Transient Shaping Research Articles

Drivers and consequences of bacteriophage host range.

Bacteriophages are obligate parasites of bacteria characterized by the breadth of hosts that they can infect. This "host range" depends on the genotypes and morphologies of the phage and the bacterial host, but also on the environment in which they are interacting. Understanding phage host range is critical to predicting the impacts of these parasites in their natural host communities and their utility as therapeutic agents, but is also key to predicting how phages evolve and in doing so drive evolutionary change in their host populations, including through movement of genes among unrelated bacterial genomes. Here, we explore the drivers of phage infection and host range from the molecular underpinnings of the phage-host interaction to the ecological context in which they occur. We further evaluate the importance of intrinsic, transient, and environmental drivers shaping phage infection and replication, and discuss how each influences host range over evolutionary time. The host range of phages has great consequences in phage-based application strategies, as well as natural community dynamics, and we therefore highlight both recent developments and key open questions in the field as phage-based therapeutics come back into focus.

Reference tracking and transient response shaping of uncertain quasi one-sided Lipschitz nonlinear systems

This work addresses the reference tracking problem for uncertain systems with quasi one-sided Lipschitz nonlinearity. The uncertainty is assumed to be of a norm bound parametric type. Moreover, transient response shaping using the concept of ‘return time’ is also proposed. The controller design relies on the solution of Linear Matrix Inequalities (LMIs) and hence is computationally efficient. The proposed control law is linear in states, and thus the implementation is often straightforward. To illustrate the capability and simplicity of the proposed theory, three design examples are included.

Artifact-free and high-temporal-resolution in vivo opto-electrophysiology with microLED optoelectrodes

The combination of in vivo extracellular recording and genetic-engineering-assisted optical stimulation is a powerful tool for the study of neuronal circuits. Precise analysis of complex neural circuits requires high-density integration of multiple cellular-size light sources and recording electrodes. However, high-density integration inevitably introduces stimulation artifact. We present minimal-stimulation-artifact (miniSTAR) μLED optoelectrodes that enable effective elimination of stimulation artifact. A multi-metal-layer structure with a shielding layer effectively suppresses capacitive coupling of stimulation signals. A heavily boron-doped silicon substrate silences the photovoltaic effect induced from LED illumination. With transient stimulation pulse shaping, we reduced stimulation artifact on miniSTAR μLED optoelectrodes to below 50 μVpp, much smaller than a typical spike detection threshold, at optical stimulation of >50 mW mm–2 irradiance. We demonstrated high-temporal resolution (<1 ms) opto-electrophysiology without any artifact-induced signal quality degradation during in vivo experiments. MiniSTAR μLED optoelectrodes will facilitate functional mapping of local circuits and discoveries in the brain.

Optoelectronic generation of transient waveforms for UWB radars with rejected frequencies

AbstractIn this paper, a new design of an optoelectronic system for transient waveforms shaping, with a selection of rejected frequencies, is presented. The generation of short pulses is performed with several optoelectronic generators using photoconductive semiconductor switches (PCSS) operating in linear switching mode and triggered via a laser pulse. With the appropriate number of generators, the system generates a spectrum ranging from 300 MHz to 3 GHz, with rejected frequencies at 900 MHz and 1.8 GHz. A PCSS characterization has been set up to determine the necessary parameters for the establishment of an optoelectronic generator model on Keysight Advanced Design System software (ADS). Experimental tests have been realized using measurement benches to compare the simulated and measured signals.

Transient Electric Field Shaping With the Linear Combination of Configuration Field Method for Enhanced Spatial Control of Microwave Plasmas

The demonstration of enhanced spatial control of nanosecond microwave plasmas generated by the time reversal plasma source is presented in this paper. This new microwave plasma source relies on the spatio-temporal control of the electric field inside an all-metal plasma reactor by modifying the waveform of a high power microwave signal. More specifically, it originally used the spatio-temporal focusing capabilities of the time reversal method to focus a high electric field in a small location. However, a parasitic microwave breakdown can still occur at sharp corners or wedges inside the cavity due to the local enhancement of the residual electric field during time reversal focusing. Thus, it is proposed to use the linear combination of configuration field method to improve field control inside the reactor. Its transient electric field shaping capabilities turn out to be a good candidate for the development of a low pressure microwave “plasma brush”.

Robust reference tracking and transient response shaping of a class of nonlinear systems

This work examines stabilisation and reference tracking problems for uncertain deterministic as well as switched stochastic nonlinear systems. The concept of input state stability is employed here in the tracking problems. Additionally, an attempt is made to improve the transient performance of deterministic nonlinear systems by employing the notion of return time which is applicable to a broader class of nonlinearities. The transient performances are compared using the Integral Square Error (ISE). The control law is linear in states and thus is easy to implement. The optimisation problem is formulated in a framework of Linear Matrix Inequalities (LMIs). The proposed design is tested on simulation examples. The advantages are established on benchmark problems from the literature like Control of the Wing Rocket Aircraft and the Continuously Stirred Tank Chemical Reactor (CSTR). As per the author's knowledge, not much work is reported on these problems.

Precise Transient Electric Field Shaping With Prescribed Amplitude Pattern by Discrete Time Reversal

Generation of arbitrarily shaped transient electric fields in a prescribed bounded region, especially with high precision and low sidelobes, is a challenging fundamental issue with applications ranging from electromagnetic (EM) switch, microwave chemotherapy to wireless power transfer. In this work, we study for the first time the transmission of the EM field excited by point current sources (PCSs) in time reversal cavity (TRC) or time reversal mirror (TRM) from the view of EM radiation. We first decompose the predefined area into a number of spatial grids, those are all utilized as PCSs here. When the electric field of one PCS is calculated, other PCSs are treated as secondary sources. We can get the whole electric field distribution by calculating these grids one by one. Based on this theory, we choose the closed TRC/TRM as excitation transmitters to construct arbitrarily shaped electric field inside TRC/TRM, whose excitation can be synthesized after all the TRC/TRM elements capture their responses to the known probing signals emitted from probe antennas situated at all grids. Thanks to the spatial and temporal focusing property of time reversal (TR), a set of the TR focusing field is produced simultaneously with their focal spots spaced by grids. We successfully and dynamically demonstrate the simple generation method for different desired transient electric fields, and observe the electric distribution during the process of getting desired shaped electric field with time under different limited given regions.

An Integral Droop for Transient Power Allocation and Output Impedance Shaping of Hybrid Energy Storage System in DC Microgrid

Power allocation in hybrid energy storage systems (HESSs) is an important issue for dc microgrids. In this paper, an integral droop (ID), inspired by the electrical characteristics of capacitor charging/discharging process, is proposed and applied to a cluster of energy storages (ESs) with high ramp rates. Through the coordination of the ID and conventional V-P droop, the transient power allocation in HESSs can be intrinsically realized in a decentralized manner. The high-frequency components of power demand can be compensated by the ESs with ID, whereas the ESs with V-P droop respond to the smooth change of load power. Additionally, the ID coefficient can be designed according to the nominal ramp rate of the ESs with slow response, which helps to extend the lifespan of the HESS. On the other hand, to easily assess the stability of the system feeding constant power loads, a minimum relative impedance criterion (MRIC) is developed. Based on MRIC, it is revealed that the proposed ID can shape the output impedance of the HESS and stabilize the entire system. The feasibility and effectiveness of ID are verified by both simulations and experimental results.

The effect of transient density profile shaping on transport in large stellarators and heliotrons

Transport studies of pellet fuelling experiments on LHD are reported. Spatio-temporal evolutions after pellet injection into LHD discharges show cases where central density increases on the time scale of particle transport processes. Both the temperature gradient and the density gradient change during the density relaxation, the latter even in sign. The resulting thermodynamic forces influence radial electric fields—both as a driving term but also by, e.g. affecting the E r dependence of ion transport. Magnetic fluctuations have been found to be induced by pellet injection but die out with the relaxation of the pressure profile.

The Social Network Gamer’s Experience of Play

We address the subjective experience of social network gamers playing Restaurant City, a game hosted on Facebook. We adopted a netnographic approach to studying the culture of transient Internet communities shaping the player off-line communities. Fieldwork was conducted over the entire life span of the game (3 years). Data were analyzed using a qualitative thematic approach and the software EdEt. The results describe the evolution of the gaming experience through online interaction and its importance in everyday off-line life. Players were observed to play an important role in the production of social meanings associated with gaming and with the gaming community online and off-line. We discuss the implications of our findings regarding how the gaming process is a far more complex scenario than envisaged by a business vision based on acquisition, retention, and monetization.

An electrochemical calibration unit for hydrogen analysers

Determination of hydrogen in solids such as high strength steels or other metals in the ppb or ppm range requires hot-extraction or melt-extraction. Calibration of commercially available hydrogen analysers is performed either by certified reference materials CRMs, often having limited availability and reliability or by gas dosing for which the determined value significantly depends on atmospheric pressure and the construction of the gas dosing valve. The sharp and sudden appearance of very high gas concentrations from gas dosing is very different from real effusion transients and is therefore another source of errors. To overcome these limitations, an electrochemical calibration method for hydrogen analysers was developed and employed in this work. Exactly quantifiable, faradaic amounts of hydrogen can be produced in an electrochemical reaction and detected by the hydrogen analyser. The amount of hydrogen is exactly known from the transferred charge in the reaction following Faradays law; and the current time program determines the apparent hydrogen effusion transient. Random effusion transient shaping becomes possible to fully comply with real samples. Evolution time and current were varied for determining a quantitative relationship. The device was used to produce either diprotium (H2) or dideuterium (D2) from the corresponding electrolytes. The functional principle is electrochemical in nature and thus an automation is straightforward, can be easily implemented at an affordable price of 1–5% of the hydrogen analysers price.

Output transient trajectory shaping control for a class of nonlinear systems

SUMMARYThis paper presents a transient trajectory shaping (TTS) control method for the SISO strict feedback nonlinear systems. The TTS control refers to explicitly constraining the system output tracking error transient trajectories within predesigned time‐varying boundaries while they are converging to equilibrium. By this method, the boundaries of system output transient trajectories can be designed a priori according to the system transient control performance requirements in both symmetric and asymmetric ways. With a class of time‐varying boundary functions, control laws can be devised by utilizing the enhanced differential unbounded function techniques. Such control laws can ascertain that the system output tracking errors travel within their respectively predesigned time‐varying boundaries while converging to origin. To handle the control input exaggeration issue in TTS, input constraint control techniques are proposed to effectively reduce the required control input magnitude for second‐order systems. A numerical example is utilized to show the effectiveness of the proposed TTS control methods. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Robust control of multi-input periodic discrete-time systems with saturating actuators

This paper proposes the use of a time-varying sliding surface for robust transient shaping of periodic linear discrete-time plants subject to saturating actuators, in the presence of bounded matched uncertainties. A constructive procedure is presented, and ultimate boundedness of state trajectories is proved.

A new command governor architecture for transient response shaping

SUMMARYIn this paper, we develop a control framework for stabilization and command following of nonlinear uncertain dynamical systems. The proposed methodology consists of a new command governor architecture and an adaptive controller. The command governor is a dynamical system that adjusts the trajectory of a given command to follow an ideal reference system capturing a desired closed‐loop dynamical system behavior in transient time. Specifically, we show that the controlled nonlinear uncertain dynamical system can approach the ideal reference system by choosing the design parameter of the command governor. In addition, an adaptive element is used to asymptotically assure that the error between the controlled nonlinear uncertain dynamical system and the ideal reference system is reduced in long term. Therefore, the proposed methodology not only has closed‐loop transient and steady‐state performance guarantees but can also shape the transient response by adjusting the trajectory of the given command with the command governor. We highlight that there exists a trade‐off between the adaptive controller's learning rate and the command governor's design parameter. This key feature of our framework allows rapid suppression of system uncertainties without resorting to a high learning rate in the adaptive controller. Furthermore, we discuss the robustness properties of the proposed approach with respect to high‐frequency dynamical system content such as measurement noise and ∕ or unmodeled dynamics. A numerical example is provided to demonstrate the efficacy of the proposed architecture. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Practical stabilisation and transient shaping of discrete-time plants with saturating actuators and matched disturbances

This study proposes the use of a time-varying sliding surface for robust transient shaping of linear discrete-time multi-input plants subject to saturating actuators, in the presence of bounded matched uncertainties. A constructive procedure is presented, ultimate boundedness of state trajectories is proved and a result about the choice of tuning parameters for robust transient shaping is given. Simulation results show remarkable improvements in dynamic performances with respect to existing literature.

Input constrained non-equilibrium transient trajectory shaping via a three-stage control method for a class of non-linear systems

This study deals with the non-equilibrium transient trajectory shaping problem for non-linear, strict feedback, single-input–single-output systems by a three-stage switching control method. Through this control method, the non-linear system output tracking error can be constrained within a set of properly pre-designed boundaries when it is converging to the equilibrium point. In particular, the three-stage switching control method imposes a constant bound (the first stage), two exponentially converging time-varying functions (the second stage), and a smaller constant bound (the third stage) as the tracking error boundary in each of the three stages, respectively. By designing control laws separately in the corresponding stages, the trajectory of the system tracking error can be assured within the boundaries during transient period. The bound of the control input magnitude can be determined with the respective control law at each stage and consequently establish the tradeoff between system transient performance and the available control resource. Numerical examples are utilised to show the effectiveness of the technique.

Sliding mode control of periodic discrete-time linear systems with saturating actuators and input disturbances

AbstractThis paper proposes the use of a time-varying sliding surface for robust transient shaping of periodic linear discrete-time plants subject to saturating actuators, in the presence of bounded matched uncertainties. A constructive procedure is presented, ultimate boundedness of state trajectories is proved and a result about the choice of tuning parameters for robust transient shaping is given.

Loose eigenstructure assignment via rank-one LMI approach with application to transient response shaping in H ∞ control

This article proposes a new regional eigenstructure assignment via rank-one LMI approach. A gain parameter condition for the regional eigenvalue/eigenstructure assignment is newly derived. This assignment condition is easily combined with H ∞ design by means of enhanced LMI characterisation. In the present approach, the desired assignment of closed-loop eigenvalues (i.e. poles) are not previously fixed but constrained into individual assignment regions to bring us more design freedom than classical exact assignment. The regional assignment discussed in this article never falls into an ordinary LMI root clustering because the union of assignment regions is disjoint in general. Each closed-loop eigenvector is also constrained into individual alignment cone. To show the practical use of the extra design freedom brought by regional assignment, a transient response shaping in H ∞ design is also discussed. A useful design algorithm based on linearisation algorithm is proposed.

Inversion of sampled-data system approximates the continuous-time counterpart in a noncausal framework

Although correspondence between the poles of a continuous-time and sampled-data system with a piecewise constant input is simple and desirable from the stability viewpoint, the relationship between zeros is intricate. Inversion of a sampled-data system is mostly unstable irrespective of the stability of the continuous-time counterpart. This makes it difficult to apply inversion-based control techniques such as perfect tracking, transient response shaping or iterative learning control to sampled-data systems. Although recently developed noncausal inversion techniques help us to circumvent unboundedness of the inversion caused by unstable zeros, whether the inversion of sampled-data systems approximates the continuous-time counterpart or not as the sample period is shortened is still to be determined. This article gives a positive conclusion to this problem.

Enhancing ultrasonic imaging with low transient pulse shaping

This work deals with improving the resolution of ultrasonic ranging systems by means of preshaping the transmitter drive signals to achieve low transient acoustic pulses. As ultrasonic transducers are operated at a relatively high nominal frequency and quality factor, feedforward strategy is among the most efficient means to generate the low transient acoustic pulses. In this work, a digital signal processor and a field programmable gate array synthesize the transmitter drive signal to emit low transient pulses which are then applied to the detection of surface features. Both simulation and experiment results confirm an improved spatial detection resolution due to the lower acoustic transient interference. The drive signal synthesis process is also simpler than the conventional modulation method and should result in lower cost of implementation.