Eddy current characterization of small cracks using least square support vector machine

Science.gov (United States)

Chelabi, M.; Hacib, T.; Le Bihan, Y.; Ikhlef, N.; Boughedda, H.; Mekideche, M. R.

2016-04-01

Eddy current (EC) sensors are used for non-destructive testing since they are able to probe conductive materials. Despite being a conventional technique for defect detection and localization, the main weakness of this technique is that defect characterization, of the exact determination of the shape and dimension, is still a question to be answered. In this work, we demonstrate the capability of small crack sizing using signals acquired from an EC sensor. We report our effort to develop a systematic approach to estimate the size of rectangular and thin defects (length and depth) in a conductive plate. The achieved approach by the novel combination of a finite element method (FEM) with a statistical learning method is called least square support vector machines (LS-SVM). First, we use the FEM to design the forward problem. Next, an algorithm is used to find an adaptive database. Finally, the LS-SVM is used to solve the inverse problems, creating polynomial functions able to approximate the correlation between the crack dimension and the signal picked up from the EC sensor. Several methods are used to find the parameters of the LS-SVM. In this study, the particle swarm optimization (PSO) and genetic algorithm (GA) are proposed for tuning the LS-SVM. The results of the design and the inversions were compared to both simulated and experimental data, with accuracy experimentally verified. These suggested results prove the applicability of the presented approach.

Thermal Shock In Periodic Edge-Cracked Plate Supported By Elastic Foundation

OpenAIRE

Abd El-Fattah A. Rizk

2012-01-01

The study of the transient thermal stress problem for a periodic edge cracks in an elastic plate on an elastic foundations is investigated. This study may also be applied for circumferentially periodic cracked hollow cylinder under transient thermal stresses. Based on previous studies, the cylindrical shell may be modeled by a plate on an elastic foundation. The thermal stresses are generated due to sudden convective cooling on the boundary containing the edge cracks while the other boundary ...

Analyzing the effect of carbon fiber reinforced polymer on the crashworthiness of aluminum square hollow beam for crash box application

Science.gov (United States)

Raman, R.; Jayanth, K.; Sarkar, I.; Ravi, K.

2017-11-01

Crashworthiness of a material is a measure of its ability to absorb energy during a crash. A well-designed crash box is instrumental in protecting the costly vehicle components. A square, hollow, hybrid beam of aluminum/CFRP was subjected to dynamic axial load to analyze the effect of five different lay-up sequences on its crashworthiness. The beam was placed between two plates. Boundary conditions were imposed on them to simulate a frontal body crash test model. Modeling and dynamic analysis of composite structures was done on ABAQUS. Different orientation of carbon fibers varies the crashworthiness of the hybrid beam. Addition of CFRP layer showed clear improvement in specific energy absorption and crush force efficiency compared to pure aluminum beam. Two layers of CFRP oriented at 90° on Aluminum showed 52% increase in CFE.

Regression model of support vector machines for least squares prediction of crystallinity of cracking catalysts by infrared spectroscopy

International Nuclear Information System (INIS)

Comesanna Garcia, Yumirka; Dago Morales, Angel; Talavera Bustamante, Isneri

2010-01-01

The recently introduction of the least squares support vector machines method for regression purposes in the field of Chemometrics has provided several advantages to linear and nonlinear multivariate calibration methods. The objective of the paper was to propose the use of the least squares support vector machine as an alternative multivariate calibration method for the prediction of the percentage of crystallinity of fluidized catalytic cracking catalysts, by means of Fourier transform mid-infrared spectroscopy. A linear kernel was used in the calculations of the regression model. The optimization of its gamma parameter was carried out using the leave-one-out cross-validation procedure. The root mean square error of prediction was used to measure the performance of the model. The accuracy of the results obtained with the application of the method is in accordance with the uncertainty of the X-ray powder diffraction reference method. To compare the generalization capability of the developed method, a comparison study was carried out, taking into account the results achieved with the new model and those reached through the application of linear calibration methods. The developed method can be easily implemented in refinery laboratories

Fabrication of polymeric hollow nanospheres, hollow nanocubes and hollow plates

Science.gov (United States)

Cheng, Daming; Xia, Haibing; Chan, Hardy Sze On

2006-03-01

A facile strategy for fabricating polypyrrole-chitosan (PPy-CS) hollow nanostructures with different shapes (sphere, cube and plate) and a wide range of sizes (from 35 to 600 nm) is described. These hollow structures have been fabricated using silver bromide as a single template material for polymer nucleation and growth. PPy-CS hollow nanostructures are formed by reaction with an etching agent to remove the core. These hollow nanostructures have been extensively characterized using various techniques such as TEM, FT-IR, UV-vis, and XRD.

Mechanism of the formation of hollow spherical granules using a high shear granulator.

Science.gov (United States)

Asada, Takumi; Nishikawa, Mitsunori; Ochiai, Yasushi; Noguchi, Shuji; Kimura, Shin-Ichiro; Iwao, Yasunori; Itai, Shigeru

2018-05-30

Recently, we have developed a novel granulation technology to manufacture hollow spherical granules (HSGs) for controlled-release formulations; however, the mechanism of the granulation is still unclear. The aim of this study is to determine the mechanism of the formation of the HSGs using a high shear granulator. Samples of granulated material were collected at various times during granulation and were investigated using scanning electron microscope and X-ray computed tomography. It was observed that the granulation proceeded by drug layering to the polymer, followed by formation of a hollow in the granule. In addition, it was also found that generation of a crack in the adhered drug layer and air flow into the granules might be involved in forming the hollow in the structure. Observation of the granulation of formulations with different types of drugs and polymers indicated that negative pressure in the granules occurred and the granules caved in when the hollow was formed. The hollow-forming speed and the shell density of the hollow granules depended on the particular drug and polymer. Taken together, the granulation mechanism of HSGs was determined and this information will be valuable for HSGs technology development. Copyright © 2018 Elsevier B.V. All rights reserved.

Crack mode and life of Ti-6Al-4V under multiaxial low cycle fatigue

Directory of Open Access Journals (Sweden)

Takamoto Itoh

2015-10-01

Full Text Available This paper studies multiaxial low cycle fatigue crack mode and failure life of Ti-6Al-4V. Stress controlled fatigue tests were carried out using a hollow cylinder specimen under multiaxial loadings of λ=0, 0.4, 0.5 and 1 of which stress ratio R=0 at room temperature. λ is a principal stress ratio and is defined as λ=II/I, where I and II are principal stresses of which absolute values take the largest and middle ones, respectively. Here, the test at λ=0 is a uniaxial loading test and that at λ=1 an equi-biaxial loading test. A testing machine employed is a newly developed multiaxial fatigue testing machine which can apply push-pull and reversed torsion loadings with inner pressure onto the hollow cylinder specimen. Based on the obtained results, this study discusses evaluation of the biaxial low cycle fatigue life and crack mode. Failure life is reduced with increasing λ induced by cyclic ratcheting. The crack mode is affected by the surface condition of cut-machining and the failure life depends on the crack mode in the multiaxial loading largely.

Surface flaw in a thermally shocked hollow cylinder

International Nuclear Information System (INIS)

Kobayashi, A.S.; Emery, A.F.; Polvanich, N.; Love, W.J.

1975-01-01

The objective of this paper is to illustrate a procedure for estimating the stress intensity factors of a semi-elliptical crack located in the inner or outer surface of a thermally shocked hollow cylinder. The first step in this procedure is to estimate the transient thermal elastic stresses induced by sudden cooling of an uncracked cylinder by numerically evaluating standard heat transfer and thermal stress formulae. The stresses at the location of the crack surface in the uncracked cylinder are eliminated by the method of superposition in order to obtain a stress free crack surface. The stress intensity factors are then determined by a judicious use of two sets of solutions, one set involving stress intensity factors for a semi-elliptical crack in a flat plate and subjected to a polynomial distribution of pressure loading, and another set involving single-edge notched plates with prescribed edge-displacements and single-edge internally or externally notched cylinders with thermal shock loading. The former solutions are determined by the alternating technique in three-dimensional fracture mechanics with a fourth order polynomial pressure distribution on the crack surface where both the front and back surface effects are accounted for. The latter solutions involve two-dimensional finite element solutions of single-edge notched plates with prescribed edge-displacements and single-edge notched cylinders with thermal shock loading. By comparing these two two-dimensional solutions, an estimate of the effect of the cylindrical curvature on an edge-cracked plate is obtained. The combination of these two sets of solutions thus yields an estimate of the stress intensity factor in an internal and external semi-elliptical crack in a thermally shocked cylinder

On the measurement of the crack tip stress field as a means of determining Delta K(sub eff) under conditions of fatigue crack closure

Science.gov (United States)

Wallhead, Ian R.; Edwards, Lyndon; Poole, Peter

1994-01-01

The optical method of caustics has been successfully extended to enable stress intensity factors as low as 1MPa square root of m to be determined accurately for central fatigue cracks in 2024-T3 aluminium alloy test panels. The feasibility of using this technique to study crack closure, and to determine the effective stress intensity factor range, Delta K(sub eff), has been investigated. Comparisons have been made between the measured values of stress intensity factor, K(sub caus), and corresponding theoretical values, K(sub theo), for a range of fatigue cracks grown under different loading conditions. The values of K(sub caus) and K(sub theo) were in good agreement at maximum stress, where the cracks are fully open, while K(sub caus) exceeded K(sub theo) at minimum stress, due to crack closure. However, the levels of crack closure and values of Delta K(sub eff) obtained could not account for the variations of crack growth rate with loading conditions. It is concluded that the values of Delta K(sub eff), based on caustic measurements in a 1/square root of r stress field well outside the plastic zone, do not fully reflect local conditions which control crack tip behavior.

Universal Shapes formed by Interacting Cracks

Science.gov (United States)

Fender, Melissa; Lechenault, Frederic; Daniels, Karen

2011-03-01

Brittle failure through multiple cracks occurs in a wide variety of contexts, from microscopic failures in dental enamel and cleaved silicon to geological faults and planetary ice crusts. In each of these situations, with complicated curvature and stress geometries, pairwise interactions between approaching cracks nonetheless produce characteristically curved fracture paths known in the geologic literature as en passant cracks. While the fragmentation of solids via many interacting cracks has seen wide investigation, less attention has been paid to the details of individual crack-crack interactions. We investigate the origins of this widely observed crack pattern using a rectangular elastic plate which is notched on each long side and then subjected to quasistatic uniaxial strain from the short side. The two cracks propagate along approximately straight paths until the pass each other, after which they curve and release a lenticular fragment. We find that, for materials with diverse mechanical properties, the shape of this fragment has an aspect ratio of 2:1, with the length scale set by the initial cracks offset s and the time scale set by the ratio of s to the pulling velocity. The cracks have a universal square root shape, which we understand by using a simple geometric model and the crack-crack interaction.

Eddy current system for inspection of train hollow axles

Energy Technology Data Exchange (ETDEWEB)

Chady, Tomasz; Psuj, Grzegorz; Sikora, Ryszard; Kowalczyk, Jacek; Spychalski, Ireneusz [Department of Electrical and Computer Engineering, Faculty of Electrical Engineering, West Pomeranian University of Technology, Szczecin (Poland)

2014-02-18

The structural integrity of wheelsets used in rolling stock is of great importance to the safety. In this paper, electromagnetic system with an eddy current transducer suitable for the inspection of hollow axles have been presented. The transducer was developed to detect surface braking defects having depth not smaller than 0.5 mm. Ultrasound technique can be utilized to inspect the whole axle, but it is not sufficiently sensitive to shallow defects located close to the surface. Therefore, the electromagnetic technique is proposed to detect surface breaking cracks that cannot be detected by ultrasonic technique.

Modeling of multibranched crosslike crack growth

International Nuclear Information System (INIS)

Canessa, E.; Tanatar, B.

1991-06-01

Multibranched crosslike crack patterns formed in concentrically loaded square plates are studied in terms of fractal geometry, where the associated fractal dimension d f is calculated for their characterization. We apply simplest deterministic and stochastic approaches at a phenomenological level in an attempt to find generic features as guidelines for future experimental and theoretical work. The deterministic model for fracture propagation we apply, which is a variant of the discretized Laplace approach for randomly ramified fractal cracks proposed by Takayasu, reproduces the basic ingredients of observed complex fracture patters. The stochastic model, although is not strictly a model for crack propagation, is based on diffusion-limited aggregation (DLA) for fractal growth and produces slightly more realistic assessment of the crosslike growth of the cracks in asymmetric multibranches. Nevertheless, this simple ad-hoc DLA-version for modeling the present phenomena as well as the deterministic approach for fracture propagation give fractal dimensionality for the fracture pattern in accord with our estimations made from recent experimental data. It is found that there is a crossover of two fractal dimensions, corresponding to the core (higher d f ) and multibranched crosslike (lower D f ) regions, that contains loops, that are interpreted as representing different symmetry regions within the square plates of finite size. (author). 26 refs, 5 figs

Thermal analysis of cracked bodies using finite element techniques

International Nuclear Information System (INIS)

Hellen, T.K.; Price, R.H.; Harrison, R.P.

1975-01-01

The paper develops the potential energy equation in terms of finite element theory including thermal loads. Following this, the energy release rate and consequently the stress intensity factors are derived. Considerations of the classical near crack tip equations are made and deficiencies with the popular substitution methods are highlighted. A method of removing these deficiencies is described. Various energy methods are reconsidered in terms of the role of the thermal energy contribution to the potential energy. These methods include work of crack closure, energy compliance and virtual crack extensions with no other change in nodal geometry, and therefore only requires the recalculation of the stiffness matrices of the crack tip elements. An example of a quadratic temperature gradient parallel to the crack plane in an edge cracked plate is described. Comparisons of the various finite element methods are made and generally show good agreement. A second application compares the virtual crack extension method with an approximate analytical solution in determining stress intensity factors for a thick hollow cylinder with an axial crack for various depths through the wall thickness and for different times. Initially the cylinder is at a uniform high temperature and is then subjected to a sustained cooling shock. Analytical solutions are available for temperature and stress distributions in the uncracked pipe. The stress intensity for a shallow crack in the early stages of the transient has been determined using a superposition procedure. Comparison of the analytical and computed results shows good agreement between the methods

Analysis of crack-formation in the shielding concrete of a TRIGA Mark II reactor

International Nuclear Information System (INIS)

Linsbauer, H.; Maydl, P.

1978-01-01

Within a short time after the start-up of the reactor several cracks appeared at the concrete surface and the number and width of the cracks had grown till now. Experimental and theoretical analysis were made in order to investigate the origin of the cracks and to prevent further crack increase. Crack movement was measured by inductive gages and simultaneously the temperature of the cooling water in the reactor tank at the top and at the bottom as well as the air and the concrete temperature were recorded. The calculations of the thermal stresses were made in two independent ways: 1. Analytically, simulating the shielding concrete as an infinite hollow cylinder of constant thickness and 2. Using the Finite Element method, for a better description of the geometry. It was concluded that the cracks of the shielding concrete are exclusively caused by the thermal stresses. The thermal insulation at the lower part of the shielding is not effective. The structural system of the shielding concrete as a monolithic block without joints produces automatically tensile stresses

Shapes formed by interacting cracks

Science.gov (United States)

Daniels, Karen

2012-02-01

Brittle failure through multiple cracks occurs in a wide variety of contexts, from microscopic failures in dental enamel and cleaved silicon to geological faults and planetary ice crusts. In each of these situations, with complicated stress geometries and different microscopic mechanisms, pairwise interactions between approaching cracks nonetheless produce characteristically curved fracture paths. We investigate the origins of this widely observed ``en passant'' crack pattern by fracturing a rectangular slab which is notched on each long side and subjected to quasi-static uniaxial strain from the short side. The two cracks propagate along approximately straight paths until they pass each other, after which they curve and release a lens-shaped fragment. We find that, for materials with diverse mechanical properties, each curve has an approximately square-root shape, and that the length of each fragment is twice its width. We are able to explain the origins of this universal shape with a simple geometrical model.

A linear least squares approach for evaluation of crack tip stress field parameters using DIC

Science.gov (United States)

Harilal, R.; Vyasarayani, C. P.; Ramji, M.

2015-12-01

In the present work, an experimental study is carried out to estimate the mixed-mode stress intensity factors (SIF) for different cracked specimen configurations using digital image correlation (DIC) technique. For the estimation of mixed-mode SIF's using DIC, a new algorithm is proposed for the extraction of crack tip location and coefficients in the multi-parameter displacement field equations. From those estimated coefficients, SIF could be extracted. The required displacement data surrounding the crack tip has been obtained using 2D-DIC technique. An open source 2D DIC software Ncorr is used for the displacement field extraction. The presented methodology has been used to extract mixed-mode SIF's for specimen configurations like single edge notch (SEN) specimen and centre slant crack (CSC) specimens made out of Al 2014-T6 alloy. The experimental results have been compared with the analytical values and they are found to be in good agreement, thereby confirming the accuracy of the algorithm being proposed.

Ultrasonic/surfactant assisted of CdS nano hollow sphere synthesis and characterization

International Nuclear Information System (INIS)

Rafati, Amir Abbas; Borujeni, Ahmad Reza Afraz; Najafi, Mojgan; Bagheri, Ahmad

2011-01-01

CdS hollow nanospheres with diameters ranging from 40 to 150 nm have been synthesized by a surfactant-assisted sonochemical route. The successful vesicle templating indicates that the outer leaflet of the bilayer is the receptive surface in the controlled growth of CdS nanoparticles which provide the unique reactor for the nucleation and mineralization growth of CdS nanoparticles. The CdS nanostructures obtained were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy and photoluminescence spectroscopy. Structural characterization of hollow CdS nanospheres indicates that these products packed with square subunits having sizes between 5 and 7 nm in diameter. The formation of the hollow nanostructure was explained by a vesicle template mechanism, in which sonication and surfactant play important roles. The band-edge emission and surface luminescence of the CdS nanoparticles were observed. -Research Highlights: → CdS hollow nanospheres with diameters of 40-150 nm were synthesized. → Nanoparticles were characterized by UV/Vis and photoluminescence. → Nanospheres are composed of smaller nanocrystals with the average size of 6.8 nm. → The band gap energy of the CdS nanoparticles is higher than its bulk value.

Improvement in the reliability of shells for light water reactors by manufacture from hollow ingots

International Nuclear Information System (INIS)

Bocquet, P.; Blondeau, R.; Poitrault, I.; Badeau, J.P.; Dumont, R.

1991-01-01

The problems associated to the segregation located at the inner surface and subsurface of heavy shell forgings used in nuclear light water reactors are presented. The effect of A segregation on cold or reheat cracking HAZ has conducted fabricators to use severe welding procedures with high preheat temperature and refining HAZ grain size sequences. For shells and rings, the hollow ingot as developed by CLI, with a good control of the location of the center line of segregation, is an excellent answer to these problems. The use of core shell forgings issued from this type of hollow ingots, free of segregation at the inner surface and subsurface area, contributes, by reducing the irradiation embrittlement effect, to increase the safety factor relatively to the risk of failure of the reactor. (orig.)

Hollow-in-Hollow Carbon Spheres for Lithium-ion Batteries with Superior Capacity and Cyclic Performance

International Nuclear Information System (INIS)

Zang, Jun; Ye, Jianchuan; Fang, Xiaoliang; Zhang, Xiangwu; Zheng, Mingsen; Dong, Quanfeng

2015-01-01

Highlights: • Hollow-in-hollow structured HIHCS was synthesized via a facile templating strategy. • The HCS core and hollow carbon shell constitute the hollow-in-hollow structure. • The HIHCS exhibited superior rate capability and cycle stability as anode material. • The excellent performance is attributed to the unique hollow-in-hollow structure. - Abstract: Hollow spheres structured materials have been intensively pursued due to their unique properties for energy storage. In this paper, hollow-in-hollow carbon spheres (HIHCS) with a multi-shelled structure were successfully synthesized using a facile hard-templating procedure. When evaluated as anode material for lithium-ion batteries, the resultant HIHCS anode exhibited superior capacity and cycling stability than HCS. It could deliver reversible capacities of 937, 481, 401, 304 and 236 mAh g −1 at current densities of 0.1 A g −1 , 1 A g −1 , 2 A g −1 , 5 A g −1 and 10 A g −1 , respectively. And capacity fading is not apparent in 500 cycles at 5 A g −1 . The excellent performance of the HIHCS anode is ascribed to its unique hollow-in-hollow structure and high specific surface area.

Experimental Study on Hygrothermal Deformation of External Thermal Insulation Cladding Systems with Glazed Hollow Bead

Directory of Open Access Journals (Sweden)

Houren Xiong

2016-01-01

Full Text Available This research analyzes the thermal and strain behavior of external thermal insulation cladding systems (ETICS with Glazed Hollow Beads (GHB thermal insulation mortar under hygrothermal cycles weather test in order to measure its durability under extreme weather (i.e., sunlight and rain. Thermometers and strain gauges are placed into different wall layers to gather thermal and strain data and another instrument measures the crack dimensions after every 4 cycles. The results showed that the finishing coat shrank at early stage (elastic deformation and then the finishing coat tends to expand and become damaged at later stage (plastic deformation. The deformation of insulation layer is similar to that of the finishing coat but its variation amplitude is smaller. Deformation of substrate expanded with heat and contracted with cold due to the small temperature variation. The length and width of cracks on the finishing coat grew as the experiment progressed but with a decreasing growth rate and the cracks stopped growing around 70 cycles.

Setup of Extruded Cementitious Hollow Tubes as Containing/Releasing Devices in Self-Healing Systems

Directory of Open Access Journals (Sweden)

Alessandra Formia

2015-04-01

Full Text Available The aim of this research is to produce self-healing cementitious composites based on the use of cylindrical capsules containing a repairing agent. Cementitious hollow tubes (CHT having two different internal diameters (of 2 mm and 7.5 mm were produced by extrusion and used as containers and releasing devices for cement paste/mortar healing agents. Based on the results of preliminary mechanical tests, sodium silicate was selected as the healing agent. The morphological features of several mix designs used to manufacture the extruded hollow tubes, as well as the coatings applied to increase the durability of both core and shell materials are discussed. Three-point bending tests were performed on samples produced with the addition of the above-mentioned cementitious hollow tubes to verify the self-healing effectiveness of the proposed solution. Promising results were achieved, in particular when tubes with a bigger diameter were used. In this case, a substantial strength and stiffness recovery was observed, even in specimens presenting large cracks (>1 mm. The method is inexpensive and simple to scale up; however, further research is needed in view of a final optimization.

Automated system for crack detection using infrared thermograph

International Nuclear Information System (INIS)

Starman, Stanislav

2009-01-01

The objective of this study was the development of the automated system for crack detection on square steel bars used in the automotive industry for axle and shaft construction. The automated system for thermographic crack detection uses brief pulsed eddy currents to heat steel components under inspection. Cracks, if present, will disturb the current flow and so generate changes in the temperature profile in the crack area. These changes of temperature are visualized using an infrared camera. The image acquired by the infrared camera is evaluated through an image processing system. The advantages afforded by the system are its inspection time, its excellent flaw detection sensitivity and its ability to detect hidden, subsurface cracks. The automated system consists of four IR cameras (each side of steel bar is evaluated at a time), coil, high frequency generator and control place with computers. The system is a part of the inspection line where the subsurface and surface cracks are searched. If the crack is present, the cracked place is automatically marked. The components without cracks are then deposited apart from defective blocks. The system is fully automated and its ability is to evaluate four meter blocks within 20 seconds. This is the real reason for using this system in real industrial applications. (author)

Switching a Nanocluster Core from Hollow to Non-hollow

KAUST Repository

Bootharaju, Megalamane Siddaramappa

2016-03-24

Modulating the structure-property relationship in atomically precise nanoclusters (NCs) is vital for developing novel NC materials and advancing their applications. While promising biphasic ligand-exchange (LE) strategies have been developed primarily to attain novel NCs, understanding the mechanistic aspects involved in tuning the core and the ligand-shell of NCs in such biphasic processes is challenging. Here, we design a single phase LE process that enabled us to elucidate the mechanism of how a hollow NC (e.g., [Ag44(SR)30]4-, -SR: thiolate) converts into a non-hollow NC (e.g., [Ag25(SR)18]-), and vice versa. Our study reveals that the complete LE of the hollow [Ag44(SPhF)30]4- NCs (–SPhF: 4-fluorobenzenethiolate) with incoming 2,4-dimethylbenzenethiol (HSPhMe2) induced distortions in the Ag44 structure forming the non-hollow [Ag25(SPhMe2)18]- by a disproportionation mechanism. While the reverse reaction of [Ag25(SPhMe2)18]- with HSPhF prompted an unusual dimerization of Ag25, followed by a rearrangement step that reproduces the original [Ag44(SPhF)30]4-. Remarkably, both the forward and the backward reactions proceed through similar size intermediates that seem to be governed by the boundary conditions set by the thermodynamic and electronic stability of the hollow and non-hollow metal cores. Furthermore, the resizing of NCs highlights the surprisingly long-range effect of the ligands which are felt by atoms far deep in the metal core, thus opening a new path for controlling the structural evolution of nanoparticles.

Pipe stress intensity factors and coupled depressurization and dynamic crack propagation. 1976 Annual report

International Nuclear Information System (INIS)

Emery, A.F.; Kobayashi, A.S.; Love, W.J.

1978-04-01

This report contains the description of predictive models for the initiation and propagation of cracks in pipes and the numerical results obtained. The initiation of the crack was studied by evaluating stress intensity factors under static conditions for a series of representative flaws. Three-dimensional static stress intensity factors were determined for quarter-elliptical cracks at the corner of a hole in an infinite plate and at the corner of a bore in a rotating disk. Semi-elliptical cracks for plates in bending and in pressurized and thermally stressed hollow cylinders were also evaluated. The stress fields, in the absence of a crack, were used in the ''alternating technique'' to compute the stress intensity factors along the crack front. Parametric studies were made to assess the effects of crack thickness, the ratio of the major and minor axes of the ellipse and the thickness of the cylinders or plates. These parametric results may be used to predict critical flaw sizes for the initiation of the running crack. The initiation and propagation of axial through cracks in pressurized pipes was studied by using an elastic-plastic finite different shell code coupled with a one-dimensional thermal-hydraulic code which computed the leakage through the crack opening and the depressurization of the fluid in the pipe. The effects of large deflections and different fluid pressure profiles were investigated. The results showed that the crack opening shape is dependent upon the fracture criterion used and upon the average pressure on the crack flaps, but not upon the specific pressure profile. The consideration of large deflections changed the opening size of the crack and through the coupling with the pipe pressures, strongly affected the crack tip speed. However, for equal crack lengths, there was little difference between calculations made for large and small deflection

Experimental Investigation and Discrete Element Modelling of Composite Hollow Spheres Subjected to Dynamic Fracture

Directory of Open Access Journals (Sweden)

Arthur Coré

2017-01-01

Full Text Available This paper deals with the characterization and the numerical modelling of the collapse of composite hollow spherical structures developed to absorb energy during high velocity impacts. The structure is composed of hollow spheres (ϕ=2–30 mm made of epoxy resin and mineral powder. First of all, quasi-static and dynamic (v=5 mm·min−1 to v=2 m·s−1 compression tests are conducted at room temperature on a single sphere to study energy dissipation mechanisms. Fracture of the material appears to be predominant. A numerical model based on the discrete element method is investigated to simulate the single sphere crushing. The stress-strain-time relationship of the material based on the Ree-Eyring law is numerically implemented. The DEM modelling takes naturally into account the dynamic fracture and the crack path computed is close to the one observed experimentally in uniaxial compression. Eventually, high velocity impacts (v>100 m·s−1 of a hollow sphere on a rigid surface are conducted with an air cannon. The numerical results are in good agreement with the experimental data and demonstrate the ability of the present model to correctly describe the mechanical behavior of brittle materials at high strain rate.

Holographic entanglement entropy for hollow cones and banana shaped regions

Energy Technology Data Exchange (ETDEWEB)

Dorn, Harald [Institut für Physik und IRIS Adlershof, Humboldt-Universität zu Berlin,Zum Großen Windkanal 6, D-12489 Berlin (Germany)

2016-06-09

We consider banana shaped regions as examples of compact regions, whose boundary has two conical singularities. Their regularised holographic entropy is calculated with all divergent as well as finite terms. The coefficient of the squared logarithmic divergence, also in such a case with internally curved boundary, agrees with that calculated in the literature for infinite circular cones with their internally flat boundary. For the otherwise conformally invariant coefficient of the ordinary logarithmic divergence an anomaly under exceptional conformal transformations is observed. The construction of minimal submanifolds, needed for the entanglement entropy of cones, requires fine-tuning of Cauchy data. Perturbations of such fine-tuning leads to solutions relevant for hollow cones. The divergent parts for the entanglement entropy of hollow cones are calculated. Increasing the difference between the opening angles of their outer and inner boundary, one finds a transition between connected solutions for small differences to disconnected solutions for larger ones.

Crack identification based on synthetic artificial intelligent technique

International Nuclear Information System (INIS)

Shim, Mun Bo; Suh, Myung Won

2001-01-01

It has been established that a crack has an important effect on the dynamic behavior of a structure. This effect depends mainly on the location and depth of the crack. To identify the location and depth of a crack in a structure, a method is presented in this paper which uses synthetic artificial intelligent technique, that is, Adaptive-Network-based Fuzzy Inference System(ANFIS) solved via hybrid learning algorithm(the back-propagation gradient descent and the least-squares method) are used to learn the input(the location and depth of a crack)-output(the structural eigenfrequencies) relation of the structural system. With this ANFIS and a Continuous Evolutionary Algorithm(CEA), it is possible to formulate the inverse problem. CEAs based on genetic algorithms work efficiently for continuous search space optimization problems like a parameter identification problem. With this ANFIS, CEAs are used to identify the crack location and depth minimizing the difference from the measured frequencies. We have tried this new idea on a simple beam structure and the results are promising

Hollow-Core Fiber Lamp

Science.gov (United States)

Yi, Lin (Inventor); Tjoelker, Robert L. (Inventor); Burt, Eric A. (Inventor); Huang, Shouhua (Inventor)

2016-01-01

Hollow-core capillary discharge lamps on the millimeter or sub-millimeter scale are provided. The hollow-core capillary discharge lamps achieve an increased light intensity ratio between 194 millimeters (useful) and 254 millimeters (useless) light than conventional lamps. The capillary discharge lamps may include a cone to increase light output. Hollow-core photonic crystal fiber (HCPCF) may also be used.

Axial Compression Properties Nonlinear Analysis on Square Double Skin Steel Stub Short Columns Filled with Recycled Concrete

Directory of Open Access Journals (Sweden)

Song Bing

2016-01-01

Full Text Available Taking the mixing amount of diatomite calcined and vitrified micro bubbles(VMB as the main changing parameters, experiment studies the properties of the vitrified micro bubbles recycled concrete blocks; then this paper adopts the finite element software ANSYS to analyze the square double skin steel stub short columns filled with recycled concrete under axial compression. According to the vertical stress distribution, strain and bearing capacity of the steel tube and core concrete, we make a contrastive axial compression properties analysis on the different hollow ratio χ(0,0.35and the VMB content(0%,100%,130% of square double skin steel stub short columns filled with recycled concrete. The result shows that: Compressive strength of VMB recycled concrete increases with the increase of diatomite calcined content, when mixing amount of diatomite calcined is 3%,the compressive strength of 130% VMB content test specimen can reach 32.45 MPa;Because of the inner circular steel tube is setted which strengthening component buckling capacity and improving the ductility of the component, stress distribution of hollow components is more balance than solid components, and their axial displacements decrease by 5.6% compared with the solid components when they reach ultimate bearing capacity; When the hollow ratio is same, ultimate bearing capacity of 130% VMB content test specimen compared with the content is 0% only reduces by about 3.5%; When the VMB content is same, ultimate bearing capacity of hollow components compared with solid components increases by about 2.5%, which reducing weight as well as improving the anti-seismic performance.

A method for crack profiles identification in eddy current testing by the multi-directional scan

International Nuclear Information System (INIS)

Kojima, Fumio; Ikeda, Takuya; Nguyen, Doung

2006-01-01

This paper is concerned with a method for identification of crack shape in conducting materials. Multi-directional scanning strategies using Eddy Current Testing is performed for sizing complex natural crackings. Two dimensional measurements by means of multi-directional scan are used in a output least square identifications. (author)

Stress Intensity Factor for Interface Cracks in Bimaterials Using Complex Variable Meshless Manifold Method

Directory of Open Access Journals (Sweden)

Hongfen Gao

2014-01-01

Full Text Available This paper describes the application of the complex variable meshless manifold method (CVMMM to stress intensity factor analyses of structures containing interface cracks between dissimilar materials. A discontinuous function and the near-tip asymptotic displacement functions are added to the CVMMM approximation using the framework of complex variable moving least-squares (CVMLS approximation. This enables the domain to be modeled by CVMMM without explicitly meshing the crack surfaces. The enriched crack-tip functions are chosen as those that span the asymptotic displacement fields for an interfacial crack. The complex stress intensity factors for bimaterial interfacial cracks were numerically evaluated using the method. Good agreement between the numerical results and the reference solutions for benchmark interfacial crack problems is realized.

Preparation of TiO2 hollow fibers using poly(vinylidene fluoride) hollow fiber microfiltration membrane as a template

International Nuclear Information System (INIS)

Lu Haiqiang; Zhang Lixiong; Xing Weihong; Wang Huanting; Xu Nanping

2005-01-01

TiO 2 hollow fibers were successfully prepared by using poly(vinylidene fluoride) hollow fiber microfiltration membrane as a template. The preparation procedure includes repeated impregnation of the TiO 2 precursor in the pores of the polymeric membrane, and calcination to burn off the template, producing the TiO 2 hollow fibers. The TiO 2 hollow fibers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). TiO 2 hollow fibers with other structures, such as honeycomb monolith and spring, were also prepared by preshaping the polymeric membranes into the honeycomb structure and spring, respectively. The phase structure of the TiO 2 hollow fibers could be readily adjusted by changing the calcination temperature

Coupled FEM-DBEM method to assess crack growth in magnet system of Wendelstein 7-X

Directory of Open Access Journals (Sweden)

R. Citarella

2013-10-01

Full Text Available The fivefold symmetric modular stellarator Wendelstein 7-X (W7-X is currently under construction in Greifswald, Germany. The superconducting coils of the magnet system are bolted onto a central support ring and interconnected with five so-called lateral support elements (LSEs per half module. After welding of the LSE hollow boxes to the coil cases, cracks were found in the vicinity of the welds that could potentially limit the allowed number N of electromagnetic (EM load cycles of the machine. In response to the appearance of first cracks during assembly, the Stress Intensity Factors (SIFs were calculated and corresponding crack growth rates of theoretical semi-circular cracks of measured sizes in potentially critical position and orientation were predicted using Paris’ law, whose parameters were calibrated in fatigue tests at cryogenic temperature. In this paper the Dual Boundary Element Method (DBEM is applied in a coupled FEM-DBEM approach to analyze the propagation of multiple cracks with different shapes. For this purpose, the crack path is assessed with the Minimum Strain Energy density criterion and SIFs are calculated by the J-integral approach. The Finite Element Method (FEM is adopted to model, using the commercial codes Ansys or Abaqus;, the overall component whereas the submodel analysis, in the volume surrounding the cracked area, is performed by FEM (“FEM-FEM approach” or alternatively by DBEM (“FEM-DBEM approach”. The “FEM-FEM approach” considers a FEM submodel, that is extracted from the FEM global model; the latter provide the boundary conditions for the submodel. Such approach is affected by some restrictions in the crack propagation phase, whereas, with the “FEM-DBEM approach”, the crack propagation simulation is straightforward. In this case the submodel is created in a DBEM environment with boundary conditions provided by the global FEM analysis; then the crack is introduced and a crack propagation analysis

Hollow Micro-/Nanostructures: Synthesis and Applications

KAUST Repository

Lou, Xiong Wen (David)

2008-11-03

Hollow micro-nanostructures are of great interest in many current and emerging areas of technology. Perhaps the best-known example of the former is the use of fly-ash hollow particles generated from coal power plants as partial replacement for Portland cement, to produce concrete with enhanced strength and durability. This review is devoted to the progress made in the last decade in synthesis and applications of hollow micro-nanostructures. We present a comprehensive overview of synthetic strategies for hollow structures. These strategies are broadly categorized into four themes, which include well-established approaches, such as conventional hard-templating and soft-templating methods, as well as newly emerging methods based on sacrificial templating and template-free synthesis. Success in each has inspired multiple variations that continue to drive the rapid evolution of the field. The Review therefore focuses on the fundamentals of each process, pointing out advantages and disadvantages where appropriate. Strategies for generating more complex hollow structures, such as rattle-type and nonspherical hollow structures, are also discussed. Applications of hollow structures in lithium batteries, catalysis and sensing, and biomedical applications are reviewed. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA,.

Modified Dugdale cracks and Fictitious cracks

DEFF Research Database (Denmark)

Nielsen, Lauge Fuglsang

1998-01-01

A number of theories are presented in the literature on crack mechanics by which the strength of damaged materials can be predicted. Among these are theories based on the well-known Dugdale model of a crack prevented from spreading by self-created constant cohesive flow stressed acting in local...... areas, so-called fictitious cracks, in front of the crack.The Modified Dugdale theory presented in this paper is also based on the concept of Dugdale cracks. Any cohesive stress distribution, however, can be considered in front of the crack. Formally the strength of a material weakened by a modified...... Dugdale crack is the same as if it has been weakened by the well-known Griffith crack, namely sigma_CR = (EG_CR/phi)^1/2 where E and 1 are Young's modulus and crack half-length respectively, and G_CR is the so-called critical energy release rate. The physical significance of G_CR, however, is different...

Observation and simulation of crack growth in Zry-4

International Nuclear Information System (INIS)

Bertolino, Graciela; Meyer, Gabriel; Perez Ipina, J

2003-01-01

Security and life extension of components of nuclear reactors are the most motivating aspects that encourage to study embrittlement processes of zirconium alloys by reaction with hydrogen.Here, the use of fracture mechanics tests are suitable to monitor the material resistance of components under service.Because many times is difficult to obtain normalized probes from real size components, researchers look for alternative experimental techniques or crack growth simulation from the knowledge of particular material properties.In this work we present the results obtained after experimental observation and computer simulation of crack growth in Zry-4 probes.Experimental observation were obtained by performing flexion tests in three point probes SSEN(B) of 3 x 7 x 32 mm 3 located in the chamber of a scanning electron microscope, measuring in situ the crack length and opening when an external load is applied.Using the information obtained from stress-displacement measurements after tensile tests and the empiric relationship between crack opening and crack length, the crack growth process was simulated.Displacement field in the zone close to the crack tip was obtained by finite elements technique (Castem, DMT, CEA) assuming plain stress, a plastic bilinear homogeneous material and neglecting texture or directional anisotropy.To compare experimental observation and simulation, a grid (10 x 10 μm 2 each square) was drawn in the zone close to the crack tip by selective sputtering.Following the movement of two (three) points of the surface allows to compare uni (bi) dimensional deformation.A good agreement between observation and simulation was observed: after the crack opening grew 28 times (from 1.5 to 42 μm) the base-height relationship of a triangle involving the crack tip change 40% (35%) in the experimental observation (simulation)

Position control of desiccation cracks by memory effect and Faraday waves.

Science.gov (United States)

Nakayama, Hiroshi; Matsuo, Yousuke; Takeshi, Ooshida; Nakahara, Akio

2013-01-01

Pattern formation of desiccation cracks on a layer of a calcium carbonate paste is studied experimentally. This paste is known to exhibit a memory effect, which means that a short-time application of horizontal vibration to the fresh paste predetermines the direction of the cracks that are formed after the paste is dried. While the position of the cracks (as opposed to their direction) is still stochastic in the case of horizontal vibration, the present work reports that their positioning is also controllable, at least to some extent, by applying vertical vibration to the paste and imprinting the pattern of Faraday waves, thus breaking the translational symmetry of the system. The experiments show that the cracks tend to appear in the node zones of the Faraday waves: in the case of stripe-patterned Faraday waves, the cracks are formed twice more frequently in the node zones than in the anti-node zones, presumably due to the localized horizontal motion. As a result of this preference of the cracks to the node zones, the memory of the square lattice pattern of Faraday waves makes the cracks run in the oblique direction differing by 45 degrees from the intuitive lattice direction of the Faraday waves.

The maximum possible stress intensity factor for a crack in an unknown residual stress field

International Nuclear Information System (INIS)

Coules, H.E.; Smith, D.J.

2015-01-01

Residual and thermal stress fields in engineering components can act on cracks and structural flaws, promoting or inhibiting fracture. However, these stresses are limited in magnitude by the ability of materials to sustain them elastically. As a consequence, the stress intensity factor which can be applied to a given defect by a self-equilibrating stress field is also limited. We propose a simple weight function method for determining the maximum stress intensity factor which can occur for a given crack or defect in a one-dimensional self-equilibrating stress field, i.e. an upper bound for the residual stress contribution to K I . This can be used for analysing structures containing defects and subject to residual stress without any information about the actual stress field which exists in the structure being analysed. A number of examples are given, including long radial cracks and fully-circumferential cracks in thick-walled hollow cylinders containing self-equilibrating stresses. - Highlights: • An upper limit to the contribution of residual stress to stress intensity factor. • The maximum K I for self-equilibrating stresses in several geometries is calculated. • A weight function method can determine this maximum for 1-dimensional stress fields. • Simple MATLAB scripts for calculating maximum K I provided as supplementary material.

Method for the production of fabricated hollow microspheroids

Science.gov (United States)

Wickramanayake, Shan; Luebke, David R.

2015-06-09

The method relates to the fabrication of a polymer microspheres comprised of an asymmetric layer surrounding a hollow interior. The fabricated hollow microsphere is generated from a nascent hollow microsphere comprised of an inner core of core fluid surrounded by a dope layer of polymer dope, where the thickness of the dope layer is at least 10% and less than 50% of the diameter of the inner core. The nascent hollow microsphere is exposed to a gaseous environment, generating a vitrified hollow microsphere, which is subsequently immersed in a coagulation bath. Solvent exchange produces a fabricated hollow microsphere comprised of a densified outer skin surrounding a macroporous inner layer, which surrounds a hollow interior. In an embodiment, the polymer is a polyimide or a polyamide-imide, and the non-solvent in the core fluid and the coagulation bath is water. The fabricated hollow microspheres are particularly suited as solvent supports for gas separation processes.

Complex Hollow Nanostructures: Synthesis and Energy-Related Applications.

Science.gov (United States)

Yu, Le; Hu, Han; Wu, Hao Bin; Lou, Xiong Wen David

2017-04-01

Hollow nanostructures offer promising potential for advanced energy storage and conversion applications. In the past decade, considerable research efforts have been devoted to the design and synthesis of hollow nanostructures with high complexity by manipulating their geometric morphology, chemical composition, and building block and interior architecture to boost their electrochemical performance, fulfilling the increasing global demand for renewable and sustainable energy sources. In this Review, we present a comprehensive overview of the synthesis and energy-related applications of complex hollow nanostructures. After a brief classification, the design and synthesis of complex hollow nanostructures are described in detail, which include hierarchical hollow spheres, hierarchical tubular structures, hollow polyhedra, and multi-shelled hollow structures, as well as their hybrids with nanocarbon materials. Thereafter, we discuss their niche applications as electrode materials for lithium-ion batteries and hybrid supercapacitors, sulfur hosts for lithium-sulfur batteries, and electrocatalysts for oxygen- and hydrogen-involving energy conversion reactions. The potential superiorities of complex hollow nanostructures for these applications are particularly highlighted. Finally, we conclude this Review with urgent challenges and further research directions of complex hollow nanostructures for energy-related applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced Electrochemical Performance of Electrospun Ag/Hollow Glassy Carbon Nanofibers as Free-standing Li-ion Battery Anode

International Nuclear Information System (INIS)

Shilpa; Sharma, Ashutosh

2015-01-01

Silver with a high theoretical capacity for lithium storage is an attractive alloy based anode for Li-ion batteries, but large volume changes associated with AgLi x alloy formation leads to electrode cracking, pulverization and rapid capacity fading. A buffer matrix, like the electrospun hollow carbon nanofibers, can reduce this problem to a great extent. Herein, we demonstrate the facile synthesis of a free-standing, binder free Ag-C hybrid electrode through co-axial electrospinning, where well dispersed Ag nanoparticles are embedded in hollow carbon nanofibers. Using this approach, the long cycle life of carbon is complemented with the high lithium storage capacity of Ag, resulting in a high performance anode. The Ag-C composite electrode delivers a capacity of 739 mAh g −1 (>conventional graphite anodes) at 50 mA g −1 , with ∼85% capacity retention after 100 cycles. In addition, the Ag-C composite nanofibers are highly porous and exhibit a large accessible surface area (∼726.9 m 2 g −1 ) with an average pore diameter of ∼6.07 nm. The encapsulation of Ag in the hollow interiors not only provides additional lithium storage sites but also enhances the electronic conductivity, which combined with the reduced lithium diffusion path lengths in the nanofibers result in faster charge-discharge kinetics and hence a high rate performance

Investigation into diffusion induced plastic deformation behavior in hollow lithium ion battery electrode revealed by analytical model and atomistic simulation

International Nuclear Information System (INIS)

Li, Jia; Fang, Qihong; Wu, Hong; Liu, Youwen; Wen, Pihua

2015-01-01

Highlights: • Diffusion induced stress is established. • Yield stress is dependent upon concentration. • Plastic deformation induced stress lowers tensile stress. • Plastic deformation suppresses crack nucleation. • Plastic deformation occurs not only at lithiated phase but also at electrode interior. - Abstract: This paper is theoretically suggested to describe diffusion induced stress in the elastoplastic hollow spherical silicon electrode for plastic deformation using both analytical model and molecular simulation. Based on the plastic deformation and the yield criterion, we develop this model accounting for the lithium-ion diffusion effect in hollow electrode, focusing on the concentration and stress distributions undergoing lithium-ion insertion. The results show that the two ways, applied compressive stress to inner surface or limited inner surface with higher concentration using biological membranes maintaining concentration difference, lead to the compressive stress induced by the lithium-ion diffusion effect. Hollow spherical electrode reduces effectively diffusion induced stress through controlling and tuning electrode parameters to obtain the reasonably low yield strength. According to MD simulations, plastic deformation phenomenon not only occurs at interface layer of lithiated phase, but also penetrates at electrode interior owning to confinement imposed by lithiated phase. These criteria that radial and hoop stresses reduce dramatically when plastic deformation occurs near the end faces of hollow electrode, may help guide development of new materials for lithium-ion batteries with enhanced mechanical durability, by means of reasonable designing yield strength to maintain mechanical stress below fracture strength, thereby increasing battery life.

Stress fields around a crack lying parallel to a free surface

International Nuclear Information System (INIS)

Higashida, Yutaka; Kamada, K.

1980-12-01

A method of stress analysis for a two dimentional crack, which is subjected to internal gas pressure, and situated parallel to a free surface of a material, is presented. It is based on the concept of continuously distributed edge dislocations of two kinds, i.e. one with Burgers vector normal to the free surface and the other with parallel to it. Stress fields of individual dislocations are chosen so as to satisfy stress free boundary conditions at the free surface, by taking account of image dislocations. Distributions of the both kinds of dislocations in the crack are derived so as to give the internal gas pressure and, at the same time, to satisfy shear stress free boundary condition on the crack surface. Stress fields σsub(xx), σsub(yy) and σsub(xy) in the sub-surface layer are then determined from them. They have square root singularities at the crack-tip. (author)

Hollow bunches production

CERN Document Server

Hancock, S

2017-01-01

Hollow bunches address the issue of high-brightnessbeams suffering from transverse emittance growth in a strongspace charge regime. During the Proton Synchrotron (PS)injection plateau, the negative space charge tune shift canpush the beam onto theQy=6integer resonance. Modify-ing the longitudinal bunch profile in order to reduce the peakline charge density alleviates the detrimental impact of spacecharge. To this end we first produce longitudinally hollowphase space distributions in the PS Booster by exciting aparametric resonance with the phase loop feedback system.These inherently flat bunches are then transferred to the PS,where the beam becomes less prone to the emittance growthcaused by the integer resonance.During the late 2016 machine development sessions inthe PS Booster we profited from solved issues from 2015and managed to reliably extract hollow bunches of1.3eVsmatched longitudinal area. Furthermore, first results to cre-ate hollow bunches with larger longitudinal emittances to-wards the LHC Inject...

Adhesive liquid core optical fibers for crack detection and repairs in polymer and concrete matrices

Science.gov (United States)

Dry, Carolyn M.

1995-04-01

This work is an investigation into the feasibility of using liquid core optical fibers for the detection and self repair of cracking in cement or polymer materials generated by dynamic or static loading. These experiments rely on our current research sponsored by the National Science Foundation. It combines that work on the concept of internal adhesive delivery from hollow fibers for repair with nondestructive fiber optic analysis of the crack localization and volume within the same system. The need to monitor the internal state of civil structures and materials is great. Existing instrumentation techniques that mainly rely on magnetism, electricity, or stress gauges are limited if used for remote measurements in concrete or composites. They are sensitive to electrical magnetic noises and they degrade in the environment over time. Optical fibers are attractive because they are immune to electromagnetic interference and are sensitive over long distances. The combination of the ability to remotely measure crack occurrence in real time and determine the location and volume of crack damage in the matrix is unique in the field of optic sensors (or any sensors in general). The combination of this with crack repair, rebonding of any detached or broken fibers, and replenishment of liquid core chemicals, when necessary, make this a potentially powerful sensing and repair tool. Work on this research topic of the combination sponsored by the University of Illinois, looks very promising as a rapid innovative advance.

Method to fabricate hollow microneedle arrays

Energy Technology Data Exchange (ETDEWEB)

Kravitz, Stanley H [Placitas, NM; Ingersoll, David [Albuquerque, NM; Schmidt, Carrie [Los Lunas, NM; Flemming, Jeb [Albuquerque, NM

2006-11-07

An inexpensive and rapid method for fabricating arrays of hollow microneedles uses a photoetchable glass. Furthermore, the glass hollow microneedle array can be used to form a negative mold for replicating microneedles in biocompatible polymers or metals. These microneedle arrays can be used to extract fluids from plants or animals. Glucose transport through these hollow microneedles arrays has been found to be orders of magnitude more rapid than natural diffusion.

Evidence of fire resistance of hollow-core slabs

DEFF Research Database (Denmark)

Hertz, Kristian Dahl; Sørensen, Lars Schiøtt; Giuliani, Luisa

is therefore going on in the Netherlands about the fire resistance of hollow-core slabs. In 2014 the producers of hollow-core slabs have published a report of a project called Holcofire containing a collection of 162 fire tests on hollow-core slabs giving for the first time an overview of the fire tests made....... The present paper analyses the evidence now available for assessment of the fire resistance of extruded hollow-core slabs. The 162 fire tests from the Holcofire report are compared against the requirements for testing from the product standard for hollow-core slabs EN1168 and knowledge about the possible......Hollow-core slabs have during the past 50 years comprised a variety of different structures with different cross-sections and reinforcement. At present the extruded hollow-core slabs without cross-reinforcement in the bottom flange and usually round or oval longitudinal channels (holes...

A crack growth evaluation method for interacting multiple cracks

International Nuclear Information System (INIS)

Kamaya, Masayuki

2003-01-01

When stress corrosion cracking or corrosion fatigue occurs, multiple cracks are frequently initiated in the same area. According to section XI of the ASME Boiler and Pressure Vessel Code, multiple cracks are considered as a single combined crack in crack growth analysis, if the specified conditions are satisfied. In crack growth processes, however, no prescription for the interference between multiple cracks is given in this code. The JSME Post-Construction Code, issued in May 2000, prescribes the conditions of crack coalescence in the crack growth process. This study aimed to extend this prescription to more general cases. A simulation model was applied, to simulate the crack growth process, taking into account the interference between two cracks. This model made it possible to analyze multiple crack growth behaviors for many cases (e.g. different relative position and length) that could not be studied by experiment only. Based on these analyses, a new crack growth analysis method was suggested for taking into account the interference between multiple cracks. (author)

Out-of-plane behavior of hollow clay tile walls infilled between steel frames

International Nuclear Information System (INIS)

Butala, M.B.; Jones, W.D.; Beavers, J.E.

1991-01-01

Several Buildings at the Department of Energy (DOE) Oak Ridge Y-1 2 Plant rely on unreinforced hollow clay tile walls (HCTW) infilled between unbraced, non-moment resisting steel frames to resist natural phenomena forces, seismic and wind. One critical building relies on moment resisting steel frames in one direction while relying on unreinforced HCTWs infilled between the columns in the orthogonal direction to resist these forces. The HCTWs must act as shear walls while maintaining out-of-plane lateral stability. In assessing the safety of these buildings to seismic forces, several models to study the in- and out-of-plane effects were made and analyzed. The study of the moment resisting steel framed building indicated that bending stresses in the walls were induced by building drift and not by inertial forces per se. The discovery of this phenomenon was some what of a surprise in that the analysis performed is not typically used in design of these structures. The study indicated that the walls began to crack at their interface with the foundation at a low open-quotes gclose quotes level and that horizontal cracking at different elevations continued until the walls exhibited little bending resistance

The Electrospun Ceramic Hollow Nanofibers

Directory of Open Access Journals (Sweden)

Shahin Homaeigohar

2017-11-01

Full Text Available Hollow nanofibers are largely gaining interest from the scientific community for diverse applications in the fields of sensing, energy, health, and environment. The main reasons are: their extensive surface area that increases the possibilities of engineering, their larger accessible active area, their porosity, and their sensitivity. In particular, semiconductor ceramic hollow nanofibers show greater space charge modulation depth, higher electronic transport properties, and shorter ion or electron diffusion length (e.g., for an enhanced charging–discharging rate. In this review, we discuss and introduce the latest developments of ceramic hollow nanofiber materials in terms of synthesis approaches. Particularly, electrospinning derivatives will be highlighted. The electrospun ceramic hollow nanofibers will be reviewed with respect to their most widely studied components, i.e., metal oxides. These nanostructures have been mainly suggested for energy and environmental remediation. Despite the various advantages of such one dimensional (1D nanostructures, their fabrication strategies need to be improved to increase their practical use. The domain of nanofabrication is still advancing, and its predictable shortcomings and bottlenecks must be identified and addressed. Inconsistency of the hollow nanostructure with regard to their composition and dimensions could be one of such challenges. Moreover, their poor scalability hinders their wide applicability for commercialization and industrial use.

Evolution of nickel sulfide hollow spheres through topotactic transformation

Science.gov (United States)

Wei, Chengzhen; Lu, Qingyi; Sun, Jing; Gao, Feng

2013-11-01

In this study, a topotactic transformation route was proposed to synthesize single-crystalline β-NiS hollow spheres with uniform phase and morphology evolving from polycrystalline α-NiS hollow spheres. Uniform polycrystalline α-NiS hollow spheres were firstly prepared with thiourea and glutathione as sulfur sources under hydrothermal conditions through the Kirkendall effect. By increasing the reaction temperature the polycrystalline α-NiS hollow spheres were transformed to uniform β-NiS hollow spheres. The β-NiS crystals obtained through the topotactic transformation route not only have unchanged morphology of hollow spheres but are also single-crystalline in nature. The as-prepared NiS hollow spheres display a good ability to remove the organic pollutant Congo red from water, which makes them have application potential in water treatment.In this study, a topotactic transformation route was proposed to synthesize single-crystalline β-NiS hollow spheres with uniform phase and morphology evolving from polycrystalline α-NiS hollow spheres. Uniform polycrystalline α-NiS hollow spheres were firstly prepared with thiourea and glutathione as sulfur sources under hydrothermal conditions through the Kirkendall effect. By increasing the reaction temperature the polycrystalline α-NiS hollow spheres were transformed to uniform β-NiS hollow spheres. The β-NiS crystals obtained through the topotactic transformation route not only have unchanged morphology of hollow spheres but are also single-crystalline in nature. The as-prepared NiS hollow spheres display a good ability to remove the organic pollutant Congo red from water, which makes them have application potential in water treatment. Electronic supplementary information (ESI) available: XRD patterns; SEM images and TEM images. See DOI: 10.1039/c3nr03371f

Hollow core plasma channel generation

International Nuclear Information System (INIS)

Quast, Heinrich Martin

2018-03-01

The use of a hollow plasma channel in plasma-based acceleration has beneficial properties for the acceleration of electron and positron bunches. In the scope of the FLASHForward facility at DESY, the generation of such a plasma structure is examined. Therefore, the generation of a ring-shaped laser intensity profile with different techniques is analyzed. From the obtained intensity profiles the electron density of a hollow plasma channel is simulated in the focal region. Different parameters are scanned to understand their influence on the electron density distribution - an important parameter being, for example, the radius of the central region of the channel. In addition to the simulations, experiments are presented, during which a laser pulse is transformed into a hollow beam with a spiral phase plate. Subsequently, it forms a plasma during the interaction with hydrogen, where the plasma is imaged with interferometry. For energies above 0.9 mJ a hollow plasma structure can be observed at the location of first plasma formation.

Delayed hydride cracking: alternative pre-cracking method

International Nuclear Information System (INIS)

Mieza, Juan I.; Ponzoni, Lucio M.E.; Vigna, Gustavo L.; Domizzi, Gladys

2009-01-01

The internal components of nuclear reactors built-in Zr alloys are prone to a failure mechanism known as Delayed Hydride Cracking (DHC). This situation has triggered numerous scientific studies in order to measure the crack propagation velocity and the threshold stress intensity factor associated to DHC. Tests are carried out on fatigued pre-crack samples to ensure similar test conditions and comparable results. Due to difficulties in implementing the fatigue pre-crack method it would be desirable to replace it with a pre-crack produced by the same process of DHC, for which is necessary to demonstrate equivalence of this two methods. In this work tests on samples extracted from two Zr-2.5 Nb tubes were conducted. Some of the samples were heat treated to obtain a range in their metallurgical properties as well as different DHC velocities. A comparison between velocities measured in test samples pre-cracked by fatigue and RDIH is done, demonstrating that the pre-cracking method does not affect the measured velocity value. In addition, the incubation (t inc ), which is the time between the application of the load and the first signal of crack propagation, in samples pre-cracked by RDIH, was measured. It was found that these times are sufficiently short, even in the worst cases (lower speed) and similar to the ones of fatigued pre-cracked samples. (author)

Cascaded image analysis for dynamic crack detection in material testing

Science.gov (United States)

Hampel, U.; Maas, H.-G.

Concrete probes in civil engineering material testing often show fissures or hairline-cracks. These cracks develop dynamically. Starting at a width of a few microns, they usually cannot be detected visually or in an image of a camera imaging the whole probe. Conventional image analysis techniques will detect fissures only if they show a width in the order of one pixel. To be able to detect and measure fissures with a width of a fraction of a pixel at an early stage of their development, a cascaded image analysis approach has been developed, implemented and tested. The basic idea of the approach is to detect discontinuities in dense surface deformation vector fields. These deformation vector fields between consecutive stereo image pairs, which are generated by cross correlation or least squares matching, show a precision in the order of 1/50 pixel. Hairline-cracks can be detected and measured by applying edge detection techniques such as a Sobel operator to the results of the image matching process. Cracks will show up as linear discontinuities in the deformation vector field and can be vectorized by edge chaining. In practical tests of the method, cracks with a width of 1/20 pixel could be detected, and their width could be determined at a precision of 1/50 pixel.

Cracking of a layered medium on an elastic foundation under thermal shock

Science.gov (United States)

Rizk, Abd El-Fattah A.; Erdogan, Fazil

1988-01-01

The cladded pressure vessel under thermal shock conditions which is simulated by using two simpler models was studied. The first model (Model 1) assumes that, if the crack size is very small compared to the vessel thickness, the problem can be treated as a semi-infinite elastic medium bonded to a very thin layer of different material. However, if the crack size is of the same order as the vessel thickness, the curvature effects may not be negligible. In this case it is assumed that the relatively thin walled hollow cylinder with cladding can be treated as a composite beam on an elastic foundation (Model 2). In both models, the effect of surface cooling rate is studied by assuming the temperature boundary condition to be a ramp function. The calculated results include the transient temperature, thermal stresses in the uncracked medium and stress intensity factors which are presented as a function of time, and the duration of cooling ramp. The stress intensity factors are also presented as a function of the size and the location of the crack. The problem is solved for two bonded materials of different thermal and mechanical properties. The mathematical formulation results in two singular integral equations which are solved numerically. The results are given for two material pairs, namely an austenitic steel layer welded on a ferritic steel substrate, and a ceramic coating on ferritic steel. In the case of the yielded clad, the stress intensity factors for a crack under the clad are determined by using a plastic strip model and are compared with elastic clad results.

Hollow rods for the oil producing industry

Energy Technology Data Exchange (ETDEWEB)

Khalimova, L M; Elyasheva, M A

1970-01-01

Hollow sucker rods have several advantages over conventional ones. The hollow rods actuate the well pump and at the same time conduct produced fluids to surface. When paraffin deposition occurs, it can be minimized by injecting steam, hot oil or hot water into the hollow rod. Other chemicals, such as demulsifiers, scale inhibitors, corrosion inhibitors, etc., can also be placed in the well through the hollow rods. This reduces cost of preventive treatments, reduces number of workovers, increases oil production, and reduces cost of oil. Because the internal area of the rod is small, the passing liquids have a high velocity and thereby carry sand and dirt out of the well. This reduces pump wear between the piston and the plunger. Specifications of hollow rods, their operating characteristics, and results obtained with such rods under various circumstances are described.

Transmission properties of hollow-core photonic bandgap fibers

DEFF Research Database (Denmark)

Falk, Charlotte Ijeoma; Hald, Jan; Petersen, Jan C.

2010-01-01

Variations in optical transmission of four types of hollow-core photonic bandgap fibers are measured as a function of laser frequency. These variations influence the potential accuracy of gas sensors based on molecular spectroscopy in hollow-core fibers.......Variations in optical transmission of four types of hollow-core photonic bandgap fibers are measured as a function of laser frequency. These variations influence the potential accuracy of gas sensors based on molecular spectroscopy in hollow-core fibers....

A novel synthesis of micrometer silica hollow sphere

International Nuclear Information System (INIS)

Pan Wen; Ye Junwei; Ning Guiling; Lin Yuan; Wang Jing

2009-01-01

Silica microcapsules (hollow spheres) were synthesized successfully by a novel CTAB-stabilized water/oil emulsion system mediated hydrothermal method. The addition of urea to a solution of aqueous phase was an essential step of the simple synthetic procedure of silica hollow spheres, which leads to the formation of silica hollow spheres with smooth shell during hydrothermal process. The intact hollow spheres were obtained by washing the as-synthesized solid products with distilled water to remove the organic components. A large amount of silanol groups were retained in the hollow spheres by this facile route without calcination. The morphologies and optical properties of the product were characterized by transmission electron microscopy, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. Furthermore, on the basis of a series of SEM observations, phenomenological elucidation of a mechanism for the growth of the silica hollow spheres has been presented

Eddy-current inversion in the thin-skin limit: Determination of depth and opening for a long crack

Science.gov (United States)

Burke, S. K.

1994-09-01

A method for crack size determination using eddy-current nondestructive evaluation is presented for the case of a plate containing an infinitely long crack of uniform depth and uniform crack opening. The approach is based on the approximate solution to Maxwell's equations for nonmagnetic conductors in the limit of small skin depth and relies on least-squares polynomial fits to a normalized coil impedance function as a function of skin depth. The method is straightforward to implement and is relatively insensitive to both systematic and random errors. The procedure requires the computation of two functions: a normalizing function, which depends both on the coil parameters and the skin depth, and a crack-depth function which depends only on the coil parameters in addition to the crack depth. The practical perfomance of the method was tested using a set of simulated cracks in the form of electro-discharge machined slots in aluminum alloy plates. The crack depths and crack opening deduced from the eddy-current measurements agree with the actual crack dimensions to within 10% or better. Recommendations concerning the optimum conditions for crack sizing are also made.

Transient Stress Intensity Factors of Functionally Graded Hollow Cylinders with Internal Circumferential Cracks

Directory of Open Access Journals (Sweden)

Iman Eshraghi

Full Text Available Abstract In this paper, transient thermomechanical stress intensity factors for functionally graded cylinders with complete internal circumferential cracks are obtained using the weight function method. The finite difference method is used to calculate the time dependent temperature distribution and thermal stresses along the cylinder thickness. Furthermore, finite element analysis is performed to determine the weight function coefficients and to investigate the accuracy of the predicted stress intensity factors from the weight functions. Variation of the stress intensity factors with time and effects of the material gradation on the results are investigated, as well. It is shown that the proposed technique can be used to accurately predict transient thermomechanical stress intensity factors for functionally graded cylinders with arbitrary material gradation.

Commissioning of the first U.S. hollow fiber condensate filtration system

International Nuclear Information System (INIS)

Wilson, John A.; Mura, Michelle; Garcia, Susan E.; Giannelli, Joseph F.

2008-01-01

Exelon Corporation's Oyster Creek Generating Station, a boiling water reactor (BWR), is the first nuclear plant in the U.S. to install and operate a condensate filtration system using HFF (hollow fiber filter) technology developed in Japan. Oyster Creek is a 640 MW (electric)/1 930 MW (thermal) General Electric BWR-2 (non-jet pump plant) with cascaded heater drains. The plant began commercial operation in 1969, and is one of the two oldest operating commercial BWRs in the U.S. Both noble metal chemical addition (NMCA) and hydrogen injection are used for intergranular stress corrosion cracking (IGSCC) mitigation, and depleted zinc oxide (DZO) is injected for drywell radiation field control. The HFF filters, which were installed in preparation for the operating license renewal, were commissioned in November 2007 and are designed to treat 3 639 m 3 . h -1 (16 020 gallons per minute) using a total filtration surface area of 9 457 m 2 (101 796 ft 2 ). The particle retention rating of the hollow fibers is 0.14 μm, which is considerably smaller than the rating of 1-4 μm for filters commonly used in U.S. condensate filtration applications. System performance and monitoring results during the initial year of operation are reported, including the use of a special hollow fiber health monitoring sampling system. Feedwater and reactor water chemistry control and monitoring strategies and results are discussed, including the effects of the transition from the highest feedwater iron to among the lowest in the U.S. BWR fleet. The projected annual average feedwater iron concentration is -1 . Data on the impact of low iron operation on reactor coolant activated corrosion products and the ratio of 60 Co(soluble)/Zn(soluble), the key parameter used to suppress drywell radiation dose rates, are presented. The zinc control strategy and results are presented, including the effect of low feedwater iron on the reactor water to feedwater zinc concentration factor. The potential need and

Stress intensities for nozzle cracks in reactor vessels. Reporting period, January 1, 1976--October 31, 1976

International Nuclear Information System (INIS)

Smith, C.W.; Jolles, M.; Peters, W.H.

1976-11-01

A series of six frozen stress photoelastic tests was conducted to investigate the distribution of stress intensity factor (SIF) along a crack which occurred at the juncture of a pipe (nozzle) with a cylindrical pressure vessel. Typical photoelastic fringe patterns are shown for slices which were taken mutually orthogonal to the flaw border and the flaw surface. A typical plot of normalized apparent SIF versus square root of normalized distance from the crack tip is presented. The variation in SIF along the flaw border is given for all six different crack geometries and also the variation of SIF with varying a/T is presented. 40 references

Hollow nanocrystals and method of making

Science.gov (United States)

Alivisatos, A Paul [Oakland, CA; Yin, Yadong [Moreno Valley, CA; Erdonmez, Can Kerem [Berkeley, CA

2011-07-05

Described herein are hollow nanocrystals having various shapes that can be produced by a simple chemical process. The hollow nanocrystals described herein may have a shell as thin as 0.5 nm and outside diameters that can be controlled by the process of making.

Progressive damage during thermal shock cycling of D-gun sprayed thermal barrier coatings with hollow spherical ZrO{sub 2}-8Y{sub 2}O{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Ke, P.L. [State Key Lab for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China) and School of Metallurgy and Materials, University of Birmingham, Birmingham B15 2TT (United Kingdom)]. E-mail: csun@imr.ac.cn; Wang, Q.M. [State Key Lab for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Gong, J. [State Key Lab for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Sun, C. [State Key Lab for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Zhou, Y.C. [State Key Lab for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

2006-11-05

Thermal shock cycling behaviors of D-gun sprayed TBCs with a hollow spherical ZrO{sub 2}-8Y{sub 2}O{sub 3} (HSP-YSZ) top coat and NiCrAlY bond coat on directionally solidified Ni-base superalloys DZ125 were investigated at high temperature (1100 deg. C) {r_reversible} room temperature (RT) repeatedly by water quenching. Scanning electron microscopy (SEM) was used to characterize the coating microstructure and failure morphology. The results showed that failure of the D-gun sprayed TBC starts with crack initiation along the splats boundary in the ceramic top coat and the non-alumina oxides. The cracks propagate and coalesce with the increasing thermal cycling. The extensive cracking of the rapidly formed non-alumina oxides, resulting from the depletion of aluminum in the bond coat, aids to delamination of the outer ceramic layer. The stress distributions in TGO layer at different thermal shock cycles was measured by luminescence spectroscopy to investigate the failure mechanism of TBC system.

Formation of Uniform Hollow Silica microcapsules

Science.gov (United States)

Yan, Huan; Kim, Chanjoong

2013-03-01

Microcapsules are small containers with diameters in the range of 0.1 - 100 μm. Mesoporous microcapsules with hollow morphologies possess unique properties such as low-density and high encapsulation capacity, while allowing controlled release by permeating substances with a specific size and chemistry. Our process is a one-step fabrication of monodisperse hollow silica capsules with a hierarchical pore structure and high size uniformity using double emulsion templates obtained by the glass-capillary microfluidic technique to encapsulate various active ingredients. These hollow silica microcapsules can be used as biomedical applications such as drug delivery and controlled release.

Microring embedded hollow polymer fiber laser

Energy Technology Data Exchange (ETDEWEB)

Linslal, C. L., E-mail: linslal@gmail.com; Sebastian, S.; Mathew, S.; Radhakrishnan, P.; Nampoori, V. P. N.; Girijavallabhan, C. P.; Kailasnath, M. [International School of Photonics, Cochin University of Science and Technology, Cochin 22 (India)

2015-03-30

Strongly modulated laser emission has been observed from rhodamine B doped microring resonator embedded in a hollow polymer optical fiber by transverse optical pumping. The microring resonator is fabricated on the inner wall of a hollow polymer fiber. Highly sharp lasing lines, strong mode selection, and a collimated laser beam are observed from the fiber. Nearly single mode lasing with a side mode suppression ratio of up to 11.8 dB is obtained from the strongly modulated lasing spectrum. The microring embedded hollow polymer fiber laser has shown efficient lasing characteristics even at a propagation length of 1.5 m.

Modified Dugdale crack models - some easy crack relations

DEFF Research Database (Denmark)

Nielsen, Lauge Fuglsang

1997-01-01

the same strength as a plain Dugdale model. The critical energy release rates Gamma_CR, however, become different. Expressions (with easy computer algorithms) are presented in the paper which relate critical energy release rates and crack geometry to arbitrary cohesive stress distributions.For future...... lifetime analysis of viscoelastic materials strain energy release rates, crack geometries, and cohesive stress distributions are considered as related to sub-critical loads sigma stress-deformation tests......The Dugdale crack model is widely used in materials science to predict strength of defective (cracked) materials. A stable Dugdale crack in an elasto-plastic material is prevented from spreading by uniformly distributed cohesive stresses acting in narrow areas at the crack tips. These stresses...

Space Charge Mitigation With Longitudinally Hollow Bunches

CERN Multimedia

Oeftiger, Adrian; Rumolo, Giovanni

2016-01-01

Hollow longitudinal phase space distributions have a flat profile and hence reduce the impact of transverse space charge. Dipolar parametric excitation with the phase loop feedback systems provides such hollow distributions under reproducible conditions. We present a procedure to create hollow bunches during the acceleration ramp of CERN’s PS Booster machine with minimal changes to the operational cycle. The improvements during the injection plateau of the downstream Proton Synchrotron are assessed in comparison to standard parabolic bunches.

Hollow nanotubular toroidal polymer microrings.

Science.gov (United States)

Lee, Jiyeong; Baek, Kangkyun; Kim, Myungjin; Yun, Gyeongwon; Ko, Young Ho; Lee, Nam-Suk; Hwang, Ilha; Kim, Jeehong; Natarajan, Ramalingam; Park, Chan Gyung; Sung, Wokyung; Kim, Kimoon

2014-02-01

Despite the remarkable progress made in the self-assembly of nano- and microscale architectures with well-defined sizes and shapes, a self-organization-based synthesis of hollow toroids has, so far, proved to be elusive. Here, we report the synthesis of polymer microrings made from rectangular, flat and rigid-core monomers with anisotropically predisposed alkene groups, which are crosslinked with each other by dithiol linkers using thiol-ene photopolymerization. The resulting hollow toroidal structures are shape-persistent and mechanically robust in solution. In addition, their size can be tuned by controlling the initial monomer concentrations, an observation that is supported by a theoretical analysis. These hollow microrings can encapsulate guest molecules in the intratoroidal nanospace, and their peripheries can act as templates for circular arrays of metal nanoparticles.

Hollow spheres: crucial building blocks for novel nanostructures and nanophotonics

Directory of Open Access Journals (Sweden)

Zhong Kuo

2018-03-01

Full Text Available In this review, we summarize the latest developments in research specifically derived from the unique properties of hollow microspheres, in particular, hollow silica spheres with uniform shells. We focus on applications in nanosphere (colloidal lithography and nanophotonics. The lithography from a layer of hollow spheres can result in nanorings, from a multilayer in unique nano-architecture. In nanophotonics, disordered hollow spheres can result in antireflection coatings, while ordered colloidal crystals (CCs of hollow spheres exhibit unique refractive index enhancement upon infiltration, ideal for optical sensing. Furthermore, whispering gallery mode (WGM inside the shell of hollow spheres has also been demonstrated to enhance light absorption to improve the performance of solar cells. These applications differ from the classical applications of hollow spheres, based only on their low density and large surface area, such as catalysis and chemical sensing. We provide a brief overview of the synthesis and self-assembly approaches of the hollow spheres. We elaborate on their unique optical features leading to defect mode lasing, optomicrofluidics, and the existence of WGMs inside shell for light management. Finally, we provide a perspective on the direction towards which future research relevant to hollow spheres might be directed.

Hollow spheres: crucial building blocks for novel nanostructures and nanophotonics

Science.gov (United States)

Zhong, Kuo; Song, Kai; Clays, Koen

2018-03-01

In this review, we summarize the latest developments in research specifically derived from the unique properties of hollow microspheres, in particular, hollow silica spheres with uniform shells. We focus on applications in nanosphere (colloidal) lithography and nanophotonics. The lithography from a layer of hollow spheres can result in nanorings, from a multilayer in unique nano-architecture. In nanophotonics, disordered hollow spheres can result in antireflection coatings, while ordered colloidal crystals (CCs) of hollow spheres exhibit unique refractive index enhancement upon infiltration, ideal for optical sensing. Furthermore, whispering gallery mode (WGM) inside the shell of hollow spheres has also been demonstrated to enhance light absorption to improve the performance of solar cells. These applications differ from the classical applications of hollow spheres, based only on their low density and large surface area, such as catalysis and chemical sensing. We provide a brief overview of the synthesis and self-assembly approaches of the hollow spheres. We elaborate on their unique optical features leading to defect mode lasing, optomicrofluidics, and the existence of WGMs inside shell for light management. Finally, we provide a perspective on the direction towards which future research relevant to hollow spheres might be directed.

Development of tree hollows in pedunculate oak (Quercus robur)

OpenAIRE

Ranius, Thomas; Niklasson, Mats; Berg, Niclas

2009-01-01

Many invertebrates, birds and mammals are dependent on hollow trees. For landscape planning that aims at persistence of species inhabiting hollow trees it is crucial to understand the development of such trees. In this study we constructed an individual-based simulation model to predict diameter distribution and formation of hollows in oak tree populations. Based on tree-ring data from individual trees, we estimated the ages when hollow formation commences for pedunculate oak (Quercus robur) ...

The Fabrication of Ga2O3/ZSM-5 Hollow Fibers for Efficient Catalytic Conversion of n-Butane into Light Olefins and Aromatics

Directory of Open Access Journals (Sweden)

Jing Han

2016-01-01

Full Text Available In this study, the dehydrogenation component of Ga2O3 was introduced into ZSM-5 nanocrystals to prepare Ga2O3/ZSM-5 hollow fiber-based bifunctional catalysts. The physicochemical features of as-prepared catalysts were characterized by means of XRD, BET, SEM, STEM, NH3-TPD, etc., and their performances for the catalytic conversion of n-butane to produce light olefins and aromatics were investigated. The results indicated that a very small amount of gallium can cause a marked enhancement in the catalytic activity of ZSM-5 because of the synergistic effect of the dehydrogenation and aromatization properties of Ga2O3 and the cracking function of ZSM-5. Compared with Ga2O3/ZSM-5 nanoparticles, the unique hierarchical macro-meso-microporosity of the as-prepared hollow fibers can effectively enlarge the bifunctionality by enhancing the accessibility of active sites and the diffusion. Consequently, Ga2O3/ZSM-5 hollow fibers show excellent catalytic conversion of n-butane, with the highest yield of light olefins plus aromatics at 600 °C by 87.6%, which is 56.3%, 24.6%, and 13.3% higher than that of ZSM-5, ZSM-5 zeolite fibers, and Ga2O3/ZSM-5, respectively.

Method for producing small hollow spheres

International Nuclear Information System (INIS)

Hendricks, C.D.

1979-01-01

A method is described for producing small hollow spheres of glass, metal or plastic, wherein the sphere material is mixed with or contains as part of the composition a blowing agent which decomposes at high temperature (T >approx. 600 0 C). As the temperature is quickly raised, the blowing agent decomposes and the resulting gas expands from within, thus forming a hollow sphere of controllable thickness. The thus produced hollow spheres (20 to 10 3 μm) have a variety of application, and are particularly useful in the fabrication of targets for laser implosion such as neutron sources, laser fusion physics studies, and laser initiated fusion power plants

Efficient improvement of virtual crack extension method by a derivative of the finite element stiffness matrix

International Nuclear Information System (INIS)

Ishikawa, H.; Nakano, S.; Yuuki, R.; Chung, N.Y.

1991-01-01

In the virtual crack extension method, the stress intensity factor, K, is obtained from the converged value of the energy release rate by the difference of the finite element stiffness matrix when some crack extension are taken. Instead of the numerical difference of the finite element stiffness, a new method to use a direct dirivative of the finite element stiffness matrix with respect to crack length is proposed. By the present method, the results of some example problems, such as uniform tension problems of a square plate with a center crack and a rectangular plate with an internal slant crack, are obtained with high accuracy and good efficiency. Comparing with analytical results, the present values of the stress intensity factors of the problems are obtained with the error that is less than 0.6%. This shows the numerical assurance of the usefulness of the present method. A personal computer program for the analysis is developed

Crack modeling of rotating blades with cracked hexahedral finite element method

Science.gov (United States)

Liu, Chao; Jiang, Dongxiang

2014-06-01

Dynamic analysis is the basis in investigating vibration features of cracked blades, where the features can be applied to monitor health state of blades, detect cracks in an early stage and prevent failures. This work presents a cracked hexahedral finite element method for dynamic analysis of cracked blades, with the purpose of addressing the contradiction between accuracy and efficiency in crack modeling of blades in rotor system. The cracked hexahedral element is first derived with strain energy release rate method, where correction of stress intensity factors of crack front and formulation of load distribution of crack surface are carried out to improve the modeling accuracy. To consider nonlinear characteristics of time-varying opening and closure effects caused by alternating loads, breathing function is proposed for the cracked hexahedral element. Second, finite element method with contact element is analyzed and used for comparison. Finally, validation of the cracked hexahedral element is carried out in terms of breathing effects of cracked blades and natural frequency in different crack depths. Good consistency is acquired between the results with developed cracked hexahedral element and contact element, while the computation time is significantly reduced in the previous one. Therefore, the developed cracked hexahedral element achieves good accuracy and high efficiency in crack modeling of rotating blades.

Corrosion cracking

International Nuclear Information System (INIS)

Goel, V.S.

1985-01-01

This book presents the papers given at a conference on alloy corrosion cracking. Topics considered at the conference included the effect of niobium addition on intergranular stress corrosion cracking, corrosion-fatigue cracking in fossil-fueled-boilers, fracture toughness, fracture modes, hydrogen-induced thresholds, electrochemical and hydrogen permeation studies, the effect of seawater on fatigue crack propagation of wells for offshore structures, the corrosion fatigue of carbon steels in seawater, and stress corrosion cracking and the mechanical strength of alloy 600

Crack closure and growth behavior of short fatigue cracks under random loading (part I : details of crack closure behavior)

International Nuclear Information System (INIS)

Lee, Shin Young; Song, Ji Ho

2000-01-01

Crack closure and growth behavior of physically short fatigue cracks under random loading are investigated by performing narrow-and wide-band random loading tests for various stress ratios. Artificially prepared two-dimensional, short through-thickness cracks are used. The closure behavior of short cracks under random loading is discussed, comparing with that of short cracks under constant-amplitude loading and also that of long cracks under random loading. Irrespective of random loading spectrum or block length, the crack opening load of short cracks is much lower under random loading than under constant-amplitude loading corresponding to the largest load cycle in a random load history, contrary to the behavior of long cracks that the crack opening load under random loading is nearly the same as or slightly higher than constant-amplitude results. This result indicates that the largest load cycle in a random load history has an effect to enhance crack opening of short cracks

The Riddle of the Apparently Hollow Himalaya

Indian Academy of Sciences (India)

The Riddle of the Apparently Hollow Himalaya. Ramesh .... It was as if the Himalayas were hollow inside. ... block would be consistent with the ground elevation in such a ... Alternative models and possible preference: Many refinements of.

Analysis of crack opening stresses for center- and edge-crack tension specimens

Directory of Open Access Journals (Sweden)

Tong Di-Hua

2014-04-01

Full Text Available Accurate determination of crack opening stress is of central importance to fatigue crack growth analysis and life prediction based on the crack-closure model. This paper studies the crack opening behavior for center- and edge-crack tension specimens. It is found that the crack opening stress is affected by the crack tip element. By taking the crack tip element into account, a modified crack opening stress equation is given for the center-crack tension specimen. Crack surface displacement equations for an edge crack in a semi-infinite plate under remote uniform tension and partially distributed pressure are derived by using the weight function method. Based on these displacements, a crack opening stress equation for an edge crack in a semi-infinite plate under uniform tension has been developed. The study shows that the crack opening stress is geometry-dependent, and the weight function method provides an effective and reliable tool to deal with such geometry dependence.

A consistent partly cracked XFEM element for cohesive crack growth

DEFF Research Database (Denmark)

Asferg, Jesper L.; Poulsen, Peter Noe; Nielsen, Leif Otto

2007-01-01

Present extended finite element method (XFEM) elements for cohesive crack growth may often not be able to model equal stresses on both sides of the discontinuity when acting as a crack-tip element. The authors have developed a new partly cracked XFEM element for cohesive crack growth with extra...... enrichments to the cracked elements. The extra enrichments are element side local and were developed by superposition of the standard nodal shape functions for the element and standard nodal shape functions for a sub-triangle of the cracked element. With the extra enrichments, the crack-tip element becomes...... capable of modelling variations in the discontinuous displacement field on both sides of the crack and hence also capable of modelling the case where equal stresses are present on each side of the crack. The enrichment was implemented for the 3-node constant strain triangle (CST) and a standard algorithm...

Hollow metal nanostructures for enhanced plasmonics (Conference Presentation)

Science.gov (United States)

Genç, Aziz; Patarroyo, Javier; Sancho-Parramon, Jordi; Duchamp, Martial; Gonzalez, Edgar; Bastus, Neus G.; Houben, Lothar; Dunin-Borkowski, Rafal; Puntes, Victor F.; Arbiol, Jordi

2016-03-01

Complex metal nanoparticles offer a great playground for plasmonic nanoengineering, where it is possible to cover plasmon resonances from ultraviolet to near infrared by modifying the morphologies from solid nanocubes to nanoframes, multiwalled hollow nanoboxes or even nanotubes with hybrid (alternating solid and hollow) structures. We experimentally show that structural modifications, i.e. void size and final morphology, are the dominant determinants for the final plasmonic properties, while compositional variations allow us to get a fine tuning. EELS mappings of localized surface plasmon resonances (LSPRs) reveal an enhanced plasmon field inside the voids of hollow AuAg nanostructures along with a more homogeneous distributions of the plasmon fields around the nanostructures. With the present methodology and the appropriate samples we are able to compare the effects of hybridization at the nanoscale in hollow nanostructures. Boundary element method (BEM) simulations also reveal the effects of structural nanoengineering on plasmonic properties of hollow metal nanostructures. Possibility of tuning the LSPR properties of hollow metal nanostructures in a wide range of energy by modifying the void size/shell thickness is shown by BEM simulations, which reveals that void size is the dominant factor for tuning the LSPRs. As a proof of concept for enhanced plasmonic properties, we show effective label free sensing of bovine serum albumin (BSA) with some of our hollow nanostructures. In addition, the different plasmonic modes observed have also been studied and mapped in 3D.

Ni hollow spheres as catalysts for methanol and ethanol electrooxidation

Energy Technology Data Exchange (ETDEWEB)

Xu, Changwei [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Hu, Yonghong; Rong, Jianhua; Liu, Yingliang [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); Jiang, San Ping [School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

2007-08-15

In this paper, we successfully synthesized Ni hollow spheres consisting of needle-like nickel particles by using silica spheres as template with gold nanoparticles seeding method. The Ni hollow spheres are applied to methanol and ethanol electrooxidation in alkaline media. The results show that the Ni hollow spheres give a very high activity for alcohol electrooxidation at a very low nickel loading of 0.10 mg cm{sup -2}. The current on Ni hollow spheres is much higher than that on Ni particles. The onset potential and peak potential on Ni hollow spheres are more negative than that on Ni particles for methanol and ethanol electrooxidation. The Ni hollow spheres may be of great potential in alcohol sensor and direct alcohol fuel cells. (author)

Unsaturated Seepage Analysis of Cracked Soil including Development Process of Cracks

Directory of Open Access Journals (Sweden)

Ling Cao

2016-01-01

Full Text Available Cracks in soil provide preferential pathways for water flow and their morphological parameters significantly affect the hydraulic conductivity of the soil. To study the hydraulic properties of cracks, the dynamic development of cracks in the expansive soil during drying and wetting has been measured in the laboratory. The test results enable the development of the relationships between the cracks morphological parameters and the water content. In this study, the fractal model has been used to predict the soil-water characteristic curve (SWCC of the cracked soil, including the developmental process of the cracks. The cracked expansive soil has been considered as a crack-pore medium. A dual media flow model has been developed to simulate the seepage characteristics of the cracked expansive soil. The variations in pore water pressure at different part of the model are quite different due to the impact of the cracks. This study proves that seepage characteristics can be better predicted if the impact of cracks is taken into account.

Fabrication of Closed Hollow Bulb Obturator Using Thermoplastic Resin Material

Directory of Open Access Journals (Sweden)

Bidhan Shrestha

2015-01-01

Full Text Available Purpose. Closed hollow bulb obturators are used for the rehabilitation of postmaxillectomy patients. However, the time consuming process, complexity of fabrication, water leakage, and discoloration are notable disadvantages of this technique. This paper describes a clinical report of fabricating closed hollow bulb obturator using a single flask and one time processing method for an acquired maxillary defect. Hard thermoplastic resin sheet has been used for the fabrication of hollow bulb part of the obturator. Method. After fabrication of master cast conventionally, bulb and lid part of the defect were formed separately and joined by autopolymerizing acrylic resin to form one sized smaller hollow body. During packing procedure, the defect area was loaded with heat polymerizing acrylic resin and then previously fabricated smaller hollow body was adapted over it. The whole area was then loaded with heat cure acrylic. Further processes were carried out conventionally. Conclusion. This technique uses single flask which reduces laboratory time and makes the procedure simple. The thickness of hollow bulb can be controlled and light weight closed hollow bulb prosthesis can be fabricated. It also minimizes the disadvantages of closed hollow bulb obturator such as water leakage, bacterial infection, and discoloration.

Preparation and Application of Hollow Silica/magnetic Nanocomposite Particle

Science.gov (United States)

Wang, Cheng-Chien; Lin, Jing-Mo; Lin, Chun-Rong; Wang, Sheng-Chang

The hollow silica/cobalt ferrite (CoFe2O4) magnetic microsphere with amino-groups were successfully prepared via several steps, including preparing the chelating copolymer microparticles as template by soap-free emulsion polymerization, manufacturing the hollow cobalt ferrite magnetic microsphere by in-situ chemical co-precipitation following calcinations, and surface modifying of the hollow magnetic microsphere by 3-aminopropyltrime- thoxysilane via the sol-gel method. The average diameter of polymer microspheres was ca. 200 nm from transmission electron microscope (TEM) measurement. The structure of the hollow magnetic microsphere was characterized by using TEM and scanning electron microscope (SEM). The spinel-type lattice of CoFe2O4 shell layer was identified by using XRD measurement. The diameter of CoFe2O4 crystalline grains ranged from 54.1 nm to 8.5 nm which was estimated by Scherrer's equation. Additionally, the hollow silica/cobalt ferrite microsphere possesses superparamagnetic property after VSM measurement. The result of BET measurement reveals the hollow magnetic microsphere which has large surface areas (123.4m2/g). After glutaraldehyde modified, the maximum value of BSA immobilization capacity of the hollow magnetic microsphere was 33.8 mg/g at pH 5.0 buffer solution. For microwave absorption, when the hollow magnetic microsphere was compounded within epoxy resin, the maximum reflection loss of epoxy resins could reach -35dB at 5.4 GHz with 1.9 mm thickness.

Long-term evaluation of hollow screw and hollow cylinder dental implants : Clinical and radiographic results after 10 years

NARCIS (Netherlands)

Telleman, Gerdien; Meijer, Henny J. A.; Raghoebar, Gerry M.

Background: In 1988, an implant manufacturer offered a new dental implant system, with a wide choice of hollow cylinder (HC) and hollow screw (HS) implants. The purpose of this retrospective study of HS and HC implants was to evaluate clinical and radiographic parameters of peri-implant tissue and

Crack detecting method

International Nuclear Information System (INIS)

Narita, Michiko; Aida, Shigekazu

1998-01-01

A penetration liquid or a slow drying penetration liquid prepared by mixing a penetration liquid and a slow drying liquid is filled to the inside of an artificial crack formed to a member to be detected such as of boiler power generation facilities and nuclear power facilities. A developing liquid is applied to the periphery of the artificial crack on the surface of a member to be detected. As the slow-drying liquid, an oil having a viscosity of 56 is preferably used. Loads are applied repeatedly to the member to be detected, and when a crack is caused to the artificial crack, the permeation liquid penetrates into the crack. The penetration liquid penetrated into the crack is developed by the developing liquid previously coated to the periphery of the artificial crack of the surface of the member to be detected. When a crack is caused, since the crack is developed clearly even if it is a small opening, the crack can be recognized visually reliably. (I.N.)

Synthesis of barium-strontium titanate hollow tubes using Kirkendall effect

Science.gov (United States)

Chen, Xuncai; Im, SangHyuk; Kim, Jinsoo; Kim, Woo-Sik

2018-02-01

(BaSr)TiO3 hexagonal hollow tubes was fabricated by a solid-state interfacial reaction including a Kirkendall diffusion. Using a co-precipitation and sol-gel process, a core@shell structure of (BaSr)CO3@TiO2 rods were prepared, and then converted to (BaSr)TiO3 hollow tubes at 750 °C. This was a first achievement of single-phase crystal hollow tube. Here, the inner diameter and wall thickness of hollow tube were about 700 nm and 130 nm, respectively. The fabrication of (BaSr)TiO3 hollow tubes was monitored with scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD) to investigate their formation mechanism. The present synthetic approach would provide a new insight into the design and fabrication of hollow architectures of many perovskite oxides.

Hollow porous-wall glass microspheres for hydrogen storage

Science.gov (United States)

Heung, Leung K.; Schumacher, Ray F.; Wicks, George G.

2010-02-23

A porous wall hollow glass microsphere is provided having a diameter range of between 1 to 200 microns, a density of between 1.0 to 2.0 gm/cc, a porous-wall structure having wall openings defining an average pore size of between 10 to 1000 angstroms, and which contains therein a hydrogen storage material. The porous-wall structure facilitates the introduction of a hydrogen storage material into the interior of the porous wall hollow glass microsphere. In this manner, the resulting hollow glass microsphere can provide a membrane for the selective transport of hydrogen through the porous walls of the microsphere, the small pore size preventing gaseous or liquid contaminants from entering the interior of the hollow glass microsphere.

Hollow proppants and a process for their manufacture

Science.gov (United States)

Jones, A.H.; Cutler, R.A.

1985-10-15

Hollow, fine-grained ceramic proppants are less expensive and improve fracture control when compared to conventional proppants (dense alumina, mullite, bauxite, zirconia, etc.). Hollow proppants of the present invention have been fabricated by spray drying, followed by sintering in order to obtain a dense case and a hollow core. These proppants generally have high sphericity and roundness (Krumbein sphericity and roundness greater than 0.8), have diameters on average between 2,250 and 125 [mu]m, depending on proppant size required, and have strength equal to or greater than that of sand. The hollow core, the size of which can be controlled, permits better fracture control in hydraulic fracturing treatments since the proppant can be transported in lower viscosity fluids. Hollow proppants produced at the same cost/weight as conventional proppants also provide for lower costs, since less weight is required to fill the same volume. The fine-grained (preferably less than 5 [mu]m in diameter) ceramic case provides the strength necessary to withstand closure stresses and prevent crushing. 6 figs.

Surfactant effects of indium on cracking in AlN/GaN distributed Bragg reflectors grown via metal organic vapor phase epitaxy

Science.gov (United States)

Rodak, L. E.; Miller, C. M.; Korakakis, D.

2011-01-01

Aluminum Nitride (AlN) and Gallium Nitride (GaN) superlattice structures are often characterized by a network of cracks resulting from the large lattice mismatch and difference in thermal expansion coefficients, especially as the thickness of the layers increases. This work investigates the influence of indium as a surfactant on strain and cracking in AlN/GaN DBRs grown via Metal Organic Vapor Phase Epitaxy (MOVPE). DBRs with peak reflectivities ranging from 465 nm to 540 nm were grown and indium was introduced during the growth of the AlN layer. Image processing techniques were used to quantify the crack length per square millimeter and it was observed that indium has a significant effect on the crack formation and reduced the total crack length in these structures by a factor of two.

Crack

Science.gov (United States)

... spending time in a rehab facility or getting cognitive-behavioral therapy or other treatments. Right now, there are no medicines to treat a crack addiction. If you smoke crack, talking with a counselor ...

Adiabatic Rearrangement of Hollow PV Towers

Directory of Open Access Journals (Sweden)

Eric A Hendricks

2010-10-01

Full Text Available Diabatic heating from deep moist convection in the hurricane eyewall produces a towering annular structure of elevated potential vorticity (PV. This structure has been referred to as a hollow PV tower. The sign reversal of the radial gradient of PV satisfies the Charney-Stern necessary condition for combined barotropic-baroclinic instability. For thin enough annular structures, small perturbations grow exponentially, extract energy from the mean flow, and lead to hollow tower breakdown, with significant vortex structural and intensity change. The three-dimensional adiabatic rearrangements of two prototypical hurricane-like hollow PV towers (one thick and one thin are examined in an idealized framework. For both hollow towers, dynamic instability causes air parcels with high PV to be mixed into the eye preferentially at lower levels, where unstable PV wave growth rates are the largest. Little or no mixing is found to occur at upper levels. The mixing at lower and middle levels is most rapid for the breakdown of the thin hollow tower, consistent with previous barotropic results. For both hollow towers, this advective rearrangement of PV affects the tropical cyclone structure and intensity in a number of ways. First, the minimum central pressure and maximum azimuthal mean velocity simultaneously decrease, consistent with previous barotropic results. Secondly, isosurfaces of absolute angular momentum preferentially shift inward at low levels, implying an adiabatic mechanism by which hurricane eyewall tilt can form. Thirdly, a PV bridge, similar to that previously found in full-physics hurricane simulations, develops as a result of mixing at the isentropic levels where unstable PV waves grow most rapidly. Finally, the balanced mass field resulting from the PV rearrangement is warmer in the eye between 900 and 700 hPa. The location of this warming is consistent with observed warm anomalies in the eye, indicating that in certain instances the hurricane

Recent progress in hollow sphere-based electrodes for high-performance supercapacitors

Science.gov (United States)

Zhao, Yan; Chen, Min; Wu, Limin

2016-08-01

Hollow spheres have drawn much attention in the area of energy storage and conversion, especially in high-performance supercapacitors owing to their well-defined morphologies, uniform size, low density and large surface area. And quite some significant breakthroughs have been made in advanced supercapacitor electrode materials with hollow sphere structures. In this review, we summarize and discuss the synthesis and application of hollow spheres with controllable structure and morphology as electrode materials for supercapacitors. First, we briefly introduce the fabrication strategies of hollow spheres for electrode materials. Then, we discuss in detail the recent advances in various hollow sphere-based electrode materials for supercapacitors, including single-shelled, yolk-shelled, urchin-like, double-shelled, multi-shelled, and mesoporous hollow structure-based symmetric and asymmetric supercapacitor devices. We conclude this review with some perspectives on the future research and development of the hollow sphere-based electrode materials.

Recent progress in hollow sphere-based electrodes for high-performance supercapacitors.

Science.gov (United States)

Zhao, Yan; Chen, Min; Wu, Limin

2016-08-26

Hollow spheres have drawn much attention in the area of energy storage and conversion, especially in high-performance supercapacitors owing to their well-defined morphologies, uniform size, low density and large surface area. And quite some significant breakthroughs have been made in advanced supercapacitor electrode materials with hollow sphere structures. In this review, we summarize and discuss the synthesis and application of hollow spheres with controllable structure and morphology as electrode materials for supercapacitors. First, we briefly introduce the fabrication strategies of hollow spheres for electrode materials. Then, we discuss in detail the recent advances in various hollow sphere-based electrode materials for supercapacitors, including single-shelled, yolk-shelled, urchin-like, double-shelled, multi-shelled, and mesoporous hollow structure-based symmetric and asymmetric supercapacitor devices. We conclude this review with some perspectives on the future research and development of the hollow sphere-based electrode materials.

Fatigue crack growth rate studies on pipes and pipe welds made of austenitic stainless steel and carbon steel

International Nuclear Information System (INIS)

Arora, Punit; Singh, P.K.; Bhasin, Vivek; Vaze, K.K.; Pukazhendhi, D.M.; Gandhi, P.; Raghava, G.

2011-01-01

The objective of the present study is to understand the fatigue crack growth behavior in austenitic stainless steel and carbon steel pipes and pipe welds by carrying out analysis/predictions and experiments. The Paris law has been used for the prediction of fatigue crack growth life. To carry out the analysis, Paris constants have been determined for pipe (base) and pipe weld materials by using Compact Tension (CT)/Three Point Bend (TPB) specimens machined from the actual pipe/pipe weld. Analyses have been carried out to predict the fatigue crack growth life of pipes/pipe welds having part through cracks on the outer surface. In the analyses, Stress Intensity Factors (K) have been evaluated through two different schemes. The first scheme considers the 'K' evaluations at two points of the crack front i.e. maximum crack depth and crack tip at the outer surface. The second scheme accounts for the area averaged root mean square stress intensity factor (K RMS ) at deepest and surface points. In order to validate the analytical procedure/results, experiments have been carried out on full scale pipe and pipe welds with part through circumferential crack. Fatigue crack growth life evaluated using both schemes have been compared with experimental results. Use of stress intensity factor (K RMS ) evaluated using second scheme gives better fatigue crack growth life prediction compared to that of first scheme. (author)

Crack shape developments and leak rates for circumferential complex-cracked pipes

Energy Technology Data Exchange (ETDEWEB)

Brickstad, B.; Bergman, M. [SAQ Inspection Ltd., Stockholm (Sweden)

1997-04-01

A computerized procedure has been developed that predicts the growth of an initial circumferential surface crack through a pipe and further on to failure. The crack growth mechanism can either be fatigue or stress corrosion. Consideration is taken to complex crack shapes and for the through-wall cracks, crack opening areas and leak rates are also calculated. The procedure is based on a large number of three-dimensional finite element calculations of cracked pipes. The results from these calculations are stored in a database from which the PC-program, denoted LBBPIPE, reads all necessary information. In this paper, a sensitivity analysis is presented for cracked pipes subjected to both stress corrosion and vibration fatigue.

Hollow-duct radiation delivery system investigation

Directory of Open Access Journals (Sweden)

Kramer D.

2013-05-01

Full Text Available Investigation of hollow-duct structure for high-power laser-diode-array radiation delivery into the end-pumped large-aperture gain media is reported. A ray tracing method has been used to evaluate the performance of the structure designed for maximum transmission efficiency and output beam profile homogeneity. Variable hollow-duct lengths as well as emanating angles of laser-diode-array have been taken into account.

Hollow fiber liquid supported membranes

International Nuclear Information System (INIS)

Violante, V.

1987-01-01

The hollow fiber system are well known and developed in the scientific literature because of their applicability in the process separation units. The authors approach to a mathematical model for a particular hollow fiber system, usin liquid membranes. The model has been developed in order to obtain a suitable tool for a sensitivy analysis and for a scaling-up. This kind of investigation is very usefull from an engineering point of view, to get a spread range of information to build up a pilot plant from the laboratory scale

Experimental study on hollow structural component by explosive welding

Energy Technology Data Exchange (ETDEWEB)

Duan, Mianjun, E-mail: dmjwl@163.com [PLA University of Science and Technology, Nanjing 210007 (China); Wei, Ling, E-mail: 386006087@qq.com [Tongda College, Nanjing University of Posts and Telecommunication, Nanjing 210007 (China); Hong, Jin [PLA University of Science and Technology, Nanjing 210007 (China); Ran, Hong [Southwestern Institute of Physics, Chengdu 610041 (China); Ma, Rui; Wang, Yaohua [PLA University of Science and Technology, Nanjing 210007 (China)

2014-12-15

Highlights: • This paper relates to a study on a thin double-layers hollow structural component by using an explosive welding technology. • This thin double-layer hollow structural component is an indispensable component required for certain core equipment of thermonuclear experimental reactor. • An adjusted explosive welding technology for manufacturing an inconel625 hollow structural component was developed which cannot be made by common technology. • The result shows that a metallurgical bonding was realized by the ribs and slabs of the hollow sheet. • The shearing strength of bonding interface exceeds that of the parent metal. - Abstract: A large thin-walled hollow structural component with sealed channels is required for the vacuum chamber of a thermonuclear experimental reactor, with inconel625 as its fabrication material. This hollow structural component is rarely manufactured by normal machining method, and its manufacture is also problematic in the field of explosive welding. With this in mind, we developed an adjusted explosive welding technology which involves a two-step design, setting and annealing technology. The joints were evaluated using optical microscope and scanning electron microscope, and a mechanical experiment was conducted, involving micro-hardness test, cold helium leak test and hydraulic pressure test. The results showed that a metallurgical bonding was realized by the ribs and slabs, and the shearing strength of the bonding interface exceeded that of the parent metal. Hence, the hollow structural component has a good comprehensive mechanical performance and sealing property.

Experimental study on hollow structural component by explosive welding

International Nuclear Information System (INIS)

Duan, Mianjun; Wei, Ling; Hong, Jin; Ran, Hong; Ma, Rui; Wang, Yaohua

2014-01-01

Highlights: • This paper relates to a study on a thin double-layers hollow structural component by using an explosive welding technology. • This thin double-layer hollow structural component is an indispensable component required for certain core equipment of thermonuclear experimental reactor. • An adjusted explosive welding technology for manufacturing an inconel625 hollow structural component was developed which cannot be made by common technology. • The result shows that a metallurgical bonding was realized by the ribs and slabs of the hollow sheet. • The shearing strength of bonding interface exceeds that of the parent metal. - Abstract: A large thin-walled hollow structural component with sealed channels is required for the vacuum chamber of a thermonuclear experimental reactor, with inconel625 as its fabrication material. This hollow structural component is rarely manufactured by normal machining method, and its manufacture is also problematic in the field of explosive welding. With this in mind, we developed an adjusted explosive welding technology which involves a two-step design, setting and annealing technology. The joints were evaluated using optical microscope and scanning electron microscope, and a mechanical experiment was conducted, involving micro-hardness test, cold helium leak test and hydraulic pressure test. The results showed that a metallurgical bonding was realized by the ribs and slabs, and the shearing strength of the bonding interface exceeded that of the parent metal. Hence, the hollow structural component has a good comprehensive mechanical performance and sealing property

Assessment of fatigue crack length via plastic deformation in compact tension specimens using magnetic Barkhausen noise

International Nuclear Information System (INIS)

Reyes-Rodriguez, F. de los; Diego-Velasco, G. de; Capo-Sanchez, J.; Franco-Fidalgo, E.

2013-01-01

In this paper the influence of different parameters on crack length is determined via plastic deformation using magnetic Barkhausen noise; the compact specimens steel used in this study were 12Cr1MoV and 11Cr1Mo, which are used for steam transportation on power plants. The main objective of this paper is to determine the crack length and its incubation time using magnetic Barkhausen noise, which lets to improve the pre-cracking process prior creep crack growth rate test simulating the real conditions of high pressure and temperature of main steam lines. Results showed that mean root square and maximum pick of voltage decrease with plastic deformation for each steel analyzed in this work, on the other hand, with the increasing of plastic deformation, a logic relationship between plastic deformation and spectrum density is observed for mid frequencies values, as well as, a variation of the amplitude, width and shape of the Barkhausen signal envelope. (Author)

Ductile crack growth simulation from near crack tip dissipated energy

International Nuclear Information System (INIS)

Marie, S.; Chapuliot, S.

2000-01-01

A method to calculate ductile tearing in both small scale fracture mechanics specimens and cracked components is presented. This method is based on an estimation of the dissipated energy calculated near the crack tip. Firstly, the method is presented. It is shown that a characteristic parameter G fr can be obtained, relevant to the dissipated energy in the fracture process. The application of the method to the calculation of side grooved crack tip (CT) specimens of different sizes is examined. The value of G fr is identified by comparing the calculated and experimental load line displacement versus crack extension curve for the smallest CT specimen. With this identified value, it is possible to calculate the global behaviour of the largest specimen. The method is then applied to the calculation of a pipe containing a through-wall thickness crack subjected to a bending moment. This pipe is made of the same material as the CT specimens. It is shown that it is possible to simulate the global behaviour of the structure including the prediction of up to 90-mm crack extension. Local terms such as the equivalent stress or the crack tip opening angle are found to be constant during the crack extension process. This supports the view that G fr controls the fields in the vicinity near the crack tip. (orig.)

Engineering Porous Polymer Hollow Fiber Microfluidic Reactors for Sustainable C-H Functionalization.

Science.gov (United States)

He, Yingxin; Rezaei, Fateme; Kapila, Shubhender; Rownaghi, Ali A

2017-05-17

Highly hydrophilic and solvent-stable porous polyamide-imide (PAI) hollow fibers were created by cross-linking of bare PAI hollow fibers with 3-aminopropyl trimethoxysilane (APS). The APS-grafted PAI hollow fibers were then functionalized with salicylic aldehyde for binding catalytically active Pd(II) ions through a covalent postmodification method. The catalytic activity of the composite hollow fiber microfluidic reactors (Pd(II) immobilized APS-grafted PAI hollow fibers) was tested via heterogeneous Heck coupling reaction of aryl halides under both batch and continuous-flow reactions in polar aprotic solvents at high temperature (120 °C) and low operating pressure. X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma (ICP) analyses of the starting and recycled composite hollow fibers indicated that the fibers contain very similar loadings of Pd(II), implying no degree of catalyst leaching from the hollow fibers during reaction. The composite hollow fiber microfluidic reactors showed long-term stability and strong control over the leaching of Pd species.

Review of Synthetic Methods to Form Hollow Polymer Nanocapsules

Energy Technology Data Exchange (ETDEWEB)

Barker, Madeline T. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2014-03-13

Syntactic foams have grown in interest due to the widened range of applications because of their mechanical strength and high damage tolerance. In the past, hollow glass or ceramic particles were used to create the pores. This paper reviews literature focused on the controlled synthesis of hollow polymer spheres with diameters ranging from 100 –200 nm. By using hollow polymer spheres, syntactic foams could reach ultra-low densities.

Fatigue and Creep Crack Propagation behaviour of Alloy 617 in the Annealed and Aged Conditions

Energy Technology Data Exchange (ETDEWEB)

Julian K. Benz; Richard N. Wright

2013-10-01

The crack propagation behaviour of Alloy 617 was studied under various conditions. Elevated temperature fatigue and creep-fatigue crack growth experiments were conducted at 650 and 800 degrees C under constant stress intensity (triangle K) conditions and triangular or trapezoidal waveforms at various frequencies on as-received, aged, and carburized material. Environmental conditions included both laboratory air and characteristic VHTR impure helium. As-received Alloy 617 displayed an increase in the crack growth rate (da/dN) as the frequency was decreased in air which indicated a time-dependent contribution component in fatigue crack propagation. Material aged at 650°C did not display any influence on the fatigue crack growth rates nor the increasing trend of crack growth rate with decreasing frequency even though significant microstructural evolution, including y’ (Ni3Al) after short times, occurred during aging. In contrast, carburized Alloy 617 showed an increase in crack growth rates at all frequencies tested compared to the material in the standard annealed condition. Crack growth studies under quasi-constant K (i.e. creep) conditions were also completed at 650 degrees C and a stress intensity of K = 40 MPa9 (square root)m. The results indicate that crack growth is primarily intergranular and increased creep crack growth rates exist in the impure helium environment when compared to the results in laboratory air. Furthermore, the propagation rates (da/dt) continually increased for the duration of the creep crack growth either due to material aging or evolution of a crack tip creep zone. Finally, fatigue crack propagation tests at 800 degrees C on annealed Alloy 617 indicated that crack propagation rates were higher in air than impure helium at the largest frequencies and lowest stress intensities. The rates in helium, however, eventually surpass the rates in air as the frequency is reduced and the stress intensity is decreased which was not observed at 650

On applicability of crack shape characterization rules for multiple in-plane surface cracks

International Nuclear Information System (INIS)

Kim, Jong Min; Choi, Suhn; Park, Keun Bae; Choi, Jae Boong; Huh, Nam Su

2009-01-01

The fracture mechanics assessment parameters, such as the elastic stress intensity factor and the elastic-plastic J-integral, for a surface crack can be significantly affected by adjacent cracks. Regarding such an interaction effect, the relative distance between adjacent cracks, crack aspect ratio and loading condition were known to be important factors for multiple cracks, which affects the fracture mechanics assessment parameters. Although several guidance (ASME Sec. XI, BS7910, British Energy R6 and API RP579) on a crack interaction effect (crack combination rule) have been proposed and used for assessing the interaction effect, each guidance provides different rules for combining multiple surface cracks into a single surface crack. Based on the systematic elastic and elastic-plastic finite element analyses, the present study investigated the acceptability of the crack combination rules provided in the existing guidance, and the relevant recommendations on a crack interaction for in-plane surface cracks in a plate were discussed. To quantify the interaction effect, the elastic stress intensity factor and elastic-plastic J-integral along the crack front were used. As for the loading condition, only axial tension was considered. As a result, BS7910 seems to provide the most relevant crack combination rule for in-plane dual surface cracks, whereas API RP579 provides the most conservative results. In particular, ASME Sec. XI still seems to have some room for a revision to shorten the critical distance between two adjacent cracks for a crack combination. The overall tendency of the elastic-plastic analyses results is identical to that of the elastic analyses results.

Hollow cathode for positive ion sources

International Nuclear Information System (INIS)

Schechter, D.E.; Kim, J.; Tsai, C.C.

1979-01-01

Development to incorporate hollow cathodes into high power ion sources for neutral beam injection systems is being pursued. Hollow tube LaB 6 -type cathodes, similar to a UCLA design, have been constructed and tested in several ORNL ion source configurations. Results of testing include arc discharge parameters of >1000 and 500 amps for 0.5 and 10 second pulse lengths, respectively. Details of cathode construction and additional performance results are discussed

Polyazole hollow fiber membranes for direct contact membrane distillation

KAUST Repository

Maab, Husnul; Alsaadi, Ahmad Salem; Francis, Lijo; Livazovic, Sara; Ghaffour, NorEddine; Amy, Gary L.; Nunes, Suzana Pereira

2013-01-01

Porous hollow fiber membranes were fabricated from fluorinated polyoxadiazole and polytriazole by a dry-wet spinning method for application in desalination of Red Sea water by direct contact membrane distillation (DCMD). The data were compared with commercially available hollow fiber MD membranes prepared from poly(vinylidene fluoride). The membranes were characterized by electron microscopy, liquid entry pressure (LEP), and pore diameter measurements. Finally, the hollow fiber membranes were tested for DCMD. Salt selectivity as high as 99.95% and water fluxes as high as 35 and 41 L m -2 h-1 were demonstrated, respectively, for polyoxadiazole and polytriazole hollow fiber membranes, operating at 80 C feed temperature and 20 C permeate. © 2013 American Chemical Society.

Polyazole hollow fiber membranes for direct contact membrane distillation

KAUST Repository

Maab, Husnul

2013-08-07

Porous hollow fiber membranes were fabricated from fluorinated polyoxadiazole and polytriazole by a dry-wet spinning method for application in desalination of Red Sea water by direct contact membrane distillation (DCMD). The data were compared with commercially available hollow fiber MD membranes prepared from poly(vinylidene fluoride). The membranes were characterized by electron microscopy, liquid entry pressure (LEP), and pore diameter measurements. Finally, the hollow fiber membranes were tested for DCMD. Salt selectivity as high as 99.95% and water fluxes as high as 35 and 41 L m -2 h-1 were demonstrated, respectively, for polyoxadiazole and polytriazole hollow fiber membranes, operating at 80 C feed temperature and 20 C permeate. © 2013 American Chemical Society.

Boron nitride hollow nanospheres: Synthesis, formation mechanism and dielectric property

Energy Technology Data Exchange (ETDEWEB)

Zhong, B.; Tang, X.H. [School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209 (China); Huang, X.X., E-mail: swliza@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Xia, L. [School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209 (China); Zhang, X.D. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wang, C.J. [School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209 (China); Wen, G.W., E-mail: g.wen@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209 (China); School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

2015-04-15

Highlights: • BN hollow nanospheres are fabricated in large scale via a new CVD method. • Morphology and structure are elucidated by complementary analytical techniques. • Formation mechanism is proposed based on experimental observations. • Dielectric properties are investigated in the X-band microwave frequencies. • BN hollow nanospheres show lower dielectric loss than regular BN powders. - Abstract: Boron nitride (BN) hollow nanospheres have been successfully fabricated by pyrolyzing vapors decomposed from ammonia borane (NH{sub 3}BH{sub 3}) at 1300 °C. The final products have been extensively characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The BN hollow nanospheres were ranging from 100 to 300 nm in diameter and around 30–100 nm in thickness. The internal structure of the products was found dependent on the reaction temperatures. A possible formation mechanism of the BN hollow nanospheres was proposed on the basis of the experimental observations. Dielectric measurements in the X-band microwave frequencies (8–12 GHz) showed that the dielectric loss of the paraffin filled by the BN hollow nanospheres was lower than that filled by regular BN powders, which indicated that the BN hollow nanospheres could be potentially used as low-density fillers for microwave radomes.

High performance methanol-oxygen fuel cell with hollow fiber electrode

Science.gov (United States)

Lawson, Daniel D. (Inventor); Ingham, John D. (Inventor)

1983-01-01

A methanol/air-oxygen fuel cell including an electrode formed by open-ended ion-exchange hollow fibers having a layer of catalyst deposited on the inner surface thereof and a first current collector in contact with the catalyst layer. A second current collector external of said fibers is provided which is immersed along with the hollow fiber electrode in an aqueous electrolyte body. Upon passage of air or oxygen through the hollow fiber electrode and introduction of methanol into the aqueous electrolyte, a steady current output is obtained. Two embodiments of the fuel cell are disclosed. In the first embodiment the second metal electrode is displaced away from the hollow fiber in the electrolyte body while in the second embodiment a spiral-wrap electrode is provided about the outer surface of the hollow fiber electrode.

High-performance supercapacitors based on hollow polyaniline nanofibers by electrospinning.

Science.gov (United States)

Miao, Yue-E; Fan, Wei; Chen, Dan; Liu, Tianxi

2013-05-22

Hollow polyaniline (PANI) nanofibers with controllable wall thickness are fabricated by in situ polymerization of aniline using the electrospun poly(amic acid) fiber membrane as a template. A maximum specific capacitance of 601 F g(-1) has been achieved at 1 A g(-1), suggesting the potential application of hollow PANI nanofibers for supercapacitors. The superior electrochemical performance of the hollow nanofibers is attributed to their hollow structure, thin wall thickness, and orderly pore passages, which can drastically facilitate the ion diffusion and improve the utilization of the electroactive PANI during the charge-discharge processes. Furthermore, the high flexibility of the self-standing fiber membrane template provides possibilities for the facile construction and fabrication of conducting polymers with hollow nanostructures, which may find potential applications in various high-performance electrochemical devices.

Mercury - the hollow planet

Science.gov (United States)

Rothery, D. A.

2012-04-01

Mercury is turning out to be a planet characterized by various kinds of endogenous hole (discounting impact craters), which are compared here. These include volcanic vents and collapse features on horizontal scales of tens of km, and smaller scale depressions ('hollows') associated with bright crater-floor deposits (BCFD). The BCFD hollows are tens of metres deep and kilometres or less across and are characteristically flat-floored, with steep, scalloped walls. Their form suggests that they most likely result from removal of surface material by some kind of mass-wasting process, probably associated with volume-loss caused by removal (via sublimation?) of a volatile component. These do not appear to be primarily a result of undermining. Determining the composition of the high-albedo bluish surface coating in BCFDs will be a key goal for BepiColombo instruments such as MIXS (Mercury Imaging Xray Spectrometer). In contrast, collapse features are non-circular rimless pits, typically on crater floors (pit-floor craters), whose morphology suggests collapse into void spaces left by magma withdrawal. This could be by drainage of either erupted lava (or impact melt) or of shallowly-intruded magma. Unlike the much smaller-scale BCFD hollows, these 'collapse pit' features tend to lack extensive flat floors and instead tend to be close to triangular in cross-section with inward slopes near to the critical angle of repose. The different scale and morphology of BCFD hollows and collapse pits argues for quite different modes of origin. However, BCFD hollows adjacent to and within the collapse pit inside Scarlatti crater suggest that the volatile material whose loss was responsible for the growth of the hollows may have been emplaced in association with the magma whose drainage caused the main collapse. Another kind of volcanic collapse can be seen within a 25 km-wide volcanic vent outside the southern rim of the Caloris basin (22.5° N, 146.1° E), on a 28 m/pixel MDIS NAC image

Subsurface metals fatigue cracking without and with crack tip

Directory of Open Access Journals (Sweden)

Andrey Shanyavskiy

2013-07-01

Full Text Available Very-High-Cycle-Fatigue regime for metals was considered and mechanisms of the subsurface crack origination were introduced. In many metals first step of crack origination takes place with specific area formation because of material pressing and rotation that directed to transition in any volume to material ultra-high-plasticity with nano-structure appearing. Then by the border of the nano-structure takes place volume rotation and fracture surface creates with spherical particles which usually named Fine-Granular-Area. In another case there takes place First-Smooth-Facet occurring in area of origin due to whirls appearing by the one of the slip systems under discussed the same stress-state conditions. Around Fine-Granular-Area or First-Smooth-Facet there plastic zone appeared and, then, subsurface cracking develops by the same manner as for through cracks. In was discussed quantum-mechanical nature of fatigue crack growth in accordance with Yang’s modulus quantization for low level of deformations. New simply equation was considered for describing subsurface cracking in metals out of Fine-Granular-Area or Fist-Smooth-Facet.

[Study on Hollow Brick Wall's Surface Temperature with Infrared Thermal Imaging Method].

Science.gov (United States)

Tang, Ming-fang; Yin, Yi-hua

2015-05-01

To address the characteristic of uneven surface temperature of hollow brick wall, the present research adopts soft wares of both ThermaCAM P20 and ThermaCAM Reporter to test the application of infrared thermal image technique in measuring surface temperature of hollow brick wall, and further analyzes the thermal characteristics of hollow brick wall, and building material's impact on surface temperature distribution including hollow brick, masonry mortar, and so on. The research selects the construction site of a three-story-high residential, carries out the heat transfer experiment, and further examines the exterior wall constructed by 3 different hollow bricks including sintering shale hollow brick, masonry mortar and brick masonry. Infrared thermal image maps are collected, including 3 kinds of sintering shale hollow brick walls under indoor heating in winter; and temperature data of wall surface, and uniformity and frequency distribution are also collected for comparative analysis between 2 hollow bricks and 2 kinds of mortar masonry. The results show that improving heat preservation of hollow brick aid masonry mortar can effectively improve inner wall surface temperature and indoor thermal environment; non-uniformity of surface temperature decreases from 0. 6 to 0. 4 °C , and surface temperature frequency distribution changes from the asymmetric distribution into a normal distribution under the condition that energy-saving sintering shale hollow brick wall is constructed by thermal mortar replacing cement mortar masonry; frequency of average temperature increases as uniformity of surface temperature increases. This research provides a certain basis for promotion and optimization of hollow brick wall's thermal function.

Effects of δ-hydride precipitation at a crack tip on crack propagation in delayed hydride cracking of Zircaloy-2

Energy Technology Data Exchange (ETDEWEB)

Kubo, T., E-mail: kubo@nfd.co.jp [Nippon Nuclear Fuel Development Co., Ltd., 2163 Narita-cho, Oarai-machi, Ibaraki 311-1313 (Japan); Kobayashi, Y. [M.O.X. Co., Ltd., 1828-520 Hirasu-cho, Mito, Ibaraki 311-0853 (Japan)

2013-08-15

Highlights: • Steady state crack velocity of delayed hydride cracking in Zircaloy-2 was analyzed. • A large stress peak is induced at an end of hydride by volume expansion of hydride. • Hydrogen diffuses to the stress peak, thereby accelerating steady hydride growth. • Crack velocity was estimated from the calculated hydrogen flux into the stress peak. • There was good agreement between calculation results and experimental data. -- Abstract: Delayed hydride cracking (DHC) of Zircaloy-2 is one possible mechanism for the failure of boiling water reactor fuel rods in ramp tests at high burnup. Analyses were made for hydrogen diffusion around a crack tip to estimate the crack velocity of DHC in zirconium alloys, placing importance on effects of precipitation of δ-hydride. The stress distribution around the crack tip is significantly altered by precipitation of hydride, which was strictly analyzed using a finite element computer code. Then, stress-driven hydrogen diffusion under the altered stress distribution was analyzed by a differential method. Overlapping of external stress and hydride precipitation at a crack tip induces two stress peaks; one at a crack tip and the other at the front end of the hydride precipitate. Since the latter is larger than the former, more hydrogen diffuses to the front end of the hydride precipitate, thereby accelerating hydride growth compared with that in the absence of the hydride. These results indicated that, after hydride was formed in front of the crack tip, it grew almost steadily accompanying the interaction of hydrogen diffusion, hydride growth and the stress alteration by hydride precipitation. Finally, crack velocity was estimated from the calculated hydrogen flux into the crack tip as a function of temperature, stress intensity factor and material strength. There was qualitatively good agreement between calculation results and experimental data.

Crack retardation by load reduction during fatigue crack propagation

International Nuclear Information System (INIS)

Kim, Hyun Soo; Nam, Ki Woo; Ahn, Seok Hwan; Do, Jae Yoon

2003-01-01

Fracture life and crack retardation behavior were examined experimentally using CT specimens of aluminum alloy 5083. Crack retardation life and fracture life were a wide difference between 0.8 and 0.6 in proportion to ratio of load reduction. The wheeler model retardation parameter was used successfully to predict crack growth behavior. By using a crack propagation rule, prediction of fracture life can be evaluated quantitatively. A statistical approach based on Weibull distribution was applied to the test data to evaluate the dispersion in the retardation life and fracture life by the change of load reduction

Hollow density profile on electron cyclotron resonance heating JFT-2M plasma

International Nuclear Information System (INIS)

Yamauchi, Toshihiko; Hoshino, Katsumichi; Kawashima, Hisato; Ogawa, Toshihide; Kawakami, Tomohide; Shiina, Tomio; Ishige, Youichi

1998-01-01

The first hollow electron density profile in the central region on the JAERI Fusion Torus-2M (JFT-2M) is measured during electron cyclotron resonance heating (ECRH) with a TV Thomson scattering system (TVTS). The peripheral region is not hollow but is accumulated due to pump-out from the central region. The hollowness increases with time but is saturated at ∼40 ms and maintains a constant hollow ratio. The hollowness is strongly related to the steep temperature gradient of the heated zone. (author)

Investigation of Helicopter Longeron Cracks

Science.gov (United States)

Newman, John A.; Baughman, James; Wallace, Terryl A.

2009-01-01

Four cracked longerons, containing a total of eight cracks, were provided for study. Cracked regions were cut from the longerons. Load was applied to open the cracks, enabling crack surface examination. Examination revealed that crack propagation was driven by fatigue loading in all eight cases. Fatigue crack initiation appears to have occurred on the top edge of the longerons near geometric changes that affect component bending stiffness. Additionally, metallurgical analysis has revealed a local depletion in alloying elements in the crack initiation regions that may be a contributing factor. Fatigue crack propagation appeared to be initially driven by opening-mode loading, but at a crack length of approximately 0.5 inches (12.7 mm), there is evidence of mixed-mode crack loading. For the longest cracks studied, shear-mode displacements destroyed crack-surface features of interest over significant portions of the crack surfaces.

HOLLOW FIBRE MEMBRANE

NARCIS (Netherlands)

Wessling, Matthias; Stamatialis, Dimitrios; Kopec, K.K.; Dutczak, S.M.

2011-01-01

The present invention relates to a process for manufacturing a hollow fibre membrane having a supporting layer and a separating layer, said process comprising: (a)extruding a spinning composition comprising a first polymer and a solvent for the first polymer through an inner annular orifice of a

HOLLOW FIBRE MEMBRANE

NARCIS (Netherlands)

Wessling, Matthias; Stamatialis, Dimitrios; Kopec, K.K.; Dutczak, S.M.

2013-01-01

The present invention relates to a process for manufacturing a hollow fibre membrane having a supporting layer and a separating layer, said process comprising: (a) extruding a spinning composition comprising a first polymer and a solvent for the first polymer through an inner annular orifice of a

A novel approach to fabrication of superparamagnetite hollow silica/magnetic composite spheres

Energy Technology Data Exchange (ETDEWEB)

Yuan Junjie, E-mail: yuanjunjie@tongji.edu.c [School of Materials Science and Engineering, Tongji University, Shanghai 200092 (China); Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai 200433 (China); Zhang Xiong; Qian He [School of Materials Science and Engineering, Tongji University, Shanghai 200092 (China)

2010-08-15

We described a method for synthesizing hollow silica/magnetic composite spheres using sulfonic acid functionalized hollow silica spheres (SAFHSS) as templates. The Fe{sub 3}O{sub 4} nanoparticles were deposited on or imbedded in the hollow silica shell by a precipitation reaction. The morphologies, composition and properties of the hollow composite spheres were characterized by transmission electron microscopy, Fourier transform infrared analysis, X-ray diffraction measurement and vibrating-sample magnetometry measurement. The results indicated crystal sizes and amount of the Fe{sub 3}O{sub 4} nanoparticles on the SAFHSS. The magnetic properties of the hollow composite spheres were controlled by adjusting the proportion between Fe{sup 2+} and Fe{sup 3+} and iron ion total concentration. When appropriate loading species were added into the system, superparamagnetite hollow composite spheres were obtained. The method also could be applicable to prepare other superparamagnetite hollow silica/ferrite composite spheres.

Crack growth prediction method considering interaction between multiple cracks. Growth of surface cracks of dissimilar size under cyclic tensile and bending load

International Nuclear Information System (INIS)

Kamaya, Masayuki; Miyokawa, Eiichi; Kikuchi, Masanori

2011-01-01

When multiple cracks approach one another, the stress intensity factor is likely to change due to the interaction of the stress field. This causes change in growth rate and shape of cracks. In particular, when cracks are in parallel position to the loading direction, the shape of cracks becomes non-planar. In this study, the complex growth of interacting cracks is evaluated by using the S-Version finite element method, in which local detailed finite element mesh (local mesh) is superposed on coarse finite element model (global mesh) representing the global structure. In order to investigate the effect of interaction on the growth behavior, two parallel surface cracks are subjected to cyclic tensile or bending load. It is shown that the smaller crack is shielded by larger crack due to the interaction and stops growing when the difference in size of two cracks is significant. Based on simulations of various conditions, a procedure and criteria for evaluating crack growth for fitness-for-service assessment is proposed. According to the procedure, the interaction is not necessary to be considered in the crack growth prediction when the difference in size of two cracks exceeds the criterion. (author)

Estimation of Fatigue Crack Growth Behavior of Cracked Specimen Under Mixed-mode Loads

International Nuclear Information System (INIS)

Han, Jeong Woo; Woo, Eun Taek; Han, Seung Ho

2015-01-01

To estimate the fatigue crack propagation behavior of compact tension shear (CTS) specimen under mixed-mode loads, crack path prediction theories and Tanaka’s equation were applied. The stress intensity factor at a newly created crack tip was calculated using a finite element method via ANSYS, and the crack path and crack increment were then obtained from the crack path prediction theories, Tanaka’s equation, and the Paris’ equation, which were preprogrammed in Microsoft Excel. A new method called the finite element crack tip updating method (FECTUM) was developed. In this method, the finite element method and Microsoft Excel are used to calculate the stress intensity factors and the crack path, respectively, at the crack tip per each crack increment. The developed FECTUM was applied to simulate the fatigue crack propagation of a single-edge notched bending (SENB) specimen under eccentric three-point bending loads. The results showed that the number of cycles to failure of the specimen obtained experimentally and numerically were in good agreement within an error range of less than 3%

Estimation of Fatigue Crack Growth Behavior of Cracked Specimen Under Mixed-mode Loads

Energy Technology Data Exchange (ETDEWEB)

Han, Jeong Woo [KIMM, Daejeon (Korea, Republic of); Woo, Eun Taek; Han, Seung Ho [Dong-A University, Busan (Korea, Republic of)

2015-07-15

To estimate the fatigue crack propagation behavior of compact tension shear (CTS) specimen under mixed-mode loads, crack path prediction theories and Tanaka’s equation were applied. The stress intensity factor at a newly created crack tip was calculated using a finite element method via ANSYS, and the crack path and crack increment were then obtained from the crack path prediction theories, Tanaka’s equation, and the Paris’ equation, which were preprogrammed in Microsoft Excel. A new method called the finite element crack tip updating method (FECTUM) was developed. In this method, the finite element method and Microsoft Excel are used to calculate the stress intensity factors and the crack path, respectively, at the crack tip per each crack increment. The developed FECTUM was applied to simulate the fatigue crack propagation of a single-edge notched bending (SENB) specimen under eccentric three-point bending loads. The results showed that the number of cycles to failure of the specimen obtained experimentally and numerically were in good agreement within an error range of less than 3%.

Analysis of accuracy of Williams series approximation of stress field in cracked body – influence of area of interest around crack-tip on multi-parameter regression performance

Directory of Open Access Journals (Sweden)

J. Sobek

2017-01-01

Full Text Available A study on the accuracy of an approximation of the stress field in a cracked body is presented. Crack-tip stress tensor is expressed using the linear elastic fracture mechanics (LEFM theory in this work, more precisely via its multi-parameter formulation, i.e. by Williams power series (WPS. Determination of coefficients of terms of this series is performed using a least squares-based regression technique known as over-deterministic method (ODM for which results from finite element (FE method computation are usually taken as inputs. Main attention is paid to a detailed analysis of a suitable selection of FE nodes whose results serve as the inputs to the employed method. Two different ways of FE nodal selection are compared – nodes selected from the crack tip vicinity lying at a ring of a certain radius versus nodes selected more or less uniformly from a specified part of the test specimen body. Comparison of these approaches is made with the help of procedures developed by the authors which enable both the determination of the coefficients of terms of the analytical WPS approximation of the stress field based on the FE results and the backward reconstruction of the field (again using WPS from those determined terms’ coefficients/functions. The wedge-splitting test (WST specimen with a crack is taken as example for the study.

Evaluation of crack interaction effect for in-plane surface cracks using elastic finite element analyses

International Nuclear Information System (INIS)

Huh, Nam Su; Choi, Suhn; Park, Keun Bae; Kim, Jong Min; Choi, Jae Boong; Kim, Young Jin

2008-01-01

The crack-tip stress fields and fracture mechanics assessment parameters, such as the elastic stress intensity factor and the elastic-plastic J-integral, for a surface crack can be significantly affected by adjacent cracks. Such a crack interaction effect due to multiple cracks can magnify the fracture mechanics assessment parameters. There are many factors to be considered, for instance the relative distance between adjacent cracks, crack shape and loading condition, to quantify a crack interaction effect on the fracture mechanics assessment parameters. Thus, the current guidance on a crack interaction effect (crack combination rule), including ASME Sec. XI, BS7910, British Energy R6 and API RP579, provide different rules for combining multiple surface cracks into a single surface crack. The present paper investigates a crack interaction effect by evaluating the elastic stress intensity factor of adjacent surface cracks in a plate along the crack front through detailed 3-dimensional elastic finite element analyses. The effects of the geometric parameters, the relative distance between cracks and the crack shape, on the stress intensity factor are systematically investigated. As for the loading condition, only axial tension is considered. Based on the elastic finite element results, the acceptability of the crack combination rules provided in the existing guidance was investigated, and the relevant recommendations on a crack interaction for in-plane surface cracks in a plate were discussed

Coprecipitation-assisted hydrothermal synthesis of PLZT hollow nanospheres

International Nuclear Information System (INIS)

Zhu, Renqiang; Zhu, Kongjun; Qiu, Jinhao; Bai, Lin; Ji, Hongli

2010-01-01

Lanthanum-modified lead zirconate titanate Pb 1-x La x (Zr 1-y Ti y )O 3 (PLZT) hollow nanospheres have been successfully prepared via a template-free hydrothermal method using the well-mixed coprecipitated precursors and the KOH mineralizer. The structure, composition, and morphology of the PLZT hollow nanospheres were characterized by XRD (X-ray diffraction), ICP (inductive coupled plasma emission spectrometer), FTIR (Fourier transform infrared spectra), TG/DTA (thermogravimetric analysis and differential thermal analysis), TEM (transmission electron microscopy) and SEAD (selected area diffraction). The results show that the composition and the morphology control of the PLZT products are determined by the KOH concentration. The PLZT hollow nanospheres with uniform size of about 4 nm were synthesized in the presence of 5 M KOH. The crystalline nanoparticles can be prepared at dilute KOH, in contrast to the amorphous powders prepared at concentrated KOH. Formation mechanisms of the PLZT hollow nanospheres are also discussed.

Crack-opening area calculations for circumferential through-wall pipe cracks

Energy Technology Data Exchange (ETDEWEB)

Kishida, K.; Zahoor, A.

1988-08-01

This report describes the estimation schemes for crack opening displacement (COD) of a circumferential through-wall crack, then compares the COD predictions with pipe experimental data. Accurate predictions for COD are required to reliably predict the leak rate through a crack in leak-before-break applications.

Crack-opening area calculations for circumferential through-wall pipe cracks

International Nuclear Information System (INIS)

Kishida, K.; Zahoor, A.

1988-08-01

This report describes the estimation schemes for crack opening displacement (COD) of a circumferential through-wall crack, then compares the COD predictions with pipe experimental data. Accurate predictions for COD are required to reliably predict the leak rate through a crack in leak-before-break applications

Performance of different hollow fiber membranes for seawater desalination using membrane distillation

KAUST Repository

Francis, Lijo; Ghaffour, NorEddine; Alsaadi, Ahmad Salem; Amy, Gary L.

2014-01-01

Membrane distillation requires a highly porous hydrophobic membrane with low surface energy. In this paper, we compare the direct contact membrane distillation (DCMD) performances of four different types of in-house fabricated hollow fiber membranes and two different commercially available hollow fiber membranes. Hollow fiber membranes are fabricated using wet-jet phase inversion technique and the polymeric matrices used for the fabrication are polyvinylidine fluoride (PVDF) and polyvinyl chloride (PVC). Commercial hollow fiber membrane materials are made of polytetrafluoroethylene (PTFE) and polypropylene (PP). PVDF hollow fibers showed a superior performance among all the hollow fibers tested in the DCMD process and gave a water vapor flux of 31 kg m-2h-1 at a feed and coolant inlet temperatures of 80 and 20°C, respectively. Under the same conditions, the water vapor flux observed for PP, PTFE, and PVC hollow fiber membranes are 13, 11, and 6 kg m-2h-1, respectively, with 99.99% salt rejection observed for all membranes used.

Performance of different hollow fiber membranes for seawater desalination using membrane distillation

KAUST Repository

Francis, Lijo

2014-08-11

Membrane distillation requires a highly porous hydrophobic membrane with low surface energy. In this paper, we compare the direct contact membrane distillation (DCMD) performances of four different types of in-house fabricated hollow fiber membranes and two different commercially available hollow fiber membranes. Hollow fiber membranes are fabricated using wet-jet phase inversion technique and the polymeric matrices used for the fabrication are polyvinylidine fluoride (PVDF) and polyvinyl chloride (PVC). Commercial hollow fiber membrane materials are made of polytetrafluoroethylene (PTFE) and polypropylene (PP). PVDF hollow fibers showed a superior performance among all the hollow fibers tested in the DCMD process and gave a water vapor flux of 31 kg m-2h-1 at a feed and coolant inlet temperatures of 80 and 20°C, respectively. Under the same conditions, the water vapor flux observed for PP, PTFE, and PVC hollow fiber membranes are 13, 11, and 6 kg m-2h-1, respectively, with 99.99% salt rejection observed for all membranes used.

Crack embryo formation before crack initiation and growth in high temperature water

International Nuclear Information System (INIS)

Arioka, Koji; Yamada, Takuyo; Terachi, Takumi; Miyamoto, Tomoki

2008-01-01

Crack growth measurements were performed in high temperature water and in air to examine the role of creep on IGSCC growth using cold rolled non-sensitized Type316(UNS S31600), TT690 alloy, MA600 alloy, and Carbon steel (STPT42). In addition, crack initiation tests were performed also in high temperature water and in air using specially designed CT specimen. The obtained major results are as follows: (1) TT690 did crack in intergranularly in hydrogenated high temperature water if material is cold worked in heavily. (2) Cold worked carbon steel also cracked in intergranularly in dearated high temperature water. (3) Intergranular crack growth was recognized on cold worked 316, TT690, MA600, and carbon steel even in air which might be crack embryo of IGSCC. (4) Simple Arrhenius type temperature dependence was observed on IGSCC in high temperature water and creep crack growth in air. This suggested that intergranular crack growth rate was determined by some thermal activated reaction. (5) Vacancy condensation was recognized at just ahead of the crack tips of IGSCC and creep crack of cold worked steel. This showed that IGSCC and creep crack growth was controlled by same mechanism. (6) Clear evidence of vacancies condensation was recognized at just beneath the surface before crack initiation. This proved that crack did initiate as the result of diffusion of vacancies in the solid. And the incubation time seems to be controlled by the required time for the condensation of vacancies to the stress concentrated zone. (7) Diffusion of subsituational atoms was also driven by stress gradient. This is the important knowledge to evaluate the SCC initiation after long term operation in LWR's. Based on the observed results, IGSCC initiation and growth mechanism were proposed considering the diffusion process of cold worked induced vacancies. (author)

Methodology for construction of hollow spheres for use in physical phantoms

International Nuclear Information System (INIS)

Oliveira, A.C.H.; Lima, F.R.A.; Oliveira, F.; Vieira, J.W.

2015-01-01

In positron emission tomography (PET), quantitative evaluation of spatial resolution/object size, attenuation and scatter effects is often performed using phantoms with hollow spheres. Fillable, plastic-walled spheres are commercially available in several sizes. Radioactive solutions in any concentration can be injected into the spheres. Hollow spheres have several desirable traits, including repeatable, consistent use, and standardization across measurements at different institutions, since identical items are distributed by a single manufacturer. The objective of this work is to describe a methodology for construction of hollow spheres using rapid prototyping. It was used the software SolidWork (2014) to create five 3D models of the hollow spheres with inner diameters of 10 mm, 13 mm, 17 mm, 22 mm, and 28 mm. These models were based on hollow spheres of NEMA/IEC PET body phantom. It was used a Cubex Duo 3D printer (3D Systems) to build the hollow spheres. The material used was the ABS (acrylonitrile butadiene styrene) resin. (authors)

Electro-magnetic properties of composites with aligned Fe-Co hollow fibers

Directory of Open Access Journals (Sweden)

Seungchan Cho

2016-05-01

Full Text Available A novel Fe-Co binary hollow fiber was synthesized by electroless plating using hydrolyzed polyester fiber and its anisotropy characteristic was investigated for electromagnetic wave absorbing materials. The hollow fibers in parallel with magnetic field show higher saturated magnetization of 202 emu/g at the applied magnetic field of 10 kOe and lower coercivity (27.658 Oe, compared with the random and vertical oriented hollow fibers. From complex permittivity measurement, the Fe-Co hollow fiber composites clearly display a single dielectric resonance, located at ∼14 GHz. The Fe-Co hollow fibers not only provide excellent EM properties in GHz frequency ranges, resulting mainly from the strong resonance, but also adjust the soft magnetic properties through fiber alignments. The cavitary structure of the Fe-Co hollow fibers, not only giving rise to a dielectric loss resonance and also adjusting its peak frequency, may be a pathway to useful EM wave absorptive devices in GHz frequency ranges.

Microstructural modelling of creep crack growth from a blunted crack

NARCIS (Netherlands)

Onck, P.R.; Giessen, E. van der

1998-01-01

The effect of crack tip blunting on the initial stages of creep crack growth is investigated by means of a planar microstructural model in which grains are represented discretely. The actual linking-up process of discrete microcracks with the macroscopic crack is simulated, with full account of the

Adsorption characteristics of activated carbon hollow fibers

Directory of Open Access Journals (Sweden)

B. V. Kaludjerović

2009-01-01

Full Text Available Carbon hollow fibers were prepared with regenerated cellulose or polysulfone hollow fibers by chemical activation using sodium phosphate dibasic followed by the carbonization process. The activation process increases the adsorption properties of fibers which is more prominent for active carbone fibers obtained from the cellulose precursor. Chemical activation with sodium phosphate dibasic produces an active carbon material with both mesopores and micropores.

Manufacturing hollow obturator with resilient denture liner on post hemimaxillectomy

Directory of Open Access Journals (Sweden)

Michael Josef Kridanto Kamadjaja

2006-03-01

Full Text Available A resilient denture liner is placed in the part of the hollow obturator base that contacts to post hemimaxillectomy mucosa. Replacing the resilient denture liner can makes the hollow obturator has an intimate contact with the mucosa, so it can prevents the mouth liquid enter to the cavum nasi and sinus, also eliminates painful because of using the hollow obturator. Resilient denture liner is a soft and resilient material that applied to the fitting surface of a denture in order to allow a more distribution of load. A case was reported about using the hollow obturator with resilient denture liner on post hemimaxillectomy to overcome these problems.

Crack-tip chemistry modeling of stage I stress corrosion cracking

International Nuclear Information System (INIS)

Jones, R.H.; Simonen, E.P.

1991-10-01

Stage I stress corrosion cracking usually exhibits a very strong K dependence with Paris law exponents of up to 30. 2 Model calculations indicate that the crack velocity in this regime is controlled by transport through a salt film and that the K dependence results from crack opening controlled salt film dissolution. An ionic transport model that accounts for both electromigration through the resistive salt film and Fickian diffusion through the aqueous solution was used for these predictions. Predicted crack growth rates are in excellent agreement with measured values for Ni with P segregated to the grain boundaries and tested in IN H 2 SO 4 at +900 mV. This salt film dissolution may be applicable to stage I cracking of other materials

Analysis of short and long crack behavior and single overload effect by crack opening stress

International Nuclear Information System (INIS)

Song, Sam Hong; Lee, Kyeong Ro

1999-01-01

The study analyzed the behaviors of short and long crack as well as the effect of single tensile overload on the crack behaviors by using fatigue crack opening behavior. Crack opening stress is measured by an elastic compliance method which may precisely and continuously provide many data using strain gages during experiment. The unusual growth behaviors of short crack and crack after the single tensile overload applied, was explained by the variations of crack opening stress. In addition, fatigue crack growth rate was expressed as a linear form for short crack as for long crack by using effective stress intensity factor range as fracture mechanical parameter, which is based on crack closure concept. And investigation is performed with respect to the relation between plastic zone size formed at the crack tip and crack retardation, crack length and the number of cycles promoted or retarded, and the overload effect on the fatigue life

Fatigue crack growth from a cracked elastic particle into a ductile matrix

NARCIS (Netherlands)

Groh, S.; Olarnrithinun, S.; Curtin, W. A.; Needleman, A.; Deshpande, V. S.; Van der Giessen, E.

2008-01-01

The monotonic and cyclic crack growth rate of cracks is strongly influenced by the microstructure. Here, the growth of cracks emanating from pre-cracked micron-scale elastic particles and growing into single crystals is investigated, with a focus on the effects of (i) plastic confinement due to the

Recent evaluations of crack-opening-area in circumferentially cracked pipes

Energy Technology Data Exchange (ETDEWEB)

Rahman, S.; Brust, F.; Ghadiali, N.; Wilkowski, G.; Miura, N.

1997-04-01

Leak-before-break (LBB) analyses for circumferentially cracked pipes are currently being conducted in the nuclear industry to justify elimination of pipe whip restraints and jet shields which are present because of the expected dynamic effects from pipe rupture. The application of the LBB methodology frequently requires calculation of leak rates. The leak rates depend on the crack-opening area of the through-wall crack in the pipe. In addition to LBB analyses which assume a hypothetical flaw size, there is also interest in the integrity of actual leaking cracks corresponding to current leakage detection requirements in NRC Regulatory Guide 1.45, or for assessing temporary repair of Class 2 and 3 pipes that have leaks as are being evaluated in ASME Section XI. The objectives of this study were to review, evaluate, and refine current predictive models for performing crack-opening-area analyses of circumferentially cracked pipes. The results from twenty-five full-scale pipe fracture experiments, conducted in the Degraded Piping Program, the International Piping Integrity Research Group Program, and the Short Cracks in Piping and Piping Welds Program, were used to verify the analytical models. Standard statistical analyses were performed to assess used to verify the analytical models. Standard statistical analyses were performed to assess quantitatively the accuracy of the predictive models. The evaluation also involved finite element analyses for determining the crack-opening profile often needed to perform leak-rate calculations.

Hollow fiber membranes and methods for forming same

Science.gov (United States)

Bhandari, Dhaval Ajit; McCloskey, Patrick Joseph; Howson, Paul Edward; Narang, Kristi Jean; Koros, William

2016-03-22

The invention provides improved hollow fiber membranes having at least two layers, and methods for forming the same. The methods include co-extruding a first composition, a second composition, and a third composition to form a dual layer hollow fiber membrane. The first composition includes a glassy polymer; the second composition includes a polysiloxane; and the third composition includes a bore fluid. The dual layer hollow fiber membranes include a first layer and a second layer, the first layer being a porous layer which includes the glassy polymer of the first composition, and the second layer being a polysiloxane layer which includes the polysiloxane of the second composition.

Influence of a glide path on the dentinal crack formation of ProTaper Next system

Directory of Open Access Journals (Sweden)

Sevinç Aktemur Türker

2015-11-01

Full Text Available Objectives The aim was to evaluate dentinal crack formation after root canal preparation with ProTaper Next system (PTN with and without a glide path. Materials and Methods Forty-five mesial roots of mandibular first molars were selected. Fifteen teeth were left unprepared and served as controls. The experimental groups consist of mesiobuccal and mesiolingual root canals of remaining 30 teeth, which were divided into 2 groups (n = 15: Group PG/PTN, glide path was created with ProGlider (PG and then canals were shaped with PTN system; Group PTN, glide path was not prepared and canals were shaped with PTN system only. All roots were sectioned perpendicular to the long axis at 1, 2, 3, 4, 6, and 8 mm from the apex, and the sections were observed under a stereomicroscope. The presence/absence of cracks was recorded. Data were analyzed with chi-square tests with Yates correction. Results There were no significant differences in crack formation between the PTN with and without glide path preparation. The incidence of cracks observed in PG/PTN and PTN groups was 17.8% and 28.9%, respectively. Conclusions The creation of a glide path with ProGlider before ProTaper Next rotary system did not influence dentinal crack formation in root canals.

Water permeability evaluation of hollow cylindrical reinforced concrete structure by means of long-term water penetration test with pressure

International Nuclear Information System (INIS)

Fujiwara, Ai; Miura, Norihiko; Konishi, Kazuhiro; Tsuji, Yukikazu

2005-01-01

In order to evaluate initial permeability of large concrete structure, hollow cylindrical reinforced concrete structure, having 6 m in outer diameter, 6 m in height, 1 m in thickness, had been tested by means of 0.25 MPa of outside water pressure. As the results, although surface cracking and partial separation of joint had been observed at the inner side, no water permeation through concrete could be happened even after 5.5 years. After this test, concrete core specimen showed less water penetration within the depth of concrete cover of reinforcement. Thus it was verified that this concrete structure had very high water-tightness, and that the initial average water permeability was estimated to be about 1.6 x 10 -12 m/s. (author)

Improvement of elastic-plastic fatigue crack growth evaluation method. 2. Crack opening behavior

Energy Technology Data Exchange (ETDEWEB)

Takahashi, Yukio [Central Research Inst. of Electric Power Industry, Tokyo (Japan)

2001-05-01

Evaluation of crack growth behavior under cyclic loading is often required in the structural integrity assessment of cracked components. Closing and re-opening of the crack give large influence on crack growth rate through the change of fracture mechanics parameters. Based on the finite element analysis for a center-cracked plate, dependency of crack opening ratio on applied stress range and mean stress was examined. Simple formulae for representing the results were derived for plane stress and plane strain conditions. (author)

Study of the hollow cathode plasma electron-gun

International Nuclear Information System (INIS)

Zhang Yonghui; Jiang Jinsheng; Chang Anbi

2003-01-01

For developing a novel high-current, long pulse width electron source, the theoretics and mechanism of the hollow cathode plasma electron-gun are analyzed in detail in this paper, the structure and the physical process of hollow cathode plasma electron-gun are also studied. This gun overcomes the limitations of most high-power microwave tubes, which employ either thermionic cathodes that produce low current-density beams because of the limitation of the space charge, or field-emission cathodes that offer high current density but provide only short pulse width because of plasma closure of the accelerating gap. In the theories studying on hollow cathode plasma electron-gun, the characteristic of the hollow-cathode discharge is introduced, the action during the forming of plasma of the stimulating electrode and the modulating anode are discussed, the movement of electrons and ions and the primary parameters are analyzed, and the formulas of the electric field, beam current density and the stabilization conditions of the beam current are also presented in this paper. The numerical simulation is carried out based on Poisson's equation, and the equations of current continuity and movement. And the optimized result is reported. On this basis, we have designed a hollow-cathode-plasma electron-gun, whose output pulse current is 2 kA, and pulse width is 1 microsecond

Identification of cracks in thick beams with a cracked beam element model

Science.gov (United States)

Hou, Chuanchuan; Lu, Yong

2016-12-01

The effect of a crack on the vibration of a beam is a classical problem, and various models have been proposed, ranging from the basic stiffness reduction method to the more sophisticated model involving formulation based on the additional flexibility due to a crack. However, in the damage identification or finite element model updating applications, it is still common practice to employ a simple stiffness reduction factor to represent a crack in the identification process, whereas the use of a more realistic crack model is rather limited. In this paper, the issues with the simple stiffness reduction method, particularly concerning thick beams, are highlighted along with a review of several other crack models. A robust finite element model updating procedure is then presented for the detection of cracks in beams. The description of the crack parameters is based on the cracked beam flexibility formulated by means of the fracture mechanics, and it takes into consideration of shear deformation and coupling between translational and longitudinal vibrations, and thus is particularly suitable for thick beams. The identification procedure employs a global searching technique using Genetic Algorithms, and there is no restriction on the location, severity and the number of cracks to be identified. The procedure is verified to yield satisfactory identification for practically any configurations of cracks in a beam.

Crack Tip Parameters for Growing Cracks in Linear Viscoelastic Materials

DEFF Research Database (Denmark)

Brincker, Rune

In this paper the problem of describing the asymptotic fields around a slowly growing crack in a linearly viscoelastic material is considered. It is shown that for plane mixed mode problems the asymptotic fields must be described by 6 parameters: 2 stress intensity factors and 4 deformation...... intensity factors. In the special case of a constant Poisson ratio only 2 deformation intensity factors are needed. Closed form solutions are given both for a slowly growing crack and for a crack that is suddenly arrested at a point at the crack extension path. Two examples are studied; a stress boundary...... value problem, and a displacement boundary value problem. The results show that the stress intensity factors and the displacement intensity factors do not depend explicitly upon the velocity of the crack tip....

Fe2O3 hollow sphere nanocomposites for supercapacitor applications

Science.gov (United States)

Zhao, Yu; Wen, Yang; Xu, Bing; Lu, Lu; Ren, Reiming

2018-02-01

Nanomaterials have attracted increasing interest in electrochemical energy storage and conversion. Hollow sphere Fe2O3 nanocomposites were successfully prepared through facile low temperature water-bath method with carbon sphere as hard template. The morphology and microstructure of samples were characterized by X-ray diffraction (XRD) and Scanning electron microscope (SEM), respectively. Through hydrolysis mechanism, using ferric chloride direct hydrolysis, iron hydroxide coated on the surface of carbon sphere, after high temperature calcination can form the hollow spherical iron oxide materials. Electrochemical performances of the hollow sphere Fe2O3 nanocomposites electrodes were investigated by cyclic voltammery (CV) and galvanostatic charge/discharge. The Pure hollow sphere Fe2O3 nanocomposites achieves a specific capacitance of 125 F g-1 at the current density of 85 mA g-1. The results indicate that the uniform dispersion of hollow ball structure can effectively reduce the particle reunion in the process of charging and discharging.

Production of steam cracking feedstocks by mild cracking of plastic wastes

Energy Technology Data Exchange (ETDEWEB)

Angyal, Andras; Miskolczi, Norbert; Bartha, Laszlo; Tungler, Antal; Nagy, Lajos; Vida, Laszlo; Nagy, Gabor

2010-11-15

In this work the utility of new possible petrochemical feedstocks obtained by plastic waste cracking has been studied. The cracking process of polyethylene (PE), polyethylene-polypropylene (PEPP) and polyethylene-polystyrene (PEPS) has been carried out in a pilot scale tubular reactor. In this process mild reaction parameters has been applied, with the temperature of 530 C and the residence time of 15 min. The produced hydrocarbon fractions as light- and middle distillates were tested by using a laboratory steam cracking unit. It was concluded that the products of the mild cracking of plastic wastes could be applied as petrochemical feedstocks. Based on the analytical data it was determined that these liquid products contained in significant concentration (25-50 wt.%) of olefin hydrocarbons. Moreover the cracking of polystyrene containing raw material resulted in liquid products with significant amounts of aromatic hydrocarbons too. The steam cracking experiments proved that the products obtained by PE and PEPP cracking resulted in similar or better ethylene and propylene yields than the reference samples, however the aromatic content of PEPS products reduced the ethylene and propylene yields. (author)

The initiation of environmentally-assisted cracking in semi-elliptical surface cracks

International Nuclear Information System (INIS)

James, L.A.

1997-01-01

A criterion to predict under what conditions EAC would Initiate In cracks In a high-sulfur steel in contact with low-oxygen water was recently proposed by Wire and U. This EAC Initiation Criterion was developed using transient analyses for the diffusion of sulfides plus experimental test results. The experiments were conducted mainly on compact tension-type specimens with initial crack depths of about 2.54 mm. The present paper expands upon the work of Wire and U by presenting results for significantly deeper initial semi-elliptical surface cracks. In addition, in one specimen, the surface crack penetrated weld-deposited cladding into the high-sulfur steel. The results for the semi-elliptical surface cracks agreed quite well with the EAC Initiation Criterion, and provide confirmation of the applicability of the criterion to crack configurations with more restricted access to water

Energy-dependent expansion of .177 caliber hollow-point air gun projectiles.

Science.gov (United States)

Werner, Ronald; Schultz, Benno; Bockholdt, Britta; Ekkernkamp, Axel; Frank, Matthias

2017-05-01

Amongst hundreds of different projectiles for air guns available on the market, hollow-point air gun pellets are of special interest. These pellets are characterized by a tip or a hollowed-out shape in their tip which, when fired, makes the projectiles expand to an increased diameter upon entering the target medium. This results in an increase in release of energy which, in turn, has the potential to cause more serious injuries than non-hollow-point projectiles. To the best of the authors' knowledge, reliable data on the terminal ballistic features of hollow-point air gun projectiles compared to standard diabolo pellets have not yet been published in the forensic literature. The terminal ballistic performance (energy-dependent expansion and penetration) of four different types of .177 caliber hollow-point pellets discharged at kinetic energy levels from approximately 3 J up to 30 J into water, ordnance gelatin, and ordnance gelatin covered with natural chamois as a skin simulant was the subject of this investigation. Energy-dependent expansion of the tested hollow-point pellets was observed after being shot into all investigated target media. While some hollow-point pellets require a minimum kinetic energy of approximately 10 J for sufficient expansion, there are also hollow-point pellets which expand at kinetic energy levels of less than 5 J. The ratio of expansion (RE, calculated by the cross-sectional area (A) after impact divided by the cross-sectional area (A 0 ) of the undeformed pellet) of hollow-point air gun pellets reached values up of to 2.2. The extent of expansion relates to the kinetic energy of the projectile with a peak for pellet expansion at the 15 to 20 J range. To conclude, this work demonstrates that the hollow-point principle, i.e., the design-related enlargement of the projectiles' frontal area upon impact into a medium, does work in air guns as claimed by the manufacturers.

Recovery of uranium from seawater using amidoxime hollow fibers

International Nuclear Information System (INIS)

Saito, K.; Uezu, K.; Hori, T.; Furusaki, S.; Sugo, T.; Okamoto, J.

1988-01-01

A novel amidoxime-group-containing adsorbent of hollow-fiber form (AO-H fiber) was prepared by radiation-induced graft polymerization of acrylonitrile onto a polyethylene hollow fiber, followed by chemical conversion of the produced cyano group to an amidoxime group. Distribution of the amidoxime group was uniform throughout hollow-fiber membrane. The fixed-bed adsorption column, 30 cm in length and charged with the bundle of AO-H fibers, was found to adsorb uranium from natural seawater at a sufficiently high rate: 0.66 mg uranium per g of adsorbent in 25 days

A hollow definitive obturator fabrication technique for management of partial maxillectomy.

Science.gov (United States)

Patil, Pravinkumar Gajanan; Patil, Smita Pravinkumar

2012-11-01

Maxillary obturator prosthesis is the most frequent treatment option for management of partial or total maxillectomy. Heavy weight of the obturators is often a dislocating factor. Hollowing the prosthesis to reduce its weight is the well established fact. The alternate technique to hollow-out the prosthesis has been described in this article which is a variation of previously described processing techniques. A pre-shaped wax-bolus was incorporated inside the flasks during packing of the heat-polymerized acrylic resin to automatically create the hollow space. The processing technique described is a single step flasking procedure to construct a closed-hollow-obturator prosthesis as a single unit. To best understand the technique, this article describes management of a patient who had undergone partial maxillectomy secondary to squamous cell carcinoma rehabilitated with a hollow-obturator prosthesis.

Preparation and surface encapsulation of hollow TiO nanoparticles for electrophoretic displays

International Nuclear Information System (INIS)

Zhao Qian; Tan Tingfeng; Qi Peng; Wang Shirong; Bian Shuguang; Li Xianggao; An Yong; Liu Zhaojun

2011-01-01

Hollow black TiO nanosparticles were obtained via deposition of inorganic coating on the surface of hollow core-shell polymer latex with Ti(OBu) 4 as precursor and subsequent calcination in ammonia gas. Hollow TiO particles were characterized by scanning electron microscope, transmission electronic microscopy, X-ray diffraction, and thermogravimetric analysis. Encapsulation of TiO via dispersion polymerization was promoved by pretreating the pigments with 3-(trimethoxysilyl) propyl methacrylate, making it possible to prepare hollow TiO-polymer particles. When St and DVB were used as polymerization monomer, hollow TiO-polymer core-shell particles came into being via dispersion polymerization, and the lipophilic degree is 28.57%. Glutin-arabic gum microcapsules containing TiO-polymer particles electrophoretic liquid were prepared using via complex coacervation. It was founded that hollow TiO-polymer particles had enough electrophoretic mobility after coating with polymer.

Cracked gas generator

Energy Technology Data Exchange (ETDEWEB)

Abthoff, J; Schuster, H D; Gabler, R

1976-11-17

A small cracked-gas generator in a vehicle driven, in particular, by an air combustion engine has been proposed for the economic production of the gases necessary for low toxicity combustion from diesel fuel. This proceeds via catalytic crack-gasification and exploitation of residual heat from exhaust gases. This patent application foresees the insertion of one of the catalysts supporting the cracked-gas reaction in a container through which the reacting mixture for cracked-gas production flows in longitudinal direction. Further, air ducts are embedded in the catalyst through which exhaust gases and fresh air flow in counter direction to the cracked gas flow in the catalyst. The air vents are connected through heat conduction to the catalyst. A cracked gas constituting H/sub 2//CO/CO/sub 2//CH/sub 4/ and H/sub 2/O can be produced from the air-fuel mixture using appropriate catalysts. By the addition of 5 to 25% of cracked gas to the volume of air drawn in by the combustion engine, a more favourable combustion can be achieved compared to that obtained under normal combustion conditions.

Quarter elliptical crack growth using three dimensional finite element method and crack closure technique

Energy Technology Data Exchange (ETDEWEB)

Gozin, Mohammad-Hosein; Aghaie-Khafri, Mehrdad [K. N. Toosi University of Technology, Tehran (Korea, Republic of)

2014-06-15

Shape evolution of a quarter-elliptical crack emanating from a hole is studied. Three dimensional elastic-plastic finite element analysis of the fatigue crack closure was considered and the stress intensity factor was calculated based on the duplicated elastic model at each crack tip node. The crack front node was advanced proportional to the imposed effective stress intensity factor. Remeshing was applied at each step of the crack growth and solution mapping algorithm was considered. Crack growth retardation at free surfaces was successfully observed. A MATLAB-ABAQUS interference code was developed for the first time to perform crack growth on the basis of crack closure. Simulation results indicated that crack shape is sensitive to the remeshing strategy. Predictions based on the proposed models were in good agreement with Carlson's experiments results.

Hollow Nanospheres Array Fabrication via Nano-Conglutination Technology.

Science.gov (United States)

Zhang, Man; Deng, Qiling; Xia, Liangping; Shi, Lifang; Cao, Axiu; Pang, Hui; Hu, Song

2015-09-01

Hollow nanospheres array is a special nanostructure with great applications in photonics, electronics and biochemistry. The nanofabrication technique with high resolution is crucial to nanosciences and nano-technology. This paper presents a novel nonconventional nano-conglutination technology combining polystyrenes spheres (PSs) self-assembly, conglutination and a lift-off process to fabricate the hollow nanospheres array with nanoholes. A self-assembly monolayer of PSs was stuck off from the quartz wafer by the thiol-ene adhesive material, and then the PSs was removed via a lift-off process and the hollow nanospheres embedded into the thiol-ene substrate was obtained. Thiolene polymer is a UV-curable material via "click chemistry" reaction at ambient conditions without the oxygen inhibition, which has excellent chemical and physical properties to be attractive as the adhesive material in nano-conglutination technology. Using the technique, a hollow nanospheres array with the nanoholes at the diameter of 200 nm embedded into the rigid thiol-ene substrate was fabricated, which has great potential to serve as a reaction container, catalyst and surface enhanced Raman scattering substrate.

Biotemplate synthesis of monodispersed iron phosphate hollow microspheres

International Nuclear Information System (INIS)

Cao Feng; Li Dongxu

2010-01-01

Monodispersed iron phosphate hollow microspheres with a high degree of crystallization were prepared through a facile in situ deposition method using rape pollen grains as a biotemplate. The functional group on the surface of the pollen grains could adsorb Fe 3+ , which provided the nucleation sites for growth of iron phosphate nanoparticles. After being sintered at 600 deg. C for 10 h, the pollen grains were removed and iron phosphate hollow microspheres were obtained. A scanning electron microscope and x-ray diffraction were applied to characterize the morphology and crystalline structure of the pollen grains, iron phosphate-coated pollen grains and iron phosphate hollow microspheres. Differential scanning calorimetry and thermogravity analyses were performed to investigate the thermal behavior of the iron phosphate-coated pollen grains during the calcinations. Energy dispersive spectroscopy and Fourier transform infrared spectroscopy were utilized to investigate the interaction between the pollen grains and iron phosphate. The effect of the pollen wall on the surface morphology of these iron phosphate hollow microspheres was also proven in this work.

Biotemplate synthesis of monodispersed iron phosphate hollow microspheres

Energy Technology Data Exchange (ETDEWEB)

Cao Feng; Li Dongxu, E-mail: dongxuli@njut.edu.c [College of Materials Science and Engineering, Nanjing University of Technology, Jiangsu Nanjing 210009 (China)

2010-03-15

Monodispersed iron phosphate hollow microspheres with a high degree of crystallization were prepared through a facile in situ deposition method using rape pollen grains as a biotemplate. The functional group on the surface of the pollen grains could adsorb Fe{sup 3+}, which provided the nucleation sites for growth of iron phosphate nanoparticles. After being sintered at 600 deg. C for 10 h, the pollen grains were removed and iron phosphate hollow microspheres were obtained. A scanning electron microscope and x-ray diffraction were applied to characterize the morphology and crystalline structure of the pollen grains, iron phosphate-coated pollen grains and iron phosphate hollow microspheres. Differential scanning calorimetry and thermogravity analyses were performed to investigate the thermal behavior of the iron phosphate-coated pollen grains during the calcinations. Energy dispersive spectroscopy and Fourier transform infrared spectroscopy were utilized to investigate the interaction between the pollen grains and iron phosphate. The effect of the pollen wall on the surface morphology of these iron phosphate hollow microspheres was also proven in this work.

Application of a probabilistic model of rainfall-induced shallow landslides to complex hollows

Directory of Open Access Journals (Sweden)

A. Talebi

2008-07-01

Full Text Available Recently, D'Odorico and Fagherazzi (2003 proposed "A probabilistic model of rainfall-triggered shallow landslides in hollows" (Water Resour. Res., 39, 2003. Their model describes the long-term evolution of colluvial deposits through a probabilistic soil mass balance at a point. Further building blocks of the model are: an infinite-slope stability analysis; a steady-state kinematic wave model (KW of hollow groundwater hydrology; and a statistical model relating intensity, duration, and frequency of extreme precipitation. Here we extend the work of D'Odorico and Fagherazzi (2003 by incorporating a more realistic description of hollow hydrology (hillslope storage Boussinesq model, HSB such that this model can also be applied to more gentle slopes and hollows with different plan shapes. We show that results obtained using the KW and HSB models are significantly different as in the KW model the diffusion term is ignored. We generalize our results by examining the stability of several hollow types with different plan shapes (different convergence degree. For each hollow type, the minimum value of the landslide-triggering saturated depth corresponding to the triggering precipitation (critical recharge rate is computed for steep and gentle hollows. Long term analysis of shallow landslides by the presented model illustrates that all hollows show a quite different behavior from the stability view point. In hollows with more convergence, landslide occurrence is limited by the supply of deposits (supply limited regime or rainfall events (event limited regime while hollows with low convergence degree are unconditionally stable regardless of the soil thickness or rainfall intensity. Overall, our results show that in addition to the effect of slope angle, plan shape (convergence degree also controls the subsurface flow and this process affects the probability distribution of landslide occurrence in different hollows. Finally, we conclude that

Fire resistance of extruded hollow-core slabs

DEFF Research Database (Denmark)

Hertz, Kristian Dahl; Sørensen, Lars Schiøtt; Giuliani, Luisa

2017-01-01

to the structural codes with data derived from a standard fire test and from a thorough examination of the comprehensive test documentation available on fire exposed hollow-core slabs. Findings – Mechanisms for loss of load-bearing capacity are clarified, and evidence of the fire resistance is found. Originality......Purpose – Prefabricated extruded hollow-core slabs are preferred building components for floor structures in several countries. It is therefore important to be able to document the fire resistance of these slabs proving fulfilment of standard fire resistance requirements of 60 and 120 min found...... in most national building regulations. The paper aims to present a detailed analysis of the mechanisms responsible for the loss of loadbearing capacity of hollow-core slabs when exposed to fire. Design/methodology/approach – Furthermore, it compares theoretica calculation and assessment according...

Method and apparatus for producing small hollow spheres

International Nuclear Information System (INIS)

Hendricks, C.D.

1979-01-01

A method and apparatus are described for producing small hollow spheres of glass, metal or plastic, wherein the sphere material is mixed with or contains as part of the composition a blowing agent which decomposes at high temperature (T greater than or equal to 600 0 C). As the temperature is quickly raised, the blowing agent decomposes and the resulting gas expands from within, thus forming a hollow sphere of controllable thickness. The thus produced hollow spheres (20 to 10 3 μm) have a variety of application, and are particularly useful in the fabrication of targets for laser implosion such as neutron sources, laser fusion physics studies, and laser initiated fusion power plants

Role of plasticity-induced crack closure in fatigue crack growth

Directory of Open Access Journals (Sweden)

Jesús Toribio

2013-07-01

Full Text Available The premature contact of crack surfaces attributable to the near-tip plastic deformations under cyclic loading, which is commonly referred to as plasticity induced crack closure (PICC, has long been focused as supposedly controlling factor of fatigue crack growth (FCG. Nevertheless, when the plane-strain near-tip constraint is approached, PICC lacks of straightforward evidence, so that its significance in FCG, and even the very existence, remain debatable. To add insights into this matter, large-deformation elastoplastic simulations of plane-strain crack under constant amplitude load cycling at different load ranges and ratios, as well as with an overload, have been performed. Modeling visualizes the Laird-Smith conceptual mechanism of FCG by plastic blunting and re-sharpening. Simulation reproduces the experimental trends of FCG concerning the roles of stress intensity factor range and overload, but PICC has never been detected. Near-tip deformation patterns discard the filling-in a crack with material stretched out of the crack plane in the wake behind the tip as supposed PICC origin. Despite the absence of closure, load-deformation curves appear bent, which raises doubts about the trustworthiness of closure assessment from the compliance variation. This demonstrates ambiguities of PICC as a supposedly intrinsic factor of FCG and, by implication, favors the stresses and strains in front of the crack tip as genuine fatigue drivers.

Mercury's Hollows: New Information on Distribution and Morphology from MESSENGER Observations at Low Altitude

Science.gov (United States)

Blewett, D. T.; Stadermann, A. C.; Chabot, N. L.; Denevi, B. W.; Ernst, C. M.; Peplowski, P. N.

2014-12-01

MESSENGER's orbital mission at Mercury led to the discovery of an unusual landform not known from other airless rocky bodies of the Solar System. Hollows are irregularly shaped, shallow, rimless depressions, often occurring in clusters and with high-reflectance interiors and halos. The fresh appearance of hollows suggests that they are relatively young features. For example, hollows are uncratered, and talus aprons downslope of hollows in certain cases appear to be covering small impact craters (100-200 in diameter). Hence, some hollows may be actively forming at present. The characteristics of hollows are suggestive of formation via destruction of a volatile-bearing phase (possibly one or more sulfides) through solar heating, micrometeoroid bombardment, and/or ion impact. Previous analysis showed that hollows are associated with low-reflectance material (LRM), a color unit identified from global color images. The material hosting hollows has often been excavated from depth by basin or crater impacts. Hollows are small features (tens of meters to several kilometers), so their detection and characterization with MESSENGER's global maps have been limited. MESSENGER's low-altitude orbits provide opportunities for collection of images at high spatial resolutions, which reveal new occurrences of hollows and offer views of hollows with unprecedented detail. As of this writing, we have examined more than 21,000 images with pixel sizes Shadow-length measurements were made on 280 images, yielding the depths of 1343 individual hollows. The mean depth is 30 m, with a standard deviation of 17 m. We also explored correlations between the geographic locations of hollows and maps provided by the MESSENGER geochemical sensors (X-Ray, Gamma-Ray, and Neutron Spectrometers), including the abundances of Al/Si, Ca/Si, Fe/Si, K, Mg/Si, and S/Si, as well as total neutron cross-section. No clear compositional trends emerged; it is likely that any true compositional preference for terrain

Effect of Different Torque Settings on Crack Formation in Root Dentin.

Science.gov (United States)

Dane, Asım; Capar, Ismail Davut; Arslan, Hakan; Akçay, Merve; Uysal, Banu

2016-02-01

The aim of the present study was to observe the incidence of cracks in root canal dentin using the ProTaper Universal system (Dentsply Maillefer, Ballaigues, Switzerland) at low- and high-torque settings. Sixty-nine mandibular premolar teeth that had been extracted for different reasons were selected. The teeth were divided into 3 groups: an unprepared control group, a low-torque settings group (SX = 3, S1 = 2, S2 = 1, F1 = 1.5, F2 = 2, F3 = 2, F4 = 2 N/cm), and a high-torque settings group (SX = 4, S1 = 4, S2 = 1.5, F1 = 2, F2 = 3, F3 = 3, F4 = 3 N/cm). After a root canal procedure, all the teeth were horizontally sectioned at 2, 4, 6, and 8 mm from the apex. Then, under a stereomicroscope, all the slices were examined to determine the presence of cracks. A chi-square test was used for data analysis. The significance level was set at P = .05. There were no cracks in the unprepared control group. Vertical root fractures were not observed in any of the groups. There were significantly fewer cracks (17.4% of the sections) in the low-torque group than in the high-torque group (29.4% of the sections) (P torque than at low-torque settings. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

The fatigue life and fatigue-crack-through-thickness behavior of a surface-cracked plate, 3

International Nuclear Information System (INIS)

Nam, Ki-Woo; Matsui, Kentaro; Ando, Kotoji; Ogura, Nobukazu

1989-01-01

The LBB (leak-before-break) design is one of the most important subjects for the evaluation and the assurance of safety in pressure vessels, piping systems, LNG carriers and various other structures. In the LBB design, it is necessary to evaluate precisely the lifetime of steel plate. Furthermore, the change in crack shape that occurs during the propagation after through thickness is of paramount importance. For this reason, in a previous report, the authors proposed a simplified evaluation model for the stress intensity factor after cracking through thickness. Using this model, the crack propagation behavior, crack-opening displacement and crack shape change of surface-cracked smooth specimens and surface-cracked specimens with a stress concentration were evaluated quantitatively. The present study was also done to investigate the fatigue crack propagation behavior of surface cracks subjected to combined tensile and bending stress. Estimation of fatigue crack growth was done using the Newman-Raju formula before through thickness, and using formula (7) and (8) after through thickness. Crack length a r at just through thickness increases with increasing a bending stress. Calculated fatigue crack shape showed very good agreement with experimental one. It was also found that particular crack growth behavior and change in crack shape after cracking through thickness can be explained quantitatively using the K value based on Eqs. (7) and (8). (author)

Fundamental investigation on the impact strength of hollow fan blades

Energy Technology Data Exchange (ETDEWEB)

Ikeda, T; Miyachi, T; Sofue, Y

1985-01-01

Models of hollow fan blades were made and tested to prove that their strength is sufficient for use in real engines. The hollow blades were fabricated by diffusion bonding of two titanium alloy (6Al-4V-Ti) plates, one of which had three spanwise stiffners and the other being flat plate. The model as a nontwisted tapered blade. Impact tests were carried out on the hollow fan blade models in which the ingestion of a 1.5 pounds bird was simulated. Solid blades with the same external form were also tested by similar methods for comparison. The results of these tests show that properly designed hollow blades have sufficient stiffness and strength for use as fan blades in the turbo-fan engine.

The Nature of Mercury's Hollows, and Space Weathering Close to the Sun

Science.gov (United States)

Blewett, D. T.; Chabot, N. L.; Denevi, B. W.; Ernst, C. M.

2018-05-01

Hollows are a landform that appear to form by loss of a volatile-bearing phase from silicate rock. Hollows are very young and are likely to be forming in the present day. Hollows may be an analog for extreme weathering on near-Sun asteroids.

On fatigue crack growth in ductile materials by crack-tip blunting

DEFF Research Database (Denmark)

Tvergaard, Viggo

2004-01-01

One of the basic mechanisms for fatigue crack growth in ductile metals is that depending on crack-tip blunting under tensile loads and re-sharpening of the crack-tip during unloading. In a standard numerical analysis accounting for finite strains it is not possible to follow this process during...

Generation and propagation characteristics of a localized hollow beam

Science.gov (United States)

Xia, Meng; Wang, Zhizhang; Yin, Yaling; Zhou, Qi; Xia, Yong; Yin, Jianping

2018-05-01

A succinct experimental scheme is demonstrated to generate a localized hollow beam by using a π-phase binary bitmap and a convergent thin lens. The experimental results show that the aspect ratio of the dark-spot size of the hollow beam can be effectively controlled by the focal length of the lens. The measured beam profiles in free space also agree with the theoretical modeling. The studies hold great promise that such a hollow beam can be used to cool trapped atoms (or molecules) by Sisyphus cooling and to achieve an optically-trapped Bose–Einstein condensate by optical-potential evaporative cooling.

Hydroxyapatite nanorod-assembled porous hollow polyhedra as drug/protein carriers.

Science.gov (United States)

Yu, Ya-Dong; Zhu, Ying-Jie; Qi, Chao; Jiang, Ying-Ying; Li, Heng; Wu, Jin

2017-06-15

Hydroxyapatite (HAP) with a porous hollow structure is an ideal biomaterial owing to its excellent biocompatibility and unique architecture. In this study, HAP nanorod-assembled porous hollow polyhedra, consisting of nanorod building blocks, have been successfully prepared at room temperature or under hydrothermal circumstances using a self-sacrificing Ca(OH) 2 template strategy. The hydrothermal treatment (at 180°C for 1h) can promote the HAP nanorods to be arranged with their axial direction normal to the polyhedron surface. The HAP nanorod-assembled porous hollow polyhedra have been explored for the potential application in drug/protein delivery, using ibuprofen (IBU) as a model drug and hemoglobin (Hb) as a model protein. The experimental results indicate that the HAP nanorod-assembled porous hollow polyhedra have a relatively high drug loading capacity and protein adsorption ability, and sustained drug and protein release. The HAP nanorod-assembled porous hollow polyhedra have promising applications in various biomedical fields such as the drug and protein delivery. Copyright © 2017 Elsevier Inc. All rights reserved.

CAISSON TYPE HOLLOW FLOOR SLABS OF MONOLITHIC MULTI-STOREYED BUILDINGS

Directory of Open Access Journals (Sweden)

Malakhova Anna Nikolaevna

2016-06-01

Full Text Available One of the disadvantages of building structures made of reinforced concrete is their considerable weight. One of the trends to decrease the weight of concrete structures, including floor slabs, is the arrangement of voids in the cross-sectional building structures. In Russian and foreign practice paper, cardboard and plastic tubes has been used for creation of voids in the construction of monolithic floor slabs. Lightweight concretes were also used for production of precast hollow core floor slabs. The article provides constructive solutions of precast hollow core floor slabs and solid monolithic slabs that were used in the construction of buildings before wide use of large precast hollow core floor slabs. The article considers the application of caisson hollow core floor slabs for modern monolithic multi-storeyed buildings. The design solutions of such floor slabs, experimental investigations and computer modeling of their operation under load were described in this article. The comparative analysis of the calculation results of computer models of a hollow slabs formed of rod or plastic elements showed the similarity of calculation results.

Reliable micro-measurement of strontium is the key to cracking the life-history code in the fish otolith

International Nuclear Information System (INIS)

Markwitz, A.; Grambole, D.; Herrmann, F.; Trompetter, W.J.; Dioses, T.; Gauldie, R.W.

2000-01-01

The fish otolith is a calcium carbonate (usually aragonite) crystal that grows continuously by accretion over the life of the fish and unlike bone is not continuously re-metabolised. Consequently, the otolith has long been regarded as a potential store of information about the life history of an individual fish, and this information is encoded in the deposition pattern of trace elements in the otolith. The code has been difficult to crack. However, recent developments have show that: (1) Sr is one of the few non-mobile trace elements in the otolith; and (2) the pattern of Sr deposition summarises the effects of environment changes that affect the growth rate of the otolith crystal. The remaining difficulties in cracking the chemical code in the otolith have hinged about making reliable micro-measurements of the stable Sr content at spatial resolutions of 10 μm or less; this interval represents about 4-6 days of otolith growth in most species of fish. This paper describes high beam resolution 2 μm linear measurements, and 6 μm square measurements over narrow windows of about 300 μm square, and links these micro-measures to macro-measures of 2D maps of the entire surface of sections of otoliths up to 5 mm square at beam resolutions of 25 μm square. The otoliths used in this study are from the Jurel, or Peruvian Jack mackerel, Trachurus murphyi (Carangidae: Teleostei)

The crazy hollow formation (Eocene) of central Utah

Science.gov (United States)

Weiss, M.P.; Warner, K.N.

2001-01-01

The Late Eocene Crazy Hollow Formation is a fluviatile and lacustrine unit that was deposited locally in the southwest arm of Lake Uinta during and after the last stages of the lake the deposited the Green River Formation. Most exposures of the Crazy Hollow are located in Sanpete and Sevier Counties. The unit is characterized by a large variety of rock types, rapid facies changes within fairly short distances, and different lithofacies in the several areas where outcrops of the remnants of the formation are concentrated. Mudstone is dominant, volumetrically, but siltstone, shale, sandstone, conglomerate and several varieties of limestone are also present. The fine-grained rocks are mostly highly colored, especially in shades of yellow, orange and red. Sand grains, pebbles and small cobbles of well-rounded black chert are widespread, and "salt-and-pepper sandstone" is the conspicuous characteristic of the Crazy Hollow. The salt-and-pepper sandstone consists of grains of black chert, white chert, quartz and minor feldspar. The limestone beds and lenses are paludal and lacustrine in origin; some are fossiliferous, and contain the same fauna found in the Green River Formation. With trivial exceptions, the Crazy Hollow Formation lies on the upper, limestone member of the Green River Formation, and the beds of the two units are always accordant in attitude. The nature of the contact differs locally: at some sites there is gradation from the Green River to the Crazy Hollow; at others, rocks typical of the two units intertongue; elsewhere there is a disconformity between the two. A variety of bedrock units overlie the Crazy Hollow at different sites. In the southeasternmost districts it is overlain by the late Eocene formation of Aurora; in western Sevier County it is overlain by the Miocene-Pliocene Sevier River Formation; in northernmost Sanpete County it is overlain by the Oligocene volcanics of the Moroni Formation. At many sites bordering Sanpete and Sevier Valleys

Crack layer theory

Science.gov (United States)

Chudnovsky, A.

1987-01-01

A damage parameter is introduced in addition to conventional parameters of continuum mechanics and consider a crack surrounded by an array of microdefects within the continuum mechanics framework. A system consisting of the main crack and surrounding damage is called crack layer (CL). Crack layer propagation is an irreversible process. The general framework of the thermodynamics of irreversible processes are employed to identify the driving forces (causes) and to derive the constitutive equation of CL propagation, that is, the relationship between the rates of the crack growth and damage dissemination from one side and the conjugated thermodynamic forces from another. The proposed law of CL propagation is in good agreement with the experimental data on fatigue CL propagation in various materials. The theory also elaborates material toughness characterization.

Structural investigation of spherical hollow excipient Mannit Q by X-ray microtomography.

Science.gov (United States)

Kajihara, Ryusuke; Noguchi, Shuji; Iwao, Yasunori; Yasuda, Yuki; Segawa, Megumi; Itai, Shigeru

2015-11-10

The structure of Mannit Q particles, an excipient made by spray-drying a d-mannitol solution, and Mannit Q tablets were investigated by synchrotron X-ray microtomography. The Mannit Q particles had a spherical shape with a hollow core. The shells of the particles consisted of fine needle-shaped crystals, and columnar crystals were present in the hollows. These structural features suggested the following formation mechanism for the hollow particles:during the spray-drying process, the solvent rapidly evaporated from the droplet surface, resulting in the formation of shells made of fine needle-shaped crystals.Solvent remaining inside the shells then evaporated slowly and larger columnar crystals grew as the hollows formed. Although most of the Mannit Q particles were crushed on tableting, some of the particles retained their hollow structures, probably because the columnar crystals inside the hollows functioned as props. This demonstrated that the tablets with porous void spaces may be readily manufactured using Mannit Q. Copyright © 2015 Elsevier B.V. All rights reserved.

Curvilinear crack layer propagation

Science.gov (United States)

Chudnovsky, Alexander; Chaoui, Kamel; Moet, Abdelsamie

1987-01-01

An account is given of an experiment designed to allow observation of the effect of damage orientation on the direction of crack growth in the case of crack layer propagation, using polystyrene as the model material. The direction of crack advance under a given loading condition is noted to be determined by a competition between the tendency of the crack to maintain its current direction and the tendency to follow the orientation of the crazes at its tip. The orientation of the crazes is, on the other hand, determined by the stress field due to the interaction of the crack, the crazes, and the hole. The changes in craze rotation relative to the crack define the active zone rotation.

Emission mechanism in high current hollow cathode arcs

International Nuclear Information System (INIS)

Krishnan, M.

1976-01-01

Large (2 cm-diameter) hollow cathodes have been operated in a magnetoplasmadynamic (MPD) arc over wide ranges of current (0.25 to 17 kA) and mass flow (10 -3 to 8 g/sec), with orifice current densities and mass fluxes encompassing those encountered in low current steady-state hollow cathode arcs. Detailed cathode interior measurements of current and potential distributions show that maximum current penetration into the cathode is about one diameter axially upstream from the tip, with peak inner surface current attachment up to one cathode diameter upstream of the tip. The spontaneous attachment of peak current upstream of the cathode tip is suggested as a criterion for characteristic hollow cathode operation. This empirical criterion is verified by experiment

Evolution of ESR Technology and Equipment for Long Hollow Ingots Manufacture

Science.gov (United States)

Medovar, Lev; Stovpchenko, Ganna; Dudka, Grigory; Kozminskiy, Alexander; Fedorovskii, Borys; Lebid, Vitalii; Gusiev, Iaroslav

In this paper development of both ESR technology and equipment for hollow ingot manufacture review and analysis are presented. The real complications of hollow ingot manufacture and some tendentious issues which restrict process dissemination are discussed. An actual data of modern manufacture of as-cast pipes for heat and power engineering by traditional ESR with consumable electrode are given. Results of microstructure and nonmetal inclusion investigations have shown the high quality of as-cast ESR pipes. On the basis of these results the possibility to produce huge ESR hollows (up 5000 mm in dia) with final goal drastically to reduce setting ratio on forged shells and rings or even replace it by ESR hollows as-cast is grounded. Two new ESR technologies — consumable electrodes change and liquid metal usage — have passed pilot tests for heavy hollow production and shown very prospective results to be presented.

Hollow-core photonic band gap fibers for particle acceleration

Directory of Open Access Journals (Sweden)

Robert J. Noble

2011-12-01

Full Text Available Photonic band gap (PBG dielectric fibers with hollow cores are being studied both theoretically and experimentally for use as laser driven accelerator structures. The hollow core functions as both a longitudinal waveguide for the transverse-magnetic (TM accelerating fields and a channel for the charged particles. The dielectric surrounding the core is permeated by a periodic array of smaller holes to confine the mode, forming a photonic crystal fiber in which modes exist in frequency passbands, separated by band gaps. The hollow core acts as a defect which breaks the crystal symmetry, and so-called defect, or trapped modes having frequencies in the band gap will only propagate near the defect. We describe the design of 2D hollow-core PBG fibers to support TM defect modes with high longitudinal fields and high characteristic impedance. Using as-built dimensions of industrially made fibers, we perform a simulation analysis of prototype PBG fibers with dimensions appropriate for speed-of-light TM modes.

Method for selecting hollow microspheres for use in laser fusion targets

Science.gov (United States)

Farnum, Eugene H.; Fries, R. Jay; Havenhill, Jerry W.; Smith, Maurice Lee; Stoltz, Daniel L.

1976-01-01

Hollow microspheres having thin and very uniform wall thickness are useful as containers for the deuterium and tritium gas mixture used as a fuel in laser fusion targets. Hollow microspheres are commercially available; however, in commercial lots only a very small number meet the rigid requirements for use in laser fusion targets. Those meeting these requirements may be separated from the unsuitable ones by subjecting the commercial lot to size and density separations and then by subjecting those hollow microspheres thus separated to an external pressurization at which those which are aspherical or which have nonuniform walls are broken and separating the sound hollow microspheres from the broken ones.

Thermal fatigue cracking of austenitic stainless steels; Fissuration en fatigue thermique des aciers inoxydables austenitiques

Energy Technology Data Exchange (ETDEWEB)

Fissolo, A

2001-07-01

This report deals with the thermal fatigue cracking of austenitic stainless steels as AISI 316 LN and 304 L. Such damage has been clearly observed for some components used in Fast Breeder reactors (FBR) and Pressure Water Reactor (PWR). In order to investigate thermal fatigue, quasi-structural specimen have been used. In this frame, facilities enforcing temperature variations similar to those found under the operation conditions have been progressively developed. As for components, loading results from impeded dilatation. In the SPLASH facility, the purpose was to establish accurate crack initiation conditions in order to check the relevance of the usual component design methodology. The tested specimen is continuously heated by the passage of an electrical DC current, and submitted to cyclic thermal down shock (up to 1000 deg C/s) by means of periodical spraying of water on two opposite specimen faces. The number of cycles to crack initiation N{sub i} is deduced from periodic examinations of the quenched surfaces, by means of optical microscopy. It is considered that initiation occurs when at least one 50{mu}m to 150{open_square}m long crack is observed. Additional SPLASH tests were performed for N >> N{sub i}, with a view to investigate the evolution of a surface multiple cracking network with the number of cycles N. The CYTHIA test was mainly developed for the purpose of assessing crack growth dynamics of one isolated crack in thermal fatigue conditions. Specimens consist of thick walled tubes with a 1 mm circular groove is spark-machined at the specimen centre. During the test, the external wall of the tube is periodically heated by using a HF induction coil (1 MHz), while its internal wall is permanently cooled by flowing water. Total crack growth is derived from post-mortem examinations, whereby the thermal fatigue final rupture surface is oxidized at the end of the test. The specimen is broken afterwards under mechanical fatigue at room temperature. All the

Periodic organosilica hollow nanospheres as anode materials for lithium ion rechargeable batteries

Science.gov (United States)

Sasidharan, Manickam; Nakashima, Kenichi; Gunawardhana, Nanda; Yokoi, Toshiyuki; Ito, Masanori; Inoue, Masamichi; Yusa, Shin-Ichi; Yoshio, Masaki; Tatsumi, Takashi

2011-11-01

Polymeric micelles with core-shell-corona architecture have been found to be the efficient colloidal templates for synthesis of periodic organosilica hollow nanospheres over a broad pH range from acidic to alkaline media. In alkaline medium, poly (styrene-b-[3-(methacryloylamino)propyl] trimethylammonium chloride-b-ethylene oxide) (PS-PMAPTAC-PEO) micelles yield benzene-silica hollow nanospheres with molecular scale periodicity of benzene groups in the shell domain of hollow particles. Whereas, an acidic medium (pH 4) produces diverse hollow particles with benzene, ethylene, and a mixture of ethylene and dipropyldisulfide bridging functionalities using poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-PVP-PEO) micelles. These hollow particles were thoroughly characterized by powder X-ray diffraction (XRD), dynamic light scattering (DLS), thermogravimetric analysis (TG/DTA), Fourier transformation infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), magic angle spinning-nuclear magnetic resonance (29Si MAS NMR and 13CP-MAS NMR), Raman spectroscopy, and nitrogen adsorption/desorption analyses. The benzene-silica hollow nanospheres with molecular scale periodicity in the shell domain exhibit higher cycling performance of up to 300 cycles in lithium ion rechargeable batteries compared with micron-sized dense benzene-silica particles.Polymeric micelles with core-shell-corona architecture have been found to be the efficient colloidal templates for synthesis of periodic organosilica hollow nanospheres over a broad pH range from acidic to alkaline media. In alkaline medium, poly (styrene-b-[3-(methacryloylamino)propyl] trimethylammonium chloride-b-ethylene oxide) (PS-PMAPTAC-PEO) micelles yield benzene-silica hollow nanospheres with molecular scale periodicity of benzene groups in the shell domain of hollow particles. Whereas, an acidic medium (pH 4) produces diverse hollow particles with benzene, ethylene, and a mixture of ethylene and

An Investigation of the Sub-Microsecond Features of Dynamic Crack Propagation in PMMA and the Rdx-Based Explosive PBX 9205

Science.gov (United States)

Washabaugh, P. D.; Hill, L. G.

2007-12-01

A dynamic crack propagating in a brittle material releases enough thermal energy to produce visible light. The dynamic fracture of even macroscopically amorphous materials becomes unsteady as the crack propagation velocity approaches the material wave-speeds. The heat generated at a crack-tip, especially as it jumps, may be a mechanism to initiate a self-sustaining reaction in an energetic material. Experiments were conducted in specimens to simulate an infinite plate for ˜10 μs. The initial specimens were 152 mm square by 6 mm thick acrylic sheets, and were fabricated to study non-steady near-wave-speed crack propagation. A variant of this specimen embedded a 25 mm×3 mm PBX 9205 pellet to explore the influence of dynamic Mode-I cracks in these materials. The crack was initiated by up to 0.24 g of Detasheet placed along a precursor 50 mm long notch, with a shield to contain the reaction products and prevent propagation along the fractured surfaces. The crack was studied by means of a streak camera and a Fourier-filter of the light reflecting off the newly minted surfaces. The sub-microsecond behavior of holes initiating, preceding and coalescing with the main crack were observed in the PMMA samples. The embedding and mechanical loading of explosives by this technique did not initiate a self-sustaining reaction in preliminary testing.

Bubble template synthesis of hollow gold nanoparticles and their applications as theranostic agents

Science.gov (United States)

Huang, Chienwen

Hollow gold nanoparticle with a sub-30nm polycrystalline shell and a 50 nm hollow core has been successfully synthesized through the reduction of sodium gold sulfite by electrochemically evolved hydrogen. Such hollow gold nanoparticles exhibit unique plasmonic properties. They strongly scatter and absorb near infrared light. In this thesis we seek to understand the formation mechanism of hollow gold nanoparticles in this new synthesis process and their plasmonic properties. Also, we explore their biomedical applications as theranostic agents (therapeutic and diagnostic imaging). A lithographically patterned electrode consisting of Ag stripes on a glass substrate was used to investigate the formation process of hollow gold nanoparticles. Ag stripes served as working electrode for electrochemically evolution of hydrogen, and adjacent glass areas provided supporting surface for hydrogen nanobubbles nucleation and growth. Hydrogen nanobubbles served as both templates and reducing agents to trigger the autocatalytic disproportionation reaction of sodium gold sulfite. The effects of applied potential and the additives in the electrolyte have been studied. It has been found that the size and size distribution of hollow gold nanoparticle are directly relative to the applied potential, i.e. the hydrogen evolution rate. It has also been found the addition of Ni2+ ions can greatly improve the size distribution of hollow gold nanoparticles that can be contributed to that the newly electrodeposited nickel metal can enhance the hydrogen evolution efficiency. Another additive, ethylenediamine (EDA) can suppress the autocatalytic reaction of gold sulfite to increase the stability of sodium gold sulfite electrolyte. To capture such electrochemically evolved hydrogen nanobubbles, and subsequently to generate hollow gold nanoparticles in large numbers, alumina membranes were placed on the top of the working electrode. Anodic alumina membrane consists of ~200 nm pores, which provides

Electromagnetic wave absorption properties of composites with ultrafine hollow magnetic fibers

Energy Technology Data Exchange (ETDEWEB)

Yi, Jin Woo [Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (BK21 Granted Program), 291 Daehak-ro, Yuseong-gu, Daejeon (Korea, Republic of); Composites Research Center, Korea Institute of Materials Science, 66 Sang-nam-dong, Changwon, Gyeongnam (Korea, Republic of); Lee, Sang Bok; Kim, Jin Bong; Lee, Sang Kwan [Composites Research Center, Korea Institute of Materials Science, 66 Sang-nam-dong, Changwon, Gyeongnam (Korea, Republic of); Park, O Ok, E-mail: oopark@kaist.ac.kr [Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (BK21 Granted Program), 291 Daehak-ro, Yuseong-gu, Daejeon (Korea, Republic of); Department of Energy Systems Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), 50-1, Sang-ri, Hyeongpung-myeon, Dalseong-gun, Daegu 711-873 (Korea, Republic of)

2014-06-01

Ultrafine hollow magnetic fibers were prepared by electroless plating using hydrolyzed polyester fiber as a sacrificial substrate. These hollow fibers can be served for lightweight and efficient electromagnetic (EM) absorbing materials. As observed from SEM and EDS analysis, hollow structures consisting of Ni inner layer and Fe or Fe–Co outer layer were obtained. By introducing Co onto Fe, oxidation of the Fe layer was successfully prevented making it possible to enhance the complex permeability compared to a case in which only Fe was used. Polymeric composites containing the hollow fibers with different weight fractions and fiber lengths were prepared by a simple mixing process. The electromagnetic wave properties of the composites were measured by a vector network analyzer and it was found that the hollow magnetic fibers show a clear resonance peak of the complex permittivity around the X-band range (8–12 GHz) and the resonance frequency strongly depends on the fiber concentration and length. A possible explanation for the unique resonance is that the hollow fibers possess relatively low electrical conductivity and a long mean free path due to their oxidized phase and hollow structure. The calculated EM wave absorption with the measured EM wave properties showed that the composite containing 30 wt% hollow Ni/Fe–Co (7:3) fibers in length of 180 μm exhibited multiple absorbance peaks resulting in a broad absorption bandwidth of 4.2 GHz. It is obvious that this multiple absorbance is attributed to the resonance characteristic of the composite. - Highlights: • The ultrafine hollow fibers consist of inner Ni layer (∼100 nm) and outer Fe or Fe–Co layer (500–700 nm). • Composites with the fibers show a high permittivity as well as permeability at low weight fractions (10–30 wt%). • The composites show a permittivity resonance and the resonance frequency can be controlled by fiber content and length. • The composite absorber exhibits a double

Porous-wall hollow glass microspheres as carriers for biomolecules

Science.gov (United States)

Li, Shuyi; Dynan, William S; Wicks, George; Serkiz, Steven

2013-09-17

The present invention includes compositions of porous-wall hollow glass microspheres and one or more biomolecules, wherein the one or more biomolecules are positioned within a void location within the hollow glass microsphere, and the use of such compositions for the diagnostic and/or therapeutic delivery of biomolecules.

Fully plastic crack opening analyses of complex-cracked pipes for Ramberg-Osgood materials

International Nuclear Information System (INIS)

Jeong, Jae Uk; Choi, Jae Boong; Huh, Nam Su; Kim, Yun Jae

2016-01-01

The plastic influence functions for calculating fully plastic Crack opening displacement (COD) of complex-cracked pipes were newly proposed based on systematic 3-dimensional (3-D) elastic-plastic Finite element (FE) analyses using Ramberg-Osgood (R-O) relation, where global bending moment, axial tension and internal pressure are considered separately as a loading condition. Then, crack opening analyses were performed based on GE/EPRI concept by using the new plastic influence functions for complex-cracked pipes made of SA376 TP304 stainless steel, and the predicted CODs were compared with FE results based on deformation plasticity theory of tensile material behavior. From the comparison, the confidence of the proposed fully plastic crack opening solutions for complex-cracked pipes was gained. Therefore, the proposed engineering scheme for COD estimation using the new plastic influence functions can be utilized to estimate leak rate of a complex-cracked pipe for R-O material.

The fatigue life and fatigue crack through thickness behavior of a surface cracked plate, 2

International Nuclear Information System (INIS)

Nam, Ki-Woo; Fujibayashi, Shinpei; Ando, Kotoji; Ogura, Nobukazu.

1987-01-01

Most structures have a region where stresses concentrate, and the probability of fatigue crack initiation may be higher than in other parts. Therefore, to improve the reliability of an LBB design, it is necessary to evaluate the growth and through thickness behavior of fatigue cracks in the stress concentration part. In this paper, a fatigue crack growth test at a stress concentration region has been made on 3 % NiCrMo and HT 80 steel. Stress concentration is caused by a fillet on the plate. The main results obtained are as follows : (1) Before cracking through the plate thickness, stress concentration has a remarkable effect on the fatigue crack growth behavior and it flatens the shape of a surface crack. The crack growth behavior can be explained quantatively by using the Newman-Raju equation and the stress resolving method proposed by ASME B and P Code SecXI. (2) The da/dN-ΔK relation obtained in a stress concentration specimen shows good agreement with that obtained in a surface cracked smooth specimen. (3) It is shown that stress concentration caused by a fillet has little effect on the crack growth rate after cracking through the plate thickness. (4) By using the K value based on eq. (1), (2), particular crack growth behavior and the change in crack shape after cracking through thickness can be explained quantatively. (author)

Creating Magic Squares.

Science.gov (United States)

Lyon, Betty Clayton

1990-01-01

One method of making magic squares using a prolongated square is illustrated. Discussed are third-order magic squares, fractional magic squares, fifth-order magic squares, decimal magic squares, and even magic squares. (CW)

Hollow fiber apparatus and use thereof for fluids separations and heat and mass transfers

Energy Technology Data Exchange (ETDEWEB)

Bikson, Benjamin; Etter, Stephen; Ching, Nathaniel

2017-04-18

A hollow fiber fluid separation device includes a hollow fiber cartridge, comprising a plurality of hollow fiber membranes arranged around a central tubular core, a first tubesheet and a second tubesheet encapsulating respective distal ends of the hollow fiber bundle. The tubesheets have boreholes in fluid communication with bores of the hollow fiber membrane. In at least one of the tubesheets, the boreholes are formed radially and are in communication with the central tubular core. The hollow fiber fluid separation device can be utilized in liquid separation applications such as ultrafiltration and in gas separation processes such as air separation. The design disclosed herein is light weight and compact and is particularly advantageous at high operating temperatures when the pressure of the feed fluid introduced into the bores of hollow fibers is higher than the pressure on the shell side of the device.

Terahertz non-destructive imaging of cracks and cracking in structures of cement-based materials

Directory of Open Access Journals (Sweden)

Shujie Fan

2017-11-01

Full Text Available Cracks and crack propagation in cement-based materials are key factors leading to failure of structures, affecting safety in construction engineering. This work investigated the application of terahertz (THz non-destructive imaging to inspections on structures of cement-based materials, so as to explore the potential of THz imaging in crack detection. Two kinds of disk specimens made of plain cement mortar and UHMWPE fiber concrete were prepared respectively. A mechanical expansion load device was deployed to generate cracks and control the whole process of cracking. Experimental tests were carried out on cracked specimens by using a commercial THz time domain spectroscopy (THz-TDS during loading. The results show that crack opening and propagation could be examined by THz clearly and the material factors influence the ability of crack resistance significantly. It was found that the THz imaging of crack initiation and propagation agrees with the practical phenomenon and supplies more information about damage of samples. It is demonstrated that the damage behavior of structures of cement-based materials can be successfully detected by THz imaging.

Terahertz non-destructive imaging of cracks and cracking in structures of cement-based materials

Science.gov (United States)

Fan, Shujie; Li, Tongchun; Zhou, Jun; Liu, Xiaoqing; Liu, Xiaoming; Qi, Huijun; Mu, Zhiyong

2017-11-01

Cracks and crack propagation in cement-based materials are key factors leading to failure of structures, affecting safety in construction engineering. This work investigated the application of terahertz (THz) non-destructive imaging to inspections on structures of cement-based materials, so as to explore the potential of THz imaging in crack detection. Two kinds of disk specimens made of plain cement mortar and UHMWPE fiber concrete were prepared respectively. A mechanical expansion load device was deployed to generate cracks and control the whole process of cracking. Experimental tests were carried out on cracked specimens by using a commercial THz time domain spectroscopy (THz-TDS) during loading. The results show that crack opening and propagation could be examined by THz clearly and the material factors influence the ability of crack resistance significantly. It was found that the THz imaging of crack initiation and propagation agrees with the practical phenomenon and supplies more information about damage of samples. It is demonstrated that the damage behavior of structures of cement-based materials can be successfully detected by THz imaging.

Axisymmetric Vibration of Piezo-Lemv Composite Hollow Multilayer Cylinder

Directory of Open Access Journals (Sweden)

E. S. Nehru

2012-01-01

Full Text Available Axisymmetric vibration of an infinite piezolaminated multilayer hollow cylinder made of piezoelectric layers of 6 mm class and an isotropic LEMV (Linear Elastic Materials with Voids layers is studied. The frequency equations are obtained for the traction free outer surface with continuity conditions at the interfaces. Numerical results are carried out for the inner, middle, and outer hollow piezoelectric layers bonded by LEMV (It is hypothetical material layers and the dispersion curves are compared with that of a similar 3-layer model and of 3 and 5 layer models with inner, middle, and outer hollow piezoelectric layers bonded by CFRP (Carbon fiber reinforced plastics.

Hollow Mill for Extraction of Stripped Titanium Screws: An Easy ...

African Journals Online (AJOL)

countries. The known alternative in such condition is ... Key words: Hollow mill, stripped screws, titanium locked plates ... used a locally manufactured stainless steel hollow mill, ... head ‑ plate hole” assembly as a mono‑block single unit. In.

VALIDATION OF CRACK INTERACTION LIMIT MODEL FOR PARALLEL EDGE CRACKS USING TWO-DIMENSIONAL FINITE ELEMENT ANALYSIS

Directory of Open Access Journals (Sweden)

R. Daud

2013-06-01

Full Text Available Shielding interaction effects of two parallel edge cracks in finite thickness plates subjected to remote tension load is analyzed using a developed finite element analysis program. In the present study, the crack interaction limit is evaluated based on the fitness of service (FFS code, and focus is given to the weak crack interaction region as the crack interval exceeds the length of cracks (b > a. Crack interaction factors are evaluated based on stress intensity factors (SIFs for Mode I SIFs using a displacement extrapolation technique. Parametric studies involved a wide range of crack-to-width (0.05 ≤ a/W ≤ 0.5 and crack interval ratios (b/a > 1. For validation, crack interaction factors are compared with single edge crack SIFs as a state of zero interaction. Within the considered range of parameters, the proposed numerical evaluation used to predict the crack interaction factor reduces the error of existing analytical solution from 1.92% to 0.97% at higher a/W. In reference to FFS codes, the small discrepancy in the prediction of the crack interaction factor validates the reliability of the numerical model to predict crack interaction limits under shielding interaction effects. In conclusion, the numerical model gave a successful prediction in estimating the crack interaction limit, which can be used as a reference for the shielding orientation of other cracks.

On crack interaction effects of in-plane surface cracks using elastic and elastic-plastic finite element analyses

International Nuclear Information System (INIS)

Kim, Jong Min; Huh, Nam Su

2010-01-01

The crack-tip stress fields and fracture mechanics assessment parameters for a surface crack, such as the elastic stress intensity factor or the elastic-plastic J-integral, can be affected significantly by the adjacent cracks. Such a crack interaction effect due to multiple cracks can alter the fracture mechanics assessment parameters significantly. There are many factors to be considered, for instance the relative distance between adjacent cracks, the crack shape, and the loading condition, to quantify the crack interaction effect on the fracture mechanics assessment parameters. Thus, the current assessment codes on crack interaction effects (crack combination rules), including ASME Sec. XI, BS7910, British Energy R6 and API 579-1/ASME FFS-1, provide different rules for combining multiple surface cracks into a single surface crack. The present paper investigates crack interaction effects by evaluating the elastic stress intensity factor and the elastic-plastic J-integral of adjacent in-plane surface cracks in a plate through detailed 3-dimensional elastic and elastic-plastic finite element analyses. The effects on the fracture mechanics assessment parameters of the geometric parameters, the relative distance between two cracks, and the crack shape are investigated systematically. As for the loading condition, an axial tension is considered. Based on the finite element results, the acceptability of the crack combination rules provided in the existing guidance was investigated, and the relevant recommendations on a crack interaction for in-plane surface cracks are discussed. The present results can be used to develop more concrete guidance on crack interaction effects for crack shape characterization to evaluate the integrity of defective components

The Reflective Cracking in Flexible Pavements

Directory of Open Access Journals (Sweden)

Pais Jorge

2013-07-01

Full Text Available Reflective cracking is a major concern for engineers facing the problem of road maintenance and rehabilitation. The problem appears due to the presence of cracks in the old pavement layers that propagate into the pavement overlay layer when traffic load passes over the cracks and due to the temperature variation. The stress concentration in the overlay just above the existing cracks is responsible for the appearance and crack propagation throughout the overlay. The analysis of the reflective cracking phenomenon is usually made by numerical modeling simulating the presence of cracks in the existing pavement and the stress concentration in the crack tip is assessed to predict either the cracking propagation rate or the expected fatigue life of the overlay. Numerical modeling to study reflective cracking is made by simulating one crack in the existing pavement and the loading is usually applied considering the shear mode of crack opening. Sometimes the simulation considers the mode I of crack opening, mainly when temperature effects are predominant.

Vibration based algorithm for crack detection in cantilever beam containing two different types of cracks

Science.gov (United States)

Behzad, Mehdi; Ghadami, Amin; Maghsoodi, Ameneh; Michael Hale, Jack

2013-11-01

In this paper, a simple method for detection of multiple edge cracks in Euler-Bernoulli beams having two different types of cracks is presented based on energy equations. Each crack is modeled as a massless rotational spring using Linear Elastic Fracture Mechanics (LEFM) theory, and a relationship among natural frequencies, crack locations and stiffness of equivalent springs is demonstrated. In the procedure, for detection of m cracks in a beam, 3m equations and natural frequencies of healthy and cracked beam in two different directions are needed as input to the algorithm. The main accomplishment of the presented algorithm is the capability to detect the location, severity and type of each crack in a multi-cracked beam. Concise and simple calculations along with accuracy are other advantages of this method. A number of numerical examples for cantilever beams including one and two cracks are presented to validate the method.

Using Squares to Sum Squares

Science.gov (United States)

DeTemple, Duane

2010-01-01

Purely combinatorial proofs are given for the sum of squares formula, 1[superscript 2] + 2[superscript 2] + ... + n[superscript 2] = n(n + 1) (2n + 1) / 6, and the sum of sums of squares formula, 1[superscript 2] + (1[superscript 2] + 2[superscript 2]) + ... + (1[superscript 2] + 2[superscript 2] + ... + n[superscript 2]) = n(n + 1)[superscript 2]…

Fatigue-crack propagation in gamma-based titanium aluminide alloys at large and small crack sizes

International Nuclear Information System (INIS)

Kruzic, J.J.; Campbell, J.P.; Ritchie, R.O.

1999-01-01

Most evaluations of the fracture and fatigue-crack propagation properties of γ+α 2 titanium aluminide alloys to date have been performed using standard large-crack samples, e.g., compact-tension specimens containing crack sizes which are on the order of tens of millimeters, i.e., large compared to microstructural dimensions. However, these alloys have been targeted for applications, such as blades in gas-turbine engines, where relevant crack sizes are much smaller ( 5 mm) and (c ≅ 25--300 microm) cracks in a γ-TiAl based alloy, of composition Ti-47Al-2Nb-2Cr-0.2B (at.%), specifically for duplex (average grain size approximately17 microm) and refined lamellar (average colony size ≅150 microm) microstructures. It is found that, whereas the lamellar microstructure displays far superior fracture toughness and fatigue-crack growth resistance in the presence of large cracks, in small-crack testing the duplex microstructure exhibits a better combination of properties. The reasons for such contrasting behavior are examined in terms of the intrinsic and extrinsic (i.e., crack bridging) contributions to cyclic crack advance

Correction to the crack extension direction in numerical modelling of mixed mode crack paths

DEFF Research Database (Denmark)

Lucht, Tore; Aliabadi, M.H.

2007-01-01

In order to avoid introduction of an error when a local crack-growth criterion is used in an incremental crack growth formulation, each straight crack extension would have to be infinitesimal or have its direction corrected. In this paper a new procedure to correct the crack extension direction...

On the transition of short cracks into long fatigue cracks in reactor pressure vessel steels

Directory of Open Access Journals (Sweden)

Singh Rajwinder

2018-01-01

Full Text Available Short fatigue cracks, having dimension less than 1 mm, propagate at much faster rates (da/dN even at lower stress intensity factor range (da/dN as compared to the threshold stress intensity factor range obtained from long fatigue crack growth studies. These short cracks originate at the sub-grain level and some of them ultimately transit into critical long cracks over time. Therefore, designing the components subjected to fatigue loading merely on the long crack growth data and neglecting the short crack growth behavior can overestimate the component’s life. This aspect of short fatigue cracks become even more critical for materials used for safety critical applications such as reactor pressure vessel (RPV steel in nuclear plants. In this work, the transition behaviour of short fatigue crack gowth into long fatigue crack is studied in SA508 Grade 3 Class I low alloy steel used in RPVs. In-situ characterization of initiation, propagation and transition of short fatigue cracks is performed using fatigue stage for Scanning Electron Microscope (SEM in addition to digital microscopes fitted over a servo-hydraulic fatigue machine and correlated with the microtructural information obtained using electron backscatter diffraction (EBSD. SA508 steel having an upper bainitic microstructure have several microstructural interfaces such as phase and grain boundaries that play a significant role in controlling the short fatigue crack propagation. Specially designed and prepared short fatigue specimens (eletro-polished with varying initial crack lengths of the order of tens of microns are used in this study. The transition of such short initial cracks into long cracks is then tracked to give detailed insight into the role of each phase and phase/grain boundary with an objective of establishing Kitagawa-Takahashi diagram for the given RPV steel. The behavior of the transited long cracks is then compared with the crack propagation behavior obtained using

An initial investigation of the sub-microsecond features of dynamic crack propagation in PMMA and the RDX-based explosive PBX 9205

Science.gov (United States)

Washabaugh, Peter; Hill, Larry

2007-06-01

A dynamic crack propagating in a brittle material releases enough thermal energy to produce visible light. The dynamic fracture of even macroscopically amorphous materials becomes unsteady as the crack propagation velocity approaches the material wave-speeds. The heat generated at a crack-tip, especially as it jumps, may be a mechanism to initiate a self-sustaining reaction in an energetic material. Experiments were conducted in specimens to simulate an infinite plate for 20 μs. The initial specimens were 152 mm square by 6 mm thick acrylic sheets, and were fabricated to study non-steady near-wave-speed crack propagation. A variant of this specimen embedded a 25 mm x 3 mm PBX 9205 pellet to explore the influence of dynamic Mode-I cracks in these materials. The crack was initiated by up to 0.2 g of Detasheet placed along a precursor 50 mm long notch, with a shield to contain the reaction products and prevent propagation along the fractured surfaces. The crack was studied by means of a streak camera and a Fourier-filter of the light reflecting off the newly minted surfaces. The sub-microsecond behavior of holes initiating, preceding and coalescing with the main crack were observed in the PMMA samples. The embedding and mechanical loading of explosives by this technique did not initiate a self-sustaining reaction in preliminary testing.

Refinement and evaluation of crack-opening-area analyses for circumferential through-wall cracks in pipes

International Nuclear Information System (INIS)

Rahman, S.; Brust, F.; Ghadiali, N.; Krishnaswamy, P.; Wilkowski, G.; Choi, Y.H.; Moberg, F.; Brickstad, B.

1995-04-01

Leak-before-break (LBB) analyses for circumferentially cracked pipes are currently being conducted in the nuclear industry to justify elimination of pipe whip restraints and jet impingement shields which are present because of the expected dynamic effects from pipe rupture. The application of the LBB methodology frequently requires calculation of leak rates. These leak rates depend on the crack-opening area of a through-wall crack in the pipe. In addition to LBB analyses, which assume a hypothetical flaw size, there is also interest in the integrity of actual leaking cracks corresponding to current leakage detection requirements in NRC Regulatory Guide 1.45, or for assessing temporary repair of Class 2 and 3 pipes that have leaks as are being evaluated in ASME Section 11. This study was requested by the NRC to review, evaluate, and refine current analytical models for crack-opening-area analyses of pipes with circumferential through-wall cracks. Twenty-five pipe experiments were analyzed to determine the accuracy of the predictive models. Several practical aspects of crack-opening such as; crack-face pressure, off-center cracks, restraint of pressure-induced bending, cracks in thickness transition regions, weld residual stresses, crack-morphology models, and thermal-hydraulic analysis, were also investigated. 140 refs., 105 figs., 41 tabs

Evolution of radiation resistant hollow fibers membranes for nuclear

International Nuclear Information System (INIS)

Neelam Kumari; Raut, D.R.; Bhardwaj, Y.K.; Mohapatra, P.K.

2014-01-01

We have evaluated hollow fiber supported liquid membrane (HFSLM) technique for the separation of actinides, fission products and other valuables from the nuclear waste solutions. In this technique, ligand responsible for separation of metal ion is held in tiny pores of membrane. Any drastic change as a consequence of irradiation, like change in pore size, change in hydrophobicity of polymeric material can be fatal for separation process as it may lead dislodging of carrier ligands from the pores. It was therefore needed to study the irradiation stability of hollow fibers. We have earlier showed that polypropylene fibers were stable up to 500 radiation dose and we therefore need to look into other options. In the present work, hollow fiber membranes made from polyether ether ketone (PEEK), polysulphone (PS). Polymers were evaluated for their radiation stability after exposing to varying absorbed dose of gamma radiation. The hollow fibers were irradiated to 100 KGy, 200 KGy, 500 KGy and 1000 KGy and its changes in hydrophobicity were measured using contact angle measurement studies

Polymer blends used to develop felodipine-loaded hollow microspheres for improved oral bioavailability.

Science.gov (United States)

Pi, Chao; Feng, Ting; Liang, Jing; Liu, Hao; Huang, Dongmei; Zhan, Chenglin; Yuan, Jiyuan; Lee, Robert J; Zhao, Ling; Wei, Yumeng

2018-06-01

Felodipine (FD) has been widely used in anti-hypertensive treatment. However, it has extremely low aqueous solubility and poor bioavailability. To address these problems, FD hollow microspheres as multiple-unit dosage forms were synthesized by a solvent diffusion evaporation method. Particle size of the hollow microspheres, types of ethylcellulose (EC), amounts of EC, polyvinyl pyrrolidone (PVP) and FD were investigated based on an orthogonal experiment of three factors and three levels. In addition, the release kinetics in vitro and pharmacokinetics in beagle dogs of the optimized FD hollow microspheres was investigated and compared with Plendil (commercial FD sustained-release tablets) as a single-unit dosage form. Results showed that the optimal formulation was composed of EC 10 cp :PVP:FD (0.9:0.16:0.36, w/w). The FD hollow microspheres were globular with a hollow structure and have high drug loading (17.69±0.44%) and floating rate (93.82±4.05%) in simulated human gastric fluid after 24h. Pharmacokinetic data showed that FD hollow microspheres exhibited sustained-release behavior and significantly improved relative bioavailability of FD compared with the control. Pharmacodynamic study showed that the FD hollow microspheres could effectively lower blood pressure. Therefore, these findings demonstrated that the hollow microspheres were an effective sustained-release delivery system for FD. Copyright © 2018 Elsevier B.V. All rights reserved.

Method for sizing hollow microspheres

Science.gov (United States)

Farnum, E.H.; Fries, R.J.

1975-10-29

Hollow Microspheres may be effectively sized by placing them beneath a screen stack completely immersed in an ultrasonic bath containing a liquid having a density at which the microspheres float and ultrasonically agitating the bath.

Pressure effects in hollow and solid iron oxide nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Silva, N.J.O., E-mail: nunojoao@ua.pt [Departamento de Física and CICECO, Universidade de Aveiro, 3810-193 Aveiro (Portugal); Saisho, S.; Mito, M. [Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550 (Japan); Millán, A.; Palacio, F. [Instituto de Ciencia de Materiales de Aragón, CSIC - Universidad de Zaragoza. Departamento de Física de la Materia Condensada, Facultad de Ciencias, 50009 Zaragoza (Spain); Cabot, A. [Universitat de Barcelona and Catalonia Energy Research Institute, Barcelona (Spain); Iglesias, Ò.; Labarta, A. [Departament de Física Fonamental, Universitat de Barcelona and Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona (Spain)

2013-06-15

We report a study on the pressure response of the anisotropy energy of hollow and solid maghemite nanoparticles. The differences between the maghemite samples are understood in terms of size, magnetic anisotropy and shape of the particles. In particular, the differences between hollow and solid samples are due to the different shape of the nanoparticles and by comparing both pressure responses it is possible to conclude that the shell has a larger pressure response when compared to the core. - Highlights: ► Study of the pressure response of core and shell magnetic anisotropy. ► Contrast between hollow and solid maghemite nanoparticles. ► Disentanglement of nanoparticles core and shell magnetic properties.

Inspecting cracks in foam insulation

Science.gov (United States)

Cambell, L. W.; Jung, G. K.

1979-01-01

Dye solution indicates extent of cracking by penetrating crack and showing original crack depth clearly. Solution comprised of methylene blue in denatured ethyl alcohol penetrates cracks completely and evaporates quickly and is suitable technique for usage in environmental or structural tests.

Fatigue crack threshold relevant to stress ratio, crack wake and loading histories

International Nuclear Information System (INIS)

Okazaki, Masakazu; Iwasaki, Akira; Kasahara, Naoto

2013-01-01

Fatigue crack propagation behavior was investigated in a low alloy steel which experienced several kind of loading histories. Both the effects of stress ratio, test temperature on the fatigue crack threshold, and the change in the threshold depending on the thermo-mechanical loading histories, were experimentally investigated. It was shown that the thermo-mechanical loading history left its effect along the prior fatigue crack wake resulting in the change of fatigue crack threshold. Some discussions are made on how this type of loading history effect should be treated from engineering point of view. (author)

Theoretical prediction of low-density hexagonal ZnO hollow structures

Energy Technology Data Exchange (ETDEWEB)

Tuoc, Vu Ngoc, E-mail: tuoc.vungoc@hust.edu.vn [Institute of Engineering Physics, Hanoi University of Science and Technology, 1 Dai Co Viet Road, Hanoi (Viet Nam); Huan, Tran Doan [Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269-3136 (United States); Thao, Nguyen Thi [Institute of Engineering Physics, Hanoi University of Science and Technology, 1 Dai Co Viet Road, Hanoi (Viet Nam); Hong Duc University, 307 Le Lai, Thanh Hoa City (Viet Nam); Tuan, Le Manh [Hong Duc University, 307 Le Lai, Thanh Hoa City (Viet Nam)

2016-10-14

Along with wurtzite and zinc blende, zinc oxide (ZnO) has been found in a large number of polymorphs with substantially different properties and, hence, applications. Therefore, predicting and synthesizing new classes of ZnO polymorphs are of great significance and have been gaining considerable interest. Herein, we perform a density functional theory based tight-binding study, predicting several new series of ZnO hollow structures using the bottom-up approach. The geometry of the building blocks allows for obtaining a variety of hexagonal, low-density nanoporous, and flexible ZnO hollow structures. Their stability is discussed by means of the free energy computed within the lattice-dynamics approach. Our calculations also indicate that all the reported hollow structures are wide band gap semiconductors in the same fashion with bulk ZnO. The electronic band structures of the ZnO hollow structures are finally examined in detail.

Studies on pulsed hollow cathode capillary discharges

Energy Technology Data Exchange (ETDEWEB)

Choi, P; Dumitrescu-Zoita, C; Larour, J; Rous, J [Ecole Polytechnique, 91 - Palaiseau (France). Lab. de Physique des Milieux Ionises; Favre, M; Moreno, J; Chuaqui, H; Wyndham, E [Pontificia Univ. Catolica de Chile, Santiago (Chile). Facultad de Fisica; Zambra, M [Comision Chilena de Energia Nuclear, Santiago (Chile); Wong, C S [Univ. of Malaya, Kuala Lumpur (Malaysia). Plasma Research Lab

1997-12-31

Preliminary results on radiation characteristics of pulsed hollow cathode capillary discharges are presented. The device combines the on axis electron beam assisted ionization capabilities of the transient hollow cathode discharge with a novel high voltage low inductance geometrical design, which integrates the local energy storage into the electrode system. A nanosecond regime high temperature plasma is produced in a long, high aspect ratio capillary, with light emission in the UV to XUV region. The discharge is operated from near vacuum to pressure in the 1000 mTorr range. (author). 2 figs., 7 refs.

Chloride Penetration through Cracks in High-Performance Concrete and Surface Treatment System for Crack Healing

Directory of Open Access Journals (Sweden)

In-Seok Yoon

2012-01-01

Full Text Available For enhancing the service life of concrete structures, it is very important to minimize crack at surface. Even if these cracks are very small, the problem is to which extend these cracks may jeopardize the durability of these decks. It was proposed that crack depth corresponding with critical crack width from the surface is a crucial factor in view of durability design of concrete structures. It was necessary to deal with chloride penetration through microcracks characterized with the mixing features of concrete. This study is devoted to examine the effect of high strength concrete and reinforcement of steel fiber on chloride penetration through cracks. High strength concrete is regarded as an excellent barrier to resist chloride penetration. However, durability performance of cracked high strength concrete was reduced seriously up to that of ordinary cracked concrete. Steel fiber reinforcement is effective to reduce chloride penetration through cracks because steel fiber reinforcement can lead to reduce crack depth significantly. Meanwhile, surface treatment systems are put on the surface of the concrete in order to seal the concrete. The key-issue is to which extend a sealing is able to ensure that chloride-induced corrosion can be prevented. As a result, penetrant cannot cure cracks, however, coating and combined treatment can prevent chloride from flowing in concrete with maximum crack width of 0.06 mm and 0.08 mm, respectively.

Earthquake Source Spectral Study beyond the Omega-Square Model

Science.gov (United States)

Uchide, T.; Imanishi, K.

2017-12-01

Earthquake source spectra have been used for characterizing earthquake source processes quantitatively and, at the same time, simply, so that we can analyze the source spectra for many earthquakes, especially for small earthquakes, at once and compare them each other. A standard model for the source spectra is the omega-square model, which has the flat spectrum and the falloff inversely proportional to the square of frequencies at low and high frequencies, respectively, which are bordered by a corner frequency. The corner frequency has often been converted to the stress drop under the assumption of circular crack models. However, recent studies claimed the existence of another corner frequency [Denolle and Shearer, 2016; Uchide and Imanishi, 2016] thanks to the recent development of seismic networks. We have found that many earthquakes in areas other than the area studied by Uchide and Imanishi [2016] also have source spectra deviating from the omega-square model. Another part of the earthquake spectra we now focus on is the falloff rate at high frequencies, which will affect the seismic energy estimation [e.g., Hirano and Yagi, 2017]. In June, 2016, we deployed seven velocity seismometers in the northern Ibaraki prefecture, where the shallow crustal seismicity mainly with normal-faulting events was activated by the 2011 Tohoku-oki earthquake. We have recorded seismograms at 1000 samples per second and at a short distance from the source, so that we can investigate the high-frequency components of the earthquake source spectra. Although we are still in the stage of discovery and confirmation of the deviation from the standard omega-square model, the update of the earthquake source spectrum model will help us systematically extract more information on the earthquake source process.

Biomolecule-assisted construction of cadmium sulfide hollow spheres with structure-dependent photocatalytic activity.

Science.gov (United States)

Wei, Chengzhen; Zang, Wenzhe; Yin, Jingzhou; Lu, Qingyi; Chen, Qun; Liu, Rongmei; Gao, Feng

2013-02-25

In this study, we report the synthesis of monodispersive solid and hollow CdS spheres with structure-dependent photocatalytic abilities for dye photodegradation. The monodispersive CdS nanospheres were constructed with the assistance of the soulcarboxymthyi chitosan biopolymer under hydrothermal conditions. The solid CdS spheres were corroded by ammonia to form hollow CdS nanospheres through a dissolution-reprecipitation mechanism. Their visible-light photocatalytic activities were investigated, and the results show that both the solid and the hollow CdS spheres have visible-light photocatalytic abilities for the photodegradation of dyes. The photocatalytic properties of the CdS spheres were demonstrated to be structure dependent. Although the nanoparticles comprising the hollow spheres have larger sizes than those comprising the solid spheres, the hollow CdS spheres have better photocatalytic performances than the solid CdS spheres, which can be attributed to the special hollow structure. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Economic aspects of interlocking hollow brick system designed for industrialized building system

Science.gov (United States)

Tahir, Mahmood Md.; Saggaff, Anis; Ngian, Shek Poi; Sulaiman, Arizu

2017-11-01

Construction industry has moved forward into a technology driven where a transition is in progress from conventional method to a more advanced and mechanised system known as the Industrialised Building System (IBS). However, the need to implement the IBS should be well understood by all construction players such as designer, architect, contraction, erectors and construction workers. Therefore, there is a need to educate all these construction players which should be spearheaded by authorities such as Construction Industrial Development Board where enforcement trough building by laws as well as initiative to those that adopt the IBS in their construction. This paper reports on economic aspects of using interlocking hollow brick system in construction as an alternative method offered for Industrialized Building System. The main objective is to address the economic aspects of using interlocking block system in terms of time, costs, and utilization of manpower and to present some of the experimental tests results related to Interlocking Hollow Brick System (IHBS). Example of savings from the use of IHBS is presented in this paper by comparing the construction of two storey terrace house with build-up area of about 200 square meter with conventional construction method of typical reinforced concrete construction (RCC) compared to IHBS. The comparison shows that the implementation of IHBS can reduce construction time, cost, and utilization of man power up to 26.6% compared to the conventional method. Moreover, the construction time using IHBS can also be reduced by up to 50% as compared to the conventional construction.

Preparation of SnO 2 /Carbon Composite Hollow Spheres and Their Lithium Storage Properties

KAUST Repository

Lou, Xiong Wen; Deng, Da; Lee, Jim Yang; Archer, Lynden A.

2008-01-01

In this work, we present a novel concept of structural design for preparing functional composite hollow spheres and derived double-shelled hollow spheres. The approach involves two main steps: preparation of porous hollow spheres of one component and deposition of the other component onto both the interior and exterior surfaces of the shell as well as in the pores. We demonstrate the concept by preparing SnO2/carbon composite hollow spheres and evaluate them as potential anode materials for lithium-ion batteries. These SnO2/carbon hollow spheres are able to deliver a reversible Li storage capacity of 473 mA h g-1 after 50 cycles. Unusual double-shelled carbon hollow spheres are obtained by selective removal of the sandwiched porous SnO2 shells. © 2008 American Chemical Society.

Preparation of SnO 2 /Carbon Composite Hollow Spheres and Their Lithium Storage Properties

KAUST Repository

Lou, Xiong Wen

2008-10-28

In this work, we present a novel concept of structural design for preparing functional composite hollow spheres and derived double-shelled hollow spheres. The approach involves two main steps: preparation of porous hollow spheres of one component and deposition of the other component onto both the interior and exterior surfaces of the shell as well as in the pores. We demonstrate the concept by preparing SnO2/carbon composite hollow spheres and evaluate them as potential anode materials for lithium-ion batteries. These SnO2/carbon hollow spheres are able to deliver a reversible Li storage capacity of 473 mA h g-1 after 50 cycles. Unusual double-shelled carbon hollow spheres are obtained by selective removal of the sandwiched porous SnO2 shells. © 2008 American Chemical Society.

Size and thickness effect on magnetic structures of maghemite hollow magnetic nanoparticles

International Nuclear Information System (INIS)

Sayed, Fatima; Labaye, Yvan; Sayed Hassan, Rodaina; El Haj Hassan, Fouad; Yaacoub, Nader; Greneche, Jean-Marc

2016-01-01

The effect of surface anisotropy on the magnetic ground state of hollow maghemite nanoparticles is investigated using atomistic Monte Carlo simulation. The computer modeling is carried on hollow nanostructures as a function of size and shell thickness. It is found that the large contribution of the surface anisotropy imposes a “throttled” spin structure where the moments located at the outer surface tend to orient normal to the surface while those located at the inner surface appear to be more aligned. For increasing values of surface anisotropy in the frame of a radial model, the magnetic moments become radially oriented either inward or outward giving rise to a “hedgehog” configuration with nearly zero net magnetization. We also show the effect of the size of hollow nanoparticle on the spin behavior where the spin non-collinearity increases (for fixed value of surface anisotropy) as the diameter of the hollow nanoparticle increases due to the significant increase in surface-to-volume ratio, the thickness being constant. Moreover, the thickness of the hollow nanoparticle shell influences the spin configuration and thus the relation between surface anisotropy and the size or the thickness of the hollow nanoparticle is established.

Size and thickness effect on magnetic structures of maghemite hollow magnetic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Sayed, Fatima; Labaye, Yvan, E-mail: yvan.labaye@univ-lemans.fr [Université du Maine, Institut des Molécules et Matériaux du Mans CNRS UMR-6283 (France); Sayed Hassan, Rodaina; El Haj Hassan, Fouad [Université Libanaise, Faculté des Sciences Section I, MPLAB (Lebanon); Yaacoub, Nader, E-mail: nader.yaacoub@univ-lemans.fr; Greneche, Jean-Marc [Université du Maine, Institut des Molécules et Matériaux du Mans CNRS UMR-6283 (France)

2016-09-15

The effect of surface anisotropy on the magnetic ground state of hollow maghemite nanoparticles is investigated using atomistic Monte Carlo simulation. The computer modeling is carried on hollow nanostructures as a function of size and shell thickness. It is found that the large contribution of the surface anisotropy imposes a “throttled” spin structure where the moments located at the outer surface tend to orient normal to the surface while those located at the inner surface appear to be more aligned. For increasing values of surface anisotropy in the frame of a radial model, the magnetic moments become radially oriented either inward or outward giving rise to a “hedgehog” configuration with nearly zero net magnetization. We also show the effect of the size of hollow nanoparticle on the spin behavior where the spin non-collinearity increases (for fixed value of surface anisotropy) as the diameter of the hollow nanoparticle increases due to the significant increase in surface-to-volume ratio, the thickness being constant. Moreover, the thickness of the hollow nanoparticle shell influences the spin configuration and thus the relation between surface anisotropy and the size or the thickness of the hollow nanoparticle is established.

Preparation and photocatalytic activity of hollow ZnSe microspheres via Ostwald ripening

International Nuclear Information System (INIS)

Zhang Lihui; Yang Heqing; Xie Xiaoli; Zhang Fenghua; Li Li

2009-01-01

Hollow ZnSe microspheres were prepared via a facile hydrothermal reaction of Zn(AC) 2 .2H 2 O with Na 2 SeO 3 and ethylene glycol in NaOH solution at 180 deg. C for 12 h. The products were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectrum. The hollow microspheres with the diameters of about 2 μm are constructed from ZnSe nanoparticles with the cubic zinc blende structure, the size of hollow interiors and constituent ZnSe nanodots can be tuned by changing the reaction time. The hollow microspheres are formed via an Ostwald ripening process. Photoluminescence and photocatalytic activity of the hollow ZnSe microspheres were studied at room temperature. The results indicate that the hollow microspheres constructed from ZnSe nanoparticles display a strong near-band edge emission at 479 nm and a very weak deep defect (DD) related emission at 556 nm and a high photocatalytic activity in the photodegradation of methyl orange. The photodegradation of methyl orange catalyzed by the ZnSe microspheres is a pseudo first-order reaction

Periodic organosilica hollow nanospheres as anode materials for lithium ion rechargeable batteries.

Science.gov (United States)

Sasidharan, Manickam; Nakashima, Kenichi; Gunawardhana, Nanda; Yokoi, Toshiyuki; Ito, Masanori; Inoue, Masamichi; Yusa, Shin-ichi; Yoshio, Masaki; Tatsumi, Takashi

2011-11-01

Polymeric micelles with core-shell-corona architecture have been found to be the efficient colloidal templates for synthesis of periodic organosilica hollow nanospheres over a broad pH range from acidic to alkaline media. In alkaline medium, poly (styrene-b-[3-(methacryloylamino)propyl] trimethylammonium chloride-b-ethylene oxide) (PS-PMAPTAC-PEO) micelles yield benzene-silica hollow nanospheres with molecular scale periodicity of benzene groups in the shell domain of hollow particles. Whereas, an acidic medium (pH 4) produces diverse hollow particles with benzene, ethylene, and a mixture of ethylene and dipropyldisulfide bridging functionalities using poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-PVP-PEO) micelles. These hollow particles were thoroughly characterized by powder X-ray diffraction (XRD), dynamic light scattering (DLS), thermogravimetric analysis (TG/DTA), Fourier transformation infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), magic angle spinning-nuclear magnetic resonance ((29)Si MAS NMR and (13)CP-MAS NMR), Raman spectroscopy, and nitrogen adsorption/desorption analyses. The benzene-silica hollow nanospheres with molecular scale periodicity in the shell domain exhibit higher cycling performance of up to 300 cycles in lithium ion rechargeable batteries compared with micron-sized dense benzene-silica particles.

Thermo-elastic-plastic analysis for elastic component under high temperature fatigue crack growth rate

Science.gov (United States)

Ali, Mohammed Ali Nasser

transient thermal stresses superimposed on cyclic mechanical loading results in hollow cylinder under thermal shock in heating case and down shock cooling case. The combination of stress and strain intensity factor theoretical calculations with the experimental output recorded data shows a similar behaviour with increasing temperature, and there is a fair correlation between the profiles at the beginning and then divergence with increasing the crack length. The transient influence of high temperature in case two, giving a very high thermal shock stress as a heating or cooling effects, shifting up the combined stress, when applied a cyclic mechanical load in fraction of seconds, and the reputations of these shocks, causing a fast failure under high thermal shock stress superimposed with mechanical loading.Finally, the numerical modelling analyses three cases studied were solved due to the types of loading and types of specimen geometry by using finite element models constructed through the ANSYS Workbench version 13.0. The first case is a low cyclic fatigue case for a solid cylinder specimen simulated by applying a cyclic mechanical loading. The second is an isothermal fatigue case for solid cylinder specimen simulated by supplying different constant temperatures on the outer surface with cyclic mechanical loading, where the two cases are similar to the experimental tests and the third case, is a thermo-mechanical fatigue for a hollow cylinder model by simulating a thermal up-shock generated due to transient heating on the outer surface of the model or down shock cooling on the inner surface with the cyclic mechanical loading. The results show a good agreement with the experimental data in terms of alternative stress and life in the first case. In case two results show the strain intensity factor is increases with increasing temperature similar to the theoretical solution due to the influence of the modulus of elasticity and the difference in life estimation with the

Comparison of Dentinal Crack Formation With Reciproc, Mtwo and ProTaper Root Canal Preparation Systems

Directory of Open Access Journals (Sweden)

Nazari Moghaddam

2016-06-01

Full Text Available Background Instrumentation with rotary instruments could potentially cause dentinal cracks possibly leading to tooth fracture. Reciproc files require a single file to finalize the root canal preparation and the effect of this procedure has not been compared with other systems. Objectives The aim of this study was to compare the incidence of dentinal micro-cracks following root canal preparations with ProTaper, Mtwo and Reciproc files. Materials and Methods In an experimental in vitro trial, 80 maxillary and mandibular first molars were selected and their crowns and distal roots were cut. The roots were then examined to remove any previous cracks and defects. An impression polyether material was used to simulate teeth periodontal ligament (PDL. The teeth were divided to four experimental groups (n = 20 and prepared using Reciproc, Mtwo and ProTaper or remained unprepared as a control group. The specimens were then sectioned horizontally on 3, 5 and 9 mm from the apex and number of micro-cracks was determined by stereomicroscope. The incidence of dentinal cracks on different systems or sections were statistically analyzed by means of the chi-square test. Results Dentinal defects on 3-mm, 5-mm and 9-mm sections from the apex were noted in 10 (5.6%; 7 (3.9% and 9 (5.0% samples of all, respectively. Following canal preparation using Reciproc, ProTaper and Mtwo systems, the defects were observed in 7 (3.9%, 12 (6.7% and 7 (3.9% the sections, respectively. No significant differences were observed regarding the defect incidence on the studied instrumentation files or sections. Conclusions Regarding the study limitations, dentinal cracks were observed in all files and distances from the apex. Although there was more crack incidence in ProTaper files, no significant differences were noted regarding the studied systems and sections from the apex.

Cracking in Flexural Reinforced Concrete Members

DEFF Research Database (Denmark)

Rasmussen, Annette Beedholm; Fisker, Jakob; Hagsten, Lars German

2017-01-01

The system of cracks developing in reinforced concrete is in many aspects essential when modelling structures in both serviceability- and ultimate limit state. This paper discusses the behavior concerning crack development in flexural members observed from tests and associates it with two different...... existing models. From the investigations an approach is proposed on how to predict the crack pattern in flexural members involving two different crack systems; primary flexural cracks and local secondary cracks. The results of the approach is in overall good agreement with the observed tests and captures...... the pronounced size effect associated with flexural cracking in which the crack spacing and crack widths are approximately proportional to the depth of the member....

A simple approach to hollow maxillary complete denture fabrication: An innovative technique

Directory of Open Access Journals (Sweden)

Kathleen Manuela D'souza

2017-01-01

Full Text Available A severely atrophic maxillary arch exhibits reduced denture bearing area and increased inter-ridge distance, thus, affecting retention of the complete denture. Such clinical situations necessitate the fabrication of a hollow complete denture to reduce the weight of the prosthesis and increase retention. This article describes a simple technique to fabricate a hollow maxillary complete denture using salt and thermoplastic poly (methyl methacrylate sheet. The vacuum-formed thermoplastic matrix regulates the quantity of salt and determines its placement in the unpolymerized denture base material during the denture packing stage. The matrix lining the hollow cavity also aids to reinforce the hollow denture base.

Mesoscale cavities in hollow-core waveguides for quantum optics with atomic ensembles

Directory of Open Access Journals (Sweden)

Haapamaki C.M.

2016-08-01

Full Text Available Single-mode hollow-core waveguides loaded with atomic ensembles offer an excellent platform for light–matter interactions and nonlinear optics at low photon levels. We review and discuss possible approaches for incorporating mirrors, cavities, and Bragg gratings into these waveguides without obstructing their hollow cores. With these additional features controlling the light propagation in the hollow-core waveguides, one could potentially achieve optical nonlinearities controllable by single photons in systems with small footprints that can be integrated on a chip. We propose possible applications such as single-photon transistors and superradiant lasers that could be implemented in these enhanced hollow-core waveguides.

Synthesis and upconversion luminescence properties of YF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers derived from Y{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers

Energy Technology Data Exchange (ETDEWEB)

Li Dan; Dong Xiangting, E-mail: dongxiangting888@163.com; Yu Wensheng; Wang Jinxian; Liu Guixia [Changchun University of Science and Technology, Key Laboratory of Applied Chemistry and Nanotechnology at Universities of Jilin Province (China)

2013-06-15

YF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers were successfully fabricated via fluorination of the relevant Y{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers which were obtained by calcining the electrospun PVP/[Y(NO{sub 3}){sub 3} + Yb(NO{sub 3}){sub 3} + Er(NO{sub 3}){sub 3}] composite nanofibers. The morphology and properties of the products were investigated in detail by X-ray diffraction, scanning electron microscope, transmission electron microscope, and fluorescence spectrometer. YF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers were pure orthorhombic phase with space group Pnma and were hollow-centered structure with mean diameter of 174 {+-} 22 nm, and YF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers are composed of nanoparticles with size in the range of 30-60 nm. Upconversion emission spectrum analysis manifested that YF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers emitted strong green and weak red upconversion emissions centering at 523, 545, and 654 nm, respectively. The green and red emissions were, respectively, originated from {sup 2}H{sub 11/2}/{sup 4}S{sub 3/2} {yields} {sup 4}I{sub 15/2} and {sup 4}F{sub 9/2} {yields} {sup 4}I{sub l5/2} energy levels transitions of the Er{sup 3+} ions. Moreover, the emitting colors of YF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers were located in the green region in CIE chromaticity coordinates diagram. This preparation technique could be applied to prepare other rare earth fluoride upconversion luminescence hollow nanofibers.Graphical AbstractYF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers with orthorhombic structure were synthesized by fluorination of the electrospun Y{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers via a double-crucible method using NH{sub 4}HF{sub 2} as fluorinating agent. The mean diameter of YF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers was 174 {+-} 22 nm. The fluorination method we proposed here has been proved to be an important method, as it can not only

Mesoporous hollow spheres from soap bubbling.

Science.gov (United States)

Yu, Xianglin; Liang, Fuxin; Liu, Jiguang; Lu, Yunfeng; Yang, Zhenzhong

2012-02-01

The smaller and more stable bubbles can be generated from the large parent bubbles by rupture. In the presence of a bubble blowing agent, hollow spheres can be prepared by bubbling a silica sol. Herein, the trapped gas inside the bubble acts as a template. When the porogen, i.e., other surfactant, is introduced, a mesostructured shell forms by the co-assembly with the silica sol during sol-gel process. Morphological evolution emphasizes the prerequisite of an intermediate interior gas flow rate and high exterior gas flow rate for hollow spheres. The method is valid for many compositions from inorganic, polymer to their composites. Copyright © 2011 Elsevier Inc. All rights reserved.

Controllable Synthesis of Functional Hollow Carbon Nanostructures with Dopamine As Precursor for Supercapacitors.

Science.gov (United States)

Liu, Chao; Wang, Jing; Li, Jiansheng; Luo, Rui; Shen, Jinyou; Sun, Xiuyun; Han, Weiqing; Wang, Lianjun

2015-08-26

N-doped hollow carbon spheres (N-HCSs) are promising candidates as electrode material for supercapacitor application. In this work, we report a facile one-step synthesis of discrete and highly dispersible N-HCSs with dopamine (DA) as a carbon precursor and TEOS as a structure-assistant agent in a mixture containing water, ethanol, and ammonia. The architectures of resultant N-HCSs, including yolk-shell hollow carbon spheres (YS-HCSs), single-shell hollow carbon spheres (SS-HCSs), and double-shells hollow carbon spheres (DS-HCSs), can be efficiently controlled through the adjustment of the amount of ammonia. To explain the relation and formation mechanism of these hollow carbon structures, the samples during the different synthetic steps, including polymer/silica spheres, carbon/silica spheres and silica spheres by combustion in air, were characterized by TEM. Electrochemical measurements performed on YS-HCSs, SS-HCSs, and DS-HCSs showed high capacitance with 215, 280, and 381 F g(-1), respectively. Moreover, all the nitrogen-doped hollow carbon nanospheres showed a good cycling stability 97.0% capacitive retention after 3000 cycles. Notably, the highest capacitance of DS-HCSs up to 381 F g(-1) is higher than the capacitance reported so far for many carbon-based materials, which may be attributed to the high surface area, hollow structure, nitrogen functionalization, and double-shell architecture. These kinds of N-doped hollow-structured carbon spheres may show promising prospects as advanced energy storage materials and catalyst supports.

Innovative hydrogen storage in hollow glass-microspheres

Energy Technology Data Exchange (ETDEWEB)

Keding, M.; Schmid, G.; Tajmar, M. [Austrian Research Centers, Vienna (Austria)

2009-07-01

Hydrogen storage technologies are becoming increasingly important for a number of future applications. The Austrian Research Centers (ARC) are developing a unique hydrogen storage system that combines the advantages of both hollow glass microsphere and chemical compound hydrogen storage, but eliminates their respective drawbacks. Water is utilized as a functional liquid to carry the hollow glass microspheres that are loaded with up to 700 bar of hydrogen gas. Sodium borohydride (NaBH{sub 4}) is then injected together with the glass microspheres into a reaction chamber where the water reacts catalytically with the NaBH{sub 4} producing hydrogen and heat. The heat is then utilized to release the hydrogen from the hollow glass microspheres providing a double hydrogen generation process without any external energy or heat during storage or gas release. The paper described this hydrogen storage system with particular reference to microspheres, the coating process, the experimental facility and NaBH{sub 4} test results. It was concluded that hydrogen storage and production on demand is possible with microspheres and sodium borohydride solution. 9 refs., 16 figs.

Fabrication of Metallic Hollow Nanoparticles

Science.gov (United States)

Kim, Jae-Woo (Inventor); Choi, Sr., Sang H. (Inventor); Lillehei, Peter T. (Inventor); Chu, Sang-Hyon (Inventor); Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor)

2016-01-01

Metal and semiconductor nanoshells, particularly transition metal nanoshells, are fabricated using dendrimer molecules. Metallic colloids, metallic ions or semiconductors are attached to amine groups on the dendrimer surface in stabilized solution for the surface seeding method and the surface seedless method, respectively. Subsequently, the process is repeated with additional metallic ions or semiconductor, a stabilizer, and NaBH.sub.4 to increase the wall thickness of the metallic or semiconductor lining on the dendrimer surface. Metallic or semiconductor ions are automatically reduced on the metallic or semiconductor nanoparticles causing the formation of hollow metallic or semiconductor nanoparticles. The void size of the formed hollow nanoparticles depends on the dendrimer generation. The thickness of the metallic or semiconductor thin film around the dendrimer depends on the repetition times and the size of initial metallic or semiconductor seeds.

A General Synthesis Strategy for Hierarchical Porous Metal Oxide Hollow Spheres

Directory of Open Access Journals (Sweden)

Huadong Fu

2015-01-01

Full Text Available The hierarchical porous TiO2 hollow spheres were successfully prepared by using the hydrothermally synthesized colloidal carbon spheres as templates and tetrabutyl titanate as inorganic precursors. The diameter and wall thickness of hollow TiO2 spheres were determined by the hard templates and concentration of tetrabutyl titanate. The particle size, dispersity, homogeneity, and surface state of the carbon spheres can be easily controlled by adjusting the hydrothermal conditions and adding certain amount of the surfactants. The prepared hollow spheres possessed the perfect spherical shape, monodispersity, and hierarchically pore structures, and the further experiment verified that the present approach can be used to prepare other metal oxide hollow spheres, which could be used as catalysis, fuel cells, lithium-air battery, gas sensor, and so on.

Sharp tipped plastic hollow microneedle array by microinjection moulding

Science.gov (United States)

Yung, K. L.; Xu, Yan; Kang, Chunlei; Liu, H.; Tam, K. F.; Ko, S. M.; Kwan, F. Y.; Lee, Thomas M. H.

2012-01-01

A method of producing sharp tipped plastic hollow microneedle arrays using microinjection moulding is presented in this paper. Unlike traditional approaches, three mould inserts were used to create the sharp tips of the microneedles. Mould inserts with low surface roughness were fabricated using a picosecond laser machine. Sharp tipped plastic hollow microneedles 500 µm in height were fabricated using a microinjection moulding machine developed by the authors’ group. In addition, the strength of the microneedle was studied by simulation and penetration experiments. Results show that the microneedles can penetrate into skin, delivering liquid successfully without any breakage or severe deformation. Techniques presented in this paper can be used to fabricate sharp tipped plastic hollow microneedle arrays massively with low cost.

Sharp tipped plastic hollow microneedle array by microinjection moulding

International Nuclear Information System (INIS)

Yung, K L; Xu, Yan; Kang, Chunlei; Liu, H; Tam, K F; Ko, S M; Kwan, F Y; Lee, Thomas M H

2012-01-01

A method of producing sharp tipped plastic hollow microneedle arrays using microinjection moulding is presented in this paper. Unlike traditional approaches, three mould inserts were used to create the sharp tips of the microneedles. Mould inserts with low surface roughness were fabricated using a picosecond laser machine. Sharp tipped plastic hollow microneedles 500 µm in height were fabricated using a microinjection moulding machine developed by the authors’ group. In addition, the strength of the microneedle was studied by simulation and penetration experiments. Results show that the microneedles can penetrate into skin, delivering liquid successfully without any breakage or severe deformation. Techniques presented in this paper can be used to fabricate sharp tipped plastic hollow microneedle arrays massively with low cost. (paper)

Forged hollows (alloy 617) for PNP-hot gas collectors

International Nuclear Information System (INIS)

Hofmann, F.

1984-01-01

When the partners in the PNP-Project decided to manufacture components, such as gas collectors, from material of type alloy 617, the problem arose that required semi-fabricated products, especially forged hollows weighing several tons each, were not available. As VDM (Vereinigte Deutsche Metallwerke AG) had already experience in production of other semi-fabricated products of this alloy, attempts were made based on this knowledge, to develop manufacturing methods for forged hollows. The aim was to produce hollows as long as possible, and to keep the welding cost minimum. Welded seams are always critical during fabrication, as well as during later inspection under actual operating conditions. The three stage plan used to perform the above task illustrates the development aims is described

Monodisperse Hollow Tricolor Pigment Particles for Electronic Paper

Directory of Open Access Journals (Sweden)

Meng Xianwei

2009-01-01

Full Text Available Abstract A general approach has been designed to blue, green, and red pigments by metal ions doping hollow TiO 2. The reaction involves initial formation of PS at TiO2 core–shell nanoparticles via a mixed-solvent method, and then mixing with metal ions solution containing PEG, followed calcining in the atmosphere. The as-prepared hollow pigments exhibit uniform size, bright color, and tunable density, which are fit for electronic paper display.

Three-dimensional assembly structure of anatase TiO2 hollow microspheres with enhanced photocatalytic performance

Science.gov (United States)

Tang, Yihao; Zhan, Shuai; Wang, Li; Zhang, Bin; Ding, Minghui

The pure anatase TiO2 hollow microspheres are synthesized by a one-step template-free hydrothermal route. By defining temperature and time limits, we produce TiO2 hollow microspheres with a fluoride-mediated self-transformation. The surface morphology of TiO2 hollow microspheres was studied by SEM. The hollow microspheres have diameters of about 800 nm and are remarkably uniform. The UV-light photocatalytic activity and the stability/multifunction of TiO2 hollow microspheres structure were evaluated by photocatalytic degradation of methylene blue and photocatalytic hydrogen evolution. The excellent photocatalytic activity is attributed to large specific surface area, more active sites, unique hollow structures, and improved light scattering.

Hollow-core fibers for high power pulse delivery

DEFF Research Database (Denmark)

Michieletto, Mattia; Lyngsø, Jens K.; Jakobsen, Christian

2016-01-01

We investigate hollow-core fibers for fiber delivery of high power ultrashort laser pulses. We use numerical techniques to design an anti-resonant hollow-core fiber having one layer of non-touching tubes to determine which structures offer the best optical properties for the delivery of high power...... picosecond pulses. A novel fiber with 7 tubes and a core of 30 mu m was fabricated and it is here described and characterized, showing remarkable low loss, low bend loss, and good mode quality. Its optical properties are compared to both a 10 mu m and a 18 mu m core diameter photonic band gap hollow......-core fiber. The three fibers are characterized experimentally for the delivery of 22 picosecond pulses at 1032nm. We demonstrate flexible, diffraction limited beam delivery with output average powers in excess of 70W. (C) 2016 Optical Society of America...

Enhanced lithium storage performances of hierarchical hollow MoS₂ nanoparticles assembled from nanosheets.

Science.gov (United States)

Wang, Meng; Li, Guangda; Xu, Huayun; Qian, Yitai; Yang, Jian

2013-02-01

MoS(2), because of its layered structure and high theoretical capacity, has been regarded as a potential candidate for electrode materials in lithium secondary batteries. But it suffers from the poor cycling stability and low rate capability. Here, hierarchical hollow nanoparticles of MoS(2) nanosheets with an increased interlayer distance are synthesized by a simple solvothermal reaction at a low temperature. The formation of hierarchical hollow nanoparticles is based on the intermediate, K(2)NaMoO(3)F(3), as a self-sacrificed template. These hollow nanoparticles exhibit a reversible capacity of 902 mA h g(-1) at 100 mA g(-1) after 80 cycles, much higher than the solid counterpart. At a current density of 1000 mA g(-1), the reversible capacity of the hierarchical hollow nanoparticles could be still maintained at 780 mAh g(-1). The enhanced lithium storage performances of the hierarchical hollow nanoparticles in reversible capacities, cycling stability and rate performances can be attributed to their hierarchical surface, hollow structure feature and increased layer distance of S-Mo-S. Hierarchical hollow nanoparticles as an ensemble of these features, could be applied to other electrode materials for the superior electrochemical performance.

Investigation of Cracks Found in Helicopter Longerons

Science.gov (United States)

Newman, John A.; Baughman, James M.; Wallace, Terryl A.

2009-01-01

Four cracked longerons, containing a total of eight cracks, were provided for study. Cracked regions were cut from the longerons. Load was applied to open the cracks, enabling crack surface examination. Examination revealed that crack propagation was driven by fatigue loading in all eight cases. Fatigue crack initiation appears to have occurred on the top edge of the longerons near geometric changes that affect component bending stiffness. Additionally, metallurigical analysis has revealed a local depletion in alloying elements in the crack initiation regions that may be a contributing factor. Fatigue crack propagation appeared to be initially driven by opening-mode loading, but at a crack length of approximately 0.5 inches (12.7 mm), there is evidence of mixed-mode crack loading. For the longest cracks studied, shear-mode displacements destroyed crack-surface features of interest over significant portions of the crack surfaces.

Statistical distribution of time to crack initiation and initial crack size using service data

Science.gov (United States)

Heller, R. A.; Yang, J. N.

1977-01-01

Crack growth inspection data gathered during the service life of the C-130 Hercules airplane were used in conjunction with a crack propagation rule to estimate the distribution of crack initiation times and of initial crack sizes. A Bayesian statistical approach was used to calculate the fraction of undetected initiation times as a function of the inspection time and the reliability of the inspection procedure used.

Ultrasonic sizing of fatigue cracks

International Nuclear Information System (INIS)

Burns, D.J.

1983-12-01

Surface and buried fatigue cracks in steel plates have been sized using immersion probes as transmitters-receivers, angled to produce shear waves in the steel. Sizes have been estimated by identifying the ultrasonic waves diffracted from the crack tip and by measuring the time taken for a signal to travel to and from the crack tip. The effects of compression normal to a fatigue crack and of crack front curvature are discussed. Another diffraction technique, developed by UKAEA, Harwell, is reviewed

Novel one-step route for synthesizing CdS/polystyrene nanocomposite hollow spheres.

Science.gov (United States)

Wu, Dazhen; Ge, Xuewu; Zhang, Zhicheng; Wang, Mozhen; Zhang, Songlin

2004-06-22

CdS/polystyrene nanocomposite hollow spheres with diameters between 240 and 500 nm were synthesized under ambient conditions by a novel microemulsion method in which the polymerization of styrene and the formation of CdS nanoparticles were initiated by gamma-irradiation. The product was characterized by transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA), which show the walls of the hollow spheres are porous and composed of polystyrene containing homogeneously dispersed CdS nanoparticles. The quantum-confined effect of the CdS/polystyrene nanocomposite hollow spheres is confirmed by the ultraviolet-visible (UV-vis) and photoluminescent (PL) spectra. We propose that the walls of these nanocomposite hollow spheres originate from the simultaneous synthesis of polystyrene and CdS nanoparticles at the interface of microemulsion droplets. This novel method is expected to produce various inorganic/polymer nanocomposite hollow spheres with potential applications in the fields of materials science and biotechnology.

Eddy current crack detection capability assessment approach using crack specimens with differing electrical conductivity

Science.gov (United States)

Koshti, Ajay M.

2018-03-01

Like other NDE methods, eddy current surface crack detectability is determined using probability of detection (POD) demonstration. The POD demonstration involves eddy current testing of surface crack specimens with known crack sizes. Reliably detectable flaw size, denoted by, a90/95 is determined by statistical analysis of POD test data. The surface crack specimens shall be made from a similar material with electrical conductivity close to the part conductivity. A calibration standard with electro-discharged machined (EDM) notches is typically used in eddy current testing for surface crack detection. The calibration standard conductivity shall be within +/- 15% of the part conductivity. This condition is also applicable to the POD demonstration crack set. Here, a case is considered, where conductivity of the crack specimens available for POD testing differs by more than 15% from that of the part to be inspected. Therefore, a direct POD demonstration of reliably detectable flaw size is not applicable. Additional testing is necessary to use the demonstrated POD test data. An approach to estimate the reliably detectable flaw size in eddy current testing for part made from material A using POD crack specimens made from material B with different conductivity is provided. The approach uses additional test data obtained on EDM notch specimens made from materials A and B. EDM notch test data from the two materials is used to create a transfer function between the demonstrated a90/95 size on crack specimens made of material B and the estimated a90/95 size for part made of material A. Two methods are given. For method A, a90/95 crack size for material B is given and POD data is available. Objective of method A is to determine a90/95 crack size for material A using the same relative decision threshold that was used for material B. For method B, target crack size a90/95 for material A is known. Objective is to determine decision threshold for inspecting material A.

Hierarchical CuO hollow microspheres: Controlled synthesis for enhanced lithium storage performance

International Nuclear Information System (INIS)

Guan Xiangfeng; Li Liping; Li Guangshe; Fu Zhengwei; Zheng Jing; Yan Tingjiang

2011-01-01

Graphical abstract: Hierarchical CuO microspheres with hollow interiors were formed through self-wrapping of a single layer of radically oriented CuO nanorods, and these microspheres showed excellent cycle performance and enhanced lithium storage capacity. Display Omitted Research highlights: → Hierarchical CuO hollow microspheres were prepared by a hydrothermal method. → The CuO hollow microspheres were assembled from radically oriented nanorods. → The growth mechanism was proposed to proceed via self-assembly and Ostwald's ripening. → The microspheres showed good cycle performance and enhanced lithium storage capacity. → Hierarchical microstructures with hollow interiors promote electrochemical property. - Abstract: In this work, hierarchical CuO hollow microspheres were hydrothermally prepared without use of any surfactants or templates. By controlling the formation reaction conditions and monitoring the relevant reaction processes using time-dependent experiments, it is demonstrated that hierarchical CuO microspheres with hollow interiors were formed through self-wrapping of a single layer of radically oriented CuO nanorods, and that hierarchical spheres could be tuned to show different morphologies and microstructures. As a consequence, the formation mechanism was proposed to proceed via a combined process of self-assembly and Ostwald's ripening. Further, these hollow microspheres were initiated as the anode material in lithium ion batteries, which showed excellent cycle performance and enhanced lithium storage capacity, most likely because of the synergetic effect of small diffusion lengths in building blocks of nanorods and proper void space that buffers the volume expansion. The strategy reported in this work is reproducible, which may help to significantly improve the electrochemical performance of transition metal oxide-based anode materials via designing the hollow structures necessary for developing lithium ion batteries and the relevant

Crack propagation in teeth: a comparison of perimortem and postmortem behavior of dental materials and cracks.

Science.gov (United States)

Hughes, Cris E; White, Crystal A

2009-03-01

This study presents a new method for understanding postmortem heat-induced crack propagation patterns in teeth. The results demonstrate that patterns of postmortem heat-induced crack propagation differ from perimortem and antemortem trauma-induced crack propagation patterns. Dental material of the postmortem tooth undergoes dehydration leading to a shrinking and more brittle dentin material and a weaker dentin-enamel junction. Dentin intertubule tensile stresses are amplified by the presence of the pulp cavity, and initiates crack propagation from the internal dentin, through the dentin-enamel junction and lastly the enamel. In contrast, in vivo perimortem and antemortem trauma-induced crack propagation initiates cracking from the external surface of the enamel toward the dentin-enamel junction where the majority of the energy of the crack is dissipated, eliminating the crack's progress into the dentin. These unique patterns of crack propagation can be used to differentiate postmortem taphonomy-induced damage from antemortem and perimortem trauma in teeth.

Microfabricated hollow microneedle array using ICP etcher

Science.gov (United States)

Ji, Jing; Tay, Francis E. H.; Miao, Jianmin

2006-04-01

This paper presents a developed process for fabrication of hollow silicon microneedle arrays. The inner hollow hole and the fluidic reservoir are fabricated in deep reactive ion etching. The profile of outside needles is achieved by the developed fabrication process, which combined isotropic etching and anisotropic etching with inductively coupled plasma (ICP) etcher. Using the combination of SF6/O2 isotropic etching chemistry and Bosch process, the high aspect ratio 3D and high density microneedle arrays are fabricated. The generated needle external geometry can be controlled by etching variables in the isotropic and anisotropic cases.

Microfabricated hollow microneedle array using ICP etcher

International Nuclear Information System (INIS)

Ji Jing; Tay, Francis E H; Miao Jianmin

2006-01-01

This paper presents a developed process for fabrication of hollow silicon microneedle arrays. The inner hollow hole and the fluidic reservoir are fabricated in deep reactive ion etching. The profile of outside needles is achieved by the developed fabrication process, which combined isotropic etching and anisotropic etching with inductively coupled plasma (ICP) etcher. Using the combination of SF 6 /O 2 isotropic etching chemistry and Bosch process, the high aspect ratio 3D and high density microneedle arrays are fabricated. The generated needle external geometry can be controlled by etching variables in the isotropic and anisotropic cases

Microfabricated hollow microneedle array using ICP etcher

Energy Technology Data Exchange (ETDEWEB)

Ji Jing [Mechanical Engineering National University of Singapore, 119260, Singapore (Singapore); Tay, Francis E H [Mechanical Engineering National University of Singapore, 119260, Singapore (Singapore); Miao Jianmin [MicroMachines Center, School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore)

2006-04-01

This paper presents a developed process for fabrication of hollow silicon microneedle arrays. The inner hollow hole and the fluidic reservoir are fabricated in deep reactive ion etching. The profile of outside needles is achieved by the developed fabrication process, which combined isotropic etching and anisotropic etching with inductively coupled plasma (ICP) etcher. Using the combination of SF{sub 6}/O{sub 2} isotropic etching chemistry and Bosch process, the high aspect ratio 3D and high density microneedle arrays are fabricated. The generated needle external geometry can be controlled by etching variables in the isotropic and anisotropic cases.

Development of hollow electron beams for proton and ion collimation

CERN Document Server

Stancari, G; Kuznetsov, G; Shiltsev, V; Still, D A; Valishev, A; Vorobiev, L G; Assmann, R; Kabantsev, A

2012-01-01

Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams.

Development of hollow electron beams for proton and ion collimation

CERN Document Server

Stancari, G.; Kuznetsov, G.; Shiltsev, V.; Still, D.A.; Valishev, A.; Vorobiev, L.G.; Assmann, R.; Kabantsev, A.

2010-01-01

Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams

Predicting hollow viscus injury in blunt abdominal trauma with computed tomography.

Science.gov (United States)

Bhagvan, Savitha; Turai, Matthew; Holden, Andrew; Ng, Alexander; Civil, Ian

2013-01-01

Evaluation of blunt abdominal trauma is controversial. Computed tomography (CT) of the abdomen is commonly used but has limitations, especially in excluding hollow viscus injury in the presence of solid organ injury. To determine whether CT reports alone could be used to direct operative treatment in abdominal trauma, this study was undertaken. The trauma database at Auckland City Hospital was accessed for patients who had abdominal CT and subsequent laparotomy during a five-year period. The CT scans were reevaluated by a consultant radiologist who was blinded to operative findings. The CT findings were correlated with the operative findings. Between January 2002 and December 2007, 1,250 patients were evaluated for blunt abdominal injury with CT. A subset of 78 patients underwent laparotomy, and this formed the study group. The sensitivity and specificity of CT scan in predicting hollow viscus injury was 55.33 and 92.06 % respectively. The positive and negative predictive values were 61.53 and 89.23 % respectively. Presence of free fluid in CT scan was sensitive in diagnosing hollow viscus injury (90 %). Specific findings for hollow viscus injuries on CT scan were free intraperitoneal air (93 %), retroperitoneal air (100 %), oral contrast extravasation (100 %), bowel wall defect (98 %), patchy bowel enhancement (97 %), and mesenteric abnormality (94 %). CT alone cannot be used as a screening tool for hollow viscus injury. The decision to operate in hollow viscus injury has to be based on mechanism of injury and clinical findings together with radiological evidence.

Atomistics of crack propagation

International Nuclear Information System (INIS)

Sieradzki, K.; Dienes, G.J.; Paskin, A.; Massoumzadeh, B.

1988-01-01

The molecular dynamic technique is used to investigate static and dynamic aspects of crack extension. The material chosen for this study was the 2D triangular solid with atoms interacting via the Johnson potential. The 2D Johnson solid was chosen for this study since a sharp crack in this material remains stable against dislocation emission up to the critical Griffith load. This behavior allows for a meaningful comparison between the simulation results and continuum energy theorems for crack extension by appropriately defining an effective modulus which accounts for sample size effects and the non-linear elastic behavior of the Johnson solid. Simulation results are presented for the stress fields of moving cracks and these dynamic results are discussed in terms of the dynamic crack propagation theories, of Mott, Eshelby, and Freund

Guiding Properties of Silica/Air Hollow-Core Bragg Fibers

DEFF Research Database (Denmark)

Foroni, Matteo; Passaro, Davide; Poli, Federica

2008-01-01

The guiding properties of realistic silica/air hollow-core Bragg fibers have been investigated by calculating the dispersion curves, the confinement loss spectrum and the field distribution of the guided modes through a full-vector modal solver based on the finite element method. In particular, t...... the different possible applications, the feasibility of a DNA bio-sensor based on a hollow-core Bragg fiber has been demonstrated....

Crack-tip constraint analyses and constraint-dependent LBB curves for circumferential through-wall cracked pipes

Energy Technology Data Exchange (ETDEWEB)

Chen, Y.L.; Wang, G.Z., E-mail: gzwang@ecust.edu.cn; Xuan, F.Z.; Tu, S.T.

2015-04-15

Highlights: • Solution of constraint parameter τ* for through-wall cracked pipes has been obtained. • Constraint increases with increasing crack length and radius–thickness ratio of pipes. • Constraint-dependent LBB curve for through-wall cracked pipes has been constructed. • For increasing accuracy of LBB assessments, constraint effect should be considered. - Abstract: The leak-before-break (LBB) concept has been widely applied in the structural integrity assessments of pressured pipes in nuclear power plants. However, the crack-tip constraint effects in LBB analyses and designs cannot be incorporated. In this paper, by using three-dimensional finite element calculations, the modified load-independent T-stress constraint parameter τ* for circumferential through-wall cracked pipes with different geometries and crack sizes has been analyzed under different loading conditions, and the solutions of the crack-tip constraint parameter τ* have been obtained. Based on the τ* solutions and constraint-dependent J–R curves of a steel, the constraint-dependent LBB (leak-before-break) curves have been constructed. The results show that the constraint τ* increases with increasing crack length θ, mean radius R{sub m} and radius–thickness ratio R{sub m}/t of the pipes. In LBB analyses, the critical crack length calculated by the J–R curve of the standard high constraint specimen for pipes with shorter cracks is over-conservative, and the degree of conservatism increases with decreasing crack length θ, R{sub m} and R{sub m}/t. Therefore, the constraint-dependent LBB curves should be constructed to modify the over-conservatism and increase accuracy of LBB assessments.

Synthesis of ZnS hollow nanoneedles via the nanoscale Kirkendall effect

International Nuclear Information System (INIS)

Sun Hongyu; Chen Yan; Wang Xiaoliang; Xie Yanwu; Li Wei; Zhang Xiangyi

2011-01-01

The facile synthesis of one-dimensional II–VI semiconductor hollow nanostructures with sharp tips is of particular interest for their applications in novel nanodevices. In this study, by employing ZnO nanoneedles with lower symmetry structures as self-sacrificed templates, ZnS hollow nanoneedles with homogeneous thickness have been synthesized by a low temperature hydrothermal route through in situ chemical conversion manner and the nanoscale Kirkendall effect. The hollow needlelike structures obtained in the present study can be used as starting materials to create fantastic nanoarchitectures and may have important applications in optoelectronic nanodevices.

Effects of rust in the crack face on crack detection based on Sonic-IR method

International Nuclear Information System (INIS)

Harai, Y.; Izumi, Y.; Tanabe, H.; Takamatsu, T.; Sakagami, T.

2015-01-01

Sonic-IR, which is based on the thermographic detection of the temperature rise due to frictional heating at the defect faces under ultrasonic excitation, has an advantage in the detection of closed and small defects. However, this method has a lot of nuclear factors relating to heat generation. In this study, effects of rust in the crack faces on the crack detection based on the sonic-IR method is experimentally investigated by using crack specimens. The heat generation by ultrasonic excitation was observed regularly during rust accelerated test using original device. The distribution of temperature change around the crack was changed with the progress of rust. This change in heat generation, it believed to be due to change in the contact state of the crack surface due to rust. As a result, it was found that heat generation by ultrasonic excitation is affected by rust in the crack faces. And it was also found that crack detection can be conducted by sonic-IR even if rust was generated in the crack faces. (author)

Hollow waveguide cavity ringdown spectroscopy

Science.gov (United States)

Dreyer, Chris (Inventor); Mungas, Greg S. (Inventor)

2012-01-01

Laser light is confined in a hollow waveguide between two highly reflective mirrors. This waveguide cavity is used to conduct Cavity Ringdown Absorption Spectroscopy of loss mechanisms in the cavity including absorption or scattering by gases, liquid, solids, and/or optical elements.

Microstructured hollow fibers for ultrafiltration

NARCIS (Netherlands)

Culfaz, Pmar Zeynep; Culfaz, P.Z.; Rolevink, Hendrikus H.M.; van Rijn, C.J.M.; Lammertink, Rob G.H.; Wessling, Matthias

2010-01-01

Hollow fiber ultrafiltration membranes with a corrugated outer microstructure were prepared from a PES/PVP blend. The effect of spinning parameters such as air gap, take-up speed, polymer dope viscosity and coagulation value on the microstructure and membrane characteristics was investigated. Fibers

High temperature cracking of steels: effect of geometry on creep crack growth laws

International Nuclear Information System (INIS)

Kabiri, M.R.

2003-12-01

This study was performed at Centre des Materiaux de l'Ecole des Mines de Paris. It deals with identification and transferability of high temperature creep cracking laws of steels. A global approach, based on C * and J non-linear fracture mechanics parameters has been used to characterize creep crack initiation and propagation. The studied materials are: the ferritic steels 1Cr-1Mo-1/4V (hot and cold parts working at 540 and 250 C) used in the thermal power stations and the austenitic stainless steel 316 L(N) used in the nuclear power stations. During this thesis a data base was setting up, it regroups several tests of fatigue, creep, creep-fatigue, and relaxation. Its particularity is to contain several creep tests (27 tests), achieved at various temperatures (550 to 650 C) and using three different geometries. The relevance of the C * parameter to describe the creep crack propagation was analysed by a means of systematic study of elasto-viscoplastic stress singularities under several conditions (different stress triaxiality). It has been shown that, besides the C * parameter, a second non singular term, denoted here as Q * , is necessary to describe the local variables in the vicinity of the crack tip. Values of this constraint parameter are always negative. Consequently, application of typical creep crack growth laws linking the creep crack growth rate to the C * parameter (da/dt - C * ), will be conservative for industrial applications. Furthermore, we showed that for ferritic steels, crack incubation period is important, therefore a correlation of Ti - C * type has been kept to predict crack initiation time Ti. For the austenitic stainless steel, the relevant stage is the one of the crack propagation, so that a master curve (da/dt - C * ), using a new data analysis method, was established. Finally, the propagation of cracks has been simulated numerically using the node release technique, allowing to validate analytical expressions utilised for the experimental

Crack resistance of austenitic pipes with circumferential through-wall cracks

International Nuclear Information System (INIS)

Foerster, K.; Grueter, L.; Setz, W.; Bhandari, S.; Debaene, J.P.; Faidy, C.; Schwalbe, K.H.

1993-01-01

For monotonously increasing load the correct evaluation of the crack resistance properties of a structure is essential for safety analyses. Considerable attention has been given to the through-wall case, since this is generally believed to be the controlling case with regard to complete pipe failure. The maximum load conditions for circumferential crack growth in pipes under displacement-controlled loadings has been determined. The need for crack resistance curves, measured on circumferentially through-wall cracked straight pipes of austenitic stainless steel 316L under bending, is emphasized by the limitation in the data range on small specimens and by the differences in the procedures. To answer open questions and to improve calculational methods a joint fracture mechanics program is being performed by Electricite de France, Novatome and Siemens-Interatom. The working program contains experimental and theoretical investigations on the applicability of small-specimen data to real structures. 10 refs., 10 figs., 4 tabs

Large-scale preparation of hollow graphitic carbon nanospheres

International Nuclear Information System (INIS)

Feng, Jun; Li, Fu; Bai, Yu-Jun; Han, Fu-Dong; Qi, Yong-Xin; Lun, Ning; Lu, Xi-Feng

2013-01-01

Hollow graphitic carbon nanospheres (HGCNSs) were synthesized on large scale by a simple reaction between glucose and Mg at 550 °C in an autoclave. Characterization by X-ray diffraction, Raman spectroscopy and transmission electron microscopy demonstrates the formation of HGCNSs with an average diameter of 10 nm or so and a wall thickness of a few graphenes. The HGCNSs exhibit a reversible capacity of 391 mAh g −1 after 60 cycles when used as anode materials for Li-ion batteries. -- Graphical abstract: Hollow graphitic carbon nanospheres could be prepared on large scale by the simple reaction between glucose and Mg at 550 °C, which exhibit superior electrochemical performance to graphite. Highlights: ► Hollow graphitic carbon nanospheres (HGCNSs) were prepared on large scale at 550 °C ► The preparation is simple, effective and eco-friendly. ► The in situ yielded MgO nanocrystals promote the graphitization. ► The HGCNSs exhibit superior electrochemical performance to graphite.

Laser-driven ion acceleration with hollow laser beams

International Nuclear Information System (INIS)

Brabetz, C.; Kester, O.; Busold, S.; Bagnoud, V.; Cowan, T.; Deppert, O.; Jahn, D.; Roth, M.; Schumacher, D.

2015-01-01

The laser-driven acceleration of protons from thin foils irradiated by hollow high-intensity laser beams in the regime of target normal sheath acceleration (TNSA) is reported for the first time. The use of hollow beams aims at reducing the initial emission solid angle of the TNSA source, due to a flattening of the electron sheath at the target rear side. The experiments were conducted at the PHELIX laser facility at the GSI Helmholtzzentrum für Schwerionenforschung GmbH with laser intensities in the range from 10 18  W cm −2 to 10 20  W cm −2 . We observed an average reduction of the half opening angle by (3.07±0.42)° or (13.2±2.0)% when the targets have a thickness between 12 μm and 14 μm. In addition, the highest proton energies were achieved with the hollow laser beam in comparison to the typical Gaussian focal spot

Laser-driven ion acceleration with hollow laser beams

Energy Technology Data Exchange (ETDEWEB)

Brabetz, C., E-mail: c.brabetz@gsi.de; Kester, O. [Goethe-Universität Frankfurt am Main, 60323 Frankfurt (Germany); GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Busold, S.; Bagnoud, V. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Helmholtz-Institut Jena, 07743 Jena (Germany); Cowan, T. [Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden (Germany); Technische Universität Dresden, 01069 Dresden (Germany); Deppert, O.; Jahn, D.; Roth, M. [Technische Universität Darmstadt, 64277 Darmstadt (Germany); Schumacher, D. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany)

2015-01-15

The laser-driven acceleration of protons from thin foils irradiated by hollow high-intensity laser beams in the regime of target normal sheath acceleration (TNSA) is reported for the first time. The use of hollow beams aims at reducing the initial emission solid angle of the TNSA source, due to a flattening of the electron sheath at the target rear side. The experiments were conducted at the PHELIX laser facility at the GSI Helmholtzzentrum für Schwerionenforschung GmbH with laser intensities in the range from 10{sup 18} W cm{sup −2} to 10{sup 20} W cm{sup −2}. We observed an average reduction of the half opening angle by (3.07±0.42)° or (13.2±2.0)% when the targets have a thickness between 12 μm and 14 μm. In addition, the highest proton energies were achieved with the hollow laser beam in comparison to the typical Gaussian focal spot.

Recent progress on the fabrication of hollow microspheres

International Nuclear Information System (INIS)

Wang Aijuan; Lu Yupeng; Sun Ruixue

2007-01-01

Hollow microspheres represent a special class of materials, on which intense interest has been paid in the fields of material science, medicine, chemistry and chromatography. Several methods, including templating method, emulsion processing, high temperature smelting and layer-by-layer self-assembly technique, have been used to produce this kind of materials. However, most of the current needs for hollow microspheres are limited because of the disadvantages of these fabricating methods, such as time-consuming and relatively complex fabricating process. Spray drying method, as a simple and feasible technology, has also been used to fabricate this kind of materials. This method can improve the efficiency and save the time to some extent, and thus gains more and more interest recently. The factors of influencing the product morphology, including inlet air temperature, atomized pressure, feed rate, initial slurry concentration, primary powders size and additives, are reviewed in this paper. In addition, several kinds of typical hollow microspheres fabricated by this method are also listed particularly

Hollow Au@Pd and Au@Pt core-shell nanoparticles as electrocatalysts for ethanol oxidation reactions

KAUST Repository

Song, Hyon Min

2012-09-27

Hybrid alloys among gold, palladium and platinum become a new category of catalysts primarily due to their enhanced catalytic effects. Enhancement means not only their effectiveness, but also their uniqueness as catalysts for the reactions that individual metals may not catalyze. Here, preparation of hollow Au@Pd and Au@Pt core-shell nanoparticles (NPs) and their use as electrocatalysts are reported. Galvanic displacement with Ag NPs is used to obtain hollow NPs, and higher reduction potential of Au compared to Ag, Pd, and Pt helps to produce hollow Au cores first, followed by Pd or Pt shell growth. Continuous and highly crystalline shell growth was observed in Au@Pd core-shell NPs, but the sporadic and porous-like structure was observed in Au@Pt core-shell NPs. Along with hollow core-shell NPs, hollow porous Pt and hollow Au NPs are also prepared from Ag seed NPs. Twin boundaries which are typically observed in large size (>20 nm) Au NPs were not observed in hollow Au NPs. This absence is believed to be due to the role of the hollows, which significantly reduce the strain energy of edges where the two lattice planes meet. In ethanol oxidation reactions in alkaline medium, hollow Au@Pd core-shell NPs show highest current density in forward scan. Hollow Au@Pt core-shell NPs maintain better catalytic activities than metallic Pt, which is thought to be due to the better crystallinity of Pt shells as well as the alloy effect of Au cores. © 2012 The Royal Society of Chemistry.

Thin-walled reinforcement lattice structure for hollow CMC buckets

Science.gov (United States)

de Diego, Peter

2017-06-27

A hollow ceramic matrix composite (CMC) turbine bucket with an internal reinforcement lattice structure has improved vibration properties and stiffness. The lattice structure is formed of thin-walled plies made of CMC. The wall structures are arranged and located according to high stress areas within the hollow bucket. After the melt infiltration process, the mandrels melt away, leaving the wall structure to become the internal lattice reinforcement structure of the bucket.

Prediction of Crack Growth Aqueous Environments.

Science.gov (United States)

1983-06-01

ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT. TASK AREA & WORK UNIT NUMBERS SRI International 333 Ravenswood Avenue Menlo Park, CA 94025 II...34no crack" has at least a vestigial rupture, associated with cyclic loading of the oxide film at the crack tip. The curve labeled "crack" was obtained...be an effect of crack opening. For the data set labeled "crack", the vestigial crack, although short, is very tight and the impedance is large. Under

Morphology conserving aminopropyl functionalization of hollow silica nanospheres in toluene

Science.gov (United States)

Dobó, Dorina G.; Berkesi, Dániel; Kukovecz, Ákos

2017-07-01

Inorganic nanostructures containing cavities of monodisperse diameter distribution find applications in e.g. catalysis, adsorption and drug delivery. One of their possible synthesis routes is the template assisted core-shell synthesis. We synthesized hollow silica spheres around polystyrene cores by the sol-gel method. The polystyrene template was removed by heat treatment leaving behind a hollow spherical shell structure. The surface of the spheres was then modified by adding aminopropyl groups. Here we present the first experimental evidence that toluene is a suitable alternative functionalization medium for the resulting thin shells, and report the comprehensive characterization of the amino-functionalized hollow silica spheres based on scanning electron microscopy, transmission electron microscopy, N2 adsorption, FT-IR spectroscopy, Raman spectroscopy and electrokinetic potential measurement. Both the presence of the amino groups and the preservation of the hollow spherical morphology were unambiguously proven. The introduction of the amine functionality adds amphoteric character to the shell as shown by the zeta potential vs. pH function. Unlike pristine silica particles, amino-functionalized nanosphere aqueous sols can be stable at both acidic and basic conditions.

Process for fabricating PBI hollow fiber asymmetric membranes for gas separation and liquid separation

Science.gov (United States)

Jayaweera, Indira; Krishnan, Gopala N.; Sanjurjo, Angel; Jayaweera, Palitha; Bhamidi, Srinivas

2016-04-26

The invention provides methods for preparing an asymmetric hollow fiber, the asymmetric hollow fibers prepared by such methods, and uses of the asymmetric hollow fibers. One method involves passing a polymeric solution through an outer annular orifice of a tube-in-orifice spinneret, passing a bore fluid though an inner tube of the spinneret, dropping the polymeric solution and bore fluid through an atmosphere over a dropping distance, and quenching the polymeric solution and bore fluid in a bath to form an asymmetric hollow fiber.

Fatigue Crack Growth Rate and Stress-Intensity Factor Corrections for Out-of-Plane Crack Growth

Science.gov (United States)

Forth, Scott C.; Herman, Dave J.; James, Mark A.

2003-01-01

Fatigue crack growth rate testing is performed by automated data collection systems that assume straight crack growth in the plane of symmetry and use standard polynomial solutions to compute crack length and stress-intensity factors from compliance or potential drop measurements. Visual measurements used to correct the collected data typically include only the horizontal crack length, which for cracks that propagate out-of-plane, under-estimates the crack growth rates and over-estimates the stress-intensity factors. The authors have devised an approach for correcting both the crack growth rates and stress-intensity factors based on two-dimensional mixed mode-I/II finite element analysis (FEA). The approach is used to correct out-of-plane data for 7050-T7451 and 2025-T6 aluminum alloys. Results indicate the correction process works well for high DeltaK levels but fails to capture the mixed-mode effects at DeltaK levels approaching threshold (da/dN approximately 10(exp -10) meter/cycle).

Study on Manufacturing Process of Hollow Main Shaft by Open Die Forging

International Nuclear Information System (INIS)

Kwon, Yong Chul; Kang, Jong Hun; Kim, Sang Sik

2016-01-01

The main shaft is one of the key components connecting the rotor hub and gear box of a wind power generator. Typically, main shafts are manufactured by open die forging method. However, the main shaft for large MW class wind generators is designed to be hollow in order to reduce the weight. Additionally, the main shafts are manufactured by a casting process. This study aims to develop a manufacturing process for hollow main shafts by the open die forging method. The design of a forging process for a solid main shaft and hollow shaft was prepared by an open die forging process design scheme. Finite element analyses were performed to obtain the flow stress by a hot compression test at different temperature and strain rates. The control parameters of each forging process, such as temperature and effective strain, were obtained and compared to predict the suitability of the hollow main shaft forging process. Finally, high productivity reflecting material utilization ratio, internal quality, shape, and dimension was verified by the prototypes manufactured by the proposed forging process for hollow main shafts

Study on Manufacturing Process of Hollow Main Shaft by Open Die Forging

Energy Technology Data Exchange (ETDEWEB)

Kwon, Yong Chul [Gyeongnam Technopark, Changwon (Korea, Republic of); Kang, Jong Hun [Jungwon Univ., Goisan (Korea, Republic of); Kim, Sang Sik [Gyeongsang Natiional Univ., Jinju (Korea, Republic of)

2016-02-15

The main shaft is one of the key components connecting the rotor hub and gear box of a wind power generator. Typically, main shafts are manufactured by open die forging method. However, the main shaft for large MW class wind generators is designed to be hollow in order to reduce the weight. Additionally, the main shafts are manufactured by a casting process. This study aims to develop a manufacturing process for hollow main shafts by the open die forging method. The design of a forging process for a solid main shaft and hollow shaft was prepared by an open die forging process design scheme. Finite element analyses were performed to obtain the flow stress by a hot compression test at different temperature and strain rates. The control parameters of each forging process, such as temperature and effective strain, were obtained and compared to predict the suitability of the hollow main shaft forging process. Finally, high productivity reflecting material utilization ratio, internal quality, shape, and dimension was verified by the prototypes manufactured by the proposed forging process for hollow main shafts.

Role of hydrogen in stress corrosion cracking

International Nuclear Information System (INIS)

Mehta, M.L.

1981-01-01

Electrochemical basis for differentiation between hydrogen embrittlement and active path corrosion or anodic dissolution crack growth mechanisms is examined. The consequences of recently demonstrated acidification in crack tip region irrespective of electrochemical conditions at the bulk surface of the sample are that the hydrogen can evolve within the crack and may be involved in the cracking process. There are basically three aspects of hydrogen involvement in stress corrosion cracking. In dissolution models crack propagation is assumed to be caused by anodic dissolution on the crack tip sustained by cathodic reduction of hydrogen from electrolyte within the crack. In hydrogen induced structural transformation models it is postulated that hydrogen is absorbed locally at the crack tip producing structural changes which facilitate crack propagation. In hydrogen embrittlement models hydrogen is absorbed by stressed metal from proton reduction from the electrolyte within the crack and there is interaction between lattice and hydrogen resulting in embrittlement of material at crack tip facilitating crack propagation. In the present paper, the role of hydrogen in stress corrosion crack growth in high strength steels, austenitic stainless steels, titanium alloys and high strength aluminium alloys is discussed. (author)

SSRI Facilitated Crack Dancing

Directory of Open Access Journals (Sweden)

Ravi Doobay

2017-01-01

Full Text Available Choreoathetoid movement secondary to cocaine use is a well-documented phenomenon better known as “crack dancing.” It consists of uncontrolled writhing movements secondary to excess dopamine from cocaine use. We present a 32-year-old male who had been using cocaine for many years and was recently started on paroxetine, a selective serotonin reuptake inhibitor (SSRI for worsening depression four weeks before presentation. He had been doing cocaine every 2 weeks for the last three years and had never “crack danced” before this episode. The authors have conducted a thorough literature review and cited studies that suggest “crack dancing” is associated with excess dopamine. There has never been a documented case report of an SSRI being linked with “crack dancing.” The authors propose that the excess dopaminergic effect of the SSRI lowered the dopamine threshold for “crack dancing.” There is a communication with the Raphe Nucleus and the Substantia Nigra, which explains how the SSRI increases dopamine levels. This is the first documented case of an SSRI facilitating the “crack dance.”

Hydrothermal synthesis of lindgrenite with a hollow and prickly sphere-like architecture

International Nuclear Information System (INIS)

Xu Jiasheng; Xue Dongfeng

2007-01-01

Lindgrenite [Cu 3 (OH) 2 (MoO 4 ) 2 ] with a hollow and prickly sphere-like architecture has been synthesized via a simple and mild hydrothermal route in the absence of any external inorganic additives or organic structure-directing templates. The hierarchical lindgrenite particles are hollow and prickly spheres, which are comprised of numerous small crystal strips that are aligned perpendicularly to the spherical surface. Two factors are important for the formation of hollow and prickly architecture in the present process. One is the general phenomenon of Ostwald ripening in solution, which can be responsible for the hollow structure; the other is that lindgrenite crystals have a rhombic growth habit, which plays an important role in the formation of prickly surface. Furthermore, Cu 3 Mo 2 O 9 with the similar size and morphology can be easily obtained by a simple thermal treatment of the as-prepared lindgrenite in air atmosphere. - Graphical abstract: Lindgrenite [Cu 3 (OH) 2 (MoO 4 ) 2 ] with a hollow and prickly sphere-like architecture has been synthesized via a hydrothermal route. The hierarchical lindgrenite particles are hollow and prickly spheres, which are comprised of numerous crystal strips that are aligned perpendicularly to the spherical surface. Cu 3 Mo 2 O 9 with the similar size and morphology can be easily obtained by a thermal treatment of the as-prepared lindgrenite

Hierarchical Ag/AgCl-TiO{sub 2} hollow spheres with enhanced visible-light photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Wang, Xu Long; Yin, Hao Yong [College of Materials Environment Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Nie, Qiu Lin, E-mail: nieqiulin@hdu.edu.cn [College of Materials Environment Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Wu, Wei Wei [College of Materials Environment Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Zhang, Yang; LiYuan, Qiu [College of Science, Hangzhou Dianzi University, Hangzhou 310018 (China)

2017-01-01

The hierarchical Ag/AgCl-TiO{sub 2} hollow spheres were synthesized by depositing Ag/AgCl nanoparticles on TiO{sub 2} hollow spheres via a precipitation photoreduction method, and they were further characterized using TGA, SEM, TEM, XRD, XPS, UV–vis DRS and photoelectric chemical analysis. The analysis showed that the hierarchical Ag/AgCl-TiO{sub 2} hollow spheres exhibited the highest photocatalytic activity, which was approximately 13 times higher than that of TiO{sub 2} hollow spheres. The high photocatalytic activity of the composites is due to efficient electron-hole pairs separation at the photocatalyst interfaces, and localized surface plasmon resonance of Ag nanoparticles formed on AgCl particles in the degradation reaction. - Highlights: • TiO{sub 2} hollow spheres were prepared by a sacrificial template method. • The hollow spheres were modified with Ag/AgCl to form the heterojunctions. • The modification may produce synergistic effect of LSPR and hollow structure. • Visible light photocatalytic activity was enhanced on this hollow catalyst. • The mechanism of the improved photocatalytic performance was discussed.

High performance micro-engineered hollow fiber membranes by smart spinneret design

NARCIS (Netherlands)

de Jong, J.; Nijdam, W.; van Rijn, C.J.M.; Visser, Tymen; Bolhuis-Versteeg, Lydia A.M.; Kapantaidakis, G.; Koops, G.H.; Wessling, Matthias

2005-01-01

Can hollow fiber membranes be produced in other geometries than circular? If so, are membrane properties maintained and what could be the possible benefits of other geometries? This article gives answers and describes the fabrication of micro-structured hollow fiber membranes using micro-fabricated

Mechanics of quasi-static crack growth

Energy Technology Data Exchange (ETDEWEB)

Rice, J R

1978-10-01

Results on the mechanics of quasi-static crack growth are reviewed. These include recent studies on the geometry and stability of crack paths in elastic-brittle solids, and on the thermodynamics of Griffith cracking, including environmental effects. The relation of crack growth criteria to non-elastic rheological models is considered and paradoxes with energy balance approaches, based on singular crack models, are discussed for visco-elastic, diffuso-elastic, and elastic-plastic materials. Also, recent approaches to prediction of stable crack growth in ductile, elastic-plastic solids are discussed.

Toward power scaling in an acetylene mid-infrared hollow-core optical fiber gas laser: effects of pressure, fiber length, and pump power

Science.gov (United States)

Weerasinghe, H. W. Kushan; Dadashzadeh, Neda; Thirugnanasambandam, Manasadevi P.; Debord, Benoît.; Chafer, Matthieu; Gérôme, Frédéric; Benabid, Fetah; Corwin, Kristan L.; Washburn, Brian R.

2018-02-01

The effect of gas pressure, fiber length, and optical pump power on an acetylene mid-infrared hollow-core optical fiber gas laser (HOFGLAS) is experimentally determined in order to scale the laser to higher powers. The absorbed optical power and threshold power are measured for different pressures providing an optimum pressure for a given fiber length. We observe a linear dependence of both absorbed pump energy and lasing threshold for the acetylene HOFGLAS, while maintaining a good mode quality with an M-squared of 1.15. The threshold and mode behavior are encouraging for scaling to higher pressures and pump powers.

Nonlinear crack mechanics

International Nuclear Information System (INIS)

Khoroshun, L.P.

1995-01-01

The characteristic features of the deformation and failure of actual materials in the vicinity of a crack tip are due to their physical nonlinearity in the stress-concentration zone, which is a result of plasticity, microfailure, or a nonlinear dependence of the interatomic forces on the distance. Therefore, adequate models of the failure mechanics must be nonlinear, in principle, although linear failure mechanics is applicable if the zone of nonlinear deformation is small in comparison with the crack length. Models of crack mechanics are based on analytical solutions of the problem of the stress-strain state in the vicinity of the crack. On account of the complexity of the problem, nonlinear models are bason on approximate schematic solutions. In the Leonov-Panasyuk-Dugdale nonlinear model, one of the best known, the actual two-dimensional plastic zone (the nonlinearity zone) is replaced by a narrow one-dimensional zone, which is then modeled by extending the crack with a specified normal load equal to the yield point. The condition of finite stress is applied here, and hence the length of the plastic zone is determined. As a result of this approximation, the displacement in the plastic zone at the abscissa is nonzero

A method for manufacturing a hollow mems structure

DEFF Research Database (Denmark)

2017-01-01

The present invention relates to a method for manufacturing an at least partly hollow MEMS structure. In a first step one or more through-going openings is/are provided in core material. The one or more through-going openings is/are then covered by an etch-stop layer. After this step, a bottom...... further comprises the step of creating bottom and top conductors in the respective bottom and top layers. Finally, excess core material is removed in order to create the at least partly hollow MEMS structure which may include a MEMS inductor....

Control of Dispersion in Hollow Core Photonic Crystal Fibers

DEFF Research Database (Denmark)

Roberts, John

2007-01-01

The dispersion of hollow core photonic crystal fibers can be tailored by modifying a single ring of holes in the cladding. The dispersion can be lowered and flattened, or alternatively greatly increased, in a controlled manner.......The dispersion of hollow core photonic crystal fibers can be tailored by modifying a single ring of holes in the cladding. The dispersion can be lowered and flattened, or alternatively greatly increased, in a controlled manner....

Impacts of weld residual stresses and fatigue crack growth threshold on crack arrest under high-cycle thermal fluctuations

Energy Technology Data Exchange (ETDEWEB)

Taheri, Said, E-mail: Said.taheri@edf.fr [EDF-LAB, IMSIA, 7 Boulevard Gaspard Monge, 91120 Palaiseau Cedex (France); Julan, Emricka [EDF-LAB, AMA, 7 Boulevard Gaspard Monge, 91120 Palaiseau Cedex (France); Tran, Xuan-Van [EDF Energy R& D UK Centre/School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL (United Kingdom); Robert, Nicolas [EDF-DPN, UNIE, Strategic Center, Saint Denis (France)

2017-01-15

Highlights: • For crack growth analysis, weld residual stress field must be considered through its SIF in presence of a crack. • Presence of cracks of same depth proves their arrest, where equal depth is because mean stress acts only on crack opening. • Not considering amplitudes under a fatigue crack growth threshold (FCGT) does not compensate the lack of FGCT in Paris law. • Propagation rates are close for axisymmetric and circumferential semi-elliptical cracks. - Abstract: High cycle thermal crazing has been observed in some residual heat removal (RHR) systems made of 304 stainless steel in PWR nuclear plants. This paper deals with two types of analyses including logical argumentation and simulation. Crack arrest in networks is demonstrated due to the presence of two cracks of the same depth in the network. This identical depth may be proved assuming that mean stress acts only on crack opening and that cracks are fully open during the load cycle before arrest. Weld residual stresses (WRS) are obtained by an axisymmetric simulation of welding on a tube with a chamfer. Axisymmetric and 3D parametric studies of crack growth on: representative sequences for variable amplitude thermal loading, fatigue crack growth threshold (FCGT), permanent mean stress, cyclic counting methods and WRS, are performed with Code-Aster software using XFEM methodology. The following results are obtained on crack depth versus time: the effect of WRS on crack growth cannot be determined by the initial WRS field in absence of crack, but by the associated stress intensity factor. Moreover the relation between crack arrest depth and WRS is analyzed. In the absence of FCGT Paris’s law may give a significant over-estimation of crack depth even if amplitudes of loading smaller than FCGT have not been considered. Appropriate depth versus time may be obtained using different values of FCGT, but axisymmetric simulations do not really show a possibility of arrest for shallow cracks in

Impacts of weld residual stresses and fatigue crack growth threshold on crack arrest under high-cycle thermal fluctuations

International Nuclear Information System (INIS)

Taheri, Said; Julan, Emricka; Tran, Xuan-Van; Robert, Nicolas

2017-01-01

Highlights: • For crack growth analysis, weld residual stress field must be considered through its SIF in presence of a crack. • Presence of cracks of same depth proves their arrest, where equal depth is because mean stress acts only on crack opening. • Not considering amplitudes under a fatigue crack growth threshold (FCGT) does not compensate the lack of FGCT in Paris law. • Propagation rates are close for axisymmetric and circumferential semi-elliptical cracks. - Abstract: High cycle thermal crazing has been observed in some residual heat removal (RHR) systems made of 304 stainless steel in PWR nuclear plants. This paper deals with two types of analyses including logical argumentation and simulation. Crack arrest in networks is demonstrated due to the presence of two cracks of the same depth in the network. This identical depth may be proved assuming that mean stress acts only on crack opening and that cracks are fully open during the load cycle before arrest. Weld residual stresses (WRS) are obtained by an axisymmetric simulation of welding on a tube with a chamfer. Axisymmetric and 3D parametric studies of crack growth on: representative sequences for variable amplitude thermal loading, fatigue crack growth threshold (FCGT), permanent mean stress, cyclic counting methods and WRS, are performed with Code-Aster software using XFEM methodology. The following results are obtained on crack depth versus time: the effect of WRS on crack growth cannot be determined by the initial WRS field in absence of crack, but by the associated stress intensity factor. Moreover the relation between crack arrest depth and WRS is analyzed. In the absence of FCGT Paris’s law may give a significant over-estimation of crack depth even if amplitudes of loading smaller than FCGT have not been considered. Appropriate depth versus time may be obtained using different values of FCGT, but axisymmetric simulations do not really show a possibility of arrest for shallow cracks in

Synthesis and characterization of hollow magnetic nanospheres modified with Au nanoparticles for bio-encapsulation

Energy Technology Data Exchange (ETDEWEB)

Seisno, Satoshi, E-mail: seino@mit.eng.osaka-u.ac.jp; Suga, Kent; Nakagawa, Takashi; Yamamoto, Takao A.

2017-04-01

Hollow magnetic nanospheres modified with Au nanoparticles were successfully synthesized. Au/SiO{sub 2} nanospheres fabricated by a radiochemical process were used as templates for ferrite templating. After the ferrite plating process, Au/SiO{sub 2} templates were fully coated with magnetite nanoparticles. Dissolution of the SiO{sub 2} core lead to the formation of hollow magnetic nanospheres with Au nanoparticles inside. The hollow magnetic nanospheres consisted of Fe{sub 3}O{sub 4} grains, with an average diameter of 60 nm, connected to form the sphere wall, inside which Au grains with an average diameter of 7.2 nm were encapsulated. The Au nanoparticles immobilized on the SiO{sub 2} templates contributed to the adsorption of the Fe ion precursor and/or Fe{sub 3}O{sub 4} seeds. These hollow magnetic nanospheres are proposed as a new type of nanocarrier, as the Au grains could specifically immobilize biomolecules inside the hollow sphere. - Highlights: • A procedure to synthesize hollow magnetic nanospheres with Au inside was reported. • The Au nanoparticles inside the hollow showed high Au-S binding affinity. • The nanospheres are expected to be suitable as a new magnetic carrier for DDS.

Synthesis and characterization of hollow spherical copper phosphide (Cu 3P) nanopowders

Science.gov (United States)

Liu, Shuling; Qian, Yitai; Xu, Liqiang

2009-03-01

In this paper, hollow spherical Cu 3P nanopowders were synthesized by using copper sulfate pentahydrate (CuSO 4ṡ5H 2O) and yellow phosphorus in a mixed solvent of glycol, ethanol and water at 140-180 ∘C for 12 h. X-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), electron diffraction pattern (ED) and transmission electronic microscopy (TEM) studies show that the as-synthesized nanocrystal is pure hexagonal phase Cu 3P with a hollow spherical morphology. Based on the TEM observations, a possible aggregation growth mechanism was proposed for the formation of Cu 3P hollow structures. Meanwhile, the effects of some key factors such as solvents, reaction temperature and reaction time on the final formation of the Cu 3P hollow structure were also discussed.

Space Charge Mitigation by Hollow Bunches

CERN Multimedia

Oeftiger, AO

2014-01-01

To satisfy the requirements of the HL-LHC (High Luminosity Large Hadron Collider), the LHC injector chain will need to supply a higher brightness, i.e. deliver the same transverse beam emittances \\epsilon_{x,y} while providing a higher intensity N. However, a larger number of particles per bunch enhances space charge effects. One approach to mitigate the impact of space charge is to change the longitudinal phase space distribution: hollow bunches feature a depleted bunch centre and a densely populated periphery. Thus, the spatial line density maximum is depressed which ultimately decreases the tune spread imposed by space charge. Therefore, a higher intensity can be accepted while keeping the same overall space charge tune shift. 3 different methods to create hollow bunches in the PSBooster are simulated.

Dual layer hollow fiber sorbents for trace H2S removal from gas streams

KAUST Repository

Bhandari, Dhaval A.; Bessho, Naoki; Koros, William J.

2013-01-01

Hollow fiber sorbents are pseudo monolithic materials with potential use in various adsorption based applications. Dual layer hollow fiber sorbents have the potential to allow thermal regeneration without direct contact of the regeneration fluid with the sorbent particles. This paper considers the application of dual layer hollow fiber sorbents for a case involving trace amounts of H2S removal from a simulated gas stream and offers a comparison with single layer hollow fiber sorbents. The effect of spin dope composition and core layer zeolite loading on the gas flux, H2S transient sorption capacity and pore structure are also studied. This work can be used as a guide to develop and optimize dual layer hollow fiber sorbent properties beyond the specific example considered here. © 2013 Elsevier Ltd.

Dual layer hollow fiber sorbents for trace H2S removal from gas streams

KAUST Repository

Bhandari, Dhaval A.

2013-05-01

Hollow fiber sorbents are pseudo monolithic materials with potential use in various adsorption based applications. Dual layer hollow fiber sorbents have the potential to allow thermal regeneration without direct contact of the regeneration fluid with the sorbent particles. This paper considers the application of dual layer hollow fiber sorbents for a case involving trace amounts of H2S removal from a simulated gas stream and offers a comparison with single layer hollow fiber sorbents. The effect of spin dope composition and core layer zeolite loading on the gas flux, H2S transient sorption capacity and pore structure are also studied. This work can be used as a guide to develop and optimize dual layer hollow fiber sorbent properties beyond the specific example considered here. © 2013 Elsevier Ltd.

Novel Ultrafine Fibrous Poly(tetrafluoroethylene Hollow Fiber Membrane Fabricated by Electrospinning

Directory of Open Access Journals (Sweden)

Qinglin Huang

2018-04-01

Full Text Available Novel poly(tetrafluoroethylene (PTFE hollow fiber membranes were successfully fabricated by electrospinning, with ultrafine fibrous PTFE membranes as separation layers, while a porous glassfiber braided tube served as the supporting matrix. During this process, PTFE/poly(vinylalcohol (PVA ultrafine fibrous membranes were electrospun while covering the porous glassfiber braided tube; then, the nascent PTFE/PVA hollow fiber membrane was obtained. In the following sintering process, the spinning carrier PVA decomposed; meanwhile, the ultrafine fibrous PTFE membrane shrank inward so as to further integrate with the supporting matrix. Therefore, the ultrafine fibrous PTFE membranes had excellent interface bonding strength with the supporting matrix. Moreover, the obtained ultrafine fibrous PTFE hollow fiber membrane exhibited superior performances in terms of strong hydrophobicity (CA > 140°, high porosity (>70%, and sharp pore size distribution. The comprehensive properties indicated that the ultrafine fibrous PTFE hollow fiber membranes could have potentially useful applications in membrane contactors (MC, especially membrane distillation (MD in harsh water environments.

Interfacial Crack Arrest in Sandwich Panels with Embedded Crack Stoppers Subjected to Fatigue Loading

DEFF Research Database (Denmark)

Martakos, G.; Andreasen, J. H.; Berggreen, Christian

2017-01-01

A novel crack arresting device has been implemented in sandwich panels and tested using a special rig to apply out-of-plane loading on the sandwich panel face-sheets. Fatigue crack propagation was induced in the face-core interface of the sandwich panels which met the crack arrester. The effect o...

Synthesis and gas-sensing characteristics of α-Fe2O3 hollow balls

Directory of Open Access Journals (Sweden)

Chu Manh Hung

2016-03-01

Full Text Available The synthesis of porous metal-oxide semiconductors for gas-sensing application is attracting increased interest. In this study, α-Fe2O3 hollow balls were synthesized using an inexpensive, scalable, and template-free hydrothermal method. The gas-sensing characteristics of the semiconductors were systematically investigated. Material characterization by XRD, SEM, HRTEM, and EDS reveals that single-phase α-Fe2O3 hollow balls with an average diameter of 1.5 μm were obtained. The hollow balls were formed by self assembly of α-Fe2O3 nanoparticles with an average diameter of 100 nm. The hollow structure and nanopores between the nanoparticles resulted in the significantly high response of the α-Fe2O3 hollow balls to ethanol at working temperatures ranging from 250 °C to 450 °C. The sensor also showed good selectivity over other gases, such as CO and NH3 promising significant application.

The Effect of Canal Preparation with Four Different Rotary Systems on Formation of Dentinal Cracks: An In Vitro Evaluation.

Science.gov (United States)

Khoshbin, Elham; Donyavi, Zakiyeh; Abbasi Atibeh, Erfan; Roshanaei, Ghodratollah; Amani, Faranak

2018-01-01

Endodontic rotary systems may result in dentinal cracks. They may propagate to vertical root fracture that compromises the outcome of endodontic treatment. This study aimed to compare Neolix and Reciproc (single-file systems), Mtwo and ProTaper (conventional rotary systems) in terms of dentinal crack formation in root canal walls. This in vitro study was conducted on 110 extracted human single-rooted teeth. The teeth were randomly divided into four experimental groups ( n =25) for root canal preparation with Neolix, Reciproc, Mtwo and ProTaper systems and two control groups ( n =5). The first control group underwent root canal instrumentation with hand files while the second control group received no preparation and was only irrigated. After instrumentation, root canals were horizontally sectioned at 3, 6 and 9 mm from the apex and inspected under a stereomicroscope under 12× magnification for detection of cracks. The data were analyzed using Chi-square, GEE test and Bonferroni tests ( P ProTaper, Reciproc, Mtwo and Neolix caused cracks in 92%, 80%, 68% and 48% of samples. ProTaper caused significantly more cracks than Neolix and Mtwo ( P 0.05). All rotary systems cause dentinal cracks and it is significantly different in apical, middle and coronal third of the root. Neolix appears to be a suitable alternative to other rotary systems since use of this single-file system saves time and cost and minimizes trauma to dentinal walls.

Comparison of finite element J-integral evaluations for the blunt crack model and the sharp crack model

International Nuclear Information System (INIS)

Pan, Y.C.; Kennedy, J.M.

1983-01-01

In assessing the safety of a liquid metal fast breeder reactor (LMFBR), a major concern is that of hot sodium coming into contact with either unprotected concrete or steel-lined concrete equipment cells and containment structures. An aspect of this is the potential of concrete cracking which would significantly influence the safety assessment. Concrete cracking in finite element analysis can be modeled as a blunt crack in which the crack is assumed to be uniformly distributed throughout the area of the element. A blunt crack model based on the energy release rate and the effective strength concepts which was insensitive to the element size was presented by Bazant and Cedolin. Some difficulties were encountered in incorporating their approach into a general purpose finite element code. An approach based on the J-integral to circumvent some of the difficulties was proposed by Pan, Marchertas, and Kennedy. Alternatively, cracking can also be modeled as a sharp crack where the crack surface is treated as the boundary of the finite element mesh. The sharp crack model is adopted by most researchers and its J-integral has been well established. It is desirable to establish the correlation between the J-integrals, or the energy release rates, for the blunt crack model and the sharp crack model so that data obtained from one model can be used on the other

Crack characterization for in-service inspection planning

International Nuclear Information System (INIS)

Waale, J.; Ekstroem, P.

1995-12-01

During in-service inspection by non destructive testing the reliability is highly dependent on how the equipment is adjusted to the specific object and to the anticipated crack feature.The crack feature and morphology vary widely between different cracking mechanisms and between material types in which the cracks appear. The major objective of this study was to characterize a number of morphology parameters for common crack mechanism and structure material combinations. Critical morphology parameters are crack orientation, shape, width, surface roughness and branching. The crack parameters were evaluated from failure analyses reported from the nuclear and non-nuclear industry. In addition, a literature review was carried out on crack parameter reports and on failure analysis reports, which were further evaluated. The evaluated crack parameters were plotted and statistically processed in data groups with respect to crack mechanism and material type. The fatigue crack mechanism were classified as mechanical, thermal or corrosion fatigue and stress corrosion crack mechanism as intergranular, transgranular or inter dendritic stress corrosion cracking. Furthermore, some common weld defects were characterized for comparison. The materials were divided into three broad groups, ferritic low alloy steels, stainless steels and nickel base alloys. The results indicate significant differences between crack parameters when comparing data from different crack mechanism/material type combinations. Typical parameter values and scatter were derived for several combinations where the data was sufficient for statistical significance. 10 refs, 105 figs, 14 tabs

Crack characterization for in-service inspection planning

Energy Technology Data Exchange (ETDEWEB)

Waale, J [SAQ Inspection Ltd, Stockholm (Sweden); Ekstroem, P [ABB Atom AB, Vaesteraas (Sweden)

1995-12-01

During in-service inspection by non destructive testing the reliability is highly dependent on how the equipment is adjusted to the specific object and to the anticipated crack feature.The crack feature and morphology vary widely between different cracking mechanisms and between material types in which the cracks appear. The major objective of this study was to characterize a number of morphology parameters for common crack mechanism and structure material combinations. Critical morphology parameters are crack orientation, shape, width, surface roughness and branching. The crack parameters were evaluated from failure analyses reported from the nuclear and non-nuclear industry. In addition, a literature review was carried out on crack parameter reports and on failure analysis reports, which were further evaluated. The evaluated crack parameters were plotted and statistically processed in data groups with respect to crack mechanism and material type. The fatigue crack mechanism were classified as mechanical, thermal or corrosion fatigue and stress corrosion crack mechanism as intergranular, transgranular or inter dendritic stress corrosion cracking. Furthermore, some common weld defects were characterized for comparison. The materials were divided into three broad groups, ferritic low alloy steels, stainless steels and nickel base alloys. The results indicate significant differences between crack parameters when comparing data from different crack mechanism/material type combinations. Typical parameter values and scatter were derived for several combinations where the data was sufficient for statistical significance. 10 refs, 105 figs, 14 tabs.

Tensile cracks in creeping solids

International Nuclear Information System (INIS)

Riedel, H.; Rice, J.R.

1979-02-01

The loading parameter determining the stress and strain fields near a crack tip, and thereby the growth of the crack, under creep conditions is discussed. Relevant loading parameters considered are the stress intensity factor K/sub I/, the path-independent integral C*, and the net section stress sigma/sub net/. The material behavior is modelled as elastic-nonlinear viscous where the nonlinear term describes power law creep. At the time t = 0 load is applied to the cracked specimen, and in the first instant the stress distribution is elastic. Subsequently, creep deformation relaxes the initial stress concentration at the crack tip, and creep strains develop rapidly near the crack tip. These processes may be analytically described by self-similar solutions for short times t. Small scale yielding may be defined. In creep problems, this means that elastic strains dominate almost everywhere except in a small creep zone which grows around the crack tip. If crack growth ensues while the creep zone is still small compared with the crack length and the specimen size, the stress intensity factor governs crack growth behavior. If the calculated creep zone becomes larger than the specimen size, the stresses become finally time-independent and the elastic strain rates can be neglected. In this case, the stress field is the same as in the fully-plastic limit of power law hardening plasticity. The loading parameter which determines the near tip fields uniquely is then the path-independent integral C*.K/sub I/ and C* characterize opposite limiting cases. The case applied in a given situation is decided by comparing the creep zone size with the specimen size and the crack length. Besides several methods of estimating the creep zone size, a convenient expression for a characteristic time is derived, which characterizes the transition from small scale yielding to extensive creep of the whole specimen

Observations on Hydride Structures at the Tip of Arrested Cracks Grown under Conditions of Delayed Hydride Cracking

International Nuclear Information System (INIS)

Pettersson, Kjell; Oskarsson, Magnus; Bergqvist, Hans

2003-04-01

One sample of Zr2.5%Nb and one sample of cold worked and stress relieved Zircaloy-4 which have been tested for hydrogen induced crack growth have been examined in the crack tip region with the aim of determining the mechanism behind the growth of cracks. The proposed mechanisms are brittle failure of a crack tip hydride and hydrogen enhanced localized shear. The examinations were done by TEM and SEM. However attempts to produce a TEM specimen with a thinned region at the tip of the crack were unsuccessful in both samples. One feature observed in the Zr2.5%Nb material may however be an indication of intense shear deformation at the tip of the crack. On the other hand all observations on the Zircaloy-4 sample indicate precipitation of hydrides ahead of the crack tip and the presence of hydrides on the crack flanks

Quenching cracks - formation and possible causes

International Nuclear Information System (INIS)

Macherauch, E.; Mueller, H.; Voehringer, O.

1976-01-01

The most important principles controlling the martensitic hardening of steels containing carbon are presented, and their effects on the cracks formed by tempering are discussed. Micro-crack formation, influenced by any increase in the carbon content, is dependent on the variations of martensitic morphology; this factor is of decisive importance. Apart from micro residual stresses, macro residual stresses become increasingly involved in the crack development. This is dependent on the given content of carbon and increase in the dimensions of the samples. Based on the empirical values gained from experience about cracks formed by tempering and using a schematic diagram, the constructive influences on the propensity to cracks formed by tempering, with regard to materials and processing, are evaluated. Also the effects of thermic, mechanical and chemical after-treatments upon the propensity to tempering cracks are discussed. In conclusion, the problem of the formation of cracks in hardened parts, i.e. the elongation of the cracks under static stress, is treated briefly. (orig.) [de

Natural zeolite bitumen cracking

Energy Technology Data Exchange (ETDEWEB)

Kuznicki, S.M.; McCaffrey, W.C.; Bian, J.; Wangen, E.; Koenig, A. [Alberta Univ., Edmonton, AB (Canada). Dept. of Chemical and Materials Engineering

2006-07-01

A study was conducted to demonstrate how low cost heavy oil upgrading in the field could reduce the need for diluents while lowering the cost for pipelining. Low cost field upgrading could also contribute to lowering contaminant levels. The performance of visbreaking processes could be improved by using disposable cracking agents. In turn, the economics of field upgrading of in-situ derived bitumen would be improved. However, in order to be viable, such agents would have to be far less expensive than current commercial cracking catalysts. A platy natural zeolite was selected for modification and testing due to its unique chemical and morphological properties. A catalyst-bearing oil sand was then heat-treated for 1 hour at 400 degrees C in a sealed microreactor. Under these mild cracking conditions, the catalyst-bearing oil sand produced extractable products of much lower viscosity. The products also contained considerably more gas oil and middle distillates than raw oil sand processed under the same conditions as thermal cracking alone. According to model cracking studies using hexadecane, these modified mineral zeolites may be more active cracking agents than undiluted premium commercial FCC catalyst. These materials hold promise for partial upgrading schemes to reduce solvent requirements in the field. tabs., figs.

Environmentally assisted cracking of LWR materials

International Nuclear Information System (INIS)

Chopra, O.K.; Chung, H.M.; Kassner, T.F.; Shack, W.J.

1995-12-01

Research on environmentally assisted cracking (EAC) of light water reactor materials has focused on (a) fatigue initiation in pressure vessel and piping steels, (b) crack growth in cast duplex and austenitic stainless steels (SSs), (c) irradiation-assisted stress corrosion cracking (IASCC) of austenitic SSs, and (d) EAC in high- nickel alloys. The effect of strain rate during different portions of the loading cycle on fatigue life of carbon and low-alloy steels in 289 degree C water was determined. Crack growth studies on wrought and cast SSs have been completed. The effect of dissolved-oxygen concentration in high-purity water on IASCC of irradiated Type 304 SS was investigated and trace elements in the steel that increase susceptibility to intergranular cracking were identified. Preliminary results were obtained on crack growth rates of high-nickel alloys in water that contains a wide range of dissolved oxygen and hydrogen concentrations at 289 and 320 degree C. The program on Environmentally Assisted Cracking of Light Water Reactor Materials is currently focused on four tasks: fatigue initiation in pressure vessel and piping steels, fatigue and environmentally assisted crack growth in cast duplex and austenitic SS, irradiation-assisted stress corrosion cracking of austenitic SSs, and environmentally assisted crack growth in high-nickel alloys. Measurements of corrosion-fatigue crack growth rates (CGRs) of wrought and cast stainless steels has been essentially completed. Recent progress in these areas is outlined in the following sections

Large-scale preparation of hollow graphitic carbon nanospheres

Energy Technology Data Exchange (ETDEWEB)

Feng, Jun; Li, Fu [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Bai, Yu-Jun, E-mail: byj97@126.com [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); State Key laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Han, Fu-Dong; Qi, Yong-Xin; Lun, Ning [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Lu, Xi-Feng [Lunan Institute of Coal Chemical Engineering, Jining 272000 (China)

2013-01-15

Hollow graphitic carbon nanospheres (HGCNSs) were synthesized on large scale by a simple reaction between glucose and Mg at 550 Degree-Sign C in an autoclave. Characterization by X-ray diffraction, Raman spectroscopy and transmission electron microscopy demonstrates the formation of HGCNSs with an average diameter of 10 nm or so and a wall thickness of a few graphenes. The HGCNSs exhibit a reversible capacity of 391 mAh g{sup -1} after 60 cycles when used as anode materials for Li-ion batteries. -- Graphical abstract: Hollow graphitic carbon nanospheres could be prepared on large scale by the simple reaction between glucose and Mg at 550 Degree-Sign C, which exhibit superior electrochemical performance to graphite. Highlights: Black-Right-Pointing-Pointer Hollow graphitic carbon nanospheres (HGCNSs) were prepared on large scale at 550 Degree-Sign C Black-Right-Pointing-Pointer The preparation is simple, effective and eco-friendly. Black-Right-Pointing-Pointer The in situ yielded MgO nanocrystals promote the graphitization. Black-Right-Pointing-Pointer The HGCNSs exhibit superior electrochemical performance to graphite.

Molecular beam sampling of a hollow cathode arc

International Nuclear Information System (INIS)

Theuws, P.

1981-01-01

This thesis deals with the description of the process of molecular beam sampling of a Hollow Cathode Arc. The aim of the study is twofold, i.e. investigation of the applicability of molecular beam sampling as a plasma diagnostic and the use of a Hollow Cathode Arc as a high intensity beam source for ground state atoms and metastable state atoms in the superthermal energy range. Suitable models are introduced, describing the process of molecular beam sampling of both ground state atoms and metastable state atoms. Fast ground state atoms produced by ion-atom collisions. The experimental facilities, i.e. the Hollow Cathode Arc, the time-of-flight machine and the dye laser system are described. And an alternative detection scheme for ground state atoms is presented and experimental results on the molecular beam sampling of a low density plasma (densities 10 19 -10 20 m -3 ) in the long arc configuration are reported. The results on the short arc configuration (densities 10 21 -10 22 m -3 ) are discussed. (Auth.)

In-reactor fatigue crack propagation

International Nuclear Information System (INIS)

Ermi, A.M.; Mervyn, D.A.; Straalsund, J.L.

1979-08-01

An in-reactor fatigue experiment is being designed to determine the effect of dynamic irradiation on the fatigue crack propagation (FCP) behavior of candidate fusion first wall materials. This investigation has been prompted by studies which show gross differences in crack growth characteristics of creep rupture specimens testing by postirradiation versus dynamic in-reactor methods. The experiment utilizes miniature center-cracked-tension specimens developed specifically for in-reactor studies. In the test, a chain of eight specimens, precracked to various initial crack lengths, is stressed during irradiation to determine crack growth rate as a function of stress intensity. Load levels were chosen which result in small crack growth rates encompassing a regime of the crack growth curve not previously investigated during irradiation studies of FCP. The test will be conducted on 20% cold worked 316 stainless steel at a temperature of 425 0 C, in a sodium environment, and at a frequency of 1 cycle/min. Irradiation will occur in the Oak Ridge Research Reactor, resulting in a He/dpa ratio similar to that expected at the first wall in a fusion reactor. Detailed design of the experiment is presented, along with crack growth data obtained from prototypic testing of the experimental apparatus. These results are compared to data obtained under similar conditions generated by conventional test methods

X-ray beam transfer between hollow fibers for long-distance transport

International Nuclear Information System (INIS)

Tanaka, Yoshihito; Matsushita, Ryuki; Shiraishi, Ryutaro; Hasegawa, Takayuki; Ishikawa, Kiyoshi; Sawada, Kei; Kohmura, Yoshiki; Takahashi, Isao

2016-01-01

Fiber optics for controlling the x-ray beam trajectory has been examined at the synchrotron facility of SPring-8. Up to now, we have achieved beam deflection by several tens of milli-radian and axis shift of around 75 mm with a 1.5 m-long flexible hollow glass capillary. The achievable beam deflecting angle, axis shift, and timing delay are, in principle, proportional to the length, the square of length and the cube of length, respectively. Thus, for further applications, requiring larger beam shift and pulse delay, longer fibers are indispensable. In order to achieve long-distance transport using the fiber, we thus examined the connection transferring x-rays between fibers in an experimental hutch. The acceptance angle at the input end and the throughput efficiency of the second fiber is consistent with the consideration of the output beam divergence of the first fiber. The enhancement of the transfer efficiency is also discussed for the cases of a closer joint and the use of a refractive lens as a coupler.

X-ray beam transfer between hollow fibers for long-distance transport

Energy Technology Data Exchange (ETDEWEB)

Tanaka, Yoshihito, E-mail: tanaka@sci.u-hyogo.ac.jp; Matsushita, Ryuki; Shiraishi, Ryutaro; Hasegawa, Takayuki; Ishikawa, Kiyoshi [Graduate School of Material Science, University of Hyogo, 3-2-1 Kouto, Kamigori-cho, Sayo-gun, Hyogo 678-1297 (Japan); Sawada, Kei; Kohmura, Yoshiki [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Takahashi, Isao [Department of Physics, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337 Japan (Japan)

2016-07-27

Fiber optics for controlling the x-ray beam trajectory has been examined at the synchrotron facility of SPring-8. Up to now, we have achieved beam deflection by several tens of milli-radian and axis shift of around 75 mm with a 1.5 m-long flexible hollow glass capillary. The achievable beam deflecting angle, axis shift, and timing delay are, in principle, proportional to the length, the square of length and the cube of length, respectively. Thus, for further applications, requiring larger beam shift and pulse delay, longer fibers are indispensable. In order to achieve long-distance transport using the fiber, we thus examined the connection transferring x-rays between fibers in an experimental hutch. The acceptance angle at the input end and the throughput efficiency of the second fiber is consistent with the consideration of the output beam divergence of the first fiber. The enhancement of the transfer efficiency is also discussed for the cases of a closer joint and the use of a refractive lens as a coupler.

The effect of crack branching on the residual lifetime of machine components containing stress corrosion cracks

International Nuclear Information System (INIS)

Magdowski, R.M.; Uggowitzer, P.J.; Speidel, M.O.

1985-01-01

A comparison is presented of theoretical, numerical and experimental investigations concerning the effect of crack branching on the reduction of stress intensity at the tip of single cracks. The results indicate that the division of a single crack into n branches reduces the stress intensity at the branch tips by a factor of about 1/√n. This permits branched cracks to grow to larger depths before becoming critical. The implication is that longer residual lifetimes and longer operating times between inspections can be calculated for machine components with growing branched stress corrosion cracks. (author)

Enhancement of acoustical performance of hollow tube sound absorber

International Nuclear Information System (INIS)

Putra, Azma; Khair, Fazlin Abd; Nor, Mohd Jailani Mohd

2016-01-01

This paper presents acoustical performance of hollow structures utilizing the recycled lollipop sticks as acoustic absorbers. The hollow cross section of the structures is arranged facing the sound incidence. The effects of different length of the sticks and air gap on the acoustical performance are studied. The absorption coefficient was measured using impedance tube method. Here it is found that improvement on the sound absorption performance is achieved by introducing natural kapok fiber inserted into the void between the hollow structures. Results reveal that by inserting the kapok fibers, both the absorption bandwidth and the absorption coefficient increase. For test sample backed by a rigid surface, best performance of sound absorption is obtained for fibers inserted at the front and back sides of the absorber. And for the case of test sample with air gap, this is achieved for fibers introduced only at the back side of the absorber.

Enhancement of acoustical performance of hollow tube sound absorber

Energy Technology Data Exchange (ETDEWEB)

Putra, Azma, E-mail: azma.putra@utem.edu.my; Khair, Fazlin Abd, E-mail: fazlinabdkhair@student.utem.edu.my; Nor, Mohd Jailani Mohd, E-mail: jai@utem.edu.my [Centre for Advanced Research on Energy, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, Durian Tunggal Melaka 76100 Malaysia (Malaysia)

2016-03-29

This paper presents acoustical performance of hollow structures utilizing the recycled lollipop sticks as acoustic absorbers. The hollow cross section of the structures is arranged facing the sound incidence. The effects of different length of the sticks and air gap on the acoustical performance are studied. The absorption coefficient was measured using impedance tube method. Here it is found that improvement on the sound absorption performance is achieved by introducing natural kapok fiber inserted into the void between the hollow structures. Results reveal that by inserting the kapok fibers, both the absorption bandwidth and the absorption coefficient increase. For test sample backed by a rigid surface, best performance of sound absorption is obtained for fibers inserted at the front and back sides of the absorber. And for the case of test sample with air gap, this is achieved for fibers introduced only at the back side of the absorber.

Computational predictions of zinc oxide hollow structures

Science.gov (United States)

Tuoc, Vu Ngoc; Huan, Tran Doan; Thao, Nguyen Thi

2018-03-01

Nanoporous materials are emerging as potential candidates for a wide range of technological applications in environment, electronic, and optoelectronics, to name just a few. Within this active research area, experimental works are predominant while theoretical/computational prediction and study of these materials face some intrinsic challenges, one of them is how to predict porous structures. We propose a computationally and technically feasible approach for predicting zinc oxide structures with hollows at the nano scale. The designed zinc oxide hollow structures are studied with computations using the density functional tight binding and conventional density functional theory methods, revealing a variety of promising mechanical and electronic properties, which can potentially find future realistic applications.

A dark hollow beam from a selectively liquid-filled photonic crystal fibre

International Nuclear Information System (INIS)

Mei-Yan, Zhang; Shu-Guang, Li; Yan-Yan, Yao; Bo, Fu; Lei, Zhang

2010-01-01

This paper reports that, based on the electromagnetic scattering theory of the multipole method, a high-quality hollow beam is produced through a selectively liquid-filled photonic crystal fibre. Instead of a doughnut shape, a typical hollow beam is produced by other methods; the mode-field images of the hollow-beam photonic crystal fibre satisfy sixth-order rotation symmetry, according to the symmetry of the photonic crystal fibre (PCF) structure. A dark spot size of the liquid-filled photonic crystal fibre-generated hollow beam can be tuned by inserting liquid into the cladding region and varying the photonic crystal fibre structure parameters. The liquid-filled PCF makes a convenient and flexible tool for the guiding and trapping of atoms and the creation of all-fibre optical tweezers. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

One-pot template-free synthesis of monodisperse hollow hydrogel microspheres and their resulting properties.

Science.gov (United States)

Lim, Hyung-Seok; Kwon, Eunji; Lee, Moonjoo; Moo Lee, Young; Suh, Kyung-Do

2013-08-01

Monodisperse poly(methacrylic acid/ethyleneglycoldimethacrylate) (MAA/EGDMA) hollow microcapsules, which exhibit pH-responsive behavior, are prepared by diffusion of cationic surfactants and hydrophobic interaction. During the association of the negatively charged hydrogel microspheres and an oppositely charged surfactant (cetyltrimethylammonium bromide, CTA(+)B), the hydrophobic polymer-surfactant complexes that form are separated from the internal water; consequently, a hollow structure can be formed. Confocal laser scanning microscopy, UV spectro-scopy and zeta potential are employed to study the formation of the hollow structure during the diffusion of the cationic surfactant. The controlled release behavior of methylene blue as a model drug from the as-prepared poly(MAA/EGDMA) microcapsules with a hollow structure is investigated under different pH conditions. The hollow structure can be retained, even during repetitive pH changes. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Buckling Analysis of Edge Cracked Sandwich Plate

Directory of Open Access Journals (Sweden)

Rasha Mohammed Hussein

2016-07-01

Full Text Available This work presents mainly the buckling load of sandwich plates with or without crack for different cases. The buckling loads are analyzed experimentally and numerically by using ANSYS 15. The experimental investigation was to fabricate the cracked sandwich plate from stainless steel and PVC to find mechanical properties of stainless steel and PVC such as young modulus. The buckling load for different aspect ratio, crack length, cracked location and plate without crack found. The experimental results were compared with that found from ANSYS program. Present of crack is decreased the buckling load and that depends on crack size, crack location and aspect ratio.

Hollow Electron Beam Collimation for HL-LHC - Effects on the Beam Core

Energy Technology Data Exchange (ETDEWEB)

Fitterer, M. [Fermilab; Stancari, G. [Fermilab; Valishev, A. [Fermilab; Bruce, R. [CERN; Papotti, G [CERN; Redaelli, S. [CERN; Valentino, G. [Malta U.; Valentino, G. [CERN; Valuch, D. [CERN; Xu, C. [CERN

2017-06-13

Collimation with hollow electron beams is currently one of the most promising concepts for active halo control in the High Luminosity Large Hadron Collider (HL-LHC). To ensure the successful operation of the hollow beam collimator the unwanted effects on the beam core, which might arise from the operation with a pulsed electron beam, must be minimized. This paper gives a summary of the effect of hollow electron lenses on the beam core in terms of sources, provides estimates for HL-LHC and discusses the possible mitigation methods.

Finite-Element Analysis of Crack Arrest Properties of Fiber Reinforced Composites Application in Semi-Elliptical Cracked Pipelines

Science.gov (United States)

Wang, Linyuan; Song, Shulei; Deng, Hongbo; Zhong, Kai

2018-04-01

In nowadays, repair method using fiber reinforced composites as the mainstream pipe repair technology, it can provide security for X100 high-grade steel energy long-distance pipelines in engineering. In this paper, analysis of cracked X100 high-grade steel pipe was conducted, simulation analysis was made on structure of pipes and crack arresters (CAs) to obtain the J-integral value in virtue of ANSYS Workbench finite element software and evaluation on crack arrest effects was done through measured elastic-plastic fracture mechanics parameter J-integral and the crack arrest coefficient K, in a bid to summarize effect laws of composite CAs and size of pipes and cracks for repairing CAs. The results indicate that the K value is correlated with laying angle λ, laying length L2/D1, laying thickness T1/T2of CAs, crack depth c/T1 and crack length a/c, and calculate recommended parameters for repairing fiber reinforced composite CAs in terms of two different crack forms.

Fabrication of hollow silica–zirconia composite spheres and their activity for hydrolytic dehydrogenation of ammonia borane

Energy Technology Data Exchange (ETDEWEB)

Umegaki, Tetsuo, E-mail: umegaki.tetsuo@nihon-u.ac.jp [Department of Materials and Applied Chemistry, College of Science and Engineering, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308 (Japan); Hosoya, Tatsuya; Toyama, Naoki [Department of Materials and Applied Chemistry, College of Science and Engineering, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308 (Japan); Xu, Qiang [National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Kojima, Yoshiyuki [Department of Materials and Applied Chemistry, College of Science and Engineering, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308 (Japan)

2014-09-01

Highlights: • Hollow silica–zirconia composite spheres were fabricated on polystyrene templates by the sol–gel method. • We study the effect of preparation conditions on the activity for hydrolytic dehydrogenation of ammonia borane. • The activity of hollow silica–zirconia composite spheres depends on wall thickness. - Abstract: In this paper, we report fabrication of hollow silica–zirconia composite spheres by polystyrene (PS) template method and control of wall thickness of the hollow spheres in nanoscale. Both the hollow spheres before and after calcination were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), elemental analysis, and powder X-ray diffraction analysis (XRD). Morphology of the hollow spheres does not significantly change after calcination from the results of SEM and TEM images, while the amount of residual PS templates drastically decreases via the calcination procedure from the results of FTIR and elemental analysis. The sample after calcination mainly includes amorphous silica from the results of XRD, indicating that the hollow silica–zirconia composite spheres consist of amorphous phases and/or fine particles. Wall thicknesses of the samples after calcination are controlled by adjusting the amount of PS template suspension, and hollow silica–zirconia composite spheres with the wall thicknesses of 17.5, 15.0, 10.0, and 2.0 nm are obtained using the PS template suspension of 25.0, 33.5, 100.0, and 400.0 g, respectively. The activities of the hollow spheres for hydrolytic dehydrogenation of ammonia borane (NH{sub 3}BH{sub 3}) were compared. The evolutions of 2.0, 3.1, 5.0, and 8.0 mL hydrogen from aqueous NH{sub 3}BH{sub 3} solution were finished in about 4, 5, 3, and 7 min in the presence of the hollow spheres with wall thicknesses of 17.5, 15.0, 10.0, and 2.0 nm, respectively. The molar ratios of the hydrolytically generated hydrogen to

Hollow Micro-/Nanostructures: Synthesis and Applications

KAUST Repository

Lou, Xiong Wen (David); Archer, Lynden A.; Yang, Zichao

2008-01-01

for Portland cement, to produce concrete with enhanced strength and durability. This review is devoted to the progress made in the last decade in synthesis and applications of hollow micro-nanostructures. We present a comprehensive overview of synthetic

Tensile Strength of GFRP Reinforcing Bars with Hollow Section

Directory of Open Access Journals (Sweden)

Young-Jun You

2015-01-01

Full Text Available Fiber reinforced polymer (FRP has been proposed to replace steel as a reinforcing bar (rebar due to its high tensile strength and noncorrosive material properties. One obstacle in using FRP rebars is high price. Generally FRP is more expensive than conventional steel rebar. There are mainly two ways to reduce the cost. For example, one is making the price of each composition cost of FRP rebar (e.g., fibers, resin, etc. lower than steel rebar. Another is making an optimized design for cross section and reducing the material cost. The former approach is not easy because the steel price is very low in comparison with component materials of FRP. For the latter approach, the cost could be cut down by reducing the material cost. Therefore, an idea of making hollow section over the cross section of FRP rebar was proposed in this study by optimizing the cross section design with acceptable tensile performance in comparison with steel rebar. In this study, glass reinforced polymer (GFRP rebars with hollow section and 19 mm of outer diameter were manufactured and tested to evaluate the tensile performance in accordance with the hollowness ratio. From the test results, it was observed that the tensile strength decreased almost linearly with increase of hollowness ratio and the elastic modulus decreased nonlinearly.

Fatigue test results of flat plate specimens with surface cracks and evaluation of crack growth in structural components

International Nuclear Information System (INIS)

Shibata, Katsuyuki; Yokoyama, Norio; Ohba, Toshihiro; Kawamura, Takaichi; Miyazono, Shohachiro

1982-12-01

Part-through surface cracks are most frequently observed in the inspection of structural components, and it is one of the important subjects in the assessment of safety to evaluate appropriately the growth of such cracks during the service life of structural components. Due to the complexity of the stress at the front free surface, the crack growth at the surface shows a different behavior from the other part. Besides, an effect of interaction is caused in the growth of multiple surface cracks. These effects should be included in the growth analysis of surface part-through cracks. Authors have carried out a series of fatigue tests on some kinds of pipes with multiple cracks in the inner surface, and subsequently the fatigue test of flat plate specimens, made of Type 304L stainless steel, with a single or double surface cracks was carried out to study the basic characteristics in the growth of multiple surface cracks. Based on the results of the flat plate test. the correction factors for the front free surface (Cs) and interaction (Ci) of surface cracks were derived quantitatively by the following empirical expressions; Cs = 0.824. Ci = (0.227(a/b) 2 (sec(PI X/2) - 1) + 1)sup(1/m). Using these two correction factors, a procedure to predict the growth of surface cracks was developed by applying the crack growth formula to both the thickness and surface directions. Besides, the crack growth predictions based on the procedure of ASME Code Sex. XI, and the above procedure without the correction of the free surface and interactions on the crack growth behaviors were compared with the test results of flat plate specimens. The crack growth behavior predicted by the procedure described in this report showed the best agreement with the test results in respects of the crack growth life and the change in the crack shape. The criteria of the ASME Code did not agree with the test results. (author)

Formation of hollow atoms above a surface

Science.gov (United States)

Briand, Jean Pierre; Phaneuf, Ronald; Terracol, Stephane; Xie, Zuqi

2012-06-01

Slow highly stripped ions approaching or penetrating surfaces are known to capture electrons into outer shells of the ions, leaving the innermost shells empty, and forming hollow atoms. Electron capture occurs above and below the surfaces. The existence of hollow atoms below surfaces e.g. Ar atoms whose K and L shells are empty, with all electrons lying in the M and N shells, was demonstrated in 1990 [1]. At nm above surfaces, the excited ions may not have enough time to decay before hitting the surfaces, and the formation of hollow atoms above surfaces has even been questioned [2]. To observe it, one must increase the time above the surface by decelerating the ions. We have for the first time decelerated O^7+ ions to energies as low as 1 eV/q, below the minimum energy gained by the ions due to the acceleration by their image charge. As expected, no ion backscattering (trampoline effect) above dielectric (Ge) was observed and at the lowest ion kinetic energies, most of the observed x-rays were found to be emitted by the ions after surface contact. [4pt] [1] J. P. Briand et al., Phys.Rev.Lett. 65(1990)159.[0pt] [2] J.P. Briand, AIP Conference Proceedings 215 (1990) 513.

Mechanism of crack initiation and crack growth under thermal and mechanical fatigue loading

Energy Technology Data Exchange (ETDEWEB)

Utz, S.; Soppa, E.; Silcher, H.; Kohler, C. [Stuttgart Univ. (Germany). Materials Testing Inst.

2013-07-01

The present contribution is focused on the experimental investigations and numerical simulations of the deformation behaviour and crack development in the austenitic stainless steel X6CrNiNb18-10 under thermal and mechanical cyclic loading in HCF and LCF regimes. The main objective of this research is the understanding of the basic mechanisms of fatigue damage and the development of simulation methods, which can be applied further in safety evaluations of nuclear power plant components. In this context the modelling of crack initiation and crack growth inside the material structure induced by varying thermal or mechanical loads are of particular interest. The mechanisms of crack initiation depend among other things on the type of loading, microstructure, material properties and temperature. The Nb-stabilized austenitic stainless steel in the solution-annealed condition was chosen for the investigations. Experiments with two kinds of cyclic loading - pure thermal and pure mechanical - were carried out and simulated. The fatigue behaviour of the steel X6CrNiNb18-10 under thermal loading was studied within the framework of the joint research project [4]. Interrupted thermal cyclic tests in the temperature range of 150 C to 300 C combined with non-destructive residual stress measurements (XRD) and various microscopic investigations, e.g. in SEM (Scanning Electron Microscope), were used to study the effects of thermal cyclic loading on the material. This thermal cyclic loading leads to thermal induced stresses and strains. As a result intrusions and extrusions appear inside the grains (at the surface), at which microcracks arise and evolve to a dominant crack. Finally, these microcracks cause a continuous and significant decrease of residual stresses. The fatigue behaviour of the steel X6CrNiNb18-10 under mechanical loading at room temperature was studied within the framework of the research project [5], [8]. With a combination of interrupted LCF tests and EBSD

Mechanism of crack initiation and crack growth under thermal and mechanical fatigue loading

International Nuclear Information System (INIS)

Utz, S.; Soppa, E.; Silcher, H.; Kohler, C.

2013-01-01

The present contribution is focused on the experimental investigations and numerical simulations of the deformation behaviour and crack development in the austenitic stainless steel X6CrNiNb18-10 under thermal and mechanical cyclic loading in HCF and LCF regimes. The main objective of this research is the understanding of the basic mechanisms of fatigue damage and the development of simulation methods, which can be applied further in safety evaluations of nuclear power plant components. In this context the modelling of crack initiation and crack growth inside the material structure induced by varying thermal or mechanical loads are of particular interest. The mechanisms of crack initiation depend among other things on the type of loading, microstructure, material properties and temperature. The Nb-stabilized austenitic stainless steel in the solution-annealed condition was chosen for the investigations. Experiments with two kinds of cyclic loading - pure thermal and pure mechanical - were carried out and simulated. The fatigue behaviour of the steel X6CrNiNb18-10 under thermal loading was studied within the framework of the joint research project [4]. Interrupted thermal cyclic tests in the temperature range of 150 C to 300 C combined with non-destructive residual stress measurements (XRD) and various microscopic investigations, e.g. in SEM (Scanning Electron Microscope), were used to study the effects of thermal cyclic loading on the material. This thermal cyclic loading leads to thermal induced stresses and strains. As a result intrusions and extrusions appear inside the grains (at the surface), at which microcracks arise and evolve to a dominant crack. Finally, these microcracks cause a continuous and significant decrease of residual stresses. The fatigue behaviour of the steel X6CrNiNb18-10 under mechanical loading at room temperature was studied within the framework of the research project [5], [8]. With a combination of interrupted LCF tests and EBSD

Dynamic ductile fracture of a central crack

Science.gov (United States)

Tsai, Y. M.

1976-01-01

A central crack, symmetrically growing at a constant speed in a two dimensional ductile material subject to uniform tension at infinity, is investigated using the integral transform methods. The crack is assumed to be the Dugdale crack, and the finite stress condition at the crack tip is satisfied during the propagation of the crack. Exact expressions of solution are obtained for the finite stress condition at the crack tip, the crack shape, the crack opening displacement, and the energy release rate. All those expressions are written as the product of explicit dimensional quantities and a nondimensional dynamic correction function. The expressions reduce to the associated static results when the crack speed tends to zero, and the nondimensional dynamic correction functions were calculated for various values of the parameter involved.

Sub-Pixel Accuracy Crack Width Determination on Concrete Beams in Load Tests by Triangle Mesh Geometry Analysis

Science.gov (United States)

Liebold, F.; Maas, H.-G.

2018-05-01

This paper deals with the determination of crack widths of concrete beams during load tests from monocular image sequences. The procedure starts in a reference image of the probe with suitable surface texture under zero load, where a large number of points is defined by an interest operator. Then a triangulated irregular network is established to connect the points. Image sequences are recorded during load tests with the load increasing continuously or stepwise, or at intermittently changing load. The vertices of the triangles are tracked through the consecutive images of the sequence with sub-pixel accuracy by least squares matching. All triangles are then analyzed for changes by principal strain calculation. For each triangle showing significant strain, a crack width is computed by a thorough geometric analysis of the relative movement of the vertices.

Fatigue crack propagation behavior under creep conditions

International Nuclear Information System (INIS)

Ohji, Kiyotsugu; Kubo, Shiro

1991-01-01

The crack propagation behavior of the SUS 304 stainless steel under creep-fatigue conditions was reviewed. Cracks propagated either in purely time-dependent mode or in purely cycle-dependent mode, depending on loading conditions. The time-dependent crack propagation rate was correlated with modified J-integral J * and the cycle-dependent crack propagation rate was correlated with J-integral range ΔJ f . Threshold was observed in the cycle-dependent crack propagation, and below this threshold the time-dependent crack propagation appeared. The crack propagation rates were uniquely characterized by taking the effective values of J * and ΔJ f , when crack closure was observed. Change in crack propagation mode occurred reversibly and was predicted by the competitive damage model. The threshold disappeared and the cycle-dependent crack propagation continued in a subthreshold region under variable amplitude conditions, where the threshold was interposed between the maximum and minimum ΔJ f . (orig.)

Cracking in Drying Colloidal Films

Science.gov (United States)

Singh, Karnail B.; Tirumkudulu, Mahesh S.

2007-05-01

It has long been known that thick films of colloidal dispersions such as wet clays, paints, and coatings crack under drying. Although capillary stresses generated during drying have been recently identified as the cause for cracking, the existence of a maximum crack-free film thickness that depends on particle size, rigidity, and packing has not been understood. Here, we identify two distinct regimes for crack-free films based on the magnitude of compressive strain at the maximum attainable capillary pressure and show remarkable agreement of measurements with our theory. We anticipate our results to not only form the basis for design of coating formulations for the paints, coatings, and ceramics industry but also assist in the production of crack-free photonic band gap crystals.

Recent advances in modelling creep crack growth

International Nuclear Information System (INIS)

Riedel, H.

1988-08-01

At the time of the previous International Conference on Fracture, the C* integral had long been recognized as a promising load parameter for correlating crack growth rates in creep-ductile materials. The measured crack growth rates as a function of C* and of the temperature could be understood on the basis of micromechanical models. The distinction between C*-controlled and K I -controlled creep crack growth had been clarified and first attempts had been made to describe creep crack growth in the transient regime between elastic behavior and steady-state creep. This paper describes the progress in describing transient crack growth including the effect of primary creep. The effect of crack-tip geometry changes by blunting and by crack growth on the crack-tip fields and on the validity of C* is analyzed by idealizing the growing-crack geometry by a sharp notch and using recent solutions for the notch-tip fields. A few new three-dimensional calculations of C* are cited and important theoretical points are emphasized regarding the three-dimensional fields at crack tips. Finally, creep crack growth is described by continuum-damage models for which similarity solutions can be obtained. Crack growth under small-scale creep conditions turns out to be difficult to understand. Slightly different models yield very different crack growth rates. (orig.) With 4 figs

Effects of off-centered cracks and restraint of induced bending caused by pressure on the crack-opening-area analysis of pipes

International Nuclear Information System (INIS)

Rahman, S.; Wilkowski, G.M.; Bonora, N.

1996-01-01

Current models for the crack-opening-area analysis of pipes with circumferential through-wall cracks are based on various idealizations or assumptions which are often necessary to simplify the mathematical formulation and numerical calculation. This paper focuses on the validity of two such assumptions that involve off-centered cracks and the restraint of induced bending caused by pressure, and quantifies their effects on the crack-opening area analysis of pipes. Finite element and/or simple estimation methods were employed to compute the center-crack-opening displacement and crack-opening shape for a through-wall-cracked pipe, considering off-centered cracks and the restraint of induced bending caused by pressure. The results of the analyses show that, for both cases, the crack-opening area can be reduced significantly. For pipes with off-centered cracks, the crack-opening area can be evaluated from analyses of symmetrically centered cracks and assuming elliptical profile. For pipes with complete restraint of the induced bending caused by pressure, the reduction in crack-opening area depends on the crack size. When the crack size is small, the restraint effects can be ignored. However, when the crack size is large, the restrained crack opening can be significantly smaller than the unrestrained crack opening, depending on the length of pipe involved; hence, it may be important for the crack-opening-area and leak-rate analyses. (orig.)

Rotary compression process for producing toothed hollow shafts

Directory of Open Access Journals (Sweden)

J. Tomczak

2014-10-01

Full Text Available The paper presents the results of numerical analyses of the rotary compression process for hollow stepped shafts with herringbone teeth. The numerical simulations were performed by Finite Element Method (FEM, using commercial software package DEFORM-3D. The results of numerical modelling aimed at determining the effect of billet wall thickness on product shape and the rotary compression process are presented. The distributions of strains, temperatures, damage criterion and force parameters of the process determined in the simulations are given, too. The numerical results obtained confirm the possibility of producing hollow toothed shafts from tube billet by rotary compression methods.

Soliton formation in hollow-core photonic bandgap fibers

DEFF Research Database (Denmark)

Lægsgaard, Jesper

2009-01-01

of an approximate scaling relation is tested. It is concluded that compression of input pulses of several ps duration and sub-MW peak power can lead to a formation of solitons with ∼100 fs duration and multi-megawatt peak powers. The dispersion slope of realistic hollow-core fibers appears to be the main obstacle......The formation of solitons upon compression of linearly chirped pulses in hollow-core photonic bandgap fibers is investigated numerically. The dependence of soliton duration on the chirp and power of the input pulse and on the dispersion slope of the fiber is investigated, and the validity...

Antiresonant hollow core fiber with seven nested capillaries

DEFF Research Database (Denmark)

Antonio-Lopez, Jose E.; Habib, Selim; Van Newkirk, Amy

2016-01-01

We report an antiresonant hollow core fiber formed of 7 non-touching capillaries with inner tubes. The fiber has a core diameter of ∼33μm and a core wall of ∼780nm of thickness. We demonstrate robust single mode operation at 1064nm and broad transmission bandwidth.......We report an antiresonant hollow core fiber formed of 7 non-touching capillaries with inner tubes. The fiber has a core diameter of ∼33μm and a core wall of ∼780nm of thickness. We demonstrate robust single mode operation at 1064nm and broad transmission bandwidth....

Catalyst-Free Synthesis of Hollow-Sphere-Like ZnO and Its Photoluminescence Property

Directory of Open Access Journals (Sweden)

Junye Cheng

2014-01-01

Full Text Available Hollow-sphere-like ZnO was successfully prepared by a facile combustion route at 950°C, and no external catalysts or additives were introduced. The morphology and structure of the hollow-sphere-like ZnO were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, high-resolution transmission electron microscopy (HRTEM, and energy dispersive spectrometer (EDS. The possible growth mechanism was discussed in detail. In addition, the as-obtained hollow-sphere-like ZnO exhibited a strong green emission at 518 nm and a weak UV emission at 385 nm. We believe that the hollow-sphere-like ZnO material may be a good candidate for application in optical devices and catalyst systems.

Enhancement of the predicted drug hepatotoxicity in gel entrapped hepatocytes within polysulfone-g-poly (ethylene glycol) modified hollow fiber

International Nuclear Information System (INIS)

Shen Chong; Zhang Guoliang; Meng Qin

2010-01-01

Collagen gel-based 3D cultures of hepatocytes have been proposed for evaluation of drug hepatotoxicity because of their more reliability than traditional monolayer culture. The collagen gel entrapment of hepatocytes in hollow fibers has been proven to well reflect the drug hepatotoxicity in vivo but was limited by adsorption of hydrophobic drugs onto hollow fibers. This study aimed to investigate the impact of hollow fibers on hepatocyte performance and drug hepatotoxicity. Polysulfone-g-poly (ethylene glycol) (PSf-g-PEG) hollow fiber was fabricated and applied for the first time to suppress the drug adsorption. Then, the impact of hollow fibers was evaluated by detecting the hepatotoxicity of eight selected drugs to gel entrapped hepatocytes within PSf and PSf-g-PEG hollow fibers, or without hollow fibers. The hepatocytes in PSf-g-PEG hollow fiber showed the highest sensitivity to drug hepatotoxicity, while those in PSf hollow fiber and cylindrical gel without hollow fiber underestimated the hepatotoxicity due to either drug adsorption or low hepatic functions. Therefore, the 3D culture of gel entrapped hepatocytes within PSf-g-PEG hollow fiber would be a promising tool for investigation of drug hepatotoxicity in vitro.

Synthesis of solid and hollow ATO spheres by carbothermal reduction of ATO nanoparticles

International Nuclear Information System (INIS)

Chai Chunfang; Huang Zaiyin; Liao Dankui; Tan Xuecai; Wu Jian; Yuan Aiqun

2007-01-01

Solid and hollow ATO spheres were fabricated by heating ATO nanoparticles and graphite mixture in a tube furnace. The as-synthesized samples were characterized by EDS, XRD, FE-SEM, TEM and HRTEM. The size of the solid spheres could be controlled by adjusting the rate of Ar flow and deposition positions. The hollow spheres were synthesized in an alumina tube system under conditions of a relatively high oxygen concentration. The growth mechanism of solid and hollow spheres was analysed

Crack growth by micropore coalescence at high temperatures

International Nuclear Information System (INIS)

Beere, W.

1981-01-01

At high temperatures in the creep regime the stress distribution around a crack is different from the low temperature elastically generated distribution. The stress distribution ahead of the crack is calculated for a crack preceded by an array of growing cavities. The cavities maintain a displacement wedge ahead of the crack. When the displacement wedge is less than one-tenth the crack length the driving force for crack growth is similar to an all elastically loaded crack. When the deforming wedge exceeds the crack length the net section stress controls crack growth. An expression is derived for a crack growing by the growth and coalescence of cavities situated in the crack plane. It is predicted that at high temperatures above a critical stress intensity, the crack propagates in a brittle fashion. (author)

Remote detection of stress corrosion cracking: Surface composition and crack detection

Science.gov (United States)

Lissenden, Cliff J.; Jovanovic, Igor; Motta, Arthur T.; Xiao, Xuan; Le Berre, Samuel; Fobar, David; Cho, Hwanjeong; Choi, Sungho

2018-04-01

Chloride induced stress corrosion cracking (SCC) of austenitic stainless steel is a potential issue in long term dry storage of spent nuclear fuel canisters. In order for SCC to occur there must be a corrosive environment, a susceptible material, and a driving force. Because it is likely that the material in the heat affected zone (HAZ) of welded stainless steel structures has been sensitized as a result of chromium depletion at the grain boundaries and a thermal residual stress driving force is likely present if solution annealing is not performed, two issues are critical. Is the environment corrosive, i.e., are chlorides present in solution on the surface? And then, are there cracks that could propagate? Remote detection of chlorides on the surface can be accomplished by laser induced breakdown spectroscopy (LIBS), while cracks can be detected by shear horizontal guided waves generated by electromagnetic acoustic transducers (EMATs). Both are noncontact methods that are amenable to robotic delivery systems and harsh environments. The sensitivity to chlorine on stainless steel of a LIBS system that employs optical fiber for pulse delivery is demonstrated. Likewise, the ability of the EMAT system to detect cracks of a prescribed size and orientation is shown. These results show the potential for remote detection of Cl and cracks in dry storage spent fuel canisters.

Construction of anatase/rutile TiO2 hollow boxes for highly efficient photocatalytic performance

Science.gov (United States)

Jia, Changchao; Zhang, Xiao; Yang, Ping

2018-02-01

Hollow TiO2 hierarchical boxes with suitable anatase and rutile ratios were designed for photocatalysis. The unique hierarchical structure was fabricated via a Topotactic synthetic method. CaTiO3 cubes were acted as the sacrificial templates to create TiO2 hollow hierarchical boxes with well-defined phase distribution. The phase composition of the hollow TiO2 hierarchical boxes is similar to that of TiO2 P25 nanoparticles (∼80% anatase, and 20% rutile). Compared with nanaoparticles, TiO2 hollow boxes with hierarchical structures exhibited an excellent performance in the photocatalytic degradation of methylene blue organic pollutant. Quantificationally, the degradation rate of the hollow boxes is higher than that of TiO2 P25 nanoparticles by a factor of 2.7. This is ascribed that hollow structure provide an opportunity for using incident light more efficiently. The surface hierarchical and well-organized porous structures are beneficial to supply more active sites and enough transport channels for reactant molecules. The boxes consist of single crystal anatase and rutile combined well with each other, which gives photon-generated carriers transfer efficiently.

Pt monolayer shell on hollow Pd core electrocatalysts: Scale up synthesis, structure, and activity for the oxygen reduction reaction

Directory of Open Access Journals (Sweden)

Vukmirovic Miomir B.

2013-01-01

Full Text Available We report on synthesis, characterization and the oxygen reduction reaction (ORR kinetics of Pt monolayer shell on Pd(hollow, or Pd-Au(hollow core electrocatalysts. Comparison between the ORR catalytic activity of the electrocatalysts with hollow cores and those of Pt solid and Pt hollow nanoparticles has been obtained using the rotating disk electrode technique. Hollow nanoparticles were made using Ni or Cu nanoparticles as sacrificial templates. The Pt ORR specific and mass activities of the electrocatalysts with hollow cores were found considerably higher than those of the electrocatalysts with the solid cores. We attribute this enhanced Pt activity to the smooth surface morphology and hollow-induced lattice contraction, in addition to the mass-saving geometry of hollow particles.

21 CFR 137.190 - Cracked wheat.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 2 2010-04-01 2010-04-01 false Cracked wheat. 137.190 Section 137.190 Food and... Related Products § 137.190 Cracked wheat. Cracked wheat is the food prepared by so cracking or cutting into angular fragments cleaned wheat other than durum wheat and red durum wheat that, when tested by...

Dynamic Crack Branching - A Photoelastic Evaluation,

Science.gov (United States)

1982-05-01

0.41 mPai and a 0.18 MPa, and predicted a theoretical kinking angle of 84°whichagreed well with experimentally measured angle. After crack kinking...Consistent crack branching’at KIb = 2.04 MPaI -i- and r = 1.3 mm verified this crack branching criterion. The crack branching angle predicted by--.’ DD

Cracking of open traffic rigid pavement

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Niken Chatarina

2017-01-01

Full Text Available The research is done by observing the growth of real structure cracking in Natar, Lampung, Indonesia compared to C. Niken’s et al research and literature study. The rigid pavement was done with open traffic system. There are two main crack types on Natar rigid pavement: cracks cross the road, and cracks spreads on rigid pavement surface. The observation of cracks was analyzed by analyzing material, casting, curing, loading and shrinkage mechanism. The relationship between these analysis and shrinkage mechanism was studied in concrete micro structure. Open traffic make hydration process occur under vibration; therefore, fresh concrete was compressed and tensioned alternately since beginning. High temperature together with compression, cement dissociation, the growth of Ca2+ at very early age leads abnormal swelling. No prevention from outside water movement leads hydration process occur with limited water which caused spreads fine cracks. Limited water improves shrinkage and plastic phase becomes shorter; therefore, rigid pavement can’t accommodate the abnormal swelling and shrinking alternately and creates the spread of cracks. Discontinuing casting the concrete makes both mix under different condition, the first is shrink and the second is swell and creates weak line on the border; so, the cracks appear as cracks across the road.

Lateral rigidity of cracked concrete structures

International Nuclear Information System (INIS)

Castellani, A.; Chesi, C.

1979-01-01

Numerical results are discussed on the lateral rigidity of reinforced concrete structures with a given crack distribution. They have been favourably checked with experimental results for cylindrical shells under the effect of a thermal gradient producing vertical cracking or vertical plus horizontal cracking. The main effects characterizing the concrete behaviour are: (1) The shear transfer across a crack; (2) The shear transfer degradation after cyclic loading; (3) The tension stiffening provided by the concrete between crack and crack, in the normal stress transfer; (4) The temperature effect on the elastic moduli of concrete, when cracks are of thermal origin. Only the 1st effect is discussed on an experimental basis. Two broad cathegories of reinforced concrete structures have been investigated in this respect: shear walls of buildings and cylindrical containment structures. The main conclusions so far reached are: (1) Vertical cracks are unlikely to decrease the lateral rigidity to less than 80% of the original one, and to less than 90% when they do not involve the entire thickness of the wall; (2) The appearence of horizontal cracks can reduce the lateral rigidity by some 30% or more; (3) A noticeable but not yet evaluated influence is shown by cyclic loading. (orig.)

Facile synthesis and electrochemical performances of hollow graphene spheres as anode material for lithium-ion batteries

Science.gov (United States)

Yao, Ran-Ran; Zhao, Dong-Lin; Bai, Li-Zhong; Yao, Ning-Na; Xu, Li

2014-07-01

The hollow graphene oxide spheres have been successfully fabricated from graphene oxide nanosheets utilizing a water-in-oil emulsion technique, which were prepared from natural flake graphite by oxidation and ultrasonic treatment. The hollow graphene oxide spheres were reduced to hollow graphene spheres at 500°C for 3 h under an atmosphere of Ar(95%)/H2(5%). The first reversible specific capacity of the hollow graphene spheres was as high as 903 mAh g-1 at a current density of 50 mAh g-1. Even at a high current density of 500 mAh g-1, the reversible specific capacity remained at 502 mAh g-1. After 60 cycles, the reversible capacity was still kept at 652 mAh g-1 at the current density of 50 mAh g-1. These results indicate that the prepared hollow graphene spheres possess excellent electrochemical performances for lithium storage. The high rate performance of hollow graphene spheres thanks to the hollow structure, thin and porous shells consisting of graphene sheets.

A One-Square-Millimeter Compact Hollow Structure for Microfluidic Pumping on an All-Glass Chip

Directory of Open Access Journals (Sweden)

Xing Yue (Larry Peng

2016-04-01

Full Text Available A micro surface tension pump is a new type of low-cost, built-in, all-glass, microfluidic pump on a glass microchip fabricated by one-step glass etching. However, geometric minimization and optimization for practical use are challenging. Here, we report a one-square-millimeter, built-in, all-glass pump controlled by two-way digital gas pressure. The pump consists simply of two joint chambers and a piston between two gas control channels. It does not require pre-perfusion for initialization, and can immediately begin to run when a liquid enters its inlet channel. It is also more reliable than conventional micro pumps for practical use due to its ability to restart after the formation of a blocking bubble, which can serve as a valuable troubleshooting procedure. Its volumetric pump output was 0.5–0.7 nL·s−1 under a pump head pressure of 300 Pa.

Semi-empirical crack tip analysis

Science.gov (United States)

Chudnovsky, A.; Ben Ouezdon, M.

1988-01-01

Experimentally observed crack opening displacements are employed as the solution of the multiple crack interaction problem. Then the near and far fields are reconstructed analytically by means of the double layer potential technqiue. Evaluation of the effective stress intensity factor resulting from the interaction of the main crack and its surrounding crazes in addition to the remotely applied load is presented as an illustrative example. It is shown that crazing (as well as microcracking) may constitute an alternative mechanism to Dugdale-Berenblatt models responsible for the cancellation of the singularity at the crack tip.

Prediction of pure water stress corrosion cracking (PWSCC) in nickel base alloys using crack growth rate models

International Nuclear Information System (INIS)

Thompson, C.D.; Krasodomski, H.T.; Lewis, N.; Makar, G.L.

1995-01-01

The Ford/Andresen slip dissolution SCC model, originally developed for stainless steel components in BWR environments, has been applied to Alloy 600 and Alloy X-750 tested in deaerated pure water chemistry. A method is described whereby the crack growth rates measured in compact tension specimens can be used to estimate crack growth in a component. Good agreement was found between model prediction and measured SCC in X-750 threaded fasteners over a wide range of temperatures, stresses, and material condition. Most data support the basic assumption of this model that cracks initiate early in life. The evidence supporting a particular SCC mechanism is mixed. Electrochemical repassivation data and estimates of oxide fracture strain indicate that the slip dissolution model can account for the observed crack growth rates, provided primary rather than secondary creep rates are used. However, approximately 100 cross-sectional TEM foils of SCC cracks including crack tips reveal no evidence of enhanced plasticity or unique dislocation patterns at the crack tip or along the crack to support a classic slip dissolution mechanism. No voids, hydrides, or microcracks are found in the vicinity of the crack tips creating doubt about classic hydrogen related mechanisms. The bulk oxide films exhibit a surface oxide which is often different than the oxides found within a crack. Although bulk chromium concentration affects the rate of SCC, analytical data indicates the mechanism does not result from chromium depletion at the grain boundaries. The overall findings support a corrosion/dissolution mechanism but not one necessarily related to slip at the crack tip

A Hollow-Structured Manganese Oxide Cathode for Stable Zn-MnO₂ Batteries.

Science.gov (United States)

Guo, Xiaotong; Li, Jianming; Jin, Xu; Han, Yehu; Lin, Yue; Lei, Zhanwu; Wang, Shiyang; Qin, Lianjie; Jiao, Shuhong; Cao, Ruiguo

2018-05-05

Aqueous rechargeable zinc-manganese dioxide (Zn-MnO₂) batteries are considered as one of the most promising energy storage devices for large scale-energy storage systems due to their low cost, high safety, and environmental friendliness. However, only a few cathode materials have been demonstrated to achieve stable cycling for aqueous rechargeable Zn-MnO₂ batteries. Here, we report a new material consisting of hollow MnO₂ nanospheres, which can be used for aqueous Zn-MnO₂ batteries. The hollow MnO₂ nanospheres can achieve high specific capacity up to ~405 mAh g −1 at 0.5 C. More importantly, the hollow structure of birnessite-type MnO₂ enables long-term cycling stability for the aqueous Zn-MnO₂ batteries. The excellent performance of the hollow MnO₂ nanospheres should be due to their unique structural properties that enable the easy intercalation of zinc ions.

Effects of off-centered crack and restraint of induced bending due to pressure on the crack-opening-area analysis of pipes

International Nuclear Information System (INIS)

Rahman, S.; Ghadiali, N.; Wilkowski, G.; Bonora, N.

1995-01-01

Estimation of leak rate is an important element in developing leak-before-break (LBB) methodology for piping integrity and safety analysis of nuclear power plants. Here, current models for the crack-opening-area analysis of pipes with circumferential through-wall cracks are based on various idealizations or assumption which are often necessary to simplify the mathematical formulation and numerical calculation. This paper focuses on the validity of two such assumptions involving off-centered cracks and restraint of induced bending due to pressure and quantifies their effects on the crack-opening analysis of pipes. Both finite element and/or simple estimation methods were employed to compute the center-crack-opening displacement and crack-opening shape for a through-wall-cracked pipe considering off-centered cracks and restrain of induced bending due to pressure. The results of analyses show that for both cases the crack-opening area can be reduced significantly. For pipes with off-centered cracks, the crack-opening area can be evaluated from analyses of symmetrically centered cracks and assuming elliptical profile. For pipes with complete restraint of induced bending due to pressure, the reduction of crack-opening area depends on the crack size. When the crack size is small, the restraint effects can be ignored. However, when the crack size is larger, the restrained crack-opening can be significantly smaller than the unrestrained crack-opening depending on the length of pipe involved, and hence, may be important for the crack-opening-area and leak-rate analyses

Stress Inversion of Coal with a Gas Drilling Borehole and the Law of Crack Propagation

Directory of Open Access Journals (Sweden)

Tianjun Zhang

2017-10-01

Full Text Available For studying the law of crack propagation around a gas drilling borehole, an experimental study about coal with a cavity under uniaxial compression was carried out, with the digital speckle correlation method capturing the images of coal failure. A sequence of coal failure images and the full-field strain of failure were obtained. The strain softening characteristic was shown by the curve. A method of curve dividing—named fitting-damaging—was proposed, combining the least square fitting residual norm and damage fraction. By this method, the five stages and four key points of a stress-strain curve were defined. Then, the full-field stress was inverted by means of the theory of elasticity and the adjacent element weight sharing model. The results show that σci was 30.28–41.71 percent of σf and σcd was 83.08–87.34 percent of σf, calculated by the fitting-damaging method, agreeing with former research. The results of stress inversion showed that under a low stress level (0.15 σf < σ < 0.5 σf, microdamage evolving into plastic failure later was formed around the cavity. Under a high stress level (0.5 σf < σ < 0.85 σf, the region of stress concentration suddenly crazed and formed a brittle crack. When σ ≥ 0.85 σf, the crack was developing, crack lines were connecting with each other, and the coal finally failed. The outcome of the stress inversion was completely concomitant with the images of crack propagation. Additionally, the stress around the cavity was able to be calculated accurately.

Propagation of stress corrosion cracks in alpha-brasses

Energy Technology Data Exchange (ETDEWEB)

Beggs, Dennis Vinton [Univ. of Illinois, Urbana-Champaign, IL (United States)

1981-01-01

Transgranular and intergranular stress corrosion cracks were investigated in alpha-brasses in a tarnishing ammoniacal solution. Surface observation indicated that the transgranular cracks propagated discontinuously by the sudden appearance of a fine crack extending several microns ahead of the previous crack tip, often associated with the detection of a discrete acoustic emission (AE). By periodically increasing the deflection, crack front markings were produced on the resulting fracture surfaces, showing that the discontinuous propagation of the crack trace was representative of the subsurface cracking. The intergranular crack trace appeared to propagate continuously at a relatively blunt crack tip and was not associated with discrete AE. Under load pulsing tests with a time between pulses, Δt greater than or equal to 3 s, the transgranular fracture surfaces always exhibited crack front markings which corresponded with the applied pulses. The spacing between crack front markings, Δx, decreased linearly with Δt. With Δt less than or equal to 1.5 s, the crack front markings were in a one-to-one correspondence with applied pulses only at relatively long crack lengths. In this case, Δx = Δx* which approached a limiting value of 1 μm. No crack front markings were observed on intergranular fracture surfaces produced during these tests. It is concluded that transgranular cracking occurs by discontinuous mechanical fracture of an embrittled region around the crack tip, while intergranular cracking results from a different mechanism with cracking occurring via the film-rupture mechanism.

Two-stream sausage and hollowing instabilities in high-intensity particle beams

International Nuclear Information System (INIS)

Uhm, Han S.; Davidson, Ronald C.; Kaganovich, Igor

2001-01-01

Axisymmetric two-stream instabilities in high-intensity particle beams are investigated analytically by making use of the Vlasov-Maxwell equations in the smooth-focusing approximation. The eigenfunctions for the axisymmetric radial modes are calculated self-consistently in order to determine the dispersion relation describing collective stability properties. Stability properties for the sausage and hollowing modes, characterized by radial mode numbers n=1 and n=2, respectively, are investigated, and the dispersion relations are obtained for the complex eigenfrequency ω in terms of the axial wavenumber k and other system parameters. The eigenfunctions obtained self-consistently for the sausage and hollowing modes indicate that the perturbations exist only inside the beam. Therefore, the location of the conducting wall does not have an effect on stability behavior. The growth rates of the sausage and hollowing modes are of the same order of magnitude as that of the hose (dipole-mode) instability. Therefore, it is concluded that the axisymmetric sausage and hollowing instabilities may also be deleterious to intense ion beam propagation when a background component of electrons is presented

Sensitive Nonenzymatic Electrochemical Glucose Detection Based on Hollow Porous NiO

Science.gov (United States)

He, Gege; Tian, Liangliang; Cai, Yanhua; Wu, Shenping; Su, Yongyao; Yan, Hengqing; Pu, Wanrong; Zhang, Jinkun; Li, Lu

2018-01-01

Transition metal oxides (TMOs) have attracted extensive research attentions as promising electrocatalytic materials. Despite low cost and high stability, the electrocatalytic activity of TMOs still cannot satisfy the requirements of applications. Inspired by kinetics, the design of hollow porous structure is considered as a promising strategy to achieve superior electrocatalytic performance. In this work, cubic NiO hollow porous architecture (NiO HPA) was constructed through coordinating etching and precipitating (CEP) principle followed by post calcination. Being employed to detect glucose, NiO HPA electrode exhibits outstanding electrocatalytic activity in terms of high sensitivity (1323 μA mM-1 cm-2) and low detection limit (0.32 μM). The excellent electrocatalytic activity can be ascribed to large specific surface area (SSA), ordered diffusion channels, and accelerated electron transfer rate derived from the unique hollow porous features. The results demonstrate that the NiO HPA could have practical applications in the design of nonenzymatic glucose sensors. The construction of hollow porous architecture provides an effective nanoengineering strategy for high-performance electrocatalysts.

Highly efficient fluorescence sensing with hollow core photonic crystal fibers

DEFF Research Database (Denmark)

Smolka, Stephan; Barth, Michael; Benson, Oliver

2008-01-01

We investigate hollow core photonic crystal fibers for ultra-sensitive fluorescence detection by selectively infiltrating the central hole with fluorophores. Dye concentrations down to 10(-9) M can be detected using only nanoliter sample volumes.......We investigate hollow core photonic crystal fibers for ultra-sensitive fluorescence detection by selectively infiltrating the central hole with fluorophores. Dye concentrations down to 10(-9) M can be detected using only nanoliter sample volumes....

Crack tip stress and strain

International Nuclear Information System (INIS)

Francois, D.

1975-01-01

The study of potential energy variations in a loaded elastic solid containing a crack leads to determination of the crack driving force G. Generalization of this concept to cases other than linear elasticity leads to definition of the integral J. In a linear solid, the crack tip stress field is characterized by a single parameter: the stress-intensity factor K. When the crack tip plastic zone size is confined to the elastic singularity J=G, it is possible to establish relationship between these parameters and plastic strain (and in particular the crack tip opening displacement delta). The stress increases because of the triaxiality effect. This overload rises with increasing strain hardening. When the plastic zone size expands, using certain hypotheses, delta can be calculated. The plastic strain intensity is exclusively dependent on parameter J [fr

Evaluation of the probability of crack initiation and crack instability for a pipe with a semi-elliptical crack

International Nuclear Information System (INIS)

Le Delliou, P.; Hornet, P.

2001-01-01

This paper presents some work conducted at EDF R and D Division to evaluate the probability that a semi-elliptical crack in a pipe not only initiates but also propagates when submitted to mechanical loading such as bending and pressure combined or not with a thermal shock. The first part is related to the description of the mechanical model: the simplified methods included in the French RSE-M Code used to evaluate the J-integral as well as the principle of the determination of the crack propagation. Then, the way this deterministic approach is combined to a reliability code is described. Finally, an example is shown: the initiation and the instability of a semi-elliptical crack in a pipe submitted to combined pressure and bending moment. (author)

Cocaine (Coke, Crack) Facts

Science.gov (United States)

... That People Abuse » Cocaine (Coke, Crack) Facts Cocaine (Coke, Crack) Facts Listen Cocaine is a white ... 69 KB) "My life was built around getting cocaine and getting high." ©istock.com/ Marjot Stacey is ...

CRACK2 - Modelling calcium carbonate deposition from bicarbonate solution in cracks in concrete

International Nuclear Information System (INIS)

Brodersen, K.

2003-03-01

The numerical CRACK2 model simulates precipitation of calcite from calcium bicarbonate solution (e.g. groundwater) passing through cracks in concrete or other cementitious materials. A summary of experimental work is followed by a detailed description of the model. Hydroxyl ions are transported by diffusion in pore systems in columns of cementitious materials. The hydroxyl is precipitating calcite from a flow of bicarbonate solution in a crack connecting the ends of a row of such columns. The cementitious material is simulated as calcium hydroxide mixed with inert material but with sodium hydroxide dissolved in the pore solution. Diffusive migration of cesium as radioactive isotope is also considered. Electrical interaction of the migrating ions is taken into account. Example calculations demonstrate effects of parameter variations on distribution of precipitated calcite in the crack and on the composition of the outflowing solution, which can be compared directly with experimental results. Leaching behavior of sodium can be used to tune the model to experimental observations. The calcite is mostly precipitated on top of the original crack surface and may under certain circumstances fill the crack. The produced thin layers of low porosity calcite act as a diffusion barrier limiting contact between cement and solution. Pore closure mechanisms in such layers are discussed. Implications for safety assessment of radioactive waste disposal are shortly mentioned. The model is also relevant for conventional uses of concrete. (au)

Noncontact fatigue crack evaluation using thermoelastic

Energy Technology Data Exchange (ETDEWEB)

Kim, Ji Min; An, Yun Kyu; Sohn, Hoon [KAIST, Daejeon (Korea, Republic of)

2012-12-15

This paper proposes a noncontact thermography technique for fatigue crack evaluation under a cyclic tensile loading. The proposed technique identifies and localizes an invisible fatigue crack without scanning, thus making it possible to instantaneously evaluate an incipient fatigue crack. Based on a thermoelastic theory, a new fatigue crack evaluation algorithm is proposed for the fatigue crack tip localization. The performance of the proposed algorithm is experimentally validated. To achieve this, the cyclic tensile loading is applied to a dog bone shape aluminum specimen using a universal testing machine, and the corresponding thermal responses induced by thermoelastic effects are captured by an infrared camera. The test results confirm that the fatigue crack is well identified and localized by comparing with its microscopic images.

Assessment of cracking in dissimilar metal welds

International Nuclear Information System (INIS)

Jenssen, Anders; Norrgaard, K.; Lagerstroem, J.; Embring, G.; Tice, D.R.

2001-08-01

During the refueling in 2000, indications were observed by non-destructive testing at four locations in the reactor pressure vessel (RPV) nozzle to safe end weld in Ringhals 4. All indications were confined to the outlet nozzle (hotleg) oriented at 25 deg, a nozzle with documented repair welding. Six boat samples were removed from the four locations, and the samples were subsequently subjected to a metallographic examination. The objectives were to establish the fracture morphology, and if possible the root cause for cracking. The examination revealed that cracks were present at all four boat sample locations and that they all were confined to the weld metal, alloy 182. Cracking extended in the axial direction of the safe-end. There was no evidence of any cracks extending into the RPV-steel, or the stainless steel safe-end. All cracking was interdendritic and significantly branched. Among others, these observations strongly suggested crack propagation mainly was caused by interdendritic stress corrosion cracking. In addition, crack type defects and isolated areas on the fracture surfaces suggested the presence of hot cracking, which would have been formed during fabrication. The reason for crack initiation could not be established based on the boat samples examined. However, increased stress levels due to repair welding, cold work from grinding, and defects produced during fabrication, e. g. hot cracks, may alone or in combination have contributed to crack initiation

Porous hollow Co₃O₄ with rhombic dodecahedral structures for high-performance supercapacitors.

Science.gov (United States)

Zhang, Yi-Zhou; Wang, Yang; Xie, Ye-Lei; Cheng, Tao; Lai, Wen-Yong; Pang, Huan; Huang, Wei

2014-11-06

Porous hollow Co₃O₄ with rhombic dodecahedral structures were prepared by the calcination of ZIF-67 ([Co(mim)2; mim = 2-methylimidazolate]) rhombic dodecahedral microcrystals. A supercapacitor was successfully constructed by adopting the resulting porous hollow Co₃O₄ rhombic dodecahedral structure as the electrode material, which showed a large specific capacitance of 1100 F g(-1) and retained more than 95.1% of the specific capacitance after 6000 continuous charge-discharge cycles. The excellent capacitive properties and stability mark the porous hollow Co₃O₄ with the rhombic dodecahedral structure as one of the most promising electrode materials for high-performance supercapacitors.

Modeling of formation of binary-phase hollow nanospheres from metallic solid nanospheres

International Nuclear Information System (INIS)

Svoboda, J.; Fischer, F.D.; Vollath, D.

2009-01-01

Spontaneous formation of binary-phase hollow nanospheres by reaction of a metallic nanosphere with a non-metallic component in the surrounding atmosphere is observed for many systems. The kinetic model describing this phenomenon is derived by application of the thermodynamic extremal principle. The necessary condition of formation of the binary-phase hollow nanospheres is that the diffusion coefficient of the metallic component in the binary phase is higher than that of the non-metallic component (Kirkendall effect occurs in the correct direction). The model predictions of the time to formation of the binary-phase hollow nanospheres agree with the experimental observations

Synthesis of Hollow Silica by Stober Method with Double Polymers as Templates

International Nuclear Information System (INIS)

Nguyen, Anhthu; Park, Chang Woo; Kim, Sang Hern

2014-01-01

The hollow SiO 2 spheres with uniform size were synthesized by a modified stoeber method under the control of polyelectrolytes (PSS and PAA) as templates. This synthetic route includes the formation of spherical colloid micelle in ethanol solution, hydrolysis of TEOS under control of ammonia, and the removal of polyelectrolyte by washing or calcination. Hollow silica spheres with controllable core diameters between 100 and 270 nm and wall thickness between 15 and 50 nm have been synthesized. The influence of template solution concentration and solvent and dispersant on the formation of silica hollow spheres is studied and reported in detail

Seismic behaviour of un-cracked and cracked thin pipes

International Nuclear Information System (INIS)

Blay, N.; Brunet, G.; Gantenbein, F.; Aguilar, J.

1995-01-01

In order to evaluate the seismic behaviour of un-cracked and cracked thin pipes, subjected to high acceleration levels, seismic tests and calculations have been performed on straight thin pipes made of 316L stainless steel, loaded in pure bending by a permanent static and dynamic loading. The seismic tests were carried out on the AZALEE shaking table of the CEA laboratory TAMARIS. The influence of the elasto-plastic model with isotropic or kinematic hardening are studied. 5 refs., 7 figs., 2 tabs

Fire resistance of extruded hollow-core slabs

DEFF Research Database (Denmark)

Hertz, Kristian Dahl; Giuliani, Luisa; Sørensen, Lars Schiøtt

2016-01-01

Prefabricated extruded hollow-core slabs are preferred building components for floor structures in several countries. It is therefore important to be able to document the fire resistance of these slabs proving fulfilment of standard fire resistance requirements of 60- and 120 minutes found in most...... a standard fire test and from a thorough examination of the comprehensive test documentation available on fire exposed hollow-core slabs. Mechanisms for loss of load-bearing capacity are clarified, and evidence of the fire resistance is found. For the first time the mechanisms responsible for loss of load......-bearing capacity are identified and test results and calculation approach are for the first time Applied in accordance with each other for assessment of fire resistance of the structure....

Dislocation model of a subsurface crack

International Nuclear Information System (INIS)

Yang, F.; Li, J.C.

1997-01-01

A dislocation model of a subsurface crack parallel to the surface is presented. For tensile loading, the results agree with those of previous workers except that we studied the crack very close to the surface and found that K II (mode II stress intensity factor) approaches K I (mode I stress intensity factor) to within about 22% (K II =0.78K I ). (Note that K II is zero when the crack is far away from the surface). Using bending theory for such situations, it is found that both stress intensity factors are inversely proportional to the 3/2 power of the distance between the subsurface crack and the free surface. For shear loading, the crack faces overlap each other for the free traction condition. This indicates the failure of the model. However, there was no overlap for tensile loading even though the stresses in front of the crack oscillate somewhat when the crack is very close to the surface. copyright 1997 American Institute of Physics

Gyrator transform of Gaussian beams with phase difference and generation of hollow beam

Science.gov (United States)

Xiao, Zhiyu; Xia, Hui; Yu, Tao; Xie, Ding; Xie, Wenke

2018-03-01

The optical expression of Gaussian beams with phase difference, which is caused by gyrator transform (GT), has been obtained. The intensity and phase distribution of transform Gaussian beams are analyzed. It is found that the circular hollow vortex beam can be obtained by overlapping two GT Gaussian beams with π phase difference. The effect of parameters on the intensity and phase distributions of the hollow vortex beam are discussed. The results show that the shape of intensity distribution is significantly influenced by GT angle α and propagation distance z. The size of the hollow vortex beam can be adjusted by waist width ω 0. Compared with previously reported results, the work shows that the hollow vortex beam can be obtained without any model conversion of the light source.

Steady-state propagation of interface corner crack

DEFF Research Database (Denmark)

Veluri, Badrinath; Jensen, Henrik Myhre

2013-01-01

Steady-state propagation of interface cracks close to three-dimensional corners has been analyzed. Attention was focused on modeling the shape of the interface crack front and calculating the critical stress for steady-state propagation of the crack. The crack propagation was investigated...... on the finite element method with iterative adjustment of the crack front to estimate the critical delamination stresses as a function of the fracture criterion and corner angles. The implication of the results on the delamination is discussed in terms of crack front profiles and the critical stresses...... for propagation and the angle of intersection of the crack front with the free edge....

Crack closure, a literature study

Science.gov (United States)

Holmgren, M.

1993-08-01

In this report crack closure is treated. The state of the art is reviewed. Different empirical formulas for determining the crack closure are compared with each other, and their benefits are discussed. Experimental techniques for determining the crack closure stress are discussed, and some results from fatigue tests are also reported. Experimental data from the literature are reported.

Modeling High Pressure Micro Hollow Cathode Discharges

National Research Council Canada - National Science Library

Boeuf, Jean-Pierre; Pitchford, Leanne

2004-01-01

This report results from a contract tasking CPAT as follows: The Grantee will perform theoretical modeling of point, surface, and volume high-pressure plasmas created using Micro Hollow Cathode Discharge sources...

optimizing compressive strength characteristics of hollow building

African Journals Online (AJOL)

eobe

Keywords: hollow building Blocks, granite dust, sand, partial replacement, compressive strength. 1. INTRODUCTION ... exposed to extreme climate. The physical ... Sridharan et al [13] conducted shear strength studies on soil-quarry dust.

Fabrication and Characterization of Nanoenergetic Hollow Spherical Hexanitrostibene (HNS Derivatives

Directory of Open Access Journals (Sweden)

Xiong Cao

2018-05-01

Full Text Available The spherization of nanoenergetic materials is the best way to improve the sensitivity and increase loading densities and detonation properties for weapons and ammunition, but the preparation of spherical nanoenergetic materials with high regularization, uniform size and monodispersity is still a challenge. In this paper, nanoenergetic hollow spherical hexanitrostibene (HNS derivatives were fabricated via a one-pot copolymerization strategy, which is based on the reaction of HNS and piperazine in acetonitrile solution. Characterization results indicated the as-prepared reaction nanoenergetic products were HNS-derived oligomers, where a free radical copolymerization reaction process was inferred. The hollow sphere structure of the HNS derivatives was characterized by scanning electron microscopy (SEM, transmission electron microscope (TEM, and synchrotron radiation X-ray imaging technology. The properties of the nanoenergetic hollow spherical derivatives, including thermal decomposition and sensitivity are discussed in detail. Sensitivity studies showed that the nanoenergetic derivatives exhibited lower impact, friction and spark sensitivity than raw HNS. Thermogravimetric-differential scanning calorimeter (TG-DSC results showed that continuous exothermic decomposition occurred in the whole temperature range, which indicated that nanoenergetic derivatives have a unique role in thermal applications. Therefore, nanoenergetic hollow spherical HNS derivatives could provide a new way to modify the properties of certain energetic compounds and fabricate spherical nanomaterials to improve the charge configuration.

Silicon-Encapsulated Hollow Carbon Nanofiber Networks as Binder-Free Anodes for Lithium Ion Battery

Directory of Open Access Journals (Sweden)

Ding Nan

2014-01-01

Full Text Available Silicon-encapsulated hollow carbon nanofiber networks with ample space around the Si nanoparticles (hollow Si/C composites were successfully synthesized by dip-coating phenolic resin onto the surface of electrospun Si/PVA nanofibers along with the subsequent solidification and carbonization. More importantly, the structure and Si content of hollow Si/C composite nanofibers can be effectively tuned by merely varying the concentration of dip solution. As-synthesized hollow Si/C composites show excellent electrochemical performance when they are used as binder-free anodes for Li-ion batteries (LIBs. In particular, when the concentration of resol/ethanol solution is 3.0%, the product exhibits a large capacity of 841 mAh g−1 in the first cycle, prominent cycling stability, and good rate capability. The discharge capacity retention of it was ~90%, with 745 mAh g−1 after 50 cycles. The results demonstrate that the hollow Si/C composites are very promising as alternative anode candidates for high-performance LIBs.

Nanosized aluminum nitride hollow spheres formed through a self-templating solid-gas interface reaction

International Nuclear Information System (INIS)

Zheng Jie; Song Xubo; Zhang Yaohua; Li Yan; Li Xingguo; Pu Yikang

2007-01-01

Nanosized aluminum nitride hollow spheres were synthesized by simply heating aluminum nanoparticles in ammonia at 1000 deg. C. The as-synthesized sphere shells are polycrystalline with cavity diameters ranging from 15 to 100 nm and shell thickness from 5 to 15 nm. The formation mechanism can be explained by the nanoscale Kirkendall effect, which results from the difference in diffusion rates between aluminum and nitrogen. The Al nanoparticles served as both reactant and templates for the hollow sphere formation. The effects of precursor particle size and temperature were also investigated in terms of product morphology. Room temperature cathode luminescence spectrum of the nanosized hollow spheres showed a broad emission band centered at 415 nm, which is originated from oxygen related luminescence centers. The hollow structure survived a 4-h heat treatment at 1200 deg. C, exhibiting excellent thermal stability. - Graphical abstract: Nanosized aluminum nitride hollow spheres were synthesized by nitridation of aluminum nanoparticles at 1000 deg. C using ammonia

Metallic double shell hollow nanocages: the challenges of their synthetic techniques.

Science.gov (United States)

Mahmoud, M A; El-Sayed, M A

2012-03-06

Hollow metallic nanoparticles have been attracting the attention of many researchers in the past five years due to their new properties and potential applications. The unique structure of the hollow nanoparticles; presence of two surfaces (internal and external), and the presence of both cavities and pores in the wall surfaces of these nanoparticles are responsible for their unique properties and applications. Here the galvanic replacement technique is used to prepare nanocages made of gold, platinum, and palladium. In addition, hollow double shell nanoparticles are made of two metal shells like Au-Pt, Pt-Au, Au-Pd, Pd-Au, Pd-Pt, and Pt-Pd. Silver nanocubes are used as templates during the synthesis of hollow nanoparticles with single metal shell or double shell nanocages. Most of the problems that could affect the synthesis of solid Silver nanocubes used as template as well as the double shell nanocages and their possible solutions are discussed in a detail. The sizes and shapes of the single-shell and double-shell nanocages were characterized by a regular and high-resolution TEM. A SEM mapping technique is also used to image the surface atoms for the double shell hollow nanoparticles in order to determine the thickness of the two metal shells. In addition, optical studies are used to monitor the effect of the dielectric properties of the other metals on the plasmonic properties of the gold nanoshell in these mixed nanoparticles.

Finite element simulation for creep crack growth

International Nuclear Information System (INIS)

Miyazaki, Noriyuki; Sasaki, Toru; Nakagaki, Michihiko; Brust, F.W.

1992-01-01

A finite element method was applied to a generation phase simulation of creep crack growth. Experimental data on creep crack growth in a 1Cr-1Mo-1/4V steel compact tension specimen were numerically simulated using a node-release technique and the variations of various fracture mechanics parameters such as CTOA, J, C * and T * during creep crack growth were calculated. The path-dependencies of the integral parameters J, C * and T * were also obtained to examine whether or not they could characterize the stress field near the tip of a crack propagating under creep condition. The following conclusions were obtained from the present analysis. (1) The J integral shows strong path-dependency during creep crack growth, so that it is does not characterize creep crack growth. (2) The C * integral shows path-dependency to some extent during creep crack growth even in the case of Norton type steady state creep law. Strictly speaking, we cannot use it as a fracture mechanics parameter characterizing creep crack growth. It is, however, useful from the practical viewpoint because it correlates well the rate of creep crack growth. (3) The T * integral shows good path-independency during creep crack growth. Therefore, it is a candidate for a fracture mechanics parameter characterizing creep crack growth. (author)

Hollow volcanic tumulus caves of Kilauea Caldera, Hawaii County, Hawaii

Directory of Open Access Journals (Sweden)

William R. Halliday

1998-01-01

Full Text Available In addition to lava tube caves with commonly noted features, sizable subcrustal spaces of several types exist on the floor of Kilauea Caldera. Most of these are formed by drainage of partially stabilized volcanic structures enlarged or formed by injection of very fluid lava beneath a plastic crust. Most conspicuous are hollow tumuli, possibly first described by Walker in 1991. Walker mapped and described the outer chamber of Tumulus E-I Cave. Further exploration has revealed that it has a hyperthermic inner room beneath an adjoining tumulus with no connection evident on the surface. Two lengthy, sinuous hollow tumuli also are present in this part of the caldera. These findings support Walkers conclusions that hollow tumuli provide valuable insights into tumulus-forming mechanisms, and provide information about the processes of emplacement of pahoehoe sheet flows.

Nb2O5 hollow nanospheres as anode material for enhanced performance in lithium ion batteries

International Nuclear Information System (INIS)

Sasidharan, Manickam; Gunawardhana, Nanda; Yoshio, Masaki; Nakashima, Kenichi

2012-01-01

Graphical abstract: Nb 2 O 5 hollow nanosphere constructed electrode delivers high capacity of 172 mAh g −1 after 250 cycles and maintains structural integrity and excellent cycling stability. Highlights: ► Nb 2 O 5 hollow nanospheres synthesis was synthesized by soft-template. ► Nb 2 O 5 hollow nanospheres were investigated as anode material in Li-ion battery. ► Nanostructured electrode delivers high capacity of 172 mAh g −1 after 250 cycles. ► The electrode maintains the structural integrity and excellent cycling stability. ► Nanosized shell domain facilitates fast lithium intercalation/deintercalation. -- Abstract: Nb 2 O 5 hollow nanospheres of average diameter ca. ∼29 nm and hollow cavity size ca. 17 nm were synthesized using polymeric micelles with core–shell–corona architecture under mild conditions. The hollow particles were thoroughly characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), infrared spectroscopy (FTIR), thermal (TG/DTA) and nitrogen adsorption analyses. Thus obtained Nb 2 O 5 hollow nanospheres were investigated as anode materials for lithium ion rechargeable batteries for the first time. The nanostructured electrode delivers high capacity of 172 mAh g −1 after 250 cycles of charge/discharge at a rate of 0.5 C. More importantly, the hollow particles based electrodes maintains the structural integrity and excellent cycling stability even after exposing to high current density 6.25 A g −1 . The enhanced electrochemical behavior is ascribed to hollow cavity coupled with nanosized Nb 2 O 5 shell domain that facilitates fast lithium intercalation/deintercalation kinetics.

Low-Loss Hollow-Core Anti-Resonant Fibers With Semi-Circular Nested Tubes

DEFF Research Database (Denmark)

Habib, Selim; Bang, Ole; Bache, Morten

2016-01-01

Hollow-core fibers with a single ring of circular antiresonant tubes as the cladding provide a simple way of getting a negative-curvature hollow core, resulting in broadband low-loss transmission with little power overlap in the glass. These fibers show a significant improvement in loss performan...

Sweep gas membrane distillation in a membrane contactor with metallic hollow fibers

NARCIS (Netherlands)

Shukla, Sushumna; Benes, Nieck Edwin; Vankelecom, I.F.J.; Mericq, J.P.; Belleville, M.P.; Hengl, N.; Sanchez Marcano, Jose

2015-01-01

This work revolves around the use of porous metal hollow fibers in membrane distillation. Various stages are covered, starting from membrane synthesis up to the testing of a pilot scale membrane module. Mechanically stable metal hollow fibers have been synthesized by phase inversion of a stainless

Probabilistic fracture mechanics of nuclear structural components. Consideration of transition from embedded crack to surface crack

International Nuclear Information System (INIS)

Yagawa, Genki; Yoshimura, Shinobu; Kanto, Yasuhiro

1998-01-01

This paper describes a probabilistic fracture mechanics (PFM) analysis of aged nuclear reactor pressure vessel (RPV) material. New interpolation formulas are first derived for both embedded elliptical surface cracks and semi-elliptical surface cracks. To investigate effects of transition from embedded crack to surface crack in PFM analyses, one of PFM round-robin problems set by JSME-RC111 committee, i.e. 'aged RPV under normal and upset operating conditions' is solved, employing the interpolation formulas. (author)

The Legend of Sleepy Hollow

Institute of Scientific and Technical Information of China (English)

Washington; Irving

1987-01-01

Part Ⅰ On the Eastern shore of the Hudson River there was a little valley, among high hills, which was one of the quietest places in the whole world. This little valley had long been known by the name of SIeepy Hollow. Many strange stories about ghosts were told and retold in the village situated there.

Crack Propagation by Finite Element Method

Directory of Open Access Journals (Sweden)

Luiz Carlos H. Ricardo

2018-01-01

Full Text Available Crack propagation simulation began with the development of the finite element method; the analyses were conducted to obtain a basic understanding of the crack growth. Today structural and materials engineers develop structures and materials properties using this technique. The aim of this paper is to verify the effect of different crack propagation rates in determination of crack opening and closing stress of an ASTM specimen under a standard suspension spectrum loading from FDandE SAE Keyhole Specimen Test Load Histories by finite element analysis. To understand the crack propagation processes under variable amplitude loading, retardation effects are observed

Numerical simulation of the sustaining discharge in radio frequency hollow cathode discharge in argon

Energy Technology Data Exchange (ETDEWEB)

Jiang, Xin-Xian; He, Feng, E-mail: hefeng@bit.edu.cn; Ouyang, Ji-Ting [School of Physics, Beijing Institute of Technology, Beijing 100081 (China); Chen, Qiang, E-mail: lppmchenqiang@hotmail.com; Ge, Teng [Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Beijing 10081 (China)

2014-03-15

In this paper, a two-dimensional fluid model was developed to study the radio frequency (RF) hollow cathode discharge (HCD) in argon at 1 Torr. The evolutions of the particle density distribution and the ionization rate distribution in RF HCD at 13.56 MHz indicate that the discharge mainly occurs inside the hollow cathode. The spatio-temporal distributions of the ionization rate and the power deposition within the hollow cathode imply that sheath oscillation heating is the primary mechanism to sustain the RF HCD, whereas secondary electron emission plays a negligible role. However, as driving frequency decreases, secondary electron heating becomes a dominant mechanism to sustain the discharge in RF hollow cathode.

Hollow-Fiber Spacesuit Water Membrane Evaporator

Science.gov (United States)

Bue, Grant; Trevino, Luis; Tsioulos, Gus; Mitchell, Keith; Settles, Joseph

2013-01-01

The hollow-fiber spacesuit water membrane evaporator (HoFi SWME) is being developed to perform the thermal control function for advanced spacesuits and spacecraft to take advantage of recent advances in micropore membrane technology in providing a robust, heat-rejection device that is less sensitive to contamination than is the sublimator. After recent contamination tests, a commercial-off-the-shelf (COTS) micro porous hollow-fiber membrane was selected for prototype development as the most suitable candidate among commercial hollow-fiber evaporator alternatives. An innovative design that grouped the fiber layers into stacks, which were separated by small spaces and packaged into a cylindrical shape, was developed into a full-scale prototype for the spacesuit application. Vacuum chamber testing has been performed to characterize heat rejection as a function of inlet water temperature and water vapor back-pressure, and to show contamination resistance to the constituents expected to be found in potable water produced by the wastewater reclamation distillation processes. Other tests showed tolerance to freezing and suitability to reject heat in a Mars pressure environment. In summary, HoFi SWME is a lightweight, compact evaporator for heat rejection in the spacesuit that is robust, contamination- insensitive, freeze-tolerant, and able to reject the required heat of spacewalks in microgravity, lunar, and Martian environments. The HoFi is packaged to reject 810 W of heat through 800 hours of use in a vacuum environment, and 370 W in a Mars environment. The device also eliminates free gas and dissolved gas from the coolant loop.

Application of acoustic emission to hydride cracking

International Nuclear Information System (INIS)

Sagat, S.; Ambler, J.F.R.; Coleman, C.E.

1986-07-01

Acoustic emission has been used for over a decade to study delayed hydride cracking (DHC) in zirconium alloys. At first acoustic emission was used primarily to detect the onset of DHC. This was possible because DHC was accompanied by very little plastic deformation of the material and furthermore the amplitudes of the acoustic pulses produced during cracking of the brittle hydride phase were much larger than those from dislocation motion and twinning. Acoustic emission was also used for measuring crack growth when it was found that for a suitable amplitude threshold, the total number of acoustic emission counts was linearly related to the cracked area. Once the proportionality constant was established, the acoustic counts could be converted to the crack length. Now the proportionality between the count rate and the crack growth rate is used to provide feedback between the crack length and the applied load, using computer technology. In such a system, the stress at the crack tip can be maintained constant during the test by adjusting the applied load as the crack progresses, or it can be changed in a predetermined manner, for example, to measure the threshold stress for cracking

Fatigue-crack propagation behavior of steels in vacuum, and implications for ASME Section 11 crack growth analyses

International Nuclear Information System (INIS)

James, L.A.

1985-08-01

Section XI of the ASME Boiler and Pressure Vessel Code provides rules for the analysis of structures for which cracks or crack-like flaws have been discovered during inservice inspection. The Code provides rules for the analysis of both surface flaws as well as flaws that are embedded within the wall of the pressure vessel. In the case of surface flaws, the Code provides fatigue crack growth rate relationships for typical nuclear pressure vessel steels (e.g., ASTM A508-2 and A533-B) cycled in water environments typical of those in light-water reactors (LWR). However, for the case of embedded cracks, the Code provides crack growth relationships based on results from specimens that were cycled in an elevated temperature air environment. Although these latter relationships are often referred to as applying to ''inert'' environments, the results of this paper will show that an elevated temperature air environment is anything but inert, and that use of such relationships can result in overly pessimistic estimates of fatigue-crack growth lifetimes of embedded cracks. The reason, of course, is that embedded cracks grow in an environment that is probably much closer to a vacuum than an air environment

Hollow micro string based calorimeter device

DEFF Research Database (Denmark)

2014-01-01

positions so as to form a free released double clamped string in-between said two longitudinally distanced positions said micro-channel string comprising a microfluidic channel having a closed cross section and extending in the longitudinal direction of the hollow string, acoustical means adapted...

Crack tip fracture toughness of base glasses for dental restoration glass-ceramics using crack opening displacements.

Science.gov (United States)

Deubener, J; Höland, M; Höland, W; Janakiraman, N; Rheinberger, V M

2011-10-01

The critical stress intensity factor, also known as the crack tip toughness K(tip), was determined for three base glasses, which are used in the manufacture of glass-ceramics. The glasses included the base glass for a lithium disilicate glass-ceramic, the base glass for a fluoroapatite glass-ceramic and the base glass for a leucite glass-ceramic. These glass-ceramic are extensively used in the form of biomaterials in restorative dental medicine. The crack tip toughness was established by using crack opening displacement profiles under experimental conditions. The crack was produced by Vickers indentation. The crack tip toughness parameters determined for the three glass-ceramics differed quite significantly. The crack tip parameters of the lithium disilicate base glass and the leucite base glass were higher than that of the fluoroapatite base glass. This last material showed glass-in-glass phase separation. The discussion of the results clearly shows that the droplet glass phase is softer than the glass matrix. Therefore, the authors conclude that a direct relationship exists between the chemical nature of the glasses and the crack tip parameter. Copyright © 2011 Elsevier Ltd. All rights reserved.

Probabilistic fracture mechanics of nuclear structural components: consideration of transition from embedded crack to surface crack

International Nuclear Information System (INIS)

Yagawa, G.; Yoshimura, S.

1999-01-01

This paper describes a probabilistic fracture mechanics (PFM) analysis of aged nuclear reactor pressure vessel (RPV) material. New interpolation formulas of three-dimensional stress intensity factors are presented for both embedded elliptical surface cracks and semi-elliptical surface cracks. To investigate effects of transition from embedded crack to surface crack in PFM analyses, one of the PFM round-robin problems set by JSME-RC111 committee (i.e. aged RPV under normal and upset operating conditions) is solved, employing the interpolation formulas. (orig.)

Transformation from hollow carbon octahedra to compressed octahedra and their use in lithium-ion batteries

International Nuclear Information System (INIS)

Mei, Tao; Li, Na; Li, Qianwen; Xing, Zheng; Tang, Kaibin; Zhu, Yongchun; Qian, Yitai; Shen, Xiaoyan

2012-01-01

Graphical abstract: Schematic illustration of the transformation process from hollow carbon octahedra into deflated balloon-like compressed hollow carbon octahedra ▪. Highlights: ► We demonstrate the in situ template synthesis of hollow carbon octahedra. ► The shell thickness of hollow carbon octahedra is only 2.5 nm. ► Morphology transformation could be realized by extending of reaction time. ► The hollow structures show reversible capacity as 353 mAh g −1 after 100 cycles. -- Abstract: Hollow carbon octahedra with an average size of 300 nm and a shell thickness of 2.5 nm were prepared by a reaction starting from ferrocene and Mg(CH 3 COO) 2 ·4H 2 O at 700 °C for 10 h. They became compressed and turned into deflated balloon-like octahedra when the reaction time was increased to 16 h. It was proposed that the gas pressure generated during the reaction process induced the transformation from broken carbon hollow octahedra into deflated balloon-like compressed octahedra. X-ray powder diffraction and Raman spectroscopy indicate that the as-obtained carbon products possess a graphitic structure and high-resolution transmission electron microscopy images indicate that they have low crystallinity. Their application as an electrode shows reversible capacity of 353 mAh g −1 after 100 cycles in the charge/discharge experiments of secondary lithium ion batteries.

Compressive failure with interacting cracks

International Nuclear Information System (INIS)

Yang Guoping; Liu Xila

1993-01-01

The failure processes in concrete and other brittle materials are just the results of the propagation, coalescence and interaction of many preexisting microcracks or voids. To understand the real behaviour of the brittle materials, it is necessary to bridge the gap from the relatively matured one crack behaviour to the stochastically distributed imperfections, that is, to concern the crack propagation and interaction of microscopic mechanism with macroscopic parameters of brittle materials. Brittle failure in compression has been studied theoretically by Horii and Nemat-Nasser (1986), in which a closed solution was obtained for a preexisting flaw or some special regular flaws. Zaitsev and Wittmann (1981) published a paper on crack propagation in compression, which is so-called numerical concrete, but they did not take account of the interaction among the microcracks. As for the modelling of the influence of crack interaction on fracture parameters, many studies have also been reported. Up till now, some researcher are working on crack interaction considering the ratios of SIFs with and without consideration of the interaction influences, there exist amplifying or shielding effects of crack interaction which are depending on the relative positions of these microcracks. The present paper attempts to simulate the whole failure process of brittle specimen in compression, which includes the complicated coupling effects between the interaction and propagation of randomly distributed or other typical microcrack configurations step by step. The lengths, orientations and positions of microcracks are all taken as random variables. The crack interaction among many preexisting random microcracks is evaluated with the help of a simple interaction matrix (Yang and Liu, 1991). For the subcritically stable propagation of microcracks in mixed mode fracture, fairly known maximum hoop stress criterion is adopted to compute branching lengths and directions at each tip of the crack

Hollow organ perforation in blunt abdominal trauma: the role of diagnostic peritoneal lavage.

Science.gov (United States)

Wang, Yu-Chun; Hsieh, Chi-Hsun; Fu, Chih-Yuan; Yeh, Chun-Chieh; Wu, Shih-Chi; Chen, Ray-Jade

2012-05-01

With recent advances in radiologic diagnostic procedures, the use of diagnostic peritoneal lavage (DPL) has markedly declined. In this study, we reviewed data to reevaluate the role of DPL in the diagnosis of hollow organ perforation in patients with blunt abdominal trauma. Adult patients who had sustained blunt abdominal trauma and who were hemodynamically stable after initial resuscitation underwent an abdominal computed tomographic (CT) scan. Diagnostic peritoneal lavage was performed for patients who were indicated to receive nonoperative management and where hollow organ perforation could not be ruled out. During a 60-month period, 64 patients who had received abdominal CT scanning underwent DPL. Nineteen patients were diagnosed as having a positive DPL based on cell count ratio of 1 or higher. There were 4 patients who sustained small bowel perforation. The sensitivity and specificity of the cell count ratio for a hollow organ perforation in this study were 100% and 75%, respectively. No missed hollow organ perforations were detected. For patients with blunt abdominal trauma and hemoperitoneum who plan to receive nonoperative management, DPL is still a useful tool to exclude hollow organ perforation that is undetected by CT. Copyright © 2012 Elsevier Inc. All rights reserved.

MoS2 coated hollow carbon spheres for anodes of lithium ion batteries

International Nuclear Information System (INIS)

Zhang, Yufei; Wang, Ye; Shi, Wenhui; Yang, Huiying; Yang, Jun; Huang, Wei; Dong, Xiaochen

2016-01-01

With the assistance of resorcinol–formaldehyde, MoS 2 coated hollow carbon spheres (C@MoS 2 ) were synthesized through a facile hydrothermal route followed by heat and alkali treatments. The measurements indicate that the hollow carbon spheres with an average diameter of 300 nm and shell thickness of 20 nm. And the hollow core are uniformly covered by ultrathin MoS 2 nanosheets with a length increased to 400 nm. The unique hollow structure and the synergistic effect between carbon layer and MoS 2 nanosheets significantly enhance the rate capability and electrochemical stability of C@MoS 2 spheres as anode material of lithium-ion battery. The synthesized C@MoS 2 delivered a capacity of 750 mAh g −1 at a current density of 100 mA g −1 . More importantly, the C@MoS 2 maintained a reversible capacity of 533 mAh g −1 even at a high current density of 1000 mA g −1 . The study indicated that MoS 2 coated hollow carbon spheres can be promising anode material for next generation high-performance lithium-ion batteries. (paper)

Highly scalable ZIF-based mixed-matrix hollow fiber membranes for advanced hydrocarbon separations

KAUST Repository

Zhang, Chen

2014-05-29

ZIF-8/6FDA-DAM, a proven mixed-matrix material that demonstrated remarkably enhanced C3H6/C3H8 selectivity in dense film geometry, was extended to scalable hollow fiber geometry in the current work. We successfully formed dual-layer ZIF-8/6FDA-DAM mixed-matrix hollow fiber membranes with ZIF-8 nanoparticle loading up to 30 wt % using the conventional dry-jet/wet-quench fiber spinning technique. The mixed-matrix hollow fibers showed significantly enhanced C3H6/C3H8 selectivity that was consistent with mixed-matrix dense films. Critical variables controlling successful formation of mixed-matrix hollow fiber membranes with desirable morphology and attractive transport properties were discussed. Furthermore, the effects of coating materials on selectivity recovery of partially defective fibers were investigated. To our best knowledge, this is the first article reporting successful formation of high-loading mixed-matrix hollow fiber membranes with significantly enhanced selectivity for separation of condensable olefin/paraffin mixtures. Therefore, it represents a major step in the research area of advanced mixed-matrix membranes. © 2014 American Institute of Chemical Engineers.

Monte Carlo simulation taking account of surface crack effect for stress corrosion cracking in a stainless steel SUS 304

International Nuclear Information System (INIS)

Tohgo, Keiichiro; Suzuki, Hiromitsu; Shimamura, Yoshinobu; Nakayama, Guen; Hirano, Takashi

2008-01-01

Stress corrosion cracking (SCC) in structural metal materials occurs by initiation and coalescence of micro cracks, subcritical crack propagation and multiple large crack formation or final failure under the combination of materials, stress and corrosive environment. In this paper, a Monte Carlo simulation for the process of SCC has been proposed based on the stochastic properties of micro crack initiation and fracture mechanics concept for crack coalescence and propagation. The emphasis in the model is put on the influence of semi-elliptical surface cracks. Numerical simulations are carried out based on CBB (creviced bent beam) test results of a sensitized stainless steel SUS 304 and the influence of micro crack initiation rate and coalescence condition on the simulation results is discussed. The numerical examples indicate the applicability of the present model to a prediction of the SCC behavior in real structures. (author)

Hydride effect on crack instability of Zircaloy cladding

Energy Technology Data Exchange (ETDEWEB)

Tseng, Che-Chung, E-mail: cctseng@iner.gov.tw [Institute of Nuclear Energy Research, No. 1000, Wunhua Road, Jiaan Village, Lungtan, Township, Taoyuan County 32546, Taiwan (China); Sun, Ming-Hung [Institute of Nuclear Energy Research, No. 1000, Wunhua Road, Jiaan Village, Lungtan, Township, Taoyuan County 32546, Taiwan (China); Chao, Ching-Kong [Department of Mechanical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road, Section 4, Taipei 106, Taiwan (China)

2014-04-01

Highlights: • Radial hydrides near the crack tip had a significant effect on crack propagation. • For radial hydrides off the crack line vertically, the effect on crack propagation was notably reduced. • The longer hydride platelet resulted in a remarkable effect on crack propagation. • A long split in the radial hydride precipitate would enhance crack propagation. • The presence of circumferential hydride among radial hydrides may play an important role in crack propagation. - Abstract: A methodology was proposed to investigate the effect of hydride on the crack propagation in fuel cladding. The analysis was modeled based on an outside-in crack with radial hydrides located near its crack tip. The finite element method was used in the calculation; both stress intensity factor K{sub I} and J integral were applied to evaluate the crack stability. The parameters employed in the analysis included the location of radial hydride, hydride dimensions, number of hydrides, and the presence of circumferential hydride, etc. According to our study, the effective distance between a radial hydride and the assumed cladding surface crack for the enhancement of crack propagation proved to be no greater than 0.06 mm. For a hydride not on the crack line, it would induce a relatively minor effect on crack propagation if the vertical distance was beyond 0.05 mm. However, a longer hydride precipitate as well as double radial hydrides could have a remarkable effect on crack propagation. A combined effect of radial and circumferential hydrides was also discussed.

Mixed-mode crack tip loading and crack deflection in 1D quasicrystals

Science.gov (United States)

Wang, Zhibin; Scheel, Johannes; Ricoeur, Andreas

2016-12-01

Quasicrystals (QC) are a new class of materials besides crystals and amorphous solids and have aroused much attention of researchers since they were discovered. This paper presents a generalized fracture theory including the J-integral and crack closure integrals, relations between J1, J2 and the stress intensity factors as well as the implementation of the near-tip stress and displacement solutions of 1D QC. Different crack deflection criteria, i.e. the J-integral and maximum circumferential stress criteria, are investigated for mixed-mode loading conditions accounting for phonon-phason coupling. One focus is on the influence of phason stress intensity factors on crack deflection angles.

Creep crack extension by grain-boundary cavitation

International Nuclear Information System (INIS)

Bassani, J.L.

1981-01-01

Recent work by Riedel and coworkers has led to various descriptions of stationary and moving crack tip fields under creep conditions. For stationary and growing cracks, several flow mechanisms (e.g., elastic, time-independent plastic, primary creep, and secondary creep) can dictate the analytical form of the crack tip field. In this paper, relationship between overall loading and crack velocities are modelled based upon grain-boundary cavity growth and coalescence within the zone of concentrated strain in the crack tip field. Coupled diffusion and creep growth of the cavities is considered. Overall crack extension is taken to be intermittent on a size scale equivalent to the size of a grain. Numerical results are presented for a center-cracked panel of 304 stainless steel. (author)

Study on surface adhesion of Plasma modified Polytetrafluoroethylene hollow fiber membrane

Science.gov (United States)

Chen, Jiangrong; Zhang, Huifeng; Liu, Guochang; Guo, Chungang; Lv, Jinglie; Zhangb, Yushan

2018-01-01

Polytetrafluoroethylene (PTFE) is popular membrane material because of its excellent thermal stability, chemical stability and mechanical stability. However, the low surface energy and non-sticky property of PTFE present challenges for modification. In the present study, plasma treatment was performed to improve the surface adhesion of PTFE hollow fiber membrane. The effect of discharge voltage, treatment time on the adhesion of PTFE hollow fiber membrane was symmetrically evaluated. Results showed that the plasma treatment method contributed to improve the surface activity and roughness of PTFE hollow fiber membrane, and the adhesion strength depend significantly on discharge voltage, which was beneficial to seepage pressure of PTFE hollow fiber membrane module. The adhesion strength of PTFE membrane by plasma treated at 220V for 3min reached as high as 86.2 N, far surpassing the adhesion strength 12.7 N of pristine membrane. Furthermore, improvement of content of free radical and composition analysis changes of the plasma modified PTFE membrane were investigated. The seepage pressure of PTFE membrane by plasma treated at 220V for 3min was 0.375 MPa, which means that the plasma treatment is an effective technique to improve the adhesion strength of membrane.

Surface functionalized hollow silica particles and composites

KAUST Repository

Rodionov, Valentin

2017-05-26

Composition comprising hollow spherical silica particles having outside particle walls and inside particle walls, wherein the particles have an average particle size of about 10 nm to about 500 nm and an average wall thickness of about 10 nm to about 50 nm; and wherein the particles are functionalized with at least one organic functional group on the outside particle wall, on the inside particle wall, or on both the outside and inside particle walls, wherein the organic functional group is in a reacted or unreacted form. The organic functional group can be epoxy. The particles can be mixed with polymer precursor or a polymer material such as epoxy to form a prepreg or a nanocomposite. Lightweight but strong materials can be formed. Low loadings of hollow particles can be used.

Surface functionalized hollow silica particles and composites

KAUST Repository

Rodionov, Valentin; Khanh, Vu Bao

2017-01-01

Composition comprising hollow spherical silica particles having outside particle walls and inside particle walls, wherein the particles have an average particle size of about 10 nm to about 500 nm and an average wall thickness of about 10 nm to about 50 nm; and wherein the particles are functionalized with at least one organic functional group on the outside particle wall, on the inside particle wall, or on both the outside and inside particle walls, wherein the organic functional group is in a reacted or unreacted form. The organic functional group can be epoxy. The particles can be mixed with polymer precursor or a polymer material such as epoxy to form a prepreg or a nanocomposite. Lightweight but strong materials can be formed. Low loadings of hollow particles can be used.

Low Loss and Highly Birefringent Hollow-Core Photonic Crystal Fiber

DEFF Research Database (Denmark)

Roberts, P. John; Williams, D.P.; Mangan, Brian J.

2006-01-01

A hollow-core photonic crystal fiber design is proposed which enables both low-loss and polarization-maintained signal propagation. The design relies on an arrangement of antiresonant features positioned on the glass ring that surrounds the air core.......A hollow-core photonic crystal fiber design is proposed which enables both low-loss and polarization-maintained signal propagation. The design relies on an arrangement of antiresonant features positioned on the glass ring that surrounds the air core....

All-Silica Hollow-Core Microstructured Bragg Fibers for Biosensor Application

DEFF Research Database (Denmark)

Passaro, Davide; Foroni, Matteo; Poli, Federica

2008-01-01

The possibility to exploit all-silica hollow-core-microstructured Bragg fibers to realize a biosensor useful to detect the DNA hybridization process has been investigated. A Bragg fiber recently fabricated has been considered for the analysis performed by means of a full-vector modal solver based...... layer on the inner surface of the fiber holes can modify the fundamental mode properties. The numerical analysis results have successfully demonstrated the DNA bio-sensor feasibility in hollow-core Bragg fibers....

Fabrication and characterization of functionally graded poly(vinylidine fluoride)-silver nanocomposite hollow fibers for sustainable water recovery

KAUST Repository

Francis, Lijo

2014-12-01

Poly(vinylidine fluoride) (PVDF) asymmetric hydrophobic hollow fibers were fabricated successfully using dryjet wet spinning. Hydrophobic silver nanoparticles were synthesized and impregnated into the PVDF polymer matrix and functionally graded PVDF-silver nanocomposite hollow fibers are fabricated and tested in the direct contact membrane distillation (DCMD) process. The as-synthesized silver nanoparticles were characterized for Transmission Electron Microscopy (TEM), particle size distribution (PSD) and Ultra Violet (UV) visible spectroscopy. Both the PVDF and PVDF-silver nanocomposite asymmetric hollow fibers were characterized for their morphology, water contact angle and mechanical strength. Addition of hydrophobic silver nanoparticles was found to enhance the hydrophobicity and ~ 2.5 fold increase the mechanical strength of the hollow fibers. A water vapor flux of 31.9kg m-2 h-1 was observed at a feed inlet temperature of 80 °C and at a permeate temperature of 20 °C in the case of hollow fiber membrane modules fabricated using PVDF hollow fibers; the water vapor flux was found to be increased by about 8% and to reach 34.6kg m-2 h-1 for the hollow fiber membrane modules fabricated from the PVDF-silver nanocomposite hollow fibers at the same operating conditions with 99.99% salt rejection.

Management of maxillectomy defect with a hybrid hollow bulb obturator

Science.gov (United States)

Singh, Kamleshwar; Singh, Saumyendra V; Mishra, Niraj; Agrawal, Kaushal Kishor

2013-01-01

A woman having already undergone maxillectomy came to the department complaining of difficulty in eating and speech. During the construction of an obturator, the bulb area should be hollowed to reduce weight so that the teeth and supporting tissues are not stressed unnecessarily. The conventional open design drains fluid from the adjacent mucosa, possibly increasing the weight of the prosthesis, and is difficult to clean. The closed bulb design does not drain secretions and may cause obstruction and susceptibility to infection in the paranasal and pharyngeal regions, though it is easier to maintain. An alternative to the two designs, combining their advantages, is presented in this report. As the open hollow part of the obturator was shallow, it was easy to clean. Making the inferior part of the bulb hollow and closed led to a reduction in the overall weight of the prosthesis while increasing its resonance. PMID:23436886

Burst Pressure Prediction of Multiple Cracks in Pipelines

International Nuclear Information System (INIS)

Razak, N A; Alang, N A; Murad, M A

2013-01-01

Available industrial code such as ASME B1G, modified ASME B1G and DNV RP-F101 to assess pipeline defects appear more conservative for multiple crack like- defects than single crack-like defects. Thus, this paper presents burst pressure prediction of pipe with multiple cracks like defects. A finite element model was developed and the burst pressure prediction was compared with the available code. The model was used to investigate the effect of the distance between the cracks and the crack length. The coalescence diagram was also developed to evaluate the burst pressure of the multiple cracks. It was found as the distance between crack increases, the interaction effect comes to fade away and multiple cracks behave like two independent single cracks

Fatigue crack layer propagation in silicon-iron

Science.gov (United States)

Birol, Y.; Welsch, G.; Chudnovsky, A.

1986-01-01

Fatigue crack propagation in metal is almost always accompanied by plastic deformation unless conditions strongly favor brittle fracture. The analysis of the plastic zone is crucial to the understanding of crack propagation behavior as it governs the crack growth kinetics. This research was undertaken to study the fatigue crack propagation in a silicon iron alloy. Kinetic and plasticity aspects of fatigue crack propagation in the alloy were obtained, including the characterization of damage evolution.

Template free fabrication of hollow hematite spheres via a one-pot polyoxometalate-assisted hydrolysis process

International Nuclear Information System (INIS)

Mao Baodong; Kang Zhenhui; Wang Enbo; Tian Chungui; Zhang Zhiming; Wang Chunlei; Song Yanli; Li Meiye

2007-01-01

Uniform hollow hematite (α-Fe 2 O 3 ) spheres with diameter of about 600-700 nm and shell thickness lower than 100 nm are obtained by direct hydrothermal treatment of dilute FeCl 3 and tungstophosphoric acid H 3 PW 12 O 40 solution at 180 deg. C. The hollow spheres are composed of robust shells with small nanoparticles standing out of the surface and present a high-surface area and a weak ferromagnetic behavior at room temperature. The effect of concentration of H 3 PW 12 O 40 , reaction time and temperature for the formation of the hollow spheres are investigated in series of experiments. The formation of the hollow spheres may be ascribed to a polyoxometalte-assisted forced hydrolysis and dissolution process. - Graphical abstract: Uniform hollow hematite (α-Fe 2 O 3 ) spheres with diameter of about 600-700 nm and shell thickness lower than 100 nm are obtained by direct hydrothermal treatment of dilute FeCl 3 and tungstophosphoric acid H 3 PW 12 O 40 solution at 180 deg. C. The hollow spheres present a high surface area and weak ferromagnetic behavior at room temperature

Formation and characterization of magnetic barium ferrite hollow fibers with low coercivity via co-electrospun

Energy Technology Data Exchange (ETDEWEB)

Liu, Gui-fang, E-mail: guifang777@163.com; Zhang, Zi-dong, E-mail: 1986zzd@163.com; Dang, Feng, E-mail: dangfeng@sdu.edu.cn; Cheng, Chuan-bing, E-mail: 807033063@qq.com; Hou, Chuan-xin, E-mail: 710313782@qq.com; Liu, Si-da, E-mail: superliustar@hotmail.com

2016-08-15

BaFe{sub 12}O{sub 19} fibers and hollow fibers were successfully prepared by electrospun and co-electrospun. A very interesting result appeared in this study that hollow fibers made by co-electrospun showed low coercivity values of a few hundred oersteds, compared with the coercivity values of more than thousand oersteds for the fibers made by electrospun. So the hollow fibers with high saturation magnetization (M{sub s}) and while comparatively low coercivity (H{sub c}) exhibited strong magnetism and basically showed soft character. And this character for hollow fibers will lead to increase of the permeability for the samples which is favorable for impedance matching in microwave absorption. So these hollow fibers are promised to have use in a number of applications, such as switching and sensing applications, electromagnetic materials, microwave absorber. - Highlights: • BaFe{sub 12}O{sub 19} fibers were prepared via electrospinning successfully. • The coercivity has a value of a few hundred oersteds for the hollow fibers made by coaxial electrospun. • BaFe{sub 12}O{sub 19} with high saturation magnetization and low coercivity shows great potential in microwave absorbing application.

Causes of Early-Age Thermal Cracking of Concrete Foundation Slabs and their Reinforcement to Control the Cracking

Science.gov (United States)

Bilčík, Juraj; Sonnenschein, Róbert; Gažovičová, Natália

2017-09-01

This paper focuses on the causes and consequences of early-age cracking of mass concrete foundation slabs due to restrained volume changes. Considering the importance of water leaking through cracks in terms of the serviceability, durability and environmental impact of watertight concrete structures, emphasis is placed on the effect of temperature loads on foundation slabs. Foundation slabs are usually restrained to some degree externally or internally. To evaluate the effect of external restraints on foundation slabs, friction and interaction models are introduced. The reinforcement of concrete cannot prevent the initiation of cracking, but when cracking has occurred, it may act to reduce the spacing and width of cracks. According to EN 1992-1-1, results of calculating crack widths with local variations included in National Annexes (NAs) vary considerably. A comparison of the required reinforcement areas according to different NAs is presented.

Near-IR imaging of cracks in teeth

Science.gov (United States)

Fried, William A.; Simon, Jacob C.; Lucas, Seth; Chan, Kenneth H.; Darling, Cynthia L.; Staninec, Michal; Fried, Daniel

2014-02-01

Dental enamel is highly transparent at near-IR wavelengths and several studies have shown that these wavelengths are well suited for optical transillumination for the detection and imaging of tooth decay. We hypothesize that these wavelengths are also well suited for imaging cracks in teeth. Extracted teeth with suspected cracks were imaged at several wavelengths in the near-IR from 1300-1700-nm. Extracted teeth were also examined with optical coherence tomography to confirm the existence of suspected cracks. Several teeth of volunteers were also imaged in vivo at 1300-nm to demonstrate clinical potential. In addition we induced cracks in teeth using a carbon dioxide laser and imaged crack formation and propagation in real time using near-IR transillumination. Cracks were clearly visible using near-IR imaging at 1300-nm in both in vitro and in vivo images. Cracks and fractures also interfered with light propagation in the tooth aiding in crack identification and assessment of depth and severity.

On multiple crack detection in beam structures

Energy Technology Data Exchange (ETDEWEB)

Moradi, Shapour; Kargozarfard, Mohammad [Shahid Chamran University, Ahvaz (Iran, Islamic Republic of)