The human body compensates well for moderate climatic heat stress, but artificial environments often block or overwhelm physiological defense mechanism. Personal protective equipment (PPE) is one of sources of heat stress. It protects individual from chemical, physical, or biological hazards, but the high thermal insulation and low vapor permeability of PPE may also lead to substantial heat stress. Personal cooling is widely used to alleviate heat stress, especially for those situations where ambient environmental cooling is not economically viable or feasible. It is important to predict the physiological responses of a person wearing PPE with personal cooling to make sure that the individual is free of heat stress, as well as any additional discomfort that may occur. Air temperature, radiant temperature, humidity and air movement are the four basic environmental parameters that affect human response to thermal environments. Combined with the personal parameters of metabolic heat generated by human activity and clothing worn by a person, they provide the six fundamental factors which define human thermal environments. If personal cooling system is available, the fluid flow speed, cooling tube distribution density and fluid inlet temperature have significant effects on the human thermal comfort. It is impractical to evaluate the problem experimentally due to too many factors involved. A thermal model was developed to improve human body thermal comfort prediction. The system researched includes human body, personal cooling system, clothing and environment. An existing model of thermoregulation is taken as a starting point. Changes and additions are made to provide better prediction. Personal cooling model was developed and it includes liquid cooling model, air cooling model and ice cooling model. Thermal resistance networks for the cooling system are built up; additionally a combined model of heat and mass transfer from cooling garment through clothing to environment is developed and incorporated into the personal cooling model and thermoregulatory model. The control volume method is employed to carry out the numerical calculation. An example simulation is presented for extra-vehicular activities on Mars. The simulation results agree well with available experimental data, though a small discrepancy between simulation results and experimental data is observed during the beginning of the cooling process. Compared with a water cooling lumped model, the thermal model provides a much better prediction. For water cooling, parametric study shows that the cooling water inlet temperature and liner thermal resistance have great effects on the maximum exposure time; PPE resistance and cooling water flow rate do not have much impact on the maximum exposure time. For air cooling, cooling air flow rate, inlet temperature, relative humidity and liner resistance have great effects on the maximum exposure time.

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Thesis (PhD (Process Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Previous work has shown that microwave heating of mineral ores induces fractures around grain boundaries due to the differences in absorption of microwaves and the resulting differential thermal expansion among the various mineral phases in the ore particles. As a consequence, this reduces the energy required in subsequent grinding and enhances liberation of valuable minerals. In this study, first, the influences of different variables on bulk strength reduction of microwave treated ores have been investigated. Nine different binary ore models were constructed by randomly disseminating 10 vol.% microwave absorbing minerals in transparent matrices. Computational simulations of heating, thermal damage and unconfined compressive strength (UCS) tests on the conceptual binary ores have been undertaken by using finite-difference modelling techniques. The influence of thermo-mechanical properties of minerals on strength reduction of microwave treated ores was examined. It was shown that in general the thermal properties of the microwave absorbing mineral and the mechanical properties of the transparent matrix have the most significant effect on the strength reduction. Binary ores containing a microwave absorbing mineral that has a high thermal expansion coefficient in a strong transparent matrix achieved higher reductions in strength. The influence of absorbent phase grain size on strength reduction of ores was also quantified. It was shown that for the same energy inputs and mineral types, the reductions in strength were much higher in coarse-grained ores. It has also been shown that for the same mineralogy and treatment condition, ores with poorly disseminated heated phase achieved much higher strength reduction. The effect of microwave treatment on the mechanical state of an ore sample was also examined. It was demonstrated that unconfined compressive strength is less sensitive to microwave-induced micro-fractures and found to be a poor descriptor of liberation behaviour. A new method of characterizing damage in microwave treated ore using a continuum approach was developed. The method measures the damage around the grain boundary regions during the heating process. Using the method, it was possible to elucidate in detail the influences of power density, mineralogy, ore texture on microwave treatment of ore. It was shown that the amount of grain boundary damage incurred at a specific power density and energy input is dependent both on the ore mineralogy and its texture. The energy inputs that were required for significant (> 10%) grain boundary damage in the ores range from 0.09 to 7.06 kWh/t depending on the power density applied, the ore mineralogy and its texture. It was also shown that for a given mineralogy and ore texture there is a power density level below which no further increase in grain boundary damage is possible by increasing exposure time. The effect of pulse repetition frequency on grain boundary damage was also elucidated using the method. It was found that high pulse repetition frequencies (³ 50 Hz) resulted in an amount of grain boundary damage that was indistinguishable from that caused by continuous wave operation for a fixed energy input. It has also been shown that for a fixed microwave energy input the best result would be obtained by using the lowest possible pulse repetition frequency and highest peak pulse power. The effect of microwave treatment of ores at different treatment conditions on the extent of damage and crack pattern was also investigated in detail using bondedparticle model (BPM). It has been shown that the amount of micro-cracks and also the cracks pattern in an ore sample after microwave treatment significantly depend on its mineralogy, microwave treatment condition (power density) and absorbent phase grain size. It has also been shown that a minimum power density is required to localize damage around the grain boundary in an ore sample. This minimum power density was found to strongly depend on the ore mineralogy and its texture. Initial simulation test work concerning the effect of microwave treatment on liberation of minerals is also presented. It has been shown that microwave irradiation considerably changed the fracture pattern of an ore in simulated single particle crushing. The fracture pattern of the ore treated at high power density (Pd = 0.1 kW /mm3abs for 1 ms) was along the grain boundary and the absorbent mineral was intact. In the ore treated at lower power density for the same energy input (Pd = 1 W/mm3abs for 0.1 s) both intergranular and transgranular fractures were observed. However, in all cases the fracture patterns were preferentially localized around the grain boundary compared to that of the untreated ore. / AFRIKAANSE OPSOMMING: Vorige studies het getoon dat mikrogolfverhitting van mineraalertse tot breuke om die ertskorrelgrense aanleiding gee, omdat die verskillende mineraalfases in die ertsdeeltjies die mikrogolwe verskillend absorbeer, en dus ook verskillend uitsit. Korrelgrensbreuke verminder die vereiste energie vir latere slypwerk, en verhoog die vrystelling van waardevolle minerale. Hierdie studie het eerstens die uitwerking van verskillende veranderlikes op die algehele sterktevermindering van mikrogolfbehandelde ertse ondersoek. Hiervoor is nege verskillende binêre ertsmodelle vervaardig deur mikrogolfabsorberende minerale met ʼn volumepersentasie van 10% lukraak in deursigtige matrikse te versprei. Met behulp van eindigeverskilmodelleringstegnieke is berekeningsimulasies van verhitting, warmteskade en onbegrensde druksterkte (“unconfined compressive strength”) op die konseptuele binêre ertse uitgevoer. Die invloed van termomeganiese mineraaleienskappe op die sterktevermindering van mikrogolfbehandelde ertse is eerste onder die loep geneem. Daar is bevind dat die warmte-eienskappe van die mikrogolfabsorberende mineraal, en die meganiese eienskappe van die deursigtige matriks, die beduidendste uitwerking op sterktevermindering het. Binêre ertse wat ʼn mikrogolfabsorberende mineraal bevat met ʼn hoë warmte-uitsettingskoëffisiënt in ʼn sterk deursigtige matriks, het groter sterkteverminderings getoon. Die invloed van korrelgrootte in die absorbeerfase op die sterktevermindering van ertse is volgende versyfer. Die studie het getoon dat, op grond van dieselfde energie-insette en mineraalsoorte, grofkorrelrige ertse groter sterktevermindering ondergaan het. Eweneens is bewys dat, met dieselfde mineralogie en behandelingsomstandighede, ertse met ʼn swak verspreide verhittingsfase ook groter sterktevermindering ervaar. Die uitwerking van mikrogolfbehandeling op die meganiese toestand van ʼn ertsmonster is boonop ondersoek. Die studie het getoon dat onbegrensde druksterkte minder gevoelig vir mikrogolfgeïnduseerde mikrobreuke is, en as ʼn swak aanwyser van vrystellingsgedrag beskou word. ʼn Nuwe metode om skade by mikrogolfbehandelde ertse te tipeer is gevolglik met behulp van ʼn kontinuumbenadering ontwikkel. Dié metode meet die skade rondom die korrelgrens gedurende die verhittingsproses. Deur middel van voormelde metode was dit dus moontlik om die invloed van kragdigtheid, mineralogie en ertstekstuur op die mikrogolfbehandeling van erts deeglik te ondersoek. Daar is bevind dat die mate van korrelgrensskade by ʼn bepaalde kragdigtheid en energie-inset, van sowel die ertsmineralogie as ertstekstuur afhang. Na gelang van die toegepaste kragdigtheid, die ertsmineralogie en ertstekstuur, het die vereiste energie-insette vir beduidende (>10%) korrelgrensskade van 0,09 tot 7,06 kWh/t gewissel. Dit het voorts geblyk dat enige bepaalde mineralogie en ertstekstuur oor ʼn minimum kragdigtheidsvlak beskik, onder welke vlak geen verlenging in blootstellingstyd enige verdere korrelgrensskade kan veroorsaak nie. Die uitwerking van pulsherhaalfrekwensie op korrelgrensskade is ook met behulp van bogenoemde metode verklaar. Die studie het getoon dat, op grond van ʼn vaste energie-inset, hoë pulsherhaalfrekwensies (≥50 Hz) en gelykgolfwerking presies dieselfde hoeveelheid korrelgrensskade tot gevolg het. Volgende is daar met behulp van ʼn gebondedeeltjiemodel (“bonded-particle model”) noukeurig ondersoek ingestel na die uitwerking van verskillende mikrogolfbehandelingsomstandighede op die hoeveelheid skade en die kraakpatroon by ertse. Die studie het getoon dat die hoeveelheid mikrokrake sowel as die kraakpatroon in ʼn mikrogolfbehandelde ertsmonster in ʼn groot mate van die betrokke erts se mineralogie, mikrogolfbehandelingsomstandighede (kragdigtheid) en korrelgrootte in die absorbeerfase afhang. Daar is ook bevind dat ʼn minimum kragdigtheid nodig is om skade tot die gebied om die korrelgrens te beperk, welke minimum kragdigtheid oënskynlik grotendeels deur die ertsmineralogie en -tekstuur bepaal word. Die studie bevat ook die resultate van aanvangsimulasietoetse oor die uitwerking van mikrogolfbehandeling op mineraalvrystelling. Die toetse het getoon dat mikrogolfbestraling ʼn beduidende verandering tot gevolg het in die ertsbreekpatroon met gesimuleerde enkeldeeltjievergruising. Die breekpatroon van die erts wat by hoë kragdigtheid (Pd = 0,1 kW/mm3abs vir 1 ms) behandel is, het ál langs die korrelgrens gestrek, terwyl die absorberende mineraal nog ongeskonde was. In die erts wat by laer kragdigtheid dog dieselfde energie-inset behandel is (Pd = 1 W/mm3abs vir 0,1 s), is sowel tussenkorrel- as oorkorrelbreuke opgemerk. In teenstelling met die onbehandelde erts, was die breekpatrone by die behandelde erts egter in alle gevalle steeds merendeels rondom die korrelgrens geleë.

As a critical public safety-related structure, the long-term integrity of post-tensioned concrete containment buildings (PCCs) is necessary for continued operation of the reactors they house. In 2009, during preparations for a steam generator replacement, extensive subsurface laminar cracking was identified in a portion of the Crystal River 3 (CR3) PCC in Florida, and the plant was permanently shut down in 2013. This study investigates potential contributing factors to the identified cracking with particular focus on the effects of high early-age temperatures on the cracking risk of the concrete, on the development of the concrete properties, and on the late-age structural behavior of the concrete. Two planar, full-scale mock-ups of a portion of the CR3 PCC were constructed and instrumented with temperature and strain gauges to monitor the thermal and mechanical behavior during representative concrete curing and post-tensioning loading. Standard- and match-cured concrete specimens were tested for determination of the time- and temperature-dependent development of thermal and mechanical concrete properties, and hydration parameters were determined for the mock-up cement paste for modeling the heat generation in the concrete. These properties and parameters were utilized in 3D finite element analysis of the mock-ups in COMSOL Multiphysics and compared with experimental results. Non-destructive evaluation via shear wave tomography was conducted on the mock-ups to identify flaws and determine the effectiveness of the methods for identifying delaminations between post-tensioning ducts approximately 10 inches beneath the concrete surface. Though early-age thermal stresses were determined not to have caused cracking in the mock-ups, the high early-age concrete temperatures resulted in decreased late-age mechanical properties that were shown to contribute to greater concrete cracking risk when the mock-up was post-tensioned. Tensile stresses exceeding the tensile strength of the concrete were identified along the post-tensioning ducts when biaxial post-tensioning loads were applied in finite element analysis, but the stresses decreased rapidly with increased distance from the ducts. Through parametric modeling, increasing the tensile strength of the concrete was identified as an effective means of reducing the cracking risk in PCCs. Additionally, relationships between the mechanical properties for the standard- and match-cured specimens were identified that could enable prediction of in-place or match-cured concrete properties based only on the results of tests on fog-cured specimens.

In this paper, processing effects of electroplating and post- plating annealing on via extrusion are investigated. The study is based on two TSV structures with identical geometry but different processing conditions. Via extrusion, stress and material behaviors of the TSV structures were first compared. Electron backscatter diffraction (EBSD) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS) were used to characterize the microstructure of TSVs and the additives incorporated during electroplating. Based on the results, processing effects on via extrusion and its mechanism are discussed, including grain growth, local plasticity, and diffusional creep.

The objectives were to investigate the effects of chromium (III) picolinate (CrPic; up to 2,000 ppb of Cr) on growing pigs subjected to a variety of stressors including thermal, immune, or dietary stress and to examine the effects of CrPic on steroidogenesis from adrenocortical cells. In the thermal stress study, high ambient temperature caused reduced weight gain and feed consumption (P andlt; 0.01), and low ambient temperature caused increased feed intake and feed:gain (P andlt; 0.01). However, these effects were not moderated by CrPic, and respiratory rate, plasma cortisol, or plasma glucose were unaffected by CrPic. In the immune stress study, pigs challenged with lipopolysaccharide (LPS) lost 951 g during 12 hours post injection, while the phosphate buffer saline (PBS) injected group gained 170 g (P andlt; 0.001). The LPS group showed higher rectal temperature (P andlt; 0.05), higher respiratory rate (P andlt; 0.05), greater plasma cortisol (P andlt; 0.001), and lower plasma glucose (P andlt; 0.05) than the PBS group. These effects were not ameliorated by CrPic. In the dietary stress study, pigs fed the high-fat diet (HFD) gained weight faster (P andlt; 0.05), consumed less feed (P andlt; 0.001), and had lower feed:gain (P andlt; 0.001). Plasma insulin concentration on d 14 decreased with CrPic (P andlt; 0.05) in a linear manner (P = 0.05). Consumption of the HFD resulted in increases of slaughter weight, perirenal fat, and back fat measurements (P andlt; 0.01). The CrPic resulted in linear reductions of carcass weight, last rib fat, last lumbar fat and average backfat (P andlt; 0.10). The effects of CrPic on carcass fat measurements were more significant in barrows than gilts. In the adrenocortical cell study, forskolin stimulated cortisol and DHEAs secretion from H295R cells. CrPic inhibited aspects of steroidogenesis in agonist-stimulated adrenocortical cells. Overall, dietary CrPic was unable to moderate the stress related effects due to high ambient temperature, low ambient temperature, or an endotoxin challenge. However, CrPic attenuated effects of HFD, mainly on body fat accretion of pigs, especially in barrows, and CrPic inhibited steroidogenesis in stimulated adrenocorticoid cells.

The research presented in this dissertation consists of four topics. The first of these topics is an experimental study of rock fracturing due to rapid thermal cooling, and the other three topics are related to mine-to-optimization. This includes the development and testing of a site-specific model for blast fragmentation, the development of a technique for utilizing digital image processing and ground-based LIDAR for rock mass characterization, and an experimental study of the effects of ore blending on mineral recovery. All four topics are related through the subject of rock fracturing and rock fragmentation. The results from this research are important and can be used to improve engineering design associated with rock excavation and rock fragmentation. First of all, a successful set of laboratory experiments and 3D numerical modeling was conducted, looking at the effects of rapid thermal cooling on rock mechanical properties. The results gave the unexpected finding that depending on the rock type and the thermal conditions, rapid cooling can result in either overall crack growth or crack closing. Secondly, a site-specific model for predicting blast fragmentation was developed and tested at an open-pit copper mine in Arizona. The results provide a practical technique for developing a calibrated blasting model using digital images and digital image processing software to estimate in-situ block size, and a calibrated Schmidt hammer to estimate intact tensile strength. Thirdly, a new technique was developed to conduct cell mapping in open-pit mines using the new technologies of digital image processing and ground-based LIDAR. The results show that the use of these new technologies provide an increased accuracy and the ability for more sophisticated slope stability analyses with no increase in field time only a moderate increase in data processing time. Finally, a successful set of laboratory experiments was conducted looking at the effects of ore blending and grinding times on mineral recovery from a set of six ore from a copper mine in Arizona. The results gave the unexpected finding that for a fixed grinding time, the mineral recovery of the blended ores exceeded the average of the individual recoveries of the same ores unblended.

Today, thin film based devices are found in a wide field of applications. The main reasons are that thin film technology enables access to unique physical properties and possibilities to miniaturize devices. Thin film devices are generally described in terms such as electrical, optical and magnetical properties. However, the lifetime of these devices is often limited by mechanical stresses causing plastic deformation. An effect of the plastic deformation is hillocking where isolated features are created on the film surface. The continual need to improve performance, reduce size as well as cost is pushing thin film structures close to or beyond present fundamental understanding. Further progress requires better understanding of basic phenomena where analytical methods for characterization of thin film deformation play a crucial role. To follow the initial hillock formation during thermal treatments it is essential to have a suitable tool for achieving real-time measurements with high sensitivity over a relatively large area that does not considerably affect the film surface. Methods based on light scattering are generally very sensitive to changes in the surface topography and allow contact free measurements at high speed. In this thesis light scattering methods are investigated as tools for stress analysis of thin metal films. Detection and characterization of isolated surface features using angular resolved scattering has been investigated by simulations. Results were used in development of an optical instrument for simultaneous measurements of initial hillocking and changes in overall film stress. The instrument combines light scattering and laser beam deflection techniques. It is shown how the onset of initial hillocking in aluminum films is accompanied by stress relaxation. Real-time dark field microscopy was demonstrated as a technique for analysis of the lateral hillock distribution. Analysis of the distribution show clustering of hillocks which is supposed to be related to the microstructure of the film. It is demonstrated that copper inclusion can be used to strengthen aluminum films to withstand higher stress before hillocking occurs. The copper content also reduces the grain size and thereby the surface roughness, which results in good or even better optical performance than for pure aluminum films. / <p>NR 20140805</p>