Browsing by Author "Kebede, Tesfaye"

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    Laser dynamics with a squeezed Vacuum
    (Addis Ababa University, 1999-01) Kebede, Tesfaye; Kassahun, Fesseha (PhD)
    We present a detailed derivation ofthe c-number Langevin equations for a laser coupled to a squeezed vacuum reselVoir fi'om the conesponding operator Langevin equations. Employing these equations we investigate the effects of the squeezed vacmUll on the photon statistics, the spectnllll of intensity fluctuations, squeezing spectrum and the power spectnllll for a laser operating below tln·eshold. The same set of equations are also used to study the effects of the squeezed vacuum on the photon statistics, the power spectrum, and spectmm of intensity fluctuations for a laser operating above threshold. We find that the intensity fluctuations and laser linewidth depend on the relative phase between the squeezed vacuum and the laser
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    A Study on Managerial Effectiveness of Wereda Education Officers in a Decentralized Education System The Case of Mejengir Zone
    (Addis Ababa Univerisity, 2010-06) Kebede, Tesfaye; Yimam, Wossenu(PhD)
    This study was aimed at to examine the current managerial effectiveness of wereda education officers in a decentralized education system in Mejengeir zone of Gambella Regional state. To achieve this objective, basic questions such as the extent to which wereda education officers are effective in carrying out major managerial functions, whether the existing structure is enabling, the extent to which stakeholders are supportive, what major factors do affect effectiveness; and how to improve performance to be effective were raised. To this end, descriptive survey method was employed. The respondents were 17 wereda education officers, 17 principals and vice principals, and 137 teachers selected from 532 population based on random, purposive, and availability sampling techniques. Information was gathered quantitatively through survey questionnaires and qualitatively through interviews, document analysis and observation. 171 copies of questionnaires were filled and returned. Various statistical tools such as percentages, means, T-test and Spearman Rank Order correlation Coefficient were used for data analysis. The findings of the study revealed that wereda education officers are incompetent to undertake many of the managerial functions effectively, the current structure is not enabling, and resources and educational in put are lacking. Moreover, the technical and professional support of key role players was minimal. This implies that the current performance of wereda education officers was found to be ineffective in attaining the decentralized management of education system. It was recommended that the concerned bodies should revise the structure that can absorb the required personnel and competent educational experts should be recruited based on competency. Moreover, the working environment and employee relationship need to be improved and employees should be motivated. On top of this, key stakeholders should be able to provide the required support to minimize many of educational problems.
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    A Study on Managerial Effectiveness of Wereda Education Officers in a Decentralized Education System The Case of Mejengir Zone
    (Addis Ababa University, 2010-06) Kebede, Tesfaye; Yimam, Wossenu (PhD)
    This study was aimed at to examine the current managerial effectiveness of wereda education officers in a decentralized education system in Mejengeir zone of Gambella Regional state. To achieve this objective, basic questions such as the extent to which wereda education officers are effective in carrying out major managerial functions, whether the existing structure is enabling, the extent to which stakeholders are supportive, what major factors do affect effectiveness; and how to improve performance to be effective were raised. To this end, descriptive survey method was employed. The respondents were 17 wereda education officers, 17 principals and vice principals, and 137 teachers selected from 532 population based on random, purposive, and availability sampling techniques. Information was gathered quantitatively through survey questionnaires and qualitatively through interviews, document analysis and observation. 171 copies of questionnaires were filled and returned. Various statistical tools such as percentages, means, T-test and Spearman Rank Order correlation Coefficient were used for data analysis. The findings of the study revealed that wereda education officers are incompetent to undertake many of the managerial functions effectively, the current structure is not enabling, and resources and educational in put are lacking. Moreover, the technical and professional support of key role players was minimal. This implies that the current performance of wereda education officers was found to be ineffective in attaining the decentralized management of education system. It was recommended that the concerned bodies should revise the structure that can absorb the required personnel and competent educational experts should be recruited based on competency. Moreover, the working environment and employee relationship need to be improved and employees should be motivated. On top of this, key stakeholders should be able to provide the required support to minimize many of educational problems
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    Tautomersim and Spectral Properties of Alizarin (1,2-Dihydroxyanthracene-9, 10-Dione)
    (Addis Ababa Universty, 2007-07) Kebede, Tesfaye; Redi, Mesfin
    This paper mainly tends to explain the dual fluorescence of alizarin and its structures that are responsible for the existence of fluorescence emission spectra different from absorption spectra. And uses structural isomerism (Tautomersim) to explain the dual fluorescence shown by this compound. As well the affect of the PH of the media, polarity of the solvent and hydrogen bond forming tendency of solvents on both absorption and fluorescence emission spectra of alizarin were studied. Four alizarin tautomers were selected for simplicity that may exist in both ground and excited state or only in one of the two states. The structure of this compound is investigated both experimentally and theoretically. Experimentally its absorption, fluorescence emission spectra and 1H NMR were done and computational techniques (HF, DFT and semiemperical) were used to calculate total energy, Gibbs free energy, dipole moment, excitation energy and other molecular parameters. Key words: Alizarin, fluorescence, tautomers, computational, absorption, protic, aprotic and 1H NMR