This paper describes the design and evaluation of a robust integrator for software-implemented control systems. The integrator is constructed as a generic component in the Simulink design tool, and ...can thus be used for robust implementation of a wide range of control algorithms. The integrator is designed to support the failbounded failure model for transient bit-flips that may occur in the CPU, main memory and I/O circuits of a control system. In particular, it allows the control system to detect and recover from bit-flips that cause data errors. Robustness is achieved by sequentially executing duplicated integrator code on the same processor to support error detection, and through the use of a recovery buffer that allows a roll-back to the previous integrator state when an error is detected. The effectiveness of the robust integrator was evaluated through fault injection experiments with a PI controller, where single bit flips were injected inside the CPU of the control system. No violations of the fail-bounded model were observed in the experiments.
To increase the range of motion in the knee, posterior cruciate ligament-retaining total knee arthroplasty (TKA), which has a roll back (RB) mechanism, is used. The roll back mechanism is the complex ...movement of the femoral condyles relative to the tibial plateau, which results in translation of the tibiofemoral contact point posteriorly as the knee is flexed. This study was undertaken to assess the function of the posterior cruciate ligament (PCL) and posterior tibial tilt following PCL-retaining TKA. Eleven fresh-frozen cadaveric normal lower extremity specimens (average age: 75.4 years; range: 69 to 88 years) were obtained for this study. The test was performed on a loading frame after specimen preparation. The calcaneal bone was fixed on the rigid frame. A load of 9.5 kg was applied perpendicularly by the moving frame to femoral head through four casters. PCL strain and RB were measured before and following TKA by changing the posterior tilt of tibial component and the external rotation of femoral component. PCL strain at 105 degrees flexion in the 0 degree posterior tilt group (3.3% +/- 2.4%) was decreased in the 10 degrees posterior tilt group (0.6% +/- 0.5%), and this decrease was statistically significant (p < 0.05). RB was measured as anterior-posterior translation by using an arthroscopic probe. After TKA, RB was decreased in the medial compartment but was increased in the lateral component. These different movements of the tibiofemoral contact points consequently caused rotation in the flexion position. Posterior tilt of the tibial component decreased the efficiency of the PCL's function. Retaining the PCL physically is not the same as preserving the function of the PCL because of the lack of the ACL, the change of the joint line, the differences in articular geometry, and the balance of the ligaments.
A more recent paper published in Science last year showed that the size of subduction zone plate boundaries controls not only their velocity and curvature, but it also controls the velocities of the ...tectonic plates.\n Subduction, Mantle Flow and Mount Etna As models and observations show, the size of subduction zones provides a strong control on plate and plate boundary velocities, and the formation and destruction of mountain ranges and ocean basins. Because these melts are very buoyant, they rise to the surface and extrude as lava and volcanic ash, thereby forming Mount Etna, Future Directions Although the new theory ot subduction zone dynamics indicates that subduction zone size provides a dominant control on plate motions, plate boundary motions, mountain formation and destruction, and flow in the Earth's mantle, many questions remain.
Extendible hashing is a dynamic data structure which accommodates expansion and contraction of any stored data efficiently. In this article, an algorithm has been developed for managing concurrent ...operations on extendible hashing by achieving optimal memory utilization by supporting directly expansion and contraction, page split, and merge. The results of this study have been encouraging in the sense that it seems to provide a higher degree of concurrency compared to other algorithms on an extendible hash file.
PDF
