brief paper sliding mode observers for systems with unknown inputs a high gain approach sliding mode observers can be constructed for systems with unknown inputs if the so called observer matching condition is satisfied however most systems do not satisfy this condition to construct sliding mode observers for systems that do not satisfy the observer matching condition auxiliary outputs are generated using high gain approximate differentiators and then employed in the design of sliding mode observers the state estimation error of the proposed high gain approximate differentiator based sliding mode observer is shown to be uniformly ultimately bounded with respect to a ball whose radius is a function of design parameters finally the unknown input reconstruction using the proposed observer is analyzed and then illustrated with a numerical example

reliable h_ infty control of linear systems with adaptive mechanism this technical note studies the problem of designing reliable h controllers with adaptive mechanism for linear systems a new method for designing indirect adaptive reliable controller via state feedback is presented for actuator fault compensations based on the on line estimation of eventual faults the proposed reliable controller parameters are updated automatically to compensate the fault effects on systems a notion of adaptive h performance index is proposed to describe the disturbance attenuation performances of closed loop systems the design conditions are given in terms of solutions to a set of linear matrix inequalities lmis the resultant designs can guarantee the asymptotic stability and adaptive h performances of closed loop systems even in the cases of actuator failures the effectiveness of the proposed design method is illustrated via a numerical example

a theory of algebraic cocycles we introduce the notion of an algebraic cocycle as the algebraic analogue of a map to an eilenberg maclane space using these cocycles we develop a cohomology theory for complex algebraic varieties the theory is bigraded functorial and admits gysin maps it carries a natural cup product and a pairing to l homology chern classes of algebraic bundles are defined in the theory there is a natural transformation to singular integral cohomology theory that preserves cup products computations in special cases are carried out on a smooth variety it is proved that there are algebraic cocycles in each algebraic rational p p cohomology class in this announcement we present the outlines of a cohomology theory for algebraic varieties based on a new concept of an algebraic cocycle details will appear in fl our cohomology is a companion to the l homology theory recently studied in l f l f1 l f2 fm this homology is a bigraded theory based directly on the structure of the space of algebraic cycles it admits a natural transformation to integral homology that generalizes the usual map taking a cycle to its homology class our new cohomology theory is similarly bigraded and based on the structure of the space of algebraic cocycles it carries a ring structure coming from the complex join an elementary construction of projective geometry and it admits a natural transformation to integral cohomology chern classes are defined in the theory and transform under to the usual ones our definition of cohomology is very far from a duality construction on l homology nonetheless there is a natural and geometrically defined kronecker pairing between our morphic cohomology and l homology the foundation stone of our theory is the notion of an effective algebraic cocycle which is of some independent interest roughly speaking such a cocycle on a variety x with values in a projective variety y is a morphism from x to the space of cycles on y when x is normal this is equivalent by graphing to a cycle on x y with equidimensional fibres over x such cocycles abound in algebraic geometry and arise naturally in many circumstances the simplest perhaps is that of a flat morphism f x y whose corresponding cocycle associates to x x the pullback cycle f x many more arise naturally from synthetic constructions in projective geometry we show that every variety is rich in cocycles indeed if 1991 mathematics subject classification primary 14f99 14c05

eigenvalue problems for nonlinear differential equations on a measure chain abstract values of are determined for which there exist positive solutions of the second order differential equation on a measure chain u t a t f u t 0 t 0 1 satisfying either the conjugate boundary conditions u 0 u 1 0 or the right focal boundary conditions u 0 u 1 0 where a and f are positive valued and both lim x 0 f x x and lim x f x x exist

multiple solutions for 2mth order sturm liouville boundary value problems growth conditions are imposed on f such that the following boundary value problem 1 my 2m f t y i 1y 2i 0 i 1y 2i 1 0 i 1y 2i 1 i 1y 2i 1 1 0 0 i m 1 has an arbitrary number of positive solutions

algebraic cycles and infinite loop spaces in this paper we use recent results about the topology of chow varieties to answer an open question in infinite loop space theory that is we construct an infinite loop space structure on a certain product of eilenberg maclane spaces so that the total chern map is an infinite loop map an analogous result for the total stiefel whitney map is also proved further results on the structure of stabilized spaces of alebraic cycles are obtained and computational consequences are also outlined

brief paper actuator fault robust estimation and fault tolerant control for a class of nonlinear descriptor systems for lipschitz nonlinear descriptor systems with bounded input disturbances by solving a lyapunov equation a robust state space observer is proposed to simultaneously estimate descriptor system states actuator faults their finite times derivatives and attenuate input disturbances in any desired accuracy the considered faults can be unbounded provided that their qth derivatives are bounded the present fault estimation approaches can handle a large class of faults by using the estimates of descriptor states and faults and the linear matrix inequality lmi technique a fault tolerant control scheme is worked out the nonlinear fault tolerant control system can be made solvable causal asymptotically stable and attenuate input uncertainties in terms of the prescribed performance index only original coefficient matrices are used in the proposed state space observers and fault tolerant controllers therefore the present design approaches are preferable in applications finally a numerical example is given to illustrate the design procedure and simulations demonstrate the efficiency of the proposed design

fault estimation for a class of nonlinear systems based on intermediate estimator this technical note investigates the problem of fault estimation for a class of nonlinear systems with lipschitzian nonlinearities in most of the existing fault estimation approaches the observer matching condition should be satisfied however this condition is hard to meet for many systems to overcome this restriction a new fault estimation method is proposed where an intermediate variable is introduced and a specially designed intermediate estimator is proposed to estimate the state and the faults simultaneously by exploiting the properties of fault distribution matrix it is proved that the states of the error system are uniformly ultimately bounded simulation examples verify the effectiveness of the proposed method

multiple fixed sign solutions for a system of difference equations with sturm liouville conditions we consider the following system of difference equations d mu i k p i k u 1 k u 2 k u n k 0 k 0 1 n i 1 2 ntogether with sturm liouville boundary conditions d ju i 0 0 0 2 n m 1 z 0 w 0 h 0 d w z w n 1 z d h w 0 by using two different fixed point theorems we develop criteria for the existence of three solutions of the system which are of fixed signs on 0 1 n m examples are also included to illustrate the results obtained

milnor k theory of rings higher chow groups and applications if r is a smooth semi local algebra of geometric type over an infinite field we prove that the milnor k group kmn r surjects onto the higher chow group chn r n for all n 0 our proof shows moreover that there is an algorithmic way to represent any admissible cycle in chn r n modulo equivalence as a linear combination of symbolic elements defined as graphs of units in r as a byproduct we get a new and entirely geometric proof of results of gabber kato and rost related to the gersten resolution for the milnor k sheaf furthermore it is also shown that in the semi local pid case we have under some mild assumptions an isomorphism some applications are also given

brief paper an adaptive high gain observer for nonlinear systems in this paper the authors provide a solution to the noise sensitivity of high gain observers the resulting nonlinear observer possesses simultaneously 1 extended kalman filter s good noise filtering properties and 2 the reactivity of the high gain extended kalman filter with respect to large perturbations the authors introduce innovation as the quantity that drives the gain adaptation they prove a general convergence result propose guidelines to practical implementation and show simulation results for an example

twin solutions of boundary value problems for ordinary differential equations and finite difference equations a new twin fixed point theorem is applied first to obtain the existence of at least two positive solutions for the right focal boundary value problem y f ity 0 0 t 1 y 0 y 1 0 it is applied later to obtain the existence of at least two positive solutions for the analogous discrete right focal boundary value problem 2u k g u k 0 k 0 n u 0 u n 1 0

existence of solutions for a cantilever beam problem abstract we are concerned with the fourth order nonuniform cantilever beam problem i x w x f x w x w a w a 0 i b w b i x w x x b 0 under various assumptions on f we prove the existence of at least one two or three positive solutions for this measure chain boundary value problem using the green function approach

algebraic cycles and homotopy theory examine its homotopy groups which after a certain idealization of the space turn out to be astonishingly simple in fact for complex projective space pn the structure can be understood completely this yields new information about the topology of the classical chow varieties and establishes an explicit relationship with universal cohomology operations in the general case complete computations are difficult but we shall establish a complex suspension theorem and lay the foundations for a theory based on the homotopy groups of chow varieties to state the results we must give precise meaning to the space of subvarieties we begin with the fundamental case of subvarieties in complex projective n space pln for each pair of integers p and d with d 1 and 0 p n consider the set wp d pn of all finite formal sums

further results on variable output feedback controllers zak and hui 1993 proposed a sliding mode controller for linear multiple input multiple output mimo systems using static output feedback the author s previous paper 1996 provides an improvement of the output feedback controller of zak hui for a class of linear single input single output siso systems that eliminated two important limitations 1 system uncertainties must be bounded by the system output and 2 a requirement of a matrix inequality the controller developed previously can guarantee global closed loop stability this paper extends the previous results to linear mimo systems it is emphasized that the proposed mimo controller yields global closed loop stability whereas the one in zak hui can only guarantee local stability an application of the proposed mimo controller to an aircraft model is included to show the effectiveness of the method

algebraic cycles on real varieties and z 2 equivariant homotopy theory in this paper the spaces of algebraic cycles on a real projective variety x are studied as z 2 spaces under the action of the galois group gal c r in particular the equivariant homotopy type of the group of algebraic p cycles zp pc is computed a version of lawson homology for real varieties is proposed the real lawson homology groups are computed for a class of real varieties

fault estimation and tolerant control for fuzzy stochastic systems this paper deals with the problem of fault estimation and fault tolerant control for takagi sugeno t s fuzzy stochastic systems with sensor failures where the system under consideration contains ito type stochastic disturbances a new robust observer technique is presented to obtain the estimates of the system states and the sensor faults simultaneously and a fuzzy fault tolerant control scheme is developed to guarantee the closed loop system to be exponentially stable in mean square sufficient conditions are obtained for the existence of admissible controllers and it is shown that the reachability of the sliding mode dynamics can be guaranteed under the proposed control techniques finally a numerical example is provided to illustrate the effectiveness and applicability of the theoretic results obtained

harnack thom theorem for higher cycle groups and picard varieties we generalize the harnack thom theorem to relate the ranks of the lawson homology groups with 22 coefficients of a real quasiprojective variety with the ranks of its reduced real lawson homology groups in the case of zero cycle group we recover the classical harnack thom theorem and generalize the classical version to include real quasiprojective varieties we use weil s construction of picard varieties to construct reduced real picard groups and milnor s construction of universal bundles to construct some weak models of classifying spaces of some cycle groups these weak models are used to produce long exact sequences of homotopy groups which are the main tool in computing the homotopy groups of some cycle groups of divisors we obtain some congruences involving the picard number of a nonsingular real projective variety and the rank of its reduced real lawson homology groups of divisors

fault detection and isolation for a class of uncertain state feedback fuzzy control systems this paper investigates the fault detection and isolation fdi problem for a class of nonlinear state feedback control systems with parameter uncertainties first the considered nonlinear systems are described by multiple t s fuzzy models with uncertain grades of membership and local nonlinear parts in normal case and faulty cases then a switching technique is introduced to address the uncertain grades of membership external disturbances local nonlinear parts faults and the coupling of them in a multiple model scheme a bank of fdi observers are constructed each of which is based on the t s model that describes the system in the presence of a particular fault such that one of them can track the current system state and the corresponding observer estimate error can converge exponentially to zero finally two examples are given to illustrate the effectiveness and advantages of the new results

convergent fault estimation for linear systems with faults and disturbances the problem of convergent fault estimation for a class of linear systems with faults and disturbances is addressed for the first time in this technical note a differential equation based convergence theorem of mean sequence of estimates is proposed which provides an iterative mean estimation technique that has not been fully reported yet in the literature based on the technique a convergent fault estimation strategy for the linear system in consideration is designed and the convergence of mean sequence of fault estimates is proved theoretically an iterative algorithm is given subsequently to compute the fault estimates numerical simulation results demonstrate the effectiveness and merits of the proposed method

completions and fibrations for topological monoids we show that for a certain class of topological monoids there is a homotopy equivalence between the homotopy theoretic group completion m of a monoid m in that class and the topologized grothendieck group m associated to m the class under study is broad enough to include the chow monoids effective cycles associated to a projective algebraic variety and also the infinite symmetric products of finite cw complexes we associate principal fibrations to the completions of pairs of monoids showing the existence of long exact sequences for the naive approach to lawson homology fri91 lf91 a another proof of the eilenberg steenrod axioms for the functors x sp x in the category of finite cw complexes dold thom theorem dt56 is obtained

vanishing theorems for real algebraic cycles we establish the analogue of the friedlander mazur conjecture for teh s reduced lawson homology groups of real varieties which says that the reduced lawson homology of a real quasi projective variety x vanishes in homological degrees larger than the dimension of x in all weights as an application we obtain a vanishing of homotopy groups of the mod 2 topological groups of averaged cycles and a characterization in a range of indices of dos santos real lawson homology as the homotopy groups of the topological group of averaged cycles we also establish an equivariant poincare duality between equivariant friedlander walker real morphic cohomology and dos santos real lawson homology we use this together with an equivariant extension of the mod 2 beilinson lichtenbaum conjecture to compute some real lawson homology groups in terms of bredon cohomology

fuzzy adaptive fault tolerant control of multi agent systems with interactions between physical coupling graph and communication graph abstract this paper considers the fuzzy fault tolerant control problem for multi agent systems with interactions between physical coupling graph and communication graph the dynamics of agents are interconnected by a signed physical coupling graph and the control protocols are computed by using the information flow prescribed in a signed communication graph a novel fuzzy adaptive fault tolerant control method for agents with antagonistic interactions to achieve bipartite consensus is proposed firstly in the presence of actuator bias faults and unknown nonlinear functions different from the traditional method to estimate the weight matrix only the weight vector needs to be estimated by exchanging the order of weight vectors and fuzzy basis functions in the fuzzy logic systems finally a simulation example is given to illustrate the effectiveness of the proposed controller

eigenvalue problems for second order nonlinear dynamic equations on time scales abstract this paper is concerned with the existence and nonexistence of positive solutions of the second order nonlinear dynamic equation u t a t f u t 0 t 0 1 satisfying either the conjugate boundary conditions u 0 u 1 0 or the right focal boundary conditions u 0 u 1 0 where a and f are positive we show that there exists a 0 such that the above boundary value problem has at least two one and no positive solutions for 0 and respectively furthermore by using the semiorder method on cones of the banach space we establish an existence and uniqueness criterion for positive solution of the problem in particular such a positive solution u t of the problem depends continuously on the parameter i e u t is nondecreasing in lim 0 u 0 and lim u

existence of positive solutions to second order time scale systems in this paper the author consider the following dynamic system on a measure chain u i d d t f i t u 1 s t u 2 s t u n s t 0 email protected a b satisfying sturm liouville boundary conditions a iu i a email protected iu i d a 0 c iu i s b email protected iu i d s b 0 i 1 2 n some new results are obtained for the existence of single twin and triple positive solutions of the above system by using nonlinear alternative of leray schauder type krasnosel skii s fixed point theorem in a cone and leggett williams fixed point theorem

fuzzy model based fault tolerant design for nonlinear stochastic systems against simultaneous sensor and actuator faults this paper addresses the problem of fault estimation and fault tolerant control for a class of takagi sugeno t s fuzzy ito stochastic systems subject to simultaneously sensor and actuator faults the main difficulty in this study is that sensor faults actuator faults and stochastic noise that are governed by brownian motion are taken into simultaneous consideration in a unified framework and traditional fault tolerant approaches are not effective to solve this research issue a new descriptor fuzzy sliding mode observer approach is presented in this paper to obtain the simultaneous estimates of system state sensor fault and actuator fault vectors based on the state estimates an observer based fault tolerant control ftc scheme is developed to stabilize the resulting closed loop system finally a simulation example is provided to show the effectiveness of the proposed fault tolerant approach

positive solutions for nonlinear three point boundary value problems on time scales abstract let t be a time scale such that 0 t t consider the following three point boundary value problem on time scales u t a t f t u t 0 t 0 t u 0 u 0 0 u u t where 0 0 0 t 0 t and d t 1 0 by using fixed point theorems in cones some new and general results are obtained for the existence of single and multiple positive solutions of the above problem in particular our criteria generalize and improve some known results

three positive fixed points of nonlinear operators on ordered banach spaces we generalize the fixed point theorem of leggett williams which is a theorem giving conditions that imply the existence of three fixed points of an operator defined on a cone in a banach space we then show how to apply our theorem to prove the existence of three positive solutions to a second order discrete boundary value problem 2001 elsevier science ltd all rights reserved

on green s functions and positive solutions for boundary value problems on time scales in this paper we offer a form of self adjoint differential equations on time scales so that the associated green s function is found symmetric in the usual sense for this purpose together with the delta derivative we employ the nabla derivative as well we introduce the concepts of lebesgue delta and nabla integrals on time scales next sign properties of the green s function are investigated and existence results for positive solutions of nonlinear boundary value problems are established upper and lower bounds for these positive solutions also are given

adaptive h control in finite frequency domain for uncertain linear systems this paper is concerned with the problem of adaptive h controller design in finite frequency domains for uncertain linear systems the uncertainties are assumed to be time invariant unknown but bounded which appear affinely in the matrices of system models an adaptive mechanism is introduced to construct a novel finite frequency h controller with time varying gains by using lyapunov theory and parseval s theorem the controller design conditions are given in terms of a set of linear matrix inequalities lmis it is shown that the proposed finite frequency controller with time varying gains can achieve better h performance than the traditional ones with fixed gains finally a numerical example of the f 18 aircraft model is given to illustrate the presented theoretical results

twin solutions of boundary value problems for differential equations on measure chains a new twin fixed point theorem is applied to obtain the existence of at least two positive solutions for the right focal boundary value problem on a measure chain t y t f y t 0 t 0 1 t y 0 y 1 0

existence of two solutions of m point boundary value problem for second order dynamic equations on time scales in this paper by means of a new twin fixed point theorem in a cone the existence of at least two positive solutions of m point boundary value problem for second order dynamic equations on time scales is considered

fault detection and isolation for affine fuzzy systems with sensor faults this paper investigates the fault detection and isolation fdi problem for a class of nonlinear systems with sensor outage faults the considered nonlinear systems are described as affine fuzzy models and the system outputs are chosen as the premise variables of fuzzy models different from the existing results the influence of sensor faults on premise variables is considered as a result the well known parallel distributed compensation scheme cannot be used for fdi filters design by using the structural information encoded in the fuzzy rules the affine fuzzy system is represented by multiple operating regime based models in fault free case and faulty cases in the multiple model scheme a bank of piecewise fdi filters are constructed each of them is based on the affine fuzzy model that describes the system in the presence of a specified fault the fault dependent residual signals generated from the filters are used for detecting and isolating the specified fault the fdi filter design conditions are obtained in the formulation of linear matrix inequalities finally a numerical example is given to illustrate the effectiveness and merits of the proposed method

quaternionic algebraic cycles and reality in this paper we compute the equivariant homotopy type of spaces of algebraic cycles on real brauer severi varieties under the action of the galois group gal c r appropriate stabilizations of these spaces yield two equivariant spectra the first one classifies dupont seymour s quaternionic k theory and the other one classifies an equivariant cohomology theory 3 which is a natural recipient of characteristic classes kh x 3 x for quaternionic bundles over real spaces x

state and input estimation for a class of uncertain systems we consider here the problem of state and input estimation for a class of uncertain systems which consist of a nominally linear part and an uncertain nonlinear time varying part which can be regarded as a state dependent time varying input we obtain a lyapunov type characterization of the assumptions commonly found in the literature on this problem using this characterization we obtain estimators which using only a measured output can asymptotically estimate to any desired accuracy the system state and the input

moving algebraic cycles of bounded degree the chow moving lemma is a theorem which asserts that a given algebraic s cycle on a smooth algebraic variety x can be moved within its rational equivalence class to intersect properly a given r cycle on x provided that r s dim x cf chow s2 in the past few years there has been considerable interest in studying spaces of algebraic cycles rather than simply cycles modulo an equivalence relation with this in mind it is natural to ask whether one can move a given bounded family of s cycles on the smooth variety x to intersect properly a given bounded family of r cycles the main point of this paper is to formulate and prove just such a result in theorem 3 1 we demonstrate that for any integer e and any smooth projective variety x one can simultaniously and algebraically move all effective s cycles of degree e on x so that each such cycle meets every effective r cycle of degree e on x in proper dimension the primary motivation for this moving lemma for cycles of bounded degree was the possibility of a duality theorem between cohomology and homology theories defined in terms of homotopy groups of cycle spaces using theorem 3 1 we have proved such a duality theorem for complex quasi projective varieties in f l2 we prove our moving lemma for varieties over an arbitary infinite field permitting a proof in f v of a duality theorem for motivic cohomology and homology the reader will find that our moving lemma has numerous good properties first of all the move is given as an algebraic move parametrized by a punctured projective line on chow varietes although this move is good only for s cycles of bounded degree it is defined on all effective s cycles moreover the move starts at time 0 by expressing an effective s cycle z as a difference of effective s cycles both of which have intersection properties no worse than z finally our moving lemma is applicable to smooth quasiprojective varieties for it is stated for a possibly singular projective variety x resulting in a conclusion of proper intersection off the singular locus of x the classical motivation for the moving lemma was to define an intersection product on algebraic cycles modulo rational equivalence thereby establishing the chow ring a x some of the classical literature overlooked the question of whether or not intersection of cycles defined via a moving lemma is independent of the move e g chow r s2 on the other hand cf chev s3 one direct consequence of our moving lemma is a proof for smooth quasi projective varieties that the intersection product is indeed well defined independent of the choice of move theorem 3 4 of course the intersection product now has an intrinsic formulation for all smooth algebraic varieties due to fulton

existence theory for positive solutions to one dimensional p laplacian boundary value problems on time scales abstract in this paper we consider the one dimensional p laplacian boundary value problem on time scales p u t h t f u t 0 t a b u a b 0 u a 0 u b 0 where p u is p laplacian operator i e p u u p 2 u p 1 some new results are obtained for the existence of at least single twin or triple positive solutions of the above problem by using krasnosel skii s fixed point theorem new fixed point theorem due to avery and henderson and leggett williams fixed point theorem this is probably the first time the existence of positive solutions of one dimensional p laplacian boundary value problems on time scales has been studied

constant sign solutions for a system of integral equations on time scales we consider the following system of integral equations on a time scale t u i t email protected a s b g i t s f i s u 1 s u 2 s u n s ds email protected a s l b t email protected email protected n using a nonlinear alternative of leray schauder type and krasnosel skii s fixed point theorem we establish the existence of one or more constant sign solutions of the system the generality of the results obtained is illustrated through application to boundary value problems

rational isomorphisms between k theories and cohomology theories the well known isomorphism relating the rational algebraic k theory groups and the rational motivic cohomology groups of a smooth variety over a field of characteristic 0 is shown to be realized by a map the segre map of infinite loop spaces moreover the associated chern character map on rational homotopy groups is shown to be a ring isomorphism a technique is introduced that establishes a useful general criterion for a natural transformation of functors on quasi projective complex varieties to induce a homotopy equivalence of semi topological singular complexes since semi topological k theory and morphic cohomology can be formulated as the semi topological singular complexes associated to algebraic k theory and motivic cohomology this criterion provides a rational isomorphism between the semi topological k theory groups and the morphic cohomology groups of a smooth complex variety consequences include a riemann roch theorem for the chern character on semi topological k theory and an interpretation of the topological filtration on singular cohomology groups in k theoretic terms

triple solutions of focal boundary value problems on time scale we consider the following differential equation on a time scale t y d d t p t y s t 0 t a b t together with focal boundary conditions y a 0 y d s b 0 where a b e t and a s b by using two different fixed point theorems criteria are established for the existence of triple positive solutions of the boundary value problem we also include some examples to illustrate the results obtained

triple positive solutions for some second order boundary value problem on a measure chain in this paper we study the existence of three positive solutions for the second order two point boundary value problem on a measure chain x d d t p t f t x s t x d t 0 email protected t 1 t 2 a 1x t 1 a 2x d t 1 0 a 3x s t 2 a 4x d s t 2 0 where f t 1 s t 2 x 0 xr 0 is continuous and p t 1 s t 2 0 a nonnegative function that is allowed to vanish on some subintervals of t 1 s t 2 of the measure chain the method involves applications of a new fixed point theorem due to bai and ge z b bai w g ge existence of three positive solutions for some second order boundary value problems comput math appl 48 2004 699 707 the emphasis is put on the nonlinear term f involved with the first order delta derivative x d t

existence of multiple solutions for second order boundary value problems we give conditions on f involving pairs of lower and upper solutions which lead to the existence of at least three solutions of the two point boundary value problem y f x y y 0 x epsilon 0 1 y 0 0 y 1 in the special case f x y y f y greater than or equal to 0 we give growth conditions on f and apply our general result to show the existence of three positive solutions we give an example showing this latter result is sharp our results extend those of avery and of lakshmikantham et al

double positive solutions of three point boundary value problems for p laplacian dynamic equations on time scales a new double fixed point theorem is applied to investigate the existence of at least double positive solutions of three point boundary value problems for p laplacian dynamic equations on a time scale