3,738 research outputs found
Numerical model of journal bearing lubrication considering a bending stiffness effect
An analysis for operating characteristics of journal bearing lubrication system is performed based on the numerical model. Dynamic bearing lubrication characteristics such as oil film pressure and thickness distribution can be analyzed through a numerical model with an integration of elastohydrodynamics and multi-flexible-body dynamics (MFBD). In particular, the oil film thickness variation by elastic deformation is considered in the elastohydrodynamic analysis by applying the bending stiffness effect of journal. And the oil film thickness variation by the bending stiffness effect is applied to the fluid governing equations to calculate the oil film pressure in the elastohydrodynamic lubrication region. A series of process proposed in this study is available for the analysis of realistic elastohydrodynamic lubrication phenomenon. Also, a numerical example for the journal bearing lubrication system is demonstrated and compared with the experimental results. The numerical results considering the bending stiffness effect show a good agreement with the experimental results
BroadBEV: Collaborative LiDAR-camera Fusion for Broad-sighted Bird's Eye View Map Construction
A recent sensor fusion in a Bird's Eye View (BEV) space has shown its utility
in various tasks such as 3D detection, map segmentation, etc. However, the
approach struggles with inaccurate camera BEV estimation, and a perception of
distant areas due to the sparsity of LiDAR points. In this paper, we propose a
broad BEV fusion (BroadBEV) that addresses the problems with a spatial
synchronization approach of cross-modality. Our strategy aims to enhance camera
BEV estimation for a broad-sighted perception while simultaneously improving
the completion of LiDAR's sparsity in the entire BEV space. Toward that end, we
devise Point-scattering that scatters LiDAR BEV distribution to camera depth
distribution. The method boosts the learning of depth estimation of the camera
branch and induces accurate location of dense camera features in BEV space. For
an effective BEV fusion between the spatially synchronized features, we suggest
ColFusion that applies self-attention weights of LiDAR and camera BEV features
to each other. Our extensive experiments demonstrate that BroadBEV provides a
broad-sighted BEV perception with remarkable performance gains
On the trace theorem to Volterra-type equations with local or non-local derivatives
This paper considers traces at the initial time for solutions of evolution
equations with local or non-local derivatives in vector-valued weighted
spaces. To achieve this, we begin by introducing a generalized real
interpolation method. Within the framework of generalized interpolation theory,
we make use of stochastic process theory and two-weight Hardy's inequality to
derive our trace and extension theorems. Our results encompass findings
applicable to time-fractional equations with broad temporal weight functions
Characterizations of weighted Besov and Triebel-Lizorkin spaces with variable smoothness
In this paper, we study different types of weighted Besov and
Triebel-Lizorkin spaces with variable smoothness. The function spaces can be
defined by means of the Littlewood-Paley theory in the field of Fourier
analysis, while there are other norms arising in the theory of partial
differential equations such as Sobolev-Slobodeckij spaces. It is known that two
norms are equivalent when one considers constant regularity function spaces
without weights. We show that the equivalence still holds for variable
smoothness and weights, which is accomplished by making use of shifted maximal
functions, Peetre's maximal functions, and the reverse H\"older inequality.
Moreover, we obtain a weighted regularity estimate for time-fractional
evolution equations and a generalized Sobolev embedding theorem without
weights.Comment: 36 page
FE implementation of HAH model using FDM-based stress update algorithm for springback prediction of AHSS sheets
The homogeneous anisotropic hardening (HAH) model was implemented into a finite element (FE) code in order to predict springback for an advanced high strength steel (AHSS) sheet sample after double-stage U-draw bending. The finite difference method (FDM) was utilized as an alternative way to calculate the derivatives of this advanced distortional plasticity model allowing the update of the equivalent plastic strain and stress tensor at each time step in the user-material subroutines (UMAT and VUMAT). The FDM makes it easier to derive the stress gradient of complex yield surfaces. The proposed FDM-based stress update algorithm was verified by comparing the springback profiles after the single- and double-stage U-draw bending tests for a DP980 sheet sample predicted with analytical and numerical approaches. In addition, the springback measurement parameters and computational efficiencies depending on both approaches were also compared. The results indicate that the computational efficiency and accuracy of the FE simulations with the FDM-based stress update algorithm were similar to those of the analytical method. © 2018 Institute of Physics Publishing. All rights reserved.11Ysciescopu
Ultraviolet photodepletion spectroscopy of dibenzo-18-crown-6-ether complexes with alkali metal cations
Ultraviolet photodepletion spectra of dibenzo-18-crown-6-ether complexes with alkali metal cations (M+-DB18C6, M = Cs, Rb, K, Na, and Li) were obtained in the gas phase using electrospray ionization quadrupole ion-trap reflectron time-of-flight mass spectrometry. The spectra exhibited a few distinct absorption bands in the wavenumber region of 35450−37800 cm^(−1). The lowest-energy band was tentatively assigned to be the origin of the S_0-S_1 transition, and the second band to a vibronic transition arising from the “benzene breathing” mode in conjunction with symmetric or asymmetric stretching vibration of the bonds between the metal cation and the oxygen atoms in DB18C6. The red shifts of the origin bands were observed in the spectra as the size of the metal cation in M^+-DB18C6 increased from Li^+ to Cs^+. We suggested that these red shifts arose mainly from the decrease in the binding energies of larger-sized metal cations to DB18C6 at the electronic ground state. These size effects of the metal cations on the geometric and electronic structures, and the binding properties of the complexes at the S_0 and S_1 states were further elucidated by theoretical calculations using density functional and time-dependent density functional theories
Simultaneous VLBI Astrometry of H2O and SiO Masers toward the Semiregular Variable R Crateris
We obtained, for the first time, astrometrically registered maps of the 22.2
GHz H2O and 42.8, 43.1, and 86.2 GHz SiO maser emission toward the semiregular
b-type variable (SRb) R Crateris, at three epochs (2015 May 21, and 2016
January 7 and 26) using the Korean Very-long-baseline Interferometry Network.
The SiO masers show a ring-like spatial structure, while the H2O maser shows a
very asymmetric one-side outflow structure, which is located at the southern
part of the ring-like SiO maser feature. We also found that the 86.2 GHz SiO
maser spots are distributed in an inner region, compared to those of the 43.1
GHz SiO maser, which is different from all previously known distributions of
the 86.2 GHz SiO masers in variable stars. The different distribution of the
86.2 GHz SiO maser seems to be related to the complex dynamics caused by the
overtone pulsation mode of the SRb R Crateris. Furthermore, we estimated the
position of the central star based on the ring fitting of the SiO masers, which
is essential for interpreting the morphology and kinematics of a circumstellar
envelope. The estimated stellar coordinate corresponds well to the position
measured by Gaia
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