A crack perpendicular to and terminating at a bimaterial interface

Using dislocation simulation approach, the basic equation for a finite crack perpendicular to and terminating at a bimaterial interface is formulated. A novel expansion method is proposed for solving the problem. The complete solution to the problem, including the explicit formulae for the T stresses ahead of the crack tip and the stress intensity factors are presented. The stress held characteristics are analysed in detail. It is found that normal stresses sigma(x) and sigma(y) ahead of the crack tip, are characterised by Q fields if the crack is within a stiff material and the parameters \p(T)\ and \q(T)\ are very small, where Q is a generalised stress intensity factor for a crack normal to and terminating at the interface. If the crack is within a weak material, the normal stresses sigma(x) and sigma(y) are dominated by the Q field plus T stress.

Tensile and compressive deformation of a short-glass-fiber-reinforced liquid-crystalline polymer

Results of tensile and compression tests on a short-glass-fiber-reinforced thermotropic liquid crystalline polymer are presented. The effect of strain rate on the compression stress-strain characteristics has been investigated over a wide range of strain rates epsilon between 10(-4) and 350 s-1. The low-strain-rate tests were conducted using a screw-driven universal tensile tester, while the high-strain-rate tests were carried out using the split Hopkinson pressure bar technique. The compression modulus was shown to vary with log10 (epsilon) in a bilinear manner. The compression modulus is insensitive to strain rate in the low-strain-rate regime (epsilon = 10(-4) - 10(-2) s-1), but it increases more rapidly with epsilon at higher epsilon. The compression strength changes linearly with log10 (epsilon) over the entire strain-rate range. The fracture surfaces were examined by scanning electron microscopy.

Analysis of a second-order polarization-independent filter made of a single ring resonator and a Sagnac interferometer

A novel second-order polarization-independent filter made of a single ring resonator and a Sagnac interferometer (SRRSI) is proposed, and its filtering characteristics are investigated. By using birefringence in waveguide, a single ring resonator can be used to synthesize a filter with second-order response. Analytical formulas are derived for characteristics of the SRRSI varied with waveguide parameters.. such as the coupling coefficient; and the critical condition of a second-order Butterworth filter is given. The influence of loss in the ring resonator is also analyzed. (c) 2005 Elsevier B.V. All rights reserved.

长期重金属污染胁迫下农田土壤微生物特征研究

本论文以沈阳张士污灌区土壤为例，首次采用传统微生物生态学与现代微生物分子生态学相结合的研究方法系统地研究了污灌区长期重金属污染胁迫下原位农田土壤微生物特征。结果表明，虽然已经停止污灌十多年，张士灌区土壤耕作层（0～30 cm）仍然存在普遍的Cd污染，灌区土壤Cd含量高达1.75～3.89 mg kg-1。部分区域土壤Cd呈现向下迁移的趋势,且同时伴随有Cu、Zn复合污染。灌区土壤Cd含量较高时清水灌溉能降低土壤表层Cd含量，灌区土壤Cd含量下降到一定程度（约2 mg kg-1）后，清水灌溉对消除土壤表层Cd污染的作用消失。重金属元素中Cd对土壤微生物的影响最突出，在三个不同季节中土壤Cd与土壤微生物生物量（MBC）和微生物商（qM）呈显著负相关，与土壤微生物代谢商（qCO2）呈显著正相关。所检测的微生物指标中qM和qCO2与多种重金属元素呈显著相关性，可作为评价一定程度重金属污染的微生物指标。土壤营养元素（除P外）与微生物特征呈显著正相关性，土壤营养元素对微生物的刺激作用有可能在某种程度上掩盖了重金属对土壤微生物的负面影响。 用16S rDNA-PCR-DGGE方法，研究了不同浓度Cd胁迫下土壤Cd抗性细菌群落结构的动态变化，结果表明在Cd的胁迫下Cd抗性细菌多样性显著增加，不同土壤样品中Cd抗性细菌群落结构向相似的方向偏移，群落结构最终将可能趋向一致。Cd胁迫使敏感菌Pontibacter消失，而伯克氏菌（Burkholderia）、罗尔斯通氏菌（Ralstonia）、芽孢杆菌（Bacillus）和节杆菌（Arthrobacter）则富集成为优势菌。 从张士灌区Cd污染土壤中分离出32株Cd抗性细菌，研究了Cd抗性细菌和Cd抗性基因cadA的分布特征。这32株Cd抗性细菌分别归属于拟杆菌门(Bacteroidetes)（37.5%）、变形菌门(Proteobacteria) （37.5%）、放线菌门(Actinobacteria)（9.4%） 和厚壁菌门(Firmicutes)（15.6%）。在液体LB培养基中对Cd的抗性浓度都大于2 mmol L-1，对Zn抗性浓度介于5～13 mmol L-1。首次从Cetobacillus属的Cd抗性菌株S1基因组DNA中扩增出cadA基因的部分片断。在芽孢杆菌属(Bacillus)的4株菌N7，N9，N10和N11的基因组DNA中扩增出cadA基因的部分片断。序列分析结果表明这5株菌的cadA基因序列相似性为99％～93％，它们与坚强芽孢杆菌（Bacillus firmus） cadA 基因序列(M90750）相似性为94％～92％。系统发育分析结果表明这5株菌的cadA都与Bacillus firmus cadA 基因有着较近的亲缘关系。不同属的Cd抗性细菌间cadA基因的高度相似性揭示了cadA基因能在不同种属间转移的特性。

岩石类材料静态、动态拉伸弹性模量测试方法研究——以巴西圆盘试验和霍普金森压杆、效应为手段

As we all know, rock-like materials will absolutely show very different mechanical properties under the compressive stress and tensile stress respectively. Similarly, under the dynamic compressive stress or dynamic tensile stress, the characteristics of the dynamics showed by the rock-like materials also have great differences from the mechanical behavior under static force. Studying their similarities and differences in rock mechanics theory and practical engineering will be of great significance. Generally, there are compression modulus of elasticity and tensile modulus of elasticity corresponding to compressive stress state and the tensile stress state in the rock. Both the two kinds of elastic modulus play an extremely important role in calculation of engineering mechanics. Their reliability directly affects the accuracy and reliability of the calculation results of internal stress field and displacement field of engineering rock mass. At present, it is easy to obtain the compression modulus of elasticity in laboratory; but it is very difficult to determine the tensile modulus of elasticity with direct tensile test due to that direct tensile test is difficult to perform in laboratory in general. In order to solve this problem, this thesis invents and develops several indirect test methods to determine the static or dynamic tensile modulus of elasticity of rock-type materials with high reliability and good interoperability. For the static tensile modulus of elasticity, the analytical stress field solution has been given out for the Brazilian disc under the radial and linear concentration load with Airy stress function method. At the same time, the stress field has been modeled for the Brazilian disc test by using the finite element software of ANSYS and ADINA. The analytical stress field solution is verified to be right by comparatively researching the analytical stress field solution and the numerical stress field solution. Based on the analytical stress field solution, this thesis proposes that a strain gauge is pasted at the Brazilian disc center along the direction perpendicular to the applied force to indirectly determine the static tensile modulus of elasticity, and related measurement theory also has been developed. The method proposed here has good feasibility and high accuracy verified by the experimental results. For the dynamic tensile modulus of elasticity, two measuring methods and theories are invented here. The first one is that the Split Hopkinson Pressure Bar is used to attract the Brazilian disc to generate the dynamic load, make the dynamic tensile stress is formed at the Brazilian disc center; and also a strain gauge is pasted at the Brazilian disc center to record the deformation. The second is that, in the Hopkinson effect phenomenon, the reflection tensile stress wave is formed when the shock wave propagates to the free end of cylindrical rock bar and reflect, which can make the rock bar is under dynamic tensile stress state; and some strain gauges are pasted at the appropriate place on the rock bar to record the strain coursed by the tensile or compressive stress wave. At last, the dynamic tensile modulus of elasticity can be determined by the recorded strain and the dynamic tensile stress which can be determined by related theories developed in this thesis.

The quality of parenting of individuals who had failed to thrive as children

Parenting behaviour is determined by a range of factors including personality, psychopathology, values, social support, child characteristics and socio-cultural influences. It has also been suggested that an individual's style of child-rearing is influenced by the style of parenting that they experienced as children. The relationships between children who fail-to-thrive and their parents are often characterized by interactional difficulties. Previous research using retrospective accounts suggested that mothers of children who fail-to-thrive for non-organic reasons themselves showed high levels of abuse, neglect, and deprivation during their childhoods. However, to date no one has investigated prospectively what kinds of parents failure-to-thrive individuals become. This paper examines the parenting experiences of individuals who had received psychosocial intervention for their non-organic failure-to-thrive as children over 20 years ago. Results suggest that where initial intervention failed to bring about long-term changes in family interactional patterns, there was a greater incidence of failure-to-thrive in the next generation. These families were characterized by dissatisfaction with the child, high levels of stress associated with the parenting role, and low levels of social support. However, where the family environment in the original study had changed substantially, the former clients' outcomes were more positive with their own children. These parents tended to find interaction with their children more rewarding, had good support networks and low levels of stress. The characteristics of particular cases are discussed in detail to illustrate differences between these two groups of individuals.

Early pain in preterm infants. A model of long-term effects

There are multiple lines of evidence suggesting that in vulnerable prematurely born infants, repeated and prolonged pain exposure may affect the subsequent development of pain systems, as well as potentially contribute to alterations in long-term development and behavior. Multiple factors cumulatively contribute to altered developmental trajectories in such infants. These include characteristics of the developing organism (low tactile threshold, sensitization, rapid brain development), characteristics intrinsic to the infant (gestation, illness severity), characteristics of the experience in the neonatal intensive care unit (pain exposure and cumulative stress), and characteristics of the caregivers within their family and social context. This article provides a model for examining long-term effects of pain in the newborn period embedded in a developmental context framework.

Studies on prevulcanization of rubber latex with special reference to influence of storage and after treatments on properties of films

Systematic investigations on prevulcanization of NR latex with special reference to the influence of storage of latex and after-treatments of films, have been carried out. The other aspects studied include the effect of temperature on sulphur prevulcanization, the extent of crosslinking, tensile properties, stress relaxation characteristics, water absorption and leaching characteristics of prevulcanizcd latex films

“Studies on short polyester fiber - polyurethane elastomer composite with different interfacial bonding agents”

The work presented in this thesis is regarding the development and evaluation of new bonding agents for short polyester fiber - polyurethane elastomer composites. The conventional bonding system based on hexamethylenetetramine, resorcinol and hydrated silica was not effective as a bonding agent for the composite, as the water eliminated during the formation of the RF resin hydrolysed the urethane linkages. Four bonding agents based on MDI/'I‘DI and polypropyleneglycol, propyleneglycol and glycerol were prepared and the composite recipe was optimised with respect to the cure characteristics and mechanical properties. The flow properties, stress relaxation pattern and the thermal degradation characteristics of the composites containing different bonding agents were then studied in detail to evaluate the new bonding systems. The optimum loading of resin was 5 phr and the ratio of the -01 to isocyanate was 1:1. The cure characteristics showed that the optimum combination of cure rate and processability was given by the composite with the resin based on polypropyleneglycol/ glycerol/ 4,4’diphenylmethanediisocynate (PPG/GL/MDI). From the rheological studies of the composites with and without bonding agents it was observed that all the composites showed pseudoplastic nature and the activation energy of flow of the composite was not altered by the presence of bonding agents. Mechanical properties such as tensile strength, modulus, tear resistance and abrasion resistance were improved in the presence of bonding agents and the effect was more pronounced in the case of abrasion resistance. The composites based on MDI/GL showed better initial properties while composites with resins based on MDI/PPG showed better aging resistance. Stress relaxation showed a multistage relaxation behaviour for the composite. Within the-strain levels studied, the initial rate of relaxation was higher and the cross over time was lesser for the composite containing bonding agents. The bonding agent based on MDI/PPG/GL was found to be a better choice for improving stress relaxation characteristics with better interfacial bonding. Thennogravimetirc analysis showed that the presence of fiber and bonding agents improved the thennal stability of the polyurethane elastomer marginally and it was maximum in the case of MDI / GL based bonding agents. The kinetics of degradation was not altered by the presence of bonding agents

Estudo do comportamento de um solo mole tratado com cal, visando seu uso em fundações superficiais

Neste trabalho foi analisada a melhoria nas características de um solo mole quando tratado com cal, bem como a viabilidade técnica de se utilizar este novo material como uma camada suporte de fundações superficiais. O solo estudado classifica-se pedologicamente como Gley Húmico e a jazida localiza-se no município de Canoas/RS, às margens da BR 386. O trabalho teve as seguintes finalidades: realizar um estudo da influência dos diferentes teores de cal sobre as características tensão x deformação do solo tratado; verificar o ganho de resistência com o tempo de cura; modelar o comportamerito tensão x deformação do material tratado; realizar simulações numéricas, através do Método dos Elementos Finitos, do comportamento carga x recalque de fundações continuas flexíveis assentes sobre o novo material. Adotou-se o teor ótimo de cal (obtido pelo método de Eades & Grim, 1966) de 9% e dois valores inferiores de 7% e 5%. Realizaram-se os seguintes ensaios sobre o solo natural e as misturas de solo-cal: limites de Atterberg, compactação, granulometria, difratograma de raio X, permeabilidade (triaxial) e ensaios triaxiais adensados não drenados(CIU). Todos os ensaios foram realizados para três tempos de cura (7, 28 e 90 dias) e os corpos de prova foram curados em câmara úmida. Para modelar o comportamento tensão x deformação do solo melhorado, adotou-se o Modelo Hiperbólico e para o solo natural o Modelo Cam-Clay Modificado. O Modelo Hiperbólico foi implementado no software CRISPSO, desenvolvido na Universidade de Cambridge, Inglaterra. O software foi utilizado em um estudo paramétrico para determinar a influência do processo de estabilização no comportamento carga x recalque de fundações superficiais. Dos resultados obtidos, concluiu-se: que o método de Eades & Grim (1966) não mostrou-se adequado para determinação do teor ótimo de cal; houve, de maneira geral, melhora nas características físicas com o tratamento com cal; não houve ganho de resistência com o tempo de cura; o modelo hiperbólico representou bem o comportamento das misturas de solo cal e a colocação de uma camada de solo tratado apresenta melhoras no comportamento carga x recalque de fundações superficiais contínuas flexíveis.

The reduced modulus in the analysis of sharp instrumented indentation tests

In the analysis of instrumented indentation data, it is common practice to incorporate the combined moduli of the indenter (E-i) and the specimen (E) in the so-called reduced modulus (E-r) to account for indenter deformation. Although indenter systems with rigid or elastic tips are considered as equivalent if E-r is the same, the validity of this practice has been questioned over the years. The present work uses systematic finite element simulations to examine the role of the elastic deformation of the indenter tip in instrumented indentation measurements and the validity of the concept of the reduced modulus in conical and pyramidal (Berkovich) indentations. It is found that the apical angle increases as a result of the indenter deformation, which influences in the analysis of the results. Based upon the inaccuracies introduced by the reduced modulus approximation in the analysis of the unloading segment of instrumented indentation applied load (P)-penetration depth (delta) curves, a detailed examination is then conducted on the role of indenter deformation upon the dimensionless functions describing the loading stages of such curves. Consequences of the present results in the extraction of the uniaxial stress-strain characteristics of the indented material through such dimensional analyses are finally illustrated. It is found that large overestimations in the assessment of the strain hardening behavior result by neglecting tip compliance. Guidelines are given in the paper to reduce such overestimations.

Degradation and stabilisation of diisocyanate cured polybutadiene

Hydroxyl terminated polybutadiene (HTPB) has been used as a rocket propellant binder which is required to be stored for at least twenty years. It is found that the excellent stress-strain characteristics of this propellant can be totally lost, during this long storage, due to the deterioration of the polybutadiene chains. As a result, the propellant can not stand the service loads, which may lead to a catastrophe. The study of the HTPB binder degradation, below 80°C, has been carried out by investigating the environmental factors and the changes which occur along the macromolecular chains. Results have shown that oxygen is the main factor which causes the crosslinking and chain scission reactions. The former is the predominant reaction and proceeds rapidly under oxygen sufficient environment. The unsaturation of polymer chain, which provides the desired physical properties to the binder, was lost with the increase in crosslink density. At the same time hydroperoxides were found to form and decompose along the polymer chains. Therefore, the deterioration of the binder results from the oxidation of polymer chains. Since the oxidation reaction occurred at higher rate than oxygen diffusion rate and oxygen diffusion rate is inversely proportional to the crosslink density, the binder, below the surface layer in a thick section container, could be naturally protected under an oxygen deficient condition for a long time. Investigation of the effectiveness of antioxidants in HTPB binder has shown that the efficiency of an antioxidant depends on its ability to scavenge radicals. Generally, aromatic amines are the most effective binder antioxidants. But when a peroxide decomposer is combined with an aromatic amine at the appropriate ratio, a synergistic effect is obtained, which gives the lowest binder gel increase rate.

Reacções psicológicas e estratégias de coping parentais, face ao diagnóstico de perturbação do espectro do autismo, de um filho

Dissertação de Mestrado apresentada ao Instituto Superior de Psicologia Aplicada para obtenção de grau de Mestre na especialidade de Psicologia Clínica.

Barley genotype expressing "stay-green"-like characteristics maintains starch quality of the grain during water stress condition

The identification of "stay-green" in sorghum and its positive correlation with yield increases has encouraged attempts to incorporate "stay-green"-like traits into the genomes of other commercially important cereal crops. However, knowledge on the effects of "stay-green" expression on grain quality under extreme physiological stress is limited. This study examines impacts of "stay-green"-like expression on starch biosynthesis in barley (Hordeum vulgare L.) grain under mild, severe, and acute water stress conditions induced at anthesis. The proportions of long amylopectin branches and amylose branches in the grain of Flagship (a cultivar without "stay-green"-like characteristics) were higher at low water stress, suggesting that water stress affects starch biosynthesis in grain, probably due to early termination of grain fill. The changes in long branches can affect starch properties, such as the rates of enzymatic degradation, and hence its nutritional value. By contrast, grain from the "stay-green"-like cultivar (ND24260) did not show variation in starch molecular structure under the different water stress levels. The results indicate that the cultivar with "stay-green"-like traits has a greater potential to maintain starch biosynthesis and quality in grain during drought conditions, making the "stay-green"-like traits potentially useful in ensuring food security. (C) 2013 Elsevier Ltd. All rights reserved.

End-bearing capacity of driven piles in sand using the stress characteristics method: analysis and implementation

The method of stress characteristics has been employed to compute the end-bearing capacity of driven piles. The dependency of the soil internal friction angle on the stress level has been incorporated to achieve more realistic predictions for the end-bearing capacity of piles. The validity of the assumption of the superposition principle while using the bearing capacity equation based on soil plasticity concepts, when applied to deep foundations, has been examined. Fourteen pile case histories were compiled with cone penetration tests (CPT) performed in the vicinity of different pile locations. The end-bearing capacity of the piles was computed using different methods, namely, static analysis, effective stress approach, direct CPT, and the proposed approach. The comparison between predictions made by different methods and measured records shows that the stress-level-based method of stress characteristics compares better with experimental data. Finally, the end-bearing capacity of driven piles in sand was expressed in terms of a general expression with the addition of a new factor that accounts for different factors contributing to the bearing capacity. The influence of the soil nonassociative flow rule has also been included to achieve more realistic results.