Sharif Digital Repository

The chromatic number of a Latin square is the least number of partial transversals which cover its cells. This is just the chromatic number of its associated Latin square graph. Although Latin square graphs have been widely studied as strongly regular graphs, their chromatic numbers appear to be unexplored. We determine the chromatic number of a circulant Latin square, and find bounds for some other classes of Latin squares. With a computer, we find the chromatic number for all main classes of Latin squares of order at most eight  

In this paper, recurrent neural networks are applied to language modeling of Persian, using word embedding as word representation. To this aim, unidirectional and bidirectional Long Short-Term Memory (LSTM) networks are used, and the perplexity of Persian language models on a 100-million-word data set is evaluated. The effect of various parameters, including number of hidden layers and size of LSTM units, on the performance of the networks in reducing the perplexity of the models are investigated. Among different LSTM language models, the best perplexity, which is equal to 59.05, is achieved from a 2-layer bidirectional LSTM model. Comparing this value with the perplexity of the classical... 

The coloring of hypergraph and its special case Steiner triple systems, STS(v), is studied extensively. But the defining set of the coloring of hypergraph even its special case STS(v), has not been explored yet. We study minimum defining set and the largest minimal defining set for 3-coloring of STS(v). We determined minimum defining set and the largest minimal defining set, for all non-isomorphic STS(v), v £ 15. Also we have found the defining number for all Steiner triple systems of order v, and some lower bounds for the size of the largest minimal defining set for all Steiner triple systems of order v, for each admissible v. © 2021 Taru Publications  

The coloring of hypergraph and its special case Steiner triple systems, STS(v), is studied extensively. But the defining set of the coloring of hypergraph even its special case STS(v), has not been explored yet. We study minimum defining set and the largest minimal defining set for 3-coloring of STS(v). We determined minimum defining set and the largest minimal defining set, for all non-isomorphic STS(v), v £ 15. Also we have found the defining number for all Steiner triple systems of order v, and some lower bounds for the size of the largest minimal defining set for all Steiner triple systems of order v, for each admissible v. © 2022 Taru Publications  

Previously, we have proposed a computational model for decision-making in crisis situations called C-RPD (Computational Recognition Primed Decision). In this paper, a software development process customized for Crisis Situations Decision-Making Systems (CSDMSs) is proposed. Agile processes can skillfully manage uncertainty in software requirements and some of their features like incremental development can solve some problems in developing CSDMSs. However, these processes do not provide comprehensive solutions for issues like the lack of enough knowledge about CSDMSs, very rapid changes, urgent need to overcome security challenges, high development unpredictability, and the performance test.... 

The problem of compliance checking and assessment is to ensure that the design or implementation of a system meets some desired properties and complies with some rules or regularities. This problem is a key issue in several human and engineering application domains such as organizational management and e-governance, software and IT industries, and software and systems quality engineering. To deal with this problem, some different approaches and methods have been proposed. In addition to the approaches such as formal methods, mathematical proofs, and logical evaluations, benchmarking can be used for compliance assessment. Naturally, a set of benchmarks can shape an applied solution to... 

In this study, a new antibacklash gear mechanism design comprising three pinions and a rack is introduced. This mechanism offers several advantages compared to conventional antibacklash mechanisms, such as lower transmission error as well as lower required preload. Nonlinear dynamic modeling of this mechanism is developed to acquire insight into its dynamic behavior. It is observed that the amount of preload required to diminish the backlash depends on the applied input torque and nature of periodic mesh stiffness. Then, an attempt is made to obtain an approximate relation to find the minimum requiring preload to preserve the system's antibacklash property and reduce friction and wear on the... 

Objective: This study analyzes the effects of lifestyle, nutrition, and diets on the status and risks of apparent (symptomatic) COVID-19 infection in Iranian families. Materials and Methods: A relatively extensive questionnaire survey was conducted on more than 20,000 Iranian families (residing in more than 1000 different urban and rural areas in the Islamic Republic of Iran) to collect the big data of COVID-19 and develop a lifestyle dataset. The collected big data included the records of lifestyle effects (e.g. nutrition, water consumption resources, physical exercise, smoking, age, gender, health and disease factors, etc.) on the status of COVID-19 infection in families (i.e. residents of... 

Molecular dynamics (MD) simulations were used to study the mechanical behaviour of β-SiC at nano-scale under tensile loading. Effects of loading rate and tensile temperature on the mechanical properties and failure were studied. Modified embedded-atom method (MEAM) potential and Berendsen thermostat were utilized for modelling. Periodic boundary conditions were employed and the behaviour of material was analyzed under three-axial loading condition at which the stress–strain relation was acceptably size independent. It is shown that with increasing the loading rate from 5 m/s to 70 m/s, the failure strain increases without a remarkable change in the stress–strain relationship. The MD... 

Molecular dynamics (MD) simulations were used to study the mechanical behaviour of β-SiC at nano-scale under tensile loading. Effects of loading rate and tensile temperature on the mechanical properties and failure were studied. Modified embedded-atom method (MEAM) potential and Berendsen thermostat were utilized for modelling. Periodic boundary conditions were employed and the behaviour of material was analyzed under three-axial loading condition at which the stress- strain relation was acceptably size independent. It is shown that with increasing the loading rate from 5 m/s to 70 m/s, the failure strain increases without a remarkable change in the stress-strain relationship. The MD... 

In this investigation, the multi-objective selection and optimization of a gantry machine tool is achieved by analytic hierarchy process, multi-objective genetic algorithm, and Pareto-Edgeworth-Grierson-multi-criteria decision-making method. The objectives include maximum static deformation, the first four natural frequencies, mass, and fabrication cost of the gantry. Further structural optimization of the best configuration was accomplished using multi-objective genetic algorithm to improve all objectives except cost. The result of sensitivity analysis reveals the major contribution of columns of gantry with respect to the crossbeam's contribution. After determining the most effective... 

This article studies effects of webpage layout in an online retailer on buyer behavior towards new products and is a sequel to a study performed by authors in department stores. Webpage layout -in terms of parameters which influence buyer behavior- is formulated by two variables; pattern of prices and pattern of popularity. A novel method based on above-mentioned study, has been developed to measure these two factors, so that they can be compared against retailer sales statistics. Investigating this relationship helps both online retailers and marketing agents to better understand effect of webpage layout in promoting a newly developed product. Results show that correlation between price... 

TiO2 and transition metal (Cr, Mn, Fe, Co, Ni, Cu, and Zn) doped TiO2 nanoparticles were synthesized by the sol-gel method using 2-hydroxylethylammonium formate as an ionic liquid. All the prepared samples were calcined at 500 °C and characterized by X-ray diffraction (XRD), BET surface area determination, energy dispersive X-ray (EDX) analysis, diffuse reflectance spectroscopy (DRS), and Fourier transformed infrared (FT-IR) techniques. The studies revealed that transition metal (TM) doped nanoparticles have smaller crystalline size and higher surface area than pure TiO2. Dopant ions in the TiO2 structure caused significant absorption shift into the visible region. The results of... 

Demand-side management (DSM) and the integration of the energy hub concept as a main part of future energy networks play an essential role in the process of improving the efficiency and reliability of the power grids. In this paper, we consider a smart multi-carrier energy system in which users are equipped with energy storage and conversion devices (i.e., an energy hub). Users intend to reduce their energy payment by shifting energy consumption to off-peak hours and switching between different energy carriers. This system enables both users with shiftable loads and must-run loads to be active in a DSM program. We apply game theory to formulate the energy consumption and conversion for a... 

In this study, hydrogen generation is maximised by optimising the size and the operating conditions of an electrolyser (EL) directly connected to a photovoltaic (PV) module at different irradiance. Due to the variations of maximum power points of the PV module during a year and the complexity of the system, a nonlinear approach is considered. A mathematical model has been developed to determine the performance of the PV/EL system. The optimisation methodology presented here is based on the particle swarm optimisation algorithm. By this method, for the given number of PV modules, the optimal sizeand operating condition of a PV/EL system areachieved. The approach can be applied for different... 

Zeolite-based Ag/AgBr and Ag/AgBr/TiO 2 photocatalysts were prepared by sol-gel and deposition methods and were characterized. Their photocatalytic activities were evaluated by inactivation of Escherichia (E.) coli and the photodegradation of Acid Blue 92 and potassium permanganate. The composites containing Ag/AgBr showed the antibacterial activity in the dark by releasing Ag ions into the medium. The results for inactivation of E. coli indicated that Ag/AgBr/TiO 2 modified photocatalyst had better antibacterial activity than Ag/AgBr/zeolite, while zeolite and TiO 2/zeolite did not show any antibacterial activity under visible light and dark conditions. Photodecolarization rate was affected... 

Deep eutectic solvents (DESs), surmised as "the organic reaction medium of the century", have reverberated a new symphony throughout the present green millennium. A brief historical account of the DES systems and their physicochemical properties as task-specific and designer solvents for cross-coupling reactions are appraised including the hole theory that explains the underlying mechanistic pathway for this emerging neoteric medium. The insights into cross-coupling reactions and their applications are included, highlighting the significant achievements pertaining to the dual role of DESs as a solvent and catalyst. In addition, popular "name-reactions"for the carbon-carbon and...