Selecting the best stochastic systems for large scale engineering problems

Selecting a subset of the best solutions among large-scale problems is an important area of research. When the alternative solutions are stochastic in nature, then it puts more burden on the problem. The objective of this paper is to select a set that is likely to contain the actual best solutions with high probability. If the selected set contains all the best solutions, then the selection is denoted as correct selection. We are interested in maximizing the probability of this selection; P(CS). In many cases, the available computation budget for simulating the solution set in order to maximize P(CS) is limited. Therefore, instead of distributing these computational efforts equally likely among the alternatives, the optimal computing budget allocation (OCBA) procedure came to put more effort on the solutions that have more impact on the selected set. In this paper, we derive formulas of how to distribute the available budget asymptotically to find the approximation of P(CS). We then present a procedure that uses OCBA with the ordinal optimization (OO) in order to select the set of best solutions. The properties and performance of the proposed procedure are illustrated through a numerical example. Overall results indicate that the procedure is able to select a subset of the best systems with high probability of correct selection using small number of simulation samples under different parameter settings

Recent progress on nanomaterial-based membranes for water treatment

Nanomaterials have emerged as the new future generation materials for high-performance water treatment membranes with potential for solving the worldwide water pollution issue. The incorporation of nanomaterials in membranes increases water permeability, mechanical strength, separation efficiency, and reduces fouling of the membrane. Thus, the nanomaterials pave a new pathway for ultra-fast and extremely selective water purification membranes. Membrane enhancements after the inclusion of many nanomaterials, including nanoparticles (NPs), two-dimensional (2-D) layer materials, nanofibers, nanosheets, and other nanocomposite structural materials, are discussed in this review. Furthermore, the applications of these membranes with nanomaterials in water treatment applications, that are vast in number, are highlighted. The goal is to demonstrate the significance of nanomaterials in the membrane industry for water treatment applications. It was found that nanomaterials and nanotechnology offer great potential for the advancement of sustainable water and wastewater treatment.Internal Qatar University grant QUCG-CENG-21/22-4 and Qatar National Research Fund grant NPRP12S-0306-190247.Scopu

Efficient Approach for Selecting the Best Subset of Buffer Profile

Abstract One of the main problems with designing a production line is to find the optimal number of buffers between workstations in order to maximizes the throughput. This problem known as buffer allocation problem. Previous work in this problem focus on selecting a single buffer profile that has the maximum throughput. The objective in this paper would be to selecting from a large number of alternatives, the best subset of buffer profiles where its throughput are at its maximum. The ordinal optimization with optimal computing budget allocation approaches will be used to isolating the best subset of buffer profile, where its throughput is maximum, from the set of all alternatives. Numerical results show that the proposed algorithm finds the best subset of the puffer allocation with high probability and small replications numbers of samples

Diazepam induced oxidative DNA damage in cultured human lymphocytes

Diazepam is a benzodiazepine compound that is mainly used for anxiety, muscle spasms, seizures and insomnia. Several studies have shown that long-term Diazepam treatment is associated with oxidative stress. In this study, the possible genotoxic effect of Diazepam was examined in cultured human white blood cells using the sister chromatid exchanges (SCEs), chromosomal aberrations (CAs) and 8-hydroxy-deoxyguanosine (8-OHdG) assays. Treatment of cultured lymphocytes with different concentrations of Diazepam (1, 10 and 100 µg/mL) did not induce chromosomal DNA damage as measured using SCEs and CAs assays (P > 0.05). In addition, no effect was observed on mitotic and proliferative indices (P > 0.05). However, Diazepam induced oxidative DNA damage as measured by the 8-OHdG assay in a dose dependent manner (P < 0.001). In conclusion, Diazepam seems to induce oxidative DNA damage in cultured human lymphocytes. More in vivo studies are required to confirm current finding. Keywords: Diazepam, 8-OHdG, DNA damage, Chromosomal aberrations, Lymphocyte

Over-pumping of groundwater in Irbid governorate, northern Jordan: a conceptual model to analyze the effects of urbanization and agricultural activities on groundwater levels and salinity

The governorate of Irbid has the highest population density in Jordan and most of its water demand is supplied by groundwater. Both natural population growth and waves of migrations increased the number of its inhabitants during the last 40 years. This population growth has increased: the amount of land covered by urban and agricultural development over this time period; and the groundwater demand by 227% due to increasing of drinking water demand, urban water usage and for agricultural irrigation. As a result of the continuous pumping, groundwater levels have decreased by about 70 m and the salinity of pumped groundwater has increased by about 1000 µS/cm in some areas. A conceptual model to account for the observed changes in groundwater levels and salinity has been developed through an integrated approach of remote sensing and geographic information systems

Enhancement of Temperature Fluorescence Brightness of Zn@Si Core-Shell Quantum Dots Produced via a Unified Strategy

Despite many dedicated efforts, the fabrication of high-quality ZnO-incorporated Zinc@Silicon (Zn@Si) core&ndash;shell quantum dots (ZnSiQDs) with customized properties remains challenging. In this study, we report a new record for the brightness enhancement of ZnSiQDs prepared via a unified top-down and bottom-up strategy. The top-down approach was used to produce ZnSiQDs with uniform sizes and shapes, followed by the bottom-up method for their re-growth. The influence of various NH4OH contents (15 to 25 &micro;L) on the morphology and optical characteristics of ZnSiQDs was investigated. The ZnSiQDs were obtained from the electrochemically etched porous Si (PSi) with Zn inclusion (ZnPSi), followed by the electropolishing and sonication in acetone. EFTEM micrographs of the samples prepared without and with NH4OH revealed the existence of spherical ZnSiQDs with a mean diameter of 1.22 to 7.4 nm, respectively. The emission spectra of the ZnSiQDs (excited by 365 nm) exhibited bright blue, green, orange-yellow, and red luminescence, indicating the uniform morphology related to the strong quantum confinement ZnSiQDs. In addition, the absorption and emission of the ZnSiQDs prepared with NH4OH were enhanced by 198.8% and 132.6%, respectively. The bandgap of the ZnSiQDs conditioned without and with NH4OH was approximately 3.6 and 2.3 eV, respectively

Solar co-production of samarium and syngas via methanothermal reduction of samarium sesquioxide

This paper reports the thermodynamic analysis of the solar methanothermal reduction of Sm2O3 for the co-production of Sm and syngas in (a) Sm-Syngas open cycle, and (b) Sm-Syngas closed cycle. As per the chemical thermodynamic equilibrium modeling, the conversion of Sm2O3 into Sm increase with the increase in the CH4/Sm2O3 ratio and 100% conversion is possible at 2528 K if CH4/Sm2O3 ratio is equal to 3 is used. Exergy efficiency analysis of both open and closed cycles indicate that the QSm2O3-reduction, Qsolar, Qre-radiation, and Qquench increases with the increase in the CH4/Sm2O3 ratio. Likewise, WFC-Ideal-1, QFC-Ideal-1, and HHVsyngas-1 also increases with the upsurge in the CH4/Sm2O3 ratio. Similar observations were realized in case of Sm-Syngas closed cycle. The ?exergy (33.91%) and ?solar-to-fuel (45.93%) of the Sm-Syngas open cycle was observed to be maximum in case of CH4/Sm2O3 ratio = 3. As one of the applications, Sm was utilized toward splitting of H2O and CO2 together for the production of syngas via Sm-Syngas closed cycle. At similar operating conditions, the ?exergy-closed (45.22%) and ?solar-to-fuel-closed (61.24%) of the Sm-Syngas closed cycle was observed to be higher as compared to the Sm-Syngas open cycle. Furthermore, it was observed that, these efficiency values can be increased significantly due to the utilization of higher values of C and recycling of the heat rejected by the quench unit and H2O/CO2 splitting reactor.The authors gratefully acknowledge the financial support provided by the Qatar University Internal Grant ( QUUG-CENG-CHE-14 ? 15-10 ).Scopu