14,514 research outputs found
Safety and Mobility Impacts of Winter Weather – Phase I, August 2011
No full textHighway agencies spend millions of dollars to ensure safe and efficient winter travel. However, the effectiveness of winter weather maintenance practices on safety and mobility are somewhat difficult to quantify.
Phase I of this project investigated opportunities for improving traffic safety on state-maintained roads in Iowa during winter weather conditions.
The primary objective was to develop several preliminary means for the Iowa Department of Transportation (DOT) to identify locations of possible interest systematically with respect to winter weather-related safety performance based on crash history.
Specifically, metrics were developed to assist in identifying possible habitual, winter weather-related crash sites on state-maintained rural highways in Iowa. In addition, the current state of practice, for both domestic and international highway agency practices, regarding integration of traffic safety- and mobility-related data in winter maintenance activities and performance measures were investigated. This investigation also included previous research efforts.
Finally, a preliminary work plan, focusing on systematic use of safety-related data in support of winter maintenance activities and site evaluation, was prepared
Epistemology of modeling and simulation
No full textWhile ontology deals with the question of being or existence, epistemology deals with the question of gaining knowledge. This panel addresses the challenge of how we gain knowledge from modeling and simulation. What is the underlying philosophy of science of M&S? What are our canons of research for M&S? Is it sufficient to apply the foundational methods of the application domains, or do we need to address these questions from the standpoint of M&S as a discipline? The invited experts illuminate various facets from philosophical, mathematical, computational, and application viewpoints.Andreas Tolk, Brian L. Heath, Martin Ihrig, Jose J. Padilla, Ernest H. Page, E. Dante Suarez, Claudia Szabo, Paul Weirich, Levent Yilmazhttp://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=672139
Common Mode Currents in DC Power Routers
No full textThe grid reinforcement and energy redirection needs have led to the emergence of Back-To-Back Voltage Source Converter (BTB-VSC) based dc power routers. This paper investigates the low frequency Common Mode Currents (CMCs) that arise in the system if the employed BTB-VSCs have an un-isolated ac path connected in parallel to their output ports. Simulation results are presented to show a sensitivity analysis of lower order harmonics in CMC with respect to the operating active and reactive power of the dc router, dc link voltage, link resistance, modulation method and pole capacitance. Experimental results are shared to show existance of lower order CMC in 3-wire ac link operating in parallel with the dc power router and these are mitigated using zero sequence controller
IFN-DC have novel molecular, phenotypical and functional characteristics in comparison to IL-4/TNF-DC
No full text<p><b>Copyright information:</b></p><p>Taken from "Monocyte derived dendritic cells generated by IFN-α acquire mature dendritic and natural killer cell properties as shown by gene expression analysis"</p><p>http://www.translational-medicine.com/content/5/1/46</p><p>Journal of Translational Medicine 2007;5():46-46.</p><p>Published online 25 Sep 2007</p><p>PMCID:PMC2064912.</p><p></p> (a) Hierarchical cluster analysis of 52 genes related to NK cell function (rows) for IFN-DC and IL-4/TNF-DC preparations (columns) with expression levels obtained by Affymetrix microarray analysis. The colour scale indicates upregulation (green) and downregulation (red) of gene expression in relation to the mean expression levels of all preparations. (b) Corroboration of the microarray data by quantitative real-time PCR. The ΔCt values of 10 genes with β2-microglobulin as a reference gene were measured. Differences of the relative expression (mean ΔΔCt) of each gene were compared to the log2 of the fold change determined by microarray technology. (c) Expression of cytolytic effector molecules by DC. The intracellular expression of TRAIL and granzyme B by IFN-DC and IL-4/TNF-DC was analyzed by flow cytometry after permeabilization of cell membranes. The results are shown as mean ± SD of % positive cells. (d) Cytolytic activity of DC. Specific lysis of tumor cells by DC was measured by flow cytometric detection of propidium iodide uptake after coculture of 1 × 10CFDA-SE labeled K562 cells with different numbers of IFN-DC and IL-4/TNF-DC as indicated by the effector : target ratios. IL-2 activated NK-cells were used as a positive, and B cells as negative control. Significant differences between IFN-DC and IL-4/TNF-DC at different effector : target ratios are indicated by an asterisk (p < 0.05)
Modeling, Control, and Operation of an M-DAB DC-DC Converter for Interconnection of HVDC Grids
No full textFuture high-voltage direct-current (HVDC) networks based on voltage source converters (VSCs) will have different structures (asymmetric monopolar, bipolar, or symmetric monopolar), voltage levels, control, and protection schemes. Therefore, dc-dc converters are needed to interconnect those VSC-HVDC grids and several technical issues on their control and operational systems must be adequately addressed. A dc-dc converter based on a modular-dual active bridge (M-DAB) converter is suggested to reach a desirable interconnection of the HVDC grids and regulate power flow (PF) between them. A dynamic averaged model is proposed for the M-DAB converter and its stability is analyzed using the Lyapunov function. Moreover, a new local controller based on nonlinear control theory is proposed for the M-DAB. The new M-DAB local controller is integrated with the energy management system (EMS), by updating the PF equations, to create a complete control structure. Considering the CIGRE DCS3 HVDC test system and the studied M-DAB, static, dynamic simulation, and experimental studies are conducted and the dc-dc converter and the performance of the designed controllers and the EMS are examined and validated.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intelligent Electrical Power Grid
THE ECONOMICS OF CLEANING WINTER WHEAT FOR EXPORT: AN EVALUATION OF PROPOSED FEDERAL "CLEAN GRAIN" STANDARDS
No full textBuyer complaints about poor quality U.S. wheat have led to proposals to enforce minimum dockage standards for exports. An economic-engineering approach is used to evaluate costs and benefits of cleaning wheat in order to meet these standards for 13 possible cleaning configurations. These results are used in an optimization framework to estimate costs and benefits of cleaning all U.S. export wheat. The estimates indicate that cleaning U.S. export winter wheat to .35% dockage would cost an average of 1 cent/bu., requiring an initial capital investment of $28 million. Value of wheat lost in cleaning is a significant cost that previously has been overlooked.Agricultural and Food Policy,
Restructuring the existing medium voltage distribution grids using DC systems
No full textGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag
Cold cracking in DC-cast high strength aluminum alloy ingots: An intrinsic problem intensified by casting process parameters
No full textFor almost half a century the catastrophic failure of direct chill (DC) cast high strength aluminum alloys has been challenging the production of sound ingots. To overcome this problem, a criterion is required that can assist the researchers in predicting the critical conditions which facilitate the catastrophic failure of the ingots. This could be achieved at first glance by application of computer simulations to assess the level and distribution of residual thermal stresses. However, the simulation results are only able to show the critical locations and conditions where and when high stresses may appear in the ingots. The prediction of critical void/crack size requires simultaneous application of fracture mechanics. In this paper, we present the thermo-mechanical simulation results that indicate the critical crack size distribution in several DC-cast billets cast at various casting conditions. The simulation results were validated upon experimental DC-casting trials and revealed that the existence of voids/cracks with a considerable size is required for cold cracking to occur.Materials Science & EngineeringMechanical, Maritime and Materials Engineerin
An Investigation of User Costs and Benefits of Winter Road Closures, June 2005
No full textThis project explores the user costs and benefits of winter road closures. Severe winter weather makes travel unsafe and dramatically increases crash rates. When conditions become unsafe due to winter weather, road closures should allow users to avoid crash costs and eliminate costs associated with rescuing stranded motorists. Therefore, the benefits of road closures are the avoided safety costs. The costs of road closures are the delays that are imposed on motorists and motor carriers who would have made the trip had the road not been closed. This project investigated the costs and benefits of road closures and found that evaluating the benefits and costs is not as simple as it appears. To better understand the costs and benefits of road closures, the project investigates the literature, conducts interviews with shippers and motor carriers, and conducts case studies of road closures to determine what actually occurred on roadways during closures. The project also estimates a statistical model that relates weather severity to crash rates. Although, the statistical model is intended to illustrate the possibility to quantitatively relate measurable and predictable weather conditions to the safety performance of a roadway. In the future, weather conditions such as snow fall intensity, visibility, etc., can be used to make objective measures of the safety performance of a roadway rather than relying on subjective evaluations of field staff. The review of the literature and the interviews clearly illustrate that not all delays (increased travel time) are valued the same. Expected delays (routine delays) are valued at the generalized costs (value of the driver’s time, fuel, insurance, wear and tear on the vehicle, etc.), but unexpected delays are valued much higher because they result in interruption of synchronous activities at the trip’s destination. To reduce the costs of delays resulting from road closures, public agencies should communicate as early as possible the likelihood of a road closure
A Dynamically Reconfigurable Recursive Switched-Capacitor DC-DC Converter with Adaptive Load Ability Enhancement
No full textMultiple voltage conversion ratio (VCR) recursive switched-capacitor (SC) dc-dc converters, based on several basic 2:1 converters, are widely used for on-chip power supplies due to their flexible VCRs for higher energy efficiency. However, conventional multiple VCR SC converters usually have one or more 2:1 converters unused for some VCRs, which results in lower power density and chip area wastage. This article presents a new recursive dc-dc converter system, which can dynamically reconfigure the connection of all on-chip 2:1 converter cells so that the unused converters in the conventional designs can be reused in this new architecture for increasing the load-driving capacity, power density, and power efficiency. To validate the design, a 4-bit-input 15-ratio system was designed and fabricated in a 180-nm BCD process, which can support a maximum load current of \text{0.71}\,\text{mA} and achieves a peak power efficiency of 93.1% with 105.3\,\mu \text{A/mm} {2} chip power density from a 2-V input power supply. The measurement results show that the load-driving capacity can become 6.826×, 2.236×, and 2.175× larger than the conventional topology when the VCR is 1/2, 1/4, and 3/4, respectively. In addition, the power efficiency under these specific VCRs can also be improved considerably.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Instrumentatio
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