基于中心流形理论的小水电并网系统Hopf分岔分析

针对小水电并网系统,用Matcont软件搜寻系统的Hopf分岔点绘制分岔图;利用中心流形理论将高维电力系统降到二维模型,并通过计算二维模型分岔稳定性指标的正负判定原系统Hopf分岔类型。结果表明,分岔稳定性指标大于零时电压失稳,小于零时电压稳定。用Matlab软件对讨论结果进行数值仿真,证明理论结果的正确性。     

A codimension-two resonant bifurcation from a heteroclinic cycle with complex eigenvalues

Robust heteroclinic cycles between equilibria lose stability either through local bifurcations of their equilibria or through global bifurcations. This paper considers a global loss of stability termed a 'resonant' bifurcation. This bifurcation is usually associated with the birth or death of a nearby periodic orbit, and generically occurs in either a supercritical or subcritical manner. For a specific robust heteroclinic cycle between equilibria with complex eigenvalues we examine the codimension-two point that separates the supercritical and subcritical. We investigate the bifurcation structure and show the existence of further bifurcations of periodic orbits.     

Hue manifold

It is generally accepted that hues can be arranged so as to make a circle. The circular representation of hue has been supported by multidimensional scaling, which allows for the representation of a set of colored papers as a configuration in a Euclidean space where the distances between the papers correspond to the perceptual dissimilarities between them. In particular, when papers of various hues are evenly illuminated, they are arranged in a one-dimensional circular configuration. However, under variegated illumination we show that the same papers in fact make a two-dimensional configuration that resembles a torus.     

Multiparameter objects and multiparameter measurements

The paper discusses the features of monitored objects as multiparameter ones and the organization of quality estimation by means of multiparameter measurements.Translated from Izmeritelnaya Tekhnika, No. 11, pp. 11–14, November, 2004.     

Passage of a liquid drop through a bifurcation

Numerical simulations of the motion of a viscous liquid drop through a two-dimensional bifurcating channel are conducted using a boundary-element method for Stokes flow. The drop viscosity is assumed to be equal to the ambient fluid viscosity and the drop interface is assumed to exhibit uniform surface tension. The mean fluid pressures are prescribed at the channel inlet and two outlets, and the corresponding flow rates are computed as part of the solution. Preliminary simulations show that the shape of a two-dimensional drop moving through a channel with parallel walls is similar to that of an axisymmetric drop moving along the centerline of a circular tube. The ability of a drop to remain intact as it passes through the bifurcation is determined by the drop size and capillary number expressing the significance of surface tension. For a given drop size and channel inlet and outlet pressures, there is a critical capillary number above which a drop splits into two pieces connected by a thinning bridge. The presence of the drop has a weak effect on the inlet and outlet flow rates throughout its passage. Simulations based on a boundary-element method for a rigid particle with circular or elliptical shape reveal a significantly stronger effect due to the absence of interfacial mobility.     

Experimental investigation of a manifold heat-pipe heat exchanger

Results of experimental investigations of a heat exchanger on a manifold water heat pipe are given. An analysis is made of the temperature distribution along the heat-transfer agent path as a function of the transferred heat power. The influence of the degree of filling with the heat transfer agent on the operating characteristics of the construction is considered.Academic Scientific Complex A. V. Luikov Institute of Heat and Mass Transfer of the Academy of Sciences of Belarus, Minsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 3, pp. 397–402, May–June, 1995.     

High-throughput multiparameter analysis of individual mitochondria

Mitochondria are one of the most important organelles responsible for cellular energy metabolism and apoptosis regulation. However, single-mitochondrion analysis is challenging, because of their small sizes and the low content of organelle constituents. Here, we report the development of a sensitive and versatile platform for high-throughput multiparameter analysis of individual mitochondria. Employing specific fluorescent staining with a laboratory-built high-sensitivity flow cytometer (HSFCM), we demonstrate the simultaneous detection of side scatter, cardiolipin, and mitochondria DNA (mtDNA) of a single mitochondrion. Simultaneous measurements of side scatter, porin, and cytochrome c of individual mitochondria are reported for the first time. Correlation analysis among multiple attributes on an organelle-by-organelle basis could provide a more definitive assessment of the purity, structure integrity, and apoptosis-related proteins of isolated mitochondria than bulk measurement. This work represents a significant advancement in single-mitochondrion analysis. We believe that the HSFCM holds great potential for studying apoptotic signal transduction pathways at the single-mitochondrion level.     

The Freedericksz transition as a bifurcation problem

We consider the effects of the application of electric and magnetic fields to a homogeneously aligned nematic liquid crystal which lies between parallel plates. The average alignment of the fluid molecules is known as the director and it is set parallel to the top and bottom bounding surfaces. At a critical field strength a Freedericksz transition occurs which results in a distortion of the director field. We discuss this phenomenon from the point of view of bifurcation theory and use numerical bifurcation techniques to explore it. Imperfections in the cell, either in the applied field or the director orientation at the boundaries, are also considered. Finally, we investigate the effect of finite aspect in a two-dimensional version of the problem.     

Hopf bifurcation on a simple cubic lattice

We study Hopf bifurcation for diff erential equations defined on the space of functions on R3 which are triply periodic with respect to a simple (primitive) cubic lattice. The centre manifold theorem reduces the problem to a system of ordinary diff erential equations (ODEs) on the space (C+C)3 and symmetric under the group (O=Zc2) + T3. We abstract this group as the wreath product group O(2) /S3, and we use a general theory of symmetry - breaking bifurcations for wreath product groups to find (up to conjugacy) all branches of periodic solutions with maximal isotropy. The stability of these solutions is calculated . Branches of periodic solutions with sub-maximal isotropy can also exist. Some possibilities for bifurcations to heteroclinic cycles are explored.     

Adsorption-stimulated bifurcation transition in a silicon-porous-silicon system

It is shown that after a porous layer has been formed electrochemically on a silicon surface at elevated anode currents, the silicon-porous-silicon system is in a quasisteady nonequilibrium state from which it may be transferred under the influence of fairly weak adsorption effects. Pis’ma Zh. Tekh. Fiz. 24, 30–34 (November 12, 1998)     

Reference priors in multiparameter nonregular cases

Summary The reference prior in the sense of Bernardo is derived in some multiparameter nonregular cases. The family of densities we consider have discontinuities as some points which depend on one component of the parameter (say, ϕ) while, for fixed values of ф, the family is regular with respect to the other components (say, ϕ). We obtain the reference prior throgh an asymptotic expansion of Lindley’s measure of information. The expansion is in itself of some importance. The results are illustrated using examples.     

Generic Asymptotic Expansions

We give an expansion algorithm for germs of exp-log functions at infinity which is correct modulo Schanuels conjecture. We also show how the algorithm can be made generic. More precisely, we reduce the expansion algorithm for exp-log functions depending on parameters to the problem of deciding whether a given system of exp-log equations and inequalities in several variables admits a solution.     

Computer-aided classification of breast masses in ultrasonic B-scans using a multiparameter approach

Classification of breast masses in ultrasonic B-scan images is undertaken using a multiparameter approach. The parameters are generated on the basis of a non-Rayleigh statistic model of the backscattered envelope from the breast tissue. They can be computed automatically with minimal clinical intervention once the location of the mass is known. A new discriminant is developed that combines these parameters linearly. It is seen that this new discriminant performs classification of masses into benign or malignant better than the classification by any one of the individual parameters. The data set studied consisted of 99 cases (70 patients with benign masses and 29 patients with malignant masses). The areas under the receiver operating characteristic (ROC) curves (A/sub z/) and statistical attributes of the areas were studied to establish the enhancement in performance. The A/sub z/ value after combining all the parameters was found to be 0.8701. Upon combining this parameter with the level of suspicion (LOS) scores of a radiologist, the performance is further enhanced with an area under the (empirical) ROC of 0.94 having an operating point at a sensitivity of 0.965 and specificity of 0.87. It is suggested that this automated approach may hold promise as a means of classifying breast masses.