Search results for " Control"
showing 10 items of 7691 documents
Economic Robustness Analysis of Adaptive Chart Schemes for Monitoring the Total Nonconformities Number in Inspection Units
2015
In recent years, a variety of enhanced schemes for the c chart have been developed aimed at the effectiveness improving of the related statistical process control (SPC) procedures. However, the performance of such chart schemes can be very sensitive to values assumed for some operating and cost parameters, in particular to the considered process shift magnitude arising from out-of-control conditions. In such a circumstance, the effectiveness of such chart schemes can be subjected to substantial reductions when they are implemented in operative contexts given that, in practice, such value is unknown and it can be very difficult to accurately estimate. For this reason, in the present paper i…
A Multi-Objective Design Approach for the c Chart Considering Taguchi Loss Function
2013
The present paper proposes a multi-objective design approach for the c chart, considering in the optimization process of the chart parameters both the statistical and the economic objectives. In particular, the minimization of the hourly total quality related costs is the considered objective to carry out the economic goal, whereas the statistical objective is reached by the minimization the out-of-control average run length of the chart. A mixed integer non-linear constrained mathematical model is formulated to solve the treated multi-objective optimization problem, whereas the Pareto optimal frontier is described by the e-constraint method. In order to show the employment of the proposed …
Comparing the Economic Effectiveness of Various Adaptive Schemes for the c Chart
2013
In an attempt to improve the effectiveness of statistical process control (SPC) procedures, a variety of adaptive schemes has been developed in the last decades. However, considering control charts for attributes, relatively few works about adaptive schemes have been proposed, and most of them were proposed only recently. The common characteristic of those schemes is that one or more chart parameters are allowed to adaptively vary during the SPC operations according to the sampling information history, typically the current point plotted on the chart. In this way, the adaptive schemes are smarter than the related static ones, but they are also more complicated in terms of implementation. Th…
An Effective Double Sampling Scheme for thecControl Chart
2013
In the present paper is developed a statistical process control inspection procedure based on a new simple-to-implement and effective double sampling scheme for the c control chart, aimed at the minimization of the number of inspected observation units and warranting fixed levels for the type I and II error risks. In particular, the formulations of the false alarm risk α, the power P of the chart, and the expected number of inspected observation units for the developed inspection procedure are given, whereas a macro of Microsoft Excel is adopted to solve the tackled problem. In order to illustrate the application of the developed approach and to investigate on the influence of several opera…
Economic Design Approach for an SPC Inspection Procedure Implementing The Adaptive C Chart
2013
The present paper proposes a design approach for a statistical process control (SPC) procedure implementing a c control chart for non-conformities, with the aim to minimize the hourly total quality-related costs. The latter take into account the costs arising from the non-conforming products while the process is in-control and out-of-control, for false alarms, for assignable cause locations and system repairs, for sampling and inspection activities and for the system downtime. The proposed economic optimization approach is constrained by the expected hourly false alarms frequency, as well as the available labor resource level. A mixed integer non-linear constrained mathematical model is dev…
Characterisation and optimal design of a new double sampling <i>c</i> chart
2019
This paper proposes a new double sampling scheme for c control chart (DS-c), which was designed to improve the performance of c chart or to reduce the inspection cost. The mathematical expression required to do an exact evaluation of ARL and ASN is deduced. Further, a bi-objective genetic algorithm is implemented to obtain the optimal design of the DS-c scheme. This optimisation is aimed to simultaneously minimising the error probability type II and the ASN, guaranteeing a desired level for the error probability type I. A performance comparison between the double sampling (DS), fixed parameters (FP), variable simple size (VSS) and exponential weighted moving average (EWMA) schemes for the c…
Externalizing Behaviors and Cigarette Smoking as Predictors for Use of Illicit Drugs: A Longitudinal Study Among Finnish Adolescent Twins
2010
We examined whether externalizing problem behaviors (hyperactivity–impulsivity, aggressiveness, and inattention) predict illicit drug use independently, or whether their associations with drug use are mediated through cigarette smoking. We used a prospective longitudinal design within theFinnTwin12-17study among Finnish adolescents with baseline at age 12 and follow-up surveys at ages 14 and 17. Path models were conducted withMplusand included 1992 boys and 2123 girls. The outcome was self-reported ever use of cannabis or other illicit drugs at age 17. The predictors were: externalizing behaviors (hyperactivity–impulsivity, aggressiveness, and inattention) assessed by teachers and parents (…
Il governo del capitale intellettuale attraverso il raccordo tra modelli contabili e di System Dynamics. Una prospettiva di programmazione e controll…
2004
Il presente scritto tenta di far luce sul tema del capitale intellettuale in una prospettiva economico-aziendale, focalizzando in particolare il concetto di governo della conoscenza aziendale. La tesi sostenuta dagli autori è che i processi inerziali di sviluppo e declino della conoscenza non devono essere astrattamente ignorati, relegando l’area Organizzazione e Sistemi al rango di centro di spesa discrezionale. Questa semplicistica prospettiva di analisi può indurre il management all’adozione di politiche miopi, che portino cioè a rinviare investimenti necessari in sviluppo della conoscenza, con l’unico obiettivo di non deprimere i risultati reddituali di breve andare. A tal riguardo, si …
Reduced muscle inactivity, sedentary time and cardio-metabolic benefits : effectiveness of a one-year family-based cluster randomized controlled trial
2016
A driving hypothesis of the evolving field of sedentary behavior is that frequent muscle activity short-circuits detrimental physiological effects of sedentary time. However, the field relies mostly on observational health associations of proxy measures of muscle inactivity, like television viewing or lack of accelerometer-derived impacts. This study tested effectiveness of a family-based cluster-randomized controlled trial aimed at reducing and breaking up sedentary time at work and leisure time of families on muscle inactivity patterns, sedentary time and cardio-metabolic biomarkers. The intervention consisted of a lecture, face-to-face tailored counseling, two follow-up calls and five em…
STEM CELLS FOR TREATMENT OF CARDIOVASCULAR DISEASES: AN UMBRELLA REVIEW OF RANDOMIZED CONTROLLED TRIALS
2021
AIMS:\ud \ud Stem cells are a promising therapy for various medical conditions. The literature regarding their adoption for the clinical care of cardiovascular diseases (CVD) is still conflicting. Therefore, our aim is to assess the strength and credibility of the evidence on clinical outcomes and application of stem cells derived from systematic reviews and meta-analyses of intervention studies in CVD.\ud \ud METHODS and RESULTS:\ud \ud Umbrella review of systematic reviews with meta-analyses of randomized controlled trials (RCTs) using placebo/no intervention as control group. For meta-analyses of RCTs, outcomes with a random-effect p-value< 0.05, the GRADE (Grading of Recommendations Ass…