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Izuru Takewaki - One of the best experts on this subject based on the ideXlab platform.

  • Critical earthquake Input Energy to connected building structures using impulse Input
    Earthquakes and Structures, 2015
    Co-Authors: Yoshiyuki Fukumoto, Izuru Takewaki
    Abstract:

    A frequency-domain method is developed for evaluating the earthquake Input Energy to two building structures connected by viscous dampers. It is shown that the earthquake Input energies to respective building structures and viscous connecting dampers can be defined as works done by the boundary forces between the subsystems on their corresponding displacements. It is demonstrated that the proposed Energy transfer function is very useful for clear understanding of dependence of Energy consumption ratios in respective buildings and connecting viscous dampers on their properties. It can be shown that the area of the Energy transfer function for the total system is constant regardless of natural period and damping ratio because the constant Fourier amplitude of the Input acceleration, relating directly the area of the Energy transfer function to the Input Energy, indicates the Dirac delta function and only an initial velocity (kinetic Energy) is given in this case. Owing to the constant area property of the Energy transfer functions, the total Input Energy to the overall system including both buildings and connecting viscous dampers is approximately constant regardless of the quantity of connecting viscous dampers. This property leads to an advantageous feature that, if the Energy consumption in the connecting viscous dampers increases, the Input energies to the buildings can be reduced drastically. For the worst case analysis, critical excitation problems with respect to the impulse interval for double impulse (simplification of pulse-type impulsive ground motion) and multiple impulses (simplification of long-duration ground motion) are considered and their solutions are provided.

  • Critical double impulse Input and bound of earthquake Input Energy to building structure
    Frontiers in Built Environment, 2015
    Co-Authors: Kotaro Kojima, Kohei Fujita, Izuru Takewaki
    Abstract:

    A theory of earthquake Input Energy to building structures under single impulse is useful for disclosing the property of Energy transfer function. This property shows that the area of the Energy transfer function is constant irrespective of natural period and damping of building structures. However single impulse may be unrealistic from a certain viewpoint because the frequency characteristic of Input cannot be expressed by this Input. In order to resolve such issue, a double impulse is introduced in this paper. The frequency characteristic of the Fourier amplitude of the double impulse is found in an explicit manner and a critical excitation problem is formulated with an interval of two impulses as a variable. The solution to that critical excitation problem is derived. An upper bound of the earthquake Input Energy is then derived by taking full advantage of the property of the Energy transfer function that the area of the Energy transfer function is constant. The relation of the double impulse to the corresponding one-cycle sinusoidal wave as a representative of near-fault pulse-type waves is also investigated.

  • fundamental mechanism of earthquake response reduction in building structures with inertial dampers
    Structural Control & Health Monitoring, 2012
    Co-Authors: Izuru Takewaki, S Murakami, Shinta Yoshitomi, Masaaki Tsuji
    Abstract:

    SUMMARY Fundamental mechanisms of earthquake response reduction in building structures with inertial mass dampers are investigated. The inertial mass damper is effective with respect to relative acceleration between two nodes. The influence of inertial mass dampers on the ground-motion Input can be expressed by the influence coefficient vector to be multiplied on the ground-motion acceleration in the right-hand side of the equations of motion. It is shown that, when an inertial mass damper is taken out from one story, the component of the influence coefficient vector above that story becomes 1. This means that, if an inertial mass damper is taken out from one story, the inertial mass dampers above that story do not influence the Input acceleration above that story. This observation is supported by the closed-form expression of the influence coefficient vector. The mechanism of earthquake response reduction is also discussed from the viewpoint of earthquake Input Energy. It is shown that the earthquake Input Energy under an acceleration Input with a constant Fourier spectrum depends on the influence coefficient vector. Finally, the characteristics of earthquake response reduction via inertial mass dampers are presented for three recorded ground motions. Copyright © 2011 John Wiley & Sons, Ltd.

  • earthquake Input Energy to tall and base isolated buildings in time and frequency dual domains
    Structural Design of Tall and Special Buildings, 2009
    Co-Authors: Izuru Takewaki, Kohei Fujita
    Abstract:

    Earthquake Input energies to tall and base-isolated buildings are examined by both time-domain and frequency-domain methods. Both methods support the validity of evaluating the earthquake Input Energy each other. It is shown that both methods have different advantages and can compensate for each other. While the time-domain method has a long history and is applicable to nonlinear models as well, the frequency-domain method is characterized by the Energy transfer function and its equi-area property plays an important role in the discussion of the stability of earthquake Input Energy. This equi-area property can be derived by the residue theorem only in a simple model. It is also demonstrated that this equi-area property in multi-degree-of-freedom models can be derived by the time-domain method for an idealized model of Input motions with a constant Fourier amplitude spectrum. This idea is applied to tall and base-isolated buildings. The equi-area property of the Energy transfer function provides a stable characteristic on the Input Energy as far as the total mass of the buildings is constant. Copyright © 2008 John Wiley & Sons, Ltd.

  • frequency domain modal analysis of earthquake Input Energy to highly damped passive control structures
    Earthquake Engineering & Structural Dynamics, 2004
    Co-Authors: Izuru Takewaki
    Abstract:

    A new complex modal analysis-based method is developed in the frequency domain for efficient computation of the earthquake Input Energy to a highly damped linear elastic passive control structure. The Input Energy to the structure during an earthquake is an important measure of seismic demand. Because of generality and applicability to non-linear structures, the earthquake Input Energy has usually been computed in the time domain. It is shown here that the formulation of the earthquake Input Energy in the frequency domain is essential for deriving a bound on the earthquake Input Energy for a class of ground motions and for understanding the robustness of passively controlled structures to disturbances with various frequency contents. From the viewpoint of computational efficiency, a modal analysis-based method is developed. The importance of overdamped modes in the Energy computation of specific non-proportionally damped models is demonstrated by comparing the Energy transfer functions and the displacement transfer functions. Through numerical examinations for four recorded ground motions, it is shown that the modal analysis-based method in the frequency domain is very efficient in the computation of the earthquake Input Energy. Copyright © 2004 John Wiley & Sons, Ltd.

Lioubov Kiwiminsker - One of the best experts on this subject based on the ideXlab platform.

  • catalytic non thermal plasma reactor for abatement of toluene
    Chemical Engineering Journal, 2010
    Co-Authors: Ch Subrahmanyam, A Renken, Lioubov Kiwiminsker
    Abstract:

    A non-thermal plasma rector with a catalytic electrode made of sintered metal fibres (SMFs) was tested for the oxidative decomposition of a model VOC toluene. The Input Energy was varied in the range 160–295 J/l by varying the applied voltage between 12.5 and 22.5 kV at 200 Hz. Influence of various parameters like toluene concentration, SMF modification by Mn and Co oxides, Input Energy and ozone formation was studied. It has been observed that plasma catalytic approach is very effective for total oxidation of toluene at low Input Energy, especially at toluene concentration ≤250 ppm and SMF modification by transition metal oxides increased the performance of the reactor significantly. MnOx modification appears to be a better choice compared to CoOx, which may be attributed to the in situ decomposition of ozone leading to the formation of more reactive oxidants like atomic oxygen.

  • improved performance of non thermal plasma reactor during decomposition of trichloroethylene optimization of the reactor geometry and introduction of catalytic electrode
    Applied Catalysis B-environmental, 2007
    Co-Authors: Monica Magureanu, Ch Subrahmanyam, A Renken, N B Mandache, Vasile I Parvulescu, Lioubov Kiwiminsker
    Abstract:

    The decomposition of trichloroethylene ITCE) by non-thermal plasma was investigated in a dielectric barrier discharge (DBD) reactor with a copper rod inner electrode and compared with a plasma-catalytic reactor. The particularity of the plasma-catalytic reactor is the inner electrode made of sintered metal fibers (SMF) coated by transition metal oxides. In order to optimize the geometry of the plasma reactor, the efficiency of TCE removal was compared for different discharge gap lengths in the range of 1-5 mm. Shorter gap lengths (1-3 mm) appear to be more advantageous with respect to TCE conversion. In this case TCE conversion varies between 67% and 100% for Input Energy densities in the range of 80-480 J/l, while for the 5 turn discharge gap the conversion was lower (53-97%) for similar values of the Input Energy. As a result of TICE oxidation carbon monoxide and carbon dioxide were detected in the effluent gas. Their selectivity was rather low, in the range 14-24% for CO2 and 11-23% for CO, and was not influenced by the gap length. Several other chlorinated organic compounds were detected as reaction products. When using MnOx/SMF catalysts as the inner electrode of the DBD reactor, the TCE conversion was significantly enhanced, reaching similar to 95% at 150 J/l Input Energy. The selectivity to CO2 showed a major increase as compared to the case without catalysts, reaching 58% for Input energies above 550 J/l. (C) 2007 Elsevier B.V. All rights reserved.

Masahiro Tsukamoto - One of the best experts on this subject based on the ideXlab platform.

  • effect of Input Energy on hardness and surface quality in ti64 by sputter less selective laser melting with modulated pulse
    Journal of Laser Applications, 2021
    Co-Authors: Yuta Mizuguchi, Yuji Sato, Norio Yoshida, Masahiro Tsukamoto
    Abstract:

    A titanium alloy (Ti64) has α + β crystal orientations, and the β phase mainly appears in the SLM process since Ti64 melts above 1600 °C by laser irradiation and then solidifies. In order to control the crystal orientation and crystal grain size, the modulated pulse of laser was employed to control the heat Input Energy of laser in the SLM process in this study. After fabrication, the sample was cut to measure the Vickers hardness which was compared with that of the commercial Ti and Ti64; the continuous wave (CW) laser fabricated sample had a value close to that of pure Ti, and the fabricated sample using modulated pulse of laser had a value close to Ti64. It was considered that a phase was formed by using a CW laser and the α + β phase was formed by using modulated pulse of laser, suggesting the possibility of controlling the material structure by controlling the heat Input of one layer which was formed by these processes.

  • spatter behavior for 316l stainless steel fabricated by selective laser melting in a vacuum
    Optics and Lasers in Engineering, 2020
    Co-Authors: Yuji Sato, Sasitorn Srisawadi, Dhritti Tanprayoon, Tetsuo Suga, Tomomasa Ohkubo, Masahiro Tsukamoto
    Abstract:

    Abstract A 316L stainless steel [SS316L] plate was fabricated by selective laser melting (SLM) in a vacuum. SS316L has excellent properties such as a high corrosion resistance and hardness, but forming complicated structures is challenging due to difficulties working the material. Although SLM can fabricate complicated shapes because it builds a 3D material layer-by-layer from a powder, some issues have yet to be resolved, including dimensional accuracy, surface finishes, surface roughness, processing time, and mechanical properties such as hardness. Another issue is irradiating a metal powder by a laser generates spattering. Spattering results in an insufficient Input Energy to the powder bed because the laser is absorbed by the spatter particles. Consequently, technology to suppress the amount of spatter for SLM processes is needed. In this study, to clarify the mechanism of the spatter-free process, SS316L is fabricated by SLM and the powder behavior during laser irradiation is observed by a high-speed video camera. The amount of spatter depends on the Input Energy of the laser. At a laser fluence of 20 kJ/cm2, the amount of spatter is minimized and the surface roughness on the fabricated sample improves from 30 μm to 3.5 μm.

Narendra B. Dahotre - One of the best experts on this subject based on the ideXlab platform.

  • laser additive synthesis of high entropy alloy coating on aluminum corrosion behavior
    Materials Letters, 2015
    Co-Authors: Youkang Shon, Sameehan S Joshi, Shravana Katakam, Ravi Shanker Rajamure, Narendra B. Dahotre
    Abstract:

    High entropy alloy coatings were synthesized on aluminum substrate by laser surface engineering. Dilution from the substrate was minimized with the aid of multi layered coatings. Furthermore, higher laser Input Energy during processing lead to uniform mixing amongst the components resulting in formation of evenly distributed high entropy alloy phases throughout the matrix. This resulted in enhanced corrosion resistance for the coatings in near neutral NaCl solution.

  • Variation of structure with Input Energy during laser surface engineering of ceramic coatings on aluminum alloys
    Applied Surface Science, 2002
    Co-Authors: Puja Kadolkar, Narendra B. Dahotre
    Abstract:

    Abstract Surface modification of metal alloys using laser has become a unique tool to reduce surface related failure mechanisms such as wear, corrosion, erosion or high temperature oxidation. Laser surface engineered (LSE) ceramic coatings have been proved to enhance surface properties of Al alloys such as hardness and wear resistance. This technique has been shown to be capable of producing a wide variety of interesting metallurgical microstructure in the coating as well as in the adjoining substrate. These microstructures provide novel properties, which cannot be produced by any conventional processing technique. In addition, these coatings are metallurgically bonded, thus providing a sound and adherent interface between the coating and the substrate. In this present investigation, laser surface engineering technique has been employed to deposit ceramic (TiC) coating on aluminum alloy substrate. TiC coating was deposited on two types of aluminum substrates, alloy 2024 and 6061 using an Nd-YAG laser beam. The effect of laser processing parameters, such as power intensity and speed on the thickness, microstructure and morphology of both the coating and the heat-affected zone have been evaluated using a scanning electron microscope (SEM). Results of experiments in this study show that by controlling the process parameters it is possible to produce varied microstructures according to the surface requirement of the application.

Fabrizio Mollaioli - One of the best experts on this subject based on the ideXlab platform.

  • an Energy based methodology for the assessment of seismic demand
    Soil Dynamics and Earthquake Engineering, 2001
    Co-Authors: Luis D Decanini, Fabrizio Mollaioli
    Abstract:

    Abstract A methodology for the assessment of the seismic Energy demands imposed on structures is proposed. The research was carried out through two consecutive phases. Inelastic design Input Energy spectra for systems with a prescribed displacement ductility ratio were first developed. The study of the inelastic behavior of Energy factors and the evaluation of the response modification in comparison with the elastic case were performed by introducing two new parameters, namely: (1) the Response Modification Factor of the earthquake Input Energy (RE), representing the ratio of the elastic to inelastic Input Energy spectral values and (2) the ratio α of the area enclosed by the inelastic Input Energy spectrum in the range of periods between 0.05 and 4.0 s to the corresponding elastic value. The proposed design inelastic Energy spectra, resulting from the study of a large set of strong motion records, were obtained as a function of ductility, soil type, source-to-site distance and magnitude. Subsequently, with reference to single degree of freedom systems, the spectra of the hysteretic to Input Energy ratio were evaluated, for different soil types and target ductility ratios. These spectra, defined to evaluate the hysteretic Energy demand of structures, were described by a piecewise linear idealization that allows to distinguish three distinct regions as a function of the vibration period. In this manner, once the inelastic design Input Energy spectra were determined, the definition of the Energy dissipated by means of inelastic deformations followed directly from the knowledge of hysteretic to Input Energy ratio. The design spectra of both Input Energy and hysteretic to Input Energy ratio were defined considering an elasto-plastic behavior. Nevertheless, other constitutive models were taken into account for comparison purposes.

  • formulation of elastic earthquake Input Energy spectra
    Earthquake Engineering & Structural Dynamics, 1998
    Co-Authors: Luis D Decanini, Fabrizio Mollaioli
    Abstract:

    SUMMARY The object of this paper is to introduce a procedure for the determination of elastic design earthquake Input Energy spectra taking into account the influence of magnitude, soil type and distance from the surface projection of the fault. Firstly, an accurate selection of a large set of representative records has been realized. Secondly, the construction of the design Input Energy spectra has required determining the spectral shapes and a normalization factor which measures seismic hazard in terms of Energy. This factor, denoted as the seismic hazard Energy factor, has been defined as the area under the earthquake Input Energy spectrum in the period interval between 0)05 and 4)0 s. Finally, due to the importance of the source-to-site distance in the evaluation of the Input Energy, an investigation into the attenuation of the seismic hazard Energy factor has been carried out. ( 1998 John Wiley & Sons, Ltd. The fundamental need to improve the reliability of the current procedures of earthquake-resistant design of structures has led to the recognition of methodologies based on Energy criteria as e⁄ective tools for a comprehensive interpretation of the behaviour observed during recent destructive events. Energy-based design involves considering two essential aspects: the first is related to the establishment of Design Earthquakes, while the second concerns the evaluation of the actual Energy absorption and Energy dissipation capacities of structures. The aim of this work is to introduce a proposal which could contribute to the resolution of the first of the above-mentioned aspects, namely the definition of a design seismic action as a function of appropriate parameters providing a measure of the Energy actually transferred from soil to structures during seismic shaking. The commonly adopted design approach in terms of forces, based on both elastic and inelastic response spectra, as results from the analysis and interpretation of the observed structural behaviour is open to criticism. The most controversial and uncertain aspect of the conventional design procedures specified by the di⁄erent codes is represented by the interpretation of the elastic design spectrum as a measure of destructiveness and, by the definition of the elastic response reduction factor as a function of a presumed inelastic behaviour. This factor, also known as the behaviour factor, although it is based on the comparison between elastic and inelastic response spectra and non-linear structural analysis, is still substantially assigned by the codes according to empirical criteria. Furthermore, uncertainty often arises in various steps of these