Scheduling periodic jobs using imprecise results

One approach to avoid timing faults in hard, real-time systems is to make available intermediate, imprecise results produced by real-time processes. When a result of the desired quality cannot be produced in time, an imprecise result of acceptable quality produced before the deadline can be used. The problem of scheduling periodic jobs to meet deadlines on a system that provides the necessary programming language primitives and run-time support for processes to return imprecise results is discussed. Since the scheduler may choose to terminate a task before it is completed, causing it to produce an acceptable but imprecise result, the amount of processor time assigned to any task in a valid schedule can be less than the amount of time required to complete the task. A meaningful formulation of the scheduling problem must take into account the overall quality of the results. Depending on the different types of undesirable effects caused by errors, jobs are classified as type N or type C. For type N jobs, the effects of errors in results produced in different periods are not cumulative. A reasonable performance measure is the average error over all jobs. Three heuristic algorithms that lead to feasible schedules with small average errors are described. For type C jobs, the undesirable effects of errors produced in different periods are cumulative. Schedulability criteria of type C jobs are discussed

A novel sol-gel Bi2-xHfxO3+x/2 radiopacifier for mineral trioxide aggregates (MTA) as dental filling materials

Funding Information: The authors would like to thank Taipei Medical University Hospital for financially sup-porting this work under grant no. 110TMU-TMUH-16 and partially supported by MOST 109-2221-E-038-014. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Mineral trioxide aggregate (MTA) is well known as an effective root canal filling material for endodontics therapy. Within MTA, bismuth oxide (Bi2O3) serving as the radiopacifier still has biocompatibility concerns due to its mild cytotoxicity. In the present study, we tried to modify the Bi2O3 radiopacifier by doping hafnium ions via the sol-gel process and investigated the effects of different doping ratios (Bi2-xHfxO3+x/2, x = 0–0.3) and calcination temperatures (400–800 °C). We mixed various precursor mixtures of bismuth nitrate (Bi(NO3)3·5H2O) and hafnium sulfate (Hf(SO4)2) and controlled the calcination temperatures. The as-prepared Hf-doped Bi2O3 radiopaci-fier powders were investigated by thermogravimetric analysis (TGA), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Portland cement/radiopacifier/calcium sulfate (75/20/5) were mixed and set by deionized water (powder to water ratio = 3:1). Changes in radiopacity, diametral tensile strength (DTS), and in vitro cell viability of the hydrated MTA-like cement were carried out. The experimental results showed that the group containing radiopacifier from sol-gelled Bi/Hf (90/10) exhibited significantly higher radiopacity (6.36 ± 0.34 mmAl), DTS (2.54 ± 0.29 MPa), and cell viability (84.0±8.1%) (p < 0.05) when compared to that of Bi/Hf (100/0) powders. It is suggested that the formation of β-Bi7.78Hf0.22O12.11 phase with hafnium addition and calcining at 700 °C can prepare novel bismuth/haf-nium composite powder that can be used as an alternative radiopacifier for root canal filling mate-rials.publishersversionPeer reviewe

Thermoelectric Properties of Alumina-Doped Bi0.4Sb1.6Te3 Nanocomposites Prepared through Mechanical Alloying and Vacuum Hot Pressing

In this study, γ-Al2O3 particles were dispersed in p-type Bi0.4Sb1.6Te3 through mechanical alloying to form γ-Al2O3/Bi0.4Sb1.6Te3 composite powders. The composite powders were consolidated using vacuum hot pressing to produce nano- and microstructured composites. Thermoelectric (TE) measurements indicated that adding an optimal amount of γ-Al2O3 nanoparticles improves the TE performance of the fabricated composites. High TE performances with figure of merit (ZT) values as high as 1.22 and 1.21 were achieved at 373 and 398 K for samples containing 1 and 3 wt % γ-Al2O3 nanoparticles, respectively. These ZT values are higher than those of monolithic Bi0.4Sb1.6Te3 samples. The ZT values of the fabricated samples at 298–423 K are 1.0–1.22; these ZT characteristics make γ-Al2O3/Bi0.4Sb1.6Te3 composites suitable for power generation applications because no other material with a similarly high ZT value has been reported at this temperature range. The achieved high ZT value may be attributable to the unique nano- and microstructures in which γ-Al2O3 nanoparticles are dispersed among the grain boundary or in the matrix grain, as revealed by high-resolution transmission electron microscopy. The dispersed γ-Al2O3 nanoparticles thus increase phonon scattering sites and reduce thermal conductivity. The results indicated that the nano- and microstructured γ-Al2O3/Bi0.4Sb1.6Te3 alloy can serve as a high-performance material for application in TE devices

Simulation of hardness testing on plasma-sprayed coatings

A plasma-sprayed thermal barrier coating consisting of a NiCoCrAlY bond coat and Ce-stabilized zirconia ceramic coating was heat-treated at 400 degrees C for 1000 h, Microhardness measurements were used to evaluate microstructural variations throughout the coating, One hundred and twenty measurements were performed at both the bond coat and ceramic coating positions within the thermal barrier coating system, Both data sets were analyzed to assess whether they could be described as Gaussian (i,e,, 'normal') or Weibull distributions, The influence of the sample size, i.e., the number of microhardness tests for a group, on the mean hardness value was also evaluated by a Monte Carlo simulation procedure. The mean value, the standard deviation, the coefficient of variation, and the Weibull modulus for the subsets of data were calculated to assess these effects, The confidence for the mean value was also considered, The results indicated that the reliability of the microhardness test improved as the sample size increased, At least 20 measurements were needed to distinguish differences in microhardness between the bond coat and the ceramic coating at a 95% confidence level

Acoustic emission studies on thermal spray materials

Acoustic emission (AE) has been used to assess the integrity of ceramic coatings. The early studies enabled cracking mechanisms to be qualitatively assessed so that comparative studies of coating behavior could be formulated. The present work examines a quantitative assessment of crack populations and crack sizes so that more detailed analyses of 'crack density functions' can evolve for mechanistic studies of thermal spray materials. Coatings and solid deposits of thermally sprayed ceramic have been tested with the stress oriented in directions perpendicular and parallel to the spray direction. It has been determined that macrocracking with catastrophic failure occurs in the perpendicular orientation; whereas several distinct crack populations, consisting of micro- and macrocracking events, are observed for the parallel orientation

Scheduling periodic jobs using imprecise results

We would like to thank Mi. Swaminathan Natarajan for his contribution in the work on the model of imprecise computations and system support for processes to return imprecise results