Design and analysis of a diesel processing unit for a molten carbonate fuel cell for auxiliary power unit applications

Fuel cell-based auxiliary power units (APUs) are a promising technology for meeting global energy needs in an environmentally friendly way. This study uses diesel containing sulfur components such as dibenzothiophene (DBT) as a feed. The sulfur tolerance of molten carbonate fuel cell (MCFC) modules is not more than 0.5 ppm, as sulfur can poison the fuel cell and degrade the performance of the fuel cell module. The raw diesel feed in this study contains 10 ppm DBT, and its sulfur concentration should be reduced to 0.1 ppm. After desulfurization, the feed goes through several unit operations, including steam reforming, water-gas shift, and gas purification. Finally, hydrogen is fed to the fuel cell module, where it generates 500 kW of electrical energy. The entire process, with 52% and 89% fuel cell and overall system efficiencies, respectively, is rigorously simulated using Aspen HYSYS, and the results are input into a techno-economic analysis to calculate the minimum electricity selling price (MESP). The electricity cost for this MCFC-based APU was calculated as 1.57$/kWh. According to predictions, the cost reductions for fuel cell stacks will afford electricity selling prices of 1.51$/kWh in 2020 and 1.495$/kWh in 2030. Based on a sensitivity analysis, the diesel price and capital cost were found to have the strongest impact on the MESP.     

New approach to bone tissue engineering: simultaneous application of hydroxyapatite and bioactive glass coated on a poly(L-lactic acid) scaffold

A combination of bioceramics and polymeric nanofibers holds promising potential for bone tissue engineering applications. In the present study, hydroxyapatite (HA), bioactive glass (BG), and tricalcium phosphate (TCP) particles were coated on the surface of electrospun poly(L-lactic acid) (PLLA) nanofibers, and the capacity of the PLLA, BG-PLLA, HA-PLLA, HA-BG-PLLA, and TCP-PLLA scaffolds for bone regeneration was investigated in rat critical-size defects using digital mammography, multislice spiral-computed tomography (MSCT) imaging, and histological analysis. Electrospun scaffolds exhibited a nanofibrous structure with a homogeneous distribution of bioceramics along the surface of PLLA nanofibers. A total of 8 weeks after implantation, no sign of complication or inflammation was observed at the site of the calvarial bone defect. On the basis of imaging analysis, a higher level of bone reconstruction was observed in the animals receiving HA-, BG-, and TCP-coated scaffolds compared to an untreated control group. In addition, simultaneous coating of HA and BG induced the highest regeneration among all groups. Histological staining confirmed these findings and also showed an efficient osseointegration in HA-BG-coated nanofibers. On the whole, it was demonstrated that nanofibrous structures could serve as an appropriate support to guide the healing process, and coating their surface with bioceramics enhanced bone reconstruction. These bioceramic-coated scaffolds can be used as new bone-graft substitutes capable of efficiently inducing osteoconduction and osseointegration in orthopedic fractures and defects.     

Performance evaluation of Web server workloads in Xen‐based virtualized computer system: analytical modeling and experimental validation

Recent developments in the field of virtualization technologies have led to renewed interest in performance evaluation of these systems. Nowadays, maturity of virtualization technology has made a fuss of provisioning IT services to maximize profits, scalability and QoS. This pioneer solution facilitates deployment of datacenter applications and grid and Cloud computing services; however, there are challenges. It is necessary to investigate a trade‐off among overall system performance and revenue and to ensure service‐level agreement of submitted workloads. Although a growing body of literature has investigated virtualization overhead and virtual machines interference, there is still lack of accurate performance evaluation of virtualized systems. In this paper, we present in‐depth performance measurements to evaluate a Xen‐based virtualized Web server. Regarding this experimental study; we support our approach by queuing network modeling. Based on these quantitative and qualitative analyses, we present the results that are important for performance evaluation of consolidated workloads on Xen hypervisor. First, demands of both CPU intensive and disk intensive workloads on CPU and disk are independent from the submitted rate to unprivileged domain when dedicated core(s) are pinned to virtual machines. Second, request response time not only depends on processing time at unprivileged domain but also pertains to amount of flipped pages at Domain 0. Finally, results show that the proposed modeling methodology performs well to predict the QoS parameters in both para‐virtualized and hardware virtual machine modes by knowing the request content size. Copyright © 2015 John Wiley & Sons, Ltd.     

Fundus laser coagulation using a video system of scanning laser ophthalmoscope

We modified a scanning laser ophthalmoscope for simultaneous photocoagulation of the retina and video recording. Using a diode laser (810 nm wavelength), we produced fundus lesions that scarred within 14 days.     

Tragacanth gum-graft-polyacrylonitrile: synthesis,characterization and hydrolysis

A large number of cyanide functional groups were introduced onto the carbohydrate biopolymer tragacanth gum to yield hydrophobic graft copolymer, tragacanth gum-g-polyacrylonitrile. Thus, graft copolymerization of monomer acrylonitrile (AN) was carried out under nitrogen atmosphere using ceric ammonium nitrate (CAN) as an initiator. The highest percentage of grafting (543%) and the lowest homopolymer content (10%) were achieved through a systematic optimization of the polymerization variables, including reaction time, temperature, and concentration of CAN, AN and the gum. Evidence of grafting was examined by comparing FTIR spectra. The optimally prepared tragacanth gum-g-polyacrylonitrile copolymer was also characterized thermally and morphologically. It was hydrolyzed in alkaline medium to achieve an in-situ crosslinked hybrid network with ultra high water absorption capacity (swelling in water, 30700%; swelling in saline, 6550%). The swelling characteristic of the semi-synthetic super-absorbent hydrogel was preliminarily investigated. The chemical structure, thermal characteristics and morphology of the hydrogel hybrid product were briefly studied.     

Inverse shape design for heat conduction problems via the ball spine algorithm

ABSTRACT

In this article, a novel iterative physical-based method is introduced for solving inverse heat conduction problems. The method extends the ball spine algorithm concept, originally developed for inverse fluid flow problems, to inverse heat conduction problems by employing a subtle physical-sense rule. The inverse problem is described as a heat source embedded within a solid medium with known temperature distribution. The object is to find a body configuration satisfying a prescribed heat flux originated from a heat source along the outer surface. Performance of the proposed method is evaluated by solving many 2-D inverse heat conduction problems in which known heat flux distribution along the unknown surface is directly related to the Biot number and surface temperature distribution arbitrarily determined by the user. Results show that the proposed method has a truly low computational cost accompanied with a high convergence rate.     

Induced superabsorbency in polyester fiber

Modified polyester fibers are considered as a significant part of the polyester produced throughout the world due to the new properties and also reduced undesirable properties, compared to non-modified polyester fibers. In this study, the modification of polyester fiber properties was evaluated for its superabsorbency. The fibers obtained superabsorbency by their treatment with a special latex prepared by inverse emulsion polymerization. Different polymer latexes based on acrylic acid, sodium acrylate, acrylamide (AM) and 2-acrylamide-2-methyl propane sulfonic acid were prepared using inverse emulsion polymerization. Chemical bond (or hydrogen bond) was formed between the functional groups of the fiber surface and functional groups present in the polymer latex by heating. The modified fibers were characterized by swelling, mechanical, morphological, and thermal measurements. The effect of several modifications of parameters such as latex type, AM content in latex, aquatic-organic phase ratios of latex, modification time and modification temperature on the swelling properties of fibers were investigated. Water absorption of the unmodified fiber was 1.5 g/g which increased up to 75 g/g, significantly. This considerable development in hydrophilic characteristics of polyester fibers has led to water blocking of the fiber. Such modification did not have adverse effects on the tensile properties or thermal resistance of the polyester fiber.