Model reduction by trimming for a class of semi-Markov reliability models and the corresponding error bound

Semi-Markov processes have proved to be an effective and convenient tool to construct models of systems that achieve reliability by redundancy and reconfiguration. These models are able to depict complex system architectures and to capture the dynamics of fault arrival and system recovery. A disadvantage of this approach is that the models can be extremely large, which poses both a model and a computational problem. Techniques are needed to reduce the model size. Because these systems are used in critical applications where failure can be expensive, there must be an analytically derived bound for the error produced by the model reduction technique. A model reduction technique called trimming is presented that can be applied to a popular class of systems. Automatic model generation programs were written to help the reliability analyst produce models of complex systems. This method, trimming, is easy to implement and the error bound easy to compute. Hence, the method lends itself to inclusion in an automatic model generator

SURE reliability analysis: Program and mathematics

The SURE program is a new reliability analysis tool for ultrareliable computer system architectures. The computational methods on which the program is based provide an efficient means for computing accurate upper and lower bounds for the death state probabilities of a large class of semi-Markov models. Once a semi-Markov model is described using a simple input language, the SURE program automatically computes the upper and lower bounds on the probability of system failure. A parameter of the model can be specified as a variable over a range of values directing the SURE program to perform a sensitivity analysis automatically. This feature, along with the speed of the program, makes it especially useful as a design tool

Verifying Algorithms for Autonomous Aircraft by Simulation Generalities and Example

An open question in Air Traffic Management is what procedures can be validated by simulation where the simulation shows that the probability of undesirable events is below the required level at some confidence level. The problem is including enough realism to be convincing while retaining enough efficiency to run the large number of trials needed for high confidence. The paper first examines the probabilistic interpretation of a typical requirement by a regulatory agency and computes the number of trials needed to establish the requirement at an equivalent confidence level. Since any simulation is likely to consider only one type of event and there are several types of events, the paper examines under what conditions this separate consideration is valid. The paper establishes a separation algorithm at the required confidence level where the aircraft operates under feedback control as is subject to perturbations. There is a discussion where it is shown that a scenario three of four orders of magnitude more complex is feasible. The question of what can be validated by simulation remains open, but there is reason to be optimistic

Designing Fault-Injection Experiments for the Reliability of Embedded Systems

This paper considers the long-standing problem of conducting fault-injections experiments to establish the ultra-reliability of embedded systems. There have been extensive efforts in fault injection, and this paper offers a partial summary of the efforts, but these previous efforts have focused on realism and efficiency. Fault injections have been used to examine diagnostics and to test algorithms, but the literature does not contain any framework that says how to conduct fault-injection experiments to establish ultra-reliability. A solution to this problem integrates field-data, arguments-from-design, and fault-injection into a seamless whole. The solution in this paper is to derive a model reduction theorem for a class of semi-Markov models suitable for describing ultra-reliable embedded systems. The derivation shows that a tight upper bound on the probability of system failure can be obtained using only the means of system-recovery times, thus reducing the experimental effort to estimating a reasonable number of easily-observed parameters. The paper includes an example of a system subject to both permanent and transient faults. There is a discussion of integrating fault-injection with field-data and arguments-from-design

The secrets of mindful STEM teaching and learning

The pressure upon a Science, Technology, Engineering or Mathematcs (STEM) educators has increased as the demand for workers with stem capabilities develops while worldwide the number of students electing to specialise in stem areas is declining. In 2018, the Indonesian Ministry of Industry (KPRI) released a document titled 'Making Indonesia 4.0', stating stem teachers will be expected to produce students who have several "careers" during their working lives and have the skills needed which includes technical capabilities, creativity and innovative problem-solving. This will occur in a context where the future of work remains human and so while the new technologies have the capacity to automate many tasks, they also create as many jobs as they replace. As well as these governmental expectations, stem educators are being continually confronted with an avalanche of advice on the best ways of teaching and learning their subject. This advice comes from across the spectrum of expertise that includes parents, outstanding teacher heroes, commercial interests, and dubious 'experts' who have no pedagogical knowledge or experience. This paper will attempt to cut through this avalanche and dig down to the bedrock of successful and sustainable stem teaching and learning. While this paper is written for all stem educators, it will tend to favour examples from the mathematics and brain research disciplines

An Initial Examination for Verifying Separation Algorithms by Simulation

An open question in algorithms for aircraft is what can be validated by simulation where the simulation shows that the probability of undesirable events is below some given level at some confidence level. The problem is including enough realism to be convincing while retaining enough efficiency to run the large number of trials needed for high confidence. The paper first proposes a goal based on the number of flights per year in several regions. The paper examines the probabilistic interpretation of this goal and computes the number of trials needed to establish it at an equivalent confidence level. Since any simulation is likely to consider the algorithms for only one type of event and there are several types of events, the paper examines under what conditions this separate consideration is valid. This paper is an initial effort, and as such, it considers separation maneuvers, which are elementary but include numerous aspects of aircraft behavior. The scenario includes decisions under uncertainty since the position of each aircraft is only known to the other by broadcasting where GPS believes each aircraft to be (ADS-B). Each aircraft operates under feedback control with perturbations. It is shown that a scenario three or four orders of magnitude more complex is feasible. The question of what can be validated by simulation remains open, but there is reason to be optimistic

Ohio Livestock Waste Management Guide

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Longitudinal evaluation of cognitive functioning in young children with type 1 diabetes over 18 months

OBJECTIVE: Decrements in cognitive function may already be evident in young children with type 1 diabetes (T1D). Here we report prospectively acquired cognitive results over 18 months in a large cohort of young children with and without T1D. METHODS: 144 children with T1D (mean HbA1c: 7.9%) and 70 age-matched healthy controls (mean age both groups 8.5 years; median diabetes duration 3.9 yrs; mean age of onset 4.1 yrs) underwent neuropsychological testing at baseline and after 18-months of follow-up. We hypothesized that group differences observed at baseline would be more pronounced after 18 months, particularly in those T1D patients with greatest exposure to glycemic extremes. RESULTS: Cognitive domain scores did not differ between groups at the 18 month testing session and did not change differently between groups over the follow-up period. However, within the T1D group, a history of diabetic ketoacidosis (DKA) was correlated with lower Verbal IQ and greater hyperglycemia exposure (HbA1c area under the curve) was inversely correlated to executive functions test performance. In addition, those with a history of both types of exposure performed most poorly on measures of executive function. CONCLUSIONS: The subtle cognitive differences between T1D children and nondiabetic controls observed at baseline were not observed 18 months later. Within the T1D group, as at baseline, relationships between cognition (VIQ and executive functions) and glycemic variables (chronic hyperglycemia and DKA history) were evident. Continued longitudinal study of this T1D cohort and their carefully matched healthy comparison group is planned

Ilmu Kimia Tanaman Lauraceae Indonesia: VI. Kriptokaryon dari Cryptocarya Laevigata BL. (Lauraceae)

Ekstraksi kulit akar dan kulit barang tanaman Cryptocarya laevigata Bl. (Lauraceae) dengan n-heksan menghasilkan suatu calkon yang diidentifikasi sebagai kriptokaryon (I). Struktur senyawa ini ditetapkan berdasarkan data spektroskopi dan analisis Kristal sinar-X. Kesimpulan mengenai struktur kriptokaryon (I) mendukung saran peneliti sebelumnya, yang terlah merevisi struktur (II) yang pertama kali disarankan. C. laevigata adalah spesies kedua anggota suku Lauraceae yang telah ditemukan mengandung kriptokaryon (I). Tambahan pula, kriptokaryon (I) adalah senyawa alam kedua dari jenis flavonoid yang mengandung cincin A yang tereduksi sebagian, yang pernah ditemukan. Extraction of the root and the tree barks of Cryptocarya laevigata Bl. (Lauraceae) with n-hexane yielded a chalcone identified as cryptocaryone (I). The structure of this compound had been elucidated based on spectroscopic measurements and X-ray crystal analysis. Conclusions about the structure of cryprocaryone (I) confirm the previous suggestion, which revised the structure (ll) suggested earlier. C. laevigata is the second species of Lauraceae which contains cryptocaryone (I). Furthermore, cryptocaryone (I) is a second naturally occurring flavonoid containing a reduced A ring system which has so far been isolated