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Minimal Time of Null Controllability for the 1D Heat Equation by a Strategic Zone Profile

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Journal of Applied Mathematics and Physics 2021年第7期9卷 1707-1717页

作者： Cheikh seck Mame Libasse Laye Ane Département de Mathématiques de la FASTEF ex ENS de l’Université Cheikh Anta Diop de Dakar Dakar Sénégal Laboratoire d’Analyse Numérique et d’Informatique (LANI) de l’UFR SAT de l’Université Gaston Berger de Saint-Louis Saint-Louis Sénégal Département de mathématiques et d’Informatique de la Faculté des Sciences et Techniques de l’Université Cheikh Anta Diop de Dakar Dakar Sénégal

The aim of this work is to improve the minimum time of null controllability of the 1D heat equation by using the notion of strategic zone actuators. In fact, motivated by the work of Khodja on the null controllability of the heat equation and of El Jai on the controllability by the use of strategic zone actuators, we managed, in this work, to improve the minimal time of null controllability to the 1D heat equation. However, the restrictions and difficulties to establish the inequality of coercivity of the parabolic operator, require to seek other methods of internal control. Thus in this paper, a mixed method combining the method of moments and the notion of strategic profile was used to find a better minimal time of null controllability of the 1D heat equation.

关键词： Control Null Controllability Moment Methods Estimations Strategic Actuator

中国外企与合资企业中方中层经理频繁跳槽之原因探析

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中国外企与合资企业中方中层经理频繁跳槽之原因探析

作者： Mamadou seck 北京交通大学

学位级别：硕士

员工跳槽现象在中国极为普遍,在中国保留关键的中层管理人员也是人力资源管理的一大难点,因为在跨国人才市场上人才不仅飞走了,而且他们飞走得很快。本篇硕士论文旨在探讨中国的中层管理人员在国内的合资企业和跨国公司中主动跳槽真正... 详细信息

员工跳槽现象在中国极为普遍,在中国保留关键的中层管理人员也是人力资源管理的一大难点,因为在跨国人才市场上人才不仅飞走了,而且他们飞走得很快。本篇硕士论文旨在探讨中国的中层管理人员在国内的合资企业和跨国公司中主动跳槽真正诱因或根源,并提出一些相应的建议以解决这个管理层面的问题.该项研究的结果将会有助于国际性公司的人力资源经理确保他们的整体人才战略是合理的,能够很好的满足员工在生理、安全、社会、尊重以及自我实现等多方面的。通过涵盖组织、环境和人员组成这三方面因素的调查问卷,我们进行了一项定性研究。调查结果表明,与环境因素相比而言,组织因素是中国中层管理人员跳槽主要因素。而且,该项调查结果还表明,和新员工相比老员工更加稳定,不会轻易跳槽;和男性员工相比,女性员工跳槽的机会更大。人力资源经理应该利用各种工具和模型,比如Lee ***和Terrence ***关于如何重新架构组织的理论,以及AbrahamMaslow的需求层次理论,以便将导致员工跳槽的各种因素的真正根源进行分类和研究,进而通过匹配组织环境和员工的合理期望的方法来解决上述难题。

关键词：跳槽中国中层管理人员跨国公司合资企业

Spectroscopic Electrochemical Properties and DFT Calculation of 1-Aryltriazenes

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International Journal of Organic Chemistry 2023年第4期13卷 109-128页

作者： Insa seck Mohamed Lamine Sall Atoumane Ndiaye Samba Fama Ndoye Lalla Aïcha Ba Matar seck Organic Chemistry Coordination Laboratory Cheikh Anta Diop University of Dakar Dakar-Fann Senegal Organic Chemistry and Therapeutic Chemistry Laboratory Cheikh Anta Diop University of Dakar Dakar-Fann Senegal Organic Physical Chemistry and Environmental Analysis Laboratory Cheikh Anta Diop University of Dakar Dakar-Fann Senegal Department of Physics Cheikh Anta Diop University of Dakar Dakar-Fann Senegal Amadou Mahtar Mbow University Dakar Nafa VDN Senegal

Electrochromic materials are of great interest for their potential in eyewear protection and data storage devices, as they change colors in response to electrochemical switching. While many of the systems currently used are based on inorganic materials, organic materials such as triazenes have emerged as viable alternatives due to their unique properties, including optical properties. Triazenes are a class of organic compounds with three consecutive nitrogen atoms in an acyclic arrangement, and they have been used for a variety of applications in medicinal and synthetic chemistry. However, the effects of solvents on the UV-visible absorption spectrum of triazenes have not been fully investigated. The neutral molecules of 3,3-diisopropyl-1-phenyltriazene and 1-(4-chlorophenyl)-3-cyclopentyltriazene in acetonitrile, the UV-visible spectra corresponded respectively to HOMO → LUMO transitions with a large maximum absorption at 299.74 nm (4.1364 eV) and 299.57 nm (4.1387 eV) and the most intense oscillator strength (f = 0.6988) and (f = 0.7372). These results suggest that the electronic transitions of the compounds are highly influenced by the nature of the substituents on the triazene unit, as well as the solvent used in the experiment. The redox couple 0.92 and -0.44 V/Ag/AgCl is attributed to the phenyl group. Compound III showed an oxidation and reduction peak respectively -0.27 and -0.8 V/Ag/AgCl attributed to the phenyl molecule. The study concluded that all three compounds were electroactive and exhibited reversible characteristics with oxidizing/reducing couples. This study aims to contribute to research on the optical properties of triazenes compounds and the application of quantum chemical calculation methods for understanding their molecular structures. By investigating the solute-solvent interactions occurring in the solvation shell of the solutes, we aim to gain insights into the effects of solvents on the UV-visible absorption spectrum of triazenes. Our fin

关键词： Triazenes UV-Visible Spectroscopy Electrochemical DFT Calculations

Improved Resistance to Cracking of a Cement Mortar through the Incorporation of Crumb Rubber

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Journal of Physical Science and Application 2017年第3期7卷 37-40页

作者： Moulay Smaine Ghembaza Mbaye seck Laboratory of Civil Engineering and Environment University Djillali Liabes Sidi BelAbbes 22000 Algeria

Within a context of sustainable development, innovative processes for various applications to recycle rubber are put in place to make aggregates or crumb rubber. These uses include sports floor coverings, to manufacture of sealants, sound absorbing walls, to make roads, as an alternative fuel in cement kilns, etc. In this study, the addition of crumb rubber to mortar was investigated through optical and mechanical tests. The results showed that the incorporation of crumb rubber from used tires into mortar produced a better resistance to shrinkage cracking, but a compressive strength/tensile is reduced. This feature could lend itself to making playgrounds and sports grounds more absorbing and flexible, which would allow a more significant fall to be withstood without injury and consequently enhance the safety of playgrounds.

关键词： Max. resistance cracking cement mortar crumb rubber.

Boundary Exact Controllability of the Heat Equation in 1D by Strategic Actuators and a Linear Surjective Compact Operator

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Applied Mathematics 2020年第10期11卷 991-999页

作者： Cheikh seck Libasse Ane abd.ulaye Sène Département de Mathématiques de la FASTEF ex ENS de l’Université Cheikh Anta Diop de Dakar Sénégal Laboratoire d’Analyse Numérique et d’Informatique (LANI) de l’UFR SAT de l’Université Gaston Berger de Saint-Louis Sénégal Département de mathématiques et d’Informatique de la Faculté des Sciences et Techniques de l’Université Cheikh Anta Diop de Dakar Sénégal

In this paper we show a boundary result of controllability by a new approach using a linear, continuous and surjective operator built from the solution of the heat system. And, subsequently, the border exact controllability of the 1D heat equation through a compactness criterion and the use of strategic zone actuators were established.

关键词： Control Controllability Estimations Strategic Actuator

Scheduling Aircraft Landings at LSS Airport

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American Journal of Operations Research 2012年第2期2卷 235-241页

作者： Coumba Diallo Babacar Mbaye Ndiaye Diaraf seck Laboratory of Mathematics of Decision and Numerical Analysis Cheikh Anta Diop University Dakar Senegal Unité Mixte Internationale UMMISCO Institut de Recherche pour le Développement Bondy France

This paper presents a short contribution in air transportation, specifically in scheduling aircraft (plane) landings at Léopol Sédar Senghor (LSS) airport of Dakar. The safety of air navigation of LSS is managed by ASECNA: Agency for Air Navigation Safety in Africa and Madagascar. Scheduling aircraft landing is the problem of deciding a landing time on an appropriate runway for each aircraft in a given set of aircraft such that each aircraft lands within a predetermined time window. The separation criteria between the landing of an aircraft, and the landing of all successive aircraft, are respected. Our objective is to minimize the cost of deviation from the target times. We present a mixed-integer 0 - 1 formulation for the single runway case. Numerical experiments and comparisons based on real datasets of LSS airport are presented.

关键词： Air Traffic Control Runway Operations Scheduling Non Convex Optimization

Improving Disease Prevalence Estimates Using Missing Data Techniques

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Open Journal of Statistics 2016年第6期6卷 1110-1122页

作者： Elhadji Moustapha seck Ngesa Owino Oscar abdou Ka Diongue Pan African University Institute for Basic Sciences Technology and Innovation (PAUISTI) Nairobi Kenya Taita Taveta University Taita Taveta Kenya Universite Gaston Berger de Saint Louis Saint Louis Senegal

The prevalence of a disease in a population is defined as the proportion of people who are infected. Selection bias in disease prevalence estimates occurs if non-participation in testing is correlated with disease status. Missing data are commonly encountered in most medical research. Unfortunately, they are often neglected or not properly handled during analytic procedures, and this may substantially bias the results of the study, reduce the study power, and lead to invalid conclusions. The goal of this study is to illustrate how to estimate prevalence in the presence of missing data. We consider a case where the variable of interest (response variable) is binary and some of the observations are missing and assume that all the covariates are fully observed. In most cases, the statistic of interest, when faced with binary data is the prevalence. We develop a two stage approach to improve the prevalence estimates;in the first stage, we use the logistic regression model to predict the missing binary observations and then in the second stage we recalculate the prevalence using the observed data and the imputed missing data. Such a model would be of great interest in research studies involving HIV/AIDS in which people usually refuse to donate blood for testing yet they are willing to provide other covariates. The prevalence estimation method is illustrated using simulated data and applied to HIV/AIDS data from the Kenya AIDS Indicator Survey, 2007.

关键词： Disease Prevalence Missing Data Non-Participant Logistic Regression Model Prevalence Estimates HIV/AIDS

Recycling Tailings Seepage Water for Diogo Heavy Minerals Mine Sustainability (Northern Senegal)

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Journal of Water Resource and Protection 2018年第1期10卷 121-144页

作者： Mouhamat seck Serigne Faye Mark Robertson Michael Rose Department of Geology University Cheikh Anta Diop Dakar Senegal Grande Cote Operations (GCO) Dakar Senegal GEO-ENG Queensland Australia

The sandy Quaternary and the deep Maastrichtian aquifers located in the northern coastal zone of Senegal, from the locality of Kayar in the south to Saint-Louis in the north, constitute the main sources of water supply for urban and local needs as well as mining activities. The Quaternary aquifer that provides the water required for the irrigation of local farmlands, hosts a significant heavy mineral sands deposit currently being mined by the Grande Cote Operations (GCO). As a result of variable rainfall and increased water abstraction, this shallow aquifer has recorded a continuous water level decline since 1970, with potential negative effects on both the social and economic development of the region. The mining of heavy minerals (zircon, ilmenite, leucoxene and rutile) at GCO is realised through conventional dredging techniques that require large volumes of water (up to 60,000 m3/d). The water pumped by the dredge to enable the extraction of the heavy minerals, infiltrates into the shallow aquifer, runs-off into the dredge pond or evaporates. The objective of this study is to evaluate a water balance that enables the provision of a permanent water supply to the dredge pond, whilst minimising the risk of flooding of the cropping depressions adjacent to the mine site or drying out of the farming wells. The hydrodynamic model implemented for this purpose was calibrated and tested during the first year of operation. The Root Mean Squared Error (RMSE) obtained for the calibration is approximately 0.52 m. The predictions indicate a requirement for the system to recover part of the tailings infiltration through dewatering boreholes. The quantity of recycled water is estimated at 16,000 m3/d on average. The model simulations show an additional water requirement, extracted from the deep Maastrichtian aquifer, varying between 23,000 and 28,000 m3/d to achieve the optimum pond water level.

关键词： Mineral Sands Groundwater Modelling Dredge Pond Grande Cote Operations Fe Flow

Asymptotic Confidence Bands for Copulas Based on the Local Linear Kernel Estimator

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Applied Mathematics 2015年第12期6卷 2077-2095页

作者： Diam Ba Cheikh Tidiane seck Gane Samb Lo LERSTAD Universite Gaston Berger de Saint-LouisSaint-LouisSenegal LERSTAD Universite Alioune DiopBambeySenegal LSTA Universite Pierre et Marie CurieParisFrance

In this paper, we establish asymptotically optimal simultaneous confidence bands for the copula function based on the local linear kernel estimator proposed by Chen and Huang [1]. For this, we prove under smoothness conditions on the derivatives of the copula a uniform in bandwidth law of the iterated logarithm for the maximal deviation of this estimator from its expectation. We also show that the bias term converges uniformly to zero with a precise rate. The performance of these bands is illustrated by a simulation study. An application based on pseudo-panel data is also provided for modeling the dependence structure of Senegalese households’ expense data in 2001 and 2006.

关键词： Copula Function Kernel Estimation Local Linear Estimator Uniform in Bandwidth Consistency Simultaneous Confidence Bands