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Hardware impairments in general and amplifier nonlinearity in particular severely limit the performance of communication links. This paper analytically provides statistical results on how a nonlinear amplifier affects the quality of signals in communication systems. In particular, we propose a statistical model that describes the nonlinear distortion as a function of the input signal’s average and instantaneous power and captures the pulse-shaping and matched filters’ effects. We show through simulations and complementary measurements that the proposed model can provide an authentic connection between the communication system parameters, power amplifier nonlinearity characteristics, and the communication system performance. It serves not only as a reliable model for nonlinear distortion analysis but also as a design tool that allows optimization of signal and filter characteristics with respect to nonlinear distortion. [ABSTRACT FROM AUTHOR]

A new technique to calculate an equivalent indirect hysteresis loop, $B_{\mathrm{ ec}}$ – $H$ loop, from the distortion of the voltage measured in the magnetic excitation coil is proposed. The aim is to facilitate the industrial implementation of magnetic characterization reducing hardware and error sources of the measuring system, as pick-up coils and their conditioning stages are not necessary. With the $B_{\mathrm{ ec}}$ – $H$ technique, the characterization of two sets of materials with very different properties using a simplified electromagnetic system has been achieved. Specifically, the change in the microstructure of annealed low-carbon steel samples was monitored and the hardness of ultrahigh steel sheets was characterized. Moreover, the conventional hysteresis cycles and $B_{\mathrm{ ec}}$ – $H$ loops are compared, and the obtained lineal relationships between the parameters derived from conventional hysteresis and $B_{\mathrm{ ec}}$ – $H$ loops verify that the $B_{\mathrm{ ec}}$ – $H$ loops can provide equivalent parameters for magnetic characterization of steel samples as conventional hysteresis loops. [ABSTRACT FROM AUTHOR]

The dynamic range of a radio-over-fiber (RoF) link is fundamentally limited by the linearity of electro-optic modulators. Silicon photonic (SiP) processes offer significant potential for integration, but the plasma dispersion effect impacts the realizable spur-free dynamic range (SFDR). This article analyzes the underlying source of nonlinearity in SiP Mach–Zehnder modulator (MZM) and demonstrates fundamental limitations on intermodulation distortion. A SiGe low-noise distributed driver is co-designed for the SiP MZM to linearize and extend the bandwidth over which the SFDR remains high. The RoF transmitter achieves 1–20 GHz bandwidth and an SFDR of 109 dB $\cdot $ Hz2/3 at 11 GHz. To the best of our knowledge, this is the highest SFDR demonstrated for a SiP technology without incorporating predistortion. [ABSTRACT FROM AUTHOR]

A handy formula is presented to evaluate the effects of random surface errors on average power pattern for distorted reflector antennas. Based on the previous work of Rahmat-Samii on average power pattern degradation for random surface errors, the surface distortion-induced phase error is expanded into a second-order Taylor series expansion in radiation integral. With the probabilistic distribution of phase errors, the closed-form expressions of average power pattern and variance on boresight gain and sidelobe levels are demonstrated by this handy formula. To show the effectiveness of this formula, its applicability region is derived. The derivation clearly shows that when the root-mean-square amplitude of surface distortion is below $\lambda $ /30, the handy formula presents a good agreement with the exact one in boresight gain within a 0.1 dB computational accuracy. Comparing with the previous work, this formula can estimate the boresight gain loss by hand quickly without the exponential calculation, which will benefit the antenna design. [ABSTRACT FROM AUTHOR]

Operational amplifiers (opamps) are often designed in stages. Distortion analysis of multistage opamps is challenging due to multiple non-linearity sources. Therefore, one effective analysis method is to consider a multistage opamp model as a cascade of condensed stages, with each stage modelled by one weakly non-linear element. Then, in order to obtain a satisfactory distortion model, accurate characterisation of the non-linearity of each stage is necessary. In this Letter, the authors propose an analytical calculation method for modelling the weak non-linearity of an amplifier stage consisting of several interconnected transistors. A stage circuit model created by this method can be used to produce analytical harmonic distortion characterisation of closed-loop circuits with peripheral elements. Numerical accuracy of the analytical method has been validated by transistor-level simulation. [ABSTRACT FROM AUTHOR]

Residual stress on the machined surface and the subsurface is known to influence the distortion of thin-walled parts. Therefore, it is essential to predict the distribution of surface residual stress accurately. In this paper, the coupled distribution law of initial residual stress and machining-induced residual stress is investigated. Firstly, a model with initial residual stress is established and incorporated into thermal mechanical coupled finite element model of 2-D cutting. Then, a tensile fixture is designed to impose initial stress into a thin-walled part of Al-6061, and cutting experiments are carried out. The residual stress distribution is measured by X-ray diffraction/electropolishing method. The results of experiments and simulation show that in the plastic deformation zone, the initial residual stress has no significant influence on the distribution of the machining-induced residual stress. In the elastic deformation zone, the stress that linear grows along depth from zero to initial residual stress is superimposed on machining-induced residual stress. The mathematical model of stress coupling distribution on the surface of thin-walled parts is established by numerical method. Finally, it is found that the effect of coupled stress distribution on distortion is more significant with the decrease of thickness (from 3 to 0.5 mm) of the thin-walled parts. [ABSTRACT FROM AUTHOR]

An analytical model based on a theoretical model established in the previous work (part 1) is developed. The analytical model considers the particular case of an instantaneous high-density heat source acting on a thin pre-stressed plate. It calculates the plastic strain and the area of the zone of plastic deformation. A theoretical study is performed in order to quantify the major factors that influence the plastic strain formation. Furthermore, the work presents a calculation procedure for distortion analysis of large and complex structures, intended to be used for solving industrial tasks. The calculation procedure consists of a combination of the analytical solution and an elastic finite element analysis with the aid of the inherent strain approach. Various aspects of its application are also discussed. The calculation procedure is finally explained using a simple example. Its reliability and practicability are demonstrated through verification and validation studies. The work is dedicated to the thermal straightening of thin-walled welded structures; however, it can also be related to other processes. [ABSTRACT FROM AUTHOR]

The work deals with the elastic-plastic thermo-mechanical deformation process after spot heating of large thin plates. It promotes a new theoretical model of the process. The main target is to clarify the kinetics of the plastic strain formation during thermal straightening and to explore the main interactions. For this purpose, a simplified mechanical problem is formulated and applied. As a result, definite thermo-mechanical relations between temperature, initial strain, and accumulated plastic strain are obtained. Finally, a verification study is presented and discussed. The results contribute to extending the knowledge about the process and to establishing a theoretical background for development of applied analytical or analytical-numerical approaches for practical use in the designing and planning phases in welding production. An application to a particular case is described in an accompanying paper (part 2). [ABSTRACT FROM AUTHOR]

This letter briefly presents an interesting set of results from a non-destructive magnetic measurement method named as the distortion analysis of magnetic excitation (DAME). The time derivative of the excitation voltage ( V E ) across the coil around the electromagnetic (EM) yoke plotted as a function of total applied voltage ( V T ) (named as the DAME profile) truly reflects the magnetisation behaviour of the ferromagnetic material introduced between the poles of the EM yoke to close the magnetic flux path. The shape of the DAME profile with a peak and trough clearly reflects the subtle changes in the composition, microstructure, grain orientation and stress through their effect on the magnetisation process in the ferromagnetic material placed between the poles of the EM yoke. This letter shows that the DAME profile measurement is a simple non-destructive evaluation (NDE) method to detect and determine variations in the properties of ferromagnetic materials and has tremendous potential for several applications related to the evaluation of ferromagnetic materials and components. [ABSTRACT FROM AUTHOR]

This paper presents a method to characterize a multi-dimensional polynomial current and charge source models needed for a distortion contribution analysis technique that can identify the dominant nonlinearities and different mixing mechanisms. A separate model characterization step with carefully chosen test signals is used to break the inherent input–output correlation that otherwise complicates the model fitting. The proposed Volterra-on-top-of-harmonic-balance technique and improved polynomial fitting are then verified through the analysis of a 100-W LDMOS RF Doherty amplifier, which showed that, in this circuit, the cubic nonlinearity of the gate capacitance is the main culprit of AM–PM distortion. [ABSTRACT FROM PUBLISHER]

Sodium chromium oxide, NaCrO 2 , has received significant attention as positive electrode (cathode) for Na-ion batteries mainly due the high capacity retention of the material. In this paper, we use operando powder X-ray diffraction to investigate the structural evolution of O3–NaCrO 2 during Na-ion extraction and insertion with use of both liquid and solid-state electrolytes. This reveals a previously overlooked phase transition, causing formation of an unexplored O′3-Na x CrO 2 intermediate during Na-ion extraction (charge). The phase transitions within the electrode are investigated by sequential Rietveld refinement and distortion analysis, which shows that the discovered O′3-Na x CrO 2 intermediate accommodates the increasing interlayer repulsion and in-plane contraction with less distortion of the [NaO 6 ]-polyhedra as compared to the other observed phases. Our structural findings are corroborated by analysis of the Na-ion diffusion coefficients through the galvanostatic intermittent titration technique. Furthermore, the operando powder X-ray diffraction reveals substantial charge-discharge asymmetry with a significant preference for solid-solution and two-phase behavior during charge (Na-extraction) and discharge (Na-insertion), respectively. [Display omitted] • A new intermediate is observed during charge of NaCrO 2 cathodes. • Severe charge-discharge asymmetry is observed in the phase evolution for NaxCrO2. • The asymmetry appears to originate from differences in Na-diffusion coefficients. [ABSTRACT FROM AUTHOR]

The influence of ferritic steel samples with different case-depths on the distortion behaviour of magnetic excitation voltage has been investigated. The systematic changes in the height and position of the peak and the trough on the ((dVE/dt) vs.VT) profile (distortion analysis of the magnetic excitation, DAME profile) reflect the difference in the magnetization process and hence the effect of distortion ofVEin samples with different case-depths. This study shows the potential of this simple DAME method for evaluation of ferromagnetic steel components. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new and accurate experimental method for determining resonant frequencies of MEMS. [•] The method is based on harmonic distortion analysis of MEMS electrical voltage output. [•] Development of electrostatic energy harvesters as test samples. [•] Comparison with measurements carried out by DLTS system are presented. [•] An uncertainty as low as one part in 103 is achievable with this technique. [Copyright &y& Elsevier]

In this paper, we perform the theoretical analysis and experimental demonstration of an on-chip implementation of a Ku-band nanosecond scale time-stretching (TS) system in a 130-nm IBM 8RF CMOS process. The theory of the TS system is applicable to general TS systems. In this study, we explain the impact of the time-bandwidth product (TBP) on practical design considerations and derive the error and distortion of a general TS system based on a dispersive delay line with perfect linear group delay and all pass amplitude characteristic. We also derive the time resolution of a general TS system using both the principle of uncertainty as well as the short time Fourier transform method. This fundamental result enables a designer to understand the qualitative relationship between the TBP and the best possible resolution of the TS system. Finally, we experimentally demonstrate the TS system on chip with nanosecond group-delay variance and 12–16-GHz bandwidth. This demonstration indicates the potential for implementation of more complicated time-scaling signal-processing systems on chip, as well as a quantification of the error and distortion for such systems. [ABSTRACT FROM PUBLISHER]

The Gauss conformal mappings (GCMs) of an oblate ellipsoid of revolution to a sphere are those that transform the meridians into meridians, and the parallels into parallels of the sphere. The infinitesimal-scale function associated with these mappings depends on the geodetic latitude and contains three parameters, including the radius of the sphere. Gauss derived these constants by imposing local optimum conditions on certain parallel. We deal with the problem of finding the constants to minimize the Chebyshev or maximum norm of the logarithm of the infinitesimal-scale function on a given ellipsoidal segment (the region contained between two parallels). We show how to solve this minimax problem using the intrinsic function fminsearch of Matlab. For a particular ellipsoidal segment, we get the solution and show the alternation property characteristic of best Chebyshev approximations. For a pair of points relatively close in the ellipsoid at different latitudes, the best minimax GCM on the segment defined by these points is used to approximate the geodesic distance between them by the spherical distance between their projections on the corresponding sphere. This approach, combined with the best locally GCM if the points are on the same parallel, is illustrated by applying it to some case studies but specially to a 10° × 10° region contained between portions of two parallels and two meridians. In this case, the maximum absolute error of this spherical approximation is equal to 2.9 mm occurring at a distance about 1,360 km. This error decreases up to 0.94 mm on an 8° × 8° region of this type. So, the spherical approximation to the solution of the inverse geodesic problem by best GCM can be acceptable in many practical geodetic activities. [ABSTRACT FROM AUTHOR]

This paper presents an analysis framework for estimating spatio-temporal distortion associated with data-gathering algorithms in sensor networks. We assume that the underlying data field being sensed is spatially and temporally correlated and that the sink node performs real-time reconstruction of the field. Unlike existing work, the proposed analysis framework assumes realistic transmission schemes and network/routing parameters, such as congestion and limited transmission range. Our simulations show that, even for a simple collision-free transmission scheme and regular deployment patterns, the distortion analyses yield starkly different results, compared with the analyses performed in the absence of these assumptions. The analytical method presented in this paper could easily be extended to consider the real-time data-reconstruction problem under different transmission schemes, node distributions, and reconstruction methods. [ABSTRACT FROM AUTHOR]

In this paper, a Volterra analysis built on top of a normal harmonic balance simulation is used for a comprehensive analysis of the causes of AM-PM distortion in a LDMOS RF power amplifier (PA). The analysis shows that any nonlinear capacitors cause AM-PM. In addition, varying terminal impedances may pull the matching impedances and cause phase shift. The AM-PM is also affected by the distortion that is mixed down from the second harmonic. As a sample circuit, an internally matched 30-W LDMOS RF PA is used and the results are compared to measured AM-AM, AM-PM and large-signal S11. [ABSTRACT FROM AUTHOR]

Abstract: A discrete global grid system (DGGS) is a spatial data model that aids in global research by serving as a framework for environmental modeling, monitoring and sampling across the earth at multiple spatial scales. Topological and geometric criteria have been proposed to evaluate and compare DGGSs; two of which, intercell distance and the “cell wall midpoint” criterion, form the basis of this study. We propose evaluation metrics for these two criteria and present numerical results from these measures for several DGGSs. We also consider the impact of different design choices on these metrics, such as predominant tessellating shape, base modeling solid and partition density between recursive subdivisions. For the intercell distance metric, the Fuller–Gray DGGS performs best, while the Equal Angle DGGS performs substantially worse. For the cell wall midpoint metric, however, the Equal Angle DGGS has the lowest overall distortion with the Snyder and Fuller–Gray DGGSs also performing relatively well. Aggregation of triangles into hexagons has little impact on intercell distance measurements, although dual hexagon aggregation results in markedly different statistics and spatial patterns for the cell wall midpoint property. In all cases, partitions on the icosahedron outperform similar partitions on the octahedron. Partition density accounts for little variation. [Copyright &y& Elsevier]

This paper employs a high resolution quantization framework to study the effects of finite-rate quantization of the channel state information (CSI) on the performance of MISO systems over correlated fading channels. The contributions of this paper are twofold. First, as an application of the general distortion analysis, tight lower bounds on the capacity loss of correlated MISO systems due to the finite-rate channel quantization are provided. Closed-form expressions for the capacity loss in high-signal-to-noise ratio (SNR) and low-SNR regimes are also provided, and their analysis reveals that the capacity loss of correlated MISO channels is related to that of i.i.d. fading channels by a simple multiplicative factor which is given by the ratio of the geometric mean to the arithmetic mean of the eigenvalues of the channel covariance matrix. Second, this paper extends the general asymptotic distortion analysis to the important practical problem of suboptimal quantizers resulting from mismatches in the distortion functions, source statistics, and quantization criteria. As a specific application, two types of mismatched MISO CSI quantizers are investigated: quantizers whose codebooks are designed with minimum mean square error (MMSE) criterion but the distortion measure is the ergodic capacity loss (i.e., mismatched design criterion), and quantizers with codebook designed with a mismatched channel covariance matrix (i.e., mismatched statistics). Bounds on the channel capacity loss of the mismatched codebooks are provided and compared to that of the optimal quantizers. Finally, numerical and simulation results are presented and they confirm the tightness of theoretical distortion bounds. [ABSTRACT FROM AUTHOR]

This paper considers the development of a general framework for the analysis of transmit beamforming methods in multiple-antenna systems with finite-rate feedback. Inspired by the results of classical high-resolution quantization theory, the problem of finite-rate quantized communication system is formulated as a general fixed-rate vector quantization problem with side information available at the encoder (or the quantizer) but unavailable at the decoder. The framework of the quantization problem is sufficiently general to include quantization schemes with general non-mean-squared distortion functions and constrained source vectors. Asymptotic distortion analysis of the proposed general quantization problem is provided by extending the vector version of the Bennett's integral. Specifically, tight lower and upper bounds of the average asymptotic distortion are proposed. Sufficient conditions for the achievability of the distortion bounds are also provided and related to corresponding classical fixed-rate quantization problems. The proposed general methodology provides a powerful analytical tool to study a wide range of finite-rate feedback systems. To illustrate the utility of the framework, we consider the analysis of a finite-rate feedback multiple-input single-output (MISO) beamforming system over independent and identically distributed (i.i.d.) Rayleigh flat-fading channels. Numerical and simulation results are presented that further confirm the accuracy of the analytical results. [ABSTRACT FROM AUTHOR]

Magnetotelluric (MT) data, in the form of MT tensors, are used to estimate directly the size and spatial distribution of the electric field in northern England and southern Scotland with the aim of predicting the flow of geomagnetically induced currents (GIC) in power networks in the region. MT and Geomagnetic Deep Sounding data from a number of different field campaigns, at a period of 750 s, are employed. The MT data are cast in the form of telluric vectors, which allow a joint hypothetical event analysis (HEA) of both Geomagnetic Deep Sounding and MT data. This analysis reveals qualitatively the pervasive effects of electric field distortion in the region. Two approaches are taken to understand how the spatial structure of the regional electromagnetic field is affected by local distortions, and what the origin of these distortions might be. The dimensionality, and form of electric field distortion, of the MT tensors is investigated using the Weaver et al. and Bahr classification schemes, and by examining the misfit of a galvanic distortion model as a function of rotation angle. At sites where the galvanic distortion model is found to be appropriate the regional MT tensors are recovered using tensor decomposition techniques. It is found that recovering the regional MT response reconciles the geometry of induced currents implied by the MT data with that of the Magnetic Variation anomalies. Lilley's central impedances are used to calculate rotationally invariant effective telluric responses. In the Southern Uplands the magnitude of the effective telluric response is approximately 0.25-0.5 mV km−1 nT−1, but as the Southern Uplands Fault is approached it rises steadily to 3 mV km−1 nT−1. In the Midland Valley, the effective telluric response is approximately 0.5 mV km−1 nT−1 which rises steadily to 2.5 mV km−1 nT−1 as the Southern Uplands and Highland Boundary Faults are approached to the southeast and northwest, respectively. Therefore, the increase in the magnitude of the effective telluric response correlates with the approach of a major tectonic boundary such as the Southern Uplands Fault. These results show that the induced electric field strength varies considerably throughout the central Scotland region. In addition, the HEA indicates that due to lateral changes in conductivity structure the direction of the electric field deviates significantly from the regional direction implied by the polarization azimuth of the primary geomagnetic induction. Therefore, any attempts to model the flow of GIC in the region need to account for the spatial variation of both the magnitude and azimuth of the electric field. [ABSTRACT FROM AUTHOR]

Abstract: In comparison to state of the art fuel cell stack monitoring techniques, where for reliability and durability reasons either single cell or cell-block voltages are monitored separately, the new approach derives information about critical cell and stack status from the stack sum voltage only. The motivation for the development of such a technology is to establish a strongly simplified and low cost stack diagnosis unit. In comparison to the cell voltage monitoring (CVM) technology, where up to several hundreds voltage channels have to be measured separately or at least in pairs, the effort for wiring, contacting and instrumentation can be reduced dramatically. Critical cell operation occurs, if e.g. low air stoichiometry causes a sharp drop of voltage at a certain cell current. If in such case the current is superimposed by a small amplitude signal with specific frequency pattern, then the system response (i.e. stack voltage) will be distorted in the frequency domain. Particularly, this means that even if only one single cell is in a critical operation mode, it would cause distorted frequency fractions extractable from the entire stack voltage. Since this approach is related to the distortion of the frequency pattern only, noise and EMC issues are not significantly influencing the measuring quality. The instrumentation and processing effort is rather low and can be realized with a low cost DSP board. Measurement results for different critical stack operation modes, e.g. operation at low air or low hydrogen stoichiometry, with their correlation to the frequency distortion will be described and discussed. [Copyright &y& Elsevier]

In this paper, we propose a new spatio-temporal gait representation, called Gait Energy Image (GEI), to characterize human walking properties for individual recognition by gait. To address the problem of the lack of training templates, we also propose a novel approach for human recognition by combining statistical gait features from real and synthetic templates. We directly compute the real templates from training silhouette sequences, while we generate the synthetic templates from training sequences by simulating silhouette distortion. We use a statistical approach for learning effective features from real and synthetic templates. We compare the proposed GEI-based gait recognition approach with other gait recognition approaches on USF HumanlD Database. Experimental results show that the proposed GEI is an effective and efficient gait representation for individual recognition, and the proposed approach achieves highly competitive performance with respect to the published gait recognition approaches. [ABSTRACT FROM AUTHOR]

This paper presents an analysis technique implemented on top of normal harmonic-balance simulation, where the simulated nonlinear voltage and current spectra is used for fitting a polynomial device model around the large-signal bias point. Further, using the fitted model and spectra of the controlling voltages, the detailed structure of the third-order intermodulation distortion is calculated using a simplified form of Volterra analysis. This detailed information can be used to find the dominant causes of distortion and possible cancellation mechanisms, to study the bandwidth-dependent memory effects caused by up- or down-converted mixing results, or to find harmonic matching impedances that minimize the overall distortion. [ABSTRACT FROM AUTHOR]

SOI technology is now emerging as a mature technology applied in the analog IC design, which necessities an accurate model to describe distortion effects. In this paper a compact transistor model is proposed for distortion analysis of fully depleted SOI MOSFET operating in strong inversion regime. In the model, both short channel effects and self-heating effect (unique to SOI due to the buried oxide) are considered. To obtain a concise and accurate model, an approximation method is developed to determine the dominant physical effects in distortion analysis. The model agrees well with the experimental data. [Copyright &y& Elsevier]

• Introduction to a method measuring temperature dependent magnetic properties. • Post-determination of primary microstructure of 50CrMo4 after QT heat treatment. • Precise hardness estimation choosing the right measurement parameters. • Correlation between the effect of different precipitations and magnetic properties. • Categorisation of the effect of eddy-currents on the B-H hysteresis. This work investigates the effect of different initial microstructures on the electromagnetic magnetisation curves/hysteresis of 50CrMo4 steel and technically pure iron introducing a novel measurement method. Surprisingly little is known about the relationship between microstructure and the magnetic properties, although this is of great importance for a better understanding and multi-physics modelling of induction heat treatment. Analysis of the magnetic hysteresis and Distortion Analysis of Magnetic Excitation (DAME) are important techniques to characterise magnetic behaviour of materials. To perform these measurements, a specific measurement setup based on excitation circuit/yoke with secondary coils was implemented. Using these methods, the characterization of the effect of mechanical properties (i.e.: hardness) and different microstructures on electromagnetic magnetisation curves/hysteresis is possible with high precision. The effect of the eddy-currents on the B-H hysteresis shows a systematic behaviour, which opens the possibility for a new kind of categorisation of these effects. DAME shows a closely linear relationship with the assumed precipitation size allowing indirect analysis of the microstructure, also at elevated temperatures. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reduction of hardware requirements for magnetic characterization. • Current controlled magnetization to amplify the distortion. • Algorithm to obtain a high SNR signal representative of the distortion. • Magnetic characterization of skin pass elongation (0.2–8.9%) of IF and DP steels. • Higher sensitivity to skin pass comparing with hysteresis loop and DAME profile. The distortion analysis of magnetic excitation (DAME) method has been recently proposed to facilitate magnetic measurements for non-destructive testing in which pick-up coils are not necessary. This method is based on the distortion effect that the permeability of the sample generates on the voltage across the excitation coil. The aims of the method presented in the present paper are to amplify this distortion effect using a current mode-controlled magnetization and to extract a distortion signal, of high signal-to-noise ratio (SNR), from the voltage measured in the excitation coil by means of a demodulation technique. This methodology is applied to different skin passed steels to characterize the elongation level, which is still a challenge for conventional non-destructive electromagnetic techniques. The relationships between the parameters derived from the distortion and from the hysteresis are studied. Measurements according to the DAME method are performed to verify the improvement in sensitivity for magnetic characterization. [ABSTRACT FROM AUTHOR]