Temporal Transfer Functions Research Articles

On the temporal transfer function in STEM imaging from finite detector response time

Faster scanning in scanning transmission electron microscopy has long been desired for the ability to better control dose, minimise effects of environmental distortions, and to capture the dynamics of in-situ experiments. Advances in scan controllers and scan deflection systems have enabled scanning with pixel dwell times on the order of tens of nanoseconds. At these speeds, the finite response time of the electron detector must be considered as the signal from one electron detection event can contribute to multiple pixels, blurring the features within the image. Here we introduce a temporal transfer function (TTF) to describe and model the effects of detector response time on imaging, as well as a framework for incorporating these effects into simulation.

Transformer-based novel framework for remaining useful life prediction of lubricant in operational rolling bearings

Accurate prediction of the remaining useful life (RUL) of lubricants in rolling bearings is crucial for maintaining efficient operation of rotating machinery and ensuring timely lubricant replacement. We propose a comprehensive framework that integrates the temporal variation transfer function (TVTF), harmonic-sideband Matrix, and the harmonic frequency transformer (HarFT), a transformer-based model. This approach effectively utilizes vibration characteristics to enhance the accuracy of lubricant degradation prediction in rolling bearings. Validation with rolling bearings experiencing lubrication failure confirms that our framework significantly outperforms alternative methods in RUL prediction. The proposed framework excels in extracting and analyzing harmonic components from vibration responses, enabling detection of minute status variations due to lubricant degradation. By applying explainable artificial intelligence (XAI), it is possible to ascertain the rationale behind the RUL predicted by the HarFT model, facilitating evidence-based decisions. Our research provides a novel strategy for lubricant RUL assessment in rolling bearings, thereby improving reliability and maintenance efficiency in industrial applications.

Frequency response of certain temporal and complex transfer functions for the Interfacial 1D temperature wave

Frequency response of certain temporal and complex transfer functions for the Interfacial 1D temperature wave

On Frequency/Time Invariance of Certain Temporal and Complex Transfer Functions for the One-Dimensional Interfacial Monochromatic Neutron Density Wave

Abstract Optimization of dynamical multibeam neutron cancer therapy has recently been shown to be possible via employment of the beam frequencies of neutron waves as a control variable. The concepts of transfer functions (TF), addressed in this paper, can be essential ingredients of such optimization. Accordingly, the paper studies the dynamics of a one-dimensional (1D) monochromatic neutron density wave generated by time modulation of a boundary neutron current. It is demonstrated that a certain temporal transfer function (TTF) of both parabolic (diffusion) and low frequency hyperbolic (P−1 transport) interfacial neutron density wave happens to be frequency noninvariant with a vibrating boundary neutron current. It is proved that, only at high frequencies, both parabolic and hyperbolic interfacial neutron waves turn out to have a fully frequency-invariant and time-invariant temporal transfer function relative to such a vibrating neutron beam at the boundary. The frequency response of an associated complex transfer function is studied and demonstrated to change behavior, from a lag compensator to a fixed gain amplifier, with changing the frequency, neutron absorption and employed theory for neutron diffusion. A highlight of this paper is its illustration that mere continuity of these transfer functions can be a reflection of the correctness of the transport theory employed for modeling the neutron density waves.

Diversity of temporal response patterns in midbrain auditory neurons of frogs Batrachyla and its relevance for male vocal responses.

We investigated response selectivities of single auditory neurons in the torus semicircularis of male frogs Batrachyla leptopus (72 neurons) and B. taeniata (57 neurons) to synthetic stimuli of different temporal structures. Series of stimuli in which note and pulse rate, note and pulse structure and call duration varied systematically were presented. Neuronal responses quantified in terms of proportions of units displaying diverse temporal transfer functions are related in different modes with patterns of evoked vocal responses studied previously in these frogs. Correspondences and mismatches occurred between the auditory and vocal domains. The analysis of this evidence together with corresponding information from previous neuronal and behavioral studies in the third species of this genus, B. antartandica, indicates that different modes of preferences for acoustic communication signals can coexist within this anuran group.

Analogue Optical Spatiotemporal Differentiator

AbstractAs a significant part in optical computation, analogue optical spatial/temporal differentiators could play a great role in all‐optical signal processing, feature extraction, and optical storage. In the past few years, they have experienced rapid development but mostly for a single function. For many scenarios, optical computation with integrated functionalities is highly desired. In this work, an analogue optical spatiotemporal differentiator utilizing all‐dielectric multilayer is proposed. The film stack is specifically engineered to satisfy the requirements for both spatial and temporal transfer functions of the ideal differentiator. The time‐space performance of the device is numerically examined from the output field profile of the classical Gaussian beam or pulse. A wavelength‐scale high resolution for edge detection is attained using the integrated differentiator. This work may pave a potential way to establish ultracompact, high‐bandwidth, and real‐time optical multiple functional computation systems.

Fluxonic Processing of Photonic Synapse Events

Much of the information processing performed by a biological neuron occurs in the dendritic tree. For artificial neural systems using light for communication, it is advantageous to convert signals to the electronic domain at synaptic terminals, so dendritic computation can be performed with electrical circuits. Here, we present circuits based on Josephson junctions and mutual inductors that act as dendrites, processing signals from synapses receiving single-photon communication events with superconducting detectors. We show simulations of circuits performing basic temporal filtering, logical operations, and nonlinear transfer functions. We further show how the synaptic signal from a single photon can fan out locally in the electronic domain to enable the dendrites of the receiving neuron to process a photonic synapse event or pulse train in multiple different ways simultaneously. Such a technique makes efficient use of photons, energy, space and information.

Effects of urbanization and stormwater control measures on streamflows in the vicinity of Clarksburg, Maryland, USA

AbstractUnderstanding the efficacy of revised watershed management methods is important to mitigating the impacts of urbanization on streamflow. We evaluated the influence of land use change, primarily as urbanization, and stormwater control measures on the relationship between precipitation and stream discharge over an 8‐year period for five catchments near Clarksburg, Montgomery County, Maryland, USA. A unit‐hydrograph model based on a temporal transfer function was employed to account for and standardize temporal variation in rainfall pattern, and properly apportion rainfall to streamflow at different time lags. From these lagged relationships, we quantified a correction to the precipitation time series to achieve a hydrograph that showed good agreement between precipitation and discharge records. Positive corrections appeared to include precipitation events that were of limited areal extent and therefore not captured by our rain gages. Negative corrections were analysed for potential causal relationships. We used mixed‐model statistical techniques to isolate different sources of variance as drivers that mediate the rainfall–runoff dynamic before and after management. Seasonal periodicity mediated rainfall–runoff relationships, and land uses (i.e. agriculture, natural lands, wetlands and stormwater control measures) were statistically significant predictors of precipitation apportionment to stream discharge. Our approach is one way to evaluate actual effectiveness of management efforts in the face of complicating circumstances and could be paired with cost data to understand economic efficiency or life cycle aspects of watershed management. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Assessment of temporal resolution of multi-detector row computed tomography in helical acquisition mode using the impulse method

The purpose of this study was to propose a method for assessing the temporal resolution (TR) of multi-detector row computed tomography (CT) (MDCT) in the helical acquisition mode using temporal impulse signals generated by a metal ball passing through the acquisition plane. An 11-mm diameter metal ball was shot along the central axis at approximately 5 m/s during a helical acquisition, and the temporal sensitivity profile (TSP) was measured from the streak image intensities in the reconstructed helical CT images. To assess the validity, we compared the measured and theoretical TSPs for the 4-channel modes of two MDCT systems. A 64-channel MDCT system was used to compare TSPs and image quality of a motion phantom for the pitch factors P of 0.6, 0.8, 1.0 and 1.2 with a rotation time R of 0.5 s, and for two R/P combinations of 0.5/1.2 and 0.33/0.8. Moreover, the temporal transfer functions (TFs) were calculated from the obtained TSPs. The measured and theoretical TSPs showed perfect agreement. The TSP narrowed with an increase in the pitch factor. The image sharpness of the 0.33/0.8 combination was inferior to that of the 0.5/1.2 combination, despite their almost identical full width at tenth maximum values. The temporal TFs quantitatively confirmed these differences. The TSP results demonstrated that the TR in the helical acquisition mode significantly depended on the pitch factor as well as the rotation time, and the pitch factor and reconstruction algorithm affected the TSP shape.

The Effect of Acute Sleep Deprivation on Temporal Processing and Frequency Resolution in Normal Healthy Adults

OBJECTIVE: The study aimed at evaluating the impact of 24 hours of sleep deprivation on temporal processing and frequency resolution in normal individuals with no history of neurological and psychological deficits. MATERIALS and METHODS: Sixteen individuals with normal hearing were included in the study. Temporal modulated transfer function, gap detection test, duration discrimination test, and pitch discrimination test were carried out in all of the individuals with a baseline evaluation, followed by an intra- test evaluation after 24 hours of sleep deprivation. RESULTS: The mean gap detection test values were elevated in sleep deprivation conditions as compared to the baseline condition. The temporal modulation transfer function scores were also increased in the sleep deprivation condition when compared to the baseline condition. Individuals performed poorly for the duration discrimination test and pitch discrimination test in the sleep-deprived condition. All tests showed statistical significance between the two conditions, with p<0.005. DISCUSSION: The reduced scores may be due to the effects of sleep deprivation on working memory, arousal, attention, concentration, and also reduced metabolism in the frontal lobe.

Visualization of superluminal pulses inside a white light cavity using plane wave spatio temporal transfer functions

In a white light cavity (WLC), the group velocity is superluminal over a finite bandwidth. For a WLC-based data buffering system we recently proposed, it is important to visualize the behavior of pulses inside such a cavity. The conventional plane wave transfer functions, valid only over space that is translationally invariant, cannot be used for the space inside WLC or any cavity, which is translationally variant. Here, we develop the plane wave spatio temporal transfer function (PWSTTF) method to solve this problem, and produce visual representations of a Gaussian input pulse incident on a WLC, for all times and positions.

210 後方乱気流の計測融合シミュレーションデータのリアライゼーション : (1)微分位相解析に基づく経時的伝達関数の設計(流体工学III)

210 後方乱気流の計測融合シミュレーションデータのリアライゼーション : (1)微分位相解析に基づく経時的伝達関数の設計(流体工学III)

Testing the performance of three nonlinear methods of time seriesanalysis for prediction and downscaling of European daily temperatures

Abstract. We investigated the usability of the method of local linear models (LLM), multilayer perceptron neural network (MLP NN) and radial basis function neural network (RBF NN) for the construction of temporal and spatial transfer functions between different meteorological quantities, and compared the obtained results both mutually and to the results of multiple linear regression (MLR). The tested methods were applied for the short-term prediction of daily mean temperatures and for the downscaling of NCEP/NCAR reanalysis data, using series of daily mean, minimum and maximum temperatures from 25 European stations as predictands. None of the tested nonlinear methods was recognized to be distinctly superior to the others, but all nonlinear techniques proved to be better than linear regression in the majority of the cases. It is also discussed that the most frequently used nonlinear method, the MLP neural network, may not be the best choice for processing the climatic time series - LLM method or RBF NNs can offer a comparable or slightly better performance and they do not suffer from some of the practical disadvantages of MLPs. Aside from comparing the performance of different methods, we paid attention to geographical and seasonal variations of the results. The forecasting results showed that the nonlinear character of relations between climate variables is well apparent over most of Europe, in contrast to rather weak nonlinearity in the Mediterranean and North Africa. No clear large-scale geographical structure of nonlinearity was identified in the case of downscaling. Nonlinearity also seems to be noticeably stronger in winter than in summer in most locations, for both forecasting and downscaling.

Preference of Sensory Neural Coding for1/fSignals

We investigated the influences of different types of temporal correlations in the input signal on the functions and coding properties of neurons in the primary visual cortex (V1). We found that the temporal transfer functions of V1 neurons exhibit higher gain, and the spike responses exhibit higher coding efficiency and information transmission rates, for the 1/f (natural long-term correlation) signals than for 1/f(0) (no correlation) and 1/f(2) (stronger long-term correlation) signals. These results suggest that the intermediate long-term correlation ubiquitous to natural signals may play an important role in shaping and optimizing the machinery of neurons in their adaptation to the natural environment.

Charge trapping at high doses in an active matrix flat panel dosimeter

Active matrix flat panel dosimeters (AMFPDs) have a high density of charge trapping centers (/spl sim/3/spl times/10/sup 15//cm/sup 3/) which lead to both lag and ghosting in reconstructed dose measurements. Lag is due to charge release within the detector and is a function of the lifetime of the trapping centers within the detector. Ghosting, defined as excess charge not produced by charge release, is a phenomenon believed to be caused by reduced charge trapping probability due to the trapped charge population density being greater after exposure to a radiation field than previous to the exposure. This paper examines the characteristics of a large AMFPD (26 cm /spl times/ 26 cm) detector for long exposure times (up to 1 minute) and high doses (up to 3 Gy). This detector was operated in a direct detection mode. Nonlinear response functions were mapped as a function of exposure time and dose for an X-ray beam where the accelerating potential of the electrons was 6 megavolts (MV). Additionally, the impulse response functions (IRFs) were measured at 6 MV for the same set of exposure times and doses used for the measurement of the nonlinear mapping. These IRFs are shown to be functions of both exposure time and dose delivered to the detector. The reproducibility of dose measurements using procedures derived from this paper is discussed. The temporal transfer function (TTF), defined as the absolute value of the Fourier transform of the IRF, is introduced and several examples of the TTFs are shown and discussed.

Spatiotemporal organization of simple-cell receptive fields in area 18 of cat’s cortex

Spatiotemporal structures of receptive-fields (RF) have been studied for simple cells in area 18 of eat by measuring the temporal transfer function (TTF) over different locations (subregions) within the RF. The temporal characteristics of different subregions differed from each other in the absolute phase shift (APS) to visual stimuli. Two types of relationships can be seen: (i)The APS varied continuously from one subregion to the next: (ii) A 180 degrees -phase jump was seen as the stimulus position changed somewhere within the receptive field. Spatiotemporal receptive field profiles have been determined by applying reverse Fourier analysis to responses in the frequency domain. For the continuous type, spatial and temporal characteristics cannot be dissociated (space time inseparable) and the spatiotemporal structure is oriented. On the contrary, the spatial and temporal characteristics for the jumping type can be dissociated (space-time separable) and the structure is not oriented in the space-time plane. Based on the APSs measured at different subregions, the optimal direction of motion and optimal spatial frequency of neurons can be predicted.

Temporal resolution of the dolphin’s hearing: Evoked-potential study

Temporal resolution of the dolphin’s auditory system was studied using the auditory brain-stem-evoked response (ABR) recording in paradigms as follows: (i) paired click and pip stimulation; (ii) rhythmic click and pip stimulation; (iii) sinusoidally amplitude-modulated tones; (iv) noise burst of various duration (the temporal summation test); and (v) gap in noise detection. An integration temporal transfer function was derived from the data of all the listed experiments using a model of a linear integrator with subsequent nonlinear transform to ABR amplitude. All the experiments listed above gave strictly corresponding results. The integration transfer function consisted of an initial high-level part about 0.3-ms long and the subsequent low-level part with a decay of around 40 dB per time decade. The short initial part of the integration transfer function makes it possible to respond to paired stimuli with interstimulus intervals down to 0.2 ms, to follow rhythmic stimuli of a rate of more than 2000 Hz, and to detect gaps in noise as short as 0.1 ms. The subsequent low-level part is also important; it dictates response properties at interstimulus intervals and gap durations as loud as dozens of ms.

Detection of temporal gaps in noise in dolphins: evoked-potential study.

Temporal resolution of hearing was studied in bottlenosed dolphins by recording the auditory brain-stem response (ABR) evoked by gap in noise. Gaps shorter than 0.5 ms evoked a response combining both off- and on-components; longer gaps evoked separate off- and on-responses. Both the response to a short gap and on-response to the end of a long gap increased with increasing gap duration. On-response recovered completely at gap duration of 5-10 ms. Small but detectable response arose at gap duration as short as 0.1 ms. Contrary to the on-response after a long silence, the response to a short gap was less dependent on noise intensity. From these data, the temporal transfer function of the supposed integrator was derived assuming nonlinear transform of the integrator output to ABR amplitude. Equivalent rectangular duration of the found temporal transfer function was 0.27 ms.

Microwave Pulse Propagation Through a Corrugated Waveguide Section

ABSTRACT The propagation of a microwave phase-modulated pulse through a section of a circular corrugated waveguide with sinusoidal corrugation is considered in the single-mode approximation. The temporal transfer functions of the waveguide measured in transmission and reflection are presented and used for computation of output pulses’ intensities. It is shown that the effect of time compression of hoth output pulses can be observed under certain conditions.

Analysis of dynamic spectra in ferret primary auditory cortex. I. Characteristics of single-unit responses to moving ripple spectra.

1. Auditory stimuli referred to as moving ripples are used to characterize the responses of both single and multiple units in the ferret primary auditory cortex. Moving ripples are broadband complex sounds with a sinusoidal spectral profile that drift along the logarithmic frequency axis at a constant velocity. 2. Neuronal responses to moving ripples are locked to the phase of the ripple, i.e., they exhibit the same periodicity as that of the moving ripple profile. Neural responses are characterized as a function of ripple velocity (temporal property) and ripple frequency (spectral property). Transfer functions describing the response to these temporal and spectral modulations are constructed. Temporal transfer functions are inverse Fourier transformed to obtain impulse response functions that reflect the cell's temporal characteristics. Ripple transfer functions are inverse Fourier transformed to obtain the response field, a measure analogous to the cell's response area. These operations assume linearity in the cell's response to moving ripples. 3. Transfer functions and other response functions are shown to be fairly independent on the overall level or depth of modulation of the ripple stimuli. Only downward moving ripples were used in this study. 4. The temporal and ripple transfer functions are found to be separable, in that their shapes remain unchanged for different test parameters. Thus ripple transfer functions and response fields remain statistically similar in shape (to within an overall scale factor) regardless of the ripple velocity or whether stationary or moving ripples are used in the measurement. The same stability in shape holds for the temporal transfer functions and the impulse response functions measured with different ripple frequencies. Separability implies that the combined spectrotemporal transfer function of a cell can be written as the product of a purely ripple and a purely temporal transfer functions, and thus that the neuron can be computationally modeled as processing spectral and temporal information in two separate and successive stages. 5. The ripple parameters that characterize cortical cells are distributed somewhat evenly, with the characteristic ripple frequencies ranging from 0.2 to > 2 cycles/octave and the characteristic angular frequency typically ranging from 2 to 20 Hz. 6. Many responses exhibit periodicities in the spectral envelope of the stimulus. These periodicities are of two types. Slow rebounds, not found in the spectral envelope, and with a period of approximately 150 ms, appear with various strengths in approximately 30% of the cells. Fast regular firings with interspike intervals of approximately 10 ms are much less common and appear to correspond to interactions between the component tones that make up a ripple.