bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of spatial discretization and unsteadiness on the simulation of rocket combustors
Authors: Lempke Markus , Keller Roman , Gerlinger Peter 
Published: June 2015

SummaryThis paper investigates some important numerical aspects for the simulation of model rocket combustors. Precisely, (1) a new high‐order discretization technique (multi‐dimensional limiting process (MLP), low diffusion, and MLPld) is presented and compared with conventional second‐order schemes with different flux limiters. (2) Time accurate unsteady Reynolds‐averaged Navier–Stokes (RANS) simulations are performed to assess possible improvements in comparison with steady‐state RANS simulations. (3) Fully 3D simulations of an axisymmetric rocket combustor are compared with 2D axisymmetric ones. All studies are based on the Penn State preburner combustor experiment, which uses gaseous oxygen and hydrogen. This comprehensive study offers unique insight into how the mentioned numerical influence factors change the flow field, flame, and wall heat fluxes in the model rocket combustor. Because wall heat fluxes are known from the experiment only, numerical results are compared with LES of other authors, too. It will be shown that the high‐order spatial discretization significantly improves the agreement with measured wall heat fluxes at low additional computational cost. In general the transition from simple to more complex numerical approaches steadily improves the qualitative agreement between simulation and experiment. Copyright © 2015 John Wiley & Sons, Ltd.
Factors with an influence on the wear to excavation tools in hydroshield tunnelling in soft ground / Einflussfaktoren auf den Verschleiß der Abbauwerkzeuge beim Vortrieb mit Hydroschild‐TVM in Lockergesteinen
Authors: Köppl Florian , Thuro Kurosch , Thewes Markus 
Published: June 2015

AbstractThe wear to excavation tools is a central challenge for tunnelling with Hydroshield (TBM) in soft ground because it is one of the main causes of stoppages. Due to the inaccessibility of the processes involved and the wide range of influencing factors, there has been no method of forecasting the wear to excavation tools until now. Working from a detailed analysis of 18 tunnel drives with hydroshield TBMs, an empirical approach to investigate the factors with an influence on the wear to excavation tools was selected for the present work. The analysis enables the qualification and quantification of the essential factors with an influence on the tool life parameters of the excavation tools.Der Verschleiß der Abbauwerkzeuge ist eine zentrale Herausforderung beim Vortrieb mit Hydroschild‐TVM in Lockergesteinen, weil dieser eine Hauptursache für Vortriebsunterbrechungen ist. Bisher liegen aufgrund der Unzugänglichkeit der beteiligten Prozesse und der hohen Bandbreite an Einflussfaktoren keine Prognosemethoden für den Verschleiß der Abbauwerkzeuge vor. Mit der detaillierten Analyse von 18 Vortrieben mit Hydroschild‐TVM wurde für die vorliegende Arbeit ein empirischer Ansatz zur Untersuchung der Einflussfaktoren auf den Verschleiß der Abbauwerkzeuge gewählt. Die Analyse erlaubt die Qualifizierung und Quantifizierung der maßgeblichen Einflussfaktoren auf die Standgrößen der Abbauwerkzeuge.
Strain gauges in pre‐cast concrete segments: working principle, evaluation and interpretation / Dehnmessgeber in Tübbingsegmenten – Funktionsweise, Auswertung und Interpretation
Authors: Radončić Nedim , Kern Martin , Weissnar Martin , Moritz Bernd 
Published: June 2015

AbstractIn order to obtain an enhanced understanding of the system behaviour, especially with regard to the capacity reserves of the support and general load conditions, measurement pre‐cast concrete rings are used at the ÖBB construction lot KAT2 of the Koralm Tunnel. These are equipped with a strain gauge in each reinforcement layer, thus allowing direct measurement of the strains in every pre‐cast concrete segment.Based on this information, the stress distribution in the respective segment cross‐section can be calculated, allowing section forces determination by integrating them. The used interpolation method allows the presentation of the section forces over circumference of the entire ring based on the measurement data of each segment, while obeying the constraints by the issue of longitudinal joint capacity.The applied calculation method is verified by comparing its results with a numerical 3D analysis. The application of the method is presented by a case study of the measurement ring installation at the ÖBB construction lot KAT2 of the Koralm Tunnel. In addition, further room for research and development is briefly outlined.Um ein besseres Verständnis des Systemverhaltens – speziell im Hinblick auf die Auslastung des Ausbaus und der vorherrschenden Belastungssituation – zu erhalten, werden beim TVM‐Vortrieb auf dem Baulos Koralmtunnel 2 (KAT2) der ÖBB‐Infrastruktur AG Tübbingsegmente mit Dehnmessgebern, sogenannte Messtübbinge, verwendet. Diese sind mit Dehnmessgebern in beiden Bewehrungslagen, in denen die Dehnungen direkt gemessen werden, ausgestattet.Anhand dieser Daten kann die Spannungsverteilung im jeweiligen Tübbingquerschnitt errechnet und in weiterer Folge können über Integration die Schnittkräfte ermittelt werden. Die verwendete Interpolationsmethode ermöglicht, unter Berücksichtigung der Längsfugenbelastbarkeit, die Darstellung der Schnittkräfte über den gesamten Umfang des Tübbingrings, ausgehend von den Ergebnissen an der jeweiligen Position der Dehnmessgeber.Die angewandte Berechnungsmethode wird zur Verifizierung mit den Resultaten einer numerischen 3D‐Berechnung verglichen. Die Anwendung dieser Methodik wird anhand eines Fallbeispiels an einem Messtübbingring, der am Baulos KAT2 eingebaut wurde, vorgestellt. Zusätzlich wird noch kurz auf ausstehende Forschungsthemen und Entwicklungen eingegangen.
Wear and abrasivity: observations from EPB drives in mixed soft – rock sections
Authors: González Claudia , Arroyo Marcos , Gens Antonio 
Published: June 2015

AbstractThis paper summarizes the main observations related to geotechnical properties and tool changes that characterize the different tunnel drives in a database of 33 km of EPB tunnel records from the Barcelona area. The data have been examined in detail with regard to cutting tool replacement and performance of the mechanized excavation. The database includes tunnels in soft soils, in hard and medium rocks and in mixed soil‐rock conditions; tool changing records and geotechnical properties. Transverse and longitudinal geotechnical heterogeneity are accounted for systematically. Longitudinal heterogeneity is used to subdivide the drives in the database into homogeneous units. Transverse (within section) heterogeneity is described by a set of newly developed impact factors FI.
A simple approach based on the limit equilibrium method for evaluating passive earth pressure coefficients
Authors: Patki Mrunal A. , Mandal Jnanendra Nath , Dewaikar Dileep Moreshwar 
Published: June 2015

AbstractA numerical method is developed for evaluating critical passive earth pressure coefficients Kpγ for the case of an inclined rigid retaining wall resting against sloping cohesionless backfill. The methodology of the proposed investigation is based on the limit equilibrium approach with the assumption of a complete log spiral failure mechanism. The Kpγ coefficients obtained from this study are compared with the existing theoretical and experimental results. The proposed Kpγ values are on a par with the best upper bound solution given by Soubra and Macuh using the limit analysis method. Further, the results presented here compare fairly well with those given by Kerisel and Absi, which establishes the validity of the proposed research work. Efforts are taken to present the design tables for a wide variety of soil properties, soil‐wall interface properties and geometrical properties of the wall and the backfill.Ein einfacher Ansatz zur Bestimmung von Erdwiderstandsbeiwerten auf Basis der Methode des Grenzgleichwichts. Eine numerische Methode zur Bestimmung des kritischen Erdwiderstandsbeiwerts Kpγ wird entwickelt für den Fall einer geneigten, steifen Verbauwand vor geböschtem, kohäsionslosem Erdreich. Die Methodik der vorgeschlagenen Untersuchung basiert dabei auf dem Ansatz des Grenzgleichgewichts unter Annahme eines Versagensmechanismus mit logarithmischer Spiralform. Der mittels dieser Studie bestimmte Kpγ‐Beiwert wird mit vorhandenen theoretischen und experimentellen Ergebnissen verglichen. Es wird gezeigt, dass die vorgeschlagenen Werte für Kpγ den Werten der besten Lösung unter Verwendung des Obere‐Schranken‐Theorems nach Soubra und Macuh entsprechen, welche mit Hilfe einer Grenzwertanalyse ermittelt wurde. Darüber hinaus stimmen die hier präsentierten Ergebnisse gut mit denen von Kerisel und Absi überein, was die Gültigkeit der vorgeschlagenen Vorgehensweise belegt. Bemessungstafeln für eine große Anzahl an Bodenparametern, Boden‐Wand‐Interface Parametern und geometrischen Parametern der Wand sowie des abzustützenden Erdreichs werden eingeführt.
Hangsicherung Roggwil‐Wynau: Stabilisierung eines seit 150 Jahren bekannten Rutschhangs
Authors: Irngartinger Stefan , Steiner Walter 
Published: June 2015

AbstractLängs der Neubaustrecke zwischen Bern und Zürich musste bei Roggwil‐Wynau ein seit mehreren Jahrzehnten bekannter Rutschhang saniert werden, da die Deformationen das tolerierbare Maß überschritten hatten. Durch die intensive Überwachung der Wasserdruckverhältnisse wurde die Ursache der Deformationen in bis 30 mWS artesisch gespanntem Bergwasser (75 mWS totales Druckniveau) erkannt. Vorangegangene Versuche, den Hang mittels Rückverankerungen zu sichern, schlugen fehl. Rückrechnungen belegten die ausreichende Hangstabilität bei Reduktion des einwirkenden Bergwasserdrucks. Als Sanierungsmaßnahme wurden drei 15 m tiefe Dränageschächte ausgeführt, die durch einen Mikrotunnel miteinander verbunden und an den Vorfluter angebunden worden sind. Aus den Schächten sind anschließend bis zu 50 m lange Horizontalfilterbrunnen hergestellt worden, die das Bergwasser abführen. Durch die Maßnahme konnte der Bergwasserdruck um 30 mWS abgesenkt werden; es werden etwa 120 l/min dauerhaft dräniert. Infolge der Dränagemaßnahme kam es aufgrund der Spannungsumlagerung im Boden anfänglich zu einer Erhöhung der Deformationen. Seit etwa sechs Monaten nach Abschluss der Maßnahme verhält sich der Hang stabil, und es können keine signifikanten Deformationen mehr aufgezeichnet werden. Das Fallbeispiel verdeutlicht den maßgeblichen Einfluss der Porenwasserdruckverhältnisse auf die Hangstabilität und zeigt, dass Sanierungsmaßnahmen meist nur bei Reduktion der Einwirkungen erfolgreich sind.Stabilization of the long known landslide in Roggwil‐Wynau (Switzerland). Along the new railway line between Bern and Zürich a landslide known for several decades had to be redeveloped because the deformations had exceeded the tolerable level. The cause of the deformations in up to 30 mWS artesian mountain water (up to 75 mWS total pressure level) has been detected by intensive monitoring of water pressure conditions. Previous attempts to stabilize the slope by anchors failed. Re‐analyses confirmed the adequate slope stability by reducing the acting pore‐water pressure. As a redevelopment measure three 15 m deep drainage shafts were carried out, which have been joined by a micro‐tunnel and connected to the main outfall. Afterwards up to 50‐m‐long horizontal filter wells have been drilled which lead away the mountain water. Through the measure the hydraulic pressure could be lowered by 30 mWS; about 120 l / min are drained permanently. Through the drainage action stress redistribution occurred which caused at the first time an increase in deformation. For about six months after the end of the measure, the slope behaves stable and no significant deformations longer be recorded. The case study illustrates the significant influence of pore water pressure ratio on slope stability and shows that remediation measures are usually only successful in reducing the impacts.
Besonderheiten bei der Planung und Berechnung von oberflächennahen thermo‐aktiven Bauteilen
Authors: Kürten Sylvia , Mottaghy Darius , Ziegler Martin 
Published: June 2015

AbstractDie thermische Nutzung des Untergrunds mit sogenannten thermo‐aktiven Bauteilen ist eine zukunftsorientierte Möglichkeit zur Klimatisierung von Gebäuden. In diesem Zusammenhang ist der Energiepfahl das weltweit am weitesten verbreitete System. Flächige Bauteile, wie beispielsweise Verbau‐ oder Kellerwände verfügen jedoch durch ihre große Kontaktfläche zum Untergrund ebenfalls über ein großes Energiepotenzial. Derzeit fehlen jedoch für flächige Bauteile geeignete Berechnungsansätze, wodurch die Verbreitung dieser Technologie derzeit erschwert ist. Am Lehrstuhl für Geotechnik im Bauwesen der RWTH Aachen wurde daher in Zusammenarbeit mit der Geophysica Beratungsgesellschaft ein entsprechender Berechnungsansatz entwickelt und in die Software SHEMAT‐Suite implementiert. In dem semi‐analytischen Ansatz werden alle Wärmetransportvorgänge im Bauteil und im Absorbersystem durch eine Verschaltung von thermischen Widerständen abgebildet, während für die Abbildung des Untergrunds die Finite‐Differenzen‐Methode verwendet wird (Modell‐in‐Modell‐Ansatz). Mit diesem Ansatz ist es nun möglich, alle relevanten Faktoren sowie deren Interaktion in der Systemplanung zu berücksichtigen und eine standortspezifische und systemangepasste Anlagenplanung durchzuführen. Mit dem neuen Berechnungsansatz wurde eine umfangreiche Parameterstudie durchgeführt, mithilfe derer die maßgebenden Einflussfaktoren auf den Wärmeentzug ermittelt wurden. Als Ergebnis konnten darüber hinaus Handlungsempfehlungen für die konstruktive Durchbildung des Bauteils und den Anlagenbetrieb abgeleitet werden.Design of near‐surface energy geostructures. Energy geostructures (thermo‐active elements) are an up‐coming technique for the thermal utilisation of the ground. Currently, the energy pile is the most known and used energy geostructure in Europe and all over the world. Nevertheless, plane geostructures such as basement or retaining walls have a large energy potential due to their large contact area to the ground. However, no suitable calculation approaches exists for the design of plane energy geostructures. The chair of geotechnical engineering (RWTH Aachen University) in cooperation with Geophysica Beratungsgesellschaft mbH (Aachen) developed an appropriate calculation approach. This approach, which is based on thermal resistances, was implemented in the finite difference code SHEMAT‐Suite. So it is possible to consider all important factors and their interaction. The new model was used for an extensive parameter study. As a result, the flow rate in the heat exchanging system, the ground temperature, the groundwater flow, the pipe arrangement in the structural element and the structure of the element were identified as the decisive parameters.
The Shifting of Directors' Duties in the Vicinity of Insolvency
Authors: Keay Andrew 
Published: June 2015

AbstractDirectors are obviously critical to the management of companies, and perhaps even more so when a company is in financial difficulties. This paper examines the position of directors when their company is in the vicinity of insolvency. It provides an analytical exposition of the law that exists in common law jurisdictions where, in the vicinity of insolvency, there is a shift in the nature of the duties of its directors, namely, directors have to take into account the interest of the creditors when exercising their powers and discharging their duties. The paper endeavours to identify and discuss the main problems that exist with this shift in the nature of duties so that if other jurisdictions do consider implementing it, they are aware of the drawbacks and may be able to address them. Copyright © 2015 INSOL International and John Wiley & Sons, Ltd
The Effect of Design Parameters of an Irrigation Canal on Tuning of Coefficients and Performance of a PI Controller
Authors: Zamani Shahla , Parvaresh Rizi Atefeh , Isapoor Saeed 
Published: June 2015

AbstractThe performance and operation of irrigation networks can be improved using canal automation. This process requires the application of control systems. At the same time, the PI controller has been employed in different areas of the world. However, its adjustment for the different geometric and hydraulic conditions of canals is still considered a major problem for design. The design parameters of a canal such as bottom slope, roughness coefficient and side slope are among the determining factors of water flow dynamic behaviour. In this study, a distant downstream proportional integral feedback control with decouplers is designed for a base canal. By changing the value of design parameters in this canal, their effects on water flow behaviour and controller tuning were investigated. Canal characteristics were determined through a system identification process, and were also used to tune the controller. To simulate the control algorithms and evaluate their performance, a link of the SOBEK model and MATLAB software were used. To evaluate the performance of a well‐tuned controller during a given operation period, the maximum absolute error, integral of absolute magnitude of error and steady‐state error indicators were used. Generally, the result showed the bottom slope to have the most effect on water flow behaviour and tuning of the control algorithm. The effect of the roughness coefficient on the control algorithm and its performance is also more noticeable than the side slope. Copyright © 2015 John Wiley & Sons, Ltd.
What Does It Take to Collaborate?
Authors: Weninger Csilla , Singh Jasvindar S. , Loi Irene 
Published: June 2015

AbstractIn this commentary, the authors share insights from a collaborative project in Singapore among secondary school teachers, academics from the National Institute of Education, and the Singapore Ministry of Education. The authors highlight that the success of this collaboration was facilitated by significant institutional support at all levels and participants’ willingness to negotiate professional backgrounds, goals, and personalities.
Accelerated tissue integration into porous materials by immobilizing basic fibroblast growth factor using a biologically safe three‐step reaction
Authors: Kakinoki Sachiro , Sakai Yusuke , Fujisato Toshia , Yamaoka Tetsuji 
Published: June 2015

ABSTRACTSoft tissue integration into a porous structure is important to prevent bacterial infection of percutaneous devices and improve tissue regeneration using porous scaffolds. Here, basic fibroblast growth factor (bFGF) was immobilized on porous polymer materials using a mild and biologically safe three‐step reaction: (1) modification with a novel surface‐modification peptide (penta‐lysine‐mussel adhesive sequence, which reacts with various matrices), (2) electrostatic binding of heparin with introduced penta‐lysine, and (3) biologically specific binding of bFGF to heparin. Porous polyethylene specimens (PPSs) (D =6.0 mm,H = 2.0 mm) with a good size for tissue integration were selected as a base material, immobilized with bFGF, and subcutaneously implanted into mice. Half of the unmodified PPSs extruded out of the body on day 112 postimplantation; however, the three‐step reaction completely prevented sample rejection. Tissue integration was greatly accelerated by immobilizing bFGF. Direct physical coating of bFGF on PPS resulted in greater immobilization but lesser tissue integration than that after the three‐step bFGF immobilization, indicating that heparin binds and enhances bFGF efficacy. This three‐step bFGF immobilization reaction will be applicable to various polymeric, metallic, and ceramic materials and is a simple strategy to integrate tissue on porous medical devices or scaffolds for tissue regeneration. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 3790–3797, 2015.
Comparison of erythropoietin resistance in hemodialysis patients using calcitriol, cinacalcet, or paricalcitol
Authors: Afsar Baris , Agca Erhan , Turk Suleyman 
Published: June 2015

AbstractThe erythropoiesis‐stimulating agent (ESA) hyporesponsiveness index (EHRI) calculated as the weekly dose of EPO divided by weight (kg) divided by hemoglobin level (g/dL) has been considered useful to assess ESA resistance. Recent evidence suggests that active vitamin D, cinacalcet, and paricalcitol use may be related with lower ESA resistance. We conducted this observational cross‐sectional study to investigate ESA resistance calculated by the EHRI among patients using calcitriol, cinacalcet, and paricalcitol. Participants underwent a medical history taken, physical examination, measurement of biochemical analysis, calculation of dialysis adequacy, and EHRI. Sixty‐five patients did not receive any treatment regarding vitamin D, paricalcitol, and cinacalcet (group 1), 41 were taking only vitamin D (group 2), 50 were taking only paricalcitol (group 3), 19 were taking only cinacalcet (group 4), and 21 were taking paricalcitol + cinacalcet (group 5). The EHRI values for groups 1, 2, 3, 4, and 5 were 11.36 ± 8.72, 11.58 ± 5.72, 8.29 ± 5.54, 9.49 ± 4.61, and 8.91 ± 4.44 respectively (P =.034). Post hoc analysis showed that the EHRI differed between group 1 and group 3 (P =.017) and between group 2 and group 3 (P =.006). In linear regression analysis, use of paricalcitol was independently associated with EHRI. In conclusion, paricalcitol use was associated with lower EHRI levels as a measure of ESA resistance.
Quinine as a potential tracer for medication adherence: A pharmacokinetic and pharmacodynamic assessment of quinine alone and in combination with oxycodone in humans
Authors: Babalonis Shanna , Hampson Aidan J. , Lofwall Michelle R. , Nuzzo Paul A. , Walsh Sharon L. 
Published: June 2015

AbstractEffective strategies to monitor pharmacotherapy adherence are necessary, and sensitive biological markers are lacking. This study examined a subtherapeutic dose of quinine as a potential adherence tracer. Primary aims included examination of the plasma and urinary pharmacokinetic profile of once‐daily quinine; secondary aims assessed pharmacokinetic/pharmacodynamic interactions with oxycodone (a CYP3A and CYP2D substrate). Healthy, nondependent opioid users (n = 9) were enrolled in this within‐subject, double‐blind, placebo‐controlled inpatient study. Participants received the following oral doses: day 1, oxycodone (30 mg); days 2–4, quinine (80 mg); day 5, quinine and oxycodone (2 hours postquinine). Blood and 24‐hour urine samples were collected throughout the study, and pharmacodynamic outcomes were assessed during experimental sessions (days 1, 4, 5). Quinine displayed a plasma Tmax ∼2 hours and t1/2 ∼10 hours. Oxycodone and noroxycodone parameters (Tmax, Cmax, t1/2) were similar with or without quinine present, although drug exposure (AUC) was slightly greater when combined with quinine. No pharmacodynamic interactions were detected, and doses were safely tolerated. During washout, quinine urinary concentrations steadily declined (elimination t1/2 ∼16 hours), with a 94% decrease observed 72 hours postdose. Overall, low‐dose quinine appears to be a good candidate for a medication additive to monitor adherence for detection of missed medication.