Education reforms and the constant changes in the curriculum require school managers and educators to keep abreast of the changes and developments. In order to achieve quality education in this Information Age, there is a need to share knowledge, resources, and good practices and ensure twinning of schools. The purpose of this study was to explore perceptions, beliefs and experiences of school managers regarding knowledge sharing in schools. Qualitative methods were used to collect and analyse the data. In accordance with the qualitative approach, a phenomenological design was adopted. Data was gathered through interviews from a sample of six school managers of Further Education and Training (Grade 10 -12) schools. The findings of the study revealed that school managers perceive their role as important for the success of knowledge sharing in schools. They attribute the good performance in their schools to the educators‟ willingness to share knowledge. However, trust, good relations and respect determined the willingness to share and with whom to share knowledge in schools. School managers believe that availability of Information and Communication Technology (ICT) infrastructural resources could improve knowledge sharing practices in schools. Staff meetings, subject meetings, workshops and notice boards were identified as some of the strategies currently used for sharing knowledge. The support of the district officials and other education specialists has contributed in helping schools deal with education reforms. Communities of practice are recommended in order to improve and encourage the sharing of tacit and implicit knowledge in schools. Researchers believe that professional communities of practice enhance sharing and provide greater opportunities for knowledge creation. Policy developers, curriculum planners and district officials need to develop and adopt creative and innovative strategies to ensure effective distribution and sharing of knowledge and information among school managers and educators in schools.

No description available.

Diss. Univ. Heidelberg, 2008. / Teilw. in kyrill. Schr.

This thesis is focused on the high-frequency performance of carbon nanotube field-effect transistors (CNFETs). Such transistors show their promising performance in the nanoscale regime where quantum mechanics dominates. The short-circuit, common-source, unity-current-gain frequency ft is analyzed through regional signal-delay theory. An energy-dependent effective-mass feature has been added to an existing SP solver and used to compare with results from a constant-effective-mass SP solver. At high drain bias, where electron energies considerably higher than the edge of the first conduction sub-band may be encountered, ft for CNFETs is significantly reduced with respect to predictions using a constant effective mass. The opinion that the band-structure-determined velocity limits the high-frequency performance has been reinforced by performing simulations for p-i-n and n-i-n CNFETs. This necessitated incorporating band-to-band tunneling into the SP solver. Finally, to help put the results from different CNFETs into perspective, a meaningful comparison between CNFETs with doped-contacts and metallic contacts has been made. Band-to-band tunneling, which is a characteristic feature of p-i-n CNFETs, can also occur in n-i-n CNFETs, and it reduces the ft dramatically.

This thesis is focused on the high-frequency performance of carbon nanotube field-effect transistors (CNFETs). Such transistors show their promising performance in the nanoscale regime where quantum mechanics dominates. The short-circuit, common-source, unity-current-gain frequency ft is analyzed through regional signal-delay theory. An energy-dependent effective-mass feature has been added to an existing SP solver and used to compare with results from a constant-effective-mass SP solver. At high drain bias, where electron energies considerably higher than the edge of the first conduction sub-band may be encountered, ft for CNFETs is significantly reduced with respect to predictions using a constant effective mass. The opinion that the band-structure-determined velocity limits the high-frequency performance has been reinforced by performing simulations for p-i-n and n-i-n CNFETs. This necessitated incorporating band-to-band tunneling into the SP solver. Finally, to help put the results from different CNFETs into perspective, a meaningful comparison between CNFETs with doped-contacts and metallic contacts has been made. Band-to-band tunneling, which is a characteristic feature of p-i-n CNFETs, can also occur in n-i-n CNFETs, and it reduces the ft dramatically.

Ulm, Univ., Diss., 2008.

Zugl.: Wien, Techn. University, Diss., 2007. / Hergestellt on demand.

abstract: Semiconductor nanowires are featured by their unique one-dimensional structure which makes them promising for small scale electronic and photonic device applications. Among them, III-V material nanowires are particularly outstanding due to their good electronic properties. In bulk, these materials reveal electron mobility much higher than conventional silicon based devices, for example at room temperature, InAs field effect transistor (FET) has electron mobility of 40,000 cm2/Vs more than 10 times of Si FET. This makes such materials promising for high speed nanowire FETs. With small bandgap, such as 0.354 eV for InAs and 1.52 eV for GaAs, it does not need high voltage to turn on such devices which leads to low power consumption devices. Another feature of direct bandgap allows their applications of optoelectronic devices such as avalanche photodiodes. However, there are challenges to face up. Due to their large surface to volume ratio, nanowire devices typically are strongly affected by the surface states. Although nanowires can be grown into single crystal structure, people observe crystal defects along the wires which can significantly affect the performance of devices. In this work, FETs made of two types of III-V nanowire, GaAs and InAs, are demonstrated. These nanowires are grown by catalyst-free MOCVD growth method. Vertically nanowires are transferred onto patterned substrates for coordinate calibration. Then electrodes are defined by e-beam lithography followed by deposition of contact metals. Prior to metal deposition, however, the substrates are dipped in ammonium hydroxide solution to remove native oxide layer formed on nanowire surface. Current vs. source-drain voltage with different gate bias are measured at room temperature. GaAs nanowire FETs show photo response while InAs nanowire FETs do not show that. Surface passivation is performed on GaAs FETs by using ammonium surfide solution. The best results on current increase is observed with around 20-30 minutes chemical treatment time. Gate response measurements are performed at room temperature, from which field effect mobility as high as 1490 cm2/Vs is extracted for InAs FETs. One major contributor for this is stacking faults defect existing along nanowires. For InAs FETs, thermal excitations observed from temperature dependent results which leads us to investigate potential barriers. / Dissertation/Thesis / M.S. Electrical Engineering 2011

[pt] Este trabalho tem por objetivo estudar o (MES) FET de dupla porta de Arseneto de Gálio e algumas de suas propriedades como dispositivo de microondas. Inicialmente é desenvolvido um modelo para o FET de porta simples baseado na Aproximação do Canal Gradual, que inclue as variações com a polarização da capacitância entre a porta e o dreno e do tempo de trânsito. A partir desse modelo é obtido um outro para o FET de dupla porta. Então, as propriedades do FET de dupla porta relativas a sua aplicação como amplificador de ganho controlado e misturador são estudadas. A seguir suas propriedades que o fazem indicado para amplificador de ganho controlado são determinados. Também, a região de polarização que otimiza a isolação entre OL e RF quando ele é usado em misturadores é obtida. Usando fórmulas empíricas de forma relativamente simples e uma estratégia de aquisição de dados rápida e eficiente, obtém-se um modelo DC a partir de dados experimentais. Como exemplo de aplicação, esse modelo é usado para determinar o ponto de polarização ótimo com respeito, a ganho para um dispositivo medido. Dois amplificadores são construídos usando uma nova técnica de projeto. Essa técnica utiliza uma linha em aberto na porta 2 para manter o ganho plano sem necessidade de descassamento nas freqüências mais baixas. Em cada um dos amplificadores é usada uma técnica diferente para casamento do dreno. Esse trabalho apresenta-se como uma etapa na direção de aproveitar ao máximo o potencial desse versátil dispositivo de microondas, o FET de dupla porta. / [en] This work aims at studying the Gallium Arsenide dual gate (MÊS) FET and some of its properties as a microwave device. Initially, a model for the single gate FET is developed based upon the Gradual Approximation. It includes the gate to drain capacitance and transit time bias dependences. From this model, a model for the dual gate FET is obtained. Then, properties of the dual gate FET related to its use as gain controlled amplifier and mixer are studied. The properties that make it suitable for gain controlled amplifiers are pointed out. Also, the bias region that optmizes OL-RF rejection when it is used as a mixer, is obtained. Using a relatively simple empirical expression and a fast and efficient data acquisition strategy, a DC model is obtained from experimental data. As an example, this model is used to determine the optimum bias point with respect to gain for a measured device. Two amplifiers were built a new design technique. This technique makes use of an open line on the second gate to keep the gain flat without the need of mismatching at the lower frequencies. In each one of the amplifiers, a different technique is used to match the drain. This work is a step towards the use of the full capabilities of this versatile microwave device, the dual gate FET.

This thesis is focused on the high-frequency performance of carbon nanotube field-effect transistors (CNFETs). Such transistors show their promising performance in the nanoscale regime where quantum mechanics dominates. The short-circuit, common-source, unity-current-gain frequency ft is analyzed through regional signal-delay theory. An energy-dependent effective-mass feature has been added to an existing SP solver and used to compare with results from a constant-effective-mass SP solver. At high drain bias, where electron energies considerably higher than the edge of the first conduction sub-band may be encountered, ft for CNFETs is significantly reduced with respect to predictions using a constant effective mass. The opinion that the band-structure-determined velocity limits the high-frequency performance has been reinforced by performing simulations for p-i-n and n-i-n CNFETs. This necessitated incorporating band-to-band tunneling into the SP solver. Finally, to help put the results from different CNFETs into perspective, a meaningful comparison between CNFETs with doped-contacts and metallic contacts has been made. Band-to-band tunneling, which is a characteristic feature of p-i-n CNFETs, can also occur in n-i-n CNFETs, and it reduces the ft dramatically. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate