Self-induced Distortion Research Articles

Small polaron transport in cathode materials of rechargeable ion batteries

Small polarons are quasi-particles in materials formed by a charge carrier and its self-induced distortion. In cathode materials containing transition metal elements, small polarons play an important role in the diffusion of charge carriers. In order to grasp the fundamentals of small polarons inside cathodes, we highlight the recent progress from both experiments and simulations focusing on the formation of small polarons and their migration. Because of their strong binding to small polarons, alkali ions accompany polarons during diffusion and thus the polaron – ion couple can be considered a complex quasi-particle. The diffusion mechanism of alkali ions inside cathodic materials can be explored by a simultaneous diffusion simulation approach, which naturally and accurately depicts the diffusion of alkali ions (and alkali vacancies) and their accompanying small polarons as complex diffusion particles during alkali intercalation and de-intercalation. The successful employment of this approach paves a new direction toward elucidating the diffusion mechanism in several promising cathode materials containing transition metals. This model and its application to the investigation of the electrochemical properties of several typical cathodic materials such as NASICON, P O 4 4 − –, S O 4 4 − –, and S i O 4 4 − – anion– based compounds are comprehensively demonstrated. • Traditional polarons and small polarons are introduced and clarified. • Evidence of polaron formation is demonstrated in both experimental and theoretical aspects. • Role of small polarons in electrochemical properties is explained. • An advanced simulation approach by which ion diffusion can be precisely explored is introduced.

Viscous diffusion effects on the self-induced distortions of rectangular vortex rings

Large eddy simulation, stereoscopic particle image velocimetry, and hot-wire anemometry are conducted to study the viscous diffusion effects on the self-induced deformations of the aspect ratio 2 rectangular vortex rings at Reynolds numbers Ri = UDh/ν = 355, 877.5, 1775, 8775, 17 750 (i = 1, …, 5). The differences between the axis-switching of isolated vortex rings and rectangular jets are explained. At increased viscous effects, the rotational content of the vortices diffuses and grows in size. The high curvature corners of the rectangular vortex rings induce additional velocities which distort the topology until it appears to be rotated for 90°, the so-called axis-switching phenomenon. Strong viscous effects (R1) diffuse the ring before the switching is completed, while reduced viscous effects allow for the first (R2, R3) and second (R4, R5) switching. For R2 and R3, the rotated rectangular rings bifurcate into a pair of semi-circular topologies. Space-time mapping of the instantaneous streamwise velocity at the vortex ring axis reveals strong correlation spots for the occurrence of each axis-switching. Vortex rings are found to decelerate more quickly with increased viscous effects and hence exhibit reduced penetration rates. The temporal variation of the advection velocity of the vortex ring demonstrates major peaks in accordance with the number of axis-switchings. Trajectories of the vortex cores in two orthogonal planes demonstrate contractions/expansions conforming to the sine/cosine waves associated with the varicose instability modes. A pair of orthogonal varicose modes interacts with the phase lagging/leading equal to the quarter of a full cycle which is interestingly equal to the axis-switching frequency.

The unified theory of repression

Repression has become an empirical fact that is at once obvious and problematic. Fragmented clinical and laboratory traditions and disputed terminology have resulted in a Babel of misunderstandings in which false distinctions are imposed (e.g., between repression and suppression) and necessary distinctions not drawn (e.g., between the mechanism and the use to which it is put, defense being just one). "Repression" was introduced by Herbart to designate the (nondefensive) inhibition of ideas by other ideas in their struggle for consciousness. Freud adapted repression to the defensive inhibition of "unbearable" mental contents. Substantial experimental literatures on attentional biases, thought avoidance, interference, and intentional forgetting exist, the oldest prototype being the work of Ebbinghaus, who showed that intentional avoidance of memories results in their progressive forgetting over time. It has now become clear, as clinicians had claimed, that the inaccessible materials are often available and emerge indirectly (e.g., procedurally, implicitly). It is also now established that the Ebbinghaus retention function can be partly reversed, with resulting increases of conscious memory over time (hypermnesia). Freud's clinical experience revealed early on that exclusion from consciousness was effected not just by simple repression (inhibition) but also by a variety of distorting techniques, some deployed to degrade latent contents (denial), all eventually subsumed under the rubric of defense mechanisms ("repression in the widest sense"). Freudian and Bartlettian distortions are essentially the same, even in name, except for motive (cognitive vs. emotional), and experimentally induced false memories and other "memory illusions" are laboratory analogs of self-induced distortions.

A 10 GB/S EQUALIZER WITH INTEGRATED CLOCK AND DATA RECOVERY FOR OPTICAL COMMUNICATION SYSTEMS

A 10 Gb/s analog continuous-time equalizer with integrated clock and data recovery circuit is presented. It is designed to recover signals degraded by chromatic and polarization mode dispersion. The key components in the design are a feedforward equalizer and a decision feedback equalizer, the parameters of which are electronically adjustable. Both circuit blocks are fully described and characterized with emphasis on minimizing self-induced distortion and maximizing high-speed performance. In addition to the equalizer and the clock and data recovery, the circuit also includes an integrated automatic gain control. The circuit is implemented in a commercial 0.18 μm SiGe BiCMOS technology and consumes 900 mW. The capacity of the equalizer to mitigate signal impairments is demonstrated using three electrically generated channels.

Emotional memory failures: On forgetting and reconstructing emotional experiences

I. Wessel, D. B. Wright, Emotional Memory Failures: On Forgetting and Reconstructing Emotional Experiences. A.J. Barnier, L. Hung, M. Conway, Retrieval-induced Forgetting of Emotional and Unemotional Autobiographical Memories. R.J. McNally, S.A. Clancy, H.M. Barrett, H.A. Parker, Inhibiting Retrieval of Trauma Cues in Adults Reporting Histories of Childhood Sexual Abuse. L.B. Myers, N. Derakshan, To Forget or Not to Forget: What Do Repressors Forget and When Do They Forget? A.J. Barnier, K. Levin, A. Maher, Suppressing Thoughts of Past Events: Are Repressive Copers Good Suppressors? M.S. Shane, J.B. Peterson, Self-induced Distortions and the Allocation of Processing Resources at Encoding and Retrieval. L.J. Levine, S. Bluck, Painting with Broad Strokes: Happiness and the Malleability of Event Memory. V. Nourkova, D.M. Bernstein, E.F. Loftus, Altering Traumatic Memory.

Strong Self-Induced Distortion of a Laser Beam in a Longitudinal Gas Flow

A method for the approximate description of the propagation of an intense optical beam using mean transverse dimensions and displacements of the center of gravity is extended to longitudinal gas flows past a laser beam. The problem is reduced to integrodifferential equations for the mean radii. Solution of the aero-optic equations are obtained for strong self-induced thermal distortion of the vertical beam under conditions of developed gravitational convection and for strong self-induced thermal distortion of the beam in a longitudinal homogeneous gas flow, including at high supersonic velocities. It is shown that the results obtained are in satisfactory agreement with the numerical solutions. An analytic solution in quadratures is obtained for a plane beam in a longitudinal stream.

Compressor Rotating Stall in Uniform and Nonuniform Flow

Rotating stall in axial compressors consists of regions or cells of retarded flow moving around the annulus relative to the blades. Planar symmetry is destroyed, resulting in stalled blades in part of the annulus and unstalled blades in the remainder. The stall cell moves in the direction opposite to the rotor, relative to the blades, but since the relative speed of propagation is usually less than the rotor speed, the cell is seen to move in the same direction as the rotor from an absolute reference frame. The presence of the stall cells results in a deterioration of compressor performance since the maximum pressure ratio is not achieved in regions of retarded flow. Furthermore, since this self-induced distortion is periodic, the forced frequencies generated may coincide with the natural harmonics of the blading, tending to cause structural damage. This paper describes a series of experiments in which a single-stage, lightly loaded compressor operated under stall-free conditions and with rotating stall, both with uniform inlet flow and with distortions generated by an upstream screen of uniform porosity. Not only was the overall compressor performance determined in the traditional manner, but the distribution of static pressure over the rotor suction and pressure surfaces was measured with high response instrumentation. The rotor pressure profiles measured in both undistorted and distorted flow are presented for operation before and after the onset of rotating stall and the latter are compared with the steady flow results. It is observed that two distinctly different types of rotating stall exist depending upon whether or not an inlet flow distortion is present. These cells differ not only in macroscopic properties—rotational speed, circumferential extent, mass-averaged flow conditions, etc.—but also in detailed flow characteristics as evidenced by the rotor blade static pressure distributions. It is further observed that not all inlet distortion geometries lead to the development of rotating stall.

An Actuator Disc Analysis of Inlet Distortion and Rotating Stall in Axial Flow Turbomachines

The flow behind a rotor (or stator) blade row due to an arbitrary inlet distortion along both circumferential and spanwise directions is treated on the basis of classical actuator disc approximation. I t is shown that, in general, the spanwise and the circumferential distortion waves interact, so that the combined influence is not the sum of the influences of the two simple types of distortions. Numerical examples are then given to show the influence of the various conventional design parameters. Also illustrated is the role played by the cascade characteristics, represented by the variations of loss and exit flow angle due to changing inlet flow angles. I t is shown that both quantities exert a significant influence on the flow under inlet distortion. Using the same approach to the problem of incipient stall, the analysis shows that theoretically there can be two types of selfinduced distortion—a purely spanwise, axisymmetric type, and a traveling, circumferential plus spanwise type, the latter including a purely circumferential type as a special case. However, the analysis also indicates the interesting result that the purely circumferential type of traveling stall will, in all'likelihood, precede the other types. One aspect of dela}dng the incipient traveling (rotating) stall can then be reduced to two extremely simple rules with respect to the desirable design parameters and cascade geometry.