Motion-Compensated Compression of Dynamic Voxelized Point Clouds.

PubMed

De Queiroz, Ricardo L; Chou, Philip A

2017-05-24

Dynamic point clouds are a potential new frontier in visual communication systems. A few articles have addressed the compression of point clouds, but very few references exist on exploring temporal redundancies. This paper presents a novel motion-compensated approach to encoding dynamic voxelized point clouds at low bit rates. A simple coder breaks the voxelized point cloud at each frame into blocks of voxels. Each block is either encoded in intra-frame mode or is replaced by a motion-compensated version of a block in the previous frame. The decision is optimized in a rate-distortion sense. In this way, both the geometry and the color are encoded with distortion, allowing for reduced bit-rates. In-loop filtering is employed to minimize compression artifacts caused by distortion in the geometry information. Simulations reveal that this simple motion compensated coder can efficiently extend the compression range of dynamic voxelized point clouds to rates below what intra-frame coding alone can accommodate, trading rate for geometry accuracy.

RD Optimized, Adaptive, Error-Resilient Transmission of MJPEG2000-Coded Video over Multiple Time-Varying Channels

NASA Astrophysics Data System (ADS)

Bezan, Scott; Shirani, Shahram

2006-12-01

To reliably transmit video over error-prone channels, the data should be both source and channel coded. When multiple channels are available for transmission, the problem extends to that of partitioning the data across these channels. The condition of transmission channels, however, varies with time. Therefore, the error protection added to the data at one instant of time may not be optimal at the next. In this paper, we propose a method for adaptively adding error correction code in a rate-distortion (RD) optimized manner using rate-compatible punctured convolutional codes to an MJPEG2000 constant rate-coded frame of video. We perform an analysis on the rate-distortion tradeoff of each of the coding units (tiles and packets) in each frame and adapt the error correction code assigned to the unit taking into account the bandwidth and error characteristics of the channels. This method is applied to both single and multiple time-varying channel environments. We compare our method with a basic protection method in which data is either not transmitted, transmitted with no protection, or transmitted with a fixed amount of protection. Simulation results show promising performance for our proposed method.

Subjective audio quality evaluation of embedded-optimization-based distortion precompensation algorithms.

PubMed

Defraene, Bruno; van Waterschoot, Toon; Diehl, Moritz; Moonen, Marc

2016-07-01

Subjective audio quality evaluation experiments have been conducted to assess the performance of embedded-optimization-based precompensation algorithms for mitigating perceptible linear and nonlinear distortion in audio signals. It is concluded with statistical significance that the perceived audio quality is improved by applying an embedded-optimization-based precompensation algorithm, both in case (i) nonlinear distortion and (ii) a combination of linear and nonlinear distortion is present. Moreover, a significant positive correlation is reported between the collected subjective and objective PEAQ audio quality scores, supporting the validity of using PEAQ to predict the impact of linear and nonlinear distortion on the perceived audio quality.

Structured Set Intra Prediction With Discriminative Learning in a Max-Margin Markov Network for High Efficiency Video Coding

PubMed Central

Dai, Wenrui; Xiong, Hongkai; Jiang, Xiaoqian; Chen, Chang Wen

2014-01-01

This paper proposes a novel model on intra coding for High Efficiency Video Coding (HEVC), which simultaneously predicts blocks of pixels with optimal rate distortion. It utilizes the spatial statistical correlation for the optimal prediction based on 2-D contexts, in addition to formulating the data-driven structural interdependences to make the prediction error coherent with the probability distribution, which is desirable for successful transform and coding. The structured set prediction model incorporates a max-margin Markov network (M3N) to regulate and optimize multiple block predictions. The model parameters are learned by discriminating the actual pixel value from other possible estimates to maximize the margin (i.e., decision boundary bandwidth). Compared to existing methods that focus on minimizing prediction error, the M3N-based model adaptively maintains the coherence for a set of predictions. Specifically, the proposed model concurrently optimizes a set of predictions by associating the loss for individual blocks to the joint distribution of succeeding discrete cosine transform coefficients. When the sample size grows, the prediction error is asymptotically upper bounded by the training error under the decomposable loss function. As an internal step, we optimize the underlying Markov network structure to find states that achieve the maximal energy using expectation propagation. For validation, we integrate the proposed model into HEVC for optimal mode selection on rate-distortion optimization. The proposed prediction model obtains up to 2.85% bit rate reduction and achieves better visual quality in comparison to the HEVC intra coding. PMID:25505829

On Optimizing H. 264/AVC Rate Control by Improving R-D Model and Incorporating HVS Characteristics

NASA Astrophysics Data System (ADS)

Zhu, Zhongjie; Wang, Yuer; Bai, Yongqiang; Jiang, Gangyi

2010-12-01

The state-of-the-art JVT-G012 rate control algorithm of H.264 is improved from two aspects. First, the quadratic rate-distortion (R-D) model is modified based on both empirical observations and theoretical analysis. Second, based on the existing physiological and psychological research findings of human vision, the rate control algorithm is optimized by incorporating the main characteristics of the human visual system (HVS) such as contrast sensitivity, multichannel theory, and masking effect. Experiments are conducted, and experimental results show that the improved algorithm can simultaneously enhance the overall subjective visual quality and improve the rate control precision effectively.

Spread spectrum image watermarking based on perceptual quality metric.

PubMed

Zhang, Fan; Liu, Wenyu; Lin, Weisi; Ngan, King Ngi

2011-11-01

Efficient image watermarking calls for full exploitation of the perceptual distortion constraint. Second-order statistics of visual stimuli are regarded as critical features for perception. This paper proposes a second-order statistics (SOS)-based image quality metric, which considers the texture masking effect and the contrast sensitivity in Karhunen-Loève transform domain. Compared with the state-of-the-art metrics, the quality prediction by SOS better correlates with several subjectively rated image databases, in which the images are impaired by the typical coding and watermarking artifacts. With the explicit metric definition, spread spectrum watermarking is posed as an optimization problem: we search for a watermark to minimize the distortion of the watermarked image and to maximize the correlation between the watermark pattern and the spread spectrum carrier. The simple metric guarantees the optimal watermark a closed-form solution and a fast implementation. The experiments show that the proposed watermarking scheme can take full advantage of the distortion constraint and improve the robustness in return.

Data compression using adaptive transform coding. Appendix 1: Item 1. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Rost, Martin Christopher

1988-01-01

Adaptive low-rate source coders are described in this dissertation. These coders adapt by adjusting the complexity of the coder to match the local coding difficulty of the image. This is accomplished by using a threshold driven maximum distortion criterion to select the specific coder used. The different coders are built using variable blocksized transform techniques, and the threshold criterion selects small transform blocks to code the more difficult regions and larger blocks to code the less complex regions. A theoretical framework is constructed from which the study of these coders can be explored. An algorithm for selecting the optimal bit allocation for the quantization of transform coefficients is developed. The bit allocation algorithm is more fully developed, and can be used to achieve more accurate bit assignments than the algorithms currently used in the literature. Some upper and lower bounds for the bit-allocation distortion-rate function are developed. An obtainable distortion-rate function is developed for a particular scalar quantizer mixing method that can be used to code transform coefficients at any rate.

Joint source-channel coding for motion-compensated DCT-based SNR scalable video.

PubMed

Kondi, Lisimachos P; Ishtiaq, Faisal; Katsaggelos, Aggelos K

2002-01-01

In this paper, we develop an approach toward joint source-channel coding for motion-compensated DCT-based scalable video coding and transmission. A framework for the optimal selection of the source and channel coding rates over all scalable layers is presented such that the overall distortion is minimized. The algorithm utilizes universal rate distortion characteristics which are obtained experimentally and show the sensitivity of the source encoder and decoder to channel errors. The proposed algorithm allocates the available bit rate between scalable layers and, within each layer, between source and channel coding. We present the results of this rate allocation algorithm for video transmission over a wireless channel using the H.263 Version 2 signal-to-noise ratio (SNR) scalable codec for source coding and rate-compatible punctured convolutional (RCPC) codes for channel coding. We discuss the performance of the algorithm with respect to the channel conditions, coding methodologies, layer rates, and number of layers.

Mitigation of Engine Inlet Distortion Through Adjoint-Based Design

NASA Technical Reports Server (NTRS)

Ordaz, Irian; Rallabhandi, Sriram; Nielsen, Eric J.; Diskin, Boris

2017-01-01

The adjoint-based design capability in FUN3D is extended to allow efficient gradient- based optimization and design of concepts with highly integrated aero-propulsive systems. A circumferential distortion calculation, along with the derivatives needed to perform adjoint-based design, have been implemented in FUN3D. This newly implemented distortion calculation can be used not only for design but also to drive the existing mesh adaptation process and reduce the error associated with the fan distortion calculation. The design capability is demonstrated by the shape optimization of an in-house aircraft concept equipped with an aft fuselage propulsor. The optimization objective is the minimization of flow distortion at the aerodynamic interface plane of this aft fuselage propulsor.

Spatially adaptive bases in wavelet-based coding of semi-regular meshes

NASA Astrophysics Data System (ADS)

Denis, Leon; Florea, Ruxandra; Munteanu, Adrian; Schelkens, Peter

2010-05-01

In this paper we present a wavelet-based coding approach for semi-regular meshes, which spatially adapts the employed wavelet basis in the wavelet transformation of the mesh. The spatially-adaptive nature of the transform requires additional information to be stored in the bit-stream in order to allow the reconstruction of the transformed mesh at the decoder side. In order to limit this overhead, the mesh is first segmented into regions of approximately equal size. For each spatial region, a predictor is selected in a rate-distortion optimal manner by using a Lagrangian rate-distortion optimization technique. When compared against the classical wavelet transform employing the butterfly subdivision filter, experiments reveal that the proposed spatially-adaptive wavelet transform significantly decreases the energy of the wavelet coefficients for all subbands. Preliminary results show also that employing the proposed transform for the lowest-resolution subband systematically yields improved compression performance at low-to-medium bit-rates. For the Venus and Rabbit test models the compression improvements add up to 1.47 dB and 0.95 dB, respectively.

Optimized atom position and coefficient coding for matching pursuit-based image compression.

PubMed

Shoa, Alireza; Shirani, Shahram

2009-12-01

In this paper, we propose a new encoding algorithm for matching pursuit image coding. We show that coding performance is improved when correlations between atom positions and atom coefficients are both used in encoding. We find the optimum tradeoff between efficient atom position coding and efficient atom coefficient coding and optimize the encoder parameters. Our proposed algorithm outperforms the existing coding algorithms designed for matching pursuit image coding. Additionally, we show that our algorithm results in better rate distortion performance than JPEG 2000 at low bit rates.

Optimal Flow Control Design

NASA Technical Reports Server (NTRS)

Allan, Brian; Owens, Lewis

2010-01-01

In support of the Blended-Wing-Body aircraft concept, a new flow control hybrid vane/jet design has been developed for use in a boundary-layer-ingesting (BLI) offset inlet in transonic flows. This inlet flow control is designed to minimize the engine fan-face distortion levels and the first five Fourier harmonic half amplitudes while maximizing the inlet pressure recovery. This concept represents a potentially enabling technology for quieter and more environmentally friendly transport aircraft. An optimum vane design was found by minimizing the engine fan-face distortion, DC60, and the first five Fourier harmonic half amplitudes, while maximizing the total pressure recovery. The optimal vane design was then used in a BLI inlet wind tunnel experiment at NASA Langley's 0.3-meter transonic cryogenic tunnel. The experimental results demonstrated an 80-percent decrease in DPCPavg, the reduction in the circumferential distortion levels, at an inlet mass flow rate corresponding to the middle of the operational range at the cruise condition. Even though the vanes were designed at a single inlet mass flow rate, they performed very well over the entire inlet mass flow range tested in the wind tunnel experiment with the addition of a small amount of jet flow control. While the circumferential distortion was decreased, the radial distortion on the outer rings at the aerodynamic interface plane (AIP) increased. This was a result of the large boundary layer being distributed from the bottom of the AIP in the baseline case to the outer edges of the AIP when using the vortex generator (VG) vane flow control. Experimental results, as already mentioned, showed an 80-percent reduction of DPCPavg, the circumferential distortion level at the engine fan-face. The hybrid approach leverages strengths of vane and jet flow control devices, increasing inlet performance over a broader operational range with significant reduction in mass flow requirements. Minimal distortion level requirements are met using vanes alone, avoiding engine stall and increasing robustness of this hybrid inlet flow control approach. This design applies to aerospace applications needing flush-mounted boundary-layer-ingesting inlets.

Fast H.264/AVC FRExt intra coding using belief propagation.

PubMed

Milani, Simone

2011-01-01

In the H.264/AVC FRExt coder, the coding performance of Intra coding significantly overcomes the previous still image coding standards, like JPEG2000, thanks to a massive use of spatial prediction. Unfortunately, the adoption of an extensive set of predictors induces a significant increase of the computational complexity required by the rate-distortion optimization routine. The paper presents a complexity reduction strategy that aims at reducing the computational load of the Intra coding with a small loss in the compression performance. The proposed algorithm relies on selecting a reduced set of prediction modes according to their probabilities, which are estimated adopting a belief-propagation procedure. Experimental results show that the proposed method permits saving up to 60 % of the coding time required by an exhaustive rate-distortion optimization method with a negligible loss in performance. Moreover, it permits an accurate control of the computational complexity unlike other methods where the computational complexity depends upon the coded sequence.

2-Step scalar deadzone quantization for bitplane image coding.

PubMed

Auli-Llinas, Francesc

2013-12-01

Modern lossy image coding systems generate a quality progressive codestream that, truncated at increasing rates, produces an image with decreasing distortion. Quality progressivity is commonly provided by an embedded quantizer that employs uniform scalar deadzone quantization (USDQ) together with a bitplane coding strategy. This paper introduces a 2-step scalar deadzone quantization (2SDQ) scheme that achieves same coding performance as that of USDQ while reducing the coding passes and the emitted symbols of the bitplane coding engine. This serves to reduce the computational costs of the codec and/or to code high dynamic range images. The main insights behind 2SDQ are the use of two quantization step sizes that approximate wavelet coefficients with more or less precision depending on their density, and a rate-distortion optimization technique that adjusts the distortion decreases produced when coding 2SDQ indexes. The integration of 2SDQ in current codecs is straightforward. The applicability and efficiency of 2SDQ are demonstrated within the framework of JPEG2000.

Joint Machine Learning and Game Theory for Rate Control in High Efficiency Video Coding.

PubMed

Gao, Wei; Kwong, Sam; Jia, Yuheng

2017-08-25

In this paper, a joint machine learning and game theory modeling (MLGT) framework is proposed for inter frame coding tree unit (CTU) level bit allocation and rate control (RC) optimization in High Efficiency Video Coding (HEVC). First, a support vector machine (SVM) based multi-classification scheme is proposed to improve the prediction accuracy of CTU-level Rate-Distortion (R-D) model. The legacy "chicken-and-egg" dilemma in video coding is proposed to be overcome by the learning-based R-D model. Second, a mixed R-D model based cooperative bargaining game theory is proposed for bit allocation optimization, where the convexity of the mixed R-D model based utility function is proved, and Nash bargaining solution (NBS) is achieved by the proposed iterative solution search method. The minimum utility is adjusted by the reference coding distortion and frame-level Quantization parameter (QP) change. Lastly, intra frame QP and inter frame adaptive bit ratios are adjusted to make inter frames have more bit resources to maintain smooth quality and bit consumption in the bargaining game optimization. Experimental results demonstrate that the proposed MLGT based RC method can achieve much better R-D performances, quality smoothness, bit rate accuracy, buffer control results and subjective visual quality than the other state-of-the-art one-pass RC methods, and the achieved R-D performances are very close to the performance limits from the FixedQP method.

Rate-distortion optimized tree-structured compression algorithms for piecewise polynomial images.

PubMed

Shukla, Rahul; Dragotti, Pier Luigi; Do, Minh N; Vetterli, Martin

2005-03-01

This paper presents novel coding algorithms based on tree-structured segmentation, which achieve the correct asymptotic rate-distortion (R-D) behavior for a simple class of signals, known as piecewise polynomials, by using an R-D based prune and join scheme. For the one-dimensional case, our scheme is based on binary-tree segmentation of the signal. This scheme approximates the signal segments using polynomial models and utilizes an R-D optimal bit allocation strategy among the different signal segments. The scheme further encodes similar neighbors jointly to achieve the correct exponentially decaying R-D behavior (D(R) - c(o)2(-c1R)), thus improving over classic wavelet schemes. We also prove that the computational complexity of the scheme is of O(N log N). We then show the extension of this scheme to the two-dimensional case using a quadtree. This quadtree-coding scheme also achieves an exponentially decaying R-D behavior, for the polygonal image model composed of a white polygon-shaped object against a uniform black background, with low computational cost of O(N log N). Again, the key is an R-D optimized prune and join strategy. Finally, we conclude with numerical results, which show that the proposed quadtree-coding scheme outperforms JPEG2000 by about 1 dB for real images, like cameraman, at low rates of around 0.15 bpp.

Optimized bit extraction using distortion modeling in the scalable extension of H.264/AVC.

PubMed

Maani, Ehsan; Katsaggelos, Aggelos K

2009-09-01

The newly adopted scalable extension of H.264/AVC video coding standard (SVC) demonstrates significant improvements in coding efficiency in addition to an increased degree of supported scalability relative to the scalable profiles of prior video coding standards. Due to the complicated hierarchical prediction structure of the SVC and the concept of key pictures, content-aware rate adaptation of SVC bit streams to intermediate bit rates is a nontrivial task. The concept of quality layers has been introduced in the design of the SVC to allow for fast content-aware prioritized rate adaptation. However, existing quality layer assignment methods are suboptimal and do not consider all network abstraction layer (NAL) units from different layers for the optimization. In this paper, we first propose a technique to accurately and efficiently estimate the quality degradation resulting from discarding an arbitrary number of NAL units from multiple layers of a bitstream by properly taking drift into account. Then, we utilize this distortion estimation technique to assign quality layers to NAL units for a more efficient extraction. Experimental results show that a significant gain can be achieved by the proposed scheme.

Enhanced optical design by distortion control

NASA Astrophysics Data System (ADS)

Thibault, Simon; Gauvin, Jonny; Doucet, Michel; Wang, Min

2005-09-01

The control of optical distortion is useful for the design of a variety of optical system. The most popular is the F-theta lens used in laser scanning system to produce a constant scan velocity across the image plane. Many authors have designed during the last 20 years distortion control corrector. Today, many challenging digital imaging system can use distortion the enhanced their imaging capability. A well know example is a reversed telephoto type, if the barrel distortion is increased instead of being corrected; the result is a so-called Fish-eye lens. However, if we control the barrel distortion instead of only increasing it, the resulting system can have enhanced imaging capability. This paper will present some lens design and real system examples that clearly demonstrate how the distortion control can improve the system performances such as resolution. We present innovative optical system which increases the resolution in the field of view of interest to meet the needs of specific applications. One critical issue when we designed using distortion is the optimization management. Like most challenging lens design, the automatic optimization is less reliable. Proper management keeps the lens design within the correct range, which is critical for optimal performance (size, cost, manufacturability). Many lens design presented tailor a custom merit function and approach.

Distortionary effects of a production-sharing fiscal system in a sequential modular offshore petroleum project

NASA Astrophysics Data System (ADS)

Neves de Campos, Thiago

This research examines the distortionary effects of a discovered and undeveloped sequential modular offshore project under five different designs for a production-sharing agreement (PSA). The model differs from previous research by looking at the effect of taxation from the perspective of a host government, where the objective is to maximize government utility over government revenue generated by the project and the non-pecuniary benefits to society. This research uses Modern Asset Pricing (MAP) theory, which is able to provide a good measure of the asset value accruing to various stakeholders in the project combined with the optimal decision rule for the development of the investment opportunity. Monte Carlo simulation was also applied to incorporate into the model the most important sources of risk associated with the project and to account for non-linearity in the cash flows. For a complete evaluation of how the fiscal system affects the project development, an investor's behavioral model was constructed, incorporating three operational decisions: investment timing, capacity size and early abandonment. The model considers four sources of uncertainty that affect the project value and the firm's optimal decision: the long run oil price and short-run deviations from that price, cost escalation and the reservoir recovery rate. The optimizations outcomes show that all fiscal systems evaluated produce distortion over the companies' optimal decisions, and companies adjust their choices to avoid taxation in different ways according to the fiscal system characteristics. Moreover, it is revealed that fiscal systems with tax provisions that try to capture additional project profits based on production profitability measures leads to stronger distortions in the project investment and output profile. It is also shown that a model based on a fixed percentage rate is the system that creates the least distortion. This is because companies will be subjected to the same government share of profit oil independently of any operational decision which they can make to change the production profile to evade taxation.

LQG control of a deformable mirror adaptive optics system with time-delayed measurements

NASA Astrophysics Data System (ADS)

Anderson, David J.

1991-12-01

This thesis proposes a linear quadratic Gaussian (LQG) control law for a ground-based deformable mirror adaptive optics system. The incoming image wavefront is distorted, primarily in phase, due to the turbulent effects of the earth's atmosphere. The adaptive optics system attempts to compensate for the distortion with a deformable mirror. A Hartman wavefront sensor measures the degree of distortion in the image wavefront. The measurements are input to a Kalman filter which estimates the system states. The state estimates are processed by a linear quadratic regulator which generates the appropriate control voltages to apply to the deformable mirror actuators. The dynamics model for the atmospheric phase distortion consists of 14 Zernike coefficient states; each modeled as a first-order linear time-invariant shaping filter driven by zero-mean white Gaussian noise. The dynamics of the deformable mirror are also model as 14 Zernike coefficients with first-order deterministic dynamics. A significant reduction in total wavefront phase distortion is achieved in the presence of time-delayed measurements. Wavefront sensor sampling rate is the major factor limiting system performance. The Multimode Simulation for Optimal Filter Evaluation (MSOFE) software is the performance evaluation tool of choice for this research.

Characterization of architectural distortion on mammograms using a linear energy detector

NASA Astrophysics Data System (ADS)

Alvarez, Jorge; Narváez, Fabián.; Poveda, César; Romero, Eduardo

2013-11-01

Architectural distortion is a breast cancer sign, characterized by spiculated patterns that define the disease malignancy level. In this paper, the radial spiculae of a typical architectural distortion were characterized by a new strategy. Firstly, previously selected Regions of Interest are divided into a set of parallel and disjoint bands (4 pixels the ROI length), from which intensity integrals (coefficients) are calculated. This partition is rotated every two degrees, searching in the phase plane the characteristic radial spiculation. Then, these coefficients are used to construct a fully connected graph whose edges correspond to the integral values or coefficients and the nodes to x and y image positions. A centrality measure like the first eigenvector is used to extract a set of discriminant coefficients that represent the locations with higher linear energy. Finally, the approach is trained using a set of 24 Regions of Interest obtained from the MIAS database, namely, 12 Architectural Distortions and 12 controls. The first eigenvector is then used as input to a conventional Support Vector Machine classifier whose optimal parameters were obtained by a leave-one-out cross validation. The whole method was assessed in a set of 12 RoIs with different distribution of breast tissues (normal and abnormal), and the classification results were compared against a ground truth, already provided by the data base, showing a precision rate of 0.583%, a sensitivity rate of 0.833% and a specificity rate of 0.333%.

Dependency of Optimal Parameters of the IRIS Template on Image Quality and Border Detection Error

NASA Astrophysics Data System (ADS)

Matveev, I. A.; Novik, V. P.

2017-05-01

Generation of a template containing spatial-frequency features of iris is an important stage of identification. The template is obtained by a wavelet transform in an image region specified by iris borders. One of the main characteristics of the identification system is the value of recognition error, equal error rate (EER) is used as criterion here. The optimal values (in sense of minimizing the EER) of wavelet transform parameters depend on many factors: image quality, sharpness, size of characteristic objects, etc. It is hard to isolate these factors and their influences. The work presents an attempt to study an influence of following factors to EER: iris segmentation precision, defocus level, noise level. Several public domain iris image databases were involved in experiments. The images were subjected to modelled distortions of said types. The dependencies of wavelet parameter and EER values from the distortion levels were build. It is observed that the increase of the segmentation error and image noise leads to the increase of the optimal wavelength of the wavelets, whereas the increase of defocus level leads to decreasing of this value.

Influence of Process Parameters on the Process Efficiency in Laser Metal Deposition Welding

NASA Astrophysics Data System (ADS)

Güpner, Michael; Patschger, Andreas; Bliedtner, Jens

Conventionally manufactured tools are often completely constructed of a high-alloyed, expensive tool steel. An alternative way to manufacture tools is the combination of a cost-efficient, mild steel and a functional coating in the interaction zone of the tool. Thermal processing methods, like laser metal deposition, are always characterized by thermal distortion. The resistance against the thermal distortion decreases with the reduction of the material thickness. As a consequence, there is a necessity of a special process management for the laser based coating of thin parts or tools. The experimental approach in the present paper is to keep the energy and the mass per unit length constant by varying the laser power, the feed rate and the powder mass flow. The typical seam parameters are measured in order to characterize the cladding process, define process limits and evaluate the process efficiency. Ways to optimize dilution, angular distortion and clad height are presented.

Necessary conditions for the optimality of variable rate residual vector quantizers

NASA Technical Reports Server (NTRS)

Kossentini, Faouzi; Smith, Mark J. T.; Barnes, Christopher F.

1993-01-01

Residual vector quantization (RVQ), or multistage VQ, as it is also called, has recently been shown to be a competitive technique for data compression. The competitive performance of RVQ reported in results from the joint optimization of variable rate encoding and RVQ direct-sum code books. In this paper, necessary conditions for the optimality of variable rate RVQ's are derived, and an iterative descent algorithm based on a Lagrangian formulation is introduced for designing RVQ's having minimum average distortion subject to an entropy constraint. Simulation results for these entropy-constrained RVQ's (EC-RVQ's) are presented for memory less Gaussian, Laplacian, and uniform sources. A Gauss-Markov source is also considered. The performance is superior to that of entropy-constrained scalar quantizers (EC-SQ's) and practical entropy-constrained vector quantizers (EC-VQ's), and is competitive with that of some of the best source coding techniques that have appeared in the literature.

Optimization and Prediction of Angular Distortion and Weldment Characteristics of TIG Square Butt Joints

NASA Astrophysics Data System (ADS)

Narang, H. K.; Mahapatra, M. M.; Jha, P. K.; Biswas, P.

2014-05-01

Autogenous arc welds with minimum upper weld bead depression and lower weld bead bulging are desired as such welds do not require a second welding pass for filling up the upper bead depressions (UBDs) and characterized with minimum angular distortion. The present paper describes optimization and prediction of angular distortion and weldment characteristics such as upper weld bead depression and lower weld bead bulging of TIG-welded structural steel square butt joints. Full factorial design of experiment was utilized for selecting the combinations of welding process parameter to produce the square butts. A mathematical model was developed to establish the relationship between TIG welding process parameters and responses such as upper bead width, lower bead width, UBD, lower bead height (bulging), weld cross-sectional area, and angular distortions. The optimal welding condition to minimize UBD and lower bead bulging of the TIG butt joints was identified.

New Approach to Optimize the Apfs Placement Based on Instantaneous Reactive Power Theory by Genetic Algorithm

NASA Astrophysics Data System (ADS)

Hashemi-Dezaki, Hamed; Mohammadalizadeh-Shabestary, Masoud; Askarian-Abyaneh, Hossein; Rezaei-Jegarluei, Mohammad

2014-01-01

In electrical distribution systems, a great amount of power are wasting across the lines, also nowadays power factors, voltage profiles and total harmonic distortions (THDs) of most loads are not as would be desired. So these important parameters of a system play highly important role in wasting money and energy, and besides both consumers and sources are suffering from a high rate of distortions and even instabilities. Active power filters (APFs) are innovative ideas for solving of this adversity which have recently used instantaneous reactive power theory. In this paper, a novel method is proposed to optimize the allocation of APFs. The introduced method is based on the instantaneous reactive power theory in vectorial representation. By use of this representation, it is possible to asses different compensation strategies. Also, APFs proper placement in the system plays a crucial role in either reducing the losses costs and power quality improvement. To optimize the APFs placement, a new objective function has been defined on the basis of five terms: total losses, power factor, voltage profile, THD and cost. Genetic algorithm has been used to solve the optimization problem. The results of applying this method to a distribution network illustrate the method advantages.

On-board data management study for EOPAP

NASA Technical Reports Server (NTRS)

Davisson, L. D.

1975-01-01

The requirements, implementation techniques, and mission analysis associated with on-board data management for EOPAP were studied. SEASAT-A was used as a baseline, and the storage requirements, data rates, and information extraction requirements were investigated for each of the following proposed SEASAT sensors: a short pulse 13.9 GHz radar, a long pulse 13.9 GHz radar, a synthetic aperture radar, a multispectral passive microwave radiometer facility, and an infrared/visible very high resolution radiometer (VHRR). Rate distortion theory was applied to determine theoretical minimum data rates and compared with the rates required by practical techniques. It was concluded that practical techniques can be used which approach the theoretically optimum based upon an empirically determined source random process model. The results of the preceding investigations were used to recommend an on-board data management system for (1) data compression through information extraction, optimal noiseless coding, source coding with distortion, data buffering, and data selection under command or as a function of data activity, (2) for command handling, (3) for spacecraft operation and control, and (4) for experiment operation and monitoring.

Helical Peierls distortion: Formation of helices of polyketone and polyisocyanide

NASA Astrophysics Data System (ADS)

Cui, Chang-Xing; Kertesz, Miklos

1990-06-01

A new type of Peierls-like distortion, the formation of a helix due to the existence of partially filled crossing bands, is reported for polyketone and polyisocyanide. The torsional potential curves, optimized geometries, band structures and phonon dispersion curves are derived. A comparison with the well-known Peierls-distorted all-trans polyacetylene indicates close similarity between the two types of Peierls distortions.

The influence of maternal psychopathology on ratings of child psychiatric symptoms: an SEM analysis on cross-informant agreement.

PubMed

Müller, Jörg M; Achtergarde, Sandra; Furniss, Tilman

2011-05-01

The distorting influence of maternal depression on the ratings of child behaviour is known as the depression-distortion hypothesis. This study investigated the depression-distortion hypothesis in a clinical sample of child psychiatric preschool children and extended the depression-distortion hypothesis to maternal psychopathology-distortion hypothesis in general. Subjects were 124 children, who were referred for treatment in a Child Psychiatric Family Day Hospital for preschool children, and their parents. Children were rated on the CBCL/1.5-5 and the C-TRF/1.5-5 by their mothers, kindergarten teachers and therapists. Maternal psychopathology was assessed by self-rating with the SCL-90-R and the BDI. The appropriateness of the depression-distortion hypothesis, as well as two alternatives, the accuracy and the combinatory model, were subsequently analysed by structural equation modelling (SEM), including the ratings of all three informants. Model fit and parameter estimation supported the distortion model, suggesting that ratings of child behaviour by mothers may be biased by maternal psychopathology. Findings are discussed with regard to the existing cross-informant literature, with particular consideration of the distortion hypothesis and third person ratings of child psychopathology in preschool age.

Stabilization of Particle Discrimination Efficiencies for Neutron Spectrum Unfolding With Organic Scintillators

NASA Astrophysics Data System (ADS)

Lawrence, Chris C.; Polack, J. K.; Febbraro, Michael; Kolata, J. J.; Flaska, Marek; Pozzi, S. A.; Becchetti, F. D.

2017-02-01

The literature discussing pulse-shape discrimination (PSD) in organic scintillators dates back several decades. However, little has been written about PSD techniques that are optimized for neutron spectrum unfolding. Variation in n-γ misclassification rates and in γ/n ratio of incident fields can distort the neutron pulse-height response of scintillators and these distortions can in turn cause large errors in unfolded spectra. New applications in arms-control verification call for detection of lower-energy neutrons, for which PSD is particularly problematic. In this article, we propose techniques for removing distortions on pulse-height response that result from the merging of PSD distributions in the low-pulse-height region. These techniques take advantage of the repeatable shapes of PSD distributions that are governed by the counting statistics of scintillation-photon populations. We validate the proposed techniques using accelerator-based time-of-flight measurements and then demonstrate them by unfolding the Watt spectrum from measurement with a 252Cf neutron source.

Rate-distortion analysis of directional wavelets.

PubMed

Maleki, Arian; Rajaei, Boshra; Pourreza, Hamid Reza

2012-02-01

The inefficiency of separable wavelets in representing smooth edges has led to a great interest in the study of new 2-D transformations. The most popular criterion for analyzing these transformations is the approximation power. Transformations with near-optimal approximation power are useful in many applications such as denoising and enhancement. However, they are not necessarily good for compression. Therefore, most of the nearly optimal transformations such as curvelets and contourlets have not found any application in image compression yet. One of the most promising schemes for image compression is the elegant idea of directional wavelets (DIWs). While these algorithms outperform the state-of-the-art image coders in practice, our theoretical understanding of them is very limited. In this paper, we adopt the notion of rate-distortion and calculate the performance of the DIW on a class of edge-like images. Our theoretical analysis shows that if the edges are not "sharp," the DIW will compress them more efficiently than the separable wavelets. It also demonstrates the inefficiency of the quadtree partitioning that is often used with the DIW. To solve this issue, we propose a new partitioning scheme called megaquad partitioning. Our simulation results on real-world images confirm the benefits of the proposed partitioning algorithm, promised by our theoretical analysis. © 2011 IEEE

Attenuation of harmonic noise in vibroseis data using Simulated Annealing

NASA Astrophysics Data System (ADS)

Sharma, S. P.; Tildy, Peter; Iranpour, Kambiz; Scholtz, Peter

2009-04-01

Processing of high productivity vibroseis seismic data (such as slip-sweep acquisition records) suffers from the well known disadvantage of harmonic distortion. Harmonic distortions are observed after cross-correlation of the recorded seismic signal with the pilot sweep and affect the signals in negative time (before the actual strong reflection event). Weak reflection events of the earlier sweeps falling in the negative time window of the cross-correlation sequence are being masked by harmonic distortions. Though the amplitude of the harmonic distortion is small (up to 10-20 %) compared to the fundamental amplitude of the reflection events, but it is significant enough to mask weak reflected signals. Elimination of harmonic noise due to source signal distortion from the cross-correlated seismic trace is a challenging task since the application of vibratory sources started and it still needs improvement. An approach has been worked out that minimizes the level of harmonic distortion by designing the signal similar to the harmonic distortion. An arbitrary length filter is optimized using the Simulated Annealing global optimization approach to design a harmonic signal. The approach deals with the convolution of a ratio trace (ratio of the harmonics with respect to the fundamental sweep) with the correlated "positive time" recorded signal and an arbitrary filter. Synthetic data study has revealed that this procedure of designing a signal similar to the desired harmonics using convolution of a suitable filter with theoretical ratio of harmonics with fundamental sweep helps in reducing the problem of harmonic distortion. Once we generate a similar signal for a vibroseis source using an optimized filter, then, this filter could be used to generate harmonics, which can be subtracted from the main cross-correlated trace to get the better, undistorted image of the subsurface. Designing the predicted harmonics to reduce the energy in the trace by considering weak reflection and observed harmonics together yields the desired result (resolution of weak reflected signal from the harmonic distortion). As optimization steps proceeds forward it is possible to observe from the difference plots of desired and predicted harmonics how weak reflections evolved from the harmonic distortion gradually during later iterations of global optimization. The procedure is applied in resolving weak reflections from a number of traces considered together. For a more precise design of harmonics SA procedure needs longer computation time which is impractical to deal with voluminous seismic data. However, the objective of resolving weak reflection signal in the strong harmonic noise can be achieved with fast computation using faster cooling schedule and less number of iterations and number of moves in simulated annealing procedure. This process could help in reducing the harmonics distortion and achieving the objective of resolving the lost weak reflection events in the cross-correlated seismic traces. Acknowledgements: The research was supported under the European Marie Curie Host Fellowships for Transfer of Knowledge (TOK) Development Host Scheme (contract no. MTKD-CT-2006-042537).

Resource allocation for error resilient video coding over AWGN using optimization approach.

PubMed

An, Cheolhong; Nguyen, Truong Q

2008-12-01

The number of slices for error resilient video coding is jointly optimized with 802.11a-like media access control and the physical layers with automatic repeat request and rate compatible punctured convolutional code over additive white gaussian noise channel as well as channel times allocation for time division multiple access. For error resilient video coding, the relation between the number of slices and coding efficiency is analyzed and formulated as a mathematical model. It is applied for the joint optimization problem, and the problem is solved by a convex optimization method such as the primal-dual decomposition method. We compare the performance of a video communication system which uses the optimal number of slices with one that codes a picture as one slice. From numerical examples, end-to-end distortion of utility functions can be significantly reduced with the optimal slices of a picture especially at low signal-to-noise ratio.

Optic for an endoscope/borescope having high resolution and narrow field of view

DOEpatents

Stone, Gary F.; Trebes, James E.

2003-10-28

An optic having optimized high spatial resolution, minimal nonlinear magnification distortion while at the same time having a limited chromatic focal shift or chromatic aberrations. The optic located at the distal end of an endoscopic inspection tool permits a high resolution, narrow field of view image for medical diagnostic applications, compared to conventional optics for endoscopic instruments which provide a wide field of view, low resolution image. The image coverage is over a narrow (<20 degrees) field of view with very low optical distortion (<5% pin cushion or barrel distortion. The optic is also optimized for best color correction as well as to aid medical diagnostics.

Distortion correction of echo planar images applying the concept of finite rate of innovation to point spread function mapping (FRIP).

PubMed

Nunes, Rita G; Hajnal, Joseph V

2018-06-01

Point spread function (PSF) mapping enables estimating the displacement fields required for distortion correction of echo planar images. Recently, a highly accelerated approach was introduced for estimating displacements from the phase slope of under-sampled PSF mapping data. Sampling schemes with varying spacing were proposed requiring stepwise phase unwrapping. To avoid unwrapping errors, an alternative approach applying the concept of finite rate of innovation to PSF mapping (FRIP) is introduced, using a pattern search strategy to locate the PSF peak, and the two methods are compared. Fully sampled PSF data was acquired in six subjects at 3.0 T, and distortion maps were estimated after retrospective under-sampling. The two methods were compared for both previously published and newly optimized sampling patterns. Prospectively under-sampled data were also acquired. Shift maps were estimated and deviations relative to the fully sampled reference map were calculated. The best performance was achieved when using FRIP with a previously proposed sampling scheme. The two methods were comparable for the remaining schemes. The displacement field errors tended to be lower as the number of samples or their spacing increased. A robust method for estimating the position of the PSF peak has been introduced.

Vortex generator design for aircraft inlet distortion as a numerical optimization problem

NASA Technical Reports Server (NTRS)

Anderson, Bernhard H.; Levy, Ralph

1991-01-01

Aerodynamic compatibility of aircraft/inlet/engine systems is a difficult design problem for aircraft that must operate in many different flight regimes. Takeoff, subsonic cruise, supersonic cruise, transonic maneuvering, and high altitude loiter each place different constraints on inlet design. Vortex generators, small wing like sections mounted on the inside surfaces of the inlet duct, are used to control flow separation and engine face distortion. The design of vortex generator installations in an inlet is defined as a problem addressable by numerical optimization techniques. A performance parameter is suggested to account for both inlet distortion and total pressure loss at a series of design flight conditions. The resulting optimization problem is difficult since some of the design parameters take on integer values. If numerical procedures could be used to reduce multimillion dollar development test programs to a small set of verification tests, numerical optimization could have a significant impact on both cost and elapsed time to design new aircraft.

Landsat Data Continuity Mission (LDCM) - Optimizing X-Band Usage

NASA Technical Reports Server (NTRS)

Garon, H. M.; Gal-Edd, J. S.; Dearth, K. W.; Sank, V. I.

2010-01-01

The NASA version of the low-density parity check (LDPC) 7/8-rate code, shortened to the dimensions of (8160, 7136), has been implemented as the forward error correction (FEC) schema for the Landsat Data Continuity Mission (LDCM). This is the first flight application of this code. In order to place a 440 Msps link within the 375 MHz wide X band we found it necessary to heavily bandpass filter the satellite transmitter output . Despite the significant amplitude and phase distortions that accompanied the spectral truncation, the mission required BER is maintained at < 10(exp -12) with less than 2 dB of implementation loss. We utilized a band-pass filter designed ostensibly to replicate the link distortions to demonstrate link design viability. The same filter was then used to optimize the adaptive equalizer in the receiver employed at the terminus of the downlink. The excellent results we obtained could be directly attributed to the implementation of the LDPC code and the amplitude and phase compensation provided in the receiver. Similar results were obtained with receivers from several vendors.

High-frequency AC/DC converter with unity power factor and minimum harmonic distortion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wernekinch, E.R.

1987-01-01

The power factor is controlled by adjusting the relative position of the fundamental component of an optimized PWM-type voltage with respect to the supply voltage. Current harmonic distortion is minimized by the use of optimized firing angles for the converter at a frequency where GTO's can be used. This feature makes this approach very attractive at power levels of 100 to 600 kW. To obtain the optimized PWM pattern, a steepest descent digital computer algorithm is used. Digital-computer simulations are performed and a low-power model is constructed and tested to verify the concepts and the behavior of the model. Experimentalmore » results show that unity power factor is achieved and that the distortion in the phase currents is 10.4% at 90% of full load. This is less than achievable with sinusoidal PWM, harmonic elimination, hysteresis control, and deadbeat control for the same switching frequency.« less

Out-of-Focus Projector Calibration Method with Distortion Correction on the Projection Plane in the Structured Light Three-Dimensional Measurement System.

PubMed

Zhang, Jiarui; Zhang, Yingjie; Chen, Bo

2017-12-20

The three-dimensional measurement system with a binary defocusing technique is widely applied in diverse fields. The measurement accuracy is mainly determined by out-of-focus projector calibration accuracy. In this paper, a high-precision out-of-focus projector calibration method that is based on distortion correction on the projection plane and nonlinear optimization algorithm is proposed. To this end, the paper experimentally presents the principle that the projector has noticeable distortions outside its focus plane. In terms of this principle, the proposed method uses a high-order radial and tangential lens distortion representation on the projection plane to correct the calibration residuals caused by projection distortion. The final accuracy parameters of out-of-focus projector were obtained using a nonlinear optimization algorithm with good initial values, which were provided by coarsely calibrating the parameters of the out-of-focus projector on the focal and projection planes. Finally, the experimental results demonstrated that the proposed method can accuracy calibrate an out-of-focus projector, regardless of the amount of defocusing.

Optimization of a novel large field of view distortion phantom for MR-only treatment planning.

PubMed

Price, Ryan G; Knight, Robert A; Hwang, Ken-Pin; Bayram, Ersin; Nejad-Davarani, Siamak P; Glide-Hurst, Carri K

2017-07-01

MR-only treatment planning requires images of high geometric fidelity, particularly for large fields of view (FOV). However, the availability of large FOV distortion phantoms with analysis software is currently limited. This work sought to optimize a modular distortion phantom to accommodate multiple bore configurations and implement distortion characterization in a widely implementable solution. To determine candidate materials, 1.0 T MR and CT images were acquired of twelve urethane foam samples of various densities and strengths. Samples were precision-machined to accommodate 6 mm diameter paintballs used as landmarks. Final material candidates were selected by balancing strength, machinability, weight, and cost. Bore sizes and minimum aperture width resulting from couch position were tabulated from the literature (14 systems, 5 vendors). Bore geometry and couch position were simulated using MATLAB to generate machine-specific models to optimize the phantom build. Previously developed software for distortion characterization was modified for several magnet geometries (1.0 T, 1.5 T, 3.0 T), compared against previously published 1.0 T results, and integrated into the 3D Slicer application platform. All foam samples provided sufficient MR image contrast with paintball landmarks. Urethane foam (compressive strength ∼1000 psi, density ~20 lb/ft 3 ) was selected for its accurate machinability and weight characteristics. For smaller bores, a phantom version with the following parameters was used: 15 foam plates, 55 × 55 × 37.5 cm 3 (L×W×H), 5,082 landmarks, and weight ~30 kg. To accommodate > 70 cm wide bores, an extended build used 20 plates spanning 55 × 55 × 50 cm 3 with 7,497 landmarks and weight ~44 kg. Distortion characterization software was implemented as an external module into 3D Slicer's plugin framework and results agreed with the literature. The design and implementation of a modular, extendable distortion phantom was optimized for several bore configurations. The phantom and analysis software will be available for multi-institutional collaborations and cross-validation trials to support MR-only planning. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

A joint source-channel distortion model for JPEG compressed images.

PubMed

Sabir, Muhammad F; Sheikh, Hamid Rahim; Heath, Robert W; Bovik, Alan C

2006-06-01

The need for efficient joint source-channel coding (JSCC) is growing as new multimedia services are introduced in commercial wireless communication systems. An important component of practical JSCC schemes is a distortion model that can predict the quality of compressed digital multimedia such as images and videos. The usual approach in the JSCC literature for quantifying the distortion due to quantization and channel errors is to estimate it for each image using the statistics of the image for a given signal-to-noise ratio (SNR). This is not an efficient approach in the design of real-time systems because of the computational complexity. A more useful and practical approach would be to design JSCC techniques that minimize average distortion for a large set of images based on some distortion model rather than carrying out per-image optimizations. However, models for estimating average distortion due to quantization and channel bit errors in a combined fashion for a large set of images are not available for practical image or video coding standards employing entropy coding and differential coding. This paper presents a statistical model for estimating the distortion introduced in progressive JPEG compressed images due to quantization and channel bit errors in a joint manner. Statistical modeling of important compression techniques such as Huffman coding, differential pulse-coding modulation, and run-length coding are included in the model. Examples show that the distortion in terms of peak signal-to-noise ratio (PSNR) can be predicted within a 2-dB maximum error over a variety of compression ratios and bit-error rates. To illustrate the utility of the proposed model, we present an unequal power allocation scheme as a simple application of our model. Results show that it gives a PSNR gain of around 6.5 dB at low SNRs, as compared to equal power allocation.

New Side-Looking Rogowski Coil Sensor for Measuring Large-Magnitude Fast Impulse Currents

NASA Astrophysics Data System (ADS)

Metwally, I. A.

2015-12-01

This paper presents a new design of a side-looking "flat spiral" self-integrating Rogowski coil that is wound by twin coaxial cable with individual sheath. The coil is tested with different impulse current waveforms up to 7 kA peak value to improve its performance. The coil design is optimized to achieve bandwidth and sensitivity up to 7.854 MHz and 3.623 V/kA, respectively. The coil is calibrated versus two commercial impulse-current measurement devices at different coil-to-wire separations, coil inclination angles, and impulse current waveforms. Distortion of the coil output voltage waveform is examined by using the lumped-element model to optimize the connections of the four cable winding sheaths and the coil termination resistance. Finally, the coil frequency response is investigated to optimize the coil design parameters and achieve the desired bandwidth (large low-frequency time constant), high rate of rise, no overshoot, very small droop, high rate of fall, and no backswing.

Texture mapping via optimal mass transport.

PubMed

Dominitz, Ayelet; Tannenbaum, Allen

2010-01-01

In this paper, we present a novel method for texture mapping of closed surfaces. Our method is based on the technique of optimal mass transport (also known as the "earth-mover's metric"). This is a classical problem that concerns determining the optimal way, in the sense of minimal transportation cost, of moving a pile of soil from one site to another. In our context, the resulting mapping is area preserving and minimizes angle distortion in the optimal mass sense. Indeed, we first begin with an angle-preserving mapping (which may greatly distort area) and then correct it using the mass transport procedure derived via a certain gradient flow. In order to obtain fast convergence to the optimal mapping, we incorporate a multiresolution scheme into our flow. We also use ideas from discrete exterior calculus in our computations.

High-precision method of binocular camera calibration with a distortion model.

PubMed

Li, Weimin; Shan, Siyu; Liu, Hui

2017-03-10

A high-precision camera calibration method for binocular stereo vision system based on a multi-view template and alternative bundle adjustment is presented in this paper. The proposed method could be achieved by taking several photos on a specially designed calibration template that has diverse encoded points in different orientations. In this paper, the method utilized the existing algorithm used for monocular camera calibration to obtain the initialization, which involves a camera model, including radial lens distortion and tangential distortion. We created a reference coordinate system based on the left camera coordinate to optimize the intrinsic parameters of left camera through alternative bundle adjustment to obtain optimal values. Then, optimal intrinsic parameters of the right camera can be obtained through alternative bundle adjustment when we create a reference coordinate system based on the right camera coordinate. We also used all intrinsic parameters that were acquired to optimize extrinsic parameters. Thus, the optimal lens distortion parameters and intrinsic and extrinsic parameters were obtained. Synthetic and real data were used to test the method. The simulation results demonstrate that the maximum mean absolute relative calibration errors are about 3.5e-6 and 1.2e-6 for the focal length and the principal point, respectively, under zero-mean Gaussian noise with 0.05 pixels standard deviation. The real result shows that the reprojection error of our model is about 0.045 pixels with the relative standard deviation of 1.0e-6 over the intrinsic parameters. The proposed method is convenient, cost-efficient, highly precise, and simple to carry out.

Optimal design of tilt carrier frequency computer-generated holograms to measure aspherics.

PubMed

Peng, Jiantao; Chen, Zhe; Zhang, Xingxiang; Fu, Tianjiao; Ren, Jianyue

2015-08-20

Computer-generated holograms (CGHs) provide an approach to high-precision metrology of aspherics. A CGH is designed under the trade-off among size, mapping distortion, and line spacing. This paper describes an optimal design method based on the parametric model for tilt carrier frequency CGHs placed outside the interferometer focus points. Under the condition of retaining an admissible size and a tolerable mapping distortion, the optimal design method has two advantages: (1) separating the parasitic diffraction orders to improve the contrast of the interferograms and (2) achieving the largest line spacing to minimize sensitivity to fabrication errors. This optimal design method is applicable to common concave aspherical surfaces and illustrated with CGH design examples.

Effects of amplitude distortions and IF equalization on satellite communication system bit-error rate performance

NASA Technical Reports Server (NTRS)

Kerczewski, Robert J.; Fujikawa, Gene; Svoboda, James S.; Lizanich, Paul J.

1990-01-01

Satellite communications links are subject to distortions which result in an amplitude versus frequency response which deviates from the ideal flat response. Such distortions result from propagation effects such as multipath fading and scintillation and from transponder and ground terminal hardware imperfections. Bit-error rate (BER) degradation resulting from several types of amplitude response distortions were measured. Additional tests measured the amount of BER improvement obtained by flattening the amplitude response of a distorted laboratory simulated satellite channel. The results of these experiments are presented.

THz optical design considerations and optimization for medical imaging applications

NASA Astrophysics Data System (ADS)

Sung, Shijun; Garritano, James; Bajwa, Neha; Nowroozi, Bryan; Llombart, Nuria; Grundfest, Warren; Taylor, Zachary D.

2014-09-01

THz imaging system design will play an important role making possible imaging of targets with arbitrary properties and geometries. This study discusses design consideration and imaging performance optimization techniques in THz quasioptical imaging system optics. Analysis of field and polarization distortion by off-axis parabolic (OAP) mirrors in THz imaging optics shows how distortions are carried in a series of mirrors while guiding the THz beam. While distortions of the beam profile by individual mirrors are not significant, these effects are compounded by a series of mirrors in antisymmetric orientation. It is shown that symmetric orientation of the OAP mirror effectively cancels this distortion to recover the original beam profile. Additionally, symmetric orientation can correct for some geometrical off-focusing due to misalignment. We also demonstrate an alternative method to test for overall system optics alignment by investigating the imaging performance of the tilted target plane. Asymmetric signal profile as a function of the target plane's tilt angle indicates when one or more imaging components are misaligned, giving a preferred tilt direction. Such analysis can offer additional insight into often elusive source device misalignment at an integrated system. Imaging plane tilting characteristics are representative of a 3-D modulation transfer function of the imaging system. A symmetric tilted plane is preferred to optimize imaging performance.

Information's role in the estimation of chaotic signals

NASA Astrophysics Data System (ADS)

Drake, Daniel Fred

1998-11-01

Researchers have proposed several methods designed to recover chaotic signals from noise-corrupted observations. While the methods vary, their qualitative performance does not: in low levels of noise all methods effectively recover the underlying signal; in high levels of noise no method can recover the underlying signal to any meaningful degree of accuracy. Of the methods proposed to date, all represent sub-optimal estimators. So: Is the inability to recover the signal in high noise levels simply a consequence of estimator sub-optimality? Or is estimator failure actually a manifestation of some intrinsic property of chaos itself? These questions are answered by deriving an optimal estimator for a class of chaotic systems and noting that it, too, fails in high levels of noise. An exact, closed- form expression for the estimator is obtained for a class of chaotic systems whose signals are solutions to a set of linear (but noncausal) difference equations. The existence of this linear description circumvents the difficulties normally encountered when manipulating the nonlinear (but causal) expressions that govern. chaotic behavior. The reason why even the optimal estimator fails to recover underlying chaotic signals in high levels of noise has its roots in information theory. At such noise levels, the mutual information linking the corrupted observations to the underlying signal is essentially nil, reducing the estimator to a simple guessing strategy based solely on a priori statistics. Entropy, long the common bond between information theory and dynamical systems, is actually one aspect of a far more complete characterization of information sources: the rate distortion function. Determining the rate distortion function associated with the class of chaotic systems considered in this work provides bounds on estimator performance in high levels of noise. Finally, a slight modification of the linear description leads to a method of synthesizing on limited precision platforms ``pseudo-chaotic'' sequences that mimic true chaotic behavior to any finite degree of precision and duration. The use of such a technique in spread-spectrum communications is considered.

Minimizing embedding impact in steganography using trellis-coded quantization

NASA Astrophysics Data System (ADS)

Filler, Tomáš; Judas, Jan; Fridrich, Jessica

2010-01-01

In this paper, we propose a practical approach to minimizing embedding impact in steganography based on syndrome coding and trellis-coded quantization and contrast its performance with bounds derived from appropriate rate-distortion bounds. We assume that each cover element can be assigned a positive scalar expressing the impact of making an embedding change at that element (single-letter distortion). The problem is to embed a given payload with minimal possible average embedding impact. This task, which can be viewed as a generalization of matrix embedding or writing on wet paper, has been approached using heuristic and suboptimal tools in the past. Here, we propose a fast and very versatile solution to this problem that can theoretically achieve performance arbitrarily close to the bound. It is based on syndrome coding using linear convolutional codes with the optimal binary quantizer implemented using the Viterbi algorithm run in the dual domain. The complexity and memory requirements of the embedding algorithm are linear w.r.t. the number of cover elements. For practitioners, we include detailed algorithms for finding good codes and their implementation. Finally, we report extensive experimental results for a large set of relative payloads and for different distortion profiles, including the wet paper channel.

Minimizing distortion and internal forces in truss structures by simulated annealing

NASA Technical Reports Server (NTRS)

Kincaid, Rex K.; Padula, Sharon L.

1990-01-01

Inaccuracies in the length of members and the diameters of joints of large space structures may produce unacceptable levels of surface distortion and internal forces. Here, two discrete optimization problems are formulated, one to minimize surface distortion (DSQRMS) and the other to minimize internal forces (FSQRMS). Both of these problems are based on the influence matrices generated by a small-deformation linear analysis. Good solutions are obtained for DSQRMS and FSQRMS through the use of a simulated annealing heuristic.

Distortion management in slow-light pulse delay.

PubMed

Stenner, Michael D; Neifeld, Mark A; Zhu, Zhaoming; Dawes, Andrew M C; Gauthier, Daniel J

2005-12-12

We describe a methodology to maximize slow-light pulse delay subject to a constraint on the allowable pulse distortion. We show that optimizing over a larger number of physical variables can increase the distortion-constrained delay. We demonstrate these concepts by comparing the optimum slow-light pulse delay achievable using a single Lorentzian gain line with that achievable using a pair of closely-spaced gain lines. We predict that distortion management using a gain doublet can provide approximately a factor of 2 increase in slow-light pulse delay as compared with the optimum single-line delay. Experimental results employing Brillouin gain in optical fiber confirm our theoretical predictions.

Distortion control in 20MnCr5 bevel gears after liquid nitriding process to maintain precision dimensions

NASA Astrophysics Data System (ADS)

Mahendiran, M.; Kavitha, M.

2018-02-01

Robotic and automotive gears are generally very high precision components with limitations in tolerances. Bevel gears are more widely used and dimensionally very close tolerance components that need stability without any backlash or distortion for smooth and trouble free functions. Nitriding is carried out to enhance wear resistance of the surface. The aim of this paper is to reduce the distortion in liquid nitriding process, though plasma nitriding is preferred for high precision components. Various trials were conducted to optimize the process parameters, considering pre dimensional setting for nominal nitriding layer growth. Surface cleaning, suitable fixtures and stress relieving operations were also done to optimize the process. Micro structural analysis and Vickers hardness testing were carried out for analyzing the phase changes, variation in surface hardness and case depth. CNC gear testing machine was used for determining the distortion level. The presence of white layer was found for about 10-15μm in the case depth of 250± 3.5μm showing an average surface hardness of 670 HV. Hence the economical liquid nitriding process was successfully used for producing high hardness and wear resistant coating over 20MnCr5 material with less distortion and reduced secondary grinding process for dimensional control.

Predictive Rate-Distortion for Infinite-Order Markov Processes

NASA Astrophysics Data System (ADS)

Marzen, Sarah E.; Crutchfield, James P.

2016-06-01

Predictive rate-distortion analysis suffers from the curse of dimensionality: clustering arbitrarily long pasts to retain information about arbitrarily long futures requires resources that typically grow exponentially with length. The challenge is compounded for infinite-order Markov processes, since conditioning on finite sequences cannot capture all of their past dependencies. Spectral arguments confirm a popular intuition: algorithms that cluster finite-length sequences fail dramatically when the underlying process has long-range temporal correlations and can fail even for processes generated by finite-memory hidden Markov models. We circumvent the curse of dimensionality in rate-distortion analysis of finite- and infinite-order processes by casting predictive rate-distortion objective functions in terms of the forward- and reverse-time causal states of computational mechanics. Examples demonstrate that the resulting algorithms yield substantial improvements.

Optimization of the transmission of observable expectation values and observable statistics in continuous-variable teleportation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albano Farias, L.; Stephany, J.

2010-12-15

We analyze the statistics of observables in continuous-variable (CV) quantum teleportation in the formalism of the characteristic function. We derive expressions for average values of output-state observables, in particular, cumulants which are additive in terms of the input state and the resource of teleportation. Working with a general class of teleportation resources, the squeezed-bell-like states, which may be optimized in a free parameter for better teleportation performance, we discuss the relation between resources optimal for fidelity and those optimal for different observable averages. We obtain the values of the free parameter of the squeezed-bell-like states which optimize the central momentamore » and cumulants up to fourth order. For the cumulants the distortion between in and out states due to teleportation depends only on the resource. We obtain optimal parameters {Delta}{sub (2)}{sup opt} and {Delta}{sub (4)}{sup opt} for the second- and fourth-order cumulants, which do not depend on the squeezing of the resource. The second-order central momenta, which are equal to the second-order cumulants, and the photon number average are also optimized by the resource with {Delta}{sub (2)}{sup opt}. We show that the optimal fidelity resource, which has been found previously to depend on the characteristics of input, approaches for high squeezing to the resource that optimizes the second-order momenta. A similar behavior is obtained for the resource that optimizes the photon statistics, which is treated here using the sum of the squared differences in photon probabilities of input versus output states as the distortion measure. This is interpreted naturally to mean that the distortions associated with second-order momenta dominate the behavior of the output state for large squeezing of the resource. Optimal fidelity resources and optimal photon statistics resources are compared, and it is shown that for mixtures of Fock states both resources are equivalent.« less

New technique for real-time distortion-invariant multiobject recognition and classification

NASA Astrophysics Data System (ADS)

Hong, Rutong; Li, Xiaoshun; Hong, En; Wang, Zuyi; Wei, Hongan

2001-04-01

A real-time hybrid distortion-invariant OPR system was established to make 3D multiobject distortion-invariant automatic pattern recognition. Wavelet transform technique was used to make digital preprocessing of the input scene, to depress the noisy background and enhance the recognized object. A three-layer backpropagation artificial neural network was used in correlation signal post-processing to perform multiobject distortion-invariant recognition and classification. The C-80 and NOA real-time processing ability and the multithread programming technology were used to perform high speed parallel multitask processing and speed up the post processing rate to ROIs. The reference filter library was constructed for the distortion version of 3D object model images based on the distortion parameter tolerance measuring as rotation, azimuth and scale. The real-time optical correlation recognition testing of this OPR system demonstrates that using the preprocessing, post- processing, the nonlinear algorithm os optimum filtering, RFL construction technique and the multithread programming technology, a high possibility of recognition and recognition rate ere obtained for the real-time multiobject distortion-invariant OPR system. The recognition reliability and rate was improved greatly. These techniques are very useful to automatic target recognition.

Operational rate-distortion performance for joint source and channel coding of images.

PubMed

Ruf, M J; Modestino, J W

1999-01-01

This paper describes a methodology for evaluating the operational rate-distortion behavior of combined source and channel coding schemes with particular application to images. In particular, we demonstrate use of the operational rate-distortion function to obtain the optimum tradeoff between source coding accuracy and channel error protection under the constraint of a fixed transmission bandwidth for the investigated transmission schemes. Furthermore, we develop information-theoretic bounds on performance for specific source and channel coding systems and demonstrate that our combined source-channel coding methodology applied to different schemes results in operational rate-distortion performance which closely approach these theoretical limits. We concentrate specifically on a wavelet-based subband source coding scheme and the use of binary rate-compatible punctured convolutional (RCPC) codes for transmission over the additive white Gaussian noise (AWGN) channel. Explicit results for real-world images demonstrate the efficacy of this approach.

BPM Button Optimization to Minimize Distortion Due to Trapped Mode Heating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cameron,P.; Blednyk, A.; Kosciuk, B.

2009-05-04

The outer circumference of a BPM button and the inner circumference of the button housing comprise a transmission line. This transmission line typically presents an impedance of a few tens of ohms to the beam, and couples very weakly to the 50 ohm coaxial transmission line that comprises the signal path out of the button. The modes which are consequently excited and trapped often have quality factors of several hundred, permitting resonant excitation by the beam. The thermal distortion resulting from trapped mode heating is potentially problematic for achieving the high precision beam position measurements needed to provide the sub-micronmore » beam position stability required by light source users. We present a button design that has been optimized via material selection and component geometry to minimize both the trapped mode heating and the resulting thermal distortion.« less

Ghost artifact cancellation using phased array processing.

PubMed

Kellman, P; McVeigh, E R

2001-08-01

In this article, a method for phased array combining is formulated which may be used to cancel ghosts caused by a variety of distortion mechanisms, including space variant distortions such as local flow or off-resonance. This method is based on a constrained optimization, which optimizes SNR subject to the constraint of nulling ghost artifacts at known locations. The resultant technique is similar to the method known as sensitivity encoding (SENSE) used for accelerated imaging; however, in this formulation it is applied to full field-of-view (FOV) images. The method is applied to multishot EPI with noninterleaved phase encode acquisition. A number of benefits, as compared to the conventional interleaved approach, are reduced distortion due to off-resonance, in-plane flow, and EPI delay misalignment, as well as eliminating the need for echo-shifting. Experimental results demonstrate the cancellation for both phantom as well as cardiac imaging examples.

Ghost Artifact Cancellation Using Phased Array Processing

PubMed Central

Kellman, Peter; McVeigh, Elliot R.

2007-01-01

In this article, a method for phased array combining is formulated which may be used to cancel ghosts caused by a variety of distortion mechanisms, including space variant distortions such as local flow or off-resonance. This method is based on a constrained optimization, which optimizes SNR subject to the constraint of nulling ghost artifacts at known locations. The resultant technique is similar to the method known as sensitivity encoding (SENSE) used for accelerated imaging; however, in this formulation it is applied to full field-of-view (FOV) images. The method is applied to multishot EPI with noninterleaved phase encode acquisition. A number of benefits, as compared to the conventional interleaved approach, are reduced distortion due to off-resonance, in-plane flow, and EPI delay misalignment, as well as eliminating the need for echo-shifting. Experimental results demonstrate the cancellation for both phantom as well as cardiac imaging examples. PMID:11477638

A framework for designing and analyzing binary decision-making strategies in cellular systems†

PubMed Central

Porter, Joshua R.; Andrews, Burton W.; Iglesias, Pablo A.

2015-01-01

Cells make many binary (all-or-nothing) decisions based on noisy signals gathered from their environment and processed through noisy decision-making pathways. Reducing the effect of noise to improve the fidelity of decision-making comes at the expense of increased complexity, creating a tradeoff between performance and metabolic cost. We present a framework based on rate distortion theory, a branch of information theory, to quantify this tradeoff and design binary decision-making strategies that balance low cost and accuracy in optimal ways. With this framework, we show that several observed behaviors of binary decision-making systems, including random strategies, hysteresis, and irreversibility, are optimal in an information-theoretic sense for various situations. This framework can also be used to quantify the goals around which a decision-making system is optimized and to evaluate the optimality of cellular decision-making systems by a fundamental information-theoretic criterion. As proof of concept, we use the framework to quantify the goals of the externally triggered apoptosis pathway. PMID:22370552

A versatile photogrammetric camera automatic calibration suite for multispectral fusion and optical helmet tracking

NASA Astrophysics Data System (ADS)

de Villiers, Jason; Jermy, Robert; Nicolls, Fred

2014-06-01

This paper presents a system to determine the photogrammetric parameters of a camera. The lens distortion, focal length and camera six degree of freedom (DOF) position are calculated. The system caters for cameras of different sensitivity spectra and fields of view without any mechanical modifications. The distortion characterization, a variant of Brown's classic plumb line method, allows many radial and tangential distortion coefficients and finds the optimal principal point. Typical values are 5 radial and 3 tangential coefficients. These parameters are determined stably and demonstrably produce superior results to low order models despite popular and prevalent misconceptions to the contrary. The system produces coefficients to model both the distorted to undistorted pixel coordinate transformation (e.g. for target designation) and the inverse transformation (e.g. for image stitching and fusion) allowing deterministic rates far exceeding real time. The focal length is determined to minimise the error in absolute photogrammetric positional measurement for both multi camera systems or monocular (e.g. helmet tracker) systems. The system determines the 6 DOF position of the camera in a chosen coordinate system. It can also determine the 6 DOF offset of the camera relative to its mechanical mount. This allows faulty cameras to be replaced without requiring a recalibration of the entire system (such as an aircraft cockpit). Results from two simple applications of the calibration results are presented: stitching and fusion of the images from a dual-band visual/ LWIR camera array, and a simple laboratory optical helmet tracker.

Analyzing Reaction Rates with the Distortion/Interaction‐Activation Strain Model

PubMed Central

2017-01-01

Abstract The activation strain or distortion/interaction model is a tool to analyze activation barriers that determine reaction rates. For bimolecular reactions, the activation energies are the sum of the energies to distort the reactants into geometries they have in transition states plus the interaction energies between the two distorted molecules. The energy required to distort the molecules is called the activation strain or distortion energy. This energy is the principal contributor to the activation barrier. The transition state occurs when this activation strain is overcome by the stabilizing interaction energy. Following the changes in these energies along the reaction coordinate gives insights into the factors controlling reactivity. This model has been applied to reactions of all types in both organic and inorganic chemistry, including substitutions and eliminations, cycloadditions, and several types of organometallic reactions. PMID:28447369

Boundary-layer-ingesting inlet flow control system

NASA Technical Reports Server (NTRS)

Owens, Lewis R. (Inventor); Allan, Brian G. (Inventor)

2010-01-01

A system for reducing distortion at the aerodynamic interface plane of a boundary-layer-ingesting inlet using a combination of active and passive flow control devices is disclosed. Active flow control jets and vortex generating vanes are used in combination to reduce distortion across a range of inlet operating conditions. Together, the vortex generating vanes can reduce most of the inlet distortion and the active flow control jets can be used at a significantly reduced control jet mass flow rate to make sure the inlet distortion stays low as the inlet mass flow rate varies. Overall inlet distortion, measured and described as average SAE circumferential distortion descriptor, was maintained at a value of 0.02 or less. Advantageous arrangements and orientations of the active flow control jets and the vortex generating vanes were developed using computational fluid dynamics simulations and wind tunnel experimentations.

Optimal Micro-Vane Flow Control for Compact Air Vehicle Inlets

NASA Technical Reports Server (NTRS)

Anderson, Bernhard H.; Miller, Daniel N.; Addington, Gregory A.; Agrell, Johan

2004-01-01

The purpose of this study on micro-vane secondary flow control is to demonstrate the viability and economy of Response Surface Methodology (RSM) to optimally design micro-vane secondary flow control arrays, and to establish that the aeromechanical effects of engine face distortion can also be included in the design and optimization process. These statistical design concepts were used to investigate the design characteristics of "low unit strength" micro-effector arrays. "Low unit strength" micro-effectors are micro-vanes set at very low angles-of-incidence with very long chord lengths. They were designed to influence the near wall inlet flow over an extended streamwise distance, and their advantage lies in low total pressure loss and high effectiveness in managing engine face distortion. Therefore, this report examines optimal micro-vane secondary flow control array designs for compact inlets through a Response Surface Methodology.

Visual Perception Based Rate Control Algorithm for HEVC

NASA Astrophysics Data System (ADS)

Feng, Zeqi; Liu, PengYu; Jia, Kebin

2018-01-01

For HEVC, rate control is an indispensably important video coding technology to alleviate the contradiction between video quality and the limited encoding resources during video communication. However, the rate control benchmark algorithm of HEVC ignores subjective visual perception. For key focus regions, bit allocation of LCU is not ideal and subjective quality is unsatisfied. In this paper, a visual perception based rate control algorithm for HEVC is proposed. First bit allocation weight of LCU level is optimized based on the visual perception of luminance and motion to ameliorate video subjective quality. Then λ and QP are adjusted in combination with the bit allocation weight to improve rate distortion performance. Experimental results show that the proposed algorithm reduces average 0.5% BD-BR and maximum 1.09% BD-BR at no cost in bitrate accuracy compared with HEVC (HM15.0). The proposed algorithm devotes to improving video subjective quality under various video applications.

Quality versus intelligibility: studying human preferences for American Sign Language video

NASA Astrophysics Data System (ADS)

Ciaramello, Frank M.; Hemami, Sheila S.

2011-03-01

Real-time videoconferencing using cellular devices provides natural communication to the Deaf community. For this application, compressed American Sign Language (ASL) video must be evaluated in terms of the intelligibility of the conversation and not in terms of the overall aesthetic quality of the video. This work presents a paired comparison experiment to determine the subjective preferences of ASL users in terms of the trade-off between intelligibility and quality when varying the proportion of the bitrate allocated explicitly to the regions of the video containing the signer. A rate-distortion optimization technique, which jointly optimizes a quality criteria and an intelligibility criteria according to a user-specified parameter, generates test video pairs for the subjective experiment. Experimental results suggest that at sufficiently high bitrates, all users prefer videos in which the non-signer regions in the video are encoded with some nominal rate. As the total encoding bitrate decreases, users generally prefer video in which a greater proportion of the rate is allocated to the signer. The specific operating points preferred in the quality-intelligibility trade-off vary with the demographics of the users.

Minor Distortions with Major Consequences: Correcting Distortions in Imaging Spectrographs

PubMed Central

Esmonde-White, Francis W. L.; Esmonde-White, Karen A.; Morris, Michael D.

2010-01-01

Projective transformation is a mathematical correction (implemented in software) used in the remote imaging field to produce distortion-free images. We present the application of projective transformation to correct minor alignment and astigmatism distortions that are inherent in dispersive spectrographs. Patterned white-light images and neon emission spectra were used to produce registration points for the transformation. Raman transects collected on microscopy and fiber-optic systems were corrected using established methods and compared with the same transects corrected using the projective transformation. Even minor distortions have a significant effect on reproducibility and apparent fluorescence background complexity. Simulated Raman spectra were used to optimize the projective transformation algorithm. We demonstrate that the projective transformation reduced the apparent fluorescent background complexity and improved reproducibility of measured parameters of Raman spectra. Distortion correction using a projective transformation provides a major advantage in reducing the background fluorescence complexity even in instrumentation where slit-image distortions and camera rotation were minimized using manual or mechanical means. We expect these advantages should be readily applicable to other spectroscopic modalities using dispersive imaging spectrographs. PMID:21211158

Optimal Inlet Shape Design of N2B Hybrid Wing Body Configuration

NASA Technical Reports Server (NTRS)

Kim, Hyoungjin; Liou, Meng-Sing

2012-01-01

The N2B hybrid wing body aircraft was conceptually designed to meet environmental and performance goals for the N+2 generation transport set by the Subsonic Fixed Wing project of NASA Fundamental Aeronautics Program. In the present study, flow simulations are conducted around the N2B configuration by a Reynolds-averaged Navier-Stokes flow solver using unstructured meshes. Boundary conditions at engine fan face and nozzle exhaust planes are provided by the NPSS thermodynamic engine cycle model. The flow simulations reveal challenging design issues arising from boundary layer ingestion offset inlet and airframe-propulsion integration. Adjoint-based optimal designs are then conducted for the inlet shape to minimize the airframe drag force and flow distortion at fan faces. Design surfaces are parameterized by NURBS, and the cowl lip geometry is modified by a spring analogy approach. By the drag minimization design, flow separation on the cowl surfaces are almost removed, and shock wave strength got remarkably reduced. For the distortion minimization design, a circumferential distortion indicator DPCP(sub avg) is adopted as the design objective and diffuser bottom and side wall surfaces are perturbed for the design. The distortion minimization results in a 12.5 % reduction in the objective function.

"Can you see me now?" An objective metric for predicting intelligibility of compressed American Sign Language video

NASA Astrophysics Data System (ADS)

Ciaramello, Francis M.; Hemami, Sheila S.

2007-02-01

For members of the Deaf Community in the United States, current communication tools include TTY/TTD services, video relay services, and text-based communication. With the growth of cellular technology, mobile sign language conversations are becoming a possibility. Proper coding techniques must be employed to compress American Sign Language (ASL) video for low-rate transmission while maintaining the quality of the conversation. In order to evaluate these techniques, an appropriate quality metric is needed. This paper demonstrates that traditional video quality metrics, such as PSNR, fail to predict subjective intelligibility scores. By considering the unique structure of ASL video, an appropriate objective metric is developed. Face and hand segmentation is performed using skin-color detection techniques. The distortions in the face and hand regions are optimally weighted and pooled across all frames to create an objective intelligibility score for a distorted sequence. The objective intelligibility metric performs significantly better than PSNR in terms of correlation with subjective responses.

Active hydrogen evolution through lattice distortion in metallic MoTe2

NASA Astrophysics Data System (ADS)

Seok, Jinbong; Lee, Jun-Ho; Cho, Suyeon; Ji, Byungdo; Kim, Hyo Won; Kwon, Min; Kim, Dohyun; Kim, Young-Min; Oh, Sang Ho; Wng Kim, Sung; Lee, Young Hee; Son, Young-Woo; Yang, Heejun

2017-06-01

Engineering surface atoms of transition metal dichalcogenides (TMDs) is a promising way to design catalysts for efficient electrochemical reactions including the hydrogen evolution reaction (HER). However, materials processing based on TMDs, such as vacancy creation or edge exposure, for active HER, has resulted in insufficient atomic-precision lattice homogeneity and a lack of clear understanding of HER over 2D materials. Here, we report a durable and effective HER at atomically defined reaction sites in 2D layered semimetallic MoTe2 with intrinsic turnover frequency (TOF) of 0.14 s-1 at 0 mV overpotential, which cannot be explained by the traditional volcano plot analysis. Unlike former electrochemical catalysts, the rate-determining step of the HER on the semimetallic MoTe2, hydrogen adsorption, drives Peierls-type lattice distortion that, together with a surface charge density wave, unexpectedly enhances the HER. The active HER using unique 2D features of layered TMDs enables an optimal design of electrochemical catalysts and paves the way for a hydrogen economy.

Energy Efficiency Under Alternative Carbon Policies. Incentives, Measurement, and Interregional Effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steinberg, Daniel C.; Boyd, Erin

2015-08-28

In this report, we examine and compare how tradable mass-based polices and tradable rate-based policies create different incentives for energy efficiency investments. Through a generalized demonstration and set of examples, we show that as a result of the output subsidy they create, traditional rate-based policies, those that do not credit energy savings from efficiency measures, reduce the incentive for investment in energy efficiency measures relative to an optimally designed mass-based policy or equivalent carbon tax. We then show that this reduced incentive can be partially addressed by modifying the rate-based policy such that electricity savings from energy efficiency measures aremore » treated as a source of zero-carbon generation within the framework of the standard, or equivalently, by assigning avoided emissions credit to the electricity savings at the rate of the intensity target. These approaches result in an extension of the output subsidy to efficiency measures and eliminate the distortion between supply-side and demand-side options for GHG emissions reduction. However, these approaches do not address electricity price distortions resulting from the output subsidy that also impact the value of efficiency measures. Next, we assess alternative approaches for crediting energy efficiency savings within the framework of a rate-based policy. Finally, we identify a number of challenges that arise in implementing a rate-based policy with efficiency crediting, including the requirement to develop robust estimates of electricity savings in order to assess compliance, and the requirement to track the regionality of the generation impacts of efficiency measures to account for their interstate effects.« less

A cascaded model of spectral distortions due to spectral response effects and pulse pileup effects in a photon-counting x-ray detector for CT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cammin, Jochen, E-mail: jcammin1@jhmi.edu, E-mail: ktaguchi@jhmi.edu; Taguchi, Katsuyuki, E-mail: jcammin1@jhmi.edu, E-mail: ktaguchi@jhmi.edu; Xu, Jennifer

Purpose: Energy discriminating, photon-counting detectors (PCDs) are an emerging technology for computed tomography (CT) with various potential benefits for clinical CT. The photon energies measured by PCDs can be distorted due to the interactions of a photon with the detector and the interaction of multiple coincident photons. These effects result in distorted recorded x-ray spectra which may lead to artifacts in reconstructed CT images and inaccuracies in tissue identification. Model-based compensation techniques have the potential to account for the distortion effects. This approach requires only a small number of parameters and is applicable to a wide range of spectra andmore » count rates, but it needs an accurate model of the spectral distortions occurring in PCDs. The purpose of this study was to develop a model of those spectral distortions and to evaluate the model using a PCD (model DXMCT-1; DxRay, Inc., Northridge, CA) and various x-ray spectra in a wide range of count rates. Methods: The authors hypothesize that the complex phenomena of spectral distortions can be modeled by: (1) separating them into count-rate independent factors that we call the spectral response effects (SRE), and count-rate dependent factors that we call the pulse pileup effects (PPE), (2) developing separate models for SRE and PPE, and (3) cascading the SRE and PPE models into a combined SRE+PPE model that describes PCD distortions at both low and high count rates. The SRE model describes the probability distribution of the recorded spectrum, with a photo peak and a continuum tail, given the incident photon energy. Model parameters were obtained from calibration measurements with three radioisotopes and then interpolated linearly for other energies. The PPE model used was developed in the authors’ previous work [K. Taguchi et al., “Modeling the performance of a photon counting x-ray detector for CT: Energy response and pulse pileup effects,” Med. Phys. 38(2), 1089–1102 (2011)]. The agreement between the x-ray spectra calculated by the cascaded SRE+PPE model and the measured spectra was evaluated for various levels of deadtime loss ratios (DLR) and incident spectral shapes, realized using different attenuators, in terms of the weighted coefficient of variation (COV{sub W}), i.e., the root mean square difference weighted by the statistical errors of the data and divided by the mean. Results: At low count rates, when DLR < 10%, the distorted spectra measured by the DXMCT-1 were in agreement with those calculated by SRE only, with COV{sub W}'s less than 4%. At higher count rates, the measured spectra were also in agreement with the ones calculated by the cascaded SRE+PPE model; with PMMA as attenuator, COV{sub W} was 5.6% at a DLR of 22% and as small as 6.7% for a DLR as high as 55%. Conclusions: The x-ray spectra calculated by the proposed model agreed with the measured spectra over a wide range of count rates and spectral shapes. The SRE model predicted the distorted, recorded spectra with low count rates over various types and thicknesses of attenuators. The study also validated the hypothesis that the complex spectral distortions in a PCD can be adequately modeled by cascading the count-rate independent SRE and the count-rate dependent PPE.« less

A cascaded model of spectral distortions due to spectral response effects and pulse pileup effects in a photon-counting x-ray detector for CT

PubMed Central

Cammin, Jochen; Xu, Jennifer; Barber, William C.; Iwanczyk, Jan S.; Hartsough, Neal E.; Taguchi, Katsuyuki

2014-01-01

Purpose: Energy discriminating, photon-counting detectors (PCDs) are an emerging technology for computed tomography (CT) with various potential benefits for clinical CT. The photon energies measured by PCDs can be distorted due to the interactions of a photon with the detector and the interaction of multiple coincident photons. These effects result in distorted recorded x-ray spectra which may lead to artifacts in reconstructed CT images and inaccuracies in tissue identification. Model-based compensation techniques have the potential to account for the distortion effects. This approach requires only a small number of parameters and is applicable to a wide range of spectra and count rates, but it needs an accurate model of the spectral distortions occurring in PCDs. The purpose of this study was to develop a model of those spectral distortions and to evaluate the model using a PCD (model DXMCT-1; DxRay, Inc., Northridge, CA) and various x-ray spectra in a wide range of count rates. Methods: The authors hypothesize that the complex phenomena of spectral distortions can be modeled by: (1) separating them into count-rate independent factors that we call the spectral response effects (SRE), and count-rate dependent factors that we call the pulse pileup effects (PPE), (2) developing separate models for SRE and PPE, and (3) cascading the SRE and PPE models into a combined SRE+PPE model that describes PCD distortions at both low and high count rates. The SRE model describes the probability distribution of the recorded spectrum, with a photo peak and a continuum tail, given the incident photon energy. Model parameters were obtained from calibration measurements with three radioisotopes and then interpolated linearly for other energies. The PPE model used was developed in the authors’ previous work [K. Taguchi , “Modeling the performance of a photon counting x-ray detector for CT: Energy response and pulse pileup effects,” Med. Phys. 38(2), 1089–1102 (2011)]. The agreement between the x-ray spectra calculated by the cascaded SRE+PPE model and the measured spectra was evaluated for various levels of deadtime loss ratios (DLR) and incident spectral shapes, realized using different attenuators, in terms of the weighted coefficient of variation (COVW), i.e., the root mean square difference weighted by the statistical errors of the data and divided by the mean. Results: At low count rates, when DLR < 10%, the distorted spectra measured by the DXMCT-1 were in agreement with those calculated by SRE only, with COVW's less than 4%. At higher count rates, the measured spectra were also in agreement with the ones calculated by the cascaded SRE+PPE model; with PMMA as attenuator, COVW was 5.6% at a DLR of 22% and as small as 6.7% for a DLR as high as 55%. Conclusions: The x-ray spectra calculated by the proposed model agreed with the measured spectra over a wide range of count rates and spectral shapes. The SRE model predicted the distorted, recorded spectra with low count rates over various types and thicknesses of attenuators. The study also validated the hypothesis that the complex spectral distortions in a PCD can be adequately modeled by cascading the count-rate independent SRE and the count-rate dependent PPE. PMID:24694136

Advantages of formulating an evolution equation directly for elastic distortional deformation in finite deformation plasticity

NASA Astrophysics Data System (ADS)

Rubin, M. B.; Cardiff, P.

2017-11-01

Simo (Comput Methods Appl Mech Eng 66:199-219, 1988) proposed an evolution equation for elastic deformation together with a constitutive equation for inelastic deformation rate in plasticity. The numerical algorithm (Simo in Comput Methods Appl Mech Eng 68:1-31, 1988) for determining elastic distortional deformation was simple. However, the proposed inelastic deformation rate caused plastic compaction. The corrected formulation (Simo in Comput Methods Appl Mech Eng 99:61-112, 1992) preserves isochoric plasticity but the numerical integration algorithm is complicated and needs special methods for calculation of the exponential map of a tensor. Alternatively, an evolution equation for elastic distortional deformation can be proposed directly with a simplified constitutive equation for inelastic distortional deformation rate. This has the advantage that the physics of inelastic distortional deformation is separated from that of dilatation. The example of finite deformation J2 plasticity with linear isotropic hardening is used to demonstrate the simplicity of the numerical algorithm.

Reference View Selection in DIBR-Based Multiview Coding.

PubMed

Maugey, Thomas; Petrazzuoli, Giovanni; Frossard, Pascal; Cagnazzo, Marco; Pesquet-Popescu, Beatrice

2016-04-01

Augmented reality, interactive navigation in 3D scenes, multiview video, and other emerging multimedia applications require large sets of images, hence larger data volumes and increased resources compared with traditional video services. The significant increase in the number of images in multiview systems leads to new challenging problems in data representation and data transmission to provide high quality of experience on resource-constrained environments. In order to reduce the size of the data, different multiview video compression strategies have been proposed recently. Most of them use the concept of reference or key views that are used to estimate other images when there is high correlation in the data set. In such coding schemes, the two following questions become fundamental: 1) how many reference views have to be chosen for keeping a good reconstruction quality under coding cost constraints? And 2) where to place these key views in the multiview data set? As these questions are largely overlooked in the literature, we study the reference view selection problem and propose an algorithm for the optimal selection of reference views in multiview coding systems. Based on a novel metric that measures the similarity between the views, we formulate an optimization problem for the positioning of the reference views, such that both the distortion of the view reconstruction and the coding rate cost are minimized. We solve this new problem with a shortest path algorithm that determines both the optimal number of reference views and their positions in the image set. We experimentally validate our solution in a practical multiview distributed coding system and in the standardized 3D-HEVC multiview coding scheme. We show that considering the 3D scene geometry in the reference view, positioning problem brings significant rate-distortion improvements and outperforms the traditional coding strategy that simply selects key frames based on the distance between cameras.

Multiresponse imaging system design for improved resolution

NASA Technical Reports Server (NTRS)

Alter-Gartenberg, Rachel; Fales, Carl L.; Huck, Friedrich O.; Rahman, Zia-Ur; Reichenbach, Stephen E.

1991-01-01

Multiresponse imaging is a process that acquires A images, each with a different optical response, and reassembles them into a single image with an improved resolution that can approach 1/sq rt A times the photodetector-array sampling lattice. Our goals are to optimize the performance of this process in terms of the resolution and fidelity of the restored image and to assess the amount of information required to do so. The theoretical approach is based on the extension of both image restoration and rate-distortion theories from their traditional realm of signal processing to image processing which includes image gathering and display.

A rate distortion approach to protein symmetry.

PubMed

Wallace, Rodrick

2010-08-01

A spontaneous symmetry breaking argument is applied to the problem of protein folding, via a rate distortion analysis of the relation between genome coding and the final condensation of the protein molten globule that is, in spirit, analogous to Tlusty's (2007) exploration of the evolution of the genetic code. In the 'energy' picture, the average distortion between codon message and final protein structure, under constraints driven by evolutionary selection, serves as a temperature analog, so that low values limit the possible distribution of protein forms, producing the canonical folding funnel. A dual 'developmental' perspective sees the rate distortion function itself as the temperature analog, and permits incorporation of chaperons or toxic exposures as catalysts, driving the system to different possible outcomes or affecting the rate of convergence. The rate distortion function appears constrained by the availability of metabolic free energy, with implications for prebiotic evolution, and a nonequilibrium empirical Onsager treatment provides an adaptable statistical model that can be fitted to data, in the same manner as a regression equation. In sum, mechanistic models of protein folding fail to account for the observed spectrum of protein folding and aggregation disorders, suggesting that a biologically based cognitive paradigm describing folding will be needed for understanding the etiology, prevention, and treatment of these diseases. The developmental formalism introduced here may contribute substantially to such a paradigm.

Expansion and Compression of Time Correlate with Information Processing in an Enumeration Task.

PubMed

Wutz, Andreas; Shukla, Anuj; Bapi, Raju S; Melcher, David

2015-01-01

Perception of temporal duration is subjective and is influenced by factors such as attention and context. For example, unexpected or emotional events are often experienced as if time subjectively expands, suggesting that the amount of information processed in a unit of time can be increased. Time dilation effects have been measured with an oddball paradigm in which an infrequent stimulus is perceived to last longer than standard stimuli in the rest of the sequence. Likewise, time compression for the oddball occurs when the duration of the standard items is relatively brief. Here, we investigated whether the amount of information processing changes when time is perceived as distorted. On each trial, an oddball stimulus of varying numerosity (1-14 items) and duration was presented along with standard items that were either short (70 ms) or long (1050 ms). Observers were instructed to count the number of dots within the oddball stimulus and to judge its relative duration with respect to the standards on that trial. Consistent with previous results, oddballs were reliably perceived as temporally distorted: expanded for longer standard stimuli blocks and compressed for shorter standards. The occurrence of these distortions of time perception correlated with perceptual processing; i.e. enumeration accuracy increased when time was perceived as expanded and decreased with temporal compression. These results suggest that subjective time distortions are not epiphenomenal, but reflect real changes in sensory processing. Such short-term plasticity in information processing rate could be evolutionarily advantageous in optimizing perception and action during critical moments.

Comparison of single-microphone noise reduction schemes: can hearing impaired listeners tell the difference?

PubMed

Huber, Rainer; Bisitz, Thomas; Gerkmann, Timo; Kiessling, Jürgen; Meister, Hartmut; Kollmeier, Birger

2018-06-01

The perceived qualities of nine different single-microphone noise reduction (SMNR) algorithms were to be evaluated and compared in subjective listening tests with normal hearing and hearing impaired (HI) listeners. Speech samples added with traffic noise or with party noise were processed by the SMNR algorithms. Subjects rated the amount of speech distortions, intrusiveness of background noise, listening effort and overall quality, using a simplified MUSHRA (ITU-R, 2003 ) assessment method. 18 normal hearing and 18 moderately HI subjects participated in the study. Significant differences between the rating behaviours of the two subject groups were observed: While normal hearing subjects clearly differentiated between different SMNR algorithms, HI subjects rated all processed signals very similarly. Moreover, HI subjects rated speech distortions of the unprocessed, noisier signals as being more severe than the distortions of the processed signals, in contrast to normal hearing subjects. It seems harder for HI listeners to distinguish between additive noise and speech distortions or/and they might have a different understanding of the term "speech distortion" than normal hearing listeners have. The findings confirm that the evaluation of SMNR schemes for hearing aids should always involve HI listeners.

Analysis of adjusting effects of mounting force on frequency conversion of mounted nonlinear optics.

PubMed

Su, Ruifeng; Liu, Haitao; Liang, Yingchun; Lu, Lihua

2014-01-10

Motivated by the need to increase the second harmonic generation (SHG) efficiency of nonlinear optics with large apertures, a novel mounting configuration with active adjusting function on the SHG efficiency is proposed and mechanically and optically studied. The adjusting effects of the mounting force on the distortion and stress are analyzed by the finite element methods (FEM), as well as the contribution of the distortion and stress to the change in phase mismatch, and the SHG efficiency are theoretically stated. Further on, the SHG efficiency is calculated as a function of the mounting force. The changing trends of the distortion, stress, and the SHG efficiency with the varying mounting force are obtained, and the optimal ones are figured out. Moreover, the mechanism of the occurrence of the optimal values is studied and the adjusting strategy is put forward. Numerical results show the robust adjustment of the mounting force, as well as the effectiveness of the mounting configuration, in increasing the SHG efficiency.

System performance enhancement with pre-distorted OOFDM signal waveforms in DM/DD systems.

PubMed

Sánchez, C; Ortega, B; Capmany, J

2014-03-24

In this work we propose a pre-distortion technique for the mitigation of the nonlinear distortion present in directly modulated/detected OOFDM systems and explore the system performance achieved under varying system parameters. Simulation results show that the proposed pre-distortion technique efficiently mitigates the nonlinear distortion, achieving transmission information rates around 40 Gbits/s and 18.5 Gbits/s over 40 km and 100 km of single mode fiber links, respectively, under optimum operating conditions. Moreover, the proposed pre-distortion technique can potentially provide higher system performance to that obtained with nonlinear equalization at the receiver.

Precise X-ray and video overlay for augmented reality fluoroscopy.

PubMed

Chen, Xin; Wang, Lejing; Fallavollita, Pascal; Navab, Nassir

2013-01-01

The camera-augmented mobile C-arm (CamC) augments any mobile C-arm by a video camera and mirror construction and provides a co-registration of X-ray with video images. The accurate overlay between these images is crucial to high-quality surgical outcomes. In this work, we propose a practical solution that improves the overlay accuracy for any C-arm orientation by: (i) improving the existing CamC calibration, (ii) removing distortion effects, and (iii) accounting for the mechanical sagging of the C-arm gantry due to gravity. A planar phantom is constructed and placed at different distances to the image intensifier in order to obtain the optimal homography that co-registers X-ray and video with a minimum error. To alleviate distortion, both X-ray calibration based on equidistant grid model and Zhang's camera calibration method are implemented for distortion correction. Lastly, the virtual detector plane (VDP) method is adapted and integrated to reduce errors due to the mechanical sagging of the C-arm gantry. The overlay errors are 0.38±0.06 mm when not correcting for distortion, 0.27±0.06 mm when applying Zhang's camera calibration, and 0.27±0.05 mm when applying X-ray calibration. Lastly, when taking into account all angular and orbital rotations of the C-arm, as well as correcting for distortion, the overlay errors are 0.53±0.24 mm using VDP and 1.67±1.25 mm excluding VDP. The augmented reality fluoroscope achieves an accurate video and X-ray overlay when applying the optimal homography calculated from distortion correction using X-ray calibration together with the VDP.

JPEG2000 encoding with perceptual distortion control.

PubMed

Liu, Zhen; Karam, Lina J; Watson, Andrew B

2006-07-01

In this paper, a new encoding approach is proposed to control the JPEG2000 encoding in order to reach a desired perceptual quality. The new method is based on a vision model that incorporates various masking effects of human visual perception and a perceptual distortion metric that takes spatial and spectral summation of individual quantization errors into account. Compared with the conventional rate-based distortion minimization JPEG2000 encoding, the new method provides a way to generate consistent quality images at a lower bit rate.

Development of gradient descent adaptive algorithms to remove common mode artifact for improvement of cardiovascular signal quality.

PubMed

Ciaccio, Edward J; Micheli-Tzanakou, Evangelia

2007-07-01

Common-mode noise degrades cardiovascular signal quality and diminishes measurement accuracy. Filtering to remove noise components in the frequency domain often distorts the signal. Two adaptive noise canceling (ANC) algorithms were tested to adjust weighted reference signals for optimal subtraction from a primary signal. Update of weight w was based upon the gradient term of the steepest descent equation: [see text], where the error epsilon is the difference between primary and weighted reference signals. nabla was estimated from Deltaepsilon(2) and Deltaw without using a variable Deltaw in the denominator which can cause instability. The Parallel Comparison (PC) algorithm computed Deltaepsilon(2) using fixed finite differences +/- Deltaw in parallel during each discrete time k. The ALOPEX algorithm computed Deltaepsilon(2)x Deltaw from time k to k + 1 to estimate nabla, with a random number added to account for Deltaepsilon(2) . Deltaw--> 0 near the optimal weighting. Using simulated data, both algorithms stably converged to the optimal weighting within 50-2000 discrete sample points k even with a SNR = 1:8 and weights which were initialized far from the optimal. Using a sharply pulsatile cardiac electrogram signal with added noise so that the SNR = 1:5, both algorithms exhibited stable convergence within 100 ms (100 sample points). Fourier spectral analysis revealed minimal distortion when comparing the signal without added noise to the ANC restored signal. ANC algorithms based upon difference calculations can rapidly and stably converge to the optimal weighting in simulated and real cardiovascular data. Signal quality is restored with minimal distortion, increasing the accuracy of biophysical measurement.

Stereo depth distortions in teleoperation

NASA Technical Reports Server (NTRS)

Diner, Daniel B.; Vonsydow, Marika

1988-01-01

In teleoperation, a typical application of stereo vision is to view a work space located short distances (1 to 3m) in front of the cameras. The work presented here treats converged camera placement and studies the effects of intercamera distance, camera-to-object viewing distance, and focal length of the camera lenses on both stereo depth resolution and stereo depth distortion. While viewing the fronto-parallel plane 1.4 m in front of the cameras, depth errors are measured on the order of 2cm. A geometric analysis was made of the distortion of the fronto-parallel plane of divergence for stereo TV viewing. The results of the analysis were then verified experimentally. The objective was to determine the optimal camera configuration which gave high stereo depth resolution while minimizing stereo depth distortion. It is found that for converged cameras at a fixed camera-to-object viewing distance, larger intercamera distances allow higher depth resolutions, but cause greater depth distortions. Thus with larger intercamera distances, operators will make greater depth errors (because of the greater distortions), but will be more certain that they are not errors (because of the higher resolution).

Study of information transfer optimization for communication satellites

NASA Technical Reports Server (NTRS)

Odenwalder, J. P.; Viterbi, A. J.; Jacobs, I. M.; Heller, J. A.

1973-01-01

The results are presented of a study of source coding, modulation/channel coding, and systems techniques for application to teleconferencing over high data rate digital communication satellite links. Simultaneous transmission of video, voice, data, and/or graphics is possible in various teleconferencing modes and one-way, two-way, and broadcast modes are considered. A satellite channel model including filters, limiter, a TWT, detectors, and an optimized equalizer is treated in detail. A complete analysis is presented for one set of system assumptions which exclude nonlinear gain and phase distortion in the TWT. Modulation, demodulation, and channel coding are considered, based on an additive white Gaussian noise channel model which is an idealization of an equalized channel. Source coding with emphasis on video data compression is reviewed, and the experimental facility utilized to test promising techniques is fully described.

Optimal self-cleavage activity of the hepatitis delta virus RNA is dependent on a homopurine base pair in the ribozyme core.

PubMed Central

Been, M D; Perrotta, A T

1995-01-01

A non-Watson-Crick G.G interaction within the core region of the hepatitis delta virus (HDV) antigenomic ribozyme is required for optimal rates of self-cleavage activity. Base substitutions for either one or both G's revealed that full activity was obtained only when both G's were replaced with A's. At those positions, substitutions that generate potential Watson-Crick, G.U, heteropurine, or homopyrimidine combinations resulted in dramatically lower cleavage activity. A homopurine symmetric base pair, of the same type identified in the high-affinity binding site of the HIV RRE, is most consistent with this data. Additional features shared between the antigenomic ribozyme and the Rev binding site in the vicinity of the homopurine pairs suggest some structural similarity for this region of the two RNAs and a possible motif associated with this homopurine interaction. Evidence for a homopurine pair at the equivalent position in a modified form of the HDV genomic ribozyme was also found. With the postulated symmetric pairing scheme, large distortions in the nucleotide conformation, the sugar-phosphate backbone, or both would be necessary to accommodate this interaction at the end of a helix; we hypothesize that this distortion is critical to the structure of the active site of the ribozyme and it is stabilized by the homopurine base pair. PMID:8595561

STOP Analysis and Optimization of a Very-Low-Distortion Space Instrument: HST WFC3 Case Study

NASA Technical Reports Server (NTRS)

Kunt, Cengiz; Broduer, Steve (Technical Monitor)

2001-01-01

New generation optical instruments with very demanding stability requirements are being proposed and developed for space applications. STOP (Structural-Thermal-Optical Performance) analysis and optimization is crucial in meeting the very tight distortion budgets of these instruments. This presentation outlines STOP analysis and optimization approach in the context of WFC3 (Wide-Field Camera 3), which is a radial instrument designed to replace the Wide-Field Planetary Camera 2 (WFPC2) of the Hubble Space Telescope (HST). WFC3 houses two separate channels, UVIS and IR, and will have greater throughput and sensitivity than WFPC2. WFC3 line-of-sight alignment budget for the UVIS and IR channels are as small as 10 and 20 milli-arcsec, respectively. Its optical bench is the most critical subsystem effecting the optical stability of WFC3 hence our effort concentrates on the design and analysis of the bench and its interfaces. Structural analysis has accompanied the mechanical design of the bench since the initial concept study. A high fidelity structural Finite Element Model (FEM) of the bench has been developed and used for minimizing its thermally induced distortions as well as sizing it to meet the stiffness and strength requirements of a Shuttle launch. The bench is a composite honeycomb panel box structure with a very low planar Coefficient of Thermal Expansion (CTE) of approximately 0.1 ppm/C. Optic components are mounted to super-INVAR inserts bonded into the panels. The bench is kinematically supported on three HST latches via interface struts, which are tailored to exhibit negative CTE to cancel out the thermal motions of the latches. The interface struts also incorporate flexure elements to minimize the mechanical distortions coming into the bench from its enclosure. Bench FEM is coupled with the enclosure FEM to quantify these effects. Short term or on-orbit STOP analysis includes distortion due to the temperature variations of the bench, the struts, and the enclosure. Long term or ground-to-orbit STOP analysis includes distortional effects of gravity release, desorption, and assembly in addition to the ground-to-orbit temperature variations. A rigorous testing program has been implemented for verifying the material properties and the analysis predictions. STOP analysis results demonstrate that both the short-term and the long-term alignment budgets will be met. Presentation will cover design and analysis details that are critical to a successful implementation of the STOP analysis and optimization process.

QR images: optimized image embedding in QR codes.

PubMed

Garateguy, Gonzalo J; Arce, Gonzalo R; Lau, Daniel L; Villarreal, Ofelia P

2014-07-01

This paper introduces the concept of QR images, an automatic method to embed QR codes into color images with bounded probability of detection error. These embeddings are compatible with standard decoding applications and can be applied to any color image with full area coverage. The QR information bits are encoded into the luminance values of the image, taking advantage of the immunity of QR readers against local luminance disturbances. To mitigate the visual distortion of the QR image, the algorithm utilizes halftoning masks for the selection of modified pixels and nonlinear programming techniques to locally optimize luminance levels. A tractable model for the probability of error is developed and models of the human visual system are considered in the quality metric used to optimize the luminance levels of the QR image. To minimize the processing time, the optimization techniques proposed to consider the mechanics of a common binarization method and are designed to be amenable for parallel implementations. Experimental results show the graceful degradation of the decoding rate and the perceptual quality as a function the embedding parameters. A visual comparison between the proposed and existing methods is presented.

A model for the Pockels effect in distorted liquid crystal blue phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castles, F., E-mail: flynn.castles@materials.ox.ac.uk

2015-09-07

Recent experiments have found that a mechanically distorted blue phase can exhibit a primary linear electro-optic (Pockels) effect [F. Castles et al., Nat. Mater. 13, 817 (2014)]. Here, it is shown that flexoelectricity can account for the experimental results and a model, which is based on continuum theory but takes into account the sub-unit-cell structure, is proposed. The model provides a quantitative description of the effect accurate to the nearest order of magnitude and predicts that the Pockels coefficient(s) in an optimally distorted blue phase may be two orders of magnitude larger than in lithium niobate.

Improved distorted wave theory with the localized virial conditions

NASA Astrophysics Data System (ADS)

Hahn, Y. K.; Zerrad, E.

2009-12-01

The distorted wave theory is operationally improved to treat the full collision amplitude, such that the corrections to the distorted wave Born amplitude can be systematically calculated. The localized virial conditions provide the tools necessary to test the quality of successive approximations at each stage and to optimize the solution. The details of the theoretical procedure are explained in concrete terms using a collisional ionization model and variational trial functions. For the first time, adjustable parameters associated with an approximate scattering solution can be fully determined by the theory. A small number of linear parameters are introduced to examine the convergence property and the effectiveness of the new approach.

Rate-distortion analysis of dead-zone plus uniform threshold scalar quantization and its application--part II: two-pass VBR coding for H.264/AVC.

PubMed

Sun, Jun; Duan, Yizhou; Li, Jiangtao; Liu, Jiaying; Guo, Zongming

2013-01-01

In the first part of this paper, we derive a source model describing the relationship between the rate, distortion, and quantization steps of the dead-zone plus uniform threshold scalar quantizers with nearly uniform reconstruction quantizers for generalized Gaussian distribution. This source model consists of rate-quantization, distortion-quantization (D-Q), and distortion-rate (D-R) models. In this part, we first rigorously confirm the accuracy of the proposed source model by comparing the calculated results with the coding data of JM 16.0. Efficient parameter estimation strategies are then developed to better employ this source model in our two-pass rate control method for H.264 variable bit rate coding. Based on our D-Q and D-R models, the proposed method is of high stability, low complexity and is easy to implement. Extensive experiments demonstrate that the proposed method achieves: 1) average peak signal-to-noise ratio variance of only 0.0658 dB, compared to 1.8758 dB of JM 16.0's method, with an average rate control error of 1.95% and 2) significant improvement in smoothing the video quality compared with the latest two-pass rate control method.

Cognitive Distortion in Rheumatoid Arthritis: Relation to Depression and Disability.

ERIC Educational Resources Information Center

Smith, Timothy W.; And Others

1988-01-01

Examined the relation between cognitive distortion, as measured by the Cognitive Error Questionnaire, and both self-reported and interview-rated depression and disability in 92 rheumatoid arthritis (RA) patients. Found cognitive distortion significantly associated with depression, and also related to physical disability. Discusses the results,…

Jahn-Teller distortion in the phosphorescent excited state of three-coordinate Au(I) phosphine complexes.

PubMed

Barakat, Khaldoon A; Cundari, Thomas R; Omary, Mohammad A

2003-11-26

DFT calculations were used to optimize the phosphorescent excited state of three-coordinate [Au(PR3)3]+ complexes. The results indicate that the complexes rearrange from their singlet ground-state trigonal planar geometry to a T-shape in the lowest triplet luminescent excited state. The optimized structure of the exciton contradicts the structure predicted based on the AuP bonding properties of the ground-state HOMO and LUMO. The rearrangement to T-shape is a Jahn-Teller distortion because an electron is taken from the degenerate e' (5dxy, 5dx2-y2) orbital upon photoexcitation of the ground-state D3h complex. The calculated UV absorption and visible emission energies are consistent with the experimental data and explain the large Stokes' shifts while such correlations are not possible in optimized models that constrained the exciton to the ground-state trigonal geometry.

Television monitor field shifter and an opto-electronic method for obtaining a stereo image of optimal depth resolution and reduced depth distortion on a single screen

NASA Technical Reports Server (NTRS)

Diner, Daniel B. (Inventor)

1989-01-01

A method and apparatus is developed for obtaining a stereo image with reduced depth distortion and optimum depth resolution. Static and dynamic depth distortion and depth resolution tradeoff is provided. Cameras obtaining the images for a stereo view are converged at a convergence point behind the object to be presented in the image, and the collection-surface-to-object distance, the camera separation distance, and the focal lengths of zoom lenses for the cameras are all increased. Doubling the distances cuts the static depth distortion in half while maintaining image size and depth resolution. Dynamic depth distortion is minimized by panning a stereo view-collecting camera system about a circle which passes through the convergence point and the camera's first nodal points. Horizontal field shifting of the television fields on a television monitor brings both the monitor and the stereo views within the viewer's limit of binocular fusion.

Nonlinear distortion analysis for single heterojunction GaAs HEMT with frequency and temperature

NASA Astrophysics Data System (ADS)

Alim, Mohammad A.; Ali, Mayahsa M.; Rezazadeh, Ali A.

2018-07-01

Nonlinearity analysis using two-tone intermodulation distortion (IMD) technique for 0.5 μm gate-length AlGaAs/GaAs based high electron mobility transistor have been investigated based on biasing conditions, input power, frequency and temperature. The outcomes indicate a significant modification on the output IMD power and as well as the minimum distortion level. The input IMD power effects the output current and subsequently the threshold voltage reduces, resulting to an increment in the output IMD power. Both frequency and temperature reduces the magnitude of the output IMDs. In addition, the threshold voltage response with temperature alters the notch point of the nonlinear output IMD’s accordingly. The aforementioned investigation will help the circuit designers to evaluate the best biasing option in terms of minimum distortion, maximum gain for future design optimizations.

Intermodulation distortion and linearity performance assessment of 50-nm gate length L-DUMGAC MOSFET for RFIC design

NASA Astrophysics Data System (ADS)

Chaujar, Rishu; Kaur, Ravneet; Saxena, Manoj; Gupta, Mridula; Gupta, R. S.

2008-08-01

The distortion and linearity behaviour of MOSFETs is imperative for low-noise applications and RFICs design. In this paper, an extensive study on the RF-distortion and linearity behaviour of Laterally Amalgamated DUal Material GAte Concave (L-DUMGAC) MOSFET is performed and the influence of technology variations such as gate length, negative junction depth (NJD), substrate bias, drain bias and gate material workfunction is explored using ATLAS device simulator. Simulation results reveal that L-DUMGAC MOSFET significantly enhances the linearity and intermodulation distortion performance in terms of figure of merit (FOM) metrics: V, V, IIP3, IMD3 and higher order transconductance coefficients: gm1, gm2, gm3, proving its efficacy for RFIC design. The work, thus, optimize the device's bias point for RFICs with higher efficiency and better linearity performance.

Assessment of dosimetric impact of system specific geometric distortion in an MRI only based radiotherapy workflow for prostate

NASA Astrophysics Data System (ADS)

Gustafsson, C.; Nordström, F.; Persson, E.; Brynolfsson, J.; Olsson, L. E.

2017-04-01

Dosimetric errors in a magnetic resonance imaging (MRI) only radiotherapy workflow may be caused by system specific geometric distortion from MRI. The aim of this study was to evaluate the impact on planned dose distribution and delineated structures for prostate patients, originating from this distortion. A method was developed, in which computer tomography (CT) images were distorted using the MRI distortion field. The displacement map for an optimized MRI treatment planning sequence was measured using a dedicated phantom in a 3 T MRI system. To simulate the distortion aspects of a synthetic CT (electron density derived from MR images), the displacement map was applied to CT images, referred to as distorted CT images. A volumetric modulated arc prostate treatment plan was applied to the original CT and the distorted CT, creating a reference and a distorted CT dose distribution. By applying the inverse of the displacement map to the distorted CT dose distribution, a dose distribution in the same geometry as the original CT images was created. For 10 prostate cancer patients, the dose difference between the reference dose distribution and inverse distorted CT dose distribution was analyzed in isodose level bins. The mean magnitude of the geometric distortion was 1.97 mm for the radial distance of 200-250 mm from isocenter. The mean percentage dose differences for all isodose level bins, were  ⩽0.02% and the radiotherapy structure mean volume deviations were  <0.2%. The method developed can quantify the dosimetric effects of MRI system specific distortion in a prostate MRI only radiotherapy workflow, separated from dosimetric effects originating from synthetic CT generation. No clinically relevant dose difference or structure deformation was found when 3D distortion correction and high acquisition bandwidth was used. The method could be used for any MRI sequence together with any anatomy of interest.

Assessment of dosimetric impact of system specific geometric distortion in an MRI only based radiotherapy workflow for prostate.

PubMed

Gustafsson, C; Nordström, F; Persson, E; Brynolfsson, J; Olsson, L E

2017-04-21

Dosimetric errors in a magnetic resonance imaging (MRI) only radiotherapy workflow may be caused by system specific geometric distortion from MRI. The aim of this study was to evaluate the impact on planned dose distribution and delineated structures for prostate patients, originating from this distortion. A method was developed, in which computer tomography (CT) images were distorted using the MRI distortion field. The displacement map for an optimized MRI treatment planning sequence was measured using a dedicated phantom in a 3 T MRI system. To simulate the distortion aspects of a synthetic CT (electron density derived from MR images), the displacement map was applied to CT images, referred to as distorted CT images. A volumetric modulated arc prostate treatment plan was applied to the original CT and the distorted CT, creating a reference and a distorted CT dose distribution. By applying the inverse of the displacement map to the distorted CT dose distribution, a dose distribution in the same geometry as the original CT images was created. For 10 prostate cancer patients, the dose difference between the reference dose distribution and inverse distorted CT dose distribution was analyzed in isodose level bins. The mean magnitude of the geometric distortion was 1.97 mm for the radial distance of 200-250 mm from isocenter. The mean percentage dose differences for all isodose level bins, were  ⩽0.02% and the radiotherapy structure mean volume deviations were  <0.2%. The method developed can quantify the dosimetric effects of MRI system specific distortion in a prostate MRI only radiotherapy workflow, separated from dosimetric effects originating from synthetic CT generation. No clinically relevant dose difference or structure deformation was found when 3D distortion correction and high acquisition bandwidth was used. The method could be used for any MRI sequence together with any anatomy of interest.

Training Recurrent Neural Networks With the Levenberg-Marquardt Algorithm for Optimal Control of a Grid-Connected Converter.

PubMed

Fu, Xingang; Li, Shuhui; Fairbank, Michael; Wunsch, Donald C; Alonso, Eduardo

2015-09-01

This paper investigates how to train a recurrent neural network (RNN) using the Levenberg-Marquardt (LM) algorithm as well as how to implement optimal control of a grid-connected converter (GCC) using an RNN. To successfully and efficiently train an RNN using the LM algorithm, a new forward accumulation through time (FATT) algorithm is proposed to calculate the Jacobian matrix required by the LM algorithm. This paper explores how to incorporate FATT into the LM algorithm. The results show that the combination of the LM and FATT algorithms trains RNNs better than the conventional backpropagation through time algorithm. This paper presents an analytical study on the optimal control of GCCs, including theoretically ideal optimal and suboptimal controllers. To overcome the inapplicability of the optimal GCC controller under practical conditions, a new RNN controller with an improved input structure is proposed to approximate the ideal optimal controller. The performance of an ideal optimal controller and a well-trained RNN controller was compared in close to real-life power converter switching environments, demonstrating that the proposed RNN controller can achieve close to ideal optimal control performance even under low sampling rate conditions. The excellent performance of the proposed RNN controller under challenging and distorted system conditions further indicates the feasibility of using an RNN to approximate optimal control in practical applications.

A Method for Harmonic Sources Detection based on Harmonic Distortion Power Rate

NASA Astrophysics Data System (ADS)

Lin, Ruixing; Xu, Lin; Zheng, Xian

2018-03-01

Harmonic sources detection at the point of common coupling is an essential step for harmonic contribution determination and harmonic mitigation. The harmonic distortion power rate index is proposed for harmonic source location based on IEEE Std 1459-2010 in the paper. The method only based on harmonic distortion power is not suitable when the background harmonic is large. To solve this problem, a threshold is determined by the prior information, when the harmonic distortion power is larger than the threshold, the customer side is considered as the main harmonic source, otherwise, the utility side is. A simple model of public power system was built in MATLAB/Simulink and field test results of typical harmonic loads verified the effectiveness of proposed method.

Joint-layer encoder optimization for HEVC scalable extensions

NASA Astrophysics Data System (ADS)

Tsai, Chia-Ming; He, Yuwen; Dong, Jie; Ye, Yan; Xiu, Xiaoyu; He, Yong

2014-09-01

Scalable video coding provides an efficient solution to support video playback on heterogeneous devices with various channel conditions in heterogeneous networks. SHVC is the latest scalable video coding standard based on the HEVC standard. To improve enhancement layer coding efficiency, inter-layer prediction including texture and motion information generated from the base layer is used for enhancement layer coding. However, the overall performance of the SHVC reference encoder is not fully optimized because rate-distortion optimization (RDO) processes in the base and enhancement layers are independently considered. It is difficult to directly extend the existing joint-layer optimization methods to SHVC due to the complicated coding tree block splitting decisions and in-loop filtering process (e.g., deblocking and sample adaptive offset (SAO) filtering) in HEVC. To solve those problems, a joint-layer optimization method is proposed by adjusting the quantization parameter (QP) to optimally allocate the bit resource between layers. Furthermore, to make more proper resource allocation, the proposed method also considers the viewing probability of base and enhancement layers according to packet loss rate. Based on the viewing probability, a novel joint-layer RD cost function is proposed for joint-layer RDO encoding. The QP values of those coding tree units (CTUs) belonging to lower layers referenced by higher layers are decreased accordingly, and the QP values of those remaining CTUs are increased to keep total bits unchanged. Finally the QP values with minimal joint-layer RD cost are selected to match the viewing probability. The proposed method was applied to the third temporal level (TL-3) pictures in the Random Access configuration. Simulation results demonstrate that the proposed joint-layer optimization method can improve coding performance by 1.3% for these TL-3 pictures compared to the SHVC reference encoder without joint-layer optimization.

Parameters to Maximize 2f2-f1 Distortion Product Otoacoustic Emission Levels

ERIC Educational Resources Information Center

Horn, Jennifer H.; Pratt, Shiela R.; Durrant, John D.

2008-01-01

Purpose: Past research has established parameters for the 2f1-f2 distortion product otoacoustic emissions (DPOAEs) that enhance response levels (e.g., L1 - L2 = 10 dB; f2/f1 = 1.22; L1, L2 = 65, 55 dB SPL). These same parameters do not optimize 2f2-f1 DPOAEs. Therefore, this study was conducted to evaluate more completely those parameters that…

Detection of Hearing Loss Using 2f2-f1 and 2f1-f2 Distortion-Product Otoacoustic Emissions

ERIC Educational Resources Information Center

Fitzgerald, Tracy S.; Prieve, Beth A.

2005-01-01

Although many distortion-product otoacoustic emissions (DPOAEs) may be measured in the ear canal in response to 2 pure tone stimuli, the majority of clinical studies have focused exclusively on the DPOAE at the frequency 2f1-f2. This study investigated another DPOAE, 2f2-f1, in an attempt to determine the following: (a) the optimal stimulus…

Revolving scanning transmission electron microscopy: correcting sample drift distortion without prior knowledge.

PubMed

Sang, Xiahan; LeBeau, James M

2014-03-01

We report the development of revolving scanning transmission electron microscopy--RevSTEM--a technique that enables characterization and removal of sample drift distortion from atomic resolution images without the need for a priori crystal structure information. To measure and correct the distortion, we acquire an image series while rotating the scan coordinate system between successive frames. Through theory and experiment, we show that the revolving image series captures the information necessary to analyze sample drift rate and direction. At atomic resolution, we quantify the image distortion using the projective standard deviation, a rapid, real-space method to directly measure lattice vector angles. By fitting these angles to a physical model, we show that the refined drift parameters provide the input needed to correct distortion across the series. We demonstrate that RevSTEM simultaneously removes the need for a priori structure information to correct distortion, leads to a dramatically improved signal-to-noise ratio, and enables picometer precision and accuracy regardless of drift rate. Copyright © 2013 Elsevier B.V. All rights reserved.

Total Dose Effects on Error Rates in Linear Bipolar Systems

NASA Technical Reports Server (NTRS)

Buchner, Stephen; McMorrow, Dale; Bernard, Muriel; Roche, Nicholas; Dusseau, Laurent

2007-01-01

The shapes of single event transients in linear bipolar circuits are distorted by exposure to total ionizing dose radiation. Some transients become broader and others become narrower. Such distortions may affect SET system error rates in a radiation environment. If the transients are broadened by TID, the error rate could increase during the course of a mission, a possibility that has implications for hardness assurance.

Comparison of methods for quantitative evaluation of endoscopic distortion

NASA Astrophysics Data System (ADS)

Wang, Quanzeng; Castro, Kurt; Desai, Viraj N.; Cheng, Wei-Chung; Pfefer, Joshua

2015-03-01

Endoscopy is a well-established paradigm in medical imaging, and emerging endoscopic technologies such as high resolution, capsule and disposable endoscopes promise significant improvements in effectiveness, as well as patient safety and acceptance of endoscopy. However, the field lacks practical standardized test methods to evaluate key optical performance characteristics (OPCs), in particular the geometric distortion caused by fisheye lens effects in clinical endoscopic systems. As a result, it has been difficult to evaluate an endoscope's image quality or assess its changes over time. The goal of this work was to identify optimal techniques for objective, quantitative characterization of distortion that are effective and not burdensome. Specifically, distortion measurements from a commercially available distortion evaluation/correction software package were compared with a custom algorithm based on a local magnification (ML) approach. Measurements were performed using a clinical gastroscope to image square grid targets. Recorded images were analyzed with the ML approach and the commercial software where the results were used to obtain corrected images. Corrected images based on the ML approach and the software were compared. The study showed that the ML method could assess distortion patterns more accurately than the commercial software. Overall, the development of standardized test methods for characterizing distortion and other OPCs will facilitate development, clinical translation, manufacturing quality and assurance of performance during clinical use of endoscopic technologies.

Optimal Design of Passive Flow Control for a Boundary-Layer-Ingesting Offset Inlet Using Design-of-Experiments

NASA Technical Reports Server (NTRS)

Allan, Brian G.; Owens, Lewis R.; Lin, John C.

2006-01-01

This research will investigate the use of Design-of-Experiments (DOE) in the development of an optimal passive flow control vane design for a boundary-layer-ingesting (BLI) offset inlet in transonic flow. This inlet flow control is designed to minimize the engine fan-face distortion levels and first five Fourier harmonic half amplitudes while maximizing the inlet pressure recovery. Numerical simulations of the BLI inlet are computed using the Reynolds-averaged Navier-Stokes (RANS) flow solver, OVERFLOW, developed at NASA. These simulations are used to generate the numerical experiments for the DOE response surface model. In this investigation, two DOE optimizations were performed using a D-Optimal Response Surface model. The first DOE optimization was performed using four design factors which were vane height and angles-of-attack for two groups of vanes. One group of vanes was placed at the bottom of the inlet and a second group symmetrically on the sides. The DOE design was performed for a BLI inlet with a free-stream Mach number of 0.85 and a Reynolds number of 2 million, based on the length of the fan-face diameter, matching an experimental wind tunnel BLI inlet test. The first DOE optimization required a fifth order model having 173 numerical simulation experiments and was able to reduce the DC60 baseline distortion from 64% down to 4.4%, while holding the pressure recovery constant. A second DOE optimization was performed holding the vanes heights at a constant value from the first DOE optimization with the two vane angles-of-attack as design factors. This DOE only required a second order model fit with 15 numerical simulation experiments and reduced DC60 to 3.5% with small decreases in the fourth and fifth harmonic amplitudes. The second optimal vane design was tested at the NASA Langley 0.3- Meter Transonic Cryogenic Tunnel in a BLI inlet experiment. The experimental results showed a 80% reduction of DPCP(sub avg), the circumferential distortion level at the engine fan-face.

Optimal Design of Passive Flow Control for a Boundary-Layer-Ingesting Offset Inlet Using Design-of-Experiments

NASA Technical Reports Server (NTRS)

Allan, Brian G.; Owens, Lewis R., Jr.; Lin, John C.

2006-01-01

This research will investigate the use of Design-of-Experiments (DOE) in the development of an optimal passive flow control vane design for a boundary-layer-ingesting (BLI) offset inlet in transonic flow. This inlet flow control is designed to minimize the engine fan face distortion levels and first five Fourier harmonic half amplitudes while maximizing the inlet pressure recovery. Numerical simulations of the BLI inlet are computed using the Reynolds-averaged Navier-Stokes (RANS) flow solver, OVERFLOW, developed at NASA. These simulations are used to generate the numerical experiments for the DOE response surface model. In this investigation, two DOE optimizations were performed using a D-Optimal Response Surface model. The first DOE optimization was performed using four design factors which were vane height and angles-of-attack for two groups of vanes. One group of vanes was placed at the bottom of the inlet and a second group symmetrically on the sides. The DOE design was performed for a BLI inlet with a free-stream Mach number of 0.85 and a Reynolds number of 2 million, based on the length of the fan face diameter, matching an experimental wind tunnel BLI inlet test. The first DOE optimization required a fifth order model having 173 numerical simulation experiments and was able to reduce the DC60 baseline distortion from 64% down to 4.4%, while holding the pressure recovery constant. A second DOE optimization was performed holding the vanes heights at a constant value from the first DOE optimization with the two vane angles-of-attack as design factors. This DOE only required a second order model fit with 15 numerical simulation experiments and reduced DC60 to 3.5% with small decreases in the fourth and fifth harmonic amplitudes. The second optimal vane design was tested at the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel in a BLI inlet experiment. The experimental results showed a 80% reduction of DPCPavg, the circumferential distortion level at the engine fan face.

Distortion-free diffusion tensor imaging for evaluation of lumbar nerve roots: Utility of direct coronal single-shot turbo spin-echo diffusion sequence.

PubMed

Sakai, Takayuki; Doi, Kunio; Yoneyama, Masami; Watanabe, Atsuya; Miyati, Tosiaki; Yanagawa, Noriyuki

2018-06-01

Diffusion tensor imaging (DTI) based on a single-shot echo planer imaging (EPI-DTI) is an established method that has been used for evaluation of lumbar nerve disorders in previous studies, but EPI-DTI has problems such as a long acquisition time, due to a lot of axial slices, and geometric distortion. To solve these problems, we attempted to apply DTI based on a single-shot turbo spin echo (TSE-DTI) with direct coronal acquisition. Our purpose in this study was to investigate whether TSE-DTI may be more useful for evaluation of lumbar nerve disorders than EPI-DTI. First, lumbar nerve roots of five healthy volunteers were evaluated for optimization of imaging parameters with TSE-DTI including b-values and the number of motion proving gradient (MPG) directions. Subsequently, optimized TSE-DTI was quantitatively compared with conventional EPI-DTI by using fractional anisotropy (FA) values and visual scores in subjective visual evaluation of tractography. Lumbar nerve roots of six patients, who had unilateral neurologic symptoms in one leg, were evaluated by the optimized TSE-DTI. TSE-DTI with b-value of 400 s/mm 2 and 32 diffusion-directions could reduce the image distortion compared with EPI-DTI, and showed that the average FA values on the symptomatic side for six patients were significantly lower than those on the non-symptomatic side (P < 0.05). Tractography with TSE-DTI might show damaged areas of lumbar nerve roots without severe image distortion. TSE-DTI might improve the reproducibility in measurements of FA values for quantification of a nerve disorder, and would become a useful tool for diagnosis of low back pain. Copyright © 2018 Elsevier Inc. All rights reserved.

Subband Image Coding with Jointly Optimized Quantizers

NASA Technical Reports Server (NTRS)

Kossentini, Faouzi; Chung, Wilson C.; Smith Mark J. T.

1995-01-01

An iterative design algorithm for the joint design of complexity- and entropy-constrained subband quantizers and associated entropy coders is proposed. Unlike conventional subband design algorithms, the proposed algorithm does not require the use of various bit allocation algorithms. Multistage residual quantizers are employed here because they provide greater control of the complexity-performance tradeoffs, and also because they allow efficient and effective high-order statistical modeling. The resulting subband coder exploits statistical dependencies within subbands, across subbands, and across stages, mainly through complexity-constrained high-order entropy coding. Experimental results demonstrate that the complexity-rate-distortion performance of the new subband coder is exceptional.

Sensor Spatial Distortion, Visual Latency, and Update Rate Effects on 3D Tracking in Virtual Environments

NASA Technical Reports Server (NTRS)

Ellis, S. R.; Adelstein, B. D.; Baumeler, S.; Jense, G. J.; Jacoby, R. H.; Trejo, Leonard (Technical Monitor)

1998-01-01

Several common defects that we have sought to minimize in immersing virtual environments are: static sensor spatial distortion, visual latency, and low update rates. Human performance within our environments during large amplitude 3D tracking was assessed by objective and subjective methods in the presence and absence of these defects. Results show that 1) removal of our relatively small spatial sensor distortion had minor effects on the tracking activity, 2) an Adapted Cooper-Harper controllability scale proved the most sensitive subjective indicator of the degradation of dynamic fidelity caused by increasing latency and decreasing frame rates, and 3) performance, as measured by normalized RMS tracking error or subjective impressions, was more markedly influenced by changing visual latency than by update rate.

An Optimal Deconvolution Method for Reconstructing Pneumatically Distorted Near-Field Sonic Boom Pressure Measurements

NASA Technical Reports Server (NTRS)

Whitmore, Stephen A.; Haering, Edward A., Jr.; Ehernberger, L. J.

1996-01-01

In-flight measurements of the SR-71 near-field sonic boom were obtained by an F-16XL airplane at flightpath separation distances from 40 to 740 ft. Twenty-two signatures were obtained from Mach 1.60 to Mach 1.84 and altitudes from 47,600 to 49,150 ft. The shock wave signatures were measured by the total and static sensors on the F-16XL noseboo. These near-field signature measurements were distorted by pneumatic attenuation in the pitot-static sensors and accounting for their effects using optimal deconvolution. Measurement system magnitude and phase characteristics were determined from ground-based step-response tests and extrapolated to flight conditions using analytical models. Deconvolution was implemented using Fourier transform methods. Comparisons of the shock wave signatures reconstructed from the total and static pressure data are presented. The good agreement achieved gives confidence of the quality of the reconstruction analysis. although originally developed to reconstruct the sonic boom signatures from SR-71 sonic boom flight tests, the methods presented here generally apply to other types of highly attenuated or distorted pneumatic measurements.

Optimal operation of turbo blowers serially connected using inlet vanes

NASA Astrophysics Data System (ADS)

Jang, Choon-Man

2011-03-01

Optimal operation of the turbo blowers having an inlet vane has been studied to understand the blowers' operating performance. To analyze three-dimensional flow field in the turbo blowers serially connected, general analysis code, CFX, is introduced in the present work. SST turbulence model is employed to estimate the eddy viscosity. Throughout the numerical analysis, it is found that the flow rates of the turbo blowers can be controlled at the vane angle between 90 (full open condition) degrees and 60 degrees effectively, because pressure loss rapidly increases below 60 degree of a vane angle. Efficiency also has almost the same values from 90 degrees to 60 degrees of a vane angle. It is noted that the distorted inlet velocity generated in the small vane angle makes performance deterioration of the turbo blowers due to the local leading edge separation and the following non-uniform blade loading.

A novel data hiding scheme for block truncation coding compressed images using dynamic programming strategy

NASA Astrophysics Data System (ADS)

Chang, Ching-Chun; Liu, Yanjun; Nguyen, Son T.

2015-03-01

Data hiding is a technique that embeds information into digital cover data. This technique has been concentrated on the spatial uncompressed domain, and it is considered more challenging to perform in the compressed domain, i.e., vector quantization, JPEG, and block truncation coding (BTC). In this paper, we propose a new data hiding scheme for BTC-compressed images. In the proposed scheme, a dynamic programming strategy was used to search for the optimal solution of the bijective mapping function for LSB substitution. Then, according to the optimal solution, each mean value embeds three secret bits to obtain high hiding capacity with low distortion. The experimental results indicated that the proposed scheme obtained both higher hiding capacity and hiding efficiency than the other four existing schemes, while ensuring good visual quality of the stego-image. In addition, the proposed scheme achieved a low bit rate as original BTC algorithm.

Optimized distortion correction technique for echo planar imaging.

PubMed

Chen , N K; Wyrwicz, A M

2001-03-01

A new phase-shifted EPI pulse sequence is described that encodes EPI phase errors due to all off-resonance factors, including B(o) field inhomogeneity, eddy current effects, and gradient waveform imperfections. Combined with the previously proposed multichannel modulation postprocessing algorithm (Chen and Wyrwicz, MRM 1999;41:1206-1213), the encoded phase error information can be used to effectively remove geometric distortions in subsequent EPI scans. The proposed EPI distortion correction technique has been shown to be effective in removing distortions due to gradient waveform imperfections and phase gradient-induced eddy current effects. In addition, this new method retains advantages of the earlier method, such as simultaneous correction of different off-resonance factors without use of a complicated phase unwrapping procedure. The effectiveness of this technique is illustrated with EPI studies on phantoms and animal subjects. Implementation to different versions of EPI sequences is also described. Magn Reson Med 45:525-528, 2001. Copyright 2001 Wiley-Liss, Inc.

Drawing road networks with focus regions.

PubMed

Haunert, Jan-Henrik; Sering, Leon

2011-12-01

Mobile users of maps typically need detailed information about their surroundings plus some context information about remote places. In order to avoid that the map partly gets too dense, cartographers have designed mapping functions that enlarge a user-defined focus region--such functions are sometimes called fish-eye projections. The extra map space occupied by the enlarged focus region is compensated by distorting other parts of the map. We argue that, in a map showing a network of roads relevant to the user, distortion should preferably take place in those areas where the network is sparse. Therefore, we do not apply a predefined mapping function. Instead, we consider the road network as a graph whose edges are the road segments. We compute a new spatial mapping with a graph-based optimization approach, minimizing the square sum of distortions at edges. Our optimization method is based on a convex quadratic program (CQP); CQPs can be solved in polynomial time. Important requirements on the output map are expressed as linear inequalities. In particular, we show how to forbid edge crossings. We have implemented our method in a prototype tool. For instances of different sizes, our method generated output maps that were far less distorted than those generated with a predefined fish-eye projection. Future work is needed to automate the selection of roads relevant to the user. Furthermore, we aim at fast heuristics for application in real-time systems. © 2011 IEEE

A Scalable and Robust Multi-Agent Approach to Distributed Optimization

NASA Technical Reports Server (NTRS)

Tumer, Kagan

2005-01-01

Modularizing a large optimization problem so that the solutions to the subproblems provide a good overall solution is a challenging problem. In this paper we present a multi-agent approach to this problem based on aligning the agent objectives with the system objectives, obviating the need to impose external mechanisms to achieve collaboration among the agents. This approach naturally addresses scaling and robustness issues by ensuring that the agents do not rely on the reliable operation of other agents We test this approach in the difficult distributed optimization problem of imperfect device subset selection [Challet and Johnson, 2002]. In this problem, there are n devices, each of which has a "distortion", and the task is to find the subset of those n devices that minimizes the average distortion. Our results show that in large systems (1000 agents) the proposed approach provides improvements of over an order of magnitude over both traditional optimization methods and traditional multi-agent methods. Furthermore, the results show that even in extreme cases of agent failures (i.e., half the agents fail midway through the simulation) the system remains coordinated and still outperforms a failure-free and centralized optimization algorithm.

Episodic and Individual Effects of Elementary Students' Optimal Experience: An HLM Study

ERIC Educational Resources Information Center

Cheng, Chao-Yang; Chen, Sherry Y.; Lin, Sunny S. J.

2017-01-01

The authors defined optimal experience as a functional state of a relatively high level of concentration, time distortion, satisfaction, and enjoyment (Csikszentmihalyi, 1992) and collected data through the Day Reconstruction Method. In three random days, 147 fifth-grade students answered questionnaires for each school event in the previous day…

Factors Influencing Female Caregivers' Appraisals of Their Preschoolers' Behaviors.

PubMed

Coke, Sallie P; Moore, Leslie C

This study used the Resiliency Model of Family Stress, Adjustment, and Adaptation to explore family factors associated with primary female caregivers' appraisals of children's behaviors, distortion of their appraisals, and children's risk of having behavioral problems. A cross-sectional, correlational design was used. Data were collected from female caregivers of preschoolers. Instruments measured demographic characteristics, comfort in parenting, appraisal of behaviors, daily and parenting stress, depressive symptoms, social support, ratings of children's behaviors, and distortion in ratings. Analyses included χ 2 and simultaneous linear regression. Greater parenting discomfort and daily stress were associated with lower appraisals of children's behaviors. Caucasian race and higher distortion in behavioral ratings were associated with higher risk of behavioral problems. Caregiver's appraisal was associated with daily stress level and parenting comfort. Additional research is needed regarding how these factors affect children's behavior and causes of distorted parental views of children's behaviors. Copyright © 2016 National Association of Pediatric Nurse Practitioners. Published by Elsevier Inc. All rights reserved.

76 FR 40731 - Agency Information Collection Activities; Proposed Collection; Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-11

..., however, also requires disclosure of harmonic distortion, power bandwidth, and impedance ratings in... and receiver. The burden of disclosing the harmonic distortion, bandwidth, and impedance information...

Mitigation of Adverse Effects Caused by Shock Wave Boundary Layer Interactions Through Optimal Wall Shaping

NASA Technical Reports Server (NTRS)

Liou, May-Fun; Lee, Byung Joon

2013-01-01

It is known that the adverse effects of shock wave boundary layer interactions in high speed inlets include reduced total pressure recovery and highly distorted flow at the aerodynamic interface plane (AIP). This paper presents a design method for flow control which creates perturbations in geometry. These perturbations are tailored to change the flow structures in order to minimize shock wave boundary layer interactions (SWBLI) inside supersonic inlets. Optimizing the shape of two dimensional micro-size bumps is shown to be a very effective flow control method for two-dimensional SWBLI. In investigating the three dimensional SWBLI, a square duct is employed as a baseline. To investigate the mechanism whereby the geometric elements of the baseline, i.e. the bottom wall, the sidewall and the corner, exert influence on the flow's aerodynamic characteristics, each element is studied and optimized separately. It is found that arrays of micro-size bumps on the bottom wall of the duct have little effect in improving total pressure recovery though they are useful in suppressing the incipient separation in three-dimensional problems. Shaping sidewall geometry is effective in re-distributing flow on the side wall and results in a less distorted flow at the exit. Subsequently, a near 50% reduction in distortion is achieved. A simple change in corner geometry resulted in a 2.4% improvement in total pressure recovery.

Magnetic resonance image compression using scalar-vector quantization

NASA Astrophysics Data System (ADS)

Mohsenian, Nader; Shahri, Homayoun

1995-12-01

A new coding scheme based on the scalar-vector quantizer (SVQ) is developed for compression of medical images. SVQ is a fixed-rate encoder and its rate-distortion performance is close to that of optimal entropy-constrained scalar quantizers (ECSQs) for memoryless sources. The use of a fixed-rate quantizer is expected to eliminate some of the complexity issues of using variable-length scalar quantizers. When transmission of images over noisy channels is considered, our coding scheme does not suffer from error propagation which is typical of coding schemes which use variable-length codes. For a set of magnetic resonance (MR) images, coding results obtained from SVQ and ECSQ at low bit-rates are indistinguishable. Furthermore, our encoded images are perceptually indistinguishable from the original, when displayed on a monitor. This makes our SVQ based coder an attractive compression scheme for picture archiving and communication systems (PACS), currently under consideration for an all digital radiology environment in hospitals, where reliable transmission, storage, and high fidelity reconstruction of images are desired.

Underwater laser weld bowing distortion behavior and mechanism of thin 304 stainless steel plates

NASA Astrophysics Data System (ADS)

Huang, ZunYue; Luo, Zhen; Ao, Sansan; Cai, YangChuan

2018-10-01

Underwater laser weld bowing distortion behavior and mechanism of thin 304 stainless steel plates are studied in the paper. The influence of underwater laser welding parameters (such as laser power, welding speed, defocusing distance and gas flow rate) on weld bowing distortion was investigated through central composite rotatable design and an orthogonal test. A quadratic response model was established to evaluate the underwater laser weld bowing distortion by central composite rotatable design and the order of the impacts of the welding parameters on weld bowing distortion was studied by an orthogonal test. The weld bowing distortion after welding was determined by the digital image correlation technique. The weld bowing distortion of in-air laser welding and underwater laser welding were compared and it revealed that the shape of the in-air and underwater laser welded specimens are the same, but the weld bowing distortion amount of in-air welding is larger than that of underwater welding. Weld bowing distortion mechanism was studied by the digital image correlation technique, and it was demonstrated that weld bowing distortion is associated with the welding plate temperature gradient during laser welding. The wider weld width also resulted in larger weld bowing distortion.

Evaluation of image quality and radiation dose by adaptive statistical iterative reconstruction technique level for chest CT examination.

PubMed

Hong, Sun Suk; Lee, Jong-Woong; Seo, Jeong Beom; Jung, Jae-Eun; Choi, Jiwon; Kweon, Dae Cheol

2013-12-01

The purpose of this research is to determine the adaptive statistical iterative reconstruction (ASIR) level that enables optimal image quality and dose reduction in the chest computed tomography (CT) protocol with ASIR. A chest phantom with 0-50 % ASIR levels was scanned and then noise power spectrum (NPS), signal and noise and the degree of distortion of peak signal-to-noise ratio (PSNR) and the root-mean-square error (RMSE) were measured. In addition, the objectivity of the experiment was measured using the American College of Radiology (ACR) phantom. Moreover, on a qualitative basis, five lesions' resolution, latitude and distortion degree of chest phantom and their compiled statistics were evaluated. The NPS value decreased as the frequency increased. The lowest noise and deviation were at the 20 % ASIR level, mean 126.15 ± 22.21. As a result of the degree of distortion, signal-to-noise ratio and PSNR at 20 % ASIR level were at the highest value as 31.0 and 41.52. However, maximum absolute error and RMSE showed the lowest deviation value as 11.2 and 16. In the ACR phantom study, all ASIR levels were within acceptable allowance of guidelines. The 20 % ASIR level performed best in qualitative evaluation at five lesions of chest phantom as resolution score 4.3, latitude 3.47 and the degree of distortion 4.25. The 20 % ASIR level was proved to be the best in all experiments, noise, distortion evaluation using ImageJ and qualitative evaluation of five lesions of a chest phantom. Therefore, optimal images as well as reduce radiation dose would be acquired when 20 % ASIR level in thoracic CT is applied.

Eddy current-nulled convex optimized diffusion encoding (EN-CODE) for distortion-free diffusion tensor imaging with short echo times.

PubMed

Aliotta, Eric; Moulin, Kévin; Ennis, Daniel B

2018-02-01

To design and evaluate eddy current-nulled convex optimized diffusion encoding (EN-CODE) gradient waveforms for efficient diffusion tensor imaging (DTI) that is free of eddy current-induced image distortions. The EN-CODE framework was used to generate diffusion-encoding waveforms that are eddy current-compensated. The EN-CODE DTI waveform was compared with the existing eddy current-nulled twice refocused spin echo (TRSE) sequence as well as monopolar (MONO) and non-eddy current-compensated CODE in terms of echo time (TE) and image distortions. Comparisons were made in simulations, phantom experiments, and neuro imaging in 10 healthy volunteers. The EN-CODE sequence achieved eddy current compensation with a significantly shorter TE than TRSE (78 versus 96 ms) and a slightly shorter TE than MONO (78 versus 80 ms). Intravoxel signal variance was lower in phantoms with EN-CODE than with MONO (13.6 ± 11.6 versus 37.4 ± 25.8) and not different from TRSE (15.1 ± 11.6), indicating good robustness to eddy current-induced image distortions. Mean fractional anisotropy values in brain edges were also significantly lower with EN-CODE than with MONO (0.16 ± 0.01 versus 0.24 ± 0.02, P < 1 x 10 -5 ) and not different from TRSE (0.16 ± 0.01 versus 0.16 ± 0.01, P = nonsignificant). The EN-CODE sequence eliminated eddy current-induced image distortions in DTI with a TE comparable to MONO and substantially shorter than TRSE. Magn Reson Med 79:663-672, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Numerical and Experimental Study of Ti6Al4V Components Manufactured Using Powder Bed Fusion Additive Manufacturing

NASA Astrophysics Data System (ADS)

Zielinski, Jonas; Mindt, Hans-Wilfried; Düchting, Jan; Schleifenbaum, Johannes Henrich; Megahed, Mustafa

2017-12-01

Powder bed fusion additive manufacturing of titanium alloys is an interesting manufacturing route for many applications requiring high material strength combined with geometric complexity. Managing powder bed fusion challenges, including porosity, surface finish, distortions and residual stresses of as-built material, is the key to bringing the advantages of this process to production main stream. This paper discusses the application of experimental and numerical analysis towards optimizing the manufacturing process of a demonstration component. Powder characterization including assessment of the reusability, assessment of material consolidation and process window optimization is pursued prior to applying the identified optima to study the distortion and residual stresses of the demonstrator. Comparisons of numerical predictions with measurements show good correlations along the complete numerical chain.

Correction of distortions in distressed mothers' ratings of their preschool children's psychopathology.

PubMed

Müller, Jörg M; Furniss, Tilman

2013-11-30

The often-reported low informant agreement about child psychopathology between multiple informants has lead to various suggestions about how to address discrepant ratings. Among the factors that may lower agreement that have been discussed is informant credibility, reliability, or psychopathology, which is of interest in this paper. We tested three different models, namely, the accuracy, the distortion, and an integrated so-called combined model, that conceptualize parental ratings to assess child psychopathology. The data comprise ratings of child psychopathology from multiple informants (mother, therapist and kindergarten teacher) and ratings of maternal psychopathology. The children were patients in a preschool psychiatry unit (N=247). The results from structural equation modeling show that maternal ratings of child psychopathology were biased by maternal psychopathology (distortion model). Based on this statistical background, we suggest a method to adjust biased maternal ratings. We illustrate the maternal bias by comparing the ratings of mother to expert ratings (combined kindergarten teacher and therapist ratings) and show that the correction equation increases the agreement between maternal and expert ratings. We conclude that this approach may help to reduce misclassification of preschool children as 'clinical' on the basis of biased maternal ratings. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Cognitive distortions and gambling near-misses in Internet Gaming Disorder: A preliminary study

PubMed Central

Sescousse, Guillaume; Yu, Hongbo; Clark, Luke; Li, Hong

2018-01-01

Increased cognitive distortions (i.e. biased processing of chance, probability and skill) are a key psychopathological process in disordered gambling. The present study investigated state and trait aspects of cognitive distortions in 22 individuals with Internet Gaming Disorder (IGD) and 22 healthy controls. Participants completed the Gambling Related Cognitions Scale as a trait measure of cognitive distortions, and played a slot machine task delivering wins, near-misses and full-misses. Ratings of pleasure (“liking”) and motivation to play (“wanting”) were taken following the different outcomes, and gambling persistence was measured after a mandatory phase. IGD was associated with elevated trait cognitive distortions, in particular skill-oriented cognitions. On the slot machine task, the IGD group showed increased “wanting” ratings compared with control participants, while the two groups did not differ regarding their “liking” of the game. The IGD group displayed increased persistence on the slot machine task. Near-miss outcomes did not elicit stronger motivation to play compared to full-miss outcomes overall, and there was no group difference on this measure. However, a near-miss position effect was observed, such that near-misses stopping before the payline were rated as more motivating than near-misses that stopped after the payline, and this differentiation was attenuated in the IGD group, suggesting possible counterfactual thinking deficits in this group. These data provide preliminary evidence for increased incentive motivation and cognitive distortions in IGD, at least in the context of a chance-based gambling environment. PMID:29346434

Cognitive distortions and gambling near-misses in Internet Gaming Disorder: A preliminary study.

PubMed

Wu, Yin; Sescousse, Guillaume; Yu, Hongbo; Clark, Luke; Li, Hong

2018-01-01

Increased cognitive distortions (i.e. biased processing of chance, probability and skill) are a key psychopathological process in disordered gambling. The present study investigated state and trait aspects of cognitive distortions in 22 individuals with Internet Gaming Disorder (IGD) and 22 healthy controls. Participants completed the Gambling Related Cognitions Scale as a trait measure of cognitive distortions, and played a slot machine task delivering wins, near-misses and full-misses. Ratings of pleasure ("liking") and motivation to play ("wanting") were taken following the different outcomes, and gambling persistence was measured after a mandatory phase. IGD was associated with elevated trait cognitive distortions, in particular skill-oriented cognitions. On the slot machine task, the IGD group showed increased "wanting" ratings compared with control participants, while the two groups did not differ regarding their "liking" of the game. The IGD group displayed increased persistence on the slot machine task. Near-miss outcomes did not elicit stronger motivation to play compared to full-miss outcomes overall, and there was no group difference on this measure. However, a near-miss position effect was observed, such that near-misses stopping before the payline were rated as more motivating than near-misses that stopped after the payline, and this differentiation was attenuated in the IGD group, suggesting possible counterfactual thinking deficits in this group. These data provide preliminary evidence for increased incentive motivation and cognitive distortions in IGD, at least in the context of a chance-based gambling environment.

Liver imaging at 3.0 T: diffusion-induced black-blood echo-planar imaging with large anatomic volumetric coverage as an alternative for specific absorption rate-intensive echo-train spin-echo sequences: feasibility study.

PubMed

van den Bos, Indra C; Hussain, Shahid M; Krestin, Gabriel P; Wielopolski, Piotr A

2008-07-01

Institutional Review Board approval and signed informed consent were obtained by all participants for an ongoing sequence optimization project at 3.0 T. The purpose of this study was to evaluate breath-hold diffusion-induced black-blood echo-planar imaging (BBEPI) as a potential alternative for specific absorption rate (SAR)-intensive spin-echo sequences, in particular, the fast spin-echo (FSE) sequences, at 3.0 T. Fourteen healthy volunteers (seven men, seven women; mean age +/- standard deviation, 32.7 years +/- 6.8) were imaged for this purpose. Liver coverage (20 cm, z-axis) was always performed in one 25-second breath hold. Imaging parameters were varied interactively with regard to echo time, diffusion b value, and voxel size. Images were evaluated and compared with fat-suppressed T2-weighted FSE images for image quality, liver delineation, geometric distortions, fat suppression, suppression of the blood signal, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR). An optimized short- (25 msec) and long-echo (80 msec) BBEPI provided full anatomic, single breath-hold liver coverage (100 and 50 sections, respectively), with resulting voxel sizes of 3.3 x 2.7 x 2.0 mm and 3.3 x 2.7 x 4.0 mm, respectively. Repetition time was 6300 msec, matrix size was 160 x 192, and an acceleration factor of 2.00 was used. b Values of more than 20 sec/mm(2) showed better suppression of the blood signal but b values of 10 sec/mm(2) provided improved volume coverage and signal consistency. Compared with fat-suppressed T2-weighted FSE, the optimized BBEPI sequence provided (a) comparable image quality and liver delineation, (b) acceptable geometric distortions, (c) improved suppression of fat and blood signals, and (d) high CNR and SNR. BBEPI is feasible for fast, low-SAR, thin-section morphologic imaging of the entire liver in a single breath hold at 3.0 T. (c) RSNA, 2008.

Enhancement of the Wear Particle Monitoring Capability of Oil Debris Sensors Using a Maximal Overlap Discrete Wavelet Transform with Optimal Decomposition Depth

PubMed Central

Li, Chuan; Peng, Juan; Liang, Ming

2014-01-01

Oil debris sensors are effective tools to monitor wear particles in lubricants. For in situ applications, surrounding noise and vibration interferences often distort the oil debris signature of the sensor. Hence extracting oil debris signatures from sensor signals is a challenging task for wear particle monitoring. In this paper we employ the maximal overlap discrete wavelet transform (MODWT) with optimal decomposition depth to enhance the wear particle monitoring capability. The sensor signal is decomposed by the MODWT into different depths for detecting the wear particle existence. To extract the authentic particle signature with minimal distortion, the root mean square deviation of kurtosis value of the segmented signal residue is adopted as a criterion to obtain the optimal decomposition depth for the MODWT. The proposed approach is evaluated using both simulated and experimental wear particles. The results show that the present method can improve the oil debris monitoring capability without structural upgrade requirements. PMID:24686730

Enhancement of the wear particle monitoring capability of oil debris sensors using a maximal overlap discrete wavelet transform with optimal decomposition depth.

PubMed

Li, Chuan; Peng, Juan; Liang, Ming

2014-03-28

Oil debris sensors are effective tools to monitor wear particles in lubricants. For in situ applications, surrounding noise and vibration interferences often distort the oil debris signature of the sensor. Hence extracting oil debris signatures from sensor signals is a challenging task for wear particle monitoring. In this paper we employ the maximal overlap discrete wavelet transform (MODWT) with optimal decomposition depth to enhance the wear particle monitoring capability. The sensor signal is decomposed by the MODWT into different depths for detecting the wear particle existence. To extract the authentic particle signature with minimal distortion, the root mean square deviation of kurtosis value of the segmented signal residue is adopted as a criterion to obtain the optimal decomposition depth for the MODWT. The proposed approach is evaluated using both simulated and experimental wear particles. The results show that the present method can improve the oil debris monitoring capability without structural upgrade requirements.

Intelligibility Evaluation of Pathological Speech through Multigranularity Feature Extraction and Optimization.

PubMed

Fang, Chunying; Li, Haifeng; Ma, Lin; Zhang, Mancai

2017-01-01

Pathological speech usually refers to speech distortion resulting from illness or other biological insults. The assessment of pathological speech plays an important role in assisting the experts, while automatic evaluation of speech intelligibility is difficult because it is usually nonstationary and mutational. In this paper, we carry out an independent innovation of feature extraction and reduction, and we describe a multigranularity combined feature scheme which is optimized by the hierarchical visual method. A novel method of generating feature set based on S -transform and chaotic analysis is proposed. There are BAFS (430, basic acoustics feature), local spectral characteristics MSCC (84, Mel S -transform cepstrum coefficients), and chaotic features (12). Finally, radar chart and F -score are proposed to optimize the features by the hierarchical visual fusion. The feature set could be optimized from 526 to 96 dimensions based on NKI-CCRT corpus and 104 dimensions based on SVD corpus. The experimental results denote that new features by support vector machine (SVM) have the best performance, with a recognition rate of 84.4% on NKI-CCRT corpus and 78.7% on SVD corpus. The proposed method is thus approved to be effective and reliable for pathological speech intelligibility evaluation.

Optimal causal inference: estimating stored information and approximating causal architecture.

PubMed

Still, Susanne; Crutchfield, James P; Ellison, Christopher J

2010-09-01

We introduce an approach to inferring the causal architecture of stochastic dynamical systems that extends rate-distortion theory to use causal shielding--a natural principle of learning. We study two distinct cases of causal inference: optimal causal filtering and optimal causal estimation. Filtering corresponds to the ideal case in which the probability distribution of measurement sequences is known, giving a principled method to approximate a system's causal structure at a desired level of representation. We show that in the limit in which a model-complexity constraint is relaxed, filtering finds the exact causal architecture of a stochastic dynamical system, known as the causal-state partition. From this, one can estimate the amount of historical information the process stores. More generally, causal filtering finds a graded model-complexity hierarchy of approximations to the causal architecture. Abrupt changes in the hierarchy, as a function of approximation, capture distinct scales of structural organization. For nonideal cases with finite data, we show how the correct number of the underlying causal states can be found by optimal causal estimation. A previously derived model-complexity control term allows us to correct for the effect of statistical fluctuations in probability estimates and thereby avoid overfitting.

Performance measures for transform data coding.

NASA Technical Reports Server (NTRS)

Pearl, J.; Andrews, H. C.; Pratt, W. K.

1972-01-01

This paper develops performance criteria for evaluating transform data coding schemes under computational constraints. Computational constraints that conform with the proposed basis-restricted model give rise to suboptimal coding efficiency characterized by a rate-distortion relation R(D) similar in form to the theoretical rate-distortion function. Numerical examples of this performance measure are presented for Fourier, Walsh, Haar, and Karhunen-Loeve transforms.

Real-time distortion correction of spiral and echo planar images using the gradient system impulse response function.

PubMed

Campbell-Washburn, Adrienne E; Xue, Hui; Lederman, Robert J; Faranesh, Anthony Z; Hansen, Michael S

2016-06-01

MRI-guided interventions demand high frame rate imaging, making fast imaging techniques such as spiral imaging and echo planar imaging (EPI) appealing. In this study, we implemented a real-time distortion correction framework to enable the use of these fast acquisitions for interventional MRI. Distortions caused by gradient waveform inaccuracies were corrected using the gradient impulse response function (GIRF), which was measured by standard equipment and saved as a calibration file on the host computer. This file was used at runtime to calculate the predicted k-space trajectories for image reconstruction. Additionally, the off-resonance reconstruction frequency was modified in real time to interactively deblur spiral images. Real-time distortion correction for arbitrary image orientations was achieved in phantoms and healthy human volunteers. The GIRF-predicted k-space trajectories matched measured k-space trajectories closely for spiral imaging. Spiral and EPI image distortion was visibly improved using the GIRF-predicted trajectories. The GIRF calibration file showed no systematic drift in 4 months and was demonstrated to correct distortions after 30 min of continuous scanning despite gradient heating. Interactive off-resonance reconstruction was used to sharpen anatomical boundaries during continuous imaging. This real-time distortion correction framework will enable the use of these high frame rate imaging methods for MRI-guided interventions. Magn Reson Med 75:2278-2285, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Real-time distortion correction of spiral and echo planar images using the gradient system impulse response function

PubMed Central

Campbell-Washburn, Adrienne E; Xue, Hui; Lederman, Robert J; Faranesh, Anthony Z; Hansen, Michael S

2015-01-01

Purpose MRI-guided interventions demand high frame-rate imaging, making fast imaging techniques such as spiral imaging and echo planar imaging (EPI) appealing. In this study, we implemented a real-time distortion correction framework to enable the use of these fast acquisitions for interventional MRI. Methods Distortions caused by gradient waveform inaccuracies were corrected using the gradient impulse response function (GIRF), which was measured by standard equipment and saved as a calibration file on the host computer. This file was used at runtime to calculate the predicted k-space trajectories for image reconstruction. Additionally, the off-resonance reconstruction frequency was modified in real-time to interactively de-blur spiral images. Results Real-time distortion correction for arbitrary image orientations was achieved in phantoms and healthy human volunteers. The GIRF predicted k-space trajectories matched measured k-space trajectories closely for spiral imaging. Spiral and EPI image distortion was visibly improved using the GIRF predicted trajectories. The GIRF calibration file showed no systematic drift in 4 months and was demonstrated to correct distortions after 30 minutes of continuous scanning despite gradient heating. Interactive off-resonance reconstruction was used to sharpen anatomical boundaries during continuous imaging. Conclusions This real-time distortion correction framework will enable the use of these high frame-rate imaging methods for MRI-guided interventions. PMID:26114951

Magnetic decoupling of the linac in a low field biplanar linac-MR system.

PubMed

St Aubin, J; Steciw, S; Fallone, B G

2010-09-01

The integration of a low field biplanar magnetic resonance (MR) imager and linear accelerator (linac) causes magnetic interference at the linac due to the MR fringe fields. In order to eliminate this interference, passive and active magnetic shielding designs are investigated. The optimized design of passive magnetic shielding was performed using the finite element method. The design was required to achieve no greater than a 20% electron beam loss within the linac waveguide and electron gun, no greater than 0.06 T at the multileaf collimator (MLC) motors, and generate a distortion of the main MR imaging volume of no greater than 300 ppm. Through the superposition of the analytical solution for a single current carrying wire loop, active shielding designs in the form of three and four sets of coil pairs surrounding the linac waveguide and electron gun were also investigated. The optimized current and coil center locations that yielded the best cancellation of the MR fringe fields at the linac were determined using sequential quadratic programming. Optimized passive shielding in the form of two steel cylinders was designed to meet the required constraints. When shielding the MLC motors along with the waveguide and electron gun, the thickness of the cylinders was less than 1 mm. If magnetically insensitive MLC motors are used, no MLC shielding would be required and the waveguide shield (shielding the waveguide and electron gun) became 1.58 mm thick. In addition, the optimized current and coil spacing for active shielding was determined for both three and four coil pair configurations. The results of the active shielding optimization produced no beam loss within the waveguide and electron gun and a maximum MR field distortion of 91 ppm over a 30 cm diameter spherical volume. Very simple passive and active shielding designs have been shown to magnetically decouple the linac from the MR imager in a low field biplanar linac-MR system. The MLC passive shielding produced the largest distortion of the MR field over the imaging volume. With the use of magnetically insensitive motors, the MR field distortion drops substantially since no MLC shield is required. The active shielding designs yielded no electron beam loss within the linac.

A Novel Model for Stock Price Prediction Using Hybrid Neural Network

NASA Astrophysics Data System (ADS)

Senapati, Manas Ranjan; Das, Sumanjit; Mishra, Sarojananda

2018-06-01

The foremost challenge for investors is to select stock price by analyzing financial data which is a menial task as of distort associated and massive pattern. Thereby, selecting stock poses one of the greatest difficulties for investors. Nowadays, prediction of financial market like stock market, exchange rate and share value are very challenging field of research. The prediction and scrutinization of stock price is also a potential area of research due to its vital significance in decision making by financial investors. This paper presents an intelligent and an optimal model for prophecy of stock market price using hybridization of Adaline Neural Network (ANN) and modified Particle Swarm Optimization (PSO). The connoted model hybrid of Adaline and PSO uses fluctuations of stock market as a factor and employs PSO to optimize and update weights of Adaline representation to depict open price of Bombay stock exchange. The prediction performance of the proposed model is compared with different representations like interval measurements, CMS-PSO and Bayesian-ANN. The result indicates that proposed scheme has an edge over all the juxtaposed schemes in terms of mean absolute percentage error.

Parallel efficient rate control methods for JPEG 2000

NASA Astrophysics Data System (ADS)

Martínez-del-Amor, Miguel Á.; Bruns, Volker; Sparenberg, Heiko

2017-09-01

Since the introduction of JPEG 2000, several rate control methods have been proposed. Among them, post-compression rate-distortion optimization (PCRD-Opt) is the most widely used, and the one recommended by the standard. The approach followed by this method is to first compress the entire image split in code blocks, and subsequently, optimally truncate the set of generated bit streams according to the maximum target bit rate constraint. The literature proposes various strategies on how to estimate ahead of time where a block will get truncated in order to stop the execution prematurely and save time. However, none of them have been defined bearing in mind a parallel implementation. Today, multi-core and many-core architectures are becoming popular for JPEG 2000 codecs implementations. Therefore, in this paper, we analyze how some techniques for efficient rate control can be deployed in GPUs. In order to do that, the design of our GPU-based codec is extended, allowing stopping the process at a given point. This extension also harnesses a higher level of parallelism on the GPU, leading to up to 40% of speedup with 4K test material on a Titan X. In a second step, three selected rate control methods are adapted and implemented in our parallel encoder. A comparison is then carried out, and used to select the best candidate to be deployed in a GPU encoder, which gave an extra 40% of speedup in those situations where it was really employed.

SU-E-J-205: Dose Distribution Differences Caused by System Related Geometric Distortion in MRI-Guided Radiation Treatment System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, J; Yang, J; Wen, Z

2015-06-15

Purpose: MRI has superb soft tissue contrast but is also known for geometric distortions. The concerns and uncertainty about MRI’s geometric distortion have contributed to the hesitation of using only MRI for simulation in radiation therapy. There are two major categories of geometric distortion in MRI; system related and patient related. In this presentation, we studied the impact of system-related geometric distortion on dose distribution in a digital body phantom under an MR-Linac environment. Methods: Residual geometric distortion (after built-in geometric correction) was modeled based on phantom measurements of the system-related geometric distortions of a MRI scanner of a combinedmore » MR guided Radiation Therapy (MRgRT) system. A digital oval shaped phantom (40×25 cm) as well as one ellipsoid shaped tumor volume was created to simulate a simplified human body. The simulated tumor volume was positioned at several locations between the isocenter and the body surface. CT numbers in HUs that approximate soft tissue and tumor were assigned to the respective regions in the digital phantom. To study the effect of geometric distortion caused by system imperfections, an IMRT plan was optimized with the distorted image set with the B field. Dose distributions were re-calculated on the undistorted image set with the B field (as in MR-Linac). Results: The maximum discrepancies in both body contour and tumor boundary was less than 2 mm, which leads to small dose distribution change. For the target in the center, coverage was reduced from 98.8% (with distortion) to 98.2%; for the other peripheral target coverage was reduced from 98.4% to 95.9%. Conclusion: System related geometric distortions over the 40×25 area were within 2mm and the resulted dosimetric effects were minor for the two tumor locations in the phantom. Patient study will be needed for further investigation. The authors received a corporate research grant from Elekta.« less

Electronic structure of the metal center in the Cd(2+), Zn(2+), and Cu(2+) substituted forms of KDO8P synthase: implications for catalysis.

PubMed

Kona, Fathima; Tao, Peng; Martin, Philip; Xu, Xingjue; Gatti, Domenico L

2009-04-28

Aquifex aeolicus 3-deoxy-d-manno-octulosonate 8-phosphate synthase (KDO8PS) is active with a variety of different divalent metal ions bound in the active site. The Cd(2+), Zn(2+), and Cu(2+) substituted enzymes display similar values of k(cat) and similar dependence of K(m)(PEP) and K(m)(A5P) on both substrate and product concentrations. However, the flux-control coefficients for some of the catalytically relevant reaction steps are different in the presence of Zn(2+) or Cu(2+), suggesting that the type of metal bound in the active site affects the behavior of the enzyme in vivo. The type of metal also affects the rate of product release in the crystal environment. For example, the crystal structure of the Cu(2+) enzyme incubated with phosphoenolpyruvate (PEP) and arabinose 5-phosphate (A5P) shows the formed product, 3-deoxy-d-manno-octulosonate 8-phosphate (KDO8P), still bound in the active site in its linear conformation. This observation completes our structural studies of the condensation reaction, which altogether have provided high-resolution structures for the reactants, the intermediate, and the product bound forms of KDO8PS. The crystal structures of the Cd(2+), Zn(2+), and Cu(2+) substituted enzymes show four residues (Cys-11, His-185, Glu-222, and Asp-233) and a water molecule as possible metal ligands. Combined quantum mechanics/molecular mechanics (QM/MM) geometry optimizations reveal that the metal centers have a delocalized electronic structure, and that their true geometry is square pyramidal for Cd(2+) and Zn(2+) and distorted octahedral or distorted tetrahedral for Cu(2+). These geometries are different from those obtained by QM optimization in the gas phase (tetrahedral for Cd(2+) and Zn(2+), distorted tetrahedral for Cu(2+)) and may represent conformations of the metal center that minimize the reorganization energy between the substrate-bound and product-bound states. The QM/MM calculations also show that when only PEP is bound to the enzyme the electronic structure of the metal center is optimized to prevent a wasteful reaction of PEP with water.

High Slew-Rate Head-Only Gradient for Improving Distortion in Echo Planar Imaging: Preliminary Experience

PubMed Central

Tan, Ek T.; Lee, Seung-Kyun; Weavers, Paul T.; Graziani, Dominic; Piel, Joseph E.; Shu, Yunhong; Huston, John; Bernstein, Matt A.; Foo, Thomas K.F.

2016-01-01

Purpose To investigate the effects on echo planar imaging (EPI) distortion of using high gradient slew rates (SR) of up to 700 T/m/s for in-vivo human brain imaging, with a dedicated, head-only gradient coil. Materials and Methods Simulation studies were first performed to determine the expected echo spacing and distortion reduction in EPI. A head gradient of 42-cm inner diameter and with asymmetric transverse coils was then installed in a whole-body, conventional 3T MRI system. Human subject imaging was performed on five subjects to determine the effects of EPI on echo spacing and signal dropout at various gradient slew rates. The feasibility of whole-brain imaging at 1.5 mm-isotropic spatial resolution was demonstrated with gradient-echo and spin-echo diffusion-weighted EPI. Results As compared to a whole-body gradient coil, the EPI echo spacing in the head-only gradient coil was reduced by 48%. Simulation and in vivo results, respectively, showed up to 25-26% and 19% improvement in signal dropout. Whole-brain imaging with EPI at 1.5 mm spatial resolution provided good whole-brain coverage, spatial linearity, and low spatial distortion effects. Conclusion Our results of human brain imaging with EPI using the compact head gradient coil at slew rates higher than in conventional whole-body MR systems demonstrate substantially improved image distortion, and point to a potential for benefits to non-EPI pulse sequences. PMID:26921117

Three component vibrational time reversal communication

DOE PAGES

Anderson, Brian E.; Ulrich, Timothy J.; Ten Cate, James A.

2015-01-01

Time reversal provides an optimal prefilter matched signal to apply to a communication signal before signal transmission. Time reversal allows compensation for wave speed dispersion and can function well in reverberant environments. Time reversal can be used to focus elastic energy to each of the three components of motion independently. A pipe encased in concrete was used to demonstrate the ability to conduct communications of information using three component time reversal. Furthermore, the ability of time reversal to compensate for multi-path distortion (overcoming reverberation) will be demonstrated and the rate of signal communication will be presented. [The U.S. Department ofmore » Energy, through the LANL/LDRD Program, is gratefully acknowledged for supporting this work.]« less

Rapid cycloaddition of a diazo group with an unstrained dipolarophile.

PubMed

Aronoff, Matthew R; Gold, Brian; Raines, Ronald T

2016-06-01

The cycloaddition of a diazoacetamide with ethyl 4,4,4-trifluorocrotonate proceeds with k = 0.1 M -1 s -1 . This second-order rate constant rivals those of optimized strain-promoted azide- alkyne cycloadditions, even though the reaction does not release strain. The regioselectivity and a computational distortion/interaction analysis of the reaction energetics are consistent with the formation of an N-H…F-C hydrogen bond in the transition state and the electronic character of the trifluorocrotonate. Analogous reactions with an azidoacetamide dipole or with an acrylate or crotonate dipolarophile were much slower. These findings suggest a new strategy for the design of diazo-selective reagents for chemical biology.

Selective reinforcement of a 2m-class lightweight mirror for horizontal beam optical testing

NASA Astrophysics Data System (ADS)

Besuner, R. W.; Chow, K. P.; Kendrick, S. E.; Streetman, S.

2008-07-01

Optical testing of large mirrors for space telescopes can be challenging and complex. Demanding optical requirements necessitate both precise mirror figure and accurate prediction of zero gravity shape. Mass and packaging constraints require mirrors to be lightweighted and optically fast. Reliability and low mass imply simple mounting schemes, with basic kinematic mounts preferable to active figure control or whiffle trees. Ground testing should introduce as little uncertainty as possible, ideally employing flight mounts without offloaders. Testing mirrors with their optical axes horizontal can result in less distortion than in the vertical orientation, though distortion will increase with mirror speed. Finite element modeling and optimization tools help specify selective reinforcement of the mirror structure to minimize wavefront errors in a one gravity test, while staying within mass budgets and meeting other requirements. While low distortions are necessary, an important additional criterion is that designs are tolerant to imperfect positioning of the mounts relative to the neutral surface of the mirror substrate. In this paper, we explore selective reinforcement of a 2-meter class, f/1.25 primary mirror for the proposed SNAP space telescope. We specify designs optimized for various mount radial locations both with and without backup mount locations. Reinforced designs are predicted to have surface distortions in the horizontal beam test low enough to perform optical testing on the ground, on flight mounts, and without offloaders. Importantly, the required accuracy of mount locations is on the order of millimeters rather than tenths of millimeters.

Boundary-Layer-Ingesting Inlet Flow Control

NASA Technical Reports Server (NTRS)

Owens, Lewis R.; Allan, Brian G.; Gorton, Susan A.

2008-01-01

An experimental study was conducted to provide the first demonstration of an active flow control system for a flush-mounted inlet with significant boundary-layer-ingestion in transonic flow conditions. The effectiveness of the flow control in reducing the circumferential distortion at the engine fan-face location was assessed using a 2.5%-scale model of a boundary-layer-ingesting offset diffusing inlet. The inlet was flush mounted to the tunnel wall and ingested a large boundary layer with a boundary-layer-to-inlet height ratio of 35%. Different jet distribution patterns and jet mass flow rates were used in the inlet to control distortion. A vane configuration was also tested. Finally a hybrid vane/jet configuration was tested leveraging strengths of both types of devices. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass flow rates through the duct and the flow control actuators. The distortion and pressure recovery were measured at the aerodynamic interface plane. The data show that control jets and vanes reduce circumferential distortion to acceptable levels. The point-design vane configuration produced higher distortion levels at off-design settings. The hybrid vane/jet flow control configuration reduced the off-design distortion levels to acceptable ones and used less than 0.5% of the inlet mass flow to supply the jets.

Temperature distortion generator for turboshaft engine testing

NASA Technical Reports Server (NTRS)

Klann, G. A.; Barth, R. L.; Biesiadny, T. J.

1984-01-01

The procedures and unique hardware used to conduct an experimental investigation into the response of a small-turboshaft-engine compression system to various hot gas ingestion patterns are presented. The temperature distortion generator described herein uses gaseous hydrogen to create both steady-state and time-variant, or transient, temperature distortion at the engine inlet. The range of transient temperature ramps produced by the distortion generator during the engine tests was from less than 111 deg K/sec (200 deg R/sec) to above 611 deg K/sec (1100 deg R/sec); instantaneous temperatures to 422 deg K (760 deg R) above ambient were generated. The distortion generator was used to document the maximum inlet temperatures and temperature rise rates that the compression system could tolerate before the onset of stall for various circumferential distortions as well as the compressor system response during stall.

Metric Calibration of a Focused Plenoptic Camera Based on a 3d Calibration Target

NASA Astrophysics Data System (ADS)

Zeller, N.; Noury, C. A.; Quint, F.; Teulière, C.; Stilla, U.; Dhome, M.

2016-06-01

In this paper we present a new calibration approach for focused plenoptic cameras. We derive a new mathematical projection model of a focused plenoptic camera which considers lateral as well as depth distortion. Therefore, we derive a new depth distortion model directly from the theory of depth estimation in a focused plenoptic camera. In total the model consists of five intrinsic parameters, the parameters for radial and tangential distortion in the image plane and two new depth distortion parameters. In the proposed calibration we perform a complete bundle adjustment based on a 3D calibration target. The residual of our optimization approach is three dimensional, where the depth residual is defined by a scaled version of the inverse virtual depth difference and thus conforms well to the measured data. Our method is evaluated based on different camera setups and shows good accuracy. For a better characterization of our approach we evaluate the accuracy of virtual image points projected back to 3D space.

Distortion correction in EPI at ultra-high-field MRI using PSF mapping with optimal combination of shift detection dimension.

PubMed

Oh, Se-Hong; Chung, Jun-Young; In, Myung-Ho; Zaitsev, Maxim; Kim, Young-Bo; Speck, Oliver; Cho, Zang-Hee

2012-10-01

Despite its wide use, echo-planar imaging (EPI) suffers from geometric distortions due to off-resonance effects, i.e., strong magnetic field inhomogeneity and susceptibility. This article reports a novel method for correcting the distortions observed in EPI acquired at ultra-high-field such as 7 T. Point spread function (PSF) mapping methods have been proposed for correcting the distortions in EPI. The PSF shift map can be derived either along the nondistorted or the distorted coordinates. Along the nondistorted coordinates more information about compressed areas is present but it is prone to PSF-ghosting artifacts induced by large k-space shift in PSF encoding direction. In contrast, shift maps along the distorted coordinates contain more information in stretched areas and are more robust against PSF-ghosting. In ultra-high-field MRI, an EPI contains both compressed and stretched regions depending on the B0 field inhomogeneity and local susceptibility. In this study, we present a new geometric distortion correction scheme, which selectively applies the shift map with more information content. We propose a PSF-ghost elimination method to generate an artifact-free pixel shift map along nondistorted coordinates. The proposed method can correct the effects of the local magnetic field inhomogeneity induced by the susceptibility effects along with the PSF-ghost artifact cancellation. We have experimentally demonstrated the advantages of the proposed method in EPI data acquisitions in phantom and human brain using 7-T MRI. Copyright © 2011 Wiley Periodicals, Inc.

Comparison of two models of hemispheric specialization with unilaterally lesioned patients: material-specific impairment vs response-bias distortion.

PubMed

Guimond, Anik; Braun, Claude M J; Daigneault, Sylvie; Farmer, Jean-Pierre

2013-10-01

Validity of two models of hemispheric specialization was compared. The "material-specific impairment" model was radicalized as postulating that left hemisphere (LH) lesions impair processing of verbal material and that right hemisphere (RH) lesions impair processing of visuospatial material, independently of response-bias distortions. The "response-bias distortion" model was radicalized as postulating that LH lesions distort response style toward omissiveness and that RH lesions distort response style toward commissiveness, regardless of material-specific impairments. Participants had comparable left (N=27) or right (N=24) hemisphere cortical lesions having occurred between birth and early adolescence. Four cognitive neuropsychological tests were adjusted to optimize applicability and comparability of the two theoretical models: Rey Complex Figure, Kimura's Recurring Figures, the Story Recall subtest of the Children's Memory Scale, and the California Verbal Learning Test. Both models significantly, independently, and equally distinguished the LH from the RH patients. Both these forms of hemispheric specialization seemed to be implemented very early in life and very rigidly. Intrahemispheric lesion sites, e.g., frontal vs nonfrontal, held no significant relation to the effects described above. © 2013 Elsevier Inc. All rights reserved.

A holistic calibration method with iterative distortion compensation for stereo deflectometry

NASA Astrophysics Data System (ADS)

Xu, Yongjia; Gao, Feng; Zhang, Zonghua; Jiang, Xiangqian

2018-07-01

This paper presents a novel holistic calibration method for stereo deflectometry system to improve the system measurement accuracy. The reconstruction result of stereo deflectometry is integrated with the calculated normal data of the measured surface. The calculation accuracy of the normal data is seriously influenced by the calibration accuracy of the geometrical relationship of the stereo deflectometry system. Conventional calibration approaches introduce form error to the system due to inaccurate imaging model and distortion elimination. The proposed calibration method compensates system distortion based on an iterative algorithm instead of the conventional distortion mathematical model. The initial value of the system parameters are calculated from the fringe patterns displayed on the systemic LCD screen through a reflection of a markless flat mirror. An iterative algorithm is proposed to compensate system distortion and optimize camera imaging parameters and system geometrical relation parameters based on a cost function. Both simulation work and experimental results show the proposed calibration method can significantly improve the calibration and measurement accuracy of a stereo deflectometry. The PV (peak value) of measurement error of a flat mirror can be reduced to 69.7 nm by applying the proposed method from 282 nm obtained with the conventional calibration approach.

Redshift sensitivity of the Kaiser effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simpson, Fergus

2010-02-15

We explore potential strategies for testing general relativity via the coherent motions of galaxies. Our position at z=0 provides the reference point for distance measures in cosmology. By contrast, the cosmic microwave background at z{approx_equal}1100 acts as the point of reference for the growth of a large-scale structure. As a result, we find there is a lack of synergy between growth and distance measures. We show that, when measuring the gravitational growth index {gamma} using redshift-space distortions, typically 80% of the signal corresponds to the local growth rate at the galaxy bin location, while the remaining fraction is determined bymore » its behavior at higher redshifts. In order to clarify whether modified gravity may be responsible for the dark energy phenomenon, the aim is to search for a modification to the growth of structure. One might expect the magnitude of this deviation to be commensurate with the apparent dark energy density {Omega}{sub {Lambda}}(z). This provides an incentive to study redshift-space distortions at as low a redshift as is practical. Specifically, we find the region around z=0.5 offers the optimal balance of available volume and signal strength.« less

Experimental evaluation of thermal ratcheting behavior in UO2 fuel elements

NASA Technical Reports Server (NTRS)

Phillips, W. M.

1973-01-01

The effects of thermal cycling of UO2 at high temperatures has been experimentally evaluated to determine the rates of distortion of UO2/clad fuel elements. Two capsules were rested in the 1500 C range, one with a 50 C thermal cycle, the other with a 100 C thermal cycle. It was observed that eight hours at the lower cycle temperature produced sufficient UO2 redistribution to cause clad distortion. The amount of distortion produced by the 100 C cycle was less than double that produced by the 50 C, indicating smaller thermal cycles would result in clad distortion. An incubation period was observed to occur before the onset of distortion with cycling similar to fuel swelling observed in-pile at these temperatures.

Speech coding at low to medium bit rates

NASA Astrophysics Data System (ADS)

Leblanc, Wilfred Paul

1992-09-01

Improved search techniques coupled with improved codebook design methodologies are proposed to improve the performance of conventional code-excited linear predictive coders for speech. Improved methods for quantizing the short term filter are developed by employing a tree search algorithm and joint codebook design to multistage vector quantization. Joint codebook design procedures are developed to design locally optimal multistage codebooks. Weighting during centroid computation is introduced to improve the outlier performance of the multistage vector quantizer. Multistage vector quantization is shown to be both robust against input characteristics and in the presence of channel errors. Spectral distortions of about 1 dB are obtained at rates of 22-28 bits/frame. Structured codebook design procedures for excitation in code-excited linear predictive coders are compared to general codebook design procedures. Little is lost using significant structure in the excitation codebooks while greatly reducing the search complexity. Sparse multistage configurations are proposed for reducing computational complexity and memory size. Improved search procedures are applied to code-excited linear prediction which attempt joint optimization of the short term filter, the adaptive codebook, and the excitation. Improvements in signal to noise ratio of 1-2 dB are realized in practice.

Scalable video transmission over Rayleigh fading channels using LDPC codes

NASA Astrophysics Data System (ADS)

Bansal, Manu; Kondi, Lisimachos P.

2005-03-01

In this paper, we investigate an important problem of efficiently utilizing the available resources for video transmission over wireless channels while maintaining a good decoded video quality and resilience to channel impairments. Our system consists of the video codec based on 3-D set partitioning in hierarchical trees (3-D SPIHT) algorithm and employs two different schemes using low-density parity check (LDPC) codes for channel error protection. The first method uses the serial concatenation of the constant-rate LDPC code and rate-compatible punctured convolutional (RCPC) codes. Cyclic redundancy check (CRC) is used to detect transmission errors. In the other scheme, we use the product code structure consisting of a constant rate LDPC/CRC code across the rows of the `blocks' of source data and an erasure-correction systematic Reed-Solomon (RS) code as the column code. In both the schemes introduced here, we use fixed-length source packets protected with unequal forward error correction coding ensuring a strictly decreasing protection across the bitstream. A Rayleigh flat-fading channel with additive white Gaussian noise (AWGN) is modeled for the transmission. The rate-distortion optimization algorithm is developed and carried out for the selection of source coding and channel coding rates using Lagrangian optimization. The experimental results demonstrate the effectiveness of this system under different wireless channel conditions and both the proposed methods (LDPC+RCPC/CRC and RS+LDPC/CRC) outperform the more conventional schemes such as those employing RCPC/CRC.

Learning optimal features for visual pattern recognition

NASA Astrophysics Data System (ADS)

Labusch, Kai; Siewert, Udo; Martinetz, Thomas; Barth, Erhardt

2007-02-01

The optimal coding hypothesis proposes that the human visual system has adapted to the statistical properties of the environment by the use of relatively simple optimality criteria. We here (i) discuss how the properties of different models of image coding, i.e. sparseness, decorrelation, and statistical independence are related to each other (ii) propose to evaluate the different models by verifiable performance measures (iii) analyse the classification performance on images of handwritten digits (MNIST data base). We first employ the SPARSENET algorithm (Olshausen, 1998) to derive a local filter basis (on 13 × 13 pixels windows). We then filter the images in the database (28 × 28 pixels images of digits) and reduce the dimensionality of the resulting feature space by selecting the locally maximal filter responses. We then train a support vector machine on a training set to classify the digits and report results obtained on a separate test set. Currently, the best state-of-the-art result on the MNIST data base has an error rate of 0,4%. This result, however, has been obtained by using explicit knowledge that is specific to the data (elastic distortion model for digits). We here obtain an error rate of 0,55% which is second best but does not use explicit data specific knowledge. In particular it outperforms by far all methods that do not use data-specific knowledge.

Effects of Distortion on Mass Flow Plug Calibration

NASA Technical Reports Server (NTRS)

Sasson, Jonathan; Davis, David O.; Barnhart, Paul J.

2015-01-01

A numerical, and experimental investigation to study the effects of flow distortion on a Mass Flow Plug (MFP) used to control and measure mass-flow during an inlet test has been conducted. The MFP was first calibrated using the WIND-US flow solver for uniform (undistorted) inflow conditions. These results are shown to compare favorably with an experimental calibration under similar conditions. The effects of distortion were investigated by imposing distorted flow conditions taken from an actual inlet test to the inflow plane of the numerical simulation. The computational fluid dynamic (CFD) based distortion study only showed the general trend in mass flow rate. The study used only total pressure as the upstream boundary condition, which was not enough to define the flow. A better simulation requires knowledge of the turbulence structure and a specific distortion pattern over a range of plug positions. It is recommended that future distortion studies utilize a rake with at least the same amount of pitot tubes as the AIP rake.

Cochlea-scaled spectral entropy predicts rate-invariant intelligibility of temporally distorted sentences.

PubMed

Stilp, Christian E; Kiefte, Michael; Alexander, Joshua M; Kluender, Keith R

2010-10-01

Some evidence, mostly drawn from experiments using only a single moderate rate of speech, suggests that low-frequency amplitude modulations may be particularly important for intelligibility. Here, two experiments investigated intelligibility of temporally distorted sentences across a wide range of simulated speaking rates, and two metrics were used to predict results. Sentence intelligibility was assessed when successive segments of fixed duration were temporally reversed (exp. 1), and when sentences were processed through four third-octave-band filters, the outputs of which were desynchronized (exp. 2). For both experiments, intelligibility decreased with increasing distortion. However, in exp. 2, intelligibility recovered modestly with longer desynchronization. Across conditions, performances measured as a function of proportion of utterance distorted converged to a common function. Estimates of intelligibility derived from modulation transfer functions predict a substantial proportion of the variance in listeners' responses in exp. 1, but fail to predict performance in exp. 2. By contrast, a metric of potential information, quantified as relative dissimilarity (change) between successive cochlear-scaled spectra, is introduced. This metric reliably predicts listeners' intelligibility across the full range of speaking rates in both experiments. Results support an information-theoretic approach to speech perception and the significance of spectral change rather than physical units of time.

High slew-rate head-only gradient for improving distortion in echo planar imaging: Preliminary experience.

PubMed

Tan, Ek T; Lee, Seung-Kyun; Weavers, Paul T; Graziani, Dominic; Piel, Joseph E; Shu, Yunhong; Huston, John; Bernstein, Matt A; Foo, Thomas K F

2016-09-01

To investigate the effects on echo planar imaging (EPI) distortion of using high gradient slew rates (SR) of up to 700 T/m/s for in vivo human brain imaging, with a dedicated, head-only gradient coil. Simulation studies were first performed to determine the expected echo spacing and distortion reduction in EPI. A head gradient of 42-cm inner diameter and with asymmetric transverse coils was then installed in a whole-body, conventional 3T magnetic resonance imaging (MRI) system. Human subject imaging was performed on five subjects to determine the effects of EPI on echo spacing and signal dropout at various gradient slew rates. The feasibility of whole-brain imaging at 1.5 mm-isotropic spatial resolution was demonstrated with gradient-echo and spin-echo diffusion-weighted EPI. As compared to a whole-body gradient coil, the EPI echo spacing in the head-only gradient coil was reduced by 48%. Simulation and in vivo results, respectively, showed up to 25-26% and 19% improvement in signal dropout. Whole-brain imaging with EPI at 1.5 mm spatial resolution provided good whole-brain coverage, spatial linearity, and low spatial distortion effects. Our results of human brain imaging with EPI using the compact head gradient coil at slew rates higher than in conventional whole-body MR systems demonstrate substantially improved image distortion, and point to a potential for benefits to non-EPI pulse sequences. J. Magn. Reson. Imaging 2016;44:653-664. © 2016 International Society for Magnetic Resonance in Medicine.

Assessing the performance of different DTI motion correction strategies in the presence of EPI distortion correction.

PubMed

Taylor, Paul A; Alhamud, A; van der Kouwe, Andre; Saleh, Muhammad G; Laughton, Barbara; Meintjes, Ernesta

2016-12-01

Diffusion tensor imaging (DTI) is susceptible to several artifacts due to eddy currents, echo planar imaging (EPI) distortion and subject motion. While several techniques correct for individual distortion effects, no optimal combination of DTI acquisition and processing has been determined. Here, the effects of several motion correction techniques are investigated while also correcting for EPI distortion: prospective correction, using navigation; retrospective correction, using two different popular packages (FSL and TORTOISE); and the combination of both methods. Data from a pediatric group that exhibited incidental motion in varying degrees are analyzed. Comparisons are carried while implementing eddy current and EPI distortion correction. DTI parameter distributions, white matter (WM) maps and probabilistic tractography are examined. The importance of prospective correction during data acquisition is demonstrated. In contrast to some previous studies, results also show that the inclusion of retrospective processing also improved ellipsoid fits and both the sensitivity and specificity of group tractographic results, even for navigated data. Matches with anatomical WM maps are highest throughout the brain for data that have been both navigated and processed using TORTOISE. The inclusion of both prospective and retrospective motion correction with EPI distortion correction is important for DTI analysis, particularly when studying subject populations that are prone to motion. Hum Brain Mapp 37:4405-4424, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Distortion improvement of capsule endoscope image

NASA Astrophysics Data System (ADS)

Mang, Ou-Yang; Huang, Shih-Wei; Chen, Yung-Lin; Lin, Chu-Hsun; Lin, Tai-Yung; Kuo, Yi-Ting

2007-02-01

Distortion exists in the present capsule endoscope image resulting from the confined space and the wide-angle requirement [8]. Based on the previous two lens works, the optimal design had obtained that the field of view was about 86 degrees , and MTF was about 18% at 100 lp/mm, but distortion would go to -26%. It's difficult to add another lens on the 7mm optical path between the dome and imaging lenses for improving distortion. In order to overcome this problem, we intend to design the optical dome as another optical lens. The original dome is transparent and has an equal thickness, namely without refracting light almost. Our objective in this paper is to design the inner curvature of the dome and associate two aspheric imaging lenses in front of the CMOS sensors to advance the distortion with maintaining field of view and MTF under the same capsule volume. Furthermore, the paper proposes the real object plane of intestine is nearly a curved surface rather than an ideal flat surface. Taking those reasons under consideration, we design three imaging lenses with curved object plane and obtain the field of view is about 86 degrees , MTF is about 26% at 100 lp/mm, and the distortion improve to -7.5%. Adding the dome lens is not only to enhance the image quality, but also to maintain the tiny volume requirement.

On the rational design of compressible flow ejectors

NASA Technical Reports Server (NTRS)

Ortwerth, P. J.

1979-01-01

A fluid mechanics review of chemical laser ejectors is presented. The characteristics of ejectors with single and multiple driver nozzles are discussed. Methods to compute an optimized performance map in which secondary Mach number and performance are computed versus mass ratio, to compute the flow distortion at each optimized condition, and to determine the thrust area for the design point to match diffuser impedence are examined.

Designing a composite correlation filter based on iterative optimization of training images for distortion invariant face recognition

NASA Astrophysics Data System (ADS)

Wang, Q.; Elbouz, M.; Alfalou, A.; Brosseau, C.

2017-06-01

We present a novel method to optimize the discrimination ability and noise robustness of composite filters. This method is based on the iterative preprocessing of training images which can extract boundary and detailed feature information of authentic training faces, thereby improving the peak-to-correlation energy (PCE) ratio of authentic faces and to be immune to intra-class variance and noise interference. By adding the training images directly, one can obtain a composite template with high discrimination ability and robustness for face recognition task. The proposed composite correlation filter does not involve any complicated mathematical analysis and computation which are often required in the design of correlation algorithms. Simulation tests have been conducted to check the effectiveness and feasibility of our proposal. Moreover, to assess robustness of composite filters using receiver operating characteristic (ROC) curves, we devise a new method to count the true positive and false positive rates for which the difference between PCE and threshold is involved.

Multicore-based 3D-DWT video encoder

NASA Astrophysics Data System (ADS)

Galiano, Vicente; López-Granado, Otoniel; Malumbres, Manuel P.; Migallón, Hector

2013-12-01

Three-dimensional wavelet transform (3D-DWT) encoders are good candidates for applications like professional video editing, video surveillance, multi-spectral satellite imaging, etc. where a frame must be reconstructed as quickly as possible. In this paper, we present a new 3D-DWT video encoder based on a fast run-length coding engine. Furthermore, we present several multicore optimizations to speed-up the 3D-DWT computation. An exhaustive evaluation of the proposed encoder (3D-GOP-RL) has been performed, and we have compared the evaluation results with other video encoders in terms of rate/distortion (R/D), coding/decoding delay, and memory consumption. Results show that the proposed encoder obtains good R/D results for high-resolution video sequences with nearly in-place computation using only the memory needed to store a group of pictures. After applying the multicore optimization strategies over the 3D DWT, the proposed encoder is able to compress a full high-definition video sequence in real-time.

Polarized atomic orbitals for self-consistent field electronic structure calculations

NASA Astrophysics Data System (ADS)

Lee, Michael S.; Head-Gordon, Martin

1997-12-01

We present a new self-consistent field approach which, given a large "secondary" basis set of atomic orbitals, variationally optimizes molecular orbitals in terms of a small "primary" basis set of distorted atomic orbitals, which are simultaneously optimized. If the primary basis is taken as a minimal basis, the resulting functions are termed polarized atomic orbitals (PAO's) because they are valence (or core) atomic orbitals which have distorted or polarized in an optimal way for their molecular environment. The PAO's derive their flexibility from the fact that they are formed from atom-centered linear-combinations of the larger set of secondary atomic orbitals. The variational conditions satisfied by PAO's are defined, and an iterative method for performing a PAO-SCF calculation is introduced. We compare the PAO-SCF approach against full SCF calculations for the energies, dipoles, and molecular geometries of various molecules. The PAO's are potentially useful for studying large systems that are currently intractable with larger than minimal basis sets, as well as offering potential interpretative benefits relative to calculations in extended basis sets.

Image simulation for automatic license plate recognition

NASA Astrophysics Data System (ADS)

Bala, Raja; Zhao, Yonghui; Burry, Aaron; Kozitsky, Vladimir; Fillion, Claude; Saunders, Craig; Rodríguez-Serrano, José

2012-01-01

Automatic license plate recognition (ALPR) is an important capability for traffic surveillance applications, including toll monitoring and detection of different types of traffic violations. ALPR is a multi-stage process comprising plate localization, character segmentation, optical character recognition (OCR), and identification of originating jurisdiction (i.e. state or province). Training of an ALPR system for a new jurisdiction typically involves gathering vast amounts of license plate images and associated ground truth data, followed by iterative tuning and optimization of the ALPR algorithms. The substantial time and effort required to train and optimize the ALPR system can result in excessive operational cost and overhead. In this paper we propose a framework to create an artificial set of license plate images for accelerated training and optimization of ALPR algorithms. The framework comprises two steps: the synthesis of license plate images according to the design and layout for a jurisdiction of interest; and the modeling of imaging transformations and distortions typically encountered in the image capture process. Distortion parameters are estimated by measurements of real plate images. The simulation methodology is successfully demonstrated for training of OCR.

In situ wavefront correction and its application to micromanipulation

NASA Astrophysics Data System (ADS)

Čižmár, Tomáš; Mazilu, Michael; Dholakia, Kishan

2010-06-01

In any optical system, distortions to a propagating wavefront reduce the spatial coherence of a light field, making it increasingly difficult to obtain the theoretical diffraction-limited spot size. Such aberrations are severely detrimental to optimal performance in imaging, nanosurgery, nanofabrication and micromanipulation, as well as other techniques within modern microscopy. We present a generic method based on complex modulation for true in situ wavefront correction that allows compensation of all aberrations along the entire optical train. The power of the method is demonstrated for the field of micromanipulation, which is very sensitive to wavefront distortions. We present direct trapping with optimally focused laser light carrying power of a fraction of a milliwatt as well as the first trapping through highly turbid and diffusive media. This opens up new perspectives for optical micromanipulation in colloidal and biological physics and may be useful for various forms of advanced imaging.

Response Distortion in Adolescents Who Smoke: a Pilot Study*

PubMed Central

Stein, L. A. R.; Colby, Suzanne M.; O'Leary, Tracy A.; Monti, Peter M.; Rohsenow, Damaris J.; Spirito, Anthony; Riggs, Suzanne; Barnett, Nancy P.

2010-01-01

A wide range of data are obtained with self-report. Information obtained from persons using substances is generally reliable and valid, however, many studies show that some proportion of self-reports regarding substance use are inaccurate. This study examines self-reported response distortion in adolescents who received a brief intervention to reduce their smoking. Findings indicate that age and ethnicity of respondent may influence reported response distortion. Factors that appear to influence under- and over-reporting include social desirability and fear of repercussion. Response distortion does not appear to affect rated usefulness of the intervention, nor does intervention type appear to influence whether respondents thought the researcher wanted them to report less use. Results point to the need for further research regarding adolescents and response distortion. PMID:12556133

Controlling for Response Bias in Self-Ratings of Personality: A Comparison of Impression Management Scales and the Overclaiming Technique.

PubMed

Müller, Sascha; Moshagen, Morten

2018-04-12

Self-serving response distortions pose a threat to the validity of personality scales. A common approach to deal with this issue is to rely on impression management (IM) scales. More recently, the overclaiming technique (OCT) has been proposed as an alternative and arguably superior measure of such biases. In this study (N = 162), we tested these approaches in the context of self- and other-ratings using the HEXACO personality inventory. To the extent that the OCT and IM scales can be considered valid measures of response distortions, they are expected to account for inflated self-ratings in particular for those personality dimensions that are prone to socially desirable responding. However, the results show that neither the OCT nor IM account for overly favorable self-ratings. The validity of IM as a measure of response biases was further scrutinized by a substantial correlation with other-rated honesty-humility. As such, this study questions the use of both the OCT and IM to assess self-serving response distortions.

Optimization of pressure probe placement and data analysis of engine-inlet distortion

NASA Astrophysics Data System (ADS)

Walter, S. F.

The purpose of this research is to examine methods by which quantification of inlet flow distortion may be improved upon. Specifically, this research investigates how data interpolation effects results, optimizing sampling locations of the flow, and determining the sensitivity related to how many sample locations there are. The main parameters that are indicative of a "good" design are total pressure recovery, mass flow capture, and distortion. This work focuses on the total pressure distortion, which describes the amount of non-uniformity that exists in the flow as it enters the engine. All engines must tolerate some level of distortion, however too much distortion can cause the engine to stall or the inlet to unstart. Flow distortion is measured at the interface between the inlet and the engine. To determine inlet flow distortion, a combination of computational and experimental pressure data is generated and then collapsed into an index that indicates the amount of distortion. Computational simulations generate continuous contour maps, but experimental data is discrete. Researchers require continuous contour maps to evaluate the overall distortion pattern. There is no guidance on how to best manipulate discrete points into a continuous pattern. Using one experimental, 320 probe data set and one, 320 point computational data set with three test runs each, this work compares the pressure results obtained using all 320 points of data from the original sets, both quantitatively and qualitatively, with results derived from selecting 40 grid point subsets and interpolating to 320 grid points. Each of the two, 40 point sets were interpolated to 320 grid points using four different interpolation methods in an attempt to establish the best method for interpolating small sets of data into an accurate, continuous contour map. Interpolation methods investigated are bilinear, spline, and Kriging in Cartesian space, as well as angular in polar space. Spline interpolation methods should be used as they result in the most accurate, precise, and visually correct predictions when compared results achieved from the full data sets. Researchers were interested if fewer than the recommended 40 probes could be used - especially when placed in areas of high interest - but still obtain equivalent or better results. For this investigation, the computational results from a two-dimensional inlet and experimental results of an axisymmetric inlet were used. To find the areas of interest, a uniform sampling of all possible locations was run through a Monte Carlo simulation with a varying number of probes. A probability density function of the resultant distortion index was plotted. Certain probes are required to come within the desired accuracy level of the distortion index based on the full data set. For the experimental results, all three test cases could be characterized with 20 probes. For the axisymmetric inlet, placing 40 probes in select locations could get the results for parameters of interest within less than 10% of the exact solution for almost all cases. For the two dimensional inlet, the results were not as clear. 80 probes were required to get within 10% of the exact solution for all run numbers, although this is largely due to the small value of the exact result. The sensitivity of each probe added to the experiment was analyzed. Instead of looking at the overall pattern established by optimizing probe placements, the focus is on varying the number of sampled probes from 20 to 40. The number of points falling within a 1% tolerance band of the exact solution were counted as good points. The results were normalized for each data set and a general sensitivity function was found to determine the sensitivity of the results. A linear regression was used to generalize the results for all data sets used in this work. However, they can be used by directly comparing the number of good points obtained with various numbers of probes as well. The sensitivity in the results is higher when fewer probes are used and gradually tapers off near 40 probes. There is a bigger gain in good points when the number of probes is increased from 20 to 21 probes than from 39 to 40 probes.

Blocking reduction of Landsat Thematic Mapper JPEG browse images using optimal PSNR estimated spectra adaptive postfiltering

NASA Technical Reports Server (NTRS)

Linares, Irving; Mersereau, Russell M.; Smith, Mark J. T.

1994-01-01

Two representative sample images of Band 4 of the Landsat Thematic Mapper are compressed with the JPEG algorithm at 8:1, 16:1 and 24:1 Compression Ratios for experimental browsing purposes. We then apply the Optimal PSNR Estimated Spectra Adaptive Postfiltering (ESAP) algorithm to reduce the DCT blocking distortion. ESAP reduces the blocking distortion while preserving most of the image's edge information by adaptively postfiltering the decoded image using the block's spectral information already obtainable from each block's DCT coefficients. The algorithm iteratively applied a one dimensional log-sigmoid weighting function to the separable interpolated local block estimated spectra of the decoded image until it converges to the optimal PSNR with respect to the original using a 2-D steepest ascent search. Convergence is obtained in a few iterations for integer parameters. The optimal logsig parameters are transmitted to the decoder as a negligible byte of overhead data. A unique maxima is guaranteed due to the 2-D asymptotic exponential overshoot shape of the surface generated by the algorithm. ESAP is based on a DFT analysis of the DCT basis functions. It is implemented with pixel-by-pixel spatially adaptive separable FIR postfilters. PSNR objective improvements between 0.4 to 0.8 dB are shown together with their corresponding optimal PSNR adaptive postfiltered images.

Capacity and optimal collusion attack channels for Gaussian fingerprinting games

NASA Astrophysics Data System (ADS)

Wang, Ying; Moulin, Pierre

2007-02-01

In content fingerprinting, the same media covertext - image, video, audio, or text - is distributed to many users. A fingerprint, a mark unique to each user, is embedded into each copy of the distributed covertext. In a collusion attack, two or more users may combine their copies in an attempt to "remove" their fingerprints and forge a pirated copy. To trace the forgery back to members of the coalition, we need fingerprinting codes that can reliably identify the fingerprints of those members. Researchers have been focusing on designing or testing fingerprints for Gaussian host signals and the mean square error (MSE) distortion under some classes of collusion attacks, in terms of the detector's error probability in detecting collusion members. For example, under the assumptions of Gaussian fingerprints and Gaussian attacks (the fingerprinted signals are averaged and then the result is passed through a Gaussian test channel), Moulin and Briassouli1 derived optimal strategies in a game-theoretic framework that uses the detector's error probability as the performance measure for a binary decision problem (whether a user participates in the collusion attack or not); Stone2 and Zhao et al. 3 studied average and other non-linear collusion attacks for Gaussian-like fingerprints; Wang et al. 4 stated that the average collusion attack is the most efficient one for orthogonal fingerprints; Kiyavash and Moulin 5 derived a mathematical proof of the optimality of the average collusion attack under some assumptions. In this paper, we also consider Gaussian cover signals, the MSE distortion, and memoryless collusion attacks. We do not make any assumption about the fingerprinting codes used other than an embedding distortion constraint. Also, our only assumptions about the attack channel are an expected distortion constraint, a memoryless constraint, and a fairness constraint. That is, the colluders are allowed to use any arbitrary nonlinear strategy subject to the above constraints. Under those constraints on the fingerprint embedder and the colluders, fingerprinting capacity is obtained as the solution of a mutual-information game involving probability density functions (pdf's) designed by the embedder and the colluders. We show that the optimal fingerprinting strategy is a Gaussian test channel where the fingerprinted signal is the sum of an attenuated version of the cover signal plus a Gaussian information-bearing noise, and the optimal collusion strategy is to average fingerprinted signals possessed by all the colluders and pass the averaged copy through a Gaussian test channel. The capacity result and the optimal strategies are the same for both the private and public games. In the former scenario, the original covertext is available to the decoder, while in the latter setup, the original covertext is available to the encoder but not to the decoder.

Design of microcamera for field curvature and distortion correction in monocentric multiscale foveated imaging system

NASA Astrophysics Data System (ADS)

Wu, Xiongxiong; Wang, Xiaorui; Zhang, Jianlei; Yuan, Ying; Chen, Xiaoxiang

2017-04-01

To realize large field of view (FOV) and high-resolution dynamic gaze of the moving target, this paper proposes the monocentric multiscale foveated (MMF) imaging system based on monocentric multiscale design and foveated imaging. First we present the MMF imaging system concept. Then we analyze large field curvature and distortion of the secondary image when the spherical intermediate image produced by the primary monocentric objective lens is relayed by the microcameras. Further a type of zoom endoscope objective lens is selected as the initial structure and optimized to minimize the field curvature and distortion with ZEMAX optical design software. The simulation results show that the maximum field curvature in full field of view is below 0.25 mm and the maximum distortion in full field of view is below 0.6%, which can meet the requirements of the microcamera in the proposed MMF imaging system. In addition, a simple doublet is used to design the foveated imaging system. Results of the microcamera together with the foveated imager compose the results of the whole MMF imaging system.

Intra-Operative Dosimetry in Prostate Brachytherapy

DTIC Science & Technology

2007-11-01

of the focal spot. 2.1. Model for Reconstruction Space Transformation As illustrated in Figure 8, let A & B ( with reference frames FA & FB) be the two...simplex optimization method in MATLAB 7.0 with the search space being defined by the distortion modes from PCA. A linear combination of the modes would...arm is tracked with an X-ray fiducial system called FTRAC that is composed of optimally selected polynomial

Depth Perception In Remote Stereoscopic Viewing Systems

NASA Technical Reports Server (NTRS)

Diner, Daniel B.; Von Sydow, Marika

1989-01-01

Report describes theoretical and experimental studies of perception of depth by human operators through stereoscopic video systems. Purpose of such studies to optimize dual-camera configurations used to view workspaces of remote manipulators at distances of 1 to 3 m from cameras. According to analysis, static stereoscopic depth distortion decreased, without decreasing stereoscopitc depth resolution, by increasing camera-to-object and intercamera distances and camera focal length. Further predicts dynamic stereoscopic depth distortion reduced by rotating cameras around center of circle passing through point of convergence of viewing axes and first nodal points of two camera lenses.

Dynamic properties of the adaptive optics system depending on the temporary transformations of mirror control voltages

NASA Astrophysics Data System (ADS)

Lavrinov, V. V.; Lavrinova, L. N.

2017-11-01

The statistically optimal control algorithm for the correcting mirror is formed by constructing a prediction of distortions of the optical signal and improves the time resolution of the adaptive optics system. The prediction of distortions is based on an analysis of the dynamics of changes in the optical inhomogeneities of the turbulent atmosphere or the evolution of phase fluctuations at the input aperture of the adaptive system. Dynamic properties of the system are manifested during the temporary transformation of the stresses controlling the mirror and are determined by the dynamic characteristics of the flexible mirror.

Numerical simulation of transonic compressor under circumferential inlet distortion and rotor/stator interference using harmonic balance method

NASA Astrophysics Data System (ADS)

Wang, Ziwei; Jiang, Xiong; Chen, Ti; Hao, Yan; Qiu, Min

2018-05-01

Simulating the unsteady flow of compressor under circumferential inlet distortion and rotor/stator interference would need full-annulus grid with a dual time method. This process is time consuming and needs a large amount of computational resources. Harmonic balance method simulates the unsteady flow in compressor on single passage grid with a series of steady simulations. This will largely increase the computational efficiency in comparison with the dual time method. However, most simulations with harmonic balance method are conducted on the flow under either circumferential inlet distortion or rotor/stator interference. Based on an in-house CFD code, the harmonic balance method is applied in the simulation of flow in the NASA Stage 35 under both circumferential inlet distortion and rotor/stator interference. As the unsteady flow is influenced by two different unsteady disturbances, it leads to the computational instability. The instability can be avoided by coupling the harmonic balance method with an optimizing algorithm. The computational result of harmonic balance method is compared with the result of full-annulus simulation. It denotes that, the harmonic balance method simulates the flow under circumferential inlet distortion and rotor/stator interference as precise as the full-annulus simulation with a speed-up of about 8 times.

Personalized Progressive Addition Lenses: Correlation between Performance and Design.

PubMed

Forkel, Johanne; Reiniger, Jenny Lorén; Muschielok, Adam; Welk, Andrea; Seidemann, Anne; Baumbach, Peter

2017-02-01

A continuous set of personalized designs (design space) for progressive addition lenses (PALs) is investigated. The main goals are (1) to study how the subjects' perception of a personalized design depends on its position in the design space and (2) to compare the performance of personalized PALs to a conventional PAL with a fixed design. In a double-blind study, 51 subjects compared Rodenstock Impression FreeSign 3, which is a family of PALs with a continuously controllable personalized design, and Rodenstock Progressiv Life Free, which is a conventional PAL with a single fixed design. The positions and sizes of viewing zones and the softness of gradients of mean power and astigmatism of personalized lenses were customized to individual viewing preferences. These designs were represented as points in a design space comprising a continuum of PAL designs. Subjective ratings and experimental measurements were used to study viewing zone widths, blur gradient smoothness, amount of distortion, the feeling of safety during motion, and overall wearing comfort. (1) Far viewing zone width (experiments and ratings), near viewing zone width (experiments), blur gradient smoothness, and the amount of distortion (ratings) were significantly dependent on the position of the personalized lens design in the design space. This was consistent with the structure of the design space. (2) 82% of the subjects chose personalized lenses as their favorite. Most subjects reported higher wearing comfort and tolerability with personalized lenses than with conventional lenses. The designs of the tested personalized lenses were perceived by the subjects as intended. This is a prerequisite to the successful customization of PALs to individual wearing preferences. Possible reasons for the preference of the tested personalized lenses are the optimization with respect to individual wearing conditions and the personalization.

Experimental orofacial pain and sensory deprivation lead to perceptual distortion of the face in healthy volunteers.

PubMed

Dagsdóttir, Lilja Kristín; Skyt, Ina; Vase, Lene; Baad-Hansen, Lene; Castrillon, Eduardo; Svensson, Peter

2015-09-01

Patients suffering from persistent orofacial pain may sporadically report that the painful area feels "swollen" or "differently," a phenomenon that may be conceptualized as a perceptual distortion because there are no clinical signs of swelling present. Our aim was to investigate whether standardized experimental pain and sensory deprivation of specific orofacial test sites would lead to changes in the size perception of these face areas. Twenty-four healthy participants received either 0.2 mL hypertonic saline (HS) or local anesthetics (LA) into six regions (buccal, mental, lingual, masseter muscle, infraorbital and auriculotemporal nerve regions). Participants estimated the perceived size changes in percentage (0 % = no change, -100 % = half the size or +100 % = double the size), and somatosensory function was checked with tactile stimuli. The pain intensity was rated on a 0-10 Verbal Numerical Rating Scale (VNRS), and sets of psychological questionnaires were completed. HS and LA were associated with significant self-reported perceptual distortions as indicated by consistent increases in perceived size of the adjacent face areas (P ≤ 0.050). Perceptual distortion was most pronounced in the buccal region, and the smallest increase was observed in the auriculotemporal region. HS was associated with moderate levels of pain VNRS = 7.3 ± 0.6. Weak correlations were found between HS-evoked perceptual distortion and level of dissociation in two regions (P < 0.050). Experimental pain and transient sensory deprivation evoked perceptual distortions in all face regions and overall demonstrated the importance of afferent inputs for the perception of the face. We propose that perceptual distortion may be an important phenomenon to consider in persistent orofacial pain conditions.

A 0.18 μm biosensor front-end based on 1/f noise, distortion cancelation and chopper stabilization techniques.

PubMed

Balasubramanian, Viswanathan; Ruedi, Pierre-Francois; Temiz, Yuksel; Ferretti, Anna; Guiducci, Carlotta; Enz

2013-10-01

This paper presents a novel sensor front-end circuit that addresses the issues of 1/f noise and distortion in a unique way by using canceling techniques. The proposed front-end is a fully differential transimpedance amplifier (TIA) targeted for current mode electrochemical biosensing applications. In this paper, we discuss the architecture of this canceling based front-end and the optimization methods followed for achieving low noise, low distortion performance at minimum current consumption are presented. To validate the employed canceling based front-end, it has been realized in a 0.18 μm CMOS process and the characterization results are presented. The front-end has also been tested as part of a complete wireless sensing system and the cyclic voltammetry (CV) test results from electrochemical sensors are provided. Overall current consumption in the front-end is 50 μA while operating on a 1.8 V supply.

Expression-dependent susceptibility to face distortions in processing of facial expressions of emotion.

PubMed

Guo, Kun; Soornack, Yoshi; Settle, Rebecca

2018-03-05

Our capability of recognizing facial expressions of emotion under different viewing conditions implies the existence of an invariant expression representation. As natural visual signals are often distorted and our perceptual strategy changes with external noise level, it is essential to understand how expression perception is susceptible to face distortion and whether the same facial cues are used to process high- and low-quality face images. We systematically manipulated face image resolution (experiment 1) and blur (experiment 2), and measured participants' expression categorization accuracy, perceived expression intensity and associated gaze patterns. Our analysis revealed a reasonable tolerance to face distortion in expression perception. Reducing image resolution up to 48 × 64 pixels or increasing image blur up to 15 cycles/image had little impact on expression assessment and associated gaze behaviour. Further distortion led to decreased expression categorization accuracy and intensity rating, increased reaction time and fixation duration, and stronger central fixation bias which was not driven by distortion-induced changes in local image saliency. Interestingly, the observed distortion effects were expression-dependent with less deterioration impact on happy and surprise expressions, suggesting this distortion-invariant facial expression perception might be achieved through the categorical model involving a non-linear configural combination of local facial features. Copyright © 2018 Elsevier Ltd. All rights reserved.

Techniques for drying thick southern pine veneer

Treesearch

Peter Koch

1964-01-01

Thick veneers cut from southern pine are relatively easy to dry, but they are not easy to dry free of distortion. The research reported here was undertaken to compare five drying systems. Factors evaluated included rate of water loss, degree of distortion, and the effect on strength. Effects on gluability were also briefly studied.

Optimization of robotic welding procedures for maintenance repair of hydraulic turbines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lamarche, L.; Galopin, M.; Simoneau, R.

1996-12-31

A six axes super-compact robot is used for field repair of cavitation damages found on the discharge ring of hydraulic turbines. Optimization of overlay welding procedures to minimize surface distortion and reduce tearing forces on anchors in concrete, were studied through experimentation and FEM modelling. Planned experimentation has been used to develop optimum pulsed GMAW schedules of stainless steel overlays in 2G position. Best welding sequence was resolved through over lay welding of free plates. Each overlay consisted in one or two layers which were welded in the longitudinal and/or transverse direction of the rectangular plate. A bidirectional welding mode,more » a longitudinal layer followed by a transverse layer position and no cooling between the two layers, were found to be most effective in reducing distortion. The optimized 2G welding procedure was applied to a simulated field repair. Plate was anchored on a massive iron bracket with a set of instrumented bolts, to understand how normal tearing forces in anchors evolve. Preliminary results on FEM modelling of lateral force on anchors indicate good correlation with experiments, for an elementary design.« less

An optimization-based approach for high-order accurate discretization of conservation laws with discontinuous solutions

NASA Astrophysics Data System (ADS)

Zahr, M. J.; Persson, P.-O.

2018-07-01

This work introduces a novel discontinuity-tracking framework for resolving discontinuous solutions of conservation laws with high-order numerical discretizations that support inter-element solution discontinuities, such as discontinuous Galerkin or finite volume methods. The proposed method aims to align inter-element boundaries with discontinuities in the solution by deforming the computational mesh. A discontinuity-aligned mesh ensures the discontinuity is represented through inter-element jumps while smooth basis functions interior to elements are only used to approximate smooth regions of the solution, thereby avoiding Gibbs' phenomena that create well-known stability issues. Therefore, very coarse high-order discretizations accurately resolve the piecewise smooth solution throughout the domain, provided the discontinuity is tracked. Central to the proposed discontinuity-tracking framework is a discrete PDE-constrained optimization formulation that simultaneously aligns the computational mesh with discontinuities in the solution and solves the discretized conservation law on this mesh. The optimization objective is taken as a combination of the deviation of the finite-dimensional solution from its element-wise average and a mesh distortion metric to simultaneously penalize Gibbs' phenomena and distorted meshes. It will be shown that our objective function satisfies two critical properties that are required for this discontinuity-tracking framework to be practical: (1) possesses a local minima at a discontinuity-aligned mesh and (2) decreases monotonically to this minimum in a neighborhood of radius approximately h / 2, whereas other popular discontinuity indicators fail to satisfy the latter. Another important contribution of this work is the observation that traditional reduced space PDE-constrained optimization solvers that repeatedly solve the conservation law at various mesh configurations are not viable in this context since severe overshoot and undershoot in the solution, i.e., Gibbs' phenomena, may make it impossible to solve the discrete conservation law on non-aligned meshes. Therefore, we advocate a gradient-based, full space solver where the mesh and conservation law solution converge to their optimal values simultaneously and therefore never require the solution of the discrete conservation law on a non-aligned mesh. The merit of the proposed method is demonstrated on a number of one- and two-dimensional model problems including the L2 projection of discontinuous functions, Burgers' equation with a discontinuous source term, transonic flow through a nozzle, and supersonic flow around a bluff body. We demonstrate optimal O (h p + 1) convergence rates in the L1 norm for up to polynomial order p = 6 and show that accurate solutions can be obtained on extremely coarse meshes.

Low-cost, high-resolution, single-structure array telescopes for imaging of low-earth-orbit satellites

NASA Technical Reports Server (NTRS)

Massie, N. A.; Oster, Yale; Poe, Greg; Seppala, Lynn; Shao, Mike

1992-01-01

Telescopes that are designed for the unconventional imaging of near-earth satellites must follow unique design rules. The costs must be reduced substantially over those of the conventional telescope designs, and the design must accommodate a technique to circumvent atmospheric distortion of the image. Apertures of 12 m and more along with altitude-altitude mounts that provide high tracking rates are required. A novel design for such a telescope, optimized for speckle imaging, has been generated. Its mount closely resembles a radar mount, and it does not use the conventional dome. Costs for this design are projected to be considerably lower than those for the conventional designs. Results of a design study are presented with details of the electro-optical and optical designs.

MR-based field-of-view extension in MR/PET: B0 homogenization using gradient enhancement (HUGE).

PubMed

Blumhagen, Jan O; Ladebeck, Ralf; Fenchel, Matthias; Scheffler, Klaus

2013-10-01

In whole-body MR/PET, the human attenuation correction can be based on the MR data. However, an MR-based field-of-view (FoV) is limited due to physical restrictions such as B0 inhomogeneities and gradient nonlinearities. Therefore, for large patients, the MR image and the attenuation map might be truncated and the attenuation correction might be biased. The aim of this work is to explore extending the MR FoV through B0 homogenization using gradient enhancement in which an optimal readout gradient field is determined to locally compensate B0 inhomogeneities and gradient nonlinearities. A spin-echo-based sequence was developed that computes an optimal gradient for certain regions of interest, for example, the patient's arms. A significant distortion reduction was achieved outside the normal MR-based FoV. This FoV extension was achieved without any hardware modifications. In-plane distortions in a transaxially extended FoV of up to 600 mm were analyzed in phantom studies. In vivo measurements of the patient's arms lying outside the normal specified FoV were compared with and without the use of B0 homogenization using gradient enhancement. In summary, we designed a sequence that provides data for reducing the image distortions due to B0 inhomogeneities and gradient nonlinearities and used the data to extend the MR FoV. Copyright © 2011 Wiley Periodicals, Inc.

Photometric correction for an optical CCD-based system based on the sparsity of an eight-neighborhood gray gradient.

PubMed

Zhang, Yuzhong; Zhang, Yan

2016-07-01

In an optical measurement and analysis system based on a CCD, due to the existence of optical vignetting and natural vignetting, photometric distortion, in which the intensity falls off away from the image center, affects the subsequent processing and measuring precision severely. To deal with this problem, an easy and straightforward method used for photometric distortion correction is presented in this paper. This method introduces a simple polynomial fitting model of the photometric distortion function and employs a particle swarm optimization algorithm to get these model parameters by means of a minimizing eight-neighborhood gray gradient. Compared with conventional calibration methods, this method can obtain the profile information of photometric distortion from only a single common image captured by the optical CCD-based system, with no need for a uniform luminance area source used as a standard reference source and relevant optical and geometric parameters in advance. To illustrate the applicability of this method, numerical simulations and photometric distortions with different lens parameters are evaluated using this method in this paper. Moreover, the application example of temperature field correction for casting billets also demonstrates the effectiveness of this method. The experimental results show that the proposed method is able to achieve the maximum absolute error for vignetting estimation of 0.0765 and the relative error for vignetting estimation from different background images of 3.86%.

Plenoptic camera wavefront sensing with extended sources

NASA Astrophysics Data System (ADS)

Jiang, Pengzhi; Xu, Jieping; Liang, Yonghui; Mao, Hongjun

2016-09-01

The wavefront sensor is used in adaptive optics to detect the atmospheric distortion, which feeds back to the deformable mirror to compensate for this distortion. Different from the Shack-Hartmann sensor that has been widely used with point sources, the plenoptic camera wavefront sensor has been proposed as an alternative wavefront sensor adequate for extended objects in recent years. In this paper, the plenoptic camera wavefront sensing with extended sources is discussed systematically. Simulations are performed to investigate the wavefront measurement error and the closed-loop performance of the plenoptic sensor. The results show that there are an optimal lenslet size and an optimal number of pixels to make the best performance. The RMS of the resulting corrected wavefront in closed-loop adaptive optics system is less than 108 nm (0.2λ) when D/r0 ≤ 10 and the magnitude M ≤ 5. Our investigation indicates that the plenoptic sensor is efficient to operate on extended sources in the closed-loop adaptive optics system.

Feature-based pairwise retinal image registration by radial distortion correction

NASA Astrophysics Data System (ADS)

Lee, Sangyeol; Abràmoff, Michael D.; Reinhardt, Joseph M.

2007-03-01

Fundus camera imaging is widely used to document disorders such as diabetic retinopathy and macular degeneration. Multiple retinal images can be combined together through a procedure known as mosaicing to form an image with a larger field of view. Mosaicing typically requires multiple pairwise registrations of partially overlapped images. We describe a new method for pairwise retinal image registration. The proposed method is unique in that the radial distortion due to image acquisition is corrected prior to the geometric transformation. Vessel lines are detected using the Hessian operator and are used as input features to the registration. Since the overlapping region is typically small in a retinal image pair, only a few correspondences are available, thus limiting the applicable model to an afine transform at best. To recover the distortion due to curved-surface of retina and lens optics, a combined approach of an afine model with a radial distortion correction is proposed. The parameters of the image acquisition and radial distortion models are estimated during an optimization step that uses Powell's method driven by the vessel line distance. Experimental results using 20 pairs of green channel images acquired from three subjects with a fundus camera confirmed that the afine model with distortion correction could register retinal image pairs to within 1.88+/-0.35 pixels accuracy (mean +/- standard deviation) assessed by vessel line error, which is 17% better than the afine-only approach. Because the proposed method needs only two correspondences, it can be applied to obtain good registration accuracy even in the case of small overlap between retinal image pairs.

Real-time lens distortion correction: speed, accuracy and efficiency

NASA Astrophysics Data System (ADS)

Bax, Michael R.; Shahidi, Ramin

2014-11-01

Optical lens systems suffer from nonlinear geometrical distortion. Optical imaging applications such as image-enhanced endoscopy and image-based bronchoscope tracking require correction of this distortion for accurate localization, tracking, registration, and measurement of image features. Real-time capability is desirable for interactive systems and live video. The use of a texture-mapping graphics accelerator, which is standard hardware on current motherboard chipsets and add-in video graphics cards, to perform distortion correction is proposed. Mesh generation for image tessellation, an error analysis, and performance results are presented. It is shown that distortion correction using commodity graphics hardware is substantially faster than using the main processor and can be performed at video frame rates (faster than 30 frames per second), and that the polar-based method of mesh generation proposed here is more accurate than a conventional grid-based approach. Using graphics hardware to perform distortion correction is not only fast and accurate but also efficient as it frees the main processor for other tasks, which is an important issue in some real-time applications.

New well pattern optimization methodology in mature low-permeability anisotropic reservoirs

NASA Astrophysics Data System (ADS)

Qin, Jiazheng; Liu, Yuetian; Feng, Yueli; Ding, Yao; Liu, Liu; He, Youwei

2018-02-01

In China, lots of well patterns were designed before people knew the principal permeability direction in low-permeability anisotropic reservoirs. After several years’ production, it turns out that well line direction is unparallel with principal permeability direction. However, traditional well location optimization methods (in terms of the objective function such as net present value and/or ultimate recovery) are inapplicable, since wells are not free to move around in a mature oilfield. Thus, the well pattern optimization (WPO) of mature low-permeability anisotropic reservoirs is a significant but challenging task, since the original well pattern (WP) will be distorted and reconstructed due to permeability anisotropy. In this paper, we investigate the destruction and reconstruction of WP when the principal permeability direction and well line direction are unparallel. A new methodology was developed to quantitatively optimize the well locations of mature large-scale WP through a WPO algorithm on the basis of coordinate transformation (i.e. rotating and stretching). For a mature oilfield, large-scale WP has settled, so it is not economically viable to carry out further infill drilling. This paper circumvents this difficulty by combining the WPO algorithm with the well status (open or shut-in) and schedule adjustment. Finally, this methodology is applied to an example. Cumulative oil production rates of the optimized WP are higher, and water-cut is lower, which highlights the potential of the WPO methodology application in mature large-scale field development projects.

Effects of Visual Feedback Distortion on Gait Adaptation: Comparison of Implicit Visual Distortion Versus Conscious Modulation on Retention of Motor Learning.

PubMed

Kim, Seung-Jae; Ogilvie, Mitchell; Shimabukuro, Nathan; Stewart, Trevor; Shin, Joon-Ho

2015-09-01

Visual feedback can be used during gait rehabilitation to improve the efficacy of training. We presented a paradigm called visual feedback distortion; the visual representation of step length was manipulated during treadmill walking. Our prior work demonstrated that an implicit distortion of visual feedback of step length entails an unintentional adaptive process in the subjects' spatial gait pattern. Here, we investigated whether the implicit visual feedback distortion, versus conscious correction, promotes efficient locomotor adaptation that relates to greater retention of a task. Thirteen healthy subjects were studied under two conditions: (1) we implicitly distorted the visual representation of their gait symmetry over 14 min, and (2) with help of visual feedback, subjects were told to walk on the treadmill with the intent of attaining the gait asymmetry observed during the first implicit trial. After adaptation, the visual feedback was removed while subjects continued walking normally. Over this 6-min period, retention of preserved asymmetric pattern was assessed. We found that there was a greater retention rate during the implicit distortion trial than that of the visually guided conscious modulation trial. This study highlights the important role of implicit learning in the context of gait rehabilitation by demonstrating that training with implicit visual feedback distortion may produce longer lasting effects. This suggests that using visual feedback distortion could improve the effectiveness of treadmill rehabilitation processes by influencing the retention of motor skills.

Landsat real-time processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, E.L.

A novel method for performing real-time acquisition and processing Landsat/EROS data covers all aspects including radiometric and geometric corrections of multispectral scanner or return-beam vidicon inputs, image enhancement, statistical analysis, feature extraction, and classification. Radiometric transformations include bias/gain adjustment, noise suppression, calibration, scan angle compensation, and illumination compensation, including topography and atmospheric effects. Correction or compensation for geometric distortion includes sensor-related distortions, such as centering, skew, size, scan nonlinearity, radial symmetry, and tangential symmetry. Also included are object image-related distortions such as aspect angle (altitude), scale distortion (altitude), terrain relief, and earth curvature. Ephemeral corrections are also applied to compensatemore » for satellite forward movement, earth rotation, altitude variations, satellite vibration, and mirror scan velocity. Image enhancement includes high-pass, low-pass, and Laplacian mask filtering and data restoration for intermittent losses. Resource classification is provided by statistical analysis including histograms, correlational analysis, matrix manipulations, and determination of spectral responses. Feature extraction includes spatial frequency analysis, which is used in parallel discriminant functions in each array processor for rapid determination. The technique uses integrated parallel array processors that decimate the tasks concurrently under supervision of a control processor. The operator-machine interface is optimized for programming ease and graphics image windowing.« less

Theoretical Investigation of Calculating Temperatures in the Combining Zone of Cu/Fe Composite Plate Jointed by Explosive Welding

NASA Astrophysics Data System (ADS)

Qu, Y. D.; Zhang, W. J.; Kong, X. Q.; Zhao, X.

2016-03-01

The heat-transfer behavior of the interface of Flyer plate (or Base Plate) has great influence on the microcosmic structures, stress distributions, and interface distortion of the welded interface of composite plates by explosive welding. In this paper, the temperature distributions in the combing zone are studied for the case of Cu/Fe composite plate jointed by explosive welding near the lower limit of explosive welding. The results show that Flyer plate (Cu plate) and Base Plate (Fe plate) firstly almost have the same melting rate in the explosive welding process. Then, the melting rate of Cu plate becomes higher than that of Fe plate. Finally, the melt thicknesses of Cu plate and Fe plate trend to be different constants, respectively. Meanwhile, the melting layer of Cu plate is thicker than that of Fe plate. The research could supply some theoretical foundations for calculating the temperature distribution and optimizing the explosive welding parameters of Cu/Fe composite plate to some extent.

Mothers' Depressive State "Distorts" the Ratings of Depression They Give for Their Sons with an Autism Spectrum Disorder

ERIC Educational Resources Information Center

Bitsika, Vicki; Sharpley, Christopher F.

2016-01-01

Depression is highly prevalent in children who have an Autism Spectrum Disorder (ASD), potentially confounding accurate diagnosis and treatment planning. Although information about the depressive status of a child is often collected from parents, there is evidence of distortion in parental assessments of their offspring's depression. This…

An optimized, universal hardware-based adaptive correlation receiver architecture

NASA Astrophysics Data System (ADS)

Zhu, Zaidi; Suarez, Hernan; Zhang, Yan; Wang, Shang

2014-05-01

The traditional radar RF transceivers, similar to communication transceivers, have the basic elements such as baseband waveform processing, IF/RF up-down conversion, transmitter power circuits, receiver front-ends, and antennas, which are shown in the upper half of Figure 1. For modern radars with diversified and sophisticated waveforms, we can frequently observe that the transceiver behaviors, especially nonlinear behaviors, are depending on the waveform amplitudes, frequency contents and instantaneous phases. Usually, it is a troublesome process to tune an RF transceiver to optimum when different waveforms are used. Another issue arises from the interference caused by the waveforms - for example, the range side-lobe (RSL) caused by the waveforms, once the signals pass through the entire transceiver chain, may be further increased due to distortions. This study is inspired by the two existing solutions from commercial communication industry, digital pre-distortion (DPD) and adaptive channel estimation and Interference Mitigation (AIM), while combining these technologies into a single chip or board that can be inserted into the existing transceiver system. This device is then named RF Transceiver Optimizer (RTO). The lower half of Figure 1 shows the basic element of RTO. With RTO, the digital baseband processing does not need to take into account the transceiver performance with diversified waveforms, such as the transmitter efficiency and chain distortion (and the intermodulation products caused by distortions). Neither does it need to concern the pulse compression (or correlation receiver) process and the related mitigation. The focus is simply the information about the ground truth carried by the main peak of correlation receiver outputs. RTO can be considered as an extension of the existing calibration process, while it has the benefits of automatic, adaptive and universal. Currently, the main techniques to implement the RTO are the digital pre- or -post distortions (DPD), and the main technique to implement the AIM is the Adaptive Pulse Compression (APC). The basic algorithms and experiments with DPD will be introduced which is also the focus of this paper. The discussion of AIM algorithms will be presented in other papers, while the initial implementation of AIM and correlation receiver in FPGA devices will also be introduced in this paper.

A Robust Design Methodology for Optimal Microscale Secondary Flow Control in Compact Inlet Diffusers

NASA Technical Reports Server (NTRS)

Anderson, Bernhard H.; Keller, Dennis J.

2001-01-01

It is the purpose of this study to develop an economical Robust design methodology for microscale secondary flow control in compact inlet diffusers. To illustrate the potential of economical Robust Design methodology, two different mission strategies were considered for the subject inlet, namely Maximum Performance and Maximum HCF Life Expectancy. The Maximum Performance mission maximized total pressure recovery while the Maximum HCF Life Expectancy mission minimized the mean of the first five Fourier harmonic amplitudes, i.e., 'collectively' reduced all the harmonic 1/2 amplitudes of engine face distortion. Each of the mission strategies was subject to a low engine face distortion constraint, i.e., DC60<0.10, which is a level acceptable for commercial engines. For each of these missions strategies, an 'Optimal Robust' (open loop control) and an 'Optimal Adaptive' (closed loop control) installation was designed over a twenty degree angle-of-incidence range. The Optimal Robust installation used economical Robust Design methodology to arrive at a single design which operated over the entire angle-of-incident range (open loop control). The Optimal Adaptive installation optimized all the design parameters at each angle-of-incidence. Thus, the Optimal Adaptive installation would require a closed loop control system to sense a proper signal for each effector and modify that effector device, whether mechanical or fluidic, for optimal inlet performance. In general, the performance differences between the Optimal Adaptive and Optimal Robust installation designs were found to be marginal. This suggests, however, that Optimal Robust open loop installation designs can be very competitive with Optimal Adaptive close loop designs. Secondary flow control in inlets is inherently robust, provided it is optimally designed. Therefore, the new methodology presented in this paper, combined array 'Lower Order' approach to Robust DOE, offers the aerodynamicist a very viable and economical way of exploring the concept of Robust inlet design, where the mission variables are brought directly into the inlet design process and insensitivity or robustness to the mission variables becomes a design objective.

Pile-up correction algorithm based on successive integration for high count rate medical imaging and radiation spectroscopy

NASA Astrophysics Data System (ADS)

Mohammadian-Behbahani, Mohammad-Reza; Saramad, Shahyar

2018-07-01

In high count rate radiation spectroscopy and imaging, detector output pulses tend to pile up due to high interaction rate of the particles with the detector. Pile-up effects can lead to a severe distortion of the energy and timing information. Pile-up events are conventionally prevented or rejected by both analog and digital electronics. However, for decreasing the exposure times in medical imaging applications, it is important to maintain the pulses and extract their true information by pile-up correction methods. The single-event reconstruction method is a relatively new model-based approach for recovering the pulses one-by-one using a fitting procedure, for which a fast fitting algorithm is a prerequisite. This article proposes a fast non-iterative algorithm based on successive integration which fits the bi-exponential model to experimental data. After optimizing the method, the energy spectra, energy resolution and peak-to-peak count ratios are calculated for different counting rates using the proposed algorithm as well as the rejection method for comparison. The obtained results prove the effectiveness of the proposed method as a pile-up processing scheme designed for spectroscopic and medical radiation detection applications.

Modeling multiple time series annotations as noisy distortions of the ground truth: An Expectation-Maximization approach.

PubMed

Gupta, Rahul; Audhkhasi, Kartik; Jacokes, Zach; Rozga, Agata; Narayanan, Shrikanth

2018-01-01

Studies of time-continuous human behavioral phenomena often rely on ratings from multiple annotators. Since the ground truth of the target construct is often latent, the standard practice is to use ad-hoc metrics (such as averaging annotator ratings). Despite being easy to compute, such metrics may not provide accurate representations of the underlying construct. In this paper, we present a novel method for modeling multiple time series annotations over a continuous variable that computes the ground truth by modeling annotator specific distortions. We condition the ground truth on a set of features extracted from the data and further assume that the annotators provide their ratings as modification of the ground truth, with each annotator having specific distortion tendencies. We train the model using an Expectation-Maximization based algorithm and evaluate it on a study involving natural interaction between a child and a psychologist, to predict confidence ratings of the children's smiles. We compare and analyze the model against two baselines where: (i) the ground truth in considered to be framewise mean of ratings from various annotators and, (ii) each annotator is assumed to bear a distinct time delay in annotation and their annotations are aligned before computing the framewise mean.

Cooling rate dependence of structural order in Ni 62 Nb 38 metallic glass

DOE PAGES

Wen, Tongqi; Sun, Yang; Ye, Beilin; ...

2018-01-31

In this article, molecular dynamics (MD) simulations are performed to study the structure of Ni 62Nb 38 bulk metallic glass at the atomistic level. Structural analysis based on the cluster alignment method is carried out and a new Ni-centered distorted-icosahedra (DISICO) motif is excavated. We show that the short-range order and medium-range order in the glass are enhanced with lower cooling rate. Almost 50% of the clusters around the Ni atoms in the well-annealed Ni 62Nb 38 glass sample from our MD simulations can be classified as DISICO. It is revealed that the structural distortion with respect to the perfectmore » icosahedra is driven by chemical ordering in the distorted region of the DISICO motif. The relationship between the structure, energy, and dynamics in this glass-forming alloy during the cooling and annealing processes is also established.« less

Cooling rate dependence of structural order in Ni 62 Nb 38 metallic glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wen, Tongqi; Sun, Yang; Ye, Beilin

In this article, molecular dynamics (MD) simulations are performed to study the structure of Ni 62Nb 38 bulk metallic glass at the atomistic level. Structural analysis based on the cluster alignment method is carried out and a new Ni-centered distorted-icosahedra (DISICO) motif is excavated. We show that the short-range order and medium-range order in the glass are enhanced with lower cooling rate. Almost 50% of the clusters around the Ni atoms in the well-annealed Ni 62Nb 38 glass sample from our MD simulations can be classified as DISICO. It is revealed that the structural distortion with respect to the perfectmore » icosahedra is driven by chemical ordering in the distorted region of the DISICO motif. The relationship between the structure, energy, and dynamics in this glass-forming alloy during the cooling and annealing processes is also established.« less

Cooling rate dependence of structural order in Ni62Nb38 metallic glass

NASA Astrophysics Data System (ADS)

Wen, Tongqi; Sun, Yang; Ye, Beilin; Tang, Ling; Yang, Zejin; Ho, Kai-Ming; Wang, Cai-Zhuang; Wang, Nan

2018-01-01

Molecular dynamics (MD) simulations are performed to study the structure of Ni62Nb38 bulk metallic glass at the atomistic level. Structural analysis based on the cluster alignment method is carried out and a new Ni-centered distorted-icosahedra (DISICO) motif is excavated. We show that the short-range order and medium-range order in the glass are enhanced with lower cooling rate. Almost 50% of the clusters around the Ni atoms in the well-annealed Ni62Nb38 glass sample from our MD simulations can be classified as DISICO. It is revealed that the structural distortion with respect to the perfect icosahedra is driven by chemical ordering in the distorted region of the DISICO motif. The relationship between the structure, energy, and dynamics in this glass-forming alloy during the cooling and annealing processes is also established.

Flight Test Validation of Optimal Input Design and Comparison to Conventional Inputs

NASA Technical Reports Server (NTRS)

Morelli, Eugene A.

1997-01-01

A technique for designing optimal inputs for aerodynamic parameter estimation was flight tested on the F-18 High Angle of Attack Research Vehicle (HARV). Model parameter accuracies calculated from flight test data were compared on an equal basis for optimal input designs and conventional inputs at the same flight condition. In spite of errors in the a priori input design models and distortions of the input form by the feedback control system, the optimal inputs increased estimated parameter accuracies compared to conventional 3-2-1-1 and doublet inputs. In addition, the tests using optimal input designs demonstrated enhanced design flexibility, allowing the optimal input design technique to use a larger input amplitude to achieve further increases in estimated parameter accuracy without departing from the desired flight test condition. This work validated the analysis used to develop the optimal input designs, and demonstrated the feasibility and practical utility of the optimal input design technique.

Adaptive nonlinear Volterra equalizer for mitigation of chirp-induced distortions in cost effective IMDD OFDM systems.

PubMed

André, Nuno Sequeira; Habel, Kai; Louchet, Hadrien; Richter, André

2013-11-04

We report experimental validations of an adaptive 2nd order Volterra equalization scheme for cost effective IMDD OFDM systems. This equalization scheme was applied to both uplink and downlink transmission. Downlink settings were optimized for maximum bitrate where we achieved 34 Gb/s over 10 km of SSMF using an EML with 10 GHz bandwidth. For the uplink, maximum reach was optimized achieving 14 Gb/s using a low-cost DML with 2.5 GHz bandwidth.

Tidal Distortion and Disruption of Earth-Crossing Asteriods

NASA Technical Reports Server (NTRS)

Love, Stanley G.; Bottke, William, Jr.

1997-01-01

We represent results of numerical simulations that show Earth's tidal forces can both distort and disrupt Earth-crossing asteriods (ECAs) that have weak rubble-pile structures. Building on previous studies, we consider more realistic asteriod shapes and trajectories, test a variety of spin and rates and axis orientations, and employ a dissipation algorithm to more accurately treat collisions between particles.

Optimal Mass Transport for Shape Matching and Comparison

PubMed Central

Su, Zhengyu; Wang, Yalin; Shi, Rui; Zeng, Wei; Sun, Jian; Luo, Feng; Gu, Xianfeng

2015-01-01

Surface based 3D shape analysis plays a fundamental role in computer vision and medical imaging. This work proposes to use optimal mass transport map for shape matching and comparison, focusing on two important applications including surface registration and shape space. The computation of the optimal mass transport map is based on Monge-Brenier theory, in comparison to the conventional method based on Monge-Kantorovich theory, this method significantly improves the efficiency by reducing computational complexity from O(n2) to O(n). For surface registration problem, one commonly used approach is to use conformal map to convert the shapes into some canonical space. Although conformal mappings have small angle distortions, they may introduce large area distortions which are likely to cause numerical instability thus resulting failures of shape analysis. This work proposes to compose the conformal map with the optimal mass transport map to get the unique area-preserving map, which is intrinsic to the Riemannian metric, unique, and diffeomorphic. For shape space study, this work introduces a novel Riemannian framework, Conformal Wasserstein Shape Space, by combing conformal geometry and optimal mass transport theory. In our work, all metric surfaces with the disk topology are mapped to the unit planar disk by a conformal mapping, which pushes the area element on the surface to a probability measure on the disk. The optimal mass transport provides a map from the shape space of all topological disks with metrics to the Wasserstein space of the disk and the pullback Wasserstein metric equips the shape space with a Riemannian metric. We validate our work by numerous experiments and comparisons with prior approaches and the experimental results demonstrate the efficiency and efficacy of our proposed approach. PMID:26440265

Body-size perception, body-esteem, and parenting history in college women reporting a history of child abuse.

PubMed

Eubanks, Jessica R; Kenkel, Michaela Y; Gardner, Rick M

2006-04-01

This study investigated the relations among physical, emotional, and sexual abuse up to adolescence and subsequent perception of body size, detection of changes in body size, and body-esteem. The role of parenting history in abused participants was also examined. 38 college undergraduate women, half of whom had been abused, reported instances of abuse, childhood parenting history, and current body-esteem. A recently developed software program of Gardner and Boice was used to present a series of distorted frontal profiles of each participant's own body for the women to rate as being too wide or too thin. A psychophysical procedure called adaptive probit estimation was used to measure the amount of over- and underestimation of these ratings and whether these changes were statistically significant. Analysis showed abused participants had distorted perceptions of body size, although the direction of the distortion was not consistent. There was no difference in detection of changes in body size. Abused and nonabused participants differed on measures of body-esteem and on ratings of most parenting experiences, including experiences with both mothers and fathers.

Numerical Investigation of Vortex Generator Flow Control for External-Compression Supersonic Inlets

NASA Astrophysics Data System (ADS)

Baydar, Ezgihan

Vortex generators (VGs) within external-compression supersonic inlets for Mach 1.6 were investigated to determine their ability to increase total pressure recovery and reduce total pressure distortion. Ramp and vane-type VGs were studied. The geometric factors of interest included height, length, spacing, angle-of-incidence, and positions upstream and downstream of the inlet terminal shock. The flow through the inlet was simulated numerically through the solution of the steady-state, Reynolds-averaged Navier-Stokes equations on multi-block, structured grids using the Wind-US flow solver. The inlet performance was characterized by the inlet total pressure recovery and the radial and circumferential total pressure distortion indices at the engine face. Previous research of downstream VGs in the low-boom supersonic inlet demonstrated improvement in radial distortion up to 24% while my work on external-compression supersonic inlets improved radial distortion up to 86%, which is significant. The design of experiments and statistical analysis methods were applied to quantify the effect of the geometric factors of VGs and search for optimal VG arrays. From the analysis, VG angle-of-incidence and VG height were the most influential factors in increasing total pressure recovery and reducing distortion. The study on the two-dimensional external-compression inlet determined which passive flow control devices, such as counter-rotating vanes or ramps, reduce high distortion levels and improve the health of the boundary layer, relative to the baseline. Downstream vanes demonstrate up to 21% improvement in boundary layer health and 86% improvement in radial distortion. Upstream vanes demonstrated up to 3% improvement in boundary layer health and 9% improvement in radial distortion. Ramps showed no improvement in boundary layer health and radial distortion. Micro-VGs were preferred for their reduced viscous drag and improvement in total pressure recovery at the AIP. Although traditional VGs energize the flow with stronger vortex structures compared to micro-VGs, the AIP is affected with overwhelming amounts of reduced and enhanced flow regions. In summary, vanes are exceptional in reducing radial distortion and improving the health of the boundary layer compared to the ramps. In the study of the STEX inlet, vane-type vortex generators were the preferred devices for boundary layer flow control. In the supersonic diffuser, co-rotating vane arrays and counter-rotating vane arrays did not show improvement. In the subsonic diffuser, co-rotating vane arrays with negative angles-of-incidence and counter-rotating vane arrays were exceptional in reducing radial distortion and improving total pressure recovery. Downstream co-rotating vanes demonstrated up to 41% improvement in radial distortion whereas downstream counter-rotating vanes demonstrated up to 73% improvement. For downstream counter-rotating vanes, a polynomial trend between VG height and radial distortion indicate that increasing VG height improves inlet distortion. In summary, downstream vanes are exceptional in improving total pressure recovery compared to upstream vanes.

Analytical and experimental design and analysis of an optimal processor for image registration

NASA Technical Reports Server (NTRS)

Mcgillem, C. D. (Principal Investigator); Svedlow, M.; Anuta, P. E.

1976-01-01

The author has identified the following significant results. A quantitative measure of the registration processor accuracy in terms of the variance of the registration error was derived. With the appropriate assumptions, the variance was shown to be inversely proportional to the square of the effective bandwidth times the signal to noise ratio. The final expressions were presented to emphasize both the form and simplicity of their representation. In the situation where relative spatial distortions exist between images to be registered, expressions were derived for estimating the loss in output signal to noise ratio due to these spatial distortions. These results are in terms of a reduction factor.

Robust Airfoil Optimization to Achieve Consistent Drag Reduction Over a Mach Range

NASA Technical Reports Server (NTRS)

Li, Wu; Huyse, Luc; Padula, Sharon; Bushnell, Dennis M. (Technical Monitor)

2001-01-01

We prove mathematically that in order to avoid point-optimization at the sampled design points for multipoint airfoil optimization, the number of design points must be greater than the number of free-design variables. To overcome point-optimization at the sampled design points, a robust airfoil optimization method (called the profile optimization method) is developed and analyzed. This optimization method aims at a consistent drag reduction over a given Mach range and has three advantages: (a) it prevents severe degradation in the off-design performance by using a smart descent direction in each optimization iteration, (b) there is no random airfoil shape distortion for any iterate it generates, and (c) it allows a designer to make a trade-off between a truly optimized airfoil and the amount of computing time consumed. For illustration purposes, we use the profile optimization method to solve a lift-constrained drag minimization problem for 2-D airfoil in Euler flow with 20 free-design variables. A comparison with other airfoil optimization methods is also included.

Surveying multidisciplinary aspects in real-time distributed coding for Wireless Sensor Networks.

PubMed

Braccini, Carlo; Davoli, Franco; Marchese, Mario; Mongelli, Maurizio

2015-01-27

Wireless Sensor Networks (WSNs), where a multiplicity of sensors observe a physical phenomenon and transmit their measurements to one or more sinks, pertain to the class of multi-terminal source and channel coding problems of Information Theory. In this category, "real-time" coding is often encountered for WSNs, referring to the problem of finding the minimum distortion (according to a given measure), under transmission power constraints, attainable by encoding and decoding functions, with stringent limits on delay and complexity. On the other hand, the Decision Theory approach seeks to determine the optimal coding/decoding strategies or some of their structural properties. Since encoder(s) and decoder(s) possess different information, though sharing a common goal, the setting here is that of Team Decision Theory. A more pragmatic vision rooted in Signal Processing consists of fixing the form of the coding strategies (e.g., to linear functions) and, consequently, finding the corresponding optimal decoding strategies and the achievable distortion, generally by applying parametric optimization techniques. All approaches have a long history of past investigations and recent results. The goal of the present paper is to provide the taxonomy of the various formulations, a survey of the vast related literature, examples from the authors' own research, and some highlights on the inter-play of the different theories.

3D reconstruction of laser projective point with projection invariant generated from five points on 2D target.

PubMed

Xu, Guan; Yuan, Jing; Li, Xiaotao; Su, Jian

2017-08-01

Vision measurement on the basis of structured light plays a significant role in the optical inspection research. The 2D target fixed with a line laser projector is designed to realize the transformations among the world coordinate system, the camera coordinate system and the image coordinate system. The laser projective point and five non-collinear points that are randomly selected from the target are adopted to construct a projection invariant. The closed form solutions of the 3D laser points are solved by the homogeneous linear equations generated from the projection invariants. The optimization function is created by the parameterized re-projection errors of the laser points and the target points in the image coordinate system. Furthermore, the nonlinear optimization solutions of the world coordinates of the projection points, the camera parameters and the lens distortion coefficients are contributed by minimizing the optimization function. The accuracy of the 3D reconstruction is evaluated by comparing the displacements of the reconstructed laser points with the actual displacements. The effects of the image quantity, the lens distortion and the noises are investigated in the experiments, which demonstrate that the reconstruction approach is effective to contribute the accurate test in the measurement system.

System for objective assessment of image differences in digital cinema

NASA Astrophysics Data System (ADS)

Fliegel, Karel; Krasula, Lukáš; Páta, Petr; Myslík, Jiří; Pecák, Josef; Jícha, Marek

2014-09-01

There is high demand for quick digitization and subsequent image restoration of archived film records. Digitization is very urgent in many cases because various invaluable pieces of cultural heritage are stored on aging media. Only selected records can be reconstructed perfectly using painstaking manual or semi-automatic procedures. This paper aims to answer the question what are the quality requirements on the restoration process in order to obtain acceptably close visual perception of the digitally restored film in comparison to the original analog film copy. This knowledge is very important to preserve the original artistic intention of the movie producers. Subjective experiment with artificially distorted images has been conducted in order to answer the question what is the visual impact of common image distortions in digital cinema. Typical color and contrast distortions were introduced and test images were presented to viewers using digital projector. Based on the outcome of this subjective evaluation a system for objective assessment of image distortions has been developed and its performance tested. The system utilizes calibrated digital single-lens reflex camera and subsequent analysis of suitable features of images captured from the projection screen. The evaluation of captured image data has been optimized in order to obtain predicted differences between the reference and distorted images while achieving high correlation with the results of subjective assessment. The system can be used to objectively determine the difference between analog film and digital cinema images on the projection screen.

Effects of EPI distortion correction pipelines on the connectome in Parkinson's Disease

NASA Astrophysics Data System (ADS)

Galvis, Justin; Mezher, Adam F.; Ragothaman, Anjanibhargavi; Villalon-Reina, Julio E.; Fletcher, P. Thomas; Thompson, Paul M.; Prasad, Gautam

2016-03-01

Echo-planar imaging (EPI) is commonly used for diffusion-weighted imaging (DWI) but is susceptible to nonlinear geometric distortions arising from inhomogeneities in the static magnetic field. These inhomogeneities can be measured and corrected using a fieldmap image acquired during the scanning process. In studies where the fieldmap image is not collected, these distortions can be corrected, to some extent, by nonlinearly registering the diffusion image to a corresponding anatomical image, either a T1- or T2-weighted image. Here we compared two EPI distortion correction pipelines, both based on nonlinear registration, which were optimized for the particular weighting of the structural image registration target. The first pipeline used a 3D nonlinear registration to a T1-weighted target, while the second pipeline used a 1D nonlinear registration to a T2-weighted target. We assessed each pipeline in its ability to characterize high-level measures of brain connectivity in Parkinson's disease (PD) in 189 individuals (58 healthy controls, 131 people with PD) from the Parkinson's Progression Markers Initiative (PPMI) dataset. We computed a structural connectome (connectivity map) for each participant using regions of interest from a cortical parcellation combined with DWI-based whole-brain tractography. We evaluated test-retest reliability of the connectome for each EPI distortion correction pipeline using a second diffusion scan acquired directly after the participants' first. Finally, we used support vector machine (SVM) classification to assess how accurately each pipeline classified PD versus healthy controls using each participants' structural connectome.

Pricing schemes for new drugs: a welfare analysis.

PubMed

Levaggi, Rosella

2014-02-01

Drug price regulation is acquiring increasing significance in the investment choices of the pharmaceutical sector. The overall objective is to determine an optimal trade-off between the incentives for innovation, consumer protection, and value for money. However, price regulation is itself a source of distortion. In this study, we examine the welfare properties of listing through a bargaining process and value-based pricing schemes. The latter are superior instruments to uncertain listing processes for maximising total welfare, but the distribution of the benefits between consumers and the industry depends on rate of rebate chosen by the regulator. However, through an appropriate choice, it is always possible to define a value-based pricing scheme with risk sharing, which both consumers and the industry prefer to an uncertain bargaining process. Copyright © 2013 Elsevier Ltd. All rights reserved.

Holographic Formation of Diffraction Elements for Transformation of Light Beams in Liquid Crystal - Photopolymer Compositions

NASA Astrophysics Data System (ADS)

Semkin, A. O.; Sharangovich, S. N.

2018-03-01

A theoretical model of holographic formation of diffractive optical elements for transformation of light beam field into Bessel-like fields in liquid crystal - photopolymer (LC-PPM) composite materials with a dyesensitizer is developed. Results of numerical modeling of kinetics ofvariation of the refractive index of a material in the process of formation with different relationships between the photopolymerization rates and diffusion processes are presented. Based on the results of numerical simulation, it is demonstrated that when the photopolarization process dominates, the diffractive element being formed is distorted. This leads to a change in the light field distribution at its output and consequently, to ineffective transformation of the reading beam. Thus, the necessity of optimizing of the recording conditions and of the prepolymeric composition to increase the transformation efficiency of light beam fields is demonstrated.

Baryon acoustic oscillations in 2D: Modeling redshift-space power spectrum from perturbation theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taruya, Atsushi; Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa, Chiba 277-8568; Nishimichi, Takahiro

2010-09-15

We present an improved prescription for the matter power spectrum in redshift space taking proper account of both nonlinear gravitational clustering and redshift distortion, which are of particular importance for accurately modeling baryon acoustic oscillations (BAOs). Contrary to the models of redshift distortion phenomenologically introduced but frequently used in the literature, the new model includes the corrections arising from the nonlinear coupling between the density and velocity fields associated with two competitive effects of redshift distortion, i.e., Kaiser and Finger-of-God effects. Based on the improved treatment of perturbation theory for gravitational clustering, we compare our model predictions with the monopolemore » and quadrupole power spectra of N-body simulations, and an excellent agreement is achieved over the scales of BAOs. Potential impacts on constraining dark energy and modified gravity from the redshift-space power spectrum are also investigated based on the Fisher-matrix formalism, particularly focusing on the measurements of the Hubble parameter, angular diameter distance, and growth rate for structure formation. We find that the existing phenomenological models of redshift distortion produce a systematic error on measurements of the angular diameter distance and Hubble parameter by 1%-2%, and the growth-rate parameter by {approx}5%, which would become non-negligible for future galaxy surveys. Correctly modeling redshift distortion is thus essential, and the new prescription for the redshift-space power spectrum including the nonlinear corrections can be used as an accurate theoretical template for anisotropic BAOs.« less

Cascade Optimization Strategy Maximizes Thrust for High-Speed Civil Transport Propulsion System Concept

NASA Technical Reports Server (NTRS)

1995-01-01

The design of a High-Speed Civil Transport (HSCT) air-breathing propulsion system for multimission, variable-cycle operations was successfully optimized through a soft coupling of the engine performance analyzer NASA Engine Performance Program (NEPP) to a multidisciplinary optimization tool COMETBOARDS that was developed at the NASA Lewis Research Center. The design optimization of this engine was cast as a nonlinear optimization problem, with engine thrust as the merit function and the bypass ratios, r-values of fans, fuel flow, and other factors as important active design variables. Constraints were specified on factors including the maximum speed of the compressors, the positive surge margins for the compressors with specified safety factors, the discharge temperature, the pressure ratios, and the mixer extreme Mach number. Solving the problem by using the most reliable optimization algorithm available in COMETBOARDS would provide feasible optimum results only for a portion of the aircraft flight regime because of the large number of mission points (defined by altitudes, Mach numbers, flow rates, and other factors), diverse constraint types, and overall poor conditioning of the design space. Only the cascade optimization strategy of COMETBOARDS, which was devised especially for difficult multidisciplinary applications, could successfully solve a number of engine design problems for their flight regimes. Furthermore, the cascade strategy converged to the same global optimum solution even when it was initiated from different design points. Multiple optimizers in a specified sequence, pseudorandom damping, and reduction of the design space distortion via a global scaling scheme are some of the key features of the cascade strategy. HSCT engine concept, optimized solution for HSCT engine concept. A COMETBOARDS solution for an HSCT engine (Mach-2.4 mixed-flow turbofan) along with its configuration is shown. The optimum thrust is normalized with respect to NEPP results. COMETBOARDS added value in the design optimization of the HSCT engine.

Analysis and optimization of hybrid excitation permanent magnet synchronous generator for stand-alone power system

NASA Astrophysics Data System (ADS)

Wang, Huijun; Qu, Zheng; Tang, Shaofei; Pang, Mingqi; Zhang, Mingju

2017-08-01

In this paper, electromagnetic design and permanent magnet shape optimization for permanent magnet synchronous generator with hybrid excitation are investigated. Based on generator structure and principle, design outline is presented for obtaining high efficiency and low voltage fluctuation. In order to realize rapid design, equivalent magnetic circuits for permanent magnet and iron poles are developed. At the same time, finite element analysis is employed. Furthermore, by means of design of experiment (DOE) method, permanent magnet is optimized to reduce voltage waveform distortion. Finally, the validity of proposed design methods is validated by the analytical and experimental results.

Transient Evoked and Distortion Product Otoacoustic Emissions in a Group of Neonates

PubMed Central

Silva, Giovanna Cesar; Delecrode, Camila Ribas; Kemp, Adriana Tahara; Martins, Fabiana; Cardoso, Ana Claudia Vieira

2015-01-01

Introduction The most commonly used method in neonatal hearing screening programs is transient evoked otoacoustic emissions in the first stage of the process. There are few studies comparing transient evoked otoacoustic emissions with distortion product, but some authors have investigated the issue. Objective To correlate the results of transient evoked and distortion product otoacoustic emissions in a Brazilian maternity hospital. Methods This is a cross-sectional, comparative, and prospective study. The study included 579 newborns, ranging from 6 to 54 days of age, born in a low-risk maternity hospital and assessed for hearing loss. All neonates underwent hearing screening by transient evoked and distortion product otoacoustic emissions. The results were analyzed using the Spearman correlation test to relate the two procedures. Results The pass index on transient evoked otoacoustic emissions was 95% and on distortion product otoacoustic emissions was 91%. The comparison of the two procedures showed that 91% of neonates passed on both procedures, 4.5% passed only on transient evoked otoacoustic emissions, 0.5% passed only on distortion product otoacoustic emissions, and 4% failed on both procedures. The inferential analysis showed a significant strong positive relationship between the two procedures. Conclusion The failure rate was higher in distortion product otoacoustic emissions when compared with transient evoked; however, there was correlation between the results of the procedures. PMID:26157501

Using High Resolution Design Spaces for Aerodynamic Shape Optimization Under Uncertainty

NASA Technical Reports Server (NTRS)

Li, Wu; Padula, Sharon

2004-01-01

This paper explains why high resolution design spaces encourage traditional airfoil optimization algorithms to generate noisy shape modifications, which lead to inaccurate linear predictions of aerodynamic coefficients and potential failure of descent methods. By using auxiliary drag constraints for a simultaneous drag reduction at all design points and the least shape distortion to achieve the targeted drag reduction, an improved algorithm generates relatively smooth optimal airfoils with no severe off-design performance degradation over a range of flight conditions, in high resolution design spaces parameterized by cubic B-spline functions. Simulation results using FUN2D in Euler flows are included to show the capability of the robust aerodynamic shape optimization method over a range of flight conditions.

Optimal Micro-Jet Flow Control for Compact Air Vehicle Inlets

NASA Technical Reports Server (NTRS)

Anderson, Bernhard H.; Miller, Daniel N.; Addington, Gregory A.; Agrell, Johan

2004-01-01

The purpose of this study on micro-jet secondary flow control is to demonstrate the viability and economy of Response Surface Methodology (RSM) to optimally design micro-jet secondary flow control arrays, and to establish that the aeromechanical effects of engine face distortion can also be included in the design and optimization process. These statistical design concepts were used to investigate the design characteristics of "low mass" micro-jet array designs. The term "low mass" micro-jet may refers to fluidic jets with total (integrated) mass flow ratios between 0.10 and 1.0 percent of the engine face mass flow. Therefore, this report examines optimal micro-jet array designs for compact inlets through a Response Surface Methodology.

Numerical Modeling of Flow Control in a Boundary-Layer-Ingesting Offset Inlet Diffuser at Transonic Mach Numbers

NASA Technical Reports Server (NTRS)

Allan, Brian G.; Owens, Lewis R.

2006-01-01

This paper will investigate the validation of the NASA developed, Reynolds-averaged Navier-Stokes (RANS) flow solver, OVERFLOW, for a boundary-layer-ingesting (BLI) offset (S-shaped) inlet in transonic flow with passive and active flow control devices as well as a baseline case. Numerical simulations are compared to wind tunnel results of a BLI inlet experiment conducted at the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel. Comparisons of inlet flow distortion, pressure recovery, and inlet wall pressures are performed. The numerical simulations are compared to the BLI inlet data at a free-stream Mach number of 0.85 and a Reynolds number of approximately 2 million based on the fanface diameter. The numerical simulations with and without tunnel walls are performed, quantifying tunnel wall effects on the BLI inlet flow. A comparison is made between the numerical simulations and the BLI inlet experiment for the baseline and VG vane cases at various inlet mass flow rates. A comparison is also made to a BLI inlet jet configuration for varying actuator mass flow rates at a fixed inlet mass flow rate. Overall, the numerical simulations were able to predict the baseline circumferential flow distortion, DPCP avg, very well within the designed operating range of the BLI inlet. A comparison of the average total pressure recovery showed that the simulations were able to predict the trends but had a negative 0.01 offset when compared to the experimental levels. Numerical simulations of the baseline inlet flow also showed good agreement with the experimental inlet centerline surface pressures. The vane case showed that the CFD predicted the correct trends in the circumferential distortion levels for varying inlet mass flow but had a distortion level that was nearly twice as large as the experiment. Comparison to circumferential distortion measurements for a 15 deg clocked 40 probe rake indicated that the circumferential distortion levels are very sensitive to the symmetry of the flow and that a misalignment of the vanes in the experiment could have resulted in this difference. The numerical simulations of the BLI inlet with jets showed good agreement with the circumferential inlet distortion levels for a range of jet actuator mass flow ratios at a fixed inlet mass flow rate. The CFD simulations for the jet case also predicted an average total pressure recovery offset that was 0.01 lower than the experiment as was seen in the baseline. Comparisons of the flow features for the jet cases revealed that the CFD predicted a much larger vortex at the engine fan-face when compare to the experiment.

Numerical Modeling of Flow Control in a Boundary-Layer-Ingesting Offset Inlet Diffuser at Transonic Mach Numbers

NASA Technical Reports Server (NTRS)

Allan Brian G.; Owens, Lewis, R.

2006-01-01

This paper will investigate the validation of a NASA developed, Reynolds-averaged Navier-Stokes (RANS) flow solver, OVERFLOW, for a boundary-layer-ingesting (BLI) offset (S-shaped) inlet in transonic flow with passive and active flow control devices as well as the baseline case. Numerical simulations are compared to wind tunnel results of a BLI inlet conducted at the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel. Comparisons of inlet flow distortion, pressure recovery, and inlet wall pressures are performed. The numerical simulations are compared to the BLI inlet data at a freestream Mach number of 0.85 and a Reynolds number of approximately 2 million based on the length of the fan-face diameter. The numerical simulations with and without wind tunnel walls are performed, quantifying effects of the tunnel walls on the BLI inlet flow measurements. The wind tunnel test evaluated several different combinations of jet locations and mass flow rates as well as a vortex generator (VG) vane case. The numerical simulations will be performed on a single jet configuration for varying actuator mass flow rates at a fix inlet mass flow condition. Validation of the numerical simulations for the VG vane case will also be performed for varying inlet mass flow rates. Overall, the numerical simulations were able to predict the baseline circumferential flow distortion, DPCPavg, very well for comparisons made within the designed operating range of the BLI inlet. However the CFD simulations did predict a total pressure recovery that was 0.01 lower than the experiment. Numerical simulations of the baseline inlet flow also showed good agreement with the experimental inlet centerline surface pressures. The vane case showed that the CFD predicted the correct trends in the circumferential distortion for varying inlet mass flow but had a distortion level that was nearly twice as large as the experiment. Comparison to circumferential distortion measurements for a 15 deg clocked 40 probe rake indicated that the circumferential distortion levels are very sensitive to the symmetry of the flow and that a miss alignment of the vanes in the experiment could have resulted in this difference. The numerical simulations of the BLI inlet with jets showed good agreement with the circumferential inlet distortion levels for a range of jet actuator mass flow ratios at a fixed inlet mass flow rate. The CFD simulations for the jet case also predicted an average total pressure recovery that was 0.01 lower than the experiment as was seen in the baseline. Comparison of the flow features the jet case revealed that the CFD predicted a much larger vortex at the engine fan-face when compare to the experiment.

Two-Dimensional Bifurcated Inlet Variable Cowl Lip Test Completed in 10- by 10-Foot Supersonic Wind Tunnel

NASA Technical Reports Server (NTRS)

Hoffman, T. R.

2000-01-01

Researchers at the NASA Glenn Research Center at Lewis Field successfully tested a variable cowl lip inlet at simulated takeoff conditions in Glenn s 10- by 10-Foot Supersonic Wind Tunnel (10x10 SWT) as part of the High-Speed Research Program. The test was a follow-on to the Two-Dimensional Bifurcated (2DB) Inlet/Engine test. At the takeoff condition for a High-Speed Civil Transport aircraft, the inlet must provide adequate airflow to the engine with an acceptable distortion level and high-pressure recovery. The test was conducted to study the effectiveness of installing two rotating lips on the 2DB Inlet cowls to increase mass flow rate and eliminate or reduce boundary layer flow separation near the lips. Hardware was mounted vertically in the test section so that it extended through the tunnel ceiling and that the 2DB Inlet was exposed to the atmosphere above the test section. The tunnel was configured in the aerodynamic mode, and exhausters were used to pump down the tunnel to vacuum levels and to provide a maximum flow rate of approximately 58 lb/sec. The test determined the (1) maximum flow in the 2DB Inlet for each variable cowl lip, (2) distortion level and pressure recovery for each lip configuration, (3) boundary layer conditions near variable lips inside the 2DB Inlet, (4) effects of a wing structure adjacent to the 2DB Inlet, and (5) effects of different 2DB Inlet exit configurations. It also employed flow visualization to generate enough qualitative data on variable lips to optimize the variable lip concept. This test was a collaborative effort between the Boeing Company and Glenn. Extensive inhouse support at Glenn contributed significantly to the progress and accomplishment of this test.

An Optical Flow-Based Full Reference Video Quality Assessment Algorithm.

PubMed

K, Manasa; Channappayya, Sumohana S

2016-06-01

We present a simple yet effective optical flow-based full-reference video quality assessment (FR-VQA) algorithm for assessing the perceptual quality of natural videos. Our algorithm is based on the premise that local optical flow statistics are affected by distortions and the deviation from pristine flow statistics is proportional to the amount of distortion. We characterize the local flow statistics using the mean, the standard deviation, the coefficient of variation (CV), and the minimum eigenvalue ( λ min ) of the local flow patches. Temporal distortion is estimated as the change in the CV of the distorted flow with respect to the reference flow, and the correlation between λ min of the reference and of the distorted patches. We rely on the robust multi-scale structural similarity index for spatial quality estimation. The computed temporal and spatial distortions, thus, are then pooled using a perceptually motivated heuristic to generate a spatio-temporal quality score. The proposed method is shown to be competitive with the state-of-the-art when evaluated on the LIVE SD database, the EPFL Polimi SD database, and the LIVE Mobile HD database. The distortions considered in these databases include those due to compression, packet-loss, wireless channel errors, and rate-adaptation. Our algorithm is flexible enough to allow for any robust FR spatial distortion metric for spatial distortion estimation. In addition, the proposed method is not only parameter-free but also independent of the choice of the optical flow algorithm. Finally, we show that the replacement of the optical flow vectors in our proposed method with the much coarser block motion vectors also results in an acceptable FR-VQA algorithm. Our algorithm is called the flow similarity index.

Computer tools for face seal analyses developed at John Crane

NASA Technical Reports Server (NTRS)

Wu, Shifeng

1994-01-01

The purposes of the computer tools for face seal analysis are new product optimization, existing seals on new applications, existing seals on off-duty conditions, and trouble-shooting. Discussed in this viewgraph presentation are interface forces, friction/heat generation, heat transfer/temperature distribution, axisymmetric pressure/thermal distortion, leakage, and an example case.

Memory conformity affects inaccurate memories more than accurate memories.

PubMed

Wright, Daniel B; Villalba, Daniella K

2012-01-01

After controlling for initial confidence, inaccurate memories were shown to be more easily distorted than accurate memories. In two experiments groups of participants viewed 50 stimuli and were then presented with these stimuli plus 50 fillers. During this test phase participants reported their confidence that each stimulus was originally shown. This was followed by computer-generated responses from a bogus participant. After being exposed to this response participants again rated the confidence of their memory. The computer-generated responses systematically distorted participants' responses. Memory distortion depended on initial memory confidence, with uncertain memories being more malleable than confident memories. This effect was moderated by whether the participant's memory was initially accurate or inaccurate. Inaccurate memories were more malleable than accurate memories. The data were consistent with a model describing two types of memory (i.e., recollective and non-recollective memories), which differ in how susceptible these memories are to memory distortion.

SU-G-IeP1-08: MR Geometric Distortion Dependency On Imaging Sequence, Acquisition Orientation and Receiver Bandwidth of a Dedicated 1.5T MR-Simulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Law, M; Yuan, J; Wong, O

Purpose: To investigate the 3D geometric distortion of four potential MR sequences for radiotheraptic applications, and its dependency on sequence-type, acquisition-orientation and receiver-bandwidth from a dedicated 1.5T 700mm-wide bore MR-simulator (Magnetom-Aera, Sienmens Healthcare, Erlangen, Germany), using a large customized geometric accuracy phantom. Methods: This work studied 3D gradient-echo (VIBE) and spin-echo (SPACE) sequences for anatomical imaging; a specific ultra-short-TE sequence (PETRA) potentially for bone imaging and MR-based dosimetry; and a motion-insensitive sequence (BLADE) for dynamic applications like 4D-MRI. Integrated geometric-correction was employed, three orthogonal acquisition-orientations and up to three receiver-bandwidths were used, yielding 27 acquisitions for testing (Table 1a).A customizedmore » geometric accuracy phantom (polyurethane, MR/CT invisible, W×L×H:55×55×32.5cm3) was constructed and filled with 3892 spherical markers (6mm diameter, MR/CT visible) arranged on a 25mm-interval 3D isotropic-grid (Fig.1). The marker positions in MR images were quantitatively calculated and compared against those in the CT-reference using customized MatLab scripts. Results: The average distortion within various diameter-of-spherical-volumes (DSVs) and the usable DSVs under various distortion limits were measured (Tables 1b-c). It was observed that distortions fluctuated when sequence-type, acquisition-orientation or receiver-bandwidth changed (e.g. within 300mm-DSV, the lowest/highest average distortions of VIBE were 0.40mm/0.59mm, a 47.5% difference). According to AAPM-TG66 (<1mm distortion, left-most column of Table 1c), PETRA (Largest-DSV:253.9mm) has the potential on brain treatment, while BLADE (Largest-DSV:207.2mm) may need improvement for thoracic/abdominal applications. The results of VIBE (Largest-DSVs:294.3mm, the best among tested acquisitions) and SPACE (Largest-DSVs:267.7mm) suggests their potentials on head and neck applications. These Largest-DSVs were attained on different acquisition-orientations and receiver-bandwidths. Conclusion: Geometric distortion was shown to be dependent on sequence-type, acquisition-orientation and receiver-bandwidth. In the experiment, no configuration in any one of these factors could consistently reduce distortion while the others were varying. The distortion analysis result is a valuable guideline for sequence selection and optimization for MR-aided radiotherapy applications.« less

Ground mapping resolution accuracy of a scanning radiometer from a geostationary satellite.

PubMed

Stremler, F G; Khalil, M A; Parent, R J

1977-06-01

Measures of the spatial and spatial rate (frequency) mapping of scanned visual imagery from an earth reference system to a spin-scan geostationary satellite are examined. Mapping distortions and coordinate inversions to correct for these distortions are formulated in terms of geometric transformations between earth and satellite frames of reference. Probabilistic methods are used to develop relations for obtainable mapping resolution when coordinate inversions are employed.

Global distortion of GPS networks associated with satellite antenna model errors

NASA Astrophysics Data System (ADS)

Cardellach, E.; Elósegui, P.; Davis, J. L.

2007-07-01

Recent studies of the GPS satellite phase center offsets (PCOs) suggest that these have been in error by ˜1 m. Previous studies had shown that PCO errors are absorbed mainly by parameters representing satellite clock and the radial components of site position. On the basis of the assumption that the radial errors are equal, PCO errors will therefore introduce an error in network scale. However, PCO errors also introduce distortions, or apparent deformations, within the network, primarily in the radial (vertical) component of site position that cannot be corrected via a Helmert transformation. Using numerical simulations to quantify the effects of PCO errors, we found that these PCO errors lead to a vertical network distortion of 6-12 mm per meter of PCO error. The network distortion depends on the minimum elevation angle used in the analysis of the GPS phase observables, becoming larger as the minimum elevation angle increases. The steady evolution of the GPS constellation as new satellites are launched, age, and are decommissioned, leads to the effects of PCO errors varying with time that introduce an apparent global-scale rate change. We demonstrate here that current estimates for PCO errors result in a geographically variable error in the vertical rate at the 1-2 mm yr-1 level, which will impact high-precision crustal deformation studies.

Global Distortion of GPS Networks Associated with Satellite Antenna Model Errors

NASA Technical Reports Server (NTRS)

Cardellach, E.; Elosequi, P.; Davis, J. L.

2007-01-01

Recent studies of the GPS satellite phase center offsets (PCOs) suggest that these have been in error by approx.1 m. Previous studies had shown that PCO errors are absorbed mainly by parameters representing satellite clock and the radial components of site position. On the basis of the assumption that the radial errors are equal, PCO errors will therefore introduce an error in network scale. However, PCO errors also introduce distortions, or apparent deformations, within the network, primarily in the radial (vertical) component of site position that cannot be corrected via a Helmert transformation. Using numerical simulations to quantify the effects of PC0 errors, we found that these PCO errors lead to a vertical network distortion of 6-12 mm per meter of PCO error. The network distortion depends on the minimum elevation angle used in the analysis of the GPS phase observables, becoming larger as the minimum elevation angle increases. The steady evolution of the GPS constellation as new satellites are launched, age, and are decommissioned, leads to the effects of PCO errors varying with time that introduce an apparent global-scale rate change. We demonstrate here that current estimates for PCO errors result in a geographically variable error in the vertical rate at the 1-2 mm/yr level, which will impact high-precision crustal deformation studies.

SU-F-P-48: The Quantitative Evaluation and Comparison of Image Distortion and Loss of X-Ray Images Between Anti-Scattered Grid and Moire Compensation Processing in Digital Radiography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, W; Jung, J; Kang, Y

Purpose: To quantitatively analyze the influence image processing for Moire elimination has in digital radiography by comparing the image acquired from optimized anti-scattered grid only and the image acquired from software processing paired with misaligned low-frequency grid. Methods: Special phantom, which does not create scattered radiation, was used to acquire non-grid reference images and they were acquired without any grids. A set of images was acquired with optimized grid, aligned to pixel of a detector and other set of images was acquired with misaligned low-frequency grid paired with Moire elimination processing algorithm. X-ray technique used was based on consideration tomore » Bucky factor derived from non-grid reference images. For evaluation, we analyze by comparing pixel intensity of acquired images with grids to that of reference images. Results: When compared to image acquired with optimized grid, images acquired with Moire elimination processing algorithm showed 10 to 50% lower mean contrast value of ROI. Severe distortion of images was found with when the object’s thickness was measured at 7 or less pixels. In this case, contrast value measured from images acquired with Moire elimination processing algorithm was under 30% of that taken from reference image. Conclusion: This study shows the potential risk of Moire compensation images in diagnosis. Images acquired with misaligned low-frequency grid results in Moire noise and Moire compensation processing algorithm used to remove this Moire noise actually caused an image distortion. As a result, fractures and/or calcifications which are presented in few pixels only may not be diagnosed properly. In future work, we plan to evaluate the images acquired without grid but based on 100% image processing and the potential risks it possesses.« less

Enhanced encrypted reversible data hiding algorithm with minimum distortion through homomorphic encryption

NASA Astrophysics Data System (ADS)

Bhardwaj, Rupali

2018-03-01

Reversible data hiding means embedding a secret message in a cover image in such a manner, to the point that in the midst of extraction of the secret message, the cover image and, furthermore, the secret message are recovered with no error. The goal of by far most of the reversible data hiding algorithms is to have improved the embedding rate and enhanced visual quality of stego image. An improved encrypted-domain-based reversible data hiding algorithm to embed two binary bits in each gray pixel of original cover image with minimum distortion of stego-pixels is employed in this paper. Highlights of the proposed algorithm are minimum distortion of pixel's value, elimination of underflow and overflow problem, and equivalence of stego image and cover image with a PSNR of ∞ (for Lena, Goldhill, and Barbara image). The experimental outcomes reveal that in terms of average PSNR and embedding rate, for natural images, the proposed algorithm performed better than other conventional ones.

Management of Total Pressure Recovery, Distortion and High Cycle Fatigue in Compact Air Vehicle Inlets

NASA Technical Reports Server (NTRS)

Anderson, Bernhard H.; Baust, Henry D.; Agrell, Johan

2002-01-01

It is the purpose of this study to demonstrate the viability and economy of Response Surface Methods (RSM) and Robustness Design Concepts (RDC) to arrive at micro-secondary flow control installation designs that maintain optimal inlet performance over a range of the mission variables. These statistical design concepts were used to investigate the robustness properties of 'low unit strength' micro-effector installations. 'Low unit strength' micro-effectors are micro-vanes set at very low angles-of-incidence with very long chord lengths. They were designed to influence the near wall inlet flow over an extended streamwise distance, and their advantage lies in low total pressure loss and high effectiveness in managing engine face distortion.

Development of 1-m primary mirror for a spaceborne camera

NASA Astrophysics Data System (ADS)

Kihm, Hagyong; Yang, Ho-Soon; Rhee, Hyug-Gyo; Lee, Yun-Woo

2015-09-01

We present the development of a 1-m lightweight mirror system for a spaceborne electro-optical camera. The mirror design was optimized to satisfy the performance requirements under launch loads and space environment. The mirror made of Zerodur® has pockets at the back surface and three square bosses at the rim. Metallic bipod flexures support the mirror at the bosses and adjust the mirror's surface distortion due to gravity. We also show an analytical formulation of the bipod flexure, where compliance and stiffness matrices of the bipod flexure are derived to estimate theoretical performance and to make initial design guidelines. Optomechanical performances such as surface distortions due to gravity is explained. Environmental verification of the mirror is achieved by vibration tests.

Dichroic beamsplitter for high energy laser diagnostics

DOEpatents

LaFortune, Kai N [Livermore, CA; Hurd, Randall [Tracy, CA; Fochs, Scott N [Livermore, CA; Rotter, Mark D [San Ramon, CA; Hackel, Lloyd [Livermore, CA

2011-08-30

Wavefront control techniques are provided for the alignment and performance optimization of optical devices. A Shack-Hartmann wavefront sensor can be used to measure the wavefront distortion and a control system generates feedback error signal to optics inside the device to correct the wavefront. The system can be calibrated with a low-average-power probe laser. An optical element is provided to couple the optical device to a diagnostic/control package in a way that optimizes both the output power of the optical device and the coupling of the probe light into the diagnostics.

Automatic source camera identification using the intrinsic lens radial distortion

NASA Astrophysics Data System (ADS)

Choi, Kai San; Lam, Edmund Y.; Wong, Kenneth K. Y.

2006-11-01

Source camera identification refers to the task of matching digital images with the cameras that are responsible for producing these images. This is an important task in image forensics, which in turn is a critical procedure in law enforcement. Unfortunately, few digital cameras are equipped with the capability of producing watermarks for this purpose. In this paper, we demonstrate that it is possible to achieve a high rate of accuracy in the identification by noting the intrinsic lens radial distortion of each camera. To reduce manufacturing cost, the majority of digital cameras are equipped with lenses having rather spherical surfaces, whose inherent radial distortions serve as unique fingerprints in the images. We extract, for each image, parameters from aberration measurements, which are then used to train and test a support vector machine classifier. We conduct extensive experiments to evaluate the success rate of a source camera identification with five cameras. The results show that this is a viable approach with high accuracy. Additionally, we also present results on how the error rates may change with images captured using various optical zoom levels, as zooming is commonly available in digital cameras.

P2-type Na2/3Mn1-xAlxO2 cathode material for sodium-ion batteries: Al-doped enhanced electrochemical properties and studies on the electrode kinetics

NASA Astrophysics Data System (ADS)

Pang, Wei-Lin; Zhang, Xiao-Hua; Guo, Jin-Zhi; Li, Jin-Yue; Yan, Xin; Hou, Bao-Hua; Guan, Hong-Yu; Wu, Xing-Long

2017-07-01

Recently, sodium-ion batteries (SIBs) have been considered as the promising alternative for lithium-ion batteries. Although layered P2-type transition metal oxides are an important class of cathode materials for SIBs, there are still some hurdles for the practical applications, including low specific capacity as well as poor cycling and rate properties. In this study, the electrochemical properties of layered Mn-based oxides have been effectively improved via Al doping, which cannot only promote the formation of layered P2-type structure in the preparation processes but also stabilize the lattice during the successive Na-intercalation/deintercalation due to suppression of the Jahn-Teller distortion of Mn3+. Among the as-prepared series of Na2/3Mn1-xAlxO2 (x = 0, 1/18, 1/9, and 2/9), Na2/3Mn8/9Al1/9O2 with x = 1/9 exhibits the optimal doping effect with the best electrochemical properties, in terms of the highest specific capacity of 162.3 mA h g-1 at 0.1 C, the highest rate capability, and the best cycling stability in comparison to the undoped Na2/3MnO2 and the other two materials with different Al-doped contents. Both cyclic voltammetry at varied scan rates and galvanostatic intermittent titration technique disclose the optimal electrode kinetics (the highest Na-diffusion coefficient) of the best Na2/3Mn8/9Al1/9O2.

Parental Cognitive Errors Mediate Parental Psychopathology and Ratings of Child Inattention.

PubMed

Haack, Lauren M; Jiang, Yuan; Delucchi, Kevin; Kaiser, Nina; McBurnett, Keith; Hinshaw, Stephen; Pfiffner, Linda

2017-09-01

We investigate the Depression-Distortion Hypothesis in a sample of 199 school-aged children with ADHD-Predominantly Inattentive presentation (ADHD-I) by examining relations and cross-sectional mediational pathways between parental characteristics (i.e., levels of parental depressive and ADHD symptoms) and parental ratings of child problem behavior (inattention, sluggish cognitive tempo, and functional impairment) via parental cognitive errors. Results demonstrated a positive association between parental factors and parental ratings of inattention, as well as a mediational pathway between parental depressive and ADHD symptoms and parental ratings of inattention via parental cognitive errors. Specifically, higher levels of parental depressive and ADHD symptoms predicted higher levels of cognitive errors, which in turn predicted higher parental ratings of inattention. Findings provide evidence for core tenets of the Depression-Distortion Hypothesis, which state that parents with high rates of psychopathology hold negative schemas for their child's behavior and subsequently, report their child's behavior as more severe. © 2016 Family Process Institute.

Impulsivity and cognitive distortions in pathological gamblers attending the UK National Problem Gambling Clinic: a preliminary report.

PubMed

Michalczuk, R; Bowden-Jones, H; Verdejo-Garcia, A; Clark, L

2011-12-01

Pathological gambling (PG) is a form of behavioural addiction that has been associated with elevated impulsivity and also cognitive distortions in the processing of chance, probability and skill. We sought to assess the relationship between the level of cognitive distortions and state and trait measures of impulsivity in treatment-seeking pathological gamblers. Thirty pathological gamblers attending the National Problem Gambling Clinic, the first National Health Service clinic for gambling problems in the UK, were compared with 30 healthy controls in a case-control design. Cognitive distortions were assessed using the Gambling-Related Cognitions Scale (GRCS). Trait impulsivity was assessed using the UPPS-P, which includes scales of urgency, the tendency to be impulsive in positive or negative mood states. Delay discounting rates were taken as a state measure of impulsive choice. Pathological gamblers had elevated impulsivity on several UPPS-P subscales but effect sizes were largest (Cohen's d>1.4) for positive and negative urgency. The pathological gamblers also displayed higher levels of gambling distortions, and elevated preference for immediate rewards, compared to controls. Within the pathological gamblers, there was a strong relationship between the preference for immediate rewards and the level of cognitive distortions (R2=0.41). Impulsive choice in the gamblers was correlated with the level of gambling distortions, and we hypothesize that an impulsive decision-making style may increase the acceptance of erroneous beliefs during gambling play.

On Several Fundamental Problems of Optimization, Estimation, and Scheduling in Wireless Communications

NASA Astrophysics Data System (ADS)

Gao, Qian

For both the conventional radio frequency and the comparably recent optical wireless communication systems, extensive effort from the academia had been made in improving the network spectrum efficiency and/or reducing the error rate. To achieve these goals, many fundamental challenges such as power efficient constellation design, nonlinear distortion mitigation, channel training design, network scheduling and etc. need to be properly addressed. In this dissertation, novel schemes are proposed accordingly to deal with specific problems falling in category of these challenges. Rigorous proofs and analyses are provided for each of our work to make a fair comparison with the corresponding peer works to clearly demonstrate the advantages. The first part of this dissertation considers a multi-carrier optical wireless system employing intensity modulation (IM) and direct detection (DD). A block-wise constellation design is presented, which treats the DC-bias that conventionally used solely for biasing purpose as an information basis. Our scheme, we term it MSM-JDCM, takes advantage of the compactness of sphere packing in a higher dimensional space, and in turn power efficient constellations are obtained by solving an advanced convex optimization problem. Besides the significant power gains, the MSM-JDCM has many other merits such as being capable of mitigating nonlinear distortion by including a peak-to-power ratio (PAPR) constraint, minimizing inter-symbol-interference (ISI) caused by frequency-selective fading with a novel precoder designed and embedded, and further reducing the bit-error-rate (BER) by combining with an optimized labeling scheme. The second part addresses several optimization problems in a multi-color visible light communication system, including power efficient constellation design, joint pre-equalizer and constellation design, and modeling of different structured channels with cross-talks. Our novel constellation design scheme, termed CSK-Advanced, is compared with the conventional decoupled system with the same spectrum efficiency to demonstrate the power efficiency. Crucial lighting requirements are included as optimization constraints. To control non-linear distortion, the optical peak-to-average-power ratio (PAPR) of LEDs can be individually constrained. With a SVD-based pre-equalizer designed and employed, our scheme can achieve lower BER than counterparts applying zero-forcing (ZF) or linear minimum-mean-squared-error (LMMSE) based post-equalizers. Besides, a binary switching algorithm (BSA) is applied to improve BER performance. The third part looks into a problem of two-phase channel estimation in a relayed wireless network. The channel estimates in every phase are obtained by the linear minimum mean squared error (LMMSE) method. Inaccurate estimate of the relay to destination (RtD) channel in phase 1 could affect estimate of the source to relay (StR) channel in phase 2, which is made erroneous. We first derive a close-form expression for the averaged Bayesian mean-square estimation error (ABMSE) for both phase estimates in terms of the length of source and relay training slots, based on which an iterative searching algorithm is then proposed that optimally allocates training slots to the two phases such that estimation errors are balanced. Analysis shows how the ABMSE of the StD channel estimation varies with the lengths of relay training and source training slots, the relay amplification gain, and the channel prior information respectively. The last part deals with a transmission scheduling problem in a uplink multiple-input-multiple-output (MIMO) wireless network. Code division multiple access (CDMA) is assumed as a multiple access scheme and pseudo-random codes are employed for different users. We consider a heavy traffic scenario, in which each user always has packets to transmit in the scheduled time slots. If the relay is scheduled for transmission together with users, then it operates in a full-duplex mode, where the packets previously collected from users are transmitted to the destination while new packets are being collected from users. A novel expression of throughput is first derived and then used to develop a scheduling algorithm to maximize the throughput. Our full-duplex scheduling is compared with a half-duplex scheduling, random access, and time division multiple access (TDMA), and simulation results illustrate its superiority. Throughput gains due to employment of both MIMO and CDMA are observed.

Study of the solar coronal hole rotation

NASA Astrophysics Data System (ADS)

Oghrapishvili, N. B.; Bagashvili, S. R.; Maghradze, D. A.; Gachechiladze, T. Z.; Japaridze, D. R.; Shergelashvili, B. M.; Mdzinarishvili, T. G.; Chargeishvili, B. B.

2018-06-01

Rotation of coronal holes is studied using data from SDO/AIA for 2014 and 2015. A new approach to the treatment of data is applied. Instead of calculated average angular velocities of each coronal hole centroid and then grouping them in latitudinal bins for calculating average rotation rates of corresponding latitudes, we compiled instant rotation rates of centroids and their corresponding heliographic coordinates in one matrix for further processing. Even unfiltered data showed clear differential nature of rotation of coronal holes. We studied possible reasons for distortion of data by the limb effects to eliminate some discrepancies at high latitudes caused by the high order of scattering of data in that region. A study of the longitudinal distribution of angular velocities revealed the optimal longitudinal interval for the best result. We examined different methods of data filtering and realized that filtration using targeting on the local medians of data with a constant threshold is a more acceptable approach that is not biased towards a predefined notion of an expected result. The results showed a differential pattern of rotation of coronal holes.

Compress compound images in H.264/MPGE-4 AVC by exploiting spatial correlation.

PubMed

Lan, Cuiling; Shi, Guangming; Wu, Feng

2010-04-01

Compound images are a combination of text, graphics and natural image. They present strong anisotropic features, especially on the text and graphics parts. These anisotropic features often render conventional compression inefficient. Thus, this paper proposes a novel coding scheme from the H.264 intraframe coding. In the scheme, two new intramodes are developed to better exploit spatial correlation in compound images. The first is the residual scalar quantization (RSQ) mode, where intrapredicted residues are directly quantized and coded without transform. The second is the base colors and index map (BCIM) mode that can be viewed as an adaptive color quantization. In this mode, an image block is represented by several representative colors, referred to as base colors, and an index map to compress. Every block selects its coding mode from two new modes and the previous intramodes in H.264 by rate-distortion optimization (RDO). Experimental results show that the proposed scheme improves the coding efficiency even more than 10 dB at most bit rates for compound images and keeps a comparable efficient performance to H.264 for natural images.

Wireless Energy Harvesting Two-Way Relay Networks with Hardware Impairments.

PubMed

Peng, Chunling; Li, Fangwei; Liu, Huaping

2017-11-13

This paper considers a wireless energy harvesting two-way relay (TWR) network where the relay has energy-harvesting abilities and the effects of practical hardware impairments are taken into consideration. In particular, power splitting (PS) receiver is adopted at relay to harvests the power it needs for relaying the information between the source nodes from the signals transmitted by the source nodes, and hardware impairments is assumed suffered by each node. We analyze the effect of hardware impairments [-20]on both decode-and-forward (DF) relaying and amplify-and-forward (AF) relaying networks. By utilizing the obtained new expressions of signal-to-noise-plus-distortion ratios, the exact analytical expressions of the achievable sum rate and ergodic capacities for both DF and AF relaying protocols are derived. Additionally, the optimal power splitting (OPS) ratio that maximizes the instantaneous achievable sum rate is formulated and solved for both protocols. The performances of DF and AF protocols are evaluated via numerical results, which also show the effects of various network parameters on the system performance and on the OPS ratio design.

Relation between film character and wafer alignment: critical alignment issues on HV device for VLSI manufacturing

NASA Astrophysics Data System (ADS)

Lo, Yi-Chuan; Lee, Chih-Hsiung; Lin, Hsun-Peng; Peng, Chiou-Shian

1998-06-01

Several continuous splits for wafer alignment target topography conditions to improve epitaxy film alignment were applied. The alignment evaluation among former layer pad oxide thickness (250 angstrom - 500 angstrom), drive oxide thickness (6000 angstrom - 10000 angstrom), nitride film thickness (600 angstrom - 1500 angstrom), initial oxide etch (fully wet etch, fully dry etch and dry plus wet etch) will be split to this experiment. Also various epitaxy deposition recipe such as: epitaxy source (SiHCl2 or SiCHCl3) and growth rate (1.3 micrometer/min approximately 2.0 micrometer/min) will be used to optimize the process window for alignment issue. All the reflectance signal and cross section photography of alignment target during NIKON stepper alignment process will be examined. Experimental results show epitaxy recipe plays an important role to wafer alignment. Low growth rate with good performance conformity epitaxy lead to alignment target avoid washout, pattern shift and distortion. All the results (signal monitor and film character) combined with NIKON's stepper standard laser scanning alignment system will be discussed in this paper.

Dynamic Reconstruction and Multivariable Control for Force-Actuated, Thin Facesheet Adaptive Optics

NASA Technical Reports Server (NTRS)

Grocott, Simon C. O.; Miller, David W.

1997-01-01

The Multiple Mirror Telescope (MMT) under development at the University of Arizona takes a new approach in adaptive optics placing a large (0.65 m) force-actuated, thin facesheet deformable mirror at the secondary of an astronomical telescope, thus reducing the effects of emissivity which are important in IR astronomy. However, The large size of the mirror and low stiffness actuators used drive the natural frequencies of the mirror down into the bandwidth of the atmospheric distortion. Conventional adaptive optics takes a quasi-static approach to controlling the, deformable mirror. However, flexibility within the control bandwidth calls for a new approach to adaptive optics. Dynamic influence functions are used to characterize the influence of each actuator on the surface of the deformable mirror. A linearized model of atmospheric distortion is combined with dynamic influence functions to produce a dynamic reconstructor. This dynamic reconstructor is recognized as an optimal control problem. Solving the optimal control problem for a system with hundreds of actuators and sensors is formidable. Exploiting the circularly symmetric geometry of the mirror, and a suitable model of atmospheric distortion, the control problem is divided into a number of smaller decoupled control problems using circulant matrix theory. A hierarchic control scheme which seeks to emulate the quasi-static control approach that is generally used in adaptive optics is compared to the proposed dynamic reconstruction technique. Although dynamic reconstruction requires somewhat more computational power to implement, it achieves better performance with less power usage, and is less sensitive than the hierarchic technique.

Coherent free space optics communications over the maritime atmosphere with use of adaptive optics for beam wavefront correction.

PubMed

Li, Ming; Cvijetic, Milorad

2015-02-20

We evaluate the performance of the coherent free space optics (FSO) employing quadrature array phase-shift keying (QPSK) modulation over the maritime atmosphere with atmospheric turbulence compensated by use of adaptive optics (AO). We have established a comprehensive FSO channel model for maritime conditions and also made a comprehensive comparison of performance between the maritime and terrestrial atmospheric links. The FSO links are modeled based on the intensity attenuation resulting from scattering and absorption effects, the log-amplitude fluctuations, and the phase distortions induced by turbulence. The obtained results show that the FSO system performance measured by the bit-error-rate (BER) can be significantly improved when the optimization of the AO system is achieved. Also, we find that the higher BER is observed in the maritime FSO channel with atmospheric turbulence, as compared to the terrestrial FSO systems if they experience the same turbulence strength.

Conditional Entropy-Constrained Residual VQ with Application to Image Coding

NASA Technical Reports Server (NTRS)

Kossentini, Faouzi; Chung, Wilson C.; Smith, Mark J. T.

1996-01-01

This paper introduces an extension of entropy-constrained residual vector quantization (VQ) where intervector dependencies are exploited. The method, which we call conditional entropy-constrained residual VQ, employs a high-order entropy conditioning strategy that captures local information in the neighboring vectors. When applied to coding images, the proposed method is shown to achieve better rate-distortion performance than that of entropy-constrained residual vector quantization with less computational complexity and lower memory requirements. Moreover, it can be designed to support progressive transmission in a natural way. It is also shown to outperform some of the best predictive and finite-state VQ techniques reported in the literature. This is due partly to the joint optimization between the residual vector quantizer and a high-order conditional entropy coder as well as the efficiency of the multistage residual VQ structure and the dynamic nature of the prediction.

Generation-3 programmable array microscope (PAM) with digital micro-mirror device (DMD)

NASA Astrophysics Data System (ADS)

De Beule, Pieter A. A.; de Vries, Anthony H. B.; Arndt-Jovin, Donna J.; Jovin, Thomas M.

2011-03-01

We report progress on the construction of an optical sectioning programmable array microscope (PAM) implemented with a digital micro-mirror device (DMD) spatial light modulator (SLM) utilized for both fluorescence illumination and detection. The introduction of binary intensity modulation at the focal plane of a microscope objective in a computer controlled pixilated mode allows the recovery of an optically sectioned image. Illumination patterns can be changed very quickly, in contrast to static Nipkow disk or aperture correlation implementations, thereby creating an optical system that can be optimized to the optical specimen in a convenient manner, e.g. for patterned photobleaching, photobleaching reduction, or spatial superresolution. We present a third generation (Gen-3) dual path PAM module incorporating the 25 kHz binary frame rate TI 1080p DMD and a newly developed optical system that offers diffraction limited imaging with compensation of tilt angle distortion.

3D scene reconstruction based on multi-view distributed video coding in the Zernike domain for mobile applications

NASA Astrophysics Data System (ADS)

Palma, V.; Carli, M.; Neri, A.

2011-02-01

In this paper a Multi-view Distributed Video Coding scheme for mobile applications is presented. Specifically a new fusion technique between temporal and spatial side information in Zernike Moments domain is proposed. Distributed video coding introduces a flexible architecture that enables the design of very low complex video encoders compared to its traditional counterparts. The main goal of our work is to generate at the decoder the side information that optimally blends temporal and interview data. Multi-view distributed coding performance strongly depends on the side information quality built at the decoder. At this aim for improving its quality a spatial view compensation/prediction in Zernike moments domain is applied. Spatial and temporal motion activity have been fused together to obtain the overall side-information. The proposed method has been evaluated by rate-distortion performances for different inter-view and temporal estimation quality conditions.

Feasibility study of a synthesis procedure for array feeds to improve radiation performance of large distorted reflector antennas

NASA Technical Reports Server (NTRS)

Stutzman, W. L.; Takamizawa, K.; Werntz, P.; Lapean, J.; Barts, R.; Shen, B.; Dunn, D.

1992-01-01

The topics covered include the following: (1) performance analysis of the Gregorian tri-reflector; (2) design and performance of the type 6 reflector antenna; (3) a new spherical main reflector system design; (4) optimization of reflector configurations using physical optics; (5) radiometric array design; and (7) beam efficiency studies.

A Study on CPH and Debate Summary in FLL

ERIC Educational Resources Information Center

Liu, Zhiliang

2009-01-01

The optimal age in FLL (foreign language learning) for children has been discussed over 50 years but there is no satisfactory conclusion for us. However, the notion "the younger, the better" in FLL has a big market in the world. As a result, the distorted hypothesis is being spread widely as a true and complete theory. Specifically…

Optimizing the Experience of Flow for Adults with Aphasia: A Focus on Environmental Factors

ERIC Educational Resources Information Center

Sather, Thomas W.; Howe, Tami; Nelson, Nickola Wolf; Lagerwey, Mary

2017-01-01

Flow has been described as positive experiences of intense concentration, distorted time passage, and a loss of self-consciousness that result from matching task difficulty to a person's skill level. It has been studied in many different populations and has been associated with a number of positive outcomes, including improved life satisfaction…

Wavefront Reconstruction and Mirror Surface Optimizationfor Adaptive Optics

DTIC Science & Technology

2014-06-01

TERMS Wavefront reconstruction, Adaptive optics , Wavelets, Atmospheric turbulence , Branch points, Mirror surface optimization, Space telescope, Segmented...contribution adapts the proposed algorithm to work when branch points are present from significant atmospheric turbulence . An analysis of vector spaces...estimate the distortion of the collected light caused by the atmosphere and corrected by adaptive optics . A generalized orthogonal wavelet wavefront

Optimization of white matter tractography for pre-surgical planning and image-guided surgery.

PubMed

Arfanakis, Konstantinos; Gui, Minzhi; Lazar, Mariana

2006-01-01

Accurate localization of white matter fiber tracts in relation to brain tumors is a goal of critical importance to the neurosurgical community. White matter fiber tractography by means of diffusion tensor magnetic resonance imaging (DTI) is the only non-invasive method that can provide estimates of brain connectivity. However, conventional tractography methods are based on data acquisition techniques that suffer from image distortions and artifacts. Thus, a large percentage of white matter fiber bundles are distorted, and/or terminated early, while others are completely undetected. This severely limits the potential of fiber tractography in pre-surgical planning and image-guided surgery. In contrast, Turboprop-DTI is a technique that provides images with significantly fewer distortions and artifacts than conventional DTI data acquisition methods. The purpose of this study was to evaluate fiber tracking results obtained from Turboprop-DTI data. It was demonstrated that Turboprop may be a more appropriate DTI data acquisition technique for tracing white matter fibers than conventional DTI methods, especially in applications such as pre-surgical planning and image-guided surgery.

Shape Classification Using Wasserstein Distance for Brain Morphometry Analysis.

PubMed

Su, Zhengyu; Zeng, Wei; Wang, Yalin; Lu, Zhong-Lin; Gu, Xianfeng

2015-01-01

Brain morphometry study plays a fundamental role in medical imaging analysis and diagnosis. This work proposes a novel framework for brain cortical surface classification using Wasserstein distance, based on uniformization theory and Riemannian optimal mass transport theory. By Poincare uniformization theorem, all shapes can be conformally deformed to one of the three canonical spaces: the unit sphere, the Euclidean plane or the hyperbolic plane. The uniformization map will distort the surface area elements. The area-distortion factor gives a probability measure on the canonical uniformization space. All the probability measures on a Riemannian manifold form the Wasserstein space. Given any 2 probability measures, there is a unique optimal mass transport map between them, the transportation cost defines the Wasserstein distance between them. Wasserstein distance gives a Riemannian metric for the Wasserstein space. It intrinsically measures the dissimilarities between shapes and thus has the potential for shape classification. To the best of our knowledge, this is the first. work to introduce the optimal mass transport map to general Riemannian manifolds. The method is based on geodesic power Voronoi diagram. Comparing to the conventional methods, our approach solely depends on Riemannian metrics and is invariant under rigid motions and scalings, thus it intrinsically measures shape distance. Experimental results on classifying brain cortical surfaces with different intelligence quotients demonstrated the efficiency and efficacy of our method.

Shape Classification Using Wasserstein Distance for Brain Morphometry Analysis

PubMed Central

Su, Zhengyu; Zeng, Wei; Wang, Yalin; Lu, Zhong-Lin; Gu, Xianfeng

2015-01-01

Brain morphometry study plays a fundamental role in medical imaging analysis and diagnosis. This work proposes a novel framework for brain cortical surface classification using Wasserstein distance, based on uniformization theory and Riemannian optimal mass transport theory. By Poincare uniformization theorem, all shapes can be conformally deformed to one of the three canonical spaces: the unit sphere, the Euclidean plane or the hyperbolic plane. The uniformization map will distort the surface area elements. The area-distortion factor gives a probability measure on the canonical uniformization space. All the probability measures on a Riemannian manifold form the Wasserstein space. Given any 2 probability measures, there is a unique optimal mass transport map between them, the transportation cost defines the Wasserstein distance between them. Wasserstein distance gives a Riemannian metric for the Wasserstein space. It intrinsically measures the dissimilarities between shapes and thus has the potential for shape classification. To the best of our knowledge, this is the first work to introduce the optimal mass transport map to general Riemannian manifolds. The method is based on geodesic power Voronoi diagram. Comparing to the conventional methods, our approach solely depends on Riemannian metrics and is invariant under rigid motions and scalings, thus it intrinsically measures shape distance. Experimental results on classifying brain cortical surfaces with different intelligence quotients demonstrated the efficiency and efficacy of our method. PMID:26221691

Painful stimulation and transient blocking of nerve transduction due to local anesthesia evoke perceptual distortions of the face in healthy volunteers.

PubMed

Skyt, Ina; Dagsdóttir, Lilja; Vase, Lene; Baad-Hansen, Lene; Castrillon, Eduardo; Roepstorff, Andreas; Jensen, Troels Staehelin; Svensson, Peter

2015-04-01

Anecdotally, orofacial pain patients sometimes report that the painful face area feels "swollen." Because there are no clinical signs of swelling, such illusions may represent perceptual distortions. In this study, we examine whether nociceptive stimulation can lead to perceptual distortion of the face in a way similar to that of local anesthesia. Sixteen healthy participants received injections of .4 mL hypertonic saline to induce short-term nociceptive stimulation, .4 mL mepivacaine (local anesthetic) to transiently block nerve transduction, and .4 mL isotonic saline as a control condition. Injections were administered in both the infraorbital and the mental nerve regions. Perceptual distortions were conceptualized as perceived changes in magnitude of the injected areas and the lips, and they were measured using 1) a verbal subjective rating scale and 2) a warping procedure. Prior to the study, participants filled in several psychological questionnaires. This study shows that both nociceptive stimulation (P < .05) and transient blocking of nerve transduction (P < .05) can lead to perceptual distortion of the face. A test-retest experiment including 9 new healthy subjects supported the results. Perceptual distortions were positively correlated with the psychological variable of dissociation in several conditions (P < .05). Perceptual distortions may therefore be influenced by somatosensory changes and psychological mechanisms. Knowledge of the factors that influence the perception of the face is important to understand the possible implications of perceptual distortions in orofacial pain disorders (and possibly other chronic pain states). Such information may ultimately open up new avenues of treatment for persistent orofacial pain. Copyright © 2015 American Pain Society. Published by Elsevier Inc. All rights reserved.

Functional modulation of a protein folding landscape via side-chain distortion

PubMed Central

Kelch, Brian A.; Salimi, Neema L.; Agard, David A.

2012-01-01

Ultrahigh-resolution (< 1.0 Å) structures have revealed unprecedented and unexpected details of molecular geometry, such as the deformation of aromatic rings from planarity. However, the functional utility of such energetically costly strain is unknown. The 0.83 Å structure of α-lytic protease (αLP) indicated that residues surrounding a conserved Phe side-chain dictate a rotamer which results in a ∼6° distortion along the side-chain, estimated to cost 4 kcal/mol. By contrast, in the closely related protease Streptomyces griseus Protease B (SGPB), the equivalent Phe adopts a different rotamer and is undistorted. Here, we report that the αLP Phe side-chain distortion is both functional and conserved in proteases with large pro regions. Sequence analysis of the αLP serine protease family reveals a bifurcation separating those sequences expected to induce distortion and those that would not, which correlates with the extent of kinetic stability. Structural and folding kinetics analyses of family members suggest that distortion of this side-chain plays a role in increasing kinetic stability within the αLP family members that use a large Pro region. Additionally, structural and kinetic folding studies of mutants demonstrate that strain alters the folding free energy landscape by destabilizing the transition state (TS) relative to the native state (N). Although side-chain distortion comes at a cost of foldability, it suppresses the rate of unfolding, thereby enhancing kinetic stability and increasing protein longevity under harsh extracellular conditions. This ability of a structural distortion to enhance function is unlikely to be unique to αLP family members and may be relevant in other proteins exhibiting side-chain distortions. PMID:22635267

Doping effects on structural and magnetic properties of Heusler alloys Fe2Cr1-xCoxSi

NASA Astrophysics Data System (ADS)

Liu, Yifan; Ren, Lizhu; Zheng, Yuhong; He, Shikun; Liu, Yang; Yang, Ping; Yang, Hyunsoo; Teo, Kie Leong

2018-05-01

In this work, 30nm Fe2Cr1-xCoxSi (FCCS) magnetic films were deposited on Cr buffered MgO (100) substrates by sputtering. Fe2Cr0.5Co0.5Si exhibits the largest magnetization and optimal ordered L21 cubic structure at in-situ annealing temperature (Tia) of 450°C. The Co composition dependence of crystalline structures, surface morphology, defects, lattice distortions and their correlation with the magnetic properties are analyzed in detail. The Co-doped samples show in-plane M-H loops with magnetic squareness ratio of 1 and increasing anisotropy energy density with Co composition. Appropriate Co doping composition promotes L21 phase but higher Co composition converts L21 to B2 phase. Doping effect and lattice mismatch both are proved to increase the defect density. In addition, distortions of the FCCS lattice are found to be approximately linear with Co composition. The largest lattice distortion (c/a) is 0.969 for Fe2Cr0.25Co0.75Si and the smallest is 0.983 for Fe2CrSi. Our analyses suggest that these tetragonal distortions mainly induced by an elastic stress from Cr buffer account for the large in-plane anisotropy energy. This work paves the way for further tailoring the magnetic and structural properties of quaternary Heusler alloys.

Optimization of the axial compressor flow passage to reduce the circumferential distortion

NASA Astrophysics Data System (ADS)

Popov, G.; Kolmakova, D.; Shklovets, A.; Ermakov, A.

2015-08-01

This work is motivated by the necessity to reduce the effects of the flow circumferential distortion in the flow passage of the aircraft gas turbine engine (GTE). In previous research, the authors have proposed the approaches to decrease of the flow circumferential distortion arising from the mid-support racks of GTE compressor and having a negative impact on the blade rows, located upstream. In particular, the idea of introducing the circumferentially non-uniform blade pitch and profile stagger angle of guide vanes located in front of the support was contributed in order to redistribute the flow and decrease the dynamic stresses in the rotor wheel of the same stage. During the research presented in this paper, another principal of reduction of the flow circumferential distortion was chosen. Firstly, the variants of upgrading the existing support racks were found. Secondly, the new design of support was offered. Both the first and the second version of the support design variation took into account the availability of technological and structural limitations associated with the location of oil pipes, springs and others elements in the support racks. Investigations of modified design showed that the support with altered racks provides a reduction of dynamic stresses by 20% at resonance with the most dangerous harmonic, and the new design of support can give the decrease of 30%.

Effect of fibroids not distorting the endometrial cavity on the outcome of in vitro fertilization treatment: a retrospective cohort study.

PubMed

Yan, Lei; Ding, Lingling; Li, Chunyan; Wang, Yu; Tang, Rong; Chen, Zi-Jiang

2014-03-01

To investigate the effect of fibroids that do not distort the endometrial cavity on IVF/intracytoplasmic sperm injection (ICSI) outcomes and to identify certain fibroid subgroups that may be deleterious to fertility outcomes. Retrospective cohort study. University-based reproductive medicine center. A total of 10,268 patients undergoing IVF/ICSI between 2009 and 2011 in our unit. Transvaginal ultrasound and hysteroscopy; controlled ovarian hyperstimulation and IVF/ICSI; strict matching criteria. Cycle cancellation, clinical pregnancy, miscarriage, and delivery rates. We included 249 patients with fibroids who underwent IVF/ICSI. Higher day 3 FSH levels were found in women with fibroids compared with in control subjects. No significant differences were found in IVF/ICSI outcomes between the two groups. Patients with intramural fibroids with the largest diameter <2.85 cm or the sum of reported diameters <2.95 cm had a significantly higher delivery rate than patients with larger fibroids. A significant negative effect on delivery rate was noted when intramural fibroids with the largest diameter greater than 2.85 cm were considered, compared with matched controls without fibroids. Our results suggest that although non-cavity-distorting fibroids do not affect IVF/ICSI outcomes, intramural fibroids greater than 2.85 cm in size significantly impair the delivery rate of patients undergoing IVF/ICSI. Copyright © 2014 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

Optimized Controller Design for a 12-Pulse Voltage Source Converter Based HVDC System

NASA Astrophysics Data System (ADS)

Agarwal, Ruchi; Singh, Sanjeev

2017-12-01

The paper proposes an optimized controller design scheme for power quality improvement in 12-pulse voltage source converter based high voltage direct current system. The proposed scheme is hybrid combination of golden section search and successive linear search method. The paper aims at reduction of current sensor and optimization of controller. The voltage and current controller parameters are selected for optimization due to its impact on power quality. The proposed algorithm for controller optimizes the objective function which is composed of current harmonic distortion, power factor, and DC voltage ripples. The detailed designs and modeling of the complete system are discussed and its simulation is carried out in MATLAB-Simulink environment. The obtained results are presented to demonstrate the effectiveness of the proposed scheme under different transient conditions such as load perturbation, non-linear load condition, voltage sag condition, and tapped load fault under one phase open condition at both points-of-common coupling.

Constellation labeling optimization for bit-interleaved coded APSK

NASA Astrophysics Data System (ADS)

Xiang, Xingyu; Mo, Zijian; Wang, Zhonghai; Pham, Khanh; Blasch, Erik; Chen, Genshe

2016-05-01

This paper investigates the constellation and mapping optimization for amplitude phase shift keying (APSK) modulation, which is deployed in Digital Video Broadcasting Satellite - Second Generation (DVB-S2) and Digital Video Broadcasting - Satellite services to Handhelds (DVB-SH) broadcasting standards due to its merits of power and spectral efficiency together with the robustness against nonlinear distortion. The mapping optimization is performed for 32-APSK according to combined cost functions related to Euclidean distance and mutual information. A Binary switching algorithm and its modified version are used to minimize the cost function and the estimated error between the original and received data. The optimized constellation mapping is tested by combining DVB-S2 standard Low-Density Parity-Check (LDPC) codes in both Bit-Interleaved Coded Modulation (BICM) and BICM with iterative decoding (BICM-ID) systems. The simulated results validate the proposed constellation labeling optimization scheme which yields better performance against conventional 32-APSK constellation defined in DVB-S2 standard.

Distortion products in auditory fMRI research: Measurements and solutions.

PubMed

Norman-Haignere, Sam; McDermott, Josh H

2016-04-01

Nonlinearities in the cochlea can introduce audio frequencies that are not present in the sound signal entering the ear. Known as distortion products (DPs), these added frequencies complicate the interpretation of auditory experiments. Sound production systems also introduce distortion via nonlinearities, a particular concern for fMRI research because the Sensimetrics earphones widely used for sound presentation are less linear than most high-end audio devices (due to design constraints). Here we describe the acoustic and neural effects of cochlear and earphone distortion in the context of fMRI studies of pitch perception, and discuss how their effects can be minimized with appropriate stimuli and masking noise. The amplitude of cochlear and Sensimetrics earphone DPs were measured for a large collection of harmonic stimuli to assess effects of level, frequency, and waveform amplitude. Cochlear DP amplitudes were highly sensitive to the absolute frequency of the DP, and were most prominent at frequencies below 300 Hz. Cochlear DPs could thus be effectively masked by low-frequency noise, as expected. Earphone DP amplitudes, in contrast, were highly sensitive to both stimulus and DP frequency (due to prominent resonances in the earphone's transfer function), and their levels grew more rapidly with increasing stimulus level than did cochlear DP amplitudes. As a result, earphone DP amplitudes often exceeded those of cochlear DPs. Using fMRI, we found that earphone DPs had a substantial effect on the response of pitch-sensitive cortical regions. In contrast, cochlear DPs had a small effect on cortical fMRI responses that did not reach statistical significance, consistent with their lower amplitudes. Based on these findings, we designed a set of pitch stimuli optimized for identifying pitch-responsive brain regions using fMRI. These stimuli robustly drive pitch-responsive brain regions while producing minimal cochlear and earphone distortion, and will hopefully aid fMRI researchers in avoiding distortion confounds. Copyright © 2016 Elsevier Inc. All rights reserved.

Distortion Products in Auditory fMRI Research: Measurements and Solutions

PubMed Central

Norman-Haignere, Sam; McDermott, Josh H.

2016-01-01

Nonlinearities in the cochlea can introduce audio frequencies that are not present in the sound signal entering the ear. Known as distortion products (DPs), these added frequencies complicate the interpretation of auditory experiments. Sound production systems also introduce distortion via nonlinearities, a particular concern for fMRI research because the Sensimetrics earphones widely used for sound presentation are less linear than most high-end audio devices (due to design constraints). Here we describe the acoustic and neural effects of cochlear and earphone distortion in the context of fMRI studies of pitch perception, and discuss how their effects can be minimized with appropriate stimuli and masking noise. The amplitude of cochlear and Sensimetrics earphone DPs were measured for a large collection of harmonic stimuli to assess effects of level, frequency, and waveform amplitude. Cochlear DP amplitudes were highly sensitive to the absolute frequency of the DP, and were most prominent at frequencies below 300 Hz. Cochlear DPs could thus be effectively masked by low-frequency noise, as expected. Earphone DP amplitudes, in contrast, were highly sensitive to both stimulus and DP frequency (due to prominent resonances in the earphone’s transfer function), and their levels grew more rapidly with increasing stimulus level than did cochlear DP amplitudes. As a result, earphone DP amplitudes often exceeded those of cochlear DPs. Using fMRI, we found that earphone DPs had a substantial effect on the response of pitch-sensitive cortical regions. In contrast, cochlear DPs had a small effect on cortical fMRI responses that did not reach statistical significance, consistent with their lower amplitudes. Based on these findings, we designed a set of pitch stimuli optimized for identifying pitch-responsive brain regions using fMRI. These stimuli robustly drive pitch-responsive brain regions while producing minimal cochlear and earphone distortion, and will hopefully aid fMRI researchers in avoiding distortion confounds. PMID:26827809

Stereotactic radiosurgery planning of vestibular schwannomas: Is MRI at 3 Tesla geometrically accurate?

PubMed

Schmidt, M A; Wells, E J; Davison, K; Riddell, A M; Welsh, L; Saran, F

2017-02-01

MRI is a mandatory requirement to accurately plan Stereotactic Radiosurgery (SRS) for Vestibular Schwannomas. However, MRI may be distorted due not only to inhomogeneity of the static magnetic field and gradients but also due to susceptibility-induced effects, which are more prominent at higher magnetic fields. We assess geometrical distortions around air spaces and consider MRI protocol requirements for SRS planning at 3 T. Hardware-related distortion and the effect of incorrect shimming were investigated with structured test objects. The magnetic field was mapped over the head on five volunteers to assess susceptibility-related distortion in the naso-oro-pharyngeal cavities (NOPC) and around the internal ear canal (IAC). Hardware-related geometric displacements were found to be less than 0.45 mm within the head volume, after distortion correction. Shimming errors can lead to displacements of up to 4 mm, but errors of this magnitude are unlikely to arise in practice. Susceptibility-related field inhomogeneity was under 3.4 ppm, 2.8 ppm, and 2.7 ppm for the head, NOPC region and IAC region, respectively. For the SRS planning protocol (890 Hz/pixel, approximately 1 mm 3 isotropic), susceptibility-related displacements were less than 0.5 mm (head), and 0.4 mm (IAC and NOPC). Large displacements are possible in MRI examinations undertaken with lower receiver bandwidth values, commonly used in clinical MRI. Higher receiver bandwidth makes the protocol less vulnerable to sub-optimal shimming. The shimming volume and the CT-MR co-registration must be considered jointly. Geometric displacements can be kept under 1 mm in the vicinity of air spaces within the head at 3 T with appropriate setting of the receiver bandwidth, correct shimming and employing distortion correction. © 2017 The Authors. Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Prospects for measuring cosmic microwave background spectral distortions in the presence of foregrounds

NASA Astrophysics Data System (ADS)

Abitbol, Maximilian H.; Chluba, Jens; Hill, J. Colin; Johnson, Bradley R.

2017-10-01

Measurements of cosmic microwave background (CMB) spectral distortions have profound implications for our understanding of physical processes taking place over a vast window in cosmological history. Foreground contamination is unavoidable in such measurements and detailed signal-foreground separation will be necessary to extract cosmological science. In this paper, we present Markov chain Monte Carlo based spectral distortion detection forecasts in the presence of Galactic and extragalactic foregrounds for a range of possible experimental configurations, focusing on the Primordial Inflation Explorer (PIXIE) as a fiducial concept. We consider modifications to the baseline PIXIE mission (operating ≃ 12 months in distortion mode), searching for optimal configurations using a Fisher approach. Using only spectral information, we forecast an extended PIXIE mission to detect the expected average non-relativistic and relativistic thermal Sunyaev-Zeldovich distortions at high significance (194σ and 11σ, respectively), even in the presence of foregrounds. The ΛCDM Silk damping μ-type distortion is not detected without additional modifications of the instrument or external data. Galactic synchrotron radiation is the most problematic source of contamination in this respect, an issue that could be mitigated by combining PIXIE data with future ground-based observations at low frequencies (ν ≲ 15-30 GHz). Assuming moderate external information on the synchrotron spectrum, we project an upper limit of |μ| < 3.6 × 10-7 (95 per cent c.l.), slightly more than one order of magnitude above the fiducial ΛCDM signal from the damping of small-scale primordial fluctuations, but a factor of ≃250 improvement over the current upper limit from COBE/Far Infrared Absolute Spectrophotometer. This limit could be further reduced to |μ| < 9.4 × 10-8 (95 per cent c.l.) with more optimistic assumptions about extra low-frequency information and would rule out many alternative inflation models and provide new constraints on decaying particle scenarios.

Comparison of Engine/Inlet Distortion Measurements with MEMS and ESP Pressure Sensors

NASA Technical Reports Server (NTRS)

Soto, Hector L.; Hernandez, Corey D.

2004-01-01

A study of active-flow control in a small-scale boundary layer ingestion inlet was conducted at the NASA Langley Basic Aerodynamic Research Tunnel (BART). Forty MEMS pressure sensors, in a rake style configuration, were used to examine both the mean (DC) and high frequency (AC) components of the total pressure across the inlet/engine interface plane. The mean component was acquired and used to calculate pressure distortion. The AC component was acquired separately, at a high sampling rate, and is used to study the unsteady effects of the active-flow control. An identical total pressure rake, utilizing an Electronically Scanned Pressure (ESP) system, was also used to calculate distortion; a comparison of the results obtained using the two rakes is presented.

Frequency shifts in distortion-product otoacoustic emissions evoked by swept tones

PubMed Central

Shera, Christopher A.; Abdala, Carolina

2016-01-01

When distortion-product otoacoustic emissions (DPOAEs) are evoked using stimuli whose instantaneous frequencies change rapidly and continuously with time (swept tones), the oscillatory interference pattern known as distortion-product fine structure shifts slightly along the frequency axis in the same direction as the sweep. By analogy with the temporal mechanisms thought to underlie the differing efficacies of up- and down-swept stimuli as perceptual maskers (e.g., Schroeder-phase complexes), fine-structure shifts have been ascribed to the phase distortion associated with dispersive wave propagation in the cochlea. This paper tests an alternative hypothesis and finds that the observed shifts arise predominantly as a methodological side effect of the analysis procedures commonly used to extract delayed emissions from the measured time waveform. Approximate expressions for the frequency shifts of DPOAE distortion and reflection components are derived, validated with computer simulations, and applied to account for DPOAE fine-structure shifts measured in human subjects. Component magnitudes are shown to shift twice as much as component phases. Procedures for compensating swept-tone measurements to obtain estimates of the total DPOAE and its components measured at other sweep rates or in the sinusoidal steady state are presented. PMID:27586726

Pulsed Power Bibliography. Volume 1. Indices.

DTIC Science & Technology

1983-08-01

REPETITION RATES «e»7 A 100 KV, FAST, HIGH EHEROY. NONUNIFORM FIELD DISTORTION SWITCH MM CROWBARRIHO TECHNIGUE FOR HIGH-VOLTAGE CAPACITOR SAHKS...EMISSION IN THE ELECTRICAL EXPLOSION OF A THIH METAL FOIL • lair , O.T.A. 427) STATISTICAL TIME LAOS IN GAS DISCHARGE GAPS IRRADIATED WITH A...7 A 111 KV. FAST. HIGH ENERGY, NONUNIFORM FIELD DISTORTION SWITCH MM A 3 MA. ill KV FAST CAPACITOR IANK FOR A SHOCK-HEATED TORUS 7217 A LOW

Cross-Layer Resource Allocation for Wireless Visual Sensor Networks and Mobile Ad Hoc Networks

DTIC Science & Technology

2014-10-01

MMD), minimizes the maximum dis- tortion among all nodes of the network, promoting a rather unbiased treatment of the nodes. We employed the Particle...achieve the ideal tradeoff between the transmitted video quality and energy consumption. Each sensor node has a bit rate that can be used for both...Distortion (MMD), minimizes the maximum distortion among all nodes of the network, promoting a rather unbiased treatment of the nodes. For both criteria

Effects of bending-torsional duct-induced swirl distortion on aerodynamic performance of a centrifugal compressor

NASA Astrophysics Data System (ADS)

Hou, Hongjuan; Wang, Leilei; Wang, Rui; Yang, Yanzhao

2017-04-01

A turbocharger compressor working in commercial vehicles, especially in some passenger cars, often works together with some pipes with complicated geometry as an air intake system, due to limit of available space in internal combustion engine compartments. These pipes may generate various distortions of physical parameters of the air at the inlet of the compressor and therefore the compressor aerodynamic performance deteriorates. Sometimes, the turbocharging engine fails to work at some operation points. This paper investigates the effects of various swirl distortions induced by different bending-torsional intake ducts on the aerodynamic performance of a turbocharger compressor by both 3D numerical simulations and experimental measurements. It was found that at the outlet of the pipes the different inlet ducts can generate different swirl distortions, twin vortices and bulk-like vortices with different rotating directions. Among them, the bulk-like vortices not only affect seriously the pressure distribution in the impeller domain, but also significantly deteriorate the compressor performance, especially at high flow rate region. And the rotating direction of the bulk-like vortices is also closely associated with the efficiency penalty. Besides the efficiency, the transient flow rate through a single impeller channel, or the asymmetric mass flow crossing the whole impeller, can be influenced by two disturbances. One is from the upstream bending-torsional ducts; other one is from the downstream volute.

Opto-Mechanical Analyses for Performance Optimization of Lightweight Grazing-Incidence Mirrors

NASA Technical Reports Server (NTRS)

Roche, Jacqueline; Kolodziejczak, Jeff; Odell, Steve; Eisner, Ronald; Ramsey, Brian; Gubarev, Mikhail

2013-01-01

New technology in grazing-incidence mirror fabrication and assembly is necessary to achieve sub-arcsecond optics for large-area x-ray telescopes. In order to define specifications, an understanding of performance sensitivity to design parameters is crucial. MSFC is undertaking a systematic study to specify a mounting approach, mirror substrate, and testing method. Because the lightweight mirrors are typically flimsy, they are susceptible to significant distortion due to mounting and gravitational forces. Material properties of the mirror substrate along with its thickness and dimensions significantly affect the distortions caused by mounting and gravity. A parametric study of these properties and their relationship to mounting and testing schemes will indicate specifications for the design of the next generation of lightweight grazing-incidence mirrors. Initial results will be reported.

Opto-mechanical Analyses for Performance Optimization of Lightweight Grazing-incidence Mirrors

NASA Technical Reports Server (NTRS)

Roche, Jacqueline M.; Kolodziejczak, Jeffery J.; Odell, Stephen L.; Elsner, Ronald F.; Weisskopf, Martin C.; Ramsey, Brian; Gubarev, Mikhail V.

2013-01-01

New technology in grazing-incidence mirror fabrication and assembly is necessary to achieve subarcsecond optics for large-area x-ray telescopes. In order to define specifications, an understanding of performance sensitivity to design parameters is crucial. MSFC is undertaking a systematic study to specify a mounting approach, mirror substrate, and testing method. Lightweight mirrors are typically flimsy and are, therefore, susceptible to significant distortion due to mounting and gravitational forces. Material properties of the mirror substrate along with its dimensions significantly affect the distortions caused by mounting and gravity. A parametric study of these properties and their relationship to mounting and testing schemes will indicate specifications for the design of the next generation of lightweight grazing-incidence mirrors. Here we report initial results of this study.

Opto-mechanical Analyses for Performance Optimization of Lightweight Grazing-incidence Mirrors

NASA Technical Reports Server (NTRS)

Roche, Jacqueline; Kolodsiejczak, Jeffrey; Odell, Stephen; Elsner, Ronald; Weisskopf, Martin; Ramsey, Brian; Gubarev, Mikhail

2013-01-01

New technology in grazing-incidence mirror fabrication and assembly is necessary to achieve sub-arcsecond optics for large-area x-ray telescopes. In order to define specifications, an understanding of performance sensitivity to design parameters is crucial. MSFC is undertaking a systematic study to specify a mounting approach, mirror substrate, and testing method. Because the lightweight mirrors are typically flimsy, they are susceptible to significant distortion due to mounting and gravitational forces. Material properties of the mirror substrate along with its thickness and dimensions significantly affect the distortions caused by mounting and gravity. A parametric study of these properties and their relationship to mounting and testing schemes will indicate specifications for the design of the next generation of lightweight grazing-incidence mirrors. Initial results will be reported.

Worst case encoder-decoder policies for a communication system in the presence of an unknown probabilistic jammer

NASA Astrophysics Data System (ADS)

Cascio, David M.

1988-05-01

States of nature or observed data are often stochastically modelled as Gaussian random variables. At times it is desirable to transmit this information from a source to a destination with minimal distortion. Complicating this objective is the possible presence of an adversary attempting to disrupt this communication. In this report, solutions are provided to a class of minimax and maximin decision problems, which involve the transmission of a Gaussian random variable over a communications channel corrupted by both additive Gaussian noise and probabilistic jamming noise. The jamming noise is termed probabilistic in the sense that with nonzero probability 1-P, the jamming noise is prevented from corrupting the channel. We shall seek to obtain optimal linear encoder-decoder policies which minimize given quadratic distortion measures.

Effect of quantum well position on the distortion characteristics of transistor laser

NASA Astrophysics Data System (ADS)

Piramasubramanian, S.; Ganesh Madhan, M.; Radha, V.; Shajithaparveen, S. M. S.; Nivetha, G.

2018-05-01

The effect of quantum well position on the modulation and distortion characteristics of a 1300 nm transistor laser is analyzed in this paper. Standard three level rate equations are numerically solved to study this characteristics. Modulation depth, second order harmonic and third order intermodulation distortion of the transistor laser are evaluated for different quantum well positions for a 900 MHz RF signal modulation. From the DC analysis, it is observed that optical power is maximum, when the quantum well is positioned near base-emitter interface. The threshold current of the device is found to increase with increasing the distance between the quantum well and the base-emitter junction. A maximum modulation depth of 0.81 is predicted, when the quantum well is placed at 10 nm from the base-emitter junction, under RF modulation. The magnitude of harmonic and intermodulation distortion are found to decrease with increasing current and with an increase in quantum well distance from the emitter base junction. A minimum second harmonic distortion magnitude of -25.96 dBc is predicted for quantum well position (230 nm) near to the base-collector interface for 900 MHz modulation frequency at a bias current of 20 Ibth. Similarly, a minimum third order intermodulation distortion of -38.2 dBc is obtained for the same position and similar biasing conditions.

Forecasting of magnitude and duration of currency crises based on the analysis of distortions of fractal scaling in exchange rate fluctuations

NASA Astrophysics Data System (ADS)

Uritskaya, Olga Y.

2005-05-01

Results of fractal stability analysis of daily exchange rate fluctuations of more than 30 floating currencies for a 10-year period are presented. It is shown for the first time that small- and large-scale dynamical instabilities of national monetary systems correlate with deviations of the detrended fluctuation analysis (DFA) exponent from the value 1.5 predicted by the efficient market hypothesis. The observed dependence is used for classification of long-term stability of floating exchange rates as well as for revealing various forms of distortion of stable currency dynamics prior to large-scale crises. A normal range of DFA exponents consistent with crisis-free long-term exchange rate fluctuations is determined, and several typical scenarios of unstable currency dynamics with DFA exponents fluctuating beyond the normal range are identified. It is shown that monetary crashes are usually preceded by prolonged periods of abnormal (decreased or increased) DFA exponent, with the after-crash exponent tending to the value 1.5 indicating a more reliable exchange rate dynamics. Statistically significant regression relations (R=0.99, p<0.01) between duration and magnitude of currency crises and the degree of distortion of monofractal patterns of exchange rate dynamics are found. It is demonstrated that the parameters of these relations characterizing small- and large-scale crises are nearly equal, which implies a common instability mechanism underlying these events. The obtained dependences have been used as a basic ingredient of a forecasting technique which provided correct in-sample predictions of monetary crisis magnitude and duration over various time scales. The developed technique can be recommended for real-time monitoring of dynamical stability of floating exchange rate systems and creating advanced early-warning-system models for currency crisis prevention.

Spectral Re-Growth Reduction for CCSDS 8-D 8-PSK TCM

NASA Technical Reports Server (NTRS)

Borah, Deva K.

2002-01-01

This report presents a study on the CCSDS recommended 8-dimensional 8 PSK Trellis Coded Modulation (TCM) scheme. The important steps of the CCSDS scheme include: conversion of serial data into parallel form, differential encoding, convolutional encoding, constellation mapping, and filtering the 8-PSK symbols using the square root raised cosine (SRRC) pulses. The last step, namely the filtering of the 8 PSK symbols using SRRC pulses, significantly affects the bandwidth of the signal. If a nonlinear power amplifier is used, the SRRC filtered signal creates spectral regrowth. The purpose of this report is to investigate a technique, called the smooth phase interpolated keying (SPIK), that can provide an alternative to SRRC filtering so that good spectral as well as power efficiencies can be obtained with the CCSDS encoder. The results of this study show that the CCSDS encoder does not affect the spectral shape of the SRRC filtered signal or the SPIK signal. When a nonlinear traveling wave tube amplifier (TWTA) is used, the spectral performance of the SRRC signal degrades significantly while the spectral performance of SPIK remains unaffected. The degrading effect of a nonlinear solid state power amplifier (SSPA) on SRRC is found to be less than that due to a nonlinear TWTA. However, in both cases, the spectral performance of the SRRC modulated signal is worse than that of the SPIK signal. The bit error rate (BER) performance of the SRRC signal in a linear amplifier environment is about 2.5 dB better than that of the SPIK signal when both the receivers use algorithms of similar complexity. In a nonlinear TWTA environment, the SRRC signal requires accurate phase tracking since the TWTA introduces additional phase distortion. This problem does not arise with SPIK signal due to its constant envelope property. When a nonlinear amplifier is used, the SRRC method loses nearly 1 dB in the bit error rate performance. The SPIK signal does not lose any performance. Thus the performance gap between SRRC and SPIK reduces. The BER performance of SPIK can be improved even further by using a more optimal receiver. A similar optimal receiver for SRRC is quite complex since the amplifier distorts the pulse shape. However, this requires further investigation and is not covered in this report.

Communication and cooperation in underwater acoustic networks

NASA Astrophysics Data System (ADS)

Yerramalli, Srinivas

In this thesis, we present a study of several problems related to underwater point to point communications and network formation. We explore techniques to improve the achievable data rate on a point to point link using better physical layer techniques and then study sensor cooperation which improves the throughput and reliability in an underwater network. Robust point-to-point communications in underwater networks has become increasingly critical in several military and civilian applications related to underwater communications. We present several physical layer signaling and detection techniques tailored to the underwater channel model to improve the reliability of data detection. First, a simplified underwater channel model in which the time scale distortion on each path is assumed to be the same (single scale channel model in contrast to a more general multi scale model). A novel technique, which exploits the nature of OFDM signaling and the time scale distortion, called Partial FFT Demodulation is derived. It is observed that this new technique has some unique interference suppression properties and performs better than traditional equalizers in several scenarios of interest. Next, we consider the multi scale model for the underwater channel and assume that single scale processing is performed at the receiver. We then derive optimized front end pre-processing techniques to reduce the interference caused during single scale processing of signals transmitted on a multi-scale channel. We then propose an improvised channel estimation technique using dictionary optimization methods for compressive sensing and show that significant performance gains can be obtained using this technique. In the next part of this thesis, we consider the problem of sensor node cooperation among rational nodes whose objective is to improve their individual data rates. We first consider the problem of transmitter cooperation in a multiple access channel and investigate the stability of the grand coalition of transmitters using tools from cooperative game theory and show that the grand coalition in both the asymptotic regimes of high and low SNR. Towards studying the problem of receiver cooperation for a broadcast channel, we propose a game theoretic model for the broadcast channel and then derive a game theoretic duality between the multiple access and the broadcast channel and show that how the equilibria of the broadcast channel are related to the multiple access channel and vice versa.

Computational Evaluation of Inlet Distortion on an Ejector Powered Hybrid Wing Body at Takeoff and Landing Conditions

NASA Technical Reports Server (NTRS)

Tompkins, Daniel M.; Sexton, Matthew R.; Mugica, Edward A.; Beyar, Michael D.; Schuh, Michael J.; Stremel, Paul M.; Deere, Karen A.; McMillin, Naomi; Carter, Melissa B.

2016-01-01

Due to the aft, upper surface engine location on the Hybrid Wing Body (HWB) planform, there is potential to shed vorticity and separated wakes into the engine when the vehicle is operated at off-design conditions and corners of the envelope required for engine and airplane certification. CFD simulations were performed of the full-scale reference propulsion system, operating at a range of inlet flow rates, flight speeds, altitudes, angles of attack, and angles of sideslip to identify the conditions which produce the largest distortion and lowest pressure recovery. Pretest CFD was performed by NASA and Boeing, using multiple CFD codes, with various turbulence models. These data were used to make decisions regarding model integration, characterize inlet flow distortion patterns, and help define the wind tunnel test matrix. CFD was also performed post-test; when compared with test data, it was possible to make comparisons between measured model-scale and predicted full-scale distortion levels. This paper summarizes these CFD analyses.

Decreasing Distortion Energies without Strain: Diazo-Selective 1,3-Dipolar Cycloadditions.

PubMed

Gold, Brian; Aronoff, Matthew R; Raines, Ronald T

2016-07-15

The diazo group has attributes that complement those of the azido group for applications in chemical biology. Here, we use computational analyses to provide insights into the chemoselectivity of the diazo group in 1,3-dipolar cycloadditions. Dipole distortion energies are responsible for ∼80% of the overall energetic barrier for these reactions. Here, we show that diazo compounds, unlike azides, provide an opportunity to decrease that barrier substantially without introducing strain into the dipolarophile. The ensuing rate enhancement is due to the greater nucleophilic character of a diazo group compared to that of an azido group, which can accommodate decreased distortion energies without predistortion. The tuning of distortion energies with substituents in a diazo compound or dipolarophile can enhance reactivity and selectivity in a predictable manner. Notably, these advantages of diazo groups are amplified in water. Our findings provide a theoretical framework that can guide the design and application of both diazo compounds and azides in "orthogonal" contexts, especially for biological investigations.

Endogenous fertility, Ricardian equivalence, and debt management policy.

PubMed

Lapan, H E; Enders, W

1990-03-01

This paper develops a model in which dynastic families optimally determine fertility. Government debt represents a tax on future generations and on childbearing; the Ricardian Equivalence Hypothesis does not hold. Debt is welfare reducing in that it distorts the fertility decision. An increase in government debt induces a decline in fertility and an increase in the steady state capital/labor ratio. If a government inherits an existing stock of debt, the 1st-best policy is to eliminate the debt immediately. In other situations the optimal debt management policy will not, in general, entail a total elimination of the debt.

Vortex Generators in a Streamline-Traced, External-Compression Supersonic Inlet

NASA Technical Reports Server (NTRS)

Baydar, Ezgihan; Lu, Frank K.; Slater, John W.; Trefny, Charles J.

2017-01-01

Vortex generators within a streamline-traced, external-compression supersonic inlet for Mach 1.66 were investigated to determine their ability to increase total pressure recovery and reduce total pressure distortion. The vortex generators studied were rectangular vanes arranged in counter-rotating and co-rotating arrays. The vane geometric factors of interest included height, length, spacing, angle-of-incidence, and positions upstream and downstream of the inlet terminal shock. The flow through the inlet was simulated numerically through the solution of the steady-state, Reynolds-averaged Navier-Stokes equations on multi-block, structured grids using the Wind-US flow solver. The vanes were simulated using a vortex generator model. The inlet performance was characterized by the inlet total pressure recovery and the radial and circumferential total pressure distortion indices at the engine face. Design of experiments and statistical analysis methods were applied to quantify the effect of the geometric factors of the vanes and search for optimal vane arrays. Co-rotating vane arrays with negative angles-of-incidence positioned on the supersonic diffuser were effective in sweeping low-momentum flow from the top toward the sides of the subsonic diffuser. This distributed the low-momentum flow more evenly about the circumference of the subsonic diffuser and reduced distortion. Co-rotating vane arrays with negative angles-of-incidence or counter-rotating vane arrays positioned downstream of the terminal shock were effective in mixing higher-momentum flow with lower-momentum flow to increase recovery and decrease distortion. A strategy of combining a co-rotating vane array on the supersonic diffuser with a counter-rotating vane array on the subsonic diffuser was effective in increasing recovery and reducing distortion.

MATLAB Simulation of UPQC for Power Quality Mitigation Using an Ant Colony Based Fuzzy Control Technique

PubMed Central

Kumarasabapathy, N.; Manoharan, P. S.

2015-01-01

This paper proposes a fuzzy logic based new control scheme for the Unified Power Quality Conditioner (UPQC) for minimizing the voltage sag and total harmonic distortion in the distribution system consequently to improve the power quality. UPQC is a recent power electronic module which guarantees better power quality mitigation as it has both series-active and shunt-active power filters (APFs). The fuzzy logic controller has recently attracted a great deal of attention and possesses conceptually the quality of the simplicity by tackling complex systems with vagueness and ambiguity. In this research, the fuzzy logic controller is utilized for the generation of reference signal controlling the UPQC. To enable this, a systematic approach for creating the fuzzy membership functions is carried out by using an ant colony optimization technique for optimal fuzzy logic control. An exhaustive simulation study using the MATLAB/Simulink is carried out to investigate and demonstrate the performance of the proposed fuzzy logic controller and the simulation results are compared with the PI controller in terms of its performance in improving the power quality by minimizing the voltage sag and total harmonic distortion. PMID:26504895

Sitting in the Pilot's Seat; Optimizing Human-Systems Interfaces for Unmanned Aerial Vehicles

NASA Technical Reports Server (NTRS)

Queen, Steven M.; Sanner, Kurt Gregory

2011-01-01

One of the pilot-machine interfaces (the forward viewing camera display) for an Unmanned Aerial Vehicle called the DROID (Dryden Remotely Operated Integrated Drone) will be analyzed for optimization. The goal is to create a visual display for the pilot that as closely resembles an out-the-window view as possible. There are currently no standard guidelines for designing pilot-machine interfaces for UAVs. Typically, UAV camera views have a narrow field, which limits the situational awareness (SA) of the pilot. Also, at this time, pilot-UAV interfaces often use displays that have a diagonal length of around 20". Using a small display may result in a distorted and disproportional view for UAV pilots. Making use of a larger display and a camera lens with a wider field of view may minimize the occurrences of pilot error associated with the inability to see "out the window" as in a manned airplane. It is predicted that the pilot will have a less distorted view of the DROID s surroundings, quicker response times and more stable vehicle control. If the experimental results validate this concept, other UAV pilot-machine interfaces will be improved with this design methodology.

Using pre-distorted PAM-4 signal and parallel resistance circuit to enhance the passive solar cell based visible light communication

NASA Astrophysics Data System (ADS)

Wang, Hao-Yu; Wu, Jhao-Ting; Chow, Chi-Wai; Liu, Yang; Yeh, Chien-Hung; Liao, Xin-Lan; Lin, Kun-Hsien; Wu, Wei-Liang; Chen, Yi-Yuan

2018-01-01

Using solar cell (or photovoltaic cell) for visible light communication (VLC) is attractive. Apart from acting as a VLC receiver (Rx), the solar cell can provide energy harvesting. This can be used in self-powered smart devices, particularly in the emerging ;Internet of Things (IoT); networks. Here, we propose and demonstrate for the first time using pre-distortion pulse-amplitude-modulation (PAM)-4 signal and parallel resistance circuit to enhance the transmission performance of solar cell Rx based VLC. Pre-distortion is a simple non-adaptive equalization technique that can significantly mitigate the slow charging and discharging of the solar cell. The equivalent circuit model of the solar cell and the operation of using parallel resistance to increase the bandwidth of the solar cell are discussed. By using the proposed schemes, the experimental results show that the data rate of the solar cell Rx based VLC can increase from 20 kbit/s to 1.25 Mbit/s (about 60 times) with the bit error-rate (BER) satisfying the 7% forward error correction (FEC) limit.

Family Typology and Appraisal of Preschoolers' Behavior by Female Caregivers.

PubMed

Coke, Sallie P; Moore, Leslie C

2015-01-01

Children with vulnerable caregivers may be at risk for being labeled as having behavior problems when typical behaviors are viewed by their caregivers as problematic, and therefore, research examining the accuracy of the caregivers' perceptions of children's behaviors is needed. The purpose of this study was to use the resiliency model of family stress, adjustment, and adaptation as the theoretical foundation to explore family factors associated with the primary female caregiver's appraisal of her child's behavior, the extent to which the primary female caregiver's appraisal of her child's behavior may be distorted, and the child's level of risk of having a behavioral problem. A cross-sectional, correlational design was used. Data were collected from female caregivers of preschoolers (N = 117). Family factors, demographic characteristics, comfort in parenting, appraisal of behaviors, daily stress, parenting stress, depressive symptoms, social support, ratings of children's behaviors, and distortion in the ratings were measured. Associations were studied using ANOVA, ANCOVA, and chi-squared tests. Family typology was not associated with the female caregiver's appraisals of her child's behavior (p = .31). Distortion of the caregiver's rating of her child's behavior was not associated with family hardiness (high or low; p = .20.) but was associated with having a child with an elevated risk for behavioral problems (p < .01). Families classified as vulnerable were significantly more likely to have a child with elevated risks of having behavioral problems than families classified as secure or regenerative. Findings emphasized the association between family factors (hardiness and coherence) and young children's behaviors. Additional research is needed into how these factors affect the young child's behavior and what causes a caregiver to have a distorted view of her child's behavior.

Harmonic Optimization in Voltage Source Inverter for PV Application using Heuristic Algorithms

NASA Astrophysics Data System (ADS)

Kandil, Shaimaa A.; Ali, A. A.; El Samahy, Adel; Wasfi, Sherif M.; Malik, O. P.

2016-12-01

Selective Harmonic Elimination (SHE) technique is the fundamental switching frequency scheme that is used to eliminate specific order harmonics. Its application to minimize low order harmonics in a three level inverter is proposed in this paper. The modulation strategy used here is SHEPWM and the nonlinear equations, that characterize the low order harmonics, are solved using Harmony Search Algorithm (HSA) to obtain the optimal switching angles that minimize the required harmonics and maintain the fundamental at the desired value. Total Harmonic Distortion (THD) of the output voltage is minimized maintaining selected harmonics within allowable limits. A comparison has been drawn between HSA, Genetic Algorithm (GA) and Newton Raphson (NR) technique using MATLAB software to determine the effectiveness of getting optimized switching angles.

Channel modeling, signal processing and coding for perpendicular magnetic recording

NASA Astrophysics Data System (ADS)

Wu, Zheng

With the increasing areal density in magnetic recording systems, perpendicular recording has replaced longitudinal recording to overcome the superparamagnetic limit. Studies on perpendicular recording channels including aspects of channel modeling, signal processing and coding techniques are presented in this dissertation. To optimize a high density perpendicular magnetic recording system, one needs to know the tradeoffs between various components of the system including the read/write transducers, the magnetic medium, and the read channel. We extend the work by Chaichanavong on the parameter optimization for systems via design curves. Different signal processing and coding techniques are studied. Information-theoretic tools are utilized to determine the acceptable region for the channel parameters when optimal detection and linear coding techniques are used. Our results show that a considerable gain can be achieved by the optimal detection and coding techniques. The read-write process in perpendicular magnetic recording channels includes a number of nonlinear effects. Nonlinear transition shift (NLTS) is one of them. The signal distortion induced by NLTS can be reduced by write precompensation during data recording. We numerically evaluate the effect of NLTS on the read-back signal and examine the effectiveness of several write precompensation schemes in combating NLTS in a channel characterized by both transition jitter noise and additive white Gaussian electronics noise. We also present an analytical method to estimate the bit-error-rate and use it to help determine the optimal write precompensation values in multi-level precompensation schemes. We propose a mean-adjusted pattern-dependent noise predictive (PDNP) detection algorithm for use on the channel with NLTS. We show that this detector can offer significant improvements in bit-error-rate (BER) compared to conventional Viterbi and PDNP detectors. Moreover, the system performance can be further improved by combining the new detector with a simple write precompensation scheme. Soft-decision decoding for algebraic codes can improve performance for magnetic recording systems. In this dissertation, we propose two soft-decision decoding methods for tensor-product parity codes. We also present a list decoding algorithm for generalized error locating codes.

Optimum inhomogeneity of local lattice distortions in La2CuO4+y

PubMed Central

Poccia, Nicola; Ricci, Alessandro; Campi, Gaetano; Fratini, Michela; Puri, Alessandro; Gioacchino, Daniele Di; Marcelli, Augusto; Reynolds, Michael; Burghammer, Manfred; Saini, Naurang Lal; Aeppli, Gabriel; Bianconi, Antonio

2012-01-01

Electronic functionalities in materials from silicon to transition metal oxides are, to a large extent, controlled by defects and their relative arrangement. Outstanding examples are the oxides of copper, where defect order is correlated with their high superconducting transition temperatures. The oxygen defect order can be highly inhomogeneous, even in optimal superconducting samples, which raises the question of the nature of the sample regions where the order does not exist but which nonetheless form the “glue” binding the ordered regions together. Here we use scanning X-ray microdiffraction (with a beam 300 nm in diameter) to show that for La2CuO4+y, the glue regions contain incommensurate modulated local lattice distortions, whose spatial extent is most pronounced for the best superconducting samples. For an underdoped single crystal with mobile oxygen interstitials in the spacer La2O2+y layers intercalated between the CuO2 layers, the incommensurate modulated local lattice distortions form droplets anticorrelated with the ordered oxygen interstitials, and whose spatial extent is most pronounced for the best superconducting samples. In this simplest of high temperature superconductors, there are therefore not one, but two networks of ordered defects which can be tuned to achieve optimal superconductivity. For a given stoichiometry, the highest transition temperature is obtained when both the ordered oxygen and lattice defects form fractal patterns, as opposed to appearing in isolated spots. We speculate that the relationship between material complexity and superconducting transition temperature Tc is actually underpinned by a fundamental relation between Tc and the distribution of ordered defect networks supported by the materials. PMID:22961255

Deconvolution of the vestibular evoked myogenic potential.

PubMed

Lütkenhöner, Bernd; Basel, Türker

2012-02-07

The vestibular evoked myogenic potential (VEMP) and the associated variance modulation can be understood by a convolution model. Two functions of time are incorporated into the model: the motor unit action potential (MUAP) of an average motor unit, and the temporal modulation of the MUAP rate of all contributing motor units, briefly called rate modulation. The latter is the function of interest, whereas the MUAP acts as a filter that distorts the information contained in the measured data. Here, it is shown how to recover the rate modulation by undoing the filtering using a deconvolution approach. The key aspects of our deconvolution algorithm are as follows: (1) the rate modulation is described in terms of just a few parameters; (2) the MUAP is calculated by Wiener deconvolution of the VEMP with the rate modulation; (3) the model parameters are optimized using a figure-of-merit function where the most important term quantifies the difference between measured and model-predicted variance modulation. The effectiveness of the algorithm is demonstrated with simulated data. An analysis of real data confirms the view that there are basically two components, which roughly correspond to the waves p13-n23 and n34-p44 of the VEMP. The rate modulation corresponding to the first, inhibitory component is much stronger than that corresponding to the second, excitatory component. But the latter is more extended so that the two modulations have almost the same equivalent rectangular duration. Copyright © 2011 Elsevier Ltd. All rights reserved.

Small Scale Mass Flow Plug Calibration

NASA Technical Reports Server (NTRS)

Sasson, Jonathan

2015-01-01

A simple control volume model has been developed to calculate the discharge coefficient through a mass flow plug (MFP) and validated with a calibration experiment. The maximum error of the model in the operating region of the MFP is 0.54%. The model uses the MFP geometry and operating pressure and temperature to couple continuity, momentum, energy, an equation of state, and wall shear. Effects of boundary layer growth and the reduction in cross-sectional flow area are calculated using an in- integral method. A CFD calibration is shown to be of lower accuracy with a maximum error of 1.35%, and slower by a factor of 100. Effects of total pressure distortion are taken into account in the experiment. Distortion creates a loss in flow rate and can be characterized by two different distortion descriptors.

Electrohydrodynamic distortion of sample streams in continuous flow electrophoresis

NASA Technical Reports Server (NTRS)

Rhodes, Percy H.; Snyder, Robert S.; Roberts, Glyn O.

1989-01-01

Continuous flow electrophoresis experiments were carried out, using an electrolyte and a sample both made of aqueous solutions of phosphate buffer (with polystyrene latex added for visibility), to investigate causes of the sample spreading in this procedure. It is shown theoretically that an electric field perpendicular to a circular filament of conducting fluid surrounded by a fluid of different conductivity produces an electrohydrodynamic flow, which distorts the filament into an ellipse. Experimental results were found to be fully consistent with theretical predictions. It was found that the rate of distortion of the sample stream into a ribbon was proportional to the square of the applied voltage gradient. Furthermore, the orientation of the ribbon depends on the ratios of dielectric constant and electrical conductivity between the buffer and the sample.

Optimized Delivery System Achieves Enhanced Endomyocardial Stem Cell Retention

PubMed Central

Behfar, Atta; Latere, Jean-Pierre; Bartunek, Jozef; Homsy, Christian; Daro, Dorothee; Crespo-Diaz, Ruben J.; Stalboerger, Paul G.; Steenwinckel, Valerie; Seron, Aymeric; Redfield, Margaret M.; Terzic, Andre

2014-01-01

Background Regenerative cell-based therapies are associated with limited myocardial retention of delivered stem cells. The objective of this study is to develop an endocardial delivery system for enhanced cell retention. Methods and Results Stem cell retention was simulated in silico using one and three-dimensional models of tissue distortion and compliance associated with delivery. Needle designs, predicted to be optimal, were accordingly engineered using nitinol – a nickel and titanium alloy displaying shape memory and super-elasticity. Biocompatibility was tested with human mesenchymal stem cells. Experimental validation was performed with species-matched cells directly delivered into Langendorff-perfused porcine hearts or administered percutaneously into the endocardium of infarcted pigs. Cell retention was quantified by flow cytometry and real time quantitative polymerase chain reaction methodology. Models, computing optimal distribution of distortion calibrated to favor tissue compliance, predicted that a 75°-curved needle featuring small-to-large graded side holes would ensure the highest cell retention profile. In isolated hearts, the nitinol curved needle catheter (C-Cath) design ensured 3-fold superior stem cell retention compared to a standard needle. In the setting of chronic infarction, percutaneous delivery of stem cells with C-Cath yielded a 37.7±7.1% versus 10.0±2.8% retention achieved with a traditional needle, without impact on biocompatibility or safety. Conclusions Modeling guided development of a nitinol-based curved needle delivery system with incremental side holes achieved enhanced myocardial stem cell retention. PMID:24326777

Feasibility of online IMPT adaptation using fast, automatic and robust dose restoration

NASA Astrophysics Data System (ADS)

Bernatowicz, Kinga; Geets, Xavier; Barragan, Ana; Janssens, Guillaume; Souris, Kevin; Sterpin, Edmond

2018-04-01

Intensity-modulated proton therapy (IMPT) offers excellent dose conformity and healthy tissue sparing, but it can be substantially compromised in the presence of anatomical changes. A major dosimetric effect is caused by density changes, which alter the planned proton range in the patient. Three different methods, which automatically restore an IMPT plan dose on a daily CT image were implemented and compared: (1) simple dose restoration (DR) using optimization objectives of the initial plan, (2) voxel-wise dose restoration (vDR), and (3) isodose volume dose restoration (iDR). Dose restorations were calculated for three different clinical cases, selected to test different capabilities of the restoration methods: large range adaptation, complex dose distributions and robust re-optimization. All dose restorations were obtained in less than 5 min, without manual adjustments of the optimization settings. The evaluation of initial plans on repeated CTs showed large dose distortions, which were substantially reduced after restoration. In general, all dose restoration methods improved DVH-based scores in propagated target volumes and OARs. Analysis of local dose differences showed that, although all dose restorations performed similarly in high dose regions, iDR restored the initial dose with higher precision and accuracy in the whole patient anatomy. Median dose errors decreased from 13.55 Gy in distorted plan to 9.75 Gy (vDR), 6.2 Gy (DR) and 4.3 Gy (iDR). High quality dose restoration is essential to minimize or eventually by-pass the physician approval of the restored plan, as long as dose stability can be assumed. Motion (as well as setup and range uncertainties) can be taken into account by including robust optimization in the dose restoration. Restoring clinically-approved dose distribution on repeated CTs does not require new ROI segmentation and is compatible with an online adaptive workflow.

Automated detection scheme of architectural distortion in mammograms using adaptive Gabor filter

NASA Astrophysics Data System (ADS)

Yoshikawa, Ruriha; Teramoto, Atsushi; Matsubara, Tomoko; Fujita, Hiroshi

2013-03-01

Breast cancer is a serious health concern for all women. Computer-aided detection for mammography has been used for detecting mass and micro-calcification. However, there are challenges regarding the automated detection of the architectural distortion about the sensitivity. In this study, we propose a novel automated method for detecting architectural distortion. Our method consists of the analysis of the mammary gland structure, detection of the distorted region, and reduction of false positive results. We developed the adaptive Gabor filter for analyzing the mammary gland structure that decides filter parameters depending on the thickness of the gland structure. As for post-processing, healthy mammary glands that run from the nipple to the chest wall are eliminated by angle analysis. Moreover, background mammary glands are removed based on the intensity output image obtained from adaptive Gabor filter. The distorted region of the mammary gland is then detected as an initial candidate using a concentration index followed by binarization and labeling. False positives in the initial candidate are eliminated using 23 types of characteristic features and a support vector machine. In the experiments, we compared the automated detection results with interpretations by a radiologist using 50 cases (200 images) from the Digital Database of Screening Mammography (DDSM). As a result, true positive rate was 82.72%, and the number of false positive per image was 1.39. There results indicate that the proposed method may be useful for detecting architectural distortion in mammograms.

Eddy current compensated double diffusion encoded (DDE) MRI.

PubMed

Mueller, Lars; Wetscherek, Andreas; Kuder, Tristan Anselm; Laun, Frederik Bernd

2017-01-01

Eddy currents might lead to image distortions in diffusion-weighted echo planar imaging. A method is proposed to reduce their effects on double diffusion encoding (DDE) MRI experiments and the thereby derived microscopic fractional anisotropy (μFA). The twice-refocused spin echo scheme was adapted for DDE measurements. To assess the effect of individual diffusion encodings on the image distortions, measurements of a grid of plastic rods in water were performed. The effect of eddy current compensation on μFA measurements was evaluated in the brains of six healthy volunteers. The use of an eddy current compensation reduced the signal variation. As expected, the distortions caused by the second encoding were larger than those of the first encoding, entailing a stronger need to compensate for them. For an optimal result, however, both encodings had to be compensated. The artifact reduction strongly improved the measurement of the μFA in ventricles and gray matter by reducing the overestimation. An effect of the compensation on absolute μFA values in white matter was not observed. It is advisable to compensate both encodings in DDE measurements for eddy currents. Magn Reson Med 77:328-335, 2017. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Temperature Distribution and Influence Mechanism on Large Reflector Antennas under Solar Radiation

NASA Astrophysics Data System (ADS)

Wang, C. S.; Yuan, S.; Liu, X.; Xu, Q.; Wang, M.; Zhu, M. B.; Chen, G. D.; Duan, Y. H.

2017-10-01

The solar impact on antenna must be lessened for the large reflector antenna operating at high frequencies to have great electromagnetic performances. Therefore, researching the temperature distribution and its influence on large reflector antenna is necessary. The variation of solar incidence angle is first calculated. Then the model is simulated by the I-DEAS software, with the temperature, thermal stress, and thermal distortion distribution through the day obtained. In view of the important influence of shadow on antenna structure, a newly proposed method makes a comprehensive description of the temperature distribution on the reflector and its influence through the day by dividing a day into three different periods. The sound discussions and beneficial summary serve as the scientific foundation for the engineers to compensate the thermal distortion and optimize the antenna structure.

Structural origins of broadband emission from layered Pb-Br hybrid perovskites.

PubMed

Smith, Matthew D; Jaffe, Adam; Dohner, Emma R; Lindenberg, Aaron M; Karunadasa, Hemamala I

2017-06-01

Through structural and optical studies of a series of two-dimensional hybrid perovskites, we show that broadband emission upon near-ultraviolet excitation is common to (001) lead-bromide perovskites. Importantly, we find that the relative intensity of the broad emission correlates with increasing out-of-plane distortion of the Pb-(μ-Br)-Pb angle in the inorganic sheets. Temperature- and power-dependent photoluminescence data obtained on a representative (001) perovskite support an intrinsic origin to the broad emission from the bulk material, where photogenerated carriers cause excited-state lattice distortions mediated through electron-lattice coupling. In contrast, most inorganic phosphors contain extrinsic emissive dopants or emissive surface sites. The design rules established here could allow us to systematically optimize white-light emission from layered hybrid perovskites by fine-tuning the bulk crystal structure.

TARGETED THERAPY: Generic imatinib — impact on frontline and salvage therapy for CML

PubMed Central

Gorkin, Larry; Kantarjian, Hagop

2017-01-01

Imatinib has revolutionized the treatment of chronic myeloid leukaemia (CML). In 2016, generic imatinib will be introduced into the US market. We analyse the potential impact of this new product on patient care and optimal CML therapy, and comment on the effect that distorted cancer drug pricing in the USA will have on treatment for patients with limited therapeutic options. PMID:27098218

JWST ISIM Primary Structure and Kinematic Mount Configuration

NASA Technical Reports Server (NTRS)

Bartoszyk, Andrew; Carnahan, Tim; Hendricks, Steve; Kaprielian, Charles; Kuhn, Jonathan; Kunt, Cengiz

2004-01-01

In this presentation we will review the evolution of the ISIM primary structure tube topology and kinematic mount configuration to the current baseline concept. We will also show optimization procedures used and challenges resulting from complex joints under launch loads. Two additional key ISIM structure challenges of meeting thermal distortion and stability requirements and metal-composite bonded joint survivability at cryogenic temperatures are covered in other presentations.

``Smart'' baroreception along the aortic arch, with reference to essential hypertension

NASA Astrophysics Data System (ADS)

Kember, G. C.; Zamir, M.; Armour, J. A.

2004-11-01

Beat-to-beat regulation of heart rate is dependent upon sensing of local stretching or local “disortion” by aortic baroreceptors. Distortions of the aortic wall are due mainly to left ventricular output and to reflected waves arising from the arterial tree. Distortions are generally believed to be useful in cardiac control since stretch receptors or aortic baroreceptors embedded in the adventitia of the aortic wall, transduce the distortions to cardiovascular neural reflex pathways responsible for beat-to-beat regulation of heart rate. Aortic neuroanatomy studies have also found a continuous strip of mechanosensory neurites spread along the aortic inner arch. Although their purpose is now unknown, such a combined sensing capacity would allow measurement of the space and time dependence of inner arch wall distortions due, among other things, to traveling waves associated with pulsatile flow in an elastic tube. We call this sensing capability-“smart baroreception.” In this paper we use an arterial tree model to show that the cumulative effects of wave reflections, from many sites far downstream, have a surprisingly pronounced effect on the pressure distribution in the root segment of the tree. By this mechanism global hemodynamics can be focused by wave reflections back to the aortic arch, where they can rapidly impact cardiac control via smart baroreception. Such sensing is likely important to maintain efficient heart function. However, alterations in the arterial tree due to aging and other natural processes can lead in such a system to altered cardiac control and essential hypertension.

Self-citation rate and impact factor in the field of plastic and reconstructive surgery.

PubMed

Miyamoto, Shimpei

2018-02-01

Journal ranking based on the impact factor (IF) can be distorted by self-citation. The aim of this study is to investigate the present status of self-citation in the plastic surgery journals and its effect on the journals' IFs. IF, IF without self-citations (corrected IF), self-cited rate, and self-citing rate for 11 plastic surgery journals were investigated from 2009-2015, by reviewing the Journal Citation Report ® . The correlations of the IF with the self-cited rate and the self-citing rate were statistically assessed. In addition, Plastic and Reconstructive Surgery was compared with 15 top journals from other surgical specialties in 2015. IF was significantly correlated with the self-cited rate (R: 0.594, p = 0.001) and the self-citing rate (R: 0.824, p < 0.001). The self-cited rate of Plastic and Reconstructive Surgery in 2015 was higher than that of top journals from other surgical specialties. The IFs of Microsurgery and Journal of Cranio-Maxillo-Facial Surgery increased greatly in recent years, but they were inflated by high self-cited and self-citing rates. The self-citation rate positively affects the IF in plastic surgery journals. A high concentration of self-citation of some journals could distort the ranking among plastic surgery journals in general.

Improved power control using optimal adjustable coefficients for three-phase photovoltaic inverter under unbalanced grid voltage.

PubMed

Wang, Qianggang; Zhou, Niancheng; Lou, Xiaoxuan; Chen, Xu

2014-01-01

Unbalanced grid faults will lead to several drawbacks in the output power quality of photovoltaic generation (PV) converters, such as power fluctuation, current amplitude swell, and a large quantity of harmonics. The aim of this paper is to propose a flexible AC current generation method by selecting coefficients to overcome these problems in an optimal way. Three coefficients are brought in to tune the output current reference within the required limits of the power quality (the current harmonic distortion, the AC current peak, the power fluctuation, and the DC voltage fluctuation). Through the optimization algorithm, the coefficients can be determined aiming to generate the minimum integrated amplitudes of the active and reactive power references with the constraints of the inverter current and DC voltage fluctuation. Dead-beat controller is utilized to track the optimal current reference in a short period. The method has been verified in PSCAD/EMTDC software.

Improved Power Control Using Optimal Adjustable Coefficients for Three-Phase Photovoltaic Inverter under Unbalanced Grid Voltage

PubMed Central

Wang, Qianggang; Zhou, Niancheng; Lou, Xiaoxuan; Chen, Xu

2014-01-01

Unbalanced grid faults will lead to several drawbacks in the output power quality of photovoltaic generation (PV) converters, such as power fluctuation, current amplitude swell, and a large quantity of harmonics. The aim of this paper is to propose a flexible AC current generation method by selecting coefficients to overcome these problems in an optimal way. Three coefficients are brought in to tune the output current reference within the required limits of the power quality (the current harmonic distortion, the AC current peak, the power fluctuation, and the DC voltage fluctuation). Through the optimization algorithm, the coefficients can be determined aiming to generate the minimum integrated amplitudes of the active and reactive power references with the constraints of the inverter current and DC voltage fluctuation. Dead-beat controller is utilized to track the optimal current reference in a short period. The method has been verified in PSCAD/EMTDC software. PMID:25243215

Resource optimized TTSH-URA for multimedia stream authentication in swallowable-capsule-based wireless body sensor networks.

PubMed

Wang, Wei; Wang, Chunqiu; Zhao, Min

2014-03-01

To ease the burdens on the hospitalization capacity, an emerging swallowable-capsule technology has evolved to serve as a remote gastrointestinal (GI) disease examination technique with the aid of the wireless body sensor network (WBSN). Secure multimedia transmission in such a swallowable-capsule-based WBSN faces critical challenges including energy efficiency and content quality guarantee. In this paper, we propose a joint resource allocation and stream authentication scheme to maintain the best possible video quality while ensuring security and energy efficiency in GI-WBSNs. The contribution of this research is twofold. First, we establish a unique signature-hash (S-H) diversity approach in the authentication domain to optimize video authentication robustness and the authentication bit rate overhead over a wireless channel. Based on the full exploration of S-H authentication diversity, we propose a new two-tier signature-hash (TTSH) stream authentication scheme to improve the video quality by reducing authentication dependence overhead while protecting its integrity. Second, we propose to combine this authentication scheme with a unique S-H oriented unequal resource allocation (URA) scheme to improve the energy-distortion-authentication performance of wireless video delivery in GI-WBSN. Our analysis and simulation results demonstrate that the proposed TTSH with URA scheme achieves considerable gain in both authenticated video quality and energy efficiency.

An ideal observer analysis of visual working memory.

PubMed

Sims, Chris R; Jacobs, Robert A; Knill, David C

2012-10-01

Limits in visual working memory (VWM) strongly constrain human performance across many tasks. However, the nature of these limits is not well understood. In this article we develop an ideal observer analysis of human VWM by deriving the expected behavior of an optimally performing but limited-capacity memory system. This analysis is framed around rate-distortion theory, a branch of information theory that provides optimal bounds on the accuracy of information transmission subject to a fixed information capacity. The result of the ideal observer analysis is a theoretical framework that provides a task-independent and quantitative definition of visual memory capacity and yields novel predictions regarding human performance. These predictions are subsequently evaluated and confirmed in 2 empirical studies. Further, the framework is general enough to allow the specification and testing of alternative models of visual memory (e.g., how capacity is distributed across multiple items). We demonstrate that a simple model developed on the basis of the ideal observer analysis-one that allows variability in the number of stored memory representations but does not assume the presence of a fixed item limit-provides an excellent account of the empirical data and further offers a principled reinterpretation of existing models of VWM. PsycINFO Database Record (c) 2012 APA, all rights reserved.

Optimal Operation of a Josephson Parametric Amplifier for Vacuum Squeezing

NASA Astrophysics Data System (ADS)

Malnou, M.; Palken, D. A.; Vale, Leila R.; Hilton, Gene C.; Lehnert, K. W.

2018-04-01

A Josephson parametric amplifier (JPA) can create squeezed states of microwave light, lowering the noise associated with certain quantum measurements. We experimentally study how the JPA's pump influences the phase-sensitive amplification and deamplification of a coherent tone's amplitude when that amplitude is commensurate with vacuum fluctuations. We predict and demonstrate that, by operating the JPA with a single current pump whose power is greater than the value that maximizes gain, the amplifier distortion is reduced and, consequently, squeezing is improved. Optimizing the singly pumped JPA's operation in this fashion, we directly observe 3.87 ±0.03 dB of vacuum squeezing over a bandwidth of 30 MHz.

Investigation of a 7-pole/6-slot Halbach-magnetized permanent-magnet linear alternator used for free-piston stirling engines

NASA Astrophysics Data System (ADS)

Zheng, Ping; Tong, Chengde; Zhao, Jing; Yu, Bin; Li, Lin; Bai, Jingang; Zhang, Lu

2012-04-01

This paper investigates a 7-pole/6-slot Halbach-magnetized permanent-magnet linear alternator used for free piston Stirling engines (FPSEs). Taking the advantages of Halbach array, a 1 kW prototype alternator is designed. Considering the rms value of electromotive force (EMF) and harmonic distortion, the optimal length ratio of the axial- and radial-magnetized permanent magnets and thicknesses of the permanent magnets are optimized by 2D finite element method. The alternator detent force, which is an important factor for smooth operation of FPSEs, is studied by optimizing slot tip and end tooth. The load and thermal performances of the final design are simulated. A prototype alternator was designed, built and tested. Experimental data indicated satisfactory design.

The effect of MRET polymer compound on SAR values of RF phones.

PubMed

Smirnov, Igor

2008-01-01

This article is related to the proposed hypothesis and experimental data regarding the ability of defined polar polymer compound (MRET polymer) applied to RF phones to increase the dielectric permittivity of water based solutions and to reduce the SAR (Specific Absorption Rate) values inside the "phantom head" filled with the jelly simulating muscle and brain tissues. Due to the high organizational state of fractal structures of MRET polymer compounds and the phenomenon of piezoelectricity, this polymer generates specific subtle, low frequency, non-coherent electromagnetic oscillations (optimal random field) that can affect the hydrogen lattice of the molecular structure of water and subsequently modify the electrodynamic properties of water. The increase of dielectric permittivity of water finally leads to the reduction of the absorption rate of the electromagnetic field by living tissue. The reduction of SAR values is confirmed by the research conducted in June - July of 2006 at RF Exposure Laboratory in Escondido, California. This test also confirmed that the application of MRET polymer to RF phones does not significantly affect the air measurements of RF phone signals, and subsequently does not lead to any significant distortion of transmitted RF signals.

Hybrid vision activities at NASA Johnson Space Center

NASA Technical Reports Server (NTRS)

Juday, Richard D.

1990-01-01

NASA's Johnson Space Center in Houston, Texas, is active in several aspects of hybrid image processing. (The term hybrid image processing refers to a system that combines digital and photonic processing). The major thrusts are autonomous space operations such as planetary landing, servicing, and rendezvous and docking. By processing images in non-Cartesian geometries to achieve shift invariance to canonical distortions, researchers use certain aspects of the human visual system for machine vision. That technology flow is bidirectional; researchers are investigating the possible utility of video-rate coordinate transformations for human low-vision patients. Man-in-the-loop teleoperations are also supported by the use of video-rate image-coordinate transformations, as researchers plan to use bandwidth compression tailored to the varying spatial acuity of the human operator. Technological elements being developed in the program include upgraded spatial light modulators, real-time coordinate transformations in video imagery, synthetic filters that robustly allow estimation of object pose parameters, convolutionally blurred filters that have continuously selectable invariance to such image changes as magnification and rotation, and optimization of optical correlation done with spatial light modulators that have limited range and couple both phase and amplitude in their response.

Power spectrum precision for redshift space distortions

NASA Astrophysics Data System (ADS)

Linder, Eric V.; Samsing, Johan

2013-02-01

Redshift space distortions in galaxy clustering offer a promising technique for probing the growth rate of structure and testing dark energy properties and gravity. We consider the issue of to what accuracy they need to be modeled in order not to unduly bias cosmological conclusions. Fitting for nonlinear and redshift space corrections to the linear theory real space density power spectrum in bins in wavemode, we analyze both the effect of marginalizing over these corrections and of the bias due to not correcting them fully. While naively subpercent accuracy is required to avoid bias in the unmarginalized case, in the fitting approach the Kwan-Lewis-Linder reconstruction function for redshift space distortions is found to be accurately selfcalibrated with little degradation in dark energy and gravity parameter estimation for a next generation galaxy redshift survey such as BigBOSS.

GNSS Signal Authentication Via Power and Distortion Monitoring

NASA Astrophysics Data System (ADS)

Wesson, Kyle D.; Gross, Jason N.; Humphreys, Todd E.; Evans, Brian L.

2018-04-01

We propose a simple low-cost technique that enables civil Global Positioning System (GPS) receivers and other civil global navigation satellite system (GNSS) receivers to reliably detect carry-off spoofing and jamming. The technique, which we call the Power-Distortion detector, classifies received signals as interference-free, multipath-afflicted, spoofed, or jammed according to observations of received power and correlation function distortion. It does not depend on external hardware or a network connection and can be readily implemented on many receivers via a firmware update. Crucially, the detector can with high probability distinguish low-power spoofing from ordinary multipath. In testing against over 25 high-quality empirical data sets yielding over 900,000 separate detection tests, the detector correctly alarms on all malicious spoofing or jamming attacks while maintaining a <0.6% single-channel false alarm rate.

A hybrid LBG/lattice vector quantizer for high quality image coding

NASA Technical Reports Server (NTRS)

Ramamoorthy, V.; Sayood, K.; Arikan, E. (Editor)

1991-01-01

It is well known that a vector quantizer is an efficient coder offering a good trade-off between quantization distortion and bit rate. The performance of a vector quantizer asymptotically approaches the optimum bound with increasing dimensionality. A vector quantized image suffers from the following types of degradations: (1) edge regions in the coded image contain staircase effects, (2) quasi-constant or slowly varying regions suffer from contouring effects, and (3) textured regions lose details and suffer from granular noise. All three of these degradations are due to the finite size of the code book, the distortion measures used in the design, and due to the finite training procedure involved in the construction of the code book. In this paper, we present an adaptive technique which attempts to ameliorate the edge distortion and contouring effects.

High-Rate Capable Floating Strip Micromegas

NASA Astrophysics Data System (ADS)

Bortfeldt, Jonathan; Bender, Michael; Biebel, Otmar; Danger, Helge; Flierl, Bernhard; Hertenberger, Ralf; Lösel, Philipp; Moll, Samuel; Parodi, Katia; Rinaldi, Ilaria; Ruschke, Alexander; Zibell, André

2016-04-01

We report on the optimization of discharge insensitive floating strip Micromegas (MICRO-MEsh GASeous) detectors, fit for use in high-energy muon spectrometers. The suitability of these detectors for particle tracking is shown in high-background environments and at very high particle fluxes up to 60 MHz/cm2. Measurement and simulation of the microscopic discharge behavior have demonstrated the excellent discharge tolerance. A floating strip Micromegas with an active area of 48 cm × 50 cm with 1920 copper anode strips exhibits in 120 GeV pion beams a spatial resolution of 50 μm at detection efficiencies above 95%. Pulse height, spatial resolution and detection efficiency are homogeneous over the detector. Reconstruction of particle track inclination in a single detector plane is discussed, optimum angular resolutions below 5° are observed. Systematic deviations of this μTPC-method are fully understood. The reconstruction capabilities for minimum ionizing muons are investigated in a 6.4 cm × 6.4 cm floating strip Micromegas under intense background irradiation of the whole active area with 20 MeV protons at a rate of 550 kHz. The spatial resolution for muons is not distorted by space charge effects. A 6.4 cm × 6.4 cm floating strip Micromegas doublet with low material budget is investigated in highly ionizing proton and carbon ion beams at particle rates between 2 MHz and 2 GHz. Stable operation up to the highest rates is observed, spatial resolution, detection efficiencies, the multi-hit and high-rate capability are discussed.

Gender Differences in Rating Stressful Events, Depression, and Depressive Cognition.

ERIC Educational Resources Information Center

Sowa, Claudia J.; Lustman, Patrick J.

1984-01-01

Administered the Life Stress Questionnaire, the Beck Depression Inventory, and the Automatic Thought Questionnaire to 140 students. Results showed significant sex differences. Men reported more stressful life change, but women rated the impact of stressors more severely and had higher depression. Men exhibited greater distortions in cognitive…

3.375-Gb/s RGB-LED based WDM visible light communication system employing PAM-8 modulation with phase shifted Manchester coding.

PubMed

Chi, Nan; Zhang, Mengjie; Zhou, Yingjun; Zhao, Jiaqi

2016-09-19

Optical background noise and second-order nonlinear distortions are two main challenges faced by indoor high-speed VLC system. In this paper, a novel phase shifted Manchester (PS-Manchester) coding based on PAM-8 is proposed and experimentally demonstrated to mitigate these noise and distortions. With the aid of PS-Manchester coding and WDM, a total data rate of 3.375-Gb/s can be successfully achieved in the RGB-LED based VLC system. The BER is under 7% HD-FEC limit of 3.8x10^-3 after 1-m indoor free space transmission. To the best of our knowledge, this is the highest data rate ever achieved in PAM VLC systems.

Clinical utility of contrast-enhanced spectral mammography as an adjunct for tomosynthesis-detected architectural distortion.

PubMed

Patel, Bhavika K; Naylor, Michelle E; Kosiorek, Heidi E; Lopez-Alvarez, Yania M; Miller, Adrian M; Pizzitola, Victor J; Pockaj, Barbara A

Supplement tomosynthesis-detected architectural distortions (AD) with CESM to better characterize malignant vs benign lesions. Retrospective review CESM prior to biopsied AD. Pathology: benign, radial scar, or malignant. 49 lesions (45 patients). 29 invasive cancers, 1 DCIS (range, 0.4-4.7cm); 9 radial scars; 10 benign. 37 (75.5%) ADs had associated enhancement. PPV 78.4% (29/37), sensitivity 96.7% (29/30); specificity, 57.9% (11/19); NPV, 91.7% (11/12). False-positive rate 21.6% (8/37); false-negative rate, 8.3% (1/12). Accuracy 81.6% (40/49). High sensitivity and NPV of CESM in patients with AD is promising as an adjunct tool in diagnosing malignancy and avoiding unnecessary biopsy, respectively. Copyright © 2017 Elsevier Inc. All rights reserved.

Noise tolerance in wavelength-selective switching of optical differential quadrature-phase-shift-keying pulse train by collinear acousto-optic devices.

PubMed

Goto, Nobuo; Miyazaki, Yasumitsu

2014-06-01

Optical switching of high-bit-rate quadrature-phase-shift-keying (QPSK) pulse trains using collinear acousto-optic (AO) devices is theoretically discussed. Since the collinear AO devices have wavelength selectivity, the switched optical pulse trains suffer from distortion when the bandwidth of the pulse train is comparable to the pass bandwidth of the AO device. As the AO device, a sidelobe-suppressed device with a tapered surface-acoustic-wave (SAW) waveguide and a Butterworth-type filter device with a lossy SAW directional coupler are considered. Phase distortion of optical pulse trains at 40 to 100  Gsymbols/s in QPSK format is numerically analyzed. Bit-error-rate performance with additive Gaussian noise is also evaluated by the Monte Carlo method.

Fundamentals of Coherent Synchrotron Radiation in Storage Rings

NASA Astrophysics Data System (ADS)

Sannibale, F.; Byrd, J. M.; Loftsdottir, A.; Martin, M. C.; Venturini, M.

2004-05-01

We present the fundamental concepts for producing stable broadband coherent synchrotron radiation (CSR) in the terahertz frequency region in an electron storage ring. The analysis includes distortion of bunch shape from the synchrotron radiation (SR), enhancing higher frequency coherent emission and limits to stable emission due to a microbunching instability excited by the SR. We use these concepts to optimize the performance of a source for CSR emission.

Reducing Stator Current Harmonics for a Doubly-Fed Induction Generator Connected to a Distorted Grid

DTIC Science & Technology

2013-09-01

electric grid voltage harmonics, which is a potential obstacle for implementing stable wind -energy systems. Two existing rotor voltage controllers...electric grid voltage harmonics, which is a potential obstacle for implementing stable wind -energy systems. Two existing rotor voltage controllers...speed of the DFIG can be adjusted to optimize turbine efficiency for given wind conditions. A common method for controlling the operating speed is

Polarimeter Blind Deconvolution Using Image Diversity

DTIC Science & Technology

2007-09-01

significant presence when imaging through turbulence and its ease of production in the labora- tory. An innovative algorithm for detection and estimation...1.2.2.2 Atmospheric Turbulence . Atmospheric turbulence spatially distorts the wavefront as light passes through it and causes blurring of images in an...intensity image . Various values of β are used in the experiments. The optimal β value varied with the input and the algorithm . The hybrid seemed to

Identifying the Cost of Non-monetary Incentives (ICONIC)

DTIC Science & Technology

2009-12-01

topics. a. Inspection Optimization Model The Environmental Protection Agency (EPA) developed a linear programming model designed for a state air...and other special pays that can distort the environment and amenities that the next assignment offers.23 The primary objective of this work is to...Government Printing Office, 2005). http://www.gao.gov/new.items/d06125.pdf (accessed September 28, 2008). Van Boening, Mark, Tanja F. Blackstone

Helicopter TEM parameters analysis and system optimization based on time constant

NASA Astrophysics Data System (ADS)

Xiao, Pan; Wu, Xin; Shi, Zongyang; Li, Jutao; Liu, Lihua; Fang, Guangyou

2018-03-01

Helicopter transient electromagnetic (TEM) method is a kind of common geophysical prospecting method, widely used in mineral detection, underground water exploration and environment investigation. In order to develop an efficient helicopter TEM system, it is necessary to analyze and optimize the system parameters. In this paper, a simple and quantitative method is proposed to analyze the system parameters, such as waveform, power, base frequency, measured field and sampling time. A wire loop model is used to define a comprehensive 'time constant domain' that shows a range of time constant, analogous to a range of conductance, after which the characteristics of the system parameters in this domain is obtained. It is found that the distortion caused by the transmitting base frequency is less than 5% when the ratio of the transmitting period to the target time constant is greater than 6. When the sampling time window is less than the target time constant, the distortion caused by the sampling time window is less than 5%. According to this method, a helicopter TEM system, called CASHTEM, is designed, and flight test has been carried out in the known mining area. The test results show that the system has good detection performance, verifying the effectiveness of the method.

The Effect of Plug-in Electric Vehicles on Harmonic Analysis of Smart Grid

NASA Astrophysics Data System (ADS)

Heidarian, T.; Joorabian, M.; Reza, A.

2015-12-01

In this paper, the effect of plug-in electric vehicles is studied on the smart distribution system with a standard IEEE 30-bus network. At first, harmonic power flow analysis is performed by Newton-Raphson method and by considering distorted substation voltage. Afterward, proper sizes of capacitors is selected by cuckoo optimization algorithm to reduce the power losses and cost and by imposing acceptable limit for total harmonic distortion and RMS voltages. It is proposed that the impact of generated current harmonics by electric vehicle battery chargers should be factored into overall load control strategies of smart appliances. This study is generalized to the different hours of a day by using daily load curve, and then optimum time for charging of electric vehicles batteries in the parking lots are determined by cuckoo optimization algorithm. The results show that injecting harmonic currents of plug-in electric vehicles causes a drop in the voltage profile and increases power loss. Moreover, charging the vehicle batteries has more impact on increasing the power losses rather than the harmonic currents effect. Also, the findings showed that the current harmonics has a great influence on increasing of THD. Finally, optimum working times of all parking lots was obtained for the utilization cost reduction.

Design of angle-resolved illumination optics using nonimaging bi-telecentricity for 193 nm scatterfield microscopy.

PubMed

Sohn, Martin Y; Barnes, Bryan M; Silver, Richard M

2018-03-01

Accurate optics-based dimensional measurements of features sized well-below the diffraction limit require a thorough understanding of the illumination within the optical column and of the three-dimensional scattered fields that contain the information required for quantitative metrology. Scatterfield microscopy can pair simulations with angle-resolved tool characterization to improve agreement between the experiment and calculated libraries, yielding sub-nanometer parametric uncertainties. Optimized angle-resolved illumination requires bi-telecentric optics in which a telecentric sample plane defined by a Köhler illumination configuration and a telecentric conjugate back focal plane (CBFP) of the objective lens; scanning an aperture or an aperture source at the CBFP allows control of the illumination beam angle at the sample plane with minimal distortion. A bi-telecentric illumination optics have been designed enabling angle-resolved illumination for both aperture and source scanning modes while yielding low distortion and chief ray parallelism. The optimized design features a maximum chief ray angle at the CBFP of 0.002° and maximum wavefront deviations of less than 0.06 λ for angle-resolved illumination beams at the sample plane, holding promise for high quality angle-resolved illumination for improved measurements of deep-subwavelength structures using deep-ultraviolet light.

High-speed adaptive contact-mode atomic force microscopy imaging with near-minimum-force

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, Juan; Zou, Qingze, E-mail: qzzou@rci.rutgers.edu

In this paper, an adaptive contact-mode imaging approach is proposed to replace the traditional contact-mode imaging by addressing the major concerns in both the speed and the force exerted to the sample. The speed of the traditional contact-mode imaging is largely limited by the need to maintain precision tracking of the sample topography over the entire imaged sample surface, while large image distortion and excessive probe-sample interaction force occur during high-speed imaging. In this work, first, the image distortion caused by the topography tracking error is accounted for in the topography quantification. Second, the quantified sample topography is utilized inmore » a gradient-based optimization method to adjust the cantilever deflection set-point for each scanline closely around the minimal level needed for maintaining stable probe-sample contact, and a data-driven iterative feedforward control that utilizes a prediction of the next-line topography is integrated to the topography feeedback loop to enhance the sample topography tracking. The proposed approach is demonstrated and evaluated through imaging a calibration sample of square pitches at both high speeds (e.g., scan rate of 75 Hz and 130 Hz) and large sizes (e.g., scan size of 30 μm and 80 μm). The experimental results show that compared to the traditional constant-force contact-mode imaging, the imaging speed can be increased by over 30 folds (with the scanning speed at 13 mm/s), and the probe-sample interaction force can be reduced by more than 15% while maintaining the same image quality.« less

High-speed adaptive contact-mode atomic force microscopy imaging with near-minimum-force.

PubMed

Ren, Juan; Zou, Qingze

2014-07-01

In this paper, an adaptive contact-mode imaging approach is proposed to replace the traditional contact-mode imaging by addressing the major concerns in both the speed and the force exerted to the sample. The speed of the traditional contact-mode imaging is largely limited by the need to maintain precision tracking of the sample topography over the entire imaged sample surface, while large image distortion and excessive probe-sample interaction force occur during high-speed imaging. In this work, first, the image distortion caused by the topography tracking error is accounted for in the topography quantification. Second, the quantified sample topography is utilized in a gradient-based optimization method to adjust the cantilever deflection set-point for each scanline closely around the minimal level needed for maintaining stable probe-sample contact, and a data-driven iterative feedforward control that utilizes a prediction of the next-line topography is integrated to the topography feeedback loop to enhance the sample topography tracking. The proposed approach is demonstrated and evaluated through imaging a calibration sample of square pitches at both high speeds (e.g., scan rate of 75 Hz and 130 Hz) and large sizes (e.g., scan size of 30 μm and 80 μm). The experimental results show that compared to the traditional constant-force contact-mode imaging, the imaging speed can be increased by over 30 folds (with the scanning speed at 13 mm/s), and the probe-sample interaction force can be reduced by more than 15% while maintaining the same image quality.

Intra Frame Coding In Advanced Video Coding Standard (H.264) to Obtain Consistent PSNR and Reduce Bit Rate for Diagonal Down Left Mode Using Gaussian Pulse

NASA Astrophysics Data System (ADS)

Manjanaik, N.; Parameshachari, B. D.; Hanumanthappa, S. N.; Banu, Reshma

2017-08-01

Intra prediction process of H.264 video coding standard used to code first frame i.e. Intra frame of video to obtain good coding efficiency compare to previous video coding standard series. More benefit of intra frame coding is to reduce spatial pixel redundancy with in current frame, reduces computational complexity and provides better rate distortion performance. To code Intra frame it use existing process Rate Distortion Optimization (RDO) method. This method increases computational complexity, increases in bit rate and reduces picture quality so it is difficult to implement in real time applications, so the many researcher has been developed fast mode decision algorithm for coding of intra frame. The previous work carried on Intra frame coding in H.264 standard using fast decision mode intra prediction algorithm based on different techniques was achieved increased in bit rate, degradation of picture quality(PSNR) for different quantization parameters. Many previous approaches of fast mode decision algorithms on intra frame coding achieved only reduction of computational complexity or it save encoding time and limitation was increase in bit rate with loss of quality of picture. In order to avoid increase in bit rate and loss of picture quality a better approach was developed. In this paper developed a better approach i.e. Gaussian pulse for Intra frame coding using diagonal down left intra prediction mode to achieve higher coding efficiency in terms of PSNR and bitrate. In proposed method Gaussian pulse is multiplied with each 4x4 frequency domain coefficients of 4x4 sub macro block of macro block of current frame before quantization process. Multiplication of Gaussian pulse for each 4x4 integer transformed coefficients at macro block levels scales the information of the coefficients in a reversible manner. The resulting signal would turn abstract. Frequency samples are abstract in a known and controllable manner without intermixing of coefficients, it avoids picture getting bad hit for higher values of quantization parameters. The proposed work was implemented using MATLAB and JM 18.6 reference software. The proposed work measure the performance parameters PSNR, bit rate and compression of intra frame of yuv video sequences in QCIF resolution under different values of quantization parameter with Gaussian value for diagonal down left intra prediction mode. The simulation results of proposed algorithm are tabulated and compared with previous algorithm i.e. Tian et al method. The proposed algorithm achieved reduced in bit rate averagely 30.98% and maintain consistent picture quality for QCIF sequences compared to previous algorithm i.e. Tian et al method.

Cognitive distortions and ADHD in pathological gambling: A national longitudinal case-control cohort study.

PubMed

Romo, Lucia; Legauffre, Cindy; Guilleux, Alice; Valleur, Marc; Magalon, David; Fatséas, Mélina; Chéreau-Boudet, Isabelle; Luquiens, Amandine; Vénisse, Jean-Luc; Grall-Bronnec, Marie; Challet-Bouju, Gaëlle

2016-12-01

Introduction The primary outcome of our study was to assess the links between the level of cognitive distortions and the severity of gambling disorder. We also aimed at assessing the links between patient gambling trajectories and attention deficit and hyperactivity disorder (ADHD). Materials and methods The study population (n = 628) was comprised of problem and non-problem gamblers of both sexes between 18 and 65 years of age, who reported gambling on at least one occasion during the previous year. Data encompassed socio-demographic characteristics, gambling habits, the South Oaks Gambling Screen, the Gambling Attitudes and Beliefs Survey - 23, the Wender Utah Rating Scale - Child, and the Adult ADHD Self-report Scale. Results The cognitive distortions with the greatest correlation to the severity of gambling disorder were the "Chasing" and "Emotions." These two dimensions were able to distinguish between problem gamblers seeking treatment or not. While age of onset of gambling and length of gambling practice were not associated with the level of distorted cognitions, a period of abstinence of at least 1 month was associated with a lower level of distorted cognitions. The presence of ADHD resulted in a higher level of distorted cognitions. Conclusion Cognitive work is essential to the prevention, and the treatment, of pathological gambling, especially with respect to emotional biases and chasing behavior. The instauration of an abstinence period of at least 1 month under medical supervision could be a promising therapeutic lead for reducing gambling-related erroneous thoughts and for improving care strategies of pathological gamblers.

Cognitive distortions and ADHD in pathological gambling: A national longitudinal case-control cohort study

PubMed Central

Romo, Lucia; Legauffre, Cindy; Guilleux, Alice; Valleur, Marc; Magalon, David; Fatséas, Mélina; Chéreau-Boudet, Isabelle; Luquiens, Amandine; Vénisse, Jean-Luc; Grall-Bronnec, Marie; Challet-Bouju, Gaëlle

2016-01-01

Introduction The primary outcome of our study was to assess the links between the level of cognitive distortions and the severity of gambling disorder. We also aimed at assessing the links between patient gambling trajectories and attention deficit and hyperactivity disorder (ADHD). Materials and methods The study population (n = 628) was comprised of problem and non-problem gamblers of both sexes between 18 and 65 years of age, who reported gambling on at least one occasion during the previous year. Data encompassed socio-demographic characteristics, gambling habits, the South Oaks Gambling Screen, the Gambling Attitudes and Beliefs Survey – 23, the Wender Utah Rating Scale – Child, and the Adult ADHD Self-report Scale. Results The cognitive distortions with the greatest correlation to the severity of gambling disorder were the “Chasing” and “Emotions.” These two dimensions were able to distinguish between problem gamblers seeking treatment or not. While age of onset of gambling and length of gambling practice were not associated with the level of distorted cognitions, a period of abstinence of at least 1 month was associated with a lower level of distorted cognitions. The presence of ADHD resulted in a higher level of distorted cognitions. Conclusion Cognitive work is essential to the prevention, and the treatment, of pathological gambling, especially with respect to emotional biases and chasing behavior. The instauration of an abstinence period of at least 1 month under medical supervision could be a promising therapeutic lead for reducing gambling-related erroneous thoughts and for improving care strategies of pathological gamblers. PMID:27774813

Precluding nonlinear ISI in direct detection long-haul fiber optic systems

NASA Technical Reports Server (NTRS)

Swenson, Norman L.; Shoop, Barry L.; Cioffi, John M.

1991-01-01

Long-distance, high-rate fiber optic systems employing directly modulated 1.55-micron single-mode lasers and conventional single-mode fiber suffer severe intersymbol interference (ISI) with a large nonlinear component. A method of reducing the nonlinearity of the ISI, thereby making linear equalization more viable, is investigated. It is shown that the degree of nonlinearity is highly dependent on the choice of laser bias current, and that in some cases the ISI nonlinearity can be significantly reduced by biasing the laser substantially above threshold. Simulation results predict that an increase in signal-to-nonlinear-distortion ratio as high as 25 dB can be achieved for synchronously spaced samples at an optimal sampling phase by increasing the bias current from 1.2 times threshold to 3.5 times threshold. The high SDR indicates that a linear tapped delay line equalizer could be used to mitigate ISI. Furthermore, the shape of the pulse response suggests that partial response precoding and digital feedback equalization would be particularly effective for this channel.

Space shuttle Ku-band integrated rendezvous radar/communications system study

NASA Technical Reports Server (NTRS)

1976-01-01

The results are presented of work performed on the Space Shuttle Ku-Band Integrated Rendezvous Radar/Communications System Study. The recommendations and conclusions are included as well as the details explaining the results. The requirements upon which the study was based are presented along with the predicted performance of the recommended system configuration. In addition, shuttle orbiter vehicle constraints (e.g., size, weight, power, stowage space) are discussed. The tradeoffs considered and the operation of the recommended configuration are described for an optimized, integrated Ku-band radar/communications system. Basic system tradeoffs, communication design, radar design, antenna tradeoffs, antenna gimbal and drive design, antenna servo design, and deployed assembly packaging design are discussed. The communications and radar performance analyses necessary to support the system design effort are presented. Detailed derivations of the communications thermal noise error, the radar range, range rate, and angle tracking errors, and the communications transmitter distortion parameter effect on crosstalk between the unbalanced quadriphase signals are included.

Optimization of 3D Field Design

NASA Astrophysics Data System (ADS)

Logan, Nikolas; Zhu, Caoxiang

2017-10-01

Recent progress in 3D tokamak modeling is now leveraged to create a conceptual design of new external 3D field coils for the DIII-D tokamak. Using the IPEC dominant mode as a target spectrum, the Finding Optimized Coils Using Space-curves (FOCUS) code optimizes the currents and 3D geometry of multiple coils to maximize the total set's resonant coupling. The optimized coils are individually distorted in space, creating toroidal ``arrays'' containing a variety of shapes that often wrap around a significant poloidal extent of the machine. The generalized perturbed equilibrium code (GPEC) is used to determine optimally efficient spectra for driving total, core, and edge neoclassical toroidal viscosity (NTV) torque and these too provide targets for the optimization of 3D coil designs. These conceptual designs represent a fundamentally new approach to 3D coil design for tokamaks targeting desired plasma physics phenomena. Optimized coil sets based on plasma response theory will be relevant to designs for future reactors or on any active machine. External coils, in particular, must be optimized for reliable and efficient fusion reactor designs. Work supported by the US Department of Energy under DE-AC02-09CH11466.

Development efforts to improve curved-channel microchannel plates

NASA Technical Reports Server (NTRS)

Corbett, M. B.; Feller, W. B.; Laprade, B. N.; Cochran, R.; Bybee, R.; Danks, A.; Joseph, C.

1993-01-01

Curved-channel microchannel plate (C-plate) improvements resulting from an ongoing NASA STIS microchannel plate (MCP) development program are described. Performance limitations of previous C-plates led to a development program in support of the STIS MAMA UV photon counter, a second generation instrument on the Hubble Space Telescope. C-plate gain, quantum detection efficiency, dark noise, and imaging distortion, which are influenced by channel curvature non-uniformities, have all been improved through use of a new centrifuge fabrication technique. This technique will be described, along with efforts to improve older, more conventional shearing methods. Process optimization methods used to attain targeted C-plate performance goals will be briefly characterized. Newly developed diagnostic measurement techniques to study image distortion, gain uniformity, input bias angle, channel curvature, and ion feedback, will be described. Performance characteristics and initial test results of the improved C-plates will be reported. Future work and applications will also be discussed.

Role of the local structure in superconductivity of LaO0.5F0.5BiS2-x Se x system

NASA Astrophysics Data System (ADS)

Paris, E.; Mizuguchi, Y.; Hacisalihoglu, M. Y.; Hiroi, T.; Joseph, B.; Aquilanti, G.; Miura, O.; Mizokawa, T.; Saini, N. L.

2017-04-01

We have studied the local structure of LaO0.5F0.5BiS2-x Se x by Bi L1-edge extended x-ray absorption fine structure (EXAFS). We find a significant effect of Se substitution on the local atomic correlations with a gradual elongation of average in-plane Bi-S bondlength. The associated mean square relative displacement, measuring average local distortions in the BiS2 plane, hardly shows any change for small Se substitution, but decreases significantly for x≥slant 0.6 . The Se substitution appears to suppress the local distortions within the BiS2 plane that may optimize in-plane orbital hybridization and hence the superconductivity. The results suggest that the local structure of the BiS2-layer is one of the key ingredients to control the physical properties of the BiS2-based dichalcogenides.

An information hidden model holding cover distributions

NASA Astrophysics Data System (ADS)

Fu, Min; Cai, Chao; Dai, Zuxu

2018-03-01

The goal of steganography is to embed secret data into a cover so no one apart from the sender and intended recipients can find the secret data. Usually, the way the cover changing was decided by a hidden function. There were no existing model could be used to find an optimal function which can greatly reduce the distortion the cover suffered. This paper considers the cover carrying secret message as a random Markov chain, taking the advantages of a deterministic relation between initial distributions and transferring matrix of the Markov chain, and takes the transferring matrix as a constriction to decrease statistical distortion the cover suffered in the process of information hiding. Furthermore, a hidden function is designed and the transferring matrix is also presented to be a matrix from the original cover to the stego cover. Experiment results show that the new model preserves a consistent statistical characterizations of original and stego cover.

Distortion of some of the basic principles of public health practice in India.

PubMed

Banerji, Debabar

2006-01-01

India's political leadership has chosen personnel from the Indian Administrative Service cadre of generalist administrators and from the clinician-dominated cadre of the Central Health Services to run the country's health service system. The personnel's inadequate or distorted understanding of some of the basic principles of public health practice--such as developing an epidemiological approach to solving community health problems, choice of appropriate technology, and optimization of health service systems--has had a very deleterious effect on the health service system. These administrators have become vulnerable to manipulation by personnel from international agencies, who also have questionable public health credentials, to create space for imposition of their technocentric, ill-conceived, and ill-designed agenda. To rationalize adoption of such an obviously faulty agenda, they have to be ahistorical, apolitical, and atheoretical and indulge in misinformation, disinformation, and suppression and manipulation of information. This amounts to what Navarro has termed "intellectual fascism."

Improved maximum average correlation height filter with adaptive log base selection for object recognition

NASA Astrophysics Data System (ADS)

Tehsin, Sara; Rehman, Saad; Awan, Ahmad B.; Chaudry, Qaiser; Abbas, Muhammad; Young, Rupert; Asif, Afia

2016-04-01

Sensitivity to the variations in the reference image is a major concern when recognizing target objects. A combinational framework of correlation filters and logarithmic transformation has been previously reported to resolve this issue alongside catering for scale and rotation changes of the object in the presence of distortion and noise. In this paper, we have extended the work to include the influence of different logarithmic bases on the resultant correlation plane. The meaningful changes in correlation parameters along with contraction/expansion in the correlation plane peak have been identified under different scenarios. Based on our research, we propose some specific log bases to be used in logarithmically transformed correlation filters for achieving suitable tolerance to different variations. The study is based upon testing a range of logarithmic bases for different situations and finding an optimal logarithmic base for each particular set of distortions. Our results show improved correlation and target detection accuracies.

Mitigation of time-varying distortions in Nyquist-WDM systems using machine learning

NASA Astrophysics Data System (ADS)

Granada Torres, Jhon J.; Varughese, Siddharth; Thomas, Varghese A.; Chiuchiarelli, Andrea; Ralph, Stephen E.; Cárdenas Soto, Ana M.; Guerrero González, Neil

2017-11-01

We propose a machine learning-based nonsymmetrical demodulation technique relying on clustering to mitigate time-varying distortions derived from several impairments such as IQ imbalance, bias drift, phase noise and interchannel interference. Experimental results show that those impairments cause centroid movements in the received constellations seen in time-windows of 10k symbols in controlled scenarios. In our demodulation technique, the k-means algorithm iteratively identifies the cluster centroids in the constellation of the received symbols in short time windows by means of the optimization of decision thresholds for a minimum BER. We experimentally verified the effectiveness of this computationally efficient technique in multicarrier 16QAM Nyquist-WDM systems over 270 km links. Our nonsymmetrical demodulation technique outperforms the conventional QAM demodulation technique, reducing the OSNR requirement up to ∼0.8 dB at a BER of 1 × 10-2 for signals affected by interchannel interference.

Origin and Correction of Magnetic Field Inhomogeneity at the Interface in Biphasic NMR Samples

PubMed Central

Martin, Bryan T.; Chingas, G. C.

2012-01-01

The use of susceptibility matching to minimize spectral distortion of biphasic samples layered in a standard 5 mm NMR tube is described. The approach uses magic angle spinning (MAS) to first extract chemical shift differences by suppressing bulk magnetization. Then, using biphasic coaxial samples, magnetic susceptibilities are matched by titration with a paramagnetic salt. The matched phases are then layered in a standard NMR tube where they can be shimmed and examined. Line widths of two distinct spectral lines, selected to characterize homogeneity in each phase, are simultaneously optimized. Two-dimensional distortion-free, slice-resolved spectra of an octanol/water system illustrate the method. These data are obtained using a 2D stepped-gradient pulse sequence devised for this application. Advantages of this sequence over slice-selective methods are that acquisition efficiency is increased and processing requires only conventional software. PMID:22459062

An integrated approach to improving noisy speech perception

NASA Astrophysics Data System (ADS)

Koval, Serguei; Stolbov, Mikhail; Smirnova, Natalia; Khitrov, Mikhail

2002-05-01

For a number of practical purposes and tasks, experts have to decode speech recordings of very poor quality. A combination of techniques is proposed to improve intelligibility and quality of distorted speech messages and thus facilitate their comprehension. Along with the application of noise cancellation and speech signal enhancement techniques removing and/or reducing various kinds of distortions and interference (primarily unmasking and normalization in time and frequency fields), the approach incorporates optimal listener expert tactics based on selective listening, nonstandard binaural listening, accounting for short-term and long-term human ear adaptation to noisy speech, as well as some methods of speech signal enhancement to support speech decoding during listening. The approach integrating the suggested techniques ensures high-quality ultimate results and has successfully been applied by Speech Technology Center experts and by numerous other users, mainly forensic institutions, to perform noisy speech records decoding for courts, law enforcement and emergency services, accident investigation bodies, etc.

Knee implant imaging at 3 Tesla using high-bandwidth radiofrequency pulses.

PubMed

Bachschmidt, Theresa J; Sutter, Reto; Jakob, Peter M; Pfirrmann, Christian W A; Nittka, Mathias

2015-06-01

To investigate the impact of high-bandwidth radiofrequency (RF) pulses used in turbo spin echo (TSE) sequences or combined with slice encoding for metal artifact correction (SEMAC) on artifact reduction at 3 Tesla in the knee in the presence of metal. Local transmit/receive coils feature increased maximum B1 amplitude, reduced SAR exposition and thus enable the application of high-bandwidth RF pulses. Susceptibility-induced through-plane distortion scales inversely with the RF bandwidth and the view angle, hence blurring, increases for higher RF bandwidths, when SEMAC is used. These effects were assessed for a phantom containing a total knee arthroplasty. TSE and SEMAC sequences with conventional and high RF bandwidths and different contrasts were tested on eight patients with different types of implants. To realize scan times of 7 to 9 min, SEMAC was always applied with eight slice-encoding steps and distortion was rated by two radiologists. A local transmit/receive knee coil enables the use of an RF bandwidth of 4 kHz compared with 850 Hz in conventional sequences. Phantom scans confirm the relation of RF bandwidth and through-plane distortion, which can be reduced up to 79%, and demonstrate the increased blurring for high-bandwidth RF pulses. In average, artifacts in this RF mode are rated hardly visible for patients with joint arthroplasties, when eight SEMAC slice-encoding steps are applied, and for patients with titanium fixtures, when TSE is used. The application of high-bandwidth RF pulses by local transmit coils substantially reduces through-plane distortion artifacts at 3 Tesla. © 2014 Wiley Periodicals, Inc.

The impact of galaxy formation on satellite kinematics and redshift-space distortions

NASA Astrophysics Data System (ADS)

Orsi, Álvaro A.; Angulo, Raúl E.

2018-04-01

Galaxy surveys aim to map the large-scale structure of the Universe and use redshift-space distortions to constrain deviations from general relativity and probe the existence of massive neutrinos. However, the amount of information that can be extracted is limited by the accuracy of theoretical models used to analyse the data. Here, by using the L-Galaxies semi-analytical model run over the Millennium-XXL N-body simulation, we assess the impact of galaxy formation on satellite kinematics and the theoretical modelling of redshift-space distortions. We show that different galaxy selection criteria lead to noticeable differences in the radial distributions and velocity structure of satellite galaxies. Specifically, whereas samples of stellar mass selected galaxies feature satellites that roughly follow the dark matter, emission line satellite galaxies are located preferentially in the outskirts of haloes and display net infall velocities. We demonstrate that capturing these differences is crucial for modelling the multipoles of the correlation function in redshift space, even on large scales. In particular, we show how modelling small-scale velocities with a single Gaussian distribution leads to a poor description of the measured clustering. In contrast, we propose a parametrization that is flexible enough to model the satellite kinematics and that leads to an accurate description of the correlation function down to sub-Mpc scales. We anticipate that our model will be a necessary ingredient in improved theoretical descriptions of redshift-space distortions, which together could result in significantly tighter cosmological constraints and a more optimal exploitation of future large data sets.

[Design of a Component and Transmission Imaging Spectrometer].

PubMed

Sun, Bao-peng; Zhang, Yi; Yue, Jiang; Han, Jing; Bai, Lian-fa

2015-05-01

In the reflection-based imaging spectrometer, multiple reflection(diffraction) produces stray light and it is difficult to assemble. To address that, a high performance transmission spectral imaging system based on general optical components was developed. On the basis of simple structure, the system is easy to assemble. And it has wide application and low cost compared to traditional imaging spectrometers. All components in the design can be replaced according to different application situations, having high degree of freedom. In order to reduce the influence of stray light, a method based on transmission was introduced. Two sets of optical systems with different objective lenses were simulated; the parameters such as distortion, MTF and aberration.were analyzed and optimized in the ZEMAX software. By comparing the performance of system with different objective len 25 and 50 mm, it can be concluded that the replacement of telescope lens has little effect on imaging quality of whole system. An imaging spectrometer is developed successfully according design parameters. The telescope lens uses double Gauss structures, which is beneficial to reduce field curvature and distortion. As the craftsmanship of transmission-type plane diffraction grating is mature, it can be used without modification and it is easy to assemble, so it is used as beam-split. component of the imaging spectrometer. In addition, the real imaging spectrometer was tested for spectral resolution and distortion. The result demonstrates that the system has good ability in distortion control, and spectral resolution is 2 nm. These data satisfy the design requirement, and obtained spectrum of deuterium lamp through calibrated system are ideal results.

Distorted Carbon Nitride Structure with Substituted Benzene Moieties for Enhanced Visible Light Photocatalytic Activities.

PubMed

Kim, Hyejin; Gim, Suji; Jeon, Tae Hwa; Kim, Hyungjun; Choi, Wonyong

2017-11-22

Carbon nitride (CN) is being intensively investigated as a low-cost visible light active photocatalyst, but its practical applications are limited because of the fast charge pair recombination and low visible light absorption. Here, we introduce a new strategy for enhancing its visible light photocatalytic activity by designing the CN structure in which the nitrogen of tertiary amine is substituted with a benzene molecule connected by three heptazine rings. The intramolecular benzene doping induced the structural changes from planar symmetric structure to distorted geometry, which could be predicted by density functional theory calculation. This structural distortion facilitated the spatial separation of photogenerated charge pairs and retarded charge recombination via exciton dissociation. Such unique properties of the benzene-incorporated CN were confirmed by the photoluminescence (PL) and photoelectrochemical analyses. The optimal loading of benzene doping reduced the PL of the conjugated ring system (π → π* transition) but enhanced the PL of the forbidden n → π* transition at the nitrogen atoms with lone pair electrons due to the distortion from the planar geometry. The photoelectrode of benzene-doped CN exhibited higher photocurrent and lower charge transfer resistance than bare CN electrode, indicating that the photogenerated charge pairs are more efficiently separated. As a result, the benzene-doped CN markedly increased the photocatalytic activity for the degradation of various organic pollutants and that for H 2 O 2 production (via O 2 reduction). This study proposes a simple strategy for chemical structural modification of carbon nitride to boost the visible light photocatalytic activity.

Evaluation of Probe-Induced Flow Distortion of Campbell CSAT3 Sonic Anemometers by Numerical Simulation

NASA Astrophysics Data System (ADS)

Huq, Sadiq; De Roo, Frederik; Foken, Thomas; Mauder, Matthias

2017-10-01

The Campbell CSAT3 sonic anemometer is one of the most popular instruments for turbulence measurements in basic micrometeorological research and ecological applications. While measurement uncertainty has been characterized by field experiments and wind-tunnel studies in the past, there are conflicting estimates, which motivated us to conduct a numerical experiment using large-eddy simulation to evaluate the probe-induced flow distortion of the CSAT3 anemometer under controlled conditions, and with exact knowledge of the undisturbed flow. As opposed to wind-tunnel studies, we imposed oscillations in both the vertical and horizontal velocity components at the distinct frequencies and amplitudes found in typical turbulence spectra in the surface layer. The resulting flow-distortion errors for the standard deviations of the vertical velocity component range from 3 to 7%, and from 1 to 3% for the horizontal velocity component, depending on the azimuth angle. The magnitude of these errors is almost independent of the frequency of wind speed fluctuations, provided the amplitude is typical for surface-layer turbulence. A comparison of the corrections for transducer shadowing proposed by both Kaimal et al. (Proc Dyn Flow Conf, 551-565, 1978) and Horst et al. (Boundary-Layer Meteorol 155:371-395, 2015) show that both methods compensate for a larger part of the observed error, but do not sufficiently account for the azimuth dependency. Further numerical simulations could be conducted in the future to characterize the flow distortion induced by other existing types of sonic anemometers for the purposes of optimizing their geometry.

Numerical analysis of flow interaction of turbine system in two-stage turbocharger of internal combustion engine

NASA Astrophysics Data System (ADS)

Liu, Y. B.; Zhuge, W. L.; Zhang, Y. J.; Zhang, S. Y.

2016-05-01

To reach the goal of energy conservation and emission reduction, high intake pressure is needed to meet the demand of high power density and high EGR rate for internal combustion engine. Present power density of diesel engine has reached 90KW/L and intake pressure ratio needed is over 5. Two-stage turbocharging system is an effective way to realize high compression ratio. Because turbocharging system compression work derives from exhaust gas energy. Efficiency of exhaust gas energy influenced by design and matching of turbine system is important to performance of high supercharging engine. Conventional turbine system is assembled by single-stage turbocharger turbines and turbine matching is based on turbine MAP measured on test rig. Flow between turbine system is assumed uniform and value of outlet physical quantities of turbine are regarded as the same as ambient value. However, there are three-dimension flow field distortion and outlet physical quantities value change which will influence performance of turbine system as were demonstrated by some studies. For engine equipped with two-stage turbocharging system, optimization of turbine system design will increase efficiency of exhaust gas energy and thereby increase engine power density. However flow interaction of turbine system will change flow in turbine and influence turbine performance. To recognize the interaction characteristics between high pressure turbine and low pressure turbine, flow in turbine system is modeled and simulated numerically. The calculation results suggested that static pressure field at inlet to low pressure turbine increases back pressure of high pressure turbine, however efficiency of high pressure turbine changes little; distorted velocity field at outlet to high pressure turbine results in swirl at inlet to low pressure turbine. Clockwise swirl results in large negative angle of attack at inlet to rotor which causes flow loss in turbine impeller passages and decreases turbine efficiency. However negative angle of attack decreases when inlet swirl is anti-clockwise and efficiency of low pressure turbine can be increased by 3% compared to inlet condition of clockwise swirl. Consequently flow simulation and analysis are able to aid in figuring out interaction mechanism of turbine system and optimizing turbine system design.

Investigating the variability of memory distortion for an analogue trauma.

PubMed

Strange, Deryn; Takarangi, Melanie K T

2015-01-01

In this paper, we examine whether source monitoring (SM) errors might be one mechanism that accounts for traumatic memory distortion. Participants watched a traumatic film with some critical (crux) and non-critical (non-crux) scenes removed. Twenty-four hours later, they completed a memory test. To increase the likelihood participants would notice the film's gaps, we inserted visual static for the length of each missing scene. We then added manipulations designed to affect people's SM behaviour. To encourage systematic SM, before watching the film, we warned half the participants that we had removed some scenes. To encourage heuristic SM some participants also saw labels describing the missing scenes. Adding static highlighting, the missing scenes did not affect false recognition of those missing scenes. However, a warning decreased, while labels increased, participants' false recognition rates. We conclude that manipulations designed to affect SM behaviour also affect the degree of memory distortion in our paradigm.

Sensitivity of boundary-layer stability to base-state distortions at high Mach numbers

NASA Astrophysics Data System (ADS)

Park, Junho; Zaki, Tamer

2017-11-01

The stability diagram of high-speed boundary layers has been established by evaluating the linear instability modes of the similarity profile, over wide ranges of Reynolds and Mach numbers. In real flows, however, the base state can deviate from the similarity profile. Both the base velocity and temperature can be distorted, for example due to roughness and thermal wall treatments. We review the stability problem of high-speed boundary layer, and derive a new formulation of the sensitivity to base-state distortion using forward and adjoint parabolized stability equations. The new formulation provides qualitative and quantitative interpretations on change in growth rate due to modifications of mean-flow and mean-temperature in heated high-speed boundary layers, and establishes the foundation for future control strategies. This work has been funded by the Air Force Office of Scientific Research (AFOSR) Grant: FA9550-16-1-0103.

Compressed Speech Technology: Implications for Learning and Instruction.

ERIC Educational Resources Information Center

Sullivan, LeRoy L.

This paper first traces the historical development of speech compression technology, which has made it possible to alter the spoken rate of a pre-recorded message without excessive distortion. Terms used to describe techniques employed as the technology evolved are discussed, including rapid speech, rate altered speech, cut-and-spliced speech, and…

Correcting power and p-value calculations for bias in diffusion tensor imaging.

PubMed

Lauzon, Carolyn B; Landman, Bennett A

2013-07-01

Diffusion tensor imaging (DTI) provides quantitative parametric maps sensitive to tissue microarchitecture (e.g., fractional anisotropy, FA). These maps are estimated through computational processes and subject to random distortions including variance and bias. Traditional statistical procedures commonly used for study planning (including power analyses and p-value/alpha-rate thresholds) specifically model variability, but neglect potential impacts of bias. Herein, we quantitatively investigate the impacts of bias in DTI on hypothesis test properties (power and alpha-rate) using a two-sided hypothesis testing framework. We present theoretical evaluation of bias on hypothesis test properties, evaluate the bias estimation technique SIMEX for DTI hypothesis testing using simulated data, and evaluate the impacts of bias on spatially varying power and alpha rates in an empirical study of 21 subjects. Bias is shown to inflame alpha rates, distort the power curve, and cause significant power loss even in empirical settings where the expected difference in bias between groups is zero. These adverse effects can be attenuated by properly accounting for bias in the calculation of power and p-values. Copyright © 2013 Elsevier Inc. All rights reserved.

Low-rate image coding using vector quantization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makur, A.

1990-01-01

This thesis deals with the development and analysis of a computationally simple vector quantization image compression system for coding monochrome images at low bit rate. Vector quantization has been known to be an effective compression scheme when a low bit rate is desirable, but the intensive computation required in a vector quantization encoder has been a handicap in using it for low rate image coding. The present work shows that, without substantially increasing the coder complexity, it is indeed possible to achieve acceptable picture quality while attaining a high compression ratio. Several modifications to the conventional vector quantization coder aremore » proposed in the thesis. These modifications are shown to offer better subjective quality when compared to the basic coder. Distributed blocks are used instead of spatial blocks to construct the input vectors. A class of input-dependent weighted distortion functions is used to incorporate psychovisual characteristics in the distortion measure. Computationally simple filtering techniques are applied to further improve the decoded image quality. Finally, unique designs of the vector quantization coder using electronic neural networks are described, so that the coding delay is reduced considerably.« less

The VIMOS Public Extragalactic Redshift Survey. Measuring the growth rate of structure around cosmic voids

NASA Astrophysics Data System (ADS)

Hawken, A. J.; Granett, B. R.; Iovino, A.; Guzzo, L.; Peacock, J. A.; de la Torre, S.; Garilli, B.; Bolzonella, M.; Scodeggio, M.; Abbas, U.; Adami, C.; Bottini, D.; Cappi, A.; Cucciati, O.; Davidzon, I.; Fritz, A.; Franzetti, P.; Krywult, J.; Le Brun, V.; Le Fèvre, O.; Maccagni, D.; Małek, K.; Marulli, F.; Polletta, M.; Pollo, A.; Tasca, L. A. M.; Tojeiro, R.; Vergani, D.; Zanichelli, A.; Arnouts, S.; Bel, J.; Branchini, E.; De Lucia, G.; Ilbert, O.; Moscardini, L.; Percival, W. J.

2017-11-01

We aim to develop a novel methodology for measuring thegrowth rate of structure around cosmic voids. We identified voids in the completed VIMOS Public Extragalactic Redshift Survey (VIPERS), using an algorithm based on searching for empty spheres. We measured the cross-correlation between the centres of voids and the complete galaxy catalogue. The cross-correlation function exhibits a clear anisotropy in both VIPERS fields (W1 and W4), which is characteristic of linear redshift space distortions. By measuring the projected cross-correlation and then de-projecting it we are able to estimate the un-distorted cross-correlation function. We propose that given a sufficiently well-measured cross-correlation function one should be able to measure the linear growth rate of structure by applying a simple linear Gaussian streaming model for the redshift space distortions (RSD). Our study of voids in 306 mock galaxy catalogues mimicking the VIPERS fields suggests that VIPERS is capable of measuring β, the ratio of the linear growth rate to the bias, with an error of around 25%. Applying our method to the VIPERS data, we find a value for the redshift space distortion parameter, β = 0.423-0.108+0.104 which, given the bias of the galaxy population we use, gives a linear growth rate of f σ8 = 0.296-0.078+0.075 at z = 0.727. These results are consistent with values observed in parallel VIPERS analyses that use standard techniques. Based on observations collected at the European Southern Observatory, Cerro Paranal, Chile, using the Very Large Telescope under programs 182.A-0886 and partly 070.A-9007. Also based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS.

Design of a spoke-type permanent-magnet motor with optimal winding configuration for electric vehicle applications

NASA Astrophysics Data System (ADS)

Chen, Qian; Liu, Guohai; Gong, Wensheng; Qu, Li; Zhao, Wenxiang; Shen, Yue

2012-04-01

The spoke-type motor has higher torque density than the conventional one resulting from its structure for concentrating flux from permanent magnets (PMs). However, this motor suffers from the serious distortion of back electromotive force (EMF). This paper proposes a cost-effective approach to design a spoke-type motor with lower harmonics of back-EMF for electric vehicle. The key is to superimpose the coil-EMF of one phase in such a way that the harmonics of the phase-EMF can be canceled, resulting in essentially sinusoidal waveforms. By using finite element method (FEM), an optimal coil-EMF vectors distribution for minimum harmonics of the phase-EMF is obtained and verified. In addition, the co-simulation technology is adopted to verify that the torque ripple under the optimal winding configuration can be significantly suppressed.

Positronium signature in organic liquid scintillators for neutrino experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franco, D.; Consolati, G.; Trezzi, D.

2011-01-15

Electron antineutrinos are commonly detected in liquid scintillator experiments via inverse {beta} decay by looking at the coincidence between the reaction products: neutrons and positrons. Prior to positron annihilation, an electron-positron pair may form an orthopositronium (o-Ps) state, with a mean lifetime of a few nanoseconds. Even if the o-Ps decay is speeded up by spin-flip or pick-off effects, it may introduce distortions in the photon emission time distribution, crucial for position reconstruction and pulse shape discrimination algorithms in antineutrino experiments. Reversing the problem, the o-Ps-induced time distortion represents a new signature for tagging antineutrinos in liquid scintillator. In thismore » article, we report the results of measurements of the o-Ps formation probability and lifetime for the most used solvents for organic liquid scintillators in neutrino physics (pseudocumene, linear alkyl benzene, phenylxylylethane, and dodecane). We characterize also a mixture of pseudocumene +1.5 g/l of 2,5-diphenyloxazole, a fluor acting as wavelength shifter. In the second part of the article, we demonstrate that the o-Ps-induced distortion of the scintillation photon emission time distributions represent an optimal signature for tagging positrons on an event by event basis, potentially enhancing the antineutrino detection.« less

Entropy studies on beam distortion by atmospheric turbulence

NASA Astrophysics Data System (ADS)

Wu, Chensheng; Ko, Jonathan; Davis, Christopher C.

2015-09-01

When a beam propagates through atmospheric turbulence over a known distance, the target beam profile deviates from the projected profile of the beam on the receiver. Intuitively, the unwanted distortion provides information about the atmospheric turbulence. This information is crucial for guiding adaptive optic systems and improving beam propagation results. In this paper, we propose an entropy study based on the image from a plenoptic sensor to provide a measure of information content of atmospheric turbulence. In general, lower levels of atmospheric turbulence will have a smaller information size while higher levels of atmospheric turbulence will cause significant expansion of the information size, which may exceed the maximum capacity of a sensing system and jeopardize the reliability of an AO system. Therefore, the entropy function can be used to analyze the turbulence distortion and evaluate performance of AO systems. In fact, it serves as a metric that can tell the improvement of beam correction in each iteration step. In addition, it points out the limitation of an AO system at optimized correction as well as the minimum information needed for wavefront sensing to achieve certain levels of correction. In this paper, we will demonstrate the definition of the entropy function and how it is related to evaluating information (randomness) carried by atmospheric turbulence.

Wireless Power Transfer for Distributed Estimation in Sensor Networks

NASA Astrophysics Data System (ADS)

Mai, Vien V.; Shin, Won-Yong; Ishibashi, Koji

2017-04-01

This paper studies power allocation for distributed estimation of an unknown scalar random source in sensor networks with a multiple-antenna fusion center (FC), where wireless sensors are equipped with radio-frequency based energy harvesting technology. The sensors' observation is locally processed by using an uncoded amplify-and-forward scheme. The processed signals are then sent to the FC, and are coherently combined at the FC, at which the best linear unbiased estimator (BLUE) is adopted for reliable estimation. We aim to solve the following two power allocation problems: 1) minimizing distortion under various power constraints; and 2) minimizing total transmit power under distortion constraints, where the distortion is measured in terms of mean-squared error of the BLUE. Two iterative algorithms are developed to solve the non-convex problems, which converge at least to a local optimum. In particular, the above algorithms are designed to jointly optimize the amplification coefficients, energy beamforming, and receive filtering. For each problem, a suboptimal design, a single-antenna FC scenario, and a common harvester deployment for colocated sensors, are also studied. Using the powerful semidefinite relaxation framework, our result is shown to be valid for any number of sensors, each with different noise power, and for an arbitrarily number of antennas at the FC.

Distortion of online reputation by excess reciprocity: quantification and estimation of unbiased reputation

NASA Astrophysics Data System (ADS)

Aste, Tomaso; Livan, Giacomo; Caccioli, Fabio

The peer-to-peer (P2P) economy relies on establishing trust in distributed networked systems, where the reliability of a user is assessed through digital peer-review processes that aggregate ratings into reputation scores. Here we present evidence of a network effect which biases digital reputations, revealing that P2P networks display exceedingly high levels of reciprocity. In fact, these are so large that they are close to the highest levels structurally compatible with the networks reputation landscape. This indicates that the crowdsourcing process underpinning digital reputation is significantly distorted by the attempt of users to mutually boost reputation, or to retaliate, through the exchange of ratings. We uncover that the least active users are predominantly responsible for such reciprocity-induced bias, and that this fact can be exploited to obtain more reliable reputation estimates. Our findings are robust across different P2P platforms, including both cases where ratings are used to vote on the content produced by users and to vote on user profiles.

Fast mode decision based on human noticeable luminance difference and rate distortion cost for H.264/AVC

NASA Astrophysics Data System (ADS)

Li, Mian-Shiuan; Chen, Mei-Juan; Tai, Kuang-Han; Sue, Kuen-Liang

2013-12-01

This article proposes a fast mode decision algorithm based on the correlation of the just-noticeable-difference (JND) and the rate distortion cost (RD cost) to reduce the computational complexity of H.264/AVC. First, the relationship between the average RD cost and the number of JND pixels is established by Gaussian distributions. Thus, the RD cost of the Inter 16 × 16 mode is compared with the predicted thresholds from these models for fast mode selection. In addition, we use the image content, the residual data, and JND visual model for horizontal/vertical detection, and then utilize the result to predict the partition in a macroblock. From the experimental results, a greater time saving can be achieved while the proposed algorithm also maintains performance and quality effectively.

Topology Optimization for Reducing Additive Manufacturing Processing Distortions

DTIC Science & Technology

2017-12-01

features that curl or warp under thermal load and are subsequently struck by the recoater blade /roller. Support structures act to wick heat away and...was run for 150 iterations. The material properties for all examples were Young’s modulus E = 1 GPa, Poisson’s ratio ν = 0.25, and thermal expansion...the element-birth model is significantly more computationally expensive for a full op- timization run . Consider, the computational complexity of a

Portable Ultrasound Imaging of the Brain for Use in Forward Battlefield Areas

DTIC Science & Technology

2011-03-01

ultrasound measurement of skull thickness and sound speed, phase correction of beam distortion, the tomographic reconstruction algorithm, and the final...produce a coherent imaging source. We propose a corrective technique that will use ultrasound-based phased -array beam correction [3], optimized...not expected to be a significant factor in the ability to phase -correct the imaging beam . In addition to planning (2.2.1), the data is also be used

Optimum shape control of flexible beams by piezo-electric actuators

NASA Technical Reports Server (NTRS)

Baz, A.; Poh, S.

1987-01-01

The utilization of piezoelectric actuators in controlling the static deformation and shape of flexible beams is examined. An optimum design procedure is presented to enable the selection of the optimal location, thickness and excitation voltage of the piezoelectric actuators in a way that would minimize the deflection of the beam to which these actuators are bonded. Numerical examples are presented to illustrate the application of the developed optimization procedure in minimizing structural deformation of beams using ceramic and polymeric piezoelectric actuators bonded to the beams with a typical bonding agent. The obtained results emphasize the importance of the devised rational produce in designing beam-actuator systems with minimal elastic distortions.

Static deflection control of flexible beams by piezo-electric actuators

NASA Technical Reports Server (NTRS)

Baz, A. M.

1986-01-01

This study deals with the utilization of piezo-electric actuators in controlling the static deformation of flexible beams. An optimum design procedure is presented to enable the selection of the optimal location, thickness and excitation voltage of the piezo-electric actuators in a way that would minimize the deflection of the beam to which these actuators are bonded. Numerical examples are presented to illustrate the application of the developed optimization procedure in minimizing the structural deformation of beams of different materials when subjected to different loading and end conditions using ceramic or polymeric piezo-electric actuators. The results obtained emphasize the importance of the devised rational procedure in designing beam-actuator systems with minimal elastic distortions.

Improved techniques for outgoing wave variational principle calculations of converged state-to-state transition probabilities for chemical reactions

NASA Technical Reports Server (NTRS)

Mielke, Steven L.; Truhlar, Donald G.; Schwenke, David W.

1991-01-01

Improved techniques and well-optimized basis sets are presented for application of the outgoing wave variational principle to calculate converged quantum mechanical reaction probabilities. They are illustrated with calculations for the reactions D + H2 yields HD + H with total angular momentum J = 3 and F + H2 yields HF + H with J = 0 and 3. The optimization involves the choice of distortion potential, the grid for calculating half-integrated Green's functions, the placement, width, and number of primitive distributed Gaussians, and the computationally most efficient partition between dynamically adapted and primitive basis functions. Benchmark calculations with 224-1064 channels are presented.

An analytical optimization model for infrared image enhancement via local context

NASA Astrophysics Data System (ADS)

Xu, Yongjian; Liang, Kun; Xiong, Yiru; Wang, Hui

2017-12-01

The requirement for high-quality infrared images is constantly increasing in both military and civilian areas, and it is always associated with little distortion and appropriate contrast, while infrared images commonly have some shortcomings such as low contrast. In this paper, we propose a novel infrared image histogram enhancement algorithm based on local context. By constraining the enhanced image to have high local contrast, a regularized analytical optimization model is proposed to enhance infrared images. The local contrast is determined by evaluating whether two intensities are neighbors and calculating their differences. The comparison on 8-bit images shows that the proposed method can enhance the infrared images with more details and lower noise.

An Inlet Distortion Assessment During Aircraft Departures at High Angle of Attack for an F/A-18A Aircraft

NASA Technical Reports Server (NTRS)

Steenken, William G.; Williams, John G.; Yuhas, Andrew J.; Walsh, Kevin R.

1997-01-01

The F404-GE-400-powered F/A-18A High Alpha Research Vehicle (HARV) was used to examine the quality of inlet airflow during departed flight maneuvers, that is, during flight outside the normal maneuvering envelope where control surfaces have little or no effectiveness. Six nose-left and six nose-right departures were initiated at Mach numbers between 0.3 and 0.4 at an altitude of 35 kft. The entry yaw rates were approximately 40 to 90 deg/sec. Engine surges were encountered during three of the nose-left and one of the nose-right departures. Time-variant inlet-total-pressure distortion levels at the engine face did not significantly exceed those at maximum angle-of-attack and sideslip maneuvers during controlled flight. Surges caused by inlet distortion levels resulted from a combination of high levels of inlet distortion and rapid changes in aircraft position. These rapid changes indicate a combination of engine support and gyroscopic loads being applied to the engine structure that impact the aerodynamic stability of the compressor through changes in the rotor-to-case clearances. This document presents the slides from an oral presentation.

Vibrational sum-frequency generation spectroscopy of lipid bilayers at repetition rates up to 100 kHz

NASA Astrophysics Data System (ADS)

Yesudas, Freeda; Mero, Mark; Kneipp, Janina; Heiner, Zsuzsanna

2018-03-01

Broadband vibrational sum-frequency generation (BB-VSFG) spectroscopy has become a well-established surface analytical tool capable of identifying the orientation and structure of molecular layers. A straightforward way to boost the sensitivity of the technique could be to increase the laser repetition rate beyond that of standard BB-VSFG spectrometers, which rely on Ti:sapphire lasers operating at repetition rates of 1-5 kHz. Nevertheless, possible thermally induced artifacts in the vibrational spectra due to higher laser average powers are unexplored. Here, we discuss laser power induced temperature accumulation effects that distort the BB-VSFG spectra of 1,2-diacyl-sn-glycero-3-phosphocholine at an interface between two transparent phases at repetition rates of 5, 10, 50, and 100 kHz at constant pulse energy. No heat-induced distortions were found in the spectra, suggesting that the increase in the laser repetition rate provides a feasible route to an improved signal-to-noise ratio or shorter data acquisition times in BB-VSFG spectroscopy for thin films on transparent substrates. The results have implications for future BB-VSFG spectrometers pushing the detection limit for molecular layers with low surface coverage.

Multi-objective Optimization of Pulsed Gas Metal Arc Welding Process Using Neuro NSGA-II

NASA Astrophysics Data System (ADS)

Pal, Kamal; Pal, Surjya K.

2018-05-01

Weld quality is a critical issue in fabrication industries where products are custom-designed. Multi-objective optimization results number of solutions in the pareto-optimal front. Mathematical regression model based optimization methods are often found to be inadequate for highly non-linear arc welding processes. Thus, various global evolutionary approaches like artificial neural network, genetic algorithm (GA) have been developed. The present work attempts with elitist non-dominated sorting GA (NSGA-II) for optimization of pulsed gas metal arc welding process using back propagation neural network (BPNN) based weld quality feature models. The primary objective to maintain butt joint weld quality is the maximization of tensile strength with minimum plate distortion. BPNN has been used to compute the fitness of each solution after adequate training, whereas NSGA-II algorithm generates the optimum solutions for two conflicting objectives. Welding experiments have been conducted on low carbon steel using response surface methodology. The pareto-optimal front with three ranked solutions after 20th generations was considered as the best without further improvement. The joint strength as well as transverse shrinkage was found to be drastically improved over the design of experimental results as per validated pareto-optimal solutions obtained.

Joint Denoising/Compression of Image Contours via Shape Prior and Context Tree

NASA Astrophysics Data System (ADS)

Zheng, Amin; Cheung, Gene; Florencio, Dinei

2018-07-01

With the advent of depth sensing technologies, the extraction of object contours in images---a common and important pre-processing step for later higher-level computer vision tasks like object detection and human action recognition---has become easier. However, acquisition noise in captured depth images means that detected contours suffer from unavoidable errors. In this paper, we propose to jointly denoise and compress detected contours in an image for bandwidth-constrained transmission to a client, who can then carry out aforementioned application-specific tasks using the decoded contours as input. We first prove theoretically that in general a joint denoising / compression approach can outperform a separate two-stage approach that first denoises then encodes contours lossily. Adopting a joint approach, we first propose a burst error model that models typical errors encountered in an observed string y of directional edges. We then formulate a rate-constrained maximum a posteriori (MAP) problem that trades off the posterior probability p(x'|y) of an estimated string x' given y with its code rate R(x'). We design a dynamic programming (DP) algorithm that solves the posed problem optimally, and propose a compact context representation called total suffix tree (TST) that can reduce complexity of the algorithm dramatically. Experimental results show that our joint denoising / compression scheme outperformed a competing separate scheme in rate-distortion performance noticeably.

Dispersion-convolution model for simulating peaks in a flow injection system.

PubMed

Pai, Su-Cheng; Lai, Yee-Hwong; Chiao, Ling-Yun; Yu, Tiing

2007-01-12

A dispersion-convolution model is proposed for simulating peak shapes in a single-line flow injection system. It is based on the assumption that an injected sample plug is expanded due to a "bulk" dispersion mechanism along the length coordinate, and that after traveling over a distance or a period of time, the sample zone will develop into a Gaussian-like distribution. This spatial pattern is further transformed to a temporal coordinate by a convolution process, and finally a temporal peak image is generated. The feasibility of the proposed model has been examined by experiments with various coil lengths, sample sizes and pumping rates. An empirical dispersion coefficient (D*) can be estimated by using the observed peak position, height and area (tp*, h* and At*) from a recorder. An empirical temporal shift (Phi*) can be further approximated by Phi*=D*/u2, which becomes an important parameter in the restoration of experimental peaks. Also, the dispersion coefficient can be expressed as a second-order polynomial function of the pumping rate Q, for which D*(Q)=delta0+delta1Q+delta2Q2. The optimal dispersion occurs at a pumping rate of Qopt=sqrt[delta0/delta2]. This explains the interesting "Nike-swoosh" relationship between the peak height and pumping rate. The excellent coherence of theoretical and experimental peak shapes confirms that the temporal distortion effect is the dominating reason to explain the peak asymmetry in flow injection analysis.

Multi-pass encoding of hyperspectral imagery with spectral quality control

NASA Astrophysics Data System (ADS)

Wasson, Steven; Walker, William

2015-05-01

Multi-pass encoding is a technique employed in the field of video compression that maximizes the quality of an encoded video sequence within the constraints of a specified bit rate. This paper presents research where multi-pass encoding is extended to the field of hyperspectral image compression. Unlike video, which is primarily intended to be viewed by a human observer, hyperspectral imagery is processed by computational algorithms that generally attempt to classify the pixel spectra within the imagery. As such, these algorithms are more sensitive to distortion in the spectral dimension of the image than they are to perceptual distortion in the spatial dimension. The compression algorithm developed for this research, which uses the Karhunen-Loeve transform for spectral decorrelation followed by a modified H.264/Advanced Video Coding (AVC) encoder, maintains a user-specified spectral quality level while maximizing the compression ratio throughout the encoding process. The compression performance may be considered near-lossless in certain scenarios. For qualitative purposes, this paper presents the performance of the compression algorithm for several Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) and Hyperion datasets using spectral angle as the spectral quality assessment function. Specifically, the compression performance is illustrated in the form of rate-distortion curves that plot spectral angle versus bits per pixel per band (bpppb).

The effect of encoding conditions on learning in the prototype distortion task.

PubMed

Lee, Jessica C; Livesey, Evan J

2017-06-01

The prototype distortion task demonstrates that it is possible to learn about a category of physically similar stimuli through mere observation. However, there have been few attempts to test whether different encoding conditions affect learning in this task. This study compared prototypicality gradients produced under incidental learning conditions in which participants performed a visual search task, with those produced under intentional learning conditions in which participants were required to memorize the stimuli. Experiment 1 showed that similar prototypicality gradients could be obtained for category endorsement and familiarity ratings, but also found (weaker) prototypicality gradients in the absence of exposure. In Experiments 2 and 3, memorization was found to strengthen prototypicality gradients in familiarity ratings in comparison to visual search, but there were no group differences in participants' ability to discriminate between novel and presented exemplars. Although the Search groups in Experiments 2 and 3 produced prototypicality gradients, they were no different in magnitude to those produced in the absence of stimulus exposure in Experiment 1, suggesting that incidental learning during visual search was not conducive to producing prototypicality gradients. This study suggests that learning in the prototype distortion task is not implicit in the sense of resulting automatically from exposure, is affected by the nature of encoding, and should be considered in light of potential learning-at-test effects.

Association of uterine fibroids and pregnancy outcomes after ovarian stimulation-intrauterine insemination for unexplained infertility.

PubMed

Styer, Aaron K; Jin, Susan; Liu, Dan; Wang, Baisong; Polotsky, Alex J; Christianson, Mindy S; Vitek, Wendy; Engmann, Lawrence; Hansen, Karl; Wild, Robert; Legro, Richard S; Coutifaris, Christos; Alvero, Ruben; Robinson, Randal D; Casson, Peter; Christman, Gregory M; Christy, Alicia; Diamond, Michael P; Eisenberg, Esther; Zhang, Heping; Santoro, Nanette

2017-03-01

To investigate the association of non-cavity-distorting uterine fibroids and pregnancy outcomes after ovarian stimulation-intrauterine insemination (OS-IUI) in couples with unexplained infertility. Secondary analysis from a prospective, randomized, multicenter clinical trial investigating fertility outcomes after OS-IUI. Reproductive Medicine Network clinical sites. Nine hundred couples with unexplained infertility who participated in the Assessment of Multiple Intrauterine Gestations from Ovarian Stimulation (AMIGOS) clinical trial. Participants were randomized to one of three arms (clomiphene citrate, letrozole, or gonadotropins), and treatment was continued for up to four cycles or until pregnancy was achieved. Conception (serum hCG increase), clinical pregnancy (fetal cardiac activity), and live birth rates. A total of 102/900 participants (11.3%) had at least one documented fibroid and a normal uterine cavity. Women with fibroids were older, more likely to be African American, had a greater uterine volume, lower serum antimüllerian hormone levels, and fewer antral follicles than women without fibroids. In conception cycles, clinical pregnancy rates were significantly lower in participants with fibroids than in those without uterine fibroids. Pregnancy loss before 12 weeks was more likely in African American women with fibroids compared with non-African American women with fibroids. There was no difference in conception and live birth rates in subjects with and without fibroids. No differences were observed in conception and live birth rates in women with non-cavity-distorting fibroids and those without fibroids. These findings provide reassurance that pregnancy success is not impacted in couples with non-cavity-distorting fibroids undergoing OS-IUI for unexplained infertility. NCT01044862. Copyright © 2016 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

Influence of video compression on the measurement error of the television system

NASA Astrophysics Data System (ADS)

Sotnik, A. V.; Yarishev, S. N.; Korotaev, V. V.

2015-05-01

Video data require a very large memory capacity. Optimal ratio quality / volume video encoding method is one of the most actual problem due to the urgent need to transfer large amounts of video over various networks. The technology of digital TV signal compression reduces the amount of data used for video stream representation. Video compression allows effective reduce the stream required for transmission and storage. It is important to take into account the uncertainties caused by compression of the video signal in the case of television measuring systems using. There are a lot digital compression methods. The aim of proposed work is research of video compression influence on the measurement error in television systems. Measurement error of the object parameter is the main characteristic of television measuring systems. Accuracy characterizes the difference between the measured value abd the actual parameter value. Errors caused by the optical system can be selected as a source of error in the television systems measurements. Method of the received video signal processing is also a source of error. Presence of error leads to large distortions in case of compression with constant data stream rate. Presence of errors increases the amount of data required to transmit or record an image frame in case of constant quality. The purpose of the intra-coding is reducing of the spatial redundancy within a frame (or field) of television image. This redundancy caused by the strong correlation between the elements of the image. It is possible to convert an array of image samples into a matrix of coefficients that are not correlated with each other, if one can find corresponding orthogonal transformation. It is possible to apply entropy coding to these uncorrelated coefficients and achieve a reduction in the digital stream. One can select such transformation that most of the matrix coefficients will be almost zero for typical images . Excluding these zero coefficients also possible reducing of the digital stream. Discrete cosine transformation is most widely used among possible orthogonal transformation. Errors of television measuring systems and data compression protocols analyzed In this paper. The main characteristics of measuring systems and detected sources of their error detected. The most effective methods of video compression are determined. The influence of video compression error on television measuring systems was researched. Obtained results will increase the accuracy of the measuring systems. In television image quality measuring system reduces distortion identical distortion in analog systems and specific distortions resulting from the process of coding / decoding digital video signal and errors in the transmission channel. By the distortions associated with encoding / decoding signal include quantization noise, reducing resolution, mosaic effect, "mosquito" effect edging on sharp drops brightness, blur colors, false patterns, the effect of "dirty window" and other defects. The size of video compression algorithms used in television measuring systems based on the image encoding with intra- and inter prediction individual fragments. The process of encoding / decoding image is non-linear in space and in time, because the quality of the playback of a movie at the reception depends on the pre- and post-history of a random, from the preceding and succeeding tracks, which can lead to distortion of the inadequacy of the sub-picture and a corresponding measuring signal.

Compression performance of HEVC and its format range and screen content coding extensions

NASA Astrophysics Data System (ADS)

Li, Bin; Xu, Jizheng; Sullivan, Gary J.

2015-09-01

This paper presents a comparison-based test of the objective compression performance of the High Efficiency Video Coding (HEVC) standard, its format range extensions (RExt), and its draft screen content coding extensions (SCC). The current dominant standard, H.264/MPEG-4 AVC, is used as an anchor reference in the comparison. The conditions used for the comparison tests were designed to reflect relevant application scenarios and to enable a fair comparison to the maximum extent feasible - i.e., using comparable quantization settings, reference frame buffering, intra refresh periods, rate-distortion optimization decision processing, etc. It is noted that such PSNR-based objective comparisons generally provide more conservative estimates of HEVC benefit than are found in subjective studies. The experimental results show that, when compared with H.264/MPEG-4 AVC, HEVC version 1 provides a bit rate savings for equal PSNR of about 23% for all-intra coding, 34% for random access coding, and 38% for low-delay coding. This is consistent with prior studies and the general characterization that HEVC can provide about a bit rate savings of about 50% for equal subjective quality for most applications. The HEVC format range extensions provide a similar bit rate savings of about 13-25% for all-intra coding, 28-33% for random access coding, and 32-38% for low-delay coding at different bit rate ranges. For lossy coding of screen content, the HEVC screen content coding extensions achieve a bit rate savings of about 66%, 63%, and 61% for all-intra coding, random access coding, and low-delay coding, respectively. For lossless coding, the corresponding bit rate savings are about 40%, 33%, and 32%, respectively.

Rating the YouTube Indian: Viewer Ratings of Native American Portrayals on a Viral Video Site

ERIC Educational Resources Information Center

Kopacz, Maria A.; Lawton, Bessie Lee

2011-01-01

Online outlets for user-generated content (UGC) like YouTube have created environments for alternative depictions of marginalized groups, as UGC can be contributed by anyone with basic technology access. Preliminary findings on UGC relating to Native Americans confirm some favorable departures from the distortions prevalent in the old media. The…

Evaluation and economic impact analysis of different treatment options for ankle distortions in occupational accidents.

PubMed

Audenaert, Amaryllis; Prims, Jente; Reniers, Genserik L L; Weyns, Dirk; Mahieu, Peter; Audenaert, Emmanuel

2010-10-01

Appropriate use of diagnostic and treatment modalities are essential for rational use of resources. The aim of this study is to evaluate the use of diagnostic modalities and different treatment options and their economic impacts following an acute ankle distortion resulting from an occupational accident. We evaluated the type-of-treatment impact on the victims' course of recovery as well as its impact on the associated accident costs. Research was carried out in Belgium. An ankle distortion victims' database consisting of 200 cases of (Belgian) occupational accidents during the period 2005-2007 was analysed. Patients who were prescribed immobilization or the use of adjuvant support or physical therapy (118 cases) were not employed during a period of 37 days on average, with a mean total cost of 3140.14 Euros caused by the ankle sprain. Patients without any adjuvant therapy (82 cases) were characterized by an unemployment rate of 15 days on average, and a total cost of 1077.86 Euros. Cast immobilization, although its application is not supported by evidence-based literature, was still applied in 36% of the population studied and resulted in the longest average absence of work of 42 days with an obvious significant increase in medical and total costs. Our results show a high rate of inappropriate use of cast immobilizations for ankle distortions. From an economic point of view and for the same clinical endpoint (being full resumption of the occupational activities), simple conventional treatment, consisting of rest, ice, compression and elevation at diagnosis with allowance of early weight bearing in the further clinical course, leads to the quickest full resumption of activities in combination with the lowest medical costs, if compared with any other kind of treatment. © 2010 Blackwell Publishing Ltd.

Panorama parking assistant system with improved particle swarm optimization method

NASA Astrophysics Data System (ADS)

Cheng, Ruzhong; Zhao, Yong; Li, Zhichao; Jiang, Weigang; Wang, Xin'an; Xu, Yong

2013-10-01

A panorama parking assistant system (PPAS) for the automotive aftermarket together with a practical improved particle swarm optimization method (IPSO) are proposed in this paper. In the PPAS system, four fisheye cameras are installed in the vehicle with different views, and four channels of video frames captured by the cameras are processed as a 360-deg top-view image around the vehicle. Besides the embedded design of PPAS, the key problem for image distortion correction and mosaicking is the efficiency of parameter optimization in the process of camera calibration. In order to address this problem, an IPSO method is proposed. Compared with other parameter optimization methods, the proposed method allows a certain range of dynamic change for the intrinsic and extrinsic parameters, and can exploit only one reference image to complete all of the optimization; therefore, the efficiency of the whole camera calibration is increased. The PPAS is commercially available, and the IPSO method is a highly practical way to increase the efficiency of the installation and the calibration of PPAS in automobile 4S shops.

Optimal foraging, not biogenetic law, predicts spider orb web allometry.

PubMed

Gregorič, Matjaž; Kiesbüy, Heine C; Lebrón, Shakira G Quiñones; Rozman, Alenka; Agnarsson, Ingi; Kuntner, Matjaž

2013-03-01

The biogenetic law posits that the ontogeny of an organism recapitulates the pattern of evolutionary changes. Morphological evidence has offered some support for, but also considerable evidence against, the hypothesis. However, biogenetic law in behavior remains underexplored. As physical manifestation of behavior, spider webs offer an interesting model for the study of ontogenetic behavioral changes. In orb-weaving spiders, web symmetry often gets distorted through ontogeny, and these changes have been interpreted to reflect the biogenetic law. Here, we test the biogenetic law hypothesis against the alternative, the optimal foraging hypothesis, by studying the allometry in Leucauge venusta orb webs. These webs range in inclination from vertical through tilted to horizontal; biogenetic law predicts that allometry relates to ontogenetic stage, whereas optimal foraging predicts that allometry relates to gravity. Specifically, pronounced asymmetry should only be seen in vertical webs under optimal foraging theory. We show that, through ontogeny, vertical webs in L. venusta become more asymmetrical in contrast to tilted and horizontal webs. Biogenetic law thus cannot explain L. venusta web allometry, but our results instead support optimization of foraging area in response to spider size.

Quantitative metrics for evaluating parallel acquisition techniques in diffusion tensor imaging at 3 Tesla.

PubMed

Ardekani, Siamak; Selva, Luis; Sayre, James; Sinha, Usha

2006-11-01

Single-shot echo-planar based diffusion tensor imaging is prone to geometric and intensity distortions. Parallel imaging is a means of reducing these distortions while preserving spatial resolution. A quantitative comparison at 3 T of parallel imaging for diffusion tensor images (DTI) using k-space (generalized auto-calibrating partially parallel acquisitions; GRAPPA) and image domain (sensitivity encoding; SENSE) reconstructions at different acceleration factors, R, is reported here. Images were evaluated using 8 human subjects with repeated scans for 2 subjects to estimate reproducibility. Mutual information (MI) was used to assess the global changes in geometric distortions. The effects of parallel imaging techniques on random noise and reconstruction artifacts were evaluated by placing 26 regions of interest and computing the standard deviation of apparent diffusion coefficient and fractional anisotropy along with the error of fitting the data to the diffusion model (residual error). The larger positive values in mutual information index with increasing R values confirmed the anticipated decrease in distortions. Further, the MI index of GRAPPA sequences for a given R factor was larger than the corresponding mSENSE images. The residual error was lowest in the images acquired without parallel imaging and among the parallel reconstruction methods, the R = 2 acquisitions had the least error. The standard deviation, accuracy, and reproducibility of the apparent diffusion coefficient and fractional anisotropy in homogenous tissue regions showed that GRAPPA acquired with R = 2 had the least amount of systematic and random noise and of these, significant differences with mSENSE, R = 2 were found only for the fractional anisotropy index. Evaluation of the current implementation of parallel reconstruction algorithms identified GRAPPA acquired with R = 2 as optimal for diffusion tensor imaging.

Estimating Ω from Galaxy Redshifts: Linear Flow Distortions and Nonlinear Clustering

NASA Astrophysics Data System (ADS)

Bromley, B. C.; Warren, M. S.; Zurek, W. H.

1997-02-01

We propose a method to determine the cosmic mass density Ω from redshift-space distortions induced by large-scale flows in the presence of nonlinear clustering. Nonlinear structures in redshift space, such as fingers of God, can contaminate distortions from linear flows on scales as large as several times the small-scale pairwise velocity dispersion σv. Following Peacock & Dodds, we work in the Fourier domain and propose a model to describe the anisotropy in the redshift-space power spectrum; tests with high-resolution numerical data demonstrate that the model is robust for both mass and biased galaxy halos on translinear scales and above. On the basis of this model, we propose an estimator of the linear growth parameter β = Ω0.6/b, where b measures bias, derived from sampling functions that are tuned to eliminate distortions from nonlinear clustering. The measure is tested on the numerical data and found to recover the true value of β to within ~10%. An analysis of IRAS 1.2 Jy galaxies yields β=0.8+0.4-0.3 at a scale of 1000 km s-1, which is close to optimal given the shot noise and finite size of the survey. This measurement is consistent with dynamical estimates of β derived from both real-space and redshift-space information. The importance of the method presented here is that nonlinear clustering effects are removed to enable linear correlation anisotropy measurements on scales approaching the translinear regime. We discuss implications for analyses of forthcoming optical redshift surveys in which the dispersion is more than a factor of 2 greater than in the IRAS data.

Evaluation of preprocessing steps to compensate for magnetic field distortions due to body movements in BOLD fMRI

PubMed Central

Barry, Robert L.; Williams, Joy M.; Klassen, L. Martyn; Gallivan, Jason P.; Culham, Jody C.

2009-01-01

Blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is currently the dominant technique for non-invasive investigation of brain functions. One of the challenges with BOLD fMRI, particularly at high fields, is compensation for the effects of spatiotemporally varying magnetic field inhomogeneities (ΔB0) caused by normal subject respiration, and in some studies, movement of the subject during the scan to perform tasks related to the functional paradigm. The presence of ΔB0 during data acquisition distorts reconstructed images and introduces extraneous fluctuations in the fMRI time series that decrease the BOLD contrast-to-noise ratio. Optimization of the fMRI data-processing pipeline to compensate for geometric distortions is of paramount importance to ensure high quality of fMRI data. To investigate ΔB0 caused by subject movement, echo-planar imaging scans were collected with and without concurrent motion of a phantom arm. The phantom arm was constructed and moved by the experimenter to emulate forearm motions while subjects remained still and observed a visual stimulation paradigm. These data were then subjected to eight different combinations of preprocessing steps. The best preprocessing pipeline included navigator correction, a complex phase regressor, and spatial smoothing. The synergy between navigator correction and phase regression reduced geometric distortions better than either step in isolation, and preconditioned the data to make them more amenable to the benefits of spatial smoothing. The combination of these steps provided a 10% increase in t-statistics compared to only navigator correction and spatial smoothing, and reduced the noise and false activations in regions where no legitimate effects would occur. PMID:19695810

Patch Based Synthesis of Whole Head MR Images: Application to EPI Distortion Correction.

PubMed

Roy, Snehashis; Chou, Yi-Yu; Jog, Amod; Butman, John A; Pham, Dzung L

2016-10-01

Different magnetic resonance imaging pulse sequences are used to generate image contrasts based on physical properties of tissues, which provide different and often complementary information about them. Therefore multiple image contrasts are useful for multimodal analysis of medical images. Often, medical image processing algorithms are optimized for particular image contrasts. If a desirable contrast is unavailable, contrast synthesis (or modality synthesis) methods try to "synthesize" the unavailable constrasts from the available ones. Most of the recent image synthesis methods generate synthetic brain images, while whole head magnetic resonance (MR) images can also be useful for many applications. We propose an atlas based patch matching algorithm to synthesize T 2 -w whole head (including brain, skull, eyes etc) images from T 1 -w images for the purpose of distortion correction of diffusion weighted MR images. The geometric distortion in diffusion MR images due to in-homogeneous B 0 magnetic field are often corrected by non-linearly registering the corresponding b = 0 image with zero diffusion gradient to an undistorted T 2 -w image. We show that our synthetic T 2 -w images can be used as a template in absence of a real T 2 -w image. Our patch based method requires multiple atlases with T 1 and T 2 to be registeLowRes to a given target T 1 . Then for every patch on the target, multiple similar looking matching patches are found on the atlas T 1 images and corresponding patches on the atlas T 2 images are combined to generate a synthetic T 2 of the target. We experimented on image data obtained from 44 patients with traumatic brain injury (TBI), and showed that our synthesized T 2 images produce more accurate distortion correction than a state-of-the-art registration based image synthesis method.

A New Finite Difference Q-compensated RTM Algorithm in Tilted Transverse Isotropic (TTI) Media

NASA Astrophysics Data System (ADS)

Zhou, T.; Hu, W.; Ning, J.

2017-12-01

Attenuating anisotropic geological body is difficult to image with conventional migration methods. In such kind of scenarios, recorded seismic data suffer greatly from both amplitude decay and phase distortion, resulting in degraded resolution, poor illumination and incorrect migration depth in imaging results. To efficiently obtain high quality images, we propose a novel TTI QRTM algorithm based on Generalized Standard Linear Solid model combined with a unique multi-stage optimization technique to simultaneously correct the decayed amplitude and the distorted phase velocity. Numerical tests (shown in the figure) demonstrate that our TTI QRTM algorithm effectively corrects migration depth, significantly improves illumination, and enhances resolution within and below the low Q regions. The result of our new method is very close to the reference RTM image, while QRTM without TTI cannot get a correct image. Compared to the conventional QRTM method based on a pseudo-spectral operator for fractional Laplacian evaluation, our method is more computationally efficient for large scale applications and more suitable for GPU acceleration. With the current multi-stage dispersion optimization scheme, this TTI QRTM method best performs in the frequency range 10-70 Hz, and could be used in a wider frequency range. Furthermore, as this method can also handle frequency dependent Q, it has potential to be applied in imaging deep structures where low Q exists, such as subduction zones, volcanic zones or fault zones with passive source observations.

Lawson's Shoehorn, or Should the Philosophy of Science Be Rated 'X'?

ERIC Educational Resources Information Center

Allchin, Douglas

2003-01-01

Addresses Lawson's (2002) interpretations of Galileo's discovery of the moons of Jupiter and other cases that exhibit historical errors. Suggests that such cases can distort history and lessons about the nature of science. (SOE)

Optimization of Pockels electric field in transverse modulated optical voltage sensor

NASA Astrophysics Data System (ADS)

Huang, Yifan; Xu, Qifeng; Chen, Kun-Long; Zhou, Jie

2018-05-01

This paper investigates the possibilities of optimizing the Pockels electric field in a transverse modulated optical voltage sensor with a spherical electrode structure. The simulations show that due to the edge effect and the electric field concentrations and distortions, the electric field distributions in the crystal are non-uniform. In this case, a tiny variation in the light path leads to an integral error of more than 0.5%. Moreover, a 2D model cannot effectively represent the edge effect, so a 3D model is employed to optimize the electric field distributions. Furthermore, a new method to attach a quartz crystal to the electro-optic crystal along the electric field direction is proposed to improve the non-uniformity of the electric field. The integral error is reduced therefore from 0.5% to 0.015% and less. The proposed method is simple, practical and effective, and it has been validated by numerical simulations and experimental tests.

Pattern recognition with composite correlation filters designed with multi-object combinatorial optimization

DOE PAGES

Awwal, Abdul; Diaz-Ramirez, Victor H.; Cuevas, Andres; ...

2014-10-23

Composite correlation filters are used for solving a wide variety of pattern recognition problems. These filters are given by a combination of several training templates chosen by a designer in an ad hoc manner. In this work, we present a new approach for the design of composite filters based on multi-objective combinatorial optimization. Given a vast search space of training templates, an iterative algorithm is used to synthesize a filter with an optimized performance in terms of several competing criteria. Furthermore, by employing a suggested binary-search procedure a filter bank with a minimum number of filters can be constructed, formore » a prespecified trade-off of performance metrics. Computer simulation results obtained with the proposed method in recognizing geometrically distorted versions of a target in cluttered and noisy scenes are discussed and compared in terms of recognition performance and complexity with existing state-of-the-art filters.« less

Pattern recognition with composite correlation filters designed with multi-object combinatorial optimization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Awwal, Abdul; Diaz-Ramirez, Victor H.; Cuevas, Andres

Composite correlation filters are used for solving a wide variety of pattern recognition problems. These filters are given by a combination of several training templates chosen by a designer in an ad hoc manner. In this work, we present a new approach for the design of composite filters based on multi-objective combinatorial optimization. Given a vast search space of training templates, an iterative algorithm is used to synthesize a filter with an optimized performance in terms of several competing criteria. Furthermore, by employing a suggested binary-search procedure a filter bank with a minimum number of filters can be constructed, formore » a prespecified trade-off of performance metrics. Computer simulation results obtained with the proposed method in recognizing geometrically distorted versions of a target in cluttered and noisy scenes are discussed and compared in terms of recognition performance and complexity with existing state-of-the-art filters.« less

Audio fingerprint extraction for content identification

NASA Astrophysics Data System (ADS)

Shiu, Yu; Yeh, Chia-Hung; Kuo, C. C. J.

2003-11-01

In this work, we present an audio content identification system that identifies some unknown audio material by comparing its fingerprint with those extracted off-line and saved in the music database. We will describe in detail the procedure to extract audio fingerprints and demonstrate that they are robust to noise and content-preserving manipulations. The main feature in the proposed system is the zero-crossing rate extracted with the octave-band filter bank. The zero-crossing rate can be used to describe the dominant frequency in each subband with a very low computational cost. The size of audio fingerprint is small and can be efficiently stored along with the compressed files in the database. It is also robust to many modifications such as tempo change and time-alignment distortion. Besides, the octave-band filter bank is used to enhance the robustness to distortion, especially those localized on some frequency regions.

Monitoring probe for groundwater flow

DOEpatents

Looney, Brian B.; Ballard, Sanford

1994-01-01

A monitoring probe for detecting groundwater migration. The monitor features a cylinder made of a permeable membrane carrying an array of electrical conductivity sensors on its outer surface. The cylinder is filled with a fluid that has a conductivity different than the groundwater. The probe is placed in the ground at an area of interest to be monitored. The fluid, typically saltwater, diffuses through the permeable membrane into the groundwater. The flow of groundwater passing around the permeable membrane walls of the cylinder carries the conductive fluid in the same general direction and distorts the conductivity field measured by the sensors. The degree of distortion from top to bottom and around the probe is precisely related to the vertical and horizontal flow rates, respectively. The electrical conductivities measured by the sensors about the outer surface of the probe are analyzed to determine the rate and direction of the groundwater flow.

Monitoring probe for groundwater flow

DOEpatents

Looney, B.B.; Ballard, S.

1994-08-23

A monitoring probe for detecting groundwater migration is disclosed. The monitor features a cylinder made of a permeable membrane carrying an array of electrical conductivity sensors on its outer surface. The cylinder is filled with a fluid that has a conductivity different than the groundwater. The probe is placed in the ground at an area of interest to be monitored. The fluid, typically saltwater, diffuses through the permeable membrane into the groundwater. The flow of groundwater passing around the permeable membrane walls of the cylinder carries the conductive fluid in the same general direction and distorts the conductivity field measured by the sensors. The degree of distortion from top to bottom and around the probe is precisely related to the vertical and horizontal flow rates, respectively. The electrical conductivities measured by the sensors about the outer surface of the probe are analyzed to determine the rate and direction of the groundwater flow. 4 figs.

EFFECT OF MASSIVE NEUTRON EXPOSURE ON THE DISTORTION OF REACTOR GRAPHITE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Helm, J.W.; Davidson, J.M.

1963-05-28

Distortion of reactor-grade graphites was studied at varying neutron exposures ranging up to 14 x 10/sup 21/ neutrons per cm/sup 2/ (nvt)/sup */ at temperatures of irradiation ranging from 425 to 800 deg C. This exposure level corresponds to approximately 100,000 megawatt days per adjacent ton of fuel (Mwd/ At) in a graphite-moderated reactor. A conventionalcoke graphite, CSF, and two needle-coke graphites, NC-7 and NC-8, were studied. At all temperatures of irradiation the contraction rate of the samples cut parallel to the extrusion axis increased with increasing neutron exposure. For parallel samples the needle- coke graphites and the CSF graphitemore » contracted approximately the same amount. In the transverse direction the rate of cortraction at the higher irradiation temperntures appeared to be decreasing. Volume contractions derived from the linear contractions are discussed. (auth)« less

Hexapole-compensated magneto-optical trap on a mesoscopic atom chip

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joellenbeck, S.; Mahnke, J.; Randoll, R.

2011-04-15

Magneto-optical traps on atom chips are usually restricted to small atomic samples due to a limited capture volume caused primarily by distorted field configurations. Here we present a magneto-optical trap based on a millimeter-sized wire structure which generates a magnetic field with minimized distortions. Together with the loading from a high-flux two-dimensional magneto-optical trap, we achieve a loading rate of 8.4x10{sup 10} atoms/s and maximum number of 8.7x10{sup 9} captured atoms. The wire structure is placed outside of the vacuum to enable a further adaptation to new scientific objectives. Since all magnetic fields are applied locally without the need formore » external bias fields, the presented setup will facilitate parallel generation of Bose-Einstein condensates on a conveyor belt with a cycle rate above 1 Hz.« less

Stiffness management of sheet metal parts using laser metal deposition

NASA Astrophysics Data System (ADS)

Bambach, Markus; Sviridov, Alexander; Weisheit, Andreas

2017-10-01

Tailored blanks are established solutions for the production of load-adapted sheet metal components. In the course of the individualization of production, such semi-finished products are gaining importance. In addition to tailored welded blanks and tailored rolled blanks, patchwork blanks have been developed which allow a local increase in sheet thickness by welding, gluing or soldering patches onto sheet metal blanks. Patchwork blanks, however, have several limitations, on the one hand, the limited freedom of design in the production of patchwork blanks and, on the other hand, the fact that there is no optimum material bonding with the substrate. The increasing production of derivative and special vehicles on the basis of standard vehicles, prototype production and the functionalization of components require solutions with which semi-finished products and sheet metal components can be provided flexibly with local thickenings or functional elements with a firm metallurgical bond to the substrate. An alternative to tailored and patchwork blanks is, therefore, a free-form reinforcement applied by additive manufacturing via laser metal deposition (LMD). By combining metal forming and additive manufacturing, stiffness can be adapted to the loads based on standard components in a material-efficient manner and without the need to redesign the forming tools. This paper details a study of the potential of stiffness management by LMD using a demonstrator part. Sizing optimization is performed and part distortion is taken into account to find an optimal design for the cladding. A maximum stiffness increase of 167% is feasible with only 4.7% additional mass. Avoiding part distortion leads to a pareto-optimal design which achieves 95% more stiffness with 6% added mass.

A New Pulse Pileup Rejection Method Based on Position Shift Identification

NASA Astrophysics Data System (ADS)

Gu, Z.; Prout, D. L.; Taschereau, R.; Bai, B.; Chatziioannou, A. F.

2016-02-01

Pulse pileup events degrade the signal-to-noise ratio (SNR) of nuclear medicine data. When such events occur in multiplexed detectors, they cause spatial misposition, energy spectrum distortion and degraded timing resolution, which leads to image artifacts. Pulse pileup is pronounced in PETbox4, a bench top PET scanner dedicated to high sensitivity and high resolution imaging of mice. In that system, the combination of high absolute sensitivity, long scintillator decay time (BGO) and highly multiplexed electronics lead to a significant fraction of pulse pileup, reached at lower total activity than for comparable instruments. In this manuscript, a new pulse pileup rejection method named position shift rejection (PSR) is introduced. The performance of PSR is compared with a conventional leading edge rejection (LER) method and with no pileup rejection implemented (NoPR). A comprehensive digital pulse library was developed for objective evaluation and optimization of the PSR and LER, in which pulse waveforms were directly recorded from real measurements exactly representing the signals to be processed. Physical measurements including singles event acquisition, peak system sensitivity and NEMA NU-4 image quality phantom were also performed in the PETbox4 system to validate and compare the different pulse pile-up rejection methods. The evaluation of both physical measurements and model pulse trains demonstrated that the new PSR performs more accurate pileup event identification and avoids erroneous rejection of valid events. For the PETbox4 system, this improvement leads to a significant recovery of sensitivity at low count rates, amounting to about 1/4th of the expected true coincidence events, compared to the LER method. Furthermore, with the implementation of PSR, optimal image quality can be achieved near the peak noise equivalent count rate (NECR).

Fabric geometry distortion during composites processing

NASA Technical Reports Server (NTRS)

Chen, Julie

1994-01-01

Waviness and tow misalignment are often cited as possible causes of data scatter and lower compression stiffness and strength in textile composites. Strength differences of as much as 40 percent have been seen in composites that appear to have the same basic material and structural properties -- i.e., yarn orientation, yarn size, interlacing geometry. Fabric geometry distortion has been suggested as a possible reason for this discrepancy, but little quantitative data or substantial evidence exists. The focus of this research is to contribute to the present understanding of the causes and effects of geometric distortion in textile composites. The initial part of the study was an attempt to gather qualitative information on a variety of textile structures. Existing and new samples confirmed that structures with a significant direction presence would be more susceptible to distortion due to the compaction process. Thus, uniweaves (fiber vol frac: 54-72 percent) biaxial braids (vf: 34-58 percent) demonstrated very little fabric geometry distortion. In stitched panels, only slight buckling of z-direction stitches was observed, primarily near the surface. In contrast, for structures with high compaction ratios -- e.g., large cylindrical yarns (2.5:1) orpowder towpreg (4:1) -- there were visible distortions where previously smooth and periodic undulations were transformed to abrupt changes in direction. A controlled study of the effect of forming pressure on distortion was conducted on type 162 glass plain weave fabrics. Panels (6 x 6 in) were produced via a resin infusion type setup, but with an EPON 815 epoxy resin. Pressures ranging from hand layup to 200 psi were used (vf: 34-54 percent). Photomicrographs indicated that at pressures up to 50 psi, large changes in thickness were due primarily to resin squeeze out. At higher pressures, when intimate contact was made between the layers, there was some tow flattening and in-plane shifting to optimize nesting. However, even at 200 psi the period and amplitude of the tow undulation remained constant, suggesting that for this relatively fine fabric, distortions from compaction were not a problem. Because of the interest in using larger tows (to reduce cost) and more complex structures, tests were also run on 2D triaxial glass braid (113 yd/lb at 0, 225 yd/lb at +/- 45). Forming pressures of 20, 50, 200, and 500 psi were used, and short block compression tests were run. The 500 psi specimen had a 10 percent decrease in modulus and an almost 50 percent decrease in strength (vs. 20 psi). Because the total fiber wgt/panel was kept constant, the thickness varied from 0.32 to 0.22 in (49-70 percent vf). Yet, the strength value is clearly below what would be expected, even with the decrease in thickness. Photomicrographs of these samples will be taken to determine if more fabric distortion exists in the 500 psi specimens. Finally, because the ultimate goal is to be able to predict and control distortion in a variety of textile structures, a model compaction test was developed to directly measure the deformation of the tows during compaction. Layers of dry glass fabric were placed in a mold with a clear plexiglass window. The yarn amplitude and period was then calculated using image analysis of the videotaped deformation. Preliminary tests demonstrated the feasibility of this technique for simple fabrics with large tows.

Waveform agile high-power fiber laser illuminators for directed-energy weapon systems

NASA Astrophysics Data System (ADS)

Engin, Doruk; Lu, Wei; Kimpel, Frank; Gupta, Shantanu

2012-06-01

A kW-class fiber-amplifier based laser illuminator system at 1030nm is demonstrated. At 125 kHz pulse repetition rate, 1.9mJ energy per pulse (235W average power) is achieved for 100nsec pulses with >72% optical conversion efficiency, and at 250kHz repetition, >350W average power is demonstrated, limited by the available pumps. Excellent agreement is established between the experimental results and dynamic fiber amplifier simulation, for predicting the pulse shape, spectrum and ASE accumulation throughout the fiber-amplifier chain. High pulse-energy, high power fiber-amplifier operation requires careful engineering - minimize ASE content throughout the pre-amplifier stages, use of large mode area gain fiber in the final power stage for effective pulse energy extraction, and pulse pre-shaping to compensate for the laser gain-saturation induced intra-pulse and pulse-pattern dependent distortion. Such optimization using commercially available (VLMA) fibers with core size in the 30-40μm range is estimated to lead to >4mJ pulse energy for 100nsec pulse at 50kHz repetition rate. Such waveform agile high-power, high-energy pulsed fiber laser illuminators at λ=1030nm satisfies requirements for active-tracking/ranging in high-energy laser (HEL) weapon systems, and in uplink laser beacon for deep space communication.

The HLMA project: determination of high Δm2 LMA mixing parameters and constraint on |Ue3| with a new reactor neutrino experiment

NASA Astrophysics Data System (ADS)

Schönert, Stefan; Lasserre, Thierry; Oberauer, Lothar

2003-03-01

In the forthcoming months, the KamLAND experiment will probe the parameter space of the solar large mixing angle MSW solution as the origin of the solar neutrino deficit with ν¯e's from distant nuclear reactors. If however the solution realized in nature is such that Δm2sol>~2×10-4 eV2 (thereafter named the HLMA region), KamLAND will only observe a rate suppression but no spectral distortion and hence it will not have the optimal sensitivity to measure the mixing parameters. In this case, we propose a new medium baseline reactor experiment located at Heilbronn (Germany) to pin down the precise value of the solar mixing parameters. In this paper, we present the Heilbronn detector site, we calculate the ν¯e interaction rate and the positron spectrum expected from the surrounding nuclear power plants. We also discuss the sensitivity of such an experiment to |Ue3| in both normal and inverted neutrino mass hierarchy scenarios. We then outline the detector design, estimate background signals induced by natural radioactivity as well as by in situ cosmic ray muon interaction, and discuss a strategy to detect the anti-neutrino signal `free of background'.

A motion compensation technique using sliced blocks and its application to hybrid video coding

NASA Astrophysics Data System (ADS)

Kondo, Satoshi; Sasai, Hisao

2005-07-01

This paper proposes a new motion compensation method using "sliced blocks" in DCT-based hybrid video coding. In H.264 ? MPEG-4 Advance Video Coding, a brand-new international video coding standard, motion compensation can be performed by splitting macroblocks into multiple square or rectangular regions. In the proposed method, on the other hand, macroblocks or sub-macroblocks are divided into two regions (sliced blocks) by an arbitrary line segment. The result is that the shapes of the segmented regions are not limited to squares or rectangles, allowing the shapes of the segmented regions to better match the boundaries between moving objects. Thus, the proposed method can improve the performance of the motion compensation. In addition, adaptive prediction of the shape according to the region shape of the surrounding macroblocks can reduce overheads to describe shape information in the bitstream. The proposed method also has the advantage that conventional coding techniques such as mode decision using rate-distortion optimization can be utilized, since coding processes such as frequency transform and quantization are performed on a macroblock basis, similar to the conventional coding methods. The proposed method is implemented in an H.264-based P-picture codec and an improvement in bit rate of 5% is confirmed in comparison with H.264.

Habit, custom, and power: a multi-level theory of population health.

PubMed

Zimmerman, Frederick J

2013-03-01

In multi-level theory, individual behavior flows from cognitive habits, either directly through social referencing, rules of thumb, or automatic behaviors; or indirectly through the shaping of rationality itself by framing or heuristics. Although behavior does not arise from individually rational optimization, it generally appears to be rational, because the cognitive habits that guide behavior evolve toward optimality. However, power imbalances shaped by particular social, political, and economic structures can distort this evolution, leading to individual behavior that fails to maximize individual or social well-being. Replacing the dominant rational-choice paradigm with a multi-level theoretical paradigm involving habit, custom, and power will enable public health to engage in rigorous new areas of research. Copyright © 2013 Elsevier Ltd. All rights reserved.

Model-based occluded object recognition using Petri nets

NASA Astrophysics Data System (ADS)

Zhou, Chuan; Hura, Gurdeep S.

1998-09-01

This paper discusses the use of Petri nets to model the process of the object matching between an image and a model under different 2D geometric transformations. This transformation finds its applications in sensor-based robot control, flexible manufacturing system and industrial inspection, etc. A description approach for object structure is presented by its topological structure relation called Point-Line Relation Structure (PLRS). It has been shown how Petri nets can be used to model the matching process, and an optimal or near optimal matching can be obtained by tracking the reachability graph of the net. The experiment result shows that object can be successfully identified and located under 2D transformation such as translations, rotations, scale changes and distortions due to object occluded partially.

Theoretical and experimental investigations of coincidences in Poisson distributed pulse trains and spectral distortion caused by pulse pileup

NASA Astrophysics Data System (ADS)

Bristow, Quentin

1990-03-01

The occurrence rates of pulse strings, or sequences of pulses with interarrival times less than the resolving time of the pulse-height analysis system used to acquire spectra, are derived from theoretical considerations. Logic circuits were devised to make experimental measurements of multiple pulse string occurrence rates in the output from a scintillation detector over a wide range of count rates. Markov process theory was used to predict state transition rates in the logic circuits, enabling the experimental data to be checked rigorously for conformity with those predicted for a Poisson distribution. No fundamental discrepancies were observed. Monte Carlo simulations, incorporating criteria for pulse pileup inherent in the operation of modern analog to digital converters, were used to generate pileup spectra due to coincidences between two pulses (first order pileup) and three pulses (second order pileup) for different semi-Gaussian pulse shapes. Coincidences between pulses in a single channel produced a basic probability density function spectrum. The use of a flat spectrum showed the first order pileup distorted the spectrum to a linear ramp with a pileup tail. A correction algorithm was successfully applied to correct entire spectra (simulated and real) for first and second order pileups.

Can journalistic "false balance" distort public perception of consensus in expert opinion?

PubMed

Koehler, Derek J

2016-03-01

Media critics have expressed concern that journalistic "false balance" can distort the public's perceptions of what ought to be noncontroversial subjects (e.g., climate change). I report several experiments testing the influence of presenting conflicting comments from 2 experts who disagree on an issue (balance condition) in addition to a complete count of the number of experts on a panel who favor either side. Compared with a control condition, who received only the complete count, participants in the balance condition gave ratings of the perceived agreement among the experts that did not discriminate as clearly between issues with and without strong expert consensus. Participants in the balance condition also perceived less agreement among the experts in general, and were less likely to think that there was enough agreement among experts on the high-consensus issues to guide government policy. Evidently, "false balance" can distort perceptions of expert opinion even when participants would seem to have all the information needed to correct for its influence. (c) 2016 APA, all rights reserved).

Turbulence heterodyne coherent mitigation of orbital angular momentum multiplexing in a free space optical link by auxiliary light.

PubMed

Yang, Chunyong; Xu, Chuang; Ni, Wenjun; Gan, Yu; Hou, Jin; Chen, Shaoping

2017-10-16

A novel scheme is proposed to mitigate the atmospheric turbulence effect in free space optical (FSO) communication employing orbital angular momentum (OAM) multiplexing. In this scheme, the Gaussian beam is used as an auxiliary light with a common-path to obtain the distortion information caused by atmospheric turbulence. After turbulence, the heterodyne coherent detection technology is demonstrated to realize the turbulence mitigation. With the same turbulence distortion, the OAM beams and the Gaussian beam are respectively utilized as the signal light and the local oscillation light. Then the turbulence distortion is counteracted to a large extent. Meanwhile, a phase matching method is proposed to select the specific OAM mode. The discrimination between the neighboring OAM modes is obviously improved by detecting the output photocurrent. Moreover, two methods of beam size adjustment have been analyzed to achieve better performance for turbulence mitigation. Numerical results show that the system bit error rate (BER) can reach 10 -5 under strong turbulence in simulation situation.

22 W average power multiterawatt femtosecond laser chain enabling 1019 W/cm2 at 100 Hz

NASA Astrophysics Data System (ADS)

Clady, R.; Azamoum, Y.; Charmasson, L.; Ferré, A.; Utéza, O.; Sentis, M.

2018-05-01

We measure the wavefront distortions of a high peak power ultrashort (23 fs) laser system under high average power load. After 6 min—100 Hz operation of the laser at full average power (> 22 W after compression), the thermally induced wavefront distortions reach a steady state and the far-field profile of the laser beam no longer changes. By means of a deformable mirror located after the vacuum compressor, we apply a static pre-compensation to correct those aberrations allowing us to demonstrate a dramatic improvement of the far-field profile at 100 Hz with the reduction of the residual wavefront distortions below λ/16 before focusing. The applied technique provides 100 Hz operation of the femtosecond laser chain with stable pulse characteristics, corresponding to peak intensity above 1019 W/cm2 and average power of 19 W on target, which enables the study of relativistic optics at high repetition rate using a moderate f-number focusing optics ( f/4.5).

An investigation of the open-loop amplification of Reynolds number dependent processes by wave distortion

NASA Technical Reports Server (NTRS)

Purdy, K. R.; Ventrice, M. B.; Fang, J.

1972-01-01

Analytical and experimental studies were initiated to determine if the response of a constant temperature hot wire anemometer to acoustic oscillations could serve as an analog to the response of the drop vaporization burning rate process to acoustic oscillations, and, perhaps, also as an analog to any Reynolds number dependent process. The motivation behind this study was a recent analytical study which showed that distorted acoustic oscillations could amplify the open-loop response of vaporization limited combustion. This type of amplification may be the cause of unstable combustion in liquid propellant rocket engines. The analytical results obtained for the constant temperature anemometer are similar in nature to those previously obtained for vaporization limited combustion and indicate that the response is dependent on the amount and type of distortion as well as other factors, such as sound pressure level, Mach number and hot wire temperature. Preliminary results indicate qualitative agreement between theory and experiment.

Scalable L-infinite coding of meshes.

PubMed

Munteanu, Adrian; Cernea, Dan C; Alecu, Alin; Cornelis, Jan; Schelkens, Peter

2010-01-01

The paper investigates the novel concept of local-error control in mesh geometry encoding. In contrast to traditional mesh-coding systems that use the mean-square error as target distortion metric, this paper proposes a new L-infinite mesh-coding approach, for which the target distortion metric is the L-infinite distortion. In this context, a novel wavelet-based L-infinite-constrained coding approach for meshes is proposed, which ensures that the maximum error between the vertex positions in the original and decoded meshes is lower than a given upper bound. Furthermore, the proposed system achieves scalability in L-infinite sense, that is, any decoding of the input stream will correspond to a perfectly predictable L-infinite distortion upper bound. An instantiation of the proposed L-infinite-coding approach is demonstrated for MESHGRID, which is a scalable 3D object encoding system, part of MPEG-4 AFX. In this context, the advantages of scalable L-infinite coding over L-2-oriented coding are experimentally demonstrated. One concludes that the proposed L-infinite mesh-coding approach guarantees an upper bound on the local error in the decoded mesh, it enables a fast real-time implementation of the rate allocation, and it preserves all the scalability features and animation capabilities of the employed scalable mesh codec.

Market failure, policy failure and other distortions in chronic disease markets

PubMed Central

Watts, Jennifer J; Segal, Leonie

2009-01-01

Background The increasing prevalence of chronic disease represents a significant burden on most health systems. This paper explores the market failures and policy failures that exist in the management of chronic diseases. Discussion There are many sources of market failure in health care that undermine the efficiency of chronic disease management. These include incomplete information as well as information asymmetry between providers and consumers, the effect of externalities on consumer behaviour, and the divergence between social and private time preference rates. This has seen government and policy interventions to address both market failures and distributional issues resulting from the inability of private markets to reach an efficient and equitable distribution of resources. However, these have introduced a series of policy failures such as distorted re-imbursement arrangements across modalities and delivery settings. Summary The paper concludes that market failure resulting from a preference of individuals for 'immediate gratification' in the form of health care and disease management, rather than preventative services, where the benefits are delayed, has a major impact on achieving an efficient allocation of resources in markets for the management of chronic diseases. This distortion is compounded by government health policy that tends to favour medical and pharmaceutical interventions further contributing to distortions in the allocation of resources and inefficiencies in the management of chronic disease. PMID:19534822

Acoustic droplet vaporization is initiated by superharmonic focusing.

PubMed

Shpak, Oleksandr; Verweij, Martin; Vos, Hendrik J; de Jong, Nico; Lohse, Detlef; Versluis, Michel

2014-02-04

Acoustically sensitive emulsion droplets composed of a liquid perfluorocarbon have the potential to be a highly efficient system for local drug delivery, embolotherapy, or for tumor imaging. The physical mechanisms underlying the acoustic activation of these phase-change emulsions into a bubbly dispersion, termed acoustic droplet vaporization, have not been well understood. The droplets have a very high activation threshold; its frequency dependence does not comply with homogeneous nucleation theory and localized nucleation spots have been observed. Here we show that acoustic droplet vaporization is initiated by a combination of two phenomena: highly nonlinear distortion of the acoustic wave before it hits the droplet and focusing of the distorted wave by the droplet itself. At high excitation pressures, nonlinear distortion causes significant superharmonics with wavelengths of the order of the droplet size. These superharmonics strongly contribute to the focusing effect; therefore, the proposed mechanism also explains the observed pressure thresholding effect. Our interpretation is validated with experimental data captured with an ultrahigh-speed camera on the positions of the nucleation spots, where we find excellent agreement with the theoretical prediction. Moreover, the presented mechanism explains the hitherto counterintuitive dependence of the nucleation threshold on the ultrasound frequency. The physical insight allows for the optimization of acoustic droplet vaporization for therapeutic applications, in particular with respect to the acoustic pressures required for activation, thereby minimizing the negative bioeffects associated with the use of high-intensity ultrasound.

Acoustic droplet vaporization is initiated by superharmonic focusing

PubMed Central

Shpak, Oleksandr; Verweij, Martin; Vos, Hendrik J.; de Jong, Nico; Lohse, Detlef; Versluis, Michel

2014-01-01

Acoustically sensitive emulsion droplets composed of a liquid perfluorocarbon have the potential to be a highly efficient system for local drug delivery, embolotherapy, or for tumor imaging. The physical mechanisms underlying the acoustic activation of these phase-change emulsions into a bubbly dispersion, termed acoustic droplet vaporization, have not been well understood. The droplets have a very high activation threshold; its frequency dependence does not comply with homogeneous nucleation theory and localized nucleation spots have been observed. Here we show that acoustic droplet vaporization is initiated by a combination of two phenomena: highly nonlinear distortion of the acoustic wave before it hits the droplet and focusing of the distorted wave by the droplet itself. At high excitation pressures, nonlinear distortion causes significant superharmonics with wavelengths of the order of the droplet size. These superharmonics strongly contribute to the focusing effect; therefore, the proposed mechanism also explains the observed pressure thresholding effect. Our interpretation is validated with experimental data captured with an ultrahigh-speed camera on the positions of the nucleation spots, where we find excellent agreement with the theoretical prediction. Moreover, the presented mechanism explains the hitherto counterintuitive dependence of the nucleation threshold on the ultrasound frequency. The physical insight allows for the optimization of acoustic droplet vaporization for therapeutic applications, in particular with respect to the acoustic pressures required for activation, thereby minimizing the negative bioeffects associated with the use of high-intensity ultrasound. PMID:24449879

Jahn-Teller distortion of Mn3+-occupied octahedra in red beryl from Utah indicated by optical spectroscopy

NASA Astrophysics Data System (ADS)

Fridrichová, Jana; Bačík, Peter; Ertl, Andreas; Wildner, Manfred; Dekan, Július; Miglierini, Marcel

2018-01-01

Red beryl from Utah is chemically homogeneous and contains only Fe < 0.163, Mn < 0.018, and Mg < 0.016 apfu. Channel sites contain only up to Cs 0.011, K 0.009, Rb 0.004, and Na 0.004 apfu. This suggests only very slight tetrahedral (Cs,K,Rb)Li□-1Be-1 substitution, octahedral Na(Fe2+,Mg)□-1Al-1 substitution can be excluded. Fe and Mn are trivalent as documented by Mössbauer spectroscopy and optical absorption spectroscopy. Red beryl optimized formula is ∼[(Cs,Rb,K)0.02□0.98]Σ1.00□1.00(Al1.79Fe3+0.16Mn3+0.02Ti4+0.02Mg0.01)Σ2.00Be3(Si6O18). Location of Mn3+ was estimated to the octahedral Al3+ site, other choices are improbable due to the bond-length requirements. No Mn3+-induced Jahn-Teller structural distortion was detected due to site symmetry restrictions and small Mn3+ content. However, optical spectroscopy shows broad band at ∼7190 cm-1 assigned to the excited level of the spin-allowed pseudo-tetragonal split E ground state of elongated six-fold Mn3+ coordination. Crystal field calculations indicate that the local Mn3+ environment complies well with crystal chemical expectations for Jahn-Teller distorted Mn3+O6 octahedra.

Electrode surface profile and the performance of condenser microphones.

PubMed

Fletcher, N H; Thwaites, S

2002-12-01

Condenser microphones of all types are traditionally made with a planar electrode parallel to an electrically conducting diaphragm, additional diaphragm stiffness at acoustic frequencies being provided by the air enclosed in a cavity behind the diaphragm. In all designs, the motion of the diaphragm in response to an acoustic signal is greatest near its center and reduces to zero at its edges. Analysis shows that this construction leads to less than optimal sensitivity and to harmonic distortion at high sound levels when the diaphragm motion is appreciable compared with its spacing from the electrode. Microphones of this design are also subject to acoustic collapse of the diaphragm under the influence of pressure pulses such as might be produced by wind. A new design is proposed in which the electrode is shaped as a shallow dish, and it is shown that this construction increases the sensitivity by about 4.5 dB, and also completely eliminates harmonic distortion originating in the cartridge.

Theoretical modeling on the laser-induced phase deformation of liquid crystal optical phased shifter

NASA Astrophysics Data System (ADS)

Zhou, Zhuangqi; Wang, Xiangru; Zhuo, Rusheng; He, Xiaoxian; Wu, Liang; Wang, Xiaolin; Tan, Qinggui; Qiu, Qi

2018-03-01

To improve the working condition of liquid crystal phase shifter on incident laser power, a theoretical model on laser induced phase distortion is built on the physics of heat deposition and heat transfer. Four typical factors (absorption, heat sink structure, cooling fluid rate, and substrate) are analyzed to evaluate the influence of phase distortion when a relative high-power laser is pumped into the liquid crystal phase shifter. Flow rate of cooling fluid and heat sink structure are the most important two factors on improving the limit of incident laser power. Meanwhile, silicon wafer is suggested to replace the back glass contacting the heat sink, because of its higher heat transfer coefficient. If the device is fabricated on the conditions that: the total absorption is 5% and it has a strong heat sink structure with a flow rate of 0.01 m/s, when the incident laser power is 110W, the laser-induced phase deformation on the center is diminished to be less than 0.06, and the maximum temperature increase on the center is less than 1K degree.

Time dependent turbulence modeling and analytical theories of turbulence

NASA Technical Reports Server (NTRS)

Rubinstein, R.

1993-01-01

By simplifying the direct interaction approximation (DIA) for turbulent shear flow, time dependent formulas are derived for the Reynolds stresses which can be included in two equation models. The Green's function is treated phenomenologically, however, following Smith and Yakhot, we insist on the short and long time limits required by DIA. For small strain rates, perturbative evaluation of the correlation function yields a time dependent theory which includes normal stress effects in simple shear flows. From this standpoint, the phenomenological Launder-Reece-Rodi model is obtained by replacing the Green's function by its long time limit. Eddy damping corrections to short time behavior initiate too quickly in this model; in contrast, the present theory exhibits strong suppression of eddy damping at short times. A time dependent theory for large strain rates is proposed in which large scales are governed by rapid distortion theory while small scales are governed by Kolmogorov inertial range dynamics. At short times and large strain rates, the theory closely matches rapid distortion theory, but at long times it relaxes to an eddy damping model.

100 mm diameter rod laser amplifiers made of different Nd:glasses

NASA Astrophysics Data System (ADS)

Shaykin, A. A.; Kuzmin, A. A.; Shaikin, I. A.; Potemkin, A. K.; Arbuzov, V. I.; Hu, Lili; Wen, Lei; Khazanov, Е A.

2018-03-01

We measured the dependence of the weak signal gain of 100 mm diameter rod amplifiers on pump energy and transverse coordinates for four neodymium glass grades. The highest gain was obtained in N31-05 (China), and the highest radial gain uniformity in KGSS-0180 glass (Russia). The data obtained enable the optimal glass grade to be chosen for each specific problem by finding a compromise between maximum output energy and minimum distortion of beam profile.

Multipurpose Rotating Rake Arrays for Integrated Inlet and Fan Stage Performance Measurement

NASA Technical Reports Server (NTRS)

Wolter, John D.

2017-01-01

Low-pressure-ratio fan stage performance measurement requires precise measurement of conditions upstream and downstream of the fan stage. This presentation will discuss the rotating rake arrays used for the recent Boundary Layer Ingesting Inlet-Distortion-Tolerant Fan experiment in the NASA Glenn 8 by 6 foot wind tunnel. To achieve precise measurements, simulations of the rake sampling from pre-test CFD (Computerized Fluid Dynamics) solutions were used to optimize the number and locations of rake instruments.

Inference Control Mechanism for Statistical Database: Frequency-Imposed Data Distortions.

ERIC Educational Resources Information Center

Liew, Chong K.; And Others

1985-01-01

Introduces two data distortion methods (Frequency-Imposed Distortion, Frequency-Imposed Probability Distortion) and uses a Monte Carlo study to compare their performance with that of other distortion methods (Point Distortion, Probability Distortion). Indications that data generated by these two methods produce accurate statistics and protect…

CRADA Final Report: Weld Predictor App

DOE Office of Scientific and Technical Information (OSTI.GOV)

Billings, Jay Jay

Welding is an important manufacturing process used in a broad range of industries and market sectors, including automotive, aerospace, heavy manufacturing, medical, and defense. During welded fabrication, high localized heat input and subsequent rapid cooling result in the creation of residual stresses and distortion. These residual stresses can significantly affect the fatigue resistance, cracking behavior, and load-carrying capacity of welded structures during service. Further, additional fitting and tacking time is often required to fit distorted subassemblies together, resulting in non-value added cost. Using trial-and-error methods to determine which welding parameters, welding sequences, and fixture designs will most effectively reduce distortionmore » is a time-consuming and expensive process. For complex structures with many welds, this approach can take several months. For this reason, efficient and accurate methods of mitigating distortion are in-demand across all industries where welding is used. Analytical and computational methods and commercial software tools have been developed to predict welding-induced residual stresses and distortion. Welding process parameters, fixtures, and tooling can be optimized to reduce the HAZ softening and minimize weld residual stress and distortion, improving performance and reducing design, fabrication and testing costs. However, weld modeling technology tools are currently accessible only to engineers and designers with a background in finite element analysis (FEA) who work with large manufacturers, research institutes, and universities with access to high-performance computing (HPC) resources. Small and medium enterprises (SMEs) in the US do not typically have the human and computational resources needed to adopt and utilize weld modeling technology. To allow an engineer with no background in FEA and SMEs to gain access to this important design tool, EWI and the Ohio Supercomputer Center (OSC) developed the online weld application software tool “WeldPredictor” ( https://eweldpredictor.ewi.org ). About 1400 users have tested this application. This project marked the beginning of development on the next version of WeldPredictor that addresses many outstanding features of the original, including 3D models, allow more material hardening laws, model material phase transformation, and uses open source finite element solvers to quickly solve problems (as opposed to expensive commercial tools).« less

Characterizing Background Events in Neutron Transmutation Doped Thermistors for CUORE-0

NASA Astrophysics Data System (ADS)

Dutta, Suryabrata; Cuore Collaboration

2017-09-01

The Cryogenic Underground Observatory for Rare Events (CUORE) is a ton-scale neutrinoless double-beta decay experiment operating at the Laboratori Nazionali del Gran Sasso (LNGS). The experiment is comprised of 988 TeO2 bolometric crystals arranged into 19 towers and operated at a temperature of 15 mK. A neutron-transmutation-doped (NTD) Ge thermistor measures the thermal response from particles incident on the crystals. However, bulk and surface contamination of the NTD thermistors themselves produce distorted thermal responses inside the thermistor volume. Although these pulses are efficiently removed from the double-beta decay analysis by pulse shape cuts, they can be used to extract information about thermistor contamination. I will present a multifaceted approach to characterize these events, in which I implement an improved hot-electron thermal model, Geant4 Monte Carlo simulations of background events, and data from a previous experiment, CUORE-0, reprocessed with a new optimal filter. Using this approach, rates and energy deposition from contamination inside the NTD thermistors are measured, giving us better understanding of a CUORE background source.

Transparent silicon strip sensors for the optical alignment of particle detector systems

NASA Astrophysics Data System (ADS)

Blum, W.; Kroha, H.; Widmann, P.

1996-02-01

Modern large-area precision tracking detectors require increasing accuracy for the alignment of their components. A novel multi-point laser alignment system has been developed for such applications. The position of detector components with respect to reference laser beams is monitored by semi-transparent optical position sensors which work on the principle of silicon strip photodiodes. Two types of custom designed transparent strip sensors, based on crystalline and on amorphous silicon as active material, have been studied. The sensors are optimized for the typical diameters of collimated laser beams of 3-5 mm over distances of 10-20 m. They provide very high position resolution, on the order of 1 μm, uniformly over a wide measurement range of several centimeters. The preparation of the sensor surfaces requires special attention in order to achieve high light transmittance and minimum distortion of the traversing laser beams. At selected wavelengths, produced by laser diodes, transmission rates above 90% have been achieved. This allows to position more than 30 sensors along one laser beam. The sensors will be equipped with custom designed integrated readout electronics.

Generic distortion model for metrology under optical microscopes

NASA Astrophysics Data System (ADS)

Liu, Xingjian; Li, Zhongwei; Zhong, Kai; Chao, YuhJin; Miraldo, Pedro; Shi, Yusheng

2018-04-01

For metrology under optical microscopes, lens distortion is the dominant source of error. Previous distortion models and correction methods mostly rely on the assumption that parametric distortion models require a priori knowledge of the microscopes' lens systems. However, because of the numerous optical elements in a microscope, distortions can be hardly represented by a simple parametric model. In this paper, a generic distortion model considering both symmetric and asymmetric distortions is developed. Such a model is obtained by using radial basis functions (RBFs) to interpolate the radius and distortion values of symmetric distortions (image coordinates and distortion rays for asymmetric distortions). An accurate and easy to implement distortion correction method is presented. With the proposed approach, quantitative measurement with better accuracy can be achieved, such as in Digital Image Correlation for deformation measurement when used with an optical microscope. The proposed technique is verified by both synthetic and real data experiments.

Combatting nonlinear phase noise in coherent optical systems with an optimized decision processor based on machine learning

NASA Astrophysics Data System (ADS)

Wang, Danshi; Zhang, Min; Cai, Zhongle; Cui, Yue; Li, Ze; Han, Huanhuan; Fu, Meixia; Luo, Bin

2016-06-01

An effective machine learning algorithm, the support vector machine (SVM), is presented in the context of a coherent optical transmission system. As a classifier, the SVM can create nonlinear decision boundaries to mitigate the distortions caused by nonlinear phase noise (NLPN). Without any prior information or heuristic assumptions, the SVM can learn and capture the link properties from only a few training data. Compared with the maximum likelihood estimation (MLE) algorithm, a lower bit-error rate (BER) is achieved by the SVM for a given launch power; moreover, the launch power dynamic range (LPDR) is increased by 3.3 dBm for 8 phase-shift keying (8 PSK), 1.2 dBm for QPSK, and 0.3 dBm for BPSK. The maximum transmission distance corresponding to a BER of 1 ×10-3 is increased by 480 km for the case of 8 PSK. The larger launch power range and longer transmission distance improve the tolerance to amplitude and phase noise, which demonstrates the feasibility of the SVM in digital signal processing for M-PSK formats. Meanwhile, in order to apply the SVM method to 16 quadratic amplitude modulation (16 QAM) detection, we propose a parameter optimization scheme. By utilizing a cross-validation and grid-search techniques, the optimal parameters of SVM can be selected, thus leading to the LPDR improvement by 2.8 dBm. Additionally, we demonstrate that the SVM is also effective in combating the laser phase noise combined with the inphase and quadrature (I/Q) modulator imperfections, but the improvement is insignificant for the linear noise and separate I/Q imbalance. The computational complexity of SVM is also discussed. The relatively low complexity makes it possible for SVM to implement the real-time processing.

Using CMB spectral distortions to distinguish between dark matter solutions to the small-scale crisis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diacoumis, James A.D.; Wong, Yvonne Y.Y., E-mail: j.diacoumis@unsw.edu.au, E-mail: yvonne.y.wong@unsw.edu.au

The dissipation of small-scale perturbations in the early universe produces a distortion in the blackbody spectrum of cosmic microwave background photons. In this work, we propose to use these distortions as a probe of the microphysics of dark matter on scales 1 Mpc{sup -1}∼< k ∼< 10{sup 4} Mpc{sup -1}. We consider in particular models in which the dark matter is kinetically coupled to either neutrinos or photons until shortly before recombination, and compute the photon heating rate and the resultant μ-distortion in both cases. We show that the μ-parameter is generally enhanced relative to ΛCDM for interactions with neutrinos,more » and may be either enhanced or suppressed in the case of interactions with photons. The deviations from the ΛCDM signal are potentially within the sensitivity reach of a PRISM-like experiment if σ{sub DM-γ} ∼> 1.1 × 10{sup -30} (m{sub DM}/GeV) cm{sup 2} and σ{sub DM-ν} ∼> 4.8 × 10{sup -32} (m{sub DM}/GeV) cm{sup 2} for time-independent cross sections, and σ{sup 0}{sub DM-γ} ∼> 1.8 × 10{sup -40} (m{sub DM}/GeV) cm{sup 2} and σ{sup 0}{sub DM-ν} ∼> 2.5 × 10{sup -47} (m{sub DM}/GeV) cm{sup 2} for cross sections scaling as temperature squared, coinciding with the parameter regions in which late kinetic decoupling may serve as a solution to the small-scale crisis. Furthermore, these μ-distortion signals differ from those of warm dark matter (no deviation from ΛCDM) and a suppressed primordial power spectrum (a strongly suppressed or negative μ-parameter), demonstrating that CMB spectral distortion can potentially be used to distinguish between solutions to the small-scale crisis.« less

Item Response Modeling of Forced-Choice Questionnaires

ERIC Educational Resources Information Center

Brown, Anna; Maydeu-Olivares, Alberto

2011-01-01

Multidimensional forced-choice formats can significantly reduce the impact of numerous response biases typically associated with rating scales. However, if scored with classical methodology, these questionnaires produce ipsative data, which lead to distorted scale relationships and make comparisons between individuals problematic. This research…

Sub-Nyquist Sampling and Moire-Like Waveform Distortions

NASA Technical Reports Server (NTRS)

Williams, Glenn L.

2000-01-01

Investigations of aliasing effects in digital waveform sampling have revealed the existence of a mathematical field and a pseudo-alias domain lying to the left of a "Nyquist line" in a plane defining the boundary between two domains of sampling. To the right of the line lies the classic alias domain. For signals band-limited below the Nyquist limit, displayed output may show a false modulation envelope. The effect occurs whenever the sample rate and the signal frequency are related by ratios of mutually prime integers. Belying the principal of a 10:1 sampling ratio being "good enough", this distortion easily occurs in graphed one-dimensional waveforms and two-dimensional images and occurs daily on television.

Model of Atmospheric Links on Optical Communications from High Altitude

NASA Technical Reports Server (NTRS)

Subich, Christopher

2004-01-01

Optical communication links have the potential to solve many of the problems of current radio and microwave links to satellites and high-altitude aircraft. The higher frequency involved in optical systems allows for significantly greater signal bandwidth, and thus information transfer rate, in excess of 10 Gbps, and the highly directional nature of laser-based signals eliminates the need for frequency-division multiplexing seen in radio and microwave links today. The atmosphere, however, distorts an optical signal differently than a microwave signal. While the ionosphere is one of the most significant sources of noise and distortion in a microwave or radio signal, the lower atmosphere affects an optical signal more significantly. Refractive index fluctuations, primarily caused by changes in atmospheric temperature and density, distort the incoming signal in both deterministic and nondeterministic ways. Additionally, suspended particles, such as those in haze or rain, further corrupt the transmitted signal. To model many of the atmospheric effects on the propagating beam, we use simulations based on the beam-propagation method. This method, developed both for simulation of signals in waveguides and propagation in atmospheric turbulence, separates the propagation into a diffraction and refraction problem. The diffraction step is an exact solution, within the limits of numerical precision, to the problem of propagation in free space, and the refraction step models the refractive index variances over a segment of the propagation path. By applying refraction for a segment of the propagation path, then diffracting over that same segment, this method forms a good approximation to true propagation through the atmospheric medium. Iterating over small segments of the total propagation path gives a good approximation to the problem of propagation over the entire path. Parameters in this model, such as initial beam profile and atmospheric constants, are easily modified in a simulation such as this, which allows for the rapid analysis of different propagation scenarios. Therefore, this method allows the development of a near-optimal system design for a wide range of situations, typical of what would be seen in different atmospheric conditions over a receiving ground station. A simulation framework based upon this model was developed in FORTRAN, and for moderate grid sizes and propagation distances these simulations are computable in reasonable time on a standard workstation. This presentation will discuss results thus far.

Homogeneous Electrocatalytic Reduction of Carbon Dioxide to Carbon Monoxide by Ni(cyclam)

NASA Astrophysics Data System (ADS)

Froehlich, Jesse Dan

The homogeneous electrochemical reduction of CO2 by the molecular catalyst [Ni(cyclam)]2+ was studied by electrochemistry and infrared spectroelectrochemistry. This catalyst has been previously shown to have increased CO2 reduction activity when adsorbed on a mercury electrode. The homogeneous reactivity, without a mercury electrode, was often ignored in the literature. Ni(cyclam) was found to efficiently and selectively produce CO at moderate overpotentials in both aqueous and mixed organic solvent systems in a homogenous fashion at an inert glassy carbon electrode. Methylated analogs of Ni(cyclam) were also studied and observed to have more positive reduction potentials and attenuated CO2 reduction activity. The electrochemical kinetics were probed by varying CO2 substrate and proton concentrations. Products of CO2 reduction are observed in infrared spectra obtained from spectroelectrochemical experiments. The two major species observed were a Ni(I) carbonyl, [Ni(cyclam)(CO)]+, and a Ni(II) coordinated bicarbonate, [Ni(cyclam)(CO2OH)] +. The rate-limiting step during electrocatalysis was determined to be CO loss from the deactivated species, [Ni(cyclam)(CO)]+, to produce the active catalyst, [Ni(cyclam)]+. Another macrocyclic complex, [Ni(TMC)]+, was deployed as a CO scavenger in order to inhibit the deactivation of [Ni(cyclam)] + by CO. Addition of the CO scavenger was shown to dramatically increase the catalytic current observed for CO2 reduction by [Ni(cyclam)] +. Evidence for the [Ni(TMC)]+ acting as a CO scavenger includes the observation of [Ni(TMC)(CO)]+ by IR. Density functional theory calculations, probing the optimized geometry of the [Ni(cyclam)(CO)] + species, are also presented. These findings have implications on the increased activity for CO2 reduction when [Ni(cyclam)] + is adsorbed on a mercury electrode. The [Ni(cyclam)(CO)] + structure has significant distortion of the Ni center out of the plane of the cyclam nitrogens. This distortion strengthens the Ni-CO interaction by increasing back-bonding interactions. This leads to the hypothesis that the mercury surface, through Hg-Ni interactions, prevents the distorted geometry seen in solution leading to a more planar geometry. This helps to destabilize the carbonyl adduct which inhibits the extent of CO poisoning of the catalyst when adsorbed on a mercury electrode. Alternative approaches to prevent CO poisoning without using such a toxic substance as mercury are critical to improving this unique catalytic system.

Optical Nonlinearities in Semiconductors for Limiting.

NASA Astrophysics Data System (ADS)

Wu, Yuan-Yen

I have conducted detailed experimental and theoretical studies of the nonlinear optical properties of semiconductor materials useful for optical limiting. I have constructed optical limiters utilizing two-photon absorption along with photogenerated carrier defocusing as well as the bound electronic nonlinearity using the semiconducting material ZnSe. I have optimized the focusing geometry to achieve a large dynamic range while maintaining a low limiting energy for the device. The ZnSe monolithic optical limiter has achieved a limiting energy as low as 13 nJ (corresponding to 300W peak power) and a dynamic range as large as 10 ^5 at 532 nm using psec pulses. Theoretical analysis showed that the ZnSe device has a broad-band response covering the wavelength range from 550 nm to 800 nm. Moreover, I found that existing theoretical models (e.g. the Auston model and the band-resonant model using Boltzmann statistics) adequately describe the photo-generated carriers refractive nonlinearity in ZnSe. Material nonlinear optical parameters, such as the two-photon absorption coefficient beta _2 = 5.5 cm/GW, the refraction per unit carrier density sigma_{rm n} = -0.8cdot 10^ {-21}cm^3 and the bound electronic refraction n_2 = -4cdot 10^{ -11}esu, have been measured via time-integrated beam distortion experiments in the near field. A numerical code has been written to simulate the beam distortion in order to extract the previously mentioned material parameters. In addition, I have performed time-resolved distortion measurements that provide an intuitive picture of the carrier generation process via two-photon absorption. I also characterized the optical nonlinearities in a ZnSe Fabry-Perot thin film structure (an interference filter). I concluded that the nonlinear absorption alone in the thin film is insufficient to build an effective optical limiter, as it did not show a net change in refraction using psec pulses. An innovative numerical program was developed to simulate the nonlinear beam propagation inside the Fabry-Perot structure. For comparison, pump-probe experiments were performed using both thin film and bulk ZnSe. The results showed relatively long carrier lifetimes (>300 psec) in both samples. A numerical code was written to fit the pump-probe experimental results. The fitting yielded that carrier lifetimes (recombination through traps), radiative decay rate, two-photon absorption coefficient as well as the free carrier absorption coefficient for ZnSe bulk material.

Uncertainty in the analysis of the overall equipment effectiveness on the shop floor

NASA Astrophysics Data System (ADS)

Rößler, M. P.; Abele, E.

2013-06-01

In this article an approach will be presented which supports transparency regarding the effectiveness of manufacturing equipment by combining the fuzzy set theory with the method of the overall equipment effectiveness analysis. One of the key principles of lean production and also a fundamental task in production optimization projects is the prior analysis of the current state of a production system by the use of key performance indicators to derive possible future states. The current state of the art in overall equipment effectiveness analysis is usually performed by cumulating different machine states by means of decentralized data collection without the consideration of uncertainty. In manual data collection or semi-automated plant data collection systems the quality of derived data often diverges and leads optimization teams to distorted conclusions about the real optimization potential of manufacturing equipment. The method discussed in this paper is to help practitioners to get more reliable results in the analysis phase and so better results of optimization projects. Under consideration of a case study obtained results are discussed.

Performance of turbo high-pitch dual-source CT for coronary CT angiography: first ex vivo and patient experience.

PubMed

Morsbach, Fabian; Gordic, Sonja; Desbiolles, Lotus; Husarik, Daniela; Frauenfelder, Thomas; Schmidt, Bernhard; Allmendinger, Thomas; Wildermuth, Simon; Alkadhi, Hatem; Leschka, Sebastian

2014-08-01

To evaluate image quality, maximal heart rate allowing for diagnostic imaging, and radiation dose of turbo high-pitch dual-source coronary computed tomographic angiography (CCTA). First, a cardiac motion phantom simulating heart rates (HRs) from 60-90 bpm in 5-bpm steps was examined on a third-generation dual-source 192-slice CT (prospective ECG-triggering, pitch 3.2; rotation time, 250 ms). Subjective image quality regarding the presence of motion artefacts was interpreted by two readers on a four-point scale (1, excellent; 4, non-diagnostic). Objective image quality was assessed by calculating distortion vectors. Thereafter, 20 consecutive patients (median, 50 years) undergoing clinically indicated CCTA were included. In the phantom study, image quality was rated diagnostic up to the HR75 bpm, with object distortion being 1 mm or less. Distortion increased above 1 mm at HR of 80-90 bpm. Patients had a mean HR of 66 bpm (47-78 bpm). Coronary segments were of diagnostic image quality for all patients with HR up to 73 bpm. Average effective radiation dose in patients was 0.6 ± 0.3 mSv. Our combined phantom and patient study indicates that CCTA with turbo high-pitch third-generation dual-source 192-slice CT can be performed at HR up to 75 bpm while maintaining diagnostic image quality, being associated with an average radiation dose of 0.6 mSv. • CCTA is feasible with the turbo high-pitch mode. • Turbo high-pitch CCTA provides diagnostic image quality up to 73 bpm. • The radiation dose of high-pitch CCTA is 0.6 mSv on average.

Revising a priority list based on cost-effectiveness: the role of the prominence effect and distorted utility judgments.

PubMed

Baron, J; Ubel, P A

2001-01-01

People sometimes object to the results of cost-effectiveness analysis when the analysis produces a ranking of options based on both cost and benefit. We suggest 2 new reasons for these objections: the prominence effect, in which people attend mostly to a more prominent attrbute (benefit as opposed to cost), and distortion of utility judgments. We simulated the production of a cost-effectiveness ranking list in 3 experiments using questionnaires on the World Wide Web. Subjects rated the utility of 16 health benefits using either rating scale or person trade-off elicitation methods. In some experiments, subjects were asked to rate the utility of the health benefits with attention also to the cost of achieving the benefits. In all experiments, at the end, subjects were shown a priority list based on their own utility judgments and were asked whether they wanted to move any of the health benefits up or down the list. In all experiments, subjects wanted to give higher priority to treatments with higher benefit, even when they also had higher cost. They thus wanted to give less weight to high cost (which would, by itself, lead to lower ranking) and more weight to benefit than the weight implied by their own prior judgments. The desire for revision was reduced when subjects made their utility judgments after indicating whether the utility was above or below the midpoint of the scale (a manipulation previously found to reduce distortion). The desire to change cost-effectiveness rankings is in part a preference reversal phenomenon that occurs because people attend mainly to the benefit of health interventions as opposed to cost, when they examine the ranking. People should be wary of tinkering with priority lists by examining the lists themselves.

Risk preferences impose a hidden distortion on measures of choice impulsivity.

PubMed

Lopez-Guzman, Silvia; Konova, Anna B; Louie, Kenway; Glimcher, Paul W

2018-01-01

Measuring temporal discounting through the use of intertemporal choice tasks is now the gold standard method for quantifying human choice impulsivity (impatience) in neuroscience, psychology, behavioral economics, public health and computational psychiatry. A recent area of growing interest is individual differences in discounting levels, as these may predispose to (or protect from) mental health disorders, addictive behaviors, and other diseases. At the same time, more and more studies have been dedicated to the quantification of individual attitudes towards risk, which have been measured in many clinical and non-clinical populations using closely related techniques. Economists have pointed to interactions between measurements of time preferences and risk preferences that may distort estimations of the discount rate. However, although becoming standard practice in economics, discount rates and risk preferences are rarely measured simultaneously in the same subjects in other fields, and the magnitude of the imposed distortion is unknown in the assessment of individual differences. Here, we show that standard models of temporal discounting -such as a hyperbolic discounting model widely present in the literature which fails to account for risk attitudes in the estimation of discount rates- result in a large and systematic pattern of bias in estimated discounting parameters. This can lead to the spurious attribution of differences in impulsivity between individuals when in fact differences in risk attitudes account for observed behavioral differences. We advance a model which, when applied to standard choice tasks typically used in psychology and neuroscience, provides both a better fit to the data and successfully de-correlates risk and impulsivity parameters. This results in measures that are more accurate and thus of greater utility to the many fields interested in individual differences in impulsivity.

A demographic explanation for the recent rise in European fertility.

PubMed

Bongaarts, John; Sobotka, Tomáš

2012-01-01

Between 1998 and 2008 European countries experienced the first continent-wide increase in the period total fertility rate (TFR) since the 1960s. After discussing period and cohort influences on fertility trends, we examine the role of tempo distortions of period fertility and different methods for removing them. We highlight the usefulness of a new indicator: the tempo- and parity-adjusted total fertility rate (TFRp*). This variant of the adjusted total fertility rate proposed by Bongaarts and Feeney also controls for the parity composition of the female population and provides more stable values than the indicators proposed in the past. Finally, we estimate levels and trends in tempo and parity distribution distortions in selected countries in Europe. Our analysis of period and cohort fertility indicators in the Czech Republic, Netherlands, Spain, and Sweden shows that the new adjusted measure gives a remarkable fit with the completed fertility of women in prime childbearing years in a given period, which suggests that it provides an accurate adjustment for tempo and parity composition distortions. Using an expanded dataset for ten countries, we demonstrate that adjusted fertility as measured by TFRp* remained nearly stable since the late 1990s. This finding implies that the recent upturns in the period TFR in Europe are largely explained by a decline in the pace of fertility postponement. Other tempo-adjusted fertility indicators have not indicated such a large role for the diminishing tempo effect in these TFR upturns. As countries proceed through their postponement transitions, tempo effects will decline further and eventually disappear, thus putting continued upward pressure on period fertility. However, such an upward trend may be obscured for a few years by the effects of economic recession.

Non-destructive geometric and refractive index characterization of single and multi-element lenses using optical coherence tomography

NASA Astrophysics Data System (ADS)

El-Haddad, Mohamed T.; Tao, Yuankai K.

2018-02-01

Design of optical imaging systems requires careful balancing of lens aberrations to optimize the point-spread function (PSF) and minimize field distortions. Aberrations and distortions are a result of both lens geometry and glass material. While most lens manufacturers provide optical models to facilitate system-level simulation, these models are often not reflective of true system performance because of manufacturing tolerances. Optical design can be further confounded when achromatic or proprietary lenses are employed. Achromats are ubiquitous in systems that utilize broadband sources due to their superior performance in balancing chromatic aberrations. Similarly, proprietary lenses may be custom-designed for optimal performance, but lens models are generally not available. Optical coherence tomography (OCT) provides non-contact, depth-resolved imaging with high axial resolution and sensitivity. OCT has been previously used to measure the refractive index of unknown materials. In a homogenous sample, the group refractive index is obtained as the ratio between the measured optical and geometric thicknesses of the sample. In heterogenous samples, a method called focus-tracking (FT) quantifies the effect of focal shift introduced by the sample. This enables simultaneous measurement of the thickness and refractive index of intermediate sample layers. Here, we extend the mathematical framework of FT to spherical surfaces, and describe a method based on OCT and FT for full characterization of lens geometry and refractive index. Finally, we validate our characterization method on commercially available singlet and doublet lenses.

CO₂ emission mitigation and fossil fuel markets: Dynamic and international aspects of climate policies

DOE PAGES

Bauer, Nico; Bosetti, Valentina; Hamdi-Cherif, Meriem; ...

2015-01-01

This paper explores a multi-model scenario ensemble to assess the impacts of idealized and non-idealized climate change stabilization policies on fossil fuel markets. Under idealized conditions climate policies significantly reduce coal use in the short- and long-term. Reductions in oil and gas use are much smaller, particularly until 2030, but revenues decrease much more because oil and gas prices are higher than coal prices. A first deviation from optimal transition pathways is delayed action that relaxes global emission targets until 2030 in accordance with the Copenhagen pledges. Fossil fuel markets revert back to the no-policy case: though coal use increasesmore » strongest, revenue gains are higher for oil and gas. To balance the carbon budget over the 21st century, the long-term reallocation of fossil fuels is significantly larger—twice and more—than the short-term distortion. This amplifying effect results from coal lock-in and inter-fuel substitution effects to balance the full-century carbon budget. The second deviation from the optimal transition pathway relaxes the global participation assumption. The result here is less clear-cut across models, as we find carbon leakage effects ranging from positive to negative because trade and substitution patterns of coal, oil, and gas differ across models. In summary, distortions of fossil fuel markets resulting from relaxed short-term global emission targets are more important and less uncertain than the issue of carbon leakage from early mover action.« less

CO₂ emission mitigation and fossil fuel markets: Dynamic and international aspects of climate policies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauer, Nico; Bosetti, Valentina; Hamdi-Cherif, Meriem

This paper explores a multi-model scenario ensemble to assess the impacts of idealized and non-idealized climate change stabilization policies on fossil fuel markets. Under idealized conditions climate policies significantly reduce coal use in the short- and long-term. Reductions in oil and gas use are much smaller, particularly until 2030, but revenues decrease much more because oil and gas prices are higher than coal prices. A first deviation from optimal transition pathways is delayed action that relaxes global emission targets until 2030 in accordance with the Copenhagen pledges. Fossil fuel markets revert back to the no-policy case: though coal use increasesmore » strongest, revenue gains are higher for oil and gas. To balance the carbon budget over the 21st century, the long-term reallocation of fossil fuels is significantly larger—twice and more—than the short-term distortion. This amplifying effect results from coal lock-in and inter-fuel substitution effects to balance the full-century carbon budget. The second deviation from the optimal transition pathway relaxes the global participation assumption. The result here is less clear-cut across models, as we find carbon leakage effects ranging from positive to negative because trade and substitution patterns of coal, oil, and gas differ across models. In summary, distortions of fossil fuel markets resulting from relaxed short-term global emission targets are more important and less uncertain than the issue of carbon leakage from early mover action.« less

CO2 emissions mitigation and fossil fuel markets: Dynamic and international aspects of climate policies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauer, Nico; Bosetti, Valentina; Hamdi-Cherif, Meriem

This paper explores a multi-model scenario ensemble to assess the impacts of idealized and non-idealized climate change stabilization policies on fossil fuel markets. Under idealized conditions climate policies significantly reduce coal use in the short- and long-term. Reductions in oil and gas use are much smaller, particularly until 2030, but revenues decrease much more because oil and gas prices are higher and decrease with mitigation. A first deviation from the optimal transition pathway relaxes global emission targets until 2030, in accordance with the Copenhagen pledges and regionally-specific low-carbon technology targets. Fossil fuel markets revert back to the no-policy case: thoughmore » coal use increases strongest, revenue gains are higher for oil and gas. To balance the carbon budget over the 21st century, the long-term reallocation of fossil fuels is significantly larger - twice and more - than the short-term distortion. This amplifying effect results from coal lock-in and inter-fuel substitution effects. The second deviation from the optimal transition pathway relaxes the global participation assumption. The result here is less clear cut across models, as we find carbon leakage effects ranging from positive to negative because leakage and substitution patterns of coal, oil, and gas differ. In summary, distortions of fossil fuel markets resulting from relaxed short-term global emission targets are more important and less uncertain than the issue of carbon leakage from early mover action.« less

Beam shaping for laser-based adaptive optics in astronomy.

PubMed

Béchet, Clémentine; Guesalaga, Andrés; Neichel, Benoit; Fesquet, Vincent; González-Núñez, Héctor; Zúñiga, Sebastián; Escarate, Pedro; Guzman, Dani

2014-06-02

The availability and performance of laser-based adaptive optics (AO) systems are strongly dependent on the power and quality of the laser beam before being projected to the sky. Frequent and time-consuming alignment procedures are usually required in the laser systems with free-space optics to optimize the beam. Despite these procedures, significant distortions of the laser beam have been observed during the first two years of operation of the Gemini South multi-conjugate adaptive optics system (GeMS). A beam shaping concept with two deformable mirrors is investigated in order to provide automated optimization of the laser quality for astronomical AO. This study aims at demonstrating the correction of quasi-static aberrations of the laser, in both amplitude and phase, testing a prototype of this two-deformable mirror concept on GeMS. The paper presents the results of the preparatory study before the experimental phase. An algorithm to control amplitude and phase correction, based on phase retrieval techniques, is presented with a novel unwrapping method. Its performance is assessed via numerical simulations, using aberrations measured at GeMS as reference. The results predict effective amplitude and phase correction of the laser distortions with about 120 actuators per mirror and a separation of 1.4 m between the mirrors. The spot size is estimated to be reduced by up to 15% thanks to the correction. In terms of AO noise level, this has the same benefit as increasing the photon flux by 40%.

Shaping your career to maximize personal satisfaction in the practice of oncology.

PubMed

Shanafelt, Tait; Chung, Harold; White, Heather; Lyckholm, Laurie Jean

2006-08-20

The practice of oncology can be a source of both great satisfaction and great stress. Although many oncologists experience burnout, depression, and dissatisfaction with work, others experience tremendous career satisfaction and achieve a high overall quality of life. Identifying professional goals, optimizing career fit, identifying and managing stressors specific to practice type, and achieving the optimal personal work-life balance can increase the likelihood of individual oncologists' achieving personal and professional satisfaction. In this article, we will explore how oncologists can accomplish these tasks and will examine several pervasive professional myths that often distort perspective. The article concludes in a conversation with four oncologists regarding what they find most meaningful about their work, how they manage career-specific stressors, and how they achieve balance between their personal and professional lives.

Multiband phase-modulated radio over IsOWC link with balanced coherent homodyne detection

NASA Astrophysics Data System (ADS)

Zong, Kang; Zhu, Jiang

2017-11-01

In this paper, we present a multiband phase-modulated radio over intersatellite optical wireless communication (IsOWC) link with balanced coherent homodyne detection. The proposed system can provide high linearity for transparent transport of multiband radio frequency (RF) signals and better receiver sensitivity than intensity modulated with direct detection (IM/DD) system. The exact analytical expression of signal to noise and distortion ratio (SNDR) is derived considering the third-order intermodulation product and amplifier spontaneous emission (ASE) noise. Numerical results of SNDR with various number of subchannels and modulation index are given. Results indicate that the optimal modulation index exists to maximize the SNDR. With the same system parameters, the value of the optimal modulation index will decrease with the increase of number of subchannels.

Optimized Mouse Models for Liver Fibrosis.

PubMed

Kim, Yong Ook; Popov, Yury; Schuppan, Detlef

2017-01-01

Fibrosis is the excessive accumulation of extracellular matrix components due to chronic injury, with collagens as predominant structural components. Liver fibrosis can progress to cirrhosis, which is characterized by a severe distortion of the delicate hepatic vascular architecture, the shunting of the blood supply away from hepatocytes and the resultant functional liver failure. Cirrhosis is associated with a highly increased morbidity and mortality and represents the major hard endpoint in clinical studies of chronic liver diseases. Moreover, cirrhosis is a strong cofactor of primary liver cancer. In vivo models are indispensable tools to study the cellular and molecular mechanisms of liver fibrosis and to develop specific antifibrotic therapies towards clinical translation. Here, we provide a detailed description of select optimized mouse models of liver fibrosis and state-of-the-art fibrosis readouts.

Color Image Enhancement Using Multiscale Retinex Based on Particle Swarm Optimization Method

NASA Astrophysics Data System (ADS)

Matin, F.; Jeong, Y.; Kim, K.; Park, K.

2018-01-01

This paper introduces, a novel method for the image enhancement using multiscale retinex and practical swarm optimization. Multiscale retinex is widely used image enhancement technique which intemperately pertains on parameters such as Gaussian scales, gain and offset, etc. To achieve the privileged effect, the parameters need to be tuned manually according to the image. In order to handle this matter, a developed retinex algorithm based on PSO has been used. The PSO method adjusted the parameters for multiscale retinex with chromaticity preservation (MSRCP) attains better outcome to compare with other existing methods. The experimental result indicates that the proposed algorithm is an efficient one and not only provides true color loyalty in low light conditions but also avoid color distortion at the same time.

Distortion and Residual Stress Control in Integrally Stiffened Structure Produced by Direct Metal Deposition

NASA Technical Reports Server (NTRS)

Lin, Shih-Yung; Hoffman, Eric K.; Domack, Marcia S.

2007-01-01

2-D thermo-mechanical model developed to characterize distortion and residual stresses in integral structure produced by DMD. Demonstrated as a tool to guide experimental development of DMD fabrication process for aero structures. Distortion and residual stresses are local to deposit. Most distortion develops during deposition of the first few layers; Little change in distortion or residual stresses after fifth deposit layer Most of distortion is localized just beneath the build. Thicker build plates and the use of build lands results in greatest decrease in levels of distortion. Pre-straining shown to reduce distortion. Difficult to implement, particularly for complex stiffener arrays. Clamp position has complex effect on distortion and stresses. Overall distortion reduced with decreasing clamp clearance. Larger clamp clearances induce bending. Use of pre-heat and active cooling show minor influence on panel distortion. Generate changes in thermal gradients in the build plate.

Detection and Rectification of Distorted Fingerprints.

PubMed

Si, Xuanbin; Feng, Jianjiang; Zhou, Jie; Luo, Yuxuan

2015-03-01

Elastic distortion of fingerprints is one of the major causes for false non-match. While this problem affects all fingerprint recognition applications, it is especially dangerous in negative recognition applications, such as watchlist and deduplication applications. In such applications, malicious users may purposely distort their fingerprints to evade identification. In this paper, we proposed novel algorithms to detect and rectify skin distortion based on a single fingerprint image. Distortion detection is viewed as a two-class classification problem, for which the registered ridge orientation map and period map of a fingerprint are used as the feature vector and a SVM classifier is trained to perform the classification task. Distortion rectification (or equivalently distortion field estimation) is viewed as a regression problem, where the input is a distorted fingerprint and the output is the distortion field. To solve this problem, a database (called reference database) of various distorted reference fingerprints and corresponding distortion fields is built in the offline stage, and then in the online stage, the nearest neighbor of the input fingerprint is found in the reference database and the corresponding distortion field is used to transform the input fingerprint into a normal one. Promising results have been obtained on three databases containing many distorted fingerprints, namely FVC2004 DB1, Tsinghua Distorted Fingerprint database, and the NIST SD27 latent fingerprint database.

Grids in topographic maps reduce distortions in the recall of learned object locations.

PubMed

Edler, Dennis; Bestgen, Anne-Kathrin; Kuchinke, Lars; Dickmann, Frank

2014-01-01

To date, it has been shown that cognitive map representations based on cartographic visualisations are systematically distorted. The grid is a traditional element of map graphics that has rarely been considered in research on perception-based spatial distortions. Grids do not only support the map reader in finding coordinates or locations of objects, they also provide a systematic structure for clustering visual map information ("spatial chunks"). The aim of this study was to examine whether different cartographic kinds of grids reduce spatial distortions and improve recall memory for object locations. Recall performance was measured as both the percentage of correctly recalled objects (hit rate) and the mean distance errors of correctly recalled objects (spatial accuracy). Different kinds of grids (continuous lines, dashed lines, crosses) were applied to topographic maps. These maps were also varied in their type of characteristic areas (LANDSCAPE) and different information layer compositions (DENSITY) to examine the effects of map complexity. The study involving 144 participants shows that all experimental cartographic factors (GRID, LANDSCAPE, DENSITY) improve recall performance and spatial accuracy of learned object locations. Overlaying a topographic map with a grid significantly reduces the mean distance errors of correctly recalled map objects. The paper includes a discussion of a square grid's usefulness concerning object location memory, independent of whether the grid is clearly visible (continuous or dashed lines) or only indicated by crosses.

The impact of mixed, hope and forgiveness-focused marital counselling on interpersonal cognitive distortions of couples filing for divorce.

PubMed

Navidian, A; Bahari, F

2014-09-01

Divorce and conflict are overlapping processes. Previous findings suggest that spirituality-related interventions in mental health nursing may play a significant role in reducing the level and amount of conflict. We examined the effects of hope and forgiveness-focused marital counselling and a combination of the two intervention types on interpersonal cognitive distortions of couples filing for divorce in Isfahan, Iran. We conducted a quasi-experimental study with a pre-test and post-test design. Of 440 couples referred to the Crisis Intervention Center undergoing pre-divorce counselling, 60 were randomly assigned to four groups: hope-focused, forgiveness-focused, mixed and control. Data were gathered using the Interpersonal Cognitive Distortions Scale and analysed using the non-parametric Kruskal-Wallis, Mann-Whitney's U and Wilcoxon tests. Hope- and forgiveness-focused interventions did not have a significant effect on the total number of interpersonal cognitive distortions in comparison with the control group. However, the mixed intervention significantly reduced irrational expectations and interpersonal rejection among couples. Combining hope- and forgiveness-focused interventions can be used to decrease irrational marital beliefs among couples. In addition, rating the level of conflict among couples is important for determining the type of intervention that should be used by mental health nurses (psycho-educational or therapeutic). © 2013 John Wiley & Sons Ltd.

Pulse repetition rate multiplication by Talbot effect in a coaxial fiber

NASA Astrophysics Data System (ADS)

Dhingra, Nikhil; Saxena, Geetika Jain; Anand, Jyoti; Sharma, Enakshi K.

2018-03-01

We use a coaxial fiber, which is a cylindrical coupled waveguide structure consisting of two concentric cores, the inner rod and an outer ring core as a first order dispersive media to achieve temporal Talbot effect for pulse repetition rate multiplication (PRRM) in high bit rate optical fiber communication. It is observed that for an input Gaussian pulse train with pulse width, 2τ0=1ps at a repetition rate of 40 Gbps (repetition period, T=25ps), an output repetition rate of 640 Gbps can be achieved without significant distortion at a length of 40.92 m.

The influence of thickness on density of an I-2 bituminous mix.

DOT National Transportation Integrated Search

1978-01-01

From this very limited study, it was concluded that (1) even when the road cross section was distorted, the contractor did an excellent job of controlling the average application rate; (2) the percent compaction, while acceptably high, did not increa...

Uneven segregation of sporophytic self-incompatibility alleles in Arabidopsis lyrata.

PubMed

Bechsgaard, J; Bataillon, T; Schierup, M H

2004-05-01

Self-incompatibility in Arabidopsis lyrata is sporophytically controlled by the multi-allelic S-locus. Self-incompatibility alleles (S-alleles) are under strong negative frequency dependent selection because pollen carrying common S-alleles have fewer mating opportunities. Population genetics theory predicts that deleterious alleles can accumulate if linked to the S-locus. This was tested by studying segregation of S-alleles in 11 large full sib families in A. lyrata. Significant segregation distortion leading to an up to fourfold difference in transmission rates was found in six families. Differences in transmission rates were not significantly different in reciprocal crosses and the distortions observed were compatible with selection acting at the gametic stage alone. The S-allele with the largest segregation advantage is also the most recessive, and is very common in natural populations concordant with its apparent segregation advantage. These results imply that frequencies of S-alleles in populations of A. lyrata cannot be predicted based on simple models of frequency-dependent selection alone.

A hybrid method for synthetic aperture ladar phase-error compensation

NASA Astrophysics Data System (ADS)

Hua, Zhili; Li, Hongping; Gu, Yongjian

2009-07-01

As a high resolution imaging sensor, synthetic aperture ladar data contain phase-error whose source include uncompensated platform motion and atmospheric turbulence distortion errors. Two previously devised methods, rank one phase-error estimation algorithm and iterative blind deconvolution are reexamined, of which a hybrid method that can recover both the images and PSF's without any a priori information on the PSF is built to speed up the convergence rate by the consideration in the choice of initialization. To be integrated into spotlight mode SAL imaging model respectively, three methods all can effectively reduce the phase-error distortion. For each approach, signal to noise ratio, root mean square error and CPU time are computed, from which we can see the convergence rate of the hybrid method can be improved because a more efficient initialization set of blind deconvolution. Moreover, by making a further discussion of the hybrid method, the weight distribution of ROPE and IBD is found to be an important factor that affects the final result of the whole compensation process.

MAPPING GROWTH AND GRAVITY WITH ROBUST REDSHIFT SPACE DISTORTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwan, Juliana; Lewis, Geraint F.; Linder, Eric V.

2012-04-01

Redshift space distortions (RSDs) caused by galaxy peculiar velocities provide a window onto the growth rate of large-scale structure and a method for testing general relativity. We investigate through a comparison of N-body simulations to various extensions of perturbation theory beyond the linear regime, the robustness of cosmological parameter extraction, including the gravitational growth index {gamma}. We find that the Kaiser formula and some perturbation theory approaches bias the growth rate by 1{sigma} or more relative to the fiducial at scales as large as k > 0.07 h Mpc{sup -1}. This bias propagates to estimates of the gravitational growth indexmore » as well as {Omega}{sub m} and the equation-of-state parameter and presents a significant challenge to modeling RSDs. We also determine an accurate fitting function for a combination of line-of-sight damping and higher order angular dependence that allows robust modeling of the redshift space power spectrum to substantially higher k.« less

Advanced coding and modulation schemes for TDRSS

NASA Technical Reports Server (NTRS)

Harrell, Linda; Kaplan, Ted; Berman, Ted; Chang, Susan

1993-01-01

This paper describes the performance of the Ungerboeck and pragmatic 8-Phase Shift Key (PSK) Trellis Code Modulation (TCM) coding techniques with and without a (255,223) Reed-Solomon outer code as they are used for Tracking Data and Relay Satellite System (TDRSS) S-Band and Ku-Band return services. The performance of these codes at high data rates is compared to uncoded Quadrature PSK (QPSK) and rate 1/2 convolutionally coded QPSK in the presence of Radio Frequency Interference (RFI), self-interference, and hardware distortions. This paper shows that the outer Reed-Solomon code is necessary to achieve a 10(exp -5) Bit Error Rate (BER) with an acceptable level of degradation in the presence of RFI. This paper also shows that the TCM codes with or without the Reed-Solomon outer code do not perform well in the presence of self-interference. In fact, the uncoded QPSK signal performs better than the TCM coded signal in the self-interference situation considered in this analysis. Finally, this paper shows that the E(sub b)/N(sub 0) degradation due to TDRSS hardware distortions is approximately 1.3 dB with a TCM coded signal or a rate 1/2 convolutionally coded QPSK signal and is 3.2 dB with an uncoded QPSK signal.

Optical ground station optimization for future optical geostationary satellite feeder uplinks

NASA Astrophysics Data System (ADS)

Camboulives, A.-R.; Velluet, M.-T.; Poulenard, S.; Saint-Antonin, L.; Michau, V.

2017-02-01

An optical link based on a multiplex of wavelengths at 1:55 μm is foreseen to be a valuable alternative to the conventional radio-frequencies for the feeder link of the next-generation of high throughput geostationary satellite. Considering the limited power of lasers envisioned for feeder links, the beam divergence has to be dramatically reduced. Consequently, the beam pointing becomes a key issue. During its propagation between the ground station and a geostationary satellite, the optical beam is deflected (beam wandering), and possibly distorted (beam spreading), by atmospheric turbulence. It induces strong fluctuations of the detected telecom signal, thus increasing the bit error rate (BER). A steering mirror using a measurement from a beam coming from the satellite is used to pre-compensate the deflection. Because of the point-ahead angle between the downlink and the uplink, the turbulence effects experienced by both beams are slightly different, inducing an error in the correction. This error is characterized as a function of the turbulence characteristics as well as of the terminal characteristics, such as the servo-loop bandwidth or the beam diameter, and is included in the link budget. From this result, it is possible to predict intensity fluctuations detected by the satellite statistically (mean intensity, scintillation index, probability of fade, etc.)). The final objective is to optimize the different parameters of an optical ground station capable of mitigating the impact of atmospheric turbulence on the uplink in order to be compliant with the targeted capacity (1Terabit/s by 2025).

Detection and tracking of human targets in indoor and urban environments using through-the-wall radar sensors

NASA Astrophysics Data System (ADS)

Radzicki, Vincent R.; Boutte, David; Taylor, Paul; Lee, Hua

2017-05-01

Radar based detection of human targets behind walls or in dense urban environments is an important technical challenge with many practical applications in security, defense, and disaster recovery. Radar reflections from a human can be orders of magnitude weaker than those from objects encountered in urban settings such as walls, cars, or possibly rubble after a disaster. Furthermore, these objects can act as secondary reflectors and produce multipath returns from a person. To mitigate these issues, processing of radar return data needs to be optimized for recognizing human motion features such as walking, running, or breathing. This paper presents a theoretical analysis on the modulation effects human motion has on the radar waveform and how high levels of multipath can distort these motion effects. From this analysis, an algorithm is designed and optimized for tracking human motion in heavily clutter environments. The tracking results will be used as the fundamental detection/classification tool to discriminate human targets from others by identifying human motion traits such as predictable walking patterns and periodicity in breathing rates. The theoretical formulations will be tested against simulation and measured data collected using a low power, portable see-through-the-wall radar system that could be practically deployed in real-world scenarios. Lastly, the performance of the algorithm is evaluated in a series of experiments where both a single person and multiple people are moving in an indoor, cluttered environment.

Designing a space-based galaxy redshift survey to probe dark energy

NASA Astrophysics Data System (ADS)

Wang, Yun; Percival, Will; Cimatti, Andrea; Mukherjee, Pia; Guzzo, Luigi; Baugh, Carlton M.; Carbone, Carmelita; Franzetti, Paolo; Garilli, Bianca; Geach, James E.; Lacey, Cedric G.; Majerotto, Elisabetta; Orsi, Alvaro; Rosati, Piero; Samushia, Lado; Zamorani, Giovanni

2010-12-01

A space-based galaxy redshift survey would have enormous power in constraining dark energy and testing general relativity, provided that its parameters are suitably optimized. We study viable space-based galaxy redshift surveys, exploring the dependence of the Dark Energy Task Force (DETF) figure-of-merit (FoM) on redshift accuracy, redshift range, survey area, target selection and forecast method. Fitting formulae are provided for convenience. We also consider the dependence on the information used: the full galaxy power spectrum P(k), P(k) marginalized over its shape, or just the Baryon Acoustic Oscillations (BAO). We find that the inclusion of growth rate information (extracted using redshift space distortion and galaxy clustering amplitude measurements) leads to a factor of ~3 improvement in the FoM, assuming general relativity is not modified. This inclusion partially compensates for the loss of information when only the BAO are used to give geometrical constraints, rather than using the full P(k) as a standard ruler. We find that a space-based galaxy redshift survey covering ~20000deg2 over with σz/(1 + z) <= 0.001 exploits a redshift range that is only easily accessible from space, extends to sufficiently low redshifts to allow both a vast 3D map of the universe using a single tracer population, and overlaps with ground-based surveys to enable robust modelling of systematic effects. We argue that these parameters are close to their optimal values given current instrumental and practical constraints.

Fast words boundaries localization in text fields for low quality document images

NASA Astrophysics Data System (ADS)

Ilin, Dmitry; Novikov, Dmitriy; Polevoy, Dmitry; Nikolaev, Dmitry

2018-04-01

The paper examines the problem of word boundaries precise localization in document text zones. Document processing on a mobile device consists of document localization, perspective correction, localization of individual fields, finding words in separate zones, segmentation and recognition. While capturing an image with a mobile digital camera under uncontrolled capturing conditions, digital noise, perspective distortions or glares may occur. Further document processing gets complicated because of its specifics: layout elements, complex background, static text, document security elements, variety of text fonts. However, the problem of word boundaries localization has to be solved at runtime on mobile CPU with limited computing capabilities under specified restrictions. At the moment, there are several groups of methods optimized for different conditions. Methods for the scanned printed text are quick but limited only for images of high quality. Methods for text in the wild have an excessively high computational complexity, thus, are hardly suitable for running on mobile devices as part of the mobile document recognition system. The method presented in this paper solves a more specialized problem than the task of finding text on natural images. It uses local features, a sliding window and a lightweight neural network in order to achieve an optimal algorithm speed-precision ratio. The duration of the algorithm is 12 ms per field running on an ARM processor of a mobile device. The error rate for boundaries localization on a test sample of 8000 fields is 0.3

Phased array ghost elimination.

PubMed

Kellman, Peter; McVeigh, Elliot R

2006-05-01

Parallel imaging may be applied to cancel ghosts caused by a variety of distortion mechanisms, including distortions such as off-resonance or local flow, which are space variant. Phased array combining coefficients may be calculated that null ghost artifacts at known locations based on a constrained optimization, which optimizes SNR subject to the nulling constraint. The resultant phased array ghost elimination (PAGE) technique is similar to the method known as sensitivity encoding (SENSE) used for accelerated imaging; however, in this formulation is applied to full field-of-view (FOV) images. The phased array method for ghost elimination may result in greater flexibility in designing acquisition strategies. For example, in multi-shot EPI applications ghosts are typically mitigated by the use of an interleaved phase encode acquisition order. An alternative strategy is to use a sequential, non-interleaved phase encode order and cancel the resultant ghosts using PAGE parallel imaging. Cancellation of ghosts by means of phased array processing makes sequential, non-interleaved phase encode acquisition order practical, and permits a reduction in repetition time, TR, by eliminating the need for echo-shifting. Sequential, non-interleaved phase encode order has benefits of reduced distortion due to off-resonance, in-plane flow and EPI delay misalignment. Furthermore, the use of EPI with PAGE has inherent fat-water separation and has been used to provide off-resonance correction using a technique referred to as lipid elimination with an echo-shifting N/2-ghost acquisition (LEENA), and may further generalized using the multi-point Dixon method. Other applications of PAGE include cancelling ghosts which arise due to amplitude or phase variation during the approach to steady state. Parallel imaging requires estimates of the complex coil sensitivities. In vivo estimates may be derived by temporally varying the phase encode ordering to obtain a full k-space dataset in a scheme similar to the autocalibrating TSENSE method. This scheme is a generalization of the UNFOLD method used for removing aliasing in undersampled acquisitions. The more general scheme may be used to modulate each EPI ghost image to a separate temporal frequency as described in this paper. Copyright (c) 2006 John Wiley & Sons, Ltd.

Phased array ghost elimination

PubMed Central

Kellman, Peter; McVeigh, Elliot R.

2007-01-01

Parallel imaging may be applied to cancel ghosts caused by a variety of distortion mechanisms, including distortions such as off-resonance or local flow, which are space variant. Phased array combining coefficients may be calculated that null ghost artifacts at known locations based on a constrained optimization, which optimizes SNR subject to the nulling constraint. The resultant phased array ghost elimination (PAGE) technique is similar to the method known as sensitivity encoding (SENSE) used for accelerated imaging; however, in this formulation is applied to full field-of-view (FOV) images. The phased array method for ghost elimination may result in greater flexibility in designing acquisition strategies. For example, in multi-shot EPI applications ghosts are typically mitigated by the use of an interleaved phase encode acquisition order. An alternative strategy is to use a sequential, non-interleaved phase encode order and cancel the resultant ghosts using PAGE parallel imaging. Cancellation of ghosts by means of phased array processing makes sequential, non-interleaved phase encode acquisition order practical, and permits a reduction in repetition time, TR, by eliminating the need for echo-shifting. Sequential, non-interleaved phase encode order has benefits of reduced distortion due to off-resonance, in-plane flow and EPI delay misalignment. Furthermore, the use of EPI with PAGE has inherent fat-water separation and has been used to provide off-resonance correction using a technique referred to as lipid elimination with an echo-shifting N/2-ghost acquisition (LEENA), and may further generalized using the multi-point Dixon method. Other applications of PAGE include cancelling ghosts which arise due to amplitude or phase variation during the approach to steady state. Parallel imaging requires estimates of the complex coil sensitivities. In vivo estimates may be derived by temporally varying the phase encode ordering to obtain a full k-space dataset in a scheme similar to the autocalibrating TSENSE method. This scheme is a generalization of the UNFOLD method used for removing aliasing in undersampled acquisitions. The more general scheme may be used to modulate each EPI ghost image to a separate temporal frequency as described in this paper. PMID:16705636

Compensation of non-ideal beam splitter polarization distortion effect in Michelson interferometer

NASA Astrophysics Data System (ADS)

Liu, Yeng-Cheng; Lo, Yu-Lung; Liao, Chia-Chi

2016-02-01

A composite optical structure consisting of two quarter-wave plates and a single half-wave plate is proposed for compensating for the polarization distortion induced by a non-ideal beam splitter in a Michelson interferometer. In the proposed approach, the optimal orientations of the optical components within the polarization compensator are determined using a genetic algorithm (GA) such that the beam splitter can be treated as a free-space medium and modeled using a unit Mueller matrix accordingly. Two implementations of the proposed polarization controller are presented. In the first case, the compensator is placed in the output arm of Michelson interferometer such that the state of polarization of the interfered output light is equal to that of the input light. However, in this configuration, the polarization effects induced by the beam splitter in the two arms of the interferometer structure cannot be separately addressed. Consequently, in the second case, compensator structures are placed in the Michelson interferometer for compensation on both the scanning and reference beams. The practical feasibility of the proposed approach is introduced by considering a Mueller polarization-sensitive (PS) optical coherence tomography (OCT) structure with three polarization controllers in the input, reference and sample arms, respectively. In general, the results presented in this study show that the proposed polarization controller provides an effective and experimentally-straightforward means of compensating for the polarization distortion effects induced by the non-ideal beam splitters in Michelson interferometers and Mueller PS-OCT structures.

Projective rectification of infrared images from air-cooled condenser temperature measurement by using projection profile features and cross-ratio invariability.

PubMed

Xu, Lijun; Chen, Lulu; Li, Xiaolu; He, Tao

2014-10-01

In this paper, we propose a projective rectification method for infrared images obtained from the measurement of temperature distribution on an air-cooled condenser (ACC) surface by using projection profile features and cross-ratio invariability. In the research, the infrared (IR) images acquired by the four IR cameras utilized are distorted to different degrees. To rectify the distorted IR images, the sizes of the acquired images are first enlarged by means of bicubic interpolation. Then, uniformly distributed control points are extracted in the enlarged images by constructing quadrangles with detected vertical lines and detected or constructed horizontal lines. The corresponding control points in the anticipated undistorted IR images are extracted by using projection profile features and cross-ratio invariability. Finally, a third-order polynomial rectification model is established and the coefficients of the model are computed with the mapping relationship between the control points in the distorted and anticipated undistorted images. Experimental results obtained from an industrial ACC unit show that the proposed method performs much better than any previous method we have adopted. Furthermore, all rectified images are stitched together to obtain a complete image of the whole ACC surface with a much higher spatial resolution than that obtained by using a single camera, which is not only useful but also necessary for more accurate and comprehensive analysis of ACC performance and more reliable optimization of ACC operations.

Joint Chroma Subsampling and Distortion-Minimization-Based Luma Modification for RGB Color Images With Application.

PubMed

Chung, Kuo-Liang; Hsu, Tsu-Chun; Huang, Chi-Chao

2017-10-01

In this paper, we propose a novel and effective hybrid method, which joins the conventional chroma subsampling and the distortion-minimization-based luma modification together, to improve the quality of the reconstructed RGB full-color image. Assume the input RGB full-color image has been transformed to a YUV image, prior to compression. For each 2×2 UV block, one 4:2:0 subsampling is applied to determine the one subsampled U and V components, U s and V s . Based on U s , V s , and the corresponding 2×2 original RGB block, a main theorem is provided to determine the ideally modified 2×2 luma block in constant time such that the color peak signal-to-noise ratio (CPSNR) quality distortion between the original 2×2 RGB block and the reconstructed 2×2 RGB block can be minimized in a globally optimal sense. Furthermore, the proposed hybrid method and the delivered theorem are adjusted to tackle the digital time delay integration images and the Bayer mosaic images whose Bayer CFA structure has been widely used in modern commercial digital cameras. Based on the IMAX, Kodak, and screen content test image sets, the experimental results demonstrate that in high efficiency video coding, the proposed hybrid method has substantial quality improvement, in terms of the CPSNR quality, visual effect, CPSNR-bitrate trade-off, and Bjøntegaard delta PSNR performance, of the reconstructed RGB images when compared with existing chroma subsampling schemes.

Numerical Analysis of the Performance of Millimeter-Wave RoF-Based Cellular Backhaul Links

NASA Astrophysics Data System (ADS)

Pham, Thu A.; Pham, Hien T. T.; Le, Hai-Chau; Dang, Ngoc T.

2017-08-01

In this paper, we study the performance of a next-generation cellular backhaul network that is based on a hybrid architecture using radio-over-fiber (RoF) and millimeter-wave (MMW) techniques. We develop a mathematic model and comprehensively analyze the performance of a MMW/RoF-based backhaul downlink under the impacts of various physical layer impairments originated from both optical fiber and wireless links. More specifically, the effects of nonlinear distortion, chromatic dispersion, fading, and many types of noises including shot noise, thermal noise, amplifier noise, and relative intensity noise are investigated. The numerical results show that the nonlinear distortion, fiber dispersion, and wireless fading are key factors that limit the system performance. Setting the modulation index properly helps minimize the effect of nonlinear distortion while implementing dispersion shifted optical fibers could be used to reduce the impact of dispersion and as a result, they can improve the bit-error rate. Moreover, it is also verified that, to mitigate the effect of multipath fading, remote radio heads should be located as near the remote antenna units as possible.

Optimization of Selective Laser Melting by Evaluation Method of Multiple Quality Characteristics

NASA Astrophysics Data System (ADS)

Khaimovich, A. I.; Stepanenko, I. S.; Smelov, V. G.

2018-01-01

Article describes the adoption of the Taguchi method in selective laser melting process of sector of combustion chamber by numerical and natural experiments for achieving minimum temperature deformation. The aim was to produce a quality part with minimum amount of numeric experiments. For the study, the following optimization parameters (independent factors) were chosen: the laser beam power and velocity; two factors for compensating the effect of the residual thermal stresses: the scale factor of the preliminary correction of the part geometry and the number of additional reinforcing elements. We used an orthogonal plan of 9 experiments with a factor variation at three levels (L9). As quality criterias, the values of distortions for 9 zones of the combustion chamber and the maximum strength of the material of the chamber were chosen. Since the quality parameters are multidirectional, a grey relational analysis was used to solve the optimization problem for multiple quality parameters. As a result, according to the parameters obtained, the combustion chamber segments of the gas turbine engine were manufactured.

Optimal methodologies for terahertz time-domain spectroscopic analysis of traditional pigments in powder form

NASA Astrophysics Data System (ADS)

Ha, Taewoo; Lee, Howon; Sim, Kyung Ik; Kim, Jonghyeon; Jo, Young Chan; Kim, Jae Hoon; Baek, Na Yeon; Kang, Dai-ill; Lee, Han Hyoung

2017-05-01

We have established optimal methods for terahertz time-domain spectroscopic analysis of highly absorbing pigments in powder form based on our investigation of representative traditional Chinese pigments, such as azurite [blue-based color pigment], Chinese vermilion [red-based color pigment], and arsenic yellow [yellow-based color pigment]. To accurately extract the optical constants in the terahertz region of 0.1 - 3 THz, we carried out transmission measurements in such a way that intense absorption peaks did not completely suppress the transmission level. This required preparation of pellet samples with optimized thicknesses and material densities. In some cases, mixing the pigments with polyethylene powder was required to minimize absorption due to certain peak features. The resulting distortion-free terahertz spectra of the investigated set of pigment species exhibited well-defined unique spectral fingerprints. Our study will be useful to future efforts to establish non-destructive analysis methods of traditional pigments, to construct their spectral databases, and to apply these tools to restoration of cultural heritage materials.

Sensor fusion display evaluation using information integration models in enhanced/synthetic vision applications

NASA Technical Reports Server (NTRS)

Foyle, David C.

1993-01-01

Based on existing integration models in the psychological literature, an evaluation framework is developed to assess sensor fusion displays as might be implemented in an enhanced/synthetic vision system. The proposed evaluation framework for evaluating the operator's ability to use such systems is a normative approach: The pilot's performance with the sensor fusion image is compared to models' predictions based on the pilot's performance when viewing the original component sensor images prior to fusion. This allows for the determination as to when a sensor fusion system leads to: poorer performance than one of the original sensor displays, clearly an undesirable system in which the fused sensor system causes some distortion or interference; better performance than with either single sensor system alone, but at a sub-optimal level compared to model predictions; optimal performance compared to model predictions; or, super-optimal performance, which may occur if the operator were able to use some highly diagnostic 'emergent features' in the sensor fusion display, which were unavailable in the original sensor displays.

Optimal Micro-Scale Secondary Flow Control for the Management of High Cycle Fatigue and Distortion in Compact Inlet Diffusers

NASA Technical Reports Server (NTRS)

Anderson, Bernhard H.; Keller, Dennis J.

2002-01-01

The purpose of this study on micro-scale secondary flow control (MSFC) is to study the aerodynamic behavior of micro-vane effectors through their factor (i.e., the design variable) interactions and to demonstrate how these statistical interactions, when brought together in an optimal manner, determine design robustness. The term micro-scale indicates the vane effectors are small in comparison to the local boundary layer height. Robustness in this situation means that it is possible to design fixed MSFC robust installation (i.e.. open loop) which operates well over the range of mission variables and is only marginally different from adaptive (i.e., closed loop) installation design, which would require a control system. The inherent robustness of MSFC micro-vane effector installation designs comes about because of their natural aerodynamic characteristics and the manner in which these characteristics are brought together in an optimal manner through a structured Response Surface Methodology design process.

Individual spectral densities and molecular motion in polycrystalline hexamethylbenzene-d18

NASA Astrophysics Data System (ADS)

Hoatson, Gina L.; Vold, Robert L.; Tse, Tak Y.

1994-04-01

Methods are described for obtaining the orientation dependence of individual motional spectral densities, J1(ω0) and J2(2ω0), from deuterium spin relaxation experiments on polycrystalline materials. Spectral density measurements provide detailed information in a motional regime too fast to be studied by the two-dimensional (2D) exchange method. Their potential as a source of detailed kinetic and geometric information is illustrated for hexamethylbenzene-d18 (HMB). The relaxation behavior of HMB cannot be explained exclusively by six-site jumps around the C6v axis. Agreement between the experimentally determined spectral densities and simulations is improved if the methyl rotation is explicitly included. At ambient temperature the experimental data are best fitted with the simultaneous jump rates, k6=3.85×108 s-1 and k3=5.0×1011 s-1. This is significantly different from the rate determined using a simple six-site jump model, k6=3.9×109 s-1. Geometric distortions of the methyl rotation axes can account for the observed motionally averaged electric field gradient tensor. When these distortions are included in analysis of the spectral density data, there is a small, but significant, improvement in the fit. k3 is unchanged and the best fit k6 is reduced to 2.2×108 s-1, with distortions out of plane by δ=2.5° and in plane ɛ=ɛ'=1.202.

Optimizing the Attitude Control of Small Satellite Constellations for Rapid Response Imaging

NASA Astrophysics Data System (ADS)

Nag, S.; Li, A.

2016-12-01

Distributed Space Missions (DSMs) such as formation flight and constellations, are being recognized as important solutions to increase measurement samples over space and time. Given the increasingly accurate attitude control systems emerging in the commercial market, small spacecraft now have the ability to slew and point within few minutes of notice. In spite of hardware development in CubeSats at the payload (e.g. NASA InVEST) and subsystems (e.g. Blue Canyon Technologies), software development for tradespace analysis in constellation design (e.g. Goddard's TAT-C), planning and scheduling development in single spacecraft (e.g. GEO-CAPE) and aerial flight path optimizations for UAVs (e.g. NASA Sensor Web), there is a gap in open-source, open-access software tools for planning and scheduling distributed satellite operations in terms of pointing and observing targets. This paper will demonstrate results from a tool being developed for scheduling pointing operations of narrow field-of-view (FOV) sensors over mission lifetime to maximize metrics such as global coverage and revisit statistics. Past research has shown the need for at least fourteen satellites to cover the Earth globally everyday using a LandSat-like sensor. Increasing the FOV three times reduces the need to four satellites, however adds image distortion and BRDF complexities to the observed reflectance. If narrow FOV sensors on a small satellite constellation were commanded using robust algorithms to slew their sensor dynamically, they would be able to coordinately cover the global landmass much faster without compensating for spatial resolution or BRDF effects. Our algorithm to optimize constellation satellite pointing is based on a dynamic programming approach under the constraints of orbital mechanics and existing attitude control systems for small satellites. As a case study for our algorithm, we minimize the time required to cover the 17000 Landsat images with maximum signal to noise ratio fall-off and minimum image distortion among the satellites, using Landsat's specifications. Attitude-specific constraints such as power consumption, response time, and stability were factored into the optimality computations. The algorithm can integrate cloud cover predictions, specific ground and air assets and angular constraints.

Route Monopolie and Optimal Nonlinear Pricing

NASA Technical Reports Server (NTRS)

Tournut, Jacques

2003-01-01

To cope with air traffic growth and congested airports, two solutions are apparent on the supply side: 1) use larger aircraft in the hub and spoke system; or 2) develop new routes through secondary airports. An enlarged route system through secondary airports may increase the proportion of route monopolies in the air transport market.The monopoly optimal non linear pricing policy is well known in the case of one dimension (one instrument, one characteristic) but not in the case of several dimensions. This paper explores the robustness of the one dimensional screening model with respect to increasing the number of instruments and the number of characteristics. The objective of this paper is then to link and fill the gap in both literatures. One of the merits of the screening model has been to show that a great varieD" of economic questions (non linear pricing, product line choice, auction design, income taxation, regulation...) could be handled within the same framework.VCe study a case of non linear pricing (2 instruments (2 routes on which the airline pro_ddes customers with services), 2 characteristics (demand of services on these routes) and two values per characteristic (low and high demand of services on these routes)) and we show that none of the conclusions of the one dimensional analysis remain valid. In particular, upward incentive compatibility constraint may be binding at the optimum. As a consequence, they may be distortion at the top of the distribution. In addition to this, we show that the optimal solution often requires a kind of form of bundling, we explain explicitly distortions and show that it is sometimes optimal for the monopolist to only produce one good (instead of two) or to exclude some buyers from the market. Actually, this means that the monopolist cannot fully apply his monopoly power and is better off selling both goods independently.We then define all the possible solutions in the case of a quadratic cost function for a uniform distribution of agent types and explain the implications for airlines in terms of service differentiation.

Ripple distribution for nonlinear fiber-optic channels.

PubMed

Sorokina, Mariia; Sygletos, Stylianos; Turitsyn, Sergei

2017-02-06

We demonstrate data rates above the threshold imposed by nonlinearity on conventional optical signals by applying novel probability distribution, which we call ripple distribution, adapted to the properties of the fiber channel. Our results offer a new direction for signal coding, modulation and practical nonlinear distortions compensation algorithms.

Distortion Representation of Forecast Errors for Model Skill Assessment and Objective Analysis

NASA Technical Reports Server (NTRS)

Hoffman, Ross N.

2001-01-01

We completed the formulation of the smoothness penalty functional this past quarter. We used a simplified procedure for estimating the statistics of the FCA solution spectral coefficients from the results of the unconstrained, low-truncation FCA (stopping criterion) solutions. During the current reporting period we have completed the calculation of GEOS-2 model-equivalent brightness temperatures for the 6.7 micron and 11 micron window channels used in the GOES imagery for all 10 cases from August 1999. These were simulated using the AER-developed Optimal Spectral Sampling (OSS) model.

Figures of merit for microwave photonic phase shifters based on semiconductor optical amplifiers.

PubMed

Sancho, Juan; Lloret, Juan; Gasulla, Ivana; Sales, Salvador; Capmany, José

2012-05-07

We theoretically and experimentally compare the performance of two fully tunable phase shifter structures based on semiconductor optical amplifiers (SOA) by means of several figures of merit common to microwave photonic systems. A single SOA stage followed by a tailored notch filter is compared with a cascaded implementation comprising three SOA-based phase shifter stages. Attention is focused on the assessment of the RF net gain, noise figure and nonlinear distortion. Recommendations on the performance optimization of this sort of approaches are detailed.

A Model Describing Stable Coherent Synchrotron Radiation in Storage Rings

NASA Astrophysics Data System (ADS)

Sannibale, F.; Byrd, J. M.; Loftsdóttir, Á.; Venturini, M.; Abo-Bakr, M.; Feikes, J.; Holldack, K.; Kuske, P.; Wüstefeld, G.; Hübers, H.-W.; Warnock, R.

2004-08-01

We present a model describing high power stable broadband coherent synchrotron radiation (CSR) in the terahertz frequency region in an electron storage ring. The model includes distortion of bunch shape from the synchrotron radiation (SR), which enhances higher frequency coherent emission, and limits to stable emission due to an instability excited by the SR wakefield. It gives a quantitative explanation of several features of the recent observations of CSR at the BESSYII storage ring. We also use this model to optimize the performance of a source for stable CSR emission.

Numerical Simulation of Cast Distortion in Gas Turbine Engine Components

NASA Astrophysics Data System (ADS)

Inozemtsev, A. A.; Dubrovskaya, A. S.; Dongauser, K. A.; Trufanov, N. A.

2015-06-01

In this paper the process of multiple airfoilvanes manufacturing through investment casting is considered. The mathematical model of the full contact problem is built to determine stress strain state in a cast during the process of solidification. Studies are carried out in viscoelastoplastic statement. Numerical simulation of the explored process is implemented with ProCASTsoftware package. The results of simulation are compared with the real production process. By means of computer analysis the optimization of technical process parameters is done in order to eliminate the defect of cast walls thickness variation.