Coding graphene metasurface modeling using MoM‐GEC method for dynamic diffusion and scattering control at Terahertz range

In this article, we present an electromagnetic study of electrically programmable graphene‐based metasurface with individual scattering control. Our investigation is based on the method of moments combined with the generalized equivalent circuit (MoM‐GEC) approach. We show that, tuning the unit cell's conductivity leads to change its input impedance and scattering matrix. So, each unit cell of the metasurface exhibits' a dynamic phase response that can be switched between 0° and ?180° by controlling high transmission and total reflection states. Based on this feature, a 1‐bit coding metasurface consisting of discrete codes of “0” and “1” is used to synthesis 3D beams. Hence, tailorable anomalous reflection and diffusion are studied under normal incidence at a fixed frequency of 3.9 THz. This survey opens new opportunities in the domain of Terahertz beam engineering and security scanner applications.     

A robust hybrid artificial neural network double frontier data envelopment analysis approach for assessing sustainability of power plants under uncertainty

To assess sustainability of power plants, this paper presents a novel hybrid method. To this end, self‐organizing map method of artificial neural networks is employed. Then, a double frontier data envelopment analysis is developed to rank power plants in each cluster of decision‐making units. Because outputs of power plants might be uncertain, a robust optimization approach is incorporated into proposed double frontier data envelopment analysis model to present ranks that are robust against different uncertainties. A case study is given to validate the proposed model. The case study shows that the proposed model can present improvement solutions that guide power plants towards efficient frontier and far from inefficient frontier. Given the results, decision makers can decide on which power plants should be closed and which power plants should be expanded.     

Localization of RFID-equipped assets during the operation phase of facilities

Indoor localization has gained importance as it has the potential to improve various processes related to the lifecycle management of facilities and to deliver personalized and location-based services (LBSs). Radio Frequency Identification (RFID) based systems, on the other hand, have been widely used in different applications in construction and maintenance. This paper investigates the usage of RFID technology for indoor localization of RFID equipped assets during the operation phase of facilities. The location-related data on RFID tags attached to assets are extracted from a Building Information Model (BIM) and can provide context-aware information inside the building which can improve Facilities Management (FM) processes. First, using the current location of the assets saved on the tags attached to fixed assets, an FM personnel is able to read tags from a distance and locate them on a floor plan. Fixed tags with known positions act as reference tags for RFID reader localization techniques. In this scenario, the user can also estimate his/her location by scanning the surrounding reference tags. Furthermore, the paper investigates an approach to locate moveable assets using received signals from available reference tags in the building based on pattern matching and clustering algorithms. As a result, a user equipped with an RFID reader is able to estimate his/her location, as well as the location of target assets, without having access to any Real-Time Location System (RTLS) infrastructure. Several case studies are used to demonstrate the feasibility of the proposed methods.     

Ultrasound-assisted adsorption of textile dyes using modified nanoclay: Central composite design optimization

The removal of two anionic dyes, C.I. Acid Orange 7 (AO7) and C.I. Acid Red 17 (AR17), by ultrasound-assisted adsorption on the modified nanoclay in aqueous solutions was studied. The modified nanoclay was characterized by SEM/EDX, BET, XRD and FT-IR techniques. The average crystal size for the interlayer spacing of the modified nanoclay was about 14.3 nm. Central composite design (CCD) was used for the optimization of the operational parameters, including the initial dye concentration, sonication time, adsorbent dosage and temperature. The results demonstrated a good agreement between the predicted values obtained by the model and the experimental values for both AO7 (R²= 0.959) and AR17 (R²=0.971).     

Application of response surface methodology and central composite rotatable design for modeling the influence of some operating variables of the lab scale thickener performance

This study discussed the application of response surface methodology (RSM) and central composite rotatable design (CCRD) for modeling and optimization of the influence of some operating variables on the performance of a lab scale thickener for dewatering of tailing in the flotation circuit. Four thickener operating variables, namely feed flowrate, solid percent, flocculant dosage and feedwell height were changed during the tests based on CCRD. The ranges of values of the thickener variables used in the design were a feed flowrate of 9–21 L/min, solid percent of 8%–20%, flocculant dosage of 1.25–4.25 g/t and feedwell height of 16–26 cm. A total of 30 thickening tests were conducted using lab scale thickener on flotation tailing obtained from the Sarcheshmeh copper mine, Iran. The underflow solid percent and bed height were expressed as functions of four operating parameters of thickener. Predicted values were found to be in good agreement with experimental values (R² values of 0.992 and 0.997 for underflow solid percent and bed height, respectively). This study has shown that the RSM and CCRD could efficiently be applied for the modeling of thickener for dewatering of flotation tailing.     

Convex cone-based ranking of decision-making units in DEA

OR Spectrum - One of the major research streams in data envelopment analysis (DEA) is ranking decision-making units (DMUs). Utilizing a multicriteria decision-making technique, we develop a novel...     

Current technologies in the extraction,enrichment and analytical detection of tocopherols and tocotrienols: A review

During the past few years the scientific and medical community has been confronted with a continual interest in vitamin E with the interest prompted by new discoveries. Tocopherols and tocotrienols, commonly known as vitamin E, are extremely invaluable compounds and have various nutritional functionalities and benefits to human health. Great deals of research projects have been launched in order to develop effective methods for the extraction of vitamin E. By and large, three distinct extractive methods are usually employed: supercritical fluid extraction (SFE), molecular distillation, and adsorption methods. These methods are sensitive to different experimental conditions, such as pressure, temperature, and flow rate with noticeable effects on the efficiency of the extraction and enrichment of vitamin E. This review has covered the most commonly adapted extraction methods and has probed into the extraction yields under variable operational parameters.