Mechanism Modeling and Simulation Based on Dimensional Deviation

To analyze the effects on motion characteristics of mechanisms of dimensional variations, a study on random dimensional deviation generation techniques for 3D models on the basis of the present mechanical modeling software was carried out, which utilized the redeveloped interfaces provided by the modeling software to develop a random dimensional deviation generation system with certain probability distribution characteristics. This system has been used to perform modeling and simulation of the specific mechanical time delayed mechanism under multiple deviation varieties, simulation results indicate the dynamic characteristics of the mechanism are influenced significantly by the dimensional deviation in the tolerance distribution range, which should be emphasized in the design.

The effect of f(T) gravity on an interplanetary clock and its time transfer link

As an extension of the＂teleparallel＂equivalent of general relativity,f（T）gravity is proposed to explain some puzzling cosmological behaviors,such as accelerating expansion of the Universe.Given the fact that modified gravity also has impacts on the Solar System,we might test it during future interplanetary missions with ultrastable clocks.In this work,we investigate the effects of f（T）gravity on the dynamics of the clock and its time transfer link.Under these influences,theΛ-term and theα-term of f（T）gravity play important roles.Here,Λis the cosmological constant andαrepresents a model parameter in f（T）gravity that determines the divergence from teleparallel gravity at the first order approximation.We find that the signal of f（T）gravity in the time transfer is much more difficult to detect with the current state of development for clocks than those effects on dynamics of an interplanetary spacecraft with a bounded orbit with parameters 0.5 au≤a≤5.5 au and 0≤e≤0.1.

APPLICATION OF Ct-PARAMETER FOR CREEP-FATIGUE CRACK GROWTH WITH SLOW LOAD RISING CONDITION

Most of the assessment equations for Ct which is a wellknown fracture parameter characterizing high temperature crack growth rates, have limited applicability to constant load conditions after sudden loading. However, crack growth due to creep can also occur under load varying conditions when load rising time is so long that accumulated creep deformation near the crack tip is not negligible.In this paper, the estimation equation of the Ctparameter which can be applied to the case of slow load rising, i.e., (Ct)r, is explained. And the correlation between (Ct)r at the end of the load increasing period and Ct at the beginning of the succeeding load hold period is discussed. Finite element analyses of several cases with various loading conditions were performed and results were presented to show the effectiveness of the proposed Ct estimation scheme. The general applicability of the equation is also discussed.

Is it the time to reconsider the choice of valves for cardiac surgery： mechanical or bioprosthetic？

Valvular heart disease is a pathologic process involving one or more of the four valves(aortic,pulmonary,mitral and tricuspid)of the heart typified by stenosis or regurgitation and leading to patient symptoms.The most common causes are tissue degeneration,rheumatic fever and congenital heart diseases.Aortic valve replacement(AVR)using either mechanical or bioprosthetic(tissue)valves via open-heart surgical

Effects of relaxation time on start-up time for starting flow of Maxwell fluid in a pipe

Although the analytical solution of the starting flow of Maxwell fluid in a pipe has been derived for a long time, the effect of relaxation time λ on start-up time ts of this flow is still not well understood. Especially, there exist a series of jumps on the ts-λ. curve. In this paper we introduce a normalized mechanical energy by mode decomposition and mathematical analogy to describe the start-up process. An improved definition of start-up time is presented based on the normalized mechanical energy. It is proved that the ts-λ. curve contains a series of jumps if λ is larger than a critical value. The exact positions of the jumps are determined and the physical reason of the jumps is discussed.

MECHANICAL RELAXATION TIME OF A TWO-COMPONENT EPOXY NETWORKLiClO_4 POLYMER ELECTROLYTE

The mechanical relaxation time of a two-component epoxy network-LiClO_4 system as a polymer electrolyte was investigated. The network is composed of diglycidyl ether of polyethylene glycol (DGEPEG) and triglycidyl ether of glycerol (TGEG), wherein LiCIO_4 was incorporated and acts as both the ionic carrier and the curing catalyst. As the relaxation time is informative to the segmental mobility, which is known to be essential for ionic conductivity, the average relaxation times of the specimens were determined through master curve construction. Experimental results showed that the salt concentration, molecular weight of PEG in DGEPEG and DGEPEG/TGEG ratio have profound effect on the relaxation time of the specimen. Among these factors , the former reinforces the network chains, leading to lengthen the relaxation time, whereas the latter two are in favour of the chain flexibility and show an opposite effect. The findings was rationalized in terms of the free volume concept.

Ehrenfest Approach to the Adiabatic Invariants and Calculation of the Intervals of Time Entering the Energy Emission Process in Simple Quantum Systems

In the first step, the Ehrenfest reasoning concerning the adiabatic invariance of the angular orbital momentum is applied to the electron motion in the hydrogen atom. It is demonstrated that the time of the energy emission from the quantum level n+1 to level n can be deduced from the orbital angular momentum examined in the hydrogen atom. This time is found precisely equal to the time interval dictated by the Joule-Lenz law governing the electron transition between the levels n+1 and n. In the next step, the mechanical parameters entering the quantum systems are applied in calculating the time intervals characteristic for the electron transitions. This concerns the neighbouring energy levels in the hydrogen atom as well as the Landau levels in the electron gas submitted to the action of a constant magnetic field.

Finite-time non-fragile filtering for nonlinear networked control systems via a mixed time/event-triggered transmission mechanism

This paper is aimed at investigating the problem of mixed time/event-triggered finite-time non-fragile filtering for nonlinear networked control systems with delay.First,a fuzzy nonlinear networked control system model is established by interval type-2(IT2)Takagi-Sugeno(T-S)fuzzy model,the designed non-fragile filter resolves the filter parameter uncertainties and uses different membership functions from the IT2 T-S fuzzy model.Second,a novel mixed time/event-triggered transmission mechanism is proposed,which decreases the waste of network resources.Next,Bernoulli random variables are used to describe the cases of random switching mixed time/event-triggered transmission mechanism.Then,the error filtering system is designed by considering a Lyapunov function and a sufficient condition of finite-time boundedness.In addition,the existence conditions for the finite-time non-fragile filter are given by the linear matrix inequalities(LMIs).Finally,two simulation results are presented to prove the effectiveness of the obtained method.

The Study on the Mechanical Properties of Optical Fiber With Long-Term Time Aging

The fiber properties depending on the coating thickness and long-term time aging were investigated. The coating strip forces of optical fiber were strongly increased with secondary coating thickness. But it did not change with time aging up to 90 days. The tensile strength and stress corrosion parameters of coated fiber were increased with time aging also but the increasing rate was quite different depending on the coating