12,753 research outputs found

    Variable Temperature-Scanning Hall Probe Microscopy (VT-SHPM) with GaN/AlGaN Two-Dimensional Electron Gas (2DEG) Micro Hall Sensors in 4.2-425K range, Using Novel Quartz Tuning Fork AFM Feedback

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    In this report, we present the fabrication and variable temperature (VT) operation of Hall sensors, based on GaN/AlGaN heterostructure with a two-dimensional electron gas (2DEG) as an active layer, integrated with Quartz Tuning Fork (QTF) in atomic force-guided (AFM) scanning Hall probe microscopy (SHPM). Physical strength and wide band gap of GaN/AlGaN heterostructure makes it a better choice to be used for SHPM at elevated temperatures, compared to other compound semiconductors (AlGaAs/GaAs and InSb), which are unstable due to their narrower band gap and physical degradation at high temperatures. GaN/AlGaN micro Hall probes were produced using optical lithography and reactive ion etching. The active area, Hall coefficient, carrier concentration and series resistance of the Hall sensors were ~14m x 14m, 10m7/G at 4.2K, 6.3 x 1012cm-2 and 12k7 at room temperature and 7m7/G, 8.9 x 1012cm-2 and 24k7 at 400K, respectively. A novel method of AFM feedback using QTF has been adopted. This method provides an advantage over STM feedback, which limits the operation of SHPM the conductive samples and failure of feedback due to high leakage currents at high temperatures. Simultaneous scans of magnetic and topographic data at various pressures (from atmospheric pressure to high vacuum) from 4.2K to 425K will be presented for different samples to illustrate the capability of GaN/AlGaN Hall sensors in VT-SHP

    Meaning Management: A Framework for Leadership Ontology

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    Leadership is a multifaceted and complex subject of research and demands a sound ontological stance that guides studies for the development of more integrative leadership theories. In this paper, I propose the leadership ontology PVA (perception formation – value creation – achievement realization) and associate it with the two existing leadership ontologies: TRIPOD (leader – member – shared goals) and DAC (direction – alignment – commitment). The leadership ontology PVA, based on a new theory called “meaning management,” consists of three circularly supporting functions: cognitive function to form perception, creative function to generate value, and communicative function to realize higher levels of achievement. The PVA is an epistemology-laden ontology since the meaning management theory allows one to make propositions that explicitly link its three functions with the leadership outcomes: perception, value, and achievement. Moreover, the PVA leadership ontology transcends and includes both the conventional TRIPOD ontology and the DAC ontology

    Magnetic sensitive scanning probe microscopy

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    Magnetically sensitive scanning probe microscopes have been solving scientific and engineering problems over the last two decades. The magnetic dipole fields generated by a spherical magnetic particle with radius a decay with math. As the magnetic features of interest become smaller and smaller, the sensitivity of the apparatus has to be improved dramatically in order to measure and image the magnetic features within the specimen. An overview of these powerful methods is given in this article

    A new perspective on the competitiveness of nations

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    The capability of firms to survive and to have a competitive advantage in global markets depends on, amongst other things, the efficiency of public institutions, the excellence of educational, health and communications infrastructures, as well as on the political and economic stability of their home country. The measurement of competitiveness and strategy development is thus an important issue for policy-makers. Despite many attempts to provide objectivity in the development of measures of national competitiveness, there are inherently subjective judgments that involve, for example, how data sets are aggregated and importance weights are applied. Generally, either equal weighting is assumed in calculating a final index, or subjective weights are specified. The same problem also occurs in the subjective assignment of countries to different clusters. Developed as such, the value of these type indices may be questioned by users. The aim of this paper is to explore methodological transparency as a viable solution to problems created by existing aggregated indices. For this purpose, a methodology composed of three steps is proposed. To start, a hierarchical clustering analysis is used to assign countries to appropriate clusters. In current methods, country clustering is generally based on GDP. However, we suggest that GDP alone is insufficient for purposes of country clustering. In the proposed methodology, 178 criteria are used for this purpose. Next, relationships between the criteria and classification of the countries are determined using artificial neural networks (ANNs). ANN provides an objective method for determining the attribute/criteria weights, which are, for the most part, subjectively specified in existing methods. Finally, in our third step, the countries of interest are ranked based on weights generated in the previous step. Beyond the ranking of countries, the proposed methodology can also be used to identify those attributes that a given country should focus on in order to improve its position relative to other countries, i.e., to transition from its current cluster to the next higher one

    Propfan model wind tunnel aeroelastic research results

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    Some of the single rotation propfan model wind tunnel aeroelastic findings from the experimental part of this research program are described. These findings include results for unstalled or classical flutter, blade response from separated flow excitations, and blade response from aerodynamic excitations at angled inflow conditions

    The North Cyprus Conference Sector: Establishing a Competitive Advantage

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    North Cyprus had recently positioned itself as a conference destination. Given external and internal factors such as political isolation and the over dependency on casino tourism, policymakers have recognised the importance of the conference sector in creating sustainable growth for North Cyprus’s tourism driven economy. Increasingly, Turkish conference organisers are choosing North Cyprus as a destination to host conferences. As such, Turkish conference organisers were questioned via an internet based questionnaire to determine attributes considered important within the conference destination selection process. An Importance-Performance Analysis (IPA) was performed, the findings identified that North Cyprus was perceived as a high performer with reference to; ease of accessibility, distance of destination, conference venue and accommodation price, safety and security, climate, hospitality, quality, quantity and availability of hotel rooms. However, in relation to North Cyprus, a unique application of IPA identified macro- and micro-destination attributes that North Cyprus should improve on; transportation within destination, availability of technological resources, the range of conference venues, conference staff training, destinations marketing activities and quality of local restaurants. The findings provided implications for destination managers in terms of branding, as well as conference venue and accommodation providers in terms of targeting conference organisers more effectively and promoting North Cyprus to conference sector stakeholders

    NEW COMPETITION FOR SUPERMARKETS: A CASE STUDY

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    Non-traditional retailers such as warehouse club stores, discount drug stores, and discount mass merchandisers are new competitors for traditional food retailers. It is expected that non- traditional retailers will account for roughly 14 percent of total grocery sales by the turn of the century. The impact of a particular discount mass merchandiser (Wal-Mart) on the sales of a conventional retail grocery outlet (David's Supermarket, Inc.) located in the rural areas surrounding the Dallas/Ft. Worth metroplex is analyzed in this case study. In this case study, Wal-Mart alone is responsible for about a 17 percent reduction in sales.Warehouse Club Stores, Discount Mass Merchandisers, Supermarkets, Competition., Industrial Organization, Marketing,
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