Low-temperature magnetic force microscopy was used to study the phase diagram of a La1/3Pr1/3Ca1/3MnO3 thin film grown on a (110) NdGaO3 (NGO) substrate by pulsed laser deposition. Traditionally, one can observe the phase change at the nanoscale level as the sample is cooled from room temperature through the transition temperature to liquid nitrogen temperatures, but in this case a fixed voltage ranging from 0 V to 31 V was applied before each cooling cycle. From in and ex situ transport measurements, it is observed that the temperature of the peak of the transition increases with applied field; however, the MFM images show that the magnetic transition begins at a lower temperature with the same increase in field. Thus, this dissertation shows that a new voltage control exists for the phase transition in certain manganites. / text

Transition metal oxides (TMO) have proven to exhibit novel properties such as high temperature superconductivity, magnetic ordering, charge and spin density waves, metal to insulator transitions and colossal magnetoresistance. Among these are a spin-orbit coupling (SOC) induced Mott insulator Sr2IrO4. The electric transport properties of this material remain finite even at cryogenic temperatures enabling its complex electronic structure to be investigated by a scanning tunneling microscope. At T = 77 K, we observed two features which represent the Mott gap with a value of 2D ~ 615 meV. Additionally an inelastic loss feature was observed inside this gap due to a single magnon excitation at an energy of ~ 125 meV. These features are consistent with similar measurements with other probes. In addition to these features, at T = 4.2 K lower energy features appear which are believed to be due to additional magnetic ordering. Another material that exhibits a unique physical behavior is the sliding charge density wave (CDW) material TaS3. It is a quasi-one dimensional material that forms long narrow ribbon shaped crystals. It exhibits anomalies including non-ohmic conductivity, a decrease in the Young’s modulus, a decrease in the shear modulus and voltage induced changes in the crystal’s overall length. In addition, we have observed the torsional piezo-like response, voltage induced torsional strain (VITS), in TaS3 which was first discovered by Pokrovskii et. al. in 2007. Our measurements were conducted with a helical resonator. The VITS response has a huge effective piezoelectric coefficient of ~ 104 cm/V. In addition we have concluded that the VITS is a very slow response with time constants of ~ 1 s near the CDW depinning threshold, that these time constants are dependent on the CDW current, and we suggest that the VITS is due to residual twists being initially present in the crystal.

Much of North America’s reinforced concrete infrastructure is reaching the end of its service life and careful inspection and assessment is required to ensure the appropriate capacity is maintained in these structures. The research conducted herein seeks to further the development of two new sensor technologies: fibre optic strain sensors and digital image correlation, which have the potential to provide comprehensive performance data for structures to a level of accuracy previously not possible. The research involves determining the accuracy of these sensor systems to monitor both strain and crack widths in reinforced concrete compared to conventional techniques, such as electrical resistance strain gauges. Preliminary work was also undertaken on correcting the sensor results for temperature. It was determined that temperature variations in the range of +21 °C to 20 °C, result in significant strain errors for both sensor systems. Once the results obtained from the sensors systems are corrected for temperature, crack widths are monitored in four small-scale reinforced concrete tension specimens, and strain and crack width behaviour is monitored in four full-scale beams under four point bending. One of the major problems faced when using the digital image correlation technique is out of plane movement which results in significant error. Techniques to lower this error are addressed. In addition, obtaining a more robust understanding of the effects of temperature on crack widths, stiffness, strength and short term creep behaviour of reinforced concrete elements is explored to improve structural monitoring and numerical models used for analysis. Four full-scale beams, two at room temperature and two at 20 °C, were loaded to failure under four point bending. A comparison of the room temperature and low temperature test results show that the cracks tend to close up at lower temperatures in members that are free to expand and contract. This behaviour results in a potential increase in shear capacity for beams at lower temperatures. The low temperature beams also saw a minor increase in strength, but saw no noticeable increase in stiffness. Lastly, short term creep behaviour was reduced in the low temperature beams once the formation of ice occurred. / Thesis (Master, Civil Engineering) -- Queen's University, 2012-10-31 11:08:32.631

Monolitinio pastato įrąžoms skaičiuoti, projektuotojas kurdamas pastato skaičiuotinį modelį, jį traktuoja kaip ,,akimirksniu“ pastatytą. Pastato statybos metu nuolatinė apkrova nuo perdangų savojo svorio, auga palaipsniui, betonuojant aukštą po aukšto, kol galiausiai, užbetonuojamas paskutinis aukštas. Darbe pasiūlytas ir skaitiškai realizuotas modelis, įvertinantis betono ir armatūros įtempių bei deformacijų kitimo istoriją dėl laike palaipsniui augančios apkrovos nuo perdangų savojo svorio. Darbe taikomas superpozicijos principas betono valkšnumo deformacijoms, atsižvelgiant į Volterra lygtį. Pasiūlyta matematinė formuluotė pagrįsta matriciniu skaičiavimu ir apibendrintąja funkcijos vidurkio teorema taikant betono valkšnumui. Skaitiniu būdu gauti rezultatai patikrinti analitiškai. Modelis pritaikytas daugiaaukščio pastato papildomų šlyties jėgų perdangose, atsirandančių dėl gretimų kolonų skirtingų poslinkių vystymosi per laiką radimui. Gauti rezultatai patikrinti su apytikslio skaičiavimo rezultatais, taikant normų EC-2 reikalavimus betono valkšnumo deformacijoms. Perdangų praspaudimą kolona, kai pastarosios yra greta pastato standumo branduolių, kurių deformatyvumas yra ženkliai mažesnis, reiktų tikrinti atsižvelgiant į papildomas šlyties jėgas, atsirandančias dėl betono susitraukimo ir valkšnumo įtakos. Darbo apimtis – 99 p. teksto, 54 iliustr., 12 lent. ir 9 literatūros šaltiniai. Atskirai pridedami priedai. / The designer calculates a building as an instantly built. However, during construction the permanent load is increasing gradually because the floors are built step by step. This paper introduces a numerically implemented mathematical model for the column analysis accounting for the stress and strain change in reinforcement and concrete with time due to the increasing in time permanent loads induced by the self-weight of each slab during construction. The mathematical formulation is based on the superposition principle for the creep strain described by Volterra's integro-differential equation and involves a matrix solution of linear equations derived via application of the generalized mean theorem for integration. The results obtained are also verified analytically. Finally, the proposed model is applied to calculate extra shear forces caused by the deflections appearing to the adjacent columns of different cross-sections. The results obtained are also compared with the approximate calculation treating the building as an instantly built. The results indicate that additional shear forces due to different displacements of the adjacent columns are quite mild. However, the additional shear forces can be sufficiently high, if the column is located near the high stiffness walls in a non-sway building. In this case, the extra shear forces should be determined via time-dependent analysis accounting on the creep and shrinkage strains relying on the gradually increasing load during... [to full text]

Harsh realities exist in the South African Police Service (SAPS) that require concepts such as burnout and work engagement to be studied in the context of work-related well-being. Although these difficulties relate to police officials experiencing work-related trauma, more stressors seem to manifest on an organisational level, which in turn affects the psychological well-being of police officials. This study seeks to focus on the burnout and engagement of members of the Local Criminal and Record Centre (LCRC) in the SAPS. The members of the LCRC are exposed to severe occupational stressors relating to their job content, which necessitates research in occupational stress relating to the health of SAPS members. For the purposes of this study, the model of occupational stress, commitment and ill health of Cartwright and Cooper (2002) will be utilised to explain strain and organisational commitment. Work-related well-being, on the other hand, can best be explained by referring to the model of well-being developed by Schaufeli and Bakker (200 1 ). Since job demands play a central role in burnout, it is necessary to implement preventive organisationally-based strategies to address high job demands. Upon reviewing stress research, it became clear that a serious lack of intervention research exists. Little information is available about the work-related well-being of SAPS members, whilst no documented research could be found regarding the effects of an intervention programme on the work-related well-being of LCRC members. The study aimed at utilising three levels of intervention (primary, secondary and tertiary) on organisational and individual level. An integrated classification scheme of both the positive and negative aspects of work-related well-being on the organisational and individual level was developed and presented to members from the LCRC over a one-year period. The research method for each of the three articles of this study consisted of a brief literature review and an empirical study. An availability non-randomised sample was selected because the entire in-tact group of the LCRC of the SAPS (N=111) in the North West Province was included in the study. A survey design was used to achieve the research objectives of both Articles 1 and 2, whilst a longitudinal survey design was utilised in Article 3, where the same instruments were administered at two different times (over a one-year period) to the same group of participants. The measuring instruments used in this study are the Maslach Burnout Inventory-General Survey (MBI-GS), Utrecht Work Engagement Scale (UWES), Job Demands-Resources Scale (JDRS), Health subscales, Organisational Commitment subscales, the ASSET questionnaire and a biographical questionnaire. Structural equation modelling was implemented to test a structural model of work-related wellbeing. A good fit was found for the model in which perceived job demands contributed to burnout which, in turn, impacted on ill health. Work wellness was determined by the relationship between two opposite constructs, namely burnout and engagement. The work-related well-being of members of the LCRC was affected by an environment of high job demands and inadequate resources. In Article 2, multiple regression analyses showed that occupational stress explained 19% of the variance in psychological ill health and 17% of the variance in physical ill health. A two-step multiple regression analysis conducted with the variables in their continuous form revealed that control was a statistically significant predictor of both physical and psychological ill health, while job overload statistically significantly predicted psychological ill health. Occupational stress also explained 17% of the variance in individual commitment and 16% of the variance in organisational commitment. It was concluded that individual commitment moderated the effects of stressful work relations on ill health. LCRC members portrayed a high risk to fall ill due to exhaustion; they were less enthusiastic about their job and tended to derive a lower sense of significance from their work. In addition, members showed a major risk for developing low affective commitment due to low work engagement. Exhaustion influenced the way members view their job demands, organisational and social support, as well as growth opportunities available to them. A lack of advancement opportunities and job insecurity contributed to feelings of exhaustion and cynicism. Another objective of this study was to evaluate interventions used to promote work-related wellbeing of LCRC members. Although no significant differences were found between the pre- and post-measurements, some positive aspects did flow from the interventions. For instance an active effort by management to address resource needs. Recommendations for future research were made. / Thesis (Ph.D. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2007.

The continuous alignment of human resource strategies, activities. processes and competencies within an ever-changing business environment poses certain challenges for the human resource profession in a global petrochemical industry. Modem business managers have realised the necessity of work wellness initiatives and that a relationship exists between employee wellness and business results, but very few companies measure whether such initiatives actually had any impact on work performance. Defining performance indicators and competence models for human resource practitioners has developed into a dynamic activity. Adaptation to continuously changing business needs has the potential to create a sense of incompetence, exhaustion, decreased motivation and dysfunctional work attitudes, collective1y defined as burnout. This highlights the need to identify and research psychological constructs that hold predictable value for the ability of human resource practitioners to prevent and overcome burnout by generating sufficient emotional energy to adapt to changing business needs, acquiring strategic human resource competencies to increase their feelings of professional efficacy and increasing their contribution towards organisational performance. The objective of this study was to determine perceived importance and actual performance of human resource practitioners in a global petrochemical company in terms of human resource roles, and to determine the influence of work wellness (burnout, engagement and workaholism) on the perceived value adding contribution of human resource practitioners in a global petrochemical company. The research method for each of the three articles of this study consisted of a brief literature review and an empirical study. Stratified samples were taken of human resource personnel (N = 128) and their internal line customers (N = 67). The measuring instruments used in this study included the Ulrich Human Resource Role Assessment Survey (HRRAS), Maslach Burnout Inventory-General Survey (MBI-GS), Utrecht Work Engagement Scale (UWES) and the Workaholism Scale. Article I compared perceptions of human resource practitioners and their internal customers regarding expected and actual contributions of human resource practitioners towards business performance in a global petrochemical company. It was found that human resource practitioners and their line customers are in agreement concerning the importance of the human resource roles that enable business performance, indicating that human resource practitioners have a good understanding of their job requirements. Both human resource practitioners and their line customers perceived the performance of human resource practitioners as average, which is lower than the expected level of performance as indicated by importance scales. In Article 2, a correlation study revealed that burnout (Exhaustion, Professional Efficacy and Cynicism) statistically significantly predicted the perceived level of performance of human resource practitioners in the organisation. It was found that Cynicism was a statistically significant predictor of the perceived level of performance of human resource practitioners in the organisation in terms of all the human resource roles (Strategic Partnering, Administrative Support, Employee Support and Change Management). Vigour and Dedication statistically significantly predicted perceived performance on the Administrative Support role. In Article 3, a three-factor model of workaholism (consisting of Compulsiveness, Involvement and Overwork) was found which showed positive relationship with burnout factors. Statistical analysis indicated that workaholism factors of the Workaholism Scale practically significantly correlate. Multiple regression analysis showed that burnout and workaholism factors can explain perceptions of human resource practitioner performance. Recommendations were made for future research. / Thesis (Ph.D. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2007.

A new torque transfer standard using metallic TBTF resonant sensor was developed to overcome the overload capability problem which occurs with conventional metallic resistance strain gauges. Previous research work, however, has shown that the first prototype of the metallic TBTF resonant sensor was not suitable for use in a torque transfer standard due to its size and subsequent sensitivity to parasitic lateral forces. To maximize the benefits from this sensor, particularly overload capability and long-term stability, in the high accuracy torque measurement application area, there is a need to develop significantly smaller devices. The aim of this thesis is to research through FEA modelling and experimental characterisation the key performance parameters required to produce a miniaturised metallic TBTF resonant sensor that provides better performance when applied in a torque measurement system. For high accuracy any torque transducer using these sensors ought to have low sensitivity to parasitic influences such as bending moments and lateral forces, which can only be achieved with reduced size. The problems with the existing design, key design issues, possible configuration and packaging solutions of the metallic TBTF resonant sensor that could be used for achieving a higher accuracy torque transfer standard are considered. Two designs of miniaturised metallic TBTF resonant sensors, SL20 and SL12, are considered and experimentally investigated. The lateral forces are reduced by 52% for SL20 design and by 80% for SL12 design when compared to the original SL40 design. A torque transducer using the SL20 design was calibrated falling into the Torque Transfer Standard class of accuracy 1 category, uncertainty 0.8%. A torque transducer using the SL12 design was made and calibration showed a class of accuracy 0.5 category, uncertainty 0.2%. The results from this research indicate that the SL12 design is suitable for use in a torque transfer standard. The SL12 design is optimal and the smallest size possible based on the overload capability design criteria requiring the tine cross sectional area to remain constant.

The telescoping cantilever beam structure is applied in many different engineering sectors to achieve weight/space optimisation for structural integrity. There has been limited theory and analysis in the public domain of the stresses and deflections involved when applying a load to such a structure. This thesis proposes (a) The Tip Reaction Model, which adapts classical mechanics to predict deflection of a two and a three section steel telescoping cantilever beam; (b) An equation to determine the Critical buckling loads for a given configuration of the two section steel telescoping cantilever beam assembly derived from first principles, in particular the energy methods; and finally (c) the derivation of a design optimization methodology, to tackle localised buckling induced by shear, torsion and a combination of both, in the individual, constituent, hollow rectangular beam sections of the telescopic assembly. Bending stress and shear stress is numerically calculated for the same structure whilst subjected to inline and offset loading. An FEA model of the structure is solved to verify the previous deflection, stress and buckling predictions made numerically. Finally an experimental setup is conducted where deflections and stresses are measured whilst a two section assembly is subjected to various loading and boundary conditions. The results between the predicted theory, FEA and experimental setup are compared and discussed. The overall conclusion is that there is good correlation between the three sets of data.

The human prion protein (PrP) gene (PRNP) codon 129 (M/V) polymorphism is a susceptibility factor for variant Creutzfeldt-Jakob Disease (vCJD) and a major determinant of clinico-pathological phenotype in sporadic CJD. The role of codon 129 in defining susceptibility and strain transmission properties has been investigated in three lines of transgenic mice that express human PrP. The human PRNP gene has directly replaced the murine version, by gene targeting, and variation at codon 129 has given the three genotype lines (HuMM, HuMV, and HuVV). The genetics of these three mouse lines are otherwise identical, and therefore differences in transmission properties can be directly attributable to the codon 129 genotype. vCJD inoculation has shown that all three codon 129 genotype mice are susceptible with a ranking of transmission efficiency of HuMM>HuMV>HuVV. HuMM mice develop the most widespread neuropathology with features similar to human vCJD. Subclinical infection was noted in each mouse line. These data suggest that the vCJD strain is transmissible to humans of each of the three codon 129 genotypes, implying that non-MM cases of human infection with bovine spongiform encephalopathy (BSE) may exist but with long subclinical incubation periods. Inoculation of material from blood transfusion associated vCJD showed no change in transmission properties suggesting that the threat of a future epidemic of human-to-human vCJD infection has not been increased by adaptation of the vCJD strain. However the route of infection, for example via blood transfusion or surgery, may be more efficient that the original oral route of BSE infection. sCJD is classified into six subgroups according to clinico-pathological features, and defined by codon 129 genotype and electrophoretic mobility type (1 or 2) of disease associated PrPSc (MM1, MM2, MV1, MV2, VV1, VV2). Typical cases from each subgroup have shown specific transmission properties suggesting that the subgrouping is defining separate disease strains. The commonest subgroup (MM1) was the most transmissible and the HuVV mouse line the most susceptible host. These data outline the transmission risk from all sCJD types to recipients of each codon 129 genotype should an infection event occur, and show the significant role of recipient codon 129 genotype in defining the clinical or subclinical state and the success or failure of transmission. This is important for determining individual risk following known exposure, and for modelling the potential of iatrogenic infection from sCJD patients.

The aim of this study was to establish whether hardiness and tenure are predictive variables for coping with shiftwork. The extent of shiftwork and shiftwork research has expanded internationally in the past decade. It has been established that shiftwork has a negative effect on shiftworkers who are predisposed to certain strain symptoms such as inefficiency, impaired health and domestic problems. However, certain inter individual differences do moderate coping with shiftwork through a process of cognitive and behavioural protective acts which modify the stressful situation and neutralise the experience of problems. Using questionnaires (Biographical, Hardiness Index and Coping with Shiftwork Questionnaire), a sample group of 75 cases was analysed. A 95 percent confidence level was used throughout with a multiple stepwise regression analysis computed. The significant r2 value = 0.18. Focus group discussions were conducted to· add qualitative information to the areas of social, domestic, work and sleep problems as well as coping strategies. The predictive variables were regressed onto a number of criterion variables, namely coping with shiftwork, work, sleep, domestic and social problems, as well as engagement and diseng.agement strategies including both strategies in all four domains (work, sleep, social and domestic). It was found that hardiness and tenure are not predictive variables for coping with shiftwork. However, hardiness, commitment and challenge are predictors for disengagement strategies so that hardy, challenged and committed individua1s will use less disengagement coping strategies and more specifically, use less domestic disengagement coping strategies. The research established hardiness as an additional personality variable linked to a primary scale of coping with shiftwork, namely disengagement. The longer term adjustment of shiftworkers (through tenure) was not established. Recommendations were made for targeted shiftwork coping programmes and more extensive classical shiftwork research in South Africa / Economics and Management Sciences / M.A. (Industrial Psychology)