The multi-scale modeling of ion-solid interactions presented can lead to a fundamentally new approach for understanding temperature evolution and damage formation. A coupling of the Monte Carlo code, SRIM, to a C FEM heat transfer code was performed, enabling a link between the damage cascade event to the subsequent heat transfer. Modeling results indicate that for 1 MeV Ni ion irradiation in Ni52.5Nb10Zr15Ti15Pt7.5, the heat transfer rate is too large for direct crystallization. Although the damage cascade induces a peak temperature of 5300 K, within 6 picoseconds the temperature is below the glass transition temperature. This result implies that there is a cooling rate of 10^14 K/s, which is much greater than the critical cooling rate for this material. Ion irradiation was performed to compare modeling with experiment. No evidence of direct crystallization is observed under TEM. Nanocrystals are formed as a consequence of series of multistage phase transitions. This provides evidence that the energy dissipation occurs too quickly for direct crystallization, as crystals are found in regions having undergone substantial compositional changes. A host of conventional electron microscopy methods were employed to characterize the structural changes induced by 1 MeV Ni ion irradiation in Ni52.5Nb10Zr15Ti15Pt7.5 and identify the phases that form, Ni3Nb, Ni3Ti and Ni3Zr. Scanning TEM analysis revealed Pt segregation near crystal regions due to irradiation. Due to a lack of Pt crystal phases observed and high concentrations of Pt in crystal regions it is postulated that Pt is substituting for Ni to form (Ni,Pt)3Nb and (Ni,Pt)3Ti.

This thesis aims to investigate the effects of gamma radiation on the properties of polycarbonate, an engineering thermoplastic which has a wide range of applications. A commercial grade polycarbonate resin, after being shaped into the required specimen forms by injection molding, was irradiated with different doses up to 180 kGy. Tensile strength was found to decrease with increasing dose. The lowest values of tensile modulus, flexural modulus and flexural strength were obtained at 96 kGy, which is also the dose at which molecular weight values showed a minimum. No remarkable changes in Shore D hardness values and NMR spectra were observed. The ATR-FTIR spectra showed that irradiation was effective on carbonyl groups in the structure. The glass transition temperatures of the specimens irradiated up to the maximum dose were lower than those of the non-irradiated specimens. The onset of weight loss at lower temperatures and steeper weight loss behavior in the TGA curves indicated decreasing thermal stability of the polymer with increasing dose.

Nitrogen oxide in water was a critical factor of eutrophication. The poor tap-water quality in Taiwan was the result of ammonia nitrogen pollution. This research used manganese dioxide as the catalyst to degrade ammonia nitrogen content in water. Controlled factors in our experiment include basic test, optimal reaction condition test, and kinetics. Real water sample was drawn from the Love River for catalysis effect test. Results were then compared with the popularly used titanium dioxide. Significant findings in this research include: 1) when the manganese dioxide content in water was 2%, the ammonia nitrogen removal rates were 31.80% under UV irradiation, and 22.21 % without light interference; 2) under UV irradiation, manganese dioxide would not affect the catalysis effect due to pH changes; 3) silicate in the water had catalysis effect, while sulfate, phosphate, and nitrate had inhibition effect; 4) manganese dioxide had catalysis effect in seawater, yet the removal rate would decrease as the salt content increases; 5) the rise of water temperature would enhance the ammonia nitrogen removal rate; 6) manganese dioxide had catalysis effect on the treatment of the Love River water, and the ammonia nitrogen removal rate reached 89.50 %; 7) in the biological test, manganese dioxide could effectively degrade the ammonia nitrogen content in water, and improve the survival rate of larval shrimp; 8) comparing to titanium dioxide, manganese dioxide had advantages of low cost, with catalysis effect in both seawater and fresh water under no light condition. As a result, manganese dioxide has significant future application potentials. In the future, this research will conduct in-depth study on kinetics of degradability of manganese dioxide catalysis on ammonia nitrogen, and to design suitable catalytic reactor for water treatment. Moreover, it is of value to broadly research manganese dioxide related catalytic products, such as catalytic spray, catalytic paint, fluorescent tube, air filter, and catalytic fan...etc.

Past research conducted by our lab demonstrated that potatoes contain significant levels of phytochemicals important to human health. However, since potatoes are not consumed raw, it is important to determine the effects of processing on these levels. Therefore, the changes in carotenoid content, antioxidant activity, and phenolic content were investigated using combinations of cultivars, cooking methods, storage treatments, and low-dose ionizing irradiation. Carotenoid content was measured via absorbance at 445 nm, 450 nm, and HPLC identification. Antioxidant activity was measured initially and at stabilization via the DPPH method and phenolic content was measured via the Folin method and HPLC identification. Microwaved, baked, fried, and raw potato samples contained more carotenoids than boiled samples. The samples microwaved, baked, and fried contained higher antioxidant activity and phenolics than the boiled or raw samples. However, the compound quercetin dihydrate appeared to decrease with cooking. Carotenoids, antioxidant activity, and phenolics appeared to decrease with storage; however, high storage temperatures and long storage times were believed to cause a dehydration and concentration of compounds, which caused levels to be equal to or greater than before storage. However, this decreasing trend was not linear and there were multiple significant interactions. The compound chlorogenic acid appeared to be quite sensitive to high temperature storage. Irradiation dose appeared to have only a minor, if any, effect on carotenoid levels. The interaction between storage time and irradiation dose was very influential on antioxidant activity. In early stages of storage, higher doses of irradiation had greater antioxidant activity, while, with continued storage, low doses had higher antioxidant activity. Exposure to irradiation appeared to cause an increase in phenolic content, determined by the Folin method. There may be a stimulation, induction, or release of some compounds due to processing; however, its magnitude is not believed to be as great as genetic control. The effects of processing can not be denied and should continue to be investigated. Future studies investigating the health properties of fruits and vegetables, particularly potatoes should include processing effects.

Increase in consumption of fresh produce over the past decade has resulted in a rise in incidents of foodborne outbreaks due to pathogens. Chemical sanitizers have been extensively used in the industry for decontamination of fresh produce. However, they are ineffective in certain commodities and under certain processing conditions, necessitating the evaluation of alternative technologies. Electron beam irradiated sliced cantaloupe were tested for 21 days of storage for total aerobic bacterial counts, texture, color and sensory parameters as a function of irradiation doses 0, 0.7 and 1.4 kGy and the wash treatments, water and 200 mg/L chlorine applied to the melons before cutting. Melons washed only with water prior to cutting had total aerobic bacterial counts of 4.0, 2.0 and 0.8 log cfu/g on day 0 at irradiation doses of 0, 0.7 and 1.4 kGy respectively. On day 0, melons washed with chlorine prior to cutting had total aerobic bacterial counts of 2.7, and 0.7 log cfu/g at irradiation doses of 0 and 0.7 kGy and below detection limit at 1.4 kGy. Texture measured as compression force was lower only for cantaloupe irradiated at 1.4 kGy. Irradiation did not affect objective color and descriptive attribute flavor and texture sensory attributes of cantaloupe. Irradiation reduced Salmonella Poona by 1.1 log cfu/g at 0.7 kGy and 3.6 log cfu/g at 1.5 kGy. The D-value of S. Poona on irradiated sliced cantaloupe was found to be 0.211 kGy. Among the spoilage organisms, lactic acid bacteria and mold were reduced effectively by irradiation but there was no significant effect on reduction of yeasts. Our results show that electron beam irradiation in combination with chemical sanitizers is effective in decontamination of fresh-cut produce. Electron microscopy images provided valuable information on attachment sites of S. Poona on cantaloupe rind. The ineffectiveness of chemical sanitizers due to possible inaccessibility to pathogens in these attachment sites provides the basis for application of irradiation in decontamination of fresh produce.

A chemical solution composed of paraffin wax, chloroform, and methyl yellow biological indicator was shaped into a solid 3-D apple phantom to determine absorbed dose from e-beams and X-rays. The purpose of this research was to determine the most uniform irradiation treatment on apple-phantoms (a complex shaped target) and GAFCHROMIC® HD-810 films using electron beams from (1) a 2 MeV Van de Graaff (VDG) accelerator, (2) a 10 MeV Linear Accelerator (LINAC), and (3) X-rays from a 5 MeV LINAC. Irradiation with the VDG accelerator confirmed that tilting the apple-phantom yaxis towards the e-beam source by 90 degrees, 45, and 22.5 degrees resulted in more uniform treatment in both the methyl yellow apple phantom and HD-810 film. The phantoms were over-exposed at the top and bottom regions when their y-axis was oriented exactly parallel to the e-beam at 22.5-degrees. The 45-degree orientation ensured uniformity throughout the whole apple surface without overexposing it at the top and bottom. In contrast, the 90-degree orientation resulted in the least effective treatment with the bottom and top region not receiving any radiation. A 10 MeV dual e-beam showed uniform penetration from top to bottom in the HD-810 film and apple phantoms. The HD-810 film responded linearly with doses up to 1.5 kGy while the methyl yellow response was non-linear up to 0.5 kGy maximum. The X-ray irradiation completely penetrated the apple phantoms from top to bottom showing excellent lateral uniformity at different penetration depths.

This study was conducted to examine the antioxidative effect of conjugated linoleic acid (CLA) in irradiated, cooked ground beef patties. The hypothesis was that CLA would be retained during irradiation and would reduce lipid oxidation that is caused by irradiation. The objective was to evaluate the effects of CLA alone and in combination with irradiation on lipid oxidation, fatty acid composition, cooking loss, moisture and fat content, and trained panel sensory evaluations of beef patties. CLA was added at 0, 1, 2, or 4% level during the grinding process. Addition of CLA during the grinding process increased CLA cis-9,trans-11 and CLA trans-10,cis-12 isomers in both irradiated and non-irradiated cooked ground beef patties (irradiated at 1.6 kGy) (P = 0.0001). Weight loss during cooking was greater in irradiated beef patties than in non-irradiated patties (P = 0.004). Irradiation reduced the serumy/bloody aromatic attribute and increased browned aromatic attribute, browned aftertaste, and wet dog/hairy aromatic attribute (P < 0.05). There was no significant main effect of irradiation on the basic tastes. The linoleic acid, CLA cis-9,trans-11, and CLA trans-10,cis-12 were decreased by irradiation (P < 0.05). Although irradiation decreased the CLA isomers, higher percentages of CLA isomers were retained in irradiated patties containing a 4% free fatty acid preparation of CLA (FFA-CLA), reflecting the ability of the FFA preparation to reduce lipid oxidation that is caused by irradiation. The thiobarbituric acid reactive substances (TBARS) values were significantly higher in irradiated, cooked ground beef patties than in non-irradiated ground beef patties (P = 0.004). Although the FFA-CLA was effective in reducing lipid oxidation that is caused by irradiation, it increased painty aromatic attribute, bitter taste, and astringent aftertaste due to the soapy flavor of the free fatty acid (all P < 0.05). The FFA-CLA decreased cooked beef/brothy and serumy/bloody aromatic attribute and browned aftertaste (all P < 0.05). The 1% triacylglycerol (TAG) preparation of CLA reduced TBARS in irradiated, cooked patties to levels seen in control, non-irradiated patties. The 1% TAG concentration also provided good retention of CLA in the cooked ground beef.

Die Anwendbarkeit des Master Curve-(MC-)Konzepts zur Charakterisierung des Zähigkeitszustandes bestrahlter Reaktordruck¬behälter-(RDB-)Stähle wurde an drei RDB-Stählen überprüft: IAEA-Referenzstahl 3JRQ57, 1JFL11 (vergleichbar mit 22NiMoCr3-7) sowie russischer WWER-440 Grundwerkstoff KAB-B. In Zugversuchen, Charpy-V-Tests, Risswiderstandskurven nach ASTM E1820 und Master Curve Tests zur Bestimmung der Referenztemperatur T0 nach ASTM E1921 wurden der unbestrahlte Ausgangszustand, je drei Bestrahlungszustände bis hin zu Neutronenfluenzen von 100∙10^18 n/cm² (E>1MeV) sowie bei 475°C/100h thermisch ausgeheilte Zustände untersucht. Mit zusätzlichen auf dem MC-Konzept basierenden Auswerteverfahren nach SINTAP, multimodalem MC-Ansatz (MML) sowie der Unified Curve erfolgte die Bewertung des Einflusses von Materialinhomogenitäten und möglicher MC-Formänderung bei hohen Fluenzen. Wie erwartet geht Neutronenbestrahlung mit Verfestigung und Duktilitätsabnahme einher, d.h. Härte, Festigkeitskennwerte, Charpy-V-Übergangstemperaturen T28J und T41J sowie T0 steigen mit der Neutronenfluenz, während die Bruchdehnung und Hochlagenzähigkeit abnehmen. Am bestrahlungsempfindlichsten reagiert der Stahl 3JRQ57, gefolgt von KAB-B und 1JFL11. Durch die Ausheilbehandlung von 475°C/100h erholen sich die Werkstoffkennwerte der Zugversuche, Charpy-V-Tests und MC-Versuche auf den jeweiligen unbestrahlten Ausgangszustand. Die technischen Ersatzkennwerte für duktile Rissinitiierung bleiben relativ unbeeinflusst von der Neutronenbestrahlung. Die MC nach ASTM E1921 beschreibt die Bruchzähigkeits-Temperaturverläufe für alle drei RDB-Stähle in allen Bestrahlungs- und Ausheilzuständen gut. Bei den niedrig und mittel bestrahlten Zuständen liegen meist mehr als 5% der KJc(1T)-Werte unterhalb der MC-Kurve für 5% Versagenswahrscheinlichkeit. Die MC beschreibt den hoch bestrahlte Zustand (ca. 100∙10^18 n/cm², E>1MeV) aller drei RDB-Stähle sehr gut, auch für Daten außerhalb des Gültigkeitsbereiches T0±50K, und auch für den bestrahlungsempfindlichen 3JRQ57 mit inhomogenem Gefüge. Die Unified Curve überbewertet den Einfluss der Neutronenbestrahlung auf die MC-Kurvenform. Eine mögliche Formänderung der MC durch Neutronenbestrahlung konnte bei keinem der drei untersuchten RDB-Stähle nachgewiesen werden.

Lorsque des ions lourds rapides pénètrent dans la matière, ils se ralentissent principalement en déposant leur énergie sur les électrons. Ceci peut conduire à de fortes densités d'excitations électroniques dans le matériau et ainsi à des modifications structurales. Dans ce travail, le fluorure de calcium (CaF2) a été utilisé pour approfondir l'étude de l'endommagement des cristaux ioniques par irradiation avec ces ions lourds rapides. Quatre techniques ont principalement été employées pour caractériser cet endommagement. Ces techniques d'analyse sont la diffraction de rayons X aux grands angles, la profilométrie de surface, la spectrométrie de rétrodiffusion Rutherford en canalisation et la spectroscopie d'absorption optique UV-visible. <br />Les résultats de ce travail montrent que le CaF2 répond de manière multiple aux excitations électroniques créées par l'irradiation. Pour des pouvoirs d'arrt supérieurs à environ 5 keV/nm, un phénomène de polygonisation semble se produire. Ceci provoque un désordre structural, un gonflement de 0,27 % du matériau et la formation de fractures. Un deuxième mécanisme d'endommagement est occasionné au-dessus d'environ 13 keV/nm et se traduit par une perte de la structure cristalline d'origine. Cependant, des centres absorbants apparaissent quel que soit le pouvoir d'arrèt des ions, ce qui indique que ces défauts ne peuvent tre la cause des deux mécanismes d'endommagement précédents. L'interprétation par un modèle de pointe thermique permet d'associer les deux seuils précédents respectivement aux énergies de fusion et de sublimation du matériau.

Cette thèse porte sur la prédiction de durée de vie du polyéthylène en ambiance nucléaire. Elle se caractérise par la recherche d'une solution non empirique au problème. Il s'agit d'établir un modèle décrivant l'évolution du polymère (y compris l'hétérogénéité induite par un contrôle de la cinétique d'oxydation par la diffusion de l'oxygène) à toute température comprise entre l'ambiante et la température de fusion du polymère, et à tout débit de dose compris entre 0 et 1 kGy.h-1, avec des durées de vie s'étalant sur plusieurs dizaines d'années. La difficulté majeure était la prise en compte d'un processus d'amorçage dual: par radiolyse du polymère et par décomposition thermique des hydroperoxydes. Nous l'avons résolue en considérant d'abord les régimes asymptotiques où l'un des processus est négligeable par rapport à l'autre. Ayant identifié les paramètres cinétiques propres à chacun des régimes, nous avons ensuite construit un modèle numérique englobant tous les processus. Dans le cas du polyéthylène non stabilisé, ce modèle a d'excellentes qualités prédictives, tant en ce qui concerne la durée de vie à fragilisation, qu'en ce qui concerne l'épaisseur de la couche oxydée. Nous sommes ensuite passés à l'étude d'échantillons de polyéthylène stabilisés par un phénol encombré et par un sulfure. L'analyse de la consommation du phénol révèle l'existence de mécanismes non encore étudiés, en particulier l'existence d'un effet "réservoir" lié à la présence d'une phase de phénol en excès. Un modèle cinétique a été élaboré, mais nous ne savons pas encore dans quelle mesure les caractéristiques prises en compte sont spécifiques aux stabilisants étudiés ou généralisables