TY  - JOUR
A1  - Zhou, Changsong
A1  - Kurths, Jürgen
T1  - Hierarchical synchronization in complex networks with heterogeneous degrees
N2  - We study synchronization behavior in networks of coupled chaotic oscillators with heterogeneous connection degrees. Our focus is on regimes away from the complete synchronization state, when the coupling is not strong enough, when the oscillators are under the influence of noise or when the oscillators are nonidentical. We have found a hierarchical organization of the synchronization behavior with respect to the collective dynamics of the network. Oscillators with more connections (hubs) are synchronized more closely by the collective dynamics and constitute the dynamical core of the network. The numerical observation of this hierarchical synchronization is supported with an analysis based on a mean field approximation and the master stability function. (C) 2006 American Institute of Physics
Y1  - 2006
UR  - http://scitation.aip.org/getpdf/servlet/ GetPDFServlet?filetype=pdf&id=CHAOEH000016000001015104000001&idtype=cvips&doi=10.1063/1.2150381&prog=normal
U6  - https://doi.org/10.1063/1.2150381
SN  - 1054-1500
ER  - 
TY  - JOUR
A1  - Zhou, Changsong
A1  - Kurths, Jürgen
T1  - Noise-induced phase synchronization and synchronization transitions in chaotic oscillators
Y1  - 2002
ER  - 
TY  - JOUR
A1  - Zhou, Changsong
A1  - Kurths, Jürgen
A1  - Hu, B.
T1  - Array-enhanced coherence resonance: Nontrivial effects of heterogeneity and spatial independence of noise
Y1  - 2001
ER  - 
TY  - JOUR
A1  - Zhou, Changsong
A1  - Kurths, Jürgen
A1  - Kiss, Istvan Z.
A1  - Hudson, J. L.
T1  - Noise-enhanced phase synchronization of chaotic oscillators
Y1  - 2002
ER  - 
TY  - JOUR
A1  - Zhou, Changsong
A1  - Motter, Adilson E.
A1  - Kurths, Jürgen
T1  - Universality in the synchronization of weighted random networks
N2  - Realistic networks display not only a complex topological structure, but also a heterogeneous distribution of weights in the connection strengths. Here we study synchronization in weighted complex networks and show that the synchronizability of random networks with a large minimum degree is determined by two leading parameters: the mean degree and the heterogeneity of the distribution of node's intensity, where the intensity of a node, defined as the total strength of input connections, is a natural combination of topology and weights. Our results provide a possibility for the control of synchronization in complex networks by the manipulation of a few parameters
Y1  - 2006
UR  - http://prl.aps.org/pdf/PRL/v96/i3/e034101
U6  - https://doi.org/10.1103/Physrevlett.96.034101
ER  - 
TY  - JOUR
A1  - Zhou, Changsong
A1  - Zemanova, Lucia
A1  - Zamora, Gorka
A1  - Hilgetag, Claus C.
A1  - Kurths, Jürgen
T1  - Hierarchical organization unveiled by functional connectivity in complex brain networks
JF  - Physical review letters
N2  - How do diverse dynamical patterns arise from the topology of complex networks? We study synchronization dynamics in the cortical brain network of the cat, which displays a hierarchically clustered organization, by modeling each node (cortical area) with a subnetwork of interacting excitable neurons. We find that in the biologically plausible regime the dynamics exhibits a hierarchical modular organization, in particular, revealing functional clusters coinciding with the anatomical communities at different scales. Our results provide insights into the relationship between network topology and functional organization of complex brain networks.
Y1  - 2006
U6  - https://doi.org/10.1103/PhysRevLett.97.238103
SN  - 0031-9007
SN  - 1079-7114
VL  - 97
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - THES
A1  - Zhou, Xu
T1  - Atmospheric interactions with land surface in the arctic based on regional climate model solutions
Y1  - 2014
ER  - 
TY  - JOUR
A1  - Zhu, Hui
A1  - Shprits, Yuri Y.
A1  - Spasojevic, M.
A1  - Drozdov, Alexander
T1  - New hiss and chorus waves diffusion coefficient parameterizations from the Van Allen Probes and their effect on long-term relativistic electron radiation-belt VERB simulations
JF  - Journal of Atmospheric and Solar-Terrestrial Physics
N2  - New wave frequency and amplitude models for the nightside and dayside chorus waves are built based on measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument onboard the Van Allen Probes. The corresponding 3D diffusion coefficients are systematically obtained. Compared with previous commonly-used (typical) parameterizations, the new parameterizations result in differences in diffusion rates that depend on the energy and pitch angle. Furthermore, one-year 3D diffusive simulations are performed using the Versatile Electron Radiation Belt (VERB) code. Both typical and new wave parameterizations simulation results are in a good agreement with observations at 0.9 MeV. However, the new parameterizations for nightside chorus better reproduce the observed electron fluxes. These parameterizations will be incorporated into future modeling efforts.
KW  - Inner magnetosphere
KW  - Radiation belts
KW  - Chorus waves
KW  - Diffusion coefficients
KW  - VERB code
Y1  - 2019
U6  - https://doi.org/10.1016/j.jastp.2019.105090
SN  - 1364-6826
SN  - 1879-1824
VL  - 193
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Zhu, Jian
A1  - Kollosche, Matthias
A1  - Lu, Tongqing
A1  - Kofod, Guggi
A1  - Suo, Zhigang
T1  - Two types of transitions to wrinkles in dielectric elastomers
JF  - Soft matter
N2  - A membrane of a dielectric elastomer coated with compliant electrodes may form wrinkles as the applied voltage is ramped up. We present a combination of experiment and theory to investigate the transition to wrinkles using a clamped membrane subject to a constant force and a voltage ramp. Two types of transitions are identified. In type-I transition, the voltage-stretch curve is N-shaped, and flat and wrinkled regions coexist in separate areas of the membrane. The type-I transition progresses by nucleation of small wrinkled regions, followed by the growth of the wrinkled regions at the expense of the flat regions, until the entire membrane is wrinkled. By contrast, in type-II transition, the voltage-stretch curve is monotonic, and the entire flat membrane becomes wrinkled with no nucleation barrier. The two types of transitions are analogous to the first and the second order phase transitions. While the type-I transition is accompanied by a jump in the vertical displacement, type-II transition is accompanied by a continuous change in the vertical displacement. Such transitions may enable applications in muscle-like actuation and energy harvesting, where large deformation and large energy of conversion are desired.
Y1  - 2012
U6  - https://doi.org/10.1039/c2sm26034d
SN  - 1744-683X
VL  - 8
IS  - 34
SP  - 8840
EP  - 8846
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Zhu, Jian
A1  - Stoyanov, Hristiyan
A1  - Kofod, Guggi
A1  - Suo, Zhigang
T1  - Large deformation and electromechanical instability of a dielectric elastomer tube actuator
N2  - This paper theoretically analyzes a dielectric elastomer tube actuator (DETA). Subject to a voltage difference between the inner and outer surfaces, the actuator reduces in thickness and expands in length, so that the same voltage will induce an even higher electric field. This positive feedback may cause the actuator to thin down drastically, resulting in electrical breakdown. We obtain an analytical solution of the actuator undergoing finite deformation when the elastomer obeys the neo-Hookean model. The critical strain of actuation is calculated in terms of various parameters of design. We also discuss the effect of the strain-stiffening on electromechanical behavior of DETAs by using the model of freely joined links. (C) 2010 American Institute of Physics. [doi:10.1063/1.3490186]
Y1  - 2010
UR  - http://jap.aip.org/
U6  - https://doi.org/10.1063/1.3490186
SN  - 0021-8979
ER  - 
TY  - JOUR
A1  - Zhu, M. Q.
A1  - Armbruster, Dieter
A1  - Katzorke, Ines
T1  - Does synchronization of networks of chaotic maps lead to control?
N2  - We consider networks of chaotic maps with different network topologies. In each case, they are coupled in such a way as to generate synchronized chaotic solutions. By using the methods of control of chaos we are controlling a single map into a predetermined trajectory. We analyze the reaction of the network to such a control. Specifically we show that a line of one-dimensional logistic maps that are unidirectionally coupled can be controlled from the first oscillator whereas a ring of diffusively coupled maps cannot be controlled for more than 5 maps. We show that rings with more elements can be controlled if every third map is controlled. The dependence of unidirectionally coupled maps on noise is studied. The noise level leads to a finite synchronization lengths for which maps can be controlled by a single location. A two-dimensional lattice is also studied. (C) 2005 American Institute of Physics
Y1  - 2005
SN  - 1054-1500
ER  - 
TY  - JOUR
A1  - Zhu, Shigen
A1  - Schulz, Burkhard
A1  - Bruma, Maria
A1  - Brehmer, Ludwig
T1  - Comparative study of the thermal properties of related aromatic polyhydrazides and poly(1,3,4-oxadiazole)s
Y1  - 1996
UR  - http://www3.interscience.wiley.com/journal/5401/home?CRETRY=1&SRETRY=0
U6  - https://doi.org/10.1002/(SICI)1099-1581(199612)7:12<879::AID-PAT600>3.0.CO;2-X
SN  - 1042-7147
ER  - 
TY  - JOUR
A1  - Zhuang, Y.
A1  - Holý, Václav
A1  - Stangl, Jochen
A1  - Darhuber, A.
A1  - Mikulik, P.
A1  - Zerlauth, S.
A1  - Schäffler, F.
A1  - Bauer, Günther
A1  - Darowski, Nora
A1  - Lübbert, Daniel
A1  - Pietsch, Ullrich
T1  - Strain relaxation in periodic arrays of Si/SiGe quantum wires determined by coplanar high-resolution x-ray diffrcation and grazing-incidence diffraction
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Zhuang, Y.
A1  - Pietsch, Ullrich
A1  - Stangl, Jochen
A1  - Holý, Vaclav
A1  - Darowski, Nora
A1  - Grenzer, Jörg
A1  - Zerlauth, S.
A1  - Schäffler, F.
A1  - Bauer, Günther
T1  - In-plane strain and shape analysis of Si/SiGe nanostructures by grazing incidence diffraction
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Zhuang, Y.
A1  - Schelling, Christoph
A1  - Stangl, Jochen
A1  - Penn, C.
A1  - Senz, S.
A1  - Schäffler, Friedrich
A1  - Roche, T.
A1  - Daniel, A.
A1  - Grenzer, Jörg
A1  - Pietsch, Ullrich
A1  - Bauer, Günther
T1  - Structural and optical properties of Si/Si{1-x}Ge{x} wires
Y1  - 2000
ER  - 
TY  - THES
A1  - Zickfeld, Kirsten
T1  - Modeling large-scale singular climate events for integrated assessment
N2  - Erkenntnisse aus paläoklimatologischen Studien, theoretischen Betrachtungen und Modellsimulationen deuten darauf hin, dass anthropogene Emissionen von Treibhausgasen und Aerosolen zu großskaligen, singulären Klimaereignissen führen könnten. Diese bezeichnen stark nichtlineare, abrupte Klimaänderungen, mit regionalen bis hin zu globalen Auswirkungen. Ziel dieser Arbeit ist die Entwicklung von Modellen zweier maßgeblicher Komponenten des Klimasystems, die singuläres Verhalten aufweisen könnten: die atlantische thermohaline Zirkulation (THC) und der indische Monsun. Diese Modelle sind so konzipiert, dass sie den Anforderungen der "Integrated Assessment"-Modellierung genügen, d.h., sie sind realistisch, recheneffizient, transparent und flexibel.   Das THC-Modell ist ein einfaches, interhemisphärisches Boxmodell, das anhand von Daten kalibriert wird, die mit einem gekoppelten Klimamodell mittlerer Komplexität erzeugt wurden. Das Modell wird durch die globale Mitteltemperatur angetrieben, die mit Hilfe eines linearen Downscaling-Verfahrens in regionale Wärme- und Süßwasserflüsse übersetzt wird. Die Ergebnisse einer Vielzahl von zeitabhängigen Simulationen zeigen, dass das Modell in der Lage ist, maßgebliche Eigenschaften des Verhaltens komplexer Klimamodelle wiederzugeben, wie die Sensitivität bezüglich des Ausmaßes, der regionalen Verteilung und der Rate der Klimaänderung.   Der indische Monsun wird anhand eines neuartigen eindimensionalen Boxmodells der tropischen Atmosphäre beschrieben. Dieses enthält Parmetrisierungen der Oberflächen- und Strahlungsflüsse, des hydrologischen Kreislaufs und derHydrologie der Landoberfläche. Trotz des hohen Idealisierungsgrades ist das Modell in der Lage, relevante Aspekte der beobachteten Monsundynamik, wie z.B. den Jahresgang des Niederschlags und das Eintritts- sowie Rückzugsdatum des Sommermonsuns, zufrieden stellend zu simulieren. Außerdem erfasst das Modell die Sensitivitätdes Monsuns bezüglich Änderungen der Treibhausgas- und Aerosolkonzentrationen, die aus komplexeren Modellen bekannt sind.   Eine vereinfachte Version des Monsunmodells wird für die Untersuchung des qualitativen Systemverhaltens in Abhängigkeit von Änderungen der Randbedingungen eingesetzt. Das bemerkenswerteste Ergebnis ist das Auftreten einer Sattelknotenbifurkation des Sommermonsuns für kritische Werte der Albedo oder der Sonneneinstrahlung. Darüber hinaus weist das Modell zwei stabile Zustände auf: neben dem niederschlagsreichen Sommermonsun besteht ein Zustand, der sich durch einen schwachen hydrologischen Kreislauf auszeichnet. Das Beachtliche an diesen Ergebnissen ist, dass anthropogene Störungen der plantetaren Albedo, wie Schwefelemissionen und/oder Landnutzungsänderungen, zu einer Destabilisierung des indischen Monsuns führen könnten.   Das THC-Boxmodell findet exemplarische Anwendung in einem "Integrated Assessment" von Klimaschutzstrategien. Basierend auf dem konzeptionellen und methodischen Gerüst des Leitplankenansatzes werden Emissionskorridore (d.h. zulässige Spannen an CO2-Emissionen) berechnet, die das Risiko eines THC-Zusammenbruchs begrenzen sowie sozioökonomische Randbedingungen berücksichtigen. Die Ergebnisse zeigen u.a. eine starke Abhängigkeit der Breite der Emissionskorridore von der Klima- und hydrologischen Sensitivität. Für kleine Werte einer oder beider Sensitivitäten liegt der obere Korridorrand bei weit höheren Emissionswerten als jene, die von plausiblen Emissionsszenarien für das 21. Jahrhundert erreicht werden. Für große Werte der Sensitivitäten hingegen, verlassen schon niedrige Emissionsszenarien den Korridor in den frühen Jahrzehnten des 21. Jahrhunderts. Dies impliziert eine Abkehr von den gegenwärtigen Emissionstrends innherhalb der kommenden Jahrzehnte, wenn das Risko eines THC Zusammenbruchs gering gehalten werden soll.   Anhand einer Vielzahl von Anwendungen - von Sensitivitäts- über Bifurkationsanalysen hin zu integrierter Modellierung - zeigt diese Arbeit den Wert reduzierter Modelle auf. Die Ergebnisse und die daraus zu ziehenden Schlussfolgerungen liefern einen wertvollen Beitrag zu der wissenschaftlichen und politischen Diskussion bezüglich der Folgen des anthropogenen Klimawandels und der langfristigen Klimaschutzziele.
N2  - Concerns have been raised that anthropogenic climate change could lead to large-scale singular climate events, i.e., abrupt nonlinear climate changes with repercussions on regional to global scales. One central goal of this thesis is the development of models of two representative components of the climate system that could exhibit singular behavior: the Atlantic thermohaline circulation (THC) and the Indian monsoon. These models are conceived so as to fulfill the main requirements of integrated assessment modeling, i.e., reliability, computational efficiency, transparency and flexibility.   The model of the THC is an interhemispheric four-box model calibrated against data generated with a coupled climate model of intermediate complexity. It is designed to be driven by global mean temperature change which is translated into regional fluxes of heat and freshwater through a linear down-scaling procedure. Results of a large number of transient climate change simulations indicate that the reduced-form THC model is able to emulate key features of the behavior of comprehensive climate models such as the sensitivity of the THC to the amount, regional distribution and rate of change in the heat and freshwater fluxes.   The Indian monsoon is described by a novel one-dimensional box model of the tropical atmosphere. It includes representations of the radiative and surface fluxes, the hydrological cycle and surface hydrology. Despite its high degree of idealization, the model satisfactorily captures relevant aspects of the observed monsoon dynamics, such as the annual course of precipitation and the onset and withdrawal of the summer monsoon. Also, the model exhibits the sensitivity to changes in greenhouse gas and sulfate aerosol concentrations that are known from comprehensive models.   A simplified version of the monsoon model is employed for the identification of changes in the qualitative system behavior against changes in boundary conditions. The most notable result is that under summer conditions a saddle-node bifurcation occurs at critical values of the planetary albedo or insolation. Furthermore, the system exhibits two stable equilibria: besides the wet summer monsoon, a stable state exists which is characterized by a weak hydrological cycle. These results are remarkable insofar, as they indicate that anthropogenic perturbations of the planetary albedo such as sulfur emissions and/or land-use changes could destabilize the Indian summer monsoon.   The reduced-form THC model is employed in an exemplary integrated assessment application. Drawing on the conceptual and methodological framework of the tolerable windows approach, emissions corridors (i.e., admissible ranges of CO2- emissions) are derived that limit the risk of a THC collapse while considering expectations about the socio-economically acceptable pace of emissions reductions. Results indicate, for example, a large dependency of the width of the emissions corridor on climate and hydrological sensitivity: for low values of climate and/or hydrological sensitivity, the corridor boundaries are far from being transgressed by any plausible emissions scenario for the 21st century. In contrast, for high values of both quantities low non-intervention scenarios leave the corridor already in the early decades of the 21st century. This implies that if the risk of a THC collapse is to be kept low, business-as-usual paths would need to be abandoned within the next two decades.   All in all, this thesis highlights the value of reduced-form modeling by presenting a number of applications of this class of models, ranging from sensitivity and bifurcation analysis to integrated assessment. The results achieved and conclusions drawn provide a useful contribution to the scientific and policy debate about the consequences of anthropogenic climate change and the long-term goals of climate protection. ---  Anmerkung: Die Autorin ist Trägerin des von der Mathematisch-Naturwissenschaftlichen Fakultät der Universität Potsdam vergebenen Michelson-Preises für die beste Promotion des Jahres 2003/2004.
KW  - Nichtlineare Dynamik
KW  - 'Reduced-Form' Modellierung
KW  - Thermohaline Atlantikzirkulation
KW  - Indischer Monsun
KW  - Integrated Assessment
KW  - Nonlinear Dynamics
KW  - Reduced-Form Modeling
KW  - Atlantic Thermohaline Circulation
KW  - Indian Monsoon
KW  - Integrated Assessment
Y1  - 2003
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-0001176
ER  - 
TY  - JOUR
A1  - Ziegler, A.
A1  - Fischer, Thomas M.
A1  - Menzel, Henning
A1  - Stumpe, Joachim
T1  - Photo-Induced modification and photo-orientation in LB-multilayers of thermotropic polymers containing azobenzene side groups
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Ziehmann, Christine
A1  - Smith, L.
A1  - Kurths, Jürgen
T1  - The bootstrap and lyapunov exponents in deterministic chaos
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Ziehmann, Christine
A1  - Smith, Leonard A.
A1  - Kurths, Jürgen
T1  - Localized Lyapunov exponents and the prediction of predictability
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Zienicke, Egbert
A1  - Seehafer, Norbert
A1  - Feudel, Fred
T1  - Bifurcations in two-dimensional Rayleigh-Bénard convection
Y1  - 1998
ER  -