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Xie X, Schaink AK, Liu S, Wang M, Rios JD, Volodin A. Simplified Methods for Modelling Dependent Parameters in Health Economic Evaluations: A Tutorial. Appl Health Econ Health Policy 2024; 22:331-341. [PMID: 38376793 DOI: 10.1007/s40258-024-00874-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/04/2024] [Indexed: 02/21/2024]
Abstract
BACKGROUND In health economic evaluations, model parameters are often dependent on other model parameters. Although methods exist to simulate multivariate normal (MVN) distribution data and estimate transition probabilities in Markov models while considering competing risks, they are technically challenging for health economic modellers to implement. This tutorial introduces easily implementable applications for handling dependent parameters in modelling. METHODS Analytical proofs and proposed simplified methods for handling dependent parameters in typical health economic modelling scenarios are provided, and implementation of these methods are illustrated in seven examples along with the SAS and R code. RESULTS Methods to quantify the covariance and correlation coefficients of correlated variables based on published summary statistics and generation of MVN distribution data are demonstrated using examples of physician visits data and cost component data. The use of univariate normal distribution data instead of MVN distribution data to capture population heterogeneity is illustrated based on the results from multiple regression models with linear predictors, and two examples are provided (linear fixed-effects model and Cox proportional hazards model). A conditional probability method is introduced to handle two or more state transitions in a single Markov model cycle and applied in examples of one- and two-way state transitions. CONCLUSIONS This tutorial proposes an extension of routinely used methods along with several examples. These simplified methods may be easily applied by health economic modellers with varied statistical backgrounds.
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Affiliation(s)
- Xuanqian Xie
- Health Technology Assessment Program, Ontario Health, 525 University Avenue, 5th Floor, Toronto, ON, M5G 2L3, Canada.
| | - Alexis K Schaink
- Health Technology Assessment Program, Ontario Health, 525 University Avenue, 5th Floor, Toronto, ON, M5G 2L3, Canada
| | - Sichen Liu
- Department of Mathematics and Statistics, University of Regina, Regina, SK, Canada
| | - Myra Wang
- Health Technology Assessment Program, Ontario Health, 525 University Avenue, 5th Floor, Toronto, ON, M5G 2L3, Canada
| | - Juan David Rios
- Health Technology Assessment Program, Ontario Health, 525 University Avenue, 5th Floor, Toronto, ON, M5G 2L3, Canada
| | - Andrei Volodin
- Department of Mathematics and Statistics, University of Regina, Regina, SK, Canada
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Shackleton DA, Castillo LIR, Hampton AJD, Volodin A, Hadjistavropoulos T. Age Differences in Thermal Pain Responses: A Direct Laboratory Comparison. J Gerontol B Psychol Sci Soc Sci 2023; 78:1521-1525. [PMID: 37104120 DOI: 10.1093/geronb/gbad065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Indexed: 04/28/2023] Open
Abstract
OBJECTIVES According to a widely cited assertion, older adults are less likely than younger individuals to express pain complaints. Age-related differences in pain responses have been discussed in the literature despite a paucity of research involving direct comparisons of younger and older adults' pain reactions (i.e., verbal, nonverbal) in the context of a single experimental investigation. Our goal was to test the hypothesis that older adults are more stoic than younger adults in their expression of pain. METHODS We measured trait stoicism as well as multiple responses to thermal pain. RESULTS In contrast to suggestions in the literature, equivalence testing indicated that older and younger adults displayed similar verbal and nonverbal pain responses. Our results suggest that older adults are no more stoic about their pain than are younger persons. DISCUSSION This is the first attempt to explore a wide array of age differences in pain expression within the context of a single experimental study.
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Affiliation(s)
| | - Louise I R Castillo
- Department of Psychology, University of Regina, Regina, Saskatchewan, Canada
| | - Amy J D Hampton
- Department of Psychology, University of Regina, Regina, Saskatchewan, Canada
| | - Andrei Volodin
- Department of Mathematics and Statistics, University of Regina, Regina, Saskatchewan, Canada
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Xie X, Schaink AK, Gao C, Gajic-Veljanoski O, Ungar WJ, Volodin A. Evaluating the correlations of cost and utility parameters from summary statistics for probabilistic analysis in economic evaluations. Expert Rev Pharmacoecon Outcomes Res 2023; 23:901-909. [PMID: 37264680 DOI: 10.1080/14737167.2023.2221436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Accepted: 05/30/2023] [Indexed: 06/03/2023]
Abstract
OBJECTIVES The correlations between economic modeling input parameters directly impact the variance and may impact the expected values of model outputs. However, correlation coefficients are not often reported in the literature. We aim to understand the correlations between model inputs for probabilistic analysis from summary statistics. METHODS We provide proof that for correlated random variables X and Y (e.g. inpatient visits and outpatient visits), the Pearson correlation coefficients of sample means and samples are equal to each other (c o r r X , Y = c o r r X - , Y - ). Therefore, when studies report summary statistics of correlated parameters, we can quantify the correlation coefficient between parameters. RESULTS We use examples to illustrate how to estimate the correlation coefficient between the incidence rates of non-severe and severe hypoglycemia events, and the common coefficient of five cost components for patients with diabetic foot ulcers. We further introduce three types of correlations for utilities and provide two examples to estimate the correlations for utilities based on published data. We also evaluate how correlations between cost parameters and utility parameters impact the cost-effectiveness results using a Markov model for major depression. CONCLUSION Incorporation of the correlations can improve the precision of cost-effectiveness results and increase confidence in evidence-based decision-making. Further empirical evidence is warranted.
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Affiliation(s)
- Xuanqian Xie
- Health Technology Assessment Program, Ontario Health, Toronto, ON, Canada
| | - Alexis K Schaink
- Health Technology Assessment Program, Ontario Health, Toronto, ON, Canada
| | - Chengyu Gao
- Department of Mathematics and Statistics, University of Regina, Regina, SK, Canada
| | | | - Wendy J Ungar
- Program of Child Health Evaluative Sciences, The Hospital for Sick Children Research Institute, Toronto, ON, Canada
- The Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, ON, Canada
| | - Andrei Volodin
- Department of Mathematics and Statistics, University of Regina, Regina, SK, Canada
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Xie X, Schaink AK, Liu S, Wang M, Volodin A. Understanding bias in probabilistic analysis in model-based health economic evaluation. Eur J Health Econ 2023; 24:307-319. [PMID: 35610397 DOI: 10.1007/s10198-022-01472-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Accepted: 04/19/2022] [Indexed: 06/15/2023]
Abstract
Guidelines of economic evaluations suggest that probabilistic analysis (using probability distributions as inputs) provides less biased estimates than deterministic analysis (using point estimates) owing to the non-linear relationship of model inputs and model outputs. However, other factors can also impact the magnitude of bias for model results. We evaluate bias in probabilistic analysis and deterministic analysis through three simulation studies. The simulation studies illustrate that in some cases, compared with deterministic analyses, probabilistic analyses may be associated with greater biases in model inputs (risk ratios and mean cost estimates using the smearing estimator), as well as model outputs (life-years in a Markov model). Point estimates often represent the most likely value of the parameter in the population, given the observed data. When model parameters have wide, asymmetric confidence intervals, model inputs with larger likelihoods (e.g., point estimates) may result in less bias in model outputs (e.g., costs and life-years) than inputs with lower likelihoods (e.g., probability distributions). Further, when the variance of a parameter is large, simulations from probabilistic analyses may yield extreme values that tend to bias the results of some non-linear models. Deterministic analysis can avoid extreme values that probabilistic analysis may encounter. We conclude that there is no definitive answer on which analytical approach (probabilistic or deterministic) is associated with a less-biased estimate in non-linear models. Health economists should consider the bias of probabilistic analysis and select the most suitable approach for their analyses.
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Affiliation(s)
- Xuanqian Xie
- Health Technology Assessment Program, Ontario Health, 130 Bloor Street West, 10th floor, Toronto, ON, M5S 1N5, Canada.
| | - Alexis K Schaink
- Health Technology Assessment Program, Ontario Health, 130 Bloor Street West, 10th floor, Toronto, ON, M5S 1N5, Canada
| | - Sichen Liu
- Department of Mathematics and Statistics, University of Regina, Regina, SK, S4S 0A2, Canada
| | - Myra Wang
- Health Technology Assessment Program, Ontario Health, 130 Bloor Street West, 10th floor, Toronto, ON, M5S 1N5, Canada
| | - Andrei Volodin
- Sino-Canada Research Centre of Nonlinear Dynamics and Noise Control, Xiamen University of Technology and the University of Regina, Xiamen University of Technology, Fujian, China.
- Department of Mathematics and Statistics, University of Regina, Regina, SK, S4S 0A2, Canada.
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Klein-Goldberg A, Voloshin T, Zemer-Tov E, Paz R, Koren L, Wainer-Katsir K, Volodin A, Koltun B, Brant B, Barsheshet Y, Kan T, Haber A, Giladi M, Weinberg U, Palti Y. PI3K Inhibition Sensitized Cancerous Cells to Tumor Treating Fields (TTFields). Int J Radiat Oncol Biol Phys 2022. [DOI: 10.1016/j.ijrobp.2022.07.1291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Donhauzer I, Olenko A, Volodin A. Strong law of large numbers for functionals of random fields with unboundedly increasing covariances. COMMUN STAT-THEOR M 2022. [DOI: 10.1080/03610926.2020.1868515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Illia Donhauzer
- Mathematics and Statistics Department, La Trobe University, Melbourne, Australia
| | - Andriy Olenko
- Mathematics and Statistics Department, La Trobe University, Melbourne, Australia
| | - Andrei Volodin
- Department of Mathematics and Statistics, University of Regina, Saskatchewan, Canada
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Klein-Goldberg A, Voloshin T, Zemer-Tov E, Paz R, Koren L, Wainer-Katsir K, Volodin A, Koltun B, Brant B, Barsheshet Y, Kan T, Haber A, Giladi M, Weinberg U, Palti Y. EP16.03-028 Cancer Cells May be Re-sensitized to Tumor Treating Fields (TTFields) Through Inhibition of the PI3K/AKT/mTOR Pathway. J Thorac Oncol 2022. [DOI: 10.1016/j.jtho.2022.07.1089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Hayek NA, Donhauzer I, Giuliano R, Olenko A, Volodin A. Asymptotics of Running Maxima for φ-Subgaussian Random Double Arrays. Methodol Comput Appl Probab 2022. [DOI: 10.1007/s11009-021-09866-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Hossain S, Pandher S, Volodin A. Generalized autoregressive moving average models: an efficient estimation approach. J STAT COMPUT SIM 2022. [DOI: 10.1080/00949655.2022.2111568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
Affiliation(s)
- Shakhawat Hossain
- Department of Mathematics and Statistics, University of Winnipeg, Winnipeg, Canada
| | - Sharandeep Pandher
- Department of Mathematics and Statistics, University of Regina, Regina, Saskatchewan, Canada
| | - Andrei Volodin
- Department of Mathematics and Statistics, University of Regina, Regina, Saskatchewan, Canada
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Xie X, Wang M, Gajic-Veljanoski O, Ye C, Blumberger DM, Volodin A. Examining the correlation between treatment effects in clinical trials and economic modelling. Expert Rev Pharmacoecon Outcomes Res 2022; 22:1071-1078. [PMID: 35582876 DOI: 10.1080/14737167.2022.2079497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
INTRODUCTION Many diseases have a sequential treatment pathway. Compared with patients without previous treatment, patients who fail initial treatment may have lower success rates with a second treatment. This phenomenon can be explained by a correlation between treatment effects. METHODS We developed a statistical model of covariance for the underlying unobserved correlation between treatments and established a mathematical expression for the magnitude of the latent correlation term. We conducted a simulation study of clinical trials to investigate the correlation between two treatments and explored clinical examples based on published literature to illustrate the identification and evaluation of these correlations. RESULTS Our simulation study confirmed that a treatment correlation reduces the probability of success for the second treatment, compared with no correlation. We found that treatment correlations may be observable in clinical trials, such as for depression and lung cancer, and the magnitude of correlation may be estimated. We illustrated that treatment correlations can be incorporated into an economic model, with possible impacts on cost-effectiveness results. Additional applications of correlation concepts are also discussed. CONCLUSIONS We evaluated the correlation between treatment effects and our approach can be applied to clinical trial design and economic modelling of sequential clinical treatment pathways.
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Affiliation(s)
| | - Myra Wang
- Ontario Health, Toronto, Ontario, Canada
| | | | - Chenglin Ye
- Oncology Biostatistics, Genentech, South San Francisco, California, USA
| | - Daniel M Blumberger
- Temerty Centre for Therapeutic Brain Intervention at the Centre for Addiction and Mental Health and Department of Psychiatry, University of Toronto, Ontario, Canada
| | - Andrei Volodin
- Department of Mathematics and Statistics, University of Regina, Regina, Saskatchewan, Canada
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Cabrera MO, Rosalsky A, Ünver M, Volodin A. A New Version of Uniform Integrability via Power Series Summability Methods. Theory Probab Appl 2022. [DOI: 10.1137/s0040585x97t990770] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Pandher SS, Hossain S, Budsaba K, Volodin A. Efficient estimation method for generalized ARFIMA models. COMMUN STAT-THEOR M 2022. [DOI: 10.1080/03610926.2022.2064503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- S. S. Pandher
- Department of Mathematics and Statistics, University of Regina, Regina, Saskatchewan, Canada
| | - S. Hossain
- Department of Mathematics and Statistics, University of Winnipeg, Winnipeg, Manitoba, Canada
| | - K. Budsaba
- Department of Mathematics and Statistics, Thammasat University, Pathum Thani, Thailand
| | - A. Volodin
- Department of Mathematics and Statistics, University of Regina, Regina, Saskatchewan, Canada
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13
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Kokaew A, Bodhisuwan W, Yang SF, Volodin A. Logarithmic confidence estimation of a ratio of binomial proportions for dependent populations. J Appl Stat 2022. [DOI: 10.1080/02664763.2022.2041566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Angkana Kokaew
- Department of Statistics, Faculty of Science, Kasetsart University, Bangkok, Thailand
| | - Winai Bodhisuwan
- Department of Statistics, Faculty of Science, Kasetsart University, Bangkok, Thailand
| | - Su-Fen Yang
- Department of Statistics, National Chengchi University, Taipei, Taiwan, ROC
| | - Andrei Volodin
- Department of Mathematics and Statistics, University of Regina, Regina, SK, Canada
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Ordóñez Cabrera M, Rosalsky A, Ünver M, Volodin A. Correction to: On the concept of B-statistical uniform integrability of weighted sums of random variables and the law of large numbers with mean convergence in the statistical sense. TEST-SPAIN 2021. [DOI: 10.1007/s11749-021-00793-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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15
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Klein-Goldberg A, Voloshin T, Zemer-Tov E, Paz R, Koren L, Wainer-Katsir K, Volodin A, Koltun B, Brant B, Giladi M, Weinberg U, Palti Y. Activated Phosphoinositide 3-Kinase/AKT/mTOR Signaling Confers Resistance to Tumor Treating Fields (TTFields). Int J Radiat Oncol Biol Phys 2021. [DOI: 10.1016/j.ijrobp.2021.07.839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Xie X, Guo J, Bremner KE, Wang M, Shah BR, Volodin A. Review and estimation of disutility for joint health states of severe and nonsevere hypoglycemic events in diabetes. J Comp Eff Res 2021; 10:961-974. [PMID: 34287017 DOI: 10.2217/cer-2021-0059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Aim: Many economic evaluations used linear or log-transformed additive methods to estimate the disutility of hypoglycemic events in diabetes, both nonsevere (NSHEs) and severe (SHEs). Methods: We conducted a literature search for studies of disutility for hypoglycemia. We used additive, minimum and multiplicative methods, and the adjusted decrement estimator to estimate the disutilities of joint health states with both NSHEs and SHEs in six scenarios. Results: Twenty-four studies reported disutilities for hypoglycemia in diabetes. Based on construct validity, the adjusted decrement estimator method likely provides less biased estimates, predicting that when SHEs occur, the additional impact from NSHEs is marginal. Conclusion: Our proposed new method provides a different perspective on the estimation of quality-adjusted life-years in economic evaluations of hypoglycemic treatments.
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Affiliation(s)
- Xuanqian Xie
- Health Technology Assessment Program, Ontario Health, Toronto, ON M5S 1N5, Canada
| | - Jennifer Guo
- Health Technology Assessment Program, Ontario Health, Toronto, ON M5S 1N5, Canada
| | - Karen E Bremner
- Toronto General Hospital Research Institute, University Health Network, Toronto, ON M5G 2C4, Canada
| | - Myra Wang
- Health Technology Assessment Program, Ontario Health, Toronto, ON M5S 1N5, Canada
| | - Baiju R Shah
- Division of Endocrinology, Sunnybrook Health Sciences Centre, Toronto, ON M4N 3M5, Canada.,Department of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Andrei Volodin
- Department of Mathematics & Statistics, University of Regina, Regina, SK S4S 0A2, Canada
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Sungboonchoo C, Yang SF, Panichkitkosolkul W, Volodin A. Logarithmic confidence intervals for the cross-product ratio of binomial proportions under different sampling schemes. COMMUN STAT-SIMUL C 2021. [DOI: 10.1080/03610918.2021.1914090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Chanakan Sungboonchoo
- Department of Mathematics and Statistics, Thammasat University, Phathum Thani, Thailand
| | - Su-Fen Yang
- Department of Statistics, National Chengchi University, Taipei City, Taiwan
| | | | - Andrei Volodin
- Department of Mathematics and Statistics, University of Regina, Regina, Canada
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Kheyri A, Amini M, Jabbari H, Bozorgnia A, Volodin A. Exponential convergence rates for the kernel bivariate distribution function estimator under NSD assumption with application to hydrology data. COMMUN STAT-THEOR M 2020. [DOI: 10.1080/03610926.2020.1808900] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- A. Kheyri
- Department of Statistics, Ordered and Spatial Data Center of Excellence, Ferdowsi University of Mashhad, Mashhad, Iran
| | - M. Amini
- Department of Statistics, Ordered and Spatial Data Center of Excellence, Ferdowsi University of Mashhad, Mashhad, Iran
| | - H. Jabbari
- Department of Statistics, Ordered and Spatial Data Center of Excellence, Ferdowsi University of Mashhad, Mashhad, Iran
| | - A. Bozorgnia
- Department of Statistics, Khayyam University, Mashhad, Iran
| | - A. Volodin
- Department of Mathematics and Statistics, University of Regina, Regina, Canada
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Singhasomboon L, Panichkitkosolkul W, Volodin A. Confidence intervals for the ratio of medians of two independent log-normal distributions. COMMUN STAT-SIMUL C 2020. [DOI: 10.1080/03610918.2020.1812649] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
| | | | - Andrei Volodin
- Department of Mathematics and Statistics, University of Regina, Saskatchewan, Canada
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Salimov R, Yang SF, Volodin A, Volodin I. Estimation of mean value of a normal distribution with constraints on the relative error and d-risk. J STAT COMPUT SIM 2020. [DOI: 10.1080/00949655.2020.1724292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Rustem Salimov
- Department of Mathematical Statistics, Kazan Federal University, Kazan, Russian Federation
| | - Su-Fen Yang
- Department of Statistics, National Chengchi University, Taipei City, Taiwan, Republic of China
| | - Andrei Volodin
- Department of Mathematics and Statistics, University of Regina, Regina, Saskatchewan, Canada
| | - Igor Volodin
- Department of Mathematical Statistics, Kazan Federal University, Kazan, Russian Federation
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Xie X, Yeung MW, Wang Z, Wang M, Gajic-Veljanoski O, Ng V, Volodin A. Comparison of the expected rewards between probabilistic and deterministic analyses in a Markov model. Expert Rev Pharmacoecon Outcomes Res 2020; 20:169-175. [DOI: 10.1080/14737167.2019.1615886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Xuanqian Xie
- Evidence Development and Standards, Health Quality Ontario, Toronto, Canada
| | - Man Wah Yeung
- Evidence Development and Standards, Health Quality Ontario, Toronto, Canada
| | - Zhuoyu Wang
- Carrefour de l'innovation et de l'évaluation en santé, Centre de recherche du Centre hospitalier de l'Universite de Montreal, Montreal, Canada
| | - Myra Wang
- Evidence Development and Standards, Health Quality Ontario, Toronto, Canada
| | | | - Vivian Ng
- Evidence Development and Standards, Health Quality Ontario, Toronto, Canada
| | - Andrei Volodin
- Department of Mathematics and Statistics, University of Regina, Regina, Canada
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22
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Ordóñez Cabrera M, Rosalsky A, Ünver M, Volodin A. On the concept of B-statistical uniform integrability of weighted sums of random variables and the law of large numbers with mean convergence in the statistical sense. TEST-SPAIN 2020. [DOI: 10.1007/s11749-020-00706-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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23
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Giuliano R, Cabrera MO, Volodin A. On the Sub-Gaussianity of the $r$-Correlograms. Theory Probab Appl 2020. [DOI: 10.1137/s0040585x97t99006x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Escourbiac F, Durocher A, Fedosov A, Hirai T, Pitts R, Gavila P, Riccardi B, Kuznetcov V, Volodin A, Komarov A. Assessment of critical heat flux margins on tungsten monoblocks of the ITER divertor vertical targets. Fusion Engineering and Design 2019. [DOI: 10.1016/j.fusengdes.2019.03.094] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Al Mutairi AO, Volodin A. Special cases in order statistics for the alternative parametrization of the Generalized Power Function Distribution. Journal of Taibah University for Science 2018. [DOI: 10.1080/16583655.2018.1465726] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- Alya O. Al Mutairi
- Department of Mathematics, Faculty of Science, Taibah University, Medina, Saudi Arabia
| | - Andrei Volodin
- Department of Mathematics and Statistics, University of Regina, Regina, Saskatchewan, Canada
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Nam TH, Hu TC, Volodin A. Maximal inequalities and strong law of large numbers for sequences of m-asymptotically almost negatively associated random variables. COMMUN STAT-THEOR M 2017. [DOI: 10.1080/03610926.2015.1048885] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Abstract
A theoretical and experimental study of the work function of few-layer graphene is reported. The influence of the number of layers on the work function is investigated in the presence of a substrate, a molecular dipole layer, and combinations of the two. The work function of few-layer graphene is almost independent of the number of layers with only a difference between monolayer and multilayer graphene of about 60 meV. In the presence of a charge-donating substrate the charge distribution is found to decay exponentially away from the substrate and this is directly reflected in the work function of few-layer graphene. A dipole layer changes the work function only when placed in between the substrate and few-layer graphene through a change of the charge transfer between the two.
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Affiliation(s)
- O Leenaerts
- Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium
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Wang X, Hu S, Volodin A. General results of complete convergence and complete moment convergence for weighted sums of some class of random variables. COMMUN STAT-THEOR M 2016. [DOI: 10.1080/03610926.2014.921308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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30
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Wu Y, Volodin A. Complete moment convergence of weighted sums for arrays of negatively dependent random variables and its applications. COMMUN STAT-THEOR M 2016. [DOI: 10.1080/03610926.2014.901365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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31
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Shen A, Zhang Y, Volodin A. On the rate of convergence in the strong law of large numbers for negatively orthant-dependent random variables. COMMUN STAT-THEOR M 2016. [DOI: 10.1080/03610926.2014.957858] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Martens K, Jeong JW, Aetukuri N, Rettner C, Shukla N, Freeman E, Esfahani DN, Peeters FM, Topuria T, Rice PM, Volodin A, Douhard B, Vandervorst W, Samant MG, Datta S, Parkin SSP. Field Effect and Strongly Localized Carriers in the Metal-Insulator Transition Material VO(2). Phys Rev Lett 2015; 115:196401. [PMID: 26588400 DOI: 10.1103/physrevlett.115.196401] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Indexed: 06/05/2023]
Abstract
The intrinsic field effect, the change in surface conductance with an applied transverse electric field, of prototypal strongly correlated VO(2) has remained elusive. Here we report its measurement enabled by epitaxial VO(2) and atomic layer deposited high-κ dielectrics. Oxygen migration, joule heating, and the linked field-induced phase transition are precluded. The field effect can be understood in terms of field-induced carriers with densities up to ∼5×10(13) cm(-2) which are trongly localized, as shown by their low, thermally activated mobility (∼1×10(-3) cm(2)/V s at 300 K). These carriers show behavior consistent with that of Holstein polarons and strongly impact the (opto)electronics of VO(2).
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Affiliation(s)
- K Martens
- IBM Research-Almaden, San Jose, California 95120, USA
- ESAT Department, KU Leuven, Leuven BE-3001, Belgium
- IMEC, Kapeldreef 75, Leuven BE-3001, Belgium
| | - J W Jeong
- IBM Research-Almaden, San Jose, California 95120, USA
| | - N Aetukuri
- IBM Research-Almaden, San Jose, California 95120, USA
| | - C Rettner
- IBM Research-Almaden, San Jose, California 95120, USA
| | - N Shukla
- Department of Electrical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - E Freeman
- Department of Electrical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - D N Esfahani
- Physics Department, University of Antwerp, Groenenborgerlaan 171 BE-2020, Antwerp BE-2020, Belgium
| | - F M Peeters
- Physics Department, University of Antwerp, Groenenborgerlaan 171 BE-2020, Antwerp BE-2020, Belgium
| | - T Topuria
- IBM Research-Almaden, San Jose, California 95120, USA
| | - P M Rice
- IBM Research-Almaden, San Jose, California 95120, USA
| | - A Volodin
- Department of Physics and Astronomy, KU Leuven, Leuven BE-3001, Belgium
| | - B Douhard
- IMEC, Kapeldreef 75, Leuven BE-3001, Belgium
| | - W Vandervorst
- IMEC, Kapeldreef 75, Leuven BE-3001, Belgium
- Department of Physics and Astronomy, KU Leuven, Leuven BE-3001, Belgium
| | - M G Samant
- IBM Research-Almaden, San Jose, California 95120, USA
| | - S Datta
- Department of Electrical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - S S P Parkin
- IBM Research-Almaden, San Jose, California 95120, USA
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Volodin A, Kuznetcov V, Davydov V, Kokoulin A, Komarov A, Mazul I, Mudyugin B, Ovchinnikov I, Stepanov N, Rulev R, Eremkin A, Rogov A, Prianikov V, Fedosov A. The high-heat-flux test facilities in the joint stock company “D.V. Efremov Institute of Electrophysical Apparatus”. Fusion Engineering and Design 2015. [DOI: 10.1016/j.fusengdes.2015.02.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Ahmed SE, Kareev I, Suraphee S, Volodin A, Volodin I. Confidence sets based on the positive part James–Stein estimator with the asymptotically constant coverage probability. J STAT COMPUT SIM 2015. [DOI: 10.1080/00949655.2014.933223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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36
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Kuznetsov V, Gorbenko A, Davydov V, Kokoulin A, Komarov A, Mazul I, Mudyugin B, Ovchinnikov I, Stepanov N, Rulev R, Volodin A. Status of the IDTF high-heat-flux test facility. Fusion Engineering and Design 2014. [DOI: 10.1016/j.fusengdes.2014.04.064] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Wang X, Xu C, Hu TC, Volodin A, Hu S. On complete convergence for widely orthant-dependent random variables and its applications in nonparametric regression models. TEST-SPAIN 2014. [DOI: 10.1007/s11749-014-0365-7] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Wang X, Hu TC, Volodin A, Hu S. Complete Convergence for Weighted Sums and Arrays of Rowwise Extended Negatively Dependent Random Variables. COMMUN STAT-THEOR M 2013. [DOI: 10.1080/03610926.2011.609321] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Giuliano Antonini R, Ngamkham T, Volodin A. On the asymptotic behavior of the sequence and series of running maxima from a real random sequence. Stat Probab Lett 2013. [DOI: 10.1016/j.spl.2012.10.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Andreev N, Chichkov V, Sviridova T, Tabachkova N, Volodin A, Van Haesendonck C, Mukovskii Y. Growth, structure, surface topography and magnetic properties of GdMnO3multiferroic epitaxial thin films. EPJ Web of Conferences 2013. [DOI: 10.1051/epjconf/20134015014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Gabrielian A, Bocharova TN, Smirnova Alexander EA, Volodin A, Harutjunyan A, Gevorkyan K, Harutjunyan G. 128 Some derivatives of 1,3-diazaadamantane strongly stimulate strand exchange reaction between short oligonucleotides. J Biomol Struct Dyn 2013. [DOI: 10.1080/07391102.2013.786370] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Santini CA, Vereecken PM, Volodin A, Groeseneken G, De Gendt S, Haesendonck CV. A study of Joule heating-induced breakdown of carbon nanotube interconnects. Nanotechnology 2011; 22:395202. [PMID: 21891859 DOI: 10.1088/0957-4484/22/39/395202] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We investigate breakdown of carbon nanotube (CNT) interconnects induced by Joule heating in air and under high vacuum conditions (10(-5) mbar). A CNT with a diameter of 18 nm, which is grown by chemical vapor deposition to connect opposing titanium nitride (TiN) electrodes, is able to carry an electrical power up to 0.6 mW before breaking down under vacuum, with a corresponding maximum current density up to 8 × 10(7) A cm(-2) (compared to 0.16 mW and 2 × 10(7) A cm(-2) in air). Decoration with electrochemically deposited Ni particles allows protection of the CNT interconnect against oxidation and improvement of the heat release through the surrounding environment. A CNT decorated with Ni particles is able to carry an increased electrical power of about 1.5 mW before breaking down under vacuum, with a corresponding maximum current density as high as 1.2 × 10(8) A cm(-2). The Joule heating produced along the current carrying CNT interconnect is able to melt the Ni particles and promotes the formation of titanium carbon nitride which improves the electrical contact between the CNT and the TiN electrodes.
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Affiliation(s)
- C A Santini
- Laboratory of Solid-State Physics and Magnetism, KULeuven, Heverlee, Belgium.
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44
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Ordóñez Cabrera M, Rosalsky A, Volodin A. Some theorems on conditional mean convergence and conditional almost sure convergence for randomly weighted sums of dependent random variables. TEST-SPAIN 2011. [DOI: 10.1007/s11749-011-0248-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Schouteden K, Volodin A, Muzychenko DA, Chowdhury MP, Fonseca A, Nagy JB, Van Haesendonck C. Probing quantized image-potential states at supported carbon nanotubes. Nanotechnology 2010; 21:485401. [PMID: 21051804 DOI: 10.1088/0957-4484/21/48/485401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Discrete image-potential states (ISs) are revealed at double-walled carbon nanotubes by means of scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) in the distance-voltage z(V) spectroscopy mode. The nanotubes are supported by flat Au(111) substrates. Due to the high sensitivity of the hot IS electrons to local variations of the surface potential, they can be considered as a sensitive probe to investigate interactions with the supporting substrate and impurities or defects at the nanotube surface. ISs provide information on the local electronic structure as well as on the electron dynamics at supported nanotubes.
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Affiliation(s)
- K Schouteden
- Laboratory of Solid-State Physics and Magnetism and Institute for Nanoscale Physics and Chemistry (INPAC), BE-3001 Leuven, Belgium.
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48
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Chen P, Hu TC, Liu X, Volodin A. On Complete Convergence for Arrays of Row-Wise Negatively Associated Random Variables. Theory Probab Appl 2008. [DOI: 10.1137/s0040585x97983079] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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50
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Boussu K, Belpaire A, Volodin A, Van Haesendonck C, Van der Meeren P, Vandecasteele C, Van der Bruggen B. Influence of membrane and colloid characteristics on fouling of nanofiltration membranes. J Memb Sci 2007. [DOI: 10.1016/j.memsci.2006.12.001] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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