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Abstract A modified thermal spike model initially proposed to account for defect formation in metals within the high heavy ion energy regime is adapted for describing the sputtering of Bi thin films under MeV Kr ions. Surface temperature profiles for both the electronic and atomic subsystems have been carefully evaluated versus the radial distance and time with introducing appropriate values of the Bi target electronic stopping power for multi-charged Kr15+ heavy ions as well as different target physical proprieties like specific heats and thermal conductivities. Then, the total sputtering yields of the irradiated Bi thin films have been determined from a spatiotemporal integration of the local atomic evaporation rate. Besides, an expected non negligible contribution of elastic nuclear collisions to the Bi target sputtering yields and ion-induced surface effects has also been considered in our calculation. Finally, the latter thermal spike model allowed us to derive numerical sputtering yields in satisfactorily agreement with existing experimental data both over the low and high heavy ion energy regions, respectively, dominated by elastic nuclear collisions and inelastic electronic collisions, in particular with our data taken recently for Bi thin films irradiated by 27.5 MeV Kr15+ heavy ions. An overall consistency of our model calculation with the predictions of sputtering yield theoretical models within the target nuclear stopping power regime was also pointed out.

High-temperature processing of rice needs close attention due to the susceptibility of rice grains to fissures. The present study was carried out to redress the lack of information on the quality of rice dried at high-temperatures using a range of drying air temperatures from 160 - 200??C and grain moisture contents varying from 27 to 33%wb. A laboratory type high temperature dryer-oven was developed and constructed, and the performance was compared with commercial fluidized-bed and spouted-bed dryers. The new column type treatment plant, targeted at small-scale rice farmers was designed to reduce milling breakages was tested for high-temperature treatments. Short term drying (160 ??? 180 seconds) of high moisture rough rice at high-temperatures such as 160 - 200??C increased head rice yield by 5 - 8% in long grain rice and 7 - 11% in medium grain rice. The head rice yield increase achieved was very close to the highest potential head rice recovery possible for a given sample. The head rice yield increase was mainly due to a hardened surface layer of the rice kernel, formed by two effects, a surface fusion and surface gelatinization during high-temperature treatment. This stress protection layer is only effective for a short period (1 - 2 minutes) at high temperatures. Tempering of treated grains, either by storing in gunny bags or rapid cooling, can secure the grains to some extent from grain breakage. The highest head rice yield increase was obtained by ceasing the high-temperature effect at the grain moisture level of 24 - 25%wb. The colour and appearance of high-temperature treated grains were closer to those of untreated grains with the toughness closer to that of parboiled rice. The setback values of high-temperature treated rice measured by RVA, which is a preferred character by consumers, were closer to aged rice. High-temperature treatments did not affect the cooking qualities except a slight increase in water absorption. The alterations in the grain due to high-temperature treatment are limited to only for 8 - 9% of the total volume (mainly outer region) of the rice grain, preserving more than 90% of the grain with raw-rice quality. Structural changes such as complexing of amylose ??? lipid, amylose -protein and denaturation of protein play a dominant role on quality changes than gelatinization. A new method introduced to measure the degree of gelatinization of pre-gelatinized rice, using hot paste viscosity by rapid visco analyser (RVA), was successful. The peak viscosity parameter in the RVA was more suitable for measuring the chemical changes in high-temperature treated rice. Spouted-bed drying technology is not suitable for high-temperature treatment due to the unfavourable conditions for the formation of a hardened layer under intermittent heating and cooling. Fluidized-bed dryers could be used for high-temperature drying, but is not cost effective for the small-scale farmer level. The novel type treatment plant was successful in reducing the amount of broken grains to almost zero, increasing the head rice yield by 50 - 120kg per 1000kg of rough rice. It was also effective as a germination arrester, inhibiting the germination ability within a very short period such as 30 - 60 seconds. This equipment is more effective as a treatment Plant as it reduces moisture by only 1.5 - 2.0% at highest head rice yield recovery. An empirical model was successfully established (R2 = 0.99) for grain moisture content (db) and drying temperature during high-temperature processing. In model validation process, a good agreement was found between predicted and experimental data. The modelling between head rice yield and high-temperature drying was unsuccessful (R2 = 0.89) mainly due the interference from other factors such as initial moisture stress due to re-wetting and uncontrolled post treatment drying environment conditions. The study revealed some breakthrough for the rice industry in addition to its quantitative evaluation of increase in head rice yield. 1. Ability to produce grains with twice the toughness of milled untreated rice, without losing colour and appearance. 2. Fissured grains, previously weakened due to moisture-stress (considered as a loss), can be successfully recovered by treating this high-temperature technique. Currently there is no method available to increase the head rice yield of this type of fissured grains except parboiling, which is not widely accepted among consumers. 3. Drying at 200??C drying temperature completely destroyed the viability of seeds within 40 -60 seconds, hence providing a remedy for germination problems in wet harvests. 4. Since high-temperature drying needs wet rough rice, early harvesting can be done which will reduce shattering losses. This enable the farmers to use the field for an inter-seasonal crop which can utilise higher residual soil moisture in the paddy fields compared to other crops.

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Faced with the twin challenges of food security and environmental protection, given the energy resource scarcity, agriculture needs to develop production systems that are highly productive, economically viable and environmentally sound. In this regard, several production systems have been recently developed. All of them share the general objective of using less energy per unit of output. / The focus of this study for red pepper, is to examine the environmental performance of a plasticulture system compared to a conventional system in terms of: (1) energy inputs per unit of output; and (2) cost per unit of output. / Energy analysis was performed to account for the total energy consumed in red pepper production under silver mulch and no-mulch. The method of process analysis was employed to account for total energy requirements for different inputs. Partial budgets for both type of production systems were constructed to estimate the costs of production. The analysis boundary was set at the farm gate. Production costs are derived from secondary data. Data on mulch yield were based on the results of an experimental trail conducted on the farm of Macdonald Campus of McGill University in the West Island of Montreal (Fava, 1996). (Abstract shortened by UMI.)