5,592 research outputs found
Earthquake Mechanism and Displacement Fields Close to Fault Zones
The Sixth Geodesy/Solid Earth and Ocean Physics (GEOP) Research Conference was held on February 4–5, 1974, at the Institute of Geophysics and Planetary Physics, University of California, San Diego, in La Jolla, California. It was attended by about 100 persons.
James N. Brune, program chairman, opened the conference and delivered the introductory address, a somewhat extended version of which is printed elsewhere in this issue. Brune's paper and the following summaries of the sessions constitute a report of the conference
Lightweight Bulldozer Attachment for Construction and Excavation on the Lunar Surface
A lightweight bulldozer blade prototype has been designed and built to be used as an excavation implement in conjunction with the NASA Chariot lunar mobility platform prototype. The combined system was then used in a variety of field tests in order to characterize structural loads, excavation performance and learn about the operational behavior of lunar excavation in geotechnical lunar simulants. The purpose of this effort was to evaluate the feasibility of lunar excavation for site preparation at a planned NASA lunar outpost. Once the feasibility has been determined then the technology will become available as a candidate element in the NASA Lunar Surface Systems Architecture. In addition to NASA experimental testing of the LANCE blade, NASA engineers completed analytical work on the expected draft forces using classical soil mechanics methods. The Colorado School of Mines (CSM) team utilized finite element analysis (FEA) to study the interaction between the cutting edge of the LANCE blade and the surface of soil. FEA was also used to examine various load cases and their effect on the lightweight structure of the LANCE blade. Overall it has been determined that a lunar bulldozer blade is a viable technology for lunar outpost site preparation, but further work is required to characterize the behavior in 1/6th G and actual lunar regolith in a vacuum lunar environment
Comparison of ISRU Excavation System Model Blade Force Methodology and Experimental Results
An Excavation System Model has been written to simulate the collection and transportation of regolith on the Moon. The calculations in this model include an estimation of the forces on the digging tool as a result of excavation into the regolith. Verification testing has been performed and the forces recorded from this testing were compared to the calculated theoretical data. A prototype lunar vehicle built at the NASA Johnson Space Center (JSC) was tested with a bulldozer type blade developed at the NASA Kennedy Space Center (KSC) attached to the front. This is the initial correlation of actual field test data to the blade forces calculated by the Excavation System Model and the test data followed similar trends with the predicted values. This testing occurred in soils developed at the NASA Glenn Research Center (GRC) which are a mixture of different types of sands and whose soil properties have been well characterized. Three separate analytical models are compared to the test data
Employees’ feelings about more meetings: An overt analysis and recommendations for improving meetings
Purpose – The purpose of this paper is to identify how employees feel about having more meetings and what can be done to improve employees’ feelings about their work meetings.
Design/methodology/approach – Data were obtained from three samples of working adults. The first was a convenience sample recruited by undergraduate students (n = 120), the second was a stratified random sample from a metropolitan area in the southern USA (n = 126), and the third was an internet-based panel sample (n = 402). Constant comparative analysis of responses to open-ended questions was used to investigate the overarching research questions.
Findings – It is found that employees enjoy meetings when they have a clear objective, and when important relevant information is shared. Consistent with conservation of resources theory, most employees are unhappy with meetings when they reduce their work-related resources (e.g. meetings constrain their time, lack structure and are unproductive).
Practical implications – The data suggest that meetings appear to be both resource-draining and resource-supplying activities in the workplace. Researchers and managers should consider overtly asking about how people feel about meetings, as a means of identifying areas for future research inquiry and targets for improvement in the workplace generally.
Originality/value – The paper describes one of the few studies on meetings that ask the participants overtly what their feelings are regarding their workplace meetings. Additionally, the paper illustrates the usefulness of qualitative data analysis as a means for further understanding workplace activities viewing respondents as informants.
Keywords United States of America, Employees behaviour, Employees attitudes, Employees participation, Meetings, Meeting demands, Qualitative research, Thematic analysi
High Energy Bounds on Soft N=4 SYM Amplitudes from AdS/CFT
Using the AdS/CFT correspondence, we study the high-energy behavior of
colorless dipole elastic scattering amplitudes in N=4 SYM gauge theory through
the Wilson loop correlator formalism and Euclidean to Minkowskian analytic
continuation. The purely elastic behavior obtained at large impact-parameter L,
through duality from disconnected AdS_5 minimal surfaces beyond the
Gross-Ooguri transition point, is combined with unitarity and analyticity
constraints in the central region. In this way we obtain an absolute bound on
the high-energy behavior of the forward scattering amplitude due to the
graviton interaction between minimal surfaces in the bulk. The dominant
"Pomeron" intercept is bounded by alpha less than or equal to 11/7 using the
AdS/CFT constraint of a weak gravitational field in the bulk. Assuming the
elastic eikonal approximation in a larger impact-parameter range gives alpha
between 4/3 and 11/7. The actual intercept becomes 4/3 if one assumes the
elastic eikonal approximation within its maximally allowed range L larger than
exp{Y/3}, where Y is the total rapidity. Subleading AdS/CFT contributions at
large impact-parameter due to the other d=10 supergravity fields are obtained.
A divergence in the real part of the tachyonic KK scalar is cured by
analyticity but signals the need for a theoretical completion of the AdS/CFT
scheme.Comment: 25 pages, 3 eps figure
Star Formation and Young Population of the HII Complex Sh2-294
The Sh2-294 HII region ionized by a single B0V star features several infrared
excess sources, a photodissociation region, and also a group of reddened stars
at its border. The star formation scenario in the region seems to be quite
complex. In this paper, we present follow-up results of Sh2-294 HII region at
3.6, 4.5, 5.8, and 8.0 microns observed with the Spitzer Space Telescope
Infrared Array Camera (IRAC), coupled with H2 (2.12 microns) observation, to
characterize the young population of the region and to understand its star
formation history. We identified 36 young stellar object (YSO, Class I, Class
II and Class I/II) candidates using IRAC color-color diagrams. It is found that
Class I sources are preferentially located at the outskirts of the HII region
and associated with enhanced H2 emission; none of them are located near the
central cluster. Combining the optical to mid-infrared (MIR) photometry of the
YSO candidates and using the spectral energy distribution fitting models, we
constrained stellar parameters and the evolutionary status of 33 YSO
candidates. Most of them are interpreted by the model as low-mass (< 4 solar
masses) YSOs; however, we also detected a massive YSO (~9 solar masses) of
Class I nature, embedded in a cloud of visual extinction of ~24 mag. Present
analysis suggests that the Class I sources are indeed younger population of the
region relative to Class II sources (age ~ 4.5 x 10^6 yr). We suggest that the
majority of the Class I sources, including the massive YSOs, are
second-generation stars of the region whose formation is possibly induced by
the expansion of the HII region powered by a ~ 4 x 10^6 yr B0 main-sequence
star.Comment: 12 pages, 7 figures, 2 tables. Accepted for publication in The
Astrophysical Journa
Valence Bond States: Link models
An isotropic anti-ferromagnetic quantum state on a square lattice is
characterized by symmetry arguments only. By construction, this quantum state
is the result of an underlying valence bond structure without breaking any
symmetry in the lattice or spin spaces. A detailed analysis of the correlations
of the quantum state is given (using a mapping to a 2D classical statistical
model and methods in field theory like mapping to the non-linear sigma model or
bosonization techniques) as well as the results of numerical treatments
(regarding exact diagonalization and variational methods). Finally, the
physical relevance of the model is motivated. A comparison of the model to
known anti-ferromagnetic Mott-Hubbard insulators is given by means of the
two-point equal-time correlation function obtained i) numerically from the
suggested state and ii) experimentally from neutron scattering on cuprates in
the anti-ferromagnetic insulator phase.Comment: 20 pages, 15 figures; added references, corrected some typos, new
sections. Published versio
Parity-violating Electron Deuteron Scattering and the Proton's Neutral Weak Axial Vector Form Factor
We report on a new measurement of the parity-violating asymmetry in
quasielastic electron scattering from the deuteron at backward angles at Q2=
0.038 (GeV/c)2. This quantity provides a determination of the neutral weak
axial vector form factor of the nucleon, which can potentially receive large
electroweak corrections. The measured asymmetry A=-3.51 +/- 0.57(stat) +/-
0.58(sys)ppm is consistent with theoretical predictions. We also report on
updated results of the previous experiment at Q2=0.091 (GeV/c)2, which are also
consistent with theoretical predictions.Comment: 4 pages, 2 figures, submitted to Phys. Rev. Let
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