58 research outputs found
Dynamic heave-pitch analysis of air cushion landing systems
A program to develop analytical tools for evaluating the dynamic performance of Air Cushion Landing Systems (ACLS) is described. The heave (vertical) motion of the ACLS was analyzed, and the analysis was extended to cover coupled heave-pitch motions. The mathematical models developed are based on a fundamental analysis of the body dynamics and fluid mechanics of the aircraft-cushion-runway interaction. The air source characteristics, flow losses in the feeding ducts, trunk and cushion, the effects of fluid compressibility, and dynamic trunk deflections, including ground contact are considered. A computer program, based on the heave-pitch analysis, was developed to simulate the dynamic behavior of an ACLS during landing impact and taxi over an irregular runway. The program outputs include ACLS motions, loadings, pressures, and flows as a function of time. To illustrate program use, three basic types of simulations were carried out. The results provide an initial indication of ACLS performance during (1) a static drop, (2) landing impact, and (3) taxi over a runway irregularity
Heave-pitch-roll analysis and testing of air cushion landing systems
The analytical tools (analysis and computer simulation) needed to explain and predict the dynamic operation of air cushion landing systems (ACLS) is described. The following tasks were performed: the development of improved analytical models for the fan and the trunk; formulation of a heave pitch roll analysis for the complete ACLS; development of a general purpose computer simulation to evaluate landing and taxi performance of an ACLS equipped aircraft; and the verification and refinement of the analysis by comparison with test data obtained through lab testing of a prototype cushion. Demonstration of simulation capabilities through typical landing and taxi simulation of an ACLS aircraft are given. Initial results show that fan dynamics have a major effect on system performance. Comparison with lab test data (zero forward speed) indicates that the analysis can predict most of the key static and dynamic parameters (pressure, deflection, acceleration, etc.) within a margin of a 10 to 25 percent
Mauna Kea, Hawaii as an Analogue Site for Future Planetary Resource Exploration: Results from the 2010 ILSO-ISRU Field-Testing Campaign
Within the framework of the International Lunar Surface Operation - In-Situ Resource Utilization Analogue Test held on January 27 - February 11, 2010 on the Mauna Kea volcano in Hawaii, a number of scientific instrument teams collaborated to characterize the field site and test instrument capabilities outside laboratory environments. In this paper, we provide a geological setting for this new field-test site, a description of the instruments that were tested during the 2010 ILSO-ISRU field campaign, and a short discussion for each instrument about the validity and use of the results obtained during the test. These results will form a catalogue that may serve as reference for future test campaigns. In this paper we provide a description and regional geological setting for a new field analogue test site for lunar resource exploration, and discuss results obtained from the 2010 ILSO-ISRU field campaign as a reference for future field-testing at this site. The following instruments were tested: a multispectral microscopic imager, MMI, a Mossbauer spectrometer, an evolved gas analyzer, VAPoR, and an oxygen and volatile extractor called RESOLVE. Preliminary results show that the sediments change from dry, organic-poor, poorly-sorted volcaniclastic sand on the surface, containing basalt, iron oxides and clays, to more water- and organic-rich, fine grained, well-sorted volcaniclastic sand, primarily consisting of iron oxides and depleted of basalt and clays. Furthermore, drilling experiments showed a very close correlation between drilling on the Moon and drilling at the test site. The ILSO-ISRU test site was an ideal location for testing strategies for in situ resource exploration at the lunar or martian surface
First Measurement of the Total Neutron Cross Section on Argon Between 100 and 800 MeV
We report the first measurement of the neutron cross section on argon in the
energy range of 100-800 MeV. The measurement was obtained with a 4.3-hour
exposure of the Mini-CAPTAIN detector to the WNR/LANSCE beam at LANL. The total
cross section is measured from the attenuation coefficient of the neutron flux
as it traverses the liquid argon volume. A set of 2,631 candidate interactions
is divided in bins of the neutron kinetic energy calculated from time-of-flight
measurements. These interactions are reconstructed with custom-made algorithms
specifically designed for the data in a time projection chamber the size of the
Mini-CAPTAIN detector. The energy averaged cross section is . A comparison
of the measured cross section is made to the GEANT4 and FLUKA event generator
packages.Comment: 5 pages, 1 table, 3 figures, submitted to Physical Review Letter
The Mini-CAPTAIN Liquid Argon Time Projection Chamber
This manuscript describes the commissioning of the Mini-CAPTAIN liquid argon
detector in a neutron beam at the Los Alamos Neutron Science Center (LANSCE),
which led to a first measurement of high-energy neutron interactions in argon.
The Mini-CAPTAIN detector consists of a Time Projection Chamber (TPC) with an
accompanying photomultiplier tube (PMT) array sealed inside a
liquid-argon-filled cryostat. The liquid argon is constantly purified and
recirculated in a closed-loop cycle during operation. The specifications and
assembly of the detector subsystems and an overview of their performance in a
neutron beam are reported.Comment: 21 pages, 27 figure
Summary of the second workshop on liquid argon time projection chamber research and development in the United States
The second workshop to discuss the development of liquid argon time projection
chambers (LArTPCs) in the United States was held at Fermilab on July 8-9, 2014. The workshop
was organized under the auspices of the Coordinating Panel for Advanced Detectors, a body that
was initiated by the American Physical Society Division of Particles and Fields. All presentations
at the workshop were made in six topical plenary sessions: i) Argon Purity and Cryogenics, ii)
TPC and High Voltage, iii) Electronics, Data Acquisition and Triggering, iv) Scintillation Light
Detection, v) Calibration and Test Beams, and vi) Software. This document summarizes the current
efforts in each of these areas. It primarily focuses on the work in the US, but also highlights work
done elsewhere in the world
Three dimensional multi-pass repair weld simulations
Full 3-dimensional (3-D) simulation of multi-pass weld repairs is now feasible and practical given the development of improved analysis tools and significantly greater computer power. This paper presents residual stress results from 3-D finite element (FE) analyses simulating a long (arc length of 62°) and a short (arc length of 20°) repair to a girth weld in a 19.6 mm thick, 432 mm outer diameter cylindrical test component. Sensitivity studies are used to illustrate the importance of weld bead inter-pass temperature assumptions and to show where model symmetry can be used to reduce the analysis size.
The predicted residual stress results are compared with measured axial, hoop and radial through-wall profiles in the heat affected zone of the test component repairs. A good overall agreement is achieved between neutron diffraction and deep hole drilling measurements and the prediction at the mid-length position of the short repair. These results demonstrate that a coarse 3-D FE model, using a ‘block-dumped’ weld bead deposition approach (rather than progressively depositing weld metal), can accurately capture the important components of a short repair weld residual stress field. However, comparisons of measured with predicted residual stress at mid-length and stop-end positions in the long repair are less satisfactory implying some shortcomings in the FE modelling approach that warrant further investigation
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Engineered Recognition of Tetravalent Zirconium and Thorium by Chelator-Protein Systems: Toward Flexible Radiotherapy and Imaging Platforms.
Targeted α therapy holds tremendous potential as a cancer treatment: it offers the possibility of delivering a highly cytotoxic dose to targeted cells while minimizing damage to surrounding healthy tissue. The metallic α-generating radioisotopes 225Ac and 227Th are promising radionuclides for therapeutic use, provided adequate chelation and targeting. Here we demonstrate a new chelating platform composed of a multidentate high-affinity oxygen-donating ligand 3,4,3-LI(CAM) bound to the mammalian protein siderocalin. Respective stability constants log β110 = 29.65 ± 0.65, 57.26 ± 0.20, and 47.71 ± 0.08, determined for the EuIII (a lanthanide surrogate for AcIII), ZrIV, and ThIV complexes of 3,4,3-LI(CAM) through spectrophotometric titrations, reveal this ligand to be one of the most powerful chelators for both trivalent and tetravalent metal ions at physiological pH. The resulting metal-ligand complexes are also recognized with extremely high affinity by the siderophore-binding protein siderocalin, with dissociation constants below 40 nM and tight electrostatic interactions, as evidenced by X-ray structures of the protein:ligand:metal adducts with ZrIV and ThIV. Finally, differences in biodistribution profiles between free and siderocalin-bound 238PuIV-3,4,3-LI(CAM) complexes confirm in vivo stability of the protein construct. The siderocalin:3,4,3-LI(CAM) assembly can therefore serve as a "lock" to consolidate binding to the therapeutic 225Ac and 227Th isotopes or to the positron emission tomography emitter 89Zr, independent of metal valence state
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