915 resultados para Semiconductor gap
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This study explores differences between men and women entrepreneurs and social entrepreneurs. It explores the barriers and discriminatory effects that hinder women’s entrepreneurship, including access to finance in the European Union. The study includes four case studies covering the situation in the Czech Republic, Italy, Sweden, and the United Kingdom.
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This paper will review the recent advances in the field of ultrashort pulse generation from optically pumped vertical-external-cavity surface-emitting lasers (OP-VECSELs). In this review, we will summarize the most significant results presented over the last 15 years, before highlighting recent breakthroughs related to mode-locked VECSELs by different research groups. Different mode-locking techniques for OP-VECSELs are described in detail. Previously, saturable absorbers, such as semiconductor saturable absorber mirrors—external, or internal as in mode-locked integrated external-cavity surface emitting lasers (MIXSEL)—, and recently, novel-material-based carbon-nanotube and graphene saturable absorbers have been employed. A new mode-locking method was presented and discussed in recent years. This method is referred to as self-mode-locking or saturable-absorber-free operation of mode-locked VECSELs. In this context, we particularly focus on achievements regarding self-mode-locking, which is considered a promising technique for the realization of high-power, compact, robust and cost-efficient ultrashort pulse lasers. To date, the presented mode-locking techniques have led to great enhancement in average powers, peak powers, and repetition rates that can be achieved with passively mode-locked VECSELs.
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Preceding research has made hardly any attempt to measure the ecological impacts of pro-environmental behaviour in an objective way. Those impacts were rather supposed or calculated. The research described herein scrutinized the ecological impact reductions achieved through pro-environmental behaviour and raised the question how much of a reduction in carbon footprint can be achieved through voluntary action without actually affecting the socio-economic determinants of life. A survey was carried out in order to measure the difference between the ecological footprint of “green” and “brown” consumers. No significant difference was found between the ecological footprints of the two groups—suggesting that individual pro-environmental attitudes and behaviour do not always reduce the environmental impacts of consumption. This finding resulted in the formulation of a new proposition called the BIG (behaviour–impact gap) problem, which is an interesting addition to research in the field of environmental awareness gaps.
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A szerző arra a kérdésre keresi a választ, hogyan alakulhat ki látványos szakadék az egyéni cselekvések iránya és azok együttes hatása között. A szándékok és tettek hatását felülírhatja a társadalmi gazdasági tényezőkből adódó tehetetlenség: a kritikus tömeg hiánya, szervezeti-infrastrukturális tényezők, kompenzációs hatások, egymás hatását kioltó cselekvések. A szerző a környezettudatosság és az ökológiai lábnyom példáján - ezerfős reprezentatív felmérésre alapozva - mutatja be, hogy az önkéntességre alapozó megközelítés sokszor túlbecsüli a fogyasztó - társadalmi-gazdasági tényezők által korlátozott - lehetőségeit és szuverenitását. _____ Behaviour impact gaps are demonstrably present in everyday life. It is increasingly found that environmental awareness in individuals fails to lead to reductions in the ecological footprint. Intensive agricultural practice reduces biodiversity in the EU even in areas where massive agri-environmental grant schemes are available and applied. Labour market training programmes do not necessarily facilitate job-finding for underprivileged segments of the society. So individual efforts may not add up or induce the expected effect. This outcome appears even for programmes that are successful in attaining the required behavioural change in a target group. The impact of attitudes and individual acts may be wiped out by structural and economic lock-ins such as trade-offs made for the gains, lack of a critical mass of actions, infrastructural deficiencies, or interfering acts of economic actors. The discrepancy between environmental awareness and ecological footprint is used to point out how awareness-raising programmes may miss their targets by overestimating the sovereignty and capabilities of consumers. Consumers are unwillingly locked into unsustainable practices and cannot be moved from that position unless economic and structural premises are also changed.
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Integrated on-chip optical platforms enable high performance in applications of high-speed all-optical or electro-optical switching, wide-range multi-wavelength on-chip lasing for communication, and lab-on-chip optical sensing. Integrated optical resonators with high quality factor are a fundamental component in these applications. Periodic photonic structures (photonic crystals) exhibit a photonic band gap, which can be used to manipulate photons in a way similar to the control of electrons in semiconductor circuits. This makes it possible to create structures with radically improved optical properties. Compared to silicon, polymers offer a potentially inexpensive material platform with ease of fabrication at low temperatures and a wide range of material properties when doped with nanocrystals and other molecules. In this research work, several polymer periodic photonic structures are proposed and investigated to improve optical confinement and optical sensing. We developed a fast numerical method for calculating the quality factor of a photonic crystal slab (PhCS) cavity. The calculation is implemented via a 2D-FDTD method followed by a post-process for cavity surface energy radiation loss. Computational time is saved and good accuracy is demonstrated compared to other published methods. Also, we proposed a novel concept of slot-PhCS which enhanced the energy density 20 times compared to traditional PhCS. It combines both advantages of the slot waveguide and photonic crystal to localize the high energy density in the low index material. This property could increase the interaction between light and material embedded with nanoparticles like quantum dots for active device development. We also demonstrated a wide range bandgap based on a one dimensional waveguide distributed Bragg reflector with high coupling to optical waveguides enabling it to be easily integrated with other optical components on the chip. A flexible polymer (SU8) grating waveguide is proposed as a force sensor. The proposed sensor can monitor nN range forces through its spectral shift. Finally, quantum dot - doped SU8 polymer structures are demonstrated by optimizing spin coating and UV exposure. Clear patterns with high emission spectra proved the compatibility of the fabrication process for applications in optical amplification and lasing.
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This study assessed the civic knowledge, skills, and attitudes of Hispanic eighth grade students in Miami-Dade County Public Schools (M-DCPS), Florida. Three hundred sixty one Hispanic students of Cuban (253), Colombian (57), and Nicaraguan (51) ancestry from 10 middle schools participated in the study. Two hundred twenty eight students were from low socio-economic status (SES) background, and 133 were of middle SES background. There were 136 boys and 225 girls. The International Association for the Evaluation of Educational Achievement Civic Education Student Questionnaire was used to collect data. The instrument assessed the students’ civic knowledge, skills, and attitudes. Multivariate analysis of variance was used to test for differences in the civic knowledge, skills, and attitudes of participants based on ancestry, SES, and gender. ^ The findings indicated that there was no significant difference in the civic knowledge, skills, and attitudes of Hispanic eighth grade students that were of Cuban, Colombian, and Nicaraguan ancestry. There was no significant difference in the civic skills and in five of the civic attitude scales for students from low SES families compared to those from middle SES families. However, there was a significant difference in the civic knowledge and in the civic attitude concerning classroom discussions and participation based on SES. The civic knowledge of middle SES students was higher than that of low SES students. Furthermore, middle SES Hispanic students displayed a higher mean score for the civic attitude of classroom discussions and participation than low SES students. There was no significant difference in the civic knowledge and in five of the civic attitude scales between boys and girls. However, there was a significant difference in the civic skills and the civic attitude of support for women’s rights between boys and girls. Hispanic girls displayed a higher mean score in civic skills than Hispanic boys. Furthermore, the mean score of civic attitude of support for women’s rights for Hispanic girls was higher than that of Hispanic boys. ^ It was concluded that Cuban, Colombian, or Nicaraguan participants did not demonstrate differences in civic attitudes and levels of civic knowledge and skills that eighth grade students possessed. In addition, when compared to boys, girls demonstrated a higher level of civic skills and a greater support for women’s rights and participation in politics and their roles in politics. Moreover, SES was demonstrated to be a key factor in the acquisition of civic knowledge, regardless of ancestry.^
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This paper presents a heuristic investigation of mixed methods organized around three pairs of opposing standpoints: methods (qualitative vs. quantitative), paradigms (constructivist vs. post positive), and inquiry approaches (dialectical vs. pragmatic).
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The author argues that learning in classroom communities of practice may reduce exclusionary school discipline practices and the discipline gap that disproportionately affect African American students. Communities of practice prioritize the social nature of learning as legitimate peripheral participation, encouraging community membership, social identity transformation, and synergistic relationships and spaces.
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The new intemationalization of the field of hospitality management has led to increased opportunities in the Russian Federation. At the same time, there are major challenges to be overcome. This article describes what needs to be accomplished to be successful at business in this New World Order.
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The relationship between trade policy and productivity growth is regarded as ambiguous in the literature. This dissertation examines under what condition the relationship would be positive (or negative). Through the use of static and dynamic analysis, we find two conflicting effects (the pro-protection effect and the pro-competitive effect) that cause the relationship to be ambiguous. If there exists a productivity gap between the import-competing and foreign industries, and if the level of protection is low (high), the relationship is positive (negative). We also show that the import-competing firm responds to a change in the protection level by choosing a level of investment in innovation which yields a different rate of productivity growth. The policy implication, therefore, is that a trade-policy maker should set the trade protection at a level which induces the firm to choose the highest rate of productivity growth, and, as a result, leading the firm to close the initial productivity gap in the most efficient way. ^
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The primary purpose of this thesis was to present a theoretical large-signal analysis to study the power gain and efficiency of a microwave power amplifier for LS-band communications using software simulation. Power gain, efficiency, reliability, and stability are important characteristics in the power amplifier design process. These characteristics affect advance wireless systems, which require low-cost device amplification without sacrificing system performance. Large-signal modeling and input and output matching components are used for this thesis. Motorola's Electro Thermal LDMOS model is a new transistor model that includes self-heating affects and is capable of small-large signal simulations. It allows for most of the design considerations to be on stability, power gain, bandwidth, and DC requirements. The matching technique allows for the gain to be maximized at a specific target frequency. Calculations and simulations for the microwave power amplifier design were performed using Matlab and Microwave Office respectively. Microwave Office is the simulation software used in this thesis. The study demonstrated that Motorola's Electro Thermal LDMOS transistor in microwave power amplifier design process is a viable solution for common-source amplifier applications in high power base stations. The MET-LDMOS met the stability requirements for the specified frequency range without a stability-improvement model. The power gain of the amplifier circuit was improved through proper microwave matching design using input/output-matching techniques. The gain and efficiency of the amplifier improve approximately 4dB and 7.27% respectively. The gain value is roughly .89 dB higher than the maximum gain specified by the MRF21010 data sheet specifications. This work can lead to efficient modeling and development of high power LDMOS transistor implementations in commercial and industry applications.
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Peer reviewed
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Peer reviewed
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Acknowledgments This work was supported by the University of Konstanz, Germany. The first author was supported by a fellowship of the Swiss National Science Foundation (Fellowship P2ZHP1_155103).