression generator.

Arranging transient process used in iterative learning control system

Considering the same initial state error in each repetitive operation in the iterative learning system, a method of arranging the transient process is given. During the current iteration, the system will track the transient function firstly, and then the expected trajectory. After several iterations, the learning system output will trend to the arranged curve, which has avoided the effect of the initial error on the controller. Also the transient time can be changed as you need, which makes the designing simple and the operation easy. Then the detailed designing steps are given via the robot system. At last the simulation of the robot system is given, which shows the validity of the method.

1/3 PURE SUB-HARMONIC SOLUTION AND FRACTAL CHARACTERISTIC OF TRANSIENT PROCESS FOR DUFFING'S EQUATION

The 1/3 sub-harmonic solution for the Duffing＇s with damping equation was investigated by using the methods of harmonic balance and numerical integration. The assumed solution is introduced, and the domain of sub-harmonic frequencies was found. The asymptotical stability of the subharmonic resonances and the sensitivity of the amplitude responses to the variation of damping coefficient were examined. Then, the subharmonic resonances were analyzed by using the techniques from the general fractal theory. The analysis indicates that the sensitive dimensions of the system time-field responses show sensitivity to the conditions of changed initial perturbation, changed damping coefficient or the amplitude of excitation, thus the sensitive dimension can clearly describe the characteristic of the transient process of the subharmonic resonances.

A 1/3 PURE SUBHARMONIC SOLUTION AND TRANSIENT PROCESS FOR THE DUFFING'S EQUATION

The 1/3 subharmonic solution for the Duffing’s equation is investigated by using the methods of harmonic balance and numerical integration. The sensitivity of parameter variation for the transient process and the transient process for the perturbance initial conditions are studied. Over and above, the precision of numerical integration method is discussed and the numerical integration method is compared with the harmonic balance method. Finally, asymptotical stability of the pure subharmonic oscillations element is inspected.

Effect of Carried-Envelope Phase on Transient Process in a Cascade-Type System

This paper investigates the effect of carried-envelope phase on transient process in a cascade-type atomic system, which is driven by two ultrashort laser pulses （probe and signal laser）. It is found that the one- and two-photon processes corresponding to pathway ｜0〉→｜1〉and ｜0〉→｜1〉→｜2〉 can be enhanced or ,suppressed by modulating the carried-envelope phases of probe laser pulse. Our numerical results also show that the transient populations of two excited states can be periodically affected by the carried-envelope phase of probe laser pulse. With certain time, the partial population transfer between two exited states can be realized just by adjusting the carried-envelope phase of probe laser pulse.

High-Accuracy Pneumatic Position Control by Applying Nonlinear Control and Arranging Transient Process

By applying a nonlinear control and arranging a transient process, the initiative error of the pneumatic servo positioning system is reduced largely, and a larger gain of the controller is used to improve the responding speed of the system at the same damping ratio. Therefore, a compromise is made among the responding speed, overshoot, robustness, adaptability and stability. In addition, a dynamic output feedback controller, including position velocity and acceleration （PVA） feedback, is designed to improve the performance of the system. And a nonlinear controller is reconstructed based on the linear output feedback controller to decrease noises and disturbances. The dynamic responses of the system are simulated and tested. Results show that the error is kept within 0.02 mm under different mass loads and the positioning transient process is smooth, without overshoot and speedy.

THEORETICAL ANALYSIS ON THE TRANSIENT PROCESS OF AC SILENT DISCHARGE

A mathematical model for analysing transient process of AC silent discharge isestablished from its physical model.Then,the breakdown characteristics and the dependence ofdischarge current density on time are calculated theoretically in this kind of AC silent discharge.They are compared with the experimental results and the deviation between the theoretical andexperimental results are discussed briefly.

EFFECTS OF NONLINEARITY ON TRANSIENT PROCESSES IN AT-CUT QUARTZ THICKNESS-SHEAR RESONATORS

We study the effects of mechanical nonlinearity arising from large thickness-shear deformation on the transient process of an AT-cut quartz plate resonator. Mindlin＇s two-dimensional plate equation is used, from which a system of first-order nonlinear differential equations governing the evolution of the vibration amplitude is obtained. Numerical solutions by the Runge-Kutta method show that in common operating conditions of quartz resonators the nonlinear effect varies from noticeable to significant. As resonators are to be made smaller and thinner in the future with about the same power requirement, nonlinear effects will become more important and need more understanding and consideration in resonator design.

Finite Element Method for the Transient Process of the Separation of External Stores from Aircraft

The adjustment and the regeneration of the flow field unstructuredmesh as well as the fi- nitelement solutions for the Euler equationsin the transient process of the separation o external stores form anaircraft at a predetermined downward translation and rotation areinvestigated. It is shown that the adjustment or regeneration ofgrids needed for moving store can be confined within a small regionaround the store and the finite element numerical solution method ofEuler equations for fixed grids can also be used for moving grids ifthe conservative fluxes F_k of fixed grids are replaced by E_k ofmoving grids. The relation-ships between F_k and E_k are alsoestablished. The numerical results For practical examples of aircraftwith external stores are shown.

Transient numerical simulation of annealing process in a conjugate combined radiation conduction heat transfer

The annealing time is an important affecting factor in the performance of many furnaces.The present work deals with the transient simulation of annealing process in a cubic furnace in which a solid element is placed in its center.As the working gas can have some radiating features,a set of governing equations including the energy balance with the radiative transfer equation(RTE)for the gray radiating medium and the conduction equation inside the solid product are numerically solved with progressing in time.Numerical results which are validated against both analytical and theoretical findings in the literature demonstrate that during the starting period,a high rate of radiant energy transfers into the solid body even at small optical thickness.This behavior which hastens the rate of heat transfer at low values of the radiation conduction parameter,causes a fast annealing process in which the solid body warms up to its maximum temperature.Moreover,it is revealed that the rate of heat transfer is an increasing function of radiation-conduction parameter.

Processing and analysis of transient pressure measurements from permanent down-hole gauges

With permanent down-hole gauges （PDGs） widely installed in oilfields around the world in recent years, a continuous stream of transient pressure data in real time is now available, which motivates a new round of research interests in further developing pressure transient processing and analysis techniques. Transient pressure measurements from PDG are characterized by long term and high volume data. These data are recorded under unconstrained circumstances, so effects due to noise, rate fluctuation and interference from other wells cannot be avoided. These effects make the measured pressure trends decline or rise and then obscure or distort the actual flow behavior, which makes subsequent analysis difficult. In this paper, the problems encountered in analysis of PDG transient pressure are investigated. A newly developed workflow for processing and analyzing PDG transient pressure data is proposed. Numerical well testing synthetic studies are performed to demonstrate these procedures. The results prove that this new technique works well and the potential for practical application looks very promising.

A two-step transient liquid phase diffusion bonding process of T91 steels

In this study, a two-step heating process is introduced for transient liquid phase （ TLP） diffusion bonding fo r sound joints with T91 heat resistant steels. At first, a short-time higher temperature heating step is addressed to melt the interlayer, followed by the second step to complete isothermal solidification at a low temperature. The most critical feature of our new method is producing a non-planar interface at the T9／ heat resistant steels joint. We propose a transitional liquid phase bonding of T91 heat resistant steels by this approach. Since joint microstructures have been studied, we tested the tensile strength to assess joint mechanical property. The result indicates that the solidified bond may contain a primary solid-solution, similar composition to the parent metal and free from precipitates. Joint tensile strength of the joint is not lower than parent materials. Joint bend＇s strengths are enhanced due to the higher metal-to-metal junction producing a non-planar bond lines. Nevertheless, the traditional transient liquid phase diffusion bonding produces planar ones. Bonding parameters of new process are 1 260 °C for 0. 5 min and 1 230 °C fo r 4 min.

The Drift of Dust Grains Induced by Transient Magnetic Field

Our experiment shows that the dust grains, suspended on the edge of the sheath of a radio-frequency discharge, undergo a contraction when switching a vertical magnetic field on, and an expansion when switching the magnetic field off. We call this kind of magnetic field "transient magnetic field". A primary analysis is proposed for the phenomenon.

Ionization process and distinctive characteristic of atmospheric pressure cold plasma jet driven resonantly by microwave pulses

In the present study,a coaxial transmission line resonator is constructed,which is always capable of generating cold microwave plasma jet plumes in ambient air in spite of using argon,nitrogen,or even air,respectively.Although the different kinds of working gas induce the different discharge performance,their ionization processes all indicate that the ionization enhancement has taken place twice in each pulsed periods,and the electron densities measured by the method of microwave Rayleigh scattering are higher than the amplitude order of 10^(18)m^(-3).The tail region of plasma jets all contain a large number of active particles,like NO,O,emitted photons,etc,but without O_(3).The formation mechanism and the distinctive characteristics are attributed to the resonance excitation of the locally enhanced electric fields,the ionization wave propulsion,and the temporal and spatial distribution of different particles in the pulsed microwave plasma jets.The parameters of plasma jet could be modulated by adjusting microwave power,modulation pulse parameters(modulation frequency and duty ratio),gas type and its flow rate,according to the requirements of application scenarios.

Study on Electromagnetic Transient Condition of EMU Passing by Phase-separation with Electric Load in High-speed Railway

Aiming at the complex electromagnetic transient process of EMU passing by phase-separation with electric load in high-speed railway, mechanism of overvoltage caused by switching off, overvoltage caused by switching on and impact current is analyzed systematically in this article. π-type equivalent circuit of feeding section is put forward in the analysis of overvoltage mechanism. Overvoltage and overcurrent model of passing by phase-separation with electric load are also built. Correctness of mechanism was validated by simulation. In addition, the methods to solve the influence on substations, transformers and protection devices in this process are put forward, which provides a new idea on passing by phase-separation with electric load technology.

Dynamic analysis of a guided projectile during engraving process

The reliability of the electronic components inside a guided projectile is highly affected by the launch dynamics of guided projectile.The engraving process plays a crucial role on determining the ballistic performance and projectile stability.This paper analyzes the dynamic response of a guided projectile during the engraving process.By considering the projectile center of gravity moving during the engraving process,a dynamics model is established with the coupling of interior ballistic equations.The results detail the stress situation of a guided projectile band during its engraving process.Meanwhile,the axial dynamic response of projectile in the several milliseconds following the engraving process is also researched.To further explore how the different performance of the engraving band can affect the dynamics of guided projectile,this paper focuses on these two aspects:(a) the effects caused by the different band geometry;and(b) the effects caused by different band materials.The time domain and frequency domain responses show that the dynamics of the projectile are quite sensitive to the engraving band width.A material with a small modulus of elasticity is more stable than one with a high modulus of elasticity.

AUTOMATIC ORDER-DETERMINATION OF TRANSIENT IN--PLANE DISPLACEMENT MOIRE PATTERNS

This paper presents a fringe-carrier method that eliminates sign ambiguity of transient moire fringes which can be used to automatically determine the relative orders. A fringe carrier is preset in the static state of the specimen and the dynamic in-plane displacements are recorded as the modulation to the frequency of the carrier fringes when the specimen is loaded by impact. According to a modulating criterion developed from the modulation degree, the fringes of the transient moire patterns keep monotonical in orders so that they can be automatically encoded in grey levels by a digital image system. The moire orders purely caused by dynamic loadings are evaluated by subtracting the grey-value of the unmodulated carrier image from that of the modulated carrier images encoded by their orders. With the subtracted moire orders the strain components can be obtained, and, correspondingly, the histograms of dynamic displacement moire images are shown with order variation by image-difference.

Analysis Process of Finite Element Method in Heat Transfer through Fabrics

According to heat transfer principle and the process of solving engineering problems by finite element method, examples were given to demonstrate how finite element analysis can be used to describe transient heat transfer through fabrics. Details were given to describe how conduction and convection affect temperature distribution and heat loss during heat transfer processes by taking advantage of the quick calculation of FEA software MSC.Marc. Experimental results show good agreement with the theoretical results.

抽水蓄能机组特性曲线对电站水力过渡过程的影响

为了研究抽水蓄能机组特性曲线对过渡过程的影响,采用三组比转速接近的已建电站的特性曲线对某电站进行了水力过渡过程计算分析。通过对比计算发现:减小飞逸曲线与机组运行轨迹线交点的单位转速,有助于降低机组最大转速上升率。初始工况点应选在特性曲线相对平滑的地方,有助于减小机组在过渡过程中的流量变化,降低蜗壳进口最大压力。“s”特性斜率变化率越小,整体越平滑,尾水管进口最小压力越高。可以为项目前期选择合适的转轮提供理论依据。

Effect of non-uniform swelling on coal multiphysics during gas injection: The triangle approach

In current dual porosity/permeability models,there exists a fundamental assumption that the adsorption-induced swelling is distributed uniformly within the representative elementary volume (REV),irrespective of its internal structures and transient processes.However,both internal structures and transient processes can lead to the non-uniform swelling.In this study,we hypothesize that the non-uniform swelling is responsible for why coal permeability in experimental measurements is not only controlled by the effective stress but also is affected by the adsorption-induced swelling.We propose a concept of the swelling triangle composed of swelling paths to characterize the evolution of the non-uniform swelling and serve as a core link in coupled multiphysics.A swelling path is determined by a dimensionless volumetric ratio and a dimensionless swelling ratio.Different swelling paths have the same start and end point,and each swelling path represents a unique swelling case.The swelling path as the diagonal of the triangle represents the case of the uniform swelling while that as the two perpendicular boundaries represents the case of the localized swelling.The paths of all intermediate cases populate inside the triangle.The corresponding relations between the swelling path and the response of coal multiphysics are established by a non-uniform swelling coefficient.We define this method as the triangle approach and corresponding models as swelling path-based ones.The proposed concept and models are verified against a long-term experimental measurement of permeability and strains under constant effective stress.Our results demonstrate that during gas injection,coal multiphysics responses have a close dependence on the swelling path,and that in both future experiments and field predictions,this dependence must be considered.