Dynamic reliability-based robust design optimization with time-variant probabilistic constraints

With the increasing complexity of engineering systems, ensuring high system reliability and system performance robustness throughout a product life cycle is of vital importance in practical engineering design. Dynamic reliability analysis, which is generally encountered due to time-variant system random inputs, becomes a primary challenge in reliability-based robust design optimization (RBRDO). This article presents a new approach to efficiently carry out dynamic reliability analysis for RBRDO. The key idea of the proposed approach is to convert time-variant probabilistic constraints to time-invariant ones by efficiently constructing a nested extreme response surface (NERS) and then carry out dynamic reliability analysis using NERS in an iterative RBRDO process. The NERS employs an efficient global optimization technique to identify the extreme time responses that correspond to the worst case scenario of system time-variant limit state functions. With these extreme time samples, a kriging-based time prediction model is built and used to estimate extreme responses for any given arbitrary design in the design space. An adaptive response prediction and model maturation mechanism is developed to guarantee the accuracy and efficiency of the proposed NERS approach. The NERS is integrated with RBRDO with time-variant probabilistic constraints to achieve optimum designs of engineered systems with desired reliability and performance robustness. Two case studies are used to demonstrate the efficacy of the proposed approach.     

Lyophilized insulin nanoparticles prepared from quaternized N-aryl derivatives of chitosan as a new strategy for oral delivery of insulin: in vitro,ex vivo and in vivo characterizations

Objective: The purpose of this research was the development, in vitro, ex vivo and in vivo characterization of lyophilized insulin nanoparticles prepared from quaternized N-aryl derivatives of chitosan.

Methods: Insulin nanoparticles were prepared from methylated N-(4-N,N-dimethylaminobenzyl), methylated N-(4 pyridinyl) and methylated N-(benzyl). Insulin nanoparticles containing non-modified chitosan and also trimethyl chiotsan (TMC) were also prepared as control. The effects of the freeze-drying process on physico-chemical properties of nanoparticles were investigated. The release of insulin from the nanoparticles was studied in vitro. The mechanism of the release of insulin from different types of nanoparticles was determined using curve fitting. The secondary structure of the insulin released from the nanoparticles was analyzed using circular dichroism and the cell cytotoxicity of nanoparticles on a Caco-2 cell line was determined. Ex vivo studies were performed on excised rat jejunum using Frantz diffusion cells. In vivo studies were performed on diabetic male Wistar rats and blood glucose level and insulin serum concentration were determined.

Results: Optimized nanoparticles with proper physico-chemical properties were obtained. The lyophilization process was found to cause a decrease in zeta potential and an increase in PdI as well as and a decrease in entrapment efficiency (EE%) and loading efficiency (LE%) but conservation in size of nanoparticles. Atomic force microscopy (AFM) images showed non-aggregated, stable and spherical to sub-spherical nanoparticles. The in vitro release study revealed higher release rates for lyophilized compared to non-lyophilized nanoparticles. Cytotoxicity studies on Caco-2 cells revealed no significant cytotoxicity for prepared nanoparticles after 3-h post-incubation but did show the concentration-dependent cytotoxicity after 24?h. The percentage of cumulative insulin determined from ex vivo studies was significantly higher in nanoparticles prepared from quaternized aromatic derivatives of chitosan. In vivo data showed significantly higher insulin intestinal absorption in nanoparticles prepared from methylated N-(4-N, N-dimethylaminobenzyl) chitosan nanoparticles compared to trimethyl chitosan.

Conclusion: These data obtained demonstrated that as the result of optimized physico-chemical properties, drug release rate, cytotoxicity profile, ex vivo permeation enhancement and increased in vivo absorption, nanoparticles prepared from N-aryl derivatives of chitosan can be considered as valuable method for the oral delivery of insulin.     

Structural and optical properties of Co-doped ZnS nanoparticles synthesized by a capping agent

Cobalt-doped Zinc sulfide (ZnS) nanoparticles were prepared by a simple chemical method using alkyl hydroxyl ethyl dimethyl ammonium chloride (YH) as capping agent. The structural and optical properties of prepared cobalt-doped ZnS nanoparticles have been characterized. X-ray diffraction patterns and transmission electron microscope images reveal pure cubic ZnS phase with size of about 5–2 nm for all cobalt-doped ZnS nanoparticles. The lattice constant of the samples decreases slightly by the introduction of Co²⁺ The absorption edge of the ZnS:Co²⁺ nanoparticles is blue-shifted as compared with that of bulk ZnS, indicating the quantum confinement effect. The photoluminescence emission band exhibits a blue shift for Co-doped ZnS nanoparticles as compared to the ZnS nanoparticles.     

Biodegradation of isoproturon using a novel Pseudomonas aeruginosa strain JS-11 as a multi-functional bioinoculant of environmental significance

Biodegradation of phenylurea herbicide isoproturon was studied in soil microcosm bioaugmented with a novel bacterial strain JS-11 isolated from wheat rhizosphere. The molecular characterization based on 16SrDNA sequence homology confirmed its identity as Pseudomonas aeruginosa strain JS-11. The herbicide was completely degraded within 20 days at ambient temperature with the rate constant of 0.08 day(-1), following the first-order rate kinetics. In stationary phase, at a cell density of 6.5 × 10(9) CFU mL(-1), the bacteria produced substantially increased amounts of indole acetic acid (IAA) in the presence of tryptophan as compared with the control. Also, the bacteria exhibited a time-dependent increase in the amount of tri-calcium phosphate solubilization in Pikovskaya's medium. Further screening of the strain JS-11 for auxiliary activities revealed its remarkable capability of producing the siderophores and hydrogen cyanide (HCN), besides antifungal activity against a common phytopathogen Fusarium oxysporum. Thus, the versatile P. aeruginosa strain JS-11 with innate potential for multifarious biological activities is envisaged as a super-bioinoculant for exploitation in the integrated bioremediation, plant growth and disease management (IBPDM) in contaminated agricultural soils.     

Coexistence of OFDM‐Based IMT‐Advanced and FM Broadcasting Systems

Coexistence analysis is extremely important in examining the possibility for spectrum sharing between orthogonal frequency‐division multiplexing (OFDM)‐based international mobile telecommunications (IMT)‐Advanced and other wireless services. In this letter, a new closed form method is derived based on power spectral density analysis in order to analyze the coexistence of OFDM‐based IMT‐Advanced systems and broadcasting frequency modulation (FM) systems. The proposed method evaluates more exact interference power of IMT‐Advanced systems in FM broadcasting systems than the advanced minimum coupling loss (A‐MCL) method. Numerical results show that the interference power is 1.3 dB and 3 dB less than that obtained using the A‐MCL method at cochannel and adjacent channel, respectively. This reduces the minimum separation distance between the two systems, which eventually saves spectrum resources.     

GULFNET: The academic network of the arab gulf countries

This article provides an overview of GULFNET and its information services, with emphasis on KACST (King Abdulaziz City for Science and Technology, Saudi Arabia) services.     

Some furan's derivatives as Corrosion Inhibitors for AI in HCI solutions

The corrosion of aluminum in HCL solutions has been carried out using polarization and weight loss methods. The effects of some furan derivatives on the corrosion rate were studied. It was found that these compounds inhibit the corrosion of Al to varying extents and they follow the order: 2, 5-dihydrofuran > 2,5-dihydro, 2,5-dimenthoxyfuran > tetrahydrofuran. The free energy changes (Δ G°_ads.) for the adsorption of these compounds were negative and they were in the same order as above. These Δ G°_ads. are in accordance with the electron densities of these compounds.     

利用上下文转移实现移动IPv6上的IMS无缝切换

Mobility support for the next generation IPv6 networks has been one of the recent research issues due to the growing demand for wireless services over internet. In the other hand, 3GPP has introduced IP Multimedia Subsystem as the next generation IP based infrastructure for wireless and wired multimedia services. In this paper we present two context transfer mechanisms based on predictive and reactive schemes, to support seamless handover in IMS over Mobile IPv6. Those schemes reduce handover latency by transferring appropriate session ＇information between the old and the new access networks. Moreover, we present two methods for QoS parameters negotiations to preserve service quality along the mobile user movement path. The performances of the proposed mechanisms are evaluated by simulations.     

Aureole nanofibers by electrospinning of PAMAM‐PEO solution

Poly(amido amine) (PAMAM) dendrimer‐polyethylene oxide (PEO) nanofibers as dendrimeric‐polymeric composite nanofibers were prepared via electrospinning of PEO solution containing PAMAM dendrimer. The resultant fibers were characterized by means of transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The morphology and thermal properties of PEO nanofibers with and without PAMAM dendrimer were compared and the effect of PAMAM concentration on morphology and thermal properties of the resultant fibers was studied. The fibers had a size range of about 400–1300 nanometer in diameter with aureole morphology in most regions. The phase change temperature, phase transition heat, and the crystallinity of the produced composite fibers were determined by DSC analyses. TGA was also used to confirm the presence of PAMAM and to determine the amount of it within the fibers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Modeling of insulated CFRP-strengthened reinforced concrete T-beam exposed to fire

The use of Fiber Reinforced Polymer (FRP) has been established as one of the possible techniques to strengthen concrete beams in flexure and shear. Carbon Fiber Reinforced Polymer (CFRP) has been identified as the material of choice in civil infrastructure applications. The fire performance of such CFRP-strengthened members and their resistance to heat transfer and to various environmental exposure factors need to be investigated. In this paper, a detailed finite element model of a CFRP-strengthened reinforced concrete T-beam is developed. The model accounts for the variation in thermal and mechanical parameters of the beams’ constituent materials with temperature, including CFRP and insulation materials. Nonlinear time domain transient thermal-stress finite element analysis is performed using the commercial software ANSYS to study the heat transfer mechanism and deformation within the beam for fire conditions initiating at the bottom of the beam. To relate the simulation to an actual case, a reinforced concrete T-beam strengthened with CFRP and fire-tested by other investigators is modeled. The progression of temperature in the beam, CFRP, reinforcing steel, and along the CFRP–concrete interface is compared to the observed fire test data. Overall, the predicted temperature results are in good agreement with the measured ones. In addition, the mid-span deflection increases nonlinearly during the fire exposure time due to the increase in the total strain on the tension side of the beams and due to concrete cracking. Successful FE modeling of this structure provides an economical, alternative solution to expensive experimental investigations.