Histopathological graded liver lesions: what role does the IVIM analysis method have?

Magnetic Resonance Materials in Physics, Biology and Medicine - This study aims to investigate three different image processing methods on quantitative parameters of IVIM sequence, as well as...     

Distributed accelerating of quantized second‐order consensus with bounded input

In this paper, the convergence speed of consensus for a second‐order integrator with the fixed undirected graph is investigated. Additionally, the quantized information and bounded control input are applied to the system. To accelerate the convergence speed, a distributed variable adjacency matrix is proposed where the links' weight are functions defined based on the distance to the neighbors. The stability of the whole system for both of the quantized and non‐quantized consensus protocol considering a general weight function is shown using Lyapunov's direct approach. Furthermore, it is mentioned that the consensus value of the position depends on the structure of the quantizer.     

Modeling viscosity of methane,nitrogen, and hydrocarbon gas mixtures at ultra-high pressures and temperatures using group method of data handling and gene expression programming techniques

Accurate gas viscosity determination is an important issue in the oil and gas industries. Experimental approaches for gas viscosity measurement are time-consuming, expensive and hardly possible at high pressures and high temperatures (HPHT). In this study, a number of correlations were developed to esti-mate gas viscosity by the use of group method of data handling (GMDH)-type neural network and gene expression programming (GEP) techniques using a large data set containing more than 3000 experimen-tal data points for methane, nitrogen, and hydrocarbon gas mixtures. It is worth mentioning that unlike many of viscosity correlations, the proposed ones in this study could compute gas viscosity at pressures ranging between 34 and 172 MPa and temperatures between 310 and 1300 K. Also, a comparison was performed between the results of these established models and the results of ten well-known models reported in the literature. Average absolute relative errors of GMDH models were obtained 4.23％, 0.64％, and 0.61％for hydrocarbon gas mixtures, methane, and nitrogen, respectively. In addition, graph-ical analyses indicate that the GMDH can predict gas viscosity with higher accuracy than GEP at HPHT conditions. Also, using leverage technique, valid, suspected and outlier data points were determined. Finally, trends of gas viscosity models at different conditions were evaluated.     

Control rod worth calculation for VVER-1000 nuclear reactor using WIMS and CITATION codes

This paper summarizes efforts related to developing a technically justifiable approach for investigating the control rod worth of VVER-1000 reactor. For this assessment, computer simulation of nuclear reactor was needed. In this study nuclear reactor behavior was modeled by WIMS code, which solves transport equation for fuel assemblies' modeling at first step, and CITATION code that solves diffusion equation for core modeling. From these two codes, neutronic calculation of reactor was performed and control rod worth was calculated. Results of this study are comparable with the plant's FSAR.On comparing results of this study and reference some unacceptable errors were discerned. To find out the cause of these errors, some efforts had been performed and finally was discerned that the method of cell calculation, i.e., DSN method, was the important cause of errors. Therefore, some analysis had been performed by WIMS in PIJ + PERSEUS method and was shown that the results were improved.     

Immobilized iron Schiff base histidine complexes on Al-MCM-41 and zeolite Y as catalyst for oxidation of cycloalkanes

Iron complexes of N-salicylidene-l-histidine with or without bipyridine ligand immobilized on Al-MCM-41 and zeolite Y designated as Fe(sal-l-his)(bipy)complex/Al-MCM-41 or Fe(sal-l-his)complex/Al-MCM-41 and Fe(sal-l-his)(bpy)complex/Y or Fe(sal-l-his)complex/Y respectively, were prepared and characterized by X-ray powder diffraction (XRD), FT-IR, N₂ adsorption/desorption and chemical analysis techniques. Fe(sal-l-his)/Al-MCM-41 and Fe(sal-l-his)(bipy)complex/Al-MCM-41 were found to successfully catalyze the oxidation of cyclohexane, methyl cyclohexane, cyclooctane and adamantane with H₂O₂. The oxidation results and promising catalytic behavior of Fe(sal-l-his)(bipy)complex/Al-MCM-41 for oxidation of cyclooctane with 90 % conversion and excellent selectivity toward the formation of cyclooctanone will be discussed in this presentation.     

Ensemble Boosting and Bagging Based Machine Learning Models for Groundwater Potential Prediction

Water Resources Management - Due to the rapidly increasing demand for groundwater, as one of the principal freshwater resources, there is an urge to advance novel prediction systems to more...     

Effects of Space Charge on the Discharge Process in an Icicle/Iced-Plate Electrode System under Positive DC Voltage

Using an icicle/iced-plate system, the corona discharge at the icicle tip was investigated under positive DC voltage. The discharge pulses were recorded and analyzed. The relationship between the discharge magnitude and the time interval before the pulse was examined. The mechanisms underlying the corona discharges at icicle tips were investigated. The influence of space charge on the discharge and the effects of the applied voltage on the time interval between two pulses were also investigated. Finally, a model for calculating the drift and diffusion of the space charge cloud was presented.     

Role of air gaps on AC withstand voltage of an ice-covered insulator string

The influence of the number and position of air gaps on the 50% AC withstand voltage, V₅₀, of a short string of 5 IEEE standard insulator units covered with ice was experimentally investigated and numerically simulated. The results show that the V₅₀ is affected by the number and position of the air gaps. The results also show that the presence of a partial arc along the air gap close to the high voltage (HV) electrode leads to a redistribution of the voltage along the ice-covered insulator. Based on the obtained results, suggestions for improving the performance of line insulators under icing conditions were proposed