bluuebunny/crossref_metadata_2025_split huggingface dataset:
Global MHD simulations of Mercury's magnetosphere with coupled planetary interior: Induction effect of the planetary conducting core on the global interaction
Authors: Jia Xianzhe , Slavin James A. , Gombosi Tamas I. , Daldorff Lars K. S. , Toth Gabor , van der Holst Bart 
Published: June 2015

AbstractMercury's comparatively weak intrinsic magnetic field and its close proximity to the Sun lead to a magnetosphere that undergoes more direct space‐weathering interactions than other planets. A unique aspect of Mercury's interaction system arises from the large ratio of the scale of the planet to the scale of the magnetosphere and the presence of a large‐size core composed of highly conducting material. Consequently, there is strong feedback between the planetary interior and the magnetosphere, especially under conditions of strong external forcing. Understanding the coupled solar wind‐magnetosphere‐interior interaction at Mercury requires not only analysis of observations but also a modeling framework that is both comprehensive and inclusive. We have developed a new global MHD model for Mercury in which the planetary interior is modeled as layers of different electrical conductivities that electromagnetically couple to the surrounding plasma environment. This new modeling capability allows us to characterize the dynamical response of Mercury to time‐varying external conditions in a self‐consistent manner. Comparison of our model results with observations by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft shows that the model provides a reasonably good representation of the global magnetosphere. To demonstrate the capability to model induction effects, we have performed idealized simulations in which Mercury's magnetosphere is impacted by a solar wind pressure enhancement. Our results show that due to the induction effect, Mercury's core exerts strong global influences on the way Mercury responds to changes in the external environment, including modifying the global magnetospheric structure and affecting the extent to which the solar wind directly impacts the surface. The global MHD model presented here represents a crucial step toward establishing a modeling framework that enables self‐consistent characterization of Mercury's tightly coupled planetary interior‐magnetosphere system.
UV solar irradiance in observations and the NRLSSI and SATIRE‐S models
Authors: Yeo K. L. , Ball W. T. , Krivova N. A. , Solanki S. K. , Unruh Y. C. , Morrill J. 
Published: June 2015

AbstractTotal solar irradiance and UV spectral solar irradiance has been monitored since 1978 through a succession of space missions. This is accompanied by the development of models aimed at replicating solar irradiance by relating the variability to solar magnetic activity. The Naval Research Laboratory Solar Spectral Irradiance (NRLSSI) and Spectral And Total Irradiance REconstruction for the Satellite era (SATIRE‐S) models provide the most comprehensive reconstructions of total and spectral solar irradiance over the period of satellite observation currently available. There is persistent controversy between the various measurements and models in terms of the wavelength dependence of the variation over the solar cycle, with repercussions on our understanding of the influence of UV solar irradiance variability on the stratosphere. We review the measurement and modeling of UV solar irradiance variability over the period of satellite observation. The SATIRE‐S reconstruction is consistent with spectral solar irradiance observations where they are reliable. It is also supported by an independent, empirical reconstruction of UV spectral solar irradiance based on Upper Atmosphere Research Satellite/Solar Ultraviolet Spectral Irradiance Monitor measurements from an earlier study. The weaker solar cycle variability produced by NRLSSI between 300 and 400 nm is not evident in any available record. We show that although the method employed to construct NRLSSI is principally sound, reconstructed solar cycle variability is detrimentally affected by the uncertainty in the SSI observations it draws upon in the derivation. Based on our findings, we recommend, when choosing between the two models, the use of SATIRE‐S for climate studies.
Relationships between convective structure and transport of aerosols to the upper troposphere deduced from satellite observations
Authors: Chakraborty Sudip , Fu Rong , Wright Jonathon S. , Massie Steven T. 
Published: June 2015

AbstractWe estimate the extent of upper tropospheric aerosol layers (UT ALs) surrounding mesoscale convective systems (MCSs) and explore the relationships between UT AL extent and the morphology, location, and developmental stage of collocated MCSs in the tropics. Our analysis is based on satellite data collected over equatorial Africa, South Asia, and the Amazon basin between June 2006 and June 2008. We identify substantial variations in the relationships between convective properties and aerosol transport by region and stage of convective development. The most extensive UT ALs over equatorial Africa are associated with mature MCSs, while the most extensive UT ALs over South Asia and the Amazon are associated with growing MCSs. Convective aerosol transport over the Amazon is weaker than that observed over the other two regions despite similar transport frequencies, likely due to the smaller sizes and shorter mean lifetimes of MCSs over the Amazon. Variations in UT ALs in the vicinity of tropical MCSs are primarily explained by variations in the horizontal sizes of the associated MCSs and are largely unrelated to aerosol loading in the lower troposphere. We also identify potentially important relationships with the number of convective cores, vertical wind shear, and convective fraction during the growing and mature stages of MCS development. Relationships between convective properties and aerosol transport are relatively weak during the decaying stage of convective development. Our results provide an interpretive framework for devising and evaluating numerical model experiments that examine relationships between convective properties and ALs in the upper troposphere.
Comparison of “warm and wet” and “cold and icy” scenarios for early Mars in a 3‐D climate model
Authors: Wordsworth Robin D. , Kerber Laura , Pierrehumbert Raymond T. , Forget Francois , Head James W. 
Published: June 2015

AbstractWe use a 3‐D general circulation model to compare the primitive Martian hydrological cycle in “warm and wet” and “cold and icy” scenarios. In the warm and wet scenario, an anomalously high solar flux or intense greenhouse warming artificially added to the climate model are required to maintain warm conditions and an ice‐free northern ocean. Precipitation shows strong surface variations, with high rates around Hellas basin and west of Tharsis but low rates around Margaritifer Sinus (where the observed valley network drainage density is nonetheless high). In the cold and icy scenario, snow migration is a function of both obliquity and surface pressure, and limited episodic melting is possible through combinations of seasonal, volcanic, and impact forcing. At surface pressures above those required to avoid atmospheric collapse (∼0.5 bar) and moderate to high obliquity, snow is transported to the equatorial highland regions where the concentration of valley networks is highest. Snow accumulation in the Aeolis quadrangle is high, indicating an ice‐free northern ocean is not required to supply water to Gale crater. At lower surface pressures and obliquities, both H2O and CO2are trapped as ice at the poles and the equatorial regions become extremely dry. The valley network distribution is positively correlated with snow accumulation produced by the cold and icy simulation at 41.8∘obliquity but uncorrelated with precipitation produced by the warm and wet simulation. Because our simulations make specific predictions for precipitation patterns under different climate scenarios, they motivate future targeted geological studies.
An analytical framework for flood water conservation considering forecast uncertainty and acceptable risk
Authors: Ding Wei , Zhang Chi , Peng Yong , Zeng Ruijie , Zhou Huicheng , Cai Ximing 
Published: June 2015

AbstractThis paper addresses how much flood water can be conserved for use after the flood season through the operation of reservoir by taking into account the residual flood control capacity (the difference between flood conveyance capacity and the expected inflow in a lead time). A two‐stage model for dynamic control of the flood‐limited water level (the maximum allowed water level during the flood season, DC‐FLWL) is established considering forecast uncertainty and acceptable flood risk. It is found that DC‐FLWL is applicable when the reservoir inflow ranges from small to medium levels of the historical records, while both forecast uncertainty and acceptable risk in the downstream affect the feasible space of DC‐FLWL. As forecast uncertainty increases (under a given risk level) or as acceptable risk level decreases (under a given forecast uncertainty level), the minimum required safety margin for flood control increases, and the chance for DC‐FLWL decreases. The derived hedging rules from the modeling framework illustrate either the dominant role of water conservation or flood control or the trade‐off between the two objectives under different levels of forecast uncertainty and acceptable risk. These rules may provide useful guidelines for conserving water from flood, especially in the area with heavy water stress. The analysis is illustrated via a case study with a real‐world reservoir in northeastern China.
Adaptive notch filters are local adaptive observers
Authors: Marino Riccardo , Tomei Patrizio 
Published: June 2015

SummarySeveral continuous‐time frequency estimators for a measured sinusoidal signal, which have been proposed in the literature, are reviewed, reinterpreted and compared both theoretically and by simulations. It is argued that adaptive notch filters are feedback algorithms that contain a local adaptive observer in the feedback loop. It is shown that the adaptive notch filter (ANF), which was originally conceived as a discrete‐time ANF, is basically equivalent to the recently proposed adapted frequency locked loop called orthogonal signal generator. They both require a sufficiently slow frequency estimation and can be interpreted as third‐order adaptive observers. They exhibit local convergence properties for the estimation errors, that is, the convergence to zero is guaranteed provided that their initial error is sufficiently small. Three adaptive observers, which were independently proposed in 2002, are third‐order frequency estimators whose estimation errors are exponentially convergent to zero from any initial condition and for any value of frequency, amplitude and phase in the measured sinusoidal signal. They have the additional advantage of not requiring the frequency estimation dynamics to be sufficiently slow. Conversely, they may be interpreted as adaptive notch filters. Second‐order frequency estimators have been proposed as well: they may be interpreted as adaptive reduced‐order observers. Copyright © 2015 John Wiley & Sons, Ltd.
Verschwundene Polymorphe: eine Neubetrachtung
Authors: Bučar Dejan‐Krešimir , Lancaster Robert W. , Bernstein Joel 
Published: June 2015

AbstractVor knapp zwanzig Jahren beschrieben Dunitz und Bernstein eine Auswahl faszinierender Fälle von “verschwundenen” Polymorphen. Der Umstand, dass eine früher einmal hergestellte Kristallform nicht mehr erhalten werden kann, ist natürlich frustrierend und kann zu einem ernsten Problem für den Festkörperchemiker werden. In diesem Aufsatz werden aktuelle Fälle und Beispiele von verschwundenen Polymorphen (sowie das Vorkommen schwer auffindbarer Kristallformen) besprochen, um die fortdauernde Bedeutung dieser oft problematischen und zugleich immer wieder faszinierenden Erscheinung in der Festkörperforschung zu demonstrieren. Einige dieser Fälle standen im Zentrum von Patentstreits. Der Aufsatz beleuchtet daher auch die komplexe Beziehung zwischen Kristallchemie und Rechtsfragen.
Photoredoxkatalysierte Semipinakol‐Umlagerung mit sichtbarem Licht: Trifluormethylierung/Ringerweiterung über einen radikalisch‐polaren Mechanismus
Authors: Sahoo Basudev , Li Jun‐Long , Glorius Frank 
Published: June 2015

AbstractEine neuartige durch sichtbares Licht vermittelte Photoredox‐katalysierte Semipinakol‐Umlagerung wurde entwickelt, die über eine 1,2‐Alkylverschiebung verläuft. In dieser Transformation schließt sich der Trifluormethylierung einer CC‐Bindung von α‐(1‐Hydroxycycloalkyl)‐substituierten Styrolderivaten eine Ringerweiterung der 1‐Hydroxycycloalkylgruppe an, um neue Cycloalkanone mit quartären, ausschließlich C‐substituierten Stereozentren aufzubauen. Die Reaktion verläuft über einen radikalisch‐polaren Crossover‐Mechanismus mit Trifluormethylierung (radikalisch) und Ringerweiterung (ionisch) in einer Transformation.
Disappearing Polymorphs Revisited
Authors: Bučar Dejan‐Krešimir , Lancaster Robert W. , Bernstein Joel 
Published: June 2015

AbstractNearly twenty years ago, Dunitz and Bernstein described a selection of intriguing cases of polymorphs that disappear. The inability to obtain a crystal form that has previously been prepared is indeed a frustrating and potentially serious problem for solid‐state scientists. This Review discusses recent occurrences and examples of disappearing polymorphs (as well as the emergence of elusive crystal forms) to demonstrate the enduring relevance of this troublesome, but always captivating, phenomenon in solid‐state research. A number of these instances have been central issues in patent litigations. This Review, therefore, also highlights the complex relationship between crystal chemistry and the law.
H∞ Control with Transients for Singular Systems
Authors: Feng Zhiguang , Lam James , Xu Shengyuan , Zhou Shaosheng 
Published: June 2015

AbstractIn this paper, the problem of a generalized type of H∞ control is investigated for continuous‐time singular systems, which treats a mixed attenuation of exogenous inputs and initial conditions. First, a performance measure that is essentially the worst‐case norm of the regulated outputs over all exogenous inputs and initial conditions is introduced. A necessary and sufficient condition is obtained to ensure the singular system to be admissible and the performance measure to be less than a prescribed scalar. Based on the criterion a sufficient condition for the existence of a state‐feedback controller is established in terms of linear matrix inequalities. Moreover, the relationship between the performance measure and the standard H∞ norm of the system is provided. Two numerical examples are given to demonstrate the properties of the obtained results.
Robust State‐and‐Disturbance Observer Design for Linear Non‐minimum‐phase Systems
Authors: Chen Min‐Shin , Lin Shih‐Yu , Tseng Ming‐Lei , Yeh Yi‐Liang , Yen Jia‐Yush 
Published: June 2015

AbstractWhen there are external disturbances acting on the system, the conventional Luenberger observer design for state estimation usually results in a biased state estimate. This paper presents a robust state and disturbance observer design that gives both accurate state and disturbance estimates in the face of large disturbances. The proposed robust observer is structurally different from the conventional one in the sense that a disturbance estimation term is included in the observer equation. With this disturbance estimation term, the robust observer design problem is skillfully transformed into a disturbance rejection control problem. We then can utilize the standard H∞ control design tools to optimize the robust observer between the disturbance rejection ability and noise immune ability. An important advantage of the proposed robust observer is that it applies to both minimum‐phase systems and non‐minimum phase systems.
Modeling distributions of travel time variability for bus operations
Authors: Ma Zhenliang , Ferreira Luis , Mesbah Mahmoud , Zhu Sicong 
Published: June 2015

SummaryBus travel time reliability performance influences service attractiveness, operating costs, and system efficiency. Better understanding of the distribution of travel time variability is a prerequisite for reliability analysis. A wide array of empirical studies has been conducted to model distribution of travel times in transport. However, depending on the data tested and approaches applied to examine the fitting performance, different conclusions have been reported. This paper aims to specify the most appropriate distribution model for the day‐to‐day travel time variability by using a novel evaluation approach and set of performance measures. Two important issues are explored using automatic vehicle location data collected on two typical bus routes over 6 months in Brisbane, namely, data aggregation influences on travel time distribution and comprehensive evaluation of performance of distribution models. The decrease of temporal aggregation of travel times tends to increase the normality of distributions. The spatial aggregation of link travel times would break up the link multimodality distributions for a busway route, but unlike for a non‐busway route. The Gaussian mixture models are evaluated as superior to its alternatives in terms of fitting accuracy, robustness, and explanatory power. The reported distribution model shows promise to fit travel times for other services with different operation environments considering its flexibility in fitting symmetric, asymmetric, and multimodal distributions. The improved statistic fitting can support more effective service reliability analysis. Copyright © 2015 John Wiley & Sons, Ltd.
Tragfähigkeit und Verformungsverhalten von Kammverbindungen
Authors: Meisel Andreas , Wallner Bernhard , Schickhofer Gerhard 
Published: June 2015

AbstractKämme für Kreuz‐ und Eckverbindungen sind wesentliche Bestandteile nahezu jedes zimmermannsmäßig errichteten Holztragwerks in Mitteleuropa. Die Anwendung dieser Verbindungen als statisch tragende Anschlüsse nach EN 1995‐1‐1 bedarf der Kenntnis der mechanischen Kenngrößen. Umso erstaunlicher ist es, dass in der Literatur bislang Angaben zur Tragfähigkeit und insbesondere zum Verformungsverhalten fehlen.In diesem Beitrag werden 26 zerstörende Prüfungen an unterschiedlichen Kammverbindungen und deren Auswertungen vorgestellt. Sowohl für die Bemessung dieser Verbindungen als auch für die Ermittlung der Steifigkeiten – abgeleitet aus dem Verformungsverhalten – werden Berechnungsvorschläge angegeben.Load‐bearing capacity and load‐bearing behaviour of notched jointsCross and corner joints using notches are important members of almost every roof structure erected by carpenters in central europe. The structural usage of these joints demands the knowledge of their load‐bearing capacity and behaviour according to EN 1995‐1‐1. It's even more astonishing, that therefore codes and literature lack information.This contribution deals with 26 tests of different notched joints and their results. Both proposals for the design and for the determination of the stiffnesses of these joints are given here.
Frühgeschichte des modernen Konstruktionsbetons
Authors: Veihelmann Karen 
Published: June 2015

AbstractNachdem in den vorangegangenen beiden Teilen des Aufsatzes zur Frühgeschichte des Betons, dessen erste Anwendungen im Molen‐ und Schleusenbau dargelegt wurden, beschreibt der nun vorliegende dritte Teil die Entwicklungen im Hochbau. Ausgehend vom Stampflehmbau (Pisé) erfuhr die Bauweise mittels Ersetzen des Bindemittels Lehm zunächst durch reinen, später durch hydraulischen Kalk sowie die verschiedenen Spielarten von Zement bedeutende Fortschritte: Aus Stampflehm wurde auf diese Weise Stampfbeton. Die Verbesserung sowohl der Witterungsbeständigkeit als auch der Druckfestigkeit schuf die Grundlage für den breitgefächerten Einsatz von Beton im Hochbau. War zunächst noch die nicht kalkulierbare Qualität des Portlandzementes dem Aufschwung des Betonbaus hinderlich, bedeutete die Einführung der ersten deutschen Zementnormen im Königreich Preußen 1878 den Durchbruch für den Beton im Hochbau, insbesondere aber als Konstruktionsmaterial für weitgespannte Brücken.On the early history of modern concrete – part III: From rammed earth to rammed concreteFollowing the first two parts of the paper on early history of modern concrete which dealt with underwater concrete structures the present part III analyses the development of concrete above ground. Based on the experience of building with rammed earth the technique was improved by replacing the binder clay by lime, later by cement: thus rammed earth became rammed concrete. This improvement of weather resistance and compressive strength opened a wide field of application of concrete above ground. In Germany, the unforeseeable quality of cement first delayed the implementation of concrete structures. It was only in 1878 when the first cement standards were introduced. From that point concrete was used for all kinds of structures, particularly for wide span bridges.
Biegeaktive Tragwerke
Authors: Lienhard Julian , Knippers Jan 
Published: June 2015

AbstractBiegeaktive Tragwerke sind gekrümmte Tragwerke, deren Geometrie und Systemsteifigkeit sich aus einer elastischen Verformung von Tragelementen ergibt. Biegung kann demnach dazu genutzt werden, komplexe räumlich gekrümmte Tragsysteme aus ursprünglich geradlinigen oder ebenen Tragelementen zu erzeugen. Bei der Arbeit mit biegeaktiven Tragstrukturen zeigt sich, dass dieser Formgebungsansatz die Entwicklung hocheffizienter Tragsysteme ermöglicht, welche – frei von tradierten typologischen Ansätzen der Tragwerkslehre – aus dem Kurzschließen von Rückstellkräften entstehen. Nach einer Definition der Begriffe und kurzen Darstellung der relevanten mechanischen sowie werkstofftechnischen Grundlagen werden in diesem Aufsatz die besonderen Eigenschaften dieser Tragwerke anhand von Fallbeispielen erläutert.Bending‐active structuresBending‐active structures are curved beam or surface structures that base their geometry and structural integrety on the elastic deformation of their initially straight or planar elements. In these lightweight structures bending is not avoided but instrumentalized to create complex curved geometries on the basis of standard semi‐finished building products. After a general introduction of material and mechanical basics this paper discusses the behavior of bending‐active structures through three case study projects.