Deconvolution methods for mitigation of transverse blurring in optical coherence tomography.

Imaging resolution in optical coherence tomography (OCT) is a key determinant for acquiring clinically useful optical biopsies of tissues. In contrast to light or confocal microscopy, the axial and transverse resolutions in OCT are independent and each can be analyzed individually. A method for mitigating transverse blurring and the apparent loss of transverse resolution in OCT by means of Gaussian beam deconvolution is presented. Such a method provides better representation of a specimen by using known physical parameters of a lens. To implement this method, deconvolution algorithms based on a focal-dependent kernel are investigated. First, the direct inverse problem is investigated using two types of regularization, truncated singular value decomposition, and Tikhonov. Second, an iterative expectation maximization algorithm, the Richardson-Lucy algorithm, with a beam-width-dependent iteration scheme is developed. A dynamically iterative Richardson-Lucy algorithm can reduce transverse blurring by providing an improvement in the transverse point-spread-function for sparse scattering samples in regions up to two times larger than the confocal region of the lens. These deblurring improvements inside and outside of the confocal region, which are validated experimentally, are possible without introducing new optical imaging hardware or acquiring multiple images of the same specimen. Implementation of this method in sparse scattering specimens, such as engineered tissues, has the potential to improve cellular detection and categorization.     

Application of parallelized analogical planning to engineering design

Analogical planning provides a means of solving engineering problems where other machine learning methods fail. Unlike many machine learning paradigms, analogy does not require numerous previous examples or a rich domain theory. Instead, analogical planners adapt knowledge of solved problems in similar domains to the current problem. Unfortunately, the analogical planning task is an expensive one. While the process of forming correspondences between a known problem and a new problem is complex, the problem of selecting a base case for the analogy is virtually intractable.This paper addresses the issue of efficiently forming analogical plans. The Anagram planning system is described, which takes advantage of the massively parallel architecture of the Connection Machine to perform base selection and map formation. Anagram provides a tractable solution to analogical planning, with a complexity that is sublinear in the size of the plans.This paper describes the Anagram system and its parallel algorithms. The paper also presents theoretical analyses and empirical results of testing the system on a large database of plans from the domain of automatic programming.     

Application of fiber optic sensors to fracture mechanics problems

An experimental study is conducted to show the application of fiber optic sensors to fracture mechanics problems. Mode I stress intensity factors are obtained using single mode optical fibers in single edge notched specimens fabricated from aluminium. A Mach–Zehnder interferometric set up is used during the experiments. The experimental results compare well with theoretical predictions.     

The Effect of Ozone Gas-Liquid Contacting Conditions in a Static Mixer on Microorganism Reduction

The effect of gas-liquid contacting conditions in a static mixer on ozone transfer efficiency and reduction of Bacillus subtilis spores was studied in an experimental ozone contactor. An empirical mathematical model was developed that related the transfer efficiency in the experimental system to the superficial liquid velocity in the mixer, the gas-liquid flow rate ratio and the height of the down-stream bubble column. Spore reduction was determined primarily by the dissolved ozone concentration-time (C_avgt_m) product in the reactive flow segment and was independent of the gas-liquid contacting conditions in the static mixer. In an integrated ozone contacting system, the static mixer should be designed to maximize ozone mass transfer while the reactive flow segment should be designed for efficient microorganism reduction.     

Key processing with control vectors

A method is presented for controlling cryptographic key usage based on control vectors. Each cryptographic key has an associated control vector that defines the permitted uses of the key within the cryptographic system. At key generation, the control vector is cryptographically coupled to the key by way of a special encryption process. Each encrypted key and control vector are stored and distributed within the cryptographic system as a single token. Decryption of a key requires respecification of the control vector. As part of the decryption process, the cryptographic hardware verifies that the requested use of the key is authorized by the control vector. This article focuses mainly on the use of control vectors in cryptosystems based on the Data Encryption Algorithm.     

Optical properties of amorphous carbon thin films prepared by plasma deposition in a graphite hollow cathode

Carbon films have been produced using a graphite hollow cathode and an r.f. plasma of hydrogen or hydrogen and argon. No hydrocarbon gas was used. The films were subjected to heat treatments up to 700 °C in air. The optical properties of the films were studied using Fourier transform IR, UV-visible, Raman, ellipsometry and photoluminescence techniques before and after the annealing. Films prepared without argon have a narrower band gap and a different photoluminescence response from films prepared with argon. The index of refraction was seen to have values between 1.7 and 2.2 depending on the preparation conditions. The optical band gap of the films was generally greater than 2 eV and the annealing process both increased the gap and reduced the density of states responsible for the large photoluminescence signal.     

Cellular automata model of gravity-driven granular flows

A cellular automata model is used to simulate a variety of granular chute flows. The model is tested against several case studies: flow down a chute, flow past an obstacle, chute flow in which complex, counter-rotating vortices result in streamwise surface stripes and flow near a boundary. The model successfully reproduces experimental observations in all of these cases. These results lead us to propose that simple, rule-based, models such as this can improve our detailed understanding of dynamics and flow within an opaque granular bed.     

Flaw density examinations of a clad boiling water reactor pressure vessel segment

As part of the Oak Ridge National Laboratory's Heavy-Section Steel Technology Program, studies have been conducted to determine flaw density in a section of reactor pressure vessel cut from the Hope Creek Unit 2 vessel. This boiling water reactor vessel was never in service. One objective was to evaluate the approximate 0.7- by 3-m (2- by 10-ft) segment of the vessel provided using ultrasonic flaw detection methods performed with both ASME Code techniques and supplemental ultrasonic methods. A second objective was to evaluate the inner surface stainless steel cladding for cracks with a high sensitivity penetrant examination. Both objectives were successfully completed. Five Code-recordable indications were detected ultrasonically; however, all were found to be anomalies associated with the cladding. One flaw was detected by the supplemental ultrasonic tests, and it was analyzed destructively. This flaw was pipelike indication, about 20 mm (0.8 in.) long extending along the length of the longitudinal weld in which it was located and was about 20 mm below the cladding surface. The flaw had a through-wall dimension (or length) of about 6 mm (0.24 in.) for an approximate 3-mm (0.1-in.) distance along the 20-mm major length. No flaws were detected by the penetrant examination of the cladding surface.