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- Patriksson, Michael, 1964, et al.
(author)
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Traffic management through link tolls - An approach utilizing side constrained traffic equilibrium models
- 1997
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In: Rendiconti del Circolo Matematico di Palermo, Serie II. ; 48, s. 147-170
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Journal article (peer-reviewed)abstract
- We propose a systematic means for achieving a set of overall traffic management or planning goals with respect to the performance of the traffic network through the use of link tolls. The primary goals are defined by a set of link flow restrictions. The tolls that achieve these goals are obtained by solving a generalization of the classical user equilibrium model which includes a set of side constraints on the link flows. The set of toll prices obtained is not necessarily unique; this fact enables the traffic planner to choose a toll scheme which satisfies exogenous constraints and which may optimize a secondary goal, such as with respect to the toll itself. The overall model is derived as a special case of a mathematical program with equilibrium constraints (MPEC) describing a Stackelberg game involving the traffic manager and the users of the network. The model is shown to yield valuable information also in the case where the management goals and exogenous toll constraints are inconsistent with each other or with the underlying network. We give several examples of possible applications of the model, including the achievement of a system optimal flow and the derivation of actions for making public transport more attractive, and propose a conceptual algorithm for solving it. The paper is hoped to provoke continued research in both theoretical and applied directions.
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- Yang, Junfeng, 1979
(author)
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Bio-diesel Spray Combustion Modeling Based on a Detailed Chemistry Approach
- 2010
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Licentiate thesis (other academic/artistic)abstract
- The increased use of bio-diesel fuel is expected to reduce emissions of carbon-containing greenhouse gases. To optimize the application of bio-diesel in internal combustion engines, a theoretical model has been developed. The bio-diesel fuels used in the modeling are Palm Methyl Ether (PME, C17H34O2) and Rapeseed Methy Ether (RME, C19H36O2), and blends of these methyl ethers with standard diesel oil. The thermo-physical properties of these bio-diesel fuels have been estimated using empirically determined thermodynamic, gas phase formulae. The description of their combustion processes has been based on the assumption that long chain methyl esters (C17~C19) decompose into short-chain methyl esters (C5}~ C11), for which combustion mechanisms are available. A comprehensive integrated chemical mechanism (with 98 species involving 395 reactions) was constructed to model the combustion of diesel oil surrogate, DOS, PME and RME. The bio-diesel fuels' physical properties and combustion mechanisms were validated using measured auto-ignition delays and laminar flame speeds. The bio-diesels physical properties and combustion mechanism were implemented into KIVA3V, rel.2 code. The KIVA3V fuel model was also extended to include mixing rules approach to calculate properties of blends of the fuel, e.g. RME50.Models of sprays of the fuels were validated against data acquired using observations of sprays in the Chalmers High Pressure /High Temperature (HP/HT) spray chamber. The liquid penetration, and average Sauter Mean Radius, SMR, for sprays of the different fuels were calculated and compared.To study the effect of bio-diesel fuels on the performance of engines, 3D CFD simulations of both a heavy duty engine (Volvo D12C) and a light duty engine (Volvo NED5) were carried our under various operating conditions. The combustion processes of the DOS and PME fuels in the NED5 engine were studied, and those of DOS, RME and RME50 in the Volvo D12C engine. Reasonable agreement between modelled and empirical in-cylinder parameters has been achieved.
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- Demirel, Isak, 1987-, et al.
(author)
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Nitric oxide activates IL-6 production and expression in human renal epithelial cells
- 2012
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In: American Journal of Nephrology. - Basel, Switzerland : S. Karger. - 0250-8095 .- 1421-9670. ; 36:6, s. 524-530
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Journal article (peer-reviewed)abstract
- Background/Aims: Increased nitric oxide (NO) production or inducible form of NO synthase activity have been documented in patients suffering from urinary tract infection (UTI), but the role of NO in this infection is unclear. We investigated whether NO can affect the host response in human renal epithelial cells by modulating IL-6 production and mRNA expression. Methods: The human renal epithelial cell line A498 was infected with a uropathogenic Escherichia coli (UPEC) strain and/or the NO donor DETA/NO. The IL-6 production and mRNA expression were evaluated by ELISA and real-time RT-PCR. IL-6 mRNA stability was evaluated by analyzing mRNA degradation by real-time RT-PCR.Results: DETA/NO caused a significant (p < 0.05) increase in IL-6 production. Inhibitors of p38 MAPK and ERK1/2 signaling, but not JNK, were shown to significantly suppress DETA/NO-induced IL-6 production. UPEC-induced IL-6 production was further increased (by 73 ± 23%, p < 0.05) in the presence of DETA/NO. The IL-6 mRNA expression increased 2.1 ± 0.17-fold in response to DETA/NO, while the UPEC-evoked increase was pronounced (20 ± 4.5-fold). A synergistic effect of DETA/NO on UPEC-induced IL-6 expression was found (33 ± 7.2-fold increase). The IL-6 mRNA stability studies showed that DETA/NO partially attenuated UPEC-induced degradation of IL-6 mRNA.Conclusions: NO was found to stimulate IL-6 in renal epithelial cells through p38 MAPK and ERK1/2 signaling pathways and also to increase IL-6 mRNA stability in UPEC-infected cells. This study proposes a new role for NO in the host response during UTI by modulating the transcription and production of the cytokine IL-6.
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- Elkotob, Muslim, et al.
(author)
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Challenges and opportunities in content distribution networks: A case study
- 2012
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In: Proceedings of the 2012 IEEE Globecom Workshops (GC Wkshps). - : IEEE Communications Society. - 9781467349413 ; , s. 1021-1026
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Conference paper (peer-reviewed)abstract
- In this paper we present some contemporary examples of research-oriented as well as commercial content delivery networks (CDN)s. We discuss how both types of CDNs complement each other in tackling the posed technical and commercial challenges. We also show which performance metrics such as quality of experience (QoE) and time to first byte (TTFB) best capture the dynamics of traffic and services in CDNs. The core of this paper is our proposed network architecture for CDN providers/operators. The architecture combines video multicast optimized trees and cross-layer coordination between the physical DWDM layer (L1) and network layer (L3) for achieving higher efficiency and lower latency values for live streaming and on demand (VoD) video. Due to the pilot implementation of the presented concept being limited in scale, we use simulations in order to perform proof-of-concept on a sufficiently large environment. Results show that there is a strong correlation between the TTFB and QoE metrics with the former taking on values as low as 75 msec in a national 3-tier network.
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- Lu, Yu-Chiao, et al.
(author)
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Applications of Hydrochar and Charcoal in the Iron and Steelmaking Industry—Part 1: Characterization of Carbonaceous Materials
- 2022
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In: Sustainability. - Basel, Switzerland : MDPI. - 2071-1050. ; 14:15, s. 9488-9488
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Journal article (peer-reviewed)abstract
- The iron and steelmaking industry faces the dilemma of the need to decrease their greenhouse gas emissions to align with decarbonization goals, while at the same time fulfill the increasing steel demand from the growing population. Replacing fossil coal and coke with biomass-based carbon materials reduces the net carbon dioxide emissions. However, there is currently a shortage of charcoal to fully cover the demand from the iron and steelmaking industry to achieve the emission-reduction goals. Moreover, the transportation and energy sectors can compete for biofuel usage in the next few decades. Simultaneously, our society faces challenges of accumulation of wastes, especially wet organic wastes that are currently not reused and recycled to their full potentials. Here, hydrothermal carbonization is a technology which can convert organic feedstocks with high moisture contents to solid fuels (hydrochar, one type of biochar) as an alternative renewable carbon material. This work studied the differences between a hydrochar, produced from lemon peels (Lemon Hydrochar), and two types of charcoals (with and without densification) and an Anthracite coal. Characterizations such as chemical and ash compositions, thermogravimetric analyses in nitrogen and carbon dioxide atmospheres, scanning electron microscope analyses of carbon surface morphologies, and pyrolysis up to 1200 °C were performed. The main conclusions from this study are the following: (1) hydrochar has a lower thermal stability and a higher reactivity compared to charcoal and Anthracite; (2) densification resulted in a reduction of the moisture pickup and CO2 reactivity of charcoal; (3) pyrolysis of Lemon Hydrochar resulted in the formation of a large amount of tar (17 wt%) and gas (39 wt%), leading to its low fixed carbon content (27 wt%); (4) a pyrolyzed hydrochar (up to 1200 °C) has a comparable higher heating value to those of charcoal and Anthracite, but its phosphorous, ash, and alkalis contents increased significantly; (5) based on the preliminary assessment, hydrochar should be blended with charcoal or Anthracite, or be upgraded through slow pyrolysis to fulfill the basic functions of carbon in the high-temperature metallurgical processes.
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| 10. |
- Hickery, Mark, et al.
(author)
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Age-related changes in the response of human articular cartilage to IL-1 alpha and transforming growth factor-beta (TGF-beta) - Chondrocytes exhibit a diminished sensitivity to TGF-beta
- 2003
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In: Journal of Biological Chemistry. - 1083-351X. ; 278:52, s. 53063-53071
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Journal article (peer-reviewed)abstract
- Cartilage glycosaminoglycan (GAG) synthesis and composition, upon which its structural integrity depends, varies with age, is modified by anabolic and catabolic stimuli, and is regulated by UDP-glucuronate availability. However, how such stimuli, prototypically represented by transforming growth factor-beta1 (TGF-beta1) and IL-1alpha, modify GAG synthesis during aging of normal human articular cartilage is not known. Using explants, we show that chondroitin sulfate (CS): total GAG ratios decrease, whereas C6S:C4S ratios increase with cartilage maturation, and that chondrocytes in the cartilage mid-zone, but not the superficial or deep zones, exhibit uridine 5'-diphosphoglucose dehydrogenase (UDPGD) activity, which is also increased in mature cartilage. We also show that IL-1alpha treatment reduces both total GAG and CS synthesis, decreases C6S: C4S ratios (less C6S), but fails to modify chondrocyte UDPGD activity at all ages. On the other hand, TGF-beta1 increases total GAG synthesis in immature, but not mature, cartilage (stimulates CS but not non-CS), age-independently decreases C6S:C4S (more C4S), and increases chondrocyte UDPGD activity in a manner inversely correlated with age. Our findings show that TGF-beta1, but not IL-1alpha, modifies matrix synthesis such that its composition more closely resembles "less mature" articular cartilage. These effects of TGF-beta1, which appear to be restricted to periods of skeletal immaturity, are closely associated although not necessarily mechanistically linked with increases in chondrocyte UDPGD activity. The antianabolic effects of IL-1alpha are, on the other hand, likely to be independent of any direct modification in UDPGD activity and manifest equally in human cartilage of all ages.
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