47 research outputs found

    Frictional interactions between tidal constituents in tide-dominated estuaries

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    When different tidal constituents propagate along an estuary, they interact because of the presence of nonlinear terms in the hydrodynamic equations. In particular, due to the quadratic velocity in the friction term, the effective friction experienced by both the predominant and the minor tidal constituents is enhanced. We explore the underlying mechanism with a simple conceptual model by utilizing Chebyshev polynomials, enabling the effect of the velocities of the tidal constituents to be summed in the friction term and, hence, the linearized hydrodynamic equations to be solved analytically in a closed form. An analytical model is adopted for each single tidal constituent with a correction factor to adjust the linearized friction term, accounting for the mutual interactions between the different tidal constituents by means of an iterative procedure. The proposed method is applied to the Guadiana (southern Portugal-Spain border) and Guadalquivir (Spain) estuaries for different tidal constituents (M2, S2, N2, O1, K1) imposed independently at the estuary mouth. The analytical results appear to agree very well with the observed tidal amplitudes and phases of the different tidal constituents. The proposed method could be applicable to other alluvial estuaries with a small tidal amplitude-to-depth ratio and negligible river discharge.info:eu-repo/semantics/publishedVersio

    Seasonal behaviour of tidal damping and residual water level slope in the Yangtze River estuary: identifying the critical position and river discharge for maximum tidal damping

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    As a tide propagates into the estuary, river discharge affects tidal damping, primarily via a friction term, attenuating tidal motion by increasing the quadratic velocity in the numerator, while reducing the effective friction by increasing the water depth in the denominator. For the first time, we demonstrate a third effect of river discharge that may lead to the weakening of the channel convergence (i.e. landward reduction of channel width and/or depth). In this study, monthly averaged tidal water levels (2003ā€“2014) at six gauging stations along the Yangtze River estuary are used to understand the seasonal behaviour of tidal damping and residual water level slope. Observations show that there is a critical value of river discharge, beyond which the tidal damping is reduced with increasing river discharge. This phenomenon is clearly observed in the upstream part of the Yangtze River estuary (between the Maanshan and Wuhu reaches), which suggests an important cumulative effect of residual water level on tideā€“river dynamics. To understand the underlying mechanism, an analytical model has been used to quantify the seasonal behaviour of tideā€“river dynamics and the corresponding residual water level slope under various external forcing conditions. It is shown that a critical position along the estuary.info:eu-repo/semantics/publishedVersio

    Template Attacks Based on the Multivariate Joint Distribution

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    For template attacks, it is ideal if templates can be built for each (data,key) pair. However, it requires a lot of power traces and computation. In this paper, firstly, the properties of the UMJD(unisource multivariate joint distribution) are studied, and then a template attack based on the UMJD is presented. For power traces with much noise, the experiments show that its attack effect is much better than that of the CPA(correlation power analysis) based template attacks and that of the SOST(sum of square wise pair t-differences) based template attacks. Secondly, the problem to build a template for each (data,key) pair can be reduced to build templates for an MMJD (multisource multivariate joint distribution). An MMJD can be divided into several UMJDs. Based on the analysis, we give a template attack that does not require large amounts of computations, and neither a large number of power traces for profiling, but with its attack effect equivalent to that of the template attack which aims to build a template for each (data,key) pair. Third, from the process of the UMJD based template attacks, using the POI (points of interest) of all variables together as the POI of the template attack is an extension to the existing conclusion on the optimal number of POI. Lastly, the UMJD can also be applied in the SOST method to obtain better quality of POI

    On the coefficients of the polynomial in the number field sieve

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    Polynomial selection is very important in number field sieve. If the yield of a pair of polynomials is closely correlated with the coefficients of the polynomials, we can select polynomials by checking the coefficients first. This can speed up the selection of good polynomials. In this paper, we aim to study the correlation between the polynomial coefficients and the yield of the polynomials. By theoretical analysis and experiments, we find that a polynomial with the ending coefficient containing more small primes is usually better in yield than the one whose ending coefficient contains less. One advantage of the ending coefficient over the leading coefficient is that the ending coefficient is bigger and can contain more small primes in root optimizing stage. Using the complete discrimination system, we also analyze the condition on coefficients to obtain more real roots

    Two Efficient and Regulatory Confidential Transaction Schemes

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    With the development of Bitcoin, Ethereum and other projects, blockchain has been widely concerned with its outstanding characteristics such as non-centralization, collective maintenance, openness and transparency. Blockchain has been widely used in finance, logistics, copyright and other fields. However, as transactions are stored in plaintext in the blockchain for public verification, the privacy of users is not well guaranteed such that many financial applications can not be adopted widely. How to securely and economically protect the privacy of transactions is worth further research. In this paper, we have proposed two efficient and regulatory confidential transaction schemes using homomorphic encryption and zero-knowledge proof. ERCO, the first scheme, turns the standard ElGamal algorithm to be additively homomorphic and expands it into four ciphertexts such that (m,r)(m,r) in the transaction can be decrypted. Its security can be reduced to DDH assumption and the transaction size is less. PailGamal, the second scheme, is based on the combination of Paillier and ElGamal algorithms. Its security can be reduced to DDH assumption and it empowers regulators greater powers to obtain transaction-related specific content. In contrast to other ElGamal-based schemes, PailGamal makes any token amount directly decrypted without calculating a discrete logarithm problem. As any (m,r)(m,r) in transactions can be decrypted directly, game theory is applied to further reduce transaction size

    PARP10 influences the proliferation of colorectal carcinoma cells, a preliminary study

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    PARP10 is an intracellular mono-ADP ribosyltransferase and recent reports suggest that it regulates proliferation of some cell types. However, its effect on the proliferation of colorectal carcinoma cells has not yet been systematically reported. We explored the influence of PARP10 on the proliferation of several colorectal carcinoma cell types and carried out initial studies on the underlying mechanisms. Inhibition of the enzymatic activity of PARP10 led to significantly decreases in proliferative ability in LoVo cells and CT26 cells in vitro and suppressed growth of CT26 tumours in the subaxilliary region in Balb/c mice in vivo. Cell-cycle arrest accompanied these observations. Expression of the nuclear transfer factor Ī²-catenin and it translocation to the nucleus were also affected and the expression of its associated signal proteins Axin2 and c-Myb were increased and decreased, respectively. We demonstrate that PARP10 promotes proliferation of those colorectal carcinoma cells which express significant levels of PARP10. This promotion is suppressed when the enzymatic activity is inhibited. Ī²-Catenin is likely to be the mediator of the antiproliferative effect

    Comparative genomics reveals adaptive evolution of Asian tapeworm in switching to a new intermediate host

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    Taenia saginata, Taenia solium and Taenia asiatica (beef, pork and Asian tapeworms, respectively) are parasitic flatworms of major public health and food safety importance. Among them, T. asiatica is a newly recognized species that split from T. saginata via an intermediate host switch āˆ¼1.14 Myr ago. Here we report the 169- and 168-Mb draft genomes of T. saginata and T. asiatica. Comparative analysis reveals that high rates of gene duplications and functional diversifications might have partially driven the divergence between T. asiatica and T. saginata. We observe accelerated evolutionary rates, adaptive evolutions in homeostasis regulation, tegument maintenance and lipid uptakes, and differential/specialized gene family expansions in T. asiatica that may favour its hepatotropism in the new intermediate host. We also identify potential targets for developing diagnostic or intervention tools against human tapeworms. These data provide new insights into the evolution of Taenia parasites, particularly the recent speciation of T. asiatica

    Evolutionary Design of Trace Form Bent Functions

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    In order to design bent functions, evolutionary algorithm based on truth table, algebraic normal form or Walsh spectra are already known. Evolutionary algorithm based on trace function form is not known to authors' knowledge. In this paper, we give an evolutionary algorithm based on the trace representation of boolean function. With the algorithm, we constructed many bent functions and made some analysis work. First we observe that all 4 a#nely inequivalent bent classes in 6-variable can be written as the linear sum of 2 or 3 monomial trace functions
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