Suitable Time Delay Research Articles

Delayed excitatory self-feedback-induced negative responses of complex neuronal bursting patterns* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11872276 and 11762001) and the Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region, China (Grant No. NJYT-20-A09).

In traditional viewpoint, excitatory modulation always promotes neural firing activities. On contrary, the negative responses of complex bursting behaviors to excitatory self-feedback mediated by autapse with time delay are acquired in the present paper. Two representative bursting patterns which are identified respectively to be “Fold/Big Homoclinic” bursting and “Circle/Fold cycle” bursting with bifurcations are studied. For both burstings, excitatory modulation can induce less spikes per burst for suitable time delay and strength of the self-feedback/autapse, because the modulation can change the initial or termination phases of the burst. For the former bursting composed of quiescent state and burst, the mean firing frequency exhibits increase, due to that the quiescent state becomes much shorter than the burst. However, for the latter bursting pattern with more complex behavior which is depolarization block lying between burst and quiescent state, the firing frequency manifests decrease in a wide range of time delay and strength, because the duration of both depolarization block and quiescent state becomes long. Therefore, the decrease degree of spike number per burst is larger than that of the bursting period, which is the cause for the decrease of firing frequency. Such reduced bursting activity is explained with the relations between the bifurcation points of the fast subsystem and the bursting trajectory. The present paper provides novel examples of paradoxical phenomenon that the excitatory effect induces negative responses, which presents possible novel modulation measures and potential functions of excitatory self-feedback/autapse to reduce bursting activities.

Analysis of Pollution in High Voltage Insulators via Laser-Induced Breakdown Spectroscopy.

Surface pollution deposition in a high voltage surface can reduce the surface flashover voltage, which is considered to be a serious accident in the transmission of electric power for the high conductivity of pollution in wet weather, such as rain or fog. Accordingly, a rapid and accurate online pollution detection method is of great importance for monitoring the safe status of transmission lines. Usually, to detect the equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD), the pollution should be collected when power cut off and bring back to lab, time-consuming, low accuracy and unable to meet the online detection. Laser-induced breakdown spectroscopy (LIBS) shows the highest potential for achieving online pollution detection, but its application in high voltage electrical engineering has only just begun to be examined. In this study, a LIBS method for quantitatively detecting the compositions of pollutions on the insulators was investigated, and the spectral characteristics of a natural pollution sample were examined. The energy spectra and LIBS analysis results were compared. LIBS was shown to detect pollution elements that were not detected by conventional energy spectroscopy and had an improved capacity to determine pollution composition. Furthermore, the effects of parameters, such as laser energy intensity and delay time, were investigated for artificial pollutions. Increasing the laser energy intensity and selecting a suitable delay time could enhance the precision and relative spectral intensities of the elements. Additionally, reducing the particle size and increasing the density achieved the same results.

Performance analysis of double-amplitude population gratings by non-overlapping unipolar pulses

We investigate the performance of the induced double-amplitude population grating (DAPG) based on spatially periodic modulation by the optical non-overlapping interaction of unipolar pulses. Considering the two typical allowed pulse configurations, the time delay requirements and the relationship between the grating amplitude, phase shift and the time delay were analyzed in detail. The results reveal that the grating amplitudes and phase can be dynamically controlled by the suitable time delay between the excited pulses. The population gratings presented here maybe offer more potential applications in nonlinear optics.

Nonlinear mechanism of excitatory autapse-induced reduction or enhancement of firing frequency of neuronal bursting

Excitatory and inhibitory effect always induces the enhancement and inhibitory effect of neural electronic activities, which is the common viewpoint of the modulations to the neural firing and plays important roles in the information processing of the nervous system. In the present paper, the Homoclinic/Homoclinic bursting pattern with alternation behavior between burst containing multiple spikes and subthreshold oscillations and the tough value of the burst lower than that of the subthreshold oscillations is chosen as representative, and the excitatory effect on the complex nonlinear dynamics of the representative bursting pattern is studied. For the excitatory autapse with suitable autaptic time delay and strength, the autaptic current pulse applied to the trough of the burst can induce the number of spikes within a burst to decrease and then the average firing frequency to decline, which presents a novel example different from the common viewpoint of the excitatory effect. The excitatory autapse induces the average firing frequency to increase in the remained parameter region of two-parameter plane of the autaptic time delay and strength. With bifurcations acquired by the fast/slow variable dissection method and phase trajectory, the subthreshold oscillations of the bursting correspond to a subthreshold limit cycle of the fast subsystem and the spike within burst corresponds to a suprathreshold limit cycle, and excitatory autaptic current can induce the transition from suprathreshold limit cycle to subthreshold limit cycle, which leads the spike to terminate in advance and is the cause for reducing the average firing frequency. The results is the present paper are compared with the phenomenon and bifurcation mechanism that the excitatory autapse can induce the spike number to decrease within a burst but the average firing frequency to increase as indicated in a recent study on the Fold/Homoclinic bursting. These results enrich the uncommon phenomenon of the neuronal electrical activities, reveal the underlying nonlinear mechanism, provide a new way to regulate the bursting pattern, and disclose the potential functions of the excitatory autapse.

Feasibility of shock-volume ignition approach in simple spherical targets driven by heavy ion beams

In this research, the new concept of the shock-volume ignition is proposed and then evaluated numerically by using a one-dimensional hydrodynamic code. The proposed model shows that it is possible to achieve higher energy gain with lower input energy inside the volume ignition framework by separating the compression and ignition stages as applied in the standard shock-ignition method. The current study intends to examine the optimum pulse shaping mode, the ignition conditions, and the physical aspects of the target performance in this new proposal for the typical simple spherical target designed previously for volume ignition studies driven by heavy-ion beams. Accordingly, a simple one-step pulse was replaced by a three-step pulse with a suitable time delay, beam power, and total input energy less than what we have used in the volume ignition correspondence. The optimal beam pulse duration and power of each stage were calculated, and the target energy gain of 72 is obtained. In addition, the required driver energy reduced by 0.74 MJ. Furthermore, the volume ignition condition with a low fuel temperature of 1.8 keV and a low implosion velocity of 1.4 × 107 cm/s was established. A twofold pressure rise due to appropriate pulse shaping was also obtained. Finally, by investigating the e-folding parameter on the fuel-pusher interface, it is found that by applying a three-step pulse, the Rayleigh-Taylor instability factor (<5) is not too dangerous in the deceleration phase. Therefore, it may be concluded that the fusion system dynamic is now more stable.

Ariyet Ocağında Kontrollü Patlatmalarla İlgili Bir Çalışma

Patlatma kaynaklı titreşimler çevre sakinlerini, tüm çevresel sorunlardan daha fazla endişelendirmektedir. Bina üst yapılarına verilen zararın patlatmadan kaynaklandığı iddia edilmektedir ve bazen bina sahibi, patlatma işlemlerini gerçekleştiren şirkete karşı dava açmaktadır. Patlatma kaynaklı titreşim problemi geçmişte kapsamlı bir şekilde araştırılmış ve devam eden araştırmalara konu olmaya devam etmektedir. Bu makale, bir otoyol prosesi kapsamında faaliyet gösteren taş ocağında yapılacak patlatmaların yüzeyden 9-10 m derindeki karstik kireçtaşlarına ve yeraltı sularına herhangi bir olumsuz etki etmemesi için gerekli çalışmaları içermektedir. Bu amaçla, titreşim ölçümü ve analizi yapılmış ve hedef bölgedeki patlatma kaynaklı yer titreşimlerini en aza indirgeyen yeni bir metodoloji uygulanmıştır. Patlatmanın neden olduğu zemin titreşiminin analizinde tepe partikül hızı ve baskın frekanslar dikkate alınmıştır. Metodoloji, hedef bölgedeki yüzey dalgalarının tahribatlı etkileşimini sağlamak için patlatma deliği gruplamaları arasında en uygun zaman gecikmelerini kullanmayı amaçlamaktadır.

Nonlinear Dynamic Chaos Theory Framework for Passenger Demand Forecasting in Smart City

Recently chaos theory has emerged as a powerful tool to address forecasting problems of nonlinear time series, since it is able to meet the dynamical and geometrical structures of very complex systems, reaching higher accuracy on the prediction values than the classical approaches. This paper aims at applying the chaos theory principles to different problems, in order to pursue high levels of accuracy on the predicted results. After the verification of the chaotic behavior of the datasets taken into analysis through the largest Lyapunov exponent research, the detection of the suitable embedding dimension and time delay has been carried out, in order to reconstruct the phase space of the underlying dynamical systems. Three different predictive methods have been proposed for different datasets. Finally, the performance comparison with the moving average model, a deep neural network based strategy, and a chaos theory based algorithm recently proposed in literature has been provided.

Bright white-light emission and multicolor outputs in time domain from a core-shell structured microcrystal

Intense white-light color emission of lanthanide-doped core-shell structured particles at microscale level was presented under 980 nm excitation. The prepared NaYF4:Yb/Er@ NaYF4:Yb/Tm microcrystals not only can effectively prevent the deleterious cross-relaxation that occurs between the Er3+ and Tm3+ due to the location of the activator ions within different layers, but also possess a high luminescence efficiency due to dimensions of the micro-scale structure. The core-shell structured microcrystals presented satisfactory capacity for color control in the white region. The results show great potential in attaining white light-emitting diodes within the field emission display on specific device applications. Furthermore, the core-shell microcrystals emit white-light that presents obvious and distinct lifetimes of green, red, and blue emissions, which could achieve multicolor emissions by setting a suitable delay time. This feature demonstrates that the core-shell structured microrods offer practical use as security ink to prevent forgery, such as in identifying currency.

Single-axial-mode Nd:YAG laser with precisely controllable laser pulse output time

In recent years, high-energy single-axial-mode Q-switched lasers have been widely studied and applied because of their wide applications such as in nonlinear optics, laser spectroscopy and light detection and ranging (LIDAR). Many applications require a Q-switched pulse that has not only single axial mode but also can be synchronized with an external system. But two most commonly used methods (the build-up time reducing technique and ramp fire technique) are difficult to achieve single-axial mode operation. In this work, we apply the ramp-hold-fire technique to an injection-seeded Nd:YAG laser. The slave oscillator is a self-filtering unstable resonator (SFUR). The SFUR oscillator can achieve a smooth spatial profile TEM<sub>00</sub> transverse mode. An RTP electro-optical crystal is adopted for intracavity phase modulator to modify the effective optical path length of the slave oscillator cavity. The seed-injection locking is realized by the ramp-hold-fire technique. The laser driver generates a pumping pulse. After a suitable time delay the driver is fired, a linear ramp voltage is applied to the RTP crystal. A photodiode detector monitors the interference signal. As soon as the interference peak is detected, the controlling electronics produces a stop signal. The ramp voltage on the RTP crystal is stopped and held at a fixed value. Then the Q-switch is fired at a set time, and finally single axial mode laser is demonstrated. Combining the advantages of intracavity phase modulation and Q-switch exact synchronization of the ramp hold fire technique, we obtain a narrow linewidth single-axial-mode laser pulse with precisely controllable output time. The laser is capable of generating 1064 nm pulse energy large than 50 mJ. The pulse build-up time is reduced by 31 ns to 48 ns. The pulse firing time is precisely controlled with jitter less than 1%. Then the frequency spectrum of the 1064 nm laser is measured with a commercial Fizeau wavemeter HighFinesse WS7. The multi-beam interference patterns of the pulse are shown to be smooth in the wavemeter. The wavelength is measured to be 1064.40416 nm and the linewidth is less than 0.5 pm which is limited by the instrument resolution. Meanwhile, the frequency stability is measured to be less than 0.1 pm (V-V) over 1700 pulses with a working frequency of 0.1 Hz.

Experimental study of double-pulse laser micro sintering: A novel laser micro sintering process

In laser micro sintering (LMS), good densification and low porosity of sintered material is often desirable for good mechanical properties. Recently, a novel LMS process, with the name of “double-pulse laser micro sintering” (DP-LMS), was proposed by the corresponding author. DP-LMS utilizes laser pulse group(s) consisting of “sintering laser pulse(s)” followed by “pressing laser pulse(s)” at a suitable delay time. This reported work has preliminarily demonstrated that, under the studied conditions, DP-LMS can produce an improved sintering result than those by LMS under similar conditions without using the “double-pulse” approach. The potential underlying mechanism has been discussed.

Simultaneous Dual-mode Emission and Tunable Multicolor in the Time Domain from Lanthanide-doped Core-shell Microcrystals.

The dual-mode emission and multicolor outputs in the time domain from core-shell microcrystals are presented. The core-shell microcrystals, with NaYF4:Yb/Er as the core and NaYF4:Ce/Tb/Eu as the shell, were successfully fabricated by employing the hydrothermal method, which confines the activator ions into a separate region and minimizes the effect of surface quenching. The material is capable of both upconversion and downshifting emission, and their multicolor outputs in response to 980 nm near-infrared (NIR) excitation laser and 252 nm, and 395 nm ultraviolet (UV) excitation light have been investigated. Furthermore, the tunable color emissions by controlling the Tb3+-Eu3+ ratio in shells and the energy transfer of Ce3+→Tb3+→Eu3+ were discussed in details. In addition, color tuning of core-shell-structured microrods from green to red region in the time domain could be obtained by setting suitable delay time. Due to downshifting multicolor outputs (time-resolved and pump-wavelength-induced downshifting) coupled with the upconversion mode, the core-shell microrods can be potentially applied to displays and high-level security.

A photoacoustic sensing probe using optical fiber acoustic delay line

In this paper, we report a new photoacoustic sensing probe design consisting of two optical fibers. One optical fiber is used for delivering the excitation light pulses. The other one serves as an acoustic delay line to relay the generated PA signal from the target to an outside ultrasound transducer. With the addition of suitable time delay, the original PA signal can be easily separated from the interference signals. To demonstrate this new design, a prototype probe was designed, fabricated and tested. The PA sensing performance was characterized with different concentration of black and red dye solutions. The testing results show that the PA sensing probe can provide good sensitivity and maintain high linearity over a wide range of concentrations. The detection of bovine blood embedded into chicken breast tissue was also conducted to demonstrate its potential usefulness for in-vivo applications.

THz field engineering in two-color femtosecond filaments using chirped and delayed laser pulses

We numerically study the influence of chirping and delaying several ionizing two-color light pulses in order to engineer terahertz (THz) wave generation in air. By means of comprehensive 3D simulations, it is shown that two chirped pulses can increase the THz yield when they are separated by a suitable time delay for the same laser energy in focused propagation geometry. To interpret these results, the local current theory is revisited and we propose an easy, accessible all-optical criterion that predicts the laser-to-THz conversion efficiencies given any input laser spectrum. In the filamentation regime, numerical simulations display evidence that a chirped pulse is able to produce more THz radiation due to propagation effects, which maintain the two colors of the laser field more efficiently coupled over long distances. A large delay between two pulses promotes multi-peaked THz spectra as well as conversion efficiencies above 10−4.

New methodology to prevent blasting damages for shallow tunnel

From all of the environmental problems, blast-induced vibrations often cause concern to surrounding residents. It is often claimed that damage to building superstructures is due to blasting, and sometimes the building owner files a lawsuit against the company that perform blasting operations. The blast-vibration problem has been thoroughly investigated in the past and continues to be the subject of ongoing research. In this study, a tunnel construction has been performed by a construction company, according to their contract they must have used drilling & blasting method for excavation in tunnel inlet and outlet portal. The population is very condensed with almost tunnel below in the vicinity houses of one or two floors, typically built with stone masonry and concrete. This situation forces the company to take extreme precautions when they are designing blasts so that the blast effects, which are mainly vibration and aerial waves, do not disturb their surrounding neighbors. For this purpose, the vibration measurement and analysis have been carried out and a new methodology in minimizing the blast induced ground vibrations at the target location, was also applied. Peak particle velocity and dominant frequencies were taken into consideration in analyzing the blast-induced ground vibration. The methodology aims to employ the most suitable time delays among blast-hole groupings to render destructive interference of surface waves at the target location.

Generation of largely elliptically polarized terahertz radiation from laser-induced plasma.

A novel all-optical control scheme is proposed to continuously tune the THz radiation polarization, where the driving laser is based on a three-pulse configuration with adjustable time delays or intensity ratio. With this scheme, not only is the circularly polarized THz radiation realized, the continuous tuning from circular polarization to linear polarization can also be obtained conveniently just by adjusting time delays or intensity ratio. Moreover, the left or the right chirality of THz radiation can be transformed between each other with suitable time delays.

Electric switching process of aligned Nb2O5 nanorods arrays

Vertically aligned Nb2O5 nanorods arrays were synthesized on metal foil by a facile and simple hydrothermal process. The well crystalized Nb2O5 nanorods grow along the [001] direction with hexagonal crystals structure. The I–V characteristics and switching process of these Nb2O5 nanorods arrays show a memristive switching alike phenomenon. It is revealed that the suitable measure delay time and negative bias could bring reasonable current values and good cycle stability, which suggests that aligned Nb2O5 nanorods arrays with multiple resistance states may have great potential applications.

Experimental investigation of atomic and ionic titanium lines, diatomic TiO γ transition and continuum background radiation via magnetically confined LIBS

Abstract This paper is focused on the clarification of the behaviour of various atomic, ionic, and TiOγ (A3Φ – X3Δ, Δν =0) diatomic transition lines as well as the continuum radiations in laser-induced titanium plasma plume by a pair of NdFeB. Depending on their different amount of impressionability from applied fields and electron-impact excitation rate, the responses of each component in optical emission spectrum and background continuum radiation to different applied magnetic field strengths (~ 0.42–1.12 T) are significantly different. At magnetic fields of 0.98 and 1.12 T, the amount of impressionability for Ti i: 388.2 nm is higher than others, while for TiOγ molecular transitions, the amount of impressionability factor in a 0.98 T field strength is considerable, because in the first moments after the laser pulse the continuum radiation is dominant, by applying an external magnetic field, this amount of radiation be reduced. The temporal evolution of the optical emission lines shows that choosing a suitable time delay and gate width has a considerable role in further impressionability of externally applied field in case of different elements. The electron density Ne varied from 0.99×1017 to 11.53×1017 cm−3, and the plasma temperature Te, was obtained in a range of 4835–16818 K by employing maximum applied field of 1.12 T. The supplementary investigations will be conducted towards further improvements of the purposeful analysis of each component in confined plasma by magneto-LIBS technique in order to find new approaches in the field of magnetic confinement.

An Efficient Tree-Based Power Saving Scheme for Wireless Sensor Networks With Mobile Sink

Wireless sensor networks (WSNs) with mobile sink are expected to increase the flexibility for gathering information in large-scale sensing and detecting environments. Energy saving becomes one of the most important features of the sensor nodes to extend their lifetime in such networks. A novel tree-based power saving scheme is proposed in this paper to reduce the energy consumption in WSNs with mobile sink. We adopt a dynamic sorting algorithm to create a tree-cluster routing structure for the sensor nodes. The main goal of this scheme is to reduce the data transmission distances of the sensor nodes by employing the tree structure and multi-hop concepts. Based on the location of mobile sink, the distances between the sensor nodes, and the residual energy of each sensor node, the proposed scheme makes an efficient decision for creating the routing structure. The energy consumption is reduced and the lifetime is extended for the sensor nodes by balancing the network load. Simulation results demonstrate the superior performance of our proposed scheme and its ability to strike the appropriate performance in the energy consumption, network lifetime, throughput, and transmission overhead. In addition, suitable delay time and number of retransmission messages can be achieved for the WSNs with mobile sink.

New Procedure for Computation of Time Delays in Propagation Function Fitting for Transient Modeling of Cables

The solution of traveling-wave equations for transient analysis of transmission lines and cables requires the identification of propagation function and characteristic admittance. A given modal propagation function can be approximated as a rational transfer function associated with an exponential time delay term. Time delays should be properly assigned prior to fitting in order to compensate excessive phase lag and avoid poor fitting results. In this paper, the existing time delay calculation formula of the universal line model (ULM) is first demonstrated using the Bode's magnitude-phase relation and its error source is explained. The underlying assumption is that a modal propagation function is a minimum phase system once a suitable time delay is removed. However, the numerical implementation of the procedure can generate delays that result in high fitting errors. Then, this paper contributes to a new method for estimating time delays and improving propagation function fitting accuracy.

Control of T cell antigen reactivity via programmed TCR downregulation.

The T cell receptor (TCR) is unique in that its affinity for ligand is unknown prior to encounter and can vary by orders of magnitude. How the immune system regulates individual T cells that display highly different reactivity to antigen remains unclear. Here we identified that activated CD4+ T cells, at the peak of clonal expansion, persistently downregulate TCR expression in proportion to the strength of initial antigen recognition. This programmed response increases the threshold for cytokine production and recall proliferation in a clone-specific manner, ultimately excluding clones with the highest antigen reactivities. Thus, programmed TCR downregulation represents a negative feedback mechanism to constrain T cell effector function with a suitable time delay, thereby allowing pathogen control while avoiding excess inflammatory damage.