scholarly journals Photoacoustic Imaging Using Combination of Eigenspace-Based Minimum Variance and Delay-Multiply-and-Sum Beamformers: Simulation Study

2017 ◽  
Author(s):  
Moein Mozaffarzadeh ◽  
Seyed Amin Ollah Izadi Avanji ◽  
Ali Mahlooiifar ◽  
Mahdi Orooji
Keyword(s):  
Simulation Study ◽  
Photoacoustic Imaging ◽  
Minimum Variance

scholarly journals Estimation a Stress-Strength Model for P (Yr:n1 < Xk:n2 ) Using the Lindley Distribution

2017 ◽  
Vol 40 (1) ◽  
pp. 105-121 ◽  
Author(s):  
Marwa Khalil
Keyword(s):  
Maximum Likelihood ◽  
Simulation Study ◽  
Real Data ◽  
Minimum Variance ◽  
Strength Model ◽  
Practical Application ◽  
Likelihood Estimator ◽  
Lindley Distribution ◽  
Minimum Variance Unbiased Estimator ◽  
Proposed Model

The problem of estimation reliability in a multicomponent stress-strength model, when the system consists of k components have strength each compo- nent experiencing a random stress, is considered in this paper. The reliability of such a system is obtained when strength and stress variables are given by Lindley distribution. The system is regarded as alive only if at least r out of k (r < k) strength exceeds the stress. The multicomponent reliability of the system is given by Rr,k . The maximum likelihood estimator (M LE), uniformly minimum variance unbiased estimator (UMVUE) and Bayes esti- mator of Rr,k are obtained. A simulation study is performed to compare the different estimators of Rr,k . Real data is used as a practical application of the proposed model.

scholarly journals Statistical approaches to computing sample size in cluster randomized trials: a simulation study

2019 ◽  
Author(s):  
Ashutosh Ranjan ◽  
Guangzi Song ◽  
Christopher S Coffey ◽  
Leslie A McClure
Keyword(s):  
Sample Size ◽  
Simulation Study ◽  
Cluster Size ◽  
Randomized Trials ◽  
Sample Size Calculation ◽  
Minimum Variance ◽  
Type I ◽  
Cluster Randomized Trials ◽  
Weighted Analysis ◽  
Cluster Randomized

Abstract Background: Cluster randomized trials, which randomize groups of individuals to an intervention, are common in health services research when one wants to evaluate improvement in a subject's outcome by intervening at an organizational level. For many such trials sample size calculation is performed under the assumption of equal cluster size. Many trials that set out to recruit equal clusters end up with unequal clusters for various reasons. This leads to a misalignment between the method used for sample size calculation and the data analysis, which may affect trial power. Various weighted analysis methods for analyzing cluster means have been suggested to overcome the problem introduced by unbalanced clusters; however, the performance of such methods has not been evaluated extensively.Methods: We examine the use of the general linear model for analysis of clustered randomized trials assuming equal cluster sizes during the planning stage but ending up with unequal clusters. We demonstrate the performance of three approaches using different weights for analyzing the cluster means: (1) the standard analysis of cluster means, (2) weighting by cluster size, and (3) minimum variance weights. Several distributions are used to generate cluster sizes to cover a wide range of patterns of imbalance. The variability in cluster size is measured by the coefficient of variation (CV). By means of a simulation study, we assess the impact of using each of the three analysis methods with respect to type I error and power of the study and how it is affected by the variability in cluster size. Results: Analyses that assumes equal clusters provide a reasonable approximation when cluster sizes vary minimally (CV < 0.30). In an analysis weighted by cluster size type I errors were inflated, and that worsened as the variation in cluster size increases. However, a minimum variance weighted analysis best maintains target power and level of significance under all degrees of imbalance considered. Conclusion: The unweighted analysis works well as an approximate method when the variation in cluster size is minimal. However, using minimum variance weights performs much better across the full range of variation in cluster size and is recommended.

scholarly journals Eigenspace-Based Minimum Variance Combined With Delay Multiply and Sum Beamformer: Application to Linear-Array Photoacoustic Imaging

2019 ◽  
Vol 25 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Moein Mozaffarzadeh ◽  
Ali Mahloojifar ◽  
Vijitha Periyasamy ◽  
Manojit Pramanik ◽  
Mahdi Orooji
Keyword(s):  
Linear Array ◽  
Photoacoustic Imaging ◽  
Minimum Variance

A Simulation Study on a Self-Tuning Portable Controller of Blood Glucose

1993 ◽  
Vol 16 (1) ◽  
pp. 51-57 ◽  
Author(s):  
P. Brunetti ◽  
C. Cobelli ◽  
P. Cruciani ◽  
P.G. Fabietti ◽  
F. Filippucci ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Blood Glucose ◽  
Simulation Study ◽  
Blood Glucose Control ◽  
Minimum Variance ◽  
Least Square ◽  
Recursive Least Square ◽  
Nonlinear Controller ◽  
Self Tuning ◽  
Patient Responses

A self-tuning, nonlinear controller was developed to drive portable or implantable micro-pumps for blood glucose control in diabetic subjects. The parameter estimation is based on a recursive least-square algorithm applied to a discrete time simplified mathematical model of the glucose system; the controller, which is integrated with the estimator, uses an-extended minimum-variance method. The software was designed to drive a micro-controller wearable unit, operating with different kinds of glucose sensors, in order to perform chemical and biological experimentations. Some strategies were introduced to avoid hypoglycaemia, even tolerating a reduction in control speed and accuracy. The whole system was tested in a simulation study, performed on a mathematical model implemented on a personal computer. The tests were performed while simulating different controller structures and settings, and patient responses. They showed a satisfactory control behaviour, mostly as far as stability and robustness are concerned, in all simulated conditions.

Eigenspace-based minimum variance beamformer combined with sign coherence factor: Application to linear-array photoacoustic imaging

Ultrasonics ◽  
2020 ◽  
Vol 108 ◽  
pp. 106174 ◽  
Author(s):  
Sadaf Shamekhi ◽  
Vijitha Periyasamy ◽  
Manojit Pramanik ◽  
Mohammad Mehrmohammadi ◽  
Babak Mohammadzadeh Asl
Keyword(s):  
Linear Array ◽  
Photoacoustic Imaging ◽  
Minimum Variance ◽  
Coherence Factor

scholarly journals Estimating the Reliability Function for a Family of Exponentiated Distributions

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Ajit Chaturvedi ◽  
Anupam Pathak
Keyword(s):  
Maximum Likelihood ◽  
Comparative Study ◽  
Simulation Study ◽  
Maximum Likelihood Estimators ◽  
Reliability Function ◽  
Minimum Variance ◽  
Unbiased Estimators

A family of exponentiated distributions is proposed. The problems of estimating the reliability function are considered. Uniformly minimum variance unbiased estimators and maximum likelihood estimators are derived. A comparative study of the two methods of estimation is done. Simulation study is preformed.

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