No abstract

Although small changes in pedicle morphometry can alter screw bending moments significantly, changes in cancellous modulus had no measurable impact on bending moments at these same loads. Bone density is likely to play a limited role in screw bending failure.

Vast ocean areas of planet Earth are exposed year-round to strong wind currents. We suggest that this untapped ocean wind power be exploited by the use of sailing ships. The availability of constantly updated meteorological information makes it possible to operate the ships in ocean areas with optimum wind power so that the propulsive ship power can be converted into electric power by means of ship-mounted hydro-power generators. Their electric power output then is fed into ship-mounted electrolyzers to convert sea water into hydrogen and oxygen. In this paper, we estimate the ship size, sail area, and generator size to produce a 1.5 MW electrical power output. We describe a new oscillating-wing hydro-power generator and present results of model tests obtained in a towing tank. Navier-Stokes computations are presented to provide an estimate of the power extraction efficiency and drag coefficient of such a generator which depends on a range of parameters such as foil maximum pitch angles, plunge amplitude, phase between pitch and plunge and load. Also, we present a discussion of the feasibility of sea water electrolysis and of the reconversion of hydrogen and oxygen into electricity by means of shore-based hydrogen-oxygen power plants.

Many organizations have proposed air launch Reusable Launch Vehicles (RLVs) due to a renewed interest generated by NASA's 2 nd Generation Space Launch Initiative. Air launched RLVs are categorized as captive on top, captive on bottom, towed, aerial refueled, and internally carried. The critical design aspects of various proposed air launch RLVs concepts are evaluated. It is found that many concepts are not possible with today's technology. The authors introduce a new air launch concept that is possible with today's technology called SwiftLaunch RLV.

In situ pedicle screw loads increased significantly as pedicle length increased and as pedicle height decreased. Pedicle screws instrumented internally with strain gages are an effective research instrument allowing measurement of in situ loading along the axis of the screw.