11,537 research outputs found
Image Encryption Based on Diffusion and Multiple Chaotic Maps
In the recent world, security is a prime important issue, and encryption is
one of the best alternative way to ensure security. More over, there are many
image encryption schemes have been proposed, each one of them has its own
strength and weakness. This paper presents a new algorithm for the image
encryption/decryption scheme. This paper is devoted to provide a secured image
encryption technique using multiple chaotic based circular mapping. In this
paper, first, a pair of sub keys is given by using chaotic logistic maps.
Second, the image is encrypted using logistic map sub key and in its
transformation leads to diffusion process. Third, sub keys are generated by
four different chaotic maps. Based on the initial conditions, each map may
produce various random numbers from various orbits of the maps. Among those
random numbers, a particular number and from a particular orbit are selected as
a key for the encryption algorithm. Based on the key, a binary sequence is
generated to control the encryption algorithm. The input image of 2-D is
transformed into a 1- D array by using two different scanning pattern (raster
and Zigzag) and then divided into various sub blocks. Then the position
permutation and value permutation is applied to each binary matrix based on
multiple chaos maps. Finally the receiver uses the same sub keys to decrypt the
encrypted images. The salient features of the proposed image encryption method
are loss-less, good peak signal-to-noise ratio (PSNR), Symmetric key
encryption, less cross correlation, very large number of secret keys, and
key-dependent pixel value replacement.Comment: 14 pages,9 figures and 5 tables;
http://airccse.org/journal/jnsa11_current.html, 201
Digital Offset Calibration of an OPAMP Towards Improving Static Parameters of 90 nm CMOS DAC
In this paper, an on-chip self-calibrated 8-bit R-2R digital-to-analog converter (DAC) based on digitally compensated input offset of the operational amplifier (OPAMP) is presented. To improve the overall DAC performance, a digital offset cancellation method was used to compensate deviations in the input offset voltage of the OPAMP caused by process variations. The whole DAC as well as offset compensation circuitry were designed in a standard 90 nm CMOS process. The achieved results show that after the self-calibration process, the improvement of 48% in the value of DAC offset error is achieved
MIRC-X: a highly-sensitive six telescope interferometric imager at the CHARA Array
MIRC-X (Michigan InfraRed Combiner-eXeter) is a new highly-sensitive
six-telescope interferometric imager installed at the CHARA Array that provides
an angular resolution equivalent of up to a 330 m diameter baseline telescope
in J and H band wavelengths ( milli-arcseconds). We
upgraded the original MIRC (Michigan InfraRed Combiner) instrument to improve
sensitivity and wavelength coverage in two phases. First, a revolutionary
sub-electron noise and fast-frame rate C-RED ONE camera based on a SAPHIRA
detector was installed. Second, a new-generation beam combiner was designed and
commissioned to (i) maximize sensitivity, (ii) extend the wavelength coverage
to J-band, and (iii) enable polarization observations. A low-latency and
fast-frame rate control software enables high-efficiency observations and
fringe tracking for the forthcoming instruments at CHARA Array. Since mid-2017,
MIRC-X has been offered to the community and has demonstrated best-case H-band
sensitivity down to 8.2 correlated magnitude. MIRC-X uses single-mode fibers to
coherently combine light of six telescopes simultaneously with an image-plane
combination scheme and delivers a visibility precision better than 1%, and
closure phase precision better than . MIRC-X aims at (i) imaging
protoplanetary disks, (ii) detecting exoplanets with precise astrometry, and
(iii) imaging stellar surfaces and star-spots at an unprecedented angular
resolution in the near-infrared. In this paper, we present the instrument
design, installation, operation, and on-sky results, and demonstrate the
imaging and astrometric capability of MIRC-X on the binary system Peg.
The purpose of this paper is to provide a solid reference for studies based on
MIRC-X data and to inspire future instruments in optical interferometry.Comment: 31 pages, 29 figures, accepted for publication in The Astronomical
Journa
Comparative study of manufacturing techniques for coronagraphic binary pupil masks: masks on substrates and free-standing masks
We present a comparative study of the manufacture of binary pupil masks for
coronagraphic observations of exoplanets. A checkerboard mask design, a type of
binary pupil mask design, was adopted, and identical patterns of the same size
were used for all the masks in order that we could compare the differences
resulting from the different manufacturing methods. The masks on substrates had
aluminum checkerboard patterns with thicknesses of 0.1/0.2/0.4/0.8/1.6m
constructed on substrates of BK7 glass, silicon, and germanium using
photolithography and chemical processes. Free-standing masks made of copper and
nickel with thicknesses of 2/5/10/20m were also realized using
photolithography and chemical processes, which included careful release from
the substrate used as an intermediate step in the manufacture. Coronagraphic
experiments using a visible laser were carried out for all the masks on BK7
glass substrate and the free-standing masks. The average contrasts were
8.4, 1.2, and 1.2 for the masks on
BK7 substrates, the free-standing copper masks, and the free-standing nickel
masks, respectively. No significant correlation was concluded between the
contrast and the mask properties. The high contrast masks have the potential to
cover the needs of coronagraphs for both ground-based and space-borne
telescopes over a wide wavelength range. Especially, their application to the
infrared space telescope, SPICA, is appropriate.Comment: 21 pates, 12 figures, 2 tables, accepted to PAS
Index to 1984 NASA Tech Briefs, volume 9, numbers 1-4
Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1984 Tech B Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences
A New ELISA Using the ANANAS Technology Showing High Sensitivity to diagnose the Bovine Rhinotracheitis from Individual Sera to Pooled Milk
Diagnostic tests for veterinary surveillance programs should be efficient, easy to use and, possibly, economical. In this context, classic Enzyme linked ImmunoSorbent Assay (ELISA) remains the most common analytical platform employed for serological analyses. The analysis of pooled samples instead of individual ones is a common procedure that permits to certify, with one single test, entire herds as "disease-free". However, diagnostic tests for pooled samples need to be particularly sensitive, especially when the levels of disease markers are low, as in the case of anti-BoHV1 antibodies in milk as markers of Infectious Bovine Rhinotracheitis (IBR) disease. The avidin-nucleic-acid-nanoassembly (ANANAS) is a novel kind of signal amplification platform for immunodiagnostics based on colloidal poly-avidin nanoparticles that, using model analytes, was shown to strongly increase ELISA test performance as compared to monomeric avidin. Here, for the first time, we applied the ANANAS reagent integration in a real diagnostic context. The monoclonal 1G10 anti-bovine IgG1 antibody was biotinylated and integrated with the ANANAS reagents for indirect IBR diagnosis from pooled milk mimicking tank samples from herds with IBR prevalence between 1 to 8%. The sensitivity and specificity of the ANANAS integrated method was compared to that of a classic test based on the same 1G10 antibody directly linked to horseradish peroxidase, and a commercial IDEXX kit recently introduced in the market. ANANAS integration increased by 5-fold the sensitivity of the 1G10 mAb-based conventional ELISA without loosing specificity. When compared to the commercial kit, the 1G10-ANANAS integrated method was capable to detect the presence of anti-BHV1 antibodies from bulk milk of gE antibody positive animals with 2-fold higher sensitivity and similar specificity. The results demonstrate the potentials of this new amplification technology, which permits improving current classic ELISA sensitivity limits without the need for new hardware investments
MYSTIC: Michigan Young STar Imager at CHARA
We present the design for MYSTIC, the Michigan Young STar Imager at CHARA.
MYSTIC will be a K-band, cryogenic, 6-beam combiner for the Georgia State
University CHARA telescope array. The design follows the image-plane
combination scheme of the MIRC instrument where single-mode fibers bring
starlight into a non-redundant fringe pattern to feed a spectrograph. Beams
will be injected in polarization-maintaining fibers outside the cryogenic dewar
and then be transported through a vacuum feedthrough into the ~220K cold volume
where combination is achieved and the light is dispersed. We will use a C-RED
One camera (First Light Imaging) based on the eAPD SAPHIRA detector to allow
for near-photon-counting performance. We also intend to support a 4-telescope
mode using a leftover integrated optics component designed for the VLTI-GRAVITY
experiment, allowing better sensitivity for the faintest targets. Our primary
science driver motivation is to image disks around young stars in order to
better understand planet formation and how forming planets might influence disk
structures.Comment: Presented at the 2018 SPIE Astronomical Telescopes + Instrumentation,
Austin, Texas, US
Index to NASA Tech Briefs, January - June 1966
Index to NASA technological innovations for January-June 196
Influence of Sulfur-Containing Diamino Acid Structure on Covalently Crosslinked Copolypeptide Hydrogels.
Biologically occurring non-canonical di-α-amino acids were converted into new di-N-carboxyanhydride (di-NCA) monomers in reasonable yields with high purity. Five different di-NCAs were separately copolymerized with tert-butyl-l-glutamate NCA to obtain covalently crosslinked copolypeptides capable of forming hydrogels with varying crosslinker density. Comparison of hydrogel properties with residue structure revealed that different di-α-amino acids were not equivalent in crosslink formation. Notably, l-cystine was found to produce significantly weaker hydrogels compared to l-homocystine, l-cystathionine, and l-lanthionine, suggesting that l-cystine may be a sub-optimal choice of di-α-amino acid for preparation of copolypeptide networks. The di-α-amino acid crosslinkers also provided different chemical stability, where disulfide crosslinks were readily degraded by reduction, and thioether crosslinks were stable against reduction. This difference in response may provide a means to fine tune the reduction sensitivity of polypeptide biomaterial networks
NASA SBIR abstracts of 1991 phase 1 projects
The objectives of 301 projects placed under contract by the Small Business Innovation Research (SBIR) program of the National Aeronautics and Space Administration (NASA) are described. These projects were selected competitively from among proposals submitted to NASA in response to the 1991 SBIR Program Solicitation. The basic document consists of edited, non-proprietary abstracts of the winning proposals submitted by small businesses. The abstracts are presented under the 15 technical topics within which Phase 1 proposals were solicited. Each project was assigned a sequential identifying number from 001 to 301, in order of its appearance in the body of the report. Appendixes to provide additional information about the SBIR program and permit cross-reference of the 1991 Phase 1 projects by company name, location by state, principal investigator, NASA Field Center responsible for management of each project, and NASA contract number are included
- …