Firing Durations Research Articles

Periodic and Non-Periodic Brainwaves Emerging via Stochastic Syncronization of Closed Loops of Firing Neurons

Periodic and non-periodic components of electrophysiological signals are modelled in terms of syncronized sequences of closed loops of firing neurons correlated according to a Markov chain. Single closed loops of firing neurons reproduce fundamental and harmonic components, appearing as lines in the power spectra at frequencies ranging from 0.5 Hz to 100 Hz. Further interesting features of the brainwave signals emerge by considering multiple syncronized sequences of closed loops. In particular, we show that fluctuations in the number of syncronized loops lead to the onset of a broadband power spectral component. By the effects of these fluctuations and the emergence of a broadband component, a highly distorted waveform and nonstationarity of the signal are observed, consistent with empirical EEG and MEG signals. The amplitudes of the periodic and aperiodic components are evaluated by using typical firing neuron pulse amplitudes and durations.

Electric thruster configuration design optimization for geostationary satellites with robotic manipulators

This paper proposes a novel electric thruster configuration design optimization scheme to implement efficient station-keeping operations for geostationary satellites. In this work, the electric thrusters are equipped with 4-DOF robotic manipulators to provide flexible control thrust in space, which consumes much less propellant than the conventional station-keeping process using fixed-position electric thrusters. To effectively determine the firing right ascensions and firing durations of each electric thruster during the station-keeping process, a novel station-keeping control strategy is developed in view of the low-thrust feature of electric thrusters and the flexible pointing capacity of robotic manipulators. A low-thrust station-keeping period includes one two-day orbit determination period and six two-day control periods, where the initial orbital elements are determined in the orbit determination period, and the electric thrusters fire to compensate the perturbations in the control periods. Based on the control strategy, the electric thruster configuration design optimization problem is formulated to minimize the total propellant consumption via optimizing the robotic manipulator joint swivel angles and firing durations simultaneously, subject to several practical engineering constraints including the station-keeping accuracy, angular momentum dumping, collision between electric thruster and solar array, and electric thruster plume. Finally, the proposed electric thruster configuration design optimization scheme is applied to real-world station-keeping problems. The simulation results show that the geostationary satellites can be successfully maintained in an assigned station-keeping window using the robotic manipulators based low-thrust station-keeping control strategy. Moreover, the optimized electric thruster configuration with robotic manipulators can save 31.58% propellant consumption compared with that of the conventional configuration owing to the favorable flexibility of control thrust, which demonstrates the effectiveness and practicality of this work.

Influence of firing temperature and duration on the hardness of dental zirconia for optimum selection of sintering conditions

In order to optimize the properties of dental zirconia, the sintering process involves firing zirconia to elevated temperatures for an extended time that can take several hours. The aim of this study is to investigate the effect of firing temperature and firing duration on the hardness of dental zirconia to indicate the optimum sintering conditions. Thirty-six zirconia specimens in shape of bars were randomly assigned to nine groups. The zirconia specimen groups were sintered using a sintering furnace with different firing temperatures (900°C, 1200°C, and 1800°C) and firing durations (6, 9, and 12 h). A total of 108 hardness measurements were conducted for all specimens (12 hardness readings per group). For each of the specimen groups, micro Vickers hardness test was performed using a load of 1 Kgf (9.807 N) and the Vickers hardness number was computed. Statistical analysis using Kruskal-Wallis test was conducted to examine the significant differences on Vickers hardness number HV among the specimen groups according to the firing parameters with 0.005 p-value used as an indicator. Results suggest that there is an association between the increase in the hardness number and the increase in firing duration at a given firing temperature. The results also indicate that there is an association between the increase in the hardness number and increase in firing temperature at a given firing duration. The greatest rate of hardness increase with time is associated with groups of firing temperature 1200°C. The highest rate of hardness increase with temperature happened during the first 6 h of sintering process. On the other hand, there is no significant increase in the hardness number when increasing the firing temperature beyond 1200°C.

A Mathematical Model Using Time Elements for Timed-Arc Petri Nets

In this work, a novel graphical and mathematical model is introduced for Timed-Arc Petri Nets. In this model, operation durations related to events are associated with arcs as firing durations. Time elements are introduced on the arcs of the model for monitoring tokens in operation durations (firing durations) of firing processes (events). In the model, the status of the system is represented as states consisting of remaining time vector for indicating the status of time elements and marking vector for indicating the status of places' state information. This feature of states allows to obtain reachability set enhanced with the time information and the timed reachability graph of the system. In this work, behavioral properties of the proposed model are also defined. Moreover, via considering real world systems, behavioral properties are analyzed and performance of the model is compared with Stretched Petri Nets which is a recently proposed type of Timed Petri Nets.

Contribution of AMPA and NMDA receptors in the spontaneous firing patterns of single neurons in autaptic culture

Single neurons in an autaptic culture exhibit various types of firing pattern with different firing durations and rhythms. However, a neuron with autapses has often been modeled as an oscillator providing a monotonic firing pattern with a constant periodicity because of the lack of a mathematical model. In the work described in this study, we use computational simulation and whole-cell patch-clamp recording to elucidate and model the mechanism by which such neurons generate various firing pattens. In the computational simulation, three types of spontaneous firing pattern, i.e., short, long-lasting, and periodic burst firing patterns are realized by changing the combination ratio of N-methyl-d-aspartate (NMDA) to α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) conductance. These three types of firing patterns are also observed in the experiments where neurons are cultured in isolation on micropatterned substrates. Using the AMPA and NMDA current models, we discuss that, in principle, autapses can regulate rhythmicity and information selection in neuronal networks.

Diagnosis of Structural and Temporal Faults for $k$ -Bounded Non-Markovian Stochastic Petri Nets

This paper concerns the diagnosis of faults for stochastic discrete event systems that behave according to non-Markovian dynamics. ${k}$ -bounded partially observed Petri nets are used to model the system structure and the sensors. Stochastic processes with probability density functions (pdf) of finite support define the dynamics. Structural and temporal faults are considered. Structural faults correspond to specific sequences of events that should satisfy precedence conditions defined with patterns. Temporal faults are defined with time constraints that must be fulfilled by the firing durations. The probabilities of consistent trajectories are computed with a numerical scheme from the collected timed measurements. The advantage of the proposed scheme is that it can be used for a large variety of pdf that may be defined either with an analytical or a numerical description. It works also for various time semantics. Diagnosis in terms of probability for faulty patterns and temporal constraints is established as a consequence.

Detection and isolation of temporal drifts in manufacturing systems with observers and control charts

Faults detection and isolation is a major issue for a large variety of manufacturing systems because such systems combine operations performed by several machines and use some common resources. The failure of a single machine slows down or even stops the whole system. This paper is about some specific insidious faults—namely temporal drifts—that affect manufacturing systems with mass production. Such temporal drifts are studied in a probabilistic setting by modeling the operation durations with random variables and by considering significant variations of the probability density function of these variable as the faults to be detected and isolated. Labeled stochastic timed Petri nets are used to model the considered systems and faults. A new class of observers—namely elementary trajectory observers—that estimate characteristic segments of the state trajectory is developed. Then, moving average control charts and observers are combined in order to detect the variations of the firing durations mean values. The proposed analysis is suitable to detect variations in the mean value of the operation durations when parameters vary gradually. It is also suitable to isolate the faults thanks to a set of minimal-size elementary trajectories consistent with the successive measurements. Detection and isolation decision functions are proposed, and the approach is illustrated on an example.

Control Design for Bounded Partially Controlled TPNs Using Timed Extended Reachability Graphs and MDP

This paper is about the design of control sequences for discrete event systems (DESs) modeled with bounded partially controlled timed Petri nets (PC-TPNs) including a set of temporal specifications that correspond to minimal firing durations. Petri nets are well-known mathematical and graphical models that are widely used to describe distributed DESs, including choices, synchronizations, and parallelisms. The domains of application include but are not restricted to manufacturing systems, computer science, and transportation networks. Including the time in the model is important to consider many control problems. This paper is more particularly concerned with control issues in timed context and uncertain environments when unexpected events occur and when control errors disturb the system behavior from the planned policy decided by the controller. To deal with such uncertainties, we propose first to build a timed extended reachability graph (TERG) that includes the time specifications when the PC-TPN behaves with an earliest firing policy. Then, the optimal paths in TERG are found by using an approach based on discrete time Markov decision processes under discounted criterion. Several simulations illustrate the benefit of our method from the computational point of view, in particular for uncertain environments.

Experimental demonstration of an end-burning swirling flow hybrid rocket engine

Within the framework of the European H2020 HYPROGEO program, an innovative hybrid engine combustion chamber compatible with satellite requirements (constant thrust over very long burn-times) had to be developed. A first test rig was designed and tested in order to better understand the functioning of this innovative combustion chamber, and to help the design of a breadboard to demonstrate the efficiency of this new engine with respect to the mission requirements. Two test campaigns, the first on the test rig with 87.5% hydrogen peroxide, and the second on the hybrid engine breadboard with 98% hydrogen peroxide, were performed under various operating conditions to demonstrate the catalytic ignitability of this new hybrid engine, and the sustainment of a stable combustion over firing durations up to 180 s. The test campaigns also enabled the identification of the main influencing parameter on the fuel regression rate for this innovative combustion chamber.

In vivo Studies of Brainstem Neurons with Respiratory Rhythm Activity in a Rat Model of Rett Syndrome

People with Rett Syndrome (RTT), a neurodevelopmental disorder caused by mutations of the MECP2 gene, show breathing abnormalities that are attributable to the high incidence of sudden death. To understand the underlying mechanisms for the breathing disorders, direct in vivo recordings from brainstem neurons with respiratory rhythm are needed, which is a challenge in mouse RTT models. The newly available rat model may allow such a study. Therefore, we performed electrophysiological recording from individual neurons of the medullary ventral respiratory group (VRG) in decerebrate Mecp2‐null and wild‐type (WT) rats. In both groups of rats, neurons with expiratory rhythm were recorded from the rostral and caudal VRG, and cells with inspiratory rhythm were found in between. Firing frequency of the inspiratory neurons was significantly lower in null rats than in WT rats, while expiratory neurons in both rostral and caudal VRG did not show such a difference. Firing durations of both expiratory and inspiratory neurons were elongated in null rats compared with the WT. The ratio of inspiratory to expiratory firing duration (Ti/Te) was lower in null rats. A large number of cells showed E‐I phase‐spanning in null rats. The null rats had a frequent breathing pattern of apneusis followed by apnea, during which inspiratory neurons showed increased firing frequency and caudal expiratory neurons showed decreased firing frequency, whereas no significant change was observed in rostral expiratory neurons. Although this breathing pattern of apneusis followed by apnea was also seen in WT rats, the firing frequency of either respiratory neurons did not seem to change. These findings suggest that Mecp2 disruption appears to cause a large scale of changes in firing activity and pattern of medullary respiratory neurons consistent with the broad range of breathing abnormalities seen in people with RTT and animal models.Support or Funding InformationThis work was supported by NIH grant R01‐NS‐073875 and International Rett Syndrome Foundation.

Cobalt-base alloy gun barrel study

Firing tests of a small caliber experimental gun barrel made of a cobalt-base alloy have been conducted with the purpose of determining the degree of wear and erosion due to excessive firing durations. The small amount of barrel material loss makes the cobalt-base alloy an excellent candidate for use as a gun liner. An unusual wear pattern resulting from this loss was observed near the muzzle. Elimination of chemical and thermal effects made a plausible explanation of the wear pattern possible.

Supervisory controller design to enforce some basic properties in timed-transition Petri nets using stretching

Supervisory controller design to enforce boundedness, reversibility, and liveness in timed-transition Petri nets with firing durations is considered. It is assumed that both controllable and uncontrollable transitions may be present and more than one transition may fire simultaneously. The approach of stretching is used to represent the state of the system. Algorithms are presented to design a supervisory controller using the forbidden states approach to enforce boundedness and reversibility simultaneously. The designed controller also guarantees T -liveness for the largest possible subset T of the set of transitions. In particular, boundedness, reversibility, and liveness are simultaneously enforced whenever it is possible. The designed controller is also the least restrictive controller which enforces boundedness and reversibility simultaneously.

Supervisory Controller Design to Enforce Some Basic Properties in Timed Petri Nets

Supervisory controller design to enforce boundedness, reversibility, and liveness in timed Petri nets with firing durations is considered. It is assumed that both controllable and uncontrollable transitions may be present and more than one transitions may fire simultaneously. The approach of stretching is used to represent the state of the system. Algorithms are presented to design a controller to enforce boundedness, reversibility, and liveness simultaneously.

Firing Temperatures and Raw Material Sources of Ancient Hittite Ceramics of Asia Minor

The firing temperature and production technology together with the provenance and source materials of a group of the Domuztepe (Cilicia, Turkey) Late-Hittite ceramics were studied by mineralogical analyses. The mineralogical (presence of basaltic minerals and the formation of forsterite and tridymite as high temperature minerals) results revealed that this group of Late-Hittite ceramics were products of a mixture of local raw materials such as basalts (10–15%) and soils developed on olivine basalts (70–75%). Evidence demonstrated that the potters of that period were highly aware of achieving temperatures well around 1000°C, despite the lack of proficiency or unwillingness to sustain prolonged firing durations, that later became the norm of cultures in Asia Minor.

Delayed inhibition creates amplitude tuning of mouse inferior collicular neurons

Nonmonotonic intensity response neurons referred as amplitude-tuned neurons are considered to be created by high-threshold inhibition in auditory system. Very limited information, however, is available on how the inhibition works for amplitude-tuned neurons. We studied the temporal response properties of these neurons with or without iontophoresis of bicuculline (gamma-aminobutyric acid A antagonist). In most neurons, the firing durations gradually reduced with the increasing amplitudes beyond the best amplitudes. Bicuculline application selectively blocked the inhibition of the sustained responses to high amplitudes and abolished the nonmonotonic intensity response properties. Our results suggest that a temporally delayed inhibition, whose latency reduced related to excitation with the increasing amplitude, is responsible for the creation of about 71% amplitude-tuned neurons in mouse inferior colliculus.

Deadlock Avoidance Controller Design for Timed Petri Nets Using Stretching

The recently introduced method, which was called ldquostretching,rdquo is extended to timed Petri nets which may have both controllable and uncontrollable transitions. Using this method, a new Petri net, called ldquostretched Petri net,rdquo which has only unit firing durations, is obtained to represent a timed-transition Petri net. Using this net, the state of the original timed Petri net can be represented easily. This representation also makes it easy to design a supervisory controller for a timed Petri net for any purpose. In this paper, supervisory controller design to avoid deadlock is considered in particular. Using this method, a controller is first designed for the stretched Petri net. Then, using this controller, a controller for the original timed Petri net is obtained. Algorithms to construct the reachability sets of the stretched and original timed Petri nets, as well as algorithms to obtain the controller for the original timed Petri net are presented. These algorithms are implemented using Matlab. Examples are also presented to illustrate the introduced approach.

Performance and Scalability of MJ Sequentially Fired Pulse Forming Networks for Linear and Nonlinear Loads

The principal advantages of the sequentially fired pulse forming network (SFPFN) over its passive analog are its utility in both linear and nonlinear load applications. Operation of the SFPFN consists of charging multiple capacitor banks to different voltage levels and sequentially firing these banks into the load at appropriate times. The load characteristics and the desired pulse attributes determine the module charge voltage and sequential firing schedule. This paper describes the pulsed power system and computer control system design of a 750-kJ SFPFN. Typical experimental results in the case of a linear load are presented and compared with simulations, and pulse-shaping capabilities are demonstrated. Scaling considerations are discussed in the case of increasing the SFPFN energy capacity to 7.5 MJ. The SFPFN uses a computer-controlled field programmable gate array to initiate the trigger signal for each module's output switch. The use of a computer-controlled firing circuit provides an opportunity to incorporate real-time load monitoring and feedback to select the optimal firing times and durations based on dynamic load conditions. The incorporation of feedback during a pulse sequence also allows for the firing sequence to be halted in the event of a fault or other potentially harmful event. The charging controller features a computer monitoring and control system to allow a single power supply to charge multiple capacitor modules by an array of switching relays, even though each module may be charged to a different voltage. In linear load testing, the SFPFN provided a relatively constant current pulse to a resistive load. Pulse-shaping capabilities are demonstrated by varying the charge voltage of individual banks prior to a firing sequence. Future applications of the SFPFN include powering a helical launcher

A Study in Classification: Style and Visual Perception

The authors explore the process by which people determine that one object is similar to, or different from, another, and investigate how the process might affect our understanding of archaeological classification. Exploratory Data Analysis [Tukey] was conducted on measurements from 159 conical fired pots excavated at al-Hiba in Iraq. Although frequency distributions of single parameters did not show clear and consistent categories, certain correlated parameters showed a clear bimodal frequency distribution into two basic shapes which matched the traditional archaeological subdivision into “cups” and “bowls.” Stylistic subdivisions perceived by undergraduate students (91, from Brooklyn College and New York University), when asked to sort profile drawings of pots (73) into perceived divisions and then group divisions into styles, agreed with the bimodal objective division. Exploratory Data Analysis can identify objective stylistic grouping of archaeological artifacts. Other findings of the authors during the conduct of this research include: (1) shape, independent of size, divides these pots into cups or bowls; (2) uniformity of surface and core colors indicates no basic differences in clays, kilns, or firing temperature and durations for nearly 1,000 years; (3) there is little inter-observer consistency in the division of the two major categories of perceived styles, but gender clearly affects the number of observed subdivisions. The study concludes with a look at statistical analyses of style in other objects and works of art and briefly explores some of the benefits that might accrue from the continued study of visual perception and art.

Three DOF Optimal Thrusters Selection and Modulation for Space Vehicles

In reaction control thrusters (RCT) propulsed space vehicles the force and/or torque derived from the control law must be translated into thrusters selection and thrusters firing durations. This has often to be done in an optimal way with respect to propellant consumption. Classical catalogue approaches to perform that rely on RCT architectural geometry symmetry properties. When such symmetries are not present at all, use of algorithms such as the linear programming “simplex” one has been advocated. But it presents some risks because the computation duration is not deterministic and no converged solution is granted in a predetermined duration. In-house studies performed at EADS Space Transportation found an optimal catalogue solution for the six DOF (degrees of freedom) problem. This algorithm has been developed for the ATV (Automated Transfer Vehicle) spacecraft. It is based on a precomputed optimal catalogue that is used onboard. However this catalogue depends on the centre of mass and this feature prevents its direct use in the pure attitude control problem. Here it is proposed an adaptation of the 6 DOF optimal catalogue to cope with 3 DOF problems and present some results

Heterogeneity within geniohyoid motor unit subpopulations in firing patterns during breathing

Respiratory motor units (MU) segregate into subpopulations, which differ in firing patterns during resting and stimulated breathing. For phrenic/diaphragm MUs, diversity also exists within subpopulations, and is greater for late than early-onset MUs. The present study characterized the extent of diversity within upper airway respiratory MU subpopulations by recording geniohyoid MUs in anesthetized cats. Inspiratory MUs (I-MU, n=21) had a wide range of firing durations (coefficient of variation (CV)=42%). In contrast, inspiratory–expiratory MUs (I/E-MU, n=19) had a narrow range of firing durations during inspiration (CV=13%), but a wide range of firing durations during expiration (CV=36%). Mean firing frequency had similar degrees of diversity among units for I-MU and I/E-MU (CV=31–40%). For I-MU firing duration correlated with mean firing frequency, whereas no such relationship was apparent for I/E-MU. Single-breath end-expiratory airway occlusion decreased heterogeneity in firing duration during inspiration and increased it during expiration, whereas end-inspiratory airway occlusion decreased heterogeneity during expiration. In conclusion, (a) there is considerable diversity within geniohyoid MU subpopulations receiving respiratory drive; (b) the degree of diversity within subpopulations differs for I-MU and I/E-MU; and (c) diversity within subpopulations in timing of activity is modulated by single-breath airway occlusion.