Sharif Digital Repository

RSA based SmartCards have been widely used in security services such as secure data transmission in many applications over the past few years. Generation of a secure key pair which is based on finding a pair of large prime numbers is an indispensable part of creating a secure channel. This paper describes a novel approach for secure and fast key generation of the public key cryptographic algorithm of RSA. This method has been implemented on a typical SmartCard equipped with a crypto-coprocessor and a true random number generator. An efficient method for generating the large random prime numbers is proposed that considerably reduces the total time required for generating a key pair. The key... 

A new high-performance architecture for decoding the irregular Low-Density Parity-Check (LDPC) codes with respect to the iterative message-passing decoding algorithm is explored. The proposed method is based on reducing the logic delays in the iterative processing of the bit nodes and check nodes leading to the increment of maximum possible frequency. The simulations show the efficiency of the proposed method in low/high-complexity graph matrices, though it is more effective in high-complexity ones. About 28% reduction of the combinational delay in the bit/check processors is explored without much impacting the area consumption. ©2007 IEEE  

This paper presents several efficient architectures of dynamic/static edge-triggered flip-flops with a compact embedded logic. The proposed structure, which benefits from the overlap period, fixes most of the drawbacks of the dynamic logic family. The design issues of setting the appropriate overlap period for this architecture are explained. The proposed overlap-based approach is compared with several state-of-the-art dynamic/static logic styles in implementing a 4-bit shift register and an odd-even sort coprocessor using different CMOS technologies. The simulation results showed that the overlap-based logic cells become much more efficient when the complexity of their embedded logic... 

In the framework of Bohmian quantum mechanics, the Klein-Gordon equation can be seen as representing a particle with mass m which is guided by a guiding wave φ(x) in a causal manner. Here a relevant question is whether Bohmian quantum mechanics is applicable to a non-linear Klein-Gordon equation? We examine this approach for φ4(x) and sine-Gordon potentials. It turns out that this method leads to equations for quantum states which are identical to those derived by field theoretical methods used for quantum solitons. Moreover, the quantum force exerted on the particle can be determined. This method can be used for other non-linear potentials as well  

In this paper we shall argue that conformal transformations give some new aspects to a metric and changes the physics that arises from the classical metric. It is equivalent to adding a new potential to relativistic Hamilton-Jacobi equation. We start by using conformal transformations on a metric and obtain modified geodesics. Then, we try to show that extra terms in the modified geodesics are indications of a background force. We obtain this potential by using variational method. Then, we see that this background potential is the same as the Bohmian non-local quantum potential. This approach gives a method stronger than Bohm's original method in deriving Bohmian quantum potential. We do not... 

Datapath designs that perform polynomial computations over Z 2n are used in many applications such as computer graphics and digital signal processing domains. As the market of such applications continues to grow, improvements in high-level synthesis and optimization techniques for multivariate polynomials have become really challenging. This paper presents an efficient algorithm for optimizing the implementation of a multivariate polynomial over Z2n in terms of the number of multipliers and adders. This approach makes use of promising heuristics to extract more complex common sub-expressions from the polynomial compared to the conventional methods. The proposed algorithm also utilizes a... 

In this paper, we propose a novel approach to extract a network of half adders from the gate-level net-list of an addition circuit while no internal equivalences exist. The technique begins with a gatelevel net-list and tries to map it into word-level adders based on an efficient bit-level adder representation. It will be shown that the proposed technique is suitable for several gate-level architectures of multipliers, as it extracts adder components in a step-wise method. This approach can also be generalized to other arithmetic circuits. In order to evaluate the effectiveness of our approach, we run it on several arithmetic circuits and compare experimental results with those of... 

This paper presents a novel automatic debugging algorithm for a postsynthesis combinational arithmetic circuit. The approach is robust under wide varieties of arithmetic circuit architectures and design optimizations. The debugging algorithm in this paper consists of three phases of partial product initialization, XOR extraction, and carry-signalmapping. The run-time complexity of conventional carry-signal-mapping algorithms, such as the approach described by Stoffel and Kunz, is exponential. However, in the proposed algorithm, by making use of some important design issues, we categorize the extracted XORs into half/full-adders to make a very fast debugging algorithm. This approach is robust... 

This paper presents a novel automatic debugging algorithm for a postsynthesis combinational arithmetic circuit. The approach is robust under wide varieties of arithmetic circuit architectures and design optimizations. The debugging algorithm in this paper consists of three phases of partial product initialization, xor extraction, and carry-signal mapping. The run-time complexity of conventional carry-signal-mapping algorithms, such as the approach described by Stoffel and Kunz, is exponential. However, in the proposed algorithm, by making use of some important design issues, we categorize the extracted xors into half/full-adders to make a very fast debugging algorithm. This approach is... 

Integer multipliers with finite output bit-widths are widely used in many Digital Signal Processing (DSP) applications. In such circuits high-level optimizations like Residue Number System (RNS) can be utilized to achieve more efficient architectures compared to the conventional binary representations. This paper presents an efficient high-level Don't-Care Optimization (DC-Opt) method for integer multipliers and in general Multiply Accumulator (MAC) units when the output result is limited to a finite bit-width. This high-level optimization approach can then be combined with logic optimizations at gate-level. Experimental results have shown major improvements in terms of area and latency... 

Alumina-silicate composite coatings were formed on titanium substrate by plasma electrolytic oxidation (PEO) process using a silicate-based electrolyte containing alumina nanoparticles. Microstructure, chemical and phase compositions, and thickness of the coatings were investigated to determine, coating mechanism and probable reactions during the process. The effect of processing time on corrosion resistance of the coatings was investigated using the potentiodynamic polarization test. Barrier layer (TiO2) formation, micro arcs occurrence, and electrolyte ionization were the main stages of PEO coating growth process. Alumina nanoparticles were incorporated into the coating by cataphoretic and... 

Plasma electrolytic oxidation (PEO) process was employed to create ceramic coatings on titanium substrate by using silicate-based electrolytes containing different concentrations of alumina nanoparticles (0, 3, 6, and 10. g/lit). The effect of alumina nanoparticles concentration on the morphology, chemical and phase composition of the PEO coatings was investigated by scanning electron microscope, energy dispersive spectrometer, and X-ray diffractometer, respectively.The corrosion behavior of samples was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests. SEM, EDS, and XRD analyses illustrated that alumina nanoparticles incorporated into the... 

We introduce dynamic plastic continuous neural network (DPCNN), which is comprised of neurons distributed in a nonlinear plastic medium where wire-like connections of neural networks are replaced with the continuous medium. We use finite element method to model the dynamic phenomenon of information processing within the DPCNNs. During the training, instead of weights, the properties of the continuous material at its different locations and some properties of neurons are modified. Input and output can be vectors and/or continuous functions over lines and/or areas. Delay and feedback from neurons to themselves and from outputs occur in the DPCNNs. We model a simple form of the DPCNN where the... 

Real-time detection of Covid-19 has definitely been the most widely-used world-wide classification problem since the start of the pandemic from 2020 until now. In the meantime, airspace opacities spreads related to lung have been of the most challenging problems in this area. A common approach to do on that score has been using chest X-ray images to better diagnose positive Covid-19 cases. Similar to most other classification problems, machine learning-based approaches have been the first/most-used candidates in this application. Many schemes based on machine/deep learning have been proposed in recent years though increasing the performance and accuracy of the system has still remained an... 

Vertically aligned ZnO@CdS nanorod heterostructure films with various loadings of CdS nanoparticle shell were synthesized and applied in photoinactivation of Escherichia coli bacteria under visible light irradiation. While neither the bare ZnO nanorods (with band-gap energy (Eg) of ∼3.28 eV) under visible light irradiation nor the nanorod heterostructures in dark exhibited any significant antibacterial activity, the ZnO@CdS nanorod heterostructures (with Eg ∼2.5-2.6 eV) could successfully inactivate the bacteria under visible light irradiation. Furthermore, it was found that an optimum loading of the CdS shell (corresponding to the effective thickness less than ∼15 nm) is required to achieve... 

Travel speeds between 25–300 mm/min and tool rotational speeds of 800 and 1250 rpm were employed for this study. The microstructure, mechanical properties and fracture surfaces of the joints were studied. Underwater environment and an increase in travel speed significantly increase the precipitates’ volume fraction, reduce the average grain and precipitate sizes of the weld nugget zones. A critical travel speed of 150 mm/min is attained in underwater welds beyond which the average grain sizes remain relatively the same. Average grain and precipitate sizes have linear relationships with the tool rotational and travel speed ratio. Optimum weld strengths of 396 and 360 MPa were obtained in the... 

This paper examines the use of pre-fabricated interlocking arms/threading in enhancing the strength of friction stir spot welded hybrid joints of AA2219/PP-C30S polypropylene polymer by varying parameter combination. The process involves the fabrication of a pre-threaded hole on the Al alloy prior to the joining process, and the threading/crest-pitch profile aids mechanical interlocking. The peak temperature, crest-pitch interlocked profiles, microstructural and mechanical properties of the joints were examined. The results show that an increase in the tool rotational speed increases the thickness of the reaction layer (between the Al and the polymer substrates), the shear-tensile load... 

Graphene oxide (GO)–chitosan composite layers with stacked layer structures were synthesized using chemically exfoliated GO sheets (with lateral dimensions of ∼1 μm and thickness of ∼1 nm), and applied as antibacterial and flexible nanostructured templates for stem cell proliferation. By increasing the GO content from zero to 6 wt%, the strength and elastic modulus of the layers increased ∼80% and 45%, respectively. Similar to the chitosan layer, the GO–chitosan composite layers showed significant antibacterial activity (>77% inactivation after only 3 h) against Staphylococcus aureus bacteria. Surface density of the actin cytoskeleton fibers of human mesenchymal stem cells (hMSCs) cultured...