Theoretical research on intensity envelope function of strong ground motion

After the time history of seismic motion is represented by superposition of a series of narrow frequency band wave groups, we obtain a general relation between wave group arrival time and derivative of phase spectra in the paper. On the basis of the relation, frequency number distribution function of wave group arrival time is completely equivalent to that of phase difference spectra. Under the assumption that phase angles of seismic motionobey uniform distribution ranged from 0 to ─ 2π, a quantitative relation between intensity envelope function of seismic motion and energy distribution function with wave group arrival time has been derived in this paper. The relation illuminates inner links among Fourier amplitude spectra and derivative of phase spectra and intensity envelope function. Some examples given by the paper support the conclusions mentioned above.

Envelope Functions of Time Histories in Seismic Safety Evaluation and Scenario Earthquakes

It has been a period of time since the concept of scenario earthquake was proposed, but this concept has rarely been used in seismic safety evaluation in China since then. Meanwhile, because of the uncertainties of magnitudes-distances pairs, there is large arbitrariness while determining the envelope function of time histories in seismic hazard analysis. In this paper, we describe a method to control the envelope functions of the time histories by introducing the most-likely combinations of magnitude and distance of the scenario earthquakes based on a probabilistic method, revise the software of the ellipse model for seismic hazard analysis, and give a computation example.

Recognition of Red Cell and Megakaryocyte Based L-Shaped Envelope Function

In order to explore the cell composition and its metabolism,it is important to let computer recognize the cells and get the counts of different cells for a sample.This paper proposes an L-shaped envelop function and the related fuzzy clustering method as a way to identify the megakaryocyte and the red cell from the sliced marrow image.This method is useful when the staining is insufficient and the color cannot be used as the identifying factor.This method uses the experimental histogram data to fit the L-shaped function and then use it as the envelop for the match test.The fuzzy c-means(FCM) performance index is used to test the adjacent area and get the minimum and finally secure the identification.The new method is not limited to megakaryocyte or red cell and can be used for general purposes of cell recognition.Tests show that this envelop function can ensure the recognition rate with different staining batches and can reach satisfied counting under similar illumination condition.

Functional Envelope of Cantor Spaces

Given a topological dynamical system （X, T）, where X is a compact metric space and T a continuous selfmap of X. Denote by S（X） the space of all continuous selfmaps of X with the compactopen topology. The functional envelope of （X,T） is the system （S（X）,FT）, where FT is defined by FT（φ） = T o φ for any φ ∈ S（X）. We show that （1） If （∑, T） is respectively weakly mixing, strongly mixing, diagonally transitive, then so is its functional envelope, where ∑ is any closed subset of a Cantor set and T a selfmap of ∑ （2） If （S（∑）,Fσ） is transitive then it is Devaney chaos, where （∑, σ） is a subshift of finite type; （3） If （∑, T） has shadowing property, then （Su （∑）, FT） has shadowing property, where ∑ is any closed subset of a Cantor set and T a selfmap of ∑; （4） If （X,T） is sensitive, where X is an interval or any closed subset of a Cantor set and T： X → X is continuous, then （Su（X）,FT） is sensitive; （5） If ∑, is a closed subset of a Cantor set with infinite points and T ：∑ →∑ is positively expansive then the entropy entv（FT） of the functional envelope of （∑, T） is infinity.

Fuzzy adaptive tracking control within the full envelope for an unmanned aerial vehicle

Motivated by the autopilot of an unmanned aerial vehicle（UAV） with a wide flight envelope span experiencing large parametric variations in the presence of uncertainties, a fuzzy adaptive tracking controller（FATC） is proposed. The controller consists of a fuzzy baseline controller and an adaptive increment, and the main highlight is that the fuzzy baseline controller and adaptation laws are both based on the fuzzy multiple Lyapunov function approach, which helps to reduce the conservatism for the large envelope and guarantees satisfactory tracking performances with strong robustness simultaneously within the whole envelope. The constraint condition of the fuzzy baseline controller is provided in the form of linear matrix inequality（LMI）, and it specifies the satisfactory tracking performances in the absence of uncertainties. The adaptive increment ensures the uniformly ultimately bounded（UUB） predication errors to recover satisfactory responses in the presence of uncertainties. Simulation results show that the proposed controller helps to achieve high-accuracy tracking of airspeed and altitude desirable commands with strong robustness to uncertainties throughout the entire flight envelope.

A method for the length-pressure hysteresis modeling of pneumatic artificial muscles

This paper presents a method for the length-pressure hysteresis modeling of pneumatic artificial muscles(PAMs)by using a modified generalized Prandtl-Ishlinskii(GPI)model.Different from the approaches for establishing the GPI models by replacing the linear envelope functions of operators with hyperbolic tangent and exponential envelop functions,the proposed model is derived by modifying the envelope functions of operators into arc tangent functions,which shows an improvement in the modeling accuracy.The effectiveness of the proposed model is verified by the experimental data of a PAM.Furthermore,its capacity in capturing the hysteresis relationship between length and pressure is testified by giving different input pressure signals.With regard to the computational efficiency,the influence of the number of operators on the modeling accuracy is discussed.Furthermore,the inversion of the GPI model is derived.Its capability of compensating the hysteresis nonlinearities is confirmed via the simulation and experimental study.