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A Simulation Study on Comparing General Class of Semiparametric Transformation Models for Survival Outcome with Time-Varying Coefficients and Covariates

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Open Journal of Statistics 2019年第2期9卷 169-180页

作者： Yemane Hailu Fissuh Tsegay Giday Woldu idriss abdelmajid idriss ahmed Abebe Zewdie Kebebe Department of Statistics College of Applied Sciences Beijing University of Technology Beijing China Department of Statistics College of Natural and Computational Sciences Aksum University Aksum Ethiopia Department of Mathematics College of Applied Sciences Beijing University of Technology Beijing China School of Software Engineering Faculty of Information Technology Beijing University of Technology Beijing China

The consideration of the time-varying covariate and time-varying coefficient effect in survival models are plausible and robust techniques. Such kind of analysis can be carried out with a general class of semiparametric transformation models. The aim of this article is to develop modified estimating equations under semiparametric transformation models of survival time with time-varying coefficient effect and time-varying continuous covariates. For this, it is important to organize the data in a counting process style and transform the time with standard transformation classes which shall be applied in this article. In the situation when the effect of coefficient and covariates change over time, the widely used maximum likelihood estimation method becomes more complex and burdensome in estimating consistent estimates. To overcome this problem, alternatively, the modified estimating equations were applied to estimate the unknown parameters and unspecified monotone transformation functions. The estimating equations were modified to incorporate the time-varying effect in both coefficient and covariates. The performance of the proposed methods is tested through a simulation study. To sum up the study, the effect of possibly time-varying covariates and time-varying coefficients was evaluated in some special cases of semiparametric transformation models. Finally, the results have shown that the role of the time-varying covariate in the semiparametric transformation models was plausible and credible.

关键词： Estimating Equation Semiparametric Transformation Models Time-to-Event Outcomes Time-Varying Coefficients Time-Varying Covariate

Dynamics of Plate Equations with Memory Driven by Multiplicative Noise on Bounded Domains

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Journal of Applied Mathematics and Physics 2024年第4期12卷 1492-1521页

作者： Mohamed Y. A. Bakhet abdelmajid Ali Dafallah Jing Wang Qiaozhen Ma Fadlallah Mustafa Mosa ahmed Eshag Mohamed Paride O. Lolika Makur Mukuac Chinor School of Mathematics University of Juba Juba South Sudan Department of Mathematics Faculty of Petroleum and Hydrology Engineering Alsalam University Almugled Sudan College of Mathematics and Statistics Northwest Normal University Lanzhou China Department of Mathematics and Physics Faculty of Education University of Kassala Kassala Sudan Department of Mathematics School of Education University of Juba Juba South Sudan

This article examines the dynamics for stochastic plate equations with linear memory in the case of bounded domain. We investigate the existence of solutions and bounded absorbing set by using the uniform pullback attractors on the tails estimates, and the asymptotic compactness of the random dynamical system is proved by decomposition method, and then we obtain the existence of a random attractor.

关键词： Plate Equations Random Attractors Memory Term Dynamical Systems

Robust Estimators for Poisson Regression

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Open Journal of Statistics 2023年第1期13卷 112-118页

作者： idriss abdelmajid idriss Weihu Cheng College of Applied Science Department of Statistics Beijing University of Technology Beijing China

The present paper proposes a new robust estimator for Poisson regression models. We used the weighted maximum likelihood estimators which are regarded as Mallows-type estimators. We perform a Monte Carlo simulation study to assess the performance of a suggested estimator compared to the maximum likelihood estimator and some robust methods. The result shows that, in general, all robust methods in this paper perform better than the classical maximum likelihood estimators when the model contains outliers. The proposed estimators showed the best performance compared to other robust estimators.

关键词： Poisson Regression Model Maximum Likelihood Estimator Robust Estimation Contaminated Model Weighted Maximum Likelihood Estimator

Weighted Maximum Likelihood Technique for Logistic Regression

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Open Journal of Statistics 2023年第6期13卷 803-821页

作者： idriss abdelmajid idriss Weihu Cheng Yemane Hailu Fissuh Department of Statistics Faculty of Science Beijing University of Technology Beijing China Department of Statistics Aksum University Tigray Ethiopia

In this paper, a weighted maximum likelihood technique (WMLT) for the logistic regression model is presented. This method depended on a weight function that is continuously adaptable using Mahalanobis distances for predictor variables. Under the model, the asymptotic consistency of the suggested estimator is demonstrated and properties of finite-sample are also investigated via simulation. In simulation studies and real data sets, it is observed that the newly proposed technique demonstrated the greatest performance among all estimators compared.

关键词： Logistic Regression Clean Model Robust Estimation Contaminated Model Weighted Maximum Likelihood Technique

Effective Mass Model Reduced to Ordinary Mass Using Newton’s, Quantum and Generalized Special Relativity

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Natural Science 2021年第9期13卷 398-406页

作者： Nagwa idriss Ali ahmed Mohamed idriss ahmed Mubarak Dirar Abd-Alla Department of Physics Faculty of Science and Art (Dariah) Qassim University Almulid KSA Department of Physics and Mathematics Hantoub Faculty of Education Gezira University Hantoub Sudan Department of Physics Faculty of Science Sudan University of Science and Technology Khartoum Sudan

The concept of the effective mass in crystals shows that the electron mass is affected by the crystal field and was experimentally verified. A useful expression for effective mass was obtained. Unfortunately this expression showed that the effective mass vanishes in the ab-sence of the external field. This is in conflict with observations which show that it reduces to the ordinary mass. To cure this defect a new model is developed assuming the existence of vacuum force as verified experimentally as shown by Casimir effect. Using Newton’s second law and the quantum expression of momentum, useful expressions were found. The same expression was found using generalized special relativity. Strikingly the three models reduced to the conventional one in the absence of vacuum, they also reduced to the ordinary electron mass in the absence of all forces.

关键词： Effective Mass Newton’s Second Quantum Momentum Generalized Special Relativity

Efficient Information Set Decoding Based on Genetic Algorithms

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International Journal of Communications, Network and System Sciences 2012年第7期5卷 423-429页

作者： ahmed Azouaoui idriss Chana Mostafa Belkasmi SIME Lab. ENSIAS Mohammed V-Souissi University Rabat Morocco

In this paper, we describe a hard-decision decoding technique based on Genetic Algorithms (HDGA), which is applicable to the general case of error correcting codes where the only known structure is given by the generating matrix G. Then we present a new soft-decision decoding based on HDGA and the Chase algorithm (SDGA). The performance of some binary and non-binary Linear Block Codes are given for HDGA and SDGA over Gaussian and Rayleigh channels. The performances show that the HDGA decoder has the same performances as the Berlekamp-Massey Algorithm (BMA) in various transmission channels. On the other hand, the performances of SDGA are equivalent to soft-decision decoding using Chase algorithm and BMA (Chase-BMA). The complexity of decoders proposed is also discussed and compared to those of other decoders.

关键词： Genetic Algorithms (GA) Error Correcting Codes RS Codes Information Set Decoding Chase Algorithm

Explanation of Pressure Effect for High Temperature Superconductors Using Pressure Dependent Schrodinger Equation and String Theory

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Natural Science 2020年第1期12卷 28-34页

作者： Einas Mohamed ahmed Mohamed Nagwa idriss Ali ahmed Musa Ibrahim Babiker Hussein Rasha Abd Elhai Mohammad Taha Mohammed idriss ahmed Mubarak Dirar Abd-Alla Department of Physics University College (Turaba) Taif University Taif KSA Department of Physics and Mathematics Hantoub Faculty of Education Algezira University Wad Madaniin-Hantoub Sudan Department of Physics Faculty of Science & Art (Dariyah) Qassim University Al-Mulida KSA Department of Physics and Mathematics Faculty of Education Albutana University Rufaa Sudan Department of Physics Faculty of Science & Art Dariyah University Buljurashi KSA Department of Physics College of Science Majmaah University Majmaah KSA Department of Physics Faculty of Science Sudan University of Science and Technology Khartoum Sudan

A pressure dependent Schrodinger equation is used to find the conditions that lead to superconductivity. When no pressure is exerted, the superconductor resistance vanishes beyond a critical temperature related to the repulsive force potential of the electron gass, where one assuming the electron total energy to be thermal, where applying mechanical pressure destroys Sc when it exceeds a certain critical value. However when the electron total energy is an assumed to be that of the free electron model and that the pressure is thermal and mechanical, the situation is different. The quantum expression for resistance shows that the increase of mechanical pressure increases the critical temperature. Such phenomenon is observed in high temperature cupper group.

关键词： Pressure Dependent Schrodinger Equation Superconductivity Critical Temperature Pressure High Temperature Superconductor

Urethral Stone: A Rare Cause of Acute Retention of Urine in Men

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Open Journal of Urology 2020年第5期10卷 145-151页

作者： ahmed Ibrahimi idriss Ziani Jihad Lakssir Hachem El Sayegh Lounis Benslimane Yassine Nouini Department of Urology A Ibn Sina University Hospital Faculty of Medicine and Pharmacy Mohammed V University Rabat Morocco

Urethral stones are a very rare form of urolithiasis, they most often originate from the upper urinary tract or bladder, and are rarely formed primarily in the urethra, it is formed on a urethral anatomical pathology in the majority of cases. The clinical symptomatology is very variable ranging from simple dysuria with penile pain to acute retention of urine. Smaller stones can be expelled spontaneously without intervention, but larger stones or complicated stones or those developed on an underlying urethral anatomical pathology require surgical treatment. The minimally invasive treatment should be the preferred route for the surgical treatment of this disease when feasible. We report the case of a young man with no particular pathological history who presented to the emergency department for acute retention of urine secondary to a primary fossa navicularis calculus, through this case, we discuss the different clinical aspects, etiology, pathogenesis, diagnosis and therapy of urethral stone in men.

关键词： Urethral Stone Meatotomy Acute Urinary Retention Penis

The First Natural Ventilation Assessment in Building Design in Djibouti

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Journal of Life Sciences 2016年第6期10卷 298-306页

作者： Abdou Idris Omar Abdoulkader Ibrahim idriss Omar Assowe Dabar Abdourazack ahmed Kayad Mohamed Said Darar Research Center at the University of Djibouti (CR UD/GRE) Faculty of Engineers Street Djanaleh B.P. 1904 Djibouti Institute for Earth Sciences Centre d'Etudes et de Recherche de Djibouti (CERD) Airportstreet B.P. 486 Djibouti

With a sustained period of economic growth, rapidly growing populations and with more diversified economies Africa need sustainable development; hence the greater need for massive investments in energy. Sub-Saharan countries such as Djibouti have the potential and ability to harness their natural ventilation as a passive cooling system for designing new houses. The rapid expansion of the Djibouti city is affecting negatively the environment and the safety and comfort of its inhabitants. Proper atmospheric urban planning and management are key to making cities environmentally friendly and sustainable. Based on energy consumption, climate conditions in Djibouti and numerical analysis using Computational Fluid Dynamics （CFD）, it is apparent that the natural ventilation creates a thermally comfortable indoor environment in buildings during the cool season of the year. Measured wind data from two measurement systems are presented and discussed. Statistical analyses, wind rose, Weibull distribution were carried out to understand the natural ventilation characteristic, which is used for evolving the basic criteria for economic viability of building in the semi-arid climate of Djibouti. The study found that it is possible to benefit from natural ventilation in buildings during the cool season of the year.

关键词： Computational Fluid Dynamics airflow simulation natural ventilation bioclimatic design weather data energy efficiency.