Industry equipment such as pressure vessels, mining equipment, heat exchang-ers, steam generators and other structures are provided with bolted closures for the purpose of in-service inspection and maintenance of internal components. Threaded connections often experience variable cyclic loads due to temperature, inner pressure and variation in the deformation of connection fittings. Often, studs and screws are not only affected by an axial load, but also by bending moments. More sophisticated high-cycle and low-cycle durability calculation meth-odologies have been already developed for threaded connections experiencing cyclic axial loads, and in these methodologies the distribution of axial load among turns is assessed quantitatively. The quantitative data of load distribu-tion in the thread enables a more accurate assessment of the influence of the constructional design particularities (connection length, material, nut and turn’s form) and the deformation stages of the connection element. These durability calculation methodologies are not applied for threaded connections that are cyclically bent, as the analytical models that are suitable for practical application in the load distribution of the turns have not been cre-ated for bent threaded connections. In this field, no models have been created to be calculated by the BE method. As the threaded connection is a complex node consisting of deformed el-ements, the load distribution among turns is influenced by the... [to full text] / Srieginės jungtys dažnai patiria ciklinių lenkimo apkrovų dėl temperatū-ros, vidaus slėgio ir jungiamųjų detalių deformacijų kitimo. Srieginėms jung-tims, kurios patiria ašinių ciklinių apkrovų jau yra sukurtos modernesnės daugiaciklio ir mažaciklio ilgaamžiškumo skaičiavimo metodikos, kuriomis detaliai kiekybiškai įvertinamas ašinės apkrovos pasiskirstymas tarp vijų. Ap-krovos pasiskirstymo sriegyje kiekybiniai duomenys leidžia detaliau ir tiksliau įvertinti konstrukcijos ypatumų (jungties ilgio, medžiagos, veržlės ir vijų for-mos) ir jungties elementų deformavimo stadijų įtaką. Tokios ilgaamžiškumo skaičiavimo metodikos cikliškai lenkiamoms srieginėms jungtims netaikomos, nes lenkiamoms srieginėms jungtims nėra sukurtų apkrovos pasiskirstymo vijose analitinių modelių, tinkamų praktiniam naudojimui. Šioje srityje taip pat nėra sukurtų ir modelių, kurie skaičiuojami baigtinių elementų metodu. Kadangi srieginė jungtis yra kompleksinis mazgas, kurį sudaro deformuo-jami elementai, tai apkrovos pasiskirstymą tarp vijų lemia jungties elementų deformacijų ir poslinkių suderinamumas. Matematiškai aprašant jungties de-formuotą būvį, reikalingi teoriniai ir eksperimentiniai duomenys, kurie atspin-dėtų jungties elementų deformavimo specifinius ypatumus, pasireiškiančius veikiant lenkimui. Disertacijoje siekiama sukurti cikliškai lenkiamų srieginių jungčių apkro-vos pasiskirstymo sriegyje skaičiavimo metodą ir pritaikyti jį mažacikliam ilga-amžiškumui skaičiuoti.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2015-12-07T22:42:59Z No. of bitstreams: 1 AlinaRochaPiresBarboza_DISSERT.pdf: 2471178 bytes, checksum: 8076374bc4ccf83252093950c45d18de (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2015-12-10T20:32:35Z (GMT) No. of bitstreams: 1 AlinaRochaPiresBarboza_DISSERT.pdf: 2471178 bytes, checksum: 8076374bc4ccf83252093950c45d18de (MD5) / Made available in DSpace on 2015-12-10T20:32:35Z (GMT). No. of bitstreams: 1 AlinaRochaPiresBarboza_DISSERT.pdf: 2471178 bytes, checksum: 8076374bc4ccf83252093950c45d18de (MD5) Previous issue date: 2014-04-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Ambientes recifais sofrem com os impactos do pisoteio humano, prejudicial ? estrutura da comunidade bent?nica. Esse trabalho objetivou 1) caracterizar a comunidade bent?nica no recife de Pirangi/RN, identificando padr?es de zona??o, e 2) avaliar o seu processo de estrutura??o sob diferentes graus de pisoteio. Foram coletados dados de abund?ncia dos organismos, porcentagem de cobertura do substrato e par?metros f?sico-qu?micos. Para responder ao primeiro objetivo, foram amostradas esta??es com diferentes tempos de exposi??o. Verificou-se a forma??o de duas zonas: uma abrangendo ?reas submersas e de menor tempo de exposi??o, de menor rugosidade e maior heterogeneidade na cobertura de substrato, relacionada a organismos como gastr?podes, caranguejos e ouri?o-do-mar; a segunda zona compreende ?reas de maior tempo de exposi??o, maior rugosidade e predom?nio de substrato rochoso, associada ? organismos como cracas, gastr?podes, bivalves e caranguejos. Conclui-se que o recife apresenta padr?o pr?prio de zona??o, influenciado tanto pelo tempo de emers?o quanto por caracter?sticas do substrato. Para o segundo objetivo deste trabalho, foram montados experimentos nas ?reas com diferentes intensidades de pisoteio, contendo os tratamentos: controle (isolado de pisoteio), isolado raspado, pisoteio e pisoteio raspado. Dados de abund?ncia, ?ndices de diversidade e cobertura viva foram comparados e os resultados mostraram que n?o houve diferen?a na estrutura da comunidade dos tratamentos raspados, por?m, a fauna raspada desses tratamentos apresentou uma abund?ncia de organismos menor na ?rea de pisoteio intermedi?rio. Entre os tratamentos n?o raspados, observou-se uma maior abund?ncia da fauna m?vel e riqueza da cobertura viva na ?rea de impacto elevado, enquanto a ?rea de pisoteio intermedi?rio apresentou uma maior porcentagem de cobertura viva. As ?reas controle iniciais e finais diferiram apenas quanto ? porcentagem de cobertura viva. As ?reas que foram raspadas e isoladas n?o diferiram do tratamento pisoteio ao t?rmino do experimento. Sugere-se que a atividade de pisoteio em Pirangi seja descentralizada. / Despite being areas of socioeconomic and ecological importance, the reef environments in northeastern Brazil have been suffering with cluttered tourism impacts, such as trampling, activity that leads to decrease in abundance of organisms, especially benthic, and loss of biodiversity. The objectives of this study were 1) to characterize the benthic community in the shallow sandstone reef of Pirangi/RN, identifying patterns of zonation, and 2) evaluate its process of structuring under different degrees of impact of trampling, providing information to the proper use of the area. Data on abundance of organisms, the percentage coverage of the substrate and physic-chemical parameters were collected. The formation of two zones on the reef was observed: one that considers submerged areas and ones with shorter time of exposure, lower roughness and higher heterogeneity in the coverage of the substrate, with a predominance of sand, foliose algae, rodolit, being related to organisms such as gastropods, crabs and sea-urchin; the second zone comprises areas with longer time of exposure, greater roughness and predominance of bedrock uncovered, being associated with organisms such as barnacles, gastropods, bivalves and crabs. It is concluded that the studied reef presents its own zonation pattern, influenced by both the time of immersion and the substrate characteristics, such as roughness and type of coverage. To answer the second objective of this study, four experimental blocks were mounted on each of the three areas of different intensities of trampling, containing the following treatments: control (isolated from trampling), shaved isolated, trampling and shaved trampling, with data collection by 11 months. The data in abundance, diversity indices and living coverage of the substrate were compared between areas and treatments. The results showed that at the trampling areas, at the end of the experiment, differences were observed between the intensities of the impact, where higher values of abundance and richness of mobile fauna and richness of live coverage (ANOVA, p <0.05) were found in the area of higher trampling intensity. For fauna withdrawal of trampled scraped treatments, it was observed in the area of greatest impact that the abundance of small benthic invertebrates is more than three times smaller than that at the area of intermediate trampling (ANOVA, p <0.05). Initial isolated areas and final ones differed only as to the percentage of live coverage, with an increase of 35% at the end of this experiment. As for the areas that were completely scraped and isolated at the end of the experiment was observed an increase in the percentage of live coverage of 11.11% compared to the initial amount in the area of intermediate impact and 37.5% in the area with greater impact, indicating recovery of the area. It is suggested that the current use of the reef of Pirangi be reviewed, with a decentralization of trampling, or a decrease in visits, so that it does not occur at high intensities

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-01-27T13:44:02Z No. of bitstreams: 1 CarolineGabrielaBezerraDeMoura_TESE.pdf: 2231934 bytes, checksum: 890994db2e35bf07a5f1e900da0830e5 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-01-31T14:50:22Z (GMT) No. of bitstreams: 1 CarolineGabrielaBezerraDeMoura_TESE.pdf: 2231934 bytes, checksum: 890994db2e35bf07a5f1e900da0830e5 (MD5) / Made available in DSpace on 2017-01-31T14:50:22Z (GMT). No. of bitstreams: 1 CarolineGabrielaBezerraDeMoura_TESE.pdf: 2231934 bytes, checksum: 890994db2e35bf07a5f1e900da0830e5 (MD5) Previous issue date: 2015-12-14 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / O objetivo desta tese ? compreender os fatores que influenciam o balan?o de carbono em reservat?rios do semi?rido do nordeste brasileiro e avaliar o efeito de peixes com diferentes h?bitos alimentares no balan?o de carbono destes ambientes. Os resultados desta tese nos mostraram que peixes com diferentes h?bitos alimentares podem influenciar o balan?o de carbono em reservat?rios (Cap?tulo I; Cap?tulo II; Capitulo III). Demonstramos atrav?s de experimentos de mesocosmos que peixes bent?voros (detrit?voros) aumentam a heterotrofia e emiss?o de CO2 para atmosfera, atrav?s da ressuspens?o de mat?ria org?nica e nutrientes presos ao sedimento, que estimulam as taxas de respira??o planct?nica e microbiana, assim como os processos de metanotrofia (Cap?tulo II). Por outro lado, peixes on?voros como a Til?pia do Nilo, favorecem a diminu??o da emiss?o de CO2 para a atmosfera, atrav?s do est?mulo da biomassa fitoplanct?nica ocasionado principalmente via cascata tr?fica pela diminui??o da biomassa de zoopl?ncton (Cap?tulo III). Al?m disso, reservat?rios que apresentam uma domin?ncia de s?lidos inorg?nicos em suspens?o pode indicar que o ambiente est? emitindo CO2 para a atmosfera. Em contrapartida, reservat?rios que apresentam uma domin?ncia de s?lidos org?nicos em suspens?o pode indicar que o ambiente esteja apreendendo CO2 da atmosfera (Cap?tulo I). Podemos concluir, que alguns fatores como a domin?ncia de s?lidos em suspens?o pode ser um indicativo da fun??o do ecossistema aqu?tico frente ao balan?o de carbono. Al?m disso, peixes com diferentes h?bitos alimentares podem influenciar o balan?o de carbono em reservat?rios. / The objective of this thesis is to understand the factors that influence the carbon balance in semi-arid reservoirs in northeastern Brazil and to evaluate the effect of the feeding characteristics in the carbon balance of these environments. The results of this thesis have shown that fish with different feeding characteristics can influence carbon balance in reservoirs (Chapter I, Chapter II, Chapter III). We have demonstrated through experiments mesocosms that benthivorous fish enhance heterotrophic and emission of CO2 to the atmosphere, through the suspension of organic matter and nutrients attached to sediment, which stimulate plankton and microbial respiration rates as well as methanotrophy processes (Chapter II). On the other hand, omnivorous fish like Nile Tilapia favor decrease CO2 emissions to the atmosphere by stimulating phytoplankton biomass mainly caused via trophic cascade by decrease in zooplankton biomass (Chapter III). In addition, reservoirs which have a predominance of inorganic suspended solids may indicate that the environment is emitting CO2 to the atmosphere. However, reservoirs have a dominance of organic suspended solids may indicate that the environment is uptake CO2 by the atmosphere (Chapter I). We can conclude, that some factors such as the dominance of suspended solids may be indicative of the of carbon balance function by aquatic ecosystem. In addition, fish with different feeding characteristics can influence the carbon balance in reservoirs.

Liquid crystals are a vast and diverse class of materials which ranges from fluids made up of simple rods, polymers and solutions, to elastomers and biological organisms. Liquid crystal phases are neither crystalline, nor a ‘normal’ isotropic liquid, but lie somewhere in between these two common states of matter. Liquid crystals have found enormous use in display devices due to their electro-optic properties. In this thesis, the optical and electro-optical properties of some chiral liquid crystalline phases are studied. The optical and electro-optical behaviour of liquid crystalline blue phases has been investigated via a detailed analysis of the reflection spectrum from thin, vertical field (VF) cells. Spectral analysis in this thesis was performed using a numerical fitting technique based on the Berreman 4x4 matrix method. The validity of the technique was proved through comparisons of independent measurements with the calculated physical parameters. A novel Kerr effect measurement method was proposed in this thesis and a known material was used to verify this new method. The Kerr constant together with its dispersion relation was measured using a white light source. An unusually large Kerr constant, K, is determined in the blue phases of a non-polymer stabilized material, ~ 3x10-9 mV-2 (BPI). The large value of K is attributed to significant pre-transitional values of the dielectric anisotropy and birefringence. K follows an inverse dependence on temperature which is more marked in BPII than BPI, and we consequently suggest that the BPI demonstrates properties best suited to electro-optic devices. The field effects in blue phase include electrostriction and the influence of the Kerr effect was separated from electrostriction phenomena for the first time in this work. Finally in the Kerr effect measurements, the Kerr constant in the optically isotropic dark conglomerate phase of a bent-core material was studied for the first time, with rather low values, ~1x10-11 mV-2. The low Kerr constant can be understood in the context of the physical properties of the material. Supercooling phenomena in the blue phase were studied through an analysis of the optical properties in thin cells. Features including the Bragg reflection peak jump and hysteresis are measured through the reflection spectra. A blue phase sample with a single orientation over an area of millimeters was prepared to help the spectra study of the blue phases. Although some previous reports indicated that there may be a new blue phase in the supercooled region, we find that there is no evidence shows that the supercooled blue phase has a different structure from the BPI.Chiral molecules have been included as dopants in achiral bent-core materials to produce a range of new chiral mixtures. Different host materials and chiral dopants have been used to produce several chiral nematic materials in which the chiral nematic phase, the underlying smectic phase and the blue phases are examined. The order parameter is determined as a function of temperature in the chiral nematic phase, and compared to that determined for several calamitic materials; no discernible difference is found. A study of the pitch divergence in the chiral nematic phase of the bent-core mixtures shows interesting properties at both low temperature (as the smectic phase is approached) and at high temperatures (at the transition to the blue phase). An unusual phase separation of the chiral dopant in the mixtures is reported, and details are deduced through a comparison between different mixtures. It is found that a dopant with similar clearing point to the bent-core material has less likelihood of phase separation. Although the blue phase temperature range is extended in these mixtures in comparison with typical values for calamitic materials, it does not extend beyond 2K in any of the materials. Both blue phase I and the fog phases are observed in these chiral bent core systems, but no BPII is observed in any of the materials studied. The small k33 (~ 2.8 pN at 10 K below clearing point) in the bent-core host material is suggested as one of the reasons that the blue phase range is not enhanced as much as may have been expected from reports by other authors.

This thesis was funded by the Natural Environment Research Council (NERC) and is presented in an alternative thesis format. The thesis consists of three separate journal articles which form a coherent research project. Paper 1 investigates the development of strong winds in a dry, idealised extratropical cyclone using the horizontal momentum equation. In particular, the southwest wind maximum that develops was found to contain air parcels from three airstreams. The development of the horizontal along-flow forces around the cyclone and along trajectories entering the southwest wind maximum were analysed. An attempt to extend this methodology to a moist, idealised extratropical cyclone was made. However, the effect of adding moisture to the initial condition was found to be negligible. The reasons for this are explored in Paper 2, which documents this finding: that the effect of moisture on the development of an idealised, baroclinic wave is sensitive to the choice of initial condition. Paper 3 applies the horizontal momentum equation diagnostics to an intense, marine extratropical cyclone that brought strong winds to Ireland and the United Kingdom on 12 February 2014. The development of strong winds in Cyclone Tini was investigated by turning off latent heat release and surface fluxes. In the absence of latent heat release a weaker wind maximum developed. However, the simulation without surface fluxes had a very similar vertical structure of the horizontal wind to the full-physics simulation, but a weaker surface wind maximum. The reason for this weaker wind maximum was analysed using the quasigeostrophic omega equation. This analysis demonstrated a maximum in forcing for descent southwest of the low both in the full-physics simulation and in the simulation without surface fluxes, however strong winds were prevented from reaching the surface in the simulation without surface fluxes because of a more stable boundary layer around the bent-back front.

Much of the interest in bent-core compounds in the last few years has centred aroundtheir potential to form nematic liquid crystal phases, which may be both biaxial andpolar. These properties offer possibilities for nematic ferroelectric switching andnonlinear optics applications. In this work, two optical properties, the refractive indices and the second ordernonlinear optical response, were investigated in the high temperature (> 170 °C)nematic phase of a series of bent-core oxadiazole compounds, of varying chain typeand length. An experimental technique, based on the acquisition and analysis of reflectionspectra from liquid crystal cells, and capable of operating at the high temperaturesrequired, was used for the measurement of refractive indices. The extraordinaryrefractive index was found to range from 1.70 to 1.78 over the nematic phase of thebent-core compounds. The ordinary refractive index varied from 1.58 to 1.62. Bothranges of values are higher than is typically observed for rod-like liquid crystals. Thebirefringence took values from ~ 0.10, in the high temperature nematic phase, to~ 0.18, close to the underlying smectic phase. A new experiment was designed, constructed and tested for the second harmonic(SH) measurements. The dependences of the SH on temperature and on scatteringangle are well explained by the theory of SH generation by the flexoelectricpolarisation induced by thermal fluctuations of the director in the nematic phase. Themaximum conversion efficiency was measured to be very low, ~ 1/10000 of apercent. No evidence for the formation of macroscopic biaxial nematic phases was found byeither the refractive indices or SH experiments. However, for the compounds havinglong nematic phases of > 50 °C, different regimes of behaviour in the uniaxialnematic phase were revealed by the SH experiments. This atypical behaviour isconsistent with other reports on these compounds. This study cannot confirm the existence of nanoscale cybotactic clusters in thenematic phases of the bent-core compounds examined but neither is it inconsistentwith them.

No description available.

Segmented regression is a type of nonlinear regression that allows differing functional forms to be fit over different ranges of the explanatory variable. This paper considers the simple segmented regression case of two linear segments that are constrained to meet, often called the linear-linear model. Parameter estimation in the case where the joinpoint between the regimes is unknown can be tricky. Using a simulation study, four estimators for the parameters of the linear-linear model are evaluated. The bias and mean squared error of the estimators are considered under differing parameter combinations and sample sizes. Parameters estimated in the model are the location of the change-point, the slope and intercept of the first segment, the change in slope from the first segment to the second, and the variance over both segments.

No description available.

No description available.