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We measured leaf photosynthetic traits in shade-grown seedlings of four tree species native to northern Japan, raised under an elevated CO2 condition, to investigate the effects of elevated CO2 on shade tolerance of deciduous broadleaf tree species with different successional traits. We considered Betula platyphylla var. japonica and Betula maximowicziana as pioneer species, Quercus mongolica var. crispula as a mid-successional species, and Acer mono as a climax species. The plants were grown under shade conditions (10% of full sunlight) in a CO2-regulated phytotron. Light compensation points (LCPs) decreased in all tree species when grown under elevated CO2 (720 μmol·mol−1), which were accompanied by higher apparent quantum yields but no photosynthetic down-regulation. LCPs in Q. mongolica and A. mono grown under elevated CO2 were lower than those in the two pioneer birch species. The LCP in Q. mongolica seedlings was not different from that of A. mono in each CO2 treatment. However, lower dark respiration rates were observed in A. mono than in Q. mongolica, suggesting higher shade tolerance in A. mono as a climax species in relation to carbon loss at night. Thus, elevated CO2 may have enhanced shade tolerance by lowering LCPs in all species, but the ranking of shade tolerance related to successional traits did not change among species under elevated CO2, i.e. the highest shade tolerance was observed in the climax species (A. mono), followed by a gap-dependent species (Q. mongolica), while lower shade tolerance was observed in the pioneer species (B. platyphylla and B. maximowicziana).

28th European Photovoltaic Solar Energy Conference and Exhibition; 3159-3162, We investigated technologies for rapidly and accurately determining the I-V curves of high-capacity crystalline silicon (c-Si) solar cells. The I-V curves of these types of c-Si solar cells, such as those with an a-Si/c-Si heterojunction structure, are dependent on the voltage sweep time and direction up to a sweep time of several hundred milliseconds. The results of the present study show that the sweep time needed for measuring more recentlydeveloped high-efficiency devices are longer than for older devices, possibly due to their higher capacitance, especially at higher bias voltages. They have also shown the type of I-V testers employed to be an important factor. The sweep time required for accurately measuring I-V curves varies according to the I-V tester being used and is affected by the tester’s individual electrical impedance and control logic. We have developed novel technology for IV testers that involves measuring high-capacity c-Si solar cells and modules using a short pulse of light. It provides the advantage of not requiring fine voltage control or real-time feedback. I-V curves of high-efficiency a-Si/c-Si heterojunction solar cells and modules measured using this novel I-V tester, which applies a single 20 - 50 msec flash of light, have shown very good agreement, typically within 0.3%, with the results measured at AIST under continuous or long-pulse (0.5 - 1 sec.) illumination.

25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain; 2663-2666, Precise measurement of the current-voltage (I-V) curve is the essential technology for characterizing the performance of the solar cells. The I-V curves of the crystalline silicon (c-Si) bare cells are usually measured by using sample stages with multiple contact probes. It has been recently recognized that the I-V curves of the c-Si bare cells can be significantly influenced by the measurement details such as the distance of the contact probes, position of the contact bars and contact pressures. In this study, possible measurement errors due to these measurement details are experimentally investigated by using different structures of bare cells and sample stages. It is shown that the maximum power Pmax can be both overestimated or underestimated due to the distribution of the electric potential in the bare cells, even when the contact probes are carefully positioned. Examples of the potential distribution along the busbars of bare cells are demonstrated. Experimental correction procedure and formula are proposed, by which "true" I-V curve can be calculated by the measured I-V curve and distribution of the electric potential.

In the course of research on quantitative assay of non-destructive measurement of radioactive waste, the have developed a unique program based on the Bayesian theory for reconstruction of transmission computed tomography (TCT) image. The reconstruction of cross-section images in the CT technology usually employs the Filtered Back Projection method. The new imaging reconstruction program reported here is based on the Bayesian Back Projection method, and it has a function of iterative improvement images by every step of measurement. Namely, this method has the capability of prompt display of a cross-section image corresponding to each angled projection data from every measurement. Hence, it is possible to observe an improved cross-section view by reflecting each projection data in almost real time. From the basic theory of Baysian Back Projection method, it can be not only applied to CT types of 1st, 2nd, and 3rd generation. This reported deals with a reconstruction program of cross-section images in the CT of 3rd generation type (fan beam projection). The performance tests of the program have been carried out using the projection data obtained with a virtual CT system (li.e,, simulation calculation with the MVP Monte Carlo code) and the real data obtained from the TCT instrument equipped with 1920ch array detectors. Finally, we have confirmed that sharp cross section images can be obtained with a spatial resolution of 0.1 mm. The present reconstruction program developed here for the gamma-ray CT can widely applied also to, for instance, the Neutron Imaging and the Positron Emission Tomography (PET).