Performance evaluation of a dental handpiece in simulation of clinical finishing using a novel 2DOF in vitro apparatus

This paper reports on the performance evaluation of a dental handpiece in simulation of clinical finishing using a novel two-degrees-of-freedom (2DOF) in vitro apparatus. The instrumented apparatus consisted of a two-dimensional computer-controlled coordinate worktable carrying a dental handpiece, a piezoelectric force dynamometer, and a high-speed data acquisition and signal conditioning system for simulating the clinical operations and monitoring the dental finishing processes. The performance of the dental handpiece was experimentally evaluated with respect to rotational speed, torque, and specific finishing energy under the applied clinical finishing conditions. The results show that the rotational speeds of the dental handpiece decreased by increasing either the depth of cut or the feed rate at a constant clinically applied air pressure and water flowrate. They also decreased when increasing both the tangential and normal finishing forces. The specific finishing energy decreased with an increase in either depth of cut or feed rate, while the finishing torque increased as either the depth of cut or the feed rate was increased. Implications of these results were to provide guidance for proper applications of dental handpieces in clinical practice.     

On the convergence rate of ordinal comparisons of random variables

The asymptotic exponential convergence rate of ordinal comparisons follows from well-known results in large deviations theory, where the critical condition is the existence of a finite moment generating function. In this note, we show that this is both a necessary and sufficient condition, and also show how one can recover the exponential convergence rate in cases where the moment generating function is not finite. In particular, by working with appropriately truncated versions of the original random variables, the exponential convergence rate can be recovered     

SLIM revisited

SLIM (spectroscopic localization by imaging), a tool for in vivo magnetic resonance spectroscopy that provides compartmental spectra from relatively few phase-encoded data, is limited by the inhomogeneities within each compartment. It is shown that the SLIM-derived spectra approach the average compartmental spectra as the number of phase encoded data approaches infinity, and the convergent rate of the error for each compartment is proportional to the size of the compartment. Numerical simulation studies are conducted to confirm the convergence property. A detailed discussion of the result is provided.     

Producing persistent, high-current, high-duty-factor H- beams for routine 1 MW operation of Spallation Neutron Source (invited)

Since 2009, the Spallation Neutron Source (SNS) has been producing neutrons with ion beam powers near 1 MW, which requires the extraction of ～50 mA H(-) ions from the ion source with a ～5% duty factor. The 50 mA are achieved after an initial dose of ～3 mg of Cs and heating the Cs collar to ～170 °C. The 50 mA normally persist for the entire 4-week source service cycles. Fundamental processes are reviewed to elucidate the persistence of the SNS H(-) beams without a steady feed of Cs and why the Cs collar temperature may have to be kept near 170 °C.     

Multi-product sequencing and lot-sizing under uncertainties: A memetic algorithm

The paper deals with a stochastic multi-product sequencing and lot-sizing problem for a line that produces items in lots. Two types of uncertainties are considered: random lead time induced by machine breakdowns and random yield to take into account part rejects. In addition, sequence dependent setup times are also included. This study focuses on maximizing the probability of producing a required quantity of items of each type for a given finite planning horizon. A decomposition approach is used to separate sequencing and lot-sizing algorithms. Previous works have shown that the sequencing sub-problem can be solved efficiently, but the lot-sizing sub-problem remains difficult. In this paper, a memetic algorithm is proposed for this second sub-problem. Computational results show that the algorithms developed can be efficiently used for large scale industrial instances.     

Relative position of limit cycles in an immune responsec

In this paper, a predator-prey model for immune response is proposed. We use the method of vector analysis to estimate the relative positions of the limit cycles in the antigen-antibody phase plane for the model.     

Performance of an HTS Generator Field Coil Under System Fault Conditions

High-temperature superconducting (HTS) coils are generally stable against transient thermal disturbances. Protection against spontaneous quenches is not a main design issue for an HTS coil. However, HTS coils used in many electric devices such as motors, generators, transformers, and current limiters will operate under over-current fault conditions, which may result in a coil quench and thermal runaway. Those electric devices should be able to ride through some grid fault conditions and remain functional. This requires a certain over-current capability of the HTS coils. This paper discusses the over-current requirements from grid faults and the thermal transient responses of a BSCCO coil. It presents the analysis results of the coil subjected to over-current pulses at different operating conditions. The study also investigates the thermal runaway current and its relationship with the over-current pulse     

Fatigue damage accumulation of cold expanded hole in aluminum alloys subjected to block loading

Fatigue damage accumulation of cold expanded hole in aluminum alloys used in land transportation components was investigated. Tests were carried out using pre-cracked SENT specimens and inserting an expanded hole at the crack tip. The degree of the cold expansion was chosen equal to 4.3%. Tests were performed in two and four block loading under constant amplitude. Two sequences were compared.The increasing and the decreasing magnitude were compared. The experimental results were compared to the damage calculated by the Miner's rule and a new simple fatigue damage indicator. This comparison shows that the ‘model of the damage stress’, which take into account of the loading history, yields a good estimation of the experimental results. Moreover, the error is minimized in comparison to the Miner's model.