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Sample records for autogenous shrinkage cracking

  1. Mitigation strategies for autogenous shrinkage cracking

    DEFF Research Database (Denmark)

    Bentz, Dale P.; Jensen, Ole Mejlhede

    2004-01-01

    As the use of high-performance concrete has increased, problems with early-age cracking have become prominent. The reduction in water-to-cement ratio, the incorporation of silica fume, and the increase in binder content of high-performance concretes all contribute to this problem. In this paper, ...

  2. Cracking in cement paste induced by autogenous shrinkage

    DEFF Research Database (Denmark)

    Lura, Pietro; Jensen, Ole Mejlhede; Weiss, Jason

    2009-01-01

    technique allows identification of microcracks while avoiding artefacts induced by unwanted restraint, drying, or temperature variations during sample preparation. Small cylindrical samples of cement paste are cast with steel rods of different diameters in their centre. The rods restrain the autogenous...

  3. Autogenous Shrinkage of High Strength Lightweight Aggregate Concrete

    Institute of Scientific and Technical Information of China (English)

    DING Qingjun; TIAN Yaogang; WANG Fazhou; ZHANG Feng; HU Shuguang

    2005-01-01

    The characteristic of autogenous shrinkage ( AS ) and its effect on high strength lightweight aggregate concrete (HSLAC) were studied. The experimental results show that the main shrinkage of high strength concrete is AS and the amount of cement can affect the AS of HSLAC remarkably. At the early stage the AS of HSLAC is lower than that of high strength normal concrete, but it has a large growth at the later stage. The AS of high strength normal concrete becomes stable at 90d age, but HSLAC still has a high AS growth. It is found that adjusting the volume rate of lightweight aggregate, mixing with a proper dosage of fly ash and raising the water saturation degree of lightweight aggregate can markedly reduce the AS rate of HSLAC.

  4. Autogenous shrinkage in high-performance cement paste: An evaluation of basic mechanisms

    DEFF Research Database (Denmark)

    Lura, Pietro; Jensen, Ole Mejlhede; van Breugel, Klaas

    2003-01-01

    In this paper, various mechanisms Suggested to cause autogenous shrinkage are presented. The mechanisms are evaluated from the point of view of their soundness and applicability to quantitative modeling of autogenous shrinkage. The capillary tension approach is advantageous, because it has a soun...

  5. Experimental Research on the Autogenous Shrinkage of MK High Performance Concrete

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Calcine and mill kaolin were used under agreeable technological conditions to generate matakaolin (MK). The autogenous shrinkage performance of high performance concrete added with MK was researched. It is shown that MK has an effective inhibitory action to early autogenous shrinkage of cement concrete, and the inhibitory action increases with the increase of MK. The autogenous shrinkage values from 24 hours after placement to 56 days are all higher than those of the contrasted concrete, among which, the value of the concrete with 5% MK is the highest. But the total shrinkage values in 56 days are all less than those of the contrasted test pieces. The total contraction after 24 h of placement decreases as the increase of MK, moreover,it is greatly less than that of the contrasted ones.

  6. Modeling and analyzing autogenous shrinkage of hardening cement paste

    NARCIS (Netherlands)

    Lu, T.; Koenders, E.A.B.

    2014-01-01

    In this paper, a conceptual model for analyzing the plastic part of autogenous deformation of cement paste based on the Arrhenius rate theory will be presented. The autogenous deformation will be calculated from the elastic deformations with inclusion of creep. Different kinds of cement paste with a

  7. Autogeneous healing and chloride ingress in cracked concrete

    NARCIS (Netherlands)

    Savija, B.; Schlangen, E.

    2016-01-01

    An experimental study of the influence of autogeneous healing on chloride ingress in cracked concrete is presented. In the study, two concrete mixtures (a Portland cement mix and a blast furnace slag mix), two healing regimes (submerged and fog room regime), two cracking ages (14 and 28 days), and m

  8. Autogenous shrinkage of Ducorit S5R ASTM C 1698-09 test method

    DEFF Research Database (Denmark)

    Damkilde, Lars

    The report deals with experimental measurement of autogenous shrinkage of Ducorit S5R according to the test method ASTM C 1698-09. This test method measures the bulk strain of a sealed cementitious specimen, at constant temperature and not subjected to external forces, from the time of final...

  9. Influence of Shrinkage-Reducing Admixtures on the Development of Plastic Shrinkage Cracks

    DEFF Research Database (Denmark)

    Lura, Pietro; Pease, Bradley Justin; Mazzotta, Guy;

    2007-01-01

    settlement of the concrete and tensile stress development in the surface of the concrete, which increase the potential for development of plastic shrinkage cracks. Specifically, this paper studies the development of plastic shrinkage cracks in mortars containing a commercially available shrinkage......-reducing admixture (SRA). Mortars containing SRA show fewer and narrower plastic shrinkage cracks than plain mortars when exposed to the same environmental conditions. It is proposed that the lower surface tension of the pore fluid in the mortars containing SRA results in less evaporation, reduced settlement......, reduced capillary tension, and lower crack-inducing stresses at the topmost layer of the mortar....

  10. The influence of superabsorbent polymers on the autogenous shrinkage properties of cement pastes with supplementary cementitious materials

    DEFF Research Database (Denmark)

    Snoeck, D.; Jensen, Ole Mejlhede; De Belie, N.

    2015-01-01

    Fly ash and blast-furnace slag containing binders are frequently used in the construction industry and it is important to know the extent of autogenous shrinkage and its (ideal) mitigation by superabsorbent polymers in these systems as a function of their age. In this paper, the autogenous shrink...

  11. Self-healing of drying shrinkage cracks in cement-based materials incorporating reactive MgO

    Science.gov (United States)

    Qureshi, T. S.; Al-Tabbaa, A.

    2016-08-01

    Excessive drying shrinkage is one of the major issues of concern for longevity and reduced strength performance of concrete structures. It can cause the formation of cracks in the concrete. This research aims to improve the autogenous self-healing capacity of traditional Portland cement (PC) systems, adding expansive minerals such as reactive magnesium oxide (MgO) in terms of drying shrinkage crack healing. Two different reactive grades (high ‘N50’and moderately high ‘92-200’) of MgO were added with PC. Cracks were induced in the samples with restraining end prisms through natural drying shrinkage over 28 days after casting. Samples were then cured under water for 28 and 56 days, and self-healing capacity was investigated in terms of mechanical strength recovery, crack sealing efficiency and improvement in durability. Finally, microstructures of the healing materials were investigated using FT-IR, XRD, and SEM-EDX. Overall N50 mixes show higher expansion and drying shrinkage compared to 92-200 mixes. Autogenous self-healing performance of the MgO containing samples were much higher compared to control (only PC) mixes. Cracks up to 500 μm were sealed in most MgO containing samples after 28 days. In the microstructural investigations, highly expansive Mg-rich hydro-carbonate bridges were found along with traditional calcium-based, self-healing compounds (calcite, portlandite, calcium silicate hydrates and ettringite).

  12. Autogenous shrinkage prediction on high-performance concrete of fly ash based on BP neural network

    Science.gov (United States)

    Wang, Baomin; Zhang, Wenping; Wang, Lijiu

    2006-11-01

    The article adopts test data of neural network for autogenous shrinkage to train and predict on the data which doesn't join training. The article's prediction is on the basis of common medium sand, 5-31.5mm limestone rubble, second class fly-ash, P.O42.5 silicate cement, considering factors include five ones such as ratio of water and cement, sand rate, content of cement, content of fly ash, etc.By adjusting various parameters of neural network structure, it obtains three optimized results of neural network simulation. The error between concrete autogtenous shrinkage value of neural network prediction and trial value is within 3%, which can meet requirement of the concrete engineering.

  13. Measurement with corrugated tubes of early-age autogenous shrinkage of cement-based material

    DEFF Research Database (Denmark)

    Tian, Qian; Jensen, Ole Mejlhede

    2009-01-01

    The use of a special corrugated mould enables transformation of volume strain into horizontal, linear strain measurement in the fluid stage. This allows continuous measurement of the autogenous shrinkage of cement-based materials since casting, and also effectively eliminates unwanted influence...... on the measuring results from gravity, temperature variation and mould restraint. In this paper the principle of the corrugated tube measurement is described. A systematic study was carried out on the influence on the measuring results of the material properties, size effects and encapsulated air in the corrugated...... tube. The experimental results show that there is a minor influence on the measuring results of the stiffness and size of the plastic tube as well as of the encapsulated air. However, the influence decreases with the hardening process and becomes negligible a few hours after final set....

  14. Plastic and free shrinkages cracking of blended white cement concrete

    Energy Technology Data Exchange (ETDEWEB)

    Rashad, A.M.; White, T.; Ariaratnam, S.; Knutson, K. [Housing and Building National Research Center, Cairo (Egypt)

    2007-07-01

    This paper presented the results of a study that investigated the plastic and free shrinkages of white portland cement concrete, concrete incorporating silica fume (SF) and concrete incorporating metakaolin (MK) compared to regular plain gray portland cement concrete. An experimental program was designed to investigate the plastic and free shrinkage of concrete containing gray and white blended cement. The paper discussed the experimental details including materials and cement types such as SF, MK, aggregate, and superplasticizer as well as concrete mixtures and specimen preparation including mixture proportions, preparation and curing of concrete specimens, and test specimens. It also presented the determination of concrete properties such as slump of fresh concrete, plastic shrinkage, and dry shrinkage. Test results and discussion of results were also provided. It was concluded that plain white portland cement concrete showed less number of plastic cracks but slightly higher average crack width compared to other concrete mixtures with MK or SF. In addition, free shrinkage behavior of plain white cement and plain gray cement matrix was comparable. 23 refs.

  15. High-performance binders with reduced autogenous shrinkage on the basis of fine cement

    Energy Technology Data Exchange (ETDEWEB)

    Martschuk, V. [Inst. of the Cement Industry, Dusseldorf (Germany)

    2001-07-01

    A study on the hydration of portland cement was presented. The paper presented special features of the chemical shrinkage of cement paste at high and low water-cement ratios. It also described the effect of silica fume on the deformation behaviour of cement paste, as well as on the behaviour of hardened binder paste at water-binder ratios of 0.40 and 0.25. High performance concrete has a high density and a tendency to chemically shrink because of its low water-cement ratio. The study showed that the autogenous shrinkage increases if silica fume is added. Theoretical calculations were performed and showed that the typical addition of silica fume results in an increase in total porosity, and therefore, to the deterioration of the packing density of the binder mixture. The specific surface area of the dry powder is also increased. It was concluded that replacing cement by optimized fine cements improves the theoretical packing density in binders. The hardened cement paste studies showed that this makes a cement that is denser with less tendency to shrink. 7 refs., 3 tabs., 8 figs.

  16. Role of ferrite and phosphorus plus sulphur in the crack sensitivity of autogenously welded type 309 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Lambert, Jr., F. J.

    1976-07-01

    A study on autogenous welding of Type 309 thin stainless steel sheet was made after experiencing cracking difficulties on several commercial heats. A relationship exists between the sum of the phosphorus plus sulfur, the ferrite control of the weld metal, and the crack sensitivity of autogenously made welds. A new simple weld test for thin-gage sheet is utilized for studying the susceptibility to cracking. A chemistry modification is suggested to alleviate possible weld cracking when autogenously welding this grade. The principles of crack sensitivity prediction could apply to other austenitic stainless steel types where chemistry limits are such that ferrite is possible.

  17. Parametric Assessment of Stress Development and Cracking in Internally Cured Restrained Mortars Experiencing Autogenous Deformations and Thermal Loading

    Directory of Open Access Journals (Sweden)

    Kambiz Raoufi

    2011-01-01

    Full Text Available A finite element model is used to examine how the properties of cementitious mortar are related to the stress development in the dual ring test. The results of this investigation are used to explain the thermal cracking behavior of mixtures containing prewetted lightweight aggregates (LWA by quantifying the contribution of several material properties individually. In addition to the beneficial effects of using the LWA as an internal curing agent to reduce the autogenous shrinkage of concrete, the LWA also helps to reduce the potential for thermal cracking due to a lower elastic modulus and increased stress relaxation. The rate of stress development, age of cracking, and magnitude of the temperature drop necessary to induce cracking in a dual ring specimen are dependent on a variety of factors, including the coefficient of thermal expansion of both the cementitious mortar and the restraining rings, elastic modulus of the mortar, creep effect of the mortar, and rate of thermal loading. Depending on the rate of cooling, cracking may or may not occur. The slowest rate of cooling (2.5∘C/h minimizes the effects of creep while cooling rates faster than 8∘C/h can produce a thermal gradient through the mortar cross-section that needs to be considered.

  18. Hydration Process and Crack Tendency of Concrete Based on Resistivity and Restrained Shrinkage Crack

    Institute of Scientific and Technical Information of China (English)

    MUAZU Bawa Samaila; WEI Xiaosheng; WANG Lei

    2016-01-01

    Hydration process, crack potential and setting time of concrete grade C30, C40 and C50 were monitored by using a non-contact electrical resistivity apparatus, a novel plastic ring mould and penetration resistance methods, respectively. The results show the highest resistivity of C30 at the early stage until a point when C50 accelerated and overtook the others. It has been experimentally conifrmed that the crossing point of C30 and C50 corresponds to the ifnal setting time of C50. From resistivity derivative curve, four different stages were observed upon which the hydration process is classiifed; these are dissolution, induction, acceleration and deceleration periods. Consequently, restrained shrinkage crack and setting time results demonstrated that C50 set and cracked the earliest. The cracking time of all the samples occurred within a reasonable experimental period thus the novel plastic ring is a convenient method for predicting concrete’s crack potential. The highest inlfection time (ti) obtained from resistivity curve and the ifnal setting time (tf) were used with crack time (tc) in coming up with mathematical models for the prediction of concrete’s cracking age for the range of concrete grade considered. Finally, an ANSYS numerical simulation supports the experimental ifndings in terms of the earliest crack age of C50 and the crack location.

  19. Shrinkage and cracking behavior of high performance concretes containing chemical admixtures

    Institute of Scientific and Technical Information of China (English)

    亓萌; 李宗津; 马保国

    2002-01-01

    Modern concretes often incorporate several chemical admixtures to alter the properties of fresh or hardened concrete. In this work, the influences of three types of chemical admixtures, calcium nitrite inhibitor (CNI), retarder (D-17) and superplasticizer (W-19) on free shrinkage and restrained shrinkage cracking of high performance concrete were experimentally investigated. The test results showed that, with the same water to binder ratio (0.4), mixtures containing D-17 of 0.25 percent or higher ratio of W-19 (2.76 percent) all exhibited a reduction in free shrinkage and shrinkage cracking width. However, the incorporations of various ratios of CNI into mixtures led to an increase in free shrinkage and shrinkage cracking width as compared to control mixture. In order to study the influence of CNI, the microstructure of concrete mixture containing CNI were investigated by Mercury Intrusion Porosimetry as well as Scanning Electronic Microscopy(SEM) technique.

  20. Crack development through plastic shrinkage in fresh concretes and mortars

    Directory of Open Access Journals (Sweden)

    Aguanell García, M.

    1989-09-01

    Full Text Available The rate of water evaporation in the exposed surfaces plays an important part in the development of cracks in fresh concretes and mortars before hardening is completed. This rate of evaporation depends on the drying power of the wind sweeping such surfaces as a function of the relative humidity, temperature and speed of the air. After many studies and research work on the subject of plastic cracking, the following axiom has been established: "Plastic shrinkage and cracking of concrete surfaces take place when water evaporates from the surface quicker than it can be replaced through exudation". Once the value of weather parameters are known, the extent of the risk of crack development can be known and preventive steps taken to overcome such risk. Obviously, such steps are all oriented to reducing or stopping evaporation and go from covering surfaces with wet sackcloth or plastic foil, through sprinkling water mists or lowering the concrete temperature, to using film-forming curing products. Another additional measure can be the addition of polypropelene fibers to the concrete while in the mixer, at the rate of 0.9 kg fiber to 1 m3 of concrete.

    En la formación de grietas en morteros y hormigones frescos, antes de finalizar el fraguado, tiene una primordial importancia la velocidad de evaporación del agua de las superficies expuestas al exterior, velocidad que depende del poder desecante de los vientos que barren estas superficies y que está en función de la humedad relativa del aire, de su temperatura y de su velocidad. Después de los múltiples estudios e investigaciones sobre este tema de la formación de las grietas plásticas, se ha llegado a establecer el siguiente axioma: "La retracción plástica y las grietas se producen, en las superficies del hormigón, cuando el agua se evapora de ellas más rápidamente que la que puede ser reemplazada por exudación." Conociendo el valor de los parámetros meteorol

  1. Effect of Pre-wetted Light-weight Aggregate on Internal Relative Humidity and Autogenous Shrinkage of Concrete

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This research indicates that the gradient of internal relative humidity (IRH) decreases rapidly within 7-day curing age in HPC.The amount of water imported by pre-wetted light-weight aggregate can regulate IRH of concrete.By importing a proper amount of water, the process of the decline of IRH can be delayed and the antogenous shrinkage can be reduced.The relationship among the amount of water imported by pre- wetted lightweight aggregate, IRH and AS was established.The result provides a new method of reducing early AS and enhancing early cracking resistance of HPC.

  2. An integrated approach to soil structure, shrinkage, and cracking in samples and layers

    CERN Document Server

    Chertkov, V Y

    2014-01-01

    A recent model showed how a clay shrinkage curve is step-by-step transformed into the shrinkage curve of an aggregated soil at any clay content if it is measured on samples so small that cracks do not occur at shrinkage. Such a shrinkage curve was called a reference curve. The present work generalizes this model to any soil sample size or layer thickness, i.e., to any crack contribution to the shrinkage curve. The approach is based on: (i) recently suggested features of an intra-aggregate structure; (ii) detailed accounting for the contributions to the soil volume and water content during shrinkage; and (iii) new concepts of lacunar factor, crack factor, and critical sample size. The following input parameters are needed for the prediction: (i) all parameters determining the basic dependence of the reference shrinkage curve; (ii) parameters determining the critical sample size (structural porosity and minimum and maximum aggregate size at maximum swelling); and (iii) initial sample size or layer thickness. A ...

  3. Influence of Superplasticizers on Strength and Shrinkage Cracking of Cement Mortar under Drying Conditions

    Institute of Scientific and Technical Information of China (English)

    MA Baoguo; WANG Xin'gang; LI Xiangguo; YANG Lei

    2007-01-01

    The effects of polynaphthalene series superplasticizers(PNS) with a low content of sodium sulfate (H-UNF),with a high content of sodium sulfate(C-UNF) and polycarboxylate type superplasticizer (PC) on strength and shrinkage cracking of cement mortar under drying conditions were investigated by means of multi-channel ellipse ring shrinkage cracking test, free shrinkage and strength test. The general effect of PNS and PC is to increase the initial cracking time of mortars, and decrease the cracking sensitivity of mortars. As for decreasing the cracking sensitivity of mortars, PC>H-UNF>C-UNF. To incorporate superplasticizers is apparently to increase the free shrinkage of mortars when keeping the constant w/b ratio and the content of cement pastes. As for the effect of controlling the volume stability of mortars, PC>C-UNF>H-UNF. Maximum crack width of mortars containing PC is lower, but the development rate of maximum crack width of mortars containing H-UNF is faster in comparison with control mortars. The flexural and compressive strengths of mortars at 28-day increase with increasing superplasticizer dosages under drying conditions. PC was superior to PNS in the aspect of increasing strength.

  4. Development of high shrinkage polyethylene terephthalate (PET) shape memory polymer tendons for concrete crack closure

    Science.gov (United States)

    Teall, Oliver; Pilegis, Martins; Sweeney, John; Gough, Tim; Thompson, Glen; Jefferson, Anthony; Lark, Robert; Gardner, Diane

    2017-04-01

    The shrinkage force exerted by restrained shape memory polymers (SMPs) can potentially be used to close cracks in structural concrete. This paper describes the physical processing and experimental work undertaken to develop high shrinkage die-drawn polyethylene terephthalate (PET) SMP tendons for use within a crack closure system. The extrusion and die-drawing procedure used to manufacture a series of PET tendon samples is described. The results from a set of restrained shrinkage tests, undertaken at differing activation temperatures, are also presented along with the mechanical properties of the most promising samples. The stress developed within the tendons is found to be related to the activation temperature, the cross-sectional area and to the draw rate used during manufacture. Comparisons with commercially-available PET strip samples used in previous research are made, demonstrating an increase in restrained shrinkage stress by a factor of two for manufactured PET filament samples.

  5. Can superabsorent polymers mitigate autogenous shrinkage of internally cured concrete without compromising the strength?

    DEFF Research Database (Denmark)

    Hasholt, Marianne Tange; Jensen, Ole Mejlhede; Kovler, Konstantin

    2012-01-01

    The paper “Super absorbing polymers as an internal curing agent for mitigation of early-age cracking of high-performance concrete bridge decks” deals with different aspects of using superabsorbent polymers (SAP) in concrete to mitigate self-desiccation. The paper concludes that “Addition of SAP...

  6. Assessment and prediction of drying shrinkage cracking in bonded mortar overlays

    Energy Technology Data Exchange (ETDEWEB)

    Beushausen, Hans, E-mail: hans.beushausen@uct.ac.za; Chilwesa, Masuzyo

    2013-11-15

    Restrained drying shrinkage cracking was investigated on composite beams consisting of substrate concrete and bonded mortar overlays, and compared to the performance of the same mortars when subjected to the ring test. Stress development and cracking in the composite specimens were analytically modeled and predicted based on the measurement of relevant time-dependent material properties such as drying shrinkage, elastic modulus, tensile relaxation and tensile strength. Overlay cracking in the composite beams could be very well predicted with the analytical model. The ring test provided a useful qualitative comparison of the cracking performance of the mortars. The duration of curing was found to only have a minor influence on crack development. This was ascribed to the fact that prolonged curing has a beneficial effect on tensile strength at the onset of stress development, but is in the same time not beneficial to the values of tensile relaxation and elastic modulus. -- Highlights: •Parameter study on material characteristics influencing overlay cracking. •Analytical model gives good quantitative indication of overlay cracking. •Ring test presents good qualitative indication of overlay cracking. •Curing duration has little effect on overlay cracking.

  7. Restrained shrinkage cracking in fiber reinforced concrete: A novel test technique

    Energy Technology Data Exchange (ETDEWEB)

    Banthia, N.; Yan, C.; Mindess, S. [Univ. of British Columbia, Vancouver, British Columbia (Canada). Dept. of Civil Engineering

    1996-01-01

    A novel experimental technique was developed to assess the cracking potential of cement-based materials when used as a bonded overlay. Specimens were cast directly on to a substrate and the assembly was subjected to a drying environment to induce cracking. Lengths and widths of the resulting cracks in the overlay were monitored as a function of time. The use of fibers was found to be very effective not only in reducing the widths of the shrinkage cracks but also in allowing multiple cracking to occur. Interestingly, these two phenomena occurred only up to a fiber volume fraction of 0.5%; at 1% by volume of fibers, only minimal cracking was seen to occur even under a particularly severe environment.

  8. Thermodynamics of Autogenous Self-healing in Cementitious Materials

    NARCIS (Netherlands)

    Huang, H.

    2014-01-01

    Concrete is a brittle composite cementitious material that easily fractures under tensile loading. Microcracks can appear throughout the concrete prior to application of any load because of temperature-induced strain and autogenous and drying shrinkage. There is no doubt that these cracks provide pr

  9. Surface Modification of Fly Ashes with Carbide Slag and Its Effect on Compressive Strength and Autogenous Shrinkage of Blended Cement Pastes

    Institute of Scientific and Technical Information of China (English)

    HAO Chengwei; DENG Min; MO Liwu; LIU Kaiwei

    2012-01-01

    Surfaces of grade Ⅲ fly ashes were modified through mixing with carbide slag and calcining at 850 ℃ for 1 h.Mineralogical compositions and surface morphology of fly ashes before and after modification were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM),respectively.Effect of surface-modified fly ashes on compressive strength and autogenous shrinkage of blended cement pastes was investigated.Microstructures of cement pastes were examined by backscattered electron (BSE) imaging and mercury intrusion porosimetry (MIP).The experimental results showed that β-C2S was formed on the surfaces of fly ashes after modification.Hydration of β-C2S on the surface-modified fly ashes densified interface zone and enhanced bond strength between particles of fly ashes and hydrated clinkers.In addition,surface modification of fly ashes tended to decrease total porosity and 10-50 nm pores of cement pastes.Surface modification of fly ashes increased compressive strength and reduced autogenous shrinkage of cement pastes.

  10. Influence of Fly Ash and Slag Powder on Autogenous Shrinkage of Cement Mortars%粉煤灰和矿粉对水泥胶砂自收缩的影响

    Institute of Scientific and Technical Information of China (English)

    肖佳; 陈雷; 邢昊

    2011-01-01

    试验研究了粉煤灰和矿粉对水泥胶砂自收缩的影响.结果表明:当胶砂比(质量比)为1∶0.5,水胶比(质量比)为0.3时,随水化龄期延长,水泥胶砂自收缩增大,早期自收缩发展急剧.粉煤灰降低了水泥胶砂的自收缩,随着粉煤灰掺量(质量分数)增大,水泥胶砂自收缩减小;掺10%和20%粉煤灰水泥胶砂的21d自收缩较纯水泥胶砂分别下降了21.1%和29.5%.水化早期(5d前),矿粉掺量(质量分数)在10%~20%时,随着矿粉掺量增大,水泥胶砂自收缩降低;掺10%和20%矿粉水泥胶砂的21 d自收缩较纯水泥胶砂分别增加了11.1%和6.6%.%The influence of fly ash and slag powder on the autogenous shrinkage of cement mortars was studied. The experiment test results indicate that the autogenous shrinkage of cement mortar made with 1:0. 5 binder to sand ratio(by mass) and 0. 3 water to binder ratio(by mass) increases with development of hydration. At early age, rate of autogenous shrinkage develops sharply. Addition of fly ash reduces the autogenous shrinkage of cement mortar, and the autogenous shrinkage of cement mortar decreases with increase of fly ash content(by mass). Compared to pure cement mortar, after hydrated for 21 d , the 10% and 20% of fly ash addition reduce autogenous shrinkage of cement mortar by 21. 1% and 29. 5% respectively. Originally within 5 d, the 10%- 20% (by mass) of slag powder addition decreases autogenous shrinkage of cement mortar. Compared to pure cement mortar, after hydrated for 21 d, the 10% and 20% of slag powder addition increase autogenous shrinkage of cement mortar by 11. 1% and 6. 6% respectively.

  11. Shrinkage and Cracking Sensitivity of Cement Mortar Containing Fly Ash, Granulated Blast-furnace Slag and Silica Fume

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A laboratory study was undertaken to investigate drying shrinkage and cracking sensitivity subjected to restrained shrinkage of mortar containing fly ash (FA), granulated blast-furnace slag (GBFS) and silica fume (SF). Six mortar mixtures including control Portland cement (PC) and FA,GBFS and SF mortar mixtures were prepared. FA replaced the cement on mass basis at the replacement ratios of 20% and 35%, GBFS replaced the cement at the replacement ratios of 40%, SF replaced the cement at the replacement ratios of 8% and the blended mixtures with 20% FA, 20% GBFS and 8% SF. Water-cementitious materials ratio and sand-cementitious materials ratio were 0.4 and 2.0 for all mixtures, respectively. The mixtures were cured at 65% relative humidity and 20℃. The drying shrinkage value, initial cracking time and cracking width of the mortar samples were measured. The results show that all the mortar mixture containing FA exhibited the decrease of drying shrinkage.Moreover, initial cracking time was markedly delayed, and the crack width of the initial crack was reduced. However, the incorporations of various ratios of GBFS and SF led to an increase of drying shrinkage, initial cracking time and cracking width as compared to control mixture.

  12. Development and construction of low-cracking high-performance concrete (LC-HPC) bridge decks: Free shrinkage tests, restrained ring tests, construction experience, and crack survey results

    Science.gov (United States)

    Yuan, Jiqiu

    2011-12-01

    The development, construction, and evaluation of low-cracking high-performance concrete (LC-HPC) bridge decks are described based on laboratory test results and experiences gained during the construction of 13 LC-HPC bridge decks in Kansas, along with another deck bid under the LC-HPC specifications but for which the owner did not enforce the specification. This study is divided into four parts covering (1) an evaluation of the free shrinkage properties of LC-HPC candidate mixtures, (2) an investigation of the relationship between the evaporable water content in the cement paste and the free shrinkage of concrete, (3) a study of the restrained shrinkage performance of concrete using restrained ring tests, and (4) a description of the construction and preliminary evaluation of LC-HPC and control bridge decks constructed in Kansas. The first portion of the study involves evaluating the effects of the duration of curing, fly ash, and a shrinkage reducing admixture (SRA) on the free-shrinkage characteristics of concrete mixtures. The results indicate that an increase of curing period reduces free shrinkage. With 7 days of curing, concretes containing fly ash as a partial replacement for cement exhibit higher free shrinkage than concretes with 100% portland cement. When the curing period is increased to 14, 28, and 56 days, the adverse effect of adding fly ash on free shrinkage is minimized and finally reversed. The addition of an SRA significantly reduces free shrinkage for both the 100% portland cement mixture and the mixture containing fly ash. The second portion of the study investigates the relationship between the evaporable water content in the cement paste and the free shrinkage of concrete. A linear relationship between free shrinkage and evaporable water content in the cement paste is observed. For a given mixture, specimens cured for a longer period contain less evaporable water and exhibit lower free shrinkage and less weight loss in the free shrinkage

  13. Syneresis cracks: subaqueous shrinkage in argillaceous sediments caused by earthquake-induced dewatering

    Science.gov (United States)

    Pratt, Brian R.

    1998-04-01

    Syneresis cracks, often confused with subaerial desiccation phenomena, are traditionally ascribed to subaqueous shrinkage whereby salinity changes caused deflocculation of clay. This and other previously proposed mechanisms fail to account for their occurrence in low-energy, typically non-evaporitic facies, stratigraphically sporadic distribution, intrastratal formation under shallow burial depths, variation in morphology, degree of contraction, generation of sedimentary dikelets as crack fills, and deformation of dikelets and enclosing layers. Instead, it is suggested that ground motion from strong synsedimentary earthquakes caused argillaceous sediments to dewater, interbedded sands and silts to be almost simultaneously liquefied and injected into the resulting fissures, and then these dikelets to be distorted. Comparative rarity of syneresis cracks in Phanerozoic versus Precambrian marine strata is considered to be primarily an evolutionary consequence of theological changes caused by increased organic binding of clay flocs in the water column, greater input of organic matter into the sediment, and the diversification of sediment-dwelling bacteria and meiofauna in Phanerozoic deposits.

  14. Influence of MB-value of Manufactured Sand on the Shrinkage and Cracking of High Strength Concrete

    Institute of Scientific and Technical Information of China (English)

    WANG Jiliang; YANG Zhifeng; NIU Kaimin; KE Guoju; ZHOU Mingkai

    2009-01-01

    The relation between methylene blue (MB) value of MS and its limestone dust content and clay content was investigated. The effects of MB value ranging from 0.35 to 2.5 on the workability of fresh concrete and crack propagation characteristics at the age of 24 hours, and effects on the mechanical properties, dry shrinkage of the harden concrete were tested. The experimental results show that the MB value is not related with the limestone dust content of MS, but in direct proportion to clay content. With the increase of MB value, the concrete workability decreases, and the flexural strength and 7 d compressive strength reduce markedly, whearas the 28 d compressive strength is not affected. When the MB-value is less than or equal to 1.35, the change of the MB-valuehas a little influence on early plastic cracking and dry shrinkage property of concrete, but when the MB-value is more than 1.35, the tendency of plastic cracking and dry shrinkage is remarkable.

  15. Effect of Pulverized Fuel Ashes on Autogenous Shrinkage and Compressive Strength of Cement Pastes%粉煤灰对水泥浆体自收缩和抗压强度的影响

    Institute of Scientific and Technical Information of China (English)

    郝成伟; 邓敏; 莫立武; 刘开伟

    2011-01-01

    Autogenous shrinkage of cement pastes with different contents of pulverized fuel ashes(PFA) and different water-to-binder ratio were measured by a shrinkage test device. Compressive strength of sealed cement paste were also measured. The influence of PFA on the pore structures and micrograph of hydration products were investigated through mercury intrusion porosimetry(MIP) and scanning electron microscopy(SEM) , on which the influence mechanism was analyzed. Experimental results demonstrated that autogenous shrinkage of cement pastes decreased with the increased contents of PFA at early age (before 7 d) , this may be ascribed to inhibition of PFA on the shrinkage. After 7 d, however, both autogenous shrinkage, and compressive strength of cement pastes increased. This may be attributed to decrease of pore radius and densification of cement hydration products due to the pozzolanic reaction of fly ash.%设计组装了水泥浆体自收缩测量装置,进行了不同粉煤灰掺量和水胶比的水泥浆体自收缩和抗压强度测试,采用压汞测孔仪(MIP)、扫描电镜(SEM)等测试技术研究了粉煤灰对水泥浆体孔结构、产物形貌等微观结构的影响,并对其影响机理进行了分析.结果表明:粉煤灰能够有效抑制水泥浆体的早期自收缩,在7d前,其自收缩随着粉煤灰掺量的增加而减小;与纯硅酸盐水泥浆体相比,粉煤灰水泥浆体7d后的抗压强度增幅较大,但自收缩增长速率也趋于增大;火山灰反应引起的孔径细化、水化产物结构致密是粉煤灰影响水泥浆体自收缩和抗压强度的根本原因.

  16. Influence and Mechanism of Lightweight Aggregates Pre-Saturated with Shrinkage Reducing Admixtures on Autogenous Shrinkage of Cement Mortar%减缩剂预饱和轻骨料对水泥砂浆自收缩的影响及机理

    Institute of Scientific and Technical Information of China (English)

    党玉栋; 钱觉时; 乔墩; 张琳; 贾兴文; 陆福高

    2011-01-01

    Internal curing (IC) and utilizing the shrinkage reducing admixture (SRA) are two effective methods of autogenous shrinkage mitigation. However, IC and SRA have some marked deficiencies when they are used individually. This paper investigated the influences of light weight aggregates pre-saturated with shrinkage reducing admixtures (SRA-LWA) on the autogenous shrinkage and strength of cement mortar; meanwhile, the effects of SRA-LWA on hydration degree and microstructre of interfacial transition zone (ITZ) were also examined. The results indicate that the SRA could reduce the release rate of solution by decreasing the solution's surface tension and increasing the viscosity. With the same amount of SRA, the ability of autogenous shrinkage reduction of SRA-LWA was similar to that of the SRA mixed with cement mortar (SRA-Mixed). However, the SRA-LWA could diminish the adverse impacts of SRA on cement hydration and strength of cement mortar significantly. Further, comparing to light weight aggregates pre-saturated with water (Water-LWA), the SRA-LWA had a more remarkable contribution to shrinkage reduction, and showed the evidence of lower porosity and denser microstructure of ITZ nearby the LWA.%使用内养护(IC)和减缩剂(SRA)是两种可有效降低水泥基材料自收缩的方法,但两者单独采用时存在明显不足.试验研究了减缩剂预饱和的轻骨料对水泥砂浆自收缩、强度、水化程度以及骨料一水泥石基体界面过渡区域的影响.结果表明:由于减缩剂降低溶液表面张力并增加溶液黏度,减缩剂溶液相比水从轻骨料中释放速率明显降低;与直接内掺减缩剂相比,当减缩剂引入量相等时,减缩剂预饱和轻骨料对砂浆自收缩降低程度相近,但其对砂浆强度不利影响则大大降低;与饱水轻骨料内养护措施相比,减缩剂预饱和轻骨料能够显著降低砂浆的自收缩,明显改善骨料与浆体界面区域的孔隙率和微观结构.

  17. Subaqueous shrinkage cracks in the Sheepbed mudstone: Implications for early fluid diagenesis, Gale crater, Mars

    Science.gov (United States)

    Siebach, K. L.; Grotzinger, J. P.; Kah, L. C.; Stack, K. M.; Malin, M.; Léveillé, R.; Sumner, D. Y.

    2014-07-01

    The Sheepbed mudstone, Yellowknife Bay formation, Gale crater, represents an ancient lakebed now exhumed and exposed on the Martian surface. The mudstone has four diagenetic textures, including a suite of early diagenetic nodules, hollow nodules, and raised ridges and later diagenetic light-toned veins that crosscut those features. In this study, we describe the distribution and characteristics of the raised ridges, a network of short spindle-shaped cracks that crosscut bedding, do not form polygonal networks, and contain two to four layers of isopachous, erosion-resistant cement. The cracks have a clustered distribution within the Sheepbed member and transition laterally into concentrations of nodules and hollow nodules, suggesting that these features formed penecontemporaneously. Because of the erosion-resistant nature of the crack fills, their three-dimensional structure can be observed. Cracks that transition from subvertical to subhorizontal orientations suggest that the cracks formed within the sediment rather than at the surface. This observation and comparison to terrestrial analogs indicate that these are syneresis cracks—cracks that formed subaqueously. Syneresis cracks form by salinity changes that cause sediment contraction, mechanical shaking of sediment, or gas production within the sediment. Examination of diagenetic features within the Sheepbed mudstone favors a gas production mechanism, which has been shown to create a variety of diagenetic morphologies comparable to the raised ridges and hollow nodules. The crack morphology and the isopachous, layered cement fill show that the cracks were filled in the phreatic zone and that the Sheepbed mudstone remained fluid saturated after deposition and through early burial and lithification.

  18. Crack Mitigation in Concrete: Superabsorbent Polymers as Key to Success?

    Directory of Open Access Journals (Sweden)

    Arn Mignon

    2017-02-01

    Full Text Available Cracking is a major concern in building applications. Cracks may arise from shrinkage, freeze/thawing and/or structural stresses, amongst others. Several solutions can be found but superabsorbent polymers (SAPs seem to be interesting to counteract these problems. At an early age, the absorbed water by the SAPs may be used to mitigate autogenous and plastic shrinkage. The formed macro pores may increase the freeze/thaw resistance. The swelling upon water ingress may seal a crack from intruding fluids and may regain the overall water-tightness. The latter water may promote autogenous healing. The use of superabsorbent polymers is thus very interesting. This review paper summarizes the current research and gives a critical note towards the use of superabsorbent polymers in cementitious materials.

  19. HETEK - Control of Early Age Cracking in Concrete

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Christensen, Søren Lolk; Dela, Birgitte Friis;

    1997-01-01

    This report deals with autogenous shrinkage of two concretes and the corresponding mortars. The theory of self-desiccation and autogenous deformation is presented. Autogenous shrinkage of mortar is measuredin a paste dilatometer at constant and varying temperatures. Similarly the autogenous...

  20. Influence of ultra-fine fly ash on hydration shrinkage of cement paste

    Institute of Scientific and Technical Information of China (English)

    GAO Ying-li; ZHOU Shi-qiong

    2005-01-01

    Hydration shrinkage generated by cement hydration is the cause of autogenous shrinkage of high strength concrete. It may result in the volume change and even cracking of mortar and concrete. According to the data analysis in a series of experimental studies, the influence of ultra-fine fly ash on the hydration shrinkage of composite cementitious materials was investigated. It is found that ultra-fine fly ash can reduce the hydration shrinkage of cement paste effectively, and the more the ultra-fine fly ash, the less the hydration shrinkage. Compared with cement paste without the ultra-fine fly ash, the shrinkage ratio of cement paste reduces from 23.4% to 39.7% when the ultra-fine fly ash replaces cement from 20% to 50%. Moreover, the microscopic mechanism of the ultra-fine fly ash restraining the hydration shrinkage was also studied by scanning electron microscopy, X-ray diffraction and hydrated equations. The results show that the hydration shrinkage can be restrained to a certain degree because the ultra-fine fly ash does not participate in the hydration at the early stage and the secondary hydration products are different at the later stage.

  1. Autogenous Deformation of Concrete

    DEFF Research Database (Denmark)

    Autogenous deformation of concrete can be defined as the free deformation of sealed concrete at a constant temperature. A number of observed problems with early age cracking of high-performance concretes can be attributed to this phenomenon. During the last 10 years , this has led to an increased...... focus on autogenous deformation both within concrete practice and concrete research. Since 1996 the interest has been significant enough to hold international, yearly conferences entirely devoted to this subject. The papers in this publication were presented at two consecutive half-day sessions...... at the American Concrete Institute’s Fall Convention in Phoenix, Arizona, October 29, 2002. All papers have been reviewed according to ACI rules. This publication, as well as the sessions, was sponsored by ACI committee 236, Material Science of Concrete. The 12 presentations from 8 different countries indicate...

  2. Identification of microcracks caused by autogenous shrinkage

    DEFF Research Database (Denmark)

    Lura, Pietro; Jensen, Ole Mejlhede; Guang, Ye;

    2005-01-01

    allows detection of microcracks while avoiding artifacts induced by unwanted restraint, drying or temperature variations. The technique consists of casting small circular cylindrical samples of cement pastes in silicone moulds. Steel rods of different diameters are cast into the cement paste to restrain...

  3. 驱动滚筒缩孔缩裂缺陷的消除%Elimination of Shrinkage Crack of Head Roll Contraction Cavities

    Institute of Scientific and Technical Information of China (English)

    李宏兴

    2016-01-01

    针对系列驱动滚筒普遍存在的缩孔、缩裂等铸造缺陷,分析了依据传统理论设计的铸造工艺存在的问题,按照均衡凝固理论重新设计,改进了驱动滚筒铸件的浇冒口位置、大小和形状,解决了驱动滚筒铸件的缺陷。%Aimed at casting defects like contraction cavities and shrinkage crack common to head rolls, this article has analyzed the problems of casting technique designed conventional theories, redesigned the castings according to the proportional solidiifcation theory, made improvement on the position, size and shape of riser and sprue of head roll castings and solved the defects of this kind of castings.

  4. Can superabsorbent polymers mitigate shrinkage in cementitious materials blended with supplementary cementitious materials?

    DEFF Research Database (Denmark)

    Snoeck, Didier; Jensen, Ole Mejlhede; De Belie, Nele

    2016-01-01

    A promising way to mitigate autogenous shrinkage in cementitious materials with a low water-to-binder ratio is internal curing by the use of superabsorbent polymers. Superabsorbent polymers are able to absorb multiple times their weight in water and can be applied as an internal water reservoir...... shrinkage in materials blended with fly ash or blast-furnace slag remain scarce, especially after one week of age. This paper focuses on the autogenous shrinkage by performing manual and automated shrinkage measurements up to one month of age. Without superabsorbent polymers, autogenous shrinkage...... was reduced in cement pastes with the supplementary cementitious materials versus Portland cement pastes. At later ages, the rate of autogenous shrinkage is higher due to the pozzolanic activity of the supplementary cementitious materials. Internal curing by means of superabsorbent polymers is successful...

  5. Experimental Research on Early-age Plastic Shrinkage Cracking of Pre-Mixed Mortar by Slab Test Method%预拌砂浆早期塑性收缩开裂平板法试验研究

    Institute of Scientific and Technical Information of China (English)

    吴其峰; 张航

    2014-01-01

    基于平板开裂试验方法,采用正交设计研究了不同因素对预拌砂浆早期塑性收缩开裂的影响。试验结果表明,砂细度模数2.6,粉煤灰I级和外加剂掺量1.2%能有效抑制塑性裂缝的产生和扩展,显著提高砂浆抵抗塑性开裂的能力。%Based on the experimental method of slab test method, the effects of different factors on the plastic shrinkage cracking of pre-mixed mortar were researched by using orthogonal design.The results indicated that sand fineness modulus 2.6,class I fly ash and admixture dosage 1.2% restrained the generation and propagation of plastic shrinkage cracking effectively and improved the crack resistance ability of pre-mixed mortar obviously.

  6. Analysis, prediction, and case studies of early-age cracking in bridge decks

    Science.gov (United States)

    ElSafty, Adel; Graeff, Matthew K.; El-Gharib, Georges; Abdel-Mohti, Ahmed; Mike Jackson, N.

    2016-06-01

    Early-age cracking can adversely affect strength, serviceability, and durability of concrete bridge decks. Early age is defined as the period after final setting, during which concrete properties change rapidly. Many factors can cause early-age bridge deck cracking including temperature change, hydration, plastic shrinkage, autogenous shrinkage, and drying shrinkage. The cracking may also increase the effect of freeze and thaw cycles and may lead to corrosion of reinforcement. This research paper presents an analysis of causes and factors affecting early-age cracking. It also provides a tool developed to predict the likelihood and initiation of early-age cracking of concrete bridge decks. Understanding the concrete properties is essential so that the developed tool can accurately model the mechanisms contributing to the cracking of concrete bridge decks. The user interface of the implemented computer Excel program enables the user to input the properties of the concrete being monitored. The research study and the developed spreadsheet were used to comprehensively investigate the issue of concrete deck cracking. The spreadsheet is designed to be a user-friendly calculation tool for concrete mixture proportioning, temperature prediction, thermal analysis, and tensile cracking prediction. The study also provides review and makes recommendations on the deck cracking based mainly on the Florida Department of Transportation specifications and Structures Design Guidelines, and Bridge Design Manuals of other states. The results were also compared with that of other commercially available software programs that predict early-age cracking in concrete slabs, concrete pavement, and reinforced concrete bridge decks. The outcome of this study can identify a set of recommendations to limit the deck cracking problem and maintain a longer service life of bridges.

  7. The soil reference shrinkage curve

    CERN Document Server

    Chertkov, V Y

    2014-01-01

    A recently proposed model showed how a clay shrinkage curve is transformed to the soil shrinkage curve at the soil clay content higher than a critical one. The objective of the present work was to generalize this model to the soil clay content lower a critical one. I investigated (i) the reference shrinkage curve, that is, one without cracks; (ii) the superficial layer of aggregates, with changed pore structure compared with the intraaggregate matrix; and (iii) soils with sufficiently low clay content where there are large pores inside the intraaggregate clay (so-called lacunar pores). The methodology is based on detail accounting for different contributions to the soil volume and water content during shrinkage. The key point is the calculation of the lacunar pore volume variance at shrinkage. The reference shrinkage curve is determined by eight physical soil parameters: (1) oven-dried specific volume; (2) maximum swelling water content; (3) mean solid density; (4) soil clay content; (5) oven-dried structural...

  8. Influence of fly ash fineness on water requirement and shrinkage of blended cement mortars

    Directory of Open Access Journals (Sweden)

    Vanissorn Vimonsatit

    2015-12-01

    Full Text Available In this paper, the influence of fly ash fineness on water requirement and shrinkage of blended cement mortar was studied. The results indicate that the water requirement and shrinkage characteristic of the blended cement mortar are dependent on fly ash fineness and replacement level. The use of coarse fly ash slightly reduces the water requirement but greatly reduced the drying and the autogenous shrinkage of the blended cement mortars and the reduction is more with an increase in the fly ash replacement level. The finer fly ashes further reduce the water requirement, but increase the drying and the autogenous shrinkages as compared with coarser fly ash. The incorporation of superplasticizer drastically reduces the water requirement, but the effect on the drying and autogenous shrinkages of the normal Portland cement mortar is small. However, for the fly ash mortar, the use of superplasticizer results in a decrease in drying shrinkage and in a substantial increase in the autogenous shrinkage particularly for the fine fly ash at a high replacement level.

  9. 表观密度和聚丙烯纤维对泡沫混凝土收缩开裂的影响%Effect of the Apparent Density and Polypropylene Fiber on Drying Shrinkage Cracking Properties of Foam Concrete

    Institute of Scientific and Technical Information of China (English)

    马一平; 李国友; 杨利香; 张乐

    2012-01-01

    Foamed concrete of low apparent density was prepared by using Portland cement as binder, the ap parent density and compressive strength of this concrete reached to 130kg/m3 and 0. 23MPa, respectively. The results indicate that the lower density of foamed concrete can decrease the compressive strength and elastic modulus, reduce the degree of plastic shrinkage. In addition, adding polypropylene fiber significantly improves resistance drying shrin kage and the early drying shrinkage cracking of hardened foamed concrete.%以普通硅酸盐水泥为胶凝材料制备了表观密度达130kg/m3、强度为0.23MPa的低表现密度泡沫混凝土.探讨了表现密度和聚丙烯纤维对泡沫混凝土性能的影响.结果表明,表观密度的下降可显著降低泡沫混凝土的强度和弹性模量,减轻塑性收缩开裂程度;聚丙烯纤维对低表现密度泡沫混凝土干燥收缩和硬化早期干缩开裂的抑制效果显著.

  10. 土壤表面干缩裂隙形态定量分析及其数值模拟%Morphological quantity analysis of soil surface shrinkage crack and its numerical simulation

    Institute of Scientific and Technical Information of China (English)

    朱磊; 陈玖泓; 刘德东

    2016-01-01

    Soil cracking is a common phenomenon in nature, which has great influence on soil properties, plant growth and soil moisture transfer. This study aimed to reveal the development law and formation mechanism of dry shrinkage cracks on the soil surface. Soil crack evolution test was carried out in 1-m2 soil in Yellow River irrigation area (105°40′E, 37°28′N) of Ningxia Zhongning County. Soil was irrigated to saturate condition, and dried under sunlight to form cracks. A Canon digital camera was used to take crack pictures every 2 h for 3 days. The picture was processed through binarization, noise removal and edge extraction of fracture for extraction of morphological properties. Minkowski area, length and Euler number were to quantify crackers. The cracker evolution was simulated through morphological dilation and erosion operation. The model assumed that the soil critical strain field followed normal distribution. Friction was taken as soil static adhesion force, and grid structure contraction frequency represented soil moisture evaporation intensity in hexagonal network structure composed of nodes. In the simulation, vertical interaction between layers of the soil was ignored, and the clay was considered as elastic material. The distance between each node in hexagonal structural network was reduced gradually on behalf of the soil evaporation. The reducing of distance between each node could cause the changing of force between network nodes, which resulted in soil cracking. The model was solved using program written by C++ language under the CodeLite platform and generated Tiff image as output. By comparison of crack area, crack length, euler number density that calculated by analyzing experiment pictures and images the program produced, it could be drawn that crack morphology could be described by Minkowski area, length, euler number density effectively; each parameter had its own variation as morphological analysis results did, among which area density

  11. The influence of shrinkage reducing admixtures on plastic shrinkage

    Directory of Open Access Journals (Sweden)

    Mora, J.

    2003-12-01

    Full Text Available Shrinkage reducing admixtures (SRAs are viable alternatives for reducing plastic shrinkage cracking in concrete. The objective of the present paper is to study early age plastic shrinkage in restrained concrete elements, where three different SRAs have been used. The influence of the admixture is analyzed through the following measurements: capillary pressure, evaporation, temperature evolution, crack evolution and settlement. The tests for studying the cracking and deformation were made on two different configurations (i.e., restrained prisms with reduced cross-section and restrained panel, in a wind tunnel, with controlled wind temperature and velocity. The conclusions obtained indicate the viability of the use of this type of admixture and the usefulness of the test methods.

    Los aditivos reductores de retracción (SRAs se plantean, hoy en día, como una alternativa viable para reducir la fisuración por retracción plástica. El objetivo del presente artículo es conocer mejor y predecir el comportamiento a primeras edades de la retracción plástica en elementos estructurales coaccionados, a los que se les ha añadido diversos aditivos reductores de retracción (tres tipos diferentes. Esta influencia se analiza a través de las siguientes propiedades: presión capilar, evaporación, evolución de temperaturas, evolución de fisuración, y deformaciones verticales de asentamiento. Los ensayos para estudiar la fisuración y las deformaciones se han realizado sobre diferentes configuraciones (prisma restringido con estrangulamiento y panel restringido, en un túnel de viento, con temperaturas y velocidades de viento controladas. Las conclusiones obtenidas señalan la viabilidad del empleo de este tipo de aditivos y la bondad de los métodos experimentales utilizados.

  12. Veterinary autogenous vaccines.

    Science.gov (United States)

    Hera, A; Bures, J

    2004-01-01

    Autogenous vaccines remain a regulatory issue. They are demanded by practising veterinarians and by animal owners and they are quite widely used, mainly in Central European Countries, the Czech Republic, Hungary and Slovak Republic having probably the longest tradition with these products in Central Europe. The scope given in Article 3, Para. 2 (and/or Article 4 for some countries) of Directive 2001/82/EC applies to these products in the Acceding Countries. As these products are exempt from the harmonised regulation at the EU level, they are regulated by individual countries, the regulation varying from practically no regulatory measures in certain countries to a quite complex and demanding regulation in the other countries. Both risks and benefits are related to these products and they shall be taken into account when regulatory measures are considered. The major risks related to veterinary autogenous vaccines relate to possibility of transmission of TSE agents or other viral, bacterial and/or fungal contaminants. As appropriate and well balanced regulation of these products is deemed necessary, considering the risks related to these products, and based on the fact that national regulatory measures could be considered as a trade barrier under certain circumstances, harmonisation of the key issues or legal admission of the nationally based regulatory measures, including movement of these products from the other Member States, shall be laid down in the EU legislation. The veterinary autogenous vaccines complying with basic quality and safety requirements are thus a very useful tool in the animal health and welfare management but their use should be restricted to situations where there is no authorised veterinary medicinal product available and veterinary autogenous vaccines must not be allowed to replace good farming or veterinary practices.

  13. Study on Early Autogenous Shrinkage and Cracking Sensitivity of Highway Concrete Containing Ultra-Fine Fly Ash%UFA道路混凝土早期自收缩及开裂敏感性研究

    Institute of Scientific and Technical Information of China (English)

    高英力; 马保国

    2007-01-01

    目的 研究掺超细粉煤灰(Ultra-fine Fly Ash,简称UFA)的道路混凝土早期自收缩特征及UFA对混凝土早期开裂敏感性的影响规律.方法 以UFA等量取代水泥配制UFA道路混凝土,采用自行改进设计的混凝土自收缩测试装置测试混凝土早龄期(72h以内)的自收缩变形,并利用平板式限制收缩开裂试验方法研究混凝土成型26h内的表面开裂特征;在试验基础上,评价UFA道路混凝土的早期开裂敏感性.结果 随着UFA的掺入,混凝土的早期自收缩变形显著减小,在保持相同流动度条件下,明显低于基准混凝土,早期抗裂性能也优于基准混凝土,且随UFA掺量的增加,早期抗裂性能随之增强.结论 掺入适量的UFA可有效地减小道路混凝土的早期自收缩,从而降低早期开裂敏感性,延长路面结构的服役寿命,并为UFA在实际工程中的应用提供了理论和技术支持.

  14. Shrinkage Properties of Cement Stabilized Gravel

    DEFF Research Database (Denmark)

    Lund, Mia Schou Møller; Hansen, Kurt Kielsgaard

    2014-01-01

    Cement stabilized gravel is an attractive material in road construction because its strength prop-erties are accommodating the increasingly higher requirements to the bearing capacity of a base course. However, reflection cracking of cement stabilized gravel is a major concern. In this pa......-per the shrinkage properties of cement stabilized gravel have been documented under various temperature and relative humidity conditions. Two cement contents corresponding to a 28-days compressive strength of 6.2 MPa and 12.3 MPa have been tested and compared. It is found that the coefficient of linear expansion...... for the two cement contents is 9.9 × 10-6 ⁰C-1 and 11.3 × 10-6 ⁰C-1, respectively. Furthermore, it is found that reflecting cracking can mainly be explained by temperature dependent shrinkage rather than moisture dependent shrinkage....

  15. Shrinkage anisotropy characteristics from soil structure and initial sample/layer size

    CERN Document Server

    Chertkov, V Y

    2014-01-01

    The objective of this work is a physical prediction of such soil shrinkage anisotropy characteristics as variation with drying of (i) different sample/layer sizes and (ii) the shrinkage geometry factor. With that, a new presentation of the shrinkage anisotropy concept is suggested through the sample/layer size ratios. The work objective is reached in two steps. First, the relations are derived between the indicated soil shrinkage anisotropy characteristics and three different shrinkage curves of a soil relating to: small samples (without cracking at shrinkage), sufficiently large samples (with internal cracking), and layers of similar thickness. Then, the results of a recent work with respect to the physical prediction of the three shrinkage curves are used. These results connect the shrinkage curves with the initial sample size/layer thickness as well as characteristics of soil texture and structure (both inter- and intra-aggregate) as physical parameters. The parameters determining the reference shrinkage c...

  16. AUTOGENIC THERAPY IN TENSION HEADACHE

    OpenAIRE

    Amruthraj, Brunda; Mishra, H.; Kumaraiah, V.

    1987-01-01

    SUMMARY Ten subjects diagnosed as Psychalgia were taken for study. A multiple baseline design was adapted and clients were subjected to 30 sessions of autogenic training. They were assessed using physiological (EMG and thermal change) and behavioural measures (Visual analogue scale and behavioural symptom checklist). Findings revealed autogenic therapy to be effective in reducing tension headache.

  17. Cure shrinkage in epoxy grouts for grouted repairs

    Science.gov (United States)

    Shamsuddoha, Md.; Islam, Md. Mainul; Aravinthan, Thiru; Manalo, Allan; Lau, Kin-tak

    2013-08-01

    Structures can go through harsh environmental adversity and can experience material loss and cracks during their service lives. Infill material is used to ensure a supporting bed for a grouted repair. Epoxy grouts are used for repairing and rehabilitating structures, such as foundations, bridges, piers, transportation pipelines, etc., because they are resistant to typical chemicals and possess superior mechanical properties than other grouts. The resin based infill used inside the void or cracked space of the repair is vulnerable to shrinkage. When these filled grouts have high resin content, cracks can develop from residual stresses, which can affect the load transfer performance. It follows that interlayer separation and cracking of infill layer can occur in a grouted repair. In this study, volumetric shrinkage of two epoxy grouts was measured over 28 days using a Pycnometer. The highest volumetric shrinkage measured after 7 days was found to be 2.72%. The results suggest that the volumetric shrinkage can be reduced to 1.1% after 7 days, through the introduction of a coarse aggregate filler; a 2.5 times reduction in shrinkage. About 98% and 92% of the total shrinkage over the 28 day period, of the unfilled and filled grouts respectively, was found to occur within 7 days of mixing. The gel-time shrinkages were also calculated, to determine the "postgel" part of the curing contraction which subsequently produces residual stresses in the hardened grout systems.

  18. The effect of fibers on the loss of water by evaporation and shrinkage of concrete

    Directory of Open Access Journals (Sweden)

    N. M. P. Pillar

    Full Text Available Shrinkage is one of the least desirable attributes in concrete. Large areas of exposed concrete surfaces , such as in shotcrete tunnel linings, where it is practically impossible to make a moist cure, are highly susceptible to plastic shrinkage at early ages. The autogenous and drying shrinkage can lead to states of greater than threshold strength, causing fracture, mechanical damage and lack of durability of concrete structures. The addition of fibers can greatly reduce plastic shrinkage, but has limited effect in mitigating autogenous and drying shrinkage. To evaluate the performance of polypropylene and steel fibers to understand their effect on shrinkage of concrete, a study was carried out to relate the loss of water from the paste and the shrinkage during the first 28 days of age, and compare it with a control mix without fiber. The loss of water was obtained by the weight loss of the specimens at different ages, since the only component that could contribute for the loss of weight was the water lost by the paste of the concrete. And the paste itself is the only source of shrinkage. Uniaxial compressive tests from very early ages enabled the determination of time when plastic shrinkage ended. It was observed that the control concrete mix lost three times more water and developed plastic and drying shrinkage 60 % higher than the fiber reinforced concrete mixes. It was possible to demonstrate that the reduced loss of water caused by the incorporation of fibers is related to the mitigation of plastic shrinkage. It was observed that the fibers are effective to restrain the movement of water through the cement paste in the plastic state, however such effect is limited after concrete starts the hardening state.

  19. Effect of Cement Type on Autogenous Deformation of Cement-Based Materials

    DEFF Research Database (Denmark)

    Pietro, Lura; Ye, Guang; van Breugel, Klaas

    2004-01-01

    In this paper, measurements of non-evaporable water content, chemical shrinkage, autogenous deformation, internal relative humidity (RH), pore solution composition, and early-age elastic modulus are presented and discussed. All experiments were performed on Portland cement and blast-furnace slag...... (BFS) cement pastes. Self-desiccation shrinkage of the BFS cement paste was modeled based on the RH measurements, following the capillary-tension approach. The main findings of this study are: 1) self-desiccation shrinkage can be related to self-desiccation both for Portland and for BFS cement pastes......, taking into account the influence of the dissolved salts in the pore solution, 2) the BFS cement paste studied shows pronounced self-desiccation and self-desiccation shrinkage, mainly caused by its very fine pore structure....

  20. The physical effects of an intra-aggregate structure on soil shrinkage

    CERN Document Server

    Chertkov, V Y

    2014-01-01

    Clay and soil containing it have shrinkage curves that are qualitatively different in shape. The objective of this work is to qualitatively show with maximum simplicity, how a clay shrinkage curve turns into a soil shrinkage curve. Because of the crack volume the measured shrinkage curve is not the single-valued feature of a soil. We use a concept of the reference shrinkage curve that is only stipulated by soil shrinkage without cracking, single-valued, and qualitatively similar to an observed shrinkage curve. We also use new concepts of an intra-aggregate soil structure: (i) a rigid superficial layer of aggregates that loses water during shrinkage; and (ii) lacunar pores (micro-cracks) inside an intra-aggregate clay that change in volume during shrinkage. Then, through a series of consecutive steps, illustrating each step by a separate graphic presentation, we move from a clay shrinkage curve to a soil shrinkage curve with predicted qualitative features that coincide with those experimentally observed in num...

  1. Evaluating plastic shrinkage and permeability of polypropylene fiber reinforced concrete

    Directory of Open Access Journals (Sweden)

    G.M. Sadiqul Islam

    2016-12-01

    Full Text Available Plastic concrete is susceptible to develop cracks due to shrinkage in dry and windy conditions. Addition of fibers could reduce propagation of this crack. On the other hand, permeability determines the durability properties of concrete. This study evaluated strength, plastic shrinkage and permeability (gas and water of concrete incorporating ‘polypropylene’ fiber (aspect ratio 300 in various proportions (viz. 0.10%, 0.15%, 0.2%, 0.25% and 0.3% by volume of concrete. Plane concrete samples were also prepared and tested for reference purpose. Inclusion of 0.1% fiber gave minor reduction (2% in compressive strength while the tensile strength increased by 39% with same fiber content compared to the plain concrete. A significant reduction in crack generation, appearance period of first crack and crack area between plane concrete and fiber reinforced concretes was found. The experimental result with inclusion of 0.1–0.3% fiber in concrete indicated that plastic shrinkage cracks were reduced by 50–99% compared to the plain concrete. For reference concrete (without fiber, test within the high temperature and controlled humidity chamber gave higher crack width than the acceptable limit (3 mm specified by the ACI 224. With the inclusion of 0.1% fiber reduced the crack width down to 1 mm and the trend was continued with the addition of more fibers. However, results showed that with the addition of polypropylene fiber both water and gas permeability coefficient was increased. Therefore, it is concluded that the fiber reinforced concrete would work better for plastic shrinkage susceptible structural elements (flat elements such as slab; however, it requires careful judgement while applying to a water retaining structures.

  2. Shrinkage reduction of dental composites by addition of expandable zirconia filler

    DEFF Research Database (Denmark)

    Skovgaard, M.; Almdal, Kristoffer; Sørensen, Bent F.;

    2011-01-01

    A problem with dental resin composites is the polymerization shrinkage, which makes the filling loosen from the tooth or induces crack formation. We have developed an expandable metastable tetragonal zirconia filler, which upon reaction with water, is able to counter the polymer shrinkage...

  3. Magnitude, modeling and significance of swelling and shrinkage processes in clay soils.

    NARCIS (Netherlands)

    Bronswijk, J.J.B.

    1991-01-01

    The dynamic process of swelling and shrinkage in clay soils has significant practical consequences, such as the rapid transport of water and solutes via shrinkage cracks to the subsoil, and the destruction of buildings and roads on clay soils. In order to develop measuring methods and computer simul

  4. Development of spraying agent for reducing drying shrinkage of mortar

    Science.gov (United States)

    Fujiwara, Hiromi; Maruoka, Masanori; Liu, Lingling

    2017-02-01

    Mortar used to repair is sometimes exposed to drying state in early ages after construction and a few days later water is sprayed frequently on the surface of the mortar in order to prevent cracks. This research studied on shrinkage characteristic of mortar subjected to drying conditions like this. The result showed that the water spraying on the mortar after initial drying did not have any effect to prevent shrinkage, but increased. And it also showed when various chemical agents are mixed and used in watersprayingit had the prevention effect on shrinkage. This report was to understand this kind of phenomenon and clarify the mechanism. In addition, based on the results, the new spraying agent was developed to reduce drying shrinkage.

  5. On Early Age Crack Formation in FRC Slabs

    DEFF Research Database (Denmark)

    Olesen, John Forbes; Stang, Henrik

    1997-01-01

    The problem of early age crack formation in FRC slabs due to restrained temperature and shrinkage deformations, is given an analytical treatment. A model taking into account the ageing properties of the tensile softening curve and the continued development in the temperature and shrinkage...... deformations after crack initiation, is presented. Based on this model a design strategy for FRC slabs is outlined....

  6. Plastic shrinkage of mortars with shrinkage reducing admixture and lightweight aggregates studied by neutron tomography

    Energy Technology Data Exchange (ETDEWEB)

    Wyrzykowski, Mateusz, E-mail: mateusz.wyrzykowski@empa.ch [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Dübendorf (Switzerland); Lodz University of Technology, Department of Building Physics and Building Materials, Lodz (Poland); Trtik, Pavel [Paul Scherrer Institute, Laboratory for Neutron Scattering and Imaging, Villigen (Switzerland); Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Dübendorf (Switzerland); Münch, Beat [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Dübendorf (Switzerland); Weiss, Jason [Purdue University, School of Civil Engineering, West Lafayette (United States); Vontobel, Peter [Paul Scherrer Institute, Laboratory for Neutron Scattering and Imaging, Villigen (Switzerland); Lura, Pietro [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Dübendorf (Switzerland); ETH Zurich, Institute for Building Materials (IfB), Zurich (Switzerland)

    2015-07-15

    Water transport in fresh, highly permeable concrete and rapid water evaporation from the concrete surface during the first few hours after placement are the key parameters influencing plastic shrinkage cracking. In this work, neutron tomography was used to determine both the water loss from the concrete surface due to evaporation and the redistribution of fluid that occurs in fresh mortars exposed to external drying. In addition to the reference mortar with a water to cement ratio (w/c) of 0.30, a mortar with the addition of pre-wetted lightweight aggregates (LWA) and a mortar with a shrinkage reducing admixture (SRA) were tested. The addition of SRA reduced the evaporation rate from the mortar at the initial stages of drying and reduced the total water loss. The pre-wetted LWA released a large part of the absorbed water as a consequence of capillary pressure developing in the fresh mortar due to evaporation.

  7. GENERALIZED DOUBLE PARETO SHRINKAGE.

    Science.gov (United States)

    Armagan, Artin; Dunson, David B; Lee, Jaeyong

    2013-01-01

    We propose a generalized double Pareto prior for Bayesian shrinkage estimation and inferences in linear models. The prior can be obtained via a scale mixture of Laplace or normal distributions, forming a bridge between the Laplace and Normal-Jeffreys' priors. While it has a spike at zero like the Laplace density, it also has a Student's t-like tail behavior. Bayesian computation is straightforward via a simple Gibbs sampling algorithm. We investigate the properties of the maximum a posteriori estimator, as sparse estimation plays an important role in many problems, reveal connections with some well-established regularization procedures, and show some asymptotic results. The performance of the prior is tested through simulations and an application.

  8. Physical modeling of the soil swelling curve vs. the shrinkage curve

    CERN Document Server

    Chertkov, V Y

    2014-01-01

    Physical understanding of the links between soil swelling, texture, structure, cracking, and sample size is of great interest for the physical understanding of many processes in the soil-air-water system and for applications in civil, agricultural, and environmental engineering. The background of this work is an available chain of interconnected physical shrinkage curve models for clay, intra-aggregate matrix, aggregated soil without cracks, and soil with cracks. The objective of the work is to generalize these models to the case of swelling, and to construct the physical-swelling-model chain with a step-by-step transition from clay to aggregated soil with cracks. The generalization is based on thorough accounting for the analogies and differences between shrinkage and swelling and the corresponding use, modification, or replacement of the soil shrinkage features. Two specific soil swelling features to be used are: (i) air entrapping in pores of the contributing clay; and (ii) aggregate destruction with the f...

  9. The geometry of soil crack networks

    CERN Document Server

    Chertkov, V Y

    2014-01-01

    The subject of this work is the modification and specification of an approach to detail the estimation of soil crack network characteristics. The modification aims at accounting for the corrected soil crack volume based on the corrected shrinkage geometry factor compared to known estimates of crack volume and shrinkage geometry factor. The mode of the correction relies on recent results of the soil reference shrinkage curve. The main exposition follows the preliminary brief review of available approaches to dealing with the geometry of soil crack networks and gives a preliminary brief summary of the approach to be modified and specified. To validate and illustrate the modified approach the latter is used in the analysis of available data on soil cracking in a lysimeter.

  10. Minimum Reinforcement in Concrete Structures under Restrained Shrinkage and Thermal Actions

    DEFF Research Database (Denmark)

    Christiansen, Morten Bo; Nielsen, Mogens Peter

    1999-01-01

    The present paper deals with minimum reinforcement to ensure limitation of crack widths in concrete structures subjected to small imposed strains, such as those from restrained shrinkage or thermal actions. A theory is presented, which models the behaviour of a tensile member from zero load...... to first yielding of reinforcement. The theory takes into account the formation of each crack. However, concluding the paper, a simple design formula is given, which provides the amount of reinforcement, necessary to ensure a given crack width....

  11. Shrinkage and Expansive Strain of Concrete with Fly Ash and Expansive Agent

    Institute of Scientific and Technical Information of China (English)

    GAO Peiwei; LU Xiaolin; TANG Mingshu

    2009-01-01

    The effects of fly ash and MgO-type expansive agent on the shrinkage and expan-sive strain of concrete with high magnesia cement were investigated. The results show that high volumes of fly ash may reduce the shrinkage strain of concrete and inhibit the expansive strain of concrete with MgO-type expansive agent, but can not eliminate the shrinkage of concrete. MgO-type expansive agent may produce expansive strain and compensate the shrinkage strain of concrete, re-lieve the cracking risk, but the hydration product of magnesia tends to get together in paste and pro-duce expansive cracking of concrete with high magnesia content according to SEM observation.

  12. Spontaneous shrinkage of vestibular schwannoma

    Directory of Open Access Journals (Sweden)

    Rossana Romani

    2016-01-01

    Conclusion: Early WWR management can be associated with spontaneous shrinkage of VS over time. Prospective clinical study of larger numbers of such cases using the UK VS database may help to identify predictive factors for the spontaneous regression of VS.

  13. Preparation of High Shrinkage Polypropylene

    Institute of Scientific and Technical Information of China (English)

    吕文军; 王华平; 李建梅; 张玉梅

    2001-01-01

    The common PP chips have been used to prepare high shrinkage PP fibers with shrinkage in boiling water higher than 50%. Meanwhile, the process conditions on fiber structure and properties have been discussed in detail. With the increase of drawing temperature, the shrinkage in boiling water of the fiber increases at first,and then decreases in the temperature range from 70℃ to 100℃. The better drawing temperature is from 75℃ to 85℃ according to the melt index of the PP material. The shrinkage in boiling water of PP fiber increases with the increase of pump delivery. The orientation factor and crystallinity increase with the increase of drawing temperature. With an increase in drawing temperature,unit-cell numbers and monomer unit numbers in every crystal nucleus tend to increase, but unit volume crystal nucleus tend to reduce.

  14. Effect of the Key Mixture Parameters on Shrinkage of Reactive Powder Concrete

    OpenAIRE

    Shamsad Ahmad; Ahmed Zubair; Mohammed Maslehuddin

    2014-01-01

    Reactive powder concrete (RPC) mixtures are reported to have excellent mechanical and durability characteristics. However, such concrete mixtures having high amount of cementitious materials may have high early shrinkage causing cracking of concrete. In the present work, an attempt has been made to study the simultaneous effects of three key mixture parameters on shrinkage of the RPC mixtures. Considering three different levels of the three key mixture factors, a total of 27 mixtures of RPC w...

  15. Accounting for PDMS shrinkage when replicating structures

    DEFF Research Database (Denmark)

    Madsen, Morten Hannibal; Feidenhans'l, Nikolaj Agentoft; Hansen, Poul-Erik

    2014-01-01

    are seldom applied to counteract the shrinkage of PDMS. Also, to perform metrological measurements using replica techniques one has to take the shrinkage into account. Thus we report a study of the shrinkage of PDMS with several different mixing ratios and curing temperatures. The shrinkage factor, with its...

  16. Cracking of open traffic rigid pavement

    Directory of Open Access Journals (Sweden)

    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.

  17. Autogenous Phenomena in Cement-Based Materials

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede

    Denne afhandling er skrevet med henblik på opnåelse af den danske doktorgrad i teknik, dr.techn. Den vedrører autogene fænomener i cementbaserede materialer – primært deformation og ændring af den relative luftfugtighed (RF). I afhandlingen er det belyst, hvordan betydningen af disse fænomener bl...

  18. Quantification of shrinkage microcracking in young mortar with fluorescence light microscopy and ESEM

    NARCIS (Netherlands)

    Bisschop, J.; Van Mier, J.C.M.

    1999-01-01

    In this paper a method is described to quantify shrinkage microcracking in young mortar by means of crack mapping. Visualisation of the microcracks is realised with two techniques: Fluorescence Light Microscopy (FLM) and Environmental Scanning Electron Microscopy (ESEM). The preliminary results obta

  19. Effect of the key mixture parameters on shrinkage of reactive powder concrete.

    Science.gov (United States)

    Ahmad, Shamsad; Zubair, Ahmed; Maslehuddin, Mohammed

    2014-01-01

    Reactive powder concrete (RPC) mixtures are reported to have excellent mechanical and durability characteristics. However, such concrete mixtures having high amount of cementitious materials may have high early shrinkage causing cracking of concrete. In the present work, an attempt has been made to study the simultaneous effects of three key mixture parameters on shrinkage of the RPC mixtures. Considering three different levels of the three key mixture factors, a total of 27 mixtures of RPC were prepared according to 3(3) factorial experiment design. The specimens belonging to all 27 mixtures were monitored for shrinkage at different ages over a total period of 90 days. The test results were plotted to observe the variation of shrinkage with time and to see the effects of the key mixture factors. The experimental data pertaining to 90-day shrinkage were used to conduct analysis of variance to identify significance of each factor and to obtain an empirical equation correlating the shrinkage of RPC with the three key mixture factors. The rate of development of shrinkage at early ages was higher. The water to binder ratio was found to be the most prominent factor followed by cement content with the least effect of silica fume content.

  20. Effect of the Key Mixture Parameters on Shrinkage of Reactive Powder Concrete

    Directory of Open Access Journals (Sweden)

    Shamsad Ahmad

    2014-01-01

    Full Text Available Reactive powder concrete (RPC mixtures are reported to have excellent mechanical and durability characteristics. However, such concrete mixtures having high amount of cementitious materials may have high early shrinkage causing cracking of concrete. In the present work, an attempt has been made to study the simultaneous effects of three key mixture parameters on shrinkage of the RPC mixtures. Considering three different levels of the three key mixture factors, a total of 27 mixtures of RPC were prepared according to 33 factorial experiment design. The specimens belonging to all 27 mixtures were monitored for shrinkage at different ages over a total period of 90 days. The test results were plotted to observe the variation of shrinkage with time and to see the effects of the key mixture factors. The experimental data pertaining to 90-day shrinkage were used to conduct analysis of variance to identify significance of each factor and to obtain an empirical equation correlating the shrinkage of RPC with the three key mixture factors. The rate of development of shrinkage at early ages was higher. The water to binder ratio was found to be the most prominent factor followed by cement content with the least effect of silica fume content.

  1. Cracking Tendency of Restrained Concrete at Early Ages

    Institute of Scientific and Technical Information of China (English)

    BA Hengjing; SU Anshuang; GAO Xiaojian; TAO Qi

    2008-01-01

    A modified testing system characterized by full automation, steady operation and high accuracy of strain and stress measurements was developed to determine the cracking tendency of high strength concrete (HSC) in restrained condition at early ages. The shrinkage stress and the tensile creep behavior of HSC at early ages were investigated. The influence of W/C ratio and curing conditions on the early-age shrinkage stress and tensile creep was evaluated. It was found that the lower W/C ratio and drying curing condition resulted in higher shrinkage stress, stress induced tensile creep and greater cracking tendency.

  2. The shrinkage in lime mortars

    Directory of Open Access Journals (Sweden)

    Sánchez, J. A.

    1997-03-01

    Full Text Available Nowadays, the methodology existing to measure the shrinkage in air, developed for paste and cement mortars, has serious problems to be applied to lime mortars, due to its different mechanism of hardening several modifications in Norms UNE 80-113-86 y 80-112-89 make possible the determination of the shrinkage in these traditional mortars.

    La metodología existente en la actualidad para la medida de la retracción de secado, desarrollada para las pastas y los morteros de cemento, presenta serios problemas a la hora de su aplicación a los morteros de cal debido a su distinto mecanismo de endurecimiento. Algunas modificaciones de las normas UNE 80-113-86 y 80-112-89 hacen posible la determinación de la retracción en estos morteros tradicionales.

  3. Autogenic training as a therapy for adjustment disorder in adults

    OpenAIRE

    Jojić Boris R.; Leposavić Ljubica M.

    2005-01-01

    Introduction. Autogenic training is a widely recognised psychotherapy technique. The British School of Autogenic Training cites a large list of disorders, states, and changes, where autogenic training may prove to be of help. We wanted to explore the application of autogenic training as a therapy for adjustment disorder in adults. Our sample consisted of a homogeneous group of 35 individuals, with an average age of 39.3±1.6 years, who were diagnosed with adjustment disorder, F 43.2, in accord...

  4. Autogenic training as a therapy for adjustment disorder in adolescents

    OpenAIRE

    Jojić Boris R.; Leposavić Ljubica M.

    2005-01-01

    INTRODUCTION Autogenic training is a widespread technique used in psychotherapy. The British school of autogenic training cites a large list of diseases, health states, and life changes, in which autogenic training can be of help. We wanted to explore the application of autogenic training as a therapy for adjustment disorder in adolescents. The sample consisted of a homogeneous group of 31 individuals, with an average age of 17.3±0.2 years, who were diagnosed with adjustment disorder, F 43.2,...

  5. Shrinkage modeling of concrete reinforced by palm fibres in hot dry environments

    Science.gov (United States)

    Akchiche, Hamida; Kriker, Abdelouahed

    2017-02-01

    The cement materials, such as concrete and conventional mortar present very little resistance to traction and cracking, these hydraulic materials which induces large withdrawals on materials and cracks in structures. The hot dry environments such as: the Saharan regions of Algeria, Indeed, concrete structures in these regions are very fragile, and present high shrinkage. Strengthening of these materials by fibers can provide technical solutions for improving the mechanical performance. The aim of this study is firstly, to reduce the shrinkage of conventional concrete with its reinforcement with date palm fibers. In fact, Algeria has an extraordinary resources in natural fibers (from Palm, Abaca, Hemp) but without valorization in practical areas, especially in building materials. Secondly, to model the shrinkage behavior of concrete was reinforced by date palm fibers. In the literature, several models for still fiber concrete were founded but few are offers for natural fiber concretes. To do so, a still fiber concretes model of YOUNG - CHERN was used. According to the results, a reduction of shrinkage with reinforcement by date palm fibers was showed. A good ability of molding of shrinkage of date palm reinforced concrete with YOUNG - CHERN Modified model was obtained. In fact, a good correlation between experimental data and the model data was recorded.

  6. Autogenic training as a therapy for adjustment disorder in adolescents

    Directory of Open Access Journals (Sweden)

    Jojić Boris R.

    2005-01-01

    Full Text Available INTRODUCTION Autogenic training is a widespread technique used in psychotherapy. The British school of autogenic training cites a large list of diseases, health states, and life changes, in which autogenic training can be of help. We wanted to explore the application of autogenic training as a therapy for adjustment disorder in adolescents. The sample consisted of a homogeneous group of 31 individuals, with an average age of 17.3±0.2 years, who were diagnosed with adjustment disorder, F 43.2, in accordance with ICD 10 search criteria. OBJECTIVE The aim of our work was to figure out the influence of autogenic training on adjustment disorder, through biophysical and biochemical indicators, and to research the efficacy of autogenic training as a therapy for adjustment disorder in adolescents. METHOD We observed adjustment disorder indicators and their changes in three phases, using initial, final, and control values, which we measured immediately before the beginning, immediately after the completion, and six months after the completion, of the practical course in autogenic training. We measured systolic and diastolic arterial blood pressure, brachial pulse rates, cortisol levels in plasma, cholesterol levels in blood, as well as glucose concentrations. During that period, autogenic training was employed as the sole therapy. RESULTS The study confirmed our preliminary assumptions. The measurements we performed showed that arterial blood pressure, pulse rates, cholesterol and cortisol concentrations, after the application of autogenic training among adolescents suffering from adjustment disorder, were lower than the initial values. They remained lower even six months after the completion of the practical course in autogenic training. CONCLUSION We concluded that autogenic training significantly decreases the values of physiological indicators of adjustment disorder, diminishes the effects of stress in an individual, and eases the adaptation of

  7. Shrinkage behavior of self-compacting concrete

    Institute of Scientific and Technical Information of China (English)

    Farhad ASLANI; Shami NEJADI

    2012-01-01

    In the structures where long-term behavior should be monitored and controlled,creep and shrinkage effects have to be included precisely in the analysis and design procedures.Shrinkage varies with the constituent and mixture proportions,and depends on the curing conditions and the work environment as well.Self-compacting concrete (SCC) contains combinations of various components,such as aggregate,cement,superplasticizer,water-reducing agent and other ingredients which affect the properties of the SCC including shrinkage.Hence,the realistic prediction shrinkage strains of SCC are an important requirement of the design process for this type of concrete structures.This study reviews the accuracy of the conventional concrete (CC) shrinkage prediction models proposed by the international codes of practice,including CEB-FIP (1990),ACI 209R (1997),Eurocode 2 (2001),JSCE (2002),AASHTO (2004; 2007) and AS 3600 (2009).Also,SCC shrinkage prediction models proposed by Poppe and De Schutter (2005),Larson (2007),Cordoba (2007) and Khayat and Long (2010) are reviewed.Further,a new shrinkage prediction model based on the comprehensive analysis on both of the available models,i.e.,the CC and the SCC is proposed.The predicted shrinkage strains are compared with the actual measured shrinkage strains in 165 mixtures of SCC and 21 mixtures of CC.

  8. Modelling autogenous expansion for magnesia concrete in arch dams

    Institute of Scientific and Technical Information of China (English)

    Feng JIN; Guoxin ZHANG; Xiaoqing LUO; Chuhan ZHANG

    2008-01-01

    Magnesia Concrete is a kind of expansive con-crete used in Chinese hydraulic engineering more and more widely. To evaluate the effects of autogenous expan-sion on the stresses of arch dams, a simple model of auto-genous expansion for Magnesia Concrete in dam engineering is presented. This model is based on three assumptions: 1) the total amount of autogenous expan-sion of Magnesia Concrete is related only to the properties of materials and mixing of concrete; 2) the autogenous expansion of Magnesia Concrete is irreversible due to the irreversibility of hydration reaction of Magnesia in the concrete; 3) the autogenous expansion strain rates of Magnesia Concrete bear a relation between temperature and residual Magnesia per unit volume of concrete. The model is verified by some experimental data of autogen-ous expansion of Magnesia Concrete and field-measured data of an arch dam in China. Embedded into finite ele-ment arch dam simulation software, this model is employed to simulate the effects of autogenous expansion of Magnesia Concrete in hydraulic engineering.

  9. Compressed sensing recovery via nonconvex shrinkage penalties

    Science.gov (United States)

    Woodworth, Joseph; Chartrand, Rick

    2016-07-01

    The {{\\ell }}0 minimization of compressed sensing is often relaxed to {{\\ell }}1, which yields easy computation using the shrinkage mapping known as soft thresholding, and can be shown to recover the original solution under certain hypotheses. Recent work has derived a general class of shrinkages and associated nonconvex penalties that better approximate the original {{\\ell }}0 penalty and empirically can recover the original solution from fewer measurements. We specifically examine p-shrinkage and firm thresholding. In this work, we prove that given data and a measurement matrix from a broad class of matrices, one can choose parameters for these classes of shrinkages to guarantee exact recovery of the sparsest solution. We further prove convergence of the algorithm iterative p-shrinkage (IPS) for solving one such relaxed problem.

  10. A cure shrinkage model for analyzing the stresses and strains in encapsulated assemblies

    Science.gov (United States)

    Chambers, R. S.; Lagasse, R. R.; Guess, T. R.; Plazek, D. J.; Bero, C.

    Electrical component assemblies are encapsulated to provide delicate parts with voltage isolation and protection against damage caused by shock, vibration, and harsh atmospheric environments. During cure, thermosetting resins shrink and harden simultaneously. If the natural deformation of the resin is constrained by adhesion to the mold or to relatively stiff embedded components, cure shrinkage stresses are generated in the encapsulant. Subsequent cooling or thermal cycling produces additional stresses that are caused by the mismatches in thermal strains among the materials in the encapsulated assembly. Although cure shrinkage stresses frequently are neglected because they are considerably smaller than thermal stresses, cure shrinkage stresses can cause delamination or fractures in the encapsulant, since the partially cured resin is not as tough as the fully cured material. Cracks generated during cure can compromise performance (e.g., permit dielectric breakdown), degrade a component's protection, and grow under subsequent thermal cycling producing residual stresses that differ from those found in uncracked assemblies.

  11. A cure shrinkage model for analyzing the stresses and strains in encapsulated assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, R.S.; Lagasse, R.R.; Guess, T.R. [Sandia National Labs., Albuquerque, NM (United States); Plazek, D.J.; Bero, C. [Pittsburgh Univ., PA (United States). Dept. of Materials Science and Engineering

    1992-12-31

    Electrical component assemblies are encapsulated to provide delicate parts with voltage isolation and protection against damage caused by shock, vibration, and harsh atmospheric environments. During cure, thermosetting resins shrink and harden simultaneously. If the natural deformation of the resin is constrained by adhesion to the mold or to relatively stiff embedded components, cure shrinkage stresses are generated in the encapsulant. Subsequent cooling or thermal cycling produces additional stresses that are caused by the mismatches in thermal strains among the materials in the encapsulated assembly. Although cure shrinkage stresses frequently are neglected because they are considerably smaller than thermal stresses, cure shrinkage stresses can cause delamination or fractures in the encapsulant, since the partially cured resin is not as tough as the fully cured material. Cracks generated during cure can compromise performance (e. g., permit dielectric breakdown), degrade a component`s protection, and grow under subsequent thermal cycling producing residual stresses that differ from those found in uncracked assemblies. 3 refs., 11 figs.

  12. [Autogenic training in psychophysiological preparation for parachute jumps].

    Science.gov (United States)

    Reshetnikov, M M

    1978-01-01

    The efficiency of specific psychophysiological preparation--autogenic training--to parachute jumps was measured in two groups of cadets (test subjects and controls). Hetero- and autogenic training was carried out according to a scheme specially developed for this type of activity. The study of questionnaires and physiological data demonstrated that the specific psychophysiological preparation by means of autogenic training for a certain type of activity helped to develop active self-control over one's own state and emotions, alleviated tension, arrested adverse neurotic manifestations (sleep disturbances, depression, anxiety), contributed to the feeling of confidence in the successful completion of the jump and promoted positive tuning towards subsequent jumps.

  13. Selective Formation of Zigzag Edges in Graphene Cracks.

    Science.gov (United States)

    Fujihara, Miho; Inoue, Ryosuke; Kurita, Rei; Taniuchi, Toshiyuki; Motoyui, Yoshihito; Shin, Shik; Komori, Fumio; Maniwa, Yutaka; Shinohara, Hisanori; Miyata, Yasumitsu

    2015-09-22

    We report the thermally induced unconventional cracking of graphene to generate zigzag edges. This crystallography-selective cracking was observed for as-grown graphene films immediately following the cooling process subsequent to chemical vapor deposition (CVD) on Cu foil. Results from Raman spectroscopy show that the crack-derived edges have smoother zigzag edges than the chemically formed grain edges of CVD graphene. Using these cracks as nanogaps, we were also able to demonstrate the carrier tuning of graphene through the electric field effect. Statistical analysis of visual observations indicated that the crack formation results from uniaxial tension imparted by the Cu substrates together with the stress concentration at notches in the polycrystalline graphene films. On the basis of simulation results using a simplified thermal shrinkage model, we propose that the cooling-induced tension is derived from the transient lattice expansion of narrow Cu grains imparted by the thermal shrinkage of adjacent Cu grains.

  14. Autogenous Transplantation for Replacing a Hopeless Tooth

    Science.gov (United States)

    Zakershahrak, Mehrsa; Moshari, Amirabbas; Vatanpour, Mehdi; Khalilak, Zohreh; Jalali Ara, Afsoon

    2017-01-01

    Autogenous tooth transplantation (ATT) is a simple and reasonable choice for replacing the missing teeth when a proper donor tooth is available. This report presents a case of successful ATT of a maxillary right third molar for replacement of mandibular right second molar with a concomitant endodontic-periodontal disease. The mandibular second molar was believed to be hopeless due to a severe damage to coronal tooth structure, inappropriate root canal treatment and apical radiolucency. After extraction of mandibular second molar and maxillary third molar (the donor), the tooth was re-implanted into the extracted socket of second molar site. Root canal therapy was then performed. After 3 years, clinical and radiographic examinations revealed satisfying results, with no signs and symptoms. The patient is asymptomatic and the transplanted tooth is still functional with no signs of marginal periodontal pathosis. Radiographies showed bone regeneration in the site of previous extensive periapical lesion, normal periodontal ligament with no signs of root resorption. PMID:28179939

  15. Influence of Nano-SiO2 on the Consistency, Setting Time, Early-Age Strength, and Shrinkage of Composite Cement Pastes

    Directory of Open Access Journals (Sweden)

    Yu Chen

    2016-01-01

    Full Text Available The study outlined the raw materials and mix proportions to prepare composite cement pastes with the addition of silica-based micro- and nanoparticles. The effects of amorphous nano-SiO2 on the early-age properties, including the consistency, setting time, early-age strength, and chemical and autogenous shrinkages, were investigated. Under the condition of the same dosage of superplasticizer used, the consistency of cement paste with nano-SiO2 is higher than that with silica fume. Significant reductions of the initial and final setting times are observed especially for nano-SiO2 addition groups, and the time difference between the initial and final setting times goes up with the increasing proportions of nano-SiO2. The addition of nano-SiO2 is more helpful to the improvement of early-age strengths of the paste with or without fly ash admixed than silica fume additive for the same mass proportion. Both the chemical and autogenous shrinkages of cement paste develop with the increasing amount of micro- or nanolevel silica particles; however, nano-SiO2 plays a more active role than silica fume in inspiring early-age shrinkage. The physical and chemical mechanisms of nano-SiO2 in cement paste are also discussed.

  16. Breast specimen shrinkage following formalin fixation

    Directory of Open Access Journals (Sweden)

    Horn CL

    2014-02-01

    Full Text Available Christopher L Horn, Christopher Naugler Department of Pathology and Laboratory Medicine, University of Calgary, and Calgary Laboratory Services, Calgary, AB, Canada Abstract: Accurate measurement of primary breast tumors and subsequent surgical margin assessment is critical for pathology reporting and resulting patient therapy. Anecdotal observations from pathology laboratory staff indicate possible shrinkage of breast cancer specimens due to the formalin fixation process. As a result, we conducted a prospective study to investigate the possible shrinkage effects of formalin fixation on breast cancer specimens. The results revealed no significant changes in tumor size, but there were significant changes in the distance to all surgical resection margins from the unfixed to fixed state. This shrinkage effect could interfere with the accuracy of determining distance to margin assessment and tumor-free margin assessment. Thus, changes in these measurements due to the formalin fixation process have the potential to alter treatment options for the patient. Keywords: breast margins, formalin, shrinkage, cancer

  17. A Shrinkage Estimator for Combination of Bioassays

    Institute of Scientific and Technical Information of China (English)

    Jian Xiong; D.G. Chen; Zhen-hai Yang

    2007-01-01

    A shrinkage estimator and a maximum likelihood estimator are proposed in this paper for combination of bioassays. The shrinkage estimator is obtained in closed form which incorporates prior information just on the common log relative potency after the homogeneity test for combination of bioassays is accepted. It is a practical improvement over other estimators which require iterative procedure to obtain the estimator for the relative potency. A real data is also used to show the superiorities for the newly-proposed procedures.

  18. Volumetric polymerization shrinkage of contemporary composite resins

    Directory of Open Access Journals (Sweden)

    Halim Nagem Filho

    2007-10-01

    Full Text Available The polymerization shrinkage of composite resins may affect negatively the clinical outcome of the restoration. Extensive research has been carried out to develop new formulations of composite resins in order to provide good handling characteristics and some dimensional stability during polymerization. The purpose of this study was to analyze, in vitro, the magnitude of the volumetric polymerization shrinkage of 7 contemporary composite resins (Definite, Suprafill, SureFil, Filtek Z250, Fill Magic, Alert, and Solitaire to determine whether there are differences among these materials. The tests were conducted with precision of 0.1 mg. The volumetric shrinkage was measured by hydrostatic weighing before and after polymerization and calculated by known mathematical equations. One-way ANOVA (a or = 0.05 was used to determine statistically significant differences in volumetric shrinkage among the tested composite resins. Suprafill (1.87±0.01 and Definite (1.89±0.01 shrank significantly less than the other composite resins. SureFil (2.01±0.06, Filtek Z250 (1.99±0.03, and Fill Magic (2.02±0.02 presented intermediate levels of polymerization shrinkage. Alert and Solitaire presented the highest degree of polymerization shrinkage. Knowing the polymerization shrinkage rates of the commercially available composite resins, the dentist would be able to choose between using composite resins with lower polymerization shrinkage rates or adopting technical or operational procedures to minimize the adverse effects deriving from resin contraction during light-activation.

  19. Development of novel low shrinkage dental nanocomposite

    Science.gov (United States)

    Sun, Yi; Wu, Xiaorong; Liu, Yanju; Xie, Weili; Sun, Shouhua

    2009-07-01

    It has been the focus to develop low shrinkage dental composite resins in recent ten years. A major difficulty in developing low shrinkage dental materials is their deficiency in mechanical properties to clinical use. This paper reviews the present investigations of low shrinkage dental composite resins and attempts to develop a novel system with multifunctional POSS incorporated. In this paper, it is especially interesting to evaluate the influences of shrinkage with different weight percentage of POSS (0~15wt%) incorporated in dental composite resins. Their double bond conversions are evaluated and their microstructures are characterized with Fourier-transform infra-red spectroscopy and X-ray diffraction. Their mechanical properties are also presented in this paper. The results show that the shrinkage of nanocomposites with POSS can be reduced effectively from 3.53% to 2.18%. The mechanical properties of this novel system, such as strength, hardness and toughness, are also enhanced greatly. Especially with 2wt%POSS incorporated, the best integrative improved effects are revealed. The mechanism of shrinkage is discussed.

  20. Estimating crack growth in temperature damaged concrete

    Science.gov (United States)

    Recalde, Juan Jose

    2009-12-01

    Evaluation of the structural condition of deteriorated concrete infrastructure and evaluation of new sustainable cementitious materials require an understanding of how the material will respond to applied loads and environmental exposures. A fundamental understanding of how microstructural changes in these materials relate to changes in mechanical properties and changes in fluid penetrability is needed. The ability to provide rapid, inexpensive assessment of material characteristics and relevant engineering properties is valuable for decision making and asset management purposes. In this investigation, the effects of changes in dynamic elastic properties with water content and fluid penetrability properties before and after a 300°C exposure were investigated based on estimates of the crack density parameter from dry and saturated cracked media. The experimental and analytical techniques described in this dissertation allow calculation of a value for the crack density parameter using nondestructive determination of wet and dry dynamic shear modulus of relatively thin disks. The techniques were used to compare a conventional concrete mixture to several mixtures with enhanced sustainability characteristics. The three enhanced sustainable materials investigated were a very high fly ash mixture, a magnesium phosphate cement based mortar, and a magnesium phosphate cement based concrete, and were compared to a conventional concrete mixture. The analysis provided both quantitative assessment of changes with high temperature damage and autogenous healing, and estimates of changes in mean crack trace lengths. The results showed that water interaction, deterioration due to damage, and autogenous healing recovery were different for the magnesium phosphate cement based mixtures than the portland cement based concrete mixtures. A strong correlation was found between log-transformed Air Permeability Index, dynamic shear modulus, and crack density parameter. The findings imply

  1. Durability and Shrinkage Characteristics of Self-Compacting Concretes Containing Recycled Coarse and/or Fine Aggregates

    Directory of Open Access Journals (Sweden)

    Mehmet Gesoglu

    2015-01-01

    Full Text Available This paper addresses durability and shrinkage performance of the self-compacting concretes (SCCs in which natural coarse aggregate (NCA and/or natural fine aggregate (NFA were replaced by recycled coarse aggregate (RCA and/or recycled fine aggregate (RFA, respectively. A total of 16 SCCs were produced and classified into four series, each of which included four mixes designed with two water to binder (w/b ratios of 0.3 and 0.43 and two silica fume replacement levels of 0 and 10%. Durability properties of SCCs were tested for rapid chloride penetration, water sorptivity, gas permeability, and water permeability at 56 days. Also, drying shrinkage accompanied by the water loss and restrained shrinkage of SCCs were monitored over 56 days of drying period. Test results revealed that incorporating recycled coarse and/or fine aggregates aggravated the durability properties of SCCs tested in this study. The drying shrinkage and restrained shrinkage cracking of recycled aggregate (RA concretes had significantly poorer performance than natural aggregate (NA concretes. The time of cracking greatly prolonged as the RAs were used along with the increase in water/binder ratio.

  2. Soil cracking modelling using the mesh-free SPH method

    CERN Document Server

    Bui, H H; Kodikara, J; Sanchez, M

    2015-01-01

    The presence of desiccation cracks in soils can significantly alter their mechanical and hydrological properties. In many circumstances, desiccation cracking in soils can cause significant damage to earthen or soil supported structures. For example, desiccation cracks can act as the preference path way for water flow, which can facilitate seepage flow causing internal erosion inside earth structures. Desiccation cracks can also trigger slope failures and landslides. Therefore, developing a computational procedure to predict desiccation cracking behaviour in soils is vital for dealing with key issues relevant to a range of applications in geotechnical and geo-environment engineering. In this paper, the smoothed particle hydrodynamics (SPH) method will be extended for the first time to simulate shrinkage-induced soil cracking. The main objective of this work is to examine the performance of the proposed numerical approach in simulating the strong discontinuity in material behaviour and to learn about the crack ...

  3. Consequences of preferential flow in cracking clay soils for contamination-risk of shallow aquifers

    NARCIS (Netherlands)

    Oostindie, K.; Bronswijk, J.J.B.

    1995-01-01

    A method is presented to asses the contamination risk of aquifers covered with cracking clay soils, with special emphasis on preferential flow through shrinkage cracks. A water extraction area was divided into units with homogeneous soil types and hydrological conditions. For each unit, a one-dimens

  4. Detection and Influence of Shrinkage Pores and Nonmetallic Inclusions on Fatigue Life of Cast Aluminum Alloys

    Science.gov (United States)

    Tijani, Yakub; Heinrietz, André; Stets, Wolfram; Voigt, Patrick

    2013-12-01

    In the current study, test bars of cast aluminum alloys EN AC-AlSi8Cu3 and EN AC-AlSi7Mg0.3 were produced with a defined amounts of shrinkage pores and oxides. For this purpose, a permanent mold with heating and cooling devices for the generation of pores was constructed. The oxides were produced by contaminating the melt. The specimens and their corresponding defect distributions were examined and quantified by X-ray computer tomography (CT) and quantitative metallography, respectively. A special test algorithm for the simultaneous image analyses of pores and oxides was developed. Fatigue tests were conducted on the defective samples. It was found that the presence of shrinkage pores lowers the fatigue strength, and only few oxide inclusions were found to initiate fatigue cracks when shrinkage pores are present. The results show that the pore volume is not sufficient to characterize the influence of shrinkage pores on fatigue life. A parametric model for the calculation of fatigue life based on the pore parameters obtained from CT scans was implemented. The model accounts for the combined impact of pore location, size, and shape on fatigue life reduction.

  5. Basin Depth Control on the Autogenic Timescale of Fluviodeltaic Systems

    Science.gov (United States)

    Carlson, B.; Kim, W.; Piliouras, A.

    2013-12-01

    ABSTRACT Autogenic processes are inherent processes in sediment transport that influence landscape building and leave distinct signatures in the sedimentary record. It is of great interest to understand autogenic processes in order to decouple internal processes from external controls, such as tectonics or climate change. Here we present results from a series of delta-building experiments to determine the variability of the fluviodeltaic autogenic timescale in response to varying basin water depth. This internal timescale was measured as the time that is required for the delta topset to be reworked through a full cycle of storage and release of sediment. The topset aggrades by fluvial sedimentation until it reaches a maximum slope, at which point a large amount of sediment starts to release, typically resulting in strong channelization. This is followed by a period of avulsions, lateral migration, and backfilling of channels on the topset. These storage and release events are repeated. We used time-lapse images to track shoreline positions and observe changes in progradation rate. The changes in topset topography were also used to determine storage and release duration. The experimental results indicate that the autogenic timescales generally increase with increasing basin water depth. These observations may be explained by the amount of time required to build a lobe with an area large enough to trigger a switch from a lobe-building release event to a backfilling storage event. Individual lobes show a similar surface area regardless of basin depth in the experiments. Deeper basin depth simply requires a larger volume to be filled within this area, thus more time to complete one autogenic process. However, when channel depth is significantly smaller than basin depth, e.g., in very deep basins, stochastic variability in sediment transport and channel lateral mobility outweighs the autogenic cyclicity. This study suggests that internal dynamics and its stratigraphic

  6. Creep and shrinkage effects on integral abutment bridges

    Science.gov (United States)

    Munuswamy, Sivakumar

    Integral abutment bridges provide bridge engineers an economical design alternative to traditional bridges with expansion joints owing to the benefits, arising from elimination of expensive joints installation and reduced maintenance cost. The superstructure for integral abutment bridges is cast integrally with abutments. Time-dependent effects of creep, shrinkage of concrete, relaxation of prestressing steel, temperature gradient, restraints provided by abutment foundation and backfill and statical indeterminacy of the structure introduce time-dependent variations in the redundant forces. An analytical model and numerical procedure to predict instantaneous linear behavior and non-linear time dependent long-term behavior of continuous composite superstructure are developed in which the redundant forces in the integral abutment bridges are derived considering the time-dependent effects. The redistributions of moments due to time-dependent effects have been considered in the analysis. The analysis includes nonlinearity due to cracking of the concrete, as well as the time-dependent deformations. American Concrete Institute (ACI) and American Association of State Highway and Transportation Officials (AASHTO) models for creep and shrinkage are considered in modeling the time dependent material behavior. The variations in the material property of the cross-section corresponding to the constituent materials are incorporated and age-adjusted effective modulus method with relaxation procedure is followed to include the creep behavior of concrete. The partial restraint provided by the abutment-pile-soil system is modeled using discrete spring stiffness as translational and rotational degrees of freedom. Numerical simulation of the behavior is carried out on continuous composite integral abutment bridges and the deformations and stresses due to time-dependent effects due to typical sustained loads are computed. The results from the analytical model are compared with the

  7. Measuring techniques for autogenous strain of cement paste

    DEFF Research Database (Denmark)

    Lura, Pietro; Jensen, Ole Mejlhede

    2006-01-01

    Volumetric measurement of autogenous strain is frequently performed by placing the fresh cement paste in a rubber membrane submerged in water. The volume change of the cement paste is measured by the amount of water displaced by the submerged sample. Volumetric and linear measurements of autogenous...... of the volumetric method. Water absorption is driven by a lowering of the water activity in the cement paste due to dissolved salts in the pore fluid and to self-desiccation. From the moment of casting, significant water uptake was registered in all experiments. This water uptake influenced the volumetric...... on the same cement pastes....

  8. Measuring techniques for autogenous strain of cement paste

    DEFF Research Database (Denmark)

    Lura, Pietro; Jensen, Ole Mejlhede

    2007-01-01

    Volumetric measurement of autogenous strain is frequently performed by placing the fresh cement paste in a rubber membrane submerged in water. The volume change of the cement paste is measured by the amount of water displaced by the submerged sample. Volumetric and linear measurements of autogenous...... of the volumetric method. Water absorption is driven by a lowering of the water activity in the cement paste due to dissolved salts in the pore fluid and to self-desiccation. From the moment of casting, significant water uptake was registered in all experiments. This water uptake influenced the volumetric...... on the same cement pastes....

  9. A Bayesian Shrinkage Approach for AMMI Models.

    Science.gov (United States)

    da Silva, Carlos Pereira; de Oliveira, Luciano Antonio; Nuvunga, Joel Jorge; Pamplona, Andrezza Kéllen Alves; Balestre, Marcio

    2015-01-01

    Linear-bilinear models, especially the additive main effects and multiplicative interaction (AMMI) model, are widely applicable to genotype-by-environment interaction (GEI) studies in plant breeding programs. These models allow a parsimonious modeling of GE interactions, retaining a small number of principal components in the analysis. However, one aspect of the AMMI model that is still debated is the selection criteria for determining the number of multiplicative terms required to describe the GE interaction pattern. Shrinkage estimators have been proposed as selection criteria for the GE interaction components. In this study, a Bayesian approach was combined with the AMMI model with shrinkage estimators for the principal components. A total of 55 maize genotypes were evaluated in nine different environments using a complete blocks design with three replicates. The results show that the traditional Bayesian AMMI model produces low shrinkage of singular values but avoids the usual pitfalls in determining the credible intervals in the biplot. On the other hand, Bayesian shrinkage AMMI models have difficulty with the credible interval for model parameters, but produce stronger shrinkage of the principal components, converging to GE matrices that have more shrinkage than those obtained using mixed models. This characteristic allowed more parsimonious models to be chosen, and resulted in models being selected that were similar to those obtained by the Cornelius F-test (α = 0.05) in traditional AMMI models and cross validation based on leave-one-out. This characteristic allowed more parsimonious models to be chosen and more GEI pattern retained on the first two components. The resulting model chosen by posterior distribution of singular value was also similar to those produced by the cross-validation approach in traditional AMMI models. Our method enables the estimation of credible interval for AMMI biplot plus the choice of AMMI model based on direct posterior

  10. A Bayesian Shrinkage Approach for AMMI Models.

    Directory of Open Access Journals (Sweden)

    Carlos Pereira da Silva

    Full Text Available Linear-bilinear models, especially the additive main effects and multiplicative interaction (AMMI model, are widely applicable to genotype-by-environment interaction (GEI studies in plant breeding programs. These models allow a parsimonious modeling of GE interactions, retaining a small number of principal components in the analysis. However, one aspect of the AMMI model that is still debated is the selection criteria for determining the number of multiplicative terms required to describe the GE interaction pattern. Shrinkage estimators have been proposed as selection criteria for the GE interaction components. In this study, a Bayesian approach was combined with the AMMI model with shrinkage estimators for the principal components. A total of 55 maize genotypes were evaluated in nine different environments using a complete blocks design with three replicates. The results show that the traditional Bayesian AMMI model produces low shrinkage of singular values but avoids the usual pitfalls in determining the credible intervals in the biplot. On the other hand, Bayesian shrinkage AMMI models have difficulty with the credible interval for model parameters, but produce stronger shrinkage of the principal components, converging to GE matrices that have more shrinkage than those obtained using mixed models. This characteristic allowed more parsimonious models to be chosen, and resulted in models being selected that were similar to those obtained by the Cornelius F-test (α = 0.05 in traditional AMMI models and cross validation based on leave-one-out. This characteristic allowed more parsimonious models to be chosen and more GEI pattern retained on the first two components. The resulting model chosen by posterior distribution of singular value was also similar to those produced by the cross-validation approach in traditional AMMI models. Our method enables the estimation of credible interval for AMMI biplot plus the choice of AMMI model based on direct

  11. Сalculation theory for shrinkage stresses in cellular concrete wall panels in carbonation processes with account of creep

    Directory of Open Access Journals (Sweden)

    Chepurnenko Anton Sergeevich

    2016-12-01

    Full Text Available The task of comprehensive analysis presented in this article is a development of theory of calculation of shrinkage stresses in cellular concrete wall panels; such stresses occur due to carbonation of concrete because of the creep of material. Analytical dependences characterizing the influence of carbonation on the modulus of elasticity, shrinkage and creep of autoclaved cellular concrete, as well as the regularity of variation of carbonation degree as per thickness of the wall panels depending on time, were obtained. The proposed theory of calculation of shrinkage stresses in cellular concrete wall panels, with account of concrete creep, makes it possible to predict the influence of carbonation processes on crack resistance thereof, and thus to develop measures of technological and structural nature, in order to improve their operational reliability and durability.

  12. Polymerization shrinkage, flexural and compression properties of low-shrinkage dental resin composites.

    Science.gov (United States)

    Park, Jeong-Kil; Lee, Geun-Ho; Kim, Jong-Hwa; Park, Mi-Gyoung; Ko, Ching-Chang; Kim, Hyung-Il; Kwon, Yong Hoon

    2014-01-01

    This study evaluated the polymerization shrinkage, flexural and compressive properties of low-shrinkage resin composites. For the study, four methacrylate-based and one silorane-based resin composites were light cured using three different light-curing units (LCUs) and their polymerization shrinkage, flexural (strength (FS) and modulus (FM)) and compressive (strength (CS) and modulus (CM)) properties were evaluated. Data were statistically analyzed using ANOVA and a post-hoc Tukey test. The polymerization shrinkage ranged approximately 7.6-14.2 μm for 2-mm thick specimens depending on the resin product and LCU. Filtek LS showed the least shrinkage while the rest shrank approximately 13.2-14.2 μm. However, Filtek LS showed the greatest shrinkage difference for the used LCUs. FS and CS of the tested specimens ranged 96.2-152.1 MPa and 239.2-288.4 MPa, respectively, depending on the resin product and LCU. The highest and lowest FS and FM were recorded for the methacrylate-based resin composites. Among the specimens, Filtek LS showed the lowest CS and CM.

  13. Cracking resistance performance of super vertical-distance pumped SFRC

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The mix ratio of steel fiber reinforced concrete(SFRC)was optimized using the principles that workability must meet the pumping demand and anti-cracking performance should be optimal.The effect of SFRC on the initial cracking load,the ultimate load and the crack width of the reinforced concrete (RC) member were analyzed in this paper.It was found that the admixture had good preservation of moisture and adhesion and the fibers distributed homogeneously in one hour out of the machine.According to the pumping results,the SFRC could be pumped vertically up to 306 m.Based on the standard computation formula of cracks,the maximum crack width of an RC member with 0.8% steel fiber (by volume) is about 32% lower than that of standard RC member.Through an experimental research on full-scale model tests for the steel and concrete composite anchorage zone on a pylon,the SFRC not only remarkably increases the crack resistance and the ultimate load,but the initial load also improves 33% approximately.It is also indicated that plastic shrinkage cracking of SFRC in which volume fraction of steel fibers is 0.8% can be restrained obviously and the unrestrained drying shrinkage can be diminished by about 50% at early age.The results confirmed that the SFRC can lessen the shrinkage crack of concrete and enhance markedly the direct tensile strength.Therefore,the SFRC can solve the key question of crack resistance for the anchorage zone of a bridge tower.

  14. Shrinkage of dental composite in simulated cavity measured with digital image correlation.

    Science.gov (United States)

    Li, Jianying; Thakur, Preetanjali; Fok, Alex S L

    2014-07-21

    Polymerization shrinkage of dental resin composites can lead to restoration debonding or cracked tooth tissues in composite-restored teeth. In order to understand where and how shrinkage strain and stress develop in such restored teeth, Digital Image Correlation (DIC) was used to provide a comprehensive view of the displacement and strain distributions within model restorations that had undergone polymerization shrinkage. Specimens with model cavities were made of cylindrical glass rods with both diameter and length being 10 mm. The dimensions of the mesial-occlusal-distal (MOD) cavity prepared in each specimen measured 3 mm and 2 mm in width and depth, respectively. After filling the cavity with resin composite, the surface under observation was sprayed with first a thin layer of white paint and then fine black charcoal powder to create high-contrast speckles. Pictures of that surface were then taken before curing and 5 min after. Finally, the two pictures were correlated using DIC software to calculate the displacement and strain distributions. The resin composite shrunk vertically towards the bottom of the cavity, with the top center portion of the restoration having the largest downward displacement. At the same time, it shrunk horizontally towards its vertical midline. Shrinkage of the composite stretched the material in the vicinity of the "tooth-restoration" interface, resulting in cuspal deflections and high tensile strains around the restoration. Material close to the cavity walls or floor had direct strains mostly in the directions perpendicular to the interfaces. Summation of the two direct strain components showed a relatively uniform distribution around the restoration and its magnitude equaled approximately to the volumetric shrinkage strain of the material.

  15. Effect of Expansive Admixtures on the Shrinkage and Mechanical Properties of High-Performance Fiber-Reinforced Cement Composites

    Directory of Open Access Journals (Sweden)

    Won-Chang Choi

    2013-01-01

    Full Text Available High-performance fiber-reinforced cement composites (HPFRCCs are characterized by strain-hardening and multiple cracking during the inelastic deformation process, but they also develop high shrinkage strain. This study investigates the effects of replacing Portland cement with calcium sulfoaluminate-based expansive admixtures (CSA EXAs to compensate for the shrinkage and associated mechanical behavior of HPFRCCs. Two types of CSA EXA (CSA-K and CSA-J, each with a different chemical composition, are used in this study. Various replacement ratios (0%, 8%, 10%, 12%, and 14% by weight of cement of CSA EXA are considered for the design of HPFRCC mixtures reinforced with 1.5% polyethylene (PE fibers by volume. Mechanical properties, such as shrinkage compensation, compressive strength, flexural strength, and direct tensile strength, of the HPFRCC mixtures are examined. Also, crack width and development are investigated to determine the effects of the EXAs on the performance of the HPFRCC mixtures, and a performance index is used to quantify the performance of mixture. The results indicate that replacements of 10% CSA-K (Type 1 and 8% CSA-J (Type 2 considerably enhance the mechanical properties and reduce shrinkage of HPFRCCs.

  16. Autogenous tooth transplantation: an alternative to replace extracted tooth

    Directory of Open Access Journals (Sweden)

    David B. Kamadjaja

    2015-09-01

    Full Text Available Background: The gold standard treatment to replace missing tooth is dental implants, however, in certain cases, such as in young patients its placement is contraindicated. Autogenous tooth transplantation, which has been widely done in Scandinavian countries for many years, may become a good alternative to overcome this problem. Purpose: This article attempted to provide information about the indication, treatment planning, surgical technique and the successful result of autogenous tooth transplantation. Case: A fifteen year old male patient presented with large caries and periapical disease of his lower left first molar, which was partially erupted and the roots was not fully formed in radiograph. Case management: Autogenous tooth transplantation procedure was performed consisting of extraction of #36, odontectomy of #38 followed by its implantation to socket #36 and fixation of the transplanted tooth to the adjacent teeth. Post operative evaluation was done on regular basis within 18 months period. There was no complaint, the tooth was clinically stable and no evidence of periodontal problem. Serial radiographs showed healing of alveolar bone and periodontal tissue, and the complete root formation was evident by 18 months post operatively. Conclusion: Autogenous tooth transplantation is a potential alternative to replace extracted tooth. Provided that the case be properly planned and operation carefully performed, successful result of this treatment can be achieved.

  17. Measuring autogenous strain of concrete with corrugated moulds

    DEFF Research Database (Denmark)

    Tian, Qian; Jensen, Ole Mejlhede

    2008-01-01

    A reliable technique to quantify autogenous strain is a prerequisite to numerical modeling in stress calculations for high performance concrete. The introducing of a special kind of corrugated tube mould helps to transforming volume strain measurement into liner strain measurement in horizontal...

  18. 30 CFR 35.20 - Autogenous-ignition temperature test.

    Science.gov (United States)

    2010-07-01

    ...-constantan or chromelalumel—and a potentiometer shall be used for all temperature measurements. (3) Syringe...) Temperature control. Each autotransformer shall be so adjusted that the temperature at the neck, mid-section... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Autogenous-ignition temperature test....

  19. Autogenic training: a narrative and quantitative review of clinical outcome.

    Science.gov (United States)

    Linden, W

    1994-09-01

    This review of controlled outcome research on Autogenic Training complements the literature by pooling narrative and quantitative approaches, by including only studies with experimental controls, by integrating the English and German literature, and by adding research findings published since the last review. Whereas previous reviews have already reported positive effects of Autogenic Training for migraine, insomnia, and test anxiety, additional supportive findings for angina pectoris, asthma, childbirth, eczema, hypertension, infertility, Raynaud's disease, and recovery from myocardial infarction are discussed here. The impact of protocol variations on outcome is described, and the specificity of Autogenic Training relative to other stress management techniques is highlighted. Quantitative findings suggested that Autogenic Training was associated with medium-sized pre- to posttreatment effects ranging from d = .43 for biological indices of change to d = .58 for psychological and behavioral indices thus matching effect sizes for other biobehavioral treatment techniques like biofeedback and muscular relaxation. Length of treatment did not affect clinical outcome. The discussion emphasizes how narrative and quantitative strategies complement one another.

  20. Treatment of Childhood Migraine Using Autogenic Feedback Training.

    Science.gov (United States)

    Labbe, Elise L.

    1984-01-01

    Compared autogenic feedback training with a waiting-list control group as a treatment for children (N=28) with migraine headaches. Children in the treatment condition were significantly improved at the end of treatment and at one-month and six-month follow-up. No improvement was found for the children in the control condition. (BH)

  1. Discrete multiscale wavelet shrinkage and integrodifferential equations

    Science.gov (United States)

    Didas, S.; Steidl, G.; Weickert, J.

    2008-04-01

    We investigate the relation between discrete wavelet shrinkage and integrodifferential equations in the context of simplification and denoising of one-dimensional signals. In the continuous setting, strong connections between these two approaches were discovered in 6 (see references). The key observation is that the wavelet transform can be understood as derivative operator after the convolution with a smoothing kernel. In this paper, we extend these ideas to the practically relevant discrete setting with both orthogonal and biorthogonal wavelets. In the discrete case, the behaviour of the smoothing kernels for different scales requires additional investigation. The results of discrete multiscale wavelet shrinkage and related discrete versions of integrodifferential equations are compared with respect to their denoising quality by numerical experiments.

  2. Application of digital image correlation to full-field measurement of shrinkage strain of dental composites

    Institute of Scientific and Technical Information of China (English)

    Jian-ying LI; Andrew LAU; Alex S.L.FOK

    2013-01-01

    Objectives:Polymerization shrinkage of dental composites remains a major concern in restorative dentistry because it can lead to micro-cracking of the tooth and debonding at the tooth-restoration interface.The aim of this study was to measure the full-field polymerization shrinkage of dental composites using the optical digital image correlation (DIC) method and to evaluate how the measurement is influenced by the factors in experiment setup and image analysis.Methods:Four commercial dental composites,Premise Dentine,Z100,Z250 and Tetric EvoCeram,were tested.Composite was first placed into a slot mould to form a bar specimen with rectangular-section of 4 mm×2 mm,followed by the surface painting to create irregular speckles.Curing was then applied at one end of the specimen while the other part were covered against curing light for simulating the clinical curing condition of composite in dental cavity.The painted surface was recorded by a charge-coupled device (CCD) camera before and after curing.Subsequently,the volumetric shrinkage of the specimen was calculated with specialist DIC software based on image cross correlation.In addition,a few factors that may influence the measuring accuracy,including the subset window size,speckle size,illumination light and specimen length,were also evaluated.Results:The volumetric shrinkage of the specimen generally decreases with increasing distance from the irradiated surface with a conspicuous exception being the composite Premise Dentine as its maximum shrinkage occurred at a subsurface distance of about 1 mm instead of the irradiated surface.Zl00 had the greatest maximum shrinkage strain,followed by Z250,Tetric EvoCeram and then Premise Dentine.Larger subset window size made the shrinkage strain contour smoother.But the cost was that some details in the heterogeneity of the material were lost.Very small subset window size resulted in a lot of noise in the data,making it difficult to discern the general pattern in the strain

  3. Regularized brain reading with shrinkage and smoothing

    OpenAIRE

    Wehbe, Leila; Ramdas, Aaditya; Steorts, Rebecca C.; Shalizi, Cosma Rohilla

    2014-01-01

    Functional neuroimaging measures how the brain responds to complex stimuli. However, sample sizes are modest, noise is substantial, and stimuli are high dimensional. Hence, direct estimates are inherently imprecise and call for regularization. We compare a suite of approaches which regularize via shrinkage: ridge regression, the elastic net (a generalization of ridge regression and the lasso), and a hierarchical Bayesian model based on small area estimation (SAE). We contrast regularization w...

  4. Nearest shrunken centroids via alternative genewise shrinkages

    Science.gov (United States)

    Choi, Byeong Yeob; Bair, Eric; Lee, Jae Won

    2017-01-01

    Nearest shrunken centroids (NSC) is a popular classification method for microarray data. NSC calculates centroids for each class and “shrinks” the centroids toward 0 using soft thresholding. Future observations are then assigned to the class with the minimum distance between the observation and the (shrunken) centroid. Under certain conditions the soft shrinkage used by NSC is equivalent to a LASSO penalty. However, this penalty can produce biased estimates when the true coefficients are large. In addition, NSC ignores the fact that multiple measures of the same gene are likely to be related to one another. We consider several alternative genewise shrinkage methods to address the aforementioned shortcomings of NSC. Three alternative penalties were considered: the smoothly clipped absolute deviation (SCAD), the adaptive LASSO (ADA), and the minimax concave penalty (MCP). We also showed that NSC can be performed in a genewise manner. Classification methods were derived for each alternative shrinkage method or alternative genewise penalty, and the performance of each new classification method was compared with that of conventional NSC on several simulated and real microarray data sets. Moreover, we applied the geometric mean approach for the alternative penalty functions. In general the alternative (genewise) penalties required fewer genes than NSC. The geometric mean of the class-specific prediction accuracies was improved, as well as the overall predictive accuracy in some cases. These results indicate that these alternative penalties should be considered when using NSC. PMID:28199352

  5. Comparative Study of Shrinkage and Non-Shrinkage Model of Food Drying

    Science.gov (United States)

    Shahari, N.; Jamil, N.; Rasmani, KA.

    2016-08-01

    A single phase heat and mass model has always been used to represent the moisture and temperature distribution during the drying of food. Several effects of the drying process, such as physical and structural changes, have been considered in order to increase understanding of the movement of water and temperature. However, the comparison between the heat and mass equation with and without structural change (in terms of shrinkage), which can affect the accuracy of the prediction model, has been little investigated. In this paper, two mathematical models to describe the heat and mass transfer in food, with and without the assumption of structural change, were analysed. The equations were solved using the finite difference method. The converted coordinate system was introduced within the numerical computations for the shrinkage model. The result shows that the temperature with shrinkage predicts a higher temperature at a specific time compared to that of the non-shrinkage model. Furthermore, the predicted moisture content decreased faster at a specific time when the shrinkage effect was included in the model.

  6. Polymerization shrinkage assessment of dental resin composites: a literature review.

    Science.gov (United States)

    Kaisarly, Dalia; Gezawi, Moataz El

    2016-09-01

    Composite restorations are widely used worldwide, but the polymerization shrinkage is their main disadvantage that may lead to clinical failures and adverse consequences. This review reports, currently available in vitro techniques and methods used for assessing the polymerization shrinkage. The focus lies on recent methods employing three-dimensional micro-CT data for the evaluation of polymerization shrinkage: volumetric measurement and the shrinkage vector evaluation through tracing particles before and after polymerization. Original research articles reporting in vitro shrinkage measurements and shrinkage stresses were included in electronic and hand-search. Earlier methods are easier, faster and less expensive. The procedures of scanning the samples in the micro-CT and performing the shrinkage vector evaluation are time consuming and complicated. Moreover, the respective software is not commercially available and the various methods for shrinkage vector evaluation are based on different mathematical principles. Nevertheless, these methods provide clinically relevant information and give insight into the internal shrinkage behavior of composite applied in cavities and how boundary conditions affect the shrinkage vectors. The traditional methods give comparative information on polymerization shrinkage of resin composites, whereas using three-dimensional micro-CT data for volumetric shrinkage measurement and the shrinkage vector evaluation is a highly accurate method. The methods employing micro-CT data give the researchers knowledge related to the application method and the boundary conditions of restorations for visualizing the shrinkage effects that could not be seen otherwise. Consequently, this knowledge can be transferred to the clinical situation to optimize the material manipulation and application techniques for improved outcomes.

  7. A cure shrinkage model for analyzing the stresses and strains in encapsulated assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, R.S.; Lagasse, R.R.; Guess, T.R. (Sandia National Labs., Albuquerque, NM (United States)); Plazek, D.J.; Bero, C. (Pittsburgh Univ., PA (United States). Dept. of Materials Science and Engineering)

    1992-01-01

    Electrical component assemblies are encapsulated to provide delicate parts with voltage isolation and protection against damage caused by shock, vibration, and harsh atmospheric environments. During cure, thermosetting resins shrink and harden simultaneously. If the natural deformation of the resin is constrained by adhesion to the mold or to relatively stiff embedded components, cure shrinkage stresses are generated in the encapsulant. Subsequent cooling or thermal cycling produces additional stresses that are caused by the mismatches in thermal strains among the materials in the encapsulated assembly. Although cure shrinkage stresses frequently are neglected because they are considerably smaller than thermal stresses, cure shrinkage stresses can cause delamination or fractures in the encapsulant, since the partially cured resin is not as tough as the fully cured material. Cracks generated during cure can compromise performance (e. g., permit dielectric breakdown), degrade a component's protection, and grow under subsequent thermal cycling producing residual stresses that differ from those found in uncracked assemblies. 3 refs., 11 figs.

  8. Do low-shrink composites reduce polymerization shrinkage effects?

    Science.gov (United States)

    Tantbirojn, D; Pfeifer, C S; Braga, R R; Versluis, A

    2011-05-01

    Progress in polymer science has led to continuous reduction of polymerization shrinkage, exemplified by a new generation of "low-shrink composites". The common inference that shrinkage stress effects will be reduced in teeth restored with such restoratives with lower shrinkage was tested in extracted human premolars. Mesio-occluso-distal slot-shaped cavities were cut and restored with a conventional (SupremePlus) or low-shrink (RefleXions, Premise, Kalore, and LS) composite (N = 5). We digitized the coronal surfaces before and 10 min after restoration to determine cuspal deflection from the buccal and lingual volume change/area. We also determined the main properties involved (total shrinkage, post-gel shrinkage, degree of conversion, and elastic modulus), as well as microleakage, to verify adequate bonding. It was shown that, due to shrinkage stresses, buccal and lingual surfaces pulled inward after restoration (9-14 microns). Only Kalore and LS resulted in significantly lower tooth deformation (ANOVA/Student-Newman-Keuls post hoc, p = 0.05). The other two low-shrink composites, despite having the lowest and highest total shrinkage values, did not cause significant differences in cuspal deflection. Deflection seemed most related to the combination of post-gel shrinkage and elastic modulus. Therefore, even for significantly lower total shrinkage values, shrinkage stress is not necessarily reduced.

  9. Autogenous tooth transplantation for replacing a lost tooth: case reports

    OpenAIRE

    Kang, Ji-Youn; Chang, Hoon-Sang; Hwang,Yun-Chan; Hwang, In-Nam; Oh, Won-Mann; LEE, Bin-Na

    2013-01-01

    The autogenous tooth transplantation is an alternative treatment replacing a missing tooth when a suitable donor tooth is available. It is also a successful treatment option to save significant amount of time and cost comparing implants or conventional prosthetics. These cases, which required single tooth extraction due to deep caries and severe periodontal disease, could have good results by transplanting non-functional but sound donor tooth to the extraction site.

  10. Reducing Shrinkage in Canned and Frozen Mushrooms

    OpenAIRE

    Gormley, T. R. (Thomas Ronan); Walshe, P.E.

    1982-01-01

    The process involving a preliminary soaking of the mushrooms in water for 20 min followed by a chill storage period followed by a further water soak for 2 hr, and known as the 3S process, gave a considerable reduction in total shrinkage in both brown and white strain canned mushrooms compared with the control samples. Water uptake by the mushrooms in the 3S process was greatest when the soaking water temperature was between 20 and 30°C and had a pH of 8. Citric acid in the blanch water enhanc...

  11. Mechanical Self-shrinkage of Artillery Barrels

    Directory of Open Access Journals (Sweden)

    Ioan Ciorba

    2012-09-01

    Full Text Available Objective of this paper is to define what self-shrink artillery barrel is. She is considered to be a compound barrel like as a thick-walled tube (k>2, in his wall being introduced a state of stress and strain using specific technological proceeds. This type of treatment is aimed to increase the artillery barrel load capacity and wear resistance in operation. The experimental part was realized using an industrial plant at Mechanical Factory of Resita. This part presents a comparative study between mechanical self-shrinkage on artillery head barrel, first using a mandrel and seconds a ball.

  12. Huadong sintering model about expansion and shrinkage

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The whole sintering course from the beginning of heating to the end of heat preservation stage was studied by taking into account the influence of pressing. It was found that there exist expanding mechanism and shrinking mechanism in the sintering process, and the expanding mechanism is always acting before the shrinking mechanism. Whether the sintering body shrinks or expands depends on the interaction between the two mechanisms. And according to this, the Huadong sintering model in account of expansion and shrinkage mechanism was given.

  13. Physical modeling of shrink-swell cycles and cracking in a clayey vadose zone

    CERN Document Server

    Chertkov, V Y

    2014-01-01

    Physical understanding of the crack origin and quantitative physical prediction of the crack volume variation far from the clay soil surface are necessary to protect the underlying aquifers from pollutants. The basis of this work is an available physical model for predicting the shrinkage and swelling curves in the maximum water content range (the primary curves) and crack volume variation. The objective of the work is to generalize this model to the conditions of the deep layer of a clayey vadose zone with the overburden pressure, multiple shrinkage-swelling, and variation of water content in a small range. We aim to show that the scanning shrinkage and swelling curves, and steady shrink-swell cycles existing in such conditions, inevitably lead to the occurrence of cracks and a hysteretic crack volume. The generalization is based on the transition to the increasingly complex soil medium from the contributive clay, through the intra-aggregate matrix and aggregated soil with no cracking, to the soil with crack...

  14. Towards a first classification of aerosol shrinkage events

    Directory of Open Access Journals (Sweden)

    E. Alonso-Blanco

    2015-09-01

    Full Text Available This work presents for the first time a classification of shrinkage events based on the aerosol processes that precede them. To this end, 3.5 years of continuous measurements (from 2009 to 2012 of aerosol size distributions, obtained with a Scanning Mobility Particle Sizer (SMPS at an urban background site in Southern Europe, have been interpreted. 48 shrinkage events were identified and analysed, all occurring during spring and summer when the atmospheric conditions are more favourable for their development. In this study the shrinkage events took place mostly towards the end of the day, and their occurrence could be associated to atmospheric dilution conditions and a reduction in photochemical activity. The shrinkage rate (SR varied between −1.0 and −11.1 nm h−1 (average value of −4.7 ± 2.6 nm h−1. Changes in particle concentrations corresponding to the nucleation and Aitken modes were detected, whereby an increase in the number of particles in the nucleation mode often coincided with a reduction in the Aitken mode. The accumulation mode did not undergo significant changes during these processes. In addition, in some cases, a dilution of the total particle number concentration in the ambient air was observed. Following the proposed methodology, three groups of events have been identified: Group I (NPF + shrinkage, Group II (aerosol growth process + shrinkage and Group III (pure shrinkage events. The largest number of shrinkage events has been observed in the absence of prior processes, i.e. pure shrinkage events, followed by Group I events and finally Group II events. Although this analysis has confirmed that the triggering of shrinkage events is clearly linked to the atmospheric situation and the characteristics of the measurement area, this classification may contribute to a better understanding of the processes involved and the features that characterize shrinkage events.

  15. Autogenous Regulation of Splicing of the Transcript of a Yeast Ribosomal Protein Gene

    Science.gov (United States)

    Dabeva, Mariana D.; Post-Beittenmiller, Martha A.; Warner, Jonathan R.

    1986-08-01

    The gene for a yeast ribosomal protein, RPL32, contains a single intron. The product of this gene appears to participate in feedback control of the splicing of the intron from the transcript. This autogenous regulation of splicing provides a striking analogy to the autogenous regulation of translation of ribosomal proteins in Escherichia coli.

  16. Influence of temperature on autogenous deformation and relative humidity change in hardening cement paste

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Hansen, Per Freiesleben

    1999-01-01

    This paper deals with autogenous deformation and autogenous relative humidity change (RH change) in hardening cement paste. Theoretical considerations and experimental data are presented, which elucidate the influence of temperature on these properties. This is an important subject in the control...

  17. Adjuvant auricular electroacupuncture and autogenic training in rheumatoid arthritis: a randomized controlled trial. Auricular acupuncture and autogenic training in rheumatoid arthritis

    DEFF Research Database (Denmark)

    Bernateck, M; Becker, M; Schwake, C

    2008-01-01

    BACKGROUND: In contrast to psychological interventions the usefulness of acupuncture as an adjuvant therapy in rheumatoid arthritis (RA) has not yet been demonstrated. OBJECTIVE: The efficacy of auricular electroacupuncture (EA) was directly compared with autogenic training (AT). METHODS: Patients...

  18. Autogenic therapy: Techniques, foundations, health and clinical applications, and empirical support

    Directory of Open Access Journals (Sweden)

    Manuel R. Abuín

    2016-12-01

    Full Text Available Autogenic therapy emerges from the "autogenic training" method created by Schultz, and its development incorporates different therapeutic methods based on a psychophysiological approach. All these methods promote homeostatic self-regulatory brain processes. The aims of this paper are to describe and analyse the autogenic methods, the psychophysiological and neurophysiological processes involved, and their effective applications in both health and clinical fields. For these purposes, beside reviewing the earlier work by Schultz and Luthe, an electronic search of literature was conducted in order to find relevant contributions on these topics. Results show a big development of autogenic methods until the 80s, with an enormous amount of applications and studies on the psychophysiological and neurophysiological changes related to the practice of autogenic training. However, their expansion during the last 25 years has been much lower in comparison with other methods such as mindfulness and hypnosis. Possible causes are discussed and new challenges are suggested

  19. Decalcificated human dentin matrix in autogenous repair of skull defects

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@In the management of traumatic skull defect, the classical treatment has usually been adopted, i.e.,primary debridement and secondary repair of bone defect, especially in cases of open lacerated skull fracture. 1 In general, the use of prosthetic material in repair is often not so satisfactory either in China or abroad. Decalcificated human dentin matrix (DHDM)has been used in autogenous repair of traumatic skull defect in primary operation and a good curative effect has been gained since the time from September 1996 to March 1998. Clinical results and CT scanning observation are reported in the following.

  20. Autogenous electrolyte, non-pyrolytically produced solid capacitor structure

    Science.gov (United States)

    Sharp, D.J.; Armstrong, P.S.; Panitz, J.K.G.

    1998-03-17

    A solid electrolytic capacitor is described having a solid electrolyte comprising manganese dioxide dispersed in an aromatic polyamide capable of further cure to form polyimide linkages, the solid electrolyte being disposed between a first electrode made of valve metal covered by an anodic oxide film and a second electrode opposite the first electrode. The electrolyte autogenously produces water, oxygen, and hydroxyl groups which act as healing substances and is not itself produced pyrolytically. Reduction of the manganese dioxide and the water molecules released by formation of imide linkages result in substantially improved self-healing of anodic dielectric layer defects. 2 figs.

  1. Autogenic-feedback training: A countermeasure for orthostatic intolerance

    Science.gov (United States)

    Cowings, Patricia S.; Toscano, William B.; Kamiya, Joe; Miller, Neal E.; Pickering, Thomas G.

    1991-01-01

    NASA has identified cardiovascular deconditioning as a serious biomedical problem associated with long-duration exposure to microgravity in space. High priority has been given to the development of countermeasures for this disorder and the resulting orthostatic intolerance experienced by crewmembers upon their return to the 1g norm of Earth. The present study was designed to examine the feasibility of training human subjects to control their own cardiovascular responses to gravitational stimulation (i.e., a tilt table). Using an operant conditioning procedure, Autogenic-Feedback Training (AFT), we would determine if subjects could learn to increase their own blood pressure voluntarily.

  2. Effectiveness of shrinkage-reducing admixtures on Portland pozzolan cement concrete

    Directory of Open Access Journals (Sweden)

    Videla, C.

    2005-06-01

    Full Text Available Drying shrinkage causes tensile stress in restrained concrete members. Since all structural elements are subject to some degree of restraint, drying shrinkage is regarded to be one of the main causes of concrete cracking. The purpose of the present study was to evaluate the effectiveness of SRA in reducing drying shrinkage strain in Portland pozzolan cement concrete. The major variables examined included slump, admixture type and dose, and specimen size. The measured results indicate that any of the admixtures used in the study significantly reduced shrinkage. Concrete manufactured with shrinkage reducing admixtures shrank an average of 43% less than concrete without admixtures. As a rule, the higher the dose of admixture, the higher was its shrinkage reduction performance. The experimental results were compared to the shrinkage strain estimated with the ACI 209, CEB MC 90, B3, GL 2000, Sakata 1993 and Sakata 2001 models. Although none of these models was observed to accurately describe the behaviour of Portland pozzolan cement concrete with shrinkage reducing admixtures, the Sakata 2001 model, with a weighted coefficient of variation of under 30%, may be regarded to be roughly adequate.

    La retracción por secado es un fenómeno intrínseco del hormigón que produce tensiones de tracción en elementos restringidos de hormigón. Puesto que todos los elementos presentan algún grado de retracción, se considera a la retracción por secado como una de las principales causas de agrietamiento en proyectos de construcción en hormigón. Por lo tanto, el objetivo de esta investigación fue evaluar la efectividad de los aditivos reductores de retracción (SRA en hormigones fabricados con cemento Portland puzolánico. Las variables principales estudiadas incluyen el asentamiento de cono de Abrams, marca y dosis de aditivo reductor de retracción, y tamaño de espécimen de hormigón. Los resultados obtenidos permiten concluir que el uso de

  3. Drying Shrinkage of Recycled Aggregate Reinforced Concrete Shear Wall%再生骨料钢筋混凝土剪力墙干燥收缩性能

    Institute of Scientific and Technical Information of China (English)

    崔正龙; 庄宇; 汪振双

    2011-01-01

    在约束条件下对再生骨科钢筋混凝土剪力墙和普通钢筋混凝土剪力墙进行了干燥收缩应变测试,同时观察墙体表面干燥收缩裂缝产生的情况.结果表明:2种剪力墙内部收缩应变均明显小于相应的外表面收缩应变;2种剪力墙内部收缩应变相差不大;再生骨料钢筋混凝土剪力墙外表面收缩应变明显比普通钢筋混凝土剪力墙小,而细微收缩裂缝则明显增多.%Drying shrinkage strains of recycled aggregate reinforced concrete shear wall and common reinforced concrete shear wall were measured under constraint conditions, and cracks situations on shear wall surface were observed. The results reveal that for recycled aggregate reinforced concrete shear wall and common reinforced concrete shear wall, the internal shrinkage strain are obviously less than surface shrinkage strain. There is a little difference of internal shrinkage strains between recycled aggregate reinforced concrete shear wall and common reinforced concrete shear wall. The surface shrinkage strain of recycled aggregate reinforced concrete shear wall is obviously lower than that of common reinforced concrete shear wall, while micro shrinkage cracks is obviously more than the latter.

  4. Effective Expansion: Balance between Shrinkage and Hygroscopic Expansion.

    Science.gov (United States)

    Suiter, E A; Watson, L E; Tantbirojn, D; Lou, J S B; Versluis, A

    2016-05-01

    The purpose of this study was to investigate the relationship between hygroscopic expansion and polymerization shrinkage for compensation of polymerization shrinkage stresses in a restored tooth. One resin-modified glass-ionomer (RMGI) (Ketac Nano, 3M ESPE), 2 compomers (Dyract, Dentsply; Compoglass, Ivoclar), and a universal resin-based composite (Esthet•X HD, Dentsply) were tested. Volumetric change after polymerization ("total shrinkage") and during 4 wk of water storage at 37°C was measured using an optical method (n= 10). Post-gel shrinkage was measured during polymerization using a strain gauge method (n= 10). Extracted human molars with large mesio-occluso-distal slot preparations were restored with the tested restorative materials. Tooth surfaces at baseline (preparation), after restoration, and during 4 wk of 37°C water storage were scanned with an optical scanner to determine cuspal flexure (n= 8). Occlusal interface integrity was measured using dye penetration. Data were analyzed using analysis of variance and post hoc tests (significance level 0.05). All tested materials shrunk after polymerization. RMGI had the highest total shrinkage (4.65%) but lowest post-gel shrinkage (0.35%). Shrinkage values dropped significantly during storage in water but had not completely compensated polymerization shrinkage after 4 wk. All restored teeth initially exhibited inward (negative) cuspal flexure due to polymerization shrinkage. Cuspal flexure with the RMGI restoration was significantly less (-6.4 µm) than with the other materials (-12.1 to -14.1 µm). After 1 d, cuspal flexure reversed to +5.0 µm cuspal expansion with the RMGI and increased to +9.3 µm at 4 wk. After 4 wk, hygroscopic expansion compensated cuspal flexure in a compomer (Compoglass) and reduced flexure with Dyract and resin-based composite. Marginal integrity (93.7% intact restoration wall) was best for the Compoglass restorations and lowest (73.1%) for the RMGI restorations. Hygroscopic

  5. Anisotropic shrinkage characteristics of tape cast alumina

    Science.gov (United States)

    Patwardhan, Jaideep Suresh

    Dimensional control during sintering is a major issue in ceramics processing to avoid high post-sintering costs associated with machining of the fired ceramic part to desired tolerances and dimensions. Ceramic forming processes such as tape casting, injection molding, and extrusion involve shear of anisotropic particles resulting in preferential alignment of the particles in the green body. This preferential alignment causes directionality in mechanical, electrical, optical, and magnetic properties and most importantly warpage or distortion during sintering. A large effort has been devoted to synthesizing ceramic green bodies with minimal density gradients and uniform packing and modeling the sintering behavior evolution but little effort has been devoted to characterizing orientation of particles and the effect of preferential alignment on sintering shrinkage anisotropy. A systematic study was initiated to study the effect of processing variables such as shear rate, solids loading, temperature, and binder content on aqueous tape cast alumina. Three different alumina systems: A16-SG, Baikowski RC-UFX DBM and RC-LS DBM were investigated. Aqueous tapes of high solids loading alumina (56 vol. %) were tape cast at various speeds and thicknesses and assuming plane Couette flow a shear rate regime of 21--270 s-1 was investigated. Higher shear rates and high solids loading resulted in higher in-plane anisotropy whereas the anisotropy in the thickness direction was higher for low solids loading systems. The anisotropy was found to be fairly constant above a certain critical shear rate (˜100 s-1) irrespective of the temperature and the solids loading and this correlated with the viscosity-shear rate relationship of the cast slips. The higher shrinkage anisotropy in the thickness direction for the low solids loading systems (35 and 45 vol. %) was attributed to the higher amount of organics in the slip required to sustain the suitable viscosity for tape casting and

  6. Comparative Analysis of Measured and Predicted Shrinkage Strain in Concrete

    Directory of Open Access Journals (Sweden)

    Kossakowski P. G.

    2014-06-01

    Full Text Available The article discusses the issues related to concrete shrinkage. The basic information on the phenomenon is presented as well as the factors that determine the contraction are pointed out and the stages of the process are described. The guidance for estimating the shrinkage strain is given according to Eurocode standard PN-EN 1992-1-1:2008. The results of studies of the samples shrinkage strain of concrete C25/30 are presented with a comparative analysis of the results estimated by the guidelines of the standard according to PN-EN 1992-1- 1:2008

  7. Self-Shrinkage Behaviors of Waste Paper Fiber Reinforced Cement Paste considering Its Self-Curing Effect at Early-Ages

    Directory of Open Access Journals (Sweden)

    Zhengwu Jiang

    2016-01-01

    Full Text Available The aim of this paper was to study how the early-age self-shrinkage behavior of cement paste is affected by the addition of the waste paper fibers under sealed conditions. Although the primary focus was to determine whether the waste paper fibers are suitable to mitigate self-shrinkage as an internal curing agent under different adding ways, evaluating their strength, pore structure, and hydration properties provided further insight into the self-cured behavior of cement paste. Under the wet mixing condition, the waste paper fibers could mitigate the self-shrinkage of cement paste and, at additions of 0.2% by mass of cement, the waste paper fibers were found to show significant self-shrinkage cracking control while providing some internal curing. In addition, the self-curing efficiency results were analyzed based on the strength and the self-shrinkage behaviors of cement paste. Results indicated that, under a low water cement ratio, an optimal dosage and adding ways of the waste paper fibers could enhance the self-curing efficiency of cement paste.

  8. 减缩剂与内养护复合对水泥砂浆性能的影响%Influence of Combination of Shrinkage Reducing Admixture with Internal Curing on Properties of Cement Mortar

    Institute of Scientific and Technical Information of China (English)

    党玉栋; 钱觉时; 郭清春; 王智; 贾兴文

    2013-01-01

    Influence of shrinkage reducing admixture(SRA),internal curing(IC) by using saturated lightweight aggregate,and SRA combined with IC on shrinkage,cement hydration and compressive strength of cement mortar cured under sealed and drying conditions were investigated.For sealed curing,compared with SRA or IC mixtures,when the IC and SRA were used together,the autogenous shrinkage of cement mortar was significantly reduced,which was resulted from the reduction of internal relative humidity drop,a microdilatancy in length was observed in 7 d age,moreover,the ultimate autogenous shrinkage of the mortar was below 100× 10-6 at 28 d age.On the other hand,for drying condition,compared with only using IC,the SRA can significantly enhance the drying shrinkage reduction of internally cured mortar.However,since the moisture loss of internally cured mortar was larger than that of using SRA only,the drying shrinkage of mortar with adding IC and SRA together was greater than that of adding SRA only.Nevertheless,the combination was contributed to the cement hydration and strength development of mortar compared with that of using SRA only.%研究了密封和干燥条件下,使用减缩剂、饱和轻骨料内养护以及两者复合使用对砂浆收缩、水化以及抗压强度的影响.结果表明:密封条件下,较减缩剂和内养护单独使用,两者复合使用能进一步抑制砂浆内部相对湿度的下降,进而使体系自收缩发展速率和水平显著降低,砂浆7d内保持微膨胀状态,28d自收缩率低于100×10-6;干燥条件下,相比仅使用内养护,复合减缩剂后砂浆干燥收缩明显降低,但由于内养护使砂浆失水量增大,复合减缩剂后减缩效果不及仅使用减缩剂的砂浆;两者复合使用后能够显著降低减缩剂单独使用时对水泥水化和砂浆强度的不利影响.

  9. Assessment of early-age cracking of high-performance concrete in restrained ring specimens

    Directory of Open Access Journals (Sweden)

    Quang-phu NGUYEN NGUYEN

    2010-03-01

    Full Text Available High-performance concrete (HPC is stronger and more durable than conventional concrete. However, shrinkage and shrinkage cracking are common phenomena in HPC, especially early-age cracking. This study assessed early-age cracking of HPC for two mixtures using restrained ring tests. The two mixtures were produced with water/binder mass ratio (mW/mB of 0.22 and 0.40, respectively. The results show that, with greater steel thickness, the higher degree of restraint resulted in a higher interface pressure and earlier cracking. With steel thickness of 6 mm, 19 mm, and 30 mm, the age of cracking were, respectively, 12 days, 8 days, and 5.4 days with the mW/mB = 0.22 mixture; and 22.5 days, 12.6 days, and 7.1 days with the mW/mB = 0.40 mixture. Cases of the same steel thickness show that the ring specimens with a thicker concrete wall crack later. With the mW/mB = 0.22 mixture, concrete walls with thicknesses of 37.5 mm, 75 mm, and 112.5 mm cracked at 3.4 days, 8.0 days, and 9.8 days, respectively; with the mW/mB = 0.40 mixture, the ages of cracking were 7.1 days, 12.6 days, and 16.0 days, respectively.

  10. Crack formation and fracture energy of normal and high strength concrete

    Indian Academy of Sciences (India)

    F H Wittmann

    2002-08-01

    The crack path through composite materials such as concrete depends on the mechanical interaction of inclusions with the cement-based matrix. Fracture energy depends on the deviations of a real crack from an idealized crack plane. Fracture energy and strain softening of normal, high strength, and self-compacting concrete have been determined by means of the wedge splitting test. In applying the numerical model called “numerical concrete” crack formation in normal and high strength concrete is simulated. Characteristic differences of the fracture process can be outlined. Finally results obtained are applied to predict shrinkage cracking under different boundary conditions. Crack formation of high strength concrete has to be seriously controlled in order to achieve the necessary durability of concrete structures.

  11. Nanocavity Shrinkage and Preferential Amorphization during Irradiation in Silicon

    Institute of Scientific and Technical Information of China (English)

    ZHU Xian-Fang; WANG Zhan-Guo

    2005-01-01

    @@ We model the recent experimental results and demonstrate that the internal shrinkage of nanocavities in silicon is intrinsically associated with preferential amorphization as induced by self-ion irradiation.

  12. Applying strain into graphene by SU-8 resist shrinkage

    Science.gov (United States)

    Takamura, Makoto; Hibino, Hiroki; Yamamoto, Hideki

    2016-07-01

    We investigated the use of the shrinkage of SU-8 resist caused by thermal annealing to apply strain into graphene grown by the chemical-vapor-deposition (CVD) method. We demonstrate that the shrinkage of resist deposited on top of graphene on a substrate induces a local tensile strain within a distance of 1-2 μm from the edge of the resist. The thermal shrinkage of SU-8 will allow us to design the local strain in graphene on substrates. We also show that the shrinkage induces a large tensile strain in graphene suspended between two bars of SU-8. We expect that a much larger strain can be induced by suppressing defects in CVD-grown graphene.

  13. Fast shrinkage of tropical glaciers in Colombia

    Science.gov (United States)

    Ceballos, Jorge Luis; Euscátegui, Christian; Ramírez, Jair; Cañon, Marcela; Huggel, Christian; Haeberli, Wilfried; Machguth, Horst

    As a consequence of ongoing atmospheric temperature rise, tropical glaciers belong to the unique and threatened ecosystems on Earth, as defined by the Intergovernmental Panel on Climate Change (Houghton and others, 2001). Worldwide glacier monitoring, especially as part of the Global Climate Observing System (GCOS), includes the systematic collection of data on such perennial surface ice masses. Several peaks in the sierras of Colombia have lost their glacier cover during recent decades. Today, high-altitude glaciers still exist in Sierra Nevada de Santa Marta, in Sierra Nevada del Cocuy and on the volcanoes of Nevados del Ruiz, de Santa Isabel, del Tolima and del Huila. Comparison of reconstructions of maximum glacier area extent during the Little Ice Age with more recent information from aerial photographs and satellite images clearly documents a fast-shrinking tendency and potential disappearance of the remaining glaciers within the next few decades. In the past 50 years, Colombian glaciers have lost 50% or more of their area. Glacier shrinkage has continued to be strong in the last 15 years, with a loss of 10-50% of the glacier area. The relationship between fast glacier retreat and local, regional and global climate change is now being investigated. Preliminary analyses indicate that the temperature rise of roughly 1° C in the last 30 years recorded at high-altitude meteorological stations exerts a primary control on glacier retreat. The investigations on the Colombian glaciers thus corroborate earlier findings concerning the high sensitivity of glaciers in the wet inner tropics to temperature rise. To improve understanding of fast glacier retreat in Colombia, a modern monitoring network has been established according to the multilevel strategy of the Global Terrestrial Network for Glaciers (GTN-G) within GCOS. The observations are also contributions to continued assessments of hazards from the glacier-covered volcanoes and to integrated global change

  14. Method to determine factors contributing to thermoplastic sheet shrinkage

    Science.gov (United States)

    Rensch, Greg J.; Frye, Brad A.

    A test method is presented for the determination of shrinkage behavior in vacuum-formed thermoplastic resin sheeting, as presently simulated for various resin lots, sheet-gage thicknesses, sheet orientations, and mold profiles. The thermoforming machine and vacuum-forming mold characteristics are discussed. It is established that the four variable factors exert statistically significant effects on the shrinkage response of three Declar resin lots, but that these are of no real practical significance for either engineering or manufacturing operations.

  15. Accurate characterisation of post moulding shrinkage of polymer parts

    DEFF Research Database (Denmark)

    Neves, L. C.; De Chiffre, L.; González-Madruga, D.;

    2015-01-01

    The work deals with experimental determination of the shrinkage of polymer parts after injection moulding. A fixture for length measurements on 8 parts at the same time was designed and manufactured in Invar, mounted with 8 electronic gauges, and provided with 3 temperature sensors. The fixture...... of post moulding shrinkage of polymer parts was developed. Expanded uncertainties (k=2) of 3 μm were obtained....

  16. Gear Crack Propagation Investigation

    Science.gov (United States)

    1995-01-01

    Reduced weight is a major design goal in aircraft power transmissions. Some gear designs incorporate thin rims to help meet this goal. Thin rims, however, may lead to bending fatigue cracks. These cracks may propagate through a gear tooth or into the gear rim. A crack that propagates through a tooth would probably not be catastrophic, and ample warning of a failure could be possible. On the other hand, a crack that propagates through the rim would be catastrophic. Such cracks could lead to disengagement of a rotor or propeller from an engine, loss of an aircraft, and fatalities. To help create and validate tools for the gear designer, the NASA Lewis Research Center performed in-house analytical and experimental studies to investigate the effect of rim thickness on gear-tooth crack propagation. Our goal was to determine whether cracks grew through gear teeth (benign failure mode) or through gear rims (catastrophic failure mode) for various rim thicknesses. In addition, we investigated the effect of rim thickness on crack propagation life. A finite-element-based computer program simulated gear-tooth crack propagation. The analysis used principles of linear elastic fracture mechanics, and quarter-point, triangular elements were used at the crack tip to represent the stress singularity. The program had an automated crack propagation option in which cracks were grown numerically via an automated remeshing scheme. Crack-tip stress-intensity factors were estimated to determine crack-propagation direction. Also, various fatigue crack growth models were used to estimate crack-propagation life. Experiments were performed in Lewis' Spur Gear Fatigue Rig to validate predicted crack propagation results. Gears with various backup ratios were tested to validate crack-path predictions. Also, test gears were installed with special crack-propagation gages in the tooth fillet region to measure bending-fatigue crack growth. From both predictions and tests, gears with backup ratios

  17. Autogenic reaction synthesis of photocatalysts for solar fuel generation

    Energy Technology Data Exchange (ETDEWEB)

    Ingram, Brian J.; Pol, Vilas G.; Cronauer, Donald C.; Ramanathan, Muruganathan

    2016-04-19

    In one preferred embodiment, a photocatalyst for conversion of carbon dioxide and water to a hydrocarbon and oxygen comprises at least one nanoparticulate metal or metal oxide material that is substantially free of a carbon coating, prepared by heating a metal-containing precursor compound in a sealed reactor under a pressure autogenically generated by dissociation of the precursor material in the sealed reactor at a temperature of at least about 600.degree. C. to form a nanoparticulate carbon-coated metal or metal oxide material, and subsequently substantially removing the carbon coating. The precursor material comprises a solid, solvent-free salt comprising a metal ion and at least one thermally decomposable carbon- and oxygen-containing counter-ion, and the metal of the salt is selected from the group consisting of Mn, Ti, Sn, V, Fe, Zn, Zr, Mo, Nb, W, Eu, La, Ce, In, and Si.

  18. Adjuvant auricular electroacupuncture and autogenic training in rheumatoid arthritis: a randomized controlled trial

    DEFF Research Database (Denmark)

    Bernateck, M.; Becker, M.; Schwacke, C.

    2008-01-01

    BACKGROUND: In contrast to psychological interventions the usefulness of acupuncture as an adjuvant therapy in rheumatoid arthritis (RA) has not yet been demonstrated. OBJECTIVE: The efficacy of auricular electroacupuncture (EA) was directly compared with autogenic training (AT). METHODS: Patients...

  19. Peculiarities of application the method of autogenic training in the correction of eating behavior

    OpenAIRE

    Shebanova, Vitaliya

    2014-01-01

    The article presented peculiarities of applying the method of autogenic training in the correction of eating disorders. Described stages of correction work with desadaptive eating behavior. Author makes accent on the rules self-assembly formula intentions.

  20. Effect of light-curing units and activation mode on polymerization shrinkage and shrinkage stress of composite resins.

    Science.gov (United States)

    Lopes, Lawrence Gonzaga; Franco, Eduardo Batista; Pereira, José Carlos; Mondelli, Rafael Francisco Lia

    2008-01-01

    The aim of this study was to evaluate the polymerization shrinkage and shrinkage stress of composites polymerized with a LED and a quartz tungsten halogen (QTH) light sources. The LED was used in a conventional mode (CM) and the QTH was used in both conventional and pulse-delay modes (PD). The composite resins used were Z100, A110, SureFil and Bisfil 2B (chemical-cured). Composite deformation upon polymerization was measured by the strain gauge method. The shrinkage stress was measured by photoelastic analysis. The polymerization shrinkage data were analyzed statistically using two-way ANOVA and Tukey test (p contraction and the stress values when compared to CM. LED generated the same stress as QTH in conventional mode. Regardless of the activation mode, SureFil produced lower contraction and stress values than the other light-cured resins. Conversely, Z100 and A110 produced the greatest contraction and stress values. As expected, the chemically cured resin generated lower shrinkage and stress than the light-cured resins. In conclusion, The PD mode effectively decreased contraction stress for Z100 and A110. Development of stress in light-cured resins depended on the shrinkage value.

  1. TESTING AND ANALYSIS OF CAP CONCRETE STRESS AND STRAIN DUE TO SHRINKAGE, CREEP, AND EXPANSION FINAL REPORT

    Energy Technology Data Exchange (ETDEWEB)

    Guerrero, H.; Restivo, M.

    2011-08-01

    In-situ decommissioning of Reactors P- and R- at the Savannah River Site will require filling the reactor vessels with a special concrete based on materials such as magnesium phosphate, calcium aluminate or silica fume. Then the reactor vessels will be overlain with an 8 ft. thick layer of Ordinary Portland Cement (OPC) steel reinforced concrete, called the 'Cap Concrete'. The integrity of this protective layer must be assured to last for a sufficiently long period of time to avoid ingress of water into the reactor vessel and possible movement of radioactive contamination into the environment. During drying of this Cap Concrete however, shrinkage strains are set up in the concrete as a result of diffusion and evaporation of water from the top surface. This shrinkage varies with depth in the poured slab due to a non-uniform moisture distribution. This differential shrinkage results in restraint of the upper layers with larger shrinkage by lower layers with lesser displacements. Tensile stresses can develop at the surface from the strain gradients in the bulk slab, which can lead to surface cracking. Further, a mechanism called creep occurs during the curing period or early age produces strains under the action of restraining forces. To investigate the potential for surface cracking, an experimental and analytical program was started under TTQAP SRNL-RP-2009-01184. Slab sections made of Cap Concrete mixture were instrumented with embedded strain gages and relative humidity sensors and tested under controlled environmental conditions of 23 C and relative humidities (RH) of 40% and 80% over a period of 50 days. Calculation methods were also developed for predictions of stress development in the full-scale concrete placement over the reactor vessels. These methods were evaluated by simulating conditions for the test specimens and the calculation results compared to the experimental data. A closely similar test with strain gages was performed by Kim and Lee for

  2. Changes of Ca2+ activated potassium channels and cellular proliferation in autogenous vein grafts

    Institute of Scientific and Technical Information of China (English)

    钱济先; 宋胜云; 马保安; 范清宇

    2003-01-01

    Objective: To investigate changes of Ca2+ activated potassium channels (KCa) in autogenous vein grafts. Methods: Contraction of venous ring was measured by means of perfusion in vitro. The intimal rabbits proliferation of vascular and proliferation of cultured smooth muscle cells(vascular smooth muscle cells, VSMCs)were observed by the means of computerised image analysis and MTT method respectively. Furthermore, whole cell mode of patch clamp was used to record KCa of VSMCs isolated from autogenous vein grafts. Results: One week after transplantation there were no significant differences of contraction and intimal relative thickness between autogenous vein grafts and control. Contraction and intimal relative thickness of autogenous vein graft were significantly increased 2 weeks after transplantation (P<0.05, n=8 vs control), and they was more enhanced 4 weeks after vein transplantation (P<0.01, n=8 vs control).TEA(blocker of Ca2+ activated potassium channels)increased MTT A490 nm value of VSMCs from femoral vein in a dose dependent manner(P<0.05, n=8). KCa current density was significantly attenuated in VSMCs from autogenous vein grafts (1-4) week after transplantation(P<0.05, n=5).Conclusion: KCa is inhibited in autogenous vein graft, which account for vasospasm and intimal proliferation.

  3. Geosynthetic clay liners shrinkage under simulated daily thermal cycles.

    Science.gov (United States)

    Sarabadani, Hamid; Rayhani, Mohammad T

    2014-06-01

    Geosynthetic clay liners are used as part of composite liner systems in municipal solid waste landfills and other applications to restrict the escape of contaminants into the surrounding environment. This is attainable provided that the geosynthetic clay liner panels continuously cover the subsoil. Previous case histories, however, have shown that some geosynthetic clay liner panels are prone to significant shrinkage and separation when an overlying geomembrane is exposed to solar radiation. Experimental models were initiated to evaluate the potential shrinkage of different geosynthetic clay liner products placed over sand and clay subsoils, subjected to simulated daily thermal cycles (60°C for 8 hours and 22°C for 16 hours) modelling field conditions in which the liner is exposed to solar radiation. The variation of geosynthetic clay liner shrinkage was evaluated at specified times by a photogrammetry technique. The manufacturing techniques, the initial moisture content, and the aspect ratio (ratio of length to width) of the geosynthetic clay liner were found to considerably affect the shrinkage of geosynthetic clay liners. The particle size distribution of the subsoil and the associated suction at the geosynthetic clay liner-subsoil interface was also found to have significant effects on the shrinkage of the geosynthetic clay liner.

  4. Effect of light-curing units and activation mode on polymerization shrinkage and shrinkage stress of composite resins

    Directory of Open Access Journals (Sweden)

    Lawrence Gonzaga Lopes

    2008-02-01

    Full Text Available The aim of this study was to evaluate the polymerization shrinkage and shrinkage stress of composites polymerized with a LED and a quartz tungsten halogen (QTH light sources. The LED was used in a conventional mode (CM and the QTH was used in both conventional and pulse-delay modes (PD. The composite resins used were Z100, A110, SureFil and Bisfil 2B (chemical-cured. Composite deformation upon polymerization was measured by the strain gauge method. The shrinkage stress was measured by photoelastic analysis. The polymerization shrinkage data were analyzed statistically using two-way ANOVA and Tukey test (p<0.05, and the stress data were analyzed by one-way ANOVA and Tukey's test (p<0.05. Shrinkage and stress means of Bisfil 2B were statistically significant lower than those of Z100, A110 and SureFil. In general, the PD mode reduced the contraction and the stress values when compared to CM. LED generated the same stress as QTH in conventional mode. Regardless of the activation mode, SureFil produced lower contraction and stress values than the other light-cured resins. Conversely, Z100 and A110 produced the greatest contraction and stress values. As expected, the chemically cured resin generated lower shrinkage and stress than the light-cured resins. In conclusion, The PD mode effectively decreased contraction stress for Z100 and A110. Development of stress in light-cured resins depended on the shrinkage value.

  5. Crack path and fracture surface modifications in cement composites

    Directory of Open Access Journals (Sweden)

    Sajjad Ahmad

    2015-10-01

    Full Text Available There is a tremendous increase in the use of high strength and high performance self-consolidating cementitious composites due to their superior workability and mechanical strengths. Cement composites are quasi-brittle in nature and possess extremely low tensile strength as compared to their compressive strength. Due to the low tensile strength capacity, cracks develop in cementitious composites due to the drying shrinkage, plastic settlements and/or stress concentrations (due to external restrains and/or applied stresses etc. These cracks developed at the nanoscale may grow rapidly due to the applied stresses and join together to form micro and macro cracks. The growth of cracks from nanoscale to micro and macro scale is very rapid and may lead to sudden failure of the cement composites. The present paper reports the modifications in the crack growth pattern of the high performance cement composites to achieve enhanced ductility and toughness. The objective was accomplished by the incorporation of the micro sized inert particulates in the cement composite matrix. The results indicate that the incorporation of micro sized inert particles acted as the obstacles in the growth of the cracks thus improving the ductility and the energy absorption capacity of the self-consolidating cementitious composites.

  6. Modified Dugdale cracks and Fictitious cracks

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang

    1998-01-01

    (displacement) respectively of material considered. The practical applicability of the two models is limited such that predicted strength sigma_CR must be less than sigma_L/3, which corresponds to an assumption that fictitious cracks are much smaller than real crack lengths considered. The reason......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...... 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...

  7. Brain shrinkage and subdural effusion associated with ACTH administration.

    Science.gov (United States)

    Satoh, J; Takeshige, H; Hara, H; Fukuyama, Y

    1982-01-01

    Sequential computed tomographic (CT) studies of 11 patients (aged five months to seven years) with intractable epilepsy treated with synthetic ACTH-Z showed brain shrinkage in all cases. Brain shrinkage started to appear on daily ACTH injections for seven days, reached the maximum within four weeks of administration (14 injections every day and then 7 injections every other day), and almost returned to the original status in seven out of nine cases which were followed up for one to three months after the therapy. The subjects aged less than two years showed more remarkable brain shrinkage than did those aged more than five years. Furthermore, two other cases were complicated by subdural effusion after ACTH therapy. It is the authors' assumption that both of these phenomena are caused by the high concentration of corticosteroid through a change of the water and electrolyte contents in the brain.

  8. Reconstruction of the mandible with a poly(D,L-lactide) scaffold, autogenous corticocancellous bone graft, and autogenous platelet-rich plasma: an animal experiment.

    NARCIS (Netherlands)

    Fennis, J.P.M.; Stoelinga, P.J.W.; Merkx, M.A.T.; Jansen, J.A.

    2005-01-01

    An animal study is presented, evaluating a method of mandibular reconstruction using a poly(D,Llactide) (PDLLA) scaffold. Six goats underwent a continuity resection of the mandibular angle. The defect was bridged with a preshaped PDLLA scaffold, filled with an autogenous particulate bone graft from

  9. Hydration of Portoguese cements, measurement and modelling of chemical shrinkage

    DEFF Research Database (Denmark)

    Maia, Lino; Geiker, Mette Rica; Figueiras, Joaquim A.

    2008-01-01

    form of the dispersion model. The development of hydration varied between the investigated cements; based on the measured data the degree of hydration after 24 h hydration at 20 C varied between 40 and 50%. This should be taken into account when comparing properties of concrete made from the different......Development of cement hydration was studied by measuring the chemical shrinkage of pastes. Five types of Portuguese Portland cement were used in cement pastes with . Chemical shrinkage was measured by gravimetry and dilatometry. In gravimeters results were recorded automatically during at least...

  10. Optimal linear shrinkage corrections of sample LMMSE and MVDR estimators

    OpenAIRE

    2012-01-01

    La proposició d'estimadors shrinkage òptims que corregeixen la degradació dels mètodes sample LMMSE i sample MUDR en el règim on el número de mostres és petit en comparació a la dimensió de les observacions. [ANGLÈS] This master thesis proposes optimal shrinkage estimators that counteract the performance degradation of the sample LMMSE and sample MVDR methods in the regime where the sample size is small compared to the observation dimension. [CASTELLÀ] Esta máster tesis propone estimado...

  11. Sinusfloor elevation and grafting with autogenous iliac crest bone.

    Science.gov (United States)

    van den Bergh, J P; ten Bruggenkate, C M; Krekeler, G; Tuinzing, D B

    1998-12-01

    Insufficient bone height in the posterior area of the maxilla, due to expansion of the maxillary sinus and atrophic reduction of the alveolar process of the maxilla, represents a contra-indication for insertion of dental implants. This anatomic problem can, in many cases, be solved by augmentation of the floor of the maxillary sinus. This surgical technique was introduced by Tatum. The so-called top hinge door method creates a new floor of the maxillary sinus at a more cranial level. Underneath this new floor the existing space is filled with a bone graft. Implantation in the alveolar process with increased bone height allows insertion of dental implants. This sinus grafting technique was used in the present study. In total, 62 sinusfloor elevations were performed with cancellous iliac bone grafts in 42 patients. In those 62 augmented sinuses, 161 ITI screw type implants were inserted. The follow-up was 1-6 years after implantation. In 2 cases infections occurred. One implant needed an extended integration time. No implants were lost. The ITI solid screw implant appears to be a suitable implant following sinusfloor elevation operations, due to its rough surface, its shape and the size of the thread. The sinusfloor elevation procedure with autogenous cancellous bone graft appears to be a valuable and reliable pre-implantological procedure, provided a proper pre-operative investigation and careful surgery are performed. This procedure allows dental implant placement with a high success rate.

  12. Autogenic training: a meta-analysis of clinical outcome studies.

    Science.gov (United States)

    Stetter, Friedhelm; Kupper, Sirko

    2002-03-01

    Autogenic training (AT) is a self-relaxation procedure by which a psychophysiological determined relaxation response is elicited. A meta-analysis was performed to evaluate the clinical effectiveness of AT. Seventy-three controlled outcome studies were found (published 1952-99). Sixty studies (35 randomized controlled trials [RCT]) qualified for inclusion in the meta-analysis. Medium-to-large effect sizes (ES) occurred for pre-post comparisons of disease-specific AT-effects, with the RCTs showing larger ES. When AT was compared to real control conditions, medium ES were found. Comparisons of AT versus other psychological treatment mostly resulted in no effects or small negative ES. This pattern of results was stable at follow-up. Unspecific AT-effects (i.e., effects on mood, cognitive performance, quality of life, and physiological variables) tended to be even larger than main effects. Separate meta-analyses for different disorders revealed a significant reduction of the heterogeneity of ES. Positive effects (medium range) of AT and of AT versus control in the meta-analysis of at least 3 studies were found for tension headache/migraine, mild-to-moderate essential hypertension, coronary heart disease, asthma bronchiale, somatoform pain disorder (unspecified type), Raynaud's disease, anxiety disorders, mild-to-moderate depression/dysthymia, and functional sleep disorders.

  13. Reorganization of the Brain and Heart Rhythm During Autogenic Meditation

    Directory of Open Access Journals (Sweden)

    Dae-Keun eKim

    2014-01-01

    Full Text Available The underlying changes in heart coherence that are associated with reported EEG changes in response to meditation have been explored. We measured EEG and heart rate variability (HRV before and during autogenic meditation. Fourteen subjects participated in the study. Heart coherence scores were significantly increased during meditation compared to the baseline. We found near significant decrease in high beta absolute power, increase in alpha relative power and significant increases in lower(alpha and higher(above beta band coherence during 3 minute epochs of heart coherent meditation compared to 3 minute epochs of heart noncoherence at baseline. The coherence and relative power increase in alpha band and absolute power decrease in high beta band could reflect relaxation state during the heart coherent meditation. The coherence increase in the higher(above beta band could reflect cortico-cortical local integration and thereby affect cognitive reorganization, simultaneously with relaxation. Further research is still needed for a confirmation of heart coherence as a simple window for the meditative state.

  14. Drying shrinkage of mortars with limestone filler and blast-furnace slag

    Directory of Open Access Journals (Sweden)

    Carrasco, M. F.

    2003-12-01

    Full Text Available During the 1990's the use of cements made with port land clinker and two mineral admixtures, called ternary or blended cements, has grown considerably. Nowadays, cements containing several combinations of fly ash and silica fume, blast-furnace slag and silica fume or blast-furnace slag and limestone filler are commonly used. There are numerous works on the influence of blended cements on the fresh state and mechanical properties of mortar and concrete, but the their deformations due to drying shrinkage are not so well described. Analysis of drying shrinkage is relevant because this property influences the possibility of cracking occurrence and, hence, the deterioration of mechanical and durable properties of concrete structures. This paper evaluates the influence on the drying shrinkage of mortars of variable contents of limestone filler and/or blast-furnace slag in Portland cement. Additionally, flexion strength and non evaporable water content were evaluated. Test results show that the inclusion of these mineral admixtures, Joint or separately, increments drying shrinkage of mortars at early ages. Despite this fact, mortars made with limestone filler cement are less susceptible to cracking than mortars made with cements incorporating blast-furnace slag or both admixtures.

    Durante los años 90 el uso de cementos fabricados con clínker Portland y dos adiciones suplementarias (cementos ternarios o compuestos se ha incrementado en forma considerable. En la práctica, es cada vez más común el empleo de estos cementos conteniendo combinaciones de ceniza volante y humo de sílice, escoria y humo de sílice o escoria y filler calcáreo. En la actualidad existen numerosos estudios sobre la influencia de los cementos compuestos en las características en estado fresco y las propiedades mecánicas de morteros y hormigones, pero las deformaciones que estos materiales sufren debido a la retracción por secado no son tan conocidas. El análisis de

  15. Brain structural alterations in obsessive-compulsive disorder patients with autogenous and reactive obsessions.

    Directory of Open Access Journals (Sweden)

    Marta Subirà

    Full Text Available Obsessive-compulsive disorder (OCD is a clinically heterogeneous condition. Although structural brain alterations have been consistently reported in OCD, their interaction with particular clinical subtypes deserves further examination. Among other approaches, a two-group classification in patients with autogenous and reactive obsessions has been proposed. The purpose of the present study was to assess, by means of a voxel-based morphometry analysis, the putative brain structural correlates of this classification scheme in OCD patients. Ninety-five OCD patients and 95 healthy controls were recruited. Patients were divided into autogenous (n = 30 and reactive (n = 65 sub-groups. A structural magnetic resonance image was acquired for each participant and pre-processed with SPM8 software to obtain a volume-modulated gray matter map. Whole-brain and voxel-wise comparisons between the study groups were then performed. In comparison to the autogenous group, reactive patients showed larger gray matter volumes in the right Rolandic operculum. When compared to healthy controls, reactive patients showed larger volumes in the putamen (bilaterally, while autogenous patients showed a smaller left anterior temporal lobe. Also in comparison to healthy controls, the right middle temporal gyrus was smaller in both patient subgroups. Our results suggest that autogenous and reactive obsessions depend on partially dissimilar neural substrates. Our findings provide some neurobiological support for this classification scheme and contribute to unraveling the neurobiological basis of clinical heterogeneity in OCD.

  16. Numerical model predictions of autogenic fluvial terraces and comparison to climate change expectations

    Science.gov (United States)

    Limaye, Ajay B. S.; Lamb, Michael P.

    2016-03-01

    Terraces eroded into sediment (alluvial) and bedrock (strath) preserve an important history of river activity. River terraces are thought to form when a river switches from a period of slow vertical incision and valley widening to fast vertical incision and terrace abandonment. Consequently, terraces are often interpreted to reflect changing external drivers including tectonics, sea level, and climate. In contrast, the intrinsic unsteadiness of lateral migration in rivers may generate terraces even under constant rates of vertical incision without external forcing. To explore this mechanism, we simulate landscape evolution by a vertically incising, meandering river and isolate the age and geometry of autogenic river terraces. Modeled autogenic terraces form for a wide range of lateral and vertical incision rates and are often paired and longitudinally extensive for intermediate ratios of vertical-to-lateral erosion rate. Autogenic terraces have a characteristic reoccurrence time that scales with the time for relief generation. There is a preservation bias against older terraces due to reworking of previously visited parts of the valley. Evolving, spatial differences in bank strength between bedrock and sediment reduce terrace formation frequency and length, favor pairing, and can explain sublinear terrace margins at valley boundaries. Age differences and geometries for modeled autogenic terraces are consistent, in cases, with natural terraces and overlap with metrics commonly attributed to terrace formation due to climate change. We suggest a new phase space of terrace properties that may allow differentiation of autogenic terraces from terraces formed by external drivers.

  17. UFA水泥基材料早期自收缩与干燥收缩研究%Early autogenous shrinkage and dry shrinkage of cement based materials containing ultra-fine fly ash

    Institute of Scientific and Technical Information of China (English)

    高英力; 周士琼; 马保国

    2008-01-01

    低水胶比条件下水泥基材料的自收缩率已超过干燥收缩率成为导致混凝土过早开裂的隐患.以超细粉煤灰(ultra-fine fly ash,UFA)等量取代水泥20%~40%,配制了UFA水泥基复合胶凝材料,分别对固定水胶比和变水胶比两种情况下的UFA水泥砂浆早期(7 d前)自收缩变形和干燥收缩变形进行试验研究.结果表明,在固定水胶比条件下,砂浆的自收缩率随UFA掺量增加递减,而干缩率却随之增大;在变水胶比条件下,砂浆的自收缩率随水胶比的增加递减,干缩率随之增大.且回归分析表明两种情况下砂浆的自收缩及干燥收缩变形均表现出较好的线性相关;UFA对水泥基材料改性作用明显,在保持相同流动度条件下,UFA的掺入可有效降低用水量,早期及后期强度能赶上甚至超过基准水泥胶砂,弥补了UFA早期不水化所引发的早期强度低缺陷;微观测试表明,UFA在水泥基材料中起到了较好的密实填充、减水分散及增强作用.

  18. Effect of processing conditions on shrinkage in injection molding

    NARCIS (Netherlands)

    Jansen, K.M.B.; Dijk, van D.J.; Husselman, M.H.

    1998-01-01

    A systematic study on the effect of processing conditions on mold shrinkage was undertaken for seven common thermoplastic polymers. It turned out that the holding pressure was always the key parameter. The effect of the melt temperature is slightly less important. Injection velocity and mold tempera

  19. Cure shrinkage effects in epoxy and polycyanate matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Spellman, G.P.

    1995-12-22

    A relatively new advanced composite matrix, polycyanate ester, was evaluated for cure shrinkage. The chemical cure shrinkage of composites is difficult to model but a number of clever experimental techniques are available to the investigator. In this work the method of curing a prepreg layup on top of a previously cured laminate of identical ply composition is utilized. The polymeric matrices used in advanced composites have been primarily epoxies and therefore a common system of this type, Fiberite 3501-6, was used as a base case material. Three polycyanate matrix systems were selected for the study. These are: Fiberite 954-2A, YLA RS-3, and Bryte Technology BTCy-1. The first three of these systems were unidirectional prepreg with carbon fiber reinforcement. The Bryte Technology material was reinforced with E-glass fabric. The technique used to evaluate cure shrinkage results in distortion of the flatness of an otherwise symmetric laminate. The first laminate is cured in a conventional fashion. An identical layup is cured on this first laminate. During the second cure all constituents are exposed to the same thermal cycles. However, only the new portion of the laminate will experience volumetric changes associate with matrix cure. The additional strain of cure shrinkage results in an unsymmetric distribution of residual stresses and an associated warpage of the laminate. The baseline material, Fiberite 3501-6, exhibited cure shrinkage that was in accordance with expectations. Cure strains were {minus}4.5E-04. The YLA RS-3 material had cure strains somewhat lower at {minus}3.2E-04. The Fiberite 954-2A cure strain was {minus}1.5E-04 that is 70% lower than the baseline material. The glass fabric material with the Bryte BTCy-1 matrix did not result in meaningful results because the processing methods were not fully compatible with the material.

  20. Bone-to-implant contact after maxillary sinus floor augmentation with Bio-Oss and autogenous bone in different ratios in mini pigs

    DEFF Research Database (Denmark)

    Jensen, Thomas; Schou, Søren; Gundersen, Hans Jørgen G;

    2012-01-01

    OBJECTIVES: The objective was to test the hypotheses: (i) no differences in bone-to-implant contact formation, and (ii) no differences between the use of autogenous mandibular or iliac bone grafts, when autogenous bone, Bio-Oss mixed with autogenous bone, or Bio-Oss is used as graft for the maxil...

  1. Cloning and expression of autogenes encoding RNA polymerases of T7-like bacteriophages

    Energy Technology Data Exchange (ETDEWEB)

    Studier, F. William (Stony Brook, NY); Dubendorff, John W. (Sound Beach, NY)

    1998-01-01

    This invention relates to the cloning and expression of autogenes encoding RNA polymerases of T7 and T7-like bacteriophages, in which the RNA polymerase gene is transcribed from a promoter which is recognized by the encoded RNA polymerase. Cloning of T7 autogenes was achieved by reducing the activity of the RNA polymerase sufficiently to permit host cell growth. T7 RNA polymerase activity was controlled by combining two independent methods: lac-repression of the recombinant lac operator-T7 promoter in the autogene and inhibition of the polymerase by T7 lysozyme. Expression systems for producing the RNA polymerases of T7 and other T7-like bacteriophages, and expression systems for producing selected gene products are described, as well as other related materials and methods.

  2. Cloning and expression of autogenes encoding RNA poly,erases of T7-like bacteriophages

    Energy Technology Data Exchange (ETDEWEB)

    Studier, F. William (Stony Brook, NY); Dubendorff, John W. (Sound Beach, NY)

    1998-01-01

    This invention relates to the cloning and expression of autogenes encoding RNA polymerases of T7 and T7-like bacteriophages, in which the RNA polymerase gene is transcribed from a promoter which is recognized by the encoded RNA polymerase. Cloning of T7 autogenes was achieved by reducing the activity of the RNA polymerase sufficiently to permit host cell growth. T7 RNA polymerase activity was controlled by combining two independent methods: lac-repression of the recombinant lac operator-T7 promoter in the autogene and inhibition of the polymerase by T7 lysozyme. Expression systems for producing the RNA polymerases of T7 and other T7-like bacteriophages, and expression systems for producing selected gene products are described, as well as other related materials and methods.

  3. Cloning and expression of autogenes encoding RNA polymerases of T7-like bacteriophages

    Energy Technology Data Exchange (ETDEWEB)

    Studier, F.W.; Dubendorff, J.W.

    1998-10-20

    This invention relates to the cloning and expression of autogenes encoding RNA polymerases of T7 and T7-like bacteriophages, in which the RNA polymerase gene is transcribed from a promoter which is recognized by the encoded RNA polymerase. Cloning of T7 autogenes was achieved by reducing the activity of the RNA polymerase sufficiently to permit host cell growth. T7 RNA polymerase activity was controlled by combining two independent methods: lac-repression of the recombinant lac operator-T7 promoter in the autogene and inhibition of the polymerase by T7 lysozyme. Expression systems for producing the RNA polymerases of T7 and other T7-like bacteriophages, and expression systems for producing selected gene products are described, as well as other related materials and methods. 12 figs.

  4. Cloning and expression of autogenes encoding RNA polymerases of T7-like bacteriophages

    Energy Technology Data Exchange (ETDEWEB)

    Studier, F.W.; Dubendorff, J.W.

    1998-11-03

    This invention relates to the cloning and expression of autogenes encoding RNA polymerases of T7 and T7-like bacteriophages, in which the RNA polymerase gene is transcribed from a promoter which is recognized by the encoded RNA polymerase. Cloning of T7 autogenes was achieved by reducing the activity of the RNA polymerase sufficiently to permit host cell growth. T7 RNA polymerase activity was controlled by combining two independent methods: lac-repression of the recombinant lac operator-T7 promoter in the autogene and inhibition of the polymerase by T7 lysozyme. Expression systems for producing the RNA polymerases of T7 and other T7-like bacteriophages, and expression systems for producing selected gene products are described, as well as other related materials and methods. 12 figs.

  5. Evaluation of Aquacel Ag for Autogenous Skin Donor Sites.

    Science.gov (United States)

    Haith, Linwood R; Stair-Buchmann, Megan E; Ackerman, Bruce H; Herder, Diane; Reigart, Cynthia L; Stoering, Marla; Guilday, Robert E; Patton, Mary Lou; Ross, Kerry M

    2015-01-01

    An ongoing objective of burn research is to evaluate wound dressings and develop new treatments to expedite wound healing. This was a single-center, prospective, randomized, controlled study to evaluate the effectiveness of Aquacel Ag as a dressing for autogenous skin donor sites compared with Xeroform. We hypothesized that donor sites treated with Aquacel Ag would heal faster. Patients were considered for enrollment if they required skin grafting with two donor sites >100 cm at least 2 inches apart. Dressings were observed daily starting on post-op day #2 until discharge and then weekly in the outpatient burn clinic. Assessments evaluated pain, infection, and reapplication. Photographs were taken on post-op day #2, upon "90% re-epithelialization," and at post-op day #30-45. Scar assessments and blinded photographic reviews were completed to assess cosmetic healing. Twenty-nine patients completed the study. Re-epithelialization occurred faster with Xeroform (15.2 days vs. 17.6 days). Daily pain scores were higher with Xeroform (6.72 vs. 5.68) and Aquacel Ag needed to be replaced more often (1.72 times vs. 0.10 times). Three patients developed donor site infections with Aquacel Ag. Scar scores between the donor sites were not statistically significant. The blinded photo review concluded that Xeroform had a better cosmetic outcome (24 vs. 10%). Although patients complained of more pain with Xeroform, it demonstrated shorter healing times and better cosmetic outcomes. Aquacel Ag needed to be replaced more often and represented the only three donor site infections.

  6. Repair process of surgical defects filled with autogenous bone grafts in tibiae of diabetic rats

    Directory of Open Access Journals (Sweden)

    Jônatas Caldeira Esteves

    2008-10-01

    Full Text Available From a biological standpoint, the best material for reconstruction of bone defects is the autogenous bone graft. However, as tissue healing is affected under diabetic conditions, major changes might take place in the revascularization, incorporation, replacement and remodeling phases of the grafted area. The purpose of this study was to assess the bone healing process in surgical wounds prepared in tibiae of diabetic rats and filled with autogenous bone. Forty male rats (Rattus norvegicus albinus, Wistar were randomly assigned to receive an endovenous injection (penile vein of either citrate buffer solution (Group 1 - control; n=20 or streptozotocin dissolved in citrate buffer solution (35 mg/kg to induce diabetes (Group 2 - diabetic; n=20. After determination of glycemia, the animals were anesthetized and the anterolateral regions of the tibiae of both limbs were shaved, antisepsis was performed and longitudinal incisions were made in each limb. The tibiae were exposed and two 2mm-diameter surgical cavities were prepared: one in the right limb, filled with particulate autogenous bone and the other in the left limb, filled with blood clot. The animals were euthanized at 10 and 30 postoperative days. The anatomic pieces were obtained, submitted to laboratory processing and sections were stained by hematoxylin and eosin and Masson's Trichrome for histomorphologic and histometric analyses. In both groups, the wounds filled with autogenous bone graft showed better results than those filled with blood clot. The control group showed higher new bone formation in wounds filled with autogenous bone graft at 30 days than the diabetic group, but without statistical significance. It may be concluded that, in general, the new bone formation occurred with autogenous graft was quantitatively similar between control and diabetic groups and qualitatively better in the control group.

  7. Autogenous tooth transplants for the pediatric dental patient: report of three cases.

    Science.gov (United States)

    Kennedy, David

    2013-01-01

    There are select instances where autogenous tooth transplantation should be considered as part of the overall management of the developing occlusion in the child patient. These circumstances occur when there are missing mandibular premolars in Class II malocclusions with good faces, unevenly distributed agenesis, missing or lost incisors, and ectopic teeth. The purposes of this paper were to educate pediatric dentists about the autogenous tooth transplantation technique, its success, its potential advantages and disadvantages and to report on three cases treated with autogenesis tooth transplantation.

  8. Autogenous vein graft thrombosis following exposure to calcium-free solutions (calcium paradox).

    Science.gov (United States)

    Nozick, J H; Farnsworth, P; Montefusco, C M; Parsonnet, V; Ruigrok, T J; Zimmerman, A N

    1981-01-01

    The morphological and functional effects of calcium-free and calcium-containing solutions on canine jugular vein intima were examined under conditions which closely resemble those techniques currently employed in peripheral vascular and aortocoronary bypass surgery. Veins that had been exposed only to calcium-containing solutions remained patent for the duration of the experimental period. Vein perfusion with a calcium-free solution, however, resulted in disruption of the jugular vein intima once calcium ions were reintroduced. Autogenous as a femoral arterial graft became thrombosed within 60 minutes. It is therefore suggested that vein grafts of autogenous origin be irrigated with calcium-containing solutions to prevent intimal damage and thrombosis.

  9. A Monte Carlo Evaluation of Estimated Parameters of Five Shrinkage Estimate Formuli.

    Science.gov (United States)

    Newman, Isadore; And Others

    1979-01-01

    A Monte Carlo simulation was employed to determine the accuracy with which the shrinkage in R squared can be estimated by five different shrinkage formulas. The study dealt with the use of shrinkage formulas for various sample sizes, different R squared values, and different degrees of multicollinearity. (Author/JKS)

  10. Study of ‘real’ shrinkage by ESEM observations and digital image analysis

    NARCIS (Netherlands)

    Jankovic, D.

    2007-01-01

    Defining the 'real' shrinkage values of concrete is still a subject of much debate. In shrinkage experiments size effects are inherently present. Through an attempt to determine the real shrinkage of cement-based materials, these size effects have to be eliminated or at least reduced as much a possi

  11. New particle growth and shrinkage observed in subtropical environments

    Directory of Open Access Journals (Sweden)

    L.-H. Young

    2012-07-01

    Full Text Available We present the first systematic analysis for new particle formation (NPF, growth and shrinkage of new particles observed at four different sites in subtropical Central Taiwan. A total of 14 NPF events were identified during 137 days of ambient measurements during a cold and warm season. The derived nucleation rates of 1 nm particles (J1 and growth rates were in the range of 39.6–252.9 cm−3 s−1 and 6.5–14.5 nm h−1, respectively. The NPF events occurred on days either with low condensation sink (CS, increased morning traffic emissions and the breakup of nocturnal inversion layer (type A, or with high CS, minimum levels of primary traffic emissions and enhanced atmospheric dilution (type B. On non-event days, the particle number concentrations were mostly driven by traffic emissions. We have also observed shrinkage of new particles (type A-S and B-S, reversal of growth, during five out of the 14 NPF events. In intense shrinkage cases, the grown particles shrank back to the smallest measurable size of ~10 nm, thereby creating a unique "arch-like" shape in the size distribution contour plot. The particle shrinkage rates ranged from 5.1 to 7.6 nm h−1. The ratios of shrinkage-to-growth rates were mostly in the range of 0.40–0.65, suggesting that a large fraction of the condensable species that contributed to growth were likely semi-volatile. The particle shrinkage was related to air masses with low CS due to atmospheric dilution, high ambient temperature and low relative humidity and such atmospheric conditions may have facilitated the evaporation of semi-volatile species from the particles to the gas phase. Our observations show that the new particle growth may be a~reversible process and the evaporating semi-volatile species are important for the growth of new particles to cloud condensation nuclei sizes.

  12. Crack layer theory

    Science.gov (United States)

    Chudnovsky, A.

    1984-01-01

    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.

  13. INTERRELATION OF RHOMBICITY AND OCCURRENCE OF INTERNAL CRACKS AT CONTINUOUS CASTING OF SORTED SLUG

    Directory of Open Access Journals (Sweden)

    Ju. A. Samojlovich

    2008-01-01

    Full Text Available Analysis of deformations and stresses in cross section of sorted uninterruptedly-casted slugs at their solidification and cooling within limits of crystallizer with the aim of determination of possibilities for occurrence of internal cracks of diagonal type is carried out on basis of mathematical modeling, the peculiarities of the slug skin cooling at its shrinkage and separation from crystallizer wall are revealed.

  14. Effect of crack propagation on crack tip fields

    Directory of Open Access Journals (Sweden)

    F.V. Antunes

    2013-07-01

    Full Text Available Crack closure influences fatigue crack growth rate and must be included in the design of components. Plasticity induced crack closure is intimately linked with the crack tip plastic deformation, which becomes residual as the crack propagates. The objective here is to study numerically the effect of crack propagation on crack tip fields. The transient effect observed at the beginning of crack propagation is linked to the hardening behavior of material. The effect of mesh refinement is studied, and a singular behavior is evident, which is explained by the sharp crack associated with mesh topology, composed of a regular pattern of square elements. The plastic zone size measured perpendicularly to crack flank in the residual plastic wake is quantified and compared with literature models. Finally, the removal of material at the first node behind crack tip with load cycling was observed for plane strain state and some hardening models in plane stress state.

  15. Three Dimensional Numerical Simulation for the Driving Force of Weld Solidification Cracking

    Institute of Scientific and Technical Information of China (English)

    Zhibo DONG; Yanhong WEI; Renpei LIU; Zujue DONG

    2005-01-01

    The double ellipsoidal model of heat source is used to analyze the thermal distributions with a three dimensional finite element method (FEM). In the mechanical model, solidification effects are treated by a dynamic element rebirth scheme. The driving force is obtained in the cracking susceptible temperature range. Moreover, this paper presents the effect of solidification shrinkage, external restraint, weld start locations and material properties on the driving force. The comparison between the simulated driving force and the experimental measurements of the material resistance predicts the susceptibility of weld metal solidification cracking.

  16. Numerical Analysis of Hot Cracking in Laser-Hybrid Welded Tubes

    Directory of Open Access Journals (Sweden)

    Moritz Oliver Gebhardt

    2013-01-01

    Full Text Available In welding experiments conducted on heavy wall pipes, the penetration mode (full or partial penetration occurred to be a significant factor influencing appearance of solidification cracks. To explain the observed phenomena and support further optimization of manufacturing processes, a computational model was developed, which used a sophisticated strategy to model the material. High stresses emerged in the models in regions which showed cracking during experiments. In partial penetration welding, they were caused by the prevention of weld shrinkage due to the cold and strong material below the joint. Another identified factor having an influence on high stress localization is bulging of the weld.

  17. Combinatorial Selection and Least Absolute Shrinkage via the CLASH Algorithm

    CERN Document Server

    Kyrillidis, Anastasios

    2012-01-01

    The least absolute shrinkage and selection operator (LASSO) for linear regression exploits the geometric interplay of the $\\ell_2$-data error objective and the $\\ell_1$-norm constraint to arbitrarily select sparse models. Guiding this uninformed selection process with sparsity models has been precisely the center of attention over the last decade in order to improve learning performance. To this end, we alter the selection process of LASSO to explicitly leverage combinatorial sparsity models (CSMs) via the combinatorial selection and least absolute shrinkage (CLASH) operator. We provide concrete guidelines how to leverage combinatorial constraints within CLASH, and characterize CLASH's guarantees as a function of the set restricted isometry constants of the sensing matrix. Finally, our experimental results show that CLASH can outperform both LASSO and model-based compressive sensing in sparse estimation.

  18. Exploiting tumor shrinkage through temporal optimization of radiotherapy

    CERN Document Server

    Unkelbach, Jan; Hong, Theodore; Papp, David; Ramakrishnan, Jagdish; Salari, Ehsan; Wolfgang, John; Bortfeld, Thomas

    2013-01-01

    In multi-stage radiotherapy, a patient is treated in several stages separated by weeks or months. This regimen has been motivated mostly by radiobiological considerations, but also provides an approach to reduce normal tissue dose by exploiting tumor shrinkage. The paper considers the optimal design of multi-stage treatments, motivated by the clinical management of large liver tumors for which normal liver dose constraints prohibit the administration of an ablative radiation dose in a single treatment. We introduce a dynamic tumor model that incorporates three factors: radiation induced cell kill, tumor shrinkage, and tumor cell repopulation. The design of multi-stage radiotherapy is formulated as a mathematical optimization problem in which the total dose to the liver is minimized, subject to delivering the prescribed dose to the tumor. Based on the model, we gain insight into the optimal administration of radiation over time, i.e. the optimal treatment gaps and dose levels. We analyze treatments consisting ...

  19. Analysis of Shrinkage on Thick Plate Part using Genetic Algorithm

    Directory of Open Access Journals (Sweden)

    Najihah S.N.

    2016-01-01

    Full Text Available Injection moulding is the most widely used processes in manufacturing plastic products. Since the quality of injection improves plastic parts are mostly influenced by process conditions, the method to determine the optimum process conditions becomes the key to improving the part quality. This paper presents a systematic methodology to analyse the shrinkage of the thick plate part during the injection moulding process. Genetic Algorithm (GA method was proposed to optimise the process parameters that would result in optimal solutions of optimisation goals. Using the GA, the shrinkage of the thick plate part was improved by 39.1% in parallel direction and 17.21% in the normal direction of melt flow.

  20. Modelling of elastoplastic damage in concrete due to desiccation shrinkage

    Science.gov (United States)

    Bourgeois, F.; Burlion, N.; Shao, J. F.

    2002-07-01

    We present a numerical modelling of elastoplastic damage due to drying shrinkage of concrete in the framework of mechanics of partially saturated porous media. An elastoplastic model coupled with isotropic damage is first formulated. Two plastic flow mechanisms are involved, controlled by applied stress and suction, respectively. A general concept of net effective stress is used in take into account effects of capillary pressure and material damage on stress-controlled plastic deformation. Damage evolution depends both on elastic and plastic strains. The model's parameters are determined or chosen from relevant experimental data. Comparisons between numerical simulations and experimental data are presented to show the capacity of model to reproduce mains features of concrete behaviour under mechanical loading and during drying shrinkage of concrete. An example of application concerning drying of a concrete wall is finally presented. The results obtained allow to show potential capacity of proposed model for numerical modelling of complex coupling processes in concrete structures.

  1. Reversible cerebral shrinkage in kwashiorkor: an MRI study.

    Science.gov (United States)

    Gunston, G D; Burkimsher, D; Malan, H; Sive, A A

    1992-08-01

    Protein energy malnutrition is associated with cerebral atrophy which may be detrimental to intellectual development. The aim of this study was to document the anatomical abnormalities which lead to the appearance of cerebral atrophy using magnetic resonance imaging (MRI) in the acute stage of kwashiorkor and to monitor changes during nutritional rehabilitation. Twelve children aged 6 to 37 months requiring admission to hospital for the treatment of kwashiorkor were studied. The children were evaluated clinically, biochemically, and by MRI of their brains on admission and 30 and 90 days later. Brain shrinkage was present in every child on admission. White and grey matter appeared equally affected and the myelination was normal for age. At 90 days, the cerebral changes had resolved in nine and improved substantially in the remainder, by which time serum proteins and weight for age were within the normal range. The findings of this study suggest that brain shrinkage associated with kwashiorkor reverses rapidly with nutritional rehabilitation.

  2. Shrinkage and trajectory of the flat jet with inclination angle

    Institute of Scientific and Technical Information of China (English)

    Shufeng Ye; Yusheng Xie; Hongzhi Guo; Ye Huang; Shantong Jin

    2003-01-01

    The performance of the flat jet with an inclination angle was investigated by a water model. A mathematical model for theshrinkage and the trajectory of the flat jet with an inclination angle was derived theoretically and verified by experimental data of thewater model. The experimental results indicate that the inclination angle (α) has no influence on the shrinkage of the flat jet, theshrinkage of the flat jet along the width direction decreases with the increasing of the initial velocity at the exit (u0) and the initialthickness of the flat jet (t0). Enough bigger initial exit velocity (u0) and initial thickness can suppress the shrinkage of the flat jetalong the width direction and keep the flat jet stabilized. In addition, the trajectory of the flat jet with an inclination angle is parabolicand must be taking into consideration when to determine the striking distance.

  3. New System of Shrinkage Measurement through Cement Mortars Drying

    Science.gov (United States)

    Morón, Carlos; Saiz, Pablo; Ferrández, Daniel; García-Fuentevilla, Luisa

    2017-01-01

    Cement mortar is used as a conglomerate in the majority of construction work. There are multiple variants of cement according to the type of aggregate used in its fabrication. One of the major problems that occurs while working with this type of material is the excessive loss of moisture during cement hydration (setting and hardening), known as shrinkage, which provokes a great number of construction pathologies that are difficult to repair. In this way, the design of a new sensor able to measure the moisture loss of mortars at different age levels is useful to establish long-term predictions concerning mortar mass volume loss. The purpose of this research is the design and fabrication of a new capacitive sensor able to measure the moisture of mortars and to relate it with the shrinkage. PMID:28272297

  4. Swell Potential, Collapse Potential, Wetting and Drying Cycles, Cracks, Number of Segment

    Directory of Open Access Journals (Sweden)

    Abdulrahman T. Al Zubaydi

    2013-05-01

    Full Text Available Many of the soils undergo volumetric changes due to the change in the water content. Swell-shrink and collapse behavior of those soils affects the stress state in soil and the interacted structures. Shrinkage in the soil produce cracks of different patterns, and affects the swelling potential in next wetting cycle.This study covers swelling and collapsing properties of four different soils from Mosul city. The changes in swelling and collapsing properties with respect to number of wetting and drying cycles have been investigated. Also, A shrinkage cracks have been studied with aid of digital image after each drying cycle. Number of segments and area of cracks calculated with aid of AutoCAD package.Results indicated that, the collapse potential is influenced by soil type (soil composition and applied loads. As the applied loads increase the collapse potential increases. For sandy soil the collapse potential decreased with increasing wetting and drying cycles, and for the clayey soils, swell potential decreased while collapse potential increased with these cycles. It has been shown that the cracks increase with wetting-drying cycles. Larger values of percent crack area to the initial sample area has been observed in the soil that contain more clay content than other types of soils.

  5. Research and Application of the Mathematic Model for the Washing Shrinkage of Woven Fabric

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Having analyzed the relationships between washing shrinkage and weaving technique, parameters, material properties of woven fabrics and studied the shrinkage mechanism and its mathematical model of the plain fabric,researchers set up a shrinkage model of the twills and satins and proposed a method for calculating the washing shrinkage based on weaving technique and parameters of fabrics. Shrinkage experiments of silk habotai, silk twill and silk satin fabrics were performed. The results were compared with those of the theoretical computations, and it has been proven that the theoretical method is reliable.

  6. Polymerization shrinkage of flowable resin-based restorative materials

    OpenAIRE

    Stavridakis, Minos M; Dietschi, Didier; Krejci, Ivo

    2005-01-01

    This study measured the linear polymerization displacement and polymerization forces induced by polymerization shrinkage of a series of flowable resin-based restorative materials. The materials tested were 22 flowable resin-based restorative materials (Admira Flow, Aelite Flow, Aeliteflow LV, Aria, Crystal Essence, Definite Flow, Dyract Flow, Filtek Flow, FloRestore, Flow-it, Flow-Line, Freedom, Glacier, OmegaFlo, PermaFlo, Photo SC, Revolution 2, Star Flow, Synergy Flow, Tetric Flow, Ultrase...

  7. Super-resolution optical telescopes with local light diffraction shrinkage

    OpenAIRE

    Changtao Wang; Dongliang Tang; Yanqin Wang; Zeyu Zhao; Jiong Wang; Mingbo Pu; Yudong Zhang; Wei Yan; Ping Gao; Xiangang Luo

    2015-01-01

    Suffering from giant size of objective lenses and infeasible manipulations of distant targets, telescopes could not seek helps from present super-resolution imaging, such as scanning near-field optical microscopy, perfect lens and stimulated emission depletion microscopy. In this paper, local light diffraction shrinkage associated with optical super-oscillatory phenomenon is proposed for real-time and optically restoring super-resolution imaging information in a telescope system. It is found ...

  8. Investigation on Cracking of Concrete Shear Wall under Exceeded Temperature Differences Rate

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In situ, the changes of temperature, deformation, and stressing of steel bar of C40 reinforced concrete shear wall were measured, respectively. The results are obvious that the temperature change of climate is one of the most effective factors which could lead the concrete shear wall to cracking at earlier age. The temperature differences between inside and outside concrete shear wall are so large that the concrete will gain larger shrinkage. This larger shrinkage which is caused by the temperature reducing ratio will gain the strained action of head, end and reinforced steel bar of concrete shear wall. This action can lead to tensile stress on the surface and inside concrete shear wall. If the tensile stress would exceed the pull strength of concrete, the concrete shear wall would crack and cause deterioration. Thus, the enhancing curing of concrete shear wall in suit at earlier age, and controlling temperature reducing ratio and deform caused by shrinkage, will be available treatments which control occurring and developing of cracking on concrete shear wall.

  9. PREDIKSI SHRINKAGE UNTUK MENGHINDARI CACAT PRODUK PADA PLASTIC INJECTION

    Directory of Open Access Journals (Sweden)

    Agus Dwi Anggono

    2015-05-01

    Full Text Available Plastic injection merupakan proses manufactur untuk membuat produk dengan bahan dasar plastic atau dalam kesempatan ini polypropylene. Pada proses tersebut seringkali terjadi cacat produk seperti pengerutan, retak, dimensi tidak sesuai dan kerusakan saat produk keluar dari mould, sehingga banyak material yang terbuang percuma. Meskipun cacat produk tersebut dipengaruhi banyak factor, tetapi yang paling utama adalah masalah shrinkage, atau penyusutan material setelah terjadi pendinginan. Sangat penting untuk melakukan prediksi lebih awal terjadinya penyusutan setelah pendinginan untuk menghindari cacat produk. Dalam penelitian ini akan dilakukan prediksi shrinkage yang akan digunakan untuk material polypropylene dengan cara perhitungan standar. Pembuatan modeling dalam bentuk 3D (tiga dimensi injection molding baik cavity maupun corenya dengan menggunakan CATIA, kemudian dilakukan analisis dengan software MoldFlow untuk pembuatan mesh dan memberikan batasan panas pada komponen sehingga dapat diketahui mode penyusutannya. Analisis ini akan memberikan gambaran tentang distribusi panas pada mould dan memberikan tentang gambaran aliran fluida. Pada analisis tersebut dapat dilihat gejala terjadinya cacat produk, jika hal itu terjadi maka perlu dilakukan perubahan shrinkage, sampai diperoleh hasil analisis yang baik.

  10. Visualization study on distortion of a metal frame by polymerization shrinkage and thermal contraction of resin.

    Science.gov (United States)

    Kakino, Ken; Endo, Kazuhiko; Hashimoto, Masanori; Furuta, Kunihiko; Ohno, Hiroki

    2014-01-01

    Three types of metal specimens (ring-shaped, plate-shaped, and a simulated anterior arch) for distortion observations were made from Au-Ag-Pd-Cu alloy. Distortion due to polymerization shrinkage and thermal contraction of a heat-curing acrylic resin containing 4-META (4-methacryloyloxyethyl trimellitate anhydride, 4-META resin) could be visualized for the ring-shaped specimen, which showed increasing distortion of the metal frame upon adhesion of the resin to the outer metal surface. Distortion of the plateshaped specimen adhering to 4-META resin decreased with increasing thickness of the cured resin. The distortion of the metal frame simulating an anterior arch of a six-unit bridge with a facing composite resin showed that the curvature of the metal frame was larger after curing of the facing composite resin. However, it recovered most of its original curvature with an associated increase in the number of cracks between the crowns after trimming the resin to a tooth profile.

  11. Guided bone regeneration using autogenous tooth bone graft in implant therapy: case series.

    Science.gov (United States)

    Kim, Young-Kyun; Kim, Su-Gwan; Bae, Ji-Hyun; Um, In-Woong; Oh, Ji-Su; Jeong, Kyung-In

    2014-04-01

    Recently, techniques have been reported that involve the preparation of extracted teeth from patients used as particulated bone graft materials for bone graft purposes. For implant placement and bone graft, autogenous teeth bone graft materials were used in 15 patients, and clinically excellent results were obtained. In histological examination, favorable bony healing by osteoconduction was observed.

  12. Histological evaluation of healing after transalveolar maxillary sinus augmentation with bioglass and autogenous bone

    DEFF Research Database (Denmark)

    Stavropoulos, Andreas; Sima, Catalin; Sima, Andrea;

    2012-01-01

    OBJECTIVES: The aim was to evaluate histologically the outcome of a bioglass and autogenous bone (at 1 : 1 ratio) composite implantation for transalveolar sinus augmentation. METHODS: In 31 patients, during implant installation ca. 4 months after sinus augmentation, biopsies were harvested throug...

  13. Evaluation of Autogenous Engineered Septal Cartilage Grafts in Rabbits: A Minimally Invasive Preclinical Model

    Directory of Open Access Journals (Sweden)

    Anton Kushnaryov

    2014-01-01

    Full Text Available Objectives. (1 Evaluate safety of autogenous engineered septal neocartilage grafts and (2 compare properties of implanted grafts versus controls. Study Design. Prospective, basic science. Setting. Research laboratory. Methods. Constructs were fabricated from septal cartilage and then cultured in vitro or implanted on the nasal dorsum as autogenous grafts for 30 or 60 days. Rabbits were monitored for local and systemic complications. Histological, biochemical, and biomechanical properties of constructs were evaluated. Results. No serious complications were observed. Implanted constructs contained more DNA (P<0.01 and less sGAG perDNA (P<0.05 when compared with in vitro controls. Confined compressive aggregate moduli were also higher in implanted constructs (P<0.05 and increased with longer in vivo incubation time (P<0.01. Implanted constructs displayed resorption rates of 20–45 percent. Calcium deposition in implanted constructs was observe. Conclusion. Autogenous engineered septal cartilage grafts were well tolerated. As seen in experiments with athymic mice, implanted constructs accumulated more DNA and less sGAG when compared with in vitro controls. Confined compressive aggregate moduli were higher in implanted constructs. Implanted constructs displayed resorption rates similar to previously published studies using autogenous implants of native cartilage.

  14. Neural progenitor cells from human induced pluripotent stem cells generated less autogenous immune response.

    Science.gov (United States)

    Huang, Ke; Liu, PengFei; Li, Xiang; Chen, ShuBin; Wang, LiHui; Qin, Li; Su, ZhengHui; Huang, WenHao; Liu, Juli; Jia, Bei; Liu, Jie; Cai, JingLei; Pei, DuanQing; Pan, GuangJin

    2014-02-01

    The breakthrough development of induced pluripotent stem cells (iPSCs) raises the prospect of patient-specific treatment for many diseases through the replacement of affected cells. However, whether iPSC-derived functional cell lineages generate a deleterious immune response upon auto-transplantation remains unclear. In this study, we differentiated five human iPSC lines from skin fibroblasts and urine cells into neural progenitor cells (NPCs) and analyzed their immunogenicity. Through co-culture with autogenous peripheral blood mononuclear cells (PBMCs), we showed that both somatic cells and iPSC-derived NPCs do not stimulate significant autogenous PBMC proliferation. However, a significant immune reaction was detected when these cells were co-cultured with allogenous PBMCs. Furthermore, no significant expression of perforin or granzyme B was detected following stimulation of autogenous immune effector cells (CD3(+)CD8(-) T cells, CD3(+)CD8(+) T cells or CD3(-)CD56(+) NK cells) by NPCs in both PBMC and T cell co-culture systems. These results suggest that human iPSC-derived NPCs may not initiate an immune response in autogenous transplants, and thus set a base for further preclinical evaluation of human iPSCs.

  15. Starch hydrolysis in autogenerative high pressure digestion: Gelatinisation and saccharification as rate limiting steps

    NARCIS (Netherlands)

    Lindeboom, R.E.F.; Ding, L.; Weijma, J.; Plugge, C.M.; Lier, van J.B.

    2014-01-01

    Autogenerative high pressure digestion (AHPD) provides an integrated biogas upgrading technology, capable of producing biogas with a CH4 content exceeding 95% at pressures up to 90 bar. Hydrolysis is generally regarded as the rate-limiting step in the anaerobic digestion of complex organic matter, g

  16. Acromioclavicular Reconstruction using Autogenous Semitendinosus Tendon Graft and the Importance of Postoperative Rehabilitation: A Case Report

    Directory of Open Access Journals (Sweden)

    Jade PY Ho

    2013-11-01

    Full Text Available We present a case of chronic acromioclavicular joint dislocation (Rockwood type 5 in which the choice of acromioclavicular reconstruction using autogenous semitendinosus tendon graft was made due to its superiority in anatomical reconstruction of the coracoclavicular ligaments, and the impact of postoperative rehabilitation on the recovery of this patient. We also discuss the rationale behind this.

  17. Augmentation of localized defects of the anterior maxillary ridge with autogenous bone before insertion of implants

    NARCIS (Netherlands)

    Raghoebar, GM; Batenburg, RHK; Vissink, A; Reintsema, H

    1996-01-01

    Purpose: This study evaluated the applicability of intraorally harvested autogenous bone grafts for the augmentation of the narrow maxillary alveolar ridge to enable insertion of implants for single tooth replacement. Materials and Methods: Local defects of the anterior maxilla were reconstructed in

  18. Sealing of cracks in cement using microencapsulated sodium silicate

    Science.gov (United States)

    Giannaros, P.; Kanellopoulos, A.; Al-Tabbaa, A.

    2016-08-01

    Cement-based materials possess an inherent autogenous self-healing capability allowing them to seal, and potentially heal, microcracks. This can be improved through the addition of microencapsulated healing agents for autonomic self-healing. The fundamental principle of this self-healing mechanism is that when cracks propagate in the cementitious matrix, they rupture the dispersed capsules and their content (cargo material) is released into the crack volume. Various healing agents have been explored in the literature for their efficacy to recover mechanical and durability properties in cementitious materials. In these materials, the healing agents are most commonly encapsulated in macrocontainers (e.g. glass tubes or capsules) and placed into the material. In this work, microencapsulated sodium silicate in both liquid and solid form was added to cement specimens. Sodium silicate reacts with the calcium hydroxide in hydrated cement paste to form calcium-silicate-hydrate gel that fills cracks. The effect of microcapsule addition on rheological and mechanical properties of cement is reported. It is observed that the microcapsule addition inhibits compressive strength development in cement and this is observed through a plateau in strength between 28 and 56 days. The improvement in crack-sealing for microcapsule-containing specimens is quantified through sorptivity measurements over a 28 day healing period. After just seven days, the addition of 4% microcapsules resulted in a reduction in sorptivity of up to 45% when compared to specimens without any microcapsule addition. A qualitative description of the reaction between the cargo material and the cementitious matrix is also provided using x-ray diffraction analysis.

  19. Quantity effect of radial cracks on the cracking propagation behavior and the crack morphology.

    Directory of Open Access Journals (Sweden)

    Jingjing Chen

    Full Text Available In this letter, the quantity effect of radial cracks on the cracking propagation behavior as well as the circular crack generation on the impacted glass plate within the sandwiched glass sheets are experimentally investigated via high-speed photography system. Results show that the radial crack velocity on the backing glass layer decreases with the crack number under the same impact conditions during large quantities of repeated experiments. Thus, the "energy conversion factor" is suggested to elucidate the physical relation between the cracking number and the crack propagation speed. Besides, the number of radial crack also takes the determinative effect in the crack morphology of the impacted glass plate. This study may shed lights on understanding the cracking and propagation mechanism in laminated glass structures and provide useful tool to explore the impact information on the cracking debris.

  20. Modelling of Corrosion Cracks

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    Modelling of corrosion cracking of reinforced concrete structures is complicated as a great number of uncertain factors are involved. To get a reliable modelling a physical and mechanical understanding of the process behind corrosion in needed.......Modelling of corrosion cracking of reinforced concrete structures is complicated as a great number of uncertain factors are involved. To get a reliable modelling a physical and mechanical understanding of the process behind corrosion in needed....

  1. Effect of aluminum silicate fiber modification on crack-resistance of a ceramic mould

    Directory of Open Access Journals (Sweden)

    Jiang Yehua

    2012-11-01

    Full Text Available To improve the crack-resistance of the mould for silica sol bonded quartz based ceramic mould casting, aluminum silicate fibers with the diameter ranging from 5 µm to 25 µm and the length about 1 mm were dispersed in the ceramic mould. The effect of the aluminum silicate fibers on the tensile strength, shrinkage rate and the cracking trend of the ceramic mould were investigated. In the ceramic slurry, quartz sand was applied as ceramic aggregate, silica sol containing 30% silicon dioxide as bonder, and the weight ratio of quartz sand to silica sol was 2.69; the dispersed fibers changed from 0 to 0.24vol.%. The mould samples were formed after the slurry was poured and gelled at room temperature, and then sintered at different temperatures ranging from 100 to 800 ℃ to measure the tensile strength and shrinkage rate. The results show that, with the aluminum silicate fiber addition increasing from 0 to 0.24vol.%, the tensile strength increases linearly from 0.175 MPa to 0.236 MPa, and the shrinkage rate decreases linearly from 1.75% to 1.68% for the ceramic mould sintered at 400 ℃, from 1.37% to 1.31% for the ceramic mould at room temperature. As the sintering temperature was raised from 100 ℃ to 800 ℃, the tensile strength increases, and the shrinkage rate decreases at all temperatures, compared with those without fiber dispersion, but their variation patterns remain the same. Furthermore, the cracking trend of the mould and its decreasing proportion were defined and analyzed quantitatively considering both effects of the fiber dispersion on the strength and shrinkage. The cracking trend appears to decrease linearly with increasing fiber content and to reach the maximum reduction of 28.8% when 0.24vol.% fiber was dispersed. Therefore, the investigation proposes a new method to improve the crack-resistance of the ceramic mould, i.e., inorganic fiber dispersion into the ceramic mould.

  2. Sparse electromagnetic imaging using nonlinear iterative shrinkage thresholding

    KAUST Repository

    Desmal, Abdulla

    2015-04-13

    A sparse nonlinear electromagnetic imaging scheme is proposed for reconstructing dielectric contrast of investigation domains from measured fields. The proposed approach constructs the optimization problem by introducing the sparsity constraint to the data misfit between the scattered fields expressed as a nonlinear function of the contrast and the measured fields and solves it using the nonlinear iterative shrinkage thresholding algorithm. The thresholding is applied to the result of every nonlinear Landweber iteration to enforce the sparsity constraint. Numerical results demonstrate the accuracy and efficiency of the proposed method in reconstructing sparse dielectric profiles.

  3. Sonar target enhancement by shrinkage of incoherent wavelet coefficients.

    Science.gov (United States)

    Hunter, Alan J; van Vossen, Robbert

    2014-01-01

    Background reverberation can obscure useful features of the target echo response in broadband low-frequency sonar images, adversely affecting detection and classification performance. This paper describes a resolution and phase-preserving means of separating the target response from the background reverberation noise using a coherence-based wavelet shrinkage method proposed recently for de-noising magnetic resonance images. The algorithm weights the image wavelet coefficients in proportion to their coherence between different looks under the assumption that the target response is more coherent than the background. The algorithm is demonstrated successfully on experimental synthetic aperture sonar data from a broadband low-frequency sonar developed for buried object detection.

  4. Photoelastic study of shrinkage fitted components for a gasturbine engine

    Science.gov (United States)

    Govindaraju, T. V.; Maheshappa, H.; Govindaraju, N.; Gargesa, G.

    A 3D photoelastic model of shrink-fitted components of a gas turbine engine such as low-pressure main shaft and compressor adopter shaft (or hub) are used to perform a photo-elastic investigation of shrink-fitted components for different relative thickness ratio and different contact length ratio. The relative rigidity of the hub is found to increase as the relative thickness ratio increases, and the relative rigidity is found to increase as the contact length ratio decreases. An optimization of the geometry of the shrinkage-fitted components is also obtained.

  5. Modeling crack growth during Li insertion in storage particles using a fracture phase field approach

    Science.gov (United States)

    Klinsmann, Markus; Rosato, Daniele; Kamlah, Marc; McMeeking, Robert M.

    2016-07-01

    Fracture of storage particles is considered to be one of the major reasons for capacity fade and increasing power loss in many commercial lithium ion batteries. The appearance of fracture and cracks in the particles is commonly ascribed to mechanical stress, which evolves from inhomogeneous swelling and shrinkage of the material when lithium is inserted or extracted. Here, a coupled model of lithium diffusion, mechanical stress and crack growth using a phase field method is applied to investigate how the formation of cracks depends on the size of the particle and the presence or absence of an initial crack, as well as the applied flux at the boundary. The model shows great versatility in that it is free of constraints with respect to particle geometry, dimension or crack path and allows simultaneous observation of the evolution of lithium diffusion and crack growth. In this work, we focus on the insertion process. In particular, we demonstrate the presence of intricate fracture phenomena, such as, crack branching or complete breakage of storage particles within just a single half cycle of lithium insertion, a phenomenon that was only speculated about before.

  6. Shrinkage and microstructural development during drying of organically modified silica xerogels

    Energy Technology Data Exchange (ETDEWEB)

    Raman, N.K. [New Mexico Univ., Albuquerque, NM (United States); Wallace, S. [Nanopore Corp., Albuquerque, NM (United States); Brinker, C.J. [New Mexico Univ., Albuquerque, NM (United States)]|[Sandia National Labs., Albuquerque, NM (United States)

    1996-07-01

    We have studied the different driving forces behind syneresis in MTES/TEOS gels by aging them in different H{sub 2}O/EtOH pore fluids. We show using shrinkage, density, contact angle, and N{sub 2} sorption measurements, the influence of gel/solvent interactions on the microstructural evolution during drying. Competing effects of syneresis (that occurs during aging) and drying shrinkage resulted in the overall linear shrinkage of the organically modified gels to be constant at {approximately}50%. Increasing the hydrophobicity of the gels caused the driving force for syneresis to change from primarily condensation reactions to a combination of condensation and solid/liquid interfacial energy. In addition the condensation driven shrinkage was observed to be irreversible, whereas the interfacial free energy driven shrinkage was observed to be partially reversible. Nitrogen sorption experiments show that xerogels with the same overall extent of shrinkage can have vastly different microstructures due to the effects of microphase separation.

  7. Collapse-type shrinkage characteristics in plantation-grown eucalypts: I . Correlations of basic density and some structural indices with shrinkage and collapse properties

    Institute of Scientific and Technical Information of China (English)

    WUYi-qiang; HAYASHIKazuo; LIUYuan; CAIYing-chun; SUGIMORIMasatoshi; LUOJian-ju

    2005-01-01

    Collapse-type shrinkage is one of highly refractory drying defects in low-medium density plantation-grown eucalypt wood used as solid wood products. Basic density (BD), microfibril angle (MFA), double fibre cell wall thickness (DWT), proportion of ray parenchyma (RP), unit cell wall shrinkage, total shrinkage and residual collapse, which are associated with collapse-type shrinkage characteristics, were investigated by using simple regression method for three species of collapse-susceptible Eucalyptus urophyll, E. grandis and E.urophyllaxE.grandis, planted at Dong-Men Forest Farm in Guangxi autonomous region, China. The results indicated that : unit cell wall shrinkage had a extremely strong positive correlation with BD, moderately strong positive correlation with DWT, and a weakly or moderately negative correlation with RP and MFA; total shrinkage was positively correlated with BD, DWT and RP and negatively related to MFA, but not able to be predicted ideally by any examined factors alone owing to lower R2 value (R2≤0.5712); residual collapse was negatively correlated with BD and DWT, linearly positively correlated with MFA, and had strongly positive linear correlation with RP. It is concluded that BD can be used as single factor (R2≥0.9412) to predicate unit cell wall shrinkage and RP is the relatively sound indicator for predicting residual collapse

  8. Early-age volume changes of extrudable reactive powder concrete

    Directory of Open Access Journals (Sweden)

    De Noirfontaine M.N.

    2010-06-01

    Full Text Available This article presents a study on the early-age autogenous deformations of Extrudable Reactive Powder Concretes (ERPCs, especially designed for the making of concrete pipes by extrusion. Different ERPC mixtures, with variable amounts of polycarboxylate superplasticizer (SP, have been investigated. Results on 28-day mechanical properties, early-age hydration rate, autogenous shrinkage and premature cracking risk are analyzed and discussed in relation with the ERPC mix parameters.

  9. Early-age volume changes of extrudable reactive powder concrete

    Science.gov (United States)

    Cherkaoui, K.; Courtial, M.; Dunstetter, F.; Khelidj, A.; Mounanga, P.; de Noirfontaine, M. N.

    2010-06-01

    This article presents a study on the early-age autogenous deformations of Extrudable Reactive Powder Concretes (ERPCs), especially designed for the making of concrete pipes by extrusion. Different ERPC mixtures, with variable amounts of polycarboxylate superplasticizer (SP), have been investigated. Results on 28-day mechanical properties, early-age hydration rate, autogenous shrinkage and premature cracking risk are analyzed and discussed in relation with the ERPC mix parameters.

  10. Early-age volume changes of extrudable reactive powder concrete

    OpenAIRE

    De Noirfontaine M.N.; Mounanga P.; Khelidj A.; Dunstetter F.; Cherkaoui K.; Courtial M.

    2010-01-01

    This article presents a study on the early-age autogenous deformations of Extrudable Reactive Powder Concretes (ERPCs), especially designed for the making of concrete pipes by extrusion. Different ERPC mixtures, with variable amounts of polycarboxylate superplasticizer (SP), have been investigated. Results on 28-day mechanical properties, early-age hydration rate, autogenous shrinkage and premature cracking risk are analyzed and discussed in relation with the ERPC mix parameters.

  11. Impaired decision-making and brain shrinkage in alcoholism.

    Science.gov (United States)

    Le Berre, A-P; Rauchs, G; La Joie, R; Mézenge, F; Boudehent, C; Vabret, F; Segobin, S; Viader, F; Allain, P; Eustache, F; Pitel, A-L; Beaunieux, H

    2014-03-01

    Alcohol-dependent individuals usually favor instant gratification of alcohol use and ignore its long-term negative consequences, reflecting impaired decision-making. According to the somatic marker hypothesis, decision-making abilities are subtended by an extended brain network. As chronic alcohol consumption is known to be associated with brain shrinkage in this network, the present study investigated relationships between brain shrinkage and decision-making impairments in alcohol-dependent individuals early in abstinence using voxel-based morphometry. Thirty patients performed the Iowa Gambling Task and underwent a magnetic resonance imaging investigation (1.5T). Decision-making performances and brain data were compared with those of age-matched healthy controls. In the alcoholic group, a multiple regression analysis was conducted with two predictors (gray matter [GM] volume and decision-making measure) and two covariates (number of withdrawals and duration of alcoholism). Compared with controls, alcoholics had impaired decision-making and widespread reduced gray matter volume, especially in regions involved in decision-making. The regression analysis revealed links between high GM volume in the ventromedial prefrontal cortex, dorsal anterior cingulate cortex and right hippocampal formation, and high decision-making scores (Palcoholism may result from impairment of both emotional and cognitive networks.

  12. Response Predicting LTCC Firing Shrinkage: A Response Surface Analysis Study

    Energy Technology Data Exchange (ETDEWEB)

    Girardi, Michael; Barner, Gregg; Lopez, Cristie; Duncan, Brent; Zawicki, Larry

    2009-02-25

    The Low Temperature Cofired Ceramic (LTCC) technology is used in a variety of applications including military/space electronics, wireless communication, MEMS, medical and automotive electronics. The use of LTCC is growing due to the low cost of investment, short development time, good electrical and mechanical properties, high reliability, and flexibility in design integration (3 dimensional (3D) microstructures with cavities are possible)). The dimensional accuracy of the resulting x/y shrinkage of LTCC substrates is responsible for component assembly problems with the tolerance effect that increases in relation to the substrate size. Response Surface Analysis was used to predict product shrinkage based on specific process inputs (metal loading, layer count, lamination pressure, and tape thickness) with the ultimate goal to optimize manufacturing outputs (NC files, stencils, and screens) in achieving the final product design the first time. Three (3) regression models were developed for the DuPont 951 tape system with DuPont 5734 gold metallization based on green tape thickness.

  13. Physical Model of Drying Shrinkage of Recycled Aggregate Concrete

    Institute of Scientific and Technical Information of China (English)

    GUO Yuanchen; WANG Xue; QIAN Jueshi

    2015-01-01

    We prepared concretes (RC0, RC30, and RC100) with three different mixes. The pore-size distribution parameters of RAC were examined by high-precision mercury intrusion method (MIM) and nuclear magnetic resonance (NMR) imaging. A capillary-bundle physical model with random-distribution pores (improved model, IM) was established according to the parameters, and dry-shrinkage strain values were calculated and verified. Results show that in all pore types, capillary pores, and gel pores have the greatest impacts on concrete shrinkage, especially for pores 2.5-50 and 50-100 nm in size. The median radii are 34.2, 31, and 34 nm for RC0, RC30, and RC100, respectively. Moreover, the internal micropore size distribution of RC0 differs from that of RC30 and RC100, and the pore descriptions of MIM and NMR are consistent both in theory and in practice. Compared with the traditional capillary-bundle model, the calculated results of IM have higher accuracy as demonstrated by experimental veriifcation.

  14. Internal curing with lightweight aggregate produced from biomass-derived waste

    Energy Technology Data Exchange (ETDEWEB)

    Lura, Pietro, E-mail: pietro.lura@empa.ch [Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf (Switzerland); Institute for Building Materials (IfB), ETH Zürich (Switzerland); Wyrzykowski, Mateusz [Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf (Switzerland); Department of Building Physics and Building Materials, Lodz University of Technology (Poland); Tang, Clarence [Siam Research and Innovation, SCG Cement–Building Materials, Saraburi (Thailand); Lehmann, Eberhard [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland)

    2014-05-01

    Shrinkage of concrete may lead to cracking and ultimately to a reduction of the service life of concrete structures. Among known methods for shrinkage mitigation, internal curing with porous aggregates was successfully utilized in the last couple of decades for decreasing autogenous and drying shrinkage. In this paper, the internal curing performance of pre-saturated lightweight aggregates produced from biomass-derived waste (bio-LWA) was studied. In the first part of this paper, the microstructure of the bio-LWA is investigated, with special focus on their pore structure and on their water absorption and desorption behavior. The bio-LWA has large porosity and coarse pore structure, which allows them to release the entrained water at early age and counteract self-desiccation and autogenous shrinkage. In the second part, the efficiency of internal curing in mortars incorporating the bio-LWA is examined by neutron tomography, internal relative humidity and autogenous deformation measurements.

  15. Design changes of device to investigation of alloys linear contraction and shrinkage stresses

    Directory of Open Access Journals (Sweden)

    J. Mutwil

    2009-07-01

    Full Text Available Some design changes in device elaborated by author to examination of linear contraction and shrinkage stresses progress of metals and alloys during– and after solidification have been described. The introduced changes have been focused on design of closing of shrinkage test rod mould. The introduced changes have been allowed to simplify a mounting procedure of thermocouples measuring a temperature of the shrinkage rod casting (in 6 points. Exemplary investigation results of linear contraction and shrinkage stresses development in Al-Si13.5% alloy have been presented.

  16. The Formation of Carbon Nanostructures via Catalytic Pyrolysis of Naphthalene under Its Autogenic Pressure

    Directory of Open Access Journals (Sweden)

    Chao-Gang Wang

    2015-01-01

    Full Text Available The formation of carbon nanotubes (CNTs, spherical carbon nanocapsules (CNCs, and carbon spheres (CSs is accomplished by using the method of reactions under autogenic pressure at elevated temperatures (RAPET. A powder mixture of naphthalene and nickel acetate tetrahydrate is dissociated under its autogenic pressure. The resultant CNTs and CNCs exhibit good graphitic quality, and the diameters range from 50~200 nm. Smooth and monodisperse CSs with the diameter ranging from 5~10 μm can be obtained by pyrolysis of pure naphthalene. Our results show that the reaction temperature and catalyst proportion play a key role in the formation of carbon nanostructures with RAPET method.

  17. Combined use of autogenic therapy and biofeedback in training effective control of heart rate by humans

    Science.gov (United States)

    Cowings, P. S.

    1977-01-01

    Experiments were performed on 24 men and women (aged 20-27 yr) in three equal groups who were taught to control their own heart rates by autogenic training and biofeedback under dark and sound-isolated conditions. Group I was parasympathetic dominant, group II was sympathetic dominant, and group III consisted of parasympathetic-dominant subjects and controls who received only biofeedback of their own heart rates. The results corroborate three hypotheses: (1) subjects with para-sympathetic-dominant autonomic profiles perform in a way that is both qualitatively and quantitatively different from subjects with sympathetic-dominant autonomic profiles; (2) tests of interindividual variability yield data relevant to individual performance in visceral learning tasks; and (3) the combined use of autogenic training, biofeedback, and verbal feedback is suitable for conditioning large stable autonomic responses in humans.

  18. Operational Applications of Autogenic Feedback Training Exercise as a Treatment for Airsickness in the Military

    Science.gov (United States)

    Gebreyesus, Fiyore; Cowings, Patricia S.; Toscano, William B.

    2012-01-01

    Airsickness is experienced by about 50% of military aviators some time in their career. Aviators who suffer from recurrent episodes of airsickness are typically referred to the Naval Aerospace Medical Institute (NAMI) at Pensacola where they undergo extensive evaluation and 8 weeks of training in the Self-Paced Airsickness Desensitization (SPAD) program. Researchers at NASA Ames have developed an alternative mitigation training program, Autogenic Feedback Training Exercise (AFTE) that has demonstrated an 80% success rate for improving motion sickness tolerance.

  19. Crack-free conditions in welding of glass by ultrashort laser pulse.

    Science.gov (United States)

    Miyamoto, Isamu; Cvecek, Kristian; Schmidt, Michael

    2013-06-17

    The spatial distribution of the laser energy absorbed by nonlinear absorption process in bulk glass w(z) is determined and thermal cycles due to the successive ultrashort laser pulse (USLP) is simulated using w(z) based on the transient thermal conduction model. The thermal stress produced in internal melting of bulk glass by USLP is qualitatively analyzed based on a simple thermal stress model, and crack-free conditions are studied in glass having large coefficient of thermal expansion. In heating process, cracks are prevented when the laser pulse impinges into glass with temperatures higher than the softening temperature of glass. In cooling process, shrinkage stress is suppressed to prevent cracks, because the embedded molten pool produced by nonlinear absorption process behaves like an elastic body under the compressive stress field unlike the case of CW-laser welding where the molten pool having a free surface produced by linear absorption process is plastically deformed under the compressive stress field.

  20. Stress/strain distributions for weld metal solidification crack in stainless steels

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper has simulated the driving force of solidification crack of stainless steels, that is, stress/strain field in the trail of molten pool. Firstly, the effect of the deformation in the molten pool was eliminated after the element rebirth method was adopted. Secondly, the influence of solidification shrinkage was taken into account by increasing thermal expansion coefficients of the steels at elevated temperatures. Finally, the stress/strain distributions of different conditions have been computed and analyzed. Furthermore, the driving force curves of the solidification crack of the steels have been obtained by converting strain-time curves into strain-temperature curves, which founds a basis for predicting welding solidification crack.

  1. Synthesis of MgB2 at Low Temperature and Autogenous Pressure

    Directory of Open Access Journals (Sweden)

    Ian D. R. Mackinnon

    2014-05-01

    Full Text Available High quality, micron-sized interpenetrating grains of MgB2, with high density, are produced at low temperatures (~420 °C < T < ~500 °C under autogenous pressure by pre-mixing Mg powder and NaBH4 and heating in an Inconel 601 alloy reactor for 5–15 h. Optimum production of MgB2, with yields greater than 75%, occurs for autogenous pressure in the range 1.0 MPa to 2.0 MPa, with the reactor at ~500 °C. Autogenous pressure is induced by the decomposition of NaBH4 in the presence of Mg and/or other Mg-based compounds. The morphology, transition temperature and magnetic properties of MgB2 are dependent on the heating regime. Significant improvement in physical properties accrues when the reactor temperature is held at 250 °C for >20 min prior to a hold at 500 °C.

  2. Autogenous standard versus inside-out vein graft to repair facial nerve in rabbits

    Institute of Scientific and Technical Information of China (English)

    TANG Jie; WANG Xue-mei; HU Jing; LUO En; QI Meng-chun

    2008-01-01

    To evaluate autogenous vein grafts and inside-out vein grafts as conduits for the defects repair in the rabbit facial nerves.Methods:The 10 mm segments of buccal division of facial nerve were transected for 48 rabbits in this study.Then the gaps were immediately repaired by autogenous vein grafts or inside-out vein grafts in different groups. All the animals underwent the whisker movement test and electrophysiologic test during the following 16 weeks at different time points postoperatively. Subsequently,the histological examination was performed to observe the facial nerve regeneration morphologically.Results:At 8 weeks after operation,the facial nerve regeneration has significant difference between the experimental group and the control group in electrophysiologic test and histological observation. However,at the end of this study,16 weeks after operation,there was no significant difference between inside-out vein grafts and standard vein grafts in enhancing peripheral nerve regeneration.Conclusion:This study suggest that both kinds of vein grafts play positive roles in facial nerve regeneration after being repaired immediately,but the autogenous inside-out vein grafts might accelerate and facilitate axonal regeneration as compared with control.

  3. Bone formation by autogenous grafting of cultured bone/porous ceramic constructs in a dog

    Energy Technology Data Exchange (ETDEWEB)

    Iida, J.; Ueda, Y.; Ohgushi, H.; Takakura, Y. [Nara Medical Univ., Kashihara (Japan). Dept. of Orthopedic Surgery; Yoshikawa, T. [Nara Medical Univ., Kashihara (Japan). Dept. of Orthopedic Surgery; Nara Medical Univ., Kashihara (Japan). Dept. of Phathology; Uemura, T.; Tateishi, T. [National Inst. for Advanced Interdisciplinary Research (NAIR), Ibaraki (Japan). Tsukuba Research Center; Enomoto, Y.; Ichijima, K. [Nara Medical Univ., Kashihara (Japan). Dept. of Phathology

    2001-07-01

    Five ml of bone marrow was collected from the humerus of a 6 month old female dog by needle aspiration. The marrow was cultured in T-75 flask and expand the marrow mesenchymal cells. After 1 week in primary culture, cells were released by trypsin treatment, concentrated and loaded onto porous hydroxyapatite (HA) blocks. The marrow/HA constructs were subcultured in the presence of dexamethasone and beta-glycerophosphate (osteogenic medium). After 2 weeks of subculture, the autogenous cultured bone/HA constructs were subcutaneously implanted into the back of the dog. Histological findings of the constructs at 3 weeks after implantation revealed thick layer of lamellar bone together with active osteoblasts lining in many pore areas of the HA. High alkaline phosphatase activity could be detected in the construct. These results indicate that autogenous cultured bone/HA constructs can produce extensive bone formation after implantation in a large animal(dog). Therefore, based upon the fact that human marrow-derived culture bone/HA construct possesses osteogenic potential when it is grafted into nude mice, it can be expected that autogenous human cultured bone/ceramic grafts may be useful to reconstruct bone in the clinical setting. (orig.)

  4. Alternative method to treat oroantral communication and fistula with autogenous bone graft and platelet rich firbin

    Science.gov (United States)

    Niedzielska, Iwona; Borgiel-Marek, Halina; Różanowski, Bartosz

    2016-01-01

    Background Removing a tooth from the jaw results in the occurrence of oroantral communication in beneficial anatomic conditions or in the case of a iatrogenic effect. Popularized treatments of the oroantral communication have numerous faults. Large bone defect eliminates the chance to introduce an implant. Purpose of this work was assessment of the usefulness of autogenous bone graft and PRF in normal bone regeneration in the site of oroantral communication. Material and Methods Bone regeneration in the site of oroantral communication was assessed in 20 patients. Bone defects were supplemented autogenous bone graft from mental protuberance in 14 cases and from oblique line in 6 cases. The graft was covered with a PRF membrane. Results In the study group in all cases closure of the oroantral communication was observed. The average width of the alveolar was 13 mm and the average height was 12.5 mm. In 3 patients an average increase of alveolar height of 1.5 mm was observed. Conclusions This method may be the best option to prepare alveolar for new implant and prosthetic solutions. Key words:Oroantral communication, oroantral fistula, autogenous bone graft, bone regeneration, platelet rich fibrin. PMID:27475687

  5. Differences in latent inhibition as a function of the autogenous-reactive OCD subtype.

    Science.gov (United States)

    Lee, Han-Joo; Telch, Michael J

    2010-07-01

    We examined differences in a visual search-based latent inhibition (LI) task in 48 non-treatment seeking individuals diagnosed with obsessive-compulsive disorder (OCD) and 26 non-OCD controls, using a visual search-based LI task as a function of participants' primary obsessional presentation based on the autogenous-reactive subtype model of obsessions (Lee & Kwon, 2003; Lee & Telch, 2007). We hypothesized that LI would be significantly attenuated among OCD participants whose primary obsessions were characterized by aversive impulses, images, or thoughts with sexual, aggressive, blasphemous, and repulsive themes (autogenous obsessions) due to their weakened attentional inhibitory mechanisms and elevated schizotypal personality features, as compared with those whose primary obsessions were characterized by somewhat realistic aversive mental intrusions about contamination, mistakes, accidents, or disarray (reactive obsession) and non-OCD controls. Results showed that those primarily displaying autogenous obsessions failed to display LI, whereas those primarily displaying reactive obsessions and non-OCD controls displayed significant LI effects. Our data suggest that the magnitude of LI varies as a function of primary obsessional presentations among individuals with OCD.

  6. Bone Formation in Maxillary Sinus Lift Using Autogenous Bone Graft at 2 and 6 Months

    Science.gov (United States)

    Netto, Henrique Duque; Miranda Chaves, Maria das Graças Alfonso; Aatrstrup, Beatriz; Guerra, Renata; Olate, Sergio

    2016-01-01

    SUMMARY The aim of this study is to compare the bone formation in maxillary sinus lift with an autogenous bone graft in histological evaluation at 2 or 6 months. A comparative study was designed where 10 patients with missing teeth bilaterally in the posterior zone of the maxilla were selected. Patients received a particulate autogenous bone graft under the same surgical conditions, selecting a site to collect a biopsy and histological study at two months and another at six months postoperatively. Histomorphometry was performed and were used Kolmogorov-Smirnov test, student’s t-test and Spearman’s correlation coefficient, considering a value of p<0.05. Differences were observed in inflammatory infiltrate and vascularization characteristics; however, the group analyzed at two months presented 38.12% ± 6.64 % of mineralized tissue, whereas the group studied at 6 months presented an average of 38.45 ± 9.27 %. There were no statistical differences between the groups. It is concluded that the bone formation may be similar in intrasinus particulate autogenous bone grafts in evaluations at two or six months; under these conditions, early installation of implants is viable. PMID:27867255

  7. A new view on bone graft in dental implantation: Autogenous bone mixed with titanium granules

    Directory of Open Access Journals (Sweden)

    Yeke Wu

    2013-01-01

    Full Text Available Introduction : Dental implants have been widely applied in clinic for many years. However, the success rate is still challenging mainly because of bone deficiency. An ideal bone graft is traditionally thought to guide and induce new bone regeneration as well as been absorbed completely by human body. The Hypothesis: Autogenous bone mixed with titanium granules might be an ideal bone graft for dental implantation. Evaluation of the Hypothesis: First, we analyzed advantages of grafts of autogenous bone mixed with titanium granules, such as serving as a s scaffold for wound healing and tissue regeneration, creating sui microenvironment for implant-bone integration, shortening the new bone′s creeping distance, etc. Then we creatively hypothesized a novel alternative bone graft with premixed autogenous bone and non-absorbent titanium granules. Apart from repairing bone deficiency, our hypothesis could promote the integration between new bone and titanium implant from the perspective of microenvironment. We believe that the method is promising and worth extension in clinical application.

  8. Effect of Modified Polymer on Crack Resistance of Mortar

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    At present, the basic technical principle in China is to adopt polymers to modifying the properties of mortar so as to improve the crack-resistance of construction structures and to strengthen their water-resisting and climate-resisting properties as well. However, how polymer acts on anti-crack mortar is short of systematic research. Theoretical exposition of polymer mortar is basically explained by Ohama Model, which is cement slaking and polymer coating are carried on together and mutually-cross web structure interweaved with liquid and polymer coating. But anti-crack mortar has its own special characteristics because of fewer polymers mixed in it and its high viscosity. So this paper is to showing how different polymers affect its crack-resistance cannot be reflected from this theory. Vinyl-acetate ethylene (VAC/E) has been selected as representation of polymerization, whose property is modified by compounding it from some inorganic components, such as talc, CaCO3 and so on. And then the mechanics property and shrinkage of anti-crack polymer mortar is tested when different amount of polymers is added as admixture of mortar. The result indicates that, the working performance and mechanics property of the polymer mortar are worse mixed VAC/E only. It basically meets the demands for mechanics strength and working performance when mixed both VAC/E and CaCO3. While it achieves much better mechanical property and working performance than the two former when mixed VAC/E,talc and CaCO3; the result of corresponding scanning electron microscopy (SEM) of sample indicates that the internal result of the polymer mortar, compared with classical Ohama Model, has a particularity that its structure is formed by polymer coating instead of filling up the intervals among cement grains.

  9. Topology optimization of reinforced concrete structures considering control of shrinkage and strength failure

    DEFF Research Database (Denmark)

    Luo, Yangjun; Wang, Michael Yu; Zhou, Mingdong;

    2015-01-01

    To take into account the shrinkage effect in the early stage of Reinforced Concrete (RC) design, an effective continuum topology optimization method is presented in this paper. Based on the power-law interpolation, shrinkage of concrete is numerically simulated by introducing an additional design...

  10. Effect of modulated photo-activation on polymerization shrinkage behavior of dental restorative resin composites

    NARCIS (Netherlands)

    T.T. Tauböck; A.J. Feilzer; W. Buchalla; C.J. Kleverlaan; I. Krejci; T. Attin

    2014-01-01

    This study investigated the influence of modulated photo-activation on axial polymerization shrinkage, shrinkage force, and hardening of light- and dual-curing resin-based composites. Three light-curing resin composites (SDR bulk-fill, Esthet X flow, and Esthet X HD) and one dual-curing material (Re

  11. Influence of Cure Shrinkage on Process-Induced Stress and Deformation in Thick Thermosetting Composites

    Science.gov (United States)

    1992-07-01

    unidirectional composite micromechanics model The constituent fiber properties (constant), the resin properties and chemical shrinkage (cure dependent...during cure. Changes in the resin properties directly influence the mechanical properties in the composite, and chemical shrinkage represents a...xA (5) The expansion coefficients, otL and or, are based on the micromechanics model utilizing constant fiber properties. cure dependent resin

  12. Modeling dental composite shrinkage by digital image correlation and finite element methods

    Science.gov (United States)

    Chen, Terry Yuan-Fang; Huang, Pin-Sheng; Chuang, Shu-Fen

    2014-10-01

    Dental composites are light-curable resin-based materials with an inherent defect of polymerization shrinkage which may cause tooth deflection and debonding of restorations. This study aimed to combine digital image correlation (DIC) and finite element analysis (FEA) to model the shrinkage behaviors under different light curing regimens. Extracted human molars were prepared with proximal cavities for composite restorations, and then divided into three groups to receive different light curing protocols: regular intensity, low intensity, and step-curing consisting of low and high intensities. For each tooth, the composite fillings were consecutively placed under both unbonded and bonded conditions. At first, the shrinkage of the unbonded restorations was analyzed by DIC and adopted as the setting of FEA. The simulated shrinkage behaviors obtained from FEA were further validated by the measurements in the bonded cases. The results showed that different light curing regimens affected the shrinkage in unbonded restorations, with regular intensity showing the greatest shrinkage strain on the top surface. The shrinkage centers in the bonded cases were located closer to the cavity floor than those in the unbonded cases, and were less affected by curing regimens. The FEA results showed that the stress was modulated by the accumulated light energy density, while step-curing may alleviate the tensile stress along the cavity walls. In this study, DIC provides a complete description of the polymerization shrinkage behaviors of dental composites, which may facilitate the stress analysis in the numerical investigation.

  13. Effect of cure cycle on enthalpy relaxation and post shrinkage in neat epoxy and epoxy composites

    DEFF Research Database (Denmark)

    Jensen, Martin; Jakobsen, Johnny

    2016-01-01

    . Enthalpy recovery is found to exert a minor impact on the sample dimension during reheating since a non-reversing shrinkage is observed during reheating. This shrinkage is ascribed to structural changes on molecular level in the specimen and it is inferred that samples with a high initial disorder only...

  14. To develop a quantitative method for predicting shrinkage porosity in squeeze casting

    Institute of Scientific and Technical Information of China (English)

    Shaomin Li; Kenichiro Mine; Shinji Sanakanishi; Koichi Anzai

    2009-01-01

    In order to secure high strength and high elongation of suspension parts, it is critical to predict shrinkage porosity quantitatively. A new simulation method for quantitative predic'don of shrinkage porosity when replenishing molten metal has been proposed for squeeze casting process. To examine the accuracy of the calculation model, the proposed method was applied to a plate model.

  15. Monitoring of collagen shrinkage by use of second harmonic generation microscopy

    Science.gov (United States)

    Lin, Sung-Jan; Chen, Jau-Shiuh; Lo, Wen; Sun, Yen; Chen, Wei-Liang; Chan, Jung-Yi; Tan, Hsin-Yuan; Lin, Wei-Chou; Hsu, Chih-Jung; Young, Tai-Horng; Jee, Shiou-Hwa; Dong, Chen-Yuan

    2006-02-01

    Thermal treatment induced collagen shrinkage has a great number of applications in medical practice. Clinically, the there is lack of reliable non-invasive methods to quantify the shrinkage. Overt treatment by heat application can lead to devastating results. We investigate the serial changes of collagen shrinkage by thermal treatment of rat tail tendons. The change in length is correlated with the finding in second harmonic generation microscopy and histology. Rat tail tendon shortens progressively during initial thermal treatment. After a certain point in time, the length then remains almost constant despite further thermal treatment. The intensity of second harmonic generation signals also progressively decreases initially and then remains merely detectable upon further thermal treatment. It prompts us to develop a mathematic model to quantify the dependence of collagen shrinkage on changes of SHG intensity. Our results show that SHG intensity can be used to predict the degree of collagen shrinkage during thermal treatment for biomedical applications.

  16. Autogenous bone graft combined with polylactic polyglycolic acid polymer for treatment of dehiscence around immediate dental implants.

    Science.gov (United States)

    Hassan, Khalid S

    2009-11-01

    The use of composite bone grafts in dehiscence defects around immediate dental implants are aimed at improving the outcome of the regenerative process. The present study was designed to evaluate the efficacy of combinations of autogenous bone graft with a synthetic copolymer polylactic and polyglycolic acid (Fisiograft) on bone healing of buccal dehiscence defects around immediate dental implants. Sixteen adult male patients who each received an immediate implant for a single tooth replacement at a maxillary anterior or premolar site were included in this study. Patients were divided into 2 groups. One group received immediate dental implants augmented with autogenous bone graft combined with Fisiograft. The other group received immediate dental implants augmented with autogenous bone graft alone. The results revealed that both treatment modalities led to significant improvements for the primary outcome regarding bone fill as well as a significant reduction of probing pocket depth and gain of attachment level. Moreover, there were slightly statistically significant differences between the groups. In conclusion, the combination of autogenous bone graft and Fisiograft showed a slight superiority to autogenous bone graft alone, suggesting that it could be an optimum bone substitute for treatment of dehiscence around immediate dental implant.

  17. Fatigue Crack Topography.

    Science.gov (United States)

    1984-01-01

    evaluating ciack initiation time and crack propagation, prgram I was used for performing the major fatigue test with the aircraft structure. In...advantage to begin with the end of the fracture, this is especially so in the case of the quantitative evaluation of striations. The overload fracture...Select the Measuring Line for Quantitative Evaluation Actually, the fatigue fracture should be inspected completely from the point of origin to the

  18. Utopia Cracks and Polygons

    Science.gov (United States)

    2003-01-01

    MGS MOC Release No. MOC2-339, 23 April 2003This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a pattern of polygonal cracks and aligned, elliptical pits in western Utopia Planitia. The picture covers an area about 3 km (about 1.9 mi) wide near 44.9oN, 274.7oW. Sunlight illuminates the scene from the left.

  19. A theoretical and experimental analysis of polymerization shrinkage of bone cement: A potential major source of porosity.

    Science.gov (United States)

    Gilbert, J L; Hasenwinkel, J M; Wixson, R L; Lautenschlager, E P

    2000-10-01

    A theoretical basis for understanding polymerization shrinkage of bone cement is presented based on density changes in converting monomer to polymer. Also, an experimental method, based on dilatometry and the Archimedes' principle is presented for highly precise and accurate measurement of unconstrained volumetric shrinkage of bone cement. Furthermore, a theoretical and experimental analysis of polymerization shrinkage in a constrained deformational state is presented to demonstrate that porosity can develop due to shrinkage. Six bone-cement conditions (Simplex-Ptrade mark vacuum and hand mixed, Endurancetrade mark vacuum mixed, and three two-solution experimental bone cements with higher initial monomer levels) were tested for volumetric shrinkage. It was found that shrinkage varied statistically (ptheory that they are the result of shrinkage. The results of this study show that shrinkage of bone cement under certain constrained conditions may result in the development of porosity at the implant-bone cement interface and elsewhere in the polymerizing cement mantle.

  20. Autogenous bone graft and ePTFE membrane in the treatment of peri-implantitis. II. Stereologic and histologic observations in cynomolgus monkeys

    DEFF Research Database (Denmark)

    Schou, Søren; Holmstrup, Palle; Skovgaard, Lene Theil;

    2003-01-01

    autogenous bone graft; guided bone regeneration; histology; membrane; non-human primates; oral implants; osseointegration; pathalogy; peri-implantitis; stereology; treatment......autogenous bone graft; guided bone regeneration; histology; membrane; non-human primates; oral implants; osseointegration; pathalogy; peri-implantitis; stereology; treatment...

  1. Maxillary sinus floor elevation surgery with BioOss (R) mixed with a bone marrow concentrate or autogenous bone : test of principle on implant survival and clinical performance

    NARCIS (Netherlands)

    Rickert, D.; Vissink, A.; Slot, Jan; Sauerbier, S.; Meijer, H. J. A.; Raghoebar, G. M.

    2014-01-01

    The purpose of this study was to assess implant survival and 1-year clinical performance of implants placed in the posterior maxilla that had been subjected to maxillary sinus floor elevation surgery with bovine bone mineral (BioOss (R)) mixed with autogenous bone marrow concentrate or autogenous bo

  2. Polymerisation shrinkage versus layer thickness of a dentine bonding resin: Method development

    Directory of Open Access Journals (Sweden)

    Jafarzadeh T

    2002-07-01

    Full Text Available Dentine bonding systems are usually unfilled, and so their shrinkage may be significant. High"nshrinkage may cause internal stress at the interface between resin-composite restoration and the dentine"nsubstrate. Failure of the adhesive interface may be observed due to the interna! stress. The aims of this"nstudy were:"nA To obtain a suitable method for measuring the kinetics of polymerisation shrinkage in unfilled resm at different thicknesses, particularly for thin films."nB Consideraing the effect of thickness on shrinkage."nScotchbond Multipurpose (3M adhesive bond resin was used. To overcome the particular challenges presented by thin films, a filled-ring measurement procedure was used. Also, a non-contact laser analogue displacement sensor system was developed and applied to measure polymerisation shrinkage. Regression analysis was performed on a complete data set. Non-linear regression analysis established a logarithmic relationship between polymerisation shrinkage and layer thickness. The method applied in this study was found to be sensitive and accurate procedure for determining photo-polymerisation shrinkage of thin films. Polymerisation shrinkage increased with logarithmic of the adhesive thickness.

  3. Compositional Changes for Reduction of Polymerisation-Induced Shrinkage in Holographic Photopolymers

    Directory of Open Access Journals (Sweden)

    D. Cody

    2016-01-01

    Full Text Available Polymerisation-induced shrinkage is one of the main reasons why many photopolymer materials are not used for certain applications including holographic optical elements and holographic data storage. Here, two compositional changes for the reduction of shrinkage in an acrylamide-based photopolymer are reported. A holographic interferometric technique was used to study changes in the dynamics of the shrinkage processes occurring in the modified photopolymer during holographic recording in real time. Firstly, the effect of the replacement of the acrylamide monomer in the photopolymer composition with a larger monomer molecule, diacetone acrylamide, on polymerisation-induced shrinkage has been studied. A reduction in relative shrinkage of 10–15% is obtained using this compositional change. The second method tested for shrinkage reduction involved the incorporation of BEA-type zeolite nanoparticles in the acrylamide-based photopolymer. A reduction in relative shrinkage of 13% was observed for acrylamide photopolymer layers doped with 2.5% wt. BEA zeolites in comparison to the undoped photopolymer.

  4. Importance of shrinkage in empirical bayes estimates for diagnostics: problems and solutions.

    Science.gov (United States)

    Savic, Radojka M; Karlsson, Mats O

    2009-09-01

    Empirical Bayes ("post hoc") estimates (EBEs) of etas provide modelers with diagnostics: the EBEs themselves, individual prediction (IPRED), and residual errors (individual weighted residual (IWRES)). When data are uninformative at the individual level, the EBE distribution will shrink towards zero (eta-shrinkage, quantified as 1-SD(eta (EBE))/omega), IPREDs towards the corresponding observations, and IWRES towards zero (epsilon-shrinkage, quantified as 1-SD(IWRES)). These diagnostics are widely used in pharmacokinetic (PK) pharmacodynamic (PD) modeling; we investigate here their usefulness in the presence of shrinkage. Datasets were simulated from a range of PK PD models, EBEs estimated in non-linear mixed effects modeling based on the true or a misspecified model, and desired diagnostics evaluated both qualitatively and quantitatively. Identified consequences of eta-shrinkage on EBE-based model diagnostics include non-normal and/or asymmetric distribution of EBEs with their mean values ("ETABAR") significantly different from zero, even for a correctly specified model; EBE-EBE correlations and covariate relationships may be masked, falsely induced, or the shape of the true relationship distorted. Consequences of epsilon-shrinkage included low power of IPRED and IWRES to diagnose structural and residual error model misspecification, respectively. EBE-based diagnostics should be interpreted with caution whenever substantial eta- or epsilon-shrinkage exists (usually greater than 20% to 30%). Reporting the magnitude of eta- and epsilon-shrinkage will facilitate the informed use and interpretation of EBE-based diagnostics.

  5. Investigations of linear contraction and shrinkage stresses development in hypereutectic al-si binary alloys

    Directory of Open Access Journals (Sweden)

    J. Mutwil

    2009-07-01

    Full Text Available Shrinkage phenomena during solidification and cooling of hypereutectic aluminium-silicon alloys (AlSi18, AlSi21 have been examined. A vertical shrinkage rod casting with circular cross-section (constant or fixed: tapered has been used as a test sample. Two type of experiments have been conducted: 1 on development of the test sample linear dimension changes (linear expansion/contraction, 2 on development of shrinkage stresses in the test sample. By the linear contraction experiments the linear dimension changes of the test sample and the metal test mould as well a temperature in six points of the test sample have been registered. By shrinkage stresses examination a shrinkage tension force and linear dimension changes of the test sample as well a temperature in three points of the test sample have been registered. Registered time dependences of the test bar and the test mould linear dimension changes have shown, that so-called pre-shrinkage extension has been mainly by mould thermal extension caused. The investigation results have shown that both: the linear contraction as well as the shrinkage stresses development are evident dependent on metal temperature in a warmest region the sample (thermal centre.

  6. Frontalis Sling Operation using Silicone Rod Compared with Autogenous Fascia Lata for Simple Congenital Ptosis

    Directory of Open Access Journals (Sweden)

    Purnima Rajkarnikar Sthapit

    2014-09-01

    Full Text Available Introduction: To evaluate the cosmetic results and recurrence of unilateral frontalis sling surgery using a silicone rod compared with autogenous fascia lata in cases of simple congenital ptosis. Methods: This is a retrospective comparative study of 59 patients who underwent a frontalis sling operation for congenital ptosis. Patients were divided into two groups according to the sling material used; an autogeneous fascia lata (fl group (n = 24 and a silicone rod group (sl (n = 35. Cosmetic results and recurrence rates were compared between these 2 groups. The cosmetic results of the frontalis sling operation were assessed as good, fair, or poor based on the difference between the Margin Reflex Distance of both eyelids and graded as good if the difference in two eyes was ≤1mm and poor if it was 2mm or more. Recurrence was defined as the conversion of the cosmetic result from good or fair to poor category. Results: At postoperative day seven and 30, MRD of both the groups were good but on three months follow-up MRD of silicon rod group dropped, however it was not statistically significant .Lid contour was good in both the groups, however, lid symmetry was poor in two cases of fascia lata at three months follow-up. Repeat surgery for poor outcome was done in 8.6% of cases in silicon rod and 8.3% of fascia lata group. Conclusions: The frontalis sling operation using either a silicone rod or autogenous fascia lata showed equally good cosmetic results and lower recurrence rate at three months follow up. Keywords: congenital ptosis; fascia lata; frontalis sling surgery; margin reflex distance; silicone rod.

  7. Evaluation of ABM/P-15 versus autogenous bone in an ovine lumbar interbody fusion model.

    Science.gov (United States)

    Sherman, Blake P; Lindley, Emily M; Turner, A Simon; Seim, Howard B; Benedict, James; Burger, Evalina L; Patel, Vikas V

    2010-12-01

    A prospective, randomized study was performed in an ovine model to compare the efficacy of an anorganic bovine-derived hydroxyapatite matrix combined with a synthetic 15 amino acid residue (ABM/P-15) in facilitating lumbar interbody fusion when compared with autogenous bone harvested from the iliac crest. P-15 is a biomimetic to the cell-binding site of Type-I collagen for bone-forming cells. When combined with ABM, it creates the necessary scaffold to initiate cell invasion, binding, and subsequent osteogenesis. In this study, six adult ewes underwent anterior-lateral interbody fusion at L3/L4 and L4/L5 using PEEK interbody rings filled with autogenous bone at one level and ABM/P-15 at the other level and no additional instrumentation. Clinical CT scans were obtained at 3 and 6 months; micro-CT scans and histomorphometry analyses were performed after euthanization at 6 months. Clinical CT scan analysis showed that all autograft and ABM/P-15 treated levels had radiographically fused outside of the rings at the 3-month study time point. Although the clinical CT scans of the autograft treatment group showed significantly better fusion within the PEEK rings than ABM/P-15 at 3 months, micro-CT scans, clinical CT scans, and histomorphometric analyses showed there were no statistical differences between the two treatment groups at 6 months. Thus, ABM/P-15 was as successful as autogenous bone graft in producing lumbar spinal fusion in an ovine model, and it should be further evaluated in clinical studies.

  8. Autogenous bone block in the treatment of teeth with hopeless prognosis

    Directory of Open Access Journals (Sweden)

    Nymphea Pandit

    2012-01-01

    Full Text Available Background: Autogenous bone graft, although considered as a gold standard, has been relegated to background because of limited quantity and donor site morbidity. Revival of interest in its use has been reflected by its tremendous capacity for regeneration in less than ideal situation. Bone blocks have been used for implant site augmentation, with varied success. Aim: Aim of the study was to evaluate the efficacy of autogenous bone block in the regeneration of bone, for saving teeth with a hopeless prognosis. Settings and Design: A total of six patients and 12 sites with grade II and III mobile teeth were treated with autogenous bone blocks and fiber splinting. Subjects and Methods: Attachment loss, probing depths, and radiographic bone loss were recorded at baseline and at 12 months interval. Statistical Analysis Used: The Student paired t test was used for evaluation of the changes from baseline to 12 months. Results: At 12 months post-operatively, there was a highly significant amount of bone gain as compared to the baseline. The mean amount of bone loss reduced from 9.41 ± 1.16 to 5.41 ± 1.01. The clinical attachment loss reduced from 7.37 ± 1.24 mm to 3.79 ± 0.89 mm and probing depth reduced from 7 ± 1.67 mm to 5.5 ± 0.63 mm. The grafted bone was observed to have been incorporated with the host bone in most of the sites as evidenced by radiographs. Conclusions: For teeth with hopeless prognosis, this method can be considered to be a very viable alternative to extraction and replacement by costly implants.

  9. Augmentation of the rat jaw with autogeneic cortico-cancellous bone grafts and guided tissue regeneration.

    Science.gov (United States)

    Donos, Nikolaos; Kostopoulos, Lambros; Karring, Thorkild

    2002-04-01

    The aim of the present study was to evaluate the effect of augmenting the maxillary alveolar ridge and the lateral aspect of the mandible with onlay autogeneic cortico-cancellous bone grafts that were covered with e-PTFE membranes. The experiment was carried out in 51 rats. In 15 rats, the edentulous maxillary jaw between the incisor and the first molar was augmented by means of an autogeneic ischiac bone graft that was fixed with a gold-coated microimplant. In one side, the graft was covered with an e-PTFE membrane, while the other side, which served as control, was treated without a membrane. In the other 36 rats, the lateral aspect of the mandible was augmented in both sides by means of an autogeneic ischiac bone graft that was fixed with a gold-coated or a titanium microimplant. In one side, the augmented area was covered with an e-PTFE membrane, while the contralateral side was treated without a membrane. Histological analysis at 60, 120 and 180 days after augmentation of the maxilla showed that, in the case of the test sites (where most of the membranes were either exposed or lost), the bone grafts presented extensive resorption and there was a lack of bone continuity between the graft and the recipient site. Similar findings were made at the non-membrane-treated control sides. In the case of augmentation of the mandible with membranes, the bone grafts were not resorbed, but were integrated into newly formed bone at the recipient site. In the control sides, the grafts presented varying degrees of resorption and integration into the recipient bone. It is concluded that, in comparison to bone grafting alone, onlay ischiac bone grafting combined with guided tissue regeneration eliminates the risk of bone graft resorption and ensures integration of the graft into newly formed bone at the recipient site, provided that closure of the operated area can be maintained during healing.

  10. Crack Tip Parameters for Growing Cracks in Linear Viscoelastic Materials

    DEFF Research Database (Denmark)

    Brincker, Rune

    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....

  11. Autogenous control of PspF, a constitutively active enhancer-binding protein of Escherichia coli.

    OpenAIRE

    Jovanovic, G; Dworkin, J; Model, P

    1997-01-01

    Escherichia coli sigma54-dependent phage shock protein operon (pspA to -E) transcription is under the control of PspF, a constitutively active activator. Sigma70-dependent transcription of pspF is under autogenous control by wild-type PspF but not by a DNA-binding mutant, PspF deltaHTH. Negative autoregulation of PspF is continual and not affected by stimuli, like f1 pIV, that induce the pspA to -E operon. PspF production is independent of PspA (the negative regulator of the pspA to -E operon...

  12. Stepwise surgical approach to diabetic partial foot amputations with autogenous split thickness skin grafting

    Directory of Open Access Journals (Sweden)

    Crystal L. Ramanujam

    2016-06-01

    Full Text Available In the surgical treatment of severe diabetic foot infections, substantial soft tissue loss often accompanies partial foot amputations. These sizeable soft tissue defects require extensive care with the goal of expedited closure to inhibit further infection and to provide resilient surfaces capable of withstanding long-term ambulation. Definitive wound closure management in the diabetic population is dependent on multiple factors and can have a major impact on the risk of future diabetic foot complications. In this article, the authors provide an overview of autogenous skin grafting, including anatomical considerations, clinical conditions, surgical approach, and adjunctive treatments, for diabetic partial foot amputations.

  13. A thermal comparator sensor for measuring autogenous deformation in hardening Portland cement paste

    DEFF Research Database (Denmark)

    Østergaard, Thomas; Jensen, Ole Mejlhede

    2003-01-01

    of the thermal comparator is based on thermal expansion of aluminium. A particular characteristic of the measuring system is the fixation of the thermal comparator sensor to the deforming specimen. The modular system ensures effective thermostatic control of the hydrating cement paste samples. The technique......This paper describes a simple and accurate experimental device specially developed to measure autogenous deformation in hardening cement-based materials. The measuring system consists of a so-called thermal comparator sensor and a modular thermostatically controlled system. The operating principle...

  14. Histomorphometric evaluation of bone regeneration using autogenous bone and beta-tricalcium phosphate in diabetic rabbits

    Directory of Open Access Journals (Sweden)

    Živadinović Milka

    2016-01-01

    Full Text Available Background/Aim. The mechanism of impaired bone healing in diabetes mellitus includes different tissue and cellular level activities due to micro- and macrovascular changes. As a chronic metabolic disease with vascular complications, diabetes affects a process of bone regeneration as well. The therapeutic approach in bone regeneration is based on the use of osteoinductive autogenous grafts as well as osteoconductive synthetic material, like a β-tricalcium phosphate. The aim of the study was to determine the quality and quantity of new bone formation after the use of autogenous bone and β-tricalcium phosphate in the model of calvarial critical-sized defect in rabbits with induced diabetes mellitus type I. Methods. The study included eight 4-month-old Chincilla rabbits with alloxan-induced diabetes mellitus type I. In all animals, there were surgically created two calvarial bilateral defects (diameter 12 mm, which were grafted with autogenous bone and β-tricalcium phosphate (n = 4 or served as unfilled controls (n = 4. After 4 weeks of healing, animals were sacrificed and calvarial bone blocks were taken for histologic and histomorphometric analysis. Beside descriptive histologic evaluation, the percentage of new bone formation, connective tissue and residual graft were calculated. All parameters were statistically evaluated by Friedman Test and post hock Wilcoxon Singed Ranks Test with a significance of p < 0.05. Results. Histology revealed active new bone formation peripherally with centrally located connective tissue, newly formed woven bone and well incorporated residual grafts in all treated defects. Control samples showed no bone bridging of defects. There was a significantly more new bone in autogeonous graft (53% compared with β-tricalcium phosphate (30%, (p < 0.030 and control (7%, (p < 0.000 groups. A significant difference was also recorded between β-tricalcium phosphate and control groups (p < 0.008. Conclusion. In the present

  15. Flood control and shrinkage in the Haihe River Mouth

    Institute of Scientific and Technical Information of China (English)

    胡世雄; 王兆印; 李行伟

    2001-01-01

    Because of overusing water resources in the upper and middle reaches of the Haihe Basin, less and less water flows to the river mouth. The Haihe River flow is cut off in most time of the seasons, sediment deposited in the river mouth channel is rarely scoured away, and many of the river mouth channels have been shrinking quickly. The discharge capacity of the channel is consequently reduced greatly, which results in more and more serious flood hazard. Many tide gates have been built for storing fresh water and preventing the salty and turbid water. The channel downstream of the gate is silting up and people have to dredge the channel every year before the flood season. This paper studies the laws of the siltation and strategies controlling channel shrinkage. The strategies are digger dredging, trailer dredging, scouring with pumping water or storing tidal water, building double guiding dikes and building a new gate. Comparison of various strategies is performed, suggesting the most effective strategy con

  16. An improved adaptive wavelet shrinkage for ultrasound despeckling

    Indian Academy of Sciences (India)

    P Nirmala Devi; R Asokan

    2014-08-01

    Ultrasound imaging is the most widely used medical diagnostic technique for clinical decision making, due to its ability to make real time imaging for moving structures, low cost and safety. However, its usefulness is degraded by the presence of signal dependent speckle noise. Several wavelet-based denoising schemes have been reported in the literature for the removal of speckle noise. This study proposes a new and improved adaptive wavelet shrinkage in the translational invariant domain. It exploits the knowledge of the correlation of the wavelet coefficients within and across the resolution scales. A preliminary coefficient classification representing useful image information and noise is performed with a novel inter-scale dependency measure. The spatial context adaptation of the wavelet coefficients within a subband is achieved by a local spatial adaptivity indicator, determined by using a truncation threshold. A weighted signal variance is estimated based on this measure and used in the determination of a subband adaptive threshold. The proposed thresholding function aims to reduce the fixed bias of the soft thresholding approach. Experiments conducted with the proposed filter are compared with the existing filtering algorithms in terms of Peak-Signal to Noise Ratio (PSNR), Mean Square Error (MSE), Structural Similarity IndexMeasure (SSIM), Equivalent Number of Looks (ENL) and Edge Preservation Index (EPI). A comparison of the results shows that the proposed filter achieves an improvement in terms of quantitative measures and in terms of visual quality of the images.

  17. Shrinkage/swelling of compacted clayey loose and dense soils

    Science.gov (United States)

    Nowamooz, Hossein; Masrouri, Farimah

    2009-11-01

    This Note presents an experimental study performed on expansive compacted loose and dense samples using osmotic oedometers. Several successive wetting and drying cycles were applied in a suction range between 0 and 8 MPa under different values of constant net vertical stress (15, 30, and 60 kPa). During the suction cycles, the dense samples showed cumulative swelling strains, while the loose samples showed volumetric shrinkage accumulation. At the end of the suction cycles, the volumetric strains converged to an equilibrium stage that indicated elastic behavior of the swelling soil for any further hydraulic variations. At this stage, the compression curves for the studied soil at the different imposed suctions (0, 2, and 8 MPa) converged towards the saturated state curve for the high applied vertical stresses. We defined this pressure as the saturation stress(P). The compression curves provided sufficient data to examine the soil mechanical behavior at the equilibrium stage. To cite this article: H. Nowamooz, F. Masrouri, C. R. Mecanique 337 (2009).

  18. Shrinkage, abrasion, erosion and sorption of clay plasters

    Directory of Open Access Journals (Sweden)

    Minke, G.

    2011-09-01

    Full Text Available At the Buildung Research Institute (FEB, Faculty of Architecture, University of Kassel, Germany, in the last years several hundred tests were made to study the characteristics of different loam mortars in respect of their linear shrinkage, absorption of humidity and their resistance against abrasion and erosion. In order to get data about abrasion and erosion new test methods and special apparatusses were developed. The mortars tested, chosen from the market, showed extremely varying test results.

    En el Laboratorio de Construcciones Experimentales (FEB de la Facultad de Arquitectura, Universidad de Kassel, Alemania, fueron testeados cientos de diferentes pruebas de revoque de barro para estudiar su contracción durante el secado, su absorción de humedad y su resistencia contra abrasión, erosión y absorción. Para recibir datos sobre abrasión y erosión, nuevas aparatos y metodos fueron desarrollados. Los resultados de los revoques comprados en el mercado muestran gran diferencias en los valores.

  19. Super-resolution optical telescopes with local light diffraction shrinkage

    Science.gov (United States)

    Wang, Changtao; Tang, Dongliang; Wang, Yanqin; Zhao, Zeyu; Wang, Jiong; Pu, Mingbo; Zhang, Yudong; Yan, Wei; Gao, Ping; Luo, Xiangang

    2015-12-01

    Suffering from giant size of objective lenses and infeasible manipulations of distant targets, telescopes could not seek helps from present super-resolution imaging, such as scanning near-field optical microscopy, perfect lens and stimulated emission depletion microscopy. In this paper, local light diffraction shrinkage associated with optical super-oscillatory phenomenon is proposed for real-time and optically restoring super-resolution imaging information in a telescope system. It is found that fine target features concealed in diffraction-limited optical images of a telescope could be observed in a small local field of view, benefiting from a relayed metasurface-based super-oscillatory imaging optics in which some local Fourier components beyond the cut-off frequency of telescope could be restored. As experimental examples, a minimal resolution to 0.55 of Rayleigh criterion is obtained, and imaging complex targets and large targets by superimposing multiple local fields of views are demonstrated as well. This investigation provides an access for real-time, incoherent and super-resolution telescopes without the manipulation of distant targets. More importantly, it gives counterintuitive evidence to the common knowledge that relayed optics could not deliver more imaging details than objective systems.

  20. An Iterative Shrinkage Approach to Total-Variation Image Restoration

    CERN Document Server

    Michailovich, Oleg

    2009-01-01

    The problem of restoration of digital images from their degraded measurements plays a central role in a multitude of practically important applications. A particularly challenging instance of this problem occurs in the case when the degradation phenomenon is modeled by an ill-conditioned operator. In such a case, the presence of noise makes it impossible to recover a valuable approximation of the image of interest without using some a priori information about its properties. Such a priori information is essential for image restoration, rendering it stable and robust to noise. Particularly, if the original image is known to be a piecewise smooth function, one of the standard priors used in this case is defined by the Rudin-Osher-Fatemi model, which results in total variation (TV) based image restoration. The current arsenal of algorithms for TV-based image restoration is vast. In the present paper, a different approach to the solution of the problem is proposed based on the method of iterative shrinkage (aka i...

  1. Polymerization Shrinkage and Flexural Modulus of Flowable Dental Composites

    Directory of Open Access Journals (Sweden)

    Janaína Cavalcanti Xavier

    2010-09-01

    Full Text Available Linear polymerization shrinkage (LPS, flexural strength (FS and modulus of elasticity (ME of low-viscosity resin composites (Admira Flow™, Grandio Flow™/VOCO; Filtek Z350 Flow™/3M ESPE; Tetric Flow™/Ivoclar-Vivadent was evaluated using a well-established conventional micro-hybrid composite as a standard (Filtek Z250™/3M ESPE. For the measurement of LPS, composites were applied to a cylindrical metallic mould and polymerized (n = 8. The gap formed at the resin/mould interface was observed using SEM (1500×. For FS and ME, specimens were prepared according to the ISO 4049 specifications (n = 10. Statistical analysis of the data was performed with one-way ANOVA and the Tukey test. The conventional resin presented significantly lower LPS associated with high FS and ME, but only the ME values of the conventional resin differed significantly from the low-viscosity composites. The relationship between ME and LPS of low-viscosity resin composites when used as restorative material is a critical factor in contraction stress relief and marginal leakage.

  2. INTER-GROUP IMAGE REGISTRATION BY HIERARCHICAL GRAPH SHRINKAGE.

    Science.gov (United States)

    Ying, Shihui; Wu, Guorong; Liao, Shu; Shen, Dinggang

    2013-12-31

    In this paper, we propose a novel inter-group image registration method to register different groups of images (e.g., young and elderly brains) simultaneously. Specifically, we use a hierarchical two-level graph to model the distribution of entire images on the manifold, with intra-graph representing the image distribution in each group and the inter-graph describing the relationship between two groups. Then the procedure of inter-group registration is formulated as a dynamic evolution of graph shrinkage. The advantage of our method is that the topology of entire image distribution is explored to guide the image registration. In this way, each image coordinates with its neighboring images on the manifold to deform towards the population center, by following the deformation pathway simultaneously optimized within the graph. Our proposed method has been also compared with other state-of-the-art inter-group registration methods, where our method achieves better registration results in terms of registration accuracy and robustness.

  3. Laser-induced scleral shrinkage for refractive surgery

    Science.gov (United States)

    Ren, Qiushi; Simon, Gabriel; Parel, Jean-Marie A.; Shen, Jin-Hui

    1994-06-01

    We investigate the laser refractive scleroplasty (LRS) as a potential minimal-invasive method for correcting post-operative astigmatism. The scleral shrinkage near limbus was induced on 6 cadaver eyes using a 200 micrometers fiber optic probe coupled to a pulsed Ho:YAG laser. The diameter of the treatment spot was 0.8 mm. The output energy measured at tip was 60.2+/- 0.6 mJ. The treatments consisted of multiple sector patterns placed along the major axis of astigmatism parallel to the limbus, and round patterns placed along the limbus. Three treatment spots were applied on each side of the sector. The separation among sectors and limbus is 1 mm. Keratometry and topography of the cornea were measured after each sector or round pattern treatment. Effect of 5 and 10 pulses at each treatment spot were compared. Histology was performed to evaluate laser tissue damage. The major axis of astigmatism was shifted 90 degrees after the sector pattern treatment and amount of dioptric change increased when adding a new treatment or using more treatment pulses. However, the spherical equivalent of the eyes was essentially unchanged. The keratometry of the corneas remained the same after the round pattern treatment. Laser refractive scleroplasty may be applied for the correction of post-operative astigmatism.

  4. CHANNEL SHRINKAGE AND ITS INSTABILITY IN THE LOWER YELLOW RIVER1

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    From the mid 1980s through the late 1990s, the channel of the lower Yellow River experienced serious shrinkage, which has decreased the flood conveyance of the channel and the sediment carrying capacity of the flow, raised the water levels of floods, and, thus, severely threatened the safety of flood control along the river. The completion of Xiaolangdi Dam in 1999 could help mitigate the channel shrinkage problem, but the situation has not changed yet. This paper analyses the characteristics, mechanisms, and conditions resulting in channel shrinkage, points out channel instabilities, and puts forward approaches of channel rehabilitation.

  5. Cryptography cracking codes

    CERN Document Server

    2014-01-01

    While cracking a code might seem like something few of us would encounter in our daily lives, it is actually far more prevalent than we may realize. Anyone who has had personal information taken because of a hacked email account can understand the need for cryptography and the importance of encryption-essentially the need to code information to keep it safe. This detailed volume examines the logic and science behind various ciphers, their real world uses, how codes can be broken, and the use of technology in this oft-overlooked field.

  6. Properties and application of low-shrinkage resin composite%低聚合收缩复合树脂的性能及其应用

    Institute of Scientific and Technical Information of China (English)

    叶韵瑶

    2012-01-01

    聚合收缩是复合树脂的主要缺陷之一,易引起复合树脂与牙体之间形成间隙,产生釉质裂纹和牙尖移动,导致充填失败.近年来,一种以矽油基底基环氧化物为基质成分的新型复合树脂,以低聚合收缩率为特点,成为研究的热点.本文就这种新型复合树脂的性能和粘接等方面作一综述.%Polymerization shrinkage is one of the major deficiencies of resin composite, it may lead to gap between teeth and the filling resin composite, enamel cracks and cuspal deflection, and finally to restoration failure. Recently, a new low-shrinkage resin composite which is based on the new ring-opening silorane chemistry is made to overcome the problem. This review was to introduce the research progresses on the properties and adhesive system.

  7. Development of digital image correlation method to analyse crack variations of masonry wall

    Indian Academy of Sciences (India)

    Shih-Heng Tung; Ming-Hsiang Shih; Wen-Pei Sung

    2008-12-01

    The detection of crack development in a masonry wall forms an important study for investigating the earthquake resistance capability of the masonry structures. Traditionally, inspecting the structure and documenting the findings were done manually. The procedures are time-consuming, and the results are sometimes inaccurate. Therefore, the digital image correlation (DIC) technique is developed to identify the strain and crack variations. This technique is non-destructive for inspecting the whole displacement and strain field. Tests on two masonry wall samples were performed to verify the performance of the digital image correlation method. The phenomena of micro cracks, strain concentration situation and nonuniform deformation distribution which could not have been observed preciously by manual inspection are successfully identified using DIC. The crack formation tendencies on masonry wall can be observed at an earlier stage by this proposed method. These results show a great application potential of the DIC technique for various situations such as inspecting shrinkage-induced cracks in fresh concrete, masonry and reinforced concrete structures, and safety of bridges.

  8. Multiaxial mixed-mode cracking - small crack initiation and propagation

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, M. de; Reis, L.; Li Bin [Lisbon Univ. (Portugal). ICEMS - Inst. of Material and Surface Science and Engineering

    2006-07-01

    Both the fatigue crack path and fatigue life of CK45 steel and 42CrMo4 steel under various multiaxial loading paths are studied in this paper. The replica method was applied to monitor the crack initiation and small crack growth, the fractographic analyses were carried out on the fracture surface and the crack initiation angle was measured. The effects of non-proportional loading on both the crack path and fatigue life were studied, and the flattening of asperities on the crack surface due to compressive normal stress was also observed. An improved model is proposed based on correcting the strain range parameter of the ASME code approach, taking into account the additional hardening caused by the non-proportional loading path, which can improve the predictions of the fatigue lives for various non-proportional loading paths and provide an easy way to overcome the drawbacks of the current ASME code approach for non-proportional fatigue. Based on these corrected strain range parameters, a strain intensity factor range is used to correlate with the experimental results of small crack growth rates. It is concluded that the orientation of the early crack growth can be predicted well by the critical damage plane, but the fatigue life can not be predicted accurately using only the parameters on the critical plane, since the damage on all the planes contributes to fatigue damage as stated by the integral approaches. (orig.)

  9. Catalytic cracking of lignites

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, M.; Nowak, S.; Naegler, T.; Zimmermann, J. [Hochschule Merseburg (Germany); Welscher, J.; Schwieger, W. [Erlangen-Nuernberg Univ. (Germany); Hahn, T. [Halle-Wittenberg Univ., Halle (Germany)

    2013-11-01

    A most important factor for the chemical industry is the availability of cheap raw materials. As the oil price of crude oil is rising alternative feedstocks like coal are coming into focus. This work, the catalytic cracking of lignite is part of the alliance ibi (innovative Braunkohlenintegration) to use lignite as a raw material to produce chemicals. With this new one step process without an input of external hydrogen, mostly propylene, butenes and aromatics and char are formed. The product yield depends on manifold process parameters. The use of acid catalysts (zeolites like MFI) shows the highest amount of the desired products. Hydrogen rich lignites with a molar H/C ratio of > 1 are to be favoured. Due to primary cracking and secondary reactions the ratio between catalyst and lignite, temperature and residence time are the most important parameter to control the product distribution. Experiments at 500 C in a discontinuous rotary kiln reactor show yields up to 32 wt-% of hydrocarbons per lignite (maf - moisture and ash free) and 43 wt-% char, which can be gasified. Particularly, the yields of propylene and butenes as main products can be enhanced four times to about 8 wt-% by the use of catalysts while the tar yield decreases. In order to develop this innovative process catalyst systems fixed on beads were developed for an easy separation and regeneration of the used catalyst from the formed char. (orig.)

  10. Physicochemical Characteristics of Bone Substitutes Used in Oral Surgery in Comparison to Autogenous Bone

    Directory of Open Access Journals (Sweden)

    Antoine Berberi

    2014-01-01

    Full Text Available Bone substitutes used in oral surgery include allografts, xenografts, and synthetic materials that are frequently used to compensate bone loss or to reinforce repaired bone, but little is currently known about their physicochemical characteristics. The aim of this study was to evaluate a number of physical and chemical properties in a variety of granulated mineral-based biomaterials used in dentistry and to compare them with those of autogenous bone. Autogenous bone and eight commercial biomaterials of human, bovine, and synthetic origins were studied by high-resolution X-ray diffraction, atomic absorption spectrometry, and laser diffraction to determine their chemical composition, calcium release concentration, crystallinity, and granulation size. The highest calcium release concentration was 24. 94 mg/g for Puros and the lowest one was 2.83 mg/g for Ingenios β-TCP compared to 20.15 mg/g for natural bone. The range of particles sizes, in terms of median size D50, varied between 1.32 μm for BioOss and 902.41 μm for OsteoSponge, compared to 282.1 μm for natural bone. All samples displayed a similar hexagonal shape as bone, except Ingenios β-TCP, Macrobone, and OsteoSponge, which showed rhomboid and triclinic shapes, respectively. Commercial bone substitutes significantly differ in terms of calcium concentration, particle size, and crystallinity, which may affect their in vivo performance.

  11. Treatment of an Immature Autogenous Arteriovenous Fistula with Percutaneous Transluminal Angioplasty

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyoung Rae [Kangwon National University, Chuncheon (Korea, Republic of)

    2008-11-15

    The purpose of this study was to evaluate the efficacy of percutaneous transluminal angioplasty (PTA) in facilitating maturation of autogenous arteriovenous fistulae. There were 12 immature autogenous arteriovenous fistulae. We performed 15 PTAs transvenously. Post-intervention anatomic and clinical successes were estimated, and the 6-month and 1-year primary and secondary patency rates were calculated using Kaplan-Meier analysis. All immature fistulae had underlying stenosis (n=20): arteriovenous anastomosis (n=1) and venous outflow (n=19): 1) within 5 cm from the anastomosis (n=10); 2) more than 5 cm but less than 10 cm from the anastomosis (n=5); 3) more than 10 cm from the anastomosis, including central veins (n=4). Six fistulae had two or more stenoses. Repeat intervention was necessary in two patients. The anatomical success rate was 94.3%, and the clinical success rate was 86.7%. The 6-month and 1-year primary patency rates were 72.7% and 54.5%, and the secondary patency rates were 100% and 81.8%, respectively. All immature hemodialysis fistulae have underlying stenosis, most of which are located near the arteriovenous anastomosis. Early interventional procedures are helpful in the salvage and maintenance of immature arteriovenous fistulae, with a high degree of success

  12. Autogenous tibial strut grafts used in severe kyphoscoliosis:surgical policies and preliminary results

    Institute of Scientific and Technical Information of China (English)

    CHEN Hui; QIU Yong; WANG Bin; YU Yang; ZHU Ze-zhang ZHU Li-hua

    2005-01-01

    Background Surgery for severe kyphoscoliosis is frequently unsatisfying because of loss of correction, high rate of pseudarthrosis and neurological complications.Several authors reported that the anterior fusion with strut grafts might improve the surgical outcome.This article describes and assesses the surgical strategies and the application of autogenous tibial strut in the treatment of severe kyphoscoliosis.Results The mean preoperative and postoperative kyphosis was 82°and 52°respectively, and the mean scoliosis was 84°and 44°respectively.Complications included pseudarthrosis (2 cases, one with graft fracture and the other with hook displacement), posterior elements fractures (4), pleura penetrations (3, in the plastic surgery of the thoracic cage), dura tear (2), exudative pleuritis (2, in the anterior surgery), and tibia fracture of the harvesting site (1).The mean loss of correction in coronal and sagittal plane was 6° and 7° respectively.Except for 1 case, the patients with incomplete paraplegia showed improvements to varying extents.Conclusion Autogenous tibial strut can provide excellent support to the kyphoscoliotic spine: it reduces pseudarthrodic rate, loss of correction and complications of graft harvest, it also prevents the occurrence of neurological impairment.

  13. Full-thickness tissue engineered skin constructed with autogenic bone marrow mesenchymal stem cells

    Institute of Scientific and Technical Information of China (English)

    HE LiJuan; PEI XueTao; NAN Xue; WANG YunFang; GUAN LiDong; BAI CiXian; SHI ShuangShuang; YUAN HongFeng; CHEN Lin; LIU DaQing

    2007-01-01

    To explore the feasibility of repairing clinical cutaneous deficiency, autogenic bone marrow mesenchymal stem cells (BMSCs) were isolated and differentiated into epidermal cells and fibroblasts in vitro supplemented with different inducing factors and biomaterials to construct functional tissueengineered skin. The results showed that after 72 h induction, BMSCs displayed morphologic changes such as typical epidermal cell arrangement, from spindle shape to round or oval; tonofibrils, melanosomes and keratohyaline granules were observed under a transmission electronic microscope. The differentiated cells expressed epidermal stem cell surface marker CK19 (59.66%±4.2%) and epidermal cells differentiation marker CK10. In addition, the induced epidermal cells acquired the anti-radiation capacity featured by lowered apoptosis following exposure to UVB. On the other hand, the collagen microfibrils deposition was noticed under a transmission electronic microscope after differentiating into dermis fibroblasts; RT-PCR identified collagen type Ⅰ mRNA expression in differentiated cells;radioimmunoassay detected the secretion of interleukin-6 (IL-6) and interleukin-8 (IL-8) (up to 115.06pg/mL and 0.84 ng/mL, respectively). Further in vivo implanting BMSCs with scaffold material shortened skin wound repair significantly. In one word, autogenic BMSCs have the potential to differentiate into epidermal cells and fibroblasts in vitro, and show clinical feasibility acting as epidermis-like and dermis-like seed cells in skin engineering.

  14. Pure orbital blowout fractures reconstructed with autogenous bone grafts: functional and aesthetic outcomes.

    Science.gov (United States)

    Kronig, S A J; van der Mooren, R J G; Strabbing, E M; Stam, L H M; Tan, J A S L; de Jongh, E; van der Wal, K G H; Paridaens, D; Koudstaal, M J

    2016-04-01

    The purpose of this study was to investigate the ophthalmic clinical findings following surgical reconstruction with autogenous bone grafts of pure blowout fractures. A retrospective review of 211 patients who underwent surgical repair of an orbital fracture between October 1996 and December 2013 was performed. Following data analysis, 60 patients who were followed up over a period of 1 year were included. A solitary floor fracture was present in 38 patients and a floor and a medial wall fracture in 22 patients. Comparing preoperative findings between these two groups, preoperative diplopia and enophthalmos were almost twice as frequent in the group with additional medial wall fractures: diplopia 8% and 14% and enophthalmos 18% and 55%, respectively. One year following surgery there was no diplopia present in either group. In the solitary floor fracture group, 3% still had enophthalmos. It can be concluded that at 1 year following the repair of pure orbital floor fractures using autogenous bone, good functional and aesthetic results can be obtained. In the group with both floor and medial wall fractures, no enophthalmos was found when both walls were reconstructed. When the medial wall was left unoperated, 29% of patients still suffered from enophthalmos after 1 year.

  15. Full-thickness tissue engineered skin constructed with autogenic bone marrow mesenchymal stem cells

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    To explore the feasibility of repairing clinical cutaneous deficiency, autogenic bone marrow mesen-chymal stem cells (BMSCs) were isolated and differentiated into epidermal cells and fibroblasts in vitro supplemented with different inducing factors and biomaterials to construct functional tissue- engineered skin. The results showed that after 72 h induction, BMSCs displayed morphologic changes such as typical epidermal cell arrangement, from spindle shape to round or oval; tonofibrils, melano-somes and keratohyaline granules were observed under a transmission electronic microscope. The differentiated cells expressed epidermal stem cell surface marker CK19 (59.66% ± 4.2%) and epidermal cells differentiation marker CK10. In addition, the induced epidermal cells acquired the anti-radiation capacity featured by lowered apoptosis following exposure to UVB. On the other hand, the collagen microfibrils deposition was noticed under a transmission electronic microscope after differentiating into dermis fibroblasts; RT-PCR identified collagen type I mRNA expression in differentiated cells; radioimmunoassay detected the secretion of interleukin-6 (IL-6) and interleukin-8 (IL-8) (up to 115.06 pg/mL and 0.84 ng/mL, respectively). Further in vivo implanting BMSCs with scaffold material short-ened skin wound repair significantly. In one word, autogenic BMSCs have the potential to differentiate into epidermal cells and fibroblasts in vitro, and show clinical feasibility acting as epidermis-like and dermis-like seed cells in skin engineering.

  16. Mechanical properties, volumetric shrinkage and depth of cure of short fiber-reinforced resin composite.

    Science.gov (United States)

    Tsujimoto, Akimasa; Barkmeier, Wayne W; Takamizawa, Toshiki; Latta, Mark A; Miyazaki, Masashi

    2016-01-01

    The mechanical properties, volumetric shrinkage and depth of cure of a short fiber-reinforced resin composite (SFRC) were investigated in this study and compared to both a bulk fill resin composite (BFRC) and conventional glass/ceramic-filled resin composite (CGRC). Fracture toughness, flexural properties, volumetric shrinkage and depth of cure of the SFRC, BFRC and CGRC were measured. SFRC had significantly higher fracture toughness than BFRCs and CGRCs. The flexural properties of SFRC were comparable with BFRCs and CGRCs. SFRC showed significantly lower volumetric shrinkage than the other tested resin composites. The depth of cure of the SFRC was similar to BFRCs and higher than CGRCs. The data from this laboratory investigation suggests that SFRC exhibits improvements in fracture toughness, volumetric shrinkage and depth of cure when compared with CGRC, but depth of cure of SFRC was similar to BFRC.

  17. Marginal adaptation of a low-shrinkage silorane-based composite: A SEM-analysis

    DEFF Research Database (Denmark)

    Schmidt, Malene; Bindslev, Preben Hørsted; Poulsen, Sven;

    2012-01-01

    shrinkage, has been marketed. Objective. To investigate whether reduced polymerization shrinkage improves the marginal adaptation of composite restorations. Material and methods. A total of 156 scanning electron microscopy (SEM) pictures (78 baseline, 78 follow-up) of the occlusal part of Class II......-casts of the restorations were used for SEM pictures at x 16 magnification. Pictures from baseline and follow-up (398 days, SD 29 days) were randomized and the examiner was blinded to the material and the age of the restoration. Stereologic measurements were used to calculate the length and the width of the marginal......Introduction. Shrinkage during polymerization of resin-based composite materials may lead to gap formation and hamper the marginal adaptaion of the restorations. To reduce the problem of polymerization shrinkage, a new composite material (Filtek™ Silorane, 3M-ESPE, Germany), with a reduced...

  18. Influence of Technological Parameters of Furane Mixtures on Shrinkage Creation in Ductile Cast Iron Castings

    Directory of Open Access Journals (Sweden)

    Vasková I.

    2014-10-01

    Full Text Available Ductile cast iron (GS has noticed great development in last decades and its boom has no analogue in history humankind. Ductile iron has broaden the use of castings from cast iron into areas, which where exclusively domains for steel castings. Mainly by castings, which weight is very high, is the propensity to shrinkage creation even higher. Shrinkage creation influences mainly material, construction of casting, gating system and mould. Therefore, the main realized experiment was to ascertain the influence of technological parameters of furane mixture on shrinkage creation in castings from ductile iron. Together was poured 12 testing items in 3 moulds forto determine and compare the impact of various technological parameters forms the propensity for shrinkage in the casting of LGG.

  19. Numerical Simulation on Open Wellbore Shrinkage and Casing Equivalent Stress in Bedded Salt Rock Stratum

    Directory of Open Access Journals (Sweden)

    Jianjun Liu

    2013-01-01

    Full Text Available Most salt rock has interbed of mudstone in China. Owing to the enormous difference of mechanical properties between the mudstone interbed and salt rock, the stress-strain and creep behaviors of salt rock are significantly influenced by neighboring mudstone interbed. In order to identify the rules of wellbore shrinkage and casings equivalent stress in bedded salt rock stratum, three-dimensional finite difference models were established. The effects of thickness and elasticity modulus of mudstone interbed on the open wellbore shrinkage and equivalent stress of casing after cementing operation were studied, respectively. The results indicate that the shrinkage of open wellbore and equivalent stress of casings decreases with the increase of mudstone interbed thickness. The increasing of elasticity modulus will reduce the shrinkage of open wellbore and casing equivalent stress. Research results can provide the scientific basis for the design of mud density and casing strength.

  20. Numerical simulation on open wellbore shrinkage and casing equivalent stress in bedded salt rock stratum.

    Science.gov (United States)

    Liu, Jianjun; Zhang, Linzhi; Zhao, Jinzhou

    2013-01-01

    Most salt rock has interbed of mudstone in China. Owing to the enormous difference of mechanical properties between the mudstone interbed and salt rock, the stress-strain and creep behaviors of salt rock are significantly influenced by neighboring mudstone interbed. In order to identify the rules of wellbore shrinkage and casings equivalent stress in bedded salt rock stratum, three-dimensional finite difference models were established. The effects of thickness and elasticity modulus of mudstone interbed on the open wellbore shrinkage and equivalent stress of casing after cementing operation were studied, respectively. The results indicate that the shrinkage of open wellbore and equivalent stress of casings decreases with the increase of mudstone interbed thickness. The increasing of elasticity modulus will reduce the shrinkage of open wellbore and casing equivalent stress. Research results can provide the scientific basis for the design of mud density and casing strength.

  1. Strength and Drying Shrinkage of Alkali-Activated Slag Paste and Mortar

    Directory of Open Access Journals (Sweden)

    Mao-chieh Chi

    2012-01-01

    Full Text Available The aim of this study is to investigate the strengths and drying shrinkage of alkali-activated slag paste and mortar. Compressive strength, tensile strength, and drying shrinkage of alkali-activated slag paste and mortar were measured with various liquid/slag ratios, sand/slag ratios, curing ages, and curing temperatures. Experimental results show that the higher compressive strength and tensile strength have been observed in the higher curing temperature. At the age of 56 days, AAS mortars show higher compressive strength than Portland cement mortars and AAS mortars with liquid/slag ratio of 0.54 have the highest tensile strength in all AAS mortars. In addition, AAS pastes of the drying shrinkage are higher than AAS mortars. Meanwhile, higher drying shrinkage was observed in AAS mortars than that observed comparable Portland cement mortars.

  2. Study of swelling-shrinkage regularity of montmorillonite crystal and its relation with matric suction

    Institute of Scientific and Technical Information of China (English)

    谭罗荣; 孔令伟

    2001-01-01

    The swell-shrinking mineral of saturated and unsaturated expansive soil has important effect on engineering mechanical behavior. Based on the swelling-shrinkage change regularity of montmorillonite crystal in this paper, the actions between various interlayers of montmorillonite crystal are generally summarized as two kinds of action potentials-shrinkage potential and swelling potential. Moreover, through the experimental research and analysis, the expression formula for variations of the swelling potential and shrinkage potential with interlayer distance is presented, and the regularity of matric suction variations with interlayer distance is also obtained for unsaturated expansive soil. It may provide a new theoretical basis and research path for further research on the swelling-shrinkage mechanism of expansive soil and matric suction potential of unsaturated soil.

  3. Measurement of composite shrinkage using a fibre optic Bragg grating sensor.

    Science.gov (United States)

    Milczewski, M S; Silva, J C C; Paterno, A S; Kuller, F; Kalinowski, H J

    2007-01-01

    Fibre Bragg grating is used to determine resin-based composite shrinkage. Two composite resins (Freedom from SDI and Z100 from 3M) were tested to determine the polymerization contraction behaviour. Each sample of resin was prepared with an embedded fibre Bragg grating. A LED activation unit with wavelength from 430 nm to 470 nm (Dabi Atlante) was used for resin polymerization. The wavelength position of the peak in the optical reflection spectra of the sensor was measured. The wavelength shift was related to the shrinkage deformation of the samples. Temperature and strain evolution during the curing phase of the material was monitored. The shrinkage in the longitudinal direction was 0.15 +/- 0.02% for resin Z100 (3M) and 0.06+/-0.01% for Freedom (SDI); two-thirds of shrinkage occurred after the first 50 s of illumination.

  4. Tumor shrinkage by cyclopamine tartrate through inhibiting hedgehog signaling

    Institute of Scientific and Technical Information of China (English)

    Qipeng Fan; Arash Garrossian; Massoud Garrossian; Dale Gardner; Jingwu Xie; Dongsheng Gu; Miao He; Hailan Liu; Tao Sheng; Guorui Xie; Ching-xin Li; Xiaoli Zhang; Brandon Wainwright

    2011-01-01

    The link of hedgehog (Hh) signaling activation to human cancer and synthesis of a variety of Hh signaling inhibitors raise great expectation that inhibiting Hh signaling may be effective in human cancer treatment. Cyclopamine (Cyc), an alkaloid from the Veratrum plant, is a specific natural product inhibitor of the Hh pathway that acts by targeting smoothened (SMO) protein. However, its poor solubility, acid sensitivity, and weak potency relative to other Hh antagonists prevent the clinical development of Cyc as a therapeutic agent. Here, we report properties of cyclopamine tartrate salt (CycT) and its activities in Hh signaling-mediated cancer in vitro and in vivo. Unlike Cyc, CycT is water soluble (5-10 mg/mL). The median lethal dose (LD) of CycT was 62.5 mg/kg body weight compared to 43.5 mg/kg for Cyc, and the plasma half-life (T) of CycT was not significantly different from that of Cyc. We showed that CycT had a higher inhibitory activity for Hh signaling-dependent motor neuron differentiation than did Cyc (IC = 50nmol/L for CycT vs. 300 nmol/L for Cyc). We also tested the antitumor effectiveness of these Hh inhibitors using two mouse models of basal cell carcinomas (K14cre:Ptch1and K14cre:SmoM2). After topical application of CycT or Cyc daily for 21 days, we found that all CycT-treated mice had tumor shrinkage and decreased expression of Hh target genes. Taken together, we found that CycT is an effective inhibitor of Hh signaling-mediated carcinogenesis.

  5. Influence of rare earths on shrinkage porosity in thin walled ductile cast iron

    DEFF Research Database (Denmark)

    Pedersen, Karl Martin; Tiedje, Niels Skat

    2009-01-01

    Ductile cast iron has been cast in test bars with thickness from 2 to 10 mm. The rare earth elements La and Ce have been added to some of the castings to evaluate their influence on microstructure and shrinkage tendency. Both La and Ce increased the graphite nodule count, especially for thickness...... the temperature T-1, which is controlled by the growth of off-eutectic austenite dendrites, increased the shrinkage tendency....

  6. Study on a New Method of Reducing the Water Shrinkage of Rabbit Hair Knitted Fabrics

    Institute of Scientific and Technical Information of China (English)

    PAN Fu-kui; WANG Shan-yuan; LONG Min; YANG Guang-ming

    2005-01-01

    In order to reduce the water shrinkage of rabbit hair knitted fabrics, a new method is developed, which is blending rabbit hairs with a little bit of blaze. The sericin on the blaze which can swell and melt in hot and wet condition[1] can cohere the rabbit hairs through special processing. So the relative movement among fibers could be restricted. The testing results show that the water shrinkage of rabbit hair knitted fabrics can be greatly reduced after processed.

  7. Astrocytic mechanisms explaining neural-activity-induced shrinkage of extraneuronal space

    DEFF Research Database (Denmark)

    Østby, Ivar; Øyehaug, Leiv; Einevoll, Gaute T;

    2009-01-01

    Neuronal stimulation causes approximately 30% shrinkage of the extracellular space (ECS) between neurons and surrounding astrocytes in grey and white matter under experimental conditions. Despite its possible implications for a proper understanding of basic aspects of potassium clearance and astr......Neuronal stimulation causes approximately 30% shrinkage of the extracellular space (ECS) between neurons and surrounding astrocytes in grey and white matter under experimental conditions. Despite its possible implications for a proper understanding of basic aspects of potassium clearance...

  8. Pore Structure and Influence of Recycled Aggregate Concrete on Drying Shrinkage

    OpenAIRE

    Yuanchen Guo; Jueshi Qian; Xue Wang

    2013-01-01

    Pore structure plays an important role in the drying shrinkage of recycled aggregate concrete (RAC). High-precision mercury intrusion and water evaporation were utilized to study the pore structure of RAC, which has a different replacement rate of recycled concrete aggregate (RCA), and to analyze its influence on drying shrinkage. Finally, a fractal-dimension calculation model was established based on the principles of mercury intrusion and fractal-geometry theory. Calculations were performed...

  9. Denoising of Mechanical Vibration Signals Using Quantum-Inspired Adaptive Wavelet Shrinkage

    OpenAIRE

    2014-01-01

    The potential application of a quantum-inspired adaptive wavelet shrinkage (QAWS) technique to mechanical vibration signals with a focus on noise reduction is studied in this paper. This quantum-inspired shrinkage algorithm combines three elements: an adaptive non-Gaussian statistical model of dual-tree complex wavelet transform (DTCWT) coefficients proposed to improve practicability of prior information, the quantum superposition introduced to describe the interscale dependencies of DTCWT co...

  10. Polymerization Shrinkage of Dental Composites Registered by a Video-imaging Device. A pilot study

    OpenAIRE

    Afaag, Ali; Sandelin, Benjamin

    2014-01-01

    The use of composite materials for dental fillings has become more common due to demands for more esthetic filling materials and a national ban against using mercury-containing products, among others dental amalgam. However, one of the drawbacks with composites is their polymerization shrinkage. Filler particles are incorporated into composites among other things to minimize the shrinkage. The sizes of the filler particles have in recent years become smaller and most composites have nano-part...

  11. A new method for chill and shrinkage control in ladle treated ductile iron

    Institute of Scientific and Technical Information of China (English)

    Torbj(o)rn Skaland

    2006-01-01

    The paper is undertaken with the objective of describing a new method for treating ductile cast iron in a ladle process, where the main objective is to minimize formation of eutectic carbides and shrinkage porosity during solidification. The suppression of carbide formation is associated with the nucleating properties of the nodularizer and inoculant alloys. By nucleating properties it is understood the number and potency of nuclei formed by an alloy addition. The nodularizer and inoculant additions also influence ductile iron solidification shrinkage. Some alloys may give good protection against shrinkage while others tend to promote more shrinkage.The use of vanous rare earth elements is found to have a pronounced impact on these conditions. It has been discovered that the use of pure lanthanum as the primary rare earth source in the magnesium ferrosilicon nodularizer surprisingly further improves the performance of the ductile iron ladle treatment method compared to similar methods using cerium or mishmetal bearing nodularizers. The nucleating properties are substantially improved and the risk for carbides (chill) and shrinkage formation in the sandwich or tundish ladle treated ductile iron is then minimized.The paper describes this new ladle treatment concept in detail, and gives examples from successful testing of the new nodularizing technology and how it simultaneously affects and minimizes critical ductile iron chill and shrinkage tendencies.

  12. Effect on effective diffusion coefficients and investigation of shrinkage during osmotic dehydration of apricot

    Energy Technology Data Exchange (ETDEWEB)

    Togrul, Inci Turk; Ispir, Ayse [Firat University, Engineering Faculty, Department of Chemical Engineering, 23279 Elazig (Turkey)

    2007-10-15

    This article represents the results of the variation in density and shrinkage of apricots during its osmotic dehydration. Shrinkage was investigated by means of dimensionless volume, diameter and length. Various osmotic agents such as sucrose, glucose, fructose, maltodextrin and sorbitol were used. It was found that the shrinkage of apricots could be well correlated with the moisture content of the sample during osmotic dehydration. The relationship between dimensionless parameters and moisture content was investigated by using eight non-linear models for each osmotic agent. It was find that the following proposed model can be confidently use for explaining the effect of shrinkage during osmotic dehydration of apricots.V/V{sub 0},D/D{sub 0},L/L{sub 0},{rho}/{rho}{sub 0}=a+b. exp (cX)+d. exp (e.X{sup f})In addition, the osmotic dehydration kinetics of apricots with and without shrinkage was studied. The effective diffusivities calculated from the diffusional model with and without shrinkage varied from 10.342 x 10{sup -9} m{sup 2}/s to 5.139 x 10{sup -9} and from 1.755 x 10{sup -10} and 0.767 x 10{sup -10} m{sup 2}/s, respectively. (author)

  13. Transient brain shrinkage in infantile spasms after ACTH treatment. Report of two cases.

    Science.gov (United States)

    Maekawa, K; Ohta, H; Tamai, I

    1980-02-01

    This is the report of two cases of infantile spasms, manifesting transient brain shrinkage in computerized tomography (CT) after ACTH treatment. ACTH was given for 8 weeks to a 8-months-old Japanese girl with infantile spasms. First CT performed at 2 weeks after the final ACTH injection, displayed moderate brain shrinkage. Second CT at 4 months showed marked diminution of the shrinkage. ACTH was also given for 8 weeks to a 14 months old Japanese boy with infantile spasms. First CT, just before ACTH treatment, showed mild cortical atrophy, the second at 7 days after the final ACTH injection revealed marked brain shrinkage and moderate ventricular dilatation, and the third at 2 months, disclosed mild improvement of the shrinkage. ACTH or corticoateroid has widespread effects on the developing nervous system. In animal experiments, ACTH or steroids interfere with brain growth of young rats. CT findings of transient brain shrinkage in a child with infantile spasms might suggest that intensive treatment with ACTH or steroids in infancy interferes with brain growth as seen in the results of animal experiments.

  14. Drying Shrinkage of Cement-Based Materials Under Conditions of Constant Temperature and Varying Humidity

    Institute of Scientific and Technical Information of China (English)

    MA Bao-guo; WEN Xiao-dong; WANG Ming-yuan; YAN Jia-jia; Gao Xiao-jian

    2007-01-01

    Currently,deformations along the central axis of specimens were usually measured under fixed environmental conditions. Seldom were the effects of environmental factors on the drying-shrinkage deformation of cement-based material considered. For this paper, the drying-shrinkage deformation at different w/b ratios and different additions to mortars was investigated under different environments at a temperature of 20 ℃ and humidity ranging from 100% to 50%. The specimens were cured in water for 28 days before measurement. The results illustrate that mortar shows much less shrinkage under various drying conditions when a lower w/b ratio is adopted. With a decrease in relative humidity the speed of drying-shrinkage becomes gradually lower. The addition of silica fume reduces the drying-shrinkage of mortar under higher relative humidity, because the pore structure of mortar with silica fume becomes more refined. The addition of fly ash increases the total porosity and the volume of coarse pores in the mortar. The drying-shrinkage of mortar under different conditions increases with the addition of more of fly ash.

  15. Microcomputed Tomography Evaluation of Polymerization Shrinkage of Class I Flowable Resin Composite Restorations.

    Science.gov (United States)

    Sampaio, C S; Chiu, K-J; Farrokhmanesh, E; Janal, M; Puppin-Rontani, R M; Giannini, M; Bonfante, E A; Coelho, P G; Hirata, R

    The present study aimed to characterize the pattern and volume of polymerization shrinkage of flowable resin composites, including one conventional, two bulk fill, and one self-adhesive. Standardized class I preparations (2.5 mm depth × 4 mm length × 4 mm wide) were performed in 24 caries-free human third molars that were randomly divided in four groups, according to the resin composite and adhesive system used: group 1 = Permaflo + Peak Universal Bond (PP); group 2 = Filtek Bulk Fill + Scotchbond Universal (FS); group 3 = Surefil SDR + XP Bond (SX); and group 4 = Vertise flow self-adhering (VE) (n=6). Each tooth was scanned three times using a microcomputed tomography (μCT) apparatus. The first scan was done after the cavity preparation, the second after cavity filling with the flowable resin composite before curing, and the third after it was cured. The μCT images were imported into three-dimensional rendering software, and volumetric polymerization shrinkage percentage was calculated for each sample. Data were submitted to one-way analysis of variance and post hoc comparisons. No significant difference was observed among PP, FS, and VE. SX bulk fill resin composite presented the lowest values of volumetric shrinkage. Shrinkage was mostly observed along the occlusal surface and part of the pulpal floor. In conclusion, polymerization shrinkage outcomes in a 2.5-mm deep class I cavity were material dependent, although most materials did not differ. The location of shrinkage was mainly at the occlusal surface.

  16. The effect of mucosal cuff shrinkage around dental implants during healing abutment replacement.

    Science.gov (United States)

    Nissan, J; Zenziper, E; Rosner, O; Kolerman, R; Chaushu, L; Chaushu, G

    2015-10-01

    Soft tissue shrinkage during the course of restoring dental implants may result in biological and prosthodontic difficulties. This study was conducted to measure the continuous shrinkage of the mucosal cuff around dental implants following the removal of the healing abutment up to 60 s. Individuals treated with implant-supported fixed partial dentures were included. Implant data--location, type, length, diameter and healing abutments' dimensions--were recorded. Mucosal cuff shrinkage, following removal of the healing abutments, was measured in bucco-lingual direction at four time points--immediately after 20, 40 and 60 s. anova was used to for statistical analysis. Eighty-seven patients (49 women and 38 men) with a total of 311 implants were evaluated (120 maxilla; 191 mandible; 291 posterior segments; 20 anterior segments). Two-hundred and five (66%) implants displayed thick and 106 (34%) thin gingival biotype. Time was the sole statistically significant parameter affecting mucosal cuff shrinkage around dental implants (P < 0.001). From time 0 to 20, 40 and 60 s, the mean diameter changed from 4.1 to 4.07, 3.4 and 2.81 mm, respectively. The shrinkage was 1%, 17% and 31%, respectively. The gingival biotype had no statistically significant influence on mucosal cuff shrinkage (P = 0.672). Time required replacing a healing abutment with a prosthetic element should be minimised (up to 20/40 s), to avoid pain, discomfort and misfit.

  17. Experiences on IGSCC crack manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Veron, P. [Equipos Nucleares, S.A., Maliano (Spain)

    1997-02-01

    The author presents his experience in manufacturing IGSCC realistic defects, mainly in INCONEL 600 MA Steam Generator Tubes. From that experience he extracts some knowledge about this cracking (influence of chemistry in the environment, stress state, crack growth rate, and occurrence in laboratory condition of break before leak).

  18. HYDROGEN TRANSFER IN CATALYTIC CRACKING

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Hydrogen transfer is an important secondary reaction of catalytic cracking reactions, which affects product yield distribution and product quality. It is an exothermic reaction with low activation energy around 43.3 kJ/mol. Catalyst properties and operation parameters in catalytic cracking greatly influence the hydrogen transfer reaction. Satisfactory results are expected through careful selection of proper catalysts and operation conditions.

  19. 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

    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...... was used to solve the non-linear equations. The performance of the element is illustrated by modelling fracture mechanical benchmark tests. Investigations were carried out on the performance of the element for different crack lengths within one element. The results are compared with previously obtained...

  20. Crack Identification in Reinforced Concrete Beams Using Ansys Software

    Directory of Open Access Journals (Sweden)

    T. Subramani

    2014-06-01

    Full Text Available Analytical determination of displacements and stresses in reinforced concrete material was difficult task and engineers had to rely on empirical formulas because concrete consists of heterogeneous material and creep and shrinkage influenced deformations in it. Due to these complexities engineers in past had been facing difficulties in coping such problems, but with the advancement of digital computerization and modern numerical methods for analysis such as finite element method, these problems can be addressed in a very efficient way. There were two ways to carry out modelling in ANSYS software, one was smeared approach and the other one was discrete. In the past, Smeared approach was used to identify the cracks in RC beam using ANSYS but in this work it was extended using discrete approach of modelling and shear cracks were identified in RC beam and load deflection curve was simulated which showed good agreement with the experimental results. Beams, made of brittle materials like concrete or cement, show increasing crack development during their service life due to mechanical and environmental loadings. This local damage can be translated into a reduction of the local bending stiffness. Stiffness modifications, while assuming constant mass distribution, can be observed by monitoring the vibration behaviour of the beam. In this paper the modal parameters of an undamaged beam are monitored and compared with the vibration behaviour of the beam subjected to controlled damaging. Selected stiffness parameters in the finite element model are adjusted in such a way that the computed modal quantities match the measured quantities. FEMtools has been used to establish a damage distribution in beams associated with increasing stress patterns. State of the art scanning laser modal equipment has been used for this purpose. It has been found that modal updating is indeed a possible tool to reconstruct the damage patterns.

  1. Spacing of crack patterns driven by steady-state cooling or drying and influenced by a solidification boundary

    Science.gov (United States)

    Hofmann, Martin; Bahr, Hans-Achim; Weiss, Hans-Jürgen; Bahr, Ute; Balke, Herbert

    2011-03-01

    Regular columnar joints that originate from networklike crack patterns can be observed in basalt and, on a much smaller scale, in dried starch slurry. Here, the basalt columns are idealized by a periodic array of parallel cracks driven by steady-state cooling. By means of a bifurcation analysis, the minimal possible crack spacing for sustained propagation of the crack array is calculated. It can be shown qualitatively that the minimal possible crack spacing for sustained propagation increases with decreasing velocity. This is confirmed by numerical calculations. The latent heat released at the solidification front is taken into account in the thermomechanical linear-elastic model of propagating shrinkage. Our calculations show that the solidification front is positioned not far ahead of the crack tips, which influences the result considerably. The results agree reasonably well with new measured data of basalt columns. By use of the analogy between contraction due to cooling and that due to drying the model is applied for columns in dried cornstarch, too, showing good agreement with recent experimental data.

  2. 混凝土的收缩机理——建造更耐用、更持久的工程%Understanding Shrinkage Mechanisms-a Contribution to More Durable and Sustainable Constructions

    Institute of Scientific and Technical Information of China (English)

    F. H. Wittmann; 赵继增; 张鹏

    2008-01-01

    干燥收缩是混凝土的一个复杂性质,测定时存在一个长期的内部应力作用过程.通过两种主要的物理作用机理:吸附作用和分离压力作用,解释了混凝土的干燥收缩机理,并对基于两种机理建立的预测方法与试验结果进行了比较.主要包括:(1)水分在窄裂口处的直接观测;(2)不同材料的吸附曲线和吸附长度变化;(3)新拌混凝土和早期混凝土的毛细收缩;(4)防水处理混凝土的收缩机理;(5)离子浓度对收缩的影响.研究结果表明,吸附作用在水泥基材料的收缩作用中仅起到次要的作用.收缩是混凝土结构在干燥过程中产生裂缝的根源,而裂缝的存在又会降低腐蚀环境下混凝土结构的使用寿命.因此,更好地理解混凝土的收缩机理有助于今后建造更耐用、更持久的结构工程.%First of all it is outlined that shrinkage as measured on drying concrete is not a simple material property but the complex response of a given specimen to long lasting time-dependent internal stresses. Then the physical basis of two frequently cited approaches to explain the origin of hygral shrinkage is briefly described: capillary action and disjoining pressure. The predictions of the two concepts are compared with experimental findings. The following examples have been selected for a critical comparison: (1) direct observation of the interaction of water in a narrow gap, (2) sorption and length change isotherms of different materials, (3) capillary shrinkage of fresh and young concrete, (4) shrinkage of water repellent concrete, and (5) influence of ion concentration on shrinkage. From the presented results it can be concluded that capillary action plays a minor role in the process of shrinkage of cement-based materials. Shrinkage is at the origin of crack formation in drying concrete structures. Cracks reduce service life in aggressive environment. Better understanding real shrinkage mechanisms will help to build more

  3. Probabilistic Analysis of Crack Width

    Directory of Open Access Journals (Sweden)

    J. Marková

    2000-01-01

    Full Text Available Probabilistic analysis of crack width of a reinforced concrete element is based on the formulas accepted in Eurocode 2 and European Model Code 90. Obtained values of reliability index b seem to be satisfactory for the reinforced concrete slab that fulfils requirements for the crack width specified in Eurocode 2. However, the reliability of the slab seems to be insufficient when the European Model Code 90 is considered; reliability index is less than recommended value 1.5 for serviceability limit states indicated in Eurocode 1. Analysis of sensitivity factors of basic variables enables to find out variables significantly affecting the total crack width.

  4. Analysis of Crack Arrest Toughness.

    Science.gov (United States)

    1988-01-15

    vload(m) vp tn(m) Vertical Source Load (kN) on wedge HY80 Finite Element 0.0122 0.0099 3.81x10 -4 144 Steel Calculations Experiment 0.0122 --- 3.74x10-4...curve, are bona fide measures of the fracture arrest capability of tough ductile steels . The second is that the J-values represent the crack driving...fibrous mode of crack extension. (b) A new test method for studying fast fracture and arrest in tough steels . (c) Measurements of fast fracture and crack

  5. A computational algorithm for crack determination: The multiple crack case

    Science.gov (United States)

    Bryan, Kurt; Vogelius, Michael

    1992-01-01

    An algorithm for recovering a collection of linear cracks in a homogeneous electrical conductor from boundary measurements of voltages induced by specified current fluxes is developed. The technique is a variation of Newton's method and is based on taking weighted averages of the boundary data. The method also adaptively changes the applied current flux at each iteration to maintain maximum sensitivity to the estimated locations of the cracks.

  6. Retrograde tracing of fluorescent gold after autogenous nerve transplantation on spinal cord injured in rats

    DEFF Research Database (Denmark)

    Lin, X; Liu, W; Ding, Ming;

    2016-01-01

    Objective To investigate the changes of the fluorescent gold retrograde tracing autogenous nerve transplantation on spinal cord injured in rats. Methods The animals were divided into two groups, with modified Allen impact method to establish model of spinal cord injury. After 4 weeks......, the transplantation group using autologous sural nerve graft to repair spinal cord injury period and non-transplantation group was only exposed incision without treatment. In the 4, 6 and 8 weeks after operation, the retrograde tracing of FG Fluoro-Gold was performed to discover the recovery of the axial plasma.......01). Conclusion After spinal cord injury, autologous nerve graft was repaired and survived well and promote the recovery of spinal cord injury segment shaft pulp transportation function....

  7. Autogenous wisdom tooth transplantation: A case series with 6-9 months follow-up

    Directory of Open Access Journals (Sweden)

    Tatjana Nimcenko

    2014-01-01

    Full Text Available Tooth transplantation can be considered a valid and predictable treatment option for rehabilitating young patients with permanent teeth loss. This study presents several cases of successful autogenous tooth transplantation with a 6-9 months follow-up. Tooth auto-transplantation can be considered a reasonable option for replacing missing teeth when a donor tooth is available. The auto-transplantation of a right mandibular third molar with compromised function and esthetics to replace the residual roots resulting from coronal destruction due to extensive carious lesion of the second molar in the same quadrant as shown in the presented cases can result a viable treatment alternative especially in a young patient that cannot undergo dental implant therapy. Transplantation of mature third molar seems to be a promising method for replacing a lost permanent molar tooth and restoring esthetics and function. This clinical procedure showed excellent functional and esthetical long-term results in the analyzed cases.

  8. Autogenous wisdom tooth transplantation: A case series with 6-9 months follow-up

    Science.gov (United States)

    Nimčenko, Tatjana; Omerca, Gražvydas; Bramanti, Ennio; Cervino, Gabriele; Laino, Luigi; Cicciù, Marco

    2014-01-01

    Tooth transplantation can be considered a valid and predictable treatment option for rehabilitating young patients with permanent teeth loss. This study presents several cases of successful autogenous tooth transplantation with a 6-9 months follow-up. Tooth auto-transplantation can be considered a reasonable option for replacing missing teeth when a donor tooth is available. The auto-transplantation of a right mandibular third molar with compromised function and esthetics to replace the residual roots resulting from coronal destruction due to extensive carious lesion of the second molar in the same quadrant as shown in the presented cases can result a viable treatment alternative especially in a young patient that cannot undergo dental implant therapy. Transplantation of mature third molar seems to be a promising method for replacing a lost permanent molar tooth and restoring esthetics and function. This clinical procedure showed excellent functional and esthetical long-term results in the analyzed cases. PMID:25540668

  9. Supplementation of autogenous bone graft with coralline hydroxyapatite in posterior spine fusion for idiopathic adolescent scoliosis.

    Science.gov (United States)

    Mashoof, A Allen; Siddiqui, Saqib A; Otero, Marilyn; Tucci, James J

    2002-10-01

    Twenty-seven consecutive patients with adolescent idiopathic scoliosis underwent posterior spinal fusion with pediatric Texas Scottish Rite Hospital instrumentation. Coralline hydroxyapatite (Interpore, Irvine, Calif) was mixed with limited autograft from posterior iliac crest (an approximate 70/30 ratio of coralline hydroxyapatite to autograft). Patient evaluation was based on clinical and radiographic findings. On initial radiographic evaluation, a "snowstorm" appearance consistent with the exoskeleton of the coralline hydroxyapatite was observed. After two years, the fusion mass had a "marble-like" appearance with distinct decreased visibility of the disk spaces in the fusion mass. This latter stage of "marbilization correlated with solid fusion clinically. All patients achieved solid fusion at an average follow-up of 27 months. Coralline hydroxyapatite is safe, biocompatible, and effective in augmenting autogenous bone graft in the treatment of idiopathic adolescent scoliosis with posterior spinal fusion. In addition to decreased donor site morbidity, this may be invaluable in cases where there is insufficient autograft available.

  10. Psychosomatic aspects in idiopathic infertility: effects of treatment with autogenic training.

    Science.gov (United States)

    O'Moore, A M; O'Moore, R R; Harrison, R F; Murphy, G; Carruthers, M E

    1983-01-01

    It has long been recognised that there is a relationship between emotional stress and some forms of infertility. We have endeavoured to estimate "stress' levels before and after Autogenic Training in 15 couples with infertility of at least two years' duration. Potential stress markers were: plasma prolactin, total urinary free cortisol and catecholamines, and four psychological tests: Spielberger State-Trait anxiety scale, Taylor Manifest Anxiety Scale, the Cattell 16 personality factor questionnaire, and the Eysenck Personality Questionnaire. A control group of ten normal couples was included for comparison. The biochemical finding of higher mean prolactin levels in the female patients vs their controls was of particular interest. The significant reduction of the prolactin level, in parallel with decreased anxiety scores following treatment, supports the hypothesis that the elevated prolactin levels in these patients are indeed linked with emotional stress.

  11. Autogenic-feedback training: A preventive method for space adaptation syndrome

    Science.gov (United States)

    Cowings, Patricia S.; Sharp, Joseph C.; Toscano, William B.; Kamiya, Joe; Miller, Neal E.

    1987-01-01

    The progress made to date on the reduction of data for Spacelab 3 Shuttle experiment, No. 3AFT23 is reported. Four astronauts participated as subjects in this experiment. Crewmen A and B served as treatment subjects (i.e., received preflight training for control of their own motion sickness symptoms) and Crewmen C and D served as control (i.e., did not receive training). A preliminary evaluation of Autogenic Feedback Training (AFT) was made from visual inspections of graphs that were generated from the preflight and inflight and inflight physiological data which included: (1) Baseline rotating chair tests for all crewmen; (2) Posttraining rotating chair tests of treatment groups subjects; (3) Preflight data from Joint Integrated Simulations for all crewmen; and (4) Flight data for all crewmen during mission days 0 through 4, and mission day 6 for treatment subjects only. A summary of the findings suggested by these data is outlined.

  12. Effect of Autogenous Arc Welding Processes on Tensile and Impact Properties of Ferritic Stainless Steel Joints

    Institute of Scientific and Technical Information of China (English)

    A K Lakshminarayanan; K Shanmugam; V Balasubramanian

    2009-01-01

    The effect of autogeneous arc welding processes on tensile and impact properties of ferritic stainless steel conformed to AISI 409M grade is studied.Rolled plates of 4 mm thickness have been used as the base material for preparing single pass butt welded jointa.Tensile and impact properties,microhardness,microstructure,and fracture surface morphology of continuous current gas tungsten arc welding (CCGTAW),pulsed current gas tungsten arc welding (PCGTAW),and plasma arc welding (PAW) joints are evaluated and the results are compared.It is found that the PAW joints of ferritic stainless steel show superior tensile and impact properties when compared with CCGTAW and PCGTAW joints,and this is mainly due to lower heat input,finer fusion zone grain diameter,and higher fusion zone hardness.

  13. Cracks in Utopia

    Science.gov (United States)

    1999-01-01

    Many of the craters found on the northern plains of Mars have been partly filled or buried by some material (possibly sediment). The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image presented here (MOC2-136b, above left) shows a high-resolution view of a tiny portion of the floor of one of these northern plains craters. The crater, located in Utopia Planitia at 44oN, 258oW, is shown on the right (MOC2-136a)with a small white box to indicate the location of the MOC image. The MOC image reveals that the material covering the floor of this crater is cracked and pitted. The origin and source of material that has been deposited in this crater is unknown.The MOC image was acquired in June 1999 and covers an area only 1.1 kilometers (0.7 miles) wide at a resolution of 1.8 meters (6 feet) per pixel. The context picture is a mosaic of Viking 2 orbiter images 010B53 and 010B55, taken in 1976. Both images are illuminated from the left. Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  14. Physical Shrinkage Relationship in Soils of Dissimilar Lithologies in Central Southeastern Nigeria

    Science.gov (United States)

    Onweremadu, E. U.; Akamigbo, F. O. R.; Igwe, C. A.

    This study investigated the relationship between volume shrinkage properties of soils derived from different parent materials in Central Southeastern Nigeria as they related to selected soil physical properties. Using a free survey technique and guided by a geological map of the area, field sampling was conducted in the early months of 2005. Routine analyses were done using collected soil samples. Results showed significant (pwaterholding capacity, Atterberg limits and Co-efficient Of Linear Extensibility (COLE) among the 6 studied soil groups. Volume shrinkage results indicated severe shrinkage (20-30%) rating for soils derived from Shale, moderate shrinkage (10-20%) for soils formed over Lower Coal Measures and Falsebedded Sandstones and slight shrinkage (0-10%) ratings for the rest. The COLE, used as an index of VS correlated significantly (pwaterholding capacity (WHC), Liquid Limit (LL), Plastic Limit (PL), Plasticity Index (PI) and clay content. A model was generated which expressed good predictive relationship between COLE and selected physical properties (R = 0.87; R2 = 0.75; 1-R2 = 0.25, RMSE = 0.01 and Bias = +0.00001), indicating high accuracy and little over-estimation by the model. More soil and soil related variables may further improve generated model (s), thus should be included in future studies.

  15. Effects of Manufactured-sand on Dry Shrinkage and Creep of High-strength Concrete

    Institute of Scientific and Technical Information of China (English)

    ZHOU Mingkai; WANG Jiliang; ZHU Lide; HE Tusheng

    2008-01-01

    The influences of natural sand, manufactured-sand (MS) and stone-dust (SD) in the manufactured-sand on workability, compressive strength, elastic modulus, drying shrinkage and creep properties of high-strength concrete (HSC) were tested and compared. The results show that the reasonable content (7%-10.5%) of SD in MS will not deteriorate the workability of MS-HSC. It could even improve the workability. Moreover, the compressive strength increases gradually with the increasing SD content,and the MS-HSC with low SD content (smaller than 7%) has the elastic modulus which approaches that of the natural sand HSC, but the elastic modulus reduces when the SD content is high. The influence of the SD content on drying shrinkage performance of MS-HSC is closely related to the hydration age. The shrinkage rate of MS-HSC in the former 7 d age is higher than that of the natural sand HSC, but the difference of the shrinkage rate in the late age is not marked. Meanwhile the shrinkage rate reduces as the fly ash is added; the specific creep and creep coefficient of MS-HSC with 7% SD are close to those of the natural sand HSC.

  16. Modified creep and shrinkage prediction model B3 for serviceability limit state analysis of composite slabs

    Science.gov (United States)

    Gholamhoseini, Alireza

    2016-03-01

    Relatively little research has been reported on the time-dependent in-service behavior of composite concrete slabs with profiled steel decking as permanent formwork and little guidance is available for calculating long-term deflections. The drying shrinkage profile through the thickness of a composite slab is greatly affected by the impermeable steel deck at the slab soffit, and this has only recently been quantified. This paper presents the results of long-term laboratory tests on composite slabs subjected to both drying shrinkage and sustained loads. Based on laboratory measurements, a design model for the shrinkage strain profile through the thickness of a slab is proposed. The design model is based on some modifications to an existing creep and shrinkage prediction model B3. In addition, an analytical model is developed to calculate the time-dependent deflection of composite slabs taking into account the time-dependent effects of creep and shrinkage. The calculated deflections are shown to be in good agreement with the experimental measurements.

  17. Drying Shrinkage Behaviour of Fibre Reinforced Concrete Incorporating Polyvinyl Alcohol Fibres and Fly Ash

    Directory of Open Access Journals (Sweden)

    Amin Noushini

    2014-01-01

    Full Text Available The current study assesses the drying shrinkage behaviour of polyvinyl alcohol fibre reinforced concrete (PVA-FRC containing short-length (6 mm and long-length (12 mm uncoated monofilament PVA fibres at 0.125%, 0.25%, 0.375%, and 0.5% volumetric fractions. Fly ash is also used as a partial replacement of Portland cement in all mixes. PVA-FRC mixes have been compared to length change of control concrete (devoid of fibres at 3 storage intervals: early-age (0–7 days, short-term (0–28 days, and long-term (28–112 days intervals. The shrinkage results of FRC and control concrete up to 112 days indicated that all PVA-FRC mixes exhibited higher drying shrinkage than control. The shrinkage exhibited by PVA-FRC mixes ranged from 449 to 480 microstrain, where this value was only 427 microstrain in the case of control. In addition, the longer fibres exhibited higher mass loss, thus potentially contributing to higher shrinkage.

  18. Pore Structure and Influence of Recycled Aggregate Concrete on Drying Shrinkage

    Directory of Open Access Journals (Sweden)

    Yuanchen Guo

    2013-01-01

    Full Text Available Pore structure plays an important role in the drying shrinkage of recycled aggregate concrete (RAC. High-precision mercury intrusion and water evaporation were utilized to study the pore structure of RAC, which has a different replacement rate of recycled concrete aggregate (RCA, and to analyze its influence on drying shrinkage. Finally, a fractal-dimension calculation model was established based on the principles of mercury intrusion and fractal-geometry theory. Calculations were performed to study the pore-structure fractal dimension of RAC. Results show the following. (1 With the increase in RCA content, the drying shrinkage values increase gradually. (2 Pores with the greatest impact on concrete shrinkage are those whose sizes ranging from 2.5 nm to 50 nm and from 50 nm to 100 nm. In the above two ranges, the proportions of RAC are greater than those of RC0 (natural aggregate concrete, NAC, which is the main reason the shrinkage values of RAC are greater than those of NAC. (3 The pore structure of RAC has good fractal feature, and the addition of RCA increases the complexity of the pore surface of concrete.

  19. A Pore-Centric Model for Combined Shrinkage and Gas Porosity in Alloy Solidification

    Science.gov (United States)

    Khalajzadeh, Vahid; Carlson, Kent D.; Backman, Daniel G.; Beckermann, Christoph

    2017-04-01

    A unified model has been developed for combined gas- and shrinkage-induced pore formation during solidification of metal alloys. The model is based on a pore-centric approach, in which the temporal evolution of the pore radius is calculated as a function of cooling rate, thermal gradient, gas diffusion, and shrinkage. It accounts for the effect of porosity formation on the liquid velocity within the mushy zone. Simulations for an aluminum alloy show that the porosity transitions smoothly from shrinkage-induced to gas-induced as the Niyama value is increased. A Blake (cavitation) instability is observed to occur when the porosity is both gas- and shrinkage-driven. A revised dimensionless Niyama curve for pure shrinkage is presented. The experimentally observed gas porosity trend that the pore volume decreases with increasing cooling rate is well predicted. The pore-centric formulation allows the present model to be solved locally, at any point in a casting, during a regular casting simulation.

  20. The effects of dimensional mould sizes on volumetric shrinkage strain of lateritic soil

    Directory of Open Access Journals (Sweden)

    John Engbonye SANI

    2016-07-01

    Full Text Available Dimensional influences of specimen size on the volumetric shrinkage strain values of a lateritic soil for waste containment system have not been researched upon. Therefore, this paper presents the result of a laboratory study on the volumetric shrinkage strain (VSS of lateritic soil at three different dimensional sizes of mould (split former mould, proctor mould and California bearing ratio mould at three energy levels; British standard light (BSL, West African standard (WAS and British standard heavy (BSH respectively. Compactions were done at different molding water content of -2% to +6% optimum moisture content (OMC. At -2% to +2% molding water content for the split former mould the volumetric shrinkage strain met the requirement of not more than 4% while at +4% and +6% only the WAS and BSH met the requirement. The proctor mould and the CBR mould on the other hand gave a lower value of volumetric shrinkage strain in all compactive effort and the values are lower than the 4% safe VSS suggested by Tay et al., (2001. Based on the VSS values obtained if the CBR mould can be used to model site condition it is recommended for use to simulate site condition for Volumetric shrinkage strain for all molding water content and compactive effort.

  1. Perceptual shrinkage of a one-way motion path with high-speed motion.

    Science.gov (United States)

    Nakajima, Yutaka; Sakaguchi, Yutaka

    2016-07-28

    Back-and-forth motion induces perceptual shrinkage of the motion path, but such shrinkage is hardly perceived for one-way motion. If the shrinkage is caused by temporal averaging of stimulus position around the endpoints, it should also be induced for one-way motion at higher motion speeds. In psychophysical experiments with a high-speed projector, we tested this conjecture for a one-way motion stimulus at various speeds (4-100 deg/s) along a straight path. Results showed that perceptual shrinkage of the motion path was robustly observed in higher-speed motion (faster than 66.7 deg/s). In addition, the amount of the forwards shift at the onset position was larger than that of the backwards shift at the offset position. These results demonstrate that high-speed motion can induce shrinkage, even for a one-way motion path. This can be explained by the view that perceptual position is represented by the integration of the temporal average of instantaneous position and the motion representation.

  2. Shrinkage and growth compensation in common sunflowers: refining estimates of damage

    Science.gov (United States)

    Sedgwick, James A.; Oldemeye, John L.; Swenson, Elizabeth L.

    1986-01-01

    Shrinkage and growth compensation of artificially damaged common sunflowers (Helianthus annuus) were studied in central North Dakota during 1981-1982 in an effort to increase accuracy of estimates of blackbird damage to sunflowers. In both years, as plants matured damaged areas on seedheads shrank at a greater rate than the sunflower heads themselves. This differential shrinkage resulted in an underestimation of the area damaged. Sunflower head and damaged-area shrinkage varied widely by time and degree of damage and by size of the seedhead damaged. Because variation in shrinkage by time of damage was so large, predicting when blackbird damage occurs may be the most important factor in estimating seed loss. Yield'occupied seed area was greater (P < 0.05) for damaged than undamaged heads and tended to increase as degree of damage inflicted increased, indicating growth compensation was occurring in response to lost seeds. Yields of undamaged seeds in seedheads damaged during early seed development were higher than those of heads damaged later. This suggested that there was a period of maximal response to damage when plants were best able to redirect growth to seeds remaining in the head. Sunflowers appear to be able to compensate for damage of ≤ 15% of the total hear area. Estimates of damage can be improved by applying empirical results of differential shrinkage and growth compensations.

  3. Shrinkage Characteristics of Experimental Polymer Containing Composites under Controlled Light Curing Modes

    Directory of Open Access Journals (Sweden)

    Alain Pefferkorn

    2012-01-01

    Full Text Available The adsorption of polymethylmethacrylate polymer of different molecular weight at the aerosil/ethyleneglycol- or 1,3 butanediol-dimethacrylate interfaces was determined to provide microstructured networks. Their structural characteristics were determined to be controlled by the amount of polymer initially supplied to the system. The sediment (the settled phase characteristics, determined as a function of the polymer concentration and the rate of the polymerization shrinkage determined for composite resins, obtained by extrusion of the sediment after centrifugation, were found to be correlated. The specific role of the adsorbed polymer was found to be differently perturbed with the supplementary supply of dimethacrylate based monomer additives. Particularly, the bisphenol A dimethacrylate that generated crystals within the sediment was found to impede the shrinkage along the crystal lateral faces and strongly limit the shrinkage along its basal faces. Addition of ethyleneglycol- or polyethylene-glycoldimethacrylate monomers was determined to modify the sedimentation characteristics of the aerosil suspension and the shrinkage properties of the composites. Finally, the effects of stepwise light curing methods with prolonged lighting-off periods were investigated and found to modify the development and the final values of the composite shrinkage.

  4. Peridynamic model for fatigue cracking.

    Energy Technology Data Exchange (ETDEWEB)

    Silling, Stewart Andrew; Abe Askari (Boeing)

    2014-10-01

    The peridynamic theory is an extension of traditional solid mechanics in which the field equations can be applied on discontinuities, such as growing cracks. This paper proposes a bond damage model within peridynamics to treat the nucleation and growth of cracks due to cyclic loading. Bond damage occurs according to the evolution of a variable called the "remaining life" of each bond that changes over time according to the cyclic strain in the bond. It is shown that the model reproduces the main features of S-N data for typical materials and also reproduces the Paris law for fatigue crack growth. Extensions of the model account for the effects of loading spectrum, fatigue limit, and variable load ratio. A three-dimensional example illustrates the nucleation and growth of a helical fatigue crack in the torsion of an aluminum alloy rod.

  5. Properties evaluation of silorane, low-shrinkage, non-flowable and flowable resin-based composites in dentistry

    OpenAIRE

    Maia, Rodrigo R.; Reis, Rodrigo S.; Moro, André F.V.; Perez, Cesar R.; Bárbara M. Pessôa; Dias, Katia R.H.C.

    2015-01-01

    Purpose. This study tested the null hypothesis that different classes of direct restorative dental materials: silorane-based resin, low-shrinkage and conventional (non-flowable and flowable) resin-based composite (RBC) do not differ from each other with regard to polymerization shrinkage, depth of cure or microhardness. Methods. 140 RBC samples were fabricated and tested by one calibrated operator. Polymerization shrinkage was measured using a gas pycnometer both before and immediately after ...

  6. 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...

  7. Fiber Sensing of Micro -Crack

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Optical fiber sensors are used for sensing micro-cracking in composite and metal materials in aerospace applications. The sensing mechanism is based on the detection of acoustic emission signals, which are known to emanate from micro-cracks when they grow under further loading. The sensor head consists of a fiber Bragg grating that is capable of detecting acoustic emission signals generated by pencil lead breaking, of frequencies up to 200 kHz.

  8. Low-shrink composite resins: a review of their history, strategies for managing shrinkage, and clinical significance.

    Science.gov (United States)

    Pitel, Mark L

    2013-09-01

    Despite numerous advances in composite resin technology over the course of many decades, shrinkage behavior and the resultant stresses inherent to direct placed composite restorations continue to challenge clinicians. This overview of composite resins includes a review of their history and development along with a discussion of strategies for reducing polymerization shrinkage. An assessment of the clinical significance of these materials is also provided, including a discussion of the differences between polymerization shrinkage and stress, incremental layering versus bulk placement, and the emergence of lower shrinkage stress monomer chemistry.

  9. Computed tomography evaluation of autogenous graft in sinus lift surgery; Analise por tomografia computadorizada do enxerto autogeno na cirurgia de 'sinus lift'

    Energy Technology Data Exchange (ETDEWEB)

    Ajzen, Sergio Aron; Moscatiello, Rafael Andrade; Lima, Aida Maria Custodio de; Moscatiello, Vitoria Aparecida Muglia; Helio Kiitiro Yamashita [Universidade Federal de Sao Paulo (UNIFESP/EPM), SP (Brazil). Dept. de Diagnostico por Imagem; Mosacatiello, Rafael Muglia; Nishiguchi, Celso Itiro [Universidade Federal de Sao Paulo (UNIFESP/EPM), SP (Brazil). Disciplina de Tecnica Operatoria e Cirurgia Experimental; Alves, Maria Teresa de Seixas [Universidade Federal de Sao Paulo (UNIFESP/EPM), SP (Brazil). Disciplina de Anatomia Patologica

    2001-02-01

    The objective was to quantify bone formation within autogenous bone grafts and autogenous bone grafts in combination with platelet-rich plasma obtained either from apheresis or centrifugation using computed tomography. This prospective, double-blind study was conducted in 34 male and female adult patients (mean age of 28 years and 8 months), with either unilateral or bilateral pneumatization of the maxillary sinuses, requiring bone graft for dental implant. All patients were submitted to computed tomography examinations prior and six months after sinus lift surgery. Fifty-three maxillary sinuses were operated and divided into three distinct groups: autogenous bone graft, autogenous bone graft in combination with platelet-rich plasma obtained by centrifugation, and autogenous bone graft in combination with platelet-rich plasma obtained by apheresis. The results showed that computed tomography demonstrated bone growth in height and width between the initial and the follow-up computed tomography scans in all three groups. However, no statistical difference was found either for bone height or width. It was concluded that clinical evidence demonstrates the effectiveness of autogenous bone grafts, particularly when used in combination with bone growth factors such as platelet-rich plasma, which allow prosthetic and functional restoration of maxillofacial structures through fixation of dental implants. (author)

  10. Analysis of internal crack in a six-ton P91 ingot

    Directory of Open Access Journals (Sweden)

    Jing-an Yang

    2016-05-01

    Full Text Available P91 is a new kind of heat-resistant and high-tensile steel. It can be extruded after ingot casting and can be widely used for different pipes in power plants. However, due to its mushy freezing characteristics, a lack of feeding in the ingot center often generates many defects, such as porosity and crack. A six-ton P91 ingot was cast and sliced, and a representative part of the longitudinal section was inspected in more detail. The morphology of crack-like defects was examined by X-ray high energy industrial CT and reconstructed by 3D software. There are five main portions of defects larger than 200 mm3, four of which are interconnected. These initiated from continuous liquid film, and then were torn apart by excessive tensile stress within the brittle temperature range (BTR. The 3D FEM analysis of thermo-mechanical simulation was carried out to analyze the formation of porosity and internal crack defects. The results of shrinkage porosity and Niyama values revealed that the center of the ingot suffers from inadequate feeding. Several criteria based on thermal and mechanical models were used to evaluate the susceptibility of hot crack formation. The Clyne and Davies’ criterion and Katgerman’s criterion successfully predicted the high hot crack susceptibility in the ingot center. Six typical locations in the longitudinal section had been chosen for analysis of the stresses and strains evolution during the BTR. Locations in the defects region showed the highest tensile stresses and relative high strain values, while other locations showed either low tensile stresses or low strain values. In conclusion, hot crack develops only when stress and strain exceed a threshold value at the same time during the BTR.

  11. Polymerization shrinkage and contraction force of composite resin restorative inserted with "Megafiller".

    Science.gov (United States)

    Tani, Y; Nambu, T; Ishikawa, A; Katsuyama, S

    1993-12-01

    This study quantified the contraction force and polymerization shrinkage of composite resins with/without beta-Quartz Glass Ceramic Inserts (BQCI) as "Megafiller". The materials used for the determination included a chemically cured composite and five light-cured composites. The system for measuring contraction force consisted of a transparent teflon tube for preparing the specimen, a small load cell, a dynamic strain gauge and a pen-recorder. After the composite was packed into the teflon mold, a BQCI (Type R3) was inserted through the opening and the specimen was cured. Linear polymerization shrinkage of the composites was measured every 10 seconds from the start of mixing or irradiation to 90 minutes by the mercury bath method. Three pieces each of BQCI (Type T3) were inserted in each specimen. The results suggested that BQCI was markedly effective in reducing polymerization shrinkage, but was not always effective in reducing the contraction force during polymerization.

  12. Dental composite resins: measuring the polymerization shrinkage using optical fiber Bragg grating sensors

    Science.gov (United States)

    Ottevaere, H.; Tabak, M.; Chah, K.; Mégret, P.; Thienpont, H.

    2012-04-01

    Polymerization shrinkage of dental composite materials is recognized as one of the main reasons for the development of marginal leakage between a tooth and filling material. As an alternative to conventional measurement methods, we propose optical fiber Bragg grating (FBG) based sensors to perform real-time strain and shrinkage measurements during the curing process of dental resin cements. We introduce a fully automated set-up to measure the Bragg wavelength shift of the FBG strain sensors and to accurately monitor the linear strain and shrinkage of dental resins during curing. Three different dental resin materials were studied in this work: matrix-filled BisGMA-based resins, glass ionomers and organic modified ceramics.

  13. Fast approach to infrared image restoration based on shrinkage functions calibration

    Science.gov (United States)

    Zhang, Chengshuo; Shi, Zelin; Xu, Baoshu; Feng, Bin

    2016-05-01

    High-quality image restoration in real time is a challenge for infrared imaging systems. We present a fast approach to infrared image restoration based on shrinkage functions calibration. Rather than directly modeling the prior of sharp images to obtain the shrinkage functions, we calibrate them for restoration directly by using the acquirable sharp and blurred image pairs from the same infrared imaging system. The calibration method is employed to minimize the sum of squared errors between sharp images and restored images from the blurred images. Our restoration algorithm is noniterative and its shrinkage functions are stored in the look-up tables, so an architecture solution of pipeline structure can work in real time. We demonstrate the effectiveness of our approach by testing its quantitative performance from simulation experiments and its qualitative performance from a developed wavefront coding infrared imaging system.

  14. Hormone replacement therapy and age-related brain shrinkage: regional effects.

    Science.gov (United States)

    Raz, Naftali; Rodrigue, Karen M; Kennedy, Kristen M; Acker, James D

    2004-11-15

    Neuroprotective properties of estrogen have been established in animal models, but clinical trials of hormone replacement therapy (HRT) produced contradictory results. We examined the impact of HRT on age-related regional changes in human brain volume. Six brain regions were measured twice, five years apart, in 12 healthy women who took HRT and in matched controls who did not. The controls showed a typical pattern of differential brain shrinkage in the association cortices and the hippocampus with no change in the primary visual cortex. In contrast, women who took HRT showed comparable shrinkage of the hippocampus but no significant shrinkage of the neocortex. Future large scale studies may benefit from applying regional rather than global measures in assessment of brain integrity.

  15. Adaptive contourlet-wavelet iterative shrinkage/thresholding for remote sensing image restoration

    Institute of Scientific and Technical Information of China (English)

    Nu WEN; Shi-zhi YANG; Cheng-jie ZHU; Sheng-cheng CUI

    2014-01-01

    In this paper, we present an adaptive two-step contourlet-wavelet iterative shrinkage/thresholding (TcwIST) algorithm for remote sensing image restoration. This algorithm can be used to deal with various linear inverse problems (LIPs), including image deconvolution and reconstruction. This algorithm is a new version of the famous two-step iterative shrinkage/thresholding (TwIST) algorithm. First, we use the split Bregman Rudin-Osher-Fatemi (ROF) model, based on a sparse dictionary, to decom-pose the image into cartoon and texture parts, which are represented by wavelet and contourlet, respectively. Second, we use an adaptive method to estimate the regularization parameter and the shrinkage threshold. Finally, we use a linear search method to find a step length and a fast method to accelerate convergence. Results show that our method can achieve a signal-to-noise ratio improvement (ISNR) for image restoration and high convergence speed.

  16. Cell shrinkage as a signal to apoptosis in NIH 3T3 fibroblasts

    DEFF Research Database (Denmark)

    Friis, Martin B; Friborg, Christel R; Schneider, Linda;

    2005-01-01

    Cell shrinkage is a hallmark of the apoptotic mode of programmed cell death, but it is as yet unclear whether a reduction in cell volume is a primary activation signal of apoptosis. Here we studied the effect of an acute elevation of osmolarity (NaCl or sucrose additions, final osmolarity 687...... mosmol l(-1)) on NIH 3T3 fibroblasts to identify components involved in the signal transduction from shrinkage to apoptosis. After 1.5 h the activity of caspase-3 started to increase followed after 3 h by the appearance of many apoptotic-like bodies. The caspase-3 activity increase was greatly enhanced...... in cells expressing a constitutively active G protein, Rac (RacV12A3 cell), indicating that Rac acts upstream to caspase-3 activation. The stress-activated protein kinase, p38, was significantly activated by phosphorylation within 30 min after induction of osmotic shrinkage, the phosphorylation being...

  17. Thermal assisted ion shrinkage (TAIS) of fluorinated polyimide for optical telecommunication devices

    Science.gov (United States)

    Trigaud, T.; Moliton, J. P.; Quillat, M.; Chiron, D.

    1999-06-01

    In the framework of the development of low cost optical devices for telecommunications, here is studied the shrinkage of 6FDA-ODA polyimide films by ion irradiation as a function of five parameters: the ion fluence, the ion fluence rate, the ion energy, the ion nature and the target temperature. In the 30-350 keV energy range for impinging ions, the shrinkage remains constant whatever the tested fluence rate is. An upper limit appears for fluences above 10 16 ions cm -2. The etching is linearly dependent on the ion beam energy and reaches a maximum around 1 μm by thermal assisted ion shrinkage (TAIS) with Na + irradiations.

  18. Hormone-dependent shrinkage of a sphenoid wing meningioma after pregnancy: case report.

    Science.gov (United States)

    Kerschbaumer, Johannes; Freyschlag, Christian F; Stockhammer, Günter; Taucher, Susanne; Maier, Hans; Thomé, Claudius; Seiz-Rosenhagen, Marcel

    2016-01-01

    Meningiomas are known to be associated with female sex hormones. Worsening neurological symptoms or newly diagnosed meningiomas have been described in the context of elevated levels of sex hormones, for example, in pregnancy. To the authors' knowledge, tumor shrinkage after the normalization of hormones has not been described, even if it is known that neurological deficits due to meningioma compression may improve after giving birth. A 32-year-old female patient presented with severe headache and vision disturbances at the end of her second pregnancy. Magnetic resonance imaging revealed an extended mass at the lateral left-sided sphenoid wing that was suspected to be a meningioma. After delivery, the patient's symptoms improved, and MRI obtained 2 months postpartum showed significant shrinkage of the lesion. Significant tumor shrinkage can occur after pregnancy. Thus, repeat imaging is indicated in these patients.

  19. Regional brain shrinkage over two years: individual differences and effects of pro-inflammatory genetic polymorphisms.

    Science.gov (United States)

    Persson, N; Ghisletta, P; Dahle, C L; Bender, A R; Yang, Y; Yuan, P; Daugherty, A M; Raz, N

    2014-12-01

    We examined regional changes in brain volume in healthy adults (N=167, age 19-79years at baseline; N=90 at follow-up) over approximately two years. With latent change score models, we evaluated mean change and individual differences in rates of change in 10 anatomically-defined and manually-traced regions of interest (ROIs): lateral prefrontal cortex (LPFC), orbital frontal cortex (OF), prefrontal white matter (PFw), hippocampus (Hc), parahippocampal gyrus (PhG), caudate nucleus (Cd), putamen (Pt), insula (In), cerebellar hemispheres (CbH), and primary visual cortex (VC). Significant mean shrinkage was observed in the Hc, CbH, In, OF, and PhG, and individual differences in change were noted in all regions, except the OF. Pro-inflammatory genetic variants modified shrinkage in PhG and CbH. Carriers of two T alleles of interleukin-1β (IL-1β C-511T, rs16944) and a T allele of methylenetetrahydrofolate reductase (MTHFR C677T, rs1801133) polymorphisms showed increased PhG shrinkage. No effects of a pro-inflammatory polymorphism for C-reactive protein (CRP-286C>A>T, rs3091244) or apolipoprotein (APOE) ε4 allele were noted. These results replicate the pattern of brain shrinkage observed in previous studies, with a notable exception of the LPFC, thus casting doubt on the unique importance of prefrontal cortex in aging. Larger baseline volumes of CbH and In were associated with increased shrinkage, in conflict with the brain reserve hypothesis. Contrary to previous reports, we observed no significant linear effects of age and hypertension on regional brain shrinkage. Our findings warrant further investigation of the effects of neuroinflammation on structural brain change throughout the lifespan.

  20. Sparse contrast-source inversion using linear-shrinkage-enhanced inexact Newton method

    KAUST Repository

    Desmal, Abdulla

    2014-07-01

    A contrast-source inversion scheme is proposed for microwave imaging of domains with sparse content. The scheme uses inexact Newton and linear shrinkage methods to account for the nonlinearity and ill-posedness of the electromagnetic inverse scattering problem, respectively. Thresholded shrinkage iterations are accelerated using a preconditioning technique. Additionally, during Newton iterations, the weight of the penalty term is reduced consistently with the quadratic convergence of the Newton method to increase accuracy and efficiency. Numerical results demonstrate the applicability of the proposed method.

  1. Method and application of wavelet shrinkage denoising based on genetic algorithm

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Genetic algorithm (GA) based on wavelet transform threshold shrinkage (WTS) and translation-invafiant threshold shrinkage (TIS) is introduced into the method of noise reduction, where parameters used in WTS and TIS, such as wavelet function,decomposition levels, hard or soft threshold and threshold can be selected automatically. This paper ends by comparing two noise reduction methods on the basis of their denoising performances, computation time, etc. The effectiveness of these methods introduced in this paper is validated by the results of analysis of the simulated and real signals.

  2. Alcohol consumption and frontal lobe shrinkage: study of 1432 non-alcoholic subjects

    OpenAIRE

    Kubota, M.; Nakazaki, S.; Hirai, S.; Saeki, N; YAMAURA, A.; Kusaka, T

    2001-01-01

    OBJECTIVES—To evaluate the influences of chronic alcohol consumption on brain volume among social drinkers, as it is well known that alcohol misusers have a high risk of brain shrinkage.
METHODS—Frontal lobe volumes on MRI were compared with the current alcohol habits of consecutive 1432 non-alcoholic subjects.
RESULTS—After adjusting for other variables, age was found to be the most powerful promoting factor for the shrinkage with a odds ratio of 2.8 (95% confidence i...

  3. Mining pharmacovigilance data using Bayesian logistic regression with James-Stein type shrinkage estimation.

    Science.gov (United States)

    An, Lihua; Fung, Karen Y; Krewski, Daniel

    2010-09-01

    Spontaneous adverse event reporting systems are widely used to identify adverse reactions to drugs following their introduction into the marketplace. In this article, a James-Stein type shrinkage estimation strategy was developed in a Bayesian logistic regression model to analyze pharmacovigilance data. This method is effective in detecting signals as it combines information and borrows strength across medically related adverse events. Computer simulation demonstrated that the shrinkage estimator is uniformly better than the maximum likelihood estimator in terms of mean squared error. This method was used to investigate the possible association of a series of diabetic drugs and the risk of cardiovascular events using data from the Canada Vigilance Online Database.

  4. Hinge-free topology optimization with embedded translation-invariant differentiable wavelet shrinkage

    DEFF Research Database (Denmark)

    Yoon, G. H.; Kim, Y. Y.; Bendsøe, Martin P.;

    2004-01-01

    In topology optimization applications for the design of compliant mechanisms, the formation of hinges is typically encountered. Often such hinges are unphysical artifacts that appear due to the choice of discretization spaces for design and analysis. The objective of this work is to present a new...... in the multiscale design space. To imbed the shrinkage method implicitly in the optimization formulation and thus facilitate sensitivity analysis, the shrinkage method is made differentiable by means of differentiable versions of logical operators. The validity of the present method is confirmed by solving typical...... two-dimensional compliant mechanism design problems....

  5. Hard and Soft Tissue Management of a Localized Alveolar Ridge Atrophy with Autogenous Sources and Biomaterials: A Challenging Clinical Case

    Science.gov (United States)

    Andreoni, D.

    2016-01-01

    Particularly in the premaxillary area, the stability of hard and soft tissues plays a pivotal role in the success of the rehabilitation from both a functional and aesthetic aspect. The present case report describes the clinical management of a localized alveolar ridge atrophy in the area of the upper right canine associated with a thin gingival biotype with a lack of keratinized tissue. An autogenous bone block harvested from the chin associated with heterologous bone particles was used to replace the missing bone, allowing for a prosthetic driven implant placement. Soft tissues deficiency was corrected by means of a combined epithelialized and subepithelial connective tissue graft. The 3-year clinical and radiological follow-up demonstrated symmetric gingival levels of the upper canines, with physiological peri-implant probing depths and bone loss. Thus, the use of autogenous tissues combined with biomaterials might be considered a reliable technique in case of highly aesthetic demanding cases.

  6. Hard and Soft Tissue Management of a Localized Alveolar Ridge Atrophy with Autogenous Sources and Biomaterials: A Challenging Clinical Case

    Directory of Open Access Journals (Sweden)

    C. Maiorana

    2016-01-01

    Full Text Available Particularly in the premaxillary area, the stability of hard and soft tissues plays a pivotal role in the success of the rehabilitation from both a functional and aesthetic aspect. The present case report describes the clinical management of a localized alveolar ridge atrophy in the area of the upper right canine associated with a thin gingival biotype with a lack of keratinized tissue. An autogenous bone block harvested from the chin associated with heterologous bone particles was used to replace the missing bone, allowing for a prosthetic driven implant placement. Soft tissues deficiency was corrected by means of a combined epithelialized and subepithelial connective tissue graft. The 3-year clinical and radiological follow-up demonstrated symmetric gingival levels of the upper canines, with physiological peri-implant probing depths and bone loss. Thus, the use of autogenous tissues combined with biomaterials might be considered a reliable technique in case of highly aesthetic demanding cases.

  7. Autogenous grafts for condylar reconstruction in treatment of TMJ ankylosis: current concepts and considerations for the future.

    Science.gov (United States)

    Khadka, A; Hu, J

    2012-01-01

    Temporomandibular joint (TMJ) ankylosis is characterized by difficulty or inability to open the mouth due to fusion of the temporal and the mandible, resulting in facial symmetry/deformity, malocclusion and dental problems. The only treatment option for TMJ ankylosis is surgical with or without condylar reconstruction. Various autogenous grafts are available for condylar reconstruction after freeing the ankylotic mass such as costochondral, sternoclavicular, fibular, coronoid, and metatarsophalangeal. Costochondral graft is preferred by surgeons, but distraction osteogenesis is slowly gaining popularity and may ultimately become the standard procedure, providing a cost-effective approach with low morbidity and excellent functional outcomes. Tissue engineering is another budding field which has shown promising results in animal studies but has not been applied to humans. To date, there is no ideal autogenous graft for condylar reconstruction that satisfies the complex anatomy and the myriad of functions of a missing condyle.

  8. Fiber Bragg grating sensors as a tool to evaluate the influence of filler on shrinkage of geopolymer matrices

    Science.gov (United States)

    Campopiano, Stefania; Iadicicco, Agostino; Messina, Francesco; Ferone, Claudio; Cioffi, Raffaele

    2015-05-01

    Geopolymer matrices represent one of the main sustainable alternatives to ordinary Portland cement (OPC) and other clinker-based blended cements. Real scale applications are limited and a relevant amount of data is still needed to assess the early age and long-term behavior of these systems. Particularly, the early-age monitoring of geopolymers represent a key parameter for mix design optimization. Most of the available methods for the measurement of temperature evolution due to polycondensation kinetics and early age deformations are related to laboratory activities. The upscaling to in situ techniques represents a crucial step toward technological assessment. To this aim, authors propose to use Fiber Bragg Gratings (FBGs) embedded in the geopolymer matrices. Starting from a case study by authors related to the design of externally bonded fiber reinforced geopolymers for strengthening of existing structures, the matrix was optimized in terms of quartz filler content. The measurements carried out by means of FBG sensors allowed to reduce filler content respect to the abovementioned work. Particularly, quartz content can be reduced by 50%. The temperature associated to polycondensation was slightly below 65°C for the three studied systems, limiting the use of designed metakaolin geopolymer to non-massive structures, since thermal cracking could occur, unless further research will be able to assess the viability of retardants. The experimental results confirm that FBG represent an accurate method for simultaneous shrinkage and temperature measurements for geopolymers and the application in real scale structures for remote sensing could help to create database on inner temperatures and early age deformations.

  9. Fatigue reliability of cracked engineering structures

    Science.gov (United States)

    Lanning, David Bruce, Jr.

    1997-12-01

    This study investigates the reliability of engineering structures containing fatigue cracks. Stress concentrations and welded joints are probable locations for the initiation and propagation of fatigue cracks. Due to the many unknowns of loading, materials properties, crack sizes and crack shapes present at these locations, a statistics-based reliability analysis is valuable in the careful consideration of these many different random factors involved in a fatigue life analysis, several of which are expanded upon in this study. The basic problem of a crack near a stress concentration is first considered. A formulation for the aspect ratio (a/c) of a propagating semi-elliptical fatigue crack located at the toe of a welded T-joint is developed using Newman and Raju's stress intensity factor for a cracked flat plate with a weld magnification factor and compared to that of a cracked flat plate, and the reliability in terms of fatigue lifetime is calculated with the aid of Paris' crack propagation equation for membrane and bending loadings. Crack closure effects are then introduced in the consideration of short crack effects, where crack growth rates typically may exceed those found using traditional linear elastic fracture mechanics solutions for long cracks. The probability of a very small, microstructurally influenced crack growing to a size influenced by local plastic conditions is calculated utilizing the probability of a crack continuing to grow past an obstacle, such as a grain boundary. The result is then combined with the probability for failure defined using the crack closure-modified Paris equation to find an overall reliability for the structure. Last, the probability of fracture is determined when a crack front encounters regions of non-uniform toughness, such as typical in the heat affected zone of a welded joint. An expression for the effective crack lengths of the dissimilar regions is derived, and used in a weakest-link fracture model in the evaluation

  10. Properties evaluation of silorane, low-shrinkage, non-flowable and flowable resin-based composites in dentistry

    Directory of Open Access Journals (Sweden)

    Rodrigo R. Maia

    2015-06-01

    Full Text Available Purpose. This study tested the null hypothesis that different classes of direct restorative dental materials: silorane-based resin, low-shrinkage and conventional (non-flowable and flowable resin-based composite (RBC do not differ from each other with regard to polymerization shrinkage, depth of cure or microhardness.Methods. 140 RBC samples were fabricated and tested by one calibrated operator. Polymerization shrinkage was measured using a gas pycnometer both before and immediately after curing with 36 J/cm2 light energy density. Depth of cure was determined, using a penetrometer and the Knoop microhardness was tested from the top surface to a depth of 5 mm.Results. Considering polymerization shrinkage, the authors found significant differences (p < 0.05 between different materials: non-flowable RBCs showed lower values compared to flowable RBCs, with the silorane-based resin presenting the smallest shrinkage. The low shrinkage flowable composite performed similarly to non-flowable with significant statistical differences compared to the two other flowable RBCs. Regarding to depth of cure, low-shrinkage flowable RBC, were most effective compared to other groups. Microhardness was generally higher for the non-flowable vs. flowable RBCs (p < 0.05. However, the values for low-shrinkage flowable did not differ significantly from those of non-flowable, but were significantly higher than those of the other flowable RBCs.Clinical Significance. RBCs have undergone many modifications as they have evolved and represent the most relevant restorative materials in today’s dental practice. This study of low-shrinkage RBCs, conventional RBCs (non-flowable and flowable and silorane-based composite—by in vitro evaluation of volumetric shrinkage, depth of cure and microhardness—reveals that although filler content is an important determinant of polymerization shrinkage, it is not the only variable that affects properties of materials that were tested in

  11. 自体脂肪移植治疗川字纹%Autogenous Fat Grafting for Glabellar Wrinkles

    Institute of Scientific and Technical Information of China (English)

    祝联; 李丹

    2012-01-01

    Objective To explore the effect of local autogenous fat grafting for glabellar wrinkles. Methods From September 2010 to April 2012, autogenous fat was grafted in sub-dermis of glabellar wrinkles in 8 cases. The transferee! fat strengthened the local skin tension, and made the wrinkle expand and smooth. Results Three months after autogenous fat grafting, glabellar wrinkles were disappeared in all cases with local smooth skin Left. The wrinkle was reappeared in half a year only in one case. Conclusion Local autogenous fat grafting could provide suspension and filling for the specific kind of glabellar wrinkles, and this method is simple, safe and effective,%目的 探索自体脂肪移植治疗川字纹的临床疗效.方法 201O年9月至2012年4月,对8例川字纹患者的累及皮肤区域内进行真皮下自体脂肪注射,提升局部皮肤张力.结果 8例川字纹患者均随访1年,自体脂肪移植3个月后川字纹皱折消失,局部皮肤平坦;6个月后只有1例患者川字纹复发.结论 对于特定类型的川字纹,局部自体脂肪移植可使得发生皱折的皮肤得到充填和支撑,本方法操作简便、安全,疗效良好.

  12. The RANK/ RANKL/ OPG interaction in the repair of autogenous bone grafts in female rats with estrogen deficiency

    Directory of Open Access Journals (Sweden)

    Tábata de Mello TERA

    2014-01-01

    Full Text Available The aim of this study was to evaluate the resorption process during the repair of autogenous bone grafts with or without coverage by an expanded polytetrafluoroethylene (e-PTFE membrane in female rats with estrogen deficiency using the immunohistochemical technique. Eighty female rats were randomly divided into two groups (OVX and SHAM. The 40 female rats in the OVX group were subjected to ovariectomy, and the 40 female rats in the SHAM group were subjected to simulated ovariectomy. The two groups were further divided in subgroup E, which was subjected to surgery for placement of autogenous bone graft (ABG, and subgroup ME, in which the ABG was covered with an e-PTFE membrane. The animals were killed at 0, 7, 21, 45 and 60 days. The specimens were analyzed using immunohistochemistry for the bone resorption markers RANK, RANK-L and Osteoprotegerin (OPG. A higher remodeling rate was observed at 7 and 21 days after the autogenous bone grafts, when the markers were more intensely expressed. At the final time point, the specimens presented similar characteristics to those observed at the initial time point. The expression of immunohistochemical markers was not altered by the estrogen deficiency. The presence of the e-PTFE membrane delayed the bone resorption process, influencing the immunohistochemical expression of markers.

  13. SHORT FATIGUE CRACK PARAMETER BASED ON THE TOTAL CRACK AREA

    Institute of Scientific and Technical Information of China (English)

    Z.X.Wu; X.C.Wu

    2001-01-01

    The progressive fatigue damage of a material is closely related to the whole populationof cracks on the surface of an un-notched specimen.In order to understand whichparameter is a more useful indicator of fatigue damage,rotatory bending fatigue testswere carried out using smooth specimens of medium-carbon steel.The behavior ofshort crack propagation during fatigue was examined and a new parameter "totalcrack area" was suggested.The aim of this paper is to extend the research on fatiguedamage in the already studied steel and to study how these damage parameters arecorrelated with the process of fatigue damage in order to evaluate the effectiveness ofdamage detection methods.

  14. Ultrasonography-guided Balloon Angioplasty in an Autogenous Arteriovenous Fistula: Preliminary Results

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ji Chang [Daejeon St Mary' s Hospital, Daejeon (Korea, Republic of); Cho, June Sik [Chungnam National University College of Medicine, Daejeon (Korea, Republic of)

    2007-09-15

    Percutaneous trasnluminal angioplasty (PTA) of a malfunctioning arteriovenous fistula (AVF) in hemodialysis patients requires the use of contrast angiography and fluoroscopy guidance. We attempted to perform this procedure under duplex ultrasound guidance to reduce the amount of contrast agent administered and to reduce the radiation dose during the interventional procedures. From September 2006 to February 2007, 45 patients received interventional treatment due to malfunctioning hemodialysis access in our hospital. Among the patients, we selected 10 patients diagnosed with stenosis of an autogenous arteriovenous fistula based on a physical examination. There were six males and four females aged 51-78 years (mean age, 59 years). Seven of these patients had a Brescia-Cinimo type fistula and three patients had a basilic vein transposition. All procedures were performed in the angiography suite. All procedures that required angioplasty were performed under duplex ultrasound guidance and then contrast angiography was performed to confirm the final patency of the vessels. Conventional angioplasty was also performed under fluoroscopy guidance for any lesions that required an additional angioplasty. The volume flow before and after the PTA and procedure time were recorded. Clinical success was defined as the performance of one or more successful hemodialysis sessions after treatment. Eight of ten patients did not require an additional angioplasty by conventional angiography after the duplex- guided angioplasty. One case showed recoiling of stenosis after the duplex-guided PTA and another case was missed at duplex scanning due to the extremely short nature of the recoiling of stenosis. The mean volume flow before and after PTA was 167 ml/min (range, 80-259 ml/min) and 394.2 ml/min (range, 120-586 ml/min), respectively. No complications associated with the duplex-guide procedure occurred. In nine cases, PTA enabled hemodialysis to be conducted more than one time. In one

  15. IDENTIFICATION OF CRACKED ROTOR BY WAVELET TRANSFORM

    Institute of Scientific and Technical Information of China (English)

    邹剑; 陈进; 蒲亚鹏

    2002-01-01

    The dynamic equation of cracked rotor in rotational frame was modelled, the numerical simulation solutions of the cracked rotor and the uncracked rotor were obtained. By the wavelet transform, the time-frequency properties of the cracked rotor and the uncracked rotor were discussed, the difference of the time-frequency properties between the cracked rotor and the uncracked rotor was compared. A new detection algorithm using wavelet transform to identify crack was proposed. The experiments verify the availability and validity of the wavelet transform in identification of crack.

  16. The tissue shrinkage phenomenon on surgical margins in oral and oropharyngeal squamous cell carcinoma

    Institute of Scientific and Technical Information of China (English)

    David González-Ballester

    2016-01-01

    Aim: One of the most important factors associated with recurrence rate and overall survival is the status of surgical margin of resection free of disease. However, sometimes, the margins measured intra-operatively at the time of surgery differ of those measured by the pathologist in the histopathologic analysis. Faced with this dilemma, a literature review of the best available evidence was conducted in an attempt to determine how the phenomenon of tissue shrinkage may influence on the surgical margin of resection in patients undergoing oral and oropharyngeal squamous cell carcinoma (SCC).Methods: An electronic and manual search was conducted by one reviewer. A combination of controlled Medical Subjects Headings and keywords were used as search strategy. Inclusion and exclusion criteria were established.Results: Finally, after an exhaustive selection process, four articles fulfilled the inclusion criteria and were analyzed. All articles reported a decrease of surgical margin after resection. The tumor site and tumor stage seem to influence in degree of margin shrinkage.Conclusion:Tissue shrinkage on surgical margins of resection in oral SCC is a tangible phenomenon. There is a significant discrepancy between margins measured intraoperatively previous to resection and margins measured by pathologist after histologic processing. The highest percentage of retraction occurs at the time of resection. Margin shrinkage based on tumor site and tumor stage should be considered by any oncologic surgeon to ensure adequate margins of resection cleared of tumor.

  17. Sequential shrinkage and swelling underlie P2X7-stimulated lymphocyte phosphatidylserine exposure and death.

    Science.gov (United States)

    Taylor, Simon R J; Gonzalez-Begne, Mireya; Dewhurst, Stephen; Chimini, Giovanna; Higgins, Christopher F; Melvin, James E; Elliott, James I

    2008-01-01

    Patterns of change in cell volume and plasma membrane phospholipid distribution during cell death are regarded as diagnostic means of distinguishing apoptosis from necrosis, the former being associated with cell shrinkage and early phosphatidylserine (PS) exposure, whereas necrosis is associated with cell swelling and consequent lysis. We demonstrate that cell volume regulation during lymphocyte death stimulated via the purinergic receptor P2X7 is distinct from both. Within seconds of stimulation, murine lymphocytes undergo rapid shrinkage concomitant with, but also required for, PS exposure. However, within 2 min shrinkage is reversed and swelling ensues ending in cell rupture. P2X7-induced shrinkage and PS translocation depend upon K+ efflux via KCa3.1, but use a pathway of Cl- efflux distinct from that previously implicated in apoptosis. Thus, P2X7 stimulation activates a novel pathway of cell death that does not conform to those conventionally associated with apoptosis and necrosis. The mixed apoptotic/necrotic phenotype of P2X7-stimulated cells is consistent with a potential role for this death pathway in lupus disease.

  18. A modelling study of drying shrinkage damage in concrete repair systems

    NARCIS (Netherlands)

    Lukovic, M.; Savija, B.; Schlangen, E.; Ye, G.; van Breugel, K.

    2014-01-01

    Differential shrinkage between repair material and concrete substrate is considered to be the main cause of premature failure of repair systems (Martinola, Sadouki et al. 2001, Beushausen and Alexander 2007). Magnitude of induced stresses depends on many factors, for example the amount of restraint,

  19. Astrocytic mechanisms explaining neural-activity-induced shrinkage of extraneuronal space.

    Directory of Open Access Journals (Sweden)

    Ivar Østby

    2009-01-01

    Full Text Available Neuronal stimulation causes approximately 30% shrinkage of the extracellular space (ECS between neurons and surrounding astrocytes in grey and white matter under experimental conditions. Despite its possible implications for a proper understanding of basic aspects of potassium clearance and astrocyte function, the phenomenon remains unexplained. Here we present a dynamic model that accounts for current experimental data related to the shrinkage phenomenon in wild-type as well as in gene knockout individuals. We find that neuronal release of potassium and uptake of sodium during stimulation, astrocyte uptake of potassium, sodium, and chloride in passive channels, action of the Na/K/ATPase pump, and osmotically driven transport of water through the astrocyte membrane together seem sufficient for generating ECS shrinkage as such. However, when taking into account ECS and astrocyte ion concentrations observed in connection with neuronal stimulation, the actions of the Na(+/K(+/Cl(- (NKCC1 and the Na(+/HCO(3 (- (NBC cotransporters appear to be critical determinants for achieving observed quantitative levels of ECS shrinkage. Considering the current state of knowledge, the model framework appears sufficiently detailed and constrained to guide future key experiments and pave the way for more comprehensive astroglia-neuron interaction models for normal as well as pathophysiological situations.

  20. Brain shrinkage in alcoholics is not caused by changes in hydration: a pathological study.

    OpenAIRE

    Harper, C. G.; Kril, J J; Daly, J.M.

    1988-01-01

    Measurement of the water content of the cerebral white matter in 26 control and 24 alcoholic cases supports in vivo MRI studies and previous necropsy studies which appeared to show an increase in the water content in the alcoholic group. This negates the hypothesis that reversible brain shrinkage in alcoholics is caused by changes in the state of hydration.

  1. Differential brain shrinkage over 6 months shows limited association with cognitive practice.

    Science.gov (United States)

    Raz, Naftali; Schmiedek, Florian; Rodrigue, Karen M; Kennedy, Kristen M; Lindenberger, Ulman; Lövdén, Martin

    2013-07-01

    The brain shrinks with age, but the timing of this process and the extent of its malleability are unclear. We measured changes in regional brain volumes in younger (age 20-31) and older (age 65-80) adults twice over a 6 month period, and examined the association between changes in volume, history of hypertension, and cognitive training. Between two MRI scans, 49 participants underwent intensive practice in three cognitive domains for 100 consecutive days, whereas 23 control group members performed no laboratory cognitive tasks. Regional volumes of seven brain structures were measured manually and adjusted for intracranial volume. We observed significant mean shrinkage in the lateral prefrontal cortex, the hippocampus, the caudate nucleus, and the cerebellum, but no reliable mean change of the prefrontal white matter, orbital-frontal cortex, and the primary visual cortex. Individual differences in change were reliable in all regions. History of hypertension was associated with greater cerebellar shrinkage. The cerebellum was the only region in which significantly reduced shrinkage was apparent in the experimental group after completion of cognitive training. Thus, in healthy adults, differential brain shrinkage can be observed in a narrow time window, vascular risk may aggravate it, and intensive cognitive activity may have a limited effect on it.

  2. Significant reversibility of alcoholic brain shrinkage within 3 weeks of abstinence.

    Science.gov (United States)

    Trabert, W; Betz, T; Niewald, M; Huber, G

    1995-08-01

    Chronic alcoholism is often associated with brain shrinkage or atrophy. During recent years, it has been demonstrated that this shrinkage is, at least in part, reversible when abstinence is maintained. There are different hypotheses concerning the mechanisms for this reversibility, but many questions are still open. Especially the time conditions for these reversible changes are subject of discussion. Twenty-eight male patients with severe alcohol dependence were investigated in a computed tomographic study at the beginning of abstinence and 3 weeks later. Planimetric evaluation of 5 selected slices revealed a significant decrease in liquor areas and an increase of brain volume. The densitometric analysis showed an increase in brain tissue density. In a multiple regression approach it was shown that the reversibility was mostly influenced by the age of the patients. Our results support neither the hypothesis of an increase in brain water as the most important principle for reversibility in alcoholic brain shrinkage nor the hypothesis of augmented dendritic growth. Other mechanisms like reduced (during chronic intoxication) and normalized (during abstinence) cerebral hemoperfusion have to be considered as possible mechanisms for the reversibility of alcoholic brain shrinkage.

  3. Shrinkages in heavy-sized cast components of nodular cast iron – NDT and fatigue

    Directory of Open Access Journals (Sweden)

    Bleicher Christoph

    2014-06-01

    Full Text Available Material defects like shrinkages, dross, pores and chunky graphite are likely to occur in thick-walled castings and are a challenge for the foundries and their customers. These defects are mostly detected with handheld ultrasonic testing (UT or X-ray analysis. Within a research project done at the Fraunhofer Institute for Structural Durability and System Reliability LBF, the fatigue of Dross, shrinkages and chunky graphite in thick-walled cast material GGG-40 was estimated based on X-ray and fatigue tests on bending specimens. High fatigue reductions were received for the different material imperfections. Based on these impressions a further research project was executed at the Fraunhofer LBF to get an estimation of the informational value of UT in relation to fatigue of shrinkages in thick-walled castings of the material EN-GJS-400-18U-LT, EN-GJS-450-18 and EN-GJS-700-2. With the help of X-ray analysis and the UT technique Sampling Phased Array (SPA information about geometry and density were derived for a numerical analysis of shrinkages in thick-walled castings concerning fatigue. The following text summarizes the fatigue results achieved in the two research projects with the help of the X-ray and UT analysis.

  4. Numerical Analysis of Influence of the Mold Material on the Distribution of Shrinkage Cavities

    Directory of Open Access Journals (Sweden)

    R. Dyja

    2013-01-01

    Full Text Available Production of castings, like any other field of technology is aimed at providing high-quality product, free from defects. One of the maincauses of defects in castings is the phenomenon of shrinkage of the casting. This phenomenon causes the formation of shrinkage cavitiesand porosity in the casting. The major preventive measure is supplementing a shortage of liquid metal. For supplement to be effective, it is necessary to use risers in proper shapes. Usually, the risers are selected on the basis of determination the place of formation of hot-spots in the castings. Although in these places the shrinkage defects are most likely to occur, shape and size of these defects are also affected by other factors. The article describes the original program setting out the shape and location of possible cavities in the casting. In the program is also taken into account the effect of temperature on the change in volume of liquid metal and the resultant differences in the shape and size of formed shrinkage cavities. The aim of the article is to describe the influence that have material properties of the mold on the simulation results.

  5. Porous stainless steel hollow fibers with shrinkage-controlled small radial dimensions

    NARCIS (Netherlands)

    Luiten-Olieman, Mieke W.J.; Raaijmakers, Michiel J.T.; Winnubst, Louis; Wessling, Matthias; Nijmeijer, Arian; Benes, Nieck E.

    2011-01-01

    A method is presented for the preparation of thin (∼250 μm) porous stainless steel hollow fiber membranes based on dry–wet spinning of a particle-loaded polymer solution followed by heat treatment. Extraordinarily small radial dimensions were achieved by controlled shrinkage during thermal treatment

  6. Shrinkage kinetics of a methacrylate- and a silorane-based resin composite: effect on marginal integrity

    NARCIS (Netherlands)

    Gregor, L.; Bortolotto, T.; Feilzer, A.J.; Krejci, I.

    2013-01-01

    Purpose: To evaluate the relation between the linear displacement (LD), shrinkage force (SF) and marginal adaptation of a methacrylate- and a silorane-based composite. Materials and Methods: The LD and SF of 8 samples made of Filtek Supreme XT (methacrylate-based composite) and Filtek Silorane (silo

  7. Shrinkage of bubbles and drops in the lattice Boltzmann equation method for nonideal gases

    Science.gov (United States)

    Zheng, Lin; Lee, Taehun; Guo, Zhaoli; Rumschitzki, David

    2014-03-01

    One characteristic of multiphase lattice Boltzmann equation (LBE) methods is that the interfacial region has a finite (i.e., noninfinitesimal) thickness known as a diffuse interface. In simulations of, e.g., bubble or drop dynamics, for problems involving nonideal gases, one frequently observes that the diffuse interface method produces a spontaneous, nonphysical shrinkage of the bubble or drop radius. In this paper, we analyze in detail a single-fluid two-phase model and use a LBE model for nonideal gases in order to explain this fundamental problem. For simplicity, we only investigate the static bubble or droplet problem. We find that the method indeed produces a density shift, bubble or droplet shrinkage, as well as a critical radius below which the bubble or droplet eventually vanishes. Assuming that the ratio between the interface thickness D and the initial bubble or droplet radius r0 is small, we analytically show the existence of this density shift, bubble or droplet radius shrinkage, and critical bubble or droplet survival radius. Numerical results confirm our analysis. We also consider droplets on a solid surface with different curvatures, contact angles, and initial droplet volumes. Numerical results show that the curvature, contact angle, and the initial droplet volume have an effect on this spontaneous shrinkage process, consistent with the survival criterion.

  8. Properties of a New Dental Photocurable Matrix Resin with Low Shrinkage

    Institute of Scientific and Technical Information of China (English)

    FU Jing; JIA Fang; XU Haiping; JI Baohui; LIU Xiaoqing

    2011-01-01

    In order to reduce the amount of volumetric shrinkage that occurs in dental composites as a result of curing, a new kind of dental matrix resin combining bisphenol-S-bis(3-meth acry late-2-hydroxy propyl)ether(BisS-GMA) with the expanding monomer unsaturated spiro orthoesters 2-methylene-1, 4, 6-trispiro[4, 4] nonane (SOE) was prepared, with triethylene glycol dimethacrylate (TEGDMA) as diluent. CQ (camphorquinone) of 1wt% and DMAEMA (2-(dimethylamino) ethyl meth acrylate) of 2wt% were used as photoinitiation system to initiate the copolymerization of the matrix resins. The performance including volumetric shrinkage, degree of conversion and condition of the ring-opening reaction of SOE, as well as curing time and the tensile bond strength were investigated respectively by the dilatometer, Fourier transfer infrared, the universal testing machine, and so on.The ring-opening polymerization of SOE occurred. Meanwhile, the obtain copolymers were crosslinked. The matrix resin containing BisS-GMA and SOE showed a reduced amount of volumetric shrinkage at 1.52%, which is a promising strategy for obtaining a polymer with a low amount of volumetric shrinkage. Furthermore, the other properties were not compromised.

  9. Urban shrinkage, local housing markets and the role of voluntary community organisations

    DEFF Research Database (Denmark)

    Larsen, Jacob Norvig

    Since the beginning of the crisis in 2007-08 urban shrinkage has hit a large number of Danish municipalities, towns and villages outside the two major metropolitan areas in the country .Abandoned homes, plunging property prices and out-migration are among the major symptoms. As a consequence of t...

  10. Review of Environmentally Assisted Cracking

    Science.gov (United States)

    Sadananda, K.; Vasudevan, A. K.

    2011-02-01

    Many efforts have been made in the past by several researchers to arrive at some unifying principles governing the embrittlement phenomena. An inescapable conclusion reached by all these efforts was that the behavior is very complex. Hence, recognizing the complexity of material/environment behavior, we focus our attention here only in extracting some similarities in the experimental trends to arrive at some generic principles of behavior. Crack nucleation and growth are examined under static load in the presence of internal and external environments. Stress concentration, either pre-existing or in-situ generated, appears to be a requirement for embrittlement. A chemical stress concentration factor is defined for a given material/environment system as the ratio of failure stress with and without the damaging chemical environment. All factors that affect the buildup of the required stress concentration, such as planarity of slip, stacking fault energy, etc., also affect the stress-corrosion behavior. The chemical stress concentration factor is coupled with the mechanical stress concentration factor. In addition, generic features for all systems appear to be (a) an existence of a threshold stress as a function of concentration of the damaging environment and flow properties of the material, and (b) an existence of a limiting threshold as a function of concentration, indicative of a damage saturation for that environment. Kinetics of crack growth also depends on concentration and the mode of crack growth. In general, environment appears to enhance crack tip ductility on one side by the reduction of energy for dislocation nucleation and glide, and to reduce cohesive energy for cleavage, on the other. These two opposing factors are coupled to provide environmentally induced crack nucleation and growth. The relative ratio of these two opposing factors depends on concentration and flow properties, thereby affecting limiting thresholds. The limiting concentration or

  11. Assessment of murine brain tissue shrinkage caused by different histological fixatives using magnetic resonance and computed tomography imaging.

    Science.gov (United States)

    Wehrl, Hans F; Bezrukov, Ilja; Wiehr, Stefan; Lehnhoff, Mareike; Fuchs, Kerstin; Mannheim, Julia G; Quintanilla-Martinez, Leticia; Kohlhofer, Ursula; Kneilling, Manfred; Pichler, Bernd J; Sauter, Alexander W

    2015-05-01

    Especially for neuroscience and the development of new biomarkers, a direct correlation between in vivo imaging and histology is essential. However, this comparison is hampered by deformation and shrinkage of tissue samples caused by fixation, dehydration and paraffin embedding. We used magnetic resonance (MR) imaging and computed tomography (CT) imaging to analyze the degree of shrinkage on murine brains for various fixatives. After in vivo imaging using 7 T MRI, animals were sacrificed and the brains were dissected and immediately placed in different fixatives, respectively: zinc-based fixative, neutral buffered formalin (NBF), paraformaldehyde (PFA), Bouin-Holland fixative and paraformaldehyde-lysine-periodate (PLP). The degree of shrinkage based on mouse brain volumes, radiodensity in Hounsfield units (HU), as well as non-linear deformations were obtained. The highest degree of shrinkage was observed for PLP (68.1%, P brain shrinkage and only small deformations and is therefore recommended for in vivo ex vivo comparison studies.

  12. Taguchi design and flower pollination algorithm application to optimize the shrinkage of triaxial porcelain containing palm oil fuel ash

    Science.gov (United States)

    Zainudin, A.; Sia, C. K.; Ong, P.; Narong, O. L. C.; Nor, N. H. M.

    2017-01-01

    In the preparation of triaxial porcelain from Palm Oil Fuel Ash (POFA), a new parameter variable must be determined. The parameters involved are the particle size of POFA, percentage of POFA in triaxial porcelain composition, moulding pressure, sintering temperature and soaking time. Meanwhile, the shrinkage is the dependent variable. The optimization process was investigated using a hybrid Taguchi design and flower pollination algorithm (FPA). The interaction model of shrinkage was derived from regression analysis and found that the shrinkage is highly dependent on the sintering temperature followed by POFA composition, moulding pressure, POFA particle size and soaking time. The interaction between sintering temperature and soaking time highly affects the shrinkage. From the FPA process, targeted shrinkage approaching zero values were predicted for 142 μm particle sizes of POFA, 22.5 wt% of POFA, 3.4 tonne moulding pressure, 948.5 °C sintering temperature and 264 minutes soaking time.

  13. Shrinkage Behaviour of Spheroidal Graphite Cast Iron in Green and Dry Sand Molds for the Benchmarking of Solidification Simulation

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The effects of metallurgical and processing parameters on the formation of shrinkage cavities and porosities in spheroidal graphite cast iron have been studied, considering the parameters of carbon equivalent, inoculation, casting modulus, mold type (green or dry) and pouring temperature within specific ranges of these variables. Based on the orthogonal experiments, the metallurgical and processing parameters of the minimum casting shrinkage and the maximum casting shrinkage were obtained, and the effects of metallurgical and processing parameters on the formation of shrinkage cavities and porosities in spheroidal graphite cast iron castings were discussed. Finally,two regression equations relating these variables to the formation of shrinkage porosity were derived based upon the orthogonal experiments conducted.

  14. Cracking and corrosion recovery boiler

    Energy Technology Data Exchange (ETDEWEB)

    Suik, H. [Tallinn Technical University, Horizon Pulp and Paper, Tallinn (Estonia)

    1998-12-31

    The corrosion of heat surfaces and the cracking the drums are the main problems of the recovery boiler. These phenomena have been appeared during long-term operation of boiler `Mitsubishi - 315` erected at 1964. Depth of the crack is depending on the number of shutdowns and on operation time. Corrosion intensity of different heat surfaces is varying depend on the metal temperature and the conditions at place of positioning of tube. The lowest intensity of corrosion is on the bank tubes and the greatest is on the tubes of the second stage superheater and on the tubes at the openings of air ports. (orig.) 5 refs.

  15. Modified Dugdale crack models - some easy crack relations

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang

    1997-01-01

    are assumed to be self created by local materials flow. The strength sigma_CR predictid by the Dugdale model is sigma_CR =(E Gamma_CR/phi1)^½ where E and 1 are Young’s modulus and crack half-length respectively of the material considered. The so-called critical strain energy rate is Gamma_CR = sigma......_Ldelta_CR where sigma_L is strength, and at the same time constant flow stress, of the uncracked material while delta_CR is flow limit (displacement).Obviously predictions by the Dugdale model are most reliable for materials with stress-strain relations where flow can actually be described (or well approximated......) by a constant flow stress (sigma_L). A number of materials, however, do not at all exhibit this kind of flow. Such materials are considered in this paper by Modified Dugdale crack models which apply for any cohesive stress distribution in crack front areas. Formally modified Dugdale crack models exhibit...

  16. Properties evaluation of silorane, low-shrinkage, non-flowable and flowable resin-based composites in dentistry.

    Science.gov (United States)

    Maia, Rodrigo R; Reis, Rodrigo S; Moro, André F V; Perez, Cesar R; Pessôa, Bárbara M; Dias, Katia R H C

    2015-01-01

    Purpose. This study tested the null hypothesis that different classes of direct restorative dental materials: silorane-based resin, low-shrinkage and conventional (non-flowable and flowable) resin-based composite (RBC) do not differ from each other with regard to polymerization shrinkage, depth of cure or microhardness. Methods. 140 RBC samples were fabricated and tested by one calibrated operator. Polymerization shrinkage was measured using a gas pycnometer both before and immediately after curing with 36 J/cm(2) light energy density. Depth of cure was determined, using a penetrometer and the Knoop microhardness was tested from the top surface to a depth of 5 mm. Results. Considering polymerization shrinkage, the authors found significant differences (p flowable RBCs showed lower values compared to flowable RBCs, with the silorane-based resin presenting the smallest shrinkage. The low shrinkage flowable composite performed similarly to non-flowable with significant statistical differences compared to the two other flowable RBCs. Regarding to depth of cure, low-shrinkage flowable RBC, were most effective compared to other groups. Microhardness was generally higher for the non-flowable vs. flowable RBCs (p flowable did not differ significantly from those of non-flowable, but were significantly higher than those of the other flowable RBCs. Clinical Significance. RBCs have undergone many modifications as they have evolved and represent the most relevant restorative materials in today's dental practice. This study of low-shrinkage RBCs, conventional RBCs (non-flowable and flowable) and silorane-based composite-by in vitro evaluation of volumetric shrinkage, depth of cure and microhardness-reveals that although filler content is an important determinant of polymerization shrinkage, it is not the only variable that affects properties of materials that were tested in this study.

  17. UFA水泥基材料早期自干燥及自收缩研究%Research on Early Self-desiccation and Autogenous Shrinkage of Cement-based Materials Containing Ultra-fine Fly Ash

    Institute of Scientific and Technical Information of China (English)

    高英力; 马保国; 周士琼

    2007-01-01

    基于水泥石孔隙理论对超细粉煤灰(Ultra-fine fly ash,简称UFA)水泥基材料的早期自干燥效应进行了理论分析及试验研究.在此基础上,采用改进的混凝土自收缩试验装置对UFA混凝土的早期自收缩变形进行了测试.结果表明,相比于基准水泥石,UFA水泥石内部自干燥程度大大降低;且随着UFA的掺入,混凝土早期水化反应的有效水灰比增大,自收缩变形随之减小,进一步证明水泥基材料早期内部孔隙的自干燥效应与混凝土的早期自收缩变形具有较好的相关性.

  18. 平板法在掺锂渣高性能混凝土抗裂方面的应用%Application of flat band method in the crack aspect of lithium slag mixed HPC

    Institute of Scientific and Technical Information of China (English)

    李剑波; 陈海; 慈军

    2011-01-01

    采用正交试验法,通过平板开裂试验研究了不同掺量锂渣对混凝土塑性收缩、自收缩裂缝的影响,结果表明:锂渣混凝土早期裂缝的最大宽度、总长度以及总面积随锂渣掺量的增大而趋于减少。%Using the orthogonal test method,through the flat band cracking test,this paper researched the influence of lithium slag mixed to concrete plastic shrinkage and since the shrinkage crack.The results showed that:the increase of lithium slag mixed was accor

  19. Measurement, growth types and shrinkage of newly formed aerosol particles at an urban research platform

    Science.gov (United States)

    Salma, Imre; Németh, Zoltán; Weidinger, Tamás; Kovács, Boldizsár; Kristóf, Gergely

    2016-06-01

    Budapest platform for Aerosol Research and Training (BpART) was created for advancing long-term on-line atmospheric measurements and intensive aerosol sample collection campaigns in Budapest. A joint study including atmospheric chemistry or physics, meteorology, and fluid dynamics on several-year-long data sets obtained at the platform confirmed that the location represents a well-mixed, average atmospheric environment for the city centre. The air streamlines indicated that the host and neighbouring buildings together with the natural orography play an important role in the near-field dispersion processes. Details and features of the airflow structure were derived, and they can be readily utilised for further interpretations. An experimental method to determine particle diffusion losses in the differential mobility particle sizer (DMPS) system of the BpART facility was proposed. It is based on CPC-CPC (condensation particle counter) and DMPS-CPC comparisons. Growth types of nucleated particles observed in 4 years of measurements were presented and discussed specifically for cities. Arch-shaped size distribution surface plots consisting of a growth phase followed by a shrinkage phase were characterised separately since they supply information on nucleated particles. They were observed in 4.5 % of quantifiable nucleation events. The shrinkage phase took 1 h 34 min in general, and the mean shrinkage rate with standard deviation was -3.8 ± 1.0 nm h-1. The shrinkage of particles was mostly linked to changes in local atmospheric conditions, especially in global radiation and the gas-phase H2SO4 concentration through its proxy, or to atmospheric mixing in few cases. Some indirect results indicate that variations in the formation and growth rates of nucleated particles during their atmospheric transport could be a driving force of shrinkage for particles of very small sizes and on specific occasions.

  20. The effect of Emdogain gel on periodontal regeneration in autogenous transplanted dog′s teeth

    Directory of Open Access Journals (Sweden)

    Manuel Marques Ferreira

    2014-01-01

    Full Text Available Aim: The aim of this study was to assess the enamel matrix derivative (EMD as biomaterial used in autogenous tooth transplantation. Material and Methods: The study consisted of 3 beagle dogs, 5 months old, in which six incisors and six premolars were transplanted to mechanically prepared recipient alveolar sockets. One group of teeth was transplanted to a recipient bed, with EMD in the root surface. The second groups of teeth were transplanted using saline solution in the root surface. Every week, clinical examinations were done. Nine weeks later, the animals were killed and the specimens decalcified and prepared for histological and imunohistochemical analysis. Periodontal healing was evaluated by undertaking histomorphometric investigation and analyzed using the Mann- Whitney test (P = 0.05. Results: In both groups, all the transplanted teeth survived. Between the experimental groups, there was statistically significant difference in the complete healing (P = 0.004. There was statistically significant difference between the treatment group in the occurrence of inflammatory root resorption (P = 0.015 and the occurrence of replacement root resorption (P = 0.041. Conclusions: Emdogain gel used on the surface of transplanted teeth improves the occurrence of complete healing and reduces root resorption.

  1. Cephalic Arch Stenosis in Autogenous Haemodialysis Fistulas: Treatment With the Viabahn Stent-Graft

    Energy Technology Data Exchange (ETDEWEB)

    Shawyer, Andrew, E-mail: andrew.shawyer@bartsandthelondon.nhs.uk [The Royal London Hospital, Radiology Department (United Kingdom); Fotiadis, Nicos I., E-mail: fotiadis.nicholas@gmail.com [Royal Marsden Hospital, Radiology Department, The Royal Marsden NHS Foundation Trust (United Kingdom); Namagondlu, Girish, E-mail: girish.namagondlu@bartsandthelondon.nhs.uk [The Royal London Hospital, Renal Medicine Department (United Kingdom); Iyer, Arun, E-mail: arun.iyer@bartsandthelondon.nhs.uk [The Royal London Hospital, Radiology Department (United Kingdom); Blunden, Mark, E-mail: mark.blunden@bartsandthelondon.nhs.uk; Raftery, Martin, E-mail: martin.raftery@bartsandthelondon.nhs.uk; Yaqoob, Magdi, E-mail: magdi.yaqoob@bartsandthelondon.nhs.uk [The Royal London Hospital, Renal Medicine Department (United Kingdom)

    2013-02-15

    Cephalic arch stenosis (CAS) is an important and common cause of dysfunction in autogenous haemodialysis fistulas that requires multiple reinterventions and aggressive surveillance. We evaluated the safety and efficacy of the Viabahn stent-graft for the management of CAS. Between April 2005 and October 2011, 11 consecutive patients [four men and seven women (mean age 56.7 years)] with CAS and dysfunctional fistulas were treated with insertion of 11 Viabahn stent-grafts. Six stent-grafts were inserted due to residual stenosis after angioplasty and five for fistuloplasty-induced rupture. No patient was lost to follow-up. The technical and clinical success rate was 100 %. Primary access patency rates were 81.8 % [95 % confidence interval (CI) 0.482-0.977] at 6 months and 72.7 % (95 % CI 0.390-0.939) at 12 months. Secondary access patency rates were 90.9 % at 6 months (95 % CI 0.587-0.997). There were no procedure-related complications. Mean follow-up was 543.8 days (range 156-2,282). The use of the Viabahn stent-graft in the management of CAS is technically feasible and, in this small series, showed patency rates that compare favorably with historical data of angioplasty and bare stents.

  2. Effect of percutaneous transluminal angioplasty on the stenosis of autogenous radiocephalic ateriovenous fistula for hemodialysis

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Sun Min; Kim, Jeong Ho; Byun, Sung Su; Kang, Jin MMo; Choi, Sang Tae; Kim, Jong Woo; Kim, Hyung Sik; Choi, Hye Young [Gachon University Gil Medical Center, Incheon (Korea, Republic of); Park, Jae Hyung [Dept. of Radiology, Seonam University College of Medicine, Myongji Hospital, Goyang (Korea, Republic of)

    2016-02-15

    The purpose of this study was to evaluate the effectiveness of percutaneous transluminal angioplasty (PTA) on stenosis of autogenous radiocephalic arteriovenous fistula (RCF) for hemodialysis and to determine the factors influencing patency. This retrospective study included 136 patients referred for PTA of RCF stenosis between March 2005 and July 2014. The technical success rate, complications, and patency rate were evaluated. The following factors were analyzed as they might influence patency: age, gender, site and duration of arteriovenous fistula, underlying disease, body mass index, hypercholesterolemia, smoking, peripheral artery or coronary artery occlusive disease, stenosis length/grade, cutting balloon, and balloon size. The initial technical success rate was 91.9% (125/136). Complications included vessel rupture (n = 2) and vessel dissection (n = 2). The patency rates at 6, 12, 24, and 48 months after PTA were 81.9, 67.1, 52.7, and 42.3%, respectively. The patency rate was higher in cases with longer (> 3 cm) stenosis (p = 0.04). Use of cutting balloon and larger size of balloon catheter made the patency longer, but this difference was not statistically significant (p = 0.637, 0.258). PTA is a safe and effective way to manage stenosis in RCF. The length of stenosis was the only factor which affected the patency rate in this study.

  3. Histological evaluation of the influence of magnetic field application in autogenous bone grafts in rats

    Directory of Open Access Journals (Sweden)

    Ponzoni Deise

    2009-01-01

    Full Text Available Abstract Background Bone grafts are widely used in oral and maxillofacial reconstruction. The influence of electromagnetic fields and magnets on the endogenous stimulation of target tissues has been investigated. This work aimed to assess the quality of bone healing in surgical cavities filled with autogenous bone grafts, under the influence of a permanent magnetic field produced by in vivo buried devices. Methods Metal devices consisting of commercially pure martensitic stainless steel washers and titanium screws were employed. Thirty male Wistar rats were divided into 3 experimental and 3 control groups. A surgical bone cavity was produced on the right femur, and a bone graft was collected and placed in each hole. Two metallic washers, magnetized in the experimental group but not in the control group, were attached on the borders of the cavity. Results The animals were sacrificed on postoperative days 15, 45 and 60. The histological analysis of control and experimental samples showed adequate integration of the bone grafts, with intense bone neoformation. On days 45 and 60, a continued influence of the magnetic field on the surgical cavity and on the bone graft was observed in samples from the experimental group. Conclusion The results showed intense bone neoformation in the experimental group as compared to control animals. The intense extra-cortical bone neoformation observed suggests that the osteoconductor condition of the graft may be more susceptible to stimulation, when submitted to a magnetic field.

  4. Silicate minerals for CO2 scavenging from biogas in Autogenerative High Pressure Digestion.

    Science.gov (United States)

    Lindeboom, Ralph E F; Ferrer, Ivet; Weijma, Jan; van Lier, Jules B

    2013-07-01

    Autogenerative High Pressure Digestion (AHPD) is a novel concept that integrates gas upgrading with anaerobic digestion by selective dissolution of CO2 at elevated biogas pressure. However, accumulation of CO2 and fatty acids after anaerobic digestion of glucose resulted in pH 3-5, which is incompatible with the commonly applied high-rate methanogenic processes. Therefore, we studied the use of wollastonite, olivine and anorthosite, with measured composition of CaSi1.05O3.4, Mg2Fe0.2Ni0.01Si1.2O5.3 and Na0.7Ca1K0.1Mg0.1Fe0.15Al3.1Si4O24, respectively, to scavenge CO2 during batch AHPD of glucose. Depending on the glucose to mineral ratio the pH increased to 6.0-7.5. Experiments with wollastonite showed that Ca(2+)-leaching was caused by volatile fatty acid (VFA) production during glucose digestion. At 1, 3 and 9 bar, the CH4 content reached 74%, 86% and 88%, respectively, indicating CO2 scavenging. Fixation of produced CO2 by CaCO3 precipitation in the sludge was confirmed by Fourier Transferred-InfraRed, Combined Field emission Scanning Electron Microscopy-Energy-dispersive X-ray spectroscopy and Thermogravimetric Analysis-Mass Spectroscopy.

  5. Autogenic-Feedback Training: A Potential Treatment for Orthostatic Intolerance in Aerospace Crews

    Science.gov (United States)

    Cowings, P. S.; Toscano, W. B.; Miller, N. E.; Pickering, T. G.; Shapiro, D.; Stevenson, J.; Maloney, S.; Knapp, J.

    1994-01-01

    Postflight orthostatic intolerance has been identified as a serious biomedical problem associated with long-duration exposure to microgravity in space. High priority has been given to the development of countermeasures for this disorder that are both effective and practical. A considerable body of clinical research has demonstrated that people can be taught to increase their own blood pressure voluntarily, and that this is an effective treatment for chronic orthostatic intolerance in paralyzed patients. The current pilot study was designed to examine the feasibility of adding training in control of blood pressure to an existing preflight training program designed to facilitate astronaut adaptation to microgravity. Using an operant conditioning procedure, autogenic-feedback training (AFT), three men and two women participated in four to nine training (15-30-minute) sessions. At the end of training, the average increase in systolic and diastolic pressure, as well as mean arterial pressures, that the subjects made ranged between 20 and 50 mm Hg under both supine and 45 deg head-up tilt conditions. These findings indicate that AFT may be a useful alternative treatment or supplement to existing approaches for preventing postflight orthostatic intolerance. Furthermore, the use of operant conditioning methods for training cardiovascular responses may contribute to the general understanding of the mechanisms of orthostatic intolerance.

  6. Autogenic-feedback training: A potential treatment for post-flight orthostatic intolerance in aerospace crews

    Science.gov (United States)

    Cowings, Patricia S.; Toscano, William B.; Miller, Neil E.; Pickering, Thomas G.; Shapiro, David

    1993-01-01

    Postflight orthostatic intolerance was identified as a serious biomedical problem associated with long duration exposure to microgravity in space. High priority was given to the development of countermeasures for this disorder which are both effective and practical. A considerable body of clinical research demonstrated that people can be taught to increase their own blood pressure voluntarily and that this is an effective treatment for chronic orthostatic intolerance in paralyzed patients. The present pilot study was designed to examine the feasibility of adding training in control of blood pressure to an existing preflight training program designed to facilitate astronaut adaptation to microgravity. Using an operant conditioning procedure, Autogenic-Feedback Training (AFT), three men and two women participated in four to nine (15-30 training sessions). At the end of training, the average increase in systolic and diastolic pressure, as well as mean arterial pressures that the subjects made, ranged between 20 and 5O mmHg under both supine and 45 deg head-up tilt conditions. These findings suggest that AFT may be a useful alternative treatment or supplement to existing approaches for preventing postflight orthostatic intolerance. Further, the use of operant conditioning methods for training cardiovascular responses may contribute to the general understanding of the mechanisms of orthostatic intolerance.

  7. A Novel Albumin-Based Tissue Scaffold for Autogenic Tissue Engineering Applications

    Science.gov (United States)

    Li, Pei-Shan; -Liang Lee, I.; Yu, Wei-Lin; Sun, Jui-Sheng; Jane, Wann-Neng; Shen, Hsin-Hsin

    2014-07-01

    Tissue scaffolds provide a framework for living tissue regeneration. However, traditional tissue scaffolds are exogenous, composed of metals, ceramics, polymers, and animal tissues, and have a defined biocompatibility and application. This study presents a new method for obtaining a tissue scaffold from blood albumin, the major protein in mammalian blood. Human, bovine, and porcine albumin was polymerised into albumin polymers by microbial transglutaminase and was then cast by freeze-drying-based moulding to form albumin tissue scaffolds. Scanning electron microscopy and material testing analyses revealed that the albumin tissue scaffold possesses an extremely porous structure, moderate mechanical strength, and resilience. Using a culture of human mesenchymal stem cells (MSCs) as a model, we showed that MSCs can be seeded and grown in the albumin tissue scaffold. Furthermore, the albumin tissue scaffold can support the long-term osteogenic differentiation of MSCs. These results show that the albumin tissue scaffold exhibits favourable material properties and good compatibility with cells. We propose that this novel tissue scaffold can satisfy essential needs in tissue engineering as a general-purpose substrate. The use of this scaffold could lead to the development of new methods of artificial fabrication of autogenic tissue substitutes.

  8. Centrifugation-assisted Assembly of Colloidal Silica into Crack-Free and Transferrable Films with Tunable Crystalline Structures.

    Science.gov (United States)

    Fan, Wen; Chen, Min; Yang, Shu; Wu, Limin

    2015-07-10

    Self-assembly of colloidal particles into colloidal films has many actual and potential applications. While various strategies have been developed to direct the assembly of colloidal particles, fabrication of crack-free and transferrable colloidal film with controllable crystal structures still remains a major challenge. Here we show a centrifugation-assisted assembly of colloidal silica spheres into free-standing colloidal film by using the liquid/liquid interfaces of three immiscible phases. Through independent control of centrifugal force and interparticle electrostatic repulsion, polycrystalline, single-crystalline and quasi-amorphous structures can be readily obtained. More importantly, by dehydration of silica particles during centrifugation, the spontaneous formation of capillary water bridges between particles enables the binding and pre-shrinkage of the assembled array at the fluid interface. Thus the assembled colloidal films are not only crack-free, but also robust and flexible enough to be easily transferred on various planar and curved substrates.

  9. FRACTAL KINEMATICS OF CRACK PROPAGATION IN GEOMATERIALS

    Institute of Scientific and Technical Information of China (English)

    谢和平

    1995-01-01

    Experimental results indicate that propagation paths of cracks in geomaterials are often irregular, producing rough fracture surfaces which are fractal. A formula is derived for the fractal kinematics of crack propagation in geomaterials. The formula correlates the dynamic and static fracture toughnesses with crack velocity, crack length and a microstructural parameter, and allows the fractal dimension to be obtained. From the equations for estimating crack velocity and fractal dimension it can be shown that the measured crack velocity, Vo , should be much smaller than the fractal crack velocity, V. It can also be shown that the fractal dimension of the crack propagation path can be calculated directly from Vo and from the fracture toughness.

  10. Interacting Cracks in an Environmentally Assisted Fracture

    Science.gov (United States)

    Levandovsky, Artem; Balazs, Anna

    2006-03-01

    We perform the study of environmentally assisted fracture within the framework of a lattice model. Formation of an ensemble of environmentally assisted microcracks, their coalescence and formation of crack ``avalanches'' lead to a very rich dynamical picture. Under specific condition crack healing can occur due to cohesive forces, which hold material together and tend to pull atoms together even if they are separated by a crack over several lattice units. We investigate the dynamical interplay between crack formation, arrest, healing and re-cracking. The goal here is to provide an understanding of the conditions leading to the phenomena of crack healing that happens along with the crack formation. We study the morphology of crack patterns with the intentions to establish a way to enhance the healing property of a material sample.

  11. HYDROTHERMAL CRACKING OF RESIDUAL OILS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The hydrothermal cracking of heavy oils, such as Canadian oil sand bitumen and Arabian heavy vacuum residue, as well as their model compound were performed over sulfided Ni/Al2O3 and NiMo/Al2O3 catalysts under 663~703 K and 6.0~8.0 MPa of hydrogen pressure in a batch autoclave reactor. According to the reaction mechanism of hydrothermal cracking, a small amount of free redical initiators, such as di-tert-peroxide, sulfur, etc., was added into the feed to generate free redicals at lower temperature, and obviously showed promotional effect on the conversion of hydrocarbons. The reaction mechanisms of hydrothermal cracking as well as the enhancing effect of initiators were studied by a probe reaction with 1-phenyldodecane as a model compound. The hydrothermal cracking of hydrocarbon proceeded via free redical mechanism and hydrogenating quench. The initiators might easily generate free redicals under reaction temperature, these redicals might abstract H from hydrocarbon molecule and reasonably initiate the chain reactions, therefore, promote the conversion of hydrocarbon even at lower reaction temperature.

  12. China Cracks Down Internet Piracy

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

      National Copyright Administration of China carried out a special operation to crack down on behaviors involving network infringement and piracy from September to December in 2005 ,according to the speech of Yan Xiaohong,Deputy Commissioner of National Copyright Administration on the Press Conference of the State Council.Now the relevant conditions are as follows:……

  13. China Cracks Down Internet Piracy

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ National Copyright Administration of China carried out a special operation to crack down on behaviors involving network infringement and piracy from September to December in 2005 ,according to the speech of Yan Xiaohong,Deputy Commissioner of National Copyright Administration on the Press Conference of the State Council.Now the relevant conditions are as follows:

  14. Confining crack propagation in defective graphene.

    Science.gov (United States)

    López-Polín, Guillermo; Gómez-Herrero, Julio; Gómez-Navarro, Cristina

    2015-03-11

    Crack propagation in graphene is essential to understand mechanical failure in 2D materials. We report a systematic study of crack propagation in graphene as a function of defect content. Nanoindentations and subsequent images of graphene membranes with controlled induced defects show that while tears in pristine graphene span microns length, crack propagation is strongly reduced in the presence of defects. Accordingly, graphene oxide exhibits minor crack propagation. Our work suggests controlled defect creation as an approach to avoid catastrophic failure in graphene.

  15. 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

  16. 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 i...

  17. Differential performance on the go/no-go task as a function of the autogenous-reactive taxonomy of obsessions: findings from a non-treatment seeking sample.

    Science.gov (United States)

    Lee, Han-Joo; Yost, Brittanie P; Telch, Michael J

    2009-04-01

    It has been suggested that obsessive-compulsive disorder is characterized by impaired inhibitory control. Response inhibition is a cognitive process required for one to cancel or suppress dominant but inappropriate responses. The present study examined response inhibition among non-treatment seeking individuals diagnosed with OCD and individuals with low levels of OCD symptoms using a computerized visual go/no-go task. Specifically, we sought to examine a prediction from the autogenous-reactive subtype model of obsessions (Lee, H.-J., & Kwon, S.-M. (2003). Two different types of obsession: autogenous obsessions and reactive obsessions. Behaviour Research and Therapy, 41, 11-29; Lee, H.-J., & Telch, M. J. (2008). Autogenous obsessions and reactive obsessions. In J. Abramowitz, S. Taylor, & D. McKay (Eds.), Obsessive-compulsive disorder: subtypes and spectrum conditions. New York: Elsevier., asserting that OCD individuals presenting with the autogenous subtype of obsessions will display greater difficulty in inhibitory control relative to individuals presenting with obsessions of the reactive subtype. Results showed that individuals with OCD of the autogenous subtype displayed more deficient inhibitory control on the visual go/no-go task as indexed by a longer response delay between the original stimuli set and the reversed stimuli set compared to individuals with OCD of the reactive subtype or individuals with low levels of OCD symptoms.

  18. Preparation of High Impermeable and Crack-resistance Chemical Admixture and Its Mechanism

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A kind of high impermeable and crack-resistance chemical admixture (HICRCA) was prepared, which is a compound chemical admixture composed of an expansion ingredient,density ingredient, and organic hydrophobic poreblocking ingredient. The results of the experiments indicate that the addition of HICRCA improves mortar and concrete in the following performances:(1) perfect workability: slump is more than 22cm, the slump after 3h is about 16cm; (2)high impermeability:for the mortar,the pervious height under a water pressure of 1.5MPa is 1.5cm,for the concrete, the pervious height under a water pressure of 5.0MPa is 2.2cm;(3)high crack-resistance:there is a micro-expansion at the age of 90d;(4)high compressivestrength:compared with the controlled concrete,the compressive strengths at the age of 3d and 28d are improved by 66.4% and 62.0%, respectively.At the same time,the effects of different curing condition on mortar and concrete expansive and shrinkage performance were studied.In addition,the impermeable and crack-resistance mechanism was investigated in the present paper.

  19. Fatigue crack growth simulations of 3-D linear elastic cracks under thermal load by XFEM

    Institute of Scientific and Technical Information of China (English)

    Himanshu PATHAK[1; Akhilendra SINGH[2; I.V. SINGH[3; S. K. YADAV[3

    2015-01-01

    This paper deals with the fatigue crack growth simulations of three-dimensional linear elastic cracks by XFEM under cyclic thermal load. Both temperature and displacement approximations are extrinsically enriched by Heaviside and crack front enrichment functions. Crack growth is modelled by successive linear extensions, and the end points of these linear extensions are joined by cubic spline segments to obtain a modified crack front. Different crack geometries such as planer, non-planer and arbitrary spline shape cracks are simulated under thermal shock, adiabatic and isothermal loads to reveal the sturdiness and versatility of the XFEM approach.

  20. Ultrastructural evaluation of shrinkage artefacts induced by fixatives and embedding resins on osteocyte processes and pericellular space dimensions.

    Science.gov (United States)

    Shah, Furqan A; Johansson, Bengt R; Thomsen, Peter; Palmquist, Anders

    2015-04-01

    The integrity of the interface between the osteocyte (Ot) process and the canalicular wall was investigated in terms of change in the lateral dimensions of the Ot process in relation to the canalicular width, i.e., widening of the pericellular space. This has been interpreted as shrinkage of the Ot process relative to the canalicular wall during sample preparation stages of fixation, dehydration, and resin embedding. Sprague-Dawley rat tibial cross-sections were prepared for transmission electron microscopy (TEM). Four different fixative preparations: paraformaldehyde (PF), modified Karnovsky's (MK), glutaraldehyde (GRR) with ruthenium red (GRR), and zinc formalin (ZF); and two different embedding resins: LR Gold (LRG) and Epon812 (Epon) were evaluated. It was found that for LRG embedding, formalin-only fixatives (PF and ZF) induced lower shrinkage than GRR-containing fixatives (MK and GRR). In contrast, for Epon embedding, MK showed the highest shrinkage, while no differences were found between the remaining fixatives (PF, ZF, and GRR). All formalin-containing fixatives (MK, PF, and ZF) induced similar shrinkage in both embedding media. The most dramatic difference was for GRR fixation, which in combination with LRG embedding showed ∼ 62% more shrinkage than with Epon embedding, suggesting that the combination of GRR fixation and LRG embedding synergistically amplifies Ot shrinkage. These differences likely suggest a role of the resin in secondarily influencing the tissue structure following fixation. Further, the work confirms LRG as a poor embedding medium for bone specimens, as it causes large variations in shrinkage depending on fixation.

  1. Inhibiting Corrosion Cracking: Crack Tip Chemistry and Physics.

    Science.gov (United States)

    1986-03-14

    5 5. Swuzary 113 Rferences 114 wl NO 4L iv . List of Figuring 1. Microipette pulling machine . 29 2. Anodic polarization of 7075-T6 Al alloy in dilute...environment has a strong effect on microplastic behavior at the tip of a fatigue crack. Stolz and Pelloux suggest that nitrate ion competes with chloride...Crystalline Na2 N 20 29H20 precipitates when the filtrate is placed in a vacunm desiccator over sulfuric acid. The filtered precipitate is washed

  2. CRACK REASON ANALYSIS OF DAMAGED CARBONITRIDED PART

    Directory of Open Access Journals (Sweden)

    Karin Kocúrová

    2010-03-01

    Full Text Available The article deals with the analysis of a damaged part, which was designed for use in a mechanical clutch of a car. The crack in the part was found during the production inspection. The aim of metallographic and fractography analyses of the fracture surfaces was to discover the reasons for the crack. The reason for creating the crack was the formation of smaller cracks in the production during pressing process of the semiproduct. These cracks even grew after the following thermochemical treatment. The fracture was initiated during the straightening process of quenched part.

  3. Crack branching in carbon steel. Fracture mechanisms

    Science.gov (United States)

    Syromyatnikova, A. S.; Alekseev, A. A.; Levin, A. I.; Lyglaev, A. V.

    2010-04-01

    The fracture surfaces of pressure vessels made of carbon steel that form during crack branching propagation are examined by fractography. Crack branching is found to occur at a crack velocity higher than a certain critical value V > V c . In this case, the material volume that is involved in fracture and depends on the elastoplastic properties of the material and the sample width has no time to dissipate the energy released upon crack motion via the damage mechanisms intrinsic in the material under given deformation conditions (in our case, via cracking according to intragranular cleavage).

  4. 腹式呼吸和自生训练对心率及指温影响的初步探讨%The Effects of Abdominal Breathing and Autogenic Training on Heart Rate and Finger Temperature

    Institute of Scientific and Technical Information of China (English)

    张秀阁; 闫克乐

    2001-01-01

    Objective: To examine the effects of autogenic training and abdominal breathing on heart rate and finger temperature. Methods: Forty-five healthy female university students were randomly assigned to three groups:control、autogenic training and deep abdominal breathing groups, and their physiological effects were compared. Results:The result of this experiment showed that both autogenic training and abdominal breathing increased finger temperature significantly, however, the increase magnitude didn't show significant differences in two groups.During autogenic training, the heart rate of autogenic training group declined significantly,the heart rate of deep abdominal breathing group decreased significantly after deep abdominal breathing. The decrease magnitude between the three groups showed no significant differences. Conclusion: Both the present techniques can decrease heart rate and increase finger temperature.

  5. Self-organization in irregular landscapes: Detecting autogenic interactions from field data using descriptive statistics and dynamical systems theory

    Science.gov (United States)

    Larsen, L.; Watts, D.; Khurana, A.; Anderson, J. L.; Xu, C.; Merritts, D. J.

    2015-12-01

    The classic signal of self-organization in nature is pattern formation. However, the interactions and feedbacks that organize depositional landscapes do not always result in regular or fractal patterns. How might we detect their existence and effects in these "irregular" landscapes? Emergent landscapes such as newly forming deltaic marshes or some restoration sites provide opportunities to study the autogenic processes that organize landscapes and their physical signatures. Here we describe a quest to understand autogenic vs. allogenic controls on landscape evolution in Big Spring Run, PA, a landscape undergoing restoration from bare-soil conditions to a target wet meadow landscape. The contemporary motivation for asking questions about autogenic vs. allogenic controls is to evaluate how important initial conditions or environmental controls may be for the attainment of management objectives. However, these questions can also inform interpretation of the sedimentary record by enabling researchers to separate signals that may have arisen through self-organization processes from those resulting from environmental perturbations. Over three years at Big Spring Run, we mapped the dynamic evolution of floodplain vegetation communities and distributions of abiotic variables and topography. We used principal component analysis and transition probability analysis to detect associative interactions between vegetation and geomorphic variables and convergent cross-mapping on lidar data to detect causal interactions between biomass and topography. Exploratory statistics revealed that plant communities with distinct morphologies exerted control on landscape evolution through stress divergence (i.e., channel initiation) and promoting the accumulation of fine sediment in channels. Together, these communities participated in a negative feedback that maintains low energy and multiple channels. Because of the spatially explicit nature of this feedback, causal interactions could not

  6. A moment projection method for population balance dynamics with a shrinkage term

    Science.gov (United States)

    Wu, Shaohua; Yapp, Edward K. Y.; Akroyd, Jethro; Mosbach, Sebastian; Xu, Rong; Yang, Wenming; Kraft, Markus

    2017-02-01

    A new method of moments for solving the population balance equation is developed and presented. The moment projection method (MPM) is numerically simple and easy to implement and attempts to address the challenge of particle shrinkage due to processes such as oxidation, evaporation or dissolution. It directly solves the moment transport equation for the moments and tracks the number of the smallest particles using the algorithm by Blumstein and Wheeler (1973) [41]. The performance of the new method is measured against the method of moments (MOM) and the hybrid method of moments (HMOM). The results suggest that MPM performs much better than MOM and HMOM where shrinkage is dominant. The new method predicts mean quantities which are almost as accurate as a high-precision stochastic method calculated using the established direct simulation algorithm (DSA).

  7. Denoising of Mechanical Vibration Signals Using Quantum-Inspired Adaptive Wavelet Shrinkage

    Directory of Open Access Journals (Sweden)

    Yan-long Chen

    2014-01-01

    Full Text Available The potential application of a quantum-inspired adaptive wavelet shrinkage (QAWS technique to mechanical vibration signals with a focus on noise reduction is studied in this paper. This quantum-inspired shrinkage algorithm combines three elements: an adaptive non-Gaussian statistical model of dual-tree complex wavelet transform (DTCWT coefficients proposed to improve practicability of prior information, the quantum superposition introduced to describe the interscale dependencies of DTCWT coefficients, and the quantum-inspired probability of noise defined to shrink wavelet coefficients in a Bayesian framework. By combining all these elements, this signal processing scheme incorporating the DTCWT with quantum theory can both reduce noise and preserve signal details. A practical vibration signal measured from a power-shift steering transmission is utilized to evaluate the denoising ability of QAWS. Application results demonstrate the effectiveness of the proposed method. Moreover, it achieves better performance than hard and soft thresholding.

  8. Light-Curing Volumetric Shrinkage in Dimethacrylate-Based Dental Composites by Nanoindentation and PAL Study

    Science.gov (United States)

    Shpotyuk, Olha; Adamiak, Stanislaw; Bezvushko, Elvira; Cebulski, Jozef; Iskiv, Maryana; Shpotyuk, Oleh; Balitska, Valentina

    2017-01-01

    Light-curing volumetric shrinkage in dimethacrylate-based dental resin composites Dipol® is examined through comprehensive kinetics research employing nanoindentation measurements and nanoscale atomic-deficient study with lifetime spectroscopy of annihilating positrons. Photopolymerization kinetics determined through nanoindentation testing is shown to be described via single-exponential relaxation function with character time constants reaching respectively 15.0 and 18.7 s for nanohardness and elastic modulus. Atomic-deficient characteristics of composites are extracted from positron lifetime spectra parameterized employing unconstrained x3-term fitting. The tested photopolymerization kinetics can be adequately reflected in time-dependent changes observed in average positron lifetime (with 17.9 s time constant) and fractional free volume of positronium traps (with 18.6 s time constant). This correlation proves that fragmentation of free-volume positronium-trapping sites accompanied by partial positronium-to-positron traps conversion determines the light-curing volumetric shrinkage in the studied composites.

  9. Stein-Rule Estimation and Generalized Shrinkage Methods for Forecasting Using Many Predictors

    DEFF Research Database (Denmark)

    Hillebrand, Eric Tobias; Lee, Tae-Hwy

    We examine the Stein-rule shrinkage estimator for possible improvements in estimation and forecasting when there are many predictors in a linear time series model. We consider the Stein-rule estimator of Hill and Judge (1987) that shrinks the unrestricted unbiased OLS estimator towards a restricted...... biased principal component (PC) estimator. Since the Stein-rule estimator combines the OLS and PC estimators, it is a model-averaging estimator and produces a combined forecast. The conditions under which the improvement can be achieved depend on several unknown parameters that determine the degree......-to-noise ratio is low, the PC estimator is superior. If the signal-to-noise ratio is high, the OLS estimator is superior. In out-of-sample forecasting with AR(1) predictors, the Stein-rule shrinkage estimator can dominate both OLS and PC estimators when the predictors exhibit low persistence....

  10. Influence of waxes remelting used in investment casting on their thermal properties and linear shrinkage

    Directory of Open Access Journals (Sweden)

    K. Grzeskowiak

    2015-04-01

    Full Text Available This paper presents the results of thermal properties and linear shrinkage of jewelry waxes utilized in investment casting. Three types of jewelry waxes were cyclically processed (by heating, holding in a molten state and coolingin the temperature range between 25 and 90 °C for about 7 hours. The samples were tested after 5th, 10th and 15thcycle. The remelting was designed to simulate the process of waxes reusability for production of patterns. Changes in thermal properties of waxes were determined using differential scanning calorimetry (DSC and linear shrinkage values were specified. The conducted examinations allowed to establish the way of multiple utilization of waxes in producing precise models.

  11. Non-linear shrinkage estimation of large-scale structure covariance

    Science.gov (United States)

    Joachimi, Benjamin

    2017-03-01

    In many astrophysical settings, covariance matrices of large data sets have to be determined empirically from a finite number of mock realizations. The resulting noise degrades inference and precludes it completely if there are fewer realizations than data points. This work applies a recently proposed non-linear shrinkage estimator of covariance to a realistic example from large-scale structure cosmology. After optimizing its performance for the usage in likelihood expressions, the shrinkage estimator yields subdominant bias and variance comparable to that of the standard estimator with a factor of ∼50 less realizations. This is achieved without any prior information on the properties of the data or the structure of the covariance matrix, at a negligible computational cost.

  12. Characterization of a gel in the cell wall to elucidate the paradoxical shrinkage of tension wood.

    Science.gov (United States)

    Clair, Bruno; Gril, Joseph; Di Renzo, Francesco; Yamamoto, Hiroyuki; Quignard, Françoise

    2008-02-01

    Wood behavior is characterized by high sensibility to humidity and strongly anisotropic properties. The drying shrinkage along the fibers, usually small due to the reinforcing action of cellulosic microfibrils, is surprisingly high in the so-called tension wood, produced by trees to respond to strong reorientation requirements. In this study, nitrogen adsorption-desorption isotherms of supercritically dried tension wood and normal wood show that the tension wood cell wall has a gel-like structure characterized by a pore surface more than 30 times higher than that in normal wood. Syneresis of the tension wood gel explains its paradoxical drying shrinkage. This result could help to reduce technological problems during drying. Potential applications in biomechanics and biomimetics are worth investigating, considering that, in living trees, tension wood produces tensile growth stresses 10 times higher than that of normal wood.

  13. Early age shrinkage pattern of concrete on replacement of fine aggregate with industrial by-product

    Directory of Open Access Journals (Sweden)

    R.K. Mishra

    2016-10-01

    Full Text Available This is an experimental work carried out to investigate early age shrinkage pattern of concrete, prepared, on 50% replacement of industrial by-product (like pond ash and granulated blast furnace slag as fine aggregate using OPC, PPC and PSC as a binder. This is to observe the effect of pond ash and slag as they are having some cementitious properties and effect of cement type is also discussed. All the mixes were prepared keeping in view of pumpable concrete without any super plasticizers. Higher shrinkage value indicates the presence of more bleed water or internal moisture. It is concluded that slag is the best option for fine aggregate replacement for concrete making and durable structure.

  14. The effect of using hybrid nanomaterials on drying shrinkage and strength of cement pastes

    Directory of Open Access Journals (Sweden)

    Saaid I. Zaki

    2016-04-01

    Full Text Available The aim of this work is to study the effect of nanomaterials on the properties of cement paste, the experimental program included three parts: a- two types of nanosilica, locally produced NS1 and imported NS2, b- nanoclay (NC and c- Hybrid nanoparticles (NS1 & NC. In each part, cement paste was used with different percentages of nanoparticles. Compressive strength and drying shrinkage tests were applied in each part on the cured and uncured samples. The results showed that the compressive strength improved in the cement paste mixtures in the cured condition, the optimum percentages was 1% for NS1, 1% for NS2, 5% for NC, and 5% (0.5%NS1 & 4.5%NC for hybrid nanoparticles. The drying shrinkage increases with adding nanosilica and hybrid nanoparticles, while it decreases when adding NC.

  15. Minimal volume regulation after shrinkage of red blood cells from five species of reptiles

    DEFF Research Database (Denmark)

    Kristensen, Karina; Berenbrink, Michael; Koldkjær, Pia

    2008-01-01

    Red blood cells (RBCs) from most vertebrates restore volume upon hypertonic shrinkage and the mechanisms underlying this regulatory volume increase (RVI) have been studied extensively in these cells. Despite the phylogenetically interesting position of reptiles, very little is known about their red...... cell function. The present study demonstrates that oxygenated RBCs in all major groups of reptiles exhibit no or a very reduced RVI upon ~ 25% calculated hyperosmotic shrinkage. Thus, RBCs from the snakes Crotalus durissus and Python regius, the turtle Trachemys scripta and the alligator Alligator...... was not characterized. It seems, therefore, that the RVI response based on NHE activation was lost among the early sauropsids that gave rise to modern reptiles and birds, while it was retained in mammals. An RVI response has then reappeared in birds, but based on activation of the NKCC. Alternatively, the absence...

  16. Edge detection algorithm based on ICA-domain shrinkage in noisy images

    Institute of Scientific and Technical Information of China (English)

    HAN XianHua; DAI ShuiYan; LI Jian; XIA GuoRong

    2008-01-01

    We propose a robust edge detection method based on ICA-domain shrinkage (independent component analysis). It is known that most basis functions extracted from natural images by ICA are sparse and similar to localized and oriented receptive fields, and in the proposed edge detection method, a target image is first transformed by ICA basis functions and then the edges are detected or reconstructed with sparse components. Furthermore, by applying a shrinkage algorithm to filter out the components of noise in ICA-domain, we can readily obtain the sparse components of the original image, resulting in a kind of robust edge detection even for a noisy image with a very low SN ratio. The efficiency of the proposed method is demonstrated by experiments with some natural images.

  17. Effect of selected physical properties of waxes on investments and casting shrinkage.

    Science.gov (United States)

    Ito, M; Yamagishi, T; Oshida, Y; Munoz, C A

    1996-02-01

    This study evaluated the relationship between flow characteristics, bending strength, and softening temperature of paraffin and dental inlay waxes to casting shrinkage when patterns were invested with a phosphate-bonded investment. This study found that the casting shrinkage decreased as the flow of the wax pattern increased. If a low flow wax is used or if there is a need for a thick pattern, the size of the casting ring should be increased. When wax patterns are formed for cast restorations, it is important to select the type of wax with the most desirable properties for the margin and the occlusal portions. Moreover, to accurately fabricate castings, it is necessary to understand the physical properties of the chosen waxes.

  18. Bayesian-based Wavelet Shrinkage for SAR Image Despeckling Using Cycle Spinning

    Institute of Scientific and Technical Information of China (English)

    ZHANG De-xiang; GAO Qing-wei; CHEN Jun-ning

    2006-01-01

    A novel and efficient speckle noise reduction algorithm based on Bayesian wavelet shrinkage using cycle spinning is proposed. First, the sub-band decompositions of non-logarithmically transformed SAR images are shown. Then, a Bayesian wavelet shrinkage factor is applied to the decomposed data to estimate noise-free wavelet coefficients. The method is based on the Mixture Gaussian Distributed (MGD) modeling of sub-band coefficients. Finally, multi-resolution wavelet coefficients are reconstructed by wavelet-threshold using cycle spinning. Experimental results show that the proposed despeckling algorithm is possible to achieve an excellent balance between suppresses speckle effectively and preserves as many image details and sharpness as possible. The new method indicated its higher performance than the other speckle noise reduction techniques and minimizing the effect of pseudo-Gibbs phenomena.

  19. Accelerated Path-following Iterative Shrinkage Thresholding Algorithm with Application to Semiparametric Graph Estimation

    Science.gov (United States)

    Zhao, Tuo; Liu, Han

    2016-01-01

    We propose an accelerated path-following iterative shrinkage thresholding algorithm (APISTA) for solving high dimensional sparse nonconvex learning problems. The main difference between APISTA and the path-following iterative shrinkage thresholding algorithm (PISTA) is that APISTA exploits an additional coordinate descent subroutine to boost the computational performance. Such a modification, though simple, has profound impact: APISTA not only enjoys the same theoretical guarantee as that of PISTA, i.e., APISTA attains a linear rate of convergence to a unique sparse local optimum with good statistical properties, but also significantly outperforms PISTA in empirical benchmarks. As an application, we apply APISTA to solve a family of nonconvex optimization problems motivated by estimating sparse semiparametric graphical models. APISTA allows us to obtain new statistical recovery results which do not exist in the existing literature. Thorough numerical results are provided to back up our theory. PMID:28133430

  20. Fissure formation in coke. 2: Effect of heating rate, shrinkage and coke strength

    Energy Technology Data Exchange (ETDEWEB)

    D.R. Jenkins; M.R. Mahoney [CSIRO, North Ryde, NSW (Australia). Mathematical and Information Sciences

    2010-07-15

    We investigate the effects of the heating rate, coke shrinkage and coke breakage strength upon the fissure pattern developed in a coke oven charge during carbonisation. This is done principally using a mechanistic model of the formation of fissures, which considers them to be an array of equally spaced fissures, whose depth follows a 'period doubling' pattern based upon the time history of the fissures. The model results are compared with pilot scale coke oven experiments. The results show that the effect of heating rate on the fissure pattern is different to the effect of coke shrinkage, while the effect of coke breakage strength on the pattern is less pronounced. The results can be seen in both the shape and size of resulting coke lumps after stabilisation. The approach gives the opportunity to consider means of controlling the carbonisation process in order to tune the size of the coke lumps produced. 7 refs., 18 figs., 4 tabs.

  1. Shrinkage-based diagonal discriminant analysis and its applications in high-dimensional data.

    Science.gov (United States)

    Pang, Herbert; Tong, Tiejun; Zhao, Hongyu

    2009-12-01

    High-dimensional data such as microarrays have brought us new statistical challenges. For example, using a large number of genes to classify samples based on a small number of microarrays remains a difficult problem. Diagonal discriminant analysis, support vector machines, and k-nearest neighbor have been suggested as among the best methods for small sample size situations, but none was found to be superior to others. In this article, we propose an improved diagonal discriminant approach through shrinkage and regularization of the variances. The performance of our new approach along with the existing methods is studied through simulations and applications to real data. These studies show that the proposed shrinkage-based and regularization diagonal discriminant methods have lower misclassification rates than existing methods in many cases.

  2. Alternating grain orientation and weld solidification cracking

    Science.gov (United States)

    Kou, S.; Le, Y.

    1985-10-01

    A new mechanism for reducing weld solidification cracking was proposed, based on the concept of the crack path and resistance to crack propagation, and its effectiveness was verified in magnetically oscillated GTA welds of a rather crack susceptible material 2014 aluminum alloy. This mechanism, i.e., alternating grain orientation, was most pronounced in welds made with transverse arc oscillation of low frequency and high amplitude, and solidification cracking was dramatically reduced in these welds. The effect of the arc oscillation pattern, amplitude, and frequency on the formation of alternating columnar grains and the reduction of solidification cracking in GTA welds of 2014 aluminum alloy was examined and explained. The present study demonstrated for the first time that columnar grains can, in fact, be very effective in reducing solidification cracking, provided that they are oriented favorably.

  3. NASA-Navy Telemedicine: Autogenic Feedback Training Exercises for Motion Sickness

    Science.gov (United States)

    Acromite, Michael T.; Cowings, Patricia; Toscano, William; Davis, Carl; Porter, Henry O.

    2010-01-01

    Airsickness is the most significant medical condition affecting naval aviation training. A 2001 study showed that airsickness was reported in 81% of naval aviation students and was associated with 82% of below average flight scores. The cost to a single training air-wing was over $150,000 annually for fuel and maintenance costs alone. Resistent cases are sent to the Naval Aerospace Medical Institute (NAMI) for evaluation and desensitization in the self-paced airsickness desensitization (SPAD) program. This approach is 75% successful, but can take up to 8 weeks at a significant travel cost. NASA Ames Research Center's Autogenic Feedback Training Exercises (AFTE) uses physiological and biofeedback training for motion sickness prevention. It has a remote capability that has been used from Moffett Field, CA to Atlanta, GA . AFTE is administered in twelve (30-minute) training sessions. The success rate for the NASA AFTE program has been over 85%. Methods: Implementation Phases: Phase I: Transfer NASA AFTE to NAMI; NASA will remotely train aviation students at NAMI. Phase II: NAMI-centered AFTE application with NASA oversight. Phase III: NAMI-centered AFTE to remotely train at various Navy sites. Phase IV: NAMI to offer Tri-service application and examine research opportunities. Results: 1. Use available telemedicine connectivity between NAMI and NASA. 2. Save over $2,000 per student trained. 3. Reduce aviation training attrition. 4. Provide standardization of multi-location motion sickness training. 5. Future tri-service initiatives. 6. Data to NASA and Navy for QA and research opportunities.

  4. Clinical trial comparing autogenous fascia lata sling and Gore-Tex suspension in bilateral congenital ptosis

    Directory of Open Access Journals (Sweden)

    Elsamkary MA

    2016-03-01

    Full Text Available Mahmoud Ahmed Elsamkary,1 Maged Maher Salib Roshdy1,2 1Ophthalmology Department, Faculty of Medicine, Ain Shams University, Cairo, Egypt; 2Pediatric Ophthalmology Department, Al Watany Eye Hospital, Cairo, Egypt Purpose: To study the effect of autogenous fascia lata sling (AFLS versus Gore-Tex suspension (GTS regarding the functional and aesthetic outcomes in patients with bilateral congenital ptosis. Patients and methods: A prospective comparative randomized single-center study enrolled 110 patients with bilateral congenital ptosis. One group (n=55 underwent AFLS and the second group (n=55 underwent GTS. Exclusion criteria were good levator function, absent Bell’s phenomenon, and abnormal ocular motility. Follow-up period was 2 years. Functional outcome was measured from digital photos by analysis of upper eyelid margin position relative to the superior limbus and classified as very good (<3 mm, good (3–5 mm, poor (>5 mm, and recurrent. Aesthetic outcome was assessed in terms of lid contour, symmetry of eyelid height, and lid crease presence. Complications were also reported. Results: Failure rate (recurrence and complications was less in AFLS (P=0.035. Symmetrical lid height and good contour were more frequently attained by AFLS (P=0.007 and 0.047, respectively. However, the frequency of very good, good, poor, recurrence, lagopthalmos, ectropion, infection, and formed lid crease individually showed no statistically significant difference (P=0.252, 0.482, 1, 0.489, 0.438, 1, 0.618, and 0.506, respectively. Conclusion: AFLS is a better choice in surgery for patients with bilateral congenital ptosis because it has fewer complications and a lesser recurrence rate than GTS. Keywords: ptosis surgery, surgical outcomes, ptosis recurrence, lagophthalmos

  5. Current concepts and future approaches to the development of autologous/autogenous vaccines for veterinary use.

    Science.gov (United States)

    Tollis, M

    2004-01-01

    Current classification of autologous/autogenous (A/A) vaccines is commonly based on the concept of strain/antigen specificity associated with targeted treatment of a restricted number of animals. However, fulfilling these two conditions is not sufficient for immune-veterinary immunebiologicals to be excluded from the provisions of Directive 2001/82/EC. Indeed, non-inactivated A/A vaccines are not automatically considered out of the scope of the community code relating to veterinary medicinal products, in particular to immune-biologicals. As a major consequence of the "regulatory" exclusion from the requirements of EU rules, A/A vaccines can be usually manufactured and distributed without having obtained a marketing authorization by the competent authority of a Member State. Furthermore, strain specificity enables veterinarians to consider the use of these vaccines in quite a large variety of epidemiological circumstances where no "conventional" vaccines are yet available or are considered efficacious. In addition, in contrast to "conventional" vaccines, which are considered exclusively as a preventive tool against infectious diseases, A/A vaccines can also be used to treat "continuing" infections. Although the limited scientific value of these products and the poor investigations of the effector mechanisms involved are widely recognized, their use is still claimed in conditions where disorders in the immune system are suspected. Today, a more appropriate definition of A/A vaccines is one that takes into account their historical tradition and practical use, such as stable- or herd-specific vaccines, custom ("..ized") vaccines, therapeutic vaccines, pharmavaccines, vaccines used for biological therapy, etc. Although acknowledging the "regulatory autonomy" of A/A vaccines versus "conventional" vaccines, here it will be presented as an overview of the necessary points to consider, to guarantee an acceptable standard in the development and control of this particular

  6. [Studies on the pour type resin for denture. (II) Curing shrinkage (author's transl)].

    Science.gov (United States)

    Nagata, K

    1976-09-01

    This study was to investigate the influence of concentration of crossliniking agents in the monomer and pressure applied on the curing shrinkage in pour type resins. A pressure could improve the dimentional accuracy in both case of the syrup and the power-liquid type resins, on the other hand crosslinking agents gave adversed effect on the dimentional accuracy of the pour type resins, especially on that of the group.

  7. Correlation between shrinkage and infection of implanted synthetic meshes using an animal model of mesh infection.

    OpenAIRE

    Mamy, Laurent; Letouzey, Vincent; Lavigne, Jean-Philippe; Garric, Xavier; Gondry, Jean; Mares, Pierre; De Tayrac, Renaud

    2010-01-01

    International audience; INTRODUCTION AND HYPOTHESIS: The aim of this study was to evaluate a link between mesh infection and shrinkage. METHODS: Twenty-eight Wistar rats were implanted with synthetic meshes that were either non-absorbable (polypropylene (PP), n = 14) or absorbable (poly (D: ,L: -lactic acid) (PLA94), n = 14). A validated animal incisionnal abdominal hernia model of mesh infection was used. Fourteen meshes (n = 7 PLA94 and n = 7 PP meshes) were infected intraoperatively with 1...

  8. Influence of raw materials composition on firing shrinkage, porosity, heat conductivity and microstructure of ceramic tiles

    Science.gov (United States)

    Kurovics, E.; Buzimov, A. Y.; Gömze, L. A.

    2016-04-01

    In this work some new raw material compositions from alumina, conventional brick-clays and sawdust were mixed, compacted and heat treated by the authors. Depending on raw material compositions and firing temperatures the specimens were examined on shrinkage, water absorption, heat conductivity and microstructures. The real raised experiments have shown the important role of firing temperature and raw material composition on color, heat conductivity and microstructure of the final product.

  9. Shrinkage of Mt. Bogda Glaciers of Eastern Tian Shan in Central Asia during 1962-2006

    Institute of Scientific and Technical Information of China (English)

    Kaiming Li; Zhongqin Li; Cuiyun Wang; Baojuan Huai

    2016-01-01

    Many small mountain glaciers have been reported undergoing strong shrinkage, and it is therefore important to understand how they respond to climate change. The availability of topographic maps from 1962, Landsat TM imagery from 1990 and ASTER (Advanced Spaceborne Thermal Emission and Radiometer) imagery from 2006 and field investigation of some glaciers allow a comprehensive analysis of glacier change based on glacier size and topography on Mt. Bogda. Results include:(1) an overall loss of a glacierized area by 31.18±0.31 km2 or 21.6%from 1962 to 2006, (2) a marked dependence of glacier area shrinkage on initial size, with smaller glaciers experiencing higher shrinkage levels, (3) the disappearance of 12 small glaciers, (4) a striking difference in area loss between the southern and northern slopes of 25%and 17%, respectively. A subset of the investigated glaciers shows that the area 57.45±0.73 km2 in 1962 reduced to 54.79±0.561 km2 in 1990 and 48.88±0.49 km2 in 2006, with a relative area reduction of 4.6% during 1962–1990, and 10.8%during 1990–2006. The corresponding volume waste increased from 6.9%to 10.2%. Three reference glaciers were investigated in 1981 and revisited in 2009. Their terminus experienced a marked recession. Meteorological data from stations around Mt. Bogda reveals that glacier shrinkage is correlated with winter warming and an extension of the ablation period. Precipitation on the northwest side of the range shows a marked increase, with a slight increase on the southeast side.

  10. Evolutionary trajectory of white spot syndrome virus (WSSV genome shrinkage during spread in Asia.

    Directory of Open Access Journals (Sweden)

    Mark P Zwart

    Full Text Available BACKGROUND: White spot syndrome virus (WSSV is the sole member of the novel Nimaviridae family, and the source of major economic problems in shrimp aquaculture. WSSV appears to have rapidly spread worldwide after the first reported outbreak in the early 1990s. Genomic deletions of various sizes occur at two loci in the WSSV genome, the ORF14/15 and ORF23/24 variable regions, and these have been used as molecular markers to study patterns of viral spread over space and time. We describe the dynamics underlying the process of WSSV genome shrinkage using empirical data and a simple mathematical model. METHODOLOGY/PRINCIPAL FINDINGS: We genotyped new WSSV isolates from five Asian countries, and analyzed this information together with published data. Genome size appears to stabilize over time, and deletion size in the ORF23/24 variable region was significantly related to the time of the first WSSV outbreak in a particular country. Parameter estimates derived from fitting a simple mathematical model of genome shrinkage to the data support a geometric progression (k<1 of the genomic deletions, with k = 0.371 ± 0.150. CONCLUSIONS/SIGNIFICANCE: The data suggest that the rate of genome shrinkage decreases over time before attenuating. Bioassay data provided support for a link between genome size and WSSV fitness in an aquaculture setting. Differences in genomic deletions between geographic WSSV isolates suggest that WSSV spread did not follow a smooth pattern of geographic radiation, suggesting spread of WSSV over long distances by commercial activities. We discuss two hypotheses for genome shrinkage, an adaptive and a neutral one. We argue in favor of the adaptive hypothesis, given that there is support for a link between WSSV genome size and fitness.

  11. Autogeneous Laser and Hybrid Laser Arc Welding of T-joint Low Alloy Steel with Fiber Laser Systems

    Science.gov (United States)

    Unt, A.; Lappalainen, E.; Salminen, A.

    This paper is focused on the welding of low alloy steels S355 and AH36 in thicknesses 6, 8 and 10 mm in T-joint configuration using either autogeneous laser welding or laser-arc hybrid welding (HLAW) with high power fiber lasers. The aim was to obtain understanding of the factors influencing the size of the fillet and weld geometry through methodologically studying effects of laser power, welding speed, beam alignment relative to surface, air gap, focal point position and order of processes (in case of HLAW) and to get a B quality class welds in all thicknesses after parameter optimization.

  12. Team management of atrophic edentulism with autogenous inlay, veneer, and split grafts and endosseous implants: case reports.

    Science.gov (United States)

    Collins, T A; Brown, G K; Johnson, N; Massey, J A; Nunn, B D

    1995-02-01

    Predictable success of autogenous graft and implant reconstructions is critically dependent on preoperative alignment and prosthetic considerations planned by the surgeon and the restorative dentist in a team approach. In such cases the surgeon has an opportunity to place accurate bone grafts that allow implants to be secured in both the correct position and correct axis for good prosthetic restoration. With careful thought, the restorative dentist and surgeon can plan the location, shape, and volume of an implant-graft reconstruction. Nine requirements for successful onlay grating with implants and five case reports illustrating the team approach are presented.

  13. Autogenic incision and terrace formation resulting from abrupt late-glacial base-level fall, lower Chippewa River, Wisconsin, USA

    Science.gov (United States)

    Faulkner, Douglas J.; Larson, Phillip H.; Jol, Harry M.; Running, Garry L.; Loope, Henry M.; Goble, Ronald J.

    2016-08-01

    A paucity of research exists regarding the millennial-scale response of inland alluvial streams to abrupt base-level fall. Studies of modern systems indicate that, over short time scales, the response is a diffusion-like process of upstream-propagating incision. In contrast, evidence from the lower Chippewa River (LCR), located in the upper Midwest of the USA, suggests that autogenic controls operating over time scales of several millennia can overwhelm diffusion, resulting in incision that is prolonged and episodic. During the Last Glacial Maximum, the LCR drained the Chippewa Lobe of the Laurentide Ice Sheet to the glacial upper Mississippi River (UMR). As a meltwater stream, it aggraded and filled its valley with glacial outwash, as did its largest tributaries, which were also meltwater streams. Its nonglacial tributaries aggraded, too, filling their valleys with locally derived sediment. During deglaciation, the UMR incised at least twice, abruptly lowering the LCR's base level - ~ 15 m at 16 ka or earlier and an additional 40 m at ca. 13.4 ka. Each of these base-level falls initiated incision of the LCR, led by upstream migrating knickpoints. The propagation of incision has, however, been a lengthy process. The optically stimulated luminescence (OSL) ages of terrace alluvium indicate that, by 13.5 ka, incision had advanced up the LCR only 15 km, and by 9 ka, only 55 km. The process has also been episodic, resulting in the formation of fill-cut terraces (inferred from GPR surveys and exposures of terrace alluvium) that are younger and more numerous in the upstream direction. Autogenic increases in sediment load and autogenic bed armoring, the result of periodic tributary-stream rejuvenation and preferential winnowing of fines by the incising river, may have periodically caused knickpoint migration and incision to slow and possibly stop, allowing lateral erosion and floodplain formation to dominate. A decline in sediment flux from stabilizing incised tributary

  14. Biaxial Fatigue Cracking from Notch

    Science.gov (United States)

    2013-03-04

    Leevers (reference 11) noticed that the variation in  from 0 to 2 has little effect on the da/dN in PVC ( polyvinyl - chloride ), but reduces the da/dN...under biaxial rotating and bending. Ahmad (reference 2) formulated a model for the biaxial fatigue crack growth in aggressive environment, outlined by...1962, Vol. 90, pp. 238-239. 20. ASM Handbook , Vol. 12 Fractography: 1992, p. 430, 438. 21. Metals Handbook , Vol. 9 Fractography and Atlas of

  15. The effect of resin shades on microhardness, polymerization shrinkage, and color change of dental composite resins.

    Science.gov (United States)

    Jeong, Tae-Sung; Kang, Ho-Seung; Kim, Sung-Ki; Kim, Shin; Kim, Hyung-Il; Kwon, Yong Hoon

    2009-07-01

    The present study sought to evaluate the effect of resin shades on the degree of the polymerization. To this end, response variables affected by the degree of polymerization were examined in this study - namely, microhardness, polymerization shrinkage, and color change. Two commercial composite resins of four different shades were employed in this study: shades A3, A3.5, B3, and C3 of Z250 (Z2) and shades A3, A3.5, B3, and B4 of Solitaire 2 (S2). After light curing, the reflectance/absorbance, microhardness, polymerization shrinkage, and color change of the specimens were measured. On reflectance and absorbance, Z2 and S2 showed similar distribution curves regardless of the resin shade, with shade A3.5 of Z2 and shade A3 of S2 exhibiting the lowest/highest distributions. Similarly for attenuation coefficient and microhardness, the lowest/highest values were exhibited by shade A3.5 of Z2 and shade A3 of S2. On polymerization shrinkage, no statistically significant differences were observed among the different shades of Z2. Similarly for color change, Z2 specimens exhibited only a slight (DeltaE*=0.5-0.9) color change after immersion in distilled water for 10 days, except for shades A3 and A3.5. Taken together, results of the present study suggested that the degree of polymerization of the tested composite resins was minimally affected by resin shade.

  16. Statistical mechanics provides novel insights into microtubule stability and mechanism of shrinkage.

    Science.gov (United States)

    Jain, Ishutesh; Inamdar, Mandar M; Padinhateeri, Ranjith

    2015-02-01

    Microtubules are nano-machines that grow and shrink stochastically, making use of the coupling between chemical kinetics and mechanics of its constituent protofilaments (PFs). We investigate the stability and shrinkage of microtubules taking into account inter-protofilament interactions and bending interactions of intrinsically curved PFs. Computing the free energy as a function of PF tip position, we show that the competition between curvature energy, inter-PF interaction energy and entropy leads to a rich landscape with a series of minima that repeat over a length-scale determined by the intrinsic curvature. Computing Langevin dynamics of the tip through the landscape and accounting for depolymerization, we calculate the average unzippering and shrinkage velocities of GDP protofilaments and compare them with the experimentally known results. Our analysis predicts that the strength of the inter-PF interaction (E(s)(m)) has to be comparable to the strength of the curvature energy (E(b)(m)) such that E(s)(m) - E(b)(m) ≈ 1kBT, and questions the prevalent notion that unzippering results from the domination of bending energy of curved GDP PFs. Our work demonstrates how the shape of the free energy landscape is crucial in explaining the mechanism of MT shrinkage where the unzippered PFs will fluctuate in a set of partially peeled off states and subunit dissociation will reduce the length.

  17. The influence of polymerization shrinkage of resin cements on bonding to metal.

    Science.gov (United States)

    Verzijden, C W; Feilzer, A J; Creugers, N H; Davidson, C L

    1992-02-01

    During the setting of a resin composite cement (RCC) used as an adhesive between a resin-bonded bridge and tooth structure, the adhesion may be disrupted by the development of shrinkage stress. The aim of this study was to investigate the influence of the shrinkage stress of three different RCCs on their adhesive and cohesive qualities when bonded to metal surfaces in a rigid set-up. Two opposing parallel NiCr discs (Wiron 77) were mounted in a tensilometer at a mutual distance of 200 microns and cemented with Panavia Ex, Clearfil F2, or Microfill Pontic C. The alloy surfaces were treated by either electrolytic etching, sand-blasting, silane-coating, or tin-plating. During setting, the discs were kept at their original mutual distance to simulate the extreme clinical situation of "complete" rigidity, where the casting and the tooth cannot move toward each other. The developing shrinkage stress was recorded continuously. During setting, the adhesive strength of the RCCs to silane-coated surfaces was always higher than their early cohesive strength. Electrolytically-etched surfaces as well as sand-blasted surfaces showed, in almost all cases, adhesive failure. The tin-plated samples showed mainly adhesive failure at the metal/resin interface. The highest bond strength values were found for silane-coated surfaces in combination with Clearfil F2.

  18. Non-uniform shrinkage of multiple-walled carbon nanotubes under in situ electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Lunxiong [South China Normal University, Brain Science Institute, Guangzhou (China); Xiamen University, China-Australia Joint Laboratory for Functional Nanomaterials and Physics Department, Xiamen (China); Su, Jiangbin [Xiamen University, China-Australia Joint Laboratory for Functional Nanomaterials and Physics Department, Xiamen (China); Chang Zhou University, School of Mathematics and Physics, Changzhou (China); Zhu, Xianfang [Xiamen University, China-Australia Joint Laboratory for Functional Nanomaterials and Physics Department, Xiamen (China)

    2016-10-15

    Instability of multiple-walled carbon nanotubes (MWCNTs) was investigated by in situ transmission electron microscopy at room temperature. Specially, the non-uniform shrinkage of tubes was found: The pristine MWCNT shrank preferentially in its axial direction from the most curved free cap end of the tube, but the shrinkage of the tube diameter was offset by the axial shrinkage: For the complex MWCNT, the two inner MWCNTs also preferentially axially shrank from their most curved cap ends and separated from each other. However, for the effect of the radial pressure from the out walls which enveloped the two inner tubes and the tube amorphization, the two inner tubes were extruded to come close to each other and finally touched again. The new ''evaporation'' and ''diffusion'' mechanisms of carbon atoms as driven by the nano-curvature of CNT and the electron beam-induced athermal activation were suggested to explain the above phenomena. (orig.)

  19. DH and ESPI laser interferometry applied to the restoration shrinkage assessment

    Science.gov (United States)

    Campos, L. M. P.; Parra, D. F.; Vasconcelos, M. R.; Vaz, M.; Monteiro, J.

    2014-01-01

    In dental restoration postoperative marginal leakage is commonly associated to polymerization shrinkage effects. In consequence the longevity and quality of restorative treatment depends on the shrinkage mechanisms of the composite filling during the polymerization. In this work the development of new techniques for evaluation of those effects under light-induced polymerization of dental nano composite fillings is reported. The composite resins activated by visible light, initiate the polymerization process by absorbing light in wavelengths at about 470 nm. The techniques employed in the contraction assessment were digital holography (DH) and Electronic Speckle Pattern Interferometry (ESPI) based on laser interferometry. A satisfactory resolution was achieved in the non-contact displacement field measurements on small objects concerning the experimental dental samples. According to a specific clinical protocol, natural teeth were used (human mandibular premolars). A class I cavity was drilled and restored with nano composite material, according to Black principles. The polymerization was monitored by DH and ESPI in real time during the cure reaction of the restoration. The total displacement reported for the material in relation of the tooth wall was 3.7 μm (natural tooth). The technique showed the entire tooth surface (wall) deforming during polymerization shrinkage.

  20. Statistical mechanics provides novel insights into microtubule stability and mechanism of shrinkage.

    Directory of Open Access Journals (Sweden)

    Ishutesh Jain

    2015-02-01

    Full Text Available Microtubules are nano-machines that grow and shrink stochastically, making use of the coupling between chemical kinetics and mechanics of its constituent protofilaments (PFs. We investigate the stability and shrinkage of microtubules taking into account inter-protofilament interactions and bending interactions of intrinsically curved PFs. Computing the free energy as a function of PF tip position, we show that the competition between curvature energy, inter-PF interaction energy and entropy leads to a rich landscape with a series of minima that repeat over a length-scale determined by the intrinsic curvature. Computing Langevin dynamics of the tip through the landscape and accounting for depolymerization, we calculate the average unzippering and shrinkage velocities of GDP protofilaments and compare them with the experimentally known results. Our analysis predicts that the strength of the inter-PF interaction (E(s(m has to be comparable to the strength of the curvature energy (E(b(m such that E(s(m - E(b(m ≈ 1kBT, and questions the prevalent notion that unzippering results from the domination of bending energy of curved GDP PFs. Our work demonstrates how the shape of the free energy landscape is crucial in explaining the mechanism of MT shrinkage where the unzippered PFs will fluctuate in a set of partially peeled off states and subunit dissociation will reduce the length.

  1. Influence Of Volcanic Scoria On Mechanical Strength, Chemical Resistance And Drying Shrinkage Of Mortars

    Directory of Open Access Journals (Sweden)

    Al-Swaidani A.

    2014-09-01

    Full Text Available In the study, three types of cement have been prepared; one CEM I type (the control sample and two blended cements: CEM II/A-P and CEM II/B-P (EN 197-1, each of them with three replacement levels of volcanic scoria: (10 %, 15 %, 20 % wt. and (25 %, 30 %, 35 % wt., respectively. Strength development of mortars has been investigated at 2, 7, 28 and 90 days curing. Evaluation of chemical resistance of mortars containing scoria-based cements has been investigated through exposure to 5 % sulphate and 5 % sulphuric acid solutions in accordance with ASTM C1012 & ASTM 267, respectively. Drying shrinkage has been evaluated in accordance with ASTM C596. Test results showed that at early ages, the mortars containing CEM II/B-P binders had strengths much lower than that of the control mortar. However, at 90 days curing, the strengths were comparable to the control mortar. In addition, the increase of scoria significantly improved the sulphate resistance of mortars. Further, an increase in scoria addition improved the sulphuric acid resistance of mortar, especially at the early days of exposure. The results of drying shrinkage revealed that the CEM II/B-P mortar bars exhibited a greater contraction when compared to the control mortar, especially at early ages. However, drying shrinkage of mortars was not influenced much at longer times.

  2. Low shrinkage composite resins: influence on sealing ability in unfavorable C-factor cavities

    Directory of Open Access Journals (Sweden)

    Eliza Burlamaqui Klautau

    2011-02-01

    Full Text Available The present investigation observed the sealing ability of low shrinkage composite resins in large and deep cavities, placed and photocured in one increment. Large, deep cavities (5.0 mm diameter and 2.5 mm deep surrounded by enamel were prepared in bovine teeth, which were then divided into five groups. Groups 1, 2, 3 and 4: acid conditioning + Adper Single Bond (3M/ESPE, St Paul, MN, USA and restoration with Aelite LS Posterior (BISCO Inc. Schaumburg, IL, USA (G1; Filtek Z-350 (3M/ESPE,St Paul, MN, USA (G2; Filtek Z-350 Flow (3M/ESPE, St Paul, MN, USA (G3; Premisa (KERR Corporation, Orange, CA, USA (G4. Group 5: Silorane Adhesive system (3M/ESPE, St Paul, MN, USA + restoration with Filtek Low Shrinkage Posterior P90 (3M/ESPE, St Paul, MN, USA. After polymerization, the teeth were immersed in 0.5% basic fuchsine solution and immediately washed. Using the Imagetool Software, the extent of dye along the margins was calculated as a percentage of total perimeter. The restorations were then transversally sectioned and the depth of dye penetration was calculated in mm, using the same software. Kruskal-Wallis analysis for all groups showed no statistical differences for extent (p = 0.54 or depth (p = 0.8364 of dye penetration. According to this methodology, the so-called low shrinkage composite resins had the same sealing ability compared to regular and flowable nanocomposite materials.

  3. A Study of Shrinkage Stress Reduction and Mechanical Properties of Nanogel-Modified Resin Systems.

    Science.gov (United States)

    Liu, Jiancheng; Howard, Gregory D; Lewis, Steven H; Barros, Matthew D; Stansbury, Jeffrey W

    2012-11-01

    A series of nanogel compositions were prepared from urethane dimethacrylate (UDMA) and isobornyl methacrylate (IBMA) in the presence of a thiol chain transfer agent. The linear oligomer of IBMA was synthesized by a similar solution polymerization technique. The nanogels were prepared with different crosslinker concentrations to achieve varied branching densities and molecular weights. The prepolymers were dispersed in triethylene glycol dimethacrylate at loading levels ranging from 10 wt% to 50 wt%. Photopolymerization reaction kinetics of all prepolymer modified systems were enhanced relative to the nanogel-free control during early stage polymerization while limiting conversion was similar for most samples. Volumetric polymerization shrinkage was reduced proportionally with the prepolymer content while the corresponding decrease in polymerization stress was potentially greater than an additive linear behavior. Flexural strength for inert linear polymer-modified systems decreased significantly with the increase in the prepolymer content; however, with an increase in the crosslinker concentration within the nanogel additives, and an increase in the concentration of residual pendant reactive sites, flexural strength was maintained or improved regardless of the nanogel loading level. This demonstrates that covalent attachment rather than just physical entanglement with the polymer matrix is important for effective polymer mechanical reinforcement by nanogel additives. Reactive nanogel additives can be considered as a practical, generic means to achieve substantial reductions in polymerization shrinkage and shrinkage stress in common polymers.

  4. Large-proportional shrunken bio-replication of shark skin based on UV-curing shrinkage

    Science.gov (United States)

    Chen, Huawei; Che, Da; Zhang, Xin; Yue, Yue; Zhang, Deyuan

    2015-01-01

    The shark skin effect has attracted worldwide attention because of its superior drag reduction. As the product of natural selection, the maximum drag reduction of shark skin is found in its normal living environment. Large-proportional shrinkage of shark skin morphology is greatly anticipated for its adaptation to faster fluid flow. One novel approach, large-proportional shrunken bio-replication, is proposed as a method to adjust the optimal drag reduction region of shark skin based on the shrinkage of UV-cured material. The shark skin is taken as a replica template to allow large-proportional shrinking in the drag reduction morphology by taking advantage of the shrinkage of UV-curable material. The accuracy of the large-proportional shrunken bio-replication approach is verified by a comparison between original and shrunken bio-replicated shark skin, which shows that the shrinking ratio can reach 23% and the bio-replication accuracy is higher than 95%. In addition, the translation of the optimum drag reduction peak of natural surface function to various applications and environments is proved by drag reduction experiments.

  5. Moisture Diffusivity and Shrinkage of Fruit and Cladode of Opuntia ficus-indica during Infrared Drying

    Directory of Open Access Journals (Sweden)

    Amira Touil

    2014-01-01

    Full Text Available Drying behaviour of prickly pear cladodes and fruits was studied with an Infrared dryer. The volume shrinkage for Opuntia ficus-indica products is calculated and a linear relation was established to describe the experimental variation of shrinkage of the product versus its moisture content. Effective diffusion coefficient of moisture transfer was determined using the Fick law at three drying temperatures (40, 50, and 60°C. Shrinkage was also included into the diffusion model for the determination of the effective diffusion coefficient. The obtained results of the effective moisture diffusivity, for the cladode and the fruit, were evaluated in the range of 1.77 × 10−10–5.07 × 10−10 m2/s and 2.53 × 10−10–7.6 × 10−10 m2/s, respectively. The values of the activation energies for cladode and fruit were estimated to be 45.39 and 47.79 kJ/mol, respectively. However, these values of moisture diffusivity were estimated independently of the evolution of moisture content during drying process. Therefore, a correlation (full quadratic equation for moisture diffusivity as a function of moisture content and temperature was developed. The parameters are obtained by a multilinear regression method. This equation was found satisfactory to describe the diffusivity evolution function of moisture content and temperature with correlation coefficients of 91.5 and 95%.

  6. Shrinkage-based diagonal Hotelling’s tests for high-dimensional small sample size data

    KAUST Repository

    Dong, Kai

    2015-09-16

    DNA sequencing techniques bring novel tools and also statistical challenges to genetic research. In addition to detecting differentially expressed genes, testing the significance of gene sets or pathway analysis has been recognized as an equally important problem. Owing to the “large pp small nn” paradigm, the traditional Hotelling’s T2T2 test suffers from the singularity problem and therefore is not valid in this setting. In this paper, we propose a shrinkage-based diagonal Hotelling’s test for both one-sample and two-sample cases. We also suggest several different ways to derive the approximate null distribution under different scenarios of pp and nn for our proposed shrinkage-based test. Simulation studies show that the proposed method performs comparably to existing competitors when nn is moderate or large, but it is better when nn is small. In addition, we analyze four gene expression data sets and they demonstrate the advantage of our proposed shrinkage-based diagonal Hotelling’s test.

  7. The Growth of Small Corrosion Fatigue Cracks in Alloy 7075

    Science.gov (United States)

    Piascik, Robert S.

    2015-01-01

    The corrosion fatigue crack growth characteristics of small (greater than 35 micrometers) surface and corner cracks in aluminum alloy 7075 is established. The early stage of crack growth is studied by performing in situ long focal length microscope (500×) crack length measurements in laboratory air and 1% sodium chloride (NaCl) environments. To quantify the "small crack effect" in the corrosive environment, the corrosion fatigue crack propagation behavior of small cracks is compared to long through-the-thickness cracks grown under identical experimental conditions. In salt water, long crack constant K(sub max) growth rates are similar to small crack da/dN.

  8. Fatigue cracks in Eurofer 97 steel: Part II. Comparison of small and long fatigue crack growth

    Science.gov (United States)

    Kruml, T.; Hutař, P.; Náhlík, L.; Seitl, S.; Polák, J.

    2011-05-01

    The fatigue crack growth rate in the Eurofer 97 steel at room temperature was measured by two different methodologies. Small crack growth data were obtained using cylindrical specimens with a shallow notch and no artificial crack starters. The growth of semicircular cracks of length between 10-2000 μm was followed in symmetrical cycling with constant strain amplitude ( R ɛ = -1). Long crack data were measured using standard CT specimen and ASTM methodology, i.e. R = 0.1. The growth of cracks having the length in the range of 10-30 mm was measured. It is shown that the crack growth rates of both types of cracks are in a very good agreement if J-integral representation is used and usual assumptions of the crack closure effects are taken into account.

  9. Fatigue cracks in Eurofer 97 steel: Part II. Comparison of small and long fatigue crack growth

    Energy Technology Data Exchange (ETDEWEB)

    Kruml, T., E-mail: kruml@ipm.cz [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Zizkova 22, CZ 61662 Brno (Czech Republic); Hutar, P.; Nahlik, L.; Seitl, S.; Polak, J. [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Zizkova 22, CZ 61662 Brno (Czech Republic)

    2011-05-01

    The fatigue crack growth rate in the Eurofer 97 steel at room temperature was measured by two different methodologies. Small crack growth data were obtained using cylindrical specimens with a shallow notch and no artificial crack starters. The growth of semicircular cracks of length between 10-2000 {mu}m was followed in symmetrical cycling with constant strain amplitude (R{sub {epsilon}} = -1). Long crack data were measured using standard CT specimen and ASTM methodology, i.e. R = 0.1. The growth of cracks having the length in the range of 10-30 mm was measured. It is shown that the crack growth rates of both types of cracks are in a very good agreement if J-integral representation is used and usual assumptions of the crack closure effects are taken into account.

  10. Computed tomographic studies of the basis pedunculi in chronic hemiplegic patients: Topographic correlation between cerebral lesion and midbrain shrinkage

    Energy Technology Data Exchange (ETDEWEB)

    Warabi, T.; Miyasaka, K.; Inoue, K.; Nakamura, N.

    1987-09-01

    A computed tomographic method for analyzing the shrinkage of the basis pedunculi (BP) due to the secondary degeneration of the descending fibers was applied in correlation to the site of cerebral lesions in 89 chronic hemiplegic patients. Cerebral lesions in the anterior corona radiata or the anterior limb of the capsula interna caused shrinkage of the medial BP. Lesions in the central corona radiata or the genu and posterior limb of the capsula interna caused shrinkage of the central BP, while lesions of the posterior corona radiata or the posterior limb of the capsula interna caused shrinkage of the lateral BP. These results suggested that CT images are able to reveal the principle sites of atrophy of the descending fiber tracts in chronic hemiplegia.

  11. Effect of cyclic loading on microleakage of silorane based composite compared with low shrinkage methacrylate-based composites

    Directory of Open Access Journals (Sweden)

    Hamid Kermanshah

    2016-01-01

    Conclusion: Silorane did not provide better marginal seal than the low shrinkage methacrylate-based composites (except Aelite. In addition, cyclic loading did not affect the marginal microleakage of evaluated composite restorations .

  12. Crack propagation in fracture mechanical graded structures

    Directory of Open Access Journals (Sweden)

    B. Schramm

    2015-10-01

    Full Text Available The focus of manufacturing is more and more on innovative and application-oriented products considering lightweight construction. Hence, especially functional graded materials come to the fore. Due to the application-matched functional material gradation different local demands such as absorbability, abrasion and fatigue of structures are met. However, the material gradation can also have a remarkable influence on the crack propagation behavior. Therefore, this paper examines how the crack propagation behavior changes when a crack grows through regions which are characterized by different fracture mechanical material properties (e.g. different threshold values KI,th, different fracture toughness KIC. In particular, the emphasis of this paper is on the beginning of stable crack propagation, the crack velocity, the crack propagation direction as well as on the occurrence of unstable crack growth under static as well as cyclic loading. In this context, the developed TSSR-concept is presented which allows the prediction of crack propagation in fracture mechanical graded structures considering the loading situation (Mode I, Mode II and plane Mixed Mode and the material gradation. In addition, results of experimental investigations for a mode I loading situation and numerical simulations of crack growth in such graded structures confirm the theoretical findings and clarify the influence of the material gradation on the crack propagation behavior.

  13. Water transfer properties and shrinkage in lime-based rendering mortars

    Science.gov (United States)

    Arizzi, A.; Cultrone, G.

    2012-04-01

    aspect to be considered in the evaluation of the decay caused by water is the high shrinkage suffered by renders when they are applied on an extended surface (i.e. a wall), especially when they are aerial lime-based mortars. The shrinkage causes the formation of fissures that become an easy way for water to entry and diffuse through the mortar pore system. This factor is rarely taken into consideration during the hydric assays performed in the laboratory, since mortar samples of 4x4x16 or 4x4x4 cm in size do not undergo to such degree of shrinkage. For this reason, we have also studied the shrinkage of these mortars and considered it in the final assessment of mortars hydric properties. The shrinkage was evaluated according to a non-standardized method, by means of a shrinkage-measuring device that measures the mortar dimensional variations over time. This measurement has shown that the highest the lime content the biggest the mortar shrinkage and, consequently, the strongest the decay due to water.

  14. Four-Phase Dendritic Model for the Prediction of Macrosegregation, Shrinkage Cavity, and Porosity in a 55-Ton Ingot

    Science.gov (United States)

    Ge, Honghao; Ren, Fengli; Li, Jun; Han, Xiujun; Xia, Mingxu; Li, Jianguo

    2017-03-01

    A four-phase dendritic model was developed to predict the macrosegregation, shrinkage cavity, and porosity during solidification. In this four-phase dendritic model, some important factors, including dendritic structure for equiaxed crystals, melt convection, crystals sedimentation, nucleation, growth, and shrinkage of solidified phases, were taken into consideration. Furthermore, in this four-phase dendritic model, a modified shrinkage criterion was established to predict shrinkage porosity (microporosity) of a 55-ton industrial Fe-3.3 wt pct C ingot. The predicted macrosegregation pattern and shrinkage cavity shape are in a good agreement with experimental results. The shrinkage cavity has a significant effect on the formation of positive segregation in hot top region, which generally forms during the last stage of ingot casting. The dendritic equiaxed grains also play an important role on the formation of A-segregation. A three-dimensional laminar structure of A-segregation in industrial ingot was, for the first time, predicted by using a 3D case simulation.

  15. Audio-Visual and Autogenic Relaxation Alter Amplitude of Alpha EEG Band, Causing Improvements in Mental Work Performance in Athletes.

    Science.gov (United States)

    Mikicin, Mirosław; Kowalczyk, Marek

    2015-09-01

    The aim of the present study was to investigate the effect of regular audio-visual relaxation combined with Schultz's autogenic training on: (1) the results of behavioral tests that evaluate work performance during burdensome cognitive tasks (Kraepelin test), (2) changes in classical EEG alpha frequency band, neocortex (frontal, temporal, occipital, parietal), hemisphere (left, right) versus condition (only relaxation 7-12 Hz). Both experimental (EG) and age-and skill-matched control group (CG) consisted of eighteen athletes (ten males and eight females). After 7-month training EG demonstrated changes in the amplitude of mean electrical activity of the EEG alpha bend at rest and an improvement was significantly changing and an improvement in almost all components of Kraepelin test. The same examined variables in CG were unchanged following the period without the intervention. Summing up, combining audio-visual relaxation with autogenic training significantly improves athlete's ability to perform a prolonged mental effort. These changes are accompanied by greater amplitude of waves in alpha band in the state of relax. The results suggest usefulness of relaxation techniques during performance of mentally difficult sports tasks (sports based on speed and stamina, sports games, combat sports) and during relax of athletes.

  16. Morphology of autogenous bone graft and castor oil polyurethane in the infraorbital rim of rabbits: a comparative study

    Directory of Open Access Journals (Sweden)

    Mendonça José Carlos Garcia de

    2006-01-01

    Full Text Available PURPOSE: Morphological study comparing castor oil polyurethane and autogenous bone graft to repair bone defect in zygomatic bone of rabbits. METHODS: Twenty-four adult, male New Zealand rabbits were randomly distributed between two groups of twelve. Bone defects of 5mm in diameter were cut through the zygomatic bone and filled with polyurethane discs in the experimental group or autogenous bone harvested from the tibia in the control group. Animals were sacrificed after 30, 60 or 90 days, and the zygomatic bones were macro- and microscopically analyzed. Student's, Fisher's, chi-squared and McNemar's tests were used for statistical analysis. RESULTS: Both the castor oil polyurethane and the autograft adapted well to the defect, with no need for fixation. Fibrous connective tissue encapsulated the polyurethane, but no inflammation or giant cell reaction was observed. Acidophilic and basophilic areas were observed inside the micropores of the polyurethane, suggesting cell nuclei. After 90 days, bone repair with a lamellar pattern of organization was observed in the control group. CONCLUSION: The castor oil polyurethane was biocompatible and did not cause inflammation. It may be considered an alternative to fill bone defects.

  17. Workability’s recreation methodic with application of cupping massage and autogenic training of women student teams’ basketball players

    Directory of Open Access Journals (Sweden)

    Kozina Zh.L.

    2015-04-01

    Full Text Available Purpose: to experimentally subsituate effectiveness of non traditional complex methodic of recreation in female basketball players’ training process. Material: 22 basketball players of women student’s team participated in the research. Pedagogic testing was conducted by 12 tests in special physical and technical fitness. Psycho-physiological testing was conducted by program PSYCHO-DIAGNOSTIC. Groups were trained by identical programs during 9 weeks. Results: we authors observed increased physical and technical fitness of basketball players. Besides, quantity of mistakes in response to visual irritator reduced. It indirectly witnesses about strengthening of nervous processes. There was registered influence of mind on quality of organism’s recreation after physical loads. Conclusions: the authors recommend methodic of cupping massage, combined with autogenic training. Autogenic training implies repeated pronouncing by instructor (or independently by sportswomen of text, describing coming turn by turn natural images. Peculiarities of massage were influence of massage passes on muscles and ligaments. Cupping massage was used after warming up classic massage techniques.

  18. Reconstruction of maxillary ridge atrophy caused by dentoalveolar trauma, using autogenous block bone graft harvested from chin: a case report

    Directory of Open Access Journals (Sweden)

    Francisley Ávila Souza

    2014-06-01

    Full Text Available Background: Dentoalveolar trauma, especially when involving front teeth, negatively affect the patient’s life; in particular, tooth avulsion is a complex injury that affects multiple tissues, and no treatment option offers stable long-term outcomes. The aim of this study was to report a case of reconstruction of atrophic anterior alveolar ridge after tooth loss, performed with autograft harvested from the chin, and subsequent prosthetic rehabilitation with the use of an osseointegrated implant. Case report: A 23-years-old Caucasian girl, presented an atrophic alveolar bone in the area of tooth 11, as a result of tooth resorption 10 years after a tooth reimplantation procedure. Reconstruction was performed with autogenous bone harvested from the chin. After 6-months healing period to allow autograft incorporation, a dental implant was inserted. After further 6- months, a screw-retained implant supported metal-ceramic prosthesis was fabricated. Results The prosthetic rehabilitation was successful, and after a follow-up period of 5 years, the achieved result was stable. Conclusion: It can be concluded that the autogenous bone graft harvested from the chin, is a safe and effective option for alveolar ridge defects reconstruction, allowing a subsequent placement of a dental implant supporting a prosthetic restoration.

  19. Rehabilitation of atrophic maxilla using the combination of autogenous and allogeneic bone grafts followed by protocol-type prosthesis.

    Science.gov (United States)

    Margonar, Rogério; dos Santos, Pâmela Letícia; Queiroz, Thallita Pereira; Marcantonio, Elcio

    2010-11-01

    Currently, there are several techniques for the rehabilitation of atrophic maxillary ridges in literature. The grafting procedure using autogenous bone is considered ideal by many researchers, as it shows osteogenic capability and causes no antigenic reaction. However, this type of bone graft has some shortcomings, mainly the restricted availability of donor sites. In recent years, several alternatives have been investigated to supply the disadvantages of autogenous bone grafts. In such studies, allogeneic bone grafts, which are obtained from individuals with different genetic load, but from the same species, have been extensively used. They can be indicated in cases of arthroplasty, surgical knee reconstruction, large bone defects, and in oral and maxillofacial reconstruction. Besides showing great applicability and biocompatibility, this type of bone is available in unlimited quantities. On the other hand, allogeneic bone may have the disadvantage of transmitting infectious diseases. Atrophic maxillae can be treated with bone grafts followed by osseointegrated implants to obtain aesthetic and functional oral rehabilitation. This study aimed to show the viability of allogeneic bone grafting in an atrophic maxilla, followed by oral rehabilitation with dental implant and protocol-type prosthesis within a 3-year follow-up period by means of a clinical case report.

  20. Controlling fatigue crack paths for crack surface marking and growth investigations

    Directory of Open Access Journals (Sweden)

    S. Barter

    2016-01-01

    Full Text Available While it is well known that fatigue crack growth in metals that display confined slip, such as high strength aluminium alloys, develop crack paths that are responsive to the loading direction and the local microstructural orientation, it is less well known that such paths are also responsive to the loading history. In these materials, certain loading sequences can produce highly directional slip bands ahead of the crack tip and by adjusting the sequence of loads, distinct fracture surface features or progression marks, even at very small crack depths can result. Investigating the path a crack selects in fatigue testing when particular combinations of constant and variable amplitude load sequences are applied is providing insight into crack growth. Further, it is possible to design load sequences that allow very small amounts of crack growth to be measured, at very small crack sizes, well below the conventional crack growth threshold in the aluminium alloy discussed here. This paper reports on observations of the crack path phenomenon and a novel test loading method for measuring crack growth rates for very small crack depths in aluminium alloy 7050-T7451 (an important aircraft primary structural material. The aim of this work was to firstly generate short- crack constant amplitude growth data and secondly, through the careful manipulation of the applied loading, to achieve a greater understanding of the mechanisms of fatigue crack growth in the material being investigated. A particular focus of this work is the identification of the possible sources of crack growth retardation and closure in these small cracks. Interpreting these results suggests a possible mechanism for why small fatigue crack growth through this material under variable amplitude loading is faster than predicted from models based on constant amplitude data alone.

  1. Online Bridge Crack Monitoring with Smart Film

    Directory of Open Access Journals (Sweden)

    Benniu Zhang

    2013-01-01

    Full Text Available Smart film crack monitoring method, which can be used for detecting initiation, length, width, shape, location, and propagation of cracks on real bridges, is proposed. Firstly, the fabrication of the smart film is developed. Then the feasibility of the method is analyzed and verified by the mechanical sensing character of the smart film under the two conditions of normal strain and crack initiation. Meanwhile, the coupling interference between parallel enameled wires of the smart film is discussed, and then low-frequency detecting signal and the custom communication protocol are used to decrease interference. On this basis, crack monitoring system with smart film is designed, where the collected crack data is sent to the remote monitoring center and the cracks are simulated and recurred. Finally, the monitoring system is applied to six bridges, and the effects are discussed.

  2. Air flow through smooth and rough cracks

    Energy Technology Data Exchange (ETDEWEB)

    Kula, H.-G.; Sharples, S. [Sheffield Univ. (United Kingdom). Dept. of Building Science

    1994-12-31

    A series of laboratory experiments are described which investigated the effect of surface roughness on the air flow characteristics of simple, straight-through, no-bend cracks with smooth and rough internal surfaces. The crack thicknesses used in the study were 1.0, 1.5 and 2.0mm. The crack lengths, in the direction of flow, were 50.8mm and 76.2mm. For the rough cracks the roughness was simulated with two different grades of commercially available energy-cloth (grade 60 and 100). The experimental results were satisfactorily fitted to a quadratic relationship between {Delta}p and Q of the form {Delta}p = AQ + BQ{sup 2} for both the smooth and rough crack data. The effect of roughness on the reduction of air flowing through a crack is also discussed. (author)

  3. Crack Propagation in Bamboo's Hierarchical Cellular Structure

    Science.gov (United States)

    Habibi, Meisam K.; Lu, Yang

    2014-07-01

    Bamboo, as a natural hierarchical cellular material, exhibits remarkable mechanical properties including excellent flexibility and fracture toughness. As far as bamboo as a functionally graded bio-composite is concerned, the interactions of different constituents (bamboo fibers; parenchyma cells; and vessels.) alongside their corresponding interfacial areas with a developed crack should be of high significance. Here, by using multi-scale mechanical characterizations coupled with advanced environmental electron microscopy (ESEM), we unambiguously show that fibers' interfacial areas along with parenchyma cells' boundaries were preferred routes for crack growth in both radial and longitudinal directions. Irrespective of the honeycomb structure of fibers along with cellular configuration of parenchyma ground, the hollow vessels within bamboo culm affected the crack propagation too, by crack deflection or crack-tip energy dissipation. It is expected that the tortuous crack propagation mode exhibited in the present study could be applicable to other cellular natural materials as well.

  4. Numerical Study of Corrosion Crack Opening

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle; Frandsen, Henrik Lund; Svensson, Staffan

    2008-01-01

    for the corrosion crack opening. Experiments and theoretical analysis by a numerical method, FEM, support that the relation between the reduction of the reinforcement bar diameter due to corrosion and the corresponding increase in crack width for a given time interval, measured on the surface of a concrete specimen...... is proportional. More recently, the constant of proportionality, the so-called crack-corrosion index, has been studied further with respect to its dependence on the diameter of the reinforcement and the concrete cover. In the present paper the above-mentioned work is presented and extended with more realistic 3D......-models of the cracked concrete beam. The crack-corrosion index is evaluated for a variation of different parameters, i.e. bar diameter, concrete cover, crack length and type of corrosion product. This paper is an extended version of a paper by Thoft-Christensen et al. (2005) presented at the IFIP WG 7.5 Conference...

  5. Crack problem in a long cylindrical superconductor

    Science.gov (United States)

    Yong, Hua-Dong; Zhou, You-He; Zeng, Jun

    2008-12-01

    In this work, the general problem of a center crack in a long cylindrical superconductor is studied. The dependence of the stress intensity factor on the parameters, including the crack length and the applied field, is investigated. We presented a simple model in which the effect of the crack on the critical current is taken into account. It is assumed that the crack forms a perfect barrier to the flow of current. The Bean model and the Kim model are considered for the critical state. Based on the complex potential and boundary collocation methods, the stress intensity factor under the magnetic field is obtained for a long cylindrical superconductor containing a central crack. The results show that the crack length and the applied field have significant effects on the fracture behavior of the superconductor.

  6. Case report: a case of intractable Meniere's disease treated with autogenic training

    Directory of Open Access Journals (Sweden)

    Nakai Kimiko

    2008-01-01

    Full Text Available Abstract Background Psychological stress plays an important role in the onset and course of Meniere's disease. Surgical therapy and intratympanic gentamicin treatment are options for cases that are intractable to conventional medical therapy. Psychotherapy, however, including autogenic training (AT, which can be used for general relaxation, is not widely accepted. This paper describes the successful administration of AT in a subject suffering from intractable Meniere's disease. Case presentation A 51-year-old male patient has suffered from fluctuating right sensorineural hearing loss with vertigo since 1994. In May 2002, he was first admitted to our hospital due to a severe vertigo attack accompanied by right sensorineural hearing loss. Spontaneous nystagmus toward the right side was observed. Since April 2004, he has experienced vertigo spells with right-sided tinnitus a few times per month that are intractable to conventional medical therapy. After four months, tympanic tube insertion was preformed in the right tympanic membrane. Intratympanic injection of dexamethasone was ineffective. He refused Meniett therapy and intratympanic gentamicin injection. In addition to his vertigo spells, he suffered from insomnia, tinnitus, and anxiety. Tranquilizers such as benzodiazepines and antidepressants such as serotonin selective re-uptake inhibitors (SSRIs failed to stop the vertigo and only slightly improved his insomnia. In December 2006, the patient began psychological counseling with a psychotherapist. After brief psychological counseling along with cognitive behavior therapy (CBT, he began AT. He diligently and regularly continued his AT training in his home according to a written timetable. His insomnia, tinnitus, and vertigo spells disappeared within a few weeks after only four psychotherapy sessions. In order to master the six standard formulas of AT, he underwent two more sessions. Thereafter, he underwent follow-up for 9 months with no

  7. DBEM crack propagation for nonlinear fracture problems

    Directory of Open Access Journals (Sweden)

    R. Citarella

    2015-10-01

    Full Text Available A three-dimensional crack propagation simulation is performed by the Dual Boundary Element Method (DBEM. The Stress Intensity Factors (SIFs along the front of a semi elliptical crack, initiated from the external surface of a hollow axle, are calculated for bending and press fit loading separately and for a combination of them. In correspondence of the latter loading condition, a crack propagation is also simulated, with the crack growth rates calculated using the NASGRO3 formula, calibrated for the material under analysis (steel ASTM A469. The J-integral and COD approaches are selected for SIFs calculation in DBEM environment, where the crack path is assessed by the minimum strain energy density criterion (MSED. In correspondence of the initial crack scenario, SIFs along the crack front are also calculated by the Finite Element (FE code ZENCRACK, using COD, in order to provide, by a cross comparison with DBEM, an assessment on the level of accuracy obtained. Due to the symmetry of the bending problem a pure mode I crack propagation is realised with no kinking of the propagating crack whereas for press fit loading the crack propagation becomes mixed mode. The crack growth analysis is nonlinear because of normal gap elements used to model the press fit condition with added friction, and is developed in an iterative-incremental procedure. From the analysis of the SIFs results related to the initial cracked configuration, it is possible to assess the impact of the press fit condition when superimposed to the bending load case.

  8. Transition from Multiple Macro-Cracking to Multiple Micro-Cracking in Cementitious Composites

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jun; LENG Bing

    2008-01-01

    This paper presents an experimental study of the possibility of transition from multiple macro-cracking to multiple micro-cracking in cementitious composites.Conventional polyvinyl alcohol fiber reinforced cementitious composites normally exhibit macroscopic strain-hardening and multiple cracking after the first cracks appear.However,the individual crack width at the saturated stage is normally 60 to 80 μm.In the current study,the effect of fine aggregate size on the cracking performance,especially the individual crack width in the strain-hardening stage was studied by bending tests.The results show that the individual crack widths can be reduced from 60-80 μm to 10-30 μm by modifying the particle size of the fine aggregates used in the composites.

  9. Crack

    Science.gov (United States)

    ... rate, breathing rate, blood pressure , and body temperature decreased appetite and less need for sleep feelings of restlessness, ... effects include: gangrene in the bowels resulting from decreased blood ... chest pain reduced appetite, plus health problems associated with not eating a ...

  10. SPIRALING CRACKS IN THIN SHEETS

    OpenAIRE

    2010-01-01

    En este trabajo de tesis presentamos dos experimentos en que trayectorias de fracturas sumamente reproducibles son obtenidas en láminas delgadas frágiles. En ambos casos, a partir de configuraciones iniciales sumamente simples y pequeñas, las trayectorias obtenidas son espirales logarítmicas de gran tamao. Nuestro primer experimento consiste en un crack que se inicia desde un corte recto hecho en una lámina delgada y que es forzado a propagarse por medio de empujar con un objeto sólido....

  11. Fatigue Crack Closure - A Review

    Science.gov (United States)

    1990-09-01

    gauge along the crack line. They used CCT speci- mens of high tensile strength steel ( HY80 ). The measured value of U was found to be a minimum at the...ultrasonic surface wave technique on 12.5mm thick specimens of 2024-T851, 2024-T351, Al 2219, Ti-6AI-4V and 17-4 PH steel . Most of the results were...medium and high strength steels . Exami- nation of the fracture surfaces suggested that raising the mean stress in low fracture toughness steels could

  12. Fatigue crack growth detect, assess, avoid

    CERN Document Server

    Richard, Hans Albert

    2016-01-01

    This book offers a concise introduction to fatigue crack growth, based on practical examples. It discusses the essential concepts of fracture mechanics, fatigue crack growth under constant and variable amplitude loading and the determination of the fracture-mechanical material parameters. The book also introduces the analytical and numerical simulation of fatigue crack growth as well as crack initiation. It concludes with a detailed description of several practical case studies and some exercises. The target group includes graduate students, researchers at universities and practicing engineers.

  13. Crack depth determination with inductive thermography

    Science.gov (United States)

    Oswald-Tranta, B.; Schmidt, R.

    2015-05-01

    Castings, forgings and other steel products are nowadays usually tested with magnetic particle inspection, in order to detect surface cracks. An alternative method is active thermography with inductive heating, which is quicker, it can be well automated and as in this paper presented, even the depth of a crack can be estimated. The induced eddy current, due to its very small penetration depth in ferro-magnetic materials, flows around a surface crack, heating this selectively. The surface temperature is recorded during and after the short inductive heating pulse with an infrared camera. Using Fourier transformation the whole IR image sequence is evaluated and the phase image is processed to detect surface cracks. The level and the local distribution of the phase around a crack correspond to its depth. Analytical calculations were used to model the signal distribution around cracks with different depth and a relationship has been derived between the depth of a crack and its phase value. Additionally, also the influence of the heating pulse duration has been investigated. Samples with artificial and with natural cracks have been tested. Results are presented comparing the calculated and measured phase values depending on the crack depth. Keywords: inductive heating, eddy current, infrared

  14. Investigations of Low Temperature Time Dependent Cracking

    Energy Technology Data Exchange (ETDEWEB)

    Van der Sluys, W A; Robitz, E S; Young, B A; Bloom, J

    2002-09-30

    The objective of this project was to investigate metallurgical and mechanical phenomena associated with time dependent cracking of cold bent carbon steel piping at temperatures between 327 C and 360 C. Boiler piping failures have demonstrated that understanding the fundamental metallurgical and mechanical parameters controlling these failures is insufficient to eliminate it from the field. The results of the project consisted of the development of a testing methodology to reproduce low temperature time dependent cracking in laboratory specimens. This methodology was used to evaluate the cracking resistance of candidate heats in order to identify the factors that enhance cracking sensitivity. The resultant data was integrated into current available life prediction tools.

  15. Wettability Induced Crack Dynamics and Morphology

    CERN Document Server

    Ghosh, Udita Uday; Bhandari, Aditya Bikram; Chakraborty, Suman; DasGupta, Sunando

    2014-01-01

    Substrate wettability alteration induced control over crack formation process in thin colloidal films has been addressed in the present study. Colloidal nanosuspension (53nm, mean particle diameter) droplets have been subjected to natural drying to outline the effects of substrate surface energies over the dry-out characteristics with emphasis on crack dynamics, crack morphology and underlying particle arrangements. Experimental findings indicate that number of cracks formed decreases with increase in substrate hydrophobicity. These physical phenomena have been explained based on the magnitude of stress dissipation incurred by the substrate. DLVO predictions are also found to be in tune with the reported experimental investigations.

  16. Expansive Soil Crack Depth under Cumulative Damage

    Directory of Open Access Journals (Sweden)

    Bei-xiao Shi

    2014-01-01

    Full Text Available The crack developing depth is a key problem to slope stability of the expansive soil and its project governance and the crack appears under the roles of dry-wet cycle and gradually develops. It is believed from the analysis that, because of its own cohesion, the expansive soil will have a certain amount of deformation under pulling stress but without cracks. The soil body will crack only when the deformation exceeds the ultimate tensile strain that causes cracks. And it is also believed that, due to the combined effect of various environmental factors, particularly changes of the internal water content, the inherent basic physical properties of expansive soil are weakened, and irreversible cumulative damages are eventually formed, resulting in the development of expansive soil cracks in depth. Starting from the perspective of volumetric strain that is caused by water loss, considering the influences of water loss rate and dry-wet cycle on crack developing depth, the crack developing depth calculation model which considers the water loss rate and the cumulative damages is established. Both the proposal of water loss rate and the application of cumulative damage theory to the expansive soil crack development problems try to avoid difficulties in matrix suction measurement, which will surely play a good role in promoting and improving the research of unsaturated expansive soil.

  17. Fatigue Crack Closure Analysis Using Digital Image Correlation

    Science.gov (United States)

    Leser, William P.; Newman, John A.; Johnston, William M.

    2010-01-01

    Fatigue crack closure during crack growth testing is analyzed in order to evaluate the critieria of ASTM Standard E647 for measurement of fatigue crack growth rates. Of specific concern is remote closure, which occurs away from the crack tip and is a product of the load history during crack-driving-force-reduction fatigue crack growth testing. Crack closure behavior is characterized using relative displacements determined from a series of high-magnification digital images acquired as the crack is loaded. Changes in the relative displacements of features on opposite sides of the crack are used to generate crack closure data as a function of crack wake position. For the results presented in this paper, remote closure did not affect fatigue crack growth rate measurements when ASTM Standard E647 was strictly followed and only became a problem when testing parameters (e.g., load shed rate, initial crack driving force, etc.) greatly exceeded the guidelines of the accepted standard.

  18. On the application of cohesive crack modeling in cementitious materials

    DEFF Research Database (Denmark)

    Stang, Henrik; Olesen, John Forbes; Poulsen, Peter Noe;

    2007-01-01

    Cohesive crack models-in particular the Fictitious Crack Model - are applied routinely in the analysis of crack propagation in concrete and mortar. Bridged crack models-where cohesive stresses are assumed to exist together with a stress singularity at the crack tip-on the other hand, are used....... Further, a quantitative condition is established indicating when a bridged crack model can be approximated with a cohesive crack model with smooth crack closure in terms of the ratio between the energy dissipation associated with the crack tip and the process zone....

  19. Crack spacing of unsaturated soils in the critical state

    Institute of Scientific and Technical Information of China (English)

    SUN JiChao; WANG GuangQian; SUN QiCheng

    2009-01-01

    The cracking mechanism of unsaturated soils due to evaporation is poorly understood, and the magnitude of crack spacing is usually hard to estimate. In this work, cracks were postulated to occur suc-cedently rather than simultaneously, that is, secondary cracks appear after primary cracks as evaporation continues. Formulae of the secondary crack spacing and secondary trend crack spacing were then derived after stress analysis. The calculated spacing values were consistent with the published experimental data. Meanwhile, the effect of the Poisson ratio on the crack spacing was analyzed, which showed that the magnitude of crack spacing was proportional to the Poisson ratio in the range of [0.30,0.35].

  20. Maxillary sinus floor augmentation with Bio-Oss or Bio-Oss mixed with autogenous bone as graft in animals: a systematic review

    DEFF Research Database (Denmark)

    Jensen, Thomas; Schou, S; Stavropoulos, A

    2012-01-01

    The objective of the present systematic review was to test the hypothesis of no differences between the use of Bio-Oss or Bio-Oss mixed with autogenous bone as graft for maxillary sinus floor augmentation (MSFA) applying the lateral window technique, as evaluated in animals. A MEDLINE (PubMed...