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The rice leafroller Cnaphalocrocis exigua (Butler) in the only species of the rice leaf folder/roller complex in Fiji. It is one of the major rice pests in the country, its pest status being exacerbrated by the cultivation of high-yielding varieties with minimal pest resistance. Detailed studies on the biology of the moth, in particular on the development, emergence, mating and flight behaviour, effect of adult nutrition on fecundity, egg hatchability and longevity, effect of larval nutrition on larval survival, pupation, pupal weight, pupal eclosion, and fecundity, egg hatchability and longevity of resultant adults, parasitism, and population ecology of C. exigua were carried out in Fiji from 1985 to 1987, and from June to August 1990. This study showed that there are several parasitoids of C. exigua in Fiji, and of those the egg and larval parasitoids Trichogramma sp. and Trathala flavo-orbitalis (Cameron) respectively are significant biotic mortality factors. Their impact as natural suppressors of C. exigua in fields of high yielding rice varieties was, however, inadequate to prevent C. exigua reaching damaging levels. Since C. exigua responds strongly to rice varietal differences, plant nitrogen status, and seasonal factors, is suspected to utilise pheromones during mating, and has numerous biocontrol agents in South East Asia and the Philippines, it appears to be an excellent candidate for an integrated pest management (IPM) program in Fiji. Before IPM strategies can be formulated, however, further investigations on rice varietal resistance, exploitation of exotic parasitoids and pathogens, and detailed studies on the possible presence of sex pheromones need to be conducted. / Doctor of Philosophy (PhD)

This research investigates the safety performance of two types of pedestrian crossing control systems by examining driver compliance at these crosswalks in Winnipeg. The research analyzes driver compliance as a function of type of treatment, weather conditions, pedestrian approach location, and site characteristics. In addition, the research analyzes driver compliance before-and-after the implementation of 30 km/h speed limits in school zones. The findings from this research suggest that: (1) treatment and certain site characteristics (i.e., number of lanes) have a significant impact on driver compliance at crosswalks; and (2) weather conditions, pedestrian approach locations, and reduced speed school zones likely impact driver compliance at crosswalks but the findings were not always statistically significant. The research recognizes numerous factors that influence driver compliance and in turn pedestrian safety at crosswalks and highlights the importance of considering these factors in the provision, selection, and maintenance of pedestrian crossing control systems. / October 2015

This thesis presents the development and validation of a high ductility seismic resistant steel brace connector called the Yielding Brace System (YBS) that improves the earthquake performance of steel braced frame buildings. The connector is comprised of two steel castings which dissipate seismic energy through flexural yielding of specially designed triangular yielding fingers. In this body of work, the need for such a system is presented along with a summary of previously developed steel castings for enhanced earthquake performance of building structures. The development of the YBS concept is then discussed in detail and equations are developed to predict the elastic and plastic response of a YBS connector based on the geometry of the yielding fingers. The low-cycle fatigue life of the cast steel material used for the yielding elements of the YBS is characterized based on the results of several cyclic, small-scale yielding fingers tests and a low-cycle fatigue life prediction model is derived. Following this, the design of a prototype connector for the second storey brace of a fictitious six storey sample building located in Los Angeles is presented. This design is conducted using the low-cycle fatigue prediction model, the response prediction equations and non-linear finite element analysis. Results of four full-scale prototype tests are then presented. Two of the tests are axial tests of the device alone, while the other two are full-scale braced frame tests. Finally, the design of a 12-storey sample building is presented. This building design is then evaluated via non-linear time-history analysis using the FEMA P-695 methodology. The results from these analyses are then discussed and compared to a similar study conducted on the same building designed with buckling restrained braces. This work shows that the Yielding Brace System is a highly ductile, seismic resistant brace that can be used as an alternative to the buckling restrained brace with the potential to provide a stiffer structure with increased ductility.

This thesis presents the development and validation of a high ductility seismic resistant steel brace connector called the Yielding Brace System (YBS) that improves the earthquake performance of steel braced frame buildings. The connector is comprised of two steel castings which dissipate seismic energy through flexural yielding of specially designed triangular yielding fingers. In this body of work, the need for such a system is presented along with a summary of previously developed steel castings for enhanced earthquake performance of building structures. The development of the YBS concept is then discussed in detail and equations are developed to predict the elastic and plastic response of a YBS connector based on the geometry of the yielding fingers. The low-cycle fatigue life of the cast steel material used for the yielding elements of the YBS is characterized based on the results of several cyclic, small-scale yielding fingers tests and a low-cycle fatigue life prediction model is derived. Following this, the design of a prototype connector for the second storey brace of a fictitious six storey sample building located in Los Angeles is presented. This design is conducted using the low-cycle fatigue prediction model, the response prediction equations and non-linear finite element analysis. Results of four full-scale prototype tests are then presented. Two of the tests are axial tests of the device alone, while the other two are full-scale braced frame tests. Finally, the design of a 12-storey sample building is presented. This building design is then evaluated via non-linear time-history analysis using the FEMA P-695 methodology. The results from these analyses are then discussed and compared to a similar study conducted on the same building designed with buckling restrained braces. This work shows that the Yielding Brace System is a highly ductile, seismic resistant brace that can be used as an alternative to the buckling restrained brace with the potential to provide a stiffer structure with increased ductility.

Thesis (Ph. D.)--University of Chicago, Dept. of Economics, June 1999. / Includes bibliographical references. Also available on the Internet.

[pt] O presente trabalho consiste num estudo experimental de laboratório, no qual procurou-se analisar o comportamento tensão-deformação-resistência de um solo residual jovem de biotita gnaisse na condição saturada. Foram realizados ensaios de compressão isotrópica e edométrico através dos quais foi definida a tensão de pré- adensamento do solo em estudo. Posteriormente foram realizados ensaios triaxiais de compressão e extensão seguindo diferentes trajetórias de tensão, com a utilização de instrumentação interna (ELETRONÍVEIS) para medição das deformações axiais. A utilização dos ELETRONÍVEIS possibilitou a identificação de uma superfície de escoamento no espaço de tensões de compressão e de extensão. Foi analisado o módulo secante de deformabilidade obtido com o uso do LSCDT e dos ELETRONÍVEIS a partir dos ensaios triaxiais. O estudo microestrutural do solo feito através de lâminas delgadas, analisadas ao microscópio óptico e eletrônico de varredura, possibilitou a verificação de cimentação entre os grãos do solo. Esta é causada pela cimentação do ferro liberado através da intemperização dos minerais de granada e biotita. / [en] The present work consists of experimental analysis to study the stress-strain-strenght behaviour of saturated young residual soil in laboratory. In a first moment isotropic compression and oedometric tests where made in order to define the overconsolidation stress of the studied soil. Further, compression and extension triaxial tests where made following diferent stress paths. The axial strain have been measured through internal instrumentation (Electrolevels).A yield surface could be observed, when the sample where submitted to compression and also to extension. The secant modulus of deformability, obtained through the use of LSCDT and electrolevels used in the triaxial tests, have been analised. A microstructural study of the soil have been made from thin sections of soil, analised on the scanning electronic microscope and optical microscope, where could be possible to observe link between grains. It was caused to iron originated from weathering of biotite and garnet minerals. / [es] EL presente trabajo consiste en un estudio experimental de laboratorio en el que se analiza el comportamiento tensión-deformación-resistencia de un suelo residual joven de bioptita gnaise en la condición saturada. Fueron realizados ensayos de compresión isotrópica y edométrico. A través de ellos, se definió la tensión de preadensamiento del suelo en estudio. Posteriormente se realizaron ensayos triaxiales de compresión y extensión utilizando diferentes trayectorias de tensión, con el empleo de instrumentación interna (electroníveles) para medir las deformaciones axiales. La utilización de los electroníveles hizo posible la identificación de una superfície de corriente en el espacio de tensiones de compresión y de extensión. Fue analizado el módulo secante de deformabilidad que se obtuvo con el uso del LSCDT y de los electroníveles a partir de los ensayos triaxiales. El estudio microextructural del suelo, realizado a través de láminas delgadas, analizadas al microscópio óptico y electrónico de barrido, posibilitó la verificación de cimentación entre los granos del suelo.Esta cimentación se debe a la cimentación del hierro liberado a través de la intemperización de los minerales de granada y bioptita.

There is growing interest in learning the impacts of agricultural technologies especially in developing economies. Economic analysis may entail assessment of employment and time allocation effects of new technologies. An issue of importance in South Asia is the impacts of technological change on a specific type of occupation: rural non-farm activities. In order to fully understand these effects, the research must integrate gender differences and determine if the results would be similar irrespective of gender. This paper particularly looks at the effects of HYV adoption on time allocation and labor force participation of men and women in non-farm activities. In estimating the effects of HYV adoption on non-farm labor supply, information on the dependent variable, supply of non-farm labor (or the number of days worked while engaged in non-farm labor), is not available for individuals who do not participate in non-farm labor. Hence sample selection or self-selection of individuals occurs. A feasible approach to the problem of sample selection is the use of Heckman's Two Stage Selection Correction Model. Income functions were estimated for males and females while correcting for the sample selection of non-farm wage earners. An enhanced understanding of the conceptual links among HYV adoption, non-farm labor supply, and gender issues is achieved by discussing the Farm Household Model. The constrained maximization which is drawn from the Farm Household Model would bring about demand functions and reduced form functions for adoption and labor supply. The reduced-form equations are estimated at the individual level for the following: adoption of HYV technology in rice cultivation, and non-farm labor supply of both adult males and females. Regression results are presented for both Ordinary least squares (OLS) and Tobit estimates. HYV adoption and non-farm labor supply of men and women are influenced by several factors in Bangladesh. The household characteristics assumed to potentially determine technology adoption and non-farm labor decisions are the following: non-farm wages per month of the males and females, farm size, asset value, ratio of yield per decimal land of high-yielding to traditional variety of rice, HYV yield, local variety yield, and the ratio of variance of yield per decimal land of HYV to traditional or local varieties. The empirical findings suggest that the decision to adopt HYV technology is determined primarily by farm size, value of total assets of the household, ratio of yield per decimal of land of high-yielding to traditional variety of rice, and the ratio of variance of yield per decimal of land of high-yielding to traditional variety of rice. A larger farm size or land owned in decimal unit increases the non-farm labor supply of females, but not of men. HYV yield is significant and positive, while the local variety yield is significant and negative. This means that higher HYV yields increase the supply of non-farm labor of women, while higher local or traditional yields lower women's supply of non-farm labor. / Master of Science

Cette étude s'intéresse à la fissuration des structures multi-perforées, soumises à des sollicitations pouvant aller de la plasticité confinée à la plasticité généralisée. Le cas d'étude considéré est celui des chambres de combustion des turbomachines aéronautiques. Le matériau utilisé est le Haynes 188, un superalliage à base de Cobalt, spécialement conçu pour ce type d'applications. La fissuration des structures multi-percées a été souvent étudiée dans des conditions de plasticité confinée. Ces études doivent être étendues au domaine de la plasticité généralisée.Afin d'étudier les interactions entre fissures et perçages, une éprouvette originale a été conçue. Dans le but de reproduire un motif de base simplifié correspondant aux trous de refroidissement des chambres de combustion, l'éprouvette est percée en son centre par trois trous. Des essais de fissuration isotherme à 900°C sous des chargements de fatigue ont été réalisés avec des niveaux de chargement allant de la plasticité confinée à la plasticité généralisée. Ces essais ont permis d'étudier la durée de vie du motif de base. A partir des résultats expérimentaux de contrainte et de déformation, les essais ont été modélisés à une échelle dite macroscopique avec un modèle de fissuration en énergie. Dans le but d'améliorer la description des essais, la modélisation a été ensuite réalisée à une échelle intermédiaire, dite mésoscopique, à partir de calculs par éléments finis. / The purpose of this study is to investigate crack growth of multi-perforated structures when loading can vary from small scale yielding to large scale yielding conditions. In this study we focus on combustion chambers of aerospace engines. The material used in crack growth tests is the Haynes 188, a cobalt based superalloy, specially developed for this type of applications. Studies on crack growth of multi-perforated structures are often made in small scale yielding conditions. These studies have to be extended to large scale yielding conditions.In order to study interactions between cracks and perforations, an original specimen has been developed. The specimen is perforated in the center by three holes inspired by cooling holes of combustion chambers. Fatigue crack growth tests at 900°C have been conducted with loads from small scale to large scale yielding conditions. These tests were used to study life of a base pattern. Using experimental stresses and strains, tests were modeled at a macroscopic scale with an energy based crack growth model. In order to improve experimental results description, tests were modeled at an intermediate mesoscopic scale using finite element calculations.

Dans cette thèse, nous étudions deux systèmes désordonnés du point de vue du de la transition de dépiégeage (depinning). Dans les deux cas, la dynamique est régie par la compétition entre un paysage aléatoire qui tend à induire des fluctuations et des interactions élastiques qui tendent à les limiter. Dans la première partie, nous développons un modèle mésoscopique simplifié qui vise à rendre compte des propriétés génériques de la plasticité des matériaux amorphes. La déformation plastique des matériaux amorphes présente une phénoménologie qui rappelle les propriétés critiques observées au voisinage d'une transition de dépiégeage: émergence d'un seuil critique (ici la contrainte plastique), dynamique d'avalanches, etc. L'interaction élastique à l'oeuvre dans ce modèle de plasticité dérive directement de la solution élastique d'Eshelby associée à la présence d'une inclusion plastique dans une matrice élastique. Nous montrons que cette interaction anisotrope et à longue portée est caractérisée par la présence de modes mous. ces derniers ont un impact dramatique sur la localisation et les fluctuations de déformation plastique qui augmentent de manière diffusive. Cette phénoménologie n'est pas présente dans le dépiégeage tel qu'il est souvent traité, par exemple avec une approche champ moyen. Nous montrons que les bandes de cisaillement sont des modes mous de l'intéraction d'Eshelby et affectent aussi bien la localisation que les propriétés universelles. Par ailleurs, en testant deux cas extrèmes, nous avons trouvé que les détails du paysage désordonné n'ont pas d'impact particulier sur les propriétés universelles. En application de ce travail, nous montrons que le renforcement des matériaux amorphes par des inclusions dures est relié à la percolation des bandes de cisaillement entre les inclusions. Dans la deuxième partie, nous étudions la morphologie d'une ligne de démouillage en recul sur des surfaces inhomogènes. Contrairement aux modèles de dépiégeage standard, nous développons ici une méthode permettant de décrire le régime de grandes déformations de la ligne de contact et le déchirement de la couche. Nous montrons l'existence d'une concentration seuil des inhomogeneités. Au delà de cette concentration, la ligne s'arrête à une distance finie et autour de la concentration critique, présente des propriétés de type critique. / In the present thesis, two disordered systems are investigated from the depinning perspective. In both of them, the dynamics is governed by the competition between elastic interactions and a disordered landscape. In the first part, we use a simplified mesoscopic model to investigate the generic properties of amorphous plasticity. The yielding of amorphous materials shows universal properties similar to the depinning transition. As such, it is often described by mean field approaches. Here we show that the soft modes present in the interaction kernel (based on the Eshelby solution for a plastic inclusion in an elastic matrix) have a dramatic impact on localization and result in diffusively increasing plastic strain fluctuations. This additional phenomenology is absent in standard depinning and, despite its important consequences, is disregarded in mean field descriptions. We show that shear bands are soft modes of the Eshelby interaction kernel and, besides localization, they affect the universal properties as well. At the same time, we found by testing two extreme cases that the form of the disordered landscape has no considerable impact on the universal properties. As an application, we show that the reinforcement of amorphous materials by hard inclusions is related to the percolation of shear bands in between the inclusions. In the second part of the thesis, we study the morphology of a receding dewetting line on inhomogeneous surfaces. Unlike in standard depinning models, here we developed a method suitable to describe the large deformation regime of the contact line and tearing up of the layer. We show the existence of a threshold concentration of inhomogeneities. Above this concentration the line stops within at finite distance, and around the critical concentration it features critical-like properties.