Fatigue reliability assessment of a historic railway bridge designed by Gustave Eiffel

The evolution of the railway traffic during the last century is studied as preliminary step towards the estimation of the remaining service life of a historical bridge. The selected case study concerns the El Ourit Bridge, designed in 1889 by Gustave Eiffel and located close to the town of Tlemcen, in Algeria. A finite element model of the structure is built and the response of the bridge to train-crossing loads is numerically evaluated with the purpose of identifying the element most affected by stress variations. The Palmgren–Miner accumulation model is used to quantify the fatigue damage in this element. A limit state function based on this criterion is formulated; then, a fully probabilistic approach is adopted by assuming that the stress amplitude, the fatigue strength and the damage threshold value play the role of random variables. The obtained results are discussed in order to evaluate the residual service life of the bridge.     

Quality of service analysis and improvement with cross layer power allocation in multirelay networks

Quality of service (QoS) guarantee is the main performance metric for designing future wireless networks. For real time applications over wireless links, statistical delay QoS guarantee is the most important QoS metrics. The main goal of this paper is studying the effects of multi‐decode‐and‐forward‐relaying transmission on delay QoS guarantee and user satisfaction. For this end, we first propose an approach to simplify the analysis of statistical delay QoS guarantee by the use of a curve named QoS analysis curve. The QoS analysis curve of any system is based on its effective capacity (EC) function. So, we derive a closed‐form expression for the EC function of a multi‐decode‐and‐forward‐relay network to reduce the computational complexity of finding this quantity. After that, for improving the QoS guarantee performance of a multi‐decode‐and‐forward‐relaying system, the EC of the system is maximized by the use of power allocation (PA) technique. At first, an adaptive PA (APA) algorithm is proposed in which the source and relays PA policies are derived analytically. Although, the overhead of this algorithm is large, it significantly improves the statistical delay QoS guarantee performance. Then, for the systems that cannot tolerate the required large overhead of APA, a fixed PA scheme is presented, which is based on particle swarm optimization algorithm. There is a tradeoff between providing the delay QoS guarantee and the required overhead, in selecting APA or fixed PA schemes. The numerical results validate our analytical outcomes and evaluate our proposed algorithms.     

Assessment of hydraulic conductivity in the multi-layered aquifer system of the Bengal Basin,Bangladesh, by performing slug tests

Bulletin of Engineering Geology and the Environment - Various studies have described upon importance of the performance of multilevel slug tests to assess hydraulic conductivity of aquifer...     

Synthesis,Biological Evaluation and 2D-QSAR Study of Halophenyl Bis-Hydrazones as Antimicrobial and Antitubercular Agents

In continuation of our endeavor towards the development of potent and effective antimicrobial agents, three series of halophenyl bis-hydrazones (14a–n, 16a–d, 17a and 17b) were synthesized and evaluated for their potential antibacterial, antifungal and antimycobacterial activities. These efforts led to the identification of five molecules 14c, 14g, 16b, 17a and 17b (MIC range from 0.12 to 7.81 μg/mL) with broad antimicrobial activity against Mycobacterium tuberculosis; Aspergillus fumigates; Gram positive bacteria, Staphylococcus aureus, Streptococcus pneumonia, and Bacillis subtilis; and Gram negative bacteria, Salmonella typhimurium, Klebsiella pneumonia, and Escherichia coli. Three of the most active compounds, 16b, 17a and 17b, were also devoid of apparent cytotoxicity to lung cancer cell line A549. Amphotericin B and ciprofloxacin were used as references for antifungal and antibacterial screening, while isoniazid and pyrazinamide were used as references for antimycobacterial activity. Furthermore, three Quantitative Structure Activity Relationship (QSAR) models were built to explore the structural requirements controlling the different activities of the prepared bis-hydrazones.     

Thermophysical Properties of Short Carbon Fiber/SiC Multilayer Composites Prepared by Tape Casting and Pressureless Sintering

C_sf/SiC multilayer composites for thermal conductivity (TC) test in three directions were successively prepared by tape casting and pressureless sintering. After 1500°C/5 h oxidation treatment, short carbon fibers were oxidized which produced many pores. However, a core area, which was composed by short carbon fiber, SiC, and few SiO₂, was still observed. TC properties of C_sf/SiC multilayer composites were highly anisotropic. The TC was decreased with the increase in fiber amount. C_sf/SiC multilayer composites demonstrated the highest TC along the tape casting direction and the lowest TC through the thickness direction, which is favorable for thermal protection purpose.     

In Situ Production of Biofunctionalized Few‐Layer Defect‐Free Microsheets of Graphene

Biological interfacing of graphene has become crucial to improve its biocompatibility, dispersability, and selectivity. However, biofunctionalization of graphene without yielding defects in its sp²‐carbon lattice is a major challenge. Here, a process is set out for biofunctionalized defect‐free graphene synthesis through the liquid phase ultrasonic exfoliation of raw graphitic material assisted by the self‐assembling fungal hydrophobin Vmh2. This protein (extracted from the edible fungus Pleurotus ostreatus) is endowed with peculiar physicochemical properties, exceptional stability, and versatility. The unique properties of Vmh2 and, above all, its superior hydrophobicity, and stability allow to obtain a highly concentrated (≈440–510 μg mL^?1) and stable exfoliated material (ζ‐potential, +40/+70 mV). In addition controlled centrifugation enables the selection of biofunctionalized few‐layer defect‐free micrographene flakes, as assessed by Raman spectroscopy, atomic force microscopy, scanning electron microscopy, and electrophoretic mobility. This biofunctionalized product represents a high value added material for the emerging applications of graphene in the biotechnological field such as sensing, nanomedicine, and bioelectronics technologies.     

TCE dechlorination rates, pathways, and efficiency of nanoscale iron particles with different properties

Nanoscale Fe0 particles are a promising technology for in situ remediation of trichloroethene (TCE) plumes and TCE-DNAPL source areas, butthe physical and chemical properties controlling their reactivity are not yet understood. Here, the TCE reaction rates, pathways, and efficiency of two nanoscale Fe0 particles are measured in batch reactors: particles synthesized from sodium borohydride reduction of ferrous iron (Fe/B) and commercially available particles (RNIP). Reactivity was determined under iron-limited (high [TCE]) and excess iron (low [TCE]) conditions and with and without added H2. Particle efficiency, defined as the fraction of the Fe0 in the particles that is used to dechlorinate TCE, was determined under iron-limited conditions. Both particles had a core/shell structure and similar specific surface areas (approximately 30 m2/g). Using excess iron, Fe/B transformed TCE into ethane (80%) and C3-C6 coupling products (20%). The measured surface area normalized pseudo-first-order rate constant for Fe/B (1.4 x 10(-)2 L.h(-1).m(-2) is approximately 4-fold higher than for RNIP (3.1 x 10-(3) L.h(-1).m(-2). All the Fe0 in Fe/B was accessible for TCE dechlorination, and 92 +/- 0.7% of the Fe0 was used to reduce TCE. For Fe/B, H2 evolved from reduction of water (H+) was subsequently used for TCE dechlorination, and adding H2 to the reactor increased both the dechlorination rate and the mass of TCE reduced, indicating that a catalytic pathway exists. RNIP yielded unsaturated products (acetylene and ethene). Nearly half (46%) of the Fe0 in RNIP was unavailable for TCE dechlorination over the course of the experiment and remained in the particles. Adding H2 did not change the reaction rate or efficiency of RNIP. Despite this, the mass of TCE dechlorinated per mass of Fe0 added was similar for both particles due to the less saturated products formed from RNIP. The oxide shell composition and the boron content are the most likely causes for the differences between the particle types.