Biomechanical Analysis of Spinal Load in Motor-Manual Cutting

Two Norwegian cutting instructors have been used as models for demonstration of "correct" and "poor" working postures in motor-manual cutting. This enabled estimation of the intervertebral disc compression forces at L5/Sl-level. The results/when related to defined lifting hazard levels shows that the compressive forces are greater in all "poor" postures compared with corresponding "correct" postures. Furthermore, relating to the lifting hazard levels, it becomes obvious that even correct working techniques in the felling and bunching sequences entails hazardous compressive forces in the lumbar column. This is probably one of the main causes of the high incidence of lower back injuries among loggers. Training courses for better technique and adminstrative or engineering controls to eliminate the peak loads are still needed in forestry

Method to determine the optimal parameters of the Arecibo 46.8-MHz antenna system

The spherical reflector at the Arecibo Observatory (AO) offers great advantages for the design of simple and inexpensive high performance steerable antennas at VHF. Light and small feeds have the added benefit that they can be quickly installed in the Arecibo platform. It is important to evaluate the performance of any given feed including the effects of the spherical reflector. The optimization is emphasized of two parameters, namely, the distance below the focal point of the reflector and the beam width of a point feed. For the design of the feed at 46.8 MHz at the AO there were other requirements independent of MST (mesosphere stratosphere troposphere) work. The design of the primary array is discussed along with its performance with the AO spherical reflector

A Comparison of Motor-Manual Cleaning Methods on the Norwegian West Coast

Time consumption, heart rate, sagittal load moments for the low back, perceived exertion, and tool preferences were measured during motor-manual cleaning with chain saws and cleaning saws in western Norway. While no difference was found in heart rate or perceived cardiovascular exertion, the chain saw was observed to have the lowest time consumption per ha of the two tools. Calculated sagittal load moments and local feeling of strain in the low back were significantly higher for the chain saw than the cleaning saw. The difference in time consumption between the two tools was greatest for the least experienced personnel in steep terrain. However, because of the higher risk for low back pain, the chain saw could only be recommended on relatively steep slopes. The cleaning saw was preferred most often by the most experienced forestry workers in stands of high removal density

Performance and loads data from an outdoor hover test of a Lynx tail rotor

A Lynx tail rotor was tested in hover at the Outdoor Aerodynamic Research Facility at NASA Ames Research Center. The test objectives were to measure the isolated rotor performance to provide a baseline for subsequent testing, and to operate the rotor throughout the speed and collective envelope before testing in the NFAC 40- by 80-Foot Wind Tunnel. Rotor forces and blade bending moments were measured at ambient wind conditions from zero to 6.23 m/sec. The test envelope was limited to rotor speeds of 1550 to 1850 rpm and minus 13 deg to plus 20 deg of blade collective pitch. The isolated rotor performance and blade loads data are presented

Effects of three-nucleon forces and two-body currents on Gamow-Teller strengths

We optimize chiral interactions at next-to-next-to leading order to observables in two- and three-nucleon systems, and compute Gamow-Teller transitions in carbon-14, oxygen-22 and oxygen-24 using consistent two-body currents. We compute spectra of the daughter nuclei nitrogen-14, fluorine-22 and fluorine-24 via an isospin-breaking coupled-cluster technique, with several predictions. The two-body currents reduce the Ikeda sum rule, corresponding to a quenching factor q^2 ~ 0.84-0.92 of the axial-vector coupling. The half life of carbon-14 depends on the energy of the first excited 1+ state, the three-nucleon force, and the two-body current

Casimir Energy of a Spherical Shell

The Casimir energy for a conducting spherical shell of radius $a$ is computed using a direct mode summation approach. An essential ingredient is the implementation of a recently proposed method based on Cauchy's theorem for an evaluation of the eigenfrequencies of the system. It is shown, however, that this earlier calculation uses an improper set of modes to describe the waves exterior to the sphere. Upon making the necessary corrections and taking care to ensure that no mathematically ill-defined expressions occur, the technique is shown to leave numerical results unaltered while avoiding a longstanding criticism raised against earlier calculations of the Casimir energy.Comment: LaTeX, 14 pages, 1 figur

Anyonic physical observables and spin phase transition

The quantization of charged matter system coupled to Chern-Simons gauge fields is analyzed in a covariant gauge fixing, and gauge invariant physical anyon operators satisfying fractional statistics are constructed in a symmetric phase, based on Dirac's recipe performed on QED. This method provides us a definite way of identifying physical spectrums free from gauge ambiguity and constructing physical anyon operators under a covariant gauge fixing. We then analyze the statistical spin phase transition in a symmetry-broken phase and show that the Higgs mechanism transmutes an anyon satisfying fractional statistics into a canonical boson, a spin 0 Higgs boson or a topologically massive photon.Comment: 14 pages, added references, a few improvement

Excited hadrons on the lattice: Mesons

We present results for masses of excited mesons from quenched calculations using chirally improved quarks at pion masses down to 350 MeV. The key features of our analysis are the use of a matrix of correlators from various source and sink operators and a basis which includes quark sources with different spatial widths, thereby improving overlap with states exhibiting radial excitations.Comment: 8 pages, 8 figures; version accepted to PR