Search

We re-examine the puzzling pattern of lead-lag returns among economically-linked firms. Our results show that investors consistently underreact to information from lead firms that arrives continuously, while information with the same cumulative returns arriving in discrete amounts is quickly absorbed into price. This finding holds across many different types of economic linkages, including shared-analyst-coverage. We conclude that the ǣfrog in the panǥ (FIP) momentum effect is pervasive in co-momentum settings, suggesting that information discreteness (ID) serves as a cognitive trigger that reduces investor inattention and improves inter-firm news transmission.

With the rapid advancement of digital processors, filters have been commonly implemented using microcomputers. In this study, a low-cost and compact Arduino Uno development board was used to realize digital lead and lag compensators. Arduino boards are very affordable. Consequently, they were investigated to see if they were capable of preserving the frequency response of continuous-time compensators. The experiments required a set of equipment including a function generator, an Arduino Uno development board, a PC-based oscilloscope, and a laptop. The signal frequency was varied from 0 to 500 Hz. Two discretization methods were employed, namely bilinear transformation and matched pole-zero mapping. The results showed that an Arduino Uno board can be utilized to implement lead and lag compensators to some extent. The discrete-time compensator preserved the capability of filtering out certain frequencies. The change in DC gain was negligible, however, there was a significant difference in the cut-off frequency and transient slope. For both discretization methods, the frequency responses at high frequency experienced a rippling profile.

This note considers the problem of output feedback stabilization for a class of nonlinear planar systems with unknown structures and measurements which prevent the construction of conventional state observers. By taking advantage of the stability-increasing capability of a lead compensator, we propose a dynamic output feedback controller to globally stabilize the uncertain planar systems. For the special case of linear planar systems with unknown coefficients, a finite-time output feedback stabilizer based on a nonlinear compensator is constructed for a faster convergence rate.

This paper presents a post-fault current control strategy for dual three-phase Interior Permanent Magnet (IPM) synchronous machines. The current controllers are designed based on the Vector Space Decomposition (VSD) algorithm. This take into account the equivalent harmonic inductance variation, which is then used to introduce the post-fault compensation control. A double three-phase IPM machine is modelled and operated in three different operating conditions: nominal, one three-phase set in short-circuit (SC), and one three-phase set in open-circuit (OC). By keeping the current loop bandwidth constant, the proposed fault-tolerant current controllers guarantee the same dynamic performance of the remaining healthy module after the faults occurred. In OC fault, the proportional and integral (PI) controllers are redesigned while adapting the inductance variation. For the SC case, constant stability margins are provided by cascading a novel lag compensator to the nominal controller. The current dynamics responses are analysed in both healthy and faulty conditions by means of Matlab/Simulink simulations. Experimental results on a 30kW six-phase IPM machine prototype with isolated neutral points and supplied by two custom three-phase converters, are demonstrating the effectiveness of the proposed control strategies.

On the battlefield of today, it has become an important requirement to hit moving or fixed targets by using tank or artillery ammunition with high precision. However, while there are many articles on guiding tactical missiles, it cannot found sufficient scientific study for guiding tank ammunition in the related literature. In this study, the laser BR-guidance method is offered to the classic tank ammunition with a diameter of 155 mm in order to give the tank a precision strike capacity, as different from the literature. First of all, an ammunition model is created with coefficients of the mass, inertia, and surface area and friction. In addition, an autopilot dynamic is modeled for the pitch and roll axes of the ammunition. Also, the atmosphere model and environmental factors are added to the model. In order to control this nonlinear model, a lead-compensator and a PD-controller are designed. In order for the results to be transferred to a real application, the accelerations obtained must basically be produced by the electric motors that will drive the control surfaces to be designed. At the end of the study, it is seen that both controllers can produce lateral accelerations within limits without reaching high saturation.

This article deals with the study of mathematical models and the assessment of the stability of the motion of ships, investigating properties of the system such as kinetics and stability. This is essential for the selection of suitable control methods according to the requirements set out for the problem. Some control methods require the author to specify control parameters before the operation of the system can be started. Therefore, the survey of the article is useful for the above problem. Control methods through simulation results (PID controller, lag compensator, and lead compensator) give me results that reflect properties of the system (the stability of the operation cycle of the ship model). In addition, control methods for this model, which serve for research and education, are also presented below. Simulation is done by Matlab.

The literature mentions multiple factors that can affect the accuracy of estimating the project duration in highway construction, such as weather, location, and soil conditions. However, there are other factors that have not been explored, yet they can have significant impact on the accuracy of the project time estimate. Recently, TxDOT raised a concern regarding the importance of the proper estimating of the lead/lag times in project schedules. These lead/lag times are often determined based on the engineer’s experience. However, inaccurate estimates of the lead/lag time can result in unrealistic project durations. In order to investigate this claim, the study utilizes four time sensitivity measures (TSM), namely the Criticality Index (CI), Significance Index (SI), Cruciality Index (CRI), and the Schedule Sensitivity Index (SSI) to statistically analyze and draw conclusions regarding the impact of the lead/lag time estimates on the total duration in highway projects. An Excel-based scheduling software was developed with Monte Carlo simulation capabilities to calculate these TSM. The results from this paper show that the variability of some lead/lag times can significantly impact the accuracy of the estimated total project duration. It was concluded that the current practices used for estimating the lead/lag times are insufficient. As such, it is recommended to utilize more robust methods, such as the time sensitivity measures, to accurately estimate the lead/lad times in the projects scheduled.

We set up an agent-based model where the parameters of firms’ pricing heuristics are determined through evolutionary learning. We argue that there are several key ingredients that result in the emergence of the lead–lag pattern in the money growth–inflation relationship. First, a realistic representation of money creation through a lending mechanism is essential. Second, there must be considerable heterogeneity in the distribution of newly created deposits and in the associated changes in demand at the individual firm level.

Purpose To develop a simplified aluminum compensator system for total body irradiation (TBI) that is easy to assemble and modify in a short period of time for customized patient treatments. Methods The compensator is composed of a combination of 0.3 cm thick aluminum bars, two aluminum T‐tracks, spacers, and metal bolts. The system is mounted onto a plexiglass block tray. The design consists of 11 fixed sectors spanning from the patient's head to feet. The outermost sectors utilize 7.6 cm wide aluminum bars, while the remaining sectors use 2.5 cm wide aluminum bars. There is a magnification factor of 5 from the compensator to the patient treatment plane. Each bar of aluminum is interconnected at each adjacent sector with a tongue and groove arrangement and fastened to the T‐track using a metal washer, bolt, and nut. Inter‐bar leakage of the compensator was tested using a water tank and diode. End‐to‐end measurements were performed with an ion chamber in a solid water phantom and also with a RANDO phantom using internal and external optically stimulated luminescent detectors (OSLDs). In‐vivo patient measurements from the first 20 patients treated with this aluminum compensator were compared to those from 20 patients treated with our previously used lead compensator system. Results The compensator assembly time was reduced to 20–30 min compared to the 2–4 h it would take with the previous lead design. All end‐to‐end measurements were within 10% of that expected. The median absolute in‐vivo error for the aluminum compensator was 3.7%, with 93.8% of measurements being within 10% of that expected. The median error for the lead compensator system was 5.3%, with 85.1% being within 10% of that expected. Conclusion This design has become the standard compensator at our clinic. It allows for quick assembly and customization along with meeting the Task Group 29 recommendations for dose uniformity.

The lead-lag relationship between stocks is an interesting phenomenon, which has been empirically seen to widely exist in stock markets. This paper aims to discover the dynamic patterns of the dail...

Proportional-Integral (PI) controllers are widely accepted industrial controllers. These controllers also find their applications in wind energy conversion systems (WECSs). Although such controllers are well researched and developed too, their linear nature and sensitivity of their gains towards variations in plant’s parameter are some noticeable disadvantages associated with them. Moreover, tuning of their gains involves certain approximations, which leads to demean their accuracy. On contrary, the designing of lag-compensators is procedural and discussed well in literature. Although such compensators could not have drawn the attention of wind turbine manufacturers but may a potential candidate for future developments. The focus of this paper is to design phase-lag compensators and use them to extract maximum available power in the wind, at every wind speed upto its rated value. Ability of the compensators is assessed through detailed simulation of a PMSG based WECS in MATLAB/Simulink environment. Observed responses are motivating and demonstrates the effectiveness of the designed compensators.

This paper investigates the lead-lag effect from a complex network perspective. We first detect the lead-lag effect between individual stocks based on CSI 300 index in Chinese stock market and then...

Electric spring is a custom power device, primarily being used for the voltage stability/voltage regulation of a customer’s electrical installation. The idea of electric spring has primarily been derived from the concept of mechanical spring, to damp out the oscillations or variations in the voltage due to intermittency of renewable energy sources that are present in the distribution system. This paper explores the idea of electric spring through the development of its mathematical model and control strategy. A controller based on the Lead–Lag compensator for controlling the electric spring, which in turn is a power electronic converter and is controlling the voltage across the critical load by inserting a controlled voltage of an appropriate magnitude and phase in series with the noncritical load, is designed and validated through simulation.

We generalize the single regression-type cointegration model of Engle and Granger (Econometrica 55(2):251–276, 1987) from the lead–lag relationship perspective. A leading series is introduced into the model as an independent variable to express the long-run relationship between the leading and lagging variables if the disturbance term is stationary. The theoretical analysis shows that the estimators of the coefficients with true lead–lag intervals have stochastic characteristics equivalent to those of Engle and Granger (1987). Monte Carlo simulations suggest that inappropriate interval selection leads to seriously biased estimators and that the identification of the lead–lag intervals is successful when using the adjusted coefficient of determination. This accuracy is caused by the difference in order between the true interval and candidates, which increases the variance of disturbance proportionally. The farther the candidates are from the true interval, the more autocorrelation increases; further, it cannot be absorbed by the unit root test, which considers the autocorrelations of disturbance. This causes a severe deterioration in the power of cointegration testing. Therefore, cointegration analysis without considering the lead–lag interval may lead economists to overlook the important long-run relationship between the pair of variables.

A new approach for modeling lead–lag relationships in high-frequency financial markets is proposed. The model accommodates non-synchronous trading and market microstructure noise as well as intraday variations of lead–lag relationships, which are essential for empirical applications. A simple statistical methodology for analyzing the proposed model is presented, as well. The methodology is illustrated by an empirical study to detect lead–lag relationships between the S&P 500 index and its two derivative products.

To improve the robustness and stability of the LCL inverter connected to weak grid, this paper proposes a novel active damping based on voltage of point common coupling ( $\text{v}_{pcc}$ ) feedback. A phase lead compensator is proposed in the $\text{v}_{pcc}$ feedback loop to compensate system phase margin (PM). Theoretical analysis of the effectiveness, detailed parameter setting, stability analysis for proposed active damping adopting lead compensator, named as LC AD, are all described. Simulation and experiment results show that comparing to conventional high pass filter (HPF) AD, the proposed LC AD provides more effective damping effect for the LCL inverter adopting quasi-proportional resonant (QPR) controller under weak grid.

Classical control methods are still in vogue because of their ability to guide us, rather intuitively, in achieving desired responses with appropriate tradeoffs. Nevertheless, there are some inherent limitations and difficulties. This article puts forward some of the questions that troubled us and proposes a new approach to the lead-lag compensation of single-input, single-output, linear time-invariant systems, the ones we were introduced to in our first course on control systems. The target specifications we have taken are meant for standard second-order systems. We show that both the transient and steady-state needs are met using the proposed nonconventional lag-lead compensator. The superiority of this new compensator model is reported in this article with some case studies as well as experimental results.

This paper investigates three-dimensional aerodynamic effects due to radial flow on lead–lag damping of a rotor in forward flight conditions. Three-dimensional effects in this study are restricted to yawed flow aerodynamics and radial flow coupling between blade segments. These effects are included in the ONERA dynamic stall model, and lead–lag damping for an isolated torsionally stiff rotor is calculated for different forward flight conditions. This augmented aerodynamic model with three-dimensional effects and Peters–He dynamic wake model improves the correlation of lead–lag damping with experimental data at high advance ratios. The effect of modeling static lift characteristics on damping correlation is also presented. Finally, a modification to the trailing edge separation point–based static lift model for improved yawed flow modeling amenable to aeromechanical stability analysis is proposed.

This paper deals with a Twin Rotor Aerodynamic System (TRAS). It is a Multi-Input Multi-Output (MIMO) system with high crosscoupling between its two channels. It proposes a hybrid design procedure that combines frequency response and root locus approaches. The proposed controller is designated as PID-Lead Compensator (PIDLC); the PID controller was designed in previous work using frequency response design specifications, while the lead compensator is proposed in this paper and is designed using the root locus method. A general explicit formula for angle computations in any of the four quadrants is also given. The lead compensator is designed by shifting the dominant closed-loop poles slightly to the left in the s-plane. This has the effect of enhancing the relative stability of the closed-loop system by eliminating the oscillation in its transient part but at the expense of greater rise time. However, for some applications, long rise time may be an allowable price to get rid of undesired oscillation. To demonstrate the proposed hybrid controller's performance numerically, a new performance index, designated by Integral Reciprocal Time Absolute Error (IRTAE), is defined as a figure to measure the oscillation of the response in its transient part. The proposed controller enhances this performance index by 0.6771%. Although the relative enhancement of the performance index is small, it contributes to eliminating the oscillation of the response in its transient part. Simulation results are performed on the MATLAB/Simulink environment.

This paper analyses Disturbance Observer- (DOb-) based robust force control systems in the discrete-time domain. The robust force controller is implemented using velocity and acceleration measurements. A DOb is employed in an inner-loop to achieve robustness, and another DOb, viz. Reaction Force Observer (RFOb), is employed in an outer-loop to estimate interaction forces and improve the performance of force control. First, the inner-loop is analysed. It is shown that the DOb works as a phase-lead/lag compensator tuned by the nominal design parameters in the inner-loop. The phase margin of the inner-loop controller and the bandwidth of the velocity-based (i.e., conventional) DOb are constrained not only by noise-sensitivity but also by the waterbed effect. This explains why we observe unstable responses as the bandwidth of the conventional DOb increases in practice. To eliminate the design constraint due to the waterbed effect, this paper proposes an acceleration-based DOb. Then, the robust force controller is analysed. It is shown that the design parameters of the RFOb have a notable effect on the stability of the robust force control system. For example, the robust force controller has a non-minimum phase zero (zeros) when the RFOb is not properly tuned. This may cause severe stability and performance problems when conducting force control applications. By using the stability and robustness analyses, this paper proposes new design tools which enable one to synthesize a high-performance robust force control system. Simulations and experiments are presented to validate the proposed analysis and synthesis methods.

This paper proposes a new model order reduction technology for the simplification of the complexity of large scale models. The proposed technique is focused on the Mihailov stability approach that guarantees the stability of the reduced model constrained that the complex system is stable. In this scheme, the denominator coefficients of the approximated simplified system are computed by using the Mihailov stability algorithm and the truncation method is used for the determination of coefficients of the numerator polynomial. The effectiveness and efficiency of the proposed approach are illustrated by comparing the step responses of the given system and approximated lower order models. The error indices such as integral square error (ISE), relative integral square error (RISE), integral absolute error (IAE) and integral time weighted absolute error (ITAE) are used as performance indices for comparing the proposed scheme with other existing standard reduced order modeling methods. The obtained reduced model is used for the designing of controllers for the original complex system. A new scheme for the determination of controllers is also proposed for the large scale models with help of reduced order modeling. The proposed technique is validated by applying it to an eighth order flexible-missile control system and a third order fuel control system. The simulation results show the dominance of the proposed methodologies over the latest model diminution techniques available in the literature.

A nitrifying activated sludge process with ammonium feedback and inflow feedforward control is studied. The feedback and feedforward measurements are subject to time delay and the control loop includes a saturation. A Hammerstein-based model is therefore identified, including process delays and the nonlinearity. A Monod-type nonlinearity is used, as motivated by the oxygen injection efficiency reduction, with increasing dissolved oxygen concentration. The proposed feedback control strategy includes tuning of a linear lag compensator that has a limited low-frequency gain which allows global stability to be established with the Popov criterion. The feedforward controller attenuates the disturbance and provides an overall improvement of the control strategy. The performance of the combined feedback and feedforward aeration controller is evaluated with a benchmark model.

This paper discusses the effect of multi-objective function in angle stability improvement for a single machine connected to an infinite bus system (SMIB). Minimum damping ratio, ξmin and maximum damping factor, σmax which are commonly used to indicate oscillatory stability condition in power system are merge in certain ratio to produce a multi-objective function, FMO. This new index brings the advantages of the two indices without compromising the weakness of the index involved. In this study, FMO is applied to tune parameters of static var compensator with proportional-integral-derivative controller (SVC-PID) to improve damping efficiency in SMIB. The result is compared with a system connected to power system stabilizer attached with lead lag controller (PSS-LL). The parameters of SVC-PID and PSS-LL are optimized by particle swarm optimization method. Validation based on speed response, phase plane and determination of eigenvalues confirms that the proposed FMO is more effective for solving angle stability problems compared to single objective function.

The control delay weakens the active damping (AD) performance of digitally controlled LCL/LLCL -type grid-connected inverters (GCIs). The equivalent virtual impedance paralleled with the filter branch explains the effect of the capacitor-current-feedback AD. However, the virtual impedance appears capacitive or even negative due to the delay, which significantly weakens the effectiveness of AD. This paper proposes a single-cycle-lag compensator (SCLC) to eliminate the adverse effects caused by the control delay. The method retains effectiveness in applications with high resonant frequency or large control delay. It keeps system a positive equivalent resistance with a high equivalent inductance. The positive equivalent resistance leads to positive damping effect, while the high equivalent inductance causing little resonant frequency deviation can be neglected. Moreover, the effect of the impedance variation that causes the resonant frequency deviation is analyzed and the restrictions of the proposed method are discussed. By optimizing the LCL/LLCL filter parameters, the adaptability of the SCLC to the grid impedance variation can be further improved. With the SCLC, the LCL/LLCL -type GCIs achieve better steady-state and dynamic performances. Finally, experimental results are presented to verify the proposed method.

To eliminate harmonic components in estimated speed and position information generated by inverter non-linearities for the interior permanent-magnet synchronous motor (IPMSM) sensorless control, a second-order lead compensator-based quadrature phase-locked loop (SOLC-Q-PLL) is proposed for the sliding mode observer. An adaptive super-twisting sliding mode observer is taken to estimate back electromotive forces (EMFs) for IPMSM. Harmonic components in estimated position information generated by inverter non-linearities are analysed. Being dependent on the corresponding analysis, the SOLC-Q-PLL is proposed to eliminate sixth position estimation errors only by introducing a second-order lead compensator without causing phase delay for the phase-locked loop system. The introduction of the second-order lead compensator does not influence the bandwidth of the phase-locked loop system so that a fast transient response can be achieved, and this algorithm is easy to implement digitally due to its simple structure. Eventually, a series of experiments are conducted to validate the capability of the proposed algorithm.

This study presents an inverter current sampled double-loop proportional multi-resonant (PMR)-based control technique for three-level (3L) three-phase four-leg (3P4L) advanced T-type neutral point clamped (AT-NPC) stand-alone mode inverter. Apart from the conventional linear controller the PMR controller has the ability to track a sinusoidal reference and does not require any axis transformation. Therefore, the main advantage of the proposed control technique for a 3P4L inverter is to independently control the output phase voltages when feeding a single phase and/or three phase loads. This is achieved by the inverter current sampled double-loop controller with a lead compensator in order to increase the control system phase margin unlike the capacitor current sampled controller. Thus, the harmonic compensation capability of the controller is increased which strengthens the controller against highly non-linear load types. The design procedures of the controller for the system are analytically explained. Then, the steady-state and dynamic performance of the controller is tested in a 3L 3P4L AT-NPC inverter system through many simulations and experimental studies. The results verify the fast-dynamic performance and the achievement of the low total harmonic distortion with a maximum of 2.89% for the 3L 3P4L AT-NPC inverter system even under serious non-linear load type. Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [215E357] This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) under Project 215E357. WOS:000520421100025 2-s2.0-85082387573

A new lead–lag damper concept using a fluidic flexible matrix composite (F2MC) tube is presented in this paper. A model is developed for an articulated rotor blade integrated with an F2MC damper consisting of an F2MC tube, an inertia track, an orifice, and a hydraulic accumulator. Benchtop tests using a 4.5-ft rotor blade demonstrate the performance of a smallscale F2MC damper. The blade–damper system model predictions are verified by comparing experimentally measured and model-predicted frequency response data. In benchtop tests, the model predicts blade damping ratios of up to 0.34 with the F2MC damper. A simplified articulated blade based on the UH-60 rotor is simulated to assess the feasibility of a full-scale F2MC damper. Simulation results predict that the damper can generate blade damping ratios of over 0.30 at low blade lag angles.

In this paper, the systematic design procedure of the proposed lead-lag direct power model predictive controller (L2DP-MPC) for active-front-end (AFE) rectifier is presented. First, the parametric design procedure of the linear proportional-integrator (PI) and lead-lag controllers are described. Then, in the lead-lag control system, the inner-loop current controller is replaced by the non-linear DP-MPC controller to form the proposed L2DP-MPC. Moreover, a comparative study between four designed controllers including the PI, lead-lag, PI-DP-MPC, and the proposed L2DP-MPC is performed from various aspects. All of the controllers are applied to the three-level active-neutral-point-clamped (3L-ANPC) AFE rectifier to evaluate the performance of each controller. The presented simulation results verify the performance, feasibility, and superiority of the proposed L2DP-MPC over the PI, lead-lag, and PI-DP-MPC methods.

The use of control algorithms in inverter topologies is becoming more attractive for integration of wind and photovoltaic (PV) energy with a grid. Among the various inverters, the non-isolated inverter topology has gotten a huge attention for fixing the problem of leakage current issue with other inverters. In this paper, a linear control strategy is offered for the grid connected non-isolated PV inverter. The proposed scheme consists of a proportional resonance (PR) controller with lag compensator (LC). This controller offers lower oscillation in output grid current and better steady state performance for the grid-tied PV inverter systems. The analytical comparison of proposed control scheme and the other control strategies are mentioned in this work. The simulation results indicate the improvements of the performance for the proposed controller in terms of reference tracking ability, total harmonic distortion (THD), and the supplied dc bus voltages of the grid-injected PV inverter systems. This proposed controller can enhance the performance of the PV systems by reducing energy consumption during load change and faulty condition.

This paper investigates the lead–lag relationships in high-frequency data. We propose multinomial dynamic time warping (MDTW) that deals with non-synchronous observation, vast data, and time-varying lead–lag. MDTW directly estimates the lead–lags without lag candidates. Its computational complexity is linear with respect to the number of observation and it does not depend on the number of lag candidates. The experiments adopting artificial data and market data illustrate the effectiveness of our method compared to the existing methods.

Current studies on the ball-on-plate (BoP) problem are mainly focused on platforms with a fixed base and use a vision system to detect the ball. However, relevant works on legged robots are not available, especially on six-parallel-legged robots using pure haptic information. This paper proposes a novel BoP motion planning method for six-parallel-legged robots walking on irregular terrain based on pure haptic information. First, a six-parallel-legged robot with seven six-dimensional force/torque sensors is introduced. Then, a complete model of the BoP system on the robot is built by considering the six-degree-of-freedom motion of the body. Further, a measurement model of the ball state based on pure haptic information is built, and a low-pass filter, lead compensator, and Kalman filter are applied to extract useful information from the noisy sensor data. An impedance controller is proposed to control the ball, and a novel motion planner with five sub-planners is introduced to address the problem of walking on irregular terrain. Finally, experiments are conducted on the prototype to validate the method. The results show that the method performs robustly when the robot traverses irregular terrains.

Granger causality tests are being supplanted by new methods such as the Lead‐Lag Ratio, particularly in finance where data arrives at random times and systematic sampling often produces spurious results. Existing approaches are insufficient; outside of block‐sampling using a bootstrap, the lead‐lag ratio has generally been assessed against a benchmark of 1 without regard for statistical significance. We use simulations to generate a response surface for the Lead‐Lag Ratio. Our modelled critical values are applied to reassess the findings of three previous studies of lead/lag relations between financial return series with high frequency data. Our response surface method proves to be a convenient and efficient alternative to using a bootstrap.

The present work focuses on comparing a robust and a parameter-varying control design approach for automatically regulating blood pressure in critical hypotensive patients using vasopressor drug infusion. Mean arterial pressure (MAP) response of a patient subject to vasoactive drugs is modeled by a first-order dynamical system with time-varying parameters and a time-varying delay in the control input which limits the implementation of conventional control techniques. Two methods are examined to address the variability and the time-varying delay of the physiological response to the drug. First, a Pade approximation is used to transform the infinite-dimensional delay problem into a finite-dimensional model represented in the form of a non-minimum phase (NMP) system. A systematic parameter-varying loop-shaping control is proposed to provide the closed-loop system with stability and tracking performance in the presence of measurement noise and disturbances. Second, an internal model control (IMC) strategy is examined to design a fixed proportional-integral-derivative (PID) controller cascaded with a lag compensator by considering the time-varying model to be a perturbed uncertain system. To account for system uncertainty, the small-gain theorem is employed by which robust stability conditions are investigated. The proposed control methods are applied to critical hypotensive patient resuscitation to regulate MAP while considering the limitations posed by the time-varying parameters of the physiological response model and the large time-varying delay. Simulation results are provided and compared to evaluate the performance of the proposed control actions under various hypotensive scenarios.

The lead–lag relationship in finance markets has always been the focus point of many researches. The linear Granger causality, a classic method for the research of lead–lag relationship, has been extensively analyzed for markets of spot, future and option, but the nonlinear causality between spot and option markets has attracted little attention. This article first analyzes the linear and nonlinear Granger Causality among Shanghai Stock Exchange 50 (SSE 50) index futures, SSE 50ETF spot and options markets, and compares the effects of different time frequencies on test results. From the results of Granger causality test, we demonstrate some significant lead–lag relationships via 1-hour data, whereas the 5-minutes data may be detrimental to nonparametric Granger causality test. Furthermore, from the 1-minute data, we find that within one day, some different short-term lead–lag relationships appear, and they often contradict to the directions obtained from entire sample spanning 1 year. In search of the more detailed volatile causalities, we employ the nonparametric thermal optimal path (TOP) method on 5-minutes data, finding it potentially an expansion to the traditional Granger method, due to its ability to process high frequency data.

The linkages between crude oil spot and futures markets are widely studied in previous literatures. Most of these conventional methods are static, linear and parametric. In order to overcome this difficulty, we employ the nonparametric and nonlinear symmetric thermal optimal path (TOPS) method to determine the time-dependent lead–lag relationship between two time series. Based on the daily, weekly, monthly spot and futures returns for maturities of one, two, three and four months of the West Texas Intermediate (WTI) crude oil benchmark, we apply the TOPS method together with self-consistent test to investigate the time-varying lead–lag dependences between spot and futures markets from 1987 to 2017. We find that, for total three data sets with different frequencies, the TOPS paths indicate an alternate lead–lag structure instead of a dominance between spot and futures markets in most of the time periods. For the daily data, the lead–lag relationship between the two markets exists within one day except on some specific days. Moreover, without considering the units of time, on average, the lead–lag steps between the two markets are diminishing with the increasing frequency. Roughly speaking, these periods with strong lead–lag signals coincide with major influential changes in the oil and stock markets and the geopolitics, which can reflect real economic, financial and geopolitical regime changes. All in all, the results show that the lead–lag relationship between the spot and futures oil markets exists only temporarily.

This study was supported by the Institute of Management Research, Seoul National University.

This paper investigates the enactment of battery energy storage system (BESS) and static compensator (STATCOM) in enhancing large-scale power system transient voltage and frequency stability, and improving power export capacity within two interconnected power systems. A PI-lead and lead-lag controlled BESS is proposed for multimachine power system to provide simultaneous voltage and frequency regulation within the defined battery state-of-charge ranges and an equivalent Finnish transmission grid is used to evaluate the system performance. According to Australian National Electricity Market grid requirements, the performances of the proposed control schemes are compared with conventional PI controlled BESS and STATCOM under multiple temporary and permanent fault conditions. In addition, two adjacent disturbance events are also applied to evaluate system performance with BESS and STATCOM. Through simulation results, it is shown that when there is a ${\text{44}\%}$ increase in power export and the STATCOM fails, incorporating BESS improves the performance and justifies the novelty of this study. Moreover, the proposed lead-lag controlled BESS manifests better transient performance than BESS with PI-lead and traditional PI controller, in the event of divergent temporary and permanent faults.

This study examines the co-movement and lead-lag casuality relationship between the bitcoin and five currencies using wavelet methods. This study focuses on the dependence and casuality relationships in different time scales (short-term, intermediate-term, and long-term scales). The wavelet method results provide three implications: (1) The continuos wavelet power analysis shows that bitcoin returns has a high power in the short and intermediate-term scales over the period from mid-2011 to 2014. (2) The cross wavelet power transformation indicates the strong covariances between bitcoin and currency returns over the periods from mid-2011 to 2014, and this covariance decayed. (3) The wavelet coherence results identify a high level of co-movement between the bitcoin and currency returns at intermediate and long-term scales and bitcoin leading CNY, JPY, and USDX (as arrows approach to the right and up) over periods 2017-2018. Therefore, we find the co-movement and lead-lag causability relationships between bitcoin and currency markets.