Impact Energy of Functionally Graded Steels with Crack Divider Configuration

Functionally graded steels were produced via electroslag remelting process using the primary electrodes of plain carbon and austenitic stainless steels. Charpy impact energy of as-prepared specimens was measured in the form of crack divider. The obtained results show that the impact energy of the specimens depends on the type and the volume fraction of the present phases. Based on the rule of mixtures, a mathematical model, which correlates the impact energy of functionally graded steels to the impact energ...     

On optimal relaying strategies for VANETs over double Nakagami-m fading channels

Wireless Networks - Vehicular ad hoc networks (VANETs) are able to facilitate data exchange among vehicles and provide diverse data services. The benefits of cooperative communications are such as...     

Computational fluid dynamics on the hydrodynamic characteristics of the conical cap tray

This paper addresses an investigation on the hydrodynamic behavior of a new type of cap trays called conical cap tray (ConCap tray). A 3-D computational fluid dynamics model was developed to predict the hydrodynamics of the ConCap tray which is operated in the spray regime. The model considers two phase flow of gas and liquid in a VOF-like code framework. The homogeneous multiple size group model (MUSIG model) and shear stress transport (SST) turbulence model were implemented. Detailed insights into the hydrodynamic behavior of the inside of the cones were obtained. The relation between velocity, pressure and cross section area of the flow inside the cone also was formulated. The computational fluid dynamic (CFD) results show that the pressure variation in the cones forces the liquid on the tray to be highly turbulent, which leads to deform the interface to break up. Effect of different riser heights was also studied by CFD simulations. The results show that the riser height has a significant role in the hydrodynamics of the tray, especially in uniform gas distribution in the tray and reducing weeping rates.     

Alcohol Synthesis from Syngas over K2CO3/CoS/MoS2 on Activated Carbon

Supported K₂CO₃/Co–MoS₂ on activated carbon was prepared by a co-impregnation technique and has been characterized by X-ray diffraction (XRD) and BET. Active ingredients ranged from 39 to 66% and included molysulfide and cobalt sulfide. XRD analysis indicates that cobalt and molybdenum sulfides are found in the Co₃S₄ and Co₉S₈ phases. These catalysts were performance tested in a fixed-bed reactor under higher alcohol synthesis conditions, 2000–2400 psig and 270–330°C. Active chemicals on the carbon extrudates decreased the surface area dramatically, as measured by BET. Surprisingly, at the high level of active chemicals, alcohol productivity and selectivity were decreased. An increase in the reaction temperature led to a decrease in the selectivity of methanol and an increase in selectivity of hydrocarbons. Total alcohol productivity was also increased as gas hourly space velocity (GHSV) was increased. Co₉S₈ may play a role in the catalyst aging process. In prolonged reaction periods (140 h), sulfur is lost from the surface, possibly as H₂S. The quantity of Co₉S₈ on the surface appears to increase as the catalyst ages.     

Fast automatic medical image segmentation based on spatial kernel fuzzy c-means on level set method

Fast two-cycle (FTC) model is an efficient and the fastest Level set image segmentation. But, its performance is highly dependent on appropriate manual initialization. This paper proposes a new algorithm by combining a spatially constrained kernel-based fuzzy c-means (SKFCM) algorithm and an FTC model to overcome the mentioned problem. The approach consists of two successive stages. First, the SKFCM makes a rough segmentation to select the initial contour automatically. Then, a fuzzy membership matrix of the region of interest, which is generated by the SKFCM, is used in the next stage to produce an initial contour. Eventually, the FTC scheme segments the image by a curve evolution based on the level set. Moreover, the fuzzy membership degree from the SKFCM is incorporated into the fidelity term of the Chan–Vese model to improve the robustness and accuracy, and it is utilized for the data-dependent speed term of the FTC. A performance evaluation of the proposed algorithm is carried out on the synthetic and real images. The experimental results show that the proposed algorithm has advantages in accuracy, computational time and robustness against noise in comparison with the KFCM, the SKFCM, the hybrid model of the KFCM and the FTC, and five different level set methods on medical image segmentation.     

Pre-processing data to predict groundwater levels using the fuzzy standardized evapotranspiration and precipitation index (SEPI)

Due to sudden declines in groundwater levels in Neyshabur Plain, one of the most important parts of water supply management programs at the catchment scale is to accurately predict the groundwater level fluctuations. In this paper, the rainfall data from 22 rain gauges and evapotranspiration stations during the period of 1974–2015 were used to find the cumulative effects of rainfall and evapotranspiration on fluctuations in groundwater levels. First, using the Hargreaves-Samani method, the modified evapotranspiration was calculated on the plain. Using the Kriging method, the average amount of precipitation and evapotranspiration of the reference plant was also calculated. Then, employing the fuzzy logic, the fuzzy standardized evapotranspiration and precipitation index (SEPI) was produced. The correlation results between SEPI indicator and fluctuations in groundwater levels showed that the long-term time scales had greater correlations. Thus, the correlations for the time scales of 30, 36, 42, 48, 54 and 60 months were respectively obtained as 0.56, 0.68, 0.71, 0.69, 0.59 and 046. These six parameters were used for principal components analysis (PCA) and the selection criteria (SC) index was used to select the properties affecting every component. The ranking results of testing local linear regression with PCA (LLR-PCA) and dynamic local linear regression with PCA (DLLR-PCA) models, Broyden, Fletcher, Goldfarb, Shanno algorithm with PCA (BFGS-PCA) neural network and Conjugate Gradient-PCA indicated that the DLLR model with three main components had the best performance so that the values of R², RMSE, MBE and MAE were obtained as 0.84, 0.215, 0.028 and 0.162, respectively. The results generally showed that due to severe linearity between SEPI indicator and its time scales, the use of PCA is essential for simulating fluctuations of the groundwater levels.     

Game theory based models to analyze water conflicts in the Middle Route of the South-to-North Water Transfer Project in China

This study applied game theory based models to analyze and solve water conflicts concerning water allocation and nitrogen reduction in the Middle Route of the South-to-North Water Transfer Project in China. The game simulation comprised two levels, including one main game with five players and four sub-games with each containing three sub-players. We used statistical and econometric regression methods to formulate payoff functions of the players, economic valuation methods (EVMs) to transform non-monetary value into economic one, cost-benefit Analysis (CBA) to compare the game outcomes, and scenario analysis to investigate the future uncertainties. The validity of game simulation was evaluated by comparing predictions with observations. The main results proved that cooperation would make the players collectively better off, though some player would face losses. However, players were not willing to cooperate, which would result in a prisoners' dilemma. Scenarios simulation results displayed that players in water scare area could not solve its severe water deficit problem without cooperation with other players even under an optimistic scenario, while the uncertainty of cooperation would come from the main polluters. The results suggest a need to design a mechanism to reduce the risk of losses of those players by a side payment, which provides them with economic incentives to cooperate.     

Unilateral digital clubbing in a hemodialysis patient

We present an unusual case of a chronic hemodialysis patient with moderate diffuse acrocyanosis and prominent unilateral clubbing of his right hand fingers, with classic physical features of hypertrophic osteoarthropathy. The patient's left hand, which had a functioning arteriovenous fistula, did not show any evidence of clubbing. We briefly discuss the different theories in regards to the pathogenesis of clubbing, and the potential role of arteriovenous fistula in preventing its occurrence.