Simulation, design optimization, and experimental validation of a silver SPND for neutron flux mapping in the Tehran MTR

Saghafi, Mahdi,Ayyoubzadeh, Seyed Mohsen,Terman, Mohammad Sadegh Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.12

This paper deals with the simulation-based design optimization and experimental validation of the characteristics of an in-core silver Self-Powered Neutron Detector (SPND). Optimized dimensions of the SPND are determined by combining Monte Carlo simulations and analytical methods. As a first step, the Monte Carlo transport code MCNPX is used to follow the trajectory and fate of the neutrons emitted from an external source. This simulation is able to seamlessly integrate various phenomena, including neutron slowing-down and shielding effects. Then, the expected number of beta particles and their energy spectrum following a neutron capture reaction in the silver emitter are fetched from the TENDEL database using the JANIS software interface and integrated with the data from the first step to yield the origin and spectrum of the source electrons. Eventually, the MCNPX transport code is used for the Monte Carlo calculation of the ballistic current of beta particles in the various regions of the SPND. Then, the output current and the maximum insulator thickness to avoid breakdown are determined. The optimum design of the SPND is then manufactured and experimental tests are conducted. The calculated design parameters of this detector have been found in good agreement with the obtained experimental results.

Zn-Co oxide electrodes with excellent capacitive behavior for using supercapacitor application

M. Saghafi,Sh. Zangeneh 한국물리학회 2019 Current Applied Physics Vol.19 No.6

In the present study, super-capacitive behavior of spinel Zn-Co oxides (with different Zn+2/Co+2 mol ratio) has been thoroughly investigated. The spinel of transition metal oxides with different morphologies has been synthesized with hydrothermal method on Ni foam as substrate layer. The specific capacitance of the Zn-Co oxide electrode prepared at 180 °C for 5 h with different Zn+2/Co+2 mol ratios of 1:0, 2:1, 1:1, 1:2, 0:1 were investigated and measured 405, 842, 726, 1237, 705 F g−1, respectively at 50 mV s−1 scan rate. Zn-Co oxide with Zn+2/Co+2 mol ratio of 1:2 was also synthesized at two different temperatures of 120 and 150 °C for 5 h with the specific capacitance of 1147, 917 F g−1 at 50 mV s−1 scan rate, respectively. Among the obtained data, the sample with Zn+2/Co+2 mol ratio of 1:2 prepared at 180 °C for 5 h possessed highest specific capacitance. The cyclic life of this electrode showed 92% capacitance retention after 1000 cycle of charge-discharge. All results revealed that Zn-Co oxides had excellent supercapacitive properties due to multiple oxidation states and fast ion/ electron transfer at the surface of electrode which could be offered as suitable devices for energy storage applications.

Longitudinal unzipping of carbon nanotubes and their electrochemical performance in supercapacitors

M. Saghafi,F. Mahboubi,S. Mohajerzadeh,M. Fathi,R. Holze 한국물리학회 2014 Current Applied Physics Vol.14 No.10

The capacitive properties of graphene nanoribbons (GNRs) with different reduction levels were investigated. GNRs have been synthesized through thermal reduction of oxidized GNRs in the temperature range 100e400 C. Oxidized GNRs were synthesized by longitudinal unzipping of multi-walled carbon nanotubes (MWCNTs) by means of chemical treatments. Scanning electron microscopy and transmission electron microscopy observations showed, that the efficient tube unzipping yielded improved effective surface area without any tube annihilation by the unzipping process of MWCNTs. Electrochemical studies indicated that through unzipping of MWCNTs, specific capacitance increased from 8 to 28 F g1 at discharge current density of 0.5 A g1, confirming increased active surface area and increased defect density in the MWCNTs surface. Unzipping of MWCNTs resulted in decreased rate capability of the electrode because of low electrical conductivity due to oxidization during the unzipping process. Thermal reduction of unzipped sample affected both specific capacitance and rate capability of electrodes. The highest specific capacitance of 62 F g1 at discharge current density of 0.5 A g1 was obtained for the sample unzipped and thermally annealed at about 150 C. The amount of oxygen-containing groups was shown to be an important factor influencing the performance of the GNRs. These results make unzipped MWCNTs promising electrode materials for supercapacitor applications.

The Effect of Foeniculum Vulgare (Fennel) on Body Composition in Postmenopausal Women with Excess Weight: A Double-blind Randomized Placebo-controlled Trial

( Nafiseh Saghafi ),( Masumeh Ghazanfarpour ),( Talat Khadivzadeh ),( Masoudeh Babakhanian ),( Maliheh Afiat ) 대한폐경학회 2017 대한폐경학회지 Vol.23 No.3

Objectives: The goal of this study was to evaluate the effect of fennel on body composition. Methods: This study is a secondary analysis of a double-blind, randomized, placebo-controlled trial. Fifty-four out of 60 patients were able to successfully complete the original study. Seven out of 54 patients were excluded because they were not overweight and obese. Thus, 47 women were included in this secondary analysis. Of these 47 women, 22 were in the fennel group and 25 were in placebo group. Body weight, body mass index (BMI) as well as fat distribution was measured at the baseline and after a three-month follow-up. Results: Comparison of fennel and placebo groups did not reveal any significant effect in terms of body weight, BMI, waist and hip circumferences and fat distribution. Also, the results of paired t-test did not variation of these parameters across groups before and after 12-week treatment. Conclusions: Menopausal women in fennel group experienced a slight increase in body weight and fat distribution, which was not significant. Further studies with larger sample sizes are recommended to validate the results of this study. (J Menopausal Med 2017;23:166-171)

Real-time Estimation of Break Sizes during LOCA in Nuclear Power Plants Using NARX Neural Network

Mahdi Saghafi,Mohammad B. Ghofrani 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.3

This paper deals with break size estimation of loss of coolant accidents (LOCA) using a nonlinearautoregressive with exogenous inputs (NARX) neural network. Previous studies used static approaches,requiring time-integrated parameters and independent firing algorithms. NARX neural network is able todirectly deal with time-dependent signals for dynamic estimation of break sizes in real-time. The casestudied is a LOCA in the primary system of Bushehr nuclear power plant (NPP). In this study, number ofhidden layers, neurons, feedbacks, inputs, and training duration of transients are selected by performingparametric studies to determine the network architecture with minimum error. The developed NARXneural network is trained by error back propagation algorithm with different break sizes, covering 5%e100% of main coolant pipeline area. This database of LOCA scenarios is developed using RELAP5thermal-hydraulic code. The results are satisfactory and indicate feasibility of implementing NARX neuralnetwork for break size estimation in NPPs. It is able to find a general solution for break size estimationproblem in real-time, using a limited number of training data sets. This study has been performed in theframework of a research project, aiming to develop an appropriate accident management support tool forBushehr NPP.

Seismic Behavior of High-Performance Fiber-Reinforced Cement Composites Beam-Column Connection with High Damage Tolerance

Mohammad Hossein Saghafi,Hashem Shariatmadar,Ali Kheyroddin 한국콘크리트학회 2019 International Journal of Concrete Structures and M Vol.13 No.1

The purpose of this study is to investigate and evaluate the feasibility of using high-performance fiber-reinforced cement composites (HPFRCC) to satisfy the requirement of transverse reinforcement in beam-column joint under seismic loads. The basic mechanical properties of the HPFRCCs are determined by compression, uniaxial tension, and direct shear tests. Four half-scale exterior beam-column connections are cast and tested under cyclic loads. The cracking patterns, hysteresis behavior, ductility, energy dissipation with damping characteristics and joint shear capacity of the HPFRCC beam-column connections are analyzed, investigated, and compared to the cyclic responses of normal concrete connections designed with/without seismic criteria of ACI. The test results revealed that HPFRCC connections considerably enhances shear and flexural capacity and also improved the deformation and damage tolerance behavior in post-cracking stage comparing to normal concrete connections in ultimate stages. Also, the failure mode of HPFRCC specimens changed from shear mode to flexural mode comparing to the connections without seismic details. Severe damages are observed in normal concrete connection designed without considering seismic criteria. Wide diagonal cracking and damage are observed on the designed NC connections under large cyclic displacement at drift 6%. However, in HPFRCC connections, joint remained intact without any cracks and damage until the test end. This implies that the shear stress requirement can be satisfied without any need to the transverse reinforcement in the HPFRCC joint.

Inter Religious Dialogue an Effective Factor on Tourism

Mohammad Djavad Saghafi,Aynaz Lotfata 세계문화관광학회 2008 Conference Proceedings Vol.9 No.0

Nowadays, inter religious dialogue is not a regional or national necessity. It is necessary globally and internationally. Human being is social creature and needs dialogue so wisdom of human is the wisdom of dialogue .In addition, humans indirectly or directly have fulfilled all scientific and cultural accomplishment by dialogue. Undoubtedly, The growth of dialogue appreciates a important notion, grasping dialogue as one of the arts and skills for culture exchanging firmly. Religions are the most important factor in forming and diversity of culture when religions agree with dialogue and the culture of dialogue is stabled among them, it eases dialogue in all aspects of cultures and civilizations, communication among societies will be possible. Tourism industry is one of the accomplishment of cultural dialogue which not only is a kind of industry but also it is a science, art and knowledge. The interpretation of tourism as the acknowledgement of the global culture, having critic outlook toward oneself and others, paying attention to heritage makes everybody get new experience. Religious dialogue not only can have cultural perceptual and moral outcomes but also it requires challenge in the aspects of economy among different societies. Along with globalization economy which playa major role in relations among nations and tribes, becomes stronger and creates some new ideas to make the economy not as a fixed power but as an issue which is growing daily that represents the growth and improvement of cultural tourism and uniting different nations as a result and this is achievable by shaping and reshaping the issue of inter religious dialogue. Tourism extends our knowledge and information in two way : we can know ourselves and others better.

Behavior-Based Acceleration Commanded Formation Flight Control

Touraj Soleymani,Fariborz Saghafi 제어로봇시스템학회 2010 제어로봇시스템학회 국제학술대회 논문집 Vol.2010 No.10

In this paper, the design of a formation flight controller is investigated. Each vehicle in the formation is controlled by designing two separate control loops. The formation flight controller placed in the outer loop employs behavior-based control as a distributed control strategy to steer the vehicle by producing acceleration commands and the control system placed in the inner loop is to convert these commands to the actuator commands. Leader following architecture is applied to define the structure for the formation flight. To study the pragmatic issues of the proposed formation flight controller, it is implemented into multiple micro air vehicles which are modeled by a six-degree-of-freedom dynamics. Finally, simulations were carried out to verify the effectiveness of the system.

Localization of the Optic Disc Center in Retinal Images Based on the Harris Corner Detector

Amin Dehghani,Mohammad-Shahram Moin,Mohammad Saghafi 대한의용생체공학회 2012 Biomedical Engineering Letters (BMEL) Vol.2 No.3

Purpose Localizing the optic disc and its center is the first step of most identification, segmentation algorithms and diagnosing some diseases on fundus photographs such as diabetic retinopathy. Despite the importance of optic disc localization, there is not very accurate and fast method for localizing the center of optic disc in retinal images. Therefore,we propose a robust and fast algorithm for localizing the center of optic disc. Methods Based on the property of optic disc, vessels originate from the center of optic disc and the number of the vessels in the vicinity of optic disc is more than others regions in the retinal images. Therefore, we can see the largest number of corners and bifurcations around the optic disc in the retinal images. In this paper, a robust method based on Harris corner detector is proposed. Using the Harris corner detector, corners and bifurcations are found in the retinal images. Then, we use a moving window near the size of optic disc to count the number of corners. Finally, the center of windows in which the high number of corners are located, is obtained and the mean of these centers is considered as the center of optic disc. The DRIVE, STARE and a local dataset including 273 retinal images are used to evaluate the proposed algorithm. Results The success rate is 97.5%, 87.65% and 97.8% for DRIVE, STARE and a local dataset. The average distance between the estimated and the manually identified optic disc centers is 4.61, 11 and 9 pixels for the DRIVE, STARE and local dataset respectively. Comparing the results of our proposed method and counterpart methods verifies the effectiveness of the proposed method. Conclusions In this paper, we proposed a new method for localizing the center of optic disc based on corners and bifurcations obtained using Harris corner detector. Comparing the results of our proposed method and counterpart methods verifies the effectiveness of the proposed method.

A new interleaved high step up converter with low voltage stress on the main switches

Babak Tohidi,Majid Delshad,Hadi Saghafi 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.26 No.4

In this paper, a new interleaved high step-up converter with low voltage stress on the switches is proposed. In the proposed converter, soft switching is provided for all switches by just one auxiliary switch, which decreases the conduction loss of auxiliary circuit. Also, the auxiliary circuit is expanded on the converter with more input branches. In the converter all main switches operate under zero voltage switching condition and auxiliary switch operate under zero current switching condition. Because of the interleaved structure, the reliability of converter increases and input current ripples decreases. The clamp capacitor in the converter not only absorb the voltage spikes across the switch due to leakage inductance, but also improve voltage gain. The proposed converter is fully analyzed and to verify the theoretical analysis, a 100 W prototype was implemented. Also, to show the effectiveness of auxiliary circuit on conduction EMI, EMI of the proposed converter comprised with hard switching counterpart.