振荡压路机名义荡幅的探讨

根据对振荡轮原地不滑转振荡时的理论和仿真分析,提出了振荡压路机名义荡幅是振荡轮原地不滑转振荡时荡幅的极限值,给出了名义荡幅的求解方法,从而得出了名义荡幅的表达式,发现振荡压路机原地不滑转振荡时振荡轮的荡幅是随频率比和阻尼比变化的。在公式推导的基础上结合具体工程算例指出,工作荡幅与名义荡幅是两个完全不同的概念。

振荡压实效果的理论分析

通过建立振荡压路机的单自由度系统振动模型，对振荡压路机的动态响应进行了定性分析，建立了土壤的动作用力以及荡幅的数学表达式，然后利用有限单元法研究了土的压实过程及其在压实过程中的应力状态，并由此分析振荡压实的特点与适用范围。

垂荡板对Truss Spar平台垂荡性能的影响分析

为了研究垂荡板对Truss Spar平台垂荡性能的影响,在建立Truss Spar平台垂向波浪载荷计算模型的基础上,基于柯莱根-卡彭特数Kc计算了Truss Spar平台的黏性阻尼,提出了垂荡响应幅值的理论计算方法,并将理论计算结果与AQWA软件的仿真结果进行对比。分析结果表明:2种分析方法下垂荡响应幅值趋势一致,峰值较为接近,而且理论计算方法计算速度明显优于仿真分析方法;基于Kc数的垂荡响应幅值理论计算方法能快速有效地分析设有垂荡板的海洋平台的垂荡响应;黏性阻尼能够有效抑制Truss Spar平台的垂荡响应,在垂荡响应分析中不可或缺,垂荡板贡献的黏性阻尼是总黏性阻尼的主要组成部分。所得结论可为合理确定Truss Spar平台垂荡响应幅值提供参考。

当前国际金融市场动荡加剧的必然性

当前国际金融市场动荡的原因固然是多方面的,但从世界经济发展的角度分析。

Design and implementation of digital closed-loop drive control system of a MEMS gyroscope

In order to effectively control the working state of the gyroscope in drive mode, the drive characteristics of the micro electromechanical system （MEMS） gyroscope are analyzed in principle. A novel drive circuit for the MEMS gyroscope in digital closed-loop control is proposed, which utilizes a digital phase-locked loop （PLL） in frequency control and an automatic gain control （AGC） method in amplitude control. A digital processing circuit with a field programmable gate array （FPGA） is designed and the experiments are carried out. The results indicate that when the temperature changes, the drive frequency can automatically track the resonant frequency of gyroscope in drive mode and that of the oscillating amplitude holds at a set value. And at room temperature, the relative deviation of the drive frequency is 0.624 ×10^-6 and the oscillating amplitude is 8.0 ×10^-6, which are 0. 094% and 18. 39% of the analog control program, respectively. Therefore, the control solution of the digital PLL in frequency and the AGC in amplitude is feasible.

Non-linear Viscoelastic Rheological Properties of PCC/PEG Suspensions

The shear thinning and shear thickening rheological properties of PCC/PEG suspension were investigated with the increase of oscillatory amplitude stress at different constant frequencies. The results show that the complex viscosity was initially independent of stress amplitude and obvious shear thinning occurred, then dramatic shear thickening took place after reaching the minimum viscosity. Typically, in a constant frequency of 5 rad/s, the elastic modulus, viscous modulus, and tanδ （δ is the out-of-phase angle） vs. the stress amplitude was investigated. It is found that the elastic modulus initially appeared to be independent of stress amplitude and then exhibited a rapid decrease, but the viscous modulus was independent of amplitude stress at lower amplitude stress. After reaching the minimum value the viscous modulus showed a rapid increase. On the other hand, tanδ increased from 0.6 to 92, which indicates that the transition from elastic to viscous had taken place and tanδ showed a steep increase when shear thickening occurred. Lissajous plots are shown for the dissipated energy vs. different maximum stress amplitude in the shear thinning and shear thickening regions. The relationship of dissipated energy vs. maximum stress amplitude was determined, which follows a power law. In the shear thinning region the exponent was 1.91, but it steeply increases to 3.97 in the shear thickening region.

A 1.1GHz LC VCO with Automatic Amplitude Control for Tuner Applications

This paper presents an LC VCO with auto-amplitude control （AAC）, in which pMOS FETs are used,and the varactors are directly connected to ground to widen the linear range of Kvco. The AAC circuitry adds little noise to the VCO but provides it with robust performance over a wide temperature and carrier frequency range.The VCO is fabricated in a chartered 50GHz 0.35μm SiGe BiCMOS process. The measurements show that it has - 127. 27dBc/Hz phase noise at 1MHz offset and a linear gain of 32.4MHz/V between 990MHz and 1.14GHz.The whole circuit draws 6. 6mA current from 5V supply.

Phase Synchronization of Coupled Rossler Oscillators： Amplitude Effect

Phase synchronization of two linearly coupled Rossler oscillators with parameter misfits is explored. It is found that depending on parameter mismatches, the synchronization of phases exhibits different manners. The synchronization regime can be divided into three regimes. For small mismatches, the amplitude-insensitive regime gives the phase-dominant synchronization; When the parameter misfit increases, the amplitudes and phases of oscillators are correlated） and the amplitudes will dominate the synchronous dynamics for very large mismatches. The lag time among phases exhibits a power law when phase synchronization is achieved.

Transition to Amplitude Death in Coupled System with Small Number of Nonlinear Oscillators

In this work, we investigate the amplitude death in coupled system with small number of nonlinear oscillators. We show how the transitions to the partial and the complete amplitude deathes happen. We also show that the partial amplitude death can be found in globally coupled oscillators either.

Numerical Study of an Oscillating Smaller Cylinder in the Wake of an Upstream Larger Cylinder

A numerical study of flow around two tandem cylinders with unequal diameters was carried out. The upstream larger cylinder was fixed and the downstream smaller cylinder was allowed to oscillate in the transverse direction only. Comparisons of the experimental and numerical results were made to investigate the effects of the gap ratio on the maximum vibration amplitude and vortex shedding frequency. The results showed that the vibration response of the smaller cylinder was significantly affected by the presence of the upstream larger cylinder, and resulted in greatly reduced vibration amplitudes. With an increasing gap ratio, the vibration amplitude increased. However, the magnitude was lower than that corresponding to a single cylinder (with the same diameter as that of the downstream smaller cylinder) under the same flow conditions.

Characteristic of the equivalent impedance for an mxn RLC network with an arbitrary boundary

Considerable progress has been made recently in the development of techniques to determine exactly two-point resistances in networks of various topologies. In particular, a general resistance formula of a non-regular mxn resistor network with an arbitrary boundary is determined by the recursion-transform （RT） method. However, research on the complex impedance network is more difficult than that on the resistor network, and it is a problem worthy of study since the equivalent impedance has many different properties from equivalent resistance. In this study, the equivalent impedance of a non-regular mxn RLC network with an arbitrary boundary is studied based on the resistance formula, and the oscillation characteristics and resonance properties of the equivalent impedance are discovered. In the RLC network, it is found that our formula leads to the occurrence of resonances at the boundary condition holding a series of specific values with an external alternating current source. This curious result suggests the possibility of practical applications of our formula to resonant circuits.

The velocity field around two interacting cavitation bubbles in an ultrasound field

A model is developed to calculate the distribution of first-order velocity field caused by the coupled bubbles in an ultrasound field. Using this model, numerical investigations of velocity field have been made when the two identical bubbles are driven well below resonance by an acoustic field with pressure amplitude exceeding cavitation threshold. Three representative kinestates of the coupled bubbles were chosen for analyzing the velocity distribution of surrounding liquid. The results show that the nonlinear oscillations of a bubble pair affect violently the radial velocity distribution of surrounding liquid, especially in the expanding phase. Symmetry of the tangential velocity distribution implies a possibility of attraction or repulsion of the bubble pairs.

Influence of Noise on Stability of the Ecosystem

Based on a simplified predator-prey model, the influence of noise on the ecosystem has been studied. The results show the following facts. （i） For all parameter vaJues, the existence of noise maintains the oscillatory state of the ecosystem, and enough strong noise can destroy the ecosystem, which means the annihilation of the species. （ii） Comparing to oscillation with small amplitude, while the ecosystem oscillates explosively with large amplitude, it is more likely to lose balance. In addition, the small-amplitude oscillation takes on higher level of regularity. All the numerical results are reasonable comparing to the general knowledge about ecosystem.

Evolution of downsized crescent-shaped dune in wind tunnel experiment

The migration of a downsized crescent-shaped dune was investigated in a wind tunnel experiment.Quantified upwind influx and vertical oscillation of the sand bed were introduced to modulate the saturation level of the sand flux above the dune surface to affect dune evolution.The evolution was recorded by top-view photography and then abstracted as the evolution of self-defined characteristic quantities using a digital image processing algorithm.The results showed that,in contrast to the case for spanwise quantities,the evolution of streamwise quantities corresponds to a linear increase in the modulation magnitude more positively and in a monotonic and convergent manner.In contrast with quantities on the windward face,the changes in quantities with respect to the horns were nonmonotonic with time and almost uncorrelated with the variation in modulation strength,which reveals the distinctiveness of leeside evolution.