Harmonic maps and twistorial structures

We introduce the notion of Riemannian twistorial structure and we show that it provides new natural constructions of harmonic maps.Comment: 15 page

Attitude Determination from Single-Antenna Carrier-Phase Measurements

A model of carrier phase measurement (as carried out by a satellite navigation receiver) is formulated based on electromagnetic theory. The model shows that the phase of the open-circuit voltage induced in the receiver antenna with respect to a local oscillator (in the receiver) depends on the relative orientation of the receiving and transmitting antennas. The model shows that using a {\it single} receiving antenna, and making carrier phase measurements to seven satellites, the 3-axis attitude of a user platform (in addition to its position and time) can be computed relative to an initial point. This measurement model can also be used to create high-fidelity satellite signal simulators that take into account the effect of platform rotation as well as translation.Comment: 12 pages, and one figure. Published in J. Appl. Phys. vol. 91, No. 7, April 1, 200

Is unicompartmental-to-unicompartmental revision knee arthroplasty a reliable option? Case-control study

AbstractBackgroundIn selected patients with failed unicompartmental knee arthroplasty (UKA), revision UKA is a reliable option and may even provide lower morbidity rates and better functional outcomes compared to revision total knee arthroplasty.Material and methodsIn a multicentre retrospective study of 425 knees requiring revision surgery after UKA, 36 knees were managed with revision UKA.ResultsOf the 36 knees, 3 (8.33%) required iterative revision surgery, for aseptic loosening. After a mean follow-up of 8.3 years, the mean IKS knee and function scores were high (93.81/100 and 90.77/100, respectively).DiscussionIn carefully selected patients, UKA-to-UKA revision performed according to a rigorous operative technique deserves a role in the surgical strategy for failed UKA.Level of evidenceIII, multicentre retrospective case-control study

Reducing Work Content in Early Stage Naval Ship Designs

Naval Postgraduate School Acquisition Research Progra

Mean magnitude variations of earthquakes as a function of depth: Different crustal stress distribution depending on tectonic setting

International audienceThe mean magnitude of earthquakes in the Gulf of Corinth is found to increase strongly with depth (b-value decreases), whereas the dip of fault planes decreases. The b-value difference of 0.25, between shallow and deep earthquake distributions, is based on about 7,000 events and therefore is statistically highly significant. The same is true in California, but opposite patterns are observed in southern Iceland and in western Nagano, Japan. Because large mean magnitudes (low b-values) are indicative of relatively high stress levels, we propose that in the detachment layer at about 9 ± 2 km depth, earthquakes are generated at higher stresses than in the shallower parts of the crust. The correlation of low b-values with low faulting dips can be taken as line of evidence that low b-values map high stress regimes

Reducing Work Content in Early Stage Naval Ship Designs

Naval Postgraduate School Acquisition Research Progra

Impact of 90 minutes running exercise on plantar loading of the forefoot: a prospective study on symptom-free athletes

Many studies have demonstrated that individuals who engage in running exercises appear to develop musculo-skeletal injuries more frequently [1]. Considering the foot, the most common injuries include stress fractures of the metatarsals, plantar fasciitis, tibialis posterior lesions and ankle sprains. Studies have been conducted who analysed the loading characteristics of the foot in repeated measurement designs – before and after exercise – in order to find a pathomechanical pathway for metatarsal stress fractures [2-4]. The published studies evaluated the in-shoe plantar pressure during treadmill running [2,3] or barefoot after a marathon [4]. To date, no investigation have been conducted who evaluated the impact of a regular training session onto the forefoot loading characteristics. The objective of this investigation was therefore to identify changes in loading characteristics of the foot after a 90 minute running exercise

High-speed FPGA 10's complement adders-subtractors

This paper first presents a study on the classical BCD adders from which a carry-chain type adder is redesigned to fit within the Xilinx FPGA's platforms. Some new concepts are presented to compute the P and G functions for carry-chain optimization purposes. Several alternative designs are presented. Then, attention is given to FPGA implementations of add/subtract algorithms for 10's complement BCD numbers. Carry-chain type circuits have been designed on 4-input LUTs (Virtex-4, Spartan-3) and 6-input LUTs (Virtex-5) Xilinx FPGA platforms. All designs are presented with the corresponding time performance and area consumption figures. Results have been compared to straight implementations of a decimal ripple-carry adder and an FPGA 2's complement binary adder-subtractor using the dedicated carry logic, both carried out on the same platform. Better time delays have been registered for decimal numbers within the same range of operands.This work is supported by the Universities FASTA, Mar del Plata, Argentina, UNCPBA Tandil, Argentina, UAM ,Madrid, Spain, and URV, Tarragona, Spain; it has been partially granted by the CICYT of Spain under contract TEC2007- 68074-C02-02/MIC