Perceptual Processes as Charting Operators

Visual space perception has been a topic of sustained research since the nineteenth century. Much of this research into the geometry of visual space, however, required observers to make judgments about spatial relationships between isolated points in total darkness. While a sizeable number of previous investigations have now explored visual space perception in outdoor natural environments, nearly all of the previous investigations evaluating the curvature of visual space have utilized only small numbers of observers. In the current experiment, a large number (30) of observers adjusted triangular configurations of markers in an outdoor field until they appeared either as equilateral or right triangles in depth. There was a wide range of outcomes, such that the observers’ judgments were consistent with elliptic, Euclidean, and hyperbolic geometry. There is thus no single consistent relationship between physical space and perceived space. Furthermore, the geometry of visual space frequently changes as the size of spatial configurations is varied—for many observers, judgments for small configurations are consistent with elliptic or Euclidean geometry while judgments for large configurations are frequently consistent with hyperbolic geometry.

In the cercal system of the cockroach Periplaneta americana, primary sensory interneurons exhibiting a sharp directional sensitivity respond to wind in a linear manner whereas those exhibiting an omnidirectional sensitivity respond nonlinearly. For example, the wind-evoked response in an identifiable, nonspiking local interneuron, 101, which responds preferentially to wind from the left versus the right, is characterized exclusively by a differential first-order (linear) kernel. However, the slow potential response in a cercal giant interneuron, GI-1, is omnidirectional, and characterized by a second-order (nonlinear) kernel with an elongated depolarizing peak on the diagonal with two off-diagonal valleys. We here examined the neural circuitry underlying the linear and nonlinear representations of wind information by the deprivation of inputs from particular sets of cercal hair afferents. Electrical stimulation of the ipsilateral (related to the soma) cercal nerve elicited a depolarizing potential in 101, which was followed by delayed hyperpolarization. A continuous flow of 10(-4) M picrotoxin, which selectively blocked this delayed hyperpolarization, resulted in a significant change in the 101 response from linear to nonlinear. Because no frequency-doubling response was observed, the nonlinearity is due to signal compression (or rectification) that reflects the mechanical property of cercal afferents. This is consistent with the hypothesis that the linear representation in 101 is based on a subtraction process between two subsets of particular column hairs, whose best optimal directions are opposite to each other.

1. We studied the responses of rat hypoglossal and cat lumbar motoneurones to a variety of excitatory and inhibitory injected current transients during repetitive discharge. The amplitudes and time courses of the transients were comparable to those of the synaptic currents underlying unitary and small compound postsynaptic potentials (PSPs) recorded in these cells. Poisson trains of ten of these excitatory and ten inhibitory current transients were combined with an additional independent, high-frequency random waveform to approximate band limited white noise. The white noise waveform was then superimposed on long duration (39 s) suprathreshold current steps. 2. We measured the effects of each of the current transients on motoneurone discharge by compiling peristimulus time histograms (PSTHs) between the times of occurrence of individual current transients and motoneurone discharges. We estimated the changes in membrane potential associated with each current transient by approximating the passive response of the motoneurone with a simple resistance-capacitance circuit. The relations between the features of these simulated PSPs and those of the PSTHs were similar to those reported previously for real PSPs: the short-latency PSTH peak (or trough) was generally longer than the initial phase of the PSP derivative, but shorter than the time course of the PSP itself. Linear models of the PSP to PSTH transform based on the PSP time course, the time derivative of the PSP, or a linear combination of the two parameters could not reproduce the full range of PSTH profiles observed. 3. We also used the responses of the motoneurones to the white noise stimulus to derive zero-, first- and second-order Wiener kernels, which provide a quantitative description of the relation between injected current and discharge probability. The convolution integral computed for an injected current waveform and the first-order Wiener kernel should provide the best linear prediction of the associated PSTH. This linear model provided good matches to the PSTHs associated with a wide range of current transients. However, for the largest amplitude current transients, a significant improvement in the PSTH match was often achieved by expanding the model to include the convolution of the second-order Wiener kernel with the input. 4. The overall transformation of current inputs into firing rate could be approximated by a second-order Wiener model, i.e. a cascade of a dynamic, linear filter followed by a static non-linearity. At a given mean firing rate, the non-linear component of the response of the motoneurone could be described by the square of the linear component multiplied by a constant coefficient. The amplitude of the response of the linear component increased with the average firing rate, whereas the value of the multiplicative coefficient in the non-linear component decreased. As a result, the overall transform could be predicted from the mean firing rate and the linear impulse response, yielding a relatively simple, general description of the motoneurone input-output function.

The shape of an RF pulse is distorted upon propagating through an X-band accelerator structure due to dispersive effects. This distortion together with beam loading introduce energy spread between 192 bunches. In order to minimize this energy spread we modify the input RF pulse shape. The pulse propagation, energy gain, and beam loading are modeled with a mode-matching computer code and a circuit model. A 2D model and a circuit model of a complete 60 cm structure, consisting of 55 cells and input and output couplers is analyzed. This structure operates with a 5{pi}/6 phase advance per cell. Dispersive effects for this structure are more significant than for previously studied 2{pi}/3 phase advance accelerating structures. Experimental results are compared with the theoretical model and excellent agreement is obtained for the propagation of an RF pulse through the structure.

Understanding Central Processes

This article interrogates the theoretical articulations of the body–space nexus through the formulation of an alternative methodological framework. It advances the premise that body and space cannot be reduced to physical parameters or representational models; rather, they are continually reconstituted through experience, perception, cultural contexts, and relational processes. Against the backdrop of fragmented spatial, phenomenological, and socio-political readings of space, Joseph Kosuth’s “One and Three Chairs” [1965] is posited as a conceptual compass, while semiotic instruments are mobilized as analytical devices. Within this constellation, the body–space relation is examined through a trialectical configuration that couples three relational modalities—distance, togetherness, and plurality—with three representational dimensions: object, image, and definition. The analysis shows how each modality delineates a distinct regime of bodily–spatial interaction and exposes the ways in which these regimes become manifest within architectural experience, social production, and conceptual potential. Within this framework, the notion of the flesh of space is advanced to describe space as a relational field in which bodies, materials, images, and definitions become mutually entangled. The principal contribution of this study lies in advancing a methodological orientation that transcends normative metrics and reductionist representational paradigms, thereby enabling body–space relations to be apprehended through relational dynamics and multilayered processes of signification. In doing so, this article provides a critical ground for rethinking architectural epistemology from a more flexible, experiential, and plural perspective, and proposes a transferable analytical scaffold for future case-based and design-oriented research.

The relationship between chromatically modulated stimuli and visual evoked potentials (VEPs) was considered. VEPs of normal subjects elicited by chromatically modulated stimuli were measured under several color adaptations, and their binary kernels were estimated. Up to the second-order, binary kernels obtained from VEPs were so characteristic that the VEP-chromatic modulation system showed second-order nonlinearity. First-order binary kernels depended on the color of the stimulus and adaptation, whereas second-order kernels showed almost no difference. This result indicates that the waveforms of first-order binary kernels reflect perceived color (hue). This supports the suggestion that kernels of VEPs include color responses, and could be used as a probe with which to examine the color visual system.

Correlation analysis is applied to estimate the first- and second-order kernels in a Volterra series expansion of bilinear systems. The kernels are estimated for a simulation model of a nuclear fission process. The method yields good estimates of the first-order kernel under noisy input-output measurements. However, the estimation of the second-order kernel is not satisfactory, due to the presence of higher order Volterra kernels. A new algorithm is developed to identify the parameter matrix B which characterizes the nonlinear part of a bilinear system. The estimation of the second-order kernel is significantly improved.

SummaryThe issues of cluster synchronization and state estimation for a class of nonlinear complex dynamical networks are concurrently focused in this study. In precise, led by the design of complex dynamical networks, a proportional integral‐based observer is implemented for achieving robustness, by the virtue of which the states of examined networks are estimated. Thereupon, a proportional integral observer‐based hybrid triggered control scheme is proposed, wherein, the switch‐over between time‐ and event‐ triggered scheme is governed through a Bernoulli distributed random variable. Further, with the application of mixed and passivity performance technique, the external disturbances for the addressed complex dynamical networks are reduced. Based on the Lyapunov stability theory, the requisite sufficient conditions in respect of linear matrix inequalities are provided which ensures the discussed complex dynamical network's synchronization phenomenon. In a further, the presented criteria are exploited for the attainment of required controller, proportional and integral gain matrices. In conclusion, the applicability of proposed results and efficacy of the undertaken strategy are evidently proven with the illustration of two numerical examples with Chua's circuit and Goodwin oscillator model.

Accurate representation of processes associated with energy extraction from subsurface formations often requires models which account for chemical interactions between different species in the presence of multiphase flow. In this study, we focus on modeling of acid stimulation in the near-well region. For the chemical processes which include a dissolution of rock material, an issue arises with the predictive representation of flow. Taking into account the spatial scale of discretization, some of simulation control volumes can have values of porosity close to 1, which makes an application of Darcy's law inconsistent and requires employing a true momentum equation such as the Darcy-Brinkman-Stokes (DBS) equation. The DBS equation automatically switches the description between Darcy equation in control volumes with low porosity and Stokes equation in grid blocks with high porosity. For chemical reactions, we propose a local nonlinear solution technique that allows solving the balance of solid species separately yet retaining the full coupling with rest of the equations. Finally, we study the impact of multiphase flow. The DBS approach is not well established for multiphase flow description. Therefore we employ a hybrid approach, where we assume that the single-phase DBS flow and the multiphase Darcy flow occur in separate regions. We test the accuracy and performance of both approaches on realistic models of practical interest.

We present analytic force-free solutions modeling rotating stars and black holes immersed in the magnetic field of a thin disk that terminates at an inner radius. The solutions are exact in flat spacetime and approximate in Kerr spacetime. The compact object produces a conical jet whose properties carry information about its nature. For example, the jet from a star is surrounded by a current sheet, while that of a black hole is smooth. We compute an effective resistance in each case and compare to the canonical values used in circuit models of energy extraction. These solutions illustrate all of the basic features of the Blandford-Znajek process for energy extraction and jet formation in a clean setting.

Efficient Maximum Power Point Tracking (MPPT) techniques play a vital role in optimizing energy extraction from photovoltaic (PV) systems, primarily due to the high sensitivity of photovoltaic panel (PVP) characteristics to varying environmental parameters, including ambient temperature and solar irradiance. Conventional MPPT methods generally depend on identifying and following reference points, which are extracted from variables closely related to the Maximum Power Point (MPP) on the external current-voltage characteristics of PVP. In response to the limitations inherent to traditional approaches, this study proposes an advanced lookup table strategy to generate highly accurate reference values explicitly as functions of measured ambient temperature and solar irradiance. Initially, this research employs the two-diodes electrical circuit model to rigorously define the foundational relationships between ambient temperature, irradiance, and photovoltaic panel performance. Subsequently, contemporary advanced extraction methods based on recent academic literature were applied, enabling accurate identification of the MPP coordinates. Creating an effective lookup table requires comprehensive and detailed experimental datasets, which are often insufficient or unevenly distributed in practical scenarios. To address this challenge, the Shepard global interpolation method was integrated into the model development process, effectively mitigating datasets limitations through accurate interpolation of missing data points. This approach significantly elevates the precision and robustness of MPPT models. A comprehensive case study, conducted with real-world experimental datasets, rigorously validated the accuracy and reliability of the proposed interpolation-based lookup table. The results confirm substantial enhancements in MPPT accuracy, facilitating greater energy extraction efficiency and improved overall performance in practical photovoltaic applications. DOI: 10.61416/ceai.v27i4.9541

Response inhibition is a key component of executive functioning, but the role of perceptual processes has only recently been focused. Although the interrelation of incoming information and resulting behavioural (motor) effects is well-known to depend on gain control mechanisms, the causal role of sensory gain modulation for response inhibition is elusive. We investigate it using a somatosensory response inhibition (Go/Nogo) task and examine the effects of parietal (somatosensory) cathodal and sham tDCS stimulation on a behavioural and neurophysiological level. For the latter, we combine event-related potential (ERP) and source localization analyses. Behavioural results reveal that cathodal stimulation leads to superior inhibition performance as compared to sham stimulation depending on the intensity of tDCS stimulation. The neurophysiological data show that an early (perceptual) subprocess of the Nogo-N2 ERP-component is differentially modulated by the type of stimulation but not a later (response-related) Nogo-N2 subcomponent. Under cathodal stimulation, the early N2 amplitude is reduced and the right inferior frontal gyrus (BA45) is less active. Cathodal tDCS likely enhances inhibition performance via decreasing the efficiency of gain control and the impact of sensory stimuli to trigger prepotent responses. Thereby, response inhibition processes, associated with structures of the response inhibition network, become less demanded.

Kinetic energy plays an important role in the energy management of dynamic soaring which is a non-powered flight mode by which a flying object (aerial vehicle, bird) extracts energy from horizontally moving air. Therefore, it is important to use an appropriate kinetic energy concept. It is shown that kinetic energy based on inertial speed as speed relating to an inertial reference system is adequate for this purpose. The treatment of this kinetic energy form is conducted on a fundamental level involving the equations of motion as well as on a specific level dealing with the energy transfer between the wind and an aerial vehicle or a bird during the individual phases of dynamic soaring. Choosing an adequate kinetic energy concept is particularly important for problems such as optimizing dynamic soaring for maximizing the energy gain from the wind.

In this paper we investigate the equatorial causal (time-like and null) circular geodesics of the Kerr–Newman–Taub–NUT (Newman–Unti–Tamburino) black hole in four-dimensional Lorentzian geometry. The special characteristics of this black hole are that it is of Petrov–Pirani type-D and the photon trajectories are doubly degenerate principal null congruence. We derive the conditions for the existence of the innermost stable circular orbit, marginally bound circular orbit and circular photon orbit in the background of Kerr–Newman–Taub–NUT (KNTN) spacetime. The effective potential for both time-like and null cases have been studied. It is shown that the presence of the NUT parameter deforms the shape of the effective potential in contrast with the zero NUT parameter. We further investigate the energy extraction by the Penrose process for this spacetime. It is shown that the efficiency of this black hole depends on both the charge and NUT parameter. It is observed that the energy gain is maximum when the NUT parameter goes to zero value and for the maximum spin value. When the value of the NUT parameter is increasing, the energy gain is decreasing.