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Samuels, Robert J., i Nancy E. Mathis. "Orientation Specific Thermal Properties of Polyimide Film". Journal of Electronic Packaging 123, nr 3 (10.03.2000): 273–77. http://dx.doi.org/10.1115/1.1347986.
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The present study examines the relationship between thermal conductivity and planarity in polyimide films. The samples tested were specially prepared to range in orientation from three dimensionally random to highly planar. The molecular structure and orientation of the polyimide film have been characterized by polarizing microscope techniques, while the thermal conductivity measurements were done using a new rapid nondestructive technique. This correlation represents the first time thermal conductivity has been measured by modified hot wire techniques and related to the internal structure of polyimide. This work contributes to a deeper theoretical understanding of thermal conductivity and heat transfer mechanisms as they relate to orientation. Thermal conductivity evaluation could provide a new tool in the arsenal of structural characterization techniques. This relationship between thermal conductivity and orientation is key for applications of directional heat dissipation in the passive layers of chip assemblies. Such a correlation has potential to speed the development cycles of new materials during formulation as well as assure properties during production.
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Jamroziak, Krzysztof, i Miroslaw Bocian. "Analysis of Non-Classical Models which Have been Subjected to Percussive Loads Using Equations of Energy and Power". Advanced Materials Research 1036 (październik 2014): 608–13. http://dx.doi.org/10.4028/www.scientific.net/amr.1036.608.
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The article presents an analysis of impact energy dissipation process with selected non-classical dynamic models. Identification of impact energy dissipation phenomena in layered mechanical systems (for example: composite ballistic shields) is a great challenge, because on the one hand a model with parameters responsible for the energy dissipation is being sought on the one hand and on the other it is necessary to optimise the number of parameters. The sought model should be reduced to a simple description of the phenomenon and should contain a complex reproduction of the whole mechanical system. In this case the impact energy dissipation was described using selected degenerate systems. Models were treated by extortion surge having a specific impulse of force. The mathematical description of the pulse excitation was carried out using the energy and potency balance equations. The verification of mathematical identification equations was conducted using a computer simulation technique for the selected model’s parameters.
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Shang, Shou Ping, i Rong Shen. "HPFL Strip Strengthening Method for Masonry Structure". Advanced Materials Research 374-377 (październik 2011): 2593–98. http://dx.doi.org/10.4028/www.scientific.net/amr.374-377.2593.
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Due to the various advantages, e.g. low cost, simple construction and high reliability, the HPFL strip reinforcement technique has been widely used in the field of civil engineering. A survey of related literatures on the research and application of the HPFL strip reinforcement technique for Masonry structures were shown in this paper. The HPFL strip reinforcement technique can significantly improve the properties of the wall, e.g. the aseismatic capacity, shear resistant strength, ductility, energy dissipation. Moreover, based on the real engineering structures, the specific design and construction method were presented in this paper.
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CHEN, CHUNHONG, JIANG ZHAO i MAJID AHMADI. "A NOVEL STATE ENCODING ALGORITHM FOR LOW POWER IMPLEMENTATION". Journal of Circuits, Systems and Computers 14, nr 03 (czerwiec 2005): 597–604. http://dx.doi.org/10.1142/s0218126605002428.
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State encoding problem assigns binary codes to given symbolic states such that a specific objective function such as power dissipation can be optimized in the final implementation. In this paper, we present a novel encoding technique to minimize the switching activity of any given FSMs for low power design. The experiments with standard benchmarks show that the proposed algorithm is a significant improvement over previous ones.
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Yu, Byunggyu, i Seok-Cheol Ko. "Power dissipation analysis of PV module under partial shading". International Journal of Electrical and Computer Engineering (IJECE) 11, nr 2 (1.04.2021): 1029. http://dx.doi.org/10.11591/ijece.v11i2.pp1029-1035.
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Photovoltaic (PV) generation has been growing dramatically over the last years and it ranges from small, rooftop-mounted or building integrated systems, to large utility scale power stations. Especially for rooftop-mounted PV system, PV modules are serially connected to match with PV inverter input voltage specification. For serially connected PV system, shading is a problem since the shaded PV module reduces the output whole string of PV modules. The excess power from the unshaded PV module is dissipated in the shaded PV module. In this paper, power dissipation of PV module under partial shading is analyzed with circuit analysis for series connected PV modules. The specific current and voltage operating point of the shaded PV module are analyzed under shading. PSIM simulation tool is used to verify the power dissipation analysis. When there is no bypass diode and three solar modules are connected in series, upto 39.1% of the total maximum PV power is dissipated in the shaded PV module. On the other hand, when the bypass is attached, 0.3% of the total maximum power is generated as a loss in the shaded PV module. The proposed analysis technique of shaded PV module could be used in PV system performance analysis, especially for maximum power point tracking (MPPT) performance.
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Marsden, J. E., i M. West. "Discrete mechanics and variational integrators". Acta Numerica 10 (maj 2001): 357–514. http://dx.doi.org/10.1017/s096249290100006x.
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This paper gives a review of integration algorithms for finite dimensional mechanical systems that are based on discrete variational principles. The variational technique gives a unified treatment of many symplectic schemes, including those of higher order, as well as a natural treatment of the discrete Noether theorem. The approach also allows us to include forces, dissipation and constraints in a natural way. Amongst the many specific schemes treated as examples, the Verlet, SHAKE, RATTLE, Newmark, and the symplectic partitioned Runge–Kutta schemes are presented.
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Zhang, Qi, Xi Chen i David Guéry-Odelin. "Connection between Inverse Engineering and Optimal Control in Shortcuts to Adiabaticity". Entropy 23, nr 1 (9.01.2021): 84. http://dx.doi.org/10.3390/e23010084.
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We consider fast high-fidelity quantum control by using a shortcut to adiabaticity (STA) technique and optimal control theory (OCT). Three specific examples, including expansion of cold atoms from the harmonic trap, atomic transport by moving harmonic trap, and spin dynamics in the presence of dissipation, are explicitly detailed. Using OCT as a qualitative guide, we demonstrate how STA protocols designed from inverse engineering method can approach with very high precision optimal solutions built about physical constraints, by a proper choice of the interpolation function and with a very reduced number of adjustable parameters.
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Zhang, Qi, Xi Chen i David Guéry-Odelin. "Connection between Inverse Engineering and Optimal Control in Shortcuts to Adiabaticity". Entropy 23, nr 1 (9.01.2021): 84. http://dx.doi.org/10.3390/e23010084.
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We consider fast high-fidelity quantum control by using a shortcut to adiabaticity (STA) technique and optimal control theory (OCT). Three specific examples, including expansion of cold atoms from the harmonic trap, atomic transport by moving harmonic trap, and spin dynamics in the presence of dissipation, are explicitly detailed. Using OCT as a qualitative guide, we demonstrate how STA protocols designed from inverse engineering method can approach with very high precision optimal solutions built about physical constraints, by a proper choice of the interpolation function and with a very reduced number of adjustable parameters.
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Majzik, Zsolt, Martin Setvín, Andreas Bettac, Albrecht Feltz, Vladimír Cháb i Pavel Jelínek. "Simultaneous current, force and dissipation measurements on the Si(111) 7×7 surface with an optimized qPlus AFM/STM technique". Beilstein Journal of Nanotechnology 3 (15.03.2012): 249–59. http://dx.doi.org/10.3762/bjnano.3.28.
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We present the results of simultaneous scanning-tunneling and frequency-modulated dynamic atomic force microscopy measurements with a qPlus setup. The qPlus sensor is a purely electrical sensor based on a quartz tuning fork. If both the tunneling current and the force signal are to be measured at the tip, a cross-talk of the tunneling current with the force signal can easily occur. The origin and general features of the capacitive cross-talk will be discussed in detail in this contribution. Furthermore, we describe an experimental setup that improves the level of decoupling between the tunneling-current and the deflection signal. The efficiency of this experimental setup is demonstrated through topography and site-specific force/tunneling-spectroscopy measurements on the Si(111) 7×7 surface. The results show an excellent agreement with previously reported data measured by optical interferometric deflection.
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Tharajak, Jirasak, Tippaban Palathai i Narongrit Sombatsompop. "Scratch Resistance and Adhesion Properties of PEEK Coating Filled with h-BN Nanoparticles". Advanced Materials Research 747 (sierpień 2013): 303–6. http://dx.doi.org/10.4028/www.scientific.net/amr.747.303.
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Effects of h-BN particles on mechanical properties and adhesion of semi-crystalline poly (ether-ether-ketone) (PEEK) coatings were studied. PEEK powder was mixed with various contents of h-BN nanoparticle in ethanol under ultrasonic mixing. As-mixed powders were sprayed onto low carbon steel substrate with thermal spray technique. The hardness, scratch hardness, specific scratch wear rate, prevailing deformation mechanisms and adhesion were obtained from scratch tests by varying the applied load. The damage geometry on scratched polymer surfaces and scratch wear volume loss were examined using scanning electron microscope (SEM) and surface profilometer, respectively. The results indicated that the addition of h-BN content improved the hardness of the composite. In addition, the specific scratch wear rate and the adhesion between PEEK coatings and substrate decreased with increasing h-BN content. The poor adhesion resulted from the reductions of flow-ability and viscosity between PEEK and substrate caused by heat dissipation from the h-BN particles.
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Magnani, Federico, Abdelkader Bensada, Sergio Cinnirella, Francesco Ripullone i Marco Borghetti. "Hydraulic limitations and water-use efficiency in Pinus pinaster along a chronosequence". Canadian Journal of Forest Research 38, nr 1 (styczeń 2008): 73–81. http://dx.doi.org/10.1139/x07-120.
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Hydraulic constraints to water transport and water-use efficiency were studied in a Pinus pinaster Ait. chronosequence in Italy, consisting of four even-aged stands ranging from young (10 years old) to mature (75 years old), to explore the mechanisms involved in the decline of stand productivity as tree grow taller. Leaf-specific transpiration was estimated from sapflow rates measured by the heat dissipation technique, leaf-specific hydraulic conductance was computed from the slope of the relationship between transpiration and leaf water potential, long-term water-use efficiency was estimated from carbon isotope discrimination (Δ13C) in xylem cores, and photosynthetic capacity was assessed from CO2 assimilation/CO2 intercellular concentration curves. Leaf-specific transpiration decreased with stand development, suggesting a reduction in stomatal conductance, and a negative relationship was found between leaf-specific hydraulic conductance and tree height, suggesting a role of hydraulic constraints in the decline of current annual increment. Minimum daily leaf water potential did not change with stand height, suggesting that homeostasis in leaf water potential is achieved through a reduction in leaf transpiration. The Δ13C values increased with stand development, indicating a decline of water-use efficiency. Leaf level stomatal conductance was higher in the younger stand; no significant difference in maximum carboxylation rate was found among stands.
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Stepanov, Rodion, Peter Frick, Vladimir Dulin i Dmitriy Markovich. "Analysis of mean and fluctuating helicity measured by TomoPIV in swirling jet". EPJ Web of Conferences 180 (2018): 02097. http://dx.doi.org/10.1051/epjconf/201818002097.
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Important role of helicity was theoretically predicted for the generation of large-scale magnetic fields and atmospheric vortices. Helicity can lead to a reduction of turbulent dissipation in the atmosphere or in a specific constrained flow, e.g. in pipe. We use the TomoPIV data (42 cube of grid points, resolution 0.84 mm) to measure 3D velocity field of turbulent swirling flows. We study spatial distribution of the mean and fluctuating components of energy and helicity. We find that helical turbulence excitation and decay along stream of the jet strongly depend on the inflow swirl. We observe spatial separation of turbulent flow with different sign of helicity while integrated values are conserves. It is shown that large scale swirling flow induces helicity at the small scales. Our results bring valuable materials for benchmark the modern numerical simulations with turbulent closure technique.
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Rezaiee-Pajand, Mohammad, i Mahdi Karimi-Rad. "A New Explicit Time Integration Scheme for Nonlinear Dynamic Analysis". International Journal of Structural Stability and Dynamics 16, nr 09 (listopad 2016): 1550054. http://dx.doi.org/10.1142/s0219455415500546.
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An explicit time integration method is presented for the linear and nonlinear dynamic analyses of structures. Using two parameters and employing the Taylor series expansion, a family of second-order accurate methods for the solution of dynamic problems is derived. The proposed scheme includes the central difference method as a special case, while damping is shown to exert no effect on the solution accuracy. The proposed method is featured by the following facts: (i) the relative period error is almost zero for specific values of the parameters; (ii) the numerical dissipation contained can help filter out spurious high-frequency components; and (iii) the crucial lower modes are generally unaffected in the integration. Although the proposed method is conditionally stable, it has an appropriate region of stability, and is self-starting. The numerical tests indicate the improved performance of the proposed technique over the central difference method.
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Warner, Amy, Ann Kjellstedt, Alba Carreras, Gerhard Böttcher, Xiao-Rong Peng, Patrick Seale, Nicholas Oakes i Daniel Lindén. "Activation of β3-adrenoceptors increases in vivo free fatty acid uptake and utilization in brown but not white fat depots in high-fat-fed rats". American Journal of Physiology-Endocrinology and Metabolism 311, nr 6 (1.12.2016): E901—E910. http://dx.doi.org/10.1152/ajpendo.00204.2016.
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Activation of brown adipose tissue (BAT) and browning of white adipose tissue (WAT) present potential new therapies for obesity and type 2 diabetes. Here, we examined the effects of β3-adrenergic stimulation on tissue-specific uptake and storage of free fatty acids (FFA) and its implications for whole body FFA metabolism in diet-induced obese rats using a multi-radiotracer technique. Male Wistar rats were high fat-fed for 12 wk and administered β3-agonist CL316,243 (CL, 1 mg·kg−1·day−1) or saline via osmotic minipumps during the last 3 wk. The rats were then fasted and acutely infused with a tracer mixture ([14C]palmitate and the partially metabolized R-[3H]bromopalmitate) under anesthesia. CL infusion decreased body weight gain and fasting plasma glucose levels. While core body temperature was unaffected, infrared thermography showed an increase in tail heat dissipation following CL infusion. Interestingly, CL markedly increased both FFA storage and utilization in interscapular and perirenal BAT, whereas the flux of FFA to skeletal muscle was decreased. In this rat model of obesity, only sporadic populations of beige adipocytes were detected in the epididymal WAT depot of CL-infused rats, and there was no change in FFA uptake or utilization in WAT following CL infusion. In summary, β3-agonism robustly increased FFA flux to BAT coupled with enhanced utilization. Increased BAT activation most likely drove the increased tail heat dissipation to maintain thermostasis. Our results emphasize the quantitative role of brown fat as the functional target of β3-agonism in obesity.
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Katsura, Toshiya, Hiroshi Mizuuchi, Yukiya Hashimoto i Ken-Ichi Inui. "Transport of procainamide via H+/tertiary amine antiport system in rabbit intestinal brush-border membrane". American Journal of Physiology-Gastrointestinal and Liver Physiology 279, nr 4 (1.10.2000): G799—G805. http://dx.doi.org/10.1152/ajpgi.2000.279.4.g799.
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Transport characteristics of procainamide in the brush-border membrane isolated from rabbit small intestine were studied by a rapid-filtration technique. Procainamide uptake by brush-border membrane vesicles was stimulated by an outward H+ gradient (pHin= 6.0, pHout = 7.5) against a concentration gradient (overshoot phenomenon), and this stimulation was reduced when the H+ gradient was subjected to rapid dissipation by the presence of a protonophore, FCCP. An outward H+gradient-dependent procainamide uptake was not caused by H+diffusion potential. The initial uptake of procainamide was inhibited by other tertiary amines with N-dimethyl or N-diethyl moieties in their structures, such as triethylamine, dimethylaminoethyl chloride, and diphenhydramine, but not by tetraethylammonium and thiamine. Furthermore, procainamide uptake was stimulated by preloading the vesicles with these tertiary amines ( trans-stimulation effect), indicating the existence of a specific transport system for tertiary amines. These findings indicate that procainamide transport in the intestinal brush-border membrane is mediated by the H+/tertiary amine antiport system that recognizes N-dimethyl or N-diethyl moieties in the structures of tertiary amines.
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Gjengedal, Sondre, Vegard Brøtan, Ole T. Buset, Erik Larsen, Olav Å. Berg, Ole Torsæter, Randi K. Ramstad, Bernt O. Hilmo i Bjørn S. Frengstad. "Fluid flow through 3D-printed particle beds: a new technique for understanding, validating, and improving predictability of permeability from empirical equations". Transport in Porous Media 134, nr 1 (6.07.2020): 1–40. http://dx.doi.org/10.1007/s11242-020-01432-x.
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AbstractThe application of 3D technology for fabrication of artificial porous media samples improves porous media flow studies. The geometrical characteristics of a porous media pore channel: the channel shape, size, porosity, specific surface, expansion ratio, contraction ratio, and the tortuous pathway of the channel can be controlled through advanced additive manufacturing techniques (3D printing), computed tomography imagery (CT imaging) and image analysis methods. These 3D technologies have here been applied to construct and analyze four homogeneous porous media samples with predefined geometrical properties that are otherwise impossible to construct with conventional methods. Uncertainties regarding the geometrical properties are minimized because the 3D-printed porous media samples can be evaluated with CT imaging after fabrication. It is this combination of 3D technology that improves the data acquisition and data interpretation and contributes to new insight into the phenomenon of fluid flow through porous media. The effects of the individual geometrical properties on the fluid flow are then accounted for in permeability experiments in a Hassler flow cell. The results of the experimental work are used to test the theoretical foundation of the Kozeny–Carman equation and the extended version known as the Ergun equation. These equations are developed from analogies to the Hagen–Poiseuille flow equation. Based on the results from the laboratory experiments in this study, an analytical equation based on the analytical Navier–Stokes equations is presented as an alternative to the Hagen–Poiseuille analogy for porous media channels with non-uniform channel geometries. The agreement between experiment and the new equation reveals that the dissipating losses of mechanical energy in porous media flows are not a result of frictional shear alone. The mechanical losses are also a result of pressure dissipation that arise due to the non-uniformity of the channel geometry, which induced spatial variations to the strain rate field and induce acceleration of the velocity field in the flow through the porous medium. It is this acceleration that causes a divergence from linear flow conditions as the Stokes flow criterion (Re ≪ 1) is breached and causes the convective acceleration term to affect the flow behavior. The suggested modifications of theory and the presented experiments prove that the effects of surface roughness (1) do not alter the flow behavior in the Darcy flow regime or (2) in the Forchheimer flow regime. This implies that the flow is still laminar for the Forchheimer flow velocities tested.
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Kit, E., A. Cherkassky, T. Sant i H. J. S. Fernando. "In Situ Calibration of Hot-Film Probes Using a Collocated Sonic Anemometer: Implementation of a Neural Network". Journal of Atmospheric and Oceanic Technology 27, nr 1 (1.01.2010): 23–41. http://dx.doi.org/10.1175/2009jtecha1320.1.
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Abstract Although the integral quantities of atmospheric turbulence are conveniently measured using sonic anemometers, obtaining relevant finescale variables such as the kinetic energy dissipation using conventional hot-film/wire techniques remains a challenge because of two main difficulties. The first difficulty is the mean wind variability, which causes violation of the requirement that mean winds have a specific alignment with the hot-film/wire probe. To circumvent this problem, a combination of collocated sonic and hot-film anemometers, with the former measuring mean winds and aligning the latter in the appropriate wind direction via an automated platform, is successfully designed and implemented. The second difficulty is the necessity of frequent and onerous calibrations akin to hot-film anemometry that lead to logistical difficulties during outdoor (field) measurements. This is addressed by employing sonic measurements to calibrate the hot films in the same combination, with the output (velocity) to input (voltage) transfer function for the hot film derived using a neural network (NN) model. The NN is trained using low-pass-filtered hot-film and sonic data taken in situ. This new hot-film calibration procedure is compared with the standard calibration method based on an external calibrator. It is inferred that the sonic-based NN method offers great potential as an alternative to laborious standard calibration techniques, particularly in the laboratory and in stable atmospheric boundary layer settings. The NN approximation technique is found to be superior to the conventionally used polynomial fitting methods when used in conjunction with unevenly spaced calibration velocity data generated by sonic anemometers.
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Mazurkiewicz, Andrzej, i Andrzej Poprzeczka. "Evaluation of the quality of layers applied by LDT laser metal deposition". AUTOBUSY – Technika, Eksploatacja, Systemy Transportowe 19, nr 6 (30.06.2018): 591–96. http://dx.doi.org/10.24136/atest.2018.140.
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The article presents the results of a study of C45 carbon steel hardfacing using laser metal deposition with Stellit Co-21 powder. The microstructure of the cross-section of samples prepared with different scanning speed and the amount of used powder at constant laser power was observed. Analyzing the cross-sectional areas of the samples, it was found that, at specific production parameters, cracks occur in weld overlay, which should be associated with the amount of heat supplied and discharged, especially at the unheated basis.This may be confirmed by the presence of deposits of weakly branched dendrites in the microstructure, which should be related to the directional heat dissipation process and rapid directional crystallization. It is possible to regulate these phenomena by selecting appropriate processing parameters. The microstructure analysis of cross-sectional areas of samples after hardfacing using LDT technique indicates good metallurgical quality of the deposit with a small heat affected zone of about 660÷760m. The microhardness measurements on the sample cross-sections indicated a wide micohardness distribution ranging from 510HV1 in the weld overlay, about 410HV1 in the heat affected zone, to 270HV1 in the C45 steel base.
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Miyake, Shojiro, Takanori Shindo i Masatoshi Miyake. "Regression Analysis of the Effect of Bias Voltage on Nano- and Macrotribological Properties of Diamond-Like Carbon Films Deposited by a Filtered Cathodic Vacuum Arc Ion-Plating Method". Journal of Nanomaterials 2014 (2014): 1–13. http://dx.doi.org/10.1155/2014/657619.
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Diamond-like carbon (DLC) films are deposited by bend filtered cathodic vacuum arc (FCVA) technique with DC and pulsed bias voltage. The effects of varying bias voltage on nanoindentation and nanowear properties were evaluated by atomic force microscopy. DLC films deposited with DC bias voltage of −50 V exhibited the greatest hardness at approximately 50 GPa, a low modulus of dissipation, low elastic modulus to nanoindentation hardness ratio, and high nanowear resistance. Nanoindentation hardness was positively correlated with the Raman peak ratioId/Ig, whereas wear depth was negatively correlated with this ratio. These nanotribological properties highly depend on the films’ nanostructures. The tribological properties of the FCVA-DLC films were also investigated using a ball-on-disk test. The average friction coefficient of DLC films deposited with DC bias voltage was lower than that of DLC films deposited with pulse bias voltage. The friction coefficient calculated from the ball-on-disk test was correlated with the nanoindentation hardness in dry conditions. However, under boundary lubrication conditions, the friction coefficient and specific wear rate had little correlation with nanoindentation hardness, and wear behavior seemed to be influenced by other factors such as adhesion strength between the film and substrate.
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Tsuchida, Satoshi, i Hiroshi Kuratsuji. "Stochastic theory of polarized light in nonlinear birefringent media: An application to optical rotation". International Journal of Modern Physics B 32, nr 12 (3.05.2018): 1850147. http://dx.doi.org/10.1142/s0217979218501473.
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A stochastic theory is developed for the light transmitting the optical media exhibiting linear and nonlinear birefringence. The starting point is the two-component nonlinear Schrödinger equation (NLSE). On the basis of the ansatz of “soliton” solution for the NLSE, the evolution equation for the Stokes parameters is derived, which turns out to be the Langevin equation by taking account of randomness and dissipation inherent in the birefringent media. The Langevin equation is converted to the Fokker–Planck (FP) equation for the probability distribution by employing the technique of functional integral on the assumption of the Gaussian white noise for the random fluctuation. The specific application is considered for the optical rotation, which is described by the ellipticity (third component of the Stokes parameters) alone: (i) The asymptotic analysis is given for the functional integral, which leads to the transition rate on the Poincaré sphere. (ii) The FP equation is analyzed in the strong coupling approximation, by which the diffusive behavior is obtained for the linear and nonlinear birefringence. These would provide with a basis of statistical analysis for the polarization phenomena in nonlinear birefringent media.
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Pimont, François, Jean-Luc Dupuy, Rodman R. Linn, Jeremy A. Sauer i Domingo Muñoz-Esparza. "Pressure-Gradient Forcing Methods for Large-Eddy Simulations of Flows in the Lower Atmospheric Boundary Layer". Atmosphere 11, nr 12 (11.12.2020): 1343. http://dx.doi.org/10.3390/atmos11121343.
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Turbulent flows over forest canopies have been successfully modeled using Large-Eddy Simulations (LES). Simulated winds result from the balance between a simplified pressure gradient forcing (e.g., a constant pressure-gradient or a canonical Ekman balance) and the dissipation of momentum, due to vegetation drag. Little attention has been paid to the impacts of these forcing methods on flow features, despite practical challenges and unrealistic features, such as establishing stationary velocity or streak locking. This study presents a technique for capturing the effects of a pressure-gradient force (PGF), associated with atmospheric patterns much larger than the computational domain for idealized simulations of near-surface phenomena. Four variants of this new PGF are compared to existing forcings, for turbulence statistics, spectra, and temporal averages of flow fields. Results demonstrate that most features of the turbulent flow are captured. The variants can either enable modelers to prescribe a wind speed and direction at a reference height close to the ground as required in wildfire simulations, and/or mitigate streaks locking by reproducing the stability of the Ekman balance. Conditions of use, benefits, and drawbacks are discussed. PGF approaches, therefore, provide a viable solution for precursor inflows, including for the specific domains used in fire simulations.
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Bryan, L. J., i S. R. O'Donnell. "Demonstration of catecholamine and resorcinolamine derivatives as formaldehyde-induced fluorescence in protein models." Journal of Histochemistry & Cytochemistry 36, nr 6 (czerwiec 1988): 615–20. http://dx.doi.org/10.1177/36.6.3367047.
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We assessed in protein droplet models the potential use of the formaldehyde condensation method for histochemical demonstration of a wide range of catecholamines and resorcinolamines. The experiments showed that all of the amines tested, except salbutamol and carbuterol, formed fluorophores, and that the fluorescence was specific [i.e., there was no fluorescence in the absence of formaldehyde, the fluorescence was quenched by water, and the fluorophores were subject to photodecomposition by the exciting (405-nm) light]. Peak wavelengths of the emission spectra were 480-485 nm for fluorophores of resorcinolamine derivatives. The fluorescence intensity of the catecholamines was greater than that of the resorcinolamines. Fluorophore formation was not hindered by substitution of t-butyl, phenylisoprophyl, or p-hydroxyphenylisopropyl on the amino-N in catecholamines (t-butylnorepinephrine, Cc24, Cc25, respectively) or resorcinolamines (terbutaline, Th1161, fenoterol, respectively), and fluorophores also formed for catecholamines with the amino-N in a ring structure (rimiterol) or with a long alkyl chain substituted on the amino-N (hexoprenaline). Our study showed that fluorescence microphotometry can be used to detect a range of drugs that are catecholamines or resorcinolamines, and hence it should be possible to use this technique to study the properties of dissipation of these amines in tissues.
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Gómez López, Modesto, Nadia Mabel Pérez-Vielma, Haydee González Martínez, Eleazar Lara Padilla, Cindy Bandala, María Cristina González Torres i Ángel Miliar-García. "NLRP3, IL-1β, and Caspase-1 Gene Transcript Identification and Expression by QCM-D in Obese Children". Journal of Sensors 2019 (17.04.2019): 1–14. http://dx.doi.org/10.1155/2019/4323056.
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Background. Obesity in children is highly prevalent in Mexican population. Adipose tissue has been related to specific pro- and anti-inflammatory cytokine and inflammasome gene and protein expression patterns. Actually, there is no existing biosensor for detecting gene expression patterns in children with obesity. The quartz crystal microbalance with dissipation monitoring (QCM-D) has been used as a transducer for DNA biosensor design. Results. In this study, the gene expression pattern of IL-1β, NLRP3, and CASPASE-1 in children with obesity was successfully determined by means of QCM-D. Gene expression patterns were validated with those obtained by quantitative polymerase chain reaction (qPCR), a validated molecular biology technique for gene expression quantification. QCM-D analysis of the detected mass corresponding results for each of the genes showed a major detected mass for IL-1β, followed by similar NLRP3 and constitutive gene 18S deposited mass and a smaller deposited mass for CASPASE-1. Surprisingly, when comparing mRNA gene expression results for NLRP3, IL-1β, and CASPASE-1 obtained with qPCR and QCM-D, similar patterns were found, revealing greatest expression of IL-1β, followed by NLRP3, with CASPASE-1 being the molecule of least expression in the group of children with obesity. AFM images illustrate the step-by-step changes that took place on the quartz surface. Conclusions. QCM-D proved successfully for determining the gene transcripts and expression of NLRP3, IL-1β, and CASPASE-1 in children with obesity, with similar results validated by qPCR. “QCM-D decreases detection costs compared with a validated molecular biology technique.” The QCM-D biosensor developed by our group was successful for gene expression determination; in the future, it can be used for molecular diagnosis.
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Kaltakci, M. Y., M. Ozturk i M. H. Arslan. "An experimental investigation for external RC shear wall applications". Natural Hazards and Earth System Sciences 10, nr 9 (16.09.2010): 1941–50. http://dx.doi.org/10.5194/nhess-10-1941-2010.
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Abstract. The strength and rigidity of most reinforced concrete (RC) buildings in Turkey, which are frequently hit by destructive earthquakes, is not at a sufficient level. Therefore, the result of earthquakes is a significant loss of life and property. The strengthening method most commonly preferred for these type of RC buildings is the application of RC infilled walls (shear walls) in the frame openings of the building. However, since the whole building has to be emptied and additional heavy costs arise during this type of strengthening, users prefer not to strengthen their buildings despite the heavy risk they are exposed to. Therefore, it is necessary to develop easier-to-apply and more effective methods for the rapid strengthening of housing and the heavily-used public buildings which cannot be emptied during the strengthening process (such as hospitals and schools). This study empirically analyses the different methods of a new system which can meet this need. In this new system, named "external shear wall application", RC shear walls are applied on the external surface of the building, along the frame plane rather than in the building. To this end, 7 test samples in 1/2 and 1/3 geometrical scale were designed to analyse the efficiency of the strengthening technique where the shear wall leans on the frame from outside of the building (external shear wall application) and of the strengthening technique where a specific space is left between the frame and the external shear wall by using a coupling beam to connect elements (application of external shear wall with coupling beam). Test results showed that the maximum lateral load capacity, initial rigidity and energy dissipation behaviours of the samples strengthened with external shear wall were much better than those of the bare frames.
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Levitt, Michael R., Michael C. Barbour, Sabine Rolland du Roscoat, Christian Geindreau, Venkat K. Chivukula, Patrick M. McGah, John D. Nerva, Ryan P. Morton, Louis J. Kim i Alberto Aliseda. "Computational fluid dynamics of cerebral aneurysm coiling using high-resolution and high-energy synchrotron X-ray microtomography: comparison with the homogeneous porous medium approach". Journal of NeuroInterventional Surgery 9, nr 8 (12.07.2016): 00.1–00. http://dx.doi.org/10.1136/neurintsurg-2016-012479.
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BackgroundComputational modeling of intracranial aneurysms provides insights into the influence of hemodynamics on aneurysm growth, rupture, and treatment outcome. Standard modeling of coiled aneurysms simplifies the complex geometry of the coil mass into a homogeneous porous medium that fills the aneurysmal sac. We compare hemodynamics of coiled aneurysms modeled from high-resolution imaging with those from the same aneurysms modeled following the standard technique, in an effort to characterize sources of error from the simplified model.MaterialsPhysical models of two unruptured aneurysms were created using three-dimensional printing. The models were treated with coil embolization using the same coils as those used in actual patient treatment and then scanned by synchrotron X-ray microtomography to obtain high-resolution imaging of the coil mass. Computational modeling of each aneurysm was performed using patient-specific boundary conditions. The coils were modeled using the simplified porous medium or by incorporating the X-ray imaged coil surface, and the differences in hemodynamic variables were assessed.ResultsX-ray microtomographic imaging of coils and incorporation into computational models were successful for both aneurysms. Porous medium calculations of coiled aneurysm hemodynamics overestimated intra-aneurysmal flow, underestimated oscillatory shear index and viscous dissipation, and over- or underpredicted wall shear stress (WSS) and WSS gradient compared with X-ray-based coiled computational fluid dynamics models.ConclusionsComputational modeling of coiled intracranial aneurysms using the porous medium approach may inaccurately estimate key hemodynamic variables compared with models incorporating high-resolution synchrotron X-ray microtomographic imaging of complex aneurysm coil geometry.
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Zhu, Zhiyong, Ana Sierra, Colin M. L. Burnett, Biyi Chen, Ekaterina Subbotina, Siva Rama Krishna Koganti, Zhan Gao i in. "Sarcolemmal ATP-sensitive potassium channels modulate skeletal muscle function under low-intensity workloads". Journal of General Physiology 143, nr 1 (16.12.2013): 119–34. http://dx.doi.org/10.1085/jgp.201311063.
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ATP-sensitive potassium (KATP) channels have the unique ability to adjust membrane excitability and functions in accordance with the metabolic status of the cell. Skeletal muscles are primary sites of activity-related energy consumption and have KATP channels expressed in very high density. Previously, we demonstrated that transgenic mice with skeletal muscle–specific disruption of KATP channel function consume more energy than wild-type littermates. However, how KATP channel activation modulates skeletal muscle resting and action potentials under physiological conditions, particularly low-intensity workloads, and how this can be translated to muscle energy expenditure are yet to be determined. Here, we developed a technique that allows evaluation of skeletal muscle excitability in situ, with minimal disruption of the physiological environment. Isometric twitching of the tibialis anterior muscle at 1 Hz was used as a model of low-intensity physical activity in mice with normal and genetically disrupted KATP channel function. This workload was sufficient to induce KATP channel opening, resulting in membrane hyperpolarization as well as reduction in action potential overshoot and duration. Loss of KATP channel function resulted in increased calcium release and aggravated activity-induced heat production. Thus, this study identifies low-intensity workload as a trigger for opening skeletal muscle KATP channels and establishes that this coupling is important for regulation of myocyte function and thermogenesis. These mechanisms may provide a foundation for novel strategies to combat metabolic derangements when energy conservation or dissipation is required.
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Malairuang, Kwanruthai, Morakot Krajang, Jatuporn Sukna, Krongchan Rattanapradit i Saethawat Chamsart. "High Cell Density Cultivation of Saccharomyces cerevisiae with Intensive Multiple Sequential Batches Together with a Novel Technique of Fed-Batch at Cell Level (FBC)". Processes 8, nr 10 (21.10.2020): 1321. http://dx.doi.org/10.3390/pr8101321.
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High cell density cultivation (HCDC) is developed for the production of microbial biomasses and their products. They must be produced from high concentrations of substrate, e.g., glucose or sucrose. In batch culture, a high concentration of those sugars >40–50% (w/v) cannot efficiently be utilized because of a dissolved O2 limitation causing the Crabtree effect that produces toxic by-products, i.e., ethanol and/or acetate, that inhibit cell growth. To prevent this effect, the HCDC is conducted with the fed-batch strategies. However, it has many disadvantages, i.e., complicated operations. To overcome those problems, this study was designed to use a new, efficient C-source (carbon source) substrate, namely dextrin, an oligomer of glucose. It can be utilized by yeast at a very high concentration of ~100 g/L although using just batch cultivation. As it is gradually hydrolyzed to release glucose molecules and gradually assimilated into the cells as “fed-batch at the cell level” (FBC), it prevents the yeast cell system from undergoing the Crabtree effect. In this research, the types of medium, the types of sugar compared with dextrin, and the concentrations of yeast extract (YE) were studied. The batch production medium (BPM) with dextrin and YE performed very good results. The concentrations of dextrin for yeast cultivation were studied in the aerobic batch 5-L bioreactors. Its optimum concentration was at 90 g/L with 9 g/L of YE in 3× BPM. It was operated at 3 W/kg energy dissipation rate per unit mass (ε¯T) and 3 vvm airflow rate. Further, the intensive multiple sequential batch (IMSB) technique of high intensities of agitation speed and airflow was developed to achieve higher yield and productivity. The maximum values of cell biomass, specific growth rate, yield coefficient, productivity, and efficiency were at 55.17 g/L, 0.21 h−1, 0.54 g/g, 2.30 g/L/h, and 98.18%, respectively. The studies of cell growth kinetics, biochemical engineering mass balances, and fluid dynamics for the design of impeller speeds of the 5-L bioreactors during the cultivations of yeast using dextrin at the high concentrations were successful. The results can be used for the scale-up of bioreactor for the industrial production of yeast cell biomass at high concentrations.
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Mao, Kuanmin, Michael Yu Wang, Zhiwei Xu i Tianning Chen. "Simulation and Characterization of Particle Damping in Transient Vibrations". Journal of Vibration and Acoustics 126, nr 2 (1.04.2004): 202–11. http://dx.doi.org/10.1115/1.1687401.
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Particle damping is a technique of providing damping with granular particles embedded within small holes in a vibrating structure. The particles absorb kinetic energy through particle-to-wall and particle-to-particle frictional collisions. While the concept of particle damping seems to be simple and it has been used successfully in many fields for vibration reduction, it is difficult to predict the damping characteristics due to complex collisions in the dense particle flow. In this paper, we utilize the 3D discrete element method (DEM) for computer simulation and characterization of particle damping. With the DEM modeling tool validated with experimental results, it is shown that the particle damping can achieve a very high value of specific damping capacity. Furthermore, simulations provide information of particle motions within the container hole during three different regions and help explain their associated damping characteristics. The particle damping is a combination of the impact and the friction damping. The damping is found to be highly nonlinear as the rate of energy dissipation depends on amplitude. Particularly, the damping effect results in a linear decay in amplitude over a finite period of time. These characteristics are examined with respect to a simple single-mass impact damper and a dry-friction damper. It is concluded that the particle damping is a mix of these two damping mechanisms. It is further shown that the relative significance of these damping mechanisms depends on a particular arrangement of the damper. This study represents an effort towards a deeper understanding of particle damping to provide a comprehensive methodology for its analysis and design.
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Jaquetti, Roberto Kirmayr, José Francisco de Carvalho Gonçalves, Henrique Eduardo Mendonça Nascimento, Karen Cristina Pires da Costa, Jair Max Furtunato Maia i Flávia Camila Schimpl. "Fertilization and seasonality influence on the photochemical performance of tree legumes in forest plantation for area recovery in the Amazon". PLOS ONE 16, nr 5 (21.05.2021): e0243118. http://dx.doi.org/10.1371/journal.pone.0243118.
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N-fixing leguminous species can reach atmospheric dinitrogen gas (N2), having an advantage under N-limited degraded environments. These N-fixers are constantly used as facilitative species. Chlorophyll a fluorescence (ChF) acknowledges how different species take up and use light energy during photosynthesis. These techniques assess stress and performance responses to photosynthesis and are used for the selection of species with potential for reforestation. Six Fabaceae species were selected for this study: three nonfixing species (Cenostigma tocantinum, Senna reticulata and Dipteryx odorata) and three N-fixing species (Clitoria fairchildiana, Inga edulis and Acacia spp.). Variations in chlorophyll fluorescence under high vs. low water and nutrient conditions were studied. Multivariate analysis was performed to detect the effects of seasonality and fertilization on dark-adapted ChF two years after the experiment was established. The correlation among ChF variables and growth, photosynthesis and foliar nutrient concentrations was evaluated. Under high water- and nutrient-availability conditions, plants exhibited an enhanced performance index on absorption basis values correlated with electron transport fluxes. Under drought and nutrient-poor conditions, most species exhibit increased energy dissipation as photoprotection. High interspecific variation was found; therefore, species-specific responses should be considered in future ChF studies. Corroborating the ability to colonize high-light environments, N-fixers showed an increased performance index correlated with electron transport and Zn and N foliar concentrations. Negative correlations were found between photosynthesis and trapped fluxes. Diameter growth was positively correlated with electron transport fluxes. Given the different responses among species, ChF is an effective technique to screen for seasonality, fertilization and species effects and should be considered for use during forest restoration. Finally, the addition of fertilization treatments may facilitate tropical forest restoration due to the importance of nutrients in physiological processes. N-fixers showed high photochemical performance and tolerance to abiotic stress in degraded areas and therefore should be included to support ecosystem biomass restoration.
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Badri, Mohammed, i Harold M. Mooney. "Q measurements from compressional seismic waves in unconsolidated sediments". GEOPHYSICS 52, nr 6 (czerwiec 1987): 772–84. http://dx.doi.org/10.1190/1.1442344.
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Several processing methods in both time and frequency domains have been used to compute the in‐situ specific dissipation function 1/Q, or its inverse, the quality factor Q, in water‐saturated unconsolidated sediments. These methods are based on measurements of spectral amplitude ratio, peak‐to‐peak and first‐peak amplitude ratio, rise time, pulse broadening, and the Futterman causal attenuation operator of an attenuating signal. Compressional seismic waves were generated from explosive sources ranging in size from 1 to 64 mg of silver azide and recorded at a depth of 7.62 m below the surface near Wendover, Utah. The medium consisted of silty sandy clays with mean grain size diameter of 7.48 μm and water saturation of 70 percent. The hydrophone receivers were spirally distributed at distances ranging from 25 to 200 m from the source. An average Q value of 26 was obtained using analysis of spectral amplitude ratios over the frequency range 450–725 Hz for the five different sizes of explosive sources. Measurements of peak amplitude ratio produced an average Q value of 123. The computed Q value from the rise‐time method is found to have a wide range of Q values, from 50 to 207. The Q values determined from the pulse‐broadening technique ranged from 25 to 158 for quarter‐cycle measurements and from 26 to 114 for half‐cycle measurements. The Futterman causal attenuation operator yields high Q values, on the order of 200 to 300. The wide variation of the computed Q values indicates that different computational techniques can result in different Q values for the same type of materials. Results show that the rise‐time and pulse‐broadening methods are probably source‐dependent. This makes the spectral amplitude‐ratio method preferable to these two methods since it is independent of the source. A correct geometrical spreading factor appears to be sufficient to account for the observed amplitude decay with distance, which makes the Q value computed from the Futterman operator questionable. This suggests that the Q value computed from the spectral‐ratio method is probably more reliable than values computed by other techniques.
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Henning, Stephan W., Luke Jenkins, Sidni Hale, Christopher G. Wilson, John Tennant, Justin Moses, Mike Palmer i Robert N. Dean. "Manual Assembly of 400um Bumped-Die GaN Power Semiconductor Devices". International Symposium on Microelectronics 2012, nr 1 (1.01.2012): 000514–23. http://dx.doi.org/10.4071/isom-2012-poster_hale.
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Until recently, power semiconductors were usually produced as TO, power-PAK, and D-PAK style packaging, due to die size, thermal dissipation requirements, and the vertical flow of current through the devices. The introduction of GaN to power semiconductors has allowed manufactures to produce devices with approximately 9% the footprint of similar rated D-PAK Si MOSFETs. In addition, GaN semiconductors have much better theoretical limits of specific on-resistance to breakdown voltage, when compared to Si and SiC. As of now, GaN devices offer very good performance at much less the cost of SiC, very small footprints, no reverse recovery losses of a body diode, very low RDS(ON), and very fast turn-on and turn-off times due to QGS in single-digit nC range. GaN semiconductors are expected to make vast improvements over the next decade. Unfortunately, this decrease in package size has made design prototyping significantly more challenging. Traditional manual solder iron assembly is not sufficient for these devices. Difficulties include board design, device handling, alignment, solder reflow, flux residue removal, and post-assembly inspection. The EPC 2014 and 2015 devices both have a 4mm pitch and are 1.85mm2 and 6.70mm2, respectively. In many situations, the decreased pitch and small overall size of these devices mandate the use of automated assembly equipment, such as a pick & place, to ensure quality and repeatability of assembly. However, this may not be feasible for initial prototyping, due to cost and time constraints. Here we will present a technique for manual assembly of these chip scale devices, applied specifically to the EPC 2014 and 2015. This should decrease the cost and turn time for prototype assembly when utilizing these types of chip scale packaged power semiconductor devices.
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Bassi, Roberto, i Luca Dall'Osto. "Dissipation of Light Energy Absorbed in Excess: The Molecular Mechanisms". Annual Review of Plant Biology 72, nr 1 (17.06.2021): 47–76. http://dx.doi.org/10.1146/annurev-arplant-071720-015522.
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Light is essential for photosynthesis. Nevertheless, its intensity widely changes depending on time of day, weather, season, and localization of individual leaves within canopies. This variability means that light collected by the light-harvesting system is often in excess with respect to photon fluence or spectral quality in the context of the capacity of photosynthetic metabolism to use ATP and reductants produced from the light reactions. Absorption of excess light can lead to increased production of excited, highly reactive intermediates, which expose photosynthetic organisms to serious risks of oxidative damage. Prevention and management of such stress are performed by photoprotective mechanisms, which operate by cutting down light absorption, limiting the generation of redox-active molecules, or scavenging reactive oxygen species that are released despite the operation of preventive mechanisms. Here, we describe the major physiological and molecular mechanisms of photoprotection involved in the harmless removal of the excess light energy absorbed by green algae and land plants. In vivo analyses of mutants targeting photosynthetic components and the enhanced resolution of spectroscopic techniques have highlighted specific mechanisms protecting the photosynthetic apparatus from overexcitation. Recent findings unveil a network of multiple interacting elements, the reaction times of which vary from a millisecond to weeks, that continuously maintain photosynthetic organisms within the narrow safety range between efficient light harvesting and photoprotection.
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Akram, A., S. Ahmad, A. Rehman Jami, M. Sufyan i U. Zahid. "Variations in the expansion and shear scalars for dissipative fluids". Modern Physics Letters A 33, nr 13 (30.04.2018): 1850076. http://dx.doi.org/10.1142/s0217732318500761.
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This work is devoted to the study of some dynamical features of spherical relativistic locally anisotropic stellar geometry in f(R) gravity. In this paper, a specific configuration of tanh f(R) cosmic model has been taken into account. The mass function through technique introduced by Misner–Sharp has been formulated and with the help of it, various fruitful relations are derived. After orthogonal decomposition of the Riemann tensor, the tanh modified structure scalars are calculated. The role of these tanh modified structure scalars (MSS) has been discussed through shear, expansion as well as Weyl scalar differential equations. The inhomogeneity factor has also been explored for the case of radiating viscous locally anisotropic spherical system and spherical dust cloud with and without constant Ricci scalar corrections.
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Khan, Sadeque Reza, Sumanth Kumar Pavuluri, Gerard Cummins i Marc P. Y. Desmulliez. "Wireless Power Transfer Techniques for Implantable Medical Devices: A Review". Sensors 20, nr 12 (19.06.2020): 3487. http://dx.doi.org/10.3390/s20123487.
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Wireless power transfer (WPT) systems have become increasingly suitable solutions for the electrical powering of advanced multifunctional micro-electronic devices such as those found in current biomedical implants. The design and implementation of high power transfer efficiency WPT systems are, however, challenging. The size of the WPT system, the separation distance between the outside environment and location of the implanted medical device inside the body, the operating frequency and tissue safety due to power dissipation are key parameters to consider in the design of WPT systems. This article provides a systematic review of the wide range of WPT systems that have been investigated over the last two decades to improve overall system performance. The various strategies implemented to transfer wireless power in implantable medical devices (IMDs) were reviewed, which includes capacitive coupling, inductive coupling, magnetic resonance coupling and, more recently, acoustic and optical powering methods. The strengths and limitations of all these techniques are benchmarked against each other and particular emphasis is placed on comparing the implanted receiver size, the WPT distance, power transfer efficiency and tissue safety presented by the resulting systems. Necessary improvements and trends of each WPT techniques are also indicated per specific IMD.
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Sarwar, Waseem, i Rehan Sarwar. "Vibration Control Devices for Building Structures and Installation Approach: A Review". Civil and Environmental Engineering Reports 29, nr 2 (1.06.2019): 74–100. http://dx.doi.org/10.2478/ceer-2019-0018.
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Abstract Retrofit and structural design with vibration control devices have been proven repeatedly to be feasible seismic hazard mitigation approach. To control the structural response; supplemental energy dissipation devices have been most commonly used for energy absorption. The passive control system has been successfully incorporated in mid to high rise buildings as an appropriate energy absorbing system to suppress seismic and wind-induced excitation. The considerable theses that are highlighted include vibration control devices, the dynamic behavior of devices; energy dissipation mechanism, devices installation approach and building guidelines for structural analysis and design employing vibration control devices also, design concern that is specific to building with vibration control devices. The following four types of supplemental damping devices have been investigated in this review: metallic devices, friction devices, viscous fluid devices, and viscoelastic devices. Although numerous devices installation techniques available, more precisely, devices installation approaches have been reviewed in this paper, including Analysis and Redesign approach (Lavan A/R), standard placement approach, simplified sequential search algorithm, and Takewaki approach.
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Caprili, Silvia, Francesco Morelli, Walter Salvatore i Agnese Natali. "Design and Analysis of Automated Rack Supported Warehouses". Open Civil Engineering Journal 12, nr 1 (29.06.2018): 150–66. http://dx.doi.org/10.2174/1874149501812010150.
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Background: The lack of codified standards for the design of automated rack supported warehouses forced engineers to use personal experience and commonly accepted rules. Objective: This paper investigates the efficacy of applying Eurocodes’ rules for the design and analysis of automated rack supported warehouses. Structural performance, construction feasibility and economic effort are considered. Method: A typical case study building was designed following the two approaches proposed by Eurocodes: elastic and dissipative. Results: The satisfaction of the capacity design requirements, used for dissipative approach, was not always possible. Analyses showed the development of non-uniform collapse mechanisms and yielding patterns. Conclusion: Specific design rules and analysis techniques shall be developed accounting for the structural performance of automated rack supported warehouses.
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Fialko, N., A. Stepanova, R. Navrodskaya i S. Shevchuk. "EXERGIC EFFICIENCY OF THE HEAT RECOVERY UNIT FOR WASTE GASES OF A HEAT ENGINE OF A COGENERATION PLANT". Thermophysics and Thermal Power Engineering 42, nr 3 (19.06.2020): 56–60. http://dx.doi.org/10.31472/ttpe.3.2020.6.
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The paper presents the results of a study of the efficiency of a heat recovery unit for waste gases of a heat engine of a cogeneration plant. The possibilities of using for this purpose the discrete-modular principle and complex methods of analyzing the efficiency of heat recovery systems, which are based on the methods of exergo-dissipative functions and exergic balances, are analyzed. The design features of the heat exchanger are considered and a conclusion is made about the possibility of presenting it as a system of eight discrete modules. The results of calculating the exergy characteristics for each of the eight heat exchanger modules, performed within the framework of the indicated methods, are presented. A regular decrease in exergy losses and heat-exergy criterion of efficiency is observed during the transition from the first to the eighth module of the heat recovery unit. However, exergy characteristics for the third and fourth modules of the heat exchanger are somewhat higher than the indicated dependence suggests. This indicates the thermodynamic imperfection of these modules. The main exergy losses in all heat exchanger modules are associated with losses due to heat transfer from flue gases to the wall. An insignificant discrepancy between the values of the total exergy losses calculated within the framework of the methods used indicates that both methods can be used in various heat recovery schemes. However, in each specific case, it is necessary to choose a methodology with which it is possible to identify individual elements that need optimization or constructive improvement. Particular attention is paid to the comparative analysis of the selected techniques and consideration of the advantages and disadvantages of their use in various cases. It is noted that the technique based on the integral balance method of exergy analysis can be considered effective due to the small number of initial parameters and the simplicity of the analytical and calculation methods. The advantage of the technique using exergo-dissipative functions is that it allows one to differentiate exergy losses in a heat exchanger and establish the causes and areas of their localization.
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Muñoz-Esparza, Domingo, Robert D. Sharman i Wiebke Deierling. "Aviation Turbulence Forecasting at Upper Levels with Machine Learning Techniques Based on Regression Trees". Journal of Applied Meteorology and Climatology 59, nr 11 (listopad 2020): 1883–99. http://dx.doi.org/10.1175/jamc-d-20-0116.1.
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AbstractWe explore the use of machine learning (ML) techniques, namely, regression trees (RT), for the purpose of aviation turbulence forecasting at upper levels [20–45 kft (~6–14 km) in altitude]. In particular, we develop a series of RT-based algorithms that include random forests (RF) and gradient-boosted regression trees (GBRT) methods. Numerical weather prediction model prognostic variables and derived turbulence diagnostics based on 6-h forecasts from the 3-km High-Resolution Rapid Refresh model are used as features to train these data-driven models. Training and evaluation are based on turbulence estimates of eddy dissipation rate (EDR) obtained from automated in situ aircraft reports. Our baseline RF model, consisting of 100 trees with 30 layers of maximum depth, significantly reduces forecast errors for EDR < 0.1 m2/3 s−1 (which corresponds roughly to null and light turbulence) when compared with a simple regression model, increasing the probability of detection and in turn reducing the number of false alarms. Model complexity reduction via GBRT and feature-relevance analyses is performed, indicating that considerable execution speedups can be achieved while maintaining the model’s predictive skill. Overall, the ML models exhibit enhanced performance in discriminating the EDR forecast among the light, moderate, and severe turbulence categories. In addition, these artificial intelligence techniques significantly simplify the generation of new NWP and grid-spacing specific turbulence forecast products.
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Globus, Tatiana, Igor Sizov i Boris Gelmont. "Sub-THz specific relaxation times of hydrogen bond oscillations in E.coli thioredoxin. Molecular dynamics and statistical analysis". Faraday Discuss. 171 (2014): 179–93. http://dx.doi.org/10.1039/c4fd00029c.
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Hydrogen bonds (H-bonds) in biological macromolecules are important for the molecular structure and functions. Since interactions via hydrogen bonds are weaker than covalent bonds, it can be expected that atomic movements involving H-bonds have low frequency vibrational modes. Sub-Terahertz (sub-THz) vibrational spectroscopy that combines measurements with molecular dynamics (MD) computational prediction has been demonstrated as a promising approach for biological molecule characterization. Multiple resonance absorption lines have been reported. The knowledge of relaxation times of atomic oscillations is critical for the successful application of THz spectroscopy for hydrogen bond characterization. The purpose of this work is to use atomic oscillations in the 0.35–0.7 THz range, found from molecular dynamic (MD) simulations of E.coli thioredoxin (2TRX), to study relaxation dynamics of two intra-molecular H-bonds, O⋯H–N and O⋯H–C. Two different complimentary techniques are used in this study, one is the analysis of the statistical distribution of relaxation time and dissipation factor values relevant to low frequency oscillations, and the second is the analysis of the autocorrelation function of low frequency quasi-periodic movements. By studying hydrogen bond atomic displacements, it was found that the atoms are involved in a number of collective oscillations, which are characterized by different relaxation time scales ranging from 2–3 ps to more than 150 ps. The existence of long lasting relaxation processes opens the possibility to directly observe and study H-bond vibrational modes in sub-THz absorption spectra of bio-molecules if measured with an appropriate spectral resolution. The results of measurements using a recently developed frequency domain spectroscopic sensor with a spectral resolution of 1 GHz confirm the MD analysis.
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Iturri, Jagoba, Andreas Breitwieser, Dietmar Pum, Uwe Sleytr i José Toca-Herrera. "Electrochemical-QCMD Control over S-Layer (SbpA) Recrystallization with Fe2+ as Specific Ion for Self-Assembly Induction". Applied Sciences 8, nr 9 (25.08.2018): 1460. http://dx.doi.org/10.3390/app8091460.
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The critical role of divalent ions (M²+) in the self-assembly of SbpA S-layer proteins (from Lysinibacillus sphaericus CCM 2177) into crystalline structures has been reported in several studies. Hence, ions such as magnesium, barium, nickel and, most commonly, calcium (Ca²+) have proven to trigger both protein-protein and protein-substrate interactions involved in the two-stage non-classical pathway recrystallization followed by SbpA units. As a result, two dimensional, crystalline nanometric sheets in a highly ordered tetrameric state (p4) can be formed on top of different surfaces. The use of iron in its ferrous state (Fe2+) as self-assembly inducing candidate has been omitted so far due to its instability under aerobic conditions, tending to natural oxidation to the ferric (Fe3+) state. In this work, the potentiality of assembling fully functional S-layers from iron (II) salts (FeCl2 and FeSO4) is described for the first time. A combination of chemical (oxidation retardants) and electrical (−1 V potential) factors has been applied to effectively act against such an oxidizing trend. Formation of the respective crystalline films has been followed by means of Electrochemical Quartz Crystal Microbalance with Dissipation (EQCM-D) measurements and complementary Atomic Force Microscopy (AFM) topography studies, which prove the presence of squared lattice symmetry at the end of the recrystallization process. Both techniques, together with additional electrochemical tests performed over the ion permeability of both types of S-layer coatings formed, show the influence of the counterion chosen (chloride vs. sulphate) in the final packing and performance of the S-layer. The presence of an underlying Secondary Cell Wall Polymer (SCWP) as in the natural case contributes to pair both systems, due to the high lateral motility freedom provided by this biopolymer to SbpA units in comparison to uncoated substrates.
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Drougkas, Dimitris, Evagelos Karatsis, Maria Papagiannaki, Serafeim Chatzimoisiadis, Fotini Arabatzi, Stergios Maropoulos i Alexander Tsouknidas. "Gait-Specific Optimization of Composite Footwear Midsole Systems, Facilitated through Dynamic Finite Element Modelling". Applied Bionics and Biomechanics 2018 (23.12.2018): 1–9. http://dx.doi.org/10.1155/2018/6520314.
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Objective. During the last century, running shoes have been subject to drastic changes with incremental however improvements as to injury prevention. This may be, among others, due to the limited insight that experimental methodologies can provide on their 3D in situ response. The objective of this study was to demonstrate the effectiveness of finite element (FE) modelling techniques, in optimizing a midsole system as to the provided cushioning capacity. Methods. A commercial running shoe was scanned by means of micro computed tomography and its gel-based midsole, reverse-engineered to a 200 μm accuracy. The resulting 3D model was subjected to biorealistic loading and boundary conditions, in terms of time-varying plantar pressure distribution and shoe-ground contact constraints. The mesh grid of the FE model was verified as to its conceptual soundness and validated against velocity-driven impact tests. Nonlinear material properties were assigned to all entities and the model subjected to a dynamic FE analysis. An optimization function (based on energy absorption criteria) was employed to determine the optimum gel volume and position, as to accommodate sequential cushioning in the rear-, mid-, and forefoot, of runner during stance phase. Results. The in situ developing stress fields suggest that the shock dissipating properties of the midsole could be significantly improved. Altering the position of the gel pads and varying their volume led to different midsole responses that could be tuned more efficiently to the specific strike and pronation pattern. Conclusions. The results suggest that midsole design can be significantly improved through biorealistic FE modelling, thus providing a new platform for the conceptual redesign and/or optimization of modern footwear.
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Marschik, Christian, Wolfgang Roland, Marius Dörner, Georg Steinbichler i Volker Schöppner. "Leakage-Flow Models for Screw Extruders". Polymers 13, nr 12 (9.06.2021): 1919. http://dx.doi.org/10.3390/polym13121919.
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Many theoretical analyses of extrusion ignore the effect of the flight clearance when predicting the pumping capability of a screw. This might be reasonable for conventional extruder screws with “normal” clearances but leads to errors when more advanced screw designs are considered. We present new leakage-flow models that allow the effect of the flight clearance to be included in the analysis of melt-conveying zones. Rather than directly correcting the drag and pressure flows, we derived regression models to predict locally the shear-thinning flow through the flight clearance. Using a hybrid modeling approach that includes analytical, numerical, and data-based modeling techniques enabled us to construct fast and accurate regressions for calculating flow rate and dissipation rate in the leakage gap. Using the novel regression models in combination with network theory, the new approximations consider the effect of the flight clearance in the predictions of pumping capability, power consumption and temperature development without modifying the equations for the down-channel flow. Unlike other approaches, our method is not limited to any specific screw designs or processing conditions.
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Scholl, Dean, Mike Cooley, Steve R. Williams, Dana Gebhart, David Martin, Anna Bates i Robert Mandrell. "An Engineered R-Type Pyocin Is a Highly Specific and Sensitive Bactericidal Agent for the Food-Borne Pathogen Escherichia coli O157:H7". Antimicrobial Agents and Chemotherapy 53, nr 7 (6.04.2009): 3074–80. http://dx.doi.org/10.1128/aac.01660-08.
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ABSTRACT Some strains of Pseudomonas aeruginosa produce R-type pyocins, which are high-molecular-weight phage tail-like protein complexes that have bactericidal activity against other Pseudomonas strains. These particles recognize and bind to bacterial surface structures via tail fibers, their primary spectrum determinant. R-type pyocins kill the cell by contracting a sheath-like structure and inserting their hollow core through the cell envelope, resulting in dissipation of the cellular membrane potential. We have retargeted an R-type pyocin to Escherichia coli O157:H7 by fusing a tail spike protein from an O157-specific phage, φV10, to the pyocin tail fiber. The φV10 tail spike protein recognizes and degrades the O157 lipopolysaccharide. This engineered pyocin, termed AVR2-V10, is sensitive and specific, killing 100% of diverse E. coli O157:H7 isolates but no other serotypes tested. AVR2-V10 can kill E. coli O157:H7 on beef surfaces, making it a candidate agent for the elimination of this pathogen from food products. All rare AVR2-V10-resistant mutants isolated and examined have lost the ability to produce the O157 antigen and are expected to have compromised virulence. In addition, E. coli O157:H7 exposed to and killed by AVR2-V10 do not release Shiga toxin, as is often the case with many antibiotics, suggesting potential therapeutic applications. The demonstration that a novel R-type pyocin can be created in the laboratory by fusing a catalytic tail spike from the family Podoviridae to a tail fiber of a member of the family Myoviridae is evidence that the plasticity observed among bacteriophage tail genes can, with modern molecular techniques, be exploited to produce nonnatural, targeted antimicrobial agents.
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Barón, Matilde, Mónica Pineda i María Luisa Pérez-Bueno. "Picturing pathogen infection in plants". Zeitschrift für Naturforschung C 71, nr 9-10 (1.09.2016): 355–68. http://dx.doi.org/10.1515/znc-2016-0134.
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AbstractSeveral imaging techniques have provided valuable tools to evaluate the impact of biotic stress on host plants. The use of these techniques enables the study of plant-pathogen interactions by analysing the spatial and temporal heterogeneity of foliar metabolism during pathogenesis. In this work we review the use of imaging techniques based on chlorophyll fluorescence, multicolour fluorescence and thermography for the study of virus, bacteria and fungi-infected plants. These studies have revealed the impact of pathogen challenge on photosynthetic performance, secondary metabolism, as well as leaf transpiration as a promising tool for field and greenhouse management of diseases. Images of standard chlorophyll fluorescence (Chl-F) parameters obtained during Chl-F induction kinetics related to photochemical processes and those involved in energy dissipation, could be good stress indicators to monitor pathogenesis. Changes on UV-induced blue (F440) and green fluorescence (F520) measured by multicolour fluorescence imaging in pathogen-challenged plants seem to be related with the up-regulation of the plant secondary metabolism and with an increase in phenolic compounds involved in plant defence, such as scopoletin, chlorogenic or ferulic acids. Thermal imaging visualizes the leaf transpiration map during pathogenesis and emphasizes the key role of stomata on innate plant immunity. Using several imaging techniques in parallel could allow obtaining disease signatures for a specific pathogen. These techniques have also turned out to be very useful for presymptomatic pathogen detection, and powerful non-destructive tools for precision agriculture. Their applicability at lab-scale, in the field by remote sensing, and in high-throughput plant phenotyping, makes them particularly useful. Thermal sensors are widely used in crop fields to detect early changes in leaf transpiration induced by both air-borne and soil-borne pathogens. The limitations of measuring photosynthesis by Chl-F at the canopy level are being solved, while the use of multispectral fluorescence imaging is very challenging due to the type of light excitation that is used.
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Speich, S., H. Dijkstra i M. Ghil. "Successive bifurcations in a shallow-water model applied to the wind-driven ocean circulation". Nonlinear Processes in Geophysics 2, nr 3/4 (31.12.1995): 241–68. http://dx.doi.org/10.5194/npg-2-241-1995.
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Abstract. Climate - the "coarse-gridded" state of the coupled ocean - atmosphere system - varies on many time and space scales. The challenge is to relate such variation to specific mechanisms and to produce verifiable quantitative explanations. In this paper, we study the oceanic component of the climate system and, in particular, the different circulation regimes of the mid-latitude win driven ocean on the interannual time scale. These circulations are dominated by two counterrotating, basis scale gyres: subtropical and subpolar. Numerical techniques of bifurcation theory are used to stud the multiplicity and stability of the steady-state solution of a wind-driven, double-gyre, reduced-gravity, shallow water model. Branches of stationary solutions and their linear stability are calculated systematically as parameter are varied. This is one of the first geophysical studies i which such techniques are applied to a dynamical system with tens of thousands of degrees of freedom. Multiple stationary solutions obtain as a result of nonlinear interactions between the two main recirculating cell (cyclonic and anticyclonic) of the large- scale double-gyre flow. These equilibria appear for realistic values of the forcing and dissipation parameters. They undergo Hop bifurcation and transition to aperiodic solutions eventually occurs. The periodic and chaotic behaviour is probably related to an increased number of vorticity cells interaction with each other. A preliminary comparison with observations of the Gulf Stream and Kuroshio Extensions suggests that the intern variability of our simulated mid-latitude ocean is a important factor in the observed interannual variability o these two current systems.
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Valente, Marco. "Seismic Strengthening of Non-Ductile R/C Structures Using Infill Wall or Ductile Steel Bracing". Advanced Materials Research 602-604 (grudzień 2012): 1583–87. http://dx.doi.org/10.4028/www.scientific.net/amr.602-604.1583.
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This study deals with the seismic assessment and retrofitting of existing non-ductile R/C structures and the issue of selecting effective strengthening solutions is addressed. A displacement based procedure using nonlinear static pushover analyses is adopted in order to assess the main characteristics of the original structure and to select valuable retrofitting strategies. The procedure is applied to a four-storey R/C frame tested at the JRC ELSA Laboratory some years ago. The R/C frame was designed for gravity loads without specific earthquake-resistant provisions. Accurate numerical models are developed to reproduce the seismic response of the R/C frame in both the original and retrofitted configurations. The effectiveness of two strengthening techniques is examined. First, a retrofitting intervention is carried out by adding a concrete shear wall to the short bay of the frame. This solution is efficient in controlling global lateral drift and thus reducing damage in structural members. Then, a retrofitting solution involving the introduction of eccentric steel bracing is investigated in order to reduce the displacement demand and to increase the energy dissipation capacity of the frame. Nonlinear dynamic analyses are performed to assess and compare the seismic response of the frame in the original and retrofitted configurations.
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Habib, Giuseppe, Fanni Kádár i Bálint Papp. "Impulsive vibration mitigation through a nonlinear tuned vibration absorber". Nonlinear Dynamics 98, nr 3 (listopad 2019): 2115–30. http://dx.doi.org/10.1007/s11071-019-05312-y.
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Abstract The dynamics of a nonlinear passive vibration absorber conceived to mitigate vibrations of a nonlinear host structure is considered in this paper. The system under study is composed of a primary system, consisting of an undamped nonlinear oscillator of Duffing type, and a nonlinear dynamic vibration absorber, denominated nonlinear tuned vibration absorber (NLTVA). The NLTVA consists of a small mass, attached to the host structure through a linear damper, a linear and a cubic spring. The host structure is subject to free vibrations and the performance of the NLTVA is evaluated with respect to the minimal time required to dissipate a specific amount of the mechanical energy of the system. In order to characterize the dynamics of the system, a combination of numerical and analytical techniques is implemented. In particular, on the basis of the first-order reduced model, slow invariant manifolds of the transient dynamics are identified, which enable to estimate the absorber performance. Results illustrate that two different dynamical paths exist and the system can undergo either of them, depending on the initial conditions and on the value of the absorber nonlinear stiffness coefficient. One path leads to a very fast vibration mitigation, and therefore to a favorable behavior, while the other one causes a very slow energy dissipation.
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Naveen, Jesuarockiam, Mohammad Jawaid, Kheng Lim Goh, Degalhal Mallikarjuna Reddy, Chandrasekar Muthukumar, Tamil Moli Loganathan i Koduri Naga Ganapathy Lakshmi Reshwanth. "Advancement in Graphene-Based Materials and Their Nacre Inspired Composites for Armour Applications—A Review". Nanomaterials 11, nr 5 (8.05.2021): 1239. http://dx.doi.org/10.3390/nano11051239.
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The development of armour systems with higher ballistic resistance and light weight has gained considerable attention as an increasing number of countries are recognising the need to build up advanced self-defence system to deter potential military conflicts and threats. Graphene is a two dimensional one-atom thick nanomaterial which possesses excellent tensile strength (130 GPa) and specific penetration energy (10 times higher than steel). It is also lightweight, tough and stiff and is expected to replace the current aramid fibre-based polymer composites. Currently, insights derived from the study of the nacre (natural armour system) are finding applications on the development of artificial nacre structures using graphene-based materials that can achieve high toughness and energy dissipation. The aim of this review is to discuss the potential of graphene-based nanomaterials with regard to the penetration energy, toughness and ballistic limit for personal body armour applications. This review addresses the cutting-edge research in the ballistic performance of graphene-based materials through theoretical, experimentation as well as simulations. The influence of fabrication techniques and interfacial interactions of graphene-based bioinspired polymer composites for ballistic application are also discussed. This review also covers the artificial nacre which is shown to exhibit superior mechanical and toughness behaviours.
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Chaves, Manuela M., João P. Maroco i João S. Pereira. "Understanding plant responses to drought — from genes to the whole plant". Functional Plant Biology 30, nr 3 (2003): 239. http://dx.doi.org/10.1071/fp02076.
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In the last decade, our understanding of the processes underlying plant response to drought, at the molecular and whole-plant levels, has rapidly progressed. Here, we review that progress. We draw attention to the perception and signalling processes (chemical and hydraulic) of water deficits. Knowledge of these processes is essential for a holistic understanding of plant resistance to stress, which is needed to improve crop management and breeding techniques. Hundreds of genes that are induced under drought have been identified. A range of tools, from gene expression patterns to the use of transgenic plants, is being used to study the specific function of these genes and their role in plant acclimation or adaptation to water deficit. However, because plant responses to stress are complex, the functions of many of the genes are still unknown. Many of the traits that explain plant adaptation to drought — such as phenology, root size and depth, hydraulic conductivity and the storage of reserves — are those associated with plant development and structure, and are constitutive rather than stress induced. But a large part of plant resistance to drought is the ability to get rid of excess radiation, a concomitant stress under natural conditions. The nature of the mechanisms responsible for leaf photoprotection, especially those related to thermal dissipation, and oxidative stress are being actively researched. The new tools that operate at molecular, plant and ecosystem levels are revolutionising our understanding of plant response to drought, and our ability to monitor it. Techniques such as genome-wide tools, proteomics, stable isotopes and thermal or fluorescence imaging may allow the genotype–phenotype gap to be bridged, which is essential for faster progress in stress biology research.
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Wilcoxon, R. K., i A. Moutsoglou. "Second Law Analysis in Assessing Constant Power Input Systems". Journal of Heat Transfer 113, nr 2 (1.05.1991): 321–28. http://dx.doi.org/10.1115/1.2910564.
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A criterion for comparing the relative performance of various heat transfer augmentation methods used in constant power input systems is introduced. The analysis is based on the principle of minimizing the rate of total entropy generation. The heat transfer load (HTL), a parameter determined by the operating requirements of the heat dissipating process that indicates the difficulty of the heat transfer duty to be performed, is defined in the present study. By comparing the irreversibility distribution ratio (φ) of various configurations at a given heat transfer load, the most exergy efficient system can be selected. The data for three different types of fin configurations used in two constant power input applications (electronic equipment and internal turbine blade cooling) are utilized in demonstrating the technique. The results indicate which specific fin geometry of the particular configuration type analyzed will transfer the dissipated heat at the specified base surface temperature while requiring the least pumping power. Although the φ versus HTL criterion is applied to only fins in this study, the method can be extended to many other applications such as jet impingement cooling or mass transfer.