Automatic switching matrix

DOEpatents

Schlecht, Martin F.; Kassakian, John G.; Caloggero, Anthony J.; Rhodes, Bruce; Otten, David; Rasmussen, Neil

1982-01-01

An automatic switching matrix that includes an apertured matrix board containing a matrix of wires that can be interconnected at each aperture. Each aperture has associated therewith a conductive pin which, when fully inserted into the associated aperture, effects electrical connection between the wires within that particular aperture. Means is provided for automatically inserting the pins in a determined pattern and for removing all the pins to permit other interconnecting patterns.

The impact of in-situ stress and outcrop-based fracture geometry on hydraulic aperture and upscaled permeability in fractured reservoirs

NASA Astrophysics Data System (ADS)

Bisdom, Kevin; Bertotti, Giovanni; Nick, Hamidreza M.

2016-10-01

Aperture has a controlling impact on porosity and permeability and is a source of uncertainty in modeling of naturally fractured reservoirs. This uncertainty results from difficulties in accurately quantifying aperture in the subsurface and from a limited fundamental understanding of the mechanical and diagenetic processes that control aperture. In the absence of cement bridges and high pore pressure, fractures in the subsurface are generally considered to be closed. However, experimental work, outcrop analyses and subsurface data show that some fractures remain open, and that aperture varies even along a single fracture. However, most fracture flow models consider constant apertures for fractures. We create a stress-dependent heterogeneous aperture by combining Finite Element modeling of discrete fracture networks with an empirical aperture model. Using a modeling approach that considers fractures explicitly, we quantify equivalent permeability, i.e. combined matrix and stress-dependent fracture flow. Fracture networks extracted from a large outcropping pavement form the basis of these models. The results show that the angle between fracture strike and σ1 has a controlling impact on aperture and permeability, where hydraulic opening is maximum for an angle of 15°. At this angle, the fracture experiences a minor amount of shear displacement that allows the fracture to remain open even when fluid pressure is lower than the local normal stress. Averaging the heterogeneous aperture to scale up permeability probably results in an underestimation of flow, indicating the need to incorporate full aperture distributions rather than simplified aperture models in reservoir-scale flow models.

Direct aperture optimization: a turnkey solution for step-and-shoot IMRT.

PubMed

Shepard, D M; Earl, M A; Li, X A; Naqvi, S; Yu, C

2002-06-01

IMRT treatment plans for step-and-shoot delivery have traditionally been produced through the optimization of intensity distributions (or maps) for each beam angle. The optimization step is followed by the application of a leaf-sequencing algorithm that translates each intensity map into a set of deliverable aperture shapes. In this article, we introduce an automated planning system in which we bypass the traditional intensity optimization, and instead directly optimize the shapes and the weights of the apertures. We call this approach "direct aperture optimization." This technique allows the user to specify the maximum number of apertures per beam direction, and hence provides significant control over the complexity of the treatment delivery. This is possible because the machine dependent delivery constraints imposed by the MLC are enforced within the aperture optimization algorithm rather than in a separate leaf-sequencing step. The leaf settings and the aperture intensities are optimized simultaneously using a simulated annealing algorithm. We have tested direct aperture optimization on a variety of patient cases using the EGS4/BEAM Monte Carlo package for our dose calculation engine. The results demonstrate that direct aperture optimization can produce highly conformal step-and-shoot treatment plans using only three to five apertures per beam direction. As compared with traditional optimization strategies, our studies demonstrate that direct aperture optimization can result in a significant reduction in both the number of beam segments and the number of monitor units. Direct aperture optimization therefore produces highly efficient treatment deliveries that maintain the full dosimetric benefits of IMRT.

Multi-aperture digital coherent combining for free-space optical communication receivers.

PubMed

Geisler, David J; Yarnall, Timothy M; Stevens, Mark L; Schieler, Curt M; Robinson, Bryan S; Hamilton, Scott A

2016-06-13

Space-to-ground optical communication systems can benefit from reducing the size, weight, and power profiles of space terminals. One way of reducing the required power-aperture product on a space platform is to implement effective, but costly, single-aperture ground terminals with large collection areas. In contrast, we present a ground terminal receiver architecture in which many small less-expensive apertures are efficiently combined to create a large effective aperture while maintaining excellent receiver sensitivity. This is accomplished via coherent detection behind each aperture followed by digitization. The digitized signals are then combined in a digital signal processing chain. Experimental results demonstrate lossless coherent combining of four lasercom signals, at power levels below 0.1 photons/bit/aperture.

Quantitative model of transport-aperture coordination during reach-to-grasp movements.

PubMed

Rand, Miya K; Shimansky, Y P; Hossain, Abul B M I; Stelmach, George E

2008-06-01

It has been found in our previous studies that the initiation of aperture closure during reach-to-grasp movements occurs when the hand distance to target crosses a threshold that is a function of peak aperture amplitude, hand velocity, and hand acceleration. Thus, a stable relationship between those four movement parameters is observed at the moment of aperture closure initiation. Based on the concept of optimal control of movements (Naslin 1969) and its application for reach-to-grasp movement regulation (Hoff and Arbib 1993), it was hypothesized that the mathematical equation expressing that relationship can be generalized to describe coordination between hand transport and finger aperture during the entire reach-to-grasp movement by adding aperture velocity and acceleration to the above four movement parameters. The present study examines whether this hypothesis is supported by the data obtained in experiments in which young adults performed reach-to-grasp movements in eight combinations of two reach-amplitude conditions and four movement-speed conditions. It was found that linear approximation of the mathematical model described the relationship among the six movement parameters for the entire aperture-closure phase with very high precision for each condition, thus supporting the hypothesis for that phase. Testing whether one mathematical model could approximate the data across all the experimental conditions revealed that it was possible to achieve the same high level of data-fitting precision only by including in the model two additional, condition-encoding parameters and using a nonlinear, artificial neural network-based approximator with two hidden layers comprising three and two neurons, respectively. This result indicates that transport-aperture coordination, as a specific relationship between the parameters of hand transport and finger aperture, significantly depends on the condition-encoding variables. The data from the aperture-opening phase also fit a linear model, whose coefficients were substantially different from those identified for the aperture-closure phase. This result supports the above hypothesis for the aperture-opening phase, and consequently, for the entire reach-to-grasp movement. However, the fitting precision was considerably lower than that for the aperture-closure phase, indicating significant trial-to-trial variability of transport-aperture coordination during the aperture-opening phase. Implications for understanding the neural mechanisms employed by the CNS for controlling reach-to-grasp movements and utilization of the mathematical model of transport-aperture coordination for data analysis are discussed.

Formation and function of a new pollen aperture pattern in angiosperms: The proximal sulcus of Tillandsia leiboldiana (Bromeliaceae).

PubMed

Albert, Béatrice; Matamoro-Vidal, Alexis; Raquin, Christian; Nadot, Sophie

2010-02-01

Pollen grains are generally surrounded by an extremely resistant wall interrupted in places by apertures that play a key role in reproduction; pollen tube growth is initiated at these sites. The shift from a proximal to distal aperture location is a striking innovation in seed plant reproduction. Reversals to proximal aperture position have only very rarely been described in angiosperms. The genus Tillandsia belongs to the Bromeliaceae family, and its aperture pattern has been described as distal monosulcate, the most widespread aperture patterns recorded in monocots and basal angiosperms. Here we report developmental and functional elements to demonstrate that the sulcate aperture in Tillandsia leiboldiana is not distal as previously described but proximal. Postmeitotic tetrad observation indicates unambiguously the proximal position of the sulcus, and in vitro germination of pollen grains confirms that the aperture is functional. This is the first report of a sulcate proximal aperture with proximal germination. The observation of microsporogenesis reveals specific features in the patterns of callose thickenings in postmeiotic tetrads.

Energy acceptance and on momentum aperture optimization for the Sirius project

NASA Astrophysics Data System (ADS)

Dester, P. S.; Sá, F. H.; Liu, L.

2017-07-01

A fast objective function to calculate Touschek lifetime and on momentum aperture is essential to explore the vast search space of strength of quadrupole and sextupole families in Sirius. Touschek lifetime is estimated by using the energy aperture (dynamic and physical), RF system parameters and driving terms. Non-linear induced betatron oscillations are considered to determine the energy aperture. On momentum aperture is estimated by using a chaos indicator and resonance crossing considerations. Touschek lifetime and on momentum aperture constitute the objective function, which was used in a multi-objective genetic algorithm to perform an optimization for Sirius.

A Ploidy-Sensitive Mechanism Regulates Aperture Formation on the Arabidopsis Pollen Surface and Guides Localization of the Aperture Factor INP1

PubMed Central

Reeder, Sarah H.; Lee, Byung Ha; Fox, Ronald; Dobritsa, Anna A.

2016-01-01

Pollen presents a powerful model for studying mechanisms of precise formation and deposition of extracellular structures. Deposition of the pollen wall exine leads to the generation of species-specific patterns on pollen surface. In most species, exine does not develop uniformly across the pollen surface, resulting in the formation of apertures–openings in the exine that are species-specific in number, morphology and location. A long time ago, it was proposed that number and positions of apertures might be determined by the geometry of tetrads of microspores–the precursors of pollen grains arising via meiotic cytokinesis, and by the number of last-contact points between sister microspores. We have tested this model by characterizing Arabidopsis mutants with ectopic apertures and/or abnormal geometry of meiotic products. Here we demonstrate that contact points per se do not act as aperture number determinants and that a correct geometric conformation of a tetrad is neither necessary nor sufficient to generate a correct number of apertures. A mechanism sensitive to pollen ploidy, however, is very important for aperture number and positions and for guiding the aperture factor INP1 to future aperture sites. In the mutants with ectopic apertures, the number and positions of INP1 localization sites change depending on ploidy or ploidy-related cell size and not on INP1 levels, suggesting that sites for aperture formation are specified before INP1 is brought to them. PMID:27177036

A geometrical optics approach for modeling aperture averaging in free space optical communication applications

NASA Astrophysics Data System (ADS)

Yuksel, Heba; Davis, Christopher C.

2006-09-01

Intensity fluctuations at the receiver in free space optical (FSO) communication links lead to a received power variance that depends on the size of the receiver aperture. Increasing the size of the receiver aperture reduces the power variance. This effect of the receiver size on power variance is called aperture averaging. If there were no aperture size limitation at the receiver, then there would be no turbulence-induced scintillation. In practice, there is always a tradeoff between aperture size, transceiver weight, and potential transceiver agility for pointing, acquisition and tracking (PAT) of FSO communication links. We have developed a geometrical simulation model to predict the aperture averaging factor. This model is used to simulate the aperture averaging effect at given range by using a large number of rays, Gaussian as well as uniformly distributed, propagating through simulated turbulence into a circular receiver of varying aperture size. Turbulence is simulated by filling the propagation path with spherical bubbles of varying sizes and refractive index discontinuities statistically distributed according to various models. For each statistical representation of the atmosphere, the three-dimensional trajectory of each ray is analyzed using geometrical optics. These Monte Carlo techniques have proved capable of assessing the aperture averaging effect, in particular, the quantitative expected reduction in intensity fluctuations with increasing aperture diameter. In addition, beam wander results have demonstrated the range-cubed dependence of mean-squared beam wander. An effective turbulence parameter can also be determined by correlating beam wander behavior with the path length.

Differential Optical Synthetic Aperture Radar

DOEpatents

Stappaerts, Eddy A.

2005-04-12

A new differential technique for forming optical images using a synthetic aperture is introduced. This differential technique utilizes a single aperture to obtain unique (N) phases that can be processed to produce a synthetic aperture image at points along a trajectory. This is accomplished by dividing the aperture into two equal "subapertures", each having a width that is less than the actual aperture, along the direction of flight. As the platform flies along a given trajectory, a source illuminates objects and the two subapertures are configured to collect return signals. The techniques of the invention is designed to cancel common-mode errors, trajectory deviations from a straight line, and laser phase noise to provide the set of resultant (N) phases that can produce an image having a spatial resolution corresponding to a synthetic aperture.

High Resolution Full-Aperture ISAR Processing through Modified Doppler History Based Motion Compensation

PubMed Central

Song, Jung-Hwan; Lee, Kee-Woong; Lee, Woo-Kyung; Jung, Chul-Ho

2017-01-01

A high resolution inverse synthetic aperture radar (ISAR) technique is presented using modified Doppler history based motion compensation. To this purpose, a novel wideband ISAR system is developed that accommodates parametric processing over extended aperture length. The proposed method is derived from an ISAR-to-SAR approach that makes use of high resolution spotlight SAR and sub-aperture recombination. It is dedicated to wide aperture ISAR imaging and exhibits robust performance against unstable targets having non-linear motions. We demonstrate that the Doppler histories of the full aperture ISAR echoes from disturbed targets are efficiently retrieved with good fitting models. Experiments have been conducted on real aircraft targets and the feasibility of the full aperture ISAR processing is verified through the acquisition of high resolution ISAR imagery. PMID:28555036

Aperture averaging in strong oceanic turbulence

NASA Astrophysics Data System (ADS)

Gökçe, Muhsin Caner; Baykal, Yahya

2018-04-01

Receiver aperture averaging technique is employed in underwater wireless optical communication (UWOC) systems to mitigate the effects of oceanic turbulence, thus to improve the system performance. The irradiance flux variance is a measure of the intensity fluctuations on a lens of the receiver aperture. Using the modified Rytov theory which uses the small-scale and large-scale spatial filters, and our previously presented expression that shows the atmospheric structure constant in terms of oceanic turbulence parameters, we evaluate the irradiance flux variance and the aperture averaging factor of a spherical wave in strong oceanic turbulence. Irradiance flux variance variations are examined versus the oceanic turbulence parameters and the receiver aperture diameter are examined in strong oceanic turbulence. Also, the effect of the receiver aperture diameter on the aperture averaging factor is presented in strong oceanic turbulence.

Multi-Aperture Digital Coherent Combining for Free-Space Optical Communication Receivers

DTIC Science & Technology

2016-04-21

Distribution A: Public Release; unlimited distribution 2016 Optical Society of America OCIS codes: (060.1660) Coherent communications; (070.2025) Discrete ...Coherent combining algorithm Multi-aperture coherent combining enables using many discrete apertures together to create a large effective aperture. A

Cavity-excited Huygens' metasurface antennas for near-unity aperture illumination efficiency from arbitrarily large apertures

PubMed Central

Epstein, Ariel; Wong, Joseph P. S.; Eleftheriades, George V.

2016-01-01

One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators. PMID:26790605

Study on characteristics of the aperture-averaging factor of atmospheric scintillation in terrestrial optical wireless communication

NASA Astrophysics Data System (ADS)

Shen, Hong; Liu, Wen-xing; Zhou, Xue-yun; Zhou, Li-ling; Yu, Long-Kun

2018-02-01

In order to thoroughly understand the characteristics of the aperture-averaging effect of atmospheric scintillation in terrestrial optical wireless communication and provide references for engineering design and performance evaluation of the optics system employed in the atmosphere, we have theoretically deduced the generally analytic expression of the aperture-averaging factor of atmospheric scintillation, and numerically investigated characteristics of the apertureaveraging factor under different propagation conditions. The limitations of the current commonly used approximate calculation formula of aperture-averaging factor have been discussed, and the results showed that the current calculation formula is not applicable for the small receiving aperture under non-uniform turbulence link. Numerical calculation has showed that aperture-averaging factor of atmospheric scintillation presented an exponential decline model for the small receiving aperture under non-uniform turbulent link, and the general expression of the model was given. This model has certain guiding significance for evaluating the aperture-averaging effect in the terrestrial optical wireless communication.

Preferential pathways in complex fracture systems and their influence on large scale transport

NASA Astrophysics Data System (ADS)

Willmann, M.; Mañé, R.; Tyukhova, A.

2017-12-01

Many subsurface applications in complex fracture systems require large-scale predictions. Precise predictions are difficult because of the existence of preferential pathways at different scales. The intrinsic complexity of fracture systems increases within fractured sedimentary formations, because also the coupling of fractures and matrix has to be taken into account. This interplay of fracture system and the sedimentary matrix is strongly controlled by the actual fracture aperture of an individual fracture. And an effective aperture cannot be easily be determined because of the preferential pathways along the fracture plane. We investigate the influence of these preferential pathways on large scale solute transport and upscale the aperture. By explicitly modeling flow and particle tracking in individual fractures, we develop a new effective transport aperture, which is weighted by the aperture along the preferential paths, a Lagrangian aperture. We show that this new aperture is consistently larger than existing definitions of effective flow and transport apertures. Finally, we apply our results to a fractured sedimentary formation in Northern Switzerland.

Cavity-excited Huygens' metasurface antennas for near-unity aperture illumination efficiency from arbitrarily large apertures.

PubMed

Epstein, Ariel; Wong, Joseph P S; Eleftheriades, George V

2016-01-21

One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators.

Rotating Aperture System

DOEpatents

Rusnak, Brian; Hall, James M.; Shen, Stewart; Wood, Richard L.

2005-01-18

A rotating aperture system includes a low-pressure vacuum pumping stage with apertures for passage of a deuterium beam. A stator assembly includes holes for passage of the beam. The rotor assembly includes a shaft connected to a deuterium gas cell or a crossflow venturi that has a single aperture on each side that together align with holes every rotation. The rotating apertures are synchronized with the firing of the deuterium beam such that the beam fires through a clear aperture and passes into the Xe gas beam stop. Portions of the rotor are lapped into the stator to improve the sealing surfaces, to prevent rapid escape of the deuterium gas from the gas cell.

Results of aperture area comparisons for exo-atmospheric total solar irradiance measurements.

PubMed

Johnson, B Carol; Litorja, Maritoni; Fowler, Joel B; Shirley, Eric L; Barnes, Robert A; Butler, James J

2013-11-20

Exo-atmospheric solar irradiance measurements made by the solar irradiance community since 1978 have incorporated limiting apertures with diameters measured by a number of metrology laboratories using a variety of techniques. Knowledge of the aperture area is a critical component in the conversion of radiant flux measurements to solar irradiance. A National Aeronautics and Space Administration (NASA) Earth Observing System (EOS) sponsored international comparison of aperture area measurements of limiting apertures provided by solar irradiance researchers was performed, the effort being executed by the National Institute of Standards and Technology (NIST) in coordination with the EOS Project Science Office. Apertures that had institutional heritage with historical solar irradiance measurements were measured using the absolute aperture measurement facility at NIST. The measurement technique employed noncontact video microscopy using high-accuracy translation stages. We have quantified the differences between the participating institutions' aperture area measurements and find no evidence to support the hypothesis that preflight aperture area measurements were the root cause of discrepancies in long-term total solar irradiance satellite measurements. Another result is the assessment of uncertainties assigned to methods used by participants. We find that uncertainties assigned to a participant's values may be underestimated.

Coded aperture solution for improving the performance of traffic enforcement cameras

NASA Astrophysics Data System (ADS)

Masoudifar, Mina; Pourreza, Hamid Reza

2016-10-01

A coded aperture camera is proposed for automatic license plate recognition (ALPR) systems. It captures images using a noncircular aperture. The aperture pattern is designed for the rapid acquisition of high-resolution images while preserving high spatial frequencies of defocused regions. It is obtained by minimizing an objective function, which computes the expected value of perceptual deblurring error. The imaging conditions and camera sensor specifications are also considered in the proposed function. The designed aperture improves the depth of field (DoF) and subsequently ALPR performance. The captured images can be directly analyzed by the ALPR software up to a specific depth, which is 13 m in our case, though it is 11 m for the circular aperture. Moreover, since the deblurring results of images captured by our aperture yield fewer artifacts than those captured by the circular aperture, images can be first deblurred and then analyzed by the ALPR software. In this way, the DoF and recognition rate can be improved at the same time. Our case study shows that the proposed camera can improve the DoF up to 17 m while it is limited to 11 m in the conventional aperture.

Image quality affected by diffraction of aperture structure arrangement in transparent active-matrix organic light-emitting diode displays.

PubMed

Tsai, Yu-Hsiang; Huang, Mao-Hsiu; Jeng, Wei-de; Huang, Ting-Wei; Lo, Kuo-Lung; Ou-Yang, Mang

2015-10-01

Transparent display is one of the main technologies in next-generation displays, especially for augmented reality applications. An aperture structure is attached on each display pixel to partition them into transparent and black regions. However, diffraction blurs caused by the aperture structure typically degrade the transparent image when the light from a background object passes through finite aperture window. In this paper, the diffraction effect of an active-matrix organic light-emitting diode display (AMOLED) is studied. Several aperture structures have been proposed and implemented. Based on theoretical analysis and simulation, the appropriate aperture structure will effectively reduce the blur. The analysis data are also consistent with the experimental results. Compared with the various transparent aperture structure on AMOLED, diffraction width (zero energy position of diffraction pattern) of the optimize aperture structure can be reduced 63% and 31% in the x and y directions in CASE 3. Associated with a lenticular lens on the aperture structure, the improvement could reach to 77% and 54% of diffraction width in the x and y directions. Modulation transfer function and practical images are provided to evaluate the improvement of image blurs.

Investigation of novel fractal shape of the nano-aperture as a metasurface for bio sensing application

NASA Astrophysics Data System (ADS)

Heydari, Samaneh; Rastan, Iman; Parvin, Amin; Pirooj, Azadeh; Zarrabi, Ferdows B.

2017-01-01

Recently, nano-aperture is noticed due to its good transmission in the optical regime. Also, the nano-apertures are developed at the metasurface design for circular polarization; for this aim, various shapes of the nano-aperture are suggested. To reach this objective, we have developed a novel Jerusalem cross fractal shape for a mid-infrared application. We have simulated various formations of the nano-fractal Jerusalem cross based on a simple cross to show the effect of nano-aperture shape on electrical field enhancement in the near-field which is important in spectroscopy and optical imaging. In addition, we have used a single layer graphene over the aperture as a coat for making reconfigurable characteristic also creating a membrane for placement of nano-particle over the aperture. Implementation of the graphene is an amendment to the transfer of the nano-apertures. The biological materials with a thickness of 80 nm have been placed over the graphene layer and the Figures of Merits (FOM) have been obtained. Additionally, the prototype of nano-antenna is independent from incident wave polarization. The Finite Difference Time Domain (FDTD) calculations have been implemented in the simulation and modeling the nano-apertures.

Quasi-linearly polarized hybrid modes in tapered and metal-coated tips with circular apertures: understanding the functionality of aperture tips

NASA Astrophysics Data System (ADS)

Tugchin, B. N.; Janunts, N.; Steinert, M.; Dietrich, K.; Kley, E. B.; Tünnermann, A.; Pertsch, T.

2017-06-01

In this study, we investigate analytically and experimentally the roles of quasi-linearly polarized (LP), hybrid, plasmonic and photonic modes in optical detection and excitation with aperture tips in scanning near-field optical microscopy. Aperture tips are tapered and metal-coated optical fibers where small circular apertures are made at the apex. In aperture tips, there exist plasmonic modes that are bound at the interface of the metal cladding to the inner dielectric fiber and photonic modes that are guided in the area of the increased index in the dielectric fiber core. The fundamental photonic mode, although excited by the free-space Gaussian beam, experiences cutoff and turns into an evanescent mode. The photonic mode also becomes lossier than the plasmonic mode toward the tip aperture, and its power decay due to absorption and reflection is expected to be at least 10-9. In contrast, the fundamental plasmonic mode has no cutoff and thus reaches all the way to the tip aperture. Due to the non-adiabaticity of both modes’ propagations through the taper below a core radius of 600 nm, there occurs coupling between the modes. The transmission efficiency of the plasmonic mode, including the coupling efficiency and the propagation loss, is expected to be about 10-6 that is at least 3 orders of magnitude larger than that of the photonic mode. Toward the tip aperture, the longitudinal field of the photonic mode becomes stronger than the transverse ones while the transverse fields always dominate for the plasmonic mode. Experimentally, we obtain polarization resolved images of the near-field at the tip aperture and compare with the x- and y-components of the fundamental quasi-LP plasmonic and photonic modes. The results show that not only the pattern but also the intensity ratios of the x- and y-components of the aperture near-field match with that of the fundamental plasmonic mode. Consequently, we conclude that only the plasmonic mode reaches the tip aperture and thus governs the near-field interaction outside the tip aperture. Our conclusion remains valid for all aperture tips regardless of the cladding metal type that mainly influences the total transmission efficiency of the aperture tip.

Synthetic aperture imaging in astronomy and aerospace: introduction.

PubMed

Creech-Eakman, Michelle J; Carney, P Scott; Buscher, David F; Shao, Michael

2017-05-01

Aperture synthesis methods allow the reconstruction of images with the angular resolutions exceeding that of extremely large monolithic apertures by using arrays of smaller apertures together in combination. In this issue we present several papers with techniques relevant to amplitude interferometry, laser radar, and intensity interferometry applications.

Electron microscope aperture system

NASA Technical Reports Server (NTRS)

Heinemann, K. (Inventor)

1976-01-01

An electron microscope including an electron source, a condenser lens having either a circular aperture for focusing a solid cone of electrons onto a specimen or an annular aperture for focusing a hollow cone of electrons onto the specimen, and an objective lens having an annular objective aperture, for focusing electrons passing through the specimen onto an image plane are described. The invention also entails a method of making the annular objective aperture using electron imaging, electrolytic deposition and ion etching techniques.

Determination of the paraxial focal length using Zernike polynomials over different apertures

NASA Astrophysics Data System (ADS)

Binkele, Tobias; Hilbig, David; Henning, Thomas; Fleischmann, Friedrich

2017-02-01

The paraxial focal length is still the most important parameter in the design of a lens. As presented at the SPIE Optics + Photonics 2016, the measured focal length is a function of the aperture. The paraxial focal length can be found when the aperture approaches zero. In this work, we investigate the dependency of the Zernike polynomials on the aperture size with respect to 3D space. By this, conventional wavefront measurement systems that apply Zernike polynomial fitting (e.g. Shack-Hartmann-Sensor) can be used to determine the paraxial focal length, too. Since the Zernike polynomials are orthogonal over a unit circle, the aperture used in the measurement has to be normalized. By shrinking the aperture and keeping up with the normalization, the Zernike coefficients change. The relation between these changes and the paraxial focal length are investigated. The dependency of the focal length on the aperture size is derived analytically and evaluated by simulation and measurement of a strong focusing lens. The measurements are performed using experimental ray tracing and a Shack-Hartmann-Sensor. Using experimental ray tracing for the measurements, the aperture can be chosen easily. Regarding the measurements with the Shack-Hartmann- Sensor, the aperture size is fixed. Thus, the Zernike polynomials have to be adapted to use different aperture sizes by the proposed method. By doing this, the paraxial focal length can be determined from the measurements in both cases.

Characterization of fracture aperture for groundwater flow and transport

NASA Astrophysics Data System (ADS)

Sawada, A.; Sato, H.; Tetsu, K.; Sakamoto, K.

2007-12-01

This paper presents experiments and numerical analyses of flow and transport carried out on natural fractures and transparent replica of fractures. The purpose of this study was to improve the understanding of the role of heterogeneous aperture patterns on channelization of groundwater flow and dispersion in solute transport. The research proceeded as follows: First, a precision plane grinder was applied perpendicular to the fracture plane to characterize the aperture distribution on a natural fracture with 1 mm of increment size. Although both time and labor were intensive, this approach provided a detailed, three dimensional picture of the pattern of fracture aperture. This information was analyzed to provide quantitative measures for the fracture aperture distribution, including JRC (Joint Roughness Coefficient) and fracture contact area ratio. These parameters were used to develop numerical models with corresponding synthetic aperture patterns. The transparent fracture replica and numerical models were then used to study how transport is affected by the aperture spatial pattern. In the transparent replica, transmitted light intensity measured by a CCD camera was used to image channeling and dispersion due to the fracture aperture spatial pattern. The CCD image data was analyzed to obtain the quantitative fracture aperture and tracer concentration data according to Lambert-Beer's law. The experimental results were analyzed using the numerical models. Comparison of the numerical models to the transparent replica provided information about the nature of channeling and dispersion due to aperture spatial patterns. These results support to develop a methodology for defining representative fracture aperture of a simplified parallel fracture model for flow and transport in heterogeneous fractures for contaminant transport analysis.

An integrated structural and geochemical study of fracture aperture growth in the Campito Formation of eastern California

NASA Astrophysics Data System (ADS)

Doungkaew, N.; Eichhubl, P.

2015-12-01

Processes of fracture formation control flow of fluid in the subsurface and the mechanical properties of the brittle crust. Understanding of fundamental fracture growth mechanisms is essential for understanding fracture formation and cementation in chemically reactive systems with implications for seismic and aseismic fault and fracture processes, migration of hydrocarbons, long-term CO2 storage, and geothermal energy production. A recent study on crack-seal veins in deeply buried sandstone of east Texas provided evidence for non-linear fracture growth, which is indicated by non-elliptical kinematic fracture aperture profiles. We hypothesize that similar non-linear fracture growth also occurs in other geologic settings, including under higher temperature where solution-precipitation reactions are kinetically favored. To test this hypothesis, we investigate processes of fracture growth in quartzitic sandstone of the Campito Formation, eastern California, by combining field structural observations, thin section petrography, and fluid inclusion microthermometry. Fracture aperture profile measurements of cemented opening-mode fractures show both elliptical and non-elliptical kinematic aperture profiles. In general, fractures that contain fibrous crack-seal cement have elliptical aperture profiles. Fractures filled with blocky cement have linear aperture profiles. Elliptical fracture aperture profiles are consistent with linear-elastic or plastic fracture mechanics. Linear aperture profiles may reflect aperture growth controlled by solution-precipitation creep, with the aperture distribution controlled by solution-precipitation kinetics. We hypothesize that synkinematic crack-seal cement preserves the elliptical aperture profiles of elastic fracture opening increments. Blocky cement, on the other hand, may form postkinematically relative to fracture opening, with fracture opening accommodated by continuous solution-precipitation creep.

Propagation of various dark hollow beams through an apertured paraxial ABCD optical system

NASA Astrophysics Data System (ADS)

Cai, Yangjian; Ge, Di

2006-08-01

Propagation of a dark hollow beam (DHB) of circular, elliptical or rectangular symmetry through an apertured paraxial ABCD optical system is investigated. Approximate analytical formulas for various DHBs propagating through an apertured paraxial optical system are derived by expanding the hard-aperture function into a finite sum of complex Gaussian functions in terms of a tensor method. Some numerical results are given. Our formulas provide a convenient way for studying the propagation of various DHBs through an apertured paraxial optical system.

Method of forming aperture plate for electron microscope

NASA Technical Reports Server (NTRS)

Heinemann, K. (Inventor)

1974-01-01

An electron microscope is described with an electron source a condenser lens having either a circular aperture for focusing a solid cone of electrons onto a specimen or an annular aperture for focusing a hollow cone of electrons onto the specimen. It also has objective lens with an annular objective aperture, for focusing electrons passing through the specimen onto an image plane. A method of making the annular objective aperture using electron imaging, electrolytic deposition and ion etching techniques is included.

Material Measurements Using Groundplane Apertures

NASA Technical Reports Server (NTRS)

Komisarek, K.; Dominek, A.; Wang, N.

1995-01-01

A technique for material parameter determination using an aperture in a groundplane is studied. The material parameters are found by relating the measured reflected field in the aperture to a numerical model. Two apertures are studied which can have a variety of different material configurations covering the aperture. The aperture cross-sections studied are rectangular and coaxial. The material configurations involved combinations of single layer and dual layers with or without a resistive exterior resistive sheet. The resistivity of the resistive sheet can be specified to simulate a perfect electric conductor (PEC) backing (0 Ohms/square) to a free space backing (infinity Ohms/square). Numerical parameter studies and measurements were performed to assess the feasibility of the technique.

Examples of current radar technology and applications, chapter 5, part B

NASA Technical Reports Server (NTRS)

1975-01-01

Basic principles and tradeoff considerations for SLAR are summarized. There are two fundamental types of SLAR sensors available to the remote sensing user: real aperture and synthetic aperture. The primary difference between the two types is that a synthetic aperture system is capable of significant improvements in target resolution but requires equally significant added complexity and cost. The advantages of real aperture SLAR include long range coverage, all-weather operation, in-flight processing and image viewing, and lower cost. The fundamental limitation of the real aperture approach is target resolution. Synthetic aperture processing is the most practical approach for remote sensing problems that require resolution higher than 30 to 40 m.

Design of precise assembly equipment of large aperture optics

NASA Astrophysics Data System (ADS)

Pei, Guoqing; Xu, Xu; Xiong, Zhao; Yan, Han; Qin, Tinghai; Zhou, Hai; Yuan, Xiaodong

2017-05-01

High-energy solid-state laser is an important way to achieve laser fusion research. Laser fusion facility includes thousands of various types of large aperture optics. These large aperture optics should be assembled with high precision and high efficiency. Currently, however, the assembly of large aperture optics is by man's hand which is in low level of efficiency and labor-intensive. Here, according to the characteristics of the assembly of large aperture optics, we designed three kinds of grasping devices. Using Finite Element Method, we simulated the impact of the grasping device on the PV value and the RMS value of the large aperture optics. The structural strength of the grasping device's key part was analyzed. An experiment was performed to illustrate the reliability and precision of the grasping device. We anticipate that the grasping device would complete the assembly of large aperture optics precisely and efficiently.

Nonparaxial propagation and focusing properties of azimuthal-variant vector fields diffracted by an annular aperture.

PubMed

Gu, Bing; Xu, Danfeng; Pan, Yang; Cui, Yiping

2014-07-01

Based on the vectorial Rayleigh-Sommerfeld integrals, the analytical expressions for azimuthal-variant vector fields diffracted by an annular aperture are presented. This helps us to investigate the propagation behaviors and the focusing properties of apertured azimuthal-variant vector fields under nonparaxial and paraxial approximations. The diffraction by a circular aperture, a circular disk, or propagation in free space can be treated as special cases of this general result. Simulation results show that the transverse intensity, longitudinal intensity, and far-field divergence angle of nonparaxially apertured azimuthal-variant vector fields depend strongly on the azimuthal index, the outer truncation parameter and the inner truncation parameter of the annular aperture, as well as the ratio of the waist width to the wavelength. Moreover, the multiple-ring-structured intensity pattern of the focused azimuthal-variant vector field, which originates from the diffraction effect caused by an annular aperture, is experimentally demonstrated.

Measurements of pore-scale flow through apertures

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

Chojnicki, Kirsten

Pore-scale aperture effects on flow in pore networks was studied in the laboratory to provide a parameterization for use in transport models. Four cases were considered: regular and irregular pillar/pore alignment with and without an aperture. The velocity field of each case was measured and simulated, providing quantitatively comparable results. Two aperture effect parameterizations were considered: permeability and transmission. Permeability values varied by an order of magnitude between the cases with and without apertures. However, transmission did not correlate with permeability. Despite having much greater permeability the regular aperture case permitted less transmission than the regular case. Moreover, both irregularmore » cases had greater transmission than the regular cases, a difference not supported by the permeabilities. Overall, these findings suggest that pore-scale aperture effects on flow though a pore-network may not be adequately captured by properties such as permeability for applications that are interested in determining particle transport volume and timing.« less

Design and analysis of a sub-aperture scanning machine for the transmittance measurements of large-aperture optical system

NASA Astrophysics Data System (ADS)

He, Yingwei; Li, Ping; Feng, Guojin; Cheng, Li; Wang, Yu; Wu, Houping; Liu, Zilong; Zheng, Chundi; Sha, Dingguo

2010-11-01

For measuring large-aperture optical system transmittance, a novel sub-aperture scanning machine with double-rotating arms (SSMDA) was designed to obtain sub-aperture beam spot. Optical system full-aperture transmittance measurements can be achieved by applying sub-aperture beam spot scanning technology. The mathematical model of the SSMDA based on a homogeneous coordinate transformation matrix is established to develop a detailed methodology for analyzing the beam spot scanning errors. The error analysis methodology considers two fundamental sources of scanning errors, namely (1) the length systematic errors and (2) the rotational systematic errors. As the systematic errors of the parameters are given beforehand, computational results of scanning errors are between -0.007~0.028mm while scanning radius is not lager than 400.000mm. The results offer theoretical and data basis to the research on transmission characteristics of large optical system.

Aperture Shield Materials Characterized and Selected for Solar Dynamic Space Power System

NASA Technical Reports Server (NTRS)

1995-01-01

The aperture shield in a solar dynamic space power system is necessary to prevent thermal damage to the heat receiver should the concentrated solar radiation be accidentally or intentionally focused outside of the heat receiver aperture opening and onto the aperture shield itself. Characterization of the optical and thermal properties of candidate aperture shield materials was needed to support the joint U.S./Russian solar dynamic space power effort for Mir. The specific objective of testing performed at the NASA Lewis Research Center was to identify a high-temperature material with a low specular reflectance, a low solar absorptance, and a high spectral emittance so that during an off-pointing event, the amount of solar energy reflecting off the aperture shield would be small, the ratio of solar absorptance to spectral emittance would provide the lowest possible equilibrium temperature, and the integrity of the aperture shield would remain intact.

Feasibility of Very Large Sparse Aperture Deployable Antennas

DTIC Science & Technology

2014-03-27

FEASIBILITY OF VERY LARGE SPARSE APERTURE DEPLOYABLE ANTENNAS THESIS Jason C. Heller, Captain...States. AFIT-ENY-14-M-24 FEASIBILITY OF VERY LARGE SPARSE APERTURE DEPLOYABLE ANTENNAS THESIS Presented to the Faculty...UNLIMITED AFIT-ENY-14-M-24 FEASIBILITY OF VERY LARGE SPARSE APERTURE DEPLOYABLE ANTENNAS Jason C. Heller, B.S., Aerospace

Finding Optimal Apertures in Kepler Data

NASA Astrophysics Data System (ADS)

Smith, Jeffrey C.; Morris, Robert L.; Jenkins, Jon M.; Bryson, Stephen T.; Caldwell, Douglas A.; Girouard, Forrest R.

2016-12-01

With the loss of two spacecraft reaction wheels precluding further data collection for the Kepler primary mission, even greater pressure is placed on the processing pipeline to eke out every last transit signal in the data. To that end, we have developed a new method to optimize the Kepler Simple Aperture Photometry (SAP) photometric apertures for both planet detection and minimization of systematic effects. The approach uses a per cadence modeling of the raw pixel data and then performs an aperture optimization based on signal-to-noise ratio and the Kepler Combined Differential Photometric Precision (CDPP), which is a measure of the noise over the duration of a reference transit signal. We have found the new apertures to be superior to the previous Kepler apertures. We can now also find a per cadence flux fraction in aperture and crowding metric. The new approach has also been proven to be robust at finding apertures in K2 data that help mitigate the larger motion-induced systematics in the photometry. The method further allows us to identify errors in the Kepler and K2 input catalogs.

The SAMI Galaxy Survey: can we trust aperture corrections to predict star formation?

NASA Astrophysics Data System (ADS)

Richards, S. N.; Bryant, J. J.; Croom, S. M.; Hopkins, A. M.; Schaefer, A. L.; Bland-Hawthorn, J.; Allen, J. T.; Brough, S.; Cecil, G.; Cortese, L.; Fogarty, L. M. R.; Gunawardhana, M. L. P.; Goodwin, M.; Green, A. W.; Ho, I.-T.; Kewley, L. J.; Konstantopoulos, I. S.; Lawrence, J. S.; Lorente, N. P. F.; Medling, A. M.; Owers, M. S.; Sharp, R.; Sweet, S. M.; Taylor, E. N.

2016-01-01

In the low-redshift Universe (z < 0.3), our view of galaxy evolution is primarily based on fibre optic spectroscopy surveys. Elaborate methods have been developed to address aperture effects when fixed aperture sizes only probe the inner regions for galaxies of ever decreasing redshift or increasing physical size. These aperture corrections rely on assumptions about the physical properties of galaxies. The adequacy of these aperture corrections can be tested with integral-field spectroscopic data. We use integral-field spectra drawn from 1212 galaxies observed as part of the SAMI Galaxy Survey to investigate the validity of two aperture correction methods that attempt to estimate a galaxy's total instantaneous star formation rate. We show that biases arise when assuming that instantaneous star formation is traced by broad-band imaging, and when the aperture correction is built only from spectra of the nuclear region of galaxies. These biases may be significant depending on the selection criteria of a survey sample. Understanding the sensitivities of these aperture corrections is essential for correct handling of systematic errors in galaxy evolution studies.

A scheiner-principle vernier optometer

NASA Astrophysics Data System (ADS)

Cushman, William B.

1989-06-01

A method and optometer apparatus is disclosed for measuring the dark focus of accommodation. In a preferred embodiment, the optometer apparatus includes: a pinhole aperture plate having first and second horizontally positioned apertures disposed on opposite sides of a first optical axis; first and second orthogonally-oriented polarizing filters respectively covering the first and second horizontally positioned apertures; a positive lens having an optical axis on the first optical axis and being positioned at a distance of approximately one focal length from the pinhole aperture plate; a lens system having an optical axis on the first optical axis; a slit aperture plate having a vertical slit and being disposed on the first optical axis and between the positive lens and the lens system; third and fourth vertically positioned polarizing filters selectively disposed adjacent to the slit aperture plate to divide the slit vertically, a monochromatic light source for propagating light along the first optical axis through the lens system; and movable means attached to the slit aperture plate, the lens system and the monochromatic light source for moving the slit aperture plate.

Self characterization of a coded aperture array for neutron source imaging

NASA Astrophysics Data System (ADS)

Volegov, P. L.; Danly, C. R.; Fittinghoff, D. N.; Guler, N.; Merrill, F. E.; Wilde, C. H.

2014-12-01

The neutron imaging system at the National Ignition Facility (NIF) is an important diagnostic tool for measuring the two-dimensional size and shape of the neutrons produced in the burning deuterium-tritium plasma during the stagnation stage of inertial confinement fusion implosions. Since the neutron source is small (˜100 μm) and neutrons are deeply penetrating (>3 cm) in all materials, the apertures used to achieve the desired 10-μm resolution are 20-cm long, triangular tapers machined in gold foils. These gold foils are stacked to form an array of 20 apertures for pinhole imaging and three apertures for penumbral imaging. These apertures must be precisely aligned to accurately place the field of view of each aperture at the design location, or the location of the field of view for each aperture must be measured. In this paper we present a new technique that has been developed for the measurement and characterization of the precise location of each aperture in the array. We present the detailed algorithms used for this characterization and the results of reconstructed sources from inertial confinement fusion implosion experiments at NIF.

Phenomenology of electromagnetic coupling: Conductors penetrating an aperture

NASA Astrophysics Data System (ADS)

Wright, D. B.; King, R. J.

1987-06-01

The purpose of this study was to investigate the coupling effects of penetrating conductors through free-standing apertures. This penetrating conductor and aperture arrangement are referred to as a modified aperture. A penetrating conductor is defined here to be a thin, single wire bent twice at 90 angles. The wire was inserted through a rectangular aperture in a metal wall. Vertical segments on both sides of the wall coupled energy from one region to the other. Energy was incident upon the modified aperture from what is referred to as the exterior region. The amount of coupling was measured by a D sensor on the other (interior) side of the wall. This configuration of an aperture in a metal wall was used as opposed to an aperture in a cavity in order to simplify the interpretation of resulting data. The added complexity of multiple cavity resonances was therefore eliminated. Determining the effects of penetrating conductors on aperture coupling is one of several topics being investigated as part of on-going research at Lawrence Livermore National Laboratory on the phenomenology of electromagnetic coupling. These phenomenology studies are concerned with the vulnerability of electronic systems to high intensity electromagnetic fields. The investigation is relevant to high altitude EMP (HEMP), enhanced HEMP (EHEMP), and high power microwave (HPM) coupling.

Electromagnetic Scattering from Arbitrarily Shaped Aperture Backed by Rectangular Cavity Recessed in Infinite Ground Plane

NASA Technical Reports Server (NTRS)

Cockrell, C. R.; Beck, Fred B.

1997-01-01

The electromagnetic scattering from an arbitrarily shaped aperture backed by a rectangular cavity recessed in an infinite ground plane is analyzed by the integral equation approach. In this approach, the problem is split into two parts: exterior and interior. The electromagnetic fields in the exterior part are obtained from an equivalent magnetic surface current density assumed to be flowing over the aperture and backed by an infinite ground plane. The electromagnetic fields in the interior part are obtained in terms of rectangular cavity modal expansion functions. The modal amplitudes of cavity modes are determined by enforcing the continuity of the electric field across the aperture. The integral equation with the aperture magnetic current density as an unknown is obtained by enforcing the continuity of magnetic fields across the aperture. The integral equation is then solved for the magnetic current density by the method of moments. The electromagnetic scattering properties of an aperture backed by a rectangular cavity are determined from the magnetic current density. Numerical results on the backscatter radar cross-section (RCS) patterns of rectangular apertures backed by rectangular cavities are compared with earlier published results. Also numerical results on the backscatter RCS patterns of a circular aperture backed by a rectangular cavity are presented.

Sub-aperture stitching test of a cylindrical mirror with large aperture

NASA Astrophysics Data System (ADS)

Xue, Shuai; Chen, Shanyong; Shi, Feng; Lu, Jinfeng

2016-09-01

Cylindrical mirrors are key optics of high-end equipment of national defense and scientific research such as high energy laser weapons, synchrotron radiation system, etc. However, its surface error test technology develops slowly. As a result, its optical processing quality can not meet the requirements, and the developing of the associated equipment is hindered. Computer Generated-Hologram (CGH) is commonly utilized as null for testing cylindrical optics. However, since the fabrication process of CGH with large aperture is not sophisticated yet, the null test of cylindrical optics with large aperture is limited by the aperture of the CGH. Hence CGH null test combined with sub-aperture stitching method is proposed to break the limit of the aperture of CGH for testing cylindrical optics, and the design of CGH for testing cylindrical surfaces is analyzed. Besides, the misalignment aberration of cylindrical surfaces is different from that of the rotational symmetric surfaces since the special shape of cylindrical surfaces, and the existing stitching algorithm of rotational symmetric surfaces can not meet the requirements of stitching cylindrical surfaces. We therefore analyze the misalignment aberrations of cylindrical surfaces, and study the stitching algorithm for measuring cylindrical optics with large aperture. Finally we test a cylindrical mirror with large aperture to verify the validity of the proposed method.

Reconfigurable metasurface aperture for security screening and microwave imaging

NASA Astrophysics Data System (ADS)

Sleasman, Timothy; Imani, Mohammadreza F.; Boyarsky, Michael; Pulido-Mancera, Laura; Reynolds, Matthew S.; Smith, David R.

2017-05-01

Microwave imaging systems have seen growing interest in recent decades for applications ranging from security screening to space/earth observation. However, hardware architectures commonly used for this purpose have not seen drastic changes. With the advent of metamaterials a wealth of opportunities have emerged for honing metasurface apertures for microwave imaging systems. Recent thrusts have introduced dynamic reconfigurability directly into the aperture layer, providing powerful capabilities from a physical layer with considerable simplicity. The waveforms generated from such dynamic metasurfaces make them suitable for application in synthetic aperture radar (SAR) and, more generally, computational imaging. In this paper, we investigate a dynamic metasurface aperture capable of performing microwave imaging in the K-band (17.5-26.5 GHz). The proposed aperture is planar and promises an inexpensive fabrication process via printed circuit board techniques. These traits are further augmented by the tunability of dynamic metasurfaces, which provides the dexterity necessary to generate field patterns ranging from a sequence of steered beams to a series of uncorrelated radiation patterns. Imaging is experimentally demonstrated with a voltage-tunable metasurface aperture. We also demonstrate the aperture's utility in real-time measurements and perform volumetric SAR imaging. The capabilities of a prototype are detailed and the future prospects of general dynamic metasurface apertures are discussed.

Side information in coded aperture compressive spectral imaging

NASA Astrophysics Data System (ADS)

Galvis, Laura; Arguello, Henry; Lau, Daniel; Arce, Gonzalo R.

2017-02-01

Coded aperture compressive spectral imagers sense a three-dimensional cube by using two-dimensional projections of the coded and spectrally dispersed source. These imagers systems often rely on FPA detectors, SLMs, micromirror devices (DMDs), and dispersive elements. The use of the DMDs to implement the coded apertures facilitates the capture of multiple projections, each admitting a different coded aperture pattern. The DMD allows not only to collect the sufficient number of measurements for spectrally rich scenes or very detailed spatial scenes but to design the spatial structure of the coded apertures to maximize the information content on the compressive measurements. Although sparsity is the only signal characteristic usually assumed for reconstruction in compressing sensing, other forms of prior information such as side information have been included as a way to improve the quality of the reconstructions. This paper presents the coded aperture design in a compressive spectral imager with side information in the form of RGB images of the scene. The use of RGB images as side information of the compressive sensing architecture has two main advantages: the RGB is not only used to improve the reconstruction quality but to optimally design the coded apertures for the sensing process. The coded aperture design is based on the RGB scene and thus the coded aperture structure exploits key features such as scene edges. Real reconstructions of noisy compressed measurements demonstrate the benefit of the designed coded apertures in addition to the improvement in the reconstruction quality obtained by the use of side information.

Near-Field Terahertz Transmission Imaging at 0.210 Terahertz Using a Simple Aperture Technique

DTIC Science & Technology

2015-10-01

This report discusses a simple aperture useful for terahertz near-field imaging at .2010 terahertz ( lambda = 1.43 millimeters). The aperture requires...achieve a spatial resolution of lambda /7. The aperture can be scaled with the assistance of machinery found in conventional machine shops to achieve similar results using shorter terahertz wavelengths.

RF verification tasks underway at the Harris Corporation for multiple aperture reflector system

NASA Technical Reports Server (NTRS)

Gutwein, T. A.

1982-01-01

Mesh effects on gain and patterns and adjacent aperture coupling effects for "pie" and circular apertures are discussed. Wire effects for Harris model with Langley scale model results included for assessing D/lamda effects, and wire effects with adjacent aperture coupling were determined. Reflector surface distortion effects (pillows and manufacturing roughness) were studied.

Dual aperture dipole magnet with second harmonic component

DOEpatents

Praeg, Walter F.

1985-01-01

An improved dual aperture dipole electromagnet includes a second-harmonic frequency magnetic guide field winding which surrounds first harmonic frequency magnetic guide field windings associated with each aperture. The second harmonic winding and the first harmonic windings cooperate to produce resultant magnetic waveforms in the apertures which have extended acceleration and shortened reset portions of electromagnet operation.

Dual aperture dipole magnet with second harmonic component

DOEpatents

Praeg, W.F.

1983-08-31

An improved dual aperture dipole electromagnet includes a second-harmonic frequency magnetic guide field winding which surrounds first harmonic frequency magnetic guide field windings associated with each aperture. The second harmonic winding and the first harmonic windings cooperate to produce resultant magnetic waveforms in the apertures which have extended acceleration and shortened reset portions of electromagnet operation.

The electromagnetic modeling of thin apertures using the finite-difference time-domain technique

NASA Technical Reports Server (NTRS)

Demarest, Kenneth R.

1987-01-01

A technique which computes transient electromagnetic responses of narrow apertures in complex conducting scatterers was implemented as an extension of previously developed Finite-Difference Time-Domain (FDTD) computer codes. Although these apertures are narrow with respect to the wavelengths contained within the power spectrum of excitation, this technique does not require significantly more computer resources to attain the increased resolution at the apertures. In the report, an analytical technique which utilizes Babinet's principle to model the apertures is developed, and an FDTD computer code which utilizes this technique is described.

Partially Filled Aperture Interferometric Telescopes: Achieving Large Aperture and Coronagraphic Performance

NASA Astrophysics Data System (ADS)

Moretto, G.; Kuhn, J.; Langlois, M.; Berdugyna, S.; Tallon, M.

2017-09-01

Telescopes larger than currently planned 30-m class instruments must break the mass-aperture scaling relationship of the Keck-generation of multi-segmented telescopes. Partially filled aperture, but highly redundant baseline interferometric instruments may achieve both large aperture and high dynamic range. The PLANETS FOUNDATION group has explored hybrid telescope-interferometer concepts for narrow-field optical systems that exhibit coronagraphic performance over narrow fields-of-view. This paper describes how the Colossus and Exo-Life Finder telescope designs achieve 10x lower moving masses than current Extremely Large Telescopes.

Extended Aperture Photometry of K2 RR Lyrae stars

NASA Astrophysics Data System (ADS)

Plachy, Emese; Klagyivik, Péter; Molnár, László; Sódor, Ádám; Szabó, Róbert

2017-10-01

We present the method of the Extended Aperture Photometry (EAP) that we applied on K2 RR Lyrae stars. Our aim is to minimize the instrumental variations of attitude control maneuvers by using apertures that cover the positional changes in the field of view thus contain the stars during the whole observation. We present example light curves that we compared to the light curves from the K2 Systematics Correction (K2SC) pipeline applied on the automated Single Aperture Photometry (SAP) and on the Pre-search Data Conditioning Simple Aperture Photometry (PDCSAP) data.

Microfabricated high-bandpass foucault aperture for electron microscopy

DOEpatents

Glaeser, Robert; Cambie, Rossana; Jin, Jian

2014-08-26

A variant of the Foucault (knife-edge) aperture is disclosed that is designed to provide single-sideband (SSB) contrast at low spatial frequencies but retain conventional double-sideband (DSB) contrast at high spatial frequencies in transmission electron microscopy. The aperture includes a plate with an inner open area, a support extending from the plate at an edge of the open area, a half-circle feature mounted on the support and located at the center of the aperture open area. The radius of the half-circle portion of reciprocal space that is blocked by the aperture can be varied to suit the needs of electron microscopy investigation. The aperture is fabricated from conductive material which is preferably non-oxidizing, such as gold, for example.

Active Correction of Aperture Discontinuities-Optimized Stroke Minimization. I. A New Adaptive Interaction Matrix Algorithm

NASA Astrophysics Data System (ADS)

Mazoyer, J.; Pueyo, L.; N'Diaye, M.; Fogarty, K.; Zimmerman, N.; Leboulleux, L.; St. Laurent, K. E.; Soummer, R.; Shaklan, S.; Norman, C.

2018-01-01

Future searches for bio-markers on habitable exoplanets will rely on telescope instruments that achieve extremely high contrast at small planet-to-star angular separations. Coronagraphy is a promising starlight suppression technique, providing excellent contrast and throughput for off-axis sources on clear apertures. However, the complexity of space- and ground-based telescope apertures goes on increasing over time, owing to the combination of primary mirror segmentation, the secondary mirror, and its support structures. These discontinuities in the telescope aperture limit the coronagraph performance. In this paper, we present ACAD-OSM, a novel active method to correct for the diffractive effects of aperture discontinuities in the final image plane of a coronagraph. Active methods use one or several deformable mirrors that are controlled with an interaction matrix to correct for the aberrations in the pupil. However, they are often limited by the amount of aberrations introduced by aperture discontinuities. This algorithm relies on the recalibration of the interaction matrix during the correction process to overcome this limitation. We first describe the ACAD-OSM technique and compare it to the previous active methods for the correction of aperture discontinuities. We then show its performance in terms of contrast and off-axis throughput for static aperture discontinuities (segmentation, struts) and for some aberrations evolving over the life of the instrument (residual phase aberrations, artifacts in the aperture, misalignments in the coronagraph design). This technique can now obtain the Earth-like planet detection threshold of {10}10 contrast on any given aperture over at least a 10% spectral bandwidth, with several coronagraph designs.

Diffraction smoothing aperture for an optical beam

DOEpatents

Judd, O'Dean P.; Suydam, Bergen R.

1976-01-01

The disclosure is directed to an aperture for an optical beam having an irregular periphery or having perturbations imposed upon the periphery to decrease the diffraction effect caused by the beam passing through the aperture. Such apertures are particularly useful with high power solid state laser systems in that they minimize the problem of self-focusing which frequently destroys expensive components in such systems.

Application of synthetic aperture radars for the ground displacement monitoring in mineral mining areas

NASA Astrophysics Data System (ADS)

Dobrynchenko, VV; Kokorinand, IS; Shebalkova, LV

2018-03-01

The authors discuss applicability of synthesized aperture radars to monitorthe ground surface displacement in mineral mining areas in terms of a synthesized-aperture interferometric radar. The operation principle of the interferometric method is demonstrated on studies of the ground surface displacements in areas of oil and gas reservoirs. The advantages of the synthetic aperture radar are substantiated.

Vacuum aperture isolator for retroreflection from laser-irradiated target

DOEpatents

Benjamin, Robert F.; Mitchell, Kenneth B.

1980-01-01

The disclosure is directed to a vacuum aperture isolator for retroreflection of a laser-irradiated target. Within a vacuum chamber are disposed a beam focusing element, a disc having an aperture and a recollimating element. The edge of the focused beam impinges on the edge of the aperture to produce a plasma which refracts any retroreflected light from the laser's target.

47 CFR 25.134 - Licensing provisions of Very Small Aperture Terminal (VSAT) and C-band Small Aperture Terminal...

Code of Federal Regulations, 2011 CFR

2011-10-01

... Terminal (VSAT) and C-band Small Aperture Terminal (CSAT) networks. 25.134 Section 25.134 Telecommunication...) and C-band Small Aperture Terminal (CSAT) networks. (a)(1) VSAT networks operating in the 12/14 GHz bands. All applications for digital VSAT networks granted on or before September 15, 2005, with a...

47 CFR 25.134 - Licensing provisions of Very Small Aperture Terminal (VSAT) and C-band Small Aperture Terminal...

Code of Federal Regulations, 2010 CFR

2010-10-01

... Terminal (VSAT) and C-band Small Aperture Terminal (CSAT) networks. 25.134 Section 25.134 Telecommunication...) and C-band Small Aperture Terminal (CSAT) networks. (a)(1) VSAT networks operating in the 12/14 GHz bands. All applications for digital VSAT networks granted on or before September 15, 2005, with a...

TRIPPy: Trailed Image Photometry in Python

NASA Astrophysics Data System (ADS)

Fraser, Wesley; Alexandersen, Mike; Schwamb, Megan E.; Marsset, Michaël; Pike, Rosemary E.; Kavelaars, J. J.; Bannister, Michele T.; Benecchi, Susan; Delsanti, Audrey

2016-06-01

Photometry of moving sources typically suffers from a reduced signal-to-noise ratio (S/N) or flux measurements biased to incorrect low values through the use of circular apertures. To address this issue, we present the software package, TRIPPy: TRailed Image Photometry in Python. TRIPPy introduces the pill aperture, which is the natural extension of the circular aperture appropriate for linearly trailed sources. The pill shape is a rectangle with two semicircular end-caps and is described by three parameters, the trail length and angle, and the radius. The TRIPPy software package also includes a new technique to generate accurate model point-spread functions (PSFs) and trailed PSFs (TSFs) from stationary background sources in sidereally tracked images. The TSF is merely the convolution of the model PSF, which consists of a moffat profile, and super-sampled lookup table. From the TSF, accurate pill aperture corrections can be estimated as a function of pill radius with an accuracy of 10 mmag for highly trailed sources. Analogous to the use of small circular apertures and associated aperture corrections, small radius pill apertures can be used to preserve S/Ns of low flux sources, with appropriate aperture correction applied to provide an accurate, unbiased flux measurement at all S/Ns.

Manipulation of surface plasmon resonance of a graphene-based Au aperture antenna in visible and near-infrared regions

NASA Astrophysics Data System (ADS)

Wan, Yuan; An, Yashuai; Tao, Zhi; Deng, Luogen

2018-03-01

Behaviors of surface plasmon resonance (SPR) of a graphene-based Au aperture antenna are investigated in visible and near-infrared (vis-NIR) regions. Compared with the SPR wavelength of a traditional Au aperture antenna, the SPR wavelength of the graphene-based Au aperture antenna shows a remarkable blue shift due to the redistribution of the electric field in the proposed structure. The electric field of the graphene-based Au aperture antenna is highly localized on the surface of the graphene in the aperture and redistributed to be a standing wave. Moreover, the SPR of a graphene-based Au aperture antenna is sensitive to the thickness and the refractive index of the dielectric layer, the graphene Fermi energy, the refractive index of the environment and the polarization direction of the incident light. Finally, we find the wavelength, intensity and phase of the reflected light of the graphene-based Au aperture antenna array can be actively modulated by varying the graphene Fermi energy. The proposed structure provides a promising platform for realizing a tunable optical filter, a highly sensitive refractive index sensor, and other actively tunable optical and optoelectronic devices.

Self characterization of a coded aperture array for neutron source imaging

DOE PAGES

Volegov, P. L.; Danly, C. R.; Fittinghoff, D. N.; ...

2014-12-15

The neutron imaging system at the National Ignition Facility (NIF) is an important diagnostic tool for measuring the two-dimensional size and shape of the neutrons produced in the burning DT plasma during the stagnation stage of ICF implosions. Since the neutron source is small (~100 μm) and neutrons are deeply penetrating (>3 cm) in all materials, the apertures used to achieve the desired 10-μm resolution are 20-cm long, triangular tapers machined in gold foils. These gold foils are stacked to form an array of 20 apertures for pinhole imaging and three apertures for penumbral imaging. These apertures must be preciselymore » aligned to accurately place the field of view of each aperture at the design location, or the location of the field of view for each aperture must be measured. In this paper we present a new technique that has been developed for the measurement and characterization of the precise location of each aperture in the array. We present the detailed algorithms used for this characterization and the results of reconstructed sources from inertial confinement fusion implosion experiments at NIF.« less

Dark-field microscopic image stitching method for surface defects evaluation of large fine optics.

PubMed

Liu, Dong; Wang, Shitong; Cao, Pin; Li, Lu; Cheng, Zhongtao; Gao, Xin; Yang, Yongying

2013-03-11

One of the challenges in surface defects evaluation of large fine optics is to detect defects of microns on surfaces of tens or hundreds of millimeters. Sub-aperture scanning and stitching is considered to be a practical and efficient method. But since there are usually few defects on the large aperture fine optics, resulting in no defects or only one run-through line feature in many sub-aperture images, traditional stitching methods encounter with mismatch problem. In this paper, a feature-based multi-cycle image stitching algorithm is proposed to solve the problem. The overlapping areas of sub-apertures are categorized based on the features they contain. Different types of overlapping areas are then stitched in different cycles with different methods. The stitching trace is changed to follow the one that determined by the features. The whole stitching procedure is a region-growing like process. Sub-aperture blocks grow bigger after each cycle and finally the full aperture image is obtained. Comparison experiment shows that the proposed method is very suitable to stitch sub-apertures that very few feature information exists in the overlapping areas and can stitch the dark-field microscopic sub-aperture images very well.

Lambmeat colour values (HunterLab CIE and reflectance) are influenced by aperture size (5 mm v. 25 mm).

PubMed

Holman, Benjamin W B; Ponnampalam, Eric N; van de Ven, Remy J; Kerr, Matthew G; Hopkins, David L

2015-02-01

The effect of aperture size on the assessment of lamb meat colour values (L*, a*, b* and R630/580)was investigated. Two experiments using 2 HunterLab MiniScan colorimeters (large [25 mm] and small [5 mm] apertures) were conducted: 1) coloured tiles were measured and 2) unaged lamb (n = 65) m. longissimus lumborum (LL) and m. semimembranosus (SM) muscles were measured over 2.5 d under simulated retail display. For Experiment three, 2 different colorimeters were used on lamb (n = 36) LL aged for 6 weeks before measurement over 4 don simulated retail display. Coloured tile a* and b* values were unaffected by aperture size, but L* values and the R630/580 ratio were influenced by aperture size. The effect of aperture size on lamb meat colour measurements varied with display time and muscle type. The large aperture size generally provided the highest colorimetric values, and is recommended for measuring lamb meat colour.

The Information Content of Interferometric Synthetic Aperture Radar: Vegetation and Underlying Surface Topography

NASA Technical Reports Server (NTRS)

Treuhaft, Robert N.

1996-01-01

This paper first gives a heuristic description of the sensitivity of Interferometric Synthetic Aperture Radar to vertical vegetation distributions and underlying surface topography. A parameter estimation scenario is then described in which the Interferometric Synthetic Aperture Radar cross-correlation amplitude and phase are the observations from which vegetation and surface topographic parameters are estimated. It is shown that, even in the homogeneous-layer model of the vegetation, the number of parameters needed to describe the vegetation and underlying topography exceeds the number of Interferometric Synthetic Aperture Radar observations for single-baseline, single-frequency, single-incidence-angle, single-polarization Interferometric Synthetic Aperture Radar. Using ancillary ground-truth data to compensate for the underdetermination of the parameters, forest depths are estimated from the INSAR data. A recently-analyzed multibaseline data set is also discussed and the potential for stand-alone Interferometric Synthetic Aperture Radar parameter estimation is assessed. The potential of combining the information content of Interferometric Synthetic Aperture Radar with that of infrared/optical remote sensing data is briefly discussed.

Measurements of Aperture Averaging on Bit-Error-Rate

NASA Technical Reports Server (NTRS)

Bastin, Gary L.; Andrews, Larry C.; Phillips, Ronald L.; Nelson, Richard A.; Ferrell, Bobby A.; Borbath, Michael R.; Galus, Darren J.; Chin, Peter G.; Harris, William G.; Marin, Jose A.;

Double Wigner distribution function of a first-order optical system with a hard-edge aperture.

PubMed

Pan, Weiqing

2008-01-01

The effect of an apertured optical system on Wigner distribution can be expressed as a superposition integral of the input Wigner distribution function and the double Wigner distribution function of the apertured optical system. By introducing a hard aperture function into a finite sum of complex Gaussian functions, the double Wigner distribution functions of a first-order optical system with a hard aperture outside and inside it are derived. As an example of application, the analytical expressions of the Wigner distribution for a Gaussian beam passing through a spatial filtering optical system with an internal hard aperture are obtained. The analytical results are also compared with the numerical integral results, and they show that the analytical results are proper and ascendant.

A functional probe with bowtie aperture and bull's eye structure for nanolithograph

NASA Astrophysics Data System (ADS)

Wang, Shuo; Li, Xu-Feng; Wang, Qiao; Guo, Ying-Yan; Pan, Shi

2012-10-01

The bowtie aperture surrounded by concentric gratings (the bull's eye structure) integrated on the near-field scanning optical microscopy (NSOM) probe (aluminum coated fiber tip) for nanolithography has been investigated using the finite-difference time domain (FDTD) method. By modifying the parameters of the bowtie aperture and the concentric gratings, a maximal field enhancement factor of 391.69 has been achieved, which is 18 times larger than that obtained from the single bowtie aperture. Additionally, the light spot depends on the gap size of the bowtie aperture and can be confined to sub-wavelength. The superiority of the combination of the bowtie aperture and the bull's eye structure is confirmed, and the mechanism for the electric field enhancement in this derived structure is analyzed.

Measurements of aperture averaging on bit-error-rate

NASA Astrophysics Data System (ADS)

Bastin, Gary L.; Andrews, Larry C.; Phillips, Ronald L.; Nelson, Richard A.; Ferrell, Bobby A.; Borbath, Michael R.; Galus, Darren J.; Chin, Peter G.; Harris, William G.; Marin, Jose A.; Burdge, Geoffrey L.; Wayne, David; Pescatore, Robert

2005-08-01

We report on measurements made at the Shuttle Landing Facility (SLF) runway at Kennedy Space Center of receiver aperture averaging effects on a propagating optical Gaussian beam wave over a propagation path of 1,000 m. A commercially available instrument with both transmit and receive apertures was used to transmit a modulated laser beam operating at 1550 nm through a transmit aperture of 2.54 cm. An identical model of the same instrument was used as a receiver with a single aperture that was varied in size up to 20 cm to measure the effect of receiver aperture averaging on Bit Error Rate. Simultaneous measurements were also made with a scintillometer instrument and local weather station instruments to characterize atmospheric conditions along the propagation path during the experiments.

Initial Results of Aperture Area Comparisons for Exo-Atmospheric Total Solar Irradiance Measurements

NASA Technical Reports Server (NTRS)

Johnson, B. Carol; Litorja, Maritoni; Fowler, Joel B.; Butler, James J.

2009-01-01

In the measurement of exo-atmospheric total solar irradiance (TSI), instrument aperture area is a critical component in converting solar radiant flux to irradiance. In a May 2000 calibration workshop for the Total Irradiance Monitor (TIM) on the Earth Observing System (EOS) Solar Radiation and Climate Experiment (SORCE), the solar irradiance measurement community recommended that NASA and NISI coordinate an aperture area measurement comparison to quantify and validate aperture area uncertainties and their overall effect on TSI uncertainties. From May 2003 to February 2006, apertures from 4 institutions with links to the historical TSI database were measured by NIST and the results were compared to the aperture area determined by each institution. The initial results of these comparisons are presented and preliminary assessments of the participants' uncertainties are discussed.

Functionalized apertures for the detection of chemical and biological materials

DOEpatents

Letant, Sonia E.; van Buuren, Anthony W.; Terminello, Louis J.; Thelen, Michael P.; Hope-Weeks, Louisa J.; Hart, Bradley R.

2010-12-14

Disclosed are nanometer to micron scale functionalized apertures constructed on a substrate made of glass, carbon, semiconductors or polymeric materials that allow for the real time detection of biological materials or chemical moieties. Many apertures can exist on one substrate allowing for the simultaneous detection of numerous chemical and biological molecules. One embodiment features a macrocyclic ring attached to cross-linkers, wherein the macrocyclic ring has a biological or chemical probe extending through the aperture. Another embodiment achieves functionalization by attaching chemical or biological anchors directly to the walls of the apertures via cross-linkers.

Development of the Synthetic Aperture Radiometer ESTAR and the Next Generation

NASA Technical Reports Server (NTRS)

LeVine, David M.; Haken, Michael; Swift, Calvin T.

2004-01-01

ESTAR is a research instrument built to develop the technology of aperture synthesis for passive remote sensing of Earth from space. Aperture synthesis is an interferometric technology that addresses the problem of putting large antenna apertures in space to achieve the spatial resolution needed for remote sensing at long wavelengths ESTAR was a first step (synthesis only across track and only at horizontal polarization). The development has progressed to a new generation instrument that is dual polarized and does aperture synthesis in two dimensions. Among the plans for the future is technology to combine active and passive remote sensing.

Aperture tolerances for neutron-imaging systems in inertial confinement fusion.

PubMed

Ghilea, M C; Sangster, T C; Meyerhofer, D D; Lerche, R A; Disdier, L

2008-02-01

Neutron-imaging systems are being considered as an ignition diagnostic for the National Ignition Facility (NIF) [Hogan et al., Nucl. Fusion 41, 567 (2001)]. Given the importance of these systems, a neutron-imaging design tool is being used to quantify the effects of aperture fabrication and alignment tolerances on reconstructed neutron images for inertial confinement fusion. The simulations indicate that alignment tolerances of more than 1 mrad would introduce measurable features in a reconstructed image for both pinholes and penumbral aperture systems. These simulations further show that penumbral apertures are several times less sensitive to fabrication errors than pinhole apertures.

Plasmonic nanofocusing with a metallic pyramid and an integrated C-shaped aperture

NASA Astrophysics Data System (ADS)

Lindquist, Nathan C.; Johnson, Timothy W.; Nagpal, Prashant; Norris, David J.; Oh, Sang-Hyun

2013-05-01

We demonstrate the design, fabrication and characterization of a near-field plasmonic nanofocusing probe with a hybrid tip-plus-aperture design. By combining template stripping with focused ion beam lithography, a variety of aperture-based near-field probes can be fabricated with high optical performance. In particular, the combination of large transmission through a C-shaped aperture aligned to the sharp apex (<10 nm radius) of a template-stripped metallic pyramid allows the efficient delivery of light--via the C-shaped aperture--while providing a nanometric hotspot determined by the sharpness of the tip itself.

Phase dependence of transport-aperture coordination variability reveals control strategy of reach-to-grasp movements.

PubMed

Rand, Miya K; Shimansky, Y P; Hossain, Abul B M I; Stelmach, George E

2010-11-01

Based on an assumption of movement control optimality in reach-to-grasp movements, we have recently developed a mathematical model of transport-aperture coordination (TAC), according to which the hand-target distance is a function of hand velocity and acceleration, aperture magnitude, and aperture velocity and acceleration (Rand et al. in Exp Brain Res 188:263-274, 2008). Reach-to-grasp movements were performed by young adults under four different reaching speeds and two different transport distances. The residual error magnitude of fitting the above model to data across different trials and subjects was minimal for the aperture-closure phase, but relatively much greater for the aperture-opening phase, indicating considerable difference in TAC variability between those phases. This study's goal is to identify the main reasons for that difference and obtain insights into the control strategy of reach-to-grasp movements. TAC variability within the aperture-opening phase of a single trial was found minimal, indicating that TAC variability between trials was not due to execution noise, but rather a result of inter-trial and inter-subject variability of motor plan. At the same time, the dependence of the extent of trial-to-trial variability of TAC in that phase on the speed of hand transport was sharply inconsistent with the concept of speed-accuracy trade-off: the lower the speed, the larger the variability. Conversely, the dependence of the extent of TAC variability in the aperture-closure phase on hand transport speed was consistent with that concept. Taking into account recent evidence that the cost of neural information processing is substantial for movement planning, the dependence of TAC variability in the aperture-opening phase on task performance conditions suggests that it is not the movement time that the CNS saves in that phase, but the cost of neuro-computational resources and metabolic energy required for TAC regulation in that phase. Thus, the CNS performs a trade-off between that cost and TAC regulation accuracy. It is further discussed that such trade-off is possible because, due to a special control law that governs optimal switching from aperture opening to aperture closure, the inter-trial variability of the end of aperture opening does not affect the high accuracy of TAC regulation in the subsequent aperture-closure phase.

Control of aperture closure during reach-to-grasp movements in parkinson’s disease

PubMed Central

Rand, M. K.; Smiley-Oyen, A. L.; Shimansky, Y. P.; Bloedel, J. R.; Stelmach, G. E.

2007-01-01

This study examined whether the pattern of coordination between arm-reaching toward an object (hand transport) and the initiation of aperture closure for grasping is different between PD patients and healthy individuals, and whether that pattern is affected by the necessity to quickly adjust the reach-to-grasp movement in response to an unexpected shift of target location. Subjects reached for and grasped a vertical dowel, the location of which was indicated by illuminating one of the three dowels placed on a horizontal plane. In control conditions, target location was fixed during the trial. In perturbation conditions, target location was shifted instantaneously by switching the illumination to a different dowel during the reach. The hand distance from the target at which the subject initiated aperture closure (aperture closure distance) was similar for both the control and perturbation conditions within each group of subjects. However, that distance was significantly closer to the target in the PD group than in the control group. The timing of aperture closure initiation varied considerably across the trials in both groups of subjects. In contrast, aperture closure distance was relatively invariant, suggesting that aperture closure initiation was determined by spatial parameters of arm kinematics rather than temporal parameters. The linear regression analysis of aperture closure distance showed that the distance was highly predictable based on the following three parameters: the amplitude of maximum grip aperture, hand velocity, and hand acceleration. This result implies that a control law, the arguments of which include the above parameters, governs the initiation of aperture closure. Further analysis revealed that the control law was very similar between the subject groups under each condition as well as between the control and perturbation conditions for each group. Consequently, the shorter aperture closure distance observed in PD patients apparently is a result of the hypometria of their grip aperture and bradykinesia of hand transport movement, rather than a consequence of a deficit in transport-grasp coordination. It is also concluded that the perturbation of target location does not disrupt the transport-grasp coordination in either healthy individuals or PD patients. PMID:16307233

Control of aperture closure during reach-to-grasp movements in Parkinson's disease.

PubMed

Rand, M K; Smiley-Oyen, A L; Shimansky, Y P; Bloedel, J R; Stelmach, G E

2006-01-01

This study examined whether the pattern of coordination between arm-reaching toward an object (hand transport) and the initiation of aperture closure for grasping is different between PD patients and healthy individuals, and whether that pattern is affected by the necessity to quickly adjust the reach-to-grasp movement in response to an unexpected shift of target location. Subjects reached for and grasped a vertical dowel, the location of which was indicated by illuminating one of the three dowels placed on a horizontal plane. In control conditions, target location was fixed during the trial. In perturbation conditions, target location was shifted instantaneously by switching the illumination to a different dowel during the reach. The hand distance from the target at which the subject initiated aperture closure (aperture closure distance) was similar for both the control and perturbation conditions within each group of subjects. However, that distance was significantly closer to the target in the PD group than in the control group. The timing of aperture closure initiation varied considerably across the trials in both groups of subjects. In contrast, aperture closure distance was relatively invariant, suggesting that aperture closure initiation was determined by spatial parameters of arm kinematics rather than temporal parameters. The linear regression analysis of aperture closure distance showed that the distance was highly predictable based on the following three parameters: the amplitude of maximum grip aperture, hand velocity, and hand acceleration. This result implies that a control law, the arguments of which include the above parameters, governs the initiation of aperture closure. Further analysis revealed that the control law was very similar between the subject groups under each condition as well as between the control and perturbation conditions for each group. Consequently, the shorter aperture closure distance observed in PD patients apparently is a result of the hypometria of their grip aperture and bradykinesia of hand transport movement, rather than a consequence of a deficit in transport-grasp coordination. It is also concluded that the perturbation of target location does not disrupt the transport-grasp coordination in either healthy individuals or PD patients.

A Morphogenetic Model Accounting for Pollen Aperture Pattern in Flowering Plants.

PubMed

Ressayre; Godelle; Mignot; Gouyon

1998-07-21

Pollen grains are embeddded in an extremely resistant wall. Apertures are well defined places where the pollen wall is reduced or absent that permit pollen tube germination. Pollen grains are produced by meiosis and aperture number definition appears to be linked with the partition that follows meiosis and leads to the formation of a tetrad of four haploid microspores. In dicotyledonous plants, meiosis is simultaneous which means that cytokinesis occurs once the two nuclear divisions are completed. A syncitium with the four nuclei stemming from meiosis is formed and cytokinesis isolates simulataneously the four products of meiosis. We propose a theoretical morphogenetic model which takes into account part of the features of the ontogeny of the pollen grains. The nuclei are considered as attractors acting upon a morphogenetic substance distributed within the cytoplasm of the dividing cell. This leads to a partition of the volume of the cell in four domains that is similar to the observations of cytokinesis in the studied species. The most widespread pattern of aperture distribution in dicotyledonous plants (three apertures equidistributed on the pollen grain equator) can be explained by bipolar interactions between nuclei stemming from the second meiotic division, and observed variations on these patterns by disturbances of these interactions. In numerous plant species, several pollen grains differing in aperture number are produced by a single individual. The distribution of the different morphs within tetrads indicates that the four daughter cells can have different aperture number. The model provides an explanation for the duplication of one of the apertures of a three-aperture pollen grain leading to a four-aperture one and in parallel it gives an explanation for how heterogeneous tetrads can be formed.Copyright 1998 Academic Press

Diffraction of cosine-Gaussian-correlated Schell-model beams.

PubMed

Pan, Liuzhan; Ding, Chaoliang; Wang, Haixia

2014-05-19

The expression of spectral density of cosine-Gaussian-correlated Schell-model (CGSM) beams diffracted by an aperture is derived, and used to study the changes in the spectral density distribution of CGSM beams upon propagation, where the effect of aperture diffraction is emphasized. It is shown that, comparing with that of GSM beams, the spectral density distribution of CGSM beams diffracted by an aperture has dip and shows dark hollow intensity distribution when the order-parameter n is big enough. The central intensity increases with increasing truncation parameter of aperture. The comparative study of spectral density distributions of CGSM beams with aperture and that of without aperture is performed. Furthermore, the effect of order-parameter n and spatial coherence of CGSM beams on the spectral density distribution is discussed in detail. The results obtained may be useful in optical particulate manipulation.

Measurements of Dynamic Effects in FNAL 11 T Nb 3Sn Dipole Models

DOE PAGES

Velev, Gueorgui; Strauss, Thomas; Barzi, Emanuela; ...

2018-01-17

Fermilab, in collaboration with CERN, has developed a twin-aperture 11 T Nb 3Sn dipole suitable for the high-luminosity LHC upgrade. During 2012-2014, a 2-m long single-aperture dipole demonstrator and three 1-m long single-aperture dipole models were fabricated by FNAL and tested at its Vertical Magnet Test Facility. Collared coils from two of the 1-m long models were then used to assemble the first twin-aperture dipole demonstrator. This magnet had extensive testing in 2015-2016, including quench performance, quench protection, and field quality studies. Here, this paper reports the results of measurements of persistent current effects in the single-aperture and twin-aperture 11more » T Nb 3Sn dipoles and compares them with similar measurements in previous NbTi magnets« less

A Spherical Active Coded Aperture for 4π Gamma-ray Imaging

DOE PAGES

Hellfeld, Daniel; Barton, Paul; Gunter, Donald; ...

2017-09-22

Gamma-ray imaging facilitates the efficient detection, characterization, and localization of compact radioactive sources in cluttered environments. Fieldable detector systems employing active planar coded apertures have demonstrated broad energy sensitivity via both coded aperture and Compton imaging modalities. But, planar configurations suffer from a limited field-of-view, especially in the coded aperture mode. In order to improve upon this limitation, we introduce a novel design by rearranging the detectors into an active coded spherical configuration, resulting in a 4pi isotropic field-of-view for both coded aperture and Compton imaging. This work focuses on the low- energy coded aperture modality and the optimization techniquesmore » used to determine the optimal number and configuration of 1 cm 3 CdZnTe coplanar grid detectors on a 14 cm diameter sphere with 192 available detector locations.« less

Measurements of Dynamic Effects in FNAL 11 T Nb 3Sn Dipole Models

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

Velev, Gueorgui; Strauss, Thomas; Barzi, Emanuela

Fermilab, in collaboration with CERN, has developed a twin-aperture 11 T Nb 3Sn dipole suitable for the high-luminosity LHC upgrade. During 2012-2014, a 2-m long single-aperture dipole demonstrator and three 1-m long single-aperture dipole models were fabricated by FNAL and tested at its Vertical Magnet Test Facility. Collared coils from two of the 1-m long models were then used to assemble the first twin-aperture dipole demonstrator. This magnet had extensive testing in 2015-2016, including quench performance, quench protection, and field quality studies. Here, this paper reports the results of measurements of persistent current effects in the single-aperture and twin-aperture 11more » T Nb 3Sn dipoles and compares them with similar measurements in previous NbTi magnets« less

The sonar aperture and its neural representation in bats.

PubMed

Heinrich, Melina; Warmbold, Alexander; Hoffmann, Susanne; Firzlaff, Uwe; Wiegrebe, Lutz

2011-10-26

As opposed to visual imaging, biosonar imaging of spatial object properties represents a challenge for the auditory system because its sensory epithelium is not arranged along space axes. For echolocating bats, object width is encoded by the amplitude of its echo (echo intensity) but also by the naturally covarying spread of angles of incidence from which the echoes impinge on the bat's ears (sonar aperture). It is unclear whether bats use the echo intensity and/or the sonar aperture to estimate an object's width. We addressed this question in a combined psychophysical and electrophysiological approach. In three virtual-object playback experiments, bats of the species Phyllostomus discolor had to discriminate simple reflections of their own echolocation calls differing in echo intensity, sonar aperture, or both. Discrimination performance for objects with physically correct covariation of sonar aperture and echo intensity ("object width") did not differ from discrimination performances when only the sonar aperture was varied. Thus, the bats were able to detect changes in object width in the absence of intensity cues. The psychophysical results are reflected in the responses of a population of units in the auditory midbrain and cortex that responded strongest to echoes from objects with a specific sonar aperture, regardless of variations in echo intensity. Neurometric functions obtained from cortical units encoding the sonar aperture are sufficient to explain the behavioral performance of the bats. These current data show that the sonar aperture is a behaviorally relevant and reliably encoded cue for object size in bat sonar.

Theoretical calculations and experimental verification for the pumping effect caused by the dynamic micro-tapered angle

NASA Astrophysics Data System (ADS)

Cai, Yufei; Zhang, Jianhui; Zhu, Chunling; Huang, Jun; Jiang, Feng

2016-05-01

The atomizer with micro cone apertures has advantages of ultra-fine atomized droplets, low power consumption and low temperature rise. The current research of this kind of atomizer mainly focuses on the performance and its application while there is less research of the principle of the atomization. Under the analysis of the dispenser and its micro-tapered aperture's deformation, the volume changes during the deformation and vibration of the micro-tapered aperture on the dispenser are calculated by coordinate transformation. Based on the characters of the flow resistance in a cone aperture, it is found that the dynamic cone angle results from periodical changes of the volume of the micro-tapered aperture of the atomizer and this change drives one-way flows. Besides, an experimental atomization platform is established to measure the atomization rates with different resonance frequencies of the cone aperture atomizer. The atomization performances of cone aperture and straight aperture atomizers are also measured. The experimental results show the existence of the pumping effect of the dynamic tapered angle. This effect is usually observed in industries that require low dispersion and micro- and nanoscale grain sizes, such as during production of high-pressure nozzles and inhalation therapy. Strategies to minimize the pumping effect of the dynamic cone angle or improve future designs are important concerns. This research proposes that dynamic micro-tapered angle is an important cause of atomization of the atomizer with micro cone apertures.

Multi-tube fuel nozzle with mixing features

DOEpatents

Hughes, Michael John

2014-04-22

A system includes a multi-tube fuel nozzle having an inlet plate and a plurality of tubes adjacent the inlet plate. The inlet plate includes a plurality of apertures, and each aperture includes an inlet feature. Each tube of the plurality of tubes is coupled to an aperture of the plurality of apertures. The multi-tube fuel nozzle includes a differential configuration of inlet features among the plurality of tubes.

Comprehensive Fractal Description of Porosity of Coal of Different Ranks

PubMed Central

Ren, Jiangang; Zhang, Guocheng; Song, Zhimin; Liu, Gaofeng; Li, Bing

2014-01-01

We selected, as the objects of our research, lignite from the Beizao Mine, gas coal from the Caiyuan Mine, coking coal from the Xiqu Mine, and anthracite from the Guhanshan Mine. We used the mercury intrusion method and the low-temperature liquid nitrogen adsorption method to analyze the structure and shape of the coal pores and calculated the fractal dimensions of different aperture segments in the coal. The experimental results show that the fractal dimension of the aperture segment of lignite, gas coal, and coking coal with an aperture of greater than or equal to 10 nm, as well as the fractal dimension of the aperture segment of anthracite with an aperture of greater than or equal to 100 nm, can be calculated using the mercury intrusion method; the fractal dimension of the coal pore, with an aperture range between 2.03 nm and 361.14 nm, can be calculated using the liquid nitrogen adsorption method, of which the fractal dimensions bounded by apertures of 10 nm and 100 nm are different. Based on these findings, we defined and calculated the comprehensive fractal dimensions of the coal pores and achieved the unity of fractal dimensions for full apertures of coal pores, thereby facilitating, overall characterization for the heterogeneity of the coal pore structure. PMID:24955407

Single-frequency 3D synthetic aperture imaging with dynamic metasurface antennas.

PubMed

Boyarsky, Michael; Sleasman, Timothy; Pulido-Mancera, Laura; Diebold, Aaron V; Imani, Mohammadreza F; Smith, David R

2018-05-20

Through aperture synthesis, an electrically small antenna can be used to form a high-resolution imaging system capable of reconstructing three-dimensional (3D) scenes. However, the large spectral bandwidth typically required in synthetic aperture radar systems to resolve objects in range often requires costly and complex RF components. We present here an alternative approach based on a hybrid imaging system that combines a dynamically reconfigurable aperture with synthetic aperture techniques, demonstrating the capability to resolve objects in three dimensions (3D), with measurements taken at a single frequency. At the core of our imaging system are two metasurface apertures, both of which consist of a linear array of metamaterial irises that couple to a common waveguide feed. Each metamaterial iris has integrated within it a diode that can be biased so as to switch the element on (radiating) or off (non-radiating), such that the metasurface antenna can produce distinct radiation profiles corresponding to different on/off patterns of the metamaterial element array. The electrically large size of the metasurface apertures enables resolution in range and one cross-range dimension, while aperture synthesis provides resolution in the other cross-range dimension. The demonstrated imaging capabilities of this system represent a step forward in the development of low-cost, high-performance 3D microwave imaging systems.

Simultaneous displacement and slope measurement in electronic speckle pattern interferometry using adjustable aperture multiplexing.

PubMed

Lu, Min; Wang, Shengjia; Aulbach, Laura; Koch, Alexander W

2016-08-01

This paper suggests the use of adjustable aperture multiplexing (AAM), a method which is able to introduce multiple tunable carrier frequencies into a three-beam electronic speckle pattern interferometer to measure the out-of-plane displacement and its first-order derivative simultaneously. In the optical arrangement, two single apertures are located in the object and reference light paths, respectively. In cooperation with two adjustable mirrors, virtual images of the single apertures construct three pairs of virtual double apertures with variable aperture opening sizes and aperture distances. By setting the aperture parameter properly, three tunable spatial carrier frequencies are produced within the speckle pattern and completely separate the information of three interferograms in the frequency domain. By applying the inverse Fourier transform to a selected spectrum, its corresponding phase difference distribution can thus be evaluated. Therefore, we can obtain the phase map due to the deformation as well as its slope of the test surface from two speckle patterns which are recorded at different loading events. By this means, simultaneous and dynamic measurements are realized. AAM has greatly simplified the measurement system, which contributes to improving the system stability and increasing the system flexibility and adaptability to various measurement requirements. This paper presents the AAM working principle, the phase retrieval using spatial carrier frequency, and preliminary experimental results.

Shaped Apertures in Photoresist Films Enhance the Lifetime and Mechanical Stability of Suspended Lipid Bilayers

PubMed Central

Kalsi, Sumit; Powl, Andrew M.; Wallace, B.A.; Morgan, Hywel; de Planque, Maurits R.R.

2014-01-01

Planar lipid bilayers suspended in apertures provide a controlled environment for ion channel studies. However, short lifetimes and poor mechanical stability of suspended bilayers limit the experimental throughput of bilayer electrophysiology experiments. Although bilayers are more stable in smaller apertures, ion channel incorporation through vesicle fusion with the suspended bilayer becomes increasingly difficult. In an alternative bilayer stabilization approach, we have developed shaped apertures in SU8 photoresist that have tapered sidewalls and a minimum diameter between 60 and 100 μm. Bilayers formed at the thin tip of these shaped apertures, either with the painting or the folding method, display drastically increased lifetimes, typically >20 h, and mechanical stability, being able to withstand extensive perturbation of the buffer solution. Single-channel electrical recordings of the peptide alamethicin and of the proteoliposome-delivered potassium channel KcsA demonstrate channel conductance with low noise, made possible by the small capacitance of the 50 μm thick SU8 septum, which is only thinned around the aperture, and unimpeded proteoliposome fusion, enabled by the large aperture diameter. We anticipate that these shaped apertures with micrometer edge thickness can substantially enhance the throughput of channel characterization by bilayer lipid membrane electrophysiology, especially in combination with automated parallel bilayer platforms. PMID:24739164

Design quadrilateral apertures in binary computer-generated holograms of large space bandwidth product.

PubMed

Wang, Jing; Sheng, Yunlong

2016-09-20

A new approach for designing the binary computer-generated hologram (CGH) of a very large number of pixels is proposed. Diffraction of the CGH apertures is computed by the analytical Abbe transform and by considering the aperture edges as the basic diffracting elements. The computation cost is independent of the CGH size. The arbitrary-shaped polygonal apertures in the CGH consist of quadrilateral apertures, which are designed by assigning the binary phases using the parallel genetic algorithm with a local search, followed by optimizing the locations of the co-vertices with a direct search. The design results in high performance with low image reconstruction error.

Method for correcting imperfections on a surface

DOEpatents

Sweatt, William C.; Weed, John W.

1999-09-07

A process for producing near perfect optical surfaces. A previously polished optical surface is measured to determine its deviations from the desired perfect surface. A multi-aperture mask is designed based on this measurement and fabricated such that deposition through the mask will correct the deviations in the surface to an acceptable level. Various mask geometries can be used: variable individual aperture sizes using a fixed grid for the apertures or fixed aperture sizes using a variable aperture spacing. The imperfections are filled in using a vacuum deposition process with a very thin thickness of material such as silicon monoxide to produce an amorphous surface that bonds well to a glass substrate.

Broadband light funneling in ultrasubwavelength channels having periodic connected unfilled apertures

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

Subramania, Ganapathi Subramanian; Brener, Igal; Foteinopoulou, Stavroula

2017-08-01

A structure for broadband light funneling comprises a two-dimensional periodic array of connected ultrasubwavelength apertures, each aperture comprising a large sub-aperture that aids in the coupling of the incoming incident light and a small sub-aperture that funnels a significant fraction of the incident light power. The structure possesses all the capabilities of prior extraordinary optical transmission platforms, yet operates nonresonantly on a distinctly different mechanism. The structure demonstrates efficient ultrabroadband funneling of optical power confined in an area as small as .about.(.lamda./500).sup.2, where optical fields are enhanced, thus exhibiting functional possibilities beyond resonant platforms.

Ion mobility spectrometer with virtual aperture grid

DOEpatents

Pfeifer, Kent B.; Rumpf, Arthur N.

2010-11-23

An ion mobility spectrometer does not require a physical aperture grid to prevent premature ion detector response. The last electrodes adjacent to the ion collector (typically the last four or five) have an electrode pitch that is less than the width of the ion swarm and each of the adjacent electrodes is connected to a source of free charge, thereby providing a virtual aperture grid at the end of the drift region that shields the ion collector from the mirror current of the approaching ion swarm. The virtual aperture grid is less complex in assembly and function and is less sensitive to vibrations than the physical aperture grid.

Transverse mode selection in vertical-cavity surface-emitting lasers via deep impurity-induced disordering

NASA Astrophysics Data System (ADS)

O'Brien, Thomas R.; Kesler, Benjamin; Dallesasse, John M.

2017-02-01

Top emission 850-nm vertical-cavity surface-emitting lasers (VCSELs) demonstrating transverse mode selection via impurity-induced disordering (IID) are presented. The IID apertures are fabricated via closed ampoule zinc diffusion. A simple 1-D plane wave model based on the intermixing of Group III atoms during IID is presented to optimize the mirror loss of higher-order modes as a function of IID strength and depth. In addition, the impact of impurity diffusion into the cap layer of the lasers is shown to improve contact resistance. Further investigation of the mode-dependent characteristics of the device imply an increase in the thermal impedance associated with the fraction of IID contained within the oxide aperture. The optimization of the ratio of the IID aperture to oxide aperture is experimentally determined. Single fundamental mode output of 1.6 mW with 30 dBm side mode suppression ratio is achieved by a 3.0 μm oxide-confined device with an IID aperture of 1.3 μm indicating an optimal IID aperture size of 43% of the oxide aperture.

A neural network simulating human reach-grasp coordination by continuous updating of vector positioning commands.

PubMed

Ulloa, Antonio; Bullock, Daniel

2003-10-01

We developed a neural network model to simulate temporal coordination of human reaching and grasping under variable initial grip apertures and perturbations of object size and object location/orientation. The proposed model computes reach-grasp trajectories by continuously updating vector positioning commands. The model hypotheses are (1) hand/wrist transport, grip aperture, and hand orientation control modules are coupled by a gating signal that fosters synchronous completion of the three sub-goals. (2) Coupling from transport and orientation velocities to aperture control causes maximum grip apertures that scale with these velocities and exceed object size. (3) Part of the aperture trajectory is attributable to an aperture-reducing passive biomechanical effect that is stronger for larger apertures. (4) Discrepancies between internal representations of targets partially inhibit the gating signal, leading to movement time increases that compensate for perturbations. Simulations of the model replicate key features of human reach-grasp kinematics observed under three experimental protocols. Our results indicate that no precomputation of component movement times is necessary for online temporal coordination of the components of reaching and grasping.

Probability density of aperture-averaged irradiance fluctuations for long range free space optical communication links.

PubMed

Lyke, Stephen D; Voelz, David G; Roggemann, Michael C

2009-11-20

The probability density function (PDF) of aperture-averaged irradiance fluctuations is calculated from wave-optics simulations of a laser after propagating through atmospheric turbulence to investigate the evolution of the distribution as the aperture diameter is increased. The simulation data distribution is compared to theoretical gamma-gamma and lognormal PDF models under a variety of scintillation regimes from weak to strong. Results show that under weak scintillation conditions both the gamma-gamma and lognormal PDF models provide a good fit to the simulation data for all aperture sizes studied. Our results indicate that in moderate scintillation the gamma-gamma PDF provides a better fit to the simulation data than the lognormal PDF for all aperture sizes studied. In the strong scintillation regime, the simulation data distribution is gamma gamma for aperture sizes much smaller than the coherence radius rho0 and lognormal for aperture sizes on the order of rho0 and larger. Examples of how these results affect the bit-error rate of an on-off keyed free space optical communication link are presented.

Dual-band plasmonic resonator based on Jerusalem cross-shaped nanoapertures

NASA Astrophysics Data System (ADS)

Cetin, Arif E.; Kaya, Sabri; Mertiri, Alket; Aslan, Ekin; Erramilli, Shyamsunder; Altug, Hatice; Turkmen, Mustafa

2015-06-01

In this paper, we both experimentally and numerically introduce a dual-resonant metamaterial based on subwavelength Jerusalem cross-shaped apertures. We numerically investigate the physical origin of the dual-resonant behavior, originating from the constituting aperture elements, through finite difference time domain calculations. Our numerical calculations show that at the dual-resonances, the aperture system supports large and easily accessible local electromagnetic fields. In order to experimentally realize the aperture system, we utilize a high-precision and lift-off free fabrication method based on electron-beam lithography. We also introduce a fine-tuning mechanism for controlling the dual-resonant spectral response through geometrical device parameters. Finally, we show the aperture system's highly advantageous far- and near-field characteristics through numerical calculations on refractive index sensitivity. The quantitative analyses on the availability of the local fields supported by the aperture system are employed to explain the grounds behind the sensitivity of each spectral feature within the dual-resonant behavior. Possessing dual-resonances with large and accessible electromagnetic fields, Jerusalem cross-shaped apertures can be highly advantageous for wide range of applications demanding multiple spectral features with strong nearfield characteristics.

A simplified model to evaluate the effect of fluid rheology on non-Newtonian flow in variable aperture fractures

NASA Astrophysics Data System (ADS)

Felisa, Giada; Ciriello, Valentina; Longo, Sandro; Di Federico, Vittorio

2017-04-01

Modeling of non-Newtonian flow in fractured media is essential in hydraulic fracturing operations, largely used for optimal exploitation of oil, gas and thermal reservoirs. Complex fluids interact with pre-existing rock fractures also during drilling operations, enhanced oil recovery, environmental remediation, and other natural phenomena such as magma and sand intrusions, and mud volcanoes. A first step in the modeling effort is a detailed understanding of flow in a single fracture, as the fracture aperture is typically spatially variable. A large bibliography exists on Newtonian flow in single, variable aperture fractures. Ultimately, stochastic modeling of aperture variability at the single fracture scale leads to determination of the flowrate under a given pressure gradient as a function of the parameters describing the variability of the aperture field and the fluid rheological behaviour. From the flowrate, a flow, or 'hydraulic', aperture can then be derived. The equivalent flow aperture for non-Newtonian fluids of power-law nature in single, variable aperture fractures has been obtained in the past both for deterministic and stochastic variations. Detailed numerical modeling of power-law fluid flow in a variable aperture fracture demonstrated that pronounced channelization effects are associated to a nonlinear fluid rheology. The availability of an equivalent flow aperture as a function of the parameters describing the fluid rheology and the aperture variability is enticing, as it allows taking their interaction into account when modeling flow in fracture networks at a larger scale. A relevant issue in non-Newtonian fracture flow is the rheological nature of the fluid. The constitutive model routinely used for hydro-fracturing modeling is the simple, two-parameter power-law. Yet this model does not characterize real fluids at low and high shear rates, as it implies, for shear-thinning fluids, an apparent viscosity which becomes unbounded for zero shear rate and tends to zero for infinite shear rate. On the contrary, the four-parameter Carreau constitutive equation includes asymptotic values of the apparent viscosity at those limits; in turn, the Carreau rheological equation is well approximated by the more tractable truncated power-law model. Results for flow of such fluids between parallel walls are already available. This study extends the adoption of the truncated power-law model to variable aperture fractures, with the aim of understanding the joint influence of rheology and aperture spatial variability. The aperture variation, modeled within a stochastic or deterministic framework, is taken to be one-dimensional and perpendicular to the flow direction; for stochastic modeling, the influence of different distribution functions is examined. Results are then compared with those obtained for pure power-law fluids for different combinations of model parameters. It is seen that the adoption of the pure power law model leads to significant overestimation of the flowrate with respect to the truncated model, more so for large external pressure gradient and/or aperture variability.

The in vivo response to a novel Ti coating compared with polyether ether ketone: evaluation of the periphery and inner surfaces of an implant.

PubMed

Walsh, William Robert; Pelletier, Matthew H; Christou, Chris; He, Jiawei; Vizesi, Frank; Boden, Scott D

2018-02-26

Increasing bone ongrowth and ingrowth of polyether ether ketone (PEEK) interbody fusion devices has the potential to improve clinical outcomes. This study evaluated the in vivo response of promoting new bone growth and bone apposition with NanoMetalene (NM) compared with PEEK alone in a cancellous implantation site with an empty aperture. This is a randomized control animal study. Implants and funding for this study were provided by SeaSpine (60,000 USD). Cylindrical dowels with two apertures were prepared as PEEK with a sub-micron layer of the titanium (NM). The titanium coating was applied over the entire implant (Group 1) or just the apertures (Group 2). Polyether ether ketone implants with no coating served as controls (Group 3). Implants were placed in the cancellous bone of the distal femur or proximal tibia with no graft material placed in the apertures in eight adult sheep. Bone ongrowth to the surface of the implant and ingrowth into the apertures was assessed at 4 and 8 weeks after surgery with micro-computed tomography (CT) and undecalcified histology. The apertures in the implants were notably empty in the PEEK group at 4 and 8 weeks. In contrast, new bone formation into the apertures was found in samples coated with NM even though no graft material was placed into the defect. The bone growing into the aperture tracked along the titanium layer. Apertures with the titanium coating demonstrated significantly more bone by micro-CT qualitative grading compared with PEEK with average bone coverage scores of Group 1 (NM) 1.62±0.89, Group 2 (NM apertures only) 1.62±0.77, and Group 3 (PEEK) 0.43±0.51, respectively, at 4 weeks (p<.01) and Group 1 (NM) 1.79±1.19, Group 2 (NM apertures only) 1.98±1.18, and Group 3 (PEEK) 0.69±0.87, respectively, at 8 weeks (p<.05). The amount of bone in the apertures (ingrowth) quantified using the volumetric data from the micro-CT supported an overall increase in bone volume inside the apertures with the titanium coating compared with PEEK. Histology showed newly formed woven bone tracked along the surface of the titanium in the apertures. The PEEK interface presented the typical nonreactive fibrous tissue inside the apertures at 4 weeks and some focal contact with bone on the outside at 4 weeks and 8 weeks. Micro-CT and histology demonstrated bone ongrowth to the surfaces coated with NM where the newly formed bone tracked along the thin titanium-coated surfaces. Polyether ether ketone surfaces presented the nonreactive fibrous tissue at the interface as previously reported in preclinical scenarios. Copyright © 2018. Published by Elsevier Inc.

Diffracted wavefield by an arbitrary aperture from Maggi-Rubinowicz transformation

NASA Astrophysics Data System (ADS)

Ganci, S.

2008-01-01

Fraunhofer diffraction patterns through apertures in opaque screens are the cases of most interest in optics. The major purpose of this paper is to establish a general and explicit formula for calculating diffracted wavefield from Maggi-Rubinowicz transformation. The 2-D integration (Rayleigh-Sommerfeld or Helmholtz-Kirchhoff integral formulas) is reduced to a 1-D integration over the rim of the aperture. Some examples for elliptical and polygonal apertures are given.

Influence of pressure change during hydraulic tests on fracture aperture.

PubMed

Ji, Sung-Hoon; Koh, Yong-Kwon; Kuhlman, Kristopher L; Lee, Moo Yul; Choi, Jong Won

2013-03-01

In a series of field experiments, we evaluate the influence of a small water pressure change on fracture aperture during a hydraulic test. An experimental borehole is instrumented at the Korea Atomic Energy Research Institute (KAERI) Underground Research Tunnel (KURT). The target fracture for testing was found from the analyses of borehole logging and hydraulic tests. A double packer system was developed and installed in the test borehole to directly observe the aperture change due to water pressure change. Using this packer system, both aperture and flow rate are directly observed under various water pressures. Results indicate a slight change in fracture hydraulic head leads to an observable change in aperture. This suggests that aperture change should be considered when analyzing hydraulic test data from a sparsely fractured rock aquifer. © 2012, The Author(s). Groundwater © 2012, National Ground Water Association.

Phase retrieval with the transport-of-intensity equation in an arbitrarily-shaped aperture by iterative discrete cosine transforms

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

Huang, Lei; Zuo, Chao; Idir, Mourad

A novel transport-of-intensity equation (TIE) based phase retrieval method is proposed with putting an arbitrarily-shaped aperture into the optical wavefield. In this arbitrarily-shaped aperture, the TIE can be solved under non-uniform illuminations and even non-homogeneous boundary conditions by iterative discrete cosine transforms with a phase compensation mechanism. Simulation with arbitrary phase, arbitrary aperture shape, and non-uniform intensity distribution verifies the effective compensation and high accuracy of the proposed method. Experiment is also carried out to check the feasibility of the proposed method in real measurement. Comparing to the existing methods, the proposed method is applicable for any types of phasemore » distribution under non-uniform illumination and non-homogeneous boundary conditions within an arbitrarily-shaped aperture, which enables the technique of TIE with hard aperture become a more flexible phase retrieval tool in practical measurements.« less

Phase retrieval with the transport-of-intensity equation in an arbitrarily-shaped aperture by iterative discrete cosine transforms

DOE PAGES

Huang, Lei; Zuo, Chao; Idir, Mourad; ...

2015-04-21

A novel transport-of-intensity equation (TIE) based phase retrieval method is proposed with putting an arbitrarily-shaped aperture into the optical wavefield. In this arbitrarily-shaped aperture, the TIE can be solved under non-uniform illuminations and even non-homogeneous boundary conditions by iterative discrete cosine transforms with a phase compensation mechanism. Simulation with arbitrary phase, arbitrary aperture shape, and non-uniform intensity distribution verifies the effective compensation and high accuracy of the proposed method. Experiment is also carried out to check the feasibility of the proposed method in real measurement. Comparing to the existing methods, the proposed method is applicable for any types of phasemore » distribution under non-uniform illumination and non-homogeneous boundary conditions within an arbitrarily-shaped aperture, which enables the technique of TIE with hard aperture become a more flexible phase retrieval tool in practical measurements.« less

Micro Ring Grating Spectrometer with Adjustable Aperture

NASA Technical Reports Server (NTRS)

Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor); Choi, Sang H. (Inventor)

2012-01-01

A spectrometer includes a micro-ring grating device having coaxially-aligned ring gratings for diffracting incident light onto a target focal point, a detection device for detecting light intensity, one or more actuators, and an adjustable aperture device defining a circular aperture. The aperture circumscribes a target focal point, and directs a light to the detection device. The aperture device is selectively adjustable using the actuators to select a portion of a frequency band for transmission to the detection device. A method of detecting intensity of a selected band of incident light includes directing incident light onto coaxially-aligned ring gratings of a micro-ring grating device, and diffracting the selected band onto a target focal point using the ring gratings. The method includes using an actuator to adjust an aperture device and pass a selected portion of the frequency band to a detection device for measuring the intensity of the selected portion.

Electrostatically clean solar array

NASA Technical Reports Server (NTRS)

Stern, Theodore Garry (Inventor); Krumweide, Duane Eric (Inventor)

2004-01-01

Provided are methods of manufacturing an electrostatically clean solar array panel and the products resulting from the practice of these methods. The preferred method uses an array of solar cells, each with a coverglass where the method includes machining apertures into a flat, electrically conductive sheet so that each aperture is aligned with and undersized with respect to its matched coverglass sheet and thereby fashion a front side shield with apertures (FSA). The undersized portion about each aperture of the bottom side of the FSA shield is bonded to the topside portions nearest the edges of each aperture's matched coverglass. Edge clips are attached to the front side aperture shield edges with the edge clips electrically and mechanically connecting the tops of the coverglasses to the solar panel substrate. The FSA shield, edge clips and substrate edges are bonded so as to produce a conductively grounded electrostatically clean solar array panel.

Variable aperture collimator for high energy radiation

DOEpatents

Hill, Ronald A.

1984-05-22

An apparatus is disclosed providing a variable aperture energy beam collimator. A plurality of beam opaque blocks are in sliding interface edge contact to form a variable aperture. The blocks may be offset at the apex angle to provide a non-equilateral aperture. A plurality of collimator block assemblies may be employed for providing a channel defining a collimated beam. Adjacent assemblies are inverted front-to-back with respect to one another for preventing noncollimated energy from emerging from the apparatus. An adjustment mechanism comprises a cable attached to at least one block and a hand wheel mechanism for operating the cable. The blocks are supported by guide rods engaging slide brackets on the blocks. The guide rods are pivotally connected at each end to intermediate actuators supported on rotatable shafts to change the shape of the aperture. A divergent collimated beam may be obtained by adjusting the apertures of adjacent stages to be unequal.

Optical transmission through silver film with compound periodic array of annular apertures

NASA Astrophysics Data System (ADS)

Zhang, Yue; Yao, Wen-jie; Yu, Hong

2015-03-01

Recently, some kinds of structures have been found to show the property of extraordinary optical transmission (EOT). In this paper, we present a novel composite structure based on array of annular apertures (AAA) with compound lattice. The lattice includes two kinds of annular apertures with the same outer radius and different inner radii. The transmission spectrum of this compound periodic AAA can be achieved by adding up the spectra of two corresponding simple periodic AAAs, and the transmission shows EOT property. The transmission peaks of this kind of structure can be adjusted to desire wavelengths by changing the inner radius of aperture or the index of the dielectric material in the aperture. This structure can be used as a filter with dual pass bands when the difference between inner radii or indices of dielectric inside is large enough for two kinds of apertures.

Beam Combination for Stellar Imager and its Application to Full-Aperture Imaging

NASA Technical Reports Server (NTRS)

Mozurkewich, D.; Carpenter, K. G.; Lyon, R. G.

2007-01-01

Stellar Imager (SI) will be a Space-Based telescope consisting of 20 to 30 separated apertures. It is designed for UV/Optical imaging of stellar surfaces and asteroseismology. This report describes details of an alternative optical design for the beam combiner, dubbed the Spatial Frequency Remapper (SFR). It sacrifices the large field of view of the Fizeau combiner. In return, spectral resolution is obtained with a diffraction grating rather than an array of energy-resolving detectors. The SFR design works in principle and has been implemented with MIRC at CHARA for a small number of apertures. Here, we show the number of optical surfaces can be reduced and the concept scales gracefully to the large number of apertures needed for Stellar Imager. We also describe a potential application of this spatial frequency remapping to improved imaging with filled aperture systems. For filled-aperture imaging, the SFR becomes the core of an improved aperture masking system. To date, aperture-masking has produced the best images with ground-based telescopes but at the expense of low sensitivity due to short exposures and discarding most of the light collected by the telescope. This design eliminates the light-loss problem previously claimed to be inherent in all aperture-masking designs. We also argue that at least in principle, the short-integration time limit can also be overcome. With these improvements, it becomes an ideal camera for TPF-C; since it can form speckle-free images in the presence of wavefront errors, it should significantly relax the stability requirements of the current designs.

Maximizing the potential of direct aperture optimization through collimator rotation

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

Milette, Marie-Pierre; Otto, Karl; Medical Physics, BC Cancer Agency-Vancouver Centre, Vancouver, British Columbia

Intensity-modulated radiation therapy (IMRT) treatment plans are conventionally produced by the optimization of fluence maps followed by a leaf sequencing step. An alternative to fluence based inverse planning is to optimize directly the leaf positions and field weights of multileaf collimator (MLC) apertures. This approach is typically referred to as direct aperture optimization (DAO). It has been shown that equivalent dose distributions may be generated that have substantially fewer monitor units (MU) and number of apertures compared to fluence based optimization techniques. Here we introduce a DAO technique with rotated apertures that we call rotating aperture optimization (RAO). The advantagesmore » of collimator rotation in IMRT have been shown previously and include higher fluence spatial resolution, increased flexibility in the generation of aperture shapes and less interleaf effects. We have tested our RAO algorithm on a complex C-shaped target, seven nasopharynx cancer recurrences, and one multitarget nasopharynx carcinoma patient. A study was performed in order to assess the capabilities of RAO as compared to fixed collimator angle DAO. The accuracy of fixed and rotated collimator aperture delivery was also verified. An analysis of the optimized treatment plans indicates that plans generated with RAO are as good as or better than DAO while maintaining a smaller number of apertures and MU than fluence based IMRT. Delivery verification results show that RAO is less sensitive to tongue and groove effects than DAO. Delivery time is currently increased due to the collimator rotation speed although this is a mechanical limitation that can be eliminated in the future.« less

Near-Field Scanning Optical Microscopy and Raman Microscopy.

NASA Astrophysics Data System (ADS)

Harootunian, Alec Tate

1987-09-01

Both a one dimensional near-field scanning optical microscope and Raman microprobe were constructed. In near -field scanning optical microscopy (NSOM) a subwavelength aperture is scanned in the near-field of the object. Radiation transmitted through the aperture is collected to form an image as the aperture scans over the object. The resolution of an NSOM system is essentially wavelength independent and is limited by the diameter of the aperture used to scan the object. NSOM was developed in an effort to provide a nondestructive in situ high spatial resolution probe while still utilizing photons at optical wavelengths. The Raman microprobe constructed provided vibrational Raman information with spatial resolution equivalent that of a conventional diffraction limited microscope. Both transmission studies and near-field diffration studies of subwavelength apertures were performed. Diffraction theories for a small aperture in an infinitely thin conducting screen, a slit in a thick conducting screen, and an aperture in a black screen were examined. All three theories indicate collimation of radiation to the size to the size of the subwavelength aperture or slit in the near-field. Theoretical calculations and experimental results indicate that light transmitted through subwavelength apertures is readily detectable. Light of wavelength 4579 (ANGSTROM) was transmitted through apertures with diameters as small as 300 (ANGSTROM). These studies indicate the feasibility of constructing an NSOM system. One dimensional transmission and fluorescence NSOM systems were constructed. Apertures in the tips of metallized glass pipettes width inner diameters of less than 1000 (ANGSTROM) were used as a light source in the NSOM system. A tunneling current was used to maintain the aperture position in the near-field. Fluorescence NSOM was demonstrated for the first time. Microspectroscopic and Raman microscopic studies of turtle cone oil droplets were performed. Both the Raman vibrational frequencies and the Raman excitation data indicate that the carotenoids are unaggregated. The carotenoid astaxanthin was identified in the orange and red droplets by Raman microscopy. Future applications for both Raman microscopy and near-field microscopy were proposed. Four methods of near-field distance regulation were also examined. Finally, theoretical exposure curves for near-field lithography were calculated. Both the near-field lithographic results and the near field diffraction studies indicate essentially wavelength independent resolution. (Abstract shortened with permission of author.).

Growth Of Organic Semiconductor Thin Films with Multi-Micron Domain Size and Fabrication of Organic Transistors Using a Stencil Nanosieve.

PubMed

Fesenko, Pavlo; Flauraud, Valentin; Xie, Shenqi; Kang, Enpu; Uemura, Takafumi; Brugger, Jürgen; Genoe, Jan; Heremans, Paul; Rolin, Cédric

2017-07-19

To grow small molecule semiconductor thin films with domain size larger than modern-day device sizes, we evaporate the material through a dense array of small apertures, called a stencil nanosieve. The aperture size of 0.5 μm results in low nucleation density, whereas the aperture-to-aperture distance of 0.5 μm provides sufficient crosstalk between neighboring apertures through the diffusion of adsorbed molecules. By integrating the nanosieve in the channel area of a thin-film transistor mask, we show a route for patterning both the organic semiconductor and the metal contacts of thin-film transistors using one mask only and without mask realignment.

Low-Cost Large Aperture Telescopes for Optical Communications

NASA Technical Reports Server (NTRS)

Hemmati, Hamid

2006-01-01

Low-cost, 0.5-1 meter ground apertures are required for near-Earth laser communications. Low-cost ground apertures with equivalent diameters greater than 10 meters are desired for deep-space communications. This presentation focuses on identifying schemes to lower the cost of constructing networks of large apertures while continuing to meet the requirements for laser communications. The primary emphasis here is on the primary mirror. A slumped glass spherical mirror, along with passive secondary mirror corrector and active adaptive optic corrector show promise as a low-cost alternative to large diameter monolithic apertures. To verify the technical performance and cost estimate, development of a 1.5-meter telescope equipped with gimbal and dome is underway.

Shock wave absorber having apertured plate

DOEpatents

Shin, Y.W.; Wiedermann, A.H.; Ockert, C.E.

1983-08-26

The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

Effect of turbulence on the beam quality of apertured partially coherent beams.

PubMed

Ji, Xiaoling; Ji, Guangming

2008-06-01

The effects of turbulence on the beam quality of apertured partially coherent beams have been studied both analytically and numerically. Taking the Gaussian Schell-model (GSM) beam as a typical example of partially coherent beams, closed-form expressions for the average intensity, mean-squared beam width, power in the bucket, beta parameter, and Strehl ratio of apertured partially coherent beams propagating through atmospheric turbulence are derived. It is shown that the smaller the beam truncation parameter is, the less affected by turbulence the apertured partially coherent beams are. Furthermore, the apertured partially coherent beams are less sensitive to the effects of turbulence than unapertured ones. The main results are interpreted physically.

Apparatus and method for deterministic control of surface figure during full aperture polishing

DOEpatents

Suratwala, Tayyab Ishaq; Feit, Michael Dennis; Steele, William Augustus

2013-11-19

A polishing system configured to polish a lap includes a lap configured to contact a workpiece for polishing the workpiece; and a septum configured to contact the lap. The septum has an aperture formed therein. The radius of the aperture and radius the workpiece are substantially the same. The aperture and the workpiece have centers disposed at substantially the same radial distance from a center of the lap. The aperture is disposed along a first radial direction from the center of the lap, and the workpiece is disposed along a second radial direction from the center of the lap. The first and second radial directions may be opposite directions.

Shock wave absorber having apertured plate

DOEpatents

Shin, Yong W.; Wiedermann, Arne H.; Ockert, Carl E.

1985-01-01

The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

Synthetic aperture radar range - Azimuth ambiguity design and constraints

NASA Technical Reports Server (NTRS)

Mehlis, J. G.

1980-01-01

Problems concerning the design of a system for mapping a planetary surface with a synthetic aperture radar (SAR) are considered. Given an ambiguity level, resolution, and swath width, the problems are related to the determination of optimum antenna apertures and the most suitable pulse repetition frequency (PRF). From the set of normalized azimuth ambiguity ratio curves, the designer can arrive at the azimuth antenna length, and from the sets of normalized range ambiguity ratio curves, he can arrive at the range aperture length or pulse repetition frequency. A procedure based on this design method is shown in an example. The normalized curves provide results for a SAR using a uniformly or cosine weighted rectangular antenna aperture.

Propagation of Bessel-Gaussian beams through a double-apertured fractional Fourier transform optical system.

PubMed

Tang, Bin; Jiang, Chun; Zhu, Haibin

2012-08-01

Based on the scalar diffraction theory and the fact that a hard-edged aperture function can be expanded into a finite sum of complex Gaussian functions, an approximate analytical solution for Bessel-Gaussian (BG) beams propagating through a double-apertured fractional Fourier transform (FrFT) system is derived in the cylindrical coordinate. By using the approximate analytical formulas, the propagation properties of BG beams passing through a double-apertured FrFT optical system have been studied in detail by some typical numerical examples. The results indicate that the double-apertured FrFT optical system provides a convenient way for controlling the properties of the BG beams by properly choosing the optical parameters.

High-contrast terahertz modulator based on extraordinary transmission through a ring aperture.

PubMed

Shu, Jie; Qiu, Ciyuan; Astley, Victoria; Nickel, Daniel; Mittleman, Daniel M; Xu, Qianfan

2011-12-19

We demonstrated extraordinary THz transmission through ring apertures on a metal film. Transmission of 60% was obtained with an aperture-to-area ratio of only 1.4%. We show that the high transmission can be suppressed by over 18 dB with a thin layer of free carriers in the silicon substrate underneath the metal film. This result suggests that CMOS-compatible terahertz modulators can be built by controlling the carrier density near the aperture.

Experimental investigations of 3 mm aperture PPLN structures

NASA Astrophysics Data System (ADS)

Kolker, D.; Pronyushkina, A.; Boyko, A.; Kostyukova, N.; Trashkeev, S.; Nuyshkov, B.; Shur, V.

2017-01-01

We are reporting about investigation of domestic 3 mm aperture periodically polled lithium niobate (PPLN) structures for cascaded mid-IR OPO. Wide aperture periodically poled MgO-doped lithium niobate (LiNbO3) structures at multigrating, fan-out and multi fan-out configuration were prepared at “Labfer LTD”. Laser source based on such structures can be used for special applications. Four different PPLN structures were investigated and effective aperture for effective pumping was defined.

New approach for extraordinary transmission through an array of subwavelength apertures using thin ENNZ metamaterial liners.

PubMed

Baladi, Elham; Pollock, Justin G; Iyer, Ashwin K

2015-08-10

Extraordinary transmission (ET) through a periodic array of subwavelength apertures on a perfect metallic screen has been studied extensively in recent years, and has largely been attributed to diffraction effects, for which the periodicity of the apertures, rather than their dimensions, dominates the response. The transmission properties of the apertures at resonance, on the other hand, are not typically considered 'extraordinary' because they may be explained using more conventional aperture-theoretical mechanisms. This work describes a novel approach for achieving ET in which subwavelength apertures are made to resonate by lining them using thin, epsilon-negative and near-zero (ENNZ) metamaterials. The use of ENNZ metamaterials has recently proven successful in miniaturizing circular waveguides by strongly reducing their natural cutoff frequencies, and the theory is adapted here for the design of subwavelength apertures in a metallic screen. We present simulations and proof-of-concept measurements at microwave frequencies that demonstrate ET for apertures measuring one-quarter of a wavelength in diameter and suggest the potential for even more dramatic miniaturization simply by engineering the ENNZ metamaterial dispersion. The results exhibit a fano-like profile whose frequency varies with the properties of the metamaterial liner, but is independent of period. It is suggested that similar behaviour can be obtained at optical frequencies, where ENNZ metamaterials may be realized using appropriately arranged chains of plasmonic nanoparticles.

A Computational Model for Aperture Control in Reach-to-Grasp Movement Based on Predictive Variability

PubMed Central

Takemura, Naohiro; Fukui, Takao; Inui, Toshio

2015-01-01

In human reach-to-grasp movement, visual occlusion of a target object leads to a larger peak grip aperture compared to conditions where online vision is available. However, no previous computational and neural network models for reach-to-grasp movement explain the mechanism of this effect. We simulated the effect of online vision on the reach-to-grasp movement by proposing a computational control model based on the hypothesis that the grip aperture is controlled to compensate for both motor variability and sensory uncertainty. In this model, the aperture is formed to achieve a target aperture size that is sufficiently large to accommodate the actual target; it also includes a margin to ensure proper grasping despite sensory and motor variability. To this end, the model considers: (i) the variability of the grip aperture, which is predicted by the Kalman filter, and (ii) the uncertainty of the object size, which is affected by visual noise. Using this model, we simulated experiments in which the effect of the duration of visual occlusion was investigated. The simulation replicated the experimental result wherein the peak grip aperture increased when the target object was occluded, especially in the early phase of the movement. Both predicted motor variability and sensory uncertainty play important roles in the online visuomotor process responsible for grip aperture control. PMID:26696874

Eyeglass: A Very Large Aperture Diffractive Space Telescope

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

Hyde, R; Dixit, S; Weisberg, A

2002-07-29

Eyeglass is a very large aperture (25-100 meter) space telescope consisting of two distinct spacecraft, separated in space by several kilometers. A diffractive lens provides the telescope's large aperture, and a separate, much smaller, space telescope serves as its mobile eyepiece. Use of a transmissive diffractive lens solves two basic problems associated with very large aperture space telescopes; it is inherently fieldable (lightweight and flat, hence packagable and deployable) and virtually eliminates the traditional, very tight, surface shape tolerances faced by reflecting apertures. The potential drawback to use of a diffractive primary (very narrow spectral bandwidth) is eliminated by correctivemore » optics in the telescope's eyepiece. The Eyeglass can provide diffraction-limited imaging with either single-band, multiband, or continuous spectral coverage. Broadband diffractive telescopes have been built at LLNL and have demonstrated diffraction-limited performance over a 40% spectral bandwidth (0.48-0.72 {micro}m). As one approach to package a large aperture for launch, a foldable lens has been built and demonstrated. A 75 cm aperture diffractive lens was constructed from 6 panels of 1 m thick silica; it achieved diffraction-limited performance both before and after folding. This multiple panel, folding lens, approach is currently being scaled-up at LLNL. We are building a 5 meter aperture foldable lens, involving 72 panels of 700 {micro}m thick glass sheets, diffractively patterned to operate as coherent f/50 lens.« less

Transport of Particle Swarms Through Variable Aperture Fractures

NASA Astrophysics Data System (ADS)

Boomsma, E.; Pyrak-Nolte, L. J.

2012-12-01

Particle transport through fractured rock is a key concern with the increased use of micro- and nano-size particles in consumer products as well as from other activities in the sub- and near surface (e.g. mining, industrial waste, hydraulic fracturing, etc.). While particle transport is often studied as the transport of emulsions or dispersions, particles may also enter the subsurface from leaks or seepage that lead to particle swarms. Swarms are drop-like collections of millions of colloidal-sized particles that exhibit a number of unique characteristics when compared to dispersions and emulsions. Any contaminant or engineered particle that forms a swarm can be transported farther, faster, and more cohesively in fractures than would be expected from a traditional dispersion model. In this study, the effects of several variable aperture fractures on colloidal swarm cohesiveness and evolution were studied as a swarm fell under gravity and interacted with the fracture walls. Transparent acrylic was used to fabricate synthetic fracture samples with (1) a uniform aperture, (2) a converging region followed by a uniform region (funnel shaped), (3) a uniform region followed by a diverging region (inverted funnel), and (4) a cast of a an induced fracture from a carbonate rock. All of the samples consisted of two blocks that measured 100 x 100 x 50 mm. The minimum separation between these blocks determined the nominal aperture (0.5 mm to 20 mm). During experiments a fracture was fully submerged in water and swarms were released into it. The swarms consisted of a dilute suspension of 3 micron polystyrene fluorescent beads (1% by mass) with an initial volume of 5μL. The swarms were illuminated with a green (525 nm) LED array and imaged optically with a CCD camera. The variation in fracture aperture controlled swarm behavior. Diverging apertures caused a sudden loss of confinement that resulted in a rapid change in the swarm's shape as well as a sharp increase in its velocity. Converging apertures caused swarms to decelerate rapidly and become trapped in the transition point between the converging and parallel regions for apertures less than 2.5 mm. In uniform aperture fractures, an optimal aperture range (5 mm to 15 mm) exists where swarm velocity was higher and the swarm maintained cohesion over a longer distance. For apertures below this range the swarms were strongly slowed due to drag from the wall, while for larger apertures the swarm velocity approached an asymptote due to the loss of the walls influence. The transport of particle swarms in fractures is strongly controlled by aperture distribution. While drag from the fracture does slow swarms, especially at small apertures, much of the interesting behavior (shape changes in diverging fracture, optimal aperture in parallel fracture) is best explained by fracture induced preferential confinement that controls the evolution of the swarm. When this confinement is suddenly changed, the swarm responds quickly and dramatically to its new environment. This has important implications for the understanding of contaminant dispersal in subsurface fracture networks because the type of aperture variation can exert a strong influence on particle swarm transport. Acknowledgment: The authors wish to acknowledge support of this work by the Geosciences Research Program, Office of Basic Energy Sciences US Department of Energy (DE-FG02-09ER16022).

Obstacle traversal and route choice in flying honeybees: Evidence for individual handedness

PubMed Central

Ong, Marielle; Bulmer, Michael; Groening, Julia

2017-01-01

Flying insects constantly face the challenge of choosing efficient, safe and collision-free routes while navigating through dense foliage. We examined the route-choice behavior of foraging honeybees when they encountered a barrier which could be traversed by flying through one of two apertures, positioned side by side. When the bees’ choice behavior was averaged over the entire tested population, the two apertures were chosen with equal frequency when they were equally wide. When the apertures were of different width, the bees, on average, showed a preference for the wider aperture, which increased sharply with the difference between the aperture widths. Thus, bees are able to discriminate the widths of oncoming gaps and choose the passage which is presumably safer and quicker to transit. Examination of the behavior of individual bees revealed that, when the two apertures were equally wide, ca. 55% of the bees displayed no side bias in their choices. However, the remaining 45% showed varying degrees of bias, with one half of them preferring the left-hand aperture, and the other half the right-hand aperture. The existence of distinct individual biases was confirmed by measuring the times required by biased bees to transit various aperture configurations: The transit time was longer if a bee’s intrinsic bias forced it to engage with the narrower aperture. Our results show that, at the population level, bees do not exhibit ‘handedness’ in choosing routes; however, individual bees display an idiosyncratic bias that can range from a strong left bias, through zero bias, to a strong right bias. In honeybees, previous studies of olfactory and visual learning have demonstrated clear biases at the population level. To our knowledge, our study is the first to uncover the existence of individually distinct biases in honeybees. We also show how a distribution of biases among individual honeybees can be advantageous in facilitating rapid transit of a group of bees through a cluttered environment, without any centralized decision-making or control. PMID:29095830

SU-F-T-142: An Analytical Model to Correct the Aperture Scattered Dose in Clinical Proton Beams

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

Sun, B; Liu, S; Zhang, T

2016-06-15

Purpose: Apertures or collimators are used to laterally shape proton beams in double scattering (DS) delivery and to sharpen the penumbra in pencil beam (PB) delivery. However, aperture-scattered dose is not included in the current dose calculations of treatment planning system (TPS). The purpose of this study is to provide a method to correct the aperture-scattered dose based on an analytical model. Methods: A DS beam with a non-divergent aperture was delivered using a single-room proton machine. Dose profiles were measured with an ion-chamber scanning in water and a 2-D ion chamber matrix with solid-water buildup at various depths. Themore » measured doses were considered as the sum of the non-contaminated dose and the aperture-scattered dose. The non-contaminated dose was calculated by TPS and subtracted from the measured dose. Aperture scattered-dose was modeled as a 1D Gaussian distribution. For 2-D fields, to calculate the scatter-dose from all the edges of aperture, a sum of weighted distance was used in the model based on the distance from calculation point to aperture edge. The gamma index was calculated between the measured and calculated dose with and without scatter correction. Results: For a beam with range of 23 cm and aperture size of 20 cm, the contribution of the scatter horn was ∼8% of the total dose at 4 cm depth and diminished to 0 at 15 cm depth. The amplitude of scatter-dose decreased linearly with the depth increase. The 1D gamma index (2%/2 mm) between the calculated and measured profiles increased from 63% to 98% for 4 cm depth and from 83% to 98% at 13 cm depth. The 2D gamma index (2%/2 mm) at 4 cm depth has improved from 78% to 94%. Conclusion: Using the simple analytical method the discrepancy between the measured and calculated dose has significantly improved.« less

Coded diffraction system in X-ray crystallography using a boolean phase coded aperture approximation

NASA Astrophysics Data System (ADS)

Pinilla, Samuel; Poveda, Juan; Arguello, Henry

2018-03-01

Phase retrieval is a problem present in many applications such as optics, astronomical imaging, computational biology and X-ray crystallography. Recent work has shown that the phase can be better recovered when the acquisition architecture includes a coded aperture, which modulates the signal before diffraction, such that the underlying signal is recovered from coded diffraction patterns. Moreover, this type of modulation effect, before the diffraction operation, can be obtained using a phase coded aperture, just after the sample under study. However, a practical implementation of a phase coded aperture in an X-ray application is not feasible, because it is computationally modeled as a matrix with complex entries which requires changing the phase of the diffracted beams. In fact, changing the phase implies finding a material that allows to deviate the direction of an X-ray beam, which can considerably increase the implementation costs. Hence, this paper describes a low cost coded X-ray diffraction system based on block-unblock coded apertures that enables phase reconstruction. The proposed system approximates the phase coded aperture with a block-unblock coded aperture by using the detour-phase method. Moreover, the SAXS/WAXS X-ray crystallography software was used to simulate the diffraction patterns of a real crystal structure called Rhombic Dodecahedron. Additionally, several simulations were carried out to analyze the performance of block-unblock approximations in recovering the phase, using the simulated diffraction patterns. Furthermore, the quality of the reconstructions was measured in terms of the Peak Signal to Noise Ratio (PSNR). Results show that the performance of the block-unblock phase coded apertures approximation decreases at most 12.5% compared with the phase coded apertures. Moreover, the quality of the reconstructions using the boolean approximations is up to 2.5 dB of PSNR less with respect to the phase coded aperture reconstructions.

Beam aperture modifier design with acoustic metasurfaces

NASA Astrophysics Data System (ADS)

Tang, Weipeng; Ren, Chunyu

2017-10-01

In this paper, we present a design concept of acoustic beam aperture modifier using two metasurface-based planar lenses. By appropriately designing the phase gradient profile along the metasurface, we obtain a class of acoustic convex lenses and concave lenses, which can focus the incoming plane waves and collimate the converging waves, respectively. On the basis of the high converging and diverging capability of these lenses, two kinds of lens combination scheme, including the convex-concave type and convex-convex type, are proposed to tune up the incoming beam aperture as needed. To be specific, the aperture of the acoustic beam can be shrunk or expanded through adjusting the phase gradient of the pair of lenses and the spacing between them. These lenses and the corresponding aperture modifiers are constructed by the stacking ultrathin labyrinthine structures, which are obtained by the geometry optimization procedure and exhibit high transmission coefficient and a full range of phase shift. The simulation results demonstrate the effectiveness of our proposed beam aperture modifiers. Due to the flexibility in aperture controlling and the simplicity in fabrication, the proposed modifiers have promising potential in applications, such as acoustic imaging, nondestructive evaluation, and communication.

CWG - MUTUAL COUPLING PROGRAM FOR CIRCULAR WAVEGUIDE-FED APERTURE ARRAY (IBM PC VERSION)

NASA Technical Reports Server (NTRS)

Bailey, M. C.

1994-01-01

Mutual Coupling Program for Circular Waveguide-fed Aperture Array (CWG) was developed to calculate the electromagnetic interaction between elements of an antenna array of circular apertures with specified aperture field distributions. The field distributions were assumed to be a superposition of the modes which could exist in a circular waveguide. Various external media were included to provide flexibility of use, for example, the flexibility to determine the effects of dielectric covers (i.e., thermal protection system tiles) upon the impedance of aperture type antennas. The impedance and radiation characteristics of planar array antennas depend upon the mutual interaction between all the elements of the array. These interactions are influenced by several parameters (e.g., the array grid geometry, the geometry and excitation of each array element, the medium outside the array, and the internal network feeding the array.) For the class of array antenna whose radiating elements consist of small holes in a flat conducting plate, the electromagnetic problem can be divided into two parts, the internal and the external. In solving the external problem for an array of circular apertures, CWG will compute the mutual interaction between various combinations of circular modal distributions and apertures. CWG computes the mutual coupling between various modes assumed to exist in circular apertures that are located in a flat conducting plane of infinite dimensions. The apertures can radiate into free space, a homogeneous medium, a multilayered region or a reflecting surface. These apertures are assumed to be excited by one or more modes corresponding to the modal distributions in circular waveguides of the same cross sections as the apertures. The apertures may be of different sizes and also of different polarizations. However, the program assumes that each aperture field contains the same modal distributions, and calculates the complex scattering matrix between all mode and aperture combinations. The scattering matrix can then be used to determine the complex modal field amplitudes for each aperture with a specified array excitation. CWG is written in VAX FORTRAN for DEC VAX series computers running VMS (LAR-15236) and IBM PC series and compatible computers running MS-DOS (LAR-15226). It requires 360K of RAM for execution. To compile the source code for the PC version, the NDP Fortran compiler and linker will be required; however, the distribution medium for the PC version of CWG includes a sample MS-DOS executable which was created using NDP Fortran with the -vms compiler option. The standard distribution medium for the PC version of CWG is a 3.5 inch 1.44Mb MS-DOS format diskette. The standard distribution medium for the VAX version of CWG is a 1600 BPI 9track magnetic tape in DEC VAX BACKUP format. The VAX version is also available on a TK50 tape cartridge in DEC VAX BACKUP format. Both machine versions of CWG include an electronic version of the documentation in Microsoft Word for Windows format. CWG was developed in 1993 and is a copyrighted work with all copyright vested in NASA.

CWG - MUTUAL COUPLING PROGRAM FOR CIRCULAR WAVEGUIDE-FED APERTURE ARRAY (VAX VMS VERSION)

NASA Technical Reports Server (NTRS)

Bailey, M. C.

1994-01-01

Mutual Coupling Program for Circular Waveguide-fed Aperture Array (CWG) was developed to calculate the electromagnetic interaction between elements of an antenna array of circular apertures with specified aperture field distributions. The field distributions were assumed to be a superposition of the modes which could exist in a circular waveguide. Various external media were included to provide flexibility of use, for example, the flexibility to determine the effects of dielectric covers (i.e., thermal protection system tiles) upon the impedance of aperture type antennas. The impedance and radiation characteristics of planar array antennas depend upon the mutual interaction between all the elements of the array. These interactions are influenced by several parameters (e.g., the array grid geometry, the geometry and excitation of each array element, the medium outside the array, and the internal network feeding the array.) For the class of array antenna whose radiating elements consist of small holes in a flat conducting plate, the electromagnetic problem can be divided into two parts, the internal and the external. In solving the external problem for an array of circular apertures, CWG will compute the mutual interaction between various combinations of circular modal distributions and apertures. CWG computes the mutual coupling between various modes assumed to exist in circular apertures that are located in a flat conducting plane of infinite dimensions. The apertures can radiate into free space, a homogeneous medium, a multilayered region or a reflecting surface. These apertures are assumed to be excited by one or more modes corresponding to the modal distributions in circular waveguides of the same cross sections as the apertures. The apertures may be of different sizes and also of different polarizations. However, the program assumes that each aperture field contains the same modal distributions, and calculates the complex scattering matrix between all mode and aperture combinations. The scattering matrix can then be used to determine the complex modal field amplitudes for each aperture with a specified array excitation. CWG is written in VAX FORTRAN for DEC VAX series computers running VMS (LAR-15236) and IBM PC series and compatible computers running MS-DOS (LAR-15226). It requires 360K of RAM for execution. To compile the source code for the PC version, the NDP Fortran compiler and linker will be required; however, the distribution medium for the PC version of CWG includes a sample MS-DOS executable which was created using NDP Fortran with the -vms compiler option. The standard distribution medium for the PC version of CWG is a 3.5 inch 1.44Mb MS-DOS format diskette. The standard distribution medium for the VAX version of CWG is a 1600 BPI 9track magnetic tape in DEC VAX BACKUP format. The VAX version is also available on a TK50 tape cartridge in DEC VAX BACKUP format. Both machine versions of CWG include an electronic version of the documentation in Microsoft Word for Windows format. CWG was developed in 1993 and is a copyrighted work with all copyright vested in NASA.

Detonator-activated ball shutter

DOEpatents

McWilliams, Roy A.; von Holle, William G.

1983-01-01

A detonator-activated ball shutter for closing an aperture in about 300.mu. seconds. The ball shutter containing an aperture through which light, etc., passes, is closed by firing a detonator which propels a projectile for rotating the ball shutter, thereby blocking passage through the aperture.

Large-aperture plasma-assisted deposition of inertial confinement fusion laser coatings.

PubMed

Oliver, James B; Kupinski, Pete; Rigatti, Amy L; Schmid, Ansgar W; Lambropoulos, John C; Papernov, Semyon; Kozlov, Alexei; Spaulding, John; Sadowski, Daniel; Chrzan, Z Roman; Hand, Robert D; Gibson, Desmond R; Brinkley, Ian; Placido, Frank

2011-03-20

Plasma-assisted electron-beam evaporation leads to changes in the crystallinity, density, and stresses of thin films. A dual-source plasma system provides stress control of large-aperture, high-fluence coatings used in vacuum for substrates 1m in aperture.

Split in phase singularities of an optical vortex by off-axis diffraction through a simple circular aperture

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

Taira, Yoshitaka; Zhang, Shukui

Here, diffraction patterns of an optical vortex through several shaped apertures reveal its topological charge. In this letter, we theoretically and experimentally show that diffraction of a Laguerre Gaussian beam through a circular aperture at an off-axis position can be used to determine the magnitude and sign of the topological charge. To our knowledge, this is the first time that a simple circular aperture has been used to detect orbital angular momentum of an incident optical vortex.

Split in phase singularities of an optical vortex by off-axis diffraction through a simple circular aperture.

PubMed

Taira, Yoshitaka; Zhang, Shukui

2017-04-01

Diffraction patterns of an optical vortex through several shaped apertures reveal its topological charge. In this Letter, we theoretically and experimentally show that diffraction of a Laguerre Gaussian beam through a circular aperture at an off-axis position can be used to determine the magnitude and sign of the topological charge. To our knowledge, this is the first time that a simple circular aperture has been used to detect orbital angular momentum of an incident optical vortex.

Split in phase singularities of an optical vortex by off-axis diffraction through a simple circular aperture

DOE PAGES

Taira, Yoshitaka; Zhang, Shukui

2017-03-29

Here, diffraction patterns of an optical vortex through several shaped apertures reveal its topological charge. In this letter, we theoretically and experimentally show that diffraction of a Laguerre Gaussian beam through a circular aperture at an off-axis position can be used to determine the magnitude and sign of the topological charge. To our knowledge, this is the first time that a simple circular aperture has been used to detect orbital angular momentum of an incident optical vortex.

Improved moving source photometry with TRIPPy

NASA Astrophysics Data System (ADS)

Alexandersen, Mike; Fraser, Wesley Cristopher

2017-10-01

Photometry of moving sources is more complicated than for stationary sources, because the sources trail their signal out over more pixels than a point source of the same magnitude. Using a circular aperture of same size as would be appropriate for point sources can cut out a large amount of flux if a moving source moves substantially relative to the size of the aperture during the exposure, resulting in underestimated fluxes. Using a large circular aperture can mitigate this issue at the cost of a significantly reduced signal to noise compared to a point source, as a result of the inclusion of a larger background region within the aperture.Trailed Image Photometry in Python (TRIPPy) solves this problem by using a pill-shaped aperture: the traditional circular aperture is sliced in half perpendicular to the direction of motion and separated by a rectangle as long as the total motion of the source during the exposure. TRIPPy can also calculate the appropriate aperture correction (which will depend both on the radius and trail length of the pill-shaped aperture), and has features for selecting good PSF stars, creating a PSF model (convolved moffat profile + lookup table) and selecting a custom sky-background area in order to ensure no other sources contribute to the background estimate.In this poster, we present an overview of the TRIPPy features and demonstrate the improvements resulting from using TRIPPy compared to photometry obtained by other methods with examples from real projects where TRIPPy has been implemented in order to obtain the best-possible photometric measurements of Solar System objects. While TRIPPy has currently mainly been used for Trans-Neptunian Objects, the improvement from using the pill-shaped aperture increases with source motion, making TRIPPy highly relevant for asteroid and centaur photometry as well.

APT: Aperture Photometry Tool

NASA Astrophysics Data System (ADS)

Laher, Russ

2012-08-01

Aperture Photometry Tool (APT) is software for astronomers and students interested in manually exploring the photometric qualities of astronomical images. It has a graphical user interface (GUI) which allows the image data associated with aperture photometry calculations for point and extended sources to be visualized and, therefore, more effectively analyzed. Mouse-clicking on a source in the displayed image draws a circular or elliptical aperture and sky annulus around the source and computes the source intensity and its uncertainty, along with several commonly used measures of the local sky background and its variability. The results are displayed and can be optionally saved to an aperture-photometry-table file and plotted on graphs in various ways using functions available in the software. APT is geared toward processing sources in a small number of images and is not suitable for bulk processing a large number of images, unlike other aperture photometry packages (e.g., SExtractor). However, APT does have a convenient source-list tool that enables calculations for a large number of detections in a given image. The source-list tool can be run either in automatic mode to generate an aperture photometry table quickly or in manual mode to permit inspection and adjustment of the calculation for each individual detection. APT displays a variety of useful graphs, including image histogram, and aperture slices, source scatter plot, sky scatter plot, sky histogram, radial profile, curve of growth, and aperture-photometry-table scatter plots and histograms. APT has functions for customizing calculations, including outlier rejection, pixel “picking” and “zapping,” and a selection of source and sky models. The radial-profile-interpolation source model, accessed via the radial-profile-plot panel, allows recovery of source intensity from pixels with missing data and can be especially beneficial in crowded fields.

Transport of Particle Swarms Through Fractures

NASA Astrophysics Data System (ADS)

Boomsma, E.; Pyrak-Nolte, L. J.

2011-12-01

The transport of engineered micro- and nano-scale particles through fractured rock is often assumed to occur as dispersions or emulsions. Another potential transport mechanism is the release of particle swarms from natural or industrial processes where small liquid drops, containing thousands to millions of colloidal-size particles, are released over time from seepage or leaks. Swarms have higher velocities than any individual colloid because the interactions among the particles maintain the cohesiveness of the swarm as it falls under gravity. Thus particle swarms give rise to the possibility that engineered particles may be transported farther and faster in fractures than predicted by traditional dispersion models. In this study, the effect of fractures on colloidal swarm cohesiveness and evolution was studied as a swarm falls under gravity and interacts with fracture walls. Transparent acrylic was used to fabricate synthetic fracture samples with either (1) a uniform aperture or (2) a converging aperture followed by a uniform aperture (funnel-shaped). The samples consisted of two blocks that measured 100 x 100 x 50 mm. The separation between these blocks determined the aperture (0.5 mm to 50 mm). During experiments, a fracture was fully submerged in water and swarms were released into it. The swarms consisted of dilute suspensions of either 25 micron soda-lime glass beads (2% by mass) or 3 micron polystyrene fluorescent beads (1% by mass) with an initial volume of 5μL. The swarms were illuminated with a green (525 nm) LED array and imaged optically with a CCD camera. In the uniform aperture fracture, the speed of the swarm prior to bifurcation increased with aperture up to a maximum at a fracture width of approximately 10 mm. For apertures greater than ~15 mm, the velocity was essentially constant with fracture width (but less than at 10 mm). This peak suggests that two competing mechanisms affect swarm velocity in fractures. The wall provides both drag, which slows the swarm, and a cohesive force that prevents swarm expansion and the corresponding decrease in particle density. For apertures >15mm, though the drag force is small, the loss of swarm cohesion dominates. In small apertures (<5mm), the drag from the wall dominates causing a loss in speed even though there is strong confinement. From a force-based particle interaction approach, the initial simulation did not capture the observed experimental behavior, i.e., the distinct peak in swarm velocities was not observed. For the funnel shaped aperture, the swarm was observed to bifurcate immediately upon reaching the intersection between the converging aperture and the uniform aperture portions of the fracture. Furthermore, converging apertures resulted in the deceleration of a swarm. Thus, the rate of transport of particle swarms is strongly affected by fracture aperture. Acknowledgment: The authors wish to acknowledge support of this work by the Geosciences Research Program, Office of Basic Energy Sciences US Department of Energy (DE-FG02-09ER16022).

Shaping the beam profile of a partially coherent beam by a phase aperture

NASA Astrophysics Data System (ADS)

Wu, Gaofeng; Cai, Yangjian; Chen, Jun

2011-08-01

By use of a tensor method, an analytical formula for a partially coherent Gaussian Schell-model (GSM) beam truncated by a circular phase aperture propagating through a paraxial ABCD optical system is derived. The propagation properties of a GSM beam truncated by a circular phase aperture in free space are studied numerically. It is found that the circular phase aperture can be used to shape the beam profile of a GSM beam and generate partially coherent dark hollow or flat-topped beam, which is useful in many applications, e.g., optical trapping, free-space optical communication, and material thermal processing. The propagation factor of a GSM beam truncated by a circular phase aperture is also analyzed.

Apparatus and method for deterministic control of surface figure during full aperture pad polishing

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

Suratwala, Tayyab Ishaq; Feit, Michael Douglas; Steele, William Augustus

A polishing system configured to polish a lap includes a lap configured to contact a workpiece for polishing the workpiece; and a septum configured to contact the lap. The septum has an aperture formed therein. The radius of the aperture and radius the workpiece are substantially the same. The aperture and the workpiece have centers disposed at substantially the same radial distance from a center of the lap. The aperture is disposed along a first radial direction from the center of the lap, and the workpiece is disposed along a second radial direction from the center of the lap. Themore » first and second radial directions may be opposite directions.« less

Laser fresnel distance measuring system and method

NASA Technical Reports Server (NTRS)

Campbell, Jonathan W. (Inventor); Lehner, David L. (Inventor); Smalley, Larry L. (Inventor); Smith, legal representative, Molly C. (Inventor); Sanders, Alvin J. (Inventor); Earl, Dennis Duncan (Inventor); Allison, Stephen W. (Inventor); Smith, Kelly L. (Inventor)

2008-01-01

A method and system for determining range to a target are provided. A beam of electromagnetic energy is transmitted through an aperture in an opaque screen such that a portion of the beam passes through the aperture to generate a region of diffraction that varies as a function of distance from the aperture. An imaging system is focused on a target plane in the region of diffraction with the generated image being compared to known diffraction patterns. Each known diffraction pattern has a unique value associated therewith that is indicative of a distance from the aperture. A match between the generated image and at least one of the known diffraction patterns is indicative of a distance between the aperture and target plane.

Space Vehicle Valve System

NASA Technical Reports Server (NTRS)

Kelley, Anthony R. (Inventor); Lindner, Jeffrey L. (Inventor)

2014-01-01

The present invention is a space vehicle valve system which controls the internal pressure of a space vehicle and the flow rate of purged gases at a given internal pressure and aperture site. A plurality of quasi-unique variable dimension peaked valve structures cover the purge apertures on a space vehicle. Interchangeable sheet guards configured to cover valve apertures on the peaked valve structure contain a pressure-activated surface on the inner surface. Sheet guards move outwardly from the peaked valve structure when in structural contact with a purge gas stream flowing through the apertures on the space vehicle. Changing the properties of the sheet guards changes the response of the sheet guards at a given internal pressure, providing control of the flow rate at a given aperture site.

Thumb-actuated two-axis controller

NASA Technical Reports Server (NTRS)

Hollow, R. H. (Inventor)

1986-01-01

A two axis joystick controller is described. It produces at least one output signal in relation to pivotal displacement of a member with respect to an intersection of the two axes. The member is pivotally movable on a support with respect to the two axes. The support has a centrally disposed aperture. A light source is mounted on the pivotally movable member above the aperture to direct light through the aperture. A light sensor is mounted below the aperture in the support at the intersection of the two axes to receive the light from the light source directed through the aperture. The light sensor produces at least one output signal related to a location on the sensor at which the light from the light source strikes the sensor.

Apparatus, systems, and methods for ultrasound synthetic aperature focusing

DOEpatents

Schuster, George J.; Crawford, Susan L.; Doctor, Steven R.; Harris, Robert V.

2005-04-12

One form of the present invention is a technique for interrogating a sample with ultrasound which includes: generating ultrasonic energy data corresponding to a volume of a sample and performing a synthetic aperture focusing technique on the ultrasonic energy data. The synthetic aperture focusing technique includes: defining a number of hyperbolic surfaces which extend through the volume at different depths and a corresponding number of multiple element accumulation vectors, performing a focused element calculation procedure for a group of vectors which are representative of the interior of a designated aperture, performing another focused element calculation procedure for vectors corresponding to the boundary of the aperture, and providing an image corresponding to features of the sample in accordance with the synthetic aperture focusing technique.

Detonator-activated ball shutter

DOEpatents

McWilliams, R.A.; Holle, W.G. von.

1983-08-16

A detonator-activated ball shutter for closing an aperture in about 300[mu] seconds. The ball shutter containing an aperture through which light, etc., passes, is closed by firing a detonator which propels a projectile for rotating the ball shutter, thereby blocking passage through the aperture. 3 figs.

Gas Flux and Density Surrounding a Cylindrical Aperture in the Free Molecular Flow Regime

NASA Technical Reports Server (NTRS)

Soulas, George C.

2011-01-01

The equations for rigorously calculating the particle flux and density surrounding a cylindrical aperture in the free molecular flow regime are developed and presented. The fundamental equations for particle flux and density from a reservoir and a diffusely reflecting surface will initially be developed. Assumptions will include a Maxwell-Boltzmann speed distribution, equal particle and wall temperatures, and a linear flux distribution along the cylindrical aperture walls. With this information, the equations for axial flux and density surrounding a cylindrical aperture will be developed. The cylindrical aperture will be divided into multiple volumes and regions to rigorously determine the surrounding axial flux and density, and appropriate limits of integration will be determined. The results of these equations will then be evaluated. The linear wall flux distribution assumption will be assessed. The axial flux and density surrounding a cylindrical aperture with a thickness-to-radius ratio of 1.25 will be presented. Finally, the equations determined in this study will be verified using multiple methods.

Dynamically reconfigurable holographic metasurface aperture for a Mills-Cross monochromatic microwave camera.

PubMed

Yurduseven, Okan; Marks, Daniel L; Fromenteze, Thomas; Smith, David R

2018-03-05

We present a reconfigurable, dynamic beam steering holographic metasurface aperture to synthesize a microwave camera at K-band frequencies. The aperture consists of a 1D printed microstrip transmission line with the front surface patterned into an array of slot-shaped subwavelength metamaterial elements (or meta-elements) dynamically tuned between "ON" and "OFF" states using PIN diodes. The proposed aperture synthesizes a desired radiation pattern by converting the waveguide-mode to a free space radiation by means of a binary modulation scheme. This is achieved in a holographic manner; by interacting the waveguide-mode (reference-wave) with the metasurface layer (hologram layer). It is shown by means of full-wave simulations that using the developed metasurface aperture, the radiated wavefronts can be engineered in an all-electronic manner without the need for complex phase-shifting circuits or mechanical scanning apparatus. Using the dynamic beam steering capability of the developed antenna, we synthesize a Mills-Cross composite aperture, forming a single-frequency all-electronic microwave camera.

Light-efficient photography.

PubMed

Hasinoff, Samuel W; Kutulakos, Kiriakos N

2011-11-01

In this paper, we consider the problem of imaging a scene with a given depth of field at a given exposure level in the shortest amount of time possible. We show that by 1) collecting a sequence of photos and 2) controlling the aperture, focus, and exposure time of each photo individually, we can span the given depth of field in less total time than it takes to expose a single narrower-aperture photo. Using this as a starting point, we obtain two key results. First, for lenses with continuously variable apertures, we derive a closed-form solution for the globally optimal capture sequence, i.e., that collects light from the specified depth of field in the most efficient way possible. Second, for lenses with discrete apertures, we derive an integer programming problem whose solution is the optimal sequence. Our results are applicable to off-the-shelf cameras and typical photography conditions, and advocate the use of dense, wide-aperture photo sequences as a light-efficient alternative to single-shot, narrow-aperture photography.

Design and analysis of a worm gear turntable off-axis assembly method in a three-grating monochromator.

PubMed

Chen, Jianjun; Cui, Jicheng; Yao, Xuefeng; Liu, Jianan; Sun, Ci

2018-04-01

To solve the problem where the actual grating aperture decreases with an increasing scanning angle during the scanning of a three-grating monochromator, we propose an off-axis assembly method for the worm gear turntable that makes it possible to suppress this aperture reduction. We simulated and compared the traditional assembly method with the off-axis assembly method in the three-grating monochromator. Results show that the actual grating aperture can be improved by the off-axis assembly method. In fact, for any one of the three gratings, when the monochromator outputs the longest wavelength in the corresponding wavelength band, the actual grating aperture increases by 45.93%. Over the entire monochromator output band, the actual grating aperture increased by an average of 32.56% and can thus improve the monochromator's output energy. Improvement of the actual grating aperture can also reduce the stray light intensity in the monochromator and improve its output signal-to-noise ratio.

INDEXING MECHANISM

DOEpatents

Kock, L.J.

1959-09-22

A device is presented for loading and unloading fuel elements containing material fissionable by neutrons of thermal energy. The device comprises a combination of mechanical features Including a base, a lever pivotally attached to the base, an Indexing plate on the base parallel to the plane of lever rotation and having a plurality of apertures, the apertures being disposed In rows, each aperture having a keyway, an Index pin movably disposed to the plane of lever rotation and having a plurality of apertures, the apertures being disposed in rows, each aperture having a keyway, an index pin movably disposed on the lever normal to the plane rotation, a key on the pin, a sleeve on the lever spaced from and parallel to the index pin, a pair of pulleys and a cable disposed between them, an open collar rotatably attached to the sleeve and linked to one of the pulleys, a pin extending from the collar, and a bearing movably mounted in the sleeve and having at least two longitudinal grooves in the outside surface.

SU-8 microcantilever with an aperture, fluidic channel, and sensing mechanisms for biological and other applications.

PubMed

Gaitas, Angelo; Hower, Robert W

2014-09-15

We describe a method for fabricating an aperture on a fluidic cantilever device using SU-8 as a structural material. The device can ultimately be used for patch clamping, microinjections, fluidic delivery, fluidic deposition, and micromaterial removal. In the first generation of this device, the initial aperture diameter is 10 μ m and is fabricated on a silicon-on-insulator (SOI) wafer that is structurally used to define the aperture. The aperture can be reduced in size through mask design. This self-aligned process allows for patterning on the sharp tip projecting out of the fluidic plane on the cantilever and is batch fabricated, reducing the cost and time for manufacture. The initial mask, SOI device layer thickness, and the width of the base of the tip define the size of the aperture. The SU-8 micromachined cantilever includes an electrode and a force sensing mechanism. The cantilever can be easily integrated with an atomic force microscope or an optical microscope.

A precise method for adjusting the optical system of laser sub-aperture

NASA Astrophysics Data System (ADS)

Song, Xing; Zhang, Xue-min; Yang, Jianfeng; Xue, Li

2018-02-01

In order to adapt to the requirement of modern astronomical observation and warfare, the resolution of the space telescope is needed to improve, sub-aperture stitching imaging technique is one method to improve the resolution, which could be used not only the foundation and space-based large optical systems, also used in laser transmission and microscopic imaging. A large aperture main mirror of sub-aperture stitching imaging system is composed of multiple sub-mirrors distributed according to certain laws. All sub-mirrors are off-axis mirror, so the alignment of sub-aperture stitching imaging system is more complicated than a single off-axis optical system. An alignment method based on auto-collimation imaging and interferometric imaging is introduced in this paper, by using this alignment method, a sub-aperture stitching imaging system which is composed of 12 sub-mirrors was assembled with high resolution, the beam coincidence precision is better than 0.01mm, and the system wave aberration is better than 0.05λ.

A novel beamformer design method for medical ultrasound. Part I: Theory.

PubMed

Ranganathan, Karthik; Walker, William F

2003-01-01

The design of transmit and receive aperture weightings is a critical step in the development of ultrasound imaging systems. Current design methods are generally iterative, and consequently time consuming and inexact. We describe a new and general ultrasound beamformer design method, the minimum sum squared error (MSSE) technique. The MSSE technique enables aperture design for arbitrary beam patterns (within fundamental limitations imposed by diffraction). It uses a linear algebra formulation to describe the system point spread function (psf) as a function of the aperture weightings. The sum squared error (SSE) between the system psf and the desired or goal psf is minimized, yielding the optimal aperture weightings. We present detailed analysis for continuous wave (CW) and broadband systems. We also discuss several possible applications of the technique, such as the design of aperture weightings that improve the system depth of field, generate limited diffraction transmit beams, and improve the correlation depth of field in translated aperture system geometries. Simulation results are presented in an accompanying paper.

Laboratory measurements of shock propagation through spherical cavities in an optically accessible polymer.

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

Chojnicki, Kirsten; Cooper, Marcia A.; Guo, Shuyue

Pore-scale aperture effects on flow in pore networks was studied in the laboratory to provide a parameterization for use in transport models. Four cases were considered: regular and irregular pillar/pore alignment with and without an aperture. The velocity field of each case was measured and simulated, providing quantitatively comparable results. Two aperture effect parameterizations were considered: permeability and transmission. Permeability values varied by an order of magnitude between the cases with and without apertures. However, transmission did not correlate with permeability. Despite having much greater permeability the regular aperture case permitted less transmission than the regular case. Moreover, both irregularmore » cases had greater transmission than the regular cases, a difference not supported by the permeabilities. Overall, these findings suggest that pore-scale aperture effects on flow though a pore-network may not be adequately captured by properties such as permeability for applications that are interested in determining particle transport volume and timing.« less

Spatial imaging of UV emission from Jupiter and Saturn

NASA Technical Reports Server (NTRS)

Clarke, J. T.; Moos, H. W.

1981-01-01

Spatial imaging with the IUE is accomplished both by moving one of the apertures in a series of exposures and within the large aperture in a single exposure. The image of the field of view subtended by the large aperture is focussed directly onto the detector camera face at each wavelength; since the spatial resolution of the instrument is 5 to 6 arc sec and the aperture extends 23.0 by 10.3 arc sec, imaging both parallel and perpendicular to dispersion is possible in a single exposure. The correction for the sensitivity variation along the slit at 1216 A is obtained from exposures of diffuse geocoronal H Ly alpha emission. The relative size of the aperture superimposed on the apparent discs of Jupiter and Saturn in typical observation is illustrated. By moving the planet image 10 to 20 arc sec along the major axis of the aperture (which is constrained to point roughly north-south) maps of the discs of these planets are obtained with 6 arc sec spatial resolution.

Performance limits of ion extraction systems with non-circular apertures

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

Shagayda, A., E-mail: shagayda@gmail.com; Madeev, S.

A three-dimensional computer simulation is used to determine the perveance limitations of ion extraction systems with non-circular apertures. The objective of the study is to analyze the possibilities to improve mechanical strength of the ion optics made of carbon-carbon composite materials. Non-circular grid apertures are better suited to the physical structure of carbon-carbon composite materials, than conventionally used circular holes in a hexagonal pattern, because they allow a fewer number of cut fibers. However, the slit-type accelerating systems, usually regarded as the main alternative to the conventional ion optics, have an intolerably narrow range of operating perveance values at whichmore » there is no direct ion impingement on the acceleration grid. This paper presents results of comparative analysis of a number of different ion optical systems with non-circular apertures and conventional ion optical systems with circular apertures. It has been revealed that a relatively wide perveance range without direct ion impingement may be obtained with apertures shaped as a square with rounded corners. Numerical simulations show that this geometry may have equivalent perveance range as the traditional geometry with circular apertures while being more mechanically robust. In addition, such important characteristics, as the effective transparency for both the ions and the neutral atoms, the height of the potential barrier reflecting the downstream plasma electrons and the angular divergence of the beamlet also can be very close to these parameters for the optics with circular apertures.« less

Ultrafast Synthetic Transmit Aperture Imaging Using Hadamard-Encoded Virtual Sources With Overlapping Sub-Apertures.

PubMed

Ping Gong; Pengfei Song; Shigao Chen

2017-06-01

The development of ultrafast ultrasound imaging offers great opportunities to improve imaging technologies, such as shear wave elastography and ultrafast Doppler imaging. In ultrafast imaging, there are tradeoffs among image signal-to-noise ratio (SNR), resolution, and post-compounded frame rate. Various approaches have been proposed to solve this tradeoff, such as multiplane wave imaging or the attempts of implementing synthetic transmit aperture imaging. In this paper, we propose an ultrafast synthetic transmit aperture (USTA) imaging technique using Hadamard-encoded virtual sources with overlapping sub-apertures to enhance both image SNR and resolution without sacrificing frame rate. This method includes three steps: 1) create virtual sources using sub-apertures; 2) encode virtual sources using Hadamard matrix; and 3) add short time intervals (a few microseconds) between transmissions of different virtual sources to allow overlapping sub-apertures. The USTA was tested experimentally with a point target, a B-mode phantom, and in vivo human kidney micro-vessel imaging. Compared with standard coherent diverging wave compounding with the same frame rate, improvements on image SNR, lateral resolution (+33%, with B-mode phantom imaging), and contrast ratio (+3.8 dB, with in vivo human kidney micro-vessel imaging) have been achieved. The f-number of virtual sources, the number of virtual sources used, and the number of elements used in each sub-aperture can be flexibly adjusted to enhance resolution and SNR. This allows very flexible optimization of USTA for different applications.

Analysis of fluid flow and solute transport through a single fracture with variable apertures intersecting a canister: Comparison between fractal and Gaussian fractures

NASA Astrophysics Data System (ADS)

Liu, L.; Neretnieks, I.

Canisters with spent nuclear fuel will be deposited in fractured crystalline rock in the Swedish concept for a final repository. The fractures intersect the canister holes at different angles and they have variable apertures and therefore locally varying flowrates. Our previous model with fractures with a constant aperture and a 90° intersection angle is now extended to arbitrary intersection angles and stochastically variable apertures. It is shown that the previous basic model can be simply amended to account for these effects. More importantly, it has been found that the distributions of the volumetric and the equivalent flow rates are all close to the Normal for both fractal and Gaussian fractures, with the mean of the distribution of the volumetric flow rate being determined solely by the hydraulic aperture, and that of the equivalent flow rate being determined by the mechanical aperture. Moreover, the standard deviation of the volumetric flow rates of the many realizations increases with increasing roughness and spatial correlation length of the aperture field, and so does that of the equivalent flow rates. Thus, two simple statistical relations can be developed to describe the stochastic properties of fluid flow and solute transport through a single fracture with spatially variable apertures. This obviates, then, the need to simulate each fracture that intersects a canister in great detail, and allows the use of complex fractures also in very large fracture network models used in performance assessment.

Sensory substitution information informs locomotor adjustments when walking through apertures.

PubMed

Kolarik, Andrew J; Timmis, Matthew A; Cirstea, Silvia; Pardhan, Shahina

2014-03-01

The study assessed the ability of the central nervous system (CNS) to use echoic information from sensory substitution devices (SSDs) to rotate the shoulders and safely pass through apertures of different width. Ten visually normal participants performed this task with full vision, or blindfolded using an SSD to obtain information regarding the width of an aperture created by two parallel panels. Two SSDs were tested. Participants passed through apertures of +0, +18, +35 and +70 % of measured body width. Kinematic indices recorded movement time, shoulder rotation, average walking velocity across the trial, peak walking velocities before crossing, after crossing and throughout a whole trial. Analyses showed participants used SSD information to regulate shoulder rotation, with greater rotation associated with narrower apertures. Rotations made using an SSD were greater compared to vision, movement times were longer, average walking velocity lower and peak velocities before crossing, after crossing and throughout the whole trial were smaller, suggesting greater caution. Collisions sometimes occurred using an SSD but not using vision, indicating that substituted information did not always result in accurate shoulder rotation judgements. No differences were found between the two SSDs. The data suggest that spatial information, provided by sensory substitution, allows the relative position of aperture panels to be internally represented, enabling the CNS to modify shoulder rotation according to aperture width. Increased buffer space indicated by greater rotations (up to approximately 35 % for apertures of +18 % of body width) suggests that spatial representations are not as accurate as offered by full vision.

An analysis of beamed wireless power transfer in the Fresnel zone using a dynamic, metasurface aperture

NASA Astrophysics Data System (ADS)

Smith, David R.; Gowda, Vinay R.; Yurduseven, Okan; Larouche, Stéphane; Lipworth, Guy; Urzhumov, Yaroslav; Reynolds, Matthew S.

2017-01-01

Wireless power transfer (WPT) has been an active topic of research, with a number of WPT schemes implemented in the near-field (coupling) and far-field (radiation) regimes. Here, we consider a beamed WPT scheme based on a dynamically reconfigurable source aperture transferring power to receiving devices within the Fresnel region. In this context, the dynamic aperture resembles a reconfigurable lens capable of focusing power to a well-defined spot, whose dimension can be related to a point spread function. The necessary amplitude and phase distribution of the field imposed over the aperture can be determined in a holographic sense, by interfering a hypothetical point source located at the receiver location with a plane wave at the aperture location. While conventional technologies, such as phased arrays, can achieve the required control over phase and amplitude, they typically do so at a high cost; alternatively, metasurface apertures can achieve dynamic focusing with potentially lower cost. We present an initial tradeoff analysis of the Fresnel region WPT concept assuming a metasurface aperture, relating the key parameters such as spot size, aperture size, wavelength, and focal distance, as well as reviewing system considerations such as the availability of sources and power transfer efficiency. We find that approximate design formulas derived from the Gaussian optics approximation provide useful estimates of system performance, including transfer efficiency and coverage volume. The accuracy of these formulas is confirmed through numerical studies.

Realization of a video-rate distributed aperture millimeter-wave imaging system using optical upconversion

NASA Astrophysics Data System (ADS)

Schuetz, Christopher; Martin, Richard; Dillon, Thomas; Yao, Peng; Mackrides, Daniel; Harrity, Charles; Zablocki, Alicia; Shreve, Kevin; Bonnett, James; Curt, Petersen; Prather, Dennis

2013-05-01

Passive imaging using millimeter waves (mmWs) has many advantages and applications in the defense and security markets. All terrestrial bodies emit mmW radiation and these wavelengths are able to penetrate smoke, fog/clouds/marine layers, and even clothing. One primary obstacle to imaging in this spectrum is that longer wavelengths require larger apertures to achieve the resolutions desired for many applications. Accordingly, lens-based focal plane systems and scanning systems tend to require large aperture optics, which increase the achievable size and weight of such systems to beyond what can be supported by many applications. To overcome this limitation, a distributed aperture detection scheme is used in which the effective aperture size can be increased without the associated volumetric increase in imager size. This distributed aperture system is realized through conversion of the received mmW energy into sidebands on an optical carrier. This conversion serves, in essence, to scale the mmW sparse aperture array signals onto a complementary optical array. The side bands are subsequently stripped from the optical carrier and recombined to provide a real time snapshot of the mmW signal. Using this technique, we have constructed a real-time, video-rate imager operating at 75 GHz. A distributed aperture consisting of 220 upconversion channels is used to realize 2.5k pixels with passive sensitivity. Details of the construction and operation of this imager as well as field testing results will be presented herein.

Performance limits of ion extraction systems with non-circular apertures.

PubMed

Shagayda, A; Madeev, S

2016-04-01

A three-dimensional computer simulation is used to determine the perveance limitations of ion extraction systems with non-circular apertures. The objective of the study is to analyze the possibilities to improve mechanical strength of the ion optics made of carbon-carbon composite materials. Non-circular grid apertures are better suited to the physical structure of carbon-carbon composite materials, than conventionally used circular holes in a hexagonal pattern, because they allow a fewer number of cut fibers. However, the slit-type accelerating systems, usually regarded as the main alternative to the conventional ion optics, have an intolerably narrow range of operating perveance values at which there is no direct ion impingement on the acceleration grid. This paper presents results of comparative analysis of a number of different ion optical systems with non-circular apertures and conventional ion optical systems with circular apertures. It has been revealed that a relatively wide perveance range without direct ion impingement may be obtained with apertures shaped as a square with rounded corners. Numerical simulations show that this geometry may have equivalent perveance range as the traditional geometry with circular apertures while being more mechanically robust. In addition, such important characteristics, as the effective transparency for both the ions and the neutral atoms, the height of the potential barrier reflecting the downstream plasma electrons and the angular divergence of the beamlet also can be very close to these parameters for the optics with circular apertures.

Synthetic aperture design for increased SAR image rate

DOEpatents

Bielek, Timothy P [Albuquerque, NM; Thompson, Douglas G [Albuqerque, NM; Walker, Bruce C [Albuquerque, NM

2009-03-03

High resolution SAR images of a target scene at near video rates can be produced by using overlapped, but nevertheless, full-size synthetic apertures. The SAR images, which respectively correspond to the apertures, can be analyzed in sequence to permit detection of movement in the target scene.

Pulsed particle beam vacuum-to-air interface

DOEpatents

Cruz, G.E.; Edwards, W.F.

1987-06-18

A vacuum-to-air interface is provided for a high-powered, pulsed particle beam accelerator. The interface comprises a pneumatic high speed gate valve, from which extends a vacuum-tight duct, that terminates in an aperture. Means are provided for periodically advancing a foil strip across the aperture at the repetition rate of the particle pulses. A pneumatically operated hollow sealing band urges foil strip, when stationary, against and into the aperture. Gas pressure means periodically lift off and separate foil strip from aperture, so that it may be readily advanced. 5 figs.

Planetary Remote Sensing Science Enabled by MIDAS (Multiple Instrument Distributed Aperture Sensor)

NASA Technical Reports Server (NTRS)

Pitman, Joe; Duncan, Alan; Stubbs, David; Sigler, Robert; Kendrick, Rick; Chilese, John; Lipps, Jere; Manga, Mike; Graham, James; dePater, Imke

2004-01-01

The science capabilities and features of an innovative and revolutionary approach to remote sensing imaging systems, aimed at increasing the return on future space science missions many fold, are described. Our concept, called Multiple Instrument Distributed Aperture Sensor (MIDAS), provides a large-aperture, wide-field, diffraction-limited telescope at a fraction of the cost, mass and volume of conventional telescopes, by integrating optical interferometry technologies into a mature multiple aperture array concept that addresses one of the highest needs for advancing future planetary science remote sensing.

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

Hellfeld, Daniel; Barton, Paul; Gunter, Donald

Gamma-ray imaging facilitates the efficient detection, characterization, and localization of compact radioactive sources in cluttered environments. Fieldable detector systems employing active planar coded apertures have demonstrated broad energy sensitivity via both coded aperture and Compton imaging modalities. But, planar configurations suffer from a limited field-of-view, especially in the coded aperture mode. In order to improve upon this limitation, we introduce a novel design by rearranging the detectors into an active coded spherical configuration, resulting in a 4pi isotropic field-of-view for both coded aperture and Compton imaging. This work focuses on the low- energy coded aperture modality and the optimization techniquesmore » used to determine the optimal number and configuration of 1 cm 3 CdZnTe coplanar grid detectors on a 14 cm diameter sphere with 192 available detector locations.« less

Hubble Space Telescope faint object spectrograph instrument handbook, version 5.0

NASA Technical Reports Server (NTRS)

Kinney, A. L. (Editor)

1994-01-01

This version of the FOS Instrument Handbook is for the refurbished telescope, which is affected by an increase in throughput, especially for the smaller apertures, a decrease in efficiency due to the extra reflections of the COSTAR optics, and a change in focal length. The improved PSF affects all exposure time calculations due to better aperture throughputs and increases the spectral resolution. The extra reflections of COSTAR decrease the efficiency by 10-20 percent. The change in focal length affects the aperture sizes as projected on the sky. The aperture designations that are already in use both in the exposure logsheets and in the project data base (PDB) have not been changed. Apertures are referred to here by their size, followed by the designation used on the exposure logsheet.

Highly uniform parallel microfabrication using a large numerical aperture system

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

Zhang, Zi-Yu; Su, Ya-Hui, E-mail: ustcsyh@ahu.edu.cn, E-mail: dongwu@ustc.edu.cn; Zhang, Chen-Chu

In this letter, we report an improved algorithm to produce accurate phase patterns for generating highly uniform diffraction-limited multifocal arrays in a large numerical aperture objective system. It is shown that based on the original diffraction integral, the uniformity of the diffraction-limited focal arrays can be improved from ∼75% to >97%, owing to the critical consideration of the aperture function and apodization effect associated with a large numerical aperture objective. The experimental results, e.g., 3 × 3 arrays of square and triangle, seven microlens arrays with high uniformity, further verify the advantage of the improved algorithm. This algorithm enables the laser parallelmore » processing technology to realize uniform microstructures and functional devices in the microfabrication system with a large numerical aperture objective.« less

Method and apparatus for shadow aperture backscatter radiography (SABR) system and protocol

NASA Technical Reports Server (NTRS)

Shedlock, Daniel (Inventor); Jacobs, Alan M. (Inventor); Jacobs, Sharon Auerback (Inventor); Dugan, Edward (Inventor)

2010-01-01

A shadow aperture backscatter radiography (SABR) system includes at least one penetrating radiation source for providing a penetrating radiation field, and at least one partially transmissive radiation detector, wherein the partially transmissive radiation detector is interposed between an object region to be interrogated and the radiation source. The partially transmissive radiation detector transmits a portion of the illumination radiation field. A shadow aperture having a plurality of radiation attenuating regions having apertures therebetween is disposed between the radiation source and the detector. The apertures provide illumination regions for the illumination radiation field to reach the object region, wherein backscattered radiation from the object is detected and generates an image by the detector in regions of the detector that are shadowed by the radiation attenuation regions.

Mid-frequency MTF compensation of optical sparse aperture system.

PubMed

Zhou, Chenghao; Wang, Zhile

2018-03-19

Optical sparse aperture (OSA) can greatly improve the spatial resolution of optical system. However, because of its aperture dispersion and sparse, its mid-frequency modulation transfer function (MTF) are significantly lower than that of a single aperture system. The main focus of this paper is on the mid-frequency MTF compensation of the optical sparse aperture system. Firstly, the principle of the mid-frequency MTF decreasing and missing of optical sparse aperture are analyzed. This paper takes the filling factor as a clue. The method of processing the mid-frequency MTF decreasing with large filling factor and method of compensation mid-frequency MTF with small filling factor are given respectively. For the MTF mid-frequency decreasing, the image spatial-variant restoration method is proposed to restore the mid-frequency information in the image; for the mid-frequency MTF missing, two images obtained by two system respectively are fused to compensate the mid-frequency information in optical sparse aperture image. The feasibility of the two method are analyzed in this paper. The numerical simulation of the system and algorithm of the two cases are presented using Zemax and Matlab. The results demonstrate that by these two methods the mid-frequency MTF of OSA system can be compensated effectively.

Effects of Vertical Direction and Aperture Size on the Perception of Visual Acceleration.

PubMed

Mueller, Alexandra S; González, Esther G; McNorgan, Chris; Steinbach, Martin J; Timney, Brian

2016-02-06

It is not well understood whether the distance over which moving stimuli are visible affects our sensitivity to the presence of acceleration or our ability to track such stimuli. It is also uncertain whether our experience with gravity creates anisotropies in how we detect vertical acceleration and deceleration. To address these questions, we varied the vertical extent of the aperture through which we presented vertically accelerating and decelerating random dot arrays. We hypothesized that observers would better detect and pursue accelerating and decelerating stimuli that extend over larger than smaller distances. In Experiment 1, we tested the effects of vertical direction and aperture size on acceleration and deceleration detection accuracy. Results indicated that detection is better for downward motion and for large apertures, but there is no difference between vertical acceleration and deceleration detection. A control experiment revealed that our manipulation of vertical aperture size affects the ability to track vertical motion. Smooth pursuit is better (i.e., with higher peak velocities) for large apertures than for small apertures. Our findings suggest that the ability to detect vertical acceleration and deceleration varies as a function of the direction and vertical extent over which an observer can track the moving stimulus. © The Author(s) 2016.

Water flow in high-speed handpieces.

PubMed

Cavalcanti, Bruno Neves; Serairdarian, Paulo Isaías; Rode, Sigmar Mello

2005-05-01

This study measured the water flow commonly used in high-speed handpieces to evaluate the water flow's influence on temperature generation. Different flow speeds were evaluated between turbines that had different numbers of cooling apertures. Two water samples were collected from each high-speed handpiece at private practices and at the School of Dentistry at São José dos Campos. The first sample was collected at the customary flow and the second was collected with the terminal opened for maximum flow. The two samples were collected into weighed glass receptacles after 15 seconds of turbine operation. The glass receptacles were reweighed and the difference between weights was recorded to calculate the water flow in mL/min and for further statistical analysis. The average water flow for 137 samples was 29.48 mL/min. The flow speeds obtained were 42.38 mL/min for turbines with one coolant aperture; 34.31 mL/min for turbines with two coolant apertures; and 30.44 mL/min for turbines with three coolant apertures. There were statistical differences between turbines with one and three coolant apertures (Tukey-Kramer multiple comparisons test with P < .05). Turbine handpieces with one cooling aperture distributed more water for the burs than high-speed handpieces with more than one aperture.

Possible Overlaps Between Blobs, Grism Apertures, and Dithers

NASA Astrophysics Data System (ADS)

Ryan, R. E.; McCullough, P. R.

2017-06-01

We present a investigation into possible overlaps between the known IR blobs with the grism aperture reference positions and the IR dither patterns. Each aperture was designed to place the science target (e.g. a specific star) on a cosmetically clean area of the IR detector. Similarly, the dither patterns were designed to mitigate cosmetic defects by rarely (or ideally never) placing such targets on known defects. Because blobs accumulate with time, the originally defined apertures and dither patterns may no longer accomplish their goals, it is important to reverify these combinations. We find two potential overlaps between the blob, aperture, and dither combinations, but do not recommend any changes to the current suite of aperture references positions and/or dither patterns for two reasons. First, one of the overlaps occurs with a dither/aperture combination that is seldom used for high-value science operations, but rather more common for wide-field surveys/mosaics. Second, the other overlap is 8.7 pix from a blob that has a fiducial radius of 10 pix, which already represents a very conservative distance. We conclude that a similar analysis should be repeated as new blobs occur, to continue to ensure ideal operations for high-value science targets. The purpose of this report is to document the analysis in order to facilitate its repetition in the future.

Observation of enhanced spontaneous emission in dielectrically apertured microcavities

NASA Astrophysics Data System (ADS)

Graham, Luke Alan

The effects of enhanced spontaneous emission are important in determining the low threshold characteristics of oxide confined vertical cavity semiconductor lasers. This enhancement effect increases as Q/V, where Q = λ/Δλ for the cavity and V is the mode volume. In particular we investigate the effects of mode diameter on enhancement in microcavity structures with successively smaller dielectric apertures. These structures were fabricated by etching and back filling with SiO 2 and by lateral steam oxidation. For both cavities, InAlGaAs quantum dot emitters were used in the active region in order to avoid carrier diffusion and recombination at the side walls. Decay data was obtained at 10 K using time resolved photoluminescence of individual microcavities, and arrays. The detector used here is based on a silicon avalanche photodiode operated in ``Geiger'' mode. It provides a resolution of 350 ps and a quantum efficiency of ~1% at a wavelength of 1 μm. For the etched aperture structures we observed enhancement factors as high as 1.4 for the 1 μm diameter cavities with a maximum Q ~ 200. The enhancement is limited by the low Qs induced by etched side wall scattering. For 1 μm apertures fabricated by lateral steam oxidation, a Q of 450 is obtained with an enhancement factor of 2.3. In these devices we show that the enhancement is limited by distribution of quantum dots throughout the aperture region. Dots resonant with the cavity and located along the aperture edge decay more slowly than those in the center, leading to spatial hole burning effects in the decay data. Microcavities with aperture sizes ranging from 1-5 μm and Qs greater than 5000 are also demonstrated. We show 0th and 1 st order mode spacings as a function of aperture size and from this data calculate the transverse optical mode diameter as a function of aperture diameter. We find that the optical mode size becomes larger than the aperture size for diameters of ~2.5 μm and below and that this is correlated with a steep drop in Q for smaller apertures. We also find that the upper limit in cavity Q in these structures appears to come from losses induced by the MgF2/ZnSe e-beam deposited DBRs.

Registered particles onboard identification in the various apertures of GAMMA-400 space gamma-telescope

NASA Astrophysics Data System (ADS)

Arkhangelskaja, Irene

2016-07-01

GAMMA-400 (Gamma Astronomical Multifunctional Modular Apparatus) will be the gamma-telescope onboard international satellite gamma-observatory designed for particle registration in the wide energy band. Its parameters are optimized for detection of gamma-quanta with the energy ˜ 100 GeV in the main aperture. The main scientific goals of GAMMA-400 are to investigate fluxes of γ-rays and the electron-positron cosmic ray component possibly generated by dark matter particles decay or annihilation and to search for and study in detail discrete γ-ray sources, to investigate the energy spectra of Galactic and extragalactic diffuse γ-rays, and to study γ-ray bursts and γ-emission from the active Sun. This article presents analysis of detected events identification procedures and energy resolution in three apertures provide particles registration both from upper and lateral directions based on GAMMA-400 modeling due special designed software. Time and segmentation methods are used to reject backsplash (backscattering particles created when high energy γ-rays interact with the calorimeter's matter and move in the opposite direction) in the main aperture while only energy deposition analysis allows to reject this effect in the additional and lateral ones. The main aperture provides the best angular (all strip layers information analysis) and energy (energy deposition in the all detectors studying) resolution in the energy range 0.1 - 3 × 10^{3} GeV. The energy resolution in this band is 1%. Triggers in the main aperture will be formed using information about particle direction provided by time of flight system and presence of charged particle or backsplash signal formed according to analysis of energy deposition in combination of all two-layers anticoincidence systems individual detectors. In the additional aperture gamma-telescope allows to register events in the energy band 10 × 10^{-3} - 3 × 10^{3} GeV. The additional aperture energy resolution provides due to energy deposition analysis and is the same as in the main aperture. Gamma-quanta, electrons/positrons and light nuclei with energy E>10 GeV also are registered in the lateral aperture. This aperture allows detecting of low-energy gammas in the ranges of 0.2 - 10 MeV and high energy ones from 10 MeV to several TeV with energy resolution 8% - 2% and 2% correspondingly.

Penalization of aperture complexity in inversely planned volumetric modulated arc therapy

PubMed Central

Younge, Kelly C.; Matuszak, Martha M.; Moran, Jean M.; McShan, Daniel L.; Fraass, Benedick A.; Roberts, Donald A.

2012-01-01

Purpose: Apertures obtained during volumetric modulated arc therapy (VMAT) planning can be small and irregular, resulting in dosimetric inaccuracies during delivery. Our purpose is to develop and integrate an aperture-regularization objective function into the optimization process for VMAT, and to quantify the impact of using this objective function on dose delivery accuracy and optimized dose distributions. Methods: An aperture-based metric (“edge penalty”) was developed that penalizes complex aperture shapes based on the ratio of MLC side edge length and aperture area. To assess the utility of the metric, VMAT plans were created for example paraspinal, brain, and liver SBRT cases with and without incorporating the edge penalty in the cost function. To investigate the dose calculation accuracy, Gafchromic EBT2 film was used to measure the 15 highest weighted apertures individually and as a composite from each of two paraspinal plans: one with and one without the edge penalty applied. Films were analyzed using a triple-channel nonuniformity correction and measurements were compared directly to calculations. Results: Apertures generated with the edge penalty were larger, more regularly shaped and required up to 30% fewer monitor units than those created without the edge penalty. Dose volume histogram analysis showed that the changes in doses to targets, organs at risk, and normal tissues were negligible. Edge penalty apertures that were measured with film for the paraspinal plan showed a notable decrease in the number of pixels disagreeing with calculation by more than 10%. For a 5% dose passing criterion, the number of pixels passing in the composite dose distributions for the non-edge penalty and edge penalty plans were 52% and 96%, respectively. Employing gamma with 3% dose/1 mm distance criteria resulted in a 79.5% (without penalty)/95.4% (with penalty) pass rate for the two plans. Gradient compensation of 3%/1 mm resulted in 83.3%/96.2% pass rates. Conclusions: The use of the edge penalty during optimization has the potential to markedly improve dose delivery accuracy for VMAT plans while still maintaining high quality optimized dose distributions. The penalty regularizes aperture shape and improves delivery efficiency. PMID:23127107

Improved Modeling of Open Waveguide Aperture Radiators for use in Conformal Antenna Arrays

NASA Astrophysics Data System (ADS)

Nelson, Gregory James

Open waveguide apertures have been used as radiating elements in conformal arrays. Individual radiating element model patterns are used in constructing overall array models. The existing models for these aperture radiating elements may not accurately predict the array pattern for TEM waves which are not on boresight for each radiating element. In particular, surrounding structures can affect the far field patterns of these apertures, which ultimately affects the overall array pattern. New models of open waveguide apertures are developed here with the goal of accounting for the surrounding structure effects on the aperture far field patterns such that the new models make accurate pattern predictions. These aperture patterns (both E plane and H plane) are measured in an anechoic chamber and the manner in which they deviate from existing model patterns are studied. Using these measurements as a basis, existing models for both E and H planes are updated with new factors and terms which allow the prediction of far field open waveguide aperture patterns with improved accuracy. These new and improved individual radiator models are then used to predict overall conformal array patterns. Arrays of open waveguide apertures are constructed and measured in a similar fashion to the individual aperture measurements. These measured array patterns are compared with the newly modeled array patterns to verify the improved accuracy of the new models as compared with the performance of existing models in making array far field pattern predictions. The array pattern lobe characteristics are then studied for predicting fully circularly conformal arrays of varying radii. The lobe metrics that are tracked are angular location and magnitude as the radii of the conformal arrays are varied. A constructed, measured array that is close to conforming to a circular surface is compared with a fully circularly conformal modeled array pattern prediction, with the predicted lobe angular locations and magnitudes tracked, plotted and tabulated. The close match between the patterns of the measured array and the modeled circularly conformal array verifies the validity of the modeled circularly conformal array pattern predictions.

Tracking Characteristics of a Triangular-Aperture Mounted Optical Head Slider to Which a Polarized Violet Laser Source Is Applied

NASA Astrophysics Data System (ADS)

Ohkubo, Toshifumi; Park, Majung; Hirata, Masakazu; Oumi, Manabu; Nakajima, Kunio

In near-field optical recording, the combination of a triangular aperture and a polarized illuminating light is thought to be one of the most promising breakthroughs for improving both spatial resolution and signal-to-noise ratio. In light of this, we have already fabricated a triangular-aperture mounted optical head slider and demonstrated its superior performance while clarifying the influence of the polarization direction on the spatial resolution in the circumferential direction. When the polarization direction was perpendicular to the bottom side (which is parallel to the slider trailing edge) of the aperture, the highest spatial resolution and signal contrast were obtained, in spite of the usage of a fairly large aperture, indicating the presence of clear readout signal waveforms corresponding down to 100 nm line-and-space (L/S) patterns. In this study, we tried to experimentally clarify the influence of the polarization direction of the illuminating light on an aperture's field spread in the radial direction. In order to concretely evaluate the field spread, we prepared 1-mm-long linearly arranged (in the circumferential direction) L/S patterns on a metal-layered medium, and a piezo-electric actuator combined positioner. Intersecting the aperture at two portions of the tracks, directly acquired signal waveforms could be successfully transformed into the waveforms that would be obtained if the aperture had crossed the track at right angles. The field spreads in the radial direction were estimated to be approximately 250 nm when the polarization direction was perpendicular to the bottom side. In contrast, when the polarization direction was 45 degrees, the stationary field spread in the radial direction was estimated to be approximately 350 - 370 nm. It could be confirmed experimentally that both the highest spatial resolution in the circumferential direction and the smallest field spread in the radial direction were realized with the combination of the triangular aperture and the illuminating polarized light whose direction was perpendicular to the bottom side. Based on these results, the signal-to-noise ratio will be evaluated and discussed in the future with respect to the above-mentioned optimum aperture structure and conditions.

Power Spectrum of Atmospheric Scintillation for the Deep Space Network Goldstone Ka-Band Downlink

NASA Technical Reports Server (NTRS)

Ho, C.; Wheelon, A.

2004-01-01

Dynamic signal fluctuations due to atmospheric scintillations may impair the Ka-band (around 32-GHz) link sensitivities for a low-margin Deep Space Network (DSN) receiving system. The ranges of frequency and power of the fast fluctuating signals (time scale less than 1 min) are theoretically investigated using the spatial covariance and turbulence theory. Scintillation power spectrum solutions are derived for both a point receiver and a finite-aperture receiver. The aperture-smoothing frequency ((omega(sub s)), corner frequency ((omega(sub c)), and damping rate are introduced to define the shape of the spectrum for a finite-aperture antenna. The emphasis is put on quantitatively describing the aperture-smoothing effects and graphically estimating the corner frequency for a large aperture receiver. Power spectral shapes are analyzed parametrically in detail through both low- and high-frequency approximations. It is found that aperture-averaging effects become significant when the transverse correlation length of the scintillation is smaller than the antenna radius. The upper frequency or corner frequency for a finite-aperture receiver is controlled by both the Fresnel frequency and aperture-smoothing frequency. Above the aperture-smoothing frequency, the spectrum rolls off at a much faster rate of exp (-omega(sup 2)/omega(sup 2, sub s), rather than omega(sup -8/3), which is customary for a point receiver. However, a relatively higher receiver noise level can mask the fast falling-off shape and make it hard to be identified. We also predict that when the effective antenna radius a(sub r) less than or = 6 m, the corner frequency of its power spectrum becomes the same as that for a point receiver. The aperture-smoothing effects are not obvious. We have applied these solutions to the scenario of a DSN Goldstone 34-m-diameter antenna and predicted the power spectrum shape for the receiving station. The maximum corner frequency for the receiver (with omega(sub s) = 0.79 omega(sub 0) is found to be 0.44 Hz (or 1.0 omega(sub 0), while the fading rate (or fading slope) is about 0.06 dB/s.

In vitro comparative optical bench analysis of a spherical and aspheric optic design of the same IOL model.

PubMed

Tandogan, Tamer; Auffarth, Gerd U; Choi, Chul Y; Liebing, Stephanie; Mayer, Christian; Khoramnia, Ramin

2017-02-08

To analyse objective optical properties of the spherical and aspheric design of the same intraocular lens (IOL) model using optical bench analysis. This study entailed a comparative analysis of 10 spherical C-flex 570 C and 10 aspheric C-flex 970 C IOLs (Rayner Intraocular Lenses Ltd., Hove, UK) of 26 diopters [D] using an optical bench (OptiSpheric, Trioptics, Germany). In all lenses, we evaluated the modulation transfer function (MTF) at 50 lp/mm and 100 lp/mm and the Strehl Ratio using a 3-mm (photopic) and 4.5-mm (mesopic) aperture. At 50 lp/mm, the MTF values were 0.713/0.805 (C-flex 570 C/C-flex 970 C) for a 3-mm aperture and 0.294/0.591 for a 4.5-mm aperture. At 100 lp/mm, the MTF values were 0.524/0.634 for a 3-mm aperture and 0.198/0.344 for a 4.5-mm aperture. The Strehl Ratio was 0.806/0.925 and 0.237/0.479 for a 3-mm and 4.5-mm aperture respectively. A Mann-Whitney U test revealed all intergroup differences to be statistically significant (p < 0.01). The aspheric IOL design achieved higher MTF values than the spherical design of the same IOL for both apertures. Moreover, the differences between the two designs of the IOL were more prominent for larger apertures. This suggests that the evaluated IOL provides enhanced optical quality to patients with larger pupils or working under mesopic conditions.

Shape of the piriform aperture in Gorilla gorilla, Pan troglodytes, and modern Homo sapiens: characterization and polymorphism analysis.

PubMed

Schmittbuhl, M; Le Minor, J M; Allenbach, B; Schaaf, A

1998-07-01

By using new methodologies based on automatic image analysis, the shape of the piriform aperture was analyzed in Gorilla gorilla (33 males, 13 females), Pan troglodytes (35 males, 22 females), and modern Homo sapiens (30 males, 12 females). The determination of the piriform aperture index (breadth/height) allowed the authors to demonstrate a marked elongation of the aperture in Homo compared with Gorilla and Pan. Individual characterization of the shape was possible with great precision and without ambiguity by using Fourier analysis. An absolute, interspecific partition between Gorilla, Pan, and Homo resulted from the canonical discriminant analysis of the Fourier descriptors. However, a closeness of shape between some individuals in Pan and some in Gorilla and Homo was observed, demonstrating a morphological continuum of the shape of the piriform aperture in hominoids: Pan was in intermediate position between Gorilla and Homo. Interspecific differences between Homo and the group Pan-Gorilla were explained principally by the differences in elongation (amplitude of the second harmonic) and pentagonality (amplitude of the fifth harmonic) and by differences in orientation of quadrangularity (phase of the fourth harmonic). Differences in the shape of the piriform aperture between Pan and Gorilla were explained by differences in orientation of elongation (phase of the second harmonic) and by differences in the component of triangularity (amplitude of the third harmonic). In Gorilla and Pan, the little, elongated, and relatively trapezoidal piriform aperture seems to be a shared primitive feature (plesiomorphic), whereas an elongated piriform aperture seems to be a characteristic and derived feature (apomorphic) of modern Homo sapiens.

Adjustable liquid aperture to eliminate undesirable light in holographic projection.

PubMed

Wang, Di; Liu, Chao; Li, Lei; Zhou, Xin; Wang, Qiong-Hua

2016-02-08

In this paper, we propose an adjustable liquid aperture to eliminate the undesirable light in a holographic projection. The aperture is based on hydrodynamic actuation. A chamber is formed with a cylindrical tube. A black droplet is filled in the sidewall of the cylinder tube and the outside space is the transparent oil which is immiscible with the black droplet. An ultrathin glass sheet is attached on the bottom substrate of the device and a black shading film is secured to the central area of the glass sheet. By changing the volume of the black droplet, the black droplet will move to the middle or sidewall due to hydrodynamic actuation, so the device can be used as an adjustable aperture. A divergent spherical wave and a solid lens are used to separate the focus planes of the reconstructed image and diffraction beams induced by the liquid crystal on silicon in the holographic projection. Then the aperture is used to eliminate the diffraction beams by adjusting the size of the liquid aperture and the holographic projection does not have undesirable light.

Focusing optical waves with a rotationally symmetric sharp-edge aperture

NASA Astrophysics Data System (ADS)

Hu, Yanwen; Fu, Shenhe; Li, Zhen; Yin, Hao; Zhou, Jianying; Chen, Zhenqiang

2018-04-01

While there has been various kinds of patterned structures proposed for wave focusing, these patterned structures usually involve complicated lithographic techniques since the element size of the patterned structures should be precisely controlled in microscale or even nanoscale. Here we propose a new and straightforward method for focusing an optical plane wave in free space with a rotationally symmetric sharp-edge aperture. The focusing phenomenon of wave is realized by superposition of a portion of the higher-order symmetric plane waves generated from the sharp edges of the apertures, in contrast to previously focusing techniques which usually depend on a curved phase. We demonstrate both experimentally and theoretically the focusing effect with a series of apertures having different rotational symmetry, and find that the intensity of the hotspots could be controlled by the symmetric strength of the sharp-edge apertures. The presented results would advance the conventional wisdom that light would diffract in all directions and become expanding when it propagates through an aperture. The proposed method is easy to be processed, and might open potential applications in interferometry, image, and superresolution.

Interface and process for enhanced transmission of non-circular ion beams between stages at unequal pressure

DOEpatents

Tang, Keqi [Richland, WA; Shvartsburg, Alexandre A [Richland, WA; Smith, Richard D [Richland, WA

2008-03-04

The invention discloses a new interface with non-circular conductance limit aperture(s) useful for effective transmission of non-circular ion beams between stages with different gas pressure. In particular, the invention provides an improved coupling of field asymmetric waveform ion mobility spectrometry (FAIMS) analyzers of planar or side-to-side geometry to downstream stages such as mass spectrometry or ion mobility spectrometry. In this case, the non-circular aperture is rectangular; other geometries may be optimum in other applications. In the preferred embodiment, the non-circular aperture interface is followed by an electrodynamic ion funnel that may focus wide ion beams of any shape into tight circular beams with virtually no losses. The jet disrupter element of the funnel may also have a non-circular geometry, matching the shape of arriving ion beam. The improved sensitivity of planar FAIMS/MS has been demonstrated in experiments using a non-contiguous elongated aperture but other embodiments (e.g., with a contiguous slit aperture) may be preferable, especially in conjunction with an ion funnel operated at high pressures.

Production and evaluation of Ighu from selected cassava varieties using a motorized shredder—a response surface analysis

PubMed Central

Iwe, Madu O; Agiriga, Ann N

2013-01-01

Cassava varieties, TME419, TMS30572, and TMS98/0505, were planted and harvested at 3-month intervals of 10, 13, and 16 months, respectively. A central composite response surface design was used to study the effects of the variables cassava variety, harvesting time, and shredding aperture on selected physicochemical properties of Ighu samples. Regression models showed that the experimental variables had significant (P ≤ 0.05) effects on the hydrogen cyanide, moisture content, thickness, and width of dry Ighu. Minimum values obtainable for the physicochemical properties were 8.1195 mg/kg (10-month, 3-mm shredding aperture from TMS98/0505), 7.58% (13-month, 3-mm shredding aperture from TME419), 0.19 mm (13-month, 3-mm shredding aperture and from TMS30572), and 0.99 mm (16-month, 3-mm shredding aperture from TME419) for hydrogen cyanide, moisture content, thickness, and width, respectively. In addition, Ighu produced from 3-mm shredding aperture (TMS30572) at 10-month harvest was the most preferred of all the samples. PMID:24804057

Field Quality Study of a 1-m-Long Single-Aperture 11-T Nb$$_3$$Sn Dipole Model for LHC Upgrades

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

Chlachidze, G.; DiMarco, J.; Andreev, N.

2014-01-01

FNAL and CERN are carrying out a joint R&D program with the goal of building a 5.5-m-long twin-aperture 11-T Nb_3Sn dipole prototype that is suitable for installation in the LHC. An important part of the program is the development and test of a series of short single-aperture and twin-aperture dipole models with a nominal field of 11 T at the LHC operation current of 11.85 kA and 20% margin. This paper presents the results of magnetic measurements of a 1-m-long single-aperture Nb_3Sn dipole model fabricated and tested recently at FNAL, including geometrical field harmonics and effects of coil magnetization andmore » iron yoke saturation.« less

Modular method of detection, localization, and counting of multiple-taxon pollen apertures using bag-of-words

NASA Astrophysics Data System (ADS)

Lozano-Vega, Gildardo; Benezeth, Yannick; Marzani, Franck; Boochs, Frank

2014-09-01

Accurate recognition of airborne pollen taxa is crucial for understanding and treating allergic diseases which affect an important proportion of the world population. Modern computer vision techniques enable the detection of discriminant characteristics. Apertures are among the important characteristics which have not been adequately explored until now. A flexible method of detection, localization, and counting of apertures of different pollen taxa with varying appearances is proposed. Aperture description is based on primitive images following the bag-of-words strategy. A confidence map is estimated based on the classification of sampled regions. The method is designed to be extended modularly to new aperture types employing the same algorithm by building individual classifiers. The method was evaluated on the top five allergenic pollen taxa in Germany, and its robustness to unseen particles was verified.

Terahertz-wave near-field imaging with subwavelength resolution using surface-wave-assisted bow-tie aperture

NASA Astrophysics Data System (ADS)

Ishihara, Kunihiko; Ohashi, Keishi; Ikari, Tomofumi; Minamide, Hiroaki; Yokoyama, Hiroyuki; Shikata, Jun-ichi; Ito, Hiromasa

2006-11-01

We demonstrate the terahertz-wave near-field imaging with subwavelength resolution using a bow-tie shaped aperture surrounded by concentric periodic structures in a metal film. A subwavelength aperture with concentric periodic grooves, which are known as a bull's eye structure, shows extremely large enhanced transmission beyond the diffraction limit caused by the resonant excitation of surface waves. Additionally, a bow-tie aperture exhibits extraordinary field enhancement at the sharp tips of the metal, which enhances the transmission and the subwavelength spatial resolution. We introduced a bow-tie aperture to the bull's eye structure and achieved high spatial resolution (˜λ/17) in the near-field region. The terahertz-wave near-field image of the subwavelength metal pattern (pattern width=20μm) was obtained for the wavelength of 207μm.

Versatile, high-sensitivity faraday cup array for ion implanters

DOEpatents

Musket, Ronald G.; Patterson, Robert G.

2003-01-01

An improved Faraday cup array for determining the dose of ions delivered to a substrate during ion implantation and for monitoring the uniformity of the dose delivered to the substrate. The improved Faraday cup array incorporates a variable size ion beam aperture by changing only an insertable plate that defines the aperture without changing the position of the Faraday cups which are positioned for the operation of the largest ion beam aperture. The design enables the dose sensitivity range, typically 10.sup.11 -10.sup.18 ions/cm.sup.2 to be extended to below 10.sup.6 ions/cm.sup.2. The insertable plate/aperture arrangement is structurally simple and enables scaling to aperture areas between <1 cm.sup.2 and >750 cm.sup.2, and enables ultra-high vacuum (UHV) applications by incorporation of UHV-compatible materials.

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

Yasui, Keisuke, E-mail: k.yasui.20@west-med.jp; Toshito, Toshiyuki; Omachi, Chihiro

Purpose: In the authors’ proton therapy system, the patient-specific aperture can be attached to the nozzle of spot scanning beams to shape an irradiation field and reduce lateral fall-off. The authors herein verified this system for clinical application. Methods: The authors prepared four types of patient-specific aperture systems equipped with an energy absorber to irradiate shallow regions less than 4 g/cm{sup 2}. The aperture was made of 3-cm-thick brass and the maximum water equivalent penetration to be used with this system was estimated to be 15 g/cm{sup 2}. The authors measured in-air lateral profiles at the isocenter plane and integralmore » depth doses with the energy absorber. All input data were obtained by the Monte Carlo calculation, and its parameters were tuned to reproduce measurements. The fluence of single spots in water was modeled as a triple Gaussian function and the dose distribution was calculated using a fluence dose model. The authors compared in-air and in-water lateral profiles and depth doses between calculations and measurements for various apertures of square, half, and U-shaped fields. The absolute doses and dose distributions with the aperture were then validated by patient-specific quality assurance. Measured data were obtained by various chambers and a 2D ion chamber detector array. Results: The patient-specific aperture reduced the penumbra from 30% to 70%, for example, from 34.0 to 23.6 mm and 18.8 to 5.6 mm. The calculated field width for square-shaped apertures agreed with measurements within 1 mm. Regarding patient-specific aperture plans, calculated and measured doses agreed within −0.06% ± 0.63% (mean ± SD) and 97.1% points passed the 2%-dose/2 mm-distance criteria of the γ-index on average. Conclusions: The patient-specific aperture system improved dose distributions, particularly in shallow-region plans.« less

Size constancy in bat biosonar? Perceptual interaction of object aperture and distance.

PubMed

Heinrich, Melina; Wiegrebe, Lutz

2013-01-01

Perception and encoding of object size is an important feature of sensory systems. In the visual system object size is encoded by the visual angle (visual aperture) on the retina, but the aperture depends on the distance of the object. As object distance is not unambiguously encoded in the visual system, higher computational mechanisms are needed. This phenomenon is termed "size constancy". It is assumed to reflect an automatic re-scaling of visual aperture with perceived object distance. Recently, it was found that in echolocating bats, the 'sonar aperture', i.e., the range of angles from which sound is reflected from an object back to the bat, is unambiguously perceived and neurally encoded. Moreover, it is well known that object distance is accurately perceived and explicitly encoded in bat sonar. Here, we addressed size constancy in bat biosonar, recruiting virtual-object techniques. Bats of the species Phyllostomus discolor learned to discriminate two simple virtual objects that only differed in sonar aperture. Upon successful discrimination, test trials were randomly interspersed using virtual objects that differed in both aperture and distance. It was tested whether the bats spontaneously assigned absolute width information to these objects by combining distance and aperture. The results showed that while the isolated perceptual cues encoding object width, aperture, and distance were all perceptually well resolved by the bats, the animals did not assign absolute width information to the test objects. This lack of sonar size constancy may result from the bats relying on different modalities to extract size information at different distances. Alternatively, it is conceivable that familiarity with a behaviorally relevant, conspicuous object is required for sonar size constancy, as it has been argued for visual size constancy. Based on the current data, it appears that size constancy is not necessarily an essential feature of sonar perception in bats.

Nozzle geometry for organic vapor jet printing

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

Forrest, Stephen R.; McGraw, Gregory

A first device is provided. The device includes a print head. The print head further includes a first nozzle hermetically sealed to a first source of gas. The first nozzle has an aperture having a smallest dimension of 0.5 to 500 microns in a direction perpendicular to a flow direction of the first nozzle. At a distance from the aperture into the first nozzle that is 5 times the smallest dimension of the aperture of the first nozzle, the smallest dimension perpendicular to the flow direction is at least twice the smallest dimension of the aperture of the first nozzle.

Rectifying antenna and method of manufacture

NASA Technical Reports Server (NTRS)

Bhansali, Shekhar (Inventor); Buckle, Kenneth (Inventor); Goswami, D. Yogi (Inventor); Stefanakos, Elias (Inventor); Weller, Thomas (Inventor)

2006-01-01

In accordance with the present invention, an aperture rectenna is provided where the substrate is transparent and of sufficient mechanical strength to support the fabricated structure above it. An aperture antenna is deposited on the transparent substrate and a metal-insulator-metal (MIM) diode is constructed on top of the aperture antenna. There is an insulating layer between the aperture antenna metal and the metal ground plane optimized to maximize the collection of incident radiation. The top of the structure is capped with a metal ground plane layer, which also serves as the DC connection points for each rectenna element.

Directional radiation detectors

DOEpatents

Dowell, Jonathan L.

2017-09-12

Directional radiation detectors and systems, methods, and computer-readable media for using directional radiation detectors to locate a radiation source are provided herein. A directional radiation detector includes a radiation sensor. A radiation attenuator partially surrounds the radiation sensor and defines an aperture through which incident radiation is received by the radiation sensor. The aperture is positioned such that when incident radiation is received directly through the aperture and by the radiation sensor, a source of the incident radiation is located within a solid angle defined by the aperture. The radiation sensor senses at least one of alpha particles, beta particles, gamma particles, or neutrons.

X-band noise temperature effects of rain on DSN antenna feedhorns

NASA Technical Reports Server (NTRS)

Slobin, S. D.; Franco, M. M.; Clauss, R. C.

1982-01-01

Simulated rain tests were carried out to determine the noise temperature contribution of liquid water adhering to the aperture cover material on both a standard DSN X-band feedhorn and on an S/X-band common aperture feedhorn. It was found that for the particular common aperture feedhorn tested, system noise temperature increases were much greater when the plastic horn cover material was old and weathered than when it was new. The age and condition of the aperture cover material is believed to be a major factor in the amount of degradation experienced by a telecommunications system during rain events.

Nozzle geometry for organic vapor jet printing

DOEpatents

Forrest, Stephen R; McGraw, Gregory

2015-01-13

A first device is provided. The device includes a print head. The print head further includes a first nozzle hermetically sealed to a first source of gas. The first nozzle has an aperture having a smallest dimension of 0.5 to 500 microns in a direction perpendicular to a flow direction of the first nozzle. At a distance from the aperture into the first nozzle that is 5 times the smallest dimension of the aperture of the first nozzle, the smallest dimension perpendicular to the flow direction is at least twice the smallest dimension of the aperture of the first nozzle.

Foucault imaging by using non-dedicated transmission electron microscope

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

Taniguchi, Yoshifumi; Matsumoto, Hiroaki; Harada, Ken

2012-08-27

An electron optical system for observing Foucault images was constructed using a conventional transmission electron microscope without any special equipment for Lorentz microscopy. The objective lens was switched off and an electron beam was converged by a condenser optical system to the crossover on the selected area aperture plane. The selected area aperture was used as an objective aperture to select the deflected beam for Foucault mode, and the successive image-forming lenses were controlled for observation of the specimen images. The irradiation area on the specimen was controlled by selecting the appropriate diameter of the condenser aperture.

Optimization of Transmit Parameters in Cardiac Strain Imaging With Full and Partial Aperture Coherent Compounding.

PubMed

Sayseng, Vincent; Grondin, Julien; Konofagou, Elisa E

2018-05-01

Coherent compounding methods using the full or partial transmit aperture have been investigated as a possible means of increasing strain measurement accuracy in cardiac strain imaging; however, the optimal transmit parameters in either compounding approach have yet to be determined. The relationship between strain estimation accuracy and transmit parameters-specifically the subaperture, angular aperture, tilt angle, number of virtual sources, and frame rate-in partial aperture (subaperture compounding) and full aperture (steered compounding) fundamental mode cardiac imaging was thus investigated and compared. Field II simulation of a 3-D cylindrical annulus undergoing deformation and twist was developed to evaluate accuracy of 2-D strain estimation in cross-sectional views. The tradeoff between frame rate and number of virtual sources was then investigated via transthoracic imaging in the parasternal short-axis view of five healthy human subjects, using the strain filter to quantify estimation precision. Finally, the optimized subaperture compounding sequence (25-element subperture, 90° angular aperture, 10 virtual sources, 300-Hz frame rate) was compared to the optimized steered compounding sequence (60° angular aperture, 15° tilt, 10 virtual sources, 300-Hz frame rate) via transthoracic imaging of five healthy subjects. Both approaches were determined to estimate cumulative radial strain with statistically equivalent precision (subaperture compounding E(SNRe %) = 3.56, and steered compounding E(SNRe %) = 4.26).

Perception of Affordance during Short-Term Exposure to Weightlessness in Parabolic Flight

PubMed Central

Bourrelly, Aurore; McIntyre, Joseph; Morio, Cédric; Despretz, Pascal; Luyat, Marion

2016-01-01

We investigated the role of the visual eye-height (VEH) in the perception of affordance during short-term exposure to weightlessness. Sixteen participants were tested during parabolic flight (0g) and on the ground (1g). Participants looked at a laptop showing a room in which a doorway-like aperture was presented. They were asked to adjust the opening of the virtual doorway until it was perceived to be just wide enough to pass through (i.e., the critical aperture). We manipulated VEH by raising the level of the floor in the visual room by 25 cm. The results showed effects of VEH and of gravity on the perceived critical aperture. When VEH was reduced (i.e., when the floor was raised), the critical aperture diminished, suggesting that widths relative to the body were perceived to be larger. The critical aperture was also lower in 0g, for a given VEH, suggesting that participants perceived apertures to be wider or themselves to be smaller in weightlessness, as compared to normal gravity. However, weightlessness also had an effect on the subjective level of the eyes projected into the visual scene. Thus, setting the critical aperture as a fixed percentage of the subjective visual eye-height remains a viable hypothesis to explain how human observers judge visual scenes in terms of potential for action or “affordances”. PMID:27097218

Energy, momentum and propagation of non-paraxial high-order Gaussian beams in the presence of an aperture

NASA Astrophysics Data System (ADS)

Stilgoe, Alexander B.; Nieminen, Timo A.; Rubinsztein-Dunlop, Halina

2015-12-01

Non-paraxial theories of wave propagation are essential to model the interaction of highly focused light with matter. Here we investigate the energy, momentum and propagation of the Laguerre-, Hermite- and Ince-Gaussian solutions (LG, HG, and IG) of the paraxial wave equation in an apertured non-paraxial regime. We investigate the far-field relationships between the LG, HG, and IG solutions and the vector spherical wave function (VSWF) solutions of the vector Helmholtz wave equation. We investigate the convergence of the VSWF and the various Gaussian solutions in the presence of an aperture. Finally, we investigate the differences in linear and angular momentum evaluated in the paraxial and non-paraxial regimes. The non-paraxial model we develop can be applied to calculations of the focusing of high-order Gaussian modes in high-resolution microscopes. We find that the addition of an aperture in high numerical aperture optical systems does not greatly affect far-field properties except when the beam is significantly clipped by an aperture. Diffraction from apertures causes large distortions in the near-field and will influence light-matter interactions. The method is not limited to a particular solution of the paraxial wave equation. Our model is constructed in a formalism that is commonly used in scattering calculations. It is thus applicable to optical trapping and other optical investigations of matter.

Pinch aperture proprioception: reliability and feasibility study

PubMed Central

Yahya, Abdalghani; von Behren, Timothy; Levine, Shira; dos Santos, Marcio

2018-01-01

[Purpose] To establish the reliability and feasibility of a novel pinch aperture device to measure proprioceptive joint position sense. [Subjects and Methods] Reliability of the pinch aperture device was assessed in 21 healthy subjects. Following familiarization with a 15° target position of the index finger and thumb, subjects performed 5 trials in which they attempted to actively reproduce the target position without visual feedback. This procedure was repeated at a testing session on a separate date, and the between-session intraclass correlation coefficient (ICC) was calculated. In addition, extensor tendon vibration was applied to 19 healthy subjects, and paired t-tests were conducted to compare performance under vibration and no-vibration conditions. Pinch aperture proprioception was also assessed in two individuals with known diabetic neuropathy. [Results] The pinch aperture device demonstrated excellent reliability in healthy subjects (ICC 0.88, 95% confidence interval 0.70–0.95). Tendon vibration disrupted pinch aperture proprioception, causing subjects to undershoot the target position (18.1 ± 2.6° vs. 14.8° ± 0.76, p<0.001). This tendency to undershoot the target position was also noted in individuals with diabetic neuropathy. [Conclusion] This study describes a reliable, feasible, and functional means of measuring finger proprioception. Further research should investigate the assessment and implications of pinch aperture proprioception in neurological and orthopedic populations. PMID:29765192

Characterization of an air jet haptic lump display.

PubMed

Bianchi, Matteo; Gwilliam, James C; Degirmenci, Alperen; Okamura, Allison M

2011-01-01

During manual palpation, clinicians rely on distributed tactile information to identify and localize hard lumps embedded in soft tissue. The development of tactile feedback systems to enhance palpation using robot-assisted minimally invasive surgery (RMIS) systems is challenging due to size and weight constraints, motivating a pneumatic actuation strategy. Recently, an air jet approach has been proposed for generating a lump percept. We use this technique to direct a thin stream of air through an aperture directly on the finger pad, which indents the skin in a hemispherical manner, producing a compelling lump percept. We hypothesize that the perceived parameters of the lump (e.g. size and stiffness) can be controlled by jointly adjusting air pressure and the aperture size through which air escapes. In this work, we investigate how these control variables interact to affect perceived pressure on the finger pad. First, we used a capacitive tactile sensor array to measure the effect of aperture size on output pressure, and found that peak output pressure increases with aperture size. Second, we performed a psychophysical experiment for each aperture size to determine the just noticeable difference (JND) of air pressure on the finger pad. Subject-averaged pressure JND values ranged from 19.4-24.7 kPa, with no statistical differences observed between aperture sizes. The aperture-pressure relationship and the pressure JND values will be fundamental for future display control.

Grating-flanked plasmonic coaxial apertures for efficient fiber optical tweezers.

PubMed

Saleh, Amr A E; Sheikhoelislami, Sassan; Gastelum, Steven; Dionne, Jennifer A

2016-09-05

Subwavelength plasmonic apertures have been foundational for direct optical manipulation of nanoscale specimens including sub-100 nm polymeric beads, metallic nanoparticles and proteins. While most plasmonic traps result in two-dimensional localization, three-dimensional manipulation has been demonstrated by integrating a plasmonic aperture on an optical fiber tip. However, such 3D traps are usually inefficient since the optical mode of the fiber and the subwavelength aperture only weakly couple. In this paper we design more efficient optical-fiber-based plasmonic tweezers combining a coaxial plasmonic aperture with a plasmonic grating coupler at the fiber tip facet. Using full-field finite difference time domain analysis, we optimize the grating design for both gold and silver fiber-based coaxial tweezers such that the optical transmission through the apertures is maximized. With the optimized grating, we show that the maximum transmission efficiency increases from 2.5% to 19.6% and from 1.48% to 16.7% for the gold and silver structures respectively. To evaluate their performance as optical tweezers, we calculate the optical forces and the corresponding trapping potential on dielectric particles interacting with the apertures. We demonstrate that the enahncement in the transmission translates into an equivalent increase in the optical forces. Consequently, the optical power required to achieve stable optical trapping is significantly reduced allowing for efficient localization and 3D manipulation of sub-30 nm dielectric particles.

Nonimaging light concentrator with uniform irradiance

DOEpatents

Winston, Roland; Gee, Randy C.

2003-04-01

A nonimaging light concentrator system including a primary collector of light, an optical mixer disposed near the focal zone for collecting light from the primary collector, the optical mixer having a transparent entrance aperture, an internally reflective housing for substantially total internal reflection of light, a transparent exit aperture and an array of photovoltaic cells disposed near the transparent exit aperture.

Variable-aperture screen

DOEpatents

Savage, George M.

1991-01-01

Apparatus for separating material into first and second portions according to size including a plurality of shafts, a plurality of spaced disks radiating outwardly from each of the shafts to define apertures and linkage interconnecting the shafts for moving the shafts toward or away from one another to vary the size of the apertures while the apparatus is performing the separating function.

Coupled Effects of non-Newtonian Rheology and Aperture Variability on Flow in a Single Fracture

NASA Astrophysics Data System (ADS)

Di Federico, V.; Felisa, G.; Lauriola, I.; Longo, S.

2017-12-01

Modeling of non-Newtonian flow in fractured media is essential in hydraulic fracturing and drilling operations, EOR, environmental remediation, and to understand magma intrusions. An important step in the modeling effort is a detailed understanding of flow in a single fracture, as the fracture aperture is spatially variable. A large bibliography exists on Newtonian and non-Newtonian flow in variable aperture fractures. Ultimately, stochastic or deterministic modeling leads to the flowrate under a given pressure gradient as a function of the parameters describing the aperture variability and the fluid rheology. Typically, analytical or numerical studies are performed adopting a power-law (Oswald-de Waele) model. Yet the power-law model, routinely used e.g. for hydro-fracturing modeling, does not characterize real fluids at low and high shear rates. A more appropriate rheological model is provided by e.g. the four-parameter Carreau constitutive equation, which is in turn approximated by the more tractable truncated power-law model. Moreover, fluids of interest may exhibit yield stress, which requires the Bingham or Herschel-Bulkely model. This study employs different rheological models in the context of flow in variable aperture fractures, with the aim of understanding the coupled effect of rheology and aperture spatial variability with a simplified model. The aperture variation, modeled within a stochastic or deterministic framework, is taken to be one-dimensional and i) perpendicular; ii) parallel to the flow direction; for stochastic modeling, the influence of different distribution functions is examined. Results for the different rheological models are compared with those obtained for the pure power-law. The adoption of the latter model leads to overestimation of the flowrate, more so for large aperture variability. The presence of yield stress also induces significant changes in the resulting flowrate for assigned external pressure gradient.

Beyond-laboratory-scale prediction for channeling flows through subsurface rock fractures with heterogeneous aperture distributions revealed by laboratory evaluation

NASA Astrophysics Data System (ADS)

Ishibashi, Takuya; Watanabe, Noriaki; Hirano, Nobuo; Okamoto, Atsushi; Tsuchiya, Noriyoshi

2015-01-01

The present study evaluates aperture distributions and fluid flow characteristics for variously sized laboratory-scale granite fractures under confining stress. As a significant result of the laboratory investigation, the contact area in fracture plane was found to be virtually independent of scale. By combining this characteristic with the self-affine fractal nature of fracture surfaces, a novel method for predicting fracture aperture distributions beyond laboratory scale is developed. Validity of this method is revealed through reproduction of the results of laboratory investigation and the maximum aperture-fracture length relations, which are reported in the literature, for natural fractures. The present study finally predicts conceivable scale dependencies of fluid flows through joints (fractures without shear displacement) and faults (fractures with shear displacement). Both joint and fault aperture distributions are characterized by a scale-independent contact area, a scale-dependent geometric mean, and a scale-independent geometric standard deviation of aperture. The contact areas for joints and faults are approximately 60% and 40%. Changes in the geometric means of joint and fault apertures (µm), em, joint and em, fault, with fracture length (m), l, are approximated by em, joint = 1 × 102 l0.1 and em, fault = 1 × 103 l0.7, whereas the geometric standard deviations of both joint and fault apertures are approximately 3. Fluid flows through both joints and faults are characterized by formations of preferential flow paths (i.e., channeling flows) with scale-independent flow areas of approximately 10%, whereas the joint and fault permeabilities (m2), kjoint and kfault, are scale dependent and are approximated as kjoint = 1 × 10-12 l0.2 and kfault = 1 × 10-8 l1.1.

Article, component, and method of forming an article

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

Lacy, Benjamin Paul; Itzel, Gary Michael; Kottilingam, Srikanth Chandrudu

An article and method of forming an article are provided. The article includes a body portion separating an inner region and an outer region, an aperture in the body portion, the aperture fluidly connecting the inner region to the outer region, and a conduit extending from an outer surface of the body portion at the aperture and being arranged and disposed to controllably direct fluid from the inner region to the outer region. The method includes providing a body portion separating an inner region and an outer region, providing an aperture in the body portion, and forming a conduit overmore » the aperture, the conduit extending from an outer surface of the body portion and being arranged and disposed to controllably direct fluid from the inner region to the outer region. The article is arranged and disposed for insertion within a hot gas path component.« less

System and method for phase retrieval for radio telescope and antenna control

NASA Technical Reports Server (NTRS)

Dean, Bruce H. (Inventor)

2013-01-01

Disclosed herein are systems, methods, and non-transitory computer-readable storage media for radio phase retrieval. A system practicing the method gathers first data from radio waves associated with an object observed via a first aperture, gathers second data from radio waves associated with the object observed via an introduced second aperture associated with the first aperture, generates reduced noise data by incoherently subtracting the second data from the first data, and performs phase retrieval for the radio waves by modeling the reduced noise data using a single Fourier transform. The first and second apertures are at different positions, such as side by side. This approach can include determining a value Q which represents a ratio of wavelength times a focal ratio divided by pixel spacing. This information can be used to accurately measure and correct alignment errors or other optical system flaws in the apertures.

The Effect of a Pre-Lens Aperture on the Temperature Range and Image Uniformity of Microbolometer Infrared Cameras

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

Dinwiddie, Ralph Barton; Parris, Larkin S.; Lindal, John M.

This paper explores the temperature range extension of long-wavelength infrared (LWIR) cameras by placing an aperture in front of the lens. An aperture smaller than the lens will reduce the radiance to the sensor, allowing the camera to image targets much hotter than typically allowable. These higher temperatures were accurately determined after developing a correction factor which was applied to the built-in temperature calibration. The relationship between aperture diameter and temperature range is linear. The effect of pre-lens apertures on the image uniformity is a form of anti-vignetting, meaning the corners appear brighter (hotter) than the rest of the image.more » An example of using this technique to measure temperatures of high melting point polymers during 3D printing provide valuable information of the time required for the weld-line temperature to fall below the glass transition temperature.« less

Variable-energy collimator for high-energy radiation

DOEpatents

Hill, R.A.

1982-03-03

An apparatus is disclosed providing a variable aperture energy beam collimator. A plurality of beam opaque blocks are in sliding interface edge contact to form a variable aperture. The blocks may be offset at the apex angle to provide a non-equilateral aperture. A plurality of collimator block assemblies may be employed for providing a channel defining a collimated beam. Adjacent assemblies are inverted front-to-back with respect to one another for preventing noncollimated ;energy from emergine from the apparatus. An adjustment mechanism comprises a cable attached to at least one block and a hand wheel mechanism for operating the cable. The blocks are supported by guide rods engaging slide brackets on the blocks. The guide rods are pivotally connected at each end to intermediate actuators supported on rotatable shafts to change the shape of the aperture. A divergent collimated beam may be obtained by adjusting the apertures of adjacent stages to be unequal.

High-resolution coded-aperture design for compressive X-ray tomography using low resolution detectors

NASA Astrophysics Data System (ADS)

Mojica, Edson; Pertuz, Said; Arguello, Henry

2017-12-01

One of the main challenges in Computed Tomography (CT) is obtaining accurate reconstructions of the imaged object while keeping a low radiation dose in the acquisition process. In order to solve this problem, several researchers have proposed the use of compressed sensing for reducing the amount of measurements required to perform CT. This paper tackles the problem of designing high-resolution coded apertures for compressed sensing computed tomography. In contrast to previous approaches, we aim at designing apertures to be used with low-resolution detectors in order to achieve super-resolution. The proposed method iteratively improves random coded apertures using a gradient descent algorithm subject to constraints in the coherence and homogeneity of the compressive sensing matrix induced by the coded aperture. Experiments with different test sets show consistent results for different transmittances, number of shots and super-resolution factors.

First imagery generated by near-field real-time aperture synthesis passive millimetre wave imagers at 94 GHz and 183 GHz

NASA Astrophysics Data System (ADS)

Salmon, Neil A.; Mason, Ian; Wilkinson, Peter; Taylor, Chris; Scicluna, Peter

2010-10-01

The first passive millimetre wave (PMMW) imagery is presented from two proof-of-concept aperture synthesis demonstrators, developed to investigate the use of aperture synthesis for personnel security screening and all weather flying at 94 GHz, and satellite based earth observation at 183 GHz [1]. Emission from point noise sources and discharge tubes are used to examine the coherence on system baselines and to measure the point spread functions, making comparisons with theory. Image quality is examined using near field aperture synthesis and G-matrix calibration imaging algorithms. The radiometric sensitivity is measured using the emission from absorbers at elevated temperatures acting as extended sources and compared with theory. Capabilities of the latest Field Programmable Gate Arrays (FPGA) technologies for aperture synthesis PMMW imaging in all-weather and security screening applications are examined.

Method for separating FEL output beams from long wavelength radiation

DOEpatents

Neil, George; Shinn, Michelle D.; Gubeli, Joseph

2016-04-26

A method for improving the output beam quality of a free electron laser (FEL) by reducing the amount of emission at wavelengths longer than the electron pulse length and reducing the amount of edge radiation. A mirror constructed of thermally conductive material and having an aperture therein is placed at an oblique angle with respect to the beam downstream of the bending magnet but before any sensitive use of the FEL beam. The aperture in the mirror is sized to deflect emission longer than the wavelength of the FEL output while having a minor impact on the FEL output beam. A properly sized aperture will enable the FEL radiation, which is coherent and generally at a much shorter wavelength than the bending radiations, to pass through the aperture mirror. The much higher divergence bending radiations will subsequently strike the aperture mirror and be reflected safely out of the way.

A pump driving liquid cooling circuit method for the aperture of an infrared cold optical system

NASA Astrophysics Data System (ADS)

Xie, RongJian

2017-06-01

To enhance the optical recognition and wavelength filtering of an infrared cold optical system, some lens need to be maintained within a certain temperature range, which requires specific thermal management of the aperture. A 250K liquid cooling circuit designed for this purpose is introduced, and the experimental results established and operated in a vacuum environmental simulation chamber is carried out and analyzed. A practical cooling power source of radiation cooling equipment is adopted and the sun exposure heat load is imitated by array of planar membrane heaters attached on the specific designed structure of the aperture. Controlling the aperture temperature and improving the optical system performance are proved effective. Numerical optimization of the cooling circuit and simulation of the aperture are performed , and the factors affect the optical system performance in the mean time are also investigated.

Radius of curvature controlled mirror

DOEpatents

Neil, George R.; Rathke, John Wickham; Schultheiss, Thomas John; Shinn, Michelle D.; Dillon-Townes, Lawrence A.

2006-01-17

A controlled radius of curvature mirror assembly comprising: a distortable mirror having a reflective surface and a rear surface; and in descending order from the rear surface; a counter-distortion plate; a flow diverter having a flow diverter aperture at the center thereof; a flow return plate having a flow return aperture at the center thereof; a thermal isolation plate having a thermal isolation plate aperture at the center thereof and a flexible heater having a rear surface and a flexible heater aperture at the center thereof; a double walled tube defining a coolant feed chamber and a coolant return chamber; said coolant feed chamber extending to and through the flow diverter aperture and terminating at the counter-distortion plate and the coolant return chamber extending to and through the thermal isolation backplate and terminating at the flow diverter; and a coolant feed and a coolant return exit at the rear of said flexible heater.

A polyvalent harmonic coil testing method for small-aperture magnets

NASA Astrophysics Data System (ADS)

Arpaia, Pasquale; Buzio, Marco; Golluccio, Giancarlo; Walckiers, Louis

2012-08-01

A method to characterize permanent and fast-pulsed iron-dominated magnets with small apertures is presented. The harmonic coil measurement technique is enhanced specifically for small-aperture magnets by (1) in situ calibration, for facing search-coil production inaccuracy, (2) rotating the magnet around its axis, for correcting systematic effects, and (3) measuring magnetic fluxes by stationary coils at different angular positions for measuring fast pulsed magnets. This method allows a quadrupole magnet for particle accelerators to be characterized completely, by assessing multipole field components, magnetic axis position, and field direction. In this paper, initially the metrological problems arising from testing small-aperture magnets are highlighted. Then, the basic ideas of the proposed method and the architecture of the corresponding measurement system are illustrated. Finally, experimental validation results are shown for small-aperture permanent and fast-ramped quadrupole magnets for the new linear accelerator Linac4 at CERN (European Organization for Nuclear Research).

Performance analysis of fiber-based free-space optical communications with coherent detection spatial diversity.

PubMed

Li, Kangning; Ma, Jing; Tan, Liying; Yu, Siyuan; Zhai, Chao

2016-06-10

The performances of fiber-based free-space optical (FSO) communications over gamma-gamma distributed turbulence are studied for multiple aperture receiver systems. The equal gain combining (EGC) technique is considered as a practical scheme to mitigate the atmospheric turbulence. Bit error rate (BER) performances for binary-phase-shift-keying-modulated coherent detection fiber-based free-space optical communications are derived and analyzed for EGC diversity receptions through an approximation method. To show the net diversity gain of a multiple aperture receiver system, BER performances of EGC are compared with a single monolithic aperture receiver system with the same total aperture area (same average total incident optical power on the aperture surface) for fiber-based free-space optical communications. The analytical results are verified by Monte Carlo simulations. System performances are also compared for EGC diversity coherent FSO communications with or without considering fiber-coupling efficiencies.

Method of Modeling and Simulation of Shaped External Occulters

NASA Technical Reports Server (NTRS)

Lyon, Richard G. (Inventor); Clampin, Mark (Inventor); Petrone, Peter, III (Inventor)

2016-01-01

The present invention relates to modeling an external occulter including: providing at least one processor executing program code to implement a simulation system, the program code including: providing an external occulter having a plurality of petals, the occulter being coupled to a telescope; and propagating light from the occulter to a telescope aperture of the telescope by scalar Fresnel propagation, by: obtaining an incident field strength at a predetermined wavelength at an occulter surface; obtaining a field propagation from the occulter to the telescope aperture using a Fresnel integral; modeling a celestial object at differing field angles by shifting a location of a shadow cast by the occulter on the telescope aperture; calculating an intensity of the occulter shadow on the telescope aperture; and applying a telescope aperture mask to a field of the occulter shadow, and propagating the light to a focal plane of the telescope via FFT techniques.

Compensation in the presence of deep turbulence using tiled-aperture architectures

NASA Astrophysics Data System (ADS)

Spencer, Mark F.; Brennan, Terry J.

2017-05-01

The presence of distributed-volume atmospheric aberrations or "deep turbulence" presents unique challenges for beam-control applications which look to sense and correct for disturbances found along the laser-propagation path. This paper explores the potential for branch-point-tolerant reconstruction algorithms and tiled-aperture architectures to correct for the branch cuts contained in the phase function due to deep-turbulence conditions. Using wave-optics simulations, the analysis aims to parameterize the fitting-error performance of tiled-aperture architectures operating in a null-seeking control loop with piston, tip, and tilt compensation of the individual optical beamlet trains. To evaluate fitting-error performance, the analysis plots normalized power in the bucket as a function of the Fried coherence diameter, the log-amplitude variance, and the number of subapertures for comparison purposes. Initial results show that tiled-aperture architectures with a large number of subapertures outperform filled-aperture architectures with continuous-face-sheet deformable mirrors.

Adaptive Control Of Woofer-Tweeter Adaptive Optics

DTIC Science & Technology

2009-03-01

the actuator geometry and the matrix F describes the lowpass filter. The columns of T form a set of basis vectors in the space of the master...set equal to the simulated aperture size of 76 cm. The tweeter DM has 39 actuators across the aperture with a spacing of 2 cm for a total of 1521...actuators over the square aperture. The

Convection venting lensed reflector-type compact fluorescent lamp system

DOEpatents

Pelton, B.A.; Siminovitch, M.

1997-07-29

Disclosed herein is a fluorescent lamp housing assembly capable of providing convection cooling to the lamp and the ballast. The lens of the present invention includes two distinct portions, a central portion and an apertured portion. The housing assembly further includes apertures so that air mass is able to freely move up through the assembly and out ventilation apertures. 12 figs.

Convection venting lensed reflector-type compact fluorescent lamp system

DOEpatents

Pelton, Bruce A.; Siminovitch, Michael

1997-01-01

Disclosed herein is a fluorescent lamp housing assembly capable of providing convection cooling to the lamp and the ballast. The lens of the present invention includes two distinct portions, a central portion and an apertured portion. The housing assembly further includes apertures so that air mass is able to freely move up through the assembly and out ventilation apertures.

Variable-aperture screen

DOEpatents

Savage, G.M.

1991-10-29

Apparatus is described for separating material into first and second portions according to size including a plurality of shafts, a plurality of spaced disks radiating outwardly from each of the shafts to define apertures and linkage interconnecting the shafts for moving the shafts toward or away from one another to vary the size of the apertures while the apparatus is performing the separating function. 10 figures.

47 CFR 25.134 - Licensing provisions for Very Small Aperture Terminal (VSAT) and C-band Small Aperture Terminal...

Code of Federal Regulations, 2014 CFR

2014-10-01

... Applications and Licenses Earth Stations § 25.134 Licensing provisions for Very Small Aperture Terminal (VSAT... affected adjacent satellite operators by the operation of the non-conforming earth station. (b) VSAT...) VSAT networks operating in the 12/14 GHz bands may use more than one hub earth station, and the hubs...

High aperture off-axis parabolic mirror applied in digital holographic microscopy

NASA Astrophysics Data System (ADS)

Kalenkov, Georgy S.; Kalenkov, Sergey G.; Shtanko, Alexander E.

2018-04-01

An optical scheme of recording digital holograms of micro-objects based on high numerical aperture off-axis parabolic mirror forming a high aperture reference wave is suggested. Registration of digital holograms based on the proposed optical scheme is confirmed experimentally. Application of the proposed approach for hyperspectral holograms registration of micro-objects in incoherent light is discussed.

Synthetic Aperture Acoustic Imaging of Non-Metallic Cords

DTIC Science & Technology

2012-04-01

Washington Headquarters Services , Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA, 22202-4302...collected with a research prototype synthetic aperture acoustic ( SAA ) imaging system. SAA imaging is an emerging technique that can serve as an...inexpensive alternative or logical complement to synthetic aperture radar (SAR). The SAA imaging system uses an acoustic transceiver (speaker and

Comparison of PSF maxima and minima of multiple annuli coded aperture (MACA) and complementary multiple annuli coded aperture (CMACA) systems

NASA Astrophysics Data System (ADS)

Ratnam, Challa; Lakshmana Rao, Vadlamudi; Lachaa Goud, Sivagouni

2006-10-01

In the present paper, and a series of papers to follow, the Fourier analytical properties of multiple annuli coded aperture (MACA) and complementary multiple annuli coded aperture (CMACA) systems are investigated. First, the transmission function for MACA and CMACA is derived using Fourier methods and, based on the Fresnel-Kirchoff diffraction theory, the formulae for the point spread function are formulated. The PSF maxima and minima are calculated for both the MACA and CMACA systems. The dependence of these properties on the number of zones is studied and reported in this paper.

Grasp cueing and joint attention.

PubMed

Tschentscher, Nadja; Fischer, Martin H

2008-10-01

We studied how two different hand posture cues affect joint attention in normal observers. Visual targets appeared over lateralized objects, with different delays after centrally presented hand postures. Attention was cued by either hand direction or the congruency between hand aperture and object size. Participants pressed a button when they detected a target. Direction cues alone facilitated target detection following short delays but aperture cues alone were ineffective. In contrast, when hand postures combined direction and aperture cues, aperture congruency effects without directional congruency effects emerged and persisted, but only for power grips. These results suggest that parallel parameter specification makes joint attention mechanisms exquisitely sensitive to the timing and content of contextual cues.

Saturation of the anisoplanatic error in horizontal imaging scenarios

NASA Astrophysics Data System (ADS)

Beck, Jeffrey; Bos, Jeremy P.

2017-09-01

We evaluate the piston-removed anisoplanatic error for smaller apertures imaging over long horizontal paths. Previous works have shown that the piston and tilt compensated anisoplanatic error saturates to values less than one squared radian. Under these conditions the definition of the isoplanatic angle is unclear. These works focused on nadir pointing telescope systems with aperture sizes between five meters and one half meter. We directly extend this work to horizontal imaging scenarios with aperture sizes smaller than one half meter. We assume turbulence is constant along the imaging path and that the ratio of the aperture size to the atmospheric coherence length is on the order of unity.

Spin ejector

DOEpatents

Andersen, John A.; Flanigan, John J.; Kindley, Robert J.

1978-01-01

The disclosure relates to an apparatus for spin ejecting a body having a flat plate base containing bosses. The apparatus has a base plate and a main ejection shaft extending perpendicularly from the base plate. A compressible cylindrical spring is disposed about the shaft. Bearings are located between the shaft and the spring. A housing containing a helical aperture releasably engages the base plate and surrounds the shaft bearings and the spring. A piston having an aperture follower disposed in the housing aperture is seated on the spring and is guided by the shaft and the aperture. The spring is compressed and when released causes the piston to spin eject the body.

A simple method for evaluating the wavefront compensation error of diffractive liquid-crystal wavefront correctors.

PubMed

Cao, Zhaoliang; Mu, Quanquan; Hu, Lifa; Lu, Xinghai; Xuan, Li

2009-09-28

A simple method for evaluating the wavefront compensation error of diffractive liquid-crystal wavefront correctors (DLCWFCs) for atmospheric turbulence correction is reported. A simple formula which describes the relationship between pixel number, DLCWFC aperture, quantization level, and atmospheric coherence length was derived based on the calculated atmospheric turbulence wavefronts using Kolmogorov atmospheric turbulence theory. It was found that the pixel number across the DLCWFC aperture is a linear function of the telescope aperture and the quantization level, and it is an exponential function of the atmosphere coherence length. These results are useful for people using DLCWFCs in atmospheric turbulence correction for large-aperture telescopes.

Complementary bowtie aperture for localizing and enhancing optical magnetic field

NASA Astrophysics Data System (ADS)

Zhou, Nan; Kinzel, Edward C.; Xu, Xianfan

2011-08-01

Nanoscale bowtie antenna and bowtie aperture antenna have been shown to generate strongly enhanced and localized electric fields below the diffraction limit in the optical frequency range. According to Babinet's principle, their complements will be efficient for concentrating and enhancing magnetic fields. In this Letter, we discuss the enhancement of magnetic field intensity of nanoscale complementary bowtie aperture as well as complementary bowtie aperture antenna, or diabolo nanoantenna. We show that the complementary bowtie antenna resonates at a smaller wavelength and thus is more suitable for applications near visible wavelengths. The near-field magnetic intensity can be further enhanced by the addition of groove structures that scatter surface plasmon.

Prototype development of a Geostationary Synthetic Thinned Aperture Radiometer, GeoSTAR

NASA Technical Reports Server (NTRS)

Tanner, A. B.; Wilson, W. J.; Kangaslahti, P. P.; Lambrigsten, B. H.; Dinardo, S. J.; Piepmeier, J. R.; Ruf, C. S.; Rogacki, S.; Gross, S. M.; Musko, S.

2004-01-01

Preliminary details of a 2-D synthetic aperture radiometer prototype operating from 50 to 55 GHz will be presented. The laboratory prototype is being developed to demonstrate the technologies and system design needed to do millimeter-wave atmospheric soundings with high spatial resolution from Geostationary orbit. The concept is to deploy a large thinned aperture Y-array on a geostationary satellite, and to use aperture synthesis to obtain images of the Earth without the need for a large mechanically scanned antenna. The laboratory prototype consists of a Y-array of 24 horn antennas, MMIC receivers, and a digital cross-correlation sub-system.

Matched Field Processing Based on Least Squares with a Small Aperture Hydrophone Array.

PubMed

Wang, Qi; Wang, Yingmin; Zhu, Guolei

2016-12-30

The receiver hydrophone array is the signal front-end and plays an important role in matched field processing, which usually covers the whole water column from the sea surface to the bottom. Such a large aperture array is very difficult to realize. To solve this problem, an approach called matched field processing based on least squares with a small aperture hydrophone array is proposed, which decomposes the received acoustic fields into depth function matrix and amplitudes of the normal modes at the beginning. Then all the mode amplitudes are estimated using the least squares in the sense of minimum norm, and the amplitudes estimated are used to recalculate the received acoustic fields of the small aperture array, which means the recalculated ones contain more environmental information. In the end, lots of numerical experiments with three small aperture arrays are processed in the classical shallow water, and the performance of matched field passive localization is evaluated. The results show that the proposed method can make the recalculated fields contain more acoustic information of the source, and the performance of matched field passive localization with small aperture array is improved, so the proposed algorithm is proved to be effective.

Matched Field Processing Based on Least Squares with a Small Aperture Hydrophone Array

PubMed Central

Wang, Qi; Wang, Yingmin; Zhu, Guolei

2016-01-01

The receiver hydrophone array is the signal front-end and plays an important role in matched field processing, which usually covers the whole water column from the sea surface to the bottom. Such a large aperture array is very difficult to realize. To solve this problem, an approach called matched field processing based on least squares with a small aperture hydrophone array is proposed, which decomposes the received acoustic fields into depth function matrix and amplitudes of the normal modes at the beginning. Then all the mode amplitudes are estimated using the least squares in the sense of minimum norm, and the amplitudes estimated are used to recalculate the received acoustic fields of the small aperture array, which means the recalculated ones contain more environmental information. In the end, lots of numerical experiments with three small aperture arrays are processed in the classical shallow water, and the performance of matched field passive localization is evaluated. The results show that the proposed method can make the recalculated fields contain more acoustic information of the source, and the performance of matched field passive localization with small aperture array is improved, so the proposed algorithm is proved to be effective. PMID:28042828

High pressure capillary connector

DOEpatents

Renzi, Ronald F.

2005-08-09

A high pressure connector capable of operating at pressures of 40,000 psi or higher is provided. This connector can be employed to position a first fluid-bearing conduit that has a proximal end and a distal end to a second fluid-bearing conduit thereby providing fluid communication between the first and second fluid-bearing conduits. The connector includes (a) an internal fitting assembly having a body cavity with (i) a lower segment that defines a lower segment aperture and (ii) an interiorly threaded upper segment, (b) a first member having a first member aperture that traverses its length wherein the first member aperture is configured to accommodate the first fluid-bearing conduit and wherein the first member is positioned in the lower segment of the internal fitting assembly, and (c) a second member having a second member aperture that traverses its length wherein the second member is positioned in the upper segment of the fitting assembly and wherein a lower surface of the second member is in contact with an upper surface of the first member to assert a compressive force onto the first member and wherein the first member aperture and the second member aperture are coaxial.

Aging and the Visual Perception of Motion Direction: Solving the Aperture Problem.

PubMed

Shain, Lindsey M; Norman, J Farley

2018-07-01

An experiment required younger and older adults to estimate coherent visual motion direction from multiple motion signals, where each motion signal was locally ambiguous with respect to the true direction of pattern motion. Thus, accurate performance required the successful integration of motion signals across space (i.e., accurate performance required solution of the aperture problem) . The observers viewed arrays of either 64 or 9 moving line segments; because these lines moved behind apertures, their individual local motions were ambiguous with respect to direction (i.e., were subject to the aperture problem). Following 2.4 seconds of pattern motion on each trial (true motion directions ranged over the entire range of 360° in the fronto-parallel plane), the observers estimated the coherent direction of motion. There was an effect of direction, such that cardinal directions of pattern motion were judged with less error than oblique directions. In addition, a large effect of aging occurred-The average absolute errors of the older observers were 46% and 30.4% higher in magnitude than those exhibited by the younger observers for the 64 and 9 aperture conditions, respectively. Finally, the observers' precision markedly deteriorated as the number of apertures was reduced from 64 to 9.

Electromagnetic Field Penetration Studies

NASA Technical Reports Server (NTRS)

Deshpande, M.D.

2000-01-01

A numerical method is presented to determine electromagnetic shielding effectiveness of rectangular enclosure with apertures on its wall used for input and output connections, control panels, visual-access windows, ventilation panels, etc. Expressing EM fields in terms of cavity Green's function inside the enclosure and the free space Green's function outside the enclosure, integral equations with aperture tangential electric fields as unknown variables are obtained by enforcing the continuity of tangential electric and magnetic fields across the apertures. Using the Method of Moments, the integral equations are solved for unknown aperture fields. From these aperture fields, the EM field inside a rectangular enclosure due to external electromagnetic sources are determined. Numerical results on electric field shielding of a rectangular cavity with a thin rectangular slot obtained using the present method are compared with the results obtained using simple transmission line technique for code validation. The present technique is applied to determine field penetration inside a Boeing-757 by approximating its passenger cabin as a rectangular cavity filled with a homogeneous medium and its passenger windows by rectangular apertures. Preliminary results for, two windows, one on each side of fuselage were considered. Numerical results for Boeing-757 at frequencies 26 MHz, 171-175 MHz, and 428-432 MHz are presented.

Can-out hatch assembly and positioning system

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

Basnar, P.J.; Frank, R.C.; Hoh, J.C.

1985-07-03

A can-out hatch assembly is adapted to engage in a sealed manner the upper end of a covered sealed container around an aperture in a sealed chamber and to remove the cover from the container permitting a contaminant to be transferred between the container and the chamber while isolating internal portions of the container and chamber from the surrounding environment. A swing bracket is coupled at a first end thereof to the inner, lower wall of the sealed container adjacent to the aperture therein. To a second end of the swing bracket is mounted a hatch cover which may bemore » positioned in sealed engagement about the chamber's aperture by rotating the hatch cover in a first direction when the swing bracket is in the full down position. Rotation of the hatch cover in a second direction release it from sealed engagement with the chamber's aperture. A lid support rod also coupled to the second end of the swing bracket and inserted through an aperture in the center of the hatch cover may be rotated for theadably engaging the container's cover whereupon the cover may be removed from the container and the hatch cover displaced from the aperture by pivoting displacement of the swing bracket. The contaminant may then be either removed from the container and placed within the sealed chamber, or vice versa, followed by positioning of the cover upon the container and the hatch cover over the aperture in a sealed manner.« less

Multi-port valve

DOEpatents

Lewin, Keith F.

1997-04-15

A multi-port valve for regulating, as a function of ambient air having varying wind velocity and wind direction in an open-field control area, the distribution of a fluid, particularly carbon dioxide (CO.sub.2) gas, in a fluid distribution system so that the control area remains generally at an elevated fluid concentration or level of said fluid. The multi-port valve generally includes a multi-port housing having a plurality of outlets therethrough disposed in a first pattern of outlets and at least one second pattern of outlets, and a movable plate having a plurality of apertures extending therethrough disposed in a first pattern of apertures and at least one second pattern of apertures. The first pattern of apertures being alignable with the first pattern of outlets and the at least one second pattern of apertures being alignable with the second pattern of outlets. The first pattern of apertures has a predetermined orientation with the at least one second pattern of apertures. For an open-field control area subject to ambient wind having a low velocity from any direction, the movable plate is positioned to equally distribute the supply of fluid in a fluid distribution system to the open-field control area. For an open-field control area subject to ambient wind having a high velocity from a given direction, the movable plate is positioned to generally distribute a supply of fluid in a fluid distribution system to that portion of the open-field control area located upwind.

Multi-port valve

DOEpatents

Lewin, K.F.

1997-04-15

A multi-port valve is described for regulating, as a function of ambient air having varying wind velocity and wind direction in an open-field control area, the distribution of a fluid, particularly carbon dioxide (CO{sub 2}) gas, in a fluid distribution system so that the control area remains generally at an elevated fluid concentration or level of said fluid. The multi-port valve generally includes a multi-port housing having a plurality of outlets there through disposed in a first pattern of outlets and at least one second pattern of outlets, and a movable plate having a plurality of apertures extending there through disposed in a first pattern of apertures and at least one second pattern of apertures. The first pattern of apertures being alignable with the first pattern of outlets and the at least one second pattern of apertures being alignable with the second pattern of outlets. The first pattern of apertures has a predetermined orientation with the at least one second pattern of apertures. For an open-field control area subject to ambient wind having a low velocity from any direction, the movable plate is positioned to equally distribute the supply of fluid in a fluid distribution system to the open-field control area. For an open-field control area subject to ambient wind having a high velocity from a given direction, the movable plate is positioned to generally distribute a supply of fluid in a fluid distribution system to that portion of the open-field control area located upwind. 7 figs.

Can-out hatch assembly and positioning system

DOEpatents

Basnar, P.J.; Frank, R.C.; Hoh, J.C.

1985-07-03

A can-out hatch assembly is adapted to engage in a sealed manner the upper end of a covered sealed container around an aperture in a sealed chamber and to remove the cover from the container permitting a contaminant to be transferred between the container and the chamber while isolating internal portions of the container and chamber from the surrounding environment. A swing bracket is coupled at a first end thereof to the inner, lower wall of the sealed container adjacent to the aperture therein. To a second end of the swing bracket is mounted a hatch cover which may be positioned in sealed engagement about the chamber's aperture by rotating the hatch cover in a first direction when the swing bracket is in the full down position. Rotation of the hatch cover in a second direction release it from sealed engagement with the chamber's aperture. A lid support rod also coupled to the second end of the swing bracket and inserted through an aperture in the center of the hatch cover may be rotated for theadably engaging the container's cover whereupon the cover may be removed from the container and the hatch cover displaced from the aperture by pivoting displacement of the swing bracket. The contaminant may then be either removed from the container and placed within the sealed chamber, or vice versa, followed by positioning of the cover upon the container and the hatch cover over the aperture in a sealed manner.

Can-out hatch assembly and positioning system

DOEpatents

Basnar, Paul J.; Frank, Robert C.; Hoh, Joseph C.

1986-01-01

A can-out hatch assembly is adapted to engage in a sealed manner the upper end of a covered sealed container around an aperture in a sealed chamber and to remove the cover from the container permitting a contaminant to be transferred between the container and the chamber while isolating internal portions of the container and chamber from the surrounding environment. A swing bracket is coupled at a first end thereof to the inner, lower wall of the sealed container adjacent to the aperture therein. To a second end of the swing bracket is mounted a hatch cover which may be positioned in sealed engagement about the chamber's aperture by rotating the hatch cover in a first direction when the swing bracket is in the full down position. Rotation of the hatch cover in a second direction releases it from sealed engagement with the chamber's aperture. A lid support rod also coupled to the second end of the swing bracket and inserted through an aperture in the center of the hatch cover may be rotated for threadably engaging the container's cover whereupon the cover may be removed from the container and the hatch cover displaced from the aperture by pivoting displacement of the swing bracket. The contaminant may then be either removed from the container and placed within the sealed chamber, or vice versa, followed by positioning of the cover upon the container and the hatch cover over the aperture in a sealed manner.

Can-out hatch assembly and positioning system

DOEpatents

Basnar, Paul J.; Frank, Robert C.; Hoh, Joseph C.

1986-01-07

A can-out hatch assembly is adapted to engage in a sealed manner the upper end of a covered sealed container around an aperture in a sealed chamber and to remove the cover from the container permitting a contaminant to be transferred between the container and the chamber while isolating internal portions of the container and chamber from the surrounding environment. A swing bracket is coupled at a first end thereof to the inner, lower wall of the sealed container adjacent to the aperture therein. To a second end of the swing bracket is mounted a hatch cover which may be positioned in sealed engagement about the chamber's aperture by rotating the hatch cover in a first direction when the swing bracket is in the full down position. Rotation of the hatch cover in a second direction releases it from sealed engagement with the chamber's aperture. A lid support rod also coupled to the second end of the swing bracket and inserted through an aperture in the center of the hatch cover may be rotated for threadably engaging the container's cover whereupon the cover may be removed from the container and the hatch cover displaced from the aperture by pivoting displacement of the swing bracket. The contaminant may then be either removed from the container and placed within the sealed chamber, or vice versa, followed by positioning of the cover upon the container and the hatch cover over the aperture in a sealed manner.

Design of the polar neutron-imaging aperture for use at the National Ignition Facility.

PubMed

Fatherley, V E; Barker, D A; Fittinghoff, D N; Hibbard, R L; Martinez, J I; Merrill, F E; Oertel, J A; Schmidt, D W; Volegov, P L; Wilde, C H

2016-11-01

The installation of a neutron imaging diagnostic with a polar view at the National Ignition Facility (NIF) required design of a new aperture, an extended pinhole array (PHA). This PHA is different from the pinhole array for the existing equatorial system due to significant changes in the alignment and recording systems. The complex set of component requirements, as well as significant space constraints in its intended location, makes the design of this aperture challenging. In addition, lessons learned from development of prior apertures mandate careful aperture metrology prior to first use. This paper discusses the PHA requirements, constraints, and the final design. The PHA design is complex due to size constraints, machining precision, assembly tolerances, and design requirements. When fully assembled, the aperture is a 15 mm × 15 mm × 200 mm tungsten and gold assembly. The PHA body is made from 2 layers of tungsten and 11 layers of gold. The gold layers include 4 layers containing penumbral openings, 4 layers containing pinholes and 3 spacer layers. In total, there are 64 individual, triangular pinholes with a field of view (FOV) of 200 μm and 6 penumbral apertures. Each pinhole is pointed to a slightly different location in the target plane, making the effective FOV of this PHA a 700 μm square in the target plane. The large FOV of the PHA reduces the alignment requirements both for the PHA and the target, allowing for alignment with a laser tracking system at NIF.

Thermal drawdown-induced flow channeling in a single fracture in EGS

DOE PAGES

Guo, Bin; Fu, Pengcheng; Hao, Yue; ...

2016-01-28

Here, the evolution of flow pattern along a single fracture and its effects on heat production is a fundamental problem in the assessments of engineered geothermal systems (EGS). The channelized flow pattern associated with ubiquitous heterogeneity in fracture aperture distribution causes non-uniform temperature decrease in the rock body, which makes the flow increasingly concentrated into some preferential paths through the action of thermal stress. This mechanism may cause rapid heat production deterioration of EGS reservoirs. In this study, we investigated the effects of aperture heterogeneity on flow pattern evolution in a single fracture in a low-permeability crystalline formation. We developedmore » a numerical model on the platform of GEOS to simulate the coupled thermo-hydro-mechanical processes in a penny-shaped fracture accessed via an injection well and a production well. We find that aperture heterogeneity generally exacerbates flow channeling and reservoir performance generally decreases with longer correlation length of aperture field. The expected production life is highly variable (5 years to beyond 30 years) when the aperture correlation length is longer than 1/5 of the well distance, whereas a heterogeneous fracture behaves similar to a homogeneous one when the correlation length is much shorter than the well distance. Besides, the mean production life decreases with greater aperture standard deviation only when the correlation length is relatively long. Although flow channeling is inevitable, initial aperture fields and well locations that enable tortuous preferential paths tend to deliver long heat production lives.« less

Modulation of hand aperture during reaching in persons with incomplete cervical spinal cord injury.

PubMed

Stahl, Victoria A; Hayes, Heather B; Buetefisch, Cathrin M; Wolf, Steven L; Trumbower, Randy D

2015-03-01

The intact neuromotor system prepares for object grasp by first opening the hand to an aperture that is scaled according to object size and then closing the hand around the object. After cervical spinal cord injury (SCI), hand function is significantly impaired, but the degree to which object-specific hand aperture scaling is affected remains unknown. Here, we hypothesized that persons with incomplete cervical SCI have a reduced maximum hand opening capacity but exhibit novel neuromuscular coordination strategies that permit object-specific hand aperture scaling during reaching. To test this hypothesis, we measured hand kinematics and surface electromyography from seven muscles of the hand and wrist during attempts at maximum hand opening as well as reaching for four balls of different diameters. Our results showed that persons with SCI exhibited significantly reduced maximum hand aperture compared to able-bodied (AB) controls. However, persons with SCI preserved the ability to scale peak hand aperture with ball size during reaching. Persons with SCI also used distinct muscle coordination patterns that included increased co-activity of flexors and extensors at the wrist and hand compared to AB controls. These results suggest that motor planning for aperture modulation is preserved even though execution is limited by constraints on hand opening capacity and altered muscle co-activity. Thus, persons with incomplete cervical SCI may benefit from rehabilitation aimed at increasing hand opening capacity and reducing flexor-extensor co-activity at the wrist and hand.

Modulation of hand aperture during reaching in persons with incomplete cervical spinal cord injury

PubMed Central

Stahl, Victoria; Hayes, Heather B; Buetefisch, Cathrin; Wolf, Steven L; Trumbower, Randy D

2014-01-01

The intact neuromotor system prepares for object grasp by first opening the hand to an aperture that is scaled according to object size and then closing the hand around the object. After cervical spinal cord injury (SCI), hand function is significantly impaired, but the degree to which object-specific hand aperture scaling is affected remains unknown. Here we hypothesized that persons with incomplete cervical SCI have a reduced maximum hand opening capacity but exhibit novel neuromuscular coordination strategies that permit object-specific hand aperture scaling during reaching. To test this hypothesis, we measured hand kinematics and surface electromyography (EMG) from seven muscles of the hand and wrist during attempts at maximum hand opening as well as reaching for four balls of different diameters. Our results showed that persons with SCI exhibited significantly reduced maximum hand aperture compared to able-bodied (AB) controls. However, persons with SCI preserved the ability to scale peak hand aperture with ball size during reaching. Persons with SCI also used distinct muscle coordination patterns that included increased co-activity of flexors and extensors at the wrist and hand compared to AB controls. These results suggest that motor planning for aperture modulation is preserved even though execution is limited by constraints on hand opening capacity and altered muscle co-activity. Thus, persons with incomplete cervical SCI may benefit from rehabilitation aimed at increasing hand opening capacity and reducing flexor-extensor co-activity at the wrist and hand. PMID:25511164

Spillage and flux density on a receiver aperture lip. [of solar thermal collector

NASA Technical Reports Server (NTRS)

Jaffe, L. D.

1985-01-01

In a dish-type point-focusing solar thermal collector, the spillage and the flux density on the receiver aperture lip are related in a very simple way, if the aperture is circular and centered on the optical axis. Specifically, the flux density on the lip is equal to the spillage times the peak flux density in the plane of the lip.

Simultaneous Transmit and Receive Performance of an 8-channel Digital Phased Array

DTIC Science & Technology

2017-01-16

Lincoln Laboratory Lexington, Massachusetts, USA Abstract—The Aperture- Level Simultaneous Transmit and Re- ceive (ALSTAR) architecture enables extremely...In [1], the Aperture- Level Simultaneous Transmit and Receive (ALSTAR) architecture was proposed for achieving STAR using a fully digital phased array...Aperture- Level Simultaneous Transmit and Receive (ALSTAR) architecture enables STAR functionality in a digital phased array without the use of specialized

47 CFR 25.134 - Licensing provisions of Very Small Aperture Terminal (VSAT) and C-band Small Aperture Terminal...

Code of Federal Regulations, 2012 CFR

2012-10-01

... Applications and Licenses Earth Stations § 25.134 Licensing provisions of Very Small Aperture Terminal (VSAT... maximum outbound downlink EIRP density of +10.0 dBW/4 kHz per carrier and earth station antennas with... Order in the Matter of Routine Licensing of Earth Stations in the 6 GHz and 14 GHz Bands Using Antennas...

47 CFR 25.134 - Licensing provisions for Very Small Aperture Terminal (VSAT) and C-band Small Aperture Terminal...

Code of Federal Regulations, 2013 CFR

2013-10-01

... Applications and Licenses Earth Stations § 25.134 Licensing provisions for Very Small Aperture Terminal (VSAT... maximum outbound downlink EIRP density of +10.0 dBW/4 kHz per carrier and earth station antennas with... Order in the Matter of Routine Licensing of Earth Stations in the 6 GHz and 14 GHz Bands Using Antennas...

Solar concentrator with restricted exit angles

DOEpatents

Rabl, Arnulf; Winston, Roland

1978-12-19

A device is provided for the collection and concentration of radiant energy and includes at least one reflective side wall. The wall directs incident radiant energy to the exit aperture thereof or onto the surface of energy absorber positioned at the exit aperture so that the angle of incidence of radiant energy at the exit aperture or on the surface of the energy absorber is restricted to desired values.

3D synthetic aperture for controlled-source electromagnetics

NASA Astrophysics Data System (ADS)

Knaak, Allison

Locating hydrocarbon reservoirs has become more challenging with smaller, deeper or shallower targets in complicated environments. Controlled-source electromagnetics (CSEM), is a geophysical electromagnetic method used to detect and derisk hydrocarbon reservoirs in marine settings, but it is limited by the size of the target, low-spatial resolution, and depth of the reservoir. To reduce the impact of complicated settings and improve the detecting capabilities of CSEM, I apply synthetic aperture to CSEM responses, which virtually increases the length and width of the CSEM source by combining the responses from multiple individual sources. Applying a weight to each source steers or focuses the synthetic aperture source array in the inline and crossline directions. To evaluate the benefits of a 2D source distribution, I test steered synthetic aperture on 3D diffusive fields and view the changes with a new visualization technique. Then I apply 2D steered synthetic aperture to 3D noisy synthetic CSEM fields, which increases the detectability of the reservoir significantly. With more general weighting, I develop an optimization method to find the optimal weights for synthetic aperture arrays that adapts to the information in the CSEM data. The application of optimally weighted synthetic aperture to noisy, simulated electromagnetic fields reduces the presence of noise, increases detectability, and better defines the lateral extent of the target. I then modify the optimization method to include a term that minimizes the variance of random, independent noise. With the application of the modified optimization method, the weighted synthetic aperture responses amplifies the anomaly from the reservoir, lowers the noise floor, and reduces noise streaks in noisy CSEM responses from sources offset kilometers from the receivers. Even with changes to the location of the reservoir and perturbations to the physical properties, synthetic aperture is still able to highlight targets correctly, which allows use of the method in locations where the subsurface models are built from only estimates. In addition to the technical work in this thesis, I explore the interface between science, government, and society by examining the controversy over hydraulic fracturing and by suggesting a process to aid the debate and possibly other future controversies.

Aperture-free star formation rate of SDSS star-forming galaxies

NASA Astrophysics Data System (ADS)

Duarte Puertas, S.; Vilchez, J. M.; Iglesias-Páramo, J.; Kehrig, C.; Pérez-Montero, E.; Rosales-Ortega, F. F.

2017-03-01

Large area surveys with a high number of galaxies observed have undoubtedly marked a milestone in the understanding of several properties of galaxies, such as star-formation history, morphology, and metallicity. However, in many cases, these surveys provide fluxes from fixed small apertures (e.g. fibre), which cover a scant fraction of the galaxy, compelling us to use aperture corrections to study the global properties of galaxies. In this work, we derive the current total star formation rate (SFR) of Sloan Digital Sky Survey (SDSS) star-forming galaxies, using an empirically based aperture correction of the measured Hα flux for the first time, thus minimising the uncertainties associated with reduced apertures. All the Hα fluxes have been extinction-corrected using the Hα/ Hβ ratio free from aperture effects. The total SFR for 210 000 SDSS star-forming galaxies has been derived applying pure empirical Hα and Hα/ Hβ aperture corrections based on the Calar Alto Legacy Integral Field Area (CALIFA) survey. We find that, on average, the aperture-corrected SFR is 0.65 dex higher than the SDSS fibre-based SFR. The relation between the SFR and stellar mass for SDSS star-forming galaxies (SFR-M⋆) has been obtained, together with its dependence on extinction and Hα equivalent width. We compare our results with those obtained in previous works and examine the behaviour of the derived SFR in six redshift bins, over the redshift range 0.005 ≤ z ≤ 0.22. The SFR-M⋆ sequence derived here is in agreement with selected observational studies based on integral field spectroscopy of individual galaxies as well as with the predictions of recent theoretical models of disc galaxies. A table of the aperture-corrected fluxes and SFR for 210 000 SDSS star-forming galaxies and related relevant data is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/599/A71 Warning, no authors found for 2017A&A...599A..51.

4D Light Field Imaging System Using Programmable Aperture

NASA Technical Reports Server (NTRS)

Bae, Youngsam

2012-01-01

Complete depth information can be extracted from analyzing all angles of light rays emanated from a source. However, this angular information is lost in a typical 2D imaging system. In order to record this information, a standard stereo imaging system uses two cameras to obtain information from two view angles. Sometimes, more cameras are used to obtain information from more angles. However, a 4D light field imaging technique can achieve this multiple-camera effect through a single-lens camera. Two methods are available for this: one using a microlens array, and the other using a moving aperture. The moving-aperture method can obtain more complete stereo information. The existing literature suggests a modified liquid crystal panel [LC (liquid crystal) panel, similar to ones commonly used in the display industry] to achieve a moving aperture. However, LC panels cannot withstand harsh environments and are not qualified for spaceflight. In this regard, different hardware is proposed for the moving aperture. A digital micromirror device (DMD) will replace the liquid crystal. This will be qualified for harsh environments for the 4D light field imaging. This will enable an imager to record near-complete stereo information. The approach to building a proof-ofconcept is using existing, or slightly modified, off-the-shelf components. An SLR (single-lens reflex) lens system, which typically has a large aperture for fast imaging, will be modified. The lens system will be arranged so that DMD can be integrated. The shape of aperture will be programmed for single-viewpoint imaging, multiple-viewpoint imaging, and coded aperture imaging. The novelty lies in using a DMD instead of a LC panel to move the apertures for 4D light field imaging. The DMD uses reflecting mirrors, so any light transmission lost (which would be expected from the LC panel) will be minimal. Also, the MEMS-based DMD can withstand higher temperature and pressure fluctuation than a LC panel can. Robotics need near complete stereo images for their autonomous navigation, manipulation, and depth approximation. The imaging system can provide visual feedback

The influence of swarm deformation on the velocity behavior of falling swarms of particles

NASA Astrophysics Data System (ADS)

Mitchell, C. A.; Pyrak-Nolte, L. J.; Nitsche, L.

2017-12-01

Cohesive particle swarms have been shown to exhibit enhanced sedimentation in fractures for an optimal range of fracture apertures. Within this range, swarms travel farther and faster than a disperse (particulate) solution. This study aims to uncover the physics underlying the enhanced sedimentation. Swarm behavior at low Reynolds number in a quiescent unbounded fluid and between smooth rigid planar boundaries is investigated numerically using direct-summation, particle-mesh (PM) and particle-particle particle-mesh (P3M) methods - based upon mutually interacting viscous point forces (Stokeslet fields). Wall effects are treated with a least-squares boundary singularity method. Sub-structural effects beyond pseudo-liquid behavior (i.e., particle-scale interactions) are approximated by the P3M method much more efficiently than with direct summation. The model parameters are selected from particle swarm experiments to enable comparison. From the simulations, if the initial swarm geometry at release is unaffected by the fracture aperture, no enhanced transport occurs. The swarm velocity as a function of apertures increases monotonically until it asymptotes to the swarm velocity in an open tank. However, if the fracture aperture affects the initial swarm geometry, the swarm velocity no longer exhibits a monotonic behavior. When swarms are released between two parallel smooth walls with very small apertures, the swarm is forced to reorganize and quickly deform, which results in dramatically reduced swarm velocities. At large apertures, the swarm evolution is similar to that of a swarm in open tank and quickly flattens into a slow speed torus. In the optimal aperture range, the swarm maintains a cohesive unit behaving similarly to a falling sphere. Swarms falling in apertures less than or greater than the optimal aperture range, experience a level of anisotropy that considerably decreases velocities. Unraveling the physics that drives swarm behavior in fractured porous media is important for understanding particle sedimentation and contaminant spreading in the subsurface. Acknowledgment: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Geosciences Research Program under Award Number (DE-FG02-09ER16022).

Aperture Photometry Tool

NASA Astrophysics Data System (ADS)

Laher, Russ R.; Gorjian, Varoujan; Rebull, Luisa M.; Masci, Frank J.; Fowler, John W.; Helou, George; Kulkarni, Shrinivas R.; Law, Nicholas M.

2012-07-01

Aperture Photometry Tool (APT) is software for astronomers and students interested in manually exploring the photometric qualities of astronomical images. It is a graphical user interface (GUI) designed to allow the image data associated with aperture photometry calculations for point and extended sources to be visualized and, therefore, more effectively analyzed. The finely tuned layout of the GUI, along with judicious use of color-coding and alerting, is intended to give maximal user utility and convenience. Simply mouse-clicking on a source in the displayed image will instantly draw a circular or elliptical aperture and sky annulus around the source and will compute the source intensity and its uncertainty, along with several commonly used measures of the local sky background and its variability. The results are displayed and can be optionally saved to an aperture-photometry-table file and plotted on graphs in various ways using functions available in the software. APT is geared toward processing sources in a small number of images and is not suitable for bulk processing a large number of images, unlike other aperture photometry packages (e.g., SExtractor). However, APT does have a convenient source-list tool that enables calculations for a large number of detections in a given image. The source-list tool can be run either in automatic mode to generate an aperture photometry table quickly or in manual mode to permit inspection and adjustment of the calculation for each individual detection. APT displays a variety of useful graphs with just the push of a button, including image histogram, x and y aperture slices, source scatter plot, sky scatter plot, sky histogram, radial profile, curve of growth, and aperture-photometry-table scatter plots and histograms. APT has many functions for customizing the calculations, including outlier rejection, pixel “picking” and “zapping,” and a selection of source and sky models. The radial-profile-interpolation source model, which is accessed via the radial-profile-plot panel, allows recovery of source intensity from pixels with missing data and can be especially beneficial in crowded fields.

Predicting mineral precipitation in fractures: The influence of local heterogeneity on the feedback between precipitation and permeability

NASA Astrophysics Data System (ADS)

Jones, T.; Detwiler, R. L.

2016-12-01

Long-term subsurface energy production and contaminant storage strategies often rely on induced-mineralization to control the transport of dissolved ions. In low-permeability rocks, precipitation is most likely to occur in fractures that act as leakage pathways for fluids that are in chemical disequilibrium with the formation minerals. These fractures are commonly idealized as parallel-plate channels with uniform surface mineralogy, and as a result, our predictions often suggest that precipitation leads to fast permeability reduction. However, natural fractures contain both heterogeneous mineralogy and three-dimensional surface roughness, and our understanding of how precipitation affects local permeability in these environments is limited. To examine the impacts of local heterogeneity on the feedback between mineral precipitation and permeability, we performed two long-term experiments in transparent analog fractures: (i) uniform-aperture and (ii) variable-aperture. We controlled the initial heterogeneous surface mineralogy in both experiments by seeding the bottom borosilicate fracture surfaces with randomly distributed clusters of CaCO3 crystals. Continuous flow ISCO pumps injected a well-mixed CaCl2-NaHCO3 solution, log(ΩCaCO3) = 1.44, into the fracture at 0.5 ml/min and transmitted-light techniques provided high-resolution (83 x 83 µm), direct measurements of aperture and fluid transport across the fracture. In experiment (i), precipitation decreased local aperture at discrete CaCO3 reaction sites near the fracture inlet, but transport variations across the fracture remained relatively small due to the initial lack of aperture heterogeneity. In contrast, the feedback between precipitation and aperture in experiment (ii) focused flow into large-aperture, preferential flow paths that contained significantly less CaCO3 area than the fracture scale average. Precipitation-induced aperture reduction in (ii) reduced dissolved ion transport into small-aperture regions of the fracture that were abundant with CaCO3 and led to a 72% decrease in measured precipitation rate. These results suggest that incorporating the effects of local heterogeneity may dramatically improve our ability to predict precipitation-induced permeability alterations in fractured rocks.

Three dimensional fracture aperture and porosity distribution using computerized tomography

NASA Astrophysics Data System (ADS)

Wenning, Q.; Madonna, C.; Joss, L.; Pini, R.

2017-12-01

A wide range of geologic processes and geo-engineered applications are governed by coupled hydromechanical properties in the subsurface. In geothermal energy reservoirs, quantifying the rate of heat transfer is directly linked with the transport properties of fractures, underscoring the importance of fracture aperture characterization for achieving optimal heat production. In this context, coupled core-flooding experiments with non-invasive imaging techniques (e.g., X-Ray Computed Tomography - X-Ray CT) provide a powerful method to make observations of these properties under representative geologic conditions. This study focuses on quantifying fracture aperture distribution in a fractured westerly granite core by using a recently developed calibration-free method [Huo et al., 2016]. Porosity is also estimated with the X-ray saturation technique using helium and krypton gases as saturating fluids, chosen for their high transmissibility and high CT contrast [e.g., Vega et al., 2014]. The westerly granite sample (diameter: 5 cm, length: 10 cm) with a single through-going rough-walled fracture was mounted in a high-pressure aluminum core-holder and placed inside a medical CT scanner for imaging. During scanning the pore fluid pressure was undrained and constant, and the confining pressure was regulated to have the desired effective pressure (0.5, 5, 7 and 10 MPa) under loading and unloading conditions. 3D reconstructions of the sample have been prepared in terms of fracture aperture and porosity at a maximum resolution of (0.24×0.24×1) mm3. Fracture aperture maps obtained independently using helium and krypton for the whole core depict a similar heterogeneous aperture field, which is also dependent on confining pressure. Estimates of the average hydraulic aperture from CT scans are in quantitative agreement with results from fluid flow experiments. However, the latter lack of the level of observational detail achieved through imaging, which further evidence the presence of strong heterogeneities in fracture aperture at the mm-scale. These results exemplify the use of non-destructive imaging to determine fracture aperture maps, which can be used to address flow channelization and heat transfer that cannot be obtained from core-flooding experiments alone.

Temporal dosimeter and method

DOEpatents

Warner, Benjamin P.; Lopez, Thomas A.

2003-09-30

The invention includes a temporal dosimeter. One dosimeter embodiment includes a housing that is opaque to visible light but transparent to ionizing radiation. The dosimeter also includes a sensor for recording dosages of ionizing radiation, a drive mechanism, a power source, and rotatable shields that work together to produce a compound aperture to unveil different portions of the sensor at different times to ionizing radiation. Another dosimeter embodiment includes a housing, a sensor, a shield with an aperture portion, and a linear actuator drive mechanism coupled to the sensor for moving the sensor past the aperture portion. The sensor turns as it moves past the aperture, tracing a timeline record of exposure to ionizing radiation along a helical path on the sensor.

Class of near-perfect coded apertures

NASA Technical Reports Server (NTRS)

Cannon, T. M.; Fenimore, E. E.

1977-01-01

Coded aperture imaging of gamma ray sources has long promised an improvement in the sensitivity of various detector systems. The promise has remained largely unfulfilled, however, for either one of two reasons. First, the encoding/decoding method produces artifacts, which even in the absence of quantum noise, restrict the quality of the reconstructed image. This is true of most correlation-type methods. Second, if the decoding procedure is of the deconvolution variety, small terms in the transfer function of the aperture can lead to excessive noise in the reconstructed image. It is proposed to circumvent both of these problems by use of a uniformly redundant array (URA) as the coded aperture in conjunction with a special correlation decoding method.

Electromagnetic Formation Flight (EMFF) for Sparse Aperture Arrays

NASA Technical Reports Server (NTRS)

Kwon, Daniel W.; Miller, David W.; Sedwick, Raymond J.

2004-01-01

Traditional methods of actuating spacecraft in sparse aperture arrays use propellant as a reaction mass. For formation flying systems, propellant becomes a critical consumable which can be quickly exhausted while maintaining relative orientation. Additional problems posed by propellant include optical contamination, plume impingement, thermal emission, and vibration excitation. For these missions where control of relative degrees of freedom is important, we consider using a system of electromagnets, in concert with reaction wheels, to replace the consumables. Electromagnetic Formation Flight sparse apertures, powered by solar energy, are designed differently from traditional propulsion systems, which are based on V. This paper investigates the design of sparse apertures both inside and outside the Earth's gravity field.

Adaptive optics technique to overcome the turbulence in a large-aperture collimator.

PubMed

Mu, Quanquan; Cao, Zhaoliang; Li, Dayu; Hu, Lifa; Xuan, Li

2008-03-20

A collimator with a long focal length and large aperture is a very important apparatus for testing large-aperture optical systems. But it suffers from internal air turbulence, which may limit its performance and reduce the testing accuracy. To overcome this problem, an adaptive optics system is introduced to compensate for the turbulence. This system includes a liquid crystal on silicon device as a wavefront corrector and a Shack-Hartmann wavefront sensor. After correction, we can get a plane wavefront with rms of about 0.017 lambda (lambda=0.6328 microm) emitted out of a larger than 500 mm diameter aperture. The whole system reaches diffraction-limited resolution.

Rule of Thumb Proposing the Size of Aperture Expected to be Sufficient to Resolve Double Stars with Given Parameters

NASA Astrophysics Data System (ADS)

Knapp, Wilfried

2018-01-01

Visual observation of double stars is an anachronistic passion especially attractive for amateurs looking for sky objects suitable for visual observation even in light polluted areas. Session planning then requires a basic idea which objects might be suitable for a given equipment—this question is a long term issue for visual double star observers and obviously not easy to answer, especially for unequal bright components. Based on a reasonably large database with limited aperture observations (done with variable aperture equipment iris diaphragm or aperture masks) a heuristic approach is used to derive a statistically well founded Rule of Thumb formula.

Terahertz Near-Field Imaging Using Enhanced Transmission through a Single Subwavelength Aperture

NASA Astrophysics Data System (ADS)

Ishihara, Kunihiko; Ikari, Tomofumi; Minamide, Hiroaki; Shikata, Jun-ichi; Ohashi, Keishi; Yokoyama, Hiroyuki; Ito, Hiromasa

2005-07-01

We demonstrate terahertz (THz) near-field imaging using resonantly enhanced transmission of THz-wave radiation (λ˜ 200 μm) through a bull’s eye structure (a single subwavelength aperture surrounded by concentric periodic grooves in a metal plate). The bull’s eye structure shows extremely large enhanced transmission, which has the advantage for a single subwavelength aperture. The spatial resolution for the bull’s eye structure (with an aperture diameter d=100 μm) is evaluated in the near-field region, and a resolution of 50 μm (corresponding to λ/4) is achieved. We obtain the THz near-field images of the subwavelength metal pattern with a spatial resolution below the diffraction limit.

Pulsed particle beam vacuum-to-air interface

DOEpatents

Cruz, Gilbert E.; Edwards, William F.

1988-01-01

A vacuum-to-air interface (10) is provided for a high-powered, pulsed particle beam accelerator. The interface comprises a pneumatic high speed gate valve (18), from which extends a vacuum-tight duct (26), that termintes in an aperture (28). Means (32, 34, 36, 38, 40, 42, 44, 46, 48) are provided for periodically advancing a foil strip (30) across the aperture (28) at the repetition rate of the particle pulses. A pneumatically operated hollow sealing band (62) urges foil strip (30), when stationary, against and into the aperture (28). Gas pressure means (68, 70) periodically lift off and separate foil strip (30) from aperture (28), so that it may be readily advanced.

Early development in synthetic aperture lidar sensing and processing for on-demand high resolution imaging

NASA Astrophysics Data System (ADS)

Bergeron, Alain; Turbide, Simon; Terroux, Marc; Marchese, Linda; Harnisch, Bernd

2017-11-01

The quest for real-time high resolution is of prime importance for surveillance applications specially in disaster management and rescue mission. Synthetic aperture radar provides meter-range resolution images in all weather conditions. Often installed on satellites the revisit time can be too long to support real-time operations on the ground. Synthetic aperture lidar can be lightweight and offers centimeter-range resolution. Onboard airplane or unmanned air vehicle this technology would allow for timelier reconnaissance. INO has developed a synthetic aperture radar table prototype and further used a real-time optronic processor to fulfill image generation on-demand. The early positive results using both technologies are presented in this paper.

High power 808 nm vertical cavity surface emitting laser with multi-ring-shaped-aperture structure

NASA Astrophysics Data System (ADS)

Hao, Y. Q.; Shang, C. Y.; Feng, Y.; Yan, C. L.; Zhao, Y. J.; Wang, Y. X.; Wang, X. H.; Liu, G. J.

2011-02-01

The carrier conglomeration effect has been one of the main problems in developing electrically pumped high power vertical cavity surface emitting laser (VCSEL) with large aperture. We demonstrate a high power 808 nm VCSEL with multi-ring-shaped-aperture (MRSA) to weaken the carrier conglomeration effect. Compared with typical VCSEL with single large aperture (SLA), the 300-μm-diameter VCSEL with MRSA has more uniform near field and far field patterns. Moreover, MRSA laser exhibits maximal CW light output power 0.3 W which is about 3 times that of SLA laser. And the maximal wall-plug efficiency of 17.4% is achieved, higher than that of SLA laser by 10%.

Mode trap for absorbing transverse modes of an accelerated electron beam

DOEpatents

Chojnacki, Eric P.

1994-01-01

A mode trap to trap and absorb transverse modes formed by a beam in a linear accelerator includes a waveguide having a multiplicity of electrically conductive (preferably copper) irises and rings, each iris and ring including an aperture, and the irises and rings being stacked in a side-by-side, alternating fashion such that the apertures of the irises and rings are concentrically aligned. An absorbing material layer such as a dielectric is embedded in each iris and ring, and this absorbing material layer encircles, but is circumferentially spaced from its respective aperture. Each iris and ring includes a plurality of circumferentially spaced slots around its aperture and extending radially out toward its absorbing material layer.

Axial flow plasma shutter

DOEpatents

Krausse, George J.

1988-01-01

A shutter (36) is provided for controlling a beam, or current, of charged particles in a device such as a thyratron (10). The substrate (38) defines an aperture (60) with a gap (32) which is placeable within the current. Coils (48) are formed on the substrate (38) adjacent the aperture (60) to produce a magnetic field for trapping the charged particles in or about aperture (60). The proximity of the coils (48) to the aperture (60) enables an effective magnetic field to be generated by coils (48) having a low inductance suitable for high frequency control. The substantially monolithic structure including the substrate (38) and coils (48) enables the entire shutter assembly (36) to be effectively located with respect to the particle beam.

The FRD and transmission of the 270-m GRACES optical fiber link and a high numerical aperture fiber for astronomy

NASA Astrophysics Data System (ADS)

Pazder, John; Fournier, Paul; Pawluczyk, Rafal; van Kooten, Maaike

2014-07-01

We report results of the extensive development work done on the 270-m optical fiber link for the GRACES project and a preliminary investigations into a high numerical aperture fiber for astronomy. The Gemini Remote Access CFHT ESPaDOnS Spectrograph (GRACES) is an instrumentation experiment to link ESPaDOnS, a bench-mounted highresolution optical spectrograph at CFHT, to the Gemini-North telescope with an optical fiber link. A 270-m fiber link with less than 14% Focal Ratio Degradation (FRD) has been developed jointly by HIA and FiberTech Optica for the experiment. A preliminary study has been conducted by HIA into a high numerical aperture fiber (0.26 numerical aperture) with the intended application of wide field optical spectrographs fiber fed from the telescope prime focus. The Laboratory test results of FRD, transmission, and stability for the GRACES fiber link and preliminary FRD measurements of the high numerical aperture fiber tests are reported.

Maximum nondiffracting propagation distance of aperture-truncated Airy beams

NASA Astrophysics Data System (ADS)

Chu, Xingchun; Zhao, Shanghong; Fang, Yingwu

2018-05-01

Airy beams have called attention of many researchers due to their non-diffracting, self-healing and transverse accelerating properties. A key issue in research of Airy beams and its applications is how to evaluate their nondiffracting propagation distance. In this paper, the critical transverse extent of physically realizable Airy beams is analyzed under the local spatial frequency methodology. The maximum nondiffracting propagation distance of aperture-truncated Airy beams is formulated and analyzed based on their local spatial frequency. The validity of the formula is verified by comparing the maximum nondiffracting propagation distance of an aperture-truncated ideal Airy beam, aperture-truncated exponentially decaying Airy beam and exponentially decaying Airy beam. Results show that the formula can be used to evaluate accurately the maximum nondiffracting propagation distance of an aperture-truncated ideal Airy beam. Therefore, it can guide us to select appropriate parameters to generate Airy beams with long nondiffracting propagation distance that have potential application in the fields of laser weapons or optical communications.

Optical monitoring system for a turbine engine

DOEpatents

Lemieux, Dennis H; Smed, Jan P; Williams, James P; Jonnalagadda, Vinay

2013-05-14

The monitoring system for a gas turbine engine including a viewing tube assembly having an inner end and an outer end. The inner end is located adjacent to a hot gas flow path within the gas turbine engine and the outer end is located adjacent to an outer casing of the gas turbine engine. An aperture wall is located at the inner end of the viewing tube assembly and an optical element is located within the viewing tube assembly adjacent to the inner end and is spaced from the aperture wall to define a cooling and purge chamber therebetween. An aperture is defined in the aperture wall for passage of light from the hot gas flow path to the optical element. Swirl passages are defined in the viewing tube assembly between the aperture wall and the optical element for passage of cooling air from a location outside the viewing tube assembly into the chamber, wherein swirl passages effect a swirling movement of air in a circumferential direction within the chamber.

INJECTION OPTICS FOR THE JLEIC ION COLLIDER RING

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

Morozov, Vasiliy; Derbenev, Yaroslav; Lin, Fanglei

2016-05-01

The Jefferson Lab Electron-Ion Collider (JLEIC) will accelerate protons and ions from 8 GeV to 100 GeV. A very low beta function at the Interaction Point (IP) is needed to achieve the required luminosity. One consequence of the low beta optics is that the beta function in the final focusing (FF) quadrupoles is extremely high. This leads to a large beam size in these magnets as well as strong sensitivity to errors which limits the dynamic aperture. These effects are stronger at injection energy where the beam size is maximum, and therefore very large aperture FF magnets are required tomore » allow a large dynamic aperture. A standard solution is a relaxed injection optics with IP beta function large enough to provide a reasonable FF aperture. This also reduces the effects of FF errors resulting in a larger dynamic aperture at injection. We describe the ion ring injection optics design as well as a beta-squeeze transition from the injection to collision optics.« less

High-resolution imaging gamma-ray spectroscopy with externally segmented germanium detectors

NASA Technical Reports Server (NTRS)

Callas, J. L.; Mahoney, W. A.; Varnell, L. S.; Wheaton, W. A.

1993-01-01

Externally segmented germanium detectors promise a breakthrough in gamma-ray imaging capabilities while retaining the superb energy resolution of germanium spectrometers. An angular resolution of 0.2 deg becomes practical by combining position-sensitive germanium detectors having a segment thickness of a few millimeters with a one-dimensional coded aperture located about a meter from the detectors. Correspondingly higher angular resolutions are possible with larger separations between the detectors and the coded aperture. Two-dimensional images can be obtained by rotating the instrument. Although the basic concept is similar to optical or X-ray coded-aperture imaging techniques, several complicating effects arise because of the penetrating nature of gamma rays. The complications include partial transmission through the coded aperture elements, Compton scattering in the germanium detectors, and high background count rates. Extensive electron-photon Monte Carlo modeling of a realistic detector/coded-aperture/collimator system has been performed. Results show that these complicating effects can be characterized and accounted for with no significant loss in instrument sensitivity.

High-performance etching of multilevel phase-type Fresnel zone plates with large apertures

NASA Astrophysics Data System (ADS)

Guo, Chengli; Zhang, Zhiyu; Xue, Donglin; Li, Longxiang; Wang, Ruoqiu; Zhou, Xiaoguang; Zhang, Feng; Zhang, Xuejun

2018-01-01

To ensure the etching depth uniformity of large-aperture Fresnel zone plates (FZPs) with controllable depths, a combination of a point source ion beam with a dwell-time algorithm has been proposed. According to the obtained distribution of the removal function, the latter can be used to optimize the etching time matrix by minimizing the root-mean-square error between the simulation results and the design value. Owing to the convolution operation in the utilized algorithm, the etching depth error is insensitive to the etching rate fluctuations of the ion beam, thereby reducing the requirement for the etching stability of the ion system. As a result, a 4-level FZP with a circular aperture of 300 mm was fabricated. The obtained results showed that the etching depth uniformity of the full aperture could be reduced to below 1%, which was sufficiently accurate for meeting the use requirements of FZPs. The proposed etching method may serve as an alternative way of etching high-precision diffractive optical elements with large apertures.

Large aperture diffractive space telescope

DOEpatents

Hyde, Roderick A.

2001-01-01

A large (10's of meters) aperture space telescope including two separate spacecraft--an optical primary objective lens functioning as a magnifying glass and an optical secondary functioning as an eyepiece. The spacecraft are spaced up to several kilometers apart with the eyepiece directly behind the magnifying glass "aiming" at an intended target with their relative orientation determining the optical axis of the telescope and hence the targets being observed. The objective lens includes a very large-aperture, very-thin-membrane, diffractive lens, e.g., a Fresnel lens, which intercepts incoming light over its full aperture and focuses it towards the eyepiece. The eyepiece has a much smaller, meter-scale aperture and is designed to move along the focal surface of the objective lens, gathering up the incoming light and converting it to high quality images. The positions of the two space craft are controlled both to maintain a good optical focus and to point at desired targets which may be either earth bound or celestial.

Lamination cooling system

DOEpatents

Rippel, Wally E.; Kobayashi, Daryl M.

2005-10-11

An electric motor, transformer or inductor having a lamination cooling system including a stack of laminations, each defining a plurality of apertures at least partially coincident with apertures of adjacent laminations. The apertures define a plurality of cooling-fluid passageways through the lamination stack, and gaps between the adjacent laminations are sealed to prevent a liquid cooling fluid in the passageways from escaping between the laminations. The gaps are sealed by injecting a heat-cured sealant into the passageways, expelling excess sealant, and heat-curing the lamination stack. The apertures of each lamination can be coincident with the same-sized apertures of adjacent laminations to form straight passageways, or they can vary in size, shape and/or position to form non-axial passageways, angled passageways, bidirectional passageways, and manifold sections of passageways that connect a plurality of different passageway sections. Manifold members adjoin opposite ends of the lamination stack, and each is configured with one or more cavities to act as a manifold to adjacent passageway ends. Complex manifold arrangements can create bidirectional flow in a variety of patterns.

Formation of annular plasma downstream by magnetic aperture in the helicon experimental device

NASA Astrophysics Data System (ADS)

Ghosh, Soumen; Yadav, S.; Barada, K. K.; Chattopadhyay, P. K.; Ghosh, J.; Pal, R.; Bora, D.

2017-02-01

In the Helicon eXperimental (HeX) device, the geometric aperture is fixed, but the position of the magnetic aperture can be varied. Working with Argon gas in the pressure range of 1 - 10 × 10 - 4 mbar, an annular plasma (density ˜ 10 16 m - 3 ) is formed downstream, always in front of the magnetic aperture. This occurs irrespective of the relative position of the geometric aperture or the presence of a radial electric field. This is in contrary to the earlier proposition made by others that a radial electric field is necessary to produce a hollow plasma profile. Instead, the ionization of neutrals in the radially outer region by the tail electrons, rotating fast due to gradient-B drift in the azimuthal direction, seems to account for the observed off-axis density peaking in the present experiment. This also explains the variation of the plasma annulus diameter seen here by changing the input radio frequency power ( 100 - 800 W ) .

Polygonal shaft hole rotor

DOEpatents

Hussey, John H.; Rose, John Scott; Meystrik, Jeffrey J.; White, Kent Lee

2001-01-23

A laminated rotor for an induction motor has a plurality of ferro-magnetic laminations mounted axially on a rotor shaft. Each of the plurality of laminations has a central aperture in the shape of a polygon with sides of equal length. The laminations are alternatingly rotated 180.degree. from one another so that the straight sides of the polygon shaped apertures are misaligned. As a circular rotor shaft is press fit into a stack of laminations, the point of maximum interference occurs at the midpoints of the sides of the polygon (i.e., at the smallest radius of the central apertures of the laminations). Because the laminates are alternatingly rotated, the laminate material at the points of maximum interference yields relatively easily into the vertices (i.e., the greatest radius of the central aperture) of the polygonal central aperture of the next lamination as the shaft is inserted into the stack of laminations. Because of this yielding process, the amount of force required to insert the shaft is reduced, and a tighter fit is achieved.

Sparse synthetic aperture with Fresnel elements (S-SAFE) using digital incoherent holograms

PubMed Central

Kashter, Yuval; Rivenson, Yair; Stern, Adrian; Rosen, Joseph

2015-01-01

Creating a large-scale synthetic aperture makes it possible to break the resolution boundaries dictated by the wave nature of light of common optical systems. However, their implementation is challenging, since the generation of a large size continuous mosaic synthetic aperture composed of many patterns is complicated in terms of both phase matching and time-multiplexing duration. In this study we present an advanced configuration for an incoherent holographic imaging system with super resolution qualities that creates a partial synthetic aperture. The new system, termed sparse synthetic aperture with Fresnel elements (S-SAFE), enables significantly decreasing the number of the recorded elements, and it is free from positional constrains on their location. Additionally, in order to obtain the best image quality we propose an optimal mosaicking structure derived on the basis of physical and numerical considerations, and introduce three reconstruction approaches which are compared and discussed. The super-resolution capabilities of the proposed scheme and its limitations are analyzed, numerically simulated and experimentally demonstrated. PMID:26367947

Measuring electrode assembly

DOEpatents

Bordenick, John E.

1989-01-01

A pH measuring electrode assembly for immersion in a solution includes an enclosed cylindrical member having an aperture at a lower end thereof. An electrolyte is located in the cylindrical member above the level of the aperture and an electrode is disposed in this electrolyte. A ring formed of an ion porous material is mounted relative to the cylindrical member so that a portion of this ring is rotatable relative to and is covering the aperture in the cylindrical member. A suitable mechanism is also provided for indicating which one of a plurality of portions of the ring is covering the aperture and to keep track of which portions of the ring have already been used and become clogged. Preferably, the electrode assembly also includes a glass electrode member in the center thereof including a second electrolyte and electrode disposed therein. The cylindrical member is resiliently mounted relative to the glass electrode member to provide for easy rotation of the cylindrical member relative to the glass electrode member for changing of the portion of the ring covering the aperture.

Large-aperture space optical system testing based on the scanning Hartmann.

PubMed

Wei, Haisong; Yan, Feng; Chen, Xindong; Zhang, Hao; Cheng, Qiang; Xue, Donglin; Zeng, Xuefeng; Zhang, Xuejun

2017-03-10

Based on the Hartmann testing principle, this paper proposes a novel image quality testing technology which applies to a large-aperture space optical system. Compared with the traditional testing method through a large-aperture collimator, the scanning Hartmann testing technology has great advantages due to its simple structure, low cost, and ability to perform wavefront measurement of an optical system. The basic testing principle of the scanning Hartmann testing technology, data processing method, and simulation process are presented in this paper. Certain simulation results are also given to verify the feasibility of this technology. Furthermore, a measuring system is developed to conduct a wavefront measurement experiment for a 200 mm aperture optical system. The small deviation (6.3%) of root mean square (RMS) between experimental results and interferometric results indicates that the testing system can measure low-order aberration correctly, which means that the scanning Hartmann testing technology has the ability to test the imaging quality of a large-aperture space optical system.

Development of large-aperture electro-optical switch for high power laser at CAEP

NASA Astrophysics Data System (ADS)

Zhang, Xiongjun; Wu, Dengsheng; Zhang, Jun; Lin, Donghui; Zheng, Jiangang; Zheng, Kuixing

2015-02-01

Large-aperture electro-optical switch based on plasma Pockels cell (PPC) is one of important components for inertial confinement fusion (ICF) laser facility. We have demonstrated a single-pulse driven 4×1 PPC with 400mm×400mm aperture for SGIII laser facility. And four 2×1 PPCs modules with 350mm×350mm aperture have been operated in SGII update laser facility. It is different to the PPC of NIF and LMJ for its simple operation to perform Pockels effect. With optimized operation parameters, the PPCs meet the SGII-U laser requirement of four-pass amplification control. Only driven by one high voltage pulser, the simplified PPC system would be provided with less associated diagnostics, and higher reliability. To farther reduce the insert loss of the PPC, research on the large-aperture PPC based on DKDP crystal driven by one pulse is developed. And several single-pulse driven PPCs with 80mm×80mm DKDP crystal have been manufactured and operated in laser facilities.

Laboratory demonstration of image reconstruction for coherent optical system of modular imaging collectors (COSMIC)

NASA Technical Reports Server (NTRS)

Traub, W. A.

1984-01-01

The first physical demonstration of the principle of image reconstruction using a set of images from a diffraction-blurred elongated aperture is reported. This is an optical validation of previous theoretical and numerical simulations of the COSMIC telescope array (coherent optical system of modular imaging collectors). The present experiment utilizes 17 diffraction blurred exposures of a laboratory light source, as imaged by a lens covered by a narrow-slit aperture; the aperture is rotated 10 degrees between each exposure. The images are recorded in digitized form by a CCD camera, Fourier transformed, numerically filtered, and added; the sum is then filtered and inverse Fourier transformed to form the final image. The image reconstruction process is found to be stable with respect to uncertainties in values of all physical parameters such as effective wavelength, rotation angle, pointing jitter, and aperture shape. Future experiments will explore the effects of low counting rates, autoguiding on the image, various aperture configurations, and separated optics.

Radiation Characteristics of Cavity Backed Aperture Antennas in Finite Ground Plane Using the Hybrid FEM/MoM Technique and Geometrical Theory of Diffraction

NASA Technical Reports Server (NTRS)

Reddy, C. J.; Deshpande, M. D.; Cockrell, C. R.; Beck, F. B.

1996-01-01

A technique using hybrid Finite Element Method (FEM)/Method of Moments (MoM), and Geometrical Theory of Diffraction (GTD) is presented to analyze the radiation characteristics of cavity fed aperture antennas in a finite ground plane. The cavity which excites the aperture is assumed to be fed by a cylindrical transmission line. The electromagnetic (EM) fields inside the cavity are obtained using FEM. The EM fields and their normal derivatives required for FEM solution are obtained using (1) the modal expansion in the feed region and (2) the MoM for the radiating aperture region(assuming an infinite ground plane). The finiteness of the ground plane is taken into account using GTD. The input admittance of open ended circular, rectangular, and coaxial line radiating into free space through an infinite ground plane are computed and compared with earlier published results. Radiation characteristics of a coaxial cavity fed circular aperture in a finite rectangular ground plane are verified with experimental results.

System and method for linearly amplifying optical analog signals by backward Raman scattering

DOEpatents

Lin, Cheng-Heui

1988-01-01

A system for linearly amplifying an optical analog signal by backward stimulated Raman scattering comprises a laser source for generating a pump pulse; and an optic fiber having two opposed apertures, a first aperture for receiving the pump pulse and a second aperture for receiving the optical analog signal, wherein the optical analog signal is linearly amplified to an amplified optical analog signal.

System and method for linearly amplifying optical analog signals by backward Raman scattering

DOEpatents

Lin, Cheng-Heui

1988-07-05

A system for linearly amplifying an optical analog signal by backward stimulated Raman scattering comprises a laser source for generating a pump pulse; and an optic fiber having two opposed apertures, a first aperture for receiving the pump pulse and a second aperture for receiving the optical analog signal, wherein the optical analog signal is linearly amplified to an amplified optical analog signal.

The solid angle (geometry factor) for a spherical surface source and an arbitrary detector aperture

DOE PAGES

Favorite, Jeffrey A.

2016-01-13

It is proven that the solid angle (or geometry factor, also called the geometrical efficiency) for a spherically symmetric outward-directed surface source with an arbitrary radius and polar angle distribution and an arbitrary detector aperture is equal to the solid angle for an isotropic point source located at the center of the spherical surface source and the same detector aperture.

Electromagnetic pulse coupling through an aperture into a two-parallel-plate region

NASA Technical Reports Server (NTRS)

Rahmat-Samii, Y.

1978-01-01

Analysis of electromagnetic-pulse (EMP) penetration via apertures into cavities is an important study in designing hardened systems. In this paper, an integral equation procedure is developed for determining the frequency and consequently the time behavior of the field inside a two-parallel-plate region excited through an aperture by an EMP. Some discussion of the numerical results is also included in the paper for completeness.

A Method for Quantifying, Visualising, and Analysing Gastropod Shell Form

PubMed Central

Liew, Thor-Seng; Schilthuizen, Menno

2016-01-01

Quantitative analysis of organismal form is an important component for almost every branch of biology. Although generally considered an easily-measurable structure, the quantification of gastropod shell form is still a challenge because many shells lack homologous structures and have a spiral form that is difficult to capture with linear measurements. In view of this, we adopt the idea of theoretical modelling of shell form, in which the shell form is the product of aperture ontogeny profiles in terms of aperture growth trajectory that is quantified as curvature and torsion, and of aperture form that is represented by size and shape. We develop a workflow for the analysis of shell forms based on the aperture ontogeny profile, starting from the procedure of data preparation (retopologising the shell model), via data acquisition (calculation of aperture growth trajectory, aperture form and ontogeny axis), and data presentation (qualitative comparison between shell forms) and ending with data analysis (quantitative comparison between shell forms). We evaluate our methods on representative shells of the genera Opisthostoma and Plectostoma, which exhibit great variability in shell form. The outcome suggests that our method is a robust, reproducible, and versatile approach for the analysis of shell form. Finally, we propose several potential applications of our methods in functional morphology, theoretical modelling, taxonomy, and evolutionary biology. PMID:27280463

Open-split interface for mass spectrometers

DOEpatents

Diehl, John W.

1991-01-01

An open-split interface includes a connector body having four leg members projecting therefrom within a single plane, the first and third legs being coaxial and the second and fourth legs being coaxial. A tubular aperture extends through the first and third legs and a second tubular aperture extends through the second and fourth legs, connecting at a juncture within the center of the connector body. A fifth leg projects from the connector body and has a third tubular aperture extending therethrough to the juncture of the first and second tubular apertures. A capillary column extends from a gas chromatograph into the third leg with its end adjacent the juncture. A flow restrictor tube extends from a mass spectrometer through the first tubular aperture in the first and third legs and into the capillary columnm end, so as to project beyond the end of the third leg within the capillary column. An annular gap between the tube and column allows excess effluent to pass to the juncture. A pair of short capillary columns extend from separate detectors into the second tubular aperture in the second and fourth legs, and are oriented with their ends spaced slightly from the first capillary column end. A sweep flow tube is mounted in the fifth leg so as to supply a helium sweep flow to the juncture.

Evolutionary stasis in pollen morphogenesis due to natural selection.

PubMed

Matamoro-Vidal, Alexis; Prieu, Charlotte; Furness, Carol A; Albert, Béatrice; Gouyon, Pierre-Henri

2016-01-01

The contribution of developmental constraints and selective forces to the determination of evolutionary patterns is an important and unsolved question. We test whether the long-term evolutionary stasis observed for pollen morphogenesis (microsporogenesis) in eudicots is due to developmental constraints or to selection on a morphological trait shaped by microsporogenesis: the equatorial aperture pattern. Most eudicots have three equatorial apertures but several taxa have independently lost the equatorial pattern and have microsporogenesis decoupled from aperture pattern determination. If selection on the equatorial pattern limits variation, we expect to see increased variation in microsporogenesis in the nonequatorial clades. Variation of microsporogenesis was studied using phylogenetic comparative analyses in 83 species dispersed throughout eudicots including species with and without equatorial apertures. The species that have lost the equatorial pattern have highly variable microsporogenesis at the intra-individual and inter-specific levels regardless of their pollen morphology, whereas microsporogenesis remains stable in species with the equatorial pattern. The observed burst of variation upon loss of equatorial apertures shows that there are no strong developmental constraints precluding variation in microsporogenesis, and that the stasis is likely to be due principally to selective pressure acting on pollen morphogenesis because of its implication in the determination of the equatorial aperture pattern. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Hydrocephalus secondary to obstruction of the lateral apertures in two dogs.

PubMed

Kent, M; Glass, E N; Haley, A C; Shaikh, L S; Sequel, M; Blas-Machado, U; Bishop, T M; Holmes, S P; Platt, S R

2016-11-01

Traditionally, hydrocephalus is divided into communicating or non-communicating (obstructive) based on the identification of a blockage of cerebrospinal fluid (CSF) flow through the ventricular system. Hydrocephalus ex vacuo refers to ventricular enlargement as a consequence of neuroparenchymal loss. Hydrocephalus related to obstruction of the lateral apertures of the fourth ventricles has rarely been described. The clinicopathologic findings in two dogs with hydrocephalus secondary to obstruction of the lateral apertures of the fourth ventricle are reported. Signs were associated with a caudal cervical spinal cord lesion in one dog and a caudal brain stem lesion in the other dog. Magnetic resonance imaging (MRI) disclosed dilation of the ventricular system, including the lateral recesses of the fourth ventricle. In one dog, postmortem ventriculography confirmed obstruction of the lateral apertures. Microscopic changes were identified in the choroid plexus in both dogs, yet a definitive cause of the obstructions was not identified. The MRI findings in both dogs are similar to membranous occlusion of the lateral and median apertures in human patients. MRI detection of dilation of the entire ventricular system in the absence of an identifiable cause should prompt consideration of an obstruction of the lateral apertures. In future cases, therapeutic interventions aimed at re-establishing CSF flow or ventriculoperitoneal catheterisation should be considered. © 2016 Australian Veterinary Association.

Effective aperture of X-ray compound refractive lenses.

PubMed

Kohn, V G

2017-05-01

A new definition of the effective aperture of the X-ray compound refractive lens (CRL) is proposed. Both linear (one-dimensional) and circular (two-dimensional) CRLs are considered. It is shown that for a strongly absorbing CRL the real aperture does not influence the focusing properties and the effective aperture is determined by absorption. However, there are three ways to determine the effective aperture in terms of transparent CRLs. In the papers by Kohn [(2002). JETP Lett. 76, 600-603; (2003). J. Exp. Theor. Phys. 97, 204-215; (2009). J. Surface Investig. 3, 358-364; (2012). J. Synchrotron Rad. 19, 84-92; Kohn et al. (2003). Opt. Commun. 216, 247-260; (2003). J. Phys. IV Fr, 104, 217-220], the FWHM of the X-ray beam intensity just behind the CRL was used. In the papers by Lengeler et al. [(1999). J. Synchrotron Rad. 6, 1153-1167; (1998). J. Appl. Phys. 84, 5855-5861], the maximum intensity value at the focus was used. Numerically, these two definitions differ by 50%. The new definition is based on the integral intensity of the beam behind the CRL over the real aperture. The integral intensity is the most physical value and is independent of distance. The new definition gives a value that is greater than that of the Kohn definition by 6% and less than that of the Lengeler definition by 41%. A new approximation for the aperture function of a two-dimensional CRL is proposed which allows one to calculate the two-dimensional CRL through the one-dimensional CRL and to obtain an analytical solution for a complex system of many CRLs.

Design of the polar neutron-imaging aperture for use at the National Ignition Facility

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

Fatherley, V. E., E-mail: vef@lanl.gov; Martinez, J. I.; Merrill, F. E.

2016-11-15

The installation of a neutron imaging diagnostic with a polar view at the National Ignition Facility (NIF) required design of a new aperture, an extended pinhole array (PHA). This PHA is different from the pinhole array for the existing equatorial system due to significant changes in the alignment and recording systems. The complex set of component requirements, as well as significant space constraints in its intended location, makes the design of this aperture challenging. In addition, lessons learned from development of prior apertures mandate careful aperture metrology prior to first use. This paper discusses the PHA requirements, constraints, and themore » final design. The PHA design is complex due to size constraints, machining precision, assembly tolerances, and design requirements. When fully assembled, the aperture is a 15 mm × 15 mm × 200 mm tungsten and gold assembly. The PHA body is made from 2 layers of tungsten and 11 layers of gold. The gold layers include 4 layers containing penumbral openings, 4 layers containing pinholes and 3 spacer layers. In total, there are 64 individual, triangular pinholes with a field of view (FOV) of 200 μm and 6 penumbral apertures. Each pinhole is pointed to a slightly different location in the target plane, making the effective FOV of this PHA a 700 μm square in the target plane. The large FOV of the PHA reduces the alignment requirements both for the PHA and the target, allowing for alignment with a laser tracking system at NIF.« less

Evaluating the effect of internal aperture variability on transport in kilometer scale discrete fracture networks

DOE PAGES

Makedonska, Nataliia; Hyman, Jeffrey D.; Karra, Satish; ...

2016-08-01

The apertures of natural fractures in fractured rock are highly heterogeneous. However, in-fracture aperture variability is often neglected in flow and transport modeling and individual fractures are assumed to have uniform aperture distribution. The relative importance of in-fracture variability in flow and transport modeling within kilometer-scale fracture networks has been under debate for a long time, since the flow in each single fracture is controlled not only by in-fracture variability but also by boundary conditions. Computational limitations have previously prohibited researchers from investigating the relative importance of in-fracture variability in flow and transport modeling within large-scale fracture networks. We addressmore » this question by incorporating internal heterogeneity of individual fractures into flow simulations within kilometer scale three-dimensional fracture networks, where fracture intensity, P 32 (ratio between total fracture area and domain volume) is between 0.027 and 0.031 [1/m]. The recently developed discrete fracture network (DFN) simulation capability, dfnWorks, is used to generate kilometer scale DFNs that include in-fracture aperture variability represented by a stationary log-normal stochastic field with various correlation lengths and variances. The Lagrangian transport parameters, non-reacting travel time, , and cumulative retention, , are calculated along particles streamlines. As a result, it is observed that due to local flow channeling early particle travel times are more sensitive to in-fracture aperture variability than the tails of travel time distributions, where no significant effect of the in-fracture aperture variations and spatial correlation length is observed.« less

Quantify fluid saturation in fractures by light transmission technique and its application

NASA Astrophysics Data System (ADS)

Ye, S.; Zhang, Y.; Wu, J.

2016-12-01

The Dense Non-Aqueous Phase Liquids (DNAPLs) migration in transparent and rough fractures with variable aperture was studied experimentally using a light transmission technique. The migration of trichloroethylene (TCE) in variable-aperture fractures (20 cm wide x 32.5 cm high) showed that a TCE blob moved downward with snap-off events in four packs with apertures from 100 μm to 1000 μm, and that the pattern presented a single and tortuous cluster with many fingers in a pack with two apertures of 100 μm and 500 μm. The variable apertures in the fractures were measured by light transmission. A light intensity-saturation (LIS) model based on light transmission was used to quantify DNAPL saturation in the fracture system. Known volumes of TCE, were added to the chamber and these amounts were compared to the results obtained by LIS model. Strong correlation existed between results obtained based on LIS model and the known volumes of T CE. Sensitivity analysis showed that the aperture was more sensitive than parameter C2 of LIS model. LIS model was also used to measure dyed TCE saturation in air sparging experiment. The results showed that the distribution and amount of TCE significantly influenced the efficient of air sparging. The method developed here give a way to quantify fluid saturation in two-phase system in fractured medium, and provide a non-destructive, non-intrusive tool to investigate changes in DNAPL architecture and flow characteristics in laboratory experiments. Keywords: light transmission, fluid saturation, fracture, variable aperture AcknowledgementsFunding for this research from NSFC Project No. 41472212.

Evaluating the effect of internal aperture variability on transport in kilometer scale discrete fracture networks

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

Makedonska, Nataliia; Hyman, Jeffrey D.; Karra, Satish

The apertures of natural fractures in fractured rock are highly heterogeneous. However, in-fracture aperture variability is often neglected in flow and transport modeling and individual fractures are assumed to have uniform aperture distribution. The relative importance of in-fracture variability in flow and transport modeling within kilometer-scale fracture networks has been under debate for a long time, since the flow in each single fracture is controlled not only by in-fracture variability but also by boundary conditions. Computational limitations have previously prohibited researchers from investigating the relative importance of in-fracture variability in flow and transport modeling within large-scale fracture networks. We addressmore » this question by incorporating internal heterogeneity of individual fractures into flow simulations within kilometer scale three-dimensional fracture networks, where fracture intensity, P 32 (ratio between total fracture area and domain volume) is between 0.027 and 0.031 [1/m]. The recently developed discrete fracture network (DFN) simulation capability, dfnWorks, is used to generate kilometer scale DFNs that include in-fracture aperture variability represented by a stationary log-normal stochastic field with various correlation lengths and variances. The Lagrangian transport parameters, non-reacting travel time, , and cumulative retention, , are calculated along particles streamlines. As a result, it is observed that due to local flow channeling early particle travel times are more sensitive to in-fracture aperture variability than the tails of travel time distributions, where no significant effect of the in-fracture aperture variations and spatial correlation length is observed.« less

Vibrotactile grasping force and hand aperture feedback for myoelectric forearm prosthesis users.

PubMed

Witteveen, Heidi J B; Rietman, Hans S; Veltink, Peter H

2015-06-01

User feedback about grasping force and hand aperture is very important in object handling with myoelectric forearm prostheses but is lacking in current prostheses. Vibrotactile feedback increases the performance of healthy subjects in virtual grasping tasks, but no extensive validation on potential users has been performed. Investigate the performance of upper-limb loss subjects in grasping tasks with vibrotactile stimulation, providing hand aperture, and grasping force feedback. Cross-over trial. A total of 10 subjects with upper-limb loss performed virtual grasping tasks while perceiving vibrotactile feedback. Hand aperture feedback was provided through an array of coin motors and grasping force feedback through a single miniature stimulator or an array of coin motors. Objects with varying sizes and weights had to be grasped by a virtual hand. Percentages correctly applied hand apertures and correct grasping force levels were all higher for the vibrotactile feedback condition compared to the no-feedback condition. With visual feedback, the results were always better compared to the vibrotactile feedback condition. Task durations were comparable for all feedback conditions. Vibrotactile grasping force and hand aperture feedback improves grasping performance of subjects with upper-limb loss. However, it should be investigated whether this is of additional value in daily-life tasks. This study is a first step toward the implementation of sensory vibrotactile feedback for users of myoelectric forearm prostheses. Grasping force feedback is crucial for optimal object handling, and hand aperture feedback is essential for reduction of required visual attention. Grasping performance with feedback is evaluated for the potential users. © The International Society for Prosthetics and Orthotics 2014.

In vivo visualization of robotically implemented synthetic tracked aperture ultrasound (STRATUS) imaging system using curvilinear array

NASA Astrophysics Data System (ADS)

Zhang, Haichong K.; Aalamifar, Fereshteh; Boctor, Emad M.

2016-04-01

Synthetic aperture for ultrasound is a technique utilizing a wide aperture in both transmit and receive to enhance the ultrasound image quality. The limitation of synthetic aperture is the maximum available aperture size limit determined by the physical size of ultrasound probe. We propose Synthetic-Tracked Aperture Ultrasound (STRATUS) imaging system to overcome the limitation by extending the beamforming aperture size through ultrasound probe tracking. With a setup involving a robotic arm, the ultrasound probe is moved using the robotic arm, while the positions on a scanning trajectory are tracked in real-time. Data from each pose are synthesized to construct a high resolution image. In previous studies, we have demonstrated the feasibility through phantom experiments. However, various additional factors such as real-time data collection or motion artifacts should be taken into account when the in vivo target becomes the subject. In this work, we build a robot-based STRATUS imaging system with continuous data collection capability considering the practical implementation. A curvilinear array is used instead of a linear array to benefit from its wider capture angle. We scanned human forearms under two scenarios: one submerged the arm in the water tank under 10 cm depth, and the other directly scanned the arm from the surface. The image contrast improved 5.51 dB, and 9.96 dB for the underwater scan and the direct scan, respectively. The result indicates the practical feasibility of STRATUS imaging system, and the technique can be potentially applied to the wide range of human body.

SU-C-BRB-02: Symmetric and Asymmetric MLC Based Lung Shielding and Dose Optimization During Translating Bed TBI

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

Ahmed, S; Kakakhel, MB; Ahmed, SBS

2015-06-15

Purpose: The primary aim was to introduce a dose optimization method for translating bed total body irradiation technique that ensures lung shielding dynamically. Symmetric and asymmetric dynamic MLC apertures were employed for this purpose. Methods: The MLC aperture sizes were defined based on the radiological depth values along the divergent ray lines passing through the individual CT slices. Based on these RD values, asymmetrically shaped MLC apertures were defined every 9 mm of the phantom in superior-inferior direction. Individual MLC files were created with MATLAB™ and were imported into Eclipse™ treatment planning system for dose calculations. Lungs can be shieldedmore » to an optimum level by reducing the MLC aperture width over the lungs. The process was repeated with symmetrically shaped apertures. Results: Dose-volume histogram (DVH) analysis shows that the asymmetric MLC based technique provides better dose coverage to the body and optimum shielding of the lungs compared to symmetrically shaped beam apertures. Midline dose homogeneity is within ±3% with asymmetric MLC apertures whereas it remains within ±4.5% with symmetric ones (except head region where it drops down to −7%). The substantial over and under dosage of ±5% at tissue interfaces has been reduced to ±2% with asymmetric MLC technique. Lungs dose can be reduced to any desired limit. In this experiment lungs dose was reduced to 80% of the prescribed dose, as was desired. Conclusion: The novel asymmetric MLC based technique assures optimum shielding of OARs (e.g. lungs) and better 3-D dose homogeneity and body-dose coverage in comparison with the symmetric MLC aperture optimization. The authors acknowledge the financial and infrastructural support provided by Pakistan Institute of Engineering & Applied Sciences (PIEAS), Islamabad and Aga Khan University Hospital (AKUH), Karachi during the course of this research project. Authors have no conflict of interest with any national / international body for the presented work.« less

Size Constancy in Bat Biosonar? Perceptual Interaction of Object Aperture and Distance

PubMed Central

Heinrich, Melina; Wiegrebe, Lutz

2013-01-01

Perception and encoding of object size is an important feature of sensory systems. In the visual system object size is encoded by the visual angle (visual aperture) on the retina, but the aperture depends on the distance of the object. As object distance is not unambiguously encoded in the visual system, higher computational mechanisms are needed. This phenomenon is termed “size constancy”. It is assumed to reflect an automatic re-scaling of visual aperture with perceived object distance. Recently, it was found that in echolocating bats, the ‘sonar aperture’, i.e., the range of angles from which sound is reflected from an object back to the bat, is unambiguously perceived and neurally encoded. Moreover, it is well known that object distance is accurately perceived and explicitly encoded in bat sonar. Here, we addressed size constancy in bat biosonar, recruiting virtual-object techniques. Bats of the species Phyllostomus discolor learned to discriminate two simple virtual objects that only differed in sonar aperture. Upon successful discrimination, test trials were randomly interspersed using virtual objects that differed in both aperture and distance. It was tested whether the bats spontaneously assigned absolute width information to these objects by combining distance and aperture. The results showed that while the isolated perceptual cues encoding object width, aperture, and distance were all perceptually well resolved by the bats, the animals did not assign absolute width information to the test objects. This lack of sonar size constancy may result from the bats relying on different modalities to extract size information at different distances. Alternatively, it is conceivable that familiarity with a behaviorally relevant, conspicuous object is required for sonar size constancy, as it has been argued for visual size constancy. Based on the current data, it appears that size constancy is not necessarily an essential feature of sonar perception in bats. PMID:23630598

SU-E-T-567: Neutron Dose Equivalent Evaluation for Pencil Beam Scanning Proton Therapy with Apertures

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

Geng, C; Nanjing University of Aeronautics and Astronautics, Nanjing; Schuemann, J

Purpose: To determine the neutron contamination from the aperture in pencil beam scanning during proton therapy. Methods: A Monte Carlo based proton therapy research platform TOPAS and the UF-series hybrid pediatric phantoms were used to perform this study. First, pencil beam scanning (PBS) treatment pediatric plans with average spot size of 10 mm at iso-center were created and optimized for three patients with and without apertures. Then, the plans were imported into TOPAS. A scripting method was developed to automatically replace the patient CT with a whole body phantom positioned according to the original plan iso-center. The neutron dose equivalentmore » was calculated using organ specific quality factors for two phantoms resembling a 4- and 14-years old patient. Results: The neutron dose equivalent generated by the apertures in PBS is 4–10% of the total neutron dose equivalent for organs near the target, while roughly 40% for organs far from the target. Compared to the neutron dose equivalent caused by PBS without aperture, the results show that the neutron dose equivalent with aperture is reduced in the organs near the target, and moderately increased for those organs located further from the target. This is due to the reduction of the proton dose around the edge of the CTV, which causes fewer neutrons generated in the patient. Conclusion: Clinically, for pediatric patients, one might consider adding an aperture to get a more conformal treatment plan if the spot size is too large. This work shows the somewhat surprising fact that adding an aperture for beam scanning for facilities with large spot sizes reduces instead of increases a potential neutron background in regions near target. Changran Geng is supported by the Chinese Scholarship Council (CSC) and the National Natural Science Foundation of China (Grant No. 11475087)« less

Evaluation of the CT Parameters to Suppress Renal Cysts Pseudoenhancement Effect: Influence of the Virtual Monochromatic Spectral Images, the Model-based Iterative Reconstruction Algorithm and the Aperture Size in Phantom Model.

PubMed

Sugisawa, Koichi; Ichikawa, Katsuhiro; Minamishima, Kazuya; Hasegawa, Masakazu; Yamada, Yoshitake; Jinzaki, Masahiro

2017-01-01

The purpose of this study was to evaluate the effect of the virtual monochromatic spectral images (VMSI) and the model-based iterative reconstruction (MBIR) images, to evaluate the influence of the aperture size (40- and 20-mm beam) on renal pseudoenhancement (PE) compared with the filtered back projection (FBP) images. The renal compartment-CT phantom was filled with iodinated contrast material diluted to the attenuation of 180 Hounsfield units (HU) at 120 kV. The water-filled spherical structures, which simulate cyst, were inserted into the renal compartment. Those diameters were 7, 15 and 25 mm. These were scanned by conventional mode (helical scan, 120 kV-FBP) and dual energy mode. 70 keV-VMSI were reconstructed from the dual energy mode, and MBIR images were reconstructed from conventional mode at 40- and 20-mm aperture. Additionally, the phantom was scanned using non-helical mode with 20-mm aperture, and FBP images were reconstructed. The CT value of the PE for cyst areas was measured for these images. The CT values of the cysts were 20.0-14.3 HU on the FBP images, 12.8-12.7 HU on the 70 keV-VMSI (PE-inhibition ratio was 36.0-11.2%) and 16.2-14.0 HU on the MBIR images (19.0-2.1%), respectively, at 40-mm aperture. The PE-inhibition ratio scanned by 20-mm aperture was improved by 28.0% with FBP, 32.8% with 70 keV-VMSI and 29.6% with MBIR compared with 40-mm aperture. One of the FBP images with non-helical mode was 11.6 HU. The best CT technique to minimize PE was the combination of 70 keV-VMSI and 20-mm aperture.

Effect of Aperture Field Variability, Flow Rate, and Ionic Strength on Colloid Transport in Single Fractures: Laboratory-Scale Experiments and Numerical Simulation

NASA Astrophysics Data System (ADS)

Zheng, Q.; Dickson, S.; Guo, Y.

2007-12-01

A good understanding of the physico-chemical processes (i.e., advection, dispersion, attachment/detachment, straining, sedimentation etc.) governing colloid transport in fractured media is imperative in order to develop appropriate bioremediation and/or bioaugmentation strategies for contaminated fractured aquifers, form management plans for groundwater resources to prevent pathogen contamination, and identify suitable radioactive waste disposal sites. However, research in this field is still in its infancy due to the complex heterogeneous nature of fractured media and the resulting difficulty in characterizing this media. The goal of this research is to investigate the effects of aperture field variability, flow rate and ionic strength on colloid transport processes in well characterized single fractures. A combination of laboratory-scale experiments, numerical simulations, and imaging techniques were employed to achieve this goal. Transparent replicas were cast from natural rock fractures, and a light transmission technique was employed to measure their aperture fields directly. The surface properties of the synthetic fractures were characterized by measuring the zeta-potential under different ionic strengths. A 33 (3 increased to the power of 3) factorial experiment was implemented to investigate the influence of aperture field variability, flow rate, and ionic strength on different colloid transport processes in the laboratory-scale fractures, specifically dispersion and attachment/detachment. A fluorescent stain technique was employed to photograph the colloid transport processes, and an analytical solution to the one-dimensional transport equation was fit to the colloid breakthrough curves to calculate the average transport velocity, dispersion coefficient, and attachment/detachment coefficient. The Reynolds equation was solved to obtain the flow field in the measured aperture fields, and the random walk particle tracking technique was employed to model the colloid transport experiments. The images clearly show the development of preferential pathways for colloid transport in the different aperture fields and under different flow conditions. Additionally, a correlation between colloid deposition and fracture wall topography was identified. This presentation will demonstrate (1) differential transport between colloid and solute in single fractures, and the relationship between differential transport and aperture field statistics; (2) the relationship between the colloid dispersion coefficient and aperture field statistics; and (3) the relationship between attachment/detachment, aperture field statistics, fracture wall topography, flow rate, and ionic strength. In addition, this presentation will provide insight into the application of the random walk particle tracking technique for modeling colloid transport in variable-aperture fractures.

Liquid blocking check valve

DOEpatents

Merrill, John T.

1984-01-01

A liquid blocking check valve useful particularly in a pneumatic system utilizing a pressurized liquid fill chamber. The valve includes a floatable ball disposed within a housing defining a chamber. The housing is provided with an inlet aperture disposed in the top of said chamber, and an outlet aperture disposed in the bottom of said chamber in an offset relation to said inlet aperture and in communication with a cutaway side wall section of said housing.

Unmanned Aircraft Systems (UAS) Sensor and Targeting

DTIC Science & Technology

2010-07-27

4.7.1 Objective. The objective of this subtest is to determine the detection performance of the Synthetic Aperture Radar (SAR) with the radar...Detection SAR – Synthetic Aperture Radar 4.7.3 Data Required. Section 5.1 outlines general test data required. The following additional data may...m – meter No. – Number PC – Probability of Classification SAR – Synthetic Aperture Radar 4.8.3 Data Required. Section 5.1 outlines

Switched Antenna Array Tile for Real-Time Microwave Imaging Aperture

DTIC Science & Technology

2016-06-26

Switched Antenna Array Tile for Real -Time Microwave Imaging Aperture William F. Moulder, Janusz J. Majewski, Charles M. Coldwell, James D. Krieger...Fast Imaging Algorithm 10mm 250mm Switched Array Tile Fig. 1. Diagram of real -time imaging array, with fabricated antenna tile. except for antenna...formed. IV. CONCLUSIONS A switched array tile to be used in a real time imaging aperture has been presented. Design and realization of the tile were

Distributed Beam Former for Distributed-Aperture Electronically Steered Antennas

DTIC Science & Technology

2006-11-01

of planar or conformal aperture, it will be replaced by a distributed aperture configuration with a base-band digital network that is used to combine...beam forming network that can be designed with pre-set scanning directions. The beam former for this stage can be realized using a printed Butler...matrix (Bona et al, 2002; Neron and Delisle, 2005), a printed Rotman lens (Kilic and Dahlstrom, 2005) or other switched time delay system. The

Acquisition of Cooperative Small Unmanned Aerial Systems for Advancing Man Machine Interface Research

DTIC Science & Technology

2016-08-24

global sensor field of views (FOVs), mimicking biological systems such as an insect fly eye , but allowing multiple aperture configurations. Due to...synthetic, global sensor field of views (FOVs), mimicking biological systems such as an insect fly eye , but allowing multiple aperture configurations. Due to...such as an insect fly eye , but allowing multiple aperture configurations. Due to the desired nature of distributed networked aerial vehicles (for the

Field Quality Measurements in the FNAL Twin-Aperture 11 T Dipole for LHC Upgrades

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

Strauss, T.; Apollinari, G.; Apollinari, G.

2016-11-08

FNAL and CERN are developing an 11 T Nb3Sn dipole suitable for installation in the LHC to provide room for additional collimators. Two 1 m long collared coils previously tested at FNAL in single-aperture dipole configuration were assembled into the twin-aperture configuration and tested including magnet quench performance and field quality. The results of magnetic measurements are reported and discussed in this paper.

Multifrequency Aperture-Synthesizing Microwave Radiometer System (MFASMR). Volume 1

NASA Technical Reports Server (NTRS)

Wiley, C. A.; Chang, M. U.

1981-01-01

Background material and a systems analysis of a multifrequency aperture - synthesizing microwave radiometer system is presented. It was found that the system does not exhibit high performance because much of the available thermal power is not used in the construction of the image and because the image that can be formed has a resolution of only ten lines. An analysis of image reconstruction is given. The system is compared with conventional aperture synthesis systems.

Apodised aperture using rotation of plane of polarization

DOEpatents

Simmons, W.W.; Leppelmeier, G.W.; Johnson, B.C.

1975-09-01

An apodised aperture based on the rotation of plane of polarization producing desirable characteristics on a transmitted light beam such as beam profiling in high flux laser amplifier chains is described. The apodised aperture is made with a lossless element by using one or more polarizers and/or analyzers and magneto-optical Faraday means for selectively rotating the plane of polarized radiation over the cross section to effect the desired apodisation. (auth)

Method and apparatus for making absolute range measurements

DOEpatents

Earl, Dennis D [Knoxville, TN; Allison, Stephen W [Knoxville, TN; Cates, Michael R [Oak Ridge, TN; Sanders, Alvin J [Knoxville, TN

2002-09-24

This invention relates to a method and apparatus for making absolute distance or ranging measurements using Fresnel diffraction. The invention employs a source of electromagnetic radiation having a known wavelength or wavelength distribution, which sends a beam of electromagnetic radiation through a screen at least partially opaque at the wavelength. The screen has an aperture sized so as to produce a Fresnel diffraction pattern. A portion of the beam travels through the aperture to a detector spaced some distance from the screen. The detector detects the central intensity of the beam as well as a set of intensities displaced from a center of the aperture. The distance from the source to the target can then be calculated based upon the known wavelength, aperture radius, and beam intensity.

Phase singularities of the transverse field component of high numerical aperture dark-hollow Gaussian beams in the focal region

NASA Astrophysics Data System (ADS)

Liu, Pusheng; Lü, Baida

2007-04-01

By using the vectorial Debye diffraction theory, phase singularities of high numerical aperture (NA) dark-hollow Gaussian beams in the focal region are studied. The dependence of phase singularities on the truncation parameter δ and semi-aperture angle α (or equally, NA) is illustrated numerically. A comparison of phase singularities of high NA dark-hollow Gaussian beams with those of scalar paraxial Gaussian beams and high NA Gaussian beams is made. For high NA dark-hollow Gaussian beams the beam order n additionally affects the spatial distribution of phase singularities, and there exist phase singularities outside the focal plane, which may be created or annihilated by variation of the semi-aperture angle in a certain region.

Fuel cell subassemblies incorporating subgasketed thrifted membranes

DOEpatents

Iverson, Eric J; Pierpont, Daniel M; Yandrasits, Michael A; Hamrock, Steven J; Obradovich, Stephan J; Peterson, Donald G

2014-01-28

A fuel cell roll good subassembly is described that includes a plurality of individual electrolyte membranes. One or more first subgaskets are attached to the individual electrolyte membranes. Each of the first subgaskets has at least one aperture and the first subgaskets are arranged so the center regions of the individual electrolyte membranes are exposed through the apertures of the first subgaskets. A second subgasket comprises a web having a plurality of apertures. The second subgasket web is attached to the one or more first subgaskets so the center regions of the individual electrolyte membranes are exposed through the apertures of the second subgasket web. The second subgasket web may have little or no adhesive on the subgasket surface facing the electrolyte membrane.

Fuel cell subassemblies incorporating subgasketed thrifted membranes

DOEpatents

Iverson, Eric J.; Pierpont, Daniel M.; Yandrasits, Michael A.; Hamrock, Steven J.; Obradovich, Stephan J.; Peterson, Donald G.

2016-03-01

A fuel cell roll good subassembly is described that includes a plurality of individual electrolyte membranes. One or more first subgaskets are attached to the individual electrolyte membranes. Each of the first subgaskets has at least one aperture and the first subgaskets are arranged so the center regions of the individual electrolyte membranes are exposed through the apertures of the first subgaskets. A second subgasket comprises a web having a plurality of apertures. The second subgasket web is attached to the one or more first subgaskets so the center regions of the individual electrolyte membranes are exposed through the apertures of the second subgasket web. The second subgasket web may have little or no adhesive on the subgasket surface facing the electrolyte membrane.

Enhanced retinal vasculature imaging with a rapidly configurable aperture

PubMed Central

Sapoznik, Kaitlyn A.; Luo, Ting; de Castro, Alberto; Sawides, Lucie; Warner, Raymond L.; Burns, Stephen A.

2018-01-01

In adaptive optics scanning laser ophthalmoscope (AOSLO) systems, capturing multiply scattered light can increase the contrast of the retinal microvasculature structure, cone inner segments, and retinal ganglion cells. Current systems generally use either a split detector or offset aperture approach to collect this light. We tested the ability of a spatial light modulator (SLM) as a rapidly configurable aperture to use more complex shapes to enhance the contrast of retinal structure. Particularly, we varied the orientation of a split detector aperture and explored the use of a more complex shape, the half annulus, to enhance the contrast of the retinal vasculature. We used the new approach to investigate the influence of scattering distance and orientation on vascular imaging. PMID:29541524

Dynamically variable spot size laser system

NASA Technical Reports Server (NTRS)

Gradl, Paul R. (Inventor); Hurst, John F. (Inventor); Middleton, James R. (Inventor)

2012-01-01

A Dynamically Variable Spot Size (DVSS) laser system for bonding metal components includes an elongated housing containing a light entry aperture coupled to a laser beam transmission cable and a light exit aperture. A plurality of lenses contained within the housing focus a laser beam from the light entry aperture through the light exit aperture. The lenses may be dynamically adjusted to vary the spot size of the laser. A plurality of interoperable safety devices, including a manually depressible interlock switch, an internal proximity sensor, a remotely operated potentiometer, a remotely activated toggle and a power supply interlock, prevent activation of the laser and DVSS laser system if each safety device does not provide a closed circuit. The remotely operated potentiometer also provides continuous variability in laser energy output.

Aperture shape dependencies in extended depth of focus for imaging camera by wavefront coding

NASA Astrophysics Data System (ADS)

Sakita, Koichi; Ohta, Mitsuhiko; Shimano, Takeshi; Sakemoto, Akito

2015-02-01

Optical transfer functions (OTFs) on various directional spatial frequency axes for cubic phase mask (CPM) with circular and square apertures are investigated. Although OTF has no zero points, it has a very close value to zero for a circular aperture at low frequencies on diagonal axis, which results in degradation of restored images. The reason for close-to-zero value in OTF is also analyzed in connection with point spread function profiles using Fourier slice theorem. To avoid close-to-zero condition, square aperture with CPM is indispensable in WFC. We optimized cubic coefficient α of CPM and coefficients of digital filter, and succeeded to get excellent de-blurred images at large depth of field.

Electron diffusion through the baffle aperture of a hollow cathode thruster

NASA Technical Reports Server (NTRS)

Brophy, J. R.; Wilbur, P. J.

1979-01-01

The use of a hollow cathode in place of an oxide cathode to increase thruster operating lifetimes requires, among other things, the addition of a baffle to restrict the flow of electrons from the hollow cathode. A theoretical model is developed which relates the baffle aperture area of a hollow-cathode thruster to the magnetic flux density and plasma properties in the aperture region, with the result that this model could be used as an aid in thruster design. Extensive Langmuir probing is undertaken to verify the validity of the model and demonstrate its capability. It is shown that the model can be used to calculate the aperture area required to effect discharge operation at a specified discharge voltage and arc current.

Transverse circular-polarized Bessel beam generation by inward cylindrical aperture distribution.

PubMed

Pavone, S C; Ettorre, M; Casaletti, M; Albani, M

2016-05-16

In this paper the focusing capability of a radiating aperture implementing an inward cylindrical traveling wave tangential electric field distribution directed along a fixed polarization unit vector is investigated. In particular, it is shown that such an aperture distribution generates a non-diffractive Bessel beam whose transverse component (with respect to the normal of the radiating aperture) of the electric field takes the form of a zero-th order Bessel function. As a practical implementation of the theoretical analysis, a circular-polarized Bessel beam launcher, made by a radial parallel plate waveguide loaded with several slot pairs, arranged on a spiral pattern, is designed and optimized. The proposed launcher performance agrees with the theoretical model and exhibits an excellent polarization purity.

A technique for measurement of earth station antenna G/T by radio stars and Applications Technology Satellites.

NASA Technical Reports Server (NTRS)

Kochevar, H. J.

1972-01-01

A new technique has been developed to accurately measure the G/T of a small aperture antenna using geostationary satellites and the well established radio star method. A large aperture antenna having the capability of accurately measuring its G/T by using a radio star of known power density is used to obtain an accurate G/T to use as a reference. The CNR of both the large and small aperture antennas are then measured using an Applications Technology Satellite (ATS). After normalizing the two C/N ratios to the large antenna system noise temperature the G/T or the gain G of the small aperture antenna can then be determined.

Mode trap for absorbing transverse modes of an accelerated electron beam

DOEpatents

Chojnacki, E.P.

1994-05-31

A mode trap to trap and absorb transverse modes formed by a beam in a linear accelerator includes a waveguide having a multiplicity of electrically conductive (preferably copper) irises and rings, each iris and ring including an aperture, and the irises and rings being stacked in a side-by-side, alternating fashion such that the apertures of the irises and rings are concentrically aligned. An absorbing material layer such as a dielectric is embedded in each iris and ring, and this absorbing material layer encircles, but is circumferentially spaced from its respective aperture. Each iris and ring includes a plurality of circumferentially spaced slots around its aperture and extending radially out toward its absorbing material layer. 9 figs.

Ultrafast treatment plan optimization for volumetric modulated arc therapy (VMAT)

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

Men Chunhua; Romeijn, H. Edwin; Jia Xun

2010-11-15

Purpose: To develop a novel aperture-based algorithm for volumetric modulated arc therapy (VMAT) treatment plan optimization with high quality and high efficiency. Methods: The VMAT optimization problem is formulated as a large-scale convex programming problem solved by a column generation approach. The authors consider a cost function consisting two terms, the first enforcing a desired dose distribution and the second guaranteeing a smooth dose rate variation between successive gantry angles. A gantry rotation is discretized into 180 beam angles and for each beam angle, only one MLC aperture is allowed. The apertures are generated one by one in a sequentialmore » way. At each iteration of the column generation method, a deliverable MLC aperture is generated for one of the unoccupied beam angles by solving a subproblem with the consideration of MLC mechanic constraints. A subsequent master problem is then solved to determine the dose rate at all currently generated apertures by minimizing the cost function. When all 180 beam angles are occupied, the optimization completes, yielding a set of deliverable apertures and associated dose rates that produce a high quality plan. Results: The algorithm was preliminarily tested on five prostate and five head-and-neck clinical cases, each with one full gantry rotation without any couch/collimator rotations. High quality VMAT plans have been generated for all ten cases with extremely high efficiency. It takes only 5-8 min on CPU (MATLAB code on an Intel Xeon 2.27 GHz CPU) and 18-31 s on GPU (CUDA code on an NVIDIA Tesla C1060 GPU card) to generate such plans. Conclusions: The authors have developed an aperture-based VMAT optimization algorithm which can generate clinically deliverable high quality treatment plans at very high efficiency.« less

Precise Aperture-Dependent Motion Compensation with Frequency Domain Fast Back-Projection Algorithm.

PubMed

Zhang, Man; Wang, Guanyong; Zhang, Lei

2017-10-26

Precise azimuth-variant motion compensation (MOCO) is an essential and difficult task for high-resolution synthetic aperture radar (SAR) imagery. In conventional post-filtering approaches, residual azimuth-variant motion errors are generally compensated through a set of spatial post-filters, where the coarse-focused image is segmented into overlapped blocks concerning the azimuth-dependent residual errors. However, image domain post-filtering approaches, such as precise topography- and aperture-dependent motion compensation algorithm (PTA), have difficulty of robustness in declining, when strong motion errors are involved in the coarse-focused image. In this case, in order to capture the complete motion blurring function within each image block, both the block size and the overlapped part need necessary extension leading to degeneration of efficiency and robustness inevitably. Herein, a frequency domain fast back-projection algorithm (FDFBPA) is introduced to deal with strong azimuth-variant motion errors. FDFBPA disposes of the azimuth-variant motion errors based on a precise azimuth spectrum expression in the azimuth wavenumber domain. First, a wavenumber domain sub-aperture processing strategy is introduced to accelerate computation. After that, the azimuth wavenumber spectrum is partitioned into a set of wavenumber blocks, and each block is formed into a sub-aperture coarse resolution image via the back-projection integral. Then, the sub-aperture images are straightforwardly fused together in azimuth wavenumber domain to obtain a full resolution image. Moreover, chirp-Z transform (CZT) is also introduced to implement the sub-aperture back-projection integral, increasing the efficiency of the algorithm. By disusing the image domain post-filtering strategy, robustness of the proposed algorithm is improved. Both simulation and real-measured data experiments demonstrate the effectiveness and superiority of the proposal.

Ultrafast treatment plan optimization for volumetric modulated arc therapy (VMAT).

PubMed

Men, Chunhua; Romeijn, H Edwin; Jia, Xun; Jiang, Steve B

2010-11-01

To develop a novel aperture-based algorithm for volumetric modulated are therapy (VMAT) treatment plan optimization with high quality and high efficiency. The VMAT optimization problem is formulated as a large-scale convex programming problem solved by a column generation approach. The authors consider a cost function consisting two terms, the first enforcing a desired dose distribution and the second guaranteeing a smooth dose rate variation between successive gantry angles. A gantry rotation is discretized into 180 beam angles and for each beam angle, only one MLC aperture is allowed. The apertures are generated one by one in a sequential way. At each iteration of the column generation method, a deliverable MLC aperture is generated for one of the unoccupied beam angles by solving a subproblem with the consideration of MLC mechanic constraints. A subsequent master problem is then solved to determine the dose rate at all currently generated apertures by minimizing the cost function. When all 180 beam angles are occupied, the optimization completes, yielding a set of deliverable apertures and associated dose rates that produce a high quality plan. The algorithm was preliminarily tested on five prostate and five head-and-neck clinical cases, each with one full gantry rotation without any couch/collimator rotations. High quality VMAT plans have been generated for all ten cases with extremely high efficiency. It takes only 5-8 min on CPU (MATLAB code on an Intel Xeon 2.27 GHz CPU) and 18-31 s on GPU (CUDA code on an NVIDIA Tesla C1060 GPU card) to generate such plans. The authors have developed an aperture-based VMAT optimization algorithm which can generate clinically deliverable high quality treatment plans at very high efficiency.

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

Spitznagel, D

Purpose: The use of protons for radiation therapy is growing rapidly. One consequence of protons interacting with different media is activation. These nuclear reactions induced by the protons, scattered neutrons, and gamma rays, activate different materials encountered, particularly by the therapists. The purpose of this study was to examine the derived nuclides from the activation, and also the decay rate. Methods: The study was conducted in our proton therapy facility. Protons are derived from a synchrocyclotron and pass through field shipping systems, apertures, and range compensators to define the beam within the patient.Included materials of concerns measured; the patient supportmore » couch, sheet rock in the wall, solid plastics used for quality assurance and dosimetry, and the passive scattering system itself, which includes brass apertures, and Lucite or blue wax compensators. All devices were studied post irradiation using gamma spectroscopy to determine the nuclides, and a sodium iodine scintillation detector to measure decay, particularly when the dose rate fell to background levels. Results: We have also determined from the measurements we will maintain brass apertures for three months before sending them for scrap. Some of the radionuclides arrived from these measurements included Na-22 for the blue wax compensator, C1-34m for the sheetrock, and Sc-44 and Co-60 for the brass apertures. We found compensators made out of Lucite or wax decayed to background in 2 hours. The patient support couch decayed to background in approximately 40 minutes, and sheet rock decayed in 80 minutes. In terms of the aperture layers, the most proximal aperture slab had much higher activity than the distal slab. Also the proximal sides of the slabs were much more activate than the distal. Conclusion: We have given proper instruction to therapists performing quality assurance in terms of the handled plastics, and to handle apertures rapidly as possible.« less

Oblong-Shaped-Focused Transducers for Intravascular Ultrasound Imaging.

PubMed

Lee, Junsu; Jang, Jihun; Chang, Jin Ho

2017-03-01

In intravascular ultrasound (IVUS) imaging, a transducer is inserted into a blood vessel and rotated to obtain image data. For this purpose, the transducer aperture is typically less than 0.5 mm in diameter, which causes natural focusing to occur in the imaging depth ranging from 1 to 5 mm. Due to the small aperture, however, it is not viable to conduct geometric focusing in order to enhance the spatial resolution of IVUS images. Furthermore, this hampers narrowing the slice thickness of a cross-sectional scan plane in the imaging depth, which leads to lowering spatial and contrast resolutions of IVUS images. To solve this problem, we propose an oblong-shaped-focused transducer for IVUS imaging. Unlike the conventional IVUS transducers with either a circular or a square flat aperture, the proposed transducer has an oblong aperture of which long side is positioned along a blood vessel. This unique configuration makes it possible to conduct geometric focusing at a desired depth in the elevation direction. In this study, furthermore, it is demonstrated that a spherically shaped aperture in both lateral and elevation directions also improves lateral resolution, compared to the conventional flat aperture. To ascertain this, the conventional and the proposed IVUS transducers were designed and fabricated to evaluate and to compare their imaging performances through wire phantom and tissue-mimicking phantom experiments. For the proposed 50-MHz IVUS transducer, a PZT piece of 0.5 × 1.0 mm 2 was spherically shaped for elevation focus at 3 mm by using the conventional press-focusing technique whereas the conventional one has a flat aperture of 0.5 × 0.5 mm 2 . The experimental results demonstrated that the proposed IVUS transducer is capable of improving spatial and contrast resolutions of IVUS images.

SU-E-T-666: Radionuclides and Activity of the Patient Apertures Used in a Proton Beam of Wobbling System

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

Wang, B.Y.; Chen, H.H.; Tsai, H.Y.

2015-06-15

Purpose: To identify the radionuclides and quantify the activity of the patient apertures used in a 190-MeV proton beam of wobbling system. Methods: A proton beam of wobbling system in the first proton center in Taiwan, Chang Gung Memorial Hospital at Linkou, was used to bombard the patient apertures. The patient aperture was composed of 60.5 % copper, 39.4 % Zinc, 0.05 % iron, 0.05 % lead. A protable high-purity germanium (HPGe) coaxial detector was used to measure the spectra of the induced nuclides of patient apertures. The analysis of the spectra and the identification of the radionuclides were preliminarilymore » operated by the Nuclide Navigator III Master Library. On the basis of the results by Nuclide Navigator III Master Library, we manually selected the reliable nuclides by the gamma-ray energies, branching ratio, and half life. In the spectra, we can quantify the activity of radionuclides by the Monte Carlo efficiency transfer method. Results: In this study, the radioisotopes activated in patient apertures by the 190-MeV proton beam were divided into two categories. The first category is long half-life radionuclides, such as Co-56 (half life, 77.3 days). Other radionuclides of Cu-60, Cu-61, Cu-62, Cu-66, and Zn-62 have shorter half life. The radionuclide of Cu-60 had the highest activity. From calculation with the efficiency transfer method, the deviations between the computed results and the measured efficiencies were mostly within 10%. Conclusion: To identify the radionuclides and quantify the activity helps us to estimate proper time intervals for cooling the patient apertures. This study was supported by the grants from the Chang Gung Memorial Hospital (CMRPD1C0682)« less

Aperture efficiency of integrated-circuit horn antennas

NASA Technical Reports Server (NTRS)

Guo, Yong; Lee, Karen; Stimson, Philip; Potter, Kent; Rutledge, David

1991-01-01

The aperture efficiency of silicon integrated-circuit horn antennas has been improved by optimizing the length of the dipole probes and by coating the entire horn walls with gold. To make these measurements, a new thin-film power-density meter was developed for measuring power density with accuracies better than 5 percent. The measured aperture efficiency improved from 44 percent to 72 percent at 93 GHz. This is sufficient for use in many applications which now use machined waveguide horns.

Throughput of diffraction-limited field optics systems for infrared and millimetric telescopes

NASA Technical Reports Server (NTRS)

Hildebrand, R. H.; Winston, R.

1982-01-01

Telescopes for submillimeter wavelengths have point spread functions some millimeters or centimeters in diameter, but the detectors may be only fractions of a millimeter in size. Thus a field aperture and collecting optics are needed. Optimizing the aperture by a calculation of the effects of diffraction on signal and resolution as a function of size of the collecting aperture is shown. Calculations are compared to experimental results from observations of Mars at submillimeter wavelengths.

Fluid sampling device

NASA Technical Reports Server (NTRS)

Studenick, D. K. (Inventor)

1977-01-01

An inlet leak is described for sampling gases, more specifically, for selectively sampling multiple fluids. This fluid sampling device includes a support frame. A plurality of fluid inlet devices extend through the support frame and each of the fluid inlet devices include a longitudinal aperture. An opening device that is responsive to a control signal selectively opens the aperture to allow fluid passage. A closing device that is responsive to another control signal selectively closes the aperture for terminating further fluid flow.

Receiver for solar energy collector having improved aperture aspect

DOEpatents

McIntire, William R.

1984-01-01

A secondary concentrator for use in receiver systems for linear focusing primary concentrators is provided with reflector wings at each end. The wings increase the capture of light rays reflected from areas adjacent the rim of a primary concentrator, increasing the apparent aperture size of the absorber as viewed from the rim of the primary concentrator. The length, tilt, and curvature of the wing reflectors can be adjusted to provide an absorber having a desired aperture aspect.

ION ACCELERATION SYSTEM

DOEpatents

Luce, J.S.; Martin, J.A.

1960-02-23

Well focused, intense ion beams are obtained by providing a multi- apertured source grid in front of an ion source chamber and an accelerating multi- apertured grid closely spaced from and in alignment with the source grid. The longest dimensions of the elongated apertures in the grids are normal to the direction of the magnetic field used with the device. Large ion currents may be withdrawn from the source, since they do not pass through any small focal region between the grids.

Note on use of slope diffraction coefficients for aperture antennas on finite ground planes

NASA Technical Reports Server (NTRS)

Cockrell, C. R.; Beck, F. B.

1995-01-01

The use of slope diffraction coefficients along with regular diffraction coefficients for calculating the radiation patterns of aperture antennas in a finite ground plane is investigated. Explicit expressions for regular diffraction coefficients and slope diffraction coefficients are presented. The expressions for the incident magnetic field in terms of the magnetic current in the aperture are given. The slope of the incident magnetic field is calculated and closed form expressions are presented.

Performance of multi-aperture grid extraction systems for an ITER-relevant RF-driven negative hydrogen ion source

NASA Astrophysics Data System (ADS)

Franzen, P.; Gutser, R.; Fantz, U.; Kraus, W.; Falter, H.; Fröschle, M.; Heinemann, B.; McNeely, P.; Nocentini, R.; Riedl, R.; Stäbler, A.; Wünderlich, D.

2011-07-01

The ITER neutral beam system requires a negative hydrogen ion beam of 48 A with an energy of 0.87 MeV, and a negative deuterium beam of 40 A with an energy of 1 MeV. The beam is extracted from a large ion source of dimension 1.9 × 0.9 m2 by an acceleration system consisting of seven grids with 1280 apertures each. Currently, apertures with a diameter of 14 mm in the first grid are foreseen. In 2007, the IPP RF source was chosen as the ITER reference source due to its reduced maintenance compared with arc-driven sources and the successful development at the BATMAN test facility of being equipped with the small IPP prototype RF source ( {\\sim}\\frac{1}{8} of the area of the ITER NBI source). These results, however, were obtained with an extraction system with 8 mm diameter apertures. This paper reports on the comparison of the source performance at BATMAN of an ITER-relevant extraction system equipped with chamfered apertures with a 14 mm diameter and 8 mm diameter aperture extraction system. The most important result is that there is almost no difference in the achieved current density—being consistent with ion trajectory calculations—and the amount of co-extracted electrons. Furthermore, some aspects of the beam optics of both extraction systems are discussed.

Effects of Aperture Size on Q factor and Shielding Effectiveness of a Cubic Resonator

NASA Astrophysics Data System (ADS)

Parr, Stefan; Chromy, Stephan; Dickmann, Stefan; Schaarschmidt, Martin

2017-09-01

The EMC properties of a cubic metallic shield are highly affected by its resonances. At the resonant frequencies, the shielding effectiveness (SE) collapses, which results in high field strengths inside the cavity. This can cause failure or even breakdown of electronic devices inside the shield. The resonant behaviour is mainly determined by the quality or Q factor of the shield. In this paper, the effects of the aperture size on the Q factor and the SE of an electrically large, cubic shield are analysed. At first, a method is developed in order to determine the Q factor based on the resonance behaviour of the shield in time domain. Only the first resonance of the shield is considered therefore. The results are evaluated for different aperture diameters and compared with theory for the Q factor. The dominant coupling mechanism of electromagnetic energy into the shield is thus identified. Then the effect of aperture size on the SE is analysed. The excitation of resonances is very probable if the interfering signal is an ultrawideband (UWB) pulse, which constitutes a typical intentional electromagnetic interference (IEMI) scenario. Therefore, the relation between aperture size and SE is analysed using the theory of the transient SE for a broadband signal with a constant spectral density distribution. The results show, that a worst case aperture size exists, where the SE has its minimum.

A novel three-dimensional image reconstruction method for near-field coded aperture single photon emission computerized tomography

PubMed Central

Mu, Zhiping; Hong, Baoming; Li, Shimin; Liu, Yi-Hwa

2009-01-01

Coded aperture imaging for two-dimensional (2D) planar objects has been investigated extensively in the past, whereas little success has been achieved in imaging 3D objects using this technique. In this article, the authors present a novel method of 3D single photon emission computerized tomography (SPECT) reconstruction for near-field coded aperture imaging. Multiangular coded aperture projections are acquired and a stack of 2D images is reconstructed separately from each of the projections. Secondary projections are subsequently generated from the reconstructed image stacks based on the geometry of parallel-hole collimation and the variable magnification of near-field coded aperture imaging. Sinograms of cross-sectional slices of 3D objects are assembled from the secondary projections, and the ordered subset expectation and maximization algorithm is employed to reconstruct the cross-sectional image slices from the sinograms. Experiments were conducted using a customized capillary tube phantom and a micro hot rod phantom. Imaged at approximately 50 cm from the detector, hot rods in the phantom with diameters as small as 2.4 mm could be discerned in the reconstructed SPECT images. These results have demonstrated the feasibility of the authors’ 3D coded aperture image reconstruction algorithm for SPECT, representing an important step in their effort to develop a high sensitivity and high resolution SPECT imaging system. PMID:19544769

Studies of the resonant interaction of photons with surface plasmons and sub-wavelength apetures in metallo-dielectric structures

NASA Astrophysics Data System (ADS)

Stark, Peter Randolph Hazard

Since the publication of the work by Thomas Ebbesen, et al. in 1998 on the extraordinary optical transmission of photons through sub-wavelength apertures in metallic films there has been tremendous interest in the phenomenon and applications of it. This dissertation is a compilation of investigations into applications of the extraordinary optical transmission through apertures in metallo-dielectric structures. Asymmetric metallo-dielectric structures (structures in which the dielectric functions of the dielectrics are not equivalent in a dielectric/metal film/dielectric stack) are fabricated by either sputtering or thermal evaporation. Apertures in the metal film are milled using a focused ion beam instrument. Transmission of photons through the apertures is characterized by the following photosensitive methods: direct exposure of photoresist, exposure of charged coupled devices through intermediate optics, direct exposure of a fluorescent medium and subsequent collection through intermediate optics and subsequent collection via photomultiplier tubes and CCD, collection by a photocathodic material and direct collection by photomultiplier tubes. Results indicate not only the extraordinary transmission discovered by Ebbesen et al.; but, in contravention to previously held theory, that photons emitted from such subwavelength apertures in asymmetric metallo-dielectric structures (aperture diameters typically

Backscatter RCS for TE and TM excitations of dielectric-filled cavity-backed apertures in two-dimensional bodies

NASA Technical Reports Server (NTRS)

Goggans, Paul M.; Shumpert, Thomas H.

1991-01-01

Transverse electric (TE) and transverse magnetic (TM) scattering from dielectric-filled, cavity-backed apertures in two-dimensional bodies are treated using the method of moments technique to solve a set of combined-field integral equations for the equivalent induced electric and magnetic currents on the exterior of the scattering body and on the associated aperture. Results are presented for the backscatter radar cross section (RCS) versus the electrical size of the scatterer for two different dielectric-filled cavity-backed geometries. The first geometry is a circular cylinder of infinite length which has an infinite length slot aperture along one side. The cavity inside the cylinder is dielectric filled and is also of circular cross section. The two cylinders (external and internal) are of different radii and their respective longitudinal axes are parallel but not collocated. The second is a square cylinder of infinite length which has an infinite length slot aperture along one side. The cavity inside the square cylinder is dielectric-filled and is also of square cross section.

Gametophytic vs. sporophytic control of pollen aperture number: a generational conflict.

PubMed

Till-Bottraud, Irène; Gouyon, Pierre-Henri; Ressayre, Adrienne; Godelle, Bernard

2012-11-01

In flowering plants, the haploid phase is reduced to the pollen grain and embryo sac. These reproductive tissues (gametophytes) are actually distinct individuals that have a different genome from the plant (sporophyte), and are more or less independent. The morphology of pollen grains, particularly the openings permitting pollen tube germination (apertures), is crucial for determining the outcome of pollen competition. Many species of flowering plants simultaneously produce pollen grains with different aperture numbers in a single individual (heteromorphism). In this paper, we show that the heteromorphic pollen aperture pattern depends on the genetic control of pollen morphogenesis. This points out a conflict of interest between genes expressed in the sporophyte and genes expressed in the gametophyte. More generally, such a conflict should exist whenever heteromorphism is an ESS resulting from a bet-hedging strategy. For pollen aperture, heteromorphism has been observed in about 40% of angiosperm species, suggesting that conflicting situations are the rule. In this context, the sporo-gametophytic conflict could be one of the factors that led to the reduction of the haploid phase in plants. 2012 Elsevier Inc. All rights reserved

Numerical analysis of fundamental mode selection of a He-Ne laser by a circular aperture

NASA Astrophysics Data System (ADS)

He, Xin; Zhang, Bin

2011-11-01

In the He-Ne laser with an integrated cavity made of zerodur, the inner face performance of the gain tube is limited by the machining techniques, which tends to influence the beam propagation and transverse mode distribution. In order to improve the beam quality and select out the fundamental mode, an aperture is usually introduced in the cavity. In the process of laser design, the Fresnel-Kirchhoff diffraction integral equation is adopted to calculate the optical field distributions on each interface. The transit matrix is obtained based on self-reproducing principle and finite element method. Thus, optical field distribution on any interface and field loss of each transverse mode could be acquired by solving the eigenvalue and eigenvector of the transit matrix. For different-sized apertures in different positions, we could get different matrices and corresponding calculation results. By comparing these results, the optimal size and position of the aperture could be obtained. As a result, the feasibility of selecting fundamental mode in a zerodur He-Ne laser by a circular aperture has been verified theoretically.

Multi-port valve assembly

DOEpatents

Guggenheim, S. Frederic

1986-01-01

A multi-port fluid valve apparatus is used to control the flow of fluids through a plurality of valves and includes a web, which preferably is a stainless steel endless belt. The belt has an aperture therethrough and is progressed, under motor drive and control, so that its aperture is moved from one valve mechanism to another. Each of the valve mechanisms comprises a pair of valve blocks which are held in fluid-tight relationship against the belt. Each valve block consists of a block having a bore through which the fluid flows, a first seal surrounding the bore and a second seal surrounding the first seal, with the distance between the first and second seals being greater than the size of the belt aperture. In order to open a valve, the motor progresses the belt aperture to where it is aligned with the two bores of a pair of valve blocks, such alignment permitting a flow of the fluid through the valve. The valve is closed by movement of the belt aperture and its replacement, within the pair of valve blocks, by a solid portion of the belt.

Plural output optimetric sample cell and analysis system

NASA Technical Reports Server (NTRS)

Haley, F. C. (Inventor)

1971-01-01

An apparatus suitable for receiving a sample for optimetric analysis includes a sample cell comprising an opaque hollow tube. Several apertures are defined in the wall of the tubing and a lens barrel which extends beyond to opposite surfaces of the wall is supported within at least one of the apertures. A housing is provided with one channel for receiving the sample cell and a series of channels extending from the exterior housing to the sample cell apertures. A filter element is housed in each of these latter channels. These channels slidingly receive an excitation light source for a photodetector cell to permit selective focusing. A sample cell containing at least three apertures in the walls can be mounted for rotation relative to a light source or photoconduction means for simultaneous or alternative optimetric determination of the components of a single sample. The sample cell is fabricated by supporting a lens barrel within the aperture. A molten portion of glass is deposited in the lens barrel and cooled while in a horizontal position to form a lens having an acceptable angle.

Ionospheric effects on synthetic aperture radar at VHF

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

Fitzgerald, T.J.

1997-02-01

Synthetic aperture radars (SAR) operated from airplanes have been used at VHF because of their enhanced foliage and ground penetration compared to radars operated at UHF. A satellite-borne VHF SAR would have considerable utility but in order to operate with high resolution it would have to use both a large relative bandwidth and a large aperture. The presence of the ionosphere in the propagation path of the radar will cause a deterioration of the imaging because of dispersion over the bandwidth and group path changes in the imaged area over the collection aperture. In this paper we present calculations ofmore » the effects of a deterministic ionosphere on SAR imaging for a radar operated with a 100 MHz bandwidth centered at 250 MHz and over an angular aperture of 23{degrees}. The ionosphere induces a point spread function with an approximate half-width of 150 m in the slant-range direction and of 25 m in the cross-range direction compared to the nominal resolution of 1.5 m in both directions.« less

Proof of Concept Coded Aperture Miniature Mass Spectrometer Using a Cycloidal Sector Mass Analyzer, a Carbon Nanotube (CNT) Field Emission Electron Ionization Source, and an Array Detector.

PubMed

Amsden, Jason J; Herr, Philip J; Landry, David M W; Kim, William; Vyas, Raul; Parker, Charles B; Kirley, Matthew P; Keil, Adam D; Gilchrist, Kristin H; Radauscher, Erich J; Hall, Stephen D; Carlson, James B; Baldasaro, Nicholas; Stokes, David; Di Dona, Shane T; Russell, Zachary E; Grego, Sonia; Edwards, Steven J; Sperline, Roger P; Denton, M Bonner; Stoner, Brian R; Gehm, Michael E; Glass, Jeffrey T

2018-02-01

Despite many potential applications, miniature mass spectrometers have had limited adoption in the field due to the tradeoff between throughput and resolution that limits their performance relative to laboratory instruments. Recently, a solution to this tradeoff has been demonstrated by using spatially coded apertures in magnetic sector mass spectrometers, enabling throughput and signal-to-background improvements of greater than an order of magnitude with no loss of resolution. This paper describes a proof of concept demonstration of a cycloidal coded aperture miniature mass spectrometer (C-CAMMS) demonstrating use of spatially coded apertures in a cycloidal sector mass analyzer for the first time. C-CAMMS also incorporates a miniature carbon nanotube (CNT) field emission electron ionization source and a capacitive transimpedance amplifier (CTIA) ion array detector. Results confirm the cycloidal mass analyzer's compatibility with aperture coding. A >10× increase in throughput was achieved without loss of resolution compared with a single slit instrument. Several areas where additional improvement can be realized are identified. Graphical Abstract ᅟ.

Proof of Concept Coded Aperture Miniature Mass Spectrometer Using a Cycloidal Sector Mass Analyzer, a Carbon Nanotube (CNT) Field Emission Electron Ionization Source, and an Array Detector

NASA Astrophysics Data System (ADS)

Amsden, Jason J.; Herr, Philip J.; Landry, David M. W.; Kim, William; Vyas, Raul; Parker, Charles B.; Kirley, Matthew P.; Keil, Adam D.; Gilchrist, Kristin H.; Radauscher, Erich J.; Hall, Stephen D.; Carlson, James B.; Baldasaro, Nicholas; Stokes, David; Di Dona, Shane T.; Russell, Zachary E.; Grego, Sonia; Edwards, Steven J.; Sperline, Roger P.; Denton, M. Bonner; Stoner, Brian R.; Gehm, Michael E.; Glass, Jeffrey T.

2018-02-01

Despite many potential applications, miniature mass spectrometers have had limited adoption in the field due to the tradeoff between throughput and resolution that limits their performance relative to laboratory instruments. Recently, a solution to this tradeoff has been demonstrated by using spatially coded apertures in magnetic sector mass spectrometers, enabling throughput and signal-to-background improvements of greater than an order of magnitude with no loss of resolution. This paper describes a proof of concept demonstration of a cycloidal coded aperture miniature mass spectrometer (C-CAMMS) demonstrating use of spatially coded apertures in a cycloidal sector mass analyzer for the first time. C-CAMMS also incorporates a miniature carbon nanotube (CNT) field emission electron ionization source and a capacitive transimpedance amplifier (CTIA) ion array detector. Results confirm the cycloidal mass analyzer's compatibility with aperture coding. A >10× increase in throughput was achieved without loss of resolution compared with a single slit instrument. Several areas where additional improvement can be realized are identified.

Position measurement of the direct drive motor of Large Aperture Telescope

NASA Astrophysics Data System (ADS)

Li, Ying; Wang, Daxing

2010-07-01

Along with the development of space and astronomy science, production of large aperture telescope and super large aperture telescope will definitely become the trend. It's one of methods to solve precise drive of large aperture telescope using direct drive technology unified designed of electricity and magnetism structure. A direct drive precise rotary table with diameter of 2.5 meters researched and produced by us is a typical mechanical & electrical integration design. This paper mainly introduces position measurement control system of direct drive motor. In design of this motor, position measurement control system requires having high resolution, and precisely aligning the position of rotor shaft and making measurement, meanwhile transferring position information to position reversing information corresponding to needed motor pole number. This system has chosen high precision metal band coder and absolute type coder, processing information of coders, and has sent 32-bit RISC CPU making software processing, and gained high resolution composite coder. The paper gives relevant laboratory test results at the end, indicating the position measurement can apply to large aperture telescope control system. This project is subsidized by Chinese National Natural Science Funds (10833004).

Multiplexed two in-line holographic recordings for flow characterization in a flexible vessel

NASA Astrophysics Data System (ADS)

Lobera, Julia; Palero, Virginia; Roche, Eva M.; Gómez Climente, Marina; López Torres, Ana M.; Andrés, Nieves; Arroyo, M. Pilar

2017-06-01

The simultaneous presence of the real and virtual images in the hologram reconstruction is inherent in the in-line holography. This drawback can be overcome with a shifted knife-edge aperture at the focal plane of the imaging lens. The shifted aperture DIH produces holograms where the real and virtual images are completely separated. In this paper we propose a modification of the shifted aperture DIH that allows recording two holograms simultaneously using one camera, while retaining the simplicity of the in-line configuration and the advantage of the shifted-aperture strategy. As in typical stereoscopy, the advantage of this configuration is limited by the angle between the two illuminating beams, and therefore the aperture size. Some improvement on the out-of-plane resolution can be expected from a combined analysis of the multiplexed holograms. In order to compare this technique with other in-line holographic configurations, several experiments have been performed to study the spatial resolution along the optical axis. The capabilities of the different techniques for characterizing the flow in a flexible and transparent model of a carotid bifurcation are also investigated.

Measuring electrode assembly

DOEpatents

Bordenick, J.E.

1988-04-26

A pH measuring electrode assembly for immersion in a solution includes an enclosed cylindrical member having an aperture at a lower end thereof. An electrolyte is located in the cylindrical member above the level of the aperture and an electrode is disposed in this electrolyte. A ring formed of an ion porous material is mounted relative to the cylindrical member so that a portion of this ring is rotatable relative to and is covering the aperture in the cylindrical member. A suitable mechanism is also provided for indicating which one of a plurality of portions of the ring is covering the aperture and to keep track of which portions of the ring have already been used and become clogged. Preferably, the electrode assembly also includes a glass electrode member in the center thereof including a second electrolyte and electrode disposed therein. The cylindrical member is resiliently mounted relative to the glass electrode member to provide for easy rotation of the cylindrical member relative to the glass electrode member for changing of the portion of the ring covering the aperture. 2 figs.

The application of Fresnel zone plate based projection in optofluidic microscopy.

PubMed

Wu, Jigang; Cui, Xiquan; Lee, Lap Man; Yang, Changhuei

2008-09-29

Optofluidic microscopy (OFM) is a novel technique for low-cost, high-resolution on-chip microscopy imaging. In this paper we report the use of the Fresnel zone plate (FZP) based projection in OFM as a cost-effective and compact means for projecting the transmission through an OFM's aperture array onto a sensor grid. We demonstrate this approach by employing a FZP (diameter = 255 microm, focal length = 800 microm) that has been patterned onto a glass slide to project the transmission from an array of apertures (diameter = 1 microm, separation = 10 microm) onto a CMOS sensor. We are able to resolve the contributions from 44 apertures on the sensor under the illumination from a HeNe laser (wavelength = 633 nm). The imaging quality of the FZP determines the effective field-of-view (related to the number of resolvable transmissions from apertures) but not the image resolution of such an OFM system--a key distinction from conventional microscope systems. We demonstrate the capability of the integrated system by flowing the protist Euglena gracilis across the aperture array microfluidically and performing OFM imaging of the samples.

Interference Mitigation Effects on Synthetic Aperture Radar Coherent Data Products

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

Musgrove, Cameron

For synthetic aperture radars radio frequency interference from sources external to the radar system and techniques to mitigate the interference can degrade the quality of the image products. Usually the radar system designer will try to balance the amount of mitigation for an acceptable amount of interference to optimize the image quality. This dissertation examines the effect of interference mitigation upon coherent data products of fine resolution, high frequency synthetic aperture radars using stretch processing. Novel interference mitigation techniques are introduced that operate on single or multiple apertures of data that increase average coherence compared to existing techniques. New metricsmore » are applied to evaluate multiple mitigation techniques for image quality and average coherence. The underlying mechanism for interference mitigation techniques that affect coherence is revealed.« less

Analysis of aperture averaging measurements. [laser scintillation data on the effect of atmospheric turbulence on signal fluctuations

NASA Technical Reports Server (NTRS)

Fried, D. L.

1975-01-01

Laser scintillation data obtained by the NASA Goddard Space Flight Center balloon flight no. 5 from White Sands Missile Range on 19 October 1973 are analyzed. The measurement data, taken with various size receiver apertures, were related to predictions of aperture averaging theory, and it is concluded that the data are in reasonable agreement with theory. The following parameters are assigned to the vertical distribution of the strength of turbulence during the period of the measurements (daytime), for lambda = 0.633 microns, and the source at the zenith; the aperture averaging length is d sub o = 0.125 m, and the log-amplitude variance is (beta sub l)2 = 0.084 square nepers. This corresponds to a normalized point intensity variance of 0.40.

Digital equalization of time-delay array receivers on coherent laser communications.

PubMed

Belmonte, Aniceto

2017-01-15

Field conjugation arrays use adaptive combining techniques on multi-aperture receivers to improve the performance of coherent laser communication links by mitigating the consequences of atmospheric turbulence on the down-converted coherent power. However, this motivates the use of complex receivers as optical signals collected by different apertures need to be adaptively processed, co-phased, and scaled before they are combined. Here, we show that multiple apertures, coupled with optical delay lines, combine retarded versions of a signal at a single coherent receiver, which uses digital equalization to obtain diversity gain against atmospheric fading. We found in our analysis that, instead of field conjugation arrays, digital equalization of time-delay multi-aperture receivers is a simpler and more versatile approach to accomplish reduction of atmospheric fading.

High density protein crystal growth

NASA Technical Reports Server (NTRS)

Rouleau, Robyn (Inventor); Hedden, Douglas Keith (Inventor); Delucas, Lawrence (Inventor)

2004-01-01

A protein crystal growth assembly including a crystal growth cell and further including a cell body having a top side and a bottom side and a first aperture defined therethrough, the cell body having opposing first and second sides and a second aperture defined therethrough. A cell barrel is disposed within the cell body, the cell barrel defining a cavity alignable with the first aperture of the cell body, the cell barrel being rotatable within the second aperture. A reservoir is coupled to the bottom side of the cell body and a cap having a top side is disposed on the top side of the cell body. The protein crystal growth assembly may be employed in methods including vapor diffusion crystallization, liquid to liquid crystallization, batch crystallization, and temperature induction batch mode crystallization.

Design studies of large aperture, high-resolution Earth science microwave radiometers compatible with small launch vehicles

NASA Technical Reports Server (NTRS)

Schroeder, Lyle C.; Bailey, M. C.; Harrington, Richard F.; Kendall, Bruce M.; Campbell, Thomas G.

1994-01-01

High-spatial-resolution microwave radiometer sensing from space with reasonable swath widths and revisit times favors large aperture systems. However, with traditional precision antenna design, the size and weight requirements for such systems are in conflict with the need to emphasize small launch vehicles. This paper describes tradeoffs between the science requirements, basic operational parameters, and expected sensor performance for selected satellite radiometer concepts utilizing novel lightweight compactly packaged real apertures. Antenna, feed, and radiometer subsystem design and calibration are presented. Preliminary results show that novel lightweight real aperture coupled with state-of-the-art radiometer designs are compatible with small launch systems, and hold promise for high-resolution earth science measurements of sea ice, precipitation, soil moisture, sea surface temperature, and ocean wind speeds.

Combination induction plasma tube and current concentrator for introducing a sample into a plasma

DOEpatents

Hull, Donald E.; Bieniewski, Thomas M.

1988-01-01

An induction plasma tube in combination with a current concentrator. The rent concentrator has a substantially cylindrical body having an open end and a partially closed end which defines an aperture. A first slot extends the longitudinal length of the cylindrical body and a second slot extends radially outward from the aperture. Together the first and second slots form a single L-shaped slot. The current concentrator is disposed within a volume bounded by an induction coil substantially along the axis thereof, and when power is applied to the induction coil a concentrated current is induced within the current concentrator aperture. The concentrator is moveable relative to the coil along the longitudinal axis of the coil to control the amount of current which is concentrated at the aperture.

SAVI: Synthetic apertures for long-range, subdiffraction-limited visible imaging using Fourier ptychography

PubMed Central

Holloway, Jason; Wu, Yicheng; Sharma, Manoj K.; Cossairt, Oliver; Veeraraghavan, Ashok

2017-01-01

Synthetic aperture radar is a well-known technique for improving resolution in radio imaging. Extending these synthetic aperture techniques to the visible light domain is not straightforward because optical receivers cannot measure phase information. We propose to use macroscopic Fourier ptychography (FP) as a practical means of creating a synthetic aperture for visible imaging to achieve subdiffraction-limited resolution. We demonstrate the first working prototype for macroscopic FP in a reflection imaging geometry that is capable of imaging optically rough objects. In addition, a novel image space denoising regularization is introduced during phase retrieval to reduce the effects of speckle and improve perceptual quality of the recovered high-resolution image. Our approach is validated experimentally where the resolution of various diffuse objects is improved sixfold. PMID:28439550

Thermal protection apparatus

DOEpatents

Bennett, Gloria A.; Moore, Troy K.

1988-01-01

An apparatus for thermally protecting heat sensitive components of tools. The apparatus comprises a Dewar for holding the heat sensitive components. The Dewar has spaced-apart inside and outside walls, an open top end and a bottom end. An insulating plug is located in the top end. The inside wall has portions defining an inside wall aperture located at the bottom of the Dewar and the outside wall has portions defining an outside wall aperture located at the bottom of the Dewar. A bottom connector has inside and outside components. The inside component sealably engages the inside wall aperture and the outside component sealably engages the outside wall aperture. The inside component is operatively connected to the heat sensitive components and to the outside component. The connections can be made with optical fibers or with electrically conducting wires.

Sub-aperture switching based ptychographic iterative engine (sasPIE) method for quantitative imaging

NASA Astrophysics Data System (ADS)

Sun, Aihui; Kong, Yan; Jiang, Zhilong; Yu, Wei; Liu, Fei; Xue, Liang; Wang, Shouyu; Liu, Cheng

2018-03-01

Though ptychographic iterative engine (PIE) has been widely adopted in the quantitative micro-imaging with various illuminations as visible light, X-ray and electron beam, the mechanical inaccuracy in the raster scanning of the sample relative to the illumination always degrades the reconstruction quality seriously and makes the resolution reached much lower than that determined by the numerical aperture of the optical system. To overcome this disadvantage, the sub-aperture switching based PIE method is proposed: the mechanical scanning in the common PIE is replaced by the sub-aperture switching, and the reconstruction error related to the positioning inaccuracy is completely avoided. The proposed technique remarkably improves the reconstruction quality, reduces the complexity of the experimental setup and fundamentally accelerates the data acquisition and reconstruction.

Microscale ion trap mass spectrometer

DOEpatents

Ramsey, J. Michael; Witten, William B.; Kornienko, Oleg

2002-01-01

An ion trap for mass spectrometric chemical analysis of ions is delineated. The ion trap includes a central electrode having an aperture; a pair of insulators, each having an aperture; a pair of end cap electrodes, each having an aperture; a first electronic signal source coupled to the central electrode; a second electronic signal source coupled to the end cap electrodes. The central electrode, insulators, and end cap electrodes are united in a sandwich construction where their respective apertures are coaxially aligned and symmetric about an axis to form a partially enclosed cavity having an effective radius r.sub.0 and an effective length 2z.sub.0, wherein r.sub.0 and/or z.sub.0 are less than 1.0 mm, and a ratio z.sub.0 /r.sub.0 is greater than 0.83.

TRIPPy: Python-based Trailed Source Photometry

NASA Astrophysics Data System (ADS)

Fraser, Wesley C.; Alexandersen, Mike; Schwamb, Megan E.; Marsset, Michael E.; Pike, Rosemary E.; Kavelaars, JJ; Bannister, Michele T.; Benecchi, Susan; Delsanti, Audrey

2016-05-01

TRIPPy (TRailed Image Photometry in Python) uses a pill-shaped aperture, a rectangle described by three parameters (trail length, angle, and radius) to improve photometry of moving sources over that done with circular apertures. It can generate accurate model and trailed point-spread functions from stationary background sources in sidereally tracked images. Appropriate aperture correction provides accurate, unbiased flux measurement. TRIPPy requires numpy, scipy, matplotlib, Astropy (ascl:1304.002), and stsci.numdisplay; emcee (ascl:1303.002) and SExtractor (ascl:1010.064) are optional.

Compact organic vapor jet printing print head

DOEpatents

Forrest, Stephen R; McGraw, Gregory

2013-12-24

A first device is provided. The first device includes a print head, and a first gas source hermetically sealed to the print head. The print header further includes a first layer comprising a plurality of apertures, each aperture having a smallest dimension of 0.5 to 500 microns. A second layer is bonded to the first layer. The second layer includes a first via in fluid communication with the first gas source and at least one of the apertures. The second layer is made of an insulating material.

The Segmented Aperture Interferometric Nulling Testbed (SAINT) I: overview and air-side system description

NASA Astrophysics Data System (ADS)

Hicks, Brian A.; Lyon, Richard G.; Petrone, Peter; Ballard, Marlin; Bolcar, Matthew R.; Bolognese, Jeff; Clampin, Mark; Dogoda, Peter; Dworzanski, Daniel; Helmbrecht, Michael A.; Koca, Corina; Shiri, Ron

2016-07-01

This work presents an overview of the Segmented Aperture Interferometric Nulling Testbed (SAINT), a project that will pair an actively-controlled macro-scale segmented mirror with the Visible Nulling Coronagraph (VNC). SAINT will incorporate the VNC's demonstrated wavefront sensing and control system to refine and quantify end-to-end high-contrast starlight suppression performance. This pathfinder testbed will be used as a tool to study and refine approaches to mitigating instabilities and complex diffraction expected from future large segmented aperture telescopes.

Electromagnetic field scattering by a triangular aperture.

PubMed

Harrison, R E; Hyman, E

1979-03-15

The multiple Laplace transform has been applied to analysis and computation of scattering by a double triangular aperture. Results are obtained which match far-field intensity distributions observed in experiments. Arbitrary polarization components, as well as in-phase and quadrature-phase components, may be determined, in the transform domain, as a continuous function of distance from near to far-field for any orientation, aperture, and transformable waveform. Numerical results are obtained by application of numerical multiple inversions of the fully transformed solution.

Linear Frequency Modulated Signals VS Orthogonal Frequency Division Multiplexing Signals for Synthetic Aperture Radar Systems

DTIC Science & Technology

2014-06-01

antenna beamwidth and R is the range distance. Antenna beam width  is proportional to the real aperture size and is given as antennaL ...18) where  is the wavelength and antennaL is the physical length of the radar antenna; therefore, cross-range resolution for a real aperture... antennaL R  (20) A value of 50 meters for cross-range resolution is rather high and signifies poor resolution. Under these conditions, obtaining

Wigner distribution function of Hermite-cosine-Gaussian beams through an apertured optical system.

PubMed

Sun, Dong; Zhao, Daomu

2005-08-01

By introducing the hard-aperture function into a finite sum of complex Gaussian functions, the approximate analytical expressions of the Wigner distribution function for Hermite-cosine-Gaussian beams passing through an apertured paraxial ABCD optical system are obtained. The analytical results are compared with the numerically integrated ones, and the absolute errors are also given. It is shown that the analytical results are proper and that the calculation speed for them is much faster than for the numerical results.

Determination of Individual Temperatures and Luminosities in Eclipsing Binary Star Systems.

DTIC Science & Technology

1983-06-20

one to select one of five aperture sizes, ranging from .01" to .199". Each position has two stops: one sets the aperture in the center of the field of...comparing stellar field patterns to the finder chart. This step was the most surprisingly difficult of the entire observational procedure, since star... fields never quite seemed to agree exactly with those published on the SAO atlas. Once the system is located, it is centered in the smallest aperture which

Impulse Response Shaping for Ultra Wide Band SAR in a Circular Flight Path

NASA Technical Reports Server (NTRS)

Jin, Michael Y.

1996-01-01

An ultra wide band SAR (synthetic aperture radar) has potential applications on imaging underground objects. Flying this SAR in a circular flight path is an efficient way to acquire high resolution images from a localized area. This paper characterizes the impulse response of sucha system. The results indicate that to achieve an image with a more uniformed resolution over the entire imaged area, proper weighting coeficients should be applied to both the principle aperture and the complimentary aperture.

The Application of MP-FTS to Aperture Synthesis

NASA Astrophysics Data System (ADS)

Hattori, M.; Ohta, I. S.; Matsuo, H.; Shibata, Y.

2000-12-01

The application of the Martin-Puplett type Fourier transform spectrometer to aperture synthesis is considered. The configuration of the mirrors and beam splitters and the fundamental mathematical elements of the system are summarized. We show that the system can measure spectrally resolved spatial distribution of the Stokes parameters of sources as interfered signals. An original Martin-Puplett type Fourier transform spectrometer that can be applied to aperture synthesis in mm and sub-mm wave bands has been constructed. The preliminary results of our laboratory experiments are reported.

Noncoherent Combination Of Optical-Heterodyne Outputs

NASA Technical Reports Server (NTRS)

Chen, Chien-Chung; Lesh, James R.

1990-01-01

In proposed scheme for reception of amplitude- or frequency-modulated signals transmitted optically through atmosphere, main receiver aperture divided into subapertures equipped with receivers, and outputs of receivers combined noncoherently. Multiple subaperture receivers used instead of attempting to focus all light from single large aperture onto one receiver. Outputs of receivers combined after demodulation. System will not perform as well as fully coherent system, but surpasses single-large-aperture system in presence of atmospheric turbulence. Offers superior performance in presence of distorted wavefront and/or imperfect receiver optics.

Electrospray device

NASA Technical Reports Server (NTRS)

Demmons, Nathaniel (Inventor); Roy, Thomas (Inventor); Spence, Douglas (Inventor); Martin, Roy (Inventor); Hruby, Vladimir (Inventor); Ehrbar, Eric (Inventor); Zwahlen, Jurg (Inventor)

2011-01-01

An electrospray device includes an electrospray emitter adapted to receive electrospray fluid; an extractor plate spaced from the electrospray emitter and having at least one aperture; and a power supply for applying a first voltage between the extractor plate and emitter for generating at least one Taylor cone emission through the aperture to create an electrospray plume from the electrospray fluid, the extractor plate as well as accelerator and shaping plates may include a porous, conductive medium for transporting and storing excess, accumulated electrospray fluid away from the aperture.

A Radar/Radiometer Instrument for Mapping Soil Moisture and Ocean Salinity

NASA Technical Reports Server (NTRS)

Hildebrand, Peter H.; Hilliard, Laurence; Rincon, Rafael; LeVine, David; Mead, James

2003-01-01

The RadSTAR instrument combines an L-band, digital beam-forming radar with an L-band synthetic aperture, thinned array (STAR) radiometer. The RadSTAR development will support NASA Earth science goals by developing a novel, L-band scatterometer/ radiometer that measures Earth surface bulk material properties (surface emissions and backscatter) as well as surface characteristics (backscatter). Present, real aperture airborne L-Band active/passive measurement systems such as the JPUPALS (Wilson, et al, 2000) provide excellent sampling characteristics, but have no scanning capabilities, and are extremely large; the huge JPUPALS horn requires a the C-130 airborne platform, operated with the aft loading door open during flight operation. The approach used for the upcoming Aquarius ocean salinity mission or the proposed Hydros soil mission use real apertures with multiple fixed beams or scanning beams. For real aperture instruments, there is no upgrade path to scanning over a broad swath, except rotation of the whole aperture, which is an approach with obvious difficulties as aperture size increases. RadSTAR will provide polarimetric scatterometer and radiometer measurements over a wide swath, in a highly space-efficient configuration. The electronic scanning approaches provided through STAR technology and digital beam forming will enable the large L-band aperture to scan efficiently over a very wide swath. RadSTAR technology development, which merges an interferometric radiometer with a digital beam forming scatterometer, is an important step in the path to space for an L-band scatterometer/radiometer. RadSTAR couples a patch array antenna with a 1.26 GHz digital beam forming radar scatterometer and a 1.4 GHz STAR radiometer to provide Earth surface backscatter and emission measurements in a compact, cross-track scanning instrument with no moving parts. This technology will provide the first L-band, emission and backscatter measurements in a compact aircraft instrument and will be ideally suited to large apertures, possibly at GEO, and could possibly be implemented on a swarm of micro-satellites. This instrument will have wide application for validation studies, and will have application for other microwave frequencies.

SU-E-T-614: Plan Averaging for Multi-Criteria Navigation of Step-And-Shoot IMRT

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

Guo, M; Gao, H; Craft, D

2015-06-15

Purpose: Step-and-shoot IMRT is fundamentally discrete in nature, while multi-criteria optimization (MCO) is fundamentally continuous: the MCO planning consists of continuous sliding across the Pareto surface (the set of plans which represent the tradeoffs between organ-at-risk doses and target doses). In order to achieve close to real-time dose display during this sliding, it is desired that averaged plans share many of the same apertures as the pre-computed plans, since dose computation for apertures generated on-the-fly would be expensive. We propose a method to ensure that neighboring plans on a Pareto surface share many apertures. Methods: Our baseline step-and-shoot sequencing methodmore » is that of K. Engel (a method which minimizes the number of segments while guaranteeing the minimum number of monitor units), which we customize to sequence a set of Pareto optimal plans simultaneously. We also add an error tolerance to study the relationship between the number of shared apertures, the total number of apertures needed, and the quality of the fluence map re-creation. Results: We run tests for a 2D Pareto surface trading off rectum and bladder dose versus target coverage for a clinical prostate case. We find that if we enforce exact fluence map recreation, we are not able to achieve much sharing of apertures across plans. The total number of apertures for all seven beams and 4 plans without sharing is 217. With sharing and a 2% error tolerance, this number is reduced to 158 (73%). Conclusion: With the proposed method, total number of apertures can be decreased by 42% (averaging) with no increment of total MU, when an error tolerance of 5% is allowed. With this large amount of sharing, dose computations for averaged plans which occur during Pareto navigation will be much faster, leading to a real-time what-you-see-is-what-you-get Pareto navigation experience. Minghao Guo and Hao Gao were partially supported by the NSFC (#11405105), the 973 Program (#2015CB856000) and the Shanghai Pujiang Talent Program (#14PJ1404500)« less

SU-F-T-89: Investigation of Simultaneous Optimization of Photon and Electron Apertures for Mixed Beam Radiotherapy Based On An Academic Case

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

Mueller, S; Joosten, A; Fix, MK

Purpose: To estimate the dosimetric potential of mixed beam radiotherapy (MBRT) by using a single process optimizing the shape and weight of photon and electron apertures simultaneously based on Monte Carlo beamlet dose distributions. Methods: A simulated annealing based direct aperture optimization capable to perform simultaneous optimization was developed to generate treatment plans for MERT, photon-IMRT and MBRT. Both photon and electron apertures are collimated with the photon-MLC and are delivered in a segmented manner. For dosimetric comparison and for investigating the dependency on the number of apertures, photon-IMRT, MERT and MBRT plans were generated for an academic case consistingmore » of a water phantom containing two shallow PTVs differing in the maximal depth of 5 and 7 cm, respectively and two OARs in distal and lateral direction to the PTVs. Results: For the superficial PTV, the dose homogeneity (V95%–V107%) and the mean dose (in percent of the prescribed dose) to the distal and the lateral OARs of the MBRT plan (94.9%, 16.9%, 17.8%) are superior or comparable to those for the MERT (74%, 18.4%, 15.4%) and the photon-IMRT plan (89.4%, 20.8%, 24.7%). For the enlarged PTV, the dosimetric superiority of MBRT compared to MERT and photon-IMRT is even more pronounced. Furthermore, an MBRT plan with 12 electron and 10 photon apertures lead to an objective function value 38% lower than that of a photon-IMRT plan with 40 apertures. Conclusion: The results of simultaneous optimization for MBRT are promising with regards to further OAR sparing and improved dose coverage to the PTV compared to photon-IMRT and MERT. Especially superficial targets with deeper subparts (>5 cm) could substantially benefit. Moreover, MBRT seems to be a possible solution of two downsides of photon-IMRT, namely the extended low dose bath and the requirement of numerous apertures. This work was supported by Varian Medical Systems. This work was supported by Varian Medical Systems.« less

NOVEL FLOW DEVICE

DOEpatents

Brockwell, R.E.

1963-11-26

The design of hollow, porous-walled articles is presented. By this invention a hollow, porous-walled article is made by stacking thin, centrally apertured plates having grooves extending from their central aperture to their periphery. (AEC)

NIAC Phase II Orbiting Rainbows: Future Space Imaging with Granular Systems

NASA Technical Reports Server (NTRS)

Quadrelli, Marco B.; Basinger, Scott; Arumugam, Darmindra; Swartzlander, Grover

2017-01-01

Inspired by the light scattering and focusing properties of distributed optical assemblies in Nature, such as rainbows and aerosols, and by recent laboratory successes in optical trapping and manipulation, we propose a unique combination of space optics and autonomous robotic system technology, to enable a new vision of space system architecture with applications to ultra-lightweight space optics and, ultimately, in-situ space system fabrication. Typically, the cost of an optical system is driven by the size and mass of the primary aperture. The ideal system is a cloud of spatially disordered dust-like objects that can be optically manipulated: it is highly reconfigurable, fault-tolerant, and allows very large aperture sizes at low cost. This new concept is based on recent understandings in the physics of optical manipulation of small particles in the laboratory and the engineering of distributed ensembles of spacecraft swarms to shape an orbiting cloud of micron-sized objects. In the same way that optical tweezers have revolutionized micro- and nano-manipulation of objects, our breakthrough concept will enable new large scale NASA mission applications and develop new technology in the areas of Astrophysical Imaging Systems and Remote Sensing because the cloud can operate as an adaptive optical imaging sensor. While achieving the feasibility of constructing one single aperture out of the cloud is the main topic of this work, it is clear that multiple orbiting aerosol lenses could also combine their power to synthesize a much larger aperture in space to enable challenging goals such as exo-planet detection. Furthermore, this effort could establish feasibility of key issues related to material properties, remote manipulation, and autonomy characteristics of cloud in orbit. There are several types of endeavors (science missions) that could be enabled by this type of approach, i.e. it can enable new astrophysical imaging systems, exo-planet search, large apertures allow for unprecedented high resolution to discern continents and important features of other planets, hyperspectral imaging, adaptive systems, spectroscopy imaging through limb, and stable optical systems from Lagrange-points. Furthermore, future micro-miniaturization might hold promise of a further extension of our dust aperture concept to other more exciting smart dust concepts with other associated capabilities. Our objective in Phase II was to experimentally and numerically investigate how to optically manipulate and maintain the shape of an orbiting cloud of dust-like matter so that it can function as an adaptable ultra-lightweight surface. Our solution is based on the aperture being an engineered granular medium, instead of a conventional monolithic aperture. This allows building of apertures at a reduced cost, enables extremely fault-tolerant apertures that cannot otherwise be made, and directly enables classes of missions for exoplanet detection based on Fourier spectroscopy with tight angular resolution and innovative radar systems for remote sensing. In this task, we have examined the advanced feasibility of a crosscutting concept that contributes new technological approaches for space imaging systems, autonomous systems, and space applications of optical manipulation. The proposed investigation has matured the concept that we started in Phase I to TRL 3, identifying technology gaps and candidate system architectures for the space-borne cloud as an aperture.

Analysis of compound parabolic concentrators and aperture averaging to mitigate fading on free-space optical links

NASA Astrophysics Data System (ADS)

Wasiczko, Linda M.; Smolyaninov, Igor I.; Davis, Christopher C.

2004-01-01

Free space optics (FSO) is one solution to the bandwidth bottleneck resulting from increased demand for broadband access. It is well known that atmospheric turbulence distorts the wavefront of a laser beam propagating through the atmosphere. This research investigates methods of reducing the effects of intensity scintillation and beam wander on the performance of free space optical communication systems, by characterizing system enhancement using either aperture averaging techniques or nonimaging optics. Compound Parabolic Concentrators, nonimaging optics made famous by Winston and Welford, are inexpensive elements that may be easily integrated into intensity modulation-direct detection receivers to reduce fading caused by beam wander and spot breakup in the focal plane. Aperture averaging provides a methodology to show the improvement of a given receiver aperture diameter in averaging out the optical scintillations over the received wavefront.

Design of wavefront coding optical system with annular aperture

NASA Astrophysics Data System (ADS)

Chen, Xinhua; Zhou, Jiankang; Shen, Weimin

2016-10-01

Wavefront coding can extend the depth of field of traditional optical system by inserting a phase mask into the pupil plane. In this paper, the point spread function (PSF) of wavefront coding system with annular aperture are analyzed. Stationary phase method and fast Fourier transform (FFT) method are used to compute the diffraction integral respectively. The OTF invariance is analyzed for the annular aperture with cubic phase mask under different obscuration ratio. With these analysis results, a wavefront coding system using Maksutov-Cassegrain configuration is designed finally. It is an F/8.21 catadioptric system with annular aperture, and its focal length is 821mm. The strength of the cubic phase mask is optimized with user-defined operand in Zemax. The Wiener filtering algorithm is used to restore the images and the numerical simulation proves the validity of the design.

A finite difference-time domain technique for modeling narrow apertures in conducting scatterers

NASA Technical Reports Server (NTRS)

Demarest, Kenneth R.

1987-01-01

The finite difference-time domain (FDTD) technique has proven to be a valuable tool for the calculation of the transient and steady state scattering characteristics of relatively complex scatterer and source configurations. In spite of its usefulness, it exhibits serious deficiencies when used to analyze geometries that contain fine detail. An FDTD technique is described that utilizes Babinet's principle to decouple the regions on both sides of the aperture. The result is an FDTD technique that is capable of modeling apertures that are much smaller than the spatial grid used in the analysis and yet is not perturbed by numerical noise when used in the 'scattered field' mode. Numerical results are presented that show the field penetration through cavity-backed apertures that are much smaller than the spatial grid used during the solution.

Synthetic aperture integration (SAI) algorithm for SAR imaging

DOEpatents

Chambers, David H; Mast, Jeffrey E; Paglieroni, David W; Beer, N. Reginald

2013-07-09

A method and system for detecting the presence of subsurface objects within a medium is provided. In some embodiments, the imaging and detection system operates in a multistatic mode to collect radar return signals generated by an array of transceiver antenna pairs that is positioned across the surface and that travels down the surface. The imaging and detection system pre-processes the return signal to suppress certain undesirable effects. The imaging and detection system then generates synthetic aperture radar images from real aperture radar images generated from the pre-processed return signal. The imaging and detection system then post-processes the synthetic aperture radar images to improve detection of subsurface objects. The imaging and detection system identifies peaks in the energy levels of the post-processed image frame, which indicates the presence of a subsurface object.

Variable aperture-based ptychographical iterative engine method

NASA Astrophysics Data System (ADS)

Sun, Aihui; Kong, Yan; Meng, Xin; He, Xiaoliang; Du, Ruijun; Jiang, Zhilong; Liu, Fei; Xue, Liang; Wang, Shouyu; Liu, Cheng

2018-02-01

A variable aperture-based ptychographical iterative engine (vaPIE) is demonstrated both numerically and experimentally to reconstruct the sample phase and amplitude rapidly. By adjusting the size of a tiny aperture under the illumination of a parallel light beam to change the illumination on the sample step by step and recording the corresponding diffraction patterns sequentially, both the sample phase and amplitude can be faithfully reconstructed with a modified ptychographical iterative engine (PIE) algorithm. Since many fewer diffraction patterns are required than in common PIE and the shape, the size, and the position of the aperture need not to be known exactly, this proposed vaPIE method remarkably reduces the data acquisition time and makes PIE less dependent on the mechanical accuracy of the translation stage; therefore, the proposed technique can be potentially applied for various scientific researches.

Measurement accuracies in band-limited extrapolation

NASA Technical Reports Server (NTRS)

Kritikos, H. N.

1982-01-01

The problem of numerical instability associated with extrapolation algorithms is addressed. An attempt is made to estimate the bounds for the acceptable errors and to place a ceiling on the measurement accuracy and computational accuracy needed for the extrapolation. It is shown that in band limited (or visible angle limited) extrapolation the larger effective aperture L' that can be realized from a finite aperture L by over sampling is a function of the accuracy of measurements. It is shown that for sampling in the interval L/b absolute value of xL, b1 the signal must be known within an error e sub N given by e sub N squared approximately = 1/4(2kL') cubed (e/8b L/L')(2kL') where L is the physical aperture, L' is the extrapolated aperture, and k = 2pi lambda.

Closure for milliliter scale bioreactor

DOEpatents

Klein, David L.; Laidlaw, Robert D.; Andronaco, Gregory; Boyer, Stephen G.

2010-12-14

A closure for a microreactor includes a cap that is configured to be inserted into a well of the microreactor. The cap, or at least a portion of the cap, is compliant so as to form a seal with the well when the cap is inserted. The cap includes an aperture that provides an airway between the inside of the well to the external environment when the cap is inserted into the well. A porous plug is inserted in the aperture, e.g., either directly or in tube that extends through the aperture. The porous plug permits gas within the well to pass through the aperture while preventing liquids from passing through to reduce evaporation and preventing microbes from passing through to provide a sterile environment. A one-way valve may also be used to help control the environment in the well.

An Analytical Approach for Performance Enhancement of FSO Communication System Using Array of Receivers in Adverse Weather Conditions

NASA Astrophysics Data System (ADS)

Nagpal, Shaina; Gupta, Amit

2017-08-01

Free Space Optics (FSO) link exploits the tremendous network capacity and is capable of offering wireless communications similar to communications through optical fibres. However, FSO link is extremely weather dependent and the major effect on FSO links is due to adverse weather conditions like fog and snow. In this paper, an FSO link is designed using an array of receivers. The disparity of the link for very high attenuation conditions due to fog and snow is analysed using aperture averaging technique. Further effect of aperture averaging technique is investigated by comparing the systems using aperture averaging technique with systems not using aperture averaging technique. The performance of proposed model of FSO link has been evaluated in terms of Q factor, bit error rate (BER) and eye diagram.

Central obscuration effects on optical synthetic aperture imaging

NASA Astrophysics Data System (ADS)

Wang, Xue-wen; Luo, Xiao; Zheng, Li-gong; Zhang, Xue-jun

2014-02-01

Due to the central obscuration problem exists in most optical synthetic aperture systems, it is necessary to analyze its effects on their image performance. Based on the incoherent diffraction limited imaging theory, a Golay-3 type synthetic aperture system was used to study the central obscuration effects on the point spread function (PSF) and the modulation transfer function (MTF). It was found that the central obscuration does not affect the width of the central peak of the PSF and the cutoff spatial frequency of the MTF, but attenuate the first sidelobe of the PSF and the midfrequency of the MTF. The imaging simulation of a Golay-3 type synthetic aperture system with central obscuration proved this conclusion. At last, a Wiener Filter restoration algorithm was used to restore the image of this system, the images were obviously better.

Reverse slapper detonator

DOEpatents

Weingart, Richard C.

1990-01-01

A reverse slapper detonator (70), and methodology related thereto, are provided. The detonator (70) is adapted to be driven by a pulse of electric power from an external source (80). A conductor (20) is disposed along the top (14), side (18), and bottom (16) surfaces of a sheetlike insulator (12). Part of the conductor (20) comprises a bridge (28), and an aperture (30) is positioned within the conductor (20), with the bridge (28) and the aperture (30) located on opposite sides of the insulator (12). A barrel (40) and related explosive charge (50) are positioned adjacent to and in alignment with the aperture (30), and the bridge (28) is buttressed with a backing layer (60). When the electric power pulse vaporizes the bridge (28), a portion of the insulator (12) is propelled through the aperture (30) and barrel (40), and against the explosive charge (50), thereby detonating it.

Aperture effects in squid jet propulsion.

PubMed

Staaf, Danna J; Gilly, William F; Denny, Mark W

2014-05-01

Squid are the largest jet propellers in nature as adults, but as paralarvae they are some of the smallest, faced with the inherent inefficiency of jet propulsion at a low Reynolds number. In this study we describe the behavior and kinematics of locomotion in 1 mm paralarvae of Dosidicus gigas, the smallest squid yet studied. They swim with hop-and-sink behavior and can engage in fast jets by reducing the size of the mantle aperture during the contraction phase of a jetting cycle. We go on to explore the general effects of a variable mantle and funnel aperture in a theoretical model of jet propulsion scaled from the smallest (1 mm mantle length) to the largest (3 m) squid. Aperture reduction during mantle contraction increases propulsive efficiency at all squid sizes, although 1 mm squid still suffer from low efficiency (20%) because of a limited speed of contraction. Efficiency increases to a peak of 40% for 1 cm squid, then slowly declines. Squid larger than 6 cm must either reduce contraction speed or increase aperture size to maintain stress within maximal muscle tolerance. Ecological pressure to maintain maximum velocity may lead them to increase aperture size, which reduces efficiency. This effect might be ameliorated by nonaxial flow during the refill phase of the cycle. Our model's predictions highlight areas for future empirical work, and emphasize the existence of complex behavioral options for maximizing efficiency at both very small and large sizes.

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.

Echo scintillation Index affected by cat-eye target's caliber with Cassegrain lens

NASA Astrophysics Data System (ADS)

Shan, Cong-miao; Sun, Hua-yan; Zhao, Yan-zhong; Zheng, Yong-hui

2015-10-01

The optical aperture of cat-eye target has the aperture averaging effect to the active detecting laser of active laser detection system, which can be used to identify optical targets. The echo scintillation characteristics of the transmission-type lens target have been studied in previous work. Discussing the differences of the echo scintillation characteristics between the transmission-type lens target and Cassegrain lens target can be helpful to targets classified. In this paper, the echo scintillation characteristics of Cat-eye target's caliber with Cassegrain lens has been discussed . By using the flashing theory of spherical wave in the weak atmospheric turbulence, the annular aperture filter function and the Kolmogorov power spectrum, the analytic expression of the scintillation index of the cat-eye target echo of the horizontal path two-way transmission was given when the light is normal incidence. Then the impact of turbulence inner and outer scale to the echo scintillation index and the analytic expression of the echo scintillation index at the receiving aperture were presented using the modified Hill spectrum and the modified Von Karman spectrum. Echo scintillation index shows the tendency of decreasing with the target aperture increases and different ratios of the inner and outer aperture diameter show the different echo scintillation index curves. This conclusion has a certain significance for target recognition in the active laser detection system that can largely determine the target type by largely determining the scope of the cat-eye target which depending on echo scintillation index.

ImSyn: photonic image synthesis applied to synthetic aperture radar, microscopy, and ultrasound imaging

NASA Astrophysics Data System (ADS)

Turpin, Terry M.; Lafuse, James L.

1993-02-01

ImSynTM is an image synthesis technology, developed and patented by Essex Corporation. ImSynTM can provide compact, low cost, and low power solutions to some of the most difficult image synthesis problems existing today. The inherent simplicity of ImSynTM enables the manufacture of low cost and reliable photonic systems for imaging applications ranging from airborne reconnaissance to doctor's office ultrasound. The initial application of ImSynTM technology has been to SAR processing; however, it has a wide range of applications such as: image correlation, image compression, acoustic imaging, x-ray tomographic (CAT, PET, SPECT), magnetic resonance imaging (MRI), microscopy, range- doppler mapping (extended TDOA/FDOA). This paper describes ImSynTM in terms of synthetic aperture microscopy and then shows how the technology can be extended to ultrasound and synthetic aperture radar. The synthetic aperture microscope (SAM) enables high resolution three dimensional microscopy with greater dynamic range than real aperture microscopes. SAM produces complex image data, enabling the use of coherent image processing techniques. Most importantly SAM produces the image data in a form that is easily manipulated by a digital image processing workstation.

Spectral domain optical coherence tomography with extended depth-of-focus by aperture synthesis

NASA Astrophysics Data System (ADS)

Bo, En; Liu, Linbo

2016-10-01

We developed a spectral domain optical coherence tomography (SD-OCT) with an extended depth-of-focus (DOF) by synthetizing aperture. For a designated Gaussian-shape light source, the lateral resolution was determined by the numerical aperture (NA) of the objective lens and can be approximately maintained over the confocal parameter, which was defined as twice the Rayleigh range. However, the DOF was proportional to the square of the lateral resolution. Consequently, a trade-off existed between the DOF and lateral resolution, and researchers had to weigh and judge which was more important for their research reasonably. In this study, three distinct optical apertures were obtained by imbedding a circular phase spacer in the sample arm. Due to the optical path difference between three distinct apertures caused by the phase spacer, three images were aligned with equal spacing along z-axis vertically. By correcting the optical path difference (OPD) and defocus-induced wavefront curvature, three images with distinct depths were coherently summed together. This system digitally refocused the sample tissue and obtained a brand new image with higher lateral resolution over the confocal parameter when imaging the polystyrene calibration beads.

Effect of orofacial exercises on oral aperture in adults with systemic sclerosis

PubMed Central

Yuen, Hon K.; Marlow, Nicole M.; Reed, Susan G.; Summerlin, Lisa M.; Leite, Renata S.; Mahoney, Samantha; Silver, Richard M.

2012-01-01

Purpose To examine the effect of a home orofacial exercise program on increasing oral aperture among adults with systemic sclerosis (SSc). Method Forty-eight adults with SSc were assigned randomly to the multi-faceted oral health intervention or usual dental care control group. Participants with an oral aperture of < 40 mm in the intervention group received an orofacial exercise program, which included daily manual mouth-stretching and oral augmentation exercises twice a day with a total of 6 minutes for 6 months. The outcome measure was oral aperture which was measured at baseline, 3-months, and 6-months intervals. Results A significantly larger increase in oral aperture for participants received the orofacial exercise program was found when compared to those in the usual care at 3 months (P=0.01), but not at 6 months evaluation. Participants’ adherence rate to the exercise program was low (48.9%). Conclusions The orofacial exercise program intervention for adults with SSc and microstomia did not show significant improvement at 6 months. In addition to the low exercise adherence rate, insufficient frequencies, repetitions, and durations of the orofacial exercises may contribute to these results. PMID:21951278

Cubic law with aperture-length correlation: implications for network scale fluid flow

NASA Astrophysics Data System (ADS)

Klimczak, Christian; Schultz, Richard A.; Parashar, Rishi; Reeves, Donald M.

2010-06-01

Previous studies have computed and modeled fluid flow through fractured rock with the parallel plate approach where the volumetric flow per unit width normal to the direction of flow is proportional to the cubed aperture between the plates, referred to as the traditional cubic law. When combined with the square root relationship of displacement to length scaling of opening-mode fractures, total flow rates through natural opening-mode fractures are found to be proportional to apertures to the fifth power. This new relationship was explored by examining a suite of flow simulations through fracture networks using the discrete fracture network model (DFN). Flow was modeled through fracture networks with the same spatial distribution of fractures for both correlated and uncorrelated fracture length-to-aperture relationships. Results indicate that flow rates are significantly higher for correlated DFNs. Furthermore, the length-to-aperture relations lead to power-law distributions of network hydraulic conductivity which greatly influence equivalent permeability tensor values. These results confirm the importance of the correlated square root relationship of displacement to length scaling for total flow through natural opening-mode fractures and, hence, emphasize the role of these correlations for flow modeling.

Simulation of co-phase error correction of optical multi-aperture imaging system based on stochastic parallel gradient decent algorithm

NASA Astrophysics Data System (ADS)

He, Xiaojun; Ma, Haotong; Luo, Chuanxin

2016-10-01

The optical multi-aperture imaging system is an effective way to magnify the aperture and increase the resolution of telescope optical system, the difficulty of which lies in detecting and correcting of co-phase error. This paper presents a method based on stochastic parallel gradient decent algorithm (SPGD) to correct the co-phase error. Compared with the current method, SPGD method can avoid detecting the co-phase error. This paper analyzed the influence of piston error and tilt error on image quality based on double-aperture imaging system, introduced the basic principle of SPGD algorithm, and discuss the influence of SPGD algorithm's key parameters (the gain coefficient and the disturbance amplitude) on error control performance. The results show that SPGD can efficiently correct the co-phase error. The convergence speed of the SPGD algorithm is improved with the increase of gain coefficient and disturbance amplitude, but the stability of the algorithm reduced. The adaptive gain coefficient can solve this problem appropriately. This paper's results can provide the theoretical reference for the co-phase error correction of the multi-aperture imaging system.

SYNMAG PHOTOMETRY: A FAST TOOL FOR CATALOG-LEVEL MATCHED COLORS OF EXTENDED SOURCES

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

Bundy, Kevin; Yasuda, Naoki; Hogg, David W.

2012-12-01

Obtaining reliable, matched photometry for galaxies imaged by different observatories represents a key challenge in the era of wide-field surveys spanning more than several hundred square degrees. Methods such as flux fitting, profile fitting, and PSF homogenization followed by matched-aperture photometry are all computationally expensive. We present an alternative solution called 'synthetic aperture photometry' that exploits galaxy profile fits in one band to efficiently model the observed, point-spread-function-convolved light profile in other bands and predict the flux in arbitrarily sized apertures. Because aperture magnitudes are the most widely tabulated flux measurements in survey catalogs, producing synthetic aperture magnitudes (SYNMAGs) enablesmore » very fast matched photometry at the catalog level, without reprocessing imaging data. We make our code public and apply it to obtain matched photometry between Sloan Digital Sky Survey ugriz and UKIDSS YJHK imaging, recovering red-sequence colors and photometric redshifts with a scatter and accuracy as good as if not better than FWHM-homogenized photometry from the GAMA Survey. Finally, we list some specific measurements that upcoming surveys could make available to facilitate and ease the use of SYNMAGs.« less

Plasmonic micropolarizers for full Stokes vector imaging

NASA Astrophysics Data System (ADS)

Peltzer, J. J.; Bachman, K. A.; Rose, J. W.; Flammer, P. D.; Furtak, T. E.; Collins, R. T.; Hollingsworth, R. E.

2012-06-01

Polarimetric imaging using micropolarizers integrated on focal plane arrays has previously been limited to the linear components of the Stokes vector because of the lack of an effective structure with selectivity to circular polarization. We discuss a plasmonic micropolarizing filter that can be tuned for linear or circular polarization as well as wavelength selectivity from blue to infrared (IR) through simple changes in its horizontal geometry. The filter consists of a patterned metal film with an aperture in a central cavity that is surrounded by gratings that couple to incoming light. The aperture and gratings are covered with a transparent dielectric layer to form a surface plasmon slab waveguide. A metal cap covers the aperture and forms a metal-insulator-metal (MIM) waveguide. Structures with linear apertures and gratings provide sensitivity to linear polarization, while structures with circular apertures and spiral gratings give circular polarization selectivity. Plasmonic TM modes are transmitted down the MIM waveguide while the TE modes are cut off due to the sub-wavelength dielectric thickness, providing the potential for extremely high extinction ratios. Experimental results are presented for micropolarizers fabricated on glass or directly into the Ohmic contact metallization of silicon photodiodes. Extinction ratios for linear polarization larger than 3000 have been measured.

Sutureless Corneal Transplantation Apparatus And Method

DOEpatents

Rowsey, J. James

1996-12-17

An eye with a cornea repaired without sutures comprising a donor material in the shape of a partial sphere having a generally central extent, the central extent being of the size and shape of the central portion of a cornea of an eye, the central extent having a periphery of a fixed diameter with an exterior surface in a convex configuration and an interior surface in a concave configuration and with an essentially common thickness throughout, the central extent having a plurality of corneal flaps extending radially from the periphery of the central extent, the flaps having exterior surfaces as a continuation of the exterior surface of the central extent; and a recipient eye in the shape of a partial sphere having a circular aperture in the cornea at its central portion, the central aperture being of a size and shape essentially that of the periphery of the central extent of the donor material, the aperture being of a common thickness at the periphery of the aperture, the central portion having pockets and with the central extent of the donor material located within the aperture of the recipient eye and with the flaps of the central extent being imbricated into the pockets of the recipient eye.

An all-optronic synthetic aperture lidar

NASA Astrophysics Data System (ADS)

Turbide, Simon; Marchese, Linda; Terroux, Marc; Babin, François; Bergeron, Alain

2012-09-01

Synthetic Aperture Radar (SAR) is a mature technology that overcomes the diffraction limit of an imaging system's real aperture by taking advantage of the platform motion to coherently sample multiple sections of an aperture much larger than the physical one. Synthetic Aperture Lidar (SAL) is the extension of SAR to much shorter wavelengths (1.5 μm vs 5 cm). This new technology can offer higher resolution images in day or night time as well as in certain adverse conditions. It could be a powerful tool for Earth monitoring (ship detection, frontier surveillance, ocean monitoring) from aircraft, unattended aerial vehicle (UAV) or spatial platforms. A continuous flow of high-resolution images covering large areas would however produce a large amount of data involving a high cost in term of post-processing computational time. This paper presents a laboratory demonstration of a SAL system complete with image reconstruction based on optronic processing. This differs from the more traditional digital approach by its real-time processing capability. The SAL system is discussed and images obtained from a non-metallic diffuse target at ranges up to 3m are shown, these images being processed by a real-time optronic SAR processor origiinally designed to reconstruct SAR images from ENVISAT/ASAR data.

Functional Form of the Radiometric Equation for the SNPP VIIRS Reflective Solar Bands: An Initial Study

NASA Technical Reports Server (NTRS)

Lei, Ning; Xiong, Xiaoxiong

2016-01-01

The Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership (SNPP) satellite is a passive scanning radiometer and an imager, observing radiative energy from the Earth in 22 spectral bands from 0.41 to 12 microns which include 14 reflective solar bands (RSBs). Extending the formula used by the Moderate Resolution Imaging Spectroradiometer instruments, currently the VIIRS determines the sensor aperture spectral radiance through a quadratic polynomial of its detector digital count. It has been known that for the RSBs the quadratic polynomial is not adequate in the design specified spectral radiance region and using a quadratic polynomial could drastically increase the errors in the polynomial coefficients, leading to possible large errors in the determined aperture spectral radiance. In addition, it is very desirable to be able to extend the radiance calculation formula to correctly retrieve the aperture spectral radiance with the level beyond the design specified range. In order to more accurately determine the aperture spectral radiance from the observed digital count, we examine a few polynomials of the detector digital count to calculate the sensor aperture spectral radiance.

A concept of a wide aperture klystron with RF absorbing drift tubes for a linear collider

NASA Astrophysics Data System (ADS)

Dolbilov, G. V.; Azorsky, N. I.; Fateev, A. A.; Lebedev, N. I.; Petrov, V. A.; Shvetsov, V. S.; Yurkov, M. V.; Balakin, V. E.; Avrakhov, P. V.; Kazakov, S. Yu.; Solyak, N. A.; Teryaev, V. E.; Vogel, V. F.

1996-02-01

This paper is devoted to a problem of the optimal design of the electrodynamic structure of the X-band klystron for a linear collider. It is shown that the optimal design should provide a large aperture and a high power gain, about 80 dB. The most severe problem arising here is that of parasitic self-excitation of the klystron, which becomes more complicated at increasing aperture and power gain. Our investigations have shown that traditional methods for suppressing the self-excitation become ineffective at the desired technical parameters of the klystron. In this paper we present a novel concept of a wide aperture klystron with distributed suppression of parasitic oscillations. Results of an experimental study of the wide-aperture relativistic klystron for VLEPP are presented. Investigations have been performed using the driving beam of the JINR LIA-3000 induction accelerator ( E = 1 MeV, I = 250 A, τ = 250 ns). To suppress self-excitation parasitic modes we have used the technique of RF absorbing drift tubes. As a result, we have obtained design output parameters of the klystron and achieved a level of 100 MW output power.

Optimization of Dynamic Aperture of PEP-X Baseline Design

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

Wang, Min-Huey; /SLAC; Cai, Yunhai

2010-08-23

SLAC is developing a long-range plan to transfer the evolving scientific programs at SSRL from the SPEAR3 light source to a much higher performing photon source. Storage ring design is one of the possibilities that would be housed in the 2.2-km PEP-II tunnel. The design goal of PEPX storage ring is to approach an optimal light source design with horizontal emittance less than 100 pm and vertical emittance of 8 pm to reach the diffraction limit of 1-{angstrom} x-ray. The low emittance design requires a lattice with strong focusing leading to high natural chromaticity and therefore to strong sextupoles. Themore » latter caused reduction of dynamic aperture. The dynamic aperture requirement for horizontal injection at injection point is about 10 mm. In order to achieve the desired dynamic aperture the transverse non-linearity of PEP-X is studied. The program LEGO is used to simulate the particle motion. The technique of frequency map is used to analyze the nonlinear behavior. The effect of the non-linearity is tried to minimize at the given constrains of limited space. The details and results of dynamic aperture optimization are discussed in this paper.« less

SHIELD: FITGALAXY -- A Software Package for Automatic Aperture Photometry of Extended Sources

NASA Astrophysics Data System (ADS)

Marshall, Melissa

2013-01-01

Determining the parameters of extended sources, such as galaxies, is a common but time-consuming task. Finding a photometric aperture that encompasses the majority of the flux of a source and identifying and excluding contaminating objects is often done by hand - a lengthy and difficult to reproduce process. To make extracting information from large data sets both quick and repeatable, I have developed a program called FITGALAXY, written in IDL. This program uses minimal user input to automatically fit an aperture to, and perform aperture and surface photometry on, an extended source. FITGALAXY also automatically traces the outlines of surface brightness thresholds and creates surface brightness profiles, which can then be used to determine the radial properties of a source. Finally, the program performs automatic masking of contaminating sources. Masks and apertures can be applied to multiple images (regardless of the WCS solution or plate scale) in order to accurately measure the same source at different wavelengths. I present the fluxes, as measured by the program, of a selection of galaxies from the Local Volume Legacy Survey. I then compare these results with the fluxes given by Dale et al. (2009) in order to assess the accuracy of FITGALAXY.

Electric field divertor plasma pump

DOEpatents

Schaffer, Michael J.

1994-01-01

An electric field plasma pump includes a toroidal ring bias electrode (56) positioned near the divertor strike point of a poloidal divertor of a tokamak (20), or similar plasma-confining apparatus. For optimum plasma pumping, the separatrix (40) of the poloidal divertor contacts the ring electrode (56), which then also acts as a divertor plate. A plenum (54) or other duct near the electrode (56) includes an entrance aperture open to receive electrically-driven plasma. The electrode (56) is insulated laterally with insulators (63,64), one of which (64) is positioned opposite the electrode at the entrance aperture. An electric field E is established between the ring electrode (56) and a vacuum vessel wall (22), with the polarity of the bias applied to the electrode being relative to the vessel wall selected such that the resultant electric field E interacts with the magnetic field B already existing in the tokamak to create an E.times.B/B.sup.2 drift velocity that drives plasma into the entrance aperture. The pumped plasma flow into the entrance aperture is insensitive to variations, intentional or otherwise, of the pump and divertor geometry. Pressure buildups in the plenum or duct connected to the entrance aperture in excess of 10 mtorr are achievable.

Electric field divertor plasma pump

DOEpatents

Schaffer, M.J.

1994-10-04

An electric field plasma pump includes a toroidal ring bias electrode positioned near the divertor strike point of a poloidal divertor of a tokamak, or similar plasma-confining apparatus. For optimum plasma pumping, the separatrix of the poloidal divertor contacts the ring electrode, which then also acts as a divertor plate. A plenum or other duct near the electrode includes an entrance aperture open to receive electrically-driven plasma. The electrode is insulated laterally with insulators, one of which is positioned opposite the electrode at the entrance aperture. An electric field E is established between the ring electrode and a vacuum vessel wall, with the polarity of the bias applied to the electrode being relative to the vessel wall selected such that the resultant electric field E interacts with the magnetic field B already existing in the tokamak to create an E [times] B/B[sup 2] drift velocity that drives plasma into the entrance aperture. The pumped plasma flow into the entrance aperture is insensitive to variations, intentional or otherwise, of the pump and divertor geometry. Pressure buildups in the plenum or duct connected to the entrance aperture in excess of 10 mtorr are achievable. 11 figs.

Design of an integrated aerial image sensor

NASA Astrophysics Data System (ADS)

Xue, Jing; Spanos, Costas J.

2005-05-01

The subject of this paper is a novel integrated aerial image sensor (IAIS) system suitable for integration within the surface of an autonomous test wafer. The IAIS could be used as a lithography processing monitor, affording a "wafer's eye view" of the process, and therefore facilitating advanced process control and diagnostics without integrating (and dedicating) the sensor to the processing equipment. The IAIS is composed of an aperture mask and an array of photo-detectors. In order to retrieve nanometer scale resolution of the aerial image with a practical photo-detector pixel size, we propose a design of an aperture mask involving a series of spatial phase "moving" aperture groups. We demonstrate a design example aimed at the 65nm technology node through TEMPEST simulation. The optimized, key design parameters include an aperture width in the range of 30nm, aperture thickness in the range of 70nm, and offer a spatial resolution of about 5nm, all with comfortable fabrication tolerances. Our preliminary simulation work indicates the possibility of the IAIS being applied to the immersion lithography. A bench-top far-field experiment verifies that our approach of the spatial frequency down-shift through forming large Moire patterns is feasible.

Conceptual study of an optical aperture synthesis system for high resolution astronomy

NASA Astrophysics Data System (ADS)

Calvel, Bertrand

2018-04-01

This paper, "Conceptual study of an optical aperture synthesis system for high resolution astronomy," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

Process for manufacturing shell membrane force and deflection sensor

NASA Technical Reports Server (NTRS)

Park, Yong-Lae (Inventor); Moslehi, Behzad (Inventor); Black, Richard James (Inventor); Cutkosky, Mark R. (Inventor); Chau, Kelvin K. (Inventor)

2012-01-01

A sensor for force is formed from an elastomeric cylinder having a region with apertures. The apertures have passageways formed between them, and an optical fiber is introduced into these passageways, where the optical fiber has a grating for measurement of tension positioned in the passageways between apertures. Optionally, a temperature measurement sensor is placed in or around the elastomer for temperature correction, and if required, a copper film may be deposited in the elastomer for reduced sensitivity to spot temperature variations in the elastomer near the sensors.

Compact organic vapor jet printing print head

DOEpatents

Forrest, Stephen; McGraw, Gregory

2016-02-02

A first device is provided. The first device includes a print head, and a first gas source hermetically sealed to the print head. The print head further includes a first layer further comprising a plurality of apertures, each aperture having a smallest dimension of 0.5 to 500 microns. A second layer is bonded to the first layer. The second layer includes a first via in fluid communication with the first gas source and at least one of the apertures. The second layer is made of an insulating material.

Force and deflection sensor with shell membrane and optical gratings and method of manufacture

NASA Technical Reports Server (NTRS)

Park, Yong-Lae (Inventor); Moslehi, Behzad (Inventor); Black, Richard James (Inventor); Cutkosky, Mark R. (Inventor); Chau, Kelvin K (Inventor)

2011-01-01

A sensor for force is formed from an elastomeric cylinder having a region with apertures. The apertures have passageways formed between them, and an optical fiber is introduced into these passageways, where the optical fiber has a grating for measurement of tension positioned in the passageways between apertures. Optionally, a temperature measurement sensor is placed in or around the elastomer for temperature correction, and if required, a copper film may be deposited in the elastomer for reduced sensitivity to spot temperature variations in the elastomer near the sensors.

Sensing more modes with fewer sub-apertures: the LIFTed Shack-Hartmann wavefront sensor.

PubMed

Meimon, Serge; Fusco, Thierry; Michau, Vincent; Plantet, Cédric

2014-05-15

We propose here a novel way to analyze Shack-Hartmann wavefront sensor images in order to retrieve more modes than the two centroid coordinates per sub-aperture. To do so, we use the linearized focal-plane technique (LIFT) phase retrieval method for each sub-aperture. We demonstrate that we can increase the number of modes sensed with the same computational burden per mode. For instance, we show the ability to control a 21×21 actuator deformable mirror using a 10×10 lenslet array.

Wavefront Control Testbed (WCT) Experiment Results

NASA Technical Reports Server (NTRS)

Burns, Laura A.; Basinger, Scott A.; Campion, Scott D.; Faust, Jessica A.; Feinberg, Lee D.; Hayden, William L.; Lowman, Andrew E.; Ohara, Catherine M.; Petrone, Peter P., III

2004-01-01

The Wavefront Control Testbed (WCT) was created to develop and test wavefront sensing and control algorithms and software for the segmented James Webb Space Telescope (JWST). Last year, we changed the system configuration from three sparse aperture segments to a filled aperture with three pie shaped segments. With this upgrade we have performed experiments on fine phasing with line-of-sight and segment-to-segment jitter, dispersed fringe visibility and grism angle;. high dynamic range tilt sensing; coarse phasing with large aberrations, and sampled sub-aperture testing. This paper reviews the results of these experiments.

Ringfield lithographic camera

DOEpatents

Sweatt, W.C.

1998-09-08

A projection lithography camera is presented with a wide ringfield optimized so as to make efficient use of extreme ultraviolet radiation from a large area radiation source (e.g., D{sub source} {approx_equal} 0.5 mm). The camera comprises four aspheric mirrors optically arranged on a common axis of symmetry. The camera includes an aperture stop that is accessible through a plurality of partial aperture stops to synthesize the theoretical aperture stop. Radiation from a mask is focused to form a reduced image on a wafer, relative to the mask, by reflection from the four aspheric mirrors. 11 figs.

Sheath effects on current collection by particle detectors with narrow acceptance angles

NASA Technical Reports Server (NTRS)

Singh, N.; Baugher, C. R.

1981-01-01

Restriction of the aperture acceptance angle of an ion or electron trap on an attracting spacecraft significantly alters the volt-ampere characteristics of the instrument in a low Mach number plasma. It is shown when the angular acceptance of the aperture is restricted the current to the collector tends to be independent of the Debye length. Expressions for the RPA characteristics for both a thin sheath and a thick sheath are derived; and it is shown that as the aperture is narrowed the curves tend toward equivalence.

Compact organic vapor jet printing print head

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

Forrest, Stepehen R; McGraw, Gregory

A first device is provided. The first device includes a print head, and a first gas source hermetically sealed to the print head. The print head further includes a first layer further comprising a plurality of apertures, each aperture having a smallest dimension of 0.5 to 500 microns. A second layer is bonded to the first layer. The second layer includes a first via in fluid communication with the first gas source and at least one of the apertures. The second layer is made of an insulating material.

Radar studies related to the earth resources program. [remote sensing programs

NASA Technical Reports Server (NTRS)

Holtzman, J.

1972-01-01

The radar systems research discussed is directed toward achieving successful application of radar to remote sensing problems in such areas as geology, hydrology, agriculture, geography, forestry, and oceanography. Topics discussed include imaging radar and evaluation of its modification, study of digital processing for synthetic aperture system, digital simulation of synthetic aperture system, averaging techniques studies, ultrasonic modeling of panchromatic system, panchromatic radar/radar spectrometer development, measuring octave-bandwidth response of selected targets, scatterometer system analysis, and a model Fresnel-zone processor for synthetic aperture imagery.

TRACKING SIMULATIONS NEAR HALF-INTEGER RESONANCE AT PEP-II

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

Nosochkov, Yuri

2003-05-13

Beam-beam simulations predict that PEP-II luminosity can be increased by operating the horizontal betatron tune near and above a half-integer resonance. However, effects of the resonance and its synchrotron sidebands significantly enhance betatron and chromatic perturbations which tend to reduce dynamic aperture. In the study, chromatic variation of horizontal tune near the resonance was minimized by optimizing local sextupoles in the Interaction Region. Dynamic aperture was calculated using tracking simulations in LEGO code. Dependence of dynamic aperture on the residual orbit, dispersion and {beta} distortion after correction was investigated.

Weld monitor and failure detector for nuclear reactor system

DOEpatents

Sutton, Jr., Harry G.

1987-01-01

Critical but inaccessible welds in a nuclear reactor system are monitored throughout the life of the reactor by providing small aperture means projecting completely through the reactor vessel wall and also through the weld or welds to be monitored. The aperture means is normally sealed from the atmosphere within the reactor. Any incipient failure or cracking of the weld will cause the environment contained within the reactor to pass into the aperture means and thence to the outer surface of the reactor vessel where its presence is readily detected.

Evaluation of the cosmic-ray induced background in coded aperture high energy gamma-ray telescopes

NASA Technical Reports Server (NTRS)

Owens, Alan; Barbier, Loius M.; Frye, Glenn M.; Jenkins, Thomas L.

1991-01-01

While the application of coded-aperture techniques to high-energy gamma-ray astronomy offers potential arc-second angular resolution, concerns were raised about the level of secondary radiation produced in a thick high-z mask. A series of Monte-Carlo calculations are conducted to evaluate and quantify the cosmic-ray induced neutral particle background produced in a coded-aperture mask. It is shown that this component may be neglected, being at least a factor of 50 lower in intensity than the cosmic diffuse gamma-rays.

Development and evaluation of aperture-based complexity metrics using film and EPID measurements of static MLC openings

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

Götstedt, Julia; Karlsson Hauer, Anna; Bäck, Anna, E-mail: anna.back@vgregion.se

Purpose: Complexity metrics have been suggested as a complement to measurement-based quality assurance for intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). However, these metrics have not yet been sufficiently validated. This study develops and evaluates new aperture-based complexity metrics in the context of static multileaf collimator (MLC) openings and compares them to previously published metrics. Methods: This study develops the converted aperture metric and the edge area metric. The converted aperture metric is based on small and irregular parts within the MLC opening that are quantified as measured distances between MLC leaves. The edge area metricmore » is based on the relative size of the region around the edges defined by the MLC. Another metric suggested in this study is the circumference/area ratio. Earlier defined aperture-based complexity metrics—the modulation complexity score, the edge metric, the ratio monitor units (MU)/Gy, the aperture area, and the aperture irregularity—are compared to the newly proposed metrics. A set of small and irregular static MLC openings are created which simulate individual IMRT/VMAT control points of various complexities. These are measured with both an amorphous silicon electronic portal imaging device and EBT3 film. The differences between calculated and measured dose distributions are evaluated using a pixel-by-pixel comparison with two global dose difference criteria of 3% and 5%. The extent of the dose differences, expressed in terms of pass rate, is used as a measure of the complexity of the MLC openings and used for the evaluation of the metrics compared in this study. The different complexity scores are calculated for each created static MLC opening. The correlation between the calculated complexity scores and the extent of the dose differences (pass rate) are analyzed in scatter plots and using Pearson’s r-values. Results: The complexity scores calculated by the edge area metric, converted aperture metric, circumference/area ratio, edge metric, and MU/Gy ratio show good linear correlation to the complexity of the MLC openings, expressed as the 5% dose difference pass rate, with Pearson’s r-values of −0.94, −0.88, −0.84, −0.89, and −0.82, respectively. The overall trends for the 3% and 5% dose difference evaluations are similar. Conclusions: New complexity metrics are developed. The calculated scores correlate to the complexity of the created static MLC openings. The complexity of the MLC opening is dependent on the penumbra region relative to the area of the opening. The aperture-based complexity metrics that combined either the distances between the MLC leaves or the MLC opening circumference with the aperture area show the best correlation with the complexity of the static MLC openings.« less

Growth Kinematics of Opening-Mode Fractures

NASA Astrophysics Data System (ADS)

Eichhubl, P.; Alzayer, Y.; Laubach, S.; Fall, A.

2014-12-01

Fracture aperture is a primary control on flow in fractured reservoirs of low matrix permeability including unconventional oil and gas reservoirs and most geothermal systems. Guided by principles of linear elastic fracture mechanics, fracture aperture is generally assumed to be a linear function of fracture length and elastic material properties. Natural opening-mode fractures with significant preserved aperture are observed in core and outcrop indicative of fracture opening strain accommodated by permanent solution-precipitation creep. Fracture opening may thus be decoupled from length growth if the material effectively weakens after initial elastic fracture growth by either non-elastic deformation processes or changes in elastic properties. To investigate the kinematics of fracture length and aperture growth, we reconstructed the opening history of three opening-mode fractures that are bridged by crack-seal quartz cement in Travis Peak Sandstone of the SFOT-1 well, East Texas. Similar crack-seal cement bridges had been interpreted to form by repeated incremental fracture opening and subsequent precipitation of quartz cement. We imaged crack-seal cement textures for bridges sampled at varying distance from the tips using scanning electron microscope cathodoluminescence, and determined the number and thickness of crack-seal cement increments as a function of position along the fracture length and height. Observed trends in increment number and thickness are consistent with an initial stage of fast fracture propagation relative to aperture growth, followed by a stage of slow propagation and pronounced aperture growth. Consistent with fluid inclusion observations indicative of fracture opening and propagation occurring over 30-40 m.y., we interpret the second phase of pronounced aperture growth to result from fracture opening strain accommodated by solution-precipitation creep and concurrent slow, possibly subcritical, fracture propagation. Similar deformation mechanisms are envisioned to govern fracture growth over shorter timescales in reactive chemical subsurface environments including CO2 reservoirs, organic-rich shales, and geothermal systems.

SU-E-T-295: Simultaneous Beam Sampling and Aperture Shape Optimization for Station Parameter Optimized Radiation Therapy (SPORT)

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

Zarepisheh, M; Li, R; Xing, L

Purpose: Station Parameter Optimized Radiation Therapy (SPORT) was recently proposed to fully utilize the technical capability of emerging digital LINACs, in which the station parameters of a delivery system, (such as aperture shape and weight, couch position/angle, gantry/collimator angle) are optimized altogether. SPORT promises to deliver unprecedented radiation dose distributions efficiently, yet there does not exist any optimization algorithm to implement it. The purpose of this work is to propose an optimization algorithm to simultaneously optimize the beam sampling and aperture shapes. Methods: We build a mathematical model whose variables are beam angles (including non-coplanar and/or even nonisocentric beams) andmore » aperture shapes. To solve the resulting large scale optimization problem, we devise an exact, convergent and fast optimization algorithm by integrating three advanced optimization techniques named column generation, gradient method, and pattern search. Column generation is used to find a good set of aperture shapes as an initial solution by adding apertures sequentially. Then we apply the gradient method to iteratively improve the current solution by reshaping the aperture shapes and updating the beam angles toward the gradient. Algorithm continues by pattern search method to explore the part of the search space that cannot be reached by the gradient method. Results: The proposed technique is applied to a series of patient cases and significantly improves the plan quality. In a head-and-neck case, for example, the left parotid gland mean-dose, brainstem max-dose, spinal cord max-dose, and mandible mean-dose are reduced by 10%, 7%, 24% and 12% respectively, compared to the conventional VMAT plan while maintaining the same PTV coverage. Conclusion: Combined use of column generation, gradient search and pattern search algorithms provide an effective way to optimize simultaneously the large collection of station parameters and significantly improves quality of resultant treatment plans as compared with conventional VMAT or IMRT treatments.« less

Role of vision in aperture closure control during reach-to-grasp movements.

PubMed

Rand, Miya K; Lemay, Martin; Squire, Linda M; Shimansky, Yury P; Stelmach, George E

2007-08-01

We have previously shown that the distance from the hand to the target at which finger closure is initiated during the reach (aperture closure distance) depends on the amplitude of peak aperture, as well as hand velocity and acceleration. This dependence suggests the existence of a control law according to which a decision to initiate finger closure during the reach is made when the hand distance to target crosses a threshold that is a function of the above movement-related parameters. The present study examined whether the control law is affected by manipulating the visibility of the hand and the target. Young adults made reach-to-grasp movements to a dowel under conditions in which the target or the hand or both were either visible or not visible. Reaching for and grasping a target when the hand and/or target were not visible significantly increased transport time and widened peak aperture. Aperture closure distance was significantly lengthened and wrist peak velocity was decreased only when the target was not visible. Further analysis showed that the control law was significantly different between the visibility-related conditions. When either the hand or target was not visible, the aperture closure distance systematically increased compared to its value for the same amplitude of peak aperture, hand velocity, and acceleration under full visibility. This implies an increase in the distance-related safety margin for grasping when the hand or target is not visible. It has been also found that the same control law can be applied to all conditions, if variables describing hand and target visibility were included in the control law model, as the parameters of the task-related environmental context, in addition to the above movement-related parameters. This suggests that that the CNS utilizes those variables for controlling grasp initiation based on a general control law.

Role of vision in aperture closure control during reach-to-grasp movements

PubMed Central

Rand, Miya K.; Lemay, Martin; Squire, Linda M.; Shimansky, Yury P.; Stelmach, George E.

2007-01-01

We have previously shown that the distance from the hand to the target at which finger closure is initiated during the reach (aperture closure distance) depends on the amplitude of peak aperture, as well as hand velocity and acceleration. This dependence suggests the existence of a control law according to which a decision to initiate finger closure during the reach is made when the hand distance to target crosses a threshold that is a function of the above movement-related parameters. The present study examined whether the control law is affected by manipulating the visibility of the hand and the target. Young adults made reach-to-grasp movements to a dowel under conditions in which the target or the hand or both were either visible or not visible. Reaching for and grasping a target when the hand and/or target were not visible significantly increased transport time and widened peak aperture. Aperture closure distance was significantly lengthened and wrist peak velocity was decreased only when the target was not visible. Further analysis showed that the control law was significantly different between the visibility-related conditions. When either the hand or target was not visible, the aperture closure distance systematically increased compared to its value for the same amplitude of peak aperture, hand velocity, and acceleration under full visibility. This implies an increase in the distance-related safety margin for grasping when the hand or target is not visible. It has been also found that the same control law can be applied to all conditions, if variables describing hand and target visibility were included in the control law model, as the parameters of the task-related environmental context, in addition to the above movement-related parameters. This suggests that that the CNS utilizes those variables for controlling grasp initiation based on a general control law. PMID:17476491

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

Moteabbed, M; Depauw, N; Kooy, H

Purpose: To investigate the dosimetric benefits of pencil beam scanning (PBS) compared with passive scattered (PS) proton therapy for treatment of pediatric head&neck patients as a function of the PBS spot size and explore the advantages of using apertures in PBS. Methods: Ten pediatric patients with head&neck cancers treated by PS proton therapy at our institution were retrospectively selected. The histologies included rhabdomyosarcoma, ependymoma, astrocytoma, craniopharyngioma and germinoma. The prescribed dose ranged from 36 to 54 Gy(RBE). Five PBS plans were created for each patient using variable spot size (average sigma at isocenter) and choice of beam specific apertures: (1)more » 10mm spots, (2) 10mm spots with apertures, (3) 6mm spots, (4) 6mm spots with apertures, and (5) 3mm spots. The plans were optimized for intensity modulated proton therapy (IMPT) with no single beam uniformity constraints. Dose volume indices as well as equivalent uniform dose (EUD) were compared between PS and PBS plans. Results: Although target coverage was clinically adequate for all cases, the plans with largest (10mm) spots provide inferior quality compared with PS in terms of dose to organs-at-risk (OAR). However, adding apertures to these plans ensured lower OAR dose than PS. The average EUD difference between PBS and PS plans over all patients and organs at risk were (1) 2.5%, (2) −5.1%, (3) -5%, (4) −7.8%, and (5) −9.5%. As the spot size decreased, more conformal plans were achieved that offered similar target coverage but lower dose to the neighboring healthy organs, while alleviating the need for using apertures. Conclusion: The application of PBS does not always translate to better plan qualities compared to PS depending on the available beam spot size. We recommend that institutions with spot size larger than ∼6mm at isocenter consider using apertures to guarantee clinically comparable or superior dosimetric efficacy to PS treatments.« less

Controlled deterministic implantation by nanostencil lithography at the limit of ion-aperture straggling

NASA Astrophysics Data System (ADS)

Alves, A. D. C.; Newnham, J.; van Donkelaar, J. A.; Rubanov, S.; McCallum, J. C.; Jamieson, D. N.

2013-04-01

Solid state electronic devices fabricated in silicon employ many ion implantation steps in their fabrication. In nanoscale devices deterministic implants of dopant atoms with high spatial precision will be needed to overcome problems with statistical variations in device characteristics and to open new functionalities based on controlled quantum states of single atoms. However, to deterministically place a dopant atom with the required precision is a significant technological challenge. Here we address this challenge with a strategy based on stepped nanostencil lithography for the construction of arrays of single implanted atoms. We address the limit on spatial precision imposed by ion straggling in the nanostencil—fabricated with the readily available focused ion beam milling technique followed by Pt deposition. Two nanostencils have been fabricated; a 60 nm wide aperture in a 3 μm thick Si cantilever and a 30 nm wide aperture in a 200 nm thick Si3N4 membrane. The 30 nm wide aperture demonstrates the fabricating process for sub-50 nm apertures while the 60 nm aperture was characterized with 500 keV He+ ion forward scattering to measure the effect of ion straggling in the collimator and deduce a model for its internal structure using the GEANT4 ion transport code. This model is then applied to simulate collimation of a 14 keV P+ ion beam in a 200 nm thick Si3N4 membrane nanostencil suitable for the implantation of donors in silicon. We simulate collimating apertures with widths in the range of 10-50 nm because we expect the onset of J-coupling in a device with 30 nm donor spacing. We find that straggling in the nanostencil produces mis-located implanted ions with a probability between 0.001 and 0.08 depending on the internal collimator profile and the alignment with the beam direction. This result is favourable for the rapid prototyping of a proof-of-principle device containing multiple deterministically implanted dopants.

Ambiguity Of Doppler Centroid In Synthetic-Aperture Radar

NASA Technical Reports Server (NTRS)

Chang, Chi-Yung; Curlander, John C.

1991-01-01

Paper discusses performances of two algorithms for resolution of ambiguity in estimated Doppler centroid frequency of echoes in synthetic-aperture radar. One based on range-cross-correlation technique, other based on multiple-pulse-repetition-frequency technique.

Upflow bioreactor having a septum and an auger and drive assembly

DOEpatents

Hansen, Carl S.; Hansen, Conly L.

2007-11-06

An upflow bioreactor includes a vessel having an inlet and an outlet configured for upflow operation. A septum is positioned within the vessel and defines a lower chamber and an upper chamber. The septum includes an aperture that provides fluid communication between the upper chamber and lower chamber. The bioreactor also includes an auger positioned in the aperture of the septum. The vessel includes an opening in the top for receiving the auger. The auger extends from a drive housing, which is position over the opening and provides a seal around the opening. The drive housing is adjustable relative to the vessel. The position of the auger in the aperture can be adjusted by adjusting the drive housing relative to the vessel. The auger adjustment mechanism allows the auger to be accurately positioned within the aperture. The drive housing can also include a fluid to provide an additional seal around the shaft of the auger.

Simultaneous usage of pinhole and penumbral apertures for imaging small scale neutron sources from inertial confinement fusion experiments.

PubMed

Guler, N; Volegov, P; Danly, C R; Grim, G P; Merrill, F E; Wilde, C H

2012-10-01

Inertial confinement fusion experiments at the National Ignition Facility are designed to understand the basic principles of creating self-sustaining fusion reactions by laser driven compression of deuterium-tritium (DT) filled cryogenic plastic capsules. The neutron imaging diagnostic provides information on the distribution of the central fusion reaction region and the surrounding DT fuel by observing neutron images in two different energy bands for primary (13-17 MeV) and down-scattered (6-12 MeV) neutrons. From this, the final shape and size of the compressed capsule can be estimated and the symmetry of the compression can be inferred. These experiments provide small sources with high yield neutron flux. An aperture design that includes an array of pinholes and penumbral apertures has provided the opportunity to image the same source with two different techniques. This allows for an evaluation of these different aperture designs and reconstruction algorithms.

Article and method for making an article

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

Lacy, Benjamin Paul; Schick, David Edward; Kottilingam, Srikanth Chandrudu

An article and a method for making shaped cooling holes in an article are provided. The method includes the steps of depositing a metal alloy powder to form an initial layer including at least one aperture, melting the metal alloy powder with a focused energy source to transform the powder layer to a sheet of metal alloy, sequentially depositing an additional layer of the metal alloy powder to form a layer including at least one aperture corresponding to the at least one aperture in the initial layer, melting the additional layer of the metal alloy powder with the focused energymore » source to increase the sheet thickness, and repeating the steps of sequentially depositing and melting the additional layers of metal alloy powder until a structure including at least one aperture having a predetermined profile is obtained. The structure is attached to a substrate to make the article.« less

Article and method for making an article

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

Lacy, Benjamin Paul; Schick, David Edward; Kottilingam, Srikanth Chandrudu

An article and a method for making shaped cooling holes in an article are provided. The method includes the steps of providing a metal alloy powder; forming an initial layer with the metal alloy powder, the initial layer having a preselected thickness and a preselected shape, the preselected shape including at least one aperture; sequentially forming an additional layer over the initial layer with the metal alloy powder, the additional layer having a second preselected thickness and a second preselected shape, the second preselected shape including at least one aperture corresponding to the at least one aperture in the initialmore » layer; and joining the additional layer to the initial layer, forming a structure having a predetermined thickness, a predetermined shape, and at least one aperture having a predetermined profile. The structure is attached to a substrate to make the article.« less

A comparison between GO/aperture-field and physical-optics methods for offset reflectors

NASA Technical Reports Server (NTRS)

Rahmat-Samii, Y.

1984-01-01

Both geometrical optics (GO)/aperture-field and physical-optics (PO) methods are used extensively in the diffraction analysis of offset parabolic and dual reflectors. An analytical/numerical comparative study is performed to demonstrate the limitations of the GO/aperture-field method for accurately predicting the sidelobe and null positions and levels. In particular, it is shown that for offset parabolic reflectors and for feeds located at the focal point, the predicted far-field patterns (amplitude) by the GO/aperture-field method will always be symmetric even in the offset plane. This, of course, is inaccurate for the general case and it is shown that the physical-optics method can result in asymmetric patterns for cases in which the feed is located at the focal point. Representative numerical data are presented and a comparison is made with available measured data.

PIC Modeling of Argon Plasma Flow in MNX

NASA Astrophysics Data System (ADS)

Cohen, Samuel; Sefkow, Adam

2007-11-01

A linear helicon-heated plasma device - the Magnetic Nozzle Experiment (MNX) at the Princeton Plasma Physics Laboratory - is used for studies of the formation of strong electrostatic double layers near mechanical and magnetic apertures and the acceleration of plasma ions into supersonic directed beams. In order to characterize the role of the aperture and its involvement with ion acceleration, detailed particle-in-cell simulations are employed to study the effects of the surrounding boundary geometry on the plasma dynamics near the aperture region, within which the transition from a collisional to collisionless regime occurs. The presence of a small superthermal electron population is examined, and the model includes a background neutral population which can be ionized by energetic electrons. By self-consistently evaluating the temporal evolution of the plasma in the vicinity of the aperture, the formation mechanism of the double layer is investigated.

An Aperture Photometry Pipeline for K2 Data

NASA Astrophysics Data System (ADS)

Buzasi, Derek L.; Carboneau, Lindsey; Lezcano, Andy; Vydra, Ekaterina

2016-01-01

As part of an ongoing research program with undergraduate students at Florida Gulf Coast University, we have constructed an aperture photometry pipeline for K2 data. The pipeline performs dynamic automated aperture mask definition for all targets in the K2 fields, followed by aperture photometry and detrending. Our pipeline is currently used to support a number of projects, including studies of stellar rotation and activity, red giant asteroseismology, gyrochronology, and exoplanet searches. In addition, output is used to support an undergraduate class on exoplanets aimed at a student audience of both majors and non-majors. The pipeline is designed for both batch and single-target use, and is easily extensible to data from other missions, and pipeline output is available to the community. This paper will describe our pipeline and its capabilities and illustrate the quality of the results, drawing on all of the applications for which it is currently used.

Characteristic investigation of Golay9 multiple mirror telescope with a spherical primary mirror

NASA Astrophysics Data System (ADS)

Wu, Feng; Wu, Quanying; Zhu, Xifang; Xiang, Ruxi; Qian, Lin

2017-10-01

The sparse aperture provides a novel solution to the manufacturing difficulties of modern super large telescopes. Golay configurations are optimal in the sparse aperture family. Characteristics of the Golay9 multiple mirror telescope having a spherical primary mirror are investigated. The arrangement of the nine sub-mirrors is discussed after the planar Golay9 configuration is analyzed. The characteristics of the entrance pupil are derived by analyzing the sub-aperture shapes with different relative apertures and sub-mirror sizes. Formulas about the fill factor and the overlay factor are deduced. Their maximal values are presented based on the derived tangency condition. Formulas for the point spread function (PSF) and the modulation transfer function (MTF) of the Golay9 MMT are also deduced. Two Golay9 MMT have been developed by Zemax simulation. Their PSF, MTF, fill factors, and overlay factors prove that our theoretical results are consistent with the practical simulation ones.

Determination of Electron Optical Properties for Aperture Zoom Lenses Using an Artificial Neural Network Method.

PubMed

Isik, Nimet

2016-04-01

Multi-element electrostatic aperture lens systems are widely used to control electron or charged particle beams in many scientific instruments. By means of applied voltages, these lens systems can be operated for different purposes. In this context, numerous methods have been performed to calculate focal properties of these lenses. In this study, an artificial neural network (ANN) classification method is utilized to determine the focused/unfocused charged particle beam in the image point as a function of lens voltages for multi-element electrostatic aperture lenses. A data set for training and testing of ANN is taken from the SIMION 8.1 simulation program, which is a well known and proven accuracy program in charged particle optics. Mean squared error results of this study indicate that the ANN classification method provides notable performance characteristics for electrostatic aperture zoom lenses.

Vaporization chambers and associated methods

DOEpatents

Turner, Terry D.; Wilding, Bruce M.; McKellar, Michael G.; Shunn, Lee P.

2017-02-21

A vaporization chamber may include at least one conduit and a shell. The at least one conduit may have an inlet at a first end, an outlet at a second end and a flow path therebetween. The shell may surround a portion of each conduit and define a chamber surrounding the portion of each conduit. Additionally, a plurality of discrete apertures may be positioned at longitudinal intervals in a wall of each conduit, each discrete aperture of the plurality of discrete apertures sized and configured to direct a jet of fluid into each conduit from the chamber. A liquid may be vaporized by directing a first fluid comprising a liquid into the inlet at the first end of each conduit, directing jets of a second fluid into each conduit from the chamber through discrete apertures in a wall of each conduit and transferring heat from the second fluid to the first fluid.

Diffraction patterns in Fresnel approximation of periodic objects for a colorimeter of two apertures

NASA Astrophysics Data System (ADS)

Cortes-Reynoso, Jose-German R.; Suarez-Romero, Jose G.; Hurtado-Ramos, Juan B.; Tepichin-Rodriguez, Eduardo; Solorio-Leyva, Juan Carlos

2004-10-01

In this work, we present a study of Fresnel diffraction of periodic structures in an optical system of two apertures. This system of two apertures was used successfully for measuring color in textile samples solving the problems of illumination and directionality that present current commercial equipments. However, the system is sensible to the spatial frequency of the periodic sample"s area enclosed in its optical field of view. The study of Fresnel diffraction allows us to establish criteria for geometrical parameters of measurements in order to assure invariance in angular rotations and spatial positions. In this work, we use the theory of partial coherence to calculate the diffraction through two continuous apertures. In the calculation process, we use the concept of point-spread function of the system for partial coherence, in this way we avoid complicated statistical processes commonly used in the partial coherence theory.

Generation of topologically diverse acoustic vortex beams using a compact metamaterial aperture

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

Naify, Christina J., E-mail: christina.naify@nrl.navy.mil; Rohde, Charles A.; Martin, Theodore P.

2016-05-30

Here, we present a class of metamaterial-based acoustic vortex generators which are both geometrically simple and broadly tunable. The aperture overcomes the significant limitations of both active phasing systems and existing passive coded apertures. The metamaterial approach generates topologically diverse acoustic vortex waves motivated by recent advances in leaky wave antennas by wrapping the antenna back upon itself to produce an acoustic vortex wave antenna. We demonstrate both experimentally and analytically that this single analog structure is capable of creating multiple orthogonal orbital angular momentum modes using only a single transducer. The metamaterial design makes the aperture compact, with amore » diameter nearly equal to the excitation wavelength and can thus be easily integrated into high-density systems. Applications range from acoustic communications for high bit-rate multiplexing to biomedical devices such as microfluidic mixers.« less

Deployable reflector configurations

NASA Astrophysics Data System (ADS)

Meinel, A. B.; Meinel, M. P.; Woolf, N. J.

Both the theoretical reasons for considering a non-circular format for the Large Deployable Reflector, and a potentially realizable concept for such a device, are discussed. The optimum systems for diffraction limited telescopes with incoherent detection have either a single filled aperture, or two such apertures as an interferometer to synthesize a larger aperture. For a single aperture of limited area, a reflector in the form of a slot can be used to give increased angular resolution. It is shown how a 20 x 8 meter telescope can be configured to fit the Space Shuttle bay, and deployed with relatively simple operations. The relationship between the sunshield design and the inclination of the orbit is discussed. The possible use of the LDR as a basic module to permit the construction of supergiant space telescopes and interferometers both for IR/submm studies and for the entire ultraviolet through mm wave spectral region is discussed.

Deployable reflector configurations. [for space telescope

NASA Technical Reports Server (NTRS)

Meinel, A. B.; Meinel, M. P.; Woolf, N. J.

1983-01-01

Both the theoretical reasons for considering a non-circular format for the Large Deployable Reflector, and a potentially realizable concept for such a device, are discussed. The optimum systems for diffraction limited telescopes with incoherent detection have either a single filled aperture, or two such apertures as an interferometer to synthesize a larger aperture. For a single aperture of limited area, a reflector in the form of a slot can be used to give increased angular resolution. It is shown how a 20 x 8 meter telescope can be configured to fit the Space Shuttle bay, and deployed with relatively simple operations. The relationship between the sunshield design and the inclination of the orbit is discussed. The possible use of the LDR as a basic module to permit the construction of supergiant space telescopes and interferometers both for IR/submm studies and for the entire ultraviolet through mm wave spectral region is discussed.

Thermal response of solar receiver aperture plates during sun walk-off

NASA Technical Reports Server (NTRS)

Wen, L.; Roschke, J.

1982-01-01

The tracking mechanism for a point-focusing concentrator may be subject to failure. If this should occur, the solar image will travel across the aperture plate, and it may also impinge on the adjacent support structure. Such an event is called 'sun walk-off'. The present investigation is concerned with the transient response of different aperture plate materials to the intense heating produced in a typical walk-off situation for parabolic dish concentrators. Receivers for two solar module systems are considered, including a high-temperature receiver that utilizes a 2-milliradian (mrad) concentrator, and a lower-temperature receiver which is coupled with a 4-mrad concentrator. It is found that during a walk-off situation the solar image travels in a straight line in the radial direction. The results obtained for a copper aperture plate were disappointing. It appears that passive metallic plates without cooling or other protective support cannot withstand the intense heating.

Rapid Optical Shutter, Chopper, Modulator and Deflector

NASA Technical Reports Server (NTRS)

Danehy, Paul M. (Inventor)

2017-01-01

An optical device with a light source and a detector is provided. A digital micromirror device positioned between the detector and the light source may deflect light beams projected from the light source. An aperture in front of the detector may block an incoming light beam from the detector when the incoming light beam is incident on the detector outside of a passable incident range and including an aperture opening configured to pass the incoming light beam to the detector when the incoming light beam is incident on the detector within a passable incident range. The digital micromirror device may rotate between a first position causing the light beam to pass through the aperture opening and a second position causing the light beam to be blocked by the aperture. The optical device may be configured to operate as a shutter, chopper, modulator and/or deflector.

GeoSTAR - A Synthetic Aperture Microwave Sounder for Geostationary Missions

NASA Technical Reports Server (NTRS)

Lambrigtsen, Bjorn; Wilson, William; Tanner, Alan; Kangaslahti, Pekka

2004-01-01

The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) is a new microwave atmospheric sounder under development. It will bring capabilities similar to those now available on low-earth orbiting environmental satellites to geostationary orbit - where such capabilities have not been available. GeoSTAR will synthesize the multimeter aperture needed to achieve the required spatial resolution, which will overcome the obstacle that has prevented a GEO microwave sounder from being implemented until now. The synthetic aperture approach has until recently not been feasible, due to the high power needed to operate the on-board high-speed massively parallel processing system required for 2D-synthesis, as well as a number of system and calibration obstacles. The development effort under way at JPL, with important contributions from the Goddard Space Flight Center and the University of Michigan, is intended to demonstrate the measurement concept and retire much of the technology risk.

Near-Field Optical Flying Head with Protruding Aperture and Its Fabrication

NASA Astrophysics Data System (ADS)

Hirata, Masakazu; Oumi, Manabu; Nakajima, Kunio; Ohkubo, Toshifumi

2005-05-01

One of the most important parameters related to the near-field readout principle is aperture-to-media spacing (effective spacing). We proposed a near-field optical head with a protruding aperture that can reduce the effective spacing beyond the mechanical limit of the flying height and localize the near-field on the medium. Using nanostep lithography, we fabricated the protruding aperture, whose extension is 20 nm with 5 nm accuracy, so that the effective spacing is successfully reduced to 50 nm on a 3.2× 3.6 mm flying head. We demonstrated signal readout with a 150 nm-long line-and-space pattern in chromium with the head. The flying height was estimated to be 75 nm, so that the effective spacing was 54 nm. The circumferential speed was 2.7 m/s and the signal frequency was 9.1 MHz. We also propose a promising structure for an optical head of higher density.

Solar energy apparatus with apertured shield

NASA Technical Reports Server (NTRS)

Collings, Roger J. (Inventor); Bannon, David G. (Inventor)

1989-01-01

A protective apertured shield for use about an inlet to a solar apparatus which includesd a cavity receiver for absorbing concentrated solar energy. A rigid support truss assembly is fixed to the periphery of the inlet and projects radially inwardly therefrom to define a generally central aperture area through which solar radiation can pass into the cavity receiver. A non-structural, laminated blanket is spread over the rigid support truss in such a manner as to define an outer surface area and an inner surface area diverging radially outwardly from the central aperture area toward the periphery of the inlet. The outer surface area faces away from the inlet and the inner surface area faces toward the cavity receiver. The laminated blanket includes at least one layer of material, such as ceramic fiber fabric, having high infra-red emittance and low solar absorption properties, and another layer, such as metallic foil, of low infra-red emittance properties.

Variable aperture-based ptychographical iterative engine method.

PubMed

Sun, Aihui; Kong, Yan; Meng, Xin; He, Xiaoliang; Du, Ruijun; Jiang, Zhilong; Liu, Fei; Xue, Liang; Wang, Shouyu; Liu, Cheng

2018-02-01

A variable aperture-based ptychographical iterative engine (vaPIE) is demonstrated both numerically and experimentally to reconstruct the sample phase and amplitude rapidly. By adjusting the size of a tiny aperture under the illumination of a parallel light beam to change the illumination on the sample step by step and recording the corresponding diffraction patterns sequentially, both the sample phase and amplitude can be faithfully reconstructed with a modified ptychographical iterative engine (PIE) algorithm. Since many fewer diffraction patterns are required than in common PIE and the shape, the size, and the position of the aperture need not to be known exactly, this proposed vaPIE method remarkably reduces the data acquisition time and makes PIE less dependent on the mechanical accuracy of the translation stage; therefore, the proposed technique can be potentially applied for various scientific researches. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Technology gap assessment for a future large-aperture ultraviolet-optical-infrared space telescope

NASA Astrophysics Data System (ADS)

Bolcar, Matthew R.; Balasubramanian, Kunjithapatham; Crooke, Julie; Feinberg, Lee; Quijada, Manuel; Rauscher, Bernard J.; Redding, David; Rioux, Norman; Shaklan, Stuart; Stahl, H. Philip; Stahle, Carl M.; Thronson, Harley

2016-10-01

The Advanced Technology Large Aperture Space Telescope (ATLAST) team identified five key technology areas to enable candidate architectures for a future large-aperture ultraviolet/optical/infrared (LUVOIR) space observatory envisioned by the NASA Astrophysics 30-year roadmap, "Enduring Quests, Daring Visions." The science goals of ATLAST address a broad range of astrophysical questions from early galaxy and star formation to the processes that contributed to the formation of life on Earth, combining general astrophysics with direct-imaging and spectroscopy of habitable exoplanets. The key technology areas are internal coronagraphs, starshades (or external occulters), ultra-stable large-aperture telescope systems, detectors, and mirror coatings. For each technology area, we define best estimates of required capabilities, current state-of-the-art performance, and current technology readiness level (TRL), thus identifying the current technology gap. We also report on current, planned, or recommended efforts to develop each technology to TRL 5.

Solar dynamic modules for Space Station Freedom: The relationship between fine-pointing control and thermal loading of the aperture plate

NASA Technical Reports Server (NTRS)

Quinn, Roger D.; Kerslake, Thomas W.

1992-01-01

Dynamic simulations of Space Station Freedom (SSF) configured with solar dynamic (SD) power modules were performed. The structure was subjected to Space Shuttle docking disturbances, while being controlled with a 'natural' vibration and tracking control approach. Three control cases were investigated for the purpose of investigating the relationship between actuator effort, SD pointing, and thermal loading on the receiver aperture plate. Transient, one-dimensional heat transfer analyses were performed to conservatively predict temperatures of the multi-layered receiver aperture plate assembly and thermal stresses in its shield layer. Results indicate that the proposed aperture plate is tolerant of concentrated flux impingement during short-lived structural disturbances. Pointing requirements may be loosened and the requirement control torques lessened from that previously specified. Downsizing and simplifying the joint drive system should result in a considerable savings mass.

Design considerations for eye-safe single-aperture laser radars

NASA Astrophysics Data System (ADS)

Starodubov, D.; McCormick, K.; Volfson, L.

2015-05-01

The design considerations for low cost, shock resistant, compact and efficient laser radars and ranging systems are discussed. The reviewed approach with single optical aperture allows reducing the size, weight and power of the system. Additional design benefits include improved stability, reliability and rigidity of the overall system. The proposed modular architecture provides simplified way of varying the performance parameters of the range finder product family by selecting the sets of specific illumination and detection modules. The performance operation challenges are presented. The implementation of non-reciprocal optical elements is considered. The cross talk between illumination and detection channels for single aperture design is reviewed. 3D imaging capability for the ranging applications is considered. The simplified assembly and testing process for single aperture range finders that allows to mass produce the design are discussed. The eye safety of the range finder operation is summarized.

Ultra-Tuning of the Rare-Earth fcu-MOF Aperture Size for Selective Molecular Exclusion of Branched Paraffins.

PubMed

Assen, Ayalew H; Belmabkhout, Youssef; Adil, Karim; Bhatt, Prashant M; Xue, Dong-Xu; Jiang, Hao; Eddaoudi, Mohamed

2015-11-23

Using isoreticular chemistry allows the design and construction of a new rare-earth metal (RE) fcu-MOF with a suitable aperture size for practical steric adsorptive separations. The judicious choice of a relatively short organic building block, namely fumarate, to bridge the 12-connected RE hexanuclear clusters has afforded the contraction of the well-defined RE-fcu-MOF triangular window aperture, the sole access to the two interconnected octahedral and tetrahedral cages. The newly constructed RE (Y(3+) and Tb(3+)) fcu-MOF analogues display unprecedented total exclusion of branched paraffins from normal paraffins. The resultant window aperture size of about 4.7 Å, regarded as a sorbate-size cut-off, enabled a complete sieving of branched paraffins from normal paraffins. The results are supported by collective single gas and mixed gas/vapor adsorption and calorimetric studies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Prototype Development of a Geostationary Synthetic Thinned Aperture Radiometer, GeoSTAR

NASA Technical Reports Server (NTRS)

Tanner, Alan B.; Wilson, William J.; Kangaslahti, Pekka P.; Lambrigsten, Bjorn H.; Dinardo, Steven J.; Piepmeier, Jeffrey R.; Ruf, Christopher S.; Rogacki, Steven; Gross, S. M.; Musko, Steve

2004-01-01

Preliminary details of a 2-D synthetic aperture radiometer prototype operating from 50 to 58 GHz will be presented. The instrument is being developed as a laboratory testbed, and the goal of this work is to demonstrate the technologies needed to do atmospheric soundings with high spatial resolution from Geostationary orbit. The concept is to deploy a large sparse aperture Y-array from a geostationary satellite, and to use aperture synthesis to obtain images of the earth without the need for a large mechanically scanned antenna. The laboratory prototype consists of a Y-array of 24 horn antennas, MMIC receivers, and a digital cross-correlation sub-system. System studies are discussed, including an error budget which has been derived from numerical simulations. The error budget defines key requirements, such as null offsets, phase calibration, and antenna pattern knowledge. Details of the instrument design are discussed in the context of these requirements.

A difference-matrix metaheuristic for intensity map segmentation in step-and-shoot IMRT delivery.

PubMed

Gunawardena, Athula D A; D'Souza, Warren D; Goadrich, Laura D; Meyer, Robert R; Sorensen, Kelly J; Naqvi, Shahid A; Shi, Leyuan

2006-05-21

At an intermediate stage of radiation treatment planning for IMRT, most commercial treatment planning systems for IMRT generate intensity maps that describe the grid of beamlet intensities for each beam angle. Intensity map segmentation of the matrix of individual beamlet intensities into a set of MLC apertures and corresponding intensities is then required in order to produce an actual radiation delivery plan for clinical use. Mathematically, this is a very difficult combinatorial optimization problem, especially when mechanical limitations of the MLC lead to many constraints on aperture shape, and setup times for apertures make the number of apertures an important factor in overall treatment time. We have developed, implemented and tested on clinical cases a metaheuristic (that is, a method that provides a framework to guide the repeated application of another heuristic) that efficiently generates very high-quality (low aperture number) segmentations. Our computational results demonstrate that the number of beam apertures and monitor units in the treatment plans resulting from our approach is significantly smaller than the corresponding values for treatment plans generated by the heuristics embedded in a widely use commercial system. We also contrast the excellent results of our fast and robust metaheuristic with results from an 'exact' method, branch-and-cut, which attempts to construct optimal solutions, but, within clinically acceptable time limits, generally fails to produce good solutions, especially for intensity maps with more than five intensity levels. Finally, we show that in no instance is there a clinically significant change of quality associated with our more efficient plans.

Application of Ruze Equation for Inflatable Aperture Antennas

NASA Technical Reports Server (NTRS)

Welch, Bryan W.

2008-01-01

Inflatable aperture reflector antennas are an emerging technology that NASA is investigating for potential uses in science and exploration missions. As inflatable aperture antennas have not been proven fully qualified for space missions, they must be characterized properly so that the behavior of the antennas can be known in advance. To properly characterize the inflatable aperture antenna, testing must be performed in a relevant environment, such as a vacuum chamber. Since the capability of having a radiofrequency (RF) test facility inside a vacuum chamber did not exist at NASA Glenn Research Center, a different methodology had to be utilized. The proposal to test an inflatable aperture antenna in a vacuum chamber entailed performing a photogrammetry study of the antenna surface by using laser ranging measurements. A root-mean-square (rms) error term was derived from the photogrammetry study to calculate the antenna surface loss as described by the Ruze equation. However, initial testing showed that problems existed in using the Ruze equation to calculate the loss due to errors on the antenna surface. This study utilized RF measurements obtained in a near-field antenna range and photogrammetry data taken from a laser range scanner to compare the expected performance of the test antenna (via the Ruze equation) with the actual RF patterns and directivity measurements. Results showed that the Ruze equation overstated the degradation in the directivity calculation. Therefore, when the photogrammetry study is performed on the test antennas in the vacuum chamber, a more complex equation must be used in light of the fact that the Ruze theory overstates the loss in directivity for inflatable aperture reflector antennas.

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

Rottmann, J; Berbeco, R; Keall, P

Purpose: To maximize normal tissue sparing for treatments requiring motion encompassing margins. Motion mitigation techniques including DMLC or couch tracking can freeze tumor motion within the treatment aperture potentially allowing for smaller treatment margins and thus better sparing of normal tissue. To enable for a safe application of this concept in the clinic we propose adapting margins dynamically in real-time during radiotherapy delivery based on personalized tumor localization confidence. To demonstrate technical feasibility we present a phantom study. Methods: We utilize a realistic anthropomorphic dynamic thorax phantom with a lung tumor model embedded close to the spine. The tumor, amore » 3D-printout of a patient's GTV, is moved 15mm peak-to-peak by diaphragm compression and monitored by continuous EPID imaging in real-time. Two treatment apertures are created for each beam, one representing ITV -based and the other GTV-based margin expansion. A soft tissue localization (STiL) algorithm utilizing the continuous EPID images is employed to freeze tumor motion within the treatment aperture by means of DMLC tracking. Depending on a tracking confidence measure (TCM), the treatment aperture is adjusted between the ITV and the GTV leaf. Results: We successfully demonstrate real-time personalized margin adjustment in a phantom study. We measured a system latency of about 250 ms which we compensated by utilizing a respiratory motion prediction algorithm (ridge regression). With prediction in place we observe tracking accuracies better than 1mm. For TCM=0 (as during startup) an ITV-based treatment aperture is chosen, for TCM=1 a GTV-based aperture and for 0« less

Design and Analysis of the Aperture Shield Assembly for a Space Solar Receiver

NASA Technical Reports Server (NTRS)

Strumpf, Hal J.; Trinh, Tuan; Westelaken, William; Krystkowiak, Christopher; Avanessian, Vahe; Kerslake, Thomas W.

1997-01-01

A joint U.S./Russia program has been conducted to design, develop, fabricate, launch, and operate the world's first space solar dynamic power system on the Russian Space Station Mir. The goal of the program was to demonstrate and confirm that solar dynamic power systems are viable for future space applications such as the International Space Station (ISS). The major components of the system include a solar receiver, a closed Brayton cycle power conversion unit, a power conditioning and control unit, a solar concentrator, a radiator, a thermal control system, and a Space Shuttle carrier. Unfortunately, the mission was demanifested from the ISS Phase 1 Space Shuttle Program in 1996. However, NASA Lewis is proposing to use the fabricated flight hardware as part of an all-American flight demonstration on the ISS in 2002. The present paper concerns the design and analysis of the solar receiver aperture shield assembly. The aperture shield assembly comprises the front face of the cylindrical receiver and is located at the focal plane of the solar concentrator. The aperture shield assembly is a critical component that protects the solar receiver structure from highly concentrated solar fluxes during concentrator off-pointing events. A full-size aperture shield assembly was fabricated. This unit was essentially identical to the flight configuration, with the exception of materials substitution. In addition, a thermal shock test aperture shield assembly was fabricated. This test article utilized the flight materials and was used for high-flux testing in the solar simulator test rig at NASA Lewis. This testing is described in a companion paper.

Edge detection for optical synthetic aperture based on deep neural network

NASA Astrophysics Data System (ADS)

Tan, Wenjie; Hui, Mei; Liu, Ming; Kong, Lingqin; Dong, Liquan; Zhao, Yuejin

2017-09-01

Synthetic aperture optics systems can meet the demands of the next-generation space telescopes being lighter, larger and foldable. However, the boundaries of segmented aperture systems are much more complex than that of the whole aperture. More edge regions mean more imaging edge pixels, which are often mixed and discretized. In order to achieve high-resolution imaging, it is necessary to identify the gaps between the sub-apertures and the edges of the projected fringes. In this work, we introduced the algorithm of Deep Neural Network into the edge detection of optical synthetic aperture imaging. According to the detection needs, we constructed image sets by experiments and simulations. Based on MatConvNet, a toolbox of MATLAB, we ran the neural network, trained it on training image set and tested its performance on validation set. The training was stopped when the test error on validation set stopped declining. As an input image is given, each intra-neighbor area around the pixel is taken into the network, and scanned pixel by pixel with the trained multi-hidden layers. The network outputs make a judgment on whether the center of the input block is on edge of fringes. We experimented with various pre-processing and post-processing techniques to reveal their influence on edge detection performance. Compared with the traditional algorithms or their improvements, our method makes decision on a much larger intra-neighbor, and is more global and comprehensive. Experiments on more than 2,000 images are also given to prove that our method outperforms classical algorithms in optical images-based edge detection.

RF Performance of Membrane Aperture Shells

NASA Technical Reports Server (NTRS)

Flint, Eirc M.; Lindler, Jason E.; Thomas, David L.; Romanofsky, Robert

2007-01-01

This paper provides an overview of recent results establishing the suitability of Membrane Aperture Shell Technology (MAST) for Radio Frequency (RF) applications. These single surface shells are capable of maintaining their figure with no preload or pressurization and minimal boundary support, yet can be compactly roll stowed and passively self deploy. As such, they are a promising technology for enabling a future generation of RF apertures. In this paper, we review recent experimental and numerical results quantifying suitable RF performance. It is shown that candidate materials possess metallic coatings with sufficiently low surface roughness and that these materials can be efficiently fabricated into RF relevant doubly curved shapes. A numerical justification for using a reflectivity metric, as opposed to the more standard RF designer metric of skin depth, is presented and the resulting ability to use relatively thin coating thickness is experimentally validated with material sample tests. The validity of these independent film sample measurements are then confirmed through experimental results measuring RF performance for reasonable sized doubly curved apertures. Currently available best results are 22 dBi gain at 3 GHz (S-Band) for a 0.5m aperture tested in prime focus mode, 28dBi gain for the same antenna in the C-Band (4 to 6 GHz), and 36.8dBi for a smaller 0.25m antenna tested at 32 GHz in the Ka-Band. RF range test results for a segmented aperture (one possible scaling approach) are shown as well. Measured antenna system actual efficiencies (relative to the unachievable) ideal for these on axis tests are generally quite good, typically ranging from 50 to 90%.

Addendum to proceedings of the 1978 Synthetic Aperture Radar Technology Conference

NASA Technical Reports Server (NTRS)

1978-01-01

Various research projects on synthetic aperture radar are reported, including SAR calibration techniques. Slot arrays, sidelobe suppression, and wide swaths on satellite-borne radar were examined. The SAR applied to remote sensing was also considered.

Characterising rock fracture aperture-spacing relationships using power-law relationships: some considerations

NASA Astrophysics Data System (ADS)

Brook, Martin; Hebblewhite, Bruce; Mitra, Rudrajit

2016-04-01

The size-scaling of rock fractures is a well-studied problem in geology, especially for permeability quantification. The intensity of fractures may control the economic exploitation of fractured reservoirs because fracture intensity describes the abundance of fractures potentially available for fluid flow. Moreover, in geotechnical engineering, fractures are important for parameterisation of stress models and excavation design. As fracture data is often collected from widely-spaced boreholes where core recovery is often incomplete, accurate interpretation and representation of fracture aperture-frequency relationships from sparse datasets is important. Fracture intensity is the number of fractures encountered per unit length along a sample scanline oriented perpendicular to the fractures in a set. Cumulative frequency of fractures (F) is commonly related to fracture aperture (A) in the form of a power-law (F = aA-b), with variations in the size of the a coefficient between sites interpreted to equate to fracture frequency for a given aperture (A). However, a common flaw in this approach is that even a small change in b can have a large effect on the response of the fracture frequency (F) parameter. We compare fracture data from the Late Permian Rangal Coal Measures from Australia's Bowen Basin, with fracture data from Jurassic carbonates from the Sierra Madre Oriental, northeastern Mexico. Both power-law coefficient a and exponent b control the fracture aperture-frequency relationship in conjunction with each other; that is, power-laws with relatively low a coefficients have relatively high b exponents and vice versa. Hence, any comparison of different power-laws must take both a and b into consideration. The corollary is that different sedimentary beds in the Sierra Madre carbonates do not show ˜8× the fracture frequency for a given fracture aperture, as based solely on the comparison of coefficient a. Rather, power-law "sensitivity factors" developed from both Sierra Madre and the Bowen Basin span similar ranges, indicating that the factor of increase in frequency (F) for a doubling of aperture size (A) shows similar relationships and variability from both sites. Despite their limitations, we conclude that fracture aperture-frequency power-law relationships are valid and, when interpreted carefully, provide a useful basis for comparing rock fracture distributions across different sites.

Coupled Thermo-Hydro-Chemical (THC) Modeling of Hypogene Karst Evolution in a Prototype Mountain Hydrologic System

NASA Astrophysics Data System (ADS)

Chaudhuri, A.; Rajaram, H.; Viswanathan, H. S.; Zyvoloski, G.

2011-12-01

Hypogene karst systems are believed to develop when water flowing upward against the geothermal gradient dissolves limestone as it cools. We present a comprehensive THC model incorporating time-evolving fluid flow, heat transfer, buoyancy effects, multi-component reactive transport and aperture/permeability change to investigate the origin of hypogene karst systems. Our model incorporates the temperature and pressure dependence of the solubility and dissolution kinetics of calcite. It also allows for rigorous representation of temperature-dependent fluid density and its influence on buoyancy forces at various stages of karstification. The model is applied to investigate karstification over geological time scales in a prototype mountain hydrologic system. In this system, a high water table maintained by mountain recharge, drives flow downward through the country rock and upward via a high-permeability fault/fracture. The pressure boundary conditions are maintained constant in time. The fluid flux through the fracture remains nearly constant even though the fracture aperture and permeability increase by dissolution, largely because the permeability of the country rock is not altered significantly due to slower dissolution rates. However, karstification by fracture dissolution is not impeded even though the fluid flux stays nearly constant. Forced and buoyant convection effects arise due to the increased permeability of the evolving fracture system. Since in reality the aperture varies significantly within the fracture plane, the initial fracture aperture is modeled as a heterogeneous random field. In such a heterogeneous aperture field, the water initially flows at a significant rate mainly through preferential flow paths connecting the relatively large aperture zones. Dissolution is more prominent at early time along these flow paths, and the aperture grows faster within these paths. With time, the aperture within small sub-regions of these preferential flow paths grows to a point where the permeability is large enough for the onset of buoyant convection. As a result, a multitude of buoyant convection cells form that take on a two-dimensional (2D) maze-like appearance, which could represent a 2D analog of the three-dimensional (3D) mazework pattern widely thought to be characteristic of hypogene cave systems. Although computational limitations limited us to 2D, we suggest that similar process interactions in a 3D network of fractures and faults could produce a 3D mazework.

High-Flux, High-Temperature Thermal Vacuum Qualification Testing of a Solar Receiver Aperture Shield

NASA Technical Reports Server (NTRS)

Kerslake, Thomas W.; Mason, Lee S.; Strumpf, Hal J.

1997-01-01

As part of the International Space Station (ISS) Phase 1 program, NASA Lewis Research Center (LERC) and the Russian Space Agency (RSA) teamed together to design, build and flight test the world's first orbital Solar Dynamic Power System (SDPS) on the Russian space station Mir. The Solar Dynamic Flight Demonstration (SDFD) program was to operate a nominal 2 kWe SDPS on Mir for a period up to 1-year starting in late 1997. Unfortunately, the SDFD mission was demanifested from the ISS phase 1 shuttle program in early 1996. However, substantial flight hardware and prototypical flight hardware was built including a heat receiver and aperture shield. The aperture shield comprises the front face of the cylindrical cavity heat receiver and is located at the focal plane of the solar concentrator. It is constructed of a stainless steel plate with a 1-m outside diameter, a 0.24-m inside diameter and covered with high-temperature, refractory metal Multi-Foil Insulation (MFI). The aperture shield must minimize heat loss from the receiver cavity, provide a stiff, high strength structure to accommodate shuttle launch loads and protect receiver structures from highly concentrated solar fluxes during concentrator off-pointing events. To satisfy Mir operational safety protocols, the aperture shield was required to accommodate direct impingement of the intensely concentrated solar image for a 1-hour period. To verify thermal-structural durability under the anticipated high-flux, high-temperature loading, an aperture shield test article was constructed and underwent a series of two tests in a large thermal vacuum chamber configured with a reflective, point-focus solar concentrator and a solar simulator. The test article was positioned near the focal plane and exposed to concentrated solar flux for a period of 1-hour. In the first test, a near equilibrium temperature of 1862 K was attained in the center of the shield hot spot. In the second test, with increased incident flux, a near equilibrium temperature of 2072 K was achieved. The aperture shield sustained no visible damage as a result of the exposures. This paper describes the aperture shield thermal-vacuum qualification test program including the test article, test facility, procedures, data collection, test success criteria, results and conclusions.

Understanding Volcanic Inflation of Long Valley Caldera, California, from Differential Synthetic Aperture Radar observations

NASA Technical Reports Server (NTRS)

Webb, F.; Hensley, S.; Rosen, P.; Langbein, J.

1994-01-01

The results using interferometric synthetic aperture radar(SAR) to measure the co-seismic displacement from the June 28, 1992 Landers earthquake suggest that this technique may be applicable to other problems in crustal deformation.

Integrated optics applied to astronomical aperture synthesis: general concept for space and ground based applications

NASA Astrophysics Data System (ADS)

Pierre, Kern; Malbet, Fabien; Berger, Jean Philippe; Rousselet-Perraut, Karine; Schanen, Isabelle; Nabias, Laurent; Benech, Pierre

2018-04-01

This paper, "Integrated optics applied to astronomical aperture synthesis: general concept for space and ground based applications," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

Integrated optics applied to astronomical aperture synthesis III: simulation of components optimized for astronomical interferometry

NASA Astrophysics Data System (ADS)

Nabias, Laurent; Schanen, Isabelle; Berger, Jean-Philippe; Kern, Pierre; Malbet, Fabien; Benech, Pierre

2018-04-01

This paper, "Integrated optics applied to astronomical aperture synthesis III: simulation of components optimized for astronomical interferometry," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

Space shuttle search and rescue experiment using synthetic aperture radar

NASA Technical Reports Server (NTRS)

Sivertson, W. E., Jr.; Larson, R. W.; Zelenka, J. S.

1977-01-01

The feasibility of a synthetic aperture radar for search and rescue applications was demonstrated with aircraft experiments. One experiment was conducted using the ERIM four-channel radar and several test sites in the Michigan area. In this test simple corner-reflector targets were successfully imaged. Results from this investigation were positive and indicate that the concept can be used to investigate new approaches focused on the development of a global search and rescue system. An orbital experiment to demonstrate the application of synthetic aperture radar to search and rescue is proposed using the space shuttle.

Focal shift and the axial optical coordinate for high-aperture systems of finite Fresnel number.

PubMed

Sheppard, Colin J R; Török, Peter

2003-11-01

Analytic expressions are given for the on-axis intensity predicted by the Rayleigh-Sommerfeld and Kirchhoff diffraction integrals for a scalar optical system of high numerical aperture and finite value of Fresnel number. A definition of the axial optical coordinate is introduced that is valid for finite values of Fresnel number, for high-aperture systems, and for observation points distant from the focus. The focal shift effect is reexamined. For the case when the focal shift is small, explicit expressions are given for the focal shift and the axial peak in intensity.

Large aperture deformable mirror with a transferred single-crystal silicon membrane actuated using large-stroke PZT Unimorph Actuators

NASA Technical Reports Server (NTRS)

Hishinumat, Yoshikazu; Yang, Eui - Hyeok (EH)

2005-01-01

We have demonstrated a large aperture (50 mm x 50 mm) continuous membrane deformable mirror (DM) with a large-stroke piezoelectric unimorph actuator array. The DM consists of a continuous, large aperture, silicon membrane 'transferred' in its entirety onto a 20 x 20 piezoelectric unimorph actuator array. A PZT unimorph actuator, 2.5 mm in diameter with optimized PZT/Si thickness and design showed a deflection of 5.7 [m at 20V. An assembled DM showed an operating frequency bandwidth of 30 kHz and influence function of approximately 30%.

Diffraction Analysis of Antennas With Mesh Surfaces

NASA Technical Reports Server (NTRS)

Rahmat-Samii, Yahya

1987-01-01

Strip-aperture model replaces wire-grid model. Far-field radiation pattern of antenna with mesh reflector calculated more accurately with new strip-aperture model than with wire-grid model of reflector surface. More adaptable than wire-grid model to variety of practical configurations and decidedly superior for reflectors in which mesh-cell width exceeds mesh thickness. Satisfies reciprocity theorem. Applied where mesh cells are no larger than tenth of wavelength. Small cell size permits use of simplifying approximation that reflector-surface current induced by electromagnetic field is present even in apertures. Approximation useful in calculating far field.

Ringfield lithographic camera

DOEpatents

Sweatt, William C.

1998-01-01

A projection lithography camera is presented with a wide ringfield optimized so as to make efficient use of extreme ultraviolet radiation from a large area radiation source (e.g., D.sub.source .apprxeq.0.5 mm). The camera comprises four aspheric mirrors optically arranged on a common axis of symmetry with an increased etendue for the camera system. The camera includes an aperture stop that is accessible through a plurality of partial aperture stops to synthesize the theoretical aperture stop. Radiation from a mask is focused to form a reduced image on a wafer, relative to the mask, by reflection from the four aspheric mirrors.

High-numerical-aperture-based virtual point detectors for photoacoustic tomography

NASA Astrophysics Data System (ADS)

Li, Changhui; Wang, Lihong V.

2008-07-01

The focal point of a high-numerical-aperture (NA) ultrasonic transducer can be used as a virtual point detector. This virtual point detector detects omnidirectionally over a wide acceptance angle. It also combines a large active transducer surface and a small effective virtual detector size. Thus the sensitivity is high compared with that of a real point detector, and the aperture effect is small compared with that of a finite size transducer. We present two kinds of high-NA-based virtual point detectors and their successful application in photoacoustic tomography. They can also be applied in other ultrasound-related fields.

Microwave Bandpass Filter Based on Mie-Resonance Extraordinary Transmission

PubMed Central

Pan, Xiaolong; Wang, Haiyan; Zhang, Dezhao; Xun, Shuang; Ouyang, Mengzhu; Fan, Wentao; Guo, Yunsheng; Wu, Ye; Huang, Shanguo; Bi, Ke; Lei, Ming

2016-01-01

Microwave bandpass filter structure has been designed and fabricated by filling the periodically metallic apertures with dielectric particles. The microwave cannot transmit through the metallic subwavelength apertures. By filling the metallic apertures with dielectric particles, a transmission passband with insertion loss 2 dB appears at the frequency of 10–12 GHz. Both simulated and experimental results show that the passband is induced by the Mie resonance of the dielectric particles. In addition, the passband frequency can be tuned by the size and the permittivity of the dielectric particles. This approach is suitable to fabricate the microwave bandpass filters. PMID:27992440

Fabrication of the pinhole aperture for AdaptiSPECT

PubMed Central

Kovalsky, Stephen; Kupinski, Matthew A.; Barrett, Harrison H.; Furenlid, Lars R.

2015-01-01

AdaptiSPECT is a pre-clinical pinhole SPECT imaging system under final construction at the Center for Gamma-Ray Imaging. The system is designed to be able to autonomously change its imaging configuration. The system comprises 16 detectors mounted on translational stages to move radially away and towards the center of the field-of-view. The system also possesses an adaptive pinhole aperture with multiple collimator diameters and pinhole sizes, as well as the possibility to switch between multiplexed and non-multiplexed imaging configurations. In this paper, we describe the fabrication of the AdaptiSPECT pinhole aperture and its controllers. PMID:26146443

Selecting Pixels for Kepler Downlink

NASA Technical Reports Server (NTRS)

Bryson, Stephen T.; Jenkins, Jon M.; Klaus, Todd C.; Cote, Miles T.; Quintana, Elisa V.; Hall, Jennifer R.; Ibrahim, Khadeejah; Chandrasekaran, Hema; Caldwell, Douglas A.; Van Cleve, Jeffrey E.;