Yes / Condition monitoring of micro injection moulding is an effective way of understanding the processing effects of variable parameter settings. This paper reports an experimental study that investigates the characteristics of the demoulding behaviour in micro injection moulding (A mu-IM) with a focus on the process factors that affect parts' quality. Using a Cyclic Olefin Copolyme (COC) microfluidics demonstrator, the demoulding performance was studied as a function of four process parameters (melt temperature, mould temperature, holding pressure and injection speed), employing the design of experiment approach. The results provide empirical evidences on the effect that processing parameters have on demoulding conditions in A mu-IM, and identifies combinations of parameters that can be used to achieve the optimal processing conditions in regards to demoulding behaviour of micro parts. It was concluded that there was a direct correlation between the applied pressure during part filling, holding phases and the demoulding characteristic factors of the A mu-IM cycle such as ejection force, integral and time.

This study evaluated the temperature variability that existed in refrigerated table grape consignments over a two-day journey from two suppliers in southern Spain, to client managed facilities in England. In order to inhibit senescence, perishable foods are transported in temperature-controlled transport to maximize shelf life. However, thermal dynamics suggests that uniform spatial temperature is not necessarily achieved despite a constant set point. As fruit exposed to suboptimal temperatures is more likely to exhibit undesirable quality issues, knowledge of spatial temperature can direct quality control team members to these potentially problematic pallets within an inbound shipment. Warmer temperatures were identified on the passenger side of both trailers, at the rear of both trailers, and in lower pallet layers. Furthermore, heightened temperature was recorded in lower pallet layers in close proximity to the refrigeration return unit. The Supplier 2 shipment, set at 4oC, exhibited more spatially uniform temperatures compared to the Supplier 1 shipment set at 1oC. This implies that an operational compromise may exist: a higher but more uniform temperature or a lower but more variable temperature. In addition, analysis of airflow distribution suggested that airflow could be improved specifically in lower pallet layers and towards the rear of the trailer. Improved circulation will promote improved temperature uniformity for quality maintenance.

As we scale down each process generation the degree of control we have on device parameters decreases. We are left to contend with a great deal of variability in process and environmental parameters. Process variation impacts dopant concentration, channel length, oxide thickness and other device parameters. Temperature variation too affects several parameters, amongst them are the threshold voltage and carrier mobility. All of these variations can either be margined for during design or compensated for dynamically. In this paper the technique of adaptive body bias is successfully applied to compensate for the variation in design so that the circuit operates at no more than 10 percent of the optimal pvt (process voltage temperature) point while minimizing leakage. / text

A rail-to-rail op-amp with high stability over temperature variation at 1-V supply voltage is presented in this thesis. It incorporates a modified CM adapter and a modified bandgap reference. First, the modified CM adapter utilizes a level-shifting technique to shift the input common mode voltage of 0-1 V to the level below 0.1 V. By introducing this circuit as the front-end block of the proposed op-amp, the PMOS differential input stage can be operated appropriately with the rail-to-rail input common mode range. Second, the modified bandgap reference that combines two voltages with opposite temperature coefficients generates a temperature-insensitive bias current to the input stage. Besides, by the technique of cascading a diode with an additional BJT, the junction area of the original diodes can be reduced and in the actual application, fewer parallel-connected BJTs are needed. The two circuits are applied to the proposed op-amp operated at 1-V supply voltage in TSMC 1P4M 0.35£gm CMOS technology. At 25¢J, the dc gain is 78.9 dB and unity-gain bandwidth is 3.73 MHz. The phase margin is 42.9¢X. For the temperature from 0¢J to 75¢J, the frequency response is temperature-insensitive and the dc gain variation is 2dB. The layout view of the proposed op-amp is also presented and the area is 0.2 mm2.

Microchannels and micro pin fins have been employed for almost four decades in the cooling of microelectronic devices and research is still being done in this field to improve the thermal performance of these micro heat sinks. In this research, the constructal design and computational fluid dynamics code was used with a goal-driven optimisation tool to numerically investigate the thermal performance of a novel design of combining microchannels and micro pin fins for microelectronic cooling applications. Existing designs of microchannels were first optimised and thereafter, three to seven rows of micro pin fins were inserted into the microchannels to investigate whether there was further improvement in thermal performance. The microchannels and micro pin fins were both embedded in a highly conductive solid substrate. three-dimensional geometric structure of the combined micro heat sink was optimised to achieve the objective of maximised thermal conductance, which is also minimised thermal resistance under various design conditions. The micro heat sinks investigated in the study were the single microchannel, two-layered microchannels with parallel and counter flow configurations, three-layered microchannels with parallel and counter flow configurations, the single microchannel with circular-, square- and hexagonal-shaped micro pin-fin inserts and the two-layered microchannels with circular-shaped micro pin-fin inserts. A numerical computational fluid dynamics (CFD) package with a goal-driven optimisation tool, which employs the finite-volume method, was used to analyse the fluid flow and heat transfer in the micro heat sinks investigated in this work. The thermal performances of all the micro heat sinks were compared for different application scenarios. Furthermore, the temperature variation on the heated base of the solid substrate was studied for the different micro heat sinks to investigate which of the heat sink designs minimised the temperature rise on the heated base best. This is very important in microelectronic cooling applications because temperature rise affects the reliability of the device. The heat sink design that best maximised thermal conductance and minimised temperature rise on the heated base was chosen as the best for microelectronic cooling. For all the cases considered, fixed volume constraints and manufacturing constraints were applied to ensure real-life applicability. It was concluded that optimal heat sink design for different application scenarios could be obtained speedily when a CFD package which had an optimisation tool was used. / Thesis (PhD)--University of Pretoria, 2016. / Mechanical and Aeronautical Engineering / PhD / Unrestricted

Cities are often warmer than their surroundings, and this can lead to more energy being used to cool buildings. This study looks at one city, London, and assesses the impact of the urban environment on the amount of energy used for air-conditioning. There are three main strands to the work. First, it was important to determine just how great the variation in air temperature is, and how this varies through time and through the urban space. Eighty measurement stations were established along radiating lines from the centre of London as far as rural areas. These measured the air temperature simultaneously at hourly intervals for over a year. Second, to support the main data acquisition, short-term tests within London looked at specific aspects of the urban environment that affect air temperature: the effects of vegetation in parks, and facade colour in streets. Third, the impact on energy use of the measured temperature variation was then determined by using simulation to model a standard building in different urban contexts. The mean heat island intensity was found to vary with distance from the centre of London, and with the local degree of urbanization at any given distance. The maximum intensity reached 8°C on occasion but was more usually 1-2°C in the daytime and 3-4°C at night. The proximity of areas of vegetation, such as parks, to a site was associated with cooler daytime temperatures. The annual cooling load for a standard building at the centre of London was found to be 25% more than at a rural site. However, at the most urban sites over-shadowing reduced the cooling load to 14% more than at a rural site. Heating load decreased towards the centre, but on balance total annual load (for heating and cooling) rose towards the centre to 8.5% more than rural use, and then reduced at the most overshadowed sites. The balance of the effect of urbanization on heating and cooling load depended on the level of internal gain in the building. This study makes a significant contribution to understanding the balance of the impact of urban environments on the energy used for cooling and heating buildings.

Animals must balance multiple, fitness-related traits in environments that are complex and characterized by co-varying factors, such as co-variation in temperature and food availability. Thus, experiments manipulating multiple environmental factors provide valuable insight into the role of the environment in shaping not only important traits (e.g., dispersal capacity or reproduction), but also trait-trait interactions (e.g., trade-offs between traits). We employed a multi-factorial design to manipulate variation in temperature (constant 28°C vs. 28±5°C daily cycle) and food availability (unlimited vs. intermittent access) throughout development in the sand field cricket, Gryllus firmus. We found that fitness-related, life-history traits and trait trade-offs can be developmentally plastic in response to variation in temperature and food availability. Variability in temperature and food availability influenced development, growth, body size, reproductive investment, and/or flight capacity, and food availability also affected survival to adulthood. Further, both constant temperature and unlimited food availability promoted investment into key components of somatic and reproductive tissues while reducing investment into flight capacity. We develop an experimental and statistical framework to reveal shifts in correlative patterns of investment into different life-history traits. This approach can be applied to a range of animal systems to investigate how environmental complexity influences traits and trait trade-offs.

A manutenção de espécies de anfíbios anuros na caatinga, um bioma que sofre um processo de aridificação, suscita perguntas sobre quais aspectos fisiológicos e evolutivos estão envolvidos nesse contexto. O argumento de que a plasticidade fenotípica permite que uma população sobreviva perante mudanças ambientais parece uma explicação plausível. A temperatura e sua variação foram eleitas como representativas da alteração ambiental, tendo como referência os valores correspondentes da floresta atlântica. Essa comparação fundamentou-se na evidência de que a caatinga assemelhava-se a uma floresta úmida antes da aridificação. Utilizamos como marco teórico um trabalho central de Smith-Gill e Berven (1979), que mostrou que a sensibilidade térmica da diferenciação é maior que a do crescimento em larvas de anuros. A hipótese central foi que a plasticidade de desenvolvimento da espécie Rhinella granulosa, presente na caatinga, é maior que das espécies Rhinella ornata e Rhinella icterica, habitantes da floresta atlântica. O método principal foi de comparar normas de reação térmicas de taxa de crescimento, tempo de desenvolvimento, massa na metamorfose e temperatura crítica máxima (TCMax) das espécies. Para isso, regimes térmicos foram simulados em laboratório a fim de representarem microhabitats típicos da floresta e da caatinga. A interação entre moda e variação da temperatura foi significativa para as espécies Rhinella ornata e Rhinella icterica. As espécies de floresta foram muito plásticas. Quando submetidas a regimes típicos da caatinga, apresentaram um aumento de duas vezes da taxa média de crescimento e um terço do tempo médio de desenvolvimento, em comparação com regimes de floresta. As larvas apresentaram variação individual de sensibilidade térmica, sendo que uma parte da amostra não seguiu a regra de Smith-Gill e Berven (1979), apresentando sensibilidade da diferenciação similar a do desenvolvimento. Como conseqüência, mantiveram sua massa na metamorfose canalizada em 0,25g mesmo diante de maiores picos de temperatura. A TCMax foi maior para R. granulosa, porém menos plástica que das espécies de floresta. Os resultados não corroboraram a nossa hipótese, uma vez que as espécies de floresta parecem ser mais plásticas que a espécie da caatinga. / The lasting presence of anuran amphibian species in the Caatinga, an environment that has been undergoing a desertification process, raises questions regarding the physiological and evolutionary aspects involved. The argument that phenotypic plasticity allows for the survival of populations in face of environmental changes seems to provide a plausible explanation. Temperature and its variation were elected as representatives of the desertification process. Based on the evidence that the Caatinga was originally a humid forest, correspondent values for the Atlantic forest were used as reference for comparison. The theoretical framework adopted assumes that the thermal sensitivity of differentiation in anuran larvae is higher than growth sensitivity (Smith-Gill and Berven, 1979). Our main hypothesis was that the developmental plasticity of the Caatinga species Rhinella granulosa is greater than those of Atlantic forest species Rhinella ornata and Rhinella icterica. We compared thermal reaction norms of growth rate, development time, metamorphic mass and critical thermal maxima (CTMax) for each species. Larvae were submitted to thermal regimes typical of the Caatinga and the Atlantic forest. A significant interaction between thermal mode and variation was detected for both Rhinella ornata and Rhinella icterica. Forest species appeared very plastic. When submitted to Caatinga thermal regimes, they displayed double growth rate and a third of development time in comparison to when they were submitted to Atlantic forest thermal regimes. The larvae presented individual variation in thermal sensitivity. Indeed, a fraction of the sample did not follow Smith-Gill and Bervens rule and displayed thermal sensitivity of differentiation similar to growth sensitivity. As a consequence, they maintained their metamorphic mass canalized at 0,25g in face of higher temperatures. Although Rhinella granulosa\'s CTMax was higher than for the forest species, it presented less plasticity. The results have not supported our hypothesis as the Atlantic forest species seems more plastic than the Caatinga species.

A manutenção de espécies de anfíbios anuros na caatinga, um bioma que sofre um processo de aridificação, suscita perguntas sobre quais aspectos fisiológicos e evolutivos estão envolvidos nesse contexto. O argumento de que a plasticidade fenotípica permite que uma população sobreviva perante mudanças ambientais parece uma explicação plausível. A temperatura e sua variação foram eleitas como representativas da alteração ambiental, tendo como referência os valores correspondentes da floresta atlântica. Essa comparação fundamentou-se na evidência de que a caatinga assemelhava-se a uma floresta úmida antes da aridificação. Utilizamos como marco teórico um trabalho central de Smith-Gill e Berven (1979), que mostrou que a sensibilidade térmica da diferenciação é maior que a do crescimento em larvas de anuros. A hipótese central foi que a plasticidade de desenvolvimento da espécie Rhinella granulosa, presente na caatinga, é maior que das espécies Rhinella ornata e Rhinella icterica, habitantes da floresta atlântica. O método principal foi de comparar normas de reação térmicas de taxa de crescimento, tempo de desenvolvimento, massa na metamorfose e temperatura crítica máxima (TCMax) das espécies. Para isso, regimes térmicos foram simulados em laboratório a fim de representarem microhabitats típicos da floresta e da caatinga. A interação entre moda e variação da temperatura foi significativa para as espécies Rhinella ornata e Rhinella icterica. As espécies de floresta foram muito plásticas. Quando submetidas a regimes típicos da caatinga, apresentaram um aumento de duas vezes da taxa média de crescimento e um terço do tempo médio de desenvolvimento, em comparação com regimes de floresta. As larvas apresentaram variação individual de sensibilidade térmica, sendo que uma parte da amostra não seguiu a regra de Smith-Gill e Berven (1979), apresentando sensibilidade da diferenciação similar a do desenvolvimento. Como conseqüência, mantiveram sua massa na metamorfose canalizada em 0,25g mesmo diante de maiores picos de temperatura. A TCMax foi maior para R. granulosa, porém menos plástica que das espécies de floresta. Os resultados não corroboraram a nossa hipótese, uma vez que as espécies de floresta parecem ser mais plásticas que a espécie da caatinga. / The lasting presence of anuran amphibian species in the Caatinga, an environment that has been undergoing a desertification process, raises questions regarding the physiological and evolutionary aspects involved. The argument that phenotypic plasticity allows for the survival of populations in face of environmental changes seems to provide a plausible explanation. Temperature and its variation were elected as representatives of the desertification process. Based on the evidence that the Caatinga was originally a humid forest, correspondent values for the Atlantic forest were used as reference for comparison. The theoretical framework adopted assumes that the thermal sensitivity of differentiation in anuran larvae is higher than growth sensitivity (Smith-Gill and Berven, 1979). Our main hypothesis was that the developmental plasticity of the Caatinga species Rhinella granulosa is greater than those of Atlantic forest species Rhinella ornata and Rhinella icterica. We compared thermal reaction norms of growth rate, development time, metamorphic mass and critical thermal maxima (CTMax) for each species. Larvae were submitted to thermal regimes typical of the Caatinga and the Atlantic forest. A significant interaction between thermal mode and variation was detected for both Rhinella ornata and Rhinella icterica. Forest species appeared very plastic. When submitted to Caatinga thermal regimes, they displayed double growth rate and a third of development time in comparison to when they were submitted to Atlantic forest thermal regimes. The larvae presented individual variation in thermal sensitivity. Indeed, a fraction of the sample did not follow Smith-Gill and Bervens rule and displayed thermal sensitivity of differentiation similar to growth sensitivity. As a consequence, they maintained their metamorphic mass canalized at 0,25g in face of higher temperatures. Although Rhinella granulosa\'s CTMax was higher than for the forest species, it presented less plasticity. The results have not supported our hypothesis as the Atlantic forest species seems more plastic than the Caatinga species.

Animals must balance multiple, fitness-related traits in environments that are complex and characterized by co-varying factors, such as co-variation in temperature and food availability. Thus, experiments manipulating multiple environmental factors provide valuable insight into the role of the environment in shaping not only important traits (e.g., dispersal capacity or reproduction), but also trait-trait interactions (e.g., trade-offs between traits). We employed a multi-factorial design to manipulate variation in temperature (constant 28°C vs. 28±5°C daily cycle) and food availability (unlimited vs. intermittent access) throughout development in the sand field cricket, Gryllus firmus. We found that fitness-related, life-history traits and trait trade-offs can be developmentally plastic in response to variation in temperature and food availability. Variability in temperature and food availability influenced development, growth, body size, reproductive investment, and/or flight capacity, and food availability also affected survival to adulthood. Further, both constant temperature and unlimited food availability promoted investment into key components of somatic and reproductive tissues while reducing investment into flight capacity. We develop an experimental and statistical framework to reveal shifts in correlative patterns of investment into different life-history traits. This approach can be applied to a range of animal systems to investigate how environmental complexity influences traits and trait trade-offs.