1,721,245 research outputs found
Frictional modes of barrel shaped piston rings under flooded lubrication
No full textA friction force measurement system using the floating liner method was developed to study the frictional behavior of piston rings. The measurement system was designed to control the effect of the secondary piston motion and to control temperatures of the cylinder wall and oil. The friction force between the barrel shaped piston ring and the cylinder liner was measured under flooded oil supply conditions. The measured friction forces were classified into five frictional modes with regard to the combination of predominant lubrication regimes (boundary, mixed and hydrodynamic lubrication) and stroke regions (mid-stroke and dead centers). The modes were identified on a Stribeck diagram, where the friction coefficients were evaluated both at mid-stroke and at the dead centers. (C) 2000 Published by Elsevier Science Ltd
Measurement devices for piston assembly friction and oil film thickness
No full textA technique for estimating the instantaneous frictional force between the piston assembly and the cylinder wall has been developed by improving the moveable bore technique. The technique can be easily applied to small multi-cylinder engines since its structure is simple and stable so that the measuring range could be extended. The reliability of the friction data can be improved by a newly proposed compensation method. The technique was applied to a four cylinder SI engine under various engine speeds. engine loads. and oil viscosity. An instrument for measuring the oil film thickness on the piston rings was also developed by using the commercially available gap sensors. It as possible to measure the oil film thickness,, on thin oil ring rails as well as on the compression rings. The frictional characteristics were established as a relationship between frictional mean effective pressure and a parameter which is the product of the piston mean speed and the oil viscosity.Korean Ministry of Industry and Energy under the scheme of the Enterprise of the Next Generation Vehicle Technolog
Smart passive system based on magnetorheological damper
No full textMagnetorheological (MR) dampers are one of the most promising control devices for civil engineering applications to earthquake hazard mitigation, because they have many advantages such as small power requirement, reliability, and low price to manufacture. To reduce the responses of the controlled structure by using MR dampers, a control system including a power supply, controller, and sensors is needed. However, when a lot of MR dampers are applied to large-scale civil structures, such as cable-stayed bridges and high-rise buildings, the control system becomes complex. Thus, it is not easy to install and to maintain the MR damper-based control system. In this paper, to resolve the above difficulties, a smart passive system is proposed, which is based on an MR damper system. The smart passive system consists of an MR damper and an electromagnetic induction (EMI) system that uses a permanent magnet and a coil. According to the Faraday law of induction, the EMI system that is attached to the MR damper produces electric energy. The produced energy is applied to the MR damper to vary the damping characteristics of the damper. Thus, the smart passive system does not require any power at all. Furthermore, the output of electric energy is Proportional to input loads such as earthquakes, which means the smart passive system has adaptability by itself without any controller or corresponding sensors. Therefore, it is easy to build up and maintain the proposed smart passive system. To verify the effectiveness of the proposed smart passive system, the performance is compared with that of the normal MR damper-based control system. The numerical results show that the smart passive system has comparable performance to the normal MR damper-based control system
Fluorescence sensing systems for gold and silver species
No full textBesides the noble physical appearance of gold and silver, their novel chemical properties attracted the modern technology for various industrial, chemical and biological uses including medical applications. The widespread use of gold and silver, however, can cause potential hazards to our environment. Therefore, suitable detection methods are a prerequisite for the evaluation of their harmful effects as well as for studying their beneficial biological properties. Due to the several advantages over the conventional analytical methods, the fluorescence detection of gold and silver has become an active research area in recent years. In this review, we provide an overview of the reported fluorescent detection systems for gold and silver species, and discuss their sensing properties with promising features. The future scope of developments in this field of research is also mentioned.117158sciescopu
An experimental study of semiactive modal neuro-control scheme using MR damper for building structure
No full textIn this study, a semiactive modal neuro-control scheme which combines the modal neuro-control algorithm with a semiactive MR damper is proposed, and its effectiveness is experimentally verified through a series of shaking table tests. A modal neuro-control scheme uses modal coordinates as inputs of neuro-controller. Hence, it is more convenient to design the controller compared with conventional neuro-control schemes. A Kalman filter is introduced to estimate modal states from measurements. Moreover, the clipped algorithm is adopted to provide an appropriate command voltage to an MR damper. For shaking table tests, a scaled three-story shear building model is considered. Two types of semiactive modal neuro-controllers are trained with a reproduced El Centro earthquake for their own purposes. The performance of the proposed semiactive modal neuro-control scheme is compared with that of the passive-optimal case. In the experiments, the proposed semiactive modal neuro-controllers show better performance than the passive-optimal case, especially in adaptability over various excitations and reducing inter-story drifts as well as accelerations. Moreover, the proposed scheme can be designed for specific purpose which fulfills the designer's requirement (e. g., focusing on reducing inter-story drifts). Therefore, the proposed semiactive modal neuro-controller can be effectively used in reducing seismic responses of large engineering structures
Seismic protection of base isolated structures using smart passive control system
No full textThe effectiveness of the newly developed smart passive control system employing a magnetorheological (MR) damper and an electromagnetic induction (EMI) part for seismic protection of base isolated structures is numerically investigated. An EMI part in the system consists of a permanent magnet and a coil, which changes the kinetic energy of the deformation of an MR damper into the electric energy (i.e. the induced current) according to the Faraday's law of electromagnetic induction. In the smart passive control system, the damping characteristics of an MR damper are varied with the current input generated from an EMI part. Hence, it does not need any control system consisting of sensors, a controller and an external power source. This makes the system much simpler as well as more economic. To verify the efficacy of the smart passive control system, a series of numerical simulations are carried out by considering the benchmark base isolated structure control problems. The numerical simulation results show that the smart passive control system has the comparable control performance to the conventional MR damper-based semiactive control system. Therefore, the smart passive control system could be considered as one of the promising control devices for seismic protection of seismically excited base isolated structures
Seismic protection of base-isolated building with nonlinear isolation system using smart passive control strategy
No full textThis paper numerically investigates the applicability of the magnetorheological (MR) damper-based smart passive control system with the electromagnetic induction (EMI) part to the seismic protection of base-isolated building structures with nonlinear isolation systems such as friction pendulum bearings and lead-rubber bearings. The EMI part consists of a permanent and a solenoid coil, which produces the electrical energy (i.e. induced current) according to Faraday's law of EMI. The produced electric energy is applied to the MR damper to change the damping characteristics by itself without any controller as well as sensors for reducing structural responses. To verify the efficacy of the smart passive control system to a nonlinear base-isolated building, a series of numerical simulations are carried out by considering the phase II benchmark nonlinear base-isolated structure control problem. It is demonstrated from the numerical simulation results that the smart passive control system has the comparable or superior control performance to the conventional MR damper-based semiactive control system. Therefore, the smart passive control system could be considered as one of the promising control devices for seismic protection of seismically excited nonlinear base-isolated structures. Copyright (c) 2008 John Wiley & Sons, Ltd
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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