Concurrent estimation of efficiency,effectiveness and returns to scale

In recent years, data envelopment analysis (DEA) has been widely used to assess both efficiency and effectiveness. Accurate measurement of overall performance is a product of concurrent consideration of these measures. There are a couple of well-known methods to assess both efficiency and effectiveness. However, some issues can be found in previous methods. The issues include non-linearity problem, paradoxical improvement solutions, efficiency and effectiveness evaluation in two independent environments: dividing an operating unit into two autonomous departments for performance evaluation and problems associated with determining economies of scale. To overcome these issues, this paper aims to develop a series of linear DEA methods to estimate efficiency, effectiveness, and returns to scale of decision-making units (DMUs), simultaneously. This paper considers the departments of a DMU as a united entity to recommend consistent improvements. We first present a model under constant returns to scale (CRS) assumption, and examine its relationship with one of existing network DEA model. We then extend model under variable returns to scale (VRS) condition, and again its relationship with one of existing network DEA models is discussed. Next, we introduce a new integrated two-stage additive model. Finally, an in-depth analysis of returns to scale is provided. A case study demonstrates applicability of the proposed models.     

Structural insights of mechanically induced aluminum-doped hydroxyapatite nanoparticles by Rietveld refinement

Aluminum doped hydroxyapatite(HA:Al~(3+)) nanopowders were successfully prepared via a simple and efficient one-pot mechanochemical route. The effects of dopant loading on phase compositions and structural features were assessed by Rietveld analysis. The XRD-Rietveld refinement revealed the stabilization of HA in hexagonal structure for all the samples. The sharpness and intensity of the apatite-derived XRD peaks decreased as the dopant content increased to 10% due to the increase in lattice imperfections and mechanically induced amorphization. The incorporation of Al3+into the HA lattice decreased the unit cell parameters. From the FTIR measurements, the representing bands of apatite were identified in all cases. The mechanosynthesized nanopowders consisted of nanospheroids with an average size of 44 ± 20 nm and therefore are promising for bone tissue regeneration.     

Using the Fuzzy Clustering and Principle Component Analysis for Assessing the Impact of Potential Evapotranspiration Calculation Method On the Modified RDI Index

The modified reconnaissance drought index (RDIe) which is a modified version of RDI is presented for assessing drought conditions with an emphasis on agricultural drought. The potential evapotranspiration (PET) and effective rainfall are required climatic variables to calculate RDIe. Although the FAO Penman–Monteith (FPM) equation is the reference method for determining the PET, due to the need for data of a large number of climatic variables it is difficult to use in areas with shortage climatic data. Therefore, in this research, using the fuzzy clustering (FC) and principle component analysis (PCA) methods, the influence of PET calculation methods including FPM (used as reference method), FAO Penman (FP), Hargreaves-Samani (HS), Blaney-Criddle (BC), Turc (Tu), Jensen-Haise (JH), Priestley–Taylor (PT) and FAO24 Radiation (Ra) methods on the RDIe (in 1, 3 and 12-month time scales) was assessed. In this study the climatic data series of 5 stations in Fars province, Iran from 1989 to 2018 was used. Based on the results of PCA model, in short-term time scales (1 and 3-month), the calculated RDIe values based on the HS method (at 100% of stations) and in long-term time scale (annual) based on the FP method (at 60% of stations) had the highest correlation with RDIe based on the FPM method. According to the results of FC method, in 1-month time scale, the values of RDIe using PT and HS methods (at 100% and 80% of selected stations, respectively), in 3-month time scale, the values of RDIe using PT, HS and Ra methods (at 100% of stations) and in annual time scale, the values of RDIe using FP method (at 60% of stations) had the highest similarities with the values of RDIe using FPM. Therefore, it is recommended to replace the FPM method with HS (in 1 and 3-month time scales) and FP (in 12-month time scales) methods in areas with minimum available meteorological data.

     

A Novel Predictive Technique for Estimating the Hydrate Inhibition Effects of Single and Mixed Thermodynamic Inhibitors

A new correlation has been developed for predicting hydrate inhibition characteristics, as well as water freezing point depression of aqueous solutions containing salts and/or organic inhibitors. The correlation has been developed using hydrate inhibition/freezing point depression data at different concentrations of salt and/or organic inhibitor generated using a previously reported thermodynamic model. Independent data have been used in examining the reliability of this method. The predictions of this correlation are in acceptable agreement with the independent experimental data, demonstrating the reliability of this predictive technique for estimating the hydrate inhibition effects of salts and/or organic inhibitors.     

An Adaptable Job Submission System Based on Moderate Price-Adjusting Policy in Market-Based Grids

A market-based computational grid is made up of large sets of heterogeneous and geographically distributed resources that are gathered into virtual organizations for executing consumer’s applications. One of the most important challenges in market-based grid systems is the management of grid users, which is called resource providers and consumers. The existing methods provide some alternative mechanisms for this problem, but they are not fully adequate. To address this problem, we propose an enhanced approach for adjusting price of grid resource using new effective parameters of microeconomic issue and also for prioritizing current jobs in the queue. This proposed approach is integrated with a cooperative method among local schedulers to accept jobs based on auction model. The results conclude that the inclusion of new parameters in price-adjusting affects the payment budget and job submission behavior of the schedulers. The evaluations of experimental results prove a remarkable performance of the proposed approach in diverse conditions and job workloads.     

Material removal mechanism in ultrasonic-assisted grinding of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> by single-grain scratch test

Alumina is an advanced ceramic that is frequently used in high-performance applications. Grinding of alumina is usually associated with micro-cracks and deteriorated surface quality. Ultrasonic-assisted grinding has been introduced in several applications as a promising method to overcome these constraints. In order to get a deeper knowledge of the characteristics of material removal mechanisms in alumina during grinding with ultrasonic stimulation of the workpiece, single-grain scratch tests were performed and the theoretical and experimental kinematics of grain-workpiece engagement were investigated. It was shown that in the real contact conditions, interrupted contact conditions happen, which is analogous to the theoretical model. The measured workpiece resonance frequency and mode shape were very close to the design conditions. The investigations show that the superposition of ultrasonic vibration into the grinding process increases the material removal of each grain. This result fully correlates with the presented theoretical analysis. Additionally, it was found that the impact action of ultrasonic-assisted grinding induces chipping around the produced scratch.     

A new method for scaling of earthquake records using input energy of structures

Nonlinear response history analysis is conducted as the most trusted and accurate method in the seismic analysis and design of buildings. Since the selection of appropriate records is inherent in this procedure, numerous attempts have been made to use earthquake records that represent a good prediction of future earthquakes. Scaling existing earthquake records is considered as one of the most important tools to fulfill this goal. This paper introduces a new method for scaling ground motion time histories in which elastic input energy is considered as intensity measure. In the new scaling procedure, the scale factor is obtained by minimizing the residual between the elastic input energy of structures for the desired records and the maximum probable input energy of the target spectrum. The efficiency and the accuracy of the proposed method are evaluated and compared with those resulting from the method of ASCE/SEI 7. The results demonstrate that the records scaled with the proposed method lead to more accurate and efficient demand parameters.     

Effect of Ablation Casting on Microstructure and Casting Properties of A356 Aluminium Casting Alloy

Recently the Ablation Casting Technology was invented as a new casting process to improve foundry products quality. In this study, the effects of processing variables on the porosity content, microstructure and feedability of A356 casting alloy were investigated. Secondary dendrite arm spacing (SDAS) and eutectic silicon morphologies were studied to evaluate the influence of Ablation Casting on the microstructure. Casting density was measured in order to identify porosity content and feedability of ablated and nonablated specimens. In addition, solidification behavior of the samples was investigated by using thermal analysis technique. The cooling curves and the first derivative curves were plotted and compared with each other. Results showed the ablation process could increase solidification rate significantly. In addition, the microstructural evidences revealed that Ablation Casting process results in more fine and homogeneous structure compared to the nonablated casting. The feedability improved, SDAS reduced to 35% and porosity content decreased to 3.84 vol.% by implementing this process. It concluded the Ablation Casting is an effective process to gain higher quality in aluminum foundry.