1,690 research outputs found

    Improving ADR in the States' Criminal Justice Systems: A Case that States Should Adopt the U.S. Military's System of Nonjudicial Punishment

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    Published in cooperation with the American Bar Association Section of Dispute Resolutio

    An Integrated IGBT Active Gate Driver with Fast Feed-Forward Variable Current

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    The Insulated-Gate Bipolar Transistor (IGBT) is a hybrid of bipolar and MOSFET transistors. As a consequence, IGBTs can handle higher current typical of bipolar transistors with the ease of control typical of MOSFETs. These characteristics make IGBTs desirable for high power Switch Mode Power Supplies (SMPS). In high power systems such as these, devices must be very reliable, as device failures may result in safety hazards such as fires in addition to the failure of the system. Conventional Gate Driver (CGD) circuits typically design for reliability in these systems by including a resistor between the gate driver and gate of the IGBT. This slows the switching waveforms, reducing stress on the IGBT while sacrificing efficiency. This solution is suboptimal, however, and as such Active Gate Drivers (AGD) have been designed to control voltage and current slopes through the IGBT by modulating the gate signal. AGD circuits found on the market today consist of a combination of an CGD with external components to implement the variable current necessary for protection. This requires a large amount of area on a Printed Circuit Board (PCB), and thus can be costly. Therefore, it can be desirable to integrate the AGD functionality into an on-chip system. In this thesis, an AGD is designed, fabricated and analyzed to show that IGBT gate voltage can be controlled in a manner capable of reducing overvoltage, as well as slowed when desired using an on-chip system. The current provided by this gate driver is controlled by feedback signals indicating the switching state of the device, as well as input bits that determine total output current

    To lead or not to lead : analysis of the sprint in track cycling

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    This paper uses a statistical analysis of match sprint outcomes to guide tactical decisions in this highly tactical contest and to provide competitors and coaches with a potential, marginal gain. Logistic regression models are developed to predict the probability of the leading rider winning at different points of the race, based on how the race proceeds up to each point. Key tactics are successfully identified from the models, including how the leading rider might hold the lead and how the following rider might optimise overtaking

    Electrowetting of liquid marbles

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    Electrowetting of water drops on structured superhydrophobic surfaces are known to cause an irreversible change from a slippy (Cassie-Baxter) to a sticky (Wenzel) regime. An alternative approach to using a water drop on a superhydrophobic surface to obtain a non-wetting system is to use a liquid marble on a smooth solid substrate. A liquid marble is a droplet coated in hydrophobic grains, which therefore carries its own solid surface structure as a conformal coating. Such droplets can be considered as perfect non-wetting systems having contact angles to smooth solid substrates of close to 180 degrees. In this work we report the electrowetting of liquid marbles made of water coated with hydrophobic lycopodium grains and show that the electrowetting is completely reversible. Marbles are shown to return to their initial contact angle for both ac and dc electrowetting and without requiring a threshold voltage to be exceeded. Furthermore, we provide a proof-of-principle demonstration that controlled motion of marbles on a finger electrode structure is possible

    Hawaii Deep Water Cable Program : phase II reassessment of cable vessel availability

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    The report, "Preliminary Cable Vessel Ship Inventory and Capabilities," summarized a survey of existing cable vessels to determine their applicability and availability to the HDWC Program. This report concluded that none of the existing vessels were applicable to the program without major modifications to the cable handling equipment. As a result of technical discussions with Parsons, HECO and DOE, HD&C was requested to reassess the applicability and availability of the most likely candidate cable vessels

    Electrowetting on superhydrophobic SU-8 patterned surfaces

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    Electrowetting on micro-patterned layers of SU-8 photoresist with an amorphous Teflon (R) coating has been observed. The cosine of the contact angle is shown to be proportional to the square of the applied voltage for increasing bias. However, this does not apply below 40 V and we suggest that this may be explained in terms of penetration of fluid into the pattern of the surface. Assuming that the initial application of a bias voltage converts the drop from Cassie-Baxter to Wenzel regime, we have used this as a technique to estimate the roughness factor of the surface

    Extraction of Thematic Roles from Dictionary Definitions

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    Toward a Relation Hierarchy for Information Retrieval

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    Natural language text can be seen as a symbolic representation of a cognitive state of the creator that comprises concepts and the relations among those concepts. Much work has been done in Information Science, especially within Information Retrieval (IR), concerning the handling of concepts, most notably in the form of keywords. Much less effort has been spent toward the understanding and handling of the semantic relations that contextually bind concepts together. While it has been shown (Wang, et al., 1985) that the use of these semantic relations for query enhancement can increase retrieval effectiveness, the proper handling of semantic relations has a much wider application than just query enhancement. Once relations inherent in text are identified and captured, they can be used to provide contextual information to the concepts in the representations of the text, which otherwise would be treated as if they were independent and separate

    Self-organization of hydrophobic soil and granular surfaces

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    Soil can become extremely water repellent following forest fires or oil spillages, thus preventing penetration of water and increasing runoff and soil erosion. Here the authors show that evaporation of a droplet from the surface of a hydrophobic granular material can be an active process, lifting, self-coating, and selectively concentrating small solid grains. Droplet evaporation leads to the formation of temporary liquid marbles and, as droplet volume reduces, particles of different wettabilities compete for water-air interfacial surface area. This can result in a sorting effect with self-organization of a mixed hydrophobic-hydrophilic aggregate into a hydrophobic shell surrounding a hydrophilic core

    Effect of Particle Size on Droplet Infiltration into Hydrophobic Porous Media As a Model of Water Repellent Soil

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    The wettability of soil is of great importance for plants and soil biota, and in determining the risk for preferential flow, surface runoff, flooding,and soil erosion. The molarity of ethanol droplet (MED) test is widely used for quantifying the severity of water repellency in soils that show reduced wettability and is assumed to be independent of soil particle size. The minimum ethanol concentration at which droplet penetration occurs within a short time (≀10 s) provides an estimate of the initial advancing contact angle at which spontaneous wetting is expected. In this study, we test the assumption of particle size independence using a simple model of soil, represented by layers of small (0.2–2 mm) diameter beads that predict the effect of changing bead radius in the top layer on capillary driven imbibition. Experimental results using a three-layer bead system show broad agreement with the model and demonstrate a dependence of the MED test on particle size. The results show that the critical initial advancing contact angle for penetration can be considerably less than 90° and varies with particle size, demonstrating that a key assumption currently used in the MED testing of soil is not necessarily valid
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