some notes on the paper cone metric spaces and fixed point theorems of contractive mappings abstract huang and zhang reviewed cone metric spaces in 2007 huang long guang zhang xian cone metric spaces and fixed point theorems of contractive mappings j math anal appl 332 2007 1468 1476 we shall prove that there are no normal cones with normal constant m 1 and for each k 1 there are cones with normal constant m k also by providing non normal cones and omitting the assumption of normality in some results of huang long guang zhang xian cone metric spaces and fixed point theorems of contractive mappings j math anal appl 332 2007 1468 1476 we obtain generalizations of the results

contraction and approximate contraction with an application to multi point boundary value problems abstract the paper deals with some general iterative methods in n metric spaces the obtained results are more explicit than those known in the literature and provides error estimates when the sequence obtained on a floating point system starts oscillating a stopping criteria and error estimates at that stage are provided an application to multi point boundary value problems is also given

fixed points of weak contractions in cone metric spaces abstract cone metric spaces are generalizations of metric spaces where the metric is banach space valued weak contractions are generalizations of the banach s contraction mapping which have been studied by several authors in the present work we establish a unique fixed point result for weak contractions in cone metric spaces our result is supported by an example

common fixed points for maps on cone metric space the purpose of this paper is to generalize and to unify fixed point theorems of das and naik ciric jungck huang and zhang on complete cone metric space

coincidence and fixed point theorems for generalized ψ φ weak nonlinear contraction in ordered k metric spaces in this paper we establish coincidence and fixed point theorems for a pair of mappings satisfying a new generalized j f weak nonlinear contraction type condition in ordered k metric spaces the presented results generalize and extend the very recent results of choudhury and metiya b s choudhury and n metiya the point of coincidence and common fixed point for a pair of mappings in cone metric spaces computers and mathematics with applications 60 2010 1686 1695

fixed point for set valued mappings satisfying an implicit relation in partially ordered metric spaces abstract let x be a partially ordered set and d be a complete metric on x let f g be two set valued mappings on x we obtained sufficient conditions for the existence of common fixed point of f and g satisfying an implicit relation in partially ordered set x

cone metric spaces and fixed point theorems of contractive mappings in this paper we introduce cone metric spaces prove some fixed point theorems of contractive mappings on cone metric spaces

how to construct random functions a constructive theory of randomness for functions based on computational complexity is developed and a pseudorandom function generator is presented this generator is a deterministic polynomial time algorithm that transforms pairs g r where g is any one way function and r is a random k bit string to polynomial time computable functions r 1 2 k 1 2 k these r s cannot be distinguished from random functions by any probabilistic polynomial time algorithm that asks and receives the value of a function at arguments of its choice the result has applications in cryptography random constructions and complexity theory

analysis of aperiodicities in nearly periodic waveforms waveforms from the oscillations of sustained tone acoustic musical instruments are never precisely periodic the source of their aperiodicity is instrument dependent and typically small with the exception of some studies on the period fluctuations of bowed string instruments musical instrument aperiodicities have never been quantitatively characterized this paper introduces two techniques for the characterization of nearly periodic waveforms the norm difference method and the fourier transform of sonograms the former is appropriate for the study of cycle to cycle fluctuations and yields its best results for fluctuations that have a typical time scale of up to 16 periods of the nominally periodic oscillation the second method is appropriate for a frequency range of 2 hz to approximately 100 hz the ranges of applicability overlap for pitch frequencies in the treble region the techniques are described in detail and explored with various computer constructed waveforms with appropriate properties de

a simple unpredictable pseudo random number generator two closely related pseudo random sequence generators are presented the 1 p generator with input p a prime outputs the quotient digits obtained on dividing 1 by p the x 2 bmod n generato

fixed point theorems for generalized contractions in ordered metric spaces abstract the purpose of this paper is to present some fixed point results for self generalized contractions in ordered metric spaces our results generalize and extend some recent results of a c m ran m c reurings a c m ran m c reurings a fixed point theorem in partially ordered sets and some applications to matrix equations proc amer math soc 132 2004 1435 1443 j j nieto r rodriguez lopez j j nieto r rodriguez lopez contractive mapping theorems in partially ordered sets and applications to ordinary differential equations order 22 2005 223 239 j j nieto r rodriguez lopez existence and uniqueness of fixed points in partially ordered sets and applications to ordinary differential equations acta math sin engl ser 23 2007 2205 2212 j j nieto r l pouso r rodriguez lopez j j nieto r l pouso r rodriguez lopez fixed point theorem theorems in ordered abstract sets proc amer math soc 135 2007 2505 2517 a petrusel i a rus a petrusel i a rus fixed point theorems in ordered l spaces proc amer math soc 134 2006 411 418 and r p agarwal m a el gebeily d o regan r p agarwal m a el gebeily d o regan generalized contractions in partially ordered metric spaces appl anal in press as applications existence and uniqueness results for fredholm and volterra type integral equations are given

a digital signature scheme secure against adaptive chosen message attacks we present a digital signature scheme based on the computational difficulty of integer factorization the scheme possesses the novel property of being robust against an adaptive chosen message attack an adversary who receives signatures for messages of his choice where each message may be chosen in a way that depends on the signatures of previously chosen messages cannot later forge the signature of even a single additional message this may be somewhat surprising since in the folklore the properties of having forgery being equivalent to factoring and being invulnerable to an adaptive chosen message attack were considered to be contradictory more generally we show how to construct a signature scheme with such properties based on the existence of a claw free pair of permutations a potentially weaker assumption than the intractibility of integer factorization the new scheme is potentially practical signing and verifying signatures are reasonably fast and signatures are compact

discrimination of musical instrument sounds resynthesized with simplified spectrotemporal parameters the perceptual salience of several outstanding features of quasiharmonic time variant spectra was investigated in musical instrument sounds spectral analyses of sounds from seven musical instruments clarinet flute oboe trumpet violin harpsichord and marimba produced time varying harmonic amplitude and frequency data six basic data simplifications and five combinations of them were applied to the reference tones amplitude variation smoothing coherent variation of amplitudes over time spectral envelope smoothing forced harmonic frequency variation frequency variation smoothing and harmonic frequency flattening listeners were asked to discriminate sounds resynthesized with simplified data from reference sounds resynthesized with the full data averaged over the seven instruments the discrimination was very good for spectral envelope smoothing and amplitude envelope coherence but was moderate to poor in decreasing order for forced harmonic frequency variation frequency variation smoothing frequency flattening and amplitude variation smoothing discrimination of combinations of simplifications was equivalent to that of the most potent constituent simplification objective measurements were made on the spectral data for harmonic amplitude harmonic frequency and spectral centroid changes resulting from simplifications these measures were found to correlate well with discrimination results indicating that listeners have access to a relatively fine grained sensory representation of musical instrument sounds

cramer damgard signatures revisited efficient flat tree signatures based on factoring at crypto 96 cramer and damgard proposed an efficient tree based signature scheme that is provably secure against adaptive chosen message attacks under the assumption that inverting rsa is computationally infeasible in this paper we show how to modify their basic construction in order to achieve a scheme that is provably secure under the assumption that factoring large composites of a certain form is hard our scheme is as efficient as the original cramer damgard solution while relying on a seemingly weaker intractability assumption

fixed point theorems for weakly contractive mappings in partially ordered sets abstract the purpose of this paper is to present some fixed point theorems for weakly contractive maps in a complete metric space endowed with a partial order

a note on cone metric fixed point theory and its equivalence abstract the main aim of this paper is to investigate the equivalence of vectorial versions of fixed point theorems in generalized cone metric spaces and scalar versions of fixed point theorems in general metric spaces in usual sense we show that the banach contraction principles in general metric spaces and in t v s cone metric spaces are equivalent our theorems also extend some results in huang and zhang 2007 l g huang x zhang cone metric spaces and fixed point theorems of contractive mappings j math anal appl 332 2007 1468 1476 rezapour and hamlbarani 2008 sh rezapour r hamlbarani some notes on the paper cone metric spaces and fixed point theorems of contractive mappings j math anal appl 345 2008 719 724 and others

optimal error correction for computationally bounded noise for adversarial but computationally bounded models of error we construct appealingly simple and efficient cryptographic encoding and unique decoding schemes whose error correction capability is much greater than classically possible in particular 1 for binary alphabets we construct positive rate coding schemes that are uniquely decodable under a 1 2 error rate for any constant 0 2 for large alphabets we construct coding schemes that are uniquely decodable under a 1 r error rate for any information rate r 0 our results for large alphabets are actually optimal since the computationally bounded but adversarial channel can simulate the behavior of the q ary symmetric channel where q denotes the size of the alphabet the capacity of which is known to be upper bounded by 1 r our results hold under minimal assumptions on the communication infrastructure namely 1 we allow the channel to be more powerful than the receiver and 2 we only assume that some information about the sender a public key is known in particular we do not require any shared secret key or joint local state between sender and receivers

characterizing the clarinet tone measurements of lyapunov exponents correlation dimension and unsteadiness the clarinet tone is produced by a self sustained oscillation involving nonlinearity between the flow through the reed and the mechanical response of the reed and acoustic coupling via the air column response regimes of oscillation include periodic biperiodic and other quasi periodic signals yet even a nominally periodic tone has small but perceptually and musically important deviations that are obscured in a conventional power spectrum such deviations may be due to the nonlinear dynamics underlying sound production or to perturbations in the performer s control of the instrument via changes in lip embouchure blowing pressure and vocal tract configuration techniques based upon experimental nonlinear dynamics and short time signal processing are applied to the acoustic signal measured within the clarinet mouthpiece to assess the role of these additional deviations on sound production these include the lyapunov exponent correlation dimension and a normalized period synchronous energy variance

how to generate cryptographically strong sequences of pseudo random bits we give a set of conditions that allow one to generate 50 50 unpredictable bits based on those conditions we present a general algorithmic scheme for constructing polynomial time deterministic algorithms that stretch a short secret random input into a long sequence of unpredictable pseudo random bits we give an implementation of our scheme and exhibit a pseudo random bit generator for which any efficient strategy for predicting the next output bit with better than 50 50 chance is easily transformable to an equally efficient algorithm for solving the discrete logarithm problem in particular if the discrete logarithm problem cannot be solved in probabilistic polynomial time no probabilistic polynomial time algorithm can guess the next output bit better than by flipping a coin if head guess 0 if tail guess 1

fail stop signatures fail stop signatures can briefly be characterized as digital signatures that allow the signer to prove that a given forged signature is indeed a forgery after such a proof has been published the system can be stopped this type of security is strictly stronger than that achievable with ordinary digital signatures as introduced by diffie and hellman in 1976 and formally defined by goldwasser micali and rivest in 1988 which was widely regarded as the strongest possible definition this paper formally defines fail stop signatures and shows their relation to ordinary digital signatures a general construction and actual schemes derived from it follow they are efficient enough to be used in practice next we prove lower bounds on the efficiency of any fail stop signature scheme in particular we show that the number of secret random bits needed by the signer the only parameter where the complexity of all our constructions deviates from ordinary digital signatures by more than a small constant factor cannot be reduced significantly

approximation of fixed points of weakly contractive nonself maps in banach spaces abstract let k be a closed convex subset of a real uniformly smooth banach space e suppose k is a nonexpansive retract of e with p as the nonexpansive retraction let t k e be a d weakly contractive map such that a fixed point x int k of t exists it is proved that a descent like approximation sequence converges strongly to x furthermore if k is a nonempty closed convex subset of an arbitrary real banach space and t k k is a uniformly continuous d weakly contractive map with f t x k tx x it is proved that a descent like approximation sequence converges strongly to x f t

how to sign given any trapdoor permutation a digital signature scheme is presented which is based on the existence of any trapdoor permutation the scheme is secure in the strongest possible natural sense namely it is secure against existential forgery under adaptive chosen message attack

the point of coincidence and common fixed point for a pair of mappings in cone metric spaces in this paper the existence of a point of coincidence and a common fixed point for two weakly compatible maps on a cone metric space has been established the two mappings are assumed to satisfy certain weak inequalities supporting examples are also given