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Journal articles on the topic 'Bottom of variable thickness'
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1
Yuriy, Khomyak, Naumenko Ievgeniia, Zheglova Victoriia, and Popov Vadim. "MINIMIZING THE MASS OF A FLAT BOTTOM OF CYLINDRICAL APPARATUS." Eastern-European Journal of Enterprise Technologies 2, no. 1 (92) (2018): 42–50. https://doi.org/10.15587/1729-4061.2018.126141.
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In the bodies of cylindrical apparatuses that operate under pressure, one of the weak elements is a flat bottom whose thickness is increased by 4…5 times in comparison with the wall thickness. This is due to the fact that the bottom is exposed to a more unfavorable bending deformation compared to the wall that «works» on stretching. In order to reduce specific metal consumption for the bottom, we propose the optimization of the shape of a radial cross-section by a rational redistribution of the material: to increase thickness of the bottom in the region of its contact with the wall and to significantly reduce it in the central zone. To describe a variable thickness of the bottom, we applied the Gauss equation with an arbitrary parameter that determines the intensity of change in the thickness in radial direction. We have obtained a general solution to the differential equation of the problem on bending a bottom at a given law of change in its thickness, which is represented using the hypergeometric Kummer’s functions. A technique for concretizing the resulting solution was proposed and implemented, based on the application of conditions of contact between a cylindrical shell and a bottom. The solution derived was used to minimize the mass of the bottom. We have designed a zone of transition from the bottom to the wall whose strength was verified by the method of finite elements under actual conditions
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Xin, Tengda, Hua Wang, Cunyan Cui, and Jiguang Zhao. "An optimal design model for the wall thickness of the propellant tank." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 234, no. 2 (2019): 445–56. http://dx.doi.org/10.1177/0954410019867218.
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The propellant tank is a vital part for the liquid rocket, and the optimal design of the propellant tank is a significant research to develop the heavy rocket. This paper aims at providing an optimal design model for tank wall thickness. Through establishing the tank mathematical model, analyzing the stress distributions of tank, and defining the equivalent stress of tank, the wall thickness parameters of tank roof, cylinder, and bottom are obtained. The effects of tank parameters on the wall thickness are analyzed to determine the distribution rules of tank roof, cylinder, and bottom wall thickness parameters. Combined with the safety factor that is defined as the ratio of the material's ultimate stress to the maximum equivalent stress, the optimal design model with invariable tank roof and bottom wall thicknesses and variable tank cylinder wall thickness is established. Finally, the optimal design model is verified by comparing the optimal tank with the original tank. The results show that the optimal design model can effectively decrease the mass of the tank and improve the stress distribution of the tank.
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Taibi, Mohammed, Younes Abouelhanoune, and Fouad Dimane. "Transient Heat Transfer Analysis in Metal Plates with Variable Thickness." Journal of Physical Science 35, no. 1 (2024): 1–12. http://dx.doi.org/10.21315/jps2024.35.1.1.
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Nonlinear transient heat transfer via conduction–radiation is a dynamic topic of long-standing interest with applications ranging from aeronautical and mechanical engineering to industrial and civil security. To gain a better understanding of the performances of materials having thermal proprieties that change during nonlinear heat transfer, several studies using the finite element method (FEM) have been conducted. Such studies apply nonlinear thermal material characteristics to describe the complete system under different loading conditions in each region by adjusting the temperature values for the other three edges and the thickness parameter with Dirichlet boundary conditions. As a result, while modeling and simulating temperature distributions for such situations, nonlinearities generated by temperature-dependent thermal conductivity must be considered. In this work, we focus on the analysis of coupled transient heat transfer through two metal plates with temperature-dependent thermal characteristics in which the temperature is fixed along the bottom edge and heat is transferred from both the top and bottom faces of the two plates. FEM is employed to solve the nonlinear heat equation and compute the temperature as a function of time for variable thickness. The study examines the effect of modifying the thickness parameter values on the temperature distribution over time for various edge values over 5,000 s.
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Kang, Jae-Hoon. "Vibration Analysis of Complete Conical Shells with Variable Thickness." International Journal of Structural Stability and Dynamics 14, no. 04 (2014): 1450001. http://dx.doi.org/10.1142/s0219455414500011.
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A three-dimensional (3D) method of analysis is presented for determining the free vibration frequencies of complete (not truncated) conical shells with linearly varying thickness. The complete conical shells free or clamped at the bottom edge with a free vertex are investigated. Unlike conventional shell theories, which are mathematically 2D, the present method is based upon the 3D dynamic equations of elasticity. Displacement components ur, uθ and uz in the radial, circumferential and axial directions, respectively, are taken to be periodic in θ and in time, and expressed by algebraic polynomials in the r- and z-directions. Potential (strain) and kinetic energies of the complete conical shell are formulated. The Ritz method is used to solve the eigenvalue problem, yielding the upper bound values of the frequencies by minimization. As the degree of the polynomials is increased, frequencies converge to the exact values, with four-digit exactitude demonstrated for the first five frequencies. The frequencies from the present 3D method are compared with those from other 3D approaches and 2D shell theory by previous researchers.
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Barton, N. G., C. H. Li, and S. J. Spencer. "Control of a surface of discontinuity in continuous thickness." Journal of the Australian Mathematical Society. Series B. Applied Mathematics 33, no. 3 (1992): 269–89. http://dx.doi.org/10.1017/s0334270000007050.
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AbstractThis paper examines the control of an interface between a suspension of sedimenting particles in liquid and a bed of dense-packed particles at the bottom of the suspension. The problem arises in the operation of continuous thickeners (e.g. in mineral processing) and is here mathematically described by a first order inhomogeneous partial differential equation for the concentration C(x, t) of particles. The controlled variable is the height H* of the bed, and the control variables are the volume fluxes injected at the feed level and removed at the bed. A strategy to control the interface is devised, and control is confirmed and demonstrated by a series of numerical experiments.
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Kim, Do Bum, and Byong Jeong Choi. "Evaluation of Flexural Strength about Shape of the Steel Plate-Concrete Composite Beam with Bolt." Advanced Materials Research 1021 (August 2014): 144–47. http://dx.doi.org/10.4028/www.scientific.net/amr.1021.144.
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The composite beam is efficient and easy to construction. But deformation capacity is degraded with thickness of bottom tension plate. The composition ratio by shear connector have a decisive effect on deformation capacity. This research evaluated the flexural strength and deflection with variable of thickness and protrusion length. The effect of composite ratio and shear connector was analyzed through fracture behaviors and distribution of strain through two point loading test.
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Ivošević, Špiro, Romeo Meštrović, and Nataša Kovač. "A Probabilistic Method for Estimating the Percentage of Corrosion Depth on the Inner Bottom Plates of Aging Bulk Carriers." Journal of Marine Science and Engineering 8, no. 6 (2020): 442. http://dx.doi.org/10.3390/jmse8060442.
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This paper presents an approach for the model estimating the probabilistic percent corrosion depth for inner bottom plates of fuel oil tanks located in the double bottom of aging bulk carriers. Assuming that corrosion begins after four years of exploitation, a statistical approach to investigations on the ratio of the corrosion rate and the average initial inner bottom plate’s thickness of considered bulk carriers is given. We consider this ratio to be a random variable since it is included in the usual linear corrosion model. By applying adequate statistical tests to the available empirical dataset, three best fitted three-parameter distributions for estimating the cumulative density function and the probability density function of the random variable were obtained. These three distributions were further used to estimate the studied percentage of corrosion depth. Lastly, we present the corresponding numerical and graphical results concerning the obtained statistical and empirical results and give concluding remarks.
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Arcone, Steven A., and Allan J. Delaney. "Airborne River-Ice Thickness Profiling with Helicopter-Borne UHF Short-Pulse Radar." Journal of Glaciology 33, no. 115 (1987): 330–40. http://dx.doi.org/10.1017/s0022143000008923.
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AbstractThe ice-thickness profiling performance of a helicopter-mounted short-pulse radar operating at approximate center frequencies of 600 and 900 MHz was assessed. The antenna packages were mounted 1.2 m off the skid of a small helicopter whose speed and altitude were varied from about 1.8 to 9 m/s and 3 to 12 m. Clutter from the helicopter offered minimal interference with the ice data. Data were acquired in Alaska over lakes (as a proving exercise) and two rivers, whose conditions varied from open water to over 1.5 m of solid ice with numerous frazil-ice formations. The most readily interpretable data were acquired when the ice or snow surface was smooth. Detailed surface investigations on the Tanana River revealed good correlations of echo delay with solid ice depth, but an insensitivity to frazil-ice depth due to its high water content. On the Yukon River, coinciding temporally coherent surface and bottom reflections were associated with solid ice and smooth surfaces. All cases of incoherent surface returns (scatter) occurred over ice rubble. Rough-surface scattering was always followed by the appearance of bottom scattering but, in many cases, including a hanging-wall formation of solid frazil ice, bottom scattering occurred beneath coherent, smooth-surface reflections. Areas of incoherent bottom scattering investigated by drilling revealed highly variable ice conditions, including frazil ice. The minimum ice thickness that could be resolved from the raw data was about 0.2 m with the 600 MHz antenna and less than 0.15 m with the 900 MHz antenna.
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Arcone, Steven A., and Allan J. Delaney. "Airborne River-Ice Thickness Profiling with Helicopter-Borne UHF Short-Pulse Radar." Journal of Glaciology 33, no. 115 (1987): 330–40. http://dx.doi.org/10.3189/s0022143000008923.
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AbstractThe ice-thickness profiling performance of a helicopter-mounted short-pulse radar operating at approximate center frequencies of 600 and 900 MHz was assessed. The antenna packages were mounted 1.2 m off the skid of a small helicopter whose speed and altitude were varied from about 1.8 to 9 m/s and 3 to 12 m. Clutter from the helicopter offered minimal interference with the ice data. Data were acquired in Alaska over lakes (as a proving exercise) and two rivers, whose conditions varied from open water to over 1.5 m of solid ice with numerous frazil-ice formations. The most readily interpretable data were acquired when the ice or snow surface was smooth. Detailed surface investigations on the Tanana River revealed good correlations of echo delay with solid ice depth, but an insensitivity to frazil-ice depth due to its high water content. On the Yukon River, coinciding temporally coherent surface and bottom reflections were associated with solid ice and smooth surfaces. All cases of incoherent surface returns (scatter) occurred over ice rubble. Rough-surface scattering was always followed by the appearance of bottom scattering but, in many cases, including a hanging-wall formation of solid frazil ice, bottom scattering occurred beneath coherent, smooth-surface reflections. Areas of incoherent bottom scattering investigated by drilling revealed highly variable ice conditions, including frazil ice. The minimum ice thickness that could be resolved from the raw data was about 0.2 m with the 600 MHz antenna and less than 0.15 m with the 900 MHz antenna.
10
Luan, Yingcheng, Yuan Ma, Weiguang Zhang, Yuqing Zhang, Tao Ma, and Jusang Lee. "Adaptability evaluation of pavement structure to replacement treatment subgrade of black cotton soil." Transportation Safety and Environment 2, no. 1 (2020): 69–80. http://dx.doi.org/10.1093/tse/tdaa004.
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Abstract Aiming at the typical engineering problem of black cotton soil (BCS) subgrade under the alternation of dry and wet climate in the region of Nairobi, Kenya, this paper takes the pavement structure as the research object, and the numerical calculation model of BCS subgrade is established based on the consolidation coupling theory of unsaturated soil. Taking the modulus and thickness of the subbase as variables, the deformation characteristics and additional stresses of different pavement structures are analysed. Then the adaptability of different pavement structures to replacement treatment subgrade of BCS is evaluated by gray incidence decision analysis method. The results show that whatever the pavement structure is, neither subgrade modulus nor thickness is sensitive to the pavement surface deformation, and the deformation differences between each pavement structure are more obvious in wet season; the additional stress at control layer bottom and pavement surface decreases with the increase of subbase modulus, whereas the stress may increase at subbase bottom; the additional stress at subbase bottom, control layer bottom and pavement surface all decreases with the increase of subbase thickness for pavement Structure I and II. For pavement Structure III, the change of subbase thickness is not sensitive to the additional stress at the control layer bottom and pavement surface, whereas the stress at subbase bottom increases with the increase of subbase thickness. It is concluded that the most adaptable structure is pavement Structure I, which can minimize the comprehensive level of pavement settlement and additional stress.
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STUROVA, IZOLDA V. "Time-dependent response of a heterogeneous elastic plate floating on shallow water of variable depth." Journal of Fluid Mechanics 637 (September 18, 2009): 305–25. http://dx.doi.org/10.1017/s0022112009990504.
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The problem of unsteady behaviour of a floating thin plate is solved. The simultaneous motion of the plate and the fluid is considered within the framework of linear shallow-water theory. It is assumed that the bottom is not uniform in depth under the heterogeneous plate represented by an infinitely extended strip of finite width. The elastic deflection of the plate is expressed by a superposition of modal functions of a homogeneous beam with free edge conditions. The time-dependent unknown amplitudes are determined from the solution of a linear set of ordinary differential equations with constant coefficients. The eigenvalues of this set are determined numerically. Proposed method is used for the solution of three unsteady problems: the scattering of localized surface wave by an elastic plate, decay of the initial deformation of the plate in the fluid at rest and the action of a periodic load on a plate. Numerical calculations are performed for the ice sheet with the variable thickness and various bottom topographies.
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Prasad, R., and D. P. Rao. "Theoretical Performance of a Solar Pond With Enhanced Ground Energy Storage." Journal of Solar Energy Engineering 118, no. 2 (1996): 101–6. http://dx.doi.org/10.1115/1.2847962.
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A method was proposed earlier by the authors for the enhancement of energy storage in the ground beneath solar ponds employing the trapezoidal-shaped trenches at the bottom of the pond. The theoretical performance of the solar pond with trapezoidal trenches is presented for constant and variable energy extraction patterns. The results indicate that the trenches could be effective in reducing the thickness of lower convective layer and hence the salt requirement of the pond. However, the effectiveness of the trenches seems to be dependent on the energy extraction pattern. For the constant extraction pattern of 63.9 W m−2, it is found that 36.5 percent reduction in the salt requirement can be achieved with 3-m deep trenches compared to the flat-bottom pond. For the variable extraction pattern, the reduction was only 21.5 percent.
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Fang, Weihua, Zhi Chen, and Yepeng Xu. "Accurate Solution for Orthotropic Beams with Continuously Variable Cross Sections." Mathematical Problems in Engineering 2022 (October 14, 2022): 1–9. http://dx.doi.org/10.1155/2022/4777608.
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Orthotropic materials and components are widely used in various engineering fields, such as aerospace, energy, infrastructure, and water conservancy projects. The orthotropic components such as slabs and beams cannot be investigated accurately by using traditional beam theory because it is unable to take more elastic constants into account. The precise stress distribution of orthotropic simply supported beams of any thickness is determined in this article. Meanwhile, all undetermined coefficients of the stress function are derived by performing a Fourier sine series expansion upon the bottom and top surfaces of the beam. It shows that the resolution corresponds well with the numerical analysis findings from the finite element method. It indicates rapid convergence and can obtain high-precision and high stress analysis results, which has a good application prospect in engineering.
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An, Hong Ping, Jian Sheng Liu, Jian Guo Wu, and Ji Hong Tian. "Research on the Blank Used in Integral Forming of a Lager Head with Supporting Table." Advanced Materials Research 139-141 (October 2010): 561–66. http://dx.doi.org/10.4028/www.scientific.net/amr.139-141.561.
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Three-dimension rigid-plastic finite element software, DEFORM-3D, was used to simulate the integral forming processing of a lager thick-wall semi-sphere head with supporting tables. Influencing factors of integral forming, such as initial blank shape, radius of corner at the bottom of the protrusions and the preforming mode etc, were researched quantitatively. A double layer frustum cone blank was determined, which can reduce the variable amplitude of the wall thickness and cause a uniform wall thickness distribution. When radius of corner at the bottom of the protrusions of the machined blank was in 100~130mm, no crack occurred at the bottom of the any supporting tables and a rational size can be obtained after forming. Using mode C (two banding protrusions) to forging the blank for machining can prevent the center metal from thinning and reduce additional tensile stress. Based on the simulation research, the 1:3 scale experiment was done in 31.5MN hydraulic press and the test piece was measured. The result shows that the error between simulation data and test data is less than 5%, which verified the feasibility of integral forming and provided an important reference for virtual production.
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Hong, Zhong, Kunhong Li, Mingjun Su, and Guangmin Hu. "Improved spectral clustering approach — A new tool for unsupervised seismic facies analysis of variable window length." Interpretation 9, no. 2 (2021): T407—T420. http://dx.doi.org/10.1190/int-2020-0059.1.
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The traditional constant time window-based waveform classification method is a robust tool for seismic facies analysis. However, when the interval thickness is seismically variable, the fixed time window is not able to contain the complete geologic information of interest. Therefore, the constant time window-based waveform classification method is inapplicable to conduct seismic facies analysis. To expand the application scope of seismic waveform classification in the strata with varying thickness, we have proposed a novel scheme for unsupervised seismic facies analysis of variable window length. The input of the top and bottom horizons can guarantee the comprehensive geologic information of the target interval. Throughout the whole workflow, we use the dynamic time warping (DTW) distance to measure the similarities between seismic waveforms of different lengths. First, we improve the traditional spectral clustering algorithm by replacing the Euclidean distance with the DTW distance. Therefore, it can be applicable in the interval of variable thickness. Second, to solve the problem of large computation when applying the improved spectral clustering approach, we adopt the method of seismic data thinning based on the technology of the superpixel. We combine these two algorithms and perform the integrated workflow of improved spectral clustering. The experiments on synthetic data show that the proposed workflow outperforms the traditional fixed time window-based clustering algorithm in recognizing the boundaries of different lithologies and lithologic associations with varying thickness. The practical application shows great promise for reservoir characterization of interval with varying thickness. The plane map of waveform classification provides convincing reference to delineate reservoir distribution of the data set.
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Zhang, Yiming, and Jiping Liu. "Effects of Ice-Microstructure-Based Inherent Optical Properties Parameterization in the CICE Model." Remote Sensing 16, no. 9 (2024): 1494. http://dx.doi.org/10.3390/rs16091494.
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The constant inherent optical properties (IOPs) for sea ice currently applied in sea ice models do not realistically represent the dividing of shortwave radiative fluxes in sea ice and the ocean below it. Here we implement a parameterization of variable IOPs based on ice microstructures in the Los Alamos sea ice model, version 6.0 (CICE6) and investigate its effects on the simulation of the dividing of shortwave radiation and sea ice in the Arctic. Our sensitivity experiments indicate that variable IOP parameterization results in strong seasonal variation for the IOP parameters, typically reaching the seasonal maximum in the boreal summer. With such large differences, variable IOP parameterization leads to increased absorbed solar radiation at the surface and in the interior of Arctic sea ice relative to constant IOPs, up to ~3 W/m2, but decreased solar radiation penetrating into the ocean, up to ~5–6 W/m2. The changes in the dividing of shortwave fluxes in sea ice and the ocean below it induced by the variable IOPs have significant influence on Arctic sea ice thickness by modulating surface and bottom melting and frazil ice formation (increasing surface melting by ~16% and reducing bottom melting by ~11% in summer).
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Lal, Roshan, and Rahul Saini. "Vibration analysis of functionally graded circular plates of variable thickness under thermal environment by generalized differential quadrature method." Journal of Vibration and Control 26, no. 1-2 (2019): 73–87. http://dx.doi.org/10.1177/1077546319876389.
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The vibration of functionally graded circular plates of variable thickness under a thermal environment is analyzed when the nodal lines are concentric circles by using the generalized differential quadrature method for the nonlinear temperature distribution in the thickness direction. The parabolic variation in thickness along the radial direction is controlled by a taper constant. The plate material is graded in the transverse direction and its mechanical properties are temperature-dependent. The thermal environment over the top and bottom surfaces of the plate is assumed to be uniform. Hamilton's principle has been used in obtaining the governing differential equations for thermo-elastic equilibrium and axisymmetric motion for such a plate model employing Kirchhoff plate theory. Numerical results for thermal displacements and natural frequencies of clamped and simply supported plates have been obtained using MATLAB. The effect of the taper constant, volume fraction index, and temperature difference on the vibration characteristics has been analyzed for the lowest three modes of vibration. A study in which the plate material has temperature-independent properties has also been performed. The accuracy of the present technique is verified by comparing the results with those available in the literature.
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Chichester, Ben, Catherine Rychert, Nicholas Harmon, et al. "Seafloor sediment thickness beneath the VoiLA broad-band ocean-bottom seismometer deployment in the Lesser Antilles from P-to-S delay times." Geophysical Journal International 223, no. 3 (2020): 1758–68. http://dx.doi.org/10.1093/gji/ggaa360.
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SUMMARY Broad-band ocean-bottom seismometer (OBS) deployments present an opportunity to investigate the seafloor sediment thickness, which is important for constraining sediment deposition, and is also useful for subsequent seismological analyses. The Volatile Recycling in the Lesser Antilles (VoiLA) project deployed 34 OBSs over the island arc, fore- and backarc of the Lesser Antilles subduction zone for 15 months from 2016 to 2017. Using the amplitudes and delay times of P-to-S (Ps) scattered waves from the conversion of teleseismic earthquake Pwaves at the crust–sediment boundary and pre-existing relationships developed for Cascadia, we estimate sediment thickness beneath each OBS. The delay times of the Ps phases vary from 0.20 ± 0.06 to 3.55 ± 0.70 s, generally increasing from north to south. Using a single-sediment and single-crystalline crust earth model in each case, we satisfactorily model the observations of eight OBSs. At these stations we find sediment thicknesses range from 0.43 ± 0.45 to 5.49 ± 3.23 km. To match the observations of nine other OBSs, layered sediment and variable thickness crust is required in the earth model to account for wave interference effects on the observed arrivals. We perform an inversion with a two-layer sediment and a single-layer crystalline crust in these locations finding overall sediment thicknesses of 1.75 km (confidence region: 1.45–2.02 km) to 7.93 km (confidence region: 6.32–11.05 km), generally thinner than the initial estimates based on the pre-existing relationships. We find agreement between our modelled velocity structure and the velocity structure determined from the VoiLA active-source seismic refraction experiment at the three common locations. Using the Ps values and estimates from the VoiLA refraction experiment, we provide an adjusted relationship between delay time and sediment equations for the Lesser Antilles. Our new relationship is ${{H}} = {{1.42}}{{\rm d}}{{{t}}^{ {1.44}}}$ , where H is sediment thickness in kilometres and dt is mean observed Ps delay time in seconds, which may be of use in other subduction zone settings with thick seafloor sediments.
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LYASHUK, Oleg, Mykhailo LEVKOVYCH, Yuriy VOVK, et al. "THE STUDY OF STRESS-STRAIN STATE ELEMENTS OF THE TRUCK SEMI-TRAILER BODY BOTTOM." Scientific Journal of Silesian University of Technology. Series Transport 118 (March 1, 2023): 161–72. http://dx.doi.org/10.20858/sjsutst.2023.118.11.
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Research on the influence of geometric parameters of body bottom elements on the stress-strain state (SSS) of the truck with the general application of computer simulation methods was conducted. The nature of the change in static stress and displacement depending on the change in the proportions of the cross-section of the channel at fixed geometric dimensions of the workpiece and the thickness of the workpiece and the bottom material of the body has been studied. Analytical, numerical and experimental methods were used in the study of the stress-strain state of the metal structure of car bodies. Its weight minimization is an important aspect of a truck body design. Because an excess weight leads to increased production costs, reduced payload and reduced fuel efficiency. According to the concept of weight reduction with the provision of a given strength, the body model with variable parameters of the bottom elements is modelled and analyzed. CAD - body models and analysis of the stress-strain state of the channels of the bottom of the bodies have been performed using the software package SolidWorks.
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Yuana, XiaoBei, JunCai Li, Peng Zhang, YiLi Dai, and KaiJun Rui. "Factors Influencing Ground Settlements on Different Geomorphology Units Based on Principal Component Analysis." MATEC Web of Conferences 175 (2018): 04038. http://dx.doi.org/10.1051/matecconf/201817504038.
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Based on the case Nanjing Metro Line 4, the method Principal Component Analysis (PCA) was used to study the influence of ground settlement by shield tunnel construction on different geomorphology units. Correlation analysis and weighted least square method (WLS) were applied for variables selection and to obtain their relationship with settlement. 5-7 principal components could be used to present the initial 19- 21 variables after decreasing the dimensions of data. For the floodplain of Yangtze River, variable parameters that highly linearly dependent on settlement were depth of tunnel, distance between the roof of tunnel and the bottom of soft soil layer, thickness of soft soil, compression modulus of soil that tunnel passed through and speed of the cutter head. For the Qinhuai ancient channel, variable parameters were Poisson's ratio, porosities, moisture content, unit weight, cohesion, internal friction angle, compression modulus of soil that tunnel passed through, advancing speed, earth chamber pressure. For the terrace of Yangtze River, variable parameters were cohesion, porosities, moisture content, Poisson's ratio, compression modulus and unit weight of soil. In addition, for the geomorphology unit with col landform, variable parameters were different. Residuals of regression formula are small, which will have certain reference value in practical engineering.
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Giustiniani, Michela, Umberta Tinivella, Chiara Sauli, and Bruno Della Vedova. "Distribution of the gas hydrate stability zone in the Ross Sea, Antarctica." Andean Geology 45, no. 1 (2017): 78. http://dx.doi.org/10.5027/andgeov45n1-2989.
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The theoretical gas hydrates stability zone (GHSZ) in the Ross Sea area was evaluated by mean of a steady state simple approach by using bathymetric data, sea bottom temperature, a variable geothermal gradient and assuming that the natural gas is methane. The results from our study suggest that bathymetry and distribution of the GHSZ are correlated; in fact, the GHSZ reaches a maximum (ca. 400 m) in the basins, where the water temperature is the lowest, and decreases in the banks with thickness ranging between 7 and
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S., Logesh*, Ramesh R., and Padmanaban I. "Compatability Behaviour on Cold Formed Steel for I Section and C Section in Variable Parameters." Regular issue 10, no. 7 (2021): 68–73. http://dx.doi.org/10.35940/ijitee.g8863.0510721.
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This Study represents compatibility on Cold formed steel in I-Section beams and C-section beams with variable length parameters was 1000mm, 1500mm, 2000 mm under simply supported end condition subjected to uniformly distributed loading. The Cold formed steel is of shell type in Numerical simulation is carried out using the Software ABAQUS. For validation the series of parameters studies have been carried out using the numerical model of different parameters, such as the effect of length, width, thickness. CFS I-Section steel in various thickness of 1mm, 2mm, 3mm and 4mm with same loading conditions. CFS C-Section steel in various uneven flange width such as 500mm at the top flange and bottom flange of different width such as 400mm, 300mm, 200mm respectively in variable lengths with various loading conditions and with the thickness of about 1mm. For both I-Section and C-Section Beams the Effective Length ranges, MISES(max and min) and deflections(max and min) were taken for the analyse of the Sections. This study gives the way of finding the effective Section by the analysis of behaviour of I-Section beam and C-Section beam through the deflection results in various length variations in the beam Section using the ABAQUS software for finding the Structural behaviour in the more accuracy manner by applying meshing more finer for the Element Section in the Analyse of beam. The loading condition and the supporting condition applied to the beam section in different loading for getting the effective Section. For further stability in effective section we can use different types of connection.
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S.Logesh, R.Ramesh, and Padmanaban I. "Compatability Behaviour on Cold Formed Steel for I Section and C Section in Variable Parameters." International Journal of Innovative Technology and Exploring Engineering (IJITEE) 10, no. 7 (2021): 68–73. https://doi.org/10.35940/ijitee.G8863.0510721.
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This Study represents compatibility on Cold formed steel in I-Section beams and C-section beams with variable length parameters was 1000mm, 1500mm, 2000 mm under simply supported end condition subjected to uniformly distributed loading. The Cold formed steel is of shell type in Numerical simulation is carried out using the Software ABAQUS. For validation the series of parameters studies have been carried out using the numerical model of different parameters, such as the effect of length, width, thickness. CFS I-Section steel in various thickness of 1mm, 2mm, 3mm and 4mm with same loading conditions. CFS C-Section steel in various uneven flange width such as 500mm at the top flange and bottom flange of different width such as 400mm, 300mm, 200mm respectively in variable lengths with various loading conditions and with the thickness of about 1mm. For both I-Section and C-Section Beams the Effective Length ranges, MISES(max and min) and deflections(max and min) were taken for the analyse of the Sections. This study gives the way of finding the effective Section by the analysis of behaviour of I-Section beam and C-Section beam through the deflection results in various length variations in the beam Section using the ABAQUS software for finding the Structural behaviour in the more accuracy manner by applying meshing more finer for the Element Section in the Analyse of beam. The loading condition and the supporting condition applied to the beam section in different loading for getting the effective Section. For further stability in effective section we can use different types of connection.
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Hamza, M. M., Oluwafemi Job Ejiwole, H. Usman, A. Almu, Aminu Hamisu, and Muawiya Musa. "Effect of Variable Thermal Conductivity on Oscillatory Magnetized Couette Flow in a Channel Filled with Porous Material." UMYU Scientifica 3, no. 4 (2024): 218–31. https://doi.org/10.56919/usci.2434.017.
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Study’s Excerpt The influence of temperature-dependent thermal properties on oscillatory magnetic Couette fluid flows within a porous channel is investigated. New analytical expressions for key fluid flow characteristics, including velocity, temperature, and concentration are provided. The findings revealed that variations in thermal conductivity enhance heat transfer efficiency, reduce thermal boundary layer thickness, and significantly affect temperature gradients. Full Abstract The primary purpose of this study is to determine how temperature-dependent thermal properties affect oscillatory magnetic Couette fluid flows in a channel containing porous materials. A regular perturbation approach was used to analytically characterize the flow fluid boundary conditions of the governing equations. The expressions of velocity, temperature, concentration, skin friction, Nusselt number, and Sherwood number have been obtained, and the results are displayed graphically for various controlling parameters of the models. The results show that varying thermal conductivity on fluid flow of the model of both Nu0 and Nu1 enhanced heat transfer efficiency, reduction in thermal boundary layer thickness of the fluid leading to an increase in convective heat transfer coefficient and increase in the temperature gradients near the bottom plate and near the top plate respectively.
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Alfeehan, Ashraf Abdulhadi, Hassan Issa Abdulkareem, and Shahad Hameed Mutashar. "Flexural behavior of sustainable reactive powder concrete bubbled slab flooring elements." Challenge Journal of Structural Mechanics 3, no. 2 (2017): 81. http://dx.doi.org/10.20528/cjsmec.2017.04.010.
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Voided slabs are reinforced concrete slabs in which voids allow to reduce the amount of concrete. The bubbled deck slab is a new and sustainable biaxial floor system to be used as a self-supporting concrete floor. The use of voided slabs leads to decrease the consumption of materials and improve the insulation properties for enhancing the objectives of sustainability. This study presents an investigation into the flexural behavior of sustainable Reactive Powder Concrete RPC bubbled slab flooring elements. Six one-way slabs were cast and tested up to the failure. The adopted variables in this study are: the volumetric ratio of steel fibers, type of slab; bubbled or solid, placing of reinforcement and thickness of slab. The effect of each variable on the ultimate load, deflection and strain has been discussed. The results show that increasing the percent of steel fibers from 1% to 2% in solid and bubbled slabs decreases the deflection by (18.75%) and (50%) respectively. As well as, the deflection increases by (41%) for bubbled slab compared to the solid slab. The slabs reinforced with top and bottom steel meshes show less deflection than slabs reinforced by only bottom steel mesh.
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Pirmohammadi, Mohsen, Majid Ghassemi, and Mohsen Hamedi. "MHD Convection of an Electrically Conductive Fluid with Variable Thermal Conductivity." Applied Mechanics and Materials 110-116 (October 2011): 232–38. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.232.
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The effect of temperature-dependent thermal conductivity on the magneto-convection in a low Prandtl number liquid is investigated numerically. The liquid is contained in a closed square cavity with isothermal vertical walls kept at different temperatures. The top and bottom walls are assumed to be insulated. To solve the governing non-linear differential equations (mass, momentum and energy) a finite volume code based on SIMPLER algorithm is utilized. The results for different Rayleigh numbers (Ra), Hartmann numbers (Ha) and temperature coefficient of thermal conductivity (η) are presented in form of streamlines, isotherms and Nusselt number. It is found that the heat transfer decreases appreciably across the cavity with a decrease in thermal conductivity. It is observed that at low Hartmann number (Ha=30) the thermal boundary layer is formed near the side walls and as η increases the thickness of these boundaries decreases. Also it is found that as non-dimensional thermal conductivity increases the peak of velocity profile increases; however, this phenomenon is very weak at high Hartmann number.
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Kurapov, A. L., J. S. Allen, G. D. Egbert, and R. N. Miller. "Modeling Bottom Mixed Layer Variability on the Mid-Oregon Shelf during Summer Upwelling." Journal of Physical Oceanography 35, no. 9 (2005): 1629–49. http://dx.doi.org/10.1175/jpo2768.1.
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Abstract Results from a model of wind-driven circulation are analyzed to study spatial and temporal variability in the bottom mixed layer (BML) on the mid-Oregon shelf in summer 2001. The model assimilates acoustic Doppler profiler velocities from two cross-shore lines of moorings 90 km apart to provide improved accuracy of near-bottom velocities and turbulence variables in the area between the mooring lines. Model results suggest that the response of the BML thickness to upwelling- and downwelling-favorable winds differs qualitatively between an area of “simple” bathymetric slope at 45°N and a wider shelf area east of Stonewall Bank (44.5°N). At 45°N, the BML grows in response to downwelling-favorable conditions, in agreement with known theories. East of Stonewall Bank, the BML thickness is increased following upwelling events. In this area, the southward upwelling jet detaches from the coast and flows over a wider part of the Oregon shelf, creating conditions for Ekman pumping near the bottom. Based on computations of bottom stress curl, the vertical pumping velocity in this area may reach 15 m day−1 following periods of intensified upwelling-favorable winds. A column of denser, near-bottom water upwelled over the Ekman flow convergence area is tilted as a result of vertical shear in horizontal velocities, causing unstable stratification and convective overturning. As a result of this process, BML thickness values east of Stonewall Bank can be in excess of 20 m following upwelling, comparable to maximum values at 45°N following downwelling.
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Zhang, Rongfan, Hongwei Li, Ying Zheng, and Xin Zuo. "Research on ultrasonic testing method of rotating component based on a 6-DOF robot." Journal of Physics: Conference Series 2355, no. 1 (2022): 012012. http://dx.doi.org/10.1088/1742-6596/2355/1/012012.
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Abstract Some rotating components have the structural characteristics of variable thickness and variable curvature. The conventional ultrasonic testing is inappropriate for these components because of bad coupling and too many uncertainties. In order to meet the testing requirements of high-volume, high-efficiency and high-precision, the corresponding ultrasonic automatic detection program is proposed. A 6-DOF industrial robot is used to realize the precise control of the transducer position and posture, and combines the independent turntable to complete the spiral fast scan of the specimen. Based on the multi-Gaussian beam model and the internal flat-bottom hole flaw scattering model of specimen, the flaw ultrasonic measurement model is established. The system parameters, component material parameters and component surface parameters are all introduced to the ultrasonic measurement model to generate a series of flaw-sizing curves. An accurate flaw sizing method based on DGS(Distance-Gain-Size)curve predicted by regular reflector is proposed. The scanning experiment results of the reference specimen show that the minimum Ø 0.8mm artificial flat-bottom-hole flaw in the workpiece can be detected effectively, and the sizing error is less than Ø 0.3mm equivalent.
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Seuthe, Thomas, Markus Eberstein, Rolf Petersen, and Hans-Jürgen Amann. "Ceramic decals – predesigned thick-film sensors for variable surfaces." International Symposium on Microelectronics 2015, no. 1 (2015): 000262–66. http://dx.doi.org/10.4071/isom-2015-wa42.
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Manufacturing of ceramic multilayer applications by deposition techniques like screen printing, dispensing, or aerosol jet printing is state of the art today. However, in an industrial environment it is a complex challenge to integrate all equipment for precise paste handling and screen print of the microstructures in an existing production line. Moreover, big sized devices or items with a curved surface cannot be handled with standard screen print equipment. To overcome these limitations, a decal technology was investigated. The functional layers are stacked on non-adhesive paper by screen print, fulfilling all demands on precision in line/space ratio and layer thickness. Afterwards, a polymer varnish is printed on top of the stack, which allows to transfer the high precision thick film assembly to nearly any application surface including non-planar surfaces. Since the layers are co-fired, the sintering behavior of the materials has to be regulated. The top layer needs to remain porous until the organic burn-out and the sintering of the bottom layer is complete. Ways to obtain thick film metallization and isolation pastes which have satisfying firing behavior are examined, and the excellent functional properties are discussed. The performance of the developed thick film decals is demonstrated on the example of an alarm sensor on tempered safety glass for windows.
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Chaudhuri, Reaz A. "Three-Dimensional Singular Stress Fields and Interfacial Crack Path Instability in Bicrystalline Superlattices of Orthorhombic/Tetragonal Symmetries." Crystals 14, no. 6 (2024): 523. http://dx.doi.org/10.3390/cryst14060523.
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First, a recently developed eigenfunction expansion technique, based in part on the separation of the thickness variable and partly utilizing a modified Frobenius-type series expansion technique in conjunction with the Eshelby–Stroh formalism, is employed to derive three-dimensional singular stress fields in the vicinity of the front of an interfacial crack weakening an infinite bicrystalline superlattice plate, made of orthorhombic (cubic, hexagonal, and tetragonal serving as special cases) phases of finite thickness and subjected to the far-field extension/bending, in-plane shear/twisting, and anti-plane shear loadings, distributed through the thickness. Crack-face boundary and interface contact conditions as well as those that are prescribed on the top and bottom surfaces of the bicrystalline superlattice plate are exactly satisfied. It also extends a recently developed concept of the lattice crack deflection (LCD) barrier to a superlattice, christened superlattice crack deflection (SCD) energy barrier for studying interfacial crack path instability, which can explain crack deflection from a difficult interface to an easier neighboring cleavage system. Additionally, the relationships of the nature (easy/easy, easy/difficult, or difficult/difficult) interfacial cleavage systems based on the present solutions with the structural chemistry aspects of the component phases (such as orthorhombic, tetragonal, hexagonal, as well as FCC (face-centered cubic) transition metals and perovskites) of the superlattice are also investigated. Finally, results pertaining to the through-thickness variations in mode I/II/III stress intensity factors and energy release rates for symmetric hyperbolic sine-distributed loads and their skew-symmetric counterparts that also satisfy the boundary conditions on the top and bottom surfaces of the bicrystalline superlattice plate under investigation also form an important part of the present investigation.
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Albayati, Amjad H., Yasmin S. Ajool, and Abbas A. Allawi. "Comparative Analysis of Reinforced Asphalt Concrete Overlays: Effects of Thickness and Temperature." Materials 16, no. 17 (2023): 5990. http://dx.doi.org/10.3390/ma16175990.
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Reflection cracking in asphalt concrete (AC) overlays is a common form of pavement deterioration that occurs when underlying cracks and joints in the pavement structure propagate through an overlay due to thermal and traffic-induced movement, ultimately degrading the pavement’s lifespan and performance. This study aims to determine how alterations in overlay thickness and temperature conditions, the incorporation of chopped fibers, and the use of geotextiles influence the overlay’s capacity to postpone the occurrence of reflection cracking. To achieve the above objective, a total of 36 prism specimens were prepared and tested using an overlay testing machine (OTM). The variables considered in this study were the thickness of the overlay (40, 50, and 60 mm), temperature (20, 30, and 40 °C), mix type (reference mix and mix modified with 10% chopped fibers by weight of asphalt cement), and the inclusion of geotextile fabric at two positions (one-third of the depth from the base and at the bottom). The research outcomes revealed that a decreased temperature and thicker overlay led to a higher resistance to crack initiation and full propagation, as indicated by the values of critical fracture energy (Gc) and crack progression rate (CPR). Furthermore, the study observed the enhanced crack resistance of overlays in the presence of geotextiles, whether at the bottom or one-third of the depth from the bottom, with superior performance of the former. Despite a slight enhancement in certain properties, the incorporation of chopped fibers in the overlays did not substantially improve the overall performance compared to the reference specimens. Overall, the study provides valuable insights into the variables that influence the ability of AC overlays to mitigate reflection cracking. These findings will aid engineers and designers in making informed decisions regarding overlay design and construction.
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Antunes, Lucas, Pascal Masson, Julien Amouroux, et al. "Notched Gate and Graded Gate Oxide Processing for Reduced Capacitance Application in RF MOSFETs." ECS Meeting Abstracts MA2024-02, no. 20 (2024): 1829. https://doi.org/10.1149/ma2024-02201829mtgabs.
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As the demands of RF applications are rising, optimization of internal MOSFETs capacitances is a key issue to improve the cut-off frequency. In this abstract we report the development of a novel N-MOS architecture processed on 8-inch SOI wafers. This architecture has a gate oxide with variable thickness along the channel and a reduced bottom gate length aiming at minimizing Gate to Drain/Source capacitance (1) (2). This improvement on Gate to Drain/Source capacitance mainly comes from a decrease in overlap capacitances as described in (3). The new process flow is composed as usual until Poly-Si gate etching. By controlling the species flow and process time during plasma etching steps, over etch at the bottom of the gate is performed (fig.1(a,b)). Poly-Si gate notching engineering is possible due to reduction of the passivation layer thickness at the bottom of the gate during plasma etch. As described in (4) the gate is first etched using a HBr/CL2/O2 chemistry until reaching close to the bottom of the gate, allowing the formation of a passivation layer made of SiOxCly and the anisotropy of the etch. To etch the remaining thickness HBr flow is augmented while CL2 and O2 flow are reduced, preventing formation of passivation layer. This leads to isotropic etch of the bottom gate and reduction of the gate length as regard to the top Poly-Si dimension. This over-etch reduces the physical gate length without changing the effective and the on-mask gate lengths, leading to overlap capacitance reduction. To produce gate oxide with variable thickness under gate sidewalls a two-steps process is performed. First, full plate oxide is grown before poly-Si deposition to act as middle gate thickness. Then undercut is performed, consisting of lateral etching of the gate oxide under gate sidewall after gate etch (fig.2.a). To achieve this undercut, hydrofluoric acid (HF) wet etch has been chosen. First trials with very low HF concentration become quickly saturated leading to small lengths under gate sidewalls (fig.2.b). Then more acidic solutions were used allowing satisfying undercut lengths (fig.2.c). Finally rapid thermal oxidation (RTO) is performed to obtain an oxide bird beak at both gate side as both Poly-Si gate and Si from the active region react with ambient O2 in the chamber. This leads to a gate oxide with variable thickness along the channel (fig.3(a.b)) which has both effects: to get smoother poly-Si foot and a down step in the active between channel and Source/Drain regions. During this process step, a built-in spacer on the gate sides for LDD implantation is formed. RTO process step has grown a thicker oxide over Source/Drain areas which has to be reduced to allow an accurate LDD implantation, this is done by anisotropic etching. After these new steps, the process goes back to a standard N-MOS process flow. Some early versions of the notched gate have been investigated (5), and these experiments and details on processing recipe seem promising for electrical results. As poly-Si foot has been smoothed and graded gate oxide (GGO) on top of overlaps region is formed. It would allow a reduction in parasitic capacitances improving cut-off frequency of RF applications. References RF LDMOSFET with Graded Gate Structure. Xu Shuming, Foo Pan Dow. Toronto : s.n., 2001. 1th International Symposium on Power Semiconductor Devices and ICs. ISPSD'99 Proceedings. pp. 221-224. DOI:10.1109. Notched-Gate pMOSFET with ALD TiN/High-κ Gate Stack Formed by Selective Wet Etching. Zhang, D. Wu and J. Lu and P.-E. Hellström and M. Östling and S.-L. s.l. : The Electrochemical Society, Inc., 2004, Electrochemical and Solid-State Letters, Vol. 7, p. 228. 10.1149/1.1795612. A simple efficient model of parasitic capacitances of deep-submicron LDD MOSFETs. Fabien Pregaldiny, Christophe Lallement,Daniel Mathiot. s.l. : Solid State Electronics, 2002, Vol. 46, pp. 2191–2198. https://doi.org/10.1016/S0038-1101(02)00248-4. Design of notched gate processes in high density plasmas. J. Foucher, G. Cunge, L. Vallier, and O. Joubert. s.l. : AVS: Science & Technology of Materials, Interfaces, and Processing, 2002, Vols. Journal of Vacuum Science & Technology B 20,. http://dx.doi.org/10.1116/1.1505959. Notched gate MOSFET for capacitance reduction in RF SOI technology. al, L. Antunes et. s.l. : 2023 IEEE International Conference on Design, Test and Technology of Integrated Systems (DTTIS), 2023. doi: 10.1109/DTTIS59576.2023.10348288. Figure 1
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Hajjiah, Ali, Fahad Parmouneh, Afshin Hadipour, Manoj Jaysankar, and Tom Aernouts. "Light Management Enhancement for Four-Terminal Perovskite-Silicon Tandem Solar Cells: The Impact of the Optical Properties and Thickness of the Spacer Layer between Sub-Cells." Materials 11, no. 12 (2018): 2570. http://dx.doi.org/10.3390/ma11122570.
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Mechanical stacking of a thin film perovskite-based solar cell on top of crystalline Si (cSi) solar cell has recently attracted a lot of attention as it is considered a viable route to overcome the limitations of cSi single junction power conversion efficiency. Effective light management is however crucial to minimize reflection or parasitic absorption losses in either the top cell or in the light in-coupling of the transmitted light to the bottom sub-cell. The study here is focused on calculating an optimum performance of a four-terminal mechanically stacked tandem structure by varying the optical property and thickness of the spacer between top and bottom sub-cells. The impact of the nature of the spacer material, with its refractive index and absorption coefficient, as well as the thickness of that layer is used as variables in the optical simulation. The optical simulation is done by using the transfer matrix-method (TMM) on a stack of a semi-transparent perovskite solar cell (top cell) mounted on top of a cSi interdigitated back contact (IBC) solar cell (bottom cell). Two types of perovskite absorber material are considered, with very similar optical properties. The total internal and external short circuit current (Jsc) losses for the semitransparent perovskite top cell as a function of the different optical spacers (material and thickness) are calculated. While selecting the optical spacer materials, Jsc for both silicon (bottom cell) and perovskite (top cell) were considered with the aim to optimize the stack for maximum overall short circuit current. From these simulations, it was found that this optimum in our four-terminal tandem occurred at a thickness of the optical spacer of 160 nm for a material with refractive index n = 1.25. At this optimum, with a combination of selected semi-transparent perovskite top cell, the simulated maximum overall short circuit current (Jsc-combined, max) equals to 34.31 mA/cm2. As a result, the four-terminal perovskite/cSi multi-junction solar cell exhibits a power conversion efficiency (PCE) of 25.26%, as the sum of the perovskite top cell PCE = 16.50% and the bottom IBC cSi cell PCE = 8.75%. This accounts for an improvement of more than 2% absolute when compared to the stand-alone IBC cSi solar cell with 23.2% efficiency.
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Yao, X. L., X. H. Huang, Z. Y. Shi, and W. Xiao. "Reducing bubble generation and sweepdown effect on a research vessel with a moonpool." Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 235, no. 2 (2021): 303–10. http://dx.doi.org/10.1177/1475090221997247.
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Some research vessels set moonpools for sonars installation. The moonpool provides a relatively good working environment for sonar in a harsh marine environment. At the same time, other acoustic detection equipment are installed along the ship bottom behind the moonpool. Due to the exist of the sonar with a variable cross-section, the number of bubbles generated in the moonpool increases. The bubbles generated in the moonpool expel and flow along the vessel bottom to the stern, which leads to the sweepdown effect. The performance of the sonar and other acoustic detection equipment degrades by the bubbles around. However, the research on reducing bubble generation in the moonpool and sweepdown effects is rare. So in present paper the reduction effects of damping devices such as the flange and choke deck on the bubble generation in the moonpool are investigated experimentally. Then, in order to reduce the sweepdown effects of bubbles on the ship bottom, three other damping devices which are double flaps, diversion channel and wedge are investigated. It can be seen that through reducing the area of bubble leakage in the moonpool the distribution position of bubbles can be effectively restricted and the width and thickness of the bubbles reduce.
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Khudair Abbass, Ghufran, and Ali Hameed Aziz. "STRUCTURAL PERFORMANCE OF COMPOSITE BOX BEAMS WITH CORRODED BOTTOM FLANGE UNDER MONOTONIC AND REPEATED LOADS." Journal of Engineering and Sustainable Development 27, no. 4 (2023): 545–57. http://dx.doi.org/10.31272/jeasd.27.4.10.
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The current research is dedicated to studying the flexural behavior of composite box beams with corroded bottom flanges. Six simply supported beam specimens were manufactured and tested. The composite box beams were fabricated with steel box beams of 1100mm, 100mm, and 100mm for length, width, and height, respectively, while the concrete deck slabs were made with dimensions of 1100mm, 400mm, and 50mm for length, width, and thickness, respectively. The composite sections were formed by connecting the RC deck slabs with the steel box beams by using a headed shear connector. Three main variables were considered; the load type (monotonic or repeated), bottom flange thickness (with or without corrosion), and whether to consider or ignore the strengthening by CFRP strip. Experimental results indicated that the ultimate loads were decreased by 29-33% for the corroded bottom flange beam specimens; while the ultimate loads for the strengthened beam specimens were increased by 60-67% as compared with the un-strengthened corroded corresponding beam specimens. Also, the change of the applied loads from monotonic to repeated leads to a reduction of the ultimate load by 17-22%.
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Joshib, Dr Raghavendra. "Investigation on Tensile and Compression Properties of 3D Printed PLA Material for Various Infill Percentage." INTERANTIONAL JOURNAL OF SCIENTIFIC RESEARCH IN ENGINEERING AND MANAGEMENT 09, no. 01 (2025): 1–9. https://doi.org/10.55041/ijsrem41134.
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This work aims to study the effect of process parameters such as infill percentage by keeping other parameters like printing temperature, nozzle diameter, layer height, top and bottom layer thickness, print bed temperature constant during preparation of the test specimens on mechanical properties of FDM printed parts. In the present project, specimen is made with PLA material having different infill percentages which is in turn tested for its mechanical properties like tensile, compression and impact strength. The results are compared with each other various combinations. Thus, this project is conducted to get the average of the strength and mechanical properties. One variable at a time approach has been adopted to carry out the work.
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Lee, Dukhyung, Dohee Lee, Hyeong Seok Yun, and Dai-Sik Kim. "Angstrom-Scale Active Width Control of Nano Slits for Variable Plasmonic Cavity." Nanomaterials 11, no. 9 (2021): 2463. http://dx.doi.org/10.3390/nano11092463.
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Nanogap slits can operate as a plasmonic Fabry–Perot cavity in the visible and infrared ranges due to the gap plasmon with an increased wavenumber. Although the properties of gap plasmon are highly dependent on the gap width, active width tuning of the plasmonic cavity over the wafer length scale was barely realized. Recently, the fabrication of nanogap slits on a flexible substrate was demonstrated to show that the width can be adjusted by bending the flexible substrate. In this work, by conducting finite element method (FEM) simulation, we investigated the structural deformation of nanogap slit arrays on an outer bent polydimethylsiloxane (PDMS) substrate and the change of the optical properties. We found that the tensile deformation is concentrated in the vicinity of the gap bottom to widen the gap width proportionally to the substrate curvature. The width widening leads to resonance blueshift and field enhancement decrease. Displacement ratio ((width change)/(supporting stage translation)), which was identified to be proportional to the substrate thickness and slit period, is on the order of 10−5 enabling angstrom-scale width control. This low displacement ratio comparable to a mechanically controllable break junction highlights the great potential of nanogap slit structures on a flexible substrate, particularly in quantum plasmonics.
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Liu, Dan, Guoliang Chen, Zhonghao Huang, et al. "P‐7.11: Effect of etching conditions, MoNb thickness on gate profile and CD Bias of ADS Pro TFT." SID Symposium Digest of Technical Papers 55, S1 (2024): 1083–86. http://dx.doi.org/10.1002/sdtp.17284.
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The etched MoNb/Cu stack film is widely used as gate electrodes for ADS Pro TFTs. The CD Bias and profile angle(PA) are two important performance parameters for wet etching. The product‐specific bottom MoNb thickness and the fluctuation of wet etching conditions(time, temperature, and Cu ion concentration) make it difficult to precisely control the etching quality, thus it is of great significance to identify the influence of the above two factors on CD Bias and PAs. In this paper, the wet etching time, temperature and Cu ion concentration are taken as independent variables, and 11 different etching conditions are arranged based on the uniform experiments design to etch MoNb/Cu samples with two different MoNb thicknesses. The experiments reseluts shows that for the etched two MoNb/Cu stacks (15/300 nm, 30/300 nm) samples, the CD Bias and PAs are in the range of 0.22~0.73 µm and 40~51°, respectively. Both the CD Bias and PAs increase with the bottom MoNb thickness, etching temperature, etching time or Cu concentration, and the PAs increases with CD Bias. The etchant may form a reflux path during the etching process, along which the etching rate decreases. The difference between the etching rates at the top and bottom of the electrode contributes to the increase of PAs and CD Bias with etching severity. In the MoNb/Cu sidewall, MoNb acts as an anode due to the low corrosion potential, and the galvanic effect leads to the acceleration of MoNb etching, which ultimately results in the increase of PA and CD Bias under the thick MoNb.
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Park, Min Jae, Robel Wondimu Alemayehu, and Young K. Ju. "Fire Resistance Performance of Steel–Polymer Prefabricated Composite Floors Using Standard Fire Tests." Polymers 14, no. 7 (2022): 1488. http://dx.doi.org/10.3390/polym14071488.
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In this study, the fire resistance performance of steel–polymer prefabricated composite floors, which have a sandwich-type structure, was assessed via standard fire tests and analyzed using finite element analysis. This form of analysis should consider two aspects, namely the thermal and structural fields, so as to simulate complicated material properties and large deformations. As previous studies have already conducted analysis in the thermal field, this study entailed only the structural analysis based on the temperature distributions obtained from the thermal analysis. The variables of the specimens were the thicknesses of the top and bottom steel plates and polymers. According to the analysis results, the top steel plate thickness had no impact on the stability ratings, a criterion for fire resistance performance, whereas the bottom steel plate showed a linear correlation with the stability rating. An equation for the stability rating of composite floors was proposed, and an equation for fire resistance performance was devised based on the insulation ratings, which were obtained from the thermal analysis results.
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Abdel-Gawad, Esraa H., Mohamed A. El-Naggar, Mervat A. Abdel-Kawi, Gomaa H. Sedahmed, and Mahmoud M. Taha. "Mass and Heat Transfer at the Bottom of Cylindrical Unbaffled Stirred Tank Reactor and Possible Applications." Key Engineering Materials 932 (September 20, 2022): 11–19. http://dx.doi.org/10.4028/p-07e90r.
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Liquid-solid mass and heat (by analogy) transfer at the bottom of a cylindrical stirred vessel were studied by using the well-known electrochemical technique. Variables studied included the impeller geometry and its rotational speed. Results revealed that the radial flow impeller is preferable over the axial flow one in terms of mass transfer enhancement, additionally, increasing the impeller rotational speed led to an increase in the mass transfer coefficient. Results were correlated by dimensionless equations. Application of these equations in the design and operation of an improved catalytic biochemical reactor suitable for conducting diffusion-controlled immobilized cell (or enzyme) reactions was highlighted. These equations can serve in predicting the corrosion rate and corrosion allowance required to calculate the bottom thickness of the agitated vessel in its design stage. Furthermore, these equations can be used in estimating the heat lost from the tank bottom, accordingly, design an effective cooling jacket surrounding the agitated vessel bottom in case of exothermic biochemical reactions to avoid thermal degradation of the biomass.
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Oliynyk, Oleksandr Y., Sergiy V. Telyma, Yuriy I. Kalugin, and Yevheniy O. Oliynyk. "An analysis of the influence of the biofilm heterogeneity on the effectiveness of organic pollution removal in bioreactors." Environmental safety and natural resources 47, no. 3 (2023): 5–20. http://dx.doi.org/10.32347/2411-4049.2023.3.5-20.
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A mathematical model of biological purification of wastewater from organic pollutants in the conditions of an aeration tank with a fixed biocenosis (biofilm of microorganisms) is presented. At the same time the peculiarities of the formation and modeling of a complex heterogeneous stratified structure of a biofilm with variable processes and parameters along its thickness are considered and taken into account on in particular the processes of mass transfer and concentration of microorganisms. It shown that the treatment processes in heterogeneous stratified biofilm are designated by the effective diffusion coefficient which is depended on the pollutions concentration. Owing to that the pollutions concentration is changing of along the biofilm thickness and increase from the surface to the biofilm bottom the decreasing of the effective diffusion coefficient is observed. On the base of the provided experimental investigations the change of the effective diffusion parameter along the biofilm thickness may be specified according to linear law. The quantity criteria of the first and zero order kinetic and Monod equation were used in the practical calculations. Ascertain that the substrate removal have a place on the early part of the biofilm which amounts to 20–25% from the its full thickness. On the base of the created biofilm model of the heterogeneous-stratified structure the comparative analysis and valuation of the different investigations of the pollutions removal during the treatment processes at using of the homogeneous and heterogeneous structure of the biofilm were treated. It was designated that the pollutions removal effectiveness depends on the biofilm features. So at the some main parameters the homogeneous and stratified biofilms indicate almost the same microbial activity and the difference depends on the effective diffusion coefficient on the biofilm output. In the dependence on the hydrodynamic conditions of the treatment processes the homogeneous biofilm activity may be lower, higher or similar one of the stratified biofilm. Heterogeneous biofilm has the lower activity near the biofilm bottom at the high values of the effectiveness coefficient than the homogeneous one at the average values of this coefficient and the substrate against of the which the microorganisms growth is depended on to penetrate more in depth in stratified biofilm than in homogeneous one.
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Gao, Ninghua, Junwei Lian, Zhaohui Xu, and Haojie Jiang. "An equivalent temperature model of three-dimensional steady heat conduction analysis for a fiber metal laminated plate coated with a thermal barrier." Thermal Science, no. 00 (2019): 445. http://dx.doi.org/10.2298/tsci190704445g.
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In this paper, an equivalent temperature model of three-dimensional steady heat conduction analysis for a fiber metal laminated plate coated with a thermal barrier (CFML) is presented. The separate variable method (SVM) and equivalent temperature (ET) method are applied comprehensively to solve the temperature field at the interface between the thermal barrier and top aluminum 2024-T3 layer for the fiber metal laminated (FML) structure firstly, and values of other layers? temperature and thermal contact resistance are obtained based on balance principle of heat flux between respective adjacent top and bottom layers subsequently. The aim of this research is to understand the influences of kinds of fiber species, numbers of FML layers, thickness ratio between total CFML structure and thermal barrier as well as temperature distributed function on the values of thermal contact resistance between respective adjacent layers and temperature distribution from top to bottom surfaces for the CFML structure. Especially, the ratio of thermal contact resistance between maximum and minimum values are about 5 times no matter considering one or two kinds of fiber species. Besides the present results (mainly geometrical and physical parameters? effect) could guide engineers designing the CFML structures to adapt to high-temperature environment especially aerospace temperature environment.
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Abbas, Ali Laftah, Abbas Haraj Mohammed, Raad Dheyab Khalaf, and Khattab Saleem Abdul-Razzaq. "Finite Element Analysis and Optimization of Steel Girders with External Prestressing." Civil Engineering Journal 4, no. 7 (2018): 1490. http://dx.doi.org/10.28991/cej-0309189.
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Optimization is a process through which the best possible values of design variables are achieved under the given of constraints and in accordance to a selected optimization objective function. Steel I-girders have been used widely in different fields, which are generally fabricated by connecting two plate flanges, a flat web and a series of longitudinal or transverse stiffeners together. The use of steel girder with external prestressing has been used in many countries as a means of strengthening bridges. The purpose of this paper is to develop a finite element model for the optimization of a steel girder with external prestressing. The ANSYS finite element software package was used to find the optimum cross section dimension for the steel girder. Two objective functions are considered in this study there are optimization of the strain energy and total volume of the girder. The design variables are the width of top flange, the thickness of top flange, the width of bottom flange, the thickness of bottom flange, the height of the web, the width of the web and area of prestressing tendons. Two type of steel girder are considered there are steel girder without prestressing and steel girder with prestressing. The results for volume minimization shows that the optimum cross section for steel girder with prestressing smaller than for steel girder without prestressing.
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Park, Yonghui, Changwoo Lee, Jinyul Kim, Dongwook Kim, Hyunjun Ahn, and Woonbong Hwang. "Parametric Analysis for Minimizing the Edge Waves in the Roll Forming." International Journal of Automotive and Mechanical Engineering 15, no. 3 (2018): 5480–99. http://dx.doi.org/10.15282/ijame.15.3.2018.6.0421.
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To identify the cause of edge waves and to minimize them, which are frequently occurring on the steel pipe manufacturing site, the shape of the edge part of skelp has been confirmed according to a design variable and operating condition. In particular, parametric studies were carried out on the variation in the thickness of skelp, tskelp, the roll gap between upper and bottom rolls, troll, at the forming stage 1, Forming 1, the roll shape, toffset, of the Forming 1, and the material property of skelp to study the generation of edge waves, because these parameters have been determined by field engineers extemporaneously without any physical estimation. For this purpose, the roll design and operating conditions used in the field were applied to the finite element analysis model, and the distribution of contact force between the rolls and skelp, and the distribution of effective plastic strain on the skelp were investigated. The fact that adjusting to tskelp and troll arbitrarily without changing to the roll shape can cause not only the edge waves but also the center waves, was carried out. Especially, the edge waves were reduced without the irregular contact pressure by changing the surface of the upper roll that is offset by target tskelp in the normal direction of the surface of the bottom roll in the Forming 1, when the target thickness is tskelp. Moreover, there is no significant difference in the vertical load applied to the rolls when high-strength steels are used or when low-strength steels are used, it is necessary to predict the local maximum and minimum of contact pressure between the skelp and rolls and the shape of the upper roll of the Forming 1 should be modified to decrease irregular contact pressure instead of any design modifications.
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Yun, Yeon Jun, Seok Joon Jang, and Hyun Do Yun. "Damage Tolerance of Reinforced Concrete (RC) Beams with a Layer of PE Fiber Reinforced Strain-Hardening Cement Composite (PE-SHCC)." Applied Mechanics and Materials 372 (August 2013): 219–22. http://dx.doi.org/10.4028/www.scientific.net/amm.372.219.
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This work evaluated the applicability of polyethylene (PE) fiber reinforced strain-hardening cement composite (PE-SHCC) layer at the bottom of reinforced concrete (RC) beams to improve the flexural performance and cracking behavior. PE-SHCC material with specific compressive strength of 70MPa was reinforced with 1.5% PE fibers at the volume fraction. Four RC beams with cross-section of 130 x 170mm and length of 1,460mm were made and tested under four-point monotonic loading. Three beams were layered with PE-SHCC material and one whole RC beam was a control specimen for comparison. Principal variable is the thickness of PE-SHCC layer; 20, 40 and 60mm that are equivalent to 11, 23 and 35% of beams depth. Experimental results indicated that the addition of PE-SHCC layer enhanced the crack-damage mitigation of RC beams and improve the structural behavior, such as strength and ductility, of RC beams.
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Zeybek, Özer. "Design of cylindrical steel liquid tanks with stepped walls using One-foot method." Challenge Journal of Structural Mechanics 7, no. 4 (2021): 162. http://dx.doi.org/10.20528/cjsmec.2021.04.001.
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Cylindrical steel tanks are used in most countries to store bulk volumes of both solid and liquid products such as water, oil, gasoline and grain. Such steel tanks are prone to buckling when subjected to external pressure either due to vacuum or due to wind. These types of shell structures are generally controlled by elastic buckling failure because of the thin wall thickness. Cylindrical shells are commonly constructed with stepwise variable wall thickness due to economic reasons. The thickness of the tank shell wall is designed to increase from top to bottom because the stress resultants on the tank wall gradually increase towards the base of the tank. For open-top tanks, a primary stiffening ring is required at or near the top to maintain roundness under all loads. Stress resultants in a primary stiffening ring were previously identified by the Author for uniform wall thick tanks. In this new study, the applicability of this hand calculation method in stepped wall tanks has been investigated. Pursuant to this goal, a specified tank shell was designed considering One-foot method. Then, the stepped wall tank was transformed into an equivalent 1-course tank for hand calculation. Using the previously developed hand calculation method by Author, a test for the in-plane bending moment in the ring was conducted to achieve an acceptable value for stepped wall tanks. The analysis results show that the previously proposed method for uniform wall thick tanks may also be used for stepped wall tanks considering an equivalent thickness. On the other hand, using Linear Buckling Analysis (LBA), the buckling mode was obtained for two different stepped wall tanks in the study.
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Gacitúa, Guisella, José A. Uribe, Ryan Wilson, Thomas Loriaux, Jorge Hernández, and Andrés Rivera. "50 MHz helicopter-borne radar data for determination of glacier thermal regime in the central Chilean Andes." Annals of Glaciology 56, no. 70 (2015): 193–201. http://dx.doi.org/10.3189/2015aog70a953.
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AbstractDespite their importance as freshwater reservoirs for downstream river systems, few glaciers in central Chile have been comprehensively surveyed. This study presents ground-penetrating radar (GPR) and field-based observations for characterizing the englacial and basal conditions of Glaciar Olivares Alfa (33°110 S, 70°130 W), central Chilean Andes. Using a 50 MHz radar mounted onto a helicopter platform, data were collected covering large portions of the glacier accumulation and ablation zones. The radar data revealed boundaries of a temperate-ice layer at the base of the eastern body of Glaciar Olivares Alfa which appears to be covered by colder ice that extends throughout large parts of the glacier. The thickness of the temperate ice layer is highly variable across the glacier, being on average 40% of the total ice thickness. Radar data analyses reveal regions of cold ice at the bottom/base of the glacier and also patterns of highly saturated sediments beneath the glacier. Using GPR data, this study represents the most exhaustive analysis of glacier ice structure performed in the central Chilean Andes. The results will enable improved estimations of the glacier’s mass balance and ice dynamics, helping us to understand its further development and its impact on water availability.
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He, Changshu, Chengpeng Qiu, Zhiqiang Zhang, et al. "Microstructure and Mechanical Properties of 6061 Al/AZ31 Mg Joints Friction Stir Lap Welded by a Tool with Variable-Pitch Thread Pin." Metals 11, no. 1 (2020): 34. http://dx.doi.org/10.3390/met11010034.
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Sheets of 6061-T6 aluminum alloy (thickness = 3 mm) and AZ31 magnesium alloy were friction stir lap welded by a tool with a variable-pitch thread pin (coarse-threaded in the upper part and fine-threaded in the lower part). For the same rotation speed and welding speed, the heat input was higher in joints with an upper Al alloy (Configuration Al-Mg) than in those with an upper Mg alloy (Configuration Mg-Al). In Configuration Al-Mg, these two dissimilar metals were poorly mixed and Al dominated the stirred zone (SZ). Many intermetallic compounds (IMCs) of Al3Mg2 formed inside the SZ. In Configuration Mg-Al, Mg alloy bands, flocculent Al12Mg17 bands, and minor Al alloy bands intersected in the SZ, forming a complex onion-ring structure. Moreover, a complex mechanical interlocking structure developed at the bottom interface of the SZ. The maximum tensile shear strengths of the Al-Mg and Mg-Al lap configurations were 160.3 and 217 N/mm, respectively, at 700 rpm. The higher tensile shear strength of the Mg-Al configuration primarily represented less IMCs and complex mechanical interlocking structures in the SZ.
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Liu, Zhiyong, and Alberto N. Conejo. "Development of a Novel Dimensionless Relationship to Describe Mass Transfer in Ladles Due to Bottom Gas Injection." Processes 13, no. 1 (2024): 5. https://doi.org/10.3390/pr13010005.
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In the quest to design reactors with a higher productivity, their mixing efficiency should be highly improved. The mass transfer coefficient is a parameter that measures the rate of the refining rates and has been extensively investigated in the past; however, most of the correlations developed in steelmaking are based on the effect of the gas flow rate or its alternative form, stirring energy. The gas flow rate can play a big role in mass transfer but there are many more variables involved. This work has investigated the combined effect of five variables on the mass transfer coefficient due to bottom gas injection with two injection devices: the gas flow rate, the radial position and the separation angle of the porous plugs, the slag thickness, and the ladle aspect ratio. A novel expression in a dimensionless form has been developed, which accurately predicts the mass transfer coefficient. The expression proposed indicates that increasing the gas flow rate, the slag thickness, the ladle aspect ratio, and the separation angle also increases the mass transfer coefficient. On the contrary, increasing the radial position away from the center affects mass transfer, especially at high gas flow rates. Based on the experimental data and their practical application, an optimum layout for the injection of gas is suggested to optimize both mass transfer and the mixing intensity of liquid steel.
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Mackay, J. Ross, and C. R. Burn. "The first 20 years (1978-1979 to 1998-1999) of active-layer development, Illisarvik experimental drained lake site, western Arctic coast, Canada1." Canadian Journal of Earth Sciences 39, no. 11 (2002): 1657–74. http://dx.doi.org/10.1139/e02-068.
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Active-layer thickness, snow depth, minimum soil temperatures, near-surface ground ice, soil heave, and permafrost temperatures have been measured for over 20 years following the 1978 artificial drainage of Lake Illisarvik. Measurements of active-layer thickness and other variables have been made at 25-m intervals along the major and minor axes of the oval-shaped drained-lake bed. Permafrost aggradation commenced in the lake bottom during the first winter following drainage. Before the establishment of vegetation, there was little snow cover, minimum ground temperatures were low, and the active layer was relatively thin. However, both snow depth and minimum ground temperatures have risen where vegetation has grown, the active layer has thickened, and in response, the temperature in permafrost has gradually increased. In the lake bottom, the change in snow depth associated with vegetation growth has been the dominant control on variation in active-layer thickness and not summer weather conditions, which are well correlated with thaw depths along an active-layer course established in the adjacent tundra. Changes in elevation of the surface of the lake bed have been measured with respect to some 40 bench marks anchored in permafrost, and indicate vertical movements of the surface associated with frost heave, thaw subsidence, and the growth of aggradational ice. The ground ice content of near-surface permafrost determined by drilling is in close agreement with the measured uplift of the lake bed. The rate of growth of aggradational ice has been ~0.5 cm a1 over 20 years.