| 1. |
- Amin, Muhammad, et al.
(författare)
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Performance of Asar and Genç and Huang and Yang’s Two-Parameter Estimation Methods for the Gamma Regression Model
- 2019
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Ingår i: Iranian Journal of Science and Technology, Transactions A: Science. - : Springer. - 1028-6276 .- 2364-1819. ; 43:6, s. 2951-2963
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Tidskriftsartikel (refereegranskat)abstract
- This study assesses the performance of two-parameter estimation methods to combat multicollinearity in the Gamma regression model. We derived optimal values for two-parameter estimation methods in the Gamma regression model. Furthermore, we proposed some estimation methods to estimate the shrinkage parameters and these methods improve the efficiency of the two-parameter estimator. We compare the performance of these estimators by means of Monte Carlo simulation study where the mean squared error (MSE) is considered as a performance criterion. Finally, consider a reaction rate data to evaluate the performance of the estimators. The simulation and numerical example results showed that the two-parameter biased estimators have smaller MSE than the maximum likelihood estimator under certain conditions.
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| 2. |
- Esmaeili, M, et al.
(författare)
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EFFECT OF THE EXTRINSIC AND TEMPORAL CARRIERS ON RADIATIVE RECOMBINATION OF III-NITRIDE NANOSTRUCTURES
- 2008
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Ingår i: IRANIAN JOURNAL OF SCIENCE AND TECHNOLOGY TRANSACTION A-SCIENCE. - 1028-6276. ; 32:A3, s. 207-213
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Tidskriftsartikel (refereegranskat)abstract
- Due to many important applications, the group III-Nitride semiconductors have recently attracted remarkable attention among semiconductor researchers and engineers. In this paper, we report on the impact of extrinsic and temporal carriers on the screening of polarization internal fields. The optical efficiency of GaN/AlGaN multiple quantum well (MQW) nanostructures were studied by means of photoluminescence (PL) and time-resolved PL measurements. Extrinsic carriers come from Si doping in the barriers, while temporal carriers originate when the samples are excited by laser beam. The emission peaks of MQWs in PL spectra of the undoped and low-doped samples show a shift towards higher energy levels as excitation intensity increases, while the other samples do not exhibit such a phenomenon due to the dominance of the extrinsic carriers. The transient data confirm the results of the PL measurements.
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| 3. |
- Ledari, A. A., et al.
(författare)
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Lambda BV as a Non Separable Dual Space
- 2010
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Ingår i: Iranian Journal of Science and Technology Transaction a-Science. - 1028-6276. ; 34:A3, s. 237-244
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Tidskriftsartikel (refereegranskat)abstract
- Let C be a field of subsets of a set I. Also, let Lambda = {lambda(i)}(i=1)(infinity) be a non-decreasing positive sequence of real numbers such that lambda(1) = 1, 1/lambda(i) -> 0 and Sigma(infinity)(i=1) 1/lambda(i) = infinity. In this paper we prove that Lambda BV of all the games of Lambda-bounded variation on C is a non-separable and norm dual Banach space of the space of simple games on C. We use this fact to establish the existence of a linear mapping T from Lambda BV onto F A (finitely additive set functions) which is positive, efficient and satisfies a weak form of symmetry, namely invariance under a semigroup of automorphisms of (I, C).
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| 4. |
- Momeni, H. R., et al.
(författare)
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Apoptosis in cultured spinal cord slices of neonatal mouse
- 2008
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Ingår i: Iranian Journal of Science and Technology Transaction A: Science. - 1028-6276. ; 32:A2, s. 109-116
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Tidskriftsartikel (refereegranskat)abstract
- Organotypic spinal cord slices from neonatal mammals could be a powerful model for evaluation of cell survival but also cell death mechanisms. The aim of this study was to establish an in vitro model for investigating cell survival and mechanism involved in cell death in neonatal spinal cord slices. The spinal cord was sliced and incubated into culture medium. The MTT assay was carried out to assess the viability of the slices and fluorescent staining was used to study morphological features of apoptosis, where as nucleosomal DNA fragmentation was detected using agarose gel electrophoresis. The results of the present study demonstrated that the slices could be maintained in culture up to 14 days. Both neurons and glial cells died by apoptosis and application of a general caspase inhibitor neither affected slice survival nor nucleosomal DNA fragmentation after 24 h in culture. In addition, the inhibitor failed to block apoptosis in neurons and glial cells in the cultured slices. Our results suggest that in the cultured slices, apoptosis is the main reason for neuron and glial cell death, which occurs by a caspase-independent mechanism.
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| 5. |
- Qasim, Muhammad, et al.
(författare)
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Biased Adjusted Poisson Ridge Estimators-Method and Application
- 2020
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Ingår i: Iranian Journal of Science and Technology Transaction A: Science. - : Springer. - 1028-6276 .- 2364-1819. ; 44, s. 1775-1789
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Tidskriftsartikel (refereegranskat)abstract
- Mansson and Shukur (Econ Model 28:1475-1481, 2011) proposed a Poisson ridge regression estimator (PRRE) to reduce the negative effects of multicollinearity. However, a weakness of the PRRE is its relatively large bias. Therefore, as a remedy, Turkan and Ozel (J Appl Stat 43:1892-1905, 2016) examined the performance of almost unbiased ridge estimators for the Poisson regression model. These estimators will not only reduce the consequences of multicollinearity but also decrease the bias of PRRE and thus perform more efficiently. The aim of this paper is twofold. Firstly, to derive the mean square error properties of the Modified Almost Unbiased PRRE (MAUPRRE) and Almost Unbiased PRRE (AUPRRE) and then propose new ridge estimators for MAUPRRE and AUPRRE. Secondly, to compare the performance of the MAUPRRE with the AUPRRE, PRRE and maximum likelihood estimator. Using both simulation study and real-world dataset from the Swedish football league, it is evidenced that one of the proposed, MAUPRRE ((k) over cap (q4)) performed better than the rest in the presence of high to strong (0.80-0.99) multicollinearity situation.
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