reversible watermark using the difference expansion of a generalized integer transform a reversible watermarking algorithm with very high data hiding capacity has been developed for color images the algorithm allows the watermarking process to be reversed which restores the exact original image the algorithm hides several bits in the difference expansion of vectors of adjacent pixels the required general reversible integer transform and the necessary conditions to avoid underflow and overflow are derived for any vector of arbitrary length also the potential payload size that can be embedded into a host image is discussed and a feedback system for controlling this size is developed in addition to maximize the amount of data that can be hidden into an image the embedding algorithm can be applied recursively across the color components simulation results using spatial triplets spatial quads cross color triplets and cross color quads are presented and compared with the existing reversible watermarking algorithms these results indicate that the spatial quad based algorithm allows for hiding the largest payload at the highest signal to noise ratio

low distortion transform for reversible watermarking this paper proposes a low distortion transform for prediction error expansion reversible watermarking the transform is derived by taking a simple linear predictor and by embedding the expanded prediction error not only into the current pixel but also into its prediction context the embedding ensures the minimization of the square error introduced by the watermarking the proposed transform introduces less distortion than the classical prediction error expansion for complex predictors such as the median edge detector or the gradient adjusted predictor reversible watermarking algorithms based on the proposed transform are analyzed experimental results are provided

pseudo hermiticity and generalized pt and cpt symmetries we study certain linear and antilinear symmetry generators and involution operators associated with pseudo hermitian hamiltonians and show that the theory of pseudo hermitian operators provides a simple explanation for the recent results of bender brody and jones quant ph 0208076 on the cpt symmetry of a class of pt symmetric non hermitian hamiltonians we present a natural extension of these results to the class of diagonalizable pseudo hermitian hamiltonians h with a discrete spectrum in particular we introduce generalized parity p time reversal t and charge conjugation c operators and establish the pt and cpt invariance of h

adaptive lossless steganographic scheme with centralized difference expansion in this paper a novel adaptive lossless data hiding scheme is presented that is capable of offering greater embedding capacity than the existing schemes unlike the fixed hiding capacity each block provides in most of the currently available lossless data hiding approaches the proposed method utilizes a block based lossless data embedding algorithm where the quantity of the hidden information each block bears is variable to both reduce the image distortion and increase the hiding capacity the payload of each block depends on its cover image complexity due to the fact that schemes with difference expansion tend to damage the image quality seriously in the edge areas in the proposed scheme smoother areas are chosen to conceal more secret bits this way a better balance can be reached between the embedding ratio and the stego image quality in addition when recovered the cover image can came back to its old self to the last bit without any distortion at all experimental results as this paper will show have demonstrated that the proposed method is capable of hiding more secret data while maintaining imperceptible stego image quality degradation

recursive histogram modification establishing equivalency between reversible data hiding and lossless data compression state of the art schemes for reversible data hiding rdh usually consist of two steps first construct a host sequence with a sharp histogram via prediction errors and then embed messages by modifying the histogram with methods such as difference expansion and histogram shift in this paper we focus on the second stage and propose a histogram modification method for rdh which embeds the message by recursively utilizing the decompression and compression processes of an entropy coder we prove that for independent identically distributed i i d gray scale host signals the proposed method asymptotically approaches the rate distortion bound of rdh as long as perfect compression can be realized i e the entropy coder can approach entropy therefore this method establishes the equivalency between reversible data hiding and lossless data compression experiments show that this coding method can be used to improve the performance of previous rdh schemes and the improvements are more significant for larger images

multilevel reversible data hiding based on histogram modification of difference images reversible data hiding has drawn considerable attention in recent years reversibility allows original media to be completely recovered from marked media without distortion after embedded message has been extracted in this paper we propose a multilevel reversible data hiding scheme based on the difference image histogram modification that uses the peak point to hide messages through a joint imperceptibility and hiding capacity evaluation we show that our proposed scheme uses a multilevel hiding strategy to achieve large hiding capacity and keep distortion low performance comparisons with other existing reversible hiding schemes are provided to demonstrate the validity of our proposed scheme

statistical model of nearly complete elastic rough surface contact abstract in the area of homogeneous isotropic linear elastic rough surface normal contact many classic statistical models have been developed which are only valid in the early contact when real area of contact is infinitesimally small e g the greenwood williamson gw model in this article newly developed statistical models built under the framework of the i gw ii nayak bush and iii greenwood s simplified elliptic models extend the range of application of the classic statistical models to the case of nearly complete contact nearly complete contact is the stage when the ratio of the real area of contact to the nominal contact area approaches unity at nearly complete contact the non contact area consists of a finite number of the non contact regions over a finite nominal contact area each non contact region is treated as a mode i crack the area of each non contact region and the corresponding trapped volume within each non contact region are determined by the analytical solutions in the linear elastic fracture mechanics respectively for a certain average contact pressure not only can the real area of contact be determined by the newly developed statistical models but also the average interfacial gap rough surface is restricted to the geometrically isotropic surface i e the corresponding statistical parameters are independent of the direction of measurement relations between the average contact pressure non contact area and average interfacial gap for different combinations of statistical parameters are compared between newly developed statistical models the relations between non contact area and average contact pressure predicted by the current models are also compared with that by persson s theory of contact the analogies between the classic statistical models and the newly developed models are also explored

similarity and fractality in the modelling of roughness by a multilevel profile with hierarchical structure some modern scaling and fractal approaches to the characterization of surface roughness are under consideration a new mathematical model of a multilevel profile suitable for flexible simulation of roughness is presented as a development from these approaches the iterative construction of the model is described it is shown that the profile is a hierarchical structure with self affine and fractal features its geometrical properties are studied both analytically and numerically and some of them are proved to be of the renormalization type the profile contour length can be finite or infinite depending on the chosen values of the structural parameters some characteristics including the bearing curve and the upper volume function of the profile and the corresponding prestructures are calculated

reversible data embedding into images using wavelet techniques and sorting the proliferation of digital information in our society has enticed a lot of research into data embedding techniques that add information to digital content like images audio and video in this paper we investigate high capacity lossless data embedding methods that allow one to embed large amounts of data into digital images or video in such a way that the original image can be reconstructed from the watermarked image we present two new techniques one based on least significant bit prediction and sweldens lifting scheme and another that is an improvement of tian s technique of difference expansion the new techniques are then compared with various existing embedding methods by looking at capacity distortion behavior and capacity control

adhesive contact of the weierstrass profile the weierstrass series was considered in ciavarella et al ciavarella et al 2000 proc r soc lond a 456 387405 doi 10 1098 rspa 2000 0522 to describe a linear contact problem between a ri

generalized pt symmetry and real spectra the fact that eigenvalues of pt symmetric hamiltonians h can be real for some values of ap arameter and complex for others is explained by showing that the matrix elements ofh a ndhence the secular equation are real not only for pt but also for an ya ntiunitary operator a satisfying a 2k 1w ith k odd the argument is illustrated by a 2 2m atrix hamiltonian and two examples of the generalization are given

pt symmetric quantum mechanics this paper proposes to broaden the canonical formulation of quantum mechanics ordinarily one imposes the condition h h on the hamiltonian where represents the mathematical operation of complex conjugation and matrix transposition this conventional hermiticity condition is sufficient to ensure that the hamiltonian h has a real spectrum however replacing this mathematical condition by the weaker and more physical requirement h h where represents combined parity reflection and time reversal pt one obtains new classes of complex hamiltonians whose spectra are still real and positive this generalization of hermiticity is investigated using a complex deformation h p2 x2 ix e of the harmonic oscillator hamiltonian where e is a real parameter the system exhibits two phases when e 0 the energy spectrum of h is real and positive as a consequence of pt symmetry however when 1 e 0 the spectrum contains an infinite number of complex eigenvalues and a finite number of real positive eigenvalues b

general framework to histogram shifting based reversible data hiding histogram shifting hs is a useful technique of reversible data hiding rdh with hs based rdh high capacity and low distortion can be achieved efficiently in this paper we revisit the hs technique and present a general framework to construct hs based rdh by the proposed framework one can get a rdh algorithm by simply designing the so called shifting and embedding functions moreover by taking specific shifting and embedding functions we show that several rdh algorithms reported in the literature are special cases of this general construction in addition two novel and efficient rdh algorithms are also introduced to further demonstrate the universality and applicability of our framework it is expected that more efficient rdh algorithms can be devised according to the proposed framework by carefully designing the shifting and embedding functions

conductance of rough random profiles abstract recently the real contact area and the compliance and electrical resistance for a rough surface defined with a weierstrass series have been studied under the assumption that superposed self affine sine waves had well separated wavelengths extending the celebrated procedures pioneered by archard archard j f 1957 elastic deformation and the laws of friction proc r soc lond a 243 190 205 here more realistic fractal rough surface profiles are considered by using the weierstrass series with random phases and with much lower separation of the various scales using a full or a hybrid numerical analytical technique a non linear layer algorithm is developed which is a very efficient approximate tool to study this problem avoiding the need for averaging over various realizations of profiles with random phases the multiscale problem is solved by a cascade of 2 scales problems each of which is solved with a few elements for an imposed contact area deriving load as a function of indentation and the conductance by differentiation using barber s analogy theorem dimensionless results for the conductance as a function of applied pressures show that the conductance seems to be close to a power law at low loads and is nearly linear at intermediate loads following the normalized single sinusoidal case except at the origin at high loads the conductance becomes strongly dependent on fractal dimension because of weak dependence on the contribution of small wavelength scales higher order terms in the series since roughness tends to be squeezed out the conductance tends to increase more than linearly more so the smaller is the fractal dimension however another limit could be found in terms of the finite size of the specimen which may suggest reaching a finite limit the resulting curves could then be sigmoidal as confirmed by qualitative comparisons with experiments in the literature

non self adjoint hamiltonians with complex eigenvalues motivated by what one observes dealing with pt symmetric quantum mechanics we discuss what happens if a physical system is driven by a diagonalizable hamiltonian with not all real eigenvalues in particular we consider the functional structure related to systems living in finite dimensional hilbert spaces and we show that certain intertwining relations can be deduced also in this case if we introduce suitable antilinear operators we also analyze a simple model computing the transition probabilities in the broken and in the unbroken regime

optimal transition probability of reversible data hiding for general distortion metrics and its applications recently a recursive code construction rcc approaching the rate distortion bound of reversible data hiding rdh was proposed however to estimate the rate distortion bound or execute rcc one should first estimate the optimal transition probability matrix otpm by previous methods otpm can be effectively estimated only for some specific distortion metrics such as square error distortion or l 1 norm in this paper we proposed a unified framework of estimating the otpm for general distortion metrics with which we can calculate the rate distortion bound of rdh for general cases and extend rcc to improve state of the art rdh schemes based on any distortion metrics

linear elastic contact of the weierstrass profile a contact problem is considered in which an elastic half plane is pressed against a rigid fractally rough surface whose profile is defined by a weierstrass series it is shown that no applied mean pressure is sufficiently large to ensure full contact and indeed there are not even any contact areas of finite dimension the contact area consists of a set of fractal character for all values of the geometric and loading parameters a solution for the partial contact of a sinusoidal surface is used to develop a relation between the contact pressure distribution at scale n 1 and that at scale n recursive numerical integration of this relation yields the contact area as a function of scale an analytical solution to the same problem appropriate at large n is constructed following a technique due to archard this is found to give a very good approximation to the numerical results even at small n except for cases where the dimensionless applied load is large the contact area is found to decrease continuously with n tending to a power law behaviour at large n which corresponds to a limiting fractal dimension of 2 d where d is the fractal dimension of the surface profile however it is not a simple fractal in the sense that it deviates from the power law form at low n at which there is also a dependence on the applied load contact segment lengths become smaller at small scales but an appropriately normalized size distribution tends to a limiting function at large n the authors dedicate this paper to the memory of dr j f archard 1918 1989

distortion reduction for histogram modification based reversible data hiding abstract the histogram modification hm method proposed by ni et al is very efficient for reversible data hiding rdh besides the excellent execution time performance ni et al s hm based rdh hmrdh method has a high psnr lower bound of marked images in this short communication an observation on ni et al s hm based rdh hmrdh method is pointed out that the distortion of the marked image from ni et al s method is dependent on the number of 1 s in the watermark from this observation we first present a watermark complement scheme to reduce the distortion occurred in ni et al s hmrdh method later combinatorial analysis for average distortion ratio of the proposed scheme is provided this analysis motivates us to present a block based complement scheme to improve the distortion reduction further the tradeoff between the distortion and the number of partitioned blocks is also investigated taking nine well known trademarks as the test watermarks and two cover images with different types of content experimental results demonstrated the distortion reduction and higher psnr lower bound advantages of the proposed block based watermark complement scheme

reversible data hiding based on an adaptive pixel embedding strategy and two layer embedding recently peng et al proposed a reversible data hiding rdh method based on pixel value ordering pvo and prediction error expansion in their method the maximum and minimum of a pixel block are predicted and modified to embed data and reversibility is guaranteed by keeping the pvo of each block invariant after embedding in this paper a novel rdh method is proposed by incorporating an adaptive pixel modification strategy into peng et al s work in our method the smoother a block the more data it can carry unlike peng et al s method which embeds data uniformly ours can embed data e g 2 4 or 6 bits adaptively into a block according to the local complexity specifically the local complexity is classified into four levels according to the strength of the correlation between each block and its neighborhood then the number of pixels to be modified is determined by the complexity level such that more bits are embedded into a block located in a smoother region moreover two embedding layers are utilized together to further decrease the embedding distortion extensive experiments verify that the proposed method outperforms penget al s ou et al s li et al s sachnev et al s and hong et al s works

temporal and spatial correlation based reversible data hiding for rgb cfa videos abstract considering a mosaic video in which each mosaic image could be captured by any of the existing eleven rgb color filter array cfa structures and each mosaic pixel contains only one primary color this paper proposes a novel spatial and temporal correlation based reversible data hiding rdh method in the proposed rdh method an intellectual switching strategy to select the spatial correlation based or the temporal prediction scheme to maximize the quality improvement of the marked mosaic videos under fixed embedding capacity based on eight test mosaic videos the experimental results demonstrate that in terms of peak signal to noise ratio psnr color psnr cpsnr structure similarity ssim index motion based video integrity evaluation movie index and human perceptual effect the proposed rdh method clearly outperforms the spatial correlation based rdh method by yang et al and the other four state of the art rdh methods

a novel reversible image data hiding scheme based on pixel value ordering and dynamic pixel block partition recently various efficient reversible data hiding schemes based on pixel value ordering have been proposed for embedding messages into high fidelity images in these schemes after dividing the cover image into equal sized blocks the pixels within a given block are ordered according to their values and data embedding is achieved by modifying the maximum and minimum values of each block for a given embedding capacity the optimal block size is exhaustively searched so that the embedding distortion is minimized these pixel value ordering based schemes perform fairly well especially for low embedding capacity however to obtain a larger embedding capacity a smaller block size should be used which usually leads to a dramatic quality degradation of the marked image in this paper to address this drawback and to enhance the performance of pixel value ordering based embedding further a novel reversible data hiding method is proposed instead of using equal sized blocks a dynamic blocking strategy is used to divide the cover image adaptively into various sized blocks specifically flat image areas are preferentially divided into smaller blocks to retain high embedding capacity whereas rough areas are divided into larger blocks to avoid decreasing peak signal to noise ratio as a result the proposed scheme can provide a larger embedding capacity than current pixel value ordering based schemes while keeping distortion low the superiority of the proposed method is also experimentally verified

incipient sliding of rough surfaces in contact a multiscale numerical analysis in this paper the cattaneo theory of frictional contact is extended to elastic half spaces in contact through rough disordered interfaces the discrete version of the cattaneo theorem is provided and represents the basis of a multiscale numerical contact algorithm mathematical surfaces with imposed roughness as well as experimentally digitised ones are analysed by means of a numerical method the evolution of the contact domain at different resolution is investigated roughness of the interfaces provides lacunarity of the contact domains whose fractal dimension is always smaller than 2 0 when a tangential force is applied the extent of the stick area decreases in the same way as the contact area develops with increasing pressure and the slip area is found to be proportional to the tangential force as predicted by cattaneo theory the evolution of the shear centroid as well as the amount of dissipated energy up to full sliding are provided finally it is shown that at a sufficient level of discretization the distribution of contact pressures is multifractal

expansion embedding techniques for reversible watermarking reversible watermarking enables the embedding of useful information in a host signal without any loss of host information tian s difference expansion technique is a high capacity reversible method for data embedding however the method suffers from undesirable distortion at low embedding capacities and lack of capacity control due to the need for embedding a location map we propose a histogram shifting technique as an alternative to embedding the location map the proposed technique improves the distortion performance at low embedding capacities and mitigates the capacity control problem we also propose a reversible data embedding technique called prediction error expansion this new technique better exploits the correlation inherent in the neighborhood of a pixel than the difference expansion scheme prediction error expansion and histogram shifting combine to form an effective method for data embedding the experimental results for many standard test images show that prediction error expansion doubles the maximum embedding capacity when compared to difference expansion there is also a significant improvement in the quality of the watermarked image especially at moderate embedding capacities

high capacity multiple regions of interest watermarking for medical images the new scheme allows multiple rois of a medical image to be selected and kept lossless while regions of non interest roni are collated for embedding watermarks the proposed technique has achieved high capacity watermarking and high psnr peak signal to noise ratio for the embedding loop times t from 1 to 5 psnr is improved from 12 6 to 27 7 and bpp is improved from 63 to 600 watermarking techniques have been widely used for copyright protection broadcast monitoring and data authentication in medical images to protect patient s private information against tampering by unauthorized persons a region of interest roi in a medical image contains valuable diagnostic information and thus must be preserved to avoid medical misdiagnosis current state of the art medical image watermarking techniques only allow single roi data preservation aiming for high embedding capacity and high image fidelity we present a novel medical image watermarking scheme which allows multiple rois to be selected and kept lossless whereas regions of non interest ronis are collated for watermark embedding the watermark is compressed and the embedding is conducted in frequency domain to avoid piracy experimental results show that the proposed technique has significantly achieved high capacity and high psnr peak signal to noise ratio as compared against eight existing similar techniques in addition our technique allows flexible adjustment on a variable that controls the tradeoff between image fidelity and embedding capacity

efficient reversible data hiding for color filter array images a reversible data hiding algorithm which uses prediction errors in the color difference domain for mosaic images with the bayer color filter array cfa is proposed furthermore the proposed algorithm can be extended to deal with the digital time delay and integration dtdi mosaic images and lukac and plataniotis lp mosaic images experimental results on cfa dtdi and lp mosaic images demonstrate that the proposed algorithm can achieve high embedding capacity while maintaining good image quality

calculation of the hidden symmetry operator in symmetric quantum mechanics in a recent paper it was shown that if a hamiltonian h has an unbroken symmetry then it also possesses a hidden symmetry represented by the linear operator the operator commutes with both h and the inner product with respect to is associated with a positive norm and the quantum theory built on the associated hilbert space is unitary in this paper it is shown how to construct the operator for the non hermitian symmetric hamiltonian h 1 2p2 1 2x2 ix3 using perturbative techniques it is also shown how to construct the operator for h 1 2p2 1 2x2 x4 using nonperturbative methods

an alternative construction of the positive inner product for pseudo hermitian hamiltonians examples in this paper we build on our earlier proposal for the construction of a positive inner product for pseudo hermitian hamiltonians and present examples to clarify the procedure we focus on two detailed calculations where the method is used namely a simple generalized 2 2 matrix pseudo hermitian hamiltonian which can be diagonalized and a second system where the hamiltonian cannot be diagonalized but can be described as a perturbation of the harmonic oscillator when the quantum mechanical system cannot be diagonalized exactly our construction can be carried out perturbatively and we develop the general formalism for such a perturbative calculation systematically for real eigenvalues in this paper we build on our earlier proposal for the construction of a positive inner product for pseudo hermitian hamiltonians and present examples to clarify the procedure we focus on two detailed calculations where the method is used namely a simple generalized 2 2 matrix pseudo hermitian hamiltonian which can be diagonalized and a second system where the hamiltonian cannot be diagonalized but can be described as a perturbation of the harmonic oscillator when the quantum mechanical system cannot be diagonalized exactly our construction can be carried out perturbatively and we develop the general formalism for such a perturbative calculation systematically for real eigenvalues

a unified theory of surface roughness the properties of the peaks and summits of a rough surface are predicted on the assumption that the surface is two dimensional random noise the important result is that in non dimensional form the answers depend only to a minor degree on the parameters describing the surface or on the sampling interval used on the other hand the absolute values are strongly dependent on the sampling interval experimental results on a real surface agree remarkably well with the predictions