Multiscale Control Research Articles

Black phosphorus: a two-dimensional reductant for in situ nanofabrication

The reducing capability of two-dimensional black phosphorus is demonstrated. The high reducing ability and unique two-dimensional morphology of black phosphorus not only facilitate in situ synthesis of Au nanoparticles and BP@Au composites, but also enable multiscale control of local reduction of GO to reduced GO (rGO). The novel two-dimensional reductant has large potential in various in situ nanofabrication applications.

Multiscale Entropy Analysis of the Differential RR Interval Time Series Signal and Its Application in Detecting Congestive Heart Failure

Cardiovascular systems essentially have multiscale control mechanisms. Multiscale entropy (MSE) analysis permits the dynamic characterization of the cardiovascular time series for both short-term and long-term processes, and thus can be more illuminating. The traditional MSE analysis for heart rate variability (HRV) is performed on the original RR interval time series (named as MSE_RR). In this study, we proposed an MSE analysis for the differential RR interval time series signal, named as MSE_dRR. The motivation of using the differential RR interval time series signal is that this signal has a direct link with the inherent non-linear property of electrical rhythm of the heart. The effectiveness of the MSE_RR and MSE_dRR were tested and compared on the long-term MIT-Boston’s Beth Israel Hospital (MIT-BIH) 54 normal sinus rhythm (NSR) and 29 congestive heart failure (CHF) RR interval recordings, aiming to explore which one is better for distinguishing the CHF patients from the NSR subjects. Four RR interval length for analysis were used ( N = 500 , N = 1000 , N = 2000 and N = 5000 ). The results showed that MSE_RR did not report significant differences between the NSR and CHF groups at several scales for each RR segment length type (Scales 7, 8 and 10 for N = 500 , Scales 3 and 10 for N = 1000 , Scales 2 and 3 for both N = 2000 and N = 5000 ). However, the new MSE_dRR gave significant separation for the two groups for all RR segment length types except N = 500 at Scales 9 and 10. The area under curve (AUC) values from the receiver operating characteristic (ROC) curve were used to further quantify the performances. The mean AUC of the new MSE_dRR from Scales 1–10 are 79.5%, 83.1%, 83.5% and 83.1% for N = 500 , N = 1000 , N = 2000 and N = 5000 , respectively, whereas the mean AUC of MSE_RR are only 68.6%, 69.8%, 69.6% and 67.1%, respectively. The five-fold cross validation support vector machine (SVM) classifier reports the classification Accuracy ( A c c ) of MSE_RR as 73.5%, 75.9% and 74.6% for N = 1000 , N = 2000 and N = 5000 , respectively, while for the new MSE_dRR analysis accuracy was 85.5%, 85.6% and 85.6%. Different biosignal editing methods (direct deletion and interpolation) did not change the analytical results. In summary, this study demonstrated that compared with MSE_RR, MSE_dRR reports better statistical stability and better discrimination ability for the NSR and CHF groups.

Multiscale structural and electronic control of molybdenum disulfide foam for highly efficient hydrogen production

Hydrogen production through water splitting has been considered as a green, pure and high-efficient technique. As an important half-reaction involved, hydrogen evolution reaction is a complex electrochemical process involving liquid-solid-gas three-phase interface behaviour. Therefore, new concepts and strategies of material design are needed to smooth each pivotal step. Here we report a multiscale structural and electronic control of molybdenum disulfide foam to synergistically promote the hydrogen evolution process. The optimized three-dimensional molybdenum disulfide foam with uniform mesopores, vertically aligned two-dimensional layers and cobalt atoms doping demonstrated a high hydrogen evolution activity and stability. In addition, density functional theory calculations indicate that molybdenum disulfide with moderate cobalt doping content possesses the optimal activity. This study demonstrates the validity of multiscale control in molybdenum disulfide via overall consideration of the mass transport, and the accessibility, quantity and capability of active sites towards electrocatalytic hydrogen evolution, which may also be extended to other energy-related processes.

Multi-scale control influences sense of agency: Investigating intentional binding using event-control approach.

Control exercised by humans through interactions with the environment is critical for sense of agency. Here, we investigate how control at multiple levels influence implicit sense of agency measured using intentional binding. Participants are asked to hit a moving target using a joystick with noisy control followed by an intentional binding task initiated by the target hitting action. Perceptual-motor level control was manipulated through noise in the joystick controller (experiment 1) and goal-level control in terms of feedback about successful hit (experiments 2a and 2b). In the first experiment, intentional binding increased with amount of joystick control only when goal was not achieved and independent otherwise suggesting that the two levels interact hierarchically. In the second experiment, the estimated duration was dependent on when participants knew about goal completion. The results are similar to those obtained with explicit measures of sense of agency indicating that multi-scale event control influences agency.

Application of Media Art Visual Communication Concept in Multi-Scale Control

Color is the dominant element of visual communication design. For cities, color is one of their characteristics. Improving the overall style of a city through the control and planning of architectural color has been a hot issue in urban control and planning in recent years. Considering color pollution in urban planning, we analyze the important role of color in visual communication design from the perspective of the visual communication concept of media art. The current situation of residential building colors in Shanghai City is investigated. We determine the residents’ preferences and requirements related to architectural exterior color on the basis of a data analysis of color and material selection, color matching, composition, and others. This study changes the traditional architectural color design concept that centers on individuals and lacks overall control. Specifically, we construct a set of multi-scale color controlling and planning systems at the macro-, meso-, and micro-scales. We also guide and control the urban architectural color such that it is in accordance with the systematic color planning strategy. This method enables the systematic and holistic external color planning of urban residential buildings.

Simulation and control of water-gas shift packed bed reactor with inter-stage cooling

Water-Gas Shift Reaction (WGSR) has become one of the well-known pathways for H2 production in industries. The issue with WGSR is that it is kinetically favored at high temperatures but thermodynamically favored at low temperatures, thus requiring careful consideration in the control design in order to ensure that the temperature used does not deactivate the catalyst. This paper studies the effect of a reactor arrangement with an inter-stage cooling implemented in the packed bed reactor to look at its effect on outlet temperature. A mathematical model is developed based on one-dimensional heat and mass transfers which incorporate the intra-particle effects. It is shown that the placement of the inter-stage cooling and the outlet temperature exiting the inter-stage cooling have strong influence on the reaction conversion. Several control strategies are explored for the process. It is shown that a feedback- feedforward control strategy using Multi-scale Control (MSC) is effective to regulate the reactor temperature profile which is critical to maintaining the catalysts activity.

A unified double-loop multi-scale control strategy for NMP integrating-unstable systems

This paper presents a new control strategy which unifies the direct and indirect multi-scale control schemes via a double-loop control structure. This unified control strategy is proposed for controlling a class of highly nonminimum-phase processes having both integrating and unstable modes. This type of systems is often encountered in fed-batch fermentation processes which are very difficult to stabilize via most of the existing well-established control strategies. A systematic design procedure is provided where its applicability is demonstrated via a numerical example.

Analytical tuning method for cascade control system via multi-scale control scheme

Cascade control strategy has been widely used in process industry owing to its superior disturbance rejection performance over that of the standard single-loop control. Designing the cascade control system is a challenging task, especially for an unstable time-delay process. In this paper, based on the multi-scale control scheme, a new analytical tuning method is presented. The method is applicable to stable and unstable processes where it can be implemented through a fixed or variable tuning approach. In the variable tuning approach, one adjustable tuning parameter is sufficient to obtain desired cascade control performance with the aid of a set of analytical tuning formulae providing direct relationship between the controller parameters and model parameters. Meanwhile, the fixed tuning approach uses a set of empirically developed rules to determine the controller parameters. Numerical studies demonstrate the effectiveness of the proposed method compared with several established cascade control designs reported in the literature.

Heuristic-based multi-scale control procedure of simultaneous multi-loop PID tuning for multivariable processes

A multi-loop PID control system is widely used in process industry where finding good values for the controller parameters is very challenging without systematic procedures. In this paper, based on the multi-scale control scheme a simultaneous multi-loop tuning method for an arbitrary n×n MIMO processes is proposed. The salient feature of the method is that it reduces the multi-loop PID tuning parameters from 4n to only 4 common multi-scale control parameters. Both heuristic- and optimization-based procedures are proposed in order to apply the simultaneous tuning method, which should substantially simplify difficult multi-loop tuning involving numerous controller parameters. To ensure adequate robustness of the multi-loop control system, the balanced sensitivity function is used with the tuning method. Numerical studies based on 2×2, 3×3, 4×4 and 5×5 MIMO processes demonstrate the effectiveness of the tuning method.

Vacuum Arc Remelting Process of High-Alloy Bearing Steel and Multi-Scale Control of Solidification Structure

Utilizing Pro-cast software, the whole vacuum arc remelting process of high-alloy bearing steel ingot (the diameter was 160 mm and the high was 600 mm) was simulated. And moving face quality and moving boundary conditions were added to the simulation. Purposes of the simulation were to explore the influence of smelting powers on the temperature field, pool shape and solidification microstructure in vacuum arc remelting process. The depth of molten bath gradually increased and stabilized finally and the pool shape transferred from flat to funnel. When smelting power increased, the depth of molten pool became deeper and the width of mushy zone slightly reduced; the size of primary dendrite and secondary dendrite spacing increased significantly; the percentage and size of columnar crystals also increased. A reasonable power-time cure was given to guide industrial melting after simulation, the size of molten pool morphology and microstructure were controlled in an ideal range under the reasonable cure. The simulated grain morphology agreed well with the experimental pickling result.

Inexact linear solvers for control volume discretizations in porous media

We discuss the construction of multi-level inexact linear solvers for control volume discretizations for porous media. The methodology forms a contrast to standard iterative solvers by utilizing an algebraic hierarchy of approximations which preserve the conservative structure of the underlying control volume. Our main result is the generalization of multiscale control volume methods as multi-level inexact linear solvers for conservative discretizations through the design of a particular class of preconditioners. This construction thereby bridges the gap between multiscale approximation and linear solvers. The resulting approximation sequence is referred to as inexact solvers. We seek a conservative solution, in the sense of control-volume discretizations, within a prescribed accuracy. To this end, we give an abstract guaranteed a posteriori error bound relating the accuracy of the linear solver to the underlying discretization. These error bounds are explicitly computable for the grids considered herein. The afore-mentioned hierarchy of conservative approximations can also be considered in the context of multi-level upscaling, and this perspective is highlighted in the text as appropriate. The new construction is supported by numerical examples highlighting the performance of the inexact linear solver realized in both a multi- and two-level context for two- and three-dimensional heterogeneous problems defined on structured and unstructured grids. The numerical examples assess the performance of the approach both as an inexact solver, as well in comparison to standard algebraic multigrid methods.

Multiscale control of summertime persistent heavy precipitation events over South China in association with synoptic, intraseasonal, and low-frequency background

This study examines persistent and short-lived heavy precipitation events (PHPEs and SHPEs, respectively) in South China during summer (July–September) 1975–2009 in association with large-scale circulation and moisture processes at different timescales. Compared to SHPEs, PHPEs are characterized by long-lasting enhanced convection and cyclonic moisture circulation as well as strengthened moisture convergence over South China. Examination of environmental variables at different timescales suggests that intraseasonal and synoptic components play a deterministic role in regulating the overall changes in convection and moisture convergence, while the low-frequency background state plays only a marginal role. Further analysis of the moisture divergence terms also reveals that the overall changes in moisture divergence during PHPEs and SHPEs stem primarily from variations in the intraseasonal and synoptic wind fields rather than in the humidity fields. Overall, it is found that the location and strength of the intraseasonal oscillation (ISO) and the synoptic disturbances play a decisive role in controlling the severity and duration of rainfall events over South China. The synchronization and persistence of the enhanced convection and moisture circulation of the ISO and synoptic disturbances jointly contribute to prolonged heavy precipitation over South China, while the weakening and asynchrony of the associated convection and moisture circulation at different timescales result in rainfall events of weaker intensity and shorter duration.

Inter-Communicative Decentralized Multi-Scale Control (ICD-MSC) Scheme: A New Approach to Overcome MIMO Process Interactions

Abstract Decentralized PID control has been extensively used in process industry due to its functional simplicity. But designing an effective decentralized PID control system is very challenging because of process interactions and dead times, which often impose limitations on control performance. In practice, to alleviate the detrimental effect of process interactions on control performance, decoupling controllers are often incorporated into a decentralized control scheme. In many cases, these conventional decoupling controllers are not physically realizable or too complex for practical implementation. In this paper, we propose an alternative scheme to overcome the performance limitation imposed by process interactions. This new control scheme is extended from the SISO multi-scale control scheme previously developed for nonminimum-phase processes. The salient feature of the new control scheme lies in its communicative structure enabling collaborative communication among all the sub-controllers in the system. This communicative structure serves the purpose of reducing the detrimental effect of process interactions leading to improved control performance and performance robustness. Extensive numerical study shows that the new control scheme is able to outperform some existing decentralized control schemes augmented with traditional decoupling controllers.

Decentralized Control Design for Ethanol Fermentation by Zymomonas Mobilis – Multi-Scale Control Approach

This paper deals with the decentralized control design for ethanol fermentation by Zymomonas mobilis. Extractive fermentation has been proposed to improve the ethanol yield and productivity due to product inhibition. The complexity of biological systems and significant process variability can always lead to ineffective control system performance. In this paper, a 2x2 and 3x3 multi-scale control systems have been proposed. It is shown that the PID control design based on the multi-scale control scheme is effective for complex high-order systems.

Continental hydrosystem modelling: the concept of nested stream–aquifer interfaces

Abstract. Coupled hydrological-hydrogeological models, emphasising the importance of the stream–aquifer interface, are more and more used in hydrological sciences for pluri-disciplinary studies aiming at investigating environmental issues. Based on an extensive literature review, stream–aquifer interfaces are described at five different scales: local [10 cm–~10 m], intermediate [~10 m–~1 km], watershed [10 km2–~1000 km2], regional [10 000 km2–~1 M km2] and continental scales [>10 M km2]. This led us to develop the concept of nested stream–aquifer interfaces, which extends the well-known vision of nested groundwater pathways towards the surface, where the mixing of low frequency processes and high frequency processes coupled with the complexity of geomorphological features and heterogeneities creates hydrological spiralling. This conceptual framework allows the identification of a hierarchical order of the multi-scale control factors of stream–aquifer hydrological exchanges, from the larger scale to the finer scale. The hyporheic corridor, which couples the river to its 3-D hyporheic zone, is then identified as the key component for scaling hydrological processes occurring at the interface. The identification of the hyporheic corridor as the support of the hydrological processes scaling is an important step for the development of regional studies, which is one of the main concerns for water practitioners and resources managers. In a second part, the modelling of the stream–aquifer interface at various scales is investigated with the help of the conductance model. Although the usage of the temperature as a tracer of the flow is a robust method for the assessment of stream–aquifer exchanges at the local scale, there is a crucial need to develop innovative methodologies for assessing stream–aquifer exchanges at the regional scale. After formulating the conductance model at the regional and intermediate scales, we address this challenging issue with the development of an iterative modelling methodology, which ensures the consistency of stream–aquifer exchanges between the intermediate and regional scales. Finally, practical recommendations are provided for the study of the interface using the innovative methodology MIM (Measurements–Interpolation–Modelling), which is graphically developed, scaling in space the three pools of methods needed to fully understand stream–aquifer interfaces at various scales. In the MIM space, stream–aquifer interfaces that can be studied by a given approach are localised. The efficiency of the method is demonstrated with two examples. The first one proposes an upscaling framework, structured around river reaches of ~10–100 m, from the local to the watershed scale. The second example highlights the usefulness of space borne data to improve the assessment of stream–aquifer exchanges at the regional and continental scales. We conclude that further developments in modelling and field measurements have to be undertaken at the regional scale to enable a proper modelling of stream–aquifer exchanges from the local to the continental scale.

Algorithm of Multi Sensor Data Fusion based on BP Neural Network and Multi-scale Model Predictive Control

Algorithm of Multi Sensor Data Fusion based on BP Neural Network and Multi-scale Model Predictive Control

Generalized multi-scale control scheme for cascade processes with time-delays

The cascade control is a well-known technique in process industry to improve regulatory control performance. The use of the conventional PI/PID controllers has often been found to be ineffective for cascade processes with long time-delays. Recent literature report has shown that the multi-scale control (MSC) scheme is capable of providing improved performance over the conventional PID controllers for processes characterized by long time-delays as well as slow RHP zeros. This paper presents an extension of this basic MSC scheme to cascade processes with long time-delays. This new cascade MSC scheme is applicable to self-regulating, integrating and unstable processes. Extensive numerical studies demonstrate the effectiveness of the cascade MSC scheme compared with some well-established cascade control strategies.

Multi-loop design of multi-scale controllers for multivariable processes

Based on the recently proposed (SISO) multi-scale control scheme, a new approach is introduced to design multi-loop controllers for multivariable processes. The basic feature of the multi-scale control scheme is to decompose a given plant into a sum of basic modes. To achieve good nominal control performance and performance robustness, a set of sub-controllers are designed based on the plant modes in such a way that they are mutually enhanced with each other so as to optimize the overall control objective. It is shown that the designed multi-scale controller is equivalent to a conventional PID controller augmented with a filter. The multi-scale control scheme offers a systematic approach to designing multi-loop PID controllers augmented with filters. Numerical studies show that the proposed multi-loop multi-scale controllers provide improved nominal performance and performance robustness over some well-established multi-loop PID controller schemes.

A Model Predictive Control Strategy Based on Consistency in Wavelet Projections

This paper proposes a novel method of system modelling and control based on the idea of consistency in wavelet projections. Although the idea of consistency has been a familiar knowledge in the theory of generalized sampling, extension of it in the arena of system modelling and control is relatively new. It is proposed here that nonlinear approximation could be used for predicting system output that is consistent with the signal component of the desired output measurement. This imposes a number of equality and inequality constraints on wavelet projections of the input and the output. As a natural consequence, the control design problem can be viewed in the framework of multi-scale model predictive control. Idea of consistency can be further used to design a linear control law that minimizes error in least squares sense in the chosen forecast horizon. The technique of controller realization is demonstrated based on the simulation data with the point kinetics model of a nuclear reactor.

The miR-126–VEGFR2 axis controls the innate response to pathogen-associated nucleic acids

MicroRNA-126 (miR-126) is a microRNA predominately expressed by endothelial cells and controls angiogenesis. We found miR-126 was required for the innate response to pathogen-associated nucleic acids, and that miR-126-deficient mice had increased susceptibility to pseudotyped-HIV infection. miRNA profiling and deep-sequencing indicated that miR-126 was highly and specifically expressed by plasmacytoid dendritic cells (pDCs). miR-126 controlled the survival and function of pDCs, and regulated expression ofinnate response genes, including Tlr7, Tlr9 and Nfkb1, as well as Kdr, which encodes VEGF-receptor 2 (VEGFR2). Deletion of Kdr in DCs resulted in reduced type I interferon production, supporting a role for VEGFR2 in miR-126 regulation of pDCs. These studies identify the miR-126–VEGFR2 axis as an important regulator of the innate response that operates through multiscale control of pDCs.