Width Of Plateaus Research Articles

The magnetic properties of spin-1/2 two-leg ladders with dimerized legs and trimerized modulation of rung exchange

The zero-temperature magnetic properties of spin-1/2 two-leg ladders with staggered and columnar dimerized legs and trimerized modulated rung exchange is studied using the numerical Lanczos method. A clear picture of the influence of different dimerizations on the appearance of magnetization plateaus is provided. It is found that the magnetization curve of the staggered ladders exhibits two plateaus at values 1/3Msat and 2/3Msat, and columnar ladders have an additional plateau at half of the saturation. The width of plateaus in staggered ladders is independent of dimerization on legs but in columnar ladders depends. The width of mid-plateau increases by enhancing the dimerized parameter on legs but others behave inversely. In addition, the effect of the dimerized parameter is studied on other functions as the energy gap, the on-rung spin–spin correlation and dimer order parameter.

Laboratory analysis of superelastic NiTi compression springs

The force/compression characteristics of 32 commercially available nickel titanium (NiTi) compression springs from seven distributors were investigated in vitro in order to support the orthodontist in deciding to select an appropriate spring for a given treatment. The geometrical properties of the coil springs, i.e., inner spring diameter, winding diameter and winding configuration, differed significantly, as well as the alloy composition and the thermo-mechanical treatment of the springs. All springs were mounted on a guiding rod made of an orthodontic steel wire (dimension: 0.016″ × 0.022″), were compressed to a maximum extent and then relieved. Force/compression characteristics were measured at ambient temperatures of 27°C, 37°C and 47°C. Three specimens were taken from each individual compression spring of a certain manufacturer and batch to check for constant material behaviour. A possible influence of sterilization on the mechanical properties of the compression springs was studied by autoclaving one spring of each manufacturer five times (6 minutes at 134°C) and subsequently performing a force/deflection measurement. The NiTi compression springs were classified into three groups and covered a broad range of orthodontic forces between 0.5 N and 3.5 N. The width of the superelastic plateaus of the different NiTi coil springs reached from 0% to 66% of relative compression. An increase in the application temperature from 27°C to 47°C caused a rise in the height and a shortening of the width of the super-elastic plateau. The resultant change in plateau force was as high as 0.4 N to 0.9 N, depending on the spring type investigated, the width of the plateaus was shortened by 4.0% to 15% of relative compression. All compression springs investigated displayed constant material behaviour within a certain batch. However, differences from one batch to another had a high level of significance. Forces on the plateau varied from one batch to the other by about ±18%. An influence of sterilization on the force/compression behaviour could not be proved. Consequently, springs made of superelastic NiTi alloys cover a broad field of application with predefined and nearly constant force levels.