Analysis Of Measured Data Research Articles

Uncovering the Root Causes of Stall Flutter in a Wide Chord Fan Blisk

Flutter was encountered at part speeds in a scaled wide chord fan blisk designed for a civil aeroengine during a rig test when the fan bypass flow was throttled toward its stall boundary. Analysis of the blade tip timing measurement data revealed that the fan blades vibrated at the first flap (1F) mode with nodal diameters of two and three. To facilitate a further rig test and ultimately eliminate the flutter problem, a numerical campaign was launched to help understand the root causes of the flutter. Both the influence coefficient method (ICM) and the traveling wave method (TWM) were employed in the numerical investigation to analyze unsteady flows due to blade vibration, with the intention to corroborate different numerical results and take advantage of each method. To eliminate nonphysical reflections, a sponge layer with an inflated mesh size was used for the extended inlet and outlet regions. Steady flow field and unsteady flow field were examined to relate them to the blade flutter. The influences of vibration frequency, mass flow rate, shock, boundary layer separation and acoustic mode propagation behaviors on the fan flutter stability were also investigated. Particular attention was paid to the acoustic mode propagation behaviors.

Density measurements for the National Ignition Facility (NIF) opacity platform

The Opacity Platform on the National Ignition Facility (NIF) has been developed to measure opacities at varying densities and temperatures relevant to the solar interior and thermal cooling rates in white dwarf stars. The typical temperatures reached at NIF range between 150 and 210eV, which allow these measurements to be performed experimentally. The captured opacities are crucial to validating radiation-hydrodynamic models that are used in astrophysics. The NIF opacity platform has a unique new capability that allows in situ measurement of the sample expansion. The sample expansion data are used to better understand the plasma conditions in our experiments by inferring the sample density throughout the duration of the laser drive. We present the details of the density measurement technique, data analysis, and recent results for Fe and MgO.

Electrochemical Polarization Part 2: Electrochemical Devices

In this paper, examples of polarization measurements with a battery, electric double-layer capacitor, and fuel cell are discussed. The analysis of the polarization of a real cell and analytical methodology are described. In battery section, the rate capability is examined in detail and the origin of the different rate properties is discussed. Charge/discharge tests and self-discharge measurements are performed in the electric double-layer capacitor. Detailed measurement conditions and data analysis methods are introduced in the fuel cell section. The contents indicated in each section are very useful for interpreting the obtained experimental data.

Multi-frequency hyperthermia characterisation via calorimetry and AC magnetometry measurements

Hyperthermia characterisation of magnetic nanoparticles (MNP) is challenging, with highly variable results reported by different laboratories and large uncertainties associated with the measured values. Here, two experimental methods for probing the heating power of MNP for magnetic field hyperthermia (MFH) therapy are compared. The first technique is calorimetry using a bespoke non-adiabatic system capable of measurements at varying frequencies and intensities of magnetic drive-field. Heat losses during calorimetry were compensated for by incorporating a loss-parameter and fitting process during analysis of the raw measurement data to calculate the sample’s specific loss power (SLP). The second technique was AC magnetometry to measure the sample hysteresis when exposed to drive-fields with variable frequencies and amplitudes. The area of the measured hysteresis loop is used to calculate the SLP. Two distinct commercial magnetic nanoparticle systems (Ferucarbotran and RCL-01) were studied using both measurement techniques at varying drive-field frequencies and intensities. Estimates of the intrinsic loss power (ILP) parameter were made based on detailed analysis of the SLP values for multiple frequencies and intensities for each nanoparticle system and experimental approach. For both nanoparticle systems, the calorimetry technique produced higher estimates of the ILP than the AC magnetometry technique. Despite these variations, the results were encouragingly similar, with all values falling within the calculated uncertainty envelopes and relative differences in the results for the two nanoparticles systems being consistent between the measurement techniques (suggesting systematic errors). Furthermore, the experimentally determined values showed strong agreement with literature. The presented study highlights the potential value of carrying out hyperthermia characterisations with differing drive-field types and measurement methods. This approach can reduce inaccuracies by assisting in identifying outliers and aiding the identification of measurements which fall within the Linear-Response Regime for the given nanoparticle. Thus, the presented approach offers additional security when characterising the ILP of MNP.

대한민국 남해상(부산-제주도)에서의 TVWS 가용채널 이용에 관한 연구

This paper describes the first study in Korea on the use of available TV white space (TVWS) channels that can be used in the South Sea for terrestrial digital television (DTV) broadcasting bands. Focusing on the Busan-Jeju route in the Soutn Sea of Korea, the possibility of using TVWS frequencies of DTV broadcast signals (channels 14-51 and 470∼698 MHz) was studied. Through the characteristic analysis of domestic DTV channels and other unusual measurement data, the DTV spillover signals of Japan are confirmed, and it is deduced that the available TVWS channels that could be used in the South Sea are affected. The analysis confirmed that channel No. 39 (623 MHz) can be used as an available channel for TVWS without interference from existing DTV channels in all seas between Busan Port and Jeju Port. Additionally, two channels, channel 45 (659 MHz) and 47 (671 MHz), were found to be available for the TVWS frequencies on the Busan-Jeju Island route section, excluding Busan Port and Jeju Port.

Intelligent measurement and detection data analysis and application

In measuring technique is widely used, the measurement test data acquisition, processing, management is the most common operation link, because each link related to data information is relatively more, practice is more complex, so in order to ensure the accuracy of the calibration data and results, the current research scholars use intelligent technology to build a new platform for the collection and management system, It can effectively solve the problems existing in intelligent metering detection. Therefore, on the basis of understanding the current situation of measurement detection data collection and intelligent management, I deeply discuss how to use intelligent measurement detection reasonably according to the measurement detection management system of mobile Internet. The final results show that the intelligent measurement detection technology system can achieve comprehensive control of basic functions on the basis of obtaining more data information.

Intelligent measurement and detection data analysis and application

In measuring technique is widely used, the measurement test data acquisition, processing, management is the most common operation link, because each link related to data information is relatively more, practice is more complex, so in order to ensure the accuracy of the calibration data and results, the current research scholars use intelligent technology to build a new platform for the collection and management system, It can effectively solve the problems existing in intelligent metering detection. Therefore, on the basis of understanding the current situation of measurement detection data collection and intelligent management, I deeply discuss how to use intelligent measurement detection reasonably according to the measurement detection management system of mobile Internet. The final results show that the intelligent measurement detection technology system can achieve comprehensive control of basic functions on the basis of obtaining more data information.

Eye Dynamics and Engineering Network Consortium: Baseline Characteristics of a Randomized Trial in Healthy Adults

To improve understanding of intraocular pressure (IOP) and its variance, this project identifies systemic and ocular characteristics of healthy eyes of adult volunteers including IOP variation, ocular biometrics, and aqueous humor dynamics (AHDs). These data serve as baseline controls for further studies from the Eye Dynamics and Engineering Network (EDEN) Consortium. Multicenter open-label clinical trial in healthy adults randomized to 1 week treatment with 2 approved glaucoma drugs in a crossover design. Among 135 healthy participants, 122 participants (aged 55.2 ± 8.8 years; 92 females, 30 males) completed the protocol. Participants from the University of Michigan, Mayo Clinic, and University of Nebraska Medical Center underwent measurements of ocular biometrics, AHD, and IOP using 4 tonometers. Intraocular pressure data during 3 study visits without glaucoma medications were used in the analysis. The PhenX Toolkit survey acquired standardized data on medical history, surgical history, medications, smoking and alcohol exposures, and physical measures. The variability of IOP measurements within eyes was assessed as visit-to-visit IOP variation, within-visit IOP variation, and within-visit positional IOP variation. The concordance (or correlation) between eyes was also assessed. Average positional change of > 4.7 mmHg was detected with a range of 0.5-11.0 mmHg. Pearson correlation of IOP between eyes within a visit was 0.87 (95% confidence interval [CI], 0.82-0.91) for Goldmann applanation tonometry, 0.91 (95% CI, 0.88-0.94) for Icare rebound tonometry, and 0.91 (95% CI, 0.88-0.94) for pneumatonometry. There was a 4% to 12% asymmetric fluctuation of 3 mmHg or more between eyes between visits using rebound tonometry, 9% with Goldmann applanation tonometry, and 3% to 4% by pneumotonometry. The coefficient of variation between visits for the same eye ranged from 11.2% to 12.9% for pneumatonometry, from 13.6% to 17.4% for rebound tonometry, and 15.8% to 16.2% for Goldmann applanation tonometry. The current study from the EDEN Consortium describes measurement methods and data analyses with emphasis on IOP variability. Future papers will focus on changes in ocular biometrics and AHD with timolol or latanoprost treatment. Proprietary or commercial disclosure may be found after the references.

Intelligent Compaction: An Improved Quality Monitoring and Control of Asphalt Pavement Construction Technology

In transport sector, improving the quality of road construction plays a crucial role in developing a more sustainable and cost-effective infrastructure network. Intelligent Compaction (IC) has been actively studied as a novel and promising technology for quality monitoring and control in asphalt road construction. However, a successful application of IC in pavement construction is still bothered by its accuracy and stability in quality evaluation. This paper proposed AICV– Acceleration Intelligent Compaction Value, a new evaluation index for harmonic intelligent compaction quality evaluation and with a higher accuracy than the frequently used index CMV– Compaction Measurement Value. In order to optimize the evaluation of the compaction quality uniformity of asphalt pavement, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\sigma $ </tex-math></inline-formula> of Normal Distribution is adopted to estimate the compaction uniformity. The statistical analyses of the field measurement data show that, both CMV and AICV are applicable to evaluate the uniformity of compaction quality. However, the dispersion degree of AICV is far less than that of CMV, indicating that AICV is more stable as an index for compaction quality evaluation. By using spatial statistics, the spatial correlation distance of the compaction quality is further obtained, which gives to an assessment of the influence range of intelligent roller. Overall, the study provides a basis for improving the quality control of asphalt pavement construction by means of more delicate monitoring of the compaction process.

ASSESSMENT AND EVALUATION IN HIGHER EDUCATION QUALITY MANAGEMENT

The process of education quality management in combination with evaluation and analytical activity is considered in this research as an activity to implement the goals and coordinate the activities of all components of the educational system, its subjects and achievement of the planned results based on management decisions, the validity and predictability of which enhance the evaluation and analytical activity. Objective assessments of learning outcomes based on the theory of pedagogical measurements have a priority role in providing information base for evaluation and analytical activities in education quality management. These measurements should be the basis for recognition, analysis, functioning, development, forecasting and improvement of education quality management systems. A systematic and prioritised approach to quality management should be developed at different levels, from the macro level to the quality management of the individual educational organisation. A sound use of information in education quality management requires the construction of a hierarchy and interconnection of information flows. This systematic approach should be comprehensive, combining dynamic, comparative, differentiating and predictive analysis of assessment-analytical data. When carrying out assessment-analytical activities based on measurement results in education quality management, a set of scientific requirements for information base characteristics should be taken into account, contextual factors in the analysis and interpretation of measurement data should be taken into account. The requirements primarily include the use of measurement models and design, high reliability and validity of the results of assessment and evaluation activities, extensive use of dynamic approach to assessment of learning quality and ensuring compatibility of assessment and evaluation results, the use of balanced indicators of educational quality, operable in measurement. A system of balanced indicators of the quality of learning achievements, structured according to the levels of education quality management, is presented.

Microdetection of Chromium Mixed–Valences using CuNi/Ti Electrode and Linear Sweep Voltammetry

An electrode of non-precious metal has the potency to be utilized as a working electrode for voltammetry measurements of Cr&lt;sup&gt;3+&lt;/sup&gt; and Cr&lt;sup&gt;6+&lt;/sup&gt;. The analytical performance of the electrode in determining specific metal species qualitatively and quantitatively was studied. The detection data were recorded and analyzed using cyclic voltammetry (CV) and linear sweep voltammetry (LSV), whereas scanning electron microscope (SEM) and X-ray diffraction (XRD) spectroscopy were used to determine the surface morphology and the presence of crystalline in the electrode. Electroanalytical performance was determined by linear sweep voltammetry. The results show that the reduction of Cr&lt;sup&gt;6+&lt;/sup&gt; to Cr&lt;sup&gt;3+&lt;/sup&gt; appeared at +0.84 V (vs Ag/AgCl) and the reduction of Cr&lt;sup&gt;3+&lt;/sup&gt; to Cr&lt;sup&gt;2+&lt;/sup&gt; at +0.74 V (vs Ag/Ag). The optimum conditions for measuring Cr&lt;sup&gt;3+&lt;/sup&gt; were found at pH 6, deposition time of 30 seconds, and a scan rate of 160 mVs&lt;sup&gt;-1&lt;/sup&gt;. The optimum pH for measuring Cr&lt;sup&gt;6+&lt;/sup&gt; is 4, deposition time of 60 seconds, and a scan rate of 140 mVs&lt;sup&gt;-1&lt;/sup&gt;. The regression curve for the Cr&lt;sup&gt;3+&lt;/sup&gt; is linear in concentration 1 – 10 gL&lt;sup&gt;-1&lt;/sup&gt; with a correlation coefficient of 0.9883 and a detection limit of 2.08 gL&lt;sup&gt;-1&lt;/sup&gt;. While the Cr&lt;sup&gt;6+&lt;/sup&gt; is linear in the range of 1 – 10 gL&lt;sup&gt;-1&lt;/sup&gt; with a correlation coefficient of 0.99 and a detection limit of 2.18 gL&lt;sup&gt;-1&lt;/sup&gt;. There is a slight difference in the individual measurement current and the mixture of Cr&lt;sup&gt;3+&lt;/sup&gt; and Cr&lt;sup&gt;6+&lt;/sup&gt; but with a good agreement for the oxidation-reduction potential. The measurement data analysis shows the feasibility of the electrode and the measurement system developed.

Detection of Nanobubbles on Lubricant-Infused Surfaces Using AFM Meniscus Force Measurements.

So far, the presence of nanobubbles on lubricant-infused surfaces (LIS) has been overlooked, because of the difficulty in detecting them in such a complex system. We recently showed that anomalously large interfacial slip measured on LIS is explained by the presence of nanobubbles [Vega-Sánchez, Peppou-Chapman, Zhu and Neto, Nat. Commun., 2022 13, 351]. Crucial to drawing this conclusion was the use of atomic force microscopy (AFM) force-distance spectroscopy (meniscus force measurements) to directly image nanobubbles on LIS. This technique provided vital direct evidence of the spontaneous nucleation of nanobubbles on lubricant-infused hydrophobic surfaces. In this paper, we describe in detail the data collection and analysis of AFM meniscus force measurements on LIS and show how these powerful measurements can quantify both the thickness and distribution of multiple coexisting fluid layers (i.e., gas and oil) over a nanostructured surface. Using this technique, thousands of force curves were automatically analyzed. The results show that the interfacial tension of the nanobubbles is reduced from 52 ± 9 mN m-1 to 39 ± 4 mN m-1 by the presence of the silicone oil layer.

Improved rainfall and temperature satellite dataset in areas with scarce weather stations data: case study in Ancash, Peru

Rainfall and temperature variables play an important role in understanding meteorology at global and regional scales. However, the availability of meteorological information in areas of complex topography is difficult, as the density of weather stations is often very low. In this study, we focused on improving existing satellite products for these areas, using Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM) data for rainfall and Modern Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2) data for air temperature. Our objective was to propose a model that improves the accuracy and correlation of satellite data with observed data on a monthly scale during 2012-2017. The improvement of rainfall satellite data was performed using 4 regions: region 1 Santa (R1Sn), region 2 Marañón (R2Mr), region 3 Pativilca (R3Pt) and region 4 Pacific (R4Pc). For temperature, a model based on the use of the slope obtained between temperature and altitude data was used. In addition, the reliability of the TRMM, GPM and MERRA-2 data was analyzed based on the ratio of the mean square error, PBIAS, Nash-Sutcliffe efficiency (NSE) and correlation coefficient. The final products obtained from the model for temperature are reliable with R2 ranging from 0.72 to 0.95 for the months of February and August respectively, while the improved rainfall products obtained are shown to be acceptable (NSE≥0.6) for the regions R1Sn, R2Mr and R3Pt. However, in R4Pc it is unacceptable (NSE&lt;0.4), reflecting that the additive model is not suitable in regions with low rainfall values.

Uncertainty quantification of structural flexibility identified from input–output measurement data for reliability analysis

AbstractIn contrast to the traditional uncertainty quantification of the modal parameters identified from the output‐only measurement data, this study develops an uncertainty propagation and quantification method for structural flexibility identified from input–output measurement data and then uses the derived flexibility matrix for structural reliability analysis. First, a novel procedure for variance estimations of the complete system matrix of the state‐space model is derived based on first‐order perturbation theory. Then, the mode scaling factors and integrated modal flexibility are subsequently derived and quantified. Finally, the predicted displacements and their uncertainty intervals are used to implement the reliability analysis in terms of the structural displacement serviceability limit state (SLS). The accuracies of the derived expressions are verified by a numerical example through the comparison of variance values estimated from Monte Carlo simulations. The simulation example also indicates that we can expect to identify structural parameters with higher reliability if the input force to the structure is measured, and the identified modal scaling and corresponding flexibility matrix undergo more uncertainty than those of the modal parameters. Finally, we apply the proposed uncertainty quantification method to a scaled three‐story frame structure to demonstrate its practicability. The proposed method bridges a gap between the identified structural flexibility and structural reliability analysis directly by the probability category.

Multi-dimensional modeling of mixture preparation in a direct injection engine fueled with gaseous hydrogen

With the recent advances of direct injection (DI) technology, introducing hydrogen into the combustion chamber through DI is being considered as a viable approach to circumvent backfire and pre-ignition encountered in early generations of hydrogen engines. As part of a broader vision to develop a robust numerical model to study hydrogen spark ignition (SI) combustion in internal combustion (IC) engines, the present numerical investigation focuses on mixture preparation in a hydrogen DI SI engine. This study is carried out with a single hole injector with gaseous hydrogen injected at 100 bar injection pressure. Simulations are carried out for high and low tumble configurations and validated against optical data acquired from planar laser induced fluorescence (PLIF) measurements. Varying mesh configurations are investigated for the impact on in-cylinder mixture distribution. A particular emphasis is placed on the effect of nozzle geometry and mesh orientation near the wall. Overall, the computational model is found to predict the mixture distribution in the combustion cylinder reasonably well. The results showed that the alignment of mesh with the flow direction is important to achieve good agreement between numerical analysis and optical measurement data.

1D TEMPERATURE TOMOGRAPHY OF A FLAME, BASED ON VIS-NIR SPECTROMETRY

ABSTRACT This paper describes a novel method for the determination of the temperature distributions within a firebox of a coal power plant. Beside the temperature distributions, this method also allows for determining the particulate matter density and its spatial distribution. The method uses the spectroscopy approach. We present the description of the experimental setup, and the detailed mathematical model used for the measurement data analysis and interpretation. Finally, a set of experimental measurements was performed on the premises of a large commercial coal power plant. The experimental results were analyzed in order to benchmark the validity of the proposed model.

Direct-write formation of integrated bottom contacts to laser-induced graphene-like carbon

We report a simple, scalable two-step method for direct-write laser fabrication of 3D, porous graphene-like carbon electrodes from polyimide films with integrated contact plugs to underlying metal layers (Au or Ni). Irradiation at high average CO2 laser power (30 W) and low scan speed (∼18 mm s)−1 leads to formation of ‘keyhole’ contact plugs through local ablation of polyimide (initial thickness 17 μm) and graphitization of the plug perimeter wall. Top-surface laser-induced graphene (LIG) electrodes are then formed and connected to the plug by raster patterning at lower laser power (3.7 W) and higher scan speed (200 mm s)−1. Sheet resistance data (71 ± 15 Ω sq.)−1 indicates formation of high-quality surface LIG, consistent with Raman data which yield sharp first- and second-order peaks. We have also demonstrated that high-quality LIG requires a minimum initial polyimide thickness. Capacitance data measured between surface LIG electrodes and the buried metal film indicate a polyimide layer of thickness ∼7 μm remaining following laser processing. By contrast, laser graphitization of polyimide of initial thickness ∼8 μm yielded devices with large sheet resistance (>1 kΩ sq.)−1. Raman data also indicated significant disorder. Plug contact resistance values were calculated from analysis of transfer line measurement data for single- and multi-plug test structures. Contacts to buried nickel layers yielded lower plug resistances (1-plug: 158 ± 7 Ω , 4-plug: 31 ± 14 Ω) compared to contacts to buried gold (1-plug: 346 ± 37 Ω , 4-plug: 52 ± 3 Ω). Further reductions are expected for multi-plug structures with increased areal density. Proof-of-concept mm-scale LIG electrochemical devices with local contact plugs yielded rapid electron transfer kinetics (rate constant k 0 ∼ 0.017 cm s−1), comparable to values measured for exposed Au films (k 0 ∼0.023 cm s)−1. Our results highlight the potential for integration of LIG-based sensor electrodes with semiconductor or roll-to-roll manufacturing.

Use of Repeated Measures Data Analysis for Field Trials with Annual and Perennial Crops.

Field studies conducted over time to collect any type of plant response to a set of treatments are often not treated as repeated measures data. The most used approaches for statistical analyses of this type of longitudinal data are based on separate analyses such as ANOVA, regression, or time contrasts. In many instances, during the review of manuscripts, reviewers have asked researchers to treat year, for example, as a random effect and ignore the interactions between year and other main effects. One drawback of this approach is that the correlation between measurements taken on the same subject over time is ignored. Here, we show that avoiding the covariance between measurements can induce erroneous (e.g., no differences reported when they exist, or differences reported when they actually do not exist) inference of treatment effects. Another issue that has received little attention for statistical inference of multi-year field experiments is the combination of fixed, random, and repeated measurement effects in the same statistical model. This type of analysis requires a more in-depth understanding of modeling error terms and how the statistical software used translates the statistical language of the given command into mathematical computations. Ignoring possible significant interactions among repeated, fixed, and random effects might lead to an erroneous interpretation of the data set. In this manuscript, we use data from two field experiments that were repeated during two and three consecutive years on the same plots to illustrate different modeling strategies and graphical tools with an emphasis on the use of mixed modeling techniques with repeated measures.

Magnetometric Investigations of Biomagnetic Signals: Magnetocardiography

Introduction. Superconducting magnetometers based on SQUIDs (SQUID- Superconducting QUantum Interference Device) are currently used to register weak magnetic fields generated in various human organs and measured outside the body (in the environment). The creation of information technology, which is a set of methods and software tools combined into a technological chain that ensures registration, storage, pre-processing, analysis of measurement data and automatic diagnostic output, is an essential science-intensive component that determines the possibilities and success of the applied use of non-contact diagnostic systems of the human heart The purpose. Article presents new algorithms for spatial analysis of cardiomagnetic signal measurement results. The algorithms are based on the inverse problem solution, when the magnetic field source is matched to the spatial distribution of the magnetic signal and the parameters and spatial configuration of the source are determined. A model of the cardiomagnetic source was used in the form of a system of current density vectors, which are distributed in a plane that is parallel to the measurement plane and crosses the volume of the heart. Results. The inverse problem is solved using the apparatus of two-dimensional integral Fourier transformations. The data transformation algorithm allows to correctly take into account the design of the magnetic flux transformer (the dimensions of the pickup coils, their spatial location and the electrical connection scheme). Algorithm modifications have been developed for most of the known (implemented in existing magnetocardiographs) designs of magnetic flux transformers of the first and second order gradientometers. The operation of the algorithm is modeled on real data of magnetometric investigations of the human heart. Investigations have shown that the application of the proposed algorithms allows obtaining new information about the spatial configuration of the magnetic signal source in the human heart, which can be used in the future for the diagnosis of human heart diseases. Keywords: magnetocardiography, inverse problem of magnetostatics, Fourier transform, SQUID gradientometer.

Empirical estimation of the eigenmodes of macroscale cortical dynamics: Reconciling neural field eigenmodes and resting-state networks

Neural field theories successfully describe normal, awake mesoscale to macroscale brain activity using linearized partial differential equations that involve a Laplacian operator. These neural field theories therefore predict spatial brain activity patterns that are simple, smooth eigenfunctions of the Laplacian operator that satisfy the Helmholtz equation and extend across the entire cortex. However, complex, localized spatial patterns such as resting-state networks have been proposed from data analysis of brain activity measurements, primarily fMRI. Using Human Connectome Project data, the Helmholtz eigenmode prediction of neural field theory is shown to be consistent with eigenvectors of both fMRI and MEG covariance matrices. It is explained why these Helmholtz equation eigenmodes have been difficult to observe due to their similar spectra, effects of covariant input stimuli to the brain, and measurement noise. This implies that complex spatial patterns like resting-state networks may be the result of complex input to the brain but simple intrinsic brain dynamics, rather than simple stimuli and complex brain dynamics, as assumed in many existing models.