Science.gov

Sample records for optical model evaluation

  1. Optical Storage Performance Modeling and Evaluation.

    ERIC Educational Resources Information Center

    Behera, Bailochan; Singh, Harpreet

    1990-01-01

    Evaluates different types of storage media for long-term archival storage of large amounts of data. Existing storage media are reviewed, including optical disks, optical tape, magnetic storage, and microfilm; three models are proposed based on document storage requirements; performance analysis is considered; and cost effectiveness is discussed.…

  2. Optical CD metrology model evaluation and refining for manufacturing

    NASA Astrophysics Data System (ADS)

    Wang, S.-B.; Huang, C. L.; Chiu, Y. H.; Tao, H. J.; Mii, Y. J.

    2009-03-01

    Optical critical dimension (OCD) metrology has been well-accepted as standard inline metrology tool in semiconductor manufacturing since 65nm technology node for its un-destructive and versatile advantage. Many geometry parameters can be obtained in a single measurement with good accuracy if model is well established and calibrated by transmission electron microscopy (TEM). However, in the viewpoint of manufacturing, there is no effective index for model quality and, based on that, for model refining. Even, when device structure becomes more complicated, like strained silicon technology, there are more parameters required to be determined in the afterward measurement. The model, therefore, requires more attention to be paid to ensure inline metrology reliability. GOF (goodness-of-fitting), one model index given by a commercial OCD metrology tool, for example, is not sensitive enough while correlation and sensitivity coefficient, the other two indexes, are evaluated under metrology tool noise only and not directly related to inline production measurement uncertainty. In this article, we will propose a sensitivity matrix for measurement uncertainty estimation in which each entry is defined as the correlation coefficient between the corresponding two floating parameters and obtained by linearization theorem. The uncertainty is estimated in combination of production line variation and found, for the first time, much larger than that by metrology tool noise alone that indicates model quality control is critical for nanometer device production control. The uncertainty, in comparison with production requirement, also serves as index for model refining either by grid size rescaling or structure model modification. This method is verified by TEM measurement and, in the final, a flow chart for model refining is proposed.

  3. Dedicated spectrometers based on diffractive optics: design, modelling and evaluation

    NASA Astrophysics Data System (ADS)

    Løvhaugen, O.; Johansen, I.-R.; Bakke, K. A. H.; Fismen, B. G.; Nicolas, S.

    The described design of diffractive optical elements for low cost IR-spectrometers gives a built-in wavelength reference and allows 'spectral arithmetic' to be implemented in the optical performance of the DOE. The diffractive element combines the function of the lenses and the grating and eliminates the need for alignment of those components in the standard scanned grating spectrometer design. The element gives out a set of foci, each with one spectral component, which are scanned across a detector, thus relaxing the demands for scan angle control. It can thus be regarded as an alternative solution to a beam splitter and band pass filter instrument. Software tools have been designed to ease the adaptation of the design to different applications. To model the performance of the spectrometers we have implemented a scalar Rayleigh-Sommerfeldt diffraction model. The gold-coated elements are produced by injection moulding using a compact disc (CD) moulding technique and mould inlays mastered by e-beam lithography. The optimized selection of wavelength bands and the classification of the measured signal use a combination of principal component analysis and robust statistical methods. Typical applications will be material characterization of recycled plastics and gas monitoring. Spectrometers for two different applications have been built and tested. Comparisons between the design goals and the measured performance have been made and show good agreements.

  4. ModelE2-TOMAS development and evaluation using aerosol optical depths, mass and number concentrations

    NASA Astrophysics Data System (ADS)

    Lee, Y. H.; Adams, P. J.; Shindell, D. T.

    2014-09-01

    The TwO-Moment Aerosol Sectional microphysics model (TOMAS) has been integrated into the state-of-the-art general circulation model, GISS ModelE2. TOMAS has the flexibility to select a size resolution as well as the lower size cutoff. A computationally efficient version of TOMAS is used here, which has 15 size bins covering 3 nm to 10 μm aerosol dry diameter. For each bin, it simulates the total aerosol number concentration and mass concentrations of sulphate, pure elementary carbon (hydrophobic), mixed elemental carbon (hydrophilic), hydrophobic organic matter, hydrophilic organic matter, sea salt, mineral dust, ammonium, and aerosol-associated water. This paper provides a detailed description of the ModelE2-TOMAS model and evaluates the model against various observations including aerosol precursor gas concentrations, aerosol mass and number concentrations, and aerosol optical depths. Additionally, global budgets in ModelE2-TOMAS are compared with those of other global aerosol models, and the TOMAS model is compared to the default aerosol model in ModelE2, which is a bulk aerosol model. Overall, the ModelE2-TOMAS predictions are within the range of other global aerosol model predictions, and the model has a reasonable agreement with observations of sulphur species and other aerosol components as well as aerosol optical depth. However, ModelE2-TOMAS (as well as the bulk aerosol model) cannot capture the observed vertical distribution of sulphur dioxide over the Pacific Ocean possibly due to overly strong convective transport. The TOMAS model successfully captures observed aerosol number concentrations and cloud condensation nuclei concentrations. Anthropogenic aerosol burdens in the bulk aerosol model running in the same host model as TOMAS (ModelE2) differ by a few percent to a factor of 2 regionally, mainly due to differences in aerosol processes including deposition, cloud processing, and emission parameterizations. Larger differences are found for naturally

  5. Optical modeling and physical performances evaluations for the JT-60SA ECRF antenna

    NASA Astrophysics Data System (ADS)

    Platania, P.; Figini, L.; Farina, D.; Isayama, A.; Kobayashi, T.; Micheletti, D.; Moriyama, S.; Moro, A.; Sozzi, C.

    2015-12-01

    The purpose of this work is the optical modeling and physical performances evaluations of the JT-60SA ECRF launcher system. The beams have been simulated with the electromagnetic code GRASP® and used as input for ECCD calculations performed with the beam tracing code GRAY, capable of modeling propagation, absorption and current drive of an EC Gaussion beam with general astigmatism. Full details of the optical analysis has been taken into account to model the launched beams. Inductive and advanced reference scenarios has been analysed for physical evaluations in the full poloidal and toroidal steering ranges for two slightly different layouts of the launcher system.

  6. Optical modeling and physical performances evaluations for the JT-60SA ECRF antenna

    SciTech Connect

    Platania, P. Figini, L.; Farina, D.; Micheletti, D.; Moro, A.; Sozzi, C.; Isayama, A.; Kobayashi, T.; Moriyama, S.

    2015-12-10

    The purpose of this work is the optical modeling and physical performances evaluations of the JT-60SA ECRF launcher system. The beams have been simulated with the electromagnetic code GRASP® and used as input for ECCD calculations performed with the beam tracing code GRAY, capable of modeling propagation, absorption and current drive of an EC Gaussion beam with general astigmatism. Full details of the optical analysis has been taken into account to model the launched beams. Inductive and advanced reference scenarios has been analysed for physical evaluations in the full poloidal and toroidal steering ranges for two slightly different layouts of the launcher system.

  7. Solar optical codes evaluation for modeling and analyzing complex solar receiver geometries

    NASA Astrophysics Data System (ADS)

    Yellowhair, Julius; Ortega, Jesus D.; Christian, Joshua M.; Ho, Clifford K.

    2014-09-01

    Solar optical modeling tools are valuable for modeling and predicting the performance of solar technology systems. Four optical modeling tools were evaluated using the National Solar Thermal Test Facility heliostat field combined with flat plate receiver geometry as a benchmark. The four optical modeling tools evaluated were DELSOL, HELIOS, SolTrace, and Tonatiuh. All are available for free from their respective developers. DELSOL and HELIOS both use a convolution of the sunshape and optical errors for rapid calculation of the incident irradiance profiles on the receiver surfaces. SolTrace and Tonatiuh use ray-tracing methods to intersect the reflected solar rays with the receiver surfaces and construct irradiance profiles. We found the ray-tracing tools, although slower in computation speed, to be more flexible for modeling complex receiver geometries, whereas DELSOL and HELIOS were limited to standard receiver geometries such as flat plate, cylinder, and cavity receivers. We also list the strengths and deficiencies of the tools to show tool preference depending on the modeling and design needs. We provide an example of using SolTrace for modeling nonconventional receiver geometries. The goal is to transfer the irradiance profiles on the receiver surfaces calculated in an optical code to a computational fluid dynamics code such as ANSYS Fluent. This approach eliminates the need for using discrete ordinance or discrete radiation transfer models, which are computationally intensive, within the CFD code. The irradiance profiles on the receiver surfaces then allows for thermal and fluid analysis on the receiver.

  8. Evaluating the representation of aerosol optical properties using an online coupled model over the Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Palacios-Peña, Laura; Baró, Rocío; Guerrero-Rascado, Juan Luis; Alados-Arboledas, Lucas; Brunner, Dominik; Jiménez-Guerrero, Pedro

    2017-01-01

    The effects of atmospheric aerosol particles on the Earth's climate mainly depend on their optical, microphysical and chemical properties, which modify the Earth's radiative budget. The aerosol radiative effects can be divided into direct and semi-direct effects, produced by the aerosol-radiation interactions (ARIs), and indirect effects, produced by aerosol-cloud interactions (ACIs). In this sense the objective of this work is to assess whether the inclusion of aerosol radiative feedbacks in the online coupled WRF-Chem model improves the modelling outputs over the Iberian Peninsula (IP) and surrounding water areas. For this purpose, the methodology is based on the evaluation of modelled aerosol optical properties under different simulation scenarios. The evaluated data come from two WRF-Chem simulations for the IP differing in the inclusion/no-inclusion of ARIs and ACIs (RF/NRF simulations). The case studies cover two episodes with different aerosol types over the IP in 2010, namely a Saharan dust outbreak and a forest fire episode. The evaluation uses observational data from AERONET (Aerosol Robotic Network) stations and MODIS (Moderate Resolution Imaging Spectroradiometer) sensor, including aerosol optical depth (AOD) and Ångström exponent (AE). Experimental data of aerosol vertical distribution from the EARLINET (European Aerosol Research Lidar Network) Granada station are used for checking the models. The results indicate that for the spatial distribution the best-represented variable is AOD and the largest improvements when including the aerosol radiative feedbacks are found for the vertical distribution. In the case of the dust outbreak, a slight improvement (worsening) is produced over the areas with medium (high/low) levels of AOD(-9 % / +12 % of improvement) when including the aerosol radiative feedbacks. For the wildfire episode, improvements of AOD representation (up to 11 %) over areas further away from emission sources are estimated

  9. The Synthesis and Evaluation of Third-Order Optical Nonlinearities of Model Compounds Containing Benzothiazole, Benzimidazole and Benzoxazole Moieties.

    DTIC Science & Technology

    1991-02-01

    AD-A235 622 WL-TR-91-4015 THE SYNTHESIS AND EVALUATION OF THIRD-ORDER OPTICAL NONLINEARITIES OF MODEL COMPOUNDS CONTAINING BENZOTHIAZOLE ...Nonlinearities of Model Compounds Containing Benzothiazole , Benzimidazole, and Benzoxazole Moieties 12 PERSONAL AUTHOR(S) Bruce A. Reinhardt, Marilyn R...necessary and identify by block number) FIELD GROUP SUB-GROUP nonlinear optical properties benzothiazole u/ 03 degenerate four-wave mixing benzimidazole 21

  10. Microvascular anastomosis in rodent model evaluated by Fourier domain Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Huang, Yong; Tong, Dedi; Zhu, Shan; Wu, Lehao; Ibrahim, Zuhaib; Lee, WP Andrew; Brandacher, Gerald; Kang, Jin U.

    2014-03-01

    Vascular and microvascular anastomosis are critical components of reconstructive microsurgery, vascular surgery and transplant surgery. Imaging modality that provides immediate, real-time in-depth view and 3D structure and flow information of the surgical site can be a great valuable tool for the surgeon to evaluate surgical outcome following both conventional and innovative anastomosis techniques, thus potentially increase the surgical success rate. Microvascular anastomosis for vessels with outer diameter smaller than 1.0 mm is extremely challenging and effective evaluation of the outcome is very difficult if not impossible using computed tomography (CT) angiograms, magnetic resonance (MR) angiograms and ultrasound Doppler. Optical coherence tomography (OCT) is a non-invasive high-resolution (micron level), high-speed, 3D imaging modality that has been adopted widely in biomedical and clinical applications. Phaseresolved Doppler OCT that explores the phase information of OCT signals has been shown to be capable of characterizing dynamic blood flow clinically. In this work, we explore the capability of Fourier domain Doppler OCT as an evaluation tool to detect commonly encountered post-operative complications that will cause surgical failure and to confirm positive result with surgeon's observation. Both suture and cuff based techniques were evaluated on the femoral artery and vein in the rodent model.

  11. Developments in optical system evaluation, spatial modeling, chemometrics and applications with atomic spectroscopy

    NASA Astrophysics Data System (ADS)

    Rider, Michael Eugene

    1998-11-01

    High temperature plasma emission sources have spatial characteristics. The Abel inversion calculates radial responses from lateral measurements of cylindrically symmetric emission sources. This dissertation presents three aspects of making spatial measurements: (1) Evaluation of an optical setup; (2) New numerically exact routine for improved spatial modeling; and (3) Radial and lateral measurements. Optical ray tracing software was been used for critical evaluation of the design of a unique imaging spectrometer. Position, area, and angles of view are calculated as a function of position of a translating lens and the optical properties of the quartz tube. The translating lens imaging spectrometer is compared to the more common alternative of moving the source or detector and found to perform comparatively well. A new Abel inversion technique, based on numerical improvements in a matrix-based algorithm, is described. The new approach (Mabel) combines exact computation of area terms for the Abel inversion with matrix calculation capabilities present in the MATLAB TM computational environment to generate radial profiles from lateral scans of the plasma with the best accuracy possible. Results of four 1000 ring Mabel inversions are presented. Comparisons between Mabel and two other numerical methods are made for test cases commonly cited in literature and for test cases having radial and lateral profiles with analytic solutions. The effects of noise propagation and of incomplete viewing of the plasma are also presented. Temperature is one of the most fundamental characteristic of high temperature plasmas. Lateral and radial temperatures measured from different views result in different values for a given plasma emission source. Four radial temperature profiles were used to generate radial intensities of five different wavelengths on the basis of a Boltzmann distribution of energies at each temperature. Forward Mabel transforms were performed on the radial intensities

  12. Evaluation of a Micro-Optical Coherence Tomography for the Corneal Endothelium in an Animal Model

    PubMed Central

    Ang, Marcus; Konstantopoulos, Aris; Goh, Gwendoline; Htoon, Hla M.; Seah, Xinyi; Lwin, Nyein Chan; Liu, Xinyu; Chen, Si; Liu, Linbo; Mehta, Jodhbir S.

    2016-01-01

    Recent developments in optical coherence tomography (OCT) systems for the cornea have limited resolution or acquisition speed. In this study we aim to evaluate the use of a ‘micro-OCT’ (μOCT ~1 μm axial resolution) compared to existing imaging modalities using animal models of corneal endothelial disease. We used established cryoinjury and bullous keratopathy models in Sprague Dawley rats comparing ex vivo μOCT imaging in normal and diseased eyes to (1) histology; (2) in vivo confocal microscopy (IVCM); and (3) scanning electron microscopy (SEM). Qualitative and quantitative comparisons amongst imaging modalities were performed using mean endothelial cell circularity [(4π × Area)/Perimeter2] with coefficient of variation (COV). We found that μOCT imaging was able to delineate endothelial cells (with nuclei), detect inflammatory cells, and corneal layers with histology-like resolution, comparable to existing imaging modalities. The mean endothelial cell circularity score was 0.88 ± 0.03, 0.87 ± 0.04 and 0.88 ± 0.05 (P = 0.216) for the SEM, IVCM and μOCT respectively, with SEM producing homogenous endothelial cell images (COV = 0.028) compared to the IVCM (0.051) and μOCT (0.062). In summary, our preliminary study suggests that the μOCT may be useful for achieving non-contact, histology-like images of the cornea for endothelial cell evaluation, which requires further development for in vivo imaging. PMID:27416929

  13. Performance evaluation and channel modeling of MIMO free space optical communication system

    NASA Astrophysics Data System (ADS)

    Deng, Tianping; Lu, Yimin; Lu, Gang; Peng, Kai

    2005-11-01

    Free space optical communication systems represent one of the most promising approaches for addressing the emerging broadband access market, it can provide high bandwidth with no physical contact, but are hampered by signal fading effects due to particulate scattering caused by atmospheric turbulence. In this paper, we propose a new channel model of MIMO free space optical communication system. The physics meaning of this model is very clear, and its format is very simple. Mathematic results show that MIMO is a very effective way for intensity fluctuation reduction induced by turbulence, thus reduce the bit-error-rate of the system.

  14. Modeling optical behavior of birefringent biological tissues for evaluation of quantitative polarized light microscopy

    NASA Astrophysics Data System (ADS)

    van Turnhout, Mark C.; Kranenbarg, Sander; van Leeuwen, Johan L.

    2009-09-01

    Quantitative polarized light microscopy (qPLM) is a popular tool for the investigation of birefringent architectures in biological tissues. Collagen, the most abundant protein in mammals, is such a birefringent material. Interpretation of results of qPLM in terms of collagen network architecture and anisotropy is challenging, because different collagen networks may yield equal qPLM results. We created a model and used the linear optical behavior of collagen to construct a Jones or Mueller matrix for a histological cartilage section in an optical qPLM train. Histological sections of tendon were used to validate the basic assumption of the model. Results show that information on collagen densities is needed for the interpretation of qPLM results in terms of collagen anisotropy. A parameter that is independent of the optical system and that measures collagen fiber anisotropy is introduced, and its physical interpretation is discussed. With our results, we can quantify which part of different qPLM results is due to differences in collagen densities and which part is due to changes in the collagen network. Because collagen fiber orientation and anisotropy are important for tissue function, these results can improve the biological and medical relevance of qPLM results.

  15. Evaluation of fractional photothermolysis effect in a mouse model using nonlinear optical microscopy

    NASA Astrophysics Data System (ADS)

    Guo, Han Wen; Tseng, Te-Yu; Dong, Chen-Yuan; Tsai, Tsung-Hua

    2014-07-01

    Fractional photothermolysis (FP) induces discrete columns of photothermal damage in skin dermis, thereby promoting collagen regeneration. This technique has been widely used for treating wrinkles, sun damage, and scar. In this study, we evaluate the potential of multiphoton microscopy as a noninvasive imaging modality for the monitoring of skin rejuvenation following FP treatment. The dorsal skin of a nude mouse underwent FP treatment in order to induce microthermal zones (MTZs). We evaluated the effect of FP on skin remodeling at 7 and 14 days after treatment. Corresponding histology was performed for comparison. After 14 days of FP treatment at 10 mJ, the second harmonic generation signal recovered faster than the skin treated with 30 mJ, indicating a more rapid regeneration of dermal collagen at 10 mJ. Our results indicate that nonlinear optical microscopy is effective in detecting the damaged areas of MTZ and monitoring collagen regeneration following FP treatment.

  16. Fiber optic light-scattering measurement system for evaluation of embryo viability: model experiment

    NASA Astrophysics Data System (ADS)

    Itoh, Harumi; Arai, Tsunenori; Kikuchi, Makoto

    1996-05-01

    We evaluated the particle density detectability and particle size detectivity of our fiber-optic light-scattering measurement system. In order to prevent the multiple pregnancy on current in vitro fertilization-embryo transfer, we have aimed to develop a new quantitative and non- invasive method to select a single viable human embryo. We employed the measurement of mitochondria localization in an embryo, which may have the correlation with development ability. We applied the angular distribution measurement of the light-scattering intensity from the embryo to obtain the information originated from the mitochondria. The latex spheres with a diameter of 1.0 micrometers were used to simulate the scattering intensity of the mitochondria. The measurement probes of our system consisted of two fibers for illumination and sensing. They were arranged at a right angle to a microscope optical axis to measure the angular distribution of the light-scattering intensity. We observed that the light-scattering intensity increased monotonically in the range from 106 to 1010 particles per ml. Since the mitochondria density in a human embryo corresponded to 2.5 X 107 per ml in the measurement chamber, we may measure the mitochondria density in the human embryo. The angular dependence of light-scattering intensity changed with the sphere diameters. This result showed the possibility of the selective measurement of the mitochondria density in the embryo in spite of the presence of the other cell organelle. We think that our light-scattering measurement system might be applicable to the evaluation method for the embryo viability.

  17. Computational Ion Optics Design Evaluations

    NASA Technical Reports Server (NTRS)

    Malone, Shane P.; Soulas, George C.

    2004-01-01

    Ion optics computational models are invaluable tools in the design of ion optics systems. In this study a new computational model developed by an outside vendor for use at the NASA Glenn Research Center (GRC) is presented. This computational model is a gun code that has been modified to model the plasma sheaths both upstream and downstream of the ion optics. The model handles multiple species (e.g. singly and doubly-charged ions) and includes a charge-exchange model to support erosion estimations. The model uses commercially developed solid design and meshing software to allow high flexibility in ion optics geometric configurations. The results from this computational model are applied to the NEXT project to investigate the effects of crossover impingement erosion seen during the 2000-hour wear test.

  18. Evaluation of the in vivo and ex vivo optical properties in a mouse ear model

    NASA Astrophysics Data System (ADS)

    Salomatina, E.; Yaroslavsky, A. N.

    2008-06-01

    Determination of in vivo optical properties is a challenging problem. Absorption and scattering measured ex vivo are often used for in vivo applications. To investigate the validity of this approach, we have obtained and compared the optical properties of mouse ears in vivo and ex vivo in the spectral range from 370 to 1650 nm. Integrating sphere spectrophotometry in combination with the inverse Monte Carlo technique was employed to determine absorption coefficients, μa, scattering coefficients, μs, and anisotropy factors, g. Two groups of mice were used for the study. The first group was measured in vivo and ex vivo within 5-10 min post mortem. The second group was measured in vivo and ex vivo every 24 h for up to 72 h after sacrifice. Between the measurements the tissues were kept at 4 °C wrapped in a gauze moistened with saline solution. Then the specimens were frozen at -25 °C for 40 min, thawed and measured again. The results indicate that the absorption coefficients determined in vivo and ex vivo within 5-10 min post mortem differed considerably only in the spectral range dominated by hemoglobin. These changes can be attributed to rapid deoxygenation of tissue and blood post mortem. Absorption coefficients determined ex vivo up to 72 h post mortem decreased gradually with time in the spectral regions dominated by hemoglobin and water, which can be explained by the continuing loss of blood. Absorption properties of the frozen-thawed ex vivo tissues showed increase in oxygenation, which is likely caused by the release of hemoglobin from hemolyzed erythrocytes. Scattering of the ex vivo tissues decreased gradually with time in the entire spectral range due to the continuing loss of blood and partial cell damage. Anisotropy factors did not change considerably.

  19. Evaluation of prostatic optical properties and tissue response to photodynamic therapy in a canine model

    NASA Astrophysics Data System (ADS)

    Shetty, Sugandh D.; Chen, Qun; Schultz, Daniel; Wilson, Brian C.; Patterson, Michael S.; Hetzel, Fred W.; Cerny, Joseph C.

    1994-03-01

    A new modality of interstitial therapy to treat prostate cancer using photodynamic principles has been studied in a canine model. The effect of interstitial application of monochromatic light from an argon pumped dye laser at 630 nm was studied in a canine model. No significant hyperthermia was seen during the treatment. A concentric zone around the treatment fiber was seen during the treatment. A concentric zone around the treatment fiber was seen in PDT treated dogs and the maximum size was 18 mm. The data suggests that PDT may be clinically applicable in achieving tissue necrosis using interstitial light application in a solid organ like prostate.

  20. Evaluation of flow velocities after carotid artery stenting through split spectrum Doppler optical coherence tomography and computational fluid dynamics modeling

    PubMed Central

    Vuong, Barry; Genis, Helen; Wong, Ronnie; Ramjist, Joel; Jivraj, Jamil; Farooq, Hamza; Sun, Cuiru; Yang, Victor X.D.

    2014-01-01

    Hemodynamics plays a critical role in the development of atherosclerosis, specifically in regions of curved vasculature such as bifurcations exhibiting irregular blood flow profiles. Carotid atherosclerotic disease can be intervened by stent implantation, but this may result in greater alterations to local blood flow and consequently further complications. This study demonstrates the use of a variant of Doppler optical coherence tomography (DOCT) known as split spectrum DOCT (ssDOCT) to evaluate hemodynamic patterns both before and after stent implantation in the bifurcation junction in the internal carotid artery (ICA). Computational fluid dynamics (CFD) models were constructed to simulate blood velocity profiles and compared to the findings achieved through ssDOCT images. Both methods demonstrated noticeable alterations in hemodynamic patterns following stent implantation, with features such as slow velocity regions at the neck of the bifurcation and recirculation zones at the stent struts. Strong correlation between CFD models and ssDOCT images demonstrate the potential of ssDOCT imaging in the optimization of stent implantation in the clinical setting. PMID:25574447

  1. Evaluation of flow velocities after carotid artery stenting through split spectrum Doppler optical coherence tomography and computational fluid dynamics modeling.

    PubMed

    Vuong, Barry; Genis, Helen; Wong, Ronnie; Ramjist, Joel; Jivraj, Jamil; Farooq, Hamza; Sun, Cuiru; Yang, Victor X D

    2014-12-01

    Hemodynamics plays a critical role in the development of atherosclerosis, specifically in regions of curved vasculature such as bifurcations exhibiting irregular blood flow profiles. Carotid atherosclerotic disease can be intervened by stent implantation, but this may result in greater alterations to local blood flow and consequently further complications. This study demonstrates the use of a variant of Doppler optical coherence tomography (DOCT) known as split spectrum DOCT (ssDOCT) to evaluate hemodynamic patterns both before and after stent implantation in the bifurcation junction in the internal carotid artery (ICA). Computational fluid dynamics (CFD) models were constructed to simulate blood velocity profiles and compared to the findings achieved through ssDOCT images. Both methods demonstrated noticeable alterations in hemodynamic patterns following stent implantation, with features such as slow velocity regions at the neck of the bifurcation and recirculation zones at the stent struts. Strong correlation between CFD models and ssDOCT images demonstrate the potential of ssDOCT imaging in the optimization of stent implantation in the clinical setting.

  2. Models of optical absorption in amorphous semiconductors at the absorption edge — A review and re-evaluation

    NASA Astrophysics Data System (ADS)

    Ibrahim, A.; Al-Ani, S. K. J.

    1994-08-01

    Davis-Mott and Tauc models of optical absorption at the absorption edge in the high absorption coefficient region (104cm-1) are carefully reviewed with regard to their theoretical foundations, assumptions, mathematical derivations, and results. The full implications of these models are exploited, and it is found that the Davis-Mott model for negligible matrix elements between localised states could account for the cubic power law behaviour of with photon energy of some amorphous semiconductors such as a-Si. A fractional power law to find the optical band gapE opt, of the form [αħω ∝ (ħω-E opt)r; 2≤r≤3] based on Davis-Mott model is proposed in which the indexr can be a function of disorder. The Tauc model has further been extended to the case of negligible matrix elements between localised states, in which the same square power law forα vs.ħω with the same meaning of the optical gap as in the original Tauc model has resulted. A consideration of the case of unequal matrix elements for those transitions between localised states and those between extended states is also included. The meaning ofE opt has been re-assessed and it is emphasized that it is an extrapolation of delocalised states to the zero of the density of states rather than a threshold energy for the onset of some kind of optical transitions.

  3. A study of optical modeling and evaluation of color rendering property of a dual-phosphor system (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Chang, Yu-Yu; Lin, Michael; Yang, Tsung-Hsun; Chung, Te-Yuan; Lee, Xuan-Hao; Sun, Ching-Cherng

    2016-09-01

    In this thesis, on the basis of the phosphor optical models, green and red phosphor mixture optical model has been well established. Under some specific green to red phosphor doping proportions, this model can be utilized to simulate the chromatic properties, spatial CCT distributions, and packaging efficiency. There are some benefits of applying the phosphor optical model, one is that the confusion about mixture or layer phosphor configuration can perform better could be solved. Another is that the comparison and analysis of these phosphor configurations can be made not only in experiment but also in simulation, and will be more details to be discuss in the simulation. There are several types of packaging structures in high color quality applications. Consequently, the importance of phosphor optical model cannot be overestimated. After few steps above and with the help of experimental analysis and optimized in simulation, a packaging structure with high color quality and high efficiency has been approved. Finally, this light source with high performance will be utilized in the luminaire to improve the color and energy saving properties.

  4. Aerosol Optical Depth over Europe: Evaluation of the CALIOPE air quality modelling system with direct-sun AERONET observations

    NASA Astrophysics Data System (ADS)

    Basart, Sara; Pay, María. Teresa; Pérez, Carlos; Cuevas, Emilio; Jorba, Oriol; Piot, Matthias; María Baldasano, Jose

    2010-05-01

    In the frame of the CALIOPE project (Baldasano et al., 2008), the Barcelona Supercomputing Center (BSC-CNS) currently operates a high-resolution air quality forecasting system based on daily photochemical forecasts in Europe (12km x 12km resolution) with the WRF-ARW/HERMES/CMAQ modelling system (http://www.bsc.es/caliope) and desert dust forecasts over Southern Europe with BSC-DREAM8b (Pérez et al., 2006; http://www.bsc.es/projects/earthscience/DREAM). High resolution simulations and forecasts are possible through their implementation on MareNostrum supercomputer at BSC-CNS. As shown in previous air quality studies (e.g. Rodríguez et al., 2001; Jiménez-Guerrero et al., 2008), the contribution of desert dust on particulate matter levels in Southern Europe is remarkable due to its proximity to African desert dust sources. When considering only anthropogenic emissions (Baldasano et al., 2008) and the current knowledge about aerosol physics and chemistry, chemistry-transport model simulations underestimate the PM10 concentrations by 30-50%. As a first approach, the natural dust contribution from BSC-DREAM8b is on-line added to the anthropogenic aerosol output of CMAQ. The aim of the present work is the quantitative evaluation of the WRF-ARW/HERMES/ CMAQ/BSC-DREAM8b forecast system to simulate the Aerosol Optical Depth (AOD) over Europe. The performance of the modelled AOD has been quantitatively evaluated with discrete and categorical (skill scores) statistics by a comparison to direct-sun AERONET observations for 2004. The contribution of different types of aerosols will be analyzed by means of the O'Neill fine mode AOD products (O'Neill et al., 2001). A previous aerosol characterization of AERONET data was performed (Basart et al., 2009) in order to discriminate the different aerosol source contributions within the study region. The results indicate a remarkable improvement in the discrete and skill-scores evaluation (accuracy, critical success index and

  5. Evaluation of optical remote sensing parameters to improve modeling of gross primary productivity in a heterogeneous agricultural area

    NASA Astrophysics Data System (ADS)

    Schickling, A.; Damm, A.; Schween, J.; Rascher, U.; Crewell, S.; Wahner, A.

    2011-12-01

    Terrestrial photosynthesis greatly determines plant mediated exchange processes in the vegetation atmosphere system and substantially influences patterns in atmospheric carbon dioxide (CO2) concentrations and water vapor. Therefore, an accurate quantification of photosynthetic CO2 uptake, commonly referred to as gross primary productivity (GPP), is a key parameter to distinguish those atmospheric patterns on various spatio-temporal scales. Remote sensing (RS) offers the unique possibility to determine GPP at different spatial scales ranging from the local to the global scale. Attempts to estimate GPP from RS data focus on the light use efficiency (LUE) concept of Monteith which relates GPP to the absorbed photosynthetically active radiation and the efficiency of plant canopies to utilize the absorbed radiation for photosynthesis. To reliably predict GPP on different spatio-temporal scales LUE has to be linked to optical RS parameters which detect changes in photosynthetic efficiency due to environmental conditions. In this study we evaluated two optical RS parameters, namely the sun-induced fluorescence (Fs) and the photochemical reflectance index (PRI), for their potential to serve as a proxy for LUE. The parameters were derived from two ASD FieldSpec spectrometers which were operated in parallel. During several days one instrument was installed on the ground above the vegetation canopy of either a winter wheat or a sugar beet field. The second instrument was operated from a small research aircraft continuously crossing the observation sites at low altitude (< 300 m). GPP was calculated on a diurnal basis including optical parameters in Monteith's LUE concept. The calculated GPP was compared to simultaneously acquired GPP data from eddy covariance measurements. The diurnal behavior of calculated and measured GPP corresponded well indicating that optical RS parameters are able to track the diurnal response of physiological regulation of photosynthesis to changing

  6. Extended optical model for fission

    SciTech Connect

    Sin, M.; Capote, R.; Herman, M. W.; Trkov, A.

    2016-03-07

    A comprehensive formalism to calculate fission cross sections based on the extension of the optical model for fission is presented. It can be used for description of nuclear reactions on actinides featuring multi-humped fission barriers with partial absorption in the wells and direct transmission through discrete and continuum fission channels. The formalism describes the gross fluctuations observed in the fission probability due to vibrational resonances, and can be easily implemented in existing statistical reaction model codes. The extended optical model for fission is applied for neutron induced fission cross-section calculations on 234,235,238U and 239Pu targets. A triple-humped fission barrier is used for 234,235U(n,f), while a double-humped fission barrier is used for 238U(n,f) and 239Pu(n,f) reactions as predicted by theoretical barrier calculations. The impact of partial damping of class-II/III states, and of direct transmission through discrete and continuum fission channels, is shown to be critical for a proper description of the measured fission cross sections for 234,235,238U(n,f) reactions. The 239Pu(n,f) reaction can be calculated in the complete damping approximation. Calculated cross sections for 235,238U(n,f) and 239Pu(n,f) reactions agree within 3% with the corresponding cross sections derived within the Neutron Standards least-squares fit of available experimental data. Lastly, the extended optical model for fission can be used for both theoretical fission studies and nuclear data evaluation.

  7. Extended optical model for fission

    DOE PAGES

    Sin, M.; Capote, R.; Herman, M. W.; ...

    2016-03-07

    A comprehensive formalism to calculate fission cross sections based on the extension of the optical model for fission is presented. It can be used for description of nuclear reactions on actinides featuring multi-humped fission barriers with partial absorption in the wells and direct transmission through discrete and continuum fission channels. The formalism describes the gross fluctuations observed in the fission probability due to vibrational resonances, and can be easily implemented in existing statistical reaction model codes. The extended optical model for fission is applied for neutron induced fission cross-section calculations on 234,235,238U and 239Pu targets. A triple-humped fission barrier ismore » used for 234,235U(n,f), while a double-humped fission barrier is used for 238U(n,f) and 239Pu(n,f) reactions as predicted by theoretical barrier calculations. The impact of partial damping of class-II/III states, and of direct transmission through discrete and continuum fission channels, is shown to be critical for a proper description of the measured fission cross sections for 234,235,238U(n,f) reactions. The 239Pu(n,f) reaction can be calculated in the complete damping approximation. Calculated cross sections for 235,238U(n,f) and 239Pu(n,f) reactions agree within 3% with the corresponding cross sections derived within the Neutron Standards least-squares fit of available experimental data. Lastly, the extended optical model for fission can be used for both theoretical fission studies and nuclear data evaluation.« less

  8. Extended optical model for fission

    NASA Astrophysics Data System (ADS)

    Sin, M.; Capote, R.; Herman, M. W.; Trkov, A.

    2016-03-01

    A comprehensive formalism to calculate fission cross sections based on the extension of the optical model for fission is presented. It can be used for description of nuclear reactions on actinides featuring multi-humped fission barriers with partial absorption in the wells and direct transmission through discrete and continuum fission channels. The formalism describes the gross fluctuations observed in the fission probability due to vibrational resonances, and can be easily implemented in existing statistical reaction model codes. The extended optical model for fission is applied for neutron induced fission cross-section calculations on 234,235,238U and 239Pu targets. A triple-humped fission barrier is used for U,235234(n ,f ) , while a double-humped fission barrier is used for 238U(n ,f ) and 239Pu(n ,f ) reactions as predicted by theoretical barrier calculations. The impact of partial damping of class-II/III states, and of direct transmission through discrete and continuum fission channels, is shown to be critical for a proper description of the measured fission cross sections for 234,235,238U(n ,f ) reactions. The 239Pu(n ,f ) reaction can be calculated in the complete damping approximation. Calculated cross sections for U,238235(n ,f ) and 239Pu(n ,f ) reactions agree within 3% with the corresponding cross sections derived within the Neutron Standards least-squares fit of available experimental data. The extended optical model for fission can be used for both theoretical fission studies and nuclear data evaluation.

  9. Electro-optics laboratory evaluation: Deutsch optical waveguide connectors

    NASA Technical Reports Server (NTRS)

    1980-01-01

    A description of a test program evaluating the performance of an optical waveguide connector system is presented. Both quality and effectiveness of connections made in an optical fiber, performance of the equipment used and applicability of equipment and components to field conditions are reviewed.

  10. Optical parametric evaluation model for a broadband high resolution spectrograph at E-ELT (E-ELT HIRES)

    NASA Astrophysics Data System (ADS)

    Genoni, M.; Riva, M.; Pariani, G.; Aliverti, M.; Moschetti, M.

    2016-08-01

    We present the details of a paraxial parametric model of a high resolution spectrograph which can be used as a tool, characterized by good approximation and reliability, at a system engineering level. This model can be exploited to perform a preliminary evaluation of the different parameters as long as different possible architectures of high resolution spectrograph like the one under design for the E-ELT (for the moment called E-ELT HIRES in order to avoid wrong association with the HIRES spectrograph at Keck telescope). The detailed equations flow concerning the first order effects of all the spectrograph components is described; in addition a comparison with the data of a complete physical ESPRESSO spectrograph model is presented as a model proof.

  11. Honeywell FLASH fiber optic motherboard evaluations

    NASA Astrophysics Data System (ADS)

    Stange, Kent

    1996-10-01

    The use of fiber optic data transmission media can make significant contributions in achieving increasing performance and reduced life cycle cost requirements placed on commercial and military transport aircraft. For complete end-to-end fiber optic transmission, photonics technologies and techniques need to be understood and applied internally to the aircraft line replaceable units as well as externally on the interconnecting aircraft cable plant. During a portion of the Honeywell contribution to Task 2A on the Fly- by-Light Advanced System Hardware program, evaluations were done on a fiber optic transmission media implementation internal to a Primary Flight Control Computer (PFCC). The PFCC internal fiber optic transmission media implementation included a fiber optic backplane, an optical card-edge connector, and an optical source/detector coupler/installation. The performance of these optical media components were evaluated over typical aircraft environmental stresses of temperature, vibration, and humidity. These optical media components represent key technologies to the computer end-to-end fiber optic transmission capability on commercial and military transport aircraft. The evaluations and technical readiness assessments of these technologies will enable better perspectives on productization of fly-by-light systems requiring their utilizations.

  12. Evaluation of SUNY satellite-to-irradiance model performance using ECMWF GEMS daily aerosol optical depth reanalysis data

    NASA Astrophysics Data System (ADS)

    Itterly, Kyle F.

    The current version of the State University of New York (SUNY) radiative transfer model (RTM) uses climatological monthly averages derived from a National Renewable Energy Labs (NREL) gridded dataset to parameterize aerosol optical depth (AOD), water vapor and ozone. This is mostly due to the limited availability of high spatially and temporally resolved observations. Several global chemical transport models are analyzed and compared in depth to determine which daily AOD dataset should be implemented into the SUNY Model. After thorough comparison, the chemical transport model chosen was the Global and regional Earth-system Monitoring using satellite and in-situ data (GEMS) model developed by the European Center for Medium Range Weather Forecasts (ECMWF). Using daily AOD values instead of monthly climatological values, the SUNY Model better captures events of extreme aerosol loadings, which greatly improves the accuracy in calculations of direct normal irradiance (DNI) and to a lesser extent, global horizontal irradiance (GHI). In clear-sky conditions with the sun directly overhead, a change in AOD from 0.1 to 0.5 is found to cause a 55% (20%) decrease in DNI (GHI) for Desert Rock, Nevada in January. A calibration scheme is applied to the daily GEMS AOD reanalysis data. For each site, the monthly means of the GEMS daily AOD are corrected by a factor to match the currently used monthly climatological AOD in order to avoid large errors caused by changing the magnitude of the monthly average AOD. The performance of the SUNY model improved significantly for many of the stations analyzed in this work after applying the daily-calibrated GEMS AOD. The Root Mean Squared Error (RMSE) was the most notable statistical improvement, which measures the model’s precision compared to the observed measurements from a ground station, and many other statistical improvements are also evident. All 7 SURFRAD locations showed improvements in DNI RMSE after using the calibrated GEMS

  13. Optical Detection System Model.

    DTIC Science & Technology

    1982-04-01

    cases the wavelength 7 II TABLE 2 SAMPLE CONTENTS OF OPTICAL MATERIAL FILE ODSOPT.INP SRF2 3.000 0.120 13.000 9.000 0.120 0.100 0.130 0.600 0.200 0.850...N THESE ARE THE AVAILABLE FILTER TYPES: CORNING VYCOR SILICA MGF2 SRF2 VYC7905 INFRASIL SAPPHIRE MGO 1102 CDISE CBS CDTE SE ZNSE CAF2 DIAMOND

  14. Optical Path Difference Evaluation of Laser-Soldered Optical Components

    NASA Astrophysics Data System (ADS)

    Burkhardt, T.; Hornaff, M.; Burkhardt, D.; Beckert, E.

    2015-12-01

    We present Solderjet Bumping, a laser-based soldering process, as an all inorganic joining technique for optical materials and mechanical support structures. The adhesive-free bonding process enables the low-stress assembly of fragile and sensitive components for advanced optical systems. Our process addresses high demanding applications, e.g. under high energetic radiation (short wavelengths of 280 nm and below and/or high intensities), for vacuum operation, and for harsh environmental conditions. Laser-based soldering allows the low stress assembly of aligned sub-cells as key components for high quality optical systems. The evaluation of the optical path difference in fused silica and the radiation resistant LAK9G15 glass components after soldering and environmental testing shows the potential of the technique.

  15. Evaluation of Hologram Optical Elements

    DTIC Science & Technology

    1975-06-01

    SUMMARY This report is the third in a series th?c cover the investigation of the properties and applications of holo- graphic optics. This type of...Design gy 6.2. Fabrication 97 7. Single Hologram Element Properties 101 7.1. Selection of Study Parameters 101 7.2. Case 1: Q...the Important Cases to be Analyzed in the Single Hologram Element Properties Study. . .106 14 mammiammtii . •MMaWaaaiuuia ttttmrngUdttt^Mi

  16. An evaluation of uncertainty in the aerosol optical properties as represented by satellites and an ensemble of chemistry-climate coupled models over Europe

    NASA Astrophysics Data System (ADS)

    Palacios-Peña, Laura; Baró, Rocío; Jiménez-Guerrero, Pedro

    2016-04-01

    The changes in Earth's climate are produced by forcing agents such as greenhouse gases, clouds and atmospheric aerosols. The latter modify the Earth's radiative budget due to their optical, microphysical and chemical properties, and are considered to be the most uncertain forcing agent. There are two main approaches to the study of aerosols: (1) ground-based and remote sensing observations and (2) atmospheric modelling. With the aim of characterizing the uncertainties associated with these approaches, and estimating the radiative forcing caused by aerosols, the main objective of this work is to assess the representation of aerosol optical properties by different remote sensing sensors and online-coupled chemistry-climate models and to determine whether the inclusion of aerosol radiative feedbacks in this type of models improves the modelling outputs over Europe. Two case studies have been selected under the framework of the EuMetChem COST Action ES1004, when important aerosol episodes during 2010 over Europe took place: a Russian wildfires episode and a Saharan desert dust outbreak covering most of Europe. Model data comes from an ensemble of regional air quality-climate simulations performed by the working group 2 of EuMetChem, that investigates the importance of different processes and feedbacks in on-line coupled chemistry-climate models. These simulations are run for three different configurations for each model, differing in the inclusion (or not) of aerosol-radiation and aerosol-cloud interactions. The remote sensing data comes from three different sensors, MODIS (Moderate Resolution Imaging Spectroradiometer), OMI (Ozone Monitoring Instrument) and SeaWIFS (Sea-viewing Wide Field-of-view Sensor). The evaluation has been performed by using classical statistical metrics, comparing modelled and remotely sensed data versus a ground-based instrument network (AERONET). The evaluated variables are aerosol optical depth (AOD) and the Angström exponent (AE) at

  17. Optical-Microphysical Cirrus Model

    NASA Technical Reports Server (NTRS)

    Reichardt, J.; Reichardt, S.; Lin, R.-F.; Hess, M.; McGee, T. J.; Starr, D. O.

    2008-01-01

    A model is presented that permits the simulation of the optical properties of cirrus clouds as measured with depolarization Raman lidars. It comprises a one-dimensional cirrus model with explicit microphysics and an optical module that transforms the microphysical model output to cloud and particle optical properties. The optical model takes into account scattering by randomly oriented or horizontally aligned planar and columnar monocrystals and polycrystals. Key cloud properties such as the fraction of plate-like particles and the number of basic crystals per polycrystal are parameterized in terms of the ambient temperature, the nucleation temperature, or the mass of the particles. The optical-microphysical model is used to simulate the lidar measurement of a synoptically forced cirrostratus in a first case study. It turns out that a cirrus cloud consisting of only monocrystals in random orientation is too simple a model scenario to explain the observations. However, good agreement between simulation and observation is reached when the formation of polycrystals or the horizontal alignment of monocrystals is permitted. Moreover, the model results show that plate fraction and morphological complexity are best parameterized in terms of particle mass, or ambient temperature which indicates that the ambient conditions affect cirrus optical properties more than those during particle formation. Furthermore, the modeled profiles of particle shape and size are in excellent agreement with in situ and laboratory studies, i.e., (partly oriented) polycrystalline particles with mainly planar basic crystals in the cloud bottom layer, and monocrystals above, with the fraction of columns increasing and the shape and size of the particles changing from large thin plates and long columns to small, more isometric crystals from cloud center to top. The findings of this case study corroborate the microphysical interpretation of cirrus measurements with lidar as suggested previously.

  18. Acoustic Models of Optical Mirrors

    ERIC Educational Resources Information Center

    Mayer, V. V.; Varaksina, E. I.

    2014-01-01

    Students form a more exact idea of the action of optical mirrors if they can observe the wave field being formed during reflection. For this purpose it is possible to organize model experiments with flexural waves propagating in thin elastic plates. The direct and round edges of the plates are used as models of plane, convex and concave mirrors.…

  19. Modeling an optical micromachine probe

    SciTech Connect

    Mittas, A.; Dickey, F.M.; Holswade, S.C.

    1997-08-01

    Silicon micromachines are fabricated using Surface Micro-Machining (SMM) techniques. Silicon micromachines include engines that consist of orthogonally oriented linear comb drive actuators mechanically connected to a rotating gear. These gears are as small a 50-{micro}m in diameter and can be driven at rotation rates exceeding 300,000-rpm. Measuring and analyzing microengine performance is basic to micromachine development and system applications. Optical techniques offer the potential for measuring long term statistical performance data and transient responses needed to optimize designs and manufacturing techniques. The authors describe the modeling of an optical probe developed at Sandia National Laboratories. Experimental data will be compared with output from the model.

  20. Improved AWG Fourier optics model.

    PubMed

    Molina-Fernández, I; Wangüemert-Pérez, J

    2004-10-04

    In this paper we present an improved Fourier Optics model to calculate the transmission characteristics between any arbitrary pair of input/output ports (IOPs) of an Arrayed Waveguide Grating (AWG). In this model the input and output sections of the AWG are modeled using the same approximations, thus removing some reciprocity-related inconsistencies present in previously existing models. The expressions which summarize the model are compact and easily interpretable. Simple quasi-analytical expressions are also derived under the Gaussian approximation of the mode field profiles.

  1. Coupled modeling of a directly heated tubular solar receiver for supercritical carbon dioxide Brayton cycle: Optical and thermal-fluid evaluation

    SciTech Connect

    Ortega, Jesus; Khivsara, Sagar; Christian, Joshua; Ho, Clifford; Yellowhair, Julius; Dutta, Pradip

    2016-05-30

    In single phase performance and appealing thermo-physical properties supercritical carbon dioxide (s-CO2) make a good heat transfer fluid candidate for concentrating solar power (CSP) technologies. The development of a solar receiver capable of delivering s-CO2 at outlet temperatures ~973 K is required in order to merge CSP and s-CO2 Brayton cycle technologies. A coupled optical and thermal-fluid modeling effort for a tubular receiver is undertaken to evaluate the direct tubular s-CO2 receiver’s thermal performance when exposed to a concentrated solar power input of ~0.3–0.5 MW. Ray tracing, using SolTrace, is performed to determine the heat flux profiles on the receiver and computational fluid dynamics (CFD) determines the thermal performance of the receiver under the specified heating conditions. Moreover, an in-house MATLAB code is developed to couple SolTrace and ANSYS Fluent. CFD modeling is performed using ANSYS Fluent to predict the thermal performance of the receiver by evaluating radiation and convection heat loss mechanisms. Understanding the effects of variation in heliostat aiming strategy and flow configurations on the thermal performance of the receiver was achieved through parametric analyses. Finally, a receiver thermal efficiency ~85% was predicted and the surface temperatures were observed to be within the allowable limit for the materials under consideration.

  2. Coupled modeling of a directly heated tubular solar receiver for supercritical carbon dioxide Brayton cycle: Optical and thermal-fluid evaluation

    DOE PAGES

    Ortega, Jesus; Khivsara, Sagar; Christian, Joshua; ...

    2016-05-30

    In single phase performance and appealing thermo-physical properties supercritical carbon dioxide (s-CO2) make a good heat transfer fluid candidate for concentrating solar power (CSP) technologies. The development of a solar receiver capable of delivering s-CO2 at outlet temperatures ~973 K is required in order to merge CSP and s-CO2 Brayton cycle technologies. A coupled optical and thermal-fluid modeling effort for a tubular receiver is undertaken to evaluate the direct tubular s-CO2 receiver’s thermal performance when exposed to a concentrated solar power input of ~0.3–0.5 MW. Ray tracing, using SolTrace, is performed to determine the heat flux profiles on the receivermore » and computational fluid dynamics (CFD) determines the thermal performance of the receiver under the specified heating conditions. Moreover, an in-house MATLAB code is developed to couple SolTrace and ANSYS Fluent. CFD modeling is performed using ANSYS Fluent to predict the thermal performance of the receiver by evaluating radiation and convection heat loss mechanisms. Understanding the effects of variation in heliostat aiming strategy and flow configurations on the thermal performance of the receiver was achieved through parametric analyses. Finally, a receiver thermal efficiency ~85% was predicted and the surface temperatures were observed to be within the allowable limit for the materials under consideration.« less

  3. Laser beam modeling in optical storage systems

    NASA Technical Reports Server (NTRS)

    Treptau, J. P.; Milster, T. D.; Flagello, D. G.

    1991-01-01

    A computer model has been developed that simulates light propagating through an optical data storage system. A model of a laser beam that originates at a laser diode, propagates through an optical system, interacts with a optical disk, reflects back from the optical disk into the system, and propagates to data and servo detectors is discussed.

  4. Adaptive optical antennas: design and evaluation

    NASA Astrophysics Data System (ADS)

    Weyrauch, Thomas; Vorontsov, Mikhail A.; Carhart, Gary W.; Simonova, Galina V.; Beresnev, Leonid A.; Polnau, Ernst E.

    2007-09-01

    We present the design and evaluation of compact adaptive optical antennas with apertures diameters of 16 mm and 100 mm for 5Gbit/s-class free-space optical communication systems. The antennas provide a bi-directional optically transparent link between fiber-optical wavelength-division multiplex systems and allow for mitigation of atmospheric-turbulence induced wavefront phase distortions with adaptive optics components. Beam steering is implemented in the antennas either with mirrors on novel tip/tilt platforms or a fiber-tip positioning system, both enabling operation bandwidths of more than 1 kHz. Bimorph piezoelectric actuated deformable mirrors are used for low-order phase-distortion compensation. An imaging system is integrated in the antennas for coarse pointing and tracking. Beam steering and wavefront control is based on blind maximization of the received signal level using a stochastic parallel gradient descent algorithm. The adaptive optics control architecture allowed the use of feedback signals provided locally within each transceiver system and remotely by the opposite transceiver system via an RF link. First atmospheric compensation results from communication experiments over a 250 m near-ground propagation path are presented.

  5. Evaluation of the usefulness of three-dimensional optical coherence tomography in a guinea pig model of endolymphatic hydrops induced by surgical obliteration of the endolymphatic duct

    NASA Astrophysics Data System (ADS)

    Cho, Nam Hyun; Lee, Jang Woo; Cho, Jin-ho; Kim, Jeehyun; Jang, Jeong Hun; Jung, Woonggyu

    2015-03-01

    Optical coherence tomography (OCT) has advanced significantly over the past two decades and is currently used extensively to monitor the internal structures of organs, particularly in ophthalmology and dermatology. We used ethylenediamine tetra-acetic acid (EDTA) to decalcify the bony walls of the cochlea and investigated the inner structures by deep penetration of light into the cochlear tissue using OCT on a guinea pig model of endolymphatic hydrops (EH), induced by surgical obliteration of the endolymphatic duct. The structural and functional changes associated with EH were identified using OCT and auditory brainstem response tests, respectively. We also evaluated structural alterations in the cochlea using three-dimensional reconstruction of the OCT images, which clearly showed physical changes in the cochlear structures. Furthermore, we found significant anatomical variations in the EH model and conducted graphical analysis by strial atrophy for comparison. The physical changes included damage to and flattening of the organ of Corti-evidence of Reissner's membrane distention-and thinning of the lateral wall. These results indicate that observation of EDTA-decalcified cochlea using OCT is significant in examination of gradual changes in the cochlear structures that are otherwise not depicted by hematoxylin and eosin staining.

  6. Mathmatical modeling for diffractive optics

    NASA Technical Reports Server (NTRS)

    Dobson, David; Cox, J. Allen

    1993-01-01

    We consider a 'diffractive optic' to be a biperiodic surface separating two half-spaces, each having constant constitutive parameters; within a unit cell of the periodic surface and across the transition zone between the two half-spaces, the constitutive parameters can be a continuous, complex-valued function. Mathematical models for diffractive optics have been developed, and implemented as numerical codes, both for the 'direct' problem and for the 'inverse' problem. In problems of the 'direct' class, the diffractive optic is specified, and the full set of Maxwell's equations is cast in a variational form and solved numerically by a finite element approach. This approach is well-posed in the sense that existence and uniqueness of the solution can be proved and specific convergence conditions can be derived. An example of a metallic grating at a Wood anomaly is presented as a case where other approaches are known to have convergence problems. In problems of the 'inverse' class, some information about the diffracted field (e.g., the far-field intensity) is given, and the problem is to find the periodic structure in some optimal sense. Two approaches are described: phase reconstruction in the far-field approximation; and relaxed optimal design based on the Helmholtz equation. Practical examples are discussed for each approach to the inverse problem, including array generators in the far-field case and antireflective structures for the relaxed optimal design.

  7. Optical and control modeling for adaptive beam-combining experiments

    SciTech Connect

    Gruetzner, J.K.; Tucker, S.D.; Neal, D.R.; Bentley, A.E.; Simmons-Potter, K.

    1995-08-01

    The development of modeling algorithms for adaptive optics systems is important for evaluating both performance and design parameters prior to system construction. Two of the most critical subsystems to be modeled are the binary optic design and the adaptive control system. Since these two are intimately related, it is beneficial to model them simultaneously. Optic modeling techniques have some significant limitations. Diffraction effects directly limit the utility of geometrical ray-tracing models, and transform techniques such as the fast fourier transform can be both cumbersome and memory intensive. The authors have developed a hybrid system incorporating elements of both ray-tracing and fourier transform techniques. In this paper they present an analytical model of wavefront propagation through a binary optic lens system developed and implemented at Sandia. This model is unique in that it solves the transfer function for each portion of a diffractive optic analytically. The overall performance is obtained by a linear superposition of each result. The model has been successfully used in the design of a wide range of binary optics, including an adaptive optic for a beam combining system consisting of an array of rectangular mirrors, each controllable in tip/tilt and piston. Wavefront sensing and the control models for a beam combining system have been integrated and used to predict overall systems performance. Applicability of the model for design purposes is demonstrated with several lens designs through a comparison of model predictions with actual adaptive optics results.

  8. Evaluation of ITER MSE Viewing Optics

    SciTech Connect

    Allen, S; Lerner, S; Morris, K; Jayakumar, J; Holcomb, C; Makowski, M; Latkowski, J; Chipman, R

    2007-03-26

    image that then was relayed out of the port plug with more ideal (dielectric) mirrors. Engineering models of the optics, port plug, and neutral beam geometry were also created, using the CATIA ITER models. Two video conference calls with the USIPO provided valuable design guidelines, such as the minimum distance of the first optic from the plasma. A second focus of the project was the calibration of the system. Several different techniques are proposed, both before and during plasma operation. Fixed and rotatable polarizers would be used to characterize the system in the no-plasma case. Obtaining the full modulation spectrum from the polarization analyzer allows measurement of polarization effects and also MHD plasma phenomena. Light from neutral beam interaction with deuterium gas (no plasma) has been found useful to determine the wavelength of each spatial channel. The status of the optical design for the edge (upper) and core (lower) systems is included in the following figure. Several issues should be addressed by a follow-on study, including whether the optical labyrinth has sufficient neutron shielding and a detailed polarization characterization of actual mirrors.

  9. The EMEFS model evaluation

    SciTech Connect

    Barchet, W.R. ); Dennis, R.L. ); Seilkop, S.K. ); Banic, C.M.; Davies, D.; Hoff, R.M.; Macdonald, A.M.; Mickle, R.E.; Padro, J.; Puckett, K. ); Byun, D.; McHenry, J.N.

    1991-12-01

    The binational Eulerian Model Evaluation Field Study (EMEFS) consisted of several coordinated data gathering and model evaluation activities. In the EMEFS, data were collected by five air and precipitation monitoring networks between June 1988 and June 1990. Model evaluation is continuing. This interim report summarizes the progress made in the evaluation of the Regional Acid Deposition Model (RADM) and the Acid Deposition and Oxidant Model (ADOM) through the December 1990 completion of a State of Science and Technology report on model evaluation for the National Acid Precipitation Assessment Program (NAPAP). Because various assessment applications of RADM had to be evaluated for NAPAP, the report emphasizes the RADM component of the evaluation. A protocol for the evaluation was developed by the model evaluation team and defined the observed and predicted values to be used and the methods by which the observed and predicted values were to be compared. Scatter plots and time series of predicted and observed values were used to present the comparisons graphically. Difference statistics and correlations were used to quantify model performance. 64 refs., 34 figs., 6 tabs.

  10. Evaluating bio-optical models to determine chlorophyll a from hyper spectral data in the turbid coastal waters of South Carolina

    NASA Astrophysics Data System (ADS)

    Hames, J. B.; Ali, K.

    2013-12-01

    Millions of people visit the beaches of South Carolina every year and the increasing utilization of the coastal waters is leading to the deterioration of water quality and the marine ecosystem. Ecological stress on these environments is reflected by the increase in the frequency and severity of Harmful Algal Blooms (HABs). This was evident during recent summer seasons particularly in the shallow nearshore waters of Long Bay, South Carolina, an open coast embayment on the South Atlantic Bight. These aspects threaten human and marine life. The early detection of HABs in the coastal waters requires more efficient and accurate monitoring tools. Remote sensing provides synoptic view of the entire Long Bay waters at high temporal coverage and allows resource managers to effectively map and monitor algal bloom development, near real time. Various remote sensing (RS) algorithms have been developed but were mostly calibrated to low resolution global data and or other specific sites. In the summer of 2013, a suite of measurements and water samples were collected from 15 locations along the nearshore waters of Long Bay using the Grice Laboratory R/V. In this study, we evaluate the efficiency of 10 bio-optical blue-green and NIR-red based RS models applied to GER 1500 hyper spectral reflectance data to predict chlorophyll a, a proxy for phytoplankton density, in the Long Bay waters of SC. Efficiency of the algorithms performance in the study site were tested through a least squares regression and residual analysis. Results show that among the selected suite of algorithms the blue green models by Darecki and Stramski (2004) produced R2 of 0.68 with RMSE=0.39μg/l, Oc4v4 model by O'Reilly et al. (2000) gave R2 of 0.62 with RMSE=0.73ug/l, and the Oc2v4 also by O'Reilly et al (2000) gave R2 of 0.69 with RMSE=0.65. Among the NIR-red models, Moses et al (2009) two-band algorithm produced R2 of 0.75 and RMSE=1.79, and the three-band version generated R2 of 0.81 and RMSE=2.25ug

  11. Guidelines for Model Evaluation.

    DTIC Science & Technology

    1979-01-01

    by a decisionmaker. The full-scale evaluation of a complex model can be an expensive, time- consuming effort requiring diverse talents and skills...relative to PIES, were documented in a report to the Congress. 2/ An important side- effect of that document was that a foundation was laid for model...while for model evaluation there are no generally accepted standards or methods. Hence, GAO perceives the need to expand upon the lessons learned in

  12. A computer program to evaluate optical systems

    NASA Technical Reports Server (NTRS)

    Innes, D.

    1972-01-01

    A computer program is used to evaluate a 25.4 cm X-ray telescope at a field angle of 20 minutes of arc by geometrical analysis. The object is regarded as a point source of electromagnetic radiation, and the optical surfaces are treated as boundary conditions in the solution of the electromagnetic wave propagation equation. The electric field distribution is then determined in the region of the image and the intensity distribution inferred. A comparison of wave analysis results and photographs taken through the telescope shows excellent agreement.

  13. Modeling the Laser Interferometer Space Antenna Optics

    NASA Technical Reports Server (NTRS)

    Waluschka, Eugene; Pedersen, Trace R.; McNamara, Paul

    2005-01-01

    Creating an optical model of the Laser Interferometer Space antenna which can be used to predict optical sensitivities and set tolerances sufficiently well such that picometer level displacements can be reliably seen poses certain challenges. In part, because the distances between key optical elements, the proof masses, are constantly changing, at speeds of meters/second, the separation between them is about 5 million kilometers and a contributing factor to optical jitter is the self-gravity of the spacecraft. A discussion of the current state and future approach(s) to the creation of such an optical model will be presented.

  14. Climate models and model evaluation

    SciTech Connect

    Gates, W.L.

    1994-12-31

    This brief overview addresses aspects of the nature, uses, evaluation and limitations of climate models. A comprehensive global modeling capability has been achieved only for the physical climate system, which is characterized by processes that serve to transport and exchange momentum, heat and moisture within and between the atmosphere, ocean and land surface. The fundamental aim of climate modeling, and the justification for the use of climate models, is the need to achieve a quantitative understanding of the operation of the climate system and to exploit any potential predictability that may exist.

  15. Optical models of the human eye.

    PubMed

    Atchison, David A; Thibos, Larry N

    2016-03-01

    Optical models of the human eye have been used in visual science for purposes such as providing a framework for explaining optical phenomena in vision, for predicting how refraction and aberrations are affected by change in ocular biometry and as computational tools for exploring the limitations imposed on vision by the optical system of the eye. We address the issue of what is understood by optical model eyes, discussing the 'encyclopaedia' and 'toy train' approaches to modelling. An extensive list of purposes of models is provided. We discuss many of the theoretical types of optical models (also schematic eyes) of varying anatomical accuracy, including single, three and four refracting surface variants. We cover the models with lens structure in the form of nested shells and gradient index. Many optical eye models give accurate predictions only for small angles and small fields of view. If aberrations and image quality are important to consider, such 'paraxial' model eyes must be replaced by 'finite model' eyes incorporating features such as aspheric surfaces, tilts and decentrations, wavelength-dependent media and curved retinas. Many optical model eyes are population averages and must become adaptable to account for age, gender, ethnicity, refractive error and accommodation. They can also be customised for the individual when extensive ocular biometry and optical performance data are available. We consider which optical model should be used for a particular purpose, adhering to the principle that the best model is the simplest fit for the task. We provide a glimpse into the future of optical models of the human eye. This review is interwoven with historical developments, highlighting the important people who have contributed so richly to our understanding of visual optics.

  16. Optical models of the molecular atmosphere

    NASA Technical Reports Server (NTRS)

    Zuev, V. E.; Makushkin, Y. S.; Mitsel, A. A.; Ponomarev, Y. N.; Rudenko, V. P.; Firsov, K. M.

    1986-01-01

    The use of optical and laser methods for performing atmospheric investigations has stimulated the development of the optical models of the atmosphere. The principles of constructing the optical models of molecular atmosphere for radiation with different spectral composition (wideband, narrowband, and monochromatic) are considered in the case of linear and nonlinear absorptions. The example of the development of a system which provides for the modeling of the processes of optical-wave energy transfer in the atmosphere is presented. Its physical foundations, structure, programming software, and functioning were considered.

  17. Evaluations of fiber optic sensors for interior applications

    SciTech Connect

    Sandoval, M.W.; Malone, T.P.

    1996-02-01

    This report addresses the testing and evaluation of commercial fiber optic intrusion detection systems in interior applications. The applications include laying optical fiber cable above suspended ceilings to detect removal of ceiling tiles, embedding optical fibers inside a tamper or item monitoring blanket that could be placed over an asset, and installing optical fibers on a door to detect movement or penetration. Detection capability of the fiber optic sensors as well as nuisance and false alarm information were focused on during the evaluation. Fiber optic sensor processing, system components, and system setup are described.

  18. Integrated modeling of advanced optical systems

    NASA Technical Reports Server (NTRS)

    Briggs, Hugh C.; Needels, Laura; Levine, B. Martin

    1993-01-01

    This poster session paper describes an integrated modeling and analysis capability being developed at JPL under funding provided by the JPL Director's Discretionary Fund and the JPL Control/Structure Interaction Program (CSI). The posters briefly summarize the program capabilities and illustrate them with an example problem. The computer programs developed under this effort will provide an unprecedented capability for integrated modeling and design of high performance optical spacecraft. The engineering disciplines supported include structural dynamics, controls, optics and thermodynamics. Such tools are needed in order to evaluate the end-to-end system performance of spacecraft such as OSI, POINTS, and SMMM. This paper illustrates the proof-of-concept tools that have been developed to establish the technology requirements and demonstrate the new features of integrated modeling and design. The current program also includes implementation of a prototype tool based upon the CAESY environment being developed under the NASA Guidance and Control Research and Technology Computational Controls Program. This prototype will be available late in FY-92. The development plan proposes a major software production effort to fabricate, deliver, support and maintain a national-class tool from FY-93 through FY-95.

  19. Evaluating the stria content in optical glasses

    NASA Astrophysics Data System (ADS)

    Doladugina, V. S.

    2004-12-01

    This paper discusses previously unpublished results of a large collaborative project carried out by Russian and German specialists on the study of the stria content of glasses with the purpose of estimating the possibility of creating a unified standard corresponding to world requirements. A comparison of the techniques existing in the USSR and the German Democratic Republic in 1981-82 in the form of GOST [State Standard] 3521-82 and TGL 21790 did not lead to a positive result, and it was impossible to create a unified document on the evaluation and monitoring of the stria content of uncolored optical glasses. The causes of the situation thus created are explained, and possible ways of solving this problem are considered.

  20. Models of the optical properties of solids

    NASA Astrophysics Data System (ADS)

    Tropf, William J.; Thomas, Michael E.

    1992-12-01

    Physically-based optical property models of solids are a convenient means of representing the complex index of refraction as a function of frequency and temperature. This modeling approach is especially convenient considering the wide spread use of personal computers and the uncomplicated mathematical form of the models. Models provide a convenient method of cataloging measurements and interpolated between measurements. Several useful models covering absorption and scattering phenomena are presented. Together, these models allow prediction of optical properties over the spectral range from microwaves to the electronic band gap. Temperature dependence of the optical properties cover a more restricted range, but some models predict optical properties from liquid helium to melting temperatures. We have developed an optical properties code incorporating the following models: the classical (one- phonon) oscillator model, our multi-phonon model, the Urbach tail and weak absorption tail models, free-carrier model, and an empirical scatter model. These models require measured parameters which are given for common materials. Comparisons of model calculations of the refractive index, the absorption coefficient, and scattering coefficient to experimental data are presented.

  1. Optical Hall effect-model description: tutorial.

    PubMed

    Schubert, Mathias; Kühne, Philipp; Darakchieva, Vanya; Hofmann, Tino

    2016-08-01

    The optical Hall effect is a physical phenomenon that describes the occurrence of magnetic-field-induced dielectric displacement at optical wavelengths, transverse and longitudinal to the incident electric field, and analogous to the static electrical Hall effect. The electrical Hall effect and certain cases of the optical Hall effect observations can be explained by extensions of the classic Drude model for the transport of electrons in metals. The optical Hall effect is most useful for characterization of electrical properties in semiconductors. Among many advantages, while the optical Hall effect dispenses with the need of electrical contacts, electrical material properties such as effective mass and mobility parameters, including their anisotropy as well as carrier type and density, can be determined from the optical Hall effect. Measurement of the optical Hall effect can be performed within the concept of generalized ellipsometry at an oblique angle of incidence. In this paper, we review and discuss physical model equations, which can be used to calculate the optical Hall effect in single- and multiple-layered structures of semiconductor materials. We define the optical Hall effect dielectric function tensor, demonstrate diagonalization approaches, and show requirements for the optical Hall effect tensor from energy conservation. We discuss both continuum and quantum approaches, and we provide a brief description of the generalized ellipsometry concept, the Mueller matrix calculus, and a 4×4 matrix algebra to calculate data accessible by experiment. In a follow-up paper, we will discuss strategies and approaches for experimental data acquisition and analysis.

  2. Optical Turbulence Characterization by WRF model above Ngari

    NASA Astrophysics Data System (ADS)

    Wang, H.; Yao, Y.

    2013-09-01

    Atmospheric optical turbulence modeling and forecast for astronomy is a relatively recent discipline, but has played important roles in site survey for astronomical observatories and optimization of large telescope observing tables, and in the applications of adaptive optics technique and atmospheric optical transportation. The numerical approach, by use of meteorological parameters and according to parameterization of optical turbulence, can provide all the optical turbulence parameters related, such as Cn2 profile, coherent length, coherent time, seeing, isoplanatic angle, and outer scale of turbulence. This is particularly interesting for searching new sites without the long and expensive site testing campaigns with instruments. Earlier site survey results by National Astronomical Observatories of China site survey team imply that the south-west Tibet, Ngari, is one of the world best IR and sub-mm sites. For searching the best site in Ngari area of hundreds of kilometers, numerical approach by Weather and Research Forecasting (WRF) model had been used to evaluate the climatology of the optical turbulence. The WRF model is configured over a domain 200km×200km with 1km horizontal resolution and 65 vertical levels from ground to the model top(10millibars) in 2010. The initial and boundary conditions for the model are given by the 1°x1°NCEP Global Final Analysis data. The distribution and seasonal variation of optical turbulence parameters over this area are presented. The field investigation for the potential good site are also given.

  3. CMAQ Model Evaluation Framework

    EPA Pesticide Factsheets

    CMAQ is tested to establish the modeling system’s credibility in predicting pollutants such as ozone and particulate matter. Evaluation of CMAQ has been designed to assess the model’s performance for specific time periods and for specific uses.

  4. Modeling of silica nanowires for optical sensing.

    PubMed

    Lou, Jingyi; Tong, Limin; Ye, Zhizhen

    2005-03-21

    Based on evanescent-wave guiding properties of nanowire waveguides, we propose to use single-mode subwavelength-diameter silica nanowires for optical sensing. Phase shift of the guided mode caused by index change is obtained by solving Maxwell's equation, and is used as a criterion for sensitivity estimation. Nanowire sensor employing a wire-assembled Mach-Zehnder structure is modeled. The result shows that optical nanowires, especially those fabricated by taper drawing of optical fibers, are promising for developing miniaturized optical sensors with high sensitivity.

  5. VPPA weld model evaluation

    NASA Technical Reports Server (NTRS)

    Mccutcheon, Kimble D.; Gordon, Stephen S.; Thompson, Paul A.

    1992-01-01

    NASA uses the Variable Polarity Plasma Arc Welding (VPPAW) process extensively for fabrication of Space Shuttle External Tanks. This welding process has been in use at NASA since the late 1970's but the physics of the process have never been satisfactorily modeled and understood. In an attempt to advance the level of understanding of VPPAW, Dr. Arthur C. Nunes, Jr., (NASA) has developed a mathematical model of the process. The work described in this report evaluated and used two versions (level-0 and level-1) of Dr. Nunes' model, and a model derived by the University of Alabama at Huntsville (UAH) from Dr. Nunes' level-1 model. Two series of VPPAW experiments were done, using over 400 different combinations of welding parameters. Observations were made of VPPAW process behavior as a function of specific welding parameter changes. Data from these weld experiments was used to evaluate and suggest improvements to Dr. Nunes' model. Experimental data and correlations with the model were used to develop a multi-variable control algorithm for use with a future VPPAW controller. This algorithm is designed to control weld widths (both on the crown and root of the weld) based upon the weld parameters, base metal properties, and real-time observation of the crown width. The algorithm exhibited accuracy comparable to that of the weld width measurements for both aluminum and mild steel welds.

  6. New Optical Evaluation Approach for Parabolic Trough Collectors: First-Principle OPTical Intercept Calculation

    SciTech Connect

    Zhu, G.; Lewandowski, A.

    2012-11-01

    A new analytical method -- First-principle OPTical Intercept Calculation (FirstOPTIC) -- is presented here for optical evaluation of trough collectors. It employs first-principle optical treatment of collector optical error sources and derives analytical mathematical formulae to calculate the intercept factor of a trough collector. A suite of MATLAB code is developed for FirstOPTIC and validated against theoretical/numerical solutions and ray-tracing results. It is shown that FirstOPTIC can provide fast and accurate calculation of intercept factors of trough collectors. The method makes it possible to carry out fast evaluation of trough collectors for design purposes. The FirstOPTIC techniques and analysis may be naturally extended to other types of CSP technologies such as linear-Fresnel collectors and central-receiver towers.

  7. Development and evaluation of a genetic algorithm-based ocean color inversion model for simultaneously retrieving optical properties and bottom types in coral reef regions.

    PubMed

    Chang, Chih-Hua; Liu, Cheng-Chien; Chung, Hsiao-Wei; Lee, Long-Jeng; Yang, Wen-Chang

    2014-02-01

    This work presents a novel approach that integrates a shallow water semi-analytical (SSA) model and a genetic algorithm (GA) to retrieve water column inherent optical properties (IOPs) and identify bottom types simultaneously from measurement of subsurface remote sensing reflectance. This GA-SSA approach is designed based on the assumption that each pixel is homogeneous with regard to the bottom type when viewed at small (centimeter) scales, and it is validated against a synthetic data set (N=11,250) that consists of five types of bottom, three levels of bottom depth, 15 concentrations of chlorophyll-a (Chl-a), and a wide range of modeled IOP variations in clear and optically complex waters representing the coral reef environment. The results indicate that the GA-SSA approach is accurate and robust in the retrieval of IOPs and its success rate in identifying the real bottom type is limited by the level of Chl-a and bottom depth. When a pixel is homogeneous at a small scale, the maximum allowable concentrations for GA-SSA to perfectly identify all the five bottom types are 0.7  mg/m3 at 5 m bottom depth, 0.2  mg/m3 at 10 m, and 0.07  mg/m3 at 15 m. A promising 80% recognition rate of the benthic community is possible with GA-SSA when an underwater hyperspectral imager is deployed to examine the health status of coral reefs in a clean (Chl-a<1  mg/m3) and shallow (bottom depth<10  m) environment. Further study that collects field data for direct validation is required to ensure that the GA-SSA approach is also applicable in real coral reef regions.

  8. Evaluating temperature and fuel stratification for heat-release rate control in a reactivity-controlled compression-ignition engine using optical diagnostics and chemical kinetics modeling

    SciTech Connect

    Musculus, Mark P. B.; Kokjohn, Sage L.; Reitz, Rolf D.

    2015-04-23

    We investigated the combustion process in a dual-fuel, reactivity-controlled compression-ignition (RCCI) engine using a combination of optical diagnostics and chemical kinetics modeling to explain the role of equivalence ratio, temperature, and fuel reactivity stratification for heat-release rate control. An optically accessible engine is operated in the RCCI combustion mode using gasoline primary reference fuels (PRF). A well-mixed charge of iso-octane (PRF = 100) is created by injecting fuel into the engine cylinder during the intake stroke using a gasoline-type direct injector. Later in the cycle, n-heptane (PRF = 0) is delivered through a centrally mounted diesel-type common-rail injector. This injection strategy generates stratification in equivalence ratio, fuel blend, and temperature. The first part of this study uses a high-speed camera to image the injection events and record high-temperature combustion chemiluminescence. Moreover, the chemiluminescence imaging showed that, at the operating condition studied in the present work, mixtures in the squish region ignite first, and the reaction zone proceeds inward toward the center of the combustion chamber. The second part of this study investigates the charge preparation of the RCCI strategy using planar laser-induced fluorescence (PLIF) of a fuel tracer under non-reacting conditions to quantify fuel concentration distributions prior to ignition. The fuel-tracer PLIF data show that the combustion event proceeds down gradients in the n-heptane distribution. The third part of the study uses chemical kinetics modeling over a range of mixtures spanning the distributions observed from the fuel-tracer fluorescence imaging to isolate the roles of temperature, equivalence ratio, and PRF number stratification. The simulations predict that PRF number stratification is the dominant factor controlling the ignition location and growth rate of the reaction zone. Equivalence ratio has a smaller, but still significant

  9. Stereological Evaluation of the Optic Nerve Volume in Alzheimer Disease.

    PubMed

    Kusbeci, Tuncay; Kusbeci, Ozge Yilmaz; Mas, Nuket Gocmen; Karabekir, Hamit Selim; Yavas, Guliz; Yucel, Aylin

    2015-07-01

    Optic nerve damage occurs in Alzheimer disease (AD) related to the loss of the retinal ganglion cells that contribute fibers to the optic nerve and reduction of the density of axons of the optic nerve. In this study the authors evaluated optic nerve volume changes and the relation between the cerebrum and optic nerve volumes in AD patients. The study evaluated the volumetric measurements of optic nerve by applying the stereological method on magnetic resonance images (MRI). It included age-matched study and control groups, which were composed of 20 patients with probable AD and 20 healthy subjects, respectively. MRIs were analyzed by using the point-counting approach holding Cavalieri principle. There were statistically significant optic nerve volume reduction and cerebral atrophy in AD patients when compared with the age-matched control subjects (P = 0.013, P < 0.001, respectively) but there was no correlation between the optic nerve volume and cerebral volume in AD patients (r = 0.326, P = 0.160). There was a difference between optic nerve volumes of AD and control subjects. The stereological evaluation of optic nerve volume is of importance for both clinicians and anatomists and it can provide valuable information in the evaluation of morphological changes of AD in vivo.

  10. Optical Performance Modeling of FUSE Telescope Mirror

    NASA Technical Reports Server (NTRS)

    Saha, Timo T.; Ohl, Raymond G.; Friedman, Scott D.; Moos, H. Warren

    2000-01-01

    We describe the Metrology Data Processor (METDAT), the Optical Surface Analysis Code (OSAC), and their application to the image evaluation of the Far Ultraviolet Spectroscopic Explorer (FUSE) mirrors. The FUSE instrument - designed and developed by the Johns Hopkins University and launched in June 1999 is an astrophysics satellite which provides high resolution spectra (lambda/Delta(lambda) = 20,000 - 25,000) in the wavelength region from 90.5 to 118.7 nm The FUSE instrument is comprised of four co-aligned, normal incidence, off-axis parabolic mirrors, four Rowland circle spectrograph channels with holographic gratings, and delay line microchannel plate detectors. The OSAC code provides a comprehensive analysis of optical system performance, including the effects of optical surface misalignments, low spatial frequency deformations described by discrete polynomial terms, mid- and high-spatial frequency deformations (surface roughness), and diffraction due to the finite size of the aperture. Both normal incidence (traditionally infrared, visible, and near ultraviolet mirror systems) and grazing incidence (x-ray mirror systems) systems can be analyzed. The code also properly accounts for reflectance losses on the mirror surfaces. Low frequency surface errors are described in OSAC by using Zernike polynomials for normal incidence mirrors and Legendre-Fourier polynomials for grazing incidence mirrors. The scatter analysis of the mirror is based on scalar scatter theory. The program accepts simple autocovariance (ACV) function models or power spectral density (PSD) models derived from mirror surface metrology data as input to the scatter calculation. The end product of the program is a user-defined pixel array containing the system Point Spread Function (PSF). The METDAT routine is used in conjunction with the OSAC program. This code reads in laboratory metrology data in a normalized format. The code then fits the data using Zernike polynomials for normal incidence

  11. Optical Turbulence Characterization by WRF model above Ali, Tibet

    NASA Astrophysics Data System (ADS)

    Wang, Hongshuai; Yao, Yongqiang; Liu, Liyong; Qian, Xuan; Yin, Jia

    2015-04-01

    Atmospheric optical turbulence modeling and forecast for astronomy is a relatively recent discipline, but has played important roles in site survey, optimization of large telescope observing tables, and in the applications of adaptive optics technique. The numerical approach, by using of meteorological parameters and parameterization of optical turbulence, can provide all the optical turbulence parameters related, such as C2n profile, coherent length, wavefront coherent time, seeing, isoplanatic angle, and so on. This is particularly interesting for searching new sites without the long and expensive site testing campaigns with instruments. Earlier site survey results by the site survey team of National Astronomical Observatories of China imply that the south-west Tibet, Ali, is one of the world best IR and sub-mm site. For searching the best site in Ali area, numerical approach by Weather and Research Forecasting (WRF) model had been used to evaluate the climatology of the optical turbulence. The WRF model is configured over a domain 200km×200km with 1km horizontal resolution and 65 vertical levels from ground to the model top(10millibars) in 2010. The initial and boundary conditions for the model are provided by the 1° × 1° Global Final Analysis data from NCEP. The distribution and seasonal variation of optical turbulence parameters over this area are presented.

  12. Pragmatic geometric model evaluation

    NASA Astrophysics Data System (ADS)

    Pamer, Robert

    2015-04-01

    Quantification of subsurface model reliability is mathematically and technically demanding as there are many different sources of uncertainty and some of the factors can be assessed merely in a subjective way. For many practical applications in industry or risk assessment (e. g. geothermal drilling) a quantitative estimation of possible geometric variations in depth unit is preferred over relative numbers because of cost calculations for different scenarios. The talk gives an overview of several factors that affect the geometry of structural subsurface models that are based upon typical geological survey organization (GSO) data like geological maps, borehole data and conceptually driven construction of subsurface elements (e. g. fault network). Within the context of the trans-European project "GeoMol" uncertainty analysis has to be very pragmatic also because of different data rights, data policies and modelling software between the project partners. In a case study a two-step evaluation methodology for geometric subsurface model uncertainty is being developed. In a first step several models of the same volume of interest have been calculated by omitting successively more and more input data types (seismic constraints, fault network, outcrop data). The positions of the various horizon surfaces are then compared. The procedure is equivalent to comparing data of various levels of detail and therefore structural complexity. This gives a measure of the structural significance of each data set in space and as a consequence areas of geometric complexity are identified. These areas are usually very data sensitive hence geometric variability in between individual data points in these areas is higher than in areas of low structural complexity. Instead of calculating a multitude of different models by varying some input data or parameters as it is done by Monte-Carlo-simulations, the aim of the second step of the evaluation procedure (which is part of the ongoing work) is to

  13. New Evaluated Semi-Empirical Formula Using Optical Model for 14-15 MeV ( n, t) Reaction Cross Sections

    NASA Astrophysics Data System (ADS)

    Tel, E.; Durgu, C.; Aydın, A.; Bölükdemir, M. H.; Kaplan, A.; Okuducu, Ş.

    2009-12-01

    In the next century the world will face the need for new energy sources. Nuclear fusion can be one of the most attractive sources of energy from the viewpoint of safety and minimal environmental impact. Fusion will not produce CO2 or SO2 and thus will not contribute to global warming or acid rain. Achieving acceptable performance for a fusion power system in the areas of economics, safety and environmental acceptability, is critically dependent on performance of the blanket and diverter systems which are the primary heat recovery, plasma purification, and tritium breeding systems. Tritium self-sufficiency must be maintained for a commercial power plant. The hybrid reactor is a combination of the fusion and fission processes. For self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. So working out the systematics of ( n, t) reaction cross-sections are of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at energies up to 20 MeV. In this study, we have calculated non-elastic cross-sections by using optical model for ( n, t) reactions at 14-15 MeV energy. We have investigated the excitation function character and reaction Q-values depending on the asymmetry term effect for the ( n, t) reaction cross-sections. We have obtained new coefficients for the ( n, t) reaction cross-sections. We have suggested semi-empirical formulas including optical model nonelastic effects by fitting two parameters for the ( n, t) reaction cross-sections at 14-15 MeV. We have discussed the odd-even effect and the pairing effect considering binding energy systematic of the nuclear shell model for the new experimental data and new cross-sections formulas ( n, t) reactions developed by Tel et al. We have determined a different parameter groups by the classification of nuclei into even-even, even-odd and odd-even for ( n, t) reactions cross-sections. The obtained cross-section formulas

  14. Single-dose safety and pharmacokinetic evaluation of fluorocoxib A: pilot study of novel cyclooxygenase-2-targeted optical imaging agent in a canine model

    NASA Astrophysics Data System (ADS)

    Cekanova, Maria; Uddin, Md. Jashim; Legendre, Alfred M.; Galyon, Gina; Bartges, Joseph W.; Callens, Amanda; Martin-Jimenez, Tomas; Marnett, Lawrence J.

    2012-11-01

    We evaluated preclinical single-dose safety, pharmacokinetic properties, and specific uptake of the new optical imaging agent fluorocoxib A in dogs. Fluorocoxib A, N-[(5-carboxy-X-rhodaminyl)but-4-yl]-2-[1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indol-3-yl]acetamide, selectively binds and inhibits the cyclooxygenase-2 (COX-2) enzyme, which is overexpressed in many cancers. Safety pilot studies were performed in research dogs following intravenous (i.v.) administration of 0.1 and 1 mg/kg fluorocoxib A. Blood and urine samples collected three days after administration of each dose of fluorocoxib A revealed no evidence of toxicity, and no clinically relevant adverse events were noted on physical examination of exposed dogs over that time period. Pharmacokinetic parameters were assessed in additional research dogs from plasma collected at several time points after i.v. administration of fluorocoxib A using high-performance liquid chromatography analysis. The pharmacokinetic studies using 1 mg/kg showed a peak of fluorocoxib A (92±28 ng/ml) in plasma collected at 0.5 h. Tumor specific uptake of fluorocoxib A was demonstrated using a dog diagnosed with colorectal cancer expressing COX-2. Our data support the safe single-dose administration and in vivo efficacy of fluorocoxib A, suggesting a high potential for successful translation to clinical use as an imaging agent for improved tumor detection in humans.

  15. Progress in Evaluating Quantitative Optical Gas Imaging

    EPA Science Inventory

    Development of advanced fugitive emission detection and assessment technologies that facilitate cost effective leak and malfunction mitigation strategies is an ongoing goal shared by industry, regulators, and environmental groups. Optical gas imaging (OGI) represents an importan...

  16. THE ATMOSPHERIC MODEL EVALUATION TOOL

    EPA Science Inventory

    This poster describes a model evaluation tool that is currently being developed and applied for meteorological and air quality model evaluation. The poster outlines the framework and provides examples of statistical evaluations that can be performed with the model evaluation tool...

  17. Evaluation of Retinal Nerve Fiber Layer in Patients with Idiopathic Optic Perineuritis using Optical Coherence Tomography

    PubMed Central

    Byon, Ik Soo; Jung, Jae Ho; Choi, Jae-Hwan; Seo, Je Hyun; Lee, Ji Eun; Choi, Hee-Young

    2015-01-01

    Abstract The aim of this study was to assess the effect of idiopathic Optic perineuritis on the retinal nerve fiber layer, and determine the ability of optical coherence tomography to evaluate retinal nerve fiber loss after idiopathic Optic perineuritis. Four patients were assessed in this study. In all cases, average retinal nerve fiber layer was significantly thinner in the affected eye in comparison with the normal reference value and with the value for the contralateral normal eye at 12 months after the onset of optic perineuritis. Our study revealed that retinal nerve fiber layer loss occurs in idiopathic optic nerve sheath inflammation. PMID:27928329

  18. Re-evaluating the treatment of acute optic neuritis

    PubMed Central

    Bennett, Jeffrey L; Nickerson, Molly; Costello, Fiona; Sergott, Robert C; Calkwood, Jonathan C; Galetta, Steven L; Balcer, Laura J; Markowitz, Clyde E; Vartanian, Timothy; Morrow, Mark; Moster, Mark L; Taylor, Andrew W; Pace, Thaddeus W W; Frohman, Teresa; Frohman, Elliot M

    2015-01-01

    Clinical case reports and prospective trials have demonstrated a reproducible benefit of hypothalamic-pituitary-adrenal (HPA) axis modulation on the rate of recovery from acute inflammatory central nervous system (CNS) demyelination. As a result, corticosteroid preparations and adrenocorticotrophic hormones are the current mainstays of therapy for the treatment of acute optic neuritis (AON) and acute demyelination in multiple sclerosis. Despite facilitating the pace of recovery, HPA axis modulation and corticosteroids have failed to demonstrate long-term benefit on functional recovery. After AON, patients frequently report visual problems, motion perception difficulties and abnormal depth perception despite ‘normal’ (20/20) vision. In light of this disparity, the efficacy of these and other therapies for acute demyelination require re-evaluation using modern, high-precision paraclinical tools capable of monitoring tissue injury. In no arena is this more amenable than AON, where a new array of tools in retinal imaging and electrophysiology has advanced our ability to measure the anatomic and functional consequences of optic nerve injury. As a result, AON provides a unique clinical model for evaluating the treatment response of the derivative elements of acute inflammatory CNS injury: demyelination, axonal injury and neuronal degeneration. In this article, we examine current thinking on the mechanisms of immune injury in AON, discuss novel technologies for the assessment of optic nerve structure and function, and assess current and future treatment modalities. The primary aim is to develop a framework for rigorously evaluating interventions in AON and to assess their ability to preserve tissue architecture, re-establish normal physiology and restore optimal neurological function. PMID:25355373

  19. Evaluating temperature and fuel stratification for heat-release rate control in a reactivity-controlled compression-ignition engine using optical diagnostics and chemical kinetics modeling

    DOE PAGES

    Musculus, Mark P. B.; Kokjohn, Sage L.; Reitz, Rolf D.

    2015-04-23

    We investigated the combustion process in a dual-fuel, reactivity-controlled compression-ignition (RCCI) engine using a combination of optical diagnostics and chemical kinetics modeling to explain the role of equivalence ratio, temperature, and fuel reactivity stratification for heat-release rate control. An optically accessible engine is operated in the RCCI combustion mode using gasoline primary reference fuels (PRF). A well-mixed charge of iso-octane (PRF = 100) is created by injecting fuel into the engine cylinder during the intake stroke using a gasoline-type direct injector. Later in the cycle, n-heptane (PRF = 0) is delivered through a centrally mounted diesel-type common-rail injector. This injectionmore » strategy generates stratification in equivalence ratio, fuel blend, and temperature. The first part of this study uses a high-speed camera to image the injection events and record high-temperature combustion chemiluminescence. Moreover, the chemiluminescence imaging showed that, at the operating condition studied in the present work, mixtures in the squish region ignite first, and the reaction zone proceeds inward toward the center of the combustion chamber. The second part of this study investigates the charge preparation of the RCCI strategy using planar laser-induced fluorescence (PLIF) of a fuel tracer under non-reacting conditions to quantify fuel concentration distributions prior to ignition. The fuel-tracer PLIF data show that the combustion event proceeds down gradients in the n-heptane distribution. The third part of the study uses chemical kinetics modeling over a range of mixtures spanning the distributions observed from the fuel-tracer fluorescence imaging to isolate the roles of temperature, equivalence ratio, and PRF number stratification. The simulations predict that PRF number stratification is the dominant factor controlling the ignition location and growth rate of the reaction zone. Equivalence ratio has a smaller, but still

  20. Automated Environmental Simulation Model Tor Analyzing Wound Fiber Optic Bobbins

    NASA Astrophysics Data System (ADS)

    Edwards, Eugene; Ruffin, Paul B.

    1987-01-01

    The life of optical fibers under stress for an extended period of time is limited by static fatigue caused by stress corrosion in the presence of moisture. In order to predict the life of wound optical fibers, it is necessary to accelerate the aging process by simulating the storage environment (stress, temperature, and humidity) in a short period of time. Existing environmental test systems have been proven useful in the simulation of the storage environment; however, the data is limited due to the manual mode of operation. An automated environmental simulation model is developed to control, collect, process, and analyze optical loss data while measuring temperature and humidity. The environmental conditions for optical fibers wound for various applications are simulated in order to understand the interrelationships between wound fiber parameters including spool composition/design, winding tension, adhesives, and fiber cable design. Experimental investigations are carried out to expose wound optical fiber to simulated environments while monitoring changes in the optical and mechanical characteristics of the fibers. Based on the preliminary results of the data obtained, the automated simulation system is proven acceptable for performing routine modeling and evaluations. The automated system is a valuable instrument to aid in the characterization of optical fibers.

  1. Evaluation of the Optic Nerve Head in Glaucoma.

    PubMed

    Gandhi, Monica; Dubey, Suneeta

    2013-01-01

    Glaucoma is an optic neuropathy leading to changes in the intrapaillary and parapaillary regions of the optic disk. Despite technological advances, clinical identification of optic nerve head characteristics remains the first step in diagnosis. Careful examination of the disk parameters including size, shape, neuroretinal rim shape and pallor; size of the optic cup in relation to the area of the disk; configuration and depth of the optic cup; ratios of cup-to-disk diameter and cup-to-disk area; presence and location of splinter-shaped hemorrhages; occurrence, size, configuration, and location of parapapillary chorioretinal atrophy; and visibility of the retinal nerve fiber layer (RNFL) is important to differentiate between the glaucomatous and nonglaucomatous optic neuropathy. How to cite this article: Gandhi M, Dubey S. Evaluation of the Optic Nerve Head in Glaucoma. J Current Glau Prac 2013;7(3):106-114.

  2. Biophotonic Modelling of Cardiac Optical Imaging.

    PubMed

    Bishop, Martin J; Plank, Gernot

    2015-01-01

    Computational models have been recently applied to simulate and better understand the nature of fluorescent photon scattering and optical signal distortion during cardiac optical imaging. The goal of such models is both to provide a useful post-processing tool to facilitate a more accurate and faithful comparison between computational simulations of electrical activity and experiments, as well as providing essential insight into the mechanisms underlying this distortion, suggesting ways in which it may be controlled or indeed utilised to maximise the information derived from the recorded fluorescent signal. Here, we present different modelling methodologies developed and used in the field to simulate both the explicit processes involved in optical signal synthesis and the resulting consequences of the effects of photon scattering within the myocardium upon the optically-detected signal. We focus our attentions to two main types of modelling approaches used to simulate light transport in cardiac tissue, specifically continuous (reaction-diffusion) and discrete stochastic (Monte Carlo) methods. For each method, we provide both a summary of the necessary methodological details of such models, in addition to brief reviews of relevant application studies which have sought to apply these methods to elucidate important information regarding experimentally-recorded optical signals under different circumstances.

  3. Analysis of a Thin Optical Lens Model

    ERIC Educational Resources Information Center

    Ivchenko, Vladimir V.

    2011-01-01

    In this article a thin optical lens model is considered. It is shown that the limits of its applicability are determined not only by the ratio between the thickness of the lens and the modules of the radii of curvature, but above all its geometric type. We have derived the analytical criteria for the applicability of the model for different types…

  4. Modeling of laser-induced damage and optic usage at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Liao, Zhi M.; Nostrand, Mike; Carr, Wren; Bude, Jeff; Suratwala, Tayyab I.

    2016-07-01

    Modeling of laser-induced optics damage has been introduced to benchmark existing optic usage at the National Ignition Facility (NIF) which includes the number of optics exchanged for damage repair. NIF has pioneered an optics recycle strategy to allow it to run the laser at capacity since fully commissioned in 2009 while keeping the cost of optics usage manageable. We will show how the damage model is being used to evaluate strategies to streamline our optics loop efficiency, as we strive to increase the laser shot rate without increasing operating costs.

  5. Evaluation of optical properties for real photonic crystal fiber based on total variation in wavelet domain

    NASA Astrophysics Data System (ADS)

    Shen, Yan; Wang, Xin; Lou, Shuqin; Lian, Zhenggang; Zhao, Tongtong

    2016-09-01

    An evaluation method based on the total variation model (TV) in wavelet domain is proposed for modeling optical properties of real photonic crystal fibers (PCFs). The TV model in wavelet domain is set up to suppress the noise of the original image effectively and rebuild the cross section images of real PCFs with high accuracy. The optical properties of three PCFs are evaluated, including two kinds of PCFs that supplied from the Crystal Fiber A/S and a homemade side-leakage PCF, by using the combination of the proposed model and finite element method. Numerical results demonstrate that the proposed method can obtain high noise suppression ratio and effectively reduce the noise of cross section images of PCFs, which leads to an accurate evaluation of optical properties of real PCFs. To the best of our knowledge, it is the first time to denoise the cross section images of PCFs with the TV model in the wavelet domain.

  6. BioVapor Model Evaluation

    EPA Science Inventory

    General background on modeling and specifics of modeling vapor intrusion are given. Three classical model applications are described and related to the problem of petroleum vapor intrusion. These indicate the need for model calibration and uncertainty analysis. Evaluation of Bi...

  7. Evaluation of Optical Disk Jukebox Software.

    ERIC Educational Resources Information Center

    Ranade, Sanjay; Yee, Fonald

    1989-01-01

    Discusses software that is used to drive and access optical disk jukeboxes, which are used for data storage. Categories of the software are described, user categories are explained, the design of implementation approaches is discussed, and representative software products are reviewed. (eight references) (LRW)

  8. Evaluation Theory, Models, and Applications

    ERIC Educational Resources Information Center

    Stufflebeam, Daniel L.; Shinkfield, Anthony J.

    2007-01-01

    "Evaluation Theory, Models, and Applications" is designed for evaluators and students who need to develop a commanding knowledge of the evaluation field: its history, theory and standards, models and approaches, procedures, and inclusion of personnel as well as program evaluation. This important book shows how to choose from a growing…

  9. Crowded optic nerve head evaluation with optical coherence tomography in anterior ischemic optic neuropathy.

    PubMed

    Moghimi, S; Afzali, M; Akbari, M; Ebrahimi, K B; Khodabande, A; Yazdani-Abyaneh, A R; Ghafouri, S N H; Coh, P; Okhravi, S; Fard, M A

    2017-04-07

    PurposeTo characterize the optic nerve head (ONH) structure in patients with non-arteritic anterior ischemic optic neuropathy (NAION) compared to healthy control subjects using spectral domain optical coherence tomography (SD-OCT) via the enhanced depth imaging method.MethodsIn this prospective, cross-sectional, comparative study, we assessed 66 eyes of 33 patients with unilateral NAION and 31 eyes of 31 healthy normal subjects in an academic institution. The peripapillary nerve fiber layer thickness, disc area, and quantitative parameters of the ONH structures, including the Bruch's membrane opening (BMO) area, anterior laminar depth, and prelaminar thickness and depth were compared between the three groups.ResultsLinear mixed model analysis after adjusting for age, sex, and axial length showed that the BMO area was similar in eyes with NAION (1.89±0.33 mm(2)), their fellow eyes (1.85±0.35 mm(2)), and control eyes (1.88±0.37 mm(2); all P>0.99). Anterior laminar depth was also similar in the three groups. The mean prelaminar tissue thickness of the NAION eyes was 445±176 μm, which was thinner than the prelaminar tissue of their unaffected fellow eyes (mean, 539±227 μm, P=0.004), but both were thicker than the prelaminar tissue of the normal subjects (mean 243±145 μm, P=0.001 and P<0.001, respectively).ConclusionsThe thick prelaminar thickness is associated with unilateral NAION in the affected and unaffected eyes.Eye advance online publication, 7 April 2017; doi:10.1038/eye.2017.56.

  10. Optical performance simulation of free-form optics for an eye implant based on a measurement data enhanced model.

    PubMed

    Sieber, Ingo; Li, Likai; Gengenbach, Ulrich; Beckert, Erik; Steinkopf, Ralf; Yi, Allen Y

    2016-08-20

    This paper describes the application of a modeling approach for precise optical performance prediction of free-form optics-based subsystems on a demonstration model of an eye implant. The simulation model is enhanced by surface data measured on the free-form lens parts. The manufacturing of the free-form lens parts is realized by two different manufacturing processes: ultraprecision diamond machining and microinjection molding. Evaluation of both processes is conducted by a simulation of the optical performance on the basis of their surface measurement comparisons with the nominal geometry. The simulation results indicate that improvements from the process optimization of microinjection molding were obtained for the best manufacturing accuracy.

  11. Optical Computing Based on Neuronal Models

    DTIC Science & Technology

    1988-05-01

    walking, and cognition are far too complex for existing sequential digital computers. Therefore new architectures, hardware, and algorithms modeled...collective behavior, and iterative processing into optical processing and artificial neurodynamical systems. Another intriguing promise of neural nets is...with architectures, implementations, and programming; and material research s -7- called for. Our future research in neurodynamics will continue to

  12. Optical Performance Models for FDDI Links

    NASA Astrophysics Data System (ADS)

    Kimball, Robert M.

    1990-01-01

    A loss budget model to predict optical performance of Fiber Distributed Data Interface (FDDI) type networks in the premises distribution environment has been developed. This model tailors existing statistical loss budget models to the FDDI standard. It is expected that as FDDI becomes popular, fiber based distribution systems will become common. When designing a fiber distribution system it is important to understand the constraints placed on link performance by the cable plant. To determine these constraints, the model is examined numerically using a large range of initial conditions. The total link length is used as the dependent variable. This set of initial conditions corresponds to an ensemble of possible link configurations. These link configurations are studied in the context of the premises distribution environment. The model is extended to include the use of optical bypass switches. Laboratory measurement data is presented to verify the accuracy of the bypass switch model. The extended model, including the bypass switch, is examined numerically for a similar set of initial conditions. These constraints are applied to the use of bypass switches in wiring closets, between floors, and at the work location. Distance limitations are determined for FDDI links utilizing optical bypass switches.

  13. Environmental simulation evaluation of SSiC brazed optical mirrors

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Ma, Zhen; Chen, Jian; Chen, Zhongming; Liu, Xuejian; Huang, Zhengren

    2014-09-01

    Sintered silicon carbide (SSiC) is becoming one of the most important materials for the optical mirrors due to its excellent specific stiffness (E/ρ) and demission stability (λ/α). However, it is difficult to fabricate the monolithic structure SSiC optical mirror with demission of larger than Φ1.5m because of process limitation. Joining of SSiC segments (brazing) provide a good solution to prepare large size mirror optics. However, compared with the uniform properties of the monolithic structure SSiC optical mirror, the brazed mirror is composed of two materials (SSiC segments and brazing material), so the performance of optical grinding and reliability of brazed optical mirrors become the focus. In this paper, the Φ300mm and Φ600mm brazed optical mirrors was used to evaluate the reliability of different conditions. Three kinds of environmental simulation tests, including thermal stability, thermal circle and random vibration were carried out. The evaluation results show that the temperature and vibration has no obvious effects on the surface figure (RMS) of the brazed optical mirrors.

  14. Numerical model for thermal parameters in optical materials

    NASA Astrophysics Data System (ADS)

    Sato, Yoichi; Taira, Takunori

    2016-04-01

    Thermal parameters of optical materials, such as thermal conductivity, thermal expansion, temperature coefficient of refractive index play a decisive role for the thermal design inside laser cavities. Therefore, numerical value of them with temperature dependence is quite important in order to develop the high intense laser oscillator in which optical materials generate excessive heat across mode volumes both of lasing output and optical pumping. We already proposed a novel model of thermal conductivity in various optical materials. Thermal conductivity is a product of isovolumic specific heat and thermal diffusivity, and independent modeling of these two figures should be required from the viewpoint of a clarification of physical meaning. Our numerical model for thermal conductivity requires one material parameter for specific heat and two parameters for thermal diffusivity in the calculation of each optical material. In this work we report thermal conductivities of various optical materials as Y3Al5O12 (YAG), YVO4 (YVO), GdVO4 (GVO), stoichiometric and congruent LiTaO3, synthetic quartz, YAG ceramics and Y2O3 ceramics. The dependence on Nd3+-doping in laser gain media in YAG, YVO and GVO is also studied. This dependence can be described by only additional three parameters. Temperature dependence of thermal expansion and temperature coefficient of refractive index for YAG, YVO, and GVO: these are also included in this work for convenience. We think our numerical model is quite useful for not only thermal analysis in laser cavities or optical waveguides but also the evaluation of physical properties in various transparent materials.

  15. Performance evaluation of fiber optic components in nuclear plant environments

    SciTech Connect

    Hastings, M.C.; Miller, D.W.; James, R.W.

    1996-03-01

    Over the past several years, the Electric Power Research Institute (EPRI) has funded several projects to evaluate the performance of commercially available fiber optic cables, connective devices, light sources, and light detectors under environmental conditions representative of normal and abnormal nuclear power plant operating conditions. Future projects are planned to evaluate commercially available fiber optic sensors and to install and evaluate performance of instrument loops comprised of fiber optic components in operating nuclear power plant applications. The objective of this research is to assess the viability of fiber optic components for replacement and upgrade of nuclear power plant instrument systems. Fiber optic instrument channels offer many potential advantages: commercial availability of parts and technical support, small physical size and weight, immunity to electromagnetic interference, relatively low power requirements, and high bandwidth capabilities. As existing nuclear power plants continue to replace and upgrade I&C systems, fiber optics will offer a low-cost alternative technology which also provides additional information processing capabilities. Results to date indicate that fiber optics are a viable technology for many nuclear applications, both inside and outside of containments. This work is funded and manage& under the Operations & Maintenance Cost Control research target of EPRI`s Nuclear Power Group. The work is being performed by faculty and students in the Mechanical and Nuclear Engineering Departments and the staff of the Nuclear Reactor Laboratory of the Ohio State University.

  16. Air Mass Considerations in Fog Optical Modeling.

    DTIC Science & Technology

    1981-02-01

    military forces are increasingly relying on new sophis - ticated weapons systems which employ electro-optical (EO) sensors or systems in their principles of...infrared extinction coefficients. Several authors (Stewart,10 Turner et all’) have shown that models which depend upon visibility alone can lead to...Extinction by Fog, TR-77-9, Technology Laboratory, Physical Science Directorate, Redstone Arsenal, AL 11R. E. Turner et al, 1978, Model Development for E-O

  17. Optical models for silicon solar cells

    SciTech Connect

    Marshall, T.; Sopori, B.

    1995-08-01

    Light trapping is an important design feature for high-efficiency silicon solar cells. Because light trapping can considerably enhance optical absorption, a thinner substrate can be used which, in turn, can lower the bulk carrier recombination and concommitantly increase open-circuit voltage, and fill factor of the cell. The basic concepts of light trapping are similar to that of excitation of an optical waveguide, where a prism or a grating structure increases the phase velocity of the incoming optical wave such that waves propagated within the waveguide are totally reflected at the interfaces. Unfortunately, these concepts break down because the entire solar cell is covered with such a structure, making it necessary to develop new analytical approaches to deal with incomplete light trapping in solar cells. This paper describes two models that analyze light trapping in thick and thin solar cells.

  18. Instruction manual, Optical Effects Module, Model OEM

    NASA Technical Reports Server (NTRS)

    1975-01-01

    The Optical Effects Module Model OEM-1, a laboratory prototype instrument designed for the automated measurement of radiation transmission and scattering through optical samples, is described. The system comprises two main components: the Optical Effects Module Enclosure (OEME) and the Optical Effects Module Electronic Controller and Processor (OEMCP). The OEM is designed for operation in the near UV at approximately 2540A, corresponding to the most intense spectral line activated by the mercury discharge lamp used for illumination. The radiation from this source is detected in transmission and reflection through a number of selectable samples. The basic objective of this operation is to monitor in real time the accretion of possible contamination on the surface of these samples. The optical samples are exposed outside of the OEME proper to define exposure conditions and to separate exposure and measurement environments. Changes in the transmissivity of the sample are attributable to surface contamination or to bulk effects due to radiation. Surface contamination will increase radiation scattering due to Rayleigh-Gans effect or to other phenomena, depending on the characteristics size of the particulate contaminants. Thus, also scattering from the samples becomes a part of the measurement program.

  19. An optical model for composite nuclear scattering

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Townsend, L. W.

    1981-01-01

    The optical model of composite particle scattering is considered and compared to the accuracies of other models. A nonrelativistic Schroedinger equation with two-body potentials is used for the scattering of a single particle by an energy-dependent local potential. The potential for the elastic channel is composed of matrix elements of a single scattering operator taken between the ground states of the projectile and the target; the coherent amplitude is considered as dominating the scattering in the forward direction. A multiple scattering series is analytically explored and formally summed by the solution of an equivalent Schroedinger equation. Cross sections of nuclear scattering are then determined for He-4 and C-12 nuclei at 3.6 GeV/nucleus and O-16 projectiles at 2.1 GeV/nucleus, and the optical model approximations are found to be consistently lower and more accurate than approximations made by use of Glauber's theory.

  20. Re-evaluation of literature values of silver optical constants.

    PubMed

    Jiang, Yajie; Pillai, Supriya; Green, Martin A

    2015-02-09

    Silver has unique optical properties for topical applications such as plasmonics. The two most widely used silver optical data sets are the Palik handbook compilation and that determined by Johnson and Christy. Unfortunately these are inconsistent making realistic modelling of the likely performance of silver in optical applications difficult, with modelling producing either highly optimistic or very pessimistic results, depending on application. By critical examination and duplication of the original experiments leading to the widely accepted literature values, we show that both data sets have drawbacks and conclude that there is a need for an improved data set for realistic simulation of experimentally obtainable properties.

  1. Field Evaluation of Anti-Biofouling Compounds on Optical Instrumentation

    NASA Technical Reports Server (NTRS)

    McLean, Scott; Schofield, Bryan; Zibordi, Giuseppe; Lewis, Marlon; Hooker, Stanford; Weidemann, Alan

    1997-01-01

    Biofouling has been a serious question in the stability of optical measurements in the ocean, particularly in moored and drifting buoy applications. Many investigators coat optical surfaces with various compounds to reduce the amount of fouling; to our knowledge, however, there are no objective, in-situ comparative testing of these compounds to evaluate their effectiveness with respect to optical stability relative to untreated controls. We have tested a wide range of compounds at in-situ locations in Halifax Harbour and in the Adriatic Sea on passive optical sensors. Compounds tested include a variety of TBT formulations, antifungal agents, and low-friction silicone-based compounds; time-scales of up to four months were evaluated. The results of these experiments are discussed.

  2. Star testing: a novel evaluation of intraocular lens optical quality

    PubMed Central

    Mitchell, L; Molteno, A C B; Bevin, T H; Sanderson, G

    2006-01-01

    Background Despite the importance of optical quality of an intraocular lens (IOL) on visual outcomes following cataract surgery, objective data on their optical quality are not readily available, and manufacturing standards are industry regulated. The star test is a classic test of optical quality based on examination of the Airy disc and expanded diffraction rings of a point source of light, used mainly for telescope and microscope objectives. Methods A physical model eye cell allowed star testing of IOLs under conditions similar to the optical environment in which they operate. 18 IOLs were tested and results compared to actual images produced by these lenses in the model eye cell. Quantitative measures of star testing performance were developed. Results The optical performance of the IOLs varied, some performing very poorly. Most lenses (13/17) performed better in reverse orientation, while aberrations induced by the haptics of foldable IOLs were also detected. There was excellent correlation between actual images formed and star testing parameters. Conclusion Star testing IOLs was a novel biomedical application of a centuries old, inexpensive method. A concerning variation of optical quality was found, suggesting IOL optical performance data should be more readily available. Independent, authority mandated IOL optical quality standards should be developed, and results readily available to ophthalmologists. PMID:16622088

  3. RxGen General Optical Model Prescription Generator

    NASA Technical Reports Server (NTRS)

    Sigrist, Norbert

    2012-01-01

    RxGen is a prescription generator for JPL's in-house optical modeling software package called MACOS (Modeling and Analysis for Controlled Optical Systems), which is an expert optical analysis software package focusing on modeling optics on dynamic structures, deformable optics, and controlled optics. The objectives of RxGen are to simplify and automate MACOS prescription generations, reducing errors associated with creating such optical prescriptions, and improving user efficiency without requiring MACOS proficiency. RxGen uses MATLAB (a high-level language and interactive environment developed by MathWorks) as the development and deployment platform, but RxGen can easily be ported to another optical modeling/analysis platform. Running RxGen within the modeling environment has the huge benefit that variations in optical models can be made an integral part of the modeling state. For instance, optical prescription parameters determined as external functional dependencies, optical variations by controlling the in-/exclusion of optical components like sub-systems, and/or controlling the state of all components. Combining the mentioned capabilities and flexibilities with RxGen's optical abstraction layer completely eliminates the hindering aspects for requiring proficiency in writing/editing MACOS prescriptions, allowing users to focus on the modeling aspects of optical systems, i.e., increasing productivity and efficiency. RxGen provides significant enhancements to MACOS and delivers a framework for fast prototyping as well as for developing very complex controlled optical systems.

  4. Integrated Modeling Activities for the James Webb Space Telescope: Optical Jitter Analysis

    NASA Technical Reports Server (NTRS)

    Hyde, T. Tupper; Ha, Kong Q.; Johnston, John D.; Howard, Joseph M.; Mosier, Gary E.

    2004-01-01

    This is a continuation of a series of papers on the integrated modeling activities for the James Webb Space Telescope(JWST). Starting with the linear optical model discussed in part one, and using the optical sensitivities developed in part two, we now assess the optical image motion and wavefront errors from the structural dynamics. This is often referred to as "jitter: analysis. The optical model is combined with the structural model and the control models to create a linear structural/optical/control model. The largest jitter is due to spacecraft reaction wheel assembly disturbances which are harmonic in nature and will excite spacecraft and telescope structural. The structural/optic response causes image quality degradation due to image motion (centroid error) as well as dynamic wavefront error. Jitter analysis results are used to predict imaging performance, improve the structural design, and evaluate the operational impact of the disturbance sources.

  5. A Thermo-Optic Propagation Modeling Capability.

    SciTech Connect

    Schrader, Karl; Akau, Ron

    2014-10-01

    A new theoretical basis is derived for tracing optical rays within a finite-element (FE) volume. The ray-trajectory equations are cast into the local element coordinate frame and the full finite-element interpolation is used to determine instantaneous index gradient for the ray-path integral equation. The FE methodology (FEM) is also used to interpolate local surface deformations and the surface normal vector for computing the refraction angle when launching rays into the volume, and again when rays exit the medium. The method is implemented in the Matlab(TM) environment and compared to closed- form gradient index models. A software architecture is also developed for implementing the algorithms in the Zemax(TM) commercial ray-trace application. A controlled thermal environment was constructed in the laboratory, and measured data was collected to validate the structural, thermal, and optical modeling methods.

  6. Optical Imaging and Radiometric Modeling and Simulation

    NASA Technical Reports Server (NTRS)

    Ha, Kong Q.; Fitzmaurice, Michael W.; Moiser, Gary E.; Howard, Joseph M.; Le, Chi M.

    2010-01-01

    OPTOOL software is a general-purpose optical systems analysis tool that was developed to offer a solution to problems associated with computational programs written for the James Webb Space Telescope optical system. It integrates existing routines into coherent processes, and provides a structure with reusable capabilities that allow additional processes to be quickly developed and integrated. It has an extensive graphical user interface, which makes the tool more intuitive and friendly. OPTOOL is implemented using MATLAB with a Fourier optics-based approach for point spread function (PSF) calculations. It features parametric and Monte Carlo simulation capabilities, and uses a direct integration calculation to permit high spatial sampling of the PSF. Exit pupil optical path difference (OPD) maps can be generated using combinations of Zernike polynomials or shaped power spectral densities. The graphical user interface allows rapid creation of arbitrary pupil geometries, and entry of all other modeling parameters to support basic imaging and radiometric analyses. OPTOOL provides the capability to generate wavefront-error (WFE) maps for arbitrary grid sizes. These maps are 2D arrays containing digital sampled versions of functions ranging from Zernike polynomials to combination of sinusoidal wave functions in 2D, to functions generated from a spatial frequency power spectral distribution (PSD). It also can generate optical transfer functions (OTFs), which are incorporated into the PSF calculation. The user can specify radiometrics for the target and sky background, and key performance parameters for the instrument s focal plane array (FPA). This radiometric and detector model setup is fairly extensive, and includes parameters such as zodiacal background, thermal emission noise, read noise, and dark current. The setup also includes target spectral energy distribution as a function of wavelength for polychromatic sources, detector pixel size, and the FPA s charge

  7. Applied grinding wheel performance evaluation for optical fabrication

    SciTech Connect

    Piscotty, M.A.; Taylor, J.S.; Blaedel, K.L.

    1996-06-11

    We are collaborating with the Center for Optics Manufacturing (Rochester NY) to develop fine diamond grinding wheels for spherical grinding of glass optics. A standardized method for evaluating wheel performance includes in-process acoustic emission (AE). This paper includes recent AE measurements taken during the evaluation of several fine diamond grinding wheels and discusses how this new information might relate to the physical performance of the wheels. An interesting observation is also reported on the surface topography of worn bronze wheels using an interferometric profiler.

  8. Modeling discrete modulators for optical correlation

    NASA Astrophysics Data System (ADS)

    Knopp, Jerome

    1995-08-01

    The practical calculation of optical correlation filters in correlators that use spatial light modulators with discrete elements is based on the assumption that the image on the input modulator can be modeled as a modulated 2D comb function or 'bed of nails'. A 2D discrete Fourier transform (DFT) is used to calculate a filter that is also modeled as a modulated bed of nails. The sample values in the comb array are assigned to pixel values in the filter. This approach actually gives fairly good qualitative results in modeling correlation behavior. However, it cannot account in detail for the finite size of pixel elements. The DFT approach has problems when modeling modulators whose pixels' center positions cannot be aligned with corresponding sample values. A modified DFT algorithm and an interpolation scheme for modeling these situations is given. As a practical application of the method, we look at modeling an optical correlator whose pixels are not centered at positions that correspond the DFT sample values.

  9. Evanescent Field Based Photoacoustics: Optical Property Evaluation at Surfaces

    PubMed Central

    Goldschmidt, Benjamin S.; Rudy, Anna M.; Nowak, Charissa A.; Tsay, Yowting; Whiteside, Paul J. D.; Hunt, Heather K.

    2016-01-01

    Here, we present a protocol to estimate material and surface optical properties using the photoacoustic effect combined with total internal reflection. Optical property evaluation of thin films and the surfaces of bulk materials is an important step in understanding new optical material systems and their applications. The method presented can estimate thickness, refractive index, and use absorptive properties of materials for detection. This metrology system uses evanescent field-based photoacoustics (EFPA), a field of research based upon the interaction of an evanescent field with the photoacoustic effect. This interaction and its resulting family of techniques allow the technique to probe optical properties within a few hundred nanometers of the sample surface. This optical near field allows for the highly accurate estimation of material properties on the same scale as the field itself such as refractive index and film thickness. With the use of EFPA and its sub techniques such as total internal reflection photoacoustic spectroscopy (TIRPAS) and optical tunneling photoacoustic spectroscopy (OTPAS), it is possible to evaluate a material at the nanoscale in a consolidated instrument without the need for many instruments and experiments that may be cost prohibitive. PMID:27500652

  10. The simulation of adaptive optical image even and pulse noise and research of image quality evaluation

    NASA Astrophysics Data System (ADS)

    Wen, Changli; Xu, Yuannan; Xu, Rong; Liu, Changhai; Men, Tao; Niu, Wei

    2013-09-01

    As optical image becomes more and more important in adaptive optics area, and adaptive optical telescopes play a more and more important role in the detection system on the ground, and the images we get are so many that we need find a suitable method to choose good quality images automatically in order to save human power, people pay more and more attention in image's evaluation methods and their characteristics. According to different image degradation model, the applicability of different image's quality evaluation method will be different. Researchers have paid most attention in how to improve or build new method to evaluate degraded images. Now we should change our way to take some research in the models of degradation of images, the reasons of image degradation, and the relations among different degraded images and different image quality evaluation methods. In this paper, we build models of even noise and pulse noise based on their definition and get degraded images using these models, and we take research in six kinds of usual image quality evaluation methods such as square error method, sum of multi-power of grey scale method, entropy method, Fisher function method, Sobel method, and sum of grads method, and we make computer software for these methods to use easily to evaluate all kinds of images input. Then we evaluate the images' qualities with different evaluation methods and analyze the results of six kinds of methods, and finally we get many important results. Such as the characteristics of every method for evaluating qualities of degraded images of even noise, the characteristics of every method for evaluating qualities of degraded images of pulse noise, and the best method to evaluate images which affected by tow kinds of noise both and the characteristics of this method. These results are important to image's choosing automatically, and this will help we to manage the images we get through adaptive optical telescopes base on the ground.

  11. Revisiting the CALIOP Mineral Dust Optical Model

    NASA Astrophysics Data System (ADS)

    Winker, D. M.; Omar, A. H.; Liu, Z.

    2013-12-01

    The standard aerosol extinction retrieval applied to CALIOP observations relies heavily on a priori values of the lidar ratio (the ratio of extinction to 180-degree backscatter) for each of several aerosol types. The original CALIOP aerosol models were developed over 10 years ago, based on a combination of Aeronet retrievals, measurements from ground-based lidars, and theoretical scattering calculations. Both prior to and since the launch of CALIPSO, a number of studies using a variety of approaches have shown lidar ratios of around 40 sr for mineral dust. Ground-based Raman lidar measurements in Europe and Morroco, on the other hand, have consistently shown higher values of 50 to 60 sr. Reasons for this inconsistency have not been clearly identified, but may be due to geographical variability, mixtures of dust with fine-mode aerosol, multiple scattering effects on the CALIOP retrieval, other retrieval artifacts, or a combination of these. The simplest explanation for the difference between ground-based Raman and space-based retrievals of dust lidar ratio would be multiple scattering effects on the CALIOP signals. We have taken advantage of improvements in scattering codes and of recent field campaigns to re-evaluate the CALIOP optical model for mineral dust and to revisit multiple scattering effects. The original scattering phase functions used to predict multiple scattering were based on Dipole-Dipole Approximation (DDA) calculations of size-shape mixtures of irregular dust particles. At the time, the DDA calculations were limited to particles of less than 2 um diameter. Using current T-matrix codes, we are now able to compute scattering from particles as large as 10 um diameter. Applying T-matrix scattering calculations to spheroidal particles with size distributions consistent with those measured during the SAMUM campaign in Morroco, we find multiple scattering effects are similar to those predicted from the original DDA calculations. Thus multiple scattering

  12. In-flight evaluation of an optical head motion tracker

    NASA Astrophysics Data System (ADS)

    Tawada, Kazuho

    2009-05-01

    We have presented a new approach for Optical HMT (Head Motion Tracker) last year (Proc. SPIE 6955, 69550A1-11, 2008) [1]. In existing Magnetic HMT, it is inevitable to conduct pre-mapping in order to obtain sufficient accuracy because of magnetic field's distortion caused by metallic material around HMT, such as cockpit and helmet. Optical HMT is commonly known as mapping-free tracker; however, it has some disadvantages on accuracy, stability against sunlight conditions, in terms of comparison with Magnetic HMT. We have succeeded to develop new Optical HMT, which can overcome particular disadvantages by integration with two area cameras, LED markers, image processing techniques and inertial sensors with simple algorithm in laboratory level environment. We have also reported some experimental results conducted in laboratory, which proves good accuracy even in the sunlight condition. This time, we show actual performance of the Optical HMT in flight condition, including evaluation of stability against sunlight. Shimadzu Corp. and JAXA (Japan Aerospace Exploration Agency) is conducting joint research named SAVERH (Situation Awareness and Visual Enhancer for Rescue Helicopter) [2] that aims at inventing method of presenting suitable information to the pilot to support search and rescue missions by helicopters. The Optical HMT has been evaluated through a series of flight evaluation in SAVERH and demonstrated the operation concept.

  13. Evaluating Causal Models.

    ERIC Educational Resources Information Center

    Watt, James H., Jr.

    Pointing out that linear causal models can organize the interrelationships of a large number of variables, this paper contends that such models are particularly useful to mass communication research, which must by necessity deal with complex systems of variables. The paper first outlines briefly the philosophical requirements for establishing a…

  14. Model Program Evaluations. Fact Sheet

    ERIC Educational Resources Information Center

    Arkansas Safe Schools Initiative Division, 2002

    2002-01-01

    There are probably thousands of programs and courses intended to prevent or reduce violence in this nation's schools. Evaluating these many programs has become a problem or goal in itself. There are now many evaluation programs, with many levels of designations, such as model, promising, best practice, exemplary and noteworthy. "Model program" is…

  15. Optoelectronic device simulation: Optical modeling for semiconductor optical amplifiers and solid state lighting

    NASA Astrophysics Data System (ADS)

    Wang, Dong-Xue (Michael)

    2006-07-01

    transparency carrier densities; the differential gain is assumed constant accordingly. This assumption is only valid for wavelengths close to the gain peak wavelength. As a result, high accuracy for wideband wavelength conversion is not guaranteed. We proposed a steady state numerical model of wavelength converters based on cross-gain modulation in semiconductor optical amplifiers. In this model, a new model of the gain coefficient developed by Connelly was applied, which also includes the internal loss variation with the electron carrier density. Each physical variable, such as the carrier density, gain coefficient, differential gain, and internal loss, spatially varies across the SOA cavity and is numerically calculated throughout the device. This model can predicts wavelength-dependent characteristics of a wavelength converter of the SOA in both large and small signal regimes. Some key performance factors of SOA wavelength converters, such as selection of pump and probe wavelengths and power, length of SOA cavities, conversion efficiency and bandwidth, system performance difference between up and down conversions can be modeled and optimized using this numerical model. Most LED modeling techniques are based on optical ray tracing to predict the light extraction efficiency, and the light extraction efficiency is a critical parameter to evaluate LEDs. Here, we proposed a hybrid method to simulate the lighting efficiency of LED chips, where both guided wave theory and geometric optical ray tracing are applied. Guided wave optics is used to identify guided modes and leakage modes inside the LED active layer, and its device structure can be optimized to increase leakage modes so that the lighting extraction efficiency is improved. On the other hand, Monte Carlo optical ray tracing is used to quantitatively determine optical extraction efficiency. Moreover, this method can model the light distribution and far-field illumination pattern. Both single wavelength LEDs and dual

  16. Evaluation of the OSC-TV iterative reconstruction algorithm for cone-beam optical CT

    SciTech Connect

    Matenine, Dmitri Mascolo-Fortin, Julia; Goussard, Yves

    2015-11-15

    Purpose: The present work evaluates an iterative reconstruction approach, namely, the ordered subsets convex (OSC) algorithm with regularization via total variation (TV) minimization in the field of cone-beam optical computed tomography (optical CT). One of the uses of optical CT is gel-based 3D dosimetry for radiation therapy, where it is employed to map dose distributions in radiosensitive gels. Model-based iterative reconstruction may improve optical CT image quality and contribute to a wider use of optical CT in clinical gel dosimetry. Methods: This algorithm was evaluated using experimental data acquired by a cone-beam optical CT system, as well as complementary numerical simulations. A fast GPU implementation of OSC-TV was used to achieve reconstruction times comparable to those of conventional filtered backprojection. Images obtained via OSC-TV were compared with the corresponding filtered backprojections. Spatial resolution and uniformity phantoms were scanned and respective reconstructions were subject to evaluation of the modulation transfer function, image uniformity, and accuracy. The artifacts due to refraction and total signal loss from opaque objects were also studied. Results: The cone-beam optical CT data reconstructions showed that OSC-TV outperforms filtered backprojection in terms of image quality, thanks to a model-based simulation of the photon attenuation process. It was shown to significantly improve the image spatial resolution and reduce image noise. The accuracy of the estimation of linear attenuation coefficients remained similar to that obtained via filtered backprojection. Certain image artifacts due to opaque objects were reduced. Nevertheless, the common artifact due to the gel container walls could not be eliminated. Conclusions: The use of iterative reconstruction improves cone-beam optical CT image quality in many ways. The comparisons between OSC-TV and filtered backprojection presented in this paper demonstrate that OSC-TV can

  17. Evaluation of the Malvern optical particle monitor. [Volumetric size distribution

    SciTech Connect

    Anderson, R. J.; Johnson, E.

    1983-07-01

    The Malvern 2200/3300 Particle Sizer is a laser-based optical particle sizing device which utilizes the principle of Fraunhofer Diffraction as the means of particle size measurement. The instrument is designed to analyze particle sizes in the range of 1 to 1800 microns diameter through a selection of lenses for the receiving optics. It is not a single-particle counter but rather an ensemble averager over the distribution of particles present in the measuring volume. Through appropriate measurement techniques, the instrument can measure the volumetric size distribution of: solids in gas or liquid suspension; liquid droplets in gas or other immiscible liquids; and, gas bubbles in liquid. (Malvern Handbook, Version 1.5). This report details a limited laboratory evaluation of the Malvern system to determine its operational characteristics, limitations, and accuracy. This investigation focused on relatively small particles in the range of 5 to 150 microns. Primarily, well characterized particles of coal in a coal and water mixture were utilized, but a selection of naturally occurring, industrially generated, and standard samples (i.e., glass beads) wer also tested. The characteristic size parameter from the Malvern system for each of these samples was compared with the results of a Coulter particle counter (Model TA II) analysis to determine the size measurement accuracy. Most of the particulate samples were suspended in a liquid media (water or isoton, plus a dispersant) for the size characterization. Specifically, the investigations contained in this report fall into four categories: (a) Sample-to-lense distance and sample concentration studies, (b) studies testing the applicability to aerosols, (c) tests of the manufacturer supplied software, and (d) size measurement comparisons with the results of Coulter analysis. 5 references, 15 figures, 2 tables.

  18. Bond models in linear and nonlinear optics

    NASA Astrophysics Data System (ADS)

    Aspnes, D. E.

    2015-08-01

    Bond models, also known as polarizable-point or mechanical models, have a long history in optics, starting with the Clausius-Mossotti relation but more accurately originating with Ewald's largely forgotten work in 1912. These models describe macroscopic phenomena such as dielectric functions and nonlinear-optical (NLO) susceptibilities in terms of the physics that takes place in real space, in real time, on the atomic scale. Their strengths lie in the insights that they provide and the questions that they raise, aspects that are often obscured by quantum-mechanical treatments. Statics versions were used extensively in the late 1960's and early 1970's to correlate NLO susceptibilities among bulk materials. Interest in NLO applications revived with the 2002 work of Powell et al., who showed that a fully anisotropic version reduced by more than a factor of 2 the relatively large number of parameters necessary to describe secondharmonic- generation (SHG) data for Si(111)/SiO2 interfaces. Attention now is focused on the exact physical meaning of these parameters, and to the extent that they represent actual physical quantities.

  19. Tuning sum rules with window functions for optical constant evaluation

    NASA Astrophysics Data System (ADS)

    Rodríguez-de Marcos, Luis V.; Méndez, José A.; Larruquert, Juan I.

    2016-07-01

    Sum rules are a useful tool to evaluate the global consistency of a set of optical constants. We present a procedure to spectrally tune sum rules to evaluate the local consistency of optical constants. It enables enhancing the weight of a desired spectral range within the sum-rule integral. The procedure consists in multiplying the complex refractive index with an adapted function, which is named window function. Window functions are constructed through integration of Lorentz oscillators. The asymptotic decay of these window functions enables the derivation of a multiplicity of sum rules akin to the inertial sum rule, along with one modified version of f-sum rule. This multiplicity of sum rules combined with the free selection of the photon energy range provides a double way to tune the spectral contribution within the sum rule. Window functions were applied to reported data of SrF2 and of Al films in order to check data consistency over the spectrum. The use of window functions shows that the optical constants of SrF2 are consistent in a broad spectrum. Regarding Al, some spectral ranges are seen to present a lower consistency, even though the standard sum rules with no window function did not detect inconsistencies. Hence window functions are expected to be a helpful tool to evaluate the local consistency of optical constants.

  20. Evaluation of whole blood coagulation process by optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Xu, Xiangqun; Lin, Jia

    2010-11-01

    This study was to investigate the feasibility of using optical coherence tomography (OCT) to evaluate whole blood coagulation process. Attenuation coefficients and 1/e light penetration depth (D1/e) against time of human whole blood during in vitro clot formation under static were measured from the OCT profiles of reflectance vs depth. The results obtained clearly showed that the optical parameters are able to identify three stages during the in vitro blood clotting process. It is concluded that D1/e measured by OCT is a potential parameter to quantify and follow the liquid-gel transition of blood during clotting.

  1. Zero Length Intrastation Fiber Optics Links Test and Evaluation Program.

    DTIC Science & Technology

    1981-05-01

    WOirCS (Continue on, ev- icb. it r .~53r’Od Idern~f b’ lock r-urmher) Fiber Optics Digital Transmissic-, Analoo Transmission 20. AtiSTRACT (Cowfou. am...typified Defcnse Communications Systems (DCS) transmission node between DCS digital multir!exers and radios. The intent being to evaluate fiber optics...1920 under the technical dircction of the US Army Comunication Electronics Engi’-Vring In*’allation h\\keN)J (USACJEIA). Supplei.,ental testing ’.ws

  2. Optical Model and Cross Section Uncertainties

    SciTech Connect

    Herman,M.W.; Pigni, M.T.; Dietrich, F.S.; Oblozinsky, P.

    2009-10-05

    Distinct minima and maxima in the neutron total cross section uncertainties were observed in model calculations using spherical optical potential. We found this oscillating structure to be a general feature of quantum mechanical wave scattering. Specifically, we analyzed neutron interaction with 56Fe from 1 keV up to 65 MeV, and investigated physical origin of the minima.We discuss their potential importance for practical applications as well as the implications for the uncertainties in total and absorption cross sections.

  3. Statistical model for free-space optical coherent communications using adaptive optics

    NASA Astrophysics Data System (ADS)

    Anzuola, Esdras; Gladysz, Szymon

    2016-10-01

    In this paper we present a new model for describing the turbulence-induced fading that uses the representation of the phase in the aperture plane as a collection of random "cells". This model serves as input to calculate the probability density function of fading intensity. The model has two parameters: phase variance and number of wavefront cells . We derive expressions for the signal-to-noise ratio in the presence of atmospheric turbulence and adaptive optics compensation. We estimate symbol error probabilities for M-ary phase shift keying and evaluate the performance of coherent receivers as a function of the normalized aperture and the number of actuators on the deformable mirror or the number of compensated modes. We perform numerical simulations of the fading intensity for different uncompensated and compensated scenarios and we compare the results with the proposed model.

  4. Fractional-order variational optical flow model for motion estimation.

    PubMed

    Chen, Dali; Sheng, Hu; Chen, YangQuan; Xue, Dingyü

    2013-05-13

    A new class of fractional-order variational optical flow models, which generalizes the differential of optical flow from integer order to fractional order, is proposed for motion estimation in this paper. The corresponding Euler-Lagrange equations are derived by solving a typical fractional variational problem, and the numerical implementation based on the Grünwald-Letnikov fractional derivative definition is proposed to solve these complicated fractional partial differential equations. Theoretical analysis reveals that the proposed fractional-order variational optical flow model is the generalization of the typical Horn and Schunck (first-order) variational optical flow model and the second-order variational optical flow model, which provides a new idea for us to study the optical flow model and has an important theoretical implication in optical flow model research. The experiments demonstrate the validity of the generalization of differential order.

  5. Contact stresses modeling at the Panda-type fiber single-layer winding and evaluation of their impact on the fiber optic properties

    NASA Astrophysics Data System (ADS)

    Lesnikova, Yu I.; Smetannikov, O. Yu; Trufanov, A. N.; Trufanov, N. A.

    2017-02-01

    The impact of contact transverse forces on the birefringence of the single-mode polarization-maintaining Panda-type fiber is numerically modeled. It has been established that with a single-row power winding on a cylindrical mandrel, the fiber tension at winding is the principal factor that influences birefringence. When coiling the fiber based on the local defect microbending, the birefringence at the microbending point differs from that of the free fiber by 1.3%.

  6. Optical Calibration Process Developed for Neural-Network-Based Optical Nondestructive Evaluation Method

    NASA Technical Reports Server (NTRS)

    Decker, Arthur J.

    2004-01-01

    A completely optical calibration process has been developed at Glenn for calibrating a neural-network-based nondestructive evaluation (NDE) method. The NDE method itself detects very small changes in the characteristic patterns or vibration mode shapes of vibrating structures as discussed in many references. The mode shapes or characteristic patterns are recorded using television or electronic holography and change when a structure experiences, for example, cracking, debonds, or variations in fastener properties. An artificial neural network can be trained to be very sensitive to changes in the mode shapes, but quantifying or calibrating that sensitivity in a consistent, meaningful, and deliverable manner has been challenging. The standard calibration approach has been difficult to implement, where the response to damage of the trained neural network is compared with the responses of vibration-measurement sensors. In particular, the vibration-measurement sensors are intrusive, insufficiently sensitive, and not numerous enough. In response to these difficulties, a completely optical alternative to the standard calibration approach was proposed and tested successfully. Specifically, the vibration mode to be monitored for structural damage was intentionally contaminated with known amounts of another mode, and the response of the trained neural network was measured as a function of the peak-to-peak amplitude of the contaminating mode. The neural network calibration technique essentially uses the vibration mode shapes of the undamaged structure as standards against which the changed mode shapes are compared. The published response of the network can be made nearly independent of the contaminating mode, if enough vibration modes are used to train the net. The sensitivity of the neural network can be adjusted for the environment in which the test is to be conducted. The response of a neural network trained with measured vibration patterns for use on a vibration isolation

  7. Laboratory evaluation of Fecker and Loral optical IR PWI systems

    NASA Technical Reports Server (NTRS)

    Gorstein, M.; Hallock, J. N.; Houten, M.; Mcwilliams, I. G.

    1971-01-01

    A previous flight test of two electro-optical pilot warning indicators, using a flashing xenon strobe and silicon detectors as cooperative elements, pointed out several design deficiencies. The present laboratory evaluation program corrected these faults and calibrated the sensitivity of both systems in azimuth elevation and range. The laboratory tests were performed on an optical bench and consisted of three basic components: (1) a xenon strobe lamp whose output is monitored at the indicator detector to give pulse to pulse information on energy content at the receiver; (2) a strobe light attenuating optical system which is calibrated photometrically to provide simulated range; and (3) a positioning table on which the indicator system under study is mounted and which provides spatial location coordinates for all data points. The test results for both systems are tabulated.

  8. Experimental qualification by extensive evaluation of fibre optic strain sensors

    NASA Astrophysics Data System (ADS)

    Schilder, Constanze; Kusche, Nadine; Schukar, Vivien G.; Münzenberger, Sven; Habel, Wolfgang R.

    2013-09-01

    Fibre optic strain sensors used in practical applications have to provide reliable measurements. Therefore, the applied sensor and the sensor systems must be validated experimentally. This can be achieved with facilities which use physically independent measurement systems in order to avoid the influences caused by the application of a reference sensor. This paper describes the testing methods of the specially developed validation facility KALFOS for the qualification and evaluation of surface-applied strain sensors. For reliable sensor results, the performance of fibre optic strain patches with and without FBG under combined thermal and mechanical loading was investigated. Additionally, the strain gauge factor of the fibre optic strain patches with FBG was determined experimentally and compared to the specified strain gauge factor. These results will be the basis for the development of guidelines and standards concerning the application of the sensors.

  9. Optical SED models of galaxy mergers

    NASA Astrophysics Data System (ADS)

    Snyder, Gregory F.; Cox, T. J.; Hayward, Christopher C.; Hernquist, Lars; Jonsson, Patrik

    2012-08-01

    I discuss recent work in which we construct models of poststarburst galaxies by combining fully three-dimensional hydrodynamic simulations of galaxy mergers with radiative transfer calculations of dust attenuation. The poststarburst signatures can occur shortly after a bright starburst phase in gas-rich mergers, and thus offer a unique opportunity to study the formation of bulges and the effects of feedback. Several additional applications of spatially-resolved spectroscopic models of interacting galaxies include multi-wavelength studies of AGN/starburst diagnostics, mock integral field unit data to interpret the evolution of ULIRGs, and the `Green Valley'. Optical spectra of simulated major gas-rich galaxy mergers can be found at http://www.cfa.harvard.edu/~gsnyder

  10. General MACOS Interface for Modeling and Analysis for Controlled Optical Systems

    NASA Technical Reports Server (NTRS)

    Sigrist, Norbert; Basinger, Scott A.; Redding, David C.

    2012-01-01

    The General MACOS Interface (GMI) for Modeling and Analysis for Controlled Optical Systems (MACOS) enables the use of MATLAB as a front-end for JPL s critical optical modeling package, MACOS. MACOS is JPL s in-house optical modeling software, which has proven to be a superb tool for advanced systems engineering of optical systems. GMI, coupled with MACOS, allows for seamless interfacing with modeling tools from other disciplines to make possible integration of dynamics, structures, and thermal models with the addition of control systems for deformable optics and other actuated optics. This software package is designed as a tool for analysts to quickly and easily use MACOS without needing to be an expert at programming MACOS. The strength of MACOS is its ability to interface with various modeling/development platforms, allowing evaluation of system performance with thermal, mechanical, and optical modeling parameter variations. GMI provides an improved means for accessing selected key MACOS functionalities. The main objective of GMI is to marry the vast mathematical and graphical capabilities of MATLAB with the powerful optical analysis engine of MACOS, thereby providing a useful tool to anyone who can program in MATLAB. GMI also improves modeling efficiency by eliminating the need to write an interface function for each task/project, reducing error sources, speeding up user/modeling tasks, and making MACOS well suited for fast prototyping.

  11. A 4-D Climatology (1979-2009) of the Monthly Tropospheric Aerosol Optical Depth Distribution over the Mediterranean Region from a Comparative Evaluation and Blending of Remote Sensing and Model Products

    SciTech Connect

    Nabat, P.; Somot, S.; Mallet, M.; Chiapello, I.; Morcrette, J. -J.; Solmon, F.; Szopa, S.; Dulac, F.; Collins, W.; Ghan, Steven J.; Horowitz, L.; Lamarque, J.-F.; Lee, Y. H.; Naik, Vaishali; Nagashima, T.; Shindell, Drew; Skeie, R. B.

    2013-05-17

    Since the 1980s several spaceborne sensors have been used to retrieve the aerosol optical depth (AOD) over the Mediterranean region. In parallel, AOD climatologies coming from different numerical model simulations are now also available, permitting to distinguish the contribution of several aerosol types to the total AOD. In this work, we perform a comparative analysis of this unique multiyear database in terms of total AOD and of its apportionment by the five main aerosol types (soil dust, seasalt, sulfate, black and organic carbon). We use 9 different satellite-derived monthly AOD products: NOAA/AVHRR, SeaWiFS (2 products), TERRA/MISR, TERRA/MODIS, AQUA/MODIS, ENVISAT/MERIS, PARASOL/POLDER and MSG/SEVIRI, as well as 3 more historical datasets: NIMBUS7/CZCS, TOMS (onboard NIMBUS7 and Earth- Probe) and METEOSAT/MVIRI. Monthly model datasets include the aerosol climatology from Tegen et al. (1997), the climate-chemistry models LMDz-OR-INCA and RegCM-4, the multi-model mean coming from the ACCMIP exercise, and the reanalyses GEMS and MACC. Ground-based Level- 2 AERONET AOD observations from 47 stations around the basin are used here to evaluate the model and satellite data. The sensor MODIS (on AQUA and TERRA) has the best average AOD scores over this region, showing a relevant spatiotemporal variability and highlighting high dust loads over Northern Africa and the sea (spring and summer), and sulfate aerosols over continental Europe (summer). The comparison also shows limitations of certain datasets (especially MERIS and SeaWiFS standard products). Models reproduce the main patterns of the AOD variability over the basin. The MACC reanalysis is the closest to AERONET data, but appears to underestimate dust over Northern Africa, where RegCM-4 is found closer to MODIS thanks to its interactive scheme for dust emissions. The vertical dimension is also investigated using the CALIOP instrument. This study confirms differences of vertical distribution between dust aerosols

  12. A 4-D Climatology (1979-2009) of the Monthly Tropospheric Aerosol Optical Depth Distribution over the Mediterranean Region from a Comparative Evaluation and Blending of Remote Sensing and Model Products

    NASA Technical Reports Server (NTRS)

    Nabat, P.; Somot, S.; Mallet, M.; Chiapello, I; Morcrette, J. J.; Solomon, F.; Szopa, S.; Dulac, F; Collins, W.; Ghan, S.; Horowitz, L. W.; Lamarque, J. F.; Lee, Y. H.; Naik, V.; Nagashima, T.; Shindell, D.; Skeie, R.

    2013-01-01

    Since the 1980s several spaceborne sensors have been used to retrieve the aerosol optical depth (AOD) over the Mediterranean region. In parallel, AOD climatologies coming from different numerical model simulations are now also available, permitting to distinguish the contribution of several aerosol types to the total AOD. In this work, we perform a comparative analysis of this unique multiyear database in terms of total AOD and of its apportionment by the five main aerosol types (soil dust, seasalt, sulfate, black and organic carbon). We use 9 different satellite-derived monthly AOD products: NOAA/AVHRR, SeaWiFS (2 products), TERRA/MISR, TERRA/MODIS, AQUA/MODIS, ENVISAT/MERIS, PARASOL/POLDER and MSG/SEVIRI, as well as 3 more historical datasets: NIMBUS7/CZCS, TOMS (onboard NIMBUS7 and Earth- Probe) and METEOSAT/MVIRI. Monthly model datasets include the aerosol climatology from Tegen et al. (1997), the climate-chemistry models LMDz-OR-INCA and RegCM-4, the multi-model mean coming from the ACCMIP exercise, and the reanalyses GEMS and MACC. Ground-based Level- 2 AERONET AOD observations from 47 stations around the basin are used here to evaluate the model and satellite data. The sensor MODIS (on AQUA and TERRA) has the best average AOD scores over this region, showing a relevant spatio-temporal variability and highlighting high dust loads over Northern Africa and the sea (spring and summer), and sulfate aerosols over continental Europe (summer). The comparison also shows limitations of certain datasets (especially MERIS and SeaWiFS standard products). Models reproduce the main patterns of the AOD variability over the basin. The MACC reanalysis is the closest to AERONET data, but appears to underestimate dust over Northern Africa, where RegCM-4 is found closer to MODIS thanks to its interactive scheme for dust emissions. The vertical dimension is also investigated using the CALIOP instrument. This study confirms differences of vertical distribution between dust

  13. Optical trapping of a spherically symmetric sphere in the ray-optics regime: a model for optical tweezers upon cells

    SciTech Connect

    Chang Yiren; Hsu Long; Chi Sien

    2006-06-01

    Since their invention in 1986, optical tweezers have become a popular manipulation and force measurement tool in cellular and molecular biology. However, until recently there has not been a sophisticated model for optical tweezers on trapping cells in the ray-optics regime. We present a model for optical tweezers to calculate the optical force upon a spherically symmetric multilayer sphere representing a common biological cell. A numerical simulation of this model shows that not only is the magnitude of the optical force upon a Chinese hamster ovary cell significantly three times smaller than that upon a polystyrene bead of the same size, but the distribution of the optical force upon a cell is also much different from that upon a uniform particle, and there is a 30% difference in the optical trapping stiffness of these two cases. Furthermore, under a small variant condition for the refractive indices of any adjacent layers of the sphere, this model provides a simple approximation to calculate the optical force and the stiffness of an optical tweezers system.

  14. Analytical model for a polymer optical fiber under dynamic bending

    NASA Astrophysics Data System (ADS)

    Leal Junior, Arnaldo G.; Frizera, Anselmo; Pontes, Maria José

    2017-08-01

    Advantages such as sensibility in bending, high fracture toughness, and high sensibility in strain enable the application of polymer optical fibers as sensors for strain, temperature, level, and for angle measurements. In order to enhance the sensor design, this paper presents an analytical model for a side polished polymer optical fiber under dynamic bending. Differently from analytical models that use only the geometrical optics approach with no correction for the stress-optical effects, here the refractive index is corrected at every bending angle to consider the stress-optical effects observed polymer optical fibers. Furthermore, the viscoelastic response of the polymer is also considered. The model is validated in quasi-static and dynamic tests for a polymer optical fiber curvature sensor. Results show good agreement between the model and the experiments.

  15. Estimation of partial optical path length in the brain in subject-specific head models for near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Nakamura, Kotaro; Kurihara, Kazuki; Kawaguchi, Hiroshi; Obata, Takayuki; Ito, Hiroshi; Okada, Eiji

    2016-04-01

    Three-dimensional head models with the structures constructed from the MR head images of 40 volunteers were constructed to analyze light propagation in the subject-specific head models. The mean optical path length in the head and the partial optical path length in the brain at 13 fiducial points for each volunteer were estimated to evaluate the intersubject and spatial variability in the optical path lengths. Although the intersubject variability in the optical path lengths is very high, the spatial variability in the average of the mean optical path length and partial optical path length is similar to the previously reported data. The mean optical path length in the head increases, whereas the partial optical path length in the brain decreases with an increase in the depth of the brain surface. The partial optical path length is highly correlated with the depth of the brain surface in comparison to the mean optical path length in the head.

  16. Non-rotational aspherical models of the human optical system

    NASA Astrophysics Data System (ADS)

    Giovanzana, S.; Kasprzak, H. T.; Pałucki, B.; Ţălu, Ş.

    2013-12-01

    The aim of this work was to define three-dimensional (3D) non-rotational aspherical parametric models for the human cornea and lens using computational geometry and CAD representations. The hyperbolic cosine based function is used for the cornea and a parametric model is used for lens modeling. Data analysis and visualization of 3D non-rotational models were made using the Rhinoceros CAD software and MATLAB software was used for numeric computation. We combined, implemented, and evaluated these models with a 3D ray-tracing in order to fully analyze the human eye model. It was found that 3D non-rotational aspherical models for the human eye could be more accurately modeled and rendered for analysis with finite element method. The objective of this study is to present and analyze mathematical models of the cornea and lens and to highlight the potential of optical applications of the eye models containing astigmatic surfaces, which are more close to the real eye than spherosymmetric eye models.

  17. Choriocapillaris evaluation in choroideremia using optical coherence tomography angiography

    PubMed Central

    Gao, Simon S.; Patel, Rachel C.; Jain, Nieraj; Zhang, Miao; Weleber, Richard G.; Huang, David; Pennesi, Mark E.; Jia, Yali

    2016-01-01

    The choriocapillaris plays an important role in supporting the metabolic demands of the retina. Studies of the choriocapillaris in disease states with optical coherence tomography angiography (OCTA) have proven insightful. However, image artifacts complicate the identification and quantification of the choriocapillaris in degenerative diseases such as choroideremia. Here, we demonstrate a supervised machine learning approach to detect intact choriocapillaris based on training with results from an expert grader. We trained a random forest classifier to evaluate en face structural OCT and OCTA information along with spatial image features. Evaluation of the trained classifier using previously unseen data showed good agreement with manual grading. PMID:28101400

  18. Optical modeling of Fresnel zoneplate microscopes.

    PubMed

    Naulleau, Patrick P; Mochi, Iacopo; Goldberg, Kenneth A

    2011-07-10

    Defect free masks remain one of the most significant challenges facing the commercialization of extreme ultraviolet (EUV) lithography. Progress on this front requires high-performance wavelength-specific metrology of EUV masks, including high-resolution and aerial-image microscopy performed near the 13.5 nm wavelength. Arguably the most cost-effective and rapid path to proliferating this capability is through the development of Fresnel zoneplate-based microscopes. Given the relative obscurity of such systems, however, modeling tools are not necessarily optimized to deal with them and their imaging properties are poorly understood. Here we present a modeling methodology to analyze zoneplate microscopes based on commercially available optical modeling software and use the technique to investigate the imaging performance of an off-axis EUV microscope design. The modeling predicts that superior performance can be achieved by tilting the zoneplate, making it perpendicular to the chief ray at the center of the field, while designing the zoneplate to explicitly work in that tilted plane. Although the examples presented here are in the realm of EUV mask inspection, the methods described and analysis results are broadly applicable to zoneplate microscopes in general, including full-field soft-x-ray microscopes routinely used in the synchrotron community.

  19. Optical modeling of Fresnel zoneplate microscopes

    SciTech Connect

    Naulleau, Patrick P.; Mochi, Iacopo; Goldberg, Kenneth A.

    2011-07-10

    Defect free masks remain one of the most significant challenges facing the commercialization of extreme ultraviolet (EUV) lithography. Progress on this front requires high-performance wavelength-specific metrology of EUV masks, including high-resolution and aerial-image microscopy performed near the 13.5 nm wavelength. Arguably the most cost-effective and rapid path to proliferating this capability is through the development of Fresnel zoneplate-based microscopes. Given the relative obscurity of such systems, however, modeling tools are not necessarily optimized to deal with them and their imaging properties are poorly understood. Here we present a modeling methodology to analyze zoneplate microscopes based on commercially available optical modeling software and use the technique to investigate the imaging performance of an off-axis EUV microscope design. The modeling predicts that superior performance can be achieved by tilting the zoneplate, making it perpendicular to the chief ray at the center of the field, while designing the zoneplate to explicitly work in that tilted plane. Although the examples presented here are in the realm of EUV mask inspection, the methods described and analysis results are broadly applicable to zoneplate microscopes in general, including full-field soft-x-ray microscopes routinely used in the synchrotron community.

  20. Optical modeling of Fresnel zoneplate microscopes

    SciTech Connect

    Naulleau, Patrick; Mochi, Iacopo; Goldberg, Kenneth A.

    2011-04-06

    Defect free masks remain one of the most significant challenges facing the commercialization of extreme ultraviolet (EUV) lithography. Progress on this front requires high-performance wavelength-specific metrology of EUV masks, including high-resolution and aerial-image microscopy performed near the 13.5 nm wavelength. Arguably the most cost-effective and rapid path to proliferating this capability is through the development of Fresnel zoneplate-based microscopes. Given the relative obscurity of such systems, however, modeling tools are not necessarily optimized to deal with them and their imaging properties are poorly understood. Here we present a modeling methodology to analyze zoneplate microscopes based on commercially available optical modeling software and use the technique to investigate the imaging performance of an off-axis EUV microscope design. The modeling predicts that superior performance can be achieved by tilting the zoneplate, making it perpendicular to the chief ray at the center of the field, while designing the zoneplate to explicitly work in that tilted plane. Although the examples presented here are in the realm of EUV mask inspection, the methods described and analysis results are broadly applicable to zoneplate microscopes in general, including full-field soft-x-ray microscopes rou tinely used in the synchrotron community.

  1. Dynamic ray tracing for modeling optical cell manipulation.

    PubMed

    Sraj, Ihab; Szatmary, Alex C; Marr, David W M; Eggleton, Charles D

    2010-08-02

    Current methods for predicting stress distribution on a cell surface due to optical trapping forces are based on a traditional ray optics scheme for fixed geometries. Cells are typically modeled as solid spheres as this facilitates optical force calculation. Under such applied forces however, real and non-rigid cells can deform, so assumptions inherent in traditional ray optics methods begin to break down. In this work, we implement a dynamic ray tracing technique to calculate the stress distribution on a deformable cell induced by optical trapping. Here, cells are modeled as three-dimensional elastic capsules with a discretized surface with associated hydrodynamic forces calculated using the Immersed Boundary Method. We use this approach to simulate the transient deformation of spherical, ellipsoidal and biconcave capsules due to external optical forces induced by a single diode bar optical trap for a range of optical powers.

  2. Evaluating optical aberrations using fluorescent microspheres: methods, analysis, and corrective actions.

    PubMed

    Goodwin, Paul C

    2013-01-01

    Obtaining optimal performance from a microscopy system requires careful evaluation of the entire optics train of the imaging system. This evaluation starts with a fundamental evaluation of the optical components in the microscope. Concise and visual methods are provided for understanding the optical performance of the microscope as a system using subdiffraction fluorescent microspheres to evaluate both monochromatic and polychromatic aberrations. Further practical guides are given to troubleshooting optical problems and final comments are made on optimizing sample preparation.

  3. Bio-optical modeling of primary production on regional scales: the Bermuda BioOptics project

    NASA Astrophysics Data System (ADS)

    Siegel, D. A.; Westberry, T. K.; O'Brien, M. C.; Nelson, N. B.; Michaels, A. F.; Morrison, J. R.; Scott, A.; Caporelli, E. A.; Sorensen, J. C.; Maritorena, S.; Garver, S. A.; Brody, E. A.; Ubante, J.; Hammer, M. A.

    Regional to global scale estimates of primary production must rely on remotely sensed quantities. Here, we characterize in situ light-primary production relationships and assess the predictive capability of several global primary production models using a 6-yr time series collected as part of the US JGOFS Bermuda Atlantic Time Series (BATS). The consistency and longevity of this data set provide an excellent opportunity to evaluate bio-optical modeling methodologies and their predictive capabilities for estimating rates of water-column-integrated primary production, ∫PP, for use with satellite ocean-color observations. We find that existing and regionally tuned parameterizations for vertically integrated chlorophyll content and euphotic zone depth do not explain much of the observed variability at this site. Fortunately, the use of these parameterizations for light availability and harvesting capacity has little influence upon modeled rates of ∫PP. Site-specific and previously published global models of primary production both perform poorly and account for less than 40% of the variance in ∫PP. A sensitivity analysis is performed to demonstrate the importance of light-saturated rates of primary production, P sat∗, compared with other photophysiological parameters. This is because nearly one-half of ∫PP occurs under light-saturated conditions. Unfortunately, we were unable to derive a simple parameterization for P sat∗that significantly improves prediction of ∫PP. The failure of global ∫PP models to encapsulate a major portion of the observed variance is due in part to the restricted range of ∫PP observations for this site. A similar result is found comparing global chlorophyll-reflectance algorithms to the present observations. More importantly, we demonstrate that there exists a time-scale (roughly 200 d) above which the modeled distributions of ∫PP are consistent with the observational data. By low-pass filtering the observed and modeled

  4. Advocacy Evaluation: A Model for Internal Evaluation Offices.

    ERIC Educational Resources Information Center

    Sonnichsen, Richard C.

    1988-01-01

    As evaluations are more often implemented by internal staff, internal evaluators must begin to assume decision-making and advocacy tasks. This advocacy evaluation concept is described using the Federal Bureau of Investigation evaluation staff as a model. (TJH)

  5. GENOPTICS- A GENERAL OPTICAL SYSTEMS EVALUATION PROGRAM (DEC VAX VERSION)

    NASA Technical Reports Server (NTRS)

    Wilsom, M. E.

    1994-01-01

    The General Optical Systems Evaluation Program, GENOPTICS, was developed as an aid for the analysis and evaluation of optical systems that employ lenses, mirrors, diffraction gratings, and other geometrical surfaces. The GENOPTICS evaluation is performed by means of geometrical ray tracing based upon Snell's law. The GENOPTICS program can provide for the exact ray tracing of as many as 800 rays through as many as 40 surfaces. These surfaces may be planar, conic, toric, or polynomial shaped lenses, mirrors, and diffraction gratings. Each surface may be tilted about as many as three axes and may be decentered. Surfaces having bilateral symmetry may also be analyzed. GENOPTICS provides for user-oriented input and for a wide range of output for the evaluation of the optical system being analyzed. GENOPTICS provides a wide range of features for the optical system analyst. GENOPTICS performs paraxial ray tracing and computation of the third order aberrations including aspheric contribution. Graphical output can be generated for spot diagrams, radial energy distributions, and modulation transfer functions, for each object point and each color. Sag tables may be generated for any rotationally symmetric surface, with options to obtain the sag differences from a reference sphere in units of lengths or wavelengths. Statistics and plots of ray intercepts with any surface in the system may be obtained for use in vignetting analysis and beam distribution analysis. Afocal systems can be examined with image statistics generated in terms of tangents of angles with respect to the optical axis. For exact ray tracing, a ray pattern at the entrance pupil can be specified as a rectangular or polar grid, where each ray samples an equal amount of area, or as a pattern where each ray samples an equal amount of solid angle for a finite object. This latter pattern is useful in radiometric work. Input to GENOPTICS includes program control statements, system definition data, surface data, and

  6. Numerical modeling of LCD electro-optical performance

    NASA Astrophysics Data System (ADS)

    Woehler, Henning; Becker, Michael E.

    2002-06-01

    Realization of complex high information density LCDs and systematic optimization of their electro-optical and ergonomic performance would not be possible in the required time-frame without reliable numerical modeling of the electro-optical performance of such display devices. In this paper we outline the history of numerical LDC modeling starting with Berreman and van Doorn, finally arriving at modern state-of-the-art LCD-modeling in two and three dimensions. Numerical modeling of LCDs is carried out in two steps: first, the effect of the electrical field on the orientation of the liquid crystalline alignment has to be evaluated before the corresponding optical properties can be computed. Starting from LC-elasticity theory we present suitable numerical methods for computing various states of LC-deformation (stable, metastable, bistable, etc.) in one- dimensional problems Light propagation in layered anisotropic absorbing media is evaluated with methods that are based on Maxwell's equations (Berreman 4 X 4-matrix approach). This approach can be simplified to yield methods with reduced computing time and sufficient accuracy for many problems (e.g. extended Jones 2 X 2-matrix formalism). A finite element method with automatic mesh generation and refinement for computing accurate solutions in two- dimensional problems is presented and its application illustrated with examples (e.g. IPS-effect, VAN-cells, etc.). In two- and three-dimensional problems, i.e. in cells with lateral dimensions comparable to the cell thickness, a variety of different director configurations are possible for a given geometry and electrical driving and addressing, making the modeling more complicated. Moreover, local defects can occur, which should also be considered in the simulation. Suitable approaches for the director field calculation, i.e. the vector and the tensor approach, are discussed. The complexity of the problem increases considerably when a third dimension is added, e.g. the

  7. Quantitative evaluation of registration methods for atlas-based diffuse optical tomography

    NASA Astrophysics Data System (ADS)

    Wu, Xue; Eggebrecht, Adam T.; Culver, Joseph P.; Zhan, Yuxuan; Basevi, Hector; Dehghani, Hamid

    2013-06-01

    In Diffuse Optical Tomography (DOT), an atlas-based model can be used as an alternative to a subject-specific anatomical model for recovery of brain activity. The main step of the generation of atlas-based subject model is the registration of atlas model to the subject head. The accuracy of the DOT then relies on the accuracy of registration method. In this work, 11 registration methods are quantitatively evaluated. The registration method with EEG 10/20 systems with 19 landmarks and non-iterative point to point algorithm provides approximately 1.4 mm surface error and is considered as the most efficient registration method.

  8. Evaluation of a IMU with optical fiber gyros in dynamic windtunnel tests

    NASA Astrophysics Data System (ADS)

    Takizawa, Minoru; Sasa, Shuichi; Nagayasu, Masahiko; Kajoka, Hiroshi; Iizuka, Toshio

    A study of dynamic windtunnel tests using a 5 percent cable-mounted model of the NAL spaceplane was carried out to identify aerodynamic parameters of the Spaceplane at National Aerospace Laboratory (NAL). In this study, an inertial measuring unit with optical fiber gyros, which will be installed on the model and will be used to measure angular rates about three axes of the model, has been developed and evaluated in dynamic windtunnel tests. It is reported that the IMU has been used effectively in the control system of the model; however, the accuracy, resolution, and frequency response of the OFG-3 were insufficient for the dynamic windtunnel tests.

  9. Optical evaluation on the setting of cement paste

    NASA Astrophysics Data System (ADS)

    De León Martínez, H. A.; Bernal, J. J. Soto; González Mota, R.; Rosales-Candelas, I.

    2015-01-01

    In the construction area, one of the most widely used cement is the CPC 30R, it is a hydraulic binder consisting of CaO, SiO2, Al2O3 and Fe2O3, when mixed with water forms cement pastes and its four crystallographic phases start to hydrate. The diffuse reflection on cement paste can give an indication of the behaviour on optical properties on the hydration of the cement and early formation products. In this study, Portland cement (CPC) pastes were prepared with 0.45 a water to cement ratio (w/c). This work is aimed to evaluate the optical properties of cement pastes on the hydration reaction during the first 24 hours by measuring the intensity of diffuse reflection changes.

  10. Design and Performance Evaluation of Optical Ethernet Switching Architecture with Liquid Crystal on Silicon-Based Beam-Steering Technology

    NASA Astrophysics Data System (ADS)

    Cheng, Yuh-Jiuh; Chou, H.-H.; Shiau, Yhi; Cheng, Shu-Ying

    2016-07-01

    A non-blocking optical Ethernet switching architecture with liquid crystal on a silicon-based beam-steering switch and optical output buffer strategies are proposed. For preserving service packet sequencing and fairness of routing sequence, priority and round-robin algorithms are adopted at the optical output buffer in this research. Four methods were used to implement tunable fiber delay modules for the optical output buffers to handle Ethernet packets with variable bit-rates. The results reported are based on the simulations performed to evaluate the proposed switching architecture with traffic analysis under a traffic model captured from a real-core network.

  11. Optical laboratory solution and error model simulation of a linear time-varying finite element equation

    NASA Technical Reports Server (NTRS)

    Taylor, B. K.; Casasent, D. P.

    1989-01-01

    The use of simplified error models to accurately simulate and evaluate the performance of an optical linear-algebra processor is described. The optical architecture used to perform banded matrix-vector products is reviewed, along with a linear dynamic finite-element case study. The laboratory hardware and ac-modulation technique used are presented. The individual processor error-source models and their simulator implementation are detailed. Several significant simplifications are introduced to ease the computational requirements and complexity of the simulations. The error models are verified with a laboratory implementation of the processor, and are used to evaluate its potential performance.

  12. Constitutive Modeling of the Mechanical Properties of Optical Fibers

    NASA Technical Reports Server (NTRS)

    Moeti, L.; Moghazy, S.; Veazie, D.; Cuddihy, E.

    1998-01-01

    Micromechanical modeling of the composite mechanical properties of optical fibers was conducted. Good agreement was obtained between the values of Young's modulus obtained by micromechanics modeling and those determined experimentally for a single mode optical fiber where the wave guide and the jacket are physically coupled. The modeling was also attempted on a polarization-maintaining optical fiber (PANDA) where the wave guide and the jacket are physically decoupled, and found not to applicable since the modeling required perfect bonding at the interface. The modeling utilized constituent physical properties such as the Young's modulus, Poisson's ratio, and shear modulus to establish bounds on the macroscopic behavior of the fiber.

  13. Modeling propagation of coherent optical pulses through molecular vapor

    SciTech Connect

    Shore, B.W.; Eberly, J.H.

    1982-01-01

    Results of modeling the mutual coupling of coherent molecular response and coherent optical pulses during propagation are described. The propagation is treated numerically, with particular emphasis on both continuum and discrete behavior associated with the quasicontinuum model.

  14. Modeling optical absorption for thermoreflectance measurements

    NASA Astrophysics Data System (ADS)

    Yang, Jia; Ziade, Elbara; Schmidt, Aaron J.

    2016-03-01

    Optical pump-probe techniques based on thermoreflectance, such as time domain thermoreflectance and frequency domain thermoreflectance (FDTR), have been widely used to characterize the thermal conductivity of thin films and the thermal conductance across interfaces. These techniques typically use a transducer layer to absorb the pump light and improve the thermoreflectance signal. The transducer, however, complicates the interpretation of the measured signal because the approximation that all the energy from the pump beam is deposited at the transducer surface is not always accurate. In this paper, we consider the effect of laser absorption in the top layer of a multilayer sample, and derive an analytical solution for the thermoreflectance signal in the diffusion regime based on volumetric heating. We analyze the measurement sensitivity to the pump absorption depth for transducers with different thermal conductivities, and investigate the additional effect of probe laser penetration depth on the measured signal. We validate our model using FDTR measurements on 490 nm thick amorphous silicon films deposited on fused silica and silicon substrates.

  15. Quantitative security evaluation of optical encryption using hybrid phase- and amplitude-modulated keys.

    PubMed

    Sarkadi, Tamás; Koppa, Pál

    2012-02-20

    In the increasing number of system approaches published in the field of optical encryption, the security level of the system is evaluated by qualitative and empirical methods. To quantify the security of the optical system, we propose to use the equivalent of the key length routinely used in algorithmic encryption. We provide a calculation method of the number of independent keys and deduce the binary key length for optical data encryption. We then investigate and optimize the key length of the combined phase- and amplitude-modulated key encryption in the holographic storage environment, which is one of the promising solutions for the security enhancement of single- and double-random phase-encoding encryption and storage systems. We show that a substantial growth of the key length can be achieved by optimized phase and amplitude modulation compared to phase-only encryption. We also provide experimental confirmation of the model results.

  16. Evaluation of systems and components for hybrid optical firing sets

    SciTech Connect

    Landry, M.J.; Rupert, J.W.; Mittas, A.

    1989-06-01

    High-energy density light appears to be a unique energy form that may be used to enhance the nuclear safety of weapon systems. Hybrid optical firing sets (HOFS) utilize the weak-link/strong-link exclusion region concept for nuclear safety; this method is similar to present systems, but uses light to transmit power across the exclusion region barrier. This report describes the assembling, operating, and testing of fourteen HOFS. These firing sets were required to charge a capacitor-discharge unit to 2.0 and 2.5 kV (100 mJ) in less than 1 s. First, we describe the components, the measurement techniques used to evaluate the components, and the different characteristics of the measured components. Second, we describe the HOFS studied, the setups used for evaluating them, and the resulting characteristics. Third, we make recommendations for improving the overall performance and suggest the best HOFS for packaging. 36 refs., 145 figs., 14 tabs.

  17. Evaluation of embolic deflection device using optical particle tracking.

    PubMed

    Ionita, Ciprian N; Bednarek, Daniel R; Rudin, Stephen

    2013-03-29

    Trans-aortic valve replacement is a new endovascular procedure which has started to be used routinely in cardiac interventional suites. During such procedures a stent-like device containing new aortic valves is placed over the damaged ones, possibly causing calcifications to be dislodged and released in arteries leading to stroke. To prevent such events, new devices are being developed to provide distal protection to the brain supplying arteries. Currently there is a need to evaluate such device efficacy in a repeatable manner. We are proposing and investigating such a method based on particle optical tracking. We simulated such protective devices using two porous screens (150 and 200 μm pore size) which were placed in an arterial bifurcation phantom connected to a clinically relevant flow loop. A mask was acquired and gold embolic particles (100-300μm) were injected at a steady rate using a motorized injector. Optical images with 2 ms exposure were acquired at 30 fps. Images were subtracted, thresholded and filtered using a 5×5 median filter. ROI's were drawn over the main and bifurcating arteries and a particle counting algorithm was used to estimate particle flow rates in each artery for each run. The unprotected and the two protected cases were evaluated. Before filter placement, the particle flow rate was 60 and 40 %, respectively, of the main artery. After the filter placement, the particle flow rate in the protected branch was 4% and 8% of the particle flow rate in the main artery. We present a method to assess the efficacy of such devices using an optical particle tracking and counting technique.

  18. Sequentially Executed Model Evaluation Framework

    SciTech Connect

    2015-10-20

    Provides a message passing framework between generic input, model and output drivers, and specifies an API for developing such drivers. Also provides batch and real-time controllers which step the model and I/O through the time domain (or other discrete domain), and sample I/O drivers. This is a library framework, and does not, itself, solve any problems or execute any modeling. The SeMe framework aids in development of models which operate on sequential information, such as time-series, where evaluation is based on prior results combined with new data for this iteration. Has applications in quality monitoring, and was developed as part of the CANARY-EDS software, where real-time water quality data is being analyzed for anomalies.

  19. Sequentially Executed Model Evaluation Framework

    SciTech Connect

    2014-02-14

    Provides a message passing framework between generic input, model and output drivers, and specifies an API for developing such drivers. Also provides batch and real-time controllers which step the model and 1/0 through the time domain (or other discrete domain), and sample 1/0 drivers. This is a Framework library framework, and does not, itself, solve any problems or execute any modelling. The SeMe framework aids in development of models which operate on sequential information, such as time-series, where evaluation is based on prior results combined with new data for this iteration. Ha) applications in quality monitoring, and was developed as part of the CANARY-EDS software, where real-time water quality data is being analyzed

  20. A Taxonomy of Evaluation Models: Use of Evaluation Models in Program Evaluation.

    ERIC Educational Resources Information Center

    Carter, Wayne E.

    In the nine years following the passage of the Elementary Secondary Education Act (ESEA), several models have been developed to attempt to remedy the deficiencies in existing educational evaluation and decision theory noted by Stufflebeam and co-workers. Compilations of evaluation models have been undertaken and listings exist of models available…

  1. On a Decomposition Model for Optical Flow

    NASA Astrophysics Data System (ADS)

    Abhau, Jochen; Belhachmi, Zakaria; Scherzer, Otmar

    In this paper we present a variational method for determining cartoon and texture components of the optical flow of a noisy image sequence. The method is realized by reformulating the optical flow problem first as a variational denoising problem for multi-channel data and then by applying decomposition methods. Thanks to the general formulation, several norms can be used for the decomposition. We study a decomposition for the optical flow into bounded variation and oscillating component in greater detail. Numerical examples demonstrate the capabilities of the proposed approach.

  2. Infrasound Sensor Models and Evaluations

    SciTech Connect

    KROMER,RICHARD P.; MCDONALD,TIMOTHY S.

    2000-07-31

    Sandia National Laboratories has continued to evaluate the performance of infrasound sensors that are candidates for use by the International Monitoring System (IMS) for the Comprehensive Nuclear-Test-Ban Treaty Organization. The performance criteria against which these sensors are assessed are specified in ``Operational Manual for Infra-sound Monitoring and the International Exchange of Infrasound Data''. This presentation includes the results of efforts concerning two of these sensors: (1) Chaparral Physics Model 5; and (2) CEA MB2000. Sandia is working with Chaparral Physics in order to improve the capability of the Model 5 (a prototype sensor) to be calibrated and evaluated. With the assistance of the Scripps Institution of Oceanography, Sandia is also conducting tests to evaluate the performance of the CEA MB2000. Sensor models based on theoretical transfer functions and manufacturer specifications for these two devices have been developed. This presentation will feature the results of coherence-based data analysis of signals from a huddle test, utilizing several sensors of both types, in order to verify the sensor performance.

  3. Development of optical diagnostics for performance evaluation of arcjet thrusters

    NASA Technical Reports Server (NTRS)

    Cappelli, Mark A.

    1995-01-01

    Laser and optical emission-based measurements have been developed and implemented for use on low-power hydrogen arcjet thrusters and xenon-propelled electric thrusters. In the case of low power hydrogen arcjets, these laser induce fluorescence measurements constitute the first complete set of data that characterize the velocity and temperature field of such a device. The research performed under the auspices of this NASA grant includes laser-based measurements of atomic hydrogen velocity and translational temperature, ultraviolet absorption measurements of ground state atomic hydrogen, Raman scattering measurements of the electronic ground state of molecular hydrogen, and optical emission based measurements of electronically excited atomic hydrogen, electron number density, and electron temperature. In addition, we have developed a collisional-radiative model of atomic hydrogen for use in conjunction with magnetohydrodynamic models to predict the plasma radiative spectrum, and near-electrode plasma models to better understand current transfer from the electrodes to the plasma. In the final year of the grant, a new program aimed at developing diagnostics for xenon plasma thrusters was initiated, and results on the use of diode lasers for interrogating Hall accelerator plasmas has been presented at recent conferences.

  4. Fiber-optic interferometric sensors for measurements of pressure fluctuations: Experimental evaluation

    NASA Technical Reports Server (NTRS)

    Cho, Y. C.; Soderman, P. T.

    1993-01-01

    This paper addresses an anechoic chamber evaluation of a fiber-optic interferometric sensor (fiber-optic microphone), which is being developed at NASA Ames Research Center for measurements of pressure fluctuations in wind tunnels.

  5. GENOPTICS- A GENERAL OPTICAL SYSTEMS EVALUATION PROGRAM (IBM VERSION)

    NASA Technical Reports Server (NTRS)

    Howell, B. J.

    1994-01-01

    The General Optical Systems Evaluation Program, GENOPTICS, was developed as an aid for the analysis and evaluation of optical systems that employ lenses, mirrors, diffraction gratings, and other geometrical surfaces. The GENOPTICS evaluation is performed by means of geometrical ray tracing based upon Snell's law. The GENOPTICS program can provide for the exact ray tracing of as many as 800 rays through as many as 40 surfaces. These surfaces may be planar, conic, toric, or polynomial shaped lenses, mirrors, and diffraction gratings. Each surface may be tilted about as many as three axes and may be decentered. Surfaces having bilateral symmetry may also be analyzed. GENOPTICS provides for user-oriented input and for a wide range of output for the evaluation of the optical system being analyzed. GENOPTICS provides a wide range of features for the optical system analyst. GENOPTICS performs axial ray tracing and computation of the third order aberrations including aspheric contribution. The program includes a quasi-automatic ray-surface intersection selection option. Graphical output can be generated for spot diagrams, radial energy distributions, and modulation transfer functions, for each object point and each color. Sag tables may be generated for any rotationally symmetric surface, with options to obtain the sag differences from a reference sphere in units of lengths or wavelengths. Statistics and plots of ray intercepts with any surface in the system may be obtained for use in vignetting analysis and beam distribution analysis. Afocal systems can be examined with image statistics generated in terms of tangents of angles with respect to the optical axis. For exact ray tracing, a ray pattern at the entrance pupil can be specified as a rectangular or polar grid, where each ray samples an equal amount of area, or as a pattern where each ray samples an equal amount of solid angle for a finite object. This latter pattern is useful in radiometric work. Input to GENOPTICS

  6. Evaluation of the electro-optic direction sensor

    NASA Technical Reports Server (NTRS)

    Johnson, A. R.; Salomon, P. M.

    1973-01-01

    Evaluation of a no-moving-parts single-axis star tracker called an electro-optic direction sensor (EODS) concept is described and the results are given in detail. The work involved experimental evaluation of a breadboard sensor yielding results which would permit design of a prototype sensor for a specific application. The laboratory work included evaluation of the noise equivalent input angle of the sensor, demonstration of a technique for producing an acquisition signal, constraints on the useful field-of-view, and a qualitative evaluation of the effects of stray light. In addition, the potential of the silicon avalanche-type photodiode for this application was investigated. No benefit in noise figure was found, but the easily adjustable gain of the avalanche device was useful. The use of mechanical tuning of the modulating element to reduce voltage requirements was also explored. The predicted performance of EODS in both photomultiplier and solid state detector configurations was compared to an existing state-of-the-art star tracker.

  7. Evaluation on Radiometric Capability of Chinese Optical Satellite Sensors

    PubMed Central

    Yang, Aixia; Zhong, Bo; Wu, Shanlong; Liu, Qinhuo

    2017-01-01

    The radiometric capability of on-orbit sensors should be updated on time due to changes induced by space environmental factors and instrument aging. Some sensors, such as Moderate Resolution Imaging Spectroradiometer (MODIS), have onboard calibrators, which enable real-time calibration. However, most Chinese remote sensing satellite sensors lack onboard calibrators. Their radiometric calibrations have been updated once a year based on a vicarious calibration procedure, which has affected the applications of the data. Therefore, a full evaluation of the sensors’ radiometric capabilities is essential before quantitative applications can be made. In this study, a comprehensive procedure for evaluating the radiometric capability of several Chinese optical satellite sensors is proposed. In this procedure, long-term radiometric stability and radiometric accuracy are the two major indicators for radiometric evaluation. The radiometric temporal stability is analyzed by the tendency of long-term top-of-atmosphere (TOA) reflectance variation; the radiometric accuracy is determined by comparison with the TOA reflectance from MODIS after spectrally matching. Three Chinese sensors including the Charge-Coupled Device (CCD) camera onboard Huan Jing 1 satellite (HJ-1), as well as the Visible and Infrared Radiometer (VIRR) and Medium-Resolution Spectral Imager (MERSI) onboard the Feng Yun 3 satellite (FY-3) are evaluated in reflective bands based on this procedure. The results are reasonable, and thus can provide reliable reference for the sensors’ application, and as such will promote the development of Chinese satellite data. PMID:28117745

  8. Evaluation on Radiometric Capability of Chinese Optical Satellite Sensors.

    PubMed

    Yang, Aixia; Zhong, Bo; Wu, Shanlong; Liu, Qinhuo

    2017-01-22

    The radiometric capability of on-orbit sensors should be updated on time due to changes induced by space environmental factors and instrument aging. Some sensors, such as Moderate Resolution Imaging Spectroradiometer (MODIS), have onboard calibrators, which enable real-time calibration. However, most Chinese remote sensing satellite sensors lack onboard calibrators. Their radiometric calibrations have been updated once a year based on a vicarious calibration procedure, which has affected the applications of the data. Therefore, a full evaluation of the sensors' radiometric capabilities is essential before quantitative applications can be made. In this study, a comprehensive procedure for evaluating the radiometric capability of several Chinese optical satellite sensors is proposed. In this procedure, long-term radiometric stability and radiometric accuracy are the two major indicators for radiometric evaluation. The radiometric temporal stability is analyzed by the tendency of long-term top-of-atmosphere (TOA) reflectance variation; the radiometric accuracy is determined by comparison with the TOA reflectance from MODIS after spectrally matching. Three Chinese sensors including the Charge-Coupled Device (CCD) camera onboard Huan Jing 1 satellite (HJ-1), as well as the Visible and Infrared Radiometer (VIRR) and Medium-Resolution Spectral Imager (MERSI) onboard the Feng Yun 3 satellite (FY-3) are evaluated in reflective bands based on this procedure. The results are reasonable, and thus can provide reliable reference for the sensors' application, and as such will promote the development of Chinese satellite data.

  9. Novel applications of the dispersive optical model

    NASA Astrophysics Data System (ADS)

    Dickhoff, W. H.; Charity, R. J.; Mahzoon, M. H.

    2017-03-01

    A review of recent developments of the dispersive optical model (DOM) is presented. Starting from the original work of Mahaux and Sartor, several necessary steps are developed and illustrated which increase the scope of the DOM allowing its interpretation as generating an experimentally constrained functional form of the nucleon self-energy. The method could therefore be renamed as the dispersive self-energy method. The aforementioned steps include the introduction of simultaneous fits of data for chains of isotopes or isotones allowing a data-driven extrapolation for the prediction of scattering cross sections and level properties in the direction of the respective drip lines. In addition, the energy domain for data was enlarged to include results up to 200 MeV where available. An important application of this work was implemented by employing these DOM potentials to the analysis of the (d, p) transfer reaction using the adiabatic distorted wave approximation. We review these calculations which suggest that physically meaningful results are easier to obtain by employing DOM ingredients as compared to the traditional approach which relies on a phenomenologically-adjusted bound-state wave function combined with a global (nondispersive) optical-model potential. Application to the exotic 132Sn nucleus also shows great promise for the extrapolation of DOM potentials towards the drip line with attendant relevance for the physics of FRIB. We note that the DOM method combines structure and reaction information on the same footing providing a unique approach to the analysis of exotic nuclei. We illustrate the importance of abandoning the custom of representing the non-local Hartree–Fock (HF) potential in the DOM by an energy-dependent local potential as it impedes the proper normalization of the solution of the Dyson equation. This important step allows for the interpretation of the DOM potential as representing the nucleon self-energy permitting the calculations of

  10. Optical modeling in Testbed Environment for Space Situational Awareness (TESSA).

    PubMed

    Nikolaev, Sergei

    2011-08-01

    We describe optical systems modeling in the Testbed Environment for Space Situational Awareness (TESSA) simulator. We begin by presenting a brief outline of the overall TESSA architecture and focus on components for modeling optical sensors. Both image generation and image processing stages are described in detail, highlighting the differences in modeling ground- and space-based sensors. We conclude by outlining the applicability domains for the TESSA simulator, including potential real-life scenarios.

  11. Integral ceramic superstructure evaluation using time domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Sinescu, Cosmin; Bradu, Adrian; Topala, Florin I.; Negrutiu, Meda Lavinia; Duma, Virgil-Florin; Podoleanu, Adrian G.

    2014-02-01

    Optical Coherence Tomography (OCT) is a non-invasive low coherence interferometry technique that includes several technologies (and the corresponding devices and components), such as illumination and detection, interferometry, scanning, adaptive optics, microscopy and endoscopy. From its large area of applications, we consider in this paper a critical aspect in dentistry - to be investigated with a Time Domain (TD) OCT system. The clinical situation of an edentulous mandible is considered; it can be solved by inserting 2 to 6 implants. On these implants a mesostructure will be manufactured and on it a superstructure is needed. This superstructure can be integral ceramic; in this case materials defects could be trapped inside the ceramic layers and those defects could lead to fractures of the entire superstructure. In this paper we demonstrate that a TD-OCT imaging system has the potential to properly evaluate the presence of the defects inside the ceramic layers and those defects can be fixed before inserting the prosthesis inside the oral cavity. Three integral ceramic superstructures were developed by using a CAD/CAM technology. After the milling, the ceramic layers were applied on the core. All the three samples were evaluated by a TD-OCT system working at 1300 nm. For two of the superstructures evaluated, no defects were found in the most stressed areas. The third superstructure presented four ceramic defects in the mentioned areas. Because of those defects the superstructure may fracture. The integral ceramic prosthesis was send back to the dental laboratory to fix the problems related to the material defects found. Thus, TD-OCT proved to be a valuable method for diagnosing the ceramic defects inside the integral ceramic superstructures in order to prevent fractures at this level.

  12. Acousto-optic back-projection: Physical-model-based sound field reconstruction from optical projections

    NASA Astrophysics Data System (ADS)

    Yatabe, Kohei; Ishikawa, Kenji; Oikawa, Yasuhiro

    2017-04-01

    As an alternative to microphones, optical techniques have been studied for measuring a sound field. They enable contactless and non-invasive acoustical observation by detecting density variation of medium caused by sound. Although they have important advantages comparing to microphones, they also have some disadvantages. Since sound affects light at every points on the optical path, the optical methods observe an acoustical quantity as spatial integration. Therefore, point-wise information of a sound field cannot be obtained directly. Ordinarily, the computed tomography (CT) method has been applied for reconstructing a sound field from optically measured data. However, the observation process of the optical methods have not been considered explicitly, which limits the accuracy of the reconstruction. In this paper, a physical-model-based sound field reconstruction method is proposed. It explicitly formulates the physical observation process so that a model mismatch of the conventional methods is eliminated.

  13. [Nonarteritic ischemic optic neuropathy animal model and its treatment applications].

    PubMed

    Chuman, Hideki

    2014-04-01

    Nonarteritic ischemic optic neuropathy (NAION) is one of the most common acute unilaterally onset optic nerve diseases. One management problem in terms of NAION is the difficulty of differential diagnosis between NAION and anterior optic neuritis (ON). A second problem is that there is no established treatment for the acute stage of NAION. A third problem is that there is no preventive treatment for a subsequent attack on the fellow eye, estimated to occur in 15 to 25% of patients with NAION. For differentiation of acute NAION from anterior optic neuritis, we investigated the usefulness of laser speckle flowgraphy (LSFG). In the normal control group, the tissue blood flow did not significantly differ between the right and left eyes. In the NAION group, all 6 patients had 29.5% decreased mean blur rate (MBR), which correlates to optic disc blood flow, of the NAION eye compared with the unaffected eye. In the anterior ON group, all 6 cases had 15.9% increased MBR of the anterior ON eye compared with the unaffected eye. Thus, LSFG showed a difference of the underlying pathophysiology between NAION and anterior ON despite showing disc swelling in both groups and could be useful for differentiating both groups. For the treatment of acute stage of NAION, we tried to reproduce the rodent model of NAION (rNAION) developed by Bernstein and colleagues. To induce rNAION, after the administration of rose bengal(RB) (2.5 mM) into the tail vein of SD rats, the small vessels of the left optic nerve were photoactivated using a 514 nm argon green laser (RB-laser-induction). In the RB-laser-induction eyes, the capillaries within the optic disc were reduced markedly, the optic disc became swollen, and fluorescein angiography showed filling defect in the choroid and the optic disc at an early stage, followed by hyperfluorescence at a late stage. Electrophysiological evaluation revealed that visual evoked potential (VEP) amplitude was significantly decreased but an electroretinogram

  14. Evaluation strategies for CNSs: application of an evaluation model.

    PubMed

    Kennedy-Malone, L M

    1996-07-01

    Program development has become an essential role function for today's CNS, who must be able to evaluate programs to determine their efficacy. A useful evaluation guide is Stufflebeam's CIPP (context, input, process, and product) model, which includes a framework to evaluate indirect care measures directly affecting cost-effectiveness and accountability. The model's core consists of (1) context evaluation leading to informed, contemplated decisions; (2) input evaluation directing structured decisions; (3) process evaluation guiding implemented decisions; and (4) product evaluation serving to recycle decisions. Strategies for using Stufflebeam's CIPP model are described.

  15. Dynamic viscoelastic models of human skin using optical elastography

    PubMed Central

    Kearney, Steven P.; Khan, Altaf; Dai, Zoujun; Royston, Thomas J.

    2015-01-01

    A novel technique for measuring in vivo human skin viscoelastic properties using optical elastography has been developed. The technique uses geometrically focused surface (GFS) waves that allow for wide bandwidth measurements of the wave field. An analytical solution for the case of a radiating annular disk surface source was fit to experimentally measured GFS waves, enabling an estimate of the frequency-dependent surface wavenumber, which can then be related to the dynamic shear modulus. Several viscoelastic models were then fit to the dynamic shear modulus dispersion curve. Viscoelastic models were evaluated based on their overall quality of fit and variability amongst healthy volunteers. An Ecoflex phantom was used to validate the procedure and results by comparison to similar studies using the same type of phantom. For skin results, it was found that the “α” parameters from the fractional models had the least variability, with coefficients of variability of 0.15, and 0.16. The best fitting models were the standard linear solid, and the fractional Voigt, with a mean fit correlation coefficient, R2, of 0.93, 0.89, respectively. This study has demonstrated the efficacy of this new method, and with larger studies the viscoelastic skin models could be used to identify various skin diseases and their response to treatment. PMID:26305137

  16. Evaluation of colour space transformation suitability to optical temperature measurements

    NASA Astrophysics Data System (ADS)

    Ziemba, A.; Fornalik-Wajs, E.

    2016-09-01

    All optical measurement methods base on the image analysis and relation between the measured parameter and some image features. In Digital Particle Image Thermometry (DPIT), such relation represents a function between the temperature and particles’ colour (i.a. Thermochromic Liquid Crystals). For the quantitative data acquisition the “colour” information is necessary, therefore the colour spaces based on hue H are used. Due to the big number of numerical operations needed in the analysis, the choice of colour space transformation is significant due to the accuracy and computational time. In this paper commonly applied RGB to HSI colour spaces’ transformations were compared and evaluation of their suitability to temperature measurement was performed. Time of obtaining the final results was considered as the main criterion. Appropriate calculations were conducted and presented.

  17. Performance evaluation of a sensorless adaptive optics multiphoton microscope.

    PubMed

    Skorsetz, Martin; Artal, Pablo; Bueno, Juan M

    2016-03-01

    A wavefront sensorless adaptive optics technique was combined with a custom-made multiphoton microscope to correct for specimen-induced aberrations. A liquid-crystal-on-silicon (LCoS) modulator was used to systematically generate Zernike modes during image recording. The performance of the instrument was evaluated in samples providing different nonlinear signals and the benefit of correcting higher order aberrations was always noticeable (in both contrast and resolution). The optimum aberration pattern was stable in time for the samples here involved. For a particular depth location within the sample, the wavefront to be precompensated was independent on the size of the imaged area (up to ∼ 360 × 360 μm(2)). The mode combination optimizing the recorded image depended on the Zernike correction control sequence; however, the final images hardly differed. At deeper locations, a noticeable dominance of spherical aberration was found. The influence of other aberration terms was also compared to the effect of the spherical aberration.

  18. Theoretical model of the modulation transfer function for fiber optic taper

    NASA Astrophysics Data System (ADS)

    Wang, Yaoxiang; Tian, Weijian; Bin, XiangLi

    2005-02-01

    Fiber optic taper has been used more and more widely as a relay optical component in the integrated taper assembly image intensified sensors for military and medical imaging application. In this paper, the transmission characteristic of energy in the taper is analyzed, and following the generalized definition of the modulation transfer function for sampled imaging system, a spatial averaged impulse response and a corresponding MTF component that are inherent in the sampling process of taper are deduced, and the mathematical model for evaluating the modulation transfer function of fiber optic taper is built. Finally, the dynamic and static modulation transfer function curves simulated by computer have been exhibited.

  19. Modeling The Atmosphere As An Unguided Optical Communications Channel

    NASA Astrophysics Data System (ADS)

    Nuber, Raymond M.

    1989-07-01

    Due to the increasing number of applications for optical communications, methods such as computer simulation are needed for the performance analysis of these systems. The objective of this paper is to propose a system level model for simulating the Earth's atmosphere as an unguided optical communications channel. The major degradations in received optical intensity introduced by the atmosphere are scintillation, beam spreading, beam wander, and atmospheric transmissivity. The model presented here considers scintillation and beam wander to impose random fading in the received signal while beam spreading is a constant loss in intensity. Atmospheric transmissivity is treated as a filter-like channel transfer function. Relationships for the parameters of the model are given in terms of parameters which characterize the optical link. Also included is a description of an implementation of the model.

  20. SCRAM: A fast computational model for the optical performance of point focus solar central receiver systems

    NASA Astrophysics Data System (ADS)

    Bergeron, K. D.; Chiang, C. J.

    1980-04-01

    A mathematical approximation procedure, designated Sandia Central Receiver Approximation Model is described. A computational procedure which allows the user to define the heliostat field boundaries and tower height arbitrarily, generating a model for optical field performance, including shadowing, blocking, cosine, losses, and atmospheric attenuation, and which requires only a polynomial evaluation for each set of Sun angles was developed. One reason that the accuracy in field performance predictions is higher than that of the generating function for the model is that much of the error in the generating function is due to an oscillatory behavior associated with a moire pattern in the optical response of the heliostat field.

  1. A preliminary weather model for optical communications through the atmosphere

    NASA Technical Reports Server (NTRS)

    Shaik, K. S.

    1988-01-01

    A preliminary weather model is presented for optical propagation through the atmosphere. It can be used to compute the attenuation loss due to the atmosphere for desired link availability statistics. The quantitative results that can be obtained from this model provide good estimates for the atmospheric link budget necessary for the design of an optical communication system. The result is extended to provide for the computation of joint attenuation probability for n sites with uncorrelated weather patterns.

  2. ISCHEMIC MODEL OF OPTIC NERVE INJURY

    PubMed Central

    Cioffi, George A

    2005-01-01

    Purpose It is proposed that the anterior optic nerve is specifically susceptible to microcirculatory compromise contributing to the development of glaucomatous optic neuropathy. Methods Ischemic optic neuropathy was induced by delivering endothelin-1 (ET-1) to the retrobulbar space in one eye of 12 primates for 6 to 12 months. Regional ganglion cell axonal sizes and densities were compared with the normal, contralateral eyes. Results Without changes of intraocular pressure, mean axonal density was significantly decreased in ET-1 eyes compared to controls (P = .03, paired t test). Two-way matched-pair analysis of variance showed a significant effect of ET-1 on overall axonal density (P < .0001). Among the animals with significant axonal loss, the mean axonal loss was 11.6%, and loss varied from 4% to 21%. Axonal loss was commonly localized within specific quadrants. Five animals were examined for preferential axonal size loss. As a group, there appears to be a tendency toward preferential large axonal loss, but the mean axonal loss of large and small axons did not meet significant differences (P = .1) However, examination of individual animals with significant loss shows significantly greater loss of large axons as compared to the small axons in three of the animals. Conclusions Chronic optic nerve ischemia causes demonstrable and localized damage of the optic nerve, without intraocular pressure elevation. There is preferential loss of large retinal ganglion cell axons in animals with significant axonal loss. Ischemia-induced focal axonal loss is similar to human glaucoma and may represent a differential regional vulnerability. PMID:17057819

  3. Integrated structural and optical modeling of the orbiting stellar interferometer

    NASA Astrophysics Data System (ADS)

    Shaklan, Stuart B.; Yu, Jeffrey W.; Briggs, Hugh C.

    1993-11-01

    The Integrated Modeling of Optical Systems (IMOS) Integration Workbench at JPL has been used to model the effects of structural perturbations on the optics in the proposed Orbiting Stellar Interferometer (OSI). OSI consists of 3 pairs of interferometers and delay lines attached to a 7.5 meter truss. They are interferometrically monitored from a separate boom by a laser metrology system. The spatially distributed nature of the science instrument calls for a high level of integration between the optics and support structure. Because OSI is designed to achieve micro-arcsecond astrometry, many of its alignment, stability, and knowledge tolerances are in the submicron regime. The spacecraft will be subject to vibrations caused by reaction wheels and on-board equipment, as well as thermal strain due to solar and terrestrial heating. These perturbations affect optical parameters such as optical path differences and beam co-parallelism which are critical to instrument performance. IMOS provides an environment that allows one to design and perturb the structure, attach optics to structural or non-structural nodes, trace rays, and analyze the impact of mechanical perturbations on optical performance. This tool makes it simple to change the structure and immediately see performance enhancement/degradation. We have employed IMOS to analyze the effect of reaction wheel disturbances on the optical path difference in both the science and metrology interferometers.

  4. Optical coherence tomography for nondestructive evaluation of fuel rod degradation

    NASA Astrophysics Data System (ADS)

    Renshaw, Jeremy B.; Jenkins, Thomas P.; Buckner, Benjamin D.; Friend, Brian

    2015-03-01

    Nuclear power plants regularly inspect fuel rods to ensure safe and reliable operation. Excessive corrosion can cause fuel failures which can have significant repercussions for the plant, including impacts on plant operation, worker exposure to radiation, and the plant's INPO rating. While plants typically inspect for fuel rod corrosion using eddy current techniques, these techniques have known issues with reliability in the presence of tenacious, ferromagnetic crud layers that can deposit during operation, and the nondestructive evaluation (NDE) inspection results can often be in error by a factor of 2 or 3. For this reason, alternative measurement techniques, such as Optical Coherence Tomography (OCT), have been evaluated that are not sensitive to the ferromagnetic nature of the crud. This paper demonstrates that OCT has significant potential to characterize the thickness of crud layers that can deposit on the surfaces of fuel rods during operation. Physical trials have been performed on simulated crud samples, and the resulting data show an apparent correlation between the crud layer thickness and the OCT signal.

  5. Theoretical model for a Faraday anomalous dispersion optical filter

    NASA Technical Reports Server (NTRS)

    Yin, B.; Shay, T. M.

    1991-01-01

    A model for the Faraday anomalous dispersion optical filter is presented. The model predicts a bandwidth of 0.6 GHz and a transmission peak of 0.98 for a filter operating on the Cs (D2) line. The model includes hyperfine effects and is valid for arbitrary magnetic fields.

  6. The Idiographic Evaluation Model in Crime Control.

    ERIC Educational Resources Information Center

    Hurwitz, Jacob I.

    1984-01-01

    Presents some recent developments in the evaluation of crime prevention and control programs, including the increased use of process evaluation models. Describes the nature, methods, and advantages of the idiographic (or single subject) model as used in social work. (JAC)

  7. Optical Propagation Modeling for the National Ignition Facility

    SciTech Connect

    Williams, W H; Auerbach, J M; Henesian, M A; Jancaitis, K S; Manes, K R; Mehta, N C; Orth, C D; Sacks, R A; Shaw, M J; Widmayer, C C

    2004-01-12

    Optical propagation modeling of the National Ignition Facility has been utilized extensively from conceptual design several years ago through to early operations today. In practice we routinely (for every shot) model beam propagation starting from the waveform generator through to the target. This includes the regenerative amplifier, the 4-pass rod amplifier, and the large slab amplifiers. Such models have been improved over time to include details such as distances between components, gain profiles in the laser slabs and rods, transient optical distortions due to the flashlamp heating of laser slabs, measured transmitted and reflected wavefronts for all large optics, the adaptive optic feedback loop, and the frequency converter. These calculations allow nearfield and farfield predictions in good agreement with measurements.

  8. Retinal nerve fiber layer evaluation in multiple sclerosis with spectral domain optical coherence tomography

    PubMed Central

    Khanifar, Aziz A; Parlitsis, George J; Ehrlich, Joshua R; Aaker, Grant D; D’Amico, Donald J; Gauthier, Susan A; Kiss, Szilárd

    2010-01-01

    Purpose: Histopathologic studies have reported retinal nerve fiber layer (RNFL) thinning in various neurodegenerative diseases. Attempts to quantify this loss in vivo have relied on time-domain optical coherence tomography (TDOCT), which has low resolution and requires substantial interpolation of data for volume measurements. We hypothesized that the significantly higher resolution of spectral-domain optical coherence tomography (SDOCT) would better detect RNFL changes in patients with multiple sclerosis, and that RNFL thickness differences between eyes with and without optic neuritis might be identified more accurately. Methods: In this retrospective case series, patients with multiple sclerosis were recruited from the Judith Jaffe Multiple Sclerosis Center at Weill Cornell Medical College in New York. Patients with a recent clinical diagnosis of optic neuritis (less than three months) were excluded. Eyes with a history of glaucoma, optic neuropathy (other than multiple sclerosis-related optic neuritis), age-related macular degeneration, or other relevant retinal and/or optic nerve disease were excluded. Both eyes of each patient were imaged with the Heidelberg Spectralis® HRA + OCT. RNFL and macular thickness were measured for each eye using the Heidelberg OCT software. These measurements were compared with validated published normal values, and were modeled as linear functions of duration of disease. The odds of an optic neuritis diagnosis as a function of RNFL and macular thickness were calculated. Results: Ninety-four eyes were prospectively evaluated using OCT. Ages of patients ranged from 26 to 69 years, with an average age of 39 years. Peripapillary RNFL thinning was demonstrated in multiple sclerosis patients; mean RNFL thickness was 88.5 μm for individuals with multiple sclerosis compared with a reported normal value of 97 μm (P < 0.001). Eyes with a history of optic neuritis had more thinning compared with those without optic neuritis (83.0

  9. A Novel Animal Model of Partial Optic Nerve Transection Established Using an Optic Nerve Quantitative Amputator

    PubMed Central

    Wang, Xu; Li, Ying; He, Yan; Liang, Hong-Sheng; Liu, En-Zhong

    2012-01-01

    Background Research into retinal ganglion cell (RGC) degeneration and neuroprotection after optic nerve injury has received considerable attention and the establishment of simple and effective animal models is of critical importance for future progress. Methodology/Principal Findings In the present study, the optic nerves of Wistar rats were semi-transected selectively with a novel optic nerve quantitative amputator. The variation in RGC density was observed with retro-labeled fluorogold at different time points after nerve injury. The densities of surviving RGCs in the experimental eyes at different time points were 1113.69±188.83 RGC/mm2 (the survival rate was 63.81% compared with the contralateral eye of the same animal) 1 week post surgery; 748.22±134.75 /mm2 (46.16% survival rate) 2 weeks post surgery; 505.03±118.67 /mm2 (30.52% survival rate) 4 weeks post surgery; 436.86±76.36 /mm2 (24.01% survival rate) 8 weeks post surgery; and 378.20±66.74 /mm2 (20.30% survival rate) 12 weeks post surgery. Simultaneously, we also measured the axonal distribution of optic nerve fibers; the latency and amplitude of pattern visual evoke potentials (P-VEP); and the variation in pupil diameter response to pupillary light reflex. All of these observations and profiles were consistent with post injury variation characteristics of the optic nerve. These results indicate that we effectively simulated the pathological process of primary and secondary injury after optic nerve injury. Conclusions/Significance The present quantitative transection optic nerve injury model has increased reproducibility, effectiveness and uniformity. This model is an ideal animal model to provide a foundation for researching new treatments for nerve repair after optic nerve and/or central nerve injury. PMID:22973439

  10. Design and modeling of optical engine for LC rear projection display

    NASA Astrophysics Data System (ADS)

    Weng, Zhicheng; Zhang, Zengbao

    2002-12-01

    Based on analyzing the LC rear projective TV system, The OE (optical engine) for three penal LCoS rear projection TV system has been designed and modeled, The OE (optical engine) of LC rear projection display is the main component of the system, and it directly affects final performance, so the design of good color performance, high brightness and contrast and high optical efficient is the key of the system. From a commercial viewpoint, a compact size and light weight design makes it more competitive. LightTools software has a great many of powerful functions, such as modeling of optical system, analysis of illumination, modeling of machine structure, analysis of polarization and design of optical coating. We have used LightTools to analyses and optimize a whole optical engine of three penal LCoS projection display including illumination system, dividing and recombining of colors system, projection lens. At the end evaluated the performances of optical engine (parameters of output, uniformity, contract, resolution and so on).

  11. Computer Modeling for Optical Waveguide Sensors.

    DTIC Science & Technology

    1987-12-15

    COSATI CODES 18 SUBJECT TERMS (Continue on reverse it necessary and cleritify by DIock numnerl FIEL GRUP SB-GOUP Optical waveguide sensors Computer...reflection. The resultant probe beam transmission may be plotted as a function of changes in the refractive index of the surrounding fluid medium. BASIC...all angles of incidence about the critical angle ecr. It should be noted that N in equation (3) is a function of e, since = sin - l sin 8 , see

  12. An electrical model of VCSEL as optical transmitter for optical printed circuit board

    NASA Astrophysics Data System (ADS)

    Kim, Do-Kyoon; Yoon, Young-Seol; Choi, Jin-Ho; Kim, Kyung-Min; Choi, Young-Wan; Lee, Seok

    2005-03-01

    Optical interconnection is recent issue for high-speed data transmission. The limitation of high-speed electrical data transmission is caused by impedance mismatching, electric field coupling, microwave loss, and different length of the electrical signal lines. To overcome these limitations, the electrical signal in the current electrical system has to be changed by the optical signal. The most suitable optical source in the OPCB (Optical Printed Circuit Board) is VCSEL (Vertical Cavity Surface Emitting Lasers) that is low-priced and has the characteristic of vertical surface emitting. In this paper, we propose an electrical model of the VCSEL as E/O converting devices for the OPCB. The equivalent circuit of the VCSEL based on the rate equations includes carrier dynamics and material properties. The rate equation parameters are obtained by full analysis based on rate equation and experiment results. The electrical model of the VCSEL has the series resistance determined by I-V characteristic curve, and the parallel capacitance by the parasitic response of the VCSEL chip. The bandwidth of the optical interconnection is analyzed considering those parameters. We design and fabricate the optical transmitter for OPCB considering proposed electrical model of VCSEL.

  13. An Evaluation of Grazing-Incidence Optics for Neutron Imaging

    NASA Technical Reports Server (NTRS)

    Gubarev, M. V.

    2007-01-01

    The refractive index for most materials is slightly less than unity, which opens an opportunity to develop the grazing incidence neutron imaging optics. The ideal material for the optics would be natural nickel and its isotopes. Marshall Space Flight Center (MSFC) has active development program on the nickel replicated optics for use in x-ray astronomy. Brief status report on the program is presented. The results of the neutron focusing optic test carried by the MSFC team at National Institute of Standards and Technology (NIST) are also presented. Possible applications of the optics are briefly discussed.

  14. Model-based polishing of meter size optics

    NASA Astrophysics Data System (ADS)

    Kupfer, Jan-Claas; Achtsnick, Marcel; Becker, Elisabeth

    2013-09-01

    In display or semiconductor manufacturing it is a constant drive towards the use of scale effects to reduce costs per unit. For equipment suppliers this leads to ever bigger optical components. To answer this need new cost-efficient technologies are required. In the process chain, the polishing step is one of the most important as it defines the optical surface. In this work the polishing step of a planar surface of a cylindrical component is investigated. A simulation for long scanning optics starting from Preston equation has been derived. By separating the optical surface into several zones, velocity variable polishing paths have been computed. Including pressure differences at the edges so called removal maps have been plotted. At the end, it has been verified that the model approach is able to influence polishing results of meter size optics by velocity controlled polishing.

  15. Photonic encryption : modeling and functional analysis of all optical logic.

    SciTech Connect

    Tang, Jason D.; Schroeppel, Richard Crabtree; Robertson, Perry J.

    2004-10-01

    With the build-out of large transport networks utilizing optical technologies, more and more capacity is being made available. Innovations in Dense Wave Division Multiplexing (DWDM) and the elimination of optical-electrical-optical conversions have brought on advances in communication speeds as we move into 10 Gigabit Ethernet and above. Of course, there is a need to encrypt data on these optical links as the data traverses public and private network backbones. Unfortunately, as the communications infrastructure becomes increasingly optical, advances in encryption (done electronically) have failed to keep up. This project examines the use of optical logic for implementing encryption in the photonic domain to achieve the requisite encryption rates. This paper documents the innovations and advances of work first detailed in 'Photonic Encryption using All Optical Logic,' [1]. A discussion of underlying concepts can be found in SAND2003-4474. In order to realize photonic encryption designs, technology developed for electrical logic circuits must be translated to the photonic regime. This paper examines S-SEED devices and how discrete logic elements can be interconnected and cascaded to form an optical circuit. Because there is no known software that can model these devices at a circuit level, the functionality of S-SEED devices in an optical circuit was modeled in PSpice. PSpice allows modeling of the macro characteristics of the devices in context of a logic element as opposed to device level computational modeling. By representing light intensity as voltage, 'black box' models are generated that accurately represent the intensity response and logic levels in both technologies. By modeling the behavior at the systems level, one can incorporate systems design tools and a simulation environment to aid in the overall functional design. Each black box model takes certain parameters (reflectance, intensity, input response), and models the optical ripple and time delay

  16. AeroCom INSITU Project: Comparing modeled and measured aerosol optical properties

    NASA Astrophysics Data System (ADS)

    Andrews, Elisabeth; Schmeisser, Lauren; Schulz, Michael; Fiebig, Markus; Ogren, John; Bian, Huisheng; Chin, Mian; Easter, Richard; Ghan, Steve; Kokkola, Harri; Laakso, Anton; Myhre, Gunnar; Randles, Cynthia; da Silva, Arlindo; Stier, Phillip; Skeie, Ragnehild; Takemura, Toshihiko; van Noije, Twan; Zhang, Kai

    2016-04-01

    AeroCom, an open international collaboration of scientists seeking to improve global aerosol models, recently initiated a project comparing model output to in-situ, surface-based measurements of aerosol optical properties. The model/measurement comparison project, called INSITU, aims to evaluate the performance of a suite of AeroCom aerosol models with site-specific observational data in order to inform iterative improvements to model aerosol modules. Surface in-situ data has the unique property of being traceable to physical standards, which is an asset in accomplishing the overall goal of bettering the accuracy of aerosols processes and the predicative capability of global climate models. Here we compare dry, in-situ aerosol scattering and absorption data from ~75 surface, in-situ sites from various global aerosol networks (including NOAA, EUSAAR/ACTRIS and GAW) with a simulated optical properties from a suite of models participating in the AeroCom project. We report how well models reproduce aerosol climatologies for a variety of time scales, aerosol characteristics and behaviors (e.g., aerosol persistence and the systematic relationships between aerosol optical properties), and aerosol trends. Though INSITU is a multi-year endeavor, preliminary phases of the analysis suggest substantial model biases in absorption and scattering coefficients compared to surface measurements, though the sign and magnitude of the bias varies with location. Spatial patterns in the biases highlight model weaknesses, e.g., the inability of models to properly simulate aerosol characteristics at sites with complex topography. Additionally, differences in modeled and measured systematic variability of aerosol optical properties suggest that some models are not accurately capturing specific aerosol behaviors, for example, the tendency of in-situ single scattering albedo to decrease with decreasing aerosol extinction coefficient. The endgoal of the INSITU project is to identify specific

  17. Evaluating the accuracy of diffusion MRI models in white matter.

    PubMed

    Rokem, Ariel; Yeatman, Jason D; Pestilli, Franco; Kay, Kendrick N; Mezer, Aviv; van der Walt, Stefan; Wandell, Brian A

    2015-01-01

    Models of diffusion MRI within a voxel are useful for making inferences about the properties of the tissue and inferring fiber orientation distribution used by tractography algorithms. A useful model must fit the data accurately. However, evaluations of model-accuracy of commonly used models have not been published before. Here, we evaluate model-accuracy of the two main classes of diffusion MRI models. The diffusion tensor model (DTM) summarizes diffusion as a 3-dimensional Gaussian distribution. Sparse fascicle models (SFM) summarize the signal as a sum of signals originating from a collection of fascicles oriented in different directions. We use cross-validation to assess model-accuracy at different gradient amplitudes (b-values) throughout the white matter. Specifically, we fit each model to all the white matter voxels in one data set and then use the model to predict a second, independent data set. This is the first evaluation of model-accuracy of these models. In most of the white matter the DTM predicts the data more accurately than test-retest reliability; SFM model-accuracy is higher than test-retest reliability and also higher than the DTM model-accuracy, particularly for measurements with (a) a b-value above 1000 in locations containing fiber crossings, and (b) in the regions of the brain surrounding the optic radiations. The SFM also has better parameter-validity: it more accurately estimates the fiber orientation distribution function (fODF) in each voxel, which is useful for fiber tracking.

  18. Simple evaluation method of multimode polymer optical waveguides for next generation FTTH application

    NASA Astrophysics Data System (ADS)

    Sugihara, Okihiro; Kaino, Toshikuni; Shibata, Shinya; Takayama, Kazuya; Selvan, J. S.; Hirano, Koki; Ushiwaka, Takami; Yasuda, Hiroki; Itoh, Yuzo; Morimoto, Masahito; Yagi, Shogo; Sugita, Akio; Shimizu, Keishi; Akutsu, Eiichi; Matsui, Yoko; Tajiri, Kozo

    2007-09-01

    Polymer optical waveguide devices are getting popular for next generation FTTH application. In order to accelerate the development of polymer optical devices, evaluation of waveguide characteristics should be speeded up. Polymer optical chip containing a combination of 45°-angled cut waveguide, Y-splitter and S-bend structures was designed and fabricated for simple evaluation of multimode waveguides. Input launching such as light source, mode scrambler was investigated for reliable measurement.

  19. Modeling the noise figure of an acousto-optic receiver

    NASA Astrophysics Data System (ADS)

    Ristic, V. M.; Lee, J. P. Y.

    1996-02-01

    By defining the processing gain of an acousto-optic receiver as the ratio of the signal-to-noise ratio at the output of the detector to the signal-to-noise ratio of the intermediate-frequency input, one can model a noise figure for the acousto-optic receiver. The noise figure has a minimum of 0 dB and depends on the ratio of the noise power (internal to the acousto-optic cell) to the intermediate-frequency input noise power multiplied by the frequency and the spatially dependent exponential factor.

  20. Ray-tracing optical modeling of negative dysphotopsia

    NASA Astrophysics Data System (ADS)

    Hong, Xin; Liu, Yueai; Karakelle, Mutlu; Masket, Samuel; Fram, Nicole R.

    2011-12-01

    Negative dysphotopsia is a relatively common photic phenomenon that may occur after implantation of an intraocular lens. The etiology of negative dysphotopsia is not fully understood. In this investigation, optical modeling was developed using nonsequential-component Zemax ray-tracing technology to simulate photic phenomena experienced by the human eye. The simulation investigated the effects of pupil size, capsulorrhexis size, and bag diffusiveness. Results demonstrated the optical basis of negative dysphotopsia. We found that photic structures were mainly influenced by critical factors such as the capsulorrhexis size and the optical diffusiveness of the capsular bag. The simulations suggested the hypothesis that the anterior capsulorrhexis interacting with intraocular lens could induce negative dysphotopsia.

  1. Engineering Evaluation of the Optacon (OPtical to TActile CONverter). Final Report.

    ERIC Educational Resources Information Center

    DeBenedictis, John A.

    An independent engineering evaluation was conducted of the Optical to Tactile Converter (Optacon), a reading aid for the blind which senses the contrast of printed text and converts the information into a tactile presentation. Tasks performed included: user evaluation, optical, electrical, mechanical, production costs, life tests, reliability, and…

  2. Modeling and analysis of novel laser weld joint designs using optical ray tracing.

    SciTech Connect

    Milewski, J. O.

    2002-01-01

    Reflection of laser energy presents challenges in material processing that can lead to process inefficiency or process instability. Understanding the fundamentals of non-imaging optics and the reflective propagation of laser energy can allow process and weld joint designs to take advantage of these reflections to enhance process efficiency or mitigate detrimental effects. Optical ray tracing may be used within a 3D computer model to evaluate novel joint and fixture designs for laser welding that take advantage of the reflective propagation of laser energy. This modeling work extends that of previous studies by the author and provides comparison with experimental studies performed on highly reflective metals. Practical examples are discussed.

  3. Optical modelling data for room temperature optical properties of organic–inorganic lead halide perovskites

    PubMed Central

    Jiang, Yajie; Green, Martin A.; Sheng, Rui; Ho-Baillie, Anita

    2015-01-01

    The optical properties of perovskites at ambient temperatures are important both to the design of optimised solar cells as well as in other areas such as the refinement of electronic band structure calculations. Limited previous information on the optical modelling has been published. The experimental fitting parameters for optical constants of CH3NH3PbI3−xClx and CH3NH3PbI3 perovskite films are reported at 297 K as determined by detailed analysis of reflectance and transmittance data. The data in this study is related to the research article “Room temperature optical properties of organic–inorganic lead halide perovskites” in Solar Energy Materials & Solar Cells [1]. PMID:26217745

  4. Eikonal solutions to optical model coupled-channel equations

    NASA Technical Reports Server (NTRS)

    Cucinotta, Francis A.; Khandelwal, Govind S.; Maung, Khin M.; Townsend, Lawrence W.; Wilson, John W.

    1988-01-01

    Methods of solution are presented for the Eikonal form of the nucleus-nucleus coupled-channel scattering amplitudes. Analytic solutions are obtained for the second-order optical potential for elastic scattering. A numerical comparison is made between the first and second order optical model solutions for elastic and inelastic scattering of H-1 and He-4 on C-12. The effects of bound-state excitations on total and reaction cross sections are also estimated.

  5. Performance evaluation of large aperture "polished panel" optical receivers based on experimental data

    NASA Astrophysics Data System (ADS)

    Vilnrotter, V.

    Recent interest in the development of hybrid RF/Optical communications has led to the installation of a “ polished-panel” optical receiver evaluation assembly on the 34-meter research antenna at Deep-Space Station 13 (DSS-13) at NASA's Goldstone Deep Space Communications Complex1. The test setup consists of a custom aluminum panel polished to optical smoothness, and a large-sensor CCD camera designed to image the point-spread function (PSF) generated by the polished aluminum panel. Extensive data has been obtained via real-time tracking and imaging of planets and stars at DSS-13. Both “ on-source” and “ off-source” data were recorded at various elevations, enabling the development of realistic simulations and analytic models to help determine the performance of future deep-space communications systems operating with on-off keying (OOK) or pulse-position-modulated (PPM) signaling formats, and compared with the ultimate quantum bound on detection performance. Experimentally determined PSFs were scaled to provide realistic signal-distributions across a photon-counting detector array when a pulse is received, and uncoded as well as block-coded performance analyzed and evaluated for a well-known class of block codes.

  6. Performance Evaluation of Large Aperture 'Polished Panel' Optical Receivers Based on Experimental Data

    NASA Technical Reports Server (NTRS)

    Vilnrotter, Victor

    2013-01-01

    Recent interest in hybrid RF/Optical communications has led to the development and installation of a "polished-panel" optical receiver evaluation assembly on the 34-meter research antenna at Deep-Space Station 13 (DSS-13) at NASA's Goldstone Communications Complex. The test setup consists of a custom aluminum panel polished to optical smoothness, and a large-sensor CCD camera designed to image the point-spread function (PSF) generated by the polished aluminum panel. Extensive data has been obtained via realtime tracking and imaging of planets and stars at DSS-13. Both "on-source" and "off-source" data were recorded at various elevations, enabling the development of realistic simulations and analytic models to help determine the performance of future deep-space communications systems operating with on-off keying (OOK) or pulse-position-modulated (PPM) signaling formats with photon-counting detection, and compared with the ultimate quantum bound on detection performance for these modulations. Experimentally determined PSFs were scaled to provide realistic signal-distributions across a photon-counting detector array when a pulse is received, and uncoded as well as block-coded performance analyzed and evaluated for a well-known class of block codes.

  7. Refinery evaluation of optical imaging to locate fugitive emissions.

    PubMed

    Robinson, Donald R; Luke-Boone, Ronke; Aggarwal, Vineet; Harris, Buzz; Anderson, Eric; Ranum, David; Kulp, Thomas J; Armstrong, Karla; Sommers, Ricky; McRae, Thomas G; Ritter, Karin; Siegell, Jeffrey H; Van Pelt, Doug; Smylie, Mike

    2007-07-01

    Fugitive emissions account for approximately 50% of total hydrocarbon emissions from process plants. Federal and state regulations aiming at controlling these emissions require refineries and petrochemical plants in the United States to implement a Leak Detection and Repair Program (LDAR). The current regulatory work practice, U.S. Environment Protection Agency Method 21, requires designated components to be monitored individually at regular intervals. The annual costs of these LDAR programs in a typical refinery can exceed US$1,000,000. Previous studies have shown that a majority of controllable fugitive emissions come from a very small fraction of components. The Smart LDAR program aims to find cost-effective methods to monitor and reduce emissions from these large leakers. Optical gas imaging has been identified as one such technology that can help achieve this objective. This paper discusses a refinery evaluation of an instrument based on backscatter absorption gas imaging technology. This portable camera allows an operator to scan components more quickly and image gas leaks in real time. During the evaluation, the instrument was able to identify leaking components that were the source of 97% of the total mass emissions from leaks detected. More than 27,000 components were monitored. This was achieved in far less time than it would have taken using Method 21. In addition, the instrument was able to find leaks from components that are not required to be monitored by the current LDAR regulations. The technology principles and the parameters that affect instrument performance are also discussed in the paper.

  8. Root canal filling evaluation using optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Negrutiu, Meda L.; Sinescu, Cosmin; Topala, Florin; Nica, Luminita; Ionita, Ciprian; Marcauteanu, Corina; Goguta, Luciana; Bradu, Adrian; Dobre, George; Rominu, Mihai; Podoleanu, Adrian Gh.

    2010-04-01

    Endodontic therapy consists in cleaning and shaping the root canal system, removing organic debris and sealing the intra-canal space with permanent filling materials. The purpose of this study was to evaluate various root canal fillings in order to detect material defects, the marginal adaptation at the root canal walls and to assess the quality of the apical sealing. 21 extracted single-root canal human teeth were selected for this study. We instrumented all roots using NiTi rotary instruments. All canals were enlarged with a 6% taper size 30 GT instrument, 0,5 mm from the anatomical apex. The root canals were irrigated with 5% sodium hypochlorite, followed by 17% ethylenediaminetetraacetic acid (EDTA). After the instrumentation was completed, the root canals were obturated using a thermoplasticizable polymer of polyesters. In order to assess the defects inside the filling material and the marginal fit to the root canal walls, the conebeam micro-computed tomography (CBμCT) was used first. After the CBμCT investigation, time domain optical coherence tomography working in en face mode (TDefOCT) was employed to evaluate the previous samples. The TDefOCT system was working at 1300 nm and was doubled by a confocal channel at 970 nm. The results obtained by CBμCT revealed no visible defects inside the root-canal fillings and at the interfaces with the root-canal walls. TDefOCT investigations permit to visualize a more complex stratificated structure at the interface filling material/dental hard tissue and in the apical region.

  9. Optical coherence tomography for evaluation of enamel and protective coatings.

    PubMed

    Alsayed, Ehab Z; Hariri, Ilnaz; Sadr, Alireza; Nakashima, Syozi; Bakhsh, Turki A; Shimada, Yasushi; Sumi, Yasunori; Tagami, Junji

    2015-01-01

    Optical coherence tomography (OCT) is an interferometric imaging technique. This study aimed to employ OCT to evaluate four different resin-based materials including a coating containing glass-ionomer filler and calcium, a giomer, and two fluoride-releasing self-etch resins. The coating and its underlying and adjacent enamel were monitored using swept-source OCT (center wavelength: 1330 nm) at baseline, after 5,000 thermal cycles, and after 1, 4 and 7 days of demineralization (pH 4.5). The coatings showed different thicknesses (60-250 micrometers) and various levels of structural and interfacial integrity. OCT could detect a demineralization inhibition zone adjacent to the edge of the fluoride- and calcium-releasing material. Localized demineralization was occasionally observed under thinner coatings. Protection of susceptible enamel surfaces by thin resin-based bioactive coatings provides protection from demineralization. OCT can be used to non-destructively monitor the integrity of such coatings, as well as enamel changes beneath and adjacent to them.

  10. Radar Evaluation of Optical Cloud Constraints to Space Launch Operations

    NASA Technical Reports Server (NTRS)

    Merceret, Francis J.; Short, David A.; Ward, Jennifer G.

    2005-01-01

    Weather constraints to launching space vehicles are designed to prevent loss of the vehicle or mission due to weather hazards (See, e.g., Ref 1). Constraints include Lightning Launch Commit Criteria (LLCC) designed to avoid natural and triggered lightning. The LLCC currently in use at most American launch sites including the Eastern Range and Kennedy Space Center require the Launch Weather Officer to determine the height of cloud bases and tops, the location of cloud edges, and cloud transparency. The preferred method of making these determinations is visual observation, but when that isn't possible due to darkness or obscured vision, it is permissible to use radar. This note examines the relationship between visual and radar observations in three ways: A theoretical consideration of the relationship between radar reflectivity and optical transparency. An observational study relating radar reflectivity to cloud edge determined from in-situ measurements of cloud particle concentrations that determine the visible cloud edge. An observational study relating standard radar products to anvil cloud transparency. It is shown that these three approaches yield results consistent with each other and with the radar threshold specified in Reference 2 for LLCC evaluation.

  11. Marginal integrity evaluation of dental composite using optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Stan, Adrian-Tudor; Cojocariu, Andreea-Codruta; Antal, Anca Adriana; Topala, Florin; Sinescu, Cosmin; Negrutiu, Meda Lavinia; Duma, Virgil-Florin; Podoleanu, Adrian Gh.

    2016-03-01

    In clinical dental practice it is often difficult or even impossible to distinguish and control interfacial adhesive defects from adhesive restorations using visual inspection or other traditional diagnostic methods. Nonetheless, non-invasive biomedical imaging methods like Optical Coherence Tomography (OCT) may provide a better view in this diagnostic outline. The aim of this study is to explore evaluations of the marginal adaptation of class I resin composites restorations using Time Domain (TD) OCT. Posterior human teeth have been chosen for this study. The teeth were stored in 0.9% physiological saline solution prior to use. A classical round-shaped class I cavity was prepared and cavities were restored with Charisma Diamond composite by Heraeus Kulzer and using a system of etch and rinse boding. The specimens were subjected to water storage and then to thermo-cycling. Three dimensional (3-D) scans of the restoration were obtained using a TD-OCT system centered at a 1300 nm wavelength. Open marginal adaptation at the interfaces and gaps inside the composite resins materials were identified using the proposed method. In conclusion, OCT has numerous advantages which justify its use for in vitro, as well as for in vivo studies. It can therefore be considered for non-invasive and fast detection of gaps at the restoration interface.

  12. Evaluation of fingerprint deformation using optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Gutierrez da Costa, Henrique S.; Maxey, Jessica R.; Silva, Luciano; Ellerbee, Audrey K.

    2014-02-01

    Biometric identification systems have important applications to privacy and security. The most widely used of these, print identification, is based on imaging patterns present in the fingers, hands and feet that are formed by the ridges, valleys and pores of the skin. Most modern print sensors acquire images of the finger when pressed against a sensor surface. Unfortunately, this pressure may result in deformations, characterized by changes in the sizes and relative distances of the print patterns, and such changes have been shown to negatively affect the performance of fingerprint identification algorithms. Optical coherence tomography (OCT) is a novel imaging technique that is capable of imaging the subsurface of biological tissue. Hence, OCT may be used to obtain images of subdermal skin structures from which one can extract an internal fingerprint. The internal fingerprint is very similar in structure to the commonly used external fingerprint and is of increasing interest in investigations of identify fraud. We proposed and tested metrics based on measurements calculated from external and internal fingerprints to evaluate the amount of deformation of the skin. Such metrics were used to test hypotheses about the differences of deformation between the internal and external images, variations with the type of finger and location inside the fingerprint.

  13. Remark on: the neutron spherical optical-model absorption.

    SciTech Connect

    Smith, A. B.; Nuclear Engineering Division

    2007-06-30

    The energy-dependent behavior of the absorption term of the spherical neutron optical potential for doubly magic {sup 208}Pb and the neighboring {sup 209}Bi is examined. These considerations suggest a phenomenological model that results in an intuitively attractive energy dependence of the imaginary potential that provides a good description of the observed neutron cross sections and that is qualitatively consistent with theoretical concepts. At the same time it provides an alternative to some of the arbitrary assumptions involved in many conventional optical-model interpretations reported in the literature and reduces the number of the parameters of the model.

  14. Improved evaluation of optical depth components from Langley plot data

    NASA Technical Reports Server (NTRS)

    Biggar, S. F.; Gellman, D. I.; Slater, P. N.

    1990-01-01

    A simple, iterative procedure to determine the optical depth components of the extinction optical depth measured by a solar radiometer is presented. Simulated data show that the iterative procedure improves the determination of the exponent of a Junge law particle size distribution. The determination of the optical depth due to aerosol scattering is improved as compared to a method which uses only two points from the extinction data. The iterative method was used to determine spectral optical depth components for June 11-13, 1988 during the MAC III experiment.

  15. Model Performance Evaluation and Scenario Analysis (MPESA)

    EPA Pesticide Factsheets

    Model Performance Evaluation and Scenario Analysis (MPESA) assesses the performance with which models predict time series data. The tool was developed Hydrological Simulation Program-Fortran (HSPF) and the Stormwater Management Model (SWMM)

  16. Optical linear algebra processors - Noise and error-source modeling

    NASA Technical Reports Server (NTRS)

    Casasent, D.; Ghosh, A.

    1985-01-01

    The modeling of system and component noise and error sources in optical linear algebra processors (OLAPs) are considered, with attention to the frequency-multiplexed OLAP. General expressions are obtained for the output produced as a function of various component errors and noise. A digital simulator for this model is discussed.

  17. Optical linear algebra processors: noise and error-source modeling.

    PubMed

    Casasent, D; Ghosh, A

    1985-06-01

    The modeling of system and component noise and error sources in optical linear algebra processors (OLAP's) are considered, with attention to the frequency-multiplexed OLAP. General expressions are obtained for the output produced as a function of various component errors and noise. A digital simulator for this model is discussed.

  18. Modeling and model-aware signal processing methods for enhancement of optical systems

    NASA Astrophysics Data System (ADS)

    Aksoylar, Aydan

    Theoretical and numerical modeling of optical systems are increasingly being utilized in a wide range of areas in physics and engineering for characterizing and improving existing systems or developing new methods. This dissertation focuses on determining and improving the performance of imaging and non-imaging optical systems through modeling and developing model-aware enhancement methods. We evaluate the performance, demonstrate enhancements in terms of resolution and light collection efficiency, and improve the capabilities of the systems through changes to the system design and through post-processing techniques. We consider application areas in integrated circuit (IC) imaging for fault analysis and malicious circuitry detection, and free-form lens design for creating prescribed illumination patterns. The first part of this dissertation focuses on sub-surface imaging of ICs for fault analysis using a solid immersion lens (SIL) microscope. We first derive the Green's function of the microscope and use it to determine its resolution limits for bulk silicon and silicon-on-insulator (SOI) chips. We then propose an optimization framework for designing super-resolving apodization masks that utilizes the developed model and demonstrate the trade-offs in designing such masks. Finally, we derive the full electromagnetic model of the SIL microscope that models the image of an arbitrary sub-surface structure. With the rapidly shrinking dimensions of ICs, we are increasingly limited in resolving the features and identifying potential modifications despite the resolution improvements provided by the state-of-the-art microscopy techniques and enhancement methods described here. In the second part of this dissertation, we shift our focus away from improving the resolution and consider an optical framework that does not require high resolution imaging for detecting malicious circuitry. We develop a classification-based high-throughput gate identification method that utilizes

  19. Progress in NEXT Ion Optics Modeling

    NASA Technical Reports Server (NTRS)

    Emhoff, Jerold W.; Boyd, Iain D.

    2004-01-01

    Results are presented from an ion optics simulation code applied to the NEXT ion thruster geometry. The error in the potential field solver of the code is characterized, and methods and requirements for reducing this error are given. Results from a study on electron backstreaming using the improved field solver are given and shown to compare much better to experimental results than previous studies. Results are also presented on a study of the beamlet behavior in the outer radial apertures of the NEXT thruster. The low beamlet currents in this region allow over-focusing of the beam, causing direct impingement of ions on the accelerator grid aperture wall. Different possibilities for reducing this direct impingement are analyzed, with the conclusion that, of the methods studied, decreasing the screen grid aperture diameter eliminates direct impingement most effectively.

  20. System-Level Performance Evaluation of Microwave Fiber-Optic Links

    NASA Astrophysics Data System (ADS)

    Ackerman, Edward Irving

    electronic and photonic components that will yield the best combination of fiber-optic link characteristics (i.e., gain, noise figure, dynamic range, etc.) over a given frequency band, accurate link modeling techniques are set forth, verified experimentally, and then employed to evaluate the suitability of the various architectures to specific applications.

  1. Model Evaluation of Continuous Data Pharmacometric Models: Metrics and Graphics

    PubMed Central

    Nguyen, THT; Mouksassi, M‐S; Holford, N; Al‐Huniti, N; Freedman, I; Hooker, AC; John, J; Karlsson, MO; Mould, DR; Pérez Ruixo, JJ; Plan, EL; Savic, R; van Hasselt, JGC; Weber, B; Zhou, C; Comets, E

    2017-01-01

    This article represents the first in a series of tutorials on model evaluation in nonlinear mixed effect models (NLMEMs), from the International Society of Pharmacometrics (ISoP) Model Evaluation Group. Numerous tools are available for evaluation of NLMEM, with a particular emphasis on visual assessment. This first basic tutorial focuses on presenting graphical evaluation tools of NLMEM for continuous data. It illustrates graphs for correct or misspecified models, discusses their pros and cons, and recalls the definition of metrics used. PMID:27884052

  2. Model Evaluation of Continuous Data Pharmacometric Models: Metrics and Graphics.

    PubMed

    Nguyen, Tht; Mouksassi, M-S; Holford, N; Al-Huniti, N; Freedman, I; Hooker, A C; John, J; Karlsson, M O; Mould, D R; Pérez Ruixo, J J; Plan, E L; Savic, R; van Hasselt, Jgc; Weber, B; Zhou, C; Comets, E; Mentré, F

    2017-02-01

    This article represents the first in a series of tutorials on model evaluation in nonlinear mixed effect models (NLMEMs), from the International Society of Pharmacometrics (ISoP) Model Evaluation Group. Numerous tools are available for evaluation of NLMEM, with a particular emphasis on visual assessment. This first basic tutorial focuses on presenting graphical evaluation tools of NLMEM for continuous data. It illustrates graphs for correct or misspecified models, discusses their pros and cons, and recalls the definition of metrics used.

  3. Cost Modeling for Space Optical Telescope Assemblies

    NASA Technical Reports Server (NTRS)

    Stahl, H. Philip; Henrichs, Todd; Luedtke, Alexander; West, Miranda

    2011-01-01

    Parametric cost models are used to plan missions, compare concepts and justify technology investments. This paper reviews an on-going effort to develop cost modes for space telescopes. This paper summarizes the methodology used to develop cost models and documents how changes to the database have changed previously published preliminary cost models. While the cost models are evolving, the previously published findings remain valid: it costs less per square meter of collecting aperture to build a large telescope than a small telescope; technology development as a function of time reduces cost; and lower areal density telescopes cost more than more massive telescopes.

  4. Comparative evaluation of two simple diffuse reflectance models for biological tissue applications.

    PubMed

    Zonios, George; Bassukas, Ioannis; Dimou, Aikaterini

    2008-09-20

    We present a comparative evaluation of two simple diffuse reflectance models for biological tissue applications. One model is based on a widely accepted and used in biomedical optics implementation of diffusion theory, and the other one is based on a semiempirical approach derived from basic physical principles. We test the models on tissue phantoms and on human skin, utilizing a standard six-around-one optical fiber probe for light delivery and collection. We show that both models are suitable for use with an optical fiber probe and illustrate the potential, applicability, and validity range of the models.

  5. EVALUATION OF OPTICAL DETECTION METHODS FOR WATERBORNE SUSPENSIONS

    EPA Science Inventory

    Turbidimeters and optical paricle counters (OPCs) are used to monitor particulate matter in water. The response from these instruments is governed by the optical properties of the suspension and the instrument design. The recommended design criteria for turbidimeters allows for l...

  6. Evaluating Interactive Instructional Technologies: A Cognitive Model.

    ERIC Educational Resources Information Center

    Tucker, Susan A.

    Strengths and weaknesses of prevailing evaluation models are analyzed, with attention to the role of feedback in each paradigm. A framework is then presented for analyzing issues faced by evaluators of interactive instructional technologies. The current practice of evaluation relies heavily on 3 models developed over 20 years ago: (1) the…

  7. Rapid evaluation of ion thruster lifetime using optical emission spectroscopy

    NASA Technical Reports Server (NTRS)

    Rock, B. A.; Mantenieks, M. A.; Parsons, M. L.

    1985-01-01

    A major life-limiting phenomenon of electric thrusters is the sputter erosion of discharge chamber components. Thrusters for space propulsion are required to operate for extended periods of time, usually in excess of 10,000 hr. Lengthy and very costly life-tests in high-vacuum facilities have been required in the past to determine the erosion rates of thruster components. Alternative methods for determining erosion rates which can be performed in relatively short periods of time at considerably lower costs are studied. An attempt to relate optical emission intensity from an ion bombarded surface (screen grid) to the sputtering rate of that surface is made. The model used a kinetic steady-state (KSS) approach, balancing the rates of population and depopulation of ten low-lying excited states of the sputtered molybdenum atom (MoI) with those of the ground state to relate the spectral intensities of the various transitions of the MoI to the population densities. Once this is accomplished, the population density can be related to the sputtering rate of the target. Radiative and collisional modes of excitation and decay are considered. Since actual data has not been published for MoI excitation rate and decay constants, semiempirical equations are used. The calculated sputtering rate and intensity is compared to the measured intensity and sputtering rates of the 8 and 30 cm ion thrusters.

  8. α-Cluster Optical Potential Model of 40Ca

    NASA Astrophysics Data System (ADS)

    Mahmoud, Zakaria M. M.; Behairy, Kassem O.

    2017-04-01

    Elastic scattering of α + 40Ca is analyzed in the framework of the optical model. We adopted an independent α-cluster model to generate the α-cluster and matter density of 40Ca. We proposed a parametrized form for the α-cluster density and fixed its parameters according to the available experimental data about the α-particle and 40Ca nuclei. The obtained α-cluster density of 40Ca is used to generate the real part of the optical potential. The single folding procedure is used to generate this real optical potential with two different effective α-α interactions. The real calculated potential supplied with an imaginary Woods-Saxon squared potential is used to analyze 20 sets of experimental data in the energy range between 18 and 166 MeV. We found that our model is successful in reproducing the data for energies above 40 MeV and still doubtful for lower energies.

  9. α-Cluster Optical Potential Model of 40Ca

    NASA Astrophysics Data System (ADS)

    Mahmoud, Zakaria M. M.; Behairy, Kassem O.

    2017-01-01

    Elastic scattering of α + 40Ca is analyzed in the framework of the optical model. We adopted an independent α-cluster model to generate the α-cluster and matter density of 40Ca. We proposed a parametrized form for the α-cluster density and fixed its parameters according to the available experimental data about the α-particle and 40Ca nuclei. The obtained α-cluster density of 40Ca is used to generate the real part of the optical potential. The single folding procedure is used to generate this real optical potential with two different effective α-α interactions. The real calculated potential supplied with an imaginary Woods-Saxon squared potential is used to analyze 20 sets of experimental data in the energy range between 18 and 166 MeV. We found that our model is successful in reproducing the data for energies above 40 MeV and still doubtful for lower energies.

  10. Grid Erosion Modeling of the NEXT Ion Thruster Optics

    NASA Technical Reports Server (NTRS)

    Ernhoff, Jerold W.; Boyd, Iain D.; Soulas, George (Technical Monitor)

    2003-01-01

    Results from several different computational studies of the NEXT ion thruster optics are presented. A study of the effect of beam voltage on accelerator grid aperture wall erosion shows a non-monotonic, complex behavior. Comparison to experimental performance data indicates improvements in simulation of the accelerator grid current, as well as very good agreement with other quantities. Also examined is the effect of ion optics choice on the thruster life, showing that TAG optics provide better margin against electron backstreaming than NSTAR optics. The model is used to predict the change in performance with increasing accelerator grid voltage, showing that although the current collected on the accel grid downstream face increases, the erosion rate decreases. A study is presented for varying doubly-ionized Xenon current fraction. The results show that performance data is not extremely sensitive to the current fraction.

  11. Optical neural stimulation modeling on degenerative neocortical neural networks

    NASA Astrophysics Data System (ADS)

    Zverev, M.; Fanjul-Vélez, F.; Salas-García, I.; Arce-Diego, J. L.

    2015-07-01

    Neurodegenerative diseases usually appear at advanced age. Medical advances make people live longer and as a consequence, the number of neurodegenerative diseases continuously grows. There is still no cure for these diseases, but several brain stimulation techniques have been proposed to improve patients' condition. One of them is Optical Neural Stimulation (ONS), which is based on the application of optical radiation over specific brain regions. The outer cerebral zones can be noninvasively stimulated, without the common drawbacks associated to surgical procedures. This work focuses on the analysis of ONS effects in stimulated neurons to determine their influence in neuronal activity. For this purpose a neural network model has been employed. The results show the neural network behavior when the stimulation is provided by means of different optical radiation sources and constitute a first approach to adjust the optical light source parameters to stimulate specific neocortical areas.

  12. Classification of scalar and dyadic nonlocal optical response models.

    PubMed

    Wubs, M

    2015-11-30

    Nonlocal optical response is one of the emerging effects on the nanoscale for particles made of metals or doped semiconductors. Here we classify and compare both scalar and tensorial nonlocal response models. In the latter case the nonlocality can stem from either the longitudinal response, the transverse response, or both. In phenomenological scalar models the nonlocal response is described as a smearing out of the commonly assumed infinitely localized response, as characterized by a distribution with a finite width. Here we calculate explicitly whether and how tensorial models, such as the hydrodynamic Drude model and generalized nonlocal optical response theory, follow this phenomenological description. We find considerable differences, for example that nonlocal response functions, in contrast to simple distributions, assume negative and complex values. Moreover, nonlocal response regularizes some but not all diverging optical near fields. We identify the scalar model that comes closest to the hydrodynamic model. Interestingly, for the hydrodynamic Drude model we find that actually only one third (1/3) of the free-electron response is smeared out nonlocally. In that sense, nonlocal response is stronger for transverse and scalar nonlocal response models, where the smeared-out fractions are 2/3 and 3/3, respectively. The latter two models seem to predict novel plasmonic resonances also below the plasma frequency, in contrast to the hydrodynamic model that predicts standing pressure waves only above the plasma frequency.

  13. Assimilation of Bio-Optical Properties into Coupled Physical, Bio-Optical Coastal Model

    DTIC Science & Technology

    2013-01-01

    analysis (updated) fields for the bio-optical model state variables are derived from: Proc. of SPIE Vol. 8724 87240E-3 Downloaded From: http...proceedings.spiedigitallibrary.org/ on 07/11/2013 Terms of Use: http://spiedl.org/terms ),XY(XX fofa HK −+= aX fX oY (1) where is vector of the

  14. Generalized model for incoherent detection in confocal optical microscopy.

    PubMed

    Hammoum, Rachid; Hamady, Sidi Ould Saad; Fontana, Marc D

    2010-06-01

    We develop a generalized model in order to calculate the point spread functions in both the focal and the detection planes for the electric field strengths. In these calculations, based on the generalized Jones matrices, we introduce all of the interdependent parameters that could influence the spatial resolution of a confocal optical microscope. Our proposed model is more nearly complete, since we make no approximations of the scattered electric fields. These results can be successfully applied to standard confocal optical techniques to get a better understanding for more quantitative interpretations of the probe.

  15. A geometric view of adaptive optics control: boiling atmosphere model

    NASA Astrophysics Data System (ADS)

    Wiberg, Donald M.; Max, Claire E.; Gavel, Donald T.

    2004-10-01

    The separation principle of optimal adaptive optics control is derived, and definitions of controllability and observability are introduced. An exact finite dimensional state space representation of the control system dynamics is obtained without the need for truncation in modes such as Zernikes. The uncertainty of sensing uncontrollable modes confuses present adaptive optics controllers. This uncertainty can be modeled by a Kalman filter. Reducing this uncertainty permits increased gain, increasing the Strehl, which is done by an optimal control law derived here. A general model of the atmosphere is considered, including boiling.

  16. Regime-based evaluation of cloudiness in CMIP5 models

    NASA Astrophysics Data System (ADS)

    Jin, Daeho; Oreopoulos, Lazaros; Lee, Dongmin

    2017-01-01

    The concept of cloud regimes (CRs) is used to develop a framework for evaluating the cloudiness of 12 fifth Coupled Model Intercomparison Project (CMIP5) models. Reference CRs come from existing global International Satellite Cloud Climatology Project (ISCCP) weather states. The evaluation is made possible by the implementation in several CMIP5 models of the ISCCP simulator generating in each grid cell daily joint histograms of cloud optical thickness and cloud top pressure. Model performance is assessed with several metrics such as CR global cloud fraction (CF), CR relative frequency of occurrence (RFO), their product [long-term average total cloud amount (TCA)], cross-correlations of CR RFO maps, and a metric of resemblance between model and ISCCP CRs. In terms of CR global RFO, arguably the most fundamental metric, the models perform unsatisfactorily overall, except for CRs representing thick storm clouds. Because model CR CF is internally constrained by our method, RFO discrepancies yield also substantial TCA errors. Our results support previous findings that CMIP5 models underestimate cloudiness. The multi-model mean performs well in matching observed RFO maps for many CRs, but is still not the best for this or other metrics. When overall performance across all CRs is assessed, some models, despite shortcomings, apparently outperform Moderate Resolution Imaging Spectroradiometer cloud observations evaluated against ISCCP like another model output. Lastly, contrasting cloud simulation performance against each model's equilibrium climate sensitivity in order to gain insight on whether good cloud simulation pairs with particular values of this parameter, yields no clear conclusions.

  17. EPA Corporate GHG Goal Evaluation Model

    EPA Pesticide Factsheets

    The EPA Corporate GHG Goal Evaluation Model provides companies with a transparent and publicly available benchmarking resource to help evaluate and establish new or existing GHG goals that go beyond business as usual for their individual sectors.

  18. Differential program evaluation model in child protection.

    PubMed

    Lalayants, Marina

    2012-01-01

    Increasingly attention has been focused to the degree to which social programs have effectively and efficiently delivered services. Using the differential program evaluation model by Tripodi, Fellin, and Epstein (1978) and by Bielawski and Epstein (1984), this paper described the application of this model to evaluating a multidisciplinary clinical consultation practice in child protection. This paper discussed the uses of the model by demonstrating them through the four stages of program initiation, contact, implementation, and stabilization. This organizational case study made a contribution to the model by introducing essential and interrelated elements of a "practical evaluation" methodology in evaluating social programs, such as a participatory evaluation approach; learning, empowerment and sustainability; and a flexible individualized approach to evaluation. The study results demonstrated that by applying the program development model, child-protective administrators and practitioners were able to evaluate the existing practices and recognize areas for program improvement.

  19. Evaluation of Optical Magnitude of Deep Space Spacecraft

    NASA Astrophysics Data System (ADS)

    Wei, L.; Zheng-Hong, T.; Yong-da, L.

    2007-12-01

    Optical-electric technology can measure the tangential position and velocity of spacecraft. To know the feasibility of the use of optical-electric technology, it is necessary to estimate the magnitude of spacecraft first. Since the spacecrafts are non-self-illumination objects, the estimation formulas of the optical magnitude of spacecraft is constructed according to the radiation theory and the extra-atmospheric radiant emittance of the Sun in the visible light wave band. Taking Chang'e-1 as an example, the magnitude of it in different situations is calculated.

  20. Integrated framework for jitter analysis combining disturbance, structure, vibration isolator and optical model

    NASA Astrophysics Data System (ADS)

    Lee, Dae-Oen; Yoon, Jae-San; Han, Jae-Hung

    2012-04-01

    Micro-vibration induced by actuating components of the satellite can severely degrade the optical performance of high precision observation satellites. In this paper, an integrated analysis framework combining disturbance, structure, vibration isolator and optical system model is developed for evaluating the performance of optical payloads in the presence of micro-vibration, and the effectiveness of using a vibration isolator for performance enhancement. Reaction wheel generated disturbance, usually the largest anticipated disturbance, is modeled including the disturbances' interaction with the structural modes of the wheel. For structure modeling, a finite element program is used to solve for eigenvalues and eigenvectors of a structure model which are then used to create a state space model in modal form. A vibration isolator model capturing dynamics of an active isolator utilizing piezoelectric based actuator and load cell for feedback control is included to reduce the transmission of reaction wheel disturbances to the base structure. Dynamic response of the structure to reaction wheel disturbances is calculated with and without vibration isolator. The resulting jitter is used to obtain modulation transfer function (MTF) of diffraction limited optical system model, and the obtained MTF is used as spatial frequency filter for image simulation.

  1. Toward an Ecological Evaluation Model.

    ERIC Educational Resources Information Center

    Parker, Jackson; Patterson, Jerry L.

    1979-01-01

    The authors suggest that the aura of authority traditionally placed on educational research and evaluation has been based on an outdated understanding of the scientific enterprise. They outline an alternative view of science which is more ecological and provides more scope and power for evaluating educational programs. They propose a new framework…

  2. A method of rapidly evaluating image quality of NED optical system

    NASA Astrophysics Data System (ADS)

    Sun, Qi; Qiu, Chuankai; Yang, Huan

    2014-11-01

    In recent years, with the development of technology of micro-display, advanced optics and the software and hardware, near-to-eye display ( NED) optical system will have a wide range of potential applications in the fields of amusement and virtual reality. However, research on the evaluating image quality of this kind optical system is comparatively lagging behind. Although now there are some methods and equipment for evaluation, they can't be applied in commercial production because of their complex operation and inaccuracy. In this paper, an academic method is proposed and a Rapid Evaluation System (RES) is designed to evaluate the image of optical system rapidly and exactly. Firstly, a set of parameters that eyes are sensitive to and also express the quality of system should be extracted and quantized to be criterion, so the evaluation standards can be established. Then, some parameters can be detected by RES consisted of micro-display, CCD camera and computer and so on. By process of scaling, the measuring results of the RES are exact and creditable, relationship between object measurement, subjective evaluation and the RES will be established. After that, image quality of optical system can be evaluated just by detecting parameters of that. The RES is simple and the results of evaluation are exact and keeping with human vision. So the method can be used not only for optimizing design of optical system, but also for evaluation in commercial production.

  3. Evaluation of novel approach to deflectometry for high accuracy optics

    NASA Astrophysics Data System (ADS)

    Sironi, Giorgia; Canestrari, Rodolfo; Tayabaly, Kashmira; Pareschi, Giovanni

    2016-07-01

    A deflectometrical facility was developed at Italian National Institute for Astrophysics-OAB to characterize free-form optics with shape errors within few microns rms. Deflectometry is an interesting technique because it allows the fast characterization of free-form optics. The capabilities of deflectometry in measuring medium-high frequencies are well known, but the low frequencies error characterization is more challenging. Our facility design foresees an innovative approach based on the acquisition of multiple direct images to enhance the performance on the challenging low frequencies range. This contribution presents the error-budget analysis of the measuring method and a study of the configuration tolerances required to allow the use of deflectometry in the realization of optical components suitable for astronomical projects with a requirement of high accuracy for the optics. As test examples we took into account mirrors for the E-ELT telescope.

  4. Optical-based spectral modeling of infrared focal plane arrays

    NASA Astrophysics Data System (ADS)

    Mouzali, Salima; Lefebvre, Sidonie; Rommeluère, Sylvain; Ferrec, Yann; Primot, Jérôme

    2016-07-01

    We adopt an optical approach in order to model and predict the spectral signature of an infrared focal plane array. The modeling is based on a multilayer description of the structure and considers a one-dimensional propagation. It provides a better understanding of the physical phenomena occurring within the pixels, which is useful to perform radiometric measurements, as well as to reliably predict the spectral sensitivity of the detector. An exhaustive model is presented, covering the total spectral range of the pixel response. A heuristic model is also described, depicting a complementary approach that separates the different optical phenomena inside the pixel structure. Promising results are presented, validating the models through comparison with experimental results. Finally, advantages and limitations of this approach are discussed.

  5. An Evaluation of Grazing-Incidence Optics for Neutron Imaging

    NASA Technical Reports Server (NTRS)

    Gubarev, M. V.; Ramsey, B. D.; Engelhaupt, D. E.; Burgess, J.; Mildner, D. F. R.

    2007-01-01

    The focusing capabilities of neutron imaging optic based on the Wolter-1 geometry have been successfully demonstrated with a beam of long wavelength neutrons with low angular divergence.. A test mirror was fabricated using an electroformed nickel replication process at Marshall Space Flight Center. The neutron current density gain at the focal spot of the mirror is found to be at least 8 for neutron wavelengths in the range from 6 to 20 A. Possible applications of the optics are briefly discussed.

  6. Stress Optical Coefficient, Test Methodology, and Glass Standard Evaluation

    DTIC Science & Technology

    2016-05-01

    Industries, Inc. 2016 [accessed 2016 Mar 17] http://www.jnsglass.com/pdf/Starphire.pdf. bSchott North America, Inc. Schott Borofloat 33 glass data sheet...Louisville (KY): Schott North America, Inc. 2016 [accessed 2016 Mar 17]. http://www.us.schott.com/borofloat/English/attribute/mechanical...index.html. cEsco Optics, Inc. BK-7 glass property data sheet. Oak Ridge (NJ): Esco Optics, Inc. 2016 [accessed 2016 Mar 17]. https://www.escooptics.com

  7. Indoor Free Space Optic: a new prototype, realization and evaluation

    NASA Astrophysics Data System (ADS)

    Bouchet, Olivier; Besnard, Pascal; Mihaescu, Adrian

    2008-08-01

    The Free Space Optic (FSO) communication is a daily reality used by an increasing number of companies. For indoor environment, optical wireless communication becomes a good alternative with respect to radio proposals. For both technologies, the architecture is similar: emission/reception base station (Gateway or Bridge) are installed to cover zones, which are defined to ensure a quality of service. The customers may be connected to the Wireless Local Area Network (WLAN) with an adapter or module that emits and receives on this network. But due to its specific characteristics, wireless optical technology could present important advantages such as: Transmitted data security, medical immunity, high data rate, etc... Nevertheless, the optical system may have a limit on the network management aspect and link budget. The scope of this paper is to present a proposal at crossroads between optical fibre telecom system and data processing. In this document, we will present a prototype developed in Brittany during a regional collaborative project (Techim@ges). In order to answer to the management aspect and the link budget, this prototype uses an optical multiplexing technique in 1550 nm band: the Wavelength Division Multiple Access (WDMA). Moreover it also proposes a new class 1 high power emission solution. This full duplex system transmits these various wavelengths in free space, by using optical Multiplexer/Demultiplexer and optical modules. Each module has a defined and personal wavelength associated to the terminal identification (addresses MAC or IP). This approach permits a data rate at a minimum of a ten's Mbit/s per customer and potentially hundred Mbps for a line of sight system. The application field for the achieved and proposed prototype is potentially investigated from WLAN to WPAN.

  8. Feasibility of spatial frequency domain imaging (SFDI) for optically characterizing a preclinical oncology model

    PubMed Central

    Tabassum, Syeda; Zhao, Yanyu; Istfan, Raeef; Wu, Junjie; Waxman, David J.; Roblyer, Darren

    2016-01-01

    Determination of chemotherapy efficacy early during treatment would provide more opportunities for physicians to alter and adapt treatment plans. Diffuse optical technologies may be ideally suited to track early biological events following chemotherapy administration due to low cost and high information content. We evaluated the use of spatial frequency domain imaging (SFDI) to characterize a small animal tumor model in order to move towards the goal of endogenous optical monitoring of cancer therapy in a controlled preclinical setting. The effects of key measurement parameters including the choice of imaging spatial frequency and the repeatability of measurements were evaluated. The precision of SFDI optical property extractions over repeat mouse measurements was determined to be within 3.52% for move and replace experiments. Baseline optical properties and chromophore values as well as intratumor heterogeneity were evaluated over 25 tumors. Additionally, tumor growth and chemotherapy response were monitored over a 45 day longitudinal study in a small number of mice to demonstrate the ability of SFDI to track treatment effects. Optical scattering and oxygen saturation increased as much as 70% and 25% respectively in treated tumors, suggesting SFDI may be useful for preclinical tracking of cancer therapies. PMID:27867722

  9. Optical modeling of media for heat assisted magnetic recording

    NASA Astrophysics Data System (ADS)

    Ghoreyshi, Ali; Victora, R. H.

    2016-02-01

    The validity of effective medium theory for modeling nanocomposite thin films interacting with a plasmonic nanoantenna has been investigated using an optical circuit model and finite-difference time-domain simulations. We show that in the regime where the size of the optical beam generated by the nanoantenna is comparable to the feature size inside the thin film, the effective medium theory is not valid anymore. We demonstrate that using effective medium theory can cause a dramatic error in the performance analysis of applications such as heat assisted magnetic recording that work at this regime. Therefore, we develop a theoretical framework based on circuit theory at optical frequencies to study and design nanocomposite thin films for these applications.

  10. Three-dimensional fuse deposition modeling of tissue-simulating phantom for biomedical optical imaging

    NASA Astrophysics Data System (ADS)

    Dong, Erbao; Zhao, Zuhua; Wang, Minjie; Xie, Yanjun; Li, Shidi; Shao, Pengfei; Cheng, Liuquan; Xu, Ronald X.

    2015-12-01

    Biomedical optical devices are widely used for clinical detection of various tissue anomalies. However, optical measurements have limited accuracy and traceability, partially owing to the lack of effective calibration methods that simulate the actual tissue conditions. To facilitate standardized calibration and performance evaluation of medical optical devices, we develop a three-dimensional fuse deposition modeling (FDM) technique for freeform fabrication of tissue-simulating phantoms. The FDM system uses transparent gel wax as the base material, titanium dioxide (TiO2) powder as the scattering ingredient, and graphite powder as the absorption ingredient. The ingredients are preheated, mixed, and deposited at the designated ratios layer-by-layer to simulate tissue structural and optical heterogeneities. By printing the sections of human brain model based on magnetic resonance images, we demonstrate the capability for simulating tissue structural heterogeneities. By measuring optical properties of multilayered phantoms and comparing with numerical simulation, we demonstrate the feasibility for simulating tissue optical properties. By creating a rat head phantom with embedded vasculature, we demonstrate the potential for mimicking physiologic processes of a living system.

  11. Three-dimensional fuse deposition modeling of tissue-simulating phantom for biomedical optical imaging.

    PubMed

    Dong, Erbao; Zhao, Zuhua; Wang, Minjie; Xie, Yanjun; Li, Shidi; Shao, Pengfei; Cheng, Liuquan; Xu, Ronald X

    2015-01-01

    Biomedical optical devices are widely used for clinical detection of various tissue anomalies. However, optical measurements have limited accuracy and traceability, partially owing to the lack of effective calibration methods that simulate the actual tissue conditions. To facilitate standardized calibration and performance evaluation of medical optical devices, we develop a three-dimensional fuse deposition modeling (FDM) technique for freeform fabrication of tissue-simulating phantoms. The FDM system uses transparent gel wax as the base material, titanium dioxide (TiO2 ) powder as the scattering ingredient, and graphite powder as the absorption ingredient. The ingredients are preheated, mixed, and deposited at the designated ratios layer-by-layer to simulate tissue structural and optical heterogeneities. By printing the sections of human brain model based on magnetic resonance images, we demonstrate the capability for simulating tissue structural heterogeneities. By measuring optical properties of multilayered phantoms and comparing with numerical simulation, we demonstrate the feasibility for simulating tissue optical properties. By creating a rat head phantom with embedded vasculature, we demonstrate the potential for mimicking physiologic processes of a living system.

  12. Fluorescence laminar optical tomography for brain imaging: system implementation and performance evaluation

    NASA Astrophysics Data System (ADS)

    Azimipour, Mehdi; Sheikhzadeh, Mahya; Baumgartner, Ryan; Cullen, Patrick K.; Helmstetter, Fred J.; Chang, Woo-Jin; Pashaie, Ramin

    2017-01-01

    We present our effort in implementing a fluorescence laminar optical tomography scanner which is specifically designed for noninvasive three-dimensional imaging of fluorescence proteins in the brains of small rodents. A laser beam, after passing through a cylindrical lens, scans the brain tissue from the surface while the emission signal is captured by the epi-fluorescence optics and is recorded using an electron multiplication CCD sensor. Image reconstruction algorithms are developed based on Monte Carlo simulation to model light-tissue interaction and generate the sensitivity matrices. To solve the inverse problem, we used the iterative simultaneous algebraic reconstruction technique. The performance of the developed system was evaluated by imaging microfabricated silicon microchannels embedded inside a substrate with optical properties close to the brain as a tissue phantom and ultimately by scanning brain tissue in vivo. Details of the hardware design and reconstruction algorithms are discussed and several experimental results are presented. The developed system can specifically facilitate neuroscience experiments where fluorescence imaging and molecular genetic methods are used to study the dynamics of the brain circuitries.

  13. Concentrator optical characterization using computer mathematical modelling and point source testing

    NASA Technical Reports Server (NTRS)

    Dennison, E. W.; John, S. L.; Trentelman, G. F.

    1984-01-01

    The optical characteristics of a paraboloidal solar concentrator are analyzed using the intercept factor curve (a format for image data) to describe the results of a mathematical model and to represent reduced data from experimental testing. This procedure makes it possible not only to test an assembled concentrator, but also to evaluate single optical panels or to conduct non-solar tests of an assembled concentrator. The use of three-dimensional ray tracing computer programs to calculate the mathematical model is described. These ray tracing programs can include any type of optical configuration from simple paraboloids to array of spherical facets and can be adapted to microcomputers or larger computers, which can graphically display real-time comparison of calculated and measured data.

  14. Chasing the Sun - The In-Flight Evaluation of an Optical Head Tracker

    DTIC Science & Technology

    2006-03-01

    AFRL-HE-WP-TP-2006-0057 AIR FORCE RESEARCH LABORATORY Chasing the Sun - The In-Flight Evaluation of an NO, Optical Head Tracker Michael R. Sedillo...Chasing the Sun -The In-flight Evaluation of an Optical Head Tracker 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER Michael...area UNC UNC UNC code) Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. 239.18 Chasing the Sun - In-flight Evaluation of an Optical Tracker 21

  15. Using multifractals to evaluate oceanographic model skill

    NASA Astrophysics Data System (ADS)

    Skákala, Jozef; Cazenave, Pierre W.; Smyth, Timothy J.; Torres, Ricardo

    2016-08-01

    We are in an era of unprecedented data volumes generated from observations and model simulations. This is particularly true from satellite Earth Observations (EO) and global scale oceanographic models. This presents us with an opportunity to evaluate large-scale oceanographic model outputs using EO data. Previous work on model skill evaluation has led to a plethora of metrics. The paper defines two new model skill evaluation metrics. The metrics are based on the theory of universal multifractals and their purpose is to measure the structural similarity between the model predictions and the EO data. The two metrics have the following advantages over the standard techniques: (a) they are scale-free and (b) they carry important part of information about how model represents different oceanographic drivers. Those two metrics are then used in the paper to evaluate the performance of the FVCOM model in the shelf seas around the south-west coast of the UK.

  16. Numerical Modeling and Analysis of Optical Response of Electro-optic Modulators

    SciTech Connect

    Hussein, Y

    2004-04-14

    This paper presents an analysis of a LiNbO{sub 3} electro-optic modulator using the Finite Difference Time Domain (FDTD) technique, and also a new and efficient multiresolution time-domain technique for fast and accurate modeling of photonic devices. The electromagnetic fields computed by FDTD are coupled to standard electro-optic relations that characterize electro-optic interactions. This novel approach to LiNbO{sub 3} electro-optic modulators using a coupled FDTD technique allows for previously unattainable investigations into device operating bandwidth and data transmission speed. On the other hand, the proposed multiresolution approach presented in this paper solves Maxwell's Equations on nonuniform self-adaptive grids, obtained by applying wavelet transforms followed by hard thresholding. The developed technique is employed to simulate a coplanar waveguide CPW, which represents an electro-optic modulator. Different numerical examples are presented showing more than 75% CPU-time reduction, while maintaining the same degree of accuracy of standard FDTD techniques.

  17. The EMEFS model evaluation. An interim report

    SciTech Connect

    Barchet, W.R.; Dennis, R.L.; Seilkop, S.K.; Banic, C.M.; Davies, D.; Hoff, R.M.; Macdonald, A.M.; Mickle, R.E.; Padro, J.; Puckett, K.; Byun, D.; McHenry, J.N.; Karamchandani, P.; Venkatram, A.; Fung, C.; Misra, P.K.; Hansen, D.A.; Chang, J.S.

    1991-12-01

    The binational Eulerian Model Evaluation Field Study (EMEFS) consisted of several coordinated data gathering and model evaluation activities. In the EMEFS, data were collected by five air and precipitation monitoring networks between June 1988 and June 1990. Model evaluation is continuing. This interim report summarizes the progress made in the evaluation of the Regional Acid Deposition Model (RADM) and the Acid Deposition and Oxidant Model (ADOM) through the December 1990 completion of a State of Science and Technology report on model evaluation for the National Acid Precipitation Assessment Program (NAPAP). Because various assessment applications of RADM had to be evaluated for NAPAP, the report emphasizes the RADM component of the evaluation. A protocol for the evaluation was developed by the model evaluation team and defined the observed and predicted values to be used and the methods by which the observed and predicted values were to be compared. Scatter plots and time series of predicted and observed values were used to present the comparisons graphically. Difference statistics and correlations were used to quantify model performance. 64 refs., 34 figs., 6 tabs.

  18. Evaluation of space environmental effects on metals and optical thin films on EOIM-3

    NASA Technical Reports Server (NTRS)

    Vaughn, Jason A.; Linton, Roger C.; Finckenor, Miria M.; Kamenetzky, Rachel R.

    1995-01-01

    Metals and optical thin films exposed to the space environment on the Third Flight of the Evaluation of Oxygen Interactions with Materials (EOIM-3) payload, onboard Space Shuttle mission STS-46 were evaluated. The materials effects described in this paper include the effects of space exposure on various pure metals, optical thin films, and optical thin film metals. The changes induced by exposure to the space environment in the material properties were evaluated using bidirectional reflectance distribution function (BRDF), specular reflectance (250 nm to 2500 nm), ESCA, VUV reflectance (120 nm to 200 nm), ellipsometry, FTIR and optical properties. Using these analysis techniques gold optically thin film metal mirrors with nickel undercoats were observed to darken due to nickel diffusion through the gold to the surface. Also, thin film nickel mirrors formed nickel oxide due to exposure to both the atmosphere and space.

  19. Mathematical modeling and computation of the optical response from nanostructures

    NASA Astrophysics Data System (ADS)

    Sun, Yuanchang

    This dissertation studies the computational modeling for nanostructures in response to external electromagnetic fields. Light-matter interactions on nanoscale are at the heart of nano-optics. To fully characterize the optical interactions with nanostructures quantum electrodynamics (QED) must be invoked, however, the required extremely intense computation and analysis prohibit QED from applications in nano-optics. To avoid the expensive computations and be able to seize the essential quantum effects a semiclassical model is developed. The wellposedness of the model partial differential equations is established. Emphasis is placed on the optical interactions with an individual nanostructure, excitons and biexcitons effects and finite-size effects are investigated. The crucial step of our model is to couple the electromagnetic fields with the motion of the excited particles to yield a new dielectric constant which contains quantum effects of interest. A novel feature of the dielectric constant is the wavevector-dependence which leads to a multi-wave propagation inside the medium. Additional boundary conditions are proposed to deal with this situation. We proceed with incorporating this dielectric constant to Maxwell's equations, and by solving a scattering problem the quantum effects can be captured in the scattered spectra.

  20. Optical evaluation of red blood cell geometry using micropipette aspiration.

    PubMed

    Engström, K G; Möller, B; Meiselman, H J

    1992-01-01

    Although red blood cell (RBC) geometry has been extensively studied by micropipette aspiration, the small size of RBC and pipettes vs. the optical resolution of light microscopy suggests the need to consider potential errors. The present study addressed such difficulties and investigated four specific problems: (1) use of exact equations to calculate RBC membrane area and volume; (2) calibration of the pipette internal diameter (PID); (3) correction for a noncylindrical pipette barrel; (4) diffraction distortion of the RBC image. The observed PID represents a cylinder lens enlargement that can be theoretically derived from the glass/buffer refractive index ratio (1.49/1.33 = 1.12). This enlargement was experimentally confirmed by: (1) studying pipettes bent to allow measurement through the barrel (horizontal) and at the orifice (vertical), with a resulting diameter ratio of 1.12 +/- 0.01; (2) and by replacing the surrounding buffer with immersion oil and hence abolishing the lens phenomenon (ratio = 1.12 +/- 0.02). In addition, use of aspirated oil droplets demonstrated a 3.2 +/- 0.2% error when the PID is focused at a sharp, maximum diameter. The average pipette cone angle was 1.49 +/- 0.09 degrees and varied considerably with pipette pulling procedures; calculated tongue geometry inside the pipette was affected by the noncylindrical pipette barrel. The RBC diffraction error, demonstrated by touching two aspirated cells held by opposing pipettes, was 0.091 +/- 0.002 microns. The PID, cone angle, and diffraction artifacts significantly (p < 0.001) affected calculated RBC geometry (average errors up to 5.4% for area and 9.6% for volume). Two new methods to calculate, rather than directly measure, the PID from images of a single RBC, during either osmotic or pressure manipulation, were evaluated; the osmotic method closely predicted the PID, whereas the pressure method markedly underestimated the PID. Our results thus confirm the need to consider the above

  1. An evaluation of meniscal collagenous structure using optical projection tomography

    PubMed Central

    2013-01-01

    Background The collagenous structure of menisci is a complex network of circumferentially oriented fascicles and interwoven radially oriented tie-fibres. To date, examination of this micro- architecture has been limited to two-dimensional imaging techniques. The purpose of this study was to evaluate the ability of the three-dimensional imaging technique; optical projection tomography (OPT), to visualize the collagenous structure of the meniscus. If successful, this technique would be the first to visualize the macroscopic orientation of collagen fascicles in 3-D in the meniscus and could further refine load bearing mechanisms in the tissue. OPT is an imaging technique capable of imaging samples on the meso-scale (1-10 mm) at a micro-scale resolution. The technique, similar to computed tomography, takes two-dimensional images of objects from incremental angles around the object and reconstructs them using a back projection algorithm to determine three-dimensional structure. Methods Bovine meniscal samples were imaged from four locations (outer main body, femoral surface, tibial surface and inner main body) to determine the variation in collagen orientation throughout the tissue. Bovine stifles (n = 2) were obtained from a local abattoir and the menisci carefully dissected. Menisci were fixed in methanol and subsequently cut using a custom cutting jig (n = 4 samples per meniscus). Samples were then mounted in agarose, dehydrated in methanol and subsequently cleared using benzyl alcohol benzyl benzoate (BABB) and imaged using OPT. Results Results indicate circumferential, radial and oblique collagenous orientations at the contact surfaces and in the inner third of the main body of the meniscus. Imaging identified fascicles ranging from 80-420 μm in diameter. Transition zones where fascicles were found to have a woven or braided appearance were also identified. The outer-third of the main body was composed of fascicles oriented predominantly in the

  2. Large Signal Evaluation of Nonlinear HBT Model

    NASA Astrophysics Data System (ADS)

    Angelov, Iltcho; Inoue, Akira; Watanabe, Shinsuke

    The performance of recently developed Large Signal (LS) HBT model was evaluated with extensive LS measurements like Power spectrum, Load pull and Inter-modulation investigations. Proposed model has adopted temperature dependent leakage resistance and a simplified capacitance models. The model was implemented in ADS as SDD. Important feature of the model is that the main model parameters are taken directly from measurements in rather simple and understandable way. Results show good accuracy despite the simplicity of the model. To our knowledge the HBT model is one of a few HBT models which can handle high current & Power HBT devices, with significantly less model parameters with good accuracy.

  3. Simulation of optical diagnostics for crystal growth: models and results

    NASA Astrophysics Data System (ADS)

    Banish, Michele R.; Clark, Rodney L.; Kathman, Alan D.; Lawson, Shelah M.

    1991-12-01

    A computer simulation of a two-color holographic interferometric (TCHI) optical system was performed using a physical (wave) optics model. This model accurately simulates propagation through time-varying, 2-D or 3-D concentration and temperature fields as a wave phenomenon. The model calculates wavefront deformations that can be used to generate fringe patterns. This simulation modeled a proposed TriGlycine sulphate TGS flight experiment by propagating through the simplified onion-like refractive index distribution of the growing crystal and calculating the recorded wavefront deformation. The phase of this wavefront was used to generate sample interferograms that map index of refraction variation. Two such fringe patterns, generated at different wavelengths, were used to extract the original temperature and concentration field characteristics within the growth chamber. This proves feasibility for this TCHI crystal growth diagnostic technique. This simulation provides feedback to the experimental design process.

  4. Evaluating modeling tools for the EDOS

    NASA Technical Reports Server (NTRS)

    Knoble, Gordon; Mccaleb, Frederick; Aslam, Tanweer; Nester, Paul

    1994-01-01

    The Earth Observing System (EOS) Data and Operations System (EDOS) Project is developing a functional, system performance model to support the system implementation phase of the EDOS which is being designed and built by the Goddard Space Flight Center (GSFC). The EDOS Project will use modeling to meet two key objectives: (1) manage system design impacts introduced by unplanned changed in mission requirements; and (2) evaluate evolutionary technology insertions throughout the development of the EDOS. To select a suitable modeling tool, the EDOS modeling team developed an approach for evaluating modeling tools and languages by deriving evaluation criteria from both the EDOS modeling requirements and the development plan. Essential and optional features for an appropriate modeling tool were identified and compared with known capabilities of several modeling tools. Vendors were also provided the opportunity to model a representative EDOS processing function to demonstrate the applicability of their modeling tool to the EDOS modeling requirements. This paper emphasizes the importance of using a well defined approach for evaluating tools to model complex systems like the EDOS. The results of this evaluation study do not in any way signify the superiority of any one modeling tool since the results will vary with the specific modeling requirements of each project.

  5. HiPEP Ion Optics System Evaluation Using Gridlets

    NASA Technical Reports Server (NTRS)

    Willliams, John D.; Farnell, Cody C.; Laufer, D. Mark; Martinez, Rafael A.

    2004-01-01

    Experimental measurements are presented for sub-scale ion optics systems comprised of 7 and 19 aperture pairs with geometrical features that are similar to the HiPEP ion optics system. Effects of hole diameter and grid-to-grid spacing are presented as functions of applied voltage and beamlet current. Recommendations are made for the beamlet current range where the ion optics system can be safely operated without experiencing direct impingement of high energy ions on the accelerator grid surface. Measurements are also presented of the accelerator grid voltage where beam plasma electrons backstream through the ion optics system. Results of numerical simulations obtained with the ffx code are compared to both the impingement limit and backstreaming measurements. An emphasis is placed on identifying differences between measurements and simulation predictions to highlight areas where more research is needed. Relatively large effects are observed in simulations when the discharge chamber plasma properties and ion optics geometry are varied. Parameters investigated using simulations include the applied voltages, grid spacing, hole-to-hole spacing, doubles-to-singles ratio, plasma potential, and electron temperature; and estimates are provided for the sensitivity of impingement limits on these parameters.

  6. Introduction: feature issue on phantoms for the performance evaluation and validation of optical medical imaging devices.

    PubMed

    Hwang, Jeeseong; Ramella-Roman, Jessica C; Nordstrom, Robert

    2012-06-01

    The editors introduce the Biomedical Optics Express feature issue on "Phantoms for the Performance Evaluation and Validation of Optical Medical Imaging Devices." This topic was the focus of a technical workshop that was held on November 7-8, 2011, in Washington, D.C. The feature issue includes 13 contributions from workshop attendees.

  7. Development and Performance Evaluation of Optical Sensors for High Temperature Engine Applications

    NASA Technical Reports Server (NTRS)

    Adamovsky, G.; Varga, D.; Floyd, B.

    2011-01-01

    This paper discusses fiber optic sensors designed and constructed to withstand extreme temperatures of aircraft engine. The paper describes development and performance evaluation of fiber optic Bragg grating based sensors. It also describes the design and presents test results of packaged sensors subjected to temperatures up to 1000 C for prolonged periods of time.

  8. Fiber-optic interferometric sensors for measurements of pressure fluctuations - Experimental evaluation

    NASA Technical Reports Server (NTRS)

    Cho, Y. C.; Soderman, P. T.

    1993-01-01

    A fiber optic interferometric sensor that is being developed at NASA Ames Research Center for pressure fluctuation measurements in wind tunnels is considered. Preliminary evaluation indicates that the fiber optic interferometric sensor can be successfully used as an aeroacoustic sensor and is capable of providing a powerful instrument to solve complex acoustic measurement problems in wind tunnels.

  9. Detection, Evaluation, and Optimization of Optical Signals Generated by Fiber Optic Bragg Gratings Under Dynamic Excitations

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory; Lekki, John; Lock, James A.

    2002-01-01

    The dynamic response of a fiber optic Bragg grating to mechanical vibrations is examined both theoretically and experimentally. The theoretical expressions describing the consequences of changes in the grating's reflection spectrum are derived for partially coherent beams in an interferometer. The analysis is given in terms of the dominant wavelength, optical bandwidth, and optical path difference of the interfering signals. Changes in the reflection spectrum caused by a periodic stretching and compression of the grating were experimentally measured using an unbalanced Michelson interferometer, a Michelson interferometer with a non-zero optical path difference. The interferometer's sensitivity to changes in dominant wavelength of the interfering beams was measured as a function of interferometer unbalance and was compared to theoretical predictions. The theoretical analysis enables the user to determine the optimum performance for an unbalanced interferometer.

  10. A Model Evaluation Data Set for the Tropical ARM Sites

    DOE Data Explorer

    Jakob, Christian

    2008-01-15

    This data set has been derived from various ARM and external data sources with the main aim of providing modelers easy access to quality controlled data for model evaluation. The data set contains highly aggregated (in time) data from a number of sources at the tropical ARM sites at Manus and Nauru. It spans the years of 1999 and 2000. The data set contains information on downward surface radiation; surface meteorology, including precipitation; atmospheric water vapor and cloud liquid water content; hydrometeor cover as a function of height; and cloud cover, cloud optical thickness and cloud top pressure information provided by the International Satellite Cloud Climatology Project (ISCCP).

  11. Diffraction analysis and evaluation of several focus- and track-error detection schemes for magneto-optical disk systems

    NASA Technical Reports Server (NTRS)

    Bernacki, Bruce E.; Mansuripur, M.

    1992-01-01

    A commonly used tracking method on pre-grooved magneto-optical (MO) media is the push-pull technique, and the astigmatic method is a popular focus-error detection approach. These two methods are analyzed using DIFFRACT, a general-purpose scalar diffraction modeling program, to observe the effects on the error signals due to focusing lens misalignment, Seidel aberrations, and optical crosstalk (feedthrough) between the focusing and tracking servos. Using the results of the astigmatic/push-pull system as a basis for comparison, a novel focus/track-error detection technique that utilizes a ring toric lens is evaluated as well as the obscuration method (focus error detection only).

  12. Optical Channelizer Evaluation Using Empirical Data and Simulation

    NASA Technical Reports Server (NTRS)

    Ivancic,William D.

    1998-01-01

    Westinghouse Electric Corporation Division under NASA contract NAS3-25865 developed a proof-of-concept (POC) multichannel demultiplexer implemented as an acousto-optic radiofrequency (RF) with a spectrum analyzer. A detailed analysis of the experimental results indicate that the expected degradation caused by the acousto-optical channelizer is approximately 2.0 dB degradation at 10(exp -5) bit-error rate (BER) and 3.0 dB degradation at 10(exp -8) BER. This degradation may be quite acceptable when considering the excellent volume, mass, and power characteristics of acousto-optical channelizing relative to other technologies. In addition, system performance can be greatly improved by using digital pulse shaping in the modem and increasing the channel spacing from 40 to 45 kHz for 64 kbps quadrature phase-shift keying (QPSK) modulation.

  13. Performance Evaluation of the Optical AND Gate at 200 Gbps

    NASA Astrophysics Data System (ADS)

    Tripathi, Devendra Kr.

    2017-03-01

    The article explores performance investigation for the all optical AND logic gate at the 200 Gbps data rate. Numerical simulations have been executed and output pattern for the AND logic operation has been verified. Accordingly good extinction ratio of 15.8 dB has been observed. Investigations depict optimum optical performance metric with the key deign parameters as the pump power (>1e-4 W), pump current (>1 ‎Å), current injection efficiency (>0.5), modulator bias voltage (>1.25 V), modulator on off ratio (>10 dB) and the SOA reflectivity (>0 dB). The schematic is evident, simpler tender's option to endow different input combinations simultaneously. Furthermore, the outcomes are well sustainable to formulate forthcoming advanced higher data rate all-optical digital processing.

  14. Advances in DOE modeling and optical performance for SMO applications

    NASA Astrophysics Data System (ADS)

    Carriere, James; Stack, Jared; Childers, John; Welch, Kevin; Himel, Marc D.

    2010-04-01

    The introduction of source mask optimization (SMO) to the design process addresses an urgent need for the 32nm node and beyond as alternative lithography approaches continue to push out. To take full advantage of SMO routines, an understanding of the characteristic properties of diffractive optical elements (DOEs) is required. Greater flexibility in the DOE output is needed to optimize lithographic process windows. In addition, new and tighter constraints on the DOEs used for off-axis illumination (OAI) are being introduced to precisely predict, control and reduce the effects of pole imbalance and stray light on the CD budget. We present recent advancements in the modeling and optical performance of these DOEs.

  15. Optical model of transient light scattering in ferroelectric liquid crystals

    SciTech Connect

    Loiko, V. A. Konkolovich, A. V.; Miskevich, A. A.

    2009-03-15

    A static optical model is developed for the effect of field-induced transient scattering on coherent light transmission through ferroelectric liquid crystals. Scattering processes are described by introducing an optically anisotropic medium containing scatterers (transient domains). The results presented in the paper are obtained for a plane parallel layer of ferroelectric liquid crystals with a planar helicoidal structure under normal illumination with a linearly polarized plane wave. An analysis is presented of the coherent transmittance of the layer in static applied electric fields.

  16. A Model for Administrative Evaluation by Subordinates.

    ERIC Educational Resources Information Center

    Budig, Jeanne E.

    Under the administrator evaluation program adopted at Vincennes University, all faculty and professional staff are invited to evaluate each administrator above them in the chain of command. Originally based on the Purdue University "cafeteria" system, this evaluation model has been used biannually for 10 years. In an effort to simplify the system,…

  17. Program Development and Evaluation: A Modeling Process.

    ERIC Educational Resources Information Center

    Green, Donald W.; Corgiat, RayLene

    A model of program development and evaluation was developed at Genesee Community College, utilizing a system theory/process of deductive and inductive reasoning to ensure coherence and continuity within the program. The model links activities to specific measurable outcomes. Evaluation checks and feedback are built in at various levels so that…

  18. Evaluation of the global aerosol microphysical ModelE2-TOMAS model against satellite and ground-based observations

    NASA Astrophysics Data System (ADS)

    Lee, Y. H.; Adams, P. J.; Shindell, D. T.

    2015-03-01

    The TwO-Moment Aerosol Sectional (TOMAS) microphysics model has been integrated into the state-of-the-art general circulation model, GISS ModelE2. This paper provides a detailed description of the ModelE2-TOMAS model and evaluates the model against various observations including aerosol precursor gas concentrations, aerosol mass and number concentrations, and aerosol optical depths. Additionally, global budgets in ModelE2-TOMAS are compared with those of other global aerosol models, and the ModelE2-TOMAS model is compared to the default aerosol model in ModelE2, which is a one-moment aerosol (OMA) model (i.e. no aerosol microphysics). Overall, the ModelE2-TOMAS predictions are within the range of other global aerosol model predictions, and the model has a reasonable agreement (mostly within a factor of 2) with observations of sulfur species and other aerosol components as well as aerosol optical depth. However, ModelE2-TOMAS (as well as ModelE2-OMA) cannot capture the observed vertical distribution of sulfur dioxide over the Pacific Ocean, possibly due to overly strong convective transport and overpredicted precipitation. The ModelE2-TOMAS model simulates observed aerosol number concentrations and cloud condensation nuclei concentrations roughly within a factor of 2. Anthropogenic aerosol burdens in ModelE2-OMA differ from ModelE2-TOMAS by a few percent to a factor of 2 regionally, mainly due to differences in aerosol processes including deposition, cloud processing, and emission parameterizations. We observed larger differences for naturally emitted aerosols such as sea salt and mineral dust, as those emission rates are quite different due to different upper size cutoff assumptions.

  19. Comparative analysis of optical coherence tomography signal and microhardness for demineralization evaluation of human tooth enamel

    NASA Astrophysics Data System (ADS)

    de Cara, Ana Claudia Ballet; Zezell, Denise Maria; Ana, Patricia A.; Deana, Alessandro Melo; Amaral, Marcello Magri; Dias Vieira, Nilson, Jr.; de Freitas, Anderson Zanardi

    2012-06-01

    The diagnosis of dental caries at an early stage enables the implementation of conservative treatments based on dental preservation. Several diagnostic methods have been developed, like visual-tactile and radiographic are the most commons but are limited for this application. The Optical Coherence Tomography is a technique that provides information of optical properties of enamel, which may change due to the decay process. The objective of this study was to evaluate the ability of OCT to detect different stages of demineralization of tooth enamel during the development of artificial caries lesions, taking as a reference standard for comparison sectional microhardness testing. Different stages of caries lesions were simulated using the pH cycling model suggested Feathestone and modified by Argenta. The samples were exposed to 0 (control group), 5, 10, 15, 20 and 25 days at a daily regimen of three hours demineralization followed by remineralization during 20 hours. It was used an OCT system with at 930nm. Sectional images were generated in all lesion region. The results obtained from the OCT technique presented similar behavior to microhardness, except for the group 25 days, due to inability to perform indentations reading in areas of more intense demineralization. A linear relationship was observed between the OCT and microhardness techniques for detection of demineralization in enamel. This relationship will allow the use of OCT technique in quantitative assessment of mineral loss and for the evaluation of incipient caries lesions.

  20. Global optical model potential for A=3 projectiles

    NASA Astrophysics Data System (ADS)

    Pang, D. Y.; Roussel-Chomaz, P.; Savajols, H.; Varner, R. L.; Wolski, R.

    2009-02-01

    A global optical model potential (GDP08) for He3 projectiles has been obtained by simultaneously fitting the elastic scattering data of He3 from targets of 40⩽AT⩽209 at incident energies of 30⩽Einc⩽217 MeV. Uncertainties and correlation coefficients between the global potential parameters were obtained by using the bootstrap statistical method. GDP08 was found to satisfactorily account for the elastic scattering of H3 as well, which makes it a global optical potential for the A=3 nuclei. Optical model calculations using the GDP08 global potential are compared with the experimental angular distributions of differential cross sections for He3-nucleus and H3-nucleus scattering from different targets of 6⩽AT⩽232 at incident energies of 4⩽Einc⩽450 MeV. The optical potential for the doubly-magic nucleus Ca40, the low-energy correction to the real potential for nuclei with 58≲AT≲120 at Einc<30 MeV, the comparison with double-folding model calculations and the CH89 potential, and the spin-orbit potential parameters are discussed.

  1. Corrections Education Evaluation System Model.

    ERIC Educational Resources Information Center

    Nelson, Orville; And Others

    The purpose of this project was to develop an evaluation system for the competency-based vocational program developed by Wisconsin's Division of Corrections, Department of Public Instruction (DPI), and the Vocational, Technical, and Adult Education System (VTAE). Site visits were conducted at five correctional institutions in March and April of…

  2. Retinal phototoxicity: a review of standard methodology for evaluating retinal optical radiation hazards.

    PubMed

    Landry, Robert J; Bostrom, Robert G; Miller, Sharon A; Shi, Dexiu; Sliney, David H

    2011-04-01

    Optical radiation (light) safety standards can be difficult to use for the evaluation of light hazards to the retina, even for persons experienced in radiometry and photometry. This paper reviews terminology and methodology for evaluating optical radiation hazards to the retina in accordance with international standard ISO 15004-2 Ophthalmic instruments-Fundamental requirements and test methods, Part 2: Light hazard protection (2007). All optical radiation safety standards use similar methods. Specifically, this paper illustrates how to evaluate the retinal hazards from various ophthalmic instruments including the following: diffuse illumination of the cornea; incident light diverging at the cornea (direct ophthalmoscope, operation microscope, fixation lamp); and incident light converging at the cornea (indirect ophthalmoscope, fundus camera, slit lamp biomicroscope). A brief review of radiometry and the use of certified optical components by manufacturers as specified by the ISO standard is also provided. Finally, the authors provide examples of the use of photometric measurements in hazard evaluation.

  3. Model of Host-Pathogen Interaction Dynamics Links In Vivo Optical Imaging and Immune Responses

    PubMed Central

    Ale, Angelique; Crepin, Valerie F.; Collins, James W.; Constantinou, Nicholas; Habibzay, Maryam; Babtie, Ann C.

    2016-01-01

    ABSTRACT Tracking disease progression in vivo is essential for the development of treatments against bacterial infection. Optical imaging has become a central tool for in vivo tracking of bacterial population development and therapeutic response. For a precise understanding of in vivo imaging results in terms of disease mechanisms derived from detailed postmortem observations, however, a link between the two is needed. Here, we develop a model that provides that link for the investigation of Citrobacter rodentium infection, a mouse model for enteropathogenic Escherichia coli (EPEC). We connect in vivo disease progression of C57BL/6 mice infected with bioluminescent bacteria, imaged using optical tomography and X-ray computed tomography, to postmortem measurements of colonic immune cell infiltration. We use the model to explore changes to both the host immune response and the bacteria and to evaluate the response to antibiotic treatment. The developed model serves as a novel tool for the identification and development of new therapeutic interventions. PMID:27821583

  4. Experience at Los Alamos with use of the optical model for applied nuclear data calculations

    SciTech Connect

    Young, P.G.

    1994-10-01

    While many nuclear models are important in calculations of nuclear data, the optical model usually provides the basic underpinning of analyses directed at data for applications. An overview is given here of experience in the Nuclear Theory and Applications Group at Los Alamos National Laboratory in the use of the optical model for calculations of nuclear cross section data for applied purposes. We consider the direct utilization of total, elastic, and reaction cross sections for neutrons, protons, deuterons, tritons, {sup 3}He and alpha particles in files of evaluated nuclear data covering the energy range of 0 to 200 MeV, as well as transmission coefficients for reaction theory calculations and neutron and proton wave functions direct-reaction and Feshbach-Kerman-Koonin analyses. Optical model codes such as SCAT and ECIS and the reaction theory codes COMNUC, GNASH FKK-GNASH, and DWUCK have primarily been used in our analyses. A summary of optical model parameterizations from past analyses at Los Alamos will be given, including detailed tabulations of the parameters for a selection of nuclei.

  5. SCRAM: a fast computational model for the optical performance of point fucus solar central receiver systems

    SciTech Connect

    Bergeron, K. D.; Chiang, C. J.

    1980-04-01

    Because of the complexities of heliostat shadowing and blocking calculations, computational models for the optical performance of point focus central receiver (PFCR) systems tend to be too slow for many important applications, such as optimization studies based on performance with realistic weather data. In this paper, a mathematical approximation procedure, designated Sandia Central Receiver Approximation Model (SCRAM) will be described. Rather than simulating the system components from first principles, it relies on data generated by the DELSOL code of Dellin and Fish for the optical performance of PFCR systems, and abstracts a mathematical model using a stepwise regression procedure. The result is a computational procedure which allows the user to define the heliostat field boundaries and tower height arbitrarily, generating a model for optical field performance, including shadowing, blocking, cosine, losses, and atmospheric attenuation, and which requires only a polynomial evaluation for each set of sun angles. A comparison with DELSOL for three different fields on three representative days indicates that the rms error of the approximation is 1-3% and that the new code is 1,000-3,000 times as fast as DELSOL. It is also shown that one reason that the accuracy in field performance predictions is higher than that of the generting function for the model is that much of the error in the generating function is due to an oscillatory behavior associated with a moire pattern in the optical response of the heiostat field.

  6. Underwater Optical Wireless Channel Modeling Using Monte-Carlo Method

    NASA Astrophysics Data System (ADS)

    Saini, P. Sri; Prince, Shanthi

    2011-10-01

    At present, there is a lot of interest in the functioning of the marine environment. Unmanned or Autonomous Underwater Vehicles (UUVs or AUVs) are used in the exploration of the underwater resources, pollution monitoring, disaster prevention etc. Underwater, where radio waves do not propagate, acoustic communication is being used. But, underwater communication is moving towards Optical Communication which has higher bandwidth when compared to Acoustic Communication but has shorter range comparatively. Underwater Optical Wireless Communication (OWC) is mainly affected by the absorption and scattering of the optical signal. In coastal waters, both inherent and apparent optical properties (IOPs and AOPs) are influenced by a wide array of physical, biological and chemical processes leading to optical variability. The scattering effect has two effects: the attenuation of the signal and the Inter-Symbol Interference (ISI) of the signal. However, the Inter-Symbol Interference is ignored in the present paper. Therefore, in order to have an efficient underwater OWC link it is necessary to model the channel efficiently. In this paper, the underwater optical channel is modeled using Monte-Carlo method. The Monte Carlo approach provides the most general and most flexible technique for numerically solving the equations of Radiative transfer. The attenuation co-efficient of the light signal is studied as a function of the absorption (a) and scattering (b) coefficients. It has been observed that for pure sea water and for less chlorophyll conditions blue wavelength is less absorbed whereas for chlorophyll rich environment red wavelength signal is absorbed less comparative to blue and green wavelength.

  7. (abstract) Evaluation and Development of Diamond Grids for Ion Optics

    NASA Technical Reports Server (NTRS)

    Blandino, J.; Goodwin, D.; Garner, C.

    1993-01-01

    A research program is underway to establish the feasibility of fabricating 15 cm diameter ion engine optics from polycrystalline diamond film. Because of its high thermal conductivity, low CTE, and low sputter yield, diamond film has the potential of mitigating life limiting and performance degrading processes which have hindered flight qualification of ion thrusters to date. Results of experiments are reported.

  8. An Evaluation of PC-Based Optical Character Recognition Systems.

    ERIC Educational Resources Information Center

    Schreier, E. M.; Uslan, M. M.

    1991-01-01

    The review examines six personal computer-based optical character recognition (OCR) systems designed for use by blind and visually impaired people. Considered are OCR components and terms, documentation, scanning and reading, command structure, conversion, unique features, accuracy of recognition, scanning time, speed, and cost. (DB)

  9. Evaluation of optical reflectance techniques for imaging of alveolar structure

    NASA Astrophysics Data System (ADS)

    Unglert, Carolin I.; Namati, Eman; Warger, William C.; Liu, Linbo; Yoo, Hongki; Kang, DongKyun; Bouma, Brett E.; Tearney, Guillermo J.

    2012-07-01

    Three-dimensional (3-D) visualization of the fine structures within the lung parenchyma could advance our understanding of alveolar physiology and pathophysiology. Current knowledge has been primarily based on histology, but it is a destructive two-dimensional (2-D) technique that is limited by tissue processing artifacts. Micro-CT provides high-resolution three-dimensional (3-D) imaging within a limited sample size, but is not applicable to intact lungs from larger animals or humans. Optical reflectance techniques offer the promise to visualize alveolar regions of the large animal or human lung with sub-cellular resolution in three dimensions. Here, we present the capabilities of three optical reflectance techniques, namely optical frequency domain imaging, spectrally encoded confocal microscopy, and full field optical coherence microscopy, to visualize both gross architecture as well as cellular detail in fixed, phosphate buffered saline-immersed rat lung tissue. Images from all techniques were correlated to each other and then to corresponding histology. Spatial and temporal resolution, imaging depth, and suitability for in vivo probe development were compared to highlight the merits and limitations of each technology for studying respiratory physiology at the alveolar level.

  10. Numerical modelling and image reconstruction in diffuse optical tomography

    PubMed Central

    Dehghani, Hamid; Srinivasan, Subhadra; Pogue, Brian W.; Gibson, Adam

    2009-01-01

    The development of diffuse optical tomography as a functional imaging modality has relied largely on the use of model-based image reconstruction. The recovery of optical parameters from boundary measurements of light propagation within tissue is inherently a difficult one, because the problem is nonlinear, ill-posed and ill-conditioned. Additionally, although the measured near-infrared signals of light transmission through tissue provide high imaging contrast, the reconstructed images suffer from poor spatial resolution due to the diffuse propagation of light in biological tissue. The application of model-based image reconstruction is reviewed in this paper, together with a numerical modelling approach to light propagation in tissue as well as generalized image reconstruction using boundary data. A comprehensive review and details of the basis for using spatial and structural prior information are also discussed, whereby the use of spectral and dual-modality systems can improve contrast and spatial resolution. PMID:19581256

  11. Geometric-optical Modeling of a Conifer Forest Canopy

    NASA Technical Reports Server (NTRS)

    Strahler, A. H. (Principal Investigator)

    1985-01-01

    The objective of this research is to explore how the geometry of trees in forest stands influences the reflectance of the forest as imaged from space. Most plant canopy modeling has viewed the canopy as an assemblage of plane-parallel layers on top of a soil surface. For these models, leaf angle distribution, leaf area index, and the angular transmittance and reflectance of leaves are the primary optical and geometric parameters. Such models are now sufficiently well developed to explain most of the variance in angular reflectance measurements observed from homogeneous plant canopies. However, forest canopies as imaged by airborne and spaceborne scanners exhibit considerable variance at quite a different scale. Brightness values vary strongly from one pixel to the next primarily as a function of the number of trees they contain. At this scale, the forest canopy is nonuniform and discontinuous. This research focuses on a discrete-element, geometric-optical view of the forest canopy.

  12. Evaluation of Black Carbon Estimations in Global Aerosol Models

    SciTech Connect

    Koch, D.; Schulz, M.; Kinne, Stefan; McNaughton, C. S.; Spackman, J. R.; Balkanski, Y.; Bauer, S.; Berntsen, T.; Bond, Tami C.; Boucher, Olivier; Chin, M.; Clarke, A. D.; De Luca, N.; Dentener, F.; Diehl, T.; Dubovik, O.; Easter, Richard C.; Fahey, D. W.; Feichter, J.; Fillmore, D.; Freitag, S.; Ghan, Steven J.; Ginoux, P.; Gong, S.; Horowitz, L.; Iversen, T.; Kirkevag, A.; Klimont, Z.; Kondo, Yutaka; Krol, M.; Liu, Xiaohong; Miller, R.; Montanaro, V.; Moteki, N.; Myhre, G.; Penner, J.; Perlwitz, Ja; Pitari, G.; Reddy, S.; Sahu, L.; Sakamoto, H.; Schuster, G.; Schwarz, J. P.; Seland, O.; Stier, P.; Takegawa, Nobuyuki; Takemura, T.; Textor, C.; van Aardenne, John; Zhao, Y.

    2009-11-27

    We evaluate black carbon (BC) model predictions from the AeroCom model intercomparison project by considering the diversity among year 2000 model simulations and comparing model predictions with available measurements. These model-measurement intercomparisons include BC surface and aircraft concentrations, aerosol absorption optical depth (AAOD) from AERONET and OMI retrievals and BC column estimations based on AERONET. In regions other than Asia, most models are biased high compared to surface concentration measurements. However compared with (column) AAOD or BC burden retreivals, the models are generally biased low. The average ratio of model to retrieved AAOD is less than 0.7 in South American and 0.6 in African biomass burning regions; both of these regions lack surface concentration measurements. In Asia the average model to observed ratio is 0.6 for AAOD and 0.5 for BC surface concentrations. Compared with aircraft measurements over the Americas at latitudes between 0 and 50N, the average model is a factor of 10 larger than observed, and most models exceed the measured BC standard deviation in the mid to upper troposphere. At higher latitudes the average model to aircraft BC is 0.6 and underestimate the observed BC loading in the lower and middle troposphere associated with springtime Arctic haze. Low model bias for AAOD but overestimation of surface and upper atmospheric BC concentrations at lower latitudes suggests that most models are underestimating BC absorption and should improve estimates for refractive index, particle size, and optical effects of BC coating. Retrieval uncertainties and/or differences with model diagnostic treatment may also contribute to the model-measurement disparity. Largest AeroCom model diversity occurred in northern Eurasia and the remote Arctic, regions influenced by anthropogenic sources. Changing emissions, aging, removal, or optical properties within a single model generated a smaller change in model predictions than the

  13. Evaluation of Pyro-optic Materials for Infrared Imaging

    NASA Astrophysics Data System (ADS)

    Pandey, R. K.; Kotru, Sushma; Song, Xiuyu; Donnelly, David

    2004-03-01

    Infrared detectors are needed for a wide range of applications. IR detectors operate either on the principles of photon detection or pyroelectric detection. Both these systems have their respective advantages and disadvantages. However, both of them inherently have difficulties in management of noise to signal ratio and in read-out circuitory. One of the most serious handicaps of photon detectors is requirement of cryogenic cooling for satisfactory operation. In this respect uncooled pyroelectric detectors operating at above room temperature have an advantage. An alternative to these approaches can be pyro-optic based detectors. Only a handful of materials have been found with some satisfactory level of pyro-optic coefficients appropriate for imaginig devices. Some of them are: antimony-sulfo-iodide (SbSI), molybdenum sulfide (MoS2), bismuth vanadate (BiVO4) and Pb-based titanates. Pyrooptic coefficients of these materials have been reported using presumably bulk single crystals. However, no such data are available for their thin films which would be very important for light weight integrated structured devices.In this paper we will describe the parameters and optimization protocol for the growh of thin films of these materials on thermally insulating substrates. We will also discuss their structural, electrical and optical properties. Our investigations suggest that SbSI, BiVO4 and PNZT films are attractive options for advancing the IR detecting technology by utilizing the pyro-optic effect. Integrated thin film structures might lead to the fabrication of light weight, low cost, noise immune and efficient imaging devices based on pyro-optic properties. This research is sponsored by the DEPSCoR program of the U.S. Army Research Office.

  14. B-spline image model for energy minimization-based optical flow estimation.

    PubMed

    Le Besnerais, Guy; Champagnat, Frédéric

    2006-10-01

    Robust estimation of the optical flow is addressed through a multiresolution energy minimization. It involves repeated evaluation of spatial and temporal gradients of image intensity which rely usually on bilinear interpolation and image filtering. We propose to base both computations on a single pyramidal cubic B-spline model of image intensity. We show empirically improvements in convergence speed and estimation error and validate the resulting algorithm on real test sequences.

  15. Statistical evaluation of the performance of an optimized adaptive optics arm for retinal imaging flood system

    NASA Astrophysics Data System (ADS)

    Magaña Chávez, J. L.; Medina-Márquez, J.; Valdivieso-González, L. G.; Balderas-Mata, S. E.

    2016-09-01

    In the last decade, Adaptive Optics has been used to compensate the aberrations of the eye in order to acquire high resolution retinal images. The use of high speed deformable mirrors (DMs) to accomplish this compensation in real time is of great importance. But, sometimes DMs are overused, compensating the aberrations inherent in the optical systems. In this work the evaluation of the performance of an adaptive optics system together with the imaging system will be evaluated in order to know in advance the aberrations inherent in them in order to compensate them prior the use of a DM.

  16. Continuous monitoring of arthritis in animal models using optical imaging modalities

    NASA Astrophysics Data System (ADS)

    Son, Taeyoon; Yoon, Hyung-Ju; Lee, Saseong; Jang, Won Seuk; Jung, Byungjo; Kim, Wan-Uk

    2014-10-01

    Given the several difficulties associated with histology, including difficulty in continuous monitoring, this study aimed to investigate the feasibility of optical imaging modalities-cross-polarization color (CPC) imaging, erythema index (EI) imaging, and laser speckle contrast (LSC) imaging-for continuous evaluation and monitoring of arthritis in animal models. C57BL/6 mice, used for the evaluation of arthritis, were divided into three groups: arthritic mice group (AMG), positive control mice group (PCMG), and negative control mice group (NCMG). Complete Freund's adjuvant, mineral oil, and saline were injected into the footpad for AMG, PCMG, and NCMG, respectively. LSC and CPC images were acquired from 0 through 144 h after injection for all groups. EI images were calculated from CPC images. Variations in feet area, EI, and speckle index for each mice group over time were calculated for quantitative evaluation of arthritis. Histological examinations were performed, and the results were found to be consistent with those from optical imaging analysis. Thus, optical imaging modalities may be successfully applied for continuous evaluation and monitoring of arthritis in animal models.

  17. Performance evaluation of panoramic electro-optic imagers using the TOD method

    NASA Astrophysics Data System (ADS)

    Désaulniers, Pierre; Thibault, Simon

    2011-05-01

    The triangle orientation discrimination (TOD) method is an emerging technique for the evaluation of electro-optical (EO) systems. In this method, the test pattern is a non-periodic equilateral triangle in one of four different orientations (apex up, down, left, or right), and the measurement procedure is a robust four-alternative forced-choice psychophysical process. This leads to a time-consuming task. Consequently, software models have been developed to replace the required human observers. These models base their decision on the orientation of the target using correlation between observed data and the set of four differently oriented targets. This study investigates for the first time how this method can be applied to highly distorted OE systems like hemispheric imagers. These types of systems have inherent large distortion, but the distortion should not be considered as an aberration but rather the result of the projection of a hemispheric field (3D) on a 2D sensor. The distortion deforms the image of the targets and image processing is usually performed to remove distortion and straighten the field of view. We present a comparison in accuracy and computational burden for the evaluation of EO system performance between cases where tested images are pre-processed and correlated to unchanged triangle targets and where untouched (distorted) images are correlated with position-wise distorted targets. This is a first evaluation of the application of the TOD with the goal of obtaining an image quality criterion for panoramic imagers.

  18. Performance Evaluation of 40 cm Ion Optics for the NEXT Ion Engine

    NASA Technical Reports Server (NTRS)

    Soulas, George C.; Haag, Thomas W.; Patterson, Michael J.

    2002-01-01

    The results of performance tests with two 40 cm ion optics sets are presented and compared to those of 30 cm ion optics with similar aperture geometries. The 40 cm ion optics utilized both NSTAR and TAG (Thick-Accelerator-Grid) aperture geometries. All 40 cm ion optics tests were conducted on a NEXT (NASA's Evolutionary Xenon Thruster) laboratory model ion engine. Ion optics performance tests were conducted over a beam current range of 1.20 to 3.52 A and an engine input power range of 1.1 to 6.9 kW. Measured ion optics' performance parameters included near-field radial beam current density profiles, impingement-limited total voltages, electron backstreaming limits, screen grid ion transparencies, beam divergence angles, and start-up transients. Impingement-limited total voltages for 40 cm ion optics with the NSTAR aperture geometry were 60 to 90 V lower than those with the TAG aperture geometry. This difference was speculated to be due to an incomplete burn-in of the TAG ion optics. Electron backstreaming limits for the 40 cm ion optics with the TAG aperture geometry were 8 to 19 V higher than those with the NSTAR aperture geometry due to the thicker accelerator grid of the TAG geometry. Because the NEXT ion engine provided beam flatness parameters that were 40 to 63 percent higher than those of the NSTAR ion engine, the 40 cm ion optics outperformed the 30 cm ion optics.

  19. Controllably Inducing and Modeling Optical Response from Graphene Oxide

    NASA Astrophysics Data System (ADS)

    Lombardo, Nicholas; Naumov, Anton

    Graphene, a novel 2-dimensional sp2-hybridized allotrope of Carbon, has unique electrical and mechanical properties. While it is naturally a highly conductive zero band gap semiconductor, graphene does not exhibit optical emission. It has been shown that functionalization with oxygen-containing groups elicits an opening of band gap in graphene. In this work, we aim to induce an optical response in graphene via controlled oxidation, and then explore potential origins of its photoluminescence through mathematical modeling. We employ timed ozone treatment of initially non-fluorescent reduced graphene oxide (RGO) to produce graphene oxide (GO) with specific optical properties. Oxidized material exhibits substantial changes in the absorption spectra and a broad photoluminescence feature, centered at 532 nm, which suggests the appearance of a band gap. We then explore a number of possible mechanisms for the origin of GO photoluminescence via PM3 and ab initio calculations on a functionalized single sheet of graphene. By adjusting modeling parameters to fit experimentally obtained optical transition energies we estimate the size of the sp2 graphitic regions in GO and the arrangement of functional groups that could be responsible for the observed emission.

  20. Model Performance Evaluation and Scenario Analysis (MPESA) Tutorial

    EPA Science Inventory

    This tool consists of two parts: model performance evaluation and scenario analysis (MPESA). The model performance evaluation consists of two components: model performance evaluation metrics and model diagnostics. These metrics provides modelers with statistical goodness-of-fit m...

  1. Multiple Fan-Beam Optical Tomography: Modelling Techniques

    PubMed Central

    Rahim, Ruzairi Abdul; Chen, Leong Lai; San, Chan Kok; Rahiman, Mohd Hafiz Fazalul; Fea, Pang Jon

    2009-01-01

    This paper explains in detail the solution to the forward and inverse problem faced in this research. In the forward problem section, the projection geometry and the sensor modelling are discussed. The dimensions, distributions and arrangements of the optical fibre sensors are determined based on the real hardware constructed and these are explained in the projection geometry section. The general idea in sensor modelling is to simulate an artificial environment, but with similar system properties, to predict the actual sensor values for various flow models in the hardware system. The sensitivity maps produced from the solution of the forward problems are important in reconstructing the tomographic image. PMID:22291523

  2. Fiber optic displacement measurement model based on finite reflective surface

    NASA Astrophysics Data System (ADS)

    Li, Yuhe; Guan, Kaisen; Hu, Zhaohui

    2016-10-01

    We present a fiber optic displacement measurement model based on finite reflective plate. The theoretical model was derived, and simulation analysis of light intensity distribution, reflective plate width, and the distance between fiber probe and reflective plate were conducted in details. The three dimensional received light intensity distribution and the characteristic curve of light intensity were studied as functions of displacement of finite reflective plate. Experiments were carried out to verify the established model. The physical fundamentals and the effect of operating parameters on measuring system performance were revealed in the end.

  3. X-ray scattering and optical ellipsometric studies of collagen-model peptides

    NASA Astrophysics Data System (ADS)

    Georgiev, Georgie; Cebe, Peggy; Valluzzi, Regina; Kaplan, David

    2003-03-01

    We report results of optical ellipsometry and X-ray scattering studies of structure in collagen-model peptides. Proline and hydroxyproline residues stabilize the triple-helical conformation of collagen proteins in the collagen consensus sequence. Regular modifications have been introduced into the collagen consensus sequence, forming model systems for the study of bio-macromolecular organization. The model systems are oligomers with hexapeptide sequences of the form: (Glu)5(Gly-Ala-Pro-Gly-Pro-Pro)6(Glu)5, or (Glu)5(Gly-Pro-Ala-Gly-Pro-Pro)6(Glu)5. The glutamic acid capping the ends of the hexapeptide sequences imparts solubility in water. Depending upon concentration and temperature, the peptides form lyotropic liquid crystalline structures, and maintain their order when dried to powders or films suitable for X-ray and optical studies. Through the use of the high intensity source of X-radiation at the Brookhaven National Synchrotron Light Source, phase transformation kinetics and structure development are studied in-situ, providing time-resolved characterization of these peptides. Two-dimensional optical ellipsometry provides direct measure of the optical anisotropy and retardance of the structures. The goal of our research is to evaluate the ability of these model peptides for self-assembly into liquid crystalline and true three-dimensional crystalline phases and to assess the temperature stability of resultant higher order structures.

  4. Coupling aerosol optics to the chemical transport model MATCH (v5.5.0) and aerosol dynamics module SALSA (v1)

    NASA Astrophysics Data System (ADS)

    Andersson, E.; Kahnert, M.

    2015-12-01

    Modelling aerosol optical properties is a notoriously difficult task due to the particles' complex morphologies and compositions. Yet aerosols and their optical properties are important for Earth system modelling and remote sensing applications. Operational optics models often make drastic and non realistic approximations regarding morphological properties, which can introduce errors. In this study a new aerosol optics model is implemented, in which more realistic morphologies and mixing states are assumed, especially for black carbon aerosols. The model includes both external and internal mixing of all chemical species, it treats externally mixed black carbon as fractal aggregates, and it accounts for inhomogeneous internal mixing of black carbon by use of a novel "core-grey shell" model. Simulated results of radiative fluxes, backscattering coefficients and the Ångström exponent from the new optics model are compared with results from another model simulating particles as externally mixed homogeneous spheres. To gauge the impact on the optical properties from the new optics model, the known and important effects from using aerosol dynamics serves as a reference. The results show that using a more detailed description of particle morphology and mixing states influences the optical properties to the same degree as aerosol dynamics. This is an important finding suggesting that over-simplified optics models coupled to a chemical transport model can introduce considerable errors; this can strongly effect simulations of radiative fluxes in Earth-system models, and it can compromise the use of remote sensing observations of aerosols in model evaluations and chemical data assimilation.

  5. FDTD modeling of anisotropic nonlinear optical phenomena in silicon waveguides.

    PubMed

    Dissanayake, Chethiya M; Premaratne, Malin; Rukhlenko, Ivan D; Agrawal, Govind P

    2010-09-27

    A deep insight into the inherent anisotropic optical properties of silicon is required to improve the performance of silicon-waveguide-based photonic devices. It may also lead to novel device concepts and substantially extend the capabilities of silicon photonics in the future. In this paper, for the first time to the best of our knowledge, we present a three-dimensional finite-difference time-domain (FDTD) method for modeling optical phenomena in silicon waveguides, which takes into account fully the anisotropy of the third-order electronic and Raman susceptibilities. We show that, under certain realistic conditions that prevent generation of the longitudinal optical field inside the waveguide, this model is considerably simplified and can be represented by a computationally efficient algorithm, suitable for numerical analysis of complex polarization effects. To demonstrate the versatility of our model, we study polarization dependence for several nonlinear effects, including self-phase modulation, cross-phase modulation, and stimulated Raman scattering. Our FDTD model provides a basis for a full-blown numerical simulator that is restricted neither by the single-mode assumption nor by the slowly varying envelope approximation.

  6. Mathematically Modeling the Involvement of Axons in Leber's Hereditary Optic Neuropathy

    PubMed Central

    Pan, Billy X.; Ross-Cisneros, Fred N.; Carelli, Valerio; Rue, Kelly S.; Salomao, Solange R.; Moraes-Filho, Milton N.; Moraes, Milton N.; Berezovsky, Adriana; Belfort, Rubens; Sadun, Alfredo A.

    2012-01-01

    Purpose. Leber's hereditary optic neuropathy (LHON), a mitochondrial disease, has clinical manifestations that reflect the initial preferential involvement of the papillomacular bundle (PMB). The present study seeks to predict the order of axonal loss in LHON optic nerves using the Nerve Fiber Layer Stress Index (NFL-SI), which is a novel mathematical model. Methods. Optic nerves were obtained postmortem from four molecularly characterized LHON patients with varying degrees of neurodegenerative changes and three age-matched controls. Tissues were cut in cross-section and stained with p-phenylenediamine to visualize myelin. Light microscopic images were captured in 32 regions of each optic nerve. Control and LHON tissues were evaluated by measuring axonal dimensions to generate an axonal diameter distribution map. LHON tissues were further evaluated by determining regions of total axonal depletion. Results. A size gradient was evident in the control optic nerves, with average axonal diameter increasing progressively from the temporal to nasal borders. LHON optic nerves showed an orderly loss of axons, starting inferotemporally, progressing centrally, and sparing the superonasal region until the end. Values generated from the NFL-SI equation fit a linear regression curve (R2 = 0.97; P < 0.001). Conclusions. The quantitative histopathologic data from this study revealed that the PMB is most susceptible in LHON, supporting clinical findings seen early in the course of disease onset. The present study also showed that the subsequent progression of axonal loss within the optic nerve can be predicted precisely with the NFL-SI equation. The results presented provided further insight into the pathophysiology of LHON. PMID:23060142

  7. Optical Distortion Evaluation in Large Area Windows using Interferometry

    NASA Technical Reports Server (NTRS)

    Youngquist, Robert C.; Skow, Miles; Nurge, Mark A.

    2015-01-01

    It is important that imagery seen through large area windows, such as those used on space vehicles, not be substantially distorted. Many approaches are described in the literature for measuring the distortion of an optical window, but most suffer from either poor resolution or processing difficulties. In this paper a new definition of distortion is presented, allowing accurate measurement using an optical interferometer. This new definition is shown to be equivalent to the definitions provided by the military and the standards organizations. In order to determine the advantages and disadvantages of this new approach the distortion of an acrylic window is measured using three different methods; image comparison, Moiré interferometry, and phase-shifting interferometry.

  8. The design and evaluation of grazing incidence relay optics

    NASA Technical Reports Server (NTRS)

    Davis, John M.; Chase, R. C.; Silk, J. K.; Krieger, A. S.

    1989-01-01

    X-ray astronomy, both solar and celestial, has many needs for high spatial resolution observations which have to be performed with electronic detectors. If the resolution is not to be detector limited, plate scales in excess of 25 microns arc/sec, corresponding to focal lengths greater than 5 m, are required. In situations where the physical size is restricted, the problem can be solved by the use of grazing incidence relay optics. A system was developed which employs externally polished hyperboloid-hyperboloid surfaces to be used in conjunction with a Wolter-Schwarzschild primary. The secondary is located in front of the primary focus and provides a magnification of 4, while the system has a plate scale of 28 microns arc/sec and a length of 1.9 m. The design, tolerance specification, fabrication and performance at visible and X-ray wavelengths of this optical system are described.

  9. Time-domain model of quantum-dot semiconductor optical amplifiers for wideband optical signals.

    PubMed

    Puris, D; Schmidt-Langhorst, C; Lüdge, K; Majer, N; Schöll, E; Petermann, K

    2012-11-19

    We present a novel theoretical time-domain model for a quantum dot semiconductor optical amplifier, that allows to simulate subpicosecond pulse propagation including power-based and phase-based effects. Static results including amplified spontaneous emission spectra, continuous wave amplification, and four-wave mixing experiments in addition to dynamic pump-probe simulations are presented for different injection currents. The model uses digital filters to describe the frequency dependent gain and microscopically calculated carrier-carrier scattering rates for the interband carrier dynamics. It can be used to calculate the propagation of multiple signals with different wavelengths or one wideband signal with high bitrate.

  10. Optical indication for evaluation ecological state of water areas

    SciTech Connect

    Surin, V.G.; Goloudin, R.I.

    1996-11-01

    The results of spectral measurements of reed, leaves by using a two kinds or the spectrometers at the Neva Bay and in the east part of the Gulf of Finland are discussed. It is shown that the optical properties of the coastal-aqueous vegetation depend on the presence of heavy metals in them. Key words: ecology, spectral reflectance, pollution, aqueous vegetation, remote sensing, spectrometer. 7 refs., 4 figs., 2 tabs.

  11. Comprehensive system models: Strategies for evaluation

    NASA Technical Reports Server (NTRS)

    Field, Christopher; Kutzbach, John E.; Ramanathan, V.; Maccracken, Michael C.

    1992-01-01

    The task of evaluating comprehensive earth system models is vast involving validations of every model component at every scale of organization, as well as tests of all the individual linkages. Even the most detailed evaluation of each of the component processes and the individual links among them should not, however, engender confidence in the performance of the whole. The integrated earth system is so rich with complex feedback loops, often involving components of the atmosphere, oceans, biosphere, and cryosphere, that it is certain to exhibit emergent properties very difficult to predict from the perspective of a narrow focus on any individual component of the system. Therefore, a substantial share of the task of evaluating comprehensive earth system models must reside at the level of whole system evaluations. Since complete, integrated atmosphere/ ocean/ biosphere/ hydrology models are not yet operational, questions of evaluation must be addressed at the level of the kinds of earth system processes that the models should be competent to simulate, rather than at the level of specific performance criteria. Here, we have tried to identify examples of earth system processes that are difficult to simulate with existing models and that involve a rich enough suite of feedbacks that they are unlikely to be satisfactorily described by highly simplified or toy models. Our purpose is not to specify a checklist of evaluation criteria but to introduce characteristics of the earth system that may present useful opportunities for model testing and, of course, improvement.

  12. Evaluation of material dispersion using a nanosecond optical pulse radiator.

    PubMed

    Horiguchi, M; Ohmori, Y; Miya, T

    1979-07-01

    To study the material dispersion effects on graded-index fibers, a method for measuring the material dispersion in optical glass fibers has been developed. Nanosecond pulses in the 0.5-1.7-microm region are generated by a nanosecond optical pulse radiator and grating monochromator. These pulses are injected into a GeO(2)-P(2)0(5)-doped silica graded-index fiber. Relative time delay changes between different wavelengths are used to determine material dispersion, core glass refractive index, material group index, and optimum profile parameter of the graded-index fiber. From the measured data, the optimum profile parameter on the GeO(2)-P(2)O(5)-doped silica graded-index fiber could be estimated to be 1.88 at 1.27 microm of the material dispersion free wavelength region and 1.82 at 1.55 microm of the lowest-loss wavelength region in silica-based optical fiber waveguides.

  13. Modeling the optical coupling across the anterior chamber of the eye towards polarimetric glucose sensing

    NASA Astrophysics Data System (ADS)

    Pirnstill, Casey W.; Coté, Gerard L.

    2014-02-01

    Millions of people worldwide are affected by diabetes. While glucose sensing technology has come a long way over the past several decades, the current commercially available techniques are still invasive, often leading to poor patient compliance. To minimize invasiveness, focus has been placed on optical techniques to ascertain blood glucose concentrations. Optical polarimetry has shown promise and progress as a viable technique for glucose sensing. Recent developments in polarimetric glucose sensing have been focused on overcoming time varying corneal birefringence due to motion artifacts. Beyond corneal birefringence, the next hurdle toward making this approach viable is the ability to couple polarized light across the eye's anterior chamber. The eye is ideally suited to couple light to the retina. The index mismatch between the air and cornea is partially responsible for the beam bending toward the retina and, while good for vision, it complicates our ability to couple light across the anterior chamber without using an index matching device when performing polarimetric glucose monitoring. In this report, we have designed and modeled a non-index matched coupling scheme constructed with commercially available optics. The optical ray tracing model was performed using CODE V to verify the feasibility of a reflective based non-index matched coupling scheme with respect to index of refraction and anatomical restraints. The ray tracing model was developed for a dual-wavelength system and the effect of refraction and reflection at each optical interface within the setup was evaluated. The modeling results indicate a reflective based optical coupling design could be added to existing polarimetric glucose systems thus removing the need for placing an index matched eye-coupling mechanism over the eye prior to data collection.

  14. Development of an End-to-End Model for Free-Space Optical Communications

    NASA Astrophysics Data System (ADS)

    Hemmati, H.

    2005-05-01

    Through funding by NASA's Exploration Systems Research and Technology (ESR&T) Program and the Advanced Space Technology Program (ASTP), a team, including JPL, Boeing, NASA-Glenn, and the Georgia Institute of Technology, will develop an end-to-end modeling tool for rapid architecture trade-offs of high-data-rate laser communications from lunar, martian, and outer planetary ranges. An objective of the modeling tool is to reduce the inefficient reliance on modeling of discrete subsystems or sequential development of multiple expensive and time-consuming hardware units, thereby saving significant cost and time. This dynamic, time-domain modeling tool will accept measured component and subsystem data inputs and generate "difficult to measure" characteristics required for the performance evaluation of different designs and architectural choices. The planned modeling tool will incorporate actual subsystem performance data to reduce the develop-build-evaluate-refine production cycle. The list of high-level objectives of the program includes (1) development of a bidirectional global link analysis backbone software encompassing all optical communication subsystem parameters; (2) development of a bidirectional global link simulation model encompassing all optical communication parameters; (3) interoperability of the link analysis tool with all relevant detailed subsystem design models; and (4) a validated model that is validated against known experimental data at the subsystem and system levels.

  15. Modelling the extrusion of preforms for microstructured optical fibres

    NASA Astrophysics Data System (ADS)

    Tronnolone, Hayden; Stokes, Yvonne; Crowdy, Darren

    2013-11-01

    Owing to a novel design, microstructured optical fibres (MOFs) promise the realisation of fibres with effectively any desired optical properties. MOFs are typically constructed from glass and employ a series of air channels aligned along the fibre axis to form a waveguide. The construction of MOFs by first extruding a preform and then drawing this into the final fibre has the potential to produce fibres on an industrial scale; however, this is hindered by a limited understanding of the fluid flow that arises during this process. We focus on the extrusion stage of fabrication and discuss a model of the fibre evolution based upon complex-variable techniques. The relative influence of the various physical processes involved is discussed, along with limitations of the model.

  16. Optical model for light distribution during transscleral cyclophotocoagulation

    SciTech Connect

    Nemati, B.; Dunn, A.; Welch, A.J.; Rylander, H.G. III

    1998-02-01

    Transscleral cyclophotocoagulation (TSCPC) is currently performed clinically as an effective treatment for end-stage glaucoma. We develop a theoretical model for the analysis of optical attenuation phenomena during TSCPC as a basis for selection of an optimal wavelength. A multilayered Monte Carlo model was developed to calculate the fluence and the rate of heat generation in each tissue layer for the wavelengths of Nd:YAG, diode, ruby, krypton yellow, and argon lasers. Of the five wavelengths under study, our theoretical results suggest that the diode laser wavelength offers the best penetration through the conjunctiva, sclera, and ciliary muscle and highest absorption within the ciliary pigment epithelium. {copyright} 1998 Optical Society of America.

  17. Computational modeling of femtosecond optical solitons from Maxwell's equations

    NASA Technical Reports Server (NTRS)

    Goorjian, Peter M.; Taflove, Allen; Joseph, Rose M.; Hagness, Susan C.

    1992-01-01

    An algorithm is developed that permits the direct time integration of full-vector nonlinear Maxwell's equations. This capability permits the modeling of both linear and nonlinear instantaneous and dispersive effects in the electric polarization in material media. The modeling of the optical carrier is retained. The fundamental innovation is to notice that it is possible to treat the linear and nonlinear convolution integrals, which describe the dispersion, as new dependent variables. A coupled system of nonlinear second-order ordinary differential equations can then be derived for the linear and nonlinear convolution integrals, by differentiating them in the time domain. These equations, together with Maxwell's equations, are solved to determine the electromagnetic fields in nonlinear dispersive media. Results are presented of calculations in one dimension of the propagation and collision of femtosecond electromagnetic solitons that retain the optical carrier, taking into account as the Kerr and Raman interactions.

  18. General Hubbard Model for Fermions in an Optical Lattice

    NASA Astrophysics Data System (ADS)

    Kestner, Jason; Duan, Luming

    2009-03-01

    For two-component fermions in an optical lattice, an effective general Hubbard model (GHM) with tunable on-site attraction/repulsion and occupation-dependent hopping rates emerges from very general arguments [1]. This model is quite interesting, containing as special cases both the t-J and the XXZ models. However, the experimental range of applicability and the connection between the model parameters and the actual experimental parameters must be determined explicitly. To this end, we have used a stochastic variational approach with a correlated gaussian wavefunction to numerically find the eigenstates of two atoms interacting in a 3D few-well trap. By matching the few-site spectrum of the GHM to the variational spectrum obtained, the validity of the model and the relationship between experimental and model parameters are determined. [1] L.-M. Duan, Euro. Phys. Lett. 81, 20001 (2008).

  19. Evaluation and Comparison of Computational Models

    PubMed Central

    Myung, Jay; Tang, Yun; Pitt, Mark A.

    2009-01-01

    Computational models are powerful tools that can enhance the understanding of scientific phenomena. The enterprise of modeling is most productive when the reasons underlying the adequacy of a model, and possibly its superiority to other models, are understood. This chapter begins with an overview of the main criteria that must be considered in model evaluation and selection, in particular explaining why generalizability is the preferred criterion for model selection. This is followed by a review of measures of generalizability. The final section demonstrates the use of five versatile and easy-to-use selection methods for choosing between two mathematical models of protein folding. PMID:19216931

  20. Theoretical model for high-power diamond laser optics using high-velocity liquid-metal jet impingement cooling

    NASA Astrophysics Data System (ADS)

    Palmer, James R.

    1993-02-01

    In 1988 I presented a paper, `Fly's Eye Modular Optic,' in the Los Angeles Symposium that described an optic for high power laser systems that provided for a modular system of hexagonal components that were independently cooled using a high velocity jet pointed normal to the back surface of the optical faceplate. In this paper we look at the use of diamond optical materials in concert with high velocity jet impingement heat transfer of various liquid metal mediums. By using this combination of techniques and materials we can push the laser damage threshold of optical components to even higher levels of absorbed flux density. The thrust of this paper is to develop a theoretical model for use on optical elements subject to very high continuous flux density lasers and to evaluate the use of commercial diamond substrates with conventional optical thin films and conventional substrates with CVD diamond films. In order to assume the very high absorbed flux densities, it is necessary to have a heat transfer technique capable of maintaining the optical component at a stable temperature and below the damage threshold of the optical materials. For the more common materials, thermal shock and subsequent failure in bi-axial shear have proven to be one of the major constituents of the optical damage. In this paper we look at the thermal shock, vis-a-vis, the melting point of some of the materials.

  1. Optical Thin Film Modeling: Using FTG's FilmStar Software

    NASA Technical Reports Server (NTRS)

    Freese, Scott

    2009-01-01

    Every material has basic optical properties that define its interaction with light: The index of refraction (n) and extinction coefficient (k) vary for the material as a function of the wavelength of the incident light. Also significant are the phase velocity and polarization of the incident light These inherent properties allow for the accurate modeling of light s behavior upon contact with a surface: Reflectance, Transmittance, Absorptance.

  2. Distribution Models for Optical Scintillation Due to Atmospheric Turbulence

    DTIC Science & Technology

    2005-12-12

    beam jitter is found to be a dominant effect when this radius is close to unity, and the relationship between pointing error and scintillation is...phase errors in the near Field of the transmitter. If the optical phase at each point in the transmitter plane is described by the residual, 9, within...is close to unity, and the relationship between pointing error and scintillation is examined in detail. As a result of this work, models for the mean

  3. Probabilistic Modeling of Intracranial Pressure Effects on Optic Nerve Biomechanics

    NASA Technical Reports Server (NTRS)

    Ethier, C. R.; Feola, Andrew J.; Raykin, Julia; Myers, Jerry G.; Nelson, Emily S.; Samuels, Brian C.

    2016-01-01

    Altered intracranial pressure (ICP) is involved/implicated in several ocular conditions: papilledema, glaucoma and Visual Impairment and Intracranial Pressure (VIIP) syndrome. The biomechanical effects of altered ICP on optic nerve head (ONH) tissues in these conditions are uncertain but likely important. We have quantified ICP-induced deformations of ONH tissues, using finite element (FE) and probabilistic modeling (Latin Hypercube Simulations (LHS)) to consider a range of tissue properties and relevant pressures.

  4. Nonarteritic anterior ischemic optic neuropathy (NAION) and its experimental models

    PubMed Central

    Bernstein, Steven L.; Johnson, Mary A.; Miller, Neil R.

    2011-01-01

    Anterior ischemic optic neuropathy (AION) can be divided into nonarteritic (NAION) and arteritic (AAION) forms. NAION makes up ~85% of all cases of AION, and until recently was poorly understood. There is no treatment for NAION, and its initiating causes are poorly understood, in part because NAION is not lethal, making it difficult to obtain fresh, newly affected tissue for study. In-vivo electrophysiology and post-mortem studies reveal specific responses that are associated with NAION. New models of NAION have been developed which enable insights into the pathophysiological events surrounding this disease. These models include both rodent and primate species, and the power of a `vertically integrated' multi-species approach can help in understanding the common cellular mechanisms and physiological responses to clinical NAION, and to identify potential approaches to treatment. The models utilize laser light to activate intravascular photoactive dye to induce capillary vascular thrombosis, while sparing the larger vessels. The observable optic nerve changes associated with rodent models of AION (rAION) and primate NAION (pNAION) are indistinguishable from that seen in clinical disease, including sectoral axonal involvement, and in-vivo electrophysiological data from these models are consistent with clinical data. Early post-infarct events reveal an unexpected inflammatory response, and changes in intraretinal gene expression for both stress response, while sparing outer retinal function, which occurs in AAION models. Histologically, the NAION models reveal an isolated loss of retinal ganglion cells by apoptosis. There are changes detectable by immunohistochemistry suggesting that other retinal cells mount a brisk response to retinal ganglion cell distress without themselves dying. The optic nerve ultimately shows axonal loss and scarring. Inflammation is a prominent early histological feature. This suggests that clinically, specific modulation of inflammation may

  5. [Evaluation model for municipal health planning management].

    PubMed

    Berretta, Isabel Quint; Lacerda, Josimari Telino de; Calvo, Maria Cristina Marino

    2011-11-01

    This article presents an evaluation model for municipal health planning management. The basis was a methodological study using the health planning theoretical framework to construct the evaluation matrix, in addition to an understanding of the organization and functioning designed by the Planning System of the Unified National Health System (PlanejaSUS) and definition of responsibilities for the municipal level under the Health Management Pact. The indicators and measures were validated using the consensus technique with specialists in planning and evaluation. The applicability was tested in 271 municipalities (counties) in the State of Santa Catarina, Brazil, based on population size. The proposed model features two evaluative dimensions which reflect the municipal health administrator's commitment to planning: the guarantee of resources and the internal and external relations needed for developing the activities. The data were analyzed using indicators, sub-dimensions, and dimensions. The study concludes that the model is feasible and appropriate for evaluating municipal performance in health planning management.

  6. Evaluation of Galactic Cosmic Ray Models

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.; Heiblim, Samuel; Malott, Christopher

    2009-01-01

    Models of the galactic cosmic ray spectra have been tested by comparing their predictions to an evaluated database containing more than 380 measured cosmic ray spectra extending from 1960 to the present.

  7. Modeling of optical losses in perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Taghavi, M. Javad; Houshmand, Mohammad; Zandi, M. Hossein; Gorji, Nima E.

    2016-09-01

    The optical losses within the structure of hybrid perovskite solar cells are investigated using only the optical properties of each layer e.g. refractive index and extinction coefficient. This model allows calculating the transmission/reflection rates at the interfaces and absorption loss within any layer. Then, the short circuit current density and loss percentage are calculated versus the perovskite and TiO2 thicknesses from 50 nm to 150 nm. To make our calculations closer to reality, we extracted the optical properties of each device component from the literature reports on glass/TCO/TiO2/perovskite/metal. The simulations were fitted with the experimental results of some relevant references. Our simulations show that ITO transmits the light better than SnO2 as the TCO front electrode, and the light reflection at both sides of the perovskite layer, e.g. at TiO2/perovskite and perovskite/Spiro-OMeTAD, is lower than 25%. The light interference and multiple reflections have been accounted in our calculations and finally we showed that a thicker TiO2 and perovskite cause more optical loss in current density due to stronger absorption.

  8. Evaluating Polypoidal Choroidal Vasculopathy With Optical Coherence Tomography Angiography

    PubMed Central

    Wang, Min; Zhou, Yao; Gao, Simon S.; Liu, Wei; Huang, Yongheng; Huang, David; Jia, Yali

    2016-01-01

    Purpose We observed and analyzed the morphologic characteristics of polypoidal lesions and abnormal branching vascular network (BVN) in patients with polypoidal choroidal vasculopathy (PCV) by optical coherence tomography angiography (OCTA). Methods A retrospective observational case series was done of patients with PCV. All patients were scanned with a 70-kHz spectral-domain OCT system using the split-spectrum amplitude-decorrelation angiography (SSADA) algorithm to distinguish blood flow from static tissue. The OCTA images of these patients were compared to those from indocyanine green angiography (ICGA). Semiautomated segmentation was used to further analyze the polypoidal lesion and the BVN. Results We studied 13 eyes of 13 patients 51 to 69 years old. A total of 11 patients were treatment-naive. Two patients had multiple anti-VEGF injections and one underwent photodynamic therapy (PDT). Optical coherence tomography angiography was able to detect the BVN in all cases. Using cross-sectional OCTA, BVN locations were shown to be in the space between the RPE and Bruch's membrane. Using en face OCTA, the BVN vascular pattern could be shown more clearly than by ICGA. Polypoidal lesions showed high flow signals in different patterns in 12 cases in the outer retina slab. Using cross-sectional OCTA, the polyps were shown to be just below the top of the pigment epithelial detachment (PED). In one case, the polypoidal lesion was not detectable at the outer retina slab. Conclusions Optical coherence tomography angiography is a noninvasive imaging tool for detecting vascular changes in PCV. Branching vascular networks showed more clearly on OCTA than on ICGA. Polypoidal lesions had variable patterns on OCTA and were not always detected. The OCTA patterns of the polypoidal lesions and the BVN are helpful in understanding the pathology of PCV. PMID:27472276

  9. Modeling method and preliminary model of Asteroid Toutatis from Chang'E-2 optical images

    NASA Astrophysics Data System (ADS)

    Li, Xiang-Yu; Qiao, Dong

    2014-06-01

    Shape modeling is fundamental to the analysis of dynamic environment and motion around asteroid. Chang'E-2 successfully made a flyby of Asteroid 4179 Toutatis and obtained plenty of high-resolution images during the mission. In this paper, the modeling method and preliminary model of Asteroid Toutatis are discussed. First, the optical images obtained by Chang'E-2 are analyzed. Terrain and silhouette features in images are described. Then, the modeling method based on previous radar model and preliminary information from optical images is proposed. A preliminary polyhedron model of Asteroid Toutatis is established. Finally, the spherical harmonic coefficients of Asteroid Toutatis based on the polyhedron model are obtained. Some parameters of model are analyzed and compared. Although the model proposed in this paper is only a preliminary model, this work offers a valuable reference for future high-resolution models.

  10. Non-standard Hubbard models in optical lattices: a review.

    PubMed

    Dutta, Omjyoti; Gajda, Mariusz; Hauke, Philipp; Lewenstein, Maciej; Lühmann, Dirk-Sören; Malomed, Boris A; Sowiński, Tomasz; Zakrzewski, Jakub

    2015-06-01

    Originally, the Hubbard model was derived for describing the behavior of strongly correlated electrons in solids. However, for over a decade now, variations of it have also routinely been implemented with ultracold atoms in optical lattices, allowing their study in a clean, essentially defect-free environment. Here, we review some of the vast literature on this subject, with a focus on more recent non-standard forms of the Hubbard model. After giving an introduction to standard (fermionic and bosonic) Hubbard models, we discuss briefly common models for mixtures, as well as the so-called extended Bose-Hubbard models, that include interactions between neighboring sites, next-neighbor sites, and so on. The main part of the review discusses the importance of additional terms appearing when refining the tight-binding approximation for the original physical Hamiltonian. Even when restricting the models to the lowest Bloch band is justified, the standard approach neglects the density-induced tunneling (which has the same origin as the usual on-site interaction). The importance of these contributions is discussed for both contact and dipolar interactions. For sufficiently strong interactions, the effects related to higher Bloch bands also become important even for deep optical lattices. Different approaches that aim at incorporating these effects, mainly via dressing the basis, Wannier functions with interactions, leading to effective, density-dependent Hubbard-type models, are reviewed. We discuss also examples of Hubbard-like models that explicitly involve higher p orbitals, as well as models that dynamically couple spin and orbital degrees of freedom. Finally, we review mean-field nonlinear Schrödinger models of the Salerno type that share with the non-standard Hubbard models nonlinear coupling between the adjacent sites. In that part, discrete solitons are the main subject of consideration. We conclude by listing some open problems, to be addressed in the future.

  11. Numerical Simulations of Optical Turbulence Using an Advanced Atmospheric Prediction Model: Implications for Adaptive Optics Design

    NASA Astrophysics Data System (ADS)

    Alliss, R.

    2014-09-01

    Optical turbulence (OT) acts to distort light in the atmosphere, degrading imagery from astronomical telescopes and reducing the data quality of optical imaging and communication links. Some of the degradation due to turbulence can be corrected by adaptive optics. However, the severity of optical turbulence, and thus the amount of correction required, is largely dependent upon the turbulence at the location of interest. Therefore, it is vital to understand the climatology of optical turbulence at such locations. In many cases, it is impractical and expensive to setup instrumentation to characterize the climatology of OT, so numerical simulations become a less expensive and convenient alternative. The strength of OT is characterized by the refractive index structure function Cn2, which in turn is used to calculate atmospheric seeing parameters. While attempts have been made to characterize Cn2 using empirical models, Cn2 can be calculated more directly from Numerical Weather Prediction (NWP) simulations using pressure, temperature, thermal stability, vertical wind shear, turbulent Prandtl number, and turbulence kinetic energy (TKE). In this work we use the Weather Research and Forecast (WRF) NWP model to generate Cn2 climatologies in the planetary boundary layer and free atmosphere, allowing for both point-to-point and ground-to-space seeing estimates of the Fried Coherence length (ro) and other seeing parameters. Simulations are performed using a multi-node linux cluster using the Intel chip architecture. The WRF model is configured to run at 1km horizontal resolution and centered on the Mauna Loa Observatory (MLO) of the Big Island. The vertical resolution varies from 25 meters in the boundary layer to 500 meters in the stratosphere. The model top is 20 km. The Mellor-Yamada-Janjic (MYJ) TKE scheme has been modified to diagnose the turbulent Prandtl number as a function of the Richardson number, following observations by Kondo and others. This modification

  12. A progress report on grazing incidence optics fabrication and evaluation

    NASA Technical Reports Server (NTRS)

    Teague, Peter F.; Ulmer, Melville P.; Matsui, Yutaka; Briel, Ulrich; Burkert, Wolfgang

    1989-01-01

    The progress being made on a mirror array telescope for high energies (MARTHE) project is reported. As a first step, small mirror flats and full-size Wolter I mirrors are produced that are lacquer coated (mandrels) and then coated with gold or palladium. The up-to-date results of fabricating and testing these mirrors are presented. Currently, results can be provided on the micro-roughness, marco-figure, X-ray scattering, and reflectivity up to 8 keV from flats and Wolter I mirrors as well as optical measurements of the flats.

  13. Electrical and optical evaluation aspects of public lighting systems

    NASA Astrophysics Data System (ADS)

    Tulbure, Adrian; Marc, Gheorghe; Kurt, Ünal

    2016-12-01

    This paper briefs a few issues regarding the technical validation of public lighting solutions. The novelty of the work is justified by the fact that it combines technical legislation in force [1], with practical analysis procedures [2]. Thus, in order to select the optimal solution, the paper describes a case study of measurement procedure which confirms the high electrical and optical characteristics [3] of the proposed solutions. At the end of the contribution, comparative design purposes for the two versions of modern street lighting are presented.

  14. Metrics for Evaluation of Student Models

    ERIC Educational Resources Information Center

    Pelanek, Radek

    2015-01-01

    Researchers use many different metrics for evaluation of performance of student models. The aim of this paper is to provide an overview of commonly used metrics, to discuss properties, advantages, and disadvantages of different metrics, to summarize current practice in educational data mining, and to provide guidance for evaluation of student…

  15. Evaluation Model for Career Programs. Final Report.

    ERIC Educational Resources Information Center

    Byerly, Richard L.; And Others

    A study was conducted to provide and test an evaluative model that could be utilized in providing curricular evaluation of the various career programs. Two career fields, dental assistant and auto mechanic, were chosen for study. A questionnaire based upon the actual job performance was completed by six groups connected with the auto mechanics and…

  16. Assimilation of remotely-sensed optical properties to improve marine biogeochemistry modelling

    NASA Astrophysics Data System (ADS)

    Ciavatta, Stefano; Torres, Ricardo; Martinez-Vicente, Victor; Smyth, Timothy; Dall'Olmo, Giorgio; Polimene, Luca; Allen, J. Icarus

    2014-09-01

    In this paper we evaluate whether the assimilation of remotely-sensed optical data into a marine ecosystem model improves the simulation of biogeochemistry in a shelf sea. A localized Ensemble Kalman filter was used to assimilate weekly diffuse light attenuation coefficient data, Kd(443) from SeaWiFs, into an ecosystem model of the western English Channel. The spatial distributions of (unassimilated) surface chlorophyll from satellite, and a multivariate time series of eighteen biogeochemical and optical variables measured in situ at one long-term monitoring site were used to evaluate the system performance for the year 2006. Assimilation reduced the root mean square error and improved the correlation with the assimilated Kd(443) observations, for both the analysis and, to a lesser extent, the forecast estimates, when compared to the reference model simulation. Improvements in the simulation of (unassimilated) ocean colour chlorophyll were less evident, and in some parts of the Channel the simulation of this data deteriorated. The estimation errors for the (unassimilated) in situ data were reduced for most variables with some exceptions, e.g. dissolved nitrogen. Importantly, the assimilation adjusted the balance of ecosystem processes by shifting the simulated food web towards the microbial loop, thus improving the estimation of some properties, e.g. total particulate carbon. Assimilation of Kd(443) outperformed a comparative chlorophyll assimilation experiment, in both the estimation of ocean colour data and in the simulation of independent in situ data. These results are related to relatively low error in Kd(443) data, and because it is a bulk optical property of marine ecosystems. Assimilation of remotely-sensed optical properties is a promising approach to improve the simulation of biogeochemical and optical variables that are relevant for ecosystem functioning and climate change studies.

  17. Optical modeling of graphene contacted CdTe solar cells

    NASA Astrophysics Data System (ADS)

    Aldosari, Marouf; Sohrabpoor, Hamed; Gorji, Nima E.

    2016-04-01

    For the first time, an optical model is applied on CdS/CdTe thin film solar cells with graphene front or back contact. Graphene is highly conductive and is as thin as a single atom which reduces the light reflection and absorption, and thus enhances the light transmission to CdTe layer for a wide range of wavelengths including IR. Graphene as front electrode of CdTe devices led to loss in short circuit current density of 10% ΔJsc ≤ 15% compared to the conventional electrodes of TCO and ITO at CdS thickness of dCdS = 100 nm. In addition, all the multilayer graphene electrodes with 2, 4, and 7 graphene layers led to Jsc ≤ 20 mA/cm2. Therefore, we conclude that a single monolayer graphene with hexagonal carbon network reduces optical losses and enhances the carrier collection measured as Jsc. In another structure design, we applied the optical model to graphene back contacted CdS/CdTe device. This scheme allows double side irradiation of the cell which is expected to enhance the Jsc. We obtained 1 ∼ 6 , 23, and 38 mA/cm2 for back, front and bifacial illumination of graphene contacted CdTe cell with CdS = 100 nm. The bifacial irradiated cell, to be efficient, requires an ultrathin CdTe film with dCdTe ≤ 1 μm. In this case, the junction electric field extends to the back region and collects out the generated carriers efficiently. This was modelled by absorptivity rather than transmission rate and optical losses. Since the literature suggest that ZnO can increase the graphene conductivity and enhance the Jsc, we performed our simulations for a graphene/ZnO electrode (ZnO = 100 nm) instead of a single graphene layer.

  18. SAPHIRE models and software for ASP evaluations

    SciTech Connect

    Sattison, M.B.; Schroeder, J.A.; Russell, K.D.

    1995-04-01

    The Idaho National Engineering Laboratory (INEL) over the past year has created 75 plant-specific Accident Sequence Precursor (ASP) models using the SAPHIRE suite of PRA codes. Along with the new models, the INEL has also developed a new module for SAPHIRE which is tailored specifically to the unique needs of conditional core damage probability (CCDP) evaluations. These models and software will be the next generation of risk tools for the evaluation of accident precursors by both NRR and AEOD. This paper presents an overview of the models and software. Key characteristics include: (1) classification of the plant models according to plant response with a unique set of event trees for each plant class, (2) plant-specific fault trees using supercomponents, (3) generation and retention of all system and sequence cutsets, (4) full flexibility in modifying logic, regenerating cutsets, and requantifying results, and (5) user interface for streamlined evaluation of ASP events.

  19. The Air Quality Model Evaluation International Initiative ...

    EPA Pesticide Factsheets

    This presentation provides an overview of the Air Quality Model Evaluation International Initiative (AQMEII). It contains a synopsis of the three phases of AQMEII, including objectives, logistics, and timelines. It also provides a number of examples of analyses conducted through AQMEII with a particular focus on past and future analyses of deposition. The National Exposure Research Laboratory (NERL) Computational Exposure Division (CED) develops and evaluates data, decision-support tools, and models to be applied to media-specific or receptor-specific problem areas. CED uses modeling-based approaches to characterize exposures, evaluate fate and transport, and support environmental diagnostics/forensics with input from multiple data sources. It also develops media- and receptor-specific models, process models, and decision support tools for use both within and outside of EPA.

  20. Performance evaluation of distributed wavelength assignment in WDM optical networks

    NASA Astrophysics Data System (ADS)

    Hashiguchi, Tomohiro; Wang, Xi; Morikawa, Hiroyuki; Aoyama, Tomonori

    2004-04-01

    In WDM wavelength routed networks, prior to a data transfer, a call setup procedure is required to reserve a wavelength path between the source-destination node pairs. A distributed approach to a connection setup can achieve a very high speed, while improving the reliability and reducing the implementation cost of the networks. However, along with many advantages, several major challenges have been posed by the distributed scheme in how the management and allocation of wavelength could be efficiently carried out. In this thesis, we apply a distributed wavelength assignment algorithm named priority based wavelength assignment (PWA) that was originally proposed for the use in burst switched optical networks to the problem of reserving wavelengths of path reservation protocols in the distributed control optical networks. Instead of assigning wavelengths randomly, this approach lets each node select the "safest" wavelengths based on the information of wavelength utilization history, thus unnecessary future contention is prevented. The simulation results presented in this paper show that the proposed protocol can enhance the performance of the system without introducing any apparent drawbacks.

  1. Evaluation of environmentally safe cleaning agents for diamond turned optics

    NASA Astrophysics Data System (ADS)

    Theye, Lonnie A.; Day, Robert D.; Weinrach, Jeffrey; Schubert, Rudolf; Seiffert, Stephen

    Precision machining of metal surfaces using diamond turning has increased greatly in popularity at LANL in recent years. Similar techniques are used extensively to manufacture metal mirrors for use in laser applications. The diamond turned surfaces are easily damaged, making the selection of a cleaning agent very critical. These surfaces have been traditionally cleaned using Trichloroethane (TCA) to remove residual oil remaining from the machining process. The TCA was then removed with an ethanol rinse, leaving a residue free surface. Recently, however, TCA was pronounced environmentally unsafe. Consequently, we are searching for an environmentally safe cleaning agent for these diamond turned metal optics. The concern with using alternative solvents is the potential for residual surface films that produce reflectivity changes related to a combination of wavelength, surface coverage, film thickness and dielectric properties. Therefore, we have initiated a program for testing the effectiveness of a variety of environmentally safe solvents used to clean diamond turned optical surfaces. Our basic test plan consists of comparing a number of environmentally safe solvents against the TCA/ethanol cleaning system. We have identified twelve candidate solvents, but have only been able to perform a partial test on one of them to date. This paper discusses the results obtained to date using this solvent known as P F.

  2. Estimation of kinetic model parameters in fluorescence optical diffusion tomography.

    PubMed

    Milstein, Adam B; Webb, Kevin J; Bouman, Charles A

    2005-07-01

    We present a technique for reconstructing the spatially dependent dynamics of a fluorescent contrast agent in turbid media. The dynamic behavior is described by linear and nonlinear parameters of a compartmental model or some other model with a deterministic functional form. The method extends our previous work in fluorescence optical diffusion tomography by parametrically reconstructing the time-dependent fluorescent yield. The reconstruction uses a Bayesian framework and parametric iterative coordinate descent optimization, which is closely related to Gauss-Seidel methods. We demonstrate the method with a simulation study.

  3. Fast Simulators for Satellite Cloud Optical Centroid Pressure Retrievals, 1. Evaluation of OMI Cloud Retrievals

    NASA Technical Reports Server (NTRS)

    Joiner, J.; Vasilkov, A.; Gupta, P.; Bhartia, P. K.; Veefkind, P.; Sneep, M.; de Haan, J.; Polonsky, I.; Spurr, R.

    2012-01-01

    The cloud Optical Centroid Pressure (OCP), also known as the effective cloud pressure, is a satellite-derived parameter that is commonly used in trace-gas retrievals to account for the effects of clouds on near-infrared through ultraviolet radiance measurements. Fast simulators are desirable to further expand the use of cloud OCP retrievals into the operational and climate communities for applications such as data assimilation and evaluation of cloud vertical structure in general circulation models. In this paper, we develop and validate fast simulators that provide estimates of the cloud OCP given a vertical profile of optical extinction. We use a pressure-weighting scheme where the weights depend upon optical parameters of clouds and/or aerosol. A cloud weighting function is easily extracted using this formulation. We then use fast simulators to compare two different satellite cloud OCP retrievals from the Ozone Monitoring Instrument (OMI) with estimates based on collocated cloud extinction profiles from a combination of CloudS at radar and MODIS visible radiance data. These comparisons are made over a wide range of conditions to provide a comprehensive validation of the OMI cloud OCP retrievals. We find generally good agreement between OMI cloud OCPs and those predicted by CloudSat. However, the OMI cloud OCPs from the two independent algorithms agree better with each other than either does with the estimates from CloudSat/MODIS. Differences between OMI cloud OCPs and those based on CloudSat/MODIS may result from undetected snow/ice at the surface, cloud 3-D effects, low altitude clouds missed by CloudSat, and the fact that CloudSat only observes a relatively small fraction of an OMI field-of-view.

  4. Optical coherence tomography angiography offers comprehensive evaluation of skin optical clearing in vivo by quantifying optical properties and blood flow imaging simultaneously

    NASA Astrophysics Data System (ADS)

    Guo, Li; Shi, Rui; Zhang, Chao; Zhu, Dan; Ding, Zhihua; Li, Peng

    2016-08-01

    Tissue optical clearing (TOC) is helpful for reducing scattering and enhancing the penetration depth of light, and shows promising potential in optimizing optical imaging performances. A mixture of fructose with PEG-400 and thiazone (FPT) is used as an optical clearing agent in mouse dorsal skin and evaluated with OCT angiography (Angio-OCT) by quantifying optical properties and blood flow imaging simultaneously. It is observed that FPT leads to an improved imaging performance for the deeper tissues. The imaging performance improvement is most likely caused by the FPT-induced dehydration of skin, and the reduction of scattering coefficient (more than ˜40.5%) and refractive-index mismatching (more than ˜25.3%) in the superficial (epidermal, dermal, and hypodermal) layers. A high correlation (up to ˜90%) between the relative changes in refractive-index mismatching and Angio-OCT signal strength is measured. The optical clearing rate is ˜5.83×10-5 cm/s. In addition, Angio-OCT demonstrates enhanced performance in imaging cutaneous hemodynamics with satisfactory spatiotemporal resolution and contrast when combined with TOC, which exhibits a powerful practical application in studying microcirculation.

  5. Evaluation of the stage of hemorrhage using optical diffuse reflectance spectroscopy: an in vivo study.

    PubMed

    Takeuchi, Satoru; Kawauchi, Satoko; Sato, Shunichi; Nawashiro, Hiroshi; Nagatani, Kimihiro; Kobayashi, Hiroaki; Otani, Naoki; Osada, Hideo; Wada, Kojiro; Shima, Katsuji

    2013-01-01

    Intracerebral hemorrhage (ICH) is a common and often fatal subtype of stroke. Estimation of the stage of hemorrhage allows clinicians to know when the hemorrhage occurred, even in unconscious patients, enabling decisions to be made about the optimal management and treatment strategy. After ICH, oxidative denaturation of the hemoglobin progresses, and deoxyhemoglobin is gradually converted to methemoglobin. MRI has been used to estimate the stage of hemorrhage by evaluating the status of hemoglobin. However, there is currently no bedside device that can be used for the measurement of hemoglobin derivatives in patients with hematomas. The aim of the present study was to investigate the validity of using optical diffuse reflectance spectroscopy (ODRS) for bedside evaluation of the stage of hemorrhage. An ICH model was generated in adult Sprague-Dawley male rats by stereotactically injecting 50 μl of autologous blood into the right caudate nucleus. To analyze the hemoglobin derivatives in the hematomas, ODRS measurement was performed for the rats in vivo. In all rats, we found increased absorption at around 630 nm, which indicated the formation of methemoglobin. In conclusion, the results of the present study suggest that ODRS allows clinicians to more easily evaluate the stage of hemorrhage at the patient's bedside.

  6. AeroCom INSITU Project: Comparison of Aerosol Optical Properties from In-situ Surface Measurements and Model Simulations

    NASA Astrophysics Data System (ADS)

    Schmeisser, L.; Andrews, E.; Schulz, M.; Fiebig, M.; Zhang, K.; Randles, C. A.; Myhre, G.; Chin, M.; Stier, P.; Takemura, T.; Krol, M. C.; Bian, H.; Skeie, R. B.; da Silva, A. M., Jr.; Kokkola, H.; Laakso, A.; Ghan, S.; Easter, R. C.

    2015-12-01

    AeroCom, an open international collaboration of scientists seeking to improve global aerosol models, recently initiated a project comparing model output to in-situ, surface-based measurements of aerosol optical properties. The model/measurement comparison project, called INSITU, aims to evaluate the performance of a suite of AeroCom aerosol models with site-specific observational data in order to inform iterative improvements to model aerosol modules. Surface in-situ data have the unique property of being traceable to physical standards, which is a big asset in accomplishing the overarching goal of bettering the accuracy of aerosol processes and predicative capability of global climate models. The INSITU project looks at how well models reproduce aerosol climatologies on a variety of time scales, aerosol characteristics and behaviors (e.g., aerosol persistence and the systematic relationships between aerosol optical properties), and aerosol trends. Though INSITU is a multi-year endeavor, preliminary phases of the analysis, using GOCART and other models participating in this AeroCom project, show substantial model biases in absorption and scattering coefficients compared to surface measurements, though the sign and magnitude of the bias varies with location and optical property. Spatial patterns in the biases highlight model weaknesses, e.g., the inability of models to properly simulate aerosol characteristics at sites with complex topography (see Figure 1). Additionally, differences in modeled and measured systematic variability of aerosol optical properties suggest that some models are not accurately capturing specific aerosol co-dependencies, for example, the tendency of in-situ surface single scattering albedo to decrease with decreasing aerosol extinction coefficient. This study elucidates specific problems with current aerosol models and suggests additional model runs and perturbations that could further evaluate the discrepancies between measured and modeled

  7. Full-field modeling of the longitudinal electro-optic probe.

    PubMed

    Freeman, J L; Jefferies, S R; Auld, B A

    1987-10-01

    Optical polarization changes and mode coupling due to spatially varying anisotropic perturbations in caused by electro-optic, acousto-optic, and other effects have been widely studied for both plane-wave and fiber mode propagation. A new optical S-parameter analysis of these effects, applicable to arbitrary optical field distributions, is presented. It is applied to evaluating the performance of the longitudinal electro-optic probe used for noninva-sively examining GaAs integrated circuits. Error in probe measurements of circuit voltage distributions can be characterized by considering the probe as a scanned electro-optic spatial filter.

  8. Optical modeling of volcanic ash particles using ellipsoids

    NASA Astrophysics Data System (ADS)

    Merikallio, Sini; Muñoz, Olga; Sundström, Anu-Maija; Virtanen, Timo H.; Horttanainen, Matti; de Leeuw, Gerrit; Nousiainen, Timo

    2015-05-01

    The single-scattering properties of volcanic ash particles are modeled here by using ellipsoidal shapes. Ellipsoids are expected to improve the accuracy of the retrieval of aerosol properties using remote sensing techniques, which are currently often based on oversimplified assumptions of spherical ash particles. Measurements of the single-scattering optical properties of ash particles from several volcanoes across the globe, including previously unpublished measurements from the Eyjafjallajökull and Puyehue volcanoes, are used to assess the performance of the ellipsoidal particle models. These comparisons between the measurements and the ellipsoidal particle model include consideration of the whole scattering matrix, as well as sensitivity studies on the point of view of the Advanced Along Track Scanning Radiometer (AATSR) instrument. AATSR, which flew on the ENVISAT satellite, offers two viewing directions but no information on polarization, so usually only the phase function is relevant for interpreting its measurements. As expected, ensembles of ellipsoids are able to reproduce the observed scattering matrix more faithfully than spheres. Performance of ellipsoid ensembles depends on the distribution of particle shapes, which we tried to optimize. No single specific shape distribution could be found that would perform superiorly in all situations, but all of the best-fit ellipsoidal distributions, as well as the additionally tested equiprobable distribution, improved greatly over the performance of spheres. We conclude that an equiprobable shape distribution of ellipsoidal model particles is a relatively good, yet enticingly simple, approach for modeling volcanic ash single-scattering optical properties.

  9. Comparison of wavefront sensor models for simulation of adaptive optics.

    PubMed

    Wu, Zhiwen; Enmark, Anita; Owner-Petersen, Mette; Andersen, Torben

    2009-10-26

    The new generation of extremely large telescopes will have adaptive optics. Due to the complexity and cost of such systems, it is important to simulate their performance before construction. Most systems planned will have Shack-Hartmann wavefront sensors. Different mathematical models are available for simulation of such wavefront sensors. The choice of wavefront sensor model strongly influences computation time and simulation accuracy. We have studied the influence of three wavefront sensor models on performance calculations for a generic, adaptive optics (AO) system designed for K-band operation of a 42 m telescope. The performance of this AO system has been investigated both for reduced wavelengths and for reduced r(0) in the K band. The telescope AO system was designed for K-band operation, that is both the subaperture size and the actuator pitch were matched to a fixed value of r(0) in the K-band. We find that under certain conditions, such as investigating limiting guide star magnitude for large Strehl-ratios, a full model based on Fraunhofer propagation to the subimages is significantly more accurate. It does however require long computation times. The shortcomings of simpler models based on either direct use of average wavefront tilt over the subapertures for actuator control, or use of the average tilt to move a precalculated point spread function in the subimages are most pronounced for studies of system limitations to operating parameter variations. In the long run, efficient parallelization techniques may be developed to overcome the problem.

  10. Biomechanical Assessment in Models of Glaucomatous Optic Neuropathy

    PubMed Central

    Nguyen, Thao D.; Ethier, C. Ross

    2015-01-01

    The biomechanical environment within the eye is of interest in both the regulation of intraocular pressure and the loss of retinal ganglion cell axons in glaucomatous optic neuropathy. Unfortunately, this environment is complex and difficult to determine. Here we provide a brief introduction to basic concepts of mechanics (stress, strain, constitutive relationships) as applied to the eye, and then describe a variety of experimental and computational approaches used to study ocular biomechanics. These include finite element modeling, direct experimental measurements of tissue displacements using optical and other techniques, direct experimental measurement of tissue microstructure, and combinations thereof. Thanks to notable technical and conceptual advances in all of these areas, we are slowly gaining a better understanding of how tissue biomechanical properties in both the anterior and posterior segments may influence the development of, and risk for, glaucomatous optic neuropathy. Although many challenging research questions remain unanswered, the potential of this body of work is exciting; projects underway include the coupling of clinical imaging with biomechanical modeling to create new diagnostic tools, development of IOP control strategies based on improved understanding the mechanobiology of the outflow tract, and attempts to develop novel biomechanically-based therapeutic strategies for preservation of vision in glaucoma. PMID:26115620

  11. Modeling of optical quadrature microscopy for imaging mouse embryos

    NASA Astrophysics Data System (ADS)

    Warger, William C., II; DiMarzio, Charles A.

    2008-02-01

    Optical quadrature microscopy (OQM) has been shown to provide the optical path difference through a mouse embryo, and has led to a novel method to count the total number of cells further into development than current non-toxic imaging techniques used in the clinic. The cell counting method has the potential to provide an additional quantitative viability marker for blastocyst transfer during in vitro fertilization. OQM uses a 633 nm laser within a modified Mach-Zehnder interferometer configuration to measure the amplitude and phase of the signal beam that travels through the embryo. Four cameras preceded by multiple beamsplitters record the four interferograms that are used within a reconstruction algorithm to produce an image of the complex electric field amplitude. Here we present a model for the electric field through the primary optical components in the imaging configuration and the reconstruction algorithm to calculate the signal to noise ratio when imaging mouse embryos. The model includes magnitude and phase errors in the individual reference and sample paths, fixed pattern noise, and noise within the laser and detectors. This analysis provides the foundation for determining the imaging limitations of OQM and the basis to optimize the cell counting method in order to introduce additional quantitative viability markers.

  12. Wavefront Sensing for WFIRST with a Linear Optical Model

    NASA Technical Reports Server (NTRS)

    Jurling, Alden S.; Content, David A.

    2012-01-01

    In this paper we develop methods to use a linear optical model to capture the field dependence of wavefront aberrations in a nonlinear optimization-based phase retrieval algorithm for image-based wavefront sensing. The linear optical model is generated from a ray trace model of the system and allows the system state to be described in terms of mechanical alignment parameters rather than wavefront coefficients. This approach allows joint optimization over images taken at different field points and does not require separate convergence of phase retrieval at individual field points. Because the algorithm exploits field diversity, multiple defocused images per field point are not required for robustness. Furthermore, because it is possible to simultaneously fit images of many stars over the field, it is not necessary to use a fixed defocus to achieve adequate signal-to-noise ratio despite having images with high dynamic range. This allows high performance wavefront sensing using in-focus science data. We applied this technique in a simulation model based on the Wide Field Infrared Survey Telescope (WFIRST) Intermediate Design Reference Mission (IDRM) imager using a linear optical model with 25 field points. We demonstrate sub-thousandth-wave wavefront sensing accuracy in the presence of noise and moderate undersampling for both monochromatic and polychromatic images using 25 high-SNR target stars. Using these high-quality wavefront sensing results, we are able to generate upsampled point-spread functions (PSFs) and use them to determine PSF ellipticity to high accuracy in order to reduce the systematic impact of aberrations on the accuracy of galactic ellipticity determination for weak-lensing science.

  13. Wavefront sensing for WFIRST with a linear optical model

    NASA Astrophysics Data System (ADS)

    Jurling, Alden S.; Content, David A.

    2012-09-01

    In this paper we develop methods to use a linear optical model to capture the field dependence of wavefront aberrations in a nonlinear optimization-based phase retrieval algorithm for image-based wavefront sensing. The linear optical model is generated from a ray trace model of the system and allows the system state to be described in terms of mechanical alignment parameters rather than wavefront coefficients. This approach allows joint optimization over images taken at different field points and does not require separate convergence of phase retrieval at individual field points. Because the algorithm exploits field diversity, multiple defocused images per field point are not required for robustness. Furthermore, because it is possible to simultaneously fit images of many stars over the field, it is not necessary to use a fixed defocus to achieve adequate signal-to-noise ratio despite having images with high dynamic range. This allows high performance wavefront sensing using in-focus science data. We applied this technique in a simulation model based on the Wide Field Infrared Survey Telescope (WFIRST) Intermediate Design Reference Mission (IDRM) imager using a linear optical model with 25 field points. We demonstrate sub-thousandth-wave wavefront sensing accuracy in the presence of noise and moderate undersampling for both monochromatic and polychromatic images using 25 high-SNR target stars. Using these high-quality wavefront sensing results, we are able to generate upsampled point-spread functions (PSFs) and use them to determine PSF ellipticity to high accuracy in order to reduce the systematic impact of aberrations on the accuracy of galactic ellipticity determination for weak-lensing science.

  14. Modeling of Electro Optic Polymer Electrical Characteristics in a 3 layer Optical Waveguide Modulator

    NASA Technical Reports Server (NTRS)

    Watson, Michael D.; Ashley, Paul R.; Guenthner, Andrew J.; Abushagur, Mustafa

    2004-01-01

    The electrical characteristics of electro optic polymer waveguide modulators are often described by the bulk reactance of the individual layers. However, the resistance and capacitance between the layers can significantly alter the electrical performance of a waveguide modulator. These interface characteristics are related to the boundary charge density and are strongly affected by the adhesion of the layers in the waveguide stack. An electrical reactance model has been derived to investigate this phenomenon at low frequencies. The model shows the waveguide stack frequency response has no limiting effects below the microwave range and that a true DC response requires a stable voltage for over 1000 hours. Thus, reactance of the layers is the key characteristic of optimizing the voltage across the core layer, even at very low frequencies (> 10(exp -6) Hz). The results of the model are compared with experimental data for two polymer systems and show quite good correlation.

  15. Numerical modelling of multimode fibre-optic communication lines

    SciTech Connect

    Sidelnikov, O S; Fedoruk, M P; Sygletos, S; Ferreira, F

    2016-01-31

    The results of numerical modelling of nonlinear propagation of an optical signal in multimode fibres with a small differential group delay are presented. It is found that the dependence of the error vector magnitude (EVM) on the differential group delay can be reduced by increasing the number of ADC samples per symbol in the numerical implementation of the differential group delay compensation algorithm in the receiver. The possibility of using multimode fibres with a small differential group delay for data transmission in modern digital communication systems is demonstrated. It is shown that with increasing number of modes the strong coupling regime provides a lower EVM level than the weak coupling one. (fibre-optic communication lines)

  16. Optical Property Evaluation of Next Generation Thermal Control Coatings

    NASA Technical Reports Server (NTRS)

    Jaworske, Donald A.; Deshpande, Mukund S.; Pierson, Edward A.

    2010-01-01

    Next generation white thermal control coatings were developed via the Small Business Innovative Research program utilizing lithium silicate chemistry as a binder. Doping of the binder with additives yielded a powder that was plasma spray capable and that could be applied to light weight polymers and carbon-carbon composite surfaces. The plasma sprayed coating had acceptable beginning-of-life and end-of-live optical properties, as indicated by a successful 1.5 year exposure to the space environment in low Earth orbit. Recent studies also showed the coating to be durable to simulated space environments consisting of 1 keV and 10 keV electrons, 4.5 MeV electrons, and thermal cycling. Large scale deposition was demonstrated on a polymer matrix composite radiator panel, leading to the selection of the coating for use on the Gravity Recovery And Interior Laboratory (GRAIL) mission.

  17. Finite element analysis to evaluate optical mirror deformations

    NASA Astrophysics Data System (ADS)

    Izazaga-Pérez, R.; Aguirre-Aguirre, D.; Villalobos-Mendoza, B.

    2015-10-01

    In this work we describe the use of Finite Element Analysis software to simulate the deformations of an optical mirror. We use Finite Element Method software as a tool to simulate the mirror deformations assuming that it is a thin plate that can be mechanically tensed or compressed; the Finite Element Analysis give us information about the displacements of the mirror from an initial position and the tensions that remains in the surface. The information obtained by means of Finite Element Analysis can be easily exported to a coordinate system and processed in a simulation environment. Finally, a ray-tracing subroutine is used in the obtained data giving us information in terms of aberration coefficients. We present some results of the simulations describing the followed procedure.

  18. Performance evaluation of a holographic optical neural network system

    NASA Astrophysics Data System (ADS)

    Lu, Thomas T.; Kostrzewski, Andrew A.; Chou, Hung; Wu, Shudong; Lin, Freddie S.

    1993-02-01

    One of the most outstanding properties of artificial neural networks is their capability for massive interconnection and parallel processing. Recently, specialized electronic neural network processors and VLSI neural chips have been introduced to the commercial market. The number of parallel channels they can handle is limited because of the limited parallel interconnections number with one-dimensional (1-D) electronic wires. High resolution pattern recognition problems may require a large number of neurons for parallel processing of the image. The holographic optical neural network (HONN) based on high resolution volume holographic materials is capable of providing 3-D massive parallel interconnection of tens of thousand of neurons. A HONN with 3600 neurons, contained in a portable briefcase, has been developed. Rotation-shift-scale invariant pattern recognition operations have been demonstrated with this system. System parameters, such as signal-to-noise ratio, dynamic range, and processing speed, will be discussed.

  19. Development and evaluation of optical fiber NH3 sensors for application in air quality monitoring

    NASA Astrophysics Data System (ADS)

    Huang, Yu; Wieck, Lucas; Tao, Shiquan

    2013-02-01

    Ammonia is a major air pollutant emitted from agricultural practices. Sources of ammonia include manure from animal feeding operations and fertilizer from cropping systems. Sensor technologies with capability of continuous real time monitoring of ammonia concentration in air are needed to qualify ammonia emissions from agricultural activities and further evaluate human and animal health effects, study ammonia environmental chemistry, and provide baseline data for air quality standard. We have developed fiber optic ammonia sensors using different sensing reagents and different polymers for immobilizing sensing reagents. The reversible fiber optic sensors have detection limits down to low ppbv levels. The response time of these sensors ranges from seconds to tens minutes depending on transducer design. In this paper, we report our results in the development and evaluation of fiber optic sensor technologies for air quality monitoring. The effect of change of temperature, humidity and carbon dioxide concentration on fiber optic ammonia sensors has been investigated. Carbon dioxide in air was found not interfere the fiber optic sensors for monitoring NH3. However, the change of humidity can cause interferences to some fiber optic NH3 sensors depending on the sensor's transducer design. The sensitivity of fiber optic NH3 sensors was found depends on temperature. Methods and techniques for eliminating these interferences have been proposed.

  20. Performance evaluation of 10GBASE optical transceivers for Cisco 10-gigabit Ethernet switching architecture

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaojing; Cain, Jeff C.

    2002-09-01

    This paper presents the process and methodology employed to perform evaluation and analyses for the optical interface that delivers and receives 10Gb/s Ethernet traffic on Cisco's industrial leading switching architecture. Especially, we examined in detail the optical properties for commercially available 10GBASE-LR transceiver modules, with respect to IEEE 802.3ae specifications. The sampled results under room temperature are listed for comparison. Eye diagrams were recorded as a function of transmission distance, as well as temperature variation. System stability issues are also studied following a brief introduction to Cisco standard ODVT (Optical Design Verification Test) procedure.

  1. A physical model eye with 3D resolution test targets for optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Hu, Zhixiong; Liu, Wenli; Hong, Baoyu; Hao, Bingtao; Wang, Lele; Li, Jiao

    2014-09-01

    Optical coherence tomography (OCT) has been widely employed as non-invasive 3D imaging diagnostic instrument, particularly in the field of ophthalmology. Although OCT has been approved for use in clinic in USA, Europe and Asia, international standardization of this technology is still in progress. Validation of OCT imaging capabilities is considered extremely important to ensure its effective use in clinical diagnoses. Phantom with appropriate test targets can assist evaluate and calibrate imaging performance of OCT at both installation and throughout lifetime of the instrument. In this paper, we design and fabricate a physical model eye with 3D resolution test targets to characterize OCT imaging performance. The model eye was fabricated with transparent resin to simulate realistic ophthalmic testing environment, and most key optical elements including cornea, lens and vitreous body were realized. The test targets which mimic USAF 1951 test chart were fabricated on the fundus of the model eye by 3D printing technology. Differing from traditional two dimensional USAF 1951 test chart, a group of patterns which have different thickness in depth were fabricated. By measuring the 3D test targets, axial resolution as well as lateral resolution of an OCT system can be evaluated at the same time with this model eye. To investigate this specialized model eye, it was measured by a scientific spectral domain OCT instrument and a clinical OCT system respectively. The results demonstrate that the model eye with 3D resolution test targets have the potential of qualitatively and quantitatively validating the performance of OCT systems.

  2. Evaluation of the Use of the Hopfield Neural Network Model as a Nearest-Neighbor Algorithm,

    DTIC Science & Technology

    Neural network models are receiving increasing attention because of their collective computational capabilities. This reprint evaluates the use of...the Hopfield neural network model in optically determining the nearest-neighbor of a binary bipolar test vector from a set of binary bipolar reference

  3. Design and Performance Evaluation of Sensors and Actuators for Advanced Optical Systems

    NASA Technical Reports Server (NTRS)

    Clark, Natalie

    2011-01-01

    Current state-of-the-art commercial sensors and actuators do not meet many of NASA s next generation spacecraft and instrument needs. Nor do they satisfy the DoD needs for satellite missions, especially micro/nano satellite missions. In an effort to develop advanced optical devices and instruments that meet mission requirements, NASA Langley recently completed construction of a new cleanroom housing equipment capable of fabricating high performance active optic and adaptive optic technologies including deformable mirrors, reconfigurable lenses (both refractive and diffractive), spectrometers, spectro-polarimeters, tunable filters and many other active optic devices. In addition to performance, these advanced optic technologies offer advantages in speed, size, weight, power consumption, and radiation tolerance. The active optic devices described in this paper rely on birefringent liquid crystal materials to alter either the phase or the polarization of the incoming light. Design considerations and performance evaluation results for various NASA applications are presented. Applications presented will include large space telescopes, optical communications, spacecraft windows, coronagraphs, and star trackers. Keywords: Photonics, Adaptive Optics, Tunable Filters, MEMs., MOEMs, Coronagraph, Star Tracker

  4. A time-resolved subtraction method for evaluating the optical properties of layered turbid media (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Milej, Daniel; Abdalmalak, Androu; Diop, Mamadou; Liebert, Adam; St. Lawrence, Keith

    2016-03-01

    The analysis of statistical moments of time-resolved (TR) diffuse optical signals can be used to evaluate the absorption and scattering coefficients of turbid media; however, this method requires careful measurement of the instrument response function. We propose an alternative approach that avoids this step by estimating the optical properties from the difference of TR measurements acquired at different source-detector separations. The efficiency of this method was validated using simulated data (from analytical model and Monte-Carlo simulations) and tissue-mimicking phantoms. Results for a homogenous and layered medium showed that the subtraction technique can accurately estimate the optical properties. Specifically, our preliminary results show that the method can estimate the optical properties of a homogeneous medium (simulated using μa = 0.1 mm-1, μs' = 10 mm-1) with an error less than 10 %. Accurate results were obtained at source-detector separations large enough (5 mm or greater) to resolve differences in the moments. Moreover, we also observed that the subtraction method has improved depth sensitivity compared to the classic method of moments. These results suggests that time-resolved subtraction is a simple but effective means of quantifying optical properties of turbid media, in addition to offering a new approach for obtaining spatially sensitive measurements, although additional studies are required to confirm the latter.

  5. Evaluation of aerosol optical properties of GEOS-Chem over East Asia during the DRAGON-Asia 2012 campaign

    NASA Astrophysics Data System (ADS)

    Jo, D. S.; Park, R.; Kim, J.

    2015-12-01

    A nested version of 3-D chemical transport model (GEOS-Chem v9-01-02) is evaluated over East Asia during the Distributed Regional Aerosol Gridded Observation Networks (DRAGON)-Asia 2012 campaign period, focusing on fine-mode aerosol optical depth (fAOD) and single scattering albedo (SSA). Both are important to assess the effect of anthropogenic aerosols on climate. We compare the daily mean simulated optical properties of aerosols with the observations from DRAGON-Asia campaign for March-May, 2012 (provided in level 2.0: cloud screened and quality assured). We find that the model reproduces the observed daily variability of fAOD (R=0.67), but overestimates the magnitude by 30%, which is in general consistent with other global model comparisons from ACCMIP. However, a significant high bias in the model is found compared to the observed SSA at 440 nm, which is important for determining the sign of aerosol radiative forcing. In order to understand causes for this gap we conduct several sensitivity tests by changing source magnitudes and input parameters of aerosols, affecting the aerosol optical properties under various atmospheric conditions, which allows us to reduce the gap and to find the optimal values in the model.

  6. A trap potential model investigation of the optical activity induced in dye-DNA intercalation complexes

    NASA Astrophysics Data System (ADS)

    Kamiya, Mamoru

    1988-02-01

    The fundamental features of the optical activity induced in dye-DNA intercalation complexes are studied by application of the trap potential model which is useful to evaluate the induced rotational strength without reference to detailed geometrical information about the intercalation complexes. The specific effect of the potential depth upon the induced optical activity is explained in terms of the relative magnitudes of the wave-phase and helix-phase variations in the path of an electron moving on a restricted helical segment just like an exciton trapped around the dye intercalation site. The parallel and perpendicular components of the induced rotational strength well reflect basic properties of the helicity effects about the longitudinal and tangential axes of the DNA helical cylinder. The trap potential model is applied to optimize the potential parameters so as to reproduce the ionic strength effect upon the optical activity induced to proflavine-DNA intercalation complexes. From relationships between the optimized potential parameters and ionic strengths, it is inferred that increase in the ionic strength contributes to the optical activity induced by the nearest-neighbour interaction between intercalated proflavine and DNA base pairs.

  7. Evaluating AEROCOM Models with Remote Sensing Datasets

    NASA Astrophysics Data System (ADS)

    Schutgens, N.; Gryspeerdt, E.; Weigum, N.; Veira, A.; Partridge, D.; Stier, P.

    2014-12-01

    We present an in-depth evaluation of AEROCOM models with a variety of remote sensing datasets: MODIS AOT (& AE over ocean), AERONET, AOT, AE & SSA and Maritime Aerosol Network (MAN) AOT & AE. Together these datasets provide extensive global and temporal coverage and measure both extensive (AOT) as well as intensive aerosol properties (AE & SSA). Models and observations differ strongly in their spatio-temporal sampling. Model results are typical of large gridboxes (100 by 100 km), while observations are made over much smaller areas (10 by 10 km for MODIS, even smaller for AERONET and MAN). Model results are always available in contrast to observations that are intermittent due to orbital constraints, retrieval limitations and instrument failure/maintenance. We find that differences in AOT due to sampling effects can be 100% for instantaneous values and can still be 40% for monthly or yearly averages. Such differences are comparable to or larger than typical retrieval errors in the observations. We propose strategies (temporal colocation, spatial aggregation) for reducing these sampling errors Finally, we evaluate one year of co-located AOT, AE and SSA from several AEROCOM models against MODIS, AERONET and MAN observations. Where the observational datasets overlap, they give similar results but in general they allow us to evaluate models in very different spatio-temporal domains. We show that even small datasets like MAN AOT or AERONET SSA, provide a useful standard for evaluating models thanks to temporal colocation. The models differ quite a bit from the observations and each model differs in its own way. These results are presented through global maps of yearly averaged differences, time-series of modelled and observed data, scatter plots of correlations among observables (e.g. SSA vs AE) and Taylor diagrams. In particular, we find that the AEROCOM emissions substantially underestimate wildfire emissions and that many models have aerosol that is too absorbing.

  8. RAPID OPTICAL SCREEN TOOL (ROST™) - INNOVATIVE TECHNOLOGY EVALUATION REPORT

    EPA Science Inventory

    In August 1994, a demonstration of cone penetrometer-mounted sensor technologies took place to evaluate their effectiveness in sampling and analyzing the physical and chemical characteristics of subsurface soil at hazardous waste sites. The effectiveness of each technology was ev...

  9. Evaluation of a lake whitefish bioenergetics model

    USGS Publications Warehouse

    Madenjian, Charles P.; O'Connor, Daniel V.; Pothoven, Steven A.; Schneeberger, Philip J.; Rediske, Richard R.; O'Keefe, James P.; Bergstedt, Roger A.; Argyle, Ray L.; Brandt, Stephen B.

    2006-01-01

    We evaluated the Wisconsin bioenergetics model for lake whitefish Coregonus clupeaformis in the laboratory and in the field. For the laboratory evaluation, lake whitefish were fed rainbow smelt Osmerus mordax in four laboratory tanks during a 133-d experiment. Based on a comparison of bioenergetics model predictions of lake whitefish food consumption and growth with observed consumption and growth, we concluded that the bioenergetics model furnished significantly biased estimates of both food consumption and growth. On average, the model overestimated consumption by 61% and underestimated growth by 16%. The source of the bias was probably an overestimation of the respiration rate. We therefore adjusted the respiration component of the bioenergetics model to obtain a good fit of the model to the observed consumption and growth in our laboratory tanks. Based on the adjusted model, predictions of food consumption over the 133-d period fell within 5% of observed consumption in three of the four tanks and within 9% of observed consumption in the remaining tank. We used polychlorinated biphenyls (PCBs) as a tracer to evaluate model performance in the field. Based on our laboratory experiment, the efficiency with which lake whitefish retained PCBs from their food (I?) was estimated at 0.45. We applied the bioenergetics model to Lake Michigan lake whitefish and then used PCB determinations of both lake whitefish and their prey from Lake Michigan to estimate p in the field. Application of the original model to Lake Michigan lake whitefish yielded a field estimate of 0.28, implying that the original formulation of the model overestimated consumption in Lake Michigan by 61%. Application of the bioenergetics model with the adjusted respiration component resulted in a field I? estimate of 0.56, implying that this revised model underestimated consumption by 20%.

  10. Infrared fiber optic probes for evaluation of musculoskeletal tissue pathology

    NASA Astrophysics Data System (ADS)

    Padalkar, Mugdha; McGoverin, Cushla; Onigbanjo, Quam; Spencer, Richard; Barbash, Scott; Kropf, Eric; Pleshko, Nancy

    2014-03-01

    Musculoskeletal pathology of the knee commonly occurs with aging and as a result of injury. The incidence of anterior cruciate ligament (ACL) injuries continues to increase annually, and may precede the eventual onset of osteoarthritis (OA), a debilitating and prevalent disease characterized by cartilage degeneration. Early detection of OA remains elusive, with current imaging methods lacking adequate sensitivity to detect early pathologic cartilage changes. We used mid- and near- infrared (IR) spectroscopy through arthroscopic-based fiber-optic devices to assess cartilage damage and differentiate tendon from ligament. Mid-IR spectroscopy is characterized by distinct bands and low penetration depth (< 10 μm) and near-IR spectroscopy is characterized by complex overlapping bands and greater penetration depths (< 1 cm). We have found that combined mid- and near-IR analysis greatly extends the information available through either in the analysis of soft tissues, including cartilage, ligaments and tendons. We discuss here basic science studies and the potential for translation to clinical research with novel arthroscopic probes.

  11. Evaluation of a digital optical ionizing radiation particle track detector

    SciTech Connect

    Hunter, S.R.

    1987-06-01

    An ionizing radiation particle track detector is outlined which can, in principle, determine the three-dimensional spatial distribution of all the secondary electrons produced by the passage of ionizing radiation through a low-pressure (0.1 to 10 kPa) gas. The electrons in the particle track are excited by the presence of a high-frequency AC electric field, and two digital cameras image the optical radiation produced in electronic excitation collisions of the surroundings gas by the electrons. The specific requirements of the detector for neutron dosimetry and microdosimetry are outlined (i.e., operating conditions of the digital cameras, high voltage fields, gas mixtures, etc.) along with an estimate of the resolution and sensitivity achievable with this technique. The proposed detector is shown to compare favorable with other methods for obtaining the details of the track structure, particularly in the quality of the information obtainable about the particle track and the comparative simplicity and adaptability of the detector for measuring the secondary electron track structure for many forms of ionizing radiation over a wide range of energies.

  12. Modeling bidirectional reflectance of forests and woodlands using Boolean models and geometric optics

    NASA Technical Reports Server (NTRS)

    Strahler, Alan H.; Jupp, David L. B.

    1990-01-01

    Geometric-optical discrete-element mathematical models for forest canopies have been developed using the Boolean logic and models of Serra. The geometric-optical approach is considered to be particularly well suited to describing the bidirectional reflectance of forest woodland canopies, where the concentration of leaf material within crowns and the resulting between-tree gaps make plane-parallel, radiative-transfer models inappropriate. The approach leads to invertible formulations, in which the spatial and directional variance provides the means for remote estimation of tree crown size, shape, and total cover from remotedly sensed imagery.

  13. Multi-Valued Neural Network Modified Model and Its Optical Realization,

    DTIC Science & Technology

    1995-03-07

    This paper presents a modified optical neural networK model, and the optical system, constructed with spatial light modulator PROM, can materialize...modified model improves cognitive ability of an optical neural network and also improves the storage capacity to a certain extent.

  14. Optical coherence tomography and hyperspectral imaging of vascular recovery in a model of peripheral arterial disease

    NASA Astrophysics Data System (ADS)

    Poole, Kristin M.; Sit, Wesley W.; Tucker-Schwartz, Jason M.; Duvall, Craig L.; Skala, Melissa C.

    2013-03-01

    Peripheral arterial disease (PAD) leads to an increased risk of myocardial infarction and stroke, increased mortality, and reduced quality of life. The mouse hind limb ischemia (HLI) model is the most commonly used system for studying the mechanisms of collateral vessel formation and for testing new PAD therapies, but there is a lack of techniques for acquiring physiologically-relevant, quantitative data intravitally in this model. In this work, non-invasive, quantitative optical imaging techniques were applied to the mouse HLI model over a time course. Optical coherence tomography (OCT) imaged changes in blood flow (Doppler OCT) and microvessel morphology (speckle variance OCT) through the skin of haired mice with high resolution. Hyperspectral imaging was also used to quantify blood oxygenation. In ischemic limbs, blood oxygenation in the footpad was substantially reduced after induction of ischemia followed by complete recovery by three weeks, consistent with standard measures. Three dimensional images of the vasculature distal to vessel occlusion acquired with speckle variance OCT revealed changes in OCT flow signal and vessel morphology. Taken together, OCT and hyperspectral imaging enable intravital acquisition of both functional and morphological data which fill critical gaps in understanding structure-function relationships that contribute to recovery in the mouse HLI model. Therefore, these optical imaging methods hold promise as tools for studying the mechanisms of vascular recovery and evaluating novel therapeutic treatments in preclinical studies.

  15. Saphire models and software for ASP evaluations

    SciTech Connect

    Sattison, M.B.

    1997-02-01

    The Idaho National Engineering Laboratory (INEL) over the three years has created 75 plant-specific Accident Sequence Precursor (ASP) models using the SAPHIRE suite of PRA codes. Along with the new models, the INEL has also developed a new module for SAPHIRE which is tailored specifically to the unique needs of ASP evaluations. These models and software will be the next generation of risk tools for the evaluation of accident precursors by both the U.S. Nuclear Regulatory Commission`s (NRC`s) Office of Nuclear Reactor Regulation (NRR) and the Office for Analysis and Evaluation of Operational Data (AEOD). This paper presents an overview of the models and software. Key characteristics include: (1) classification of the plant models according to plant response with a unique set of event trees for each plant class, (2) plant-specific fault trees using supercomponents, (3) generation and retention of all system and sequence cutsets, (4) full flexibility in modifying logic, regenerating cutsets, and requantifying results, and (5) user interface for streamlined evaluation of ASP events. Future plans for the ASP models is also presented.

  16. Integrated modeling of the GMT laser tomography adaptive optics system

    NASA Astrophysics Data System (ADS)

    Piatrou, Piotr

    2014-08-01

    Laser Tomography Adaptive Optics (LTAO) is one of adaptive optics systems planned for the Giant Magellan Telescope (GMT). End-to-end simulation tools that are able to cope with the complexity and computational burden of the AO systems to be installed on the extremely large telescopes such as GMT prove to be an integral part of the GMT LTAO system development endeavors. SL95, the Fortran 95 Simulation Library, is one of the software tools successfully used for the LTAO system end-to-end simulations. The goal of SL95 project is to provide a complete set of generic, richly parameterized mathematical models for key elements of the segmented telescope wavefront control systems including both active and adaptive optics as well as the models for atmospheric turbulence, extended light sources like Laser Guide Stars (LGS), light propagation engines and closed-loop controllers. The library is implemented as a hierarchical collection of classes capable of mutual interaction, which allows one to assemble complex wavefront control system configurations with multiple interacting control channels. In this paper we demonstrate the SL95 capabilities by building an integrated end-to-end model of the GMT LTAO system with 7 control channels: LGS tomography with Adaptive Secondary and on-instrument deformable mirrors, tip-tilt and vibration control, LGS stabilization, LGS focus control, truth sensor-based dynamic noncommon path aberration rejection, pupil position control, SLODAR-like embedded turbulence profiler. The rich parameterization of the SL95 classes allows to build detailed error budgets propagating through the system multiple errors and perturbations such as turbulence-, telescope-, telescope misalignment-, segment phasing error-, non-common path-induced aberrations, sensor noises, deformable mirror-to-sensor mis-registration, vibration, temporal errors, etc. We will present a short description of the SL95 architecture, as well as the sample GMT LTAO system simulation

  17. Generalized methodology for modeling and simulating optical interconnection networks using diffraction analysis

    NASA Astrophysics Data System (ADS)

    Louri, Ahmed; Major, Michael C.

    1995-07-01

    Research in the field of free-space optical interconnection networks has reached a point where simula-tors and other design tools are desirable for reducing development costs and for improving design time. Previously proposed methodologies have only been applicable to simple systems. Our goal was to develop a simulation methodology capable of evaluating the performance characteristics for a variety of different free-space networks under a range of different configurations and operating states. The proposed methodology operates by first establishing the optical signal powers at various locations in the network. These powers are developed through the simulation by diffraction analysis of the light propagation through the network. After this evaluation, characteristics such as bit-error rate, signal-to-noise ratio, and system bandwidth are calculated. Further, the simultaneous evaluation of this process for a set of component misalignments provides a measure of the alignment tolerance of a design. We discuss this simulation process in detail as well as provide models for different optical interconnection network components.

  18. Advanced optical position sensors for magnetically suspended wind tunnel models

    NASA Technical Reports Server (NTRS)

    Lafleur, S.

    1985-01-01

    A major concern to aerodynamicists has been the corruption of wind tunnel test data by model support structures, such as stings or struts. A technique for magnetically suspending wind tunnel models was considered by Tournier and Laurenceau (1957) in order to overcome this problem. This technique is now implemented with the aid of a Large Magnetic Suspension and Balance System (LMSBS) and advanced position sensors for measuring model attitude and position within the test section. Two different optical position sensors are discussed, taking into account a device based on the use of linear CCD arrays, and a device utilizing area CID cameras. Current techniques in image processing have been employed to develop target tracking algorithms capable of subpixel resolution for the sensors. The algorithms are discussed in detail, and some preliminary test results are reported.

  19. Evaluation of MODIS aerosol optical depth for semi­-arid environments in complex terrain

    NASA Astrophysics Data System (ADS)

    Holmes, H.; Loria Salazar, S. M.; Panorska, A. K.; Arnott, W. P.; Barnard, J.

    2015-12-01

    The use of satellite remote sensing to estimate spatially resolved ground level air pollutant concentrations is increasing due to advancements in remote sensing technology and the limited number of surface observations. Satellite retrievals provide global, spatiotemporal air quality information and are used to track plumes, estimate human exposures, model emissions, and determine sources (i.e., natural versus anthropogenic) in regulatory applications. Ground level PM2.5 concentrations can be estimated using columnar aerosol optical depth (AOD) from MODIS, where the satellite retrieval serves as a spatial surrogate to simulate surface PM2.5 gradients. The spatial statistical models and MODIS AOD retrieval algorithms have been evaluated for the dark, vegetated eastern US, while the semi-arid western US continues to be an understudied region with associated complexity due to heterogeneous emissions, smoke from wildfires, and complex terrain. The objective of this work is to evaluate the uncertainty of MODIS AOD retrievals by comparing with columnar AOD and surface PM2.5 measurements from AERONET and EPA networks. Data is analyzed from multiple stations in California and Nevada for three years where four major wildfires occurred. Results indicate that MODIS retrievals fail to estimate column-integrated aerosol pollution in the summer months. This is further investigated by quantifying the statistical relationships between MODIS AOD, AERONET AOD, and surface PM2.5 concentrations. Data analysis indicates that the distribution of MODIS AOD is significantly (p<0.05) different than AERONET AOD. Further, using the results of distributional and association analysis the impacts of MODIS AOD uncertainties on the spatial gradients are evaluated. Additionally, the relationships between these uncertainties and physical parameters in the retrieval algorithm (e.g., surface reflectance, Ångström Extinction Exponent) are discussed.

  20. Description and planned use of a data distribution evaluation system for fiber optic data buses

    NASA Technical Reports Server (NTRS)

    Spencer, J. L.; Himka, R. L.

    1982-01-01

    A general description of a laboratory data distribution evaluation system (DDES) is given and some plans to use the system. The DDES is a microprocessor-based evaluation system consisting of three identical terminals. The DDES provides the capability for evaluating different system protocols and data word structures by making appropriate software changes, and different transmission medias and modulation schemes by making front-end hardware changes. A data multiplexing standard for fiber optic data transmission which parallels MIL-STD-1553B has proposed four different data modulation schemes. These modulation schemes will be described along with the plans to evaluate each of them. NASA-Langley has also been developing a data distribution approach which utilizes optical wavelength division multiplexing (WDM). A four-port, four-wavelength WDM system will be described along with the planned use of the DDES to evaluate its performance.

  1. Geometrical modeling of optical phase difference for analyzing atmospheric turbulence

    NASA Astrophysics Data System (ADS)

    Yuksel, Demet; Yuksel, Heba

    2013-09-01

    Ways of calculating phase shifts between laser beams propagating through atmospheric turbulence can give us insight towards the understanding of spatial diversity in Free-Space Optical (FSO) links. We propose a new geometrical model to estimate phase shifts between rays as the laser beam propagates through a simulated turbulent media. Turbulence is simulated by filling the propagation path with spherical bubbles of varying sizes and refractive index discontinuities statistically distributed according to various models. The level of turbulence is increased by elongating the range and/or increasing the number of bubbles that the rays interact with along their path. For each statistical representation of the atmosphere, the trajectories of two parallel rays separated by a particular distance are analyzed and computed simultaneously using geometrical optics. The three-dimensional geometry of the spheres is taken into account in the propagation of the rays. The bubble model is used to calculate the correlation between the two rays as their separation distance changes. The total distance traveled by each ray as both rays travel to the target is computed. The difference in the path length traveled will yield the phase difference between the rays. The mean square phase difference is taken to be the phase structure function which in the literature, for a pair of collimated parallel pencil thin rays, obeys a five-third law assuming weak turbulence. All simulation results will be compared with the predictions of wave theory.

  2. Evaluation of Anti-fouling Materials for Optical Sensors

    DTIC Science & Technology

    1997-09-30

    Hani R., Waldron C. and Farmer D. A. (1994) Gel-Free Paint Containing Zinc Pyrithione , Cuprous Oxide, and Carboxylic Acid. U.S. Patent 5342437, Olin Corp...2. Hani R., Waldron C. and Farmer D. A. Jr. (1992) Stabilization of Paints Containing Zinc Pyrithione and Cuprous Oxide Antifouling Agents. U.S...using ESEM. The following commercially prepared formulations provided by Magellan Co., Inc. were evaluated: 1) 10,000 ppm zinc pyrithione1,2,3 + 300 ppm

  3. Differentiation of oral precancerous stages with optical coherence tomography based on the evaluation of optical scattering properties of oral mucosae

    NASA Astrophysics Data System (ADS)

    Tsai, M. T.; Lee, J. D.; Lee, Y. J.; Lee, C. K.; Jin, H. L.; Chang, F. Y.; Hu, K. Y.; Wu, C. P.; Chiang, C. P.; Yang, C. C.

    2013-04-01

    Optical coherence tomography (OCT) has been demonstrated to be a powerful tool for noninvasive, real-time oral cancer diagnosis. However, in previous reports, OCT has still been found to be difficult to use in the diagnosis of oral precancerous stages, including mild dysplasia and moderate dysplasia. In clinical applications, early diagnosis and treatment of oral cancer can greatly improve the survival rate. Therefore, in this study, we propose a new approach to differentiate the oral precancerous stages based on the evaluation of the optical scattering properties of the epithelial layer, which is where the dysplastic cells start to develop in the precancerous stages. Instead of using exponential decay fitting to evaluate the scattering properties of mucosal tissues based on the Beer-Lambert law, linear fitting of the OCT depth intensity is used to evaluate the scattering properties of normal and dysplastic cells. From the statistical results of the linear fitting, the slope, a, can be an effective indicator to discriminate healthy mucosa and moderate dysplasia when an a value equal to zero is the threshold value, and the intercept, b, can be used to differentiate healthy and dysplastic mucosae, as well as mild and moderate dysplasia, when b values of 0.15 and 0.18 are used as the threshold values, respectively. Furthermore, this approach is also applied to the determination of the safe margin between normal and abnormal mucosae, making it possible to provide real-time, in vivo inspection during oral maxillofacial surgery.

  4. Purely optical navigation with model-based state prediction

    NASA Astrophysics Data System (ADS)

    Sendobry, Alexander; Graber, Thorsten; Klingauf, Uwe

    2010-10-01

    State-of-the-art Inertial Navigation Systems (INS) based on Micro-Electro-Mechanical Systems (MEMS) have a lack of precision especially in GPS denied environments like urban canyons or in pure indoor missions. The proposed Optical Navigation System (ONS) provides bias free ego-motion estimates using triple redundant sensor information. In combination with a model based state prediction our system is able to estimate velocity, position and attitude of an arbitrary aircraft. Simulating a high performance flow-field estimator the algorithm can compete with conventional low-cost INS. By using measured velocities instead of accelerations the system states drift behavior is not as distinctive as for an INS.

  5. Model of Atmospheric Links on Optical Communications from High Altitude

    NASA Technical Reports Server (NTRS)

    Subich, Christopher

    2004-01-01

    Optical communication links have the potential to solve many of the problems of current radio and microwave links to satellites and high-altitude aircraft. The higher frequency involved in optical systems allows for significantly greater signal bandwidth, and thus information transfer rate, in excess of 10 Gbps, and the highly directional nature of laser-based signals eliminates the need for frequency-division multiplexing seen in radio and microwave links today. The atmosphere, however, distorts an optical signal differently than a microwave signal. While the ionosphere is one of the most significant sources of noise and distortion in a microwave or radio signal, the lower atmosphere affects an optical signal more significantly. Refractive index fluctuations, primarily caused by changes in atmospheric temperature and density, distort the incoming signal in both deterministic and nondeterministic ways. Additionally, suspended particles, such as those in haze or rain, further corrupt the transmitted signal. To model many of the atmospheric effects on the propagating beam, we use simulations based on the beam-propagation method. This method, developed both for simulation of signals in waveguides and propagation in atmospheric turbulence, separates the propagation into a diffraction and refraction problem. The diffraction step is an exact solution, within the limits of numerical precision, to the problem of propagation in free space, and the refraction step models the refractive index variances over a segment of the propagation path. By applying refraction for a segment of the propagation path, then diffracting over that same segment, this method forms a good approximation to true propagation through the atmospheric medium. Iterating over small segments of the total propagation path gives a good approximation to the problem of propagation over the entire path. Parameters in this model, such as initial beam profile and atmospheric constants, are easily modified in a

  6. Comparison of Three Optical Methods for Measuring Model Deformation

    NASA Technical Reports Server (NTRS)

    Burner, A. W.; Fleming, G. A.; Hoppe, J. C.

    2000-01-01

    The objective of this paper is to compare the current state-of-the-art of the following three optical techniques under study by NASA for measuring model deformation in wind tunnels: (1) video photogrammetry, (2) projection moire interferometry, and (3) the commercially available Optotrak system. An objective comparison of these three techniques should enable the selection of the best technique for a particular test undertaken at various NASA facilities. As might be expected, no one technique is best for all applications. The techniques are also not necessarily mutually exclusive and in some cases can be complementary to one another.

  7. Fluctuations and entropy in models of quantum optical resonance

    NASA Astrophysics Data System (ADS)

    Phoenix, S. J. D.; Knight, P. L.

    1988-09-01

    We use variances, entropy, and the Shannon entropy to analyse the fluctuations and quantum evolution of various simple models of quantum optical resonance. We discuss at length the properties of the single-mode radiation field coupled to a single two-level atom, and then extend our analysis to describe the micromaser in which a cavity mode is repeatedly pumped by a succession of atoms passing through the cavity. We also discuss the fluctuations in the single-mode laser theory of Scully and Lamb.

  8. Optical model methods of predicting nuclide production from spallation reactions.

    PubMed

    Ramsey, C R; Townsend, L W; Tripathi, R K; Cucinotta, F A

    1998-02-01

    Quantum mechanical optical model methods for calculating isotope production cross sections from the spallation of heavy nuclei by high-energy protons are developed from a modified abrasion-ablation collision formalism. The abrasion step is treated quantum-mechanically as a knockout process which leaves the residual prefragment nucleus in an excited state. In ablation the prefragment deexcites to produce the final fragment. The excitation energies of the prefragments are estimated from a combination of liquid drop and frictional-spectator interaction considerations. Estimates of elemental and isotopic production cross sections are in good agreement with recently published cross section measurements.

  9. Capturing optically important constituents and properties in a marine biogeochemical and ecosystem model

    NASA Astrophysics Data System (ADS)

    Dutkiewicz, S.; Hickman, A. E.; Jahn, O.; Gregg, W. W.; Mouw, C. B.; Follows, M. J.

    2015-02-01

    We present a numerical model of the ocean that couples a three-stream radiative transfer component with a marine biogeochemical-ecosystem in a dynamic three-dimensional physical framework. The radiative transfer component resolves spectral irradiance as it is absorbed and scattered within the water column. We explicitly include the effect of several optically important water constituents (the phytoplankton community, detrital particles, and coloured dissolved organic matter, CDOM). The model is evaluated against in situ observed and satellite derived products. In particular we compare to concurrently measured biogeochemical, ecosystem and optical data along a north-south transect of the Atlantic Ocean. The simulation captures the patterns and magnitudes of these data, and estimates surface upwelling irradiance analogous to that observed by ocean colour satellite instruments. We conduct a series of sensitivity experiments to demonstrate, globally, the relative importance of each of the water constituents, and the crucial feedbacks between the light field and the relative fitness of phytoplankton types, and the biogeochemistry of the ocean. CDOM has proportionally more importance at short wavelengths and in more productive waters, phytoplankton absorption is especially important at the deep chlorophyll a (Chl a) maximum, and absorption by water molecules is relatively most important in the highly oligotrophic gyres. Sensitivity experiments in which absorption by any of the optical constituents was increased led to a decrease in the size of the oligotrophic regions of the subtropical gyres: lateral nutrient supplies were enhanced as a result of decreasing high latitude productivity. Scattering does not as strongly affect the ecosystem and biogeochemistry fields within the water column but is important for setting the surface upwelling irradiance, and hence sea surface reflectance. Having a model capable of capturing bio-optical feedbacks will be important for

  10. Hemodynamic and metabolic diffuse optical monitoring in a mouse model of hindlimb ischemia.

    PubMed

    Mesquita, Rickson C; Skuli, Nicolas; Kim, Meeri N; Liang, Jiaming; Schenkel, Steve; Majmundar, Amar J; Simon, M Celeste; Yodh, Arjun G

    2010-10-15

    Murine hindlimb ischemia is a useful model for investigation of the mechanisms of peripheral arterial disease and for understanding the role of endothelial cells and generic factors affecting vascular regeneration or angiogenesis. To date, important research with these models has explored tissue reperfusion following ischemia with Laser Doppler methods, methods which provide information about superficial (~mm) vascular regeneration. In this work, we employ diffuse correlation spectroscopy (DCS) and diffuse optical spectroscopy (DOS) in mice after hindlimb ischemia. We hypothesize that vascular re-growth is not uniform in tissue, and therefore, since diffuse optical methods are capable of probing deep tissues, that the diffuse optics approach will provide a more complete picture of the angiogenesis process throughout the whole depth profile of the limb. Besides increased depth penetration, the combined measurements of DCS and DOS enable all-optical, noninvasive, longitudinal monitoring of tissue perfusion and oxygenation that reveals the interplay between these hemodynamic parameters during angiogenesis. Control mice were found to reestablish 90% of perfusion and oxygen consumption during this period, but oxygen saturation in the limb only partially recovered to about 30% of its initial value. The vascular recovery of mice with endothelial cell-specific deletion of HIF-2α was found to be significantly impaired relative to control mice, indicating that HIF-2α is important for endothelial cell functions in angiogenesis. Comparison of DOS/DCS measurements to parallel measurements in the murine models using Laser Doppler Flowmetry reveal differences in the reperfusion achieved by superficial versus deep tissue during neoangiogenesis; findings from histological analysis of blood vessel development were further correlated with these differences. In general, the combination of DCS and DOS enables experimenters to obtain useful information about oxygenation, metabolism

  11. A standard model eye with micro scale multilayer structure for ophthalmic optical coherence tomography equipment

    NASA Astrophysics Data System (ADS)

    Cao, Zhenggang; Ding, Zengqian; Hu, Zhixiong; Wen, Tao; Qiao, Wen; Liu, Wenli

    2016-10-01

    Optical coherence tomography (OCT) has been widely applied in diagnosis of eye diseases during the last 20 years. Differing from traditional two-dimension imaging technologies, OCT could also provide cross-sectional information of target tissues simultaneously and precisely. As well known, axial resolution is one of the most critical parameters impacting the OCT image quality, which determines whether an accurate diagnosis could be obtained. Therefore, it is important to evaluate the axial resolution of an OCT equipment. Phantoms always play an important role in the standardization and validation process. Here, a standard model eye with micro-scale multilayer structure was custom designed and manufactured. Mimicking a real human eye, analyzing the physical characteristic of layer structures of retina and cornea in-depth, appropriate materials were selected by testing the scattering coefficient of PDMS phantoms with difference concentration of TiO2 or BaSO4 particles. An artificial retina and cornea with multilayer-films which have a thickness of 10 to 60 micrometers for each layer were fabricated using spin coating technology. Considering key parameters of the standard model eye need to be traceable as well as accurate, the optical refractive index and layer structure thicknesses of phantoms were verified by utilizing Thickness Monitoring System. Consequently, a standard OCT model eye was obtained after the retinal or corneal phantom was embedded into a water-filled model eye which has been fabricated by 3D printing technology to simulate ocular dispersion and emmetropic refraction. The eye model was manufactured with a transparent resin to simulate realistic ophthalmic testing environment, and most key optical elements including cornea, lens and vitreous body were realized. By investigating with a research and a clinical OCT system respectively, the OCT model eye was demonstrated with similar physical properties as natural eye, and the multilayer film measurement

  12. Bio-Optical Measurement and Modeling of the California Current and Southern Oceans

    NASA Technical Reports Server (NTRS)

    Mitchell, B. Gregg; Mitchell, B. Greg

    2003-01-01

    The SIMBIOS project's principal goals are to validate standard or experimental ocean color products through detailed bio-optical and biogeochemical measurements, and to combine Ocean optical observations with modeling to contribute to satellite vicarious radiometric calibration and algorithm development.

  13. An Evaluation of Oceanographic Optical Instruments and Deployment Methodologies

    NASA Technical Reports Server (NTRS)

    Hooker, Stanford B.; Maritorena, Stephane

    1999-01-01

    The primary objective of the Sea-viewing, Wide Field-of-view Sensor (SeaWiFS) Project is to produce water- leaving radiances with an uncertainty of 5% in clear-water regions and chlorophyll a concentrations within +/- 35% over the range of 0.05-50 mg/cu m. Any global mission, like SeaWiFS, requires validation data be submitted from a wide variety of investigators which places a significant challenge on quantifying the total uncertainty associated with the in situ measurements, because each investigator follows slightly different practices when it comes to implementing all of the steps associated with collecting field data, even those with a prescribed set of protocols. This study uses data from multiple cruises to quantify the uncertainties associated with implementing data collection procedures while utilizing differing in-water optical instruments and deployment methods. A comprehensive approach is undertaken and includes: (1) the use of a portable light source and in-water intercomparisons to monitor the stability of the field radiometers, (2) alternative methods for acquiring reference measurements, and (3) different techniques for making in-water profiles. The only system to meet the 5% radiometric objective of the SeaWiFS Project was a free-fall profiler using (relatively inexpensive) modular components, although a more sophisticated (and comparatively expensive) profiler using integral components was very close and only 1% higher. A relatively inexpensive system deployed with a winch and crane was also close, but the ship shadow contamination problem increased the total uncertainty to approximately 6.5%.

  14. Evaluation of trends in wheat yield models

    NASA Technical Reports Server (NTRS)

    Ferguson, M. C.

    1982-01-01

    Trend terms in models for wheat yield in the U.S. Great Plains for the years 1932 to 1976 are evaluated. The subset of meteorological variables yielding the largest adjusted R(2) is selected using the method of leaps and bounds. Latent root regression is used to eliminate multicollinearities, and generalized ridge regression is used to introduce bias to provide stability in the data matrix. The regression model used provides for two trends in each of two models: a dependent model in which the trend line is piece-wise continuous, and an independent model in which the trend line is discontinuous at the year of the slope change. It was found that the trend lines best describing the wheat yields consisted of combinations of increasing, decreasing, and constant trend: four combinations for the dependent model and seven for the independent model.

  15. Three-dimensional non-destructive optical evaluation of laser-processing performance using optical coherence tomography

    PubMed Central

    Kim, Youngseop; Choi, Eun Seo; Kwak, Wooseop; Shin, Yongjin; Jung, Woonggyu; Ahn, Yeh-Chan; Chen, Zhongping

    2014-01-01

    We demonstrate the use of optical coherence tomography (OCT) as a non-destructive diagnostic tool for evaluating laser-processing performance by imaging the features of a pit and a rim. A pit formed on a material at different laser-processing conditions is imaged using both a conventional scanning electron microscope (SEM) and OCT. Then using corresponding images, the geometrical characteristics of the pit are analyzed and compared. From the results, we could verify the feasibility and the potential of the application of OCT to the monitoring of the laser-processing performance. PMID:24932051

  16. [Evaluation of the Dresden Tympanoplasty Model (DTM)].

    PubMed

    Beleites, T; Neudert, M; Lasurashvili, N; Kemper, M; Offergeld, C; Hofmann, G; Zahnert, T

    2011-11-01

    The training of microsurgical motor skills is essentiell for surgical education if the interests of the patient are to be safeguarded. In otosurgery the complex anatomy of the temporal bone and variations necessitate a special training before performing surgery on a patient. We therefore developed and evaluated a simplified middle ear model for acquiring first microsurgical skills in tympanoplasty.The simplified tympanoplasty model consists of the outer ear canal and a tympanic cavity. A stapes model is placed in projection of the upper posterior tympanic membrane quadrant at the medial wall of the simulated tympanic cavity. To imitate the annular ligament flexibility the stapes is fixed on a soft plastic pad. 41 subjects evaluated the model´s anatomical analogy, the comparability to the real surgical situation and the general model properties the using a special questionnaire.The tympanoplasty model was very well evaluated by all participants. It is a reasonably priced model and a useful tool in microsurgical skills training. Thereby, it closes the gap between theoretical training and real operation conditions.

  17. Polarization Drift Channel Model for Coherent Fibre-Optic Systems

    PubMed Central

    Czegledi, Cristian B.; Karlsson, Magnus; Agrell, Erik; Johannisson, Pontus

    2016-01-01

    A theoretical framework is introduced to model the dynamical changes of the state of polarization during transmission in coherent fibre-optic systems. The model generalizes the one-dimensional phase noise random walk to higher dimensions, accounting for random polarization drifts, emulating a random walk on the Poincaré sphere, which has been successfully verified using experimental data. The model is described in the Jones, Stokes and real four-dimensional formalisms, and the mapping between them is derived. Such a model will be increasingly important in simulating and optimizing future systems, where polarization-multiplexed transmission and sophisticated digital signal processing will be natural parts. The proposed polarization drift model is the first of its kind as prior work either models polarization drift as a deterministic process or focuses on polarization-mode dispersion in systems where the state of polarization does not affect the receiver performance. We expect the model to be useful in a wide-range of photonics applications where stochastic polarization fluctuation is an issue. PMID:26905596

  18. A bio-optical model for integration into ecosystem models for the Ligurian Sea

    NASA Astrophysics Data System (ADS)

    Bengil, Fethi; McKee, David; Beşiktepe, Sükrü T.; Sanjuan Calzado, Violeta; Trees, Charles

    2016-12-01

    A bio-optical model has been developed for the Ligurian Sea which encompasses both deep, oceanic Case 1 waters and shallow, coastal Case 2 waters. The model builds on earlier Case 1 models for the region and uses field data collected on the BP09 research cruise to establish new relationships for non-biogenic particles and CDOM. The bio-optical model reproduces in situ IOPs accurately and is used to parameterize radiative transfer simulations which demonstrate its utility for modeling underwater light levels and above surface remote sensing reflectance. Prediction of euphotic depth is found to be accurate to within ∼3.2 m (RMSE). Previously published light field models work well for deep oceanic parts of the Ligurian Sea that fit the Case 1 classification. However, they are found to significantly over-estimate euphotic depth in optically complex coastal waters where the influence of non-biogenic materials is strongest. For these coastal waters, the combination of the bio-optical model proposed here and full radiative transfer simulations provides significantly more accurate predictions of euphotic depth.

  19. Evaluating the thermal stability of multi-pass cells' effective optical path length using optical frequency domain reflectometer

    NASA Astrophysics Data System (ADS)

    Gao, Hong; Cao, Xiuhan; Li, Jinyi; Du, Zhenhui

    2016-10-01

    Multi-pass cells (MPCs) are commonly used to improve the sensitivity for trace gas detection using spectroscopy technologies. The determination of Effective Optical Path Length (EOPL) of a MPC is very important and challenging in applications which aim at absolute measurements. It is well-known that the temperature changing will exercise some influence on the MPCs' spatial structure, however, measurements of the influence haven't been reported which might due to the limitation of measuring method. In this paper, we used a direct high-precision measuring method with Optical Frequency Domain Reflectometer (OFDR) to evaluate the thermal stability of a multi-pass cell. To simulate the environment with a large range of temperature changing, this paper gave a series of experiments by setting the temperature control unit in system from 25 to 175 degree Celsius, and the MPC's EOPL was measured simultaneously for the investigation of temperature response. The results showed that the effective optical path length increase monotonically along with the variation of the temperature, and the rising rate is 0.5 mm/ºC with the total length of about 3 meters which should be pay attention to when the ultra-high accuracy results are demanded. To stabilize the EOPL of the system, if it is possible, the environment temperature of gas cell can be controlled with a constant temperature. In practical applications, the real-time monitoring of EOPL with a direct measuring method may be necessary.

  20. Calibration and evaluation of optical systems for full-field strain measurement

    NASA Astrophysics Data System (ADS)

    Patterson, Eann A.; Hack, Erwin; Brailly, Philippe; Burguete, Richard L.; Saleem, Qasim; Siebert, Thorsten; Tomlinson, Rachel A.; Whelan, Maurice P.

    2007-05-01

    The design and testing of a reference material for the calibration of optical systems for strain measurement is described, together with the design and testing of a standardized test material that allows the evaluation and assessment of fitness for purpose of the most sophisticated optical system for strain measurement. A classification system for the steps in the measurement process is also proposed and allows the development of a unified approach to diagnostic testing of components or sub-systems in an optical system for strain measurement based on any optical technique. The results described arise from a European study known as SPOTS whose objectives were to begin to fill the gap caused by a lack of standards.

  1. Damage induced in red blood cells by infrared optical trapping: an evaluation based on elasticity measurements

    NASA Astrophysics Data System (ADS)

    de Oliveira, Marcos A. S.; Moura, Diógenes S.; Fontes, Adriana; de Araujo, Renato E.

    2016-07-01

    We evaluated the damage caused to optically trapped red blood cells (RBCs) after 1 or 2 min of exposure to near-infrared (NIR) laser beams at 785 or 1064 nm. Damage was quantified by measuring cell elasticity using an automatic, real-time, homemade, optical tweezer system. The measurements, performed on a significant number (hundreds) of cells, revealed an overall deformability decrease up to ˜104% after 2 min of light exposure, under 10 mW optical trapping for the 785-nm wavelength. Wavelength dependence of the optical damage is attributed to the light absorption by hemoglobin. The results provided evidence that RBCs have their biomechanical properties affected by NIR radiation. Our findings establish limits for laser applications with RBCs.

  2. In vivo evaluation of optic nerve aging in adult rhesus monkey by diffusion tensor imaging

    PubMed Central

    Yan, Yumei; Li, Longchuan; Preuss, Todd M.; Hu, Xiaoping; Herndon, James G.

    2014-01-01

    Aging of the optic nerve can result in reduced visual sensitivity or vision loss. Normal optic nerve aging has been investigated previously in tissue specimens but poorly explored in vivo. In the present study, the normal aging of optic nerve was evaluated by diffusion tensor imaging (DTI) in non-human primates. Adult female rhesus monkeys at the ages of 9 to 13 years old (young group, n=8) and 21 to 27 years old (old group, n=7) were studied using parallel-imaging-based DTI on a clinical 3T scanner. Compared to young adults, the old monkeys showed 26% lower fractional anisotropy (P<0.01), and 44% greater radial diffusivity, although the latter difference was of marginal statistical significance (P=0.058). These MRI findings are largely consistent with published results of light and electron microscopic studies of optic nerve aging in macaque monkeys, which indicate a loss of fibers and degenerative changes in myelin sheaths. PMID:24649434

  3. Experimental evaluation of pilot pattern design in direct-detection optical OFDM transmission

    NASA Astrophysics Data System (ADS)

    Liu, Lilong; Yang, Xuelin; Hu, Weisheng

    2013-05-01

    Pilot patterns are experimentally investigated to characterize the frequency/time dependence of the optical orthogonal frequency division multiplexing (OFDM) signal transmission. The optical signal performance is evaluated in terms of error vector magnitude (EVM). It is shown that, the quality of the OFDM signals can be improved up to 4 dB in EVM, for 10 Gb/s, 16-QAM-encoded OFDM signals after 20 km single mode fiber (SMF) transmission with intensity-modulation and direct-detection (IMDD). The best performance is obtained by applying pilot tones for all subcarriers, which implies that the optical OFDM transmission is relatively quasi-static with respect to the subcarrier frequencies. The noise of the OFDM signals originated mainly from the amplitude/phase fluctuation of optical signal with time.

  4. Arrangement of an advanced acousto-optical processor for modeling the triple correlations of low-power optical pulse trains

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Hanessian de la Garza, Ana V.; Chavushyan, Vahram; Campos Acosta, Joaquin

    2012-02-01

    Both a high level of developing the spatially spot-like and one-dimensional input devices and the flexibility of a design inherent in two-dimensional optical systems with similar modulating components make it possible to realize various high-bit-rate opto-electronic processors. This is why a one-dimension acousto-optic technique has been involved in data processing and its modeling based on the algorithm of triple product correlations. Practically, triple product correlations originate within an optical scheme including the modulated light source, representing the first input port, and two wideaperture acousto-optical cells forming two other input ports. Due to specifically constructed lens system, initially modulated light beam is crossing sequentially the apertures of acousto-optical cells oriented at right angle to each other. Finally, a CCD-matrix integrates the received optical signal with respect to time and registers the resulting triple product correlations. In a view of arranging similar acousto-optical processor for modeling triple product correlations, we characterize a novel version of the acousto-optical cells exploiting now tellurium-dioxide crystals. Together with this, potential performances of the progressed design for similar processor are estimated as well.

  5. SNL evaluation of Gigabit Passive Optical Networks (GPON).

    SciTech Connect

    Heckart, David G.; Roybal, Glen B.; Walker, Betty R.; Pratt, Thomas Joseph; Gossage, Steven Allen; Trujillo, Sandra M.; Fischer, Bob; Brenkosh, Joseph Peter; Rudolfo, Gerald F.; Dirks, David H.; Schutt, James Alan

    2009-08-01

    Gigabit Passive Optical Networks (GPON) is a networking technology which offers the potential to provide significant cost savings to Sandia National Laboratories in the area of network operations. However, a large scale GPON deployment requires a significant investment in equipment and infrastructure. Before a large scale GPON system was acquired and built, a small GPON system manufactured by Motorola was acquired and tested. The testing performed was to determine the suitability of GPON for use at SNL. This report documents that testing. This report presents test results of GPON system consisting of Motorola and Juniper equipment. The GPON system was tested in areas of data throughput, video conferencing, VOIP, security, and operations and management. The GPON system performed well in almost all areas. GPON will not meet the needs of the low percentage of users requiring a true 1-10 Gbps network connection. GPON will also most likely not meet the need of some servers requiring dedicated throughput of 1-10 Gbps. Because of that, there will be some legacy network connections that must remain. If these legacy network connections can not be reduced to a bare minimum and possibly consolidated to a few locations, any cost savings gained by switching to GPON will be negated by maintaining two networks. A contract has been recently awarded for new GPON equipment with larger buffers. This equipment should improve performance and further reduce the need for legacy network connections. Because GPON has fewer components than a typical hierarchical network, it should be easier to manage. For the system tested, the management was performed by using the AXSVison client. Access to the client must be tightly controlled, because if client/server communications are compromised, security will be an issue. As with any network, the reliability of individual components will determine overall system reliability. There were no failures with the routers, OLT, or Sun Workstation Management

  6. Automatic real time evaluation of red blood cell elasticity by optical tweezers

    NASA Astrophysics Data System (ADS)

    Moura, Diógenes S.; Silva, Diego C. N.; Williams, Ajoke J.; Bezerra, Marcos A. C.; Fontes, Adriana; de Araujo, Renato E.

    2015-05-01

    Optical tweezers have been used to trap, manipulate, and measure individual cell properties. In this work, we show that the association of a computer controlled optical tweezers system with image processing techniques allows rapid and reproducible evaluation of cell deformability. In particular, the deformability of red blood cells (RBCs) plays a key role in the transport of oxygen through the blood microcirculation. The automatic measurement processes consisted of three steps: acquisition, segmentation of images, and measurement of the elasticity of the cells. An optical tweezers system was setup on an upright microscope equipped with a CCD camera and a motorized XYZ stage, computer controlled by a Labview platform. On the optical tweezers setup, the deformation of the captured RBC was obtained by moving the motorized stage. The automatic real-time homemade system was evaluated by measuring RBCs elasticity from normal donors and patients with sickle cell anemia. Approximately 150 erythrocytes were examined, and the elasticity values obtained by using the developed system were compared to the values measured by two experts. With the automatic system, there was a significant time reduction (60 × ) of the erythrocytes elasticity evaluation. Automated system can help to expand the applications of optical tweezers in hematology and hemotherapy.

  7. PREFACE SPECIAL ISSUE ON MODEL EVALUATION: EVALUATION OF URBAN AND REGIONAL EULERIAN AIR QUALITY MODELS

    EPA Science Inventory

    The "Preface to the Special Edition on Model Evaluation: Evaluation of Urban and Regional Eulerian Air Quality Models" is a brief introduction to the papers included in a special issue of Atmospheric Environment. The Preface provides a background for the papers, which have thei...

  8. Mesoscale Wind Predictions for Wave Model Evaluation

    DTIC Science & Technology

    2016-06-07

    SEP 1999 2. REPORT TYPE 3. DATES COVERED 00-00-1999 to 00-00-1999 4. TITLE AND SUBTITLE Mesoscale Wind Predictions for Wave Model Evaluation...unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 1 Mesoscale Wind Predictions for Wave Model...resolution (< 10 km) atmospheric wind and surface stress fields produced by an atmospheric mesoscale data assimilation system to the numerical prediction of

  9. Spatio-temporal evaluation of resolution enhancement for passive microwave soil moisture and vegetation optical depth

    NASA Astrophysics Data System (ADS)

    Gevaert, A. I.; Parinussa, R. M.; Renzullo, L. J.; van Dijk, A. I. J. M.; de Jeu, R. A. M.

    2016-03-01

    Space-borne passive microwave radiometers are used to derive land surface parameters such as surface soil moisture and vegetation optical depth (VOD). However, the value of such products in regional hydrology is limited by their coarse resolution. In this study, the land parameter retrieval model (LPRM) is used to derive enhanced resolution (∼10 km) soil moisture and VOD from advanced microwave scanning radiometer (AMSR-E) brightness temperatures sharpened by a modulation technique based on high-frequency observations. A precipitation mask based on brightness temperatures was applied to remove precipitation artefacts in the sharpened LPRM products. The spatial and temporal patterns in the resulting products are evaluated against field-measured and modeled soil moisture as well as the normalized difference vegetation index (NDVI) over mainland Australia. Results show that resolution enhancement accurately sharpens the boundaries of different vegetation types, lakes and wetlands. Significant changes in temporal agreement between LPRM products and related datasets are limited to specific areas, such as lakes and coastal areas. Spatial correlations, on the other hand, increase over most of Australia. In addition, hydrological signals from irrigation and water bodies that were absent in the low-resolution soil moisture product become clearly visible after resolution enhancement. The increased information detail in the high-resolution LPRM products should benefit hydrological studies at regional scales.

  10. Evaluation of hemodynamics changes during interventional stent placement using Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Vuong, Barry; Genis, Helen; Wong, Ronnie; Ramjist, Joel; Jivraj, Jamil; Farooq, Hamza; Sun, Cuiru; Yang, Victor X. D.

    2015-03-01

    Carotid atherosclerosis is a critical medical concern that can lead to ischemic stroke. Local hemodynamic patterns have also been associated with the development of atherosclerosis, particularly in regions with disturbed flow patterns such as bifurcations. Traditionally, this disease was treated using carotid endarterectomy, however recently there is an increasing trend of carotid artery stenting due to its minimally invasive nature. It is well known that this interventional technique creates changes in vasculature geometry and hemodynamic patterns due to the interaction of stent struts with arterial lumen, and is associated with complications such as distal emboli and restenosis. Currently, there is no standard imaging technique to evaluate regional hemodynamic patterns found in stented vessels. Doppler optical coherence tomography (DOCT) provides an opportunity to identify in vivo hemodynamic changes in vasculature using high-resolution imaging. In this study, blood flow profiles were examined at the bifurcation junction in the internal carotid artery (ICA) in a porcine model following stent deployment. Doppler imaging was further conducted using pulsatile flow in a phantom model, and then compared to computational fluid dynamics (CFD) simulation of a virtual bifurcation to assist with the interpretation of emphin vivo results.

  11. Performance evaluation of intensity modulated optical OFDM system with digital baseband distortion.

    PubMed

    Vanin, Evgeny

    2011-02-28

    Bit-Error-Ratio (BER) of intensity modulated optical orthogonal frequency division multiplexing (OFDM) system is analytically evaluated accounting for nonlinear digital baseband distortion in the transmitter and additive noise in the photo receiver. The nonlinear distortion that is caused by signal clipping and quantization is taken into consideration. The signal clipping helps to overcome the system performance limitation related to high peak-to-average power ratio (PAPR) of the OFDM signal and to minimize the value of optical power that is required for achieving specified BER. The signal quantization due to a limited bit resolution of the digital to analog converter (DAC) causes an optical power penalty in the case when the bit resolution is too low. By introducing an effective signal to noise ratio (SNR) the optimum signal clipping ratio, system BER and required optical power at the input to the receiver is evaluated for the OFDM system with multi-level quadrature amplitude modulation (QAM) applied to the optical signal subcarriers. Minimum required DAC bit resolution versus the size of QAM constellation is identified. It is demonstrated that the bit resolution of 7 and higher causes negligibly small optical power penalty at the system BER=10⁻³ when 256-QAM and a constellation of lower size is applied. The performance of the optical OFDM system is compared to the performance of the multi-level amplitude-shift keying (M-ASK) system for the same number of information bits transmitted per signal sample. It is demonstrated that in the case of the matched receiver the M-ASK system outperforms OFDM and requires 3-3.5 dB less of optical power at BER=10⁻³ when 1-4 data bits are transmitted per signal sample.

  12. Comparative evaluation of methylene blue and demeclocycline for enhancing optical contrast of gliomas in optical images

    NASA Astrophysics Data System (ADS)

    Wirth, Dennis; Snuderl, Matija; Curry, William; Yaroslavsky, Anna

    2014-09-01

    Contrast agents have shown to be useful in the detection of cancers. The goal of this study was to compare enhancement of brain cancer contrast using reflectance and fluorescence confocal imaging of two fluorophores, methylene blue (MB) and demeclocycline (DMN). MB absorbs light in the red spectral range and fluoresces in the near-infrared. It is safe for in vivo staining of human skin and breast tissue. However, its safety for staining human brain is questionable. Thus, DMN, which absorbs light in the violet spectral range and fluoresces between 470 and 570 nm, could provide a safer alternative to MB. Fresh human gliomas, obtained from surgeries, were cut in half and stained with aqueous solutions of MB and DMN, respectively. Stained tissues were imaged using multimodal confocal microscopy. Resulting reflectance and fluorescence optical images were compared with hematoxylin and eosin histopathology, processed from each imaged tissue. Results indicate that images of tissues stained with either stain exhibit comparable contrast and resolution of morphological detail. Further studies are required to establish the safety and efficacy of these contrast agents for use in human brain.

  13. Evaluating snow models for hydrological applications

    NASA Astrophysics Data System (ADS)

    Jonas, T.; Magnusson, J.; Wever, N.; Essery, R.; Helbig, N.

    2014-12-01

    Much effort has been invested in developing snow models over several decades, resulting in a wide variety of empirical and physically-based snow models. Within the two categories, models are built on the same principles but mainly differ in choices of model simplifications and parameterizations describing individual processes. In this study, we demonstrate an informative method for evaluating a large range of snow model structures for hydrological applications using an existing multi-model energy-balance framework and data from two well-instrumented sites with a seasonal snow cover. We also include two temperature-index snow models and one physically-based multi-layer snow model in our analyses. Our results show that the ability of models to predict snowpack runoff is strongly related to the agreement of observed and modelled snow water equivalent whereas such relationship is not present for snow depth or snow surface temperature measurements. For snow water equivalent and runoff, the models seem transferable between our two study sites, a behaviour which is not observed for snow surface temperature predictions due to site-specificity of turbulent heat transfer formulations. Uncertainties in the input and validation data, rather than model formulation, appear to contribute most to low model performances in some winters. More importantly, we find that model complexity is not a determinant for predicting daily snow water equivalent and runoff reliably, but choosing an appropriate model structure is. Our study shows the usefulness of the multi-model framework for identifying appropriate models under given constraints such as data availability, properties of interest and computational cost.

  14. Bio-Optical Measurement and Modeling of the California Current and Polar Oceans

    NASA Technical Reports Server (NTRS)

    Mitchell, B. Greg; Fargion, Giulietta S. (Technical Monitor)

    2001-01-01

    The principal goals of our research are to validate standard or experimental products through detailed bio-optical and biogeochemical measurements, and to combine ocean optical observations with advanced radiative transfer modeling to contribute to satellite vicarious radiometric calibration and advanced algorithm development. To achieve our goals requires continued efforts to execute complex field programs globally, as well as development of advanced ocean optical measurement protocols. We completed a comprehensive set of ocean optical observations in the California Current, Southern Ocean, Indian Ocean requiring a large commitment to instrument calibration, measurement protocols, data processing and data merger. We augmented separately funded projects of our own, as well as others, to acquire ill situ data sets we have collected on various global cruises supported by separate grants or contracts. In collaboration with major oceanographic ship-based observation programs funded by various agencies (CalCOFI, US JGOFS, NOAA AMLR, INDOEX and Japan/East Sea) our SIMBIOS effort has resulted in data from diverse bio-optical provinces. For these global deployments we generate a high-quality, methodologically consistent, data set encompassing a wide-range of oceanic conditions. Global data collected in recent years have been integrated with our on-going CalCOFI database and have been used to evaluate SeaWiFS algorithms and to carry out validation studies. The combined database we have assembled now comprises more than 700 stations and includes observations for the clearest oligotrophic waters, highly eutrophic blooms, red-tides and coastal case 2 conditions. The data has been used to validate water-leaving radiance estimated with SeaWiFS as well as bio-optical algorithms for chlorophyll pigments. The comprehensive data is utilized for development of experimental algorithms (e.g. high-low latitude pigment transition, phytoplankton absorption, and cDOM). During this period

  15. Distributed control in adaptive optics: deformable mirror and turbulence modeling

    NASA Astrophysics Data System (ADS)

    Ellenbroek, Rogier; Verhaegen, Michel; Doelman, Niek; Hamelinck, Roger; Rosielle, Nick; Steinbuch, Maarten

    2006-06-01

    Future large optical telescopes require adaptive optics (AO) systems whose deformable mirrors (DM) have ever more degrees of freedom. This paper describes advances that are made in a project aimed to design a new AO system that is extendible to meet tomorrow's specifications. Advances on the mechanical design are reported in a companion paper [6272-75], whereas this paper discusses the controller design aspects. The numerical complexity of controller designs often used for AO scales with the fourth power in the diameter of the telescope's primary mirror. For future large telescopes this will undoubtedly become a critical aspect. This paper demonstrates the feasibility of solving this issue with a distributed controller design. A distributed framework will be introduced in which each actuator has a separate processor that can communicate with a few direct neighbors. First, the DM will be modeled and shown to be compatible with the framework. Then, adaptive turbulence models that fit the framework will be shown to adequately capture the spatio-temporal behavior of the atmospheric disturbance, constituting a first step towards a distributed optimal control. Finally, the wavefront reconstruction step is fitted into the distributed framework such that the computational complexity for each processor increases only linearly with the telescope diameter.

  16. Multiscale modeling and computation of optically manipulated nano devices

    SciTech Connect

    Bao, Gang; Liu, Di; Luo, Songting

    2016-07-01

    We present a multiscale modeling and computational scheme for optical-mechanical responses of nanostructures. The multi-physical nature of the problem is a result of the interaction between the electromagnetic (EM) field, the molecular motion, and the electronic excitation. To balance accuracy and complexity, we adopt the semi-classical approach that the EM field is described classically by the Maxwell equations, and the charged particles follow the Schrödinger equations quantum mechanically. To overcome the numerical challenge of solving the high dimensional multi-component many-body Schrödinger equations, we further simplify the model with the Ehrenfest molecular dynamics to determine the motion of the nuclei, and use the Time-Dependent Current Density Functional Theory (TD-CDFT) to calculate the excitation of the electrons. This leads to a system of coupled equations that computes the electromagnetic field, the nuclear positions, and the electronic current and charge densities simultaneously. In the regime of linear responses, the resonant frequencies initiating the out-of-equilibrium optical-mechanical responses can be formulated as an eigenvalue problem. A self-consistent multiscale method is designed to deal with the well separated space scales. The isomerization of azobenzene is presented as a numerical example.

  17. Performance Evaluation of Dense Gas Dispersion Models.

    NASA Astrophysics Data System (ADS)

    Touma, Jawad S.; Cox, William M.; Thistle, Harold; Zapert, James G.

    1995-03-01

    This paper summarizes the results of a study to evaluate the performance of seven dense gas dispersion models using data from three field experiments. Two models (DEGADIS and SLAB) are in the public domain and the other five (AIRTOX, CHARM, FOCUS, SAFEMODE, and TRACE) are proprietary. The field data used are the Desert Tortoise pressurized ammonia releases, Burro liquefied natural gas spill tests, and the Goldfish anhydrous hydrofluoric acid spill experiments. Desert Tortoise and Goldfish releases were simulated as horizontal jet releases, and Burro as a liquid pool. Performance statistics were used to compare maximum observed concentrations and plume half-width to those predicted by each model. Model performance varied and no model exhibited consistently good performance across all three databases. However, when combined across the three databases, all models performed within a factor of 2. Problems encountered are discussed in order to help future investigators.

  18. Evaluation of a habitat suitability index model

    USGS Publications Warehouse

    Farmer, A.H.; Cade, B.S.; Stauffer, D.F.

    2002-01-01

    We assisted with development of a model for maternity habitat of the Indiana bat (Myotis soda/is), for use in conducting assessments of projects potentially impacting this endangered species. We started with an existing model, modified that model in a workshop, and evaluated the revised model, using data previously collected by others. Our analyses showed that higher indices of habitat suitability were associated with sites where Indiana bats were present and, thus, the model may be useful for identifying suitable habitat. Utility of the model, however, was based on a single component-density of suitable roost trees. Percentage of landscape in forest did not allow differentiation between sites occupied and not occupied by Indiana bats. Moreover, in spite of a general opinion by participants in the workshop that bodies of water were highly productive feeding areas and that a diversity of feeding habitats was optimal, we found no evidence to support either hypothesis.

  19. Integrated Modeling Activities for the James Webb Space Telescope: Structural-Thermal-Optical Analysis

    NASA Technical Reports Server (NTRS)

    Johnston, John D.; Howard, Joseph M.; Mosier, Gary E.; Parrish, Keith A.; McGinnis, Mark A.; Bluth, Marcel; Kim, Kevin; Ha, Kong Q.

    2004-01-01

    The James Web Space Telescope (JWST) is a large, infrared-optimized space telescope scheduled for launch in 2011. This is a continuation of a series of papers on modeling activities for JWST. The structural-thermal-optical, often referred to as STOP, analysis process is used to predict the effect of thermal distortion on optical performance. The benchmark STOP analysis for JWST assesses the effect of an observatory slew on wavefront error. Temperatures predicted using geometric and thermal math models are mapped to a structural finite element model in order to predict thermally induced deformations. Motions and deformations at optical surfaces are then input to optical models, and optical performance is predicted using either an optical ray trace or a linear optical analysis tool. In addition to baseline performance predictions, a process for performing sensitivity studies to assess modeling uncertainties is described.

  20. CMAQ Involvement in Air Quality Model Evaluation International Initiative

    EPA Pesticide Factsheets

    Description of Air Quality Model Evaluation International Initiative (AQMEII). Different chemical transport models are applied by different groups over North America and Europe and evaluated against observations.

  1. Optical model calculations of heavy-ion target fragmentation

    NASA Technical Reports Server (NTRS)

    Townsend, L. W.; Wilson, J. W.; Cucinotta, F. A.; Norbury, J. W.

    1986-01-01

    The fragmentation of target nuclei by relativistic protons and heavy ions is described within the context of a simple abrasion-ablation-final-state interaction model. Abrasion is described by a quantum mechanical formalism utilizing an optical model potential approximation. Nuclear charge distributions of the excited prefragments are calculated by both a hypergeometric distribution and a method based upon the zero-point oscillations of the giant dipole resonance. Excitation energies are estimated from the excess surface energy resulting from the abrasion process and the additional energy deposited by frictional spectator interactions of the abraded nucleons. The ablation probabilities are obtained from the EVA-3 computer program. Isotope production cross sections for the spallation of copper targets by relativistic protons and for the fragmenting of carbon targets by relativistic carbon, neon, and iron projectiles are calculated and compared with available experimental data.

  2. Modeling of optical wireless scattering communication channels over broad spectra.

    PubMed

    Liu, Weihao; Zou, Difan; Xu, Zhengyuan

    2015-03-01

    The air molecules and suspended aerosols help to build non-line-of-sight (NLOS) optical scattering communication links using carriers from near infrared to visible light and ultraviolet bands. This paper proposes channel models over such broad spectra. Wavelength dependent Rayleigh and Mie scattering and absorption coefficients of particles are analytically obtained first. They are applied to the ray tracing based Monte Carlo method, which models the photon scattering angle from the scatterer and propagation distance between two consecutive scatterers. Communication link path loss is studied under different operation conditions, including visibility, particle density, wavelength, and communication range. It is observed that optimum communication performances exist across the wavelength under specific atmospheric conditions. Infrared, visible light and ultraviolet bands show their respective features as conditions vary.

  3. Geometrical optical modeling considerations for LCD projector display systems

    NASA Astrophysics Data System (ADS)

    Schweyen, John C.; Garcia, Kevin J.; Gleckman, Philip L.

    1997-05-01

    End-to-end modeling of the photometric performance of LCD projection system using Monte Carlo geometrical ray tracing methods is an accurate and precise tool for predicting and improving the performance of these deices before, during and after product development. However, an accurate simulation first requires considering which physical properties contribute most to the system's photometric performance. Second, these properties must be characterized by physical measurements and translated into the tangible modeling parameters of a ray tracing program. Third, the implications of using a Monte Carlo ray tracing algorithm, and in general any other optical transformation algorithm, on radiometric accuracy must be well understood. These considerations as well as a generalized approach to the characterization and simulation of an LCD projector are described. A commercially available ray tracing program, the Advanced Systems Analysis Program, is used to demonstrate this approach. The irradiance uniformity, CIE color performance and screen brightness of an arc source LCD projector system are computed as an example.

  4. Simulations of Keratoconus Patient Vision with Optical Eye Modeling

    NASA Astrophysics Data System (ADS)

    Tan, Bo; Chen, Ying-Ling; Lewis, J. W. L.; Shi, Lei; Wang, Ming

    2007-11-01

    Keratoconus (KC) is an eye condition that involves progressive corneal thinning. Pushed by the intraocular pressure, the weakened cornea bulges outward and creates an irregular surface shape. The result is degraded vision that is difficult to correct with regular eye glasses or contact lens. In this study we use the optical lens design software, ZeMax, and patient data including cornea topography and refraction prescription to construct KC eye models. The variation of KC ``cone height'' on the cornea is used to simulate KC progression. The consequent patients' night vision and Snellen letter chart vision at 20 feet are simulated using these anatomically accurate 3-dimensional models. 100 million rays are traced for each image simulation. Animated results illustrate the change of KC visual acuity with the progression of disease. This simulation technique provides a comprehensive tool for medical training and patient consultation/education.

  5. Structural model constructing for optical handwritten character recognition

    NASA Astrophysics Data System (ADS)

    Khaustov, P. A.; Spitsyn, V. G.; Maksimova, E. I.

    2017-02-01

    The article is devoted to the development of the algorithms for optical handwritten character recognition based on the structural models constructing. The main advantage of these algorithms is the low requirement regarding the number of reference images. The one-pass approach to a thinning of the binary character representation has been proposed. This approach is based on the joint use of Zhang-Suen and Wu-Tsai algorithms. The effectiveness of the proposed approach is confirmed by the results of the experiments. The article includes the detailed description of the structural model constructing algorithm’s steps. The proposed algorithm has been implemented in character processing application and has been approved on MNIST handwriting characters database. Algorithms that could be used in case of limited reference images number were used for the comparison.

  6. Integrating the Advanced Human Eye Model (AHEM) and optical instrument models to model complete visual optical systems inclusive of the typical or atypical eye

    NASA Astrophysics Data System (ADS)

    Donnelly, William J., III

    2012-06-01

    PURPOSE: To present a commercially available optical modeling software tool to assist the development of optical instrumentation and systems that utilize and/or integrate with the human eye. METHODS: A commercially available flexible eye modeling system is presented, the Advanced Human Eye Model (AHEM). AHEM is a module that the engineer can use to perform rapid development and test scenarios on systems that integrate with the eye. Methods include merging modeled systems initially developed outside of AHEM and performing a series of wizard-type operations that relieve the user from requiring an optometric or ophthalmic background to produce a complete eye inclusive system. Scenarios consist of retinal imaging of targets and sources through integrated systems. Uses include, but are not limited to, optimization, telescopes, microscopes, spectacles, contact and intraocular lenses, ocular aberrations, cataract simulation and scattering, and twin eye model (binocular) systems. RESULTS: Metrics, graphical data, and exportable CAD geometry are generated from the various modeling scenarios.

  7. Evaluation of Usability Utilizing Markov Models

    ERIC Educational Resources Information Center

    Penedo, Janaina Rodrigues; Diniz, Morganna; Ferreira, Simone Bacellar Leal; Silveira, Denis S.; Capra, Eliane

    2012-01-01

    Purpose: The purpose of this paper is to analyze the usability of a remote learning system in its initial development phase, using a quantitative usability evaluation method through Markov models. Design/methodology/approach: The paper opted for an exploratory study. The data of interest of the research correspond to the possible accesses of users…

  8. Performance Evaluation Model for Application Layer Firewalls

    PubMed Central

    Yang, Wu; Dong, Hui; Zhang, Jiangchuan

    2016-01-01

    Application layer firewalls protect the trusted area network against information security risks. However, firewall performance may affect user experience. Therefore, performance analysis plays a significant role in the evaluation of application layer firewalls. This paper presents an analytic model of the application layer firewall, based on a system analysis to evaluate the capability of the firewall. In order to enable users to improve the performance of the application layer firewall with limited resources, resource allocation was evaluated to obtain the optimal resource allocation scheme in terms of throughput, delay, and packet loss rate. The proposed model employs the Erlangian queuing model to analyze the performance parameters of the system with regard to the three layers (network, transport, and application layers). Then, the analysis results of all the layers are combined to obtain the overall system performance indicators. A discrete event simulation method was used to evaluate the proposed model. Finally, limited service desk resources were allocated to obtain the values of the performance indicators under different resource allocation scenarios in order to determine the optimal allocation scheme. Under limited resource allocation, this scheme enables users to maximize the performance of the application layer firewall. PMID:27893803

  9. Performance Evaluation Model for Application Layer Firewalls.

    PubMed

    Xuan, Shichang; Yang, Wu; Dong, Hui; Zhang, Jiangchuan

    2016-01-01

    Application layer firewalls protect the trusted area network against information security risks. However, firewall performance may affect user experience. Therefore, performance analysis plays a significant role in the evaluation of application layer firewalls. This paper presents an analytic model of the application layer firewall, based on a system analysis to evaluate the capability of the firewall. In order to enable users to improve the performance of the application layer firewall with limited resources, resource allocation was evaluated to obtain the optimal resource allocation scheme in terms of throughput, delay, and packet loss rate. The proposed model employs the Erlangian queuing model to analyze the performance parameters of the system with regard to the three layers (network, transport, and application layers). Then, the analysis results of all the layers are combined to obtain the overall system performance indicators. A discrete event simulation method was used to evaluate the proposed model. Finally, limited service desk resources were allocated to obtain the values of the performance indicators under different resource allocation scenarios in order to determine the optimal allocation scheme. Under limited resource allocation, this scheme enables users to maximize the performance of the application layer firewall.

  10. Evaluation of help model replacement codes

    SciTech Connect

    Whiteside, Tad; Hang, Thong; Flach, Gregory

    2009-07-01

    This work evaluates the computer codes that are proposed to be used to predict percolation of water through the closure-cap and into the waste containment zone at the Department of Energy closure sites. This work compares the currently used water-balance code (HELP) with newly developed computer codes that use unsaturated flow (Richards’ equation). It provides a literature review of the HELP model and the proposed codes, which result in two recommended codes for further evaluation: HYDRUS-2D3D and VADOSE/W. This further evaluation involved performing actual simulations on a simple model and comparing the results of those simulations to those obtained with the HELP code and the field data. From the results of this work, we conclude that the new codes perform nearly the same, although moving forward, we recommend HYDRUS-2D3D.

  11. Surface error modeling of mounted large optics in high power laser system

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Xiong, Zhao; Yuan, Xiaodong

    2016-10-01

    The surface form of mounted large optics has a very important impact on the laser beam performance in high power laser system. To make the surface form to the minimized distortion and keep with the design specifications is always a difficult challenge in China's SG-III laser system which is made up of thousands meter-sized large optical units and requires to focus all 48 laser beams into nearly 600 μm-diameter spot better than 50 μm (RMS) within a few picoseconds. In this paper, a methodology integrated both 3D finite elements modeling method and nanometer-level precision metrology is proposed to evaluate the surface performance. According to various spatial frequencies, the wavefront characters of large aperture optical component are measured and provided to analyze its mounted surface characters. Assembly and mounting process will be adjusted to meet for the surface wavefront requirements both of with the data both of measured when pre-alignment and predicted for installation. By a case study of large transport mirror, the proposed approach has shown a good performance on obtaining precise surface features and guiding the optical mounting.

  12. Online to offline teaching model in optics education: resource sharing course and flipped class

    NASA Astrophysics Data System (ADS)

    Li, Xiaotong; Cen, Zhaofeng; Liu, Xiangdong; Zheng, Zhenrong

    2016-09-01

    Since the platform "Coursera" is created by the professors of Stanford University Andrew Ng and Daphne Koller, more and more universities have joined in it. From the very beginning, online education is not only about education itself, but also connected with social equality. This is especially significant for the economic transformation in China. In this paper the research and practice on informatization of optical education are described. Online to offline (O2O) education activities, such as online learning and offline meeting, online homework and online to offline discussion, online tests and online to offline evaluation, are combined into our teaching model in the course of Applied Optics. These various O2O strategies were implemented respectively in the autumn-winter small class and the spring-summer middle class according to the constructivism and the idea of open education. We have developed optical education resources such as videos of lectures, light transmission or ray trace animations, online tests, etc. We also divide the learning procedure into 4 steps: First, instead of being given a course offline, students will learn the course online; Second, once a week or two weeks, students will have a discussion in their study groups; Third, students will submit their homework and study reports; Fourth, they will do online and offline tests. The online optical education resources have been shared in some universities in China, together with new challenges to teachers and students when facing the revolution in the e-learning future.

  13. Evaluation of a Mysis bioenergetics model

    USGS Publications Warehouse

    Chipps, S.R.; Bennett, D.H.

    2002-01-01

    Direct approaches for estimating the feeding rate of the opossum shrimp Mysis relicta can be hampered by variable gut residence time (evacuation rate models) and non-linear functional responses (clearance rate models). Bioenergetics modeling provides an alternative method, but the reliability of this approach needs to be evaluated using independent measures of growth and food consumption. In this study, we measured growth and food consumption for M. relicta and compared experimental results with those predicted from a Mysis bioenergetics model. For Mysis reared at 10??C, model predictions were not significantly different from observed values. Moreover, decomposition of mean square error indicated that 70% of the variation between model predictions and observed values was attributable to random error. On average, model predictions were within 12% of observed values. A sensitivity analysis revealed that Mysis respiration and prey energy density were the most sensitive parameters affecting model output. By accounting for uncertainty (95% CLs) in Mysis respiration, we observed a significant improvement in the accuracy of model output (within 5% of observed values), illustrating the importance of sensitive input parameters for model performance. These findings help corroborate the Mysis bioenergetics model and demonstrate the usefulness of this approach for estimating Mysis feeding rate.

  14. A Simple Optical Model Well Explains Plasmonic-Nanoparticle-Enhanced Spectral Photocurrent in Optically Thin Solar Cells

    NASA Astrophysics Data System (ADS)

    Tanabe, Katsuaki

    2016-05-01

    A simple optical model for photocurrent enhancement by plasmonic metal nanoparticles atop solar cells has been developed. Our model deals with the absorption, reflection, and scattering of incident sunlight as well as radiation efficiencies on metallic nanoparticles. Our calculation results satisfactorily reproduce a series of experimental spectral data for optically thin GaAs solar cells with Ag and Al nanoparticles of various dimensions, demonstrating the validity of our modeling approach. Our model is likely to be a powerful tool for investigations of surface plasmon-enhanced thin-film solar cells.

  15. A Simple Optical Model Well Explains Plasmonic-Nanoparticle-Enhanced Spectral Photocurrent in Optically Thin Solar Cells.

    PubMed

    Tanabe, Katsuaki

    2016-12-01

    A simple optical model for photocurrent enhancement by plasmonic metal nanoparticles atop solar cells has been developed. Our model deals with the absorption, reflection, and scattering of incident sunlight as well as radiation efficiencies on metallic nanoparticles. Our calculation results satisfactorily reproduce a series of experimental spectral data for optically thin GaAs solar cells with Ag and Al nanoparticles of various dimensions, demonstrating the validity of our modeling approach. Our model is likely to be a powerful tool for investigations of surface plasmon-enhanced thin-film solar cells.

  16. Application of optical triangulation profilometry and optical phase ranging profilometry to the figure evaluation of solar mirrors

    SciTech Connect

    Griffin, J.W.; Lind, M.A.

    1980-12-01

    The techniques of optical triangulation profilometry (OTP) and optical phase ranging profilometry (OPRP) are proposed for evaluation of the figure of solar mirrors. The theoretical basis for each method is discussed and the results of initial feasibility experiments are reported. In OTP and OPRP the de-specularized mirror surface is probed with one or more visible laser beams. In OTP, two beams are required for the triangulation of coordinates on the mirror surface. In OPRP the second laser beam is retained within the instrument to form the reference leg of a long wavelength interferometer. Both methods are particularly adaptable to computer control for fast, automated analysis of mirror surfaces. In addition the proposed devices are compact and sturdy enough for easy implementation in field evaluation programs. The experimental resolution capability of the unoptimized OTP system is greater than or equal to 0.1 inch (2.54 mm). With further improvement of the beam projection and coincidence assessment systems, the design resolution goal of greater than or equal to 0.1 mm appears achievable. The results of the preliminary resolution capability experiments on the OPRP system are inconclusive. This is thought to be a result of poor performance of components comprising the modulation and detection subsystems. A full assessment of OPRP capability will require a further investigation effort.

  17. Dynamic aberration correction for conformal optics using model-based wavefront sensorless adaptive optics

    NASA Astrophysics Data System (ADS)

    Han, Xinli; Dong, Bing; Li, Yan; Wang, Rui; Hu, Bin

    2016-10-01

    For missiles and airplanes with high Mach number, traditional spherical or flat window can cause a lot of air drag. Conformal window that follow the general contour of surrounding surface can substantially decrease air drag and extend operational range. However, the local shape of conformal window changes across the Field Of Regard (FOR), leading to time-varying FOR-dependent wavefront aberration and degraded image. So the correction of dynamic aberration is necessary. In this paper, model-based Wavefront Sensorless Adaptive Optics (WSAO) algorithm is investigated both by simulation and experiment for central-obscured pupil. The algorithm is proved to be effective and the correction accuracy of using DM modes is higher than Lukosz modes. For dynamic aberration in our system, the SR can be better than 0.8 when the change of looking angle is less than 2° after t seconds which is the time delay of the control system.

  18. Chasing the Sun -- The Inflight Evaluation of an Optical Head Tracker

    DTIC Science & Technology

    2006-02-01

    the experimental design and flight test program used to evaluate the performance of an Optical Head Tracker ( OHT ) under dynamic flight and intense solar...effectively evaluate the OHT performance, as well as safety of flight considerations necessary to satisfy both AFRL and NASA strict safety...requirements. Discussions will include airborne platform selection, modification, and operations necessary to achieve maximum solar exposure on the OHT while

  19. EVALUATION OF FUGITIVE EMISSIONS USING GROUND-BASED OPTICAL REMOTE SENSING TECHNOLOGY

    EPA Science Inventory

    EPA has developed and evaluated a method for characterizing fugitive emissions from large area sources. The method, known as radial plume mapping (RPM) uses multiple-beam, scanning, optical remote sensing (ORS) instrumentation such as open-path Fourier transform infrared spectro...

  20. An evaluation of fiber optic intrusion detection systems in interior applications

    SciTech Connect

    Vigil, J.T.

    1994-03-01

    This report discusses the testing and evaluation of four commercially available fiber optic intrusion detection systems. The systems were tested under carpet-type matting and in a vaulted ceiling application. This report will focus on nuisance alarm data and intrusion detection results. Tests were conducted in a mobile office building and in a bunker.

  1. Optical modeling, design optimization, and performance analysis of a gamma camera for detection of breast cancer

    NASA Astrophysics Data System (ADS)

    Sain, John David

    2001-07-01

    This dissertation presents the research performed to develop an optical model, improve some design parameters, and analyze the performance of the UA modular gamma camera. Initially we provide a brief background on nuclear medical imaging with scintillation cameras. The key hardware components of a camera are introduced, and some of the fundamental physics involved in the detection of gamma rays is explained. Then we describe a stand-alone modular camera imaging system that was developed to image human breasts in the clinic. The hardware and software components, calibration procedure, and general operation of the system are detailed. We explain the concepts of position estimation and scatter rejection and note how they have been applied to imaging with the UA modular gamma camera. Position estimation uses the output signals of the camera to determine where an incident gamma ray interacted within the camera, and scatter rejection uses the signals to decide whether or not an incident gamma ray underwent scattering prior to being detected by the camera. Then we present an analytical optical model of the UA modular gamma camera. Taking into account physical and optical properties of the camera components, the model performs radiometric calculations to estimate the mean response of the camera to a scintillation event anywhere within the scintillation crystal. The results of several studies using the optical model to test and improve some camera design parameters are reported. Finally, we demonstrate how straightforward signal detection theory can be used to evaluate the performance of a modular gamma camera for the task of detecting signals in noisy backgrounds. Guided by the preliminary design of a dedicated breast imaging system, estimates of how well the UA modular gamma camera can detect lesions within human breasts were generated.

  2. Selecting among competing models of electro-optic, infrared camera system range performance

    USGS Publications Warehouse

    Nichols, Jonathan M.; Hines, James E.; Nichols, James D.

    2013-01-01

    Range performance is often the key requirement around which electro-optical and infrared camera systems are designed. This work presents an objective framework for evaluating competing range performance models. Model selection based on the Akaike’s Information Criterion (AIC) is presented for the type of data collected during a typical human observer and target identification experiment. These methods are then demonstrated on observer responses to both visible and infrared imagery in which one of three maritime targets was placed at various ranges. We compare the performance of a number of different models, including those appearing previously in the literature. We conclude that our model-based approach offers substantial improvements over the traditional approach to inference, including increased precision and the ability to make predictions for some distances other than the specific set for which experimental trials were conducted.

  3. Optical Measurements and Modeling to Estimate Concentrations and Fluxes of Organic Matter in the Southern Ocean

    NASA Technical Reports Server (NTRS)

    Stramski, Dariusz; Mitchell, B. Greg; Marra, John W. (Technical Monitor)

    2001-01-01

    This project was a collaboration between two Principal Investigators, Dr. Dariusz Stramski and Dr. Greg Mitchell of Scripps Institution of Oceanography, University of California San Diego. Our overall goal was to conduct optical measurements and modeling to estimate concentrations of organic matter in the Southern Ocean in support of the U.S. JGOFS Process Study in this region. Key variables and processes of high relevance to accomplish the JGOFS goals include time and space resolution of phytoplankton pigments, particulate organic carbon, and the formation and export of organic carbon. Our project focused on establishing the fundamental relationships for parameterization of these variables and processes in terms of the optical properties of seawater, and developing understanding of why the Southern Ocean differs from other low-latitude systems, or has differentiation within. Our approach builds upon historical observations that optical properties provide a useful proxy for key reservoirs of organic matter such as chlorophyll alpha (Chl) and particulate organic carbon (POC) concentrations, which are of relevance to the JGOFS objectives. We carried out detailed studies of in situ and water sample optical properties including spectral reflectance, absorption, beam attenuation, scattering, and backscattering coefficients. We evaluated the ability to estimate Chl from the spectral reflectance (ocean color) in the Southern Ocean. We examined relationships between the ocean optical properties and particulate organic carbon. We developed, for the first time, an algorithm for estimating particulate organic carbon concentration in the surface ocean from satellite imagery of ocean color. With this algorithm, we obtained maps of POC distribution in the Southern Ocean showing the seasonal progression of POC in the austral spring-summer season. We also developed a semianalytical reflectance model for the investigated polar waters based on our field measurements of absorption

  4. Optical coherence tomography and highly sensitivity troponin T for evaluating cardiac allograft vasculopathy.

    PubMed

    Garrido, Iris P; García-Lara, Juan; Pinar, Eduardo; Pastor-Pérez, Francisco; Sánchez-Mas, Jesus; Valdés-Chavarri, Mariano; Pascual-Figal, Domingo A

    2012-09-01

    Cardiac allograft vasculopathy (CAV) is a major impediment to long-term graft survival after heart transplantation. Intravascular ultrasound (IVUS) is more sensitive than coronary angiography for diagnosis, but the identification of specific plaque components or plaque composition is limited. In addition, there is an evident need for other noninvasive tools for diagnosing CAV. The aim of this study was to assess the utility of 2 new techniques for evaluating CAV: optical coherence tomography (OCT), and new high-sensitivity troponin T (hsTnT) assays. In 21 heart transplantation patients, coronary arteriography with IVUS and OCT were performed. Maximal intimal thickness (MIT) and luminal area at the most severe site were measured using the 2 techniques. Immediately before cardiac catheterization, blood samples were obtained and hsTnT levels measured. The evaluation of CAV by OCT showed a good correlation with IVUS measurements, with a mean difference in MIT of 0.0033 (95% confidence interval -0.049 to 0.043), taking advantage of lower interobserver variability (r = 0.94 for OCT vs r = 0.78 for IVUS) and better plaque characterization. When independent predictors of MIT were assessed in a multiple linear regression model, time after transplantation (β = 0.488, p = 0.004) and hsTnT (β = 0.392, p = 0.011) were the only independent predictors of MIT (R(2) = 0.591). In conclusion, this study is the first to evaluate 2 new techniques, OCT and hsTnT, in the challenging setting of CAV. The findings suggest that OCT provides lower interobserver variability and better plaque characterization than IVUS. Also, hsTnT could become a useful tool for ruling out CAV.

  5. Evaluation (not validation) of quantitative models.

    PubMed

    Oreskes, N

    1998-12-01

    The present regulatory climate has led to increasing demands for scientists to attest to the predictive reliability of numerical simulation models used to help set public policy, a process frequently referred to as model validation. But while model validation may reveal useful information, this paper argues that it is not possible to demonstrate the predictive reliability of any model of a complex natural system in advance of its actual use. All models embed uncertainties, and these uncertainties can and frequently do undermine predictive reliability. In the case of lead in the environment, we may categorize model uncertainties as theoretical, empirical, parametrical, and temporal. Theoretical uncertainties are aspects of the system that are not fully understood, such as the biokinetic pathways of lead metabolism. Empirical uncertainties are aspects of the system that are difficult (or impossible) to measure, such as actual lead ingestion by an individual child. Parametrical uncertainties arise when complexities in the system are simplified to provide manageable model input, such as representing longitudinal lead exposure by cross-sectional measurements. Temporal uncertainties arise from the assumption that systems are stable in time. A model may also be conceptually flawed. The Ptolemaic system of astronomy is a historical example of a model that was empirically adequate but based on a wrong conceptualization. Yet had it been computerized--and had the word then existed--its users would have had every right to call it validated. Thus, rather than talking about strategies for validation, we should be talking about means of evaluation. That is not to say that language alone will solve our problems or that the problems of model evaluation are primarily linguistic. The uncertainties inherent in large, complex models will not go away simply because we change the way we talk about them. But this is precisely the point: calling a model validated does not make it valid

  6. Evaluation (not validation) of quantitative models.

    PubMed Central

    Oreskes, N

    1998-01-01

    The present regulatory climate has led to increasing demands for scientists to attest to the predictive reliability of numerical simulation models used to help set public policy, a process frequently referred to as model validation. But while model validation may reveal useful information, this paper argues that it is not possible to demonstrate the predictive reliability of any model of a complex natural system in advance of its actual use. All models embed uncertainties, and these uncertainties can and frequently do undermine predictive reliability. In the case of lead in the environment, we may categorize model uncertainties as theoretical, empirical, parametrical, and temporal. Theoretical uncertainties are aspects of the system that are not fully understood, such as the biokinetic pathways of lead metabolism. Empirical uncertainties are aspects of the system that are difficult (or impossible) to measure, such as actual lead ingestion by an individual child. Parametrical uncertainties arise when complexities in the system are simplified to provide manageable model input, such as representing longitudinal lead exposure by cross-sectional measurements. Temporal uncertainties arise from the assumption that systems are stable in time. A model may also be conceptually flawed. The Ptolemaic system of astronomy is a historical example of a model that was empirically adequate but based on a wrong conceptualization. Yet had it been computerized--and had the word then existed--its users would have had every right to call it validated. Thus, rather than talking about strategies for validation, we should be talking about means of evaluation. That is not to say that language alone will solve our problems or that the problems of model evaluation are primarily linguistic. The uncertainties inherent in large, complex models will not go away simply because we change the way we talk about them. But this is precisely the point: calling a model validated does not make it valid

  7. Quantitative In Vivo Detection of Chlamydia muridarum Associated Inflammation in a Mouse Model Using Optical Imaging

    PubMed Central

    Patel, Manishkumar; Boddicker, Melissa A.; DeMaula, Christopher; Connolly, Brett; Bednar, Bohumil; Heinrichs, Jon H.; Smith, Jeffrey G.

    2015-01-01

    Chlamydia trachomatis is a bacterial sexually transmitted disease with over 1.3 million cases reported to the CDC in 2010. While Chlamydia infection is easily treated with antibiotics, up to 70% of infections are asymptomatic and go untreated. The current mouse model relies on invasive upper genital tract gross pathology readouts at ~60–80 days postinfection. High throughput optical imaging through the use of biomarkers has been successfully used to quickly evaluate several disease processes. Here we evaluate Neutrophil Elastase 680 (Elastase680) for its ability to measure Chlamydia muridarum associated inflammation in live mice using fluorescence molecular tomography (FMT) and In Vivo Imaging System (IVIS). Optical imaging was able to distinguish with statistical significance between vaccinated and nonvaccinated mice as well as mock-challenged and challenged mice 2 weeks after challenge which was 9 weeks sooner than typical gross pathological assessment. Immunohistochemistry confirmed the presence of neutrophils and correlated well with both in vivo and ex vivo imaging. In this report we demonstrate that Elastase680 can be used as a molecular imaging biomarker for inflammation associated with chlamydial infection in a mouse model and that these biomarkers can significantly decrease the time for pathology evaluation and thus increase the rate of therapeutics discovery. PMID:26663988

  8. Evaluating computational models of cholesterol metabolism.

    PubMed

    Paalvast, Yared; Kuivenhoven, Jan Albert; Groen, Albert K

    2015-10-01

    Regulation of cholesterol homeostasis has been studied extensively during the last decades. Many of the metabolic pathways involved have been discovered. Yet important gaps in our knowledge remain. For example, knowledge on intracellular cholesterol traffic and its relation to the regulation of cholesterol synthesis and plasma cholesterol levels is incomplete. One way of addressing the remaining questions is by making use of computational models. Here, we critically evaluate existing computational models of cholesterol metabolism making use of ordinary differential equations and addressed whether they used assumptions and make predictions in line with current knowledge on cholesterol homeostasis. Having studied the results described by the authors, we have also tested their models. This was done primarily by testing the effect of statin treatment in each model. Ten out of eleven models tested have made assumptions in line with current knowledge of cholesterol metabolism. Three out of the ten remaining models made correct predictions, i.e. predicting a decrease in plasma total and LDL cholesterol or increased uptake of LDL upon treatment upon the use of statins. In conclusion, few models on cholesterol metabolism are able to pass a functional test. Apparently most models have not undergone the critical iterative systems biology cycle of validation. We expect modeling of cholesterol metabolism to go through many more model topologies and iterative cycles and welcome the increased understanding of cholesterol metabolism these are likely to bring.

  9. Prehistological evaluation of benign and malignant pigmented skin lesions with optical computed tomography

    NASA Astrophysics Data System (ADS)

    Kokolakis, Athanasios; Zacharakis, Giannis; Krasagakis, Konstantin; Lasithiotakis, Konstantinos; Favicchio, Rosy; Spiliopoulos, George; Giannikaki, Elpida; Ripoll, Jorge; Tosca, Androniki

    2012-06-01

    Discrimination of benign and malignant melanocytic lesions is a major issue in clinical dermatology. Assessment of the thickness of melanoma is critical for prognosis and treatment selection. We aimed to evaluate a novel optical computed tomography (optical-CT) system as a tool for three-dimensional (3-D) imaging of melanocytic lesions and its ability to discriminate benign from malignant melanocytic lesions while simultaneously determining the thickness of invasive melanoma. Seventeen melanocytic lesions, one hemangioma, and normal skin were assessed immediately after their excision by optical-CT and subsequently underwent histopathological examination. Tomographic reconstructions were performed with a back-propagation algorithm calculating a 3-D map of the total attenuation coefficient (AC). There was a statistically significant difference between melanomas, dysplastic nevi, and non-dysplastic nevi, as indicated by Kruskal-Wallis test. Median AC values were higher for melanomas compared with dysplastic and non-dysplastic nevi. No statistically significant difference was observed when thickness values obtained by optical-CT were compared with histological thickness using a Wilcoxon sighed rank test. Our results suggest that optical-CT can be important for the immediate prehistological evaluation of biopsies, assisting the physician for a rapid assessment of malignancy and of the thickness of a melanocytic lesion.

  10. [Evaluation of therapeutic effect of new Russian drug semax in optic nerve disease].

    PubMed

    Polunin, G S; Nurieva, S M; Baiandin, D L; Sheremet, N L; Andreeva, L A

    2000-01-01

    Semax is a synthetic analog of adrenocorticotropic hormone 4-10 with a pronounced nootropic effect. It was used in the treatment of vascular, toxic allergic, and inflammatory diseases of the optic nerve and partial atrophy of the optic nerve in parallel with basic neurotrophic and antiinflammatory therapy. For evaluating the drug efficiency, the patients were divided into 3 groups, administered the drug via different routes. In group 1 semax was administered intransally as nasal drops, in group 2 by endonasal electrophoresis, and group 3 was control. Addition of semax to therapeutic complex in patients with diseases of the optic nerve had a favorable impact on the intensity and rate of recovery and improved the visual functions. Semax effectively protected nervous tissue from aftereffects of injury, particularly during the acute stage of optic nerve disease: it stimulated positive changes in the clinical picture, which were evaluated by improvement of visual acuity, extension of the total visual field, increase in the electric sensitivity and conductivity of the optic nerve, and improvement of color vision.

  11. Evaluation of Aerosol-Cloud Interactions in GISS ModelE Using ASR Observations

    NASA Astrophysics Data System (ADS)

    de Boer, G.; Menon, S.; Bauer, S. E.; Toto, T.; Bennartz, R.; Cribb, M.

    2011-12-01

    The impacts of aerosol particles on clouds continue to rank among the largest uncertainties in global climate simulation. In this work we assess the capability of the NASA GISS ModelE, coupled to MATRIX aerosol microphysics, in correctly representing warm-phase aerosol-cloud interactions. This evaluation is completed through the analysis of a nudged, multi-year global simulation using measurements from various US Department of Energy sponsored measurement campaigns and satellite-based observations. Campaign observations include the Aerosol Intensive Operations Period (Aerosol IOP) and Routine ARM Arial Facility Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO) at the Southern Great Plains site in Oklahoma, the Marine Stratus Radiation, Aerosol, and Drizzle (MASRAD) campaign at Pt. Reyes, California, and the ARM mobile facility's 2008 deployment to China. This combination of datasets provides a variety of aerosol and atmospheric conditions under which to test ModelE parameterizations. In addition to these localized comparisons, we provide the results of global evaluations completed using measurements derived from satellite remote sensors. We will provide a basic overview of simulation performance, as well as a detailed analysis of parameterizations relevant to aerosol indirect effects.

  12. Adaptive optics for reduced threshold energy in femtosecond laser induced optical breakdown in water based eye model

    NASA Astrophysics Data System (ADS)

    Hansen, Anja; Krueger, Alexander; Ripken, Tammo

    2013-03-01

    In ophthalmic microsurgery tissue dissection is achieved using femtosecond laser pulses to create an optical breakdown. For vitreo-retinal applications the irradiance distribution in the focal volume is distorted by the anterior components of the eye causing a raised threshold energy for breakdown. In this work, an adaptive optics system enables spatial beam shaping for compensation of aberrations and investigation of wave front influence on optical breakdown. An eye model was designed to allow for aberration correction as well as detection of optical breakdown. The eye model consists of an achromatic lens for modeling the eye's refractive power, a water chamber for modeling the tissue properties, and a PTFE sample for modeling the retina's scattering properties. Aberration correction was performed using a deformable mirror in combination with a Hartmann-Shack-sensor. The influence of an adaptive optics aberration correction on the pulse energy required for photodisruption was investigated using transmission measurements for determination of the breakdown threshold and video imaging of the focal region for study of the gas bubble dynamics. The threshold energy is considerably reduced when correcting for the aberrations of the system and the model eye. Also, a raise in irradiance at constant pulse energy was shown for the aberration corrected case. The reduced pulse energy lowers the potential risk of collateral damage which is especially important for retinal safety. This offers new possibilities for vitreo-retinal surgery using femtosecond laser pulses.

  13. A modeling-based assessment of acousto-optic sensing for monitoring high-intensity focused ultrasound lesion formation

    NASA Astrophysics Data System (ADS)

    Adams, Matthew Tyler

    Real-time acousto-optic (AO) sensing---a dual-wave modality that combines ultrasound with diffuse light to probe the optical properties of turbid media---has been demonstrated to non-invasively detect changes in ex vivo tissue optical properties during high-intensity focused ultrasound (HIFU) exposure. The AO signal indicates the onset of lesion formation and predicts resulting lesion volumes. Although proof-of-concept experiments have been successful, many of the underlying parameters and mechanisms affecting thermally induced optical property changes and the AO detectability of HIFU lesion formation are not well understood. In thesis, a numerical simulation was developed to model the AO sensing process and capture the relevant acoustic, thermal, and optical transport processes. The simulation required data that described how optical properties changed with heating. Experiments were carried out where excised chicken breast was exposed to thermal bath heating and changes in the optical absorption and scattering spectra (500 nm--1100 nm) were measured using a scanning spectrophotometer and an integrating sphere assembly. Results showed that the standard thermal dose model currently used for guiding HIFU treatments needs to be adjusted to describe thermally induced optical property changes. To model the entire AO process, coupled models were used for ultrasound propagation, tissue heating, and diffusive light transport. The angular spectrum method was used to model the acoustic field from the HIFU source. Spatial-temporal temperature elevations induced by the absorption of ultrasound were modeled using a finite-difference time-domain solution to the Pennes bioheat equation. The thermal dose model was then used to determine optical properties based on the temperature history. The diffuse optical field in the tissue was then calculated using a GPU-accelerated Monte Carlo algorithm, which accounted for light-sound interactions and AO signal detection. The simulation was

  14. A model evaluation checklist for process-based environmental models

    NASA Astrophysics Data System (ADS)

    Jackson-Blake, Leah

    2015-04-01

    Mechanistic catchment-scale phosphorus models appear to perform poorly where diffuse sources dominate. The reasons for this were investigated for one commonly-applied model, the INtegrated model of CAtchment Phosphorus (INCA-P). Model output was compared to 18 months of daily water quality monitoring data in a small agricultural catchment in Scotland, and model structure, key model processes and internal model responses were examined. Although the model broadly reproduced dissolved phosphorus dynamics, it struggled with particulates. The reasons for poor performance were explored, together with ways in which improvements could be made. The process of critiquing and assessing model performance was then generalised to provide a broadly-applicable model evaluation checklist, incorporating: (1) Calibration challenges, relating to difficulties in thoroughly searching a high-dimensional parameter space and in selecting appropriate means of evaluating model performance. In this study, for example, model simplification was identified as a necessary improvement to reduce the number of parameters requiring calibration, whilst the traditionally-used Nash Sutcliffe model performance statistic was not able to discriminate between realistic and unrealistic model simulations, and alternative statistics were needed. (2) Data limitations, relating to a lack of (or uncertainty in) input data, data to constrain model parameters, data for model calibration and testing, and data to test internal model processes. In this study, model reliability could be improved by addressing all four kinds of data limitation. For example, there was insufficient surface water monitoring data for model testing against an independent dataset to that used in calibration, whilst additional monitoring of groundwater and effluent phosphorus inputs would help distinguish between alternative plausible model parameterisations. (3) Model structural inadequacies, whereby model structure may inadequately represent

  15. Review on optical constants of Titan aerosols: Experimental results and modeling/observational data

    NASA Astrophysics Data System (ADS)

    Brassé, Coralie; Muñoz, Olga; Coll, Patrice; Raulin, François

    2014-05-01

    During the last years many studies have been performed to improve the experimental database of optical constants of Titan aerosols. Indeed, the determination of the optical constants of these particles is essential to quantify their capacity to absorb and to scatter solar radiation, and thus to evaluate their role on Titan's radiative balance and climate. The study of optical properties is also crucial to analyze and to better interpret many of Titan's observational data, in particular those acquired during the Cassini-Huygens mission. One way to determine Titan aerosols optical constant is to measure the optical constants of analogues of Titan complex organic material synthesized in the laboratory, usually named Titan's tholins (Sagan and Khare, 1979). But the optical constants depend on the chemical composition, the size and the shape of particles (Raulin et al., 2012). Those three parameters result from the experimental conditions such as energy source, gas mixing ratio, gas pressure, flow rate and irradiation time (Cable et al., 2012). Besides the determination of the refractive index in the laboratory, there are others methods using theoretical models or observational data. Nevertheless, theoretical models are based on laboratory data or/and observational data. The visible - near infrared spectral region of optical constants has been widely studied with laboratory analogues. Comparison of the obtained results suggest that tholins synthesized by Tran et al. (2003) and Majhoub et al. (2012) are the best representative of Titan aerosols with regards to their refractive indexes in this spectral region. The mid-infrared spectral range has been studied only by Imanaka et al. (2012) and slightly by Tran et al. (2003). In that spectral range, Titan tholins do not exhibit the features displayed by Kim and Courtin (2013) from Titan's observations. For spectral region of wavelengths smaller than 0.20µm or higher than 25µm, only the data from Khare et al. (1984) are

  16. Analytic evaluation of Kane fermion magneto-optics in two and three dimensions

    NASA Astrophysics Data System (ADS)

    Malcolm, J. D.; Nicol, E. J.

    2016-12-01

    We calculate and present an analytic form of the magneto-optical conductivity for the gapped low-energy Kane model in two and three dimensions separately. The two-dimensional case maps onto the α -T3 model at a particular value of α =1 /√{3 } . In two dimensions, two chiral sectors exist, between which there are no optically activated transitions. In three dimensions, the extra dimension of dispersion mixes the two sectors so that intra- and intersector transitions can occur. The latter type of transition can be separated out via circular polarizations of light, and it shows a distinct signature in the transverse conductivity.

  17. Virtual optical network provisioning with unified service logic processing model for software-defined multidomain optical networks

    NASA Astrophysics Data System (ADS)

    Zhao, Yongli; Li, Shikun; Song, Yinan; Sun, Ji; Zhang, Jie

    2015-12-01

    Hierarchical control architecture is designed for software-defined multidomain optical networks (SD-MDONs), and a unified service logic processing model (USLPM) is first proposed for various applications. USLPM-based virtual optical network (VON) provisioning process is designed, and two VON mapping algorithms are proposed: random node selection and per controller computation (RNS&PCC) and balanced node selection and hierarchical controller computation (BNS&HCC). Then an SD-MDON testbed is built with OpenFlow extension in order to support optical transport equipment. Finally, VON provisioning service is experimentally demonstrated on the testbed along with performance verification.

  18. Modeling silica aerogel optical performance by determining its radiative properties

    NASA Astrophysics Data System (ADS)

    Zhao, Lin; Yang, Sungwoo; Bhatia, Bikram; Strobach, Elise; Wang, Evelyn N.

    2016-02-01

    Silica aerogel has been known as a promising candidate for high performance transparent insulation material (TIM). Optical transparency is a crucial metric for silica aerogels in many solar related applications. Both scattering and absorption can reduce the amount of light transmitted through an aerogel slab. Due to multiple scattering, the transmittance deviates from the Beer-Lambert law (exponential attenuation). To better understand its optical performance, we decoupled and quantified the extinction contributions of absorption and scattering separately by identifying two sets of radiative properties. The radiative properties are deduced from the measured total transmittance and reflectance spectra (from 250 nm to 2500 nm) of synthesized aerogel samples by solving the inverse problem of the 1-D Radiative Transfer Equation (RTE). The obtained radiative properties are found to be independent of the sample geometry and can be considered intrinsic material properties, which originate from the aerogel's microstructure. This finding allows for these properties to be directly compared between different samples. We also demonstrate that by using the obtained radiative properties, we can model the photon transport in aerogels of arbitrary shapes, where an analytical solution is difficult to obtain.

  19. Modelling the optical properties of aerosols in a chemical transport model

    NASA Astrophysics Data System (ADS)

    Andersson, E.; Kahnert, M.

    2015-12-01

    According to the IPCC fifth assessment report (2013), clouds and aerosols still contribute to the largest uncertainty when estimating and interpreting changes to the Earth's energy budget. Therefore, understanding the interaction between radiation and aerosols is both crucial for remote sensing observations and modelling the climate forcing arising from aerosols. Carbon particles are the largest contributor to the aerosol absorption of solar radiation, thereby enhancing the warming of the planet. Modelling the radiative properties of carbon particles is a hard task and involves many uncertainties arising from the difficulties of accounting for the morphologies and heterogeneous chemical composition of the particles. This study aims to compare two ways of modelling the optical properties of aerosols simulated by a chemical transport model. The first method models particle optical properties as homogeneous spheres and are externally mixed. This is a simple model that is particularly easy to use in data assimilation methods, since the optics model is linear. The second method involves a core-shell internal mixture of soot, where sulphate, nitrate, ammonia, organic carbon, sea salt, and water are contained in the shell. However, by contrast to previously used core-shell models, only part of the carbon is concentrated in the core, while the remaining part is homogeneously mixed with the shell. The chemical transport model (CTM) simulations are done regionally over Europe with the Multiple-scale Atmospheric Transport and CHemistry (MATCH) model, developed by the Swedish Meteorological and Hydrological Institute (SMHI). The MATCH model was run with both an aerosol dynamics module, called SALSA, and with a regular "bulk" approach, i.e., a mass transport model without aerosol dynamics. Two events from 2007 are used in the analysis, one with high (22/12-2007) and one with low (22/6-2007) levels of elemental carbon (EC) over Europe. The results of the study help to assess the

  20. Evaluating model accuracy for model-based reasoning

    NASA Technical Reports Server (NTRS)

    Chien, Steve; Roden, Joseph

    1992-01-01

    Described here is an approach to automatically assessing the accuracy of various components of a model. In this approach, actual data from the operation of a target system is used to drive statistical measures to evaluate the prediction accuracy of various portions of the model. We describe how these statistical measures of model accuracy can be used in model-based reasoning for monitoring and design. We then describe the application of these techniques to the monitoring and design of the water recovery system of the Environmental Control and Life Support System (ECLSS) of Space Station Freedom.

  1. The development and evaluation of head probes for optical imaging of the infant head

    NASA Astrophysics Data System (ADS)

    Branco, Gilberto

    The objective of this thesis was to develop and evaluate optical imaging probes for mapping oxygenation and haemodynamic changes in the newborn infant brain. Two imaging approaches are being developed at University College London (UCL): optical topography (surface mapping of the cortex) and optical tomography (volume imaging). Both have the potential to provide information about the function of the normal brain and about a variety of neurophysiologies! abnormalities. Both techniques require an array of optical fibres/fibre bundles to be held in contact with the head, for periods of time from tens of seconds to an hour or more. The design of suitable probes must ensure the comfort and safety of the subject, and provide measurements minimally sensitive to external sources of light and patient motion. A series of prototype adaptable helmets were developed for optical tomography of the premature infant brain using the UCL 32-channel time-resolved system. They were required to attach 32 optical fibre bundles over the infant scalp, and were designed to accommodate infants with a variety of head shapes and sizes, aged between 24-weeks gestational age and term. Continual improvements to the helmet design were introduced following the evaluation of each prototype on infants in the hospital. Data were acquired to generate images revealing the concentration and oxygenation of blood in the brain, and the response of the brain to sensory stimulation. This part of the project also involved designing and testing new methods of acquiring calibration data using reference phantoms. The second focus of the project was the development of probes for use with the UCL frequency-multiplexed near-infrared topography system. This is being used to image functional activation in the infant cortex. A series of probes were developed and experiments were conducted to evaluate their sensitivity to patient motion and to compression of the probe. The probes have been used for a variety of

  2. Geometric-optical modeling of a conifer forest canopy

    NASA Technical Reports Server (NTRS)

    Li, X.; Strahler, A. H.

    1985-01-01

    A geometric-optical model of a conifer forest canopy was constructed to describe the variance of a remotely-sensed image of a forest stand. The model is driven by interpixel variance generated from three sources: (1) the number of crowns in the pixel; (2) the size of the individual crowns; and (3) the overlapping of crowns and shadows. The illumination of a tree and its shadow is described as a cone using parallel-ray geometry. The model can also be inverted to provide estimates of the size, shape and spacing of the trees using remotely-sensed imagery and a minimum of ground measurements. The results of field tests using 10-meter and 80-meter multispectral imagery of two test conifer stands in northeastern California are presented. It is shown that the model produces reasonable estimates for the geometric parameters of the stand and appears to be sufficiently robust for application to other geometric shapes corresponding to different types of vegetation.

  3. Light and optics conceptual evaluation findings from first year optometry students

    NASA Astrophysics Data System (ADS)

    Thapa, Damber; Lakshminarayanan, Vasudevan

    2014-07-01

    The Light and Optics Conceptual Evaluation (LOCE) was developed to examine conceptual understanding of basic geometric and physical optics for the Active Learning in Optics and Photonics program administered by UNESCO. This 50 item test (46 multiple choice, 4 ray-tracing short answer) was administered to entering students in the Optometry professional degree (OD) program. We wanted to determine how much of the physics/optics concepts from undergraduate physics courses (a pre-requisite for entry to the OD program) were retained. In addition, the test was administered after the first year students had taken a required course in geometric and visual optics as part of their first semester courses. The LOCE was completed by two consecutive classes to the program in 2010 (n=89) and 2011 (n=84). The tests were administered the first week of the term and the test was given without any prior notice. In addition, the test was administered to the class of 2010 students after they had completed the course in geometric and visual optics. The means of the test were 22.1 (SD=4.5; range: 12-35) and 21.3(SD=5.1; range: 11-35) for the two entering classes. There was no statistical significance between the two classes (t-test, p<0.05). Similarly there was no difference between the scores in terms of gender. The post-course test (administered during the first week of the second term) showed a statistically significant improvement (mean score went from 22.1 to 31.1, a 35% improvement). It should be noted that both groups of students performed worse in questions related to physical optics as well as lens imaging, while scoring best in questions related to refraction and reflection. These data should be taken into consideration when designing optics curricula for optometry (and other allied health programs such as opticianry or ophthalmology).

  4. Two models for evaluating landslide hazards

    USGS Publications Warehouse

    Davis, J.C.; Chung, C.-J.; Ohlmacher, G.C.

    2006-01-01

    Two alternative procedures for estimating landslide hazards were evaluated using data on topographic digital elevation models (DEMs) and bedrock lithologies in an area adjacent to the Missouri River in Atchison County, Kansas, USA. The two procedures are based on the likelihood ratio model but utilize different assumptions. The empirical likelihood ratio model is based on non-parametric empirical univariate frequency distribution functions under an assumption of conditional independence while the multivariate logistic discriminant model assumes that likelihood ratios can be expressed in terms of logistic functions. The relative hazards of occurrence of landslides were estimated by an empirical likelihood ratio model and by multivariate logistic discriminant analysis. Predictor variables consisted of grids containing topographic elevations, slope angles, and slope aspects calculated from a 30-m DEM. An integer grid of coded bedrock lithologies taken from digitized geologic maps was also used as a predictor variable. Both statistical models yield relative estimates in the form of the proportion of total map area predicted to already contain or to be the site of future landslides. The stabilities of estimates were checked by cross-validation of results from random subsamples, using each of the two procedures. Cell-by-cell comparisons of hazard maps made by the two models show that the two sets of estimates are virtually identical. This suggests that the empirical likelihood ratio and the logistic discriminant analysis models are robust with respect to the conditional independent assumption and the logistic function assumption, respectively, and that either model can be used successfully to evaluate landslide hazards. ?? 2006.

  5. Burst segmentation for void-filling scheduling and its performance evaluation in optical burst switching.

    PubMed

    Tan, Wei; Wang, Sheng; Li, Lemin

    2004-12-27

    As a promising solution for the next generation optical Internet, optical burst switching still has much to be improved, especially the design of core routers. This paper mainly focuses on channel scheduling algorithms of core routers and proposes a new practical scheduling algorithm. In the new algorithm, burst segmentation, one of the contention resolution schemes that are another major concern in core router design, is introduced. The proposed algorithm is analyzed theoretically and evaluated by computer simulations. The results show that the new algorithm, compared with existing traditional scheduling algorithms, can lower the packet loss probability and enhance the link utilization and network performance.

  6. A transparent black non-diffusing micelle gel for optical CT performance evaluation phantoms

    NASA Astrophysics Data System (ADS)

    Jordan, Kevin; Battista, Jerry

    2009-05-01

    Performance evaluation of optical CT scanners requires a set of phantoms with well known optical and geometric properties. Gels are often used and tinted with colouring agents but these suffer from wavelength dependencies, diffusion and degradation over time. In this paper we describe a new approach to creating suitable test phantoms using micelles. Adding surfactants to gelatin hydrogels allows materials insoluble in water to become suspended. Carbon black nanoparticles were dissolved into a transparent hydrogel consisting of 4% gelatine and 0.2% Triton X-100. The lack of macroscopic diffusion of the black particles was demonstrated by recording transmission images over 500 hours.

  7. Linear and Nonlinear Crosstalk Evaluation in DWDM Networks Using Optical Fourier Transformers

    NASA Astrophysics Data System (ADS)

    Llorente, R.; Clavero, R.; Ramos, F.; Marti, J.

    2005-12-01

    A novel DWDM channel monitoring technique based on the conversion from wavelength domain to time domain by performing a real-time optical Fourier transform over the whole DWDM system bandwidth is proposed and experimentally demonstrated. The use of chromatic dispersion-based optical Fourier transformers has been validated in the case of a spectrum comprising light from different uncorrelated sources. Linear and nonlinear crosstalks between the DWDM channels appear as amplitude noise at specific time positions. The correspondence of this amplitude noise with the crosstalk spectral distribution is evaluated theoretically and experimentally.

  8. Quantitative polarization and flow evaluation of choroid and sclera by multifunctional Jones matrix optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Sugiyama, S.; Hong, Y.-J.; Kasaragod, D.; Makita, S.; Miura, M.; Ikuno, Y.; Yasuno, Y.

    2016-03-01

    Quantitative evaluation of optical properties of choroid and sclera are performed by multifunctional optical coherence tomography. Five normal eyes, five glaucoma eyes and one choroidal atrophy eye are examined. The refractive error was found to be correlated with choroidal birefringence, polarization uniformity, and flow in addition to scleral birefringence among normal eyes. The significant differences were observed between the normal and the glaucoma eyes, as for choroidal polarization uniformity, flow and scleral birefringence. An automatic segmentation algorithm of retinal pigment epithelium and chorioscleral interface based on multifunctional signals is also presented.

  9. Microscopic model for all optical switching in ferromagnets

    NASA Astrophysics Data System (ADS)

    Cornelissen, T. D.; Córdoba, R.; Koopmans, B.

    2016-04-01

    The microscopic mechanism behind the all optical switching (AOS) in ferromagnets has triggered intense scientific debate. Here, the microscopic three-temperature model is utilized to describe AOS in a perpendicularly magnetized ferromagnetic Co/Pt system. We demonstrate that AOS in such a ferromagnet can be explained with the Inverse Faraday Effect (IFE). The influence of the strength and lifetime of the IFE induced field pulse on the switching process are investigated. We found that because of strong spin-orbit coupling, the minimal lifetime of the IFE needed to obtain switching is of the order of 0.1 ps, which is shorter than previously assumed. Moreover, spatial images of the domain pattern after AOS in Co/Pt, as well as their dependence on applying an opposite magnetic field, are qualitatively reproduced.

  10. Modeling the behavior of optical elements in radiation environments

    SciTech Connect

    Barlow, T.A.; Rhoades, C.E. Jr.; Merker, M.; Triplett, J.R.

    1986-11-03

    Calculation of heating caused by the deposition of x-rays in thin film optical elements is complicated because the mean free path of photo and autoionization electrons is comparable to the thin film thickness and thus the electron deposition cannot be considered local. This paper describes the modeling in a 1-D code of: (a) x-ray deposition and transport; (b) electron production, deposition and transport; and (c) thermal conduction and transport. X-ray transport is handled by multigroup discrete ordinates, electron transport is done by the method of characteristics, applied to the two term spherical harmonics expansion approximation (P1) to the Spencer-Lewis transport equation, and thermal transport is computed by a simple Richardson extrapolation of a backward Euler solution to the heat conduction equations. Results of a few test cases are presented. 8 refs., 26 figs., 2 tabs.

  11. Simulating the Wess-Zumino Supersymmetry Model in Optical Lattices

    SciTech Connect

    Yu Yue; Yang Kun

    2010-10-08

    We study a cold atom-molecule mixture in two-dimensional optical lattices. We show that, by fine-tuning the atomic and molecular interactions, the Wess-Zumino supersymmetry (SUSY) model in 2+1 dimensions emerges in the low-energy limit and can be simulated in such mixtures. At zero temperature, SUSY is not spontaneously broken, which implies identical relativistic dispersions of the atom and its superpartner, a bosonic diatom molecule. This defining signature of SUSY can be probed by single-particle spectroscopies. Thermal breaking of SUSY at a finite temperature is accompanied by a thermal Goldstone fermion, i.e., phonino excitation. This and other signatures of broken SUSY can also be probed experimentally.

  12. OPC model sampling evaluation and weakpoint "in-situ" improvement

    NASA Astrophysics Data System (ADS)

    Fu, Nan; Elshafie, Shady; Ning, Guoxiang; Roling, Stefan

    2016-10-01

    One of the major challenges of optical proximity correction (OPC) models is to maximize the coverage of real design features using sampling pattern. Normally, OPC model building is based on 1-D and 2-D test patterns with systematically changing pitches alignment with design rules. However, those features with different optical and geometric properties will generate weak-points where OPC simulation cannot precisely predict resist contours on wafer due to the nature of infinite IC designs and limited number of model test patterns. In this paper, optical property data of real design features were collected from full chips and classified to compare with the same kind of data from OPC test patterns. Therefore sample coverage could be visually mapped according to different optical properties. Design features, which are out of OPC capability, were distinguished by their optical properties and marked as weak-points. New patterns with similar optical properties would be added into model build site-list. Further, an alternative and more efficient method was created in this paper to improve the treatment of issue features and remove weak-points without rebuilding models. Since certain classification of optical properties will generate weak-points, an OPC-integrated repair algorithm was developed and implemented to scan full chip for optical properties, locate those features and then optimize OPC treatment or apply precise sizing on site. This is a named "in-situ" weak-point improvement flow which includes issue feature definition, allocation in full chip and real-time improvement.

  13. Fast Simulators for Satellite Cloud Optical Centroid Pressure Retrievals, 1. Evaluation of OMI Cloud Retrievals

    NASA Technical Reports Server (NTRS)

    Joiner, J.; Vasilkov, A. P.; Gupta, Pawan; Bhartia, P. K.; Veefkind, Pepijn; Sneep, Maarten; deHaan, Johan; Polonsky, Igor; Spurr, Robert

    2011-01-01

    We have developed a relatively simple scheme for simulating retrieved cloud optical centroid pressures (OCP) from satellite solar backscatter observations. We have compared simulator results with those from more detailed retrieval simulators that more fully account for the complex radiative transfer in a cloudy atmosphere. We used this fast simulator to conduct a comprehensive evaluation of cloud OCPs from the two OMI algorithms using collocated data from CloudSat and Aqua MODIS, a unique situation afforded by the A-train formation of satellites. We find that both OMI algorithms perform reasonably well and that the two algorithms agree better with each other than either does with the collocated CloudSat data. This indicates that patchy snow/ice, cloud 3D, and aerosol effects not simulated with the CloudSat data are affecting both algorithms similarly. We note that the collocation with CloudSat occurs mainly on the East side of OMI's swath. Therefore, we are not able to address cross-track biases in OMI cloud OCP retrievals. Our fast simulator may also be used to simulate cloud OCP from output generated by general circulation models (GCM) with appropriate account of cloud overlap. We have implemented such a scheme and plan to compare OMI data with GCM output in the near future.

  14. Modelling MEMS deformable mirrors for astronomical adaptive optics

    NASA Astrophysics Data System (ADS)

    Blain, Celia

    As of July 2012, 777 exoplanets have been discovered utilizing mainly indirect detection techniques. The direct imaging of exoplanets is the next goal for astronomers, because it will reveal the diversity of planets and planetary systems, and will give access to the exoplanet's chemical composition via spectroscopy. With this spectroscopic knowledge, astronomers will be able to know, if a planet is terrestrial and, possibly, even find evidence of life. With so much potential, this branch of astronomy has also captivated the general public attention. The direct imaging of exoplanets remains a challenging task, due to (i) the extremely high contrast between the parent star and the orbiting exoplanet and (ii) their small angular separation. For ground-based observatories, this task is made even more difficult, due to the presence of atmospheric turbulence. High Contrast Imaging (HCI) instruments have been designed to meet this challenge. HCI instruments are usually composed of a coronagraph coupled with the full onaxis corrective capability of an Extreme Adaptive Optics (ExAO) system. An efficient coronagraph separates the faint planet's light from the much brighter starlight, but the dynamic boiling speckles, created by the stellar image, make exoplanet detection impossible without the help of a wavefront correction device. The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system is a high performance HCI instrument developed at Subaru Telescope. The wavefront control system of SCExAO consists of three wavefront sensors (WFS) coupled with a 1024- actuator Micro-Electro-Mechanical-System (MEMS) deformable mirror (DM). MEMS DMs offer a large actuator density, allowing high count DMs to be deployed in small size beams. Therefore, MEMS DMs are an attractive technology for Adaptive Optics (AO) systems and are particularly well suited for HCI instruments employing ExAO technologies. SCExAO uses coherent light modulation in the focal plane introduced by the DM, for

  15. CTBT integrated verification system evaluation model supplement

    SciTech Connect

    EDENBURN,MICHAEL W.; BUNTING,MARCUS; PAYNE JR.,ARTHUR C.; TROST,LAWRENCE C.

    2000-03-02

    Sandia National Laboratories has developed a computer based model called IVSEM (Integrated Verification System Evaluation Model) to estimate the performance of a nuclear detonation monitoring system. The IVSEM project was initiated in June 1994, by Sandia's Monitoring Systems and Technology Center and has been funded by the U.S. Department of Energy's Office of Nonproliferation and National Security (DOE/NN). IVSEM is a simple, ''top-level,'' modeling tool which estimates the performance of a Comprehensive Nuclear Test Ban Treaty (CTBT) monitoring system and can help explore the impact of various sensor system concepts and technology advancements on CTBT monitoring. One of IVSEM's unique features is that it integrates results from the various CTBT sensor technologies (seismic, in sound, radionuclide, and hydroacoustic) and allows the user to investigate synergy among the technologies. Specifically, IVSEM estimates the detection effectiveness (probability of detection), location accuracy, and identification capability of the integrated system and of each technology subsystem individually. The model attempts to accurately estimate the monitoring system's performance at medium interfaces (air-land, air-water) and for some evasive testing methods such as seismic decoupling. The original IVSEM report, CTBT Integrated Verification System Evaluation Model, SAND97-25 18, described version 1.2 of IVSEM. This report describes the changes made to IVSEM version 1.2 and the addition of identification capability estimates that have been incorporated into IVSEM version 2.0.

  16. An Evaluation of Software Cost Estimating Models.

    DTIC Science & Technology

    1981-06-01

    EVALUATION OF SOFTWARE COST ESTIMATING Sep 73- Oct 79 MODELS. R14- --. R IOTNME 7. AUTHOR (.) * ce.4 **CT OR GRANT NUMBER(C.’ * ~ Robert Thibodeau K 1 F30602...review of the draft DCP begins, the program can be terminated with the approval of the highest command level which authorized it. Once DSARC review begins...concert with many other elements. Initially, we might speak of the navigation subsystem and its functions. Later, we would describe the alignment element

  17. Proton Spectroscopic Factors Deduced from Helium-3 Global Phenomenological and Microscopic Optical Model Potentials

    NASA Astrophysics Data System (ADS)

    Jenny, Lee; Pang, Dan-Yang; Han, Yin-Lu; B. Tsang, M.

    2014-09-01

    Global phenomenological GDP08 and microscopic helium-3 optical model potentials have been recently derived. We evaluate these two potential sets by comparing the elastic scattering data of 25 MeV 3He on 16O, 18O, 19F, 23Na, 24Mg, 25Mg, 26Mg, 27Al, 28Si, 30Si, 31P, 32S, 34S, 35Cl, 37Cl, and 39K isotopes. Using the deuteron angular distributions calculated with the distorted wave Born approximation model, we extract the ground-state proton spectroscopic factors from (3He, d) reactions on the same set of nuclei. The extracted proton spectroscopic factors are compared with the large-basis shell-model calculations.

  18. Ray tracing in the human eye: measurement and modeling of optical aberrations

    NASA Astrophysics Data System (ADS)

    Navarro, Rafael M.; Rodriguez, P.; Gonzalez, L.; Aporta, J.; Hdez-Matamoros, J. L.

    2004-10-01

    The rapid development of cataract and refractive surgery requires new methods to assess the optical quality of the eye. The optimized optical design of custom treatments to improve the optical performance of individual eyes requires, at least, to have the technology to (1) measure the geometry (anatomy) of the optics of the eye; (2) measure the optical performance (refractive state, aberrations, etc); (3) Build a custom optical and anatomical model of the individual eye to treat; (4) Optimal design of custom treatments. In this communication we will present the work carried out by our group to develop methods for measuring and modeling the optical performance of the eye. In particular, we will focus, first, on the Laser Ray Tracing method that we have developed to measure the optical aberrations of the eye, as a physical in vivo implementation of the classical numerical ray tracing used by optical designers; and second, on the development of custom optical models of the eye to perform that numerical ray tracing which predicts with a high fidelity experimental measurements. The methods developed have been applied to design both custom surgery and optical aids to improve optical performance.

  19. Bio-Optical Measurement and Modeling of the California Current and Polar Oceans. Chapter 13

    NASA Technical Reports Server (NTRS)

    Mitchell, B. Greg

    2001-01-01

    This Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) project contract supports in situ ocean optical observations in the California Current, Southern Ocean, Indian Ocean as well as merger of other in situ data sets we have collected on various global cruises supported by separate grants or contracts. The principal goals of our research are to validate standard or experimental products through detailed bio-optical and biogeochemical measurements, and to combine ocean optical observations with advanced radiative transfer modeling to contribute to satellite vicarious radiometric calibration and advanced algorithm development. In collaboration with major oceanographic ship-based observation programs funded by various agencies (CalCOFI, US JGOFS, NOAA AMLR, INDOEX and Japan/East Sea) our SIMBIOS effort has resulted in data from diverse bio-optical provinces. For these global deployments we generate a high-quality, methodologically consistent, data set encompassing a wide-range of oceanic conditions. Global data collected in recent years have been integrated with our on-going CalCOFI database and have been used to evaluate Sea-Viewing Wide Field-of-view Sensor (SeaWiFS) algorithms and to carry out validation studies. The combined database we have assembled now comprises more than 700 stations and includes observations for the clearest oligotrophic waters, highly eutrophic blooms, red-tides and coastal case two conditions. The data has been used to validate water-leaving radiance estimated with SeaWiFS as well as bio optical algorithms for chlorophyll pigments. The comprehensive data is utilized for development of experimental algorithms (e.g., high-low latitude pigment transition, phytoplankton absorption, and cDOM).

  20. The value of adding optics to ecosystem models: a case study

    NASA Astrophysics Data System (ADS)

    Fujii, M.; Boss, E.; Chai, F.

    2007-10-01

    Many ecosystem models have been developed to study the ocean's biogeochemical properties, but most of these models use simple formulations to describe light penetration and spectral quality. Here, an optical model is coupled with a previously published ecosystem model that explicitly represents two phytoplankton (picoplankton and diatoms) and two zooplankton functional groups, as well as multiple nutrients and detritus. Surface ocean color fields and subsurface light fields are calculated by coupling the ecosystem model with an optical model that relates biogeochemical standing stocks with inherent optical properties (absorption, scattering); this provides input to a commercially available radiative transfer model (Ecolight). We apply this bio-optical model to the equatorial Pacific upwelling region, and find the model to be capable of reproducing many measured optical properties and key biogeochemical processes in this region. Our model results suggest that non-algal particles largely contribute to the total scattering or attenuation (>50% at 660 nm) but have a much smaller contribution to particulate absorption (<20% at 440 nm), while picoplankton dominate the total phytoplankton absorption (>95% at 440 nm). These results are consistent with the field observations. In order to achieve such good agreement between data and model results, however, key model parameters, for which no field data are available, have to be constrained. Sensitivity analysis of the model results to optical parameters reveals a significant role played by colored dissolved organic matter through its influence on the quantity and quality of the ambient light. Coupling explicit optics to an ecosystem model provides advantages in generating: (1) a more accurate subsurface light-field, which is important for light sensitive biogeochemical processes such as photosynthesis and photo-oxidation, (2) additional constraints on model parameters that help to reduce uncertainties in ecosystem model

  1. Evaluation of a time-resolved stress detection method to determine tissue optical properties

    NASA Astrophysics Data System (ADS)

    Vijverberg, Helene; Thomsen, Sharon L.; Jacques, Steven L.; Oraevsky, Alexander A.

    1995-01-01

    A new method to determine optical properties of biological tissue, time-resolved stress detection (TRSD), was tested on albino rat skin, heated in vitro. The TRSD method is based on the detection of pressure waves that are generated by short laser pulses. The pressure waves carry information about the optical properties (absorption and effective attenuation coefficients) of the medium. The evaluation was done in a systematic way by comparing the results of the TRSD method with results obtained using an integrating sphere. Measurements for both methods were performed on the same skin samples to minimize biological variations. The TRSD method proved to be reasonably successful to determine optical properties of tissue for the used wavelength of 355 nm: (1) The effective attenuation coefficients of both methods agreed very well; (2) The TRSD method gave absorption coefficients of a factor 2 + 0.5 times higher than the integrating sphere method; and (3) The reduced scattering coefficients were sensitive to error.

  2. Capturing optically important constituents and properties in a marine biogeochemical and ecosystem model

    NASA Astrophysics Data System (ADS)

    Dutkiewicz, S.; Hickman, A. E.; Jahn, O.; Gregg, W. W.; Mouw, C. B.; Follows, M. J.

    2015-07-01

    We present a numerical model of the ocean that couples a three-stream radiative transfer component with a marine biogeochemical-ecosystem component in a dynamic three-dimensional physical framework. The radiative transfer component resolves the penetration of spectral irradiance as it is absorbed and scattered within the water column. We explicitly include the effect of several optically important water constituents (different phytoplankton functional types; detrital particles; and coloured dissolved organic matter, CDOM). The model is evaluated against in situ-observed and satellite-derived products. In particular we compare to concurrently measured biogeochemical, ecosystem, and optical data along a meridional transect of the Atlantic Ocean. The simulation captures the patterns and magnitudes of these data, and estimates surface upwelling irradiance analogous to that observed by ocean colour satellite instruments. We find that incorporating the different optically important constituents explicitly and including spectral irradiance was crucial to capture the variability in the depth of the subsurface chlorophyll a (Chl a) maximum. We conduct a series of sensitivity experiments to demonstrate, globally, the relative importance of each of the water constituents, as well as the crucial feedbacks between the light field, the relative fitness of phytoplankton types, and the biogeochemistry of the ocean. CDOM has proportionally more importance at attenuating light at short wavelengths and in more productive waters, phytoplankton absorption is relatively more important at the subsurface Chl a maximum, and water molecules have the greatest contribution when concentrations of other constituents are low, such as in the oligotrophic gyres. Scattering had less effect on attenuation, but since it is important for the amount and type of upwelling irradiance, it is crucial for setting sea surface reflectance. Strikingly, sensitivity experiments in which absorption by any of the

  3. Evaluation of Anterior Chamber Volume in Cataract Patients with Swept-Source Optical Coherence Tomography

    PubMed Central

    He, Wenwen; Zhu, Xiangjia; Wolff, Don; Sun, Xinghuai

    2016-01-01

    Purpose. To evaluate the anterior chamber volume in cataract patients with Swept-Source Optical Coherence Tomography (SS-OCT) and its influencing factors. Methods. Anterior chamber volume of 92 cataract patients was evaluated with SS-OCT in this cross-sectional study. Univariate analyses and multiple linear regression were used to investigate gender, age, operated eye, posterior vitreous detachment, lens opacity grading, and axial length (AXL) related variables capable of influencing the ACV. Results. The average ACV was 139.80 ± 38.21 mm3 (range 59.41 to 254.09 mm3). The average ACV was significantly larger in male patients than in female patients (P = 0.001). ACV was negatively correlated with age and LOCS III cortical (C) grading of the lens (Pearson's correlation analysis, r = −0.443, P < 0.001, and Spearman's correlation analysis, ρ = −0.450, P < 0.001). ACV was also increased with AXL (Pearson's correlation analysis, r = 0.552, P < 0.001). Multiple linear regression showed that, with all of the covariates entered into the model, gender (P = 0.002), age (P = 0.015), LOCS III C grade (P = 0.043), and AXL (P = 0.001) were still associated with ACV (F = 10.252  P < 0.001  R2 = 0.498). Conclusion. With SS-OCT, we found that, in healthy cataract patients, ACV varied significantly among different subjects. Influencing factors that contribute to reduced ACV were female gender, increased age, LOCS III C grade, and shorter AXL. PMID:27688910

  4. Evaluation of Anterior Chamber Volume in Cataract Patients with Swept-Source Optical Coherence Tomography.

    PubMed

    He, Wenwen; Zhu, Xiangjia; Wolff, Don; Zhao, Zhennan; Sun, Xinghuai; Lu, Yi

    2016-01-01

    Purpose. To evaluate the anterior chamber volume in cataract patients with Swept-Source Optical Coherence Tomography (SS-OCT) and its influencing factors. Methods. Anterior chamber volume of 92 cataract patients was evaluated with SS-OCT in this cross-sectional study. Univariate analyses and multiple linear regression were used to investigate gender, age, operated eye, posterior vitreous detachment, lens opacity grading, and axial length (AXL) related variables capable of influencing the ACV. Results. The average ACV was 139.80 ± 38.21 mm(3) (range 59.41 to 254.09 mm(3)). The average ACV was significantly larger in male patients than in female patients (P = 0.001). ACV was negatively correlated with age and LOCS III cortical (C) grading of the lens (Pearson's correlation analysis, r = -0.443, P < 0.001, and Spearman's correlation analysis, ρ = -0.450, P < 0.001). ACV was also increased with AXL (Pearson's correlation analysis, r = 0.552, P < 0.001). Multiple linear regression showed that, with all of the covariates entered into the model, gender (P = 0.002), age (P = 0.015), LOCS III C grade (P = 0.043), and AXL (P = 0.001) were still associated with ACV (F = 10.252  P < 0.001  R (2) = 0.498). Conclusion. With SS-OCT, we found that, in healthy cataract patients, ACV varied significantly among different subjects. Influencing factors that contribute to reduced ACV were female gender, increased age, LOCS III C grade, and shorter AXL.

  5. Integrated Modeling Activities for the James Webb Space Telescope (JWST): Structural-Thermal-Optical Analysis

    NASA Technical Reports Server (NTRS)

    Johnston, John D.; Parrish, Keith; Howard, Joseph M.; Mosier, Gary E.; McGinnis, Mark; Bluth, Marcel; Kim, Kevin; Ha, Hong Q.

    2004-01-01

    This is a continuation of a series of papers on modeling activities for JWST. The structural-thermal- optical, often referred to as "STOP", analysis process is used to predict the effect of thermal distortion on optical performance. The benchmark STOP analysis for JWST assesses the effect of an observatory slew on wavefront error. The paper begins an overview of multi-disciplinary engineering analysis, or integrated modeling, which is a critical element of the JWST mission. The STOP analysis process is then described. This process consists of the following steps: thermal analysis, structural analysis, and optical analysis. Temperatures predicted using geometric and thermal math models are mapped to the structural finite element model in order to predict thermally-induced deformations. Motions and deformations at optical surfaces are input to optical models and optical performance is predicted using either an optical ray trace or WFE estimation techniques based on prior ray traces or first order optics. Following the discussion of the analysis process, results based on models representing the design at the time of the System Requirements Review. In addition to baseline performance predictions, sensitivity studies are performed to assess modeling uncertainties. Of particular interest is the sensitivity of optical performance to uncertainties in temperature predictions and variations in metal properties. The paper concludes with a discussion of modeling uncertainty as it pertains to STOP analysis.

  6. Evaluation of Community Land Model Hydrologic Predictions

    NASA Astrophysics Data System (ADS)

    Li, K. Y.; Lettenmaier, D. P.; Bohn, T.; Delire, C.

    2005-12-01

    Confidence in representation and parameterization of land surface processes in coupled land-atmosphere models is strongly dependent on a diversity of opportunities for model testing, since such coupled models are usually intended for application in a wide range of conditions (regional models) or globally. Land surface models have been increasing in complexity over the past decade, which has increased the demands on data sets appropriate for model testing and evaluation. In this study, we compare the performance of two commonly used land surface schemes - the Variable Infiltration Capacity (VIC) and Community Land Model (CLM) with respect to their ability to reproduce observed water and energy fluxes in off-line tests for two large river basins with contrasting hydroclimatic conditions spanning the range from temperate continental to arctic, and for five point (column flux) sites spanning the range from tropical to arctic. The two large river basins are the Arkansas-Red in U.S. southern Great Plains, and the Torne-Kalix in northern Scandinavia. The column flux evaluations are for a tropical forest site at Reserva Jaru (ABRACOS) in Brazil, a prairie site (FIFE) near Manhattan, Kansas in the central U.S., a soybean site at Caumont (HAPEX-Monbilhy) in France, a meadow site at Cabauw in the Netherlands, and a small grassland catchment at Valday, Russia. The results indicate that VIC can reasonably well capture the land surface biophysical processes, while CLM is somewhat less successful. We suggest changes to the CLM parameterizations that would improve its general performance with respect to its representation of land surface hydrologic processes.

  7. The GRAVITY metrology system: modeling a metrology in optical fibers

    NASA Astrophysics Data System (ADS)

    Blind, N.; Huber, Heinrich; Eisenhauer, F.; Weber, J.; Gillessen, S.; Lippa, M.; Burtscher, L.; Hans, O.; Haug, M.; Haussmann, F.; Huber, S.; Janssen, A.; Kellner, S.; Kok, Y.; Ott, T.; Pfuhl, O.; Sturm, E.; Wieprecht, E.; Amorim, A.; Brandner, W.; Perrin, G.; Perraut, K.; Straubmeier, C.

    2014-07-01

    GRAVITY is the second generation VLT Interferometer (VLTI) instrument for high-precision narrow-angle astrometry and phase-referenced interferometric imaging. The laser metrology system of GRAVITY is at the heart of its astrometric mode, which must measure the distance of 2 stars with a precision of 10 micro-arcseconds. This means the metrology has to measure the optical path difference between the two beam combiners of GRAVITY to a level of 5 nm. The metrology design presents some non-common paths that have consequently to be stable at a level of 1 nm. Otherwise they would impact the performance of GRAVITY. The various tests we made in the past on the prototype give us hints on the components responsible for this error, and on their respective contribution to the total error. It is however difficult to assess their exact origin from only OPD measurements, and therefore, to propose a solution to this problem. In this paper, we present the results of a semi-empirical modeling of the fibered metrology system, relying on theoretical basis, as well as on characterisations of key components. The modeling of the metrology system regarding various effects, e.g., temperature, waveguide heating or mechanical stress, will help us to understand how the metrology behave. The goals of this modeling are to 1) model the test set-ups and reproduce the measurements (as a validation of the modeling), 2) determine the origin of the non-common path errors, and 3) propose modifications to the current metrology design to reach the required 1nm stability.

  8. Reliable clarity automatic-evaluation method for optical remote sensing images

    NASA Astrophysics Data System (ADS)

    Qin, Bangyong; Shang, Ren; Li, Shengyang; Hei, Baoqin; Liu, Zhiwen

    2015-10-01

    Image clarity, which reflects the sharpness degree at the edge of objects in images, is an important quality evaluate index for optical remote sensing images. Scholars at home and abroad have done a lot of work on estimation of image clarity. At present, common clarity-estimation methods for digital images mainly include frequency-domain function methods, statistical parametric methods, gradient function methods and edge acutance methods. Frequency-domain function method is an accurate clarity-measure approach. However, its calculation process is complicate and cannot be carried out automatically. Statistical parametric methods and gradient function methods are both sensitive to clarity of images, while their results are easy to be affected by the complex degree of images. Edge acutance method is an effective approach for clarity estimate, while it needs picking out the edges manually. Due to the limits in accuracy, consistent or automation, these existing methods are not applicable to quality evaluation of optical remote sensing images. In this article, a new clarity-evaluation method, which is based on the principle of edge acutance algorithm, is proposed. In the new method, edge detection algorithm and gradient search algorithm are adopted to automatically search the object edges in images. Moreover, The calculation algorithm for edge sharpness has been improved. The new method has been tested with several groups of optical remote sensing images. Compared with the existing automatic evaluation methods, the new method perform better both in accuracy and consistency. Thus, the new method is an effective clarity evaluation method for optical remote sensing images.

  9. Optical fluorescence spectroscopy to detect hepatic necrosis after normothermic ischemia: animal model

    NASA Astrophysics Data System (ADS)

    Romano, Renan A.; Vollet-Filho, Jose D.; Pratavieira, Sebastião.; Fernandez, Jorge L.; Kurachi, Cristina; Bagnato, Vanderlei S.; Castro-e-Silva, Orlando; Sankarankutty, Ajith K.

    2015-06-01

    Liver transplantation is a well-established treatment for liver failure. However, the success of the transplantation procedure depends on liver graft conditions. The tissue function evaluation during the several transplantation stages is relevant, in particular during the organ harvesting, when a decision is made concerning the viability of the graft. Optical fluorescence spectroscopy is a good option because it is a noninvasive and fast technique. A partial normothermic hepatic ischemia was performed in rat livers, with a vascular occlusion of both median and left lateral lobes, allowing circulation only for the right lateral lobe and the caudate lobe. Fluorescence spectra under excitation at 532 nm (doubled frequency Nd:YAG laser) were collected using a portable spectrometer (USB2000, Ocean Optics, USA). The fluorescence emission was collected before vascular occlusion, after ischemia, and 24 hours after reperfusion. A morphometric histology analysis was performed as the gold standard evaluation - liver samples were analyzed, and the percentage of necrotic tissue was obtained. The results showed that changes in the fluorescence emission after ischemia can be correlated with the amount of necrosis evaluated by a morphometric analysis, the Pearson correlation coefficient of the generated model was 0.90 and the root mean square error was around 20%. In this context, the laser-induced fluorescence spectroscopy technique after normothermic ischemia showed to be a fast and efficient method to differentiate ischemic injury from viable tissues.

  10. Generalized Ocean Color Inversion Model for Retrieving Marine Inherent Optical Properties

    NASA Technical Reports Server (NTRS)

    Werdell, P. Jeremy; Franz, Bryan A.; Bailey, Sean W.; Feldman, Gene C.; Boss, Emmanuel; Brando, Vittorio E.; Dowell, Mark; Hirata, Takafumi; Lavender, Samantha J.; Lee, ZhongPing; Loisel, Hubert; Maritorena, Stephane; Melin, Frederic; Moore, Timothy S.; Smyth, TImothy J.; Antoine, David; Devred, Emmanuel; Fantond'Andon, Odile Hembise; Mangin, Antoine

    2013-01-01

    Ocean color measured from satellites provides daily, global estimates of marine inherent optical properties (IOPs). Semi-analytical algorithms (SAAs) provide one mechanism for inverting the color of the water observed by the satellite into IOPs. While numerous SAAs exist, most are similarly constructed and few are appropriately parameterized for all water masses for all seasons. To initiate community-wide discussion of these limitations, NASA organized two workshops that deconstructed SAAs to identify similarities and uniqueness and to progress toward consensus on a unified SAA. This effort resulted in the development of the generalized IOP (GIOP) model software that allows for the construction of different SAAs at runtime by selection from an assortment of model parameterizations. As such, GIOP permits isolation and evaluation of specific modeling assumptions, construction of SAAs, development of regionally tuned SAAs, and execution of ensemble inversion modeling. Working groups associated with the workshops proposed a preliminary default configuration for GIOP (GIOP-DC), with alternative model parameterizations and features defined for subsequent evaluation. In this paper, we: (1) describe the theoretical basis of GIOP; (2) present GIOP-DC and verify its comparable performance to other popular SAAs using both in situ and synthetic data sets; and, (3) quantify the sensitivities of their output to their parameterization. We use the latter to develop a hierarchical sensitivity of SAAs to various model parameterizations, to identify components of SAAs that merit focus in future research, and to provide material for discussion on algorithm uncertainties and future ensemble applications.

  11. Optical absorbance measurements and photoacoustic evaluation of freeze-thawed polyvinyl-alcohol vessel phantoms

    NASA Astrophysics Data System (ADS)

    Arabul, M. U.; Heres, H. M.; Rutten, M.; van de Vosse, F.; Lopata, R.

    2015-03-01

    Multispectral photoacoustic (MPA) imaging is a promising tool for the diagnosis of atherosclerotic carotids. Excitation of different constituents of a plaque with different wavelengths of the light may provide morphological information to evaluate plaque vulnerability. Preclinical validation of in vivo photoacoustic (PA) imaging requires a comprehensive phantom study. In this study, the design of optically realistic vessel phantoms for photoacoustics was examined by characterizing their optical properties for different dye concentrations, and comparing those to PA measurements. Four different concentrations of Indian ink and molecular dye were added to a 15 wt% PVA and 1 wt% orgasol mixture. Next, the homogeneously mixed gels were subjected to five freeze - thaw cycles to increase the stiffness of vessel phantoms (rinner = 2:5mm, router = 4mm). For each cycle, the optical absorbance was measured between 400 nm 990 nm using a plate reader. Additionally, photoacoustic responses of each vessel phantom at 808 nm were tested with a novel, hand-held, integrated PA probe. Measurements show that the PA signal intensity increases with the optical absorber concentration (0.3 to 0.9) in close agreement with the absorbance measurements. The freeze - thaw process has no significant effect on PA intensity. However, the total attenuation of optical energy increases after each freeze-thaw cycle, which is primarily due to the increase in the scattering coefficient. In future work, the complexity of these phantoms will be increased to examine the feasibility of distinguishing different constituents with MPA imaging.

  12. Training Module on the Evaluation of Best Modeling Practices

    EPA Pesticide Factsheets

    Building upon the fundamental concepts outlined in previous modules, the objectives of this module are to explore the topic of model evaluation and identify the 'best modeling practices' and strategies for the Evaluation Stage of the model life-cycle.

  13. Scalar time domain modeling and coupling of second harmonic generation process in GaAs discontinuous optical waveguide.

    PubMed

    Massaro, A; Tasco, V; Todaro, M T; Cingolani, R; De Vittorio, M; Passaseo, A

    2008-09-15

    We present in this work the scalar potential formulation of second harmonic generation process in chi((2)) nonlinear analysis. This approach is intrinsically well suited to the applications of the concept of circuit analysis and synthesis to nonlinear optical problems, and represents a novel alternative method in the analysis of nonlinear optical waveguide, by providing a good convergent numerical solution. The time domain modeling is applied to nonlinear GaAs asymmetrical waveguide with dielectric discontinuities in the hypothesis of quasi phase matching condition in order to evaluate the efficiency conversion of the second harmonic signal. The accuracy of the modeling is validated by the good agreement with the published experimental results. The effective dielectric constant method allows to extend the analysis also to 3D optical waveguides.

  14. Identification of muscle necrosis in the mdx mouse model of Duchenne muscular dystrophy using three-dimensional optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Klyen, Blake R.; Shavlakadze, Thea; Radley-Crabb, Hannah G.; Grounds, Miranda D.; Sampson, David D.

    2011-07-01

    Three-dimensional optical coherence tomography (3D-OCT) was used to image the structure and pathology of skeletal muscle tissue from the treadmill-exercised mdx mouse model of human Duchenne muscular dystrophy. Optical coherence tomography (OCT) images of excised muscle samples were compared with co-registered hematoxylin and eosin-stained and Evans blue dye fluorescence histology. We show, for the first time, structural 3D-OCT images of skeletal muscle dystropathology well correlated with co-located histology. OCT could identify morphological features of interest and necrotic lesions within the muscle tissue samples based on intrinsic optical contrast. These findings demonstrate the utility of 3D-OCT for the evaluation of small-animal skeletal muscle morphology and pathology, particularly for studies of mouse models of muscular dystrophy.

  15. User's appraisal of yield model evaluation criteria

    NASA Technical Reports Server (NTRS)

    Warren, F. B. (Principal Investigator)

    1982-01-01

    The five major potential USDA users of AgRISTAR crop yield forecast models rated the Yield Model Development (YMD) project Test and Evaluation Criteria by the importance placed on them. These users were agreed that the "TIMELINES" and "RELIABILITY" of the forecast yields would be of major importance in determining if a proposed yield model was worthy of adoption. Although there was considerable difference of opinion as to the relative importance of the other criteria, "COST", "OBJECTIVITY", "ADEQUACY", AND "MEASURES OF ACCURACY" generally were felt to be more important that "SIMPLICITY" and "CONSISTENCY WITH SCIENTIFIC KNOWLEDGE". However, some of the comments which accompanied the ratings did indicate that several of the definitions and descriptions of the criteria were confusing.

  16. Evaluation of a mallard productivity model

    USGS Publications Warehouse

    Johnson, D.H.; Cowardin, L.M.; Sparling, D.W.; Verner, J.; Morrison, L.M.; Ralph, C.J.

    1986-01-01

    A stochastic model of mallard (Anas platyrhynchos) productivity has been developed over a 10-year period and successfully applied to several management questions. Here we review the model and describe some recent uses and improvements that increase its realism and applicability, including naturally occurring changes in wetland habitat, catastrophic weather events, and the migrational homing of mallards. The amount of wetland habitat influenced productivity primarily by affecting the renesting rate. Late snowstorms severely reduced productivity, whereas the loss of nests due to flooding was largely compensated for by increased renesting, often in habitats where hatching rates were better. Migrational homing was shown to be an important phenomenon in population modeling and should be considered when evaluating management plans.

  17. In-flight evaluation of an Optical Head Motion Tracker II

    NASA Astrophysics Data System (ADS)

    Tawada, Kazuho; Omura, Koji

    2010-04-01

    We resented a new approach for Optical HMT (Head Motion Tracker) past years (Proc. SPIE 6955, 69550A, 2008, Proc. SPIE 7326, 732607/73260L, 2009) [1]-[3]. In existing Magnetic HMT, it is inevitable to conduct pre-mapping in order to obtain sufficient accuracy because of magnetic field's distortion caused by metallic material around HMT, such as cockpit and helmet. Optical HMT is commonly known as mapping-free tracker; however, it has some disadvantages on accuracy, stability against sunlight conditions, in terms of comparison with Magnetic HMT. We had succeeded to develop new Optical HMT, which can overcome particular disadvantages by integration with two area cameras, LED markers, image processing techniques and inertial sensors with simple algorithm in laboratory level environment (2007). We have also reported some experimental results conducted in flight test, which proves good accuracy even in the sunlight condition (2008). Shimadzu Corp. and JAXA (Japan Aerospace Exploration Agency) are conducting joint research named SAVERH (Situation Awareness and Visual Enhancer for Rescue Helicopter) [2]-[3] that aims at inventing method of presenting suitable information to the pilot to support search and rescue missions by helicopters. The Optical HMT has been evaluated through a series of flight evaluation in SAVERH and demonstrated the operation concept. Through 16 flights including night flights, the potential capability of the system was demonstrated and issues for further improvement were identified.

  18. Novel approach for simultaneous wireless transmission and evaluation of optical sensors

    NASA Astrophysics Data System (ADS)

    Neumann, Niels; Schuster, Tobias; Plettemeier, Dirk

    2014-11-01

    Optical sensors can be used to measure various quantities such as pressure, strain, temperature, refractive index, pH value and biochemical reactions. The interrogation of the sensor can be performed spectrally or using a simple power measurement. However, the evaluation of the sensor signal and the subsequent radio transmission of the results is complicated and costly. A sophisticated system setup comprising a huge number of electrooptical components as well as a complete radio module is required. This is not only expensive and unreliable but also impractical within harsh environment, in limited space and in inaccessible areas. Radio-over-Fiber (RoF) technology implies signals modulated on an electrical carrier being transmitted over fiber by using optical carriers. Combining RoF techniques and optical sensors, a new class of measurement devices readable by a radio interfaces is introduced in this paper. These sensors use a modulated input signal generated by a RoF transmitter that { after being influenced by the optical sensor-is directly converted into a radio signal and transmitted. This approach enables remote read-outs of the sensor by means of wireless evaluation. Thus, costly, voluminous, power hungry and sensitive equipment in the vicinity of the measurement location is avoided. The equipment can be concentrated in a central location supporting existing radio transmission schemes (e.g. WiFi).

  19. Model for coherence transfer in a backward optical parametric oscillator

    NASA Astrophysics Data System (ADS)

    Montes, Carlos; Aschieri, Pierre; Picozzi, Antonio

    2011-09-01

    The mirrorless backward optical parametric oscillator (BOPO), where the signal and idler waves are propagating in opposite directions, will establish a distributed feedback mechanism and thus optical parametric oscillation without the need to apply mirrors or external feedback to the cavity. It has been recently demonstrated experimentally by exploiting the periodic poling technique in second-order nonlinear crystals, that the sub-micrometer structured medium achieves an efficient quasi-phase-matching of the three wave interaction in the backward configuration. A remarkable property of such BOPO is the high degree of coherence of the backward wave component, whose spectrum may be several order of magnitudes narrower than that of the pump, due to the convectioninduced phase-locking mechanism. Experimentally and numerically proved the transfer of coherent phase modulations from the pump wave to the parametrically down-converted waves, we show here that this is also possible for a broad bandwidth spectrally incoherent pump. In order to accurately describe the nonlinear counter-propagation dynamics of the three dispersive waves, we have developed for the first time to our knowledge a new numerical scheme which combines the method of the trajectories usually employed to solve the three-wave interaction and the intraband group velocity dispersion effect is performed in the spectral domain with the help of the Fast Fourier Transform (FFT) technique. The model accurately conserves the number of photons and the Manley-Rowe invariants. This allowed us to predict various configurations of MOPOs in which, thanks to the convection-induced phase-locking mechanism, a highly coherent backward wave is spontaneously generated from a highly incoherent pump wave.

  20. Design-oriented analytic model of phase and frequency modulated optical links

    NASA Astrophysics Data System (ADS)

    Monsurrò, Pietro; Saitto, Antonio; Tommasino, Pasquale; Trifiletti, Alessandro; Vannucci, Antonello; Cimmino, Rosario F.

    2016-07-01

    An analytic design-oriented model of phase and frequency modulated microwave optical links has been developed. The models are suitable for design of broadband high dynamic range optical links for antenna remoting and optical beamforming, where noise and linearity of the subsystems are a concern Digital filter design techniques have been applied to the design of optical filters working as frequency discriminator, that are the bottleneck in terms of linearity for these systems. The models of frequency modulated, phase modulated, and coherent I/Q link have been used to compare performance of the different architectures in terms of linearity and SFDR.