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This paper applies learning control to repetitive systems over fading channels at both output and input sides to improve tracking performance without applying restrictive fading conditions. Both multiplicative and additive randomness of the fading channel are addressed, and the effects of fading communication on the data are carefully analyzed. A decreasing gain sequence and a moving-average operator are introduced to modify the generic learning control algorithm to reduce the fading effect and improve control system performance. Results reveal that the tracking error converges to zero in the mean-square sense as the iteration number increases. Illustrative simulations are presented to verify the theoretical results. [ABSTRACT FROM AUTHOR]

Chaotic dynamics is widely used to design pseudo-random number generators and for other applications, such as secure communications and encryption. This paper aims to study the dynamics of the discrete-time chaotic maps in the digital (i.e., finite-precision) domain. Differing from the traditional approaches treating a digital chaotic map as a black box with different explanations according to the test results of the output, the dynamical properties of such chaotic maps are first explored with a fixed-point arithmetic, using the Logistic map and the Tent map as two representative examples, from a new perspective with the corresponding state-mapping networks (SMNs). In an SMN, every possible value in the digital domain is considered as a node and the mapping relationship between any pair of nodes is a directed edge. The scale-free properties of the Logistic map’s SMN are proved. The analytic results are further extended to the scenario of floating-point arithmetic and for other chaotic maps. Understanding the network structure of a chaotic map’s SMN in digital computers can facilitate counteracting the undesirable degeneration of chaotic dynamics in finite-precision domains, also helping to classify and improve the randomness of pseudo-random number sequences generated by iterating the chaotic maps. [ABSTRACT FROM AUTHOR]

A pair of coupled nonlinear evolution equations for the spectral functions are derived in a situation of crossing sea states characterized by two narrowband Gaussian random surface wave systems in the presence of uniform wind flow. These two equations are employed to perform stability analysis of two initially homogeneous wave spectra subject to infinitesimal perturbations. It is found that the results of the stability analysis remain qualitatively similar with the corresponding deterministic situation. The notable difference is that the growth rate of instability reduces slightly due to the effect of randomness. But, it is much higher than the growth rate of a single wave system. As the spectral bandwidth increases the growth rate of instability decreases. • Spectral transport equations are derived for a pair of random surface wavetrains. • In the model the presence of uniform wind flow is taken into account. • Stability analysis is performed for a pair of Gaussian wave spectra. • The effect of randomness is to reduce the growth rate of instability slightly. • Growth rate of instability is much higher than for a single wavetrain. [ABSTRACT FROM AUTHOR]

Abstract A smart contract enforces specific performance on anonymous users without centralization. It facilitates payment equity in commerce by providing irreversible transactions. Smart contracts are also used for illegal activities such as money laundering and ransomware. Such contracts include criminal smart contracts (CSCs), proposed in CCS'16, that can be efficiently implemented in existing scripting languages. This aggravates concerns about the dangers of CSCs. However, PublicLeaks , a CSC for leaking private data, is conditionally implemented as it is influenced by various factors. For example, PublicLeaks does not necessarily reach a desirable terminal state for a criminal leaking private information, and other possible terminal states may invalidate the CSC. In this study, we propose a CSC based on PublicLeaks by formulating random factors such as the donation ratio. Our contract forks into five terminal states, including a unique one in PublicLeaks due to randomness. We simulated the maximal probabilities of these terminal states and found that the desirable terminal state in PublicLeaks is reachable with low probabilities (lower than 25%). The terminal state where the criminal fails to leak private information is attained with relatively high probabilities (over 65%). Therefore, our simulations show that CSCs are not always as powerful as expected, and the risk posed by them can be mitigated. [ABSTRACT FROM AUTHOR]

This paper introduces a new concept of a true random number generator (TRNG) based on two stages of randomness. The first stage is based on a novel chaotic circuit, which utilizes time as a continuous random variable in a feedback loop. The second stage is based on metastability; however, in contrast to known digital solutions, a flip-flop is stimulated by chaotic initial conditions. The advantage of chaotic behavior is the circuit’s immunity to active injection side-channel attacks (e.g., a frequency attack). The circuit design parameters can also vary in a wide range, which makes the TRNG insensitive to process, voltage and temperature (PVT) conditions and tolerance. Moreover, the design is extremely simplified, and therefore, feasible to implement in simple and inexpensive reprogrammable devices (no digital clock manager, programmable delay line, or phase locked loop are required). The TRNG ensures a constant (synchronous) 1-Mb/s bit rate output without additional post-processing. The randomness tests prove a high quality of an output bit stream, which is relatively high when compared with other solutions based on similar hardware resources. [ABSTRACT FROM AUTHOR]

A high performance and high quality pseudorandom number generator is presented in this paper. It takes less than one clock cycle to generate a pseudorandom byte on an Intel core i3 processor and passes all the 6 TestU01 batteries of tests. The generator can work in either deterministic mode or non-deterministic mode. When working in deterministic mode, it can be used for high speed data encryption and in other applications that require deterministic and reproducible pseudorandom sequences. When working in non-deterministic mode, the generator behaves much like a true random number generator, but with the advantages of low cost, high performance, and general availability. It is good for many applications that currently rely on true random number generators [ABSTRACT FROM AUTHOR]

Cryptanalysis analyses various combinations among plaintexts, ciphertexts and random keys; even using differential methods or analog methods, the attackers can interpret the keys depending upon the operations in the round functions or any subset of the algorithm. The previous research emphasizes on creation of different cryptographic functions, however the randomness of such functions has not been researched significantly so far. In this paper, we have shown a random function generator which can be used for any cryptographic algorithm. This generator outputs the combination of functions in random and cannot be traced back due its randomness. The objective of our research work is not to identify a particular boolean function that is balanced or symmetric based on its input variables, our proposed work provides a random combination of generic boolean functions as used in MD5 or SHA series, block cipher round functions and stream ciphers. Moreover, the random selection of input variables for a particular function also makes it desirable for cryptographic function modules. The results of our experimentation show that the functions generated by the proposed generator provide a good non-linearity, resiliency and balanced effect. [ABSTRACT FROM AUTHOR]

We study acoustic-gravity waves in a quasi-isothermal atmosphere in the presence of a weak random addition to the vertical temperature profile, which simulates the real atmosphere of the Earth at altitudes greater than ∼ 200 km. The resulting stochastic equation is closed in the Bourret approximation. The poles of the obtained mean Green's function determine the generalized dispersion relation for acoustic-gravity waves. Two particular cases are considered: random inhomogeneities in the form of white noise (δ -correlated in space) and the opposite case of a δ -shaped noise spectrum. In both cases, instability of acoustic-gravity waves is predicted and the corresponding instability growth rates are determined. [ABSTRACT FROM AUTHOR]

We present a Python package for the efficient generation of special quasi-random structures (SQS) for atomic-scale calculations of disordered systems. Both, a Monte-Carlo approach or a systematic enumeration of structures can be used to carry out optimizations to ensure the best optimal configuration is found for given cell size and composition. We present a measure of randomness based on Warren-Cowley short-range order parameters allowing for fast analysis of atomic structures. Hence, optimal structures are found in a reasonable time for several dozens or even hundreds of atoms. Both SQS optimizations and analysis of structures can be carried out via a command-line interface or a Python API. Additional features, such as optimization towards partial ordering or independent sublattices allow the generation of atomistic models of modern complex materials. Moreover, hybrid parallelization, as well as distribution of vacancies, are supported. The output data format is compatible with ase, pymatgen and pyiron packages to be easily embeddable in complex simulation workflows. Program title: sqsgenerator CPC Library link to program files: https://doi.org/10.17632/m2sb3wzcvc.1 Developer's repository link: https://github.com/dgehringer/sqsgenerator Licensing provisions: MIT Programming language: Python, C++ Supplementary material: https://sqsgenerator.readthedocs.io Nature of problem: Many technological relevant materials, exhibit a crystalline disorder. Within atomistic modelling approaches such as Density Functional Theory (DFT) or Molecular Dynamics, disorder is modelled with a cell containing a (small) finite set of atoms. Such an atomic configuration is usually found by enumerating structures. However, since configurational space is growing exponentially efficient tools are needed to sample it properly. Solution method: Efficient quantification of disorder using a generalization of Warren-Cowley Short Range Order (WC-SRO) parameters [1,2]. By either a Monte-Carlo approach or systematic enumeration, optimal structures can be found. The software is distributed as a Python package offering a command line interface. Core parts are written in C++ and exhibit shared (OpenMP) and distributed (MPI) memory parallelism. For embedding into complex simulation workflows, the tool exposes a Python API to integrate into popular packages such as ase [3], pymatgen [4] or pyiron [5]. [1] J.M. Cowley, An approximate theory of order in alloys, Phys. Rev. 77 (5) (1950) 669–675. URL https://doi.org/10.1103/physrev.77.669. [2] J.M. Cowley, Short-range order and long-range order parameters, Phys. Rev. 138 (5A) (1965) A1384–A1389. URL https://doi.org/10.1103/physrev.138.a1384. [3] A.H. Larsen, J.J. Mortensen, J. Blomqvist, I.E. Castelli, R. Christensen, M. Dułak, J. Friis, M.N. Groves, B. Hammer, C. Hargus, E.D. Hermes, P.C. Jennings, P.B. Jensen, J. Kermode, J.R. Kitchin, E.L. Kolsbjerg, J. Kubal, K. Kaasbjerg, S. Lysgaard, J.B. Maronsson, T. Maxson, T. Olsen, L. Pastewka, A. Peterson, C. Rostgaard, J. Schiøtz, O. Schütt, M. Strange, K.S. Thygesen, T. Vegge, L. Vilhelmsen, M. Walter, Z. Zeng, K.W. Jacobsen, The atomic simulation environment—a python library for working with atoms, Journal of Physics: Condensed Matter 29 (27) (2017) 273002. URL http://stacks.iop.org/0953-8984/29/i=27/a=273002. [4] S.P. Ong, W.D. Richards, A. Jain, G. Hautier, M. Kocher, S. Cholia, D. Gunter, V.L. Chevrier, K.A. Persson, G. Ceder, Python materials genomics (pymatgen): A robust, open-source python library for materials analysis, Computational Materials Science 68 (2013) 314–319. URL https://doi.org/10.1016/j.commatsci.2012.10.028. [5] J. Janssen, S. Surendralal, Y. Lysogorskiy, M. Todorova, T. Hickel, R. Drautz, J. Neugebauer, pyiron: An integrated development environment for computational materials science, Computational Materials Science 163 (2019) 24–36. URL https://doi.org/10.1016/j.commatsci.2018.07.043. • A Python package for efficient generation of special quasi-random structures (SQS) has been developed. • Optimal SQS structures are found in a reasonable time even for dozens of atoms. • Monte-Carlo approach or a systematic enumeration of structures can be used to carry out optimizations. • The output is compatible with ase, pymatgen and pyiron for embedding in complex simulation workflows. • YAML format is used as the default for both the input and output files. [ABSTRACT FROM AUTHOR]

The paper presents a concept of a True Random Number Generator (TRNG) that utilizes phase noise of a pair of ring oscillators (ROs) to increase the variance of the initial condition of a bistable. For this purpose a special TRNG D-latch architecture (TDL) has been proposed, which can either operate in the oscillatory ring-oscillator mode or the nearly-metastable mode. The RO mode increases the probability of the nearly metastable operation of the TDL, which in turn increases the mean value and variance of the resolve time. Moreover, due to the oscillatory nature of the TDL metastability, the resolve time can be easily measured and used for further randomness harvesting in the TRNG. The proposed TRNG uses a pair of TDLs to reduce sensitivity to process or temperature variation, whereas TDLs' individual resolve time, their resolve time difference and logical state contribute to randomness. In the article, the impact of the devices' imbalance (tolerance) resulting from process variation on the resultant entropy is also explored. The proposed TRNG based on TDLs is scalable and has been implemented in modern CPLD and FPGA devices whereas the bit rate reached up to 1 Mbit. The article also discusses theoretical issues related to a transformation of phase and resolve time probability density functions and their influence on TRNG parameters. [ABSTRACT FROM PUBLISHER]

The weak-form of the efficient market hypothesis (EMH) establishes that price returns behave as a pure random process and so their outcomes cannot be forecasted. The detrended fluctuation analysis (DFA) has been widely used to test the weak-form of the EMH by showing that time series of price returns are serially uncorrelated. In this case, the DFA scaling exponent exhibits deviations from the theoretical value of 0.5. This work considers the test of the EMH for DFA implementation on a sliding window, which is an approach that is intended to monitor the evolution of markets. Under these conditions, the scaling exponent exhibits important variations over the scrutinized period that can offer valuable insights in the behavior of the market provided the estimated scaling value is kept within strict statistical tests to verify the presence or not of serial correlations in the price returns. In this work, the statistical tests are based on comparing the estimated scaling exponent with the values obtained from pure Gaussian sequences with the length of the real time series. In this way, the presence of serial correlations can be guaranteed only in terms of the confidence bands of a pure Gaussian process. The crude oil (WTI) and the USA stock (DJIA) markets are used to illustrate the methodology. [ABSTRACT FROM AUTHOR]

Typical degradation-shock failure processes have been widely investigated in current researches, and the failures caused by their dependence are described as competitive failure processes. This paper explores competitive failure modes for uncertain random fractional systems involving degradation and shock processes. We develop a wear degradation model explicitly by employing uncertain fractional differential equations in order to demonstrate the potential heredity and memorability of a system. External shocks are then considered to follow a Poisson process. Based on the classification of shock types, three definitions of reliability index for competitive failures are presented. The reliability index formulas are derived for systems with extreme shock, cumulative shock, and δ shock using chance measures. Finally, we introduce a numerical example where the results of the reliability analysis confirm the validity of proposed reliability evaluation methods. • Present three types of reliability models in uncertain random environments • Describe the degradation process by uncertain fractional differential equations • Define the reliability index of competitive failure models by chance measure • Propose three specific reliability index formulas of the proposed models • Introduce a numerical example of jet pipe servo valves [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an analysis of the multiresolution form of singular value decomposition SVD (MR-SVD) and generalizes the analysis into a random multiresolution form of singular value decomposition (R-MR-SVD) with an intrinsic randomness. The core idea behind the proposed transform is to introduce randomness in the computing process based on parameters without which one can neither decompose nor reconstruct the data correctly. The proposed transform inherits the excellent properties of MR-SVD along with its own unique features, which can be useful in many research areas. Image encryption, lossy image compression, and face recognition are the primary applications used to illustrate the practical usage of the proposed transform. [Copyright &y& Elsevier]

In order to maximize randomness of CMOS Ring Oscillators (RO) used in Random Number Generators (RNG), possibility of weak inversion operation of CMOS transistors is investigated. To predict weak inversion noise performance of RO, phase noise and jitter models of a CMOS RO in weak inversion operating region are obtained. Differential Ring Oscillator (DRO) and Inverter-based Ring Oscillator (IbRO) cases are both investigated. For each case, the model covers the flicker and the white noise component of phase noise and jitter. The derived models are verified by measurement results. 0.25 \mum standard CMOS process has been used with a supply voltage of 0.7 V for DRO and 0.5 V for IbRO. Furthermore, phase noise and jitter behavior of a CMOS RO in strong and weak inversion region are compared through analytical models, simulations, and measurements. Even though white noise component of phase noise uses two different models for weak and strong inversion regions of operation, these two models exhibit continuity. Flicker noise component in weak inversion is much lower than the one in strong inversion, which also reduces the corner frequency. For a fair comparison of randomness performances, a randomness parameter is defined and randomness equations are derived for each case. [ABSTRACT FROM PUBLISHER]

The paper introduces a new concept of a true random number generator (TRNG). Most metastability-based solutions operate on the uncertainty of a logical output state of a device (flip-flop, D-latch) aimed to be resolved from an exact metastable point. However, it has been shown that the metastable point of a bistable circuit (which is practically impossible to reach) does not guarantee absolute randomness or sufficient entropy. We propose the concept of a device in which the direct proximity of the metastable point is not mandatory. In our concept the transition times of two devices are compared. Such construction is less sensitive to the proximity of the metastable point, temperature fluctuations, and power supply instabilities. The paper briefly describes the metastability phenomena in general and other known metastability-based TRNG concepts. A new concept of a dual-metastability time-competitive generator is presented, analyzed both numerically and theoretically, and verified based on the sample circuit's implementation. Empirical and statistical test results are presented. [ABSTRACT FROM AUTHOR]

Abstract: The fracture strength of metal foams depends sensitively on the properties of the constituent material as well as the cellular architecture. A change in microscopic properties carries over to the macroscopic scale through an alteration of the mesoscopic damage and fracture mechanisms. In this paper we study these dependencies using a modelling framework that takes all these ingredients into account. We have developed a micromechanical model based on a discrete Voronoi representation of cellular metals that incorporates power-law strain hardening and damage development of the cell wall material. The influence of the relative density and material strain hardening on the cell wall damage behavior and overall fracture response is analyzed in detail. The effect of the cellular architecture is studied by varying the cell shape anisotropy and structural randomness. We also simulate the effect of post-processing heat treatments on the solid material plastic and fracture properties and how this affects the overall fracture profile and damage development. Finally, all material and architectural effects are summarized in a strength versus ductility graph, identifying trends for improved design of metallic foams. [Copyright &y& Elsevier]

Abstract: Investigations of complexity of sequences lead to important applications such as effective data compression, testing of randomness, discriminating between information sources and many others. In this paper we establish formulae describing the distribution functions of random variables representing the complexity of finite sequences introduced by Lempel and Ziv in 1976. It is known that this quantity can be used as an estimator of entropy. We show that the distribution functions depend affinely on the probabilities of the so-called “exact” sequences. [Copyright &y& Elsevier]

Abstract: In this paper, we introduce a new type of field—continuous sets, where we can exploit randomness in the non-repeating decimal expansions of irrationals for cryptographical purposes, and present two specific sets, a real interval [0,1) and a functional space F [0,1). On [0,1), we propose ideal irrational random number generator (IIRNG) which generates non-repeating random number sequence as a truly RNG by computing the decimal expansion of an randomly chosen irrational. On F [0,1), we propose integral encryption scheme (IES) with which we can encrypt an infinite message and obtain perfect security in one-time encryption by computing the integration of the message on a randomly chosen function. Either the seeds of IIRNG or the keys of IES are sufficiently safe and immune to exhaustive key search. Both IIRNG and IES require the assumption that an element of [0,1) or F [0,1) can be uniformly randomly chosen. Though the assumption cannot be achieved in classical finite machine, we present the discretization of the assumption, i.e., randomly choosing an element of U or V (the set of all possible methods of generating irrationals or functions). The immunity of seeds or keys to exhaustive key search still exists, since any finite search for a random element of U or V is inefficient. This is the basic idea of implementing IIRNG and IES in finite machine. Two corresponding examples IRNG and IBC are also presented, whose securities are guaranteed by the randomly chosen elements of U or V. [Copyright &y& Elsevier]

Testing for the randomness of a time series has been one of the most widely researched topics in time-series analysis. The present paper carries out a comparative study of the finite-sample performance of some well-known portmanteau tests in this area. Using Monte Carlo simulation experiments, we find that (i) the empirical sizes of some oft-used parametric portmanteau tests are severely undersized when the data generating process is skewed, (ii) the non-parametric portmanteau test possesses proper sizes only when the number of rank autocorrelations is chosen to be small relative to the sample size, (iii) the non-parametric portmanteau test is more powerful than the parametric portmanteau tests in the case of skewed distributions, and (iv) the choice of the number of sample autocorrelations (or rank autocorrelations) can significantly affect the size as well as the power of the tests considered. [Copyright &y& Elsevier]

In this paper, a novel graph-based adequate and concise signal representation paradigm is explored. Amplitudes of a signal can be quantized first. Then the quantization levels and transitions among these levels can be specified as vertices and edges so that the signal waveform (spectrum) can be converted to a graph thereby. This new signal representation framework can provide a promising alternative for manifesting the essential structure of random signals in the graph domain. The randomness of signal samples can be characterized by the topological features of the converted graph. In this work, we explore the connectivity of a graph to measure such randomness. A typical application, namely sparse communication signal detection, can be undertaken by the graph-connectivity metric. New pertinent theoretical analyses are also conducted here. First, the analysis on the minimum sample size for constructing a fully-connected graph from random samples is established. Second, the probability analysis of constructing a fully-connected graph with respect to a particular sample size is also derived. Third, if a graph is not fully connected, the probability distribution function of the number of edges is derived. According to Monte Carlo simulations, our proposed graph-based signal-detection method leads to outstanding performance, compared to a popular existing signal-detection technique especially when the signal-to-noise ratio is rather small. [ABSTRACT FROM AUTHOR]

Waterjet peening (WP) is usually used to roughen metallic surfaces in order to improve cell adhesion on biomedical implants. Hence, surface roughness control using WP is of prime importance for such applications. A random finite element model of WP was developed, aimed at characterizing the surface coverage (the ratio of jet-affected area over total contact area) and surface roughness (in particular, the heights distribution). One perfectly flat and three rough metallic surfaces with different initial Sa (area arithmetic mean height) were generated, impacted and compared with each other. Numerical results show that a rougher initial surface necessitates more impingements than a smooth one to attain full surface coverage. The mechanisms influencing surface topography evolution, namely plastic deformation-induced roughening, peak clipping, valley deepening and valley filling are discussed. By modeling the roughness evolution resulting from WP, it appears that the process can be applied not only to roughen but also to polish rough initial surfaces in the investigated range. The present approach allows for systematic tuning of the system parameters in order to control the surface roughness. [ABSTRACT FROM AUTHOR]