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This paper proposes an improved binary bat algorithm (IBBA) for solving static and dynamic transmission network expansion planning (TNEP) problems for standard and realistic networks considering different objective functions (OFs). The proposed IBBA has two modifications to enhance the solution quality based on multi V-shaped transfer function and adaptive search space (ASS). The IBBA is applied to solve the static TNEP problem. A two-stage procedure is employed to solve the dynamic TNEP problem. In stage-1, the adaptive neuro-fuzzy inference system (ANFIS) is utilized to find the long-term load forecasting (LTLF) up to 2039. In stage-2, the IBBA is used to solve the dynamic TNEP problem. Two OFs are considered for solving TNEP problems. The first OF achieves the investment cost reduction. The second OF aims to minimize the total costs, which include the investment cost and the total costs of energy losses and reactive power compensation (RPC). The proposed procedure is applied to Garver’s 6-bus system and the West Delta Network (WDN) as a part of the Unified Egyptian Transmission Network (UETN) to solve TNEP problems. The obtained results are compared with other methods to show the robustness of the proposed procedure for solving TNEP problems.

This paper presents a set of criteria used to identify the parameters describing a tube-load model of the arterial system to estimate central blood pressure (BP). The criteria are generalizable to accommodate for inter- and intra-subject variability encountered in the ICU. The proposed single measurement transfer function (SMTF) requires only a single peripheral pressure measurement, commonly available in the ICU, for central pressure estimation, removing the need for an additional measurement of pulse transit time, common to other central BP estimation models. The method was tested using data from six (6) porcine experiments where septic shock was induced and subsequent treatment was performed. Systolic pressure (SP), pulse pressure (PP) and root-mean-squared (RMSE) errors relative to invasive measurements of aortic pressure were used to assess accuracy. The SMTF method produced mean errors ≤5mmHg across all metrics with 84.4, 88.7 and 63.2% of SP, PP, and RMSE, respectively, within this bound of measured central pressure. Peripheral BP accuracy was also assessed as it is commonly used as a surrogate for central BP in clinical settings. Finally, two alternate methods utilizing the same model equations with additional inputs, one using the measured pulse transit time and the other minimizing the RMSE with measured aortic pressure, were implemented to compare the SMTF accuracy to best case outputs given the model equations.

Seismic qualifications of electrical equipment, such as cabinet systems, have been emerging as the key area of nuclear power plants in Korea since the 2016 Gyeongju earthquake, including the high-frequency domain. In addition, electrical equipment was sensitive to the high-frequency ground motions during the past earthquake. Therefore, this paper presents the rocking behavior of the electrical cabinet system subjected to Reg. 1.60 and UHS. The high fidelity finite element (FE) model of the cabinet related to the shaking table test data was developed. In particular, the first two global modes of the cabinet from the experimental test were 16 Hz and 24 Hz, respectively. In addition, 30.05 Hz and 37.5 Hz were determined to be the first two local modes in the cabinet. The high fidelity FE model of the cabinet using the ABAQUS platform was extremely reconciled with shaking table tests. As a result, the dynamic properties of the cabinet were sensitive to electrical instruments, such as relays and switchboards, during the shaking table test. In addition, the amplification with respect to the vibration transfer function of the cabinet was observed on the third floor in the cabinet due to localized impact corresponding to the rocking phenomenon of the cabinet under Reg.1.60 and UHS. Overall, the rocking of the cabinet system can be caused by the low-frequency oscillations and higher peak horizontal acceleration.

The central aortic pressure (CAP) provides insights into the prediction, prevention, diagnosis, and treatment of cardiovascular disease, but can't be directly measured non-invasively. Therefore, the development of a noninvasive CAP estimation method based on the non-invasively measured peripheral pressure waveform is critical for clinical decisions based on the CAP. Some existing widely applied methods, such as the generalized transfer function (GTF) method relating measured peripheral pressure to the CAP, do not or only partly account for inter-subject or intra-subject variability of the cardiovascular system. To overcome this pitfall, we propose a subject-specific central aortic pressure estimation method in this paper. The novel method presented can derive an accurate aortic pressure from the peripheral pressure based on an individualized pulse wave propagation model using a GTF method as a first guess. To develop a strategy to personalize a pulse wave propagation model one usually needs to optimize many input parameters. Therefore, we present a two-step approach with the screening method of Morris and the adaptive sparse generalized polynomial chaos expansion (agPCE) algorithm for the sensitivity analysis of the wave propagation model. First, for a-priori defined output of the model, a subset of important parameters is identified using the screening method of Morris. Next, a quantitative variance-based sensitivity analysis is performed using agPCE. This approach is applied to a 1D pulse wave propagation model to get the personalized parameters of the pulse wave propagation model for the estimation of a subject-specific central aortic pressure waveform and is validated with 26 patients. Compared with the GTF method, the proposed method showed better performance in estimating the central aortic pulse wave and predicting the parameters.

As an important electronic device, filter is applied to all kinds of electronic products. In this paper, a new ℘ -order R-L High-pass filter (HPF) modeled by the local fractional derivative (LFD) is proposed for the first time. With the help of the local fractional Laplace transform (LFLT), we obtain the non-differentiable(ND) transfer function, and present the expressions of ND amplitude-frequency characteristic (AFC) and ND phase-frequency characteristics (PFC). The corresponding parameters and properties of the ℘ -order R-L HPF are also studied. What’s interesting is that the ℘ -order R-L HPF becomesthe ordinary one in the exceptional case at ℘ = 1. The obtained results in this paper reveal the sufficiency of the local fractional derivative for analyzing the circuit systems in fractal space.

In the last past year researchers have relied on the ability of Laplace transform to solve partial, ordinary linear equations with great success. Important analysis in signal analysis including the transfer function, Bode diagram, Nyquist plot and Nichols plot are obtained based on the Laplace transform. The output of the analysis depends only on the results obtained from Laplace transform. However, one weakness of Laplace transform is that the Laplace transform of even function is odd while the Laplace transform of an old function is even which is lack of conservation of properties. On the other hand there exist a similar integral transform known as Sumudu transform has the ability to conserve the properties of the function from real space to complex space. The question that arises in the work, is the following: Can we apply the Sumudu transform to construct new transfer functions that will lead to new Bode, Nichols and Nyquist plots? this question is answered in this work.

In this paper, a control system with an extended simplified decoupled network is proposed for controlling the interactive multivariable processes. The decoupler is designed using cofactor matrix of the process and incorporated in the control loop which modifies the multivariable processes into multiple single loops. To design the PI/PID controller for each loop of MIMO processes independently, the Equivalent Transfer Function (ETF) of each loop is determined. The ETF is approximated using the static relative gains and the average propagation time between manipulated and controlled variables of the loops. Subsequently the PI/PID controller settings are calculated using SIMC tuning rules. This approach reduces the complexity in mathematical model approximation of decoupled process and improves the performance of the overall process. The maximum singular value uncertainty model is considered to ensure the robustness of the decoupled control system. Simulation results of different dimensional interactive MIMO processes are included.

Electricity demand from air conditioners are increasing every year due to increasing ambient air temperature. Several air-conditioned rooms in Thailand currently use low-efficient fixed-speed air conditioners. Prediction of heat load entering air-conditioned rooms may lead to better control of these air conditioners. In this paper, the Artificial Neural Network (ANN) model was developed, trained, and verified. Data from experiments were collected and used in the model. Sensitivity analysis showed that Tamb, Troom, and Gsolar are the major factors affecting heat load. The 3 factors were identified as the main input to the ANN model. There are 17 different model settings used in the study. The settings covered different model configurations such as the transfer function of the output layer, the transfer function of the hidden layer, the number of hidden layers and the number of neurons. It was found that an increasing number of neurons can increase the performance of the ANN model. Nonetheless, it is not conclusive that the increasing number of hidden layers can increase the performance of the model. Finally, it was found that choosing “tansig” as the transfer function of the output layer and “tansig” and “logsig” as transfer function of hidden layers offers the best model performance. Keywords: ANN model, Heat load calculation

This paper presents an active realization of fraction order Butterworth lowpass filter using a differential voltage current conveyor (DVCC) and two fractance devices (FDs). Initially, the DVCC based fractional order system transfer function is developed. Then, the transfer function of the developed system is equated with the standard fractional order Butterworth equation. By equating this, the generalized condition is obtained for which the developed system behaves like a fractional order Butterworth filter. Further, the effect of current and voltage tracking errors of DVCC, on the system response is investigated using Monte Carlo analysis. Stability of the proposed fractional order Butterworth filter is investigated by pole-zero analysis in complex W-plane. Moreover, the dependency of filter cutoff frequency, on various circuit parameters are investigated using 3D plots. Finally to validate the theoretical results, proposed fractional order Butterworth filter is simulated using R-C ladder network based fractional order capacitor, in PSpice environment using 0.5 μm MIETEC CMOS technology. Keywords: Fractance device, Fractional order filter, Ladder network, W-Plane

This paper presents an integrated analysis about dynamic performance of a Floating Offshore Wind Turbine (FOWT) OC4 DeepCwind with semi-submersible platform under real sea environment. The emphasis of this paper is to investigate how the wave mean drift force and slow-drift wave excitation load (Quadratic transfer function, namely QTF) influence the platform motions, mooring line tension and tower base bending moments. Second order potential theory is being used for computing linear and nonlinear wave effects, including first order wave force, mean drift force and slow-drift excitation loads. Morison model is utilized to account the viscous effect from fluid. This approach considers floating wind turbine as an integrated coupled system. Two time-domain solvers, SIMA (SIMO/RIFLEX/AERODYN) and FAST are being chosen to analyze the global response of the integrated coupled system under small, moderate and severe sea condition. Results show that second order mean drift force and slow-drift force will drift the floater away along wave propagation direction. At the same time, slow-drift force has larger effect than mean drift force. Also tension of the mooring line at fairlead and tower base loads are increased accordingly in all sea conditions under investigation.

This study presents the monitoring and assessment technology of a large arch dam, the Fei-Tsui arch dam in Taiwan, from both seismic response data and ambient vibration measurement collected from a wireless sensing system. Subspace identification (considering inputs) and stochastic subspace identification (output-only) are both used to extract the dynamic characteristics of the dam. Variation of the system natural frequencies of the dam with respect to reservoir water level is investigated. The system transfer function between the earthquake input and the response of the dam body is also investigated using the ARX model. By combining ambient vibration survey, seismic response data, and static monitoring, the safety assessment of the dam structure can be made.

This paper investigates how targeted interference between two well characterized sources of hydrodynamic disturbances can modify the response of premixed bluff body stabilised H 2 / CH 4 flames with and without swirl. We introduce modulations into the Flame Transfer Function (FTF) through hydrodynamic interference between the shedding of vortices/wakes from different shaped bodies upstream of the flame and the vortex roll-up at the flame base caused by acoustic forcing. By placing a set of small diameter cylinders, a streamlined body, or a swirler upstream of the bluff body and varying the distance from the dump plane, the gain and phase of the FTFs could be modulated at targeted frequencies providing a method to suppress thermoacoustic instabilities. We further investigate the flame response which shows that modulations in the fluctuating global heat release rate are caused by linear superposition along the flame front. At frequencies leading to destructive interference, large-scale wrinkling of the flame front occurs which increases the flame surface area but is offset by the simultaneous pinch-off of the flame tip which decreases flame surface area. Their combined effect reduces the amplitude of the fluctuating global heat release rate. At frequencies of constructive interference, large-scale wrinkling of the flame occurs before the flame tip pinches off, leading to an overall increase in the flame surface and amplitude of the fluctuating global heat release rate.

This article proposes a new branch-line coupler design using two trapezoid-shaped resonators, applied in side and center. The standard 35 and 50 Ohms λ/4 transmission lines (TLs) are attained through the variations of the resonator’s TLs width. Since there are not explicit formulas for the suggested trapezoidal shape resonator, the design procedure will include the derivation of new formulas to configure the LC equivalent circuit. The proposed branch-line coupler, operating at 0.95 GHz, has achieved 79 % of size reduction if compared to the conventional designs. Furthermore, the suggested design has successfully diminished the first six harmonics with a suppression level of (41, 29, 29, 28, 20, and 20) dB, respectively. the bandwidth is from 800MHz to 1GHz and The fractional bandwidth is 22.2 %.

Peatlands are valuable archives of information about past environmental conditions and represent a globally-important carbon store. Robust proxy methods are required to reconstruct past ecohydrological dynamics in high-latitude peatlands to improve our understanding of change in these carbon-rich ecosystems. The High Arctic peatlands in Svalbard are at the northern limit of current peatland distribution and have experienced rapidly rising temperatures of 0.81 °C per decade since 1958. We examine the ecology of peatland testate amoebae in surface vegetation samples from permafrost peatlands on Spitsbergen, the largest island of the Svalbard archipelago, and develop new transfer functions to reconstruct water-table depth (WTD) and pH that can be applied to understand past peatland ecosystem dynamics in response to climate change. These transfer functions are the first of their kind for peatlands in Svalbard and the northernmost developed to date. Multivariate statistical analysis shows that WTD and pore water pH are the dominant controls on testate amoeba species distribution. This finding is consistent with results from peatlands in lower latitudes with regard to WTD and supports work showing that when samples are taken across a long enough trophic gradient, peatland trophic status is an important control on the distribution of testate amoebae. No differences were found between transfer functions including and excluding the taxa with weak idiosomic tests (WISTs) that are most susceptible to decay. The final models for application to fossil samples therefore excluded these taxa. The WTD transfer function demonstrates the best performance (R2LOO = 0.719, RMSEPLOO = 3.2 cm), but the pH transfer function also performs well (R2LOO = 0.690, RMSEPLOO = 0.320). The transfer functions were applied to a core from western Spitsbergen and suggest drying conditions ~1750 CE, followed by a trend of recent wetting and increasing pH from ~1920 CE. These new transfer functions allow the reconstruction of past peatland WTD and pH in Svalbard, thereby enabling a greater understanding of long-term ecohydrological dynamics in these rapidly changing ecosystems.

Convex formulations can be used to reduce the local specific absorption rate enhancement by active medical implants of radiofrequency fields in magnetic resonance examinations while minimizing the loss of image quality. This paper demonstrates that such an optimization methodology, previously presented for strictly computational models, can be extended to a hybrid scheme using experimentally determined implant models and pre-computed fields, which can enable quasi real-time exposure optimization. The methodology determines the optimum radiofrequency field shimming condition by considering both the reduction of specific absorption rate enhancement at the tip of the implant lead, created by the interaction of the radiofrequency fields tangential to the implant trajectory with the characteristic response of the implant, and the preservation of magnetic field homogeneity, which correlates to image quality. The inputs to this workflow are those required for each implant by standard ISO 10974 evaluation, namely the validated piece-wise transfer function of the implant, the clinical routing within the patient, and the pre-computed numerical estimation of patient exposure without the implant. Optimized incident field conditions were computed to meet a range of numerical targets for specific absorption rate reduction, stepping down percentagewise from the maximum field homogeneity to the minimum exposure enhancement, for a generic implant with a flexible wire in a standard benchtop radiofrequency coil and phantom. Measurements of the corresponding specific absorption rate enhancements validated the predictions from the optimization approach within the combined confidence interval., Applied mathematical modelling, 96, ISSN:0307-904X, ISSN:1872-8480

Electron ptychography is a 4-D STEM phase-contrast imaging technique with applications to light-element and beam-sensitive materials. Although the electron dose (electrons incident per unit area on the sample) is the primary figure of merit for imaging beam-sensitive materials, it is also necessary to consider the contrast transfer properties of the imaging technique. Here, we explore the contrast transfer properties of electron ptychography. The contrast transfer of focused-probe, non-iterative electron ptychography using the single-side-band (SSB) method is demonstrated experimentally. The band-pass nature of the phase-contrast transfer function (PCTF) for SSB ptychography places strict limitations on the probe convergence semi-angles required to resolve specific sample features with high contrast. The PCTF of the extended ptychographic iterative engine (ePIE) is broader than that for SSB ptychography, although when both high and low spatial frequencies are transferred, band-pass filtering is required to remove image artefacts. Normalisation of the transfer function with respect to the noise level shows that the transfer window is increased while avoiding noise amplification. Avoiding algorithms containing deconvolution steps may also increase the dose-efficiency of ptychographic phase reconstructions.

The three-probe method for separating the spindle rotation error and the specimen form error is extensively described in the literature. An attractive feature is its application in in-process measurement. However, the resulting uncertainty is studied far less extensively. In this paper, an evaluation and propagation method for the uncertainty, as well as for an uncertainty reduction, is given based on the system transfer function (S-function). First, based on the Laplace transform, the measurement system model is developed and expressed by an S-function. Second, the propagation laws of input uncertainties are analytically deduced by computing the partial derivatives of the S-function of roundness. Then, the laws are numerically validated by Monte Carlo simulations. The uncertainty propagation laws show that the uncertainties propagate with varying amplification over the harmonic domain, and moreover, they enable the quantification of roundness uncertainty. Taking the roundness uncertainty as a decisive parameter, three approaches are proposed for uncertainty reduction: (1) the hybrid 3-PM, where two roundness estimates are combined by taking individual harmonic estimate with the lowest uncertainty, (2) the fusion 3-PM, where the weighted average is taken over the harmonic domain, and (3) the angle optimization, which minimizes the total roundness uncertainty by properly arranging the sensor angles. The angle optimization is applied to the conventional 3-PM, as well as to the hybrid and the fusion 3-PMs. The genetic algorithm is adopted to speed up the optimization process. Finally, practical roundness measurements are performed. The three-probe method for separating the spindle rotation error and the specimen form error is extensively described in the literature. An attractive feature is its application in in-process measurement. However, the resulting uncertainty is studied far less extensively. In this paper, an evaluation and propagation method for the uncertainty, as well as for an uncertainty reduction, is given based on the system transfer function (S-function). First, based on the Laplace transform, the measurement system model is developed and expressed by an S-function. Second, the propagation laws of input uncertainties are analytically deduced by computing the partial derivatives of the S-function of roundness. Then, the laws are numerically validated by Monte Carlo simulations. The uncertainty propagation laws show that the uncertainties propagate with varying amplification over the harmonic domain, and moreover, they enable the quantification of roundness uncertainty. Taking the roundness uncertainty as a decisive parameter, three approaches are proposed for uncertainty reduction: (1) the hybrid 3-PM, where two roundness estimates are combined by taking individual harmonic estimate with the lowest uncertainty, (2) the fusion 3-PM, where the weighted average is taken over the harmonic domain, and (3) the angle optimization, which minimizes the total roundness uncertainty by properly arranging the sensor angles. The angle optimization is applied to the conventional 3-PM, as well as to the hybrid and the fusion 3-PMs. The genetic algorithm is adopted to speed up the optimization process. Finally, practical roundness measurements are performed. ispartof: Precision Engineering vol:68 pages:139-157 status: Published online

10 pages, 9 figures, 1 appendix.-- This is a contribution of the Barcelona Center for Subsurface Imaging that is a Grup de Recerca de la Generalitat de Catalunya.-- Geopsy package can be downloaded from http://www.geopsy.org/ (last accessed April 2020). Results of the ARMA method were plotted using the Generic Mapping Tools (GMT) software (Wessel et al., 2013)., We propose a new method to estimate the horizontal-to-vertical (H/V) spectral ratio using microtremor measurements. The technique is based on modeling the H/V transfer function by means of an AutoRegressive Moving Average (ARMA) filter. As compared with the conventional, Fourier-based spectra processing routines, this method is efficient in extracting the fundamental resonant frequency with a higher spectral resolution. We demonstrate its usefulness by an application to several sites in northeastern Iberian Peninsula. For the data sets examined, our approach shows improvement over the Fourier transform-based method under adverse experimental conditions. We conclude that the new technique provides robust estimates of the fundamental resonance frequency and can be effective to characterize empirically the unconsolidated sediment thickness and bedrock geometry, This research was partially supported by Euskontrol, S. A., through the ISURI-1 project. The activity of J. J. Egozcue was supported by the project METhods for COmpositional analysis of DAta (CODAMET), Ministerio de Ciencia, Innovación y Universidades (Ref: RTI2018-095518-B-C22, 2019-2021), With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

This chapter explains transformation with the help of the transform function, as a tool to carry out tasks. A system could be composed of two elements in series, with each having its input-output relationships described by a differential equation, and it may not be easy to see how the output of the system as a whole is related to its input. This problem can be overcome by the transform of differential equations into a Laplace transform. This form is a much more convenient way of describing the relationship than a differential equation as it can be easily manipulated by the basic rules of algebra. The overall transfer functions of systems involving series-connected elements and systems with feedback loops. A block diagram simplifies but still gives the same overall transfer function for the system. When there is more than one input to a system, the superposition principle can be used. An important effect of having feedback in a system is the reduction of the effects of disturbance signals on the system.

This study established the preciseness of the robust MLP-firefly optimizer (MLP-FFA) artificial intelligence algorithm coupled with satellite-derived photosynthetic active radiation (PAR) data in order to forecast PAR itself using historical values for a regional Queensland location (Toowoomba). To optimize the MLP-FFA model, (1) hidden and output transfer functions; (2) number of hidden neurons; (3) training, cross-validation, and test percentage splits; and (4) number of historical lags were trialled, such that the logarithmic sigmoid hidden function and tangent sigmoid output function, with 120 hidden neurons, nine lags as inputs and a 60% training, 20% cross-validation, and 20% testing set, was finally adopted for thre forecasting of PAR. To meet the objective (Section 7.1), the MLP-FFA objective model was benchmarked with the MLP, RF, and MLR models for PAR forecasting. The findings of this study are that the performance of the MLP-FFA model, according to forecasting error directly, as well as association and error performance metrics, outperformed the MLP and RF models. MLR generally outperformed MLP-FFA, but this is most likely a result of nonstochastic monthly PAR data, and it is recommended for future work to investigate lower temporal resolution data (which in turn is more stochastic), which a more robust model like MLP-FFA is known to handle, but a poor model like MLR cannot. A lower resolution such as daily or hourly was not found at the time of this study, and manual data collection was not appropriate due to the time and cost limits of this research. Albeit, the MLP-FFA model has still been very effective in modeling PAR with very high accuracy and low error, leading to a significant contribution to research which is confirming something unknown—that the MLP-FFA model is in fact very effective at satellite-based PAR modeling with historical data as inputs for learning for a regional Queensland location. The results of this study are a significant research contribution, which can be used to forecast PAR conditions, a vital requirement for the growth of algal biofuel; these algae can be farmed in the ideal location of the sunny, subtropical Toowoomba region.

Optical propagation with transverse magnetic and transverse electric polarizations is investigated in metamaterials composed of thin-film metallo-dielectric (MD) structures. The analysis is performed using a novel simplified anisotropic transfer matrix method, the Berreman matrix method with effective medium theory, and finite element methods. In the process, appropriate spatial transfer functions are defined for propagation in the effective bulk medium and used to show negative refraction and linear focusing for certain polarizations in hyperbolic metamaterials. Simulations are compared with experimental results for MD transmission filters. Possible extensions to tunable systems are discussed, using electro-optic substrates and thin-film phase change materials, along with other applications.

By relying on the recently introduced notion of transfer function for linear hybrid systems with periodic jumps, herein we extend, for the first time, frequency-domain analysis tools – well-known and extensively used in the context of purely continuous or discrete time systems – to such a class of hybrid systems. In fact, knowledge of the transfer function allows for the frequency-domain definition of the notion of 0-th momentof the underlying hybrid system, which is instrumental, e.g. for the solution to model reduction or input-output system identification problems. It is shown, in addition, that the notion of moment based on the hybrid transfer function possesses an interesting time-domain counterpart, hence extending the results obtained for purely continuous-time systems. To further substantiate the theoretical claims, the paper is concluded by the frequency-domain robustness analysis of the classical consensus protocol in the presence of sampled measurements.

Based on a classical model of triboelectrochemistry, a new approach is proposed based on the small amplitude sine wave perturbation of one of the two main driving forces in tribocorrosion, namely the sliding velocity and the potential applied to the material. A general formalism is elaborated yielding the analytical expression of the DC steady-state and the AC responses. That allows defining of two transfer functions (current/velocity) at constant potential and (potential/current) at constant velocity. A steady state is established with the use of a pin-on-disc tribometer which ensures a constant rotating cell geometry. In the first example, the triboelectrochemical transfer function is applied to stainless steel in a borate solution. The technique was validated in terms of linearity by spectral analysis. A two-capacitive behavior was evidenced. The behavior is discussed in terms of a two-step film growth mechanism. In the second example, electrochemical impedances were measured at various pin velocities. The same general model used in the first example was modified to embody a classical kinetic description of an active-passive transition. A set of parameters were determined allowing us to describe correctly both the DC and AC behaviors of the interface and to estimate the different components of the triboelectrochemical signals. A way to split the total material loss into a reactive and a wear component is proposed.

Offshore wind turbines are subjected to cyclic loads from wind and waves, ultimately resulting in a fatigue-driven design. These cyclic loads result in cyclic shell forces above the bolted ring flange and ultimately into the cyclic loading of the bolt tension forces. To model the transfer of the shell forces into the bolt, Load Transfer Functions (LTF) are used, of which the tri-linear function according Schmidt/Neuper is the most known approximation but more contemporary approaches exist. As the LTF has a significant impact on the estimated fatigue lifetime of the bolt, it is relevant to investigate the accuracy of the currently used LTF. This paper uses in-situ monitoring data from three offshore wind turbines at the Nobelwind windfarm, each equipped with an instrumented bolt in the monopile to transition piece bolted flange connection and strain-gauges above said flange. Long-term monitoring data is used to derive empirical load transfer coefficients (LTC), i.e. the derivatives of the LTF. In parallel a finite element model (FE model) of the flange connection was developed. The found load transfer coefficients from measurements were compared to the values obtained from the function according to Schmidt/Neuper and the FE model. It is concluded that the observed LTC in the offshore wind farm were favourable compared to the values expected from Schmidt/Neuper. The FE model matched more closely, especially when the MP-flange inclination was included. The inclusion of the MP-flange inclination in the model had a positive effect on the final LTF, which was confirmed by the measurements.

Low-frequency (LF) motions of floating structures are commonly modeled as the response of an oscillator to a second-order wave excitation. We present here an empirical method that reliably estimates the oscillators parameters and quadratic transfer function (QTF) used in such models. The method is based on an active stationkeeping system that enables to accurately control external boundary conditions applied on the floating structure in a wave basin. The resulting system can be successively tuned to different frequency ranges of interest. Then, by deconvolution and optimization, LF damping and added-mass loads, as well as a response-independent wave excitation load, can be evaluated. From the wave elevation, and estimated load time series, the difference-frequency QTF is finally estimated by a cross-bi-spectral analysis, including a new treatment of statistical noise. The paper describes the proposed method in details, and illustrates it with the study of a ship-shaped floating unit in a sea-state of relevance for the fatigue design of mooring systems (steep waves, low return period).

We present an algorithm for identifying discrete-time feedback-and-feedforward subsystems with time delay that are interconnected in closed loop with a known subsystem. This frequency-domain algorithm uses only measured input and output data from a closed-loop discrete-time system, which is single input and single output. No internal signals are assumed to be measured. The orders of the unknown feedback and feedforward transfer functions are assumed to be known. We use a two-candidate-pool multi-convex-optimization approach to identify not only the feedback and feedforward transfer functions but also the feedback and feedforward time delay. The algorithm guarantees asymptotic stability of the identified closed-loop transfer function. The main analytic result shows that if the data noise is sufficiently small and the cardinality of the feedback-candidate-pool set is sufficiently large, then the identified feedforward and feedback delays are equal to the true delays, and the parameters of the identified feedforward and feedback transfer functions are arbitrarily close to the true parameters. This subsystem identification algorithm has application to modeling human-in-the-loop behavior. To demonstrate this application, we apply the new subsystem identification algorithm to data obtained from a human-in-the-loop control experiment in order to model the humans’ feedback and feedforward (with delay) control behavior.

Made available in DSpace on 2020-12-12T02:38:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-08-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) This paper proposes a new identification method based on an exponential modulation scheme for the determination of the coefficients and exponents of a fractional-order transfer function. The proposed approach has a broader scope of application compared to a previous method based on step response data, in that it allows for the use of arbitrary input signals. Moreover, it dispenses with the need for repeated simulations during the search for the best fractional exponents, which significantly reduces the computational workload involved in the identification process. Two examples involving measurement noise at the observed system output are presented to illustrate the effectiveness of the proposed method when compared to a conventional output-error optimization approach based on the polytope algorithm. In both examples, the proposed method is found to provide a better trade-off between computational workload and accuracy of the parameter estimates for different realizations of the noise. Department of Electronic Engineering Instituto Tecnológico de Aeronáutica (ITA) São José dos Campos Department of Electrical Engineering São Paulo State University (UNESP) Institute of Science and Technology Universidade Federal de São Paulo (UNIFESP) São José dos Campos School of Biological Sciences Department of Biomedical Engineering The University of Reading Department of Electrical Engineering São Paulo State University (UNESP) FAPESP: 2011/13777-8 FAPESP: 2011/17610-0 CNPq: 301227/2017-9 CNPq: 303393/2018-1 CNPq: 309872/2018-9