Top PDF Development of SiC heterojunction power devices

Development of SiC heterojunction power devices

Development of SiC heterojunction power devices

The need for efficient energy conversion is clear then; the efficient switching of energy from one form to another is an issue that impacts on all the green technologies that will become so prevalent over the next 50 years. But what makes an inverter, a rectifier or a DC-DC converter efficient? Figure 2.2 shows the simplest inverter circuit, where the application of a trigger to transistors 1 and 4 allow current flow one way through the load, whilst the triggering of 2 and 3 forces it through in the opposite direction. The use of pulse width modulation and some smoothing circuitry offers the opportunity to reduce the harmonic frequencies in this circuit after smoothing, hence creating an AC signal such as the dotted line in Figure 2.2. The peak-to-peak amplitude of the resulting A.C. signal is twice the DC current, whilst the frequency is controllable by the devices’ switching speed. The diodes in this circuit prevent any inductive reverse current from the load damaging the transistors. Further detail on this and more complex converters may be found in [29].
Show more

311 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Participants were recruited to participate in a project including longitudinal studies of the development of FXS at the University of North Carolina at Chapel Hill. The aim of the larger project was concerned with investigating the cognitive, behavioral, and psychological trajectories of children with FXS. Data for the current sample were pulled from two studies associated with previously mentioned project in order to address the longitudinal research questions of the study. The first study included boys with FXS who were seen every twelve months for an assessment (n=20). The second study included boys with FXS and typically developing boys seen every eighteen months for assessment (FXS n= 13; TD n= 17). Participants’ data were pulled from the relevant assessment ages, between ages 3 to 4 for the initial assessment (“preschool age”) and then again between ages 5 to 6 for the subsequent assessment (“school entry”). Subjects were used from both samples to increase the power of the potential findings in the analyses.
Show more

45 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Tissue engineers have extensively studied the type of cells that should be utilized when developing replacement blood vessels, while also providing a list of criteria that the replacement vessel should meet. In a general sense, to say that one has effectively created a replacement, the replacement must effectively mimic the native artery not only biologically but also in its response to mechanical load. Though the mechanical responses of some arteries have been studied extensively, not all major arteries have been mapped out and described in terms of their biomechanical properties. In particular, the properties of renal arteries have not been actively studied, resulting in a paucity of experimental data. Since such baseline data is necessary for the development of replacement renal artery constructs, the work described herein presents the results from recent studies focusing on quantifying the behavior of porcine renal arteries.
Show more

70 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

In the 1950’s, social scientists saw a need to quantify the methods of their sciences, such as sociology and anthropology. Thus many adopted terms and concepts from graph theory to help describe problems they faced. They used these ideas to help cre- ate models as well as analyze collected empirical data, linking graph theoretical ideas with social ideas such as “status, influence, cohesiveness, social roles, and identities in social networks,” [5] page 3. Around the same time, graphs became an accepted model for means of disease and information transmission. Furthermore, it was around this time that the notion of random graphs saw its early developments. This new approach saw graphs as stochastic, or probabilistic, objects rather than deterministic. All these events thus produced a surge of interest in the new field of network science. [5] chapter 1. Before any further discussion of the historical development of network science, it is important to introduce several basic concepts from graph theory. For a complete introduction to graph theory, see e.g. Diestel’s book Graph Theory [9].
Show more

78 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Clawson and Reese-Weber’s study (2003) examined the relationship between sexual risk-taking behaviors and the timing of parent-adolescent sexual communication. The study, based on Socialization Theory (Philliber, 1980), documented that timing is an important factor in predicting sexual risk-taking behavior. Two hundred and fourteen participants (101 males and 113 females) between the ages of 18 and 21 years of age completed the study questionnaire for extra course credit; the sample was 82% White and 9% African American. Clawson and Reese-Weber (2003) concluded that emphasis should be placed on encouraging parents to discuss sexuality early in their adolescents’ development, preferably prior to initiation of sexual activity. The study also suggested several areas for additional research including having a sample with more diversity, especially looking at African American adolescents, who are more likely to be sexually active then Whites (CDC, 2010). Future research should also focus on identifying if discussion of certain topics (e.g., pregnancy, sexually transmitted infections) are more strongly correlated with sexual risk-taking behavior than others (e.g., prostitution), and investigating the specific content of parent-child sexual risk communication and perceived parental attitudes related to discussions (Clawson & Reese-Weber, 2003).
Show more

181 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

While many advances were made in lighting technology over time, the continued production of solid-state lighting materials containing rare earths is in jeopardy. It is projected that rare-earth oxide demand will surpass the supply of rare-earth oxide materials. Furthermore, China controls approximately 97% of the global market. The export of these materials will also decrease due to China’s own growing demand. This supply and demand situation for rare-earth materials may eventually cause lighting research to focus more and more on the development of rare-earth free lighting materials and/or organic light emitting devices (OLEDs) 6 . A 2011 report by Philips Lighting Company, showed the critical need for rare-earths oxides to sustain the global demand for lighting materials. The main rare earth ions needed for phosphor materials are
Show more

181 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

The study that was used as a basis for the development of this thesis provided results of the performance for the GPU implementation compared to a CPU. That study achieved a significant improvement using a GPU and results were given for a comparison of 7 million reads processed in 0.432 seconds, which achieves 16.2 million reads per second performance [4]. While this method of performance measurements indicate a 3.78x improvement of the DSP implementation described in this thesis, it fails to account for the difference in architectures used. The hardware described in that study used 2 NVidia Tesla C2050 GPUs, which each contain 448 cores and consume a maximum of 247 watts. NVidia lists the running power consumption of a single GPU at 238 watts [18]. Accounting for the 2 GPUs used, the mapped bases per watt-second of the GPU implementation is 676,742.83. Compared to the DSP, which achieves 3,155,556.73 mapped bases per watt-second, there is a 4.66x improvement over the GPU. The power consumption for the performance metric for the GPU must be estimated instead of measured, only the running power for the GPUs was used in the calculations. More power would be consumed with the controlling CPU needed to operate the GPU, which would decrease the performance of the GPU a small degree more than indicated.
Show more

54 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Subjectivity is the process by which the researcher acknowledges, discusses, and takes into consideration experiences, beliefs, and assumptions that have framed the purpose for conducting the study and the researcher’s relationship to the study in terms of biases and perceived truths. 149,170 I must have acknowledged and understood through reflexivity, how my culture, race, and lived experiences impacted the development of inquiry into the phenomenon and my views and understanding of the subsequent findings. Subjective experiences are important components that justify use of the interpretivist approach to frame the study using CRT and discuss the data. Phenomena can only be understood within the context in which they are studied, 149 and experienced. As a PT, I have had experiences or subjective truths that were contextually the same as other PTs, because I have worked on an inpatient rehabilitation unit and treated persons with stroke. But being an AA, I have experienced what I perceived to be as racism, which may be the same for AAwS participating in the study. The key was not to impart my subjective truths during the research process, but to remain neutral so that I
Show more

175 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Toch composed one work for military band: Spiel für Blasorchester, Op. 39 (1926), which has been the subject of previous scholarship. This document provides a history and analysis of his remaining works for winds: Miniatur-Ouvertüre, Five Pieces for Wind Instruments and Percussion, Op. 83, and Sinfonietta for Wind Instruments and Percussion, Op. 97. Since these works encompass more than thirty-years of his career, some compositional style development is found; however, Toch’s broad treatment of melody, harmony, orchestration, and form are strikingly consistent. Each work is melodically driven and doesn’t conform fully to traditional forms. The harmonic flavor of each work is determined by melodic content. Found often are areas of full chromaticism, non-functional triads, and other ambiguous harmonies.
Show more

94 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

impairment decline) compared to youth who were non-ADHD at baseline and either non- ADHD or subthreshold ADHD at follow-up (4% and 9% decline in overall impairment, respectively). Thirty three percent of youth who were subthreshold at baseline remained in that category at follow-up and 15%-27% of those individuals showed significant decline in at least one domain of functioning and 47% declined in overall impairment at follow-up. Conclusions: The findings show the importance of examining symptom and impairment constructs separately in the consideration of their unique contributions to ADHD and subthreshold ADHD diagnoses and of acknowledging the need to examine nuanced changes in diagnostic status during development; especially functional declines. These findings may be relevant to efforts to intervene earlier in childhood and to help identify high-risk individuals who may be good candidates for targeted interventions. Key words: Attention Deficit Hyperactivity Disorder, Subthreshold ADHD, symptom and impairment trajectories, predictors of impairment. Abbreviations: RCI, reliable change index; ADHD, attention-deficit/hyperactivity disorder; DISC-IV, Diagnostic Interview Schedule for Children version IV; SDQ, Strengths and Difficulties
Show more

214 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

achievement is less likely to collaborate with an instructional coach and is less likely to support the utilization of the research-based instructional coaching model. Teachers who do not see the benefits of collaborating with an instructional coach will not tap into the resources offered by an instructional coach to improve their classroom instruction. The perceptions of teachers provide information and data that can impact how schools and school districts implement the instructional coaching model, how schools and school districts choose instructional coaches, and how schools and school districts should provide professional development for instructional coaches. Although instructional coaching typically involves only the adults in a school, it is the students who reap the benefits of an effective instructional coaching program in a school. Research from the Pathways to Success program on implementation rates after teachers attended a summer workshop that was followed-up with instructional coaching was 85% while earlier research concludes there is a less than 10% implementation rate following traditional workshops with no follow-up (Knight, 2005).
Show more

153 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

countries and maximize the effectiveness of donor aid. The Paris Declaration is based on the recognition that partner country should take ownership of development strategies. A country partner has ownership when it takes the lead in determining the goals and priorities of its own development and set the agenda for how they are to be achieved. Strengthening the country's ownership represents a shift of power in the way aid relationship worked in the past, while underlining the need for mutual accountability (OECD, 2009). With strong ownership, the prospects for progress against other Paris Declaration principles improve. If partners “own” priorities, plans and programs, they are more likely to exercise effective leadership in getting donors to align to national
Show more

144 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

may be result from the lack of differentiation of adiponectin fractions in these studies; adiponectin fractions are hypothesized to have different biological activities (i.e. high molecular weight (HMW) adiponectin is thought to regulate insulin sensitivity whereas non-HMW adiponectin plays a role in the inflammatory response). In support of this hypothesis, Aleksandrova et al. reported that total adiponectin and non-HMW adiponectin concentrations were inversely associated with risk of CRC but there was no association for HMW adiponectin 3 . While the animal studies support a role of adiponectin in CRC, investigation of the relative importance of different adiponectin fractions in CRC pathogenesis is necessary prior to the development of effective clinical therapeutic strategies.
Show more

30 Read more

Integration of HfO2 on Si/SiC heterojunctions for the gate architecture of SiC power devices

Integration of HfO2 on Si/SiC heterojunctions for the gate architecture of SiC power devices

A method of reducing leakage current in a high-K - SiC MOS capacitor has been presented, using a wafer bond- ing technique to form a Si/SiC heterojunction substrate. A range of physical analysis tools including TEM and raman spectroscopy, proved that the wafer bonding of the substrates introduced no stress and was free of con- taminants at the interface. I-V results showed that the structures could withstand 3.5 MV/cm, exceeding values attained for HfO 2 /SiO 2 /SiC and HfO 2 /SiC capacitors.

5 Read more

Development and Characterization of Hybrid SiC Power Devices.

Development and Characterization of Hybrid SiC Power Devices.

simple MOSFET gate control and much larger reverse bias SOA (RBSOA). However, due to the exponentially increasing conduction resistance with the blocking voltage, the Si MOSFET’s applications have been limited to lower voltages (<600 V). In mid 90s, a new unipolar technology based on the super-junction (SJ) concept [9] breaks the Si unipolar device’s ideal conduction resistance limit. Today SJ MOSFETs are the preferred device in offline applications which require high frequency and high voltage switches in the 600-900 V range. On the other hand, the unipolar device’s on-resistance limitation can be easily broken with the bipolar conduction mechanism. The Si IGBTs, invented in 1980s [11], have maintained the advantage of MOS gate control while introducing a bipolar conduc- tivity modulation mechanism that is far more superior to the Si BJT devices. Because of this breakthrough, the Si IGBT’s voltage rating has been expanded dramatically to cover 600 V to 6500 V. Today they are still the workhorse power switches for important high volume applications such as motor drives, electric vehicles, PV inverters, etc. Si IGBTs have the advantages of simple MOS gate control, low forward voltage drop thanks to the conductivity modulation and much lower cost compared to wide bandgap (WBG) power devices due to matured Si wafer and fabrication technology. The main disadvantage of the IGBT is the large switching losses, especially the high turn-off loss, which limits its switching frequency range and power conversion efficiency. One more disadvantage is the high conduction losses at low current densities resulting from the 0.7 V turn-on voltage needed to inject minority carriers into the drift region.
Show more

182 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

To better understand the interaction between these advanced materials, each material was implemented into FRAPCON 3.4, the preferred fuel performance code of the NRC; additionally, the material properties and the heat transfer physics associated with a gas coolant were incorporated. The implementation of carbide within FRAPCON required the development of material models that described not only the thermophysical properties of UC, such as thermal conductivity and thermal expansion, but also models for the swelling, densification, and fission gas release associated with the fuel’s irradiation behavior.
Show more

97 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Clyde disclosed he did consider leaving when the business major was not working out, but ultimately decided to stay, discussing both support and situation in making his retention decision. He felt the people are “genuinely interested in seeing me succeed, it’s more than just being a statistic or another passing student… they actually care about your career and want you to do well in life and that’s ultimately what kept me here...” Clyde’s comment is consistent with the construct of “institutional commitment to the welfare of students” proffered by Braxton, Hirschy, and McClendon (2004) in their revision of Tinto’s (1975, 1986, 1993) theory on student departure focused on students at residential colleges and universities. The construct is defined as “an abiding concern for the growth and development of students” (Braxton and Hirschy, 2005, p. 70). The authors argue that initial commitment to the institution affects perceptions of several institutional
Show more

187 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Much of the work done thus far regarding antibiotic contamination in aquatic systems has concentrated on the development and proliferation of genetic antibiotic resistance in bacteria (Daughton and Ternes, 1999; Sengeløv et al. 2003, Kim and Aga, 2007). While antibiotic resistance is perhaps the most significant human health threat of the 21st century, another large area of concern is that of ecological impact. There have been a number of laboratory-based toxicological studies, most of which suggest that antibiotics in the environment pose a "potential" ecological problem. Wilson et al. (2003) found that antibiotics reduce algal genus richness and final biomass in environmental communities. Eguchi et al. (2004) found that antibiotics reduced cell growth and that some compounds acted synergistically against eukaryotic algae. Kim and Carlson, (2007) reported high concentrations of antibiotics in freshwater stream sediments. There are numerous other studies indicated potential problems, such as Liu et al., (2011 a ), (Liu et
Show more

105 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Specifically, I argue that an actor who anticipates the active consumption of a public good will contribute significantly more to its provision than an actor who anticipates [r]

51 Read more

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Modeling of Sic Power Semiconductor Devices For Switching Converter Applications

Agrarians and Aristocrats (1981) offers a broad intellectual interpretation of the Jackson- era that characterizes the partisan divide as representative of a rift between two opposing “worldviews,” which Ashworth defines as an intellectual bundle “comprised of beliefs, fears, hopes, and a series of assumptions about government, society and the economy.” 7 The ideologies and policies of the opposing parties emanated from two conflicting perceptions of human society. The Democrats, he suggests, fundamentally conceived of the nation as a conglomeration of equal citizens, one whose proper function depended most fundamentally on vigilance against the natural tendencies of power units (“special interests,” perhaps?) to upset the healthy balance of equals. National republicans/Whigs, on the contrary, conceived of the nation as an organism, a body politic in the most literal sense, whose proper operation depended not on equality but rather on a diversity of roles served by inequality, insofar as nature doled out different capacities for different roles. The function of government was to harmonize the body, to, ideally, perfectly match one’s role to one’s capacity. Ashworth’s book makes a convincing case, for he is quite
Show more

91 Read more

Show all 10000 documents...