199 research outputs found
Effect of mesh on springback in 3D finite element analysis of flexible microrolling
In flexible microrolling, springback in thickness direction is a critical indicator to determine the forming quality. Accurate prediction of springback is one of the significant aspects in the finite element analysis of flexible microrolling. Meshing is a step of great importance in finite element analysis of manufacturing process as it directly determines the accuracy of the FEA results as well as the requested computational time. This paper presents a numerical study on revealing the mesh effects on the accuracy of springback estimation utilising ABAQUS/Standard for modelling and analyses. Two types of meshes with six mesh sizes for each mesh type are considered in this study and the optimal mesh type and mesh size have been found to obtain accurate value of springback while saving as much computational time as possible
Analytical solution of the linear fractional differential equation by Adomian decomposition method
AbstractIn this paper, we consider the n-term linear fractional-order differential equation with constant coefficients and obtain the solution of this kind of fractional differential equations by Adomian decomposition method. With the equivalent transmutation, we show that the solution by Adomian decomposition method is the same as the solution by the Green's function. Finally, we illustrate our result with some examples
The substructure and halo population of the Double Cluster and Persei
In order to study the stellar population and possible substructures in the
outskirts of Double Cluster and Persei, we investigate using the
GAIA DR2 data a sky area of about 7.5 degrees in radius around the Double
Cluster cores. We identify member stars using various criteria, including their
kinematics (viz, proper motion), individual parallaxes, as well as photometric
properties. A total of 2186 member stars in the parameter space were identified
as members. Based on the spatial distribution of the member stars, we find an
extended halo structure of and Persei, about 6 - 8 times larger than
their core radii. We report the discovery of filamentary substructures
extending to about 200 pc away from the Double Cluster. The tangential
velocities of these distant substructures suggest that they are more likely to
be the remnants of primordial structures, instead of a tidally disrupted stream
from the cluster cores. Moreover, the internal kinematic analysis indicates
that halo stars seems to be experiencing a dynamic stretching in the RA
direction, while the impact of the core components is relatively negligible.
This work also suggests that the physical scale and internal motions of young
massive star clusters may be more complex than previously thought.Comment: 9 pagges, 9 figures, Accecpted to A&
Friction and asperity contact in strip rolling
This paper reviews different aspects of friction and asperity contacts in strip rolling. The mixed film lubrication model considers the effect of asperity flattening and the lubrication within the working zone. The oil concentration of the emulsion at entry and throughout the roll bite is considered together with the thermal effects of the contacts. The actual area of contact due to asperity deformation can be determined from a 3-wavelength FEM model. The deformation of a randomly generated surface of the hot strip with oxide scale can also be modeled by an FEM method. The friction variation in the roll bite can be determined by a sensor roll, and the average friction determined from the forward slip by the marking method or laser Doppler method. The friction models in FEM modeling are also discussed
Effect of directional solidification rate on the microstructure and properties of deformation-processed Cu-7Cr-0.1Ag in situ composites
The influence of directional solidification rate on the microstructure, mechanical properties and conductivity of deformation-processed Cu-7Cr-0.1Ag in situ composites produced by thermo-mechanical processing was systematically investigated. The microstructure was analyzed by optical microscopy and scanning electronic microscopy. The mechanical properties and conductivity were evaluated by tensile-testing machine and micro-ohmmeter, respectively. The results indicate that the size, shape and distribution of second-phase Cr grains are significantly different in the Cu-7Cr-0.1Ag alloys with different growth rates. At a growth rate of 200 μm s-1, the Cr grains transform into fine Cr fiber-like grains parallel to the pulling direction from the Cr dendrites. The tensile strength of the Cu-7Cr-0.1Ag in situ composites from the directional solidification (DS) alloys is significantly higher than that from the as-cast alloy, while the conductivity of the in situ composites from the DS alloys is slightly lower than that from the as-cast alloy. The following combinations of tensile strength, elongation to fracture and conductivity of the Cu-7Cr-0.1Ag in situ composites from the DS alloy with a growth rate of 200 μm s-1 and a cumulative cold deformation strain of 8 after isochronic aging treatment for 1 h can be obtained respectively as: (i) 1067 MPa, 2.9% and 74.9% IACS; or (ii) 1018 MPa, 3.0%, and 76.0% IACS or (iii) 906 MPa, 3.3% and 77.6% IACS
Housing Market and Entrepreneurship: Micro Evidence from China
Using a unique survey data of Chinese households, we study the impact of house price growth and house price risk on entrepreneurship. House price risk, measured as the sensitivity of house price growth to local GDP growth, negatively impacts the entrepreneurship of homeowners relative to renters. This finding is concentrated only among sophisticated households and is consistent with the portfolio effect when housing and occupational choices are integral parts of the household portfolio. Moreover, a high past house price growth reduces the entrepreneurship of homeowners relative to renters. This holds for both sophisticated and unsophisticated households. We propose a new economic channel based on extrapolative belief and provide further supportive evidence
The Chocolate Chip Cookie Model: Dust Geometry of Milky-Way like Disk Galaxies
We present a new two-component dust geometry model, the \textit{Chocolate
Chip Cookie} model, where the clumpy nebular regions are embedded in a diffuse
stellar/ISM disk, like chocolate chips in a cookie. By approximating the
binomial distribution of the clumpy nebular regions with a continuous Gaussian
distribution and omitting the dust scattering effect, our model solves the dust
attenuation process for both the emission lines and stellar continua via
analytical approaches. Our Chocolate Chip Cookie model successfully fits the
inclination dependence of both the effective dust reddening of the stellar
components derived from stellar population synthesis and that of the emission
lines characterized by the Balmer decrement for a large sample of Milky-Way
like disk galaxies selected from the main galaxy sample of the Sloan Digital
Sky Survey (SDSS). Our model shows that the clumpy nebular disk is about 0.55
times thinner and 1.6 times larger than the stellar disk for MW-like galaxies,
whereas each clumpy region has a typical optical depth in band. After considering the aperture effect, our model prediction
on the inclination dependence of dust attenuation is also consistent with
observations. Not only that, in our model, the dust attenuation curve of the
stellar population naturally depends on inclination and its median case is
consistent with the classical Calzetti law. Since the modelling constraints are
from the optical wavelengths, our model is unaffected by the optically thick
dust component, which however could bias the model's prediction of the infrared
emissions.Comment: 27 pages, 11 figures, 1 tabl
ProlificDreamer: High-Fidelity and Diverse Text-to-3D Generation with Variational Score Distillation
Score distillation sampling (SDS) has shown great promise in text-to-3D
generation by distilling pretrained large-scale text-to-image diffusion models,
but suffers from over-saturation, over-smoothing, and low-diversity problems.
In this work, we propose to model the 3D parameter as a random variable instead
of a constant as in SDS and present variational score distillation (VSD), a
principled particle-based variational framework to explain and address the
aforementioned issues in text-to-3D generation. We show that SDS is a special
case of VSD and leads to poor samples with both small and large CFG weights. In
comparison, VSD works well with various CFG weights as ancestral sampling from
diffusion models and simultaneously improves the diversity and sample quality
with a common CFG weight (i.e., ). We further present various improvements
in the design space for text-to-3D such as distillation time schedule and
density initialization, which are orthogonal to the distillation algorithm yet
not well explored. Our overall approach, dubbed ProlificDreamer, can generate
high rendering resolution (i.e., ) and high-fidelity NeRF with
rich structure and complex effects (e.g., smoke and drops). Further,
initialized from NeRF, meshes fine-tuned by VSD are meticulously detailed and
photo-realistic. Project page and codes:
https://ml.cs.tsinghua.edu.cn/prolificdreamer/Comment: NeurIPS 2023 (Spotlight
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