Predicting Display Visibility Under Dynamically Changing Lighting Conditions

Display devices, more than ever, are finding their ways into electronic consumer goods as a result of recent trends in providing more functionality and user interaction. Combined with the new developments in display technology towards higher reproducible luminance range, the mobility and variation in capability of display devices are constantly increasing. Consequently, in real life usage it is now very likely that the display emission to be distorted by spatially and temporally varying reflections, and the observer's visual system to be not adapted to the particular display that she is viewing at that moment. The actual perception of the display content cannot be fully understood by only considering steady-state illumination and adaptation conditions. We propose an objective method for display visibility analysis formulating the problem as a full-reference image quality assessment problem, where the display emission under "ideal" conditions is used as the reference for real-life conditions. Our work includes a human visual system model that accounts for maladaptation and temporal recovery of sensitivity. As an example application we integrate our method to a global illumination simulator and analyze the visibility of a car interior display under realistic lighting conditions.     

Perceptually‐motivated Real‐time Temporal Upsampling of 3D Content for High‐refresh‐rate Displays

High‐refresh‐rate displays (e. g., 120 Hz) have recently become available on the consumer market and quickly gain on popularity. One of their aims is to reduce the perceived blur created by moving objects that are tracked by the human eye. However, an improvement is only achieved if the video stream is produced at the same high refresh rate (i. e. 120 Hz). Some devices, such as LCD TVs, solve this problem by converting low‐refresh‐rate content (i. e. 50 Hz PAL) into a higher temporal resolution (i. e. 200 Hz) based on two‐dimensional optical flow. In our approach, we will show how rendered three‐dimensional images produced by recent graphics hardware can be up‐sampled more efficiently resulting in higher quality at the same time. Our algorithm relies on several perceptual findings and preserves the naturalness of the original sequence. A psychophysical study validates our approach and illustrates that temporally up‐sampled video streams are preferred over the standard low‐rate input by the majority of users. We show that our solution improves task performance on high‐refresh‐rate displays.     

Twenty years of telecommunications research in BIT

This paper reflects on 20 years of behavioural research in telecommunications published in BIT. The past 20 years have seen major changes in telecommunications technology and applications. They have also seen the deregulation of telecommunications markets and the pervasive penetration of the working environment by networked systems. Papers published in BIT have reflected these changes. Some research topics have attracted continuing interest throughout this period, and two are reviewed briefly: the effect of network delays on users and the relative effectiveness of different media and user choices between them. In addition many new technical and theoretical developments have been reported. Two major theoretical trends have been the convergence between behavioural research in telecommunications and computing, and the rise in social-science-based research. The question whether published behavioural research has been able to influence the development of the technologies studied is considered. Finally, the paper speculates on future topics for research.     

Monolithic Perovskite/Silicon Tandems with >28% Efficiency: Role of Silicon-Surface Texture on Perovskite Properties

Textured silicon wafers used in silicon solar cell manufacturing offer superior light trapping, which is a critical enabler for high-performance photovoltaics. A similar optical benefit can be obtained in monolithic perovskite/silicon tandem solar cells, enhancing the current output of the silicon bottom cell. Yet, such complex silicon surfaces may affect the structural and optoelectronic properties of the overlying perovskite films. Here, through extensive characterization based on optical and microstructural spectroscopy, it is found that the main effect of such substrate morphology lies in an altering of the photoluminescence response of the perovskite, which is associated with thickness variations of the perovskite, rather than lattice strain or compositional changes. With this understanding, the design of high-performance perovskite/silicon tandems is rationalized, yielding certified power conversion efficiencies of >28%.     

Reverse engineering approach to appearance-based design of metallic and pearlescent paints

We propose a new approach to interactive design of metallic and pearlescent coatings, such as automotive paints and plastic finishes of electronic appliances. This approach includes solving the inverse problem, that is, finding pigment composition of a paint from its bidirectional reflectance distribution function (BRDF) based on a simple paint model. The inverse problem is solved by two consecutive optimizations calculated in real-time on a contemporary PC. Such reverse engineering can serve as a starting point for subsequent design of new paints in terms of appearance attributes that are directly connected to the physical parameters of our model. This allows the user to have a paint composition in parallel with the appearance being designed.     

Broadcasting Spanning Forests on a Multiple-Access Channel

The problem of finding a spanning forest of a graph in a distributed-processing environment is studied. If an input graph is weighted, then the goal is to find a minimum-weight spanning forest. The processors communicate by broadcasting. The output consists of the edges that make a spanning forest and have been broadcast on the network. Input edges are distributed among the processors, with each edge held by one processor. The underlying broadcast network is implemented as a multiple-access channel. If exactly one processor attempts to perform a broadcast, then the broadcast is successful. A message broadcast successfully is delivered to all the processors in one step. If more than one processors broadcast simultaneously, then the messages interfere with each other and no processor can receive any of them. Optimality of algorithmic solutions is investigated, by way of comparing deterministic with randomized algorithms, and adaptive with oblivious ones. Lower bounds are proved that either justify the optimality of specific algorithms or show that the optimal performance depends on a class of algorithms.     

Toward Constructive Dialogue: "The Ploughshare Of Evil" Comes Again. Commentary on the Special Section on Structural and Relational Psychoanalysis.

Comments on A. Sugarman and A. Wilson, J. F. Murray, F. Busch, Sugarman, J. L. Bachant et al, and Wilson (see PA, Vol 82:33123; 33115; 34118; 33122; 33102; and 33124, respectively), authors of the special section on contemporary structural and relational analysis, and finds little constructive dialog. Marshall states that these articles are characterized by overbroad generalizations, preemptive judgments, and premature conclusions. Marshall also states that many of the articles put relational ideas through the filter of structural psychoanalysis, in the process changing them beyond recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison study for Level set and Direct Lagrangian methods for computing Willmore flow of closed planar curves

The main goal of this paper is to present results of comparison study for the level set and direct Lagrangian methods for computing evolution of the Willmore flow of embedded planar curves. To perform such a study we construct new numerical approximation schemes for both Lagrangian as well as level set methods based on semi-implicit in time and finite/complementary volume in space discretizations. The Lagrangian scheme is stabilized in tangential direction by the asymptotically uniform grid point redistribution. Both methods are experimentally second order accurate. Moreover, we show precise coincidence of both approaches in case of various elastic curve evolutions provided that solving the linear systems in semi-implicit level set method is done in a precise way, redistancing is performed occasionally and the influence of boundary conditions on the level set function is eliminated. The authors were partly supported by the following projects and grants: the project HPC-EUROPA(RII3-CT-2003-506079), the NCMM project LC06052, VEGA 1/3321/06 grant, the project MSM 6840770010 and APVV-0247-06, APVV-RPEU-0004-06 grants.     

How membrane properties shape the discharge of motoneurons: a detailed analytical study

Electrophysiological experiments and modeling studies have shown that afterhyperpolarization regulates the discharge of lumbar motoneurons in anesthetized cats and is an important determinant of their firing properties. However, it is still unclear how firing properties depend on slow afterhyperpolarization, input conductance, and the fast currents responsible for spike generation. We study a single-compartment integrate-and-fire model with a slow potassium conductance that exponentially decays between spikes. We show that this model is analytically solvable, and we investigate how passive and active membrane properties control the discharge. We show that the model exhibits three distinct firing ranges (primary, secondary, and high frequency), and we explain the origin of these three ranges. Explicit expressions are established for the gain of the steady-state current-frequency (I-f) curve in the primary range and for the gain of the I-f curve for the first interspike interval. They show how the gain is controlled by the maximal conductance and the kinetic parameters of the afterhyperpolarization conductance. The gain also depends on the spike voltage threshold, and we compute how it is decreased by threshold accommodation (i.e., the increase of the threshold with the injected current). In contrast, the gain is not very sensitive to the input conductance. This implies that tonic synaptic activity shifts the current-frequency curve in its primary range, in agreement with experiments. Taking into account the absolute refractory period associated with spikes somewhat reduces the gain in the primary range. More importantly, it accounts for the approximately linear and steep secondary range observed in many motoneurons. In the nonphysiological high-frequency range, the behavior of the I-f curve is determined by the fast voltage-dependent currents, via the amplitude of the fast repolarization afterspike, the duration of the refractory period, and voltage threshold accommodation, if present.