Large Transient Response Research Articles

Dynamic control analysis of energy-efficient side-stream extractive distillation process for separating close-boiling mixture

To separate the close-boiling mixture comprising heptane and toluene, this study introduces an environmentally-friendly method of side-stream extractive distillation by utilizing aniline as the separating agent. This approach modifies traditional extractive distillation by adding a side rectifier, converting two-way vapor and liquid communication into one-way liquid transfer using an additional distillation section along with corresponding reboiler. Our present study investigates the dynamic control behavior for a strongly non-ideal system without and with heat integration. It focuses on achieving stable and reliable regulatory control by closely keeping the dual-product composition to their original design standards. Key control loops are pinpointed, with a specific emphasis on those centered around adjusting reboiler heat duty and side-stream flow rate within extractive column C1 to regulate the temperatures of Stages 48 and 36. Furthermore, control effectiveness is enhanced by introducing a feedforward action of reboiler heat duty-to-feed flowrate. By developing a new and robust control architecture, high feed flowrate and composition disturbances can be managed efficiently, solving the issues of oscillation and large transient response.

Kirchhoff rod-based three-dimensional dynamical model and real-time simulation for medical-magnetic guidewires

Background and Objective: Magnetic guidewire, fabricated from hard-magnetic soft composites, has recently emerged as an appropriate candidate for magnetic actuation systems to perform intravascular surgical navigation, owing to its elastic, magnetically steerable properties and good interphase with biological tissues. A suitable and efficient mathematical model for the magnetic guidewire is essential in the system to execute remote manipulation and active control. Methods: This paper presents a real-time Kirchhoff rod-based dynamical modeling approach, the magneto-elastic rod model, to simulate magnetic guidewire, which provides accurate simulations for two- and three-dimensional dynamic deflections induced by external magnetic fields and obtains deformed guidewire shapes in quasi-static status. Results: The proposed model is capable of describing the intrinsic principles of elastic body actuation by torques generated from the hard-magnetic soft matrix. The effectiveness of the developed model is validated, and the real-time simulation application is conducted via the semi-implicit numerical integration method. Conclusions: It has been shown that the presented dynamical model captures large nonlinear deformations and transient responses of the magnetic guidewire in an imitated human blood environment, which could offer robust support for the construction of a simulated magnetically driven surgical system.

Acceleration-feedback-based finite-time platoon control for interconnected vehicular system

The platoon control problem of interconnected vehicular systems is investigated in this paper studies. A finite-time adaptive sliding mode control (SMC) method based on acceleration feedback is developed to achieve platooning of interconnected vehicular systems subject to external disturbances and string stability of the closed-loop platoon system is analyzed. The string stability of the closed-loop system is achieved by applying the constant spacing (CS) strategy in the proposed adaptive sliding mode controller under zero initial steady-state error conditions. A novel error definition method is proposed to transform the non-zero initial steady-state error into the zero initial steady-state error so that the proposed algorithm can be independent of the initial steady-state errors and reduce the large transient response caused by non-zero initial steady-state errors. The salient feature of the proposed SMC law is that it does not need to know the disturbance boundary in advance. Finally, simulations and experiments are conducted to demonstrate the advantages and effectiveness of the proposed algorithm.

Transient response of a TLP-type floating offshore wind turbine under tendon failure conditions

Among various types of floating offshore wind turbines (FOWTs), the tension leg platform (TLP) floating wind turbines have relatively small motions due to stiff tendons. Similar to TLP applications in the offshore industry, tendon failure may lead to deteriorated stability and large transient responses, which should be considered as part of accidental limit state (ALS) checks at the design stage of the TLP FOWTs. This paper takes the WindStar TLP system as a representative and investigates the transient effects of one-tendon failure on the system responses. A coupled numerical model is first established using the aero-hydro-servo-elastic simulation tool FAST. Subsequent numerical simulations of tendon failure are carried out to consider different tendon breakage and turbine shutdown scenarios in both operational and parked conditions. Response statistics of key design parameters including platform motion, nacelle acceleration, and tendon tension are analyzed. The results indicate that several transient responses of the FOWT under operational conditions may be even higher than the extreme values under 50-year conditions. Our analyses also reveal that the shutdown strategies, if not applied appropriately, may have limited effects in reducing the responses of the FOWT, thus in certain scenarios threaten the safety of the tendon closest to the broken tendon if no other actions are taken. For the considered TLP FOWT, the ALS design requirements dominate over the ultimate limit state requirements. These findings can be relevant to the ALS design of TLP FOWTs.

Differential sustained and transient temporal processing across visual streams.

How do high-level visual regions process the temporal aspects of our visual experience? While the temporal sensitivity of early visual cortex has been studied with fMRI in humans, temporal processing in high-level visual cortex is largely unknown. By modeling neural responses with millisecond precision in separate sustained and transient channels, and introducing a flexible encoding framework that captures differences in neural temporal integration time windows and response nonlinearities, we predict fMRI responses across visual cortex for stimuli ranging from 33 ms to 20 s. Using this innovative approach, we discovered that lateral category-selective regions respond to visual transients associated with stimulus onsets and offsets but not sustained visual information. Thus, lateral category-selective regions compute moment-to-moment visual transitions, but not stable features of the visual input. In contrast, ventral category-selective regions process both sustained and transient components of the visual input. Our model revealed that sustained channel responses to prolonged stimuli exhibit adaptation, whereas transient channel responses to stimulus offsets are surprisingly larger than for stimulus onsets. This large offset transient response may reflect a memory trace of the stimulus when it is no longer visible, whereas the onset transient response may reflect rapid processing of new items. Together, these findings reveal previously unconsidered, fundamental temporal mechanisms that distinguish visual streams in the human brain. Importantly, our results underscore the promise of modeling brain responses with millisecond precision to understand the underlying neural computations.

State assignment method for improvement of transient response caused by controller switching

Abstract In this paper, the suppression of undesirable transient responses caused by controller switching is considered. In some cases, we switch the feedback and the observer gains in order to improve the control performance. However, such switching causes large disturbed transient response. To suppress such undesirable transient response, we propose to assign the state of the dynamical controller. This paper shows that it can be further suppressed by attaching an observer in order to suppress the transient response caused by switching, even in the case that all the states can be measured directly. The proposed assignment rule is based on the observability gramian of the post-switching closed loop system.

Temperature and precipitation projection at 1.5 and 2°C increase in global mean temperature

Based on climate model outputs from Coupled Model Intercomparison Project Phase 5 (CMIP5), we investigated the global temperature and precipitation changes when global mean temperature rises by 1.5 and 2°C relative to the pre- industrial period (1861–1900). Multi-model ensemble mean (MME) shows that for the scenarios RCP2.6, RCP4.5, RCP6.0 and RCP8.5, global mean near-surface temperature (GMST) may reach 1.5°C warming relative to the pre- industrial level (1861–1900) around the year 2036, 2028, 2033 and 2025, respectively; and reach 2°C warming in 2049 (RCP4.5), 2056 (RCP6.0) and 2039 (RCP8.5). For RCP2.6 scenario, the 2°C warming could not be seen in the multi-model ensemble mean before 2100, but can be reached in different years in single model simulations including GFDL-CM3, IPSL-CM5A-LR, IPSL-CM5A-MR and MIROC-ESM. The timing when the GMST reaches a specific warming threshold is primarily related to radiative forcing and CO2-equivalent concentrations, which show similar value when the GMST rises by the same value. Projections under all RCPs from 25 CMIP5 models show that only 6 models under RCP2.6 scenario can project a warming lower than 1.5°C relative to the pre-industrial era before 2100, while the temperature increase under other three scenarios will be more than 1.5°C. It is therefore necessary to develop a set of lower emission scenarios to limit the global warming below 1.5°C. The investigations on inter-model differences show that the model with large transient climate response (TCR), also known as warm models, may reach the 1.5 and 2°C temperature increase earlier than those with low TCR (cold models), though other factors can also affect the model to reach 1.5 or 2°C temperature increase. For the future changes of temperature and precipitation at global scale, the MME results show little distinction among different scenarios when GMST rises by the same value, indicating that the global and regional response characteristics of temperature and precipitation are independent of the RCP scenarios definition (defined by the radiative forcing by 2100). Therefore, it is possible to investigate the changes in temperature increase 0.5 under RCP8.5 scenarios. The results show that regional responses are almost the same when GMST rises by each additional 0.5°C, indicating that the temperature and precipitation will essentially change linearly. These changes are characterized by more temperature increase in higher latitudes than in low latitudes, more temperature rise in land than in ocean, and increased precipitation in wet areas and decreased precipitation in dry areas, as was commonly detected in multiple studies. This suggests that the global warming impacts could be evaluated based on the multi-model ensemble projections under any RCP scenario with as much as a collection of models. This study also shows that in China, the regional mean temperature and precipitation changes are larger than the global mean when the GMST rises by 1.5 and 2°C. The temperature may increase across all China, with the warming increases from southeast to northwest. The precipitation will increase in most areas but it may decrease in the eastern part south of 30°N, based on the MME results.

A novel intrinsic electroretinogram response in isolated mouse retina

Since the discovery of intrinsic photosensitive retinal ganglion cell (ipRGC) was reported in 2002, many features specific to this cell type have been described. However, scare information is available on the retinographic components directly reflecting ipRGC activity. In this study, we identified the electroretinogram (microERG) that reflects the photoresponses by ipRGCs in ex vivo preparations of the mouse retina, in which classical photoreceptors (cones and rods) were ablated mechanically and photochemically. MicroERG consisted of three components: a large transient ON response, a small and lazy hump 19s after the onset of the light, and a large transient OFF response. A complete microERG recording required at least 30s of light exposure. MicroERG showed the highest spectral photosensitivity at 478nm. This wavelength corresponds to the peak wavelength in the ipRGCs’ photosensitive curve. The psychophysical test using a blue light-emitting diode (LED) light (470nm) revealed that the absolute threshold illuminance for microERG was greater than 12.26 log photons/s/cm2 in both ON and OFF responses, whereas microERG was not adapted for dark. The amplitude of microERG increased linearly with irradiance. The sensitivity of temporal frequency was high in microERG (at least 100Hz), as suggested by the study on melatonin suppression by flickering light in human subjects (Zelter et al., 2014). Melatonin secretion was suppressed by light via ipRGCs and the suprachiasmatic nucleus. These properties of the photoresponse indicate that microERG may reflect the functions of ipRGC as a luminance detector in the mouse retina.

A MEMS PPA Based Active Vibration Isolator - STUDENT AWARD 3RD PLACE $500

Several types of micro-devices are adversely affected by high frequency mechanical vibrations present in the operating environment. Examples include MEMS vibratory gyroscopes and resonators, and micro-optics. Various types of MEMS vibration isolators have been developed for use in the packaging of these vibration sensitive devices. Passive isolators consist of a spring-mass-damper MEMS device and usually have a very high mechanical quality factor, which makes them susceptible to ringing at the isolator's resonant frequency. Active isolators have been realized by using state sensing of the proof mass motion and feeding one or more of these states back through an actuator to adjust the frequency response of the isolator. For example, the technique known as skyhook damping uses velocity feedback to adjust, and typically increase, the damping of the isolator. Although these technique are doable, they require state sensing or state estimation, with feedback electronics to drive the actuator. A simpler MEMS active vibration isolator architecture employs only a parallel plate actuator (PPA) with the MEMS spring-mass-damper structure. The PPA driven with a DC voltage, in its stable operating range, displaces the proof mass, which results in a change in the effective system spring constant due to the electrostatic spring softening effect. This results in a change in the resonant frequency and the quality factor of the isolator. However, due to the nonlinearities inherent in this type of device, the stable operating range is reduced as the PPA voltage is increased. Furthermore, even when the isolator is stable in steady-state, a sufficiently large transient response can also drive it into the unstable regime, resulting in the electrodes snapping into contact. In this study, the PPA based active vibrator isolator is developed and its performance is evaluated. The characteristics of the transient instability are investigated and its stable range of operation is specified, for booth external disturbances and rapid application of the control voltage. This MEMS PPA based active vibration isolator can improve performance compared to passive isolators, while being much simpler than state feedback active isolators.

Parameter-Varying Notch Filter With Tunning Mechanism For The Acquisition Of Electrocardiographic Signals Subject To Powerline Interference

Power line interference is a common problem in the acquisition of electrocardiographic signals. Different techniques have been used in order to cancel power line interference such as adaptive filters with a high quality factor. Each of these techniques have been specific disadvantages such as large transient response or the inability to track changes in the frequency of the power line interference for its removal. In this article, an alternative filtering method is presented. This method is capable to track deviations of the frequency associated to the power line interference, keeping a narrow stop band with a reduced transient response. The filtering strategy was implemented with the aid of a chpKIT max32 as a discrete-time system. Measurements results confirm the adequate operation of the proposed discrete-time filter

Large photocurrent response and external quantum efficiency in biophotoelectrochemical cells incorporating reaction center plus light harvesting complexes.

Bacterial photosynthetic reaction centers (RCs) are promising materials for solar energy harvesting, due to their high ratio of photogenerated electrons to absorbed photons and long recombination time of generated charges. In this work, photoactive electrodes were prepared from a bacterial RC-light-harvesting 1 (LH1) core complex, where the RC is encircled by the LH1 antenna, to increase light capture. A simple immobilization method was used to prepare RC-LH1 photoactive layer. Herein, we demonstrate that the combination of pretreatment of the RC-LH1 protein complexes with quinone and the immobilization method results in biophotoelectrochemical cells with a large peak transient photocurrent density and photocurrent response of 7.1 and 3.5 μA cm(-2), respectively. The current study with monochromatic excitation showed maximum external quantum efficiency (EQE) and photocurrent density of 0.21% and 2 μA cm(-2), respectively, with illumination power of ∼6 mW cm(-2) at ∼875 nm, under ambient conditions. This work provides new directions to higher performance biophotoelectrochemical cells as well as possibly other applications of this broadly functional photoactive material.

Performance Enhancement of Boost Converter Based on PID Controller Plus Linear-to-Nonlinear Translator

Here, A PID controller plus a novel linear-to-nonlinear translator is proposed and applied to the boost converter to improve the operating performance of the boost converter under large transient variations in load all over the quiescent dc input voltage range. The proposed translator is inserted between the PID controller and the main power stage such that the PID controller considers the behavior of the boost converter to be quasi-linear, thereby suppressing the effect of nonlinear behavior of the boost converter on the PID controller. Besides, variations in dc gain of the control-to-output transfer function with the translator are smaller than those without the translator, thus making system control easy to attain. Also, one-comparator counter-based sampling without any A-D converter is presented herein to realize the proposed control strategy. As mentioned above, the proposed control strategy can make the boost converter stably operated under large load transient responses all over the quiescent dc input voltage range.

Transient growth without inertia

We study transient growth in inertialess plane Couette and Poiseuille flows of viscoelastic fluids. For streamwise-constant three-dimensional fluctuations, we demonstrate analytically the existence of initial conditions that lead to quadratic scaling of both the kinetic energy density and the elastic energy with the Weissenberg number, We. This shows that in strongly elastic channel flows of viscoelastic fluids, both velocity and polymer stress fluctuations can exhibit significant transient growth even in the absence of inertia. Our analysis identifies the spatial structure of the initial conditions (i.e., components of the polymer stress tensor at t=0) responsible for this large transient growth. Furthermore, we show that the fluctuations in streamwise velocity and the streamwise component of the polymer stress tensor achieve O(We) and O(We2) growth, respectively, over a time scale O(We) before eventual asymptotic decay. We also demonstrate that the large transient responses originate from the stretching of polymer stress fluctuations by a background shear and draw parallels between streamwise-constant inertial flows of Newtonian fluids and streamwise-constant creeping flows of viscoelastic fluids. One of the main messages of this paper is that at the level of velocity fluctuation dynamics, polymer stretching and the Weissenberg number in elasticity-dominated flows of viscoelastic fluids effectively assume the role of vortex tilting and the Reynolds number in inertia-dominated flows of Newtonian fluids.

The brain’s cutting-room floor: segmentation of narrative cinema

Observers segment ongoing activity into meaningful events. Segmentation is a core component of perception that helps determine memory and guide planning. The current study tested the hypotheses that event segmentation is an automatic component of the perception of extended naturalistic activity, and that the identification of event boundaries in such activities results in part from processing changes in the perceived situation. Observers may identify boundaries between events as a result of processing changes in the observed situation. To test this hypothesis and study this potential mechanism, we measured brain activity while participants viewed an extended narrative film. Large transient responses were observed when the activity was segmented, and these responses were mediated by changes in the observed activity, including characters and their interactions, interactions with objects, spatial location, goals, and causes. These results support accounts that propose event segmentation is automatic and depends on processing meaningful changes in the perceived situation; they are the first to show such effects for extended naturalistic human activity.

Transient response of idealized glaciers to climate variations

AbstractThe transient response of glaciers to climate variations is investigated with a novel low-order model of an idealized glacier resting on uniformly inclined bedrock. The model consists of two volumes representing the accumulation and ablation areas, which are joined by a flux gate controlling mass flow according to the shallow-ice approximation. Under the assumption of a constant vertical mass-balance gradient, a volume–length scaling relation is derived which depends explicitly on mass-balance gradient and bedrock slope. Analytic expressions for the volume and area timescales are given, which are inversely proportional to the mass-balance gradient and a geometric factor which is the ratio between the vertical extent of the ablation area and the ice thickness at the equilibrium line. From the low-order model, a dynamical system in length and volume is obtained. Results from this system are in good agreement with solutions obtained from a transient finite-element model solving the full force-balance and mass-conservation equations. Under periodic forcing there are significant deviations of the length response, which show that the usual relaxation-type parameterization of length change is not well suited for short-term reactions. Switching on and off periodic climate forcing, the model glaciers show surprisingly large initial and final transient responses that have not been investigated before. These results are of significance for the interpretation of length and thickness changes observed on glaciers.

Identification and Characterization of a Y-Like Primate Retinal Ganglion Cell Type

The primate retina communicates visual information to the brain via a set of parallel pathways that originate from at least 22 anatomically distinct types of retinal ganglion cells. Knowledge of the physiological properties of these ganglion cell types is of critical importance for understanding the functioning of the primate visual system. Nonetheless, the physiological properties of only a handful of retinal ganglion cell types have been studied in detail. Here we show, using a newly developed multielectrode array system for the large-scale recording of neural activity, the existence of a physiologically distinct population of ganglion cells in the primate retina with distinctive visual response properties. These cells, which we will refer to as upsilon cells, are characterized by large receptive fields, rapid and transient responses to light, and significant nonlinearities in their spatial summation. Based on the measured properties of these cells, we speculate that they correspond to the smooth/large radiate cells recently identified morphologically in the primate retina and may therefore provide visual input to both the lateral geniculate nucleus and the superior colliculus. We further speculate that the upsilon cells may be the primate retina's counterparts of the Y-cells observed in the cat and other mammalian species.

A calcium-receptor agonist induces gustatory neural responses in bullfrogs.

The effect of calcium-sensing receptor (CaR) agonists on frog gustatory responses was studied using glossopharyngeal nerve recording and whole-cell patch-clamp recording of isolated taste disc cells. Calcimimetic NPS R-467 dissolved in normal saline solution elicited a large transient response in the nerve. The less active enantiomer of the compound, NPS S-467 induced only a small neural response. The EC(50) for NPS R-467 was about 20 microM. Cross-adaptation experiments were performed to examine the effect of 30 microM NPS R-467 and 100 microM quinine on the gustatory neural response. The magnitude of the R-467-induced response after adaptation to quinine was approximately equal to that after adaptation to normal saline solution, indicating that the receptor site for NPS R-467 is different from the site for quinine. NPS R-467 (100 microM) also induced an inward current accompanied with conductance increase and large depolarization in two (13%) of 15 rod cells, and a sustained decrease in outward current and small depolarization in six (40%) other rod cells. NPS S-467 (100 microM) induced a sustained decrease in outward current and depolarization in five (50%) of 10 rod cells. Another calcimimetic cinacalcet (100 microM) induced an inward current accompanied with conductance increase in three (27%) of 11 rod cells. The results suggest that NPS R-467 induces neural responses through cell responses unrelated to a resting K(+) conductance decrease.

Computer simulation of magnetic levitation of thin steel plate in consideration of large scale transient response

This paper describes how to simulate magnetic levitation of a thin steel plate by using electromagnets. Since the levitation system is essentially unstable, the plate is levitated by controlling the attractive magnetic force produced by the electromagnets with feedback signals: the displacement and velocity of the plate and the current of the electromagnet. As the magnetic force is the same regardless of the current direction, a bias voltage is necessary for supplying an initial current to the electromagnet. The motion equation of the plate is solved by the finite difference method. The magnetic force is obtained by using the finite element method. In this paper, we study how to improve the control performance, which becomes better by adding a current feedback and adjusting the bias voltage.

Magnetoencephalographic study of cortical activity evoked by electrogustatory stimuli.

Electrogustometry is a convenient method to examine taste acuity in clinical situations. Some basic properties of neural activity in the cerebral cortex in response to electrogustatory stimulation were revealed by measuring magnetoencephalography (MEG) signals with a whole-cortex-type system in response to varying intensities of anodal DC currents focally applied to the tongue surface in human subjects. Independent component analysis was used to eliminate stimulus artifacts in MEG signals. Electrogustatory stimulation with intensities of induced electric taste evoked responses bilaterally, mainly in the opercular-insular cortex with a mean onset latency of approximately 350 ms, while subthreshold electrogustatory stimulation induced modest responses in the cortex. Stronger stimulation induced a tingling sensation and elicited large transient responses in both the opercular-insular and somatic sensory cortices. This is the first description of the basic properties of human MEG responses to electrogustatory stimulation.

Improving the Disturbance Resistance of Magnetic Disk Drives by Using Anti-Windup and Model Following Controls with Initial Value Compensation.

We have developed a magnetic head positioning control method of a hard disk drive under conditions of variable parameters and disturbances. It consists of model following control for feed forward compensation and and-windup control for feedback compensation. By using anti-windup control for a feedback controller, slow and large transient responses near the target position are avoided and the actuator settles more quickly on the target position.