自激振荡钻具振荡力计算及影响因素分析

自激振荡钻具是利用自激振荡原理,将连续的高压钻井液转化为间歇周期性的脉冲射流,以增强钻头冲击力和减少岩屑重复破碎,进而提高机械钻速的井下工具。该工具以其结构简单、无密封件和工作可靠等优势得到广泛应用。然而由于自激振荡钻具的振荡力使用解析法难以计算,使得其结构优化和现场应用受到限制。文章基于大涡模型理论,对自激振荡钻具内部流场进行模拟,进而计算出工具振荡力的大小,并计算分析了钻井液密度、钻井液排量和工具最小水眼尺寸变化对振荡力的量化影响,指出钻井液密度和钻井液排量是影响工具振荡力的主要因素,同时现场应根据实际许用节流压降选用合适的最小水眼尺寸。文章的研究工作为工具内部结构的优化提供方法,同时也为现场合理使用该工具提供依据。

基于摩阻和振荡力的水力振荡器安放位置计算方法

水力振荡器是目前缓解定向托压最有效的方法之一。在大斜度井、大位移井、水平井等复杂结构井中应用越来越广泛,并取得了较好的应用效果。但目前没有形成一套水力振荡器合理安放位置计算方法,导致应用效果参差不齐。基于摩阻和振荡力,建立了安放位置计算模型,并制作了优选图版。现场应用效果表明,该安放位置计算方法有效可行。可为水力振荡器现场应用提供理论支持和技术指导。

振荡螺杆钻具的关键结构优化与试验研究

针对水平井钻井托压导致的机械钻速低与钻头磨损的问题,研制了振荡螺杆钻具以应对该技术难题。通过数值仿真方法,研究了动阀片位于0°~360°不同旋转位置时,振荡螺杆内部流体的速度和压力分布规律以及旋转角度与阀孔半径对静阀片进出口压降和阀片之间有效过流面积的影响规律,对阀孔内径尺寸进行优化设计;利用振荡螺杆整机试验系统对其压降和过流面积等关键性能参数进行测试,在焦页81-9HF井对样机的使用效果进行了现场测试。结果表明:压降和过流面积曲线以45°为一个周期循环,在0°~360°范围内的总体形态为“波浪形”;阀孔半径为18.5 mm时静阀片进出口压降最大且阀孔通道的过流面积大小适中,产生的振荡力最大且流速不会太低而影响振荡力的传递效果;室内测试的压降、频率与振荡力结果论证了优化结构的可靠性;现场测试表明振荡螺杆可以减小钻头和提速工具的磨损,同时还可以提升钻进效率。该研究可以为振荡螺杆的结构优化设计提供一定的理论和技术参考。

水力振荡器在C26-12X井中的应用

C26-12X井钻进至3 385 m时,滑动钻进出现严重的托压问题。为解决该问题,开展了水力振荡器缓解托压现场试验。应用效果表明,水力振荡器缓解托压效果明显,滑动钻进造斜效率提高1倍,滑动钻进行程钻速提高3.7倍,滑动钻进机械钻速提高2.17倍。C26-12X井水力振荡器的成功应用,为同类型的井解决托压问题提供了技术指导。

具有奇异振荡的三维非自治线性Kelvin-Voigt-Brinkman-Forchheimer方程的一些估计

主要研究具有奇异振荡力的三维非自治线性Kelvin-Voigt-Brinkman-Forchheimer方程,先对其具有时间相关外力的辅助线性方程进行一般估计,再通过这些一般估计推导出其具有奇异振荡力线性方程的估计.

Coarse-grained Simulations of Chemical Oscillation in Lattice Brusselator System

The oscillation behavior of a two-dimension lattice-gas Brusselator model was investigated. We have adopted a coarse-grained kinetic Monte Carlo （CG-KMC） procedure, where m×m microscopic lattice sites are grouped together to form a CG cell, upon which CG processes take place with well-defined CG rates. Such a CG approach almost fails if the CG rates are obtained by a simple local mean field （s-LMF） approximation, due to the ignorance of correlation among adjcent cells resulting fl＇om the trimolecular reaction in this nonlinear system. By proper incorporating such boundary effects, thus introduce the so-cMled b-LMF CG approach. Extensive numerical simulations demonstrate that the b-LMF method can reproduce the oscillation behavior of the system quite well, given that the diffusion constant is not too small. In addition, the deviation from the KMC results reaches a nearly zero minimum level at an intermediate cell size, which lies in between the effective diffusion length and the minimal size required to sustain a well-defined temporal oscillation.

Nucleation of Kinetic Ising Model Under Oscillating Field

We have studied the nucleation process of a two-dimensional kinetic Ising model subject to a bias oscillating external field, focusing on how the nucleation time depends on the oscillation frequency. It is found that the nucleation time shows a clear-cut minimum with the variation of oscillation frequency, wherein the average size of the critical nuclei is the smallest, indicating that an oscillating external field with an optimal frequency can be much more favorable to the nucleation process than a constant field. We have also investigated the effect of the initial phase of the external field, which helps to illustrate the occurrence of such an interesting finding.

Characterizing pressure fluctuation into single-loop oscillating heat pipe

The pressure characteristics inside single loop oscillating heat pipe （OHP） having 4.5 mm inner diameter copper tube with the loop height of 440 mm were addressed. Distilled water was used as working fluid inside the OHP with different filling ratios of 40%, 60% and 80% of total inside volume. Experimental results show that the thermal characteristics are significantly inter-related with pressure fluctuations as well as pressure frequency. And the pressure frequency also depends upon the evaporator temperature that is maintained in the range of 60-96 ℃. Piezoresistive absolute pressure sensor （Model-Kistler 4045A5） was used to take data. The investigation shows that the filling ratio of 60% gives the highest inside pressure magnitude at maximum number of pressure frequency at any of set evaporator temperature and the lowest heat flow resistance is achieved at 60% filling ratio.

Validity and reliability of three methods of stiffness assessment

Background：Stiffness is commonly assessed in relation to injury and athletic performance.The purpose of this research was to compare the validity and reliability of 3 in vivo methods of stiffness assessment using 1 cohort of participants.Methods：To determine inter-day reliability,15 female netballers were assessed for stiffness twice within 1 week using unilateral hopping（vertical stiffness）,free oscillations of the calf,and myometry of various muscles of the triceps surae.To establish convergent construct validity,stiffness was compared to static and dynamic strength measurements.Results：Test–retest stiffness results revealed that vertical stiffness produced moderate to high reliability results and myometry presented moderate to very high reliability.In contrast,the free oscillation technique displayed low to moderate reliability.Vertical stiffness demonstrated a significa t correlation with rate of force development during a squat jump,whilst myometer stiffness measurements from 3 sites in the lower limb revealed significan correlations with isometric rate of force development.Further,significan negative correlations were evident between the eccentric utilisation ratio and various myometer stiffness results.No relationships were established between the free oscillation technique and any of the performance measurements.Conclusion：These results suggest that vertical stiffness and myometry are valid and reliable methods for assessing stiffness.

Simulation of the QBO in IAP-AGCM:Analysis of momentum budget

The quasi-biennial oscillation(QBO),a dominant mode of the equatorial stratospheric(~100–1 hPa)variability,is known to impact tropospheric circulation in the middle and high latitudes.Yet,its realistic simulation in general circulation models remains a challenge.The authors examine the simulated QBO in the 69-layer version of the Institute of Atmospheric Physics Atmospheric General Circulation Model(IAP-AGCML69)and analyze its momentum budget.The authors find that the QBO is primarily caused by parameterized gravity-wave forcing due to tropospheric convection,but the downward propagation of the momentum source is significantly offset by the upward advection of zonal wind by the equatorial upwelling in the stratosphere.Resolved-scale waves act as a positive contribution to the total zonal wind tendency of the QBO over the equator with comparable magnitude to the gravity-wave forcing in the upper stratosphere.Results provide insights into the mechanism of the QBO and possible causes of differences in models.

Evaluation of the Madden-Julian oscillation in HiRAM

The aim of this study was to understand the cause of Madden–Julian oscillation(MJO)bias in the High Resolution AtmosphericModel(HiRAM)driven by observed SST through process-oriented diagnosis.Wavenumber-frequency power spectrum and composite analyses indicate that HiRAM underestimates the spectral amplitude over theMJO band and mainly produces non-propagating rather than eastward-propagating intraseasonal rainfall anomalies,as observed.Column-integrated moist static energy(MSE)budget analysis is conducted to understand the MJO propagation bias in the simulation.It is found that the bias is due to the lack of a zonally asymmetric distribution of the MSE tendency anomaly in respect to the MJO convective center,which is mainly attributable to the bias in vertical MSE advection and surface turbulent flux.Further analysis suggests that it is the unrealistic simulation of MJO vertical circulation anomalies in the upper troposphere as well as overestimation of the Rossby wave response that results in the bias.

Gravitomagnetic Effects on Collective Plasma Oscillations in Compact Stars

The effects of gravitomagnetic force on plasma oscillations are investigated using the kinetic theory of homogeneous electrically neutral plasma in the absence of external electric or magnetic field. The random phase assumption is employed neglecting the thermal motion of the electrons with respect to a fixed ion background. It is found that the gravitomagnetic force reduces the characteristic frequency of the plasma thus enhancing the refractive index of the medium. The estimates for the predicted effects are given for a typical white dwarf, pulsar, and neutron star.

Coordinated and uncoordinated design of LFO damping controllers with IPFC and PSS using ICA and SFLA

A single machine-infinite-bus(SMIB) system including the interline power flow controllers(IPFCs) and the power system stabilizer(PSS) controller is addressed. The linearized system model is considered for investigating the interactions among IPFC and PSS controllers. To improve the stability of whole system again different disturbances, a lead-lag controller is considered to produce supplementary signal. The proposed supplementary controller is implemented to improve the damping of the power system low frequency oscillations(LFOs). Imperialist optimization algorithm(ICA) and shuffled frog leaping algorithm(SFLA) are implemented to search for optimal supplementary controllers and PSS parameters. Moreover, singular value decomposition(SVD) method is utilized to select the most effective damping control signal of IPFC lead-lag controllers. To evaluate the system performance, different operating conditions are considered. Reponses of system in five modes including uncoordinated and coordinated modes of IPFC and PSS using ICA and SFLA are studied and compared. Considering the results, response of system without controller shows the highest overshoot and the longest settling time for rotor angel at the different operating conditions. In this mode of system, rotor speed has the highest overshoot. Rotor angel in the system with only PSS includes lower overshoot and oscillation than system without controller. When PSS is only implemented, rotor speed deviation has the longest settling time. Rotor speed deviation in the uncoordinated mode of IPFC and PSS shows lower overshoot than system with only PSS and without controller. It is noticeable that in this mode, rotor angel has higher overshoot than system with only PSS. The superiority of the suggested ICA-based coordinated controllers is obvious compared with SFLA-based coordinated controllers and other system modes. Responses of coordinated PSS and IPFC SFLA-based supplementary controllers include higher peak amplitude and longer settling time compared with coordinated IPFC and PSS ICA-based controllers. This comparison shows that overshoots, undershoots and the settling times are reduced considerably in coordinated mode of IPFC based controller and PSS using ICA. Analysis of the system performance shows that the proposed method has excellent response to different faults in power system.

Low Frequency Oscillations of the Heat Distribution in the Global Upper Ocean Layers

The heat distributions in the upper layers of the ocean have been studied and some important low frequency oscillations （LFOs） are already found and quantified by using various characteristic factors. In this paper, the ‘heat center＇ of a sea area is defined with a simple method. Then the temperature data set of the upper layer of the global ocean （from surface down to 400 m, 1955-2003） is analyzed to detect the possible LFOs. Not only some zonal LFOs, which were reported early, but also some strong LFOs of the vertical and meridional heat distribution, which might imply some physical sense, are detected. It should be noted that the similar vertical oscillation pattern can be found in the Pacific Ocean, Atlantic Ocean and Indian Ocean. Results from some preliminary studies show that the vertical LFO might be caused by the solar irradiance anomalies. This study may help reveal some unknown dynamical processes in the global oceans and may also benefit other related studies.

Torsional oscillations of a rigid disc bonded to multilayered poroelastic medium

This paper deals mainly with the dynamic response of a rigid disc bonded to the surface of a layered poroelastic half-space. The disc is subjected to time-harmonic torsional moment loadings. The half space under consideration consists of a number of layers with different thickness and material properties. Hankel transform techniques and transferring matrix method are used to solve the governing equations. The continuity of the displacement and stress fields between different layers enabled derivation of closed-form solutions in the transform domain. On the assumption that the contact between the disc and the half space is perfectly bonded, this dynamic mixed boundary-value problem can be reduced to dual integral equations, which are further reduced to Fredholm integral equations of the second kind and solved by numerical procedures. Selected numerical results for the dynamic impedance and displacement amplitude of the disc resting on different saturated models are presented to show the influence of the material and geometrical properties of both the saturated soil-foundation system and the nature of the load acting on it. The conclusions obtained can serve as guidelines for practical engineering.

Measurement of the Variation of Shear Velocity on Bed during a Wave Cycle

Almost all works in the field of boundary layer flow under the breaking wave consider the flow similar as the flow in an oscillating pressure tube. Although the two flows are similar, there are many differences. The results achieved in such manner are therefore also only similar to the results that can be achieved during measurements in the surf zone. Present article deals with boundary layer measurements on an inclined bottom under breaking waves. The measurements over the whole wave cycle were carried out, and the shear velocity under the breaking wave was calculated based on the measurements. It was found that there is a considerable space and time variation of the term in the surf zone. The turbulence generated during the wave breaking changes the shape of the shear velocity profile in comparison to the profile measured before breaking. As the values of shear velocity are directly correlated with the description of the whole velocity field in the wave, it can be assumed that the enhanced description of the shear velocity results in better understanding of the whole velocity field under breaking waves. Therefore, the article brings a new insight into the field and aims to make a discussion about the need to rethink the way of describing the boundary layer flow in the surf zone.

四氯化碳回收一例

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The motion of a charged particle in a magnetic field produced by a column current

To determine the motion of a charged particle in a magnetic field produced by a current flowing along a long column conductor,the equation of the motion was established on the basis of Lorentz force. Qualitative analysis and quantitative solutions demonstrated that the motion contains nonlinear oscillation. The oscillation can be treated as the perturbation of the helical motion,which the particle undergoes in a special condition. The general motion is superposition of two helixes,one as an axis spiraled by another. It is proven that the oscillation is stable.

A Categorification of the Boson Oscillator

In this paper,we investigate the categorical description of the boson oscillator.Based on the categories constructed by Khovanov,we introduce a categorification of the Fock states and the corresponding inner product of these states.We find that there are two different categorical definitions of the inner product of the Fock states.These two definitions are consistent with each other,and the decategorification results also coincide with those in conventional quantum mechanics.We also find that there are some interesting properties of the 2-morphisms which relate to the inner product of the states.

Oscillation heat transfer dynamic model for new type oscillation looped heat pipe with double liquid slugs

In order to explain the oscillation heat transfer dynamics of closed loop oscillation heat pipe (CLOHP) with two liquid slugs,analysis on the forces and heat transfer process of the partial gas-liquid phase system involving multiple parameters was carried out,and a new type oscillation heat transfer dynamic model of the CLOHP was set up based on conservation laws of mass,momentum and energy.Application results indicate that its oscillation heat transfer dynamics features depend largely on the filling rate,pipe diameter and difference in temperature.Besides,oscillation intensity and transfer performance can be improved to a large extent by increasing the temperature difference properly and enlarging the pipe diameter within a certain range under a certain filling rate.