Volume holographic imaging in transmission geometry

We address the performance of transmission geometry volume holograms as depth-selective imaging elements. We consider two simple implementations using holograms recorded with spherical and plane beams. We derive the point-spread function (PSF) of these systems using volume diffraction theory and use the PSF to estimate depth resolution. Furthermore, we show that appropriately designed objective optics can significantly improve the depth resolution or the working distance of plane-wave reference holographic imaging systems. These results are confirmed experimentally and demonstrated for objects with millimeter axial features, imaged from the 5- to 50-cm range.     

Design,fabrication and testing of elliptical crystal bender for the EXAFS beam-line at INDUS-II synchrotron source

An extended X-ray absorption fine structure (EXAFS) beam-line for X-ray absorption studies using energy dispersive geometry and position sensitive detector is being developed for the INDUS-II synchrotron source. The optical design of the beam-line has been completed based on the working principle that a single crystal bent in the shape of an ellipse by a crystal bender would act as a dispersing as well as focusing element. The heart of the beam-line is the crystal bender which has been designed on the basis of the principle of four-point bending and has been fabricated indigenously. The crystal bender is capable of producing pre-defined elliptical curvature on a crystal surface by applying different couples at the two-ends of the crystal which has variable width along its length. The focusing property of the crystal bender has been tested using a laser source and has been compared with the theoretically simulated results.     

Design and development of the AHWR—the Indian thorium fuelled innovative nuclear reactor

India has chalked out a nuclear power program based on its domestic resource position of uranium and thorium. The first stage started with setting up the Pressurized Heavy Water Reactors (PHWR) based on natural uranium and pressure tube technology. In the second phase, the fissile material base will be multiplied in Fast Breeder Reactors using the plutonium obtained from the PHWRs. Considering the large thorium reserves in India, the future nuclear power program will be based on thorium–²³³U fuel cycle. However, there is a need for the timely development of thorium-based technologies for the entire fuel cycle. The Advanced Heavy Water Reactor (AHWR) has been designed to fulfill this need. The AHWR is a 300 MW_e, vertical, pressure tube type, heavy water moderated, boiling light water cooled natural circulation reactor. The fuel consists of (Th–Pu)O₂ and (Th–²³³U)O₂ pins. The fuel cluster is designed to generate maximum energy out of ²³³U, which is bred in situ from thorium and has a slightly negative void coefficient of reactivity. For the AHWR, the well-proven pressure tube technology has been adopted and many passive safety features, consistent with the international trend, have been incorporated. A distinguishing feature which makes this reactor unique, from other conventional nuclear power reactors is the fact that it is designed to remove core heat by natural circulation, under normal operating conditions, eliminating the need of pumps. In addition to this passive feature, several innovative passive safety systems have been incorporated in the design, for decay heat removal under shut down condition and mitigation of postulated accident conditions. The design of the reactor has progressively undergone modifications and improvements based on the feedbacks from the analytical and the experimental R&D. This paper gives the details of the current design of the AHWR.     

Long-term stability and performance characteristics of crystal quartz gauge at high pressures and temperatures

Good long-term stability of high precision quartz pressure sensors is necessary for various applications ranging from pressure transient analysis to permanent monitoring systems for optimal reservoir management in the petroleum industry. A crystal quartz gauge (CQG(1 )) is a dual-mode, thickness-shear, quartz pressure sensor that has been used in oil field services for the past 8 years. High accuracy, resolution, and fast response time of this sensor enable a reliable estimate of formation permeability and oil/water interfaces in reservoirs that help reduce the overall cost of oil and gas production. The sensing resonator characteristics can be described in terms of equivalent circuit parameters (motional resistance and capacitance), resonator-Q and the short-term frequency stability of both the B- and C-modes of vibrations at various temperatures. The pressure reading errors of manufactured gauges are less than 8.89 kPa (1 psi) (plus 0.01% of the reading because of the uncertainty of the dead-weight tester). The pressure resolution is better than 20.7 Pa (0.003 psi) over a 1-s gate time. An extremely effective dynamic compensation algorithm yields corrected pressure readings with a very fast response time as short as a strain-gauge-based pressure transducer while retaining the high performance of a quartz gauge. Recent long-term stability tests of CBGs show a negligibly small drift of the order of a few tenths of 1 psi (0.1 psi=689 Pa) at 103 MPa (15 kpsi) and 175 degrees C for a period of more than 1 yr. These results confirm that the CQG characteristics exceed the demanding specifications for both the well tests and permanent monitoring systems.     

Non‐linear sloshing in partially liquid filled containers with baffles

A finite element method is used for computing the non‐linear sloshing response of liquid in a two‐dimensional rigid rectangular tank with rigid baffles. The potential formulation is considered for the liquid domain and a mixed Eulerian–Langrangian scheme is adopted. The solution is obtained by the Galerkin method. The fourth‐order Runge–Kutta method is employed to advance the solution in the time domain. A regridding technique is applied to the free surface of the liquid, which effectively eliminates the numerical instabilities without the use of artificial smoothing. Through the comparison with the available results for the rectangular tank without baffle, the validity of the present formulation is checked and then extended to the solution of tanks with rigid baffles. The effects of baffle parameters such as position, dimension and numbers on the non‐linear sloshing response are examined. The present numerical solution procedure is also applied to the non‐linear sloshing problems in a circular cylindrical container with annular baffle. Copyright © 2006 John Wiley & Sons, Ltd.     

Effect of Organoclay on the Morphology and Properties of Poly(propylene)/Poly[(butylene succinate)‐co‐adipate] Blends

The effect of organically modified clay on the morphology and properties of poly(propylene) (PP) and poly[(butylene succinate)‐co‐adipate] (PBSA) blends is studied. Virgin and organoclay modified blends were prepared by melt‐mixing of PP, PBSA and organoclay in a batch‐mixer at 190 °C. Scanning electron microscopy studies revealed a significant change in morphology of PP/PBSA blend in the presence of organoclay. The state of dispersion of silicate layers in the blend matrix was characterized by X‐ray diffraction and transmission electron microscopic observations. Dynamic mechanical analysis showed substantial improvement in flexural storage modulus of organoclay‐modified blends with respect to the neat polymer matrices or unmodified blends. Tensile properties of virgin blends also improved in the presence of organoclay. Thermal stability of virgin blends in air atmosphere dramatically improved after modification with organoclay. The effect of organoclay on the melt‐state liner viscoelastic properties of virgin blends was also studied. The non‐isothermal crystallization behavior of homopolymers, virgin, and organoclay‐modified blends were studied by differential scanning calorimeter. The effect of incorporation of organoclay on the cold crystallization behavior of PP/PBSA blends is also reported.

     

SEM and raman spectroscopy of multiwalled carbon nanotubes grown by novel technique of ash supported catalysts

Multiwalled carbon nanotubes (MWCNTs) were grown on a novel ASC catalyst and on catalyst deposited by SCC method on silicon wafer, by thermal CVD of acetylene. Fe and Ni were used as catalyst for ASC. Samples were analyzed by SEM and Raman spectroscopy. SEM analysis shows that CNTs grown on ASC have narrower diameter distribution (64+/-6 nm) compared to CNTs grown on SCC (67+/-10.5 nm). However, SEM and Raman spectroscopy studies show CNTs grown on SCC are of better quality. The same samples were studied after standard purification procedure of oxidation after annealing at high temperatures. SEM and Raman spectroscopy show that overall quality of ensemble of CNTs has improved. After annealing, diameter decreases for larger diameter approximately 200 nm nanotubes while it increases for CNTs of smaller diameter approximately 70 nm. To explain the increase in diameter of approximately 70 nm CNT's, a phenomenological model has been proposed. The results of Raman spectroscopy and SEM corroborate the proposed model.     

Segmentation of Pipe Images for Crack Detection in Buried Sewers

Abstract:   Assessing the condition of underground pipelines such as water lines, sewer pipes, and telecommunication conduits in an automated and reliable manner is vital to the safety and maintenance of buried public infrastructure. To fully automate condition assessment, it is necessary to develop robust data analysis and interpretation systems for defects in buried pipes. This article presents the development of an automated data analysis system for detecting defects in sanitary sewer pipelines. We propose a three-step method to identify and extract cracks from contrast enhanced pipe images. This method is based on mathematical morphology and curvature evaluation that detects crack-like patterns in a noisy pipe camera scanned image. As cracks are the most common defects in pipes and are indicative of the residual structural strength of the pipe, they are the focus of this study. This article discusses its implementation on 225 pipe images taken from different cities in North America and shows that the system performs very well under a variety of pipe conditions.     

Ceramic Filter for Small System Drinking Water Treatment: Evaluation of Membrane Pore Size and Importance of Integrity Monitoring

Ceramic filtration has recently been identified as a promising technology for drinking water treatment in households and small communities. This paper summarizes the results of a pilot-scale study conducted at the U.S. Environmental Protection Agency’s (EPA) Test & Evaluation (T&E) Facility in Cincinnati on two ceramic filtration cartridges with pore sizes of 0.05 and 0.01?μm to evaluate their ability to remove turbidity and microbiological contaminants such as bacteria [Bacillus subtilis ( ≈ 1.0?μm) and Escherichia coli ( ≈ 1.4?μm)], Cryptosporidium oocysts (4–6?μm), polystyrene latex (PSL) beads (2.85?μm) (a surrogate for Cryptosporidium), and MS2 bacteriophage ( ≈ 0.02?μm) (a surrogate for enteric viruses). The results demonstrated that the relatively tighter 0.01-μm cartridge performed better than the 0.05-μm cartridge in removing all the biological contaminants and surrogates. For turbidity removal, the 0.01-μm cartridge performed slightly better than the 0.05-μm cartridge; however, the permeate rate in the 0.01-μm cartridge reduced rapidly at higher feed water turbidity levels indicating that a tighter membrane should only be used with adequate pretreatment or at a low feed water turbidity to prolong membrane life. Microbiological monitoring was identified as a more sensitive indirect integrity monitoring method than turbidity and particle count monitoring to ensure effective treatment of water by ceramic filtration. Both PSL beads and B. subtilis showed potential as effective surrogates for Cryptosporidium, with B. subtilis showing higher degree of conservatism. Any opinions expressed in this article are those of the writer(s) and do not necessarily reflect the official positions and policies of the EPA. Any mention of products or trade names does not constitute recommendation for use by EPA. This document has been reviewed in accordance with EPA’s peer and administrative review policies and approved for publication.