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Abstract An alkaline earth boro-aluminosilicate glass (Eagle XG), a soda-lime glass, and a light-weight polyethylene-terephthalate (PET) foil, used as typical substrates for photovoltaics, were treated by an energetic proton beam (3 MeV, dose 106–107 Gy) corresponding to approx. 30 years of operation at low Earth orbit. Properties of the irradiated substrates were characterized by atomic force microscopy, optical absorption, optical diffuse reflectance, Raman spectroscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and terahertz (THz) spectroscopy. Minimal changes of optical and morphological properties are detected on the bare Eagle XG glass, whereas the bare PET foil exhibits pronounced increase in optical absorption, generation of photoluminescence, as well as mechanical bending. On the other hand, the identical substrates coated with Indium-tin-oxide (ITO), which is a typical material for transparent electrodes in photovoltaics, exhibit significantly higher resistance to the modifications by protons while ITO structural and electronic properties remain unchanged. The experimental results are discussed considering a potential application of these materials for missions in space.

Abstract This article announces the availability of patented technology and production equipment for the manufacture of thin-film CdTe photovoltaic (PV) modules capable of providing utility scale power. It further discusses ongoing R&D, for the period 2000–2010, which will produce PV power at costs competitive with conventional fossil fuel systems.

A simple expression for multiple reflections within a collector with a double glazed cover is proposed

Abstract Buoys carrying scientific equipment usually need continuous power supply for the operation of these equipments. These buoys can be equipped with actuators and controlled to harvest power from the heaving motion of the buoy. A two-body wave energy converter can be designed such that the buoy heaves to harvest energy while the second (lower) body carries the science equipments. This paper presents a control approach for this type of two-body wave energy converter. This control approach is a multi resonant control that attempts to maximize the harvested energy from the buoy (upper body). In this model, the actuator is attached to both bodies. The lower body however is required to have minimal heave motion. The proposed multi resonant control utilizes measurements of the buoy position. The frequencies of the measured buoy position are estimated, along with the motion amplitudes of these frequencies, and used for feedback control. Estimation is carried out using two approaches; the first uses a linear Kalman filter while the second uses an extended Kalman filter. A new method for handling the motion and actuation limitations, suitable for the multi resonant control, is proposed. Various numerical simulation results are presented in the paper. Simulation results show that the linear Kalman filter estimation approach is more robust and computationally efficient compared to the extended Kalman filter.

Accurate estimation of extreme wave conditions is critical for offshore renewable energy activities and applications. Wave power is the transport of energy by wind waves, and the capture of that energy to do useful work. Wave energy converter (WEC) devices are designed to sustain the wave-induced loads that they experience during both operational and survival sea states. The extreme values of these forces are often a key cost driver for WEC designs. These extreme loads often occur during severe storms; therefore careful examination of harsh wave conditions during the device design process is needed. Consequently the development of a specific extreme condition modeling method is essential. This paper presents a novel method for estimating extreme wave statistics, based on the hourly measured wave height maxima at the location of interest. Wave measurements, analyzed in this paper, were collected at SEM-REV offshore sea station located near the coast of France, during years 2001–2010. Note that applied statistical methodology is general and can be well applied to a measured WEC response, and its technology risk assessment. Accurate estimation of extreme wave conditions is critical for offshore renewable energy activities and applications. SEM-REV is known French wave energy test site. The method, referred to as ACER method, is presented in brief detail. ACER method provides an accurate extreme value prediction, utilizing available data efficiently. In this study the estimated return level values, obtained by ACER method, are compared to the corresponding return level values obtained by Gumbel method. Based on the overall performance of the proposed method, it is concluded that the ACER method can provide a robust and accurate prediction of extreme wave height at a given location.

Abstract There is an important concern that uranium reserves will not be sufficient for new nuclear facilities in the future. Thorium could offer a potential alternative fuel because it is three times more abundant than uranium. Thorium based nuclear fuels are important candidates for the future of nuclear fuels. The main interest is in considering thorium based fuels for burning plutonium in conventional reactors. Thoria based inert matrix fuels (IMF) are also candidates for burning plutonium and the transmutation of minor actinides. In this study, inert matrix fuel production was examined by external gelation process. Metal nitrate solution of each material (thorium nitrate, cerium nitrate, aluminum nitrate and magnesium nitrate) were mixed for the feed solution. The metal nitrate solution was 50% of total feed solution. After mixing the metal nitrate, solution polyvinyl alcohol (PVA, 10%) and tetrahydrofurfuryl alcohol (THFA, 40%) were added into mixed metal nitrate solution during stirring. PVA, THFA and metal nitrate solution were dropped through a nozzle into gelation medium ammonia solution. Then external gelation process was carried out. Cerium (Ce) was used to simulate Plutonium (Pu). Obtained gels from the external gelation process were aged, washed and dried. The powders were calcinated at 1273 K for 6 h. After calcination, the powders were pressed at 500 MPa with a manual press. Pellets were sintered at elevated temperatures (1473, 1573, 1673, 1773, 1873, and 1973 K) for 4 h. The densities of sintered pellets were measured by immersion method. Sintered pellets characteristics were determined by scanning electron microscopy, x-ray diffraction analysis and energy dispersive x-ray analysis and the results were discussed.

Abstract A comprehensive molecular dynamics study was carried out to investigate the role of thorium and uranium contents on improving the thermal and mechanical properties of the Th1-xUxO2 nuclear fuels. In this regard, several thermophysical and mechanical properties of the Th1-xUxO2 solid solutions including the lattice parameter, density, thermal expansion coefficient, specific heat capacity, thermal conductivity, thermal diffusivity, linear (heat/power) rating, elastic constants (C11, C12, C44, bulk, shear, Young's moduli, and Poisson's ratio) and the maximum radial thermal stress applied to fuel pellets were numerically investigated in a wide range of temperature and compared with experimental results. The results indicated that the Th1-xUxO2 fuels have a lower density, specific heat capacity, and thermal expansion coefficient than pure UO2 at any temperature. The results also showed that the Th1-xUxO2 fuels could increase or decrease the thermal conductivity, thermal diffusivity, and the linear heat rating of nuclear fuels depending on the uranium content (x). The amount of x in which all of the mentioned parameters can rise calculated in a wide range of temperatures. Maximum radial thermal stress was another important parameter that explicated in this paper. Results demonstrated that the Th1-xUxO2 fuels have lower maximum radial thermal stress, especially at high temperatures. These improved the thermo-mechanical properties provide the possibility of rising the fuel burnup in the thorium-based fuels compared to the uranium-based fuels.

The configuration of a biologically fertile substrate for edible plant growth during long-term manned missions to Mars constitutes one of the main challenges in space research. Mars regolith amendment with compost derived from crew and crop waste in bioregenerative life support systems (BLSS) may generate a substrate able to extend crew autonomy and long-term survival in space. In this context, the aim of our work was threefold: first, to study the geochemistry and mineralogy of Mojave Mars Simulant (MMS-1) and the physico-chemical and hydraulic properties of mixtures obtained by mixing MMS-1 and green compost at varying rates (0:100, 30:70, 70:30, 100:0; v:v); secondly, to evaluate the potential use of MMS-1 as a growing medium of two lettuce (Lactuca sativa L.) cultivars; thirdly, to assess how compost addition may impact on sustainability of space agriculture by exploiting in situ resources. MMS-1 is a coarse-textured alkaline substrate consisting mostly of plagioclase, amorphous material and secondarily of zeolite, hematite and smectites. Although it can be a source of nutrients, it lacks organic matter, nitrogen, phosphorus and sulphur, which may be supplied by compost. Both cultivars grew well on all mixtures for 19 days under fertigation. Red Salanova lettuce produced a statistically higher dry biomass, leaf number and area than Green Salanova. Leaf area and plant dry biomass were the highest on 30:70 simulant:compost mixture. Nevertheless, the 70:30 mixture was the best substrate in terms of pore-size distribution for water-plant relationship and the best compromise for plant growth and sustainable use of compost, a limited resource in BLSS. Many remaining issues warrant further investigation concerning the dynamics of compost production, standardisation of supply during space missions and representativeness of simulants to real Mars regolith.

Consider a situation where spatial heterogeneity leads to a cline, a gradual transition in dominance of two competing species. We first prove, in the context of a simplified competition–diffusion model, that there exists a stationary solution showing that the two species coexist in a transition zone. What happens then if, owing to climate change, the environmental profile moves with constant speed in space? We show here that, when the speed with which the environmental condition shifts exceeds the Fisher invasion speed of the advancing species, an expanding gap will form. We raise the question of whether such a phenomenon has been or can be observed.