For low power applications, GaN HEMTs are preferred over Si CoolMOS because of high frequency operation, low ON resistance, low capacitance and low gate charge. The high switching frequency allows reduction of filtering circuit. Low gate charge and capacitance allows high switching frequency operations and simplification of gate driver design since a low current is needed to charge the gate to turn ON the device. Low capacitance also gives high dV/dt which reduces switching losses. The cooling system requirements are reduced because of the low switching and conduction losses. The GaN HEMTs are around 10 times smaller than their Si counterparts which reduces the overall system size and increases the power density.
Abstract—The fast switching speeds and low specific conduction losses of wide band-gap semiconductors allow the realisation of high-frequency, highpower-density switching converters with dramatically reduced passive component requirements compared to Silicon technology. However, careful attention must be paid to switching cell design to mitigate the effects of circuit parasitics and fast voltage transitions which would otherwise limit the attainable switching speed and lead to increased levels of EMI. This paper presents a modular, power- cell solution which allows the creation of any two-level topology converter. The cell structure enables fast switching of wide bandgap semiconductordevices while allowing highpower converters to be fabricated using multiple, smaller commutation cells. Close integration of semiconductor dies, decoupling capacitors, gate drives and an output filter with a single ceramic substrate to act as the thermal path allows dramatic increases in power density without compromising converter performance. 1
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
The understanding of the bulk morphology of materials is important in the pharmaceutical industry and has an impact on the material’s solubility, stability, and therapeutic properties. 2 One example, reported by Kato et al., showed that the three forms of phenobarbital, a widely used anti-convulsant, had differing dissolution rates with the metastable form, form II-Ba, having the highest. 3 In this aspect, it is important to understand the correlation between the bulk properties and the crystal packing of compounds, such as in the work of Corvis et al. 4 The two polymorphic forms of glutaric acid, a common co-crystallizing agent for pharmaceuticals, were studied. They examined the bulk properties of the α-form including its thermal properties and high resolution PXRD. Through study of these bulk properties, they were able to propose a crystal structure for this elusive polymorph at higher temperatures. 4 They also studied the thermal properties to gain a better understanding of the high temperature solid-to-solid phase transition between the two forms.
Field Programmable Gate Arrays have been used for high performance computing with a great success at large performance speedups. The processors are capable of being reconfigured with a new design to meet multiple needs and are efficient at parallel tasks within the limitations of the hardware blocks available on a FPGA processor. Generally FPGAs are more complex to use, as a specific design must be mapped first before being used as a coprocessor. Often times this can be a daunting task that is quite difficult. Any modifications may cause the entire design to have to be modified. With these limitations, they are still capable of huge performance gains within a certain scope of applications. Several studies were done to explore their use within short read mapping applications.
Using this model more than doubles the number of model parameters, i.e. from 6 to 13. The simulation with diﬀuse priors showed high variations in the model parameters, therefore less informed priors than for the Bayesian LM will be considered, these are uniform distributions on a pessimistically chosen interval. The information for the intervals is extracted from the performed tests, the ob- servations in ﬁgure 1 and the previously used Bayesian LM. This leads to the following priors:
One of the most influential sociological papers was put forth in 1978 by the po- litical scientist Ithiel de Sola Pool and the mathematician Manfred Kochen in their paper “Contacts and Influence” . The paper concerns social network structure and patterns. Written in 1958, it was not published until twenty years later because the authors were not satisfied with the depth of their work. A manuscript was produced though, and the paper was un-officially circulated amongst the relevant research com- munity. The paper put forth many of the crucial issues that came to define the field for some time after. In this network, they treat people as vertices and acquaintances between two people as an edge. Issues addressed involve an individual person’s de- gree, degree distributions, average and range of degrees, high-degree people, network structure, probability of a random acquaintance, probability of shared acquaintances or neighbors, and shortest path lengths. Due to the insufficiency of empirical data, they used the random graph model. They were also the first to scientifically intro- duce the notion of the small-world effect, popularized as “6 degrees of separation”, which refers to the idea that everybody in the world is within a relatively short social distance of everybody else , page 15.
microcarriers were dispensed into ring-shaped agarose molds and shown to adhere to form living tissue constructs after several days in culture. The ability of cellularized microcarriers to adhere to one another involved cellular and extracellular matrix bridging that included the formation of epithelium-like cell layers lining the luminal and ablumenal surfaces of the constructs and the deposition of collagen and elastin fibers. The ring-shaped tissues nominally behaved as elastic solids, with a uniaxial mechanical response that is qualitatively similar to that of native vascular tissues and consistent with their elastin and collagen composition. Linearized measures of the mechanical response of the fabricated tissues at both low and high strains were observed to increase with duration of static culture, with no significant loss of stiffness following decellularization. The findings highlight the utility of cellularized macroporous gelatin microcarriers as self-adhering building blocks for the fabrication of living ring-shaped structures.
The model is implemented in the circuit simulator PSpice and is validated by comparison with Atlas finite element simulations and experimental measurements. A highpower SiC DMOSFET from CREE Inc., rated at 1200V 20A, is used for experimental validation. The device inner construction details are not available from the manufacturer. On the basis of experimental parameter extraction and literature published by CREE [ 33 ], the geometrical and doping characteristics of Figure 3.1 have been derived. These characteristics are used both for the finite element simulation model and for the PSpice model. A full set of experimental measurements is performed in order to assist model validation, including: static I-V characteristics, C-V characteristics and dynamic characterization under resistive switching conditions.
A bstract — In this context, the multilevel inverters with larger number of levels suitable for circuit integration are actively investigated. Diode- clamped multilevel inverters are regarded as the promising solution. As the number of voltage levels increases the harmonic content decreases significantly.The general function of the multilevel inverter is to synthesize a desired AC voltage from several levels of DC voltages. Multilevel inverters are mainly used in medium voltage and highpower applications to reduce the required voltage rating of the powersemiconductor switching devices. These multilevel inverters are used to increase inverter operating voltage, to minimize THD with low switching frequency, to reduce EMI due to lower voltage steps. The advantages of this multilevel approach include good power quality, good electromagnetic compatibility, low switching losses and high capability. This project proposes to study various multilevel inverter topologies, to simulate various modulating techniques for diode clamped multi level inverter fed induction motor. These modulating techniques include sinusoidal pulse width modulation, modified reference modulating techniques. i.e., trapezoidal reference, staircase reference, stepped reference, third harmonic injected reference and offset line voltage injected reference with triangular carrier waves. The main objective of this study is to reduce total harmonic distortion, comparison of THD and fundamental component for different modulation techniques. The Simulated Induction motor model is connected at the end to observe the Stator current harmonics and speed-torque characteristics.
Instead of using oil-immersed contact and complicated mechanical drive, a vacuum switch and bi- stable electromechanical actuator were used. These vacuum switches had the advantages of highpower handling capability and long life, thus, suitable for the use of the selector. The proposed diverter, consisting of two solid-state switches, was to be connected between each of the selector output leads and in parallel with those two solid-state switches. A faster form of GTO assisted tap changer with the advantage of reduced transformer outages. The speed of the intended vacuum switch moving is now controllable, since fatigue in the stainless steel bellows is the prime limitation, and reverts to fast operation during a system fault.
The traditional design of power electronics packages involves thermal cycling tests, but few, if any, studies of transient power cycling exist. For example, an extension of the traditional RC network for the junction-to-case system to a case-to-ambient (via a heat sink) system has been shown to adequately describe steady-state and long-pulse operation in insulated gate bipo- lar transistor (IGBT) modules . However, this macroscopic lumped-element model limits the usefulness under short electri- cal transient pulses, typical in modern converter operations. To find an exact thermal solution under transient power dissipation is difficult. Most research uses finite-element methods (FEMs) to achieve the exact solution –. The FEM can provide high precision at the cost of slow computing speed. One of the major disadvantages of using an FEM package for thermal simulation is that it is not easy to create a cosimulation with an electri- cal circuit simulator, which could predict the transient power dissipation from power electronic devices instantaneously.
Power electronics convert electrical energy from one form to another electronic device. Function of power electronic circuits using semiconductordevices such as switches, control or modify the voltage or current. Power electronic applications of highpower conversion equipment such as DC power supply to each of the hardware that is available at this time, such as cordless screwdriver, charger power supply for computers, mobile phones and hybrid cars. Power Electronics, including applications in which the circuit milliwatts or megawatts. Typical applications of power electronics, including AC to DC conversion, DC to AC conversion, the conversion voltage control voltage is controlled, and change the AC power source to the intensity and frequency to another frequency and the amplitude.
demonstrated an off-state breakdown voltage of ~ 1100 V. The systematic measurements of output I-V, transfer I-V, off-state breakdown voltage, capacitance – voltage characteristics and temperature characterisation results provide insights on the device performance and temperature dependence of the heterostructure characteristics. The GaN-on-Diamond epi- wafers used here were manufactured in late 2013. Devices reported here represented the first- time that a power switching device has been made with GaN-on-Diamond albeit with epitaxy designed for RF applications. The performance shown here is expected to improve with epitaxy that has been better tailored for power electronic applications.
Children with high Surgency ratings are more likely to act out in impulsive or disruptive manners (Gartstein et al., 2012). Previous literature reviews have found that the Surgency facets of activity level and social approach predict higher levels of ADHD symptoms (Nigg et al., 2004, Nigg, 2006; Casalin, et al., 2011). These traits manifest in challenging behaviors associated with ADHD such as dampened abilities in anger control and non-compliance (De Pauw & Mervielde, 2011). Also, children with ADHD were rated one standard deviation higher on the Children’s Behavior Questionnaire (Rothbart et al., 2001) scale of activity level when compared to the average rating of the general population. Additionally, activity level relates to how intensely a child exhibits other traits such as impulsivity, shyness, and approach (De Pauw & Mervielde, 2011). Surgency’s relationship to activity level (indicating hyperactivity), the stability of impulsivity, and social approach indicates the potential and value of studying the relationship between early temperament characteristics and the emergence of ADHD. This relationship has not been thoroughly examined in FXS as a possible explanation for the elevated ratings of ADHD features observed in the literature (Bailey et al., 2001; Bailey et al., 2008; Sullivan et al., 2006).
However, ferritic alloys have also been observed to have a somewhat non-uniform nanoparticle dispersion, be difficult to manufacture, and susceptible to embrittlement at high temperatures due to an undesirable phase transformation between 400°C and 550°C , . 9Cr ODS is unique in that there is the observed formation of a non- equilibrium phase, designated as the residual ferrite, which serves to greatly enhance several vital mechanical properties in comparison to both standard RAFM alloys and the fully ferritic 18Cr ODS. This is theorized to be further enhanced by sliding at weaker regions such as at the grain boundaries and packet boundaries; behaving as a fiber composite material comprising the harder residual ferrite and the softer tempered martensite.  A martensitic alloy, such as 9Cr ODS, would be best utilized in areas exposed to high temperatures, neutron doses, and mechanical strain, such as fuel cladding within the reactor pressure vessel. 18Cr ODS would be more valuable for application as structural components that are in contact with coolant, as the high chromium content lends to good resistance to corrosion.
Demand for energy has increased tremendously throughout the world due to increase numerous of loads, equipments and automation of every manual activities. These also have been high growth in population, industries and manufacturing units whose demand need to meet. Such a hike in load demand has moved mankind on the erg of critical stage of energy crisis as the generation of power throughout the sector mostly depends on conventional source of energy. This high consumption of fuel and demand of power is also a reason to blame upon for hike in fuel cost thereby the per unit Power production cost. In past few decades Renewable energy has emerged as boon for the crisis, it is one of the most important alternative energy sources. Renewable energy sources are environmental friendly, economically competitive with conventional power generation. Growth in manufacturing and newer high efficiency power converters and semiconductordevices has made the use of Renewable energy resources like Wind and solar power generation economically feasible also But renewable energy alone does not prove to be solution due to low energy conversion ratio and high initial construction cost.
The substitution of In 3+ at the M site in these materials causes the excitation band to shift near 400 nm, which causes these materials to be used as potential LED phosphors without the use of rare earth ions. The ions Al 3+ , Ga 3+ , and In 3+ occupy the M site simultaneously, which is a remarkable feat. The increased substitution of In 3+ causes the PL emission to be quenched, therefore substitutions where x ≤ 0.025 are ideal for phosphor material with an appreciable PL intensity. The increase in the temperature of the reducing atmosphere causes the PL emission to change from orange-yellow to a green-yellow color. This information is important since it is known that the combination of a blue emitting In x Ga 1-x N semiconductor combined with a yellow emitting phosphor