Journal articles: 'Distortion performance'

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Carvalho, Cesar Augusto Belchior, Genaro Mariniello da Silva, Bruna Cardoso Paz, Sylvain Barraud, Maud Vinet, Olivier Faynot, and Marcelo Antonio Pavanello. "Performance and Analysis of n-Type Vertically Stacked Nanowires Regarding Harmonic Distortion." Journal of Integrated Circuits and Systems 15, no. 2 (August 11, 2020): 1–5. http://dx.doi.org/10.29292/jics.v15i2.202.

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This paper studies the harmonic distortion (or non-linearity) of vertically stacked SOI nanosheets with different fin widths and channel lengths. The total harmonic distortion and third order harmonic distortion are used as figures of merit in this work. The four approaches applied verifies the correlation between the harmonic distortions and the variety of transistor’s dimensions available for analysis.

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Ariga, I., S. Masuda, and A. Ookita. "Inducer Stall in a Centrifugal Compressor With Inlet Distortion." Journal of Turbomachinery 109, no. 1 (January 1, 1987): 27–35. http://dx.doi.org/10.1115/1.3262066.

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The effects of inlet distortion on the inducer stall in a centrifugal compressor are investigated. Cases of both radial and circumferential distortion are investigated. It is shown that the rotating stall onset is amplified by radial distortions, and restrained by circumferential distortions. These results are compared with calculations based on the small disturbance theory. The authors find that the stall onset is governed by the characteristic parameters related to the lower flow rate region for radial distortions, but affected by those of the higher flow rate region for circumferential distortion. It is shown that the process of stall is different for each distortion pattern. Existence of inlet distortion reduces compressor performance characteristics and strongly influences the stability margin.

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Pazur, W., and L. Fottner. "The Influence of Inlet Swirl Distortions on the Performance of a Jet Propulsion Two-Stage Axial Compressor." Journal of Turbomachinery 113, no. 2 (April 1, 1991): 233–40. http://dx.doi.org/10.1115/1.2929091.

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Aeroengine intakes containing S-shaped diffusers produce different types of inlet swirl distortions and essentially a combination of a twin swirl and a bulk swirl. The main object of this investigation was to assess the influence of inlet swirl distortions on the performance of a transonic two-stage axial compressor installed in a turbo jet bypass engine Larzac 04. A typical inlet swirl distortion was simulated by a delta-wing in front of the engine. An experimental method was investigated to measure the performance map of the installed low-pressure compressor for different engine operating lines. The influence of an inlet swirl distortion with different strengths on the performance map of the compressor was investigated experimentally. It is shown that the performance parameters decrease and a temperature distortion is generated behind the compressor. As the basis of the theoretical investigations of the performance map, including inlet swirl distortions, a computing model considering four compressors working in parallel was established. The model is based on the idea that an inlet swirl distortion can be substituted by two fundamental types of swirl components, i.e., a bulk swirl corotating, and a bulk swirl counterrotating to the revolution of the compressor. Computed performance maps of the compressor will be discussed and compared with the experimental data.

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Ayub, Munirah, Chin Kim Gan, and Aida Fazliana Abdul Kadir. "Harmonic Performance of Grid-Connected PV System under Various Penetration Levels." Applied Mechanics and Materials 699 (November 2014): 486–91. http://dx.doi.org/10.4028/www.scientific.net/amm.699.486.

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This paper studies the harmonic performance of grid-connected PV system under various penetration levels. The system under study was modelled in MATLAB/Simulink environment. Current and voltage distortions were studied in terms of the percentage of Total Harmonic Distortion (THD) under different PV penetration scenarios. The results showed that the Grid-Connected PV generates a different level of harmonics distortion depending on the PV penetration level that was injected to the grid.

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Narayanan, Ram, Kyle Gallagher, Gregory Mazzaro, Anthony Martone, and Kelly Sherbondy. "Hardware Design of a High Dynamic Range Radio Frequency (RF) Harmonic Measurement System." Instruments 2, no. 3 (August 19, 2018): 16. http://dx.doi.org/10.3390/instruments2030016.

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Radio frequency (RF) circuit elements that are traditionally considered to be linear frequently exhibit nonlinear properties that affect the intended operation of many other RF systems. Devices such as RF connectors, antennas, attenuators, resistors, and dissimilar metal junctions generate nonlinear distortion that degrades primary RF system performance. The communications industry is greatly affected by these unintended and unexpected nonlinear distortions. The high transmit power and tight channel spacing of the communication channel makes communications very susceptible to nonlinear distortion. To minimize nonlinear distortion in RF systems, specialized circuits are required to measure the low level nonlinear distortions created from traditionally linear devices, i.e., connectors, cables, antennas, etc. Measuring the low-level nonlinear distortion is a difficult problem. The measurement system requires the use of high power probe signals and the capability to measure very weak nonlinear distortions. Measuring the weak nonlinear distortion becomes increasingly difficult in the presence of higher power probe signals, as the high power probe signal generates distortion products in the measurement system. This paper describes a circuit design architecture that achieves 175 dB of dynamic range which can be used to measure low level harmonic distortion from various passive RF circuit elements.

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Verma, Vishwas, Gursharanjit Singh, and AM Pradeep. "The effect of inlet distortion on low bypass ratio turbofan engines." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 234, no. 8 (March 2, 2020): 1395–413. http://dx.doi.org/10.1177/0954410020909190.

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Inlet flow non-uniformity, commonly known as inflow distortion, has been a long-standing problem in the history of gas turbine engines. Distortion can be present in the form of total pressure, total temperature or inflow incidence or any combinations of these. The search for better and robust performance requires engines that can sustain a large amount of inlet distortion without considerable loss in the thrust. In the present paper, the effect of total pressure distortion on a single-stage compressor and low bypass ratio fans are studied. Distortion near hub and tip in the form of step radial total pressure profiles is imposed at far upstream of the rotor leading edge. A systematic approach to qualitatively predict the performance maps in the presence of these distortions is discussed. Further, two extents of total pressure distortion are explored for constant inlet distortion intensity. Hub distortion is found to increase the stability margin, whereas tip distortion reduces it. On extending the distortion extent, hub distortion drastically reduces the stability margin, whereas a comparatively lower reduction in stability margin with tip distortion is observed. The critical distortion limit is observed by varying the inlet distortion extent. Also, it is found that downstream ducts in the bypass axial fan do not interact with the upstream fan. This can be exploited to perform independent simulations of the core engine from low bypass ratio fans. Hub distortion is found to drastically affect the duct performance owing to the presence of thicker upstream inlet boundary layer.

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Huan, S. L., and A. R. Pater. "Analysis and prediction of geophone performance parameters." GEOPHYSICS 50, no. 8 (August 1985): 1221–28. http://dx.doi.org/10.1190/1.1441994.

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In the past, designers relied greatly on simplified geophone models to describe the physical quantities of a geophone. Several iterations of fine tuning the geophone variables were required to achieve a desired geophone characteristic. Although many geophone prototypes were built before a geophone design was finalized, it was still impossible to assure an optimum geophone design. An easier, faster, and more accurate method of predicting geophone parameters is described and the method of computer‐aided geophone design is outlined. A description of a nonlinear geophone model is presented and a numerical method to compute the nonlinear magnetic flux density distribution is outlined. An integration algorithm is used to compute the geophone sensitivity and open‐circuit damping. The measurement of geophone distortion is described, and the harmonic distortion due to nonlinearity of sensitivity and damping is computed. The data of a geophone spring constant were obtained through a recent experiment, and the harmonic distortions caused by the nonlinearity of the spring are computed. Finally, the total harmonic distortion of a geophone is obtained. Programs developed to predict geophone sensitivity, damping, and distortion are described. It is shown that the method used to compute the nonlinear flux density distribution converges properly and the results obtained are meaningful. Three different types of geophones are analyzed and a comparison between the simulated and measured data is made. In all three cases, good correlation exists between the parameters predicted and the parameters actually measured. Information obtained by geophone parameter prediction can be very useful in the geophone design process, in optimizing geophones, and in achieving higher performance levels.

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Mistry, Chetan, and A. M. Pradeep. "Experimental Study of the Effect of Radially Distorted Inflow on a Contrarotating Fan Stage." International Journal of Rotating Machinery 2014 (2014): 1–14. http://dx.doi.org/10.1155/2014/503579.

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The paper reports results of a detailed study of hub- and tip-strong radial inflow distortion on the performance of a low speed, high aspect ratio (3.0) contrarotating fan stage. The distortion screen (placed upstream of the first rotor) covers 1/3 of the span of the blade near the hub and the casing for hub-strong and tip-strong inflow distortions, respectively. The performance of the contrarotating fan was investigated under both the radially distorted inflows and compared with the clean inflow conditions under different speed combinations of rotor-1 and rotor-2. The hub-strong radial distortion reduces the overall performance (pressure rise and efficiency) as well as the operating range by about 2 to 4% under the different speed combinations. On the other hand, it is interesting to observe that the tip covered radial distortion not only improves the pressure rise, but also increases the overall operating range by about 6 to 8%. There was, however, a 6 to 8% decrease in efficiency in this case as compared to 12 to 15% for hub-strong radial inflow distortion. The results reveal the physics of the effects of radial inflow distortion on the overall performance of the contrarotating fan stage.

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Chen, Xiaohong, Qian Sun, and Jun Hu. "Generation of Complete SAR Geometric Distortion Maps Based on DEM and Neighbor Gradient Algorithm." Applied Sciences 8, no. 11 (November 9, 2018): 2206. http://dx.doi.org/10.3390/app8112206.

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Radar-specific imaging geometric distortions (including foreshortening, layover, and shadow) that occur in synthetic aperture radar (SAR) images acquired over mountainous areas have a negative impact on the suitability of the interferometric SAR (InSAR) technique to monitor landslides. To address this issue, many distortion simulation methods have been presented to predict the areas in which distortions will occur before processing the SAR image. However, the layover and shadow regions are constituted by active as well as passive subregions. Since passive distortions are caused by active distortions and can occur in the flat area, it is difficult to distinguish the transition zone between passive distortion and non-distortion areas. In addition, passive distortion could cover part of the foreshortening or active layover/shadow areas but has generally been ignored. Therefore, failure to simulate passive distortion leads to incomplete simulated distortions. In this paper, an algorithm to define complete SAR geometric distortions and correct the boundaries among different distortions is presented based on the neighbor gradient between the passive and active distortions. It is an image-processing routine applied to a digital elevation model (DEM) of the terrain to be imaged by the available SAR data. The performance of the proposed method has been validated by the ascending and descending Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR) images acquired over the Chongqing mountainous area of China. Through the investigation of passive distortion, we can have a deeper understanding of the formation and characteristics of these distortions. Moreover, it provides very meaningful information for research on areas such as landslide monitoring.

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EBERLEIN, ERNST, and DILIP B. MADAN. "HEDGE FUND PERFORMANCE: SOURCES AND MEASURES." International Journal of Theoretical and Applied Finance 12, no. 03 (May 2009): 267–82. http://dx.doi.org/10.1142/s0219024909005282.

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The concept of the gamma of a financed return as the highest level of stress that a return distribution can withstand is introduced. Stress is measured by positive expectation under a concave distortion of the return distribution accessed. Four distortions introduced in Cherny and Madan (2008) are employed in studying the distribution of returns available in the hedge fund universe. It is shown that the skewness, peakedness and tailweightedness of the standardized investment return significantly affects the Sharpe ratios required to reach a target gamma level.

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Haley, Katarina L., Adam Jacks, Jessica D. Richardson, and Julie L. Wambaugh. "Perceptually Salient Sound Distortions and Apraxia of Speech: A Performance Continuum." American Journal of Speech-Language Pathology 26, no. 2S (June 22, 2017): 631–40. http://dx.doi.org/10.1044/2017_ajslp-16-0103.

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Purpose We sought to characterize articulatory distortions in apraxia of speech and aphasia with phonemic paraphasia and to evaluate the diagnostic validity of error frequency of distortion and distorted substitution in differentiating between these disorders. Method Study participants were 66 people with speech sound production difficulties after left-hemisphere stroke or trauma. They were divided into 2 groups on the basis of word syllable duration, which served as an external criterion for speaking rate in multisyllabic words and an index of likely speech diagnosis. Narrow phonetic transcriptions were completed for audio-recorded clinical motor speech evaluations, using 29 diacritic marks. Results Partial voicing and altered vowel tongue placement were common in both groups, and changes in consonant manner and place were also observed. The group with longer word syllable duration produced significantly more distortion and distorted-substitution errors than did the group with shorter word syllable duration, but variations were distributed on a performance continuum that overlapped substantially between groups. Conclusions Segment distortions in focal left-hemisphere lesions can be captured with a customized set of diacritic marks. Frequencies of distortions and distorted substitutions are valid diagnostic criteria for apraxia of speech, but further development of quantitative criteria and dynamic performance profiles is necessary for clinical utility.

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Ng, Eddie Yin-Kwee, Ningyu Liu, Hong Ngiap Lim, and Daniel Tan. "An Improved Integral Method for Prediction of Distorted Inlet Flow Propagation in Axial Compressor." International Journal of Rotating Machinery 2005, no. 2 (2005): 117–27. http://dx.doi.org/10.1155/ijrm.2005.117.

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An improved integral method is proposed and developed for the quantitative prediction of distorted inlet flow propagation through axial compressor. The novel integral method is formulated using more appropriate and practical airfoil characteristics, with less assumptions needed for derivation. The results indicate that the original integral method (Kim et al., 1996) underestimated the propagation of inlet flow distortion. The effects of inlet flow parameters on the propagation of inlet distortions as well as on the compressor performance and characteristic are simulated and analyzed. From the viewpoint of compressor efficiency, the propagation of inlet flow distortion is further described using a compressor critical performance and its associated critical characteristic. The results present a realistic physical insight to an axial-flow compressor behavior with a propagation of inlet distortion.

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Sankisa, Arun, Katerina Pandremmenou, Peshala V. Pahalawatta, Lisimachos P. Kondi, and Aggelos K. Katsaggelos. "SSIM-Based Distortion Estimation for Optimized Video Transmission over Inherently Noisy Channels." International Journal of Multimedia Data Engineering and Management 7, no. 3 (July 2016): 34–52. http://dx.doi.org/10.4018/ijmdem.2016070103.

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The authors present two methods for examining video quality using the Structural Similarity (SSIM) index: Iterative Distortion Estimate (IDE) and Cumulative Distortion using SSIM (CDSSIM). In the first method, three types of slices are iteratively reconstructed frame-by-frame for three different combinations of packet loss and the resulting distortions are combined using their probabilities to give the total expected distortion. In the second method, a cumulative measure of the overall distortion is computed by summing the inter-frame propagation impact to all frames affected by a slice loss. Furthermore, the authors develop a No-Reference (NR) sparse regression framework for predicting the CDSSIM metric to circumvent the real-time computational complexity in streaming video applications. The two methods are evaluated in resource allocation and packet prioritization schemes and experimental results show improved performance and better end-user quality. The accuracy of the predicted CDSSIM values is studied using standard performance measures and a Quartile-Based Prioritization (QBP) scheme.

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Hannan, R. Lynn, Gregory P. McPhee, Andrew H. Newman, and Ivo D. Tafkov. "The Effect of Relative Performance Information on Performance and Effort Allocation in a Multi-Task Environment." Accounting Review 88, no. 2 (September 1, 2012): 553–75. http://dx.doi.org/10.2308/accr-50312.

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ABSTRACT This study investigates how relative performance information (RPI) affects employee performance and allocation of effort across tasks in a multi-task environment. Based on behavioral theories, we predict that the social comparison process inherent in RPI induces both a motivation effect that results in increased effort as well as an effort distortion effect that results in the distortion of effort allocations across tasks away from the firm-preferred allocations. We also predict that both effects are magnified when the RPI is public compared to private. We argue that although the motivation effect will generally benefit performance, the effort distortion effect may be detrimental to performance. We design an experiment that isolates these two effects. Consistent with our predictions, we find that RPI induces both motivation and effort distortion effects and that both effects are magnified when the RPI is public rather than private. Although the motivation effect increases performance, we demonstrate that the effort distortion effect can decrease performance. By isolating the motivation and effort distortion effects, our study provides insights into the costs and benefits of RPI in a multi-task environment. As such, it informs accountants regarding the design of information systems and when tasks should be aggregated or disaggregated across employees. Data Availability: Data are available from the authors upon request.

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Jia, Cheng, and Hui Hui Chen. "Study of Performance of US-FE-LSPIM QUAD4 Element on Mesh Distortion." Advanced Materials Research 490-495 (March 2012): 3008–12. http://dx.doi.org/10.4028/www.scientific.net/amr.490-495.3008.

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This US-FE-LSPIM QUAD4 element is formed by using two different sets of shape functions for the trial and test functions, viz. sets of FE-LSPIM QUAD4 element shape functions and sets of classical isoparametric shape functions. For some test problems, the US-FE-LSPIM QUAD4 element has good accuracy. And by compared with FE-LSPIM QUAD4 element, the proposed element does not need to use Penalty method or Lagrange multiplier method to ensure fulfilment of exact essential boundary condition along the entire length of the edge. This paper further studies the performance of US-FE-LSPIM QUAD4 element on mesh distortion. Numerical test examples show that the element exhibits high precisions even under the mesh distortions. The US-FE-LSPIM QUAD4 element displays good tolerance to the mesh distortions

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Ji, Bingyu, Ran Li, and Changan Wu. "Rate-Distortion and Rate-Energy-Distortion Evaluations of Compressive-Sensing Video Coding." International Journal of Digital Multimedia Broadcasting 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/4589124.

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Compressive-Sensing Video Coding (CSVC) is a new video coding framework based on compressive-sensing (CS) theory. This paper presents the evaluations on rate-distortion performance and rate-energy-distortion performance of CSVC by comparing it with the popular hybrid video coding standard H.264 and distributed video coding (DVC) system DISCOVER. Experimental results show that CSVC achieves a poor rate-distortion performance when compared with H.264 and DISCOVER, but its rate-energy-distortion performance has a distinct advantage; moreover, its energy consumption of coding is approximately invariant regardless of reconstruction quality. It can be concluded that, with a limited energy budget, CSVC outperforms H.264 and DISCOVER, but its rate-distortion performance still needs improvement.

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YANG, YU-PING. "Recent Advances in the Prediction of Weld Residual Stress and Distortion - Part 1." Welding Journal 100, no. 5 (May 1, 2021): 151–70. http://dx.doi.org/10.29391/2021.100.013.

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Residual stresses and distortions are the result of complex interactions between welding heat input, the material’s high-temperature response, and joint constraint conditions. Both weld residual stress and distortion can significantly impair the performance and reliability of welded structures. In the past two decades, there have been many significant and exciting developments in the prediction and mitigation of weld residual stress and distortion. This paper reviews the recent advances in the prediction of weld residual stress and distortion by focusing on the numerical modeling theory and methods. The prediction methods covered in this paper include a thermo-mechanical-metallurgical method, simplified analysis methods, friction stir welding modeling methods, buckling distortion prediction methods, a welding cloud computational method, integrated manufacturing process modeling, and integrated computational materials engineering (ICME) weld modeling. Remaining challenges and new developments are also discussed to guide future predictions of weld residual stress and distortion.

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Wang, Yun Qiao, Zhong Yi Mei, and Yu Qing Fan. "Research on Machining Distortion due to Residual Stresses of Large Monolithic Beam." Advanced Materials Research 433-440 (January 2012): 530–37. http://dx.doi.org/10.4028/www.scientific.net/amr.433-440.530.

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Machining-induced distortion of large monolithic parts with thin walled structures creates problems in aircraft manufacturing industry. Typical monolithic beams of airframe are machined by NC machine and machining distortions are recorded. Thin walled structures are prone to distortions and dimensional instabilities due to internal stresses; therefore, stress-relieved vibration method is applied to reduce the internal stresses in blank material and results in better machining performance and dimension stability. But vibration stress-relief method doesn’t work always due to unknown reasons. Machining simulations in ANSYS are performed to predict the residual stress-induced machining distortion and simulation result is compared with the machining measurements to validate the simulation process. Cutting simulations have been executed by the element deactivation technique after developing the initial residual stresses via sequential coupled field analysis. The possibility of residual stress being relieved more reasonably and less distortion by optimized machining sequence through simulation is discussed.

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Schumacher, Johannes M. "Distortion risk measures, ROC curves, and distortion divergence." Statistics & Risk Modeling 35, no. 1-2 (January 1, 2018): 35–50. http://dx.doi.org/10.1515/strm-2017-0012.

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AbstractDistortion functions are employed to define measures of risk. Receiver operating characteristic (ROC) curves are used to describe the performance of parametrized test families in testing a simple null hypothesis against a simple alternative. This paper provides a connection between distortion functions on the one hand, and ROC curves on the other. This leads to a new interpretation of some well-known classes of distortion risk measures, and to a new notion of divergence between probability measures.

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Ashajyothi, P., V. Bhasvitha, Harish Balakumar, P. V. Manitha, and Anjana Jain. "Power Quality Improvement in 3-Phase Power System Using Artificial Neural Network Based Hybrid Filter." Journal of Computational and Theoretical Nanoscience 17, no. 1 (January 1, 2020): 396–401. http://dx.doi.org/10.1166/jctn.2020.8681.

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Harmonic-distortion is a serious problem in power systems involving linear and non-linear loads. Adding a passive-filter to the system is the most popular choice to reduce issues due to harmonic distortion. Passive-filter cannot eliminate all the harmonic components. A hybrid-filter, in which shunt active filter is serially integrated with shunt passive filter can provide better solution to the problems causing due to harmonic distortions. The paper proposes a hybrid filter with Artificial Neural Network (ANN) based control scheme. A detailed study is done by developing a Simulink model for the proposed. Here in this paper, % Total-Harmonic-Distortion (THD) of compensated load-current is referred as a performance measure of the system. Also, a controller based on ANN is fabricated for the proposed scheme and through analysis in depth is carried out, this controller performance is found comparatively satisfactory.

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Fimbombaya, Haji Said, Nerey H. Mvungi, Ndyetabura Y. Hamisi, and Hashimu U. Iddi. "Performance Evaluation of Magnetic Wireless Sensor Networks Algorithm for Traffic Flow Monitoring in Chaotic Cities." Modelling and Simulation in Engineering 2018 (October 16, 2018): 1–11. http://dx.doi.org/10.1155/2018/2591304.

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Traffic flow monitoring involves the capturing and dissemination of real-time traffic flow information for a road network. When a vehicle, a ferromagnetic object, travels along a road, it disturbs the ambient Earth’s magnetic field, causing its distortion. The resulting distortion carries vehicle signature containing traffic flow related information such as speed, count, direction, and classification. To extract such information in chaotic cities, a novel algorithm based on the resulting magnetic field distortion was developed using nonintrusive sensor localization. The algorithm extracts traffic flow information from resulting magnetic field distortions sensed by magnetic wireless sensor nodes located on the sides of the road. The model magnetic wireless sensor networks algorithm for local Earth’s magnetic field performance was evaluated through simulation using Dar es Salaam City traffic flow conditions. Simulation results for vehicular detection and count showed 93% and 87% success rates during normal and congested traffic states, respectively. Travel Time Index (TTI) was used as a congestion indicator, where different levels of congestion were evaluated depending on the traffic state with a performance of 87% and 88% success rates during normal and congested traffic flow, respectively.

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Stefanov, Andrej. "Distortion Performance of Underwater Acoustic Sensor Networks." International Journal of Distributed Sensor Networks 2015 (2015): 1–6. http://dx.doi.org/10.1155/2015/352569.

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The paper studies the distortion performance of multihop underwater acoustic sensor networks. The network is composed of bottom mounted sensor nodes and the sensor to sensor links experience Rician fading. The distortion is evaluated for the case when there is interference from other sensors in the network. The focus is on the sustainable number of hops in the network for a maximum allowed (target) route distortion requirement. Numerical examples are provided that illustrate the results of the analysis and the regions where the network operation is limited, namely, the coverage-limited region and the interference-limited region. The paper also considers the impact of retransmissions on the distortion performance. It is found that the network connectivity and robustness improve with automatic repeat request (ARQ). The improvements are manifested as a reduction of the regions of limited performance, that is, an increase of the region where the network exhibits full connectivity. The analysis results are illustrated through numerical examples.

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Shi, Lin, Baofeng Guo, Ning Han, Juntao Ma, Xiaoxiu Zhu, and Chaoxuan Shang. "Bistatic-ISAR Linear Geometry Distortion Alleviation of Space Targets." Electronics 8, no. 5 (May 20, 2019): 560. http://dx.doi.org/10.3390/electronics8050560.

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The linear geometry distortion caused by time variant bistatic angles induces the sheared shape of the bistatic inverse synthetic aperture radar (bistatic-ISAR) image. A linear geometry distortion alleviation algorithm for space targets in bistatic-ISAR systems is presented by exploiting prior information. First, we analyze formation mathematics of linear geometry distortions in the Range Doppler (RD) domain. Second, we estimate coefficients of first-order polynomial of bistatic angles by least square error (LSE) method through exploiting the imaging geometry and orbital information of space targets. Third, we compensate the linear spatial-variant terms to restore the linear geometry distortions. Consequently, the restored bistatic-ISAR image with real shape is obtained. Simulated results of the ideal point scatterers dataset and electromagnetic numerical dataset verify the performance of the proposed algorithm.

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Taghavi Zenouz, Reza, Mehran Eshaghi Sir, and Mohammad Hosein Ababaf Behbahani. "Performance of a Low Speed Axial Compressor Rotor Blade Row under Different Inlet Distortions." Mechanical Sciences 8, no. 1 (May 31, 2017): 127–36. http://dx.doi.org/10.5194/ms-8-127-2017.

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Abstract. Responses of an axial compressor isolated rotor blade row to various inlet distortions have been investigated utilizing computational fluid dynamic technique. Distortions have been imposed by five screens of different geometries, but with the same blockage ratio. These screens were embedded upstream of the rotor blade row. Flow fields are simulated in detail for compressor design point and near stall conditions. Performance curves for distorted cases are extracted and compared to the undisturbed case. Flow simulations and consequent performance characteristics show that the worst cases belong to non-symmetric blockages, i.e., those of partial circumferential configurations. These cases produce the largest wakes which can disturb the flow, considerably. Superior performances correspond to the inner and outer continuous circumferential distortion screens. Since, they produce no significant disturbances to the main flow in comparison to the non-symmetric screens.

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Suwandee, Senee, Arumona Edward Arumona, Kanad Ray, Phichai Youplao, and Preecha Yupapin. "Mindfulness Model Using Polariton Oscillation in Plasmonic Circuit for Human Performance Management." Axioms 9, no. 3 (July 8, 2020): 76. http://dx.doi.org/10.3390/axioms9030076.

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We have proposed that human life is formed on a space and time function relationship basis, which is distorted after fertilization in the ovum, from which growth is generated by a space–time distortion against the universe’s gravity. A space–time distortion’s reduction can be managed by space and time separation, which is known as mindfulness. A space–time distortion in human cells is configured by a polariton traveling in a gold grating film, which can be employed to investigate mindfulness characteristics. Mindfulness is the steady state of the time function of energy after the separation. Energy levels of mindfulness based on polariton aspects are categorized by a quantum number (n), which can be reduced to be a two-level system called Rabi oscillation by a successive filtering method. We have assumed a cell space–time distortion can reduce to reach the original state, which is the stopping state. Mindfulness with a certain frequency energy level of n = 2 was achieved. Several techniques in the practice of mindfulness based on successive filtering called meditation are given and explained, where the required levels of the mindfulness state can be achieved. The criteria of the proposed method are a low energy level (n) and high frequency (f) outputs, which can apply to having a working performance improvement.

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Zeng, Gao-rong, Zheng-ding Qiu, and Chun-e. Zhang. "Performance Analysis of Distortion-Compensated QIM Watermarking." JOURNAL OF ELECTRONICS INFORMATION & TECHNOLOGY 2010, no. 1 (February 8, 2010): 86–91. http://dx.doi.org/10.3724/sp.j.1146.2008.01774.

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Meng, Tianzhu, and John R. Buck. "Rate Distortion Bounds on Passive Sonar Performance." IEEE Transactions on Signal Processing 58, no. 1 (January 2010): 326–36. http://dx.doi.org/10.1109/tsp.2009.2031281.

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Meng, Tianzhu, and John R. Buck. "Rate distortion bounds for passive sonar performance." Journal of the Acoustical Society of America 118, no. 3 (September 2005): 1967. http://dx.doi.org/10.1121/1.4781677.

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Stefanov, Andrej. "Distortion performance of underwater acoustic mobile networks." Journal of Ocean Engineering and Science 3, no. 4 (December 2018): 382–89. http://dx.doi.org/10.1016/j.joes.2018.11.004.

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García-Gracia, M., N. El Halabi, A. Montañés, H. M. Khodr, and M. Villén. "Improvement of DEA performance against harmonic distortion." Electric Power Systems Research 80, no. 5 (May 2010): 582–91. http://dx.doi.org/10.1016/j.epsr.2009.10.012.

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Sohail, Muhammad Umer, Hossein Raza Hamdani, Asad Islam, Khalid Parvez, Abdul Munem Khan, Usman Allauddin, Muhammad Khurram, and Hassan Elahi. "Prediction of Non-Uniform Distorted Flows, Effects on Transonic Compressor Using CFD, Regression Analysis and Artificial Neural Networks." Applied Sciences 11, no. 8 (April 20, 2021): 3706. http://dx.doi.org/10.3390/app11083706.

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Non-uniform inlet flows frequently occur in aircrafts and result in chronological distortions of total temperature and total pressure at the engine inlet. Distorted inlet flow operation of the axial compressor deteriorates aerodynamic performance, which reduces the stall margin and increases blade stress levels, which in turn causes compressor failure. Deep learning is an efficient approach to predict catastrophic compressor failure, and its stability for better performance at minimum computational cost and time. The current research focuses on the development of a transonic compressor instability prediction tool for the comprehensive modeling of axial compressor dynamics. A novel predictive approach founded by an extensive CFD-based dataset for supervised learning has been implemented to predict compressor performance and behavior at different ambient temperatures and flow conditions. Artificial Neural Network-based results accurately predict compressor performance parameters by minimizing the Root Mean Square Error (RMSE) loss function. Computational results show that, as compared to the tip radial pressure distortion, hub radial pressure distortion has improved the stability range of the compressor. Furthermore, the combined effect of pressure distortion with the bulk flow has a qualitative and deteriorator effect on the compressor.

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Guo, Jin, and Jun Hu. "Development of body force model for steady inlet distortions in high-speed multistage compressor." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 231, no. 9 (July 7, 2016): 1650–59. http://dx.doi.org/10.1177/0954410016656880.

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This study aims at establishing a three-dimensional numerical model, compressor aerodynamic performance analysis model, to simulate the impact of complicated distorted flow on multistage axial flow compressor based on the body force model. The model solves the compressible three-dimensional Euler equations, which are modified to include source terms representing the effect of the blade rows. In this study, the association between blade source terms and entry Mach number together with attack angle could be established with the deviation angle model and loss model. In this paper, compressor aerodynamic performance analysis model is used to evaluate the effect of inlet circumferential total pressure distortion and swirl distortion on a five-stage high-pressure compressor. Calculated operating maps for compressor agree well with the experimental results. Meanwhile, the traveling process of inlet distortions in the multistage compressor is correctly revealed. The wide application prospect of the model can be seen in the area of inlet distortion problems.

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Belchior, Fernando Nunes, Paulo Fernando Ribeiro, and Frederico Marques Carvalho. "Comparative Analysis of Instruments Measuring Time Varying Harmonics." International Journal of Emerging Electric Power Systems 17, no. 4 (August 1, 2016): 463–69. http://dx.doi.org/10.1515/ijeeps-2015-0175.

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Abstract This paper aims to evaluate the performance of commercial class A and class S power quality (PQ) instruments when measuring time-varying harmonics. By using a high precision programmable voltage and current source, two meters from different manufacturers are analyzed and compared. Three-phase voltage signals are applied to PQ instruments, considering 3 situations of time-varying harmonic distortions, whose harmonic distortion values are in accordance with typical values found in power systems. This work is relevant considering that international standardization documents do not pay much attention to this aspect of harmonic distortion.

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Meriläinen, Esa. "Comparative Measurements on Loudspeaker Distortion: Current vs. Voltage Control." Archives of Acoustics 42, no. 1 (March 1, 2017): 71–81. http://dx.doi.org/10.1515/aoa-2017-0008.

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Abstract Modulation and harmonic distortion produced by ordinary moving-coil direct-radiator drive units are measured under current control and voltage control. A realistic two-tone test signal is used to investigate the detrimental effect of the voice coil electromotive forces on the voltage-to-current conversion that is critical with voltage control. Dramatic improvements in distortion performance are obtained with current control. Current nonlinearities in voltage-controlled speakers are shown to be the dominant source of modulation and odd harmonic distortions at signal frequencies above the fundamental resonance region. Currents in conductive voice coil formers also seem to be significant sources of distortion; with current control and non-conductive formers, odd harmonics and related modulation products virtually vanished in the upper midrange.

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Jayati, Ari Endang, Wirawan, Titiek Suryani, and Endroyono. "Nonlinear Distortion Cancellation using Predistorter in MIMO-GFDM Systems." Electronics 8, no. 6 (June 1, 2019): 620. http://dx.doi.org/10.3390/electronics8060620.

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Generalized frequency division multiplexing (GFDM) with offset quadrature amplitude modulation (OQAM) is an alternative non-orthogonal modulation scheme for future generation wireless broadband systems. The nonlinearity of high power amplifiers (HPAs) has a very significant effect on the performance of GFDM systems. In this paper, we investigate the effects of nonlinear distortion on the multiple-input multiple-output (MIMO)-GFDM system when the signal is passed the HPA, which is modeled with amplitude and phase distortion. The effects of nonlinear distortion due to the HPA include amplitude distortion, phase distortion, and the spread of signal constellations. These effects also produce harmonic signals and intermodulation outside the frequency band which results in spectral spread. This will then reduce the performance of the MIMO-GFDM system. The contributions of this paper concern three key areas. Firstly, we investigate the effects of nonlinear distortion on the MIMO-GFDM system. We also derive the new closed-form expression bit error rate (BER) in MIMO-GFDM systems that use a memoryless HPA, which is modeled using the Saleh model when passed through the additive white Gaussian noise (AWGN) channel. This model was chosen because it is simple and has AM/AM and AM/PM curves. Secondly, we propose the application of techniques for the linearization of each HPA predistorter on the transmitter side of the MIMO-GFDM system separately. This predistorter is able to compensate for nonlinear distortion caused by the HPA without memory operating in the saturation region. The main contribution of this paper is to investigate the predistorter, which can linearize nonlinear distortion in MIMO-GFDM transmitters. The performance of the proposed scheme is evaluated in terms of spectrum analysis, PAPR analysis, a constellation diagram, and bit error rate (BER) analysis. The simulation results show that the proposed predistorter design succeeds in compensating for nonlinear distortions caused by the HPA for large input back-off (IBO) values.

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Martínez-Rach, Miguel O., Pablo Piñol, Otoniel M. López, Manuel Perez Malumbres, José Oliver, and Carlos Tavares Calafate. "On the Performance of Video Quality Assessment Metrics under Different Compression and Packet Loss Scenarios." Scientific World Journal 2014 (2014): 1–18. http://dx.doi.org/10.1155/2014/743604.

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When comparing the performance of video coding approaches, evaluating different commercial video encoders, or measuring the perceived video quality in a wireless environment, Rate/distortion analysis is commonly used, where distortion is usually measured in terms of PSNR values. However, PSNR does not always capture the distortion perceived by a human being. As a consequence, significant efforts have focused on defining an objective video quality metric that is able to assess quality in the same way as a human does. We perform a study of some available objective quality assessment metrics in order to evaluate their behavior in two different scenarios. First, we deal with video sequences compressed by different encoders at different bitrates in order to properly measure the video quality degradation associated with the encoding system. In addition, we evaluate the behavior of the quality metrics when measuring video distortions produced by packet losses in mobile ad hoc network scenarios with variable degrees of network congestion and node mobility. Our purpose is to determine if the analyzed metrics can replace the PSNR while comparing, designing, and evaluating video codec proposals, and, in particular, under video delivery scenarios characterized by bursty and frequent packet losses, such as wireless multihop environments.

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PNEVMATIKAKIS, ARISTODEMOS, SPYROS BLIONAS, and DIMITRIS TRIANTIS. "PHYSICAL LAYER OF A BASE-BAND OFDM MODEM: ALGORITHMS AND PERFORMANCE." Journal of Circuits, Systems and Computers 14, no. 03 (June 2005): 631–51. http://dx.doi.org/10.1142/s0218126605002489.

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The base-band section of a modem employing Orthogonal Frequency Division Multiplexing (OFDM) is described in this paper. It utilizes the necessary algorithms to combat distortion due to the channel conditions and imperfect synchronization. A model describing these distortions is used to derive the algorithms. The system is realized in a prototype platform for the HIPERLAN/2 standard, but modifications for compliance to other broadband digital broadcasting and wireless networking OFDM systems are proposed. The performance of the prototype base-band modem is described.

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Zhang, Hang, Xiangjuan Ren, and Laurence T. Maloney. "The bounded rationality of probability distortion." Proceedings of the National Academy of Sciences 117, no. 36 (August 25, 2020): 22024–34. http://dx.doi.org/10.1073/pnas.1922401117.

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In decision making under risk (DMR) participants’ choices are based on probability values systematically different from those that are objectively correct. Similar systematic distortions are found in tasks involving relative frequency judgments (JRF). These distortions limit performance in a wide variety of tasks and an evident question is, Why do we systematically fail in our use of probability and relative frequency information? We propose a bounded log-odds model (BLO) of probability and relative frequency distortion based on three assumptions: 1) log-odds: probability and relative frequency are mapped to an internal log-odds scale, 2) boundedness: the range of representations of probability and relative frequency are bounded and the bounds change dynamically with task, and 3) variance compensation: the mapping compensates in part for uncertainty in probability and relative frequency values. We compared human performance in both DMR and JRF tasks to the predictions of the BLO model as well as 11 alternative models, each missing one or more of the underlying BLO assumptions (factorial model comparison). The BLO model and its assumptions proved to be superior to any of the alternatives. In a separate analysis, we found that BLO accounts for individual participants’ data better than any previous model in the DMR literature. We also found that, subject to the boundedness limitation, participants’ choice of distortion approximately maximized the mutual information between objective task-relevant values and internal values, a form of bounded rationality.

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Nie, Liang, Cun Li Duan, and Xu Jiang. "Improving Anti-Distortion Performance of Joint Transform Correlator." Applied Mechanics and Materials 55-57 (May 2011): 1242–46. http://dx.doi.org/10.4028/www.scientific.net/amm.55-57.1242.

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The optical joint transform correlator (JTC) has been used in target real-time recognition, but the anti-distortion performance has always been the difficult problem for recognition system, which limits its further development and application. In this paper the principle and experimental system of JTC are introduced. The effect of target distortion is analyzed and the optimization method is proposed. The synthetic discriminate function and the power subtraction are applied to process the joint power spectrum and eliminate zero-order correlation peak. The result shows that the optimization methods can enhance the output peaks and improve the anti-distortion performance of joint transform correlator for target identification.

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Mahmood, Saifeldeen Abdalmajeed. "Three Different Features Based Metric To Assess Image Quality Blindly." FES Journal of Engineering Sciences 8, no. 2 (May 23, 2020): 97–103. http://dx.doi.org/10.52981/fjes.v8i2.121.

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Abstract When creating image quality assessment metric (IQA) no confirmation all distortion types are available. Non-specific distortion blind/no-reference (NR) IQA algorithms mostly need prior knowledge about anticipated distortions. This paper introduce a generic and distortion unaware (DU) approach for IQA with No Reference (NR). The approach uses three different measuring features which are initiated from the gist of natural scenes (NS) using Log-derivatives of the parameters; a general Gaussian distribution model, two sharpness functions, and Weibull distribution. All features were analyzed and co mpared together to examine their performance. When calibrating the proposed features performance on LIVE database, experiments show they have good contribution to the state of the art IQA and they outperform the popular full-reference peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) methods. Also they show sharpness features are the best when assess both prediction monotonicity and predict accuracy evaluation among the three features categories. Besides they show asymmetric generalized Gaussian distribution (AGGD) based features have the best correlation with differential mean opinion score.

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Moreira de Sousa, Luís, Laura Poggio, and Bas Kempen. "Comparison of FOSS4G Supported Equal-Area Projections Using Discrete Distortion Indicatrices." ISPRS International Journal of Geo-Information 8, no. 8 (August 9, 2019): 351. http://dx.doi.org/10.3390/ijgi8080351.

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This study compares the performance of five popular equal-area projections supported by Free and Open Source Software for Geo-spatial (FOSS4G)—Sinusoidal, Mollweide, Hammer, Eckert IV and Homolosine. A set of 21,872 discrete distortion vindicatrices were positioned on the ellipsoid surface, centred on the cells of a Snyder icosahedral equal-area grid. These indicatrices were projected on the plane and the resulting angular and distance distortions computed, all using FOSS4G. The Homolosine is the only projection that manages to minimise angular and distance distortions simultaneously. It yields the lowest distortions among this set of projections and clearly outclasses when only land masses are considered. These results also indicate the Sinusoidal and Hammer projections to be largely outdated, imposing too large distortions to be useful. In contrast, the Mollweide and Eckert IV projections present trade-offs between visual expression and accuracy that are worth considering. However, for the purposes of storing and analysing big spatial data with FOSS4G the superior performance of the Homolosine projection makes its choice difficult to avoid.

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LIANG, QIANHUI, and MIAOLIANG ZHU. "A COMBINED APPROACH TO TEXT-DEPENDENT SPEAKER IDENTIFICATION: COMPARISON WITH PURE NEURAL NET APPROACHES." Journal of Circuits, Systems and Computers 08, no. 02 (April 1998): 273–81. http://dx.doi.org/10.1142/s0218126698000110.

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A novel approach to automatic speaker identification (ASI) is presented. Most of the present automatic speaker identification systems based on neural networks have no definite mechanisms to compensate for time distortions due to elocution. Such models have less precise information about the intraspeaker measure. The new combined approach uses both distortion-based and discriminant-based methods. The distortion-based and discriminant-based methods are dynamic time warping (DTW) and artificial neural network (ANN) respectively. This paper compares this new classifier with a pure neural net classifier for speaker identification. The performance of the combined classifier surpasses that of a pure ANN classifier for the conditions tested.

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S. R, Nirmala, Dandapat S., and Bora P. K. "Performance Evaluation of Distortion Measures for Retinal Images." International Journal of Computer Applications 17, no. 6 (March 31, 2011): 17–23. http://dx.doi.org/10.5120/2225-2835.

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Horner, Joseph L., and Peter D. Gianino. "Effects of quadratic phase distortion on correlator performance." Applied Optics 31, no. 20 (July 10, 1992): 3876. http://dx.doi.org/10.1364/ao.31.003876.

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Abuelma'atti, Muhammad Taher. "Nonlinear distortion performance of narrow stripe-geometry lasers." International Journal of Infrared and Millimeter Waves 9, no. 12 (December 1988): 1041–50. http://dx.doi.org/10.1007/bf01009298.

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Dong, Zhi Bo, Yan Hong Wei, Wen Jian Zheng, Guang Xu Hu, and Rui Ma. "Welding Sequence Optimization of TA15 Airplane Wall Panels." Materials Science Forum 704-705 (December 2011): 1045–50. http://dx.doi.org/10.4028/www.scientific.net/msf.704-705.1045.

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TA15 airplane wall panels are used widely in aircraft manufacture, which consist of some reinforced ribs and a motherboard. Therefore, welding sequences of different reinforced ribs directly determine distortion and residual stress distributions of welding wall panels, and then affect the structure service performance. Therefore, it is important to get the optimistic sequence during manufacture processing of welding wall panels. This paper analyses and predicts regularities of distributions of residual distortion and stress under four kinds of different welding sequence namely, order welding sequence, head-tail welding, head-tail symmetry welding and center symmetry welding. Compared the distortion and residual stress of four kinds of sequences, it is obvious that the welding distortion is smaller and welding quality is better under head-tail symmetry welding sequence, and the order welding sequence is the worst. The simulated distortions are in good agreement with the experiments. So this study puts forward the best welding sequence when welding airplane wall panels, which adapt to any amounts of reinforced ribs welded with the motherboard.

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Guzulescu, Nicolae, Cornel Todirică, and Daniel Lăpădat. "Image Distortion, between Unwanted Geometric Aberration and the Tool Used to Improve Observation Equipment Performance." Applied Mechanics and Materials 555 (June 2014): 751–58. http://dx.doi.org/10.4028/www.scientific.net/amm.555.751.

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An distortion aberration free optical system forms an orthoscopic image mean that is similar to original object, undeformed. Naturally imply that most optical systems are designed so that the image distortion is minimal, not to cause inconvenience to the user about either the object appearance – when it comes to a camera or camcorder, or the deformities that may cause measurement errors – when it comes to optical measurement and control equipment. However there are situations when distortion is desired to improve some performances of the observation optical system. In this article we present how distortion is used to increase the field of view, and also how distortion is used to optimize the field of view – resolution compromise.

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Ji, Xuande, Daqing He, and Yunwang Ge. "Study of Direct Torque Control Scheme for Induction Motor Based on Torque Angle Closed-Loop Control." Open Electrical & Electronic Engineering Journal 9, no. 1 (November 11, 2015): 600–609. http://dx.doi.org/10.2174/1874129001509010600.

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For disadvantages of the large flux and torque ripple and current waveform distortion of Direct Torque Control (BASIC-DTC), the DTC scheme for induction motor based on torque angle closed-loop control was presented and the proposed scheme was realized with three methods of torque angle closed-loop control. The main characteristics of three methods of torque angle closed-loop control for the proposed scheme was analyzed, emphasizing their advantages and disadvantages. The performance of three methods of torque angle closed-loop control for the proposed scheme was studied in terms of flux and torque ripple, current waveform distortion and transient responses. Simulation results showed that the proposed scheme improves the performance of induction motor BASIC-DTC by combining low flux ripple, low torque ripple and low current waveform distortion’s characteristics with fast dynamics.

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Cai, Weipeng, Cien Fan, Lian Zou, Yifeng Liu, Yang Ma, and Minyuan Wu. "Blind Image Quality Assessment Based on Classification Guidance and Feature Aggregation." Electronics 9, no. 11 (November 2, 2020): 1811. http://dx.doi.org/10.3390/electronics9111811.

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In this work, we present a convolutional neural network (CNN) named CGFA-CNN for blind image quality assessment (BIQA). A unique two-stage strategy is utilized which firstly identifies the distortion type in an image using Sub-Network I and then quantifies this distortion using Sub-Network II. Different from most deep neural networks, we extract hierarchical features as descriptors to enhance the image representation and design a feature aggregation layer in an end-to-end training manner applying Fisher encoding to visual vocabularies modeled by Gaussian mixture models (GMMs). Considering the authentic distortions and synthetic distortions, the hierarchical feature contains the characteristics of a CNN trained on the self-built dataset and a CNN trained on ImageNet. We evaluated our algorithm on four publicly available databases, and the results demonstrate that our CGFA-CNN has superior performance over other methods both on synthetic and authentic databases.

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Ravisankar, A., VS Sanapala, and S. Venugopal. "Effect of weld parameters on the dynamic performance of thin-walled centrifugal extractor rotating bowl." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 8 (August 3, 2014): 1477–90. http://dx.doi.org/10.1177/0954406214544726.

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An attempt has been made to investigate the influence of various weld parameters on the dynamic behavior of rotating bowl and thereby optimizing those parameters for the improved performance of the same. The welding input parameters play a significant role in the final distortions, which in turn cause the unbalanced mass and eccentricity, thus affecting the dynamic stability of rotor. In this regard, a synergistic approach is followed involving both finite element modeling using a coupled thermo-mechanical analysis and experimental work for estimating the induced distortion during welding. The dynamic behavior is studied comprehensively through numerical analysis by introducing the obtained distortions on the surface of the bowl after welding for different conditions such as welding speed, clamping conditions and weld sequence.

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Journal articles on the topic 'Distortion performance'

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