2,985 research outputs found
Longitudinal vibration of ring stiffened cylindrical shells containing liquids Technical report no. 7
Longitudinal vibration of ring stiffened cylindrical shells containing liquids for application to liquid fueled space vehicle booster
Some Notes on Liquid Sloshing in Compartmented Cylindrical Tanks Technical Report No. 1
Frequencies and total force response in rigid cylindrical tanks comparted into sectors by vertical walls and excited in translation to study liquid sloshin
Multi-objective engineering shape optimization using differential evolution interfaced to the Nimrod/O tool
This paper presents an enhancement of the Nimrod/O optimization tool by interfacing DEMO, an external multiobjective optimization algorithm. DEMO is a variant of differential evolution – an algorithm that has attained much popularity in the research community, and this work represents the first time that true multiobjective optimizations have been performed with Nimrod/O. A modification to the DEMO code enables multiple objectives to be evaluated concurrently. With Nimrod/O’s support for parallelism, this can reduce the wall-clock time significantly for compute intensive objective function evaluations. We describe the usage and implementation of the interface and present two optimizations. The first is a two objective mathematical function in which the Pareto front is successfully found after only 30 generations. The second test case is the three-objective shape optimization of a rib-reinforced wall bracket using the Finite Element software, Code_Aster. The interfacing of the already successful packages of Nimrod/O and DEMO yields a solution that we believe can benefit a wide community, both industrial and academic
Fuel sloshing studies Quarterly progress report no. 3
Liquid sloshing in cylindrical and spherical tank
Space construction system analysis. Part 2: Platform definition
The top level system requirements are summarized and the accompanying conceptual design for an engineering and technology verification platform (ETVP) system is presented. An encompassing statement of the system objectives which drive the system requirements is presented and the major mission and subsystem requirements are described with emphasis on the advanced communications technology mission payload. The platform design is defined and used as a reference configuration for an end to space construction analyses. The preferred construction methods and processes, the important interactions between the platform design and the construction system design and operation, and the technology development efforts required to support the design and space construction of the ETVP are outlined
Isomorphs in model molecular liquids
Isomorphs are curves in the phase diagram along which a number of static and
dynamic quantities are invariant in reduced units. A liquid has good isomorphs
if and only if it is strongly correlating, i.e., the equilibrium
virial/potential energy fluctuations are more than 90% correlated in the NVT
ensemble. This paper generalizes isomorphs to liquids composed of rigid
molecules and study the isomorphs of two systems of small rigid molecules, the
asymmetric dumbbell model and the Lewis-Wahnstrom OTP model. In particular, for
both systems we find that the isochoric heat capacity, the excess entropy, the
reduced molecular center-of-mass self part of the intermediate scattering
function, the reduced molecular center-of-mass radial distribution function to
a good approximation are invariant along an isomorph. In agreement with theory,
we also find that an instantaneous change of temperature and density from an
equilibrated state point to another isomorphic state point leads to no
relaxation. The isomorphs of the Lewis-Wahnstrom OTP model were found to be
more approximative than those of the asymmetric dumbbell model, which is
consistent with the OTP model being less strongly correlating. For both models
we find "master isomorphs", i.e., isomorphs have identical shape in the
virial/potential energy phase diagram.Comment: 20 page
Identification of tsunami deposits and liquefaction features in the Gargano area (Italy): paleoseismological implication
The Gargano region (Southeastern Italy) was hit by a M = 6.8 earthquake and inundated by a subsequent tsunami
in 1627. To better define the hazard in the region, we searched for evidence of this and prior earthquakes in
the geologic record. We identified potential earthquake-related liquefaction features and tsunami deposits in the
stratigraphic sequences of the marsh areas both north and south of the Gargano promontory. We recognized clear
liquefaction features and possible tsunamigenic sands that can be related to the 1627 seismic event in irrigation
ditch exposures and gouge cores along the Northern Gargano coast. In total, six potential tsunami sand deposits
have been recognized in two areas located close to the northern and southern coasts of the Gargano promontory.
However, ambiguous evidence comes from the paleontological analysis of these sands. Although fragments of
marine shells have been found in the coarser portion of the sand samples, foraminifera and ostracods assemblages
are typical of brackish water condition. Radiocarbon dating of three of these deposits from the Northern
Gargano coast, near the town of Lesina, suggests an average recurrence interval of 1700 years for tsunami events
in this area. Assuming that all the paleotsunamis are related to the same seismogenic source responsible for the
1627 earthquake, this average recurrence interval may be typical for that source. Radiocarbon dating of three
sand layers observed on the southern coast, close to the city of Manfredonia, suggests that the average recurrence
time for violent sea inundation there is about 1200 years
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