A modified moment resisting connection for ductile steel frames (Numerical and experimental investigation)

The seismic behavior of steel moment resisting building systems are directly affected by the local behavior of beam to column connections. In welded connections, severe stress concentrations at the connection edge coupled with imperfections of the weld roots, may contribute to significant reduction of the seismic performance. In this study, a reduced plate section connection is proposed to shift the stress concentration from the connection face. With this aim, the authors propose drilled holes at cover plates to create an intentional weak point. Applying this method, the stress concentration at the weld roots is significantly diminished and the failure mechanism is altered from premature weld fracture to ductile plate yielding around the holes. This technique eliminates unfavorable local beam failures present in some similar methods and also forces the cover plate to behave as the replaceable fuse of the connection system. As it is revealed from the finite element and experimental investigations, the strength and ductility capacity of the considered connection type is significantly improved and the behavior of the connection seems to be far less dependant of the weld root quality. This might improve the structural reliability of the connection due to the guided failure mechanism.     

Harmonic cancellation characteristics of specially connected transformers

Specially connected transformers such as V–V, Scott and Le-Blanc transformers are used to convert a three-phase supply into one or two single-phase supplies. These transformers are commonly used in the electro locomotive traction systems. This paper investigates the harmonic cancellation characteristics of such transformers. The results show that when two harmonic-producing loads are connected to each single-phase side of the transformers, the harmonics produced by the loads will cancel out at the primary sides of the transformers. The amount of cancellation is affected by transformer type and harmonic order. The study is performed for seven types of specially connected transformers.     

Modeling traffic jams in intracellular transport in axons

Irregularities in intracellular traffic in axons caused by mutations of molecular motors may lead to “traffic jams”, which often result in swelling of axons causing various neurodegenerative diseases. The purpose of this paper is to suggest a model of the formation of traffic jams in axons during molecular-motor-assisted transport of intracellular organelles utilizing transport equations developed in Smith and Simmons [D.A. Smith, R.M. Simmons, Models of motor-assisted transport of intracellular particles, Biophys. J. 80 (2001) 45–68], which describe the motion of intracellular particles under the combined action of diffusion and motor-driven transport. According to this model, large intracellular organelles are transported in the cytoplasm by a combined action of diffusion and motor-driven transport. In an axon, organelles are transported away from the neuron’s body toward the axon’s terminal by kinesin-family molecular motors running on tracks composed by microtubules; old and used components are carried back toward neuron’s body by dynein-family molecular motors. Binding/detachment kinetic processes between the organelles and microtubules are specified by first rate reaction constants; these lead to coupling between the three organelle concentrations.     

Invited review: Microbiota of the bovine udder: Contributing factors and potential implications for udder health and mastitis susceptibility

Various body sites of vertebrates provide stable and nutrient-rich ecosystems for a diverse range of commensal, opportunistic, and pathogenic microorganisms to thrive. The collective genomes of these microbial symbionts (the microbiome) provide host animals with several advantages, including metabolism of indigestible carbohydrates, biosynthesis of vitamins, and modulation of innate and adaptive immune systems. In the context of the bovine udder, however, the relationship between cow and microbes has been traditionally viewed strictly from the perspective of host-pathogen interactions, with intramammary infections by mastitis pathogens triggering inflammatory responses (i.e., mastitis) that are often detrimental to mammary tissues and cow physiology. This traditional view has been challenged by recent metagenomic studies indicating that mammary secretions of clinically healthy quarters can harbor genomic markers of diverse bacterial groups, the vast majority of which have not been associated with mastitis. These observations have given rise to the concept of “commensal mammary microbiota,” the ecological properties of which can have important implications for understanding the pathogenesis of mastitis and offer opportunities for development of novel prophylactic or therapeutic products (or both) as alternatives to antimicrobials. Studies conducted to date have suggested that an optimum diversity of mammary microbiota is associated with immune homeostasis, whereas the microbiota of mastitic quarters, or those with a history of mastitis, are considerably less diverse. Whether disruption of the diversity of udder microbiota (dysbiosis) has a role in determining mastitis susceptibility remains unknown. Moreover, little is known about contributions of various biotic and abiotic factors in shaping overall diversity of udder microbiota. This review summarizes current understanding of the microbiota within various niches of the udder and highlights the need to view the microbiota of the teat apex, teat canal, and mammary secretions as interconnected niches of a highly dynamic microbial ecosystem. In addition, host-associated factors, including physiological and anatomical parameters, as well as genetic traits that may affect the udder microbiota are briefly discussed. Finally, current understanding of the effect of antimicrobials on the composition of intramammary microbiota is discussed, highlighting the resilience of udder microbiota to exogenous perturbants.     

Effect of acid number of crude oil on oil recovery of smart water coupled with silica nanoparticles

Spontaneous imbibition (SI) is one of the most important mechanisms in reservoir engineering. In order to activate of this mechanism completely in carbonate reservoirs, wettability of these oil wet rocks should be altered to water-wet. Multi-step spontaneous imbibition tests were designed and conducted in this study. Results indicated that mixture of smart water and nano silica could increase oil recovery up to 5 percent. Effect of acid number of crude oil on oil recovery of this mixture was investigated by using three samples of crude oil during SI tests: A (0.38 mg KOH/g), B (0.25 mg KOH/g) and C (0.18 mg KOH/g). Maximum oil recovery of SI tests was recorded for oil sample C which had lowest acid number. Ion analysis of imbibing fluids indicated sharp reductions in concentration of sulfate ion in each step of SI tests which confirmed occurrence of ion exchange mechanism in the rock surface of core samples.     

A novel method for finding the best excitation frequency of MEMS vibratory gyroscope

Microsystem Technologies - In this paper, a novel method is proposed for finding the best excitation signal frequency of the MEMS vibratory gyroscope sensors. In the proposed method, the amplitude...     

Digital sinusoidal PWMs for a micro-controller based single-phase inverter,Part 2: Performance assessment–experimental

The performance, including efficiency, harmonics and dead-time effect of the three major digital sinusoidal pulse width modulations (DSPWMs) presented in Part 1 are investigated in this study using a 2 kVA single-phase full-bridge inverter. Each DSPWM is implemented using a low-cost 8-bit micro-controller and the effect of different switching frequencies on the inverter performance is analysed and the inverter switching, conduction and transformer losses investigated. The experimental results confirm the validity of the mathematical and simulation analysis presented in Part 1. The work shows that the type of DSPWM used for a single-phase full-bridge inverter and the switching frequency selected can have a significant effect on the inverter performance and that switch and transformer losses make up the majority of the inverter losses.     

Design of a micro glass cell apparatus for pure gas‐nonvolatile liquid phase behaviour study

A micro syringe is used as a constant volume cell for gas–liquid equilibrium (GLE) study. The cell is made of glass and has a volume of <100 µL. It can operate at pressures up to 13 MPa and temperatures up to 115°C. Two different experimental procedures are presented for systems with nonvolatile low and high viscosity liquids. A micro magnetic stir bar is used to mix the gas–liquid mixtures inside the cell. Since the internal volume of the cell is small, a short mixing time is sufficient for the gas–liquid mixtures to reach equilibrium. The solubility values are measured by using the pressure decay method. The experimental procedures are validated by measuring the carbon dioxide (CO₂) solubility in water and highly viscous bitumen. The experimental results are in good agreement with the available literature data which shows that the technique works well. © 2011 Canadian Society for Chemical Engineering     

Damage detection in frame structures using damage locating vectors

Among the numerous vibration based damage detection methods, some are using dynamically measured flexibility matrix to detect and locate damage in the structure. One of the methods in this category is damage locating vector (DLV). It is based on extracting a set of load vectors from flexibility shifts that cause the same deformation in damaged and undamaged structures. As a result, the damaged member can be located by studying the characterizing stress of all members. In this study, the application of DLV method on damage detection of 3D frame structure was conducted. Some factors like the number of measured DOFs and the accuracy of modal data were assumed to be ideal so that other parameters could be examined. The characterizing stress for a 3D structure and the accuracy of damage index in different damage scenarios are discussed.     

An Integration-Free Method for Inversion of Laplace Transforms: A Useful Tool for Process Control Analysis and Design

An efficient method is developed for symbolic inversion of Laplace transforms based on the differential transformation method. The proposed method is conveniently simple and, unlike the classic Bromwich theorem, is free of integration. Several illustrative examples are provided to demonstrate the applicability and reliability of our approach. In addition, a relevant, efficient computer code in Maple is provided. Our method improves the synthesis of control structures for chemical processes in a systematic manner.