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With the development of vehicle-road network technologies, the future traffic flow will appear in the form of hybrid network traffic flow for a long time. Due to the change in traffic characteristics, the current hard shoulder running strategy based on traditional traffic characteristics cannot effectively serve the hybrid network traffic flow scenario, and will even lead to the further deterioration of traffic congestion. In order to propose a hard shoulder running strategy suitable for a hybrid network environment, a traffic breakdown prediction method based on a hidden Markov model was established. Secondly, the characteristics of traffic breakdown in a hybrid network environment were analyzed. Finally, based on the traffic breakdown characteristics in a hybrid network environment, a dynamic hard shoulder running method based on the hidden Markov model was proposed. The effectiveness of HMMD-HSR was verified by simulation and comparison with HMM-HSR, LMD-HSR, and N-HSR. The simulation results show that the HMMD-HSR proposed in this paper can improve operation efficiency and reduce travel time in a congested expressway. [ABSTRACT FROM AUTHOR]

With the development of vehicle-road network technologies, the future traffic flow will appear in the form of hybrid network traffic flow for a long time. Due to the change in traffic characteristics, the current hard shoulder running strategy based on traditional traffic characteristics cannot effectively serve the hybrid network traffic flow scenario, and will even lead to the further deterioration of traffic congestion. In order to propose a hard shoulder running strategy suitable for a hybrid network environment, a traffic breakdown prediction method based on a hidden Markov model was established. Secondly, the characteristics of traffic breakdown in a hybrid network environment were analyzed. Finally, based on the traffic breakdown characteristics in a hybrid network environment, a dynamic hard shoulder running method based on the hidden Markov model was proposed. The effectiveness of HMMD-HSR was verified by simulation and comparison with HMM-HSR, LMD-HSR, and N-HSR. The simulation results show that the HMMD-HSR proposed in this paper can improve operation efficiency and reduce travel time in a congested expressway.

The focus of this paper is on the effectiveness of lightning impulse (LI) with different parameters for detecting protrusion defects in gas insulated switchgear (GIS). The study examines the 50% (U 50) breakdown probability for typical protrusion defects on the conductor of a 363 kV class GIS. A quantitative method is developed to predict breakdown voltage, calculate minimum detectable length of defect, and express the effectiveness of the LI test. The results show that there is little difference of U 50 between aperiodic and oscillating LI. Corresponding detecting effectiveness decreases for LI with long wavefront, which is expressed quantitatively by detectable area. The critical defect length detected increases with increased wavefront. This study provides a general method to express the effectiveness of LI with different parameters for detecting protrusion defects and it support the LI test for on-site testing of GIS. [ABSTRACT FROM AUTHOR]

An experimental study of laser ablation on the samples that comprise nanofilms of hafnium and zirconium dioxides on the surface of glass and silicon, and obtaining parameters of pulsed laser ablation in this work, provide new data describing the ablation mechanism. The samples were exposed to pulsed radiation from an Nd3+:YAG laser in order to measure the threshold energy density of laser ablation and determine the parameters used in the simulation of statistical distributions. Based on these data, the dependences of the parameters of laser ablation on the optical and thermophysical characteristics of these oxides were obtained. [ABSTRACT FROM AUTHOR]

The characteristics, breakdown probability, and statistical distribution of breakdown time delay under different du/dt in hundreds of nanoseconds pulse for millimeter gaps have been investigated by employing the statistical experimental method in this paper. The experimental results indicate that both the breakdown time delay and jitter are essentially decreased as the slope of the pulse voltage- du/dt is increased for 1-, 2-, and 4-mm gaps; in particular, increasing the value of du/dt is useful to obtain the smaller relative deviation of breakdown time delay under the same breakdown electric field. The breakdown probabilities for different gaps have been analyzed and a method of utilizing the Gaussian distribution function has been proposed which can be used for evaluating the statistical distribution of breakdown time delay. When the experimental condition is 100% breakdown probability, the breakdown time delay follows a Gaussian distribution. However, it is unsuitable for the fitting of breakdown time delay utilizing a Gaussian function for 2- and 4-mm gaps from the cumulative probability distributions of breakdown time delay because of the lower du/dt values and breakdown probabilities. [ABSTRACT FROM AUTHOR]

The robustness of complex network is a core issue in complex network research. We agree that not all overload nodes will be removed from the network in real networks because some effective measures can be taken to protect them. But only a few researches consider this issue. Based on previous researches, we propose a cascading model with an improved breakdown probability. Different from previous breakdown probability model, the current model brings in some parameters to explore the optimal distribution strategy of the protection resources. Furthermore, we quantify the allocation of the protection resources. We explore the relationship between the parameters of our cascading model and the robustness of three networks (two typical networks and one real network), based on which we find out the optimal value of the parameter. It in turn helps us to quantify the allocation of protection resources and form an optimal protection strategy. Our work may be helpful for improving the robustness of complex networks. [ABSTRACT FROM AUTHOR]

Spin-transfer torque magnetic tunnel junction (MTJ) is a promising candidate for nonvolatile memories thanks to its high speed, low power, infinite endurance, and easy integration with CMOS circuits. However, a relatively high current flowing through an MTJ is always required by most of the switching mechanisms, which results in a high electric field in the MTJ and a significant self-heating effect. This may lead to the dielectric breakdown of the ultrathin ( $\sim 1$ nm) oxide barrier in the MTJ and cause functional errors of hybrid CMOS/MTJ circuits. This paper analyzes the physical mechanisms of time-dependent dielectric breakdown (TDDB) in an oxide barrier and proposes an SPICE-compact model of the MTJ. The simulation results show great consistency with the experimental measurements. This model can be used to execute a more realistic design according to the constraints obtained from simulation. The users can estimate the lifetime, the operation voltage margin, and the failure probability caused by TDDB in the MTJ-based circuits. [ABSTRACT FROM AUTHOR]

The sparkover voltage of gas discharge tubes for surge voltage protection has been found to be dependent on the rate of voltage rise. At slow voltage increase, it is close to stationary voltage conditions and is assumed to be the breakdown voltage at a given pd regarding Paschen law. The deviation of stationary sparkover voltage measured on test samples is assigned to the variation of electrode conditions and illustrated as the effect of the Townsend coefficient \gamma. The increase of impulse sparkover voltage at fast voltage rise depends on the time lag of the spark breakdown where the effect of statistical and formative time lag is assessed. As an origin of ion avalanche and streamer formation, the cold-field electron emission process is considered where the Poisson probability function for rare stochastic events is concerned for the evaluation of emitted electron current. Due to the absence of applicable values for relevant system parameters, the relationship between the impulse sparkover voltage and the rate of voltage rise obtained by simulation have more or less qualitative character. Values taken for the coefficients of simulation are chosen by fitting the simulated results to the measured ones. Their relevance is verified by comparing it with the typical values of discharge quantities found in the literature. [ABSTRACT FROM AUTHOR]

The laser ablation threshold energy density of the glass nanocomposites of the different composition for the YAG-Nd laser pulse radiation experimental measurements have been fulfilled. The dependences of the laser ablation threshold parameters versus the optical and physical properties of these nanocomposites have been studied. [ABSTRACT FROM AUTHOR]

Abstract: This study investigates the mechanism of traffic breakdown and establishes a traffic flow model that precisely simulates the stochastic and dynamic processes of traffic flow at a bottleneck. The proposed model contains two models of stochastic processes associated with traffic flow dynamics: a model of platoon formation behind a bottleneck and a model of speed transitions within a platoon. After these proposed models are validated, they are applied to a simple one-way, one-lane expressway section containing a bottleneck, and the stochastic nature of traffic breakdown is demonstrated through theoretical exercises. [Copyright &y& Elsevier]

Abstract: Traffic breakdown phenomenon is prevalent in empirical traffic system observations. Traffic flow breakdown is usually defined as an amount of sudden drop in traffic flow speed when traffic demand exceeds capacity. Modeling and calculating traffic flow breakdown probability remains an important issue when analyzing the stability and reliability of transportation system. The breakdown mechanism is still mysterious to practitioners and researchers in varying manner. Treating breakdown as a random event, this paper use discrete time Markov chain (DTMC) to model traffic state transition path, as a result, a transition probability matrix can be generated from empirical observations. From empirical analysis of breakdown, we found this formulation of breakdown probability follows the Zipf distribution. Therefore, a connection from traffic flow breakdown probability to how many vehicles are occupying a certain freeway segment (e.g. a link) will be established. Following from the results, a quantitative measure of breakdown probability can be obtained to optimize ramp metering rates to achieve optimum system performance measures. [Copyright &y& Elsevier]

Abstract: Most previous existing works on cascading failures only focused on attacks on nodes rather than on edges. In this paper, we discuss the response of scale-free networks subject to two different attacks on edges during cascading propagation, i.e., edge removal by either the descending or ascending order of the loads. Adopting a cascading model with a breakdown probability of an overload edge and the initial load of an edge , where and are the degrees of the nodes connected by the edge and is a tunable parameter, we investigate the effects of two attacks for the robustness of Barabási–Albert (BA) scale-free networks against cascading failures. In the case of , our investigation by the numerical simulations leads to a counterintuitive finding that BA scale-free networks are more sensitive to attacks on the edges with the lowest loads than the ones with the highest loads, not relating to the breakdown probability. In addition, the same effect of two attacks in the case of may be useful in furthering studies on the control and defense of cascading failures in many real-life networks. We then confirm by the theoretical analysis these results observed in simulations. [Copyright &y& Elsevier]

In this paper, adopting the initial load of a node j to be $L_j = k_j^\alpha$, where kj is the degree of the node j and α is a tunable parameter that controls the strength of the initial load of a node, we propose a cascading model with a breakdown probability and explore cascading failures on a typical network, i.e., the Barabási–Albert (BA) network with scale-free property. Assume that a failed node leads only to a redistribution of the load passing through it to its neighboring nodes. According to the simulation results, we find that BA networks reach the strongest robustness level against cascading failures when α = 1 and the robustness of networks has a positive correlation with the average degree 〈k〉, not relating to the different breakdown probabilities. In addition, it is found that the robustness against cascading failures has an inversely proportional relationship with the breakdown probability of an overload node. Finally, the numerical simulations are verified by the theoretical analysis. [ABSTRACT FROM AUTHOR]

Abstract: Considering that not all overload nodes will be removed from networks due to some effective measures to protect them, we propose a new cascading model with a breakdown probability. Adopting the initial load of a node to be with and being the degree of the node and the set of its neighboring nodes, respectively, where is a tunable parameter, we investigate the relationship between some parameters and universal robustness characteristics against cascading failures on scale-free networks. According to a new measure originated from a phase transition from the normal state to collapse, the numerical simulations show that Barabási–Albert (BA) networks reach the strongest robustness level against cascading failures when the tunable parameter , while not relating to the breakdown probability. We furthermore explore the effect of the average degree for network robustness, thus obtaining a positive correlation between and network robustness. We then analyze the effect of the breakdown probability on the network robustness and confirm by theoretical predictions this universal robustness characteristic observed in simulations. Our work may have practical implications for controlling various cascading-failure-induced disasters in the real world. [Copyright &y& Elsevier]

The dependence of the performance of separate-absorption-multiplication (SAM) single-photon avalanche diodes (SPADs) on the width of the multiplication region is theoretically investigated. The theory is applied to SAM SPADs with InP homojunction multiplication regions and InAlAs-InP heterojunction multiplication regions. In both cases the absorber layer is InGaAs. Two scenarios for the dark counts are considered: (i) low-temperature operation, when the number of dark carriers is dominated by field-assisted mechanisms of band-to-band tunneling and tunneling through defects; and (ii) room-temperature operation, when the number of dark carriers in the multiplication region is dominated by the generation/recombination mechanism. The analysis utilizes a generalized theory for breakdown probability, which takes into account the random locations where dark and photogenerated carriers are produced in each layer. Depending upon the detector temperature, as the width of the multiplication region is increased the effects from the reduction in the number of dark carriers due to field-assisted generation mechanisms are counteracted by the effects from the elevation in the number of generation/recombination dark carriers. Thus, there exists an optimal width of the multiplication region that achieves the best performance of the SPAD. [ABSTRACT FROM AUTHOR]

The effects of avalanche region width, ionization coefficient ratio, and dead space on the breakdown time and timing jitter of a single-photon avalanche diode are investigated. Using a random ionization path length model, the breakdown time and the timing jitter are shown to decrease with breakdown probability, but increase with avalanche region width, decreasing ionization coefficient ratio, and ionization dead space. The model is used to compare the dependence of avalanche timing performance in Si and InP on avalanche region width. [ABSTRACT FROM PUBLISHER]

In this paper, we describe the internal winding failures of the no. 3 distribution transformer at Katayamazu substation caused by winter lightning. Almost the same internal winding part of the transformer was damaged in January 1997 and November 2001. Therefore, detailed investigations of the cause of failures were carried out. From the investigations on the measurement of the frequency characteristics of transformer windings and detailed lightning surge analysis used by Electromagnetic Transients Program (EMTP), it was found that resonance overvoltages were generated by resonance phenomena between the surge waveform passing through the transformer and the natural frequency characteristics of the transformer winding. This finding was used to improve the winding form of tap windings and install a surge protection device between tap windings. After the improvement of winding structures, it was clearly shown that the internal stress of tap windings was reduced and the breakdown probability of the damaged part was significantly reduced. [ABSTRACT FROM AUTHOR]

A rigorous model is developed for determining single-photon quantum efficiency (SPQE) of single-photon avalanche photodiodes (SPADs) with simple or heterojunction multiplication regions. The analysis assumes nanosecond gated-mode operation of the SPADs and that band-to-band tunneling of carriers is the dominant source of dark current in the multiplication region. The model is then utilized to optimize the SPQE as a function of the applied voltage, for a given operating temperature and multiplication-region structure and material. The model can be applied to SPADs with In0.52Al0.48As or InP multiplication regions as well as In0.52Al0.48As-InP heterojunction multiplication regions for wavelengths of 1.3 and 1.55 µm. The predictions show that the SPQE generally decreases with decreasing the multiplication-region thickness. Moreover, an InP multiplication region requires a lower breakdown electric field (and, hence, offers a higher SPQE) than that required by an In0.52Al0.48As layer of the same width. The model also shows that the fractional width of the In0.52Al0.48As layer in an In0.52Al0.48As-InP heterojunction multiplication region can be optimized to attain a maximum SPQE that is greater than that offered by an InP multiplication region. This effect becomes more pronounced in thin multiplication regions as a result of the increased significance of dead space. [ABSTRACT FROM AUTHOR]

This paper deals with the nature of seed electron sources in compressed [sub2] for positive polarity. We present an experimental procedure that provides evidence of the fact that collisional detachment from negative ions plays the most important role in the supply of seed electrons. Conditioning phenomena in compressed SF [sub6], N[sub2] and air have been simulated under positive lightning impulses for point-plane geometry. [ABSTRACT FROM AUTHOR]

Conducting particles in transmission and switching equipment insulated by compressed sulphur hexafluoride (SF6) can result in loss of as much as 90% of the gas dielectric strength. Particles in practical systems can exist in a wide variety of shapes and sizes, and of materials of different densities. In this paper, the effect of particle size on the probability of SF6 breakdown is discussed. Theoretical and experimental results are presented. [ABSTRACT FROM PUBLISHER]

Owing to the increment efficiency, the generation of water-in-oil (W/O) type emulsion in the flooding process affects the displacement efficiency. After the generation of emulsion in reservoir conditions, multiple mechanisms such as creaming, sedimentation, flocculation, phase inversion, coalescence, and Ostwald ripening cause the break of emulsion; and thus, the viscosity of the emulsion phase changes. However, owing to the lack of an appropriate model, the viscosity fluctuation caused by the emulsifying and demulsifying processes of the displaced phase has not been considered in general numerical simulations. In this study, a mathematical model that included the water cut, viscosity prediction, droplet displacement models, and droplet breakdown probability was established to predict the settling process of W/O type emulsion at different conditions. Multiple influencing factors, such as oil/water ratio, rotation speed, stirring time, and surfactant concentration were considered. The mathematical model for predicting emulsion settling provides excellent fitting results on the emulsion W/O system. The introduction of droplet breakdown probability can be used to adjust the prediction model to different emulsion systems. The size of the droplet is the key factor in the settling of the emulsion system. A larger droplet increases the coalescence probability, viscosity, droplet size, and descent rate. The oil/water ratio, stirring time, and rotation speed have a significant influence on the size of the emulsion droplet. More external and low water content can help generate smaller size droplets, which improves the emulsion stability. The emulsion with a different surfactant concentration possesses a similar initial condition. However, a low surfactant concentration system achieves a weaker stability during the settling process because of the relatively large droplet size and high descent rate. [Display omitted] • The droplet breakdown probability can predict emulsion settling. • The size of the droplet is a key factor for emulsion settling. • The oil/water ratio, stirring time, and rotate speed influence on the emulsion droplet size. • Surfactant concentrations possessed significant influence on emulsion stability. [ABSTRACT FROM AUTHOR]

Recently, it has been shown that the noise characteristics of heterojunction Al0.6 Ga0.4As-GaAs avalanche photodiodes (APDs) can be optimized by proper selection of the width of the Al0.6Ga0.4As layer. Similar trends have also been shown theoretically for the bandwidth characteristics. The resulting noise reduction and potential bandwidth enhancement have been attributed to the fact that the high bandgap Al0.6Ga0.4As layer serves to energize the injected electrons, thereby minimizing their first dead space in the GaAs layer. We show theoretically that the same optimized structures yield optimal breakdown-probability characteristics when the APD is operated in Geiger mode. The steep breakdown-probability characteristics, as a function of the excess bias, of thick multiplication regions (e.g., in a 1000-nm GaAs homojunction) can be mimicked in much thinner optimized Al0.6Ga0.4As-GaAs APDs (e.g., in a 40-nm Al0.6Ga0.4As and 200-nm GaAs structure) with the added advantage of having a reduced breakdown voltage (e.g., from 36.5 V to 13.7 V). [ABSTRACT FROM AUTHOR]

In this letter the dynamics of wire particles in a coaxial gas insulated transmission line (GITL) system with coated electrodes under AC voltage are studied using a computational algorithm. The possibility of the SF6 gas insulation breakdown due to the presence of metallic contaminants was computed at different applied voltages and gas pressures [ABSTRACT FROM PUBLISHER]