373 research outputs found
Hydrodynamic signatures of stationary Marangoni-driven surfactant transport
We experimentally study steady Marangoni-driven surfactant transport on the
interface of a deep water layer. Using hydrodynamic measurements, and without
using any knowledge of the surfactant physico-chemical properties, we show that
sodium dodecyl sulphate and Tergitol 15-S-9 introduced in low concentrations
result in a flow driven by adsorbed surfactant. At higher surfactant
concentration, the flow is dominated by the dissolved surfactant. Using
Camphoric acid, whose properties are {\it a priori} unknown, we demonstrate
this method's efficacy by showing its spreading is adsorption dominated
Dynamics of a camphoric acid boat at the air–water interface
We report experiments on an agarose gel tablet loaded with camphoric acid (c-boat) spontaneously set into motion by surface tension gradients on the water surface. We observe three distinct modes of c-boat motion: harmonic mode where the c-boat speed oscillates sinusoidally in time, a steady mode where the c-boat maintains constant speed, and an intermittent mode where the c-boat maintains near-zero speed between sudden jumps in speed. Whereas all three modes have been separately reported before in different systems, controlled release of Camphoric Acid (CA) from the agarose gel matrix allowed the observation of all the three modes in the same system. These three modes are a result of a competition between the driving (surface tension gradients) and drag forces acting on the c-boat. Moreover we suggest that there exist two time scales corresponding to spreading of CA and boat motion and the mismatch of these two time scales give rise to the three modes in boat motion. We reproduced all the modes of motion by varying the air–water interfacial tension using Sodium Dodecyl Sulfate (SDS)
Integrated Alternative Source of Energy System with Grid Substation
This paper discusses the modeling, simulation and optimization of integrated alternative source of energy system with grid substation. When there is a lack of energy in grid substation to meet the demand of customer load then alternative source of energy compensates energy deficiency and after that if there is excess energy available then remaining energy is stored in battery bank or sells to grid according to need. In another case when required energy is not generated by alternative sources then remaining energy is purchased from the grid and if the grid substation hasn't available these remaining energy to meet the customer load demand during the peak load then stored battery energy is also active. The size of integrated alternative source of energy system may vary from few hundred watts to ten or hundreds of MW. The possible sources of alternative energy like solar, wind and biomass are considered under this paper. Study location, Muzaffarpur district of Bihar (India), is taken because there is good potential of energy generation from alternative source of energy and still there is no any wind and solar energy power plant. The modeling and simulation of the system is done by using HOMER software and the software solve the optimization problem to minimize the total cost of system and maximum utilization of alternative source of energy
The 5f localization/delocalization in square and hexagonal americium monolayers: A FP-LAPW electronic structure study
The electronic and geometrical properties of bulk americium and square and
hexagonal americium monolayers have been studied with the full-potential
linearized augmented plane wave (FP-LAPW) method. The effects of several common
approximations are examined: (1) non-spin polarization (NSP) vs. spin
polarization (SP); (2) scalar-relativity (no spin-orbit coupling (NSO)) vs.
full-relativity (i.e., with spin-orbit (SO) coupling included); (3)
local-density approximation (LDA) vs. generalized-gradient approximation (GGA).
Our results indicate that both spin polarization and spin orbit coupling play
important roles in determining the geometrical and electronic properties of
americium bulk and monolayers. A compression of both americium square and
hexagonal monolayers compared to the americium bulk is also observed. In
general, the LDA is found to underestimate the equilibrium lattice constant and
give a larger total energy compared to the GGA calculations. While spin orbit
coupling shows a similar effect on both square and hexagonal monolayer
calculations regardless of the model, GGA versus LDA, an unusual spin
polarization effect on both square and hexagonal monolayers is found in the LDA
results as compared with the GGA results. The 5f delocalization transition of
americium is employed to explain our observed unusual spin polarization effect.
In addition, our results at the LDA level of theory indicate a possible 5f
delocalization could happen in the americium surface within the same Am II (fcc
crystal structure) phase, unlike the usually reported americium 5f
delocalization which is associated with crystal structure change. The
similarities and dissimilarities between the properties of an Am monolayer and
a Pu monolayer are discussed in detail.Comment: 22 pages, 8 figure
Combined local-density and dynamical mean field theory calculations for the compressed lanthanides Ce, Pr, and Nd
This paper reports calculations for compressed Ce (4f^1), Pr (4f^2), and Nd
(4f^3) using a combination of the local-density approximation (LDA) and
dynamical mean field theory (DMFT), or LDA+DMFT. The 4f moment, spectra, and
the total energy among other properties are examined as functions of volume and
atomic number for an assumed face-centered cubic (fcc) structure.Comment: 15 pages, 9 figure
Designing a Magnetic Measurement Data Acquisition and Control System with Reuse in Mind: A Rotating Coil System Example
Accelerator magnet test facilities frequently need to measure different
magnets on differently equipped test stands and with different instrumentation.
Designing a modular and highly reusable system that combines flexibility
built-in at the architectural level as well as on the component level addresses
this need. Specification of the backbone of the system, with the interfaces and
dataflow for software components and core hardware modules, serves as a basis
for building such a system. The design process and implementation of an
extensible magnetic measurement data acquisition and control system are
described, including techniques for maximizing the reuse of software. The
discussion is supported by showing the application of this methodology to
constructing two dissimilar systems for rotating coil measurements, both based
on the same architecture and sharing core hardware modules and many software
components. The first system is for production testing 10 m long
cryo-assemblies containing two MQXFA quadrupole magnets for the high-luminosity
upgrade of the Large Hadron Collider and the second for testing IQC
conventional quadrupole magnets in support of the accelerator system at
Fermilab
Distributed Adaptive Attitude Synchronization of Multiple Spacecraft
This paper addresses the distributed attitude synchronization problem of
multiple spacecraft with unknown inertia matrices. Two distributed adaptive
controllers are proposed for the cases with and without a virtual leader to
which a time-varying reference attitude is assigned. The first controller
achieves attitude synchronization for a group of spacecraft with a leaderless
communication topology having a directed spanning tree. The second controller
guarantees that all spacecraft track the reference attitude if the virtual
leader has a directed path to all other spacecraft. Simulation examples are
presented to illustrate the effectiveness of the results.Comment: 13 pages, 11 figures. To appear in SCIENCE CHINA Technological
Science
Вимоги видавничого відділу ІМФЕ ім. М. Т. Рильського до оформлення авторами рукописів
Industrial parts are manufactured to tolerances as no production process is capable of delivering perfectly identical parts. It is unacceptable that a plan for a manipulation task that was determined on the basis of a CAD model of a part fails on some manufactured instance of that part, and therefore it is crucial that the admitted shape variations are systematically taken into account during the planning of the task. We study the problem of orienting a part with given admitted shape variations by means of pushing with a single frictionless jaw. We use a very general model for admitted shape variations that only requires that any valid instance must contain a given convex polygon PI while it must be contained in another convex polygon PE. The problem that we solve is to determine, for a given h, the sequence of h push actions that puts all valid instances of a part with given shape variation into the smallest possible interval of final orientations. The resulting algorithm runs in O(hn) time, where n=|PI|+|PE|
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X-ray diffraction studies using diamond coated rhenium gasket to megabar pressures
X-ray diffraction studies at megabar pressures are limited by the sample thickness between the diamond anvils. High strength gaskets are desirable to improve the quality of x-ray diffraction data. We present a technique which employs a microwave plasma chemical vapor deposited diamond layer on one side of a rhenium gasket. As a test case, we show energy dispersive x-ray diffraction data on rare earth metal neodymium to 153 GPa using a synchrotron source. The increased sample thickness results in an unambiguous crystal structure determination of a monoclinic phase in neodymium above 75 GPa. [chemical vapor deposition, diamond, rhenium gasket, x-ray diffraction, neodymium
Robust grasping under object pose uncertainty
This paper presents a decision-theoretic approach to problems that require accurate placement of a robot relative to an object of known shape, such as grasping for assembly or tool use. The decision process is applied to a robot hand with tactile sensors, to localize the object on a table and ultimately achieve a target placement by selecting among a parameterized set of grasping and information-gathering trajectories. The process is demonstrated in simulation and on a
real robot. This work has been previously presented in Hsiao et al. (Workshop on Algorithmic Foundations of Robotics (WAFR), 2008; Robotics Science and Systems (RSS), 2010) and Hsiao (Relatively robust grasping, Ph.D. thesis, Massachusetts Institute of Technology, 2009).National Science Foundation (U.S.) (Grant 0712012
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