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1

Autonomous atmospheric compensation (AAC) of high resolution hyperspectral thermal infrared remote-sensing imagery  

Microsoft Academic Search

Atmospheric emission and absorption significantly modify the thermal infrared (TIR) radiation spectra from Earth's land surface. A new algorithm, autonomous atmospheric compensation (AAC), was developed to estimate and compensate for the atmospheric effects. The algorithm estimates from hyperspectral TIR measurements two atmospheric index parameters, the transmittance ratio, and the path radiance difference between strong and weak absorption channels near the

Degui Gu; Alan R. Gillespie; Anne B. Kahle; Frank D. Palluconi

2000-01-01

2

Atmospheric Compensation for Uplink Arrays via Radiometry  

NASA Technical Reports Server (NTRS)

Uplink arrays for communications applications are gaining increased visibility within the NASA and military community due to the enhanced flexibility and reliability they provide. When compared with the conventional large, single aperture antennas currently comprising the Deep Space Network (DSN), for example, smaller aperture antenna arrays have the benefits of providing fault tolerance (reduced single-point failure), reduced maintenance cost, and enhanced capabilities such as electronic beam-steering and multi-beam operation. However, signal combining of antenna array elements spaced many wavelengths apart becomes problematic due to the inherent instability of earth's turbulent atmosphere, particularly at the frequencies of interest to the DSN (i.e., Ka-band). Degradation in the power combining of the individual elements comprising the array arises due to uncorrelated phase errors introduced as the signals propagate through the troposphere. It is well known that the fundamental source of this error is due to the inhomogeneous distribution of water vapor in the atmosphere [1]. Several techniques have been proposed to circumvent this issue, including the use of phase calibration towers and a moon bounce to generate a feedback loop which would provide a means of intermittent calibration of the system phase errors (thermal drifts, atmosphere) [2,3]. However, these techniques require repositioning of the antenna elements to perform this operation which ultimately results in reduced system availability. And, though they are sufficient for compensating for slow varying phase drifts, they are insufficient to compensate for faster varying phase errors, such as those introduced by the atmosphere. In this paper, preliminary radiometry and interferometry measurements collected by the NASA Glenn Research Center are analyzed and indicate that the use of optimized water vapor radiometers as a feedback system in a communications platform could provide the necessary atmospheric compensation technique to enhance the beamforming of uplink arrays.

Nessel, James A.; Acosta, Roberto J.

2010-01-01

3

Region-based backlight compensation algorithm for images and videos  

Microsoft Academic Search

An algorithm for compensating the effects of backlight in images and videos is proposed in this work. We first determine the region of interest (ROI) to compensate mainly using a saliency map, which is based on darkness, skin color, color and texture prominency features. We then compute the compensating offset value for each pixel. Initial offset values are derived to

Dae-Young Hyun; Jun-Hee Heu; Chang-Su Kim; Sang-Uk Lee

2010-01-01

4

Generic algorithms for motion compensation and transformation  

NASA Astrophysics Data System (ADS)

In this paper, we propose algorithms that map the low-level motion compensation and transformation functions of MPEG-1/2, H.263/MPEG-4 ASP and H.264/MPEG-4 AVC video codecs onto common workflows. This way, a single discrete implementation of luma prediction, chroma prediction and residual transform stages is sufficient for all covered video coding standards. The proposed luma prediction is based on 4×4 blocks to cover the H.264 specifications as well as the elder standards. The design consists of a singular four stage pipeline for two block interpolation and two block averaging stages. Targeted for hardware implementation, a strictly linear execution is provided, avoiding branch operations. The algorithmic behavior is entirely dictated by the contents of the parameter ROM. Since chrominance prediction must cover blocks as small as 2×2 pixels, a distinct operation is proposed for chroma. The bilinear operation scheme in H.264 is able to carry out the operations for the elder standards with minor changes only. In H.264, the classic 8×8 DCT transformation was replaced by a simplified 4×4 integer transform, based on a heavily quantized DCT scheme. By modifications of a well-known multiplier-adder-based scheme, a generalized transformation stage can be derived.

Richter, Henryk; Stabernack, Benno; Müller, Erika

2008-03-01

5

A Novel Motion Compensation Algorithm for Acoustic Radiation Force Elastography  

PubMed Central

A novel method of physiological motion compensation for use with radiation force elasticity imaging has been developed. The method utilizes a priori information from finite element method models of the response of soft tissue to impulsive radiation force to isolate physiological motion artifacts from radiation force-induced displacement fields. The new algorithm is evaluated in a series of clinically realistic imaging scenarios, and its performance is compared to that achieved with previously described motion compensation algorithms. Though not without limitations, the new model-based motion compensation algorithm performs favorably in many circumstances and may be a logical choice for use with in vivo abdominal imaging.

Hsu, Stephen J.; Trahey, Gregg E.

2009-01-01

6

An efficient compensation algorithm for current transformer saturation effects  

Microsoft Academic Search

Current transformer (CT) saturation leads to inaccurate current measurement and, therefore, may cause malfunction of protective relays and control devices that use currents as input signals. This paper introduces an efficient compensation algorithm capable of converting from a sampled current waveform that is distorted by CT saturation to a compensated current waveform. Attractive features include quick response time, no cumulative

Jiuping Pan; Khoi Vu; Yi Hu

2004-01-01

7

Reliable phase unwrapping algorithm based on rotational and direct compensators.  

PubMed

Phase unwrapping still plays an important role in many data-processing chains based on phase information. Here, we introduce a new phase unwrapping approach for noisy wrapped phase maps of continuous objects to improve the accuracy and computational time requirements of phase unwrapping using a rotational compensator (RC) method. The proposed algorithm is based on compensating the singularity of discontinuity sources. It uses direct compensation for adjoining singular point (SP) pairs and uses RC for other SP pairs. The performance of the proposed method is tested through both simulated and real wrapped phase data. The proposed algorithm is faster than the original algorithm with the RC and has proved efficiency compared to other phase unwrapping methods. PMID:22108880

Heshmat, Samia; Tomioka, Satoshi; Nishiyama, Shusuke

2011-11-20

8

Broadband beamforming compensation algorithm in CI front-end acquisition  

PubMed Central

Background To increase the signal to noise ratio (SNR) and to suppress directional noise in front-end signal acquisition, microphone array technologies are being applied in the cochlear implant (CI). Due to size constraints, the dual microphone-based system is most suitable for actual application. However, direct application of the array technology will result in the low frequency roll-off problem, which can noticeably distort the desired signal. Methods In this paper, we theoretically analyze the roll-off characteristic on the basis of CI parameters and present a new low-complexity compensation algorithm. We obtain the linearized frequency response of the two-microphone array from modeling and analysis for further algorithm realization. Realization and results Linear method was used to approximate the theoretical response with adjustable delay and weight parameters. A CI dual-channel hardware platform is constructed for experimental research. Experimental results show that our algorithm performs well in compensation and realization. Discussions We discuss the effect from environment noise. Actual daily noise with more low-frequency energy will weaken the algorithm performance. A balance between low-frequency distortion and corresponding low-frequency noise need to be considered. Conclusions Our novel compensation algorithm uses linear function to obtain the desired system response, which is a low computational-complexity method for CI real-time processing. Algorithm performance is tested in CI CIS modulation and the influence of experimental distance and environmental noise were further analyzed to evaluate algorithm constraint.

2013-01-01

9

A novel motion compensation algorithm for acoustic radiation force elastography  

Microsoft Academic Search

A novel method of physiological motion compensation for use with radiation force elasticity imaging has been developed. The method utilizes a priori information from finite element method models of the response of soft tissue to impulsive radiation force to isolate physiological motion artifacts from radiation force-induced displacement fields. The new algorithm is evaluated in a series of clinically realistic imaging

Brian J. Fahey; Stephen J. Hsu; Gregg E. Trahey

2008-01-01

10

First use of cognitive algorithms in investigations under compensated gravity.  

PubMed

In the present paper the use of cognitive algorithms for solving a wide spectrum of problems which often arise in investigations under compensated gravity is suggested. Applying such algorithms in the preparation and performance of experiments provides a substantial assistance to the experimentator as the behaviour of complex processes can be described and predicted correctly even when unexpected perturbations occur. Furthermore, an essential advantage of cognitive computing consists in the fact that the description and optimisation of the processes considered are possible also in such cases in which the corresponding basic equations are not known or not treatable practically. For convenience, the basic ideas of cognitive algorithms are discussed here. Due to their special relevance for investigations under compensated gravity algorithms based on fuzzy logic (FL) and artificial neuronal networks (ANN) are elucidated more in detail. In order to illustrate some advantages of cognitive computing exemplary results for the flow field induced by coaxial rotating disks are given. This represents the first attempt to use the benefits provided by cognitive algorithms in investigations under compensated gravity. The flow field between rotating disks plays an important role not only in experiments under compensated gravity but also in a wide range of terrestrial applications. A comparison of the results found by solving the Navier-Stokes equations and those from the prediction performed by ANN adequately trained shows an excellent agreement. However, the calculation times needed by the ANN are significantly smaller than that of the direct numerical simulation. Therefore, the real time prediction of the results from a running experiment seems to be possible. PMID:11540237

Delgado, A; Nirschl, H; Becker, T h

1996-01-01

11

Enhanced rate response algorithm for orthostatic compensation pacing.  

PubMed

Upon orthostatic stress after a period of rest, the heart rate increases rapidly to maintain cardiac output and minimize the fall in arterial pressure. Pacemaker patients are often prone to a deficient response to orthostatic stress. This may cause lightheadedness and, in rare patients with autonomic dysfunction, syncope. To alleviate these undesirable consequences, an enhanced rate response algorithm was developed using an accelerometer. The pacemaker generates two signals from its accelerometer: instantaneous activity level (Act) and long-term change in activity level (ActVar). Low values of both Act and ActVar indicate a resting state. An increase in Act while ActVar remains low indicates the onset of motion after prolonged rest. Upon detecting this transition, the algorithm increases the pacing rate to a programmable orthostatic compensation rate for a programmable duration. A taped-on pacemaker with this algorithm was evaluated in three healthy women and two healthy men, 36 +/- 8 years of age. Electrocardiogram and ventricular pacing pulses were recorded by a 24-hour ambulatory system. Each trigger of the orthostatic compensation rate was verified against a > 10 beats/min increase in heart rate, a response classified as appropriate. The overall specificity of the algorithm among the five subjects was 78%. The nocturnal specificity (10 PM to 7 AM) was 98%, considerably higher than during daytime (72%). In conclusion, a pacing algorithm to alleviate orthostatic stress was developed, which was highly specific during the night hours. PMID:11139930

Mai, J; Park, E; Bornzin, G A; Hauck, G; Levine, P A

2000-11-01

12

New inverse synthetic aperture radar algorithm for translational motion compensation  

NASA Astrophysics Data System (ADS)

Inverse synthetic aperture radar (ISAR) is an imaging technique that shows real promise in classifying airborne targets in real time under all weather conditions. Over the past few years a large body of ISAR data has been collected and considerable effort has been expended to develop algorithms to form high-resolution images from this data. One important goal of workers in this field is to develop software that will do the best job of imaging under the widest range of conditions. The success of classifying targets using ISAR is predicated upon forming highly focused radar images of these targets. Efforts to develop highly focused imaging computer software have been challenging, mainly because the imaging depends on and is affected by the motion of the target, which in general is not precisely known. Specifically, the target generally has both rotational motion about some axis and translational motion as a whole with respect to the radar. The slant-range translational motion kinematic quantities must be first accurately estimated from the data and compensated before the image can be focused. Following slant-range motion compensation, the image is further focused by determining and correcting for target rotation. The use of the burst derivative measure is proposed as a means to improve the computational efficiency of currently used ISAR algorithms. The use of this measure in motion compensation ISAR algorithms for estimating the slant-range translational motion kinematic quantities of an uncooperative target is described. Preliminary tests have been performed on simulated as well as actual ISAR data using both a Sun 4 workstation and a parallel processing transputer array. Results indicate that the burst derivative measure gives significant improvement in processing speed over the traditional entropy measure now employed.

Bocker, Richard P.; Henderson, Thomas B.; Jones, Scott A.; Frieden, B. R.

1991-10-01

13

Atmospheric Compensation over Case II Waters: Simultaneous Aerosol and Water Constituent Retrieval  

NASA Astrophysics Data System (ADS)

In many algorithms designed to retrieve water constituent concentrations, an assumption of negligible water-leaving radiance is made in the near infrared (NIR) wavelengths (750-950 [nm]). This allows fairly accurate atmospheric correction to be applied to the oceanic imagery. Given this assumption, it is possible to derive model estimates of aerosol type and density and compensate for its effects in other regions of the spectrum. Unfortunately this assumption is only valid in areas of very low total suspended sediment (TSS) concentrations, such as open ocean waters. Increased TSS load causes significant back-scattering within the water, increasing the water leaving signal in the NIR region, which confounds the compensation algorithms and incorrectly attributes all the effects entirely to aerosols. A possible solution to this problem is to model suspended sediment inherent optical properties (IOPs) in the NIR using the Ocean Optical Phytoplankton Simulator (OOPS) and couple this data using atmospheric and hydrologic radiative transfer models (MODTRAN and HYDROLIGHT, respectively). These models can be combined for a given sensor geometry to predict sensor reaching radiance and match the resulting spectra with actual image spectra. This is done including the NIR which should allow us to better characterize the sediment load. Look-up tables (LUTs) of radiances from modeled atmospheres and reflectances from modeled water allow us to make this an iterative process which can be optimized to give us the best match for the pixel in question. The products of this algorithm are the water constituent concentrations and the atmospheric parameters. This process has been implemented for AVIRIS hyperspectral imagery captured over the Rochester, NY embayment with reasonable success in atmospheric and constituent retrieval.

Taylor, Donald Zoeger

14

Track covariance compensation for data misassociations: alternative data association algorithms  

NASA Astrophysics Data System (ADS)

The primary components of a target track are the estimated state vector and its error variance-covariance matrix (or simply the covariance). The estimated state indicates the location and motion of the target. The track covariance is intended to indicate the uncertainty or inaccuracy of the target state estimate. The covariance is computed by the track processor and may or may not realistically indicate the inaccuracy of the state estimate. Covariance Consistency is the property that a computed variance-covariance matrix realistically represents the covariance of the actual errors of the estimate. The computed covariance of the state estimation error is used in the computations of the data association processing function and the estimation filter; consequently, degraded track consistency might cause misassociations (correlation errors) and degraded filter processing that can degrade track performance. The computed covariance of the state estimation error is also used by downstream functions, such as the network-level resource management functions, to indicate the accuracy of the target state estimate. Hence, degraded track consistency can mislead those functions and the war fighter about accuracy of each target track. In the development of target trackers, far more attention has been given to improving the accuracy of the estimated target state than in improving the track covariance consistency. This paper addresses covariance compensation to reduce the degradation of consistence due to potential misassociations in measurement fusion using single-frame data association. This compensation approach used is also applicable to other fusion approaches and to tracking with data from a single sensor. This paper also shows how this compensation approach can be applied to a variety of data association algorithms.

Drummond, Oliver E.

2008-05-01

15

In-Scene Atmospheric Characterization and Compensation in Hyperspectral Thermal Infrared Images  

NASA Technical Reports Server (NTRS)

Compensation of thermal infrared radiometric measurements for atmospheric absorption and emission is one of the main factors limiting the accurate estimation of land surface temperatures and emissivities today.

Gillespie, A.; Alley, R.; Kahle, A.; Cothern, S.

1998-01-01

16

Sensor saturation compensated smoothing algorithm for inertial sensor based motion tracking.  

PubMed

In this paper, a smoothing algorithm for compensating inertial sensor saturation is proposed. The sensor saturation happens when a sensor measures a value that is larger than its dynamic range. This can lead to a considerable accumulated error. To compensate the lost information in saturated sensor data, we propose a smoothing algorithm in which the saturation compensation is formulated as an optimization problem. Based on a standard smoothing algorithm with zero velocity intervals, two saturation estimation methods were proposed. Simulation and experiments prove that the proposed methods are effective in compensating the sensor saturation. PMID:24806740

Dang, Quoc Khanh; Suh, Young Soo

2014-01-01

17

Sensor Saturation Compensated Smoothing Algorithm for Inertial Sensor Based Motion Tracking  

PubMed Central

In this paper, a smoothing algorithm for compensating inertial sensor saturation is proposed. The sensor saturation happens when a sensor measures a value that is larger than its dynamic range. This can lead to a considerable accumulated error. To compensate the lost information in saturated sensor data, we propose a smoothing algorithm in which the saturation compensation is formulated as an optimization problem. Based on a standard smoothing algorithm with zero velocity intervals, two saturation estimation methods were proposed. Simulation and experiments prove that the proposed methods are effective in compensating the sensor saturation.

Dang, Quoc Khanh; Suh, Young Soo

2014-01-01

18

Control algorithms for aerobraking in the Martian atmosphere  

NASA Astrophysics Data System (ADS)

The Analytic Predictor Corrector (APC) and Energy Controller (EC) atmospheric guidance concepts have been adapted to control an interplanetary vehicle aerobraking in the Martian atmosphere. Changes are made to the APC to improve its robustness to density variations. These modifications include adaptation of a new exit phase algorithm, an adaptive transition velocity to initiate the exit phase, refinement of the reference dynamic pressure calculation and two improved density estimation techniques. The modified controller with the hybrid density estimation technique is called the Mars Hybrid Predictor Corrector (MHPC), while the modified controller with a polynomial density estimator is called the Mars Predictor Corrector (MPC). A Lyapunov Steepest Descent Controller (LSDC) is adapted to control the vehicle. The LSDC lacked robustness, so a Lyapunov tracking exit phase algorithm is developed to guide the vehicle along a reference trajectory. The equilibrium glide entry phase is used for the first part of the trajectory. This algorithm, when using the hybrid density estimation technique to define the reference path, is called the Lyapunov Hybrid Tracking Controller (LHTC). With the polynomial density estimator used to define the reference trajectory, the algorithm is called the Lyapunov Tracking Controller (LTC). These four new controllers are tested using a six degree of freedom computer simulation to evaluate their robustness. MARS-GRAM is used to develop realistic atmospheres for the study. The atmospheres are then perturbed using square wave density pulses. The MHPC, MPC, LHTC and LRC show dramatic improvements in robustness over the APC and EC. The MHPC, MPC, LHTC and LTC all complete the initial phase of testing (using square wave density pulses) with no failures. The second phase tests the MHPC, MPC, LHTC and LTC against atmospheres where the inbound and outbound density functions are different. Square wave density pulses are again used, but only for the outbound leg of the trajectory. All four controllers are able to compensate for the outbound leg density pulses with no hard failures, but the algorithms are sensitive to large amplitude density pulses.

Shipley, Buford Wiley, Jr.

1991-02-01

19

Characterization and Compensation of the Atmosphere for the Inversion of AVIRIS Calibrated Radiance to Apparent Surface Reflectance  

NASA Technical Reports Server (NTRS)

Calibrated radiance spectra measured remotely record the integrated effects of the solar source, the atmosphere, and the surface. To pursue scientific research and applications, based on the molecular absorptions and constituent scattering properties of the surface, the solar source and atmosphere must be characterized and compensated in the spectra. This paper describes a set of radiative transfer spectral fitting algorithms that characterize the absorbing and scattering constituents of the atmosphere from calibrated AVIRIS spectra. These atmospheric characteristics were used in conjunction with the illumination and observation geometries to invert the AVIRIS calibrated radiance spectra to apparent surface reflectance. A validation of the algorithm was performed with in-situ reflectance spectra acquired at the time of the AVIRIS overflight over Pasadena, California, in 1994.

Green Robert O.; Roberts, Dar A.; Conel, James E.

1996-01-01

20

Atmospheric compensation in the presence of clouds: an adaptive empirical line method (AELM) approach  

NASA Astrophysics Data System (ADS)

Many algorithms exist to invert airborne imagery from units of either radiance or sensor specific digital counts to units of reflectance. These compensation algorithms remove unwanted atmospheric variability allowing objects on the ground to be analyzed. Low error levels in homogenous atmospheric conditions have been demonstrated. In many cases however, clouds are present in the atmosphere which introduce error into the inversion at unacceptable levels. For example, the relationship that is defined between sensor reaching radiance and ground reflectance in a cloud free scene will not be the same as in an adjacent region with clouds in the surround. A novel method has been developed which utilizes ground based measurements to modify the empirical line method (ELM) approach on a per-pixel basis. A physics based model of the atmosphere is used to generate a spatial correction for the ELM. Creation of this model is accomplished by analyzing whole-sky imagery to produce a cloud mask which drives input parameters to the radiative transfer (RT) code MODTRAN. The RT code is run for several different azimuth and zenith orientations to create a three-dimensional representation of the hemisphere. The model is then used to achieve a per-pixel correction by adjusting the ELM slope spatially. This method is applied to real data acquired over the atmospheric radiation measurement (ARM) site in Lamount, OK. Performance of the method is evaluated with the Hyperspectral Digital Imagery Collection Experiment (HYDICE) instrument. The sensitivity to spectral sampling is also assessed by down-sampling the HYDICE data to the spectral response of the multi-spectral system Wildfire Airborne Sensor Program LITE (WASP Lite). Finally a method to utilize this approach when additional sensors (like a sky camera) are not available is suggested.

Bartlett, Brent; Schott, John R.

2009-02-01

21

Multi-frame atmospheric compensation under moving camera conditions  

NASA Astrophysics Data System (ADS)

Multi-frame algorithms for the removal of atmospheric turbulence have proven effective under ideal conditions where the scene remains static; however, movement of the camera across a scene often introduces undesirable effects that degrade the quality of processed imagery to the point where it becomes unusable. This paper discusses the development of two solutions to this problem, each with different computational costs and levels of efficacy. We discuss a solution to this problem that uses robust registration methods to align a window of input images to each other and processes them to obtain a single improved frame, repeating the sequence of realignment and processing each time a new frame arrives. While this approach produces high quality results, the associated computational cost precludes real-time implementation, even on accelerated platforms. An alternative solution involves measuring scene movement through lightweight registration and quantification. Registration results are used to make a global determination of "safe" approaches to processing in order to avoid degraded results. This particular method is computationally inexpensive at the cost of efficacy. We discuss the performance of both of these modifications against the original, uncompensated algorithm in terms of computational cost and quality of output imagery. Additionally, we will briefly discuss future goals which aim to minimize additional computation while maximizing processing efficacy.

Paolini, Aaron L.; Bodnar, Michael R.; Ortiz, Fernando; Price, Daniel K.

2011-05-01

22

Research on GPU-Based Real-Time MTF Compensation Algorithm  

Microsoft Academic Search

MTF compensation is widely used in remote sensing applications for recovering high frequency components of images. However, MTF compensation is very time-consuming and therefore becomes a major bottleneck in the whole image pre-processing process. In order to address the above-mentioned problem, this thesis proposes a novel GPU-based real-time MTF compensation algorithm with the aim of dramatically improving the computation efficiency

Liu Yang Fang; Mi Wang; De Ren Li; Bing Xian Zhang

2011-01-01

23

Combinational-deformable-mirror adaptive optics system for atmospheric compensation in free space communication  

NASA Astrophysics Data System (ADS)

As we know that deformable-mirror (DM) is used in the adaptive optics (AO) systems to compensate atmospheric turbulence in free space optical (FSO) communication system. In order to get rid of the limitations generated by the characters of DM itself, the combinational-deformable-mirror (CDM) adaptive optics (CDM-AO) system is established to correct wave-front aberrations and improve coupling efficiency at the receiver. The analysis of the principle of CDM and the decoupling-working principle based on confinement correction algorithm (CCA) is provided, and the comparison of the correcting results between CDM-AO system and conventional AO system are given. Simulation results indicate that CDM-AO system can correct different aberrations with different characteristics and provide better correction performance than single deformable-mirror (DM) AO system. And the coupling efficiency improvement provided by the correction of AO system is numerically evaluated.

Li, Zhaokun; Cao, Jingtai; Zhao, Xiaohui; Liu, Wei

2014-06-01

24

Analytical brightness compensation algorithm for traditional polygon-based method in computer-generated holography.  

PubMed

In three-dimensional (3D) holographic display, current brightness compensation algorithm of the traditional polygon-based method experimentally obtains the compensation factor, which depends on the fabrication process. In this paper, we proposed an analytical brightness compensation method discarding the influence of the fabrication. The surface property function with the flat power spectral density and the compensation factor obtained from the simplified relationship between the original and the rotated frequencies are used to analytically compensate the radiant energy of the tilted polygon. The optical reconstruction results show the proposed method could effectively compensate the brightness and ensure the further shading process. The proposed method separates the brightness compensation from the fabrication process, which is important for deepening the investigation of the hologram fabrication and achieving realistic 3D reconstruction. PMID:23842184

Pan, Yijie; Wang, Yongtian; Liu, Juan; Li, Xin; Jia, Jia; Zhang, Zhao

2013-06-20

25

An Improved Dynamic Compensation Algorithm for Rhodium Self-Powered Neutron Detectors  

Microsoft Academic Search

Rhodium self-powered neutron detectors are utilized in many pressurized water reactors to determine the neutronic behavior within the core. In order to compensate for the inherent time delay associated with the response of these detectors, a dynamic compensation algorithm is currently used in Combustion Engineering plants to reconstruct the dynamic flux signal which is being sensed by the rhodium detectors.

M. L. Kantrowitz

1987-01-01

26

Springback compensation algorithm for tool design in creep age forming of large aluminum alloy plate  

NASA Astrophysics Data System (ADS)

The creep unified constitutive equations, which was built based on the age forming mechanism of aluminum alloy, was integrated with the commercial finite element analysis software MSC.MARC via the user defined subroutine, CREEP, and the creep age forming process simulations for7055 aluminum alloy plate parts were conducted. Then the springback of the workpiece after forming was calculated by ATOS Professional Software. Based on the combination between simulation results and calculation of springback by ATOS for the formed plate, a new weighted springback compensation algorithm for tool surface modification was developed. The compensate effects between the new algorithm and other overall compensation algorithms on the tool surface are compared. The results show that, the maximal forming error of the workpiece was reduced to below 0.2mm after 5 times compensations with the new weighted algorithm, while error rebound phenomenon occurred and the maximal forming error cannot be reduced to 0.3mm even after 6 times compensations with fixed or variable compensation coefficient, which are based on the overall compensation algorithm.

Xu, Xiaolong; Zhan, Lihua; Huang, Minghui

2013-12-01

27

Water Vapor Retrieval Using the FLAASH Atmospheric Correction Algorithm.  

National Technical Information Service (NTIS)

FLAASH (Fast Line-of-Sight Atmospheric Analysis of Spectral Hypercubes) is a first-principles atmospheric correction algorithm for visible to shortwave infrared (SWIR) hyperspectral data. The algorithm consists of two main steps. The first is retrieval of...

G. W. Felde G. P. Anderson J. A. Gardner S. M. Alder- Golden M. W. Matthew

2004-01-01

28

An impact force compensation algorithm based on a piezo force sensor for wire bonding processes  

Microsoft Academic Search

Impact force control is a key factor in wire bonding processes affecting the overall quality of the product and productivity of the process. This paper presents an impact force compensation algorithm designed for gold wire bonding processes, which uses a piezo force sensor and contains a new algorithm design to reduce the impact force of the capillary when it contacts

Jung-Han Kim; Chung-Hyuk Yim

2008-01-01

29

A scheduling algorithm using Compensating Round Robin in packet-swtiching broadband networks  

Microsoft Academic Search

A new approximation of fair queuing called Compensating Round Robin (CRR) is presented in this paper. The algorithm uses packet-by-packet\\u000a scheduler with a compensating measure. It achieves good fairness in terms of throughput, requires only O(1) time complexity to process a packet, and is simple enough to be implemented in hardware. After the performances are analyzed,\\u000a the fairness and packet

Julong Lan; Binqiang Wang; Ou Li; Jiangxing Wu

2002-01-01

30

A Fast Digital Predistortion Algorithm for Radio-Frequency Power Amplifier Linearization With Loop Delay Compensation  

Microsoft Academic Search

An adaptive, digital, baseband predistortion (PD) algorithm that compensates for the memoryless nonlinearities of radio-frequency (RF) power amplifiers (PAs) for wireless systems using non-constant-envelop modulation schemes is presented. Compared with the conventional, complex-gain predistorters based on lookup tables (LUTs), the proposed direct-learning, multilevel lookup table (ML-LUT) approach assisted by a hardware-efficient loop delay compensation scheme achieves a significant reduction in

Hao Li; Dae Hyun Kwon; Deming Chen; Yun Chiu

2009-01-01

31

Adaptive filter design based on the LMS algorithm for delay elimination in TCR/FC compensators.  

PubMed

Thyristor controlled reactor with fixed capacitor (TCR/FC) compensators have the capability of compensating reactive power and improving power quality phenomena. Delay in the response of such compensators degrades their performance. In this paper, a new method based on adaptive filters (AF) is proposed in order to eliminate delay and increase the response of the TCR compensator. The algorithm designed for the adaptive filters is performed based on the least mean square (LMS) algorithm. In this design, instead of fixed capacitors, band-pass LC filters are used. To evaluate the filter, a TCR/FC compensator was used for nonlinear and time varying loads of electric arc furnaces (EAFs). These loads caused occurrence of power quality phenomena in the supplying system, such as voltage fluctuation and flicker, odd and even harmonics and unbalancing in voltage and current. The above design was implemented in a realistic system model of a steel complex. The simulation results show that applying the proposed control in the TCR/FC compensator efficiently eliminated delay in the response and improved the performance of the compensator in the power system. PMID:21193194

Hooshmand, Rahmat Allah; Torabian Esfahani, Mahdi

2011-04-01

32

Validation and refinement of hyperspectral\\/multispectral atmospheric compensation using shadowband radiometers  

Microsoft Academic Search

First-principles atmospheric compensation of Earth-viewing spectral imagery requires atmospheric property information derived from the image itself or measured independently. A field experiment was conducted in May, 2003 at Davis, CA to investigate the consistency of atmospheric properties and surface reflectances derived from simultaneous ground-, aircraft- and satellite-based spectral measurements. The experiment involved the simultaneous collection of HyMap hyperspectral and Landsat-7

Peter A. Rochford; Prabhat K. Acharya; Steven M. Adler-Golden; Alexander Berk; Lawrence S. Bernstein; Michael W. Matthew; Steven C. Richtsmeier; Stephen Gulick; James Slusser

2005-01-01

33

Phase unwrapping algorithm based on singularity compensation for three-dimensional shape measurement  

NASA Astrophysics Data System (ADS)

Three-dimensional (3D) imaging continues to attract much research interest for its wide applications. In 3D shape measurement, the phase carries information about the object. However, phase mapping is ambiguous as the extracted phase is returned in a form that suffers from 2 ? phase jumps. In this case, the phase data must be unwrapped to be fit for use. Furthermore, sometimes the presence of noise in the measured data, in which many singular points (SPs) are found, makes general phase unwrapping algorithms fail to produce accurate unwrapped results. For this reason, we propose a new phase unwrapping method for dynamic 3D shape measurement. The new algorithm is based on compensating the singularity of discontinuity sources. It uses direct compensators for adjoining SP pairs and uses rotational compensators for other SP pairs. The proposed algorithm has been evaluated and compared with past phase unwrapping methods. Results show that the proposed method gives satisfactory unwrapped results with a low computation time.

Heshmat, Samia; Tomioka, Satoshi; Nishiyama, Shusuke

2012-11-01

34

TIGER: Development of Thermal Gradient Compensation Algorithms and Techniques  

NASA Technical Reports Server (NTRS)

In a wind tunnel facility, the direct measurement of forces and moments induced on the model are performed by a force measurement balance. The measurement balance is a precision-machined device that has strain gages at strategic locations to measure the strain (i.e., deformations) due to applied forces and moments. The strain gages convert the strain (and hence the applied force) to an electrical voltage that is measured by external instruments. To address the problem of thermal gradients on the force measurement balance NASA-LaRC has initiated a research program called TIGER - Thermally-Induced Gradients Effects Research. The ultimate goals of the TIGER program are to: (a) understand the physics of the thermally-induced strain and its subsequent impact on load measurements and (b) develop a robust thermal gradient compensation technique. This paper will discuss the impact of thermal gradients on force measurement balances, specific aspects of the TIGER program (the design of a special-purpose balance, data acquisition and data analysis challenges), and give an overall summary.

Hereford, James; Parker, Peter A.; Rhew, Ray D.

2004-01-01

35

Improved Harmony Search Algorithm for Optimal Placement and Sizing of Static Var Compensators in Power Systems  

Microsoft Academic Search

Static Var compensator (SVC) is normally used in power system to improve voltage profile and reduce system power losses. In this paper, a relatively new optimization technique named as the improved harmony search algorithm (IHS) is applied to determine optimal location and size of SVC devices in a transmission network. A multi-criterion objective function comprising of both operational objectives and

Reza Sirjani; Azah Mohamed

2011-01-01

36

Emissivity compensated spectral pyrometry—algorithm and sensitivity analysis  

NASA Astrophysics Data System (ADS)

In order to solve the problem of non-contact temperature measurements on an object with varying emissivity, a new method is herein described and evaluated. The method uses spectral radiance measurements and converts them to temperature readings. It proves to be resilient towards changes in spectral emissivity and tolerates noisy spectral measurements. It is based on an assumption of smooth changes in emissivity and uses historical values of spectral emissivity and temperature for estimating current spectral emissivity. The algorithm, its constituent steps and accompanying parameters are described and discussed. A thorough sensitivity analysis of the method is carried out through simulations. No rigorous instrument calibration is needed for the presented method and it is therefore industrially tractable.

Hagqvist, Petter; Sikström, Fredrik; Christiansson, Anna-Karin; Lennartson, Bengt

2014-02-01

37

Respiratory motion compensation algorithm of ultrasound hepatic perfusion data acquired in free-breathing  

NASA Astrophysics Data System (ADS)

Images acquired in free breathing using contrast enhanced ultrasound exhibit a periodic motion that needs to be compensated for if a further accurate quantification of the hepatic perfusion analysis is to be executed. In this work, we present an algorithm to compensate the respiratory motion by effectively combining the PCA (Principal Component Analysis) method and block matching method. The respiratory kinetics of the ultrasound hepatic perfusion image sequences was firstly extracted using the PCA method. Then, the optimal phase of the obtained respiratory kinetics was detected after normalizing the motion amplitude and determining the image subsequences of the original image sequences. The image subsequences were registered by the block matching method using cross-correlation as the similarity. Finally, the motion-compensated contrast images can be acquired by using the position mapping and the algorithm was evaluated by comparing the TICs extracted from the original image sequences and compensated image subsequences. Quantitative comparisons demonstrated that the average fitting error estimated of ROIs (region of interest) was reduced from 10.9278 +/- 6.2756 to 5.1644 +/- 3.3431 after compensating.

Wu, Kaizhi; Zhang, Xuming; Chen, Guangxie; Weng, Fei; Ding, Mingyue

2013-10-01

38

Meridional energy transport in the coupled atmosphere-ocean system: Compensation and partitioning  

NASA Astrophysics Data System (ADS)

The variability and compensation of the energy transport in the atmosphere and ocean are discussed with a hierarchy of coupled models. A state-of-the-art Coupled Model (GFDL CM2.1), an Intermediate Complexity Climate Model (GFDL ICCM) and a simple Energy Balance Model (EBM) are used in this study. For decadal time scales, a high degree of compensation is found for the transport in the Northern Hemisphere in the Atlantic sector. The variability of the total, or planetary, heat transport (PHT) is much smaller than the variability in either the atmosphere (AHT) or ocean (OHT) alone, a feature sometimes referred to as `Bjerknes compensation'. In the coupled models used, natural decadal variability stems from the Atlantic meridional overturning circulation (AMOC), and variations in the strength of the AMOC tend to lead the variability in the OHT. Furthermore, the PHT is positively correlated with the OHT, implying that the atmosphere is compensating, but imperfectly, for variations in the ocean transport. In the Southern Hemisphere no significant anticorrelation is found between OHT and AHT, consistent with the absence of decadal scale variability in the ocean. For both coupled models, the strongest anticorrelation between transports is found at the period of AMOC variability and decreases as the time scale decreases. Unlike the AHT and AMOC, the AHT and the transport in the oceanic gyres are positively correlated, suggesting that coupling between the wind-driven ocean circulation and the atmosphere militates against long-term variability involving the wind-driven flow. Moisture and sensible heat transports in the atmosphere are also positively correlated at decadal time scales. In the Northern Hemisphere compensation is weaker at low latitudes than at high. This is consistent with the notion that at low latitudes a larger fraction of the oceanic transport is due to the wind-driven warm cell, and the atmospheric and wind-driven oceanic energy transports vary in unison, preventing compensation. With the help of a two-layer EBM, we finally argue that compensation can best be interpreted as arising from the highly efficient, super-diffusive nature of the energy transport in the atmosphere, which effectively constrains the meridional temperature distribution determining the outgoing infra-red radiation.

Farneti, R.; Vallis, G. K.

2012-04-01

39

Hierarchy compensation of non-homogeneous intermittent atmospheric turbulence  

NASA Astrophysics Data System (ADS)

In this work a study both the internal turbulence energy cascade intermittency evaluated from wind speed series in the atmospheric boundary layer, as well as the role of external or forcing intermittency based on the flatness (Vindel et al 2008)is carried out. The degree of intermittency in the stratified ABL flow (Cuxart et al. 2000) can be studied as the deviation, from the linear form, of the absolute scaling exponents of the structure functions as well as generalizing for non-isotropic and non-homogeneous turbulence, even in non-inertial ranges (in the Kolmogorov-Kraichnan sense) where the scaling exponents are not constant. The degree of intermittency, evaluated in the non-local quasi-inertial range, is explained from the variation with scale of the energy transfer as well as the dissipation. The scale to scale transfer and the structure function scaling exponents are calculated and from these the intermittency parametres. The turbulent diffusivity could also be estimated and compared with Richardson's law. Some two point correlations and time lag calculations are used to investigate the time and spatial integral length scales obtained from both Lagrangian and Eulerian correlations and functions, and we compare these results with both theoretical and laboratory data. We develop a theoretical description of how to measure the different levels of intermittency following (Mahjoub et al. 1998, 2000) and the role of locality in higher order exponents of structure function analysis. Vindel J.M., Yague C. and Redondo J.M. (2008) Structure function analysis and intermittency in the ABL. Nonlin. Processes Geophys., 15, 915-929. Cuxart J, Yague C, Morales G, Terradellas E, Orbe J, Calvo J, Fernández A, Soler M R, Infante C, Buenestado P, Espinalt A, Joergensen H E, Rees J M, Vilá J, Redondo J M, Cantalapiedra R and Conangla L (2000): Stable atmospheric boundary-layer experiment in Spain (Sables 98): a report, Boundary-Layer Meteorology 96, 337-370 Mahjoub O.B., Babiano A. and Redondo J.M. (1998) Structure functions in complex flows. Journal of Flow Turbulence and Combustion. 59, 299-313. Mahjoub O.B., Redondo J.M. and Babiano A. (2000) Self similarity and intermittency in a turbulent non-homogeneous wake. Proceedings of the Eighth European Turbulence Conference. (Eds. Dopazo et al.) CIMNE, Barcelona, 783-786. Mahjoub O.B., Redondo J.M., and R. Alami, (1998) Turbulent Structure Functions in Geophysical Flows, Rapp. Comm. int. Mer Medit., 35, 126-127.

Redondo, Jose M.; Mahjoub, Otman B.; Cantalapiedra, Inma R.

2010-05-01

40

Compound control algorithm based on a novel topology of current compensation apparatus  

Microsoft Academic Search

This paper theoretically analyzes the compound control apparatus for current quality compensation which is designed as differentiation cascaded H bridge type with two modules: fundamental-frequency module and high-frequency module. The detection algorithm calculates the harmonic current and fundamental-frequency current of the load current which serve as the command current. For the purpose of eliminating the steady periodic error of system

Liu Yukun; Xiao Xiangning; Lei Xiao; Wang Xiangxu; Wang Jin

2010-01-01

41

A digital combining-weight estimation algorithm for broadband sources with the array feed compensation system  

NASA Technical Reports Server (NTRS)

An algorithm for estimating the optimum combining weights for the Ka-band (33.7-GHz) array feed compensation system was developed and analyzed. The input signal is assumed to be broadband radiation of thermal origin, generated by a distant radio source. Currently, seven video converters operating in conjunction with the real-time correlator are used to obtain these weight estimates. The algorithm described here requires only simple operations that can be implemented on a PC-based combining system, greatly reducing the amount of hardware. Therefore, system reliability and portability will be improved.

Vilnrotter, V. A.; Rodemich, E. R.

1994-01-01

42

Performance-metric driven atmospheric compensation for robust free-space laser communication  

Microsoft Academic Search

Laser Communication (LaserCom) offers some profound advantages over RF-based systems, such as higher-bandwidth, lower power consumption, and lower probability of intercept. However, the effect of turbulence on laser propagation is a significant challenge to current electro-optical systems. While atmospheric compensation techniques in space object imaging and high-energy laser weapons have been thoroughly investigated, optimizing these techniques for LaserCom has not

Peter N. Crabtree

2006-01-01

43

The Results of a Simulator Study to Determine the Effects on Pilot Performance of Two Different Motion Cueing Algorithms and Vario us Delays, Compensated and Uncompensated  

Microsoft Academic Search

A s tudy was conducted employing the Visual Motion Simulator (VMS) at the NASA Langley Research Center, Hampton, Virginia. This study compared two motion cueing algorithms, the NASA adaptive algorithm and a new optimal control based algorithm. Also, the study included the effects of transport delays and the compensation thereof. The delay compensation algorithm employed is one developed by Richard

Liwen Guo; Frank M. Cardullo; Robert J. Telban; Jacob A. Houck; Unisys Corp

44

Doppler-based motion compensation algorithm for focusing the signature of a rotorcraft.  

PubMed

A computationally efficient algorithm was developed and tested to compensate for the effects of motion on the acoustic signature of a rotorcraft. For target signatures with large spectral peaks that vary slowly in amplitude and have near constant frequency, the time-varying Doppler shift can be tracked and then removed from the data. The algorithm can be used to preprocess data for classification, tracking, and nulling algorithms. The algorithm was tested on rotorcraft data. The average instantaneous frequency of the first harmonic of a rotorcraft was tracked with a fixed-lag smoother. Then, state space estimates of the frequency were used to calculate a time warping that removed the effect of a time-varying Doppler shift from the data. The algorithm was evaluated by analyzing the increase in the amplitude of the harmonics in the spectrum of a rotorcraft. The results depended upon the frequency of the harmonics and the processing interval duration. Under good conditions, the results for the fundamental frequency of the target (~11 Hz) almost achieved an estimated upper bound. The results for higher frequency harmonics had larger increases in the amplitude of the peaks, but significantly lower than the estimated upper bounds. PMID:23363088

Goldman, Geoffrey H

2013-02-01

45

Simulation of atmospheric turbulence compensation through piston-only phase control of a laser phased array  

NASA Astrophysics Data System (ADS)

Beam propagation from a laser phased array system through the turbulent atmosphere is simulated and the ability of such a system to compensate for the atmosphere via piston-only phase control of the sub-apertures is evaluated. Directed energy (DE) applications demand more power than most lasers can produce, consequently many schemes for high power involve combining the beams from many smaller lasers into one. When many smaller lasers are combined into a phased array, phase control of the individual sub-apertures will be necessary to create a high-quality beam. Phase control of these sub-apertures could then be used to do more, such as focus, steer, and compensate for atmospheric turbulence. Atmospheric turbulence is well known to degrade the performance of both imaging systems and laser systems. Adaptive optics can be used to mitigate this degradation. Adaptive optics ordinarily involves a deformable mirror, but with phase control on each sub-aperture the need for a deformable mirror is eliminated. The simulation conducted here evaluates performance gain for a 127 element phased array in a hexagonal pattern with piston-only phase control on each element over an uncompensated array for varying levels of atmospheric turbulence. While most simulations were carried out against a 10 km tactical scenario, the turbulence profile was adjusted so performance could be evaluated as a function of the Fried Parameter (r0) and the log-amplitude variance somewhat independently. This approach is demonstrated to be generally effective with the largest percentage improvement occurring when r0 is close to the sub-aperture diameter.

McCrae, Jack E.; Van Zandt, Noah; Cusumano, Salvatore J.; Fiorino, Steven T.

2013-05-01

46

Algorithmic depth compensation improves transverse resolution and quantification in functional diffuse optical tomography  

NASA Astrophysics Data System (ADS)

One of the major challenges in diffuse optical tomography (DOT) is attributed to the severe decay of sensitivity along depth. In conventional reconstruction method using regularized inversion, it yields significant depth distortion in the reconstructed image as a cortical activation is always projected into the skull. Recently we developed a depth compensation algorithm (DCA) to minimize the depth localization error in DOT, which introduces a depth-variant weight matrix to counterbalance the severe sensitivity decay of A-matrix. The DCA algorithm has been previously validated in both laboratory phantom experiments and an in vivo human study. In this study, we first present a comprehensive analysis on how DCA alters the depth localization and spatial resolution in DOT. It reveals that DCA greatly improves the transverse resolution in sub-cortical region. Second, we present a quantification approach for DCA. By forming a spatial prior directly from the reconstructed image, this approach greatly improves the quantification accuracy in DOT.

Tian, Fenghua; Niu, Haijing; Khadka, Sabin; Lin, Zi-Jing; Liu, Hanli

2011-02-01

47

MTF compensation algorithm based on blind deconvolution for high-resolution remote sensing satellite  

NASA Astrophysics Data System (ADS)

In high resolution remote sensing satellite imaging system, image restoration is an important step to visualize ne details and mitigate the noise. The raw image data often presents poor imaging quality due to various reasons and Point Spread Function (PSF) measures such blurriness characteristic of the image using point source. Satellite image from Korea Multi-purpose Satellite 2 (KOMPSAT-2) also requires Modular Transfer Function (MTF) compensation process to achieve more realistic image which entails removing ringing artifacts at the edges and restraining excess use of denoising eect in order to keep it more realistic. This paper focuses on the deconvolution of KOMPSAT-2 image utilizing PSF attained from Korea Aerospace Research Institute compared to deconvolution with the estimated PSF blur kernel. The deconvolution algorithm considered are Richard-Lucy, Damped Richard-Lucy, Bilateral Richard-Lucy and Sparse Prior deconvolution algorithms.

Lee, Jihye; Chun, Joohwan; Lee, Donghwan

2012-05-01

48

The effects of atmospheric turbulence on precision optical measurements used for antenna-pointing compensation  

NASA Technical Reports Server (NTRS)

Blind pointing of the Deep Space Network (DSN) 70-meter antennas can be improved if distortions of the antenna structure caused by unpredictable environmental loads can be measured in real-time, and the resulting boresight shifts evaluated and incorporated into the pointing control loops. The measurement configuration of a proposed pointing compensation system includes an optical range sensor that measures distances to selected points on the antenna surface. The effect of atmospheric turbulence on the accuracy of optical distance measurements and a method to make in-situ determinations of turbulence-induced measurement errors are discussed.

Nerheim, N.

1989-01-01

49

Sheared-beam imaging: an evaluation of its optical compensation of thick atmospheric turbulence  

NASA Astrophysics Data System (ADS)

Sheared-beam imaging (SBI) should compensate the effects of an idealized layer of turbulence located either in a transmitter/detector plane or in an object plane. This motivated the study of optical compensation of SBI in the presence of uniformly distributed turbulence over long horizontal paths in the cases of ideally smooth and ideally rough extended objects. The phase error along a one-dimensional wave front resulting from SBI observation is computed numerically in the long-path regime and is compared with that of an equivalent conventional system for the case of a large smooth object. It is found that for the conditions considered the phase errors of the SBI system are greater than those of a conventional system. In the case of an ideally rough object the extra information furnished by the SBI observations does not lead to data that can be inverted to compute an image by the conventional shearing-interferometric algorithm. The phase errors in imaging a point reflector, however, are perfectly compensated.

Sica, Louis

1996-01-01

50

Spatial reduction algorithm for atmospheric chemical transport models  

PubMed Central

Numerical modeling of global atmospheric chemical dynamics presents an enormous challenge, associated with simulating hundreds of chemical species with time scales varying from milliseconds to years. Here we present an algorithm that provides a significant reduction in computational cost. Because most of the fast reactants and their quickly decomposing reaction products are localized near emission sources, we use a series of reduced chemical models of decreasing complexity with increasing distance from the source. The algorithm diagnoses the chemical dynamics on-the-run, locally and separately for every species according to its characteristic reaction time. Unlike conventional time-scale separation methods, the spatial reduction algorithm speeds up not only the chemical solver but also advection–diffusion integration. Through several examples we demonstrate that the algorithm can reduce computational cost by at least an order of magnitude for typical atmospheric chemical kinetic mechanisms.

Rastigejev, Y.; Brenner, M. P.; Jacob, D. J.

2007-01-01

51

Relative geometric projection method and argument rotation algorithm for compensation part of an image navigation and registration system  

NASA Astrophysics Data System (ADS)

The paper presents two novel methods for compensation part of an Image Navigation and Registration System (INR). Relatively geometric projection method is applied to compensate the long-term deviations caused by the excursion of orbit. It transforms the view into the body frame of satellite and uses algebraic calculation instead of the trigonometric functions. The new method avoids the repetitious calculations of trigonometric function, and can clearly show the geometric relationships among satellites, optical vectors, and deviation of optical axis. Argument rotation algorithm is applied to compensate the short-term deviations cause by the change of attitude. It is realized by a multiplicative rotation model which describes rotation of rigid frame to a spin axis. The new algorithm discards the constrained equations and singular problems, directly shows the geometric images of spinning processes, and may useful to error estimation of compensation. Both methods are demonstrated by computer simulations to be effective and decrease the amount of calculation.

Ning, Yu; Wang, Zhigang; Li, Wei

2009-12-01

52

Algorithm for Atmospheric Corrections of Aircraft and Satellite Imagery  

NASA Technical Reports Server (NTRS)

A simple and fast atmospheric correction algorithm is described which is used to correct radiances of scattered sunlight measured by aircraft and/or satellite above a uniform surface. The atmospheric effect, the basic equations, a description of the computational procedure, and a sensitivity study are discussed. The program is designed to take the measured radiances, view and illumination directions, and the aerosol and gaseous absorption optical thickness to compute the radiance just above the surface, the irradiance on the surface, and surface reflectance. Alternatively, the program will compute the upward radiance at a specific altitude for a given surface reflectance, view and illumination directions, and aerosol and gaseous absorption optical thickness. The algorithm can be applied for any view and illumination directions and any wavelength in the range 0.48 micron to 2.2 micron. The relation between the measured radiance and surface reflectance, which is expressed as a function of atmospheric properties and measurement geometry, is computed using a radiative transfer routine. The results of the computations are presented in a table which forms the basis of the correction algorithm. The algorithm can be used for atmospheric corrections in the presence of a rural aerosol. The sensitivity of the derived surface reflectance to uncertainties in the model and input data is discussed.

Fraser, Robert S.; Kaufman, Yoram J.; Ferrare, Richard A.; Mattoo, Shana

1989-01-01

53

Validation of the Atmospheric Infrared Sounder radiative transfer algorithm  

Microsoft Academic Search

Comparisons between observed AIRS radiances and radiances computed from coincident in situ profile data are used to validate the accuracy of the AIRS radiative transfer algorithm (RTA) used in version 4 processing at Goddard Space Flight Center. In situ data sources include balloon-borne measurements with RS-90 sensors and frost point hygrometers and Raman lidar measurements of atmospheric water vapor. Estimates

L. L. Strow; S. E. Hannon; S. De-Souza Machado; H. E. Motteler; D. C. Tobin

2006-01-01

54

Algorithm for atmospheric corrections of aircraft and satellite imagery  

Microsoft Academic Search

An algorithm is described for making fast atmospheric corrections. The required radiation parameters are stored in a lookup table. The procedure is to enter the lookup table with the measured radiance, wavelength, view and illumination directions, heights of observation and surface, and the aerosol and gaseous absorption optical thicknesses. The surface radiance, the irradiance incident on a surface, and surface

R. S. FRASER; R. A. FERRARE; Y. J. KAUFMAN; B. L. MARKHAM; S. MATTOO

1992-01-01

55

Effects of predetection atmospheric compensation and post-detection image processing on imagery collected at a ground-based telescope  

Microsoft Academic Search

Short exposure imagery of single and binary stars was collected at the 1.6-m Air Force Maui Optical Station (AMOS) telescope, using a low-noise CCD camera. Atmospheric turbulence effects were partially mitigated using the Compensated Imaging System (CIS), a predetection wavefront sensor and deformable mirror adaptive optical system. We present images and power spectra from both partially compensated and uncompensated short

Marsha F. Bilmont; Michael C. Roggemann; David W. Tyler; Mark A. von Bokern; David G. Voelz; John P. Albetski

1992-01-01

56

The atmospheric correction algorithm for HY-1B/COCTS  

NASA Astrophysics Data System (ADS)

China has launched her second ocean color satellite HY-1B on 11 Apr., 2007, which carried two remote sensors. The Chinese Ocean Color and Temperature Scanner (COCTS) is the main sensor on HY-1B, and it has not only eight visible and near-infrared wavelength bands similar to the SeaWiFS, but also two more thermal infrared bands to measure the sea surface temperature. Therefore, COCTS has broad application potentiality, such as fishery resource protection and development, coastal monitoring and management and marine pollution monitoring. Atmospheric correction is the key of the quantitative ocean color remote sensing. In this paper, the operational atmospheric correction algorithm of HY-1B/COCTS has been developed. Firstly, based on the vector radiative transfer numerical model of coupled oceanatmosphere system- PCOART, the exact Rayleigh scattering look-up table (LUT), aerosol scattering LUT and atmosphere diffuse transmission LUT for HY-1B/COCTS have been generated. Secondly, using the generated LUTs, the exactly operational atmospheric correction algorithm for HY-1B/COCTS has been developed. The algorithm has been validated using the simulated spectral data generated by PCOART, and the result shows the error of the water-leaving reflectance retrieved by this algorithm is less than 0.0005, which meets the requirement of the exactly atmospheric correction of ocean color remote sensing. Finally, the algorithm has been applied to the HY-1B/COCTS remote sensing data, and the retrieved water-leaving radiances are consist with the Aqua/MODIS results, and the corresponding ocean color remote sensing products have been generated including the chlorophyll concentration and total suspended particle matter concentration.

He, Xianqiang; Bai, Yan; Pan, Delu; Zhu, Qiankun

2008-10-01

57

Heterogeneity of SPECT bull`s-eyes in normal dogs: Comparison of attenuation compensation algorithms  

SciTech Connect

In normal dogs, SPECT {sup 99m}Tc Sestamibi (MIBI) and {sup 201}Tl myocardial perfusion images reconstructed with filtered backprojection (FBP) show a large decrease of counts in the septal wall (S) compared to the lateral wall (L). The authors evaluated the iterative method of Chang at 0 and 1 iterations (Chang0 and Chang1), and the Maximum Likelihood-Expectation Maximization with attenuation compensation (ML-EM-ATN) algorithm on data acquired from 5 normal dogs and from simulated projection data using a homogeneous count-density model of a normal canine myocardium in the attenuation field measured in one dog. Mean counts in the S and L regions were calculated from maximum-count circumferential profile arrays. Their results demonstrate that ML-EM-ATN and Chang1 result in improved uniformity, as measured by the S/L ratio.

DiBella, E.V.R.; Eisner, R.L.; Schmarkey, L.S.; Barclay, A.B.; Patterson, R.E.; Nowak, D.J.; Lalush, D.S.; Tsui, B.M.W. [Georgia Inst. of Technology, Atlanta, GA (United States). Dept. of Electrical Engineering] [Georgia Inst. of Technology, Atlanta, GA (United States). Dept. of Electrical Engineering; [Emory Univ., Atlanta, GA (United States). Crawford Long Hospital; [Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Biomedical Engineering

1995-08-01

58

[Application of dark pixels atmospheric correction algorithm to Hyperion imageries].  

PubMed

Atmosphere is an important factor that affects the quantitative analysis and application of remote sensing technology. In the support of IDL platform, the study takes advantages of dark pixel atmospheric correction algorithm (DPACA) to extract the optical depth of atmosphere, and then remove the atmospheric influences from each channel of the Hyperion sensor by that atmospheric parameter. The study results show that the optical depth decreases with the increase in central wavelength of the Hyperion sensor, namely the optical depth is negative versus the central wavelength of sensor. The linear model is the optimal experimental model that is used to describe that relationship, and its correlative coefficient is 0.9123. It was found that the signals recorded by the remote sensing sensor can't express the inherent optical properties and apparent optical properties in a proper manner. Additionally, the remote sensing signals are insensitive to the variations of waters qualities' samples. At the blue and green bands, the effects of atmosphere are the most serious. The spectra are completely different from the optical properties of natural waters at those bands. Compared with the theoretical spectral features of waters' optical properties, the image quality of Hyperion sensor has been perfectly improved by the DPACA. Under the condition of lacking the vertical profile data of atmosphere, the DPACA is an available approach to removing the atmospheric influence on the Hyperion imageries. PMID:21137405

Zheng, Qiu-gen; Quan, Wen-ting

2010-10-01

59

Multiangle implementation of atmospheric correction (MAIAC): 2. Aerosol algorithm  

NASA Astrophysics Data System (ADS)

An aerosol component of a new multiangle implementation of atmospheric correction (MAIAC) algorithm is presented. MAIAC is a generic algorithm developed for the Moderate Resolution Imaging Spectroradiometer (MODIS), which performs aerosol retrievals and atmospheric correction over both dark vegetated surfaces and bright deserts based on a time series analysis and image-based processing. The MAIAC look-up tables explicitly include surface bidirectional reflectance. The aerosol algorithm derives the spectral regression coefficient (SRC) relating surface bidirectional reflectance in the blue (0.47 ?m) and shortwave infrared (2.1 ?m) bands; this quantity is prescribed in the MODIS operational Dark Target algorithm based on a parameterized formula. The MAIAC aerosol products include aerosol optical thickness and a fine-mode fraction at resolution of 1 km. This high resolution, required in many applications such as air quality, brings new information about aerosol sources and, potentially, their strength. AERONET validation shows that the MAIAC and MOD04 algorithms have similar accuracy over dark and vegetated surfaces and that MAIAC generally improves accuracy over brighter surfaces due to the SRC retrieval and explicit bidirectional reflectance factor characterization, as demonstrated for several U.S. West Coast AERONET sites. Due to its generic nature and developed angular correction, MAIAC performs aerosol retrievals over bright deserts, as demonstrated for the Solar Village Aerosol Robotic Network (AERONET) site in Saudi Arabia.

Lyapustin, A.; Wang, Y.; Laszlo, I.; Kahn, R.; Korkin, S.; Remer, L.; Levy, R.; Reid, J. S.

2011-02-01

60

Error-phase compensation properties of differential phase-shifting algorithms for Fizeau fringe patterns  

NASA Astrophysics Data System (ADS)

Many researches have been reported on error-compensating Phase-Shifting Algorithms (PSAs) that eliminate or minimize the main error sources during the corresponding phase-evaluation process. However this kind of analyses have not been carried out in a similar way with respect to the Differential Phase-Shifting Algorithms (DPSAs) that provide directly the phase-difference between two fringe patterns, being unnecessary the previous calculation of each individual optical phase or even the phase-unwrapping process, if the phase-difference is small. In previous works we have studied, by numerical simulation and in a linear approximation, the quantitative response of several families of DPSAs to detuning errors, nonlinearities of detector and harmonics of the signal, achieving satisfactory results that improve those obtained subtracting the two phases calculated separately with PSAs and that provide valuable information related with the sensibilities of the analysed DPSAs. In this work the combined effect of these main error sources is presented and experiments on a Fizeau interferometer were performed to verify the main characteristics of the analysed DPSAs.

Miranda, Marta; Dorrío, Benito V.

2008-04-01

61

A Fuzzy-based Genetic Algorithm for Social Welfare Maximization by Placement and Sizing of Static Synchronous Series Compensator  

Microsoft Academic Search

This article presents a fuzzy-based genetic algorithm to maximize total social welfare and alleviate congestion by placement and sizing of one static synchronous series compensator device, considering its investment cost in a double-sided auction market. The generating units cost curves are considered to be quadratic with sine components to show the impacts of valve point loading. By adding the valve

Seyed M. H. Nabavi; Mohammad A. S. Masoum; Ahad Kazemi

2011-01-01

62

Elevated atmospheric CO2 decreases the ammonia compensation point of barley plants  

PubMed Central

The ammonia compensation point () controls the direction and magnitude of NH3 exchange between plant leaves and the atmosphere. Very limited information is currently available on how responds to anticipated climate changes. Young barley plants were grown for 2 weeks at ambient (400 ?mol mol–1) or elevated (800 ?mol mol–1) CO2 concentration with or NH4NO3 as the nitrogen source. The concentrations of and H+ in the leaf apoplastic solution were measured along with different foliar N pools and enzymes involved in N metabolism. Elevated CO2 caused a threefold decrease in the concentration in the apoplastic solution and slightly acidified it. This resulted in a decline of the from 2.25 and 2.95 nmol mol–1 under ambient CO2 to 0.37 and 0.89 nmol mol–1 at elevated CO2 in the and NH4NO3 treatments, respectively. The decrease in at elevated CO2 reflected a lower N concentration (–25%) in the shoot dry matter. The activity of nitrate reductase also declined (–45 to –60%), while that of glutamine synthetase was unaffected by elevated CO2. It is concluded that elevated CO2 increases the likelihood of plants being a sink for atmospheric NH3 and reduces episodes of NH3 emission from plants.

Schjoerring, Jan K.

2013-01-01

63

Finite element-wavelet hybrid algorithm for atmospheric tomography.  

PubMed

Reconstruction of the refractive index fluctuations in the atmosphere, or atmospheric tomography, is an underlying problem of many next generation adaptive optics (AO) systems, such as the multiconjugate adaptive optics or multiobject adaptive optics (MOAO). The dimension of the problem for the extremely large telescopes, such as the European Extremely Large Telescope (E-ELT), suggests the use of iterative schemes as an alternative to the matrix-vector multiply (MVM) methods. Recently, an algorithm based on the wavelet representation of the turbulence has been introduced in [Inverse Probl.29, 085003 (2013)] by the authors to solve the atmospheric tomography using the conjugate gradient iteration. The authors also developed an efficient frequency-dependent preconditioner for the wavelet method in a later work. In this paper we study the computational aspects of the wavelet algorithm. We introduce three new techniques, the dual domain discretization strategy, a scale-dependent preconditioner, and a ground layer multiscale method, to derive a method that is globally O(n), parallelizable, and compact with respect to memory. We present the computational cost estimates and compare the theoretical numerical performance of the resulting finite element-wavelet hybrid algorithm with the MVM. The quality of the method is evaluated in terms of an MOAO simulation for the E-ELT on the European Southern Observatory (ESO) end-to-end simulation system OCTOPUS. The method is compared to the ESO version of the Fractal Iterative Method [Proc. SPIE7736, 77360X (2010)] in terms of quality. PMID:24690653

Yudytskiy, Mykhaylo; Helin, Tapio; Ramlau, Ronny

2014-03-01

64

Control algorithms for aerobraking in the Martian atmosphere  

NASA Technical Reports Server (NTRS)

The Analytic Predictor Corrector (APC) and Energy Controller (EC) atmospheric guidance concepts were adapted to control an interplanetary vehicle aerobraking in the Martian atmosphere. Changes are made to the APC to improve its robustness to density variations. These changes include adaptation of a new exit phase algorithm, an adaptive transition velocity to initiate the exit phase, refinement of the reference dynamic pressure calculation and two improved density estimation techniques. The modified controller with the hybrid density estimation technique is called the Mars Hybrid Predictor Corrector (MHPC), while the modified controller with a polynomial density estimator is called the Mars Predictor Corrector (MPC). A Lyapunov Steepest Descent Controller (LSDC) is adapted to control the vehicle. The LSDC lacked robustness, so a Lyapunov tracking exit phase algorithm is developed to guide the vehicle along a reference trajectory. This algorithm, when using the hybrid density estimation technique to define the reference path, is called the Lyapunov Hybrid Tracking Controller (LHTC). With the polynomial density estimator used to define the reference trajectory, the algorithm is called the Lyapunov Tracking Controller (LTC). These four new controllers are tested using a six degree of freedom computer simulation to evaluate their robustness. The MHPC, MPC, LHTC, and LTC show dramatic improvements in robustness over the APC and EC.

Ward, Donald T.; Shipley, Buford W., Jr.

1991-01-01

65

Control algorithms for aerobraking in the Martian atmosphere  

NASA Astrophysics Data System (ADS)

The Analytic Predictor Corrector (APC) and Energy Controller (EC) atmospheric guidance concepts were adapted to control an interplanetary vehicle aerobraking in the Martian atmosphere. Changes are made to the APC to improve its robustness to density variations. These changes include adaptation of a new exit phase algorithm, an adaptive transition velocity to initiate the exit phase, refinement of the reference dynamic pressure calculation and two improved density estimation techniques. The modified controller with the hybrid density estimation technique is called the Mars Hybrid Predictor Corrector (MHPC), while the modified controller with a polynomial density estimator is called the Mars Predictor Corrector (MPC). A Lyapunov Steepest Descent Controller (LSDC) is adapted to control the vehicle. The LSDC lacked robustness, so a Lyapunov tracking exit phase algorithm is developed to guide the vehicle along a reference trajectory. This algorithm, when using the hybrid density estimation technique to define the reference path, is called the Lyapunov Hybrid Tracking Controller (LHTC). With the polynomial density estimator used to define the reference trajectory, the algorithm is called the Lyapunov Tracking Controller (LTC). These four new controllers are tested using a six degree of freedom computer simulation to evaluate their robustness. The MHPC, MPC, LHTC, and LTC show dramatic improvements in robustness over the APC and EC.

Ward, Donald T.; Shipley, Buford W., Jr.

1991-09-01

66

Control algorithms for aerobraking in the Martian atmosphere  

NASA Astrophysics Data System (ADS)

The Analytic Predictor Corrector (APC) and Energy Controller (EC) atmospheric guidance concepts have been adapted to control an interplanetary vehicle aerobraking in the Martian atmosphere. Modifications are made to the APC to improve its robustness to density variations. These modifications include adaptation of a new exit phase algorithm, an adaptive transition velocity to initiate the exit phase, refinement of the reference dynamic pressure calculation and two hybrid density estimation techniques. The modified controller with the hybrid density estimation technique is called the Mars Hybrid Predictor Corrector (MHPC), while the modified controller with a polynomial density estimator is called the Mars Predictor Corrector (MPC). A Lyapunov Steepest Descent Controller (LSDC) is adapted to control the vehicle. The LSDC lacked robustness, so a Lyapunov tracking exit phase algorithm is developed to guide the vehicle along a reference trajectory. The equilibrium glide entry phase is employed for the first part of the trajectory. This algorithm, when using the hybrid density estimation technique to define the reference path, is called te Lyapunov Hybrid Tracking Controller (LHTC). With the polynomial density estimator used to define the reference trajectory, the algorithm is called the Lyapunov Tracking Controller (LTC). The four new controllers are tested usig a six degree of freedom computer simulation to evaluate their robustness.

Shipley, Buford W., Jr.

1991-12-01

67

An Improved Method of Heterogeneity Compensation for the Convolution / Superposition Algorithm  

NASA Astrophysics Data System (ADS)

Purpose: To improve the accuracy of convolution/superposition (C/S) in heterogeneous material by developing a new algorithm: heterogeneity compensated superposition (HCS). Methods: C/S has proven to be a good estimator of the dose deposited in a homogeneous volume. However, near heterogeneities electron disequilibrium occurs, leading to the faster fall-off and re-buildup of dose. We propose to filter the actual patient density in a position and direction sensitive manner, allowing the dose deposited near interfaces to be increased or decreased relative to C/S. We implemented the effective density function as a multivariate first-order recursive filter and incorporated it into GPU-accelerated, multi-energetic C/S implementation. We compared HCS against C/S using the ICCR 2000 Monte-Carlo accuracy benchmark, 23 similar accuracy benchmarks and 5 patient cases. Results: Multi-energetic HCS increased the dosimetric accuracy for the vast majority of voxels; in many cases near Monte-Carlo results were achieved. We defined the per-voxel error, %|mm, as the minimum of the distance to agreement in mm and the dosimetric percentage error relative to the maximum MC dose. HCS improved the average mean error by 0.79 %|mm for the patient volumes; reducing the average mean error from 1.93 %|mm to 1.14 %|mm. Very low densities (i.e. < 0.1 g / cm3) remained problematic, but may be solvable with a better filter function. Conclusions: HCS improved upon C/S's density scaled heterogeneity correction with a position and direction sensitive density filter. This method significantly improved the accuracy of the GPU based algorithm reaching the accuracy levels of Monte Carlo based methods with performance in a few tenths of seconds per beam. Acknowledgement: Funding for this research was provided by the NSF Cooperative Agreement EEC9731748, Elekta / IMPAC Medical Systems, Inc. and the Johns Hopkins University. James Satterthwaite provided the Monte Carlo benchmark simulations.

Jacques, Robert; McNutt, Todd

2014-03-01

68

Mars Entry Atmospheric Data System Modelling and Algorithm Development  

NASA Technical Reports Server (NTRS)

The Mars Entry Atmospheric Data System (MEADS) is being developed as part of the Mars Science Laboratory (MSL), Entry, Descent, and Landing Instrumentation (MEDLI) project. The MEADS project involves installing an array of seven pressure transducers linked to ports on the MSL forebody to record the surface pressure distribution during atmospheric entry. These measured surface pressures are used to generate estimates of atmospheric quantities based on modeled surface pressure distributions. In particular, the quantities to be estimated from the MEADS pressure measurements include the total pressure, dynamic pressure, Mach number, angle of attack, and angle of sideslip. Secondary objectives are to estimate atmospheric winds by coupling the pressure measurements with the on-board Inertial Measurement Unit (IMU) data. This paper provides details of the algorithm development, MEADS system performance based on calibration, and uncertainty analysis for the aerodynamic and atmospheric quantities of interest. The work presented here is part of the MEDLI performance pre-flight validation and will culminate with processing flight data after Mars entry in 2012.

Karlgaard, Christopher D.; Beck, Roger E.; OKeefe, Stephen A.; Siemers, Paul; White, Brady; Engelund, Walter C.; Munk, Michelle M.

2009-01-01

69

A Novel Modified Omega-K Algorithm for Synthetic Aperture Imaging Lidar through the Atmosphere  

PubMed Central

The spatial resolution of a conventional imaging lidar system is constrained by the diffraction limit of the telescope's aperture. The combination of the lidar and synthetic aperture (SA) processing techniques may overcome the diffraction limit and pave the way for a higher resolution air borne or space borne remote sensor. Regarding the lidar transmitting frequency modulation continuous-wave (FMCW) signal, the motion during the transmission of a sweep and the reception of the corresponding echo were expected to be one of the major problems. The given modified Omega-K algorithm takes the continuous motion into account, which can compensate for the Doppler shift induced by the continuous motion efficiently and azimuth ambiguity for the low pulse recurrence frequency limited by the tunable laser. And then, simulation of Phase Screen (PS) distorted by atmospheric turbulence following the von Karman spectrum by using Fourier Transform is implemented in order to simulate turbulence. Finally, the computer simulation shows the validity of the modified algorithm and if in the turbulence the synthetic aperture length does not exceed the similar coherence length of the atmosphere for SAIL, we can ignore the effect of the turbulence.

Guo, Liang; Xing, Mendao; Tang, Yu; Dan, Jing

2008-01-01

70

Multi-Angle Implementation of Atmospheric Correction (MAIAC) Algorithm  

NASA Technical Reports Server (NTRS)

Multi-Angle Implementation of Atmospheric Correction (MAIAC) is a new algorithm developed for MODIS. MAIAC uses a time series analysis and processing of groups of pixels to perform simultaneous retrievals of aerosol properties and surface bidirectional reflectance without typical assumptions about the surface. It is a generic algorithm which works over both dark and bright land surfaces, including deserts. MAIAC has an internal Cloud Mask, a dynamic land-water-snow classification and a surface change mask which allows it to flexibly choose processing path over different surfaces. A distinct feature of MAIAC is a high 1 km resolution of aerosol retrievals which is required in different applications including the air quality analysis. The novel features of MAIAC include the high quality cloud mask, discrimination of aerosol type, including biomass burning smoke and dust, and detection of surface change - all required for high quality aerosol retrievals. An overview of the algorithm, results of AERONET validation, and examples of comparison with MODIS Collection 5 aerosol product and Deep Blue algorithm for different parts of the world, will be presented.

Lyapustin, A.; Wang, Y.

2012-01-01

71

Aerosol Retrieval and Atmospheric Correction Algorithms for EPIC  

NASA Technical Reports Server (NTRS)

EPIC is a multi-spectral imager onboard planned Deep Space Climate ObserVatoRy (DSCOVR) designed for observations of the full illuminated disk of the Earth with high temporal and coarse spatial resolution (10 km) from Lagrangian L1 point. During the course of the day, EPIC will view the same Earth surface area in the full range of solar and view zenith angles at equator with fixed scattering angle near the backscattering direction. This talk will describe a new aerosol retrieval/atmospheric correction algorithm developed for EPIC and tested with EPIC Simulator data. This algorithm uses the time series approach and consists of two stages: the first stage is designed to periodically re-initialize the surface spectral bidirectional reflectance (BRF) on stable low AOD days. Such days can be selected based on the same measured reflectance between the morning and afternoon reciprocal view geometries of EPIC. On the second stage, the algorithm will monitor the diurnal cycle of aerosol optical depth and fine mode fraction based on the known spectral surface BRF. Testing of the developed algorithm with simulated EPIC data over continental USA showed a good accuracy of AOD retrievals (10-20%) except over very bright surfaces.

Wang, Yujie; Lyapustin, Alexei; Marshak, Alexander; Korkin, Sergey; Herman, Jay

2011-01-01

72

Radiative transfer in the midwave infrared applicable to full spectrum atmospheric characterization  

Microsoft Academic Search

The compensation for atmospheric effects in the VNIR\\/SWIR has reached a mature stage of development with many algorithms available for application (ATREM, FLAASH, ACORN, etc.). Compensation of LWIR data is the focus of a number of promising algorithms. A gap in development exists in the MWIR where little or no atmospheric compensation work has been done yet an increased interest

Michael Griffin; Hsiao-hua Burke; John Kerekes

2004-01-01

73

The application of atmospheric correction algorithms for monitoring atmospheric pollution using Landsat TM images  

NASA Astrophysics Data System (ADS)

This paper focused on the application of effective atmospheric correction algorithm for assessing the atmospheric pollution based on the determined aerosol optical thickness. Field spectro-radiometers such as GER 1500 and HR-1024 have been used to retrieve the ground reflectance values of certain proposed calibration targets. Sun-photometers (MICROTOPS II) have been used to measure the aerosol optical thickness. Retrieved aerosol optical thickness from satellite images have been directly compared with the values found from the sun-photometer measurements as well those found from the visibility data obtained during the satellite overpass. The determined aerosol optical thickness obtained from the atmospheric path radiance component and those found from ground measurements (sun-photometer and meteorological data) acquired during the satellite overpass show very high correlations after regression analysis application.

Hadjimitsis, Diofantos G.; Themistokleous, Kyriacos P.; Papadavid, Giorgos

2008-10-01

74

Models and algorithms for vision through the atmosphere  

NASA Astrophysics Data System (ADS)

Current vision systems are designed to perform in clear weather. Needless to say, in any outdoor application, there is no escape from bad weather. Ultimately, computer vision systems must include mechanisms that enable them to function (even if somewhat less reliably) in the presence of haze, fog, rain, hail and snow. We begin by studying the visual manifestations of different weather conditions. For this, we draw on what is already known about atmospheric optics, and identify effects caused by bad weather that can be turned to our advantage; we are not only interested in what bad weather does to vision but also what it can do for vision. This thesis presents a novel and comprehensive set of models, algorithms and image datasets for better image understanding in bad weather. The models presented here can be broadly classified into single scattering and multiple scattering models. Existing single scattering models like attenuation and airlight form the basis of three new models viz., the contrast model, the dichromatic model and the polarization model. Each of these models is suited to different types of atmospheric and illumination conditions as well as different sensor types. Based on these models, we develop algorithms to recover pertinent scene properties, such as 3D structure, and clear day scene contrasts and colors, from one or more images taken under poor weather conditions. Next, we present an analytic model for multiple scattering of light in a scattering medium. From a single image of a light source immersed in a medium, interesting properties of the medium can be estimated. If the medium is the atmosphere, the weather condition and the visibility of the atmosphere can be estimated. These quantities can in turn be used to remove the glows around sources obtaining a clear picture of the scene. Based on these results, the camera serves as a "visual weather meter". Our analytic model can be used to analyze scattering in virtually any scattering medium, including fluids and tissues. Therefore, in addition to vision in bad weather, our work has implications for real-time rendering of participating media in computer graphics, medical imaging and underwater imaging. Apart from the models and algorithms, we have acquired an extensive database of images of an outdoor scene almost every hour for 9 months. This dataset is the first of its kind and includes high quality calibrated images captured under a wide variety of weather and illumination conditions and all four seasons. Such a dataset could not only be used as a testbed for validating existing appearance models (including the ones presented in this work) but also inspire new data driven models. In addition to computer vision, this dataset could be useful for researchers in other fields like graphics, image processing, remote sensing and atmospheric sciences. The database is freely distributed for research purposes and can be requested through our web site http://www.cs.columbia.edu/˜wild. We believe that this thesis opens new research directions needed for computer vision to be successful in the outdoors.

Narasimhan, Srinivasa G.

2004-11-01

75

A Novel Systematic Error Compensation Algorithm Based on Least Squares Support Vector Regression for Star Sensor Image Centroid Estimation  

PubMed Central

The star centroid estimation is the most important operation, which directly affects the precision of attitude determination for star sensors. This paper presents a theoretical study of the systematic error introduced by the star centroid estimation algorithm. The systematic error is analyzed through a frequency domain approach and numerical simulations. It is shown that the systematic error consists of the approximation error and truncation error which resulted from the discretization approximation and sampling window limitations, respectively. A criterion for choosing the size of the sampling window to reduce the truncation error is given in this paper. The systematic error can be evaluated as a function of the actual star centroid positions under different Gaussian widths of star intensity distribution. In order to eliminate the systematic error, a novel compensation algorithm based on the least squares support vector regression (LSSVR) with Radial Basis Function (RBF) kernel is proposed. Simulation results show that when the compensation algorithm is applied to the 5-pixel star sampling window, the accuracy of star centroid estimation is improved from 0.06 to 6 × 10?5 pixels.

Yang, Jun; Liang, Bin; Zhang, Tao; Song, Jingyan

2011-01-01

76

A novel systematic error compensation algorithm based on least squares support vector regression for star sensor image centroid estimation.  

PubMed

The star centroid estimation is the most important operation, which directly affects the precision of attitude determination for star sensors. This paper presents a theoretical study of the systematic error introduced by the star centroid estimation algorithm. The systematic error is analyzed through a frequency domain approach and numerical simulations. It is shown that the systematic error consists of the approximation error and truncation error which resulted from the discretization approximation and sampling window limitations, respectively. A criterion for choosing the size of the sampling window to reduce the truncation error is given in this paper. The systematic error can be evaluated as a function of the actual star centroid positions under different Gaussian widths of star intensity distribution. In order to eliminate the systematic error, a novel compensation algorithm based on the least squares support vector regression (LSSVR) with Radial Basis Function (RBF) kernel is proposed. Simulation results show that when the compensation algorithm is applied to the 5-pixel star sampling window, the accuracy of star centroid estimation is improved from 0.06 to 6 × 10(-5) pixels. PMID:22164021

Yang, Jun; Liang, Bin; Zhang, Tao; Song, Jingyan

2011-01-01

77

Hyperspectral image lossless compression algorithm based on error compensated prediction tree of multi-band prediction  

NASA Astrophysics Data System (ADS)

A new lossless compression method based on prediction tree with error compensation for hyperspectral imagery is proposed in this paper. This method incorporates the techniques of prediction tree and adaptive band prediction. The proposed method is different from previous similar approaches in that its prediction to the current band is performed by multiple bands and the error created by the prediction tree is compensated by a linear adaptive predictor for decorrelating spectral statistical redundancy. After de-correlating intraband and interband redundancy, the SPIHT (Set Partitioning in Hierarchical Trees) wavelet coding is used to encode the residual image. The proposed method achieves high compression ratio on the NASA JPL AVIRIS data.

Wang, Lang; Guo, Shuxu; Gu, Lingjia; Ren, Ruizhi

2008-08-01

78

Design of Jitter Compensation Algorithm for Robot Vision Based on Optical Flow and Kalman Filter  

PubMed Central

Image jitters occur in the video of the autonomous robot moving on bricks road, which will reduce robot operation precision based on vision. In order to compensate the image jitters, the affine transformation kinematics were established for obtaining the six image motion parameters. The feature point pair detecting method was designed based on Eigen-value of the feature windows gradient matrix, and the motion parameters equation was solved using the least square method and the matching point pairs got based on the optical flow. The condition number of coefficient matrix was proposed to quantificationally analyse the effect of matching errors on parameters solving errors. Kalman filter was adopted to smooth image motion parameters. Computing cases show that more point pairs are beneficial for getting more precise motion parameters. The integrated jitters compensation software was developed with feature points detecting in subwindow. And practical experiments were conducted on two mobile robots. Results show that the compensation costing time is less than frame sample time and Kalman filter is valid for robot vision jitters compensation.

Wang, B. R.; Jin, Y. L.; Shao, D. L.; Xu, Y.

2014-01-01

79

Hyperspectral image lossless compression algorithm based on error compensated prediction tree of multi-band prediction  

Microsoft Academic Search

A new lossless compression method based on prediction tree with error compensation for hyperspectral imagery is proposed in this paper. This method incorporates the techniques of prediction tree and adaptive band prediction. The proposed method is different from previous similar approaches in that its prediction to the current band is performed by multiple bands and the error created by the

Lang Wang; Shuxu Guo; Lingjia Gu; Ruizhi Ren

2008-01-01

80

NOTE: A simple algorithm for in vivo ocular fundus oximetry compensating for non-haemoglobin absorption and scattering  

NASA Astrophysics Data System (ADS)

An algorithm is introduced for the compensation of the influence of non-haemoglobin absorption as well as tissue scattering on blood spectra used in optical oximetry at the ocular fundus. The in vivo measured spectra were corrected by a linear transformation in order to match the reference spectra of fully oxygenated and reduced blood, respectively, at three isosbestic points (522 nm, 569 nm and 586 nm). The oxygen saturation can then be determined at a wavelength showing a high contrast between oxygenated and reduced haemoglobin (e.g., 560 nm). Reflection measurements at blood flowing through cuvettes were used to validate the algorithm. The oxygen saturation values were compared to measurements of the same samples at a laboratory haemoximeter. The mean deviation was found to be 2.65%.

Hammer, Martin; Thamm, Eike; Schweitzer, Dietrich

2002-09-01

81

An Algorithm to Atmospherically Correct Visible and Thermal Airborne Imagery  

NASA Technical Reports Server (NTRS)

The program Watts implements a system of physically based models developed by the authors, described elsewhere, for the removal of atmospheric effects in multispectral imagery. The band range we treat covers the visible, near IR and the thermal IR. Input to the program begins with atmospheric pal red models specifying transmittance and path radiance. The system also requires the sensor's spectral response curves and knowledge of the scanner's geometric definition. Radiometric characterization of the sensor during data acquisition is also necessary. While the authors contend that active calibration is critical for serious analytical efforts, we recognize that most remote sensing systems, either airborne or space borne, do not as yet attain that minimal level of sophistication. Therefore, Watts will also use semi-active calibration where necessary and available. All of the input is then reduced to common terms, in terms of the physical units. From this it Is then practical to convert raw sensor readings into geophysically meaningful units. There are a large number of intricate details necessary to bring an algorithm or this type to fruition and to even use the program. Further, at this stage of development the authors are uncertain as to the optimal presentation or minimal analytical techniques which users of this type of software must have. Therefore, Watts permits users to break out and analyze the input in various ways. Implemented in REXX under OS/2 the program is designed with attention to the probability that it will be ported to other systems and other languages. Further, as it is in REXX, it is relatively simple for anyone that is literate in any computer language to open the code and modify to meet their needs. The authors have employed Watts in their research addressing precision agriculture and urban heat island.

Rickman, Doug L.; Luvall, Jeffrey C.; Schiller, Stephen; Arnold, James E. (Technical Monitor)

2000-01-01

82

Design of error-compensating algorithms for sinusoidal phase shifting interferometry  

SciTech Connect

An improved approach to interferometry using sinusoidal phase shifting balances several harmonic components in the interference signal against each other. The resulting computationally efficient phase-estimation algorithms have low sensitivity to errors such as spurious intensity noise, vibration, and errors in the phase shift pattern. Specific example algorithms employing 8 and 12 camera frames illustrate design principles that are extendable to algorithms of any length for applications that would benefit from a simplified, sinusoidal phase shift.

Groot, Peter de

2009-12-10

83

Compensation for the effects of mutual coupling on direct data domain adaptive algorithms  

Microsoft Academic Search

This paper investigates the effects of mutual coupling between the elements of an array on direct data domain algorithms. Mutual coupling severely undermines the interference suppression capabilities of direct data domain algorithms. The method of moments (MoM) is used to evaluate the mutual coupling between the elements of a given array. The MoM admittance matrix is then used to eliminate

Raviraj S. Adve; Tapan Kumar Sarkar

2000-01-01

84

Algorithm for automatic atmospheric corrections to visible and near-IR satellite imagery  

Microsoft Academic Search

An algorithm is developed for automatic atmospheric correction of satellite imagery of the Earth's surface. The algorithm is based solely on the satellite image being corrected and on climatology of the area. It is applicable to low resolution (1 km field of view) and high resolution (10-80m field of view) imagery of land areas for the solar spectrum. The algorithm

Yoram J. Kaufman; Claudia Sendra

1988-01-01

85

CEMERLL: The Propagation of an Atmosphere-Compensated Laser Beam to the Apollo 15 Lunar Array  

NASA Technical Reports Server (NTRS)

Adaptive optics techniques can be used to realize a robust low bit-error-rate link by mitigating the atmosphere-induced signal fades in optical communications links between ground-based transmitters and deep-space probes.

Fugate, R. Q.; Leatherman, P. R.; Wilson, K. E.

1997-01-01

86

Atmospheric compensation with a speckle beacon in strong scintillation conditions: directed energy and laser communication applications  

NASA Astrophysics Data System (ADS)

Wavefront control experiments in strong scintillation conditions (scintillation index, ?1) over a 2.33km, near-horizontal, atmospheric propagation path are presented. The adaptive-optics system used comprises a tracking and a fast-beam-steering mirror as well as a 132-actuator, microelectromechanical-system, piston-type deformable mirror with a VLSI controller that implements stochastic parallel gradient descent control optimization of a system performance metric. The experiments demonstrate mitigation of atmospheric distortions with a speckle beacon typical for directed energy and free-space laser communication applications.

Weyrauch, Thomas; Vorontsov, Mikhail A.

2005-10-01

87

Atmospheric compensation with a speckle beacon in strong scintillation conditions: directed energy and laser communication applications.  

PubMed

Wavefront control experiments in strong scintillation conditions (scintillation index, approximately equal to 1) over a 2.33 km, near-horizontal, atmospheric propagation path are presented. The adaptive-optics system used comprises a tracking and a fast-beam-steering mirror as well as a 132-actuator, microelectromechanical-system, piston-type deformable mirror with a VLSI controller that implements stochastic parallel gradient descent control optimization of a system performance metric. The experiments demonstrate mitigation of atmospheric distortions with a speckle beacon typical for directed energy and free-space laser communication applications. PMID:16252651

Weyrauch, Thomas; Vorontsov, Mikhail A

2005-10-20

88

Birefringence dispersion compensation demodulation algorithm for polarized low-coherence interferometry.  

PubMed

A demodulation algorithm based on the birefringence dispersion characteristics for a polarized low-coherence interferometer is proposed. With the birefringence dispersion parameter taken into account, the mathematical model of the polarized low-coherence interference fringes is established and used to extract phase shift information between the measured coherence envelope center and the zero-order fringe, which eliminates the interferometric 2 ? ambiguity of locating the zero-order fringe. A pressure measurement experiment using an optical fiber Fabry-Perot pressure sensor was carried out to verify the effectiveness of the proposed algorithm. The experiment result showed that the demodulation precision was 0.077 kPa in the range of 210 kPa, which was improved by 23 times compared to the traditional envelope detection method. PMID:24104678

Wang, Shuang; Liu, Tiegen; Jiang, Junfeng; Liu, Kun; Yin, Jinde; Wu, Fan

2013-08-15

89

Experimental verification of a delay compensation algorithm for integrated communication and control systems  

Microsoft Academic Search

Advances in the technology of complex control systems demand high-speed and reliable communications between the individual components and subsystems for decision making and control. This can be accomplished by integrated communication and control systems which use asynchronous time-division-multiplexed networks. Unfortunately, these networks introduce randomly varying distributed delays as a result of time-division multiplexing. A predictor-controller algorithm has been developed with

ROGELIO LUCK; ASOK RAY

1994-01-01

90

An ultrasonic transducer transient compensator design based on a simplified Variable Structure Control algorithm.  

PubMed

A non-linear control method, known as Variable Structure Control (VSC), is employed to reduce the duration of ultrasonic (US) transducer transients. A physically realizable system using a simplified form of the VSC algorithm is proposed for standard piezoelectric transducers and simulated. Results indicate a VSC-controlled transmitter reduces the transient duration to less than a carrier wave cycle. Applications include high capacity ultrasound communication and localization systems. PMID:23993746

Ma, Shaodong; Wilkinson, Antony J; Paulson, Kevin S

2014-02-01

91

Adaptive Compensation of Atmospheric Turbulence in Ground-to-Ground Laser Communication Systems.  

National Technical Information Service (NTIS)

Two silicon based devices were investigated for use as an optical wave-front sensor to provide error signal inputs to an adaptive optic wave-front control system intended to reduce the effects of atmospheric turbulence in ground-to-ground laser communicat...

F. M. Davidson

2003-01-01

92

CAAS: an atmospheric correction algorithm for the remote sensing of complex waters  

NASA Astrophysics Data System (ADS)

The current SeaDAS atmospheric correction algorithm relies on the computation of optical properties of aerosols based on radiative transfer combined with a near-infrared (NIR) correction scheme (originally with assumptions of zero water-leaving radiance for the NIR bands) and several ancillary parameters to remove atmospheric effects in remote sensing of ocean colour. The failure of this algorithm over complex waters has been reported by many recent investigations, and can be attributed to the inadequate NIR correction and constraints for deriving aerosol optical properties whose characteristics are the most difficult to evaluate because they vary rapidly with time and space. The possibility that the aerosol and sun glint contributions can be derived in the whole spectrum of ocean colour solely from a knowledge of the total and Rayleigh-corrected radiances is developed in detail within the framework of a Complex water Atmospheric correction Algorithm Scheme (CAAS) that makes no use of ancillary parameters. The performance of the CAAS algorithm is demonstrated for MODIS/Aqua imageries of optically complex waters and yields physically realistic water-leaving radiance spectra that are not possible with the SeaDAS algorithm. A preliminary comparison with in-situ data for several regional waters (moderately complex to clear waters) shows encouraging results, with absolute errors of the CAAS algorithm closer to those of the SeaDAS algorithm. The impact of the atmospheric correction was also examined on chlorophyll retrievals with a Case 2 water bio-optical algorithm, and it was found that the CAAS algorithm outperformed the SeaDAS algorithm in terms of producing accurate pigment estimates and recovering areas previously flagged out by the later algorithm. These findings suggest that the CAAS algorithm can be used for applications focussing in quantitative assessments of the biological and biogeochemical properties in complex waters, and can easily be extended to other sensors such as OCM-2, MERIS and GOCI.

Shanmugam, P.

2012-01-01

93

Free-space laser communications with adaptive optics: Atmospheric compensation experiments  

NASA Astrophysics Data System (ADS)

Refractive index inhomogeneities of the turbulent air cause wave-front distortions of optical waves propagating through the atmosphere, leading to such effects as beam spreading, beam wander, and intensity fluctuations (scintillations). These distortions are responsible for severe signal fading in free-space optical communications systems and therefore compromise link reliability. Wave-front distortions can be mitigated, in principle, with adaptive optics, i.e., real-time wave-front control, reducing the likeliness of signal fading. However, adaptive optics technology, currently primarily used in astronomical imaging, needs to be adapted to the requirements of free-space optical communication systems and their specific challenges.

Weyrauch, Thomas; Vorontsov, Mikhail A.

94

An Atmospheric Guidance Algorithm Testbed for the Mars Surveyor Program 2001 Orbiter and Lander  

NASA Technical Reports Server (NTRS)

An Atmospheric Flight Team was formed by the Mars Surveyor Program '01 mission office to develop aerocapture and precision landing testbed simulations and candidate guidance algorithms. Three- and six-degree-of-freedom Mars atmospheric flight simulations have been developed for testing, evaluation, and analysis of candidate guidance algorithms for the Mars Surveyor Program 2001 Orbiter and Lander. These simulations are built around the Program to Optimize Simulated Trajectories. Subroutines were supplied by Atmospheric Flight Team members for modeling the Mars atmosphere, spacecraft control system, aeroshell aerodynamic characteristics, and other Mars 2001 mission specific models. This paper describes these models and their perturbations applied during Monte Carlo analyses to develop, test, and characterize candidate guidance algorithms.

Striepe, Scott A.; Queen, Eric M.; Powell, Richard W.; Braun, Robert D.; Cheatwood, F. McNeil; Aguirre, John T.; Sachi, Laura A.; Lyons, Daniel T.

1998-01-01

95

Assessment, Validation, and Refinement of the Atmospheric Correction Algorithm for the Ocean Color Sensors. Chapter 19  

NASA Technical Reports Server (NTRS)

The primary focus of this proposed research is for the atmospheric correction algorithm evaluation and development and satellite sensor calibration and characterization. It is well known that the atmospheric correction, which removes more than 90% of sensor-measured signals contributed from atmosphere in the visible, is the key procedure in the ocean color remote sensing (Gordon and Wang, 1994). The accuracy and effectiveness of the atmospheric correction directly affect the remotely retrieved ocean bio-optical products. On the other hand, for ocean color remote sensing, in order to obtain the required accuracy in the derived water-leaving signals from satellite measurements, an on-orbit vicarious calibration of the whole system, i.e., sensor and algorithms, is necessary. In addition, it is important to address issues of (i) cross-calibration of two or more sensors and (ii) in-orbit vicarious calibration of the sensor-atmosphere system. The goal of these researches is to develop methods for meaningful comparison and possible merging of data products from multiple ocean color missions. In the past year, much efforts have been on (a) understanding and correcting the artifacts appeared in the SeaWiFS-derived ocean and atmospheric produces; (b) developing an efficient method in generating the SeaWiFS aerosol lookup tables, (c) evaluating the effects of calibration error in the near-infrared (NIR) band to the atmospheric correction of the ocean color remote sensors, (d) comparing the aerosol correction algorithm using the singlescattering epsilon (the current SeaWiFS algorithm) vs. the multiple-scattering epsilon method, and (e) continuing on activities for the International Ocean-Color Coordinating Group (IOCCG) atmospheric correction working group. In this report, I will briefly present and discuss these and some other research activities.

Wang, Menghua

2003-01-01

96

Parallel algorithms for semi-Lagrangian transport in global atmospheric circulation models  

SciTech Connect

Global atmospheric circulation models (GCM) typically have three primary algorithmic components: columnar physics, spectral transform, and semi-Lagrangian transport. In developing parallel implementations, these three components are equally important and can be examined somewhat independently. A two-dimensional horizontal data decomposition of the three-dimensional computational grid leaves all physics computations on processor, and the only efficiency issues arise in load balancing. A recently completed study by the authors of different approaches to parallelizing the spectral transform showed several viable algorithms. Preliminary results of an analogous study of algorithmic alternatives for parallel semi-Lagrangian transport are described here.

Drake, J.B.; Worley, P.H. [Oak Ridge National Lab., TN (United States); Michalakes, J.; Foster, I.T. [Argonne National Lab., IL (United States)

1995-02-01

97

Atmospheric correction over case 2 waters with an iterative fitting algorithm  

NASA Astrophysics Data System (ADS)

A modular atmospheric correction algorithm is proposed that uses atmospheric and water contents models to predict the visible and near-infrared reflectances observed by a satellite over water. These predicted values are compared with the satellite reflectances at each pixel, and the model parameters changed iteratively with an error minimization algorithm. The default atmospheric model uses single-scattering theory with a correction for multiple scattering based on lookup tables. With this model we used parameters of the proportions of three tropospheric aerosol types. For the default water content model we need the parameters of the concentrations of chlorophyll, inorganic sediment, and gelbstoff. The diffuse attenuation and backscatter coefficients attributed to these constituents are calculated and used to derive the water-leaving reflectance. Products include water-leaving reflectance, concentrations of water constituents, and aerosol optical depth and type. We demonstrate the application of the method to sea-viewing wide field-of-view sensor by using model data.

Land, Peter E.; Haigh, Joanna D.

1996-09-01

98

Mars Entry Atmospheric Data System Trajectory Reconstruction Algorithms and Flight Results  

NASA Technical Reports Server (NTRS)

The Mars Entry Atmospheric Data System is a part of the Mars Science Laboratory, Entry, Descent, and Landing Instrumentation project. These sensors are a system of seven pressure transducers linked to ports on the entry vehicle forebody to record the pressure distribution during atmospheric entry. These measured surface pressures are used to generate estimates of atmospheric quantities based on modeled surface pressure distributions. Specifically, angle of attack, angle of sideslip, dynamic pressure, Mach number, and freestream atmospheric properties are reconstructed from the measured pressures. Such data allows for the aerodynamics to become decoupled from the assumed atmospheric properties, allowing for enhanced trajectory reconstruction and performance analysis as well as an aerodynamic reconstruction, which has not been possible in past Mars entry reconstructions. This paper provides details of the data processing algorithms that are utilized for this purpose. The data processing algorithms include two approaches that have commonly been utilized in past planetary entry trajectory reconstruction, and a new approach for this application that makes use of the pressure measurements. The paper describes assessments of data quality and preprocessing, and results of the flight data reduction from atmospheric entry, which occurred on August 5th, 2012.

Karlgaard, Christopher D.; Kutty, Prasad; Schoenenberger, Mark; Shidner, Jeremy; Munk, Michelle

2013-01-01

99

Current Status of Multi-Angle Implementation of Atmospheric Correction (MAIAC) Algorithm  

NASA Technical Reports Server (NTRS)

A new Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm has been developed for MODIS. MAIAC uses a time series and an image based rather than pixel-based processing to perform simultaneous retrievals of aerosol properties and surface bidirectional reflectance. It is a generic algorithm which works over all land surface types with the exception of snow. MAIAC has an internal Cloud Mask, a dynamic land-water-snow classification and a surface change mask which allows it to flexibly choose processing path over different surfaces. A distinct feature of MAIAC is a high 1 km resolution of aerosol retrievals including optical thickness and fine mode fraction, which is required in different applications including the air quality analysis. An overview of the algorithm, results of AERONET validation, and examples of comparison with MODIS Collection 5 aerosol product, including Deep Blue algorithm, will be presented for different parts of the world including continental USA, Persian Gulf region and India.

Lyapustin, A.; Wang, Y.

2011-01-01

100

An Atmospheric Correction Algorithm for FY-3/ MERSI Data over the Land: First Results  

NASA Astrophysics Data System (ADS)

Feng-Yun (FY-3) is the second Chinese Polar Orbiting Meteorological Satellite with global, three-dimensional, quantitative, and multispectral capabilities. Medium Resolution Spectral Imager (MERSI) has 20 channels onboard the FY-3A and FY-3B satellite. MERSI has five channels (four VIS and one thermal IR), with a spatial resolution of 250 m. Prior to the derivation of various biophysical parameters based on surface reflectance, the top of the atmosphere signal need to be radiometrically calibrated and corrected for atmospheric effects. This paper presents an atmospheric correction algorithm for FY3/MERSI in the visible to near-infrared band over the land. Previous operational correction schemes have assumed a Lambertian surface. A new atmospheric correction algorithm is developed to take into account the directional properties of the observed surface by a kernel-based Bi-directional Reflectance Distribution Function (BRDF) model. This algorithm is applied to remote sensing data from FY3/MERSI and compared with Moderate Resolution Imaging Spectro radiometer (MODIS) surface reflectance products (MOD09GA). It is found in the study that the relative accuracy of data, obtained with these two devices, was consistent with the acceptable overall accuracy of 73%. Furthermore, spatial resolution of MERSI is superior as compared to that of MODIS. Therefore, FY-3/MERSI can serve a reliable and new data source for quantifying global environmental change.

Guang, Jie; Xue, Yong; Liang, Shunlin; Liu, Qiang; Mei, LinLu; Shi, Yuanli

2014-05-01

101

High-resolution studies of the structure of the solar atmosphere using a new imaging algorithm  

NASA Astrophysics Data System (ADS)

The results of the application of a new image restoration algorithm developed by Ayers and Dainty (1988) to the multiwavelength EUV/Skylab observations of the solar atmosphere are presented. The application of the algorithm makes it possible to reach a resolution better than 5 arcsec, and thus study the structure of the quiet sun on that spatial scale. The results show evidence for discrete looplike structures in the network boundary, 5-10 arcsec in size, at temperatures of 100,000 K.

Karovska, Margarita; Habbal, Shadia Rifai

1991-04-01

102

Development of an Aircraft Approach and Departure Atmospheric Profile Generation Algorithm  

NASA Technical Reports Server (NTRS)

In support of NASA Virtual Airspace Modeling and Simulation (VAMS) project, an effort was initiated to develop and test techniques for extracting meteorological data from landing and departing aircraft, and for building altitude based profiles for key meteorological parameters from these data. The generated atmospheric profiles will be used as inputs to NASA s Aircraft Vortex Spacing System (AVOLSS) Prediction Algorithm (APA) for benefits and trade analysis. A Wake Vortex Advisory System (WakeVAS) is being developed to apply weather and wake prediction and sensing technologies with procedures to reduce current wake separation criteria when safe and appropriate to increase airport operational efficiency. The purpose of this report is to document the initial theory and design of the Aircraft Approach Departure Atmospheric Profile Generation Algorithm.

Buck, Bill K.; Velotas, Steven G.; Rutishauser, David K. (Technical Monitor)

2004-01-01

103

Retrieving Atmospheric Temperature and Moisture Profiles from NPP CRIS/ATMS Sensors Using Crimss EDR Algorithm  

NASA Technical Reports Server (NTRS)

The Joint Polar Satellite System (JPSS) is a U.S. National Oceanic and Atmospheric Administration (NOAA) mission in collaboration with the U.S. National Aeronautical Space Administration (NASA) and international partners. The NPP Cross-track Infrared Microwave Sounding Suite (CrIMSS) consists of the infrared (IR) Crosstrack Infrared Sounder (CrIS) and the microwave (MW) Advanced Technology Microwave Sounder (ATMS). The CrIS instrument is hyperspectral interferometer, which measures high spectral and spatial resolution upwelling infrared radiances. The ATMS is a 22-channel radiometer similar to Advanced Microwave Sounding Units (AMSU) A and B. It measures top of atmosphere MW upwelling radiation and provides capability of sounding below clouds. The CrIMSS Environmental Data Record (EDR) algorithm provides three EDRs, namely the atmospheric vertical temperature, moisture and pressure profiles (AVTP, AVMP and AVPP, respectively), with the lower tropospheric AVTP and the AVMP being JPSS Key Performance Parameters (KPPs). The operational CrIMSS EDR an algorithm was originally designed to run on large IBM computers with dedicated data management subsystem (DMS). We have ported the operational code to simple Linux systems by replacing DMS with appropriate interfaces. We also changed the interface of the operational code so that we can read data from both the CrIMSS science code and the operational code and be able to compare lookup tables, parameter files, and output results. The detail of the CrIMSS EDR algorithm is described in reference [1]. We will present results of testing the CrIMSS EDR operational algorithm using proxy data generated from the Infrared Atmospheric Sounding Interferometer (IASI) satellite data and from the NPP CrIS/ATMS data.

Liu, X.; Kizer, S.; Barnet, C.; Dvakarla, M.; Zhou, D. K.; Larar, A. M.

2012-01-01

104

Adaptation of a Hyperspectral Atmospheric Correction Algorithm for Multi-spectral Ocean Color Data in Coastal Waters. Chapter 3  

NASA Technical Reports Server (NTRS)

This SIMBIOS contract supports several activities over its three-year time-span. These include certain computational aspects of atmospheric correction, including the modification of our hyperspectral atmospheric correction algorithm Tafkaa for various multi-spectral instruments, such as SeaWiFS, MODIS, and GLI. Additionally, since absorbing aerosols are becoming common in many coastal areas, we are making the model calculations to incorporate various absorbing aerosol models into tables used by our Tafkaa atmospheric correction algorithm. Finally, we have developed the algorithms to use MODIS data to characterize thin cirrus effects on aerosol retrieval.

Gao, Bo-Cai; Montes, Marcos J.; Davis, Curtiss O.

2003-01-01

105

Algorithm for Simulating Atmospheric Turbulence and Aeroelastic Effects on Simulator Motion Systems  

NASA Technical Reports Server (NTRS)

Atmospheric turbulence produces high frequency accelerations in aircraft, typically greater than the response to pilot input. Motion system equipped flight simulators must present cues representative of the aircraft response to turbulence in order to maintain the integrity of the simulation. Currently, turbulence motion cueing produced by flight simulator motion systems has been less than satisfactory because the turbulence profiles have been attenuated by the motion cueing algorithms. This report presents a new turbulence motion cueing algorithm, referred to as the augmented turbulence channel. Like the previous turbulence algorithms, the output of the channel only augments the vertical degree of freedom of motion. This algorithm employs a parallel aircraft model and an optional high bandwidth cueing filter. Simulation of aeroelastic effects is also an area where frequency content must be preserved by the cueing algorithm. The current aeroelastic implementation uses a similar secondary channel that supplements the primary motion cue. Two studies were conducted using the NASA Langley Visual Motion Simulator and Cockpit Motion Facility to evaluate the effect of the turbulence channel and aeroelastic model on pilot control input. Results indicate that the pilot is better correlated with the aircraft response, when the augmented channel is in place.

Ercole, Anthony V.; Cardullo, Frank M.; Kelly, Lon C.; Houck, Jacob A.

2012-01-01

106

The Computational Complexity, Parallel Scalability, and Performance of Atmospheric Data Assimilation Algorithms  

NASA Technical Reports Server (NTRS)

The computational complexity of algorithms for Four Dimensional Data Assimilation (4DDA) at NASA's Data Assimilation Office (DAO) is discussed. In 4DDA, observations are assimilated with the output of a dynamical model to generate best-estimates of the states of the system. It is thus a mapping problem, whereby scattered observations are converted into regular accurate maps of wind, temperature, moisture and other variables. The DAO is developing and using 4DDA algorithms that provide these datasets, or analyses, in support of Earth System Science research. Two large-scale algorithms are discussed. The first approach, the Goddard Earth Observing System Data Assimilation System (GEOS DAS), uses an atmospheric general circulation model (GCM) and an observation-space based analysis system, the Physical-space Statistical Analysis System (PSAS). GEOS DAS is very similar to global meteorological weather forecasting data assimilation systems, but is used at NASA for climate research. Systems of this size typically run at between 1 and 20 gigaflop/s. The second approach, the Kalman filter, uses a more consistent algorithm to determine the forecast error covariance matrix than does GEOS DAS. For atmospheric assimilation, the gridded dynamical fields typically have More than 10(exp 6) variables, therefore the full error covariance matrix may be in excess of a teraword. For the Kalman filter this problem can easily scale to petaflop/s proportions. We discuss the computational complexity of GEOS DAS and our implementation of the Kalman filter. We also discuss and quantify some of the technical issues and limitations in developing efficient, in terms of wall clock time, and scalable parallel implementations of the algorithms.

Lyster, Peter M.; Guo, J.; Clune, T.; Larson, J. W.; Atlas, Robert (Technical Monitor)

2001-01-01

107

Atmospheric correction algorithms for ADEOS\\/OCTS ocean colar data: Performance comparison based on ship and buoy measurements  

Microsoft Academic Search

The paper aims at evaluating the performance of the atmospheric correction algorithm for the Ocean Color and Temperature Scanner (OCTS) visible band data used at Earth Observation Center (EOC) of National Space Development Agency of Japan (NASDA). The algorithm uses 10 candidate aerosol models including “Asian dust model” introduced in consideration of the unique feature of aerosols over the east

H. Fukushima; M. Toratani; S. Yamamiya; Y. Mitomi

2000-01-01

108

A procedure for testing the quality of LANDSAT atmospheric correction algorithms  

NASA Technical Reports Server (NTRS)

There are two basic methods for testing the quality of an algorithm to minimize atmospheric effects on LANDSAT imagery: (1) test the results a posteriori, using ground truth or control points; (2) use a method based on image data plus estimation of additional ground and/or atmospheric parameters. A procedure based on the second method is described. In order to select the parameters, initially the image contrast is examined for a series of parameter combinations. The contrast improves for better corrections. In addition the correlation coefficient between two subimages, taken at different times, of the same scene is used for parameter's selection. The regions to be correlated should not have changed considerably in time. A few examples using this proposed procedure are presented.

Dias, L. A. V. (principal investigator); Vijaykumar, N. L.; Neto, G. C.

1982-01-01

109

High-performance fringe-tracking algorithms utilizing statistical models of atmospheric turbulence  

NASA Astrophysics Data System (ADS)

This paper introduces a new method for tracking fringes in ground-based optical stellar interferometry at low light levels under conditions of variations in OPD due to atmospheric turbulence. Like the group delay tracking (GDT), the method involves processing of short-exposure frames of channeled spectra when operating in a fringe tracking mode. But while the GDT is based on the fast Fourier transform, the proposed method is base don the formalism of optical statistical decisions and Markov chain framework. The corresponding algorithm, doubled DBA makes it possible to utilize all available information about the problem's nonlinearities and statistics such as Poisson photon arrivals, Gaussian readout noise, the statistics of atmospheric turbulence. Simulation results show that the DBA tracks stars up to two bolometric magnitudes dimmer than is possible with the GDT.

Padilla, Carlos E.; Karlov, Valeri I.; Matson, Leslie E.; Soosaar, Keto; ten Brummelaar, Theo A.

1998-07-01

110

The Algorithm Theoretical Basis Document for the GLAS Atmospheric Data Products  

NASA Technical Reports Server (NTRS)

The purpose of this document is to present a detailed description of the algorithm theoretical basis for each of the GLAS data products. This will be the final version of this document. The algorithms were initially designed and written based on the authors prior experience with high altitude lidar data on systems such as the Cloud and Aerosol Lidar System (CALS) and the Cloud Physics Lidar (CPL), both of which fly on the NASA ER-2 high altitude aircraft. These lidar systems have been employed in many field experiments around the world and algorithms have been developed to analyze these data for a number of atmospheric parameters. CALS data have been analyzed for cloud top height, thin cloud optical depth, cirrus cloud emittance (Spinhirne and Hart, 1990) and boundary layer depth (Palm and Spinhirne, 1987, 1998). The successor to CALS, the CPL, has also been extensively deployed in field missions since 2000 including the validation of GLAS and CALIPSO. The CALS and early CPL data sets also served as the basis for the construction of simulated GLAS data sets which were then used to develop and test the GLAS analysis algorithms.

Palm, Stephen P.; Hart, William D.; Hlavka, Dennis L.; Welton, Ellsworth J.; Spinhirne, James D.

2012-01-01

111

Global Soundings of the Atmosphere from ATOVS Measurements: The Algorithm and Validation.  

NASA Astrophysics Data System (ADS)

The International Advanced Television and Infrared Observation Satellite Operational Vertical Sounder (ATOVS) Processing Package (IAPP) has been developed to retrieve the atmospheric temperature profile, moisture profile, atmospheric total ozone, and other parameters in both clear and cloudy atmospheres from the ATOVS measurements. The algorithm that retrieves these parameters contains four steps: 1) cloud detection and removal, 2) bias adjustment for ATOVS measurements, 3) regression retrieval processes, and 4) a nonlinear iterative physical retrieval. Nine (3 × 3) adjacent High-Resolution Infrared Sounder (HIRS)/3 spot observations, together with Advanced Microwave Sounding Unit-A observations remapped to the HIRS/3 resolution, are used to retrieve the temperature profile, moisture profile, surface skin temperature, total atmospheric ozone and microwave surface emissivity, and so on. ATOVS profile retrieval results are evaluated by root-mean-square differences with respect to radiosonde observation profiles. The accuracy of the retrieval is about 2.0 K for the temperature at 1-km vertical resolution and 3.0-6.0 K for the dewpoint temperature at 2-km vertical resolution in this study. The IAPP is now available to users worldwide for processing the real-time ATOVS data.

Li, Jun; Wolf, Walter W.; Menzel, W. Paul; Zhang, Wenjian; Huang, Hung-Lung; Achtor, Thomas H.

2000-08-01

112

ACTS Rain Fade Compensation  

NASA Technical Reports Server (NTRS)

Performance status of the Adaptive Rain Fade Compensation includes: (1) The rain fade protocol is functional detecting fades, providing an additional 10 dB of margin and seamless transitions to and from coded operation; (2) The stabilization of the link margins and the optimization of rain fade decision thresholds has resulted in improved BER performance; (3) Characterization of the fade compensation algorithm is ongoing.

Coney, Thom A.

1996-01-01

113

An Atmospheric Correction Algorithm Over Coastal and Inland Waters For The Siscal Project  

NASA Astrophysics Data System (ADS)

SISCAL is a pan-European project dedicated to develop facilities to provide end users with customize and easy-to-use Earth Observation data for environmental monitoring of European coastal areas, lakes and open oceans. The main task will be to create a software processor providing near-real-time information on the aquatic ecosystems, derived from satellite data. The Université du Littoral in collaboration with the HY- GEOS Firm develop an atmospheric algorithm which will be implemented in the pro- cessor . The algorithm corrects the various SISCAL Ocean Colour sensors from atmo- spheric effects over waters and inland waters. It processes SeaWiFS, MODIS, MERIS, GLI Top of Atmosphere radiances that comes from Level 1B images and provides spectral marine reflectance under the water surface. This is done for all bands that are near SeaWiFS bands. Over waters we apply a correction for scattering effects similar to SeaWiFS and referenced here as a Gordon and Wang Scheme. Over land, the algo- rithm developed by Ramon, Vidot and Santer has been adapted. The aerosol retrieval is made over Dense Dark Vegetation pixel. Besides these main outputs some flags and quality indices are given in order to assess the product quality and the product environment.

Dilligeard, E.; Ramon, D.; Vidot, J.; Santer, R.

114

Simulation of atmospheric turbulence for a qualitative evaluation of image restoration algorithms with motion detection  

NASA Astrophysics Data System (ADS)

Remote sensing applications are generally concerned with observing objects over long distances. When imaging over long horizontal paths, image resolution is limited by the atmosphere rather than by the design and quality of the optical system being used. Atmospheric turbulence can cause quite severe image degradation, the foremost effects being blurring and image motion. Recently, interest in image processing solutions has been rising, not least of all because of the comparatively low cost of computational power, and also due to an increasing number of imaging applications that require the correction of extended objects rather than point-like sources only. At present, the majority of these image processing methods aim exclusively at the restoration of static scenes. But there is a growing interest in enhancing turbulence mitigation methods to include moving objects as well. However, an unbiased qualitative evaluation of the respective restoration results proves difficult if little or no additional information on the "true image" is available. Therefore, in this paper synthetic ground truth data containing moving vehicles were generated and a first-order atmospheric propagation simulation was implemented in order to test such algorithms. The simulation employs only one phase screen and assumes isoplanatic conditions (only global image motion) while scintillation effects are ignored.

Huebner, Claudia S.; Gladysz, Szymon

2012-10-01

115

A SAR image-formation algorithm that compensates for the spatially-variant effects of antenna motion  

SciTech Connect

A synthetic aperture radar (SAR) obtains azimuth resolution by combining data from a number of points along a specified path. Uncompensated antenna motion that deviates significantly from the desired path produces spatially-variant errors in the output image. The algorithm presented in this paper corrects many of these motion-related errors. In this respect, it is similar to time-domain convolution, but it is more computationally efficient. The algorithm uses overlapped subapertures in a three-step image-formation process: coarse-resolution azimuth processing, fine-resolution range processing, and fine-resolution azimuth processing. Range migration is corrected after the first stage, based on coarse azimuth position. Prior to the final azimuth-compression step, data coordinates, are determined to fine resolution in range and coarse resolution in azimuth. This coordinate information is combined with measured motion data to generate a phase correction that removes spatially-variant errors. The algorithm is well-suited for real-time applications, particularly where large flight-path deviations must be tolerated.

Burns, B.L.; Cordaro, J.T.

1994-03-01

116

Algorithm development for intensity modulated continuous wave laser absorption spectrometry in atmospheric CO2 measurements  

NASA Astrophysics Data System (ADS)

Currently, NASA Langley Research Center (LaRC) and ITT are jointly developing algorithms for demonstration of range discrimination using ITT's laser absorption spectrometer (LAS), which is being evaluated for the future NASA Active Sensing of CO2 Emissions during Nights, Days, and Seasons (ASCENDS) mission. The objective of this Decadal Survey mission is to measure atmospheric column CO2 mixing ratios (XCO2) for improved determination of atmospheric carbon sources and sinks. Intensity Modulated Continuous Wave (IM-CW) techniques are used in this LAS approach. The LAS is designed to simultaneously measure CO2 and O2 columns, and these measurements are used to determine the required XCO2 column. The LAS measurements are enabled by the multi-channel operation of the instrument at 1.57 and 1.26-um for CO2 and O2, respectively. The algorithm development for the IM-CW techniques of the multi-channel LAS is focused on addressing key retrieval issues such as surface signal detection, thin cloud and/or aerosol layer rejection, vertical atmospheric range resolution, and optimizing the size of the measurement footprint. With these considerations, the modulation algorithm needs to maintain high enough signal-to-noise ratio (SNR) so that the mission scientific goals can be reached. A basic selection of the modulation algorithms that make XCO2 measurement and thin cloud rejection possible is the stepped frequency modulation scheme and a similar scheme of swept sine modulation. The differences between these two schemes for thin cloud rejection are small, assuming the proper selection of parameters is made. The stepped frequency approach is only a quantified version of swept sine method for the frequencies used. Swept sine scheme is a very common modulation technique for range discrimination, while the consideration of the stepped frequency scheme is based on the history of the rolling-tone modulation used in the instrument in previous successful column CO2 measurements. The stepped frequency approach provides minimal risk in the technology development for thin cloud rejection. To obtain a specified vertical resolution, a requisite bandwidth is needed for the stepped frequency/swept sine schemes. The requirements of horizontal resolution and SNR are obtained through the integration time of either stepped frequency or swept sine approaches. Based on these considerations and instrument hardware limitations, the frequencies for the intensity modulation approaches were selected and implemented in the current LAS. The LAS has six wavelength channels: 3 for CO2, 2 for O2 and 1 for background measurements. The frequencies of the stepped frequency algorithm vary from 200 to about 500 KHz with 100-KHz bandwidth in each individual channel. Reduction of potential spectral interference is also considered in the selection of the frequencies. Details of the development of the IM-CW algorithms and results from flight testing of these techniques during the spring and summer of 2011 are discussed in this paper.

Lin, B.; Harrison, F. W.; Browell, E. V.; Dobler, J. T.; Bryant, R. B.

2011-12-01

117

An atmospheric correction algorithm for remote identification of non-Lambertian surfaces and its range of validity  

SciTech Connect

The usefulness of remotely sensed surface data depends on the ability to correct for atmospheric pertubations on the image. An atmospheric correction algorithm has been proposed which removes atmospheric pertubations from off-nadir measured radiances at the top of the atmosphere in the visible and near-infrared wavelength region. The ability of the model to reproduce radiance distributions at the surface from radiances at the top of the atmosphere is tested and found to be better than 15%. The correction formalism requires as minimum information the total optical depth of the atmosphere and the surface albedo. In this study the accuracy of the model to assumptions about the aerosol phase function, the single-scattering albedo and the vertical profile of the optical depth is also tested.

Gratzki, A.; Gerstl, S.A.W.

1987-02-20

118

Technical Note: Modification of the standard gain correction algorithm to compensate for the number of used reference flat frames in detector performance studies  

SciTech Connect

Purpose: The x-ray performance evaluation of digital x-ray detectors is based on the calculation of the modulation transfer function (MTF), the noise power spectrum (NPS), and the resultant detective quantum efficiency (DQE). The flat images used for the extraction of the NPS should not contain any fixed pattern noise (FPN) to avoid contamination from nonstochastic processes. The ''gold standard'' method used for the reduction of the FPN (i.e., the different gain between pixels) in linear x-ray detectors is based on normalization with an average reference flat-field. However, the noise in the corrected image depends on the number of flat frames used for the average flat image. The aim of this study is to modify the standard gain correction algorithm to make it independent on the used reference flat frames. Methods: Many publications suggest the use of 10-16 reference flat frames, while other studies use higher numbers (e.g., 48 frames) to reduce the propagated noise from the average flat image. This study quantifies experimentally the effect of the number of used reference flat frames on the NPS and DQE values and appropriately modifies the gain correction algorithm to compensate for this effect. Results: It is shown that using the suggested gain correction algorithm a minimum number of reference flat frames (i.e., down to one frame) can be used to eliminate the FPN from the raw flat image. This saves computer memory and time during the x-ray performance evaluation. Conclusions: The authors show that the method presented in the study (a) leads to the maximum DQE value that one would have by using the conventional method and very large number of frames and (b) has been compared to an independent gain correction method based on the subtraction of flat-field images, leading to identical DQE values. They believe this provides robust validation of the proposed method.

Konstantinidis, Anastasios C.; Olivo, Alessandro; Speller, Robert D. [Department of Medical Physics and Bioengineering, University College London, London WC1E 6BT (United Kingdom)

2011-12-15

119

Simulation of atmospheric turbulence effects and mitigation algorithms on stand-off automatic facial recognition  

NASA Astrophysics Data System (ADS)

Stand-off base and force protection surveillance measures primarily rely on electro-optic and thermal imaging technology. Atmospheric turbulence causes blur, distortion and intensity fluctuations that can severely degrade the image quality of these systems. This work explores the effects of turbulence image degradation on the performance of automatic facial recognition software and also looks at the potential benefit of turbulence mitigation algorithms. The goal of this work is to understand the feasibility of long-range facial recognition in degraded imaging conditions. In order to create a large enough database to match against, simulated imagery of different ranges and turbulence conditions were created using a horizontal view turbulence simulator and a subset of the Facial Recognition Technology (FERET) database. The simulated turbulence degraded imagery was then processed with facial recognition software and the results are compared against those from the pristine image set. Finally, the performance of the facial recognition software with turbulence mitigated imagery is also presented.

Leonard, Kevin R.; Howe, Jonathan; Oxford, David E.

2012-10-01

120

Compensation for the Atmosphere in Radiance Measured by the Airborne Visible/Infrared Imaging Spectrometer and Applications to an Advanced Land Remote Sensing System  

NASA Technical Reports Server (NTRS)

The Airborne Visible/Infrared Imaging Spectrometer measures spatial images of the total upwelling spectral radiance from 400 to 2500 nm through 10 nm spectral channels. Quantitative research and application objectives for surface investigations require conversion of the measured radiance to surface reflectance or surface leaving radiance. To calculate apparent surface reflectance an estimation of atmospheric water vapor abundance, cirrus cloud effects, surface pressure elevation and aerosol optical depth is also required. Algorithms for the estimation of these parameters from the AVIRIS data themselves are described. Based upon these determined atmospheric parameters we show an example of the calculation of apparent surface reflectance from the AVIRIS-measured radiance using a radiative transfer code.

Green, R. O.; Conel, J. E.

1993-01-01

121

Tomography of the Earth's atmosphere by the spaceborne occultation radiometer ORA: Spatial inversion algorithm  

NASA Astrophysics Data System (ADS)

The occultation radiometer ORA was designed to perform measurements of O3, NO2, H2O, number density, and aerosol extinction altitude profiles in the Earth's atmosphere through the occultation method viewing the full solar disk. The experiment was mounted on the EURECA satellite and measured the relative transmission of light during about 7000 orbital sunsets and sunrises from August 11, 1992, to May 13, 1993. The spatial inversion algorithm developed to retrieve the total extinction altitude profiles from these data is described here. It is shown that the signal measured by an instrument having a large field of view can be successfully processed to give a much better altitude resolution than the one related to the angular size of the Sun. The main difficulties concern the inclusion of all refractive effects, the application of a new inversion scheme and its associated mapping strategy to refine the aerosol layer detection. The algorithm applies to fully nonlinear occultation experiments requiring global and nonheuristic inversion schemes.

Fussen, Didier; Arijs, Etienne; Leclere, Fabienne; Nevejans, Dennis; Bingen, Christine

1997-02-01

122

An algorithm for variational data assimilation of contact concentration measurements for atmospheric chemistry models  

NASA Astrophysics Data System (ADS)

Contact concentration measurement data assimilation problem is considered for convection-diffusion-reaction models originating from the atmospheric chemistry study. High dimensionality of models imposes strict requirements on the computational efficiency of the algorithms. Data assimilation is carried out within the variation approach on a single time step of the approximated model. A control function is introduced into the source term of the model to provide flexibility for data assimilation. This function is evaluated as the minimum of the target functional that connects its norm to a misfit between measured and model-simulated data. In the case mathematical model acts as a natural Tikhonov regularizer for the ill-posed measurement data inversion problem. This provides flow-dependent and physically-plausible structure of the resulting analysis and reduces a need to calculate model error covariance matrices that are sought within conventional approach to data assimilation. The advantage comes at the cost of the adjoint problem solution. This issue is solved within the frameworks of splitting-based realization of the basic convection-diffusion-reaction model. The model is split with respect to physical processes and spatial variables. A contact measurement data is assimilated on each one-dimensional convection-diffusion splitting stage. In this case a computationally-efficient direct scheme for both direct and adjoint problem solution can be constructed based on the matrix sweep method. Data assimilation (or regularization) parameter that regulates ratio between model and data in the resulting analysis is obtained with Morozov discrepancy principle. For the proper performance the algorithm takes measurement noise estimation. In the case of Gaussian errors the probability that the used Chi-squared-based estimate is the upper one acts as the assimilation parameter. A solution obtained can be used as the initial guess for data assimilation algorithms that assimilate outside the splitting stages and involve iterations. Splitting method stage that is responsible for chemical transformation processes is realized with the explicit discrete-analytical scheme with respect to time. The scheme is based on analytical extraction of the exponential terms from the solution. This provides unconditional positive sign for the evaluated concentrations. Splitting-based structure of the algorithm provides means for efficient parallel realization. The work is partially supported by the Programs No 4 of Presidium RAS and No 3 of Mathematical Department of RAS, by RFBR project 11-01-00187 and Integrating projects of SD RAS No 8 and 35. Our studies are in the line with the goals of COST Action ES1004.

Penenko, Alexey; Penenko, Vladimir

2014-05-01

123

Assessment of Polarization Effect on Efficiency of Levenberg-Marquardt Algorithm in Case of Thin Atmosphere Over Black Surface  

NASA Technical Reports Server (NTRS)

The Levenberg-Marquardt algorithm [1, 2] provides a numerical iterative solution to the problem of minimization of a function over a space of its parameters. In our work, the Levenberg-Marquardt algorithm retrieves optical parameters of a thin (single scattering) plane parallel atmosphere irradiated by collimated infinitely wide monochromatic beam of light. Black ground surface is assumed. Computational accuracy, sensitivity to the initial guess and the presence of noise in the signal, and other properties of the algorithm are investigated in scalar (using intensity only) and vector (including polarization) modes. We consider an atmosphere that contains a mixture of coarse and fine fractions. Following [3], the fractions are simulated using Henyey-Greenstein model. Though not realistic, this assumption is very convenient for tests [4, p.354]. In our case it yields analytical evaluation of Jacobian matrix. Assuming the MISR geometry of observation [5] as an example, the average scattering cosines and the ratio of coarse and fine fractions, the atmosphere optical depth, and the single scattering albedo, are the five parameters to be determined numerically. In our implementation of the algorithm, the system of five linear equations is solved using the fast Cramer s rule [6]. A simple subroutine developed by the authors, makes the algorithm independent from external libraries. All Fortran 90/95 codes discussed in the presentation will be available immediately after the meeting from sergey.v.korkin@nasa.gov by request.

Korkin, S.; Lyapustin, A.

2012-01-01

124

Network compensation for missing sensors  

NASA Technical Reports Server (NTRS)

A network learning translation invariance algorithm to compute interpolation functions is presented. This algorithm with one fixed receptive field can construct a linear transformation compensating for gain changes, sensor position jitter, and sensor loss when there are enough remaining sensors to adequately sample the input images. However, when the images are undersampled and complete compensation is not possible, the algorithm need to be modified. For moderate sensor losses, the algorithm works if the transformation weight adjustment is restricted to the weights to output units affected by the loss.

Ahumada, Albert J., Jr.; Mulligan, Jeffrey B.

1991-01-01

125

Compensation Chemistry  

ERIC Educational Resources Information Center

Congress, the news media, and the Internal Revenue Service (IRS) continue to cast a wary eye on the compensation of nonprofit leaders. Hence, any college or university board that falls short of IRS expectations in its procedures for setting the president's compensation is putting the president, other senior officials, and board members at…

Roady, Celia

2008-01-01

126

Simulation of rice plant temperatures using the UC Davis Advanced Canopy-Atmosphere-Soil Algorithm (ACASA)  

NASA Astrophysics Data System (ADS)

The thermal environment in the plant canopy affects plants’ growth processes such as flowering and ripening. High temperatures often cause grain sterility and poor filling in serial crops, and reduce their production in tropical and temperate regions. With global warming predicted, these effects have become a major concern worldwide. In this study, we observed the plant body temperature profiles for the rice canopy and simulate them using a higher-order closure micrometeorological model to understand the relationship between plant temperatures and atmospheric condition. Experiments were conducted in rice paddy during 2007-summer season under warm temperate climate in Japan. Leaf temperatures at three different height (0.3, 0.5, 0.7m) and panicle temperatures at 0.9m were measured using fine-thermocouples. The UC Davis Advanced Canopy-Atmosphere-Soil Algorithm (ACASA) was used to calculate plant body temperature profiles in the canopy. ACASA is based on the radiation transfer, higher-order closure of turbulent equations for mass and heat exchange, and detailed plant physiological parameterization for the canopy-atmosphere-soil system. Water temperature was almost constant of 21-23 C throughout the summer because of continuous irrigation. Therefore, larger difference between air temperature at 2 m and water temperature was found on daytime. Observed leaf/panicle temperature was lower near the water surface and higher on upper layer in the canopy. Difference of temperatures between 0.3 m and 0.9 m was around 3-4 C for daytime, and around 1-2 C for nighttime. Calculated result of ACASA recreated these trends of plant temperature profile sufficiently. However, the relationship between plant and air temperature in the canopy was a little different from observed, i.e. observed leaf/panicle temperature were almost the same as air temperature, in contrast the simulated air temperature was 0.5-1.5 C higher than plant temperatures for the both of daytime and night time. This could be mainly due to the overestimation of latent heat flux in the day, and longwave cooling at night, although the precise reasons are unclear. ACASA can calculate the plant temperatures from given boundary condition, so that it is expected that it will elucidate how canopy structure (mainly leaf area index) affects thermal conditions in the canopy.

Maruyama, A.; Pyles, D.; Paw U, K.

2009-12-01

127

An Adaptive Numeric Predictor-corrector Guidance Algorithm for Atmospheric Entry Vehicles. M.S. Thesis - MIT, Cambridge  

NASA Technical Reports Server (NTRS)

An adaptive numeric predictor-corrector guidance is developed for atmospheric entry vehicles which utilize lift to achieve maximum footprint capability. Applicability of the guidance design to vehicles with a wide range of performance capabilities is desired so as to reduce the need for algorithm redesign with each new vehicle. Adaptability is desired to minimize mission-specific analysis and planning. The guidance algorithm motivation and design are presented. Performance is assessed for application of the algorithm to the NASA Entry Research Vehicle (ERV). The dispersions the guidance must be designed to handle are presented. The achievable operational footprint for expected worst-case dispersions is presented. The algorithm performs excellently for the expected dispersions and captures most of the achievable footprint.

Spratlin, Kenneth Milton

1987-01-01

128

Atmospheric Correction Algorithms for ADEOS/OCTS Ocean Color Data: Performance Comparison Based on Ship and Buoy Measurements  

NASA Astrophysics Data System (ADS)

The paper aims at evaluating the performance of the atmospheric correction algorithm for the Ocean Color and Temperature Scanner (OCTS) visible band data used at Earth Observation Center (EOC) of National Space Development Agency of Japan (NASDA). The algorithm uses 10 candidate aerosol models including ``Asian dust model'' introduced in consideration of the unique feature of aerosols over the east Asian waters. Based on the observations at 670 and 865 nm bands where the reflectance of the water body can be discarded, the algorithm selects a pair of aerosol models that accounts best for the observed spectral reflectances to synthesize the aerosol reflectance in other bands. Three different schemes of the aerosol model selection are presented and their anticipated estimation error in terms of the retrieved water reflectance at 443 nm is analyzed. The results of our numerical simulation show that the standard deviation of the estimation error of the ``weighted average with iteration'' scheme is mostly within permissible level of +/-0.002 in-water reflectance at 443 nm, reducing the error by roughly a factor of 2 compared to the other schemes. The paper also evaluates the performance of the algorithm by comparing the satellite estimates of ``water-leaving radiance'' nLw and chlorophyll-a concentration with selected buoy- and ship-measured data. In comparison with the old ``CZCS-type'' atmospheric correction, the OCTS algorithm records factor 2-3 less error in estimating nLw

Fukushima, H.; Toratani, M.; Yamamiya, S.; Mitomi, Y.

129

Atmospheric Motion Vectors Derived via a New Nested Tracking Algorithm Developed for the GOES-R Advanced Baseline Imager (ABI)  

NASA Astrophysics Data System (ADS)

A new Atmospheric Motion Vector (AMV) nested tracking algorithm has been developed for the Advanced Baseline Imager (ABI) to be flown on NOAA's future GOES-R satellite. The algorithm has been designed to capture the dominant motion in each target scene from a family of local motion vectors derived for each target scene. Capturing this dominant motion is achieved through use of a two-dimensional clustering algorithm that segregates local displacements into clusters. The dominant motion is taken to be the average of the local displacements of points belonging to the largest cluster. This approach prevents excessive averaging of motion that may be occurring at multiple levels or at different scales that can lead to a slow speed bias and a poor quality AMV. A representative height is assigned to the dominant motion vector through exclusive use of cloud heights from pixels belonging to the largest cluster. This algorithm has been demonstrated to significantly improve the slow speed bias typically observed in AMVs derived from satellite imagery. Meteosat SEVERI imagery is serving as an important GOES-R ABI proxy data source for the development, testing, and validation of the GOES-R AMV algorithms given its similarities (spectral coverage, pixel resolution, and scanning rate) and performance (spectral noise, navigation/registration) to the future GOES-R ABI. The new GOES-R AMV algorithm is also being applied to the instrumentation on the current operational GOES series of satellites and is expected to replace the heritage AMV algorithm being used in NESDIS operations today. Plans at NOAA/NESDIS also include using the new GOES-R AMV algorithm to generate AMVs from the future VIIRS instrument on the NPP satellite. Details of the GOES-R ABI AMV algorithm and the validation results will be presented and discussed.

Daniels, J.; Bresky, W.; Wanzong, S.; Velden, C.

2012-12-01

130

An algorithm for retrieval of ocean surface and atmospheric parameters from the observations of the scanning multichannel microwave radiometer (SMMR)  

NASA Technical Reports Server (NTRS)

A formalism was developed which can be used to interpret the data in terms of sea surface temperature, sea surface wind speed, and the atmospheric overburden of water vapor and liquid water. It was shown with reasonable instrumental performance assumptions, these parameters could be derived to useful accuracies. Although the algorithms were not derived for use in rain, it is shown that, at least, token rain rates can be tolerated without invalidating the retrieved geophysical parameters.

Wilheit, T. T.; Chang, A. T. C.

1979-01-01

131

Assessment of Polarization Effect on Efficiency of Levenberg-Marquardt Algorithm in Case of Thin Atmosphere over Black Surface  

NASA Astrophysics Data System (ADS)

The Levenberg-Marquardt algorithm [1, 2] provides a numerical iterative solution to the problem of minimization of a function over a space of its parameters. In our work, the Levenberg-Marquardt algorithm retrieves optical parameters of a thin (single scattering) plane parallel atmosphere irradiated by collimated infinitely wide monochromatic beam of light. Black ground surface is assumed. Computational accuracy, sensitivity to the initial guess and the presence of noise in the signal, and other properties of the algorithm are investigated in scalar (using intensity only) and vector (including polarization) modes. We consider an atmosphere that contains a mixture of coarse and fine fractions. Following [3], the fractions are simulated using Henyey-Greenstein model. Though not realistic, this assumption is very convenient for tests [4, p.354]. In our case it yields analytical evaluation of Jacobian matrix. Assuming the MISR geometry of observation [5] as an example, the average scattering cosines and the ratio of coarse and fine fractions, the atmosphere optical depth, and the single scattering albedo, are the five parameters to be determined numerically. In our implementation of the algorithm, the system of five linear equations is solved using the fast Cramer's rule [6]. A simple subroutine developed by the authors, makes the algorithm independent from external libraries. All Fortran 90/95 codes discussed in the presentation will be available immediately after the meeting from sergey.v.korkin@nasa.gov by request. [1]. Levenberg K, A method for the solution of certain non-linear problems in least squares, Quarterly of Applied Mathematics, 1944, V.2, P.164-168. [2]. Marquardt D, An algorithm for least-squares estimation of nonlinear parameters, Journal on Applied Mathematics, 1963, V.11, N.2, P.431-441. [3]. Hovenier JW, Multiple scattering of polarized light in planetary atmospheres. Astronomy and Astrophysics, 1971, V.13, P.7 - 29. [4]. Mishchenko MI, Travis LD, and Lacis AA, Multiple scattering of light by particles, Cambridge: University Press, 2006. [5]. http://www-misr.jpl.nasa.gov/Mission/misrInstrument/ [6]. Habgood K, Arel I, Revisiting Cramer's rule for solving dense linear systems, In: Proceedings of the 2010 Spring Simulation Multiconference, Paper No 82. ISBN: 978-1-4503-0069-8. DOI: 10.1145/1878537.1878623.

Korkin, S.; Lyapustin, A.

2012-12-01

132

Compensation conundrum.  

PubMed

Pressured by questions tabled in parliament that point to a lack of adequate enforcement of regulations, the DCG(I) has abruptly initiated action to ensure payment of compensation for trial-related injuries. While it is astounding that non-compliance to the existing regulations could have gone unnoticed by quality assurance staff as well as by the ethics committees and the regulator, for over six years, sudden enforcement of the regulation has thrown up issues and challenges that are difficult to resolve in the absence of an adequately debated and thought-through guidance. In implementing regulations for suo moto compensation, India is seeking to establish a practice not previously tested elsewhere in the world. There is no doubt that industry must support the idea of putting patients first, but procedural considerations in fixing causality and determining the quantum of compensation promise to raise questions of morality, ethics, and jurisprudence that will not be easy to answer. PMID:22347695

Mukherjee, Shoibal

2012-01-01

133

Compensation conundrum  

PubMed Central

Pressured by questions tabled in parliament that point to a lack of adequate enforcement of regulations, the DCG(I) has abruptly initiated action to ensure payment of compensation for trial-related injuries. While it is astounding that non-compliance to the existing regulations could have gone unnoticed by quality assurance staff as well as by the ethics committees and the regulator, for over six years, sudden enforcement of the regulation has thrown up issues and challenges that are difficult to resolve in the absence of an adequately debated and thought-through guidance. In implementing regulations for suo moto compensation, India is seeking to establish a practice not previously tested elsewhere in the world. There is no doubt that industry must support the idea of putting patients first, but procedural considerations in fixing causality and determining the quantum of compensation promise to raise questions of morality, ethics, and jurisprudence that will not be easy to answer.

Mukherjee, Shoibal

2012-01-01

134

Comparison of atmospheric correction algorithms for the Coastal Zone Color Scanner  

NASA Technical Reports Server (NTRS)

Before Nimbus-7 Costal Zone Color Scanner (CZC) data can be used to distinguish between coastal water types, methods must be developed for the removal of spatial variations in aerosol path radiance. These can dominate radiance measurements made by the satellite. An assessment is presently made of the ability of four different algorithms to quantitatively remove haze effects; each was adapted for the extraction of the required scene-dependent parameters during an initial pass through the data set The CZCS correction algorithms considered are (1) the Gordon (1981, 1983) algorithm; (2) the Smith and Wilson (1981) iterative algorityhm; (3) the pseudooptical depth method; and (4) the residual component algorithm.

Tanis, F. J.; Jain, S. C.

1984-01-01

135

A joint effort to deliver satellite retrieved atmospheric CO2 concentrations for surface flux inversions: the ensemble median algorithm EMMA  

NASA Astrophysics Data System (ADS)

We analyze an ensemble of seven XCO2 retrieval algorithms for SCIAMACHY (scanning imaging absorption spectrometer of atmospheric chartography) and GOSAT (greenhouse gases observing satellite). The ensemble spread can be interpreted as regional uncertainty and can help to identify locations for new TCCON (total carbon column observing network) validation sites. Additionally, we introduce the ensemble median algorithm EMMA combining individual soundings of the seven algorithms into one new data set. The ensemble takes advantage of the algorithms' independent developments. We find ensemble spreads being often < 1 ppm but rising up to 2 ppm especially in the tropics and East Asia. On the basis of gridded monthly averages, we compare EMMA and all individual algorithms with TCCON and CarbonTracker model results (potential outliers, north/south gradient, seasonal (peak-to-peak) amplitude, standard deviation of the difference). Our findings show that EMMA is a promising candidate for inverse modeling studies. Compared to CarbonTracker, the satellite retrievals find consistently larger north/south gradients (by 0.3-0.9 ppm) and seasonal amplitudes (by 1.5-2.0 ppm).

Reuter, M.; Bösch, H.; Bovensmann, H.; Bril, A.; Buchwitz, M.; Butz, A.; Burrows, J. P.; O'Dell, C. W.; Guerlet, S.; Hasekamp, O.; Heymann, J.; Kikuchi, N.; Oshchepkov, S.; Parker, R.; Pfeifer, S.; Schneising, O.; Yokota, T.; Yoshida, Y.

2013-02-01

136

Retrieval algorithm for atmospheric dust properties from Mars Global Surveyor Thermal Emission Spectrometer data during global dust storm 2001A  

NASA Astrophysics Data System (ADS)

We present a new parameter retrieval algorithm for Mars Global Surveyor Thermal Emission Spectrometer data. The algorithm uses Newtonian first-order sensitivity functions of the infrared spectrum in response to variations in physical parameters to fit a model spectrum to the data at 499, 1099, and 1301 cm -1. The algorithm iteratively fits the model spectrum to data to simultaneously retrieve dust extinction optical depth, effective radius, and surface temperature. There are several sources of uncertainty in the results. The assumed dust vertical distribution can introduce errors in retrieved optical depth of a few tens of percent. The assumed dust optical constants can introduce errors in both optical depth and effective radius, although the systematic nature of these errors will not affect retrieval of trends in these parameters. The algorithm does not include the spectral signature of water ice, and hence data needs to be filtered against this parameter before the algorithm is applied. The algorithm also needs sufficient dust spectral signature, and hence surface-to-atmosphere temperature contrast, to successfully retrieve the parameters. After the application of data filters the algorithm is both relatively accurate and very fast, successfully retrieving parameters, as well as meaningful parameter variability and trends from tens of thousands of individual spectra on a global scale (Elteto, A., Toon, O.B. [2010]. Icarus, this issue). Our results for optical depth compare well with TES archive values when corrected by the single scattering albedo. Our results are on average 1-4 K higher in surface temperatures from the TES archive values, with greater differences at higher optical depths. Our retrieval of dust effective radii compare well with the retrievals of Wolff and Clancy (Wolff, M.J., Clancy, R.T. [2003]. J. Geophys. Res. 108 (E9), 5097) for the corresponding data selections from the same orbits.

Elteto, Attila; Toon, Owen B.

2010-12-01

137

Atmospheric correction against algorithm for NOAA-AVHRR products: theory and application  

Microsoft Academic Search

Investigation of the effect of atmospheric constituents on NOAA Advanced Very High Resolution Radiometer (AVHRR) visible and near-infrared data is presented. The general remote sensing equation, including scattering, absorption, and bidirectional reflectance effects for the AVHRR solar bands, is described. The magnitude of the atmospheric effects for AVHRR solar bands with respect to their impact on the normalized difference vegetation

D. Tanre; Brent N. Holben; Yoram J. Kaufman

1992-01-01

138

Employee Compensation.  

ERIC Educational Resources Information Center

Presents an overview of selected literature about employee compensation. Highlights include the foundations of reward and recognition systems, incentive plans, problems with merit pay, a historical perspective on performance pay, evaluation criteria and processes, self-rating, job motivation and satisfaction, employee attitudes, collective…

Osif, Bonnie A.; Harwood, Richard L.

1995-01-01

139

Improved methodology for surface and atmospheric soundings, error estimates, and quality control procedures: the atmospheric infrared sounder science team version-6 retrieval algorithm  

NASA Astrophysics Data System (ADS)

The atmospheric infrared sounder (AIRS) science team version-6 AIRS/advanced microwave sounding unit (AMSU) retrieval algorithm is now operational at the Goddard Data and Information Services Center (DISC). AIRS version-6 level-2 products are generated near real time at the Goddard DISC and all level-2 and level-3 products are available starting from September 2002. Some of the significant improvements in retrieval methodology contained in the version-6 retrieval algorithm compared to that previously used in version-5 are described. In particular, the AIRS science team made major improvements with regard to the algorithms used to (1) derive surface skin temperature and surface spectral emissivity; (2) generate the initial state used to start the cloud clearing and retrieval procedures; and (3) derive error estimates and use them for quality control. Significant improvements have also been made in the generation of cloud parameters. In addition to the basic AIRS/AMSU mode, version-6 also operates in an AIRS only (AO) mode, which produces results almost as good as those of the full AIRS/AMSU mode. The improvements of some AIRS version-6 and version-6 AO products compared to those obtained using version-5 are also demonstrated.

Susskind, Joel; Blaisdell, John M.; Iredell, Lena

2014-01-01

140

Algorithm for Simulating Atmospheric Turbulence and Aeroelastic Effects on Simulator Motion Systems.  

National Technical Information Service (NTIS)

Atmospheric turbulence produces high frequency accelerations in aircraft, typically greater than the response to pilot input. Motion system equipped flight simulators must present cues representative of the aircraft response to turbulence in order to main...

A. V. Ercole F. M. Cardullo J. A. Houck L. C. Kelly

2012-01-01

141

Atmospheric Sensitivity to Spectral Top-of-Atmosphere Solar Irradiance Perturbations, Using MODTRAN-5 Radiative Transfer Algorithm  

NASA Astrophysics Data System (ADS)

The opportunity to insert state-of-the-art solar irradiance measurements and calculations, with subtle perturbations, into a narrow spectral resolution radiative transfer model has recently been facilitated through release of MODTRAN-5 (MOD5). The new solar data are from: (1) SORCE satellite measurements of solar variability over solar rotation cycle, & (2) ultra-narrow calculation of a new solar source irradiance, extending over the full MOD5 spectral range, from 0.2 um to far-IR. MODTRAN-5, MODerate resolution radiance and TRANsmittance code, has been developed collaboratively by Air Force Research Laboratory and Spectral Sciences, Inc., with history dating back to LOWTRAN. It includes approximations for all local thermodynamic equilibrium terms associated with molecular, cloud, aerosol and surface components for emission, scattering, and reflectance, including multiple scattering, refraction and a statistical implementation of Correlated-k averaging. The band model is based on 0.1 cm-1 (also 1.0, 5.0 and 15.0 cm-1 statistical binning for line centers within the interval, captured through an exact formulation of the full Voigt line shape. Spectroscopic parameters are from HITRAN 2004 with user-defined options for additional gases. Recent validation studies show MOD5 replicates line-by-line brightness temperatures to within ~0.02ºK average and <1.0ºK RMS. MOD5 can then serve as a surrogate for a variety of perturbation studies, including the two modes for the solar source function, Io. (1) Data from the Solar Radiation and Climate Experiment (SORCE) satellite mission provide state-of-the-art measurements of UV, visible, near-IR, plus total solar radiation, on near real-time basis. These internally consistent estimates of Sun's output over solar rotation and longer time scales are valuable inputs for studying effects of Sun's radiation on Earth's atmosphere and climate. When solar rotation encounters bright plage and dark sunspots, relative variations are expected to be very small in visible wavelengths, although absolute power is substantial. SORCE's Spectral Irradiance Monitor measurements are readily included in comparative MOD5 calculations. (2) The embedded solar irradiance within MOD5 must be compatible with the chosen band model resolution binning. By matching resolutions some issues related to the correlated-k band model parameterizations can be tested. Two high resolution solar irradiances, the MOD5 default irradiance (Kurucz) and a new compilation associated with Solar Radiation Physical Modeling project (Fontenla), are compared to address the potential impact of discrepancies between any sets of irradiances. The magnitude of solar variability, as measured and calculated, can lead to subtle changes in heating/cooling rates throughout the atmosphere, as a function of altitude and wavelength. By holding chemical & dynamical responses constant, only controlled distributions of absorbing gases, aerosols and clouds will contribute to observed 1st order radiative effects.

Anderson, G.; Berk, A.; Harder, G.; Fontenla, J.; Shettle, E.; Pilewski, P.; Kindel, B.; Chetwynd, J.; Gardner, J.; Hoke, M.; Jordan, A.; Lockwood, R.; Felde, G.; Archarya, P.

2006-12-01

142

78 FR 20298 - Restoration and Compensation Determination Plan and Environmental Assessment: Aluminum Production...  

Federal Register 2010, 2011, 2012, 2013

...Oceanic and Atmospheric Administration Restoration and Compensation Determination Plan...ACTION: Notice of Availability of the Restoration and Compensation Determination Plan...entitled, ``St. Lawrence Environment Restoration and Compensation Determination...

2013-04-04

143

Numerical advection algorithms and their role in atmospheric transport and chemistry models  

NASA Technical Reports Server (NTRS)

During the last 35 years, well over 100 algorithms for modeling advection processes have been described and tested. This review summarizes the development and improvements that have taken place. The nature of the errors caused by numerical approximation to the advection equation are highlighted. Then the particular devices that have been proposed to remedy these errors are discussed. The extensive literature comparing transport algorithms is reviewed. Although there is no clear cut 'best' algorithm, several conclusions can be made. Spectral and pseudospectral techniques consistently provide the highest degree of accuracy, but expense and difficulties assuring positive mixing ratios are serious drawbacks. Schemes which consider fluid slabs bounded by grid points (volume schemes), rather than the simple specification of constituent values at the grid points, provide accurate positive definite results.

Rood, Richard B.

1987-01-01

144

An observer-based compensator for distributed delays  

NASA Technical Reports Server (NTRS)

This paper presents an algorithm for compensating delays that are distributed between the sensor(s), controller and actuator(s) within a control loop. This observer-based algorithm is specially suited to compensation of network-induced delays in integrated communication and control systems. The robustness of the algorithm relative to plant model uncertainties has been examined.

Luck, Rogelio; Ray, Asok

1990-01-01

145

Simultaneous Retrieval of Temperature, Water Vapor and Ozone Atmospheric Profiles from IASI: Compression, De-noising, First Guess Retrieval and Inversion Algorithms  

NASA Technical Reports Server (NTRS)

A fast temperature water vapor and ozone atmospheric profile retrieval algorithm is developed for the high spectral resolution Infrared Atmospheric Sounding Interferometer (IASI) space-borne instrument. Compression and de-noising of IASI observations are performed using Principal Component Analysis. This preprocessing methodology also allows, for a fast pattern recognition in a climatological data set to obtain a first guess. Then, a neural network using first guess information is developed to retrieve simultaneously temperature, water vapor and ozone atmospheric profiles. The performance of the resulting fast and accurate inverse model is evaluated with a large diversified data set of radiosondes atmospheres including rare events.

Aires, F.; Rossow, W. B.; Scott, N. A.; Chedin, A.; Hansen, James E. (Technical Monitor)

2001-01-01

146

Spatially distributed algorithm for mitigation of atmospheric distortions of the laser beam  

Microsoft Academic Search

Development of long-range laser communication devices capable of operating within Earth's atmosphere is a challenging task. Turbulence effects cause changes of the refractive index, thus creating random redistribution of optical energy in the spatial domain and imposing performance limitations on the laser systems. A mathematical model describing effects of turbulence on the optical wave propagation, based on the Rytov approximation,

Vladimir V. Nikulin; Victor A. Skormin

2003-01-01

147

Comparative study of supervised classification algorithms for the detection of atmospheric pollution  

Microsoft Academic Search

The management of atmospheric pollution using video is not yet widespread. However it is an efficient way to evaluate the polluting rejects coming from large industrial facilities when traditional captors are not usable. This paper presents a comparison of different classifiers for a monitoring system of polluting smokes. The data used in this work are stemming from a system of

D. Gacquer; V. Delcroix; F. Delmotte; S. Piechowiak

2011-01-01

148

Atmospheric Turbulence Compensation of Point Source Images Using Asynchronous Stochastic Parallel Gradient Descent Technique on AMOS 3.6m Telescope  

Microsoft Academic Search

Stochastic Parallel Gradient Descent Technique-based Adaptive Optics (SPGD-AO) system described in this presentation doesn't use conventional wave front sensor. It uses a metric signal collected by a single pixel detector placed behind a pinhole in the image plane to drive three deformable mirrors (DMs). The system is designed to compensate the image for turbulence effects. The theory behind this method

M. Voronstov; Jim F. Riker; G. Carhart; V. S. Rao Gudimetla; L. Berensev; T. Weyrauch

2007-01-01

149

Remote Sensing of the Earth s Atmosphere by the Spaceborne Occultation Radiometer, ORA: Final Inversion Algorithm  

NASA Astrophysics Data System (ADS)

We describe the final inversion algorithm developed to process solar occultation data measured in 1992 -1993 by the Occultation Radiometer (ORA) spaceborne experiment. First we develop a new method to improve the ORA total extinction altitude profiles retrieved with the previously described Natural Orthogonal Polynomial Expansion (NOPE) method. Using these improved profiles, we perform spectral inversion and obtain altitude density profiles for O3 and NO2 and extinction profiles for the aerosols. Validation of number density profiles between the Stratospheric Aerosol and Gas Experiment II (SAGE II) and the ORA shows satisfactory agreement.

Fussen, Didier; Vanhellemont, Filip; Bingen, Christine

2001-02-01

150

A simple algorithm to estimate the effective regional atmospheric parameters for thermal-inertia mapping  

USGS Publications Warehouse

A method based solely on remote sensing data has been developed to estimate those meteorological effects which are required for thermal-inertia mapping. It assumes that the atmospheric fluxes are spatially invariant and that the solar, sky, and sensible heat fluxes can be approximated by a simple mathematical form. Coefficients are determined from least-squares method by fitting observational data to our thermal model. A comparison between field measurements and the model-derived flux shows the type of agreement which can be achieved. An analysis of the limitations of the method is also provided. ?? 1981.

Watson, K.; Hummer-Miller, S.

1981-01-01

151

A Markov chain Monte Carlo algorithm for upscaled soil-vegetation-atmosphere-transfer modeling to evaluate satellite-based soil moisture measurements  

Microsoft Academic Search

A Markov chain Monte Carlo (MCMC) based algorithm was developed to derive upscaled land surface parameters for a soil-vegetation-atmosphere-transfer (SVAT) model using time series data of satellite-measured atmospheric forcings (e.g., precipitation), and land surface states (e.g., soil moisture and vegetation). This study focuses especially on the evaluation of soil moisture measurements of the Aqua satellite based Advanced Microwave Scanning Radiometer

N. N. Das; B. P. Mohanty; E. G. Njoku

2008-01-01

152

A parallel hybrid numerical algorithm for simulating gas flow and gas discharge of an atmospheric-pressure plasma jet  

NASA Astrophysics Data System (ADS)

Development of a hybrid numerical algorithm which couples weakly with the gas flow model (GFM) and the plasma fluid model (PFM) for simulating an atmospheric-pressure plasma jet (APPJ) and its acceleration by two approaches is presented. The weak coupling between gas flow and discharge is introduced by transferring between the results obtained from the steady-state solution of the GFM and cycle-averaged solution of the PFM respectively. Approaches of reducing the overall runtime include parallel computing of the GFM and the PFM solvers, and employing a temporal multi-scale method (TMSM) for PFM. Parallel computing of both solvers is realized using the domain decomposition method with the message passing interface (MPI) on distributed-memory machines. The TMSM considers only chemical reactions by ignoring the transport terms when integrating temporally the continuity equations of heavy species at each time step, and then the transport terms are restored only at an interval of time marching steps. The total reduction of runtime is 47% by applying the TMSM to the APPJ example presented in this study. Application of the proposed hybrid algorithm is demonstrated by simulating a parallel-plate helium APPJ impinging onto a substrate, which the cycle-averaged properties of the 200th cycle are presented. The distribution patterns of species densities are strongly correlated by the background gas flow pattern, which shows that consideration of gas flow in APPJ simulations is critical.

Lin, K.-M.; Hu, M.-H.; Hung, C.-T.; Wu, J.-S.; Hwang, F.-N.; Chen, Y.-S.; Cheng, G.

2012-12-01

153

A new atmospheric ray-tracing algorithm and its use in VLBI analysis  

NASA Astrophysics Data System (ADS)

Due to recent improvements of numerical weather models (NWM), ray-tracing has become an interesting and feasible method for different scientific purposes. One application in geosciences is the estimation of tropospheric delays for the correction of space geodetic techniques. Here, we present and discuss the recently developed ray-tracing algorithm from the Institute of Geodesy and Geophysics (IGG) at Vienna University of Technology. We use numerical weather model data from the European Centre for Medium-Range Weather Forecasts (ECMWF) to estimate the tropospheric total delay by solving the Eikonal equation. In addition we discuss different methods and characteristics, such as interpolation methods, resolution of the data set and the use of different refractivity constants, and we present results and differences between a 2D- and 3D-ray-tracing algorithm. As quality validation we enter the derived tropospheric delays as a priori information in our VLBI analysis software package (Vienna VLBI Software). We analyze IVS Intensive sessions from July 2010 to October 2011 which are carried out for the estimation of UT1-UTC (DUT1). The measurement of this Earth rotation angle is needed in near real-time for the accurate prediction of Universal Time (UT1) as well as for navigation purposes. Due to the small number of observables per session most parameters, which are usually estimated in VLBI analyses, are fixed to their a priori values, which should be known as accurately as possible. As an external validation of our ray-traced delays we calculate Length-of-Day (LoD) from the VLBI-derived DUT1 values and compare these to LoD from GPS.

Madzak, M.; Nafisi, V.; Böhm, J.; Schuh, H.

2012-04-01

154

Oscillator Phase Noise compensation using Kalman tracking  

Microsoft Academic Search

Phase Noise (PN) is a serious challenge in wireless transmis- sion systems as it can cause significant degradation of the sys- tem performance. Recent publications propose iterative PN compensation algorithms for single or multicarrier systems. In this paper we will present an unscented Kalman filter PN tracking algorithm working in time domain, which is inde- pendent of the underlying system.

Steffen Bittner; Andreas Frotzscher; Gerhard Fettweis; Ellie Deng

2009-01-01

155

CORDIC Architectures with Parallel Compensation of the Scale Factor  

Microsoft Academic Search

The compensation of scale factor imposes significant computation overhead on the CORDIC algorithm. In this paper we will propose two algorithms and architectures in order to perform the compensation of the scale factor in parallel with the computation of the CORDIC iterations. This way it is not necessary to carry out the final multiplication or add scaling iterations in order

Julio Villalba; J. A. Hidalgo; Emilio L. Zapata; Elisardo Antelo; Javier D. Bruguera

1995-01-01

156

Comparison of different modulation formats for polarization mode dispersion compensators  

NASA Astrophysics Data System (ADS)

We propose a polarization mode dispersion (PMD) compensation scheme for wavelength-division-multiplexing (WDM) system, in which two WDM channels share one PMD compensator at the receiver site. The effect of different modulation formats on multi-stage PMD compensators is studied and compared by numerical simulations in 40-Gb/s WDM optical fiber communication system. The degree of polarization (DOP) of single state of polarization (SOP) optical signal is used as the feedback signal in PMD compensators. The particle swarm optimization (PSO) algorithm is used as the searching algorithm in WDM systems. The compensated DOP values of return-to-zero (RZ) format and nonreturn-to-zero (NRZ) format by multi-stage PMD compensators have been increased distinctly compared to the corresponding cases without compensation. It is shown that the PSO algorithm is implemented successfully in adaptive multi-stage PMD compensation in a 40-Gb/s optical WDM system. The compensated eye diagrams for the two channels by multi-stage PMD compensators indicate that the three-stage PMD compensator which eliminates the influence of second-order PMD completely in WDM system takes the best efficiency in the multi-stage PMD compensators for RZ format and NRZ format.

Wu, Huaiyi; Chen, Lin; Wen, Shuangchun

2006-10-01

157

Radiation Exposure Compensation Program  

NSDL National Science Digital Library

This is the Justice Department's Radiation Exposure Compensation Program homepage. This site features information about the Radiation Exposure Compensation Act, including claimant categories, claim forms, and the Energy Employees Occupational Illness Compensation Program Act. This site also provides a table illustrating a summary of all claims received and compensation paid to date.

Program, U. S.

158

Hyperspectral material identification on radiance data using single-atmosphere or multiple-atmosphere modeling  

NASA Astrophysics Data System (ADS)

Reflectance-domain methods convert hyperspectral data from radiance to reflectance using an atmospheric compensation model. Material detection and identification are performed by comparing the compensated data to target reflectance spectra. We introduce two radiance-domain approaches, Single atmosphere Adaptive Cosine Estimator (SACE) and Multiple atmosphere ACE (MACE) in which the target reflectance spectra are instead converted into sensor-reaching radiance using physics-based models. For SACE, known illumination and atmospheric conditions are incorporated in a single atmospheric model. For MACE the conditions are unknown so the algorithm uses many atmospheric models to cover the range of environmental variability, and it approximates the result using a subspace model. This approach is sometimes called the invariant method, and requires the choice of a subspace dimension for the model. We compare these two radiance-domain approaches to a Reflectance-domain ACE (RACE) approach on a HYDICE image featuring concealed materials. All three algorithms use the ACE detector, and all three techniques are able to detect most of the hidden materials in the imagery. For MACE we observe a strong dependence on the choice of the material subspace dimension. Increasing this value can lead to a decline in performance.

Mariano, Adrian V.; Grossmann, John M.

2010-11-01

159

Compensator improvement for multivariable control systems  

NASA Technical Reports Server (NTRS)

A theory and the associated numerical technique are developed for an iterative design improvement of the compensation for linear, time-invariant control systems with multiple inputs and multiple outputs. A strict constraint algorithm is used in obtaining a solution of the specified constraints of the control design. The result of the research effort is the multiple input, multiple output Compensator Improvement Program (CIP). The objective of the Compensator Improvement Program is to modify in an iterative manner the free parameters of the dynamic compensation matrix so that the system satisfies frequency domain specifications. In this exposition, the underlying principles of the multivariable CIP algorithm are presented and the practical utility of the program is illustrated with space vehicle related examples.

Mitchell, J. R.; Mcdaniel, W. L., Jr.; Gresham, L. L.

1977-01-01

160

Impacts of the Convective Transport Algorithm on Atmospheric Composition and Ozone-Climate Feedbacks in GEOS-CCM  

NASA Astrophysics Data System (ADS)

Convective transport is one of the dominant factors in determining the composition of the troposphere. It is the main mechanism for lofting constituents from near-surface source regions to the middle and upper troposphere, where they can subsequently be advected over large distances. Gases reaching the upper troposphere can also be injected through the tropopause and play a subsequent role in the lower stratospheric ozone balance. Convection codes in climate models remain a great source of uncertainty for both the energy balance of the general circulation and the transport of constituents. This study uses the Goddard Earth Observing System Chemistry-Climate Model (GEOS CCM) to perform a controlled experiment that isolates the impact of convective transport of constituents from the direct changes on the atmospheric energy balance. Two multi-year simulations are conducted. In the first, the thermodynamic variable, moisture, and all trace gases are transported using the multi-plume "Relaxed-Arakawa-Schubert" (RAS) convective parameterization. In the second simulation, RAS impacts the thermodynamic energy and moisture in this standard manner, but all other constituents are transported differently. The accumulated convective mass fluxes (including entrainment and detrainment) computed at each time step of the GCM are used with a diffusive (bulk) algorithm for the vertical transport, which above all is less efficient at transporting constituents from the lower to the upper troposphere. Initial results show the expected differences in vertical structure of trace gases such as carbon monoxide, but also show differences in lower stratospheric ozone, in a region where it can potentially impact the climate state of the model. This work will investigate in more detail the impact of convective transport changes by comparing the two simulations over many years (1996-2010), focusing on comparisons with observed constituent distributions and similarities and differences of patterns of inter-annual variability caused by the convective transport algorithm. In particular, the impact on lower stratospheric composition will be isolated and the subsequent feedbacks of ozone on the climate forcing and tropopause structure will be assessed.

Pawson, S.; Nielsen, J. E.; Oman, L.; Douglass, A. R.; Duncan, B. N.; Zhu, Z.

2012-12-01

161

Impacts of the Convective Transport Algorithm on Atmospheric Composition and Ozone-Climate Feedbacks in GEOS-CCM  

NASA Technical Reports Server (NTRS)

Convective transport is one of the dominant factors in determining the composition of the troposphere. It is the main mechanism for lofting constituents from near-surface source regions to the middle and upper troposphere, where they can subsequently be advected over large distances. Gases reaching the upper troposphere can also be injected through the tropopause and play a subsequent role in the lower stratospheric ozone balance. Convection codes in climate models remain a great source of uncertainty for both the energy balance of the general circulation and the transport of constituents. This study uses the Goddard Earth Observing System Chemistry-Climate Model (GEOS CCM) to perform a controlled experiment that isolates the impact of convective transport of constituents from the direct changes on the atmospheric energy balance. Two multi-year simulations are conducted. In the first, the thermodynamic variable, moisture, and all trace gases are transported using the multi-plume Relaxed-Arakawa-Schubert (RAS) convective parameterization. In the second simulation, RAS impacts the thermodynamic energy and moisture in this standard manner, but all other constituents are transported differently. The accumulated convective mass fluxes (including entrainment and detrainment) computed at each time step of the GCM are used with a diffusive (bulk) algorithm for the vertical transport, which above all is less efficient at transporting constituents from the lower to the upper troposphere. Initial results show the expected differences in vertical structure of trace gases such as carbon monoxide, but also show differences in lower stratospheric ozone, in a region where it can potentially impact the climate state of the model. This work will investigate in more detail the impact of convective transport changes by comparing the two simulations over many years (1996-2010), focusing on comparisons with observed constituent distributions and similarities and differences of patterns of inter-annual variability caused by the convective transport algorithm. In particular, the impact on lower stratospheric composition will be isolated and the subsequent feedbacks of ozone on the climate forcing and tropopause structure will be assessed.

Pawson, S.; Nielsen, Jon E.; Oman, L.; Douglass, A. R.; Duncan, B. N.; Zhu, Z.

2012-01-01

162

Exploring the need to revise atmospheric correction algorithms of satellite sensor images for the area of Greece  

Microsoft Academic Search

A New Model Atmosphere was constructed for the area of Southern Greece in an effort to support atmospheric correction of satellite sensor images. The impact of the New Model Atmosphere on incident solar radiation was examined using the MODTRAN radiative transfer code to calculate spectral transmittances at the surface. Results were compared to the respective spectral transmittances as these resulted

C. Cartalis; A. Retalis

1996-01-01

163

Practical Atmospheric Correction Algorithms for a Multi-Spectral Sensor From the Visible Through the Thermal Spectral Regions  

SciTech Connect

Deriving information about the Earth's surface requires atmospheric corrections of the measured top-of-the-atmosphere radiances. One possible path is to use atmospheric radiative transfer codes to predict how the radiance leaving the ground is affected by the scattering and attenuation. In practice the atmosphere is usually not well known and thus it is necessary to use more practical methods. The authors will describe how to find dark surfaces, estimate the atmospheric optical depth, estimate path radiance and identify thick clouds using thresholds on reflectance and NDVI and columnar water vapor. The authors describe a simple method to correct a visible channel contaminated by a thin cirrus clouds.

Borel, C.C.; Villeneuve, P.V.; Clodium, W.B.; Szymenski, J.J.; Davis, A.B.

1999-04-04

164

Saliency driven Black Point Compensation  

NASA Astrophysics Data System (ADS)

We present a novel framework for automatically determining whether or not to apply black point compensation (BPC) in image reproduction. Visually salient objects have a larger influence on determining image quality than the number of dark pixels in an image, and thus should drive the use of BPC. We propose a simple and efficient algorithmic implementation to determine when to apply BPC based on low-level saliency estimation. We evaluate our algorithm with a psychophysical experiment on an image data set printed with or without BPC on a Canon printer. We find that our algorithm is correctly able to predict the observers' preferences in all cases when the saliency maps are unambiguous and accurate.

Lindner, Albrecht; Bonnier, Nicolas; Süsstrunk, Sabine

2011-01-01

165

Combining afternoon and morning NOAA satellites for thermal inertia estimation: 1. Algorithm and its testing with Hydrologic Atmospheric Pilot Experiment-Sahel data  

NASA Astrophysics Data System (ADS)

This is the first in a series of two papers on the thermal inertia estimation from satellite data. In this paper we have evaluated the behavior of three algorithms to retrieve surface thermal inertia from NOAA-advanced very high resolution radiometer (AVHRR) data. These are Price's [1977] algorithm, and two different algorithms based on the model of Xue and Cracknell [1995]; Xue and Cracknell's algorithm (XC), and a new approach which we have named FTA (four temperatures algorithm) since it uses four AVHRR measurements (XC plus two from NOAA morning satellites). The main advantage of the FTA is that it only uses satellite data. The algorithms were tested with a set of in situ measurements taken over a region of Niger in the frame of the Hydrologic Atmospheric Pilot Experiment-Sahel. The analysis was done in two different ways: (1) by comparing the ST (surface temperature) predicted by the algorithms with the measured ones every 10 minutes, and (2) by comparing the predicted and measured maximum and minimum ST values as well as their respective times. Our results indicate that the FTA is the most appropriate algorithm for presenting the diurnal cycle of the ground ST with these experimental data. For 90% of the cases the absolute difference between predicted and measured STs is lower than 2 K, with a standard deviation of 1.5 K that improves to 1 K when predicting the maximum and minimum STs. The FTA also predicts their respective times with a standard deviation of less than 30 min. These results suggest that it is possible to predict the minimum ST and corresponding time from NOAA data, which might be useful to forecast frost during nights of radiative cooling (cloudless and calm wind).

Sobrino, J. A.; El Kharraz, M. H.

1999-04-01

166

Image restoration technique for motion-compensated frame averaged data collected by 3D flash ladar imaging system  

NASA Astrophysics Data System (ADS)

A new image restoration algorithm is proposed to remove the effect of atmospheric turbulence on motion-compensated frame averaged data collected by a three dimensional FLASH Laser Radar (LADAR) imaging system. The algorithm simultaneously arrives at an enhanced image as well as Fried's seeing parameter through an Expectation Maximization (EM) technique. Unlike blind deconvolution algorithms that operate only on two dimensional images, this technique accounts for both the spatial and temporal mixing that is caused by the atmosphere through which the system is imaging. Additionally, due to the over-determined nature of this problem, the point-spread function parameterized by Fried's seeing parameter can be deduced without the requirement for additional assumptions or constraints. The utility of the approach lies in its application to laser illuminated imaging where processing time is important.

Neff, Brian J.; Cain, Stephen C.

2012-10-01

167

Atmospheric correction of visible to middle-infrared EOS-MODIS data over land surfaces: Background, operational algorithm and validation  

Microsoft Academic Search

The NASA moderate resolution imaging spectroradiometer (MODIS) instrument will provide a global and improved source of information for the study of land surfaces with a spatial resolution of up to 250 m. Prior to the derivation of various biophysical parameters based on surface reflectances, the top of the atmosphere signals need to be radiometrically calibrated and corrected for atmospheric effects.

E. F. Vermote; N. El Saleous; C. O. Justice; Y. J. Kaufman; J. L. Privette; L. Remer; J. C. Roger; D. Tanré

1997-01-01

168

The estimation of the constituent densities of the upper atmosphere by means of a recursive filtering algorithm  

Microsoft Academic Search

The structure of the upper atmosphere can be indirectly probed by light in order to determine the global density structure of ozone, aerosols, and neutral atmosphere. Scattered and directly transmitted light is measured by a satellite and is shown to be a nonlinear function of the state which is defined to be a point-wise decomposition of the density profiles. Dynamics

T. McGarty

1971-01-01

169

An observer-based compensator for distributed delays in integrated control systems  

NASA Technical Reports Server (NTRS)

This paper presents an algorithm for compensation of delays that are distributed within a control loop. The observer-based algorithm is especially suitable for compensating network-induced delays that are likely to occur in integrated control systems of the future generation aircraft. The robustness of the algorithm relative to uncertainties in the plant model have been examined.

Luck, Rogelio; Ray, Asok

1989-01-01

170

Distrib uted interference compensation in wireless networks  

Microsoft Academic Search

Abstract We consider a distributed power control scheme for wireless ad hoc networks, in which each user announces,a price that reflects compensation,paid by other users for their interference. We present an asynchronous,distributed algorithm for updating power levels and prices. By relating this algorithm to myopic best response updates in a fictitious game, we are able to characterize convergence using supermodular

J. Huang; R. Berry; M. L. Honig

2005-01-01

171

Inclined plane walking compensation for a humanoid robot  

Microsoft Academic Search

This paper suggested the simple compensation algorithm for a humanoid robot when walking on an inclined plane. Motion transition of the robot for varying slope can be achieved from adjusting the center of mass of the robot forward\\/backward by compensating the robot's ankle. This proposed method used the feedback from the accelerometer in the robot's body to detect the inclination

Nattapong Kaewlek; Thavida Maneewarn

2010-01-01

172

An evolutionary architecture for motion-compensated 100 Hz television  

Microsoft Academic Search

In this paper, recently developed algorithms for high quality motion-compensated up-conversion are combined in a new architecture closely resembling that of current 100 Hz consumer television sets. By merging the motion estimation and the motion compensation part, the estimated silicon area could be reduced to a level where the entire functionality can be realized with one processing chip replacing the

Gerard de Haan; Paul W. A. C. Biezen; O. A. Ojo

1995-01-01

173

RECIPES FOR WRITING ALGORITHMS FOR ATMOSPHERIC CORRECTIONS AND TEMPERATURE/EMISSIVITY SEPARATIONS IN THE THERMAL REGIME FOR A MULTI-SPECTRAL SENSOR  

SciTech Connect

This paper discusses the algorithms created for the Multi-spectral Thermal Imager (MTI) to retrieve temperatures and emissivities. Recipes to create the physics based water temperature retrieval, emissivity of water surfaces are described. A simple radiative transfer model for multi-spectral sensors is developed. A method to create look-up-tables and the criterion of finding the optimum water temperature are covered. Practical aspects such as conversion from band-averaged radiances to brightness temperatures and effects of variations in the spectral response on the atmospheric transmission are discussed. A recipe for a temperature/emissivity separation algorithm when water surfaces are present is given. Results of retrievals of skin water temperatures are compared with in-situ measurements of the bulk water temperature at two locations are shown.

C. BOREL; W. CLODIUS

2001-04-01

174

Robust springback compensation  

NASA Astrophysics Data System (ADS)

Springback simulation and springback compensation are more and more applied in productive use of die engineering. In order to successfully compensate a tool accurate springback results are needed as well as an effective compensation approach. In this paper a methodology has been introduce in order to effectively compensate tools. First step is the full process simulation meaning that not only the drawing operation will be simulated but also all secondary operations like trimming and flanging. Second will be the verification whether the process is robust meaning that it obtains repeatable results. In order to effectively compensate a minimum clamping concept will be defined. Once these preconditions are fulfilled the tools can be compensated effectively.

Carleer, Bart; Grimm, Peter

2013-12-01

175

Active variation compensation in vehicle body conceptual assembly  

Microsoft Academic Search

In this paper, an intelligent heuristic optimization algorithm in active variation compensation is proposed to improve the\\u000a dimension accuracy in the assembly of a vehicle body by finding the optimal configuration of joint types and the corresponding\\u000a assembly sequence to compensate variation accumulation in the conceptual assembly process. The authors develop and apply the\\u000a algorithm to predict variation accumulation and

Li Yubing; Chen Guanlong; Zheng Cheng; Lai Xinmin

2008-01-01

176

Results of the Compensated Earth-Moon-Earth Retroreflector Laser Link (CEMERLL) Experiment  

NASA Technical Reports Server (NTRS)

Adaptive optics techniques can be used to realize a robust low bit-error-rate link by mitigating the atmosphere-induced signal fades in optical communications links between ground-based transmitters and deep-space probes. Phase I of the Compensated Earth-Moon-Earth Retroreflector Laser Link (CEMERLL) experiment demonstrated the first propagation of an atmosphere-compensated laser beam to the lunar retroreflectors. A 1.06-micron Nd:YAG laser beam was propagated through the full aperture of the 1.5-m telescope at the Starfire Optical Range (SOR), Kirtland Air Force Base, New Mexico, to the Apollo 15 retroreflector array at Hadley Rille. Laser guide-star adaptive optics were used to compensate turbulence-induced aberrations across the transmitter's 1.5-m aperture. A 3.5-m telescope, also located at the SOR, was used as a receiver for detecting the return signals. JPL-supplied Chebyshev polynomials of the retroreflector locations were used to develop tracking algorithms for the telescopes. At times we observed in excess of 100 photons returned from a single pulse when the outgoing beam from the 1.5-m telescope was corrected by the adaptive optics system. No returns were detected when the outgoing beam was uncompensated. The experiment was conducted from March through September 1994, during the first or last quarter of the Moon.

Wilson, K. E.; Leatherman, P. R.; Cleis, R.; Spinhirne, J.; Fugate, R. Q.

1997-01-01

177

A joint effort to deliver satellite retrieved atmospheric CO2 concentrations for surface flux inversions: the ensemble median algorithm EMMA  

NASA Astrophysics Data System (ADS)

We analyze an ensemble of seven XCO2 retrieval algorithms for SCIAMACHY and GOSAT. The ensemble spread can be interpreted as regional uncertainty and can help to identify locations for new TCCON validation sites. Additionally, we introduce the ensemble median algorithm EMMA combining individual soundings of the seven algorithms into one new dataset. The ensemble takes advantage of the algorithms' independent developments. We find ensemble spreads being often <1 ppm but rising up to 2 ppm especially in the tropics and East Asia. On the basis of gridded monthly averages, we compare EMMA and all individual algorithms with TCCON and CarbonTracker model results (potential outliers, north/south gradient, seasonal (peak-to-peak) amplitude, standard deviation of the difference). Our findings show that EMMA is a promising candidate for inverse modeling studies. Compared to CarbonTracker, the satellite retrievals find consistently larger north/south gradients (by 0.3 ppm-0.9 ppm) and seasonal amplitudes (by 1.5 ppm-2.0 ppm).

Reuter, M.; Bösch, H.; Bovensmann, H.; Bril, A.; Buchwitz, M.; Butz, A.; Burrows, J. P.; O'Dell, C. W.; Guerlet, S.; Hasekamp, O.; Heymann, J.; Kikuchi, N.; Oshchepkov, S.; Parker, R.; Pfeifer, S.; Schneising, O.; Yokota, T.; Yoshida, Y.

2012-09-01

178

Blocked element compensation in phased array imaging.  

PubMed

In clinical applications using large apertures, a significant number of phased array elements may be blocked due to discontinuous acoustic windows into the body. These blocked elements produce undesired beamforming artifacts, degrading spatial and contrast resolution. To minimize these artifacts, an algorithm using multiple receive beams and the total-least-squares method is proposed. Simulations and experimental results show that this algorithm can effectively reduce imperfections in the point spread function of the imager. Combined with first-and second-order scatterer statistics derived from multiple receive beams, the algorithm is modified for blocked element compensation on distributed scattering sources. Results also indicate that compensated images are comparable to full array images, and that even full array images can be improved by removing undesired sidelobe contributions. This method, therefore, can enhance detection of low contrast lesions using large phased-array apertures. PMID:18263183

Li, P C; Flax, S W; Ebbini, E S; O'Donnell, M

1993-01-01

179

Gmti Motion Compensation  

DOEpatents

Movement of a GMTI radar during a coherent processing interval over which a set of radar pulses are processed may cause defocusing of a range-Doppler map in the video signal. This problem may be compensated by varying waveform or sampling parameters of each pulse to compensate for distortions caused by variations in viewing angles from the radar to the target.

Doerry, Armin W. (Albuquerque, NM)

2004-07-20

180

The estimation of the constituent densities of the upper atmosphere by means of a recursive filtering algorithm.  

NASA Technical Reports Server (NTRS)

The structure of the upper atmosphere can be indirectly probed by light in order to determine the global density structure of ozone, aerosols, and neutral atmosphere. Scattered and directly transmitted light is measured by a satellite and is shown to be a nonlinear function of the state which is defined to be a point-wise decomposition of the density profiles. Dynamics are imposed on the state vector and a structured estimation problem is developed. The estimation of these densities is then performed using a linearized Kalman-Bucy filter and a linearized Kushner-Stratonovich filter.

Mcgarty, T. P.

1971-01-01

181

PMD compensation techniques  

NASA Astrophysics Data System (ADS)

Mitigating PMD is still a challenge in today's optical communications. After giving the key performance indicators dictated by the statistical nature of PMD, we introduce the classification of PMD compensation schemes into 2 categories: optical and electrical PMD compensators. In a first part, we explain the operation principle of a PMD compensator by taking a detailed look at the basic optical PMD compensator and appropriate feedback signals. More complex multistage structures and a feed-forward adaptation approach are also discussed. This first part is closed by results from a one-year field trial confirming the behavior and performance of a prototype compensator. In the second part of this article, electronic equalization for PMD mitigation is explained. Starting with a discussion on performance and adaptation of linear equalizers suitable for analog electronic signal processing, finally also the Viterbi equalizer basing on digital signal processing is analyzed. A comparative review of mitigation by optical or electronic means concludes the discussion.

Bülow, Henning; Lanne, Stéphanie

182

Horizontal density compensation in ocean general circulation models  

NASA Astrophysics Data System (ADS)

Density compensation is the condition where temperature (T) and salinity (S) gradients counteract in their effect on density. Open ocean observations with SeaSoar tows and recent glider observations in the Gulf of Mexico reported in the scientific literature suggest that horizontal gradients in the surface mixed layer tend to be strongly density compensated over a range of spatial scales while in seasonal thermocline and deeper layers T,S-fronts are only partially compensated or uncompensated. We assess the capability of ocean general circulation models (OGCM) to develop horizontal density compensation as observed in the upper ocean. The physics required to evolve the initial density compensated mixed layer toward the partially compensated conditions of the thermocline is tested. Idealistic scenarios with horizontal, partially compensated density fronts in the mixed layer are examined in submesoscale-resolved run-down simulations on Hybrid Coordinate Ocean Model (HYCOM). Simulations with no atmospheric forcing show that initial Density compensation does not change substantially experiencing only minor decrease with time simultaneously with the restratification of the mixed layer by submesoscale eddies. Submesoscale fronts tend to be more compensated than mesoscale fronts. A sensitivity analysis shows that the density compensation of submesoscale fronts is particularly sensitive to the horizontal diffusion rate. Simulations with wind forcing exhibit destruction of initial density compensation due to ageostrophic frontogenesis which is confirmed by recent glider observations in the Gulf of Mexico. The lack of the model skill to develop and maintain compensated thermohaline variability is attributed to the T, S horizontal diffusion parameterization used in HYCOM and generally in modern OGCMs: it is decoupled from vertical diffusion and T and S diffusion is horizontally identical. Our findings suggest that OGCM's skill to develop compensated thermohaline variability can be advanced by providing realistic atmospheric forcing along with improving horizontal diffusion parameterization.

Koch, Andrey O.; Helber, Robert W.; Richman, James G.; Barron, Charlie N.

2013-04-01

183

Compensation of distributed delays in integrated communication and control systems  

NASA Technical Reports Server (NTRS)

The concept, analysis, implementation, and verification of a method for compensating delays that are distributed between the sensors, controller, and actuators within a control loop are discussed. With the objective of mitigating the detrimental effects of these network induced delays, a predictor-controller algorithm was formulated and analyzed. Robustness of the delay compensation algorithm was investigated relative to parametric uncertainties in plant modeling. The delay compensator was experimentally verified on an IEEE 802.4 network testbed for velocity control of a DC servomotor.

Ray, Asok; Luck, Rogelio

1991-01-01

184

Water quality monitoring by thematic mapper in coastal environments. A performance analysis of local biooptical algorithms and atmospheric correction procedures  

Microsoft Academic Search

The Thematic Mapper (TM) sensor's ability to monitor localized phenomena associated with anthropogenic pollution in coastal waters has been investigated with reference to experimental data collected on a test site in the Gulf of Naples. In situ measurements yielded the biooptical algorithms for chlorophyll and sediment retrieval as well as an optical model for the computation of the subsurface reflectance

S. Tassan; M. R. dAlcala

1993-01-01

185

Remote Sensing of Atmospheric Aerosols and Trace Gases by Means of Multifilter Rotating Shadowband Radiometer. Part I: Retrieval Algorithm  

Microsoft Academic Search

A retrieval algorithm for processing multifilter rotating shadowband radiometer (MFRSR) data from clear and partially cloudy days is described and validated. This method, while complementary to the Langley approach, uses consistency between the direct normal and diffuse horizontal measurements combined with a regression technique to simultaneously retrieve daily time series of column mean aerosol particle size, aerosol optical depth, NO2,

Mikhail D. Alexandrov; Andrew A. Lacis; Barbara E. Carlson; Brian Cairns

2002-01-01

186

The Algorithm Theoretical Basis Document for the Atmospheric Delay Correction to GLAS Laser Altimeter Ranges. Volume 8  

NASA Technical Reports Server (NTRS)

NASA s Ice, Cloud, and Land Elevation Satellite (ICESat) mission will be launched late 2001. It s primary instrument is the Geoscience Laser Altimeter System (GLAS) instrument. The main purpose of this instrument is to measure elevation changes of the Greenland and Antarctic icesheets. To accurately measure the ranges it is necessary to correct for the atmospheric delay of the laser pulses. The atmospheric delay depends on the integral of the refractive index along the path that the laser pulse travels through the atmosphere. The refractive index of air at optical wavelengths is a function of density and molecular composition. For ray paths near zenith and closed form equations for the refractivity, the atmospheric delay can be shown to be directly related to surface pressure and total column precipitable water vapor. For ray paths off zenith a mapping function relates the delay to the zenith delay. The closed form equations for refractivity recommended by the International Union of Geodesy and Geophysics (IUGG) are optimized for ground based geodesy techniques and in the next section we will consider whether these equations are suitable for satellite laser altimetry.

Herring, Thomas A.; Quinn, Katherine J.

2012-01-01

187

38 CFR 3.351 - Special monthly dependency and indemnity compensation, death compensation, pension and spouse's...  

Code of Federal Regulations, 2013 CFR

...dependency and indemnity compensation, death compensation, pension and spouse's compensation...dependency and indemnity compensation, death compensation, pension and spouse's compensation...1541(d), (e)) (6) Increased death compensation is payable to a...

2013-07-01

188

Reactive power compensator  

DOEpatents

A system and method for determining and providing reactive power compensation for an inductive load. A reactive power compensator (50,50') monitors the voltage and current flowing through each of three distribution lines (52a, 52b, 52c), which are supplying three-phase power to one or more inductive loads. Using signals indicative of the current on each of these lines when the voltage waveform on the line crosses zero, the reactive power compensator determines a reactive power compensator capacitance that must be connected to the lines to maintain a desired VAR level, power factor, or line voltage. Alternatively, an operator can manually select a specific capacitance for connection to each line, or the capacitance can be selected based on a time schedule. The reactive power compensator produces control signals, which are coupled through optical fibers (102/106) to a switch driver (110, 110') to select specific compensation capacitors (112) for connections to each line. The switch driver develops triggering signals that are supplied to a plurality of series-connected solid state switches (350), which control charge current in one direction in respect to ground for each compensation capacitor. During each cycle, current flows from ground to charge the capacitors as the voltage on the line begins to go negative from its positive peak value. The triggering signals are applied to gate the solid state switches into a conducting state when the potential on the lines and on the capacitors reaches a negative peak value, thereby minimizing both the potential difference and across the charge current through the switches when they begin to conduct. Any harmonic distortion on the potential and current carried by the lines is filtered out from the current and potential signals used by the reactive power compensator so that it does not affect the determination of the required reactive compensation.

El-Sharkawi, Mohamed A. (Renton, WA); Venkata, Subrahmanyam S. (Woodinville, WA); Chen, Mingliang (Kirkland, WA); Andexler, George (Everett, WA); Huang, Tony (Seattle, WA)

1992-01-01

189

Reactive Power Compensator.  

DOEpatents

A system and method for determining and providing reactive power compensation for an inductive load. A reactive power compensator (50,50') monitors the voltage and current flowing through each of three distribution lines (52a, 52b, 52c), which are supplying three-phase power to one or more inductive loads. Using signals indicative of the current on each of these lines when the voltage waveform on the line crosses zero, the reactive power compensator determines a reactive power compensator capacitance that must be connected to the lines to maintain a desired VAR level, power factor, or line voltage. Alternatively, an operator can manually select a specific capacitance for connection to each line, or the capacitance can be selected based on a time schedule. The reactive power compensator produces control signals, which are coupled through optical fibers (102/106) to a switch driver (110, 110') to select specific compensation capacitors (112) for connections to each line. The switch driver develops triggering signals that are supplied to a plurality of series-connected solid state switches (350), which control charge current in one direction in respect to ground for each compensation capacitor. During each cycle, current flows from ground to charge the capacitors as the voltage on the line begins to go negative from its positive peak value. The triggering signals are applied to gate the solid state switches into a conducting state when the potential on the lines and on the capacitors reaches a negative peak value, thereby minimizing both the potential difference and across the charge current through the switches when they begin to conduct. Any harmonic distortion on the potential and current carried by the lines is filtered out from the current and potential signals used by the reactive power compensator so that it does not affect the determination of the required reactive compensation. 26 figs.

El-Sharkawi, M.A.; Venkata, S.S.; Chen, M.; Andexler, G.; Huang, T.

1992-07-28

190

Unbalance vibratory displacement compensation for active magnetic bearings  

NASA Astrophysics Data System (ADS)

As the dynamic stiffness of radial magnetic bearings is not big enough, when the rotor spins at high speed, unbalance displacement vibration phenomenon will be produced. The most effective way for reducing the displacement vibration is to enhance the radial magnetic bearing stiffness through increasing the control currents, but the suitable control currents are not easy to be provided, especially, to be provided in real time. To implement real time unbalance displacement vibration compensation, through analyzing active magnetic bearings (AMB) mathematical model, the existence of radial displacement runout is demonstrated. To restrain the runout, a new control scheme-adaptive iterative learning control (AILC) is proposed in view of rotor frequency periodic uncertainties during the startup process. The previous error signal is added into AILC learning law to enhance the convergence speed, and an impacting factor ? influenced by the rotor rotating frequency is introduced as learning output coefficient to improve the rotor control effects. As a feed-forward compensation controller, AILC can provide one unknown and perfect compensatory signal to make the rotor rotate around its geometric axis through power amplifier and radial magnetic bearings. To improve AMB closed-loop control system robust stability, one kind of incomplete differential PID feedback controller is adopted. The correctness of the AILC algorithm is validated by the simulation of AMB mathematical model adding AILC compensation algorithm through MATLAB soft. And the compensation for fixed rotational frequency is implemented in the actual AMB system. The simulation and experiment results show that the compensation scheme based on AILC algorithm as feed-forward compensation and PID algorithm as close-loop control can realize AMB system displacement minimum compensation at one fixed frequency, and improve the stability of the control system. The proposed research provides a new adaptive iterative learning control algorithm and control strategy for AMB displacement minimum compensation, and provides some references for time-varied displacement minimum compensation.

Gao, Hui; Xu, Longxiang; Zhu, Yili

2013-01-01

191

H2O concentration in the middle atmosphere: Processing of LIMS radiance measurements with a research algorithm  

NASA Astrophysics Data System (ADS)

Transmittance functions as well as inversion algorithms have been developed for deriving H2O profiles from radiometer measurements. These computer programs have been applied to evaluate own stratospheric balloon occultation measurements and LIMS (Limb Infrared Monitor of the Stratosphere) radiance measurements in the H2O channel. The results are compared with the H2O profiles in the LIMS data archive. The differences between corresponding H2O profiles are discussed in dependence of altitude and latitude.

Fischer, H.

192

Measurement of Small Values of Hydrostatic Pressure with the Compensation of Atmospheric Pressure Influence / Pomiar Ma?ych Warto?ci Ci?nienia Hydrostatycznego Z Kompensacj? Wp?ywu Ci?nienia Atmosferycznego  

NASA Astrophysics Data System (ADS)

Knowledge of pressure distribution (or differential pressure ) determines the fluid flow description through the porous medium. In the case of big Reynolds numbers it is not difficult, but for laminar flows (i.e. for Re numbers Bear, 1988; Duckworth, 1983; Troskola?ski, 1957) from the scope 0.01 to 3) this description is virtually impossible on the basis of the tools available on the market. The previous study (Broda & Filipek, 2012) focused on the difficulty of measurement in the case of small differences of pressure and suggested a new original method for the measurement. A new unit for the measurement was constructed consisting of two separate measurement containers. Then the measurements were conducted, which necessitated temperature stabilization of the device and compensation of the atmospheric pressure influence on the measurement process. This paper presents the results of the continuation of research concerning the methods and equipment for the measurement of very small pressure differences. The paper includes also the experience gained from the new measurement unit, which was presented in figures 1-5 subsequently presenting the concept of measurement of small values of hydrodynamic pressure with compensation of atmospheric pressure influence fig. 1; illustration presenting the state corresponding to the case of the lack of flow through the tested item fig 2; state corresponding to the fluid flow through the tested item fig. 3; then the description of the measurement of pressure drop on the tested item fig. 4 and the measurement methodology (relations (1) - (20)). Picture of the measurement unit and its components - fig. 5. Furthermore, the authors present an exemplary measurement series and focus on the method of measurement and data processing - tables 1-8 and figures 6-8. Table 4 presents the comparison of the measurement unit used in the previous research (Broda & Filipek, 2012) and the new one - presented in the paper. It should be noted that the structure has been simplified and the measurement accuracy has increased. Znajomo?? rozk?adu ci?nienia (lub ró?nicy ci?nie?) determinuje opis przep?ywu p?ynu przez o?rodek porowaty. W przypadku du?ych liczb Reynoldsa nie nastr?cza to wi?kszych trudno?ci, lecz dla przep?ywów laminarnych (tj. dla liczb Re (Bear, 1988; Duckworth, 1983; Troskola?ski, 1957) z zakresu 0.01 do 3) jest to praktycznie niemo?liwe w oparciu o dost?pne na rynku przyrz?dy. Przyczyny powoduj?ce tak? sytuacj? zosta?y omówione w poprzednim opracowaniu (Broda i Filipek, 2012), w którym zwrócono uwag? na trudno?ci pomiarów zwi?zane z napi?ciem powierzchniowym czy w?oskowato?ci? (Adamson, 1997). Zaproponowano (Broda i Filipek, 2012) now?, autorsk? metod? pomiaru bardzo ma?ych ró?nic ci?nie? oraz skonstruowano odpowiednie stanowisko sk?adaj?ce si? z dwóch oddzielnych zbiorników pomiarowych oraz przeprowadzono pomiary. Z przeprowadzonych bada? (Broda i Filipek, 2012) wynika?a konieczno?? zastosowania stabilizacji temperatury urz?dzenia oraz kompensacji wp?ywu ci?nienia atmosferycznego na proces pomiarowy. Niniejsza publikacja przedstawia wyniki kontynuacji bada? nad metodami i aparatur? do pomiaru bardzo ma?ych ró?nic ci?nie? z uwzgl?dnieniem zdobytych do?wiadcze?, w oparciu o nowe stanowisko pomiarowe, którego zasad? dzia?ania i budow? przedstawiono na rys. 1-5, kolejno przedstawiaj?c koncepcj? wykonania pomiaru ma?ych warto?ci ci?nienia hydrodynamicznego z kompensacj? wp?ywu ci?nienia atmosferycznego rys. 1; ilustracj? obrazuj?c? stan odpowiadaj?cy przypadkowi braku przep?ywu p?ynu przez badany obiekt rys. 2; omawiaj?c stan odpowiadaj?cy przypadkowi przep?ywu p?ynu przez badany obiekt rys. 3. Kolejno omówiono stan odpowiadaj?cy pomiarowi spadku ci?nienia na badanym obiekcie rys. 4 oraz przedstawiono metodyk? pomiaru (zale?no?ci (1) - (20)). Zdj?cie stanowiska badawczego oraz jego elementów ilustruje rys. 5. W dalszej cz??ci artyku?u autorzy przedstawiaj? przyk?adow? seri? pomiarow? zwracaj

Broda, Krzysztof; Filipek, Wiktor

2013-09-01

193

Temperature Effects and Compensation-Control Methods  

PubMed Central

In the analysis of the effects of temperature on the performance of microgyroscopes, it is found that the resonant frequency of the microgyroscope decreases linearly as the temperature increases, and the quality factor changes drastically at low temperatures. Moreover, the zero bias changes greatly with temperature variations. To reduce the temperature effects on the microgyroscope, temperature compensation-control methods are proposed. In the first place, a BP (Back Propagation) neural network and polynomial fitting are utilized for building the temperature model of the microgyroscope. Considering the simplicity and real-time requirements, piecewise polynomial fitting is applied in the temperature compensation system. Then, an integral-separated PID (Proportion Integration Differentiation) control algorithm is adopted in the temperature control system, which can stabilize the temperature inside the microgyrocope in pursuing its optimal performance. Experimental results reveal that the combination of microgyroscope temperature compensation and control methods is both realizable and effective in a miniaturized microgyroscope prototype.

Xia, Dunzhu; Chen, Shuling; Wang, Shourong; Li, Hongsheng

2009-01-01

194

Compensated Temperature Sensing Device.  

National Technical Information Service (NTIS)

A compensated temperature sensing device having a sensing element capable of surviving extreme operating environments while still being able to substantially instantaneously sense temperature changes. This is accomplished by incorporating within the devic...

A. S. Meyer

1980-01-01

195

State Workers' Compensation Laws.  

National Technical Information Service (NTIS)

The document contents include: Type of law and insurance requirements for private employment; Numerical exemptions; Coverage of agricultural workers; Jurisdictions in which workers' compensation laws apply to domestic employment; Medical benefits and meth...

1989-01-01

196

State Workers' Compensation Laws.  

National Technical Information Service (NTIS)

Table of Contents: Type of Law and Insurance Requirements for Private Employment; Numerical Exemptions; Coverage of Agricultural Workers; Jurisdictions in Which Workers' Compensation Laws Aply to Domestic Employment; Medical Benefits and Methods of Physic...

1990-01-01

197

Dynamic compensation system [ships  

Microsoft Academic Search

A dynamic compensation system (DC-system) has been developed. It is used as an extension of the KaMeWa polar joystick system, where the horizontal motions of a ship are controlled by main propellers, rudders and bow thrusters. It acts like a compensator for wind and current disturbances, allowing the joystick operator to run the ship in almost all weather conditions as

C. G. Kallstrom; Kalle Theoren

1994-01-01

198

Compensation for radiation risks  

SciTech Connect

Several years ago tables of estimates of the so-called probability of causation were prepared and published to facilitate the compensation of cancer victims with an exposure to radiation prior to the diagnosis of cancer. The probability of causation is defined as the probability that a particular cancer in an individual was caused by an identified radiation exposure prior to diagnosis of the cancer. Probability of causation estimates were intended to be used to compensate victims of radiogenic cancers. We propose offering compensation to persons who received certain clearly identifiable exposures to ionizing radiation above natural background before some of them become cancer victims. First we discuss some types and circumstances of radiation exposures for which such compensation should be offered. The {open_quotes}equity postulate,{close_quotes} that compensation should restore the expected quality of life-measured in dollars-of an exposed person to that of an unexposed person, yields a formula for estimating the appropriate compensation. Interestingly this formula, first stated by D.V. Lindley, contains the probability of causation as a factor. An application of the formula to A-bomb survivor data on leukemia and discussion of estimation problems associated with this formula conclude the paper.

Groer, P.G. [Univ. of Tennessee, Knoxville, TN (United States)

1996-06-01

199

Track covariance consistency compensation performance  

NASA Astrophysics Data System (ADS)

The primary components of a target track are the estimated state vector and its error variance-covariance matrix (or simply the covariance). The estimated state indicates the location and motion of the target. The track covariance is intended to indicate the uncertainty or inaccuracy of the target state estimate. The covariance is computed by the track processor and may or may not realistically indicate the inaccuracy of the state estimate. Covariance Consistency is the property that a computed variance-covariance matrix realistically represents the covariance of the actual errors of the estimate. The computed covariance of the state estimation error is used in the computations of the data association processing function and the estimation filter; consequently, degraded track consistency might cause misassociations (correlation errors) and degraded filter processing that can degrade track performance. The computed covariance of the state estimation error is also used by downstream functions, such as the network-level resource management functions, to indicate the accuracy of the target state estimate. Hence, degraded track consistency can mislead those functions and the war fighter about the accuracy of each target track. In the development of target trackers, far more attention has been given to improving the accuracy of the estimated target state than in improving the track covariance consistency. This paper addresses covariance compensation to reduce the degradation of consistency due to potential misassociations in measurement fusion using single-frame data association. The compensation approach used is also applicable to other fusion approaches and to tracking with data from a single sensor. This paper also shows how this compensation approach can be applied to a wide variety of data association algorithms.

Drummond, Oliver E.; Dana-Bashian, David

2009-08-01

200

Delay compensation in integrated communication and control systems. II - Implementation and verification  

NASA Technical Reports Server (NTRS)

The implementation and verification of the delay-compensation algorithm are addressed. The delay compensator has been experimentally verified at an IEEE 802.4 network testbed for velocity control of a DC servomotor. The performance of the delay-compensation algorithm was also examined by combined discrete-event and continuous-time simulation of the flight control system of an advanced aircraft that uses the SAE (Society of Automotive Engineers) linear token passing bus for data communications.

Luck, Rogelio; Ray, Asok

1990-01-01

201

Real-time adaptive radiometric compensation.  

PubMed

Recent radiometric compensation techniques make it possible to project images onto colored and textured surfaces. This is realized with projector-camera systems by scanning the projection surface on a per-pixel basis. Using the captured information, a compensation image is calculated that neutralizes geometric distortions and color blending caused by the underlying surface. As a result, the brightness and the contrast of the input image is reduced compared to a conventional projection onto a white canvas. If the input image is not manipulated in its intensities, the compensation image can contain values that are outside the dynamic range of the projector. These will lead to clipping errors and to visible artifacts on the surface. In this article, we present an innovative algorithm that dynamically adjusts the content of the input images before radiometric compensation is carried out. This reduces the perceived visual artifacts while simultaneously preserving a maximum of luminance and contrast. The algorithm is implemented entirely on the GPU and is the first of its kind to run in real-time. PMID:17993705

Grundhöfer, Anselm; Bimber, Oliver

2008-01-01

202

An innovative approach to compensator design  

NASA Technical Reports Server (NTRS)

The design is considered of a computer-aided-compensator for a control system from a frequency domain point of view. The design technique developed is based on describing the open loop frequency response by n discrete frequency points which result in n functions of the compensator coefficients. Several of these functions are chosen so that the system specifications are properly portrayed; then mathematical programming is used to improve all of these functions which have values below minimum standards. To do this, several definitions in regard to measuring the performance of a system in the frequency domain are given, e.g., relative stability, relative attenuation, proper phasing, etc. Next, theorems which govern the number of compensator coefficients necessary to make improvements in a certain number of functions are proved. After this a mathematical programming tool for aiding in the solution of the problem is developed. This tool is called the constraint improvement algorithm. Then for applying the constraint improvement algorithm generalized, gradients for the constraints are derived. Finally, the necessary theory is incorporated in a Computer program called CIP (compensator Improvement Program). The practical usefulness of CIP is demonstrated by two large system examples.

Mitchell, J. R.; Mcdaniel, W. L., Jr.

1973-01-01

203

An improvement to the volcano-scan algorithm for atmospheric correction of CRISM and OMEGA spectral data  

NASA Astrophysics Data System (ADS)

The observations of Mars by the CRISM and OMEGA hyperspectral imaging spectrometers require correction for photometric, atmospheric and thermal effects prior to the interpretation of possible mineralogical features in the spectra. Here, we report on a simple, yet non-trivial, adaptation to the commonly-used volcano-scan correction technique for atmospheric CO 2, which allows for the improved detection of minerals with intrinsic absorption bands at wavelengths between 1.9 and 2.1 ?m. This volcano-scan technique removes the absorption bands of CO 2 by ensuring that the Lambert albedo is the same at two wavelengths: 1.890 and 2.011 ?m, with the first wavelength outside the CO 2 gas bands and the second wavelength deep inside the CO 2 gas bands. Our adaptation to the volcano-scan technique moves the first wavelength from 1.890 ?m to be instead within the gas bands at 1.980 ?m, and for CRISM data, our adaptation shifts the second wavelength slightly, to 2.007 ?m. We also report on our efforts to account for a slight ˜0.001 ?m shift in wavelengths due to thermal effects in the CRISM instrument.

McGuire, Patrick C.; Bishop, Janice L.; Brown, Adrian J.; Fraeman, Abigail A.; Marzo, Giuseppe A.; Frank Morgan, M.; Murchie, Scott L.; Mustard, John F.; Parente, Mario; Pelkey, Shannon M.; Roush, Ted L.; Seelos, Frank P.; Smith, Michael D.; Wendt, Lorenz; Wolff, Michael J.

2009-06-01

204

Retrieving water surface temperature from archive LANDSAT thermal infrared data: Application of the mono-channel atmospheric correction algorithm over two freshwater reservoirs  

NASA Astrophysics Data System (ADS)

Water surface temperature is a key element in characterizing the thermodynamics of waterbodies, and for irregularly-shaped inland reservoirs, LANDSAT thermal infrared images are the best alternative yet for the retrieval of this parameter. However, images must be corrected mainly for atmospheric effects in order to be fully exploitable. The objective of this study is to validate the mono-channel correction algorithm for single-band thermal infrared LANDSAT data as put forward by Jiménez-Muñoz et al. (2009). Two freshwater reservoirs in continental France were selected as study sites, and best use was made of all accessible image and field data. Results obtained are satisfactory and in accordance with the literature: r2 values are above 0.90 and root-mean-square error values are comprised between 1 and 2 °C. Moreover, paired Wilcoxon signed rank tests showed a highly significant difference between field and uncorrected image data, a very highly significant difference between uncorrected and corrected image data, and no significant difference between field and corrected image data. The mono-channel algorithm is hence recommended for correcting archive LANDSAT single-band thermal infrared data for inland waterbody monitoring and study.

Simon, R. N.; Tormos, T.; Danis, P.-A.

2014-08-01

205

Workers' Compensation and Teacher Stress.  

ERIC Educational Resources Information Center

Examines the Workers' Compensation system and teacher stress to determine if a burned-out teacher should be eligible for Workers' Compensation benefits. Concludes that although most states do not allow Workers' Compensation benefits to burned-out teachers, compensation should be granted because the injuries are real and work-related. (Contains 48…

Nisbet, Michael K.

1999-01-01

206

Clouds and the Earth's Radiant Energy System (CERES) Algorithm Theoretical Basis Document. Volume 3; Cloud Analyses and Determination of Improved Top of Atmosphere Fluxes (Subsystem 4)  

NASA Technical Reports Server (NTRS)

The theoretical bases for the Release 1 algorithms that will be used to process satellite data for investigation of the Clouds and Earth's Radiant Energy System (CERES) are described. The architecture for software implementation of the methodologies is outlined. Volume 3 details the advanced CERES methods for performing scene identification and inverting each CERES scanner radiance to a top-of-the-atmosphere (TOA) flux. CERES determines cloud fraction, height, phase, effective particle size, layering, and thickness from high-resolution, multispectral imager data. CERES derives cloud properties for each pixel of the Tropical Rainfall Measuring Mission (TRMM) visible and infrared scanner and the Earth Observing System (EOS) moderate-resolution imaging spectroradiometer. Cloud properties for each imager pixel are convolved with the CERES footprint point spread function to produce average cloud properties for each CERES scanner radiance. The mean cloud properties are used to determine an angular distribution model (ADM) to convert each CERES radiance to a TOA flux. The TOA fluxes are used in simple parameterization to derive surface radiative fluxes. This state-of-the-art cloud-radiation product will be used to substantially improve our understanding of the complex relationship between clouds and the radiation budget of the Earth-atmosphere system.

1995-01-01

207

Coupling between the University of California, Davis, Advanced Canopy-Atmosphere-Soil Algorithm (ACASA) and MM5: Preliminary Results for July 1998 for Western North America.  

NASA Astrophysics Data System (ADS)

The University of California, Davis, Advanced Canopy-Atmosphere-Soil Algorithm (ACASA) is coupled to the fifth-generation Pennsylvania State University-National Center for Atmospheric Research (NCAR) Mesoscale Model (MM5) as a land surface scheme. Simulations for July 1998 over western North America show that this coupling, the first between a mesoscale model and a land surface model of this complexity, is successful. Comparisons among model output, National Centers for Environmental Prediction-NCAR reanalysis fields, and station data show that MM5-ACASA generally reproduces near-surface temperature in a realistic fashion, but with a stronger diurnal cycle than observations suggest. A control run using the existing Louis/European Centre for Medium-Range Weather Forecasts land surface formulation produces unrealistically low temperatures associated with high latent heating and precipitation amounts over much of the model domain. Simulations of heat and moisture fluxes using the Biosphere-Atmosphere Transfer Scheme (BATS) are generally comparable to ACASA, but near-surface air temperatures reveal excessively warm conditions. Low specific-humidity values over land in both MM5-ACASA and MM5-BATS simulations and low oceanic values in all three simulations suggest a possible dry bias in MM5. Comparison statistics between modeled near-surface climatological behavior and associated fluxes at three sites show that MM5-ACASA, out of the three simulations, agrees most with observations. Sensitivity tests show that MM5 is generally more sensitive to the choice of surface scheme than it is to soil moisture initialization. Comparisons of mean carbon dioxide fluxes reveal that ACASA can be a useful tool in examining the terrestrial carbon cycle.

Pyles, R. David; Weare, Bryan C.; Tha Paw U, Kyaw; Gustafson, William

2003-05-01

208

The compensated Kalman filter.  

NASA Technical Reports Server (NTRS)

This paper introduces the compensated Kalman filter, a suboptimal state estimator which can be used to eliminate steady-state bias errors when it is used in conjunction with the mismatched steady-state (asymptotic) time-invariant Kalman-Bucy filter. The uncompensated mismatched steady state Kalman-Bucy filter exhibits bias errors whenever the nominal plant parameters used in the filter design are different from the actual plant parameters. The approach used relies on the utilization of the residual (innovations) process of the mismatched filter to estimate, via a Kalman-Bucy filter, the state estimation errors and subsequent improvements of the state estimate. The compensated Kalman filter augments the mismatched steady state Kalman-Bucy filrby the introduction of additional dynamics and feedforward integral compensation channels.

Athans, M.

1972-01-01

209

Compensation neurosis rides again.  

PubMed

Compensation neurosis (CN), also known as accident neurosis, has generally not been considered to be a 'real' disorder. In 1961 it was seemingly laid to rest by Henry Miller, a distinguished neurologist, in a sharp article which appeared in the British Medical Journal. Miller's view of patients who presented psychological symptoms following accidents or traumas was suspicious. Compensated or not, his view seemed to be that they should have their legal process finished as quickly as possible and then they will miraculously convalescence. Miller's work, it appeared, was the coup de grâce for this ill-defined diagnosis. Today, however, compensation neurosis seems to ride again. After a prolonged silence in the psychiatric literature, new papers are emerging, strongly suggesting that this vanishing diagnosis be reconsidered. This new trend will be presented. PMID:1393173

Levy, A

1992-01-01

210

Compensating For Unbalance In Pulse-Code Phase Modulation  

NASA Technical Reports Server (NTRS)

Algorithm proposed for use in pulse-code phase-modulation transmitter in which non-return-to-zero (NRZ) or biphase data modulated directly onto radio-frequency residual carrier signal. Devised to compensate somewhat for effect, upon distant receiver, of unbalance in stream of transmitted data. Formulated to compute combinations of modulation index, data rate, and transmitter power compensating for measured unbalance in transmitted data stream.

Nguyen, Tien M.; Hinedi, Sami M.

1995-01-01

211

Robust beam compensation for laser-based additive manufacturing  

Microsoft Academic Search

Today’s software for laser-based additive manufacturing compensates for the finite dimensions of the laser spot by insetting the contours of a solid part. However, features having smaller dimensions are removed by this operation, which may significantly alter the structure of thin-walled parts. To avoid potential production errors, this work describes in detail an algorithmic framework that makes beam compensation more

Maarten Moesen; Tom Craeghs; Jean-Pierre Kruth; Jan Schrooten

2011-01-01

212

Dosage compensation in birds  

Microsoft Academic Search

The Z and W sex chromosomes of birds have evolved independently from the mammalian X and Y chromosomes [1]. Unlike mammals, female birds are heterogametic (ZW), while males are homogametic (ZZ). Therefore male birds, like female mammals, carry a double dose of sex-linked genes relative to the other sex. Other animals with nonhomologous sex chromosomes possess “dosage compensation” systems to

Heather A McQueen; Derek McBride; Gino Miele; Adrian P Bird; Michael Clinton

2001-01-01

213

Reactive Power Compensating System.  

DOEpatents

The circuit was designed for the specific application of wind-driven induction generators. It has great potential for application in any situation where a varying reactive power load is present, such as with induction motors or generators, or for transmission network compensation.

Williams, Timothy J.; El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.

1985-01-04

214

SOFIA image motion compensation  

Microsoft Academic Search

We describe a laboratory simulation of an image motion compensation system for SOFIA that uses high-speed image acquisition from the science instrument HIPO as the sensing element of the system and a Newport voice-coil actuated fast steering mirror as the correcting actuator. Performance of the system when coupled to the SOFIA secondary mirror is estimated based on the known current

Edward Dunham; Peter Collins; Andreas Reinacher; Ulrich Lampater

2010-01-01

215

Photoelectric compensating tiltmeter  

Microsoft Academic Search

Summary A new instrument has been designed for recording the horizontal components of tidal variations of the Earth's field of gravity and of tidal and non-tidal tilts of the Earth's crust. After justifying the use of the individual constructional elements, the functional model of the photo-electric compensating tiltmeter, constructing in the Geophysical Institute of the CSAS and installed at the

Lumír Skalský; Vítezslav Soukup; J. Pícha

1974-01-01

216

Experimental code verification results for reflector antenna distortion compensation by array feeds  

NASA Technical Reports Server (NTRS)

Electronic compensation of reflector surface distortion using array feed with individual amplitude and phase control of the array elements is becoming increasingly attractive because of the recent advances in monolithic microwave integrated circuit (MMIC) technology. An algorithm has been developed previously using the concept of focal plane conjugate field matching in the receive mode and a computer code has been generated that predicts the proper excitation coefficients for the elements of the reflector feed array to compensate the effects of reflector surface distortion. This paper presents the results of an experimental study to verify the above compensation algorithm and in general to demonstrate the effectiveness of the array feed compensation technique.

Zaman, A. J.; Rahmat-Samii, Y.; Woo, K.

1992-01-01

217

An innovative approach to compensator design  

NASA Technical Reports Server (NTRS)

The primary goal is to present for a control system a computer-aided-compensator design technique from a frequency domain point of view. The thesis for developing this technique is to describe the open loop frequency response by n discrete frequency points which result in n functions of the compensator coefficients. Several of these functions are chosen so that the system specifications are properly portrayed; then mathematical programming is used to improve all of these functions which have values below minimum standards. In order to do this several definitions in regard to measuring the performance of a system in the frequency domain are given. Next, theorems which govern the number of compensator coefficients necessary to make improvements in a certain number of functions are proved. After this a mathematical programming tool for aiding in the solution of the problem is developed. Then for applying the constraint improvement algorithm generalized gradients for the constraints are derived. Finally, the necessary theory is incorporated in a computer program called CIP (compensator improvement program).

Mitchell, J. R.

1972-01-01

218

Temperature Compensation of Transistor Integrator.  

National Technical Information Service (NTIS)

It is shown that the temperature dependence of an inverted transistor can be very effectively used for temperature compensation. Conditions were derived for complete compensation of an integrator amplifier with emitter follower output and single-stage amp...

C. P. Wang

1964-01-01

219

Motion-compensated highly scalable video compression using an adaptive 3D wavelet transform based on lifting  

Microsoft Academic Search

This paper proposes a new framework for the construction of motion compensated wavelet transforms, with application to efficient highly scalable video compression. Motion compensated transform techniques, as distinct from motion compensated predictive coding, represent a key tool in the development of highly scalable video compression algorithms. The proposed framework overcomes a variety of limitations exhibited by existing approaches. This new

Andrew Secker; David Taubman

2001-01-01

220

Deferred Compensation Becomes More Common  

ERIC Educational Resources Information Center

A key part of the compensation package for some college and university presidents is money that they do not receive in their paychecks. Formally known as deferred compensation, such payments can take many forms, including supplemental retirement pay, severance pay, or even bonuses. With large institutions leading the way, deferred compensation has…

June, Audrey Williams

2006-01-01

221

2007 CEO Compensation Study  

NSDL National Science Digital Library

Charity Navigator provides high-quality information about charities in order "to advance a more efficient and responsive philanthropic marketplace." One of the more recently published studies is the 2007 CEO Compensation Study. Visitors can read this annotated report here in its entirety, and it contains a wealth of information about the subject. In the year 2007, their research shows that the top leaders of the 5242 largest charities in America earn an average salary of $145,270. While this amount may strike some as rather large, the report also notes that CEO compensation accounts for just 3.37% of the average organization's spending. The report contains a number of helpful charts, such as those that list average CEO salary by geographic region and by size of charity.

2007-08-01

222

ICA-based compensation for IQ imbalance in OFDM optical fiber communication  

NASA Astrophysics Data System (ADS)

A method based on the independent component analysis (ICA) is proposed to compensate the in-phase and quadrature-phase the (IQ) imbalance in orthogonal frequency division multiplexing (OFDM) optical fiber communication systems. The mathematical model of IQ imbalance system has been analyzed. Then, ICA algorithm is applied in the system to combat the mirror interference introduced by IQ imbalance. This algorithm can realize the joint compensation of both transmitter and receiver IQ imbalance with the optical channel that contains noise, attenuation and chromatic dispersion. The simulation shows that the performance degradation caused by IQ imbalance can be compensated by ICA algorithm effectively.

Jiang, Shan; Hu, Guijun; Li, Zhaoxi; Mu, Liping; Zhang, Jingdong

2014-01-01

223

Model-Based Sonar Motion Compensation for Bottom Reverberation Coherence  

Microsoft Academic Search

Much signal processing in sonar takes advantage of ping-to-ping bottom reverberation coherence. However, bottom reverberation coherence is degraded owing to environment variations including unknown sonar sensor motions from platform instability. In this paper, an algorithm is described to compensate small-scale motion of high-frequency sonar sensors which is for enhancing ping-to-ping bottom reverberation coherence. The algorithm is based on sonar modeling

Jinyun Ren; Rodney G. Vaughan

2010-01-01

224

Atmospheric Hydrocodes Using FCT Algorithms.  

National Technical Information Service (NTIS)

Several recently developed multidimensional hydrocodes for low-altitude nuclear-explosion phenomenology are described and their performance characteristics are discussed. These codes all use flux-corrected transport techniques because of the strong shocks...

J. P. Boris J. H. Gardner S. Zalesak

1975-01-01

225

Adaptive compensation of fuel dynamics in an SI engine using a switching EGO sensor  

Microsoft Academic Search

Current engine controllers employ a feedforward compensator to eliminate the effects of fuel dynamics (“wall-wetting”) on the air-fuel ratio trace. Uncompensated or improperly compensated fuel dynamics may cause significant A\\/F excursions during transient operations, accompanied by increased emissions levels. This paper describes the development of an adaptive algorithm for transient fuel compensation using only a switching exhaust gas oxygen (EGO)

P. E. Moraal

1995-01-01

226

SOFIA image motion compensation  

NASA Astrophysics Data System (ADS)

We describe a laboratory simulation of an image motion compensation system for SOFIA that uses high-speed image acquisition from the science instrument HIPO as the sensing element of the system and a Newport voice-coil actuated fast steering mirror as the correcting actuator. Performance of the system when coupled to the SOFIA secondary mirror is estimated based on the known current performance of the secondary mirror controller. The system is described and the observed performance is presented together with expectations for applicability in flight with SOFIA.

Dunham, Edward; Collins, Peter; Reinacher, Andreas; Lampater, Ulrich

2010-07-01

227

Springback Prediction, Compensation and Correlation for Automotive Stamping  

NASA Astrophysics Data System (ADS)

To reduce weight and increase fuel efficiency and safety, more and more automotive sheet stamping parts are being made of aluminum and high strength steels. Forming of such materials encounters not just reduced formability but also dimensional quality problems. Springback prediction accuracy and compensation effectiveness have been the major challenge to die development, construction and tryout. In this paper, the factors that affect the accuracy of springback prediction are discussed, which includes the effect of material models, the selection of element size, and the contact algorithms. Springback predictions of several automotive aluminum and high strength panels are compared with measurement data. The examples show that the prediction correlates with measurement data in both springback trend and magnitude. The effect of springback on final product can be reduced or eliminated through process control and die face compensation. The process control method involves finding the root causes of springback and eliminating them through process modification. The geometrical compensation of die surface is a direct way to eliminate the springback effect. The global scaling compensation method is normally limited to parts with relatively small springback. For large springback and twisting, a new approach is discussed, which takes into account of the effect of deformation and springback history. The compensation is achieved iteratively by solving a system of non-linear equations. Production dies were cut to the compensated surface, which shows that the die compensation is an efficient way to reduce springback-induced geometry deviation.

Xu, Siguang; Zhao, Kunmin; Lanker, Terry; Zhang, Jimmy; Wang, C. T.

2005-08-01

228

Design of ground motion compensation servo system  

NASA Astrophysics Data System (ADS)

This paper designs a ground motion compensation servo system based on two-dimensional pointing mirror. The servo system is mainly composed of digital control unit, analog driving unit and driving motor. Besides, the control algorithm and strategy of driving motor would be given, and based on the control strategy, a closed-loop controller which consists of current loop, velocity loop and position loop is designed and simulated. Especially, the speed loop adopts pseudo differential feed-forward (PDFF) controller to avoid extensive overshoot. Finally, the experiment results show that the designed servo system has fast response and small overshoot.

Tan, Chan; Ding, Lei; Chai, Jinguang

2013-05-01

229

Software compensated multichannel pressure sensing system  

NASA Technical Reports Server (NTRS)

A PC-based software system is described which can be used for data acquisition and thermal-error correction of a multichannel pressure-sensor system developed for use in a cryogenic environment. The software incorporates pressure-sensitivity and sensor-offset compensation files into thermal error-correction algorithms, and the sensors are calibrated by simulating the operating conditions. The system is found to be effective in the collecting, storing, and processing of multichannel pressure-sensor data to correct thermally induced offset and sensitivity errors.

Chapman, John J.

1990-01-01

230

Software compensated multichannel pressure sensing system  

NASA Astrophysics Data System (ADS)

A PC-based software system is described which can be used for data acquisition and thermal-error correction of a multichannel pressure-sensor system developed for use in a cryogenic environment. The software incorporates pressure-sensitivity and sensor-offset compensation files into thermal error-correction algorithms, and the sensors are calibrated by simulating the operating conditions. The system is found to be effective in the collecting, storing, and processing of multichannel pressure-sensor data to correct thermally induced offset and sensitivity errors.

Chapman, John J.

231

Block-classified motion compensation scheme for digital video  

SciTech Connect

A novel scheme for block-based motion compensation is introduced in which a block is classified according to the energy that is directly related to the motion activity it represents. This classification allows more flexibility in controlling the bit rate arid the signal-to-noise ratio and results in a reduction in motion search complexity. The method introduced is not dependent on the particular type of motion search algorithm implemented and can thus be used with any method assuming that the underlying matching criteria used is minimum absolute difference. It has been shown that the method is superior to a simple motion compensation algorithm where all blocks are motion compensated regardless of the energy resulting after the displaced difference.

Zafar, S. [Argonne National Lab., IL (United States). Mathematics and Computer Science Div.; Zhang, Ya-Qin [David Sarnoff Research Center, Princeton, NJ (United States); Jabbari, B. [George Mason Univ., Fairfax, VA (United States). Dept. of Electrical and Computer Engineering

1996-03-01

232

Self-compensating tensiometer and method  

DOEpatents

A pressure self-compensating tensiometer and method to in situ determine below grade soil moisture potential of earthen soil independent of changes in the volume of water contained within the tensiometer chamber, comprising a body having first and second ends, a porous material defining the first body end, a liquid within the body, a transducer housing submerged in the liquid such that a transducer sensor within the housing is kept below the working fluid level in the tensiometer and in fluid contact with the liquid and the ambient atmosphere.

Hubbell, Joel M. (Idaho Falls, ID); Sisson, James B. (Idaho Falls, ID)

2003-01-01

233

Path Following with Slip Compensation for a Mars Rover  

NASA Technical Reports Server (NTRS)

A software system for autonomous operation of a Mars rover is composed of several key algorithms that enable the rover to accurately follow a designated path, compensate for slippage of its wheels on terrain, and reach intended goals. The techniques implemented by the algorithms are visual odometry, full vehicle kinematics, a Kalman filter, and path following with slip compensation. The visual-odometry algorithm tracks distinctive scene features in stereo imagery to estimate rover motion between successively acquired stereo image pairs, by use of a maximum-likelihood motion-estimation algorithm. The full-vehicle kinematics algorithm estimates motion, with a no-slip assumption, from measured wheel rates, steering angles, and angles of rockers and bogies in the rover suspension system. The Kalman filter merges data from an inertial measurement unit (IMU) and the visual-odometry algorithm. The merged estimate is then compared to the kinematic estimate to determine whether and how much slippage has occurred. The kinematic estimate is used to complement the Kalman-filter estimate if no statistically significant slippage has occurred. If slippage has occurred, then a slip vector is calculated by subtracting the current Kalman filter estimate from the kinematic estimate. This slip vector is then used, in conjunction with the inverse kinematics, to determine the wheel velocities and steering angles needed to compensate for slip and follow the desired path.

Helmick, Daniel; Cheng, Yang; Clouse, Daniel; Matthies, Larry; Roumeliotis, Stergios

2005-01-01

234

Rain Attenuation and Doppler Shift Compensation for Satellite Communications  

Microsoft Academic Search

In high-speed multimedia satellite communication sys- tems, it is essential to provide high-quality, economical ser- vices by using efficient transmission schemes which can overcome channel impairments appearing in the satellite link. This paper introduces techniques to compensate for rain attenuation and the Doppler shift in the satellite com- munication link. An adaptive transmission technique with a control algorithm to adaptively

Sooyoung Kim Shin Shin; Kwangjae Lim Lim; Kwonhue Choi Choi; Kunseok Kang Kang

2002-01-01

235

Multiple CFOs compensation and BER analysis for cooperative communication systems  

Microsoft Academic Search

In cooperative communication systems, multiple carrier frequency offsets (MCFO) appear due to the different accuracy of the nodes' oscillators and Doppler spreads, which drastically degrades the performance of space-frequency block coded (SFBC) cooperative systems. In this paper, a MCFO compensation algorithm including modified SFBC decoder, minimum Euclidean distance decision criterion and interference reconstructing eliminator is proposed. Besides, the bit error

Yanyan Zhang; Jianhua Zhang

2009-01-01

236

Using Weighting Adjustments to Compensate for Survey Nonresponse  

ERIC Educational Resources Information Center

Weighting adjustments are used in some studies to compensate for biased estimators produced by survey nonresponse. Using data from the 2004 National Survey of Student Engagement (NSSE) and the NSSE poststratification weighting algorithm, this study found that weighting adjustments were needed for some, but not all institutions. Unfortunately, no…

Pike, Gary R.

2008-01-01

237

Closed-loop compensation of kinematic error in harmonic drives for precision control applications  

Microsoft Academic Search

We present nonlinear control algorithms to compensate for kinematic error in harmonic drives, thus forming a solid basis to improve their performance in precision positioning applications. Kinematic error, defined as deviation between expected and actual output positions, influences performance by producing static positioning error and inducing dynamic vibration effects. Its compensation is difficult because of its nonlinear behavior and dependence

Prasanna S. Gandhi; Fathi H. Ghorbel

2002-01-01

238

Research on temperature dependent characteristics and compensation methods for digital gyroscope  

Microsoft Academic Search

In recent years, MEMS gyroscope which is a kind of angular-rate-sensor has been improved greatly. In this paper, the effect of temperature changing on MEMS gyroscope is analysed. An evaluation and compensation platform based on the MCU and PC software has been fabricated. The temperature tests were done and some novel compensation algorithms were presented to fit the temperature curve.

Dachuan Liu; Xiaozhu Chi; Jian Cui; Longtao Lin; Qiancheng Zhao; Zhenchuan Yang; Guizhen Yan

2008-01-01

239

Are Reputation and Power Compensating Differentials in CEO Compensation?  

Microsoft Academic Search

This study develops and tests an inclusive, interdisciplinary model of executive com- pensation using agency theory as a founda- tion. The study introduces a theory-based multidimensional size index measure, and extends the literature by the inclusion of nonpecuniary compensation (prestige and power) in the model. The empirical test used data from chief executive oÅcer (CEO) compensation in 72 US firms

Frank L. Winfrey; John E. Logan

1998-01-01

240

Summing pressure compensation control  

SciTech Connect

This patent describes a summing pressure compensator control for hydraulic loads with at least one of the hydraulic loads being a variable displacement motor having servo means for controlling the displacement thereof, first hydraulic means responsive to the supply of fluid to the variable displacement motor to provide a first pressure signal, second hydraulic means responsive to the supply of fluid to a second hydraulic load to provide a second pressure signal, summing means for receiving the first and second pressure signals and providing a control signal proportional to the sum of the first and second pressure signals, the control signal being applied to the servo means to increase the displacement of the variable displacement motor.

Myers, H.A.

1988-04-26

241

Temperature compensated photovoltaic array  

DOEpatents

A temperature compensated photovoltaic module (20) comprised of a series of solar cells (22) having a thermally activated switch (24) connected in parallel with several of the cells (22). The photovoltaic module (20) is adapted to charge conventional batteries having a temperature coefficient (TC) differing from the temperature coefficient (TC) of the module (20). The calibration temperatures of the switches (24) are chosen whereby the colder the ambient temperature for the module (20), the more switches that are on and form a closed circuit to short the associated solar cells (22). By shorting some of the solar cells (22) as the ambient temperature decreases, the battery being charged by the module (20) is not excessively overcharged at lower temperatures. PV module (20) is an integrated solution that is reliable and inexpensive.

Mosher, Dan Michael (Plano, TX)

1997-11-18

242

Fixman compensating potential for general branched molecules.  

PubMed

The technique of constraining high frequency modes of molecular motion is an effective way to increase simulation time scale and improve conformational sampling in molecular dynamics simulations. However, it has been shown that constraints on higher frequency modes such as bond lengths and bond angles stiffen the molecular model, thereby introducing systematic biases in the statistical behavior of the simulations. Fixman proposed a compensating potential to remove such biases in the thermodynamic and kinetic properties calculated from dynamics simulations. Previous implementations of the Fixman potential have been limited to only short serial chain systems. In this paper, we present a spatial operator algebra based algorithm to calculate the Fixman potential and its gradient within constrained dynamics simulations for branched topology molecules of any size. Our numerical studies on molecules of increasing complexity validate our algorithm by demonstrating recovery of the dihedral angle probability distribution function for systems that range in complexity from serial chains to protein molecules. We observe that the Fixman compensating potential recovers the free energy surface of a serial chain polymer, thus annulling the biases caused by constraining the bond lengths and bond angles. The inclusion of Fixman potential entails only a modest increase in the computational cost in these simulations. We believe that this work represents the first instance where the Fixman potential has been used for general branched systems, and establishes the viability for its use in constrained dynamics simulations of proteins and other macromolecules. PMID:24387353

Jain, Abhinandan; Kandel, Saugat; Wagner, Jeffrey; Larsen, Adrien; Vaidehi, Nagarajan

2013-12-28

243

Fixman compensating potential for general branched molecules  

SciTech Connect

The technique of constraining high frequency modes of molecular motion is an effective way to increase simulation time scale and improve conformational sampling in molecular dynamics simulations. However, it has been shown that constraints on higher frequency modes such as bond lengths and bond angles stiffen the molecular model, thereby introducing systematic biases in the statistical behavior of the simulations. Fixman proposed a compensating potential to remove such biases in the thermodynamic and kinetic properties calculated from dynamics simulations. Previous implementations of the Fixman potential have been limited to only short serial chain systems. In this paper, we present a spatial operator algebra based algorithm to calculate the Fixman potential and its gradient within constrained dynamics simulations for branched topology molecules of any size. Our numerical studies on molecules of increasing complexity validate our algorithm by demonstrating recovery of the dihedral angle probability distribution function for systems that range in complexity from serial chains to protein molecules. We observe that the Fixman compensating potential recovers the free energy surface of a serial chain polymer, thus annulling the biases caused by constraining the bond lengths and bond angles. The inclusion of Fixman potential entails only a modest increase in the computational cost in these simulations. We believe that this work represents the first instance where the Fixman potential has been used for general branched systems, and establishes the viability for its use in constrained dynamics simulations of proteins and other macromolecules.

Jain, Abhinandan, E-mail: Abhi.Jain@jpl.nasa.gov [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109 (United States)] [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109 (United States); Kandel, Saugat; Wagner, Jeffrey; Larsen, Adrien; Vaidehi, Nagarajan, E-mail: nvaidehi@coh.org [Division of Immunology, Beckman Research Institute of the City of Hope, Duarte, California 91010 (United States)] [Division of Immunology, Beckman Research Institute of the City of Hope, Duarte, California 91010 (United States)

2013-12-28

244

Failure and Redemption of Multifilter Rotating Shadowband Radiometer (MFRSR)/Normal Incidence Multifilter Radiometer (NIMFR) Cloud Screening: Contrasting Algorithm Performance at Atmospheric Radiation Measurement (ARM) North Slope of Alaska (NSA) and Southern Great Plains (SGP) Sites  

SciTech Connect

Well-known cloud-screening algorithms, which are designed to remove cloud-contaminated aerosol optical depths (AOD) from AOD measurements, have shown great performance at many middle-to-low latitude sites around the world. However, they may occasionally fail under challenging observational conditions, such as when the sun is low (near the horizon) or when optically thin clouds with small spatial inhomogeneity occur. Such conditions have been observed quite frequently at the high-latitude Atmospheric Radiation Measurement (ARM) North Slope of Alaska (NSA) sites. A slightly modified cloud-screening version of the standard algorithm is proposed here with a focus on the ARM-supported Multifilter Rotating Shadowband Radiometer (MFRSR) and Normal Incidence Multifilter Radiometer (NIMFR) data. The modified version uses approximately the same techniques as the standard algorithm, but it additionally examines the magnitude of the slant-path line of sight transmittance and eliminates points when the observed magnitude is below a specified threshold. Substantial improvement of the multi-year (1999-2012) aerosol product (AOD and its Angstrom exponent) is shown for the NSA sites when the modified version is applied. Moreover, this version reproduces the AOD product at the ARM Southern Great Plains (SGP) site, which was originally generated by the standard cloud-screening algorithms. The proposed minor modification is easy to implement and its application to existing and future cloud-screening algorithms can be particularly beneficial for challenging observational conditions.

Kassianov, Evgueni I.; Flynn, Connor J.; Koontz, Annette S.; Sivaraman, Chitra; Barnard, James C.

2013-09-11

245

Adaptive compensation for the nonlinearity error in a heterodyne interferometer  

NASA Astrophysics Data System (ADS)

Laser interferometry has been widely used in the field of nano-metrology due to its superior properties, such as its almost unlimited resolution and its flexible set up. In practical measurements with a heterodyne laser interferometer, however, some obstacles, such as environmental and nonlinearity errors, limit its measurement accuracy. In this paper, we compensate for nonlinearity errors by applying the recursive weighted least-squares method and the robust observer based Kalman filter algorithm, consecutively. To demonstrate the performance of the two proposed algorithms, we performed simulations and experiments. The experimental results show the improved accuracy obtained by using the proposed algorithms.

Kim, Pyungjun; Kim, Kiho; You, Kwanho

2012-12-01

246

Range alignment for ISAR using genetic algorithms  

Microsoft Academic Search

Inverse synthetic aperture radar (ISAR) has a capability of obtaining fine resolution images of moving targets. Target rotation relative to the radar is the source for obtaining cross-range resolution, while the unwanted translational motion causes image blurring, which needs to be removed before imaging. Translation compensation is usually accomplished in two steps: range alignment and phase compensation. Many different algorithms

Ling Wang; Daiyin Zhu; Zhaoda Zhu

2005-01-01

247

Changing Conceptions of Employee Compensation  

ERIC Educational Resources Information Center

This paper reviews and discusses many differing forms of incentive compensation systems that are being used in today's organizations. The review traces the roots of bonus compensation from individual piece-work plans through the adoption of organization-wide gain sharing plans to the growing recognition of open-book management. Reasons for the…

Dixon, Mark R.; Hayes, Linda J.

2004-01-01

248

Alternative Teacher Compensation: A Primer  

ERIC Educational Resources Information Center

This policy primer is designed to provide base-line information about new forms of teacher pay that are emerging around the country, to support the local conversations and negotiations that will lead to the development of innovative compensation systems. It identifies reasons why teacher compensation is high on local, state, and federal policy…

Koppich, Julia E.; Rigby, Jessica

2009-01-01

249

Control optimization, stabilization and computer algorithms for aircraft applications  

NASA Technical Reports Server (NTRS)

Research related to reliable aircraft design is summarized. Topics discussed include systems reliability optimization, failure detection algorithms, analysis of nonlinear filters, design of compensators incorporating time delays, digital compensator design, estimation for systems with echoes, low-order compensator design, descent-phase controller for 4-D navigation, infinite dimensional mathematical programming problems and optimal control problems with constraints, robust compensator design, numerical methods for the Lyapunov equations, and perturbation methods in linear filtering and control.

1975-01-01

250

Defocus compensation system of long focal aerial camera based on auto-collimation  

NASA Astrophysics Data System (ADS)

Nowadays, novel aerial reconnaissance camera emphasizes on the shooting performance in high altitude or in long distance of oblique photography. In order to obtain the larger scale pictures which are easier for image interpretation, we need the camera has long focal length. But long focal length camera is easier to be influenced by environmental condition and lead to great change of lens' back focus which can result in the lens' resolution decreased greatly. So, we should do precise defocusing compensation to long focal aerial camera system. In order to realize defocusing compensation, a defocusing compensation system based on autocollimation is designed. Firstly, the reason which can lead to long focal camera's defocusing was discussed, then the factors such as changes of atmospheric pressure and temperature and oblique photographic distance were pointed out, and mathematical equation which could compute camera's defocusing amount was presented. Secondly, after camera's defocusing was analyzed, electro-optical autocollimation of higher automation and intelligent was adopted in the system. Before shooting , focal surface was located by electro-optical autocollimation focal detection mechanism, the data of airplane's height was imported through electronic control system. Defocusing amount was corrected by computing defocusing amount and the signal was send to focusing control motor. And an efficient improved mountain climb-searching algorithm was adopted for focal surface locating in the correction process. When confirming the direction of curve, the improved algorithm considered both twice focusing results and four points. If four points continue raised, the curve would be confirmed as rising direction. On the other hand, if four points continue decreased, the curve would be confirmed as decrease direction. In this way, we could avoid the local peak value appeared in two focusing steps. The defocusing compensation system consists of optical component and precise control system and precise driver component. Based on FPGA hardware system, hardware function is realized by VHDL. It has been using on some kinds of long focal CCD cameras and film cameras. It not only has good dimensional stability and structural stability in harsh environment, but also has ability of focal surface precision detection and accurate focusing.

Zhang, Yu-Ye; Zhao, Yu-Liang; Xu, Zhao-Lin

2010-05-01

251

More rain compensation results  

NASA Technical Reports Server (NTRS)

To reduce the impact of rain-induced attenuation in the 20/30 GHz band, the attenuation at a specified signal frequency must be estimated and extrapolated forward in time on the basis of a noisy beacon measurement. Several studies have used model based procedures for solving this problem in statistical inference. Perhaps the most widely used model-based paradigm leads to the Kalman filter and its lineal variants. In this formulation, the dynamic features of the attenuation are represented by a state process (x(sub t)). The observation process (y(sub t)) is derived from beacon measurements. Some ideas relating to the signal processing problems related to uplink power control are presented. It is shown that some easily implemented algorithms hold promise for use in estimating rain induced fades. The algorithms were applied to actual data generated at the Virginia Polytechnic Institute and State University (VPI) test facility. Because only one such event was studied, it is not clear that the algorithms will have the same effectiveness when a wide range of events are studied.

Sworder, D. D.; Vojak, R.

1992-01-01

252

More rain compensation results  

NASA Astrophysics Data System (ADS)

To reduce the impact of rain-induced attenuation in the 20/30 GHz band, the attenuation at a specified signal frequency must be estimated and extrapolated forward in time on the basis of a noisy beacon measurement. Several studies have used model based procedures for solving this problem in statistical inference. Perhaps the most widely used model-based paradigm leads to the Kalman filter and its lineal variants. In this formulation, the dynamic features of the attenuation are represented by a state process (x(sub t)). The observation process (y(sub t)) is derived from beacon measurements. Some ideas relating to the signal processing problems related to uplink power control are presented. It is shown that some easily implemented algorithms hold promise for use in estimating rain induced fades. The algorithms were applied to actual data generated at the Virginia Polytechnic Institute and State University (VPI) test facility. Because only one such event was studied, it is not clear that the algorithms will have the same effectiveness when a wide range of events are studied.

Sworder, D. D.; Vojak, R.

1992-08-01

253

[Vestibular compensation studies]. [Vestibular Compensation and Morphological Studies  

NASA Technical Reports Server (NTRS)

The following topics are reported: neurophysiological studies on MVN neurons during vestibular compensation; effects of spinal cord lesions on VNC neurons during compensation; a closed-loop vestibular compensation model for horizontally canal-related MVN neurons; spatiotemporal convergence in VNC neurons; contributions of irregularly firing vestibular afferents to linear and angular VOR's; application to flight studies; metabolic measures in vestibular neurons; immediate early gene expression following vestibular stimulation; morphological studies on primary afferents, central vestibular pathways, vestibular efferent projection to the vestibular end organs, and three-dimensional morphometry and imaging.

Perachio, Adrian A. (Principal Investigator)

1996-01-01

254

Compensated pulsed alternator  

DOEpatents

This invention relates to an electromechanical energy converter with inertial energy storage. The device, a single phase, two or multi-pole alternator with stationary field coils, and a rotating armature is provided. The rotor itself may be of laminated steel for slower pulses or for faster pulses should be nonmagnetic and electrically nonconductive in order to allow rapid penetration of the field as the armature coil rotates. The armature coil comprises a plurality of power generating conductors mounted on the rotor. The alternator may also include a stationary or counterrotating compensating coil to increase the output voltage thereof and to reduce the internal impedance of the alternator at the moment of peak outout. As the machine voltage rises sinusoidally, an external trigger switch is adapted to be closed at the appropriate time to create the desired output current from said alternator to an external load circuit, and as the output current passes through zero a self-commutating effect is provided to allow the switch to disconnect the generator from the external circuit.

Weldon, William F. (Austin, TX); Driga, Mircea D. (Austin, TX); Woodson, Herbert H. (Austin, TX)

1980-01-01

255

Unclaimed Injuries and Workers' Compensation Adequacy.  

National Technical Information Service (NTIS)

The workers' compensation system was designed to provide health care and compensation for workers with occupational injuries or illness without regard to fault. Nearly all workers are covered by workers' compensation insurance, but not every worker that i...

D. Lakdawalla R. Reville

2005-01-01

256

Iterative springback compensation of NUMISHEET benchmark No.1  

NASA Astrophysics Data System (ADS)

Upon unloading after the forming stage, a sheet metal product will spring back due to internal stresses. Springback is a major problem for process-planning engineers. In industrial practise, deformations due to springback are compensated manually, by doing extensive measurements on prototype parts, and altering the tool geometry by hand. This is a time consuming and costly operation. In this paper the application of two compensation algorithms, based on the finite element simulation of the forming process are discussed. The smooth displacement adjustment (SDA) method and the springforward (SF) method have been applied to several industrial products, such as the NUMISHEET 2005 benchmark No.1. With the SDA method successful compensations have been carried out. For the SF method some principal problems remain.

Lingbeek, R. A.; Huétink, J.; Ohnimus, S.; Weiher, J.

2005-08-01

257

Temperature Compensated Digital Inertial Sensor.  

National Technical Information Service (NTIS)

A circuit which maintains the inertial element of a gyroscope or accelerometer at a constant position by delivering pulses to a rebalancing motor is discussed. The circuit compensates for temperature changes by using a temperature sensor that varies the t...

P. J. Hand

1974-01-01

258

Inverse Compensation for Ferromagnetic Hysteresis.  

National Technical Information Service (NTIS)

This paper addresses the validation of an energy-based inverse compensator for hysteresis in ferromagnetic transducers. At moderate to high drive levels such transducers exhibit significant constitutive non-linearities and hysteresis due to domain mechani...

R. C. Smith R. Zrostlik

1999-01-01

259

National Compensation Survey Home Page  

NSDL National Science Digital Library

The Bureau of Labor Statistics (BLS) posts this publication online, with sections downloadable as .pdf files. The release, the National Compensation Survey, is a redesign of BLS' compensation statistics to reflect the workplace of the 21st century. From the main page, users can access the full .pdf-format text of the survey results as well as a summary, and a wealth of other related sites and documents.

260

Development and Implementation of Automatic White Balance Based on Luminance Compensation  

Microsoft Academic Search

Automatic white balance plays a key role in image signal processing circuit of image sensors, and determines image quality to a large extent. An automatic white balance algorithm based on luminance compensation is proposed. The algorithm establish the equations of RGB channels between the captured image and the natural one firstly based on the assumption that the luminance average of

Zhong Jian; Yao Suying; Xu Jiangtao

2008-01-01

261

Stray light compensation for dust analysers based on light scattering  

NASA Astrophysics Data System (ADS)

One of the key issues concerning the measurement of size and density of dust grains based on light scattering system is the compensation of the stray light due to the optical components misalignment and to the possible contamination of these components by the dust particles during the measurement runs. This paper focuses on the case study of MEDUSA (Martian Environmental DUst Systematic Analyzer), one of the experiments initially selected for the ExoMars mission, planned by the European Space Agency (ESA), with the scientific objective to study water and dust in Mars atmosphere. The MEDUSA experiment foresees an Optical System (OS) aimed at measuring atmospheric dust content and size distribution. One pump assures that the proper gas and dust flow circulates inside the instrument. This paper reports the description and trade off analysis of several techniques for the stray-light compensation implemented on the MEDUSA OS Proximity Electronics (PE) Test Board (2006), designed and manufactured by INAF-Osservatorio Astronomico di Capodimonte, in the frame of the MEDUSA Bread Board (B/B) activities. The PE Test Board can implement more than one compensation mode, such as: AC coupling, DC coupling with offset compensation via external loop and DC coupling with offset compensation via on board HW loop. The choice among the mentioned compensation modes shall be done also according to the configuration of the overall acquisition system, implemented by the Main Electronics (ME), as explained in the reported trade-off analysis. For the architecture configuration of the industrial breadboard (2008) the preferred solution was the one based on the DC coupling with on board HW loop, for which some test results are reported.

Molfese, C.; Della Corte, V.; Palumbo, P.; Esposito, F.; Colangeli, L.

2010-04-01

262

Compensating For Changes in MOS Sensors  

SciTech Connect

AirAdvice provided the following introduction: “AirAdvice uses metal oxide semiconductor (MOS) sensors for measuring total volatile organic compounds (TVOC) in air. These sensors are incorporated into AirAdvice’s indoor air quality (IAQ) monitors. The IAQ monitors are designed so that they require annual calibration to maintain acceptable accuracy. Since the MOS TVOC sensors used in the monitors change in sensitivity with time and exposure to gases, AirAdvice has developed an algorithm-based process that automatically compensates for changes in the sensors. The proposed project is to have PNNL analyze data provided by AirAdvice with these objectives: (1) assess how effective AirAdvice’s automatic drift correction process is, (2) identify any problems in the process, and (3) propose improvements to the process.”

Matzke, Brett D.

2006-09-29

263

Advances in Reversed Nested Miller Compensation  

Microsoft Academic Search

The use of two frequency compensation schemes for three-stage operational transconductance amplifiers, namely the reversed nested Miller compensation with nulling resistor (RN-MCNR) and reversed active feedback frequency compensation (RAFFC), is presented in this paper. The techniques are based on the basic RNMC and show an inherent advantage over traditional compensation strategies, especially for heavy capacitive loads. Moreover, they are implemented

Alfio Dario Grasso; Gaetano Palumbo; Salvatore Pennisi

2007-01-01

264

Design of robot accuracy compensator after calibration  

Microsoft Academic Search

A design is presented of a robot accuracy compensator after calibration, which can efficiently calculate and compensate the calibrated kinematic errors for robot manipulators. This compensator consists of a direct robot accuracy calculator (DRAC) that efficiently calculates the accurate robot Cartesian positions using a recursive formulation of the Ti matrix, and an inverse robot accuracy compensator (IRAC), that calculates the

Chi-haur Wu; Jeff Ho; Kuu-young Young

1988-01-01

265

Using Weighting Adjustments to Compensate for Survey Nonresponse  

Microsoft Academic Search

Weighting adjustments are used in some studies to compensate for biased estimators produced by survey nonresponse. Using data\\u000a from the 2004 National Survey of Student Engagement (NSSE) and the NSSE poststratification weighting algorithm, this study\\u000a found that weighting adjustments were needed for some, but not all institutions. Unfortunately, no simple criterion for determining\\u000a when weighting adjustments were needed could be

Gary R. Pike

2008-01-01

266

A novel 2-D adaptive Wiener-filter-based algorithm for mitigation of atmospheric turbulence effects in deep-space optical communications  

Microsoft Academic Search

Atmospheric turbulence along with the background noise is a major limiting factor in a typical free space optical communication link. As compared to terrestrial links, Earth based optical receivers operating in near-space and deepspace communication links are affected more severely by the turbulence, as these systems have to look directly towards the sky to maintain line of sight with the

A. Hashmi; A. A. Eftekhar; A. Adibi; F. Amoozegar

2009-01-01

267

Application of a Passive Microwave Thin Ice Algorithm to a Circumpolar Distribution of Antarctic Polynyas for 1992-2008, and Their Relation to Large-Scale Atmospheric Modes (Invited)  

NASA Astrophysics Data System (ADS)

For Antarctica, we investigate the growth of thin ice in the circumpolar polynyas using an algorithm based on the ratio of the vertically and horizontally polarized Special Sensor Microwave/Imager (SSM/I) 25-km resolution 37-GHz channels and the Advanced Microwave Scanning Radiometer (AMSR) 12.5-km resolution 36-GHz channels. In previous work, the algorithm was developed and validated in the Chukchi Sea polynyas, which with the addition of meteorological data, yields both the polynya ice thicknesses and heat fluxes. For the period 1992-2008, we use this algorithm to derive for a set of large Antarctic polynyas, the variability in space and time of the polynya ice production. From east to west, the polynyas include the Ross Ice Shelf, Mertz, Shackleton, Darnley, Eastern Weddell and Ronne Ice Shelf. Examination of the dependence of the Ronne and Ross polynya ice production on the large-scale atmospheric Southern Oscillation and Southern Annular Mode Indices (SOI, SAMI) shows that the combined indices explain 30-40% of the ice production. The presentation also investigates whether the circumpolar ice production is correlated with the Antarctic circumpolar wave that rotates around the continent and is visible in the variability of the ice edge position. The combined results suggest that a portion of the Antarctic bottom water production that is caused by brine rejection within polynyas is driven by features of the large-scale circulation.

Martin, S.; Kwok, R.; Drucker, R.

2009-12-01

268

Efficient inhomogeneity compensation using fuzzy c-means clustering models.  

PubMed

Intensity inhomogeneity or intensity non-uniformity (INU) is an undesired phenomenon that represents the main obstacle for magnetic resonance (MR) image segmentation and registration methods. Various techniques have been proposed to eliminate or compensate the INU, most of which are embedded into classification or clustering algorithms, they generally have difficulties when INU reaches high amplitudes and usually suffer from high computational load. This study reformulates the design of c-means clustering based INU compensation techniques by identifying and separating those globally working computationally costly operations that can be applied to gray intensity levels instead of individual pixels. The theoretical assumptions are demonstrated using the fuzzy c-means algorithm, but the proposed modification is compatible with a various range of c-means clustering based INU compensation and MR image segmentation algorithms. Experiments carried out using synthetic phantoms and real MR images indicate that the proposed approach produces practically the same segmentation accuracy as the conventional formulation, but 20-30 times faster. PMID:22405524

Szilágyi, László; Szilágyi, Sándor M; Benyó, Balázs

2012-10-01

269

EMITTANCE COMPENSATION FOR MAGNETIZED BEAMS  

SciTech Connect

Emittance compensation is a well established technique for minimizing the emittance of an electron beam from a RF photo-cathode gun. Longitudinal slices of a bunch have a small emittance, but due to the longitudinal charge distribution of the bunch and time dependent RF fields they are not focused in the same way, so that the direction of their phase ellipses diverges in phase space and the projected emittance is much larger. Emittance compensation reverses the divergence. At the location where the slopes of the phase ellipses coincide the beam is accelerated, so that the space charge forces are reduced. A recipe for emittance compensation is given in. For magnetized beams (where the angular momentum is non-zero) such emittance compensation is not sufficient because variations in the slice radius lead to variations in the angular speed and therefore to an increase of emittance in the rotating game. We describe a method and tools for a compensation that includes the beam magnetization.

KEWISCH,J.; CHANG, X.

2007-06-25

270

Static synchronous series compensator: A solid-state approach to the series compensation of transmission lines  

Microsoft Academic Search

This paper describes an active approach to series line compensation, in which a synchronous voltage source, implemented by a gate turn-off thyristor (GTO) based voltage-sourced inverter, is used to provide controllable series compensation. This compensator, called Static Synchronous Series Compensator (SSSC), can provide controllable compensating voltage over an identical capacitive and inductive range, independently of the magnitude of the line

L. Gyugyi; C. D. Schauder; K. K. Sen

1997-01-01

271

Multivariable adaptive algorithms for reconfigurable flight control  

Microsoft Academic Search

The application of multivariable adaptive control techniques to flight control reconfiguration is considered. The objective is to redesign automatically flight control laws to compensate for actuator failures or surface damage. Three adaptive algorithms for multivariable model reference control are compared. The availability of state measurements in this application leads to relatively simple algorithms. The respective advantages and disadvantages of the

Marc Bodson; Joseph E. Groszkiewicz

1997-01-01

272

Noise robust speech recognition using feature compensation based on polynomial regression of utterance SNR  

Microsoft Academic Search

A feature compensation (FC) algorithm based on polynomial regression of utterance signal-to-noise ratio (SNR) for noise robust automatic speech recognition (ASR) is proposed. In this algorithm, the bias between clean and noisy speech features is approximated by a set of polynomials which are estimated from adaptation data from the new environment by the expectation-maximization (EM) algorithm under the maximum likelihood

Xiaodong Cui; Abeer Alwan

2005-01-01

273

Compensation for electrical converter nonlinearities  

DOEpatents

Systems and methods are provided for delivering energy from an input interface to an output interface. An electrical system includes an input interface, an output interface, an energy conversion module between the input interface and the output interface, an inductive element between the input interface and the energy conversion module, and a control module. The control module determines a compensated duty cycle control value for operating the energy conversion module to produce a desired voltage at the output interface and operates the energy conversion module to deliver energy to the output interface with a duty cycle that is influenced by the compensated duty cycle control value. The compensated duty cycle control value is influenced by the current through the inductive element and accounts for voltage across the switching elements of the energy conversion module.

Perisic, Milun; Ransom, Ray M; Kajouke, Lateef A

2013-11-19

274

GIFTS SM EDU Level 1B Algorithms  

NASA Technical Reports Server (NTRS)

The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) SensorModule (SM) Engineering Demonstration Unit (EDU) is a high resolution spectral imager designed to measure infrared (IR) radiances using a Fourier transform spectrometer (FTS). The GIFTS instrument employs three focal plane arrays (FPAs), which gather measurements across the long-wave IR (LWIR), short/mid-wave IR (SMWIR), and visible spectral bands. The raw interferogram measurements are radiometrically and spectrally calibrated to produce radiance spectra, which are further processed to obtain atmospheric profiles via retrieval algorithms. This paper describes the GIFTS SM EDU Level 1B algorithms involved in the calibration. The GIFTS Level 1B calibration procedures can be subdivided into four blocks. In the first block, the measured raw interferograms are first corrected for the detector nonlinearity distortion, followed by the complex filtering and decimation procedure. In the second block, a phase correction algorithm is applied to the filtered and decimated complex interferograms. The resulting imaginary part of the spectrum contains only the noise component of the uncorrected spectrum. Additional random noise reduction can be accomplished by applying a spectral smoothing routine to the phase-corrected spectrum. The phase correction and spectral smoothing operations are performed on a set of interferogram scans for both ambient and hot blackbody references. To continue with the calibration, we compute the spectral responsivity based on the previous results, from which, the calibrated ambient blackbody (ABB), hot blackbody (HBB), and scene spectra can be obtained. We now can estimate the noise equivalent spectral radiance (NESR) from the calibrated ABB and HBB spectra. The correction schemes that compensate for the fore-optics offsets and off-axis effects are also implemented. In the third block, we developed an efficient method of generating pixel performance assessments. In addition, a random pixel selection scheme is designed based on the pixel performance evaluation. Finally, in the fourth block, the single pixel algorithms are applied to the entire FPA.

Tian, Jialin; Gazarik, Michael J.; Reisse, Robert A.; Johnson, David G.

2007-01-01

275

Using a Quadtree Algorithm To Assess Line of Sight  

NASA Technical Reports Server (NTRS)

A matched pair of computer algorithms determines whether line of sight (LOS) is obstructed by terrain. These algorithms were originally designed for use in conjunction with combat-simulation software in military training exercises, but could also be used for such commercial purposes as evaluating lines of sight for antennas or determining what can be seen from a "room with a view." The quadtree preparation algorithm operates on an array of digital elevation data and only needs to be run once for a terrain region, which can be quite large. Relatively little computation time is needed, as each elevation value is considered only one and one-third times. The LOS assessment algorithm uses that quadtree to answer LOS queries. To determine whether LOS is obstructed, a piecewise-planar (or higher-order) terrain skin is computationally draped over the digital elevation data. Adjustments are made to compensate for curvature of the Earth and for refraction of the LOS by the atmosphere. Average computing time appears to be proportional to the number of queries times the logarithm of the number of elevation data points. Accuracy is as high as is possible for the available elevation data, and symmetric results are assured. In the simulation, the LOS query program runs as a separate process, thereby making more random-access memory available for other computations.

Gonzalez, Joseph; Chamberlain, Robert; Tailor, Eric; Gutt, Gary

2006-01-01

276

Numerical analysis of the scaling parameter of adaptive compensation for thermal blooming effects  

NASA Astrophysics Data System (ADS)

By using the time-dependent propagation computer code, adaptive compensation for thermal blooming effects, which are induced by collimated high-energy laser (HEL) beam propagation through the atmosphere, is numerically calculated and analyzed under different conditions. The numerical results show that, with the definite adaptive optics (AO) system, the scaling parameter ND/NFB is available to evaluate the effect of adaptive compensation efficiently. Moreever, we get the scaling relation between the scaling parameter ND/NFB and the far-field Strehl ratio, which is can be described by Strehlequals1/[1+AND/NFB+B(ND/NFB)C], where A, B and C are fitting parameters. We also get the threshold of adaptive phase compensation instability (PCI) through analysis of the scaling rotation above. In addition, we discuss the difference between adaptive compensation and whole-beam compensation.

Huang, Yinbo; Wang, Yingjian; Gong, Zhiben

2002-09-01

277

PMD compensation in 10Gb/s DPSK optical communication system  

NASA Astrophysics Data System (ADS)

We established the DPSK generating and receiving system, and realized the different kind of DPSK formats. Then we demonstrated the experiment of automatic PMD compensation in 10Gb/s NRZ-DPSK, RZ33-DPSK, RZ50-DPSK, and RZ67-DPSK systems. Using the particle swarm optimization algorithm in these DPSK systems, the optical signals were successfully recovered instantly from PMD induced distortion after compensation.

Zhang, Xiaoguang; Duan, Gaoyan; Xu, Wei; Fang, Guangqing

2007-10-01

278

Application and evaluation of a motion compensation technique to breast MRI  

NASA Astrophysics Data System (ADS)

Motion induced artifacts represent a major problem in detection and diagnosis of breast cancer in dynamic contrast-enhanced magnetic resonance imaging. The goal of this paper is to evaluate the performance of a new motion correction algorithm based on different feature extraction techniques and subsequent classification techniques. Based on several simulation results, we determined the optimal motion compensation parameters, the optimal feature number and tested different classification techniques. Our results have shown that motion compensation can improve in some cases classification results.

Steinbrücker, Frank; Meyer-Bäse, Anke; Wismüller, Axel; Schlossbauer, Thomas

2009-05-01

279

STEPPED-FREQUENCY ISAR MOTION COMPENSATION USING PARTICLE SWARM OPTIMIZATION WITH AN ISLAND MODEL  

Microsoft Academic Search

Abstract—This paper proposes a motion compensation method,to compensate,for the inter-pulse phase errors caused by the target movement in stepped-frequency ISAR imaging. For this purpose, genetic algorithm, particle swarm optimization (PSO) and PSO with an island model (PSOI) were applied in the proposed procedure. Simulation results using point scatterers and measured data show that PSOI is the most efficient in the

Sang-Hong Park; Hyo-Tae Kim; Kyung-Tae Kim

2008-01-01

280

Analysis of Coding Gain and Optimal Bit Allocation in Motion-Compensated Video Compression  

NASA Astrophysics Data System (ADS)

This paper describes mathematical frameworks on temporal and spatial predictive processing in the motion-compensated video compression. Firstly, the coding gain over intra coding is derived, regarding the bit allocation algorithm and Lagrange multiplier method. The optimal ordering of three different picture types (I, P and B pictures) is clarified according to image source characteristics. Secondly, a novel framework with the block-based multihypothesis motion-compensated optimal coding gain and bit allocation are derived in a closed-form expression.

Sam?ovi?, Andreja

2012-03-01

281

Switching sequence optimization for gradient error compensation in thermometer-decoded DAC arrays  

Microsoft Academic Search

This paper discusses switching schemes for gradient error compensation in unary (thermometer-decoded) arrays of digital-to-analog converters (DACs). The absolute lower bound of integral nonlinearity (INL) by optimizing switching sequences is established and optimal switching sequences that meet the lower bound of INL are presented for linear error compensation in one-dimensional arrays. A rapidly converging algorithm is developed to obtain INL

Yonghua Cong; Randall L. Geiger

2000-01-01

282

Instantaneous power compensation in three-phase systems by using p-q-r theory  

Microsoft Academic Search

This paper proposes a novel power compensation algorithm in three-phase four-wire systems by using p-q-r theory. The p-q-r theory is compared with two previous instantaneous power theories, p-q theory and cross vector theory. The p-q-r theory provides two-degrees of freedom to control the system currents by only compensating the instantaneous imaginary power without using any energy storage element. The definition

Hyosung Kim; Frede Blaabjerg; Birgitte Bak-Jensen; Jaeho Choi

2002-01-01

283

POAM III retrieval algorithm and error analysis  

Microsoft Academic Search

This paper describes the operational version 3 algorithms used to analyze data from the Polar Ozone and Aerosol Measurement (POAM) III instrument. We include a thorough discussion of both the forward model and retrieval algorithms, including the algorithms used to derive altitude information and normalize the measured radiances to produce atmospheric transmission profiles. The operational POAM III algorithms retrieve O3,

J. D. Lumpe; R. M. Bevilacqua; K. W. Hoppel; C. E. Randall

2002-01-01

284

An algorithm for compensating secondary currents of current transformers  

Microsoft Academic Search

Current transformer (CT) saturation may cause relays to malfunction. The conventional method to deal with the problem is overdimensioning of the core so that CTs can carry up to 20 times the rated current without exceeding 10% ratio correction. However, this not only reduces the sensitivity of relays, but also increases the CT core size. This paper presents a technique

Y. C. Kang; J. K. Park; S. H. Kang; A. T. Johns; R. K. Aggarwal

1997-01-01

285

Bias phenomenon and compensation in multiple target tracking algorithms  

Microsoft Academic Search

Bias phenomenon in multiple target tracking has been observed for a long time. This paper is devoted to a study of the bias resulting from the miscorrelation in data association. One result of this paper is a necessary condition for miscorrelation to cause bias. Relying on the necessary condition and a model for data association process, techniques are developed to

Hong Lang; Cong Shan

2000-01-01

286

Reverberation compensation for speaker verification  

Microsoft Academic Search

Reverberation effects introduce a great challenge for speaker verification systems. However, only few studies considered reverberation with speaker verification. These studies did not exploit some of the advanced techniques for channel mismatch in the speaker verification literature. Contemporary techniques for channel and microphones mismatch in speaker verification are based on session variability modeling. One such method is the compensation of

Itai Peer; Boaz Rafaely; Yaniv Zigel

2008-01-01

287

Can Education Compensate for Society?  

ERIC Educational Resources Information Center

The extent to which education can compensate for social disadvantage is a matter of political controversy, especially in the context of policies for social mobility. On the one hand, to blame poor achievement on social class or poverty was seen to dodge the professional responsibility of teachers. On the other, the strong correlation between…

Pring, Richard

2011-01-01

288

Unemployment Compensation and Older Workers.  

National Technical Information Service (NTIS)

Unemployment compensation in the United States is provided through a federal-state system of unemployment insurance (UI). UI provides temporary partial wage replacement to active job seekers who are involuntarily out of work. For older workers, UI is an i...

C. J. OLeary S. A. Wandner

2000-01-01

289

Altitude Compensating Nozzle Concepts Evaluation  

NASA Technical Reports Server (NTRS)

This report contains the summary of work accomplished during summer of 2000 by Mr. Chad Hammons, undergraduate senior student, Mississippi State University/ERC in support of NASA/MSFC mission pertinent to Altitude compensating nozzle concepts evaluations. In particular, the development of automatic grid generator applicable in conducting sensitivity analysis involving Aerospike engine is described.

Soni, Bharat

2000-01-01

290

Compensation of Navajo Uranium Miners  

NSDL National Science Digital Library

This site addresses policy issues of the compensation of Navajo uranium miners. The site provides an annotated index of current issues, legislation, papers and presentations, books, and links that lead to more information on uranium miners. Imbedded links throughout the text lead to related information.

Project, World I.

291

Management Compensation: A Progress Report.  

ERIC Educational Resources Information Center

This examination of the current status of compensation for community college management and administrative personnel first summarizes the findings of a study conducted by Howard R. Bowen, which determined that, compared to business executives in comparable jobs within organizations of similar sizes, academic administrators were indeed underpaid.…

Ramstad, Bill; And Others

292

Compensated amorphous silicon solar cell  

DOEpatents

An amorphous silicon solar cell incorporates a region of intrinsic hydrogenated amorphous silicon fabricated by a glow discharge wherein said intrinsic region is compensated by P-type dopants in an amount sufficient to reduce the space charge density of said region under illumination to about zero.

Carlson, David E. (Yardley, PA)

1980-01-01

293

SAG Compensated Vibration Isolation Mount.  

National Technical Information Service (NTIS)

A sag-compensated vibration isolation mount includes a cylindrical rubber body element and a circular band extending around the body element. The band is formed from a shape-memory alloy metal which has a predetermined transition temperature. The band is ...

S. Dickinson

1993-01-01

294

Annual Pay and Compensation Report.  

ERIC Educational Resources Information Center

Presents results of the 2002 Human Resource Management Compensation Survey (n=1,084) indicating that salaries for training and development professionals increased only 1.8 percent over 2001. Tables depict salaries at various levels, by geographic area, and by industry. (JOW)

Vocino, Joe

2003-01-01

295

Issues in Managerial Compensation Research  

Microsoft Academic Search

[Excerpt] Compensation is at the core of any employment exchange (Milkovich & Newman, 1993; Simon, 1951). It is probably the most basic reason people agree to become employees and it serves as a defining characteristic of any employment relationship (March & Simon, 1958). Recently, managers have been bombarded with a profusion of ways to pay employees. There is team-based pay,

Matthew C. Bloom; George T. Milkovich

1995-01-01

296

Voltage Fluctuation Compensator for Shinkansen  

NASA Astrophysics Data System (ADS)

In AC electric Railway, three-phase voltage is changed into the single-phase circuit of two circuits with the Scott-connected transformer. If it becomes large unbalancing of the load between single-phase circuits, voltage fluctuation becomes large on three-phase side. Then, Railway Static Power Conditioner (RPC) was developed for the purpose of controlling voltage fluctuation on three-phase side. An RPC is comprised of a pair of self-commutated PWM inverters. These inverters connect the main phase and teaser feeding buses, coupled with a DC side capacitor such as a Back-To-Back (BTB) converter. In this way, the two self-commutated inverters can act as a static var compensator (SVC) to compensate for the reactive power and as an active power accommodator from one feeding bus to another. 20MVA/60kV RPCs started commercial operation in 2002 at each two substations on the newly extended Tohoku Shinkansen for compensating voltage fluctuation on three-phase side caused by traction loads, absorbing harmonic current. The results of operational testing indicate that an RPC can accommodate single-phase loads such as those of PWM-controlled Shinkansen and thyristor phase-controlled Shinkansen, and handle the exciting rush current of transformers, as well as compensate for harmonics successfully.

Uzuka, Tetsuo; Ikedo, Shouji; Ueda, Keiji; Mochinaga, Yoshifumi; Funahashi, Sadao; Ide, Koiti

297

Autocollimating compensator for controlling aspheric optical surfaces  

NASA Astrophysics Data System (ADS)

A compensator (null-corrector) for testing aspheric optical surfaces is proposed, which enables (i) independent verification of optical elements and assembling of the compensator itself, and (ii) ascertaining the compensator position in a control layout for a specified aspheric surface. The compensator consists of three spherical lenses made of the same glass. In this paper, the scope of the compensator expanded to a surface speed ˜f/2.3; a conceptual example for a nominal primary of Hubble Space Telescope is given. The autocollimating design allows significant reducing difficulties associated with practical use of lens compensators.

Terebizh, V. Yu.

2014-05-01

298

Delay compensation in integrated communication and control systems. I - Conceptual development and analysis  

NASA Technical Reports Server (NTRS)

A procedure for compensating for the effects of distributed network-induced delays in integrated communication and control systems (ICCS) is proposed. The problem of analyzing systems with time-varying and possibly stochastic delays could be circumvented by use of a deterministic observer which is designed to perform under certain restrictive but realistic assumptions. The proposed delay-compensation algorithm is based on a deterministic state estimator and a linear state-variable-feedback control law. The deterministic observer can be replaced by a stochastic observer without any structural modifications of the delay compensation algorithm. However, if a feedforward-feedback control law is chosen instead of the state-variable feedback control law, the observer must be modified as a conventional nondelayed system would be. Under these circumstances, the delay compensation algorithm would be accordingly changed. The separation principle of the classical Luenberger observer holds true for the proposed delay compensator. The algorithm is suitable for ICCS in advanced aircraft, spacecraft, manufacturing automation, and chemical process applications.

Luck, Rogelio; Ray, Asok

1990-01-01

299

Implementation of an airborne SAR motion compensation system  

NASA Astrophysics Data System (ADS)

The Canadian Department of National Defence has entered into the Phase 2 development of an airborne synthetic aperture radar motion compensation (SARMC) system, following a Phase 1 feasibility study which led to the specification of the SARMC sensor configuration and accuracy. This paper describes the hardware and software configurations of an airborne SARMC system implemented on board a Convair 580 research aircraft. The hardware configuration includes a gimballed LTN-51 inertial navigation system, a Decca Doppler radar, a baroaltimeter and a motion compensation inertial measurement subsystem (MCIMS). The MCIMS is a specially designed strapped-down inertial measurement unit mounted on the ring gear of the APS-506 radar antenna. Since motion compensation depends critically on knowledge of the MCIMS orientation with respect to the radar line-of-sight to the designated target, a laser alignment procedure was developed and performed to calibrate the azimuth encoder of the antenna ring gear. This procedure is discussed along with experimental results. Substantial effort was dedicated to streamlining the Kalman filter algorithms in the SARMC processing package to obtain a high degree of robustness and computational efficiency while optimally integrating the information from the motion compensation sensors. Preliminary flight trial data are presented and compared with simulation results to indicate the level of performance achievable with this optimized system.

Difilippo, D.; Liang, D. F.; Postema, L.; Leach, B.

1986-07-01

300

A universal algorithm for accelerator correction  

NASA Astrophysics Data System (ADS)

A general formalism for compensating accelerator lattice functions is described. It is applied to the special cases of orbit smoothing, tune adjustment, beta function compensation, local and global decoupling, and vertical dispersion suppression. Some of these algorithms are implemented, and have performed robustly, in the thin element modeling code TEAPOT, analyzing the SSC circular accelerators, sometimes with a few beam-position monotors assumed to be malfunctioning.

Talman, Richard

1992-05-01

301

Chronic pain, compensation and clinical knowledge  

Microsoft Academic Search

The nosological status of the putative clinical entity of compensation neurosis and the relationship of chronic pain complaints to compensation are explored. It is concluded that, using the traditional criteria of diagnostic validity, there is no support for the view that a specific type of psychiatric disorder related to compensation or litigation can be demonstrated. Although it has been generally

George Mendelson

1991-01-01

302

Dynamic Voltage Compensator: Transformationless control perspective  

Microsoft Academic Search

The impact of voltage quality on the operation of sensitive equipment is very critical. Dynamic Voltage Compensator (DVC) is the prime solution to mitigate the voltage quality problems. This paper investigates the compensation performance of a DVC connected to a distribution system, equipped with a simple control based on in-phase compensation and without using any transformations for reference generation. The

S. Srinath; Chandan Kumar; M. P. Selvan

2011-01-01

303

Dynamic and unbalance voltage compensation using STATCOM  

Microsoft Academic Search

This paper investigates reactive power compensation strategies to mitigate voltage quality problem in power system such as flicker, sag, swell and unbalance. We choose to utilize STATCOM (Synchronous static compensator), which encompasses advantages including, but not limit to, rapid response time and the ability to provide reactive power at low voltage, and to provide voltage compensation. Based on the operation

Shu-Jen Steven Tsai; Yun Chang

2008-01-01

304

Open-Loop Analysis of Cascode Compensation  

Microsoft Academic Search

This paper presents a new open-loop analysis for cascode compensation scheme which is often used in high speed two-stage CMOS operational amplifiers (opamps). In the proposed analysis, the effect of zeros in the transfer function is also considered. Analytical approaches in this paper show that cascode compensation is more power efficient than conventional Miller compensation especially for large capacitive loads.

Hamed Aminzadeh; Reza Lotfi

2006-01-01

305

Causal compensated perturbations in cosmology  

NASA Technical Reports Server (NTRS)

A theoretical framework is developed to calculate linear perturbations in the gravitational and matter fields which arise causally in response to the presence of stiff matter sources in a FRW cosmology. It is shown that, in order to satisfy energy and momentum conservation, the gravitational fields of the source must be compensated by perturbations in the matter and gravitational fields, and the role of such compensation in containing the initial inhomogeneities in their subsequent evolution is discussed. A complete formal solution is derived in terms of Green functions for the perturbations produced by an arbitrary source in a flat universe containing cold dark matter. Approximate Green function solutions are derived for the late-time density perturbations and late-time gravitational waves in a universe containing a radiation fluid. A cosmological energy-momentum pseudotensor is defined to clarify the nature of energy and momentum conservation in the expanding universe.

Veeraraghavan, Shoba; Stebbins, Albert

1990-01-01

306

Compensated High Temperature Strain Gage  

NASA Technical Reports Server (NTRS)

A device for measuring strain in substrates at high temperatures in which the thermally induced apparent strain is nulled is described. Two gages are used, one active gage and one compensating gage. Both gages are placed on the substrate to be gaged; the active gage is attached such that it responds to mechanical and thermally induced apparent strain while the compensating gage is attached such that it does not respond to mechanical strain and and measures only thermally induced apparent strain. A thermal blanket is placed over the two gages to maintain the gages at the same temperature. The two gages are wired as adjacent arms of a wheatstone bridge which nulls the thermally induced apparent strain giving a true reading of the mechanical strain in the substrate.

1994-01-01

307

Compensation Techniques in Accelerator Physics  

SciTech Connect

Accelerator physics is one of the most diverse multidisciplinary fields of physics, wherein the dynamics of particle beams is studied. It takes more than the understanding of basic electromagnetic interactions to be able to predict the beam dynamics, and to be able to develop new techniques to produce, maintain, and deliver high quality beams for different applications. In this work, some basic theory regarding particle beam dynamics in accelerators will be presented. This basic theory, along with applying state of the art techniques in beam dynamics will be used in this dissertation to study and solve accelerator physics problems. Two problems involving compensation are studied in the context of the MEIC (Medium Energy Electron Ion Collider) project at Jefferson Laboratory. Several chromaticity (the energy dependence of the particle tune) compensation methods are evaluated numerically and deployed in a figure eight ring designed for the electrons in the collider. Furthermore, transverse coupling optics have been developed to compensate the coupling introduced by the spin rotators in the MEIC electron ring design.

Hisham Kamal Sayed

2011-05-31

308

GIFTS SM EDU Data Processing and Algorithms  

NASA Technical Reports Server (NTRS)

The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) Sensor Module (SM) Engineering Demonstration Unit (EDU) is a high resolution spectral imager designed to measure infrared (IR) radiances using a Fourier transform spectrometer (FTS). The GIFTS instrument employs three Focal Plane Arrays (FPAs), which gather measurements across the long-wave IR (LWIR), short/mid-wave IR (SMWIR), and visible spectral bands. The raw interferogram measurements are radiometrically and spectrally calibrated to produce radiance spectra, which are further processed to obtain atmospheric profiles via retrieval algorithms. This paper describes the processing algorithms involved in the calibration stage. The calibration procedures can be subdivided into three stages. In the pre-calibration stage, a phase correction algorithm is applied to the decimated and filtered complex interferogram. The resulting imaginary part of the spectrum contains only the noise component of the uncorrected spectrum. Additional random noise reduction can be accomplished by applying a spectral smoothing routine to the phase-corrected blackbody reference spectra. In the radiometric calibration stage, we first compute the spectral responsivity based on the previous results, from which, the calibrated ambient blackbody (ABB), hot blackbody (HBB), and scene spectra can be obtained. During the post-processing stage, we estimate the noise equivalent spectral radiance (NESR) from the calibrated ABB and HBB spectra. We then implement a correction scheme that compensates for the effect of fore-optics offsets. Finally, for off-axis pixels, the FPA off-axis effects correction is performed. To estimate the performance of the entire FPA, we developed an efficient method of generating pixel performance assessments. In addition, a random pixel selection scheme is designed based on the pixel performance evaluation.

Tian, Jialin; Johnson, David G.; Reisse, Robert A.; Gazarik, Michael J.

2007-01-01

309

Video denoising using overlapped motion compensation and advanced collaborative filtering  

NASA Astrophysics Data System (ADS)

We present spatiotemporal denoising based on overlapped motion compensation and advanced collaborative filtering. First, noise-robust overlapped motion compensation is performed on a block basis for temporal grouping. Next, the K-nearest neighbors of each block are grouped in a 3D array, and the 3D array is transformed. Then, adaptive soft thresholding is performed in the 3D transform domain. In addition, a modified weighting strategy for aggregation is applied for better visual quality. Simulation results show that the proposed algorithm improves the peak signal-to-noise ratio performance by about 2 dB in comparison with the state-of-the-art technique while providing much better subjective visual quality.

Lee, Tae Hwan; Kang, Jin-Ku; Song, Byung Cheol

2012-04-01

310

28 CFR 301.318 - Civilian compensation laws distinguished.  

Code of Federal Regulations, 2010 CFR

...JUSTICE INMATE ACCIDENT COMPENSATION Compensation for Work-Related Physical Impairment... The Inmate Accident Compensation...provisions of the Inmate Accident Compensation...have sustained work-related injuries,...

2010-07-01

311

28 CFR 301.318 - Civilian compensation laws distinguished.  

Code of Federal Regulations, 2010 CFR

...JUSTICE INMATE ACCIDENT COMPENSATION Compensation for Work-Related Physical Impairment... The Inmate Accident Compensation...provisions of the Inmate Accident Compensation...have sustained work-related injuries,...

2009-07-01

312

An investigation of Bjerknes Compensation in the Southern Ocean in the CCSM4  

SciTech Connect

This project aims to understand the relationship between poleward oceanic and atmospheric heat transport in the Southern Ocean by analyzing output from the community Climate System Model Version 4 (CCSM4). In particular, time series of meridional heat transport in both the atmosphere and the ocean are used to study whether variability in ocean heat transport is balanced by opposing changes in atmospheric heat transport, called Bjerknes Compensation. It is shown that the heat storage term in the Southern Ocean has a significant impact on the oceanic heat budget; as a result, no robust coherences between oceanic and atmospheric heat transports could be found at these southern latitudes.

Weijer, Wilbert [Los Alamos National Laboratory; Kinstle, Caroline M. [Los Alamos National Laboratory

2012-08-28

313

Photorespiratory compensation: a driver for biological diversity.  

PubMed

This paper reviews how terrestrial plants reduce photorespiration and thus compensate for its inhibitory effects. As shown in the equation ? = (1/Sc/o )O/C, where ? is the ratio of oxygenation to carboxylation, Sc/o is the relative specificity of Rubisco, O is stromal O2 level and C is the stromal CO2 concentration, plants can reduce photorespiration by increasing Sc/o or C, or by reducing O. By far the most effective means of reducing ? is by concentrating CO2, as occurs in C4 and CAM plants, and to a lesser extent in plants using a glycine shuttle to concentrate CO2 into the bundle sheath. Trapping and refixation of photorespired CO2 by a sheath of chloroplasts around the mesophyll cell periphery in C3 plants also enhances C, particularly at low atmospheric CO2. O2 removal is not practical because high energy and protein investment is needed to have more than a negligible effect. Sc/o enhancement provides for modest reductions in ?, but at the potential cost of limiting the kcat of Rubisco. An effective means of decreasing ? and enhancing carbon gain is to lower leaf temperature by reducing absorbance of solar radiation, or where water is abundant, opening stomata. By using a combination of mechanisms, C3 plants can achieve substantial (>30%) reductions in ?. This may have allowed many C3 species to withstand severe competition from C4 plants in low CO2 atmospheres of recent geological time, thereby preserving some of the Earth's floristic diversity that accumulated over millions of years. PMID:23656429

Sage, R F

2013-07-01

314

Jovian atmospheres  

SciTech Connect

A conference on the atmosphere of Jupiter produced papers in the areas of thermal and ortho-para hydrogen structure, clouds and chemistry, atmospheric structure, global dynamics, synoptic features and processes, atmospheric dynamics, and future spaceflight opportunities. A session on the atmospheres of Uranus and Neptune was included, and the atmosphere of Saturn was discussed in several papers.

Allison, M.; Travis, L.D.

1986-10-01

315

Study on the compensation for a quartz accelerometer based on a wavelet neural network  

NASA Astrophysics Data System (ADS)

In the position and azimuth determination system (PADS), the bias and scale factor of a quartz flexible accelerometer exhibit a non-ignorable drift after a quick turn-on and before the thermal balance is reached inside the system at different temperatures. To solve this problem, this paper presents a system compensation scheme. The multi-point temperature sensing experiment was repeated based on the realization of the hardware platform, and a wavelet neural network was used for the temperature compensation. Studies indicated that the selection of the temperature sensing points is one of the keys to achieve an effective compensation. Results show that the compensation scheme and algorithm increase the efficiency and reduce the preparation time; meanwhile the attitude precision can be improved to 8 arcsec, which meets the specification of the system.

Pan, Yingjun; Li, Leilei; Ren, Chunhua; Luo, Haoling

2010-10-01

316

Compensation issues tough to navigate  

SciTech Connect

Monthly economic diversity column for the Tri-City Herald - excerpt pasted below: Most industries out there are feeling the shift to a more educated, thus more empowered consumer. The legal field is no exception, which is why it's no surprise that lawsuits are on the rise. Today's society is one in which people are more aware than ever of their rights, and often equally convinced of their entitlements in a number of areas. For business owners, employees represent a major source of potential lawsuits. And compensation is an area of particular concern given that many complaints against employers revolve around it in some way.

Madison, Alison L.

2012-02-12

317

Dispersion compensation for atom interferometry.  

PubMed

A new technique for maintaining high contrast in an atom interferometer is used to measure large de Broglie wave phase shifts. Dependence of an interaction induced phase on the atoms' velocity is compensated by applying an engineered counterphase. The counterphase is equivalent to a rotation, is precisely determined by a frequency, and can be used to measure phase shifts due to interactions of unknown strength. Phase shifts of 150 rad (5 times larger than previously possible) have now been measured in an atom beam interferometer, and we suggest that this technique can enable comparisons of atomic polarizability with precision of one part in 10,000. PMID:14995223

Roberts, Tony D; Cronin, Alexander D; Tiberg, Martin V; Pritchard, David E

2004-02-13

318

Charge amplifier with bias compensation  

DOEpatents

An ion beam uniformity monitor for very low beam currents using a high-sensitivity charge amplifier with bias compensation. The ion beam monitor is used to assess the uniformity of a raster-scanned ion beam, such as used in an ion implanter, and utilizes four Faraday cups placed in the geometric corners of the target area. Current from each cup is integrated with respect to time, thus measuring accumulated dose, or charge, in Coulombs. By comparing the dose at each corner, a qualitative assessment of ion beam uniformity is made possible. With knowledge of the relative area of the Faraday cups, the ion flux and areal dose can also be obtained.

Johnson, Gary W. (Livermore, CA)

2002-01-01

319

Huygens lens for angle compensation  

NASA Astrophysics Data System (ADS)

Plasmonic lenses are based on complex combinations of nanoscale high aspect ratio slits. We show that their design can be greatly simplified, keeping similar performance while releasing technological constraints. The simplified system, called Huygens lens, consists in a central aperture surrounded by several identical single mode slits in a thin gold layer that does not rely anymore on surface plasmons. The focusing behaviour with respect to the position and number of slits is investigated, and we demonstrate the interest of this design to get compact array of lenses which are able to compensate the angle of incidence of the incoming wave.

Lévesque, Quentin; Bouchon, Patrick; Pardo, Fabrice; Pelouard, Jean-Luc; Haïdar, Riad

2014-03-01

320

Phase unwrapping for noisy phase map using localized compensator.  

PubMed

Phase unwrapping for a noisy image suffers from many singular points. Singularity-spreading methods are useful for the noisy image to regularize the singularity. However, the methods have a drawback of distorting phase distribution in a regular area that contains no singular points. When the singular points are confined in some local areas, the regular region is not distorted. This paper proposes a new phase unwrapping algorithm that uses a localized compensator obtained by clustering and by solving Poisson's equation for the localized areas. The numerical results demonstrate that the proposed method can improve the accuracy compared with other singularity-spreading methods. PMID:22858936

Tomioka, Satoshi; Nishiyama, Shusuke

2012-07-20

321

LPV Antiwindup Compensation for Enhanced Flight Control Performance  

NASA Technical Reports Server (NTRS)

In this paper, we propose a saturation control scheme for linear parameter-varying (LPV) systems from an antiwindup control perspective. The proposed control approach is advantageous because it can be thought of as an augmented control algorithm from the existing control system. Moreover, the synthesis condition for an antiwindup compensator is formulated as a linear matrix inequality (LMI) optimization problem and can be solved efficiently. We have applied the LPV antiwindup controller to an F-16 longitudinal autopilot control system design to enhance aircraft safety and improve flight quality in a high angle of attack region.

Lu, Bei; Wu, Fen; Kim, Sung-Wan

2003-01-01

322

Genetic algorithms  

NASA Technical Reports Server (NTRS)

Genetic algorithms are mathematical, highly parallel, adaptive search procedures (i.e., problem solving methods) based loosely on the processes of natural genetics and Darwinian survival of the fittest. Basic genetic algorithms concepts are introduced, genetic algorithm applications are introduced, and results are presented from a project to develop a software tool that will enable the widespread use of genetic algorithm technology.

Wang, Lui; Bayer, Steven E.

1991-01-01

323

List mode reconstruction for PET with motion compensation: A simulation study  

SciTech Connect

Motion artifacts can be a significant factor that limits the image quality in high-resolution PET. Surveillance systems have been developed to track the movements of the subject during a scan. Development of reconstruction algorithms that are able to compensate for the subject motion will increase the potential of PET. In this paper we present a list mode likelihood reconstruction algorithm with the ability of motion compensation. The subject motion is explicitly modeled in the likelihood function. The detections of each detector pair are modeled as a Poisson process with time-varying rate function. The proposed method has several advantages over the existing methods. It uses all detected events and does not introduce any interpolation error. Computer simulations show that the proposed method can compensate simulated subject movements and that the reconstructed images have no visible motion artifacts.

Qi, Jinyi; Huesman, Ronald H.

2002-07-01

324

List mode reconstruction for PET with motion compensation: A simulation study  

SciTech Connect

Motion artifacts can be a significant factor that limits the image quality in high-resolution PET. Surveillance systems have been developed to track the movements of the subject during a scan. Development of reconstruction algorithms that are able to compensate for the subject motion will increase the potential of PET. In this paper we present a list mode likelihood reconstruction algorithm with the ability of motion compensation. The subject moti is explicitly modeled in the likelihood function. The detections of each detector pair are modeled as a Poisson process with time vary ingrate function. The proposed method has several advantages over the existing methods. It uses all detected events and does not introduce any interpolation error. Computer simulations show that the proposed method can compensate simulated subject movements and that the reconstructed images have no visible motion artifacts.

Qi, Jinyi; Huesman, Ronald H.

2002-07-03

325

A smart high accuracy silicon piezoresistive pressure sensor temperature compensation system.  

PubMed

Theoretical analysis in this paper indicates that the accuracy of a silicon piezoresistive pressure sensor is mainly affected by thermal drift, and varies nonlinearly with the temperature. Here, a smart temperature compensation system to reduce its effect on accuracy is proposed. Firstly, an effective conditioning circuit for signal processing and data acquisition is designed. The hardware to implement the system is fabricated. Then, a program is developed on LabVIEW which incorporates an extreme learning machine (ELM) as the calibration algorithm for the pressure drift. The implementation of the algorithm was ported to a micro-control unit (MCU) after calibration in the computer. Practical pressure measurement experiments are carried out to verify the system's performance. The temperature compensation is solved in the interval from -40 to 85 °C. The compensated sensor is aimed at providing pressure measurement in oil-gas pipelines. Compared with other algorithms, ELM acquires higher accuracy and is more suitable for batch compensation because of its higher generalization and faster learning speed. The accuracy, linearity, zero temperature coefficient and sensitivity temperature coefficient of the tested sensor are 2.57% FS, 2.49% FS, 8.1 × 10-5/°C and 29.5 × 10-5/°C before compensation, and are improved to 0.13%FS, 0.15%FS, 1.17 × 10-5/°C and 2.1 × 10-5/°C respectively, after compensation. The experimental results demonstrate that the proposed system is valid for the temperature compensation and high accuracy requirement of the sensor. PMID:25006998

Zhou, Guanwu; Zhao, Yulong; Guo, Fangfang; Xu, Wenju

2014-01-01

326

Hysteresis compensation of a porous silicon relative humidity sensor using ANN technique  

Microsoft Academic Search

This paper presents a simple technique based on well-known multilayer perceptron (MLP) neural network with back propagation training algorithm for compensating the significant error due to hysteresis in a porous silicon relative humidity sensor. The porous silicon humidity sensor has been fabricated, and its hysteresis with increasing and decreasing relative humidity has been determined experimentally by a novel phase detection

Tariqul Islam; Hiranmay Saha

2006-01-01

327

Improved current regulation for voltage source inverters using zero crossings of the compensated current errors  

Microsoft Academic Search

This paper presents a consolidated strategy for closed loop current regulation of voltage source inverters by considering the zero crossings of the compensated (noninteractive) current errors. This approach leads to algorithms that can either vary a hysteresis bandwidth or directly modulate the phase leg switching times, and are implementable either with analogue hardware or digitally on a DSP. Two alternative

G. H. Bode; D. G. Holmes

2001-01-01

328

ADAPTIVE CASCADE CONTROL OF A HYDRAULIC ACTUATOR WITH AN ADAPTIVE DEAD-ZONE COMPENSATION  

Microsoft Academic Search

This work presents a cascade controller for the trajectory tracking control of a hydraulic actuator by using adaptive algorithms to deal with parametric uncertainties together with an adaptive dead-zone compensation scheme. The hydraulic actuator is modeled as a forth order nonlinear system including the valve dynamic as a first order linear system and considering a valve with a dead-zone. Some

Mauro A. B. Cunha; Raul Guenther

329

Multiple Regions of Interest Image Coding using Compensation Scheme and Alternating Shift  

Microsoft Academic Search

Maxshift method is the efficient region of interest (ROI) coding algorithm recommended by JPEG2000. However, it cannot support the multiple ROI coding based on different degrees of interest. In the paper, a new multiple ROI coding method called BCAShift (bitplanes compensation alternating shift) is presented. For multiple ROIs, the new method can encode the significant bitplanes of ROIs and background

Li-bao Zhang; Xian-chuan Yu

2006-01-01

330

A novel algorithm of calculating the circulating current on the delta side of three phase wye-delta connected transformer  

Microsoft Academic Search

The circulating current on the delta side of wye-delta connected three-phase power transformer is hard to measure. The differential transformer protection has to adopt current phase compensation method to compensate the circulating current. However, the differential current hardly reflect the magnetic exciting current of transformer no matter what kind of current phase compensation methods used. It limits many algorithms of

Tao Zheng; Qiang Liu

2009-01-01

331

Compensation for occupational skin diseases.  

PubMed

The Korean list of occupational skin diseases was amended in July 2013. The past list was constructed according to the causative agent and the target organ, and the items of that list had not been reviewed for a long period. The revised list was reconstructed to include diseases classified by the International Classification of Diseases (10th version). Therefore, the items of compensable occupational skin diseases in the amended list in Korea comprise contact dermatitis; chemical burns; Stevens-Johnson syndrome; tar-related skin diseases; infectious skin diseases; skin injury-induced cellulitis; and skin conditions resulting from physical factors such as heat, cold, sun exposure, and ionized radiation. This list will be more practical and convenient for physicians and workers because it follows a disease-based approach. The revised list is in accordance with the International Labor Organization list and is refined according to Korean worker's compensation and the actual occurrence of occupational skin diseases. However, this revised list does not perfectly reflect the actual status of skin diseases because of the few cases of occupational skin diseases, incomplete statistics of skin diseases, and insufficient scientific evidence. Thus, the list of occupational diseases should be modified periodically on the basis of recent evidence and statistics. PMID:25006325

Song, Han-Soo; Ryou, Hyun-Chul

2014-06-01

332

Vertical vibration analysis for elevator compensating sheave  

NASA Astrophysics Data System (ADS)

Most elevators applied to tall buildings include compensating ropes to satisfy the balanced rope tension between the car and the counter weight. The compensating ropes receive tension by the compensating sheave, which is installed at the bottom space of the elevator shaft. The compensating sheave is only suspended by the compensating ropes, therefore, the sheave can move vertically while the car is traveling. This paper shows the elevator dynamic model to evaluate the vertical motion of the compensating sheave. Especially, behavior in emergency cases, such as brake activation and buffer strike, was investigated to evaluate the maximum upward motion of the sheave. The simulation results were validated by experiments and the most influenced factor for the sheave vertical motion was clarified.

Watanabe, Seiji; Okawa, Takeya; Nakazawa, Daisuke; Fukui, Daiki

2013-07-01

333

CEO compensation and hospital financial performance.  

PubMed

Growing interest in pay-for-performance and the level of chief executive officers' (CEOs') pay raises questions about the link between performance and compensation in the health sector. This study compares the compensation of nonprofit hospital CEOs in Ontario, Canada to the three longest reported and most used measures of hospital financial performance. Our sample consisted of 132 CEOs from 92 hospitals between 1999 and 2006. Unbalanced panel data were analyzed using fixed effects regression. Results suggest that CEO compensation was largely unrelated to hospital financial performance. Inflation-adjusted salaries appeared to increase over time independent of hospital performance, and hospital size was positively correlated with CEO compensation. The apparent upward trend in salary despite some declines in financial performance challenges the fundamental assumption underlying this article, that is, financial performance is likely linked to CEO compensation in Ontario. Further research is needed to understand long-term performance related to compensation incentives. PMID:19605619

Reiter, Kristin L; Sandoval, Guillermo A; Brown, Adalsteinn D; Pink, George H

2009-12-01

334

CEO Compensation and Hospital Financial Performance  

PubMed Central

Growing interest in pay-for-performance and the level of CEO pay raises questions about the link between performance and compensation in the health sector. This study compares the compensation of non-profit hospital Chief Executive Officers (CEOs) in Ontario, Canada to the three longest reported and most used measures of hospital financial performance. Our sample consisted of 132 CEOs from 92 hospitals between 1999 and 2006. Unbalanced panel data were analyzed using fixed effects regression. Results suggest that CEO compensation was largely unrelated to hospital financial performance. Inflation-adjusted salaries appeared to increase over time independent of hospital performance, and hospital size was positively correlated with CEO compensation. The apparent upward trend in salary despite some declines in financial performance challenges the fundamental assumption underlying this paper, that is, financial performance is likely linked to CEO compensation in Ontario. Further research is needed to understand long-term performance related to compensation incentives.

Reiter, Kristin L.; Sandoval, Guillermo A.; Brown, Adalsteinn D.; Pink, George H.

2010-01-01

335

Design of hysteresis-compensating iterative learning control for piezo-positioners: Application to atomic force microscopes  

Microsoft Academic Search

This article addresses hysteresis-caused positioning error in piezo-based systems, such as atomic force microscopes. First, we present the design of an iterative learning control algorithm based on the Preisach hysteresis model. For a given output bound, we determine the algorithm’s rate of convergence. Second, we compensate for creep in the piezo system to determine a hysteresis model, and then the

Kam K. Leang; Santosh Devasia

2006-01-01

336

Electronic compensation of nonlinearly interacting signals in fiber-optical transmission lines with application of nonlinear phase filters  

NASA Astrophysics Data System (ADS)

In the article the algorithm of electronic dispersion compensation of signals transmitted by fiber-optical transmission line (FOL) are reviewed, in the presence of nonlinear effects. The algorithm is based on the use of multi-tier nonlinear phase filters (NPF). In for the solution of the problem is used of unitary characteristics of NPF. Results of modeling and the efficiency analysis of this algorithm by a comparison with the known value of the error rate.

Burdin, Vladimir A.; Grigorov, Igor V.; Tsveybelman, Evgenija L.

2014-04-01

337

A temperature compensated 1 GHz STW oscillator  

Microsoft Academic Search

An improved temperature compensation technique, applied to a 1-GHz surface transverse wave (STW) oscillator using 36° rotated Y-cut quartz, is described. The parabolic temperature dependence is roughly compensated for by an analog circuit. A fine compensation is performed by simple digital circuitry keeping the total instability within ±1.4 p.p.m. over the temperature range of (-45. . .+75)°C. The key for

M. A. Taslakov; I. D. Avramov

1991-01-01

338

Compensation of low order aberrations with reflective beam shaping system  

NASA Astrophysics Data System (ADS)

Compensation of low order aberrations is essential for high power solid state slab laser. With the increase of output power, the peak-to-valley of wavefront distortion increase to dozens of micrometer. It's difficult to control the wavefront with deformable mirrors which always has limited stroke(<20?m). In this paper, a reflective beam shaping system is designed to shaping the beam spot from rectangular to squarer. The beam shaping system consists of two x-oriented cylindrical mirrors and two y-oriented cylindrical mirrors. Simulations of PID control algorithm for actively compensating of low-order aberrations with reflective beam shaping system are presented. It shows that different combinations of defocus, 0o astigmatism and 45° astigmatism, which is the main contributor of beam aberrations in slab laser, can be well compensated by adjustment of distance and rotation angle of mirrors. And the convergence is fast when the control error signal is set to a suitable combination of low order Zernike coefficients. For beam with wave aberrations (PtV=82.6?, RMS=18.2?, Z4=23.6, Z5=7.1, Z6=19.6), the adjustment of distance between mirrors is below 100mm, and the rotation angle about z-axis is below 2 degree. The wavefront aberrations are decreased to a low level (PV=0.16?, RMS=0.04?) which can be easily corrected later with DM.

Liu, Wenguang; Zhou, Qiong; Gu, Dianyu; Jiang, Zongfu

2014-05-01

339

Adaptive image backlight compensation for mobile phone users  

NASA Astrophysics Data System (ADS)

The user-friendliness and cost-effectiveness have contributed to the growing popularity of mobile phone cameras. However, images captured by such mobile phone cameras are easily distorted by a wide range of factors, such as backlight, over-saturation, and low contrast. Although several approaches have been proposed to solve the backlight problems, most of them still suffer from distorted background colors and high computational complexity. Thus, they are not deployable in mobile applications requiring real-time processing with very limited resources. In this paper, we present a novel framework to compensate image backlight for mobile phone applications based on an adaptive pixel-wise gamma correction which is computationally efficient. The proposed method is composed of two sequential stages: 1) illumination condition identification and 2) adaptive backlight compensation. Given images are classified into facial images and non-facial images to provide prior knowledge for identifying the illumination condition at first. Then we further categorize the facial images into backlight images and nonbacklight images based on local image statistics obtained from corresponding face regions. We finally compensate the image backlight using an adaptive pixel-wise gamma correction method while preserving global and local contrast effectively. To show the superiority of our algorithm, we compare our proposed method with other state-of-the-art methods in the literature.

Kong, Haejung; Jung, Chanho; Kim, Wonjun; Lee, Jaeho; Kim, Changick

2010-08-01

340

Log amplifier with pole-zero compensation  

DOEpatents

A logarithmic amplifier circuit provides pole-zero compensation for improved stability and response time over 6-8 decades of input signal frequency. The amplifer circuit includes a first operational amplifier with a first feedback loop which includes a second, inverting operational amplifier in a second feedstock loop. The compensated output signal is provided by the second operational amplifier with the log elements, i.e., resistors, and the compensating capacitors in each of the feedback loops having equal values so that each break point is offset by a compensating break point or zero.

Brookshier, W.

1985-02-08

341

Study on electronic compensation of polarization mode dispersion  

NASA Astrophysics Data System (ADS)

Two kinds of electronic compensation of polarization mode dispersion (PMD) are demonstrated in this paper, including transversal filter(TF) and feed forward equalizer(FFE) + decision feedback equalization(DFE). Compared with the normalized least-mean-square (NLMS), the least-mean-square (LMS) is the best algorithm to control the equalizers. The tap weights are adapted using the LMS algorithm until they reach stationary values. Then we focus on the structure of FFE+DFE and find out the relationship of the number of taps and BER with different structures in the same conditions. From the comparison, the work of 4-tap FFE+2-tap DFE is more effective, which has the most commercial value.

Zhu, Siyu; Liu, Jianfei; Zeng, Xiangye; Gao, Zhenbin; Liu, Zhigang; Yu, Jinlong

2006-10-01

342

Motion estimation and compensation optimization on IA32 CPU  

NASA Astrophysics Data System (ADS)

Motion estimation (ME) and compensation (MC) is critical to the performance of an encoder, because the procedure is computationally intensive. To reduce the calculation, people work out some kinds of fast search algorithms for motion estimation, and dramatically improve the performance. This paper uses the Intel Pentium CPU's MMX, XMM registers and some Single Instruction Multiple Data (SIMD) instructions to accelerate the calculation, especially, uses PNI (Prescott New Instruction). We could load more pixels' values to a register at the same time. With PNI"s instruction LDDQU, we could load 16 bytes to XMM register even they cross a cache line boundary. Therefore, we could calculate (add, subtract, average, get absolute differences) multiple samples in a single operation. The parallel operations will significantly increase the speed of the ME and MC, irrespective of which kind of search algorithm.

Du, Yihua; Liu, Chang

2005-02-01

343

Application of 3-D radiative transfer theory to atmospheric correction of land surface images  

NASA Technical Reports Server (NTRS)

Three dimensional radiative transfer theory was applied to computation of atmospheric effects on remotely sensed imagery. The atmospheric correction algorithm derived is used to estimate aerosol opacity.

Diner, D. J.; Martonchik, J. V.; Danielson, E. D.; Bruegge, C. J.

1988-01-01

344

Refractive index compensation in over-determined interferometric systems.  

PubMed

We present an interferometric technique based on a differential interferometry setup for measurement under atmospheric conditions. The key limiting factor in any interferometric dimensional measurement are fluctuations of the refractive index of air representing a dominating source of uncertainty when evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of an over-determined interferometric setup where a reference length is derived from a mechanical frame made from a material with a very low thermal coefficient. The technique allows one to track the variations of the refractive index of air on-line directly in the line of the measuring beam and to compensate for the fluctuations. The optical setup consists of three interferometers sharing the same beam path where two measure differentially the displacement while the third evaluates the changes in the measuring range, acting as a tracking refractometer. The principle is demonstrated in an experimental setup. PMID:23202037

Lazar, Josef; Holá, Miroslava; ?íp, Ond?ej; ?ížek, Martin; Hrabina, Jan; Buchta, Zden?k

2012-01-01

345

Refractive Index Compensation in Over-Determined Interferometric Systems  

PubMed Central

We present an interferometric technique based on a differential interferometry setup for measurement under atmospheric conditions. The key limiting factor in any interferometric dimensional measurement are fluctuations of the refractive index of air representing a dominating source of uncertainty when evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of an over-determined interferometric setup where a reference length is derived from a mechanical frame made from a material with a very low thermal coefficient. The technique allows one to track the variations of the refractive index of air on-line directly in the line of the measuring beam and to compensate for the fluctuations. The optical setup consists of three interferometers sharing the same beam path where two measure differentially the displacement while the third evaluates the changes in the measuring range, acting as a tracking refractometer. The principle is demonstrated in an experimental setup.

Lazar, Josef; Hola, Miroslava; Cip, Ondrej; Cizek, Martin; Hrabina, Jan; Buchta, Zdenek

2012-01-01

346

Reduced complexity genetic algorithm for motion estimation  

NASA Astrophysics Data System (ADS)

In order to achieve high video coding efficiency, a new motion estimation and compensation algorithm is proposed based on Genetic Algorithm. This algorithm exploits the uniformity and correlation in the properties of the cluster of blocks called Super-Block. These Super-Blocks have adaptive boundaries that are used to partially generate initial population for fast convergence to global minimum. Rest of the population is generated using pure Random Number Generator (RNG). This population then generates offspring which then competes within itself by the virtue of it"s fitness to survive into the next generation. The fitness value in each generation is calculated by comparing the reference frame with the predicted frame. The algorithm stops after convergence or when maximum generations are reached. This algorithm compares well against conventional algorithms like FSA (Full Search Algorithm), One-Step Method or N-Step Method in terms of number of searches, complexity, robustness and scalability.

Khanna, Rahul; van der Schaar, Mihaela

2004-01-01

347

Adaptive overlapped block motion compensation  

NASA Astrophysics Data System (ADS)

An adaptive overlapped block motion compensation (OBMC) scheme, which takes the rate, distortion and complexity factors into account, is proposed in this research. With this scheme, the encoder uses the classification information to determine which blocks could be distorted after OBMC. Then, the BMC search rather than the OBMC search is applied to these blocks. Depending on the allowed computational complexity of the decoder, the encoder chooses the best set of OBMC macroblocks which requires a higher complexity. Other macroblocks simply adopt BMC. Furthermore, the motion bit rat can be reduced by soothing the motion field of BMC blocks during motion search in the encoder. An effective group OBMC motion search scheme is applied to this new adaptive OBMC motion scheme. Experimental results show that the complexity of both the encoder and the decoder is reduced while the visual quality remains the same due to ten improvement in the oversmooth region.

Kuo, Tien-Ying; Kuo, C. C. J.

1997-10-01

348

Low compensation impurity band photoconductors  

NASA Astrophysics Data System (ADS)

Low compensation thin layer of antimony doped silicon impurity band photoconductors doped at the level 1017 - 1018 cm-3 are evaluated in moderate background photon flux in the range of 1012 s-1 with the goal to approach photon noise limitation operation in spectral ranges near 300 cm-1. Blocked impurity band photodetectors based on the same active layer geometry and thickness than the photoconductors were also implemented and measured. Spectral features including cut off wavenumbers specific to impurity band effects are investigated as a function of electric field and temperature. Spectroscopic evidence for a giant gain mechanism for photoelectrons excited from residual impurities in the blocking layer of BIB structure is found. Figures of merit of both IB and BIB elements were measured and physical mechanisms underlying the limitation of their performances are outlined.

Pasquier, S.; Sirmain, G.; Meny, Claude; Murray, A. G.; Griffin, Matthew J.; Ade, Peter A. R.; Essaleh, L.; Galibert, J.; Leotin, Jean

1994-08-01

349

Genetic Algorithms  

Microsoft Academic Search

Genetic algorithms (GAs) are search methods based on principles of natural selection and genetics (Fraser, 1957;Bremermann, 1958;Holland, 1975). We start with a brief introduction to simple genetic algorithms and associated terminology.

Kumara Sastry; David Goldberg; Graham Kendall

350

Geometrical methods for pole assignment algorithms  

Microsoft Academic Search

A differential geometry approach for the design of output feedback pole assignment compensators is presented. In a first step, the output feedback control problem is formulated as an optimization problem for smooth objective functions on Grassmann manifolds, or related spaces. A Jacobi-type numerical algorithm is proposed that achieves minimization along sequences of simple, algebraic geodesics

K. Hiiper; U. Helmke

1995-01-01

351

Homotopy Algorithm for Fixed Order Mixed H2/H(infinity) Design  

NASA Technical Reports Server (NTRS)

Recent developments in the field of robust multivariable control have merged the theories of H-infinity and H-2 control. This mixed H-2/H-infinity compensator formulation allows design for nominal performance by H-2 norm minimization while guaranteeing robust stability to unstructured uncertainties by constraining the H-infinity norm. A key difficulty associated with mixed H-2/H-infinity compensation is compensator synthesis. A homotopy algorithm is presented for synthesis of fixed order mixed H-2/H-infinity compensators. Numerical results are presented for a four disk flexible structure to evaluate the efficiency of the algorithm.

Whorton, Mark; Buschek, Harald; Calise, Anthony J.

1996-01-01

352

Phase unwrapping for noisy phase maps using rotational compensator with virtual singular points.  

PubMed

In the process of phase unwrapping for an image obtained by an interferometer or in-line holography, noisy image data may pose difficulties. Traditional phase unwrapping algorithms used to estimate a two-dimensional phase distribution include much estimation error, due to the effect of singular points. This paper introduces an accurate phase-unwrapping algorithm based on three techniques: a rotational compensator, unconstrained singular point positioning, and virtual singular points. The new algorithm can confine the effect of singularities to the local region around each singular point. The phase-unwrapped result demonstrates that accuracy is improved, compared with past methods based on the least-squares approach. PMID:20820215

Tomioka, Satoshi; Heshmat, Samia; Miyamoto, Naoki; Nishiyama, Shusuke

2010-09-01

353

Numerical Algorithms  

NSDL National Science Digital Library

CSC 325. (MAT 325) Numerical Algorithms (3) Prerequisite: CSC 112 or 121, MAT 162. An introduction to the numerical algorithms fundamental to scientific computer work. Includes elementary discussion of error, polynomial interpolation, quadrature, linear systems of equations, solution of nonlinear equations and numerical solution of ordinary differential equations. The algorithmic approach and the efficient use of the computer are emphasized.

Tagliarini, Gene

2003-04-21

354

Mechanical Steering Compensators for High Performance Motorcycles  

Microsoft Academic Search

This paper introduces the idea of using mechanical steering compensators to improve the dynamic behavior of high-performance motorcycles. These compensators are seen as possible replacements for a conventional steering damper and comprise networks of springs, dampers, and a less familiar component called the inerter. The inerter was recently introduced to allow the synthesis of arbitrary passive mechanical impedances, and finds

Simos Evangelou; David J. N. Limebeer; Robin S. Sharp; Malcolm C. Smith

2008-01-01

355

Steering compensation for high-performance motorcycles  

Microsoft Academic Search

This paper introduces the idea of using a mechanical steering compensator to influence the dynamic behaviour of a high-performance motorcycle. The compensator is seen as a possible replacement for a conventional steering damper, and comprises a network of a spring, a damper and a less familiar component called the inerter. The inerter was recently introduced to allow the synthesis of

Simos Evangelou; David J. N. Limebeer; Robin S. Sharp; Malcolm C. Smith

2004-01-01

356

Displacement Compensation of Temperature Probe Data  

NASA Technical Reports Server (NTRS)

Analysis of temperature data from a probe in a vertical Bridgman furnace growing germanium crystals revealed a displacement of the temperature profile due to conduction error. A theoretical analysis shows that the displacement compensation is independent of local temperature gradient. A displacement compensation value should become a standard characteristic of temperature probes used for temperature profile measurements.

Welch, Christopher S.; Hubert, James A.; Barber, Patrick G.

1996-01-01

357

Slip compensation for a Mars rover  

Microsoft Academic Search

A system that enables continuous slip compensation for a Mars rover has been designed, implemented, and field-tested. This system is composed of several components that allow the rover to accurately and continuously follow a designated path, compensate for slippage, and reach intended goals in high-slip environments. These components include: visual odometry, vehicle kinematics, a Kalman filter pose estimator, and a

Daniel M. Helmick; Yang Cheng; Daniel S. Clouse; Max Bajracharya; Larry H. Matthies; Stergios I. Roumeliotis

2005-01-01

358

Compensated CIC-cosine decimation filter  

Microsoft Academic Search

This paper presents efficient modification of the CIC-cosine decimation filter. The second order compensator filter is introduced at last decimation stage in order to improve the pass band of interest. The coefficients of the compensator filter are presented as canonical signed digits (CSD) and can be implemented using only adders and shifts. Consequently, the resulting filter is a multiplier free

F. J. T. Torres; G. J. Dolecek

2007-01-01

359

Job Characteristics and the Form of Compensation  

Microsoft Academic Search

In this paper we introduce a way to systematically organize the choice between different forms of compensation based upon observable job characteristics. Secondly, we explore the determinants of compensation based upon questionnaire responses concerning job characteristics and methods of pay contained in the Quality of Employment Survey (QES), the National Longitudinal Survey of Youth (NLSY), the Panel Study of Income

W. Bentley MacLeod; Daniel Parent

1998-01-01

360

Unemployment Compensation Finance and Efficiency Wages  

Microsoft Academic Search

This article examines the effects of unemployment compensation finance in a labor market in which firms pay efficiency wages. Two self-financing unemployment compensation systems are compared: one in which benefits are financed by a proportional payroll tax and another in which experience rating is introduced by taxing firms in proportion to their separations. The authors find that experience rating leads

James W. Albrecht; Susan B. Vroman

1999-01-01

361

The Older Worker's Stake in Workers' Compensation  

ERIC Educational Resources Information Center

State Workers' Compensation programs can add another barrier for older workers to surmount at the hiring gate. State programs do not furnish adequate or equitable protection, and the National Commission on State Workmen's Compensation Laws has made recommendations to improve coverage; new standards must be met by July, 1975. (Author)

Berkowitz, Monroe

1975-01-01

362

Higher Education Compensation Systems of the Future.  

ERIC Educational Resources Information Center

New methods of structuring college faculty compensation systems are needed to involve, motivate, reward, and recognize individual and group behaviors. Compensation systems of the future should support the institution's core values, recognize that success results from interdependent relationships and not only individual accomplishments, and include…

Foldesi, Robert S.

1996-01-01

363

The Norwegian system of compensation to patients.  

PubMed

In Norway we have come to the conclusion that a traditional compensation law based on negligence is not the right "tool" for handling difficult questions as to whether or not a patient shall get compensation if required after medical treatment or other forms of contact with the medical profession. The compensation scheme established in 1988 involving the public sector of the Norwegian health care system has received almost 18000 claims since Jan 1 1988, and has paid out more than 1.2 billion NOK (137 million US$) in compensation during these years. At the same time, the number of compensation claims brought before the courts has decreased. After 13 years of a provisional scheme dealing with patient injury compensation based on no-fault rules, we find that compensation claims indeed can be handled without focus on blame and negligence, and that this ensures both that the patients get equitable compensation and that unnecessary legal procedures are avoided. The system also has had a favourable impact on interaction within the health care sector and upon relationships between health care personnel and patients. PMID:15795996

Jørstad, Rolf Gunnar

2002-01-01

364

What Is Different About Worker's Compensation Patients?  

PubMed Central

Study Design Combined analysis of 2 prospective clinical studies. Objective To identify socioeconomic characteristics associated with workers’ compensation in patients with an intervertebral disc herniation (IDH) or spinal stenosis (SpS). Summary of Background Data Few studies have compared socioeconomic differences between those receiving or not receiving workers’ compensation with the same underlying clinical conditions. Methods Patients were identified from the Spine Patient Outcomes Research Trial (SPORT) and the National Spine Network (NSN) practice-based outcomes study. Patients with IDH and SpS within NSN were identified satisfying SPORT eligibility criteria. Information on disability and work status at baseline evaluation was used to categorize patients into 3 groups: workers’ compensation, other disability compensation, or work-eligible controls. Enrollment rates of patients with disability in a clinical efficacy trial (SPORT) and practice-based network (NSN) were compared. Independent socioeconomic predictors of baseline workers’ compensation status were identified in multivariate logistic regression models controlling for clinical condition, study cohort, and initial treatment designation. Results Among 3759 eligible patients (1480 in SPORT and 2279 in NSN), 564 (15%) were receiving workers’ compensation, 317 (8%) were receiving other disability compensation, and 2878 (77%) were controls. Patients receiving workers’ compensation were less common in SPORT than NSN (9.2% vs. 18.8%, P < 0.001), but patients receiving other disability compensation were similarly represented (8.9% vs. 7.7%, P = 0.19). In univariate analyses, many socioeconomic characteristics significantly differed according to baseline workers’ compensation status. In multiple logistic regression analyses, gender, educational level, work characteristics, legal action, and expectations about ability to work without surgery were independently associated with receiving workers’ compensation. Conclusion Clinical trials involving conditions commonly seen in patients with workers’ compensation may need special efforts to ensure adequate representation. Socioeconomic characteristics markedly differed between patients receiving and not receiving workers’ compensation. Identifying the independent effects of workers’ compensation on outcomes will require controlling for these baseline characteristics and other clinical features associated with disability status.

Atlas, Steven J.; Tosteson, Tor D.; Hanscom, Brett; Blood, Emily A.; Pransky, Glenn S.; Abdu, William A.; Andersson, Gunnar B.; Weinstein, James N.

2010-01-01

365

A distributed memory MultiLevel fast Physical Optics algorithm  

Microsoft Academic Search

The multilevel fast physical optics (MLPO) algorithm attains a computational complexity comparable to that of the fast Fourier transform (FFT) based techniques by using hierarchical domain decomposition and phase compensated interpolation approach. In this communication we present an optimized distributed memory algorithm, obtained by partitioning not only the radiating aperture but also the grid of far field directions. Such a

Christian Parrot; Daniel Millot; Christine Letrou; Amir Boag

2009-01-01

366

A fast algorithm for video parsing using MPEG compressed sequences  

Microsoft Academic Search

Video parsing is a fundamental operation used in many digital video applications such as digital libraries and video servers. The accuracy and execution speed of the parsing algorithm is critical if large amounts of video data are to be processed, particularly in real-time. We present a new algorithm to reconstruct DC coefficient images of a DCT and motion compensation compressed

Ke Shen; Edward J. Delp

1995-01-01

367

Static synchronous series compensator: A solid-state approach to the series compensation of transmission lines  

SciTech Connect

This paper describes an active approach to series line compensation, in which a synchronous voltage source, implemented by a gate turn-off thyristor (GTO) based voltage-sourced inverter, is used to provide controllable series compensation. This compensator, called Static Synchronous Series Compensator (SSSC), can provide controllable compensating voltage over an identical capacitive and inductive range, independently of the magnitude of the line current. It is immune to classical network resonances. In addition to series reactive compensation, with an external dc power supply it can also compensate the voltage drop across the resistive component of the line impedance. The compensation of the real part of the impedance can maintain high X/R ratio even if the line has very high degree of series compensation. Concurrent and coordinated modulation of reactive and real compensation can greatly increase power oscillation damping. The paper discusses the basic operating and performance characteristics of the SSSC, and compares them to those characterizing the more conventional compensators based on thyristor-switched or controlled series capacitors. It also presents some of the results of TNA simulations carried out with an SSSC hardware model.

Gyugyi, L.; Schauder, C.D.; Sen, K.K.

1997-01-01

368

A New Technique for Compensating Joint Limits in a Robot Manipulator  

NASA Technical Reports Server (NTRS)

A new robust, optimal, adaptive technique for compensating rate and position limits in the joints of a six degree-of-freedom elbow manipulator is presented. In this new algorithm, the unmet demand as a result of actuator saturation is redistributed among the remaining unsaturated joints. The scheme is used to compensate for inadequate path planning, problems such as joint limiting, joint freezing, or even obstacle avoidance, where a desired position and orientation are not attainable due to an unrealizable joint command. Once a joint encounters a limit, supplemental commands are sent to other joints to best track, according to a selected criterion, the desired trajectory.

Litt, Jonathan; Hickman, Andre; Guo, Ten-Huei

1996-01-01

369

Digital joint compensation of IMD3 and XMD in broadband channelized RF photonic link.  

PubMed

Based on forward distortion information acquisition and post digital signal processing (DSP), we propose and demonstrate a novel scheme to effectively suppress the third-order intermodulation distortion (IMD3) and cross-modulation distortion (XMD) in a channelized RF photonic link. The simultaneous distortion compensation capacity is studied numerically, and suppression of XMD and IMD3 by about 28 dB and 25 dB, respectively, is achieved experimentally. The scheme principle and the digital compensation procedure are discussed, which shows a simple hardware implementation and algorithm. PMID:23187382

Xie, Xiaojun; Dai, Yitang; Xu, Kun; Niu, Jian; Wang, Ruixin; Yan, Li; Ji, Yuefeng; Lin, Jintong

2012-11-01

370

Analysis and compensation of an aircraft simulator control loading system with compliant linkage. [using hydraulic equipment  

NASA Technical Reports Server (NTRS)

A hydraulic control loading system for aircraft simulation was analyzed to find the causes of undesirable low frequency oscillations and loading effects in the output. The hypothesis of mechanical compliance in the control linkage was substantiated by comparing the behavior of a mathematical model of the system with previously obtained experimental data. A compensation scheme based on the minimum integral of the squared difference between desired and actual output was shown to be effective in reducing the undesirable output effects. The structure of the proposed compensation was computed by use of a dynamic programing algorithm and a linear state space model of the fixed elements in the system.

Johnson, P. R.; Bardusch, R. E.

1974-01-01

371

Compensation of the Effect of a Detector Solenoid on the Beam Size in the ILC  

SciTech Connect

In the International Linear Collider (ILC) [1] the colliding beams must be focused to the nanometer size in order to reach the desired luminosity. The method of Weak Antisolenoid is used for the compensation of the effect of the Detector Solenoid on the beam size [2], [3]. The studies of this method require the computer simulation of the charged particle's kinematics in the arbitrarily distributed solenoidal, dipole, quadrupole and higher multipole fields. We suggest the mathematical algorithm that allows to optimize parameters of antisolenoid for different configurations of Final Focus magnets and to compensate parasitic effects of the Detector Solenoid on the beam.

Seletskiy, S.; /SLAC

2007-07-06

372

Compensation following bilateral vestibular damage.  

PubMed

Bilateral loss of vestibular inputs affects far fewer patients than unilateral inner ear damage, and thus has been understudied. In both animal subjects and human patients, bilateral vestibular hypofunction (BVH) produces a variety of clinical problems, including impaired balance control, inability to maintain stable blood pressure during postural changes, difficulty in visual targeting of images, and disturbances in spatial memory and navigational performance. Experiments in animals have shown that non-labyrinthine inputs to the vestibular nuclei are rapidly amplified following the onset of BVH, which may explain the recovery of postural stability and orthostatic tolerance that occurs within 10?days. However, the loss of the vestibulo-ocular reflex and degraded spatial cognition appear to be permanent in animals with BVH. Current concepts of the compensatory mechanisms in humans with BVH are largely inferential, as there is a lack of data from patients early in the disease process. Translation of animal studies of compensation for BVH into therapeutic strategies and subsequent application in the clinic is the most likely route to improve treatment. In addition to physical therapy, two types of prosthetic devices have been proposed to treat individuals with bilateral loss of vestibular inputs: those that provide tactile stimulation to indicate body position in space, and those that deliver electrical stimuli to branches of the vestibular nerve in accordance with head movements. The relative efficacy of these two treatment paradigms, and whether they can be combined to facilitate recovery, is yet to be ascertained. PMID:22207864

McCall, Andrew A; Yates, Bill J

2011-01-01

373

Compensation Following Bilateral Vestibular Damage  

PubMed Central

Bilateral loss of vestibular inputs affects far fewer patients than unilateral inner ear damage, and thus has been understudied. In both animal subjects and human patients, bilateral vestibular hypofunction (BVH) produces a variety of clinical problems, including impaired balance control, inability to maintain stable blood pressure during postural changes, difficulty in visual targeting of images, and disturbances in spatial memory and navigational performance. Experiments in animals have shown that non-labyrinthine inputs to the vestibular nuclei are rapidly amplified following the onset of BVH, which may explain the recovery of postural stability and orthostatic tolerance that occurs within 10?days. However, the loss of the vestibulo-ocular reflex and degraded spatial cognition appear to be permanent in animals with BVH. Current concepts of the compensatory mechanisms in humans with BVH are largely inferential, as there is a lack of data from patients early in the disease process. Translation of animal studies of compensation for BVH into therapeutic strategies and subsequent application in the clinic is the most likely route to improve treatment. In addition to physical therapy, two types of prosthetic devices have been proposed to treat individuals with bilateral loss of vestibular inputs: those that provide tactile stimulation to indicate body position in space, and those that deliver electrical stimuli to branches of the vestibular nerve in accordance with head movements. The relative efficacy of these two treatment paradigms, and whether they can be combined to facilitate recovery, is yet to be ascertained.

McCall, Andrew A.; Yates, Bill J.

2011-01-01

374

Commissioning compensator-based IMRT on the Pinnacle treatment planning system.  

PubMed

We present a systematic approach to commissioning of the compensator-based IMRT in Pinnacle treatment planning system for commercially manufactured brass compensators. Some model parameters for the beams modulated by the variable-thickness compensators can only be associated with a single compensator thickness. To intelligently choose that thickness for beam modeling, we empirically determined the most probable filter thickness occurring within the modulated portion of the compensators typically used in clinics. We demonstrated that a set of relative output factors measured with the brass slab of most probable thickness (2 cm) differs from the traditionally used open field set, and leads to improved agreement between measurements and calculations, particularly for the larger field sizes. By iteratively adjusting the modifier scatter factor and filter density, the calculated effective attenuation of the flat filters was brought to within 2% of the ion chamber measurement for the clinically-relevant range of filter thicknesses, depths and filed sizes. Beam hardening representation in Pinnacle provides for adequate depth dose modeling beyond the depth of about 5 cm. Disagreement at shallower depth for the large field sizes is likely due to the algorithm's inability to account for the low-energy scattered photons generated in the filter. The average ion chamber point dose error at isocenter for ten clinical compensator-based IMRT plans was under 1%. A biplanar 3D diode dosimeter was calibrated and validated for use with the compensators. The average gamma analysis (3%/3 mm) passing rate for ten IMRT plans was 98.9% ± 1.0%. The device is particularly attractive because it easily generates dose comparisons at both the fraction and beam levels. Overlaying dose profiles for individual beams would easily uncover any errors in compensator orientation. PMID:21587187

Opp, Daniel; Forster, Kenneth; Feygelman, Vladimir

2011-01-01

375

20 CFR 704.301 - Administration; compensation districts.  

Code of Federal Regulations, 2013 CFR

...Administration; compensation districts. 704.301 Section 704...ACT AND RELATED STATUTES SPECIAL PROVISIONS FOR LHWCA EXTENSIONS...Administration; compensation districts. For the purpose of administration...this Act, the compensation districts established under...

2013-04-01

376

20 CFR 704.401 - Administration; compensation districts.  

Code of Federal Regulations, 2013 CFR

...Administration; compensation districts. 704.401 Section 704...ACT AND RELATED STATUTES SPECIAL PROVISIONS FOR LHWCA EXTENSIONS...Administration; compensation districts. For the purpose of administration...Alaska, the compensation districts established for...

2013-04-01

377

20 CFR 704.201 - Administration; compensation districts.  

Code of Federal Regulations, 2013 CFR

...Administration; compensation districts. 704.201 Section 704...ACT AND RELATED STATUTES SPECIAL PROVISIONS FOR LHWCA EXTENSIONS District of Columbia Workmen's Compensation...Administration; compensation districts. For the purpose of...

2013-04-01

378

20 CFR 701.201 - Office of Workers' Compensation Programs.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 false Office of Workers' Compensation Programs. 701.201...LONGSHOREMEN'S AND HARBOR WORKERS' COMPENSATION ACT AND RELATED STATUTES...USE OF TERMS Office of Workers' Compensation Programs § 701.201...

2009-04-01

379

20 CFR 701.201 - Office of Workers' Compensation Programs.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Office of Workers' Compensation Programs. 701.201...LONGSHOREMEN'S AND HARBOR WORKERS' COMPENSATION ACT AND RELATED STATUTES...USE OF TERMS Office of Workers' Compensation Programs § 701.201...

2010-04-01

380

Error Compensation for Area Digital Sun Sensor  

PubMed Central

Compared to the error factors of the Linear Array Digital Sun Sensor (DSS), those of the Area Array DSS are complicated and methods used for error compensation are not valid or simple enough. This paper presents the main error factors of the Area Array DSS and proposes an effective method to compensate them. The procedure of error compensation of Area Array DSS includes three steps. First, the geometric error of calibration is compensated; second, the coordinate map method is used to compensate the error caused by optical refraction; third, the high order polynomial-fitting method is applied to calculate the tangent of the sun angles; finally, the arc tangent method is used to calculate the sun angles. Experimental results of the product of the High Accuracy Sun Sensor indicate that the precision is better than 0.02° during the cone field of view (CFOV) of 10°, and the precision is better than 0.14° during the CFOV 10° to 64°. The proposed compensation method effectively compensates the major error factors and significantly improves the measure precision of the Area APS DSS.

Li, Wen-Yang; Zhang, Gao-Fei; You, Zheng; Xing, Fei

2012-01-01

381

Atmosphere control  

NASA Technical Reports Server (NTRS)

Atmospheric control studies emphasized the carbon dioxide problem. Trace contaminants are removed by solid adsorbents and by catalytic oxidation. Humidity control and storage systems for atmospheric constituents are briefly summarized.

Jones, W. L.; Ingelfinger, A. L.

1973-01-01

382

The Atmosphere  

NSDL National Science Digital Library

This exercise is intended to reinforce the importance of Earth's atmosphere to living organisms. Topics include our bodies' interactions with the atmosphere; its composition and structure; and natural changes in the atmosphere (weather). Students will perform an actvity in which they are asked to observe and record weather conditions for four days, answer questions about their observations, and respond to a series of questions on general atmospheric characteristics. They will also learn how to convert temperature values from degrees Celsius to Fahrenheit.

Fox, Chris

383

Compensating For Doppler Shift In Laser Instrumentation  

NASA Technical Reports Server (NTRS)

Electronic tuning system continually adjusts frequency of tunable diode laser to compensate for Doppler shift caused by motion of transmitter or receiver containing laser. Doppler-shift-compensating system intended primarily for use in transmitter or receiver of laser remote-sensing or communication system to keep frequency of received signal within frequency range of narrow-band-pass filter. By use of narrow-band filter (instead of wide-band filter required in absence of Doppler compensation), signal-to-noise ratio of laser system increased. Thus, less-powerful transmitter usable.

Schwemmer, Geary K.

1990-01-01

384

Atmospheric Models for Aerocapture  

NASA Technical Reports Server (NTRS)

There are eight destinations in the solar System with sufficient atmosphere for aerocapture to be a viable aeroassist option - Venus, Earth, Mars, Jupiter, Saturn and its moon Titan, Uranus, and Neptune. Engineering-level atmospheric models for four of these targets (Earth, Mars, Titan, and Neptune) have been developed for NASA to support systems analysis studies of potential future aerocapture missions. Development of a similar atmospheric model for Venus has recently commenced. An important capability of all of these models is their ability to simulate quasi-random density perturbations for Monte Carlo analyses in developing guidance, navigation and control algorithm, and for thermal systems design. Similarities and differences among these atmospheric models are presented, with emphasis on the recently developed Neptune model and on planned characteristics of the Venus model. Example applications for aerocapture are also presented and illustrated. Recent updates to the Titan atmospheric model are discussed, in anticipation of applications for trajectory and atmospheric reconstruct of Huygens Probe entry at Titan.

Justus, C. G.; Duvall, Aleta L.; Keller, Vernon W.

2004-01-01

385

XTRAN: An Atmospheric Transmittance Code Based on XSCALE.  

National Technical Information Service (NTIS)

Several Electro-Optical Systems Atmospheric Effects Library modules require the use of XSCALE for calculation of the natural atmospheric transmittance value. XSCALE is a large (over 1600 lines of code) algorithm, which, in some cases, requires other exter...

R. Pena

1991-01-01

386

Digitally compensated beam current transformer  

NASA Astrophysics Data System (ADS)

The Spallation Neutron Source (SNS) is being built by a collaboration of six laboratories. Beam current monitors (BCMs) will be used to record the current of H-minus and H-plus beams ranging from 15 mA (tune-up in the Front End and Linac) to over 60A fully accumulated in the Ring and dumped to the load as a single pulse in the Ring to Beam Target (RTBT). The time structure of these beams ranges from 645 ns "mini" bunches at the 1.05 MHz ring revolution rate, to an overall 1 ms long macro-pulse. The requirements for the BCMs will depend upon their location within the system. The need to measure individual mini-pulses, examine the characteristics of the chopper edge, as well as the longer average current pulse of the macropulse, or long duration pulses during Linac tuning place wide requirements upon the response of current transformers. To obtain the desired accuracy and resolution, current transformers must have <1 ns rise time and droops of 0.1%/ms. This places a significant design burden on the current transformer; such a design is almost impossible to achieve. Extremely large expensive cores are needed to meet the low droop, while leakage inductance increases with size, thereby reducing the achievable rise time. In this paper, I discuss a digital compensation approach [M. Kesselman, Spallation neutron source beam current monitor electronics, PAC2001 June 18-22, 2001, Chicago, IL.] that extends the lower cut-off frequency of the current transformer, optimized for high frequency response, so that it can be used in this application with improvements in droop of the order of 1000:1. Transformer saturation (current-time product) is a separate issue and the transformer must be designed to handle the current-time product of the signal to assure it does not saturate.

Kesselman, Martin

2005-01-01

387

Interactive atmosphere  

NSDL National Science Digital Library

Where is ozone located in the atmosphere? This informational activity, part of an interactive laboratory series for grades 8-12, explores the changes in ozone concentration with altitude. Students are introduced to layers of the atmosphere and the amount of ozone found at each layer of the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. The activity also discusses why the addition of ozone to the atmosphere at different levels determines the temperatures of those levels. Students can move up and down to different layers of the atmosphere. A temperature scale is shown that runs from the surface of the Earth to the outer most reaches of the atmosphere. Copyright 2005 Eisenhower National Clearinghouse

University of Utah. Astrophysics Science Project Integrating Research and Education (ASPIRE)

2003-01-01

388

Compensation of transmission losses for true-amplitude reverse time migration  

NASA Astrophysics Data System (ADS)

The theoretical analysis of wavefield propagators plays an important role in the development of true-amplitude migration methods. We analyze how transmission losses influence the amplitudes of reverse time migration (RTM). Based on high-frequency asymptotic theory, we analyze the change in amplitude caused by transmission losses, and prove that the transmission losses of wavefield propagation prevent RTM from yielding a true-amplitude image of the reflection coefficients. The derivations and proof provide a theoretical basis for the compensation of transmission losses in true-amplitude RTM. These theoretical derivations are then implemented in an algorithm to compensate for the transmission losses in RTM. The results from numerical experiments are consistent with the theoretical analysis. The compensation of transmission loss helps to improve the amplitude accuracy of RTM.

Du, Qizhen; Fang, Gang; Gong, Xufei; Zhang, Mingqiang

2014-07-01

389

Real-time inverse hysteresis compensation of piezoelectric actuators with a modified Prandtl-Ishlinskii model.  

PubMed

This paper presents a novel real-time inverse hysteresis compensation method for piezoelectric actuators exhibiting asymmetric hysteresis effect. The proposed method directly utilizes a modified Prandtl-Ishlinskii hysteresis model to characterize the inverse hysteresis effect of piezoelectric actuators. The hysteresis model is then cascaded in the feedforward path for hysteresis cancellation. It avoids the complex and difficult mathematical procedure for constructing an inversion of the hysteresis model. For the purpose of validation, an experimental platform is established. To identify the model parameters, an adaptive particle swarm optimization algorithm is adopted. Based on the identified model parameters, a real-time feedforward controller is implemented for fast hysteresis compensation. Finally, tests are conducted with various kinds of trajectories. The experimental results show that the tracking errors caused by the hysteresis effect are reduced by about 90%, which clearly demonstrates the effectiveness of the proposed inverse compensation method with the modified Prandtl-Ishlinskii model. PMID:22755661

Gu, Guo-Ying; Yang, Mei-Ju; Zhu, Li-Min

2012-06-01

390

Medical Roles in Workers' Compensation Information Gathering.  

National Technical Information Service (NTIS)

Papers delivered at the 36th AMA Congress on Occupational Health in 1976 are provided. The Symposia topics were medical roles in workers' compensation, basic physician knowledge about radiation, medical recordkeeping and surveillance, interdisciplinary te...

M. L. Amdur

1977-01-01

391

44 CFR 295.21 - Allowable compensation.  

Code of Federal Regulations, 2010 CFR

...after December 31, 2001. (l) Donations. FEMA will compensate individual...Grande Fire not later than June 19, 2000. Donations will be valued at cost. FEMA...services not later than June 19, 2000 provided that actual revenues...

2009-10-01

392

44 CFR 295.21 - Allowable compensation.  

Code of Federal Regulations, 2010 CFR

...after December 31, 2001. (l) Donations. FEMA will compensate individual...Grande Fire not later than June 19, 2000. Donations will be valued at cost. FEMA...services not later than June 19, 2000 provided that actual revenues...

2010-10-01

393

Mainstreaming Military Compensation: Problems and Prospects.  

National Technical Information Service (NTIS)

Changes to the military retirement system in the 1980's and attention by law makers, military leadership, and service members to pay comparability between the private sector and the military indicate that current military compensation policies may be inad...

D. J. MacDonald

1998-01-01

394

Temperature compensation of light-emitting diodes  

NASA Technical Reports Server (NTRS)

Circuit which includes a thermistor-resistor combination to compensate for temperature fluctuations by supplying input voltage to light-emitting diode, maintains constant light output. Similar circuits can be used for temperature-induced variations in photodiode applications.

Deboo, G. J.; Burrous, C. N.

1972-01-01

395

Compensating for estimation smoothing in kriging  

USGS Publications Warehouse

Smoothing is a characteristic inherent to all minimum mean-square-error spatial estimators such as kriging. Cross-validation can be used to detect and model such smoothing. Inversion of the model produces a new estimator-compensated kriging. A numerical comparison based on an exhaustive permeability sampling of a 4-fr2 slab of Berea Sandstone shows that the estimation surface generated by compensated kriging has properties intermediate between those generated by ordinary kriging and stochastic realizations resulting from simulated annealing and sequential Gaussian simulation. The frequency distribution is well reproduced by the compensated kriging surface, which also approximates the experimental semivariogram well - better than ordinary kriging, but not as well as stochastic realizations. Compensated kriging produces surfaces that are more accurate than stochastic realizations, but not as accurate as ordinary kriging. ?? 1996 International Association for Mathematical Geology.

Olea, R. A.; Pawlowsky, Vera

1996-01-01

396

Compensation and Teacher Retention: A Success Story.  

ERIC Educational Resources Information Center

Describes components of successful teacher-evaluation and compensation program at the Ladue School District in suburban St. Louis, Missouri. Reports that salary increases based on performance evaluations improve teacher satisfaction and retention. (Contains 13 references.) (PKP)

Morice, Linda C.; Murray, James E.

2003-01-01

397

State Workers' Compensation Laws, January 1990.  

National Technical Information Service (NTIS)

The report presents twenty data tables on the following topics: Type of Law and Insurance Requirements for Private Employment; Numerical Exemptions; Coverage of Agricultural Workers; Jurisdictions in Which Workers' Compensation Laws Apply to Domestic Empl...

1990-01-01

398

Workers' Compensation: Key Legislation in 1981.  

ERIC Educational Resources Information Center

Contains a summary of workers' compensation legislation enacted by individual states in 1981. Higher benefit levels, broader coverage, and improved medical and rehabilitation services are among the actions taken by states to provide better protection for injured workers. (Author)

Tinsley, LaVerne C.

1982-01-01

399

Gamma Compensated, Self Powered Neutron Detector.  

National Technical Information Service (NTIS)

An improved, self-powered, gamma compensated, neutron detector is described, having two electrically conductive concentric cylindrical electrodes and a central rod emitter formed from a material which emits beta particles when bombarded by neutrons. The o...

D. P. Brown

1977-01-01

400

Domain Adaptation and Compensation for Emotion Detection.  

National Technical Information Service (NTIS)

Inspired by the recent improvements in domain adaptation and session variability compensation techniques used for speech and speaker processing, we study their effect for emotion prediction. More specifically, we investigated the use of publicly available...

D. H. TOur D. H. Tur G. Tur G. Tur L. Ferrer L. Ferrer M. H. Sanchez M. H. Sanchez

2013-01-01

401

Atmospheric gases  

NSDL National Science Digital Library

Which gases make up the atmosphere? This activity page, part of an interactive laboratory series for grades 8-12, introduces students to the gaseous components of the atmosphere. Students explore the main gases of the atmosphere using a pop-up pie chart. Descriptions of the gases and their percentages in the atmosphere are provided. Students read about water vapor in the atmosphere, and an animation shows a simplified process of precipitation. A pop-up window explains the effects of dust on the atmosphere, and a photograph shows how large amounts of dust in the atmosphere create the reds and oranges displayed in sunsets. Finally, ozone is introduced to students as a necessary component of human life on Earth. Copyright 2005 Eisenhower National Clearinghouse

University of Utah. Astrophysics Science Project Integrating Research and Education (ASPIRE)

2003-01-01

402

Spectral response compensation for photon-counting clinical x-ray CT using sinogram restoration  

NASA Astrophysics Data System (ADS)

The x-ray spectrum recorded by a photon-counting x-ray detector (PCXD) is distorted due to the following physical effects which are independent of the count rate: finite energy-resolution, Compton scattering, charge-sharing, and Kescape. If left uncompensated, the spectral response (SR) of a PCXD due to the above effects will result in image artifacts and inaccurate material decomposition. We propose a new SR compensation (SRC) algorithm using the sinogram restoration approach. The two main contributions of our proposed algorithm are: (1) our algorithm uses an efficient conjugate gradient method in which the first and second derivatives of the cost functions are directly calculated analytically, whereas a slower optimization method that requires numerous function evaluations was used in other work; (2) our algorithm guarantees convergence by combining the non-linear conjugate gradient method with line searches that satisfy Wolfe conditions, whereas the algorithm in other work is not backed by theorems from optimization theory to guarantee convergence. In this study, we validate the performance of the proposed algorithm using computer simulations. The bias was reduced to zero from 11%, and image artifacts were removed from the reconstructed images. Quantitative K-edge imaging in possible only when SR compensation is done.

Srivastava, Somesh; Cammin, Jochen; Fung, George S. K.; Tsui, Benjamin M. W.; Taguchi, Katsuyuki

2012-02-01

403

Eccentricity Compensator for Log-Polar Sensor  

Microsoft Academic Search

This paper aims at acquiring robust rotation, scale, and translation-invariant feature from a space-variant image by a fovea sensor. A proposed model of eccentricity compensator corrects deformation that occurs in a log-polar image when the fovea sensor is not centered at a target, that is, when eccentricity exists. An image simulator in discrete space remaps a compensated log-polar image using

Sota Shimizu; Joel W. Burdick

2007-01-01

404

New, compensated Carr-Purcell sequences  

NASA Astrophysics Data System (ADS)

New, compensated Carr-Purcell pulse sequences are reported, all based on x and y phase alternation of the ? pulses. The sequences compensate cumulative pulse errors for all three components of magnetization. Applications include the measurement of homonuclear dipole coupling in the presence of chemical shifts and the measurement of heteronuclear dipole coupling in magic-angle spinning experiments (REDOR). The performance of the new pulse sequences is compared experimentally to previously reported schemes.

Gullion, Terry; Baker, David B.; Conradi, Mark S.

405

Nonlinear Thermal Compensators for WGM Resonators  

NASA Technical Reports Server (NTRS)

In an alternative version of a proposed bimaterial thermal compensator for a whispering-gallery-mode (WGM) optical resonator, a mechanical element having nonlinear stiffness would be added to enable stabilization of a desired resonance frequency at a suitable fixed working temperature. The previous version was described in "Bimaterial Thermal Compensators for WGM Resonators." Both versions are intended to serve as inexpensive means of preventing (to first order) or reducing temperature-related changes in resonance frequencies.

Savchenkov, Anatoliy; Matsko, Andrey; Strekalov, Dmitry; Maleki, Lute; Yu, Nan; Iltchenko, Vladimir

2009-01-01

406

Robust flight control using parameterized compensator  

Microsoft Academic Search

The authors outline a design method for achieving the desired robustness and performance requirements of a flight control system. By using the U-parameter robust compensator design method, the compensator and the closed-loop transfer function can be formulated with free parameters, Moreover, based on a model reference approach, a simple method is introduced to minimize the H2-norm of the error between

Chih-Min Lin; R.-S. Tai; L.-Y. Lai

1992-01-01

407

Wavelength Compensation in Fused Fiber Couplers.  

NASA Astrophysics Data System (ADS)

The performance of fused fiber couplers is wavelength dependent. Wavelength spectral compensation is a technique to decrease the effect of the wavelength dependence, which is an essential task for many applications in fiber optic communication systems. Fiber devices such as wavelength -flattened couplers (WFCs) can be fabricated using wavelength spectral compensation methods. In this dissertation, wavelength spectral compensation techniques in fused biconical taper (FBT) couplers including both multimode and single-mode fiber couplers are studied in detail. In multimode fiber coupler operation, a novel theoretical model based on frustrated total internal reflection (FTIR) has been developed to effectively describe the power coupling and loss mechanism. Experimental results support the theoretical predictions. In single -mode fiber couplers, the conventional technique of fabricating WFCs is discussed. An alternative analytical model has been developed based upon coupled mode theory, which provides a relatively simple and mathematically sound explanation to the wavelength spectral compensation. Aiming to simplify WFC fabrication, a new way of constructing WFCs is proposed and demonstrated by connecting regular single-mode fiber couplers, some of which serve as wavelength spectral compensators. WFCs of various structures including 2 x 2, 1 x 3, 1 x 2 ^{N}, and 4 x 4 have been developed, and the experimental data agree with theoretical predictions of performance. Potential applications and future research directions in wavelength spectral compensation are also presented.

Wang, Zhi G.

408

Workers' compensation: 1984-88 benchmark revisions.  

PubMed

About 93.1 million workers were covered under workers' compensation laws in 1988--an increase of 11 percent from the 1984 total. Benefit amounts totaled $30.7 billion--an increase of about 56 percent since 1984. Of the total payments made under the workers' compensation program, $17.6 billion went to disabled workers, $1.6 billion to their survivors, and $11.5 billion for medical care. The Social Security Administration (SSA) is interested in measuring economic security in the United States, and workers' compensation plays a large role in that measurement. This article represents one part of our overall effort to determine the roles the various income-maintenance programs play in helping citizens of the United States achieve economic security. The figures presented here provide readers with an opportunity to review workers' compensation program operations during much of the 1980's. Workers' compensation is also important to SSA because that program is directly related to the Social Security Disability Insurance program. Since 1965, Social Security disability benefits have been subject to reduction if the beneficiary also receives workers' compensation and the combined benefits exceed 80 percent of previous earnings. In addition, SSA has been directly involved in providing income maintenance for disability from work-related diseases since 1969 when the Federal Black Lung benefits program was established. PMID:1471024

Nelson, W J

1992-01-01

409

Determination of suitable locations for power system stabilizers and static VAR compensators for damping electromechanical oscillations in large scale power systems  

Microsoft Academic Search

Efficient algorithms are presented for the solution of two important problems in the area of damping control of electromechanical oscillations in large-scale systems. The proposed algorithms allow the determination of: the most suitable generators for installing power system stabilizers; the most suitable buses in the system for placing static VAr compensators in order to damp the critical modes of oscillation.

Nelson Martins; L. T. G. Lima

1990-01-01

410

SST algorithm based on radiative transfer model  

Microsoft Academic Search

An algorithm for measuring sea surface temperature (SST) without recourse to the in-situ data for calibration has been proposed. The algorithm which is based on the recorded infrared signal by the satellite sensor is composed of three terms, namely, the surface emission, the up-welling radiance emitted by the atmosphere, and the down-welling atmospheric radiance reflected at the sea surface. This

Mohd Z. Mat Jafri; Khiruddin Abdullah; Alui Bahari

2001-01-01

411

Compensated amorphous silicon solar cell  

DOEpatents

An amorphous silicon solar cell including an electrically conductive substrate, a layer of glow discharge deposited hydrogenated amorphous silicon over said substrate and having regions of differing conductivity with at least one region of intrinsic hydrogenated amorphous silicon. The layer of hydrogenated amorphous silicon has opposed first and second major surfaces where the first major surface contacts the electrically conductive substrate and an electrode for electrically contacting the second major surface. The intrinsic hydrogenated amorphous silicon region is deposited in a glow discharge with an atmosphere which includes not less than about 0.02 atom percent mono-atomic boron. An improved N.I.P. solar cell is disclosed using a BF.sub.3 doped intrinsic layer.

Devaud, Genevieve (629 S. Humphrey Ave., Oak Park, IL 60304)

1983-01-01

412

Complex amplitude correlation for compensation of large in-plane motion in digital speckle pattern interferometry  

SciTech Connect

The use of complex amplitude correlation to compensate for large in-plane motion in digital speckle pattern interferometry is investigated. The result is compared with experiments where digital speckle photography (DSP) is used for compensation. An advantage of using complex amplitude correlation instead of intensity correlation (as in DSP) is that the phase change describing the deformation is retrieved directly from the correlation peak, and there is no need to compensate for the large movement and then use the interferometric algorithms. A discovered drawback of this method is that the correlation values drop quickly if a phase gradient larger than {pi} is present in the subimages used for cross correlation. This means that, for the complex amplitude correlation to be used, the size of the subimages must be well chosen or a third parameter in the cross-correlation algorithm that compensates for the phase variation is needed.Correlation values and wrapped phase maps from the two techniques (intensity and complex amplitude correlation) are presented.

Svanbro, Angelica; Sjoedahl, Mikael

2006-12-01

413

Estimation and Compensation of aberrations in Spatial Light Modulators  

NASA Astrophysics Data System (ADS)

The spatial light modulator (SLM) Holoeye LC-R720 is based on LCoS (Liquid Crystal on Silicon) technology. Due to the induced curvatures on the silicon plate by the production process, there are static aberrations in the wave-fronts modified by the SLM. In order to calculate the aberrated wave-front we used phase-shifting interferometry, an optimization algorithm for far field propagation, and the geometric characterization of the focal spot along the caustic. Zernike polynomials were used for expanding and comparing the wave-fronts. The aberration compensation was carried out by displaying the conjugated transmittance on the SLM. The complexity of the experimental setup and the requirements of the digital processing of each estimation method were comparatively analyzed.

Arias, Augusto; Castaneda, Roman

2011-01-01

414

Non-linear compensation techniques for coherent fibre transmission  

NASA Astrophysics Data System (ADS)

Thanks to coherent detection and digital signal processing (DSP), linear distortions such as chromatic dispersion (CD) and polarisation mode dispersion (PMD) can in principle be completely compensated for in high-speed optical transmission. And indeed, effective algorithms have been devised and extensively investigated that allow CD- and PMDresilient transmission of high-speed signals over long distances, leaving optical noise accumulation and non-linear impairments as the factors ultimately limiting reach. Considerable research has been dedicated in the last couple of years to devise methods to increase the non-linear tolerance of optical signals by means of digital signal processing. In this review paper, we present an overview of the most promising techniques, show some examples of their application and outline the status of research on this important topic.

Forzati, Marco; Mårtensson, Jonas; Chin, Hou-Man; Mussolin, Marco; Rafique, Danish; Guiomar, Fernando

2011-11-01

415

The compensation source in nitrogen doped ZnO  

NASA Astrophysics Data System (ADS)

Nitrogen doped zinc oxide (ZnO) films have been prepared by molecular beam epitaxy. The as-grown samples show n-type conduction, but they convert to p-type after being annealed in O2 atmosphere. X-ray photoelectron spectroscopy reveals that the conversion is mainly caused by the escaping of substituted N molecule (N2)O donors from the films, and photoluminescence spectroscopy confirms the extraction of (N2)O. The work shown in this paper reveals experimentally that the main compensation source in nitrogen doped ZnO is (N2)O donors instead of intrinsic donors or background impurities, and annealing in oxygen may be a promising route to p-ZnO.

Li, L.; Shan, C. X.; Li, B. H.; Yao, B.; Y Zhang, J.; Zhao, D. X.; Zhang, Z. Z.; Shen, D. Z.; Fan, X. W.; Lu, Y. M.

2008-12-01

416

Vibration isolation and pressure compensation apparatus for sensitive instrumentation  

NASA Technical Reports Server (NTRS)

A system for attenuating the inherent vibration associated with a mechanical refrigeration unit employed to cryogenically cool sensitive instruments used in measuring chemical constituents of the atmosphere is described. A modular system including an instrument housing and a reaction bracket with a refrigerator unit floated there between comprise the instrumentation system. A pair of evacuated bellows that "float' refrigerator unit and provide pressure compensation at all levels of pressure from seal level to the vacuum of space. Vibration isolators and when needed provide additional vibration damping for the refrigerator unit. A flexible thermal strap (20 K) serves to provide essentially vibration free thermal contact between cold tip of the refrigerator unit and the instrument component mounted on the IDL mount. Another flexible strap (77 K) serves to provide vibration free thermal contact between the TDL mount thermal shroud and a thermal shroud disposed about the thermal shaft.

Averill, R. D. (inventor)

1983-01-01

417

Atmospheric superrotation?  

Microsoft Academic Search

Beginning in 1958 analysis of the atmospheric drag on artificial earth satellites has provided many measurements of the rotation of the earth's thermosphere.11Atmospheric rotation is represented by the ratio: ?=(mean inertial rotation of the atmosphere)\\/(mean earth rotation). Superrotation occurs when ?>1.0. It was reported that there was a net west-to-east wind ranging from 50ms?1 to more than 200ms?1: the so-called

E. M Gaposchkin

2003-01-01

418

STATCOM for compensation of large electric arc furnace installations  

Microsoft Academic Search

High power electronic equipment, developed for the compensation of utility power transmission systems, has been successfully applied to the problem of flicker compensation in a large industrial arc furnace. Whereas conventional flicker compensation methods, using thyristor valves in conjunction with passive components, have generally failed to reduce flicker substantially the new STATCOM-based compensator provides a dramatic reduction in flicker, as

C. Schauder

1999-01-01

419

Scientific investigations of atmospheric processes  

NASA Astrophysics Data System (ADS)

Research was performed in atmospheric, dynamical, and thermodynamical processes and in other disciplines necessary to accomplish the following tasks: develop procedures for combining generalized radiative transfer codes with dynamic atmospheric model codes; perform diagnostic analysis of atmospheric processes to gain a better understanding of the evolution and development of mesoscale circulation systems and their precipitation structures; and to develop algorithms and software necessary to graphically display diagnostic sets on the MSFC McIDAS and EADS to facilitate scientific study and sensor capability evaluation. Research activities during this reporting period are detailed.

1994-01-01

420

Strategies for attenuation compensation in neurological PET studies.  

PubMed

Molecular brain imaging using positron emission tomography (PET) has evolved into a vigorous academic field and is progressively gaining importance in the clinical arena. Significant progress has been made in the design of high-resolution three-dimensional (3-D) PET units dedicated to brain research and the development of quantitative imaging protocols incorporating accurate image correction techniques and sophisticated image reconstruction algorithms. However, emerging clinical and research applications of molecular brain imaging demand even greater levels of accuracy and precision and therefore impose more constraints with respect to the quantitative capability of PET. It has long been recognized that photon attenuation in tissues is the most important physical factor degrading PET image quality and quantitative accuracy. Quantitative PET image reconstruction requires an accurate attenuation map of the object under study for the purpose of attenuation compensation. Several methods have been devised to correct for photon attenuation in neurological PET studies. Significant attention has been devoted to optimizing computational performance and to balancing conflicting requirements. Approximate methods suitable for clinical routine applications and more complicated approaches for research applications, where there is greater emphasis on accurate quantitative measurements, have been proposed. The number of scientific contributions related to this subject has been increasing steadily, which motivated the writing of this review as a snapshot of the dynamically changing field of attenuation correction in cerebral 3D PET. This paper presents the physical and methodological basis of photon attenuation and summarizes state of the art developments in algorithms used to derive the attenuation map aiming at accurate attenuation compensation of brain PET data. Future prospects, research trends and challenges are identified and directions for future research are discussed. PMID:17113312

Zaidi, Habib; Montandon, Marie-Louise; Meikle, Steve

2007-01-15

421

Pluto's atmosphere  

SciTech Connect

Airborne CCD photometer observations of Pluto's June 9, 1988 stellar occultation have yielded an occultation lightcurve, probing two regions on the sunrise limb 2000 km apart, which reveals an upper atmosphere overlying an extinction layer with an abrupt upper boundary. The extinction layer may surround the entire planet. Attention is given to a model atmosphere whose occultation lightcurve closely duplicates observations; fits of the model to the immersion and emersion lightcurves exhibit no significant derived atmosphere-structure differences. Assuming a pure methane atmosphere, surface pressures of the order of 3 microbars are consistent with the occultation data. 43 references.

Elliot, J.L.; Dunham, E.W.; Bosh, A.S.; Slivan, S.M.; Young, L.A.

1989-01-01

422

Pluto's atmosphere  

NASA Technical Reports Server (NTRS)

Airborne CCD photometer observations of Pluto's June 9, 1988 stellar occultation have yielded an occultation lightcurve, probing two regions on the sunrise limb 2000 km apart, which reveals an upper atmosphere overlying an extinction layer with an abrupt upper boundary. The extinction layer may surround the entire planet. Attention is given to a model atmosphere whose occultation lightcurve closely duplicates observations; fits of the model to the immersion and emersion lightcurves exhibit no significant derived atmosphere-structure differences. Assuming a pure methane atmosphere, surface pressures of the order of 3 microbars are consistent with the occultation data.

Elliot, J. L.; Dunham, E. W.; Bosh, A. S.; Slivan, S. M.; Young, L. A.

1989-01-01

423

Matching Pursuit for Compression and Application to Motion Compensated Video Coding  

Microsoft Academic Search

In many hybrid video compression algorithms there is aclear distinction between motion estimation and compensation(MEMC) on the one hand, and transformcoding of the residue on the other hand. By translatingMEMC into the framework of Matching Pursuit(MP), we will show that unification of both steps ispossible. Moreover, adapting the MP approach to thesmall size dictionaries involved in MEMC, it is shownthat

Martin Vetterli; Ton Kalker

1994-01-01

424

Digital non-linear compensation for high-speed long-haul transmission  

Microsoft Academic Search

Thanks to coherent detection and digital signal processing (DSP), linear distortions such as chromatic dispersion (CD) and polarisation mode dispersion (PMD) can in principle be completely compensated for in high-speed optical transmission. And indeed, effective algorithms have been devised and extensively investigated that allow CD- and PMD-resilient transmission of high-speed signals over long distances, leaving optical noise accumulation and non-linear

Marco Forzati; Jonas Martensson; Hou-Man Chin; Marco Mussolin; Danish Rafique

2011-01-01

425

Net-Shape Forging of Aerofoil Blade based on Flash Trimming and Compensation methods  

NASA Astrophysics Data System (ADS)

In this research, an automatic blade forging die shape optimisation system was developed by using direct compensation and flash trimming algorithms and integrating with the DEFORM 3D software package. To validate the developed system, a 3D blade forging case problem was simulated and optimised with and without the consideration of trimming simulation. The results were compared with actual measurement data of the forged aerofoil blade with excellent results obtained with the fast trimming simulation procedure used.

Lu, B.; Ou, H.; Armstrong, C. G.

2011-05-01

426

A novel dual heuristic programming based optimal control of a series compensator in the electric power transmission system  

Microsoft Academic Search

In this paper, the dual heuristic programming (DHP) optimization algorithm is used for the design of a nonlinear optimal neurocontroller that replaces the proportional-integral (PI) based conventional linear controller (CONVC) in the internal control of a power electronic converter based series compensator in the electric power transmission system. The performance of the proposed DHP based neurocontroller is compared with that

Jung-Wook Park; Ronald G. Harley; Ganesh K. Venayagamoorthy

2003-01-01

427

Compensation for 3D physiological motion in robotic-assisted surgery using a predictive force controller. Experimental results  

Microsoft Academic Search

This paper presents a predictive force control approach to compensate for the physiological motion induced by both respiratory and heart beating motions during cardiac surgery. It focuses on the design and implementation of the control algorithm in the context of robotized minimally invasive surgery. The controller is based on a linear predictive control loop using the force information applied on

Michel Dominici; Philippe Poignet; Rui Cortesão; Etienne Dombre; Olivier Tempier

2009-01-01

428

Novel STATCOM Controller for Mitigating SSR and Damping Power System Oscillations in a Series Compensated Wind Park  

Microsoft Academic Search

This paper addresses implementation issues associated with a novel damping control algorithm for a STATCOM in a series compensated wind park for mitigating SSR and damping power system oscillations. The IEEE first benchmark model on SSR is adopted with integrating aggregated self-excited induction generator-based wind turbine to perform the studies. The potential occurrence and mitigation of the SSR caused by

Mohamed S. El-Moursi; Birgitte Bak-Jensen; Mansour H. Abdel-Rahman

2010-01-01

429

Compensation performance of decision feedback equalizer in high speed optical communication system  

NASA Astrophysics Data System (ADS)

This paper discusses electronics dispersion compensation (EDC) by decision feedback equalizer (DFE) in high speed optical communication system using the LMS and the RLS algorithms, respectively. The theory of the decomposed DFE derived from basic concept of DFE in EDC is studied. Compared with the traditional DFE, the system complexity of new one has been reduced while it still keeps the high performance of DFE. Simulation results prove the validity of practicability and indicate that the decomposed DFE using RLS algorithm can more effectively eliminate intersymbol interference (ISI) after being transmitted long distance.

Lu, Li; Lei, Jianming; Bing, Linlin; Zou, Xuecheng

2008-11-01

430

Loop Algorithm  

NASA Astrophysics Data System (ADS)

The loop algorithm for the world-line quantum Monte Carlo method on quantum lattice models is presented. After introducing the path integral representation that maps a quantum model to a classical one, we describe the continuous imaginary time limit, cluster algorithm, and the rejection free scheme, which are the major improvements on the quantum Monte Carlo technique during the last decades. By means of the loop algorithm, one can simulate various unfrustrated quantum lattice models of millions of sites at extremely low temperatures with absolute accuracy, being free from the critical and fine-mesh slowing down and the Suzuki-Trotter discretization error. We also discuss some technical aspects of the algorithm such as effective implementation and parallelization.

Todo, Synge

431

Compensation method for random drifts of laser beams based on moving average feedback control  

NASA Astrophysics Data System (ADS)

In order to eliminate the measurement errors caused by the instability of laser beams, a real-time compensation algorithms for the random drifts of laser beams based on moving average (MA) correction mechanism was presented. By establishing a correction model with two fast steering mirrors in the beam delivery path and analyzing the pulse to pulse beam fluctuation, a real-time beam drifts correction is implemented based on closed loop feedback control, which especially focuses on reducing the pulse to pulse drifts and ground fluctuations. The simulation results show that this algorithm can control beam drifts effectively. Optimal MA can be reduced to 3n-1/2 times (n--pulse numbers in a window) without the ground vibrations. There are a series of improvements on the moving standard deviation (MSD) as well. MSD get a sudden decline at the window pulse. Meanwhile, the drifts can be restrained while loading the ground vibrations without any big jump, and the dropping amplitude is bigger than without the ground vibration. MSD drop while the whole system is controlled by this compensation method and the results are stable. The key of this compensation method for random drifts of laser beams based on moving average feedback control lies in the appropriate corrections formula. What is more, this algorithm which is practical can achieve high precision control of direction drifts.

Zhang, Lixia; Wang, Ruilin; Lin, Wumei; Liao, Zhijie

2012-10-01

432

Peer group ties and executive compensation networks.  

PubMed

Publicly traded firms in the US typically determine C.E.O. compensation by benchmarking the pay of their C.E.O.s against the pay of C.E.O.s in "peer" firms. Consequently, executive compensation is influenced not only by firm-level characteristics, but also by the selection and actions of the firm's immediate peers as well as by the structure of the executive compensation network overall. Analyzing compensation peer group choices made by the same 1183 firms for F.Y. 2007, 2008 and 2009, we find that while the typical compensation peer is similar in size and industry to the firm that chose it, deviations from this norm are common, especially among larger firms, and tend to be towards larger firms with better paid CEOs. Further analysis shows that firms who pay CEOs well relative to the pay that would be predicted from their revenues, return on assets, and industry tend to have greater aspiration bias in their group of named peers. PMID:24090860

Pittinsky, Matthew; Diprete, Thomas A

2013-11-01

433

Atmospheric infrared sounder  

NASA Technical Reports Server (NTRS)

This report summarizes the activities of two Atmospheric Infrared Sounder (AIRS) team members during the first half of 1995. Changes to the microwave first-guess algorithm have separated processing of Advanced Microwave Sounding Unit A (AMSU-A) from AMSU-B data so that the different spatial resolutions of the two instruments may eventually be considered. Two-layer cloud simulation data was processed with this algorithm. The retrieved water vapor column densities and liquid water are compared. The information content of AIRS data was applied to AMSU temperature profile retrievals in clear and cloudy atmospheres. The significance of this study for AIRS/AMSU processing lies in the improvement attributable to spatial averaging and in the good results obtained with a very simple algorithm when all of the channels are used. Uncertainty about the availability of either a Microwave Humidity Sensor (MHS) or AMSU-B for EOS has motivated consideration of possible low-cost alternative designs for a microwave humidity sensor. One possible configuration would have two local oscillators (compared to three for MHS) at 118.75 and 183.31 GHz. Retrieval performances of the two instruments were compared in a memorandum titled 'Comparative Analysis of Alternative MHS Configurations', which is attached.

Rosenkranz, Philip, W.; Staelin, David, H.

1995-01-01

434

Phase extraction and unwrapping using rotational and direct compensators for digital hologram  

NASA Astrophysics Data System (ADS)

The growing interest in the applications of digital holography interferometry has led to an increasing demand for reliable phase unwrapping techniques. In digital holography, the phase carries three-dimensional surface information about the object. However, phase mapping is ambiguous as the extracted phase is returned in a form that suffers from 2? phase jumps. Furthermore, the presence of noise in the measured data, in which many singular points (SP) are found, often makes general phase unwrapping algorithms fail to produce accurate unwrapped results. Therefore, it is necessary to use a powerful phase unwrapping method to recover the desired smooth phase surface. For this reason, we developed a phase unwrapping algorithm that is applicable to digital hologram maps. The developed algorithm solves the singularity problem caused by SPs as a result of compensating its effect by using rotational and direct compensators. We show a difference in performance between our developed phase unwrapping algorithm and other well known phase unwrapping methods for digital holographic data. In addition, the methods to extract phase information of the object from hologram maps are also investigated. Results show that the developed algorithm gives satisfactory unwrapped results with low computational time cost.

Heshmat, Samia; Tomioka, Satoshi; Nishiyama, Shusuke

2013-10-01

435

Atmospheric chemistry  

SciTech Connect

This book covers the predictive strength of atmospheric models. The book covers all of the major important atmospheric areas, including large scale models for ozone depletion and global warming, regional scale models for urban smog (ozone and visibility impairment) and acid rain, as well as accompanying models of cloud processes and biofeedbacks.

Sloane, C.S. (General Motors Research Labs., Warren, MI (United States)); Tesche, T.W. (Alpine Geophysics (US))

1991-01-01

436

Pluto's atmosphere  

Microsoft Academic Search

Airborne CCD photometer observations of Pluto's June 9, 1988 stellar occultation have yielded an occultation lightcurve, probing two regions on the sunrise limb 2000 km apart, which reveals an upper atmosphere overlying an extinction layer with an abrupt upper boundary. The extinction layer may surround the entire planet. Attention is given to a model atmosphere whose occultation lightcurve closely duplicates

J. L. Elliot; E. W. Dunham; A. S. Bosh; S. M. Slivan; L. A. Young

1989-01-01

437

Atmospheric Electricity  

Microsoft Academic Search

A number of current problems in atmospheric electricity are discussed in turn; these are: ionization equilibrium in the atmosphere; fine weather fields and currents, particularly conditions close to the earth's surface; point discharge; precipitation currents and their origin; the maintenance of the charge on the earth; the electrical structure of thunderclouds; and theories of the origin of charges in clouds.

J Alan Chalmers

1954-01-01

438

Discrete Packet Analysis for Improved Atmospheric Rejection on Modulated Laser Signals  

SciTech Connect

This slide-show discusses how the method of discrete packet analysis improves atmospheric compensation for quasi-CW fluorescence detection methods. This is key to improving remote sensing capabilities.

O'Neill, M., McKenna, I., DiBenedetto, J., Capelle, G., Trainham, R.

2012-07-19

439

Compensation electronics for staring focal plane arrays  

NASA Astrophysics Data System (ADS)

A system which provides complete offset and gain correction to the output of a hybrid (HCT/CCD) staring focal plane has been developed. This system provides high speed, real time compensation using custom processing electronics at the CCD output. A microprocessor controls the operation of the electronics and allows the user to implement any of several operating modes. The compensated output can be displayed on a high speed CRT or on a standard black and white TV monitor to enhance visual resolution. The compensation electronics described here is correcting a 64 x 64 array at pixel rates to 5 MHz. The system can be configured to operate on array sizes up to 256 x 256 at frequencies to 10 MHz as larger arrays and faster analog to digital converters become available.

Hartnett, K. J.; Butler, N. R.; Stobie, J. A.; Iwasa, S.

1981-01-01

440

Temperature compensated silicon resonators for space applications  

NASA Astrophysics Data System (ADS)

This paper presents piezoelectric transduction and frequency trimming of silicon-based resonators with a center frequency in the low megahertz regime. The temperature coefficient of frequency (TCF) of the resonators is reduced using both passive and active compensation schemes. Specifically, a novel technique utilizing oxide-refilled trenches is implemented to achieve efficient temperature compensation while maintaining compatibility with wet release processes. Using this method, we demonstrate high-Q resonators having a first-order TCF as low as 3 ppm/°C and a turnover temperature of around 90 °C, ideally suited for use in ovenized platforms. Using active tuning, the temperature sensitivity of the resonator is further compensated around the turnover temperature, demonstrating frequency instability of less than 400 ppb. Such devices are ideally suited as timing units in space applications where size, power consumption, and temperature stability are of critical importance.

Rais-Zadeh, Mina; Thakar, Vikram A.; Wu, Zhengzheng; Peczalski, Adam

2013-03-01

441

Reexamining workers' compensation: a human rights perspective.  

PubMed

Injured workers, particularly those with more severe injuries, have long experienced workers' compensation systems as stressful and demeaning, have found it difficult to obtain benefits, and, when able to obtain benefits, have found them inadequate. Moreover, the last two decades have seen a substantial erosion of the protections offered by workers' compensation. State after state has erected additional barriers to benefit receipt, making the workers' compensation experience even more difficult and degrading. These changes have been facilitated by a framing of the political debate focused on the free market paradigm, employer costs, and worker fraud and malingering. The articles in this special issue propose an alternate framework and analysis, a human rights approach, that values the dignity and economic security of injured workers and their families. PMID:22570018

Boden, Leslie I

2012-06-01

442

Rapid springback compensation for age forming based on quasi Newton method  

NASA Astrophysics Data System (ADS)

Iterative methods based on finite element simulation are effective approaches to design mold shape to compensate springback in sheet metal forming. However, convergence rate of iterative methods is difficult to improve greatly. To increase the springback compensate speed of designing age forming mold, process of calculating springback for a certain mold with finite element method is analyzed. Springback compensation is abstracted as finding a solution for a set of nonlinear functions and a springback compensation algorithm is presented on the basis of quasi Newton method. The accuracy of algorithm is verified by developing an ABAQUS secondary development program with MATLAB. Three rectangular integrated panels of dimensions 710 mm ×750 mm integrated panels with intersected ribs of 10 mm are selected to perform case studies. The algorithm is used to compute mold contours for the panels with cylinder, sphere and saddle contours respectively and it takes 57%, 22% and 33% iterations as compared to that of displacement adjustment (DA) method. At the end of iterations, maximum deviations on the three panels are 0.618 4 mm, 0.624 1 mm and 0.342 0 mm that are smaller than the deviations determined by DA method (0.740 8 mm, 0.740 8 mm and 0.713 7 mm respectively). In following experimental verification, mold contour for another integrated panel with 400 mm×380 mm size is designed by the algorithm. Then the panel is age formed in an autoclave and measured by a three dimensional digital measurement devise. Deviation between measuring results and the panel's design contour is less than 1 mm. Finally, the iterations with different mesh sizes (40 mm, 35 mm, 30 mm, 25 mm, 20 mm) in finite element models are compared and found no considerable difference. Another possible compensation method, Broyden-Fletcher-Shanmo method, is also presented based on the solving nonlinear functions idea. The Broyden-Fletcher-Shanmo method is employed to compute mold contour for the second panel. It only takes 50% iterations compared to that of DA. The proposed method can serve a faster mold contour compensation method for sheet metal forming.

Xiong, Wei; Gan, Zhong; Xiong, Shipeng; Xia, Yushan

2014-05-01

443

Gigabit Ethernet Asynchronous Clock Compensation FIFO  

NASA Technical Reports Server (NTRS)

Clock compensation for Gigabit Ethernet is necessary because the clock recovered from the 1.25 Gb/s serial data stream has the potential to be 200 ppm slower or faster than the system clock. The serial data is converted to 10-bit parallel data at a 125 MHz rate on a clock recovered from the serial data stream. This recovered data needs to be processed by a system clock that is also running at a nominal rate of 125 MHz, but not synchronous to the recovered clock. To cross clock domains, an asynchronous FIFO (first-in-first-out) is used, with the write pointer (wprt) in the recovered clock domain and the read pointer (rptr) in the system clock domain. Because the clocks are generated from separate sources, there is potential for FIFO overflow or underflow. Clock compensation in Gigabit Ethernet is possible by taking advantage of the protocol data stream features. There are two distinct data streams that occur in Gigabit Ethernet where identical data is transmitted for a period of time. The first is configuration, which happens during auto-negotiation. The second is idle, which occurs at the end of auto-negotiation and between every packet. The identical data in the FIFO can be repeated by decrementing the read pointer, thus compensating for a FIFO that is draining too fast. The identical data in the FIFO can also be skipped by incrementing the read pointer, which compensates for a FIFO draining too slowly. The unique and novel features of this FIFO are that it works in both the idle stream and the configuration streams. The increment or decrement of the read pointer is different in the idle and compensation streams to preserve disparity. Another unique feature is that the read pointer to write pointer difference range changes between compensation and idle to minimize FIFO latency during packet transmission.

Duhachek, Jeff

2012-01-01