Flexible Prime-Field Genus 2 Hyperelliptic Curve Cryptography Processor with Low Power Consumption and Uniform Power Draw

Hamid-Reza Ahmadi,Ali Afzali-Kusha,Massoud Pedram,Mahdi Mosaffa 한국전자통신연구원 2015 ETRI Journal Vol.37 No.1

This paper presents an energy-efficient (low power) prime-field hyperelliptic curve cryptography (HECC) processor with uniform power draw. The HECC processor performs divisor scalar multiplication on the Jacobian of genus 2 hyperelliptic curves defined over prime fields for arbitrary field and curve parameters. It supports the most frequent case of divisor doubling and addition. The optimized implementation, which is synthesized in a 0.13 m standard CMOS technology, performs an 81-bit divisor multiplication in 503 ms consuming only 6.55 J of energy (average power consumption is 12.76 W). In addition, we present a technique to make the power consumption of the HECC processor more uniform and lower the peaks of its power consumption.

Health monitoring of pedestrian truss bridges using cone-shaped kernel distribution

Hamid Reza Ahmadi,Diana Anvari 국제구조공학회 2018 Smart Structures and Systems, An International Jou Vol.22 No.6

With increasing traffic volumes and rising vehicle traffic, especially in cities, the number of pedestrian bridges has also increased significantly. Like all other structures, pedestrian bridges also suffer damage. In order to increase the safety of pedestrians, it is necessary to identify existing damage and to repair them to ensure the safety of the bridge structures. Owing to the shortcomings of local methods in identifying damage and in order to enhance the reliability of detection and identification of structural faults, signal methods have seen significant development in recent years. In this research, a new methodology, based on cone-shaped kernel distribution with a new damage index, has been used for damage detection in pedestrian truss bridges. To evaluate the proposed method, the numerical models of the Warren Type steel truss and the Arregar steel footbridge were used. Based on the results, the proposed method and damage index identified the damage and determined its location with a high degree of precision. Given the ease of use, the proposed method can be used to identify faults in pedestrian bridges.

Seismic investigation of pushover methods for concrete piers of curved bridges in plan

Hamid Reza Ahmadi,Nariman Namdari,Maosen Cao,Mahmoud Bayat 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.23 No.1

The use of non-linear analysis of structures in a functional way for evaluating the structural seismic behavior has attracted the attention of the engineering community in recent years. The most commonly used functional method for analysis is a non-linear static method known as the “pushover method”. In this study, for the first time, a cyclic pushover analysis with different loading protocols was used for seismic investigation of curved bridges. The finite element model of 8-span curved bridges in plan created by the ZEUS-NL software was used for evaluating different pushover methods. In order to identify the optimal loading protocol for use in astatic non-linear cyclic analysis of curved bridges, four loading protocols (suggested by valid references) were used. Along with cyclic analysis, conventional analysis as well as adaptive pushover analysis, with proven capabilities in seismic evaluation of buildings and bridges, have been studied. The non-linear incremental dynamic analysis (IDA) method has been used to examine and compare the results of pushover analyses. To conduct IDA, the time history of 20 far-field earthquake records was used and the 50% fractile values of the demand given the ground motion intensity were computed. After analysis, the base shear vs displacement at the top of the piers were drawn. Obtained graphs represented the ability of a cyclic pushover analysis to estimate seismic capacity of the concrete piers of curved bridges. Based on results, the cyclic pushover method with ISO loading protocol provided better results for evaluating the seismic investigation of concrete piers of curved bridges in plan.

Cultural Semiotics Analysis of Carpet and Furniture in Iranian Lifestyle

Hamid Reza Shairi,Maryam Ahmadi 고려대학교 응용문화연구소 2020 에피스테메 Vol.0 No.23

The present study seeks to analyze cultural semiotics of carpet and furniture place, as significant objects rooted in Iranian culture for centuries, and in the process of paradigmatic and syntagmatic, they examine the functional, anthropological, semantic and value differences in Iranian cultural discourse. Thus, the main question is “what has been the influence of carpet and furniture as the main household objects in Iranian lifestyles during the contemporary era, and what elements and concepts of our identity and culture have transformed in this interaction?”. According to the findings of this research, it can be argued that carpet, together with many of its meanings in the contemporary era, has lost its central position, become smaller and found an auxiliary function alongside other furniture. Its practical value has diminished, and sometimes has an amusing aspect, while the furniture has enjoyed many signs meanings and has not only changed Iran's lifestyle in the contemporary era, but it also caused a greater distinction and formality of communications. It also acts as a sign of power and distinctive relations. As a result, it is understood how the objects are measured and valued based on social class and tastes in the contemporary lifestyle.

Synthesis and employment of PEGDA for fabrication of superhydrophilic PVDF/PEGDA electrospun nanofibrous membranes by in-situ visible photopolymerization

Hamid Reza Ashjari,Arsalan Ahmadi,Mir Saeed Seyed Dorraji 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.1

A methodology for the synthesis of light curable poly(ethylene glycol) diacrylate (PEGDA) is described. PEGDA synthesis was confirmed using 1H NMR, 13C NMR, and infrared spectroscopy. The resin was used for fabrication of the superhydrophilic PVDF/PEGDA nanofibrous membrane in a single processing step. For the in-situ photo cross-linking reaction during electrospinning process, the electrospinning apparatus was equipped with a visible light source. Degree of conversion of double bonds during electrospinning process and interaction between the two polymers were investigated by FT-IR spectrum. To determine the potential applications of the as-prepared the membranes in wastewater treatment, parameters such as morphology, hydrophilicity and water resistance were investigated by scanning electron microscopy (SEM), tensile strength, static water contact angle (WCA) and Fourier transform infrared spectroscopy (FT-IR). The results showed that PVDF/PEGDA (40/60) nanofibrous membrane is superhydrophilic and insoluble in water.

The Effects of Hearing Aid Digital Noise Reduction and Directionality on Acceptable Noise Level

Roghayeh Ahmadi,Hamid Jalilvand,Mohammad Ebrahim Mahdavi,Fatemeh Ahmadi,Ali Reza Akbarzade Baghban 대한이비인후과학회 2018 Clinical and Experimental Otorhinolaryngology Vol.11 No.4

Objectives. Two main digital signal processing technologies inside the modern hearing aid to provide the best conditions for hearing aid users are directionality (DIR) and digital noise reduction (DNR) algorithms. There are various possible settings for these algorithms. The present study evaluates the effects of various DIR and DNR conditions (both separately and in combination) on listening comfort among hearing aid users. Methods. In 18 participants who received hearing aid fitting services from the Rehabilitation School of Shahid Beheshti University of Medical Sciences regularly, we applied acceptable noise level (ANL) as our subjective measure of listening comfort. We evaluated both of these under six different hearing aid conditions: omnidirectional-baseline, omnidirectional-broadband DNR, omnidirectional-multichannel DNR, directional, directional-broadband DNR, and directional-multichannel DNR. Results. The ANL results ranged from −3 dB to 14 dB in all conditions. The results show, among all conditions, both the omnidirectional-baseline condition and the omnidirectional-broadband DNR condition are the worst conditions for listening in noise. The DIR always reduces the amount of noise that patients received during testing. The DNR algorithm does not improve listening in noise significantly when compared with the DIR algorithms. Although both DNR and DIR algorithms yielded a lower ANL, the DIR algorithm was more effective than the DNR. Conclusion. The DIR and DNR technologies provide listening comfort in the presence of noise. Thus, user benefit depends on how the digital signal processing settings inside the hearing aid are adjusted.

Application of power spectral density function for damage diagnosis of bridge piers

Mahmoud Bayat,Hamid Reza Ahmadi,Navideh Mahdavi 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.71 No.1

During the last two decades, much joint research regarding vibration based methods has been done, leading to developing various algorithms and techniques. These algorithms and techniques can be divided into modal methods and signal methods. Although modal methods have been widely used for health monitoring and damage detection, signal methods due to higher efficiency have received considerable attention in various fields, including aerospace, mechanical and civil engineering. Signal-based methods are derived directly from the recorded responses through signal processing algorithms to detect damage. According to different signal processing techniques, signal-based methods can be divided into three categories including time domain methods, frequency domain methods, and time-frequency domain methods. The frequency domain methods are well-known and interest in using them has increased in recent years. To determine dynamic behaviours, to identify systems and to detect damages of bridges, different methods and algorithms have been proposed by researchers. In this study, a new algorithm to detect seismic damage in the bridge’s piers is suggested. To evaluate the algorithm, an analytical model of a bridge with simple spans is used. Based on the algorithm, before and after damage, the bridge is excited by a sine force, and the piers’ responses are measured. The dynamic specifications of the bridge are extracted by Power Spectral Density function. In addition, the Least Square Method is used to detect damage in the bridge’s piers. The results indicate that the proposed algorithm can identify the seismic damage effectively. The algorithm is output-only method and measuring the excitation force is not needed. Moreover, the proposed approach does not need numerical models.

Efficient parameters to predict the nonlinear behavior of FRP retrofitted RC columns

Navideh Mahdavi,Hamid Reza Ahmadi,Mahmoud Bayat 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.70 No.6

While fiber-reinforced plastic (FRP) materials have been largely used in the retrofitting of concrete buildings, its application has been limited because of some problems such as de-bonding of FRP layers from the concrete surface. This paper is the part of a wide experimental and analytical investigation about flexural retrofitting of reinforced concrete (RC) columns using FRP and mechanical fasteners (MF). A new generation of MF is proposed, which is applicable for retrofitting of RC columns. Furthermore, generally, to evaluate a retrofitted structure the nonlinear static and dynamic analyses are the most accurate methods to estimate the performance of a structure. In the nonlinear analysis of a structure, accurate modeling of structural elements is necessary for estimation the reasonable results. So for nonlinear analysis of a structure, modeling parameters for beams, columns, and beam-column joints are essential. According to the concentrated hinge method, which is one of the most popular nonlinear modeling methods, structural members shall be modeled using concentrated or distributed plastic hinge models using modeling parameters. The nonlinear models of members should be capable of representing the inelastic response of the component. On the other hand, in performance based design to make a decision about a structure or design a new one, numerical acceptance should be determined. Modeling parameters and numerical acceptance criteria are different for buildings of different types and for different performance levels. In this paper, a new method was proposed for FRP retrofitted columns to avoid FRP debonding. For this purpose, mechanical fasteners were used to achieve the composite behavior of FRP and concrete columns. The experimental results showed that the use of the new method proposed in this paper increased the flexural strength and lateral load capacity of the columns significantly, and a good composition of FRP and RC column was achieved. Moreover, the modeling parameters and acceptance criteria were presented, which were derived from the experimental study in order to use in nonlinear analysis and performance-based design approach.

Seismic investigation of cyclic pushover method for regular reinforced concrete bridge

Afshin Shafigh,Hamid Reza Ahmadi,Mahmoud Bayat 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.78 No.1

Inelastic static pushover analysis has been used in the academic-research widely for seismic analysis of structures. Nowadays, the variety pushover analysis methods have been developed, including Modal pushover, Adaptive pushover, and Cyclic pushover, in which some weaknesses of the conventional pushover method have been rectified. In the conventional pushover analysis method, the effects of cumulative growth of cracks are not considered on the reduction of strength and stiffness of RC members that occur during earthquake or cyclic loading. Therefore, the Cyclic Pushover Analysis Method (CPA) has been proposed. This method is a powerful technique for seismic evaluation of regular reinforced concrete buildings in which the first mode of them is dominant. Since the bridges have different structures than buildings, their results cannot necessarily be attributed to bridges, and more research is needed. In this study, a cyclic pushover analysis with four loading protocols (suggested by valid references) by the Opensees software was conducted for seismic evaluation of two regular reinforce concrete bridges. The modeling method was validated with the comparison of the analytical and experimental results under both cyclic and dynamic loading. The failure mode of the piers was considered in two-mode of flexural failure and also a flexural-shear failure. Along with the cyclic analysis, conventional analysis has been studied. Also, the nonlinear incremental dynamic analysis (IDA) method has been used to examine and compare the results of pushover analyses. The time history of 20 far-field earthquake records was used to conduct IDA. After analysis, the base shear vs. displacement in the middle of the deck was drawn. The obtained results show that the cyclic pushover analysis method is able to evaluate an accurate seismic behavior of the reinforced concrete piers of the bridges. Based on the results, the cyclic pushover has proper convergence with IDA. Its accuracy was much higher than the conventional pushover, in which the bridge piers failed in flexural-shear mode. But, in the flexural failure mode, the results of each two pushover methods were close approximately. Besides, the cyclic pushover method with ACI loading protocol, and ATC-24 loading protocol, can provided more accurate results for evaluating the seismic investigation of the bridges, specially if the bridge piers are failed in flexural-shear failure mode.

Probabilistic seismic demand of isolated straight concrete girder highway bridges using fragility functions

Bayat, Mahmoud,Ahmadi, Hamid Reza,Kia, Mehdi,Cao, Maosen Techno-Press 2019 Advances in concrete construction Vol.7 No.3

In this study, it has been tried to prepare an analytical fragility curves for isolated straight continues highway bridges by considering different spectral intensity measures. A three-span concrete isolated bridge has been selected and the seismic performance of the bridge has been improved by Lead Rubber Bearing (LRB). Incremental Dynamic Analysis (IDA) is applied to the bridge in longitudinal direction. A suite of 14 earthquake ground motions from medium to sever motions are scaled and used for nonlinear time history analysis. Fragility function considers the relationship of earthquake intensity measures (IM) and probability of exceeding certain Damage State (DS). A full three dimensional finite element model of the isolated bridge has been developed and analyzed. A wide range of different intensity measures are selected and the optimal intensity measure which has the less dispersion is proposed.