740 research outputs found
Determination of clay soil creepage characteristics
Results of laboratory researches of clay soil creepage according to regulations of N.N. Maslov's physicotechnical theory are stated. Tests were conducted at constant speed of deformation and continuous registration of vertical and horizontal deformations and pressure. Dependence of durability and creepage parameters from duration of preliminary condensation is established
Integrating Systems for Liquid/Substrate Characterization and Functional Printing
Gallium-Indium alloys are recently applied in fabricating soft devices, such as stretchable sensors, electric circuits, micro pumps and optics. Its printability demonstrates the possibility for a wide extension of the application. Current fabrication methods are inefficient when printing is most handled manually, and are highly dependent on material properties. There is need for a fast way to characterize material properties, and to functionally print the given shape on the substrate. This paper presents the construction of an efficiently integrated system with optical imaging and functional printing for Gallium-Indium alloys. The imaging section allows for characterization of material properties to fast and accurately determine printing parameters in printing section. A new algorithm, which extends generalized Hough Transform, is designed to determine the contact angle of sessile drops by fitting the shape based on Bashforth-Adams equation. The results are later applied in determination of featured geometry in printing. The algorithm shows relatively low errors in profiling the sessile drop shapes. However, the results are not stable for 5% of test pictures, and thus revisions are still needed. In addition, functional printing is finalized with a direct writing module and a friendly user interface. A series of the state-of-the-art algorithms are adopted in image analysis and controlling. Test printing shows its workability, flexibility and accordance to the previous work. The integrated system presents a solution for both accuracy and efficiency in Gallium-Indium alloy printing
The Formation of Fragments at Corotation in Isothermal Protoplanetary Disks
Numerical hydrodynamics simulations have established that disks which are
evolved under the condition of local isothermality will fragment into small
dense clumps due to gravitational instabilities when the Toomre stability
parameter is sufficiently low. Because fragmentation through disk
instability has been suggested as a gas giant planet formation mechanism, it is
important to understand the physics underlying this process as thoroughly as
possible. In this paper, we offer analytic arguments for why, at low ,
fragments are most likely to form first at the corotation radii of growing
spiral modes, and we support these arguments with results from 3D hydrodynamics
simulations.Comment: 21 pages, 1 figur
3D Radiative Hydrodynamics for Disk Stability Simulations: A Proposed Testing Standard and New Results
Recent three-dimensional radiative hydrodynamics simulations of
protoplanetary disks report disparate disk behaviors, and these differences
involve the importance of convection to disk cooling, the dependence of disk
cooling on metallicity, and the stability of disks against fragmentation and
clump formation. To guarantee trustworthy results, a radiative physics
algorithm must demonstrate the capability to handle both the high and low
optical depth regimes. We develop a test suite that can be used to demonstrate
an algorithm's ability to relax to known analytic flux and temperature
distributions, to follow a contracting slab, and to inhibit or permit
convection appropriately. We then show that the radiative algorithm employed by
Meji\'a (2004) and Boley et al. (2006) and the algorithm employed by Cai et al.
(2006) and Cai et al. (2007, in prep.) pass these tests with reasonable
accuracy. In addition, we discuss a new algorithm that couples flux-limited
diffusion with vertical rays, we apply the test suite, and we discuss the
results of evolving the Boley et al. (2006) disk with this new routine.
Although the outcome is significantly different in detail with the new
algorithm, we obtain the same qualitative answers. Our disk does not cool fast
due to convection, and it is stable to fragmentation. We find an effective
. In addition, transport is dominated by low-order
modes.Comment: Submitted to Ap
Genomics of a Metamorphic Timing QTL: Met1 Maps to a Unique Genomic Position and Regulates Morph and Species-Specific Patterns of Brain Transcription
Very little is known about genetic factors that regulate life history transitions during ontogeny. Closely related tiger salamanders (Ambystoma species complex) show extreme variation in metamorphic timing, with some species foregoing metamorphosis altogether, an adaptive trait called paedomorphosis. Previous studies identified a major effect quantitative trait locus (met1) for metamorphic timing and expression of paedomorphosis in hybrid crosses between the biphasic Eastern tiger salamander (Ambystoma tigrinum tigrinum) and the paedomorphic Mexican axolotl (Ambystoma mexicanum). We used existing hybrid mapping panels and a newly created hybrid cross to map the met1 genomic region and determine the effect of met1 on larval growth, metamorphic timing, and gene expression in the brain. We show that met1 maps to the position of a urodele-specific chromosome rearrangement on linkage group 2 that uniquely brought functionally associated genes into linkage. Furthermore, we found that more than 200 genes were differentially expressed during larval development as a function of met1 genotype. This list of differentially expressed genes is enriched for proteins that function in the mitochondria, providing evidence of a link between met1, thyroid hormone signaling, and mitochondrial energetics associated with metamorphosis. Finally, we found that met1 significantly affected metamorphic timing in hybrids, but not early larval growth rate. Collectively, our results show that met1 regulates species and morph-specific patterns of brain transcription and life history variation
Standing and travelling waves in the shallow-water circular hydraulic jump
A wave equation for a time-dependent perturbation about the steady
shallow-water solution emulates the metric an acoustic white hole, even upon
the incorporation of nonlinearity in the lowest order. A standing wave in the
sub-critical region of the flow is stabilised by viscosity, and the resulting
time scale for the amplitude decay helps in providing a scaling argument for
the formation of the hydraulic jump. A standing wave in the super-critical
region, on the other hand, displays an unstable character, which, although
somewhat mitigated by viscosity, needs nonlinear effects to be saturated. A
travelling wave moving upstream from the sub-critical region, destabilises the
flow in the vicinity of the jump, for which experimental support has been
given.Comment: 9 pages, REVTeX, Additional treatment on travelling waves.
Extensively revised in the publised version. Contains a full new section on
the role of nonlinearit
Processing liquid metal for conformable electronics
Future generations of robots, electronics, and assistive medical devices will include systems that are soft, elastically deformable, and may adapt their functionality in unstructured environments. This will require soft active materials for power circuits and sensing of deformation and contact pressure. Liquid-embedded elastomer electronics offer one solution as key elements of highly deformable and soft robotic systems. Several designs for stretchable conductors and soft sensory skins (including strain, pressure, and curvature sensors) based on a liquid-embedded-elastomer approach have been developed. Many of these fluid–elastomer composites utilize liquid metal alloys due to their high conductivities and inherent compliance. Understanding how these alloys can be processed for high-yield manufacturability is critical to the development of parallel processing technology, which is needed to create more complex and low-cost systems. This discussion will highlight surface interactions between droplets of gallium–indium alloys and elastomeric substrates, and the implementation of this study to selective patterning, direct-writing, and inkjet printing of hyperelastic electronic components
Modeling Mid-Infrared Variability of Circumstellar Disks with Non-Axisymmetric Structure
Recent mid-infrared observations of young stellar objects have found
significant variations possibly indicative of changes in the structure of the
circumstellar disk. Previous models of this variability have been restricted to
axisymmetric perturbations in the disk. We consider simple models of a
non-axisymmetric variation in the inner disk, such as a warp or a spiral wave.
We find that the precession of these non-axisymmetric structures produce
negligible flux variations but a change in the height of these structures can
lead to significant changes in the mid-infrared flux. Applying these models to
observations of the young stellar object LRLL 31 suggests that the observed
variability could be explained by a warped inner disk with variable scale
height. This suggests that some of the variability observed in young stellar
objects could be explained by non-axisymmetric disturbances in the inner disk
and this variability would be easily observable in future studies.Comment: 9 pages plus 16 figures and 1 appendix. Accepted to Ap
- …