Incoherent Effects Research Articles

An improved approach for multiple support response spectral analysis of a long-span high-pier railway bridge

To overcome the difficulty of performing multi-point response spectrum analysis for engineering structures under spatially varying ground motions (SVGM) using the general finite element code such as ANSYS, an approach has been developed by improving the modelling of the input ground motions in the spectral analysis. Based on the stochastic vibration analyses, the cross-power spectral density (c-PSD) matrix is adopted to model the stationary SVGM. The design response spectra are converted into the corresponding PSD model with appropriate coherency functions and apparent wave velocities. Then elements of c-PSD matrix are summarized in the row and the PSD matrix is transformed into the response spectra for a general spectral analysis. A long-span high-pier bridge under multiple support excitations is analyzed using the proposed approach considering the incoherence, wave-passage and site-response effects. The proposed approach is deemed to be an efficient numerical method that can be used for seismic analysis of large engineering structures under SVGM.

Direct Imaging of Frenkel Exciton Transport by Ultrafast Microscopy.

Long-range transport of Frenkel excitons is crucial for achieving efficient molecular-based solar energy harvesting. Understanding of exciton transport mechanisms is important for designing materials for solar energy applications. One major bottleneck in unraveling of exciton transport mechanisms is the lack of direct measurements to provide information in both spatial and temporal domains, imposed by the combination of fast energy transfer (typically ≤1 ps) and short exciton diffusion lengths (typically ≤100 nm). This challenge requires developing experimental tools to directly characterize excitation energy transport, and thus facilitate the elucidation of mechanisms. To address this challenge, we have employed ultrafast transient absorption microscopy (TAM) as a means to directly image exciton transport with ∼200 fs time resolution and ∼50 nm spatial precision. By mapping population in spatial and temporal domains, such approach has unraveled otherwise obscured information and provided important parameters for testing exciton transport models. In this Account, we discuss the recent progress in imaging Frenkel exciton migration in molecular crystals and aggregates by ultrafast microscopy. First, we establish the validity of the TAM methods by imaging singlet and triplet exciton transport in a series of polyacene single crystals that undergo singlet fission. A new singlet-mediated triplet transport pathway has been revealed by TAM, resulting from the equilibrium between triplet and singlet exciton populations. Such enhancement of triplet exciton transport enables triplet excitons to migrate as singlet excitons and leads to orders of magnitude faster apparent triplet exciton diffusion rate in the picosecond and nanosecond time scales, favorable for solar cell applications. Next we discuss how information obtained by ultrafast microscopy can evaluate coherent effects in exciton transport. We use tubular molecular aggregates that could support large exciton delocalization sizes as a model system. The initial experiments measure exciton diffusion constants of 3-6 cm2 s-1, 3-5 times higher than the incoherent limit predicted by theory, suggesting that coherent effects play a role. In summary, combining ultrafast spectroscopic methods with microscopic techniques provides a direct approach for obtaining important parameters to unravel the underlying exciton transport mechanisms in molecular solids. We discuss future directions to bridge the gap in understanding of fundamental energy transfer theories to include coherent and incoherent effects. We are still in the infancy of ultrafast microscopy, and the vast potential is not limited to the systems discussed in this Account.

Reflexión sobre Subjetividad y Juicios de Coherencia en el Trabajo

It is discussed in this paper the subjectivity issue from Vygotsky´s (1925) sociocultural perspective, considering new conceptual developments by Gonzalez (2013) as the focus of interest in this writing. On the bases of Subjective Sense and Subjective Configuration constructs the author explores a way of understanding how persons process ideas about the coherence of every day facts and experiences at work. With this purpose in mind are described several studies and the meaning of coherence there managed, as well as the effects of coherence and incoherence observed. A good understanding of coherence judgments is needed because the issue has been scarcely studied and the concept is on the basis of organizational coherence explanations. Organizational coherence is a necessary condition for organizations to survive and succeed, such as diverse economic, administrative, managerial, sociological and organizational studies have evidenced. This reflection begins with an exploration of the subjectivity concept, afterwards considers the concept of coherence in several analytical contexts in order to propose a way of understanding the coherence at work, something useful and necessary to win a better understanding of subjectivity at work. On the basis of this analysis a different way of understanding coherence in the organizational context is suggested. Received: 25/08/2016 Accepted: 28/04/2017 How to reference this article : Toro Álvarez, F. (2015). Reflexión sobre Subjetividad y Juicios de Coherencia en el Trabajo . Revista Interamericana de Psicología Ocupacional, 34(2), 93-107. Doi: 10.21772/ripo.v34n2a03

The Diagnosis of Mental Disorders Is Influenced by Automatic Causal Reasoning

Causal knowledge has been shown to affect diagnostic decisions. It is unclear, however, how causal knowledge affects diagnosis. We hypothesized that it influences intuitive reasoning processes. More precisely, we speculated that people automatically assess the coherence between observed symptoms and an assumed causal model of a disorder, which in turn affects diagnostic classification. Intuitive causal reasoning was investigated in an experimental study. Participants were asked to read clinical reports before deciding on a diagnosis. Intuitive processing was studied by analyzing reading times. It turned out that reading times were slower when causally expected consequences of present symptoms were missing or effects of absent causes were present. This causal incoherence effect was predictive of participants’ later explicit diagnostic judgments. These and related findings suggest that diagnostic judgments rely on automatic reasoning processes based on the computation of causal coherence. Potential implications of these results for the training of clinicians are discussed.

Wave-passage effect on the seismic response of suspension bridges considering local soil conditions

In this study, a comprehensive investigation of the stochastic analysis of a suspension bridge subjected to spatially varying ground motions is carried out for variable local soil cases and wave velocities. Bosphorus Suspension Bridge built in Turkey and connects Europe to Asia in Istanbul is selected as a numerical example. The spatial variability of the ground motion is considered with the incoherence, wave-passage and site-response effects. The incoherence effect is examined by taking into account Harichandran and Vanmarcke model, the site-response effect is outlined by using firm, medium and soft soil types, and the wave-passage effect is investigated by using 1000-2000, 500-1000, and 300-500 m/s wave velocities for the firm, medium and soft soils, respectively. Mean of maximum response values obtained from the spatially varying ground motions are compared with those of the specialized cases of the ground motion model. At the end of the study, it is seen that total displacements are dominated by dynamic component. The response values obtained for SMFF soil condition are generally the largest. When the varying local soil condition is considered, the variation of relative contributions of response components to the total response values for varying wave velocity cases is insignificant. Also, the variation of the wave velocity has important effect on the deck and towers total response values as compared with those of the constantly travelling wave velocity case. It is concluded that the site-response effect of ground motion on the response of suspension bridges is more important than that of the wave-passage, and the variation of the wave velocities depending on the local soil conditions, has important effects on the dynamic behavior of suspension bridge.

Effect of spatial variability of earthquakes on cable-stayed bridges

This paper focuses on the effect of spatially variable ground motions on the towers of cable-stayed bridges with 200, 400 and 600 m main spans. Seismic analysis of the bridges is performed, taking account of different sources of the spatial variability, namely; incoherence and wave passage effects. To address these effects, the response of the towers is assessed under the effect of different propagation velocities of the seismic waves and different assumptions on the coherency of the ground motion, to conclude that the effect of spatially variable motions on the seismic response of cable-stayed bridges is dependent on the assumed wave propagation velocity and rate of coherency.

Intermediate Coherent–Incoherent Charge Transport: DNA as a Case Study

We study an intermediate quantum coherent-incoherent charge transport mechanism in metal-molecule-metal junctions using Buttiker’s probe technique. This tool allows us to include incoherent effects in a controlled manner, and thus to study situations in which partial decoherence affects charge transfer dynamics. Motivated by recent experiments on intermediate coherent-incoherent charge conduction in DNA molecules, we focus on two representative structures: alternating (GC)n and stacked GnCn sequences; the latter structure is argued to support charge delocalization within G segments and, thus, an intermediate coherent–incoherent conduction. We begin our analysis with a highly simplified one-dimensional tight-binding model while introducing environmental effects through Buttiker’s probes. This minimal model allows us to gain fundamental understanding of transport mechanisms and derive analytic results for molecular resistance in different limits. We then use a more detailed ladder-model Hamiltonian to repre...

Contribution of local site-effect on the seismic response of suspension bridges to spatially varying ground motions

In this paper, it is aimed to determine the stochastic response of a suspension bridge subjected to spatially varying ground motions considering the geometric nonlinearity. Bosphorus Suspension Bridge built in Turkey and connects Europe to Asia in Istanbul is selected as a numerical example. The spatial variability of the ground motion is considered with the incoherence, wave-passage and site-response effects. The importance of site-response effect which arises from the difference in the local soil conditions at different support points of the structure is also investigated. At the end of the study, mean of the maximum and variance response values obtained from the spatially varying ground motions are compared with those of the specialised cases of the ground motion model. It is seen that each component of the spatially varying ground motion model has important effects on the dynamic behaviour of the bridge. The response values obtained from the general excitation case, which also includes the site-response effect causes larger response values than those of the homogeneous soil condition cases. The variance values calculated for the general excitation case are dominated by dynamic component at the deck and Asian side tower. The response values obtained for the site-response effect alone are larger than the response values obtained for the incoherence and wave-passage effects, separately. It can be concluded that suspension bridges are sensitive to the spatial variability of ground motion. Therefore, the incoherence, the wave-passage and especially the site-response effects should be considered in the stochastic analysis of this type of engineering structures.

A Simplified Approach to Measure the Effect of the Microvasculature in Diffusion-weighted MR Imaging Applied to Breast Tumors: Preliminary Results.

Purpose To evaluate the relative change of the apparent diffusion coefficient (ADC) at low- and medium-b-value regimens as a surrogate marker of microcirculation, to study its correlation with dynamic contrast agent-enhanced (DCE) magnetic resonance (MR) imaging-derived parameters, and to assess its potential for differentiation between malignant and benign breast tumors. Materials and Methods Ethics approval and informed consent were obtained. From May 2013 to June 2015, 61 patients diagnosed with either malignant or benign breast tumors were prospectively recruited. All patients were scanned with a 3-T MR imager, including diffusion-weighted imaging (DWI) and DCE MR imaging. Parametric analysis of DWI and DCE MR imaging was performed, including a proposed marker, relative enhanced diffusivity (RED). Spearman correlation was calculated between DCE MR imaging and DWI parameters, and the potential of the different DWI-derived parameters for differentiation between malignant and benign breast tumors was analyzed by dividing the sample into equally sized training and test sets. Optimal cut-off values were determined with receiver operating characteristic curve analysis in the training set, which were then used to evaluate the independent test set. Results RED had a Spearman rank correlation of 0.61 with the initial area under the curve calculated from DCE MR imaging. Furthermore, RED differentiated cancers from benign tumors with an overall accuracy of 90% (27 of 30) on the test set with 88.2% (15 of 17) sensitivity and 92.3% (12 of 13) specificity. Conclusion This study presents promising results introducing a simplified approach to assess results from a DWI protocol sensitive to the intravoxel incoherent motion effect by using only three b values. This approach could potentially aid in the differentiation, characterization, and monitoring of breast pathologies. © RSNA, 2016 Online supplemental material is available for this article.

Tail-Equivalent Linearization of Inelastic Multisupport Structures Subjected to Spatially Varying Stochastic Ground Motion

AbstractAfter a brief review of time- and frequency-domain tail-equivalent linearization methods (TELM) for uniform excitation problems, this paper extends TELM for application to nonlinear systems subjected to multisupport seismic excitations. The spatial variability of the ground motion is represented by a coherency function that characterizes the incoherence, wave-passage, and site-response effects. It is found that for multisupport excitation problems, it is most convenient to formulate TELM by using the ground displacement as input. The resulting tail-equivalent linear system (TELS) is defined by frequency-response functions relating the response quantity of interest to each support displacement. A method to reduce the number of random variables in the TELM analysis is introduced. The proposed method is demonstrated through numerical examples with varying structural properties and ground motion coherency in order to investigate various aspects of TELM and the major influences of differential support ...

Multiple-support seismic response of Bosporus Suspension Bridge for various random vibration methods

This paper presents a study about the spatial variability effects of ground motions on the dynamic behavior of a suspension bridge by a random vibration based spectral analysis approach and two response spectrum methods. Bosphorus Suspension Bridge built in Turkey and connects Europe to Asia in Istanbul is selected as a numerical example. The spatial variability of ground motions between the support points is taken into account with a coherency function that characterizes the incoherence, wave-passage and site-response effects. Power spectral density function and response spectrum values used in random vibration analyses are determined depending on the recordings of August 17, 1999, Kocaeli, Turkey earthquake. From the results, it can be observed that the structural responses for each random vibration analysis depend largely on the intensity and frequency contents of power spectral density functions.

Inelastic effects in molecular transport junctions: The probe technique at high bias.

We extend the Landauer-Büttiker probe formalism for conductances to the high bias regime and study the effects of environmentally induced elastic and inelastic scattering on charge current in single molecule junctions, focusing on high-bias effects. The probe technique phenomenologically incorporates incoherent elastic and inelastic effects to the fully coherent case, mimicking a rich physical environment at trivial cost. We further identify environmentally induced mechanisms which generate an asymmetry in the current, manifested as a weak diode behavior. This rectifying behavior, found in two types of molecular junction models, is absent in the coherent-elastic limit and is only active in the case with incoherent-inelastic scattering. Our work illustrates that in the low bias-linear response regime, the commonly used "dephasing probe" (mimicking only elastic decoherence effects) operates nearly indistinguishably from a "voltage probe" (admitting inelastic-dissipative effects). However, these probes realize fundamentally distinct I-V characteristics at high biases, reflecting the central roles of dissipation and inelastic scattering processes on molecular electronic transport far-from-equilibrium.

Büttiker probes for dissipative phonon quantum transport in semiconductor nanostructures

Theoretical prediction of phonon transport in modern semiconductor nanodevices requires atomic resolution of device features and quantum transport models covering coherent and incoherent effects. The nonequilibrium Green's function method is known to serve this purpose well but is numerically expensive in simulating incoherent scattering processes. This work extends the efficient Büttiker probe approach widely used in electron transport to phonons and considers salient implications of the method. Different scattering mechanisms such as impurity, boundary, and Umklapp scattering are included, and the method is shown to reproduce the experimental thermal conductivity of bulk Si and Ge over a wide temperature range. Temperature jumps at the lead/device interface are captured in the quasi-ballistic transport regime consistent with results from the Boltzmann transport equation. Results of this method in Si/Ge heterojunctions illustrate the impact of atomic relaxation on the thermal interface conductance and the importance of inelastic scattering to activate high-energy channels for phonon transport. The resultant phonon transport model is capable of predicting the thermal performance in the heterostructure efficiently.

Incoherent tunneling effects in a one-dimensional quantum walk

In this article we investigate the effects of shifting position decoherence, arising from the incoherent tunneling effect in the experimental realization of the quantum walk, on the one-dimensional discrete time quantum walk. We show that in the regime of this type of noise the quantum behavior of the walker does not vanish, in contrast to the coin decoherence for which the walker undergoes a quantum-to-classical transition even for weak noise. In particular, we show that the quadratic dependence of the variance on the time and also the coin–position entanglement, i.e. two important quantum aspects of the coherent quantum walk, are preserved in the presence of tunneling decoherence. Furthermore, we present an explicit expression for the probability distribution of the decoherent one-dimensional quantum walk in terms of the corresponding coherent probabilities, and show that this type of decoherence smooths the probability distribution.

Seismic response and design method of single large span structures to spatially random ground motions

This article aims at studying the seismic response rules and design method of single large span structures to spatially varying ground motions. A corrected earthquake power spectral density model is first proposed and applied to the following solution process. The practical solution form of the multi-support pseudo excitation method is put forward and used to analyze the seismic response. The total response is divided into the pseudo-static and relative dynamic response. A simplified single large span structural model is used as the research object to study the response law when both the wave-passage effect and incoherence effect are considered. The result shows that the wave-passage effect and incoherence effect can both increase the pseudo-static response. The relative dynamic response is influenced by the form of trigonometric function, while wave-passage frequency influences the period and coherence function results in amplitude attenuation. When the ratio of natural frequency to wave-passage frequency equals to 0.5 n ( n = 0, 1, 2,…), the structural seismic response reaches extreme value. Based on the derived response law, a method of quickly determining the most unfavorable conditions of the multi-support excitation effect is proposed for seismic design of single large span structures.

Research progress of super-continuum terahertz source based on nano-structures and terahertz lab on-chip system

The terahertz applications of bio-materials and energetic materials are hindered by the low power-intensity of the terahertz output and the narrow band of terahertz emission. So the crucial part of the development of terahertz time-domain spectroscopy (TDS) systems is the new terahertz source with broadband frequency range and high power output. As to the free-space TDS system, the system is necessarily purged by dried nitrogen gas to remove the absorbed water vapor. In addition, the low detection sensitivity also exists because of the free-space interactions between the terahertz emission and the substances. To address these problems, terahertz lab on-chip system is proposed. The local field effect in the nano-structures of on-chip system can contribute to the detection of low concentration of the substance. The present paper is composed of two sections. Firstly, a new terahertz source based on the metal nano-film can produce an intense and broad-band terahertz-infrared emission, which is comprised of incoherent terahertz-infrared signals and coherent terahertz signals. This emission can cover more than 100 THz and has an output power of up to 10 mW. This optical phenomenon mainly arises from the incoherent thermal radiation effect. Secondly, the terahertz lab on-chip systems with different transmission lines and different substrates are clarified. There exists lower loss on the on-chip system with coplanar stripline structure and copolymer substrate. High sensitivity of biological detection in terahertz band of up to 2 THz can be achieved by using this system.

Research on the random seismic response analysis for multi- and large-span structures to multi-support excitations

The pseudo excitation method (PEM) has been improved into a more practical form, on which the analytic formulae of seismic response power spectral density (PSD) of simplified large-span structural models have been derived. The analytic formulae and numerical computing results of seismic response PSD have been derived to study the mechanism of multi-support excitation effects, such as the wave-passage effect and incoherence effect, for the seismic response of multiand large-span structures. By using a multi-span truss as an example, the influence of multi-support excitation effects on the seismic response of such structures is studied.

Creep influence on structural dynamic reliability

Creep brings forth considerable influences on both static and dynamic behaviours of concrete structures. This paper intends to deepen the investigation on the creep influence on structural dynamic performance, evaluating their relationship from the view of reliability. The influencing mechanism of concrete creep on structural dynamic behaviour is first stated. Integration of the structural creep analysis by the Model B3 and the age-adjusted effective modulus method with the stochastic seismic analysis by the pseudo-excitation method is then proposed. Based on the creep-influenced structural static and stochastic seismic behaviours, formulations for the dynamic reliability with the consideration of creep effect are derived using the first-passage failure criterion and Poisson crossing assumption. A systematic numerical simulation is conducted on a long-span concrete filled steel tube arch bridge, considering (1) the creep influence on concrete mechanical properties and structural configuration and internal forces; (2) the dimensionality, wave passage effect and incoherence effect of random ground motions; and (3) the uncertainties existing in the structure and creep behaviour. Critical conclusions are drawn and it is recommended to consider the long-term effect of dead loads in seismic design to ensure structural seismic safety.

Procedimientos de humor en Théâtre sans animaux de Jean-Michel Ribes

Nous étudions les pièces du recueil Théâtre sans animaux sous l’angle de l’humour. Méthodologiquement, nous définissons deux procédés qui jouent sur les effets d’incohérence: l’insolite et l’absurde. Nous étudions ensuite ces deux procédés et les effets qu’ils produisent dans le texte de Jean-Michel Ribes. Il est mis en évidence la spécificité de l’humour de Ribes qui articule l’insolite à l’absurde.

Comparion of seismic response of single-layer reticulated dome under unform and incoherence three-directional excitations

Seismic ground motions at structural supports are spatially varying and incoherent. The spatial incoherency effects should be considered for structures with large span and multiple supports. Two single-layer reticulated domes of 120m span, with and without substructures under incoherent multiple supports and uniform excitations were modeled and analysed in this study. Time-history responses of structures are obtained and compared for simulated ground motion records. For the simulation, use of existing phase difference spectrum models and coherence models were considered, and three-directional excitations (two horizontal directions and vertical direction) are considered. The analysis results show that the spatial coherency effect can influence the seismic responses of reticulated domes. The results also indicate that the seismic spatial coherency of all three directions can be important, especially for structures without flexible substructures.