Time-shift Technique Research Articles

Soueif’s Aisha: A Portrait of Memory, Time, and Liberation

This paper explores The Returning, which is a short story written by Ahdaf Soueif. The Returning is selected from the author’s first collection of short stories entitled Aisha which was written in 1983. It is Soueif’s first fictional work. This paper focuses on the way the author depicts her female protagonist named, Aisha, as a nostalgic character. Aisha revisits her past and bumps into lost memories with her husband. Soueif also portrays Aisha’s transformation into a liberated and liberating female character. Aisha transcends time and the clutches of her past to claim a fresh start. This paper attempts to reveal how the author focuses on her protagonist’s memory and journey throughout her past, returning to the present. It also focuses on the author’s utilization of time-shift technique to depict her protagonist’s set-forth liberation and that of her story from oblivion and the chains of a lost past. This paper reveals an alternative vision of female characters detached from clichéd female portraits. It also unwinds creative images of time as flexible and co-existing entities; past, present, and future.

Time shifts to reduce the size of reservoir computers

A reservoir computer is a type of dynamical system arranged to do computation. Typically, a reservoir computer is constructed by connecting a large number of nonlinear nodes in a network that includes recurrent connections. In order to achieve accurate results, the reservoir usually contains hundreds to thousands of nodes. This high dimensionality makes it difficult to analyze the reservoir computer using tools from the dynamical systems theory. Additionally, the need to create and connect large numbers of nonlinear nodes makes it difficult to design and build analog reservoir computers that can be faster and consume less power than digital reservoir computers. We demonstrate here that a reservoir computer may be divided into two parts: a small set of nonlinear nodes (the reservoir) and a separate set of time-shifted reservoir output signals. The time-shifted output signals serve to increase the rank and memory of the reservoir computer, and the set of nonlinear nodes may create an embedding of the input dynamical system. We use this time-shifting technique to obtain excellent performance from an opto-electronic delay-based reservoir computer with only a small number of virtual nodes. Because only a few nonlinear nodes are required, construction of a reservoir computer becomes much easier, and delay-based reservoir computers can operate at much higher speeds.

Phase Doppler Anemometer - The Shift From Simulation To The Real World

A Monte Carlo type simulation program has been developed to model phase Doppler systems. The work was divided into four main sections, the development of a launch strategy of a known range of droplet sizes and trajectories, the determination of the scattered light fields using Mie theory, the generation of the photomultiplier signals, and then their processing to generate drop size estimates followed by the comparison of these data with the launched data. The signal processing portion of the simulation measured the Doppler frequency in each signal to estimate the droplet velocity. Rather than using measurements of the phase differences between the multiple Doppler-shifted signals, the time shift between the arrival times of each signal was used to estimate the dropsize. This provided a linear relationship between the dropsize and the signal time shift. The missing link in the simulation is the ability to guide the experimentalist as to the best way to acquire the signal bursts and determine how accurate the measurements would be when using a PDA system to determine the droplet size distributions in real spray flows. Thus, the only way to determine measurement accuracy is to include that in the signal processing of an actual PDA system and spray. In an assessment of the capabilities of the signal processing technique, a sequence of Doppler bursts from an actual spray characterization were recorded and used as input to the software signal processor. The Time Shift Technique was based on the use of Weighted Average calculations to determine the exact middle of each of the three photomultiplier signal bursts. However, it was found that good quality signal bursts are required. Since cycle measurement techniques are less effected by noise, a cycle technique based on the samples captured by the AD converter was added to the software. Whereas this technique did show an improvement in measurement accuracy it led to the development of a cycle technique based on the signal burst frequency. This involved a reconstruction of the original captured bursts. The measurement errors were found to be in the micron range.

Spray measurements with the time-shift technique

The time-shift technique is a well-documented technique for the size and velocity measurement of individual drops passing through one or two tightly focused laser beams. It is a counting technique, nominally applicable for pure liquid drops, but with potential to also characterize drops with embedded particles or drops containing a second dispersed phase. In the present study a novel approach to signal processing is introduced in which the signal detection and validation phase is eliminated. This extends the capabilities of the time-shift technique in two manners. For one, size and velocity estimates are made possible for drops exhibiting very poor signal structure or signal-to-noise ratio. Such signals are commonly expected when measuring complex drops, either drops with embedded nano/micro-particles (dispersions) or emulsions. Second, the size and velocity distributions are estimated not by processing of signals from individual drops (single realization counting technique), but from a large ensemble of drop signals, improving both computational speed and reducing the influence of outliers in final statistics. These capabilities are achieved without sacrificing accuracy of mean and variance estimates of size and velocity of drop ensembles. To demonstrate the advantages of this new approach, measurements of a paint spray are presented, processed using both standard processing routines and the new approach. Limitations concerning the application of this new approach are discussed in detail.

Fault Diagnosis of a Wind Turbine Gearbox Based on Improved Variational Mode Algorithm and Information Entropy.

The working environment of wind turbine gearboxes is complex, complicating the effective monitoring of their running state. In this paper, a new gearbox fault diagnosis method based on improved variational mode decomposition (IVMD), combined with time-shift multi-scale sample entropy (TSMSE) and a sparrow search algorithm-based support vector machine (SSA-SVM), is proposed. Firstly, a novel algorithm, IVMD, is presented for solving the problem where VMD parameters (K and α) need to be selected in advance, which mainly contains two steps: the maximum kurtosis index is employed to preliminarily determine a series of local optimal decomposition parameters (K and α), then from the local parameters, the global optimum parameters are selected based on the minimum energy loss coefficient (ELC). After decomposition by IVMD, the raw signal is divided into K intrinsic mode functions (IMFs), the optimal IMF(s) with abundant fault information is (are) chosen based on the minimum envelopment entropy criterion. Secondly, the time-shift technique is introduced to information entropy, the time-shift multi-scale sample entropy algorithm is applied for the analysis of the complexity of the chosen optimal IMF and extract fault feature vectors. Finally, the sparrow search algorithm, which takes the classification error rate of SVM as the fitness function, is used to adaptively optimize the SVM parameters. Next, the extracted TSMSEs are input into the SSA-SVM model as the feature vector to identify the gear signal types under different conditions. The simulation and experimental results confirm that the proposed method is feasible and superior in gearbox fault diagnosis when compared with other methods.

Spray measurements with the time-shift technique

The time-shift technique is a well-documented technique for the size and velocity measurement of individual drops passing through one or two tightly focused laser beams. It is a counting technique, nominally applicable for pure liquid drops, but with potential to also characterize drops with embedded particles or drops containing a second dispersed phase. In the present study a novel approach to signal processing is introduced in which the signal detection and validation phase is eliminated. This extends the capabilities of the time-shift technique in two manners. For one, size and velocity estimates are made possible for drops exhibiting very poor signal structure or signal-to-noise ratio. Such signals are commonly expected when measuring complex drops, either drops with embedded nano/micro-particles (dispersions) or emulsions. Second, the size and velocity distributions are estimated not by processing of signals from individual drops (single realization counting technique), but from a large ensemble of drop signals, improving both computational speed and reducing the influence of outliers in final statistics. These capabilities are achieved without sacrificing accuracy of mean and variance estimates of size and velocity of drop ensembles. To demonstrate the advantages of this new approach, measurements of a paint spray are presented, processed using both standard processing routines and the new approach. Limitations concerning the application of this new approach are discussed in detail.

Geometric optics applied to drops passing through a focused Gaussian beam.

The present study examines the scattered light intensity from a drop passing through a Gaussian beam of a diameter comparable to or smaller than the drop. This is the situation encountered when using the time-shift technique, an optical technique used to characterize drops and aerosols according to the size and the velocity. In simulating the signals received by such an instrument, the computational effort involved when using, for instance, the Generalized Lorenz-Mie Theory or vector ray-tracing, is immense and hardly practical for use in instrument design and/or optimization. In this study theoretical expressions based on geometric optics are derived as an alternative, and they are shown to adequately capture the main features of the time-shift signals. These solutions require little computational effort and can be effectively used to explore the dependencies of the signals on various input factors, thus allowing further instrument development. On the other hand, these relations are also of general interest in the field of light scattering from drops and aerosols.

Measurement of the colloidal particle concentration and size within a drop using the time-shift technique

Liquid drops containing particles of nano to micron size are omnipresent in the chemical, pharmaceutical and process industries. In order to optimize such processes, there is a need to characterize these drops in terms of size and colloidal particle concentration. This study is devoted to estimating the colloidal nanoparticle concentration within such drops by using the time-shift technique. The estimation is achieved using two different approaches. The first utilizes the signal strength generated by light scattering from the particles in the drop relative to reflective scattering from the undisturbed drop surface. The second approach monitors the attenuation of the portion of the time-shift signal generated by second-order refractive scattering, i.e. light which has passed twice through the drop. These methods have been simulated using previously developed light scattering codes based on Monte Carlo ray tracing. Corresponding experiments have been implemented to validate these two estimation methods. For this, colloidal drops were generated by mixing water with the polystyrene latex nanoparticles and varying the volume concentration. Good agreement between the experimental and simulation results has been achieved, indicating that the time-shift technique can be further developed to meet this measurement task.

Simulation of light scattering from a colloidal droplet using a polarized Monte Carlo method: application to the time-shift technique.

This study is devoted to the development and application of a Monte Carlo ray-tracing model to simulate light scattering when a colloid suspension droplet passes through a highly focused Gaussian laser sheet. Within this study, a colloidal suspension droplet refers to a spherical droplet containing multiple spherical inclusions. Such scattering scenarios arise when using the time-shift measurement technique for particle sizing. The incident laser sheet is treated as a large number of polarized light rays: the Stokes vector of each light ray is tracked, achieved by multiplication of the rotation matrix and the Mueller matrix after each scattering event. For the Monte Carlo simulation of light scattering, a very important issue is to generate the deflection angle and azimuthal angle after each scattering event. The scattering from embedded inclusions is computed using the Lorenz-Mie theory and by employing the rejection sampling technique to update the new propagation direction. Multi-reflection and refraction within the droplet is accounted for, as is total reflection at the drop interface. For this, the Mueller matrix formulation is invoked at the drop surface to update the Stokes vector. To validate this simulation code, the scattering diagram from a nanoparticle is computed with this Monte Carlo method and compared with the scattering diagram computed with the Lorenz-Mie theory, the agreement is excellent. This Monte Carlo code is then applied to simulate signals arising from a time-shift device, when a colloid suspension droplet passes through a focused polarized laser sheet, with the objective of measuring the concentration of colloidal particles in the droplet. Measurements verify the ability of the code to properly simulate this light scattering scenario.

Light scattering from a drop with an embedded particle and its exploitation in the time-shift technique

This study is devoted to light scattering from drops with an embedded particle, as would be expected in an encapsulation/coating process or with spraying of metallic paints. A ray-tracing approach is taken, in which the polarization and intensity of all rays impinging onto a defined detector aperture are documented, allowing the signal generation arising from the drop passing through a plane wave or focused Gaussian beam to be simulated. For validation of the ray-tracing code, comparisons are drawn to scattering from pure liquid drops, obtained using the Lorenz–Mie solution. When using a highly focused incident beam, the scattering corresponds to the optical arrangement of the time-shift technique and allows the capabilities of that technique to measure drops with embedded particles to be explored. The resulting detector signals for a drop with an embedded spherical particle (encapsulated particles) or an embedded circular flake (metallic paint drop) have been simulated. These signals are compared with signals arising from pure liquid drops and features are identified which could be exploited for detecting the embedded particles using the time-shift technique.

A Central Consciousness at Work Beneath the Surface Artlessness: Narrative Strategies in “Tristram Shandy”

‘The Life and Opinions of Tristram Shandy, Gentleman’ (hereafter shortened to “Tristram Shandy”) is a unique novel written by British author Laurence Sterne in the eighteenth century. While Sterne’s contemporary readers may have conflicting viewpoints about the artistic value of “Tristram Shandy” because of its surface artlessness and chaos, readers today in the contexts of such twentieth-century critical theories as postmodernism, existentialism, and deconstruction, find it congenial and more intriguing. I argue that despite the apparent chaos of this novel, the author-narrator Tristram is a central consciousness that holds the whole work together. And I believe Sterne narrates his story in such a peculiar way in conformity to his own perception of the outside world. Specifically, this paper aims to explore the inventive narrative strategies employed in Sterne’s “Tristram Shandy” in the three aspects of narrative structure, time-shifting technique and self-conscious narrator. Amazingly, “Tristram Shandy” presents a wholly new notion of creative writing, one that goes beyond its time, and has unbreakable connection with twentieth-century literature.

Modeling photon transport in turbid media for measuring colloidal concentration in drops using the time-shift technique.

Colloidal drops-suspensions, dispersions, emulsions-are widespread in the process industry but are difficult to characterize by size, velocity, and concentration of particulate matter in the drop. The present study investigates the use of the time-shift (TS) technique for such measurements. Numerically, a model based on ray tracing is developed, incorporating interactions with randomly placed monodispersed scattering centers within the spherical drop. The model creates a random walk propagation trajectory, known from radiative transfer problems. The model approximates Mie scattering from each internal particle with a Gaussian distribution. Experiments are performed using a conventional TS instrument, first with water as a reference and for validation, and then with different concentrations of a milk/water emulsion. Comparison of the modeled and received signals exhibits very good agreement, confirming the possibility of measuring the colloidal concentration in drops using the TS technique.

Characterization of Atomization Processes in Suspension/Emulsion Sprays

The characterization of suspension/emulsion sprays plays a decisive role in many industrial processes. A good example of such a process is the drying of a milk spray to produce milk powder, where the process efficiency and product quality is typically controlled by atomization parameters like flow rate, pressure, etc.. However these parameters influence directly the droplet size and droplet velocity distributions in a spray so that optimizing a spray drying process often involves adjusting the spray to a desired droplet size and droplet velocity distribution. This requires a measurement technique capable of characterizing in real time the droplets in a suspension/emulsion spray. To achieve this aim we present developments to the well-known time-shift technique for spray measurements [1][2][3][4]. This technique is based on the light scattering of a single droplet/particle from a shaped light beam and can be operated in backscatter, meaning that the detectors and light sources can be placed on one side of the measurement position, making the technique more attractive for applications with limited optical access. Using the modified time-shift technique [3][5] the milk spray created by different nozzles operated at different pressures will be characterized using the droplet size and droplet velocity distributions of this spray. Milk is an emulsion which contains water and fat particles. So in addition we will investigate, how the fat content in milk, and with it the viscosity and surface tension, influences the droplet size and droplet velocity distribution, depending for instance on nozzle type and pressure. Moreover the time-shift technique is a counting measurement technique like phase Doppler [2]; consequently the correlation between velocity and size of the droplets is available.

Time-Shifting Based Primary-Ambient Extraction for Spatial Audio Reproduction

One of the key issues in spatial audio analysis and reproduction is to decompose a signal into primary and ambient components based on their directional and diffuse spatial features, respectively. Existing approaches employed in primary-ambient extraction (PAE), such as principal component analysis (PCA), are mainly based on a basic stereo signal model. The performance of these PAE approaches has not been well studied for the input signals that do not satisfy all the assumptions of the stereo signal model. In practice, one such case commonly encountered is that the primary components of the stereo signal are partially correlated at zero lag, referred to as the primary-complex case. In this paper, we take PCA as a representative of existing PAE approaches and investigate the performance degradation of PAE with respect to the correlation of the primary components in the primary-complex case. A time-shifting technique is proposed in PAE to alleviate the performance degradation due to the low correlation of the primary components in such stereo signals. This technique involves time-shifting the input signal according to the estimated inter-channel time difference of the primary component prior to the signal decomposition using conventional PAE approaches. To avoid the switching artifacts caused by the varied time-shifting in successive time frames, overlapped output mapping is suggested. Based on the results from our experiments, PAE approaches with the proposed time-shifting technique are found to be superior to the conventional PAE approaches in terms of extraction accuracy and spatial accuracy.

Time-Shift Current Balance Technique in Four-Phase Voltage Regulator Module with 90% Efficiency for Cloud Computing

Four power stages for voltage regulator module (VRM) are adopted to provide high current driving capability and low output ripple in cloud computing. Thus, the time-shift current balance (TSCB) technique is proposed to achieve high performance power supply for servers. In addition, the power request, which includes the number of active phases and voltage identification, is acknowledged by servers for high driving capability during high throughput and high efficiency during standby mode. Furthermore, to equally distribute the current in each phase, the proposed TSCB technique in either voltage-mode or peak current-mode control improves the current balance performance and solves the stability problem. In the scale-down clouding computing prototype, the efficiency can be kept higher than 90% over a wide load current range of 2 A. In addition, the performance and operating frequency of the servers in stable operation are not limited by the VRM with the TSCB technique.

Time-shift technique for simultaneous measurement of size, velocity, and relative refractive index of transparent droplets or particles in a flow

The time-shift technique, also known as the pulsed-displacement technique, is revisited as a method to measure size, velocity, and relative refractive index of spherical, transparent particles. Building on the basic measurement principle, we introduce several new innovations, making the technique significantly more attractive for use outside of the laboratory. These innovations include two possibilities for velocity measurement, validation criteria for one- and two-detector arrangements, and approaches to achieve higher bandwidths, and, in particular, lower measurable sizes. We discuss numerous optical configuration examples to illustrate the flexibility of this technique to meet various application requirements.

Evaluation of Concrete Distributed Cracks by Ultrasonic Travel Time Shift Under an External Mechanical Perturbation: Study of Indirect and Semi-direct Transmission Configurations

Techniques based on non-linear acoustics have been proven sensitive to micro-defects in heterogeneous materials, such as concrete, but their implementation on-site is very restrictive. Ultrasonic travel time shift, a technique where a high frequency ultrasonic wave probes the medium while a low frequency elastic wave disturbs it to create a “time delay”, is a new promising technique that may be used efficiently on-site. This technique is based on nonlinear behaviour of concrete. Moreover, this technique offers the possibility of evaluating linear parameter, such as ultrasonic pulse velocity of direct waves. The scope of this paper is to study the applicability of the technique at different level of concrete damage and define its advantages, limitations in order to optimize its use. Because of the large dimensions, the geometry and limited access to various faces of existing structures, the transducers often have to be set on the same side. Two types of configurations, the indirect transmission (with incident waves at 90∘) and the semi-direct transmission (with incident waves at 45∘), were studied with cement base samples at different levels of damage (generated by freeze-thaw cycles). Up to now, test results have shown that time-shift is more sensitive when used in an indirect configuration of transmission rather than in a semi-direct configuration. Overall, the non-linear time-shift technique is much more sensitive to the initiation of cracking than linear indicators and its versatility (different indicators for different levels of damage) is of interest for rapid testing of structures.

Lévy processes through time shift on oscillator Weyl algebra

We extend the Lie{algebra time shift technique, introduced in (2), from the usual Weyl algebra (associated to the additive group of a Hilbert space H) to the generalized Weyl algebra (oscillator algebra), associated to the semi{direct product of the additive group H with the unitary group on H (the Euclidean group of H, in the terminology of (14)). While in the usual Weyl algebra the possible quantum extensions of the time shift are essentially reduced to isomorphic copies of the Wiener process, in the case of the oscilla- tor algebra a larger class of Levy process arises.Our main result is the proof of the fact that the generators of the quantum Markov semigroups, associated to these time shifts, share with the quantum extensions of the Laplacian the important property that the generalized Weyl operators are eigenoperators for them and the corresponding eigenvalues are explicitly computed in terms of the Levy{Khintchin factor of the underlying classical Levy process.

Considering wind speed correlation of WECS in reliability evaluation using the time-shifting technique

Wind power is a very useful renewable energy source that is attracting consideration around the world due to its non-exhaustive nature and its environmental and social benefits. The correlation between multiple wind sites has a significant impact on the reliability of power systems containing wind energy conversion systems (WECS). Conventional methods cannot be directly applied to evaluate the reliability of WECS in the absence of comprehensive modeling techniques that recognize the correlation of the wind speeds at different wind farm locations. This paper proposes a model for power system reliability assessment that can consider the wind speed correlation and preserve the statistical characteristics of wind speeds, such as the mean and deviation of the wind speed time series (WSTS). A time-shifting technique is used to produce a new WSTS for a given correlation between two wind sites. The optimal shifted time at the two sites is determined using a linear interpolation technique. The probability distributions of the generated power and the system reliability indices with different degrees of correlation between the two sites are compared using two reliability test systems, i.e. the RBTS and the IEEE-RTS. The results show that the proposed method is useful in evaluating the reliability of WECS with correlation between two wind sites.

Restriction of Drinking Water Abrogates Splanchnic Vasodilation and Portal Hypertension in Portal Vein-Ligated Rats

Portal hypertension is associated with splanchnic vasodilation which is claimed responsible for the maintenance of chronically elevated portal pressure. Vasopressin analogues are used in the treatment of acute variceal bleeding, since they effectively reduce splanchnic blood flow and portal pressure. Dehydration stimulates the release of endogenous vasopressin release. Here we compared the effects of deprivation of drinking water for 18 h with those of vasopressin infusion on mesenteric hemodynamics in portal vein-ligated (PVL) and sham-operated (SHAM) rats. Blood flow in the superior mesenteric artery was measured with the ultrasonic transit time shift technique. Deprivation of drinking water had no hemodynamic effects in SHAM rats, but completely reversed the mesenteric hyperemia and portal hypertension in PVL rats to figures measured in SHAM rats, without altering blood pressure. Similarly, intravenous infusion of low doses of arginine vasopressin (1–10 pmol/min) selectively reduced mesenteric blood flow in PVL rats but had little effect in SHAM rats. These data suggest that control of water balance or aquaretic drugs might have beneficial effects on splanchnic hemodynamics and portal pressure in advanced liver disease, possibly by stimulating endogenous vasopressin release.