An adaptive tabu search approach for buffer allocation problem in unreliable non-homogenous production lines

The buffer allocation problem, i.e. how much buffer storage to allow and where to place it within the line, is an important research issue in designing production lines. In this study, a novel adaptive tabu search approach is proposed for solving buffer allocation problem in unreliable and non-homogeneous production lines. The objective is to maximize the throughput of the line, which is constrained by the capacity of each buffer space and also the total buffer capacity to allocate to these spaces. Besides proposing a new strategy to tune the parameters of tabu search adaptively during the search, an experimental study is carried out to select an intelligent initial solution scheme among three alternatives so as to decrease the search effort to obtain the best solutions. The performance of the proposed approach is evaluated by computational tests and very promising results are obtained.     

Effects of sintering and zirconmullite doping on nanostructural vacancies of bovine hydroxyapatite by positron techniques

In this study, the nanostructural vacancy behavior of bovine derived hydroxyapatite (BHA) doped with powder zirconmullite (ZM) contents of 5, 7.5, 10 and 12.5 wt.% were presented at sintering temperatures of 1000, 1100, 1200 and 1300°C. ZM-doped BHA (ZM-BHA) was characterized by X-ray diffraction and positron annihilation lifetime spectroscopy (PALS). Density and hardness behavior were measured with respect to increasing sintering temperature. PALS results indicate that the longest lifetime component τ₃ of ortho-positronium (o-Ps) localized at open spaces is attributed to the vacancy site and almost constant with the ZM contents and the sintering temperatures to have a mean value of 0.680 ns (corresponding to the radius of 0.997 nm). This average value is ascribed to the OH group defects along the main crystalline line. On the other hand, the o-Ps intensity attributed to the number of vacancy sites increases almost linearly with ZM additives and sintering temperatures. The intensity is also related to the density and hardness of ZM-BHA in terms of ZM contents.     

Microwave-assisted sol–gel synthesis of alpha alumina nanopowder and study of the rheological behavior

In the present work, alpha alumina nanopowder was synthesized via a sol–gel route. After preparation of bohemite (AlOOH) sol, carbon black was added and the resultant sol was dried and calcined in microwave furnace for 10 min. XRD results showed that alpha alumina was the only crystalline phase with specific surface area, mean diameter and crystallite size of 51 m² g^?1, 100 and 25 nm, respectively. Rheological measurements revealed that the optimal content of Tiron at pH=10 is 1 and 0.1 g per 100 g nano- and micron-alumina (1.5 m² g^?1), respectively. Furthermore, the optimum solid content of the slips was determined as 35–45 and 70 wt.% for nano- and micron-alumina, respectively.     

Selective extraction of phosphatidylcholine from lecithin by supercritical carbon dioxide/ethanol mixture

Selective extraction of phosphatidylcholine (PC) from deoiled soybean lecithin using supercritical fluid (SCF) mixtures of carbon dioxide (CO₂) and ethanol was studied at moderate pressures. Temperature was varied between 60 and 80°C at pressures of 17.2 and 20.7 MPa. Ethanol was added as co-solvent to supercritical CO₂ at the levels of 10 and 12.5 wt%. Constant rate of extraction of the individual phospholipids (PL) was observed for 150 min during which the extractions were carried out. Pressure and ethanol fraction had a positive effect on the selective extraction of PC, whereas temperature had a negative effect. Under all the conditions studied, the extracts were mainly composed of PC while the extraction of the other PL was very low. Extraction at 60°C and 20.7 MPa with 10 wt% ethanol/90 wt% CO₂ SCF mixture resulted in 95% selectivity to PC.     

Effects of meteorological variables on exergetic efficiency of wind turbine power plants

This present paper deals with exergy efficiency results of the Wind Turbine Power Plants (WTPPs). Effects of meteorological variables such as air density, pressure difference between state points, humidity, and ambient temperature on exergy efficiency are discussed in a satisfactory way. Some key parameters are given monthly for the three turbines. Exergy efficiency differs from 0.23 to 0.27 while temperature is changing from 268.15 K to 308.15 K with air density 1.368–1.146 (kg/m³). While pressure difference (ΔP) between inlet and outlet of the turbine differs from 100 to 1100 (Pa), exergy efficiency decreases fairly for different wind speeds. While specific humidity is changing from 0.001 to 0.015 (kg_water/kg_{dry air}), exergy efficiency decreases gently. Generally these meteorological variables are neglected while planning WTPPs, but this neglect can cause important errors in calculations and energy plans. Obtained results indicate that while planning WTPPs meteorological variables must be taken into account.     

Extending the Colloidal Transition Metal Dichalcogenide Library to ReS2 Nanosheets for Application in Gas Sensing and Electrocatalysis

Among the large family of transition metal dichalcogenides, recently ReS₂ has stood out due to its nearly layer‐independent optoelectronic and physicochemical properties related to its 1T distorted octahedral structure. This structure leads to strong in‐plane anisotropy, and the presence of active sites at its surface makes ReS₂ interesting for gas sensing and catalysts applications. However, current fabrication methods use chemical or physical vapor deposition (CVD or PVD) processes that are costly, time‐consuming and complex, therefore limiting its large‐scale production and exploitation. To address this issue, a colloidal synthesis approach is developed, which allows the production of ReS₂ at temperatures below 360 °C and with reaction times shorter than 2h. By combining the solution‐based synthesis with surface functionalization strategies, the feasibility of colloidal ReS₂ nanosheet films for sensing different gases is demonstrated with highly competitive performance in comparison with devices built with CVD‐grown ReS₂ and MoS₂. In addition, the integration of the ReS₂ nanosheet films in assemblies together with carbon nanotubes allows to fabricate electrodes for electrocatalysis for H₂ production in both acid and alkaline conditions. Results from proof‐of‐principle devices show an electrocatalytic overpotential competitive with devices based on ReS₂ produced by CVD, and even with MoS₂, WS₂, and MoSe₂ electrocatalysts.     

Radiobiological and Treatment-Related Aspects of Spatially Fractionated Radiotherapy

The continuously evolving field of radiotherapy aims to devise and implement techniques that allow for greater tumour control and better sparing of critical organs. Investigations into the complexity of tumour radiobiology confirmed the high heterogeneity of tumours as being responsible for the often poor treatment outcome. Hypoxic subvolumes, a subpopulation of cancer stem cells, as well as the inherent or acquired radioresistance define tumour aggressiveness and metastatic potential, which remain a therapeutic challenge. Non-conventional irradiation techniques, such as spatially fractionated radiotherapy, have been developed to tackle some of these challenges and to offer a high therapeutic index when treating radioresistant tumours. The goal of this article was to highlight the current knowledge on the molecular and radiobiological mechanisms behind spatially fractionated radiotherapy and to present the up-to-date preclinical and clinical evidence towards the therapeutic potential of this technique involving both photon and proton beams.     

Spouted bed and microwave-assisted spouted bed drying of parboiled wheat

The effect of spouted bed and microwave-assisted spouted bed drying on drying rates of parboiled wheat was investigated. In addition, the effective moisture diffusivities of parboiled wheat were calculated. The drying experiments were performed using 200 g of parboiled wheat, at three different air temperatures (50, 70, 90 °C) and at two different microwave powers (3.5 W/g (db), 7.5 W/g (db)). Microwave-assisted spouted bed drying at microwave power of 3.5 W/g and 7.5 W/g reduced drying time by at least 60% and 85%, respectively compared to spouted bed drying. The effective diffusivity values were in the range of 1.44 × 10^?10–3.32 × 10^?10 in spouted bed drying while they were between 5.06 × 10^?10 and 11.3 × 10^?10 in microwave-assisted spouted bed drying at different experimental conditions.     

Urban adolescents' constructions of supports and barriers to educational and career attainment.

This study presents the educational and career goals and perceptions of supports and barriers related to these goals as described in semistructured interviews of 16 students from diverse racial and ethnic backgrounds attending 9th grade at an urban public high school in a large Northeastern city. Using consensual qualitative research (CQR) methodology (C. E. Hill et al., 2005), the authors identified categories and subcategories to students' perceptions of barriers and supports. The findings highlight students' understanding of how their proximal contexts serve potentially as both supports and barriers. Implications for educational and career interventions are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)